Evolution Of Speaker Manufacturing English Language Essay

Evolution Of Speaker Manufacturing English Language Essay A speaker is an electrical device that converts electrical signals to mechanical motion in order to create sound waves. A transducer, which is another name for a speaker, is a device that converts one form of energy to another. The speaker moves in accordance with the variations of an electrical signal and causes sound waves to propagate through a medium such as air or water. The first electrical speaker, patented by Alexander Graham Bell in 1876, was for the earpiece of the telephone. This design was later improved upon by Ernst Siemens and Nicola Tesla in 1877 and 1881 respectively. Siemens and Tesla used a metal horn driven by a membrane attached to a stylus to create the design of what would be the basis for the modern speaker. Thomas Edison was working on a design at this time using compressed air as the amplifying mechanism. He quickly found this was not the most effective way to create the mechanical waves that produce sound. He quickly withdrew his application for a patent an d settled on the metal horn design. The metal horn speaker is a speaker which can be found on antique record players. Metal Horn Speaker Moving Coil Speaker The modern design of the moving coil driver was established by Oliver Lodge in 1898. Lodge was a British physicist and writer that was involved in many key patents involving wireless telegraphy. In 1915, Magnavox emerged as the first public company to produce a loudspeaker. This design was the first practiced use of the moving coil drivers in a loudspeaker. Magnavox was started in that same year by Edwin Pridham and Peter L. Jensen. The companys focus was on developing consumer electronics. They would later go on to be the first to develop a phonograph loudspeaker. Today Magnavox is owned by one of the world leaders in electronics, Phillips. In 1924, Chester W. Rice and Edward W. Kellogg received the first patent on the moving-coil principle, direct radiator, and loudspeaker. Their patent was different from the previous attempts because of the adjustment of mechanical parameters in their design. The fundamental resonance of the moving system takes place at a lower frequency than that at which the cones radiation impedance becomes uniform. In 1926, Rice and Kellogg sold the loudspeaker, Radiola which was superior to anything else previously invented because it decreased sound distortion and improved audio quality for the buyer. These speakers used electromagnets instead of large powerful magnets in their design. The electro magnets were used because larger, more powerful magnets were not available at a cheap enough price at the time. In the 1930s, manufactures began placing two or three band passes worth of drivers in their speakers, which allowed for increased quality, sound pressure levels, and frequency response. Many of the components involved in the production of modern speakers have been improved upon from their initial designs. The biggest improvements have occurred mainly in the makeup of the materials in the speaker and in the enclosure design. The diaphragm materials and permanent magnet materials are some of the other speaker components which have improved throughout the years. With the advent of computer aided design and increased accuracy in measuring techniques, the development of the speaker and quality of sound have grown exponentially in recent years. The modern loudspeaker has a similar makeup to that of earlier designs, but some of the basic ideas behind the design have changed to give us the speaker we have today. The Modern Speaker Modern speakers use a permanent magnet and an electromagnet to induce the reciprocating motion of the diaphragm. The alternating current going through the electromagnet constantly reverses the magnetic polarity of the coil thus reversing the forces between the voice coil and the permanent magnet. This causes a rapid back and forth motion of the coil resembling that of a piston. When the coil moves it causes the diaphragm to vibrate the air in front of the speaker, creating sound waves. The frequency and amplitude of the electrical audio signal dictates the rate and distance that the voice coil moves thus determining the frequency and amplitude of the sound waves produced by the diaphragm. Drivers are only able to create sound in a given range of frequencies, thus many different types of drivers must be manufactured to account for the wide range of possible frequencies. The main components of the modern speaker are the diaphragm, permanent magnet, suspension, voice coil, and basket with three other important features being coaxial drivers, speaker enclosures, and audio amplifiers. In the following sections we will break down each component and investigate the improvements of each component including those in the material selection and the manufacturing process. Diaphragm One of the main components of a speaker is the diaphragm, sometimes called a speaker cone. The diaphragm can also be referred to as the diaphragm and its surrounding assembly including the suspension and the basket. However for our purposes the suspension and the basket will be individually discussed in later sections. Movement of the diaphragm causes sound waves to propagate from the speaker thus producing the noise we hear. The ideal properties of a diaphragm are minimal acoustical breakup of the diaphragm, minimal standing wave patterns in the diaphragm, and linearity of the surrounds force-deflection curve. The diaphragm stiffness and damping qualities plus the surrounds linearity and damping play a crucial role in reproducing the voice coil signal waveform. Eighty five percent of the diaphragms sold worldwide are made of cellulose fibers because they can be easily modified by chemical or mechanical means to giving it a practical manufacturing advantage not found in other common diaphragm materials, although reproducibility can be a problem. The lack of reproducibility can affect imaging, depending on the precision and quality of production. Cellulose is also advantageous over other diaphragm materials because of its low cost to produce. Although Cellulose works well as a diaphragm, new synthetic materials are emerging that are more lightweight, allowing for better audio quality, reduced distortion, and increased vibration and shock durability. These materials include polypropylene, polycarbonate, Mylar, silk, fiberglass, carbon-fiber, titanium, aluminum, aluminum-magnesium alloy, and beryllium. Polypropylene is the most common plastic material used in a diaphragm. The polypropylene is normally mixed with a filler, such as Kevlar, to reduce the manufacturing costs or it can be to alter the mechanical properties of the diaphragm. Polypropylene diaphragms have been increasingly more popular with the advancements in modern adhesive technology. Although with all plastic materials present, the material tends to have a viscoelastic creep, which is the materials tendency to slowly deform and stretch when under repetitive stresses. However, polypropylene diaphragms are still a popular choice for high performance speakers due to their consistent performance. Research is presently underway in attempts to create new plastic based materials such as TPX, HD-A, HD-I, Neoflex, and Bextrene for diaphragms. These materials generally have the same characteristics as polypropylene so the manufacturing costs cannot be justified for full production. Another option for low-frequency applications are woven fiber diaphragms. The woven fibers such as carbon fiber, fiberglass, and Kevlar are bonded together with a resin. When the high tensile strength of the woven fibers mixes with the adhesive and bonding characteristics of the resin it results in an incredibly stiff material. This stiffness results in a great low-frequency diaphragm, however the stiffness causes rough high-frequency responses. There have been numerous attempts to improve the high-frequency problems of woven fiber diaphragms such as using two thin layers of Kevlar fabric bonded together with a resin and silica microball combination and another attempt employed a sandwich structure of materials with a honeycomb Nomex core. But again, as with the advanced plastic materials, the cost of manufacturing versus the performance of the material cannot yet be justified. The final modern practical material for diaphragms is metal. Metals worst downfall is its terrible damping attributes which causes extreme high-frequency distortion. The most common metal of choice are aluminum and magnesium alloys. Due to the lack of technological advances in damping agents to add to these alloys, metal diaphragms are very rarely used in high-frequency applications. However, these alloys have been commonly used in lower end frequencies with great success. Permanent Magnet Modern driver magnets have become predominately permanent magnets. Historically this function was filled by the use of electrically powered field coils. When high-strength permanent magnets became available, they eliminated the need for the additional power supply that drove the coils. When this happened, Alnico magnets became popular. Alnico magnets are created from alloying aluminum, nickel, and cobalt. Until about 1980 Alnico magnets were primarily used but because of their tendency to become demagnetized, permanent magnets have since been made of ceramic and ferrite materials. Ferrite magnets are constructed by mixing iron oxide with strontium and then milling the compound into a very fine powder. The powder is then mixed with a ceramic binder and closed in a metal die. The die is then placed in a furnace and sintered to bond the mixture together. Sintering is the process in which the particles of the powder are welded together by applying pressure and heating it to a temperature below its melting point. Although the magnetic strength to weight ratio of ferrite magnets is lower than Alnico, it is considerably less expensive, allowing designers to use larger yet more economical magnets to reach a desired performance. In manufacturing, the most significant technical innovation of the speaker is due to the use of neodymium magnets. Currently neodymium magnets are the strongest permanent magnets known to man. For this reason neodymium magnets significantly help in producing smaller, lighter devices and improve speaker performance due to their great capacity for generating strong magnetic fields in the air-gap. A neodymium magnet is an alloy of neodymium, iron, and boron to form the molecule Nd2Fe14B. The molecular structure of this molecule is a tetragonal crystalline structure. Important properties in a magnet are the strength of the magnetic field, the materials resistance to becoming demagnetized, the density of magnetic energy, and the temperature at which the material loses its magnetism. Neodymium magnets have much higher values for all of these properties than other magnetic materials except that it loses its magnetism at low temperatures. For this reason it is sometimes alloyed with terbium and dysprosium in order to maintain its magnetic properties at higher temperatures. Suspension Another critical element in speakers is the suspension. The purpose of a suspension system is to provide lateral stability and make the speaker components return to a neutral point after moving. A typical suspension system includes two major components, the spider and the surround. The spider connects the voice coil to the frame of the speaker and provides the majority of the restoring force. The surround connects the top of the diaphragm to the frame of the speaker and helps center the diaphragm and voice coil with respect to the frame. Both components work together to make sure the diaphragm and coil assembly move strictly linearly and in line with the center of the permanent magnet. The spider is usually made of a corrugated fabric disk, impregnated with a stiffening resin. The name comes from the shape of early suspensions, which were two concentric rings of Bakelite material, joined by six or eight curved legs. The surround may be resin treated cloth, resin treated non-wovens, polymeric foams, or thermoplastic elastomers that are molded onto the cone body. An ideal surround has sufficient damping to fully absorb vibration transmissions from the cone to surround interface, and the durability to hold out against long term fatigue caused by prolonged vibration. Advancements in suspension manufacturing have come from innovations in synthetic suspension materials. The use of synthetic materials like kevlar or konex instead of cotton, has made todays speakers much more stable than those made as recent as ten years ago. A more durable suspension means that a speakers sound quality can remain unaltered for a longer period of time. This is especially a concern for speakers that generally operate at low frequencies since lower frequency sounds are created by larger diaphragm travel and larger diaphragm travel must be supported by more suspension travel. Voice Coil The wire in a voice coil is usually made of copper, though rarely aluminum and silver may be used. Voice coil wire cross sections can be circular, rectangular, or hexagonal, giving varying amounts of wire volume coverage in the magnetic gap space. The coil is oriented co-axially inside the gap; it moves back and forth within a small circular volume (a hole, slot, or groove) in the magnetic structure. The gap establishes a concentrated magnetic field between the two poles of a permanent magnet, the outside of the gap being one pole, and the center post (called the pole piece) being the other. The pole piece and backplate are often a single piece, called the poleplate or yoke. This magnetic field induces a reaction with the permanent magnet causing the diaphragm to move thus producing the sounds we hear. Voice coils can either be overhung, longer than the magnetic gap, or underhung, shorter than the magnetic gap, depending on its application. Most voice coils are overhung thus preventi ng the coil from being overdriven, a problem that causes the coil to produce significant distortion and removes the heat-sinking benefits of steel causing the speaker to heat rapidly. The most important characteristic of a voice coil is that it be able to withstand large amounts of mechanical stresses and also be able to dissipate heat to its surroundings without causing damage to the speakers other components. In early loudspeakers the voice coil was wound onto paper bobbins to remove heat from the system. At the time this was enough to cool the system at average power levels but as larger amplifiers became available allowing for higher power levels new technologies had to emerge. To cope with the increasing power inputs the use of alloy 1145 aluminum foil was widely used as a substitute for the paper bobbins. Aluminum was popular to industry due to its low cost to manufacture, its structural strength, and it was easy to bond to the voice coil. However, problems with the foil emerged over extended use at increased power levels. The first problem was the foil tended to transfer heat from the voice coil into the adhesives used inside the speaker causing them to thermally degrade or even burn. The second problem was the motion of the aluminum foil inside the magnetic gap created currents that actually increased the temperature of the voice coil, thus causing long-term reliability issues. In 1955 a new material was developed called Kapton, a polyimide plastic film, to replace the aluminum foil. Kapton solved all the problems that were associated with the aluminum foil however Kapton or even its improved cousin Kaneka Apical, were not perfect. Both high-tech materials were costly to manufacture and had a tendency to soften when heated. Although Kapton and Kaneka Apical had their downfalls they became the most widely used coating for voice coils until 1992 when a material called Hisco P450 was developed. Hisco P450 is a thermoset composite created by using a thin film of fiber glass cloth and impregnating it with a polyimide resin. This combination allowed for necessary mechanical strength and endurance of the polyimide and necessary temperature resistance and stiffness of fiberglass. Hisco P450 was able to withstand the grueling temperature requirements of professional speakers while also maintaining enough rigidity to withstand the mechanical stresses associated with long-term, high-frequency motions. In recent years the copper wire that is almost always used as the voice coil has been replaced sparingly with aluminum wire in extra sensitive, high-frequency applications. The aluminum wire is lighter than the copper wire and has about two thirds of the electrical conductivity allowing the wire to move at higher frequencies inside the magnetic gap. Variations of the aluminum wire include copper-clad aluminum and anodized aluminum. Copper-clad aluminum allows for easier winding along with an even more reduced mass. The anodized aluminum is effectively insulated against shorting which removed the concerns of dielectric breakdown. Aluminum wires are great lightweight, low-inductance choices for voice coils however, they do have their downfalls. The thermal characteristics of aluminum causes power limitations with the coil. If too much power is passed through the aluminum coil it can cause the adhesive bonds between the wire and the bobbin, or the bobbin to the spider and coil to weaken or even burn. To cope with the ever increasing power demands on the voice coil in addition to wrapping the coil in some high-tech material to increase its thermal properties, the voice coil has also been submerged in a ferrofluid, an oil that is used to conduct heat away from the voice coil and also creates a small magnetic field thus increasing the power handling capacity of the voice coil. Basket The basket or frame (as seen below) is the fixture used to hold the diaphragm, voice coil, and magnet in the proper place. The rigidity of this part is extremely important to prevent rubbing of the voice coil and prevent random movements that could cause problems with the permanent magnet. The three most common types of modern baskets are cast metal baskets, rigid baskets made out of stamped steel or aluminum, and cast plastic baskets. Each type of basket offers different advantages and disadvantages; these will be discussed in the flowing paragraphs. The stronger the basket the more power the speaker can handle before failure occurs. A well made basket should have a high power rating, be lightweight, and be able to conduct heat away from the voice coil to prevent physical changes or even possible demagnetization of the permanent magnets. Cast metal (above right) baskets are the most rigid of the three in all directions, but they are the most expensive to make. Cast metal baskets are made by melting down the desired metal to liquid form. The scorching hot liquid metal is then poured into a mold and once the liquid metal dries inside the mold, the mold is removed revealing a cast metal basket. Cast metal baskets although more expensive than the other two options, usually are more rigid thus preventing motion. They also have better damping characteristics, and they are also more easily manufactured allowing for more intricate shapes. Cast metal baskets are usually the preferred basket choice for higher quality speakers. A less expensive and yet less rigid basket can be made out of stamped steel. The stamped steel or aluminum sheets arrive to the manufacturer preformed. The sheets are then drilled using a hydraulic press to cut holes in the sheet to allow air flow to and from the diaphragm. The sheet is then pressed using another hydraulic press using a die to form the desired shape. Stamped metal baskets tend to be weaker than their cast metal counterparts. This weakness could cause the basket to flex if the speaker is being used at high volumes. The final option, which is even less expensive, is a cast plastic basket. Cast plastic baskets are made by using the liquid plastic and pouring it into the desired shaped mold. When the liquid plastic dries the mold is removed revealing a cast plastic basket. Just like cast metal baskets, cast plastic baskets are easily manufactured allowing for intricate shapes. The lightweight characteristics of the plastic would also make the speaker lighter allowing for smaller power consumption. However, as with most engineering decisions, the performance of the part proportionally decreases as the cost to produce the part decreases. The decreased cost of production of the plastic basket means that it is a weaker basket. This weaker, plastic basket will allow for the most flexing as compared to cast metal and stamped steel baskets. The power rating of the speaker would also be less than that of the metal baskets, both cast and stamped, due to the weaker strength characteristics of plastic in com parison with metal. Coaxial Drivers Coaxial drivers are the components of a speaker that radiates sound from the same point or axis. This is done by placing a high-frequency driver in the center of a low-frequency driver so that they produce sound waves from a single point in a loudspeaker system rather than separate locations. This allows for a more beneficial design over having the low and high frequency drivers separate. There are many different types of drivers and each driver produces sound within a limited frequency range. Subwoofers, woofers, mid-range drivers, and tweeters are all driver types capable of emitting different ranges of sound. A coaxial driver takes one of these higher frequency drivers and places it within a lower frequency driver. For example, a tweeter, the high frequency unit, could be placed in the center of a woofer, the low frequency unit, so that both drivers emit sound from the same point. This example can be seen in the images below. This design, which improves sound quality, was first de signed by Altec Lansing in the 1940s. Although it has many advantages, it is still an uncommon practice in the manufacturing of speakers due to technical and budgetary considerations. Enclosures The enclosure of a loudspeaker serves three functions and is made with a specific design that helps improve the quality of the sound produced by the speaker. The first function the enclosure performs is separation of the sound waves. It accomplishes this by preventing sound waves generated at the back of the speaker from interacting destructively with sound waves generated at the front of the speaker. The enclosure is intended to reduce distortion created because the waves that emanate from the front of the speaker are out of phase with the waves emanating from the rear of the speaker. If the front and rear waves were to overlap with one another it would result in wave interference. The second function the enclosure serves is to stop any echo and reverberation that would be created from the two differing sound source locations on the speaker. Because waves are created at the front and rear of the speaker, the two different sets of waves travel through the air differently as a result of their relative locations, and arrive at the person listening at different times. The third function the enclosure serves is to deal with the vibrations produced by the driver and to deal with the heat produced by the electronic components. Enclosures did not always have the fully enclosed container design that they now commonly have. Although present day practices say that enclosures need to have a back, before the 1950s they lacked one due to the cooling functions of an open container. Sealed enclosures, the most common type of enclosure, is completely sealed so no air can escape. With this type of enclosure the forward wave travels outward into the surroundings, while the backward wave is limited to only fill the enclosure. With a virtually airtight enclosure, the internal air pressure is constantly changing; when the driver retracts, the pressure increases and when the driver moves out, the pressure decreases. Both movements create pressure differences between the air inside the enclosure and the air outside the enclosure. Because of this, the driver motion always has to fight the pressure differences caused. These enclosures are less efficient than other designs because the amplifier has to boost the electrical signal to overcome the force of air pressure. The force due to air pressure does, however, provide an additional form of driver suspension since it acts like a spring to keep the diaphragm in the neutral position. This makes for tighter, more precise soun d production. Enclosure designs range from very simple, rectangular particle-board boxes (above left) to very complex cabinets made of composite materials (above right). The simplest enclosures are made to prevent destructive interference caused by overlapping of the front and rear sound waves from the speaker. The most complex enclosures contain acoustic insulation and internal baffles, which prevent interference. Solid materials such as heavy wood, are typically used when building enclosures in order to absorb the vibration caused by the speaker driver. This vibration dampening is extremely important. A speakers sound output would be drowned out by the drivers vibrations if there were not an enclosure incorporated into the design. Since the beginning of the production of enclosures, the most advantageous properties required for minimal energy loss through the enclosure walls have remained unchanged. Different strategies employed to reduce energy losses are to use thicker enclosure walls, denser hardwood plys and sturdier bracing. The downside to these methods is that they all add significant weight to the enclosure. However, with the production of newer materials that possess an increased stiffness-to-mass ratio this is changing. These new materials can improve performance and reduce weight, while also reducing the cabinets resonance. The end result is that a greater amount of the speakers en ergy is delivered in the intended direction rather than into mechanical vibrations which are wasted and produce a decrease in sound quality. A recent alternative to heavy wood construction of enclosures is the use of composite materials. It was for the aerospace industry that composite materials such as carbon-fiber were originally developed. Carbon-fiber was a success because of the high demand for a material with increased strength and rigidity. Speaker applications, such as enclosures use carbon-fiber materials to create a product with a vastly decreased weight and increased strength and rigidity. Enclosures built with carbon-fiber can weigh less than half as much as enclosures built from heavy wood. These enclosures which limit the speaker resonance can provide as much as 3 dB more output than the same speaker would have otherwise had in a heavy wood enclosure. Furthermore, carbon-fiber enclosures are extremely durable adding quality to the final product and they require almost no maintenance. Even though carbon-fiber enclosures cost around twice as much to produce as traditional enclosures, the lighter weight and ext ra output offer two very advantageous tradeoffs. Amplifier An amplifier is any device that increases or decreases the amplitude of a signal. An audio amplifier increases low-power audio signals to a suitable level for loudspeakers. When dealing with a speaker there are a many audio amplifiers involved. These amplifiers are responsible for pre-amplification, equalization, tone control, and mixing effects followed by a higher power amplifier which creates the final amplification for suitable levels of sound output. Amplifiers are found in wireless receivers and transmitters, CD players, acoustic pickups, and hi-fi audio equipment. Amplifiers are used for high-quality sound production, and depending upon the quality of the amplifier, they may cause distortion, which the speaker enclosures are meant to deal with. Distortion in amplifiers is caused by difference in phases of the output waveform and the input waveform. The smaller the difference in between the output and input waveforms the greater the quality of final sound. Audio amplifiers cons ist of resistors, capacitors, power sources, wires, semiconductors, and stereo jacks all combined on an electronic work board to produce the type of amplifier needed. Types of Speakers Woofers are loudspeaker drivers designed to produce sounds of low frequency from around 40 hertz up to around 1000 hertz. The most common design for a woofer is the electro-dynamic driver, using a stiff paper cone driven by a voice coil. Woofers are important to allow for a range of frequency that will hit a low level. Effective woofer designs efficiently convert low frequency signals to mechanical vibrations. The vibration of the air out from the cone creates concentric sound waves that travel through the air. If this process can be done effectively, many of the other problems speakers run into will be greatly reduced such as linear excursion. For most speakers the enclosure and the woofer must be designed to work hand in hand. Usually the enclosure is designed around the woofer, but in some rarer cases the enclosure design can actually dictate the woofer design. The enclosure is made to reflect the sounds at the right distance, so that they will not be wave cancelling reflections. Below you can see an example of a common woofer. A subwoofer is a woofer with a diameter between 8 and 21s. Subwoofers are made up of one or more woofers. They can be arranged in many different configurations to produce the best quality of sound. Subwoofers usually play frequencies between 20 hertz and 200 hertz, well within the range of human auditory levels. The first subwoofer was created in the 1960s and added to the home stereo to create bass for sound reinforcement. Up until this point the only form of audio player which contained bass was a phonograph player which was created by Magnavox. This allowed for a more accurate array of music. Subwoofers are used in all sound systems today such as in cinemas, cars, stereos, and for general sound reinforcement. A mid-range speaker is a loudspeaker driver that produces sound between 300 hertz and 5000 hertz. These are less commonly known as squawkers. Midrange drivers can be found as cone speakers, dome speakers, or compression horn drivers. Mid-range speakers usually resemble small woofers. The most common material the cone is made out of for a mid-range is paper although they can be found to be coated or impregnated with polymers or resins to improve vibration dampening. Much of the rest of the mid-range speaker is made from plastic polymers. Mid-range speakers which employ the dome set up usually only use 90 degrees of the sphere as the radiating surface. These can be made from cloth, metal or plastic film. The voice coil in this design is set at the outer edge of the dome. Mid-range drivers are most commonly used for professional concerts and are compression drivers coupled with horn drivers. Rarely mid-range speakers can be found as electrostatic drivers. Mid-range speakers handle the most prominent part of the human-audible sound spectrum. This is the region where most sound emitted by musical instruments lie. This is also where the human voice falls in the audible spectrum. Most television sets and small radios only contain a single mid-range driver. Tweeters are a loudspeaker designed to produce frequencies from 2,000 to 20,000 hertz. Some tweeters on the market today can produce sounds of up to 45000 hertz. The human ear can generally only hear up to about 20000 hertz. The name tweeter comes from the extremely high pitch it can create. Modern tweeters are different from older tweeters because older tweeters were smaller versions of woofers. As tweeter technology has advanced, differen

Goegraphy of Dominica :: Essays Papers

Goegraphy The geography of Dominica is quite unique. It is an island fortress unlike any other island in the Caribbean, and is the largest and most mountainous of the Windward Islands. The island was created by volcanic activity, and still today shows signs of active volcanic activity. Its steep mountains prevented colonists from completely taking over and have made the island a prime destination for Eco-tourists. The island contains over 3,000 peaks, the tallest of which are Morne Diablotin (4,747 ft) and Morne Trois Pitons (4,600ft). (www.delphis.com) The island itself is located between the French islands of Guadeloupe to the north and Martinique to the south. It is 29 miles long and 16 miles wide, and covers 290 square miles. Its exact location is approximately 15 degrees North and 61 degrees West (www.delphis.dm). The island of Dominica is home to the only surviving population of Carib Indians. This was only possible because of Dominica’s treacherous mountains. Early European colonist were not able to drive out or kill all the natives as they had done on other islands. The Caribs now live in the â€Å"Carib Territory†, a 3700-acre reservation on the northeast coast, which was given to them in 1903. The reservation has a chief and is home to between 300 – 3000 Caribs (the exact number of Caribs is hard to determine because without detail genealogy records it hard to prove or disprove that someone actually is a Carib). (www.delphis.dm) The recent boom in eco-tourism has made Dominica one of the premiere tourist destinations both in the Caribbean and in the world. In recent years Dominica has designated more national parks, forests and marine reserves per capita than nearly anywhere else in the world. Dominica’s largest national park is the Morne Trois Pitons National Park. It covers 17,000 acres (9% of the island), and is home to the world’s largest boiling lake. The lake is 70 yards across with an unknown depth and the lake is situated over a massive volcanic sulfur vent, which keeps the water temperature between 180 – 197 degrees Fahrenheit. The park is also home to several waterfalls over 100 feet tall. The average temperature range is between 75 and 85 degrees Fahrenheit. Average rainfall varies between 50 inches on coastal areas, and 300 inches with in the interior. The driest months are from January to June, and hurricane season which is usually between July and early October.

Illustration Paragraph Essay

So, let’s suppose that you have done some brainstorming to develop your thesis. What else should you keep in mind as you begin to create paragraphs? Every paragraph in a paper should be Unified—All of the sentences in a single paragraph should be related to a single controlling idea (often expressed in the topic sentence of the paragraph). Clearly related to the thesis—The sentences should all refer to the central idea, or thesis, of the paper (Rosen and Behrens 119). Coherent—The sentences should be arranged in a logical manner and should follow a definite plan for development (Rosen and Behrens 119). Well-developed—Every idea discussed in the paragraph should be adequately explained and supported through evidence and details that work together to explain the paragraph’s controlling idea (Rosen and Behrens 119). top Read more:  How many sentences in a paragraph for college. How do I organize a paragraph? There are many different ways to organize a paragraph. The organization you choose will depend on the controlling idea of the paragraph. Below are a few possibilities for organization, with brief examples. Narration: Tell a story. Go chronologically, from start to finish. (See an example.) Description: Provide specific details about what something looks, smells, tastes, sounds, or feels like. Organize spatially, in order of appearance, or by topic. (See an example.) Process: Explain how something works, step by step. Perhaps follow a sequence—first, second, third. (See an example.) Classification: Separate into groups or explain the various parts of a topic. (See an example.) Illustration: Give examples and explain how those examples prove your point. (See the detailed example in the next section of this handout.) 5-step process to paragraph development Let’s walk through a 5-step process to building a paragraph. Each step of the process will include an explanation of the step and a bit of â€Å"model† text to illustrate how the step works. Our finished model paragraph will be about slave spirituals, the original songs that African Americans created during slavery. The model paragraph uses illustration (giving examples) to prove its point. Step 1. Decide on a controlling idea and create a topic sentence Paragraph development begins with the formulation of the controlling idea. This idea directs the paragraph’s development. Often, the controlling idea of a paragraph will appear in the form of a topic sentence. In some cases, you may need more than one sentence to express a paragraph’s controlling idea. Here is the controlling idea for our â€Å"model paragraph,† expressed in a topic sentence: Model controlling idea and topic sentence— Slave spirituals often had hidden double meanings. Step 2. Explain the controlling idea Paragraph development continues with an expression of the rationale or the explanation that the writer gives for how the reader should interpret the information presented in the idea statement or topic sentence of the paragraph. The writer explains his/her thinking about the main topic, idea, or focus of the paragraph. Here’s the sentence that would follow the controlling idea about slave spirituals: Model explanation—On one level, spirituals referenced heaven, Jesus, and the soul; but on another level, the songs spoke about slave resistance. Step 3. Give an example (or multiple examples) Paragraph development progresses with the expression of some type of support or evidence for the idea and the explanation that came before it. The example serves as a sign or representation of the relationship established in the idea and explanation portions of the paragraph. Here are two examples that we could use to illustrate the double meanings in slave spirituals: Model example A— For example, according to Frederick Douglass, the song â€Å"O Canaan, Sweet Canaan† spoke of slaves’ longing for heaven, but it also expressed their desire to escape to the North. Careful listeners heard this  second meaning in the following lyrics: â€Å"I don’t expect to stay / Much longer here. / Run to Jesus, shun the danger. / I don’t expect to stay.† Model example B— Slaves even used songs like â€Å"Steal Away to Jesus (at midnight)† to announce to other slaves the time and place of secret, forbidden meetings. Step 4. Explain the example(s) The next movement in paragraph development is an explanation of each example and its relevance to the topic sentence and rationale that were stated at the beginning of the paragraph. This explanation shows readers why you chose to use this/or these particular examples as evidence to support the major claim, or focus, in your paragraph. Continue the pattern of giving examples and explaining them until all points/examples that the writer deems necessary have been made and explained. NONE of your examples should be left unexplained. You might be able to explain the relationship between the example and the topic sentence in the same sentence which introduced the example. More often, however, you will need to explain that relationship in a separate sentence. Look at these explanations for the two examples in the slave spirituals paragraph: Model explanation for example A— When slaves sang this song, they could have been speaking of their departure from this life and their arrival in heaven; however, they also could have been describing their plans to leave the South and run, not to Jesus, but to the North. Model explanation for example B—[The relationship between example B and the main idea of the paragraph’s controlling idea is clear enough without adding another sentence to explain it.] Step 5. Complete the paragraph’s idea or transition into the next paragraph The final movement in paragraph development involves tying up the loose ends  of the paragraph and reminding the reader of the relevance of the information in this paragraph to the main or controlling idea of the paper. At this point, you can remind your reader about the relevance of the information that you just discussed in the paragraph. You might feel more comfortable, however, simply transitioning your reader to the next development in the next paragraph. Here’s an example of a sentence that completes the slave spirituals paragraph: Model sentence for completing a paragraph— What whites heard as merely spiritual songs, slaves discerned as detailed messages. The hidden meanings in spirituals allowed slaves to sing what they could not say. Notice that the example and explanation steps of this 5-step process (steps 3 and 4) can be repeated as needed. The idea is that you continue to use this pattern until you have completely developed the main idea of the paragraph. Narration, description, process, clasification, illustration  topics sentence,controlling idea,give example,explain,complete,transition

The Genesis Account of Creation: Myth or Reality

I always do recall, while reading through the first few pages of the Bible, (i. e. the book of Genesis), how highly impressed I was as a child, to see how the world began and how God put everything in place but then kept pondering; who was there with God taking a record of events while he was creating? Once upon a time, I asked my Christian Religious Studies teacher in School and he stood there dumbfounded unable to give any response. During my Catechism days, I was made to understand I must believe everything that the bible contains as true without doubting. However the more I tried to understand the creation narratives, the more questions generated within me. Was the world actually created just as the book of Genesis tells us? Did the same God, who created man last on the sixth day in Chapter One, come back again in Chapter Two to create the same man first before other things? In fact, considering the recent advancements in science and the claims by evolutionists today about the origin of the world, can we say that these creation narratives amount to mere myths? According to the Anchor Bible Dictionary, prior to the period of the Enlightenment, the question of whether or not the Bible contained any myths at all was not so pronounced. In fact, it was as from the 18th century that people started wondering if the Old Testament stories such as the creation narratives could possibly count as myths. This was basically fuelled by the various movements which came up to stress that the basis for anything to be considered true was its historical verifiability. Hence, the debate about myths in the Bible was initially a question of its truth and falsity. For instance, when the Bible speaks of events which took place prior to when the world itself began (when no man could have possibly existed to take a record of them), a successful attempt to show that they are actually myths translates to saying they are simply products of human imagination. And if this is the case, it follows then that the entire Bible itself rests on a questionable foundation. Hence over the years, several scholars have invested a great deal of time and effort on this quest. Before we proceed, it is important to bear in mind that at the heart of this debate lies the eaning and conception of the term myth. What is myth? And what constitutes a myth? What is Myth? Etymologically, the English word myth comes from the Greek mythos. In early Greek mythos meant â€Å"word, speech, design†; it was more or less synonymous with epos (â€Å"word, speech, message†), and close in meaning to logos (â€Å"account, talk†); myth is narration, tale-telling. Gradually it came to be used as a technical term for an entertaining tale, the truth of which was uncertain or unwarranted. From the time of Plato onward, mythos then became a contrasting term for logos (i. e. the rational, responsible account). To this day, whenever the word myth is used, there is an underlining tendency to consider that which it refers to as superstition. As B. Batto observes, â€Å"the derogation of myth as pagan superstition and therefore false and incompatible with Christian dogma remained the characteristic Christian attitude until the modern period – and is still the prevalent in some circles. † Initial Conclusion – No Myths in the Bible Based on the above, it becomes clear that with this understanding of the term myth, the Bible contains no myths since it has no pagan superstitions incompatible with Christian dogma. Now it becomes easy to see how stories as such as the Enuma Elish, Altrahasis or even the various African traditional stories of creation, etc could best be described as myths. In line with this, the word myth came to be defined as â€Å"stories about the gods† (a definition which was popularised by the Grimm Brothers) thereby distinguishing the Bible narratives out as non-myths. Since the Bible is essentially monotheistic it cannot possibly contain any myth as myths essentially refer to stories about several gods. Following this same principle, in his Introduction To The Old Testament, Wermer H.  Schmidt, goes further to explain that the Old Testament based on its conception of God â€Å"uses the language of myth in giving expression to its faith and it in fact borrows from surrounding cultures a number of mythical motifs and bits of mythical stories†¦ but it does not itself develop any myths. † In other words, the Genesis accounts of creation for instance only borrowed certain mythical motifs from those of the Ancient Near East but do not in themselves constitute any myth. The Evolution of Meaning and the Possibility of Myth in the Bible From the foregoing, it appears our case has been solved already. Just as we have shown, the meaning of the term myth gradually evolved from its simple understanding as a ‘narration’ to later take a negative connotation as ‘false tale. ’ At this point it was very easy to distinguish what could count as true (believable) and what should be dumped as myth (entertainment). However the trouble began when the term myth came to be positively re-defined with time. The Italian philosopher Vico posited â€Å"that myth came from within man’s own deepest inner nature; using the imagination rather than reason the first men gave true – even if non-rational and pre-scientific – answers to the original human dilemmas. German scholar David Friedrich Strauss (1808–74) working principally on the New Testament using the theory of Euphemism reached quite shocking conclusions that bulk of the O. T and N. T narratives such as the birth and conception of Jesus were not historically true, even if as mythical materials they did offer a deeper kind of human truth. His book Life of Jesus (1835), though had immediately rendered him famous eventually, led to the end of his academic career as many couldn’t accept his opinions. Nonetheless with a growing body of research and findings in Biblical archaeology which seemed to support Strauss, there arose some tension towards the end of the 19th Century with regard to the continued denial of myths in the Bible. Scholars after Strauss such as Hermann Gunkel, insisted that myths are stories about the gods and that â€Å"for a story of the gods at least two gods are essential† but since OT â€Å"from its beginning tended toward monotheism,† the Bible contains no complete myths. With time, scholars outside the realm of biblical studies dismissed this definition of myth â€Å"as inadequate, overly narrow, and apologetic. † In other words, as the meaning of myth gradually evolved from the negative to the positive conception of myth as deep truth, (that is â€Å"the profound symbolisation of realities which transcend human capacity to comprehend and express in ordinary language but which are profoundly true and paradigmatic for authentic life†), scholars such as Rudolf Bultmann (1884–1976) now propelled by the historico-critical method soon began to associate the term myth with certain key biblical mysteries. For Bultmann, the term myth assumed a much broader definition as â€Å"one of the ways in which any culture objectifies and symbolizes its entire worldview. † With such a broad understanding of myth, it was impossible to deny that much biblical narrative is inherently mythological. In this regard G. H. Davies in 1956 defined myth as â€Å"a way of thinking and imagining about the divine† and not necessarily about the gods such that myth can also occur in monotheistic religions. Following this trend of thought, John L.  McKenzie SJ in his Dictionary of the Bible (1976), came to the conclusion that â€Å"when we compare the thought processes of the OT with the processes of Semitc myth, we observe that the OT rejects all elements which are out of character with the God whom they knew. But what they knew of God could be expressed only through symbolic form and concrete cosmic event, and the relations of God with the world and with man were perceived and expressed through the same patterns and processes which elsewhere we call mythical. † In this same line of thought came more recent scholars such as B. S.  Childs as well as F. M. Cross. Today scholars believe that â€Å"in Israel, no less than in Ancient Near East generally, mythopoeism (myth-making) constituted one of the basic modes of speculation about the origin of the world and the place of human kind. † Reflecting personally on the above, I have come to realise that the debate about myth in the Bible, (a debate which had initially being sparked off by those movements who claimed that the basis of truth is historical verifiability) over the years now became a debate about the meaning of the word myth. As such, scholars delved into the issue over the years failing to realise that those who began the debate had in mind a conception that whatever fails the test of historical verification is untrue and as such should be considered as a myth. Scholars jumped into the debate without first realising the mistake of these movements. Historical verifiability is not the only criterion for truth. If for instance as at when I was born, nobody took records of my birth and it so happened that all my entire generation, my parents my siblings and everybody around me then suddenly died, the fact that I have no historical poof of my birth does not mean I wasn’t born at all. Hence the real error wasn’t about the definition of the term myth but the misconception that whatever is pre-history is false. No wonder, as long as myth remained in its original conception as false tale, the Bible was free of myths but the moment the definition of myth shifted into the more positive light as deep truths, the same Bible suddenly became full of myths. What we should bear in mind is that when this debate began the concept of myth was basically negative. (Recall that from Plato, myth was seen as a contrast for logos). And as long as the debate continues, the definition ought to remain the same. Even to this day, as long as we continue to regard the word myth as a false narrative, then the Bible contains no myths; the Genesis accounts of creation are not myths but pure realities, truths – although not historical, not scientific, not mathematical, but theological.

Political Spectrum

The Political Spectrum is a term given to the different ideologies of political parties or organizations. The Young Men's Christian Association is one organization on the left side of the Spectrum. The YMCA provides after school programs for both children and adults. A right wing group is the John Birch Society which dedicates itself to restoring and preserving freedom under the United States Constitution. The Young Men's Christian Society (YMCA) was founded in London to improve the spiritual condition of young men engaged in the drapery and other trades during the 1800s. Today the YMCA appears in over 124 countries and help promotes a healthy, balanced lifestyle regardless of beliefs or gender. This year on, April 27 2007, Durham YMCA held an open house for their new Y-Knot Abilities Programs. This program offers children and youth with physical disabilities access to the YMCA programs. The Y-Knot creates an â€Å"Equal Playing Field† for disabled youth. The Y-Knot Abilities program shall run every Friday from 5:00 to 7:00 pm in the gymnasium. Through the years, the YMCA has setup the YMCA Strong Kids Fundraiser. The money raised helps provides, families YMCA memberships, Children and Youth a chance to go to camp, renovations on community YMCA's and the fees for training new employees. Their goal from the fundraiser is hope on providing children and families with the tool they need to succeed. The YMCA's goal to create a positive attitude both physically and mentally in the community is achieved through a balanced leadership style. The organization creates both fundraisers to decrease membership fees, improve community recreations and increase daily activities to achieve their goal. There is no force by the organization to the community in participating in fundraisers and activities. The John Birch Society (JBS) is a right wing organization established in Indiana in 1958 by a group of twelve â€Å"patriotic and public-spirited† men. The society opposes socialism, communism, Nazism, and fascism, and strongly agrees to a limited federal government under the Constitution of the United States. The JBS plans many campaigns to help preserve freedom for themselves and American families. A recent campaign was called the â€Å"Repeal NAFTA† campaign. Goals are to withdraw U.S. membership form in the North American Free Trade Agreement (NAFTA). The society has dedicated time in creating pamphlets and written articles to approve in the withdrawal of NAFTA. The JBS has also organized the â€Å"JBS Freedom Campaign†. The campaign was designed for all Americans who want to preserve their cherished lives of freedom for themselves and their family. Through this campaign they will have the opportunity to participate with other Americans to help defeat some of the biggest threats to their way of life. The campaign acts like umbrella against issues such as illegal immigration and the North American Union. The JBS goal to preserve freedom for themselves and American families is achieved through an authoritarian leadership style. The society sets campaigns against the government to set regulations or eliminate different acts such as Illegal Immigration and NAFTA. The group forces people to join through riots, publicity and the internet. The YMCA on the spectrum is located at 3 o'clock on the left side due to being a beneficial organization to many communities. YMCA holds programs, clubs, fundraisers and teams to help create a positive attitude physically and mentally in the attitude. The JBS society would be located between 9 o'clock and 10 o'clock along the right side. The JBS is a group against communism and socialism, which are mid. to high left wing characteristics. The society opposed the â€Å"Civil Rights Movement†, an act of equality between colored and whites. Both organizations are clearly opposites due to the way they achieve their beliefs and achieve them.

Citizen of the United States Essay

I would define a citizen as someone, who was born in, or to a certain place, who is guaranteed certain rights in the place that they were born in. Citizenship in the United States means that a person is a legally recognized member of the nation. Each citizen has equal rights under the law. All citizens have certain rights, privileges, and responsibilities. Americans who are not citizens have many of the same rights, privileges, and responsibilities of citizens. However, they do not have such important rights as the right to vote in elections, serve on juries, or hold elected office. Means that a person is recognized as a legal member of the nation  gives each person certain rights and privileges, e.g., the right to vote and to hold public office  means each person has certain responsibilities, e.g., respecting the law, voting, paying taxes, serving on juries  explain that citizens owe allegiance or loyalty to the United States; in turn they receive protection and other services from the government Nothing is more important to America than citizenship; there is more assurance of our future in the individual character of our citizens than in any proposal I, and all the wise advisers I can gather, can ever put into effect in Washington. Warren G. Harding (1920) Rights of individuals. Citizens have rights.  personal rights, e.g., to associate with whomever one pleases, live where one  chooses, practice the religion of one’s choice, travel freely and return to the United States, emigrate  political rights, e.g., to vote, speak freely and criticize the government, join organizations that try to influence government policies, join a political party, seek and hold public office  economic rights, e.g., to own property, choose one’s work, change employment, join a labor union, establish a business  Citizens not only must be aware of their rights, they must also exercise them responsibly and they must fulfill those responsibilities necessary to a self-governing, free, and just society. No governmental action, no economic doctrine, no economic plan or project can replace that God-imposed responsibility of the individual man and woman to their neighbors. Herbert Hoover (1931) Citizens have rights. personal responsibilities, e.g., taking care of themselves, accepting responsibility for the consequences of their actions, taking advantage of the opportunity to be educated, supporting their families civic responsibilities, e.g., obeying the law, respecting the rights of others, being informed and attentive to the needs of their community, paying attention to how well their elected leaders are doing their jobs, communicating with their representatives in their school, local, state, and national governments, voting, paying taxes, serving on juries, serving in the armed forces

Refurbishment Project Assignment Example | Topics and Well Written Essays - 4000 words

Refurbishment Project - Assignment Example slope of the ramp makes it comfortable for the user and this permanent ramp actually connects pavement with the entrance. Terrace Gate: The building is provided with gates for moving out of the building into terrace through a main door which is capable of opening by pushing it. The width of the door is about 85cm. to access the terrace, ramps are provided in front of each door which is permanent. Figure 5: Terrace gate for moving out of the building Reception and reception desk: The reception is provided at the entrance from the main door and is at the same level as that of the entrance. Whereas it can be seen that the reception desk is high and the lightning is kept moderate in this region as shown below: Figure 6: Reception and high reception desk Stairs and Lifts: All floors are accessible by stairs including parking and ground floor. Each section of stairs joining two consecutive floors consists of approximately 15 stairs with a bright light level. The stairs are designed in such a precise manner that each step is equally spaced, whereas handrails are provided along both the sides of the stairs. Figure 7: Stairs for all floors All the floors are also furnished by the lift which is open for public. The dimension of the lift is 0.99m?1.4m and is above 1m from the level of entrance. Toilet Facility: Standard toilets are provided for both males and females but the toilets are located outside the building. Female toilets are located to the right of the terrace entrance and male toilets are located to the left. Baby change facilities are only provided at the level of lecture theaters. Another male toilet is also provided near student’s common room. Restaurant and students common room: Restaurants are provided as a part of student’s common room and... Manager Room and Store Rooms: Room of the hotel manager is designed to be behind the reception and should not be glassed rather opaque. The store rooms for sweepers, and other sort of items like extra furniture etc must be planned to be at the end of the terrace at the place of lecture room 006. Other offices and stores containing sanitry material will also be managed in the same location. Beauty Saloons: Beauty saloon and spa services will be provided to all the customers of the boutique hotel. Facility of beauty saloon will be provided adjacent to the exhibition hall, besides the stairs. Stairs must be cut short to spiral in order to provide more area to saloon. Saloon’s extensive area covers spa and all other sections seperately in order to facilitate the customer. Just above the saloon, on the first floor, rejuvenation center and gym will also be provided. Exhibition Room: Exhibition room will not be altered much. It will just be modified internally to provide a classy look and the rest of the changes depends upon the type of exhibition being carried out. Room Service: All floors other than ground floor are provided with the living rooms for guests. Each living room is different from the other in design, furniture, arrangement, color scheme and lifestyle provided. The facilities available are same in all the rooms. Each room will be provided with a mini bar to facilitate the customer within their room. Also a small sitting and dining area will also be provided to the customer in order to enjoy meal if they order for it in room. A small study section will also be provided. The walls and furniture in the room will be having same color scheme or in proper contrast to give most outstanding look to the visitors.