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The following items should serve as a checklist for your process analysis/instructions paper. You need to describe a process and then provide a set of instructions loosely related to the process. For example, you might describe the process of DNA replication. For your set of instructions, however, you could write a step-by-step analysis of a lab procedure related to DNA as it may be used in law enforcement or paternity cases.
- Write for a technical/lay audience.
- Remember the distinctions we made in class between the technical and expert audiences. I don’t want something that might appear in an academic journal.
- Format this assignment carefully. If you are confused, email me, or discuss it with me during the editing sessions in class.
- Remember style principles per Williams.
- Check your grammar. Do not use Microsoft’s grammar c heck.
What follows are very general principles about the assignment:
Some Techniques of Good Technical Description
- Describe the overall appearance of the mechanism and name the material with which it is made.
- Divide the mechanism into its component parts.
- Describe the appearance of the parts, give their function, and show how they work together.
- Point out an important implication of one of the physical facts—a so-that description. For instance, describe why a certain texture is preferred.
- Give only that information that is important in the description. For instance, if color is not important, don’t mention it.
- Use figurative language—spring-like, football-shaped—and other analogies to help your reader. This can clarify and shorten the description.
Consider these questions about the mechanism:
- What is the purpose and function of the mechanism?
- How can the mechanism be divided?
- What are the purpose and function of the parts?
- How do the parts work together?
- How can the parts be divided? Is it necessary to do so?
- What are the purpose and function of the subparts?
- Which of the following are important for understanding the mechanism and its parts? Construction, materials, appearance, size, shape, texture, position.
- Are there any so-thats you need to express for the reader?
- Would the use of graphics—photographs and drawings—aid the reader?
- Are there any analogies that would clarify the description for the reader?
- What is the purpose of the description?
- Why will the reader read the process description? General interest? Application?
- What is the reader’s level of experience and knowledge in regard to the process?
- What is the purpose of the process?
- Who or what does the process?
- What are the major steps of the process?
- Are there graphics and analogies that would help the reader?
Components of Instructions
- Introduction—Includes intended audience, motivation, purpose of instructions, preview of contents, reference to glossary.
- Theory or Principles of Organization—Includes the do’s and don’ts of the operation, the theory, as much as needed, behind the operation, and sometimes historical background.
- List of Equipment and Materials Needed—Includes a list of exactly what tools are needed to accomplish the task.
- Description of the Mechanism—See previous page.
- Warnings—Used to prevent lawsuits.
- How-to Instructions—Use imperative voice, tell reader how many steps there are, use list format. Avoid jargon.
- Tips and Trouble-shooting Procedures—Includes checklist for procedures and subdivides itself into problems, possible causes, and possible remedies for a defective process.
- Glossary—Lists of all terms that may need to be defined.
The stethoscope is a listening device that amplifies and transmits body sounds to aid in detecting physical abnormalities.
This instrument has evolved from the original wooden funnel shaped instrument invented by a French physician, R.T. Lenneac, in 1819. Because of his female patients’ modesty, he found it necessary to develop a device, other than is ear, for auscultation (listening to body sounds).
This report explains to the beginning paramedical or nursing student the structure, assembly, and operating principle of the stethoscope.
The stethoscope is roughly 24 inches long and weighs about 5 ounces. The instrument consists of a sensitive sound-detecting device whose flat surface is pressed against a bodily area. This amplifying device is attached to rubber and metal tubing that transmits body sound to a listening device inserted in the ear.
Seven interlocking pieces contribute to the stethoscope’s Y-shaped metal appearance: (1) diaphragm contact piece, (2) lower tubing, (3) Y-shaped metal piece, (4) upper tubing, (5) U-shaped metal strip, (6) curved metal tubing, and (7) hollow ear plugs. These parts form a continuous unit.
Diaphragm Contact Piece
The diaphragm contact piece is a shallow metal bowl, about the size of a silver dollar (and twice its thickness), which is caused to vibrate by various body sounds.
Three separate parts make up the piece: hollow steel bowl, plastic diaphragm, and metal frame.
The stainless steel metal bowl has a concave inner surface, with concentric ridges that funnel sound toward an opening in the tapered base, then off through a hollow appendage. Lateral threads ring the outer circumference of the bowl to accommodate the interlocking metal frame. A fitted diaphragm covers the bowl’s upper opening.
The diaphragm is a plastic disk, 2 millimeters thick, 4 inches in circumference, with a molded lip around the edge. It fits flush over the metal bowl, and vibrates sound towards the ridges. A metal frame that screws onto the bowl holds the diaphragm in place.
The stainless steel frame fits over the disk and metal bowl. A one-quarter inch ridge between the inner and outer edge accommodates threads for screwing the frame to the bowl. The frames outside circumference is notched with equally spaced, perpendicular grooves—like those on the edge of a dime—to provide a gripping surface.
The diaphragm contact piece is the “heart” of the stethoscope that receives, amplifies, and transmits sound through the system of attached tubing. The diaphragm contact piece is attached to the lower tubing by an appendage on its apex (narrow end), which fits inside the tubing.
The seven major parts of the stethoscope provide support for the instrument, flexibility of movement for the operator, and ease in auscultation.
In an operating cycle, the diaphragm contact piece, placed against the skin, picks up sound impulses from the body surface. These impulses cause the plastic diaphragm to vibrate. The amplified vibrations, in turn, are carried through a tube to a dividing point. From here, the amplified sound is carried through two separate but identical series of tubes to hollow ear plugs.
Your process analysis paper should be divided into two parts:
- A process analysis
- A set of instructions “somewhat” related to the process you described.
Process Analysis. This section of the paper should describe a process (chemical, biological, technical, mental). It should contain the following sections:
- Aristotelian Definition
- Components parts or phases of the process, including function of parts or subparts.
- Description of the process.
- Graphical representation of the process.
Set of Instructions. This part of the paper should contain about ten instructions describing how to perform some procedure “somewhat” related to the process you described. It should contain the following sections:
- Brief introduction to the procedure
- Set of Materials Needed to Perform the Procedure
- Set of Warnings
- Graphical Depiction of the Process
- (Optional): Glossary
I am looking for 10-25 instructions pages, but I am really looking for a coherent unified document. You are also responsible for concision, reasonable use of passive voice, and cohesion. In addition, check for standard grammar, spelling, arrangement, and substantive truth. Keep in mind that the real test of process and instructions is the ability of someone reading them to actually complete the set of instructions successfully.
Grafting is the process of joining two pieces of living plant tissue so that they will unite and grow as one plant. In t-budding (one grafting variation), the rootstock and the scion are the two components utilized. A rootstock is a root and its associated growth buds. It becomes the lower part of the new plant after grafting. A scion is a shoot or twig that becomes the upper part of the new plant. Therefore, the rootstock will become the new root system and the scion will become the branches and leaves (as shown in Figure 1).
The grafter fits the scion and the rootstock together (as shown in the subsequent instructions) so that the cambiums line up. The cambium, or the lateral meristem, is a cylinder within the stem that produces two kinds of cells; phloem and xylem (Figure 2). The cells produced toward the inside are xylem and those generated on the outside are phloem. Phloem conducts travel of food made by leaves down the stem. Xylem conducts water and mineral nutrients up the stem.
When the grafter cuts the rootstock and scion, the cambium in each begins to make callus. Callus is a tissue made of thin-walled cells that form at the injured surface of a plant. The callus fills in the small space between the grafted rootstock and scion. Once the two new sets of callus meet, their cells interlock. Next, the callus cells differentiate into new cambium cells. These new cambium cells form a bridge between the rootstock cambium and scion cambium, a new layer running up and down the grafted plant. This bridging causes production of new vascular tissues that heal the phloem and xylem. The new healed system carries water, mineral nutrients and plant sugars up and down the stem (Figure 3).
Horticulturists consider a graft to have taken once roots have extended, new leaves have emerged and no wilting has occurred. At this time, propagators cut back the top of the stock above the graft as it is no longer needed. All future growth will now come from the grafted bud.
□ Scion (A in Figure 1)
□ Rootstock (B in Figure 1)
□ Grafting knife (Figure 2)
□ Polyethylene tape (Figure 3)
- The grafter should be eighteen years of age or older and well-versed in knife safety.
- The grafter may t-bud to repair an injured plant, change a plant into a new variety or to improve certain characteristics of a plant.
- The grafter should t-bud between May and August when the rootstock bark lifts easily.
- For successful grafting, the reader must carefully follow instructions as to how much material to cut.
Cut all the leaves and branches off the bottom
five inches of the rootstock with the grafting knife
Make a horizontal slit about ¼ – ½” in length on the rootstock using the grafting knife. While cutting, hold the stock firmly with one hand and cut with the knife in the other hand.
Then make a vertical downward slit (1-1½”) starting at the horizontal slit. These two slits will look like a letter “T”.
These cuts should be about one to two inches up the stem from ground level. Notice: both cuts should only go through the bark.
Loosen the two flaps of bark on either side of the vertical cut by slipping the handle of the knife inside and raising the two flaps slightly to separate
the tissue from the wood. (Figure 5)
Remove any leaves on the scion with a cut of the grafting knife (Figure 6).
Important: retain ½” of each leaf-stalk and the buds when cutting off leaves.
A leaf-stalk is the slender stalk by which a leaf is attached to the stem. A bud is an undeveloped shoot/twig that occurs at the tip of the stem. Note what was retained in
Choose a leaf-stalk and bud to cut.
Slice upward into the stem of the scion from about ¼” below the bud (Figure 7).
Continue to slice upward until you are about one inch above the bud (Figure 8). Lift the new cutting off once the knife is past the bud.
Make sure to keep the bud clean and moist before being inserted into the rootstock to prevent the exposed tissue from drying out.
If any wood was cut along with the bark then bend the bark away from the wood with your fingers. The wood should then fall away with a light touch.
Using the leaf-stalk as a handle, slip the newly cut bud from the scion into the T-cut on the rootstock. Make sure the stem and bud are pointed upwards in the correct growing position (see bud orientation in Figure 9).
Trim the tail (the strip of bark above the bud) neatly with the grafting knife.
Tie polyethylene tape around the cut area of the rootstock above the bud (Figure 10).
Make sure to leave the bud and leaf stalk exposed where future growth will occur.
After three to four weeks, once the bud has united with the rootstock, remove the tape by gently cutting it off with the grafting knife (Figure 11).
In late winter, cut off the top of the rootstock (½” above the grafted bud) (Figure 12).
All new growth of the plant will now come from the grafted bud.
Figure 1- Hartmann, Hudson T., et al. Plant Propagation: Principles and Practices.
New Jersey: Prentice Hall, 2002. p. 413
Figure 2- Foster, Catherine O. Plants-a-Plenty. Pennsylvania: Rodale Press, 1977. p. 26
Figure 3- Foster, Catherine O. Plants-a-Plenty. Pennsylvania: Rodale Press, 1977. p. 88
Figure 1- Hartmann, Hudson T., et al. Plant Propagation: Principles and Practices.
New Jersey: Prentice Hall, 2002. p. 428
Figure 2- Clarke, Graham and Alan Toogood. The Complete Book of Plant Propagation. London: Ward Lock Limited, 1993. p. 111
Figure 3- Clarke, Graham and Alan Toogood. The Complete Book of Plant Propagation. London: Ward Lock Limited, 1993. p. 118
Figures 4-12 – Browse, Philip MacMillan. Plant Propagation. New York: Fireside,
- p. 91
This report documents the construction steps of a BP Solar 4170 PV panel to a supervising engineer.
A PV panel is an assembly of photovoltaic material used to harness the sun’s energy to produce electricity. A PV panel is more commonly known as a solar panel.
The completed PV panel is 1595mm long, 790mm wide, 50mm tall, and weighs 15.4kg. The panel is comprised of silicon nitride solar cells connected by wires, encased in plastic and glass, and surrounded by a metal frame. The PV panel is intended to be mounted on a building to generate electricity.
The completed PV panel consists of:
- 72 – 125mm x 125mm silicon nitride solar cells
- Small flat metallic wires (to connect the cells)
- Solder (to permanently affix the wires to the cells)
- 1 piece Tedlar plastic sheet (the backing of the PV panel)
- 1 piece 3mm tempered glass, high transmission (to encase the cells, the front of the PV panel)
- 2 – 9V, 45A Schottky diodes (to prevent surges from damaging the panel)
- 2 – AWG#12 cables, one red, one black, each with a bare end and an end with a connector (for connection to a larger solar system)
- 4 – Silver Anodized Aluminum frame parts, 2 – 790mm and 2 – 1595mm (the frame)
- 8 – 3mm machine screws (to hold the panel assembly together)
PV Panel Operation
The components of PV panels that produce electricity are the solar cells. These cells are composed of a photovoltaic material and an antireflective coating. The coating enables the cells to collect as much sunlight as possible.
The photovoltaic material in solar cells is usually a silicon-based compound, such as silicon nitride in the BP 4170. Photovoltaic materials generate electricity though the Photoelectric Effect.
When solar energy hits a photovoltaic material, electrons in the material are knocked free. If these electrons move uniformly, they will create an electrical current. In order for this to happen, the photovoltaic material must be doped with other substances to produce uniform electron movement. Hence, silicon compounds doped with other materials are used instead of pure silicon.
If many of these solar cells are wired together in series and parallel, a PV panel can be created. Systems of PV panels can be wired together to form solar arrays. These arrays can be placed on buildings to generate sizable amounts of electricity (usually in the range of kilowatts).
PV Panel Assembly Instructions
Great care must be taken in the handling of the solar cells. The cells are coated with a fragile blue antireflective coating. This coating is easily removed by fingers alone. Therefore, the cells should only be handled by their edges to minimize removal of the coating.
Note that the cells are only 1mm thick. Great care must be taken not to drop or crush the cells when picking them up and placing them on the Tedlar backing of the PV panel.
Eye protection and gloves should be worn at all times to protect the solar cells as well as the assembler. The antireflective coating is manufactured in a process that uses pyrophoric chemicals. Pyrophoric chemicals spontaneously ignite when exposed to air. Their residues, such as those that could be found on the solar cells, are harmful to humans. However, these residues are not prone to spontaneous ignition.
Take care not to mar the solar cells with the hot soldering iron. In addition, solder the cells only once, because excessive heat may damage the cells.
Do not over tighten the screws that hold the PV panel together. Doing so could crack the glass or Tedlar.
- Soldering iron and lead-free solder
- Power drill with flat head screwdriver bit
PERSONAL PROTECTIVE EQUIPMENT
- Safety glasses required
- Gloves (any rubber is acceptable) required
Layout of the Solar Cells
Lay the Tedlar plastic panel on a work surface. Note the location of the two large holes on the panel. These holes will be used for the two AWG#12 cables later. Note that there are smaller holes around the Tedlar, 2 per side, to facilitate attachment of the frame.
Refer to Figure 1. Arrange the solar cells on the Tedlar backing 6 in the narrow direction of the panel, and 12 in the long direction. Do not leave gaps between the solar cells, but do center the cells so there is space on the sides. This will enable connection of the frame later.
Series Connection of the Solar Cells
Connect the individual solar cells together, in columns, using the small flat wires, solder, and a soldering iron. Refer to Figure 2. The blue lines represent where the cells should be soldered. Repeat until there are 6 unconnected columns of 12 connected cells.
Take care not to mar the solar cells with the hot soldering iron. In addition, solder the cells only once, because excessive heat may damage the cells.
Parallel Connection of the Solar Cells
Connect the columns of cells together, again using the small flat wires, solder, and soldering iron. Refer to Figure 3. The green lines represent where the cells should be soldered. The red dots represent where the Schottky diodes will be connected later.
Connection of the Diodes
Refer to Figure 3. The diodes will be connected at the red dots. However, the proper polarity of the diodes must be observed.
Refer to Figure 4. Each diode has a gray stripe on one end. This end must “point away” from the panel. That is, the side of the diode without the gray stripe must be connected to the red dots shown in Figure 3.
Solder the side of the diode without the gray stripe to the red dot area shown in Figure 3. Repeat for a second diode and the second red dot area.
Connection of the AWG#12 Wires
The AWG#12 wires must now be connected to the Schottky diodes. Feed the bare ends of the wires through the holes in the top of the PV panel. Refer to Figure 1.
Solder the bare end of one wire to the side of the diode with the gray stripe. Solder the bare end of the other wire to the side of the other diode with the gray stripe. Either wire can go with either diode, as long as there is one black wire and one red wire coming from the panel. Refer to Figure 5 to see completed wiring, including Schottky diodes.
Attachment of the Glass Panel
Refer to Figure 6. Take the piece of tempered glass and carefully place it on top of the solar cell/Tedlar assembly. Match up the long edges of the glass to the long edges of the Tedlar. Make sure that the edges of the glass are aligned flush with the edges of the Tedlar, creating a sandwich. Note that in Figure 6, the glass is blue, but the real tempered glass will be clear.
Attachment of the Frame
Lastly, the frame must be attached to hold the panel together. Slide the four aluminum frame parts on the corresponding sides. Top and bottom pieces are identical, as are side pieces, so you will receive 4 pieces; 2 of each length. Refer to Figure 7.
Fasten the frame to the panel with the screws, using the provided drill with screwdriver bit. Two screws will be used on each side. Take care not to over tighten the screws and crack the glass or Tedlar. A snug fit is all that is needed.
Schottky diode photo: http://www.yourzagi.com/motors2.htm
PV panel photos: http://www.bpsolar.com/ContentDetails.cfm?page=35
This report describes the use of the Integrated Automated Fingerprint Identification System (IAFIS) and the method of fingerprinting to a law enforcement officer.
IAFIS is a computerized system formed around a national database of criminal fingerprints and histories. The system accepts submitted fingerprints and searches for matches among its criminal records. The database is maintained by the Federal Bureau of Investigation (FBI) and contains the ten-digit fingerprint records of over 47 million people.
Law enforcement agencies gain access to IAFIS through a computer in their department that they designate as the IAFIS portal. Through the portal the agency can search the database or submit prints using software the FBI provides. IAFIS works as a giant file cabinet for the law enforcement agency, allowing for quick retrieval of records.
IAFIS is a system based on biometrics, or unique physical characteristics that can identify a person. A valid submission to IAFIS is a FBI standard ten-print card of both rolled and flat impressions. The card is either mailed to the FBI and scanned into IAFIS or electronically submitted through the FBI’s Wide Area Network.
The five subparts of IAFIS are:
- Ten-Print Based Fingerprint Identification Services
- Latent Fingerprint Services
- Subject Search and Criminal History Services
- Document and Imaging Services
- Remote Ten-Print and Latent Fingerprint Search Services
Use of IAFIS and its Subparts
All five subparts of IAFIS use as their base the Criminal Master File (CMF), which contains the fingerprints and criminal histories of the subjects. The information is submitted by local, state, and federal law enforcement agencies. Each subpart either adds to or searches the CMF.
Ten-Print Based Fingerprint Identification Services accept electronic or mailed ten-print submissions of arrested individuals from law enforcement agencies and searches for matches in IAFIS. Latent Fingerprint Services do the same with fingerprints collected at crime scenes. Subject Search and Criminal History Services search through the criminal histories in the CMF by name or alias. Document and Imaging Services insert electronic versions of documents and pictures into the CMF. Finally, Remote Ten-Print and Latent Fingerprint Search Services allow law enforcement agencies to search IAFIS for fingerprint matches using their IAFIS portal and identify matches themselves.
Once a submission is received, the system begins a search of the CMF for fingerprint matches. Each fingerprint is unique and includes loop, arch, or whirl patterns (see figure 1). The system scans and logs the pattern of each fingerprint in the submission. The pattern of the submission fingerprint becomes the object of the search. The system compares each of the fingerprint patterns in the CMF with the object pattern. For a criminal fingerprint search, this takes approximately two hours. Once the search is finished, IAFIS returns a list of the most likely matches to the submission, with the closest match at the top of the list (see figure 2).
These instructions teach law enforcement officers how to correctly take the fingerprints of a suspect. Fingerprints are needed to identify a person and to compare to prints found at crime scenes. Prints will be taken twice, first rolling each finger individually, and then taking flat impressions of fingers simultaneously. Officers should submit properly completed cards to IAFIS for comparison to known prints in the CMF.
Make sure fingers are clean and free of oils before printing; otherwise the ridges in the fingers may be obscured.
Pay close attention to the direction the fingers are rolled, as it changes depending on which hand and which finger you are printing. Roll thumbs TOWARDS the body and fingers AWAY from the body.
Make sure you place the prints in the appropriate boxes on the fingerprint card.
If the subject has irregular or deformed fingers, consult the FBI fingerprint handbook on how to print in special situations.
- Subject to Fingerprint
- Blank Fingerprint Card
- Black Ink
- Ink Roller and Plate (an ink pad may be used in place of black ink and ink plate)
- Card Holder (attached to table, approximately 39 inches from floor)
- Alcohol Wipes
Fill out the top of the fingerprint card with the subject’s personal information (all yellow areas in figure 3), leaving the other areas blank for right now. Place the fingerprint card in the card holder on the table.
Clean the subject’s fingers using the alcohol wipes. Wait 30 seconds to make sure the fingers are dry before proceeding.
If you are not using an ink pad, squeeze a quarter-sized amount of ink onto the ink plate and spread using the ink roller.
Ask the subject to stand behind and to the RIGHT of you, at arm’s length from the card holder on the table (see figure 6).
Hold the subject’s RIGHT hand at the wrist with your RIGHT hand, tucking in all the subject’s fingers except for the thumb. Hold the subject’s RIGHT thumb with your LEFT hand. Holding the thumb fingerprint-side down, place the RIGHT edge of the thumbnail on the ink plate, and roll the thumb in the ink to the LEFT edge of the nail, making sure that the thumb is inked from tip to below the first joint (see figure 7). Always roll thumbs towards the body.
Locate the block on the fingerprint card marked “1. R. Thumb” (in red in figure 8). Place the thumb ink-side down on its RIGHT side, on the RIGHT edge of the block. Roll the thumb as before, from RIGHT-nail-edge to LEFT-nail-edge and then pick the thumb up off the fingerprint card.
Repeat the rolled impressions, but roll from LEFT to RIGHT (away from the body), with the rest of the fingers on the RIGHT hand, starting with the index finger, then middle finger, then ring finger, then little finger. The order is numbered in the diagram. Make sure to place the prints in the appropriate labeled box on the fingerprint card.
Repeat the rolled impression with the LEFT hand. Grasp the LEFT hand with your RIGHT hand on the subject’s LEFT wrist keeping all the fingers except for the one being printed out of the way. Print the thumb first. In the box marked “6. L. Thumb,” roll the thumb from LEFT to RIGHT. Then print the rest of the LEFT hand fingers in the same order as step 7, rolling from RIGHT to LEFT.
Take the subject’s RIGHT hand and press all of his fingers except for the thumb together. Lightly press the fingers into the ink, then press all four fingers simultaneously onto the box marked “Right four fingers taken simultaneously,” angling the prints at a 45 degree angle in the box (see figure 11). Repeat with the subject’s LEFT hand, printing in the box marked “Left four fingers taken simultaneously.” Finally, ink both thumbs together and press both thumbs simultaneously onto the fingerprint card into the boxes marked “L. Thumb” and “R. Thumb.” Do NOT roll the thumbs, but place them flat onto the card.
Check to make sure all the prints on the card are legible. A bad print is shown in figure 12. If not legible, use an adhesive re-tab to cover the bad print block, and retake the print. Only one re-tab is allowed per box. Once any reprinting is done, clean the subject’s fingers again with an alcohol wipe and release him to appropriate custody.
Fill out the rest of the card with the necessary departmental information (areas in green).
Scan the completed card into IAFIS or send it through the mail to the FBI.
Integrated Automated Fingerprint Identification System or IAFIS. 08 Feb. 2005. Federal Bureau of Investigation. 10 Apr. 2006 <http://www.fbi.gov/hq/cjisd/iafis.htm>.
Taking Legible Fingerprints. Federal Bureau of Investigation. 10 Apr. 2006 <http://www.fbi.gov/hq/cjisd/takingfps.html>.
Figures 1, 7, 11, 12 – http://www.fbi.gov/hq/cjisd/takingfps.html
Figures 2, 14 – http://www.highered.nysed.gov/tcert/ospra/samplefpcard.html
Figure 4 – http://www.swedishcommittee.org/archive/articles/articles/2005/Electionpics/wipe_finger.jpg
Figure 5 – http://www.handanalysis.com/print7.jpg
Blank fingerprint card used in Figures 3, 8-10, 13 – http://www.fbi.gov/kids/k5th/whatwedo2.htm
March 14, 2007
Producing Sound on a Bowed String Instrument
The string instruments available today have survived of a figurative natural selection. The concept of striking (plucking) a stretched fiber is over 2000 years old, but today, only the most refined and versatile incarnations of that concept remain. Bowed instruments have a distinct advantage over those that are plucked. Plucking a string excites it once; the loudest sound occurs at the moment of release and then diminishes. Bowing a string, however, excites the string continuously, and allows the musician to modulate the volume and quality of the sound produced.
The sound of a string instrument depends on a number of fixed conditions, conditions that depend on the instrument, not the musician. Every professionally made violin, viola, cello, and bass meets several physical standards. Every instrument body is sealed shut with the exception of two f-shaped holes. Every instrument also maintains its string tension with a tailpiece and pegs (figure 1). The physical dimensions of each instrument vary depending on the maker. String length is standardized but string thickness varies by brand.
There are also a number of unfixed conditions, which depend on the musician’s facility with the bow. Because the bow weighs more at the bottom than at the top, even a simple push and pull of the bow creates two separate sounds. The sound also depends on the way a musician attacks or applies pressure to the string. The musician also controls contact point of the bow and string; or rather how close or far away from the bridge a musician plays.
Each string on the violin contacts the instrument at two critical points. The string rests between the nut, where the vibrations are neutralized, and the bridge, where the vibrations are amplified.
When the string is agitated (either by plucking or by the bow), a vibration is created. This vibration moves down the bridge and into the body of the instrument via the sound post. Inside the instrument, these vibrations reverberate along the instrument walls. Figure 2 shows a visual representation of the variety of different frequencies (Hz).
The violin also has a unique opening in the body, shaped like the letter f. These holes are intuitively called f-holes; vibrations escape through these f-holes and travel through the air to the listener.
Berg, Richard E. and Stork, David. The Physics of Sound. New Jersey: Prentice Hall, 2005
Rigden, John S. Physics and the Sound of Music. St. Louis: University of Missouri, 1977.
Wood, Alexander. The Physics of Music. Ed. J. M. Bowsher. 7th ed. London: Chapman and Hall, 1975.
Figure 1: www.cmeabaysection.org/ strings/violin.html
Figure 2: Berg. The Physics of Sound Page 327.
A cable-stayed bridge is an overpass consisting of towers and cables with the towers serving as the primary load bearing unit. The main parts of a cable-stayed bridge are the towers, the girder, the cables connecting the girder to the towers, and the terminal piers. The tower is the main load-bearing structure. It supports the live loads of the cars and trucks, the girder, and itself. The girder is the roadbed, or deck. It is the structure that cars and trucks drive on. The cables connect the girder to the tower or towers. The cables transfer most of the load of the girder to the tower. The terminal piers connect the girder to the ground. They hold the bridge in place.
The cable design for a cable-stayed bridge can be a radial design or a parallel design. A radial cable design is where all of the cables pass through or connect to the top of the tower.
Radial Cable Design
A parallel cable design is one where the cables are spaced out at equal intervals. They attach to the tower at these intervals. This cable design is also known as a “harp” design due to its resemblance to the musical instrument.
Parallel Cable Design
In both designs, the cables transfer the tension from the weight of the girder into a compression force in the tower, as shown below.
A cable stayed bridge can have one or more towers. The tower rise high over the girder, sometimes over 200 feet. The cables attach from the tower to the girder. There are four major types of tower designs. A single tower design is exactly that- one vertical tower that extends straight up from the foundation. A double tower design has two vertical towers extending from each foundation. The two towers are parallel with one another. A portal tower design looks like a double tower, except the two towers are connected by a segment at the top of the towers. An A-shaped tower design has two or more tower structures that rise from the girder and converge at a single point.
An A-shaped Tower Design
The girder consists of a roadway and the structural support underneath, which supports the girder and the live loads of the vehicles. The girder can be constructed from steel, concrete, or both. The girder must be rigid enough to resist torque from uneven flows of traffic, and at the same time be loose enough to not snap or fail during a minor earthquake or a strong wind gust.
The cable design, the tower design, and the girder all must be meticulously planned and engineered to create a structurally stable cable-stayed bridge. If constructed correctly, the cable-stayed bridge will allow traffic to safely flow over a water structure, and will add beauty and awe to a city landscape.
Instructions on How to Build a Structurally Stable Cable-stayed Bridge
For this procedure, all design plans must be drawn and reviewed by an architectural company and must be approved by the proper authorities before commencing the project. The budget for a large cable-stayed bridge must be approved by the state government. All construction contractors must submit bids before suitable ones are chosen.
- Steel cables
- Reinforced concrete
- Work Hours
- Construction machinery (Cranes, Bulldozers)
- Design Plans
- Construction workers
- Engineers (Civil, Mechanical, Materials)
- Quality Control Officials
- Any personnel on the construction site must wear a hard hat.
- Any heavy machinery must be operated only by trained professionals.
- All construction workers and engineers that will be on site must take an hour long safety course before walking on site.
Formulate a method of construction. The machinery and materials needed to complete the project must be listed. The order is which the bridge is to be built must also be specified. This should be done by the team of engineers in charge of the project.
Construct the terminal piers on each end of where the bridge will span. The piers are constructed first so that the remainder of the construction will have two definite points to work in-between.
Sink the cassions so that the soft ground underneath the future tower foundations can be removed. The removal of all loose soil, sludge, and muck at the base of every foundation is essential for the stability of the bridge. All of the wind forces, live loads, and the bridge weight force are transferred through the tower and into the foundation. The foundation must rest on solid earth.
A sunk cassion
Construct the foundation/s. The foundations are primarily made of reinforced concrete. The foundation is extended above the water level.
Build the base of the tower on top of the tower foundations. Most towers are made of steel and reinforced concrete. The tower will rise from the foundation level to the girder, and then extend high above the girder to allow the cables to attach towards the top.
A base of a tower
Begin to build the girder by extending it from the terminal piers, and finish construction of the towers. The sections of the girder between the tower and where the cables will connect with the girder are built using a cantilever method, so the cables are not needed to support these sections of the girder.
Girder and tower construction
String the cables from the tower to the girder. The cables can be lifted and placed with cranes, and in some cases, helicopters. The attachment points of the cables must be very secure so that all of the tension from the weight of the girder can be transferred to the tower.
Cranes are used to place cables
Extend the girder completely between the terminal piers.
Run tests and safety checks on the bridge to determine if it can support the intended traffic and itself. The results must be analyzed by quality control experts. They will determine if any adjustments need to be made to the bridge to ensure its safety before public use.
Add any lighting, glass, paint, or other aesthetically pleasing materials to the bridge. Make sure that this material will not sacrifice the structural integrity or overall safety of the bridge.
Cassion: a retaining structure used to allow construction workers to clear away soft mud and weak soil at the bottom of a lake or river.