Stress relaxation is the time and temperature dependent decrease of stress in a solid due to the conversation of elastic into inelastic strain. Stress relaxation data can be used to develop stress-relief heat treatments for reducing residual stresses and for the design of such mechanical elements as joints, gaskets and springs. Stress relaxation data are also an important tool for evaluating the constitutive relations governing a material' s inelastic behavior.
(Stress Relaxation Testing: A Symposium,Alfred Fox,American Society for Testing and Materials, pg. 1 )
Stress Relaxation (New and Better)
When an elasiomer is held at a constant deformation. there is a decrease as a function of time. This phenomenon can be of great importance in sealing applications, where the maierial of the seal is required to maintain a specific level of sealing force io prevent leakage. Stress Relaxation can be the dominant factor that limits the effective life of seal.
Stress relaxation is usually defined as the loss in stress expressed as a percentage of the initial stress. Thus,
The rate of stress relaxation is then the stress relaxation divided by some function of time.
(Gent A.N. Engineering With Rubber: How to Design Rubber Components, Page:181)
(My definition is better than the older one, because explain totally and give the equation)
(My definition is better than the older one, because explain totally and give the equation)
Differential scanning calorimetry ( Test Type )
Differential scanning calorimetry is a quality control method that measures the energy absorbed (endotherm) or produced (exotherm) during a specified time and temperature cycle. This technique can be used to determine whether a polymer cures in the same way from batch to batch. It can also be used to show the glass transition temperature of a polymer (generally as a break in the slope of the endothermic curve as a function of temperature).
Differential scanning calorimetry is an alternative to differential thermal analysis
(DTA) for measurement of transition temperatures of polymers, especially where a
determination has a quantitative aspect.
( Charles A. Harper, Edward M. Petrie, Plastics Materials and Processes: A Concise Encyclopedia, John Wiley & Sons Pub., 2003, p.139 )
Differential scanning calorimetry (New and Better)
Differential scanning calorimetry (DSC) is a method which is extensively used to measure heats and temper atures of various transitions and has been recognized as a very useful tool or the interpretation of thermal events as discussed and reviewed by a number of authors. In essence, the DSC measures the net rate of heat flow Q' = dQ/dT, into a sample with respect to heat flow into a reference inert sample, as the sample temperature is ramped. Fig-ure 19.17 shows a simplified schematic diagram of the heat-flux DSC cell. The constantan disk allows heat transfer to and from the reference and sample pans by thermal conduction. Due to symmetry, the the, mal resistance of the heat paths from the heater to the reference and sample pans is approximately the same. The constantan disk has two slightly raised plat-forms on which the reference and sample pans are placed. Chromel disks fixed under these platforms form area thermocouple junctions with the constantan platforms. The constantan-chromel thermocouples are in series and read the temperature difference AT be-tween the reference and sample pans. There are also alumel—chromel thermocouples attached to the chrome] disks to measure the individual reference and sample temperatures.
( My definition is best, because it gives much more detail about Differential scanning calorimetry (DSC) and used what for.)
Melt Flow Index (Melt Folw Index) (Material Property)
Melt flow index is measured using the melt indexer accoring to ASTM.The melt indexer uses a very short capillary with L/D=3.818 and a flat entry.Such capillary geometry accentuates the elasticity of melt,and the elasticity significantly influence the melt flow index.Therefore polymers with the same melt flow index (MFI) can have quite different viscosities and elasticities.MFI is measured at a low shear stress corresponding to a low shear rate.Polymers with the same MFI can have different viscosities elasticities at high shear rate,depending on their shear sensitivities.
(Chung C.I., Extrusion of Polymers:Theory and Practice, p. 132)
Melt Flow Index (Melt Folw Index) (New and Better)
Melt flow index (MFI) is find from a test. The test uses a specific size orifice or die in heated barrel, with a piston or plunger and weight on top inserted into the barrel to face the polymer through the orifice. Starting with a clean barrel, polymer is added and packed into the barrel with the plunger or piston. After a specified heating period teacher soften the resin, a weight is placed on the piston, and the molten polymer is forced through the die. The melt flow index is the amount measured in grains that exits the die in 10 minutes. Each ream system has a specific orifice length and diameter, barrel temperature, and piston load specified in ASTM D1238-86 or ISO RI 133 test meth-ods. At the end of the test, the die and barrel are cleaned.
Higher melt flow index correlates mush a lower vis-cosity resin. As the resin viscosity decreases, the flow per unit time increases. Lower melt flow index or fewer grains passing through the die in 10 minutes relates to higher viscosity.
Melt Flow Index Test Machine
(Giles H. F.Vagner R.V. Mount E. M. Extrusion: The Definitive Processing Guide And Handbook, Page:197)
(My definitions is better than old one, because support the idea with picture and explain how is obtained and used what for.)
Swiss Lever Escapement Mechanism (Mechanism)
The Swiss lever escapement mechanism: 1—hairspring, 2—balance wheel, 3—guard pin, 4—banking pin, 5—pallet fork, 6—escape wheel.
Figure shows the Swiss lever escapement mechanism. It consists of five components: a balance wheel, a hairspring, two banking pins, a pallet fork, and an escape wheel. Note that one end of the hairspring is fixed, whereas the other end is attached to the balance wheel. The balance wheel oscillates periodically under the driving force from the escape wheel through the pallet fork and the restoring force of the hairspring. It is the guard pin, which is a synthetic ruby on the balance wheel, that sends and receives impulses from the pallet fork to the balance wheel. The banking pin limits the rotation of the pallet fork. The escapement wheel rotates intermittently at a specific speed according to the frequency of the system.
(Mechatronic Systems Devices, Design, Control, Operation and Monitoring. CRC Press, 2008 p3-2)
Swiss Lever Escapement Mechanism (new and better)
Seen on figure escapement is very commonly used when the axes of the wheel and verge are parallel Here c is the centre of the wheel d that of the escapement a, d, b. In the figure a tooth a is represented as having just escaped from the pallet a and a tooth b on the opposite side of the wheel has met the pallet b the pendulum ( attached to the axis passing through d ) will not stop here but will advance a little further to the left and so the slope of the pallet b; will drive the tooth b back again a little and thus produce the recoil which may be observed very plainly in any common house clock with a seconds hand. The sloped faces of the pallets cause the teeth of the wheel to give them impulses in escaping so as to maintain the motion of the pendulum. This kind of escapement is much the most common and will probably never be superseded as it is sufficiently accurate tor ordinary purposes and is very easy to make since no particular form is required for the pallets. This escapement is said to have been invented by Dr Hooke about 200 years ago.
(Baker T. Element of mechanism: elucidating the scientific principles of the practical construction of machine, Page:81)
(This mechanism is to old it is usually used in watch, especially it is invented for watchs. So why is my definition is better ? Because of this, I think my definition is easy and easy to understand how can it used in video)
Buffering Mechanisms (Control System)
Buffering mechanisms considered include aluminum buffering, silicate mineral buffering, cation exchange, organic buffering, and the effect of anion immobilization precesses such as nitrade uptake and sulfate adsorption. The effects of acidic inputs on capacity factors such as exchange acidity, exchangable base content, and sulfate adsorption capacity are considered, as are related natural processes such as acidification due to accumulation of bases in biomass. Particular attention is paiid to intensity effects, such as the effect of increased concentration on anions associated with strong acids on the chemical composition of the soil solution, as they are likely to be highly nonlinear with the respect to the capacity factors. These include pH, aluminum mobilization, and loss of alkalinity in the soil solution, which in turn may result in acidification of drainage waters.
(Lindberg S.E., Norton S.A., Soils, Aquatic Processes, and Lake Acidification, p.1)
Buffering Mechanisms (new and better)
The discontinuity of multimedia streams results mainly from the delayed ar-rival of voice packets or visual packets at the receiving site. The playback at the receiving site would temporarily stop if no multimedia data is available. To prevent from the running out of multimedia data at the receiving site, we use two buffers, one for the visual packets and the other for the voice packets. At the spealdng site, the voice recording module stores the recorded voice data every second. The stored voice data is immediately packed as a voice packet and then mat to the receiving site. At the same time, the AAIVI at the speaking site may have performed the fitting of the speaker's faces on F consecutive frames, where F is our frame rate. The fitting results are packed into F visual packets and sent to the receiving site. Whenever a packet arrives at the receiving site, the buffering mechanism stores this packet into the visual packet buffer or the voice packet buffer depending on the packet type of this packet. As the packet size of a voice pmket is much larger than a visual packet in our design, the receiving rate of voice packets would dominate the playback at the receiving site. To reduce the probability of running out of voice packets in the voice packet buffer, our
strategy for buffering the voice packets is to specify a size threshold , say Qb, for the voice packet buffer. The playback module at the receiving site will not start to play the voices and the visual data until the number of voice packets in the voice packet buffer exceeds Qb. Apparently, the value of Qb affects the playback critically. If Qb is too large, then it would cause a long delay to visualize and hear the avatar's visual and voice outputs at the receiving site. On the contrary, if Qb is too small, then the buffering mechanical would lose its effect in preventing the running out of multimedia packets in the voice packet buffer.
Advances in Grid and Pervasive Computing:
5th International Conference, Cpc 2010, Hualien, Taiwan, May 10-13, 2010, Proceedings, Page:380)( My definition is best. Because; It expalained the definition with example. And knowadays every young people know that this feature on the computer. So it is really easy to understand this way. Also, Buffering mechanism get lots of area in the world such as in human cells, electronics etc.)
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