Distributed mechanical stress

The packaging must physically protect the product from the mechanical stresses of warehousing, handling and distribution. Mechanical stress may take a variety of forms, from impact through to vibration in transit and compression forces on stacking. The demands for mechanical protection will vary with product type glass ampoules will require greater protection than plastic eye drop bottles, for example. 

The primary packaging must physically protect the product from the mechanical stresses of warehousing, handling, and distribution. Mechanical stress may take a... 

Distributed mechanical stress In order to perform, monofilaments have to be anchored in their environment. The knot is accepted by surgeons as the only irrefutable means to anchor smooth suture material. Unfortunately, knots created unequal tension burdens placed on the knots rather than on the length of the suture line. Then, an uneven distribution of tension occurred within/across the biological tissue with potential impact on healing process, distortion of the tissue, and marked inflammatory responses to foreign body material. 

A recent major change in tissue valve design is the introduction of stentless bioprostheses. Tissue valves with no stent are believed to be better than stented valves, because the aortic root is expected to distribute mechanical stresses into the aortic tissue instead of focusing them on the leaflet tissue near the stents of traditional bioprostheses. The first stentless heart valve, the Toronto SPV valve (St. Jude Medical), was approved by the U.S. FDA in 1997. Two other stentless aortic valve designs have since then been brought to the market (i) the Medtronic Freestyle (Medtronic Inc.) and (ii) the Edwards Prima (Edwards Lifesciences) valves. Stentless bioprostheses are currently only approved for AVRs in the United States. Clinical trials with stentless mitral valves were first reported in 1992 [9], but their approval has been delayed because of questionable valve durability and the complexity of the implantation technique. 

Polyamides, like other macromolecules, degrade as a result of mechanical stress either in the melt phase, in solution, or in the soHd state (124). Degradation in the fluid state is usually detected via a change in viscosity or molecular weight distribution (125). However, in the soHd state it is possible to observe the free radicals formed as a result of polymer chains breaking under the appHed stress. If the polymer is protected from oxygen, then alkyl radicals can be observed (126). However, if the sample is exposed to air then the radicals react with oxygen in a manner similar to thermo- and photooxidation. These reactions lead to the formation of microcracks, embrittlement, and fracture, which can eventually result in failure of the fiber, film, or plastic article. 

Alternatively, reactant and product gases can be distributed to and removed from individual cells through internal pipes in a design analogous to that of filter presses, (iare must be exercised to assure an even flow distribution between the entiv and exit cells. The seals in internally manifolded stacks are generally not subject to electrical, thermal, and mechanical stresses, but are more numerous than in externally manifolded stacks. 

In order to achieve higher spin rates, it is paramount to recognize possible imbalances to prevent machine misalignment that would result in mechanical stress on the bearings as well as unnecessary noise development. The first step to avoid imbalance is a gentle run-up for a few seconds at the beginning, as shown in the upper panel of Fig. 3.4. Here the spin speed is continually raised in discrete and slow steps so that the laundry is distributed evenly around the drum. 

In aerobic composting, an air blower distributes air under the pile and maintains most of the pile in aerobic conditions for faster degradation. The piles are turned daily to redistribute material and moisture and to maintain porosity of the pile. The mechanical stress imposed by turning the compost piles facilitates... 

As we consider the mechanical properties of SPs, it is often useful to consider them in the context of entanglements, which are intermolecular interactions that transfer mechanical forces from one molecule to the next. In this chapter we use the term entanglement in a very general way, so that it includes topological entanglements (one polymer chain is physically wrapped around another), chemical entanglements (attractive intermolecular interactions between polymer chains), and surface adsorption (attractive intermolecular interactions between polymer chains and a particle surface, e.g., from a filler). The important, fundamental characteristic is that it is an interaction that allows a mechanical stress on one molecule to be distributed or transferred to another molecule with which it is entangled. 

Polarization of a ferroelectric material varies nonlinearly with the applied electric field. The P-E behaviour is characterized by a hysteresis loop and observation of the hysteresis loop is the best evidence for the existence of ferroelectrcity in a material. The hysteresis loop has its origin in the rearrangement of domains under the influence of an applied elecric field. Generally, the domains are randomly distributed, giving a net zero polarization. Under an applied field or mechanical stress, favourably oriented domains... 

In l02) the authors describe the design of an experimental plant for studies of acoustic cavitation in flowable high polymers with the help of optic methods the plant employs a flat-slit transprent-wall capillary acoustic treatment of a polymer was carried out at a frequency of 17.8 kHz, and amplitude of vibration between 0 and 15 mcm. The study was conducted on 1,2 polybutadienes of narrow molecular-mass distribution tests were arranged at room temperature. It has been demonstrated that static mechanical stresses occur in a stationary (non-flowing) polymer under the action of acoustic treatment isochrome lines in the viscosimetric tank form a cellular structure with cell size of about 1-3 mm, and in the capillary the isochromes are observed in form of longitudinal strips (Fig. 19). The authors have also found that acoustic... 

Typically, TSOFC use co- and counter-flow configurations whereas planar stacks sometimes favour cross flow simplifying manifolds attachment. The flow of air usually provides cooling to a stack in either design as does internal reforming (Sulzer Hexis). The flow regime strongly affects the distribution of gas composition, mechanical stress, stack temperature and ultimately current density. 

Abstract The oxidation of polymers such as polypropylene and polyethylene is accompanied by weak chemiluminescence. The development of sensitive photon counting systems has made it comparatively easy to measure faint light emissions and polymer chemiluminescence has become an important method to follow the initial stages in the oxidative degradation of polymers. Alternatively, chemiluminescence is used to determine the amount of hydroperoxides accumulated in a pre-oxidised polymer. Chemiluminescence has also been applied to study how irradiation or mechanical stress affects the rate of polymer oxidation. In recent years, imaging chemiluminescence has been established as a most valuable technique offering both spatial and temporal resolution of oxidation in polymers. This technique has disclosed that oxidation in polyolefins is non-uniformly distributed and proceeds by spreading. 

Together with the conveying and power characteristics, the mechanical and thermal stresses on the polymer are key features. The mechanical stress is characterized by the shear stress distribution within the polymer. In general, the shear stress is calculated as follows... 

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