Channel catfish (Ictalurus punctatus) are important to aquaculture and natural ecosystems, however little is known regarding effects of high summer temperatures, which are predicted to increase with climate change. Therefore, two studies were conducted to examine physiological effects of high temperatures on juvenile channel catfish. The first examined effects of three cycling thermal regimes (23-27°C, 27-31°C, and 31-35°C) characteristic of culture environments in Mississippi on growth, food consumption, feed conversion ratio, specific growth rate, and activity. The second study measured active and resting metabolic rates and swimming endurance at constant temperatures (27, 31, and 35°C). The best growth and feed conversion occurred at 27-31°C and activity was greatest at 31-35°C. Active metabolism and swimming endurance decreased at 35°C. These results indicate high summer temperatures reduce food consumption, increase activity, impair metabolism and endurance, and therefore present challenges to the culture and management of channel catfish.

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The fracture of water ballast tank (WBT) coatings due to thermal stresses is widely recognised as an issue. Upon coating fracture, rapid corrosion of the tanker steel structure will occur, leading to expensive structure repairs or even tanker scrapping. In this project, the fracture behaviour of two experimental WBT coatings, referred to as A and B, in the forms of free film and substrated coatings was investigated. Static tensile tests and fatigue tests of the substrated coatings were performed. A finite element model of coating cracking was developed. Thermal stress and J-integral of surface cracking defects in substrated coatings were calculated using the model, in which the effects of defect size, coating thickness, and thermal strain on coating fracture were investigated. For the first time, fracture mechanics was used to explain WBT coating fracture behaviour. The J-integral of surface defects was used to predict the onset strain of coating cracking under mechanical strains in laboratory and under thermal strains in service. A theoretical comparison between the cracking drive forces in terms of J - integrals in WBT coatings under thermal strains and mechanical strains was performed.

No description available.

Factors in fiber manufacturing procedures affect fiber¡¦s production, and the fiber quality will be affected accordingly. The residual stresses, in particular, have a significant influence on fiber quality, due to the mechanical strength and the refraction rate that has been changed. Mechanically, residual stresses may cause ruptures in the preform, reducing the intrinsic strength of the fiber and its durability; optically, it may also cause anisotropic distortions of the refractive index profiles. In the process of cooling under high temperature, fiber core and cladding will be compressed owing to the material difference and the residual stress will be in the fiber. Thermal conductance and thermal expansion coefficient contribute to the cracks on the interface and thus affect the refraction rate. Experiments have shown that quartz and Cr4+¡GYAG will rupture on the interface as a result of the huge thermal expansion coefficient. According to researches, stress in different directions will bring about fiber cracks or changes of the refraction rate. This paper mainly investigates the influence of material properties on the temperature field and thermal stress distribution in the cooling process of fiber and preform manufacturing by numerical simulations. The results show the preform temperature profile and the stress distribution in different directions. Also, through the stress distribution, the stress is known to be centered on the interface between core and cladding.

No description available.

A percentage of insulating glass (IG) units break each year due to thermally induced perimeter stresses. The glass industry has known about this problem for many years and an ASTM standard has recently been developed for the design of monolithic glass plates for thermal stresses induced by solar irradiance. It is believed that a similar standard can be developed for IG units if a proper understanding of IG thermal stresses can be developed. The objective of this research is to improve understandings of IG thermal stresses and compare the IG thermal stresses with those that develop in monolithic glass plates given similar environmental conditions. The major difference between the analysis of a monolithic glass plate and an IG unit is energy exchange due to conduction, natural convection, and long wave radiation through the gas space cavity. In IG units, conduction, natural convection, and long wave radiation combine in a nonlinear fashion that frequently requires iterative numerical analyses for determining thermal stresses in certain situations. To simplify the gas space energy exchange, a numerical propagation procedure was developed. The numerical propagation procedure combines the nonlinear effects of conduction, natural convection, and long wave radiation into a single value. Use of this single value closely approximates the nonlinear nature of the gas space energy exchange and simplifies the numerical analysis. The numerical propagation procedure was then coupled with finite element analysis to estimate thermal stresses for both monolithic glass plates and IG units. It is shown that the maximum thermal stresses that develop in IG units increase linearly with input solar irradiance during the transient phase. It is shown that an initial preload stress develops under equilibrium conditions due to the thermal bridge effects of the spacer. It is shown that IG units develop larger thermal stresses than monolithic glass plates under similar environmental conditions. Finally, it is shown that the use of low-e coatings increase IG thermal stresses and that the location of low-e coating as well as environmental conditions affect which glass plate develops larger thermal stresses.

The connection between the devices of optical fiber system is an important part of optical communication equipment. For reducing the power loss in single transfer process, we couple the light from one device to another by connecting with splicer and connector. In the optical fiber communication system, the fiber must be coupled with light source or detectors and optical amplifier. The way connect fiber by fusion splice is different from the mechanical connectors, which is small joint volume, higher mechanical strength and much stable after connecting. It is more suitable to apply on micro-package optical communication device. In the study, we confer with the temperature profile and thermal stress of fusion splice module during splicing Cr4+¡GYAG crystal fiber and single mode fiber by numerical simulations. Through adjusting the parameters, like fusion current, fusion place and the processes of splice to examine the trend of change of temperature and thermal stress.

The current packaging trend toward to smaller and thinner has pushed the manufacturing technology to the limits. During the assembly processes of IC packages, delamination at interfaces and mechanical breakage of components are common mode of failure. The induced thermal stress within the package is one of the major contributions to these failures. According to the disparity of the coefficient of thermal expansion (CTE) between different components, internal thermal stress and warpage will be induced when the package undergoes temperature excursion. In this paper, the Die attach epoxy curing and encapsulation curing process induced warpage and thermal stress were studied by finite element software Marc & Mentat. As comparison, two kinds of Molding materials of the package considered, and the result will compared with the experimental data. Finally, studied the effect of the material thickness and the impact significance of each design variable on the design objective will also be discussed.

Fuel cells are the direct energy conversion devices which convert the chemical energy of a fuel to electrical energy with much greater efficiency than conventional devices. Solid Oxide Fuel Cell (SOFC) is one of the various types of available fuel cells; wherein the major components are made of inherently brittle ceramics. Planar SOFC have the advantages of high power density and design flexibility over its counterpart tubular configuration. However, structural integrity, mechanical reliability, and durability are of great concern for commercial applications of these cells. The stress distribution in a cell is a function of geometry of fuel cell, temperature distribution, external mechanical loading and a mismatch of thermo-mechanical properties of the materials in contact. The mismatch of coefficient of thermal expansion and elastic moduli of the materials in direct contact results in the evolution of thermal stresses in the positive electrode/electrolyte/negative electrode (PEN) assembly during manufacturing and operating conditions (repeated start up and shut down steps) as well. It has long been realized and demonstrated that the durability and reliability of SOFCs is not only determined by the degradation in electrochemical performance but also by the ability of its component materials to withstand the thermal stresses. In the present work, an attempt has been made to evaluate the thermal stresses as a function of thermal and mechanical properties of the component materials assuming contribution from other factors such as thermal gradient, mechanical loading and in-service loading conditions is insignificant. Materials used in the present study include the state of art anode (Ni-YSZ), electrolyte(YSZ) and cathode materials(LM and LSM) of high temperature SOFC and also the ones being suggested for intermediate temperature SOFC Ni-SCZ as an anode, GDC and SCZ as electrolyte and LSCF as the cathode. Variation of thermo-mechanical properties namely coefficient of thermal expansion, and elastic and shear moduli were studied using thermo-mechanical analyzer and resonant ultrasound spectroscope respectively in 25-900°C temperature range. A non-linear variation in elastic and shear moduli- indicative of the structural changes in the studied temperature range was observed for most of the above mentioned materials. Coefficient of thermal expansion (CTE) was also found to increase non-linearly with temperature and sensitive to the phase transformations occurring in the materials. Above a certain temperature (high temperature region- above 600°C), a significant contribution from chemical expansion of the materials was also observed. In order to determine thermal stress distribution in the positive electrode, electrolyte, negative electrode (PEN) assembly, CTE and elastic and shear moduli of the component materials were incorporated in finite element analysis at temperature of concern. For the finite element analysis, anode supported configuration of PEN assembly (of 100mm x 100mm) was considered with 1mm thick anode, 10μm electrolyte and 30μm cathode. The results have indicated that cathode and anode layer adjacent to cathode/electrolyte and electrolyte/anode interface respectively are subjected to tensile stresses at the operating temperature of HT-SOFC (900°C) and IT-SOFC (600°C). However, the magnitude of stresses is much higher in the former case (500MPa tensile stress in cathode layer) when compared with the stress level in IT-SOFC (178MPa tensile stress in cathode layer). These high stresses might have been resulted from the higher CTE of cathode when compared with the adjacent electrolyte. However, it is worth mentioning here that in the present work, we have not considered any contribution from the residual stresses arising from fabrication and the stress relaxation from softening of the glass sealant.