Effect Of Temperature Cycling Research Articles

Studies on effects of water temperature, stocking density and feeding cycle on growth and feeding in Hirudo nipponica

Effects of different water temperature, stocking density and feeding cycle on growth, feeding and survival of Hirudo nipponica have been studied, six temperature gradients were set: 18, 22, 26, 30, 34 and 38 ℃, five stocking density gradients were set: 30, 60, 120, 180 and 240 leech/L, four feeding cycle gradients were set: 2, 5, 10 and 20 d, respectively. The results showed that there exists a significant regression relationship between water temperature and specific growth rate: y=-0.016 5x²+0.836 9x-6.847 5（R²=0.990 8）（P<0.05）, a regression analysis indicated that specific growth rate reached the maximum (3.76) at 25.36 ℃. When water temperature was beyond 30 ℃, the survival rate significantly decreased as water temperature increased （P<0.05）. The specific growth rate and survival rate decreased as stocking density increased. A linear relationship exists between the feeding cycle and the SGR: y=-0.094 1x+3.832 9（R²=0.992 7）. From this study, it can be concluded that the optimal water temperature and stocking density for the growth of H. nipponica is 22-26 ℃ and 30-120 leech/L, respectively.

Experimental Investigation on the Effects of Narrow Junction Temperature Cycles on Die-Attach Solder Layer in an IGBT Module

This paper presents a series of experiment results on the ageing effects of cyclic junction temperature variations ( $\Delta T_{j}$ ) of low amplitudes in power modules, to help the capturing of module reliability characteristics and the derivation of lifetime models in the future. Power cycling tests, for nonaged and aged modules, are designed to illustrate the failure mechanisms. Insulated gate bipolar transistor (IGBT) modules in actual converters are usually operated in a $\Delta T_{j}$ range up to 40 °C; therefore, tests are carried out to observe the effects of such narrow $\Delta T_{j}$ stress cycles on the module lifetime. It is found that the relatively minor stress cycles may not be able to directly initiate a crack but can contribute to the development of damage in the die attach solder layer due to stress concentration. Finite element analysis modeling is utilized to verify the stress concentration effect. The experiment results show that the effects of the narrow $\Delta T_{j}$ stress cycles are affected by the ageing status of the module and the stress level itself.

Effect of temperature and thermal cycling on fatigue crack growth in aluminium reinforced with GLARE bonded crack retarders

This paper presents results of fatigue crack growth testing of aluminium alloy 2624-T351 reinforced by bonded crack retarders made of GLARE fibre-metal laminate. Specimens were tested at room temperature, 70°C and −60°C. Better performance of the crack retarders in terms of increased fatigue life was achieved at room temperature than at the two temperature extremes. This is attributed to a combined effect of change in the fatigue crack growth rate at temperature in the substrate material, and residual stress generated at temperatures above or below room temperature. The change in fatigue crack growth rate was measured, and the substrate deformation and the stress intensity factors at temperature were calculated by Finite Element Analysis. In addition, the effect of thermal cycling on fatigue crack growth rate was investigated by exposing the specimens to repeated thermal cycles between 70°C and −60°C prior to fatigue testing. It is concluded that the pre-test thermal cycling has little effect on the fatigue crack growth rate.

Effect of high temperature cycling on both crack formation in ceramics and delamination of copper layers in silicon nitride active metal brazing substrates

Crack formation in Si3N4 active metal brazing (AMB) ceramic substrates and delamination of copper layers on the AMB substrates subjected to temperature cycling from −40 to 250°C were investigated to evaluate the reliability of these substrates under harsh environments. Acoustic scanning microscopy (ASM) observation of the Si3N4 substrates with 0.30mm thick Cu layers revealed crack formation beneath the corner of the copper plate after 100 cycles, whereas no cracks were detected on the Si3N4 substrate with a 0.15mm thick Cu layer, even after 1000 cycles. The residual bending strength of the Si3N4 substrates with 0.30mm thick Cu layers was 78% of the as-received substrate after 10 thermal cycles, and gradually decreased with an increase in the number of thermal cycles until ca. 65% of the initial strength after 1000 cycles. The Si3N4 substrates with 0.15mm thick Cu layers exhibited a gentler degradation of residual strength than those with 0.30mm thick Cu layers. In contrast, the residual bending strength of AlN-AMB substrates with 0.15mm or 0.30mm thick Cu layers were reduced by 50% within only 10 thermal cycles. The depth of cracks developed during the thermal cycles was measured from the fractured surface of the Si3N4-AMB and AlN-AMB substrates. The crack-growth rate in the Si3N4-AMB substrates was much slower than that in the AlN-AMB substrates, which could account for the different degradation behavior of the residual bending strength.

Effects of Serum Stored at Various Temperature and FreezeThaw Cycles on Selected Biochemical Parameters

Introduction: Preanalytical variation as a result of sample storage conditions are common issues in a large scale study since the sample has to be kept for an extended duration at ultra low temperature (-70ºC) before analysis. However, ultra low freezers may not be available in some laboratories. Sometimes, the laboratory test may need to be repeated on the previously frozen and thawed samples. The aim of this research was to study the effect of storage temperature and freeze-thaw cycles on some biochemical parameters in our laboratory. Methods: An experimental study was carried out on 50 volunteers. Serum were aliquoted and stored at 4ºC, -30ºC and -70ºC. The serum was analyzed for total cholesterol (TC), triglycerides (TG), high density-lipoprotein (HDL-C) and glucose after 3 months of storage. The effects of freeze-thaw cycles were also recorded. Results: No significant differences (p&gt;0.05) were seen in the level of the biochemical parameters between the samples stored at -70ºC and at -30ºC. The levels of selected parameters were higher after second freeze-thaw cycles as compared to the first thaw. All parameters showed significant positive correlations between the samples stored at -70ºC and the samples stored at -30ºC and 4ºC as well as between the first and second freeze-thaw cycles in samples kept at both -70ºC and -30ºC. Conclusions: Our finding suggested that the level of TC, TG and glucose in sample stored for 3 months at -70ºC are comparable with the samples stored at -30ºC. Only one freeze-thaw cycle is acceptable.

Study of damage induced by extreme thermal cycling in cyanate ester laminates and sandwich panels

Composite materials are sensible to temperature variations which can lead to the development of internal stresses. The induced stresses may be large enough to damage the material. The objective of this study is to evaluate the effects of extreme temperature cycles on three cyanate ester laminates and one sandwich panel. Thermal cycles going from −170℃ to 145℃ were conducted up to 360 cycles. Microscopic observations of the edges and the middle section of the specimens were performed to evaluate damage growth. Three types of damage were observed in the laminates: transverse microcracks, debonding between the fibers and the matrix and to a limited extent delamination. However, debonding between the fibers and the matrix were only visible on the edges of the laminates. The effect of the observed damages on the mechanical properties of the laminates was studied. Results show that properties influenced by matrix behavior were affected by thermal cycling.

87 - The Effect of Storage Temperature and Repetitive Temperature Cycling on the Post Thaw Functionality of Human Mesenchymal Stem Cells

87 - The Effect of Storage Temperature and Repetitive Temperature Cycling on the Post Thaw Functionality of Human Mesenchymal Stem Cells

Fracture Properties of CFRP–Concrete Bond Subjected to Three Environmental Conditions

AbstractThis paper presents results of a series of single shear tests of carbon fiber–reinforced polymer (CFRP) bonded concrete prisms exposed to three environmental conditions, namely, temperature cycles, wet-dry cycles, and outdoor environment, in terms of shear stress-slip relationships and fracture energies. Temperature cycles and wet-dry cycles were chosen in a manner to study the sole effects of temperature cycles and wet-dry cycles. The maximum temperature of the temperature cycles was intentionally kept below the glass transition temperature of epoxy resin. In the wet-dry cycles, specimens were exposed to varying humidity while temperatures close to ambient were maintained. Also, outdoor environmental exposure was applied to address the lack of test data on natural aging of FRP-concrete bond system. All the environmental conditions were applied for extended durations (the maximum duration of 18 months). Single shear tests (pullout test) were conducted to investigate maximum normal stress developed...

The interacting effects of food, spring temperature, and global climate cycles on population dynamics of a migratory songbird.

Although long-distance migratory songbirds are widely believed to be at risk from warming temperature trends, species capable of attempting more than one brood in a breeding season could benefit from extended breeding seasons in warmer springs. To evaluate local and global factors affecting population dynamics of the black-throated blue warbler (Setophaga caerulescens), a double-brooded long-distance migrant, we used Pradel models to analyze 25 years of mark-recapture data collected in New Hampshire, USA. We assessed the effects of spring temperature (local weather) and the El Niño Southern Oscillation index (a global climate cycle), as well as predator abundance, insect biomass, and local conspecific density on population growth in the subsequent year. Local and global climatic conditions affected warbler populations in different ways. We found that warbler population growth was lower following El Niño years (which have been linked to poor survival in the wintering grounds and low fledging weights in the breeding grounds) than La Niña years. At a local scale, populations increased following years with warm springs and abundant late-season food, but were unaffected by spring temperature following years when food was scarce. These results indicate that the warming temperature trends might have a positive effect on recruitment and population growth of black-throated blue warblers if food abundance is sustained in breeding areas. In contrast, potential intensification of future El Niño events could negatively impact vital rates and populations of this species.

A Test-Ordering Based Temperature-Cycling Acceleration Technique for 3D Stacked ICs

In a modern three-dimensional integrated circuit (3D IC), vertically stacked dies are interconnected using through silicon vias. 3D ICs are subject to undesirable temperature-cycling phenomena such as through silicon via protrusion as well as void formation and growth. These cycling effects that occur during early life result in opens, resistive opens, and stress induced carrier mobility reduction. Consequently these early-life failures lead to products that fail shortly after the start of their use. Artificially-accelerated temperature cycling, before the manufacturing test, helps to detect such early-life failures that are otherwise undetectable. A test-ordering based temperature-cycling acceleration technique is introduced in this paper that integrates a temperature-cycling acceleration procedure with pre-, mid-, and post-bond tests for 3D ICs. Moreover, it reduces the need for costly temperature chamber based temperature-cycling acceleration methods. All these result in a reduction in the overall test costs. The proposed method is a test-ordering and schedule based solution that enforces the required temperature cycling effect and simultaneously performs the tests whenever appropriate. Experimental results demonstrate the efficiency of the proposed technique.

A Study of High-Voltage p-Type MOSFET Degradation Under AC Stress

In this paper, the degradation characteristics of high-voltage (HV) p-type MOSFETs are investigated during negative unipolar ac stress on the gate electrode. The threshold voltage under ac stress is shifted gradually by both the negative-bias temperature-instability mechanism and Fowler-Nordheim degradation. We qualitatively analyze the degradation characteristics of HV p-type MOSFETs under ac stress, and observe the threshold voltage saturation for HV p-type MOSFETs at long ac stress. Based on the effects of temperature and duty cycles, we offer a suitable model of degradation saturation after long ac stress, which is caused by interface trap saturation and recovery during pulse delay timing, which is dependent on thermal activation energy.

Residual strength testing in pultruded FRP material under a variety of temperature cycles and values

This research evaluates the effects of various elevated temperature cycles and peaks on the compression behaviour of pultruded fibre reinforce polymer (FRP) samples as a means of highlighting the durability and strength of FRP material under conditions designed to replicate considerable environmental duress. The performance of the temperature affected samples are then compared with control samples not subjected to the temperature cycles in order to evaluate the effects of temperature on both the load compression achieved and any surface or material degradation as a result of the temperature cycles. The analysed FRP samples were physically characterised by a very low slenderness value in order to avoid potential local instability which characterises FRP pultruded materials. Strain-gauges were used to evaluate the trend of local deformation of the samples both in the direction of the pultruded fibres and orthogonally to them. Finite element analysis was then used to validate the experimental data also with the specific failure criteria adopted. Results suggest that even after considerable cycles of high temperature, the FRP samples still exhibited significant performance durability with relatively small impacts from material stiffness and strain effects suggesting an inherent durability and sustainability under conditions of extended environmental duress.

Temperature regulates circadian rhythms of immune responses in red swamp crayfish Procambarus clarkii.

As an ectothermic animal, crayfish immunity and their resistance to pathogen can be significantly affected by environmental factors such as light and temperature. It has been found for a long time that multiple immune parameters of animals and human are circadian-regulated by light-entrained circadian rhythm. Whether temperature also affects the immune rhythm of animals still remains unclear. In the present study, we investigated the effect of temperature cycles on the rhythm of crayfish immunity and their resistance. Survival experiments demonstrated that temperature cycles of 24 °C and 18 °C effectively entrained the circadian rhythm of crayfish resistance to Aeromonas hydrophila in constant dark. After being exposed to temperature cycles, the crayfish injected at different time points exhibited significant difference in resistance to A. hydrophila. Bacterial growth and total hemocyte count (THC) also showed circadian variation in crayfish subjected to temperature cycles, but phenoloxidase (PO) activity didn't show rhythmic change under the same conditions. Quantitative real-time PCR revealed that basal expression of crustin1 and astacidin in crayfish subjected to temperature cycles was circadian-rhythmic, but induced expression by A. hydrophila didn't show the same rhythm. In contrast, crayfish maintained at constant temperature showed completely arrhythmic in bacterial resistance, immune parameters mentioned above and the expression of antimicrobial peptides. The results present here collectively indicated that temperature cycles entrained circadian rhythm of some immune parameters and shaped crayfish resistance to bacteria.

Effect of Cooling Rate and Temperature Cycles on Polymorphic Behavior of Sunflower Oil Stearins for Applications as Trans-fat Alternatives in Foods

Fil: Herrera, Maria Lidia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Houssay. Instituto de Tecnologia En Polimeros y Nanotecnologia; Argentina

Effect of water temperature, stocking density and feeding cycle on growth of juvenile Poecilobdella manillensis

The effect of water temperature, stocking density and feeding cycle on the growth of Poecilobdella manillensis juvenile was conducted P. manillensis was conducted respectively under different conditions: water temperatures(18, 22, 26, 30,34, 38 degrees C and CT), stocking density (75, 125, 200, 275, 350 individual/L) and feeding cycle(2, 4, 6, 8, 12, 16 d). After 30 days, survival rate, weight gain rate, specific growth rate were measured. There was a significant correlation between water temperature and specific growth rate (γ = -0.066x2 + 3.543 1x -38.09, R2 = 0.837 9). Based on the regression equation, the specific growth rate of P. manillensis achieved the maximum (9.461 4) at 26.84 degrees C. And the most optimal water temperature was 26-30 degrees C. Meanwhile, the survival rates of P. manillensis was 0 at 38 degrees C in 3 d. There was significant negative correlation between density and specific growth rate (γ = -0.005 7x + 9.197 3, R2 = 0.998 3) and between feeding cycle and specific growth rate (γ = -0.468 2x + 10.574, R2 = 0.998 8).

Humidity and Temperature Cycling Effects on Cracks and Delaminations in PEMFCs

AbstractTemperature and relative humidity (hygrothermal) cycles during PEM fuel cell operation can lead to the introduction and exacerbation of micro‐scale mechanical defects. We developed a two‐dimensional finite element model based on cohesive zone theory to describe the delamination propagation at the cathodic membrane/catalyst layer interface due to temperature and hygrothermal duty cycles. Particularly, the effects of hygrothermal cycle amplitudes, relative humidity (RH) distribution profiles, and gas flow channel position were studied. It was found that doubling the hygrothermal cycle amplitude resulted in a 6‐fold increase in fatigue stresses, and a defect length growth to 0,1 mm before reaching the end of the fuel cell life (40,000 cycles). A counter intuitive result was also observed, whereby a crack located within the membrane was found to grow faster than a delamination located at the catalyst layer/membrane interface. When introducing an anode/cathode channel offset, a 2‐fold increase in the rate of delamination propagation was found compared to the case with the aligned anode and cathode channels.

Stress–strain–temperature relation for cyclically-damaged structural mild steel

Experimental results suggest that the mechanical properties of mild steel at elevated temperatures are affected by the cyclic load history previously applied to the material. This has great implications when it comes to post-earthquake fire analyzes. Therefore, it is desirable to establish the relationship for each mechanical property, not only as a function of temperature but also the damage induced by the cyclic load history. To achieve this goal, a special class of functions known as Bézier curves have been utilized in this research. These functions are used for the construction of stress–strain curves that depend on temperature and the amplitude of the previously applied strain cycles. Actual experimental results are used throughout the process for calibration and validation purposes. The proposed model proves to be highly versatile in the sense that it can successfully take the effect of temperature and pre-induced strain cycles into account, making it applicable to post-earthquake fire analyzes.

Determination of Stress Fields and Identification of Thermomechanical Parameters in a Thermally Grown Oxide under Thermal Cycling Loadings, Using Advanced Models

The presence of residual stresses in thermal oxide layers has been recognized for a long time. In the present work, the mechanical fields for chromium oxide are investigated. An extended model is established to take into account the effects of temperature and thermal cycling for the calculation of oxide stress. Numerical results are given in order to predict the influence of different parameters, especially the dependence of some material parameters with temperature. This enables to make comparison with experimental results.

Intensification of enzymatic hydrolysis of waste newspaper using ultrasound for fermentable sugar production

An effective conversion of lignocellulose into fermentable sugars is a key step in producing bioethanol in an eco-friendly and cost effective manner. In this study, the effect of ultrasound on enzymatic hydrolysis of newspaper, a potential feedstock for bioethanol production due to its high cellulosic content, was investigated. The effect of substrate loading, enzyme loading, temperature, ultrasonic power and duty cycle on the hydrolysis has been studied. Optimum conditions for conventional enzymatic hydrolysis were substrate loading of 5% (w/v), enzyme loading of 0.14% (w/v), temperature of 323K, and under these conditions and 72h of hydrolysis, reducing sugar yield of 11.569g/L was obtained. In case of ultrasound-assisted enzymatic hydrolysis approach, optimum conditions obtained were substrate loading of 3% (w/v), enzyme loading of 0.8% (w/v), sonication power of 60W, duty cycle of 70%, hydrolysis time of 6.5h and the reducing sugar yield obtained under these conditions was 27.6g/L. Approximately 2.4 times increase in the release of reducing sugar concentration was obtained by the ultrasound-assisted enzymatic hydrolysis approach. Results indicate that there is a synergistic effect obtained from the combination of ultrasound and enzymes which lowers the diffusion-limiting barrier to enzyme/substrate binding and results in an increase in reaction rate. The experimental data were also fitted in a simple three parameter kinetic model.

Transport, motility, biofilm forming potential and survival of Bacillus subtilis exposed to cold temperature and freeze–thaw

In cold climate regions, microorganisms in upper layers of soil are subject to low temperatures and repeated freeze–thaw (FT) conditions during the winter. We studied the effects of cold temperature and FT cycles on the viability and survival strategies (namely motility and biofilm formation) of the common soil bacterium and model pathogen Bacillus subtilis. We also examined the effect of FT on the transport behavior of B. subtilis at two solution ionic strengths (IS: 10 and 100 mM) in quartz sand packed columns. Finally, to study the mechanical properties of the bacteria-surface bond, a quartz crystal microbalance with dissipation monitoring (QCM-D) was used to monitor changes in bond stiffness when B. subtilis attached to a quartz substrate (model sand surface) under different environmental conditions. We observed that increasing the number of FT cycles decreased bacterial viability and that B. subtilis survived for longer time periods in higher IS solution. FT treatment decreased bacterial swimming motility and the transcription of flagellin encoding genes. Although FT exposure had no significant effect on the bacterial growth rate, it substantially decreased B. subtilis biofilm formation and correspondingly decreased the transcription of matrix production genes in higher IS solution. As demonstrated with QCM-D, the bond stiffness between B. subtilis and the quartz surface decreased after FT. Moreover, column transport studies showed higher bacterial retention onto sand grains after exposure to FT. This investigation demonstrates how temperature variations around the freezing point in upper layers of soil can influence key bacterial properties and behavior, including survival and subsequent transport.