Academic literature on the topic 'Enhanced Heat Resistance'
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Journal articles on the topic "Enhanced Heat Resistance"
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Krivenko, Pavel V., and Sergey G. Guziy. "Aluminosilicate coatings with enhanced heat- and corrosion resistance." Applied Clay Science 73 (March 2013): 65–70. http://dx.doi.org/10.1016/j.clay.2012.10.010.
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Krzemińska, Sylwia, Agnieszka Greszta, and Pamela Miśkiewicz. "Characterization of Heat Protective Aerogel-Enhanced Textile Packages." International Journal of Heat and Technology 38, no. 3 (October 15, 2020): 659–72. http://dx.doi.org/10.18280/ijht.380310.
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The aim of this study was to investigate the effects of aerogel application on the thermal properties of textile packages intended for use in protective clothing. The packages were prepared in the form of removable inserts filled with aerogel, differing in terms of fabric and design. The developed packages were tested for resistance to the three major types of heat: radiant, convective, and contact. The package variant with superior thermal performance was also evaluated for water vapor resistance. The package after incorporation of aerogel was found to approximately double radiant and convective heat resistance, with an approx. eightfold improvement for contact heat at the highest test temperature 250℃. Threshold time increased from (17.7±0.7) s to (139.9±4.9) s for the optimum aerogel-enhanced package variant with the greatest number of pouches, which met the criteria of the highest performance level. The thermal conductivity and thermal resistance of three fabrics selected for testing were tested in order to determine their basic thermal insulation properties. In general, packages containing a larger number of narrower pouches exhibited higher thermal protective performance. The results show that the developed textile packages with aerogel can be successfully used in thermal protective clothing.
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Byun, Sungjoon, Seounghwan Hyeon, and Kwan-Soo Lee. "Guide Vane for Thermal Enhancement of a LED Heat Sink." Energies 15, no. 7 (March 28, 2022): 2488. http://dx.doi.org/10.3390/en15072488.
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A guide vane was installed on a heat sink to enhance the cooling effect of light-emitting diode (LED) lights. The validity of the numerical analysis was verified against the experimental results and the result of the previous studies. The effect of the guide vane on the heat dissipation performance of the heat sink was identified. The effect of the guide vane on the heat sink was qualitatively studied using the streamline and temperature contour. The cooling effect of the heat sink was enhanced by increased air supplement to the center-bottom part. A parametric study was conducted to determine the thermal resistance according to the guide vane angle, installation height, and vane length. Optimization was performed to minimize the thermal resistance using the Kriging model and micro-genetic algorithm (MGA). The cooling performance of the heat sink was enhanced by a maximum of 17.2% when the guide vane was installed.
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Gevorgian, Gor A., Roman A. Vorobyev, German V. Pachurin, Alexey A. Filippov, Mariya V. Mukhina, and Zhanna V. Chaikina. "Optimization of Heat Treatment of Steel with Enhanced Thermal Resistance." Key Engineering Materials 839 (April 2020): 68–72. http://dx.doi.org/10.4028/www.scientific.net/kem.839.68.
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The work is dedicated to the development of the optimal technological process for the manufacture of hot stamping dies and die casting molds made of steel grade 4X5MF1С, in order to ensure the required performance characteristics. The mode of hardening heat treatment of this steel grade was established, which allows to recommend it as a heat-resistant structural material for metal products with the required yield strength σ0.2 within 750 to 1000 MPa.
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LEENANON, B., and M. A. DRAKE. "Acid Stress, Starvation, and Cold Stress Affect Poststress Behavior of Escherichia coli O157:H7 and Nonpathogenic Escherichia coli†." Journal of Food Protection 64, no. 7 (July 1, 2001): 970–74. http://dx.doi.org/10.4315/0362-028x-64.7.970.
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The effects of acid shock, acid adaptation, starvation, and cold stress of Escherichia coli O157:H7 (ATCC 43895), an rpo S mutant (FRIK 816-3), and nonpathogenic E. coli (ATCC 25922) on poststress heat resistance and freeze–thaw resistance were investigated. Following stress, heat tolerance at 56°C and freeze–thaw resistance at −20 to 21°C were determined. Heat and freeze–thaw resistance of E. coli O157:H7 and nonpathogenic E. coli was enhanced after acid adaptation and starvation. Following cold stress, heat resistance of E. coli O157:H7 and nonpathogenic E. coli was decreased, while freeze–thaw resistance was increased. Heat and freeze–thaw resistance of the rpoS mutant was enhanced only after acid adaptation. Increased or decreased tolerance of acid-adapted, starved, or cold-stressed E. coli O157:H7 cells to heat or freeze–thaw processes should be considered when processing minimally processed or extended shelf-life foods.
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Zeng, Ximin, Devarshi Ardeshna, and Jun Lin. "Heat Shock-Enhanced Conjugation Efficiency in Standard Campylobacter jejuni Strains." Applied and Environmental Microbiology 81, no. 13 (April 24, 2015): 4546–52. http://dx.doi.org/10.1128/aem.00346-15.
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ABSTRACTCampylobacter jejuni, the leading bacterial cause of human gastroenteritis in the United States, displays significant strain diversity due to horizontal gene transfer. Conjugation is an important horizontal gene transfer mechanism contributing to the evolution of bacterial pathogenesis and antimicrobial resistance. It has been observed that heat shock could increase transformation efficiency in some bacteria. In this study, the effect of heat shock onC. jejuniconjugation efficiency and the underlying mechanisms were examined. With a modifiedEscherichia colidonor strain, differentC. jejunirecipient strains displayed significant variation in conjugation efficiency ranging from 6.2 × 10−8to 6.0 × 10−3CFU per recipient cell. Despite reduced viability, heat shock of standardC. jejuniNCTC 11168 and 81-176 strains (e.g., 48 to 54°C for 30 to 60 min) could dramatically enhanceC. jejuniconjugation efficiency up to 1,000-fold. The phenotype of the heat shock-enhanced conjugation inC. jejunirecipient cells could be sustained for at least 9 h. Filtered supernatant from the heat shock-treatedC. jejunicells could not enhance conjugation efficiency, which suggests that the enhanced conjugation efficiency is independent of secreted substances. Mutagenesis analysis indicated that the clustered regularly interspaced short palindromic repeats system and the selected restriction-modification systems (Cj0030/Cj0031, Cj0139/Cj0140, Cj0690c, and HsdR) were dispensable for heat shock-enhanced conjugation inC. jejuni. Taking all results together, this study demonstrated a heat shock-enhanced conjugation efficiency in standardC. jejunistrains, leading to an optimized conjugation protocol for molecular manipulation of this organism. The findings from this study also represent a significant step toward elucidation of the molecular mechanism of conjugative gene transfer inC. jejuni.
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Wang, Shicheng, Chenyi Xu, Wei Liu, and Zhichun Liu. "Numerical Study on Heat Transfer Performance in Packed Bed." Energies 12, no. 3 (January 28, 2019): 414. http://dx.doi.org/10.3390/en12030414.
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Packed beds are widely used in industries and it is of great significance to enhance the heat transfer between gas and solid states inside the bed. In this paper, numerical simulation method is adopted to investigate the heat transfer principle in the bed at particle scale, and to develop the direct enhanced heat transfer methods in packed beds. The gas is treated as continuous phase and solved by Computational Fluid Dynamics (CFD), while the particles are treated as discrete phase and solved by the Discrete Element Method (DEM); taking entransy dissipation to evaluate the heat transfer process. Considering the overall performance and entransy dissipation, the results show that, compared with the uniform particle size distribution, radial distribution of multiparticle size can effectively improve the heat transfer performance because it optimizes the velocity and temperature field, reduces the equivalent thermal resistance of convection heat transfer process, and the temperature of outlet gas increases significantly, which indicates the heat quality of the gas has been greatly improved. The increase in distribution thickness obviously enhances heat transfer performance without reducing the equivalent thermal resistance in the bed. The result is of great importance for guiding practical engineering applications.
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BANG, W., and M. A. DRAKE. "Resistance of Cold- and Starvation-Stressed Vibrio vulnificus to Heat and Freeze-Thaw Exposure." Journal of Food Protection 65, no. 6 (June 1, 2002): 975–80. http://dx.doi.org/10.4315/0362-028x-65.6.975.
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The effects of cold storage and starvation on the subsequent heat resistance and freeze-thaw resistance of Vibrio vulnificus were studied. Three strains of V. vulnificus were evaluated. Cold stress had no effect on freeze-thaw resistance (P > 0.05). Starvation enhanced freeze-thaw resistance for one strain compared to controls (P < 0.05). V. vulnificus was not heat resistant; control populations were inactivated within 12 min at 47°C. Starvation increased heat tolerance for one strain, but differences were small from a processing perspective (P < 0.05). Cold stress had no effect on heat resistance (P > 0.05). Cold adaptation (holding 4 h at 15°C) enhanced cold temperature (5°C) tolerance. This information will be helpful in the development of methods to minimize V. vulnificus risk.
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Nguyen Tan Luon, Bao Phan Le, Do Nguyen Hoang Nga, Assoc Prof Dr Phong Mai Thanh, Assoc Prof Dr Thang Le Van, Assoc Prof Dr Kien Le Anh, and Assoc Prof Dr Phung Le Thi Kim. "Enhanced flame resistance of cellulose aerogel by ammonium polyphosphate for heat insulation." Journal of Military Science and Technology, VITTEP (December 20, 2022): 15–22. http://dx.doi.org/10.54939/1859-1043.j.mst.vittep.2022.15-22.
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Cellulose aerogels are a potential candidate for heat insulation, but one of their drawbacks is high flammability hindering their applications in practice. This study synthesized cellulose aerogels from microfibrillated cellulose fibers (MFC) extracted from discarded pineapple leaves. The procedure started with simply mixing the extracted fibers with polyamide amine-epichlorohydrin (PAE) as a chemical crosslinker and ammonium polyphosphate (APP) (10-20%) as a green and effectively flame-resistant additive, followed by freeze-drying. The produced aerogels are characterized in terms of their morphology, thermal stability and conductivity, and flame resistance via advanced and standardized methodologies including Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), thermal conductivity measurement by a heat flow meter, and UL94 horizontal burning test. The flame-resistant cellulose aerogels exhibit ultra-low density (25.5-26.8 mg/cm3), high porosity (98.0-98.2%), excellent heat insulation (35.9-36.7 mW/m۰K), and are completely flame-resistant. In addition, the varied APP content (10-20%) shows little effect on the density, heat conductivity, and thermal stability of the flame-resistant cellulose aerogels in comparison with that of the neat cellulose aerogel. Based on the findings, the synthesized flame-resistant cellulose aerogels are considered a promising bio-based heat insulation material.
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Ágoston, R., Cs Mohácsi-Farkas, and S. Pillai. "Exposure to sub-lethal temperatures induces enhanced heat resistance inListeria monocytogenes." Acta Alimentaria 39, no. 3 (September 2010): 327–36. http://dx.doi.org/10.1556/aalim.39.2010.3.9.
Full textDissertations / Theses on the topic "Enhanced Heat Resistance"
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Pathak, Sayali V. "Enhanced Heat Transfer in Composite Materials." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1368105955.
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Rajamure, Ravi Shanker. "Laser Surface Alloying of Refractory Metals on Aluminum for Enhanced Corrosion Resistance: Experimental and Computational Approaches." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700029/.
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Aluminum (Al) and its alloys are widely used in various technological applications, mainly due to the excellent thermal conductivity, non-magnetic, ecofriendly, easy formability and good recyclability. However due to the inferior corrosion resistance its applications are hampered in various engineering sectors. Besides, the corrosion related failures such as leakage of gas from pipeline, catastrophic breakdown of bridges and fire accidents in processing plants further puts the human life in jeopardy. Within the United States over $ 400 billion dollars per year are spent over research to understand and prevent the corrosion related failures. Recently, the development of transition metal(TM) aluminides (AlxTMy, where, TM = Mo, W, Ta, Nb, Cr, Zr and V) has received the global attention mainly due to high strength at elevated temperatures, light-weight, excellent corrosion and wear resistance. In light of this, surface modification via laser surface alloying (LSA) is a promising engineering approach to mitigate the corrosion and wear problems. In the present study the attempts are made to study the Al-Mo, Al-W, Al-Nb, and Al-Ta systems as a potential corrosion resistant coatings on aluminum. The refractory metal (Mo, W, Nb, Ta) precursor deposit was spray coated separately on aluminum substrate and was subsequently surface alloyed using a continuous wave diode-pumped ytterbium laser at varying laser energy densities. Microstructural analysis was conducted using scanning electron microscopy and further X-ray diffractometry was carried out to evaluate the various phases evolved during laser surface alloying. Corrosion resistance of laser alloyed coatings were evaluated using open circuit potential, cyclic potentiodynamic polarization, electrochemical impedance spectroscopy measurements were performed in 0.6 M NaCl solution (pH:6.9±0.2, 23˚C). Open circuit potential measurements indicate the more stable (steady state) potential values over long periods after laser surface alloying. Cyclic polarization results indicated reduction in the corrosion current density, enhancement in the polarization resistance, and increase in coating/protective efficiency with increase in laser energy density compared to untreated aluminum. Electrochemical impedance spectroscopy measurements also indicated an increase in charge transfer resistance after laser surface alloying of refractory metals on aluminum. Additionally, first principle calculations of thermodynamic, electronic and elastic properties of intermetallics evolved during LSA were also thoroughly investigated to correlate the corrosion performance of intermetallic coatings with these properties. The present study indicates that novel Al-Mo, Al-W, Al-Nb, and Al-Ta intermetallics has a great potential for light weight structural applications with enhanced corrosion resistance.
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Hess, Manon. "Restauration écologique des communautés végétales après éradication d'espèces invasives : Rôle de la dynamique de colonisation et des effets de priorité Using limiting similarity to enhance invasion resistance: theoretical and practical concerns Priority effects: Emerging principles for invasive plant species management Giving recipient communities a greater head start and including productive species boosts early resistance to invasion." Thesis, Avignon, 2020. http://www.theses.fr/2020AVIG0357.
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Les plantes invasives posent d’importants problèmes environnementaux et de santé publique, et leur contrôle est aujourd’hui un défi majeur. Elles rencontrent des conditions particulièrement favorables après des perturbations conduisant à une suppression du couvert végétal. La mise en place d’un couvert végétal séquestrant rapidement ces ressources parait alors une réponse probante pour réduire l’invasion. Néanmoins, les caractéristiques des communautés nécessaires pour exercer une résistance efficace dans les premières phases d’installation sont encore peu connues.Je me suis intéressée à deux mécanismes qui pourraient influencer la résistance à l’invasion des communautés végétales herbacées lors des premiers stades d’installation après une perturbation majeure, que sont (1) la ‘limiting similarity’, impliquant que la coexistence d’espèces partageant la même niche écologique est limitée par l’exclusion compétitive, et (2) les effets de priorité, qui surviennent lorsque l’installation d’une espèce affecte la performance ou la survie d’une espèce arrivant par la suite. L’examen de la littérature confirme que l’application de la ‘limiting similarity’ pour lutter contre les plantes invasives est complexe et n’a, jusqu’à aujourd’hui, fait preuve d’efficacité. Intégrer les effets de priorité aux méthodes de contrôle des plantes invasives après une perturbation semble d’avantage prometteur. Une des stratégies consiste en la mise en place d’un couvert végétal exerçant de forts effets de priorité négatifs, diminuant le succès d’installation des plantes invasives. Deux expérimentations en serre ont été réalisées à cet effet, visant à jouer sur les effets de priorité de la communauté native receveuse afin d’en comprendre l’implication dans la résistance à l’invasion. Dans une première expérimentation, le temps d’avance de la communauté receveuse sur l’arrivée de trois espèces invasives (i.e. Ambrosia artemisiifolia, Bothriochloa barbinodis et Cortaderia selloana), la composition en espèces et la densité des semis ont été manipulés. Une meilleure résistance à l’invasion a été observée lorsque les communautés produisent une forte biomasse aérienne, cette dernière étant associée à la présence d’espèces productives. Retarder l’arrivée des espèces invasives a également réduit le succès d’invasion, mais ceci uniquement lorsque la production de biomasse était suffisamment importante. Une seconde expérimentation a porté sur l’influence de l’identité de la première espèce installée dans la communauté receveuse ainsi que l’ordre de semis des espèces (semis simultané de la communauté ou séquentiel) sur la structuration de la communauté et les conséquences sur sa résistance à l’invasion par A. artemisiifolia. Des différences minimes dans la dynamique de colonisation de la communauté receveuse a substantiellement affecté sa structure, sa production de biomasse, la concentration du sol en nutriments, ainsi que sa résistance précoce à l’invasion. Le semis séquentiel a généralement diminué la résistance à l’invasion par rapport au semis simultané de l’ensemble de la communauté. Les espèces installées en premier ont généré des effets de priorité d’intensité variable, vraisemblablement par le biais de la compétition racinaire, impactant l’invasibilité.En conclusion, la dynamique de colonisation a considérablement influencé le succès d'invasion par le biais de différences de production de biomasse et de préemption des ressources. Les effets de priorité des communautés récemment établies et la résistance à l'invasion associée pourraient être améliorés en (1) maximisant le temps d’avance à la communauté receveuse par rapport aux espèces invasives, (2) introduisant des espèces capables de produire rapidement de la biomasse et de préempter les ressources du sol, et (3) évitant le semis séquentiel, en particulier lorsque les premières espèces installées sont des espèces productives fixatrices d'azoteInvasive plant species cause serious environmental and sanitary issues and their control is today a major challenge. Disturbances involving vegetation removal and an increase in resource availability offer particularly favorable conditions for invasive plant colonization. Establishing a plant cover rapidly sequestering resources could be a relevant strategy to limit invasion. However, little is known about the characteristics enabling newly established communities to exert strong invasion resistance, especially in the early growth stages.In this thesis, I focused on two potential determinants of invasion resistance of herbaceous plant communities in the early growth stages after a major disturbance, which are (1) the concept of limiting similarity, stating that the coexistence of species sharing the same ecological niche is limited by competitive exclusion, and (2) priority effects, which occur when the establishment of a species affects the performance or survival of later arriving species. The application of limiting similarity to control invasive plants appears complex, ineffective and unsuitable for the most common situations. In contrast, integrating priority effects into invasive plant management strategies seems more promising. One strategy consists in restoring a plant cover exerting strong negative priority effects, decreasing the success of subsequent invasive plant establishment. In two greenhouse experiments, I explored the role of priority effects in early invasion resistance. In a first experiment, I manipulated species composition, sowing density and the elapsed time between community sowing and invasion by Ambrosia artemisiifolia, Bothriochloa barbinodis and Cortaderia selloana. A higher invasion resistance was observed when communities produced a high aboveground biomass, which was associated with the presence of productive species. Delaying invasive species arrival also decreased invasion success, but only if it allowed a sufficient increase in biomass production. A second experiment investigated how the identity of the first native colonizer (one of two grasses: Dactylis glomerata and Lolium perenne, or one of two legumes: Onobrychis viciifolia and Trifolium repens) and the timing of species establishment (synchronous vs. sequential sowing) influenced the structuration of the recipient community and its resistance to invasion by A. artemisiifolia. Small differences in assembly history of the recipient community substantially affected community structure, biomass production, soil nutrient content, as well as early invasion resistance. Sequential sowing generally decreased invasion resistance compared with a synchronous sowing. Early colonizers generated priority effects of variable strength most likely via belowground competition, which affected A. artemisiifolia’s invasion success. A prior establishment of the N-fixing legume T. repens particularly boosted A. artemisiifolia’s performance. In conclusions, this thesis work highlights the inadequacy of revegetation strategies based on limiting similarity and reveals promising perspectives of manipulating assembly history and priority effects for designing invasion resistant communities. Assembly history significantly influenced early invasion success by inducing differences in biomass production and resource preemption by the recipient community. Priority effects of newly established communities and associated invasion resistance could be enhanced by (1) giving as much time advance as possible to the recipient community over invasives, (2) introducing species displaying an ability to rapidly produce biomass and preempt soil resources, or (3) avoiding sequential sowing especially when early colonizers are nitrogen-fixing, productive species
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Russ, Jonathan Brent. "Computational Design of Structures for Enhanced Failure Resistance." Thesis, 2021. https://doi.org/10.7916/d8-rfmz-6x23.
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The field of structural design optimization is one with great breadth and depth in many engineering applications. From the perspective of a designer, three distinct numerical methodologies may be employed. These include size, shape, and topology optimization, in which the ordering typically (but not always) corresponds to the order of increasing complexity and computational expense. This, of course, depends on the particular problem of interest and the selected numerical methods. The primary focus of this research employs density-based topology optimization with the goal of improving structural resistance to failure.
Beginning with brittle fracture, two topology optimization based formulations are proposed in which low weight designs are achieved with substantially increased fracture resistance. In contrast to the majority of the current relevant literature which favors stress constraints with linear elastic physics, we explicitly simulate brittle fracture using the phase field method during the topology optimization procedure. In the second formulation, a direct comparison is made against results obtained using conventional stress-constrained topology optimization and the improved performance is numerically demonstrated. Multiple enhancements are proposed including a numerical efficiency gain based on the Schur-complement during the analytical sensitivity analysis and a new function which provides additional path information to the optimizer, making the gradient-based optimization problem more tractable in the presence of brittle fracture physics.
Subsequently, design for ductile failure and buckling resistance is addressed and a numerically efficient topology optimization formulation is proposed which may provide significant design improvements when ductile materials are used and extreme loading situations are anticipated. The proposed scheme is examined regarding its impact on both the peak load carrying capacity of the structure and the amount of external work required to achieve this peak load, past which the structure may no longer be able to support any increase in the external force. The optimized structures are also subjected to a post-optimization verification step in which a large deformation phase field fracture model is used to numerically compare the performance of each design. Significant gains in structural strength and toughness are demonstrated using the proposed framework.
Additionally, the failure behavior of 3D-printed polymer composites is investigated, both numerically and experimentally. A large deformation phase field fracture model is derived under the assumption of plane-stress for numerical efficiency. Experimental results are compared to numerical simulations for a composite system consisting of three stiff circular inclusions embedded into a soft matrix. In particular, we examine how geometric parameters, such as the distances between inclusions and the length of initial notches affect the failure pattern in the soft composites. It is shown that the mechanical performance of the system (e.g. strength and toughness) can be tuned through selection of the inclusion positions which offers useful insight for material design.
Finally, a size optimization technique for a cardiovascular stent is proposed with application to a balloon expandable prosthetic heart valve intended for the pediatric population born with Congenital Heart Disease (CHD). Multiple open heart surgical procedures are typically required in order to replace the original diseased valve and subsequent prosthetic valves with those of larger diameter as the patient grows. Most expandable prosthetic heart valves currently in development to resolve this issue do not incorporate a corresponding expandable conduit that is typically required in a neonate without a sufficiently long Right Ventricular Outflow Tract (RVOT). Within the context of a particular design, a numerical methodology is proposed for designing a metallic stent incorporated into the conduit between layers of polymeric glue. A multiobjective optimization problem is solved, not only to resist the retractive forces of the glue layers, but also to ensure the durability of the stent both during expansion and while subject to the anticipated high cycle fatigue loading. It is demonstrated that the surrogate-based optimization strategy is effective for understanding the trade-offs between each performance metric and ultimately efficiently arriving at a single optimized design candidate. Finally, it is shown that the desired expandability of the device from 12mm to 16mm inner diameter is achievable, effectively eliminating at least one open heart surgical procedure for certain children born with CHD.
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Miller, Christopher F. "Chemical aspects of environmentally enhanced crack growth in Ni-based superalloys /." Diss., 2001. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3010418.
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YU, HSIAO-YAO, and 余曉堯. "Phase Transformation and Mechanism on Enhanced Creep-life in P9 Cr-Mo Heat-resistant Steel." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/srk247.
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碩士明志科技大學
機械工程系機械與機電工程碩士班
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This work explores mechanical properties, structural evolution, and mechanism of creep-life enhancement for widely used P9 heat-resistant steel.The 17-year-on-site used P9 alloy exhibit a higher tensile strength and a smaller elongation than the new P9 alloy from room temperature to 700oC.The P9 alloy also displays a typical ductile feature with a significantly necking profile.The P9 alloy shows phase transition sequences of α-Fe(bcc)→(Ac1~858℃)→α+γ-Fe(bcc+fcc)→(Ac3~894℃)→γ-Fe(fcc) upon heating and γ-Fe(fcc) →(Ms~352℃)→martensite(bct)→(Mf~300 ℃)→martensite(bct) upon cooling.The new P9-alloy tube mainly contains ~73.5% ferrite phase (α-Fe) and ~26.5% carbide M3C.However,the used P9-alloy tube shows four crystalline phases including ~45.9% ferrite, ~14.5% martensite, ~37.5% cementite (M3C) and ~2.7% carbide M23C6.The creep test indicates that the used P9-alloy tube has a longer creep-life (or better anti-creep ability) than the new tube.Activation energies of atomic diffusion for the new and used tubes are respectively 252.45 and 345.87 kJ/mol, indicating a decreased diffusion capability in the used tube. This work suggests that martensite laths, lath boundaries,and precipitates (such as carbides) play important roles to inhibit creep-deformation in the P9-alloy steel.
Books on the topic "Enhanced Heat Resistance"
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Yong-Yi, Wang, Gold Michael, American Society of Mechanical Engineers. Pressure Vessels and Piping Division., and Pressure Vessels and Piping Conference (2004 : San Diego, Calif.), eds. Experience with creep-strength enhanced ferritic steels and new emerging computational methods: Presented at the 2004 ASME/JSME Pressure Vessels and Piping Conference : San Diego, California, USA, July 25-29, 2004. New York, N.Y: American Society of Mechanical Engineers, 2004.
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Moore, William F., and Jane Ann Moore. Assuring That the Nation Would Long Endure, 1863. University of Illinois Press, 2017. http://dx.doi.org/10.5406/illinois/9780252038464.003.0011.
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This chapter examines Abraham Lincoln and Owen Lovejoy's united stand to assure that the nation “can long endure” amidst the war. Lincoln's Emancipation Proclamation intensified the desperation felt by slaveholders in areas close to the invading armies. While resisting and escaping slaves invigorated the political process for emancipation, the Emancipation Proclamation emboldened more resistance to slave masters and enhanced cooperation in the Union's efforts in the Civil War. This chapter begins with a discussion of the debate among antislavery leaders over reconstruction policy, along with Lincoln and Lovejoy's disagreements about issues such as the role that the federal military should take in policing the states during the transition. It then considers Lovejoy's health problems and the support for the Lincoln administration's war effort, as well as two men 's persistence in pursuing their radical agenda. It also looks at Lincoln's appeal for divine help to guide and heal the nation, highlighted by his Thanksgiving Proclamation designating August 6 “a day for National Thanksgiving, Praise and Prayer.”
Book chapters on the topic "Enhanced Heat Resistance"
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De Pauw, Ines, Carolien Boeckx, and An Wouters. "Mechanisms of Cetuximab Resistance and How to Overcome It." In Critical Issues in Head and Neck Oncology, 21–51. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63234-2_3.
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AbstractDeregulated or increased signalling of the epidermal growth factor receptor (EGFR) plays an integral role in the development of various cancer types, including head and neck squamous cell carcinoma (HNSCC), making it a compelling drug target. However, after initially promising results of EGFR-targeted therapies, such as the monoclonal antibody cetuximab, it became clear that both intrinsic and acquired therapeutic resistance are major roadblocks in the field of personalised cancer treatments.In order to unravel and overcome resistance to cetuximab, at least two strategies can be adopted.Firstly, therapeutic resistance to anti-EGFR therapy may arise from mechanisms that can compensate for reduced EGFR signalling and/or mechanisms that can modulate EGFR-dependent signalling. In this chapter, we discuss which mechanisms of cetuximab resistance are already known and which ones deserve further investigation. This enhanced knowledge will guide us to rationally design and test novel combination therapies that overcome resistance to EGFR-targeting agents in cancer treatment.Secondly, an urgent need remains to develop novel targeted treatments for single-agent or combined therapy use. In this view, due to the particular mode of activation of the EGFR receptor, involving ligand-induced homo- and heterodimerization of the four HER receptors, an increased inhibition scope of HER receptors most likely results in a more potent blockade of the HER network, preventing premature emergence of resistance and leading to a more pronounced therapeutic benefit. We discuss two multitargeted compounds, being MEHD7945A (duligotuzumab) and afatinib, in this chapter.Despite the huge efforts to unravel the molecular landscape of HNSCC, the main clinically validated target remains EGFR. However, immune checkpoints, like programmed cell death protein 1 (PD-1), are gaining clinical approvals as well. We underscore the importance of adopting rational drug combinations to enhance the therapeutic effect of the EGFR-inhibitor cetuximab and highlight the ongoing search for predictive biomarkers, with the ultimate goal of delivering individualized cancer therapy to HNSCC patients.
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Talapatra, Animesh, and Debasis Datta. "Molecular Dynamics Simulation-Based Study on Enhancing Thermal Properties of Graphene-Reinforced Thermoplastic Polyurethane Nanocomposite for Heat Exchanger Materials." In Inverse Heat Conduction and Heat Exchangers. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.86527.
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Molecular dynamics (MD) simulation-based development of heat resistance nanocomposite materials for nanoheat transfer devices (like nanoheat exchanger) and applications have been studied. In this study, MD software (Materials Studio) has been used to know the heat transport behaviors of the graphene-reinforced thermoplastic polyurethane (Gr/TPU) nanocomposite. The effect of graphene weight percentage (wt%) on thermal properties (e.g., glass transition temperature, coefficient of thermal expansion, heat capacity, thermal conductivity, and interface thermal conductance) of Gr/TPU nanocomposites has been studied. Condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field which is incorporated in both amorphous and forcite plus atomistic simulation modules within the software are used for this present study. Layer models have been developed to characterize thermal properties of the Gr/TPU nanocomposites. It is seen from the simulation results that glass transition temperature (Tg) of the Gr/TPU nanocomposites is higher than that of pure TPU. MD simulation results indicate that addition of graphene into TPU matrix enhances thermal conductivity. The present study provides effective guidance and understanding of the thermal mechanism of graphene/TPU nanocomposites for improving their thermal properties. Finally, the revealed enhanced thermal properties of nanocomposites, the interfacial interaction energy, and the free volume of polymer nanocomposites are examined and discussed.
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Esarte, Jesús, Roger R. Riehl, Simone Mancin, Jesús Mª Blanco, Maite Aresti, and Juncal Estella. "Nanofluid as Advanced Cooling Technology. Success Stories." In Heat Transfer - Design, Experimentation and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96247.
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Nanofluids are defined as heat transfer fluids with enhanced heat transfer properties by the addition of nanoparticles. Nanofluid’s stability, nanoparticles’ type and their chemical compatibility with the base fluid are essential not only to increase the nanofluid’s thermophysical properties but also to ensure a long-lasting and thermal efficient use of the equipment in which it is used. Some of these aspects are discussed in this chapter. Likewise, the improvement in terms of the heat transfer capacity (thermal resistance) that the use of nanofluids has on the heat pipes-thermosyphons is shown. On the other hand, the improvement in energy efficiency that nanofluid causes in a vapor compression system is also presented.
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Rahman, K. T. "Emerging Nano-Enable Materials in the Sports Industry." In Emerging Applications of Nanomaterials, 75–100. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902288-4.
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Within the last decade, there have been numerous innovations in integrating nanotechnology for various sports applications. Nanotechnology is a technology discipline that deals with dimensions and tolerances of less than 100 nanometers, particularly manipulating single atoms and molecules. Nanotechnology has profoundly impacted sports competition like any other revolutionary innovation in materials science. The emergence of nanomaterials and nanotechnology has greatly improved athlete's performance. Sports equipment is becoming more humanized with the development of nanotechnology because it is more convenient, protective, and rational. Commercial nanotechnology-enable sports products, including ski goggle, ski wax, tennis racket, tennis ball, golf ball, bicycle, sportswear, shoe, and more, have offered several benefits to sports sectors in comparison to traditional sports equipment and clothes. These have enhanced the athletes' performance to multifunctional features of sportswear including water resistance, anti-microbial, anti-odor, anti-stain, anti-UV, heat, and cold resistance. This chapter has focused on minimizing the gap between understanding the scientific implications and applications of nanotechnology to sports equipment and clothing, and the characterization and impact of nanomaterials in the sports industry.
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Kallel, Mouna, Amir Bahri, and Khaled Elleuch. "Investigation on the Wear Resistance of Ni-B-TiO2 Composite Coatings for Dry Crushing Application." In Handbook of Research on Tribology in Coatings and Surface Treatment, 218–44. IGI Global, 2022. http://dx.doi.org/10.4018/978-1-7998-9683-8.ch010.
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To achieve a more important service life of hammers, used in crushing process, a Ni-B-TiO2 composite coating was electrodeposited on heat treated AISI P20 using conventional and novel methods. The prepared coatings underwent different tribological tests to quantify the coating that offers the best resistance against wear. For this reason, abrasive wear tests such as pin-on-disk test and multi-pass scratch test were performed to evaluate the abrasive wear resistance of the coatings under a round counterbody (alumina ball) and a sharper contrerbody (sphero-conical indenter), respectively. In addition, the impact-sliding test was also performed to assess the impact resistance of the composite coatings. The obtained results showed that the novel method promotes the best mechanical and tribological properties of the elaborated Ni-B-TiO2 composite coating. This is attributed to the fact of adding TiO2 sol into Ni-B electrolyte which enhances the dispersive strength of the formed TiO2 nanoparticles, contrary to adding solid TiO2 nanoparticles into the electroplating bath.
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Seiler, Christian. "Cardiovascular physiology: regulation of coronary circulation." In ESC CardioMed, edited by Guido Grassi, 120–25. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0023.
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This chapter reviews coronary circulatory structural and functional aspects with a focus on human physiology and on pathophysiology relating to ischaemic heart disease. During augmented myocardial oxygen demand (e.g. during physical exercise), oxygen extraction is enhanced only marginally due to high extraction at rest. Thus, the increased demand is met by augmented coronary blood flow. The structural design of the coronary artery tree is matched to myocardial perfusion at rest, and can be derived from an economic construction principle ubiquitously present in biology: the physiological or optimality principle of minimum work. Myocardial perfusion at rest amounts to 1 mL/min/g, the level of which is maintained over a broad range of coronary perfusion pressures between 60 and 140 mmHg (coronary autoregulation). Coronary flow at rest under different coronary pressure challenges is held constant by microcirculatory resistance adaptation. Likewise, coronary flow in response to augmented myocardial metabolic challenges is increased four- to fivefold (coronary flow reserve) by a reduction in microcirculatory resistance. Active regulation of coronary microcirculatory resistance results from a balance between vasodilator and vasoconstrictor stimuli exerted by metabolic signals from the myocardium, the vascular endothelium, and neurohumoral influences. An atherosclerotic coronary stenosis is a vascular resistance in series to the downstream microcirculatory resistance inducing an epicardial coronary pressure drop. At rest, normal coronary flow is maintained due to compensatory microvascular dilatation. Hence, the capacity for further microcirculatory dilatation under increased oxygen demand is limited, that is, coronary flow reserve is reduced.
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M. Sobamowo, Gbeminiyi. "Perturbation Methods to Analysis of Thermal, Fluid Flow and Dynamics Behaviors of Engineering Systems." In A Collection of Papers on Chaos Theory and Its Applications. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96059.
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This chapter presents the applications of perturbation methods such as regular and homotopy perturbation methods to thermal, fluid flow and dynamic behaviors of engineering systems. The first example shows the utilization of regular perturbation method to thermal analysis of convective-radiative fin with end cooling and thermal contact resistance. The second example is concerned with the application of homotopy perturbation method to squeezing flow and heat transfer of Casson nanofluid between two parallel plates embedded in a porous medium under the influences of slip, Lorentz force, viscous dissipation and thermal radiation. Additionally, the dynamic behavior of piezoelectric nanobeam embedded in linear and nonlinear elastic foundations operating in a thermal-magnetic environment is analyzed using homotopy perturbation method which is presented in the third example. It is believed that the presentation in this chapter will enhance the understanding of these methods for the real world applications.
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Parthasarathi, Theivasigamani, Saiyyeda Firdous, Einstein Mariya David, Kuppan Lesharadevi, and Maduraimuthu Djanaguiraman. "Effects of High Temperature on Crops." In Advances in Plant Defense Mechanisms [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.105945.
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The effect of high-temperature situations leads to a significant reduction in yield. The elevated temperature on crops is expected to have a widespread negative effect as a consequence of global warming. Meanwhile, the global population is rapidly increasing and is predicted to be 11 billion in 2100. An increase in 70% of global food production is a challenging task to feed the increasing population. Increasing the food crop yield is crucial to meet the global food demand and ensuring food security. An increase in high temperature every year due to global warming and an increase in greenhouse gases leads to a rise in temperature. The rise in temperature significantly affects the yield; so, it is important to understand the mechanism and how to counteract high temperature on food crops. It is also important to neutralize the effect of high temperature on food crops and to increase the yield by minimizing the effect of high temperature and developing heat resistant or tolerant variety. It is essential to develop heat-tolerant crops or transgenic food crops that can assure great yield and food security for future generations. It is essential to examine the metabolic, physiological, and molecular mechanisms of food crops to have an enhanced understanding of high temperature and their effects on crops.
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Kjær, Anne Mette, and Nansozi K. Muwanga. "The Political Economy of Education Quality Initiatives in Uganda." In The Politics of Education in Developing Countries, 152–71. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198835684.003.0008.
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Uganda has seen a significant increase in access to primary education since 1996 but without an increase in quality learning. We show that there are weak political incentives to undertake reforms to enhance quality learning, for three reasons: (i) A system of decentralized rent management renders quality improvements arbitrary; (ii) There is a legacy of fee-free education playing an important part in the electoral appeal of the National Resistance Movement for rural voters; (iii) The pressure to push through education quality-enhancing reforms, whether from civil society, powerful interest groups, or parliament, is too weak to overpower incentives to address the learning crisis head-on. At the local level, the school administrations in high-performing schools were able to draw upon resourceful networks in order to mobilize local council funds and parents’ contributions, in spite of the official policy of free education.
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Joseph, Theyamma, and Jacquline C. Vadasseril. "Diabetes a Silent Killer: A Threat for Cardiorespiratory Fitness." In Cardiorespiratory Fitness - New Topics [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108164.
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Type 2 Diabetes Mellitus (T2DM) is a noncommunicable, lifestyle-related chronic metabolic disorder of global involvement, characterized by elevated blood sugar levels, manifested by hyperglycaemia, polyuria, polydipsia and polyphagia. DM is associated with acute and chronic complications which lead to reduced quality of life, premature morbidity and mortality. T2DM is linked with overweight, obesity, reduced physical activity and a genetic component. T2DM is named a silent killer because the primary disease is silent at the early stage and usually gets diagnosed when presenting with a vascular event such as stroke or heart attack. Impaired cardiorespiratory fitness plays a crucial role in acceleration of cardiovascular complications resulting in premature organ damage, morbidity and mortality. Regular physical activity, resistance training and reduction in sedentary life style along with diet control and drugs help to control DM and prevent or delay complications. This chapter deals with diabetes as a disease, its prevalence, risk factors, signs and symptoms, pathophysiology, pathogenesis and underlying mechanisms, acute and chronic complications, along with measures to enhance cardiorespiratory fitness and control DM and a word of caution to the younger generation to be aware of the silent killer.
Conference papers on the topic "Enhanced Heat Resistance"
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Goshima, Yasuhiro. "Enhanced Heat Resistance and Durability of Engine Mount Rubber." In SAE 2011 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2011. http://dx.doi.org/10.4271/2011-01-0249.
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Kim, Sungwon S., Justin A. Weibel, Timothy S. Fisher, and Suresh V. Garimella. "Thermal Performance of Carbon Nanotube Enhanced Vapor Chamber Wicks." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22929.
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Vapor chambers are often used as spreaders to dissipate high heat fluxes by taking advantage of liquid-vapor phase change. Wicking of the working fluid in vapor chambers is accomplished through capillary action, which is strongly affected by the wick structure. Traditionally, copper meshes with micrometer-scale pore sizes have been used as wicking structures, but it is expected that heat fluxes in the next generation of high-power electronic devices will cause boiling in these devices and lead to dryout with conventional wick materials. With a goal of increasing maximum heat dissipation and reducing thermal resistance, a wick structure composed of both conventional copper mesh and carbon nanotubes has been developed and characterized. The high-permeability mesh provides for a low-resistance bulk flow path while the carbon nanotubes, with their high thermal conductivity and high surface area, modify the wick surface for enhanced capillary action. CNT-enhanced integrated wicks were fabricated by sintering a copper mesh on Cu-Mo-Cu substrates, on which CNTs were grown. A thin layer of copper was evaporated onto the CNTs to improve wicking and wettability with water, the working fluid of interest. Samples grown under varying degrees of positive bias voltage and varying thicknesses of post-CNT-growth copper evaporation were fabricated, so that the surface morphology of the samples could be varied. The resultant boiling curves and associated wick thermal resistances indicate that micro/nano integrated wicks fabricated with higher positive bias voltages during CNT synthesis, and thicker copper coatings, lead to improved thermal performance and lower wick thermal resistance. Notably, heat fluxes at the heater surface of greater than 500 W/cm2 were observed without reaching a critical heat flux condition.
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Chien, Liang-Han, and C. W. Chen. "Boiling of Enhanced Surfaces at High Heat Fluxes in a Small Boiler." In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73457.
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High operating heat fluxes and small boiling space are the two major challenges to apply boiling heat transfer in electronics cooling. This experimental study seeks to find a good boiling performance surface that is suitable for cooling a CPU dissipating up to 88 W through a 14 mm × 14 mm surface area in a 15 mm × 54mm × 54mm vessel. Three structured boiling surfaces and three porous surfaces were tested in water at 60°C pool temperature. The experimental data showed that the best cross-grooved surface and the best porous surface have similar boiling performance curves. The evaporation resistances of these two surfaces vary from 0.12 to 0.26 K/W. The minimum evaporation resistance of the best cross-grooved surface was 0.125 K/W at 86.5 W. Because the evaporator area is much smaller than the condenser or the heat sink area, the thermal resistance is dominated by the evaporator. The condensation resistance of the 54mm × 54mm condensing area varies from 0.01 to 0.022 K/W, which is much smaller than the evaporation resistance of every boiling surface in the present test. This paper was also originally published as part of the Proceedings of the ASME 2005 Heat Transfer Summer Conference.
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Cano-Banda, Fernando, Ana Gallardo-Gutierrez, Jesus Garcia-Gonzalez, Abel Hernandez-Guerrero, and Luis Luviano-Ortiz. "Enhanced Heat Transfer in Radial Heat Sinks for LED Lamps." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-87958.
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A radial design of a passive heat sink for cooling LED illumination devices is analyzed numerically in order to identify the geometric shape that promotes better heat dissipation rates. Natural convection with the surrounding is considered during the operation of the heat sink. Due to the fact that natural convection is the main mechanism of heat transfer, the shape of the heat sink has a high influence in the heat dissipated. An analysis of the influence of different parameters of a heat sink is conducted in the presented study. The radial heat sink under analysis consists in a flat disc with rectangular fins on it, and the fins are distributed with a radial longitudinal orientation in a circular row arrangement. The number of rows can vary but there is a constant relation of two times the number of fins between the number of fins in an inner row and the next outer row. In order to find a correct configuration to improve the dissipation of heat, parameters like the number of fins, the length of the fins and the separation between fins are studied. The average Nusselt number and thermal resistance for each geometric configuration are compared. The output analysis provides the best shape for a maximum heat transfer.
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Xie, Xu, Changhua Nie, Li Zhan, Hua Zheng, Pengzhou Li, Wenxi Tian, and Pei Yu. "Analysis of Heat Transfer and Flow Characteristics of AP1000 Passive Residual Heat Removal Heat Exchanger." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-31230.
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In this paper, the computational fluid dynamics (CFD) method is applied to the thermal-hydraulic analysis, while the porous media model is used to simplify AP1000 passive residual heat removal heat exchanger tube. The temperature as well as flow distribution in the secondary side of the heat exchanger are obtained, aiming at analysis of natural circulation ability. It can be noted that the fluid in the secondary side of heat exchanger moves driven by the effect of thermal buoyancy, forming the natural cycle, which takes away heat in tube bundle region. The heat transfer in water tank is mainly enhanced by vortex and turbulent flow, caused by the large resistance of tube bundle region as well as large temperature difference. This phenomenon is obvious especially for the recirculation of flow near the tube bundle. The enduring change of flow rate and direction enhance the heat transfer. Besides, the big temperature difference helps to increase the driving effect of natural circulation. Consequently, the heat transfer of the tank is enhanced by above mechanism. The results of this study contribute to the capacity analysis of passive residual heat removal of natural circulation system, providing valuable information for safe operation of AP1000.
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Bougher, Thomas L., Virendra Singh, and Baratunde A. Cola. "Thermal Interface Materials From Vertically Aligned Polymer Nanotube Arrays." In ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/mnhmt2013-22226.
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A number of studies have reported enhancing the thermal conductivity of semi-crystalline polymers through mechanical stretching, but practical application of this process has proven difficult. Here we demonstrate the application of enhanced thermal conductivity in a purely amorphous polymer for a thermal interface material (TIM) without conductive fillers. Many polymer-based TIMs contain carbon fillers to enhance the thermal conductivity, however the TIMs reported herein are comprised solely of polymer nanotubes. The conjugated polymer polythiophene (Pth) is electropolymerized in nanotemplates to produce arrays of vertically aligned nanotubes, which adhere well to opposing substrates through van der Waals forces. We find that the total thermal resistances of the Pth-TIMs are a strong function of height with some dependence on bonding pressure, yet independent of applied pressure after bonding. Photoacoustic measurements show that the total thermal resistance of the TIMs ranges from 9.8 ± 3.8 to 155 ± 32 mm2-K/W depending on the array height and bonding pressure. Estimates of the component resistances indicate that the majority of the resistance is in the contact between the nanotube free tips and the opposing quartz substrate. These Pth-TIMs demonstrate that enhanced thermal conductivity polymers can be suitable for heat transfer materials without thermally conductive fillers.
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Robinson, Frank, Juan G. Cevallos, Avram Bar-Cohen, and Hugh Bruck. "Modeling and Validation of a Prototype Thermally-Enhanced Polymer Heat Exchanger." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-65684.
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Polymer heat exchangers (PHXs) have received considerable attention since their invention more than 40 years ago due to their corrosion resistance, low density and low manufacturing cost. New polymer composites with higher strengths, thermal conductivities and thermal stability promise to bridge the performance gap between polymers and corrosion resistant metals. In the present study, PHX components were injection molded using thermally enhanced polyamide 12 resin and assembled into a crossflow finned-plate heat exchanger prototype. The prototype was implemented in an air-to-water experimental test apparatus and the heat transfer results were compared to an analytical model. This comparison confirmed that a polymer composite heat exchanger (PCHX) can offer significantly enhanced heat transfer relative to a pure polymer. A thermomechanical finite element model of the PCHX was developed and validated using experimental results. At fluid pressures near ambient, the heat transfer rate of the PCHX was 28% less than could be attained with an identical titanium heat exchanger. As fluid pressures increased, the through wall conduction resistance had a larger effect on heat transfer rate, reducing the performance of the PCHX relative to the titanium heat exchanger. Stress analysis of the thermally enhanced PCHX revealed that the stresses due to pressure loading were more sensitive to heat exchanger geometry, while the stresses due to thermal loading were more sensitive to material property anisotropy.
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Taphouse, John H., and Baratunde A. Cola. "Solvent Soaking and Drying of Carbon Nanotube Forests for Enhanced Contact Area and Thermal Interface Conductance." In ASME 2013 4th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/mnhmt2013-22225.
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Forests comprised of nominally vertically aligned carbon nanotubes (CNTs), having outstanding thermal and mechanical properties, are excellent candidates for thermal interface materials (TIMs). However, the thermal performance of CNT forest TIMs has been limited by the presence of high thermal contact resistances at the CNT tip interface. The high thermal contact resistance at the CNT tip interface stems from two sources: (1) the relatively weak van der Waals type bonding, which impedes phonon transport, and (2) low contact area. In this work we will show that common solvents, such as water, can be applied to the CNT forest to increase the contact area and reduce the contact resistance by an average of 75%. Specifically, there are two likely mechanisms that can increase the contact area when a CNT forest is wet with a fluid and compressed in an interface. The first is relaxing the van der Waals interactions between contacting CNTs within the forest, consequently decreasing the stiffness of the forest and allowing it to better conform to the opposing surface. The second is the pulling of CNT tips through capillary interactions into contact with the opposing surface as the solvent evaporates. By measuring the thermal resistance of CNT TIMs before and after soaking in variety of solvents the capacity of each mechanism for reducing the contact resistance is explored.
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Daly, John. "Active Upstream Components for Enhanced Heat Transfer of Longitudinally Finned Heat Sinks." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22203.
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With the ever increasing heat flux from next-generation chips forced convection cooling is beginning to reach its limits within current standard heat sink capabilities. Methods of extending the air cooling capabilities prior to a transition to liquid or refrigerant-based cooling which is seen as costly and complex, have become more critical. This paper investigates the enhanced heat transfer by the addition of active components upstream of a longitudinally finned heat sink. This paper addresses piezoelectric fans for natural and forced convection environments. Experimental measurements are taken for a low powered DC fan operating at a frequency of 114Hz. For the forced convection experiments a fully ducted flow was used. The main thrust of the paper is to determine the effects of piezoelectrics in augmenting forced convection systems at hot component locations. The effects on pressure drop, thermal resistance and pumping power with the addition of the technology are presented. The paper concludes by reporting on the performance enhancement and limitations of the piezoelectric fans compared to the conventional longitudinally finned heat sink geometry.
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Cola, Baratunde A., Stephen L. Hodson, Xianfan Xu, and Timothy S. Fisher. "Carbon Nanotube Array Thermal Interfaces Enhanced With Paraffin Wax." In ASME 2008 Heat Transfer Summer Conference collocated with the Fluids Engineering, Energy Sustainability, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/ht2008-56483.
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Vertically oriented carbon nanotube (CNT) arrays can increase real contact in thermal interfaces and efficiently transfer heat between the mating solids. In this study, a paraffin wax that changes phase at approximately 50°C was applied to interfaces with CNT arrays directly synthesized on one side of the interface, and to foil/CNT interfaces with CNT arrays directly synthesized on one side and both sides of the foil. The bulk thermal resistances of single-sided CNT array/wax interfaces were measured using a transient photoacoustic (PA) technique to range from approximately 2 to 3 mm2·K/W under moderate pressures. The bulk thermal resistances of foil/CNT/wax interfaces were measured with the PA technique to range from approximately 10 to 20 mm2·K/W under moderate pressures. For each sample structure, the addition of paraffin wax to the CNT arrays produced significant reductions in thermal resistance. We surmise that this improved thermal performance could be a function of the wettability of paraffin wax to CNTs. A hydrophilic wetting angle of approximately 47° was observed at the interface of liquid wax and the free tips of a CNT array at 60°C, and field-emission scanning electron microscope images taken after PA testing revealed individual CNTs that were blanketed with a wax coating.
Reports on the topic "Enhanced Heat Resistance"
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Fuchs, Marcel, Ishaiah Segal, Ehude Dayan, and K. Jordan. Improving Greenhouse Microclimate Control with the Help of Plant Temperature Measurements. United States Department of Agriculture, May 1995. http://dx.doi.org/10.32747/1995.7604930.bard.
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A model of the energy balance of a transpiring crop in a greenhouse was developed in a format suitable for use in climate control algorithms aimed at dissipating excess heat during the warm periods. The model's parameters use external climatic variables as input. It incorporates radiation and convective transfer functions related to the operation of control devices like shading screens, vents, fans and enhanced evaporative cooling devices. The model identified the leaf boundary-layer resistance and the leaf stomatal and cuticular resistance as critical parameters regulating the temperature of the foliage. Special experiments evaluated these variables and established their relation to environmental factors. The research established that for heat load conditions in Mediterranean and arid climates transpiring crops maintained their foliage temperature within the range allowing high productivity. Results specify that a water supply ensuring minimum leaf resistance to remain below 100 s m-1, and a ventilation rate of 30 air exchanges per hour, are the conditions needed to achieve self cooling. Two vegetable crops, tomato and sweet pepper fulfilled maintained their leaf resistance within the prescribed range at maturity, i.e., during the critical warm season. The research evaluates the effects of additional cooling obtained from wet pad systems and spray wetting of foliage.
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Hansen, Peter J., and Amir Arav. Embryo transfer as a tool for improving fertility of heat-stressed dairy cattle. United States Department of Agriculture, September 2007. http://dx.doi.org/10.32747/2007.7587730.bard.
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The overall objective of the current proposal is to develop procedures to improve the pregnancy rate achieved following transfer of fresh or cryopreserved embryos produced in the laboratory into heat-stress recipients. The overall hypothesis is that pregnancy rate in heat-stressed lactating cows can be improved by use of embryo transfer and that additional gains in pregnancy rate can be achieved through development of procedures to cryopreserve embryos, select embryos most likely to establish and maintain pregnancy after transfer, and to enhance embryo competence for post-transfer survival through manipulation of culture conditions. The original specific objectives were to 1) optimize procedures for cryopreservation (Israel/US), 2) develop procedures for identifying embryos with the greatest potential for development and survival using the remote monitoring system called EmbryoGuard (Israel), 3) perform field trials to test the efficacy of cryopreservation and the EmbryoGuard selection system for improving pregnancy rates in heat-stressed, lactating cows (US/Israel), 4) test whether selection of fresh or frozen-thawed blastocysts based on measurement of group II caspase activity is an effective means of increasing survival after cryopreservation and post-transfer pregnancy rate (US), and 5) identify genes in blastocysts induced by insulin-like growth factor-1 (IGF-1) (US). In addition to these objectives, additional work was carried out to determine additional cellular determinants of embryonic resistance to heat shock. There were several major achievements. Results of one experiment indicated that survival of embryos to freezing could be improved by treating embryos with cytochalasin B to disrupt the cytoskeleton. An additional improvement in the efficacy of embryo transfer for achieving pregnancy in heat-stressed cows follows from the finding that IGF-1 can improve post-transfer survival of in vitro produced embryos in the summer but not winter. Expression of several genes in the blastocyst was regulated by IGF-1 including IGF binding protein-3, desmocollin II, Na/K ATPase, Bax, heat shock protein 70 and IGF-1 receptor. These genes are likely candidates 1) for developing assays for selection of embryos for transfer and 2) as marker genes for improving culture conditions for embryo production. The fact that IGF-1 improved survival of embryos in heat-stressed recipients only is consistent with the hypothesis that IGF-1 confers cellular thermotolerance to bovine embryos. Other experiments confirmed this action of IGF-1. One action of IGF-1, the ability to block heat-shock induced apoptosis, was shown to be mediated through activation of the phosphatidylinositol 3-kinase pathway. Other cellular determinants of resistance of embryos to elevated temperature were identified including redox status of the embryo and the ceramide signaling pathway. Developmental changes in embryonic apoptosis responses in response to heat shock were described and found to include alterations in the capacity of the embryo to undergo caspase-9 and caspase-3 activation as well as events downstream from caspase-3 activation. With the exception of IGF-1, other possible treatments to improve pregnancy rate to embryo transfer were not effective including selection of embryos for caspase activity, treatment of recipients with GnRH.and bilateral transfer of twin embryos. In conclusion, accomplishments achieved during the grant period have resulted in methods for improving post-transfer survival of in vitro produced embryos transferred into heat-stressed cows and have lead to additional avenues for research to increase embryo resistance to elevated temperature and improve survival to cryopreservation. In addition, embryo transfer of vitrified IVF embryos increased significantly the pregnancy rate in repeated breeder cows.
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Zhang, Hongbin, Shahal Abbo, Weidong Chen, Amir Sherman, Dani Shtienberg, and Frederick Muehlbauer. Integrative Physical and Genetic Mapping of the Chickpea Genome for Fine Mapping and Analysis of Agronomic Traits. United States Department of Agriculture, March 2010. http://dx.doi.org/10.32747/2010.7592122.bard.
Full textAbstract:
Chickpea is the third most important pulse crop in the world and ranks first in the Middle East; however, it has been subjected to only limited research in modern genomics. In the first period of this project (US-3034-98R) we constructed two large-insert BAC and BIBAC libraries, developed 325 SSR markers and mapped QTLs controlling ascochyta blight resistance (ABR) and days to first flower (DTF). Nevertheless, the utilities of these tools and results in gene discovery and marker-assisted breeding are limited due to the absence of an essential platform. The goals of this period of the project were to use the resources and tools developed in the first period of the project to develop a BAC/BIBAC physical map for chickpea and using it to identify BAC/BIBACcontigs containing agronomic genes of interest, with an emphasis on ABR and DTF, and develop DNA markers suitable for marker-assisted breeding. Toward these goals, we proposed: 1) Fingerprint ~50,000 (10x) BACs from the BAC and BIBAC libraries, assemble the clones into a genome-wide BAC/BIBAC physical map, and integrate the BAC/BIBAC map with the existing chickpea genetic maps (Zhang, USA); 2) fine-map ABR and DTFQTLs and enhance molecular tools for chickpea genetics and breeding (Shahal, Sherman and DaniShtienberg, Israel; Chen and Muehlbauer; USA); and 3) integrate the BAC/BIBAC map with the existing chickpea genetic maps (Sherman, Israel; Zhang and Chen, USA). For these objectives, a total of $460,000 was requested originally, but a total of $300,000 was awarded to the project. We first developed two new BAC and BIBAC libraries, Chickpea-CME and Chickpea- CHV. The chickpea-CMEBAC library contains 22,272 clones, with an average insert size of 130 kb and equivalent to 4.0 fold of the chickpea genome. The chickpea-CHVBIBAC library contains 38,400 clones, with an average insert size of 140 kb and equivalent to 7.5 fold of the chickpea genome. The two new libraries (11.5 x), along with the two BAC (Chickpea-CHI) and BIBAC (Chickpea-CBV) libraries (7.1 x) constructed in the first period of the project, provide libraries essential for chickpea genome physical mapping and many other genomics researches. Using these four libraries we then developed the proposed BAC/BIBAC physical map of chickpea. A total of 67,584 clones were fingerprinted, and 64,211 (~11.6 x) of the fingerprints validated and used in the physical map assembly. The physical map consists of 1,945 BAC/BIBACcontigs, with each containing an average of 39.2 clones and having an average physical length of 559 kb. The contigs collectively span ~1,088 Mb, being 1.49 fold of the 740- Mb chickpea genome. Third, we integrated the physical map with the two existing chickpea genetic maps using a total of 172 (124 + 48) SSR markers. Fourth, we identified tightly linked markers for ABR-QTL1, increased marker density at ABR-QTL2 and studied the genetic basis of resistance to pod abortion, a major problem in the east Mediterranean, caused by heat stress. Finally, we, using the integrated map, isolated the BAC/BIBACcontigs containing or closely linked to QTL4.1, QTL4.2 and QTL8 for ABR and QTL8 for DTF. The integrated BAC/BIBAC map resulted from the project will provide a powerful platform and tools essential for many aspects of advanced genomics and genetics research of this crop and related species. These includes, but are not limited to, targeted development of SNP, InDel and SSR markers, high-resolution mapping of the chickpea genome and its agronomic genes and QTLs, sequencing and decoding of all genes of the genome using the next-generation sequencing technology, and comparative genome analysis of chickpea versus other legumes. The DNA markers and BAC/BIBACcontigs containing or closely linked to ABR and DTF provide essential tools to develop SSR and SNP markers well-suited for marker-assisted breeding of the traits and clone their corresponding genes. The development of the tools and knowledge will thus promote enhanced and substantial genetic improvement of the crop and related legumes.
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Lichter, Amnon, Joseph L. Smilanick, Dennis A. Margosan, and Susan Lurie. Ethanol for postharvest decay control of table grapes: application and mode of action. United States Department of Agriculture, July 2005. http://dx.doi.org/10.32747/2005.7587217.bard.
Full textAbstract:
Original objectives: Dipping of table grapes in ethanol was determined to be an effective measure to control postharvest gray mold infection caused by Botrytis cinerea. Our objectives were to study the effects of ethanol on B.cinerea and table grapes and to conduct research that will facilitate the implementation of this treatment. Background: Botrytis cinerea is known as the major pathogen of table grapes in cold storage. To date, the only commercial technology to control it relied on sulfur dioxide (SO₂) implemented by either fumigation of storage facilities or from slow release generator pads which are positioned directly over the fruits. This treatment is very effective but it has several drawbacks such as aftertaste, bleaching and hypersensitivity to humans which took it out of the GRAS list of compounds and warranted further seek for alternatives. Prior to this research ethanol was shown to control several pathogens in different commodities including table grapes and B. cinerea. Hence it seemed to be a simple and promising technology which could offer a true alternative for storage of table grapes. Further research was however required to answer some practical and theoretical questions which remained unanswered. Major conclusions, solutions, achievements: In this research project we have shown convincingly that 30% ethanol is sufficient to prevent germination of B. cinerea and kill the spores. In a comparative study it was shown that Alternaria alternata is also rather sensitive but Rhizopus stolonifer and Aspergillus niger are less sensitive to ethanol. Consequently, ethanol protected the grapes from decay but did not have a significant effect on occurrence of mycotoxigenic Aspergillus species which are present on the surface of the berry. B. cinerea responded to ethanol or heat treatments by inducing sporulation and transient expression of the heat shock protein HSP104. Similar responses were not detected in grape berries. It was also shown that application of ethanol to berries did not induce subsequent resistance and actually the berries were slightly more susceptible to infection. The heat dose required to kill the spores was determined and it was proven that a combination of heat and ethanol allowed reduction of both the ethanol and heat dose. Ethanol and heat did not reduce the amount or appearance of the wax layers which are an essential component of the external protection of the berry. The ethanol and acetaldehyde content increased after treatment and during storage but the content was much lower than the natural ethanol content in other fruits. The efficacy of ethanol applied before harvest was similar to that of the biological control agent, Metschnikowia fructicola, Finally, the performance of ethanol could be improved synergistically by packaging the bunches in modified atmosphere films which prevent the accumulation of free water. Implications, both scientific and agricultural: It was shown that the major mode of action of ethanol is mediated by its lethal effect on fungal inoculum. Because ethanol acts mainly on the cell membranes, it was possible to enhance its effect by lowering the concentration and elevating the temperature of the treatment. Another important development was the continuous protection of the treated bunches by modified atmosphere that can solve the problem of secondary or internal infection. From the practical standpoint, a variety of means were offered to enhance the effect of the treatment and to offer a viable alternative to SO2 which could be instantly adopted by the industry with a special benefit to growers of organic grapes.