Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned ...Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles,the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.展开更多
The change of the temperature coefficient of resistivity (α) with the particle size, dp., and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and d. were controlled by heating the nano-...The change of the temperature coefficient of resistivity (α) with the particle size, dp., and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and d. were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of α with dp. and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative α arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.展开更多
To conduct regional climate change assessment for the selected location (Tbilisi) more than century period hydrometeorological observation data of day-night minimal temperature is used. In the presented paper only tem...To conduct regional climate change assessment for the selected location (Tbilisi) more than century period hydrometeorological observation data of day-night minimal temperature is used. In the presented paper only temperature negative values of whole winter season are used. The temperature field change is characterized by the following four parameters: the minimal temperature sum (winter-day temperature is less than zero) of winter frost days;frost day number;season minimal temperature and the occurrence date of season minimal temperature. The modular structure of the above listed parameters has been studied and the mathematical expressions for temporal changes of those parameters have been obtained considering dynamical norms and cyclical changes. The intensity of this change in terms of global warming has been determined. One of the main parameters determining climate change is the variations of temperature field. Despite the fact that this parameter has been modified in the large range due to numerous impacts, they kept stable and provide sustainable equilibrium of the Earth’s energy potential during long-term (several decades) period. This was the reason why the Earth climate remained unchained. As it is known, the anthropogenic impact on the environment has breached the sustainable balance of the Earth energy potential, the potential has been gradually grown almost for more than a century and is known by the name of global warming. The above-mentioned process has already created the greatest threat to the existence of Earth’s biosphere and if it still continues the catastrophic results eventually have to be expected. This led that the problem solving has been set as an urgent task. The numerous fundamental studies for all regions of the world have been carried out to assess the intensity of this process.展开更多
The application of the Unruh procedure to the Rindler approximation of the Kerr-Newman metric in the neighborhood of the event and Cauchy horizons leads, unambiguously, to the well-known positive Hawking (black hole) ...The application of the Unruh procedure to the Rindler approximation of the Kerr-Newman metric in the neighborhood of the event and Cauchy horizons leads, unambiguously, to the well-known positive Hawking (black hole) temperature at the outer horizon, but to a negative (white hole) temperature at the inner horizon. Some consequences for the heat capacities and the status of the third law of thermodynamics are also discussed.展开更多
The pastes containing different dosages of fly ash were taken into ultraviolet radiation and low temperature freeze condition simultaneously(URL)for 30 days and only ultraviolet radiation condition(UR)for 30 days afte...The pastes containing different dosages of fly ash were taken into ultraviolet radiation and low temperature freeze condition simultaneously(URL)for 30 days and only ultraviolet radiation condition(UR)for 30 days after standard curing,so as to investigate the influences of the conditions on the deterioration characteristics of the pastes.Microscopic test methods,such as XRD,TG-DTA and SEM,were used to study the UR effect on the deterioration process of hardened paste.The results show that the deterioration tests,such as URL and UR,inhibit the common development of paste strength,especially after the standard curing age of 360days.With the increase of fly ash dosage,from 0 to 50%,the reference value decreases,especially at early age.While at the later age,i e,180 and 360 days,the paste strength cured for 30 days under URL and UR conditions all increase to different extent and the strength is slightly affected very low,especially for the paste containing25%fly ash.From XRD results,URL and UR dispositions do not influence the hydration product kinds but the amount,especially Ca(OH)_2 and CaCO_3.Deterioration experiments can decrease the diffraction peak of Ca(OH)_2 sharply,and increase that of CaCO_3 rapidly,especially under only ultraviolet radiation.From TG-DTA and SEM results,with the increase of curing age,the content of Ca(OH)_2 decreases and that of CaCO_3 increases.The Ca(OH)_2 content of paste under continuous UR curing for 30 days is less than that under URL curing for 30days,which indicates that UR has more negative effects on the pastes than URL.展开更多
Aswan is famous for Granite rock art reliefs. Seti I granite rock art relief is one of the most important of them. This granite rock art relief suffers from weakness, fragility, fragmentation and peeling because of ma...Aswan is famous for Granite rock art reliefs. Seti I granite rock art relief is one of the most important of them. This granite rock art relief suffers from weakness, fragility, fragmentation and peeling because of many deterioration factors, especially environmental deterioration impacts, such as desert climate with high temperature, residential areas with cafes and shops, and air pollution from exhausts and Kima factory. They can cause chemical weathering. Scientific investigations and analyzes were conducted on this rock art relief such as USB microscope, Polarized (PM) investigation, scanning electron microscope investigation with X-ray energy dispersal unit (EDX) and X-ray diffraction (XRD) analysis to determine the nature and the degree of deterioration, as well as the chemical and mineral composition of the rock and its natural, chemical and mechanical properties. A treatment suggestion to this granite rock art relief has been done.展开更多
In the conversion of methane and propane under high temperature and pressure,the ignition delay time(IDT)is a key parameter to consider for designing an inherently safe process.In this study,the IDT characteristics of...In the conversion of methane and propane under high temperature and pressure,the ignition delay time(IDT)is a key parameter to consider for designing an inherently safe process.In this study,the IDT characteristics of methane and propane(700–1000 K,10–20 bar)were studied experimentally and using kinetic modeling tools at stoichiometric fuel-tooxygen ratios.All the experiments were conducted through insentropic compression.The reliable experimental data were obtained by using the adiabatic core hypothesis,which can be used to generate and validate the detailed chemical kinetics model.The IDTs of methane and propane were recorded by a rapid compression machine(RCM)and compared to the predicted values obtained by the NUIGMech 3.0 mechanism.To test the applicability of NUIGMech 3.0 under different reaction conditions,the influence of temperature in the range of 700–1000 K(and the influence of pressure in the range of 10–20 bar)on the IDT was studied.The results showed that NUIGMech 3.0 could reasonably reproduce the experimentally determined IDT under the wide range of conditions studied.The constant volume chemical kinetics model was used to reveal the effect of temperature on the elementary reaction,and the negative temperature coefficient(NTC)behavior of propane was also observed at 20 bar.The experimental data can serve as a reference for the correction and application of kinetic data,as well as provide a theoretical basis for the safe conversion of low-carbon hydrocarbon chemicals.展开更多
针对超高温灭菌(ultra-high temperature treated,UHT)乳在货架期内出现的脂肪上浮、水乳分离、沉淀等品质劣变问题,利用高通量测序和生物信息学等技术方法,对大型乳企采集的9份在货架期内品质劣变的UHT乳和正常质量的UHT乳样品的理化...针对超高温灭菌(ultra-high temperature treated,UHT)乳在货架期内出现的脂肪上浮、水乳分离、沉淀等品质劣变问题,利用高通量测序和生物信息学等技术方法,对大型乳企采集的9份在货架期内品质劣变的UHT乳和正常质量的UHT乳样品的理化指标、酶活性、微生物菌群进行了分析比较,并通过关联分析解析UHT灭菌乳品质劣变的关联微生物。结果表明:品质劣变UHT乳在理化指标、酶活性和微生物群分布方面与正常UHT乳有明显不同,假单胞杆菌、不动杆菌为品质劣变UHT乳中核心功能微生物且均属于常见的嗜冷菌,能够产生耐热酶,这可能是导致UHT乳腐败变质的主要原因。本研究为进一步解决UHT乳品质劣变问题提供了参考。展开更多
基金Funded by Outstanding Youth Science Foundation of Henan Province of China (No. 04120002300)
文摘Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles,the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.
基金the National Natural Science FOundation of China under grant! No.19974041the National Major Fundamental ResearCh Program-Nal
文摘The change of the temperature coefficient of resistivity (α) with the particle size, dp., and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and d. were controlled by heating the nano-Ag powders over the temperature range from 393 to 453 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of α with dp. and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 20 and 12 nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative α arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.
文摘To conduct regional climate change assessment for the selected location (Tbilisi) more than century period hydrometeorological observation data of day-night minimal temperature is used. In the presented paper only temperature negative values of whole winter season are used. The temperature field change is characterized by the following four parameters: the minimal temperature sum (winter-day temperature is less than zero) of winter frost days;frost day number;season minimal temperature and the occurrence date of season minimal temperature. The modular structure of the above listed parameters has been studied and the mathematical expressions for temporal changes of those parameters have been obtained considering dynamical norms and cyclical changes. The intensity of this change in terms of global warming has been determined. One of the main parameters determining climate change is the variations of temperature field. Despite the fact that this parameter has been modified in the large range due to numerous impacts, they kept stable and provide sustainable equilibrium of the Earth’s energy potential during long-term (several decades) period. This was the reason why the Earth climate remained unchained. As it is known, the anthropogenic impact on the environment has breached the sustainable balance of the Earth energy potential, the potential has been gradually grown almost for more than a century and is known by the name of global warming. The above-mentioned process has already created the greatest threat to the existence of Earth’s biosphere and if it still continues the catastrophic results eventually have to be expected. This led that the problem solving has been set as an urgent task. The numerous fundamental studies for all regions of the world have been carried out to assess the intensity of this process.
文摘The application of the Unruh procedure to the Rindler approximation of the Kerr-Newman metric in the neighborhood of the event and Cauchy horizons leads, unambiguously, to the well-known positive Hawking (black hole) temperature at the outer horizon, but to a negative (white hole) temperature at the inner horizon. Some consequences for the heat capacities and the status of the third law of thermodynamics are also discussed.
基金Funded by the National Key R&D Program of China(No.2016YFC0401907)the Opening Funds of Guangxi Key Laboratory of New Energy and Building Energy Saving(No.15-J-22-4-001)
文摘The pastes containing different dosages of fly ash were taken into ultraviolet radiation and low temperature freeze condition simultaneously(URL)for 30 days and only ultraviolet radiation condition(UR)for 30 days after standard curing,so as to investigate the influences of the conditions on the deterioration characteristics of the pastes.Microscopic test methods,such as XRD,TG-DTA and SEM,were used to study the UR effect on the deterioration process of hardened paste.The results show that the deterioration tests,such as URL and UR,inhibit the common development of paste strength,especially after the standard curing age of 360days.With the increase of fly ash dosage,from 0 to 50%,the reference value decreases,especially at early age.While at the later age,i e,180 and 360 days,the paste strength cured for 30 days under URL and UR conditions all increase to different extent and the strength is slightly affected very low,especially for the paste containing25%fly ash.From XRD results,URL and UR dispositions do not influence the hydration product kinds but the amount,especially Ca(OH)_2 and CaCO_3.Deterioration experiments can decrease the diffraction peak of Ca(OH)_2 sharply,and increase that of CaCO_3 rapidly,especially under only ultraviolet radiation.From TG-DTA and SEM results,with the increase of curing age,the content of Ca(OH)_2 decreases and that of CaCO_3 increases.The Ca(OH)_2 content of paste under continuous UR curing for 30 days is less than that under URL curing for 30days,which indicates that UR has more negative effects on the pastes than URL.
文摘Aswan is famous for Granite rock art reliefs. Seti I granite rock art relief is one of the most important of them. This granite rock art relief suffers from weakness, fragility, fragmentation and peeling because of many deterioration factors, especially environmental deterioration impacts, such as desert climate with high temperature, residential areas with cafes and shops, and air pollution from exhausts and Kima factory. They can cause chemical weathering. Scientific investigations and analyzes were conducted on this rock art relief such as USB microscope, Polarized (PM) investigation, scanning electron microscope investigation with X-ray energy dispersal unit (EDX) and X-ray diffraction (XRD) analysis to determine the nature and the degree of deterioration, as well as the chemical and mineral composition of the rock and its natural, chemical and mechanical properties. A treatment suggestion to this granite rock art relief has been done.
基金supported by the National Natural Science Foundation of China [Grant No. 22278452]the SINOPEC Research Institute of Safety Engineering for financially supporting this project。
文摘In the conversion of methane and propane under high temperature and pressure,the ignition delay time(IDT)is a key parameter to consider for designing an inherently safe process.In this study,the IDT characteristics of methane and propane(700–1000 K,10–20 bar)were studied experimentally and using kinetic modeling tools at stoichiometric fuel-tooxygen ratios.All the experiments were conducted through insentropic compression.The reliable experimental data were obtained by using the adiabatic core hypothesis,which can be used to generate and validate the detailed chemical kinetics model.The IDTs of methane and propane were recorded by a rapid compression machine(RCM)and compared to the predicted values obtained by the NUIGMech 3.0 mechanism.To test the applicability of NUIGMech 3.0 under different reaction conditions,the influence of temperature in the range of 700–1000 K(and the influence of pressure in the range of 10–20 bar)on the IDT was studied.The results showed that NUIGMech 3.0 could reasonably reproduce the experimentally determined IDT under the wide range of conditions studied.The constant volume chemical kinetics model was used to reveal the effect of temperature on the elementary reaction,and the negative temperature coefficient(NTC)behavior of propane was also observed at 20 bar.The experimental data can serve as a reference for the correction and application of kinetic data,as well as provide a theoretical basis for the safe conversion of low-carbon hydrocarbon chemicals.
文摘针对超高温灭菌(ultra-high temperature treated,UHT)乳在货架期内出现的脂肪上浮、水乳分离、沉淀等品质劣变问题,利用高通量测序和生物信息学等技术方法,对大型乳企采集的9份在货架期内品质劣变的UHT乳和正常质量的UHT乳样品的理化指标、酶活性、微生物菌群进行了分析比较,并通过关联分析解析UHT灭菌乳品质劣变的关联微生物。结果表明:品质劣变UHT乳在理化指标、酶活性和微生物群分布方面与正常UHT乳有明显不同,假单胞杆菌、不动杆菌为品质劣变UHT乳中核心功能微生物且均属于常见的嗜冷菌,能够产生耐热酶,这可能是导致UHT乳腐败变质的主要原因。本研究为进一步解决UHT乳品质劣变问题提供了参考。
