In the present research,we proposed a scheme to address the issues of severe heat damage,high energy consumption,low cooling system efficiency,and wastage of cold capacity in mines.To elucidate the seasonal variations...In the present research,we proposed a scheme to address the issues of severe heat damage,high energy consumption,low cooling system efficiency,and wastage of cold capacity in mines.To elucidate the seasonal variations of environmental temperature through field measurements,we selected a high-temperature working face in a deep mine as our engineering background.To enhance the heat damage control cability of the working face and minimize unnecessary cooling capac-ity loss,we introduced the multi-dimensional heat hazard prevention and control method called"Heat source barrier and cooling equipment".First,we utilize shotcrete and liquid nitrogen injection to eliminate the heat source and implemented pressure equalization ventilation to disrupt the heat transfer path,thereby creating a heat barrier.Second,we establish divi-sional prediction models for airflow temperature based on the variation patterns obtained through numerical simulation.Third,we devise the location and dynamic control strategy for the cooling equipment based on the prediction models.The results of field application show that the heat resistance and cooling linkage method comply with the safety requirement throughout the entire mining cycle while effectively reducing energy consumption.The ambient temperature is maintained below 30℃,resulting in the energy saving of 10%during the high-temperature period and over 50%during the low-temperature period.These findings serve as a valuable reference for managing heat damage in high-temperature working faces.展开更多
We study the thermal effect on skin exposed to an electromagnetic beam of time-dependent power. We consider two types of beam power time schedules. In the controlled temperature exposure, the skin surface temperature ...We study the thermal effect on skin exposed to an electromagnetic beam of time-dependent power. We consider two types of beam power time schedules. In the controlled temperature exposure, the skin surface temperature is increased quickly to a prescribed level using a high beam power;then the surface temperature is maintained at the prescribed level by adjusting the beam power adaptively. In the constant power exposure, the applied beam power is relatively low and stays unchanged over the time. We start both types of exposures at the same time and compare their internal temperatures of skin when they have the same surface temperature. In a non-dimensionalized formulation, we show that at the moment when both exposure types reach the same prescribed surface temperature level, the controlled temperature exposure has a higher internal temperature at all depths. This conclusion is mathematically rigorous and is independent of skin material properties.展开更多
The project has as its aim the design and implementation of the control of temperature in the cockpit of the prototype of neonatal life support equipment ESVIN based on the international standard IEC 60601-2-19 concer...The project has as its aim the design and implementation of the control of temperature in the cockpit of the prototype of neonatal life support equipment ESVIN based on the international standard IEC 60601-2-19 concerning the basic security and operation of the neonatal incubators. The prototype has been developed and is important because the cockpit is a new concept of medical equipment of neonatal life support. There was a modeling of the system of heating of the incubator using the concepts of system identification with the purpose of finding a mathematical model that describes the dynamic behavior of the system. Then, design and implement the strategy of feedback control with digital PID （proportional-integral-derivative） algorithm. The model allowed the design and implementation of a digital PID controller that meets in a satisfactory manner with the requirements, in accordance with the international standard. The control system implemented in the neonatal incubator ESVIN improved the effectiveness of the neonatal life support equipment in regard to temperature controller of the cockpit.展开更多
Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurate...Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurately evaluate the reliability of WPC,which is crucial for the design and maintenance of wind turbines.Firstly,the index of effective temperature(ET)is presented to quantify the effects of temperature and humidity on the semiconductor operation.A novel method is proposed to evaluate the lifetime and calculate the aging failure rates of the semiconductors considering the fluctuations of ET.Secondly,the failure mode and effect analysis(FMEA)of WPC is investigated based on the topology and control scheme.The conventional two-state reliability model of the WPC is extended to the multi-state reliability model where the partial working state under the fault-tolerant control scheme is allowed.Finally,a reliability evaluation framework is established to calculate the parameters of the WPC reliability model considering the variable failure rates and repair activities of semiconductors.Case studies are designed to verfify the proposed method using a practical wind turbine.展开更多
Reasonably designing composition and nanostructure to enhance the stability of bifunctional catalysts is highly desired for rechargeable Zn-air batteries(ZABs).Here,porous carbon nanofibers(CNFs)encapsulated CoNiFe al...Reasonably designing composition and nanostructure to enhance the stability of bifunctional catalysts is highly desired for rechargeable Zn-air batteries(ZABs).Here,porous carbon nanofibers(CNFs)encapsulated CoNiFe alloy nanoparticles(NPs)(CoNiFe/CNFs)were synthesized controllably by in-situ growth and cation etching.Electrochemical tests indicated that CoNiFe/CNFs exhibited excellent bifunctional performances in both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Using CoNiFe/CNFs as bifunctional catalysts,the assembled ZABs presented ultralong durability up to 1050 and 660 h at 5 and 25 mA cm^(-2),respectively.The assembled flexible solid-state ZABs-based polyacrylamide(PAM)hydrogel exhibited a power density of 62.9 mW cm^(-2) and 66 h durability at 2 mA cm^(-2) under ultralow temperature of -40℃.The excellent performance of CoNiFe/CNFs was ascribed to the encapsulation of CNFs by the alloy NPs and the synergy of multi-metals in the alloy NPs,because the encapsulation could suppress alloy spillage and agglomeration and protect the catalytic sites from electrolyte deterioration,thereby boosting the durability of the resulting ZABs.展开更多
The objective of the present study is to analytically investigate temperature effects of an axial-type seismic damper made of shape memory alloys(SMAs)equipped in steel frames.Based on a modified multilinear one dimen...The objective of the present study is to analytically investigate temperature effects of an axial-type seismic damper made of shape memory alloys(SMAs)equipped in steel frames.Based on a modified multilinear one dimensional constitutive model of SMAs,two types of SMAs are employed,which have different stress plateau and different stress growth rate with temperature increase.Temperature effects of SMA dampers on seismic performance upgrading are discussed in three aspects:different environment temperatures;rapid loading rate induced heat generation and different SMA fractions.The analysis indicates that the effect of environment temperature should be considered for the SMA damper in steel frames.However,the rapid loading rate induced heat generation has little adverse effect.展开更多
The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both de...The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both devices operate at the same bus, the stabilization control scheme can be carried out continuously and with flexibility. As a result, the fault currents are limited, and the generator disturbances and the turbine shaft torsional oscillations are converged quickly. In this paper, the effectiveness of the combination of both devices has been demonstrated by considering 3LG （three-lines-to-ground） fault in a two-machine infinite bus system. Also, temperature rise effect of both devices with various resistance values and weights has been demonstrated. Simulation results indicate a significant power system stability enhancement and damping turbine shaft torsional oscillations as well as with allowable temperature rise.展开更多
It is verified that the phonon scattering process and the residual linewidthare the dominant factors of the linewidth of 2210 cm^(-1) IR absorption peak except the anomalous linewidth at 200 K. By investigating the an...It is verified that the phonon scattering process and the residual linewidthare the dominant factors of the linewidth of 2210 cm^(-1) IR absorption peak except the anomalous linewidth at 200 K. By investigating the anomalities of the peak shape and thelinewidth of the peak at 200 K, we put forward a mechanism that the T_d symmetry of defect-complex corresponding to the 2210 cm^(-1) peak can he transferred into the D_(2d) symmetry as temperature rises to above 200 K. The quantitative analysis shows that the V+4H-model is indeed of two states: The T_d configuration is stable at temperature lower than 200 K, while the D_(2d) one is stable at temperature higher than 200 K. We can draw the conclusion that the V +4H-model corresponds to the 2210 cm^(-1) IR absorption peak from the symmetric breaking mechanism, which can quantitatively fit the experimental results.展开更多
The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established t...The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.展开更多
基金supported by the National Natural Science Foundation of China (51874281)the Graduate Innovation Program of China University of Mining and Technology (2022WLKXJ006)the Postgraduate Research&Practice Innovation Program of Jiangsu Province (KYCX22_2612).
文摘In the present research,we proposed a scheme to address the issues of severe heat damage,high energy consumption,low cooling system efficiency,and wastage of cold capacity in mines.To elucidate the seasonal variations of environmental temperature through field measurements,we selected a high-temperature working face in a deep mine as our engineering background.To enhance the heat damage control cability of the working face and minimize unnecessary cooling capac-ity loss,we introduced the multi-dimensional heat hazard prevention and control method called"Heat source barrier and cooling equipment".First,we utilize shotcrete and liquid nitrogen injection to eliminate the heat source and implemented pressure equalization ventilation to disrupt the heat transfer path,thereby creating a heat barrier.Second,we establish divi-sional prediction models for airflow temperature based on the variation patterns obtained through numerical simulation.Third,we devise the location and dynamic control strategy for the cooling equipment based on the prediction models.The results of field application show that the heat resistance and cooling linkage method comply with the safety requirement throughout the entire mining cycle while effectively reducing energy consumption.The ambient temperature is maintained below 30℃,resulting in the energy saving of 10%during the high-temperature period and over 50%during the low-temperature period.These findings serve as a valuable reference for managing heat damage in high-temperature working faces.
文摘We study the thermal effect on skin exposed to an electromagnetic beam of time-dependent power. We consider two types of beam power time schedules. In the controlled temperature exposure, the skin surface temperature is increased quickly to a prescribed level using a high beam power;then the surface temperature is maintained at the prescribed level by adjusting the beam power adaptively. In the constant power exposure, the applied beam power is relatively low and stays unchanged over the time. We start both types of exposures at the same time and compare their internal temperatures of skin when they have the same surface temperature. In a non-dimensionalized formulation, we show that at the moment when both exposure types reach the same prescribed surface temperature level, the controlled temperature exposure has a higher internal temperature at all depths. This conclusion is mathematically rigorous and is independent of skin material properties.
文摘The project has as its aim the design and implementation of the control of temperature in the cockpit of the prototype of neonatal life support equipment ESVIN based on the international standard IEC 60601-2-19 concerning the basic security and operation of the neonatal incubators. The prototype has been developed and is important because the cockpit is a new concept of medical equipment of neonatal life support. There was a modeling of the system of heating of the incubator using the concepts of system identification with the purpose of finding a mathematical model that describes the dynamic behavior of the system. Then, design and implement the strategy of feedback control with digital PID （proportional-integral-derivative） algorithm. The model allowed the design and implementation of a digital PID controller that meets in a satisfactory manner with the requirements, in accordance with the international standard. The control system implemented in the neonatal incubator ESVIN improved the effectiveness of the neonatal life support equipment in regard to temperature controller of the cockpit.
基金supported by the National Natural Science Foundation of China(No.52022016)China Postdoctoral Science Foundation(No.2021M693711)Fundamental Research Funds for the Central Universities(No.2021CDJQY-037)。
文摘Wind power converter(WPC)is a key part of a wind power unit which delivers electric energy to power grid.Because of a large number of semiconductors,WPC has a high failure rate.This paper proposes a method to accurately evaluate the reliability of WPC,which is crucial for the design and maintenance of wind turbines.Firstly,the index of effective temperature(ET)is presented to quantify the effects of temperature and humidity on the semiconductor operation.A novel method is proposed to evaluate the lifetime and calculate the aging failure rates of the semiconductors considering the fluctuations of ET.Secondly,the failure mode and effect analysis(FMEA)of WPC is investigated based on the topology and control scheme.The conventional two-state reliability model of the WPC is extended to the multi-state reliability model where the partial working state under the fault-tolerant control scheme is allowed.Finally,a reliability evaluation framework is established to calculate the parameters of the WPC reliability model considering the variable failure rates and repair activities of semiconductors.Case studies are designed to verfify the proposed method using a practical wind turbine.
基金supported by the National Natural Science Foundation of China(grant no.52103250)the Opening Foundation of State Key Laboratory of Organic-Inorganic Composites,China(grant no.oic-202301001)the Fundamental Research Funds for the Central Universities,China(grant no.buctrc202213).
文摘Reasonably designing composition and nanostructure to enhance the stability of bifunctional catalysts is highly desired for rechargeable Zn-air batteries(ZABs).Here,porous carbon nanofibers(CNFs)encapsulated CoNiFe alloy nanoparticles(NPs)(CoNiFe/CNFs)were synthesized controllably by in-situ growth and cation etching.Electrochemical tests indicated that CoNiFe/CNFs exhibited excellent bifunctional performances in both oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Using CoNiFe/CNFs as bifunctional catalysts,the assembled ZABs presented ultralong durability up to 1050 and 660 h at 5 and 25 mA cm^(-2),respectively.The assembled flexible solid-state ZABs-based polyacrylamide(PAM)hydrogel exhibited a power density of 62.9 mW cm^(-2) and 66 h durability at 2 mA cm^(-2) under ultralow temperature of -40℃.The excellent performance of CoNiFe/CNFs was ascribed to the encapsulation of CNFs by the alloy NPs and the synergy of multi-metals in the alloy NPs,because the encapsulation could suppress alloy spillage and agglomeration and protect the catalytic sites from electrolyte deterioration,thereby boosting the durability of the resulting ZABs.
基金The study was partially funded by the JSPS Grants-in-Aid for Challenging Exploratory Research(No.23656292)and by grants from Japan Science and Technology Agency for“Evaluation and Mitigation of Environment Impacts of Earthquake and Typhoon Disaster on Urban Area and Infrastructures”(Project Title:Refined Analysis and Damage Control of Earthquake Disaster Impact on Bridge Structures),under the Strategic Japanese-Chinese Cooperative Program on Science and Technology(S&T)for Environmental Conservation and Construction of a Society with Less Environmental Burden.
文摘The objective of the present study is to analytically investigate temperature effects of an axial-type seismic damper made of shape memory alloys(SMAs)equipped in steel frames.Based on a modified multilinear one dimensional constitutive model of SMAs,two types of SMAs are employed,which have different stress plateau and different stress growth rate with temperature increase.Temperature effects of SMA dampers on seismic performance upgrading are discussed in three aspects:different environment temperatures;rapid loading rate induced heat generation and different SMA fractions.The analysis indicates that the effect of environment temperature should be considered for the SMA damper in steel frames.However,the rapid loading rate induced heat generation has little adverse effect.
文摘The effectiveness of a combination of fault current limiter and thyristor controlled braking resistor on power system stability enhancement and damping turbine shaft torsional oscillations has been studied. If both devices operate at the same bus, the stabilization control scheme can be carried out continuously and with flexibility. As a result, the fault currents are limited, and the generator disturbances and the turbine shaft torsional oscillations are converged quickly. In this paper, the effectiveness of the combination of both devices has been demonstrated by considering 3LG （three-lines-to-ground） fault in a two-machine infinite bus system. Also, temperature rise effect of both devices with various resistance values and weights has been demonstrated. Simulation results indicate a significant power system stability enhancement and damping turbine shaft torsional oscillations as well as with allowable temperature rise.
文摘It is verified that the phonon scattering process and the residual linewidthare the dominant factors of the linewidth of 2210 cm^(-1) IR absorption peak except the anomalous linewidth at 200 K. By investigating the anomalities of the peak shape and thelinewidth of the peak at 200 K, we put forward a mechanism that the T_d symmetry of defect-complex corresponding to the 2210 cm^(-1) peak can he transferred into the D_(2d) symmetry as temperature rises to above 200 K. The quantitative analysis shows that the V+4H-model is indeed of two states: The T_d configuration is stable at temperature lower than 200 K, while the D_(2d) one is stable at temperature higher than 200 K. We can draw the conclusion that the V +4H-model corresponds to the 2210 cm^(-1) IR absorption peak from the symmetric breaking mechanism, which can quantitatively fit the experimental results.
文摘The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.
