In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate Al...In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.展开更多
Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic...Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.展开更多
The traditional combinatorial designs can be used as basic designs for constructing designs of computer experiments which have been used successfully till now in various domains such as engineering, pharmaceutical ind...The traditional combinatorial designs can be used as basic designs for constructing designs of computer experiments which have been used successfully till now in various domains such as engineering, pharmaceutical industry, etc. In this paper, a new series of generalized partially balanced incomplete blocks PBIB designs with m associated classes (m = 4, 5 and 7) based on new generalized association schemes with number of treatments v arranged in w arrays of n rows and l columns (w ≥ 2, n ≥ 2, l ≥ 2) is defined. Some construction methods of these new PBIB are given and their parameters are specified using the Combinatory Method (s). For n or l even and s divisor of n or l, the obtained PBIB designs are resolvable PBIB designs. So the Fang RBIBD method is applied to obtain a series of particular U-type designs U (wnl;) (r is the repetition number of each treatment in our resolvable PBIB design).展开更多
The mined-out areas formed by ore extraction have promoted the development of seasonal energy storage technology in underground spaces.Currently,most studies on the heat storage/release performance of backfills with e...The mined-out areas formed by ore extraction have promoted the development of seasonal energy storage technology in underground spaces.Currently,most studies on the heat storage/release performance of backfills with embedded heat exchange pipes have idealized the operating conditions,such as constant fluid inlet temperature and flow rate.However,actual operating conditions are influenced by many factors like weather conditions,surface equipment,and heat load fluctuations,making them unstable.Therefore,this paper constructs a solar-assisted heat pump coupled mine backfill body heat storage system(SAHP-MBBHSs)based on TRNSYS simulation software and verifies the accuracy of the backfill heat exchangers(BFHEs)model through experiments.Considering the influence of various external factors on the operating conditions,we investigated the long-term seasonal heat storage/release performance of the BFHEs,focusing on the effects of solar collector area,U-tube spacing,thermal conductivity of backfill materials,and heat storage start/stop time.The results show that reducing the U-tube spacing increases the fluctuation amplitude of the average temperature of the backfill body,with the maximum average fluctuation amplitude difference reaching 16.6℃between the 11th and 15th years.Delaying the onset of thermal storage reduces the storage effectiveness of the U-BFHEs,while increasing the heat release effectiveness.During the thermal storage/release interval,heat loss to the surrounding rock does not exceed 4.7%,with the minimal overall impact.The thermal conductivity of the backfill body has the greatest effect on the heat transfer effectiveness of U-BFHEs,increasing from 1 W·m^(-1)·K^(-1)to 2 W·m^(-1)·K^(-1)resulting in respective increases of 58.8%and 39.2%in the heat transfer effectiveness during the 15th year of thermal storage/release.The total heat storage-release effectiveness of the U-BFHEs does not exceed 43.7%,indicating significant room for improvement.Utilizing seasonal thermal storage in the backfill body can effectively enhance the heating performance of SAHP-MBBHSs,with the maximum average APF and HSPF values reaching 3.85 and 5.43,respectively,during the 11th-15th years of operation,maintaining high efficiency even after long-term operation.展开更多
The objective of this paper is to study the issue of uniformity on three-level U-type designs in terms of the wrap-around L2-discrepancy.Based on the known formula,we present a new lower bound of wrap-around L2-discre...The objective of this paper is to study the issue of uniformity on three-level U-type designs in terms of the wrap-around L2-discrepancy.Based on the known formula,we present a new lower bound of wrap-around L2-discrepancy for three-level U-type designs and compare it with those existing ones through figures,numerical simulation and illustrative examples.展开更多
This paper aims to develop a new robust U-type test for high dimensional regression coefficients using the estimated U-statistic of order two and refitted cross-validation error variance estimation. It is proved that ...This paper aims to develop a new robust U-type test for high dimensional regression coefficients using the estimated U-statistic of order two and refitted cross-validation error variance estimation. It is proved that the limiting null distribution of the proposed new test is normal under two kinds of ordinary models.We further study the local power of the proposed test and compare with other competitive tests for high dimensional data. The idea of refitted cross-validation approach is utilized to reduce the bias of sample variance in the estimation of the test statistic. Our theoretical results indicate that the proposed test can have even more substantial power gain than the test by Zhong and Chen(2011) when testing a hypothesis with outlying observations and heavy tailed distributions. We assess the finite-sample performance of the proposed test by examining its size and power via Monte Carlo studies. We also illustrate the application of the proposed test by an empirical analysis of a real data example.展开更多
U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The co...U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The conclusions indicate a discernible deterioration in the thermal performance of U-MDBHE attributed to heat extraction attenuation.The thermal performance deterioration leads to the oversize of U-MDBHE and hinders the widespread application of U-MDBHE.This study introduces a novel idea that the long-term thermal performance of U-MDBHE should be evaluated considering climate change(CC)and verifies that the favorable effects of CC on the thermal performance of U-MDBHE can effectively mitigate the adverse effect of heat extraction attenuation.The favorable effects of CC include reducing the heating demand(due to the reduced building heating load(BHL)caused by CC)and improving the heating supply capacity(due to the enhanced outlet temperature caused by CC).In addition,the reduced BHL under CC enhances the inlet temperature of U-MDBHE,thereby improving its operation safety.CC mitigates the heat extraction attenuation of U-MDBHE,with the strongest effect in the ascending well,followed by the descending well,and then the butted well.Case studies using experimentally validated simulations on the 30-year operation of U-MDBHE demonstrate that by mitigating the adverse effect of the heat extraction attenuation,CC reduces the accumulated energy consumption by 14.31%–26.59%and improves the operation safety by up to 100%in Harbin(severe cold region)and Beijing(cold region).This study significantly contributes to improving the long-term thermal performance of U-MDBHE.展开更多
We are examining the behavior of a composite made of ferroelectrics with strong dielectric properties and ferrites with magnetic properties due to the rising need for materials for multipurpose devices.Many applicatio...We are examining the behavior of a composite made of ferroelectrics with strong dielectric properties and ferrites with magnetic properties due to the rising need for materials for multipurpose devices.Many application avenues will be favored by the pairing of these materials’individual qualities with one another.Perovskite and U-type hexaferrite composite materials have been chosen for this study based on their magnetic and dielectric properties.The composites,(1−x)PLT−x(Ba1−3xNd2x)4Co2Fe36O60 where x=0.52,0.54,0.56,0.58 are prepared by solid state reaction method and phase formation was examined.Consideration has been given to the magnetic,dielectric,and magneto-dielectric properties.This work has established the link between the electric and magnetic domains while applying electric and magnetic forces to the materials.The magneto-dielectric research revealed magneto-electric coupling in all of the samples.However,the sample shows the maximum coupling for x=0.54 with MDR%values of 93.17%,which might be because this sample appears to have a high magneto-resistance(161%).展开更多
池式研究型反应堆是全球多用途研究堆中的重点类型,因其在安全特性、多用途性和运行维护等方面的突出表现而备受关注。在池式堆中,热功率为1~10 MW的小型研究堆方案设计最为成熟,应用场景最为广泛。为了探索未来池式研究堆堆芯设计及其...池式研究型反应堆是全球多用途研究堆中的重点类型,因其在安全特性、多用途性和运行维护等方面的突出表现而备受关注。在池式堆中,热功率为1~10 MW的小型研究堆方案设计最为成熟,应用场景最为广泛。为了探索未来池式研究堆堆芯设计及其应用场景的发展趋势,首先,根据全球开展RERTR(Reduced Enrichment Research and Test Reactor)低浓化项目并进行堆芯重新设计的小型池式研究堆不同的堆芯方案进行对比,研究分析未来小型池式研究堆堆芯可采用的燃料类型和组件结构,以及目前全球小型池式研究堆的应用情况。其次,总结了小型池式研究堆在燃料类型和堆芯结构两个方面的发展现状,汇总了研究堆各类中子应用场景的技术指标。最终,通过横向对比探究分析推判:未来小型池式研究堆将采用紧凑型堆芯设计,采用高密度的低浓缩铀燃料,以紧凑可移动式小堆芯为基础,以大水池内中子源应用设施为主要发展方向。展开更多
基金Project supported by the Major Program of the National Natural Science Foundation of China （Grant No. 60890191） and the National Key Basic Research Program of China （Grant No. 2010CB327503）.
文摘In this study, the physics-based device simulation tool Silvaco ATLAS is used to characterize the electrical properties of an AlGaN/GaN high electron mobility transistor （HEMT） with a U-type gate foot. The U-gate AlGaN/GaN HEMT mainly features a gradually changed sidewall angle, which effectively mitigates the electric field in the channel, thus obtaining enhanced off-state breakdown characteristics. At the same time, only a small additional gate capacitance and decreased gate resistance ensure excellent RF characteristics for the U-gate device. U-gate AlGaN/GaN HEMTs are feasible through adjusting the etching conditions of an inductively coupled plasma system, without introducing any extra process steps. The simulation results are confirmed by experimental measurements. These features indicate that U-gate A1GaN/GaN HEMTs might be promising candidates for use in millimeter-wave power applications.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51779110 and 51809122)the Natural Science Foundation of Jiangsu Province(Grant No.BK20191461)the Six Talent Peaks Project in Jiangsu Province(Grant No.KTHY-064).
文摘Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.
文摘The traditional combinatorial designs can be used as basic designs for constructing designs of computer experiments which have been used successfully till now in various domains such as engineering, pharmaceutical industry, etc. In this paper, a new series of generalized partially balanced incomplete blocks PBIB designs with m associated classes (m = 4, 5 and 7) based on new generalized association schemes with number of treatments v arranged in w arrays of n rows and l columns (w ≥ 2, n ≥ 2, l ≥ 2) is defined. Some construction methods of these new PBIB are given and their parameters are specified using the Combinatory Method (s). For n or l even and s divisor of n or l, the obtained PBIB designs are resolvable PBIB designs. So the Fang RBIBD method is applied to obtain a series of particular U-type designs U (wnl;) (r is the repetition number of each treatment in our resolvable PBIB design).
基金supported by National Natural Science Foundation of China(Nos.52274063,52104148,52004207,52074212)Natural Science Basic Research Plan of Shaanxi Province of China(No.2022JM-173)。
文摘The mined-out areas formed by ore extraction have promoted the development of seasonal energy storage technology in underground spaces.Currently,most studies on the heat storage/release performance of backfills with embedded heat exchange pipes have idealized the operating conditions,such as constant fluid inlet temperature and flow rate.However,actual operating conditions are influenced by many factors like weather conditions,surface equipment,and heat load fluctuations,making them unstable.Therefore,this paper constructs a solar-assisted heat pump coupled mine backfill body heat storage system(SAHP-MBBHSs)based on TRNSYS simulation software and verifies the accuracy of the backfill heat exchangers(BFHEs)model through experiments.Considering the influence of various external factors on the operating conditions,we investigated the long-term seasonal heat storage/release performance of the BFHEs,focusing on the effects of solar collector area,U-tube spacing,thermal conductivity of backfill materials,and heat storage start/stop time.The results show that reducing the U-tube spacing increases the fluctuation amplitude of the average temperature of the backfill body,with the maximum average fluctuation amplitude difference reaching 16.6℃between the 11th and 15th years.Delaying the onset of thermal storage reduces the storage effectiveness of the U-BFHEs,while increasing the heat release effectiveness.During the thermal storage/release interval,heat loss to the surrounding rock does not exceed 4.7%,with the minimal overall impact.The thermal conductivity of the backfill body has the greatest effect on the heat transfer effectiveness of U-BFHEs,increasing from 1 W·m^(-1)·K^(-1)to 2 W·m^(-1)·K^(-1)resulting in respective increases of 58.8%and 39.2%in the heat transfer effectiveness during the 15th year of thermal storage/release.The total heat storage-release effectiveness of the U-BFHEs does not exceed 43.7%,indicating significant room for improvement.Utilizing seasonal thermal storage in the backfill body can effectively enhance the heating performance of SAHP-MBBHSs,with the maximum average APF and HSPF values reaching 3.85 and 5.43,respectively,during the 11th-15th years of operation,maintaining high efficiency even after long-term operation.
基金Supported in part by the National Natural Science Foundation of China(Nos.11871237,11801576,11271147,11401596)the Fundamental Research Funds for the Central Universities(South-Central University for Nationalities(Nos.CZQ18017,CZQ19010))
文摘The objective of this paper is to study the issue of uniformity on three-level U-type designs in terms of the wrap-around L2-discrepancy.Based on the known formula,we present a new lower bound of wrap-around L2-discrepancy for three-level U-type designs and compare it with those existing ones through figures,numerical simulation and illustrative examples.
基金supported by National Natural Science Foundation of China (Grant Nos. 11071022, 11231010 and 11471223)Beijing Center for Mathematics and Information Interdisciplinary ScienceKey Project of Beijing Municipal Educational Commission (Grant No. KZ201410028030)
文摘This paper aims to develop a new robust U-type test for high dimensional regression coefficients using the estimated U-statistic of order two and refitted cross-validation error variance estimation. It is proved that the limiting null distribution of the proposed new test is normal under two kinds of ordinary models.We further study the local power of the proposed test and compare with other competitive tests for high dimensional data. The idea of refitted cross-validation approach is utilized to reduce the bias of sample variance in the estimation of the test statistic. Our theoretical results indicate that the proposed test can have even more substantial power gain than the test by Zhong and Chen(2011) when testing a hypothesis with outlying observations and heavy tailed distributions. We assess the finite-sample performance of the proposed test by examining its size and power via Monte Carlo studies. We also illustrate the application of the proposed test by an empirical analysis of a real data example.
基金supported by the Key Research and Development Projects of Shaanxi Province(Project No.2024SF-YBXM-596 and Project No.2024SF-YBXM-604)Special Fund Project of Science and Technology Innovation by Shaanxi Provincial State-owned Capital Management Budget(Project No.31228000000008/011900)+2 种基金Top Young Talent Programme of Xi’an Jiaotong University(Project No.011900/11301224030703)Qin Chuangyuan“Scientist+Engineer”Team Program(Project No.2022KXJ-039)Innovation Capability Support Program of Shaanxi Province(Project No.2021PT-028).
文摘U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The conclusions indicate a discernible deterioration in the thermal performance of U-MDBHE attributed to heat extraction attenuation.The thermal performance deterioration leads to the oversize of U-MDBHE and hinders the widespread application of U-MDBHE.This study introduces a novel idea that the long-term thermal performance of U-MDBHE should be evaluated considering climate change(CC)and verifies that the favorable effects of CC on the thermal performance of U-MDBHE can effectively mitigate the adverse effect of heat extraction attenuation.The favorable effects of CC include reducing the heating demand(due to the reduced building heating load(BHL)caused by CC)and improving the heating supply capacity(due to the enhanced outlet temperature caused by CC).In addition,the reduced BHL under CC enhances the inlet temperature of U-MDBHE,thereby improving its operation safety.CC mitigates the heat extraction attenuation of U-MDBHE,with the strongest effect in the ascending well,followed by the descending well,and then the butted well.Case studies using experimentally validated simulations on the 30-year operation of U-MDBHE demonstrate that by mitigating the adverse effect of the heat extraction attenuation,CC reduces the accumulated energy consumption by 14.31%–26.59%and improves the operation safety by up to 100%in Harbin(severe cold region)and Beijing(cold region).This study significantly contributes to improving the long-term thermal performance of U-MDBHE.
文摘We are examining the behavior of a composite made of ferroelectrics with strong dielectric properties and ferrites with magnetic properties due to the rising need for materials for multipurpose devices.Many application avenues will be favored by the pairing of these materials’individual qualities with one another.Perovskite and U-type hexaferrite composite materials have been chosen for this study based on their magnetic and dielectric properties.The composites,(1−x)PLT−x(Ba1−3xNd2x)4Co2Fe36O60 where x=0.52,0.54,0.56,0.58 are prepared by solid state reaction method and phase formation was examined.Consideration has been given to the magnetic,dielectric,and magneto-dielectric properties.This work has established the link between the electric and magnetic domains while applying electric and magnetic forces to the materials.The magneto-dielectric research revealed magneto-electric coupling in all of the samples.However,the sample shows the maximum coupling for x=0.54 with MDR%values of 93.17%,which might be because this sample appears to have a high magneto-resistance(161%).
文摘池式研究型反应堆是全球多用途研究堆中的重点类型,因其在安全特性、多用途性和运行维护等方面的突出表现而备受关注。在池式堆中,热功率为1~10 MW的小型研究堆方案设计最为成熟,应用场景最为广泛。为了探索未来池式研究堆堆芯设计及其应用场景的发展趋势,首先,根据全球开展RERTR(Reduced Enrichment Research and Test Reactor)低浓化项目并进行堆芯重新设计的小型池式研究堆不同的堆芯方案进行对比,研究分析未来小型池式研究堆堆芯可采用的燃料类型和组件结构,以及目前全球小型池式研究堆的应用情况。其次,总结了小型池式研究堆在燃料类型和堆芯结构两个方面的发展现状,汇总了研究堆各类中子应用场景的技术指标。最终,通过横向对比探究分析推判:未来小型池式研究堆将采用紧凑型堆芯设计,采用高密度的低浓缩铀燃料,以紧凑可移动式小堆芯为基础,以大水池内中子源应用设施为主要发展方向。
