AA female broilers were used to examine the effect of high temperature and β-agonist Clenbuterol (CL) on performance, carcass composition, efficiency of the deposition of energy and protein in diet, carcass character...AA female broilers were used to examine the effect of high temperature and β-agonist Clenbuterol (CL) on performance, carcass composition, efficiency of the deposition of energy and protein in diet, carcass characteristics and meat quality. The trial was 2×2 factorial design with four replicates. Experimental period was last for 24 days from 29 to 52 days after birth. There were four groups in the trial: normal temperature with no CL, nomal temperature with CL, high temperature with no CL and high temperature with CL. The normal terperature was 22±1℃, high temperature was 32±1℃. The lever of CL was administred at 3mg·kg -1 feed. There were three days withdrawal of CL before the end of the trial. The results showed that: (1) High temperature had a significantly negative influence on performance. Where feed intake, daily weight gain and feed efficiency were significantly reduced so that daily feed intake and daily weight gain reduced by 12.6% (P<0.01) and 14.4% (P<0.01), respectively. Feed/gain ratio increased by 1.9% (P<0.05). (2) At high temperature, body protein and water content decreased by 9.4% (P<0.05) and by 2.0% (P<0.05), respectively. Body fat content increased 12.4% (P<0.01). (3) Abdorminal fat significantly increased (P<0.01) at high temperature, compared with that at the normal temperature, where carcass fat ratio and abdominal fat ratio increase 5.8% and 26.4%, respectively. (4) In this trial, CL reduced feed intake significantly (P<0.01) by 6.6% and 5.1% at the normal and high temperature during the whole test period, respectively. CL had no significant influence on daily weight gain (P>0.05), but reduced feed/gain ratio by 5.0% and 5.3% at normal and high temperature, respectively. (5) Carcass analysis indicated that the CL-fed birds had a significantly higher carcass protein content (P<0.01) and lower carcass fat content (P<0.01), where body protein content increased 4.4% and 12.7% and body fat content reduced 16.0% and 17.1% for the normal and high temperature, respectively. (6) Carcass characteristics indicated that CL reduced skin fat ratio by 7.6% (P<0.01) and abdominal fat ratio 8.5% (P<0.01) at the normal temperature; at high temperature, reduced by 14% and 24%, respectively. CL increased breast musle ratio by 14.1% and 3.2%, and increased leg muscle ratio 5.2% and 3.2% at the normal and high temperature, respectively. (7) CL had no negative influence on meat quality. (8) High temperature did not change the function of CL to increase protein deposition and reduce fat deposition.展开更多
During high-speed flight,both thermal and mechani-cal loads can degrade the electrical performance of the antenna-radome system,which can subsequently affect the performance of the guidance system.This paper presents ...During high-speed flight,both thermal and mechani-cal loads can degrade the electrical performance of the antenna-radome system,which can subsequently affect the performance of the guidance system.This paper presents a method for evalu-ating the electrical performance of the radome when subjected to thermo-mechanical-electrical(TME)coupling.The method involves establishing a TME coupling model(TME-CM)based on the TME sharing mesh model(TME-SMM)generated by the tetrahedral mesh partitioning of the radome structure.The effects of dielectric temperature drift and structural deformation on the radome’s electrical performance are also considered.Firstly,the temperature field of the radome is obtained by tran-sient thermal analysis while the deformation field of the radome is obtained by static analysis.Subsequently,the dielectric varia-tion and structural deformation of the radome are accurately incorporated into the electrical simulation model based on the TME-SMM.The three-dimensional(3D)ray tracing method with the aperture integration technique is used to calculate the radome’s electrical performance.A representative example is provided to illustrate the superiority and necessity of the pro-posed method.This is achieved by calculating and analyzing the changes in the radome’s electrical performance over time dur-ing high-speed flight.展开更多
CF3I has been widely considered as a potential alternative for SF6,because it has low global warming potential(GWP)but an insulation capability that is 1.2 times greater than that of SF6.In this paper,the electron swa...CF3I has been widely considered as a potential alternative for SF6,because it has low global warming potential(GWP)but an insulation capability that is 1.2 times greater than that of SF6.In this paper,the electron swarm parameters of CF3I and its gas mixture with N2,including the effective ionization coefficient and electron drift velocity,are examined theoretically through the Boltzmann equation method in the condition of steady-state Townsend(SST)experiments.Based on the derived data of the limiting field strength of CF3I-N2gas mixture,taking into consideration of environmental aspects such as GWP,ozone depletion potential(ODP),liquefaction temperature and toxicity,we studied the possibility of applying the gas mixture as the insulation medium in gas-insulated switchgears(GIS)or cubic type gas-insulated switchgears(C-GIS).It is found that CF3I-N2gas mixtures contained 30%～70%CF3I perform comprehensively better than pure SF6and compressed N2,and especially in medium and low voltage environments,the boiling point of CF3I-N2gas mixture meets the domestic and global requirements in mid-low latitude regions.Therefore we conclude that the gas mixture is acceptable for replacing SF6as the insulation medium in C-GISs.展开更多
为了研究高温和应变率对超高性能混凝土(UHPC)劈裂抗拉性能的影响,对不同温度(20、105、200、300、400℃)作用后UHPC的质量损失率、抗压强度、弹性模量、静态和动态(应变率为1.8~6.8 s^(-1))劈裂抗拉强度进行了测试.结果表明:以2~10℃/...为了研究高温和应变率对超高性能混凝土(UHPC)劈裂抗拉性能的影响,对不同温度(20、105、200、300、400℃)作用后UHPC的质量损失率、抗压强度、弹性模量、静态和动态(应变率为1.8~6.8 s^(-1))劈裂抗拉强度进行了测试.结果表明:以2~10℃/min的加热速率升温至400℃后,所有试件均在保温期间发生爆裂性剥落;U H P C的抗压强度、弹性模量、静态劈裂抗拉强度均随温度增大而提高,300℃作用后比常温时分别提高了13.2%、19.1%和17.3%;动态劈裂抗拉强度和耗散能均具有明显的应变率效应,当应变率从1.8~2.2 s^(-1)增加到6.3~6.8 s^(-1)时,20~300℃作用后的UHPC动态劈裂抗拉强度和耗散能分别提高了69.1%~74.1%和146.7%~177.6%;高温作用后UHPC中C-S-H表面的吸附水、孔隙内自由水和凝胶结合水先后分解,增大了试件的质量损失率;基体内高温和高压环境促进了水泥水化反应和硅灰火山灰反应,提升了UHPC的致密程度,增强了钢纤维的桥连作用;在冲击荷载作用下,基体开裂速度的加快和由钢纤维拔出所致基体摩擦效应的增强导致耗散能增大.展开更多
利用浸涂法将Cr_(2)O_(3)涂覆于Al_(2)O_(3)陶瓷表面,通过高温烧结获得涂层陶瓷,并系统性地研究了Cr_(2)O_(3)涂层对样品的物质成分、微观形貌、二次电子发射系数、表面电阻率和真空沿面耐压性能的影响。结果表明:涂层陶瓷表面呈红黑色...利用浸涂法将Cr_(2)O_(3)涂覆于Al_(2)O_(3)陶瓷表面,通过高温烧结获得涂层陶瓷,并系统性地研究了Cr_(2)O_(3)涂层对样品的物质成分、微观形貌、二次电子发射系数、表面电阻率和真空沿面耐压性能的影响。结果表明:涂层陶瓷表面呈红黑色,其为Al_(2)O_(3)-Cr_(2)O_(3)固溶体、Mg Al_(2)O_(4)和Cr_(2)O_(3)三种物质的混合物。相较于Al_(2)O_(3)陶瓷,涂层表面晶粒和孔洞的尺寸均较小,其晶粒尺寸均匀性也有明显提升。高温烧结后,Al、Cr两种元素相互扩散,并且涂层中有少量从陶瓷基体迁移而来的玻璃相。高温烧结的Cr_(2)O_(3)涂层将Al_(2)O_(3)陶瓷的二次电子发射系数减小至3.22,将表面电阻率减小至4.52×10^(11)Ω,将真空沿面耐压强度增大至34.44 k V/cm,此值较Al_(2)O_(3)陶瓷提高了约108%。展开更多
文摘AA female broilers were used to examine the effect of high temperature and β-agonist Clenbuterol (CL) on performance, carcass composition, efficiency of the deposition of energy and protein in diet, carcass characteristics and meat quality. The trial was 2×2 factorial design with four replicates. Experimental period was last for 24 days from 29 to 52 days after birth. There were four groups in the trial: normal temperature with no CL, nomal temperature with CL, high temperature with no CL and high temperature with CL. The normal terperature was 22±1℃, high temperature was 32±1℃. The lever of CL was administred at 3mg·kg -1 feed. There were three days withdrawal of CL before the end of the trial. The results showed that: (1) High temperature had a significantly negative influence on performance. Where feed intake, daily weight gain and feed efficiency were significantly reduced so that daily feed intake and daily weight gain reduced by 12.6% (P<0.01) and 14.4% (P<0.01), respectively. Feed/gain ratio increased by 1.9% (P<0.05). (2) At high temperature, body protein and water content decreased by 9.4% (P<0.05) and by 2.0% (P<0.05), respectively. Body fat content increased 12.4% (P<0.01). (3) Abdorminal fat significantly increased (P<0.01) at high temperature, compared with that at the normal temperature, where carcass fat ratio and abdominal fat ratio increase 5.8% and 26.4%, respectively. (4) In this trial, CL reduced feed intake significantly (P<0.01) by 6.6% and 5.1% at the normal and high temperature during the whole test period, respectively. CL had no significant influence on daily weight gain (P>0.05), but reduced feed/gain ratio by 5.0% and 5.3% at normal and high temperature, respectively. (5) Carcass analysis indicated that the CL-fed birds had a significantly higher carcass protein content (P<0.01) and lower carcass fat content (P<0.01), where body protein content increased 4.4% and 12.7% and body fat content reduced 16.0% and 17.1% for the normal and high temperature, respectively. (6) Carcass characteristics indicated that CL reduced skin fat ratio by 7.6% (P<0.01) and abdominal fat ratio 8.5% (P<0.01) at the normal temperature; at high temperature, reduced by 14% and 24%, respectively. CL increased breast musle ratio by 14.1% and 3.2%, and increased leg muscle ratio 5.2% and 3.2% at the normal and high temperature, respectively. (7) CL had no negative influence on meat quality. (8) High temperature did not change the function of CL to increase protein deposition and reduce fat deposition.
文摘During high-speed flight,both thermal and mechani-cal loads can degrade the electrical performance of the antenna-radome system,which can subsequently affect the performance of the guidance system.This paper presents a method for evalu-ating the electrical performance of the radome when subjected to thermo-mechanical-electrical(TME)coupling.The method involves establishing a TME coupling model(TME-CM)based on the TME sharing mesh model(TME-SMM)generated by the tetrahedral mesh partitioning of the radome structure.The effects of dielectric temperature drift and structural deformation on the radome’s electrical performance are also considered.Firstly,the temperature field of the radome is obtained by tran-sient thermal analysis while the deformation field of the radome is obtained by static analysis.Subsequently,the dielectric varia-tion and structural deformation of the radome are accurately incorporated into the electrical simulation model based on the TME-SMM.The three-dimensional(3D)ray tracing method with the aperture integration technique is used to calculate the radome’s electrical performance.A representative example is provided to illustrate the superiority and necessity of the pro-posed method.This is achieved by calculating and analyzing the changes in the radome’s electrical performance over time dur-ing high-speed flight.
基金Project supported by National Natural Science Foundation of China （51177101）
文摘CF3I has been widely considered as a potential alternative for SF6,because it has low global warming potential(GWP)but an insulation capability that is 1.2 times greater than that of SF6.In this paper,the electron swarm parameters of CF3I and its gas mixture with N2,including the effective ionization coefficient and electron drift velocity,are examined theoretically through the Boltzmann equation method in the condition of steady-state Townsend(SST)experiments.Based on the derived data of the limiting field strength of CF3I-N2gas mixture,taking into consideration of environmental aspects such as GWP,ozone depletion potential(ODP),liquefaction temperature and toxicity,we studied the possibility of applying the gas mixture as the insulation medium in gas-insulated switchgears(GIS)or cubic type gas-insulated switchgears(C-GIS).It is found that CF3I-N2gas mixtures contained 30%～70%CF3I perform comprehensively better than pure SF6and compressed N2,and especially in medium and low voltage environments,the boiling point of CF3I-N2gas mixture meets the domestic and global requirements in mid-low latitude regions.Therefore we conclude that the gas mixture is acceptable for replacing SF6as the insulation medium in C-GISs.
文摘为了研究高温和应变率对超高性能混凝土(UHPC)劈裂抗拉性能的影响,对不同温度(20、105、200、300、400℃)作用后UHPC的质量损失率、抗压强度、弹性模量、静态和动态(应变率为1.8~6.8 s^(-1))劈裂抗拉强度进行了测试.结果表明:以2~10℃/min的加热速率升温至400℃后,所有试件均在保温期间发生爆裂性剥落;U H P C的抗压强度、弹性模量、静态劈裂抗拉强度均随温度增大而提高,300℃作用后比常温时分别提高了13.2%、19.1%和17.3%;动态劈裂抗拉强度和耗散能均具有明显的应变率效应,当应变率从1.8~2.2 s^(-1)增加到6.3~6.8 s^(-1)时,20~300℃作用后的UHPC动态劈裂抗拉强度和耗散能分别提高了69.1%~74.1%和146.7%~177.6%;高温作用后UHPC中C-S-H表面的吸附水、孔隙内自由水和凝胶结合水先后分解,增大了试件的质量损失率;基体内高温和高压环境促进了水泥水化反应和硅灰火山灰反应,提升了UHPC的致密程度,增强了钢纤维的桥连作用;在冲击荷载作用下,基体开裂速度的加快和由钢纤维拔出所致基体摩擦效应的增强导致耗散能增大.
文摘利用浸涂法将Cr_(2)O_(3)涂覆于Al_(2)O_(3)陶瓷表面,通过高温烧结获得涂层陶瓷,并系统性地研究了Cr_(2)O_(3)涂层对样品的物质成分、微观形貌、二次电子发射系数、表面电阻率和真空沿面耐压性能的影响。结果表明:涂层陶瓷表面呈红黑色,其为Al_(2)O_(3)-Cr_(2)O_(3)固溶体、Mg Al_(2)O_(4)和Cr_(2)O_(3)三种物质的混合物。相较于Al_(2)O_(3)陶瓷,涂层表面晶粒和孔洞的尺寸均较小,其晶粒尺寸均匀性也有明显提升。高温烧结后,Al、Cr两种元素相互扩散,并且涂层中有少量从陶瓷基体迁移而来的玻璃相。高温烧结的Cr_(2)O_(3)涂层将Al_(2)O_(3)陶瓷的二次电子发射系数减小至3.22,将表面电阻率减小至4.52×10^(11)Ω,将真空沿面耐压强度增大至34.44 k V/cm,此值较Al_(2)O_(3)陶瓷提高了约108%。
