The paper deals with the power quality analysis of interlaced four quadrant (4Q) converters with constant switching frequency. These are in fact the input stages of the locomotives and high speed trains supplied by 25...The paper deals with the power quality analysis of interlaced four quadrant (4Q) converters with constant switching frequency. These are in fact the input stages of the locomotives and high speed trains supplied by 25 kV, 50 Hz and 15 kV, 16.7 Hz lines. Due to the high power needed for the trains circulation, the 4Q converter can absorb distorted currents, whose harmonic content can affect the signaling systems and communication devices. The presence of more converters gives the opportunity, using dedicated commutation strategy, to interlace them in order to reduce the harmonic content in the absorbed current. In the paper a suitable model of more 4Q converters is developed. The control logic implemented in the model allows the evaluation of the harmonic contribution of both single converter and the interlaced configuration. The analysis is carried out through electromagnetic transient simulations.展开更多
采用熔盐顶部籽晶法从K 2 Mo 3 O 10-B 2 O 3助熔剂中生长出尺寸为20 mm的优质GdAl 3(BO 3)4(简称GAB)和Nd^3+激活的自变频激光晶体。确定了GAB晶体的透光波长范围、折射率和倍频系数随波长的变化,结果表明其在整个透光范围内均可实现...采用熔盐顶部籽晶法从K 2 Mo 3 O 10-B 2 O 3助熔剂中生长出尺寸为20 mm的优质GdAl 3(BO 3)4(简称GAB)和Nd^3+激活的自变频激光晶体。确定了GAB晶体的透光波长范围、折射率和倍频系数随波长的变化,结果表明其在整个透光范围内均可实现相位匹配。测定了Nd^3+∶GAB晶体在室温下的偏振吸收、荧光光谱和荧光寿命,进行了光谱计算,测试了晶体的自变频激光性能,实现了紫外-可见光-红外-中红外多波段激光输出。展开更多
Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)seems to employ two routes of entrance to the host cell;via membrane fusion(with the cells expressing both angiotensin converting enzyme 2(ACE2)and transmembr...Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)seems to employ two routes of entrance to the host cell;via membrane fusion(with the cells expressing both angiotensin converting enzyme 2(ACE2)and transmembrane peptidase/serine subfamily member 2/4(TMPRSS2/4))or via receptor-mediated endocytosis(to the target cells expressing only ACE2).The second mode is associated with cysteine cathepsins(probably cathepsin L)involvement in the virus spike protein(S protein)proteolytic activation.Also furin might activate the virus S protein enabling it to enter cells.Gastrointestinal tract(GIT)involvement in SARS-CoV-2 infection is evident in a subset of coronavirus disease 2019(COVID-19)patients exhibiting GIT symptoms,such as diarrhea,and presenting viral-shedding in feces.Considering the abundance and co-localization of ACE2 and TMPRSS2 in the lower GIT(especially brush-border enterocytes),these two receptors seem to be mainly involved in SARS-CoV-2 invasion of the digestive tract.Additionally,in vitro studies have demonstrated the virions capability of infection and replication in the human epithelial cells lining GIT.However,also furin and cysteine cathepsins(cathepsin L)might participate in the activation of SARS-CoV-2 spike protein contributing to the virus invasiveness within GIT.Moreover,cathepsin L(due to its involvement in extracellular matrix components degradation and remodeling,the processes enhanced during SARS-CoV-2-induced inflammation)might be responsible for the dysregulation of absorption/digestion functions of GIT,thus adding to the observed in some COVID-19 patients symptoms such as diarrhea.展开更多
High-efficiency single crystal cascaded third-harmonic generation(THG)was realized inβ-BaB_(2)O_(4)(BBO)material with special cut-angle.By analyzing effective nonlinear optical coefficient(d_(eff))of the cascaded THG...High-efficiency single crystal cascaded third-harmonic generation(THG)was realized inβ-BaB_(2)O_(4)(BBO)material with special cut-angle.By analyzing effective nonlinear optical coefficient(d_(eff))of the cascaded THG process,which was composed by type-II frequency doubling and type-I sum-frequency,the optimum phase matching(PM)direction in BBO crystal was determined to be(θ=32.1°,φ=11°).With an optimized 9-mm long sample which was processed along this direction,the highest cascaded THG conversion efficiency reached 42.3%,which is much superior to the similar components reported previously,including ADP,KDP,and Gd_(x)Y_(1-x)COB crystals.展开更多
文摘The paper deals with the power quality analysis of interlaced four quadrant (4Q) converters with constant switching frequency. These are in fact the input stages of the locomotives and high speed trains supplied by 25 kV, 50 Hz and 15 kV, 16.7 Hz lines. Due to the high power needed for the trains circulation, the 4Q converter can absorb distorted currents, whose harmonic content can affect the signaling systems and communication devices. The presence of more converters gives the opportunity, using dedicated commutation strategy, to interlace them in order to reduce the harmonic content in the absorbed current. In the paper a suitable model of more 4Q converters is developed. The control logic implemented in the model allows the evaluation of the harmonic contribution of both single converter and the interlaced configuration. The analysis is carried out through electromagnetic transient simulations.
文摘采用熔盐顶部籽晶法从K 2 Mo 3 O 10-B 2 O 3助熔剂中生长出尺寸为20 mm的优质GdAl 3(BO 3)4(简称GAB)和Nd^3+激活的自变频激光晶体。确定了GAB晶体的透光波长范围、折射率和倍频系数随波长的变化,结果表明其在整个透光范围内均可实现相位匹配。测定了Nd^3+∶GAB晶体在室温下的偏振吸收、荧光光谱和荧光寿命,进行了光谱计算,测试了晶体的自变频激光性能,实现了紫外-可见光-红外-中红外多波段激光输出。
文摘Severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)seems to employ two routes of entrance to the host cell;via membrane fusion(with the cells expressing both angiotensin converting enzyme 2(ACE2)and transmembrane peptidase/serine subfamily member 2/4(TMPRSS2/4))or via receptor-mediated endocytosis(to the target cells expressing only ACE2).The second mode is associated with cysteine cathepsins(probably cathepsin L)involvement in the virus spike protein(S protein)proteolytic activation.Also furin might activate the virus S protein enabling it to enter cells.Gastrointestinal tract(GIT)involvement in SARS-CoV-2 infection is evident in a subset of coronavirus disease 2019(COVID-19)patients exhibiting GIT symptoms,such as diarrhea,and presenting viral-shedding in feces.Considering the abundance and co-localization of ACE2 and TMPRSS2 in the lower GIT(especially brush-border enterocytes),these two receptors seem to be mainly involved in SARS-CoV-2 invasion of the digestive tract.Additionally,in vitro studies have demonstrated the virions capability of infection and replication in the human epithelial cells lining GIT.However,also furin and cysteine cathepsins(cathepsin L)might participate in the activation of SARS-CoV-2 spike protein contributing to the virus invasiveness within GIT.Moreover,cathepsin L(due to its involvement in extracellular matrix components degradation and remodeling,the processes enhanced during SARS-CoV-2-induced inflammation)might be responsible for the dysregulation of absorption/digestion functions of GIT,thus adding to the observed in some COVID-19 patients symptoms such as diarrhea.
基金Project supported by the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2017MF031 and ZR2018BF029)
文摘High-efficiency single crystal cascaded third-harmonic generation(THG)was realized inβ-BaB_(2)O_(4)(BBO)material with special cut-angle.By analyzing effective nonlinear optical coefficient(d_(eff))of the cascaded THG process,which was composed by type-II frequency doubling and type-I sum-frequency,the optimum phase matching(PM)direction in BBO crystal was determined to be(θ=32.1°,φ=11°).With an optimized 9-mm long sample which was processed along this direction,the highest cascaded THG conversion efficiency reached 42.3%,which is much superior to the similar components reported previously,including ADP,KDP,and Gd_(x)Y_(1-x)COB crystals.
