Guided by molecular networking,nine novel curvularin derivatives(1-9)and 16 known analogs(10-25)were isolated from the hydrothermal vent sediment fungus Penicillium sp.HL-50.Notably,compounds 5-7 represented a hybrid ...Guided by molecular networking,nine novel curvularin derivatives(1-9)and 16 known analogs(10-25)were isolated from the hydrothermal vent sediment fungus Penicillium sp.HL-50.Notably,compounds 5-7 represented a hybrid of curvularin and purine.The structures and absolute configurations of compounds 1-9 were elucidated via nuclear magnetic resonance(NMR)spectroscopy,X-ray diffraction,electronic circular dichroism(ECD)calculations,^(13)C NMR calculation,modified Mosher's method,and chemical derivatization.Investigation of anti-inflammatory activities revealed that compounds 7-9,11,12,14,15,and 18 exhibited significant suppressive effects against lipopolysaccharide(LPS)-induced nitric oxide(NO)production in murine macrophage RAW264.7 cells,with IC_(50)values ranging from 0.44 to 4.40μmol·L^(-1).Furthermore,these bioactive compounds were found to suppress the expression of inflammation-related proteins,including inducible NO synthase(i NOS),cyclooxygenase-2(COX-2),NLR family pyrin domain-containing protein 3(NLRP3),and nuclear factor kappa-B(NF-κB).Additional studies demonstrated that the novel compound 7 possessed potent antiinflammatory activity by inhibiting the transcription of inflammation-related genes,downregulating the expression of inflammation-related proteins,and inhibiting the release of inflammatory cytokines,indicating its potential application in the treatment of inflammatory diseases.展开更多
基波等效法是无线电能传输(wireless power transfer,WPT)技术的主要研究方法,该方法将整流性负载的基波阻抗等效为某一纯电阻,为系统的建模和分析提供基础。但该方法忽略整流性负载谐波阻抗的影响,使WPT系统的实际响应与理论分析结果...基波等效法是无线电能传输(wireless power transfer,WPT)技术的主要研究方法,该方法将整流性负载的基波阻抗等效为某一纯电阻,为系统的建模和分析提供基础。但该方法忽略整流性负载谐波阻抗的影响,使WPT系统的实际响应与理论分析结果存在较大的误差,从而影响系统的模型精度,限制WPT系统的进一步优化设计。该文以基于串/串并(series/series-parallel,S/SP)补偿网络的WPT系统为研究对象,分析利用基波等效法进行建模产生误差的原因,并提出一种基于迭代法的整流性负载基波以及各次谐波等效阻抗的精确计算方法。在此基础上,建立WPT系统的精确电路响应模型,所提模型可以有效表征发射线圈电流的畸变特性,并根据系统响应与补偿网络参数的关系获得系统逆变器开关损耗的优化设计方法。最后,搭建一台3kW的WPT系统样机,实验结果验证理论分析的正确性和可行性。展开更多
针对感应式电能传输(inductive power transfer,IPT)系统偏移造成输出电压不稳定和效率低下的问题,提出一种强抗偏移的S/SP补偿IPT系统,该系统在变耦合变自感和变耦合不变自感两种情况下均能保证较小的输出电压波动和较高的传输效率。首...针对感应式电能传输(inductive power transfer,IPT)系统偏移造成输出电压不稳定和效率低下的问题,提出一种强抗偏移的S/SP补偿IPT系统,该系统在变耦合变自感和变耦合不变自感两种情况下均能保证较小的输出电压波动和较高的传输效率。首先,基于Maxwell有限元仿真,分析罐型磁心松耦合变压器的磁通分布和磁场分布特性,总结不同方向偏移的参数变化规律。然后,提出一种提高系统抗偏移能力的S/SP补偿参数设计方法,得到相应的磁耦合机构设计准则,并结合磁仿真数据,通过数值计算方式求得系统输出波动和输入阻抗角的变化规律。最后,通过实验验证文中采用罐型磁心和新型S/SP补偿拓扑实现多方向偏移下高效率、低波动无线电能传输的可行性。在额定负载下,系统沿纵向和水平方向偏移的输出电压波动分别为2.7%和3.1%,传输效率维持在90.8%~94.3%。展开更多
In orthogonal frequency division multiplexing(OFDM)based multihop communications,the conventional decodeand-forward(DF)relay scheme severely suffers from the error propagation problem.This drawback is serious in multi...In orthogonal frequency division multiplexing(OFDM)based multihop communications,the conventional decodeand-forward(DF)relay scheme severely suffers from the error propagation problem.This drawback is serious in multihop networks as errors made by any relay node may fail the decoder at the destination in great chance.In this paper,we propose a bit error rate(BER)modified DF protocol(BMDF)which can be applied to systems where error correction channel coding and M-ary modulation are used.By modeling all links except the last one as a binary symmetric channel(BSC),we derive a log likelihood ratio(LLR)modification function relying only on the accumulated BER of all previous links to be applied to the output of the soft demapper.Furthermore,to reduce the computational complexity and signaling overhead,the modification function is simplified from its original exponential expression and less BERs are delivered between nodes by making successive subcarriers share the same BER.In addition,for situations where the channel state information(CSI)of forward link is available,the proposed BMDF can be further enhanced by combining with subcarrier pairing(SP)and power allocation(PA),where a sorted-channel gain SP scheme and a greedy PA algorithm are proposed.The simulation results verify thesignificant performance improvement to the conventional DF.展开更多
该文将移动Ad Hoc网络多播路由协议作为主要研究内容——基于树的多播路由协议MAODV(Multicast Ad Hoc On-De-mand Distance Vector Routing Protocol)。针对目前MAODV协议存在可扩展性、健壮性差的问题,该文提出了一种新的优化改进协议...该文将移动Ad Hoc网络多播路由协议作为主要研究内容——基于树的多播路由协议MAODV(Multicast Ad Hoc On-De-mand Distance Vector Routing Protocol)。针对目前MAODV协议存在可扩展性、健壮性差的问题,该文提出了一种新的优化改进协议MAODV-SP(MAODV With Stable Path),主要从两个方面对MAODV协议进行了扩展改进。首先在多播树建立方面,MAODV-SP协议采用了基于邻居变化率稳定路径选择机制,根据不同路径上各节点的邻居变化率累乘值,选择转发跳数小且局部拓扑变化小的稳定路径进行数据转发。其次在多播树维护方面,MAODV-SP协议采用了基于链路状态预测链路可用性机制,对节点的移动性和链路状况进行预测,在预测到链路断链即将发生之前,重新选择一条新的有效路由转发分组,使网络的性能达到最优。展开更多
A wideband 2×2 sequential-phase fed circularly polarized(CP)microstrip antenna array(MAA)with sequentially rotated elements is proposed.Firstly,the antenna element loaded with shorting pins is studied as compared...A wideband 2×2 sequential-phase fed circularly polarized(CP)microstrip antenna array(MAA)with sequentially rotated elements is proposed.Firstly,the antenna element loaded with shorting pins is studied as compared to the traditional counterpart.Then,a feeding network is designed to be connected together in a sequential rotation manner,resulting in forming a four-port network to allow symmetrical positioning of CP microstrip patch elements.After that,straight strips are added to the feeding network in order to increase the distance and reduce coupling between array elements.They also play a role in improving the impedance matching of the array.Finally,the proposed antenna array is designed and simulated.The results are presented that its impedance bandwidth is about 36.3%at 24.1~34.8 GHz for|S_(11)|<10 dB and axial-ratio(AR)bandwidth is about 20.4%at 24.2~29.7 GHz for AR【3 dB.Besides,a peak gain of 11.1 dBic is simulated over the operating frequency range,which is significantly improved compared to the classic and existing works.展开更多
基金funded by the National Key Research and Development Program of China(No.2022YFC2804101)the Guangdong Provincial Key R&D Program(No.2023B1111050011)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515010432)the Guangzhou Basic and Applied Basic Research Foundation(No.202201010305)the High-Level Talents Special Program of Zhejiang(No.2022R52036)。
文摘Guided by molecular networking,nine novel curvularin derivatives(1-9)and 16 known analogs(10-25)were isolated from the hydrothermal vent sediment fungus Penicillium sp.HL-50.Notably,compounds 5-7 represented a hybrid of curvularin and purine.The structures and absolute configurations of compounds 1-9 were elucidated via nuclear magnetic resonance(NMR)spectroscopy,X-ray diffraction,electronic circular dichroism(ECD)calculations,^(13)C NMR calculation,modified Mosher's method,and chemical derivatization.Investigation of anti-inflammatory activities revealed that compounds 7-9,11,12,14,15,and 18 exhibited significant suppressive effects against lipopolysaccharide(LPS)-induced nitric oxide(NO)production in murine macrophage RAW264.7 cells,with IC_(50)values ranging from 0.44 to 4.40μmol·L^(-1).Furthermore,these bioactive compounds were found to suppress the expression of inflammation-related proteins,including inducible NO synthase(i NOS),cyclooxygenase-2(COX-2),NLR family pyrin domain-containing protein 3(NLRP3),and nuclear factor kappa-B(NF-κB).Additional studies demonstrated that the novel compound 7 possessed potent antiinflammatory activity by inhibiting the transcription of inflammation-related genes,downregulating the expression of inflammation-related proteins,and inhibiting the release of inflammatory cytokines,indicating its potential application in the treatment of inflammatory diseases.
文摘基波等效法是无线电能传输(wireless power transfer,WPT)技术的主要研究方法,该方法将整流性负载的基波阻抗等效为某一纯电阻,为系统的建模和分析提供基础。但该方法忽略整流性负载谐波阻抗的影响,使WPT系统的实际响应与理论分析结果存在较大的误差,从而影响系统的模型精度,限制WPT系统的进一步优化设计。该文以基于串/串并(series/series-parallel,S/SP)补偿网络的WPT系统为研究对象,分析利用基波等效法进行建模产生误差的原因,并提出一种基于迭代法的整流性负载基波以及各次谐波等效阻抗的精确计算方法。在此基础上,建立WPT系统的精确电路响应模型,所提模型可以有效表征发射线圈电流的畸变特性,并根据系统响应与补偿网络参数的关系获得系统逆变器开关损耗的优化设计方法。最后,搭建一台3kW的WPT系统样机,实验结果验证理论分析的正确性和可行性。
文摘针对感应式电能传输(inductive power transfer,IPT)系统偏移造成输出电压不稳定和效率低下的问题,提出一种强抗偏移的S/SP补偿IPT系统,该系统在变耦合变自感和变耦合不变自感两种情况下均能保证较小的输出电压波动和较高的传输效率。首先,基于Maxwell有限元仿真,分析罐型磁心松耦合变压器的磁通分布和磁场分布特性,总结不同方向偏移的参数变化规律。然后,提出一种提高系统抗偏移能力的S/SP补偿参数设计方法,得到相应的磁耦合机构设计准则,并结合磁仿真数据,通过数值计算方式求得系统输出波动和输入阻抗角的变化规律。最后,通过实验验证文中采用罐型磁心和新型S/SP补偿拓扑实现多方向偏移下高效率、低波动无线电能传输的可行性。在额定负载下,系统沿纵向和水平方向偏移的输出电压波动分别为2.7%和3.1%,传输效率维持在90.8%~94.3%。
基金The authors would like to thank National Natural Science Foundation of China(No.61072059).
文摘In orthogonal frequency division multiplexing(OFDM)based multihop communications,the conventional decodeand-forward(DF)relay scheme severely suffers from the error propagation problem.This drawback is serious in multihop networks as errors made by any relay node may fail the decoder at the destination in great chance.In this paper,we propose a bit error rate(BER)modified DF protocol(BMDF)which can be applied to systems where error correction channel coding and M-ary modulation are used.By modeling all links except the last one as a binary symmetric channel(BSC),we derive a log likelihood ratio(LLR)modification function relying only on the accumulated BER of all previous links to be applied to the output of the soft demapper.Furthermore,to reduce the computational complexity and signaling overhead,the modification function is simplified from its original exponential expression and less BERs are delivered between nodes by making successive subcarriers share the same BER.In addition,for situations where the channel state information(CSI)of forward link is available,the proposed BMDF can be further enhanced by combining with subcarrier pairing(SP)and power allocation(PA),where a sorted-channel gain SP scheme and a greedy PA algorithm are proposed.The simulation results verify thesignificant performance improvement to the conventional DF.
文摘该文将移动Ad Hoc网络多播路由协议作为主要研究内容——基于树的多播路由协议MAODV(Multicast Ad Hoc On-De-mand Distance Vector Routing Protocol)。针对目前MAODV协议存在可扩展性、健壮性差的问题,该文提出了一种新的优化改进协议MAODV-SP(MAODV With Stable Path),主要从两个方面对MAODV协议进行了扩展改进。首先在多播树建立方面,MAODV-SP协议采用了基于邻居变化率稳定路径选择机制,根据不同路径上各节点的邻居变化率累乘值,选择转发跳数小且局部拓扑变化小的稳定路径进行数据转发。其次在多播树维护方面,MAODV-SP协议采用了基于链路状态预测链路可用性机制,对节点的移动性和链路状况进行预测,在预测到链路断链即将发生之前,重新选择一条新的有效路由转发分组,使网络的性能达到最优。
基金This work was supported by National Natural Science Foundation of China under Grant Nos.61801348 and 61971475University of Macao under Grant Nos.MYRG2017-00007-FST,MYRG2018-00073-FST,and CPG2020-00003-FSTState Key Laboratory of Millimeter Waves under Contract K202031.
文摘A wideband 2×2 sequential-phase fed circularly polarized(CP)microstrip antenna array(MAA)with sequentially rotated elements is proposed.Firstly,the antenna element loaded with shorting pins is studied as compared to the traditional counterpart.Then,a feeding network is designed to be connected together in a sequential rotation manner,resulting in forming a four-port network to allow symmetrical positioning of CP microstrip patch elements.After that,straight strips are added to the feeding network in order to increase the distance and reduce coupling between array elements.They also play a role in improving the impedance matching of the array.Finally,the proposed antenna array is designed and simulated.The results are presented that its impedance bandwidth is about 36.3%at 24.1~34.8 GHz for|S_(11)|<10 dB and axial-ratio(AR)bandwidth is about 20.4%at 24.2~29.7 GHz for AR【3 dB.Besides,a peak gain of 11.1 dBic is simulated over the operating frequency range,which is significantly improved compared to the classic and existing works.
