针对Alamouti空时块编码复用增益损失的问题,提出了两组Alamouti编码方案。在此基础上,为了改善系统的误码率(BER)性能和简化接收端复杂度,提出了将几何均值分解(GMD)算法和非线性预编码技术相结合的两组Alamouti传输方案。该方案的设...针对Alamouti空时块编码复用增益损失的问题,提出了两组Alamouti编码方案。在此基础上,为了改善系统的误码率(BER)性能和简化接收端复杂度,提出了将几何均值分解(GMD)算法和非线性预编码技术相结合的两组Alamouti传输方案。该方案的设计方法为:首先等效出两组Alamouti空时块编码系统的信道矩阵;进而,通过GMD算法对等效信道矩阵进行收发端联合设计;最后,在发射端应用脏纸(dirty paper coding,DPC)和Tomlinson-Harashima precoding(THP)非线性预编码技术,消除发送信号间的干扰,从而使系统获得更好的误码率性能。通过仿真结果对比发现,提出的系统可以显著地改善误码率性能。展开更多
The impacts of channel morphology on the residues and ecological risks of 14 polychlorinated biphenyl(PCB) congeners in water and sediment were investigated in summer(July) and autumn(September) in the Chahe River,in ...The impacts of channel morphology on the residues and ecological risks of 14 polychlorinated biphenyl(PCB) congeners in water and sediment were investigated in summer(July) and autumn(September) in the Chahe River,in Nanjing,China.The residual concentrations of trichlorobiphenyls(tri-CBs,PCB 18) and tetra-CBs(PCB 52) in water were significantly higher than those of penta-CBs to deca-CBs,and the average residual concentration of ∑PCBs(sum of 14 PCB congeners) in summer was about six times higher than in autumn.However,the residues in sediment did not change significantly.Redundancy analysis(RDA) indicated that channel morphology and the corresponding environmental indices had significant impacts on PCB residues and their composition profiles in water and sediment.The overflow weir and lake-type watercourse may remarkably reduce the residual concentration and ecological risks of PCBs in water.The highest reduction percentages of the residual concentration and ecological risks of ∑PCBs induced by an overflow weir were 78%and 67%,respectively,and those induced by a lake-type watercourse were 36%and 70%,respectively.The watercourses with different channel morphologies were ranked by residual ∑PCBs concentrations in the following descending order:the natural ecological watercourse,vertical concrete watercourse,and vegetation-type riprap watercourse.However,they were ranked by residual ∑PCBs concentrations in sediment in the following descending order:the vertical concrete watercourse,vegetation-type riprap watercourse,and natural ecological watercourse.展开更多
Si-PIN photodetectors having features such as low cost,small size,low weight,low voltage,and low power consumption are widely used as radiation detectors in electronic personal dosimeters(EPDs).The technical parameter...Si-PIN photodetectors having features such as low cost,small size,low weight,low voltage,and low power consumption are widely used as radiation detectors in electronic personal dosimeters(EPDs).The technical parameters of EPDs based on the Si-PIN photodetectors include photon energy response(PER),angular response,inherent error,and dose rate linearity.Among them,PER is a key parameter for evaluation of EPD measurement accuracy.At present,owing to the limitations of volume,power consumption,and EPD cost,the PER is usually corrected by a combination of single-channel counting techniques and filtering material methods.However,the above-mentioned methods have problems such as poor PER and low measurement accuracy.To solve such problems,in this study,a 1024-channel spectrometry system using a Si-PIN photodetector was developed and fullspectrum measurement in the reference radiation fields was conducted for radiation protection.The measurement results using the few-channel spectroscopy dose method showed that the PER could be controlled within±14%and±2%under the conditions of two and three energy intervals,respectively,with different channel numbers.The PER measured at 0°angle of radiation incidence meets the-29%to+67%requirements of IEC 61526:2010.Meanwhile,the channel number and counts-to-dose conversion factors formed in the experiment can be integrated into an EPD.展开更多
文摘针对Alamouti空时块编码复用增益损失的问题,提出了两组Alamouti编码方案。在此基础上,为了改善系统的误码率(BER)性能和简化接收端复杂度,提出了将几何均值分解(GMD)算法和非线性预编码技术相结合的两组Alamouti传输方案。该方案的设计方法为:首先等效出两组Alamouti空时块编码系统的信道矩阵;进而,通过GMD算法对等效信道矩阵进行收发端联合设计;最后,在发射端应用脏纸(dirty paper coding,DPC)和Tomlinson-Harashima precoding(THP)非线性预编码技术,消除发送信号间的干扰,从而使系统获得更好的误码率性能。通过仿真结果对比发现,提出的系统可以显著地改善误码率性能。
基金supported by the National Natural Science Foundation of China(Grants No.41371307 and 51509129)the Open Foundation of State Key Laboratory of Pollution Control and Resource Reuse(Grant No.PCRRF12010)+2 种基金the State Key Laboratory of Soil and Sustainable Agriculture(Institute of Soil Science,Chinese Academy of Sciences)foundation(Grant No.0812201228)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Top-notch Academic Programs Project(TAPP)of Jiangsu Higher Education Institutions
文摘The impacts of channel morphology on the residues and ecological risks of 14 polychlorinated biphenyl(PCB) congeners in water and sediment were investigated in summer(July) and autumn(September) in the Chahe River,in Nanjing,China.The residual concentrations of trichlorobiphenyls(tri-CBs,PCB 18) and tetra-CBs(PCB 52) in water were significantly higher than those of penta-CBs to deca-CBs,and the average residual concentration of ∑PCBs(sum of 14 PCB congeners) in summer was about six times higher than in autumn.However,the residues in sediment did not change significantly.Redundancy analysis(RDA) indicated that channel morphology and the corresponding environmental indices had significant impacts on PCB residues and their composition profiles in water and sediment.The overflow weir and lake-type watercourse may remarkably reduce the residual concentration and ecological risks of PCBs in water.The highest reduction percentages of the residual concentration and ecological risks of ∑PCBs induced by an overflow weir were 78%and 67%,respectively,and those induced by a lake-type watercourse were 36%and 70%,respectively.The watercourses with different channel morphologies were ranked by residual ∑PCBs concentrations in the following descending order:the natural ecological watercourse,vertical concrete watercourse,and vegetation-type riprap watercourse.However,they were ranked by residual ∑PCBs concentrations in sediment in the following descending order:the vertical concrete watercourse,vegetation-type riprap watercourse,and natural ecological watercourse.
基金This work was partly supported by the National Key Scientific Instruments to Develop Dedicated Program(Nos.2013YQ090811 and 2016YFF0103800)the National Key Research and Development Program(No.2017YFF0211100).
文摘Si-PIN photodetectors having features such as low cost,small size,low weight,low voltage,and low power consumption are widely used as radiation detectors in electronic personal dosimeters(EPDs).The technical parameters of EPDs based on the Si-PIN photodetectors include photon energy response(PER),angular response,inherent error,and dose rate linearity.Among them,PER is a key parameter for evaluation of EPD measurement accuracy.At present,owing to the limitations of volume,power consumption,and EPD cost,the PER is usually corrected by a combination of single-channel counting techniques and filtering material methods.However,the above-mentioned methods have problems such as poor PER and low measurement accuracy.To solve such problems,in this study,a 1024-channel spectrometry system using a Si-PIN photodetector was developed and fullspectrum measurement in the reference radiation fields was conducted for radiation protection.The measurement results using the few-channel spectroscopy dose method showed that the PER could be controlled within±14%and±2%under the conditions of two and three energy intervals,respectively,with different channel numbers.The PER measured at 0°angle of radiation incidence meets the-29%to+67%requirements of IEC 61526:2010.Meanwhile,the channel number and counts-to-dose conversion factors formed in the experiment can be integrated into an EPD.
