为提高射频识别(Radio frequency identification,RFID)标签的识别效率,本文针对RFID动态帧时隙ALOHA防冲突系统,提出了新的标签估计方法和帧长确定方案.标签估计中采用了不同的贝叶斯代价函数,提出了几种贝叶斯标签估计方法,它们的估...为提高射频识别(Radio frequency identification,RFID)标签的识别效率,本文针对RFID动态帧时隙ALOHA防冲突系统,提出了新的标签估计方法和帧长确定方案.标签估计中采用了不同的贝叶斯代价函数,提出了几种贝叶斯标签估计方法,它们的估计结果准确,而且通过减小标签数取值范围可使计算复杂度得到降低.随后,推导出一种根据标签数确定最优帧长的方案,它能使系统达到最大的信道利用率,该最大信道利用率要大于帧的时隙数等于标签数时所能达到的最大利用率.展开更多
Radio frequency identification(RFID) is a new type of non-contact automatic identification technology.Due to its low energy consumption,low cost,and its adaptability to harsh environments,it has been applied to many f...Radio frequency identification(RFID) is a new type of non-contact automatic identification technology.Due to its low energy consumption,low cost,and its adaptability to harsh environments,it has been applied to many fields.In the RFID systems,data collision is inevitable when the reader sends a communication request and multiple tags respond with simultaneous data transmission.Data collision is prone to causing problems such as:identification delay,spectrum resource waste,a decreased system throughput rate,etc.Therefore,an efficient,stable anti-collision protocol is crucial for RFID systems.This research analysed the current research into RFID anticollision protocols and summarised means for its improvement through the mechanism of implementation of different types anticollision protocols.Finally,a new direction is proposed for the future development of RFID anti-collision protocol systems.展开更多
There is increasing public concern about biological interactions with and the potential health effects of low frequency electric and magnetic fields. Recently, the ICNIRP （International Commission on Non-Ionizing Rad...There is increasing public concern about biological interactions with and the potential health effects of low frequency electric and magnetic fields. Recently, the ICNIRP （International Commission on Non-Ionizing Radiation Protection） has published new exposure guidelines with regard to these fields. The aim of this paper is to demonstrate the calculation of the currents and electric fields induced in the human body by external electric fields at 60 Hz, using numerical human models of anatomically-realistic human bodies, and to compare those results with the basic restrictions proposed by the new guidelines. As a result, in the case that a human is exposed to an electric field of 1 kV/m at 60 Hz the short-circuit current of 18 μA flows though the ankles. Furthermore, the electric field of 40 mV/m in the nervous tissue of the adult model is induced by exposure to external electric fields at the reference level, which is enough smaller than the basic restrictions established in the ICNIRP guidelines for occupational exposure.展开更多
文摘为提高射频识别(Radio frequency identification,RFID)标签的识别效率,本文针对RFID动态帧时隙ALOHA防冲突系统,提出了新的标签估计方法和帧长确定方案.标签估计中采用了不同的贝叶斯代价函数,提出了几种贝叶斯标签估计方法,它们的估计结果准确,而且通过减小标签数取值范围可使计算复杂度得到降低.随后,推导出一种根据标签数确定最优帧长的方案,它能使系统达到最大的信道利用率,该最大信道利用率要大于帧的时隙数等于标签数时所能达到的最大利用率.
基金The authors would like to thank the reviewers for their detailed reviews and constructive comments, which have helped improve the quality of this paper. This paper is supported by the National Natural Science Founda- tion of China （No. 61371092）, the Doctoral Fund of Ministry of Education of China （No.20130061120062）, and the China Postdoc- toral Science Foundation （No. 2014M551184）.
文摘Radio frequency identification(RFID) is a new type of non-contact automatic identification technology.Due to its low energy consumption,low cost,and its adaptability to harsh environments,it has been applied to many fields.In the RFID systems,data collision is inevitable when the reader sends a communication request and multiple tags respond with simultaneous data transmission.Data collision is prone to causing problems such as:identification delay,spectrum resource waste,a decreased system throughput rate,etc.Therefore,an efficient,stable anti-collision protocol is crucial for RFID systems.This research analysed the current research into RFID anticollision protocols and summarised means for its improvement through the mechanism of implementation of different types anticollision protocols.Finally,a new direction is proposed for the future development of RFID anti-collision protocol systems.
文摘There is increasing public concern about biological interactions with and the potential health effects of low frequency electric and magnetic fields. Recently, the ICNIRP （International Commission on Non-Ionizing Radiation Protection） has published new exposure guidelines with regard to these fields. The aim of this paper is to demonstrate the calculation of the currents and electric fields induced in the human body by external electric fields at 60 Hz, using numerical human models of anatomically-realistic human bodies, and to compare those results with the basic restrictions proposed by the new guidelines. As a result, in the case that a human is exposed to an electric field of 1 kV/m at 60 Hz the short-circuit current of 18 μA flows though the ankles. Furthermore, the electric field of 40 mV/m in the nervous tissue of the adult model is induced by exposure to external electric fields at the reference level, which is enough smaller than the basic restrictions established in the ICNIRP guidelines for occupational exposure.
