The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） re...The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.展开更多
In this paper, we describe an improved adaptive partial response maximum likelihood （PRML） method combining modulation code tbr signal waveform modulation multi-level disc. This improved adaptive PRML method employs...In this paper, we describe an improved adaptive partial response maximum likelihood （PRML） method combining modulation code tbr signal waveform modulation multi-level disc. This improved adaptive PRML method employs partial response equalizer and adaptive viterbi detector combining modulation code. Compared with the traditional adaptive PRML detector, the improved PRML detector additionally employs illogical sequence detector and corrector. Illogical sequence detector and corrector can aw）id the appearance of illogical sequences effectively, which do not follow the law of modulation code for signal waveform modulation multi-level disc, and obtain the correct sequences. We implement the improved PRML detector using a DSP and an FPGA chip. The experimental results show good performance. The higher efficient and lower complexity can be obtained by using the improved PRML method than by using the previous PRML method. Meanwhile, resource utilization of the improved PRML detector is not changed, but the bit error rate （BER） is reduced by more than 20%.展开更多
A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previ...A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.展开更多
With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full wavefo...With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of ii kin, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11 16 kin, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an Ms6.1 earthquake.展开更多
Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been develop...Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been developed and have become known in the civil domain. In particular, the arrival of UWB—Ultra-Wideband technology allows the design of compact and low-cost radars with multiple fields of application. In this paper, we focus on road applications, such as driving assistance with the objective of increasing safety and reducing accidents. In classical UWB radar systems, Gaussian and monocycle pulses are commonly used. In previous works, original waveforms based on orthogonal functions (Hermite and Gegenbauer) were proposed. These provide a good spatial resolution, suitable for radar detection. Another advantage of these waveforms is their multiple access capability, due to their orthogonality. The aim of the study presented in this article is to compare simulation and experimental results obtained, especially for short-range anticollision radar application, using these waveforms in one part and Gaussian and monocycle pulses in the other part. The originality of this paper relies on the new approach. Indeed, this comparison study using these waveforms has never been done before. Finally, some examples of real experiments in a real road environment with different waveforms are presented and analysed.展开更多
实际地震波形观测表明,对于大陆结构相对简单的地壳中的地震而言,有一震相出现在P波和S波之间.一般在30～50km附近发育得较好,其能量主要集中在径向分量,而垂向分量的振幅相对径向要小,切向分量上的振幅很弱,且波形以低频为主,通常没有...实际地震波形观测表明,对于大陆结构相对简单的地壳中的地震而言,有一震相出现在P波和S波之间.一般在30～50km附近发育得较好,其能量主要集中在径向分量,而垂向分量的振幅相对径向要小,切向分量上的振幅很弱,且波形以低频为主,通常没有P波尖锐.在利用FK方法计算合成地震图的基础上,发现该震相是由S波入射到自由地表形成水平传播的P波(文献称为surface P wave,自由地表P波)或者包括S波入射到地表后形成的多次P波或其散射震相.由于该震相是由S波和P波之间耦合而形成,本文将其定义为sPL(s coupled into P)震相.理论波形研究表明,sPL相对直达P波的到时差对震中距离不敏感,而随着震源深度的增加几乎呈线性增加,因此可以很好的约束震源深度.本文以2005年江西九江地震为例,证实了sPL确定震源深度的可行性和可靠性.在观测到sPL震相的情况下,离震源50km以内的一个三分量地震台站的波形就可以帮助获得可靠的震源深度,而不需要精确的震中距离.由于sPL震相出现距离较近,对于较小(三级以上)的地震也可以应用,因此在稀疏台网布局情形下sPL对于确定中小地震深度应该具有很好的应用意义.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 60977005)
文摘The sub-land/sub-pit affects the characteristic of the tracking error signal which is generated by the conventional differential phase detection （DPD） method in the signal waveform modulation multi-level （SWML） read-only disc. To solve this problem, this paper proposes a new tracking error detection method using amplitude difference. Based on the diffraction theory, the amplitude difference is proportional to the tracking error and is feasible to be used for obtaining the off-track information. The experimental system of the amplitude difference detection method is developed. The experimental results show that the tracking error signal derived from the new method has better performance in uniformity and signal-to-noise ratio than that derived from the conventional DPD method in the SWML read-only disc.
基金Project supported by the National Natural Science Foundation of China(Grant No.61127010)
文摘In this paper, we describe an improved adaptive partial response maximum likelihood （PRML） method combining modulation code tbr signal waveform modulation multi-level disc. This improved adaptive PRML method employs partial response equalizer and adaptive viterbi detector combining modulation code. Compared with the traditional adaptive PRML detector, the improved PRML detector additionally employs illogical sequence detector and corrector. Illogical sequence detector and corrector can aw）id the appearance of illogical sequences effectively, which do not follow the law of modulation code for signal waveform modulation multi-level disc, and obtain the correct sequences. We implement the improved PRML detector using a DSP and an FPGA chip. The experimental results show good performance. The higher efficient and lower complexity can be obtained by using the improved PRML method than by using the previous PRML method. Meanwhile, resource utilization of the improved PRML detector is not changed, but the bit error rate （BER） is reduced by more than 20%.
文摘A novel read channel for signal waveform modulation multi-level disc is presented in this paper. This read channel employs timing recovery system and partial response maximum likelihood detector. Compared to the previous read channel composed of level detection and run-length detection, the present read channel shows superiority in capacity increase and robust performance. Especially, relying on the partial response maximum likelihood detection, lower bit error rate can be obtained.
基金financial supported by Joint Seismological Science Foundation of China (No.200808078)National Natural Science Foundation of China (Nos.40821160549 and 41074032)
文摘With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of ii kin, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11 16 kin, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an Ms6.1 earthquake.
文摘Radars and their applications were, for a long time, reserved to national defense, air security or weather service domains. For a few years, with the emergence of new technologies, radar applications have been developed and have become known in the civil domain. In particular, the arrival of UWB—Ultra-Wideband technology allows the design of compact and low-cost radars with multiple fields of application. In this paper, we focus on road applications, such as driving assistance with the objective of increasing safety and reducing accidents. In classical UWB radar systems, Gaussian and monocycle pulses are commonly used. In previous works, original waveforms based on orthogonal functions (Hermite and Gegenbauer) were proposed. These provide a good spatial resolution, suitable for radar detection. Another advantage of these waveforms is their multiple access capability, due to their orthogonality. The aim of the study presented in this article is to compare simulation and experimental results obtained, especially for short-range anticollision radar application, using these waveforms in one part and Gaussian and monocycle pulses in the other part. The originality of this paper relies on the new approach. Indeed, this comparison study using these waveforms has never been done before. Finally, some examples of real experiments in a real road environment with different waveforms are presented and analysed.
文摘实际地震波形观测表明,对于大陆结构相对简单的地壳中的地震而言,有一震相出现在P波和S波之间.一般在30～50km附近发育得较好,其能量主要集中在径向分量,而垂向分量的振幅相对径向要小,切向分量上的振幅很弱,且波形以低频为主,通常没有P波尖锐.在利用FK方法计算合成地震图的基础上,发现该震相是由S波入射到自由地表形成水平传播的P波(文献称为surface P wave,自由地表P波)或者包括S波入射到地表后形成的多次P波或其散射震相.由于该震相是由S波和P波之间耦合而形成,本文将其定义为sPL(s coupled into P)震相.理论波形研究表明,sPL相对直达P波的到时差对震中距离不敏感,而随着震源深度的增加几乎呈线性增加,因此可以很好的约束震源深度.本文以2005年江西九江地震为例,证实了sPL确定震源深度的可行性和可靠性.在观测到sPL震相的情况下,离震源50km以内的一个三分量地震台站的波形就可以帮助获得可靠的震源深度,而不需要精确的震中距离.由于sPL震相出现距离较近,对于较小(三级以上)的地震也可以应用,因此在稀疏台网布局情形下sPL对于确定中小地震深度应该具有很好的应用意义.
