In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC compon...In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.展开更多
The binary extended Golay code has a two-level structure, which can be used in the decoding of the code. However, such structure is not limited to the Golay code, in fact, several binary linear codes can be constructe...The binary extended Golay code has a two-level structure, which can be used in the decoding of the code. However, such structure is not limited to the Golay code, in fact, several binary linear codes can be constructed by a projective method which is related to the structure. In this correspondence, the binary (4n,n + 2k, ≥min(8, n,2d)) linear codes are resulted from quaternary (n,k,d) linear block codes. Based on the structure, the efficient maximum likelihood decoding algorithms can be presented correspondingly for the derived codes.展开更多
In recent years,the use of first language(L1)in teaching of second and foreign languages(L2/FL)has been a highly con⁃troversial issue in language teaching and learning studies.This qualitative case study of four Ameri...In recent years,the use of first language(L1)in teaching of second and foreign languages(L2/FL)has been a highly con⁃troversial issue in language teaching and learning studies.This qualitative case study of four American instructors use of codeswitching in their FL teaching explores in what occasion,in what ways,and for what reasons the instructors switched between stu⁃dents’native language and target languages.The results indicate that instructors’choices are to a great extent influenced by vari⁃ous factors,including their personal preferences,class subjects,and communicative purposes.Discussions about new discoveries have also been conducted.展开更多
To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal test...To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal tests on rock samples to investigate the correlations between macro-and meso-level mechanical parameters of rock-like bonded granular materials. Then based on the artificial intelligent technology, the intelligent prediction systems for nine meso-level mechanical parameters of PFC models were obtained by creating, training and testing the prediction models with the set of data got from the orthogonal tests. Lastly the prediction systems were used to predict the meso-level mechanical parameters of one kind of sandy mudstone, and according to the predicted results the macroscopic properties of the rock were obtained by numerical tests. The maximum relative error between the numerical test results and real rock properties is 3.28% which satisfies the precision requirement in engineering. It shows that this paper provides a fast and accurate method for the determination of meso-level mechanical parameters of PFC models.展开更多
The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m s...The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power in- creasing times of larger target sidelobe is less than the power increasing times of smaller target main- lobe because of the larger target＇ s pseudo-randomness. Smaller target is integrated from larger tar- get sidelobe, which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic, a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6. 5 dB by the proposed method.展开更多
API code is introduced at first, and then a comparison of seismic character and seismic hazard between Bohai and Southern California is carried out. The analysis indicates both the seismic frequency and intensity and ...API code is introduced at first, and then a comparison of seismic character and seismic hazard between Bohai and Southern California is carried out. The analysis indicates both the seismic frequency and intensity and the seismic hazard of Bohai are much weaker than that of Southern California. API code states the strength level and deformation level of permanent structures in Southern California takes 200 a and several hundred to a few thousand years respectively. But in the reference codes in China, the seismic levels take 500 a and 10000 a for strength design and deformation design, and it seems too conservative. In China, the deformation level of class A structure takes 2%-3% probabilities of exceedance in reference period 100 a, and that of class B and C often takes 2%-3% in 50 a. Now that offshore platforms may cause server subsequent risk, it is safe to take 1% in 30 a as its deformation design level. On the basis of the above analyses and social economic level and the consistency with present codes, the strength design level and deformation design level of Chinese offshore platforms is suggested to take 200 a and 3000 a respectively.展开更多
QLC（Quad-Level Cell） NAND flash will be one of the future technologies for next generation memory chip after three-dimensional（3D） TLC（Triple-Level Cell） stacked NAND flash. In QLC device, data errors will easil...QLC（Quad-Level Cell） NAND flash will be one of the future technologies for next generation memory chip after three-dimensional（3D） TLC（Triple-Level Cell） stacked NAND flash. In QLC device, data errors will easily occur because of 2~4 data levels in the limited voltage range. This paper studies QLC NAND technology which is 4 bits per cell. QLC programming methods based on 16 voltage levels and reading method based on ＂half-change＂ Gray coding are researched. Because of the probable error impact of QLC NAND cell＇s voltage change, the solution of generating the soft information after XOR（exclusive OR） the soft bits by internal read mechanism is presented for Low-Density Parity-Check（LDPC） Belief Propagation（BP） decoding in QLC design for its system level application.展开更多
This paper presents a description and performance evaluation of a new bit-level, lossless, adaptive, and asymmetric data compression scheme that is based on the adaptive character wordlength （ACW（n）） algorithm. Th...This paper presents a description and performance evaluation of a new bit-level, lossless, adaptive, and asymmetric data compression scheme that is based on the adaptive character wordlength （ACW（n）） algorithm. The proposed scheme enhances the compression ratio of the ACW（n） algorithm by dividing the binary sequence into a number of subsequences （s）, each of them satisfying the condition that the number of decimal values （d） of the n-bit length characters is equal to or less than 256. Therefore, the new scheme is referred to as ACW（n, s）, where n is the adaptive character wordlength and s is the number of subsequences. The new scheme was used to compress a number of text files from standard corpora. The obtained results demonstrate that the ACW（n, s） scheme achieves higher compression ratio than many widely used compression algorithms and it achieves a competitive performance compared to state-of-the-art compression tools.展开更多
Tropical land snail (Achatina achatina) were collected from three areas viz.Nsit Ibom Local Government Area (NTB), Nsit Ubium Local Government Area (NTU) and Uyo Municipality (UYM), all in Akwa Ibom State to deter...Tropical land snail (Achatina achatina) were collected from three areas viz.Nsit Ibom Local Government Area (NTB), Nsit Ubium Local Government Area (NTU) and Uyo Municipality (UYM), all in Akwa Ibom State to determine the levels of Ni, Pb, Zn and Cr in their shells and muscles. Generally, the levels of all the metals in the muscles were comparatively higher than that in the shells. Correspondingly, the metals appear to have been more stable in the muscles with comparatively lower coefficients of variation than in the shells. Moreover while there was no significant correlation between the levels of all the metals in shells and muscles of NTU samples, Pb and Zn in NTB correlated very significantly. The correlation between levels of Cr in NTB samples and of Zn in UYM samples in shells and muscles were equally significant. On the whole, the levels of these metals were found to be much lower in both shells and muscles of NTU samples obtained from the “enclosed and restricted” environment than in NTB and UYM samples collected randomly from “open and unrestricted” environments.展开更多
为了解决多功能视频编码(versatile video coding,VVC)标准下具有相同编码参数的视频双压缩检测方法准确率不高的问题,提出了一种基于编码单元(coding unit,CU)尺寸、划分模式和预测模式的检测方法。对待检测的视频进行多次编解码,分析...为了解决多功能视频编码(versatile video coding,VVC)标准下具有相同编码参数的视频双压缩检测方法准确率不高的问题,提出了一种基于编码单元(coding unit,CU)尺寸、划分模式和预测模式的检测方法。对待检测的视频进行多次编解码,分析并确定VVC流中与压缩编码次数密切相关的基础码流特征;以CU尺寸、划分模式和预测模式构建高级码流特征输入支持向量机完成视频的双压缩检测。实验结果表明,与对比文献的方法相比,所提方法的视频双压缩检测准确率有较大提升,平均准确率达到了95.82%。展开更多
随着6G通信研究的深入,卫星互联网作为空天地一体化网络的重要组成部分,对高吞吐量、高可靠性和低延时的需求推动了新型编码调制技术的发展。多级编码调制与混合自动重传请求技术的结合被认为是提升6G卫星互联网性能的重要方向。提出了...随着6G通信研究的深入,卫星互联网作为空天地一体化网络的重要组成部分,对高吞吐量、高可靠性和低延时的需求推动了新型编码调制技术的发展。多级编码调制与混合自动重传请求技术的结合被认为是提升6G卫星互联网性能的重要方向。提出了一种基于多级编码调制的增量冗余重传方案,旨在优化频谱效率并增强传输可靠性。针对传统研究中多级编码调制与增量冗余重传独立设计的局限性,通过灵活的分层重传策略,使各编码层均能有效应用增量冗余重传,充分利用编码增益、分集增益和能量增益。仿真结果表明,在256QAM(Quadrature Amplitude Modulation)调制下,该方案在码率0.667时可实现约6~8 d B的性能增益,显著提升系统可靠性与重传性能。展开更多
基金supported by National Natural Science Foundation of China(No.61571061)
文摘In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.
文摘The binary extended Golay code has a two-level structure, which can be used in the decoding of the code. However, such structure is not limited to the Golay code, in fact, several binary linear codes can be constructed by a projective method which is related to the structure. In this correspondence, the binary (4n,n + 2k, ≥min(8, n,2d)) linear codes are resulted from quaternary (n,k,d) linear block codes. Based on the structure, the efficient maximum likelihood decoding algorithms can be presented correspondingly for the derived codes.
文摘In recent years,the use of first language(L1)in teaching of second and foreign languages(L2/FL)has been a highly con⁃troversial issue in language teaching and learning studies.This qualitative case study of four American instructors use of codeswitching in their FL teaching explores in what occasion,in what ways,and for what reasons the instructors switched between stu⁃dents’native language and target languages.The results indicate that instructors’choices are to a great extent influenced by vari⁃ous factors,including their personal preferences,class subjects,and communicative purposes.Discussions about new discoveries have also been conducted.
基金the National Natural Science Foundation of China (Nos. 50674083 and 51074162) for its financial support
文摘To solve the problems of blindness and inefficiency existing in the determination of meso-level mechanical parameters of particle flow code (PFC) models, we firstly designed and numerically carried out orthogonal tests on rock samples to investigate the correlations between macro-and meso-level mechanical parameters of rock-like bonded granular materials. Then based on the artificial intelligent technology, the intelligent prediction systems for nine meso-level mechanical parameters of PFC models were obtained by creating, training and testing the prediction models with the set of data got from the orthogonal tests. Lastly the prediction systems were used to predict the meso-level mechanical parameters of one kind of sandy mudstone, and according to the predicted results the macroscopic properties of the rock were obtained by numerical tests. The maximum relative error between the numerical test results and real rock properties is 3.28% which satisfies the precision requirement in engineering. It shows that this paper provides a fast and accurate method for the determination of meso-level mechanical parameters of PFC models.
基金Supported by the National Natural Science Foundation of China(Youth Science Fund)(61001190)
文摘The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power in- creasing times of larger target sidelobe is less than the power increasing times of smaller target main- lobe because of the larger target＇ s pseudo-randomness. Smaller target is integrated from larger tar- get sidelobe, which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic, a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6. 5 dB by the proposed method.
基金Important Research of the Tenth Five-year Plan from China Earthquake Administration ″Seismic hazard assessment and structure seismic fortification″ and ″Reliability of seismic fortification level of offshore platforms″.
文摘API code is introduced at first, and then a comparison of seismic character and seismic hazard between Bohai and Southern California is carried out. The analysis indicates both the seismic frequency and intensity and the seismic hazard of Bohai are much weaker than that of Southern California. API code states the strength level and deformation level of permanent structures in Southern California takes 200 a and several hundred to a few thousand years respectively. But in the reference codes in China, the seismic levels take 500 a and 10000 a for strength design and deformation design, and it seems too conservative. In China, the deformation level of class A structure takes 2%-3% probabilities of exceedance in reference period 100 a, and that of class B and C often takes 2%-3% in 50 a. Now that offshore platforms may cause server subsequent risk, it is safe to take 1% in 30 a as its deformation design level. On the basis of the above analyses and social economic level and the consistency with present codes, the strength design level and deformation design level of Chinese offshore platforms is suggested to take 200 a and 3000 a respectively.
文摘QLC（Quad-Level Cell） NAND flash will be one of the future technologies for next generation memory chip after three-dimensional（3D） TLC（Triple-Level Cell） stacked NAND flash. In QLC device, data errors will easily occur because of 2~4 data levels in the limited voltage range. This paper studies QLC NAND technology which is 4 bits per cell. QLC programming methods based on 16 voltage levels and reading method based on ＂half-change＂ Gray coding are researched. Because of the probable error impact of QLC NAND cell＇s voltage change, the solution of generating the soft information after XOR（exclusive OR） the soft bits by internal read mechanism is presented for Low-Density Parity-Check（LDPC） Belief Propagation（BP） decoding in QLC design for its system level application.
文摘This paper presents a description and performance evaluation of a new bit-level, lossless, adaptive, and asymmetric data compression scheme that is based on the adaptive character wordlength （ACW（n）） algorithm. The proposed scheme enhances the compression ratio of the ACW（n） algorithm by dividing the binary sequence into a number of subsequences （s）, each of them satisfying the condition that the number of decimal values （d） of the n-bit length characters is equal to or less than 256. Therefore, the new scheme is referred to as ACW（n, s）, where n is the adaptive character wordlength and s is the number of subsequences. The new scheme was used to compress a number of text files from standard corpora. The obtained results demonstrate that the ACW（n, s） scheme achieves higher compression ratio than many widely used compression algorithms and it achieves a competitive performance compared to state-of-the-art compression tools.
文摘Tropical land snail (Achatina achatina) were collected from three areas viz.Nsit Ibom Local Government Area (NTB), Nsit Ubium Local Government Area (NTU) and Uyo Municipality (UYM), all in Akwa Ibom State to determine the levels of Ni, Pb, Zn and Cr in their shells and muscles. Generally, the levels of all the metals in the muscles were comparatively higher than that in the shells. Correspondingly, the metals appear to have been more stable in the muscles with comparatively lower coefficients of variation than in the shells. Moreover while there was no significant correlation between the levels of all the metals in shells and muscles of NTU samples, Pb and Zn in NTB correlated very significantly. The correlation between levels of Cr in NTB samples and of Zn in UYM samples in shells and muscles were equally significant. On the whole, the levels of these metals were found to be much lower in both shells and muscles of NTU samples obtained from the “enclosed and restricted” environment than in NTB and UYM samples collected randomly from “open and unrestricted” environments.
文摘为了解决多功能视频编码(versatile video coding,VVC)标准下具有相同编码参数的视频双压缩检测方法准确率不高的问题,提出了一种基于编码单元(coding unit,CU)尺寸、划分模式和预测模式的检测方法。对待检测的视频进行多次编解码,分析并确定VVC流中与压缩编码次数密切相关的基础码流特征;以CU尺寸、划分模式和预测模式构建高级码流特征输入支持向量机完成视频的双压缩检测。实验结果表明,与对比文献的方法相比,所提方法的视频双压缩检测准确率有较大提升,平均准确率达到了95.82%。
文摘随着6G通信研究的深入,卫星互联网作为空天地一体化网络的重要组成部分,对高吞吐量、高可靠性和低延时的需求推动了新型编码调制技术的发展。多级编码调制与混合自动重传请求技术的结合被认为是提升6G卫星互联网性能的重要方向。提出了一种基于多级编码调制的增量冗余重传方案,旨在优化频谱效率并增强传输可靠性。针对传统研究中多级编码调制与增量冗余重传独立设计的局限性,通过灵活的分层重传策略,使各编码层均能有效应用增量冗余重传,充分利用编码增益、分集增益和能量增益。仿真结果表明,在256QAM(Quadrature Amplitude Modulation)调制下,该方案在码率0.667时可实现约6~8 d B的性能增益,显著提升系统可靠性与重传性能。
