In agriculture experiments, the response on a given plot may be affected by the treatments on neighboring plots as well as by the treatments applied to that plot. In this paper we consider such type of situations and ...In agriculture experiments, the response on a given plot may be affected by the treatments on neighboring plots as well as by the treatments applied to that plot. In this paper we consider such type of situations and construct circular neighbor-balanced designs (CNBDs) by the method of cyclic shifts or sets of shifts. An important feature of this method is that the properties of a design can be easily obtained from the sets of shifts instead of constructing the actual blocks of the design. That is, the off-diagonal elements of the concurrence matrix can be easily obtained from the sets of shifts. Since the suggested designs are circular, balanced and binary, so they are universally optimal.展开更多
Let W be an injective unilateral weighted shift, and let W(n) be the orthogonal direct sum of n copies of W. In this paper, we prove that, if the commutant of W is strictly cyclic, then W(n) has a unique (SI) decompos...Let W be an injective unilateral weighted shift, and let W(n) be the orthogonal direct sum of n copies of W. In this paper, we prove that, if the commutant of W is strictly cyclic, then W(n) has a unique (SI) decomposition with respect to similarity for every natural number n.展开更多
This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 cata...This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction （XRD）, Raman spectroscopy, H2-TPR, cyclic voltammetry （CV） and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity （CO conversion reaches 93.4% at 250 ℃） and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile （i.e., the reduction of surface copper oxide （crystalline forms） interacted with surface oxygen vacancies on ceria）, and the area of peak C2 and A1 （Cu^0→←Cu^2＋ in cyclic voltammetry process）, respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.展开更多
利用单一混沌系统实现的加密算法结构简单且容易被攻击,采用多个混沌系统加密是提高加密系统安全性的有效措施。文中提出一种基于循环移位和多混沌映射的图像加密算法,循环移位操作可以有效地改变图像的像素值。首先,利用分段线性混沌映...利用单一混沌系统实现的加密算法结构简单且容易被攻击,采用多个混沌系统加密是提高加密系统安全性的有效措施。文中提出一种基于循环移位和多混沌映射的图像加密算法,循环移位操作可以有效地改变图像的像素值。首先,利用分段线性混沌映射(Piecewise Linear Chaotic Map,PWLCM)和Logistic映射产生不同的混沌序列,并根据不同混沌序列生成索引矩阵和循环移位数。然后,根据索引矩阵对明文图像进行置换操作,根据循环移位数对置换图像依次做左循环移位操作。最后,通过Logistic混沌序列和PWLCM混沌序列对循环移位后的图像进行置乱和扩散操作,最终得到加密图像。对图像直方图、信息熵、差分攻击、相关性进行的测试和分析结果表明,所提加密算法具有高安全性和抵御各种攻击的能力,可以应用于图像加密系统中。展开更多
针对中国毫米波频段(45GHz),制定下一代IEEE 802.11aj无线局域网(Wireless Local Area Network,WLAN)协议标准通信系统的物理层结构及发射机发送方式,研究了一种新的适用于该标准的循环移位分集(Cyclic Shift Diversity,CSD)方案,该方...针对中国毫米波频段(45GHz),制定下一代IEEE 802.11aj无线局域网(Wireless Local Area Network,WLAN)协议标准通信系统的物理层结构及发射机发送方式,研究了一种新的适用于该标准的循环移位分集(Cyclic Shift Diversity,CSD)方案,该方案在不增加接收机额外复杂度的前提下能够获得较好的性能。同时,本文对通信系统在各种调制和编码方式(Modulation and Coding Scheme,MCS)下的性能进行了仿真和评估。结果表明,在将系统发射功率控制在20d B时,采用码率为1/2的16-QAM调制方式可以在保证误帧率性能的同时获得较高的吞吐率。展开更多
针对常规直接序列扩频水声通信数据传输速率低及M元扩频水声通信接收机复杂度高的问题,提出了一种正交频分复用(orthogonal frequency division multiplexing,OFDM)技术和循环移位键控(cyclic shift keying,CSK)技术相结合的调制方式,...针对常规直接序列扩频水声通信数据传输速率低及M元扩频水声通信接收机复杂度高的问题,提出了一种正交频分复用(orthogonal frequency division multiplexing,OFDM)技术和循环移位键控(cyclic shift keying,CSK)技术相结合的调制方式,该调制能很大程度地提高系统的带宽使用率。从理论上对该方法在高斯白噪声信道条件下的误码率进行了分析。同时,采用Chu序列作为扩频序列,通过理论推导得出其峰均功率比(peak to average power ratio,PAPR)的上限为3dB。利用实际湖试测量得到的多径信道模型,与DSSS-OFDM方法进行了误码率性能的分析比较。结果表明,新提出的方法具有很好的抗多径性能,且具有带宽利用率高、复杂度低的特点,适用于中、远程及多用户水声通信。展开更多
为降低多输入多输出正交频分复用(MIMO-OFDM,multiple input multiple output orthogonal frequency division multiplexing)系统中传统选择性映射(SLM,selected mapping)算法的计算复杂度,提出了通过信号时域循环移位和天线间信号联合...为降低多输入多输出正交频分复用(MIMO-OFDM,multiple input multiple output orthogonal frequency division multiplexing)系统中传统选择性映射(SLM,selected mapping)算法的计算复杂度,提出了通过信号时域循环移位和天线间信号联合产生更多具有不同峰均功率比(PAPR,peak to average power ratio)的备选序列集合的方法。接收端先根据发射端序列选取情况恢复出频域旋转信号,再比较反向旋转序列与最近星座点的距离来恢复原始序列。仿真结果表明,所提出的方法能有效地抑制MIMO-OFDM信号的PAPR。另外,与传统SLM算法相比,提出方法明显降低了计算复杂度,而且可以获得传统SLM方法在已知边带副信息情况下近似的比特误码率性能。展开更多
文摘In agriculture experiments, the response on a given plot may be affected by the treatments on neighboring plots as well as by the treatments applied to that plot. In this paper we consider such type of situations and construct circular neighbor-balanced designs (CNBDs) by the method of cyclic shifts or sets of shifts. An important feature of this method is that the properties of a design can be easily obtained from the sets of shifts instead of constructing the actual blocks of the design. That is, the off-diagonal elements of the concurrence matrix can be easily obtained from the sets of shifts. Since the suggested designs are circular, balanced and binary, so they are universally optimal.
文摘Let W be an injective unilateral weighted shift, and let W(n) be the orthogonal direct sum of n copies of W. In this paper, we prove that, if the commutant of W is strictly cyclic, then W(n) has a unique (SI) decomposition with respect to similarity for every natural number n.
基金supported by the National Natural Science Foundation of China (20771025)A-type Science and Technology Projects of Fujian Provincial Department of Education (JA08021)
文摘This paper presented a study on the role of yttrium addition to CuO/CeO2 catalyst for water-gas shift reaction. A single-step co-precipitation method was used for preparation of a series of yttrium doped CuO/CeO2 catalysts with yttrium content in the range of 0-5wt.%. Properties of the obtained samples were characterized and analyzed by X-ray diffraction （XRD）, Raman spectroscopy, H2-TPR, cyclic voltammetry （CV） and the BET method. The results revealed that catalytic activity was increased with the yttrium content at first, but then decreased with the further increase of yttrium content. Herein, CuO/CeO2 catalyst doped with 2wt.% of yttrium showed the highest catalytic activity （CO conversion reaches 93.4% at 250 ℃） and thermal stability for WGS reaction. The catalytic activity was correlated with the surface area, the area of peak γ of H2-TPR profile （i.e., the reduction of surface copper oxide （crystalline forms） interacted with surface oxygen vacancies on ceria）, and the area of peak C2 and A1 （Cu^0→←Cu^2＋ in cyclic voltammetry process）, respectively. Besides, Raman spectra provided evidences for a synergistic Cu-Ovacancy interaction, and it was indicated that doping yttrium may facilitate the formation of oxygen vacancies on ceria.
文摘利用单一混沌系统实现的加密算法结构简单且容易被攻击,采用多个混沌系统加密是提高加密系统安全性的有效措施。文中提出一种基于循环移位和多混沌映射的图像加密算法,循环移位操作可以有效地改变图像的像素值。首先,利用分段线性混沌映射(Piecewise Linear Chaotic Map,PWLCM)和Logistic映射产生不同的混沌序列,并根据不同混沌序列生成索引矩阵和循环移位数。然后,根据索引矩阵对明文图像进行置换操作,根据循环移位数对置换图像依次做左循环移位操作。最后,通过Logistic混沌序列和PWLCM混沌序列对循环移位后的图像进行置乱和扩散操作,最终得到加密图像。对图像直方图、信息熵、差分攻击、相关性进行的测试和分析结果表明,所提加密算法具有高安全性和抵御各种攻击的能力,可以应用于图像加密系统中。
文摘针对中国毫米波频段(45GHz),制定下一代IEEE 802.11aj无线局域网(Wireless Local Area Network,WLAN)协议标准通信系统的物理层结构及发射机发送方式,研究了一种新的适用于该标准的循环移位分集(Cyclic Shift Diversity,CSD)方案,该方案在不增加接收机额外复杂度的前提下能够获得较好的性能。同时,本文对通信系统在各种调制和编码方式(Modulation and Coding Scheme,MCS)下的性能进行了仿真和评估。结果表明,在将系统发射功率控制在20d B时,采用码率为1/2的16-QAM调制方式可以在保证误帧率性能的同时获得较高的吞吐率。
文摘针对常规直接序列扩频水声通信数据传输速率低及M元扩频水声通信接收机复杂度高的问题,提出了一种正交频分复用(orthogonal frequency division multiplexing,OFDM)技术和循环移位键控(cyclic shift keying,CSK)技术相结合的调制方式,该调制能很大程度地提高系统的带宽使用率。从理论上对该方法在高斯白噪声信道条件下的误码率进行了分析。同时,采用Chu序列作为扩频序列,通过理论推导得出其峰均功率比(peak to average power ratio,PAPR)的上限为3dB。利用实际湖试测量得到的多径信道模型,与DSSS-OFDM方法进行了误码率性能的分析比较。结果表明,新提出的方法具有很好的抗多径性能,且具有带宽利用率高、复杂度低的特点,适用于中、远程及多用户水声通信。
文摘为降低多输入多输出正交频分复用(MIMO-OFDM,multiple input multiple output orthogonal frequency division multiplexing)系统中传统选择性映射(SLM,selected mapping)算法的计算复杂度,提出了通过信号时域循环移位和天线间信号联合产生更多具有不同峰均功率比(PAPR,peak to average power ratio)的备选序列集合的方法。接收端先根据发射端序列选取情况恢复出频域旋转信号,再比较反向旋转序列与最近星座点的距离来恢复原始序列。仿真结果表明,所提出的方法能有效地抑制MIMO-OFDM信号的PAPR。另外,与传统SLM算法相比,提出方法明显降低了计算复杂度,而且可以获得传统SLM方法在已知边带副信息情况下近似的比特误码率性能。
