Reliability of a linear connected-(r,s)-out-of-(m,n):F latticesystem

A linear connected-(r,s)-out-of-(m,n):F lattice system has its components ordered like the elements of a (m,n)-matrix such that the system fails if all components in a connected (r,s)-submatrix fail. This paper proposes a recursive algorithm, named Yamamoto-Miyakawa (YM), for the system reliability. The YM algorithm requires O(s^m-r·m²·r·n) computing time. Comparisons with the existing methods show its usefulness. We prove that the reliability of the large system tends to exp(-μ·λ^r·s) as n=μ·M^η-1, m→∞ if every component has failure probability λ·M^η(r·s/), where μ, λ, η are constant, μ>0, λ>0, η>s, or r/(r-1)>η>1     

Reliability evaluation of combined k-out-of-n:F,consecutive-k-out-of-n:F and linear connected-(r, s)-out-of-(m, n):Fsystem structures

Based on a real industrial application, three new system reliability models are proposed: combined k-out-of-n:F and consecutive-k _c-out-of-n:F system; combined k-out-of-m·n:F and linear connected-(r,s)-out-of-(m,n):F system; and combined k-out-of-m·n:F consecutive-k_c-out-of-n:F and linear connected-(r,s)-out-of-(m,n):F system. Reliability evaluation algorithms are provided for these models. The computation times of the algorithms for these models are, respectively: O(n·k), O(k·n·2 ^m·s^m-r+2), O(k·n·(2k_c )^m·s^m-r+1). The algorithms are used for system reliability evaluation of furnace systems. The concept of the combined k-out-of-n:F and 1-dimensional and 2-dimensional consecutive-k-out-of-n:F systems can be extended to other variations of the consecutive-k-out-of-n:F systems, e.g., the consecutive-k-out-of-n:G system and 1-dimensional and 2-dimensional r-within-k-out-of-n:F systems. The concept of Markov chain imbeddable (MIS) systems is another excellent tool that can be used for analysis of such combined system structures     

Reliability analysis of a M1/M/G1, G21 Queueing system with a repairable service station

A queueing situation often encountered in practice is that in which the service station may fail and can be repaired. This paper considers a priority queueing system with a repairable service station, where two types of customers arrive in batches according to two homogeneous independent Poisson processes, their service time distributions are general and only one customer can be served at a time. Assume that the service station has a constant failure rate and arbitrary repair time distribution. The focus of this paper is on the reliability. Using the supplementary variable method, we obtain the Laplace transform of the pointwise availability, the pointwise failure frequency and the reliability of the service station. Furthermore, we obtain the mean steady-state availability, steady-state failure frequency and mean time to first failure of the service station.     

Bounds for reliability of k-within connected-(r, s)-out-of-(m, n) failure systems

A k-within linear connected-(r, s)-out-of-(m, n) failure system is a two-dimensional grid whose components are ordered like the elements of an (m, n)-matrix. A k-within circular connected-(r, s)-out-of (m, n) failure system consists of the intersection points of m circles centered at the same point with n rays starting from that point and crossing the circles. The components of both systems either operate or fail. By definition, a k-within (linear or circular) connected-(r, s)-out-of-(m, n) failure system fails if at least one (r, s)-submatrix contains k or more failed components. These systems are used as mathematical models for design and operation of many engineering systems. For systems with statistically independent and identically distributed components, a lower and upper bound of system reliability are derived using improved Bonferroni inequalities. These bounds are easy to compute and provide good estimates for system reliability. New bounds for the reliability of other connected-(r, s)-out-of-(m, n) failure systems existing in the current literature are also obtained. Several failure systems with various values of the parameters k, r, s, m, n and p are used as numerical examples for comparison and illustrative purposes.     

混响室中混响时间测量测点位置的探讨

在分析了混响室中引起混响时间测量随机误差之后,提出将测点置于混响室角点上,这是更为合理的测量方法。     

xPb（Y1／2Nb1／2）O3—（1—x）Pb（Zr1／2Ti1／2）O3铁电陶瓷性能研究

系统地研究了xPb(Y1/2Nb1/2)O3-(1-x)Pb(Zr1/2Ti/2)O3三元系铁电陶瓷材料,测量并计算了不同组分时的压电常数(d33)、介电常数(εT33/ε0)、机电耦合系数(kp、k31)、以及弹性柔顺系数(sK11、sE12、sK33),对0.07Pb(Y1/2Nb1/2)O3-0.93Pb(Z[1/2Ti1/2)O3材料,D33为327×10-12C/N,介电常数εT33/ε0为1350,机电耦合系数kp大于0.6,弹性常数SE11和SE33均大于17×10-12m2/N.实现发现,当x大于0.55时,xPb(Y1/2Nb1/2)O3-(1-x)Pb(Zr1/2T11/2)O3不再是铁电材料.     

(n，1，m)递归系统卷积码的盲识别

递归系统卷积码(RSC码)是Turbo码子编码器常采用的编码形式。针对(n,1,m)递归系统卷积码的盲识别问题,给出了完整的编码参数和生成多项式识别方法。首先,采用矩阵分析法先求得卷积码参数,避免后续识别生成多项式时因参数循环估计带来的额外计算量。然后,根据RSC码的特性推导出生成多项式识别模型,给出了模型的具体求解步骤,并对所采用的Walsh-Hadamard变换算法进行了介绍。最后,运用Matlab平台进行仿真验证。仿真结果表明,该方法容错性能明显优于常规方法,在误码率为10-2条件下成功识别概率能达到90%,对于Turbo码的进一步研究具有重要意义。     

New dielectric material system of Nd(Mg1/2Ti1/2)O3–CaTiO3 at microwave frequency

The microwave dielectric properties of (1 − x)CaTiO₃–xNd(Mg_1/2Ti_1/2)O₃ (0.1  x  1.0) ceramics prepared by the conventional solid state method have been investigated. The system forms a solid solution throughout the entire compositional range. The dielectric constant decreases from 152 to 27 as x varies from 0.1 to 1.0. In the (1 − x)CaTiO₃–xNd(Mg_1/2Ti_1/2)O₃ system, the microwave dielectric properties can be effectively controlled by varying the x value. At 1400 °C, 0.1CaTiO₃–0.9Nd(Mg_1/2Ti_1/2)O₃ has a dielectric constant (ε_r) of 42, a Q × f value of 35 000 GHz and a temperature coefficient of resonant frequency (τ_f) of −10 ppm/°C. As the content of Nd(Mg_1/2Ti_1/2)O₃ increases, the highest Q × f value of 43 000 GHz for x = 0.9 is achieved at the sintering temperature 1500 °C.     

Admittance spectroscopy of traps at the interfaces of (1 0 0)Si with Al2O3, ZrO2, and HfO2

Admittance (ac) measurements were carried out to determine the interface trap density (D_it) as a function of energy E in the Si bandgap at interfaces of Si with different insulating oxides (Al₂O₃, ZrO₂, HfO₂). The results are compared to those of the conventional thermal SiO₂/Si interface. The results show that a significant portion of the interface trap density in the as-deposited and de-hydrogenated samples is related to the amphoteric Si dangling bond defects (P_b0 -centers). The D_it is much enhanced for the Al-containing insulators as compared to Si/SiO₂ but can be reduced by annealing in O₂. As to annealing in H₂, efficient passivation of P_b0 centers by hydrogen is achieved for Si/ZrO₂ and Si/HfO₂ interfaces, yet it fails for Si/Al-containing oxide entities. Among the insulators studied, the results suggest HfO₂ to be the best choice of an alternative insulator.     

NaY（WO4）2：Tm,Yb晶体的上转换发光

用高频加热Czochralski法生长了Yb^3 ,Tm^3 共掺的NaY(WO4)2晶体,测量了晶体在室温下的290－2000nm内的吸收谱,并对跃迁的能级进行了指认。在972nm二级管激光器泵浦下观察到Tm^3 的793nm和457nm上转换发光,研究了NYW晶体中Yb^3 向Tm^3 进行的能量传递的机制。     

Beam-Mode Piezoelectric Properties of Ternary Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals for Medical Linear Array Applications

In this work, the dielectric and beam-mode piezoelectric properties of ternary 0.35Pb(In_1/2Nb_1/2)O₃-0.35Pb(Mg_1/3Nb_2/3)O₃-0.30PbTiO₃ (PIMNT35/35/30) piezoelectric single crystals were investigated. The Curie temperature (T _C) and rhombohedral-to-tetragonal phase-transition temperature (T _rt) are 187°C and 127°C, about 30°C higher than those of PMNT crystals. The beam-mode coupling coefficient k ₃₃ ^w was found to be 90.3%. Furthermore, 3.5-MHz linear arrays based on PIMNT35/35/30 crystals and Pb(Zr_1−x Ti _x )O₃ ceramic (PZT-5H) were simulated using PiezoCAD software. The results indicate that the sensitivity and −6 dB bandwidth of a PIMNT35/35/30 transducer would be approximately 4 dB and 20% higher, respectively, compared with a traditional PZT transducer.     

(n,1,m)RSC码的盲识别

(n,1,m)递归系统卷积码(RSC)是Turbo码分量编码采用最多的一种编码方式。针对RSC提出了基于改进欧几里德算法的识别方法,为Turbo码的识别奠定了基础。该方法首先将(2,1,m)卷积码的识别模型应用推广至(n,1,m)卷积码,即求解n个多项式的最高公因式,进而利用改进的欧几里德算法识别生成多项式。最后,实例仿真验证了该方法的有效性。     

环F2+uF2+…+uk-1F2上长为2S的(1+u)-常循环码的距离分布

研究码字的距离分布是编码理论的一个重要研究方向。该文定义了环R=F₂+uF₂+…+u^k-1F₂上的Homogeneous重量,研究了环R上长为2^S的(1+u)-常循环码的Hamming距离和Homogeneous距离。使用了有限环和域的理论,给出了环R上长为2^S的(1+u)-常循环码和循环自对偶码的结构和码字个数。并利用该常循环码的结构,确定了环R上长为2^S的(1+u)-常循环码的Hamming距离和Homogeneous距离分布。     

Nonlinear optical properties ofK2La(NO3)5.2H2O and K2Ce(NO3)5.2H2O

The harmonic generating properties of potassium lanthanum nitrate (KLN) and potassium cerium nitrate (KCN) are described. These crystals have much larger nonlinear coefficients than potassium dihydrogen phosphate (KDP) and are nearly noncritically phase matched at room temperature for Type I frequency doubling of 1.064-μm light, and for Type II doubling of light near 0.95 μm. Thus, these crystals are useful for generating blue-green light by frequency doubling high-power near-infrared lasers. The crystal growth of KLN and KCN are described by the three component phase diagrams. Crystallographic data for KCN that confirms its structural similarity to KLN are presented. The optical absorption spectra of the two materials are discussed, and the linear refractive indexes are given     

Piezoelectric Study of 0.65Pb(Mg1/3,Nb2/3)O3-0.35PTO3 Nanopoder Ceramics

The piezoelectric properties of relaxor ferroelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 ceramic prepared by a sol-gel combustion method have been investigated as function of sintering temperature. The results show that its phase structure is near the morphoteropic phase boundary (MPB), and outstanding electrical properties are obtained with this composition. The highest piezoelectric coefficients were observed for the samples sintered at temperature of 1200oC. In comparison with pure PMN ((1-x)Pb(Mg1/3Nb2/3)O3(x)PbTiO3), the substitution of 35% PT results in the decrease of sintered temperature and improved the relaxation behavior.     

30 W输出的Yb3+:KGd(WO4)2激光系统的理论设计

Yb3+:KGd（WO4）2晶体具有增益带宽大、掺杂浓度高等突出特点,是近年来引起广泛关注的可用于构建锁模飞秒和辐射平衡激光系统的激光介质。这里建立了基于准三能级系统的微观动力学理论模型,并将其应用于端面泵浦Yb3+:KGd（WO4）2种子源和激光放大系统的理论分析中。首先从速率方程出发,讨论了准三能级激光系统的种子源部分的物理特性,指出种子源部分存在着最佳的晶体长度和输出耦合镜反射率。由于Yb3+:KGd（WO4）2晶体材料的热传导率很低,研究中拟采用主控振荡功率放大结构以实现30 W量级的激光输出,并在此基础上探讨了主控振荡功率放大器部分的输出物理特性。研究结果对将来构建实用化的Yb3+:KGd（WO4）2激光系统有着重要的理论指导意义。     

Eu2+掺杂Sr5(PO4)2SiO4磷灰石荧光粉的发光性能研究

采用高温固相法制备了Sr5－x (PO₄)₂SiO₄:xEu²⁺(x =0.010,0.015,0.020,0.025,0.050, 0.100)荧光粉,研究掺杂 浓度和测试温度对荧光粉发光性能的影响。随着Eu²⁺掺杂浓度的增加,发射强度呈现 先增大后减小的变化 趋势,并在x=0.015时达到最大值。Eu 2+掺杂浓度较低时(x≤0.025),Eu²⁺取代不同格位的 Sr²⁺,使得发射 光谱具有双发射峰;当x＞0.025时,由于 存在Eu 1到Eu 2的能量传递使发射光谱中Eu 1的峰位消失,只存 在Eu 2的峰位。发射光谱随Eu²⁺浓度增大出现了红移现象,这是由于半径较小的Eu 2+(0.109nm)取代较 大的Sr²⁺(0.113nm)使得晶胞收缩,晶场强度增大,从而导 致Eu²⁺的5d能级劈裂程度增大,电子跃迁释 放能量降低。此外,测试温度增加时,发射光谱出现与Varshini方程不相符的蓝移现象,这 是晶格结构稳定性和声子辅助隧穿效应共同作用使较小波长的Eu 1的发射居于主导地位的结 果。     

低损耗、高Qm值Pb（Nb2／3Mn1／3）O3—Pb（Sb2／3Mn1／3）O3—PZT材料

研究了组分变化及掺杂对四元系Pb(Nb2/3Mn1/3)O3-Pb(Sb2/3Mn1/3）O3－PZT压电材料性能的影响,发现Zr/Ti比值在准同型相界附近该材料有最大的压电常数d33,而机械品质因数Qm值较小;Zr/Ti比偏离该相界时则机械品质因数Qm升高,相应的压电常数d33减小。通过改变Pb(Nb2/3Mn1/3)O3、Pb(Sb2/3Mn1/3)O3两组分的含量及掺入Sr、Ce等杂质,获得的材料介电损耗为0.14%,机械品质因数为2341,压电常数为216pC/N。     

Ba(Zn_(1/3)Nb_(2/3))O_3微波介质陶瓷的研究进展

3G移动通信事业的迅速发展对应用于基站的微波介质谐振器陶瓷材料的Q值提出了更高的要求。Ba(Zn1/3Nb2/3)O3微波介质陶瓷材料因为具有很高的Q值、接近于零的τf和适宜的εr而备受关注。介绍了Ba(Zn1/3Nb2/3)O3系列微波介质陶瓷的结构和性能、改性研究、纳米化制备工艺及Ba(Zn1/3Nb2/3)O3-Ba(Co1/3Nb2/3)O3复合技术,以期对该领域其他研究者有所帮助。     

用于白光LED的KNaCa2(PO4)2:Eu2+蓝色荧光粉的发光特性

采用高温固相法合成了蓝色荧光粉KNaCa₂(PO₄)₂:Eu²⁺,利用X射线衍射(XRD)和光谱技术等表征了材料的性能。结果显示,少量Eu 2+的掺入并没有影响KNaCa₂(PO₄)₂的晶体结构。 在399nm近紫外光激发下,KNaCa₂(PO₄)₂:Eu²⁺材料发 射蓝光,发射光谱为400～600nm, 主发射峰位于471nm,对应Eu²⁺的4f^65d1→ 4f⁷跃迁发射;471nm发射峰,对应的激发光 谱为250～450nm,主激发峰位于399nm,与近紫外芯片匹配很好。 以365nm近紫外光作为 激发源时,KNaCa₂(PO₄)₂:Eu²⁺材料的发射强度约为商用蓝色荧光粉BAM:Eu 2+的85%;而以 399nm近紫外光作为激发源时,相较于BAM:Eu²⁺,KNaCa₂(P O₄)₂:Eu²⁺材料具有更强的发射强 度。此外,KNaCa₂(PO₄)₂:Eu²⁺和BAM:Eu²⁺的CIE色坐标接近,均位于蓝 色区域,色坐标分别 为(0.154,0.154)和(0.141,0.112)。研究结果 表明,KN aCa₂(PO₄)₂:Eu²⁺是一种在三基色白光LED中有应用前景的蓝色荧光粉。