Isolation, DNA sequence and regulation of a new cell division cycle gene from the yeast Saccharomyces cerevisiae

A new complementation group of temperature-sensitive mutants of the yeast Saccharomyces cerevisiae (ts26-1 and ts26-2) has been isolated and characterized. This mutation maps at 40.7 cM from arg8 and 48.9 cM from arg1 on the left arm of chromosome XV of yeast, providing that it is a newly identified gene. The dumbbell-shape terminal morphology of the mutant cells at the restrictive temperatures is a characteristic of mutants defective in DNA replication. To study the defect of macromolecule synthesis in the mutant cells, DNA, RNA, and protein synthesis were measured at both permissive and restrictive temperatures. The data suggest that the primary defect of this mutation is at the initiation step of DNA synthesis. The gene has been cloned from an S. cerevisiae genomic library by rescue of the conditional lethality of the mutants. It is present as a single copy in the haploid genome. DNA-RNA hybridization of the gene has identified 1 kb RNA, which is under cell-division-cycle control. DNA sequence analysis of the gene has identified an open reading frame capable of encoding a protein of molecular weight 25,055 (214 amino acids).     

电子组件温度循环试验研究

为了使温度循环试验在有效提高电子组件的可靠性方面得以广泛应用,基于温度循环试验的机理,对电子组件温度循环试验的关键参数(温度范围、循环次数、保持时间、温变速率、风速)进行了探讨,给出了这些参数的工程经验选取值。在此基础上,借助热分析软件分析了温变速率、保持时间和风速三个参数对试验过程的影响并定性分析了三个参数间的关系。最后,提出了进行温度循环试验时应注意的问题,强调科学、正确地执行温度循环试验的重要性。     

基于可编程控制器多谐振荡器的设计与分析

在数字电路中,常常需要一种不需外加触发脉冲就能够产生具有一定频率和幅度的矩形波电路,特别是要求频率和占空比可调的这种电路,它就是多谐振荡器.文章采用可编程控制器来设计完成该功能,它具有设计简单,完成方便,频率和占空比用软件就可调试,不需要对电路重新组装的特点.     

A Water Stable,Near‐Zero‐Strain O3‐Layered Titanium‐Based Anode for Long Cycle Sodium‐Ion Battery

Layered transition metal (TM) oxides of the stoichiometry Na_xMO₂ (M = TM) have shown great promise in sodium‐ion batteries (SIBs); however, they are extremely sensitive to moisture. To date, most reported titanium‐based layered anodes exhibit a P2‐type structure. In contrast, O3‐type compounds are rarely investigated and their synthesis is challenging due to their higher percentage of unstable Ti³⁺ than the P2 type. Here, a pure phase and highly crystalline O3‐type Na_0.73Li_0.36Ti_0.73O₂ with high performance is successfully proposed in SIBs. This material delivers a reversible capacity of 108 mAh g^?1 with a stable and safe potential of 0.75 V versus Na/Na⁺. In situ X‐ray diffraction reveals that this material does not undergo any phase transitions and exhibits a near‐zero volume change upon Na⁺ insertion/de‐insertion, which ensures exceptional long cycle life over 6000 cycles. Importantly, it is found that this O3‐Na_0.73Li_0.36Ti_0.73O₂ shows superior moisture stability, even when immersed into water, which are both elusive for conventional layered TM oxides in SIBs. It is believed that the small interlayer distance and high occupation of interlayer vacancy promise such unprecedented water stability.     

电化学电容器充放电循环的微机测试系统

为了更好地评价电化学电容器的充放电循环寿命性能,采用恒定负载法进行充放电试验。测试系统硬件由微机和数据采集卡以及取样控制电路组成,应用软件的开发工具采用VB6.0,在Windows 2000操作系统下运行。系统除了能自动完成电容器充放电循环寿命试验外,还具有实时显示电容器充放电电流变化曲线,并将每个充放电循环周期的电流数据以文件的形式自动保存下来等功能。     

数据专业设计标准化若干问题的思考与实践

以数据专业设计标准化为案例,对设计流程、设计模板及加速知识共享等进行了分析,提出了“聚焦设计标准化,提升设计服务水平”的理念,并探讨了在设计服务商内部推广的可行性。     

一种新的移相全桥零电压开关PWM变换器

对于移相全桥零电压开关PWM变换器,在全负载范围内实现所有开关器件零电压开关和减少占空比丢失之间是矛盾的。如果在电路中增加一个辅助电路,根据负载情况在续流期间为滞后桥臂的零电压开关提供能量,能在全负载范围内实现所有开关器件的零电压开关和减少占空比丢失,但电路中存在严重的环流问题。文中提出新的拓扑结构通过增加一个双向开关和相应的驱动电路,有效地减少了环流带来的损耗。实例分析和仿真验证了这种拓扑的优点。     

突发自适应调制信号的调制识别算法研究

针对突发自适应调制信号中的PSK和QAM调制方式识别问题,本文提出了一种能够识别BPSK、QPSK、8PSK以及16QAM、32QAM、64QAM、128QAM、256QAM八种信号类型的盲识别算法。该算法首先对信号的循环平稳性进行了分析和讨论,给出了利用循环高阶累积量的特征实现信号识别分类的理论依据。然后,提出了三种基于循环累积量的特征分别实现了QAM和PSK类间识别、MPSK类内识别以及方形QAM与十字形QAM的识别。最后通过对MQAM信号的瞬时幅度分布特性的深入研究和分析,提出了一种基于瞬时包络平方的方差的特征实现了QAM的类内识别。该算法选择了二叉树支持向量机作为识别分类器,并设计了一种新的识别流程完成了对上述信号调制方式的识别。该算法无需精确同步,对载波相位具有较好的鲁棒性,并能够对中频信号进行识别。仿真实验表明,该算法能够实现在较低信噪比条件下突发信号的识别。      

基波平衡原理的推广

注入网络的基波电流iS1=0。则可由Gi(Um,ωS)=0和Bi(Um,ωS)=0求出基波解的频率和幅值(ωS,Um)。如果有n对合理的正实数(ωSi,Umi,i=1,2,3….n≠∞),同时满足式Gi=0和Bi=0,则原网络会对应地建立n个周期振荡。以上情况被称为基波解严格存在。若由式Gi≤0,Bi≤0解出的频率和幅值有无限多组解(ωS,Um),分布在一定连续较广范围内,这表明基波解不但在更加广泛的范围内存在,且有向负载送出实功与虚功的能力。含多个平衡点的非线性网络,能够在相空间建立多个座标体系分析网络的全局稳定性。不同的参考体系,应得出相同的结论。但用多个不同的座标体系能够发现相图性状的变化规律。     

坦克装甲车辆发动机排气发电技术研究

提出一种利用布雷顿(BRAYTON)循环的坦克装甲车辆发动机排气发电技术方案,对循环过程进行了热力学分析,并探讨了引入循环后对发动机性能的影响及在坦克装甲车辆上实现的可行性,分析研究表明该系统技术适用于坦克装甲车辆的发动机排气发电.