就地化分布式元件保护子机动作行为差异分析

分析了造成就地化分布式子机保护动作行为不一致的原因,以及子机中断机制对保护计算的影响。各子机间中断异步将导致保护离散采样、数据插值、积分计算的一系列差异,进而导致保护动作行为不一致。针对子机中断异步问题,着重介绍了就地化分布式保护子机中断同步方法,方法不依赖于外部对时源,能够在较短时间内完成各子机同步。分析计算结果表明,子机中断同步后各子机能够有效降低保护计算值差异,进而增强保护动作行为的一致性。文中同时介绍了子机中断同步在异常情形下的处理方法。     

Kirk effect and suppressing for 20 V planar active-gap LDMOS Nie Weidong(聂卫东)1, 2, Yi Fayou(易法友)2, and Yu Zongguang(于宗光)1

For 20 V planar active-gap lateral double-diffused MOSFET（LDMOS）,the sectional channel is utilized to decrease the electric field in the n-drift region below the poly gate edge in the off-state,compared with the conventional single channel.Then the n-drift concentration can be increased to decrease the Kirk effect,while keeping off-state breakdown voltage V_bd unchanged.Meanwhile the influence of the n-drift concentration and the n-drift length L_drift（the drain n⁺ diffusion to gate spacing） which are related to the Kirk effect is discussed.The trade-offs between R_dson-Area,breakdown voltage V_bd and the electrical safe operating area（e-SOA） performance of LDMOS are considered also.Finally the proposed planar active-gap LDMOS devices with varied values of L_drift are experimentally demonstrated.The experimental results show that the Kirk effect can be greatly suppressed with slight increase in the R_dson·Area parameter.     

Material, energy and spatial fields for metallogenic prediction: Theory and practice An example: Limu Sn polymetallic crisis mines

The Limu tin deposits located in the Nanling tin and tungsten-polymetallic ore belt are now facing resource depletion after decades of exploitation. Peripheral mineral exploration therefore has become an urgent task. Using mineral exploration around the Limu crisis mines as an example, we introduce a breakthrough method of how the three-field theory, i.e., the material, energy and spatial fields, is applied to intensively studies areas, a history of years of mineral exploitation and complex ore-forming systems. Taking a cue from Limu regional metallogeny, we based our investigation on the metallogenic information from geology, geophysics, geochemistry and remote sensing. We conducted our study of the three-field integrated information system, associated with metallogenic prognoses from deposits, with assignments and calculations which correct and allocate synthetic metallogenic prognosis by relying on GIS. We submitted a synthetic metaUogenic prognosis map of tin in Limu where we delineated three ore target areas. A breakthrough was achieved by finding about 4785 t of tin metal outside the Shiziling deposit, which has been confirmed by drilling. The successful application in Limu shows that this threefield theory is of scientific and practical importance and deserves to be extended to utilization.     

基于改进CORDIC算法实现高速直接数字频率合成器

设计实现了一种高速直接数字频率合成器。利用混合CORDIC算法的思想,用混合角度集代替传统正切角度集,并讨论了在二进制格式下的中间值,采用改进的混合差分CORDIC算法实现了相位幅度的转换。在确保算法的迭代精度和收敛区间的前提下,避免了传统算法中旋转方向依赖于上一次迭代的现象,提高了数据的吞吐量;同时消除了常用冗余算法引进额外电路的情况。分析了采用CORDIC算法所带来的误差,综合考虑精度和电路复杂度,确定字长和迭代次数获得14位的输出有效位。经0.18μm6M2P CMOS工艺流片,在1GHz的工作频率下,输出信号在98.6MHz处,SFDR为68.39dB,整个芯片面积为4.19mm×3.17mm。     

FPGA高性能查找表的设计与实现

从电路角度探讨了查找表(LUT)实现原理,基于双相不交叠时钟,设计实现了一种LUT,能高效地完成移位寄存器与RAM的功能扩展。基于SMIC0.25μmCMOS工艺优化设计了对应的版图,给出了相应的HSPICE仿真结果。此电路结构增强了逻辑块的性能,提高了FPGA的整体效率与灵活性,已被应用于FPGA的设计中。     

一种改进的子集可满足性算法用于FPGA布线

介绍了用布尔可满足性(SAT)和子集可满足性(sub-SAT)算法解决FPGA的详细布线问题。在布线资源固定的FPGA布线环境中,布尔公式可以证明所给电路的不可布通性,这一点要优于典型的one-net-at-a-time方法。子集可满足性方法把一个有N个约束的"严格的"SAT问题转换成一个新的"松弛的"SAT问题,仅当在原始问题中变量的不可满足个数不超过阈值k(kN)时,这一问题是可满足的。它改进了布尔可满足性,但是却产生了很多额外的变量和子句。针对这一问题,提出了用伪布尔可满足性(PBS)来消除子集可满足性公式带来的缺点。初步的实验结果表明,把这个方法加入子集可满足性方法中可以减少变量和子句数量,并显著减少运行时间。     

0.18μm混合信号RFCMOS工艺中新型低触发电压双向SCR静电防护器件的设计

提出了一类新型片上SCR静电放电防护器件,此类器件用于保护芯片双向抗击静电应力.比较和分析了四种双向SCR器件的触发电压.其中采用嵌入pMOS管或nMOS管的双向SCR器件结构具有可调触发电压,低漏电流(～pA)和开启速度快的骤回Ⅰ-Ⅴ特性,并且没有闭锁问题.该器件的抗ESD能力可达～94V/μm.此类新型ESD防护器件具有面积小、寄生效应小的特点.     

用于高压ESD保护的LDMOS中触发电压退化效应的研究

The trigger voltage walkin effect has been investigated by designing two different laterally diffused metal-oxide-semiconductor （LDMOS） transistors with an embedded silicon controlled rectifier （SCR）. By inserting a P＋ implant region along the outer and the inner boundary of the N＋ region at the drain side of a conventional LDMOS transistor, we fabricate the LDMOS-SCR and the SCR-LDMOS devices with a different triggering order in a 0.5/zm bipolar-CMOS-DMOS process, respectively. First, we perform transmission line pulse （TLP） and DC-voltage degradation tests on the LDMOS-SCR. Results show that the trigger voltage walk-in effect can be attributed to the gate oxide trap generation and charge trapping. Then, we perform TLP tests on the SCR-LDMOS. Results indicate that the trigger voltage walk-in effect is remarkably reduced. In the SCR-LDMOS, the embedded SCR is triggered earlier than the LDMOS, and the ESD current is mainly discharged by the parasitic SCR structure. The electric potential between the drain and the gate decreases significantly after snapback, leading to decreased impact ionization rates and thus reduced trap generation and charge trapping. Finally, the above explanation of the different trigger voltage walk-in behavior in LDMOS-SCR and SCR-LDMOS devices is confirmed by TCAD simulation.     

台南凹陷三叠系油气有效输导层特征分析

有效输导层是油气运移过程中实际经过的那部分输导通道。在常规储层物性研究的基础上,分析有效输导层宏观影响因素,结合油气显示数据,研究油气运移过程中流体在储层中的通道优选规律。研究工作显示:吐哈盆地台南凹陷三叠纪储层油气经历了由西向东的长距离运移过程,砂体是主要运移通道。埋藏压实作用是影响输导层物性最重要的因素,同等压实程度下,细砂岩物性最佳,三角洲内前缘和辫状三角洲平原是有利的储层形成环境。应用滑动砂地比连续计算地层砂泥岩分布,85%的油气显示小层分布在滑动砂地比大于60%的地层段内。台南凹陷有效输导层分布于研究区中部和南部,累加有效储层孔隙空间厚度在20~40 m范围。     

原子吸收分光光度法在环境分析领域中的应用

原子吸收分光光度法是国内外环境分析中最常见的方法之一,本文介绍了原子吸收分光光度法在环境分析中的应用,对美国ＥＰＡ、日本ＪＩＳ和我国现行的标准法系列和统一方法进行了比较,还报道了ＧＦＡＡＳ测定的样品消解中,可能由于用水及酸类引起的沾污问题,同时对国外ＧＦＡＳＳ法直接测定固体环境试样进行了报道,环境形态分析是ＡＡＳ法的主要应用领域,且该技术在国内外发展很快,以Ａｓ、Ｐｂ、Ｓｎ的形态分析为重点,介绍了ＧＣ－ＡＡＳ、ＨＰＬＣ－ＡＡＳ、ＩＣ－ＡＥＳ在形态分析中的应用,同时,对于使用不同的固体样品处理方法,使用ＡＡＳ测定定重金属也进行了介绍,本文引用至１９９９年国内外文献４４篇。