实用运算放大器网络中的虚地性质

本文提出用一个理想电压控制电流源(VCCS)并接于嵌在一个倒相放大器电路中的实际运算放大器(OP.amp)输入端,虚地性质(VGP)可以扩展到使用的运算放大器单位增益带宽那样高的频率.文中给出用真正运算放大器的VCCS的实用电路.用互补变换法可得出非倒相放大电路图.     

CFD在发芽罐空调系统节能改造中的应用研究

针对发芽罐空调系统能耗严重的问题,采用CFD软件Fluent模拟空调系统气流流道流场,通过添加导流板进行气流导流模拟改造。结果表明,气流导流可有效改善气流流场,增大风量或降低能耗,可提高空调系统风量17．9％,提高换热量18．8％,降低风机功耗12．5％,换热量增大6．7％;节能改造投资少、效益高。     

Phase Equilibrium Characteristics of CO2 and Ionic Liquids with [FAP]-Anion Used for Absorption-Compression Refrigeration Working Pairs

The study of the phase equilibrium characteristics of CO₂-ionic liquids(ILs)as new absorption-compression type refrigeration working pairs is of great importance.Three kinds of ILs,i.e.,[emim][FAP],[bmim][FAP]and[hmim][FAP],were chosen as potential absorbents.The solubility of CO₂in these ILs was measured experimentally within 0 to 5.0 MPa at temperatures of 293.15 K to 333.15 K,and the effects of temperature,pressure,IL anion and cation structure and stirring action on CO₂solubility were also discussed and analyzed.The results showed that the longer alkyl chains in an identical IL family,the alkyl fluoride group in IL anions and the stirring action by a magnetic stirrer had positive effects on the solubility of CO₂.In the three ILs,[hmim][FAP]possessed the best performance for CO₂absorption;the solubility of CO₂reached 0.7641 at a pressure of 5 MPa and temperature of 293.15 K,the maximum solubility measured in this work.The CO₂-[hmim][FAP]binary mixture is recommended as a potentially applicable working pair for CO₂absorption-compression refrigeration systems.     

采用超导磁选从白云鄂博矿钾板岩中回收钾长石试验研究

我国长石资源丰富,但富矿资源少,可被直接开采利用的优质钾长石资源并不多,绝大部分需通过富集才能达到工业应用的标准。内蒙古白云鄂博矿床是世界闻名的 Fe-Nb-REO超大型矿床,钾板岩属于白云鄂博矿体上部围岩。在包头钢铁（集团）公司对该铁矿40余年的开采中,已剥离的富钾板岩作为废石在矿区大量堆存,总量超过3.0亿t,每年新增剥离富钾板岩达200万t,白云鄂博矿区钾板岩资源丰富,为提高白云鄂博矿物的综合利用,实现钾长石资源的可持续发展提出从白云鄂博矿钾板岩中回收钾长石。长石矿物常与其他杂质矿物共生,特别是其中的铁等少量杂质元素,影响钾长石精矿的品质和应用。针对内蒙古白云鄂博矿钾板岩,试验的主要目的是确定有效去除高铁钾板岩中铁矿物和云母等硅酸盐类含铁杂质的工艺流程。对白云鄂博高铁富钾板岩进行工艺矿物学分析,确定了“破碎-磨矿-永磁磁选-超导磁选”试验工艺流程,以K2O品位12.66%,Na2O品位为0.6%,TFe品位为5.55%的钾板岩为原矿,在磨矿粒度-0.074mm为92%的条件下,经永磁磁选,超导磁选试验最终得到K2O品位为15.53%,回收率为54.21%,TFe品位为0.55%的钾长石精矿,结果表明利用永磁＋超导磁选工艺可以实现从钾板岩中高效回收钾长石,工艺简单可行,为从白云鄂博矿钾板岩中回收钾长石探索新的途径。     

十二烷基多季铵盐Gemini型阳离子表面活性剂的合成

控制反应物乙二胺与环氧氯丙烷的配比,得到乙二胺与环氧氯丙烷的摩尔比分别为1∶5、1∶4、1∶1的产物。然后与自制十二烷基二甲胺进一步反应制备十二烷基多季铵盐Gemini型阳离子表面活性剂,反应条件是:反应温度60℃;反应时间1h;反应溶剂、水和乙醇的混合溶剂。通过测定不同浓度下溶液的表面张力,得到其产物Ⅰ、Ⅱ的临界胶束浓度为0.05%(质量百分比)左右。说明产品具有很低的临界胶束浓度和较好的表面活性。进一步的实验证明:合成产物具有较好的发泡力、稳泡力和金属腐蚀的抑制性能,并考察了其与阴离子表面活性剂的复配性能。     

计及故障持续时间的电力系统暂态稳定分布式控制

针对电力系统故障持续时间会影响暂态稳定控制的问题, 本文提出了一种使系统在固定时间内恢复暂态稳定运行的策略. 该策略通过电力系统通信拓扑建模方法为每个发电机建立“邻居发电机”, 利用发电机本地信息和其邻居发电机的信息设计分布式控制器, 通过控制储能装置作用于受扰动后的系统, 使其在固定时间内恢复稳定运行. 其次, 此控制策略还解决了一些实际挑战, 如控制器的输入延时、外部的干扰、储能装置的容量限制等. 通过构建李雅普诺夫函数并利用图论知识对该策略展开了稳定性分析, 推导出了稳定系统的时间界限. 最后, 将控制器投入新英格兰39节点测试系统中, 并与其它控制器进行比较, 仿真结果验证了在低容量储能装置限制下和抗干扰性上控制器性能的优势.     

Hierarchical Magnetic Network Constructed by CoFe Nanoparticles Suspended Within “Tubes on Rods” Matrix Toward Enhanced Microwave Absorption

Hierarchical magnetic-dielectric composites are promising functional materials with prospective applications in microwave absorption(MA)field.Herein,a three-dimension hierarchical“nanotubes on microrods,”core–shell magnetic metal–carbon composite is rationally constructed for the first time via a fast metal–organic frameworksbased ligand exchange strategy followed by a carbonization treatment with melamine.Abundant magnetic CoFe nanoparticles are embedded within one-dimensional graphitized carbon/carbon nanotubes supported on micro-scale Mo2N rod(Mo2N@CoFe@C/CNT),constructing a special multi-dimension hierarchical MA material.Ligand exchange reaction is found to determine the formation of hierarchical magnetic-dielectric composite,which is assembled by dielectric Mo2N as core and spatially dispersed CoFe nanoparticles within C/CNTs as shell.Mo2N@CoFe@C/CNT composites exhibit superior MA performance with maximum reflection loss of−53.5 dB at 2 mm thickness and show a broad effective absorption bandwidth of 5.0 GHz.The Mo2N@CoFe@C/CNT composites hold the following advantages:(1)hierarchical core–shell structure offers plentiful of heterojunction interfaces and triggers interfacial polarization,(2)unique electronic migration/hop paths in the graphitized C/CNTs and Mo2N rod facilitate conductive loss,(3)highly dispersed magnetic CoFe nanoparticles within“tubes on rods”matrix build multi-scale magnetic coupling network and reinforce magnetic response capability,confirmed by the off-axis electron holography.     

一种用于核辐射监测信号的多微处理系统

介绍了4兆伏静电正离子加速器的监测防护系统,该系统由多个微处理器与主控机分布式分布,组成高速多通道辐射信号采集控制系统,可以对多点核辐射的能量、强度、剂量率,剂量及剂量当量进行监测.系统的核电路部分采用最新的芯片产品,合理的硬件安排,优化的软件编程,在仅更换不同的探头后,便可探测分析γ,X及快中子辐射.在参数稍做调整之后,就可以广泛应用于类似条件的其他场所的辐射监测.     

某砌体房屋底层大空间改造设计

已有砖砌体房屋底层常因功能改变而需要更大的使用空间,部分承重墙体的抽除必将导致传力途径的改变,故需对原有结构进行加固。阐述了托换技术在房屋改造加固中的应用,同时对托换技术的各设计阶段,包括基础设计、结构设计等作了分析。     

Serine Hydroxymethyltransferase 1 Is Essential for Primary-Root Growth at Low-Sucrose Conditions

Plant roots are essential organs for absorbing nutrients from the soil or medium. Sucrose functions as a vital carbon source in root development, and sucrose starvation interferes with the redox state of plant cells. However, the mechanism of root growth at sucrose starvation remains unclear. Here, we report that SHMT1 (serine hydroxymethyltransferase 1) plays a crucial role in primary-root growth. SHMT1 mutation caused decreased sugar levels, excessive H₂O₂ accumulation, and severe root-growth arrest at sucrose-free conditions, whereas plants with SHMT1 overexpression had increased sugar and decreased H₂O₂ levels, and longer primary roots. Sucrose supply fully restored root growth of shm1-2, but CO₂ alone could not, and SHMT1 is much more stable in roots than shoots at sucrose conditions, suggesting that SHMT1 accumulation in roots is critical for sucrose accumulation and root growth. Further ROS scavenging by GSH application or ROS synthesis inhibition by apocynin application or RBOHD mutation reduced H₂O₂ levels and partially restored the root-growth arrest phenotype of shm1-2 at low-sucrose conditions, suggesting that SHMT1 modulates root growth via sucrose-mediated ROS accumulation. Our findings demonstrated the role of SHMT1 in primary-root growth by regulating sucrose accumulation and ROS homeostasis in roots.