DAM中波发射机外部联锁故障又自动恢复正常检修实例

目前,数字调制(DAM)中波发射机的稳定性和可靠性比以往发射机有显著提高.然而,发射机工作涉及部件和链路繁多,一个元器件接触不良就可能导致发射机不能正常开机,因此,维护工作仍不可忽视.通过对发射机外部联锁故障红灯又自动恢复正常的故障实例展开分析和处理,以期为业内人士提供一些有益的参考.     

一种高阶温度补偿的带隙基准电压源

基于SMIC 0.18 μm CMOS工艺,设计了一种高阶温度补偿的带隙基准电压源。采用源极、漏极与栅极短接的PMOS管替代传统基准电压源中的PNP管,增加了高温区域曲率补偿电路和低温区域温度分段补偿电路。该带隙基准电压源获得了低温漂的性能。仿真结果表明,在-40 ℃~125 ℃温度范围内,该带隙基准电压源的温度系数达到1.997×10-6/℃,在频率为1 Hz、10 Hz、100 Hz、1 kHz、100 kHz时,分别获得了-77.84 dB、-77.84 dB、-77.83 dB、-77.42 dB、-48.05 dB的电源抑制比。     

Ti掩膜图形层对外延生长GaN薄膜晶体质量的影响

采用氢化物气相外延(HVPE)方法在2英寸(1英寸=2.54 cm)c面蓝宝石衬底上外延生长了高质量GaN单晶薄膜.在GaN生长过程中引入点状和条状两种金属Ti掩膜图形层,研究了不同Ti掩膜图形层对外延生长GaN薄膜晶体质量的影响.使用微分干涉相差显微镜(DICM)、扫描电子显微镜(SEM)、阴极荧光光谱(CL)、喇曼光谱和X射线衍射(XRD)对制备的GaN样品结构和形貌进行了表征分析.实验结果表明,Ti掩膜图形层的引入可以在一定程度上改善GaN薄膜的表面形貌,缓解材料中的应力,降低GaN材料中的位错密度,提高材料的结晶质量.同时发现,相比于点状图形,条状Ti图形掩膜层可以更加有效地改善GaN材料的晶体质量,将位错密度降低到3.2×106 cm-2以下.     

中国梨木虱分泌物中糖的定性定量分析

采用离子交换柱色谱法、毛细管气相色谱法分离和测定中国梨木虱分泌中的。利用标样对照法结合质谱分析确定了中国梨木虱分泌物中以葡萄糖，果糖为主的９种单糖成份。用内标法定量，并与化学法比较，得满意的结果。     

Eu3+-芦丁配合物与DNA 相互作用的电化学和紫外可见吸收光谱研究

在0.1 mol·L-1乙酸缓冲溶液中(pH=5.69), 用电化学方法和吸收光谱法研究了Eu3+-芦丁配合物和小牛胸腺DNA的相互作用. 发现Eu3+-芦丁配合物与DNA通过静电吸引和沟槽键合模式键合. 在玻碳电极上通过循环伏安法和差示脉冲法得到了键合常数(K=1.42×104 mol·L-1)和键合位点数(n=2). 用紫外可见吸收光谱研究了Eu3+和芦丁的相互作用, 以及Eu3+-芦丁配合物与DNA 的相互作用.     

银基微电极方波伏安法测定矿样中痕量铅镉

研究了银基质微电极的伏安特性，经与玻碳电极比较，具有灵敏度高、重现性好、分辨率强、线性范围宽、使用寿命长等优点。并克服了宏观电极的某些缺点，消除了充电电流的影响，基线平稳，峰形清晰。     

A modular and concise total synthesis of (+/-)-daurichromenic acid and analogues

A modular and concise total synthesis of (+/-)-daurichromenic acid has been accomplished in four steps from ethyl acetoacetate, ethyl crotonate, and trans,trans-farnesal. A series of analogues of this natural product, which has potent anti-HIV activity, were also prepared from ethyl or methyl acetoacetate and a series of readily available alpha,beta-unsaturated esters and aldehydes.     

Salt-free dyeing of cotton fabric and adsorption of reactive dyes in non-aqueous dyeing system: equilibrium,kinetics, and thermodynamics

Cellulose - In traditional water-based dyeing system, a large amount of salts and water are consumed and it is hard to treat inorganic salts in dyeing wastewater. From sustainable chemistry and...     

Effect of coexisting cations on the adsorption of cesium onto poly (β-cyclodextrin)/bentonite composite

A novel poly(β-cyclodextrin)/bentonite composite (β-CD/BNC) was successfully prepared through graft polymerisation by using ammonium persulphate–sodium bisulphate as initiators, and characterized by FT-IR and EDS. The equilibrium data fit Freundlich isotherm satisfactorily. Adsorption kinetic was fitted with pseudo-second-order. The maximum adsorption capacities for Cs⁺ by β-CD/BNC in absence and presence of Na⁺ and Mg²⁺ were 48.83 ± 0.35, 47.30 ± 0.28, and 42.52 ± 0.85 mg g^?1, respectively. Adsorption of Cs⁺ was suppressed by presence of Mg²⁺ more than Na⁺. β-CD/BNC had a higher affinity to Cs⁺ than Na⁺ and Mg²⁺. β-CD/BNC was an effective sorbent for the treatment cesium waste water.     

Regulatory Mechanism of the Enantioselective Intramolecular Enone [2+2] Photocycloaddition Reaction Mediated by a Chiral Lewis Acid Catalyst Containing Heavy Atoms

The asymmetric catalysis of the intramolecular enone [2+2] photocycloaddition has been subject of extensive experimental studies, however theoretical insight to its regulatory mechanism is still sparse. Accurate quantum chemical calculations at the CASPT2//CASSCF level of theory associated with energy‐consistent relativistic pseudopotentials provide a basis for the first regulation theory that the enantioselective reaction is predominantly controlled by the presence of relativistic effects, that is, spin–orbit coupling resulting from heavy atoms in the chiral Lewis acid catalyst.