微弱光信号检测

光功率计只能检测单通道信号,通过数字滤波系统不仅可以实现多通道同时检测弱光信号,而且较硬件电路检测来说灵活性高,检测精度也可以和进口设备相媲美。     

莫来石/SiC复相材料的烧结工艺和成分优化

利用工业氧化铝和超细氧化硅合成莫来石，并结合SiC制备出了莫莱石／SiC复相材料。研究了烧结工艺及氧化铝和氧化硅的摩尔比对复相材料密度和强度的影响，并以材料的热震残余强度为指标、利用正交设计法研究了微量添加剂的影响效果。结果表明，复相材料的体积密度随烧结温度的升高和烧结时间的延均出现先升高后降低的规律，而开口气孔率的变化规律则相反；随结合相中Al2O3与SiO2的摩尔比的提高，复相材料的密度增加、气孔密度降低，而强度则先增后减，通过烧结工艺与结合相和添加剂成分的优化，材料密度最高可达2．5g/cm^2，抗折强度达34．5MPa，耐压强度可达90MPa，热震后的残余强度率为67．2％。     

Starch from the Sago (Metroxylon sagu) Palm Tree—Properties,Prospects, and Challenges as a New Industrial Source for Food and Other Uses

ABSTRACT: The common industrial starches are typically derived from cereals (corn, wheat, rice, sorghum), tubers (potato, sweet potato), roots (cassava), and legumes (mung bean, green pea). Sago (Metroxylon sagu Rottb.) starch is perhaps the only example of commercial starch derived from another source, the stem of palm (sago palm). Sago palm has the ability to thrive in the harsh swampy peat environment of certain areas. It is estimated that there are about 2 million ha of natural sago palm forests and about 0.14 million ha of planted sago palm at present, out of a total swamp area of about 20 million ha in Asia and the Pacific Region, most of which are under‐ or nonutilized. Growing in a suitable environment with organized farming practices, sago palm could have a yield potential of up to 25 tons of starch per hectare per year. Sago starch yield per unit area could be about 3 to 4 times higher than that of rice, corn, or wheat, and about 17 times higher than that of cassava. Compared to the common industrial starches, however, sago starch has been somewhat neglected and relatively less attention has been devoted to the sago palm and its starch. Nevertheless, a number of studies have been published covering various aspects of sago starch such as molecular structure, physicochemical and functional properties, chemical/physical modifications, and quality issues. This article is intended to piece together the accumulated knowledge and highlight some pertinent information related to sago palm and sago starch studies.     

ICP-AES法测定松香甘油酯中金属离子含量

采用干法灰化处理松香甘油酯样品,以ICP-AES法测定其中Fe、A1、Zn、Cu、Pb、Ni六种金属离子的含量.最佳测定条件为:射频功率1300W,雾化器流量0.70L/min,试样提升量2,00mL/min,辅助气流量0.20L/min,等离子体流量15L/min.方法检出限为0.0002～0.006mg/L,回收率为90.81%～102.92%,相对标准偏差均小于1.05%.此法简便、快速、灵敏度高、准确性好、对环境污染小,可多元素同时测定.     

基于FPGA技术的KSKS05A型数控系统

文章介绍了 KSKS05 型数控系统的组成、功能、工作原理和电路设计特点.基于 FPGA 技术设计的硬件电路具有高度灵活通用的特点,根据功能软件的选取可实现多种任务的切换.该系统还具有轻松扩展升级的特点,只需添加相应功能的软件即可.     

Direct and transfer hydrogenation of furfural over MOF-derived Pd-Cu@C catalysts

Owing to the self-reducing ability of palladium acetate in solutions, an ethanol solution containing Pd⁰ particles was prepared and coated in-situ into copper metal–organic framework (Cu-MOF), forming Pd@Cu-MOF in a coated structure. The Pd@Cu-MOF was reduced under N₂ or H₂ to form carbon-coated Pd-Cu@C. The pyrolysis and carbonization of Cu-MOF and the reduction of Cu²⁺ were studied. The Cu-MOF under either N₂ or H₂ was pyrolyzed and carbonized, but the Cu²⁺ reduction mechanisms were different. The high-temperature carbothermic reduction of Cu²⁺ under N₂ produced Cu⁰, but during low-temperature reduction under H₂, the reducing H₂ reduced Cu²⁺ to Cu⁰. Furfural hydrogenation experiments showed that compared with H₂, the Pd-Cu@C prepared under N₂ reduction displayed higher furfural hydrogenation activity. The catalytic activity of Pd-Cu@C prepared from in-situ Pd⁰ coating was higher than the Pd/Cu@C prepared from the impregnation method. With i-propanol as the solvent, the catalytic hydrogenation of furfural under H₂ consisted of direct catalytic hydrogenation with molecular hydrogen as the hydrogen source and catalytic transfer hydrogenation with i-propanol as the hydrogen donor. The catalytic activity of direct catalytic hydrogenation is higher than the catalytic transfer hydrogenation.     

北京A380机库大跨度结构设计研究

建成后的北京A380机库将是世界最大的飞机维修库之一,其屋盖跨度362.6m,进深110rn,总高40m.机库屋盖采用钢网架与大门边桁架相结合的方案,其支承柱列为三边布置四肢钢管混凝土柱与柱间支撑,大门一边仅跨中设置一根钢筋混凝土支承柱.该机库跨度大,所建场地限高严格,屋盖悬挂荷载大,处于高烈度区,给结构设计带来很大难度.本文介绍了机库结构选型、受力特点及设计优化,以及针对上述问题的计算分析和试验研究,包括:根据风洞试验的结果调整风荷载体型系数,并分析确定各种风向角下的风振系数;采用不同程序进行整体结构地震反应分析,考虑了三维地震作用和多点输入的影响;对大门柱在各种荷载工况及其不利组合下的安全性进行有限元分析;根据机库内部温度场分析结果,合理选取计算温差,分析对结构安全的影响;对复杂节点进行足尺和大比例模型试验、有限元分析和设计优化,确保其安全可靠.     

一种新型高效油气井酸化缓蚀剂的研制

曼尼希碱是一类性能优良的缓蚀剂，并在油气井酸化作业中大量应用。为此介绍了一种新型曼尼希碱：在伯胺、甲醛、苯乙酮参与的曼尼希反应中加入丙酮，通过控制反应条件使得伯胺分子中氨基上的两个氢原子分别与苯乙酮、丙酮及甲醛发生曼尼希反应，得到该曼尼希碱，可以用作油气井酸化缓蚀剂的主剂。将该曼尼希碱与丙炔醇及有机增效剂复配后得到国内未见报道的高效油气井酸化缓蚀剂。以静态腐蚀速率为试验评价指标，用正交试验法对主剂的合成工艺条件进行优化，试验条件下获得的最佳合成工艺条件应为：总反应时间14 h，反应原料胺醛酮的配比为1∶2∶4(物质的量比)，pH值在2～3之间。同时对主剂与增效剂之间的协同作用进行了初步的探讨。静态腐蚀试验结果表明，复配后的产品具有优良的缓蚀性能。在90 ℃、20％的盐酸中加入1％的缓蚀剂，N-80钢的腐蚀速率可以降到0.96 g/(m²·h)。     

谈回火现象及解决办法

文中分别从理论上和实际生产中分析了回火现象产生的原因,并提出了具体的解决办法.     

Remote detection of corrosion activity by SQUID magnetometry across a multiphase medium under electrolyte flow conditions

Hydrodynamic induction of magnetic fields on AA2024 sample corroding in NaOH solutions was studied by a Superconducting Quantum Interference Device (SQUID) magnetometer operating in liquid helium with a spatial resolution of approximately 1 mm. The hydrodynamic generation of magnetic fields was explained in terms of electronic and ionic currents induced by corrosion potential gradients within the sample due to different solution flow velocities. The intrinsic magnetic activity of the electrolyte flow was significantly less than that of the corroding sample. The measurements demonstrated a unique capability of magnetometry to sense corrosion remotely and across the integrated media consisting of gaseous and solid dielectrics (air, plastics), electronic conductor (aluminum alloy) and ionic one (solution).