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1.
The resorcinol/formaldehyde gels containing 5% (w/v) of reactants have been prepared. After curing for seven days, the gel is treated with trifluoroacetic acid to initiate the condensation of hydroxymethyl groups. Drying of the prepared gels is done by removing water with the help of vacuum heterogeneous azeotropic distillation using amyl acetate and n-butanol. The textural properties of the gels thus obtained are compared with the properties of the gel obtained from exchange of water by acetone (control experiment). The pore volume and average pore diameter of the gel obtained from the azeotropic distillation of water with amyl acetate are 0.7663 × 10–3 m3/kg and 0.0145 m, respectively. These values are 1.5 times higher than the values obtained by vacuum heterogeneous azeotropic distillation with n-butanol and about twice than the values obtained in the control experiment. The surface areas in all the three gels are almost constant.  相似文献   
2.
It is well known that a large proportion of ferrous PM components require secondary machining operations for dimensional conformance or for producing geometrical features that cannot be generated during die compaction. Nevertheless, the machining behavior of PM parts is generally characterized as being “difficult” due to the presence of residual porosity that lowers thermal conductivity and induces interrupted cutting. Several admixed additives such as MnS and BN-h can be used to improve the machining behavior of PM steels. Nevertheless, their negative effect on mechanical properties, especially fatigue resistance, makes their utilization uninteresting for the fabrication of high-performance PM steel components. This article summarizes the work carried out to develop a novel PM steel that was especially engineered to form machinability enhancing precipitates. This new material is pre-alloyed with tin (Sn) in order to form Cu-Sn (Cu(α)) precipitates during transient liquid phase sintering. The newly developed material presents machinability improvement of 165% compared to reference material used in the PM industry as well as increases in toughness and fatigue resistance of 100% and 13%, respectively.  相似文献   
3.
提出Mn~(2+)-H_2O_2-PAR[4-(2-吡啶偶氮)-间苯二酚]新体系并用于羟自由基的检测。pH 10的硼砂-氢氧化钠缓冲溶液中Mn~(2+)-H_2O_2体系产生羟自由基,加入偶氮染料PAR,羟自由基迅速氧化PAR-Mn~(2+)螯合物分解退色,测定500nm处吸光度的变化确定羟自由基产生的量。利用所建立的实验方法对抗坏血酸清除羟自由基的能力进行测定,其结果与DPPH·(二苯代苦味肼基自由基)分光光度法和羟自由基测定试剂盒法相比。结果表明:该方法稳定性好,操作简便,测定快速,重现性稳定,相对标准偏差为1.42%,可作为一种简便的筛选抗氧化剂的方法。3种方法中抗坏血酸的IC_(50)分别为0.013、0.005、0.2 mg/mL。  相似文献   
4.
Neural Computing and Applications - This research intends to use machine learning approaches to predict tunnel geology and its construction time and costs. For this purpose, the Gaussian Process...  相似文献   
5.
Due to increased globalisation, industries are facing greater competition that is pressing companies into decreasing their expenses in order to increase their profits. As regards Swedish industry, it has been faced with substantial increases in energy prices in recent years. Barriers to energy efficiency such as imperfect information inhibit investments in energy efficiency measures, energy audits being one means of reducing barriers and overcoming imperfect information. However, an evaluation of such energy audits in Sweden reveals that it is chiefly low-cost measures that are undertaken as a result of an audit. Moreover, these audits often tend to focus on support processes such as ventilation, lighting, air compressors etc., while measures impacting production processes are often not as extensively covered, which underlines the need for further support in addition to energy audits. Decision support is practised in a variety of different disciplines such as optimization and simulation and the aim of this paper is to explore whether investment decision support practices may be used successfully towards small and medium-sized manufacturers in Sweden when complex production-related investment decisions are taken. The optimization results from the different cases, involving a foundry’s investment in a new melting unit, indicate that with no electricity price fluctuations over the day, the investment seems sound as it lowers the overall energy costs. However, with fluctuating electricity prices, there are no large differences in energy costs between the option of retaining the existing five melting furnaces at the foundry and investing in a twin furnace and removing the holding furnaces – which was the initial investment plan for the foundry in the study. It would not have been possible to achieve this outcome without the use of investment decision support such as MIND. One of the main conclusions in this paper is that investment decision support, when strategic investment decisions are to be taken, may be a means of emphasising energy efficiency for energy-intensive SMEs beyond the level of traditional energy auditing.  相似文献   
6.
以汉、维、哈、柯等具有多种书写方向的多文种电子词典软件系统开发为背景,首先指出了其中与语种相关的技术难点,提出相应的解决方案,即通过XML的标注属性和字母的UNICODE区域从属关系来判断词语的书写方向;其次计算组成词语的各个字母来自不同语言的概率来判断词语的文种;最后对开源索引工具Lucene进行修改将其成功应用到了电子词典中词库的索引中。应用结果表明该技术方案的可行性和有效性。  相似文献   
7.
In this research, the efficiency of the stabilization and solidification process in stabilizing organic pollutants from soil contaminated with petroleum compounds through cement and modified clay (organophilic clay) was investigated. The soil studied in this research was prepared from the waste disposal site of the second refining industry of engine oil located on the edge of the Salafchegan industrial city (Qom, Iran). The effect of different amounts of modified clay and cement on the stabilization and solidification process was investigated by measuring the unconfined compressive strength and the leaching concentration for treated samples with 28-day time. The experiments showed that in order to control the pollution caused by petroleum hydrocarbons in the soil, the simultaneous use of modified clay as a cementations adsorbent significantly improved the stabilization of contaminants. Using response surface methodology, it was obtained that, a combination of 22.5% modified clay and 21% cement with contaminated soil causes the lowest leak concentrations.  相似文献   
8.
This paper proposes an integrated emergency ordering and production planning scheme for a multi-item, multi-product problem in which each product is composed of several ingredients. Each item can be supplied from both cheap unreliable suppliers prone to yield uncertainty and expensive reliable suppliers. A two-stage decision-making process is proposed in which orders are placed to the unreliable suppliers during the first stage and an emergency order can be placed in the second stage. In addition, a flexible backup ordering contract between the buyer and emergency supplier is proposed. A similar two-stage decision-making process is considered for production planning, where in the first stage, the main production plan is determined and in the second stage, the decision about a limited increase in the production plan is made as an emergency decision. An integrated ordering and production planning decision process is proposed for the problem. The value of emergency decisions, including the value of emergency ordering and the value of emergency production planning evaluates the effectiveness of the emergency decisions. Due to the staggering size of the problem, sample average approximation method is used to solve the problem.  相似文献   
9.
目的:建立HPLC法分别定量测定大苞荆芥中木犀草素、芹菜素及其糖苷木犀草素-7-O-β-D-葡萄糖醛酸苷(LGCRP)、芹菜素-7-O-葡萄糖醛酸苷(AGCRP)的方法。方法:采用 C18 柱(250 mm×4.6 mm, 5 μm),以乙腈-0.1%磷酸水溶液(0.1:99.9,v/v)为流动相进行梯度洗脱,检测波长347 nm,流速1 mL/min,柱温30 ℃;优化了提取溶剂、溶剂加入量、提取时间等药材前处理方法;通过系统适用性试验,线性关系、检出限及定量限考察,精密度、重复性、稳定性及加标回收率试验,验证方法的适用性。结果:木犀草素、芹菜素和LGCRP、AGCRP分别在3.080~12.321、4.753~19.010、5.67~22.68、9.97~39.86 μg/mL范围内与各自峰面积呈良好的线性关系,r值均大于0.9993;检出限分别为0.11、0.08、0.03、0.03 μg/mL,定量限分别为0.35、0.23、0.09、0.10 μg/mL,精密度、稳定性和重复性均良好,加标回收率范围分别为98.8%~102.8%、92.9%~98.1%、93.9%~97.9%、93.7%~97.3%。结论:两套方法操作简便、灵敏度高、稳定性好、准确度高、适用性强,可用于大苞荆芥中2个黄酮及其糖苷类成分的定量测定,从而为大苞荆芥药材质量标准的制定提供依据。  相似文献   
10.
Improved column efficiencies and decreased tailing of Eu3+ and Lu3+ elution peaks with 2-hydroxy isobutyric acid, HIBA, were obtained by partial sulfonation of experimental monodisperse 5 and 10 μm, highly (>40%) crosslinked porous beads. Blocking of micropores of such highly crosslinked porous gels with n-dodecane before sulfonation further reduces the extent of sulfonation and improves column efficiency. Simultaneous choice of a smaller particle size and less sulfonation improves the column performance. The normalized performance of a monodisperse 10 μm, highly crosslinked porous resin of 0.058 meq/ml capacity was similar to that of a monodisperse 15 μm, 10% crosslinked surface sulfonated gel type resin of 0.031 meq/ml capacity for Lu3+/HIBA.  相似文献   
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