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991.
The exothermic reactor for ammonia synthesis is a primary device determining the performance of the energy storage system. The Braun-type ammonia synthesis reactor is used as the exothermic reactor to improve the heat release rate. Due to the entirely different usage scenarios and design objectives, its parameters need to be redesigned and optimized. Based on finite-time thermodynamics, a one-dimensional model is established to analyze the effects of inlet gas molar flow rate, hydrogen–nitrogen ratio, reactor length and inlet temperature on the total entropy generation rate and the total exothermic rate of the reactor. It’s found that the total exothermic rate mainly depends on the inlet molar flow rate. Furthermore, considering the minimum total entropy generation rate and maximum total exothermic rate, the NSGA-II algorithm is applied to optimize seven reactor parameters including the inlet molar flow rate, lengths and temperatures of the three reactors. Lastly, the optimized reactor is obtained from the Pareto front using three fuzzy decision methods and deviation index. Compared with the reference reactor, the total exothermic rate of the optimized reactor is improved by 12.6% while the total entropy generation rate is reduced by 3.4%. The results in this paper can provide some guidance for the optimal design and application of exothermic reactors in practical engineering. 相似文献
992.
YinQing Yao KaiChun Zhao YiYing Zhuang XiaoChao Chen Prof.Dr. Yong Lu Prof.Dr. Ye Liu 《ChemistryOpen》2022,11(4)
The one‐pot synthesis of 2,5‐furandicarboxylic acid from 2‐furoic acid with a yield of 57 % was achieved for the first time using a Pd‐catalyzed bromination‐hydroxycarbonylation tandem reaction in HOAc‐NaOAc buffer. This synthetic protocol shows major improvements compared to previously reported methods, such as using biomass‐based 2‐furoic acid as low‐cost raw material, one‐pot synthesis without isolation of intermediate products, and no need for an acidification procedure. Experiments indicate that the involved Xantphos‐modified Pd‐catalyst and the buffer solution play significant promoting roles for each individual reaction whereas Br2 (as the brominating reagent) had a negative effect on the second hydroxycarbonylation step, while CO was deleterious for the first bromination step. Hence, in this practical one‐pot synthesis, Br2 should be consumed in the first bromination step as fully as possible, and CO is introduced after the first bromination step has been completed. 相似文献
993.
在数字化油田发展的今天,光纤通信已经普及,但仍有部分单位没有实现光纤入户.这些单位还在使用机顶盒与非对称数字用户线路(Asymmetric Digital Subscriber Line,ADSL)宽带,由此带来的故障不可避免.通过分析长期在边远地区实际工作中遇到的故障,总结了机顶盒与ADSL宽带故障的各种原因和常见的... 相似文献
994.
传统湿度传感器制造工艺复杂、需有线连接信号,对此,文中提出一种纸基无芯片射频识别(Radio Frequency Identification, RFID)湿度传感器。为提升传感器谐振特性,选择非对称开口环内部分布式加载金属碎片作为传感器结构,聚乙烯醇(PVA)作为湿敏材料,使用遗传算法和HFSS射频仿真软件来设计并优化传感器结构。以喷墨打印技术制作传感器样品,采用滴涂法在传感器表面分别制备了5%、10%、15%三种质量浓度比的PVA薄膜。湿敏特性仿真及测试结果一致表明:PVA与纸基底协同作用可显著提高传感器灵敏度。随PVA浓度增加灵敏度增加,15%PVA传感器灵敏度最高,高湿灵敏度达到12.22 MHz/%RH,但随PVA浓度增加恢复特性变差,5%PVA湿度传感器具有良好的恢复特性,恢复度达83.87%。通过长期多次实验验证了PVA纸基湿度传感器具有良好的温度稳定性与中长期稳定性。与同类研究成果对比,文中设计在感湿范围及灵敏度方面有优势且制造工艺更简单,为低成本湿度传感器的大规模使用提供了可能。 相似文献
995.
996.
实验室质量体系运行的关键控制点分析 总被引:1,自引:0,他引:1
通过对十几年来实验室计量认证的经验总结,对县级实验室质量体系运行情况进行了分析。指出了质量体系运行的关键控制点、存在的问题、解决问题的方法。经分析认为,基层实验室的生存和发展必然趋势是提高自身的检测能力。 相似文献
997.
Jing-xue Wang Chao Zhang Zheng-xin Zhang Qing-dong Chen Qing-guo Zhang Zu-liang Du 《化学物理学报(中文版)》2007,20(2):191-196
X-ray diffraction (XRD) was used to investigate the microstructure and phase separation of mixed multilayers of cadmium stearate (SA) and behenate (BA) deposited onto hydrophilic glass by the Langmuir-Blodgett technique. No unitary fatty acid diffraction peaks in the XRD spectra of the mixed LB films, which reveals that domains in these samples are small and uniform. The interplanar spacing of the mixed LB films changes with the ratio of BA to SA in a step-shaped curve, which suggests that with the changing of the ratio between BA and SA, only three kinds of ordered structure form in the mixed system, and each microstructure, in particular, the short chains against long chains meshed microstructure can be maintained in a certain ratio range . In addition, for the meshed microstructure, the alkyl chains of both SA and BA stand straight or may have exactly the same small tilted angle from the substrate normal, as is indicated by the symmetric and asymmetric stretching vibration of methylene (CH2) peaks which are at 2847.80 and 2914.37 cm-1respectively in the Fourier transform infrared (FT-IR) transmission spectra. The mixed system always goes through a longitudinal regularity decreasing process when BA/SA is out of the intermediate ratio range (BA/SA: 1/5-1/1), which is illustrated by the relative XRD intensity changing with the ratio of BA/ SA in a \W" shape. These results for the mixed LB films of BA/SA provide meaningful data for choosing the mixture ratio when fabricating composite films with special structure. 相似文献
998.
催化链转移聚合制备接枝型两亲共聚物及其溶液性质研究 总被引:2,自引:0,他引:2
采用大分子单体法制备接枝型两亲共聚物, 通过表面张力仪、偏光显微镜、旋转流变仪和小角X射线衍射研究了两亲共聚物在水溶液中的聚集行为及其相结构. 首先末端带有可聚合双键的聚甲基丙烯酸叔丁酯大分子单体(PtBMA Macromonomer)通过催化链转移聚合法制备, 所用到的催化链转移剂为二水合双(二氟化硼苯二酮肟)合钴(II) (COPhBF). 然后将所得到的大分子单体与丙烯酸正丁酯(BA)进行自由基共聚得到接枝共聚物PBA-g-PtBMA, PBA-g-PtBMA中PtBMA的侧链部分在酸性条件下定量水解成聚甲基丙烯酸(PMAA)并用NaOH中和得到主链疏水侧链亲水的接枝型两亲共聚物PBA-g-P(MAA-Na+). 用Wilhelmy吊片法研究了不同浓度的两亲共聚物水溶液的表面张力, 发现其行为与小分子表面活性剂不同. 同时用动态光散射法测量了两亲共聚物水溶液中聚集体的粒度, 发现在研究的浓度范围内(0.02~10 g/L)聚集体都存在两个粒度分布峰(约30和300 nm). 浓溶液(w=37.5%)的偏光显微照片呈现层状液晶的特征图案, 而流变研究表明此时体系具有明显的粘弹性, 说明体系形成了层状液晶. 并且用小角度X射线衍射测定了层状液晶的层间距, 约为12.6 nm. 相似文献
999.
1000.
LI Cun-man XIAO Yuan-sheng XUE Xing-ya FENG Jia-tao ZHANG Xiu-li LIANG Xin-miao . Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian P. R. China . Hebei Research Centre of Analysis Testing Hebei University of Science Technology Shijiazhuang 《高等学校化学研究》2011,(3):392-396
An efficient preparative method was successfully developed for isolation and purification of unstable components from medicinal plant extracts, using a combined method of preparative high performance liquid chro-matography(HPLC) and solid-phase extraction(SPE). The aim of this study was to obtain an effective method with high preparative efficiency and importantly to avoid the transformation of unstable compounds. The preparative HPLC system was based on an LC/MS controlled four-channel autopurification sys... 相似文献