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排序方式: 共有429条查询结果,搜索用时 15 毫秒
71.
Karthik Tripurari Linxiao Zhang Yang Xu David Gidony Branislav Jovanovic Harish Krishnaswamy Peter Kinget 《Analog Integrated Circuits and Signal Processing》2016,88(2):185-206
A wide-band RF channelizer architecture using the concept of 3-way iterative down-conversion is introduced. An example RF channelizer implementation splits the input spectrum of 0.6–9 GHz into 7 channels each with a 1.2 GHz bandwidth. This RF channelizer implementation has the ability of concurrently down-converting 3 channels enabling multi-Gbps aggregate data reception. It further demonstrates the ability to rapidly switch from receiving one channel to another which is crucial for rapid spectrum analysis. A prototype of the RF channelizer has been fabricated in a 65 nm standard CMOS process. A 400 Mbps (BPSK) data reception has been demonstrated by down-converting two channels concurrently. Channel switching can be as fast as 8 ns and is always faster than \(1\,\upmu s\). The chip occupies an area of 2 mm \(\times\) 1 mm and consumes an average power of 435 mW while offering a dynamic range between 58 and 63 dB. 相似文献
72.
Increased number of cardiomyocytes in cross-sections from tachycardia-induced cardiomyopathic hearts
S Jovanovic AJ Grantham JE Tarara JC Burnett A Jovanovic A Terzic 《Canadian Metallurgical Quarterly》1999,3(2):153-155
Based on positive identification of DNA replication and mitotic division in cardiomyocytes isolated from failing hearts, it has been proposed that adult ventricular cardiomyocytes can gain the capacity to proliferate with progression of heart failure. However, due to the lack of a reliable method to distinctly image individual cardiac cells within the myocardial syntitium, such a concept still remains largely controversial. In the present study, we used laser confocal microscopy, to image cross-sections of intact myocardium stained with fluorescein-conjugated wheat germ agglutinin and propidium iodide. This approach allowed to clearly separate the profile of individual myocytes within cardiac tissue sections. We found that in the left ventricles of dogs, subjected to tachycardia-induced cardiomyopathy, the number of cells was significantly increased in both longitudinal and transversal sections. Treatment with the angiotensin-converting enzyme inhibitor, enalapril, reversed these changes to values similar to those found in controls. Therefore, this study provides evidence, at the in situ level, for cellular hyperplasia in heart failure. This supports the more general notion that adult cardiomyocytes may not be terminally differentiated, and that an increase in cell number could contribute to the increase in left ventricular mass observed with progression of disease. 相似文献
73.
The aim of this article was to investigate the effect of a NaA‐type zeolite on a polydimethylsiloxane (PDMS)–zeolite composite. The obtained results show that the introduction of a NaA‐type zeolite into polysiloxane matrices results in a change of the equilibrium degree of swelling (DSe) of composites in toluene, their hardness, and their thermal stability. With increase in the zeolite, the time required to achieve the DSe is reduced, DSe decreases, and hardness increases. A double effect of the zeolite concentration on the change of the composite characteristics was noted. At zeolite concentrations of up to 20%, there is a drastic change of the DSe and hardness with zeolite concentration, while this effect is considerably less pronounced at higher concentrations. The results obtained show that a NaA‐type zeolite plays the role of a reinforcing filler. A new mechanism of bonding the zeolite into the composite was suggested. According to this model, there is a possibility that bonds are established between the polymer and the zeolite via interaction of the π‐bond of terminal vinyl groups of PDMS with the Na cation of the zeolite. With increase in the zeolite concentration in the composite, the total number of established polymer–zeolite bonds increases, but the density of the interaction decreases. This explains the change in the characteristics of the composite with the change of zeolite concentration. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1171–1176, 2000 相似文献
74.
采用假单胞菌脂肪酶Pseudomonas sp. ECU1011催化乙酰基邻氯扁桃酸进行不对称水解,利用突变后的扁桃酸消旋酶(V29I)对拆分后的产物S-(-)-邻氯扁桃酸进行消旋,消旋后的邻氯扁桃酸经过酰化重新被利用到水解反应中,实现了酶法动态动力学拆分制备R-(-)-乙酰基邻氯扁桃酸。通过对拆分反应、拆分混合物的分离回收以及消旋反应的工艺优化,最终获得光学纯度ee>99.9%的R-(-)-乙酰基邻氯扁桃酸,其收率达80%。本研究建立的R-(-)-乙酰基邻氯扁桃酸的动态动力学拆分工艺,对其工业化应用具有重要的指导意义。 相似文献
75.
Owens C Zisser H Jovanovic L Srinivasan B Bonvin D Doyle FJ 《IEEE transactions on bio-medical engineering》2006,53(6):996-1005
Run-to-run control has been applied to several traditional batch processes in the chemical industry. The 24-h cycle of eating meals, measuring blood glucose concentrations, and delivering the correct insulin bolus, with the goal of achieving the optimal blood glucose profile, can be viewed in the same spirit as traditional batch processes such as emulsion polymerization. In this paper, we aim to exploit the "repetitive" nature of the insulin therapy of people with Type 1 diabetes. A run-to-run algorithm is used on a virtual diabetic patient model to control blood glucose concentrations. The insulin input is parameterized into the timing and amount of the dose while the glucose output is parameterized into the maximum and minimum glucose concentrations. Robustness of the algorithm to variations in the meal amount, meal timing, and insulin sensitivity parameter is addressed. In general, the algorithm is able to converge when the meal timing is varied within +/- 40 min. If the meal size is underestimated by approximately 10 grams (g), the algorithm is able to converge within a reasonable time frame for breakfast, lunch, and dinner. If the meal size is overestimated by 20-25 g, the algorithm is able to converge. When random variations in the meal timing and the meal amount are introduced, the variation on the output variables, Gmax and Gmin, scales according to the amount of variation allowed. Along with this, the insulin sensitivity of the virtual patient model is varied. The algorithm is robust for differences in insulin sensitivity less than +/- 50% of the nominal value. 相似文献
76.
Obradovic B Stojkovska J Jovanovic Z Miskovic-Stankovic V 《Journal of materials science. Materials in medicine》2012,23(1):99-107
Alginate colloid solution containing electrochemically synthesized silver nanoparticles (AgNPs) was investigated regarding
the nanoparticle stabilization and possibilities for production of alginate based nanocomposite hydrogels in different forms.
AgNPs were shown to continue to grow in alginate solutions for additional 3 days after the synthesis by aggregative mechanism
and Ostwald ripening. Thereafter, the colloid solution remains stable for 30 days and could be used alone or in mixtures with
aqueous solutions of poly(vinyl alcohol) (PVA) and poly(N-vinyl-2-pyrrolidone) (PVP) while preserving AgNPs as verified by UV–Vis spectroscopy studies. We have optimized techniques
for production of Ag/alginate microbeads and Ag/alginate/PVA beads, which were shown to efficiently release AgNPs decreasing
the Escherichia coli concentration in suspensions for 99.9% over 24 h. Furthermore, Ag/hydrogel discs based on alginate, PVA and PVP were produced
by freezing-thawing technique allowing adjustments of hydrogel composition and mechanical properties as demonstrated in compression
studies performed in a biomimetic bioreactor. 相似文献
77.
78.
Kusljevic M. D. Tomic J. J. Jovanovic L. D. 《IEEE transactions on instrumentation and measurement》2010,59(2):322-329
79.
Kimikazu Sasa Tsutomu Takahashi Yuki Tosaki Yuki Matsushi Keisuke Sueki Michiko Tamari Takahiro Amano Toshiyuki Oki Shozo Mihara Yoshihiro Yamato Yasuo Nagashima Kotaro Bessho Norikazu Kinoshita Hiroshi Matsumura 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2010,268(7-8):871-875
We present the current status and research programs of a multinuclide accelerator mass spectrometry (AMS) system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system), Japan. A maximum terminal voltage of 12 MV is available for the AMS system. The Tsukuba AMS system can measure environmental levels of long-lived radioisotopes of 14C, 26Al, 36Cl and 129I by employing a molecular pilot beam. Recently, enhancements in AMS techniques and equipment, including sample preparation, the ion source and the data acquisition system, have improved the performance of 36Cl-AMS. The standard deviation of fluctuations is typically ±2%, and the machine background level for the 36Cl/Cl ratio is lower than 1 × 10?15 with a halite sample. We have measured over 500 samples in 1 year, including samples for earth and environmental sciences and nuclear safety research. 相似文献
80.
基于精细生产的基本原理,提出了露天矿精细化开采技术体系。利用虚拟仪器技术、数据库技术,建立一个集安全生产工艺信息、隐患信号监测数据及预警决策指挥模块于一体的露天矿精细化开采信息采集与处理系统。该系统由传感器、信号硬件调理设备、数据采集卡与计算机等组成,软件平台的设计采用LabVIEW虚拟仪器软件。本系统采集项目可扩充,能够对露天开采信息进行实时采集与传输,进而实现露天矿开采工艺环节的实时监控、数据共享和安全状况的实时监测。研究成果有望改变传统露天矿山粗放式的开采模式,进一步丰富露天矿精细化开采技术体系。 相似文献