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991.
Wook Hyun Kwon Beom Jin Chung Jung Woo Park Gi Won Lee Man Chul Yoon 《Power Delivery, IEEE Transactions on》1992,7(1):160-166
The authors present a real-time network using an optical-fiber transmission line and implement the prototype network system for a proposed integrated digital protection and control system. A single network structure is investigated which supports both protection and control functions. It realizes high-speed communications among the power equipment. As a communication protocol the IEEE 802.4 token passing bus protocol with fiber-optic medium is employed, taking substation environments into account. Two implementation schemes for the communication scheme are suggested which are based on the IEEE 802.4 specifications. An allocation method is presented for setting the network parameter and some performance indices are analyzed. Through the experiments, it is shown that the proposed prototype network system satisfies the necessary requirements in substations 相似文献
992.
M. N. Labib Woo Ju-sik Choi Du-youl T. Utomo B. Fajar Chung Han-shik Jeong Hyo-min 《中南工业大学学报(英文版)》2012,19(4):953-961
Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.
The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet. Four variations
of lean angles, that is, 8°, 10°, 15° and 20°, were made at first stage impeller. Reynolds Average Navier Stokes equation
was used in simulation together with a shear-stress transport (SST) k-w turbulence model and mixing-plane approach, respectively. Three dimensional fluid flows were simplified using periodic model
to reduce the computational cost and time required. A good performance was expected that the secondary flow can be effectively
reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow.
The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in
the flow passage, which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane
downstream of impeller. The numerical solutions were performed and allowed the optimum design and operating conditions to
be obtained. 相似文献
993.
An electrical impedance tomography (EIT) system that uses the optimal current method to inject currents and the regularized Newton-Raphson algorithm to reconstruct an image of resistivity distribution is discussed. Iterative methods to derive the optimal current patterns through iterative physical measurements are developed. Direct methods to first determine the resistance matrix of a resistivity distribution through a set of current bases is injected and the measured voltage responses are stored. This permits iterative reconstruction techniques to operate on the stored data without requiring lengthy data taking from the object and reduces the effects of motion artifacts. The direct methods have superior performance as compared to the iterative methods in both optimal current and voltage generation. The results obtained with three sets of current bases are studied. 相似文献
994.
Four single crystals of fully dehydrated and partially Zn2+-exchanged zeolites Y (Si/Al?=?1.56) were prepared by the static ion-exchange method using a mixed ion-exchange solution in which Zn(NO3)2:NaCl mole ratios were 1:1 (crystal 1), 1:25 (crystal 2), 1:50 (crystal 3), and 1:100 (crystal 4), respectively, with a total concentration of 0.05 M, and followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd\(\bar {3}\)m and refined to the final error indices R1/wR2?=?0.0459/0.1454, 0.0449/0.1283, 0.0427/0.1284, and 0.0486/0.1680, respectively. Their unit-cell formulas are |Zn25Na25|[Si117Al75O384]-FAU (crystal 1), |Zn19.5Na36|[Si117Al75O384]-FAU (crystal 2), |Zn19.5Na36|[Si117Al75O384]-FAU (crystal 3), and |Zn7Na61|[Si117Al75O384]-FAU (crystal 4), respectively. The degree of Zn2+ exchange decreases from 67 to 19% as the initial concentration of Zn2+ decrease and the initial concentration of Na+ increases in given ion-exchange solutions. 相似文献
995.
996.
E‐Skin Tactile Sensor Matrix Pixelated by Position‐Registered Conductive Microparticles Creating Pressure‐Sensitive Selectors
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Insang You Song‐Ee Choi Hyejin Hwang Sang Woo Han Jin Woong Kim Unyong Jeong 《Advanced functional materials》2018,28(31)
Electronic skin (E‐skin) imitates human skin by converting external stimuli into electrical signals. E‐skin requires high flexibility and a high level of device integration. Unlike conventional E‐skin creation methods, a highly sensitive pressure sensor matrix (100 pixels cm?2) made of position‐registered elastic conductive microparticles (MPs) is created. The MPs form a Schottky junction with the bottom electrode and the current through the junction is sensitive to external pressure, forming a simple one‐selector two‐terminal device array. The Schottky junction eliminates the electrical cross talks between the sensor pixels consisting of 64 MPs in each. The flexible pressure sensor matrix is used as an artificial fingertip for Braille reading and as an electronic scale based on detailed force distribution. This work opens up the possibility that assembled MPs, which have been a long‐standing research topic in academia, can be used to make practical electronic devices. 相似文献
997.
Engineering the Electrochemical Temperature Coefficient for Efficient Low‐Grade Heat Harvesting
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Caitian Gao Yuling Yin Lu Zheng Yezhou Liu Soojin Sim Yongmin He Chao Zhu Zheng Liu Hyun‐Wook Lee Qinghong Yuan Seok Woo Lee 《Advanced functional materials》2018,28(35)
Low‐grade heat to electricity conversion has shown a large potential for sustainable energy supply. Recently, the low‐grade heat harvesting in the thermally regenerative electrochemical cycle (TREC) is a promising candidate with high energy conversion efficiency. In this system, the electrochemical temperature coefficient (α) plays a dominant role in efficient heat harvesting. However, the internal factors that affect α are still not clear and significant improvements are needed. Here, α of various Prussian Blue analogues (PBAs) is investigated and their lattice change during cation intercalation is monitored using the ex situ X‐ray diffraction (XRD) method. For the first time, it is found that α is highly related to the lattice parameter change. Large lattice shrinkage exhibits a large negative α, while lattice expansion is corresponding to a positive α. These are mainly attributed to the different phonon vibration entropy changes upon cation intercalation in various PBAs. Especially, purple cobalt hexacynoferrate delivers the largest α of ?0.89 mV K?1 and enables highly efficient heat conversion efficiency up to 2.65% (21% of relative efficiency). The results of this study provide a fundamental understanding of temperature coefficient in electrochemical reactions and pave the way for designing high‐performance material for low‐grade heat harvesting. 相似文献
998.
Polydopamine‐Graphene Oxide Flame Retardant Nanocoatings Applied via an Aqueous Liquid Crystalline Scaffold
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Hanim Kim Dae Woo Kim Vivek Vasagar Heonjoo Ha Sergei Nazarenko Christopher J. Ellison 《Advanced functional materials》2018,28(39)
A highly effective flame retardant (FR) nanocoating was developed by conducting oxidative polymerization of dopamine monomer within an aqueous liquid crystalline (LC) graphene oxide (GO) scaffold coating. Due to its high water content, the LC scaffold coating approach facilitated fast transport and polymerization of dopamine precursors into polydopamine (PDA) within the water swollen interlayer galleries. Uniform and periodically stacked (14.5 Å d‐spacing) PDA/GO nanocoatings could be universally applied on different surfaces, including macroporous flexible polyurethane (PU) foam and flat substrates such as silicon wafers. Remarkably, PDA/GO coated PU foam exhibited highly efficient flame retardant performance reflected by a 65% reduction in peak heat release rate at 5 wt% PDA/GO loading in an 80 nm thick coating. While many physically mixed flame retardants are usually detrimental to the mechanical properties of the foam, the PDA/GO coating did not affect mechanical properties substantially. In addition, the PDA/GO coatings were stable in water due to the intrinsic adhesion capability of PDA and the transformation of GO to the more hydrophobic reduced GO form. Given that PDA is produced from dopamine, a molecule prevalent in nature, these findings suggest that significant opportunities exist for new polymeric FRs derived from other natural catechols. 相似文献
999.
Hydrogels: Ascidian‐Inspired Fast‐Forming Hydrogel System for Versatile Biomedical Applications: Pyrogallol Chemistry for Dual Modes of Crosslinking Mechanism (Adv. Funct. Mater. 6/2018)
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1000.
Point‐of‐Care Diagnostics: Host Cell Mimic Polymersomes for Rapid Detection of Highly Pathogenic Influenza Virus via a Viral Fusion and Cell Entry Mechanism (Adv. Funct. Mater. 34/2018)
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