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991.
Jeongho Park Jihyung Kim Myonghee Park Kyunbyoung Ko Changeon Kang Daesik Hong 《Wireless Communications, IEEE Transactions on》2006,5(7):1622-1625
The authors present an analysis of the effect of timing offset on channel estimation for comb-type pilot-aided orthogonal frequency division multiplexing (OFDM) systems. Residual timing offset does not negatively affect the channel estimation of the pilot subcarrier, but does corrupt the channel information obtained via interpolation. This paper provides the mean square error (MSE) channel estimation performance when a linear interpolation technique is used in a comb-type pilot-aided OFDM system. Analysis shows that the performance degradation of the channel estimator due to imperfect frame synchronization is dependent on the frequency correlation of the channels and the amount of timing offset 相似文献
992.
In this paper, we propose a new architecture for multicast ATM switches with fault tolerant capability based on the Clos–Knockout switch. In the new architecture, each stage has one more redundant switch module. If one switch module is faulty, the redundant module would replace the faulty one. On the other hand, under the fault‐free condition, the redundant modules in the second and third stages will provide additional alternative internal paths, and hence improve the performance. The performance analysis shows that the cell loss probability is lower than the original architecture when all modules are fault free, and the reliability of the original architecture is improved. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
993.
Existing IP routing algorithms have been developed mainly for non‐VLAN networks. For these routing algorithms to work, an end station must be attached to its associated network. The introduction of VLAN has, however, allowed the physical location of the end station to be changed from time to time. Therefore, some extra mechanism is required to support routing in VLAN environment. Existing approaches have some drawbacks in terms of inefficiency in traffic forwarding and switch software complexity. In this paper, a simple and efficient method for routing over IP subnet VLAN in Ethernet is proposed. This method has been implemented in hardware and found to work correctly. Various measurements and analyses have been performed to verify the efficiency of this protocol. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
994.
The proposed circuit is a multiple output quasi-resonant (QR) zero-current switching (ZCS) switched-capacitor (SC) converter with a bidirectional power flow control conversion scheme. The principles of the proposed multiple output QR ZCS SC bidirectional dc–dc converter are described using a detailed circuit model for analysis. Simulation and experimental results are carried out to verify the validity and the soft switching performance of the proposed converter. The maximum efficiency achievable is about 94 and 92% for the forward and reverse power flow control schemes, respectively. The output voltage can be regulated by changing the switching frequency for the designed compensated closed-loop controller. 相似文献
995.
Minjeong Ha Seongdong Lim Jonghwa Park Doo‐Seung Um Youngoh Lee Hyunhyub Ko 《Advanced functional materials》2015,25(19):2841-2849
The development of electronic skin (e‐skin) is of great importance in human‐like robotics, healthcare, wearable electronics, and medical applications. In this paper, a bioinspired e‐skin design of hierarchical micro‐ and nano‐structured ZnO nanowire (NW) arrays in an interlocked geometry is suggested for the sensitive detection of both static and dynamic tactile stimuli through piezoresistive and piezoelectric transduction modes, respectively. The interlocked hierarchical structures enable a stress‐sensitive variation in the contact area between the interlocked ZnO NWs and also the efficient bending of ZnO NWs, which allow the sensitive detection of both static and dynamic tactile stimuli. The flexible e‐skin in a piezoresistive mode shows a high pressure sensitivity (?6.8 kPa?1) and an ultrafast response time (<5 ms), which enables the detection of minute static pressure (0.6 Pa), vibration level (0.1 m s?2), and sound pressure (≈57 dB). The flexible e‐skin in a piezoelectric mode is also demonstrated to be able to detect fast dynamic stimuli such as high frequency vibrations (≈250 Hz). The flexible e‐skins with both piezoresistive and piezoelectric sensing capabilities may find applications requiring both static and dynamic tactile perceptions such as robotic hands for dexterous manipulations and various healthcare monitoring devices. 相似文献
996.
Suk Ho Kim Jongwon Yoon Su Ok Yun Youngkyu Hwang Hun Soo Jang Heung Cho Ko 《Advanced functional materials》2013,23(11):1375-1382
To create ultrathin sticker‐type electronic devices that can be attached to unconventional substrates, it is highly desirable to develop printable membrane‐type electronics on a handling substrate and then transfer the printing to a target surface. A facile method is presented for high‐efficiency transfer printing by controlling the interfacial adhesion between a handling substrate and an ultrathin substrate in a systematic manner under mild conditions. A water‐soluble sacrificial polymer layer is employed on a dimpled handling substrate, which enables the topological confinement of the polymer residue inside and near the dimples during the etching and drying processes to reduce the interfacial adhesion gently, creating a high yield of transfer printing in a deterministic manner. As an example of an electronic device that was created using this method, a highly flexible sticker‐type ZnO thin film transistor was successfully developed with a thickness of 13 μm including a printable ultrathin substrate, which can be attached to various substrates, such as paper, plastic, and stickers. 相似文献
997.
Yuming Jiang Chen‐Khong Tham Chi‐Chung Ko 《Transactions on Emerging Telecommunications Technologies》2002,13(6):563-577
In computer networks, the Strict Priority (SP) discipline is perhaps the most common and simplest method to schedule packets from different classes of applications, each with diverse performance requirements. With this discipline, however, packets at higher priority levels can starve packets at lower priority levels. To resolve this starvation problem, we propose to assign a parameter to each priority queue in the SP discipline. The assigned parameter determines the probability or extent by which its corresponding queue is served when the queue is polled by the server. We thus form a new packet service discipline, referred to as the Probabilistic Priority (PP) discipline. By properly adjusting the assigned parameters, not only is the performance of higher priority classes satisfied, but also the performance of lower priority classes can be improved. This paper analyzes the delay performance of the PP discipline. A decomposition approach is proposed for calculating the average waiting times and their bounds are studied. Two approximation approaches are proposed to estimate the waiting times. Simulation results that validate the numerical analysis are presented and examined. A numerical example which demonstrates the use of the PP discipline to achieve service differentiation is presented. This example also shows how the assigned parameters can be determined from the results of analysis mentioned above. 相似文献
998.
Abstract: Antimicrobial activities of chitosan against lactic acid bacteria were studied to apply for controlling dongchimi (whole-radish juicy kimchi) fermentation to prevent over-ripening. Antimicrobial activity of chitosan against lactic acid bacteria such as Leuconostoc mesenteroides and Lactobacillus plantarum was assayed at 10, 20, 30, and 40 mg/L concentration in the medium. The addition of 40 mg/L of the chitosan prepared at 140 °C for 10 min showed strong inhibitory effect on the growth of L. mesenteroides and L. plantarum. The effects of addition of chitosan to dongchimi have also been studied during fermentation at different temperatures of 4, 10, and 20 °C. Addition of chitosan decreased markedly viable cell counts of lactic acid bacteria such as Leuconostoc spp. and Lactobacillus spp. at the initial stage. Subsequently the lactic acid bacteria recovered the growth to the same level as non-chitosan treated dongchimi. During the dongchimi fermentation, the addition of chitosan at larger quantity up to 1000 mg/L (CS1000) prolonged the palatable fermentation period. Addition of chitosan in the dongchimi seemed to inhibit the growth of lactic acid bacteria, thereby lowering the acid content. It, therefore, caused the shelf life to be extended and resulted in a prolonged palatable period for the dongchimi. 相似文献
999.
ABSTRACT: Change in tilapia myosin molecular conformation due to pressurization at 50 to 200 MPa for 0 to 60 min was investigated. After a 50-MPa treatment, tilapia myosins slightly decreased their total sulfhydryl contents and exposed their hydrophobic residues. Experimental results indicated that 100- and 150-MPa treatments caused an apparent unfolding of myosins and a 1-fold increase of their surface hydrophobicity ( S o ). Myosins mainly formed intermolecular disulfide bonds with pressures of 100 to 200 MPa. In addition, increasing pressures altered the myosin conformation and decreased its Ca-ATPase activity. Myosin apparently unfolded and formed disulfide bonds and hydrophobic interactions with pressurizing at 150 MPa. 相似文献
1000.
Ivona Kožárová Jana Janošová Dionýz Máté Soña Tkáčiková 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2013,30(7):978-987
The aim of the present study was to evaluate three microbial inhibition tests (MIT) based on inhibition of growth of the test organisms: (a) four plate test (FPT) containing Bacillus subtilis BGA, (b) screening test for antibiotic residues (STAR) containing Bacillus stearothermophilus var. calidolactis_ATCC 10149 and (c) the Premi®Test containing Bacillus stearothermophilus var. calidolactis. The tests were used to determine sulphamethazine (SMZ) residues in edible tissues of rabbit after oral administration up to day 15 of the withdrawal period (WP). A solvent extraction procedure was used to enhance the capability of the tests to detect SMZ residues at or below the maximum residue limit (MRL). Para-aminobenzoic acid (PABA) was employed to previously identify SMZ residues in the first stage of the residue screening. The presence of SMZ residues in the samples was confirmed and quantified by a validated HPLC method. The Premi®Test detected SMZ residues in the muscle and heart tissue up to day 9 of the WP, and in the liver, lungs and kidneys up to day 10 of the WP. The STAR detected SMZ residues in the edible organs of rabbits up to day 8 of the WP. The kidneys were positive up to day 5 of the WP, the liver until day 4 of the WP and the lungs until day 3 of the WP. No SMZ residues were detected in the muscle and heart. By using the solvent extraction procedure, SMZ residues were detected in the muscle extract up to day 10 of the WP and the muscle was positive until day 6 of the WP. No detection sensitivity was observed using the FPT. After solvent extraction, SMZ residues were detected in the muscle extract until day 8 of the WP and the muscle was positive until day 3 of the WP. No positive results were detected after the addition of PABA into/onto the agar medium. PABA at a concentration of 10 µg ml?1 completely reversed the inhibitory activity of SMZ and enabled reliable identification of SMZ in the examined samples. Using HPLC, SMZ was detected in the muscle samples until day 10 of WP (0.02 mg kg?1) and in the liver until day 12 of the WP (0.09 mg kg?1). The results obtained by the HPLC method and the limit of detection (LOD) of screening tests for SMZ (FPT 0.4 µg ml?1, STAR 0.2 µg ml?1, Premi® Test 0.05 µg ml?1) allowed us to state that the most suitable screening tests for the detection of SMZ residues in the edible tissues of rabbits at level corresponding to the MRL of 0.1 mg kg?1, established for sulphonamides, are the Premi®Test and STAR in conjunction with the solvent-extraction procedure. 相似文献