共查询到19条相似文献，搜索用时 234 毫秒
1.
In an object-based storage system, a novel scheme named EAP （extending attributes page） is presented to enhance the metadata reliability of the system by adding the user object file information attributes page for each user object and storing the file-related attributes of each user object in object-based storage devices. The EAP scheme requires no additional hardware equipments compared to a general method which uses backup metadata servers to improve the metadata reliability. Leveraging a Markov chain, this paper compares the metadata reliability of the system using the EAP scheme with that using only metadata servers to offer the file metadata service. Our results demonstrate that the EAP scheme can dramatically enhance the reliability of storage system metadata. 相似文献
2.
To efficiently exploit the performance of single instruction multiple data （SIMD） architectures for video coding, a parallel memory architecture with power-of-two memory modules is proposed. It employs two novel skewing schemes to provide conflict-free access to adjacent elements （8-bit and 16-bit data types） or with power-of-two intervals in both horizontal and vertical directions, which were not possible in previous parallel memory architectures. Area consumptions and delay estimations are given respectively with 4, 8 and 16 memory modules. Under a 0.18-pm CMOS technology, the synthesis results show that the proposed system can achieve 230 MHz clock frequency with 16 memory modules at the cost of 19k gates when read and write latencies are 3 and 2 clock cycles, respectively. We implement the proposed parallel memory architecture on a video signal processor （VSP）. The results show that VSP enhanced with the proposed architecture achieves 1.28× speedups for H.264 real-time decoding. 相似文献
3.
A continuous-time nonlinear model predictive controller （NMPC） was designed for a boiler-turbine unit. The controller was designed by optimizing a receding-horizon performance index, with the nonlinear system approximated by its Taylor series expansion with a certain order, the magnitude saturation constraints on the inputs satisfied by increasing the predictive time, and the rate saturation conditions on the actuators satisfied by tuning the time constant of the reference trajectories in a reference governor. Simulation results showed that the controller can drive the drum pressure and output power of the nonlinear boiler-turbine unit to follow their respective reference trajectories throughout a varying operation range and keep the water level deviation within tolerances. Comparison of the NMPC scheme with the generic model control （GMC） scheme indicated that the responses are slower and there are more oscillations in the responses of the water level, fuel flow input and feed water flow input in the GMC scheme when the boiler-turbine unit is operating over a wide range. 相似文献
4.
The biggest difference between Star and Trados and DéjàVu is that Star has no translation memory.When working with Trados or DéjàVu,the user will always build up the translation memory.During the translation,user can click"Set/Close Next Open/Get"in Trados translation workbench or"Add Pair to Translation Memory"in DéjàVu to send the translated sentence pair to the translation memory.In that case,translation memory is like a big storage,the more translation work the user does,the more translation units the memory has and large memory usually requires large storage space.However,Star develops a distinct function of alignment.With alignment,users can match source text and its corresponding target text as reference language pairs.This is a flexible solution of translation assistance,but it may not be as systematic as translation memory is. 相似文献
5.
We propose a medium access control （MAC） protocol for uplink transmissions in wireless local area networks （WLANs）, where both stations and access points （APs） are equipped with multiple antennas. The protocol solves some common problems in utilizing multiple input multiple output （MIMO） under the 802.11 protocol, e.g., how to deploy preamble （training sequence） used for channel estimation and how to enable simultaneous data transmissions, and facilitates two simultaneous uplink data transmissions via a cross-layer approach. Furthermore, we develop a 3D discrete-time Markov model to analyze the performance of the proposed WLAN scheme. The analytical results are verified by simulation, and numerical results show that the system throughput can be significantly improved by our proposed scheme as compared with conventional schemes. 相似文献
6.
The existing H.264/AVC rate control schemes rarely include the perceptual considerations. As a result, the improvements in visual quality are hardly comparable to those in peak signal-to-noise ratio （PSNR）. In this paper, we propose a perceptual importance analysis scheme to accurately abstract the spatial and temporal perceptual characteristics of video contents. Then we perform bit allocation at macroblock （MB） level by adopting a perceptual mode decision scheme, which adaptively updates the Lagrangian multiplier for mode decision according to the perceptual importance of each MB. Simulation results show that the proposed scheme can efficiently reduce bit rates without visual quality degradation. 相似文献
7.
Reputation-based linear cooperation for spectrum sensing in cognitive radio networks 总被引：1，自引：0，他引：1
We propose a reputation-based cooperative spectrum sensing scheme in cognitive radio （CR） networks to solve the uncertainty resulting from the multipath fading and shadowing effect. In the proposed scheme, each cooperative CR user has a reputation degree that is initialized and adjusted by the central controller, and used to weight the sensing result from the corre- sponding CR user in the linear fusion process at the central controller. A simple method for adjusting the reputation degree of CR users is also presented. We analyzed and evaluated the detection performance of the reputation-based cooperative spectrum sensing scheme. Simulation results showed that our proposed scheme alleviates the problem of corrupted detection resulting from destructive channel conditions between the primary transmitter and the CR user. The performance of our proposed scheme was improved compared to the average-based linear cooperation scheme, and was similar to that of the optimal linear cooperation scheme with feasible computational complexity. Moreover, our proposed scheme does not require knowledge of channel statistics. 相似文献
8.
The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode （LED） driving and liquid crystal display （LCD） biasing. In these applications, a regulator with small volume, fewer external components and high efficiency is highly desired. This paper proposes a projected off- and on-time boost control scheme, based on which a monolithic IC with an on-chip VDMOS with 0.2 Ω on-state resistance RDS-ON was implemented in 1.5 μm bipolar-CMOS-DMOS （BCD） process. A 12 V, 0.3 A boost regulator prototype is presented as well. With projected off-time and modulated on-time in continuous conduction mode （CCM）, a quasi fixed frequency, which is preferred for ripple control, is realized. With projected on-time and modulated off-time in discontinuous conduction mode （DCM）, pulse frequency modulation （PFM） operation, which is beneficial to light load efficiency improvement, is achieved without extra control circuitry. Measurement results show that an efficiency of 3% higher than that of a conventional method under 0.5 W output is achieved while a step load transient response comparable to that of current mode control is maintained as well. 相似文献
9.
An underground heat storage system in a double-film-covered greenhouse and an adjacent greenhouse without the heat storage system were designed on the basis of plant physiology to reduce the energy consumption in greenhouses. The results indicated that the floor temperature was respectively 5.2℃, 4.6℃ and 2.0 ℃ higher than that of the soil in the adjacent reference greenhouse after heat storage in a clear, cloudy and overcast sky in winter. Results showed that the temperature and humidity were feasible for plant growth in the heat saving greenhouse. 相似文献
10.
A （t, n） threshold signature scheme distributes the secret key and hence the signing ability to n players in a way that any set of t＋ 1 or more honest players can collaborate to sign, while any set of t players cannot. In this paper we propose an identity-based threshold signature （IBTHS） scheme from bilinear pairings. The signing phase of our scheme is non-interactive, meaning that the signing players do not need to talk to each other. We prove our scheme secure （i.e., unforgeable and robust） in the standard model （i.e., without random oracles）. No earlier proposed IBTHS scheme achieved even one of the features of being non-interactive （in the signing phase） and secure in the standard model. 相似文献
11.
Network based data management is the backup/restore mechanism used in a data storage center. This paper presents a new network based data management-NDMP-Plus, a revision of network data management protocol. Components and the working mechanism of the NDMP-Plus architecture are first discussed. Two new techniques in NDMP-Plus-virtual storage layer （VSL） and negotiation mechanism are then studied. VSL is a crucial component to achieve flexibility, and the negotiation mechanism is a key to improve performance. Furthermore, experiments are carried out to evaluate the performance of NDMP-Plus. The result suggests that NDMP-Plus has stronger flexibility and better performance than NDMP. 相似文献
12.
A novel asymmetrical pitch system for rotary wing is presented. The pitch control characteristics are studied and analyzed.
Because elastic linkage is a key part in whole asymmetrical pitch system, in order to obtain the variation of the elastic
linkage deformation, an experimental platform mainly based on the device of micro aerial vehicles (MAVs) and a new control
system mounted on TMS320LF2407 are designed. This control system has its compacted configuration and reliability. Finally,
using this system to control the MAV for simulating the flying forward, experimental results show the MAV’s flight attitude
can be controlled based on the variation of the elastic linkage.
Project supported by the National Natural Science Foundation of China (Grant No.60605028), the National High-Technology Research
and Development Program of China (Grant No.2007AA04Z225), the Shanghai Rising-Star Program (Grant Nos.07QA14024, 07QH14006),
the Shanghai Shuguang Program (Grant No.07SG47), and the Shanghai Leading Key Laboratory of Mechanical Automation and Robotics
Science Foundation (Grant No.ZZ0805) 相似文献
13.
1 Introduction Microactuators are the key devices of micro-electro-mechanical system( MEMS) . For many MEMS devicessuch as switches , optical attenuators , pumps andvalves to function, microactuators are required . Mo-tion of microactuators can be achieved by several kindsof actuation mechanisms . Electrostatic ,piezoelectric ,magnetostrictive, magnetic ,thermomechanical actua-tors have been reported[1-5].Among the different actu-ation principles ,the electrostatic actuationis predomi-nant… 相似文献
14.
A laboratory-scale trickling biofilter column,filled with Raschig rings and inoculated with Pseudomonas putida (ATCC 1785)was used to purify chlorobenzene contained waste gases.Sodium dodecyl sulfonate(SDS)was used to enhance the performance of trickling biofllter.Purification performance of the trickling biofilter was examined for chlorobenzene inlet concentration of 1.20～5.04 g/m~3 at different EBRTs between 76～153 s.Without SDS addition,with simultaneous increase in chlorobenzene inlet loading rate and gas flow rate,100% removal efficiency was achieved at EBRT of 109 s and inlet loadings below 5120 mg/m~3.Addition of SDS to nutrient solution led to improvement of trickling biofilter purification performance. By introducing 25 mg/L SDS,the removal efficiency was increased by 21% and elimination capacity up to 234 g/(m~3.h)was achieved at chlorobenzene inlet loading of 241 g/(m~3.h).Although SDS concentration experienced a low rate reduction after continuous nutrient solution recirculation,this result has little influence on trickling biofilter's removal efficiency in monitoring period. 相似文献
15.
LIU Hao ZHANG Wen-jun YANG Xiao-kang 《浙江大学学报(A卷英文版)》2006,7(10):1695-1701
INTRODUCTION In the encoding or transcoding of video stream- ing, intra refresh is introduced as a non-normative error-resilience tool. Although the intra-refresh schemes based on the rate-distortion optimization (C?té et al., 2000; Stockhammer et al., 2002) are superior to the early heuristic intra-refresh strategies, these new schemes cannot yet accurately estimate the video distortion due to time-varying packet losses, and usually ignore the inter-frame error-propagation effect. Chiou… 相似文献
16.
The bilinear Baecklund transformation (BT) provides a means of finding multisoliton solutions of some non-linear evolution equations, where Hirota‘s technique is used. In this paper, the bilinear BT for Toda lattice was modified and then some novel solutions of the Toda lattice was constructed through the modified BT. 相似文献
17.
Two types of molecular and polymer devices employing (2-(4′-biphenyl)-5-(4““““““““-tert-butylphenyl)-1,3,4-oxadiazole) (PBD)and poly(N-vinylcarbazole) (PVK) as electron transport and hole transport materials, respectively, have been fabricated. The structures of these two devices are ITO/PVK( 70 nm)/PBD(60 nm)/A1 and ITO/PVK: PBD (1:1 by mass, 70 nm)/A1. The formation of exciplex is evident by comparing the electroluminescence (EL) of a bi-layer device and the photoluminescence (PL) of a PVK and PBD mixed film.The maximum emission energy of exciplex evaluated is consistent with the peak emission of EL. Blue emissions from both devices are obtained. The type of exicplex is interpreted based on the energy level diagram of the bi-layer device. 相似文献
18.
A trinudear Mn（II） coordination complex Mna （HEDTA）2-10H20 （EDTA=ethylene diamine tetraacetic acid） 1 has been synthesized and characterized by X-ray crystal structure determination. In addition, IR spectrum, thermogravimetric analysis, electron paramagnetic resonance （EPR） spectra and magnetic susceptibility of this complex are discussed. X-ray determination indicates that six- and seven-coordinate modes between Mn（Yl） and H4EDTA exist alternately in 1. Furthermore, detailed discussion of magnetic ordering in tile temperature range of 2-300 K reveals the antiferromagnetic interactions in the complex. 相似文献
19.
In this paper, we discuss a class of piecewise linear hyperbolic maps on the 2-torus. These maps arise in the second-order digital fdter with two＇ s complement arithmetic. By introducing codings underlying the map operations, we give some admissibility conditions for symbolic sequences and find some periodic properties of these symbolic sequences. Then we use these conditions to check the admissibility of periodic symbol sequences. 相似文献