动态ECG数据压缩中理论与实验的比率失真性能的研究

1动态ECG信号压缩率失真范围的评估理论上,对于一给定信号进行编码所需的最小数据压缩率可成为被压缩信号的失真函数。当信号由更低的每秒传送位数(bps)进行编码时,失真将增加。由信号统计将可决定这个压缩率失真函数的精确特性。对于一个离散时间的静态高斯源,Berger认为:编码所产生的最小均方差失真可作为参数θ的函数Dθ,其关系由下式给出:

Ad Hoc网络和无线传感器网络中连通支配集的分布式构造(英文)

Ad hoc网络和无线传感器网络具有广泛的应用,但对于这样自组性的网络须采用分层结构的聚簇来有效管理.通过选择具有支配属性的节点构成虚拟主干以支持路由、广播及覆盖等应用.大部分的研究都集中在高效选择较小的连通支配集.全面阐述了连通支配集构造的研究进展,并依据不同的网络假设、设计目标和性能对超过20种连通支配集的构造算法进行分类和总结.指出这一领域的研究方向.

基于新型负指数期望效用的投资组合选择模型

结合现有文献对最优投资决策问题的讨论,提出了一类满足单调性和凹性的新型负指数效用函数,并给出数学和经济学上的合理解释.通过多种类型的加权函数以及对尾部的恰当描述,损失分布的厚尾现象得到更加有效地控制.利用L-统计量估计新型期望效用,并说明其合理性.进一步地,构建了兼顾多种市场摩擦因素的实际投资组合选择模型.选用中国和美国股票市场的数据进行实证研究.结果表明了新期望效用的优越性和鲁棒性.

光伏电站发电量损失研究

本文主要研究太阳能光伏发电系统的发电量损失,对影响发电量的因素进行详细分析,文中提到的因素都是主要因素,当然还有一些其他因素也会有影响,比如组件类型,组件的安装倾角方位角,地面的反射率等,最后通过对工作中得到的大量检测数据进行分析得到光伏电站的平均性能比率,希望通过以上分析能帮助大家找到提升电站发电量的方法。

THE FFD ALGORITHM FOR THE BIN PACKING PROBLEM WITH KERNEL ITEMS

The FFD algorithm is one of the most famous algorithms for the classical bin packing problem. In this paper,some versions of the FFD algorithm are considered in several bin packing problems. Especially,two of them applied to the bin packing problem with kernel items are analyzed. Tight worst-case performance ratios are obtained.

Non-Line-of-Sight Ultraviolet Communication Performance in Atmospheric Turbulence

Non-Line-of-Sight(NLOS)Ultraviolet(UV)communication uses the atmosphere as a propagation medium.As the communication range increases,turbulence becomes a significant atmospheric process that affects the propagation of optical waves.This paper presents a more accurate NLOS channel model by considering turbulence-induced Scintillation Attenuation(SA).Then,the Bit Error Rate(BER)during turbulence of the NLOS UV communication system with On-Off Keying(OOK)modulation and Maximum Likelihood(ML)detection is analysed and compared with that in free space without turbulence.The BER dependence is also analysed for different factors,including the refractive index structure parameter,transceiver range,pointing angles,transmitted power,and data rate.

Crashworthiness of extruded magnesium thin-walled square tubes

Axial compression tests were conducted on AZ31 B magnesium and A6063 aluminum thin-walled square tubes with varied lengths and induced features at different compression rates. In compression, the magnesium tubes exhibited a "local buckling and fracture" mode, with three fracture patterns, i.e."horizontal","double-oblique", and "spiral" fractures. In general, the magnesium tube showed an inferior crashworthiness to the aluminum square tube. In addition, the effects of L/W ratio, strain rate and induced features on the crashworthiness of thin-walled square tubes were investigated. With an increase in the L/W ratio(L and W represent the tube length and width, respectively) from 1 to 4, the maximal force and global specific energy absorption decreased in a power-law trend for the magnesium tubes,while they remained approximately constant for the aluminum tubes. Furthermore, as the compression rate increased from 5×10-5 to 10 m/s, the primary crashworthiness parameters of the magnesium tubes increased in an approximately exponential manner,while for the aluminum tubes,they changed slightly. Finally,the involved induced features were proven to be not an effective method to improve the specific energy absorption of magnesium tubes, thus, more trigger types,locations,and sizes will be evaluated in future to improve the energy-absorption ability.

Performance of a Dual-Hop Multi-relay Cooperative Network in a Nakagami-m Fading Environment

An exact average symbol error rate analysis for the distributed dual-hop relay cooperative network with multiple relays in a Nakagami-m fading environment is presented.In the derivation of the moment generation function of receiver Signal-to-Noise Ratio(SNR),the sectional integral method is used,instead of the cumulative density function method which is ordinarily used by the deduction of the outage probability of S-R-D link.The accurate symbol error rate of a dual-hop relay cooperative network is obtained with the closed-form Moment Genoration Function (MGF) expression.The correctness of the symbol error rate is verified through numerical simulations and is compared with other analytical methods.These deductions clearly show that the distributed cooperative diversity network presented has strong superiorities in overcoming severe fading and can achieve full diversity order.

THE PERFORMANCE OF MT-CDMA SYSTEM IN THE PRESENCE OF CARRIER FREQUENCY OFFSET

In this letter,the sensitivity of an uplink Multi-Tone Code-Division Multiple Access (MT-CDMA) system to the Carrier Frequency Offset (CFO) is investigated. The analytical expression for the Bit Error Rate (BER) of uplink MT-CDMA in the presence of CFO is derived in a multipath Rayleigh fading channel which is verified through simulations. Both Maximal Ratio Combining (MRC) and Equal Gain Combining (EGC) are considered in combining multipath signals in the analysis. It is found that the BER performance can be improved with the number of multipath increasing in the presence of CFO.

New Precoded Spatial-Multiplexing for an Erasure Event in Single Frequency Networks

In this paper, we propose a new spatial-multiplexing(SM) scheme employing an orthogonal precoder over Rayleigh-fading channels for an erasure event in single frequency networks(SFN). To optimize the precoder, the average bit error rate(BER) is evaluated and minimized through a mathematical analysis. Compared to an ordinary SM, the proposed scheme guarantees identical BER performance under non-erasure fading channels and achieves a greatly improved performance under erasure fading channels, especially for a higher erasure-ratio and SNR values. This improvement is mainly due to the increase in the diversity gain incurred by the optimized precoder over the erasure event. We also compare the performance of the proposed SM to that of the conventional constellation-rotation(CR) scheme applied to the single antenna SFN systems. The results of a computer simulation show that the performance of the new scheme is more effective than that of a conventional CR across all simulation cases.

Some Strong Deviation Theorems for Dependent Continuous Random Sequence

Let {Xn,n ≥ 1} be a sequence of arbitrary continuous random variables,we introduce the notion of limit asymptotic logarithm likelihood ratio r（ω）,as a measure of dissimilarity between probability measure P and reference measure Q.We get some strong deviation theorems for the partial sums of arbitrary continuous random variables under Chung-Teicher＇s type conditions[6-7].

Quality of Service Improvement for High-Speed Railway Communications

With the fast development of highspeed railways,a call for fulfilling the notion of communication at "anytime,anywhere" for high-speed train passengers in the Train Operating Control System is on the way.In order to make a realization of that,new railway wireless communication networks are needed.The most promising one is the Long Term Evolution for Railway which will provide broadband access,fast handover,and reliable communication for high mobility users.However,with the increase of speed,the system is subjected to high bit error rate,Doppler frequency shift and handover failure just like other system does.This paper is trying to solve these problems by employing MIMO technique.Specifically,the goal is to provide higher data rate,higher reliability,less delay,and other relative quality of services for passengers.MIMO performance analysis,resource allocation,and access control for handover and various services in a two-hop model are proposed in this paper.Analytical results and simulation results show that the proposed model and schemes perform well in improving the system performances.

Performance of an Improved One-Way Error Reconciliation Protocol Based on Key Redistribution

In data post-processing for quantum key distribution, it is essential to have a highly efficient error reconciliation protocol. Based on the key redistribution scheme, we analyze a one-way error reconciliation protocol by data simulation. The relationship between the error correction capability and the key generation efficiency of three kinds of Hamming code are demonstrated. The simulation results indicate that when the initial error rates are （0,1.5%], （1.5,4%], and （4,11%], using the Hamming （31,26）, （15,11）, and （7,4） codes to correct the error, respectively, the key generation rate will be maximized. Based on this, we propose a modified one-way error reconciliation protocol which employs a mixed Hamming code concatenation scheme. The error correction capability and key generation rate are verified through data simulation. Using the parameters of the posterior distribution based on the tested data, a simple method for estimating the bit error rate （BER） with a given confidence interval is estimated. The simulation results show that when the initial bit error rate is 10.00%, after 7 rounds of error correction, the error bits are eliminated completely, and the key generation rate is 10.36%; the BER expectation is 2.96×10^-10, and when the confidence is 95% the corresponding BER upper limit is 2.17×10^-9. By comparison, for the single （7,4） Hamming code error reconciliation scheme at a confidence of 95%,the key generation rate is only 6.09%, while the BER expectation is 5.92x 10＂9, with a BER upper limit of 4.34×10^-8. Hence, our improved protocol is much better than the original one.

COST:Coding over Spatial-Temporal Diversity for Low-Duty-Cycle WSNs

In low-duty-cycle wireless sensor networks,designers have to cope with unreliable links and limited communication capacity.In this work,we propose COST,a coding scheme that leverages spatial-temporal diversity to achieve higher energy efficiency and lower delay of packet transmissions.We particularly address long sleeping intervals in low-duty-cycle networks by exploiting multi-path diversity.Specifically,we propose to employ an erasure-coding scheme to improve reliability.With respect to energy efficiency and delivery timeliness,we formulate the problem in optimal allocation of coded blocks over multiple paths,which is then proved to be NP-hard.We further propose a near-optimal algorithm to solve the allocation problem.Through extensive simulations,we evaluate the impact of network parameters and demonstrate the effectiveness of our proposal.

Effect of Concentrate to Roughage Ratio on Cost Effective Growth Performance of Brahman Crossbred Calves

An experiment was conducted to evaluate the growth performance and cost per gain of Brahman × local crossbred bull calves receiving three diets with varying concentrate to roughage ratio （C：R） of 75：25, 65：35 and 55：45 on dry matter （DM） basis. Twelve bull calves （aging 11.5 ±1.2 months and 170.8 ± 13.0 kg live weight） divided into three equal groups were fed on three diets. The diets were balanced to 14.5% crude protein （CP） level and 10.5 MJ metabolizable energy （ME） per kg DM, formulating different concentrate mixtures. German grass （Echinoclora grousgali） and paddy straw were offered at 2：1 ratio on DM basis as roughages. The results revealed that C：R ratio did not affect （P 〉 0.05） the intake of feed and nutrients, feed efficiency （7.04, 6.94 and 6.76） and average daily gain （981,958 and 976 g）. Digestibility of nutrients was not affected （P 〉 0.05） by C：R. Animals fed diet with C：R = 55：45 had the lowest feed cost （Bangladeshi Taka 136.8 BDT/kg live weight gain）, which was increased （147.5 B DT and 153.8 BDT） non-significantly （P 〉 0.05） with the increasing level of concentrate. The diet consisting of 55% concentrate mixture showed similar results with the diet consisting of 75% concentrate mixture, but was comparatively economic. Therefore, considering the growth performance and cost per kg gain of Brahman crossbred growing calves, it may be concluded that the diet consisting of 55：45 C：R may be used for economic beef production.

The Influence of Wedge Diffuser Blade Number and Divergence Angle on the Performance of a High Pressure Ratio Centrifugal Compressor

Wedge diffuser is widely used in centrifugal compressors due to its high performance and compact size. This paper is aimed to research the influence of wedge diffuser blade number and divergence angle on centrifugal compressor performance. The impact of wedge diffuser blade number on compressor stage performance is investigated, and then the wedge diffusers with different divergence angle are studied by varying diffuser wedge angle and blade number simultaneously. It is found that wedge diffuser with 27 blades could have about 0.8% higher adiabatic efficiency and 0.14 higher total pressure ratio than the wedge diffuser with 19 blades and the best compressor performance is achieved when diffuser divergence angle is 8.3°.These results could give some advices on centrifugal compressor design.

Efficiency comparison and performance analysis of internally-cooled liquid desiccant dehumidifiers using LiCl and CaCl2 aqueous solutions

Internally-cooled dehumidifiers are efficient liquid desiccant dehumidifiers, whose performance is mainly determined by the device structure and operating conditions. Based on energy and mass conservation in the air, solution, and cooling water in the device, mathematical models are built and their theoretical performance is simulated and analyzed in this paper. A novel measure of dehumidification efficiency is introduced to evaluate the performance of internally-cooled dehumidifiers, in which the equilibrium humidity ratio of the inlet solution is calculated according to the minimum temperature in the inlet solution and the cooling water. Numerical simulations show that a counter flow between air and solution is always the most efficient, followed by cross flow, and parallel flow is the least efficient. Cooling water with the same flow direction as the solution performs better than that with a counter flow, with approximately a 5% improvement in efficiency. Compared with Ca Cl2, the dehumidification efficiency of a Li Cl solution is greater by 60%, while its exergy efficiency is less by 16%. Dehumidification efficiency can be improved with the number of air-solution heat transfer units(NTUa-s) increasing, and reduced with the air mass flow rate raised. With NTUa-s increasing, exergy efficiency can be improved, and an increase in mass flow rate of cooling water results in a decrease of efficiency. Higher solution concentration and lower inlet temperature of solution and air can achieve both higher dehumidification efficiency and exergy efficiency.

Fabrication and performance analysis of a high-coupling-efficiency and convenient-integration optical transceiver

An optical transceiver with a novel optical subassembly structure is proposed in this paper, which achieves high coupling efficiency and low assembly difficulty. The proposed optical transceiver consumes 0.9 W power and retains a small size of 28 mmx16 mmx3 mm. The fabrication process of the silicon substrate and the assembly process of the optical transceiver are demonstrated in details. Moreover, the optical transceiver is measured in order to verify its transmission performance. The clear eye diagrams and the low bit error rate （BER） less than 1013 at 10 Gbit/s per channel show good transmission characteristics of the designed optical transceiver.

Carbon-coating-increased working voltage and energy density towards an advanced Na3V2(PO4)2F3@C cathode in sodium-ion batteries

One main challenge for phosphate cathodes in sodium-ion batteries(SIBs)is to increase the working voltage and energy density to promote its practicability.Herein,an advanced Na3V2(PO4)2F3@C cathode is prepared successfully for sodium-ion full cells.It is revealed that,carbon coating can not only enhance the electronic conductivity and electrode kinetics of Na3V2(PO4)2F3@C and inhibit the growth of particles(i.e.,shorten the Na^+-migration path),but also unexpectedly for the first time adjust the dis-/charging plateaux at different voltage ranges to increase the mean voltage(from 3.59 to 3.71 V)and energy density from 336.0 to 428.5 Wh kg^-1 of phosphate cathode material.As a result,when used as cathode for SIBs,the prepared Na3V2(PO4)2F3@C delivers much improved electrochemical properties in terms of larger specifc capacity(115.9 vs.93.5 mAh g^-1),more outstanding high-rate capability(e.g.,87.3 vs.60.5 mAh g^-1 at 10 C),higher energy density,and better cycling performance,compared to pristine Na3V2(PO4)2F3.Reasons for the enhanced electrochemical properties include ionicity enhancement of lattice induced by carbon coating,improved electrode kinetics and electronic conductivity,and high stability of lattice,which is elucidated clearly through the contrastive characterization and electrochemical studies.Moreover,excellent energy-storage performance in sodium-ion full cells further demonstrate the extremely high possibility of Na3V2(PO4)2F3@C cathode for practical applications.

Stress-strain behavior of multi-phase high performance structural steel

A series of ferrite/bainite(F/B) multi-phase steels containing different volume fractions of ferrite were obtained.The effect of soft phase(ferrite) content on the work-hardening behavior of the steel was studied by the finite element simulation with V-BCC model and the modified Crussard-Jaoul(C-J) analysis.It is shown that the multi-phase steels have an excellent anti-deformation ability,such as higher stress ratio(R t1.5 /R t0.5),higher uniform elongation and lower yield to tensile strength ratio.For the F/B multi-phase steels,increasing the proportion of ferrite would help to increase the uniform elongation.However,introducing much more fraction of ferrite would not be helpful to improve the stress ratio of multi-phase steel.The ferrite plastic strain constrained by bainite would be beneficial to increasing the work hardening rate.The optimum proportion of ferrite will result both higher stress ratio and uniform elongation in multi-phase steel.