基于单总线及磁调制传感技术的直流接地故障监测装置

直流系统接地故障的诊断技术随着新原理、新手段的出现而不断地有所发展,大体上可归纳为电桥法、低频信号注入法、直流信号注入法、直流漏电流检测法等几种。电桥法依据电桥平衡原理,结构简单,成本低廉,但功能单调,仅能对系统接地给予报警。低频信号注入法是将低频信号注入直流系统母线,通过检测各个支路的低频分量来判断是否该支路发生接地。为了排除分布电容的干扰,又发展出了变频探测法、载波相位法、复值小波变换等方法,但实际使用效果并不理想。直流信号注入法是向直流母线注入一个直流信号,再监测各支路的对地电流判断是否接地。无论是注入直流还是低频交流信号,为了提高检测的灵敏度,信号幅值都很大,对直流系统会造成一定的干扰,因此信号注入法并不受欢迎。直流漏电流检测法是直接将高灵敏度的直流传感器套在各支路上,检测漏电流,判断是否存在接地,由于该方法对直流系统无任何干扰,因此已经得到广泛应用。

脉冲间隔调制解调研究

为了实现室内可见光通信调制解调,根据室内可见光通信的特点,提出了传空双头脉冲间隔调制(space dualheader-pulse interval modulation,SDH-PIM)解调方法。首先研究了双头脉冲间隔调制的原理,给出了该调制的符号结构,符号不设置保护时隙,并且符号长固定。其次在此基础上,设计出了这种调制、解调方式的实现系统。系统主要特点是采用FPGA器件实现,利用传空方式来实现信息的传输,并给出了VHDL语言实现的算法流程,最后完成了调制解调系统并进行了实验。这种调制解调系统最大优点无需同步信号,实验结果表明该调制解调方式能很好地用于可见光通信。

浅谈脉冲间隔调制解调

为能够实现室内可见光通信调制解调,依据室内可见光通信的一些特点,制定出了传空双头脉冲间隔调制解调的诸多方法。首先针对双头脉冲间隔调制原理,设计出了该调制的符号结构,一方面符号不设置保护时隙,另一方面符号长要固定。其次在上述的基础上给出了这种调制和解调方式的实现系统。系统主要依靠FPGA器件来实现,并利用传空方式来完成信息传输,而且设计出了VHDL语言实施的算法流程,最后制定出调制解调系统并实施实验验证。区别于其他系统,这种调制解调系统的最大优势是无需同步信号,实验结果也同样表明该调制解调方式能够非常有效地应用于可见光的通信。

非恒定像差非球面人工晶状体植入术后近期视觉质量评价

背景白内障手术目前已经由单纯挽救视力的手术发展为屈光性手术，因此视力不再作为术后惟一的评价标准，目前研究更多的关注在术后的视觉质量上。非球面人工晶状体（IOL）通过降低人眼的球差提高视网膜的成像质量。目的研究超声乳化白内障摘出术联合非恒定像差非球面IOL植入术后3个月年龄相关性白内障患者的视觉质量。方法采用前瞻性病例对照研究设计，纳入单纯年龄相关性白内障患者30例42眼，分别植入XL-Stabi ZO型非球面IOL（ZO组，21眼）及球面IOL（ADAPT组，21眼）。术后3个月检查患者的裸眼视力，最佳矫正视力（BCVA），明、暗、低眩光、高眩光环境下的对比敏感度（CS），明暗不同背景亮度（5％、10％、25％、100％）下的对比度视力，3、4、5mm瞳孔直径下的眼球像差，调制传递函数（MTF）及客观调节力，对2个组间的测量指标进行比较，并利用多元线性回归分析法分析cs与球差均方根、彗差均方根和患者年龄之间的关系。结果术后3个月ZO组与ADATP组间患者的裸眼视力、BCVA及球镜度数的差异均无统计学意义（P〉0．05）。暗视环境下6、12、18cpd空间频率时，低眩光6cpd、12cpd空间频率时以及高眩光12cpd、18cpd时ZO组的cs值均明显高于ADAPT组，差异均有统计学意义（P〈0．05）。暗背景对比度为100％时以及亮背景5％对比度下ZO组的对比度视力均明显高于ADAPT组，差异均有统计学意义（t=20．217，P=0．000；t=4．568，P=0．039）。3、4、5mm瞳孔直径下ZO组球差（z4）值均小于ADAPT组，差异均有统计学意义（U=63．000，P=0．000；U=52．000，P=0．000；U=36．000，P=0．000）；3mm、4mm瞳孔直径下ZO组三叶草像差（z6）值与ADAPT组比较，差异无统计学意义（U=204．000，P=0．678；U=215．000，P：0．890），5mm瞳孔直径下ZO组三叶草像差（z6）值小于ADAPT组，差异有统计学意义（U=4．000，P=0．000）；3、4、5mm瞳孔直径下ZO组的彗差（z7、z8）值与ADAPT组比较差异均无统计学意义（Z7：U=156．000，P：0．159；U=196．000，P=0．538；U=199．000，P=0．587；Z8：U=163．000，P=0．148；U=214．000，P=0．870；U=143．000，P=0．061）。高阶像差下瞳孔直径为4mm时5、10、15、20cpd4个空间频率下ZO组MTF值均高于ADAPT组，差异均有统计学意义（P〈0．05）；高阶像差下瞳孔直径为5mm时10、20、25、30cpd5个空间频率下z0组MTF值明显均高于ADAPT组，差异均有统计学意义（P〈0．05）。ZO组术眼的客观调节力稍低于ADAPT组，但2个组之间的差异无统计学意义（t=0．003，P=0．954）。多元线性回归分析表明，暗视环境下的cs变化与球差相关（β=0．544，R^2=0．519，P=0．000），而与彗差和患者的年龄无关。结论超声乳化白内障摘出术联合非恒定像差非球面IOL植入后可减少术眼的球差，其视觉质量优于球面IOL植入眼。

微小扰动下中等长高比腔体内行进波对流的高精度数值模拟

文章采用高阶紧致有限差分格式,通过二维流体力学扰动方程组的数值模拟,研究了具有较弱Soret效应下,附加一个微小的温度扰动作为扰动源的中等长高比腔体内混合流体对流系统中时空结构的发展;它在经历了瞬态的对传波、调制对传波,最终演变为稳定的定常行进波状态;并进一步研究了在中等长高比腔体内混合流体对流中从调制对传波向定常行进波的时空演化及其随瑞利数的变化规律。

EVOLUTIONARY FUZZY GUIDANCE LAW WITH SELF-ADAPTIVE REGION

Effective guidance is one of the most important tasks to the performance of air-to-air missile. The fuzzy logic controller is able to perform effectively even in situations where the information about the plant is inaccurate and the operating conditions are uncertain. Based on the proportional navigation, the fuzzy logic and the genetic algorithm are combined to develop an evolutionary fuzzy navigation law with self-adapt region for the air-to-air missile guidance. The line of sight (LOS) rate and the closing speed between the missile and the target are inputs of the fuzzy controller. The output of the fuzzy controller is the commanded acceleration. Then a nonlinear function based on the conventional fuzzy logic control is imported to change the region. This nonlinear function can be changed with the input variables. So the dynamic change of the fuzzy variable region is achieved. The guidance law is optimized by the genetic algorithm. Simulation results of air-to-air missile attack using MATLAB show that the method needs less acceleration and shorter flying time, and its realization is simple.[KH*3/4D]

一种Fabry-Perot干涉式光纤温度测量系统

分析了温度对相位的调制作用以及Fabry-Perot干涉结构检测相位变化的原理,提出了一种具有高灵敏度、高分辨率的相位调制型全光纤结构的测温控制系统.

Magnetic sensitivity technology based on microwave modulation of solid state spin system NV center

In view of the low resolution and accuracy of traditional magnetometer,a method of microwave frequency modulation technology based on nitrogen-vacancy(NV)center in diamond for magnetic detection was proposed.The magnetometer studied can reduce the frequency noise of system and improve the magnetic sensitivity by microwave frequency modulation.Firstly,ESR spectra by sweeping the microwave frequency was obtained.Further,the microwave frequency modulated was gained through the mixed high-frequency sinusoidal modulation signal generated by signal generator.In addition,the frequency through the lock-in amplifier was locked,and the signal which was proportional to the first derivative of the spectrum was obtained.The experimental results show that the sensitivity of magnetic field detection can reach 17.628 nT/Hz based on microwave frequency modulation technology.The method realizes high resolution and sensitivity for magnetic field detection.

Amplitude modulation measurement of symmetrical microwave power sensor

In order to reduce the mismatch error, a direct current （DC） calibration method is introduced when the modulated microwave signal is measured. The microwave power is input to the left section of the power sensor, and the DC power is input to the right of the power sensor. Due to the existence of parasitic loss and electromagnetic coupling, the microwave power results in a mismatch error. However, the DC power does not have the mismatch error. So the DC power applied in the right section can calibrate the mismatch error of the microwave power in the left section. The calibration factor is measured at different modulation rates and modulation depths.The measurement results show that the carrier frequency is the major factor influencing the measurement results. After calibration, the carrier frequency and the modulation rate have little effect on the output voltage. The frequency response becomes relatively flat in the frequency range up to 20 GHz, and the sensitivity on average is enhanced by about 0.12 mV/dBm. Therefore, the DC calibration method has a certain reference value for the terminal-type microwave power sensor.

Application of genetic algorithm in quasi-static fiber grating wavelength demodulation technology

A modified genetic algorithm （GA） has been proposed, which was used to wavelength demodulation in quasi-static fiber grating sensing system. The modification method of GA has been introduced and the relevant mathematical model has been established. The objective function and individual fitness evaluation strategy interrelated with GA are also established. The influence of population size, chromosome size, generations, crossover probability and mutation probability on the GA has been analyzed, and the optimal parameters of modified GA have been obtained. The simulations and experirnents, show that the modified GA can be applied to quasi-static fiber grating sensing system, and the wavelength demodulation preci- sion is equal to or less than 3 pm.

Dynamics and Mechanism of A Quorum Sensing Network Regulated by Small RNAs in Vibrio Harveyi

Bacterial quorum sensing （QS） has attracted much interests and it is an important process of cell communication. Recently, Bassler et al. studied the phenomena of QS regulated by small RNAs and the experimental data showed that smafl RNAs played important role in the QS of Vibrio harveyi and it can permit the fine-tuning of gene regulation and mmntenance of homeostasis. According to Michaelis-Menten kinetics and mass action law in this paper, we construct a mathematical model to investigate the mechanism induced QS by coexist of small RNA and signal molecular （AI） and show that there are periodic oscillation when the time delay and Hill coefficient exceed a critical value and the periodic oscillation produces the change of concentration and induces QS. These results are fit to the experimental results. In the meanwhile, we also get some theoretical value of Hopf Bifurcation on time deday. In addition, we also find this network is robust against noise.

A Wave Modulation Model of Ripples over Long Surface Waves

A study is presented on the modulation of ripples induced by a long surface wave (LW) and a new theoretical modula-tion model is proposed. In this model, the wind surface stress modulation is related to the modulation of ripple spectrum. The model results show that in the case of LW propagating in the wind direction with the wave age parameter of LW increasing, the area with enhanced shear stress shifts from the region near the LW crest on the upwind slope to the LW trough. With a smaller wave age parameter of LW, the ripple modulation has the maximum on the upwind slope in the vicinity of LW crest, while with a larger parameter the enhancement of ripple spectrum does not occur in that region. At low winds the amplitude of ripple modulation transfer function (MTF) is larger in the gravity wave range, while at moderate or high winds it changes little in the range from short gravity waves to capillary waves.

Separate Dimming Controlling and Data Transmission for an Indoor Visible Light Communication System

Simultaneous dimming controlling and data transmission are usually required in a white LED based indoor visible light communication system.However,the diming controlling of LED normally interferes the data transmission due to the modulation nonlinearity of LED.In order to solve this problem,a scheme by separating the LEDs for the functions of dimming control and data transmission respectively is proposed in this paper.In the scheme,the LEDs used for dimming control function are driven by a dc amplified circuit,and the LEDs for data transmission are driven by a digital modulation circuit respectively.In this way,the modulation distortion to the data signal caused by the modulation nonlinearity can be avoided even if the dimming is at high level dc driven current.The proof-of-concept experiment of a 2.5Mbit/s visible light communication system demonstrates that the dimming controlling and data transmission can be realized simultaneously in a simple way,and the data transmission is not affected by the dimming controlling function.Compared to previous methods,the scheme in this paper is simpler and cost effective,and makes sense when high rate data is transmitted in a visible light communication system.

A new modulation transfer function for ocean wave spectra retrieval from X-band marine radar imagery

When imaging ocean surface waves by X-band marine radar, the radar backscatter from the sea surface is modulated by the long surface gravity waves. The modulation transfer function （MTF） comprises tilt, hydrodynamic, and shadowing modulations. A conventional linear MTF was derived using HH-polarized radar observations under conditions of deep water. In this study, we propose a new quadratic polynomial MTF based on W-polarized radar measurements taken from heterogeneous nearshore wave fields. This new MTF is obtained using a radar-observed image spectrum and in situ buoy-measured wave frequency spectrum. We validate the MTF by comparing peak and mean wave periods retrieved from X-band marine radar image sequences with those measured by the buoy. It is shown that the retrieval accuracies of peak and mean wave periods of the new MTF are better than the conventional MTF. The results also show that the bias and root mean square errors of the peak and mean wave periods of the new MTF are 0.05 and 0.88 s, and 0.32 and 0.53 s, respectively, while those of the conventional MTF are 0.61 and 0.98 s, and 1.39 and 1.48 s, respectively. Moreover, it is also shown that the retrieval results are insensitive to the coefficients in the proposed MTF.

A UWB communication system based on dechirp pulse compression and OOK modulation

In this paper,a novel UWB communication system structure is proposed.The transmitted signal uses OOK modulation and chirp spread spectrum.The received signal first goes through a dechirp pulse compression process,and then is processed with a two-level sliding correlation algorithm for coarse timing synchronization and fine timing synchronization.After the SNR estimation,the signal is demodulated by an energy detection method.An integrated system level simulation model is established,and the performance of this system is evaluated over the AWGN channel,IEEE 802.15.3a CM1 and CM4 channels.The theoretical analysis and simulation results show that this UWB communication system can effectively reduce the sampling rate and signal processing speed at the receiver,and it is more suitable for long-distance and low-rate UWB communications with high spreading gain.

Attractor behavior in dilatonic(phantom) dark energy model with an especial potential

The dilaton in Weyl-Scale induced gravitational theory is regarded as a candidate of dark energy. When the potential of dilaton field is taken as the form Wσ ＋ σ^2e^-βσ2, that there exist attractor solutions to the canonical dilatonic dark energy model and the phontam model, and these attractors correspond to an equation of state ω = -1 and a cosmic density parameter Ωσ = 1, which are important features for a dark energy model and can fit with the current observations. We find a sufficient condition of the existence of a late time de Sitter attractor. The attractor behaviors, the evolutions of the state parameter ω and the cosmic density parameter Ω, the evolution of X （σ/σ0） and Y （σ/σ0^2） with respect to N（ln a）are shown numerically.

A new method of demodulating the digital frequency modulation signals

A new method of estimating the frequency-known signals from the strong background noise was presented first. Then the new method was used in the demodulation of the digital frequency modulation (FSK) signals. The new demodulation method can complete the demodulation of the FSK signals only with the carrier frequency and without any carrier phase information. The simulation results show that the performance of anti-noise of the new method is better than that of the incoherent demodulation method and the fluctuation of the carrier phase has little effect on the new method. So the new demodulation method has a fine prospect in the practical applications.

Design of Wireless Multi-media Sensor Network for Precision Agriculture

To satisfy the needs of modem pre-cision agriculture, a Precision Agriculture Sensing System （PASS） is designed, which is based on wireless multimedia sensor network. Both hardware and software of PASS are tai-lored for sensing in wide farmland without human supervision. A dedicated single-chip sensor node platform is designed specially for wireless multi-media sensor network. To guarantee the bulky data transmission, a bit-map index reliable data transmission mecha-nism is proposed. And a battery-array switch-ing system is design to power the sensor node to elongate the lifetime. The effectiveness and performance of PASS have been evaluated through comprehensive experiments and large-scale real-life deployment.

A Survey: Several Technologies of Non-Orthogonal Transmission for 5G

One key advantage of 4G OFDM system is the relatively simple receiver implementation due to the orthogonal resource allocation.However,from sum-capacity and spectral efficiency points of view,orthogonal systems are never the achieving schemes.With the rapid development of mobile communication systems,a novel concept of non-orthogonal transmission for 5G mobile communications has attracted researches all around the world.In this trend,many new multiple access schemes and waveform modulation technologies were proposed.In this paper,some promising ones of them were discussed which include Non-orthogonal Multiple Access(NOMA),Sparse Code Multiple Access(SCMA),Multi-user Shared Access(MUSA),Pattern Division Multiple Access(PDMA)and some main new waveforms including Filter-bank based Multicarrier(FBMC),Universal Filtered Multi-Carrier(UFMC),Generalized Frequency Division Multiplexing(GFDM).By analyzing and comparing features of these technologies,a research direction of guiding on future 5G multiple access and waveform are given.

Applications of cascade multilevel inverters

Cascade multilevel inverters have been developed for electric utility applications. A cascade M level inverter consists of (M 1)/2 H bridges in which each bridge's dc voltage is supported by its own dc capacitor. The new inverter can: (1) generate almost sinusoidal waveform voltage while only switching one time per fundamental cycle; (2) dispense with multi pulse inverters' transformers used in conventional utility interfaces and static var compensators; (3) enables direct parallel or series transformer less connection to medium and high voltage power systems. In short, the cascade inverter is much more efficient and suitable for utility applications than traditional multi pulse and pulse width modulation (PWM) inverters. The authors have experimentally demonstrated the superiority of the new inverter for power supply, (hybrid) electric vehicle (EV) motor drive, reactive power (var) and harmonic compensation. This paper summarizes the features, feasibility, and control schemes of the cascade inverter for utility applications including utility interface of renewable energy, voltage regulation, var compensation, and harmonic filtering in power systems. Analytical, simulated, and experimental results demonstrated the superiority of the new inverters.