A Study on Control of Interconnection Inverter with FRT and Islanding Detection Functions

In this study, the authors aim to develop the interconnection inverter ofPV （photovoltaic generation） system with FRT （fault ride thorough） function and islanding detection function, and analyze the interaction between the both functions during the momentary voltage drop by using an analytical model of distribution system interconnected plural PV systems. Moreover, the authors propose a cooperated control method of the inverters ~vith the islanding detection function and FRT function, and carry out a numerical calculation in order to verify the validity of the proposed method.

An algorithm for moving target detection in IR image based on grayscale distribution and kernel function

A fast algorithm based on the grayscale distribution of infrared target and the weighted kernel function was proposed for the moving target detection(MTD) in dynamic scene of image series. This algorithm is used to deal with issues like the large computational complexity, the fluctuation of grayscale, and the noise in infrared images. Four characteristic points were selected by analyzing the grayscale distribution in infrared image, of which the series was quickly matched with an affine transformation model. The image was then divided into 32×32 squares and the gray-weighted kernel(GWK) for each square was calculated. At last, the MTD was carried out according to the variation of the four GWKs. The results indicate that the MTD can be achieved in real time using the algorithm with the fluctuations of grayscale and noise can be effectively suppressed. The detection probability is greater than 90% with the false alarm rate lower than 5% when the calculation time is less than 40 ms.

Electrochemically reduced graphene oxide with enhanced electrocatalytic activity toward tetracycline detection

An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.

Detecting the nerve function of fibril in patients with cervicalspondylotic radiculopathy using quantitative sensory testing

BACKGROUND: Pain and sensory disability are greatly affected by subjective factors, there are no quantitative indexes to evaluate cervical spondylotic radiculopathy(CSR). The judgment on clinical body examination and chief complaint always causes nonobjective results with great individual differences. Quantitative sensory testing (QST) can be used to judge the nerve function of fibril. The application of QST for the quantitative evaluation of peripheral nervous system disease needs to be further studied. OBJECTIVE: The cold-thermal sensation and pain of patients with CSR are quantitatively analyzed by using QST technology in order to evaluate the nerve function of fibril in patients with CSR. DESIGN: Case-control observation. SETTING: Pain Center of Beijing Hospital of Ministry of Health. PARTICIPANTS: Twenty patients with CSR, including 8 males and 12 females, aged from 33 to 70 years, who received treatment between January and April 2005 in Pain Center of Beijing Hospital of Ministry of Health were involved in CSR group. All the involved patients presented symptoms in unilateral upper extremity (left side 10 patients, right side 10 patients). They did not undergo physical therapy or nerve block therapy in 1 week before examination. Eight non-CSR patients who received treatment in Pain Center concurrently were involved in the control group (2 patients with trigeminal neuralgia, 4 with osteoarthrosis of knee joint and 2 with lumbar intervertebral disc protrusion), and another 12 healthy volunteers were involved. Four non-CSR patients and 12 healthy volunteers, 8 male and 12 female, were aged from 23 to 75 years. The informed consents were obtained from all the involved subjects. METHODS: The volar thresholds of cold sensation, thermal sensation, cryalgesia of thenar eminence of both upper extremities of all the subjects were examined separately by limit method with type TSA-Ⅱ temperature sensation analysator made by Medco Company (Israel). The subjects were pre-examined to be familiar with the method for sensory discrimination and affirmation. Thenar eminence vola of bilateral upper extremities were detected. The infrared detector of a semiconductor was contacted with skin. The infrared detector could be used to heat and cool skin. A group of cold-heat water circulation device was given electric current to produce temperature gradient, which was higher or lower than skin temperature. The initial temperature of infrared detector was 32 ℃, stimulation temperature was increased or decreased progressively at 1 ℃/s, and temperature change range was 0 to 50 ℃. In the first step, subjects pressed down the button to stop the stimulation when the temperature of infrared detector was decreased progressively until the subjects felt, and the threshold of cold sensation was obtained; In the second step, the threshold of thermal sensation was obtained when the temperature of infrared detector was increased progressively until the subjects felt; In the third step, the threshold of cryalgesia was obtained when the temperature of infrared detector was decreased progressively until subjects felt; and in the fourth step, the threshold of thermalgesia was obtained when the temperature of infrared detector was increased progressively until subjects felt. Each step was conducted 4 times and the mean threshold was obtained. Before each measurement, the temperature was made to rebound to the initial temperature and kept for 10 s. MAIN OUTCOME MEASURES: The thresholds of cold sensation, thermal sensation and cryalgesia, thermalgesia of thenar eminence vola of bilateral upper extremities of all the subjects. RESULTS: Twenty patients with CSR and 20 healthy subjects participated in the final results. ① In the CSR group, the threshold of cold sensation of affected side was lower than that of intact side [(29.00±1.26) ℃ vs.(30.00±1.06) ℃, P < 0.05], and the threshold of thermal sensation of affected side was higher than that of intact side [(35.04±0.87) ℃ vs. (34.14±0.99) ℃, P < 0.05]. There were no significant differences in the thresholds of cold and thermal sensation between affected side and intact side (P > 0.05). ②In the CSR group, the difference of threshold of cold sensation, thermal sensation, cryalgesia and thermalgesia between affected side and intact side was (-1.01±0.57), (0.89±0.39), (2.49±1.10) and (-1.62±0.86) ℃, respectively , the absolute value of which was higher than that of control group, respectively [(0.04±0.28),(0.05±0.26),(0.28±1.79),(0.17±1.10) ℃,P < 0.01]. In the CSR group, the threshold of cold sensation and thermalgesia of affected side was lower than that of intact side, respectively; and the threshold of thermal sensation and cryalgesia of affected side was higher than that of intact side, respectively. CONCLUSION: The superficial sensation of affected extremity of patients with CSR is lessened as compared with that of intact extremity. There are dysfunctions of small myelinated fiber (Aδ fiber) and demyelinated fiber (C fiber) in the affected-side extremity. QST, as a mean for quantitatively evaluating the function of Aδ fiber and C fiber, plays an objective evaluative role in the diagnosis and therapeutic effect observation of CSR.

The Number and Distributions of Limit Cycles of a Cubic Hamiltonian System with Z_2-symmetry Perturbation

This paper is concerned with the number and distributions of limit cycles of a cubic Z2-symmetry Hamiltonian system under quintic perturbation.By using qualitative analysis of differential equation,bifurcation theory of dynamical systems and the method of detection function,we obtain that this system exists at least 14 limit cycles with the distribution C91 [C11 ＋ 2（C32 2C12）].

Construction, detection and microarray analysis on the Shigella flexneri 2a sitC mutant

In order to overcome the defects of difficult gene operations in low-copy suicide plasmid pCVD442,Gateway technology was applied in the construction process of recombinant plasmid for gene knockout in this study.With this improved knockout system,we inactivated sitC gene,which is associated with iron transport in Shigella flexneri 2a strain 301,to yield the mutant,MTS.The functional detection of the mutant was performed at the level of culture medium,cell and animal experiment,respectively.The gene expression profiles were compared with DNA microarray between the mutant and the wild type under iron-restricted conditions.The results showed that MTS grew obviously less well than the wild-type strains in L broth containing 150μmol/L iron chelator DIP(2,2′-dipyridyl).Addition of iron or manganese to the cultures stimulated the growth of MTS to wild-type levels in rich culture medium.In either the experiment on the ability of intracellular multiplication and cell-to-cell spread in HeLa and U937 cell lines,or the experiment on keratoconjunctivitis in guinea pigs,MTS showed no obvious changes in virulence compared with the parental strain Sf301.When 65μmol/L DIP was added to the cultured HeLa cells,the ability of intracellular multiplication of MTS reduced about 51.6%as compared with that of Sf301.The analysis of expression profiles under iron-limited condition showed that MTS was more sensitive for the change of iron deficiency than Sf301.There are 106 more up-regulated genes in MTS than in wild-type strains,which are involved in membrane transportation,amino acid metabolism and uncategorized function genes,while down-regulated genes are mainly in-volved in energy and carbohydrate metabolism.Under low iron conditions,the expression levels of known iron-transport associated genes generally increased.Additionally,the number of these genes and their increase amplitude in MTS are more than those in Sf301.Together,these results confirmed that Sit iron-transport system is important for the growth of Shigella.

Improved Flight Conflict Detection Algorithm Based on Gauss-Hermite Particle Filter

In order to improve the accuracy of free flight conflict detection and reduce the false alarm rate, an improved flight conflict detection algorithm is proposed based on Gauss-Hermite particle filter（GHPF）. The algorithm improves the traditional flight conflict detection method in two aspects：（i） New observation data are integrated into system state transition probability, and Gauss-Hermite Filter（GHF） is used for generating the importance density function.（ii） GHPF is used for flight trajectory prediction and flight conflict probability calculation. The experimental results show that the accuracy of conflict detection and tracing with GHPF is better than that with standard particle filter. The detected conflict probability is more precise with GHPF, and GHPF is suitable for early free flight conflict detection.

Exploring the tidal effect of urban business district with large-scale human mobility data

Business districts are urban areas that have various functions for gathering people,such as work,consumption,leisure and entertainment.Due to the dynamic nature of business activities,there exists significant tidal effect on the boundary and functionality of business districts.Indeed,effectively analyzing the tidal patterns of business districts can benefit the economic and social development of a city.However,with the implicit and complex nature of business district evolution,it is non-trivial for existing works to support the fine-grained and timely analysis on the tidal effect of business districts.To this end,we propose a data-driven and multi-dimensional framework for dynamic business district analysis.Specifically,we use the large-scale human trajectory data in urban areas to dynamically detect and forecast the boundary changes of business districts in different time periods.Then,we detect and forecast the functional changes in business districts.Experimental results on real-world trajectory data clearly demonstrate the effectiveness of our framework on detecting and predicting the boundary and functionality change of business districts.Moreover,the analysis on practical business districts shows that our method can discover meaningful patterns and provide interesting insights into the dynamics of business districts.For example,the major functions of business districts will significantly change in different time periods in a day and the rate and magnitude of boundaries varies with the functional distribution of business districts.

ANALYSIS OF LIMIT CYCLES TO A PERTURBED INTEGRABLE NON-HAMILTONIAN SYSTEM

Bifurcation of limit cycles to a perturbed integrable non-Hamiltonian system is investigated using both qualitative analysis and numerical exploration.The investigation is based on detection functions which are particularly effective for the perturbed integrable non-Hamiltonian system.The study reveals that the system has 3 limit cycles.By the method of numerical simulation,the distributed orderliness of the 3 limitcycles is observed,and their nicety places are determined.The study also indicates that each of the 3 limit cycles passes the corresponding nicety point.