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Journal of Jiangsu University(Natural Science Eidtion)

	2011 Vol.32 Issue.4 Published 2011-07-10

	Article

Article

	373	Design and test analysis of inertia system of test bench for tire performance
		LI Shiwu, TIAN Jingjing, YANG Zhifa, ZHANG Jing-hai, WANG Linhong
		In order to study the static and dynamic performance of tire, a bench test strategy was put forward, which included stressstrain analysis, highspeed performance test, durability test, braking performance test and mechanical properties test. Based on the requirements of tire performance tests， a test bench for comprehensive tire performance was framed, and the design method of inertia system was systematically represented. The dynamic simulation model of test bench was built up using SOLIDWORKS and ADAMS/View. The simulation analysis and road test of inertia system for test bench were conducted according to vehicle coastdown test method. The consistency check of simulation and road test results was completed, which meet engineering requirement and verified the structure rationality of inertia system of test bench. The accurate match between the inertia system and the mass of test vehicle was realized through the tire test bench.
		2011 Vol. 32 (4): 373-378 [Abstract] ( 2102 ) [HTML 1KB] [ PDF 2794KB] ( 2521 )

	379	Protection efficiency of side airbag on child occupant
		YANG Xingmei, YANG Jikuang, QI Xiangcui
		The protection effeciency on the injury risk of child occupant was evaluated when the side airbag deployed for side impact. Based on the Prescribed Structure Motion, LS-Dyna and MADYMO softwares were used to establish the simulation models. Simulations with and without deployed side airbag were carried out under Euro-NCAP side impact. The dynamic response parameters of head, neck and thorax of six-year-old child with misusing and correct using booster seat were analyzed and compared. The results indicate that the child with misusing booster seat may not receive injury risk from deployed side airbag for head and thorax. The child with correct using booster seat may receive the protective benefit from deployed side airbag for head and thorax. Whether a child misuses or uses correctly booster seat, the injury risk of neck depends on the real impact situation.
		2011 Vol. 32 (4): 379-384 [Abstract] ( 1909 ) [HTML 1KB] [ PDF 2202KB] ( 2382 )

	385	Moving vehicle detection method based on Gaussian mixture model of spatial information
		ZHANG Xiaona, HE Ren, LIU Zhiqiang, CHEN Shian, NI Jie
		By using conventional Gaussian mixture model, moving object was always detected incorrectly for the situation of dynamic variation of background image and scene, because only pixel level and time domain were classified regardless of spatial information.Based on spatial neighborhood weighted Gaussian mixture model, a moving vehicle detection method was proposed. According to spatial feature of pixel, a spatial information function was defined to restrain noisy. The neighbor information weighted class probabilities of very pixels with spatial constraint were designed and proved to be meet with two criterions of normalization and spatial continuity.Regarding space and time information, the iterative renovated parameter formula and the moving detection algorithm were proposed.The experiments of moving vehicle detection for urban traffic video sequences under different climate demonstrate that the proposed method can get better classification effeciency and accuracy with low misjudgement rate.
		2011 Vol. 32 (4): 385-388 [Abstract] ( 1932 ) [HTML 1KB] [ PDF 1608KB] ( 2680 )

	389	Design of acquisition system for road loading spectra data based on wheel force transducer
		LIU Qinghua, ZHANG Weigong
		Indirect acquisition method of using acceleration sensor was normally used to acquire road loading spectra data,leading to large detection error. According to the direct acquisition method of wheel force transducer(WFT), an acquisition system was proposed. Unidirectional concurrent bus was designed to transmit highspeed data, and bidirectional serial bus was designed to transmit data. CAN bus and scheme based on cPCI of sensor,integrated data acquisition part and upper machine schedule were adopted in hardware system. Wireless data transmission was used in wheel force transmission module of WFT. In software system, AR model which integrated with Kalman filter was adopted for denoising of primitive loading spectra. Oncar experiment was conducted on concrete and pitch roads to acquire loading spectra data. The results show that the real road surface wave can be retained after filtering, and the smalldisturbance can also be denoised. The proposed acquisition method of road loading spectra data is reliable.
		2011 Vol. 32 (4): 389-393 [Abstract] ( 2039 ) [HTML 1KB] [ PDF 2284KB] ( 1735 )

	394	Control and path analysis of airborne noise of fuel cell vehicle
		GUO Rong, YU Zhuoping, ZUO Shuguang, ZHOU Hong
		The transfer path analysis and measurement methods of airborne noise were discussed to the noise problems of middle and high frequency of fuel cell vehicle(FCV). The detection and synthesis methods of airborne noise for FCV were proposed.The correction coefficient of airborne noise synthesis was discussed in detail, and the calculation formula was deduced and programmed. To analysis airborne noise transfer path, the acoustic reciprocity method was used to deduce acoustic transfer functions. Based on the correlation between different sources and receivers, the correction coefficient was introduced to synthesize airborne noise. The effect of correction coefficient on synthesized results was compared with that regardless of correction coefficient. Combined nearfield sound signal of noise sources with the acoustic transfer functions, the total airborne noise was obtained. Contribution analysis of airborne noise illuminates that the top of auxiliary power unit of fuel cell is main airborne path. To reduce the airborne noise level, the main path noise radiation was controlled by sound isolation and sound absorption. The results show that the amplitude of middle and high frequency of interior noise are reduced apparently. The transfer path analysis method of airborne noise is proved to be reasonable.
		2011 Vol. 32 (4): 394-399 [Abstract] ( 1474 ) [HTML 1KB] [ PDF 2284KB] ( 1658 )

	400	Orthogonal test and optimization design of high-head deep-well centrifugal pump
		SHI Weidong, ZHOU Ling, LU Weigang, ZHANG Li, WANG Chuan
		In order to develop high head and high efficiency deep-well centrifugal pump, 100QJ10 deep-well centrifugal pump was taken as an example. The orthogonal experiment of L9（34）, which contains factors with three levels of outlet angle, outlet width, outside diameter of impeller back shroud, etc, was performed to design nine types of impellers. According to standard k-ε model, SIMPLEC algorithm, second-order upwind scheme which were deduced from Fluent, the whole flow field of new type two-stage deep-well centrifugal pump at the operating point was numerically simulated. Nine groups of efficiency and head for design scheme were obtained at rated condition. The effects of geometrical parameters on efficiency and head were discussed by Latin square test method. The primary and secondary factors of the design parameters were acquired by variance analysis. According to the test results, an optimum program for further design was proposed. The test of pump prototype shows that the efficiency of optimal design model pump can reach 58.41% with singlestage head of 5.2 m at rated condition. The improved efficiency and head can meet the design requirements.
		2011 Vol. 32 (4): 400-404 [Abstract] ( 1668 ) [HTML 1KB] [ PDF 1896KB] ( 1828 )

	405	Pool boiling heat transfer with addition of surfactants
		HU Zicheng, GU Jiaqiang, SONG Xinnan, WANG Qian
		Based on thermal stability experiments of surfactants and aqueous surfactant solutions, pool boiling heat transfer experiments of different aqueous surfactant solutions, 99% sodium dodecyl sulfate (SDS), Triton X-100 and Triton X-114, were carried out under atmospheric pressure. The results show that surfactants and aqueous surfactant solutions have good thermal stability under experiment conditions.Compared with water, the optimal boiling heat transfer enhancement is achieved near the critical micelle concentrations (CMC) of surfactants. When concentration of each surfactant is normalized by its CMC, the degree of boiling heat transfer enhancement of anionic surfactant SDS is superior to that of nonionic surfactants of Triton X-100 or Triton X-114 for the same heat flux. However, the degrees of heat transfer enhancement of Triton X-100 and Triton X-114 depend on the normalized concentrations. The quantity of surfactant which is carried by boiling steam depends on species of surfactant, heat flux and surfactant concentration.
		2011 Vol. 32 (4): 405-409 [Abstract] ( 1550 ) [HTML 1KB] [ PDF 2036KB] ( 2301 )

	410	Experiment and simulation of spray impingement for gasoline direct injector
		WANG Yanhua, LI Bo, LI Yunqing, CHEN Feng
		To study the characteristics of gasoline spray after wall impingement from a highpressure gasoline direct injector, a visible test rig was built to detect impinging spray development height, spray radius and spray tip growth rate. The impinging spray process was numerically simulated and verified by experimental data. According to experiment results and simulation,the effects of different injection pressure, ambient pressure, wall distance and angle and wall temperature on the characteristics of spray impingement were discussed. The results show that the spray high and radius are decreased with the increasing of ambient pressure. It is the opposite situation with the increasing of injection pressure. When the wall distance increases, spray high and fuel film thickness decrease, while spay radius increases. Increasing wall inclination and wall temperature can reduce the film thickness,while impingement wall time appear ahead for the enhenced wall inclination.
		2011 Vol. 32 (4): 410-415 [Abstract] ( 1547 ) [HTML 1KB] [ PDF 3632KB] ( 2002 )

	416	Generating algorithm of multi-axis NC engraving-path for triangular mesh model
		SUN Dianzhu, CUI Chuanhui, LI Yanrui, KANG Xincai
		In order to solve the problems of inefficiency and interference in multi-axis NC engraving tool path generation for triangular mesh model, an algorithm was proposed based on triangular mesh model. R*S tree dynamic space index structure was adopted to organize the topological neighbor relationship of triangular mesh. According to the surface feature of the triangular mesh surface model， the tool-position driving point was mapped out to obtain the transient processing area of each dive point. Based on the tangency relationship between the cutter and the triangles in the instantaneous processing area, the interference-free cutter location points were calculated by the calculation methods of surface tangent, vertex tangent and edge tangent. In order to meet required precision, interference-free multi-axis NC engravingpath could be achieved before limit machining error detection between the adjacent cutter location points and precision control by dichotomy. Experimental results show that the algorithm is efficient for the accurate and fast generation of interferential-free multi-axis NC engraving tool path of complex triangular mesh model.
		2011 Vol. 32 (4): 416-422 [Abstract] ( 1801 ) [HTML 1KB] [ PDF 3148KB] ( 1708 )

	423	Fruits recognition in complex background using binocular stereovision
		SUN Jun, LU Bing, MAO Hanping
		According to standard binocular stereovision, the system was built to locate and distinguish fruits in complex background. Based on corner clustering, a novel algorithm was proposed to establish the invariant model of local feature. In order to obtain tridimensional information of position and shape, corner pixels were extracted to complete stereovision matching. Sufficient experrments of fruits recognition show that the algorithm which is based on single fruit characteristic has poor accuracy with parallax positioning accuracy of 78%, distance accuracy of 73% and colour accuracy of 68%. However, accuracy of the algorithm which bases on three fruit characteristics reaches 89%.The algorithm in the paper is proved to be effective to establish invariant mode and can enhance the efficiency of picking matching.
		2011 Vol. 32 (4): 423-427 [Abstract] ( 1267 ) [HTML 1KB] [ PDF 2269KB] ( 1412 )

	423	Fruits recognition in complex background using binocular stereovision
		SUN Jun, LU Bing, MAO Hanping
		According to standard binocular stereovision, the system was built to locate and distinguish fruits in complex background. Based on corner clustering, a novel algorithm was proposed to establish the invariant model of local feature. In order to obtain tridimensional information of position and shape, corner pixels were extracted to complete stereovision matching. Sufficient experrments of fruits recognition show that the algorithm which is based on single fruit characteristic has poor accuracy with parallax positioning accuracy of 78%, distance accuracy of 73% and colour accuracy of 68%. However, accuracy of the algorithm which bases on three fruit characteristics reaches 89%.The algorithm in the paper is proved to be effective to establish invariant mode and can enhance the efficiency of picking matching.
		2011 Vol. 32 (4): 423-427 [Abstract] ( 1504 ) [HTML 1KB] [ PDF 2269KB] ( 1818 )

	428	Soft sensing of key state variables based on continuous hidden Markov model for fermentation process
		LIU Guohai, JIANG Xingke, MEI Congli
		To solve the online detection difficulty of the key state variables in fermentation process with instruments, a soft sensing modeling method which was based on continuous hidden Markov model (CHMM) was proposed. In order to improve the robustness of CHMM, multi-observation training sample sequences were adopted to train the CHMM, and the modified BaumWelch parameters revaluation formula was used to optimize the parameters of CHMM. The new observation vector was inputed into the CHMM model library, and the emission probability of each CHMM in the model library was calculated by Viterbi algorithm. The soft sensing result was obtained by computing the weighted average. The proposed modeling method was applied to the soft sensing modeling of cell concentration in the erythromycin fermentation process. The modeling and simulation were also complished. The results show that the CHMM soft sensing model has high prediction accuracy of cell concentration for fermentation process, which is better than that of artificial neural networks soft sensing model.
		2011 Vol. 32 (4): 428-432 [Abstract] ( 1768 ) [HTML 1KB] [ PDF 1449KB] ( 1918 )

	433	Design of 4.8 GHz low power voltage-controlled oscillator for WSN RF chip
		FAN Xiangning, ZENG Jun, LI Bin, ZHU Weiwei, CHEN Xiaoguang
		In order to meet the application requirements of frequency synthesizer for wireless sensor network (WSN) frontend, a 4.8 GHz LC voltagecontrolled oscillator (VCO) was designed and implemented based on TSMC 0.18 μm RF CMOS process. The core circuit was biased by current, and complementary differential negative resistance LC oscillator structure was adopted with a threebit switch capacitor array. Common source structure was adopted as the output buffer. Circuit design was given, and noise restriction was analyzed in detail. The chip layout was designed in Cadence with 700 μm×900 μm pad. Simulation was completed under 1.8 V supply voltage. Two SSGSS probes and a threepin DC probe were used for chip verification and measurement. The results show that the tuning range of postsimulation can achieve more than 25%, which can perfectly compensate the frequency offset due to process corners. The phase noise of postsimulation is -126.8 dBc/Hz@3 MHz for the carrier of 4.8 GHz. In actual chip detection, the tuning range is 24%, and the phase noise of -121.12 dBc/Hz is obtained at 3 MHz offset with core circuit operating current of only 2 mA.
		2011 Vol. 32 (4): 433-437 [Abstract] ( 1739 ) [HTML 1KB] [ PDF 1824KB] ( 1888 )

	438	Extended closed-loop coordinated control of interconnection-regulation and feedback for a class of systems
		LIU Xinjin, ZOU Yun
		To solve the stabilizability problem of extended closed-loop coordinated control of interconnection-regulation and feedback, a kind of coordinated controller design method was proposed. The extended closed-loop coordinated control model was firstly described. The coordinated stabilization problem was investigated for a class of systems in which the regulated part AU of the system matrix A=AO+AU had special form, i.e. all row (or column) elements were either zero or nonzero. This problem was converted equivalently to the stabilizability (detectability) problem of a linear timeinvariance system to deduce the necessary and sufficient conditions of solvability and to propose the controller design method. The results show that when the regulated part AU has special form, the corresponding coordinated control problem can be converted to unconstrained stabilizability (detectability) problem of a linear timeinvariance system, while the situation is the opposite for other forms of AU. The key of solving stabilizability problem of general coordinated control model is the mixture matrix product of Cayley product and Hadamard product.
		2011 Vol. 32 (4): 438-442 [Abstract] ( 1333 ) [HTML 1KB] [ PDF 1335KB] ( 1471 )

	443	Joint timing and phase estimation algorithm for SOQPSK signals
		LIU Xiaoming, WANG Mengrou, WU Haowei, HE Hui
		To solve the difficulty and complexity of synchronization problem in ternary shapedoffset quadrature phase shift keying(SOQPSK), a decisiondirected joint timing and carrier phase estimation algorithm was proposed. Based on Laurent representation of SOQPSK, the symbol sequence was recovered by maximum likelihood sequence detection(MLSD). The joint likelihood functions of timing and carrier phase parameter were simplified into the likelihood function of timing parameter. The estimated timing value was then recovered by parallel searching method to obtain the estimated value of carrier phase. According to the common signals of full response SOQPSK-MIL and partial response SOQPSK-TG, the complexityreduction implementation scheme of joint timing and carrier phase estimation algorithm was proposed. Simulation was completed under additive white Gaussian noise(AWGN) channel. The results show that the proposed algorithm is suitable for SOQPSK-MIL and SOQPSK-TG. The timing error variance curve is close to the theoretical limit. The carrier phase error variance is at 10-3-10-4 order of magnitude with timing offset, and close to theoretical limit without timing offset. Carrier phase error has little effect on the timing recovery algorithm.
		2011 Vol. 32 (4): 443-448 [Abstract] ( 1657 ) [HTML 1KB] [ PDF 1687KB] ( 2252 )

	449	Co-defensive scheme for selective forwarding attacks in WSN
		WANG Xinsheng, ZHAN Yongzhao, WANG Liangmin
		In view of the problems of weak effectiveness and more energy consumption of defending selective forwarding attack in wireless sensor network, a codefensive scheme was proposed. According to characters of easy positioning the nodes around transmission paths of hexagonal mesh structured topology, the nodes around transmission path were adopted to monitor packets transmission. The monitor nodes were used to judge whether there existed selective forwarding attack by monitoring packets transmission of its two neighbor nodes in transmission path, and to determine whether to replay the packets by monitoring results. Based on preparation of topology building, intrusion detection and attack defense, the effective defense was implemented. Compared with the performance of other methods, simulation was completed at NS2 condition. The results show that this method is effective for detecting selective forwarding attack with less consuming storage and energy, and can ensure reliable packets delivery to destination.
		2011 Vol. 32 (4): 449-455 [Abstract] ( 1532 ) [HTML 1KB] [ PDF 1842KB] ( 2151 )

	456	Effects of Y and multiple rare earth addition on microstructures of Al3Ti／7055 composites
		CHEN Dengbin, ZHAO Yutao, ZHU Haiyan, ZHENG Meng, CHEN Gang, ZHANG Zhao
		Insitu Al3Ti/7055 composites were synthesized by direct melt reaction method in Al-K2TiF6 system. The preparation technics was discussed and the effects of Mg, Y (0.25%) and multiple rare earth (0.1%Y+0.15%Ce) addition on microstructures of Al3Ti/7055 composites were investigated by X-ray diffraction and scanning electron microscope. The results show that the morphology and size of Al3Ti reinforcement are influenced significantly by Mg， and the optimal preparation process is composition with latter Mg alloying. The Al3Ti precipitation during solidification process are restrained by 0.25%Y addition, and lead in the uniform of Al3Ti size and morphology. The morphology of Al3Ti mainly is shotrod like. The radial growth of Al3Ti is strongly restrained by rare earth composite addition, and the main morphology is slenderrod like.
		2011 Vol. 32 (4): 456-459 [Abstract] ( 1961 ) [HTML 1KB] [ PDF 1663KB] ( 1648 )

	460	Dynamic rheological properties of modified asphalt based on linear viscoelastic range
		GUO Yongmei, NI Fujian, XIAO Peng
		In order to compare the rheological properties of different modified asphalts in a wide frequency range, base asphalt and four kinds of modified asphalts of StyreneButadieneStyrene (SBS), highelasticity, highviscosity and highstrength asphalts were determined by dynamic mechanical analysis(DMA).By strain sweep test, it is found that the linear viscoelastic range of several modified asphalts is lower than that of base asphalt for the same complex modulus value. By frequency sweep test within the linear viscoelastic range, complex modulus and phase angle master curves were constructed based on timetemperature superposition principle to identify the performance of different modified asphalts. The results show that highelasticity modified asphalt shows a marked improvement of temperature susceptibility and elastic recoverability with the shallowest complex modulus master curve and the lowest phase angle. Highviscosity and SBS modified asphalts have similar rheological properties, while the hightemperature performance of the former is better than that of the latter. Highstrength modified asphalt has the biggest complex modulus in full frequency range with the best ruttingresistance.
		2011 Vol. 32 (4): 460-463 [Abstract] ( 1588 ) [HTML 1KB] [ PDF 1537KB] ( 2320 )

	464	Fabrication of white organic light-emitting devices by physical blending
		HAN Qiang, YAO Guanxin, WANG Guangde, WANG Jing, JIANG Wenlong
		Blended the organic fluorescent materials of NPB， Alq3， DPVBi and Rubrene in a certain proportion, new white organic light-emitting devices (OLEDs) was fabricated with the structure of ITO/physical mixed layer(120 nm)/LiF/Al. The effect of Rubrene proportion on the performance of OLEDs was investigated. With the increase of Rubrene proportion, the device has a corresponding color change. The luminescence of the devices is mainly from DPVBi and Rubrene with subordinately from Alq3 .The partial holes from anode are captured by Rubrene and combined with electron to show radioluminescence, and other holes are transferred in NPB. The excitons are formed from the combine of electrons and holes, and transfer from Alq3 to Rubrene, leading in the decrease of radioluminescence of Alq3. The brightness and current efficiency of the devices show regular change with voltage.
		2011 Vol. 32 (4): 464-467 [Abstract] ( 1337 ) [HTML 1KB] [ PDF 1336KB] ( 1683 )

	468	A multiscale prediction of effective diffusion coefficient of chloride ion in hardened cement paste
		SUN Guowen, SUN Wei, ZHANG Yunsheng, LIU Zhiyong
		Based on the complex microstructure with a multiscale pore structure formed from the initial cement grains hydrate, the hardened cement paste was characterized into three-scale from down to up, C-S-H gel, hydrated products of cement and skeleton of hardened cement paste. Different homogenization models were used to predict diffusion coefficient of chloride ion and all inclusions were considered as sphere at different scale. According to multi-scale transition theory, the output parameters of low scale were considered as input parameters of higher scale. Based on the multi-scale transition theory, the quantitative relationship between the microstructure of hardened cement paste and macroscopic transport behavior of chloride ion in hardened cement paste was built for different scales one by one. By rapid chloride migration method, the diffusion coefficient of chloride ion was measured for the hardened cement paste with different ratio of water to cement of 0.23, 0.25 and 0.53. The proposed prediction was verified by the measured diffusion coefficient and reported value. The results show that predicted values of diffusion coefficient of chloride ion are consistent with experiment results, and that the different homogenization models at the different scale are reasonable.
		2011 Vol. 32 (4): 468-473 [Abstract] ( 1415 ) [HTML 1KB] [ PDF 1470KB] ( 1644 )

	474	Preparation of polyferric sulfate coagulant with titanium dioxide by-product and waste sulfuric acid
		HUANG Yongqiang, WU Tao, WU Chundu, XU Mingli, LI Jingjing
		The by-product of ferrous sulphate from titanium dioxide production and waste sulfuric acid were used to prepare polyferric sulfate (PFS) by direct oxidation. The structure of PFS was characterized by X-ray diffraction, scanning electron microscope and infrared spectrum. The turbidity removal ability of prepared PFS was compared with purchased PFS and FeSO4 in aqueous solution by growing coagulation behaviors in jartest. The results show that the prepared PFS, which is inhomogenous flake with different size and shape, is hydroxybridged polymer of iron. For simulated wastewater treatment, the prepared PFS has good turbidity removal efficiency of 95% with color removal efficiency of 80%, which is comparable with purchased PFS. Floc grows quickly and can reach balance state in short time with large average size of floc.
		2011 Vol. 32 (4): 474-477 [Abstract] ( 1320 ) [HTML 1KB] [ PDF 1983KB] ( 1991 )

	478	Biodiesel preparation from waste cooking oils
		LI Tihai, LIU Muchao, LI Jingsheng
		It takes 7-8 h to decrease the acid value(AV)of waste cooking oils from 125.46 mg·g-1 to 3 mg·g-1 for one step esterification reaction. Based on onestep process,two-step esterification process was adopted by separating intermediate to speed reaction equilibrium with normal acid and base catalysts. The optimal reaction condition is alcohol-oil ratio of 5 with catalyst amount of 1.0% at 110 ℃. The total reaction time is 4.5 h with first esterification time of 3.5 h and second esterification time of 1 h, which is shortened by 2.5-3.5 h.The AV can be decreased to 2.657 mg·g-1 after treatment. With 1% catalyst, the neutral oil was reacted with alcohol-oil ratio of 7 at 65 ℃ for 75 min. The conversion rate reaches 94% and the performance can meet the main index of 0# diesel.
		2011 Vol. 32 (4): 478-481 [Abstract] ( 1436 ) [HTML 1KB] [ PDF 1373KB] ( 1662 )

	482	Correlation between diurnal variation of purification effects and physiological characteristics of Nymphaea tetragona
		ZHAO Feng, HUANG Minsheng, LU Xiaoming, ZHANG Yong
		Based on field test method, hydroponic plant purifying-tanks were used to investigate the correlation between diurnal variation of black and malodorous river water purification and physiological characteristics of Nymphaea tetragona on a sunny day. The results indicate that with diurnal variation of light intensity, Chla, Chlb and SP contents of the leaves show doublepeak style at about 12:00 and 14:00, and POD and CAT activities of the roots show singlepeak style at about 13:00. Removal rate of CODCr, NH+4-N, TN, TP of plant purifyingtanks also show singlepeak style at 13:00. Chla, Chlb and SP contents of the leaves, POD and CAT activities of the roots have a significantly positive correlation with removal rate of CODCr, NH+4-N, TN, TP. Physiological characteristics of Nymphaea tetragona have a remarkable impact on the treatment ability of plant purifyingtanks.
		2011 Vol. 32 (4): 482-486 [Abstract] ( 1738 ) [HTML 1KB] [ PDF 1739KB] ( 2234 )

	487	Nitrogen removal of rural domestic sewage in subsurface constructed wetlands
		ZHANG Yuefeng, LIU Shentan, XIE Xiangfeng, LI Xianning, LV Xi-Wu
		Rural sewage was treated by two constructed wetlands with different substrates, and nitrogen removal efficiency and factors were studied. The results indicate that the combined substrate constructed wetland shows high nitrogen removal efficiency at hydraulic loading of 10 cm·d-1, and the average removal efficiency of ammonia nitrogen and total nitrogen are 83.2％ and 76.2％, respectively. The optimal hydraulic loading for cinder constructed wetland is 15 cm·d-1, and the average removal efficiency of ammonia nitrogen and total nitrogen are 73.9％ and 71.1％, respectively. Nitrogen removal efficiency is significantly influenced by dissolved oxygen level, organic carbon sources and nitrogen forms in constructed wetland. The shortage of dissolved oxygen and organic carbon sources in the middle and later of constructed wetlands is the key reason for the decrease of nitrogen removal. Nitrogen removal efficiency is significantly influenced by nitrogen form, and total nitrogen removal efficiency is high for the sewage with high proportion of nitrate nitrogen.
		2011 Vol. 32 (4): 487-491 [Abstract] ( 1142 ) [HTML 1KB] [ PDF 2270KB] ( 1881 )

	492	Uniform asymptotics for ruin probability in dependent risk model
		YANG Yang, HUANG Long
		In order to investigate some ruin topics in some dependent renewal risk models, an asymptotic result on negative association renewal counting process was obtained. Based on the result, a dependent renewal risk model was considered. The claim interarrival times and the claim sizes were identical distribution random variables of negative and independent association, respectively, while the common distribution belonged to the strong subexponential distribution class. According to the elementary renewal theorem of negative association random variable, the uniform asymptotic estimate for the infinitetime ruin probability and the finitetime ruin probability of insurance company was obtained. The time horizon flexibly varies within t∈［f(x),∞), and f(x) is an arbitrary increasing nonnegative function tending to infinity. Some corresponding results were generalized.
		2011 Vol. 32 (4): 492-496 [Abstract] ( 1082 ) [HTML 1KB] [ PDF 1285KB] ( 1577 )

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