2015 Vol.21

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Correlations between molar fusion entropy and the intrinsic undercoolability of liquid metals LI Chen-hui, XU Ming-qin, HAN Xiu-jun, LI Jian-guo Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 1-11.   DOI: 10.3969/j.issn.1007-2861.2014.04.014 Abstract （1669）      PDF（pc） （1794KB）（638）       Knowledge map    Save High undercoolings up to 340 K and 281 K for pure liquid iron are achieved using aerodynamic containerless levitation and a glass fluxing method, respectively. This implies that the nucleation of liquid iron under aerodynamic containerless solidification condition is closer to homogeneous nucleation. Based on the classical nucleation theory and Spaepen’s expression for solid/liquid interfacial energy, a correlation equation between intrinsic undercooling, namely, the undercooling corresponding to homogeneous nucleation and molar entropy is derived. From this equation, intrinsic undercoolings for a series of liquid metals can be predicted. Good agreement exists between the predicted and experimental results. Reference | Related Articles | Metrics | Comments（0）

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Microstructure evolution and hydrogen permeation performance of Nb30Hf35Ni35–xCox alloys LIANG Xiao, GUO Jing-jie, LI Xin-zhong, SU Yan-qing, FU Heng-zhi Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 12-19.   DOI: 10.3969/j.issn.1007-2861.2014.04.013 Abstract （1418）      PDF（pc） （8552KB）（451）       Knowledge map    Save Nb30Hf35Ni35–xCox (x = 0, 5, · · · , 35) alloys were prepared through tungsten arc-melting. The composition and structure of the alloys was analyzed with scanning electron microscope (SEM) and X-ray diffraction (XRD). Evolution of as-cast structures with the Co content was studied. Hydrogen permeation experiments were conducted at various temperatures and pressure differentials. Relationship between hydrogen permeability and composition of Nb-Hf-Ni (Co) alloys was built. It has been shown that, as the Co content increases, the content of impurities of intermetallic phase in the alloy and volume fraction of the primary bcc-Nb phase gradually reduce, while volume fraction of the bcc-Nb in the eutectic gradually increases. Eutectic morphology changes from rods to lamellas. Hydrogen permeability of the alloys increases with increasing Co content. Reference | Related Articles | Metrics | Comments（0）

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Influence of traveling magnetic field on flow in continuous casting of slab TU Ting-sheng, DENG Kang, ZHANG Zhen-qiang, REN Zhong-ming Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 20-27.   DOI: 10.3969/j.issn.1007-2861.2014.04.019 Abstract （1275）      PDF（pc） （9397KB）（543）       Knowledge map    Save This paper presents a mercury model experiment and coupling numerical simulation with Reynolds time-average model on molten metal flow in the mold of continuous casting of slab. The purpose is to study the influence of a traveling magnetic field (electromagnetic stirring) on the metal flow in the mold. The result shows that, in the mold, the stirring force from the traveling electromagnetic field makes the molten metal form a horizontal circumfluence, leading to destroy of the originally regular circumfluence. In the whole mold, the flow is three dimensional and non-symmetrical. Furthermore, the traveling magnetic field strengthens fluctuation of meniscus. The fluctuation is stronger on the side where the nozzle flow is opposite to the electromagnetic force. Reference | Related Articles | Metrics | Comments（0）

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Effect of sintering temperature and particle size on properties of porous silicon oxide ceramic core materials XU Zi-ye, XUAN Wei-dong, ZHANG Jin-yao, REN Zhong-ming, WANG Huan,MA Chen-kai, YANG Fan, YU Jian-bo, LI Chuan-jun Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 28-37.   DOI: 10.3969/j.issn.1007-2861.2014.04.016 Abstract （1737）      PDF（pc） （15031KB）（534）       Knowledge map    Save Samples of porous silicon oxide ceramic core were prepared using a heat-press molding method. The effects of different sintering temperatures and particle sizes on the structures and properties of the porous silicon oxide ceramic core were investigated. The result indicates that, as sintering temperature increases, the room temperature bending strength and high temperature bending strength increase and the porosity decreases. When the sintering temperature is 1 200°C, silicon oxide ceramic core shows the best overall performance for linear shrinkage rate of 2.75%, porosity of 24.69%, room temperature bending strength of 25.3 MPa and the high temperature bending strength of 44.23 MPa. Above 1 200°C, the room temperature bending strength and high temperature bending strength decrease obviously, while linear shrinkage rate and the porosity are stable. According to X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) fracture micrographs of the silicon oxide ceramic core, changes of the room temperature bending strength and high temperature bending strength are attributed to the differences of the compactness and cristobalite content at different sintering temperatures. In addition, the particle size of ceramic core has visible effects on porosity, linear shrinkage rate, and room temperature bending strength. The best overall property of the ceramic core occurrs when 25.33% of the particle sizes are less than 10 μm, 38.16% between 10 μm and 30 μm, 28.74% between 30 μm and 50 μm, and 7.77% greater than 50 μm but no more than 95 μm. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Epoxy resin modified by novel polyphenylene ether DUAN Jia-zhen1,2, YU Ruo-bing1,2, HU Lin1,2, JIAO Zheng3 Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 38-45.   DOI: 10.3969/j.issn.1007-2861.2014.01.028 Abstract （1615）      PDF（pc） （1847KB）（1051）       Knowledge map    Save As a curing agent and modified agent of epoxy resin, modified polyphenylene ether (MPPE) containing hydroxyl group was synthesized, and characterized by Fourier transform infrared spectroscopy (FTIR). The properties of MPPE/E51 were investigated, and the following results were obtained. The curing temperature is gradually decreased with the increase of content of E51. Thermal stability of the epoxy resin thermosets is improved with the maximum Td5% being 385 °C. The laminated sheet of MPPE/E51 has low dielectric constant (3.51, 1 GHz), dielectric loss (0.008 9, 1 GHz) and low water absorption. Impact strength of MPPE/E51 is up to 63.34 kJ/m2. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(1)

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Sensitive characteristics evaluation of electrochemical H2S gas sensor YU Wen-shuang1, LIU Ling2, GUO Yun1, YI Zhi-wei2, QIAN Yong-biao2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 46-53.   DOI: 10.3969/j.issn.1007-2861.2014.03.003 Abstract （1064）      PDF（pc） （8240KB）（556）       Knowledge map    Save The sensitive characteristics of electrochemical H2S sensor are studied by applying six sigma statistical tools. The Minitab software is used to analyze the experimental data. The results show that the gas sensor has a quick response to H2S gas, the average sensitivity is 0.82 μA/10−6H2S, the gas sensor has a good linear relationship with concentration of H2S in the measurement range of the sensor, the correlation index RSq = 99.9%, and the response time T90 < 20 s. The influences of temperature on sensitivity and on the average response value of H2S sensor are also discussed. Reference | Related Articles | Metrics | Comments（0）

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Template preparation of Ag nanoparticle arrays SERS-active substrate and highly sensitive detection of glucose GUO He-shuai1, FU Qun1, LIN Wei1, ZHENG Xian-zheng1, LU Bo2, WU Ming-hong1, LEI Yong1 Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 54-63.   DOI: 10.3969/j.issn.1007-2861.2014.03.004 Abstract （1295）      PDF（pc） （27022KB）（1444）       Knowledge map    Save A highly sensitive method for detecting glucose using Ag nanoparticle arrays surface-enhanced Raman scattering (SERS) active substrates based on the ultra-thin alumina mask (UTAM) was reported. The large-area highly ordered Ag nanoparticle arrays active substrates were fabricated using thermal evaporation with UTAM as a shadow mask in vacuum. The surface of active substrates can adsorb a layer of decanethiol/mercaptohexanol (DT/MH) self-assembled monolayers (SAM) through the surface pretreatment. Therefore the active substrates can be used for detecting glucose molecules. SERS measurement results of the active substrate with glucose molecules as probe molecules show strong SERS performance, and the enhanced signal is uniform and stable. The relative standard deviation (RSD) of the characteristic peak intensity is less than 10%. This preparation method has the advantages of simple operation and low cost. Reference | Related Articles | Metrics | Comments（0）

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Comparation of physicochemical characterization of PM2.5 collected at different heights in the air above campus ZHANG Rong-chi, LONG Ling, LU Sen-lin, LIU Ding-yu, HAO Xiao-jie, ZHANG Wen-chao, LIU Pin-wei Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 64-71.   DOI: 10.3969/j.issn.1007-2861.2014.04.001 Abstract （1178）      PDF（pc） （8528KB）（430）       Knowledge map    Save PM2.5 has become a major air pollutant. Air quality in campus has close relationship with the health of young people. This study focuses on mass concentration and physicochemical characterization of PM2.5 collected at different heights above a campus. Ambient PM2.5 particles were sampled synchronously at two heights (5 m and 40 m). Microscopic character and its chemical composition of the fine particles were characterized using scanning electron microscope-energy dispersive spectrometer (SEM-EDS). The following results are obtained. Mineral particles, soot aggregates and fly ash are ubiquitous in the campus PM2.5, and gypsum particles, unknown particles can also be found. Mass and number concentrations at 5 m are higher than that of PM2.5 collected at 40 m. The numbers of mineral particles in PM2.5 collected at 5 m are more than that of fine particles sampled at 40 m. Soot aggregates in the PM2.5 at 40 m are more abundant than that at 5 m. Both the particle types and the number of mineral particles collected during daytime are less than that sampled at night. Reference | Related Articles | Metrics | Comments（0）

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Impacts on geochemical phases of nitrogen and phosphorus in sediments of Xinanjiang River by river impounding QIAN Hui-jun, GAO Yang, CAO Man, FU Jia-nan, MA Jing, WANG Fu-shun Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 72-80.   DOI: 10.3969/j.issn.1007-2861.2014.01.031 Abstract （1200）      PDF（pc） （5222KB）（528）       Knowledge map    Save The Xinanjiang Reservoir and the related river reaches were investigated. Sediments were collected along the upstream, reservoir backwater area, central reservoir and downstream the dam. The geochemical phases of phosphorus and nitrogen were determined. The results show that the total phosphorus (TP) and total nitrogen (TN) concentrations in backwater area sediments increase by 37.3% and 34.2% respectively as compared to that in upstream sediments, for the reason of sedimentation and aquaculture input. Due to the impacts of impounding, phosphorus and nitrogen concentrations in downstream sediments decrease by 39.5% and 74.1% respectively as compared to that in reservoir sediments. Among the various forms of phosphorus, the ratio of Ca-bound phosphorus (Ca-P) (13.8%∽31.9%) and Fe-bound phosphorus (Fe-P) (11.5%∽26.2%) in total phosphorus were next only to organic phosphorus (OP) (48%∽69%). The organic phosphorus deposited in the backwater area and central reservoir sediments is gradually decomposed and transformed to Fe-P, leading to the variation in phosphorus forms along the river course. Meanwhile, organic nitrogen (ON) is the main form of TN. Its content is low in the upper reaches sediments, and increases rapidly downward toward the central reservoir, but decreases significantly in the downstream sediments. The percentage of the content of ammoniac nitrogen (NH+4 -N) in TN has less changed along the river channel. The results reveal that the presence of dam has an obvious retention effect on phosphorus and nitrogen, which also changes the stoichiometric ratio of nutrients in sediments. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Variations of nitrate and nitrite contents in vegetables during growth and storage YAN Xiao-juan1, YAN Li-jun1,2, HU Xue-feng1,3, WANG Jian4 Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 81-87.   DOI: 10.3969/j.issn.1007-2861.2014.01.034 Abstract （1208）      PDF（pc） （992KB）（660）       Knowledge map    Save Field experiments indicate that nitrate content in Chinese cabbage (brassica chinensis) is significantly raised when applying chemical fertilizers. Moreover, the nitrate content in its petioles is significantly higher than that in leaves. The nitrite content in fresh vegetables is usually less than 1 mg/kg FW (fresh weight), but may be significantly raised when it is stored. Especially, the nitrite content in vegetables sharply increases to several hundred mg/kg FW as soon as the leaves are decayed when it is stored at room temperature, posing a risk to human health. Pretreatments of vegetables before storage also significantly influence of nitrite accumulation. It should be noted that the nitrite content in vegetables stored as homogenate often increases sharply in a short term. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(1)

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A novel coupon-type electrical resistance probe for environmental corrosion monitoring FENG Bei1,2, WENG Yong-ji1,3, LI Xiang-yi1,3, LI Jun-hao1, JIAO Zheng2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 88-96.   DOI: 10.3969/j.issn.1007-2861.2104.01.030 Abstract （1296）      PDF（pc） （7521KB）（510）       Knowledge map    Save A novel electrical resistance (ER) probe is designed. It includes 4 coupons, 2 of them exposed in a corrosion environment and 2 sealed in epoxy for monitoring the environmental corrosion rates and deviations. A corrosion index P is introduced to eliminate the temperature influence. The mean corrosion rates within individual periods of time are calculated based on the P-t curves. The probe’s sensitivity in thickness is determined based on the P-Rx (corroded coupon’s resistance) curves. In addition, the influences of output line resistance and the pitting factors on the measure errors are investigated. Ratios of two contrast resistances are analyzed with a statistical method to determine the unusual fluctuation, and used as an index for sealing damage alarm. Comparison with weightlessness experiments shows that this kind of ER probes can offer approximately consistent results for quick estimation of the degree of environmental corrosion. Reference | Related Articles | Metrics | Comments（0）

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Timoshenko composite beam model analysis of steel beam and brick masonry for foundation underpinning of masonry wall XIANG Xiao-xiao, WU Li-wei, YANG Xiao Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 97-105.   DOI: 10.3969/j.issn.1007-2861.2014.01.011 Abstract （1365）      PDF（pc） （801KB）（523）       Knowledge map    Save Regarding the steel clamping beams and brick masonry between them as a composite beam and based on the Timoshenko elastic beam model, the governing equation for bending deformation of composite beam is established. The analytical solution for bending deformation of the composite beam of steel and brick masonry is presented. Considering the arch effect of the brick masonry, the foundation underpinning of the brick wall of masonry structure is investigated. The maximum deflection and maximum stresses of the steel-brick masonry composite beam for different models of H-type steel clamping beam are obtained, and the maximum length of the foundation underpinning for single stage is given. It is shown that deflection and stresses of the steel-brick masonry composite beam decrease with the model number of the H-type steel beam increasing, but the load held by the steel beam and the confining pressure of the steel-brick masonry composite beam are unchanged. Furthermore, the deflection of the Timoshenko composite beam is larger than that of the Euler composite beam, but the stresses and confining pressure are the same. Therefore, in the foundation underpinning design, the model of an Euler composite beam can be used for strength analysis, and the Timoshenko composite beam model can be used for stiffness analysis. Reference | Related Articles | Metrics | Comments（0）

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Simplified calculation of shield tunnel’s equivalent bending rigidity HUANG Yan-xiang, ZHANG Meng-xi, LI Lei Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 106-116.   DOI: 10.3969/j.issn.1007-2861.2014.01.036 Abstract （1084）      PDF（pc） （1593KB）（542）       Knowledge map    Save Based on the studies of conventional longitudinal equivalent rigidity ratio, the tunnel’s displacement and deformation are calculated using a variable rigidity beam elasticity calculation method. A simplified expression of the tunnel’s longitudinal equivalent rigidity ratio is obtained. The analysis shows that the longitudinal equivalent rigidity ratio is linearly proportional to the number of bolts. At the same time, the longitudinal equivalent rigidity ratio nearly parabolically increases with the increasing of the bolt radius. However, with the increase of segment ring thickness and the segment modulus of elasticity, the longitudinal equivalent rigidity ratio is reducing. Because of the stress concentration caused by the tunnel’s rigidity change, the tunnel longitudinal equivalent bending rigidity and effectiveness of the rigidity reduce with the increasing of depth. The proposed model is more widely applicable and is of reference value for longitudinal stability design of shield tunnels. Reference | Related Articles | Metrics | Comments（0）

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Dynamic deformation characteristics of unsaturated silt under suction control JIA Lei, SUN De-an, HAO Fei Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 117-127.   DOI: 10.3969/j.issn.1007-2861.2014.01.013 Abstract （1343）      PDF（pc） （16174KB）（1239）       Knowledge map    Save By using a suction-controllable dynamic triaxial testing system USTX-2000 for the unsaturated and saturated soils developed by GCTS Company, the dynamic deformation characteristics of unsaturated silt have been studied with suctions being controlled. Test results of dynamic deformation characteristics are obtained including the skeleton curve of dynamic stress-strain relation, dynamic modulus, and damping ratio. The following results are obtained. Skeleton curves of unsaturated silt under suction control are hyperbolic under dynamic loading, and the larger the suction, the higher the skeleton curves. The dynamic modulus of unsaturated silt increases with the increasing suction, and the effect of suction on dynamic modulus is less than that of the confining pressure. The damping ratio of unsaturated silt decreases with the increasing suction, and the effect of suction on the damping ratio is less than that of the confining pressure. Changes in the skeleton curves of dynamic stress-strain relation, dynamic modulus and damping ratio with the suction can be explained by the change in the average skeleton stress. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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High performance close-loop control of optimal PWM based on stator flux trajectory tracking SONG Wen-xiang, JIANG Shu-hao, RUAN Zhi-yong, YANG Ying, RUAN Yi Journal of Shanghai University（Natural Science Edition）    2015, 21 (1): 128-140.   DOI: 10.3969/j.issn.1007-2861.2014.03.021 Abstract （1605）      PDF（pc） （13555KB）（679）       Knowledge map    Save Lower harmonic distortion at low switching frequency requires optimal pulse patterns. But it cannot be directly used in high performance systems. A stator flux trajectory tracking control (FTTC) system is studied, and a pulse width modulation (PWM) correction method is proposed. Based on this method, dynamic modulation errors and high overcurrents as the operating conditions change are discussed. Furthermore, high performance closed-loop control of optimal PWM based on FTTC with a self-controlled machine model can be realized. Simulation results show that both fast dynamic response and low harmonics characteristic can be achieved at a low switching frequency of 200∽300 Hz. Its harmonic characteristic is more outstanding than that of model predictive direct control methods. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(1)

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Relationship between PWR primary water chemistry and material degradation WU Xin-qiang1,2,3, LIU Xia-he1,2,3, HAN En-hou1,2,3, KE Wei1,2,3 Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 141-151.   DOI: 10.3969/j.issn.1007-2861.2014.04.015 Abstract （1049）      PDF（pc） （18769KB）（428）       Knowledge map    Save Optimization of primary water chemistry is one of the most effective ways to minimize radiation field, mitigate material degradation and maintain fuel performance in pressurized water reactor (PWR) nuclear power plants. It improves characteristics of oxide scales formed on the materials of equipment due to interactions between water chemistry and materials. This article reviews the current status and related problems of the relationship between water chemistry of primary coolant and material degradation in PWR nuclear power plants. Fundamental research progress achieved in recent years on Zn-injected water chemistry (ZWC) into primary coolants of PWR is introduced. Reference | Related Articles | Metrics | Comments（0）

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Feasibility and benefits of applying grain boundary engineering to fuel cladding materials of liquid metal cooled fast breeder reactor XIA Shuang, ZHOU Bang-xin Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 152-159.   DOI: 10.3969/j.issn.1007-2861.2014.05.012 Abstract （1571）      PDF（pc） （4573KB）（647）       Knowledge map    Save Feasibility and benefits of applying grain boundary engineering (GBE) to the fuel cladding material 316 or 15-15Ti austenitic stainless steels of sodium-cooled-fastreactor for reducing void swelling and creep is discussed. GBE can be used to greatly enhance the proportion of low  coincidence site lattice (CSL) grain boundaries that are mainly of annealing twins and its variants. The cladding tubes are normally subjected to 20% cold working after solution annealing before using, which by virtue of providing a dislocation strewn matrix microstructure, contributes to the annihilations of irradiationinduced point defects. If the proportion of low CSL grain boundaries are greatly enhanced prior to the cold working, transfer of slip across the special-structured grain boundaries or pile-up against them during deformation may alter the distribution of dislocations of the microstructure, which may accommodate more defects generated during being irradiated. Reference | Related Articles | Metrics | Comments（0）

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Corrosion resistance of Zr-0.70Sn-0.35Nb-0.30Fe-xS alloy in lithiated water at 360 C GAO Chang-yuan1,2, YAO Mei-yi1,2, XU Qi-di1,2,HUANG Jiao1,2, ZHANG Jin-long1,2, ZHOU Bang-xin1,2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 160-169.   DOI: 10.3969/j.issn.1007-2861.2014.05.011 Abstract （1097）      PDF（pc） （11898KB）（296）       Knowledge map    Save The effect of adding dilute S on the corrosion resistance of Zr-0.70Sn-0.35Nb-0.30Fe alloy was investigated in lithiated water with 0.01 mol/L LiOH at 360 C/18.6 MPa by autoclave tests. The microstructures of the alloys and the oxide layers formed on the alloys were investigated by transmission electron microscope (TEM) and scanning electron microscope (SEM). Results showed that adding 5570 μg/g S degraded the corrosion resistance of Zr-0.70Sn-0.35Nb-0.30Fe alloy and the higher the S content was, the worse corrosion resistance was. Surface segregation of S and the precipitation of coarse Zr9S2 and Zr3Fe second phase particles accelerated the evolution of pores and micro-cracks formed by diffusion of defects in oxide layer, which leads to the bad corrosion resistance of Zr-0.70Sn-0.35Nb-0.30Fe-S alloy. Reference | Related Articles | Metrics | Comments（0）

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Effects of different cover rate of shop peening on residual stress and stress corrosion cracking of 800 alloy tube CAI Zhi-gang1, WANG Yong-dong2, SU Cheng1, CAO Ping1 Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 170-176.   DOI: 10.3969/j.issn.1007-2861.2014.04.020 Abstract （1117）      PDF（pc） （7364KB）（450）       Knowledge map    Save Shot peening is conducted on the outside surface of an 800 alloy heat-exchanging tube in a nuclear steam generator using a shot-peening machine. The effects on the 800 alloy tube surface micrograph, residual stress and stress corrosion cracking (SCC) in the 10%NaOH solution at high temperature and high pressure have been studied. The result shows that the shot peening can change the surface micrograph and residual stress of the 800 alloy tube. As the cover rate of shot peening is creases, the residual stress of the 800 alloy tube gradually decreases, and SCC resistance is significantly improved. Reference | Related Articles | Metrics | Comments（0）

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Uneven nodular corrosion resistance of Zr-4 alloy CHEN Chuan-ming, ZHOU Bang-xin, HUANG Jiao,GOU Shao-qiu, YAO Mei-yi, ZHANG Jin-long Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 177-181.   DOI: 10.3969/j.issn.1007-2861.2014.04.018 Abstract （970）      PDF（pc） （4612KB）（427）       Knowledge map    Save Some bright stripes with several millimeters in width and several tens of millimeters in length appeared on the surface of Zr-4 plates in certain batches of the products. Autoclave corrosion tests, composition analysis by energy dispersive spectrometer (EDS), and texture measurement were used to investigate the essentials of bright stripes and their effect on the nodular corrosion resistance. The results showed that the contents of Fe and Cr alloying elements were somewhat higher, and (0001) texture factor (fN) is larger in bright stripe area than that in the surrounding area. Nodular corrosion resistance on the bright stripe area was much better than the surrounding area after corrosion test at 500 C/10.3 MPa in superheated steam after 3 h exposure. The uneven distribution of Fe and Cr alloying elements and the difference of texture factor between the bright stripes and their surrounding area were contributed to the different nodular corrosion resistance.The uneven component of the ingot was the main reason. Reference | Related Articles | Metrics | Comments（0）

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Effect of adding dilute Si on corrosion resistance of zirconium alloys SUN Feng-tao1,2, YAO Mei-yi1,2, XU Long1,2, HUANG Jiao1,2,ZHANG Jin-long1,2, ZHOU Bang-xin1,2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 182-189.   DOI: 10.3969/j.issn.1007-2861.2014.05.008 Abstract （1111）      PDF（pc） （4716KB）（405）       Knowledge map    Save The effect of adding dilute Si(0.02%) on the corrosion resistance of Zr-1Nb and Zr-1Nb-0.8Sn-0.38Fe-0.1Cr alloys was investigated in super-heated steam at 400 C/ 10.3 MPa and in lithiated water with 0.01 mol/L LiOH at 360℃/18.6 MPa by autoclave tests. The microstructure of the alloys was investigated with transmission electron microscope (TEM) and energy dispersive spectrometer (EDS). No obvious difference was found in the corrosion resistance of the Zr-1Nb and Zr-1Nb-0.02Si alloys in the two corrosion conditions, respectively. In the case of Zr-1Nb-0.8Sn-0.38Fe-0.1Cr alloy, the corrosion resistance decreased due to the addition of Si in super-heated steam at 400 C. However,addition of Si had little effect on corrosion resistance in lithiated water with 0.01 mol/L LiOH at 360 ℃/18.6 MPa. It meant that the influence of Si addition on the corrosion resistance was related to the compositions of alloys and water chemistries. Zr5Si4 second phase particles (SPPs) were observed in Zr-1Nb-0.02Si alloy, while Zr(Nb,Fe,Cr,Si)2 SPPs were observed in Zr-1Nb-0.8Sn-0.38Fe-0.1Cr-0.02Si alloy. Compared to SPPs in Zr-1Nb and Zr-1Nb-0.8Sn-0.38Fe-0.1Cr alloys, Zr5Si4 and Zr(Nb,Fe,Cr,Si)2 SPPs are coarse. Different effects of Si addition on the corrosion resistance of the alloys are related to the SPPs. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Steganographic algorithm with histogram-preserving property SHEN Wen-feng, LI Feng-yong, ZHANG Xin-peng, YANG Qian-xing Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 190-196.   DOI: 10.3969/j.issn.1007-2861.2013.07.046 Abstract （1088）      PDF（pc） （5103KB）（502）       Knowledge map    Save To enhance security of steganography, the characteristics of the image should be kept as far as possible. This paper proposes a steganography algorithm with histogrampreserving property. Firstly, the histogram of pixel values is grouped. By calculating the maximum payload under a given distortion, the modification rate for each pixel is found and the location of pixels is got that need to be changed by syndrome trellis codes (STC). Then embedding is performed by changing those pixels using adaptive intra-group and/or inter-group adjustments. The difference in histogram between the cover and the stegoimages is very small. Experimental results show that the proposed method makes less histogram change and gives better visual quality than existing methods under the same embedding rate. Reference | Related Articles | Metrics | Comments（0）

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Self-adaptive fast mode decision algorithm for depth map intra coding SI Xiao-hua, WANG Guo-zhong, ZHAO Hai-wu, LI Guo-ping, TENG Guo-wei Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 197-205.   DOI: 10.3969/j.issn.1007-2861.2014.03.015 Abstract （1264）      PDF（pc） （1385KB）（805）       Knowledge map    Save In the high efficiency video code (HEVC) based depth video coding in 3D video coding, depth modeling mode (DMM) and a region boundary chain (RBC) mode are introduced. DMM traverses all Wedgelet patterns in the current coding unit (CU) to get the best prediction pattern. Encoding efficiency is improved significantly by these added technologies. Computation complexity is increased significantly, hindering its practical application. To reduce computation complexity, a fast depth mode decision algorithm is proposed for depth video coding based on correlation between the most probable mode and DMM and RBC mode. The proposed method divides coding blocks into flat blocks, directional blocks and texture-complicated blocks. Redundant DMM and RBC mode are skipped for flat blocks. Explicit Wedgelet search patterns are skipped for directional blocks based on directivity of non-flat blocks. Experimental results show that the proposed algorithm can reduce computational complexity of depth coding by 75.4% for all-intra test case, with BD-rate increase of only 0.4% after decoder-side view synthesis. Reference | Related Articles | Metrics | Comments（0）

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Dispersion characteristic of symmetric slab waveguide with chiral negative refractive medium XU Xiao-xue, XIAO Zhong-yin, MA Quan-wen, MA Xiao-long,LIU De-jun, WANG Zi-hua Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 206-212.   DOI: 10.3969/j.issn.1007-2861.2014.03.018 Abstract （1057）      PDF（pc） （2260KB）（390）       Knowledge map    Save According to the Maxwell equations and constitutive relations in chiral medium, the paper studies the dispersion characteristic of a symmetric slab waveguide with a chiral negative refractive medium. With the normalized frequency and propagation factor, dispersion equations expressed with normalized parameters are derived in a slab waveguide with a chiral negative refractive medium. Numerical results show that the chiral parameter has great influence on the dispersion characteristic of a slab waveguide. When the relative chiral parameter is 0.047 7, the zero order mode of a left-handed polarized wave disappears. When it is greater than 1, the core becomes a chiral negative refractive medium and the zero-order mode exists. In addition, the tendency of dispersion curves in slab wave-guide is compared with a chiral negative refractive medium and that with a general chiral medium. Reference | Related Articles | Metrics | Comments（0）

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Design of a bandpass filter with independently tunable dual-band JIAN Hao, LI Guo-hui, WANG Huan-ying, LI Wei Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 213-219.   DOI: 10.3969/j.issn.1007-2861.2014.03.017 Abstract （1234）      PDF（pc） （7028KB）（925）       Knowledge map    Save A dual bandpass filter (BPF) with two center frequencies tuned asynchronously and independently is presented. The proposed filter consists of a stepped-impedance resonator (SIR) with two-terminal shorted stubs and a dual-mode open-loop resonator. To generate additional transmission zeros and improve frequency selectivity, the common input and output coupling lines are used for these two structures. Using the odd-even mode analysis method, resonant frequencies of odd-even mode are electrically tuned due to the loaded varactors at the end of transmission line. The measured performance shows that the first passband can be tuned in a frequency range of 1.93~2.20 GHz, whereas the second passband varies from 2.78 to 3.10 GHz. Comparisons of simulated and measured results show effectiveness of the method. Reference | Related Articles | Metrics | Comments（0）

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Optimizing extraction technology of total flavonoids in Cynanchum wilfordii and its antioxidant effects YANG Shen-ming1,2, WANG Ying-shun1,2, WANG Zhen-ji1,2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (2): 220-228.   DOI: 10.3969/j.issn.1007-2861.2014.03.001 Abstract （1079）      PDF（pc） （1147KB）（353）       Knowledge map    Save Total flavonoids in Cynanchum wilfordii were extracted using an ethanol refluxing method, and the extraction procedure was optimized with orthogonal experiments. The antioxidant effects of the obtained total flavonoids on active oxygen radicals were studied. The results show the following optimum extraction parameters. The volume fraction of ethanol as extractant is 60%, the extraction temperature is 75℃, the extraction time is 60 min, and the ratio of solid to liquid is 1∶30 (g/mL). Under these conditions, the average extraction rate of total flavonoids reaches 10.79%, the average recovery rate of the added sample is 98.78%, and the scavenging effects of total flavonoids on ·OH and O−2 · are 29.2% and 36.7%, respectively, implying that the material has good ability to scavenge ·OH and O−2 ·. Reference | Related Articles | Metrics | Comments（0）

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Recent advances in the research of gaseous carbon exchange between river water and air interface DING Hu, LIU Cong-Qiang, LANG Yun-Chao, LI Si-Liang, LI Xiao-Dong, WANG Fu-Shun Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 275-285.   DOI: 10.3969/j.issn.1007-2861.2015.01.008 Abstract （950）      PDF（pc） （730KB）（761）       Knowledge map    Save Gaseous carbon exchange between river water and air interface is an important link of regional and global carbon cycle. It is essential to the precious estimation of terrestrial carbon budget and optimization of carbon cycle model. In this paper, the importance and recent progress in the study of riverine CO2/CH4 exchange between water-air interface are introduced, and insufficiency in the related study is pointed out. In the future, more researches need to be carried out on CO2/CH4 exchange between water-air interface of rivers under various geo-eco system and human impacts. Methods of paired carbon isotopes, stoichiometry, biomarker, etc., should be used to trace the sources of gaseous carbon (and other carbon forms) and their relative contributions, and to discover related carbon turn over processes. It is suggested that researches combining filed in-situ observing, traditional sample analysis, and laboratory experiments be conducted in the study of carbon exchange between multi-interfaces of soil-water, soil-air, sediment-water and water-air. Key factors that affect carbon exchange between water-air interface should be revealed. The study will provide abasis for related model development and watershed management. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Spatial and seasonal variation of dissolved inorganic carbon isotope compositions in the cascade reservoirs of the Jialing River LI Xiao-Dong, LIU Xiao-Long, YANG Zhou, LI Qin-Kai, HUANG Jun Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 286-293.   DOI: 10.3969/j.issn.1007-2861.2015.01.009 Abstract （1015）      PDF（pc） （2542KB）（704）       Knowledge map    Save The Jialing River and its cascade reservoirs were investigated. Wedensely collected water samples along the Jialing River in August 2008 (rain season) and February 2009 (dry season). We determine the contents and isotopic compositions of dissolved inorganic carbon (DIC), and discuss the sources and spatio-temporal variations of DIC. The results show that the average DIC and 13CDIC were 2 018 μmol/L and −8.6‰ in a rainy season, and 3 150 μmol/L and −6.0‰ in a dry season, showing obvious seasonal variations. The 13CDIC values in winter were heavier than in summer, similar to undammed rivers but different from lakes and reservoirs. This indicates that the hydro-geochemical characteristics of waters in the cascade reservoirs of Jialing River are similar to natural rivers Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(4)

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Carbon and nitrogen coupled biogeochemical cycle in cascade reservoirs of the Wujiang River WANG Bao-Li, LIU Cong-Jiang, WANG Fu-Shun, LIU Xiao-Long, PENG Xi, ZHAO Yan-Chuang Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 294-300.   DOI: 10.3969/j.issn.1007-2861.2015.01.013 Abstract （1112）      PDF（pc） （7861KB）（307）       Knowledge map    Save Concentrations of dissolved CO2 and NO3− were investigated in cascade reservoirs and related river reaches along the Wujiang River to understand temporal and spatial variations. The average of dissolved CO2 were (113.6±105.7) μmol·L−1, ranging from 1.6 to 934.6 μmol·L−1. The average of NO3− were (163.0±104.9) μmol·L−1, ranging from 0.4 to 632.0 μmol·L−1. Averages and amplitudes of dissolved CO2 and NO3−  in the reservoirs are less than those in the rivers. Due to different resources and influencing factors, no significant correlation was found between dissolved CO2 and NO3− in rivers. After damming, the activity of phytoplankton was enhanced, and became an important factor controlling material cycle in reservoirs. Photosynthesis and respiration couple C and N biogeochemical cycle, and dissolved CO2 and NO3−  in reservoirs were significantly correlated. The results indicate that C and N biogeochemical cycles in the original rivers are changed by cascade hydropower exploitation. Reference | Related Articles | Metrics | Comments（0）

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Impact of cascade reservoir development on N2O emissions in the Wujiang River LIU Xiao-Long, WANG Fu-Shun, BAI Li, LI Si-Liang, WANG Bao-Li, LIU Cong-Jiang, WANG Zhong-Liang Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 301-310.   DOI: 10.3969/j.issn.1007-2861.2015.01.012 Abstract （1062）      PDF（pc） （2475KB）（411）       Knowledge map    Save Dams affect hydrologic cycle and water environment through intercepting river water. Therefore, “impounded rivers” or river reservoirs often affect river basin environments. That has become a worldwide problem, especially the effect on N2O emissions. This study investigates cascade reservoirs in the Wujiang River, and analyzes therelated parameters and N2O concentrations. It has been shown that the cascade development doeshave impacts on water parameters, nitrogen loadings and N2O emission. Saturation of N2O averaged 347% in the entiresurface water represents a N2O source with respect to atmosphere, under influences of age of reservoirs, nutrient status and organic matters. N2O is emitted more in spring and summer than in winter and autumn. The key factors of influence are T, pH and DO. Organic matters and nutrient status are important in old reservoirs such as the Wujiangdu reservoir. Nitrification is a dominate process for N2O emission in surface water. But for water in discharge, denitrification is a dominate process. The annual average N2O fluxes were 0.33 μmol·m−2·h−1 for river water, 0.64 μmol·m−2·h−1 for discharge water, and 0.43 μmol·m−2·h−1 for surface water in dams. Compared to other surface water in the world, emission of N2O acts as moderate emission fluxes in the Wujiang River. High concentration in discharge water should be emphasized since it contributes huge amount of N2O emission during hydroelectric production. Reference | Related Articles | Metrics | Comments（0）

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Partial pressure and diffusion flux of dissolved carbon dioxide in the main stream of the Three Gorge Reservoir and the Caotang River in summer WU Xue-Qian, CAO Man, FU Jia-Nan, WEI Hao-Bin, JIA Xiao-Bin, DENG Bing, WANG Fu-Shun Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 311-318.   DOI: 10.3969/j.issn.1007-2861.2015.01.010 Abstract （1015）      PDF（pc） （3674KB）（475）       Knowledge map    Save From May 2013 to July 2013, monthly cruise investigation was conducted to study the partial pressure of dissolved carbon dioxide (pCO2) in the main stream of the Three Gorge Reservoir and its tributary, the Caotang River. The results show that pCO2 in the surface water of the Caotang River varied from 15.8 to 226.4 Pa, and 198.8 to 261.1 Pa for the main stream of the Three Gorge Reservoir. Along the water column of the Caotang River, the lowest value of pCO2 in surface water was 15.8 Pa, and increased rapidly with the depth, and kept stable below 5 m with a maximum value of 294.2 Pa. According to calculations, emission fluxes of CO2 in the Caotang River in the period of investigation were about 16.46, 4.91 and 30.85 mmol m−2·d−1, respectively. In the main stream of the Three Gorge Reservoir, this flux was 48.54 mmol·m−2·d−1. The results show that the main stream of the Three Gorge Reservoir is a source for atmospheric CO2, and the tributary Caotang River emits less CO2 than the main stream, even a sink for atmospheric CO2 on June. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(9)

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A Liouville type theorem of semi-linear equations on the Heisenberg group ZHANG Shu-Tao, ZHAO Qiong, HAN Ya-Zhou Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 319-330.   DOI: 10.3969/j.issn.1007-2861.2013.07.052 Abstract （853）      PDF（pc） （532KB）（604）       Knowledge map    Save Referring to the method of vector fields, this paper studies a class of semilinear  quations on the Heisenberg group and gives a Liouville type theorem, namely, the nonexistence of nontrivial positive solutions. A class of real functional constituted by leftinvariant  vector fields on the Heisenberg group is introduced. Some identities are obtained   by identical deformation. It is proved that any nonnegative solution is trivial according to   the properties of test function and some techniques such as polar coordinates formula on  the Heisenberg group and Young inequality. Related Articles | Metrics | Comments（0）

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A second order accurate mixed legendre-spherical harmonic pseudo-spectral method for the    Fisher equation DENG Hong-Mei, HUANG Wei Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 331-335.   DOI: 10.3969/j.issn.1007-2861.2014.01.038 Abstract （962）      PDF（pc） （2934KB）（493）       Knowledge map    Save The paper proposes a second mixed Legendre-spherical harmonic pseudospectral  scheme for the Fisher equation in a domain between two concentric balls. Legendre interpolation is used in the radial direction, and spherical harmonic interpolation in other  directions. The second order central difference quotient is used for time derivatives. Numerical  results show high accuracy of the proposed algorithm. Reference | Related Articles | Metrics | Comments（0）

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Global stability of an age-structured SIRS epidemic model ZHANG Zhong-Hua, SUO Yao-Hong Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 336-343.   DOI: 10.3969/j.issn.1007-2861.2014.05.010 Abstract （1351）      PDF（pc） （470KB）（478）       Knowledge map    Save An age-structured SIRS epidemic model with screening strategy and infectionage is  formulated. The basic reproductive number is defined. Global stability of equilibria   of the model are disucssed by constructing suitable Lyapunov functions. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(2)

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Eigenstrain boundary integral equation with local Eshelby matrix for ellipsoidal particles MA Hang-1, FANG Jing-Be-2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 344-355.   DOI: 10.3969/j.issn.1007-2861.2014.01.039 Abstract （1010）      PDF（pc） （13792KB）（435）       Knowledge map    Save Aiming at large scale numerical simulation of particle reinforced materials, a concept of local Eshelby matrix is introduced into a computational model of the eigenstrain boundary integral equation to solve the problem of interactions among particles. The local  Eshelby matrix can be considered as an extension of Eshelby tensor and an equivalent inclusion in a numerical form. Taking the sub-domain boundary element method as the   control, three-dimensional stress analyses are carried out for some ellipsoidal particles in infinite media with the proposed computational model. Numerical examples verify  correctness,  feasibility and high efficiency of the present model with the corresponding solution procedure, showing potential of solving large scale numerical simulations for particle reinforced  materials. Reference | Related Articles | Metrics | Comments（0） Cited: Baidu(1)

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Experiments of unidirectional and bidirectional pedestrian flows through a bottleneck in a channel YANG Xue, CHEN Li, TIAN Huan-Huan, DONG Li-Yun Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 356-363.   DOI: 10.3969/j.issn.1007-2861.2014.04.008 Abstract （1141）      PDF（pc） （10497KB）（487）       Knowledge map    Save The self-organization phenomena of pedestrian flow through a bottleneck in a channel are investigated by experiments. Different width of bottlenecks and initial distributions are taken into account. Experiments of unidirectional and bidirectional pedestrian flows through bottlenecks are carried out. Typical characteristics of pedestrian flows are observed, such as fan-shaped aggregation in front of the bottleneck, and sidling through the narrow bottleneck and oscillatory flows. These are formed because of the pedestrian behaviors i.e., following other people walking in the same direction and avoiding conflicts with those in an opposite direction. Similarities and differences between unidirectional and bidirectional pedestrian flows are discussed in the following aspects: coordination of pedestrians, flow and specific flow. It is found that the flow increases with the width of bottleneck in both cases. The specific flow in the bidirectional case deceases monotonously with the width of bottleneck. However, the specific flow in the unidirectional case decreases first, and then increases. When the width of the bottleneck is less than the shoulder-width, the unidirectional pedestrian flow is more efficient. However, the efficiency of walking in the case of bidirectional flows is higher than unidirectional flows when the bottleneck width is slightly larger than the shoulder-width. Reference | Related Articles | Metrics | Comments（0）

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Numerical study of flow separation control by setting small plate in front of leading edge of an airfoil DONG Xiao-Hua-1, SUN Xiao-Jing-2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 364-369.   DOI: 10.3969/j.issn.1007-2861.2014.01.015 Abstract （995）      PDF（pc） （6863KB）（353）       Knowledge map    Save A flow control method using a small plate in front of the leading edge of a   NACA0012 airfoil to achieve good aerodynamic performance is proposed. Effectiveness of  the proposed method is numerically studied by using a self-developed CFD program called  UCFD. At a certain angle of attack, including of parameters including length, initial installation  angle and installation position of the plate on the control of flow separation over  the airfoil are investigated. The optimal length, initial installation angle and installation  position of the small plate are obtained with an orthogonal optimization method that aims  at maximizing the lift-to-drag ratio. Numerical results suggest that this passive flow control   method can efficiently suppress flow separation. Related Articles | Metrics | Comments（0）

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Synthesis and surface properties of novel gemini surfactants DONG Bin, ZHOU Chen-Qiu, LIU Ya-Fei, ZHANG Zhang Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 370-375.   DOI: 10.3969/j.issn.1007-2861.2014.03.010 Abstract （1060）      PDF（pc） （4064KB）（574）       Knowledge map    Save A series of cationic gemini surfactants with different spacer chain lengths and hydrophobic groups were synthesized. Fourier transform infrared spectrometry(FT-IR) and mass spectrometry(MS) indicated that the structures of the products were fully identical with the design molecular. Further, measurements of the surface property were conducted, showing that all of them had lower surface tension, and their critical micelle concentration(CMC) obviously declined with the increasing length of the flexible hydrophilic spacer groups and hydrophobic groups. In addition, the emulsifying capacity was better than the traditional single-chain surfactants. Reference | Related Articles | Metrics | Comments（0）

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Synthesis and properties of phosphorus-nitrogen  containing phenolic resins HU Lin-1, YU Ruo-Bing-1, DUAN Jia-Zhen-1, JIAO Zheng-2 Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 376-383.   DOI: 10.3969/j.issn.1007-2861.2014.01.029 Abstract （1154）      PDF（pc） （1584KB）（478）       Knowledge map    Save The phosphorus-nitrogen containing phenolic resins (NP-PF) were synthesized   from formaldehyde, melamine, phenol and phosphorus-containing monomer. The effect of  NP-PF in NP-PF/F51 was investigated. The results show that (1) the curing rate of NPPF/ F51 accelerates with the increase of NP-PF contents; (2) the epoxy resin thermosets  had good thermal stability; and (3) UL94V-0 rating is achieved with a lower Al(OH)3 content  for the NP-PF/F51 system. Reference | Related Articles | Metrics | Comments（0）

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Effect of temperature on physic-chemical properties of deep eutectic solvent based on choline chloride and  polyols HE Zhi-Jiang, YAN Gao, WANG Qi-Hu, YU Xin-Lou, WU Kai, XU Yi Journal of Shanghai University（Natural Science Edition）    2015, 21 (03): 384-392.   DOI: 10.3969/j.issn.1007-2861.2014.03.005 Abstract （1437）      PDF（pc） （1806KB）（839）       Knowledge map    Save Four kinds of deep eutectic solvents (DESs) based on choline chloride and polyols  were prepared. Density, viscosity and conductivity of the four DESs were measured as  functions of temperature in the range of 303～343 K. The results show that the densities of the four DESs sare linearly dependent on temperature. Viscosities decrease with  increasing temperature, and conductivities increase rapidly with increasing temperature,both obeying the Arrhenius exponential law. The activation energy of viscosity and conductivity  were calculated with the Arrhenius formula. The electrochemical windows of the  four DESs were also tested by using cyclic voltammetry at 333 K. Reference | Related Articles | Metrics | Comments（0）

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