CONCENTRATION DISTRIBUTION OF ALLOYING ELEMENTS IN SURFACE LAYER OF Ti ALLOY MELTS

The concentration distribution of alloying elements such as Al,Sn,V,Si and Mo in surface layer of quenched Ti alloy melts(TC4,TA 7 and TC9)has been determined by EPMA.Ti al- loy samples were melted and evaporized by electron beam in water cooled copper curcible.The activity coefficient of alloy elements in Ti alloy melts are:γ_(Al)=0.009—0.018 and γ_(Sn)=0.066 —0.123 at 1921—2106℃;γ_V=0.713 at 2021℃;γ_(Si)=0.020 and γ_(Mo)=0.913 at 1921℃.The rate controlling steps of the evaporation of alloying elements Al,Sn,V,Si and Mo from Ti al- loy melts have been discussed with the data of evaporation activation energies of such alloy el- ements.

Remote Sensing Retrieval of Surface Suspended Sediment Concentration in the Yellow River Estuary

Accurate assessment of surface suspended sediment concentration （SSSC） in estuary is essential to address several important issues： erosion, water pollution, human health risks, etc. In this study, an empirical cubic retrieval model was developed for the retrieval of SSSC from Yellow River Estuary. Based on sediments and seawater collected from the Yellow River and southeastern Laizhou Bay, SSSC conditions were reproduced in the laboratory at increasing concentrations within a range common to field observations. Continu- ous spectrum measurements of the various SSSCs ranging from 1 to 5700 mg/1 were carried out using an AvaField-3 spectrometer. The results indicated the good correlation between water SSSC and spectral reflectance （Rrs） was obtained in the spectral range of 726-900 nm. At SSSC greater than 2700 mg/L, the 740-900 nm spectral range was less susceptible to the effects of spectral reflectance saturation and more suitable for retrieval of high sediment concentrations. The best correlations were obtained for the reflectance ratio of 820 nm to 490 nm. Informed by the correlation between Rrs and SSSC, a retrieval model was developed （R2 = 0.992）. The novel cubic model, which used the ratio of a near-infrared （NIR） band （740-900 nm） to a visible band （400-600 nm） as factors, provided robust quantifica- tion of high SSSC water samples. Two high SSSC centers, with an order of 103 mg/1, were found in the inversion results around the abandoned Diaokou River mouth, the present Yellow River mouth to the abandoned Qingshuigou River mouth. There was little sedi- ment exchange between the two high SSSC centers due to the directions of the residual currents and vertical mixing.

Distribution of Surface Ozone Concentration in the Clean Areas of China and Its Possible Impact on Crop Yields

From August 1994 to July 1995, ozone and its precursors were measured in the clean areas of China. The results show that in the period of crop growth, hourly mean ozone concentration, ozone concentration averaged in seven hours of daytime and accumulated ozone concentration in long period have approached or overpassed the harmful level in environmental and health standard of U. S. A. and Canada.

Polypyrrole Chitosan Cobalt Ferrite Nanoparticles Composite Layer for Measuring the Low Concentration of Fluorene Using Surface Plasmon Resonance

Fluorene is a polycyclic aromatic hydrocarbon, which is a hazardous toxic chemical in the environment. The measurement of low concentrations of fluorene is a subject of intense interest in chemistry and in the environment. Polypyrrole chitosan cobalt ferrite nanoparticles are prepared using the electrochemical method. The prepared layers are characterized using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy. The layers are used to detect fluorene using the surface plasmon resonance technique at room temperature. The composite layer is evaluated after detection of fluorene using atomic force microscopy. The fluorene is bound on the layer, and the shift of the resonance angle is about 0.0052°, corresponding to the limitation of 0.01 ppm.

Modelling of Wideband Concentric Ring Frequency Selective Surface for 5G Devices

Frequency selective surfaces(FSSs)play an important role in wireless systems as these can be used as filters,in isolating the unwanted radiation,in microstrip patch antennas for improving the performance of these antennas and in other 5G applications.The analysis and design of the double concentric ring frequency selective surface(DCRFSS)is presented in this research.In the sub-6 GHz 5G FR1 spectrum,a computational synthesis technique for creating DCRFSS based spatial filters is proposed.The analytical tools presented in this study can be used to gain a better understanding of filtering processes and for constructing the spatial filters.Variation of the loop sizes,angles of incidence,and polarization of the concentric rings are the factors which influence the transmission coefficient as per the thorough investigation performed in this paper.A novel synthesis approach based on mathematical equations that may be used to determine the physical parameters ofDCRFSSbased spatial filters is presented.The proposed synthesis technique is validated by comparing results from high frequency structure simulator(HFSS),Ansys electronic desktop circuit editor,and an experimental setup.Furthermore,the findings acquired from a unit cell are expanded to a 2×2 array,which shows identical performance and therefore proves its stability.

Impacts of Weather Conditions Modified by Urban Expansion on Surface Ozone: Comparison between the Pearl River Delta and Yangtze River Delta Regions

In this paper, the online weather research and forecasting and chemistry （WRF-Chem） model is used to explore the impacts of urban expansion on regional weather conditions and its implication on surface ozone concentrations over the Pearl River Delta（PRD） and Yangtze River Delta（YRD） regions. Two scenarios of urban maps are used in the WRF-Chem to represent the early 1990s （pre-urbanization） and the current urban distribution in the PRD and the YRD. Month-long simulation results using the above land-use scenarios for March 2001 show that urbanization increases both the day- and night-time 2-m temperatures by about 0.6℃and 1.4℃, respectively. Daytime reduction in the wind speed by about 3.0 m s-1 is larger than that for the nighttime （0.5 to 2 m s-1）. The daytime increase in the PBL height （〉 200 m） is also larger than the nighttime （50-100 m）. The meteorological conditions modified by urbanization lead to detectable ozone-concentration changes in the PRD and the YRD. Urbanization increases the nighttime surface-ozone concentrations by about 4.7%-8.5% and by about 2.9%-4.2% for the daytime. In addition to modifying individual meteorological variables, urbanization also enhances the convergence zones, especially in the PRD. More importantly, urbanization has different effects on the surface ozone for the PRD and the YRD, presumably due to their urbanization characteristics and geographical locations. Even though the PRD has a smaller increase in the surface temperature than the YRD, it has （a） weaker surface wind speed, （b） smaller increase in PBL heights, and （c） stronger convergence zones. The latter three factors outweighed the temperature increase and resulted in a larger ozone enhancement in the PRD than the YRD.

The Experimental Research on a New Multiple Curved Surfaces Compound Focus Solar Trough Collector

A new trough imaging solar collector with multiple compounding curved surfaces has been designed. Its working principle and design parameters have been introduced. The experimental curve of temperature rising of the system with time under the real weather has been given. The system efficiency and the relation between efficiency and temperature have been calculated. The test result shows that the system has the advantages of high collecting temperature and not obvious variety of the collecting efficiency with the operating temperature. Therefore, this collector is a quite ideal medium temperature solar collector.

Channel Lateral Pocket or Halo Region of NMOSFET Characterized by Interface State R G Current of the Forward Gated Diode

The channel lateral pocket or halo region of NMOSFET characterized by interface state R G current of a forward gated diode has been investigated numerically for the first time.The result of numerical analysis demonstrates that the effective surface doping concentration and the interface state density of the pocket or halo region are interface states R G current peak position dependent and amplitude dependent,respectively.It can be expressed quantitatively according to the device physics knowledge,thus,the direct characterization of the interface state density and the effective surface doping concentration of the pocket or halo becomes very easy.

Probabilistic Assessment of Reinforcing Steel Depassivation in Concrete under Aggressive Chloride Environments Based on Natural Exposure Data

The probability distributions of the critical threshold chloride concentration Ccr, the chloride diffusion coefficient D, and the surface chloride concentration Cs are determined based on the collected natural exposure data, and the probability estimation of reinforcement depassivation in concrete is presented using Monte-Carlo simulation. From sensitivity analysis of mean value for ccr, cs, and D on the depassivation probability of reinforcement, it is found that ccr, cs, and D respectively has the greatest, smaller, and the lowest effect on the probability of depassivation. Finally the effect of stress state of concrete on the reinforcement depassivation probability is analyzed. It is found that the influence of stress state becomes apparent as exposure time increases.

Concentration sensor with multilayer thin film-coupled surface plasmon resonance

A concentration sensor based on silver(Ag)/silica(SiO2)/zirconium anhydride(ZrO2)multilayer structure is proposed.Two dominant dips can be observed in the reflection spectrum,which correspond to different sensing methods.Firstly,it is demonstrated that the coupling between the surface plasmon polariton(SPP)mode and a planar waveguide mode(WGM)leads to the Fano resonance(FR).The induced bonding hybridized modes have ultra-narrow full wave at half maximum(FWHM)as well as ultra-high quality factors(Q).We can achieve a theoretical value of the refractive index sensitivity 167 times higher than conventional surface plasmon resonance(SPR)sensors with a single metal layer.Secondly,the waveguide coupling mode was examined by measuring angular spectra.A deep and sharp waveguide coupling dip was obtained.The experimental results show that with an increase in the concentration of the fill dielectric material in the surface of the system,the resonance dip exhibits a remarkable red shift,and the measured angular sensitivity is 98.04°/RIU.

Winter sea ice albedo variations in the Bohai Sea of China

Sea ice conditions in the Bohai Sea of China are sensitive to large-scale climatic variations. On the basis of CLARA-A1-SAL data, the albedo variations are examined in space and time in the winter（December, January and February） from 1992 to 2008 in the Bohai Sea sea ice region. Time series data of the sea ice concentration（SIC）, the sea ice extent（SIE） and the sea surface temperature（SST） are used to analyze their relationship with the albedo. The sea ice albedo changed in volatility appears along with time, the trend is not obvious and increases very slightly during the study period at a rate of 0.388% per decade over the Bohai Sea sea ice region.The interannual variation is between 9.93% and 14.50%, and the average albedo is 11.79%. The sea ice albedo in years with heavy sea ice coverage, 1999, 2000 and 2005, is significantly higher than that in other years; in years with light sea ice coverage, 1994, 1998, 2001 and 2006, has low values. For the monthly albedo, the increasing trend（at a rate of 0.988% per decade） in December is distinctly higher than that in January and February. The mean albedo in January（12.90%） is also distinctly higher than that in the other two months. The albedo is significantly positively correlated with the SIC and is significantly negatively correlated with the SST（significance level 90%）.

Mechanistic Model for Predicting NO_3-N Uptake by Plants and Its Verification

Some mechanistic models have been proposed to predict the No3- concentrations in the soil solution at root surface and the NO3-N uptake by plants, but all these relatively effective non-steady state models have not yet been verified by any soil culture experiment. In the present study, a mathematical model based on the nutrient transport to the roots, root length and root uptake kinetics as well as taking account of the inter-root competition was used for calculation, and soil culture experiments with rice, wheat and rape plants grown on alkali, neutral and acid soils in rhizoboxes with nylon screen as a isolator were carried out to evaluate the prediction ability of the model through comparing the measured NO3-concentrations at root surface and N uptake with the calculated values. Whether the inter-root competition for nutrients was accounted for in the model was of less importance to the calculated N uptake but could induce significant changes in the relative concentrations of NO3- at root surface. For the three soils and crops, the measured NO3-N uptake agreed well with the calculated one, and the calculated relative concentrations at root surface were approximate to the measured values. But an appropriate rectification for some conditions is necessary when the plant uptake parameter obtained in solution culture experiment is applied to soil culture. In contrast with the present non-steady state model, the predicted relative concentrations, which show an accumulation, by the Phillips' steady-state model were distinct from the measured values which show a depletion, indicating that the present model has a better prediction ability than the steady-state model.

Effect of ultrasonic impact treatment on the surface integrity of nickel alloy 718

Ultrasonic impact treatment(UIT)is a type of surface strengthening technology that can improve the fatigue properties of materials by improving the surface quality,residual stress,and other aspects.In this study,the influence of ultrasonic impact parameters on the surface integrity of nickel alloy 718 was studied.The micro stress concentration caused by the surface morphology was also explored.The cosine and exponential decay functions were used to fit and characterize the distribution of residual stress and work hardening in the surface material.The results showed that the feed rate had the greatest influence on surface roughness,stress concentration,and surface residual stress.It was not appropriate to evaluate the surface hardening effect only by the number of impacts per unit area,the ultrasonic impact parameters such as feed speed and pre extrusion depth should also be considered.The grain refinement was obvious after UIT.The multiobjective optimization of machining parameters was performed with the objective of surface stress concentration and residual stress.A surface with a smaller surface stress concentration factor and larger compressive residual stress can be obtained simultaneously using medium linear velocity,medium pre extrusion depth,and smaller feed rate.

SURFACE OZONE CHARACTERISTICS AT THREE STATIONS IN GAW OF WMO IN CHINA

The characteristics of surface O_3 on clear days at Waliguan Observatory,Lin'an regional station and Longfengshan regional station in China were analyzed in this paper.The three stations belong to Global Atmospheric Watch(GAW)of WMO.There was obvious daily variation on clear days at Lin'an.with maximum(42.9 ppb)and minimum(20.3 ppb)of daily range appearing in spring and summer.respectively.The daily variation was more regular at Lonfengshan than at Lin'an.The maximum(about 27 ppb)appeared in autumn at Longfengshan.There was no obvious daily variation and also daily range was smaller in other seasons except weaker daily variation in summer at Waliguan.But the surface O_3 concentration(SOC)in summer was higher than that in winter at Waliguan.The SOC on clear days of summer at Waliguan was over 20 ppb higher than at Longfengshan and Lin'an.The global radiation and NO_x concentration were the main factors which control the SOC on clear days at Longfengshan and Lin'an.and played important role in different seasons and areas.The transportation of air flow around the area of Qinghai-Xizang(Tibet)Plateau was the main cause for high SOC and weak daily variation in summer at Waliguan.The similar effect of transportation was obtained at the Mauna Loa Observatory.The distribution characteristics of SOC increasing with height in the troposphere determined the difference of SOC between East China and West China.

RESEARCH ON SURFACE O_3 WITH METEOROLOGICAL CONDITIONS UNDER ATMOSPHERIC BACKGROUND CONDITIONS IN NORTHEAST CHINA

Surface O_3 concentration and its precursors have been observed at Longfengshan station, Heilongjiang Province for a period of one year from August 13,1994 to July 30,1995. Relationship between surface O_3 and the meteorological conditions during this period is analyzed in this study.Observation results show that diurnal variation of surface O_3 follows a pattern of double-peaks with amplitude of 27—28 ppb under fine days in summer and autumn.Although the diurnal variation is small(14 ppb),it is still detectable when it is overcast.Diurnal variation of O_3 is irregular under rainy days.Surface O_3 concentration rises when wind speed starts to increase at 0800 BT(Beijing Time)from 0 to 6 m s^(-1)in autumn,winter and summer.Relative high surface O_3 concentration is noticed frequently when S,SSW,SW and WSW wind are encountered at the station during all seasons.At 0800 BT and 1400 BT the surface O_3 concentration increases with the increase of global radiation accordingly during fine days in winter,spring and autumn.During fine days average peak of O_3 concentration in summer is 20 ppb higher than that in winter while the average peak of global radiation in summer is almost twice as high as that in winter.The average surface O_3 concentration under fine days in autumn at Longfengshan station is 14 ppb lower in comparison to the observation results from Lin'an station where Lin'an is at about the same longitude and lower latitude,with same environment,which is mainly caused by the difference of global radiation due to different latitudes in these two areas(difference of average peak global radiation about 100 W m^(-2)).