川西亚高山人工针叶林枯枝落叶及苔藓层的持水性能

亚高山针叶林作为”长江上游生态屏障”的主体 ,具有重要的水源涵养和水土保持作用 .本文作者对川西地区典型的不同恢复阶段的人工云杉林、迹地、次生林和原始林下苔藓与枯枝落叶层贮量和持水性能进行了试验研究 .结果表明 ,人工云杉林在生态恢复过程中 ,苔藓与枯枝落叶层的贮量和持水性能均呈现出波动式递增 ,表现为 30a <4 0a <6 0a<5 0a,5 0a云杉林达到最大值 ,苔藓、枯枝落叶层的贮量分别为 10 .96× 10 3 kg/hm2 、76 .9× 10 3 kg /hm2 ,最大持水量分别为 4 4 .77× 10 3 kg /hm2 、182 .5× 10 3 kg /hm2 ,以后略有下降 .枯枝落叶层持水性能优于苔藓 ,说明枯枝落叶层在森林的水源涵养方面发挥了更为重要的作用 .人工林枯枝落叶层贮量和持水性能较天然林有所降低 ,反映了该地区在人工林的建设中应注意其生态功能的恢复 .图 2表 2参

Numerical Analysis of the High Skew Propeller of an Underwater Vehicle

A numerical analysis based on the boundary element method （BEM） was presented for the hydrodynamic performance of a high skew propeller （HSP） which is employed by an underwater vehicle （UV）. Since UVs operate at two different working conditions （surface and submerged conditions）, the design of such a propeller is a cumbersome task. This is primarily due to the fact that the resistance forces as well as the vessel efficiency under these conditions are significantly different. Therefbre, some factors are necessary for the design of the optimum propeller to utilize the power at the mentioned conditions. The design objectives of the optimum propeller are to obtain the highest possible thrust, minimum torque, and efficiency. In the current study, a 5-bladed HSP was chosen for running the UV. This propeller operated at the stern of the UV hull where the inflow velocity to the propeller was non-uniform. Some parameters of the propeller were predicted based on the UV geometrical hull and operating conditions. The computed results include the pressure distribution and the hydrodynamic characteristics of the HSP in open water conditions, and comparison of these results with those of the experimental data indicates good agreement. The propeller efficiency for both submerged and surface conditions was found to be 67% and 64%, respectively, which compared to conventional propellers is a significantly higher efficiency.

Strength and energy exchange of deep sandstone under high hydraulic conditions

To investigate the influence of confining pressure and pore water pressure on strength characteristics,energy storage state and energy release intensity at peak failure of deep sandstone,a series of triaxial compression tests under hydraulic coupling conditions are carried out.By analyzing the process of rock deformation and failure,the stress thresholds of the rock are obtained.The change trend of total energy density,elastic energy density and dissipated energy density of deep sandstone in the pre-peak stage is obtained by the graphical integration method.By comparing the dynamic energy storage level of rocks under different confining pressures,the influence of pore water pressure on the energy dissipation at stress thresholds of crack closure stress,crack initiation stress,crack damage stress and peak stress is analyzed.Based on the ratio of pre-peak total energy density to post-peak total energy density,the interaction mechanism of confining pressure and pore water pressure for the rock burst proneness of deep sandstone is studied.The experimental results show that the peak stress of sandstone increases with the increase of confining pressure,while the existence of pore water pressure can weaken the peak stress of sandstone.In the stress stage from crack closure stress to peak stress,the dynamic energy storage level of rock presents a trend of the inverse“check mark”.Meanwhile,the larger the confining pressure,the higher the energy storage level of rock.However,the pore water pressure increases the degree of energy dissipation of rock and reduces the energy storage capacity of rock,and the degree of dissipation is linear with pore water pressure.The increase of confining pressure aggravates the instability and failure of deep sandstone,while pore water pressure has the opposite effect.The research results will provide necessary data support for the stability analysis of rock mass excavation in sandstone stratum under high stress and high pore water pressure.

Micromorphological Evidences of Climatic Change in Yazd Region,Iran

The fact of, present is the key of the past, will help us to use paleosols properties as indicators of the ecological characteristics of past .time, particularly the paleoclimate. In this respect the micro- morphological properties showed to be a very good indicator. Therefore, for investigating of climate change in Ardakan-Yazd plain, Central Iran 9 pedons were digged and described. Yazd has an arid climate with less than 100 mm annual precipitation and more than 22℃ mean annual temperature （Aridic-hyper thermic soil moisture and temperature regions, respectively）. Based on the morphological and physicochemical analysis Arglic, Calcic and Gypsic diagnostic horizons have been distinguished in these soils. Thin section studied showed that the illuviated form of clay includes, infillings on channel, coating on pendant, on nodules and on grains, at lower depths and also juxtaposed calcite needles on void argillan at upper part of the profiles. Mineralogical result showed fine clay in arglic horizon, too. Considering depth and forms of these pedofeatures, we concluded that, the observed illuviated clays at lower depth must be the result of the more humid climate of the past, where the carbonates have been removed completely as pendant, nodules or coating to considerable depth, following processes, clay has been dispersed and also trans located to these depths. In contrast to these features, the juxtaposed needle calcite at the shallower depth is probably the result of drier climate of today.

Properties of Belite-Rich Portland Cement and Concrete in China

Performances of belite-rich Portland cement, or HBC （high belite cement）, and the resultant concrete are introduced by comparing with that of alite based PC （Portland cement） and concrete. The comparison study of cement properties indicates that HBC possesses the properties of less water demand for normal consistency, better compatibility with water reducer, higher later age strength after 28-day under standard curing temperature of 20 ℃, unique strength gain under elevated curing temperatures of 38-70 ℃, lower hydration heat evolution and temperature rise, lower drying shrinkage and excellent resistance to sulphate attack. These results have been demonstrated by the comparison performance evaluation of concretes prepared by HBC and PC in terms of workability, physical mechanical properties and durability when making high performance high strength concrete and massive concrete.

Effect of Some Processing Variables on the Quality Attributes of Yam Flour

The effect of varied processing variables （yam slice thickness, drying temperatures and type of drying） were investigated to determine their effects on the proximate and some functional properties of yam flour. The yam flour was produced with different slice thickness of 1, 1.5, 2.0, 2.5 and 5 cm using both conventional sun drying method and oven drying at temperatures; 40 ~C, 50 ~C, 60 ~C and 70 ~C. The moisture content of all the yam flour samples increased with increasing yam slice thickness, with the samples sun dried having the lowest values （6.20%-6.87%） followed by those dried at 70 ~C and then 60 ~C. The protein content of the yam flour samples increased with increase in slice thickness and decreased with increase in drying temperatures while the fat and the crude fibre of all the yam flour samples decreased with increase in slice thickness. The water absorption capacity of the sun dried yam flour samples decreased with increase in slice thickness while the syneresis value, bulk density and the gel strength increased with increase in slice thickness for all drying temperatures and for sun dried yam flour samples but smaller slice thickness had higher swelling capacity.

Hydrophilic characteristics of soft rock in deep mines

A series of water absorption tests on dried soft rock have been conducted by the intelligent testing system for water absorption tests in deep soft rock, including tests of water absorption with and without pres- sure. The results show that the water absorbing capacity of rock with a certain pressure is larger than that of rock without pressure： however, the relationship between the water absorbing percentage and the time can be expressed by w（t） = a（l - e^-bt）. In hi-logarithmic coordinates, the hydrophilic relationship with time in tests with pressure could be characterized by linearity, while they present concave or convex in tests without pressure. Based on the hypothesis that each influential factor is irrelevant and they have a linear correlation with the water absorbing capacity, we calculated the weight coefficient of each factor according to experimental results under different conditions. The calculations demonstrate that the effec- tive porosity, content of smectite and kaolinite are all positively correlated with the water absorption capacity of rock; meanwhile, the fractal dimension of the effective pores presents a negative correlation with the water absorption capacity of rock. The water absorption capacity with pressure increases with increasing illite, chlorite and chlorite/smectite formation and a decrease in illite/smectite formation and the fractal dimension of the effective pores, while it is opposite in tests without pressure. The weight coefficient of smectite is smallest among positive factors, and the fractal dimension of the effective pores is the smallest amongst the negative factors.

Bee Pollen in Transylvania （Romania）： Palynological Characterization and ORACFL Values of Lipophilic and Hydrophilic Extracts of Monofloral Pollen Pellets

A melissopalynological study carried out on 35 bee pollen samples from Romania （Transylvania） shows predominant species as Taraxacum officinale, Tilia sp., Ferbascum sp., Zea mays L., Onobrychis viciifolia Scop., Geranium sanguineum L., Filipendula ulmaria L., Cydonia oblonga L., Calluna vulgaris L. and Brassica sp.. This is the first time for the contribution of total phenolic （TP） and total carotenoid （TC） content to the modified oxygen radical absorbance capacity （ORACFL） values in 29 monofloral samples. Hydrophilic ORACFL （H-ORACFL） values ranged between 7.13-10.12 μmol TE/g and 6.94-22.46 μmol TE/g, whereas lipophilic ORACFL （L-ORACFL）values were between 2.19-7.79 μmol TE/g and 1.65-9.96 μmol TE/g, in multifloral and monofloral samples, respectively. It has proved the complex involvement of botanical origins on the antioxidant features with a specific occurrence. Some monofloral samples presented particular high antioxidant potential, such as Salix sp., Taraxacum officinale, Matricaria chamomilla, Cichorium intybus and the poorly studied Cirsium arvense （L.） Scop. and Scilla bifolia L.. New variables, such as soil characteristics, climates together with botanical origins, were introduced in a multivariate analysis of antioxidant data matrix, given a possible important involvement of all of them in affecting, not only the phytochemical composition, but thereafter the antioxidant capacity. All these data could be crucial to a new way of gathering, by beekeepers, depending on the market demand and the purposes for the product that has a potential for further therapeutic bioactivities investigations, and added value in the enrichment of certain products.

Influence of Mechanical Grinding on the Interface Characteristics of Rice/Wheat Straws

The mechanical grinding method was used to make rice and wheat straw flakes and the properties of the interface of straws before and after grinding were evaluated. The particle boards were prepared using two kinds of straw flakes, respectively and their physical and mechanical properties were investigated. The results showed that the rice straw was easier to be broken when compared with wheat straw and the inner surface of cells in grinded straws was exposed remarkably. The characteristic peaks of lignin and cellulose on the surface of wheat straw were more significant than rice straw. The free-radical concentrations of straws were increased dramatically after being grinded with heating in the range from I00 ~C to 200 ~C. The surface free energy of straws was also improved after being grinded and the value in wheat straw was higher than that of rice straw, which implies that wheat straw was easier to be bonded than rice straw. The physical and mechanical properties of two kinds of straw particle boards could achieve the requirements of Chinese National Standards of GB 4897.3-2003, while wheat straw particle boards had better properties than those made from rice straws.

Uncertainty and Sensitivity Analysis for the HELIOS Loop within the LACANES Benchmark

Within the OECD/NEA Benchmarking of Thermal-Hydraulic Loop Models for Lead-Alloy Cooled Advanced Nuclear Energy Systems （LACANES）, the Institute for Neutron Physics and Reactor Technology takes part in the validation process of system codes and the characterization of the thermal-hydraulic behavior of an experimental loop operated with liquid lead-bismuth-eutectics. To confirm the calculations, the results were compared to experimental data obtained from the HELIOS facility at the Seoul National University and to the results of other benchmark participants. The comparison showed that the calculations are within measurement tolerance but nevertheless discrepancies among the participants exist. The pressure drop estimation is determined by a variety of empirical correlations for the friction and the form loss coefficients. Hence, uncertainty and sensitivity measures were applied to find out which parameter is more relevant for the overall pressure drop. In the frame of this investigation, the system code TRACE and the software system for uncertainty and sensitivity, SUSA, were used. The results show that the total pressure drop varies between -30 and ＋15% related to the reference case.

Biochar Effect on Water Evaporation and Hydraulic Conductivity in Sandy Soil

Biochar, as a kind of soil amendment, has important effects on soil water retention. In this research, 4 different kinds of biochars were used to investigate their influences on hydraulic properties and water evaporation in a sandy soil from Hebei Province, China. Biochar had strong absorption ability in the sandy soil. The ratio of water content in the biochar to that in the sandy soil was less than the corresponding ratio of porosity. Because of the different hydraulic properties between the sandy soil and the biochar, the saturated hydraulic conductivity of the sandy soil gradually decreased with the increasing biochar addition. The biochar with larger pore volume and average pore diameter had better water retention. More water was retained in the sandy soil when the biochar was added in a single layer, but not when the biochar was uniformly mixed with soil. Particle size of the added biochar had a significant influence on the hydraulic properties of the mixture of sand and biochar. Grinding the biochar into powder destroyed the pore structure, which simultaneously reduced the water absorption ability and hydraulic conductivity of the biochar. For this reason, adding biochar powder to the sandy soil would not decrease the water evaporation loss of the soil itself.

Experimental study on the performance of a rotational supercavitating evaporator for desalination

Efforts have been made on experimental research of a supercavitation device for desalination, which is named rotational supercavitating evaporator （RSCE）. The RSCE is characterised by the simple construction and responsive capacity control, and only requires rough filtration of the source water for scaling- and fouling-free operations. The present study has been conducted for the water flow at temperature of around 22-30℃ and atmospheric pressure as the first step for investigation of the performance characteristics of RSCE. The multiply factor extremal experiments conducted with the Box-Wilson＇s method have revealed the salinity of the condensate, the temperature of steam inside the supercavity, and dependence of the shape of supercavity on the rate of steam extraction and rotation speed of impeller. The shape of impeller and the expected supercavitating effects it generates have been confirmed by experimental results at the rotation speed of 5430 rpm （round per minute）. The design of the steam extraction openings has been approved during the evacuation of steam. The experimental dependencies have been obtained in form of statistically valid regression equations, which can be used for engineering design of RSCE.

Characteristic of Local Boiling Heat Transfer of Ammonia and Ammonia/Water Binary Mixture on the Plate Type Evaporator

Power generation using small temperature difference such as ocean thermal energy conversion(OTEC)and discharged thermal energy conversion(DTEC)is expected to be the countermeasures against global warming problem.As ammonia and ammonia/water are used in evaporators for OTEC and DTEC as working fluids,the research of their local boiling heat transfer is important for improvement of the power generation efficiency.Measurements of local boiling heat transfer coefficients were performed for ammonia/water mixture(z=0.9-1)on a vertical flat plate heat exchanger in a range of mass flux(7.5-15 kg/m2s),heat flux(15-23 kW/m 2),and pressure(0.7-0.9 MPa).The result shows that in the case of ammonia/water mixture,the local heat transfer coefficients increase with an increase of mass flux and composition of ammonia,and decrease with an increase of heat flux.

Experimental Study on Latent Heat Storage Characteristics of W/O Emulsion-Supercooling Rate of Dispersed Water Drops by Direct Contact Heat Exchange

Recently, much attention has been paid to investigate the latent heat storage system. Using of ice heat storage system brings an equalization of electric power demand, because it will solved the electric -power-demand-concentration on day-time of summer by the air conditioning. The flowable latent heat storage material, Oil/Water type emulsion, microencapsulated latent heat material-water mixture or ice slurry, etc., is enable to transport the latent heat in a pipe. The flowable latent heat storage material can realize the pipe size reduction and system efficiency improvement. Supercooling phenomenon of the dispersed latent heat storage material in continuous phase brings the obstruction of latent heat storage. The latent heat storage rates of dispersed water drops in W/O (Water/Oil) emulsion are investigated experimentally in this study. The water drops in emulsion has the diameter within 3 ~ 25μm, the averaged water drop diameter is 7.3μm and the standard deviation is 2.9μm. The direct contact heat exchange method is chosen as the phase change rate evaluation of water drops in W/O emulsion. The supercooled temperature and the cooling rate are set as parameters of this study. The evaluation is performed by comparison between the results of this study and the past research. The obtained experimental result is shown that the 35K or more degree from melting point brings 100% latent heat storage rate of W/O emulsion. It was clarified that the supercooling rate of dispersed water particles in emulsion shows the larger value than that of the bulk water.

Effects of hydrothermal temperature on formation and decoloration characteristics of anatase TiO_2 nanoparticles

This paper describes the effects of temperature on the complex intermediate processes from the precursor to the fully-crystallized anatase TiO2 nanoparticles in hydrothermal synthesis. The anatase TiO2 nanoparticles were synthesized in a wide temperature range below 230°C. The composition, morphology, and methylene blue (MB) decoloration characteristics of the obtained products were investigated by X-ray diffraction, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, and scanning and transmission electron microscope. The dehydrating polycondensation of Ti(IV)-hydrates and the decomposition of (NH4)2Ti3O7 intermediates with the temperature increase lead to the direct formation of anatase TiO2 nanoparticles under the hydrothermal environments. The strong MB decoloration of the hydrothermal products obtained at the low (≤130°C) and high (≥180°C) temperatures are attributed to the adsorption of Ti(IV)-hydrates and the photocatalysis of anatase TiO2 nanoparticles, respectively.