PHYSICAL MODEL FOR SMALL SCALE SANDWAVES MIGRATION IN NORTH GULF OF SOUTH CHINA SEA

The aim of this paper is to investigate the mechanism of small scale sand-wave migration. According to the environmental characteristic of the north gulf of South China Sea, a quasi-3D mechanics model has been built for simulating the small scale sand wave migration. The calculation results are shown to be consistent with the observed data in the trough of sand ridge. Considering the effect of environmental actions and sand wave features, we develop an effective formula to predict sand-wave migration. It is indicated that the physical models should be used to predict the migration of the small scale sand-wave, which is rarely dominated by wave activity.

Physical property measurement of therapeutic carbon ion beam in the shallow-seated tumor therapy terminal at HIRFL

For the first time the physical properties of therapeutic carbon-ion beam supplied by, the shallow-seated tumor therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL) are measured. For a 80.55MeV/u C-12 ion beam delivered to the therapy terminal, the homogeneity of irradiation fields is 73.48%, when the beam intensity varied in the range of 0.001-0.1nA (i.e. 1 X 10(6) - 1 X 10(8) particles per second). The stability of the beam intensity within a few minutes is estimated to be 80.87%. The depth-dose distribution of the beam at the isocenter of the therapy facility is measured, and the position of the high-dose Bragg peak is found to be located at the water-equivalent depth of 13.866mm. Based on the relationship between beam energy and Bragg peak position, the corresponding beam energy at the isocenter of the therapy terminal is evaluated to be 71.71MeV/u for the original 80.55MeV/u C-12 ion beam, which consisted basically with calculation. The readout of the previously-used air-free ionization chamber regarding absorbed dose is calibrated as well in this experiment. The results indicate that the performance of the therapy facility should be optimized further to meet the requirements of clinical trial.

Physical design of the new extraction system for SFC

The HIRFL (Heavy Ion Research Facility at Lanzhou) is a cyclotron complex. Its injector is a cector focusing cyclotron with K=69. Since the HIRFL started the operation in 1989, two bigger items of improvements have been finished, the species and intensity of the accelerated particles are increased obviously. But due to the lower extraction efficiency of the SFC, on one hand, a lot of beam lost, and on other hand, outgas from the surface of the electrostatic deflector is serious because of beam hitting. Even sometimes the vacuum press is destroyed. In the paper a new physical design is made to get an extraction system of the SFC with a higher efficiency.

A mathematical model of crevice and pitting corrosion—I. The physical model

A predictive and self-consistent mathematical model incorporating the electrochemical, chemical and ionic migration processes characterizing the propagation stage of crevice and pitting corrosion in metals is described. The model predicts the steady-state solution chemistry and electrode kinetics (and hence metal penetration rates) within an active corrosion cavity as a function of the many parameters on which these depend, such as external electrode potential and crevice dimensions. The crevice is modelled as a parallel-sided slot filled with a dilute sodium chloride solution. The cavity propagation rates are found to be faster in the case of a crevice with passive walls than one with active walls. The distribution of current over the internal surface of a crevice with corroding walls can be assessed using this model, giving an indication of the future shape of the cavity. The model is extended to include a solid hydroxide precipitation reaction and considers the effect of consequent changes in the chemical and physical environment within the crevice on the predicted corrosion rates. In this paper, the model is applied to crevice and pitting corrosion in carbon steel.

Methods for physical separation and characterization of soil organic matter fractions

Turnover of soil organic matter (SOM) is coupled to the cycling of nutrients in soil through the activity of soil microorganisms. Biological availability of organic substrate in soil is related to the chemical quality of the organic material and to its degree of physical protection. SOM fractions can provide information on the turnover of organic matter (OM), provided the fractions can be related to functional or structural components in soil. Ultrasonication is commonly used to disrupt the soil structure prior to physical fractionation according to particle size, but may cause redistribution of OM among size fractions. The presence of mineral particles in size fractions can complicate estimations of OM turnover time within the fractions. Densiometric separation allows one to physically separate OM found within a specific size class from the heavier-density mineral particles. Nutrient contents and mineralization potential were determined for discrete size/density OM fractions isolated from within the macroaggregate structure of cultivated grassland soils. Eighteen percent of the total soil C and 25% of the total soil N in no-till soil was associated with fine-silt size particles having a density of 2.07-2.21 g/cm3 isolated from inside macroaggregates (enriched labile fraction or ELF). The amount of C and N sequestered in the ELF fraction decreased as the intensity of tillage increased. The specific rate of mineralization (mug net mineral N/mug total N in the fraction) for macroaggregate-derived ELF was not different for the three tillage treatments but was greater than for intact macroaggregates. The methods described here have improved our ability to quantitatively estimate SOM fractions, which in turn has increased our understanding of SOM dynamics in cultivated grassland systems.

Finite element simulation of the physical gelation of rennet casein(酶凝干酪素物理凝胶化过程的有限元模拟)

以酶凝干酪素的凝胶化过程为对象,利用有限元方法数值分析了在凝胶化过程中温度场的空间分布和时间演变规律.在此基础上,基于一阶的凝胶化动力学方程,数值模拟了凝胶体系的复剪切模量场,进而分析了材料配方、体系尺寸与冷却方案对复剪切模量场的影响规律.模拟结果表明,由于热阻的差异,体系表面的冷却速率大于内部,表面首先发生凝胶化;而由于预凝胶化阶段的平均冷却速率决定了无穷复剪切模量的值,最终体系内部的复剪切模量超过表面的.

The influence of variant PE-b-PEO segments on physical properties of LLDPE graft copolymers

A method was adopted to fix a series of polymers of PE-b-PEO with different PEO/PE segments on the chains of LLDPE. Maleic anhydride (MA) reacting with hydroxyl group of PE-b-PEO (mPE-b-PEO) was used as the intermediate. The structures of intermediates and graft copolymers were approved by H-1 NMR and FTIR. XPS analysis revealed a great amount of oxygen on the surface of grafted copolymers although the end group of PEO was fixed on the LLDPE chains through MA. Thermal properties of the graft copolymers as determined by differential scanning calorimetry (DSC) showed that PE segments in the grafted monomers could promote the heterogeneous nucleation of the polymer, increase T., and crystal growth rate.

Ab initio study on the physical properties of CoN3 and RhN3 with skutterudite structure

The elastic and electronic properties of hypothetical CoN3 and RhN3 with cubic skutterudite structure were studied by first principles calculations based on density functional theory. By choosing different initial geometries, two local minima or modifications were located on the potential energy surface, termed as modifications I and II. Both compounds are mechanically stable. For each compound, modification I is lower in energy than II. Thermodynamically stable phases can be achieved by applying pressures. Modification II is lower in energy than I at above 50 GPa for both compounds.

Structures and physical properties of n=3 Ruddlesden-Popper compounds Ca4Mn3-xNbxO10 (0 <= x <= 0.2)

The Ruddlesden-Popper series of compounds Ca4Mn3-xNbxO10(x = 0-0.2) have been prepared by solid-state methods. Structural, magnetic, electrical, and magnetoresistive studies were performed on the compounds. Nb doping caused increases in both unit cell volume and octahedral distortion. The magnetization measurements indicated that the doped samples displayed ferromagnetism-like behavior, which could be explained by the double-exchange interaction between Mn4+ and Mn3+ induced by the charge-compensation effect.

Double-ceramic-layer thermal barrier coatings of La2Zr2O7/YSZ deposited by electron beam-physical vapor deposition

Double-ceramic-layer(DCL) thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphologies and cyclic oxidation behavior of the DCL coating were studied. Both the X-ray diffraction (XRD) and thermogravimetric-differential thermal analysis (TG-DTA) prove that LZ and YSZ have good chemical applicability to form a DCL coating. The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single layer LZ coating. and even longer than that of the single layer YSZ coating. The failure of the DCL coating is a result of both the bond coat oxidation and the thermal strain between bond coat and ceramic layer generated by the thermal expansion mismatch.

Preparation and Physical Properties of LLDPE Grafted with Novel Nonionic Surfactants

Copolymers of linear low-density polyethylene (LLDPE) grafted with two novel nonionic surfactants, acrylic glycerol monostearate ester (AGMS) and acrylic polyoxyethylenesorbitan monooleate ester (ATW-EEN80), containing hydrophilic and hydrophobic groups and 1-olefin double bond were prepared by using a plasticorder at 190 degrees C. To evaluate the grafting degree, two different approaches based on H-1-NMR data were proposed, and FTIR calibration was showed to validate these methods. The rheological response of the molten polymers, determined under dynamic shear flow at small-amplitude oscillations, indicated that crosslinking formation of the chains could be decreased with increasing the monomer concentration. Their thermal behavior was studied by DSC and polarization microscope (PLM): The crystallization temperature (T-C) of grafted LLDPE shifted to higher temperature compared with neat LLDPE because the grafted chains acted as nucleating agents. Water and glycerol were used to calculate the surface free energy of grafted LLDPE films.

Thermal barrier coating of lanthanum-zirconium-cerium composite oxide made by electron beam-physical vapor deposition

Lanthanum-zirconium-cerium composite oxide (La-2(Zr0.7Ce0.3)(2)O-7, LZ7C3) as a candidate material for thermal barrier coatings (TBCs) was prepared by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, thermophysical properties, surface and cross-sectional morphologies and cyclic oxidation behavior of the LZ7C3 coating were studied. The results indicated that LZ7C3 has a high phase stability between 298 K and 1573 K, and its linear thermal expansion coefficient (TEC) is similar to that of zirconia containing 8 wt% yttria (8YSZ). The thermal conductivity of LZ7C3 is 0.87 W m(-1) K-1 at 1273 K, which is almost 60% lower than that of 8YSZ. The deviation of coating composition from the ingot can be overcome by the addition of excess CeO2 and ZrO2 during ingot preparation or by adjusting the process parameters.

Effects of polar group saturation on physical gelation of Amphiphilic polymer solutions

Monte Carlo simulation on the basis of the comblike coarse grained nonpolar/polar (NP) model has been carried out to study the polar group saturation effect on physical gelation of amphiphilic polymer solutions. The effects of polar group saturation due to hydrogen bonding or ion bridging on the sol-gel phase diagram, microstructure of aggregates, and chain conformation of amphiphilic polymer solutions under four different solvent conditions to either the nonpolar backbone or the polar side chain in amphiphilic polymer chains have been investigated. It is found that an increase of polar group saturation results in a monotonically decreased critical concentration of gelation point, which can be qualitatively supported by the dynamic theological measurements on pectin aqueous solutions. Furthermore, various solvent conditions to either the backbone or the side chain have significant impact on both chain conformation and microstructure of aggregates. When the solvent is repulsive to the nonpolar backbone but attractive to the polar side chain, the polymer chains are collapsed, and the gelation follows the mechanism of colloidal packing; at the other solvent conditions, the gelation follows the mechanism of random aggregation.

Preparation and physical properties of enhanced radiation induced crosslinking of ethylene-vinyl alcohol copolymer (EVOH)

Preparation and physical properties of ethylene-vinyl alcohol copolymer (EVOH) crosslinked by enhanced radiation have been studied through various methods. It was found that the most effective agent for irradiation-crosslinking was triallyl isocyanurate (TAIC) among four kinds of polyfunctional monomers. Gel content (65.6%) was formed for EVOH-44 (content of ethylene is 44 mol%) at 200 kGy with 5% TAIC, but for EVOH-32 (content of ethylene is 32 mol%), only 37.4% gel content was formed under the same conditions. This result showed that the more the content of ethylene units comprised in EVOH, the easier the chemical bonds could be formed between different molecular chains. Tensile strength and elastic modulus increased after crosslinking at high test temperature and elongation at break decreased at the same time. Hygroscopicity of EVOH showed noticeable decrease after enhancement radiation-crosslinking.