Fabrication of chitosan microspheres for efficient adsorption of methyl orange

In this article, morphology, structure and size controllable chitosan microspheres with high mechanical strength were synthesized by microfluidic technology combining chemical crosslinking and used as an adsorbent for methyl orange. The synthesized adsorbents were characterized using scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR), and an Energy Dispersive Spectrometer(EDS). The effect of pH revealed that the adsorption process depended on pH and the pH variation of methyl orange solution after adsorption indicated that adsorption capacity was affected through the associated role of chitosan nature and pH variation. Experimental results suggested that the as-prepared chitosan microspheres were controlled within a narrow size distribution(coefficients of variation is 1.81%), whose adsorption capacity reached to 207 mg·g^(-1) and mechanical strength was suitable to resist forces. In addition, the adsorption isotherm was well fitted with the Langmuir model, and the adsorption kinetic was best described by the pseudo-second-order kinetic model.The high performance microfluidic-synthesized chitosan microspheres have promising potentials in the applications of removing dyes from wastewater.

Movement and deformation laws of the overlying strata in paste filling stope

We combined the similar simulation with numerical simulation to analyze the movement and deforma- tion features of overlying strata caused by paste backfill mining, study the movement and deformation laws of the overlying strata in paste backfill mining, structural movement of the stope strata as well as the stope stress distribution laws. Furthermore, authors also explored the key factors to the movement and deformation of the overlying strata in paste backfill mining. The results indicate that a caving zone existed in the bending zone only in the overlying strata of the paste backfill mining. Compared with the roof caving mining, the degree of stress concentration and area of influence in the paste filling stope were apparently smaller. And the degree of destruction and area of the overlying strata decreased prominently. Also, there was no apparent strata behavior in the working face. Lastly, the filling ratio was the key to control the movement and deformation of the overlying strata. Combined with a specific engineering example, the author proved the reliability of the simulation results and provided a theoretical basis for the further extension of the paste backfill mining.

Study on hydrostatic gas lubricated non-contacting mechanical seal

The principle and characteristics of hydrostatic gas lubricated non-contacting mechanical seal （HSGLNMS） are introduced. The flow field of the gas film is established by numerical analysis of end faces of HSGLNMS. The distribution of gas film pressure and seal performance parameters inclu- ding opening force and leakage are obtained. Influence of operating parameters and sealing configu- ration on the sealing performance is studied. HSGLNMS has been designed and manufactured. Its working film thickness and leakage are measured to verify the theoretical analysis. The investigation results show that HSGLNMS demonstrates good speed adaptability, which means that the seal runs successfully with both low and high speed, showing excellent performance. The seal can be regula- ted and controlled online ; the opening force will not be raised greatly with the increasing of the num- ber of throttle orifices, but the leakage of seal increases apparently ; the uniform pressure groove im- proves the sealing performance, for example, opening force and stiffness are raised obviously. While leakage is reduced. Finally, the theoretical analysis is verified by experiment.

A DYNAMICAL INTERPRETATION OF THE WIND FIELD IN TROPICAL CYCLONES

Based on the primitive equations in polar coordinates and with the supposition that parcel velocity in tropical cyclones is in linear variation and that the distribution of surface pressure agrees with the Fujita formula, a set of equations are derived, which describe the impact of perturbations of central pressure, position of tropical cyclones, direction and velocity of movement of tropical cyclones on the wind field. It is proved that the second order approximation of the kinetic energy of tropical cyclones can be described by the equations under linear approximation. Typhoon Wipha (2007) is selected to verify the above interpretation method, and the results show that the interpretation method of the wind field could give very good results before the landfall of tropical cyclones, while making no apparent improvement after the landfall. The dynamical interpretation method in this paper is applicable to improving the forecasts of the wind field of tropical cyclones close to the coast.

Crosswind stability of high-speed trains in special cuts

Analysis of the aerodynamic performance of high-speed trains in special cuts would provide references for the critical overturning velocity and complement the operation safety management under strong winds.This work was conducted to investigate the flow structure around trains under different cut depths,slope angles using computational fluid dynamics(CFD).The high-speed train was considered with bogies and inter-carriage gaps.And the accuracy of the numerical method was validated by combining with the experimental data of wind tunnel tests.Then,the variations of aerodynamic forces and surface pressure distribution of the train were mainly analyzed.The results show that the surroundings of cuts along the railway line have a great effect on the crosswind stability of trains.With the slope angle and depth of the cut increasing,the coefficients of aerodynamic forces tend to reduce.An angle of 75°is chosen as the optimum one for the follow-up research.Under different depth conditions,the reasonable cut depth for high-speed trains to run safely is 3 m lower than that of the conventional cut whose slope ratio is 1:1.5.Furthermore,the windward slope angle is more important than the leeward one for the train aerodynamic performance.Due to the shield of appropriate cuts,the train body is in a minor positive pressure environment.Thus,designing a suitable cut can contribute to improving the operation safety of high-speed trains.

Computer simulation of flow and mixing at the duodenal stump after gastric resection

AIM： To investigate the flow and mixing at the duodenal stump after gastric resection, a computer simulation was implemented. METHODS： Using the finite element method, two different Billroth fl procedure cases （A and B） were modeled. Case A was defined with a shorter and almost straight duodenal section, while case B has a much longer and curved duodenal section. Velocity, pressure and food concentration distribution were determined and the numerical results were compared with experimental observations. RESULTS： The pressure distribution obtained by numerical simulation was in the range of the recorded experimental results. Case A had a more favorable pressure distribution in comparison with case B. However, case B had better performance in terms of food transport because of more continual food distribution, as well as better emptying of the duodena section. CONCLUSION： This study offers insight into the transport process within the duodenal stump section after surgical intervention, which can be useful for future patient-specific predictions of a surgical outcome.

Study on Running Performance of Flexible Wheels for Lunar Rovers： Relation between Stress Distribution of Flexible Wheel and Running Performance

On lunar exploration missions, the rovers which can move and explore directly are considered by various agency like NASA （National Aeronautics and Space Administration）, JAXA （Japan Aerospace Exploration Agency）, ESA （European Space Agency）. Lunar rovers are required to move on rough terrains such as craters and rear cliffs where it is scientifically very important to explore. However, there is a problem that the rovers have possibility of stack because of the lunar surface is covered with loose soil named Regolith. Therefore, this paper investigates a mechanism of kinetic behavior between the wheels of the exploration rovers and loose soil. And then, this paper proposed a flexible wheel to solve like that problems. The flexible wheel has the surface which can be changed flexibly toward rough terrain. Running experiments on loose soil which imitated regolith were carried out to observe the traversability of the flexible wheel using slip ratio. Traversality of flexible wheel was better than the circular rigid wheel. The authors believe that stress distribution is important. The stress distribution of the flexible wheels is horizontally long and stress value is small. However, the stress distribution can be changed by loaded more weight. Therefore, the relationship between the stress and the running performance was considered using this differential stress distribution. In experiments, the authors used the flexible wheel with simple structure （3 limbs）. From these considerations, the relationship between the stress of the flexible wheel and the running performance was described.

Concept Design of a New Deep Draft Platform

The authors analyzed requirements for a new deepwater platform, from conceptual design to hydrodynamic analysis.The design incorporated Deep Draft Multi-Spar (DDMS) that allowed easy fabrication, reduced costs, and provided favorable motion performance.It also provided a dry tree system and other benefits.The conceptual design process included dimension estimation, general arrangements, weight estimation, weight distribution, stability analysis, etc.A high order boundary element method based on potential theory and the modified Morison equation was used to predict the hydrodynamic and viscous effects of this new concept platform.The response amplitude operators (RAOs) were acquired and compared with those of a typical Truss Spar.The response of the platform to the JONSWAP spectra of 3 different extreme ocean conditions was analyzed to evaluate the seakeeping ability of the new concept.The results revealed favorable motion performance due to all the degrees of freedom available.