Some Analyses and Numerical Simulations of Meiyu in East Asia in 1983

In this paper the differences between Meiyu and Baiu front in 1983 have firstly been analysed, the trajectories of air on and to the north side of Meiyu and Baiu fronts during the Meiyu period have then been traced, and the forecasting and simulating of 4 sets of Meiyu onset of the year have finally been run utilizing the global model at UK Me-leorological Office. The results show: 1) Meiyu fronts are different from Baiu ones in temperature, humidity and stratification fields in lower atmosphere; and the possibly reasons for it are explained. 2) The Bay of Bengal is the main moisture source for Meiyu front, the South China Sea and the Pacific, for Baiu ones; and some existed arguments on it are also discussed. 3) The onset of Meiyu and its rainfall and rain belts are sensitive to the Tibetan Plateau, and the water vapour conditions over the Bay of Bengal and the South China Sea, but not sensitive to the SST over the equatorial area or to the East of Japan.

A numerical evaluation of continuous backfilling in cemented paste backfilled stope through an application of wick drains

Cemented paste backfill （CPB） is gaining popularity in many underground mines worldwide. Sufficient water is added into CPB to make a flowable material for pipe transportation. Barricades are built near the drawpoints to prevent in-rush of the fill slurry. To avoid barricade failures resulting from excessive backfill pressures, backfilling is typically performed with a plug pour followed by a final pour. The interval between the two pours should be shortened or removed to increase mining productivity and avoid pipe clogging. Recently, Li proposed to apply wick drains in backfilled stopes to promote drainage and consolidation. The preliminary simulations by considering an instantaneous filling indicated that the drainage of CPB can be significantly accelerated by using wick drains. Barricade was not considered. Here, some new numerical modeUings are presented with more representative filling sequences, stope geometry, and different draining configurations. The results illustrate that the stope can be backfilled continuously by using wick drains.

Numerical Simulations and Analyses of Temperature Control Loop Heat Pipe for Space CCD Camera

As one of the key units of space CCD camera,the temperature range and stability of CCD components affect the image's indexes.Reasonable thermal design and robust thermal control devices are needed.One kind of temperature control loop heat pipe(TCLHP) is designed,which highly meets the thermal control requirements of CCD components.In order to study the dynamic behaviors of heat and mass transfer of TCLHP,particularly in the orbital flight case,a transient numerical model is developed by using the well-established empirical correlations for flow models within three dimensional thermal modeling.The temperature control principle and details of mathematical model are presented.The model is used to study operating state,flow and heat characteristics based upon the analyses of variations of temperature,pressure and quality under different operating modes and external heat flux variations.The results indicate that TCLHP can satisfy the thermal control requirements of CCD components well,and always ensure good temperature stability and uniformity.By comparison between flight data and simulated results,it is found that the model is to be accurate to within 1℃.The model can be better used for predicting and understanding the transient performance of TCLHP.

Strain localization analyses of idealized sands in biaxial tests by distinct element method

This paper presents a numerical investigation on the strain localization of an idealized sand in biaxial compression tests using the distinct element method(DEM).In addition to the dilatancy and material frictional angle,the principal stress field,and distributions of void ratio,particle velocity,and the averaged pure rotation rate(APR)in the DEM specimen are examined to illustrate the link between microscopic and macroscopic variables in the case of strain localization.The study shows that strain localization of the granular material in the tests proceeds with localizations of void ratio,strain and APR,and distortions of stress field and force chains.In addition,both thickness and inclination of the shear band change with the increasing of axial swain,with the former valued around 10-14 times of mean grain diameter and the later overall described by the Mohr-Coulomb theory.

Analysis of fretting wear behavior of unloading valve of gasoline direct injection high-pressure pump

The high pressures in gasoline direct injection technology lead to structural damage in some hydraulic components,especially annular damage on the contact area of the valve ball and on the valve seat of the spherical unloading valve in the high-pressure pump.In previous study,the authors have analyzed the damage on the unloading valve and demonstrated that it is caused neither by static damage nor fatigue damage and have put forward the hypothesis of fretting wear.This paper is based on the establishment of the statically indeterminate structure of the unloading valve.The micro friction parameters(stress,friction coefficient,etc.)required for the numerical iterative calculation of fretting wear are calculated.In addition,based on the grid adaptive technology and a modified Archard wear model,the fretting wear is calculated quantitatively and is in good agreement with experimental results.Based on that verification,the wear laws of the valve ball and valve seat under the same hardness,different contact angles,and different assembly stresses,are analyzed in detail,and reasoned suggestions for the structural design and assembly design of the ball valve are given.

Rock engineering evaluation of existing and planned Salang Tunnels with high overburden through Hindukush Mountains,Afghanistan

The Kabul-Mazar Highway connects Kabul,the capital of Afghanistan,to northern provinces of the country,and further extends into Central Asian countries through the Hindukush mountains.The Salang Tunnel,which is 2600 m long,was designed by Soviet engineers in 1958 and constructed using conventional techniques in 1964.During its construction,the tunnel ranked the distinction of being the highest-altitude tunnel at 3400 m.The socioeconomic importance of the tunnel is exceptionally high,as the Hindukush Mountain range to the east and south of the country is crossed by it.Since 1964,there has been a significant increase in traffic volume.Due to the narrowness of the existing tunnel,the Ministry of Public Works(MOPW)of Afghanistan has planned the con-struction of new twin-tube tunnels.Although there have been rehabilitation and enlargement efforts for the existing tunnel,none of these renovation works have been proven effective,and challenges persist.In 2008,the MOPW initiated a pre-feasibility study for new tunnels,which was finalized in 2012,presenting various options.Subsequently,in early 2018,the MOPW commenced feasibility and detailed studies,leading to the proposal of new twin-tube tunnels,which are designated as the planned tunnels in this paper.In this study,the available geotechnical and environmental data are used to evaluate the rock engineering aspects of the tunnels,including an assessment of the in-situ stress state.A particular emphasis is placed on the reassessment and design of the support system for both the existing and planned tunnels according to RMQR and another system,respectively.The evaluation of the response and stability of the tunnels is concluded,and the implications are subsequently discussed.