Estimation of Effects of Underwater Acoustic Channel Capacity Due to the Bubbles in the High Frequency Near the Coastal Area

Zhou, Guoqing,Shim, Tae-Bo,Kim, Young-Gyu The Acoustical Society of Korea 2008 韓國音響學會誌 Vol.27 No.e3

Measurements of bubble size and distribution in the surface layer of the sea, wind speed, and variation of ocean environments were made continually over a four-day period in an experiment conducted in the South Sea of Korea during 17-20 September 2007. Theoretical background of bubble population model indicates that bubble population is a function of the depth, range and wind speed and bubble effects on sound speed shows that sound speed varies with frequency. Observational evidence exhibited that the middle size bubble population fit the model very well, however, smaller ones can not follow the model probably due to their short lifetime. Meanwhile, there is also a hysteresis effect of void fraction. Observational evidence also indicates that strong changes in sound speed are produced by the presence of swarms of micro bubbles especially from 7 kHz to 50 kHz, and calculation results are consistent with the measured data in the high frequency band, but inconsistent in the low frequency band. Based on the measurements of the sound speed and high frequency transmission configuration in the bubble layer, we present an estimation of underwater acoustic channel capacity in the bubble layer.

Research of Job Scheduling With Cloud Based On Trust Mechanism And SFLA

Xiaolan Xie,Ruikun Liu,Guoqing Zhou,Jinsheng Ni 보안공학연구지원센터 2015 International Journal of Grid and Distributed Comp Vol.8 No.1

Job scheduling under the cloud circumstance is the key techniques to impact on frequency of cloud calculation. Trust relationship is an important factor of cloud calculation and job scheduling. In order to satisfy the requirement of quality of cloud calculation service for job scheduling, this article introduced the term of trust mechanism and apply it to cloud calculation and job scheduling. It uses altered SFLA as scheduling strategy, and brings forward a model of job scheduling with cloud circumstance which is based on trust mechanism and SFLA. The simulation results showed that this algorithm with faster convergence speed can increase the trust benefit and accomplish job scheduling task well.

Numerical study for downburst wind and its load on high-rise building

Guoqing Huang,Weizhan Liu,Qiang Zhou,Zhitao Yan,Delong Zuo 한국풍공학회 2018 Wind and Structures, An International Journal (WAS Vol.27 No.2

3D simulations based on an impinging jet were carried out to investigate the flow field of a steady downburst and its effects on a high-rise building by applying the SST k-ω turbulence model. The vertical profile of radial wind speed obtained from the simulation was compared with experimental data and empirical models in order to validate the accuracy of the present numerical method. Then wind profiles and the influence of jet velocity and jet height were investigated. Focusing on a high-rise building, the flow structures around the building, pressure distributions on the building surfaces and aerodynamic forces were analyzed in order to enhance the understanding of wind load characteristics on a high-rise building immersed in a downburst.

A Study on the Present Situation and Problems of Mentoring Relationship in Modern Apprenticeship - Based on the Perspective of Students

Dr. Guoqing XU,Xu CHEN,Yingwen ZHOU 한국직업자격학회 2017 한국직업자격학회 학술대회 Vol.2017 No.10

In the new era, the development and transformation of economy and society in China need more high-quality technicians. However, the traditional and conservative talent training model is far from satisfying the demand of the new development. Therefore, Modern Apprenticeship has gradually become the optimal model for cultivating new talents in China. Because the harmony of mentoring relationship directly affects the effective implementation of Modern Apprenticeship, this article is committed to exploring the present situation and problems of this relationship based on the perspective of students, and attempting to explain the underlying reasons, which are important evidence for improving this relationship. Only by establishing a stable and harmonious mentoring relationship can we really promote the development of Modern Apprenticeship and vocational education for better.

Acoustic emission characterization of the fracture process in steel fiber reinforced concrete

Xiong Zhou,Yuyou Yang,Xiangqian Li,Guoqing Zhao 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.4

The correlation between the characteristics of acoustic emission signals and the strength parameters of concretes is investigated by combining the acoustic emission (AE) technique and steel fiber reinforced concrete (SFRC). By means of AE detection system, three kinds of steel fibers of varying content were used as reinforcement in concrete and their influence on the fracture process and the acoustic activity was considered in this paper. Analysis of the AE test results revealed that for different steel fiber contents, the role of steel fiber is different. Concave-convex steel fiber has an inhibitory effect on the control of crack expansion. Bow steel fiber has a better effect on the control of crack propagation when the fiber content is lower. The compressive strength of SFRC decrease when bow steel fiber content rises. Ultra-short can prevent early cracks of concrete.

Seismic Response Analysis Method for Lining Structure in Underground Cavern of Hydropower Station

Hao Zhou,Ming Xiao,Yang Yang,Guoqing Liu 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.3

Based on the analysis of joint shear test, the complex shear strength model of the interface between surrounding rock and lining structure, considering the interfacial bonding characteristics, shear failure mechanism and seismic dynamic deterioration effect, is established. And based on the dynamic contact force method, the dynamic calculation method of contact surface is presented, which is suitable for the dynamic analysis of the contact system between surrounding rock and lining of underground powerhouse. Then the dynamic numerical simulation method for the lining structure of underground powerhouse is formed by coupling the complex shear strength model with the dynamic calculation method of the contact surface. By using this method and based on the independently developed dynamic calculation platform of underground powerhouse, the evolution process and characteristics of seismic damage of lining structure of Yingxiuwan underground powerhouse are studied. At the same time, the numerical simulation analysis is carried out on the vibration damping measures of the lining structure. The results shows that the dynamic numerical simulation method for lining structure is effective and reasonable. In addition, the idea on the aseismic design of lining structure of underground powerhouse is put forward.

Numerical study for downburst wind and its load on high-rise building

Huang, Guoqing,Liu, Weizhan,Zhou, Qiang,Yan, Zhitao,Zuo, Delong Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.27 No.2

3D simulations based on an impinging jet were carried out to investigate the flow field of a steady downburst and its effects on a high-rise building by applying the SST k-${\omega}$ turbulence model. The vertical profile of radial wind speed obtained from the simulation was compared with experimental data and empirical models in order to validate the accuracy of the present numerical method. Then wind profiles and the influence of jet velocity and jet height were investigated. Focusing on a high-rise building, the flow structures around the building, pressure distributions on the building surfaces and aerodynamic forces were analyzed in order to enhance the understanding of wind load characteristics on a high-rise building immersed in a downburst.

Thermal-Hydraulic-Mechanical Coupling Research on Overburden Pressure Mitigated Ice Lens Growth in the Freezing Soil

Yukun Ji,Guoqing Zhou,Matthew R. Hall,Veerle Vandeginste,Xiaodong Zhao 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.4

Frost heave induced ground surface uplift can have a destructive impact on infrastructures when freezing methods are used for underground construction. The complexity of overburden pressure and the coupled heat and mass transport interaction and their relation to different water flow rates make frost heave modelling an interesting but challenging task. A frost heave model describing phase transition and multiphase interactions (liquid-crystal-soil matrix) is presented in this paper and used to investigate the kinetic growth of the ice lens. By introducing water activity determined growth rate of ice crystals, the micro- and meso-physical mechanisms underlying ice lens growth involve ice crystal nucleation, crystallization, phase transition, and water migration in the frozen fringe are explored. This work indicates that the frozen fringe thickness, the ice crystals growth and the cryogenic-suction in the frozen fringe are particularly significant in determining the ice lens growth kinetics (frost heave) under different overburden pressures. The variation in ice lens growth under various overburden pressures appears to be controlled by the water flow path, cryogenic-suction, and permeability of the frozen fringe. This research reveals the kinetic growth of the ice lens, and helps to evaluate and mitigate geological hazards when artificial ground freezing is applied.

Symplectic Elasticity Analysis of Stress in Surrounding Rock of Elliptical Tunnel

Zhongyu Jiang,Guoqing Zhou,Li Jiang 대한토목학회 2020 KSCE Journal of Civil Engineering Vol.24 No.10

A large number of non-circular tunnels are widely used in engineering practice. The application of these geometric structures not only makes the boundary conditions of mechanical problems more complex, but also makes the theoretical solution more difficult. The introduction of curvilinear coordinate system can easily transform the elliptical region into a circular region, and the physical relationship can also be adjusted accordingly. In the state space, the transformed problem can be solved by using the dual variables of Hamiltonian mechanics, and the special solution equation can be obtained. With regard to the non-homogeneous boundary conditions of general engineering problems, Fourier expansion is used to transform them into algebraic sums. According to the special solution equation, the relationship between the direction eigenvalues and the angle coefficients of each order of the expansion term is found. Then the analytical solution of the non-homogeneous problem is obtained by superposing the special solutions of the expansion terms of each order. By comparing the calculation results of the boundary stress around the elliptical tunnel, it can be seen that the results are completely consistent with the finite element calculation results, which verifies the correctness and reliability of the method in this paper. This paper analyzes the influence of internal pressure, lateral pressure coefficient and elliptical shape coefficient on the circumferential stress around the elliptical hole, and obtains the following conclusions: increasing the internal pressure of the elliptical hole can effectively reduce the circumferential compressive stress at the hole edge; when the lateral pressure coefficient approaches 1, the circumferential stress distribution around the elliptical hole tends to be uniform; the minimum value of the circumferential stress around the elliptical hole is independent of the shape coefficient, while the maximum value is closely related to the shape coefficient. The research results can not only provide specific theoretical guidance for the construction and construction of elliptical tunnel, but also expand the application scope of the symplectic elasticity method.

Behaviors of Wall and Ground due to T-shaped Excavation

Xiaodong Zhao,Guoqing Zhou,Laijun Qiao,Yangguang Chen 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

Extensive monitoring was performed on a T-shaped site with a length of 280 m, a width of 16 m, and a maximal depth of 20.4 m. The braced excavation was performed under retaining comprised of cast-in-situ bored piles and jet grouting piles. The field databased wall performance and its influences to ground were assessed by detailed comparisons with that in other excavations. It is showed that the wall deflections, ground movements and bracing forces all exhibited a typical camelback-shaped characteristic along the length direction, and a maximum 100% reduction of which was observed due to the jet grouting. The rebar near sections with varied excavation depths was in a tension state both on the excavation and the retained sides due to the twodimensional unbalanced force, and the corresponding bracing force was small. The maximum wall deflection δhm decreased asthe partitioning excavation moved horizontally, and it was less than 0.04% of the final horizontal excavation length Le. The normalized Fσmax approximately approached to be identical with the normalized Fbmax, while most of the occurring depths for Fσmax were greater than that for Fbmax.