Experimental investigation of Reynolds number effects on 2D rectangular prisms with various side ratios and rounded corners

Xinrong Wang,Ming Gu 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.21 No.2

Experiments on two-dimensional rectangular prisms with various side ratios (B/D=2, 3, and 4, where B is the along-wind dimension, and D is the across-wind dimension) and rounded corners (R/D=0%, 5%, 10%, and 15%, where R is the corner radius) are reported in this study. The tests were conducted in low-turbulence uniform flow to measure the wind pressures on the surfaces of 12 models for Reynolds numbers ranging from 1.1×105 to 6.8×105. The aerodynamic force coefficients were obtained by integrating the wind pressure coefficients around the model surface. Experimental results of wind pressure distributions, aerodynamic force coefficients, and Strouhal numbers are presented for the 12 models. The mechanisms of the Reynolds number effects are revealed by analyzing the variations of wind pressure distributions. The sensitivity of aerodynamic behavior to the Reynolds number increases with increasing side ratio or rounded corner ratio for rectangular prisms. In addition, the variations of the mean pressure distributions and the pressure correlations on the side surfaces of rectangular prisms with the rounded corner ratio are analyzed at Re=3.4×105.

Experimental study on Re number effects on aerodynamic characteristics of 2D square prisms with corner modifications

Xinrong Wang,Ming Gu 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.22 No.5

Simultaneous pressure measurements on 2D square prisms with various corner modifications were performed in uniform flow with low turbulence level, and the testing Reynolds numbers varied from 1.0 x105 to 4.8x105. Experimental models were a square prism, three chamfered-corner square prisms (B/D=5%, 10%, and 15%, where B is the chamfered corner dimension and D is the cross-sectional dimension), and six rounded-corner square prisms (R/D =5%, 10%, 15%, 20%, 30%, and 40%, where R is the corner radius). Experimental results of drag coefficients, wind pressure distributions, power spectra of aerodynamic force coefficients, and Strouhal numbers are presented. Ten models are divided into various categories according to the variations of mean drag coefficients with Reynolds number. The mean drag coefficients of models with B/D < 15% and R/D < 15% are unaffected by the Reynolds number. On the contrary, the mean drag coefficients of models with R/D=20%, 30%, and 40% are obviously dependent on Reynolds number. Wind pressure distributions around each model are analyzed according to the categorized results.The influence mechanisms of corner modifications on the aerodynamic characteristics of the square prism are revealed from the perspective of flow around the model, which can be obtained by analyzing the local pressures acting on the model surface.

Experimental and numerical study on pre-peak cyclic shear mechanism of artificial rock joints

Xinrong Liu,Yongquan Liu,Yuming Lu,Miaomiao Kou 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.3

The pre-peak cyclic shear mechanism of two-order asperity degradation of rock joints in the direct shear tests with static constant normal loads (CNL) are investigated using experimental and numerical methods. The laboratory testing rock specimens contains the idealized and regular two-order triangular-shaped asperities, which represent the specific geometrical conditions of natural and irregular waviness and unevenness of rock joint surfaces, in the pre-peak cyclic shear tests. Three different shear failure patterns of two-order triangular-shaped rock joints can be found in the experiments at constant horizontal shear velocity and various static constant normal loads in the direct and pre-peak cyclic shear tests. The discrete element method is adopted to simulate the pre-peak shear failure behaviors of rock joints with two-order triangular-shaped asperities. The rock joint interfaces are simulated using a modified smooth joint model, where microscopic scale slip surfaces are applied at contacts between discrete particles in the upper and lower rock blocks. Comparing the discrete numerical results with the experimental results, the microscopic bond particle model parameters are calibrated. Effects of cyclic shear loading amplitude, static constant normal loads and initial waviness asperity angles on the pre-peak cyclic shear failure behaviors of triangular-shaped rock joints are also numerically investigated.

Application of transient elastography in nonalcoholic fatty liver disease

Xinrong Zhang,Grace Lai-Hung Wong,Vincent Wai-Sun Wong 대한간학회 2020 Clinical and Molecular Hepatology(대한간학회지) Vol.26 No.2

Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease worldwide. Although it has become one of the leading causes of cirrhosis and hepatocellular carcinoma in the Western world, the proportion of NAFLD patients developing these complications is rather small. Therefore, current guidelines recommend noninvasive tests for the initial assessment of NAFLD. Among the available non-invasive tests, transient elastography by FibroScan® (Echosens, Paris, France) is commonly used by hepatologists in Europe and Asia, and the machine has been introduced to the United States in 2013 with rapid adoption. Transient elastography measures liver stiffness and the controlled attenuation parameter simultaneously and can serve as a one-stop examination for both liver steatosis and fibrosis. Liver stiffness measurement also correlates with clinical outcomes and can be used to select patients for varices screening. Although obesity is a common reason for measurement failures, the development of the XL probe allows successful measurements in the majority of obese patients. This article reviews the performance and limitations of transient elastography in NAFLD and highlights its clinical applications. We also discuss the reliability criteria for transient elastography examination and factors associated with false-positive liver stiffness measurements.

Comparative Hot Workability Characteristics of an Al–Si/SiCp Aluminium Matrix Composite Hybrid Reinforced with Various TiB2 Additions

Xinrong Chen,Zhiming Xu,Dingfa Fu,Hui Zhang,Jie Teng,Fulin Jiang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6

Hot compression tests were conducted on Al–Si/SiCp + TiB2 hybrid aluminium matrix composites with various TiB2contentsat temperatures from 350 to 500 °C and strain rates from 0.001 to 1 s−1. The hot workability characteristics and deformationmechanisms were investigated by combining constitutive equations, processing maps and microstructural observationsthrough scanning electron microscopy and transmission electron microscopy measurements. The results showed that therewere small differences in the peak stresses when the contents of TiB2were 3% and 5%, while the peak stress increased whenthe content of TiB2reached 8%. The contents of TiB2had little influence on the activation energy but affected the processingmaps to a certain extent. The areas of the instability zones were observed to gradually increase with increased TiB2additions. The optimal deformation conditions of the studied materials migrated from a low temperature and high strain rate to a hightemperature and low strain rate with increasing TiB2content. In addition, the flow softening mechanism transformed fromdynamic recrystallization + dynamic recovery to dynamic recovery with increasing TiB2content.

Increasing Secrecy Capacity via Joint Design of Cooperative Beamforming and Jamming

( Xinrong Guan ),( Yueming Cai ),( Weiwei Yang ),( Yunpeng Cheng ),( Junquan Hu ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.4

In this paper, we propose a hybrid cooperative scheme to improve the secrecy rate for a cooperative network in presence of multiple relays. Each relay node transmits the mixed signal consisting of weighted source signal and intentional noise. The problem of power allocation, the joint design of beamforming and jamming weights are investigated, and an iterative scheme is proposed. It is demonstrated by the numerical results that the proposed hybrid scheme further improves secrecy rate, as compared to traditional cooperative schemes.

Numerical Analysis on the Mechanical Performance of Supporting Structures and Ground Settlement Characteristics in Construction Process of Subway Station Built by Pile-Beam-Arch Method

Xinrong Liu,Yongquan Liu,Zhongping Yang,Chunmei He 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5

Pile-Beam-Arch (PBA) method is an effective approach to control the surface settlement induced by excavation to construct the subway station, especially when the station is located in the urban area with dense buildings. Based on the numerical analysis model of practical engineering, the whole construction stages of the subway station built by PBA method are simulated in this paper. The mechanical performance of supporting structures (such as piles, beams, arches, secondary lining and backfill concrete) and surface settlement characteristics during construction are investigated. The results show that the pre-supporting system of piles, beams and arches is formed in the stage of soil excavation under main tunnel arch; Station hall plate and backfill concrete are two key structures to ensure the support stiffness of PBA supporting system. In addition, compared to the bottom-up method, the top-down method for the secondary lining construction can obviously reduce the internal force of supporting structures and the surface settlement. Combined with in-situ monitoring data, three increase stages of surface settlement and the corresponding settlement ratio are gained and the characteristic of surface settlement trough is also analysed. This study is helpful for further understanding the support mechanism of PBA method and the increase law of the ground settlement during the construction of the station built by PBA method.

Experimental study on Re number effects on aerodynamic characteristics of 2D square prisms with corner modifications

Wang, Xinrong,Gu, Ming Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.22 No.5

Simultaneous pressure measurements on 2D square prisms with various corner modifications were performed in uniform flow with low turbulence level, and the testing Reynolds numbers varied from $1.0{\times}10^5$ to $4.8{\times}10^5$. Experimental models were a square prism, three chamfered-corner square prisms (B/D=5%, 10%, and 15%, where B is the chamfered corner dimension and D is the cross-sectional dimension), and six rounded-corner square prisms (R/D =5%, 10%, 15%, 20%, 30%, and 40%, where R is the corner radius). Experimental results of drag coefficients, wind pressure distributions, power spectra of aerodynamic force coefficients, and Strouhal numbers are presented. Ten models are divided into various categories according to the variations of mean drag coefficients with Reynolds number. The mean drag coefficients of models with $B/D{\leq}15%$ and $R/D{\leq}15%$ are unaffected by the Reynolds number. On the contrary, the mean drag coefficients of models with R/D=20%, 30%, and 40% are obviously dependent on Reynolds number. Wind pressure distributions around each model are analyzed according to the categorized results.The influence mechanisms of corner modifications on the aerodynamic characteristics of the square prism are revealed from the perspective of flow around the model, which can be obtained by analyzing the local pressures acting on the model surface.

The topographic effect of ground motion based on Spectral Element Method

Liu, Xinrong,Jin, Meihai,Li, Dongliang,Hu, Yuanxin,Song, Jianxue Techno-Press 2017 Geomechanics & engineering Vol.13 No.3

A Spectral Element Method for 3D seismic wave propagation simulation is derived based on the three-dimensional fluctuating elastic dynamic equation. Considering the 3D real terrain and the attenuation characteristics of the medium, the topographic effect of Wenchuan earthquake is simulated by using the Spectral Element Method (SEM) algorithm and the ASTER DEM model. Results show that the high PGA (peak ground acceleration) region was distributed along the peak and the slope side away from the epicenter in the epicenter area. The overall distribution direction of high PGA and high PGV (peak ground velocity) region is parallel to the direction of the seismogenic fault. In the epicenter of the earthquake, the ground motion is to some extent amplified under the influence of the terrain. The amplification effect of the terrain on PGA is complicated. It does not exactly lead to amplification of PGA at the ridge and the summit or attenuation of PGA in the valley.

Electrorheological properties of poly[N,N0-(2-amino-5-carboxybutyl-1,3- phenylenedimethylene)-2,20-diamino-4,40-bithiazole]

Song Xinrong,Song Kunyang,Ding Sha,Chen Yaping,Lin Yuanbin 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.2

Poly[N,N0-(2-amino-5-carboxybutyl-1,3-phenylenedimethylene)-2,20-diamino-4,40-bithiazole] was synthesized and characterized with Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Anhydrous electrorheological (ER) fluids were prepared using the polymer particles as disperse phase and bromodiphenylmethane as a disperse medium. Rheological measurements were carried out via a rotational rheometer to investigate the effects of electric field strength and the polymer particle content on the ER properties. Results indicate that suspensions of the polymer particles containing amino and carboxybutyl groups in bromodiphenylmethane exhibit a substantial ER effect.