Low-complexity distributed multiple description coding for wireless video sensor networks

Liu, Wenhui,Vijayanagar, Krishna, R.,Kim, Joohee IET 2013 IET Wireless Sensor Systems Vol.3 No.3

<P>Quality-of-service-guaranteed video communication in wireless video sensor networks (WVSNs) is extremely challenging because of the unique constraints of WVSN (e.g. limited resources of sensors and high error rates in wireless sensor networks) and the characteristics of video traffic (e.g. huge data rate and tight delay bounds). Distributed video coding (DVC) has emerged as a new video coding paradigm for video applications with resource-limited encoders. However, current DVC architectures still have several technical limitations that prevent their widespread use in real-world applications. A lowcomplexity distributed multiple description coding method that combines the principles of multiple description coding and DVC has been proposed to further improve the error resilience of DVC, while maintaining low encoder complexity and good rate-distortion performance in WVSN. Simulation results show that the proposed method is robust against transmission errors, while maintaining low encoder complexity and low system latency for resource-limited applications in WVSNs.</P>

Effect of Temperature and Strain Rate on Deformation Mode and Crack Behavior of 7B52 Laminated Aluminum Alloy Under Impact Loading

Wenhui Liu,Ping Cao,Chenbing Zhao,Yufeng Song,Changping Tang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11

The dynamic mechanical behaviors of 7B52 laminated aluminum alloy under different impact deformation conditions wereinvestigated using split Hopkinson pressure bar, optical microscopy, electron backscatter diffraction and transmission electronmicroscopy. The results show that the 7B52 laminated aluminum alloy displays positive strain rate sensitivity and negativetemperature sensitivity. Cracks are formed firstly at the interface between the 7A62 hard layer and the 7A01 middle layerunder a low strain rate of 2200 s−1. When the strain rate increases to 3500 s−1, the deformation shear band is firstly formed inthe 7A52 soft layer. The deformation shear band transformed to the transition shear band with the increase of strain rate, andthen crack initiated. Adiabatic shear bands and cracks are formed in both of the hard and soft layers when samples impactedat a high strain rate (5500 s−1). Most of the cracks and adiabatic shear bands are unable to penetrate the middle layer dueto the good toughness of the 7A01 alloy. The deformation of each layer of 7B52 laminated aluminum alloy becomes moreuniform when the temperature increases, which was attributed to the reduction of difference in strength among the threelayers and the coordinating effect of grain boundary on deformation.

Side Information Generation for Distributed Video Coding Using Spatiotemporal Joint Bilinear Upsampling

Liu, Wenhui,Vijayanagar, Krishna Rao,Kim, Joohee Taylor & Francis 2014 INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWOR Vol.2014 No.-

Study on the transient flow induced by the windbreak transition regions in a railway subject to crosswinds

Zheng-Wei Chen,Syeda Anam Hashmi,Tanghong Liu,Wenhui Li,Zhuang Sun,Dongrun Liu,Hassan Hemida,Hong-Kang Liu 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.5

Due to the complex terrain around high-speed railways, the windbreaks were established along different landforms, resulting in irregular windbreak transition regions between different subgrade infrastructures (flat ground, cutting, embankment, etc). In this paper, the effect of a windbreak transition on the wind flow around railways subjected to crosswinds was studied. Wind tunnel testing was conducted to study the wind speed change around a windbreak transition on flat ground with a uniform wind speed inflow, and the collected data were used to validate a numerical simulation based on a detached eddy simulation method. The validated numerical method was then used to investigate the effect of the windbreak transition from the flat ground to cutting (the “cutting” is a railway subgrade type formed by digging down from the original ground) for three different wind incidence angles of 90º, 75º, and 105º. The deterioration mechanism of the flow fields and the reasons behind the occurrence of the peak wind velocities were explained in detail. The results showed that for the windbreak transition on flat ground, the impact was small. For the transition from the flat ground to the cutting, the influence was relatively large. The significant increase in the wind speeds was due to the right-angle structure of the windbreak transition, which resulted in sudden changes of the wind velocity as well as the direction. In addition, the height mismatch in the transition region worsened the protective effect of a typical windbreak.

Aerodynamic analysis on the step types of a railway tunnel with non-uniform cross-section

Wenhui Li,Tanghong Liu,Xiaoshuai Huo,Zijian Guo,Yutao Xia 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.4

The pressure-mitigating effects of a high-speed train passing through a tunnel with a partially reduced cross-section are investigated via the numerical approach. A compressible, three-dimensional RNG k-ε turbulence model and a hybrid mesh strategy are adopted to reproduce that event, which is validated by the moving model test. Three step-like tunnel forms and two additional transitions at the tunnel junction are proposed and their aerodynamic performance is compared and scrutinized with a constant cross-sectional tunnel as the benchmark. The results show that the tunnel step is unrelated to the pressure mitigation effects since the case of a double-step tunnel has no advantage in comparison to a single-step tunnel, but the excavated volume is an essential matter. The pressure peaks are reduced at different levels along with the increase of the excavated earth volume and the peaks are either fitted with power or logarithmic function relationships. In addition, the Arc and Oblique-transitions have very limited gaps, and their pressure curves are identical to each other, whereas the Rec-transition leads to relatively lower pressure peaks in CP max, CP min, and ΔCP, with 5.2%, 4.0%, and 4.1% relieved compared with Oblique-transition. This study could provide guidance for the design of the novel railway tunnel.

Multi-Target Adaptive On-line Tracking based on WIHM

Wenhui Li,Hongyin Ni,Ying Wang,Peixun Liu,Yuchao Zhou 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.1

Yaw effects on train aerodynamics on a double-track viaduct: A wind tunnel study

Wenhui Li,Tanghong Liu,Pedro Martinez-Vazquez,Zhengwei Chen,Xiaoshuai Huo,Zijian Guo,Yutao Xia 한국풍공학회 2021 Wind and Structures, An International Journal (WAS Vol.33 No.3

The aerodynamic performance of a scaled high-speed train model mounted on a double-track viaduct was studied through a wind tunnel test. The pressure distribution of different loops and the centerline on the streamlined nose region, as well as the aerodynamic load coefficients of the leading car were explored under yaw effects ranging from β=-30° to β=30°. Results showed that Reynolds effects became independent when the wind speed surpassed 40 m/s, the corresponding Re of which equals 6.51 × 105 . The pressures recorded along the centerline of train nose for the upstream scenario, was more sensitive to the yaw effects as the largest pressure difference gradually broadened against yaw angles. In addition, the pressure coefficients along the centerline and symmetrical taps of the loops, approximately fit a quadratic relationship with respect to yaw angles. The presence of the tracks and viaduct decks somehow mitigated the intensity of the airflow at downstream side. The experimental test also revealed that, the upstream configuration provided higher mean side force, yawing, and rolling moments up to β=20° whereas over that angle the force and moments exhibited the opposite performance.

SPATIAL BEHAVIOR OF SOLUTION FOR THE STOKES FLOW EQUATION

Liu, Yan,Liao, Wenhui,Lin, Changhao Korean Mathematical Society 2011 대한수학회보 Vol.48 No.2

In this paper, the equation of the transient Stokes flow of an incompressible viscous fluid is studied. Growth and decay estimates are established associating some appropriate cross sectional line and area integral measures. The method of the proof is based on a first-order differential inequality leading to an alternative of Phragm$\'{e}$n-Lindell$\"{o} $f type in terms of an area measure of the amplitude in question. In the case of decay, we also indicate how to bound the total energy.

Spatial behavior of solution for the Stokes flow equation

Yan Liu,Wenhui Liao,Changhao Lin 대한수학회 2011 대한수학회보 Vol.48 No.2

In this paper, the equation of the transient Stokes flow of an incompressible viscous fluid is studied. Growth and decay estimates are established associating some appropriate cross sectional line and area integral measures. The method of the proof is based on a first-order differential inequality leading to an alternative of Phragm[문자]n-Lindel[문자]f type in terms of an area measure of the amplitude in question. In the case of decay, we also indicate how to bound the total energy.

Experimental study on the influence of Reynolds number and roll angle on train aerodynamics

Zhixiang Huang,Wenhui Li,Tanghong Liu,Li Chen 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.2

When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ=3.2 m based on a 1/20th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37×106 to Re = 1.45×106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ=0° to γ=4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ=0° to γ=4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.