Localized Surface Plasmon Resonance Properties of Concentric Dual-Ring Nanodisk

Haiwei Mu,Jianxin Wang,Qiang Liu,Wei Liu,Xianli Li,Jingwei Lv,Chao Liu,Famei Wang,Tao Sun,Paul K. Chu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.6

The extinction spectral properties based on localized surface plasmon resonance (LSPR) of the concentric dual-ring nanodisk (CDRN) structure are investigated by discrete dipole approximation (DDA) and plasmon hybridization theory. The CDRN nanostructure shows flexible tunable multipole resonances in the near-infrared regime and the coupled resonance wavelengths depend on the structural parameters of the nanostructure, which has great potential in multichannel LSPR-based bio-sensing applications.

The loss coefficient for fluctuating flow through a dominant opening in a building

Haiwei Xu,Shice Yu,Wenjuan Lou 한국풍공학회 2017 Wind and Structures, An International Journal (WAS Vol.24 No.1

Wind-induced fluctuating internal pressures in a building with a dominant opening can be described by a second-order non-linear differential equation. However, the accuracy and efficiency of the governing equation in predicting internal pressure fluctuations depend upon two ill-defined parameters: inertial coefficient CI and loss coefficient CL, since CI determines the un-damped oscillation frequency of an air slug at the opening, while CL controls the decay ratio of the fluctuating internal pressure. This study particularly focused on the value of loss coefficient and its influence factors including: opening configuration and location, internal volumes, as well as wind speed and approaching flow turbulence. A simplified formula was presented to predict loss coefficient, therefore an approximate relationship between the standard deviation of internal and external pressures can be estimated using Vickery\'s approach. The study shows that the loss coefficient governs the peak response of the internal pressure spectrum which, in turn, will directly influence the standard deviation of the fluctuating internal pressure. The approaching flow characteristic and opening location have a remarkable effect on the parameter CL.

The inertial coefficient for fluctuating flow through a dominant opening in a building

Haiwei Xu,Shice Yu,Wenjuan Lou 한국풍공학회 2014 한국풍공학회지 Vol.18 No.1

For a building with a dominant windward wall opening, the wind-induced internal pressureresponse can be described by a second-order non-linear differential equation. However, there are twoill-defined parameters in the governing equation: the inertial coefficient CI and the loss coefficient CL. Lack of knowledge of these two parameters restricts the practical use of the governing equation. This studywas primarily focused on finding an accurate reference value for CI, and the paper presents a systematicinvestigation of the factors influencing the inertial coefficient for a wind-tunnel model building including:opening configuration and location, wind speed and direction, approaching flow turbulence, the modelmaterial, and the installation method. A numerical model was used to simulate the volume deformationunder internal pressure, and to predict the bulk modulus of an experimental model. In considering thestructural flexibility, an alternative approach was proposed to ensure accurate internal volume distortions, sothat similarity of internal pressure responses between model-scale and full-scale building was maintained. The research showed 0.8 to be a reasonable standard value for the inertial coefficient.

“Load Balance” Control for a Humanoid Musculoskeletal Arm in Table Tennis Movement

Haiwei Dong,Nadia Figueroa,Abdulmotaleb El Saddik 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.4

The aim of this paper is to propose a muscle control method for a humanoid musculoskeletal arm that mimics human muscle coordination from an engineering viewpoint. As muscle control is posed as a redundancy problem, the resulting muscle force corresponds to different desired control criteria (e.g., minimizing the total metabolic energy, minimizing muscle activity). In this research, the criterion we choose is “load balance”, which is essential for reducing actuator demands on systems subject to repetitive and demanding tasks. In order to achieve a balanced force distribution throughout the muscles, we obtain a minimum-load muscle force by considering the acceleration contribution in both muscle and joint space. The orthogonal space of the minimum-load muscle force solution is designed to place the muscle force close to the midpoint of the muscle force limits. The proposed method is tested by tracking a table tennis movement of a real human subject. The results not only provide an explanation on the concepts of “minimum-load” and “balance-load”, but also show that the proposed method has advantageous properties such as computational efficiency and stability.

Strain Rate Dependence in the Nanoindentation-Induced Deformation of Mg-Al Intermetallic Compounds Produced by Packed Powder Diffusion Coating

Haiwei Chang,Mingyuan Lu,Mingxing Zhang,Andrej Atrens,Han Huang 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.5

Nanoindentation was performed on τ-Mg32(Al, Zn)49 and -Mg17Al12 intermetallic coatings and on a AZ91E Mg alloy substrate using loading rates of 0.03 to 30 mNs-1. Pop-in phenomenon was observed during loading in the two intermetallic coatings and in the substrate. Both the magnitude of the pop-ins and the time interval between two consecutive pop-ins increased with increasing loads. The phenomenon was attributed to plastic instability, which is known as the Portevin-Le Châtelier effect. The morphologies of the indent impressions at different strain rates on the τ phase, the  phase and the substrate were also investigated using atomic force microscopy. Pile-up occurred in the τ and  phases and was found independent of the strain rate; no obvious pile-up occurred on the AZ91E substrate. The AZ91E substrate exhibited creep rates greater than those of the intermetallic phases, and all of the creep rates increased with the loading rate.

A Three-way Handshaking Access Mechanism for Point to Multipoint In-band Full-duplex Wireless Networks

( Haiwei Zuo ),( Yanjing Sun ),( Changlin Lin ),( Song Li ),( Hongli Xu ),( Zefu Tan ),( Yanfen Wang ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.7

In-band Full-duplex (IBFD) wireless communication allows improved throughput for wireless networks. The current Half-duplex (HD) medium access mechanism Request to Send/Clear to Send (RTS/CTS) has been directly applied to IBFD wireless networks. However, this is only able to support a symmetric dual link, and does not provide the full advantages of IBFD. To increase network throughput in a superior way to the HD mechanism, a novel three-way handshaking access mechanism RTS/SRTS (Second Request to Send)/CTS is proposed for point to multipoint (PMP) IBFD wireless networks, which can support both symmetric dual link and asymmetric dual link communication. In this approach, IBFD wireless communication only requires one channel access for two-way simultaneous packet transmissions. We first describe the RTS/SRTS/CTS mechanism and the symmetric/asymmetric dual link transmission procedure and then provide a theoretical analysis of network throughput and delay using a Markov model. Using simulations, we demonstrate that the RTS/SRTS/CTS access mechanism shows improved performance relative to that of the RTS/CTS HD access mechanism.

A Medium Access Control Mechanism for Distributed In-band Full-Duplex Wireless Networks

( Haiwei Zuo ),( Yanjing Sun ),( Song Li ),( Qiang Ni ),( Xiaolin Wang ),( Xiaoguang Zhang ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.11

In-band full-duplex (IBFD) wireless communication supports symmetric dual transmission between two nodes and asymmetric dual transmission among three nodes, which allows improved throughput for distributed IBFD wireless networks. However, inter-node interference (INI) can affect desired packet reception in the downlink of three-node topology. The current Half-duplex (HD) medium access control (MAC) mechanism RTS/CTS is unable to establish an asymmetric dual link and consequently to suppress INI. In this paper, we propose a medium access control mechanism for use in distributed IBFD wireless networks, FD-DMAC (Full-Duplex Distributed MAC). In this approach, communication nodes only require single channel access to establish symmetric or asymmetric dual link, and we fully consider the two transmission modes of asymmetric dual link. Through FD-DMAC medium access, the neighbors of communication nodes can clearly know network transmission status, which will provide other opportunities of asymmetric IBFD dual communication and solve hidden node problem. Additionally, we leverage FD-DMAC to transmit received power information. This approach can assist communication nodes to adjust transmit powers and suppress INI. Finally, we give a theoretical analysis of network performance using a discrete-time Markov model. The numerical results show that FD-DMAC achieves a significant improvement over RTS/CTS in terms of throughput and delay.

Parallel Deblocking Filter Based on Modified Order of Accessing the Coding Tree Units for HEVC on Multicore Processor

( Haiwei Lei ),( Wenyi Liu ),( Anhong Wang ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.3

The deblocking filter (DF) reduces blocking artifacts in encoded video sequences, and thereby significantly improves the subjective and objective quality of videos. Statistics show that the DF accounts for 5-18% of the total decoding time in high-efficiency video coding. Therefore, speeding up the DF will improve codec performance, especially for the decoder. In view of the rapid development of multicore technology, we propose a parallel DF scheme based on a modified order of accessing the coding tree units (CTUs) by analyzing the data dependencies between adjacent CTUs. This enables the DF to run in parallel, providing accelerated performance and more flexibility in the degree of parallelism, as well as finer parallel granularity. We additionally solve the problems of variable privatization and thread synchronization in the parallelization of the DF. Finally, the DF module is parallelized based on the HM16.1 reference software using OpenMP technology. The acceleration performance is experimentally tested under various numbers of cores, and the results show that the proposed scheme is very effective at speeding up the DF.

The loss coefficient for fluctuating flow through a dominant opening in a building

Xu, Haiwei,Yu, Shice,Lou, Wenjuan Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.24 No.1

Wind-induced fluctuating internal pressures in a building with a dominant opening can be described by a second-order non-linear differential equation. However, the accuracy and efficiency of the governing equation in predicting internal pressure fluctuations depend upon two ill-defined parameters: inertial coefficient $C_I$ and loss coefficient $C_L$, since $C_I$ determines the un-damped oscillation frequency of an air slug at the opening, while $C_L$ controls the decay ratio of the fluctuating internal pressure. This study particularly focused on the value of loss coefficient and its influence factors including: opening configuration and location, internal volumes, as well as wind speed and approaching flow turbulence. A simplified formula was presented to predict loss coefficient, therefore an approximate relationship between the standard deviation of internal and external pressures can be estimated using Vickery's approach. The study shows that the loss coefficient governs the peak response of the internal pressure spectrum which, in turn, will directly influence the standard deviation of the fluctuating internal pressure. The approaching flow characteristic and opening location have a remarkable effect on the parameter $C_L$.

The inertial coefficient for fluctuating flow through a dominant opening in a building

Xu, Haiwei,Yu, Shice,Lou, Wenjuan Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.18 No.1

For a building with a dominant windward wall opening, the wind-induced internal pressure response can be described by a second-order non-linear differential equation. However, there are two ill-defined parameters in the governing equation: the inertial coefficient $C_I$ and the loss coefficient $C_L$. Lack of knowledge of these two parameters restricts the practical use of the governing equation. This study was primarily focused on finding an accurate reference value for $C_I$, and the paper presents a systematic investigation of the factors influencing the inertial coefficient for a wind-tunnel model building including: opening configuration and location, wind speed and direction, approaching flow turbulence, the model material, and the installation method. A numerical model was used to simulate the volume deformation under internal pressure, and to predict the bulk modulus of an experimental model. In considering the structural flexibility, an alternative approach was proposed to ensure accurate internal volume distortions, so that similarity of internal pressure responses between model-scale and full-scale building was maintained. The research showed 0.8 to be a reasonable standard value for the inertial coefficient.