Review of the Preparation and Structures of Si Nanowires, Ge Quantum Dots and Their Composites

Xiaokang Weng,Jie Yang,Dongze Li,Rongfei Wang,Feng Qiu,Chong Wang,Yu Yang 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.4

Because the motion of charge carriers in nanowires and quantum dots is restricted within nanoscale in two and three dimensions, respectively, both nanowires and quantum dots exhibit many excellent optoelectronic properties. Particularly, with the advantage of being compatible with Si integrated circuits, Silicon nanowires (SiNWs) and germanium quantum dots (GeQDs) have been extensively studied in the past few decades. In order to explore novel physical properties, the integration of SiNWs and GeQDs has attracted great attention recently. In this paper, recent researches on the preparation methods and structures of SiNWs, GeQDs and their composites are reviewed, respectively. The synthesis of SiNWs with random distribution and ordered arrays by using vapor–liquid–solid growth mechanism and metal-assisted chemical etching technique is firstly summarized. Some special structures of SiNWs are also discussed. Furthermore, the development of some novel structures of GeQDs for further improving their optical properties is reviewed. Finally, the growth mechanism and structure evolution of SiNWs/GeQDs composites are illustrated from the view of theory and experiment. The strain inGe shell layers and SiNWs, the relationship between Ge growth mode and SiNW diameter, and the distribution of GeQDs on the radial and axial directions of SiNWs are discussed in detail. The research about the growth of SiNWs/GeQDs composite structures is in its early stage, so there are many questions that need to be resolved in future.

Effect of Nanoparticle Size on the Interface Bond Energy in KTa0.5Nb0.5O3 / Polyimide Composites

Chuntian Chen,Juan Wang,Wenlong Yang,Xiaokang Li,Jingyun Zhang 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.6

The effects of particle size on the interface bond energy in KTa0.5Nb0.5O3/ polyimide composites were investigated using the molecular dynamics method. The composites of polyimide and the KTa0.5Nb0.5O3 nanoparticles with different size (0.4 nm, 0.5 nm, 0.6 nm, 0.8 nm, 1.2 nm, and 1.4 nm) have been established and simulated using the Forcite program package of Materials Studio software. The calculated results show that the interface bond energy is 38~150 Kcal/mol, which indicate the Van der Waals force exist between the nanoparticle and polyimide matrix. The interface bond energy of the smaller nanoparticle is greater than the lager nanaparticle due to the size effect. The introduction of the smaller nanoparticle could generate the stronger intermolecular bonding interaction between the nanoparticle and polyimide matrix.

Small Sample Face Recognition Algorithm based on Novel Siamese Network

( Jianming Zhang ),( Xiaokang Jin ),( Yukai Liu ),( Arun Kumar Sangaiah ),( Jin Wang ) 한국정보처리학회 2018 Journal of information processing systems Vol.14 No.6

In face recognition, sometimes the number of available training samples for single category is insufficient. Therefore, the performances of models trained by convolutional neural network are not ideal. The small sample face recognition algorithm based on novel Siamese network is proposed in this paper, which doesn’t need rich samples for training. The algorithm designs and realizes a new Siamese network model, SiameseFace1, which uses pairs of face images as inputs and maps them to target space so that the L2 norm distance in target space can represent the semantic distance in input space. The mapping is represented by the neural network in supervised learning. Moreover, a more lightweight Siamese network model, SiameseFace2, is designed to reduce the network parameters without losing accuracy. We also present a new method to generate training data and expand the number of training samples for single category in AR and labeled faces in the wild (LFW) datasets, which improves the recognition accuracy of the models. Four loss functions are adopted to carry out experiments on AR and LFW datasets. The results show that the contrastive loss function combined with new Siamese network model in this paper can effectively improve the accuracy of face recognition.

Water Disaster Susceptible Areas in Loess Multi-arch Tunnel Construction under the Lateral Recharge Condition

Zhengjun Mao,Xiaokang Wang,Ning An,Xiaojun Li,Rongyu Wei 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.10

The water disaster susceptible areas in loess multi-arch tunnels were studied. Taking Lishi multi-arch tunnel as an example, the tunnel is located in Luliang City, Shanxi Province, China, with a total length of 180 m. It is the first loess multi-arch tunnel in China. The groundwater recharge in the tunnel site is dominated by rainfall, and the surrounding rock of the tunnel is unsaturated. Considering the lateral recharge of groundwater, in this study, midas geo-technical analysis system was adopted to simulate the construction process of a middle pilot tunnel–bilateral pilot tunnel of a loess multi-arch tunnel, accounting for fluid-solid coupling. The variations in the surrounding rock stress and seepage fields of loess multi-arch tunnels during the construction process were studied. A water disaster susceptible area in a loess multi-arch tunnel was confirmed based on the catastrophe area of the displacement, stress, gross head, pore water pressure, and seepage velocity. The result show that the water disaster susceptible areas for loess multi-arch tunnels during the construction period mainly concentrated in the mid-partition, arch springs of the left and right tunnels, and the tunnel face.

Betulin induces reactive oxygen species-dependent apoptosis in human gastric cancer SGC7901 cells

Yang Li,Xiaokang Liu,Dan Jiang,Yingjia Lin,Yushi Wang,Qing Li,Linlin Liu,Ying-Hua Jin 대한약학회 2016 Archives of Pharmacal Research Vol.39 No.9

Betulin, an abundant natural compound, significantly inhibited the cell viability of advanced human gastric cancer SGC7901 cells. Mechanism study demonstrated that betulin induced apoptosis through mitochondrial Bax and Bak accumulation-mediated intrinsic apoptosis pathway. Downregulation of the anti-apoptosis proteins Bcl-2 and XIAP was involved during betulin-induced cell apoptosis. Reactive oxygen species (ROS) was generated in cells after betulin treatment in a time- and dose-dependent manner. Addition of antioxidant N-acetyl-L-cysteine (NAC) significantly attenuated betulin-induced ROS generation as well as Bcl-2 and XIAP downregulation. The mitochondrial accumulation of Bax and Bak, as well as caspase activity, was also remarkably inhibited by NAC treatment, indicating that ROS are important signaling intermediates that lead to betulin-induced apoptosis by modulating multiple apoptosis-regulating proteins in SGC7901 cells.

A Novel Fast Open-loop Phase Locking Scheme Based on Synchronous Reference Frame for Three-phase Non-ideal Power Grids

Xiong, Liansong,Zhuo, Fang,Wang, Feng,Liu, Xiaokang,Zhu, Minghua,Yi, Hao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.

Characteristic of SiC Slurry in Ultra Precision Lapping of Sapphire Substrates

Tao Yin,ZhiDa Wang,Toshiro Doi,Syuhei Kurokawa,Zhe Tan,XiaoKang Ding,Huan Lin 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6

A method is proposed in this paper to prepare a SiC slurry with SiC particles selected by an ultrasonic-assisted elutriation method to reduce substrate surface damage caused by abrasive particles during lapping. Sapphire substrate lapping experiments were carried out using the prepared SiC slurry, and the lapping performance of the slurry was analyzed. The experimental results show that the SiC particle size is a factor that directly affects the material removal rate and surface roughness Ra, of sapphire substrates. When a SiC slurry with a particle size of 630 nm was used, the material removal rate was 508 nm/h, and the surface roughness Ra was 1.9 nm; increasing the slurry concentration and the platen rotating speed can improve the material removal rate. In addition, the agglomeration of SiC particles in the slurry depends on the pH of the slurry. Efficient precision lapping of sapphire substrates can be achieved by selecting appropriately sized SiC particles and by adjusting the slurry pH to control the agglomeration and dispersion of SiC particlesto further reduce the scratches on the substrate surface during the lapping process.

Small Sample Face Recognition Algorithm Based on Novel Siamese Network

Zhang, Jianming,Jin, Xiaokang,Liu, Yukai,Sangaiah, Arun Kumar,Wang, Jin Korea Information Processing Society 2018 Journal of information processing systems Vol.14 No.6

In face recognition, sometimes the number of available training samples for single category is insufficient. Therefore, the performances of models trained by convolutional neural network are not ideal. The small sample face recognition algorithm based on novel Siamese network is proposed in this paper, which doesn't need rich samples for training. The algorithm designs and realizes a new Siamese network model, SiameseFacel, which uses pairs of face images as inputs and maps them to target space so that the $L_2$ norm distance in target space can represent the semantic distance in input space. The mapping is represented by the neural network in supervised learning. Moreover, a more lightweight Siamese network model, SiameseFace2, is designed to reduce the network parameters without losing accuracy. We also present a new method to generate training data and expand the number of training samples for single category in AR and labeled faces in the wild (LFW) datasets, which improves the recognition accuracy of the models. Four loss functions are adopted to carry out experiments on AR and LFW datasets. The results show that the contrastive loss function combined with new Siamese network model in this paper can effectively improve the accuracy of face recognition.

A Quantitative Evaluation and Comparison of Harmonic Elimination Algorithms Based on Moving Average Filter and Delayed Signal Cancellation in Phase Synchronization Applications

Xiong, Liansong,Zhuo, Fang,Wang, Feng,Liu, Xiaokang,Zhu, Minghua,Yi, Hao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2

The harmonic components of grid voltage result in oscillations of the calculated phase obtained via phase synchronization. This affects the security and stability of grid-connected converters. Moving average filter, delayed signal cancellation and their related harmonic elimination algorithms are major methods for such issues. However, all of the existing methods have their limitations in dealing with multiple harmonics issues. Furthermore, few studies have focused on a comparison and evaluation of these algorithms to achieve optimal algorithm selections in specific applications. In this paper, these algorithms are quantitatively analyzed based on the derived mathematical models. Moreover, an enhanced moving average filter and enhanced delayed signal cancellation algorithms, which are applicable for eliminating a group of selective harmonics with only one calculation block, are proposed. On this basis, both a comprehensive comparison and a quantitative evaluation of all of the aforementioned algorithms are made from several aspects, including response speed, required data storage size, sensitivity to sampling frequency, and elimination of random noise and harmonics. With the conclusions derived in this paper, better overall performance in terms of harmonic elimination can be achieved. In addition, experimental results under different conditions demonstrate the validity of this study.

A Novel Fast Open-loop Phase Locking Scheme Based on Synchronous Reference Frame for Three-phase Non-ideal Power Grids

Liansong Xiong,Fang Zhuo,Feng Wang,Xiaokang Liu,Minghua Zhu,Hao Yi 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

Rapid and accurate phase synchronization is critical for the reliable control of grid-tied inverters. However, the commonly used software phase-locked loop methods do not always satisfy the need for high-speed and accurate phase synchronization under severe grid imbalance conditions. To address this problem, this study develops a novel open-loop phase locking scheme based on a synchronous reference frame. The proposed scheme is characterized by remarkable response speed, high accuracy, and easy implementation. It comprises three functional cascaded blocks: fast orthogonal signal generation block, fast fundamental-frequency positive sequence component construction block, and fast phase calculation block. The developed virtual orthogonal signal generation method in the first block, which is characterized by noise immunity and high accuracy, can effectively avoid approximation errors and noise amplification in a wide range of sampling frequencies. In the second block, which is the foundation for achieving fast phase synchronization within 3 ms, the fundamental-frequency positive sequence components of unsymmetrical grid voltages can be achieved with the developed orthogonal signal construction strategy and the symmetrical component method. The real-time grid phase can be consequently obtained in the third block, which is free from self-tuning closed-loop control and thus improves the dynamic performance of the proposed scheme. The proposed scheme is adaptive to severe unsymmetrical grid voltages with sudden changes in magnitude, phase, and/or frequency. Moreover, this scheme is able to eliminate phase errors induced by harmonics and random noise. The validity and utility of the proposed scheme are verified by the experimental results.