Simulation Research of Multi-morphological Microstructures Chaining Mechanism of Nano-magnetic Fluid

Lei Yang,Yibiao Chen,Yao Yao,Shuaikang Wei,Yuhui Xie,Decai Li,Jun Yu,Hongming Zhou,Yiping Feng 한국자기학회 2024 Journal of Magnetics Vol.29 No.1

For nano-magnetic fluid(NMF), the magnetic nano-particle(MNP) kinematic behavior in a magnetic field and the chain-like microstructure evolution are important to study the NMF properties at the microscopic level. However, the chain structure formation mechanism and the effects of multiple environmental factors on microstructural morphology remain unclear. In this paper, the interaction of a two-particle system, chain structure formation process, microstructure evolution and response time simulation of NMF is investigated by the discrete element simulation method. The results show that the magnetic dipole and repulsive forces dominate the chain structure formation and evolution under a uniform magnetic field. MNPs assemble into chain-like structures and various complex structures along the magnetic f ield direction. The volume fraction, magnetization intensity and particle size significantly affect the microstructure and the response time. The above study can obtain the specific morphology of the microstructure at different working conditions and broaden the application of NMF in practical engineering.

냉동기에 의해 냉각되는 복사열차폐 최적설계

최연석(Y.S.Choi),Hongming Tang,김동락(D.L.Kim),양형석(H.S.Yang),이병섭(B.S.Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11

The design of thermal radiation shield cooled by a cryocooler is presented. This study is motivated mainly by our recent development of prototype superconducting magnet system for the Cyclotron K120. The superconducting magnet system is composed of the magnet cryostat, transfer line and supply cryostat. In order to minimize thermal radiation load, the superconducting coil form in the magnet cryostat is enclosed by the thermal radiation shield which is thermally connected to the first-stage cold head of a two-stage cryocooler in the supply cryostat. Since the supply cryostat is located far from the magnet cryostat large temperature gradient along the thermal shield is unavoidable. In this paper, the thermal radiation shield is optimized to minimize temperature gradient with taking into account the cryogenic load, system structure and electrical load. The effect of heat source from thermal conduction through mechanical supports on the temperature distribution of thermal radiation shield is also discussed.

Progress on the Development of Superconducting Magnet System for Cyclotron K120

Yeon Suk Choi,Dong Lak Kim,Hongming Tang,Hyung Suk Yang,Joon Sun Kang,Yu Seok Kim IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3

<P>The Korea Basic Science Institute (KBSI) has targeted a 3.1 T superconducting magnet system to be used in a K120 superconducting cyclotron as one of the next cyclotron for medical application in the Korea Institute of Radiological and Medical Sciences (KIRAMS). The main superconducting magnet should be designed to accelerate various ions for the magnetic bending limit up to 120 MeV. Several ancillary requirements such as background field, space restriction due to ion beam line, and cryostat structure need technical attention. The conceptual design activities of main superconducting magnet system are completed. A quarter-scaled prototype is designed and fabricated in order to confirm the feasibility of our design. The design and fabrication of prototype superconducting magnet system is described in this paper. Also, the detail cryogenic cooling and cryostat structure are presented.</P>

3.2-kW 9.7-GHz Polarization-maintaining Narrow-linewidth All-fiber Amplifier

Hang Liu,Yujun Feng,Xiaobo Yang,Yao Wang,Hongming Yu,Jue Wang,Wanjing Peng,Yanshan Wang,Yinhong Sun,Yi Ma,Qingsong Gao,Chun Tang 한국광학회 2024 Current Optics and Photonics Vol.8 No.1

We present a Yb-doped narrow-linewidth polarization-maintaining (PM) all-fiber amplifier that achieves a high mode-instability (MI) threshold, high output power, and 9.7-GHz spectral linewidth. Six wavelength-multiplexed laser diodes are used to pump this amplifier. First, we construct a high-power fiber amplifier based on a master oscillator-power amplifier (MOPA) configuration for experiments. Subsequently, we examine the MI threshold by individually pumping the amplifier with wavelengths of 976, 974, 981, 974, and 981 nm respectively. The experimental results demonstrate that the amplifier exhibits a high MI threshold (>3.5 kW) when pumped with a combination of wavelengths at 974 and 981 nm. Afterward, we inject an optimized phase-modulated seed with a nearly flat-top spectrum into this amplifier. Ultimately, laser output of 3.2 kW and 9.7 GHz are obtained.

PPNC: Privacy Preserving Scheme for Random Linear Network Coding in Smart Grid

( Shiming He ),( Weini Zeng ),( Kun Xie ),( Hongming Yang ),( Mingyong Lai ),( Xin Su ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.3

In smart grid, privacy implications to individuals and their families are an important issue because of the fine-grained usage data collection. Wireless communications are utilized by many utility companies to obtain information. Network coding is exploited in smart grids, to enhance network performance in terms of throughput, delay, robustness, and energy consumption. However, random linear network coding introduces a new challenge for privacy preserving due to the encoding of data and updating of coefficients in forwarder nodes. We propose a distributed privacy preserving scheme for random linear network coding in smart grid that considers the converged flows character of the smart grid and exploits a homomorphic encryption function to decrease the complexities in the forwarder node. It offers a data confidentiality privacy preserving feature, which can efficiently thwart traffic analysis. The data of the packet is encrypted and the tag of the packet is encrypted by a homomorphic encryption function. The forwarder node random linearly codes the encrypted data and directly processes the cryptotext tags based on the homomorphism feature. Extensive security analysis and performance evaluations demonstrate the validity and efficiency of the proposed scheme.

Hydrogen sulfide ameliorates abdominal aorta coarctation-induced myocardial fibrosis by inhibiting pyroptosis through regulating eukaryotic translation initiation factor 2α phosphorylation and activating PI3K/AKT1 pathway

Yaling Li,Zhixiong Wu,Jiangping Hu,Gongli Liu,Hongming Hu,Fan Ouyang,Jun Yang The Korean Society of Pharmacology 2023 The Korean Journal of Physiology & Pharmacology Vol.27 No.4

This study aimed to assess the effects of exogenous hydrogen sulfide (H₂S) on abdominal aorta coarctation (AAC) induced myocardial fibrosis (MF) and autophagy in rats. Forty-four Sprague-Dawley rats were randomly divided into control group, AAC group, AAC + H₂S group, and H₂S control group. After a model of rats with AAC was built surgically, AAC + H₂S group and H₂S group were injected intraperitoneally with H₂S (100 µmol/kg) daily. The rats in the control group and the AAC group were injected with the same amount of PBS. We observed that H₂S can improve left ventricular function and the deposition of myocardial collagen fibers, inhibit pyroptosis, down-regulate the expression of P-eif2α in myocardial tissue, and inhibit cell autophagy by activating the phosphatidylinositol 3-kinase (PI3K)/AKT1 signaling pathway (p < 0.05). In addition, angiotensin II (1 µM) H9c2 cardiomyocytes were injured in vitro experiments, and it was also observed that pyroptosis was inhibited after H₂S (400 µmol/kg) intervention, the expression of P-eif2α in cardiomyocytes was significantly down-regulated, and the PI3K/AKT1 signaling pathway was activated at the same time. Therefore, increasing the expression of P-eif2α reverses the activation of the PI3K/AKT1 signaling pathway by H₂S. In conclusion, these findings suggest that exogenous H₂S can ameliorate MF in rats with AAC by inhibiting pyroptosis, and the mechanism may be associated with inhibiting the phosphorylation of eif2α and activating the PI3K/AKT1 signaling pathway to inhibit excessive cell autophagy.