Association between levels of physical activity and low handgrip strength: Korea National Health and Nutrition Examination Survey 2014-2019

Hyungsoon Ahn,Hwa Young Choi,Moran Ki 한국역학회 2022 Epidemiology and Health Vol.44 No.-

OBJECTIVES: This study aimed to investigate the association between levels of physical activity (PA) and low handgrip strength in Korean adults. METHODS: Our cross-sectional study design included 24,109 Korean adults older than 19 years of age who participated in the Korea National Health and Nutrition Examination Survey 2014-2019. Low handgrip strength is described as hand strength less than the cut-off value of the 20th percentile of handgrip strength from a healthy population in each gender and age group. PA was categorized into three levels (inactive, active, and highly active) according to the World Health Organization’s global recommendations on PA for health. Multivariable logistic regression analysis was used to examine the association between levels of PA and low handgrip strength. RESULTS: Odds ratios (ORs) for low handgrip strength were significantly higher in middle-aged women who were active (adjusted odds ratio [aOR], 1.40; 95% confidence interval [CI], 1.15 to 1.69) and inactive (aOR, 1.47; 95% CI, 1.23 to 1.76) than in those highly active in walking exercise. Most of older people had significantly higher ORs for low handgrip strength in active compared to highly active in the context of aerobic, muscle strengthening, and walking exercise. CONCLUSIONS: Walking exercise was associated with a lower risk of sarcopenia in middle-aged women and older individuals. However, further studies are necessary to confirm the causal relationship between levels of PA and low handgrip strength.

Analytic Model of Spin-Torque Oscillators (STO) for Circuit-Level Simulation

Ahn, Sora,Lim, Hyein,Shin, Hyungsoon,Lee, Seungjun The Institute of Electronics and Information Engin 2013 Journal of semiconductor technology and science Vol.13 No.1

Spin-torque oscillators (STO) is a new device that can be used as a tunable microwave source in various wireless devices. Spin-transfer torque effect in magnetic multilayered nanostructure can induce precession of magnetization when bias current and external magnetic field are properly applied, and a microwave signal is generated from that precession. We proposed a semi-empirical circuit-level model of an STO in previous work. In this paper, we present a refined STO model which gives more accuracy by considering physical phenomena in the calculation of effective field. Characteristics of the STO are expressed as functions of external magnetic field and bias current in Verilog-A HDL such that they can be simulated with circuit-level simulators such as Hspice. The simulation results are in good agreement with the experimental data.

Circuit-Level Model of Phase-Locked Spin-Torque Oscillators

Ahn, Sora,Lim, Hyein,Kim, Miryeon,Shin, Hyungsoon,Lee, Seungjun IOP Publishing 2013 Japanese journal of applied physics Vol.52 No.4

<P>Spin-torque oscillators (STOs) are new oscillating devices based on spintronics technology with many advantageous features, i.e., nanoscale size, high tunability, and compatibility with standard silicon processing. Recent research has shown that two electrically connected STOs may operate as a single device when specific conditions are met. To overcome the limitation of the small output power of STOs, the phase-locking behavior of multiple STOs is hereby extensively investigated. In this paper, we present a circuit-level model of two coupled STOs considering the interaction between them such that it can represent the phase-locking behavior of multiple STOs. In our model, the characteristics of each STO are defined first as functions of applied DC current and external magnetic field. Then, the phase-locking condition is examined to determine the properties of the two coupled STOs on the basis of a theoretical model. The analytic model of two coupled STOs is written in Verilog-A hardware description language. The behavior of the proposed model is verified by circuit-level simulation using HSPICE with CMOS circuits including a current-mirror circuit and differential amplifiers. Simulation results with various CMOS circuits have confirmed the effectiveness of our model. (C) 2013 The Japan Society of Applied Physics</P>

Analytic Model of Spin-Torque Oscillators (STO) for Circuit-Level Simulation

Sora Ahn,Hyein Lim,Hyungsoon Shin,Seungjun Lee 대한전자공학회 2013 Journal of semiconductor technology and science Vol.13 No.1

Spin-torque oscillators (STO) is a new device that can be used as a tunable microwave source in various wireless devices. Spin-transfer torque effect in magnetic multilayered nanostructure can induce precession of magnetization when bias current and external magnetic field are properly applied, and a microwave signal is generated from that precession. We proposed a semi-empirical circuit-level model of an STO in previous work. In this paper, we present a refined STO model which gives more accuracy by considering physical phenomena in the calculation of effective field. Characteristics of the STO are expressed as functions of external magnetic field and bias current in Verilog-A HDL such that they can be simulated with circuit-level simulators such as Hspice. The simulation results are in good agreement with the experimental data.

친환경 차량 구동 모터의 초기각 자동추정에 관한 연구

안태규(Taegyu Ahn),박상민(Sangmin Park),김진문(Jinmun Kim),박형순(Hyungsoon Park) 한국자동차공학회 2019 한국자동차공학회 부문종합 학술대회 Vol.2019 No.5

In this paper, It proposes an algorithm that automatically estimates the initial angle of the rotor of a interior permanent magnet synchronous motor. The conventional passive method for estimating the initial angle takes a long time and its accuracy depends on the operator’s skill. The method of automatically estimating by applying the voltage vector is dependent on the cogging torque characteristics of the motor and the accuracy of the initial angle is reduced. Therefore, we proposed an imbalance algorithm to estimate the optimal initial angle information. The proposed method is applicable to all PMSM motors and useful to initialize to control the motor and verified through actual experiments.

Advanced Circuit-Level Model of Magnetic Tunnel Junction-based Spin-Torque Oscillator with Perpendicular Anisotropy Field

Kim, Miryeon,Lim, Hyein,Ahn, Sora,Lee, Seungjun,Shin, Hyungsoon The Institute of Electronics and Information Engin 2013 Journal of semiconductor technology and science Vol.13 No.6

Interest in spin-torque oscillators (STOs) has been increasing due to their potential use in communication devices. In particular the magnetic tunnel junction-based STO (MTJ-STO) with high perpendicular anisotropy is gaining attention since it can generate high output power. In this paper, a circuit-level model for an in-plane magnetized MTJ-STO with partial perpendicular anisotropy is proposed. The model includes the perpendicular torque and the shift field for more accurate modeling. The bias voltage dependence of perpendicular torque is represented as quadratic. The model is written in Verilog-A, and simulated using HSPICE simulator with a current-mirror circuit and a multi-stage wideband amplifier. The simulation results show the proposed model can accurately replicate the experimental data such that the power increases and the frequency decreases as the value of the perpendicular anisotropy gets close to the value of the demagnetizing field.

Advanced Circuit-Level Model of Magnetic Tunnel Junction-based Spin-Torque Oscillator withPerpendicular Anisotropy Field

Miryeon Kim,Hyein Lim,Sora Ahn,Seungjun Lee,Hyungsoon Shin 대한전자공학회 2013 Journal of semiconductor technology and science Vol.13 No.6

Interest in spin-torque oscillators (STOs) has been increasing due to their potential use in communication devices. In particular the magnetic tunnel junction-based STO (MTJ-STO) with high perpendicular anisotropy is gaining attention since it can generate high output power. In this paper, a circuit-level model for an in-plane magnetized MTJSTO with partial perpendicular anisotropy is proposed. The model includes the perpendicular torque and the shift field for more accurate modeling. The bias voltage dependence of perpendicular torque is represented as quadratic. The model is written in Verilog-A, and simulated using HSPICE simulator with a current-mirror circuit and a multi-stage wideband amplifier. The simulation results show the proposed model can accurately replicate the experimental data such that the power increases and the frequency decreases as the value of the perpendicular anisotropy gets close to the value of the demagnetizing field.