Effects of Mechanical Rotation and Vibration on Spin Currents

Mamoru Matsuo,Jun’ichi Ieda,Sadamichi Maekawa,Eiji Saitoh 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.10

We discuss theoretically the generation of spin currents in both rotationally and linearly accelerated systems. The spin-orbit interaction modified by inertial effects is derived from the low energy limit of the generally covariant Dirac equation. It is shown that the spin-orbit interaction is responsible for the generation of spin currents by mechanical rotation and vibration. We also study effects of impurity scattering on the mechanically induced spin current, and calculate the spin accumulation by solving the spin diffusion equation with the spin-source term originating from the inertial effects.

Optimum boundaries for maximum load-carrying capacity in water-lubricated composite journal bearings incorporating turbulences and inertial effects based on elastohydrodynamic analysis

김원빈,임수현,Hong Hyunsoo,정광일,On Seung Yoon,박성연,You Jun Il,Kim Seong Su 한국CDE학회 2022 Journal of computational design and engineering Vol.9 No.6

The application of polymer-based composite materials as bearing liner materials in eco-friendly water lubrication has received considerable attention owing to their superior tribological behaviors, corrosion resistance, and high damping characteristics, and their design flexibility can improve the bearing performances in response to the distribution of lubricant film pressure based on the regulation of elastic constants. However, the low viscosity and high density of water essentially cause thin-filmed lubrication accompanied by a low load-carrying capacity. Particularly, a high rotational speed enhancing the wedge effect induces turbulence and considerable inertial effect. Moreover, substantial elastic deformation of the composite bearing liners alters the formation of the lubricant film. In this study, we analyze a water-lubricated composite journal bearing system incorporating the turbulence, inertial effect, and elastic deformation of the bearing liner. Reynolds equation was modified considering the turbulence and inertial effect. The elastic deformation of the composite bearing liner was determined by solving the constitutive equation. The Reynolds equation and the constitutive equation were solved via the finite difference method and finite element method, respectively. In addition, the analytical relation for the elastic deformation was derived that suitably eliminated the requirement of solving the constitutive equation. With the introduction of the primary parameters, Sommerfeld number, Reynolds number, and deformation coefficient, the relation of the normalized minimum film thickness with respect to the parameters was modeled based on the Gaussian regression model. Accordingly, we proposed the new optimal maximum load-carrying capacity boundaries that narrowed down the operating region compared to conventional boundaries.

INERTIAL EFFECT ON CONVECTIVE FLOW IN A PASSIVE MUSHY LAYER

Dambaru Bhatta,Daniel N. Riahi,Mallikarjunaiah S. Muddamallappa 한국전산응용수학회 2012 Journal of applied mathematics & informatics Vol.30 No.3

Here we consider the inertial effect in a horizontal mushy layer during solidification of a binary alloy. Using perturbation technique,we obtain two systems, one of zero order and the other of first order. We consider a mushy layer with an impermeable mush-liquid interface and of constant permeability. The analysis reveals that the effect of inertial parameter is stabilizing in the sense that the critical Rayleigh number at the onset of motion increases by the inertial effect.

INERTIAL EFFECT ON CONVECTIVE FLOW IN A PASSIVE MUSHY LAYER

Bhatta, Dambaru,Riahi, Daniel N.,Muddamallappa, Mallikarjunaiah S. The Korean Society for Computational and Applied M 2012 Journal of applied mathematics & informatics Vol.30 No.3

Here we consider the inertial effect in a horizontal mushy layer during solidification of a binary alloy. Using perturbation technique, we obtain two systems, one of zero order and the other of first order. We consider a mushy layer with an impermeable mush-liquid interface and of constant permeability. The analysis reveals that the effect of inertial parameter is stabilizing in the sense that the critical Rayleigh number at the onset of motion increases by the inertial effect.

Rotor Speed-based Droop of a Wind Generator in a Wind Power Plant for the Virtual Inertial Control

Lee, Jinsik,Kim, Jinho,Kim, Yeon-Hee,Chun, Yeong-Han,Lee, Sang Ho,Seok, Jul-Ki,Kang, Yong Cheol The Korean Institute of Electrical Engineers 2013 Journal of Electrical Engineering & Technology Vol.8 No.5

The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.

Rotor Speed-based Droop of a Wind Generator in a Wind Power Plant for the Virtual Inertial Control

Jinsik Lee,Jinho Kim,Yeon-Hee Kim,Yeong-Han Chun,Sang Ho Lee,Jul-Ki Seok,Yong Cheol Kang 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.5

The frequency of a power system should be kept within limits to produce high-quality electricity. For a power system with a high penetration of wind generators (WGs), difficulties might arise in maintaining the frequency, because modern variable speed WGs operate based on the maximum power point tracking control scheme. On the other hand, the wind speed that arrives at a downstream WG is decreased after having passed one WG due to the wake effect. The rotor speed of each WG may be different from others. This paper proposes an algorithm for assigning the droop of each WG in a wind power plant (WPP) based on the rotor speed for the virtual inertial control considering the wake effect. It assumes that each WG in the WPP has two auxiliary loops for the virtual inertial control, i.e. the frequency deviation loop and the rate of change of frequency (ROCOF) loop. To release more kinetic energy, the proposed algorithm assigns the droop of each WG, which is the gain of the frequency deviation loop, depending on the rotor speed of each WG, while the gains for the ROCOF loop of all WGs are set to be equal. The performance of the algorithm is investigated for a model system with five synchronous generators and a WPP, which consists of 15 doubly-fed induction generators, by varying the wind direction as well as the wind speed. The results clearly indicate that the algorithm successfully reduces the frequency nadir as a WG with high wind speed releases more kinetic energy for the virtual inertial control. The algorithm might help maximize the contribution of the WPP to the frequency support.

주택매매가격과 가계부채 사이의 동태적 관계 연구

윤성민(Yoon, Seong-Min) 한국부동산학회 2018 不動産學報 Vol.74 No.-

본 연구의 목적은 주택가격과 가계부채 사이의 동태적 관계를 분석하는 것이다. 실증분석을 위해 이 두 변수와 밀접히 관련된 거시경제변수들의 2002년 12월부터 2018년 3월까지의 월별자료를 이용하여 백터오차수정모형과 임계 백터오차수정모형을 추정하고 그 결과를 분석하였는데, 주요 결과를 요약하면 다음과 같다. 첫째, 장기적으로 주택매매 가격, 금융 유동성, 소득 변수는 가계부채와 같은 방향으로 움직이고, 금리는 가계부채와 반대 방향으로 움직이는 것으로 나타났다. 둘째, 가계부채와 주택가격 및 다른 거시경제변수와의 동태적 관계를 분석하는 데는 VECM보다 TVECM이 더 적합한 것으로 나타났다. 셋째, TVECM의 추정결과, 극단상태(상태1)에서는 주택매매가격 변동이 관성효과를 보였고, 가계부채는 보통상태(상태2)와 극단상태(상태1) 모두에서 평균회귀 경향을 보였다. 이러한 결과는 주택매매가 격을 억제하는 정책을 통하여 가계부채를 단기적으로 감소시키는 정책은 극단상태에서만 효과적이라는 것을 의미한다. 다섯째, 가계부채를 억제하면 주택매매가격의 상승을 통제하는 정책은 단기적으로는 효과가 없는 것으로 나타났다. 1. CONTENTS (1) RESEARCH OBJECTIVES This study examined the dynamic relationship between house price and households debt in Korea. (2) RESEARCH METHOD We used monthly data over the period from December 2002 to March 2018, and the econometric methods of vector error correction model (VECM) and threshold VECM(TVECM). (3) RESEARCH FINDINGS In the long-run, house price, financial liquidity and income move in the same direction with the households debt, but the interest rate does in the opposite direction. In the short-run, house price, income and interest rate do not have impact on the households debt. And the TVECM is more suitable than the VECM for analyzing the dynamic relationship between house price and households debt. 2. RESULTS In the extreme regime, there exists an inertial effect in the movements of house price, whereas the movements of households debt show mean-reverting property. Only in the extreme regime, house price leads households debt, implying that controlling house price to decrease households debt is effective in the extreme regime. Policy controlling households debt to decrease house price is not effective.

Inertial Dynamic Effect on the Rates of Diffusion-Controlled Ligand-Receptor Reactions

Lee, Woo-Jin,Kim, Ji-Hyun,Lee, Sang-Youb Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.suppl8

It has been known that the inertial dynamics has a little effect on the reaction rate in solutions. In this work, however, we find that for diffusion-controlled reactions between a ligand and a receptor on the cell surface there is a noticeable inertial dynamic effect on the reaction rate. We estimate the magnitude of the inertial dynamic effect by comparing the approximate analytic results obtained with and without the inertial dynamic effect included. The magnitude of the inertial dynamic effect depends on the friction coefficient of the ligand as well as on the relative scale of the receptor size to the distance traveled by the ligand during its velocity relaxation time.

Inertial Dynamic Effect on the Rates of Diffusion-Controlled Ligand-Receptor Reactions

이우진,김지현,이상엽 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.8

It has been known that the inertial dynamics has a little effect on the reaction rate in solutions. In this work,however, we find that for diffusion-controlled reactions between a ligand and a receptor on the cell surface there is a noticeable inertial dynamic effect on the reaction rate. We estimate the magnitude of the inertial dynamic effect by comparing the approximate analytic results obtained with and without the inertial dynamic effect included. The magnitude of the inertial dynamic effect depends on the friction coefficient of the ligand as well as on the relative scale of the receptor size to the distance traveled by the ligand during its velocity relaxation time.

대형 진동대 실험을 이용한 다자유도 구조물의 관성 상호작용 평가

채종훈,윤형철,정종원 한국지반공학회 2022 한국지반공학회논문집 Vol.38 No.6

The effect of the soil-structure interaction (SSI) on has been recently evaluated in shaking table tests. However, most of these tests were conducted on single-degree-of-freedom (SDOF) superstructures and a single-pile. This study investigates the inertial interaction effect of a multi-degree-of-freedom (MDOF) superstructure system with a group piles on a large-scale shaking table test. Whereas the SDOF superstructure system shows a single-frequency amplification tendency, the MDOF superstructure system exhibited amplification tendencies of the acceleration phase and frequency responses for multiple frequencies. In addition, the amplification phenomenon between the footing and the column-type superstructure exceeded that between the footing and the wall-type superstructure, indicating a greater inertial interaction effect of the column-type superstructure. The relationship between shear force and inertial force, the relative vertical and horizontal displacements on the footing was figured out. Also, the ananlysis of dynamic p-y curve at each depth was conducted. In summary, the MDOF and SDOP superstructure systems exhibited different behaviors and the column-type superstructure exerted a higher interaction effect than the wall-type superstructure.