• Journal of Power Electronics
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• 제14권5호
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• pp.1000-1007
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• 2014

This paper proposes an on-line rotor time constant estimation strategy for indirect field oriented induction machines. The performance of the indirect field oriented control is dependent especially on the rotor time constant whose value varies according to the temperature. The proposed method calculates the difference between the nominal rotor time constant and the real value from the d- and q-axis integration terms of a proportional integral (PI) current regulator and the demanded voltages of the induction machine to regulate the current in the steady state. Because the proposed strategy has a simple structure and is available in wide speed and torque ranges, the proposed method can be easily used in the industrial field. The effectiveness of proposed strategy is verified with simulations and a 7.5kW experimental setup.

• Structural Engineering and Mechanics
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• 제24권6호
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• pp.699-707
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• 2006

In the paper, a direct method of solution of the Navier equation is presented. An orthotropic thick hollow cylinder under a one-dimensional steady-state temperature distribution and a uniform magnetic field with general types of thermal and mechanical boundary conditions is considered. The Navier equation in terms of displacement is derived and solved analytically by the direct method, and magnetothermoelastic responses and perturbation of the magnetic field vector in the orthotropic thick hollow cylinder is described. The present method is suitable for orthotropic thick hollow cylinders placed in an axial magnetic field with arbitrary thermal and mechanical boundary conditions. Finally, numerical examples are carried out and discussed.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2005년도 춘계종합학술대회
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• pp.928-930
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• 2005

With an increasing importance of the information security issues, the efficienct calculation process in terms of finite field level is becoming more important in the Elliptic curve cryptosystems. Serial multiplication architectures are based on the Mastrovito's serial multiplier structure. In this paper, we manipulate the numerical expressions so that we could suggest a 3-times as fast as (3x) the Mastrovito's multiplier using the polynomial basis. The architecture was implemented with HDL, to be evaluated and verified with EDA tools. The implemented 3x GF (Galois Field) multiplier showed 3 times calculation speed as fast as the Mastrovito's, only with the additional partial-sum generation processing unit.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.576-585
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• 2005

This paper deals with the electromagnetic field analysis of slotless brushless permanent magnet machines with three different magnetization patterns such as Halbach, parallel and radial magnetization. The magnetization modeling of Halbach, parallel and radial magnetization is performed analytically. And then, analytical solutions for open-circuit field distributions, armature reaction field distributions, flux linkages due to PMs and stator windings, torque, back-emf and inductance are derived in terms of magnetic vector potential and two-dimensional (2-d) polar coordinate systems. The analytical results are validated extensively by finite element (FE) analyses. The magnet volume required in order to produce identical flux density is compared with each magnetization. Finally, analytical solutions and derivation procedures of those presented in this paper can be applied to slotless and slotted brushless permanent magnet AC and DC machines.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.633-636
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• 2003

Most of maritime metallic structures are adopted a CP(Cathodic Protection) System for protection of corrosion in advanced country. So, we had been developed a remote corrosion monitoring control system. And we want to know the characteristics of efficiency, reliability, durability and so on. On the view point of it, we have to test in real field. in terms of design, cathodic protection systems, corrosion monitoring systems and optimal corrosion control systems compare to general commercial products. So, these systems have being studied to improve their capability. In this paper, the result of field testing center design of intelligent cathodic protection system including anodes, a real-time wireless remote corrosion monitoring and corrosion control system are described in naval ports.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.406-407
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• 2007

We report the observed peculiar double four lobe textures in CNT dispersed nematic liquid crystal under vertical field. The electro optic studies in a wide range of applied field showed that the double four lobe texture was observed only in the field range of 120 to 160v. This observed peculiar phenomena is explained in terms field induced movement of CNTs and the subsequent reorientation of Liquid crystal molecules.

• 대한수학회지
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• 제53권6호
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• pp.1431-1443
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• 2016

Let k be a global field of characteristic unequal to two. Let $C:y^2=f(x)$ be a nonsingular projective curve over k, where f(x) is a quartic polynomial over k with nonzero discriminant, and K = k(C) be the function field of C. For each prime spot p on k, let ${\hat{k}}_p$ denote the corresponding completion of k and ${\hat{k}}_p(C)$ the function field of $C{\times}_k{\hat{k}}_p$. Consider the map $$h:Br(K){\rightarrow}{\prod\limits_{\mathfrak{p}}}Br({\hat{k}}_p(C))$$, where p ranges over all the prime spots of k. In this paper, we explicitly describe all the constant classes (coming from Br(k)) lying in the kernel of the map h, which is an obstruction to the Hasse principle for the Brauer groups of the curve. The kernel of h can be expressed in terms of quaternion algebras with their prime spots. We also provide specific examples over ${\mathbb{Q}}$, the rationals, for this kernel.

• 한국자기학회지
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• 제5권5호
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• pp.762-766
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• 1995

The coercive field $H_{c}$ of amorphous Y-Fe alloys in the spin-glass state has been investigated. Foramorphous $Y_{10}Fe_{90}$ alloy, the thermal variations of $H_{c}$ in the maximum external field $H_{max}=300,\;600$ and 1 k Oe exhibit a maximum. Since spin-glass behavior is strongly affected by external magnetic fields, the maximum point moves to lower temperature with increasing $H_{max}$. The appearance of the maximum in $H_{c}$ has been discussed in terms of the change of the spin-glass state in the external magnetic field. When the value of $H_{max}$ is 55 kOe, the temperature dependence of $H_{c}$ has no maximum and shows an exponential decrease with increasing temperature. Similar trends have been observed over a wide concentration range. The concentration dependence of $H_{c}$ is associated with the magnetic phase diagram.

• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.43-48
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• 1999

Using microwave plasma-enhanced chemical vapor deposition, diamond films were successfully grown on Ti-coated glass substrates at temperatures as low as around 500$^{\circ}C$ in behalf of practical applications to field emitters. Electron emission was observed at turn-on fields below 18V-$\mu\textrm{m}$. Field emission characteristics of diamond films were discussed in terms of their crystalline qualities. diamond films with poorer crystalline qualities showed better field emission properties.

• Current Optics and Photonics
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• 제7권4호
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• pp.463-470
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• 2023

Hydroxygraphene as a kind of functionalized graphene has important applications in composite, photoelectric and biological materials. In the present study, THz and microfluidic technologies were implemented to study the THz transmission characteristics of hydroxygraphene with different concentrations and residence times in magnetic and electric fields. The results show that the THz transmission intensity decreases with the increase in sample concentration and duration of an applied electric field, while it increases by staying longer in the magnetic field. The phenomenon is analyzed and explained in terms of hydrogen bond, conductivity and scattering characteristics. The results establish a foundation for future research on the THz absorption characteristics of liquid graphene based on microfluidic technology in different external environments. It also provides technical support for the application and development of graphene in THz devices.