• Journal of the Korean Magnetics Society
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• v.25 no.1
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• pp.10-15
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• 2015

The model for the magneto-impedance of composite wires composed of highly conductive nonmagnetic metal core and soft magnetic shell was derived based on the Maxwell's equations. The Cu($100{\mu}m$ diameter)/$Ni_{80}Fe_{20}$($15{\mu}m$ thickness) core/shell composite wire was fabricated by electrodeposition. The impedance spectra for the $Cu/Ni_{80}Fe_{20}$ core/shell composite wire were measured in the frequency range of 10 kHz~10 MHz under longitudinal dc magnetic field in 0 Oe~200 Oe. The spectra of complex permeability in circumferential direction were extracted from the impedance spectra by using the derived model. The extracted spectra of complex permeability showed relaxation-type dispersion which is well curve-fitted with Debye equation with single relaxation frequency. By analyzing the magnetic field dependence of the complex permeability spectra, it has been verified that the composite wire has magnetic anisotropy in longitudinal direction and the origin of the single relaxation process is the magnetization rotation in circumferential direction.

• KDI Journal of Economic Policy
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• v.10 no.3
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• pp.29-49
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• 1988

본(本) 연구(硏究)는 Tobin의 q-이론(理論)에 입각하여 투자(投資)를 결정하고 동태적(動態的) 예산제약하(豫算制約下)에서의 외채지불능력(外債支拂能力)만을 감안한 적정소비결정(滴定消費決定)의 문제점을 논의하는 동시에 우리나라에 있어서 자본(資本)의 시장가치(市場價値), 자본(資本)의 한계생산력(限界生産力) 및 이자율간(利資率間)의 관계를 살펴보고자 함에 목적(目的)이 있다. Balassa and Williamson(1987)은 우리나라의 자본수익률(資本收益率)이 해외차입금리(海外借入金利)보다 높으므로 투자(投資)를 확대시키는 한편, 지금과 같이 호전(好轉)된 해외여건(海外與件)이 상당기간 지속(持續)될 것이며 우리나라의 신인도(信認度)가 높다는 점을 들어 소비(消費)를 확대하고 장기적으로 10억(億)~20억(億)달러의 경상수지적자(經常收支赤子)를 유지하는 것이 바람직하다고 주장하였다. 본고(本稿)는 그들의 주장(主張)을 수용(受容)하는 소비(消費)와 투자(投資)의 동태적(動態的) 최적배분(最適配分)에 관한 단순모형(單純模型)을 구축하여 그들의 주장(主張)을 계량적(計量的)으로 보다 엄밀하게 점검하는 한편, 1990년대 초에 순채권국(純債權國)이 되려는 6차계획(次計劃)의 기본방향(基本方向)이 우리나라의 과거경험(過去經驗) 및 대내외여건전망(對內外與件展望)에 비추어 타당함을 보이려고 하였다.

• Proceedings of the KIEE Conference
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• summer
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• pp.941-943
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• 2004

고정 투자율법이란 (Fixed Permeability Method : FPM) 시스템이 자기적으로 포화 상태에 있을 때 각 요소별 동작지점의 투자율을 고정하여 선형적으로 시스템을 재해석하는 방법으로, 두 가지 이상의 자계원에 의해 포화가 발생할 경우, 각각의 영향을 구분지어 포화시 철심내의 자계 비선형 문제를 해석할 수 있다. 본 논문에서는 제안된 고정 투자율법을 적용하여 자기 포화가 발생하는 영역까지를 운전 영역에 포함하는 매입형 영구 자석 전동기의 특성 값들을 추출하는 방법을 제시하였으며, 실험값과의 비교를 통해 그 타당성을 검증하였다.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.997-999
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• 2003

고정투자율법이란 (Fixed Permeability Method) 시스템이 자기적으로 포화 상태에 있을 때 각 요소별 동작지점의 투자율을 고정하여 선형적으로 시스템을 재해석하는 방법으로, 본 논문에서는 제안된 고정투자율법을 적용하여 두 가지 이상의 자계원에 의해 포화가 발생할 경우 각각의 영향을 구분 지어 포화시 철심내의 자계 비선형 문제를 해석하였다. 아울러 철심형영구 자석 선형 동기 전동기(PMLSM, Steel-Cored Permanent Magnet Linear Synchronous Motor)에서 대전류 인가시 발생하는 철심 포화 특성을 규명하였고 해석의 타당성을 실험값과의 비교를 통해 검증하였다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.211-218
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• 2014

In this paper the magnetic field properties of the soft magnetic alloys (Fe-Si-Cr and Fe-Ni-Cr) are studied in advance for the development of electro-magnetic shielding films, which could be used in the IT Devices (NFC, mobile phone, computer, etc.).As a result each of the selected soft magnetic alloy melts of the corresponding compositions is water-dispersed into the disk-shaped grains, which are soaked in polymer resin, and of which two types of thin film of thickness 0.1mm and 1mm are made by passing through the heating calendar roller. And the magnetic permeability and the shielding effectiveness of the polymer films containing the soft magnetic alloy grains are measured over the whole frequency bands from the low frequency to 10GHz. Before the experiments of the soft magnetic alloy, a special equation is proposed to estimate the permeability of the alloy, and the equation is verified with the pre-published data by MATLAB, and from which the most optimal compositions can be decided. And the SE(Shielding Effectiveness) of the polymer films containing the soft magnetic alloy grains is simulated by the HFSS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.678-683
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• 2010

This paper presents a wireless (contactless) charging technique with a new core material called permalloy. For charging portable devices wirelessly, ferrosilicon or ferrite has been conventionally used. Due to high permeability of permalloy, charging efficiency can be significantly improved and subsequently this high efficiency increases charging distance between charger and portable devices. Comparative experimental studies demonstrate that the charging performance and efficiency with permalloy employed are significantly improved. The proposed wireless charging techniques can be used to charge portable devices efficiently.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.639-643
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• 2011

Fry-drying of coal slurry is one of the upgrading low rank coal processes. It consists of slurry mixing, slurry dewatering, solvent recovery and briquetting. Cost estimation and economic feasibility are examined for the upgrading low rank coal process based on capacity of 1 million ton/yr. In case that investment costs are $100,000,000, discount rate is 12%, and service life is 20 years, the results of economic analysis are enough to satisfy the evaluation criteria of investment such as IRR, B/C ratio, NPV and discounted payback period. According to sensitivity analysis, investment value are very sensitive to raw material cost and product price. Since the bituminous coal price is currently soaring, it is expected that the investment value will increase more and more.

• Journal of the Korean Magnetics Society
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• v.20 no.3
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• pp.94-99
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• 2010

Minor B-H loop measurement for a rectangular high tensile steel was obtained by using Labview. A ferrite cores of high permeance with primary and secondary windings on the steel plate were used to form a closed loop of magnetic flux. To compensate errors due to an extremely small gap between a pair of ferrite core, and between the ferrite core and the rectangular high tensile steel, quadratic function of least square method was used. Also a 3D FEM magnetic analysis tool was used to measure H and B of the steel. B-H loop of the high tensile steel plate can be measured up to 520 A/m of a magnetic field and 0.15 T of a magnetic flux density.

• Journal of the Korean Magnetics Society
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• v.12 no.4
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• pp.154-159
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• 2002

Amorphous FeBSiNb alloy ribbons having bulk glass forming ability and high saturation magnetic flux density were produced by single-roller melt spinning apparatus in the thickness range of 22∼102㎛. With the increase of thickness, the coercive force and squareness ratio decreased, while maximum permeability and AC permeability increased. However electrical resistivity was almost constant. Furthermore refined and complex magnetic domain structure was observed in thicker ribbons owing to the change in internal magnetic anisotropy. For the alloy with the thickness of 81㎛, small coercive force of 24 mOe and high effective permeability of 12,000 at 1㎑ were obtained, those are considered to be better comparing to the conventional soft magnetic amorphous alloys (∼20 ㎛). The good soft magnetic properties of the thick FeBSiNb amorphous alloys were attributed to the decrease in surface pinning effect during wall motion, appearance of perpendicular anisotropy and resulted domain refinement.

• The KIPS Transactions:PartD
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• v.14D no.1 s.111
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• pp.107-120
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• 2007

When it tomes to IT investment, it's a challenge for the management to make the right decision. Unlike investment in other business area, it's hard to measure direct cost vs. effect in IT business. To validate the investment in IT, it is required to establish objective assessment system that both provider and beneficiary of information can accept, and it is also required to suggest an assessment tool of fixed quantity that includes measuring standards and method for the economic effect of new investment. This study, therefore, has developed IT ROI Methodology that can prove investment validity by accepting the strong points of the existing models while complementing their weak points and by analyzing IT Investment and IT Efforts. It also has built an IT ROI System that reflects the methodology which is applied to 21 companies of 5 business categories. This system is designed to provide effective and objective decision-making tool for IT investment by proving what positive impacts IT could have on business activities.