고조파 토오크 함수에 의한 전압원 PAWM인버터의 평가

권우현 경북대학교 전자기술연구소 1988 電子技術硏究誌 Vol.9 No.1

A new HTF(Harmonic torque function) which takes into account the phasor of harmonic current, and which represents torque apple content of induction motor is proposed. Through experiments and computer simulations using direct quadrature two axis model, the proposed HTF is proved to be valid. Applying this function, six-step, SPWM and TPWM pulse-amplitude-controlled inverters are evaluated and compared with each other. A good control strategy for PAWM inverters was chosen from the results. It turns out that TPWM is superior to SPWM in torque ripple content and output voltage amplitude of fundamental wave and six-step is better than PWM when carrier ratio is 9.

Crystallographic and Magnetic Properties of V2O5-doped Titanium Cobalt Ferrites

권우현,이승화,이재광,채광표 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.4

The effects of vanadium-oxide (V2O5) doping on the crystallographic and magnetic properties of titanium cobalt ferrite, Ti0.2Co1.2Fe1.6O4, are investigated. Ferrite was doped with V2O5 in the range of 0 to 3.0 wt.% by using conventional ceramic methods. Using X-ray diffraction and M¨ossbauer spectroscopy, the formation of crystallized particles was confirmed in ferrite powders. All of the samples showed a single spinel structure, and the lattice parameters were nearly constant as the doping content was increased. The average grain size of the samples increased with the V2O5 concentration up to 2.6 wt.%, and then on further addition it decreased. The average grain size showed a pronounced maximum of about 9.11 μm at 2.6 wt.% V2O5. When x = 0 in x(V2O5) wt.% doped Ti0.2Co1.2Fe1.6O4, the M¨ossbauer spectrum could be fitted with two Zeeman sextets, which is the typical spinel ferrite spectra with A and B sites. However, when x > 0.2, the M¨ossbauer spectrum could be fitted with two Zeeman sextets and one doublet. The doublets can be interpreted as resulting from non-paired Fe ions that do not participate in the A-O-B superexchange process in the spinel structure. From the variation of M¨ossbauer parameters and the absorption area ratio, the cation distribution could be determined. The magnetic behavior of the samples showed that an increase in the V2O5 content up to 2.2 wt.% led to an increase in the saturation magnetization and the coercivity after which a subsequent decrease was observed. The maximum saturation magnetization and coercivity of the samples were 69.0 emu/g and 0.36 kOe, respectively. The effects of vanadium-oxide (V2O5) doping on the crystallographic and magnetic properties of titanium cobalt ferrite, Ti0.2Co1.2Fe1.6O4, are investigated. Ferrite was doped with V2O5 in the range of 0 to 3.0 wt.% by using conventional ceramic methods. Using X-ray diffraction and M¨ossbauer spectroscopy, the formation of crystallized particles was confirmed in ferrite powders. All of the samples showed a single spinel structure, and the lattice parameters were nearly constant as the doping content was increased. The average grain size of the samples increased with the V2O5 concentration up to 2.6 wt.%, and then on further addition it decreased. The average grain size showed a pronounced maximum of about 9.11 μm at 2.6 wt.% V2O5. When x = 0 in x(V2O5) wt.% doped Ti0.2Co1.2Fe1.6O4, the M¨ossbauer spectrum could be fitted with two Zeeman sextets, which is the typical spinel ferrite spectra with A and B sites. However, when x > 0.2, the M¨ossbauer spectrum could be fitted with two Zeeman sextets and one doublet. The doublets can be interpreted as resulting from non-paired Fe ions that do not participate in the A-O-B superexchange process in the spinel structure. From the variation of M¨ossbauer parameters and the absorption area ratio, the cation distribution could be determined. The magnetic behavior of the samples showed that an increase in the V2O5 content up to 2.2 wt.% led to an increase in the saturation magnetization and the coercivity after which a subsequent decrease was observed. The maximum saturation magnetization and coercivity of the samples were 69.0 emu/g and 0.36 kOe, respectively.

Trapezoidal PWM전류원 인버터에서 초소 Speed Ripple을 위한 펄스 수 및 변조도의 결정 ( Selection of Pulses Number and Modulation Index for Minimum Speed Ripple in Trapezoidal CSI-PWM )

권우현,이치환,이창화,구본호 대한전자공학회 1988 대한전자공학회 학술대회 Vol.1988 No.7

고지질 식이 투여를 이용하여 상부위장관내시경 소견으로 진단된 원발성 장림프관 확장증

권우현,황진복,이영환,김용진,Kwon, Woo-Hyun,Hwang, Jin-Bok,Lee, Young-Hwan,Kim, Yong-Jin 대한소아소화기영양학회 1999 Pediatric gastroenterology, hepatology & nutrition Vol.2 No.1

전신 부종을 주소로 내원한 20개월된 남아에서 대변의 ${\alpha}_1$-antitrypsin clearance를 이용하여 단백상실성 장병증으로 진단하고, 상부위장관내시경을 시행하였으나 육안적 및 조직학적 소견상 특기할 만한 진단적 실마리가 관찰되지 않아, 고지질 식이를 투여 후 내시경을 시행하여 육안적, 조직학적 소견상 장림프관 확장증의 특징적인 소견이 확인되어 원발성 장림프관 확장증으로 진단된 증례이다. We experienced a case of primary intestinal lymphangiectasia in a 20-month-old boy, which was confirmed gastrofiberscopically and histologically only after a high-fat meal before the procedure. A characteristic endoscopic finding was the appearance of tiny white dots scattered in the duodenal mucosa, which were proved dilated lymph vessels in the lamina propria on histological examination. Treatment with low-fat diet and medium chain triglycerides supplementation was satisfactory.

Automatic Moving TArget Tracking System의 제작

권우현,박송배 대한전자공학회 1978 대한전자공학회 학술대회 Vol.1978 No.01

시스템 리스크(Systemoic Risk)와 거시 경제적 불안정성 - 금융위기 분석을 위한 시론적 검토 -

권우현 한국사회경제학회 2004 사회경제평론 Vol.- No.22

이 글은 금융위기를 자본축적과의 관련 속에서 어떻게 해명할 수 있을지를 탐색 해 보고자 하는 시론적인 검토이다. 여기서는 산업자본과 금융자본의 본질의 변화 및 이 두 자본형태간의 관계의 변화가 금융위기 분석에서 결정적으로 중요한 지점이라는 인식에 기초하고 있다. 이러한 두 자본형태간의 관계의 변화는 금융시스템의 성격에 의해 규정되고, 자본축적 방식에 변화를 초래하며, 그리하여 경제성장에 영향을 미친다. 즉, 특정의 금융시스템은 다른 금융시스템에 비해 시스템 리스크에 더욱 취약하다. 이 시스템 리스크의 내용에 따라 위기의 발현형태 및 성격, 즉 축적의 안정성 여부가 결정된다. 축적의 리듬, 수준 및 방향 등 거시 경제적 성장방식은 기술변화와 더불어 각각의 금융시스템이 안고 있는 시스템 리스크에 의해 좌우된다는 인식에 기초하고 있다. 이러한 인식에 기초하여 이 글에서는 '금융취약성', '금융불안정', '금융적 충격', '금융적 교란' 등으로 표현되는 시스템 리스크에 관한 제논의를 검토하고, 시스템 리스크는 미시적 효율성과 거시적 불안정성간의 딜레마 및 산업자본과 금융자본의 상호침투 메카니즘이라는 두 가지 측면에서 이해할 수 있음을 밝히고 있다. 다음으로 이러한 두 측면의 시스템 리스크에 대한 이해는 금융위기의 분석과 자본축적 방식의 해명에 중요한 의미를 가짐을 밝히고 각각의 측면에서 중요하게 고려해야 할 내용들을 검토하고 있다. This paper examines the financial crisis with relation to capital accumulation The concept 'systemic risk' describes the financial fragility or financial instability But this terms very useful in explaining the relationship between industrial and financial capital, namely relationship between real and financial capital. Thus this concept gives us a due for constructing theory of capital accumulation and crisis in which real and financial sector combining There are two reasons to use this concept First, it is possible to analyze that a certain financial system has a potential fragility internally. Second, it is possible to analyze how to influence the intrinsic fragility of financial system on the pattern of capital accumulation It is important to investigate two aspects of systemic risk to bring light on the financial crisis and slowdown of capital accumulation under systemic risk To begin with, systemic risk explains the relation between microeconomic activities and macroeconomic stabilities or instabilities. And also it explains the relationship between real sectors(industrial capital) and financial sectors(financial capital). Therefore economic growth as well as rhythm, quantitative level and direction of accumulation are influenced by systemic risk The financialization as the most prominent appearance of modern capitalism causes macroeconomic instability like as slowdown of capital accumulation(including the downward of real sector), flexibility of wage and employment Systemic risk may be useful concept for explaining this phenomenon.

저가 촉매를 이용한 선택적 촉매 환원반응 연구

권우현,이형원,이희진,김한나,김범식,홍여진,이예진,박영권 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

선택적 촉매 환원방법은 질소산화물을 저감하기에 효율적인 방법이다. 그러나 일반적으로 질소산화물을 저감하기위해 사용하는 촉매들은 대게 V₂O₅/TiO₂, Pt 등과 같은 고가인 경우가 대부분이다. 따라서 본 연구에서는 저가 촉매인 바이오 Char와 천연제올라이트, 소성한 폐촉매(FCC)를 이용한 선택적 촉매 환원 반응을 연구하고자 한다. 바이오매스 열분해를 통해 생성된 Char를 활성화하여 질소산화물 저감 촉매로써의 가능성을 확인하였다. 바이오 Char는 물리적, 화학적 활성화를 통해 Char의 활성을 높였으며, 천연제올라이트와 폐촉매(FCC)는 저온에서 좋은 활성을 보이는 Manganese를 함침법으로 담지하여 질소산화물 저감을 확인하였다. 바이오 Char는 물리적 방법인 수분처리와 화학적 방법인 KOH 처리를 하여 각각의 활성을 비교하였으며, 천연제올라이트와 폐촉매(FCC)는 Mn 담지량을 다르게하여 활성을 비교하였다.

버블붕괴 이후 일본 기업지배구조의 변화

권우현 한국사회과학연구회 2009 동향과 전망 Vol.- No.75

This study investigates the changes of corporate governance in Japan since the 1990s. Distinctive features of corporate governance in Japan in the latter half of the twentieth century were stable, long-term shareholders and extensive ownership by business corporations, often in the form of cross-shareholding. However, There have certainly been changes recently in Japanese corporate governance and its environment. Cross-shareholdings are dissolving and stable corporate shareholdings are being reduced. Major Banks are selling the shares of their trading customers. From the 1990s, many enterprises adopted two countermeasures- non-regularization of employment and reforms of the wage system- in order to restrain wage costs. In the last 10 years, circumstances surrounding employment relations have changed substantially. This has been manifested in an increase in non-regular employment and the change from seniority based pay system to a merit(performance) based one. Therefore, The new type of Japanese corporate system is now being a hybrid one in which lifetime employment practice combine with the performance based pay system. 이 논문은 버블붕괴 이후 일본 기업지배구조의 변화를 금융시스템 및 노사관계제도와의 보완성 관점에서 살펴본 것이다. ‘잃어버린 10년 또는 15년’을 거치면서 일본 기업지배구조는 변화하고 있다. 금융시스템의 변화에서 촉발된 제도변화는 기업지배구조와 기업경영전략의 변화를 거쳐 고용 및 임금제도의 개혁으로 이어졌다. 금융시스템은 전통적인 은행중심의 간접금융시스템으로부터 자본시장의 활성화를 통한 시장금융시스템으로 변화하고 있다. 기업지배구조는 메인뱅크의 기능저하, 안정주주 및 상호주식보유의 해체, 이사회제도의 개혁을 통해 미국형에 가까운 구조와 일본형의 수정이라 할 만한 구조 등으로 산업별, 기업별 다양성이 관찰되고 있다. 동시에 주주가치 중시경향이 강화되면서 비정규직 고용의 확대와 성과주의의 도입이 진행되고 있다. 전통적인 일본형 기업시스템은 장기고용을 유지하면서 성과주의를 도입하는 새로운 일본형 기업, 장기고용을 폐기하고 성과주의를 도입하는 미국형 기업, 장기고용을 폐기하고 성과주의도 도입하지 않는 쇠퇴하는 일본형 기업으로 분화되고 있다. 이 가운데 새로운 일본형 기업시스템으로 자리잡고 있는 것은 장기고용을 유지하면서 성과주의 체계를 도입하는 하이브리드형 기업형태이다.

Crystallographic and Magnetic Properties of Vanadium-substituted Li-Co-Ti Ferrite

권우현,이재광,이승화,채광표 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.6

The crystallographic and magnetic properties of vanadium-substituted lithium cobalt titanium ferrite, Li0.5+xCo0.2Ti0.2VxFe2.1−2xO4, are investigated. Ferrite was replaced with vanadium in the range of 0.00 to 0.20 in steps of 0.05 and was synthesized by using conventional ceramic methods. Using X-ray diffraction and M¨ossbauer spectroscopy, the formation of crystallized particles was confirmed in Li0.5+xCo0.2Ti0.2VxFe2.1−2xO4 ferrite powders. All of the samples showed a single phase with a spinel structure, and the lattice parameters were nearly constant as the substituted content increased. The average grain size of the samples increased with x. For x = 0 in Li0.5+xCo0.2Ti0.2VxFe2.1−2xO4, the M¨ossbauer spectrum could be fitted with two Zeeman sextets,which is the typical spinel ferrite spectra of Fe3+ with A and B sites. However, for x 0.05, the M¨ossbauer spectra could be fitted with two Zeeman sextets and one doublet. From the variations of the M¨ossbauer parameters and the absorption area ratio, the cation distribution could be determined as (Co0.2−Vx−Fe0.8−x+2)[Li0.5+xCoVTi0.2Fe1.3−x−2]O4. The magnetic behavior of the samples showed that an increase in the vanadium content led to an increase in the saturation magnetization and then to some decrease whereas the coercivity decreased. The maximum saturation magnetization was 44.81 emu/g at x = 0.05, and the maximum coercivity was 120.4 Oe at x = 0.

Crystallographic and Magnetic Properties of Mn1−xZnxFe2O4 Powders

권우현,이승화,채광표,이재광 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61

Mn1−xZnxFe2O4 powders were fabricated by using a sol-gel method, and their crystallographic and magnetic properties were investigated by using X-ray diffractometry, Mossbauer spectroscopy and vibrating sample magnetometry. All samples were annealed at 500 ℃ in a N2 atmosphere after having been refluxed for 12 hours at 90 ℃ and dried completely. Using the X-ray diffractometer, the formation of single-phased Mn1−xZnxFe2O4 powders was confirmed regardless of the Zn concentration, and the lattice distances decreased a little as the Zn concentration increased. M¨ossbauer spectra measured at room temperature showed two Zeeman sextets in the case of pure Mn ferrite and Mn1−xZnxFe2O4 (x = 0.2 and 0.4) powders. However, M¨ossbauer spectra for x = 0.6 and 0.8 consisted of two six-line sub-spectra and a single quadrupole doublet, which indicated that they were ferromagnetic and paramagnetic: As the Zn concentration increased, the magnetic properties of the Mn1−xZnxFe2O4 powders changed from ferromagnetic to non-magnetic. The saturation magnetization of a pure Mn ferrite powder was 69.5 emu/g and for x = 0.2, it was 65.1 emu/g. The saturation magnetization decreased slowly as the Zn concentration was increased up to 40% and then decreased rapidly to zero. Mn-Zn ferrite powders had a typical soft magnetic property: The coercivity of the pure Mn ferrite powder was 128 Oe. The coercivities of the Mn1−xZnxFe2O4 powders decreased linearly as the Zn concentration was increased.