短距離競走에 대한 Keller model의 고찰

정근희 濟州大學校 1986 국내석사

The Study of Patterned Media Using Nanoimprint Lithography and the Magnetic Anisotropy of Co-Pt Thin Films

정근희 성균관대학교 일반대학원 2009 국내박사

As promising high density recording media, patterned media can allow storage density to climb to a few Tb/in2. To realize patterned media, it is imperative that the magnetic materials with high perpendicular magnetic anisotropy and nanopatterning technology with low cost and high throughput are developed. In this study, Co-Pt thin films were fabricated by using electrodeposition and sputterdeposition. The effects of the microstructure, the composition, and buffer layers on the magnetic properties of films were considered. For nanoscale patternning UV nanoimprint lithography was performed at various process conditions. Also, for inexpensive process Si, polymer, and Ni mould were fabricated by self-assembly such as nanosphere and anodic aluminum oxide, respectively. Finally Co-Pt dot arrays with 50 nm diameter were fabricated and characterized. XRD and TEM for texture analysis, VSM, torque magnetometer, and MFM for magnetic property analysis, XPS and EDS for chemical analysis were introduced.

2,3,4세 유아의 마음이해능력과 또래상호작용

정근희 서울대학교 대학원 2008 국내석사

펌프제어 기반의 전기-유압식 액추에이터를 적용한 액티브 안티롤바의 설계 및 개발

정근희 울산대학교 대학원 2017 국내석사

국내외 많은 자동차 제조 업체들의 새로운 기술을 선도하기 위한 경쟁은 계속해서 이루어지고 있다. 프리미엄 고성능 메이커의 제조사들은 그들의 R&D 예산의 80%를 서스펜션, 자동차 제어력과 관련된 파라미터, 고성능 드라이브 트레인에 투자하고 있다. 이처럼 서스펜션 혁신은 차체 제어를 포함한 승차감과 주행능력을 더욱 높이고 싶어하는 모든 제조 업체와 소비자들의 욕구와 함께 진전되고 있다. 본 연구는 서스펜션 분야의 한 부분인 안티롤바(Anti-roll bar)를 주제로 한다. 안티롤바는 자동차가 코너를 돌거나 지면의 불균형으로 인해 생기는 자동차의 롤 모션을 제어한다. 이를 통해서 자동차의 승차감과 주행안정성 그리고 자동차의 전복을 예방하는데 기여한다. 액티브 안티롤바에 대한 연구는 계속 이루어지고 있으나 대부분 실험장치를 이용하지 않은 시뮬레이션에 머무르는 연구가 대부분이다. 이는 자동차에 실제로 장착해서 실험하는데 비용이 많이 들어가기 때문이다. 본 논문에서는 자동차의 롤 모멘트를 묘사하는 실험장치를 함께 고려하여 성능을 검증하였다. 기존의 액티브 안티롤바에 관한 연구는 밸브블록을 이용해서 액추에이터의 동작을 제어하였다. 밸브블록을 이용한 액추에이터는 밸브블록, 릴리프 밸브 등에서 누유를 통한 에너지 손실 그리고 밸브블록으로 인한 자동차 내의 공간 및 무게를 차지하는 단점을 가지고 있다. 따라서 이를 해결하고자 본 논문에서는 펌프제어 기반의 전기-유압식 액티브 안티롤바를 제안하였다. 본 연구에서는 자동차의 수학적 모델링과 새롭게 제안된 액티브 안티롤바의 수학적 모델링을 상세히 제시하며, 자동차의 롤 모션을 효과적으로 제어하기 위한 제어기를 설계한다. 위의 모델링 결과를 적용하여 먼저 시뮬레이션을 통해서 성능을 검증하였으며 다음으로, 실험 장치를 제작하여 제안된 액티브 안티롤바의 성능을 검증하였다. 실험장치는 자동차의 롤 모멘트를 묘사하는 부하시스템과 펌프제어 기반의 전기-유압식 액티브 안티롤바 시스템이 연결되어 있다. 부하시스템은 밸브블록을 통해서 제어되며 밸브블록의 제어를 통해서 실제 자동차가 주행을 했을 때 액티브 안티롤바가 받는 롤 모멘트를 생성하며 이때 발생하는 롤 모멘트로 인해서 실린더의 변위가 변하게 된다. 실제 자동차가 받는 롤 모멘트를 생성하기 위해서 Carsim 소프트웨어를 이용하였다. 부하시스템의 롤 모멘트 생성으로 인해서 발생되는 실린더의 변위를 제안된 액티브 안티롤바 시스템을 사용해서 발생하는 롤 모멘트를 견뎌내며 자동차의 롤 각도를 최소화 하도록 PI제어기를 적용해서 제어하였다. 실험결과를 통해서 본 논문에서 제안하는 펌프제어 기반의 액추에이터를 적용한 액티브 안티롤바 시스템이 자동차의 롤 모멘트를 제어하여 자동차의 롤 모션을 억제하는 것을 증명하였다.

初生雛에 있어서 chromium의 毒性과 다른 元素들과의 相互作用

정근희 高麗大學校 大學院 1982 국내박사

Sputtering 法에 의한 NiFeMo 多層薄膜의 巨大 磁氣 임피던스 特性에 關한 硏究

정근희 成均館大學校 大學院 2003 국내석사

Micro-manetic sensors having hidh sensitivity and quick response are great demand for control systems for modern technology. There have been many exectations in developing MR sensors since the discovery of gaint magnetoresistance(GMR). The nominal values of resistance change can be very large (∼50 % in multilayers) however, the saturation fields are also large, and the sensitivity to the field still does not exceed 1 %/Oe. Bside, there are hysteresis and temperature instability problems. On the other hand, a vey high sensitivity to an external feld is typical of magnetoimpedance(MI) in soft ferromagnetic materials with well-defind anisotropy. Thus, in (CoFe)SiB amorphous wires having almost zero magnetostriction and a circular domain strucure, impedance change with the application of an external field can be as much as 10 to 100 %/Oe at frequencies of several megahertz. Magnetic sensors based on MI in amorphous wires, ribbons have been recently develped, which demonstrate the field detecttion resolution of 10^(-6) Oe with a sensor head length of 1mm. Aiming to develop sensors with micron dimensions on the basis of MI, advantages of thin-film technology have to be used. , ti Recently, large and sensitive changes in the alternating current magnetoimpedance(MI) effect with external magnetic field in nearly zero magnetostriction amorphous wires, ribbons, and films have been studied intensively, because of the increasing perspectives of novel applications in magnetic sensors. To applicate for magnetoimpedance sensor, sputter-deposited sandwich multilayer of NiFeMo/Cu/NiFeMo was studied. Varying the thickness of NiFeMo(2d), the ratio of anisotropy field to the coercivity (HK/HC) was obtained and compared with the magnetoimpedance (MI) ratio.They showed almost same profile to 2d. The heat treatment of above samples made similar result. We could conclude that well-defined anisotropy and magnetic softness were essential for high MI ratio. 2001 Elsevier Science. All rights reserved * A thesis submitted to the committed of Graduate School, Chungnam National University in partial fulfillment of the requrements for the degree of Doctor of Philosophy in Materials Engineering conferred in February 2000. The MI effect has a classical electromagnetic behavior where the impedance is changed under the application of a longitudinal magnetic field. The electromagnetic origin of the MI effect has been conjectured to the combination of the skin effect and the field dependence of the circumferential magnetic permeability associated with the circular motion of magnetic moment. Also, magnetic permeability has several definitions as the initial(μi), normal(μ), and incremental(μΔ) permeability. The incremental(μΔ) permeability is the slope on optional dc magnetic field and responds sensitively to the dc magnetic field. Therefore the incremental permeability is directly related to the MI effect. The incremental permeability measured in the function of the sweep dc magnetic field shows various shapes and values depending on the magnetic structure in the sample. The mumetal film is made of the NiFe alloys where the soft magnetic properties are improved by adding Mo and Cu. This film has a lower coercivity(H_(c)), saturation magnetization(M_(s)), and magnetic anisotropy than NiFe thin films due to the lower local anisotropy constant(H_(k)) and structure constant(S). We have prepared mumetal films by using a R.F magnetron sputtering method. First, we have studied the parameters of sputtering for the suitable fabrication such as Ar pressure, R.F input power, thickness, etc. Second, we have investigated the influence of such sputtering parameters on the MI effect and the incremental permeability. The mumetal films with 17 mm in diameter and 1-4 ㎛ in thickness were deposited on glass substrates. Ar gas was 99.999 % pure, and Ar pressure was 0.5∼5 mTorr. R.F input power was changed from 50 W to 500 W. The changes in the incremental permeability were measured with the circle shape films and the MI effect were measured with the strip shape sample with 15 mm in length and 2 mm in width by using a lithographic method. The direction of the width in the MI sample was adjusted to the magnetic easy axis or hard axis. The major experimental results are summarized in belows. 1. The sputtering yields of mumetal films have been increasing with the increment of Ar pressures and R.F input powers due to the increment of mean free path and the incidence energy of Ar into target. The composition of films are affected strongly by the Ar pressure than the R.F input power. 2. The proper fabrication condition for the soft magnetic properties in mumetal films is 1 mTorr of Ar pressure and 400W of input power. The composition of the film was Ni_(81.1)Fe_(14.2)Cu_(1.9)Mo_(2.8).(wt.%). The coercivity is 0.35 Oe and the effective permeability measured at 1 MHz is 3050. The coercivities and the effective permeabilities are proportional to the thicknesses of films. 3. We have obtained 32 % of the incremental transverse permeability ratio(TPR) measured at 2.1 MHz and 81 % of magnetoimpedance ratio(MIR) measured at 36.5 MHz. The TPR and MIR have been increased with the effective permeability and the thickness of films. In the case of the easy axis, TPR and MIR have shown the double peak patterns due to the transverse magnetic structure, and in the case of the hard axis, TPR and MIR have shown the single peak patterns due to the longitudinal magnetic structure. Also we have confined that the depth of double peaks are proportional to the magnetic anisotropy. 4. TPR and MIR in the sample annealed by a rapid temperature annealing(RTA) method with uniaxial magnetic field are larger than that of as-deposited samples. The sensitivity has been reached as much as 40%/Oe. Because the RTA with uniaxial magnetic field relaxes internal stress of the sample and induces the magnetic anisotropy without changing their microstructures. 5. The values and the depth of double peaks of TPR and MIR curves depend on the current and frequency. Since the magnetic moments and domain wall motion are changing sensitively with the magnetic field generated by the current and frequency as well as the external magnetic field.. 6. In the sample with hard axis MIR at 60.5 MHz shows the double peaks pattern and the sensitivity is about 29 %/Oe. This result indicates that there is the magnetic ripple effect due to the dispersion of the magnetic anisotropy. The mumetal films prepared by the R.F magnetron sputtering method have ultra soft magnetic properties extended to high frequency range which can be improved by the RTA method with uniaxial magnetic field. So the mumetal film annealed by RTA method with uniaxial magnetic field can be useful for the development of high speed and high sensitivity magnetic sensors at very low magnetic field. Cross-geometrical Cr/Co/Al-Ox/Co/Ni-Fe tunnel junctions were fabricated by magnetron sputtering. The insulating layer was formed by plasma oxidation of a thin Al layer in(Ar : O_(2) = 1:2, 1:3, 1:4) mixture gas. At uncoupled spin valve structure, the TMR ratio varies from coercivity difference between two electrodes. To enhance a coercivity(H_(c)) of Co bottom layer, Cr seed layer was deposited on the glass and it led to increase in coercivity of Co layer. As Cr thickness(t= 20, 30, 50 Å) increase, H_(c) of Co layer gradually increase, which was due to the formation of a static magnetic domain wall. As a oxidation time increased, the thickness of Al-O_(x) also increase, which was based on the oxidation kinetics of the formation of Al-O_(x). When the Al layer was over oxidized, the flat Co/Al-O_(x)/Co and the increased H_(c) was obtained, which was due to a decrease of a Neel coupling field and the oxidation of Co bottom layer. However, TMR ratio gradually decrease, which is thought to be a local formation of Co-O_(x) at the lower interface. The tunnel junction having a thinner Cr thickness than 30 Å showed a optimal oxidation behavior and the TMR ratio of 14 %, which was comparable to a tunnel junction without Cr seed layer. When the thick Cr seed layer than 30 Å was used for a tunnel junction, the bias voltage dependence deteriorated due to a non uniform formation of Al-O_(x) layer. The TMR ratio was decreased to half at 0.51 V. After annealing at 200 ℃, the TMR ratio increase to 19 %. When junction was annealed at 200 ℃, the estimated tunnel barrier width decreased and barrier height increased. This suggests that the remaining Al between the Al-O_(x) and the Co surface plays an important role in the effects of annealing and oxygen moves into insulator from Co bottom layer. The applied voltage of half TMR ratio enhance from 0.51 V to 0.56 V after annealing. These junctions have potential use as low-power field sensors and memory elements.

Aminophosphonic acid의 유도체 합성에 관한 연구

정근희 高麗大學校 1975 국내석사

魏晉 閨怨詩 硏究

정근희 忠南大學校 1993 국내석사

蕭綱 詩 硏究

정근희 忠南大學校 大學院 2006 국내박사

The purpose of this study is to explore the world of Xiao Gang's poetry by closely examining his 285 poems include in Xian Qin, Han, Wei Jin, the south and north dynasty poetry collected by Lu Qinli. This research clearly argues that Xiao Gang's poetry must be properly evaluated because he challenged traditional Confucian literary approaches and pursued a new poetic genre with originality. Xiao Gang known as EmperorJianwen, developed the palace style poetry in the Liang Dynasty (502-557). Palace style poetry means the literary practice of Xiao Gang and his group members. He is most prolific and contributes himself to developing palace style writing in the Liang Dynasty. His main subjects of the palace style poetry are on female and erotic. Xiao Gang expresses aesthetic sensation rather than the moral lesson through his works. He emphasizes on a poetic theory called "licentious" in the literature. He asserts that poetry must be written with the theory which is the new view of the literature. Unlike other literary theories which focus on the moral lesson, his theory search for the freedom of writings. He emphasize that the subject of the poetry is freely chosen. He explore a variety of subjects different from erotic poems. Xiao Gang's poems combine popular literature with aristocratic literature. In conclusion, Xiao Gang's poetry asserting "licentious" theories expanded poetic subjects in the history of poetry, refined the beauty of poetic form, and provided great influence to the following period. Xiao Gang's poems affect not only the poetry of the Liang dynasty but also of other dynasties. The palace style poetry flourished for a century from Liang dynasty to early Tang. Xaio Gang's poems escpecially affect other poets in the Chen Dynasty, who imitate Xiao Gang's poetic subjects and titles.

Nucleophilic aromatic substitutions in hexamethylphosphortriamide

정근희 서강대학교 대학원 화학과 1977 국내박사