The structural distortion by a Substituent : Monosubstituted Benzene Derivative cases

Mhin, Byung-Jin 배재대학교 자연과학연구소 2004 自然科學論文集 Vol.15 No.1

The substituent dependence of geometric distortion through the two independent electronic substituent effects is analyzed for mono-substituted benzene derivatives of C_(2v). Based on resonance structures, quantitative relationships expressing the resonance and field/inductive contribution terms in bond distortions are derived. The calculated field-effect parts of C_(ipso)_C_(ortho) ring bonds increase and decrease compared to benzene for electropositive and electronegative substituents respectively. The nonbonded axial distance, C_(ipso) ‥‥C_(para') decreases for electronegative substituents and increases for electropositive substituents. As the electronegativity increases, the distance C_(ortho)‥‥C_(ortho') increases. With the π-donors, C_(meta)‥‥C_(meta') nonbonded distances are shorter compared to the ones of benzene, and for π-acceptors, they are longer. Our model based on valence bond approach predicts that the average bond length determines the area of ring, and the sum of the angle ∠C_(ortho)_C_(ipso)_C_(ortho) and ∠C_(meta)_C_(para)_C_(meta) determines the axial distance.

Simple synthetic route for hydroxyapatite colloidal nanoparticles via a Nd:YAG laser ablation in liquid medium

Mhin, Sung Wook,Ryu, Jeong Ho,Kim, Kang Min,Park, Gyeong Seon,Ryu, Han Wool,Shim, Kwang Bo,Sasaki, Takeshi,Koshizaki, Naoto Springer-Verlag 2009 APPLIED PHYSICS A MATERIALS SCIENCE AND PROCESSING Vol.96 No.2

Theoretical Study of 1,4,6,9-Tetra chlorinated dibenzo-$\rho$-dioxin anion

Mhin, Byung-Jin,Odde, Srinivas,Han, Kang-Hyun,Lee, Jung-Eun,Choi, Won-Yong 배재대학교 자연과학연구소 2005 自然科學論文集 Vol.16 No.1

The equilibrium geometry, adiabatic electron affinity, harmonic vibrational frequencies, and infrared intensities of 1,4,6,9-Tetra chlorinated dibenzo-$\rho$-dioxin anion have been studied using B3LYP method. The local minimum conformation is found to be twisted form with $D_2$ symmetry. The predicted adiabatic electron affinity is 0.54 eV. The predicted inversion barrier between twisted and planar conformers was 0.9 kcal/mol, thus we expect that experimentally observed structure seems to be planar. the characteristic IR band of 1,4,6,9-TCDD anion appears at 1510 $cm^4$, which is a benzene ring skeleton vibration mode related with CaCb and C2C3 bond. this characteristic band could be sued for identication of 1,4,6,9-TCDD anion.

Pulsed-Laser-Induced Simple Synthetic Route for Tb ₃ Al ₅ O ₁₂ :Ce ³⁺ Colloidal Nanocrystals and Their Luminescent Properties

Mhin, SungWook,Ryu, JeongHo,Kim, KangMin,Park, GyeongSeon,Ryu, HanWool,Shim, KwangBo,Sasaki, Takeshi,Koshizaki, Naoto Springer 2009 NANOSCALE RESEARCH LETTERS Vol.4 No.8

<P>Cerium-doped Tb<SUB>3</SUB>Al<SUB>5</SUB>O<SUB>12</SUB>(TAG:Ce<SUP>3+</SUP>) colloidal nanocrystals were synthesized by pulsed laser ablation (PLA) in de-ionized water and lauryl dimethylaminoacetic acid betain (LDA) aqueous solution for luminescent bio-labeling application. The influence of LDA molecules on the crystallinity, crystal morphology, crystallite size, and luminescent properties of the prepared TAG:Ce<SUP>3+</SUP>colloidal nanocrystals was investigated in detail. When the LDA solution was used, smaller average crystallite size, narrower size distribution, and enhanced luminescence were observed. These characteristics were explained by the effective role of occupying the oxygen defects on the surface of TAG:Ce<SUP>3+</SUP>colloidal nanocrystal because the amphoteric LDA molecules were attached by positively charged TAG:Ce<SUP>3+</SUP>colloidal nanocrystals. The blue-shifted phenomena found in luminescent spectra of the TAG:Ce<SUP>3+</SUP>colloidal nanocrystals could not be explained by previous crystal field theory. We discuss the 5d energy level of Ce<SUP>3+</SUP>with decreased crystal size with a phenomenological model that explains the relationship between bond distance with 5d energy level of Ce<SUP>3+</SUP>based on the concept of crystal field theory modified by covalency contribution.</P>

Processing, structure, and properties of lead-free piezoelectric NBT-BT

Mhin, Sungwook,Lee, Jung-Il,Ryu, Jeong Ho The Korea Association of Crystal Growth 2015 韓國結晶成長學會誌 Vol.25 No.4

Lead-free piezoelectric materials have been actively studied to substitute for conventional PZT based solid solution, $Pb(Zr_xTi_{1-x}O_3)$, which occurs unavoidable PbO during the sintering process. Among them, Bismuth Sodium Titanate, $Na_{0.5}Bi_{0.5}TiO_3$ (abbreviated as NBT) based solid solution is attracted for the one of excellent candidates which shows the strong ferroelectricity, Curie temperature (Tc), remnant polarization (Pr) and coercive field (Ec). Especially, the solid solution of rhombohedral phase NBT with tetragonal perovskite phase has a rhombohedral - tetragonal morphotropic phase boundary. Modified NBT with tetragonal perovskite at the region of MPB can be applied for high frequency ultrasonic application because of not only its low permittivity, high electrocoupling factor and high mechanical strength, but also effective piezoelectric activity by poling. In this study, solid state ceramic processing of NBT and modified NBT, $(Na_{0.5}Bi_{0.5})_{0.93}Ba_{0.7}TiO_3$ (abbreviated as NBT-7BT), at the region of MPB using 7 % $BaTiO_3$ as a tetragonal perovskite was introduced and the structure between NBT and NBT-7BT were analyzed using rietveld refinement. Also, the ferroelectric and piezoelectric properties of NBT-7BT such as permittivity, piezoelectric constant, polarization hysteresis and strain hysteresis loop were compared with those of pure NBT.

Phase evolution of (Ni, Co, Mn)O₄ during heat treatment with high temperature in situ X-ray diffraction

Mhin, S.,Han, H.,Kim, D.,Yeo, S.,Lee, J.I.,Ryu, J.H. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.4

Phase evolution of (Ni, Co, Mn)O<SUB>4</SUB> (NMC) for negative thermal coefficient (NTC) thermistor is investigated using high temperature X-ray diffraction. Diffraction patterns were collected during heating and cooling, allowing the observation of chemical reactions in the range of temperature between 25 and 1400<SUP>o</SUP>C. NiO, Mn<SUB>3</SUB>O<SUB>4</SUB> and CO<SUB>3</SUB>O<SUB>4</SUB> as the reactant materials were prepared using spray drying. As increasing temperature, phase transformation of Mn<SUB>3</SUB>O<SUB>4</SUB> to Mn<SUB>2</SUB>O<SUB>3</SUB> was first observed prior to the formation of NMC spinel structure at 700<SUP>o</SUP>C. Between 1000 and 1200<SUP>o</SUP>C, only spinel NMC was observed without any other phases. Also, grain growth of NMC was observed. Phase transition from cubic to tetragonal was observed during cooling. With further increasing temperature up to 1400<SUP>o</SUP>C, thermal stability of NMC decrease, which was confirmed by NiO separation due to the thermal decomposition. Thermogravimetric and differential thermal analysis are performed on NMC compound and the results support the mechanism of phase formation presented by high temperature XRD data. Also, electrical resistance of NMC is measured as a function of temperature (-40-80<SUP>o</SUP>C) and the factor of thermal sensitivity (B value) is calculated.

High-Density Crystalline/Amorphous Phase Boundaries in Electrochemically Activated Nickel-Doped Cobalt Sulfide for Efficient Oxygen Evolution Reaction

Sungwook Mhin 한국자기학회 2018 한국자기학회 학술연구발표회 논문개요집 Vol.2018 No.3

코스튬 주얼리 디자인의 구성요소 연구

민성원(Mhin, Sungwon),나건(Nah, Ken) 한국디자인지식학회 2015 디자인지식저널 Vol.33 No.-

글로벌 금융위기 이후, 지속되어 온 장기불황은 현대 사회에서 ‘가치소비’의 트렌드가 확산되고 있다. 이러한 경제 상황은 소비자들의 인식 변화를 일으켰고, ‘합리적인 감성소비"를 통해 소비욕구를 충족시켰다. 이는 실용 중심의 이성적 소비와 소비를 통해 즐거움을 얻고자 하는 감성적 소비를 동시에 추구하는 것을 의미한다. 주얼리 산업에서는 합리적인 감성소비로의 변화와 맞물려, 코스튬 주얼리(costume jewelry)의 소비가 세계적으로 증가하고 있음을 확인할 수 있었다. 이는 적은 비용으로 자신의 개성 표현을 하고싶은 현대 소비자들의 니즈를 충족시켜주기 때문으로 보인다. 코스튬 주얼리의 특징인 재료의 다양성은 형태와 재질, 색채면에서 현대 소비자들의 감성을 충족시켜 줄 수 있는 요소를 갖추고 있다. 본 연구는 이러한 소비자의 감성에 초점을 맞춘 코스튬 주얼리 디자인 구성요소를 바탕으로 향후 코스튬 주얼리 연구에 뒷받침해 줄 연구자료로써 의미가 있을 것으로 보인다. After the financial crisis across the world, the stagnation in modern society has led to the spread of trend, ‘value consumption’. The paradigm of the ‘value consumption’ changed customer’s perception in value and satisfies the desire of consumers through reasonable and emotional consumption. In other words, consumers not only want to spend wisely, but also start to pursue the emotional satisfaction through spending. The fast growth in the market of costume jewelry is supported by the trend of consumers’ reasonable and emotional spending. The popularity of the business implies that the reasonable price and unique design to please the consumers fulfill the consumers’ needs. Also, the use of a variety of raw materials with different texture, colors and patterns can give the free of selection to customers and is another reason to expand the business in the market of the costume jewelry across the world. These advantages of costume jewelry must be exploited fully, and encourage the development of domestic costume jewelry market. This research is focused on the elements that is based on design of costume jewelry as emotion of customers. Furthermore, this study will be able to support future research on costume jewelry and will be valuable for ongoing development of jewelry industry.

Electrochemically activated cobalt nickel sulfide for an efficient oxygen evolution reaction: partial amorphization and phase control

Sungwook Mhin,Hyuksu Han 한국자기학회 2019 한국자기학회 학술연구발표회 논문개요집 Vol.29 No.1

이재민 안정을 위한 임시 주거공간 내 필요요소 연구

민성원(Mhin, Sung Won),권근희(Kwon, Keun Hee),나건(Nah, Ken) 한국디지털디자인협의회 2015 디지털디자인학연구 Vol.15 No.3

세계적인 이상기후로 인한 자연재난과 재해가 증가하고, 연쇄적으로 인위재난까지 겹쳐 대규모 재해가 발생하여 인명피해와 재산피해가 상당하다. 이에 따라 이재민 등의 극한 상황에 부합하는 임시 주거공간의 필요성은 더욱 증가하고 있지만 여전히 미흡한 상황이다. 외상 후 스트레스에 의해 육체적, 정신적으로 지쳐 있는 이재민의 행태를 중심으로 하는 임시 주거공간 내 다양한 영역 확보가 필요하다는 인식 하에 재해의 특성을 대규모피해자 단위와 소규모피해자 단위로 재해석하였다. 대규모피해자 단위의 재해를 중심으로 최근 10년간 발생한 재해 상황 등을 재분류, 분석한 결과, 광역에 걸쳐 발생하는 호우 재해가 가장 큰 피해를 미치는 것을 알 수 있다. 호우의 복구기간에 따른 임시 주거공간의 필요성을 보았을 때 일주일에서 6개월 내에 이용 가능한 임시 주거공간을 고려할 필요가 있다. 임시 주거공간 내 이재민의 심리적 행태는 그리프사이클에 따라 다양한 감정 상태로 표출된다는 결과를 통해 이재민의 니즈를 분석한 결과, 첫 번째로 임시 주거공간내에서 가장 기본적인 욕구들을 해소하여 신체적 안정을 갖기를 원하며. 두 번째로 프라이버시를 보장 받을수 있는 공간 확보를 원함과 동시에 정보교환 등을 할 수 있는 이해 관계자 간의 다양한 소통 공간을 필요로 하고 있었다. 근본적으로 이재민들은 최소한 인간으로서 존엄성을 보호받기 원한다는 것을 파악할 수 있다. 따라서 임시 주거공간의 영역을 공간적 범위와 속성에 따라 주거공간, 공유공간, 편의공간으로 분류한다. 이에 대응하는 공간 내부구성의 디자인적 환경요소를 고려한 공간의 확보를 통해 절박한 상황의 이재민이 효율적으로 적응할 수 있도록 해야 한다. 이 경우, 공간의 형태, 조명, 그리고 파티션의 높이 등은 공간의 영역 성을 제공, 인지시킬 뿐만 아니라 심리적인 불안감을 해소해준다. 따라서 공간의 영역성을 고려하여 설계해야 하며, 재난 현장에 대한 신속한 대처와 건조물 설치에도 재난피해자들의 심리적 안정요소를 고려한 디자인적 연구와 그 대안의 필요가 절실한 것이다. Increased nature disasters due to the abnormal climate cause damage to the property and human worldwide. However, the need for temporary housing is increased, but harsh condition. Critical factors in temporary housing are needed for victims who suffered from post traumatic stress disorder. The properties of disasters in small and big scale are reinterpreted through case study. Big scale disasters in 10 years are reclassified. Based on the reclassification, it is suggested that available shelter from 1 week to 6 months are essential. A mental state of victims can be changed by Grief’s cycle stage. Refugees want to satisfy fundamental needs and secondly, available spaces for effective management system are needed. Finally, victims want human dignity to be protected through effective management system and private space. Temporary housing is reclassified as residential space, shared space, and convenience space based on the territory model. Elemental factors considered in space are suggested. Different factors, such as interior, lighting and the height of partition, not only make the victim to be aware of territoriality of temporary housing but also help to relieve anxiety. Therefore, territoriality of space and various factors for psychological stability of victims should be considered as design elements when the refugee camp is built.