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.

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>

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

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.

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.

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.

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

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.

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

체결강도의 분포에 영향을 미치는 변수에 관한 실증 연구

강민 ( Mhin Kang ) 한국재무관리학회 2023 財務管理硏究 Vol.40 No.6

본 연구에서는 2011~2020년의 한국 주식시장에 상장된 보통주를 대상으로 체결강도의 분포에 영향을 미치는 변수에 대해 분석하였다. 분석 결과, 한국 주식시장에서는 매수체결 거래량에 비해 매도체결 거래량이 더 큰 비중을 차지하여 체결강도의 평균은 다른 나라의 주식시장에 비해 현저히 낮은 수치로 나타난다. 또한, 연평균 체결강도와 일별 체결강도는 개인투자자의 거래 비중이 적을수록, 주식의 규모, 수익률 변동성, 비유동성이 클수록 증가한다. 한편, 일별 체결강도는 수익률의 부호에 따라 수익률에 대한 민감도가 다르고, 분포 또한 불연속적으로 분절되어 나타나는데, 이러한 경향은 개인투자자의 비중이 클수록 더 강하게 나타난다. 이는 개인투자자의 불확실성 회피, 손실 회피 성향이 반영된 결과로 추정되며, 결과적으로 개인투자자의 투자행태가 한국주식시장의 체결강도의 고유한 특징을 유발하는 주요 원인인 것으로 판단된다. In this study, we analyze the factors affecting the distribution of volume power in the Korean stock market for common stocks listed from 2011 to 2020. The empirical results show that in the Korean stock market, the proportion of sell-initiated trading volume in relation to buy-initiated trading volume is larger, resulting in a significantly lower average volume power compared to other countries' stock markets. Furthermore, annual average volume power and daily volume power increase when the proportion of individual investors' trades is lower and when the size of stocks, return volatility, and illiquidity are higher. On the other hand, daily volume power exhibits different sensitivities to profit depending on its sign, and the distribution appears discontinuous. This tendency is more pronounced when individual investors have a higher proportion of trading. This is estimated to reflect the uncertainty aversion and loss aversion tendencies of individual investors and, consequently, is considered a significant factor contributing to the unique characteristics of volume power in the Korean stock market.