• 한국세라믹학회지
• /
• 제40권7호
• /
• pp.620-624
• /
• 2003

LiCo$_{y}$Mn$_{2-y}$O$_4$ samples were synthesized by calcining a mixture of LiOH.$H_2O$, MnO$_2$ (CMD) and CoCO$_3$ calcining at 40$0^{\circ}C$ for 10 h and then calcining twice at 75$0^{\circ}C$ for 24 h in air with intermediate grinding. All the synthesized samples exhibited XRD patterns for the cubic spinel phase with a space group Fd(equation omitted)m. The electrochemical cells were charged and discharged for 30 cycles at a current density 600 $mutextrm{A}$/$\textrm{cm}^2$ between 3.5 and 4.3 V. As the value of y increases, the size of particles becomes more homogeneous. The first discharge capacity decreases as the value of y increases, its value for y=0.00 being 92.8 mAh/g. The LiMn$_2$O$_4$ exhibits much better cycling performance than that reported earlier. The cycling performance increases as the value of y increases. The efficiency of discharge capacity is 98.9％ for y=0.30. The larger lattice parameter for the smaller value of y is related to the larger discharge capacity. The more quantity of the intercalated and the deintercalated Li in the sample with the larger discharge capacity brings about the larger capacity fading rate.ate.

• 대한수학교육학회지:학교수학
• /
• 제10권2호
• /
• pp.297-317
• /
• 2008

본 연구는 중등학교에서 CAS도입을 대비한 기초연구로 CAS 환경에서 모델링 문제해결 과정과 CAS 활용방식을 조사하였다. 수학교육과정 배경과 CAS 장착 정도가 문제해결과정과 CAS 사용전략에 변인이 될 가능성을 고려하여 비교연구로 수행하였으며 한 미 고등학교 2학년생 각 8명과 26명이 연구에 참여하였다. 연구결과 고전적 상자문제에서 CAS는 기호조작명령어와 그래프로 문제해결에 도움이 되었으나 수학적 개념이나 통찰을 대신하지 않았으며, 수학적 모델의 분석과 풀이, 결과 적용과 해석, CAS사용에 있어서 집단간 질적인 차이를 보였다. 수업을 통해 CAS 장착이 비교적 안정된 미국학생들 다수가, 한국 학생들과 대조적으로, 중간값 정리를 적용하여 해의 범위를 추정하는데 CAS를 사용하였으며 여러 표상의 연결을 시도하였다. CAS는 지필기법을 대신하는 데 그치지 않고, 실수의 소수표현과 대수적 표현, 수감각과 함수의 성질, 여러 표상의 연결성 등 대수통찰에 주목하게 하는 등 CAS의 가능성과 억제력은 대수교육에서 인식론적 변화와 교육과정 변화를 초래하는 것으로 나타났다.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.380-383
• /
• 2006

The media transport system is used in a printer, a ATM(Automated Tellor Machine), and so on. The media transport system has many problems through miniaturization and rapid transportation of these machines. In the paper feeding mechanism, it is important to feed the sheet without jamming under any conditions. To avoid sheet jamming, first we need to predict the behavior of the sheet exactly. In this paper, the analysis of media behavior is based on J. Stolte's studies. In all of OA machines, a flexible beam or plate is pushed from the channel. The motion may be constrained by guides. This leads to a transient and geometrically nonlinear problem. The behavior of paper is simulated by dynamic elastica theory. The shape of guide is represented by parametric cubic curve. But J. Stolte's studies did not considered contact condition between sheet and guide. So Klarbring's Model. will be applied. And the analysis of flexible media has to include aerodynamic effect for more exact behavior analysis, because the flexible media can be deformed drastically by a little force. Therefore aerodynamic force must be applied to the governing equation. Lastly, the simulation of this model is performed, and the experiment is performed for verification of this model. The experimental results of low exit velocity are consistent with the simulation results, however experimental results of high exit velocity do not agree well with analytical results. The reason is that there may be other effects like nip Phenomena

• 한국산림과학회지
• /
• 제3권1호
• /
• pp.10-14
• /
• 1963

광야소재(光陽所在) 천연성(天然性) 소나무에 대(對)하여 조사(調査)한 결과(結果)는 다음과 같다. 1. 수고성장(樹高成長) $H=4.76+0.125D+0.0026D^2$ 2. 소나무의 입목재적식(立木材積式)은 $V=0.0000839D^{2.3}H^{0.2}$ 3. 이용재적(利用材積)과 재장간(材長間)에는 Vu=0.1708-0.0230L 4. 이용율(利用率)은 재장(材長)을 2m로 했을 때 $P=27.37D^{0.3648}$ 5. 조재가능(造材可能)한 2m 재장(材長)의 수(數)는 $N=0.0863D^{1.16}$ 6. 이용재적식(利用材積式)은 재장(材長)을 2m로 했을 경우 $Vu=0.0000159D^2H^{1.3}$ 위의 결과(結果)는 종합적(綜合的)으로 재장(材長)을 2m 후 조재(造材)할 때 이용재적(利用材積)이 가장 많다는 것을 명백(明白)히 하였다.

• 접착 및 계면
• /
• 제9권1호
• /
• pp.22-27
• /
• 2008

아크릴 점착제의 점착력을 목표 수준으로 향상시키기 위해 실험계획법을 이용하여, 2-ethyl hexyl acrylate (2-EHA), ethyl acrylate (EA), metha acrylic acid (MAA), acryl amide (AAm)를 라디칼 용액 중합하여 점착력을 측정하였다. 실험계획법은 반응표면분석법의 하나인 혼합물 설계를 이용하여 특수 3차 모형으로 분석하였으며, 그 적용은 상용프로그램인 MINITAB을 사용하였다. 수립된 실험계획에 의해 실험하고 분석한 결과, 목표하는 점착력을 얻기 위한 단량체 조성은 2-EHA (0.8861), EA (0.0639), MAA (0.03), AAm (0.02)로 나타났으며, 그 회귀분석 식은 다음과 같았다. $$y=54.8816x_1+80.7067x_2-44.4700x_3-99.0288x_1x_2+60.7706x_1x_3-441.030x_2x_3+974.341x_1x_2x_3$$.

• 한국환경과학회지
• /
• 제25권5호
• /
• pp.737-744
• /
• 2016

For electrolysis process using an insoluble electrode, electrochemical performance was greatly affected by the manufacturing method and procedure, such as the firing temperature, pre-treatment, type of precursor solution, coating method, electrode material, etc. Components of the electrode therein is one of the most important factors in electrochemical reaction. To achieve such characteristics, a appropriate ratio of the electrode material should be carefully chosen. The aim of this research was to apply experimental design method in the optimization of electrode component for the maximum generation of oxidants in electrochemical oxidation process. Mixture design, especially expanded simplex lattice design, in DOME (design of mixture experiments) with Design Expert - commercial software - was used to analyze the data. Analysis of variance (ANOVA) showed a high coefficient of determination ($R^2$) value of 0.9470, thus ensuring a satisfactory adjustment of the $3^{rd}$ order special cubic regression model with the experimental data. The application of response surface methodology (RSM) yielded the following regression equation, which is an empirical relationship between the TRO generation concentration and independent variables(mol ratio of 3 electrode components) in a real unit: TRO generation concentration $(mg/L)=TRO\;conc.=98.25{\times}[Ir]+49.71{\times}[Sn]+95.29{\times}[Sb]-16.91{\times}[Ir]{\times}[Sn]-29.47{\times}[Ir]{\times}[Sb]-22.65{\times}[Sn]{\times}[Sb]+703.19{\times}[Ir]{\times}[Sn]{\times}[Sb]$. The optimized formulation of the 3 component electrode for an high TRO (total residual oxidants) generation was acquired at mol ratio of Ir 0.406, Sn 0.210, Sb 0.384 (desirability d value, 1).

• 한국포장학회지
• /
• 제9권1호
• /
• pp.33-54
• /
• 2003

The aim of this study was to develop a model that could be used in the design of modified atmosphere packaging (MAP) for peaches. Respiratory data at 5, 10, $20^{\circ}C$ for peaches were gathered and altered for create useful respiration model. Packaging materials were conventional low density polyethylene and polypropylene with anti-fog, and anti-fungi treatments, and thickness was $30{\mu}m$ and $50{\mu}m$ each. Permeability tests were performed to find their oxygen, carbon dioxide, water vapor transmission rate as increases in temperature. Test results were then converted to logarithm format for MAP modeling. The maximum rate of oxygen uptake increased with increasing temperature. Optimum gas composition in the package system for fruits were set according to literature and upper or lower limits of oxygen and dioxide established. To predict gas composition at certain storage time, weight of fruits, film thickness, film type, and other variables, respiration rate was studied at various storage conditions. The results of tests were used to calculate Cameron's model and converted to a cubic estimation equation. The validity of the model was tested experimentally by observing actual atmospheric changes inside packages. This result of study may be useful for designing dynamic gas exchange MAP systems for similar agricultural products.

• 한국재료학회지
• /
• 제22권7호
• /
• pp.342-345
• /
• 2012

The dielectric properties and phase transformation of poled <001>-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$(PMN-x%PT) single crystals with compositions of x = 20, 30, and 35 mole% are investigated for orientations both parallel and perpendicular to the [001] poling direction. An electric-field-induced monoclinic phase was observed for the initial poled PMN-30PT and PMN-35PT samples by means of high-resolution synchrotron x-ray diffraction. The monoclinic phase appears from $-25^{\circ}C$ to $100^{\circ}C$ and from $-25^{\circ}C$ to $80^{\circ}C$ for the PMN-30PT and PMN-35PT samples, respectively. The dielectric constant (${\varepsilon}$)-temperature (T) characteristics above the Curie temperature were found to be described by the equation$(1/{\varepsilon}-1/{\varepsilon}_m)^{1/n}=(T-T_m)/C$, where ${\varepsilon}_m$ is the maximum dielectric constant and $T_m$ is the temperature giving ${\varepsilon}_m$, and n and C are constants that change with the composition. The value of n was found to be 1.82 and 1.38 for 20PT and 35PT, respectively. The results of mesh scans and the temperature-dependence of the dielectric constant demonstrate that the initial monoclinic phase changes to a single domain tetragonal phase and a to paraelectric cubic phase. In the ferroelectric tetragonal phase with a single domain state, the dielectric constant measured perpendicular to the poling direction was dramatically higher than that measured in the parallel direction. A large dielectric constant implies easier polarization rotation away from the polar axis. This enhancement is believed to be related to dielectric softening close to the morphotropic phase boundary.

• 한국융합학회논문지
• /
• 제10권4호
• /
• pp.139-145
• /
• 2019

이 논문은 복합 입체형 트러스 단위구조체에 대한 강도 및 강성을 연구하였다. 사용된 모델은카고메 모델과 정육면체 트러스 모델을 합한 core-filled 모델이다. 해석을 위해 사용한 재질 특성은 304 스테인레스 스틸로 탄성계수는 193GPa, 항복응력 215MPa이다. 이론식은 깁슨-애쉬비의 상대탄성 관계식을 바탕으로 이론식을 유도하였고, 상용도구인 Deform 3D를 사용하여 해석을 실시하였다. 결론적으로 이 단위모델에 대한 상대탄성력은 상대밀도의 1.25배와 상수 계수값과 상관관계를 형성하고, 탄성은 기공과 반비례한다. 그리고, 상대압축강도는 상대밀도와 1.25배의 상관관계를 이룬다. 이에 대한 증명은 실제 실험을 해야 하겠으며, 유도한 이론 관계식은 굽힘과 좌굴등의 기계적 거동을 추가로 고려해야 한다. 앞으로 입체공간의 구조에 따른 탄성 및 응력에 대해 지속적인 연구가 진행될 것이다.

• 대한금속재료학회지
• /
• 제46권6호
• /
• pp.338-344
• /
• 2008

The crystallization kinetics of the $Cu_{43}Zr_{43}Al_7Be_7$ bulk metallic glass were studied by differential scanning calorimetry(DSC) in the continuous heating and isothermal annealing modes. Only one major peak could be detected on the DSC traces of $Cu_{43}Zr_{43}Al_7Be_7$ bulk amorphous alloy, and the activation energy for crystallization corresponding to the peak determined by the Kissinger method was resulted of 239 kJ/mol. The isothermal kinetic, analyzed by the Johnson-Mehl-Avrami equation yielded values for the Avrami exponents in the range 1.69 to 2.37, which implied a crystallization governed by a three-dimensioned growth. Primary phases were essentially the cubic structure CuZr together with the $Cu_{10}Zr_7$ phase. At higher temperature, the CuZr disappeared while the $Cu_{10}Zr_7$ became predominant. After long term annealing at 731 K, the phases were $Cu_{10}Zr_7$, $Cu_2ZrAl$ and $Al_3Zr_5$.