• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.29-29
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• 2001

열전재료는 열전현상을 가지고 있어 열전발전과 열선냉각이 가능하기 때분에 해저용, 우주용, 군사용의 특수 전원으로 이미 실용화되어있고, 반도체, 레이저 다이오드, 적외선 검출소자 등의 냉각기로 쓰여지고 있어 많은 연구자들이 이들 재료에 대한 연구에 관을 갖고 열전특성을 향상시키기 위하여 많은 연구를 진행하고 있다 이들 열전재료는 사용 온도구역에 따라 3종류로 구분하고 있으며, 실온부근의 저온 영역(20$0^{\circ}C$)이하에서는 $Bi_2Te_3$계 재료, 중온영역(20$0^{\circ}C$~50$0^{\circ}C$)에서sms (Pb,Ge) Te계 재료, 고온영역(50$0^{\circ}C$~lOoo$^{\circ}C$)에서는 Si-Ge계 Fe Si계 재료가 이용되고 있다. 본 연구에서는 실온에서 성능지수가 높은 Bi_2(Te,Se)_3$에 대한 연구를 진행하였다. Bi_2(Te,Se)_3$계 열전재료는 기존의 공법인 Zone melting법을 이용하는 경우 성능지수가 높으나, 단위정이 Rhombohedral 구조파 기저면(basal plane)에 벽개성이 있는 관계로 재료의 적지 않은 손실과 가공상의 어려움이 있다. 또한 사료전체에 걸쳐 화학적으로 균질한 고용체를 얻는 것도 어려운 문제점으보 부각되고 있디 따라서 이와같은 문제점을 보완하기 위하여 용질원자의 편석감소, 고용도의 증가, 균일 고용체 형성, 결정립의 미세화등의 장점이 있는 급속응고법을 본 연구에 응용하였다. 본 연구에서는 위에서와 같은 급속응고의 장점과 대량 가공이 능늪한 연간압출공정을 이용하여 제조된 분말을 성형화 하였다. 특히 열간압출 가공에 있어서 압축다이 각 변화는 재료의 소성유동에 매우 중요한 역하을 하게되며, 이와 갇은 소성유동은 본 재료의 열전특성에 중요한 영향을 미치는 C 면 배양에 중요한 역할을 한 것으 로 기대된다. 이에 본 연구에서는 압출다이 각도 변화에 따른 미세조직변화와 이들 조직이 강도와 열전특성에 미치는 영향을 석하고자 한다. 압출재의 미세조직은 XRD(X Ray Diffraction), SEM(Scanning Electron Microscopy)으로 분석하였으며, 열전특성인 Seebeck계수($\alpha$)와 전기비저항( $\rho$ )은 열전측정장치로, 기계적 강도는 MTS장비를 이용하여 이루어졌다. 또한 압축다이각도 변화에 따른 결정방위 해석은 모노크로미터가 장착된 X RD장비감 이용하여 분석되었다.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.1-7
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• 2006

The Primary type of swinging motion in human movement is that which is characteristic of a pendulum. The two types of pendulums are identified as simple and compound. A simple pendulum consist of a small body suspended by a relatively long cord. Its total mass is contained within the bob. The cord is not considered to have mass. A compound pendulum, on the other hand, is any pendulum such as the human body swinging by hands from a horizontal bar. Therefore a compound pendulum depicts important motions that are harmonic, periodic, and oscillatory. In this paper one discusses and compares two algorithms of Newton's method(F = m a) and Euler's method (M = $I{\times}{\alpha}$) in compound pendulum. Through exercise model such as human body with weight(m = 50 kg), body length(L = 1.5m), and center of gravity ($L_c$ = 0.4119L) from proximal end swinging by hands from a horizontal bar, one finds kinematic variables(angle displacement / velocity / acceleration), and simulates kinematic variables by changing body lengths and body mass. BSP by Clauser et al.(1969) & Chandler et al.(1975) is used to find moment of inertia of the compound pendulum. The radius of gyration about center of gravity (CoG) is $k_c\;=\;K_c{\times}L$ (단, k= radius of gyration, K= radius of gyration /segment length), and then moment of inertia about center of gravity(CoG) becomes $I_c\;=\;m\;k_c^2$. Finally, moment of inertia about Z-axis by parallel theorem becomes $I_o\;=\;I_c\;+\;m\;k^2$. The two-order ordinary differential equations of models are solved by ND function of numeric analysis method in Mathematica5.1. The results are as follows; First, The complexity of Newton's method is much more complex than that of Euler's method Second, one could be find kinematic variables according to changing body lengths(L = 1.3 / 1.7 m) and periods are increased by body length increment(L = 1.3 / 1.5 / 1.7 m). Third, one could be find that periods are not changing by means of changing mass(m = 50 / 55 / 60 kg). Conclusively, one is intended to meditate the possibility of applying a compound pendulum to sports(balling, golf, gymnastics and so on) necessary swinging motions. Further improvements to the study could be to apply Euler's method to real motions and one would be able to develop the simulator.

• PNF and Movement
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• v.14 no.3
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• pp.185-193
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• 2016

Purpose: The purpose of this study was to investigate the effects of neck patterns in proprioceptive neuromuscular facilitation (PNF) for neck movement and the neck disability index (NDI) among adults with forward head posture. Methods: Thirty-nine subjects were randomly assigned into two groups. Subjects in the proprioceptive neuromuscular facilitation exercise group (PNFG, n = 20) received 20 minutes of PNF neck pattern (flexion-Rt. lateral flexion-Rt. rotation followed by extension-Lt. lateral flexion-Lt. rotation) 3 times weekly for 4 weeks. Outcomes were measured using absolute rotation angle (ARA), anterior weight bearing (AWB), range of flexion and extension motions (RFEM), and neck disability index (NDI) methods before and after the 4-week intervention period. Results: There were significant effects for the PNFG, pre- and post-intervention, in ARA, AWB, RFEM, and NDI. There were significant differences in ARA, AWB, RFEM, and NDI compared with CG. Conclusion: The results of this study suggest the PNF neck pattern could be beneficial for adults with forward head posture.Purpose: This study investigates how abdominal muscular exercise based on proprioceptive neuromuscular facilitation (PNF) can affect chronic low back pain patients in terms of their pulmonary function, pain, and functional disability indexes. Methods: Fourteen target subjects with chronic low back were randomly assigned to the control group (n = 7) that performed abdominal muscle exercises and the experimental group (n = 7) that performed PNF abdominal muscular exercises. The exercises were performed five times a week for six weeks. To check the change in pulmonary function, the forced expiratory volume at one second (FEV1) and visible analogue scale (VAS) were measured to check the pain level. The disability level caused by back pain was measured by the Oswestry Disability Index (ODI). A paired t-test was applied to compare the differences between the groups before and after the intervention, and an independent t-test was used to compare the differences between the groups. The level of statistical significance was set as ${\alpha}=0.05$. Results: Before and after the intervention, the experimental group showed a significant change in FEV1 (p < 0.01), and both the experimental and the control groups showed significant changes in VAS and ODI (p < 0.01). A comparison of the differences between the groups indicated that the experimental group showed more significant changes in FEV1 (p < 0.05). Conclusion: According to the study results, PNF abdominal muscular exercise effectively improved pulmonary function, pain, and functional disability indexes in subjects with chronic back pain. The proposed program can be applied to chronic back pain patients as a useful therapy.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.644-652
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• 2007

Statement of problem: Resonance frequency analysis is evaluated as the non-invasive and objective method for the evaluation of implant stability and has been increasingly used. It is necessary to evaluate the factors affect the ISQ measurement stability. Purpose: This study was performed to evaluate the effect of the autoclave sterilization and reuse of $Smartpeg^{TM}$ on ISQ measurement. Material and methods: $SmartPeg^{TM}$ (Integration Diagnostics Ltd., $G\ddot{o}teborg$, Sweden) of autoclave group (A) was autoclave sterilized 9 times and $Smartpeg^{TM}$ of reuse group (R) was reused 9 times. Ten $SmartPeg^{TM}s$ were allocated to each group and after each autoclave sterilization and reuse, implant stability quotient (ISQ) values were measured 3 times from the two directions a and b at a right angle. $Osstell^{TM}$ mentor (Integration Diagnostics Ltd. $G\ddot{o}teborg$, Sweden) was used and type 1 (article no. 100353) $Smartpeg^{TM}$ was selected according to $Smartpeg^{TM}$ reference list. Osstem Implant US II future (Osstem Co., Seoul, Korea) in $4.0mm{\times}11.5mm$ was embedded in the self-curing acrylic resin ($Orthojet^{(R)}$, Lang Dental, U.S.A.). Data was statistically analyzed by one-way ANOVA $({\alpha}=.05)$ and scheffe test was done where a significant difference exist. Correlation test was also done between ISQ value and the number of autoclave sterilization or reuse. Results: 1. In autoclave group, the means and sd. of ISQ value before autoclave sterilization were $84.97{\pm}0.41,\;84.93{\pm}0.74$ at direction a and b. There was significant differences between autoclave groups at direction a and b (P=.000). 2. In reuse group, the means and sd. of ISQ value before reuse were $85.40{\pm}0.62,\;85.50{\pm}0.57$ at direction a and b. There was no significant difference between reuse groups at direction a and b (P>.05). 3. There was a weak positive correlation between the number of reuse and ISQ value at direction a and b (${\gamma}=.207$ and .246, P<.01). Conclusion: Within the limitations of this study, the following conclusions were drawn. Till ninth reuse of $Smartpeg^{TM}$, the ISQ measurement stability did not be affected. After twice autoclave sterilization of $Smartpeg^{TM}$ the ISQ measurement stability was affected.

• Journal of the Korean Chemical Society
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• v.25 no.6
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• pp.343-350
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• 1981

The crystal and molecular structure of P-aminobenzaldehyde cyclohexylthiosemicarbazone, C14H20N4S, has been determined from 2712 integrated intensities measured on a computer controlled four circle diffractometer with monochromated $CuK_{\alpha}$, X-ray radiation. The crystals are monoclinic, space group C2/c with eight molecules in a unit cell of dimensions, a = 12.488(2), b = 12.276(4), c = 19.997(6)${\AA}$ and ${\beta}=103.55(3)^{\circ}$. The structure was solved by Patterson and Fourier method and refined by a full-matrix least squares method to a final R value of 0.058 for all reflections. The C(8)-S bond is trans to N(2)-N(3) and C(8)-N(1) is cis to N(2)-N(3) bond. The cyclohexane ring has chair conformation and makes an angle of $40.7^{\circ}$ with the benzene ring. The molecules are linked by N(2)H…S hydrogen bonds into dimer-like units which are held together by $N-H{\ldots}N$ hydrogen bonds. Sulfur accepts second rather weak hydrogen bond from N(4). An intramolecular hydrogen bond exists between N(1) and N(3) atoms.

• Physical Therapy Korea
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• v.25 no.3
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• pp.19-26
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• 2018

Background: Genu varum is also known as bow leg. It is a deformity wherein there is lateral bowing of the legs at the knee. it does give rise to pain, and persistent bowing can often give rise to discomfort in knees, hips and ankles. Objects: This study investigated the effect of narrow squats on the knee joint during a gait and distance between the knees of person with genu varum. Methods: This study analyzed 23 patient with genu varum that grade III, 12 narrow squat group and 11 genenal squat group in motion analysis laboratory. The subjects of experiment took gait before and after intervention, the range of joint motion, moment of knee joint adduction, power, distance of the knees were measured. And in order to make an analysis between groups, an paiered t-test and independent t-test was carried out. For statistical significance testing, it was decided that significance level ${\alpha}$ be .05. Results: It was shown that the group of narrow squat exercise significantly decreased in distance of knees (p<.05),In moment of adduction of knee joint, it was shown to significantly decrease in two groups (p<.05), was significantly decreased in adduction, abduction, and rotation (p<.05). In relation of peak-knee adduction moment and valgus angle, there was significant decrease in narrow squat group (p<.05). Conclusion: When the above result of study were examined, a narrow squat exercise given to the genu varum patients significantly decreased the distance between the knees, range of knee adduction and abduction, knee adduction moment, knee power. And stability gains through the decrease of excursion of knee medial part be effective for the correction of genu varum deformation.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.973-979
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• 2001

Tin-doped indium oxide (ITO) thin films were deposited using r.f. magnetron reactive sputtering and the electrical properties, such as the resistivity, carrier concentration and mobility, were investigated as a function of the sample position under a given magnetron sputtering condition. The nonhomogeneity of the electrical properties with the sample position was observed under a given magnetron sputtering condition. The resistivity of ITO thin film on the substrate which corresponded to the center of the target had a minimum value, 2∼4$\times$10$\^$-4/$\Omega$$.$cm, and it increased symmetrically when the substrate deviated from the center. The density measurement result also showed that ITO thin film deposited at the center has a maximum density of 7.0g/cm$^3$, which was a relative density of about 97%, and the density decreased symmetrically as the substrate deviated from the center. The nonhomogeneity of electrical properties with the deposition position could be explained with the incidence angle of the source beam alpha, which is related with an atomic self-shadowing effect. It was confirmed experimentally that the density in film affect both the carrier mobility and the conductivity. In the case where the density of ITO thin film is 7.0g/cm$^3$, the magnitude of the mean free path was identical with that of the grain size(the diameter of column). However, in the other cases, the mean free path was smaller than the grain size. These results showed that the scattering of the free electrons at the grain boundary is the major factor for the electrical conduction in ITO thin films having a high density, and there exists other scattering sources such as vacancies, holes, or pores in ITO thin films having a low density.ing a low density.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.174-174
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• 2000

A strong antiferromagnetic coupling in Fe/Si multilayered films (MLF) had been recently discovered and much consideration has been given to whether the coupling in the Fe/Si MLF system has the same origin as the metal/metal MLF. Nevertheless, the nature of the interfacial ron silicide is still controversial. On one hand, a metal/ semiconductor structure was suggested with a narrow band-gap semiconducting $\varepsilon$-FeSi spacer that mediates the coupling. However, some features show that the nature of coupling can be well understood in terms of the conventional metal/metal multilayered system. It is well known that both magneto-optical (MO) and optical properties of a metal depend strongly on their electronic structure that is also correlated with the atomic and chemical ordering. In this study, the nature of the interfacial regions is the Fe/Si multilayers has been investigated by the experimental and computer-simulated MO and optical spectroscopies. The Fe/Si MLF were prepared by rf-sputtering onto glass substrates at room temperature with the number of repetition N=50. The thickness of Fe sublayer was fixed at 3.0nm while the Si sublayer thickness was varied from 1.0 to 2.0 nm. The topmost layer of all the Fe/Si MLF is Fe. In order to carry out the computer simulations, the information on the MO and optical parameters of the materials that may constitute a real multilayered structure should be known in advance. For this purpose, we also prepared Fe, Si, FeSi2 and FeSi samples. The structural characterization of Fe/Si MLF was performed by low- and high -angle x-ray diffraction with a Cu-K$\alpha$ radiation and by transmission electron microscopy. A bulk $\varepsilon$-FeSi was also investigated. The MO and optical properties were measured at room temperature in the 1.0-4.7 eV energy range. The theoretical simulations of MO and optical properties for the Fe/Si MLF were performed by solving exactly a multireflection problem using the scattering matrix approach assuming various stoichiometries of a nonmagnetic spacer separating the antiferromagnetically coupled Fe layers. The simulated spectra of a model structure of FeSi2 or $\varepsilon$-FeSi as the spacer turned out to fail in explaining the experimental spectra of the Fe/Si MLF in both intensity and shape. Thus, the decisive disagreement between experimental and simulated MO and optical properties ruled out the hypothesis of FeSi2 and $\varepsilon$-FeSi as the nonmagnetic spacer. By supposing the spontaneous formation of a metallic ζ-FeSi, a reasonable agreement between experimental and simulated MO and optical spectra was obtained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.638-646
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• 2023

Recently, active research has been conducted to enhance the power characteristics and thermal stability of lithium-ion batteries (LiBs) by modifying separators using a ceramic coating method. However, since the thermal properties and surface features of the separator vary depending on the characteristics of the ceramic powders applied to the separator, it is crucial to manufacture ceramic powders optimized for the separator's performance. In this study, we evaluated the characteristics of three types of α-alumina (A-1, A-2, and A-3) produced with varying dispersant contents and milling times, in addition to commercial α-alumina (AES-11). Subsequently, the optimized powders (A-3) were coated onto the separator using an aqueous binder for comparison with the characteristics of an AES-11 coated separator and an uncoated PE separator. The A-3 coated separator improved electrolyte wettability with a low contact angle (44.69°) and increased puncture strength (538 gf). Furthermore, it exhibited excellent thermal stability, with a shrinkage value of 5.64% when exposed to 140℃ for 1 hour, compared to the AES11 coated separator (6.09%) and the bare PE separator (69.64%).

• The Journal of the Petrological Society of Korea
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• v.27 no.1
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• pp.1-15
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• 2018

The characteristics of the rock cleavage of Jurassic Geochang granite were analysed using the distribution of microcrack lengths and spacings. The length and spacing-cumulative diagrams for the six directions of rock cleavages were arranged in increasing order ($H2{\rightarrow}R1$) on the density (${\rho}$) of microcrack length. The various parameters were extracted through the combination of above two types of diagrams. The evaluation for the six directions of rock cleavages was performed using the four groups (I~IV) of parameters such as (I) intersection angle (${\alpha}-{\beta}$), exponent difference (${\lambda}_S-{\lambda}_L$), length of line (ol and ll'), length ratio (ol/os and ll'/sl'), mean length ((ss'+ll')/2), area of right-angled triangle (${\Delta}oaa_a^{\prime}$ and ${\Delta}obb_a^{\prime}$) and area difference (${\Delta}obb^{\prime}-{\Delta}oaa^{\prime}$ and ${\Delta}obb_a^{\prime}-{\Delta}oaa_a^{\prime}$), (II) length of line (oa and os) and area (${\Delta}oaa^{\prime}$), (III) length of line (sl') and length ratio (ss'/ll') and (IV) length of line (ob, ss' and ls') and area (${\Delta}obb^{\prime}$, ${\Delta}ll^{\prime}s^{\prime}$, ${\Delta}ss^{\prime}l^{\prime}$ and ⏢ll'ss'). The results of correlation analysis between the values of parameters for three rock cleavages and those for three planes are as follows. The values of parameters for three rock cleavages are in orders of (I) H(hardway, (H1 + H2)/2) < G(grain, (G1 + G2)/2) < R(rift, (R1 + R2)/2), (II) R < G < H, (III) G < H < R and (IV) H < G < R. On the contrary, the values of parameters for three planes are in orders of (I) R' < G' < H', (II) H' < G' < R' and (III and IV) R' < H' < G'. Especially the values of parameters belonging to group I and group II show mutual reverse orders. In conclusion, this type of correlation analysis is useful for discriminating three quarrying planes.