• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.108-108
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• 1998

최근의 GaN에 관한 연구는 주로 MOCVD법과 MBE법이 이용되고 있으며 대부분 800¬1$\alpha$)()t 정도의 고옹에서 이루어지고 었다. 그러나 이러한 고온 성장은 GaN 성장 과청에서 질 소 vacancy를 생성시켜 광특성을 저하시키고 청색 발광충인 InGaN 화합물에 In의 유입울 어 렵게 하며 저온에서보다 탄소 오염이 증가하는 동의 문제캠을 가지고 있다. 이러한 고온 생장 의 문제점을 해결하기 위한 방법중의 한 가지로 제시되고 있는 것이 저온 성장법이다. 본 연구 에 사용된 RPE-UHVCVD법은 Nz률 rf plasma로 $\sigma$acking하여 공급함으로써 NI-h롤 질소원으 로 사용하는 고온 성장의 청우와는 다르게 온도에 크게 의존하지 고 질소원올 공급할 수 있 어 저옹 성장이 가능하였다. 기판으로는 a - Alz03($\alpha$)()1)를 사용하였고 3족원은 TEGa(triethylgallium)이며,5족원으로는 6 6-nine Nz gas를 rf plasma로 cracking하여 활성 질소원올 공급하였다 .. Nz plasma로 질화처리 를 한 sapphire 표면 위에 G따애 핵생성충을 성장 옹도(350 t, 375 t, 400 t)와 성장시간(30 분,50 분) 그리고 VIllI비(1$\alpha$)(), 2뼈)둥을 변화시키면서 성장시킨 후 GaN 에피택시충을 450 $^{\circ}C$에서 120 분 동안 성장시켰다 .. XPS(x-ray photoelectron spectroscopy), XRD(x-ray d diffraction), AFM(atomic force microscope)둥올 이용하여 표면의 조성 및 morphology 변화와 결정성을 관찰하였다. X XPS 분석 결과 질화처리를 한 sapphire 표면에는 AlN가 형성되었다는 것을 확인 할 수 있 었으며 질화처리를 한 후 G따J 핵생성충올 성장시킨 경우에 morphology 변화를 AFM으로 살 펴본 결과 표면에 facet shape의 island가 형성되었고 이러한 결파는 질화처리 과청이 facet s shape의 island 형성을 촉진시킨다는 것을 알 수 있었다. 핵생성충의 성장온도가 중가함에 따 라 island의 모양은 round shape에서 facet shape으로 변화하였다. 이러한 표면의 morphology 변화와 GaN 에피택시충의 결정성과의 관계를 살펴보면 GaN 에피택시충 표면의 rms(root m mean square) roughness가 중가하는 경 우 XRD (j -rocking curve의 FWHM(full width half m maximum) 값이 감소하는 것으로 나타났다. 이러한 현상은 결정성의 향상이 columnar 성장과 관계가 었다는 것올 알 수 있었다 .. columnar 성장은 결함의 밀도가 낮은 column의 형생과 G GaN 에피택시충의 웅력 제거로 인해 G값{의 결정성을 향상시킬 수 있는 것으로 생각된다. 톡 히 고온 성장의 경우와는 달리 rms roughness의 중가가 100-150 A청도로 명탄한 표면올 유 지하면서 결정성을 향상시킬 수 있었다. 본 실험에서는 핵생성충올 375 t에서 30 분 생장시킨 경우에 hexagonal 모양의 island로 columnar 성장을 하였고 GaN 에피태시충의 결정성도 가장 향상되었다 이상의 결과로부터 RPE-UHVCVD법용 이용한 GaN 저온 성장에서도 GaN의 결청성올 향 상시킬 수 있음융 확인할 수 있었다.

• Food Science of Animal Resources
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• v.26 no.1
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• pp.28-36
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• 2006

This study was carried out to investigate the changes in physicochemical, microbiological and sensory properties on vacuum packaged Yakibuda products for Export during storage at $4{\pm}1^{\circ}C$ for 40 days. Yakibuda, Japanese favorite meat product, were produced with three different pork cuts or tenderloin (T1), loin (T2) and ham (T3). The pH of all produce was tend to increased with increase in storage period. After 40 days of storage, pH of T2 was significantly (p<0.05) higher compared to other treatments. TBARS and VBN values of all treatments were increased with increased storage period. The water holding capacity ranged $81.41{\sim}92.20%$ in T1, $81.13{\sim}94.51%$ in T2 and $82.93{\sim}87.50%$ in T3. The shear force of T3 was higher than that of other treatments during whole storage time. The number of microorganism (Total plate counts, Escherichia coli, Lactobacilli spp.) were below 3.0 $log_{10}CFU/cm^2$ during the whole storage period. In sensory evaluation, the score of overall acceptability were above 5.5 point in all products. The storage properties of vacuum packaged Yakibuda could be maintained for 40 days at $4{\pm}1^{\circ}C$ storage temperature.

• Korean Journal of Digital Imaging in Medicine
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• v.6 no.1
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• pp.24-30
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• 2003

Flat-panel detector(FPD) is the driving force for realizing the next gene ration of x-ray system. In this study, we developed amorphous selenium(a-Se) based flat-panel digital X-ray detector(DXD) for radiography. The prototype detector consists of an amorphous selenium layer and a thin-film transistor(TFT) array. Comparing to other papers1)-4), optimization of amorphous selenium and progress of evaporation were similar. The pixel pitch of fabricated detector was $139{\mu}m$, fill factor was 86%, and the size was 14"${\times}$8.5". Hand and test bar pattern images were acquired. A high modulation transfer function(MTF) factor was obtained: 58% at 3.0 lp/mm.

• Journal of Animal Science and Technology
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• v.53 no.2
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• pp.139-146
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• 2011

This study was carried out to investigated astaxanthin producing "Xanthophyllomyces dendrohous" on growth performances and meat quality in ducks. A total of 450 ducks (cheribery) were allotted into 3 groups. The three groups were control (commercial feed), treatment 1 (0.1% feed additives), and treatment 2 (0.2% feed additives). Each group had 3 replicates. Viable cell number of "Xanthophyllomyces dendrohous" is $1.0{\times}10^8$ cfu/g. Growth performance carried out during 39 days. Average weight gain was significantly higher (p<0.05) in treatment 2 than that of control. Feed conversion was significantly lower (p<0.05) in treatment 1 and 2 than that of control. The results of nutrients composition analysis of duck meat showed that treatment 1 and 2 had significantly lower (p<0.05) fat and cholesterol levels. Water holding capacity showed significantly higher (p<0.05) value than that of control. Both treatment groups showed lower (p<0.05) value than control in drip loss and shear force. Control showed higher unsaturated fatty acids(palmitic acid, stearic acid) content than treatment 1 and 2. Treatment 1 and 2 showed significantly lower (p<0.05) saturated fatty acids (oleic acid, linoleic acid) levels than control. These results suggested that the supplementation of feed additives containing "Xanthophyllomyces dendrohous" might be used effectively for inproving productivity and meat quality of ducks.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.3
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• pp.295-313
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• 2006

Statement of problem. Higher fracture rates were reported for Branemark implants placed in the maxilla and for 3.75 mm diameter implants installed in the posterior region. Purpose. The purpose of this study was to investigate the fracture of a fixture by finite element analysis and to compare different diameter of fixtures according to the level of alveolar bone resorption. Material and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for the 3i implant systems. Models were processed by the software programs HyperMesh and ANSA. Three-dimensional finite element models were developed for; (1) a regular titanium implant 3.75 mm in diameter and 13 mm in length (2) a regular titanium implant 4.0 mm in diameter and 13 mm in length (3) a wide titanium implant 5.0 mm in diameter and 13 mm in length each with a cementation type abutment and titanium alloy screw. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized as 650 N, and round and flat type prostheses were 12 mm in diameter, 9 mm in height were loaded to 600 N. Four loading offset points (0, 2, 4, and 6 mm from the center of the implants) were evaluated. To evaluate fixture fracture by alveolar bone resorption, we investigated the stress distribution of the fixtures according to different alveola. bone loss levels (0, 1.5, 3.5, and 5.0 mm of alveolar bone loss). Using these 12 models (four degrees of bone loss and three implant diameters), the effects of load-ing offset, the effect of alveolar bone resorption and the size of fixtures were evaluated. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView programs were used for post processing. Results. The results from our experiment are as follows: 1. Preload maintains implant-abutment joint stability within a limited offset point against occlusal force. 2. Von Mises stress of the implant, abutment screw, abutment, and bone was decreased with in-creasing of the implant diameter. 3. With severe advancing of alveolar bone resorption, fracture of the 3.75 and the 4.0 mm diameter implant was possible. 4. With increasing of bending stress by loading offset, fracture of the abutment screw was possible.

• Food Science of Animal Resources
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• v.24 no.2
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• pp.115-120
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• 2004

This study was carried out to investigate the effect of the scalding temperature at slaughtering process on meat quality and storage properties of chicken. The yellowness (b$\^$*/ value) of skin decreased at high scalding temperature (65-67$^{\circ}C$) and WHC (water holding capacity) increased from 67.04％ at low temperature (53-55$^{\circ}C$) to 69.26％ at high temperature. WBS (Warner-Bratzler Shear force) significantly increased from 1.70kg/0.5inch$^2$ to 2.54kg/0.5inch$^2$ as the scalding temperature increased (p＜0.05). TBARS (Thiobarbituric Acid-Reactive Substance) values were 0.25mgMA/kg at low temperature, 0.24mgMA/kg at middle temperature (59-61$^{\circ}C$) and 0.27mgMA/kg on 3 days of storage. Total aerobic counts (TPC) were 4.99 logCFU/mL at low temperature, 4.88 10gCFU/mL at middle temperature and 4.05 logCFU/mL. Although TPC was decreased as the scalding temperature increased. The detection rate of feather at carcass inspection was low as the scalding temperature increased and the detection rate of large feather (＞lcm) was not significantly different between middle temperature and high temperature. Exposed flesh was severe as the scalding temperature increased. In conclusion, meat color and physical properties of chicken were acceptable when the carcasses were scalded at low temperature, but they were microbiologically susceptible and uneasy to remove the feather. The yellowness (b$\^$*/ value) of skin decreased at high scalding temperature, and total aerobic counts (TPC) were decreased as the scalding temperature increased, and easy to remove the feather.

• Elastomers and Composites
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• v.39 no.1
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• pp.12-22
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• 2004

The plasma surface modification of natural rubber vulcanizate was carried out using chlorodifluoromethane in a radio-frequency (13.56 MHz) electrodeless bell type plasma reactor. The modification was qualitatively assessed by Fourier transform infrared spectroscopy. The frictional force of the plasma-treated surface was found to decrease with the time of plasma treatment. An increase in the surface polarity, as evidenced by the decrease in contact angle of a sessile drop of water and ethylene glycol on the natural rubber vulcanizate surface, was noted with the plasma modification. In the case of similar plasma treatment of glass surface, only a reduction in the polarity was observed. The use of geometric and harmonic mean methods was found to be useful to evaluate the London dispersive and specific components of surface free energy. Irrespective of the method used for evaluation, an increasing trend in the surface free energy was noted with increasing plasma treatment time. However, the harmonic mean method yielded comparatively higher values of surface free energy than the geometric mean method. The plasma surface modification was found to vary the frictional coefficient by influencing the interfacial, hysteresis and viscous components of friction in opposing dual manners.

• Korean Journal of Food Science and Technology
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• v.32 no.1
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• pp.102-110
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• 2000

Peeled garlic was stored at $-18^{\circ}C\;and\;-40^{\circ}C$, respectively and changes in main quality factors during storage were determined for $15{\sim}16$ months. The puncture force measured by texturemeter was $2709{\pm}368$ G.S at the beginning of storage and did not change significantly after the 15 months storage. Drip losses of stored garlic were 0.4% and 0.7% at $-18^{\circ}C\;and\;-40^{\circ}C$, respectively. Major flavor compounds of garlic analyzed by GC and GC/MS, such as diallyl disulfide, 1,3-dithiane, diallyl sulfide, 2-butanal, were not changed in their quantity during the frozen storage. The contents of cysteine, valine and tyrosine increased slightly notwithstanding the storage temperature. Sucrose content slightly decreased, but glucose and fructose tended to increase in garlic stored at $-18^{\circ}C$. The content of pyruvic acid, degradation product of alliin, did not change during storage at both storage temperatures. These results indicated that peeled garlic could be stored at $-18^{\circ}C$ for longer than 15 months without quality problems.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.6
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• pp.742-749
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• 2009

In order to establish the basic scientific data on the fermentation characteristics of chonggak kimchi (CGK), we studied with CGKs prepared at different seasons and stored at various temperatures ($5{\sim}23^{\circ}C$). Changes in pH and acidity of CGK fermented at different temperatures were typical. However, acidity of summer CGK stored under $15^{\circ}C$ did not reach 1.0% since the amount of reducing sugar in the summer radish was lower by over 1% than the ones from the other seasons. Growths for Leuconostoc and Lactobacillus spp. over 8.0 logCFU/mL were observed in CGKs fermented above $10^{\circ}C$. Changes in Max G, cutting force, of CGK from different seasons were apparent. Max Gs for spring and summer CGK were decreased immediately right after storage while Max Gs for winter CGKs were increased slowly during storage. According to the results of sensory evaluation, CGKs revealed the highest overall acceptability when acidity of kimchi reached $0.7{\pm}0.1%$ under the given fermentation condition. However, CGK prepared with radish from winter or summer season tasted better than the one made in the spring. But the edible periods for winter CGKs were longer, compared with summer CGKs fermented at the same temperature. In conclusion, CGK fermented at $10^{\circ}C$ in the winter season gives a better taste with longer edible duration than the other CGKs.

• The Korean Journal of Physiology
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• v.16 no.1
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• pp.13-23
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• 1982

Effects of external pH and potassium concentrations on the electrical and mechanical properties were investigated on rabbit papillary muscle. Papillary muscles were perfused in horizontal chamber with Tris Tyrode solutions and action potential along with isometric tension was recorded simultaneously. Potassium concentrations were varied between 1 and 12 mM at low(6.9), normal(7.4) and high (7.9) external pH. The following results were obtained: 1) On rasing the potassium concentration from 1 to 12 mM resting membrane potentials decreased from $-88.8{\pm}2.8$ to $-66.4{\pm}1.2\;mV$ at normal pH and the amplitude of action potential decreased from $115.1{\pm}0.7$ to $97.5{\pm}2.8\;mV$. On lowering the potassium concentration, membrane hyperpolarized and at 1 mM potassium concentration resting potentials were $-107{\pm}2.2\;mV$. Duration of action potential especially $APD_{60}{\sim}APD_{90}$ increased($APD_{90}$: $214{\pm}15.8\;ms$ at 1 mM $K^+$ to $287{\pm}18.1\;ms$ at 12 mM $K^+$). 2) During acidosis membranes hyperpolarized by more than 20 mV within 1 min. and then slow recovery was observed during the following 10 min. During alkalosis membranes depolarized about 10 mV, which were maintained until washing with normal Tyrode solutions. 3) On lowering the external pH(7.9-6.5), duration of action potential increased progressively and it was most prominent at pH 6.5 and $K^+$ 1mM. 4) Magnitude of developed tension was $0.6{\pm}0.14\;g/mm^2$ at normal pH and potassium concentration (stimulus frequency : 60/min). Relative isometric tension to normal value increased along the increment of stimulus frequency($44.2{\pm}4.2%$ at 6/min to $271{\pm}86.7%$ at 180/min). Force-frequency relations were altered quantitatively during the perfusion with different external pH solutions. 5) Developed tension did not show marked variation within the range of $2{\sim}8\;mM$ potassium concentrations. Positive inotropism was observed at less than 2 mM $K^+$ and negative inotropism beyond 12 mM $K^+$ concentrations. From the above results we concluded that the effects of potassium ion concentration on electrical and mechanical properties of rabbit papillary muscle are related to the changes in surface negative charge due to acid base disturbances.