• 동력기계공학회지
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• 제9권4호
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• pp.130-136
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• 2005

The effects of additional Mg content, the size and volume fraction of reinforcement phase on the mechanical properties of ceramic particle reinforced aluminium matrix composites fabricated by pressureless metal infiltration process were investigated. The hardness of $SiC_p/AC8A$ composites increased gradually with an increase in the additive Mg content, while the bending strength of $SiC_p/AC8A$ composites increased with an increase in additive Mg content up to 5%. However, this decreased when the level of additive Mg content was greater than 5% due to the formation of coarse precipitates by excessive Mg reaction and an increase in the porosity level. The hardness and strength of the composites increased with decreasing the size of SiC particle. It was found that the composites with smaller particles enhanced the interfacial bonding than those with bigger particles from fractography of the composites. The hardness of $Al_2O_{3p}/AC8A$ composites increased gradually with an increase in the volume fraction, however, the bending strength of $Al_2O_{3p}/AC8A$ composites decreased when the volume fraction of alumina particle was greater than 40% owing to the high porosity level.

• 한국산업융합학회 논문집
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• 제4권3호
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• pp.267-273
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• 2001

In this study, the survival rate of fiber is investigated by nozzle size difference in injection/mold sides. The survival rate of fiber is influenced about the nozzle size differ. Also, The mechanical properties of short carbon glass fiber reinforced polypropylene are experimentally measured as functions of fiber volume fraction and nozzle size difference. These mechanical properties are compared with the survival rate of fiber and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber as well as fiber volume fraction is influenced by injection processing condition, the used materials, mold conditions and nozzle sides difference, etc, In particular, the survival rate of fiber is great influenced when injection/mold nozzle sides are different more than that of the same. Consequently, the mechanical properties of short carbon/glass fiber reinforced polypropylene arc improved as the nozzle sides are the same in injection mold sides.

• 한국세라믹학회지
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• 제35권10호
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• pp.1085-1093
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• 1998

Amorphous alumina powder prepared by the fast calcination of aluminum trihydroxide(Al(OH)3 gibbsite) for 0.5 second at 580$^{\circ}C$ was investigated rehydration propeties. Phase composition crystal size and mor-phology surface area pore volume and pore size distribution of pesudo-boehmite and bayerite crystals changed with temperature time water/alumina ratio and particle size when amorphous alumina rehydrated with water. Phase compositions were examined with XRD and DTA and crystal sized morphologies were investigaed with SEM and TEM. Also rehydration properties of amorphous alumina were in-vestigated by measuring the surface area pore volume and pore size distribution.

• 자원리싸이클링
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• 제24권5호
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• pp.40-55
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• 2015

본 연구에서는 건설폐기물 기업의 폐기물처리량이 이익조정에 미치는 영향이 허용보관량 규모와 폐기물처리장 소재지에 따라서 차별적으로 나타나는지를 검증하였다. 주요 실증분석 결과 첫째, 건설폐기물 기업의 폐기물처리량은 이익조정에 영향을 미치며, 허용보관량 규모별로 규모가 작은 기업의 경우 폐기물처리량이 적을수록, 규모가 큰 기업의 경우 폐기물처리량이 많을수록 재량적 발생액을 이용한 이익조정이 이루어지는 것으로 나타났다. 둘째, 폐기물처리량이 이익조정에 미치는 영향은 폐기물처리장 소재지별로 비수도권에 소재한 기업의 경우 폐기물처리량이 적을수록, 수도권에 소재한 기업의 경우 폐기물처리량이 많을수록 재량적 발생액 및 실물활동을 통한 이익조정이 이루어지는 것으로 나타났다. 본 연구결과는 아직까지 연구되지 않은 건설폐기물 기업의 이익조정 동기 요인으로 폐기물처리량의 영향을 분석하고 그 효과가 허용보관량 규모와 폐기물처리장의 소재지 등 기업이 처한 환경에 따라 차별적으로 나타난다는 실증결과를 제시하였다는 점에서 의의가 있다.

• 대한영상의학회지
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• 제82권6호
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• pp.1534-1544
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• 2021

목적 전산화단층촬영에서 호흡에 의한 폐 용적의 변화가 폐 반고형결절의 크기와 용적에 미치는 영향을 알아보고자 한다. 대상과 방법 총 31명의 환자에서 42개의 반고형결절이 연구에 포함되었다. 먼저 총 폐활량 상태에서 전산단층화촬영을 시행 받은 후, 결절이 포함된 부분만 일호흡용적 상태에서 추가로 촬영하였다. 각각의 반고형결절의 직경과 용적을 측정하였고, 전체 폐 용적은 결절의 중심이 있는 동측 폐의 단면적으로 추정하였다. 동일한 개인 내에서 총 폐활량과 일회 호흡량 간 측정값 변화의 유의성을 통계적으로 평가하였다. 결과 총 폐활량 상태와 비교하였을 때, 일회 호흡용적 상태에서 폐 단면적은 평균 12.7 cm², 반고형결절의 직경 및 용적은 평균적으로 각각 0.5 mm와 46.4 mm³ 감소하였다(p < 0.001). 총 폐활량 상태와 일호흡량 상태 간 폐 면적 변화는 반고형결절의 직경 변화(rho = 0.341; p = 0.027) 및 부피 변화(rho = 0.401; p = 0.014)와 유의한 양의 상관관계를 보였다. 그러나 폐 용적의 변화를 고려하여 보정한 후에는 반고형결절의 평균 직경과 부피가 총 폐활량 상태와 일호흡량 상태 간 유의한 차이가 없었다(각각 p = 0.062, p = 0.124). 결론 전산화단층촬영에서 측정한 반고형결절의 크기와 용적은 동일한 환자 내에서도 촬영 당시의 폐 용적에 유의한 영향을 받는다.

• Clinics in Shoulder and Elbow
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• 제24권3호
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• pp.135-140
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• 2021

Background: We hypothesized in this study that the characteristics of retear cases vary according to surgeon volume and that surgical outcomes differ between primary and revision arthroscopic rotator cuff repair (revisional ARCR). Methods: Surgeons performing more than 12 rotator cuff repairs (RCRs) per year were defined as high-volume surgeons, and those performing fewer than 12 RCRs were considered low-volume surgeons. Of the 47 patients who underwent revisional ARCR at our clinic enrolled in this study, 21 cases were treated by high-volume surgeons and 26 cases by low-volume surgeons. In all cases, the interval between primary surgery and revisional ARCR, degree of "acromial scuffing," number of anchors, RCR technique, retear pattern, fatty infiltration, retear size, operating time, and clinical outcome were recorded. Results: During primary surgery, significantly more lateral anchors (p=0.004) were used, and the rate of use of the double-row repair technique was significantly higher (p<0.001) in the high- versus low-volume surgeon group. Moreover, the "cut-through pattern" was observed significantly more frequently among the cases treated by high- versus low-volume surgeons (p=0.008). The clinical outcomes after revisional ARCR were not different between the two groups. Conclusions: Double-row repair during primary surgery and the cut-through pattern during revisional ARCR were more frequent in the high- versus low-volume surgeon groups. However, no differences in retear site or size, fatty infiltration grade, or outcomes were observed between the groups.

• 한국응용과학기술학회지
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• 제30권4호
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• pp.602-611
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• 2013

We have investigated the influence of system composition and preparation conditions on the particle size of vitamin E acetate (VE)-loaded nanoemulsions prepared by PIC(phase inversion composition) emulsification. This method relies on the formation of very fine oil droplets when water is added to oil/surfactant mixture. The oil-to-emulsion ratio content was kept constant (5 wt.%) while the surfactant-to-oil ratio (%SOR) was varied from 50 to 200 %. Oil phase composition (vitamin E to medium chain ester ratio, %VOR) had an effect on particle size, with the smallest droplets being formed below 60 % of VOR. Food-grade non-ionic surfactants (Tween 80 and Span 80) were used as an emulsifier. The effect of f on the droplet size distribution has been studied. In our system, the droplet volume fraction, given by the oil volume fraction plus the surfactant volume fraction, was varied from 0.1 to 0.3. The droplet diameter remains less than 350 nm when O/S is fixed at 1:1. The droplet size increases gradually as the increasing the volume fraction. Particle size could also be reduced by increasing the temperature when water was added to oil/surfactant mixture. By optimizing system composition and homogenization conditions we were able to form VE-loaded nanoemulsions with small mean droplet diameters (d < 50 nm). The PIC emulsification method therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.

• 한국시뮬레이션학회논문지
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• 제13권2호
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• pp.13-21
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• 2004

The thermal-hydraulic model ARTS which was based on the RETRAN-3D code adopted in the domestic full-scope power plant simulator which was provided in 1998 by KEPRI. Since ARTS is a generalized code to model the components with control volumes, the smaller time-step size should be used even if converged solution could not get in a single volume. Therefore, dedicated models which do not force to reduce the time-step size are sometimes more suitable in terms of a real-time calculation and robustness. In the case of PRT(Pressurizer Relief Tank) model, it is consist of subcooled water in bottom and non-condensable gas in top. The sparger merged under subcooled water enhances condensation. The complicated thermal-hydraulic phenomena such as condensation, phase separation with existence of non-condensable gas makes difficult to simulate. Therefore, the PRT volume can limit the time-step size if we model it with a general control volume. To prevent the time-step size reduction due to convergence failure for simulating this component, we developed a dedicated model for PRT. The dedicated model was expected to provide substantially more accurate predictions in the analysis of the system transients. The results were resonable in terms of accuracy, real-time simulation, robustness and education of operators, complying with the ANSI/ANS-3.5-1998 simulator software performance criteria and RETRAN-3D results.

• 한국응용과학기술학회지
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• 제27권3호
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• pp.310-317
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• 2010

The electrochemical properties of electric double layer capacitor(EDLC) was studied by controlling pore size distribution and specific surface area of the activated carbon fiber(ACF). The mesoporous ACF, which was prepared by the iron exchange method, showed the tendency of increasing average pore size and decreasing total surface area. The mesoporous ACF (surface area = 2225 $m^2$/g, pore size=1.93 nm) showed increased mesopore(pore size=1~3nm) volume from 0.055 cc/g to 0.408 cc/g compared to its raw ACF. The charging capacity of the EDLC which uses the prepared mesoporous ACF also increased from 0.39 F/$cm^2$ to 0.55 F/$cm^2$. From these results, it can be known that the electrochemical properties of EDLC are mainly dependent on the specific surface area, but above the surface area 2200 $m^2$/g, it is the mesopore volume that affects the performance of the capacitor considerably. Because the increased mesopore volume results in a decreased ion mobility resistance, the charge capacitance is enhanced.

• 생물정신의학
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• 제22권3호
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• pp.118-127
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• 2015

Objectives Standardization of head size is essential for the volume study. Cortical thickness analyses are increasingly being used in many fields of neuroscience. However, it is not established whether head size correction should be done for thickness study. Methods Using the Open Access Series of Imaging Studies data, we determined cortical thickness of 316 cognitively normal participants aged 18-94 with FreeSurfer. The association between head size and cortical thickness of whole cortical mantle and in each lobe among age tertile groups was assessed. Estimated total intracranial volume (eTIV) was calculated for determining head size. Results Across all participants, cortical thickness in whole brain except some areas in cingulate and insula decreased with aging. eTIV had positive correlation with the thickness of frontal, parietal, occipital and whole brain areas. However, the age effect was not shown in whole brain of the first tertile group and in cingulate areas of the third tertile group. eTIV had negative correlation with the thickness of cingulate in the third tertile group. Gender effects were shown in some areas in third tertile group, but it would be due to difference of head size. Conclusions These findings suggest that head size standardization might be done especially in older population and in studies of paralimbic areas.