• Nuclear Engineering and Technology
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• 제18권2호
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• pp.78-84
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• 1986

일차섭동이론을 이용하여 물질밀도 감도 계수의 표현식을 유도하였다. Super-Phenix I 평형노심의 초기상태를 기준계로 택했으며 유효중배계수를 계의 응답함수로 정의했다. 볼츠만 연산자의 구성요 소인 물질밀도로 표현되는 핵연료의 농축도와 실효밀도를 입력변화로 선정했다. 위 계산을 수행하는데 전산코드시스템 (KAERI-26군 단면적 library/1DX/2DB/PERT-V)가 사용되었다. 핵연료 농축도의 유효증배계수에 대한 감도계수는 4.576로 계산되었으며, 핵연료 실효밀도의 감도 계수는 0.0756으로 계산되었다. 본 연구는 감도해석법이 대형전산코드를 이용한 직접반복계산법에 비해 계산시간의 단축과 아울러 많은 정보를 준다는 것을 보여준다.

• 한국의학물리학회지:의학물리
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• 제32권4호
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• pp.165-171
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• 2021

Purpose: This study aimed to evaluate the effect of collimator width on effective atomic number (EAN), relative electron density (RED), and stopping power ratio (SPR) measured by dual-layer dual-energy computed tomography (DL-DECT). Methods: CIRS electron density calibration phantoms with two different arrangements of material plugs were scanned by DL-DECT with two different collimator widths. The first phantom included two dense bone plugs, while the second excluded dense bone plugs. The collimator widths selected were 64 mm×0.625 mm for wider collimators and 16 mm×0.625 mm for narrow collimators. The scanning parameters were 120 kVp, 0.33 second gantry rotation, 3 mm slice thickness, B reconstruction filter, and spectral level 4. An image analysis portal system provided by a computed tomography (CT) manufacturer was used to derive the EAN and RED of the phantoms from the combination of low energy and high energy CT images. The EAN and RED were compared between the images scanned using the two different collimation widths. Results: The CT images with the wider collimation width generated more severe artifacts, particularly with high-density material (i.e., dense bone). RED and EAN for tissues (excluding lung and bones) with the wider collimation width showed significant relative differences compared to the theoretical value (4.5% for RED and 20.6% for EAN), while those with the narrow collimation width were closer to the theoretical value of each material (2.2% for EAN and 2.3% for RED). Scanning with narrow collimation width increased the accuracy of SPR estimation even with high-density bone plugs in the phantom. Conclusions: The effect of CT collimation width on EAN, RED, and SPR measured by DL-DECT was evaluated. In order to improve the accuracy of the measured EAN, RED, and SPR by DL-DECT, CT scanning should be performed using narrow collimation widths.

• Carbon letters
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• 제2권1호
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• pp.72-75
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• 2001

The performance of Li-ion system based on $LiCoO_2$ and Graphite is well optimized for the 3C applications. The charge-discharge mode, the manufacturing process, the cell performance and the thermal reactions affecting safety has been explained in the engineering point of view. The energy density of the current LIB system is in the range of 300~400 Wh/l. In order to achieve the energy density higher than 500 Wh/l, the active materials should be modified or changed. Adopting new high capacity anode materials would be effective to improve energy density.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(2)
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• pp.221-224
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• 2002

Recently, simulation of Chemical Mechanical Polis hing is becoming more important because Process parameters on the material removal rate are complicated. And pattern-depent effects are a key concern in CMP processes. In this paper, we have been studied the changes of pattern density vs. oxide thickness with Stine's simulation model. We also have estimated the effective density using optimal window size with density mask, and have made a study of the change of oxide thickness as a function of polishing time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.489-492
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• 1997

Partial discharge characteristics of normal butyl acrylate grafted low density polyethylenes were investigated by an ultrasonic sensor made of ceramic piezoelectric material. It was found that the partial discharging activities in normal butyl acrylate grafted low density polyethylenes were considerably suppressed compared to those in plain low density polyethylene. It was found that acrylic acid grafted polyethylene was more effective than normal butyl acrylate grafted low density polyethylene.

• 산업기술연구
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• 제7권
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• pp.9-14
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• 1987

The maximum specific gravity of asphaltic concrete can be calculated based on the effective specific gravity of aggregates and the specific gravity of asphalt cement. The maximum specific gravity is sometimes obtained based on the apparent specific gravity of aggregates and specific gravity of asphalt concrete. However, the apparent specific gravity is in general greater than the effective specific gravity for most aggregates. This study showed, by comparing the results obtained based on two specific gravities, that application of the apparent specific gravity instead of the effective specific gravity resulted in discrepancies in the calculated values of effective asphalt content, air void and maximum density.

• Nuclear Engineering and Technology
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• 제49권8호
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• pp.1758-1771
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• 2017

In this study, to determine the most effective alloy for shielding against gamma-rays, the gamma-ray shielding parameters of six types of cerrobend alloys have been investigated. Gamma-ray interaction with the cerrobend alloys has been discussed mainly in terms of total mass attenuation coefficient (${\mu}_t$), half value layer (HVL), tenth value layer (TVL), effective atomic number ($Z_{eff}$), and effective electron density ($N_{eff}$). These parameters have been calculated by theoretical approach using the ParShield program in a photon energy range between 0.1 MeV and 100 GeV. The dependence of these parameters on the incident photon energy and chemical composition of the cerrobend alloys has been studied.

• ETRI Journal
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• 제27권3호
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• pp.319-325
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• 2005

In this paper the effect of temperature on the electrical properties of organic semiconductor disperse orange dye 25 (OD) have been examined. Thin films of OD have been deposited on $In_{2}O_{3}$ substrates using a centrifugal machine. DC current-voltage (I-V) characteristics of the fabricated devices $(Al/OD/In_{2}O_{3)$ have been evaluated at varying temperatures ranging from 40 to $60^{\circ}C$. A rectification behavior in these devices has been observed such that the rectifying ratio increases as a function of temperature. I-V characteristics observed in $Al/OD/In_{2}O_{3)$ devices have been classified as low temperature $({\leq} 50^{\circ}C)$ and high temperature characteristics (approximately $60^{\circ}C$). Low temperature characteristics have been explained on the basis of the charge transport mechanism associated with free carriers available in OD, whereas high temperature characteristics have been explained on the basis of the trapped space-charge-limited current. Different electrical parameters such as traps factor, free carrier density, trapped carrier density, trap density of states, and effective mobility have been determined from the observed temperature dependent I-V characteristics. It has been shown that the traps factor, effective mobility, and free carrier density increase with increasing values of temperature, whilst no significant change has been observed in the trap density of states.

• Environmental Engineering Research
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• 제22권2호
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• pp.141-148
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• 2017

Globalization, industrialization, mining, and uncontrolled population growth have fostered a shortage of potable water. Therefore, it has become imperative to understand an effective and reasonable water purification technique. A renewed interest in electrocoagulation (EC) has been spurred by the search for reliable, cost-effective, water-treatment processes. This paper has elucidated a technical approach for getting rid of heavy metals and total suspended solids (TSS) from synthetic water using an aluminum electrode. The effect of operational parameters, such as current density, inter-electrode distance, operating time, and pH, were studied and evaluated for maximum efficiency. This study corroborates the correlation between current density and removal efficiency. Neutral pH and a low electrode gap have been found to aid the efficacy of the EC setup. The outcome indicates that a maximum TSS removal efficiency of 76.6% occurred at a current density of $5.3mA/cm^2$ during a contact time of 30 min. In the case of heavy metals remediation, 40 min of process time exhibited extremely reduced rates of 99%, 59.2%, and 82.1%, for Cu, Cr, and Zn, respectively. Moreover, kinetic study has also demonstrated that pollutants removal follows first-and second-order model with current density and EC time being dependent.

• 천문학회보
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• 제45권1호
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• pp.48.2-48.2
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• 2020

We present a new void definition that connects voids with clusters, the high-density counterpart. We use a pair of ΛCDM simulations whose initial density fields are sign inverted versions to each other, and study the relation between the effective void volume and the corresponding cluster mass. Massive cluster halos (M ≥ 1013M⊙/h) are identified in one simulation at z=0 by linking dark matter particles. The corresponding void to each cluster is defined in the other simulation as the region occupied by the member particles of the cluster. We find a universal functional form of density profiles at z=0 and 1. We also find a power-law relation between the void effective radius and the corresponding cluster mass. Based on these findings, we identify cluster-counterpart voids directly from a density field without using the pair information by utilizing three parameters such as the smoothing scale, density threshold, and minimum core fraction. We identified voids corresponding to clusters more massive than M ≥ 3 × 1014M⊙/h at approximately 70-74 \% level of completeness and reliability. Our results suggest that we can detect voids comparable to clusters of a particular mass-scale.