• 한국융합학회논문지
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• 제12권11호
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• pp.119-126
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• 2021

본 의료기관에서 사용되는 방사선 차폐복은 납당량 0.25 mmPb를 기준으로 제시하고 있다. 그러나 신체 각 부위별 감수성을 고려하고 사용자의 활동성을 보장할 수 있는 동시에 정밀한 방어가 가능한 차폐복 제작에 대해 연구하고자 한다. 친환경 차폐 재료를 기반으로 제작하여 기존 납 Apron의 중량 문제와 환경 문제를 해결하는 동시에 두께로 납당량과 동일한 차폐성능을 제시하고자 하였다. 제작된 차폐시트의 원단은 납당량 0.12 mmPb부터 0.32 mmPb까지 차폐시트의 두께로 조절하는 카렌더 공정을 통해 제작하였다. 각 신체 부위별 감수성을 고려한 차폐복을 제작하여 의료기관에서 상시 착용하고 있는 대상자를 통해 사용성평가를 실시하였다. 차폐복을 착용한 후 활동성이 좀 더 증가하였다는 의견이 많았으며, 무게는 0.26kg을 줄였다. 향후에는 의료기관의 종사자의 활동성을 고려한 차폐복 디자인 개선 노력이 필요할 것으로 사료된다.

• 한국세라믹학회지
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• 제54권2호
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• pp.75-85
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• 2017

Thermoelectric is a key technology for energy harvesting and solid-state cooling by direct thermal-to-electric energy conversion (or vice versa); however, the relatively low efficiency has limited thermoelectric systems to niche applications such as space power generation and small-scale or high-density cooling. To expand into larger scale power generation and cooling applications such as ATEG (automotive thermoelectric generators) and HVAC (heating, ventilation, and air conditioning), high-performance bulk thermoelectric materials and their low-cost processing are essential prerequisites. Recently, the performance of commercial thermoelectric materials including $Bi_2Te_3$-, PbTe-, skutterudite-, and half-Heusler-based compounds has been significantly improved through non-equilibrium processing technologies for defect engineering. This review summarizes material design approaches for the formation of multi-dimensional and multi-scale defect structures that can be used to manipulate both the electronic and thermal transport properties, and our recent progress in the synthesis of conventional thermoelectric materials with defect structures is described.

• Journal of Radiation Protection and Research
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• 제47권4호
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• pp.214-225
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• 2022

Background: The conventional cerium-doped Gd₂Al₂Ga₃O₁₂ (GAGG(Ce)) scintillator-based gamma-ray imager has a bulky detector, which can lead to incorrect positioning of the gammaray source if the shielding against background radiation is not appropriately designed. In addition, portability is important in complex environments such as inside nuclear power plants, yet existing gamma-ray imager based on a tungsten mask tends to be weighty and therefore difficult to handle. Motivated by the need to develop a system that is not sensitive to background radiation and is portable, we changed the material of the scintillator and the coded aperture. Materials and Methods: The existing GAGG(Ce) was replaced with Bi₄Ge₃O₁₂ (BGO), a scintillator with high gamma-ray detection efficiency but low energy resolution, and replaced the tungsten (W) used in the existing coded aperture with lead (Pb). Each BGO scintillator is pixelated with 144 elements (12 × 12), and each pixel has an area of 4 mm × 4 mm and the scintillator thickness ranges from 5 to 20 mm (5, 10, and 20 mm). A coded aperture consisting of Pb with a thickness of 20 mm was applied to the BGO scintillators of all thicknesses. Results and Discussion: Spectroscopic characterization, imaging performance, and image quality evaluation revealed the 10 mm-thick BGO scintillators enabled the portable gamma-ray imager to deliver optimal performance. Although its performance is slightly inferior to that of existing GAGG(Ce)-based gamma-ray imager, the results confirmed that the manufacturing cost and the system's overall weight can be reduced. Conclusion: Despite the spectral characteristics, imaging system performance, and image quality is slightly lower than that of GAGG(Ce), the results show that BGO scintillators are preferable for gamma-ray imaging systems in terms of cost and ease of deployment, and the proposed design is well worth applying to systems intended for use in areas that do not require high precision.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권1호
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• pp.17-25
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• 2005

This paper provides sufficient conditions for the robustness of Affine linear TFM(Transfer Function Matrix) MIMO (Multi-Input Multi-Output) uncertain systems based on Rosenbrock's DNA (Direct Nyquist Array). The parametric uncertainty is modeled through a Affine TFM MIMO description, and the unstructured uncertainty through a bounded perturbation of Affine polynomials. Gershgorin's theorem and concepts of diagonal dominance and GB(Gershgorin Bands) are extended to include model uncertainty. For this type of parametric robust performance we show robustness of the Affine TFM systems using Nyquist diagram and GB, DNA(Direct Nyquist Array). Multiloop PI/PB controllers can be tuned by using a modified version of the Ziegler-Nickels (ZN) relations. Simulation examples show the performance and efficiency of the proposed multiloop design method.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.178-184
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• 2020

The traditional methods for radiation shield design always only focus on either the structure or the components of the shields rather than both of them at the same time, which largely affects the shielding performance of the facilities, so in this paper, a novel method for designing the structure and components of shields simultaneously is put forward to enhance the shielding ability. The method is developed by using the genetic algorithm (GA) and the MCNP software. In the research, six types of shielding materials with different combinations of elements such as polyethylene (PE), lead (Pb) and Boron compounds are applied to the radiation shield design, and the performance of each material is analyzed and compared. Then two typical materials are selected based on the experiment result of the six samples, which are later verified by the Compact Accelerator Neutron Source (CANS) facility. By using this method, the optimal result can be reached rapidly, and since the design progress is semi-automatic for most procedures are completed by computer, the method saves time and improves accuracy.

• 한국지진공학회논문집
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• 제6권6호
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• pp.33-39
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• 2002

반응수정계수는 구조물의 비탄성 거동을 설계에 반영하고 설계지진력 산정시 설계강도를 탄성범위 이내로 저감시키기 위한 목적으로 사용하고 있다. 그러나 설계코드에서 채택하고 있는 반응수정계수는 과거의 지진피해로부터 관찰된 보편적 구조성능에 기인한 경험치이므로, 주기에 따른 동적성능과 구조 시스템의 구성에 따른 내진성능을 정확히 대변하지 못하고 있다. 본 연구에서는 중간모멘트 연성골조를 대상으로 N2 Method를 이용하여 반응수정계수와 내진성능을 평가하였으며, 그 결과를 미국의 IBC 2000 코드와 비교하여 이론적 타당성을 검증하였다. 해석결과 코드에 제시된 반응수정계수와 잘 부합되는 것으로 나타났으나, 동일한 구조시스템의 경우에도 주기에 따라 비교적 큰 차이를 보였다. 성능목표에 따른 사용성 기준을 설정하여 IDI를 평가한 결과, 설계지진에 대한 성능목표가 건물에 대한 내진성능을 대변하기는 어려우며 PBD(Performance Based Design)에 의거한 합리적인 접근이 필요한 것으로 판단된다.

• 한국농공학회논문집
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• 제62권3호
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• pp.29-38
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• 2020

Since some warm-mix asphalt (WMA) concretes were known to show poorer rut resistance than the hot-mix asphalt (HMA) concretes, many studies were performed in efforts of improving its performance at high temperature. The reason is assumed to be due to the moisture remaining in aggregates dried at lower temperature. Therefore, not only the rut resistance, the crack resistance of WMA concrete was also in question. In this study, fatigue life of WMA concrete was evaluated in comparison with HMA using 3-point bending (3PB) beam test. The asphalt mixtures were prepared based on Korean mix-design guide using a 13 mm dense-graded aggregate and 6 binders; two HMA binders and four WMA binders. By 3PB fatigue test, normal (unmodified) and polymer-modified WMA concretes were evaluated in comparison with normal and polymer-modified HMA concretes at a low temperature (-5℃). The results showed that most of WMA concretes showed longer fatigue lives than HMA concretes, even though the same PG binders were used for HMA and WMA. This result indicates that the WMA concretes have stronger resistance against fatigue cracking than HMA at the low temperature, and this result is in contrast to the high-temperature performance test.

• 한국화재소방학회논문지
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• 제33권1호
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• pp.76-84
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• 2019

성능위주설계(PBD)의 주방 화재시뮬레이션을 위해 요구되는 목재 가연물의 CO 및 Soot yields 정보를 제공하기 위하여, 개방 콘 칼로리미터를 활용한 실험이 수행되었다. 싱크장 제작에 널리 사용되는 MDF와 PB를 대상으로 함수율, 표면 가공처리 방식 및 색상에 따라 총 8가지의 시편이 검토되었다. 주요 결과는 다음과 같다. 동일 두께의 시편이라도 표면 가공처리 방법에 따라 깊이 방향으로의 화재확산과 관련된 열적 관통시간에 상당한 변화가 발생됨이 확인되었다. MDF와 PB series의 CO yield는 유염 연소 구간에서 연소 모드별 그리고 표면 가공처리 방식에 따라 큰 변화가 없다. 그러나 유염 연소모드에 비해 훈소 모드에서는 약 10배의 높은 $y_{CO}$가 측정되었다. 반면에 Soot yield는 연소 모드와 표면 가공처리 방식에 따라 상당한 차이를 보였다. 특히 유염 연소모드와 표면이 가공 처리된 시편에서 보다 높은 $y_{soot}$가 확인되었다. 마지막으로 PBD의 주방 화재시뮬레이션을 위하여 측정된 MDF와 PB의 $y_{CO}$ 및 $y_{soot}$ 적용 방안이 논의되었다.

• 한국병원경영학회지
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• 제13권2호
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• pp.1-19
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• 2008

BSC(balanced scorecard) is expected of the effective integrated tool of the management problem such as links of the management vision, the strategy, and the business scheme. This study discusses the recent development and problems of hospital BSC practices in in several countries. First, the article discuss the recent development and problems of hospital BSC implementation. Second, we review the links of strategic alignment with hospital's strategy and BSC on weight design, organizational culture and hospital performance. Finally, we explore hospital BSC framework that clarified easy to understand integrative approach to hospital BSC research using contingency theory model.

• 한국전기전자재료학회논문지
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• 제24권11호
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• pp.859-864
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• 2011

An operation temperature of $Pb(Zr,Ti)O_3$ based piezoelectric ultrasonic flowmeter was generally restricted to below 200$^{\circ}C$ due to a low depoling temperature of its ceramic material. Thus, a new designed piezoelectric ultrasonic flowmeter was fabricated in order to protect from the extremely hot fluid. Its structure is optimized by a finite element method to effectively stop heat flowing along a waveguide. Various materials such as Cu, Al, SUS were examined as a multi-plate radiation shield to enhance the performance of piezoelectric ultrasonic flowmeter. The SUS was evaluated as the most effective material to enhance the performance of piezoelectric ultrasonic flowmeter. As the number of plates of the radiation shield increased, the temperature at piezoelectric transducer away from the hot fluid was constantly decreased with a ratio of 3.12$^{\circ}C$ per the plate number.