• 융복합기술연구소 논문집
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• 제12권1호
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• pp.7-12
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• 2022

The reduction ratio of the magnetic gear is determined by the ratio of the number of poles between the high-speed permanent magnet layer and the low-speed permanent magnet layer. In general, it is known that the greater the least common multiple of both poles, the smaller the torque ripple called by cogging of the magnetic force generated in the magnetic gear. However, little is known about the effect of the harmonic modulator that filters the magnetic field in the magnetic gear to magnetically couple the high-speed side and the low-speed side except for the number of poles. In this study, torque ripple characteristics according to changes in modulator shape such as opening ratio and tooth thickness are analyzed using a finite element analysis tool.

• 한국분무공학회지
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• 제25권1호
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• pp.21-26
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• 2020

The objective of this work is to numerically reveal the effect of equivalence ratio change on the simultaneous reduction of NO_X and soot emissions from the simulated-EGR compression ignition engine containing CO₂. An experiment was conducted by using a single-cylinder common-rail injection system engine, an intake control system, and exhaust emissions analyzers. The numerical analysis results were validated under the same experimental conditions. To investigate the effect of equivalence ratio by simulated-EGR containing CO₂, the O₂, N₂, and CO₂ mole fraction were changed in the initial air conditions to the cylinder. The results were analyzed in terms of peak cylinder pressure, indicated mean effective pressure, indicated specific nitrogen oxide, and indicated specific soot. It was revealed that ignition delay characteristics and heat release rate (ROHR) characteristics were not significantly different according to the equivalence ratio. However, as the equivalence ratio increased from 0.68 to 0.83, the maximum combustion pressure and IMEP decreased by about 6.5% and 9.4%, respectively. In the case of ISFC, as is well known, the trend is opposite of IMEP. In the case of ISNO, as the equivalence ratio increased, less NO was generated, and as the equivalence ratio increased by 0.05, the ISSoot value of about 10% increased.

• Journal of Preventive Medicine and Public Health
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• 제32권4호
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• pp.427-434
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• 1999

Objectives: This study was conducted to determine, by reviewing the literature, whether treatment of Helicobacter pylori infection in patients with non-ulcer dyspepsia affects symptoms. Methods: We retrieved the literature using MEDLINE search, with nonulcer dyspepsia and Hericobacter pylori and treatment as key words, which were reported from 1984 to 1998, and manual literature search. The criteria for inclusion was as follows; 1) The paper should have confirmed nonulcer dyspepsia as case definition. 2) The paper should have peformed a randomized, blind trial. 3) Confirmation of Helicobacter pylori eradication should be done 4 weeks after treatment. 4) studies with no information on measurement of symptoms after treatment were not accepted. The percentage of patients with symptom improvement after eradication therapy for Helicobacter pylori infection was calculated. Cumulative odds ratio was compared by fixed effect model and random effect model as sensitivity and funnel plot was used to evaluate publication bias. Results: The overall effect size of symptom improvement was calculated by cumulative odds ratio. Cumulative odds ratio of random effect model was 4.16(95% CI: 1.55-11.19). Before integrating each effect sizes into common effect size, the homogeneity test was conducted and random effect model was selected(Cochran's Q=41.08 (d.f=10, p<0.001)). The heterogeneity across studies was evaluated and the different methodological aspects of studies led to differences between study results Conclusions: The results suggest that the eradication of Helicobacter pylori in patients with non-ulcer dyspepsia results more symptom improvement. In studios that shows the opposite results there are methodological aspects explaining the heterogeneity.

• 한국분말재료학회지
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• 제25권6호
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• pp.507-513
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• 2018

This study investigates the viability of using a Na-ion battery with a tin(Sn) anode to mitigate the vulnerability caused by volume changes during discharge and charge cycling. In general, the volume changes of carbon material do not cause any instability during intercalation into its layer structure. Sn has a high theoretical capacity of $847mAh\;g^{-1}$. However, it expands dramatically in the discharge process by alloying Na-Sn, placing the electrode under massive internal stress, and particularly straining the binder over the elastic limit. The repeating strain results in loss of active material and its electric contact, as well as capacity decrease. This paper expands the scope of fabrication of Na-ion batteries with Sn by fabricating the binder as an auxetic structure with a unique feature: a negative Poisson ratio (NPR), which increases the resistance to internal stress in the Na-Sn alloying/de-alloying processes. Electrochemical tests and micrograph images of auxetic and common binders are used to compare dimensional and structural differences. Results show that the capacity of an auxetic-structured Sn electrode is much larger than that of a Sn electrode with a common-structured binder. Furthermore, using an auxetic structured Sn electrode, stability in discharge and charge cycling is obtained.

• 인지과학
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• 제26권3호
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• pp.279-300
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• 2015

본 연구는 탐색적 수준에서 행운이 확률적 틀에 의한 의사결정 경향을 강화시키고, 불운이 이러한 경향을 약화시킨다는 예측을 검증한 것이다. 이를 위해 운 경험(행운 vs. 불운 vs. 통제) ${\times}$ 확률적 틀(높음 vs. 낮음)을 조작한 후, 사람들의 확률적 틀에 의한 의사결정 경향성에 차이가 있는지 관찰하였다. 결과적으로 행운 경험은 확률적 틀에 의한 의사결정 경향을 증가시키고, 불운 경험은 확률적 틀에 의한 의사결정을 약화시키는 이원상호작용을 관찰할 수 있었다(그림 1). 본 연구를 시작으로 확률적 틀 이외의 맥락적 틀(e.g., 긍정 vs. 부정; 맥락에 부합하는 손실 vs. 맥락과 무관한 손실)에 대한 의사결정에도 행운과 불운이 어떻게 영향을 미치는지 확인하는 연구들이 이어지길 기대한다.

• 대한기계학회논문집B
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• 제36권12호
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• pp.1151-1159
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• 2012

본 논문에서는 노즐홀 직경을 확대하여 유량을 증가시킨 DME 인젝터의 가시화 실험과 분무 해석을 수행하였다. 해석의 신뢰성을 확보하기 위하여 가시화 실험과 분무해석을 비교하였고, 실엔진 모사 조건에서 분무 해석을 수행하여 DME의 거동을 예측하였다. 분사 압력과 분위기 압력이 각각 35MPa 및 5MPa인 경우 가시화 실험과 분무 해석의 도달거리는 3.57%의 차이를 나타내었다. 실엔진 모사 해석의 경우, 완전하게 발달된 DME의 분무 도달거리는 분위기 온도와 압력의 비가 300K/MPa에서 42mm로 최대를 나타내었고, 300K/MPa미만의 영역에서 DME의 분무는 분위기 압력, 300K/MPa초과의 영역에서는 분위기 온도의 영향이 지배적임을 확인하였다.

• Structural Engineering and Mechanics
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• 제82권5호
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• pp.587-594
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• 2022

Behavior of concrete elements under the effect of high-speed projectiles has gain increasing interest recently. It's necessary to understand how far the concrete can absorb the effect of bullets in order to save the occupants when design security and military infrastructures. This study presents a total of 18 concrete slabs casted and tested under reinforcement ratios, 0%, 0.35% and 0.7%. Parameters interested were slab thickness, (50 mm, 100 mm, and 150 mm) and type of weapon. All specimens tested to investigate their response under the effect of attacking by two common types of weapon. In general, it was found that projectile penetration was controlled by their thickness regardless the steel reinforcement ratio. However, the steel reinforcement controls the damage.

• 한국경영과학회지
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• 제33권2호
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• pp.115-135
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• 2008

An interesting problem in capacitated supply chains is how to guarantee customer service levels with limited resources. One of the common approaches to solve the problem is differentiating service depending on customer classes. High-priority customers receive a better service at the cost of low-priority customers' service level. One of common criteria to determine a customer's priority in practice is whether he has made a reservation before arrival or not. Customers with a reservation usually receive service based on the time the reservation was made. We examine the effect this advance information of customer arrival has on customer service levels. We show the trade-offs between the leadtime and other system characteristics such as the proportion of high-priority customers. when the service level is high. We also suggest how to differentiate service using the asymptotic ratio of the service levels for both types of customers.

• 한국산업정보학회논문지
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• 제19권2호
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• pp.37-43
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• 2014

본 논문에서는 대부분의 선형 집적회로와 집적 주입 논리 회로에 넓게 사용되고 있는 NPN 트랜지스터의 에미터 면적의 크기에 대한 순방향 전류 이득의 영향에 대해 연구하였다. 순방향 전류이득과 에미터 면적 사이의 관계를 실험과 시뮬레이션을 통해 확인하였다. 같은 에미터 길이에서 에미터 접합 깊이가 증가 할수록 에미터 전류 이득은 감소하였다. 측면 면적에 비해 에미터 바닥 면적 비율이 증가할수록 에미터 전류이득은 증가하였다. 이론과 시뮬레이션의 결과는 실험결과와 함께 아주 잘 일치하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제35권1호
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• pp.53-59
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• 2011

디젤기관은 세계적으로 연료의 경제성 때문에 사용이 증가할 것이다. 그러나 NOx, 매연 등과 같은 배기가스를 배출한다. 본 연구는 커먼레일 연료분사 시스템에서, 연료온도, 분사 압력, 분사시간, 연료 점성에 따른 분무 특성을 실험하였다. 커먼레일 시스템에서, 디젤 연료는 분사 압력, 분사 시간에 따라 분무 형상이 다르다. 필터 압력은 연료 유동과 관련이 있는 연료 점성을 변화시키는 연료 온도에 영향을 받는다. 분무와 무화특성에 미치는 바이오 디젤 연료의 혼합율의 영향에 대해 많은 실험 조건에서 실험하였다. 바이오디젤 연료의 미립화 특성은 바이오 디젤 혼합비율이 증가하면 높은 점성 때문에 악화되는 것을 알았다.