• 한국멀티미디어학회논문지
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• 제25권8호
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• pp.1242-1250
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• 2022

When recommending cold items that do not have user-item interactions to users, even we adopt state-of-the-arts algorithms, the predicted information of cold items tends to have lower accuracy compared to warm items which have enough user-item interactions. The lack of information makes for recommender systems to recommend monotonic items which have a few top popular contents matched to user preferences. As a result, under-diversified items have a negative impact on not only recommendation diversity but also on recommendation accuracy when recommending cold items. To address the problem, we adopt a diversification algorithm which tries to make distributions of accumulated contents embedding of the two items groups, recommended items and the items in the target user's already interacted items, similar. Evaluation on a real world data set CiteULike shows that the proposed method improves not only the diversity but also the accuracy of cold item recommendation.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.437-444
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• 2007

This paper experimentally investigates the effects of oxygen-enriched air (OEA) on the running behaviors of an LPG SI engine during both start/warm-up (SW) and hot idling (HI) stages. The experiments were performed on an air-cooled, single-cylinder, 4-stroke, LPG SI engine with an electronic fuel injection system and an electrically-heated oxygen sensor. OEA containing 23% and 25% oxygen (by volume) was supplied for the experiments. The throttle position was fixed at that of idle condition. A fueling strategy was used as following: the fuel injection pulse width (FIPW) in the first cycle of injection was set 5.05 ms, and 2.6 ms in the subsequent cycles till the achieving of closed-loop control. In closed-loop mode, the FIPW was adjusted by the ECU in terms of the oxygen sensor feedback. Instantaneous engine speed, cylinder pressure, engine-out time-resolved HC, CO and NOx emissions and excess air coefficient (EAC) were measured and compared to the intake air baseline (ambient air, 21% oxygen). The results show that during SW stage, with the increase in the oxygen concentration in the intake air, the EAC of the mixture is much closer to the stoichiometric one and more oxygen is made available for oxidation, which results in evidently-improved combustion. The ignition in the first firing cycle starts earlier and peak pressure and maximum heat release rate both notably increase. The maximum engine speed is elevated and HC and CO emissions are reduced considerably. The percent reductions in HC emissions are about 48% and 68% in CO emissions about 52% and 78%; with 23% and 25% OEA, respectively, compared to ambient air. During HI stage, with OEA, the fuel amount per cycle increases due to closed-loop control, the engine speed rises, and speed stability is improved. The HC emissions notably decrease: about 60% and 80% with 23% and 25% OEA, respectively, compared to ambient air. The CO emissions remain at the same low level as with ambient air. During both SW and HI stages, intake air oxygen enrichment causes the delay of spark timing and the increased NOx emissions.

• 대한물리치료과학회지
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• 제9권2호
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• pp.151-157
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• 2002

This study examined the changes in body temperature through conductive heat applied to the body and clarified the influences of body fluid on the thermal effects. Body fluid was measured using the Segmental Bioelectrical Impedance Analysis method. The subjects consisted of 13 men and 14 women. TBW was 37.56 (4.35 L for men and 29.93 (3.12 L for women, with the former being significantly (p<0.01) higher. The amount of body fluid in the right and left legs was 6.46 (0.83 L and 6.39 (0.86 L for men and 4.78 (0.49 L and 4.78 (0.49 L for women, respectively, with men's values being significantly (p<0.01) higher than women's on both the right and left sides. The maximal change in the surface temperature was 33.93 (0.61(C at the start of a warm bath to 3407 (0.61(C after 14 min for men. In contrast, the maximal change was 33.38 (0.99(C at the start to 33.73 (0.86(C after 18 min for women. For the other sites, the maximal temperature in Depths 1 and 2 was attained earlier for men than for women. The decrease in body temperature after the end of warming was more remarkable for men. Men had fluid with a higher conductivity than women, indicating influences of body fluid on the changes in body temperature. There were few changes in body composition with a partial bath having a crossed effect, indicating that this is a safe therapeutic method for elderly people.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.25-30
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• 2001

The liquid fuel film on the cylinder liner is believed to be a major source of engine-out hydrocarbon emissions in SI engines, especially during cold start and warm-up period. Quantifying the liquid fuel film on the cylinder liner is essential to understand the engine-out hydrocarbon emissions formation in SI engines. In this research, two-dimensional visualization was carried out to quantify liquid fuel film on the quartz liner in an SI engine test rig. The visualization was based on laser-induced fluorescence and total reflection. Using a quartz liner and a special lens, only the liquid fuel on the liner was visualized. The calibration technique was developed to quantify the fluorescence signal with the thickness gage and the calibration device. The fluorescence intensity increases linearly with increase in the fuel film thickness on the quartz liner. Using this technique, the distribution of the fuel film thickness on the cylinder liner was measured quantitatively for different valve lifts and injected fuel mass in the test rig.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.73-81
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• 2006

A commercial diesel engine was converted into a dedicated natural gas engine to reduce the exhaust emissions in a retrofit of a diesel-fueled vehicle. The cylinder head and piston were remodeled into engine parts suited for a spark ignition engine using natural gas. The remodeling of the combustion chamber changed the compression ratio from 21.5 to 10.5. A multi-point port injection(MPI) system for a dedicated natural gas engine was also adopted to increase the engine power and torque through improved volumetric efficiency, to allow a rapid engine response to changes in throttle position, and to control the precise equivalence ratio during cold-start and engine warm-up. The performance and exhaust emissions of the retrofitted natural gas engine after remodeling a diesel engine are investigated. The emissions of the retrofitted natural gas engine were low enough to satisfy the limits for a transitional low emission vehicle(TLEV) in Korea. We concluded that a diesel engine can be effectively converted into a dedicated natural gas engine without any deterioration in engine performance or exhaust emissions.

• 한국분무공학회지
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• 제19권1호
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• pp.40-46
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• 2014

Recently rise in oil prices feet the burden on not only diesel vehicle driver but also LPG vehicle driver, and get interested in various way to reduce fuel costs. In this study discuss on exhaust emissions characteristics on driving cycle mode and ignition advance condition change of CNG/LPLI Bi-Fuel vehicle. Experimental test was performed by changing the conditions of fuel (LPG/CNG), spark advance (Base, $10^{\circ}CA$, $15^{\circ}CA$), and driving mode (FTP-75, HWFET, and NEDC). In case of CO emission, in the order of CNG Base, CNG S/A10, S/A15 condition are average reduced -21%, -35%, -29% respectively compared to LPG fuel. The active emission reduction from the initial engine start, spark retard is likely to be beneficial in catalyst warm-up and improve combustion stability rather than spark advance.

• 마이크로전자및패키징학회지
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• 제14권1호
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• pp.11-17
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• 2007

수은의 방전을 이용하는 CCFL, EEFL, FFL은 그 특성상 상온에서의 구동 특성과 저온에서의 구동 특성이 매우 다르며, 그 결과 수은 증기압이 충분하지 않은 저온에서 구동 시 완전 점등하지 못하고 램프별로 또는 방전 채널별로 불 균일 점등이 발생할 수 있다. 이러한 저온 시동의 어려움을 해결하기 위해, 본 논문에서는 Level Control Block (LCB) 를 포함하는 인버터를 이용하여 저온 $-20^{\circ}C$에서 최대 130 Watt로 제한된 입력전력을 이용하여 외부 전극형 면광원 램프를 이용한 LCD 백라이트가 안정되게 동작될 수 있음을 확인하였다.

• 한국농림기상학회지
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• 제4권1호
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• pp.58-63
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• 2002

1951-1980 평년기온 대비 1971-2000 평년기온 상승을 남한지역 14개 관측소 소재 시군의 1966년 대비 1990년의 인구증가 자연대수값에 회귀시켜 통계적으로 유의한 관계식을 얻었다. 이 관계식을 이용하여 도시화에 따른 승온효과를 제거할 경우, 순수한 지구 온난화 효과는 12월부터 4월 사이의 한후기에만 인정되며, 나머지 계절에는 나타나지 않았다. 남한지역의 한후기 일평균기온은 지구온난화에 의해 최대 0.6$^{\circ}C$까지 상승하였으며 일최저기온보다 일최고기온 상승폭이 컸다. 도시화에 따른 승온효과는 최대 0.3$^{\circ}C$에서 0.5$^{\circ}C$로 연 중(4월 제외) 고르게 나타났지만, 주로 일최저기온의 상승을 주도하였고 일최고기온 상승에는 거의 영향이 없었다.

• 대한디지털의료영상학회논문지
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• 제12권1호
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• pp.27-31
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• 2010

The purpose of this study was to investigated the usefulness of MR perfusion image comparing with SPECT image. A total of pediatric 30 patients(average age : 7.8) with Moyamoya disease were performed MR Perfusion with 32 channel body coil at 3T from March 01, 2010 to June 10, 2010. The MRI sequences and parameters were as followed : gradient Echo-planar imaging(EPI), TR/TE : 2000ms/50ms, FA : $90^{\circ}$, FOV : $240{\times}240$, Matrix : $128{\times}128$, Thickness : 5mm, Gap : 1.5mm. Images were obtained contrast agent administrated at a rate of 1mL/sec after scan start 10s with a total of slice 1000 images(50 phase/1 slice). It was measured with visual color image and digitize data using MRDx software(IDL version 6.2) and also, it was compared of measurement with values of normal and abnormal ratio to analyze hemodynamic change, and a comparison between perfusion MR with technique using Warm Color at SPECT examination. On MR perfusion examination, the color images from abnormal region to the red collar with rCBV(relative cerebral blood volume) and rCBF(relative cerebral blood flow) caused by increase cerebral blood flow with brain vascular occlusion in surrounding collateral circulation advancement, the blood speed relatively was depicted slowly with blue in MTT(Mean Transit Time) and TTP(Time to Peak) images. The region which was visible abnormally from MR perfusion examination visually were detected as comparison with the same SPECT examination region, would be able to confirm the identical results in MMD(Moyamoya disease)judgments. Hymo-dynamic change in MR perfusion examination produced by increase and delay cerebral blood flow. This change with digitize data and being color imaging makes enable to distinguish between normal and abnormal area. Relatively, MR perfusion examination compared with SPECT examination could bring an excellent image with spatial resolution without radiation expose.

• The Korean Journal of Pain
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• 제5권2호
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• pp.263-268
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• 1992

Ramsay Hunt 증후군으로 확진된 환자 2예를 경험하였다. 첫 예인 경우 안면신경마비가 발생하던 날 바로 방문하여 대상포진에 대한 치료와 환측 성상신경절 차단 15회, TENS, 안면운동 훈련 반복 등으로 발병 후 3주만에 완전 치유 되었으며, 두번째 환자는 발병 후 7주일 후에 방문하여 대상포진에 대한 치료는 생략하고 안면신경마비에 대한 치료라고 사료되는 환측 성상신경절 차단 50회, TENS 수백회, 안면운동 훈련 반복시행하였으나 부분적인 회복을 하였을 뿐이다. 그러므로 Ramsay Hunt 증후군의 치료도 다른 여러 질환과 마찬가지로 조기에 치료하면 회복이 빠르고 거의 완전하며, 늦어질수록 예후가 좋지 않다는 것을 경험하였다. 두 예 모두에서 대상포진 후 신경통으로의 이행은 없었다.