• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.511-513
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• 2000

종단간 전송 지연은 시각 동기, 네트워크 성능 측정 등에서 매우 중요한 요소이다. 그러나 IP에 기반하고 있는 Internet은 여러 통신망 상의 지연 요소를 정확히 전달할 수 있는 구조가 없기 때문에 종단간 전송에 있어 전송 지연을 정확하게 알 수 없다. 특히 UDP 네트워크의 경우 전송할 때와 수신할 때 경로가 같지 않기 때문에 일반적으로 일주 지연 시간을 이용하지만 각 편도 전송 지연 시간 차이는 시스템의 다른 요소에 대해서 오류 요소로 작용할 수 있다. 본 논문에서는 일주 지연 시간을 전송시 지연 시간과 수신시 지연 시간으로 따로 측정 분석하였다. 측정 결과 편도 전송 지연 시간 차이 값은 수십 밀리초 범위를 가지며 이는 NTP 등에서 시각을 동기화 할 때 통상적인 정확도, 수 밀리초를 훨씬 넘어선다. 이것은 편도 지연 시간 차이값이 시각 동기, 네트워크 성능 평가 등에서 중요한 오류값으로 작용한다는 것을 의미한다. 분석 결과를 실험 데이터에 적용할 경우 실제 편도 지연 시간에 근사한 값을 구할 수 있고 좀더 정확한 시각 동기, 네트워크 성능 평가가 가능하게 된다.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.861-866
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• 2014

This study evaluates the modeling accuracy of the existing three phase shift models on which the time domain oscillator phase noise theories are based. For the evaluation, this study investigates how accurately the three models can model the phase shift impulse train response of a simple planar oscillator. Evaluation result reveals that Kaertner model most accurately reflects the oscillator's phase shift impulse train responses for five different impulse train inputs, whereas PP model exhibited the worst performance in modeling the phase shift impulse train responses.

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.123-131
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• 1997

이 연구에서는 서로 다른 사용자 인터페이스의 대화 방식에 따라 PC통신 소프트웨어 의 사용편이성이 어떻게 달라지는가를 살펴보고자 한다. 이를 위해 현재 국내에서 이 용되고있는 3개의 PC통신소프트웨어를 대상으로 남녀대학생 18명에 의한 사용편이성 평가 시험을 실시하였다. 시험은 강사에 의한 1:1 방식에 의해 실시하였다. 평가척도로 는 학습소요시간, 시험소요시간, 정답률을 이용하였다. 실험결과, 윈도우환경에서 구현 되는 메뉴, 아이콘, 명령어를 혼합한 대화방식의 소프트웨어보다도 도스환경에서 구현된 명령어 대화방식의 소프트웨어가 학습용이성 측면에서의 사용편이성이 높을 수 있다는 점이 시사되었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.3
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• pp.1114-1121
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• 2012

There is a cause and effect relationship in that brain injury causes impairment of mental rotation and ultimately independent functional activities. The purpose of this study was to compare the effects of mental rotation on reaction time and precision between the normal adults and chronic hemiparetic stroke patients. Thirty-one patients with chronic hemiparetic stroke and twenty normal adults participated in this study. The participants conducted 2 types of tasks for mental rotation: a comparison task using mirror images, and a rotation task using angular disparity images for 2 different 3-dimensional objects. Each of the 3 possible angled shapes ($90^{\circ}$, $180^{\circ}$, and $270^{\circ}$) appeared in each pair. The test consisted of 6 mirror-reflected image pairs and 6 angular disparity image pairs visualized during angular rotation, and 12 test periods. The subjects were judged on how accurately and rapidly they could distinguish between the mirrored and non-mirrored pairs. The study measured reaction time and precision to compare the effect of mental rotation tasks. Reaction time during all 3 angular conditions were significantly longer in the stroke patients than that in the normal adult during the comparison tasks and the rotation tasks. In addition, precision during mental rotation tasks was not significantly different between normal adults and stroke patients. Our results suggest that rehabilitation therapists should keep in mind that mental rotation is more difficult in stroke population than in normal adults.

• Journal of Energy Engineering
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• v.25 no.4
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• pp.103-109
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• 2016

Polyethylene pipes has useful benefits which are anti-corrosive and flexible material, so it is used to gas pipes but also class 3 water pipes of nuclear power plant, process pipes of petrochemical plant and chemical plant. So the usage of polyethylene pipes is widely increased. But it has been limited for the usage of polyethylene, because it can not be directly detected to fusion joints by using non destructive evaluation. Polyethylene pipes are connected by two methods, one is butt fusion and the other is electrofusion. Butt fusion is widely used to connecting the pipes. It is proposed to method for determining the reliability of joints in this study that is detection of the melt flow zone at fusion joints. In this study, middle density polyethylene is used, outside diameter of the test specimen is 225mm and thickness is 20.5mm. Speed of ultrasonic of this test specimen is 2,200m/s. Test specimens were fabricated by varying the heating time which means from 0% to 130% applying time through heating plate to polyethylene for detecting melt flow zone. Also 4 additional test specimens were made, one was made that not scrapping attached surface of pipes but applying 100% of the proper heating time and the others were made to include of soil, gravel and vinly tape paper at fusion joints, that were also applied 100% of proper heating time. Ultrasonic testing to measure the melt flow zone of 20 test specimens was conducted by using 3.5MHz and 5.0MHz ultrasonic probes and melt flow zone measuring was conducted to three times at different point to one specimen. To differentiate the melt flow zone signal, post image processing was equally conducted to all test results and image levels, contrast, sharpen, threshold were adopted to all teat results and the test results were displayed gray scale. From the results, for the shorter heating times the reflection area of multiple echo have been increased, so the data was obtained from the position where it can be eliminated as much as possible. At 80% of proper heating time(168 sec.), the signal of melt flow zone was obtained clearly, so measuring could be conducted. From 7% of proper heating time(15 sec.) to shorter heating times. we could not obtain the signal because test specimen was not fused. From the result, we can verify that measuring of melt flow zone by using phased array ultrasonic imaging method is possible. And we can verify to complete and incomplete butt fusion by measuring the melt flow zone.

• KDI북한경제리뷰
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• v.23 no.2
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• pp.40-46
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• 2021

• Fire Science and Engineering
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• v.29 no.6
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• pp.13-19
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• 2015

This study was performed to test the combustive properties of Pinus rigida specimens treated with phosphorus (P) and nitrogen (N) additives. Each Pinus rigida specimen was painted three times with 15 wt% P-N additive solutions at room temperature. After drying the treated specimens, the combustion properties were examined using a cone calorimeter (ISO 5660-1). The time to ignition (TTI) for the treated specimens was 90 to 148 s except for the specimen treated with PP/$4NH_4^+$, and the time to flameout (TF) was 556 to 633 s, which was longer than that of virgin plate. While the The specimens treated with P-N additives showed 12.5 to 43.4% higher mean heat release rate ($HRR_{mean}$) and 11.8 to 43.1% higher total heat release (THR) than virgin plate. The effective heat of combustion (EHC) was by 2.9 to 17.5% lower than that of virgin plate. It can thus be concluded that the combustion-retardation properties were partially improved compared to those of virgin plate.

• Food preservation and processing industry
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• v.4 no.2
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• pp.2-7
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• 2005

신선편이 농산식품에 대한 소비자 조사에 대한 요약은 다음과 같다. 1. 과실 및 채소류의 구입 장소는 대형할인마트가 $60.5\%$로 가장 많으며 연령이 감소할수록 대형할인마트에서의 구입 빈도가 높았다. 2. 과실과 채소류의 구입 빈도는 전업주부 보다는 직장인의 구입 빈도가 높았다. 3. 신선편이 농산식품을 구입하게 된 동기는 조리시간 단축, 적정량 구입이 가장 많은 것으로 나타났으며, 구입하지 않은 이유로는 비싼 가격과 신선해 보이지 않기 때문으로 대답하였으나 향후 구입 의향에 대해서는 $68.1\%$가 긍정적인 반응을 나타내었다. 5. 신선편이 농산식품의 구입경험은 $62\%$로 식품소비층인 30-40대, 고학력일수록 더 많이 구입한 것을 알 수 있었다. 또한 구입경험이 있는 사람은 편리성, 신선함, 맛, 다양성 등의 긍정적인 반응을 보였으나 구입경험이 없는 사람은 익숙하지 않거나 비싸다고 생각하는 것으로 나타났다. 6. 신선편이 농산식품의 구매 형태는 필요한양만큼 절단된 형태를 선호 하였다. 7. 신선편이 농산식품의 적정가격 수준은 신선 과실 및 채소 가격의 $110-140\%$를 가장 많이 선택했다 8. 신선편이 농산식품의 구매 고려 품질요인으로는 신선함, 위생, 외관 등의 순 이였고 이들을 개선한다면 지속적으로 구매하겠다고 대답한 사람이 $87.7\%$로 조사되었다.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.163-176
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• 2012

Effective porosity has been measured for cement specimen as a function of vacuum time and pressure in the vacuum saturation process. Six cement specimen are used; three of them are made of the same ratio of cement and sand, the other three are 100% cement mortar, of which average porosity is about 25% and 40%, respectively. Using the 6 samples, measured effective porosities are compared and examined with 5 different vacuum pressures (2, 4, 6, 8, 10 torr) and times (20, 40, 60, 80, 100 minute), respectively. Comparing measured effective porosity from experiments when vacuum time varies from 100 minute to 20 minute with 20 minute step and vacuum pressure is fixed to 10, 6, and 2 torr, average deviation decreases as 0.6, 0.5, and 0.2% respectively. Comparing measured effective porosity from experiments when vacuum pressure varies from 2 torr to 10 torr with 2 torr step and vacuum time is fixed to 100, 60, and 20 minute, average deviation increases as vacuum time decreases. These results can be a background of suggested method of ISRM that describes the vacuum time longer than 60 minute and vacuum pressure higher than 6 torr. In this study, only qualitative discussion can be possible for the effects on the effective porosity by decreasing 20 minute vacuuming time at the same pressure or by decreasing 2 torr of vacuum pressure at the same vacuum time. This is because the sample could not reached to perfectly dried condition even though the sample were dried at $105^{\circ}C$ and following the ISRM suggested method, so that initial water content could not be the same at each experiment.

• Food Science and Preservation
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• v.18 no.6
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• pp.891-897
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• 2011

Oak barrel have been used for a long time for the aging of wine. Instead of oak barrel aging, however, roasted oak chips can be directly added in the wine before aging. In this study, Korean oak chips roasted for different time durations were used for the red wine aging, and the properties of wine aged through the addition of the roasted oak chips were characterized. No significant differences were observed in the alcohol, soluble-solid, reducing-sugar and total-acid contents based on the oak chips aging, but the total phenol content increased. The methanol, ethyl acetate, propanol, isobutanol and isoamyl alcohol contents also increased. Especially, the methanol and propanol contents increased as the roasting time was prolonged. Although the hue values were similar to one another, the intensity as well as the lightness, redness, and yellowness values were high in the wine aged with the roasted oak chips. In the sensory evaluation, the wine aged with oak chips roasted for 2 h showed the highest scores in the flavor, taste, and overall preference.