• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.481-488
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• 2009

It has been reported that the magnitude and the development rate of autogenous shrinkage of cement paste, mortar and concrete were affected by history and magnitude of inner temperature at an early age. But it was not enough to explain the relation between hydration heat and autogenous shrinkage at an early age, because there was no certain analysis on histories of hydration heat and autogenous shrinkage in previous studies. In our prior study, to understand the relationship between hydration heat and autogenous shrinkage of concrete at an early age, the analysis method for histories of hydration heat and autogenous shrinkage was suggested. Based on this method, early age properties of hydration heat and autogenous shrinkage of high strength concrete with different sizes and hydration retardation were investigated in this study. As a result of the study, properties of hydration temperature and autogenous shrinkage were different according to specimen size and hydration retardation. However, there was a close relationship between hydration temperature and autogenous shrinkage at an early age, especially between HHV and ASV as linear slopes of the sections where hydration temperature and autogenous shrinkage increase rapidly; the higher HHV, the higher ASV and the greater ultimate autogenous shrinkage. And it was found that, among the setting time, bend point and temperature increasing point, they were close relationship each other on cement hydration process.

• Korean Journal of Food Science and Technology
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• v.15 no.3
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• pp.295-301
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• 1983

The mechanical models representing the theological property of traditional Korean noodles; i.e. wheat flour noodle and wheat-sweet potato starch noddle, were investigated from the data obtained by creep and creep recovery test using a tensile tester. The rheological behavior of the noodle products could be expressed by the 6-elements Voigt model. The instantaneous elasticity, retarded elasticity, retardation time, retarded viscosity and Newtonian viscosity of the noodle products were evaluated. With the increasing cooking time, 4-elements Burger's model was applicable to represent the mechanical behavior of wheat-sweet potato starch noodle.

• Journal of Internet of Things and Convergence
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• v.1 no.1
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• pp.1-4
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• 2015

This paper aims to present the mathematical model to find the mean web object transfer latency in the slow-start phase of TCP congestion control mechanism, which is one of the main control techniques of Internet. Mean latency is an important service quality measure of end-user in the network. The application area of the proposed latency model is the narrowband environment including multi-hop wireless network and Internet of Things(IoT), where packet loss occurs in the slow-start phase only due to small window. The model finds the latency considering initial window size and the packet loss rate. Our model shows that for a given packet loss rate, round trip time and initial window size mainly affect the mean web object transfer latency. The proposed model can be applied to estimate the mean response time that end user requires in the IoT service applications.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1866-1867
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• 2011

본 논문은 웨이브 에너지 발전 시스템의 네트워크제어기 설계에 대해서 논의한다. 기계적인 오실레이터의 움직임 운동 방정식의 해를 구하면서, 시스템의 에너지 손실의 효율성을 향상 시키기 위하여 퍼지 제어 기법을 도입한다, 다양한 초기 조건에서의 바디의 움직임 방정식의 해를 수치적으로 해석하기위하여, 손실되는 에너지의 크기는 알 수 있다고 가정한다. 네트워크상에서 발생하는 시간 지연을 모델링하며, 전체 웨이브 에너지 발전 시스템은 시간 지연을 가지는 웨이브 에너지 네트워크 제어 시스템이 된다. 제안하는 퍼지 제어기와 웨이브 에너지 발전시스템은 같은 퍼지 멤버쉽 함수를 가지게 모델링한다. 전체 네트워크 폐루프 시스템의 안정도를 분석하고, 웨이브 에너지 발전시스템을 안정화 시키는 퍼지 제어기 설계를 위한 충분조건을 유도한다. 시간 지연을 가지는 네트워크에서 퍼지 제어 기법을 이용하여 웨이브 에너지 시스템의 에너지 손실을 파악한다.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.4 no.2
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• pp.175-180
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• 2001

Purpose: The advantages of air reduction are the ease of performing the procedure, reduced radiation time and lower morbidity rate if perforation occurs. But, patients who fail air reduction undergo a laparotomy at which 10% have spontaneously reduced. The first enema decreases the edema and venous congestion of bowel wall, thus repeated reduction may succeed. The aim of this study is to evaluate the efficacy of delayed repeated pneumatic reduction of intussusception in patients with failure of an initial attempt. Methods: Between January 1998 and December 1999, 21 patients with proven intussusception received repeated delayed reduction 1 to 3 hours following the first failed attempt. These patients were in stable condition and did not have peritonitis, shock or toxic sign. Results: Before reduction, the patients had symptoms and signs for 6 to 48 hours (median 24 hr). The interval from the first reduction to the repeated was 1 to 3 hours (median 2.2 hr). The success rate of repeated reductions was 76.2% (16 of 21 patients), and 23.8% (5 of 21 patients) required surgery. Four of 5 patients requiring surgery were manually reduced and 1 spontaneously reduced in the operating room. Conclusion: We recommended a repeated reduction in patients with intussusception who are in stable clinical condition after an unsuccessful initial reduction attempt.

• Proceedings of the Korean Society of Computer Information Conference
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• 2017.01a
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• pp.147-150
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• 2017

지능형 로봇의 사용자 품질을 결정하는 주요 요소들 중 하나는 짧은 부트 시간이다. 로봇 시스템에서는 부팅 과정 중에 침입자인지, 자택 순찰, 개인 비서, 엔터테인먼트와 같은 다수의 응용들이 동시에 초기화되는데, 고품질의 사용자 경험을 제공하기 위해서는 사용자 응답성이 중요한 응용들이 우선적으로 초기화되어야한다. 이를 위해 리눅스 기반 로봇 시스템에서 부트 시간을 단축하기 위한 다양한 연구들이 진행되어 왔다. 하지만 이들은 단일 응용 각각에 대한 초기화 시간을 단축하는 연구들이며, 응용들 간에 CPU, 메모리, I/O와 같은 자원 경쟁에 의한 지연 요소를 고려하지 않고 있다. 본 논문에서는 응용들 간의 각종 자원경쟁들을 고려하여 사용자 응답성이 중요한 응용을 우선적으로 초기화하기 위한 외부 컨텍스트 기반 선별적 자원 사용률 조정기법을 제안한다. 이를 리눅스 기반 시스템 상에 구현하여 검증한 결과 응용의 부트 시간이 기존 대비 33.02% 단축됨을 확인했다.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.426-429
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• 2003

In the construction process, there are many change orders differing to the initial contracts came from the social needs and environmental changes. Most of them will impact to the construction process so that its effects occur project delays. Time extension and liquidated damage in the construction process come from schedule delay whether it is excusable or not non-excusable by the owner. However, those become the delay claims if the owner and the contractor are not agreed on this situation. One of the most important thing on the delay claims is the calculation of delay. The purpose of this study is to present the method of the time delay calculation by comparison of As-Planned schedule, As-Built schedule including all delay and As-Built schedule absent owner delay.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.163-170
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• 1997

The retarding effects of MgSiF6.6H2O on the hydration of portland cement were studied. The setting time, flow value and compressive strength of mortar were measured and the mechanism of retardation was also studied by ion concentration in solution, SEM, BET, and X-ray diffraction. The results are as follows ; 1. Setting time was delayed by the addition of MgSiF6.6H2O. 2. The flow value of mortar decreases depending upon the amount of MgSiF6.6H2O. 3. The compressive strength was almost same or some increase on 28 days hydration. 4. The main retardation mechanism of MgSiF6 on the hydration of portland cement may be explained by the following hypothesis. MgSiF6 depressing the Ca++ and K+ ion concentration of cement paste solution be-cause of the recrystalization of K2SiF6 and CaF2 phase. The new products of K2SiF6 and CaF2 deposit on the surface of unhydrated cement powder and harzard the mass transfer through these layer. The low con-centration of Ca++, K+ ion in solution was decreasing the hydration rate of portland cement.

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.1-12
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• 2021

MILD(Moderate or Intense Low-oxygen Dilution) combustion has attracted attention as the clean thermal energy technology due to the lower emissions of unburnt carbon and NO_x. MILD combustion aims to enlarge the combustion reaction zone using the spontaneous ignition phenomenon of the reactants. In this study, the ignition delay time of CH₄ according to the initial temperature of reactants and the addition of CO, H₂ was investigated using a numerical approach. Ignition delay time became shorter as the increases of initial temperature and H₂ addition. But, CO addition to the fuel increase the ignition delay time. In case of H₂ addition to the fuel, the ignition delay time decreased because the higher fraction of HO₂ promotes the decomposition of methyl radical(CH₃) and produce OH radical. However, in case of CO addition to the fuel, ignition delay time inceased because a high proportion of HCO consumes H radical. There was no significant effect of HCO on the reduction of ignition delay time. Also, the increase rates of NO emissions by the addition of CO and H₂ were approximately 7% and 1%, respectively. A high proportion of NCO affects the increase in NO production rate.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.34-40
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• 2018

In this study, the optimal buffer size is calculated for seamless video playback on a mobile device. Buffer means the memory space for multimedia packet which arrives in mobile device for video play such as VOD service. If the buffer size is too large, latency time before video playback can be longer. However, if it is too short, playback service can be paused because of shortage of packets arrived. Hence, the optimal buffer size insures QoS of video playback on mobile devices. We model the process of buffering into a discret-time queueing model. Mean busy period length and mean waiting time of Geo/G/1 queue with N-policy is analyzed. After then, we uses the main performance measures to present numerical examples to decide the optimal buffer size on mobile devices. Our results enhance the user satisfaction by insuring the seamless playback and minimizing the initial delay time in VOD streaming process.