• 한국환경과학회지
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• 제17권4호
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• pp.397-403
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• 2008

The purpose of this study is to investigate weighted compaction density according to a leading density in truck, a compaction density of solid waste and composition ratios of solid waste fur calculation of a capacity of the landfill sites. The experiments for calculations of in-place density at landfill site have been conducted in S landfill site at B City. The size of vessel for measuring the compaction density was $1m^3(1m{\times}1m{\times}1m)$. The experiment tests have been carried out methods (1 time for bulldozer and 4 times for compactor) that do contain all of specification at the landfill site. Average of the loading density at the landfill site was $0.264\;ton/m^3$ ($0.113{\sim}0.487\;ton/m^3$). When the loading density for each compositions was compared, the composition of the highest average loading density ($0.474\;ton/m^3$) was miscellaneous wastes. The composition of the lowest average loading density ($0.120 ton/m^3$) was general solid waste. The reported results indicated that the compaction density at the landfill site was $0.538\;ton/m^3$, which was calculated with weighted incoming ratios of compositions. The ranges of the density for each composition were from $0.021\;ton/m^3$ to $0.221\;ton/m^3$. When the compaction density for each composition was compared, the composition with the highest average compaction density ($0.221\;ton/m^3$) was miscellaneous wastes. The composition with the lowest average compaction density ($0.021\;ton/m^3$) was general solid wastes.

• Communications for Statistical Applications and Methods
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• 제17권3호
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• pp.377-390
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• 2010

In the case of time-series analysis, it is often more convenient to rely on the frequency domain than the time domain. Spectral density is the core of the frequency-domain analysis that describes autocorrelation structures in a time-series process. Possible ways to estimate spectral density are to compute a periodogram or to average the periodogram over some frequencies with (un)equal weights. This can be an attractive tool to measure the similarity between time-series processes. We employ the metrics based on a smoothed periodogram proposed by Park and Kim (2008) for the classification of different classes of time-series processes. We consider several lag windows with unequal weights instead of a modified Daniel's window used in Park and Kim (2008). We evaluate the performance under various simulation scenarios. Simulation results reveal that the metrics used in this study split the time series into the preassigned clusters better than do the raw-periodogram based ones proposed by Caiado et al. 2006. Our metrics are applied to an economic time-series dataset.

• 한국화재소방학회논문지
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• 제31권1호
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• pp.36-41
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• 2017

단일 복도에서의 단방향 피난 이동 실험의 수행 결과, 평균 밀도 $2.36P/m^2$에서 0.55 m/s의 속도를 보이고 있다. S.F.P.E. Handbook에서 제시된 복도에서의 밀도기반 속도 수식 계산결과와 평균값을 비교할 때, 본 실험이 0.55 m/s, SFPE 수식이 0.53 m/s로서 0.02 m/s의 차이를 보였으며 데이터 별로 분석한 결과, 최대 0.38 m/s의 큰 차이를 나타내고 있다. 일부 실험결과는 보행속도의 증가에 따라 밀도가 높아짐을 보였으며 실험 결과분석은 전체 실험시간에 대한 평균 데이터를 사용하였다. 동영상에 대한 프레임단위 분석과 같은 세부적인 시간분석을 수행한다면 더욱 신뢰성 있는 데이터를 확보할 수 있을 것으로 보인다.

• Journal of the Korean Wood Science and Technology
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• 제39권1호
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• pp.60-67
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• 2011

본 연구에서는 고밀도 우드세라믹을 제조하기 위한 기초 연구로서 수지함침율 및 탄화온도에 따라 제조된 1차 탄화 우드세라믹을 수지 재 함침 후 2차 탄화하여 우드세라믹을 제조하고 밀도경사를 조사하였다. 2차 탄화 후 최소, 평균 및 최고밀도가 1차 탄화 우드세라믹보다 증가하였고, 밀도경사 비율도 증가하였다. 따라서 고밀도와 밀도경사 비율이 작은 균질한 우드세라믹을 제조하기 위해서는 2차 함침과 2차 탄화에 의한 우드세라믹 제조방법도 효과가 있는 것으로 나타났다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권11호
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• pp.566-571
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• 2004

Pulse modulation technique provide additional controling method for electron temperature and density in rf and microwave processing plasma. Transient characteristics of electron density and temperature have been measured in pulse modulated rf inductively coupled argon plasma using simple probe circuit. Electron temperature relaxation is clearly identified in the after glow stage. Controllability of average electron temperature and density depends on the modulation frequency and duty ratio. Numerical calculation of time-dependent electron density and temperature have been performed based on the global model. It has been shown that simple langmuir probe measurement method used for continuous plasma is also applicable to time-dependent measurement of pulse modulated plasma.

• 한국ITS학회 논문지
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• 제17권5호
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• pp.77-87
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• 2018

교통밀도는 교통수요와 가장 직접적인 관계가 있으므로 거시적인 지표 중에서 가장 중요하다고 알려져 있으며(Traffic Engineering, 2004), 특정시각 주어진 거리 안의 존재하는 차량의 대수로 정의한다. 하지만, 밀도는 기상과 도로조건 및 비용 상의 문제로 인하여 현장에서 직접 수집이 어렵다. 이런 이유로 속도와 교통량보다 상대적으로 연구가 활발하게 이루어지지는 않아 수집방법에 관한 다양한 시도뿐만 아니라 측정된 값의 정확도에 관한 연구가 많이 부족하다. 이에 본 논문에서는 밀도를 측정할 수 있는 방법으로 여러 대의 카메라 영상을 정합(synthesis)하는 기술을 활용하였다. 이러한 밀도수집시스템으로 수집한 밀도를 정의에 기반한 참값으로 선정하고, 이 값을 전통적인 측정방법들로 산출한 밀도와 비교하였다. 비교결과, 관계식(fundamental equation)을 이용한 산출방법으로 산출한 밀도 값이 참값과 비교하여 RMSE(Root Mean Square Error)가 1.8-2.5로 가장 참값에 가깝다. 또한 향후 밀도를 직접 수집할 때 유의하여할 수집 간격 등의 간과하기 쉬운 이슈사항을 순간밀도와 평균밀도를 산출하여 알아보았다. 실험 사이트의 실제 교통상황은 LOS B임에도 불구하고, 초 당 순간밀도는 최대(16veh/km)에서 최소 2(veh/km)의 값이 다양하게 관측되어 교통상황의 판단이 어려웠다. 하지만 30초 간격으로 15분 평균밀도는 8.3-7.9(veh/km)로 정확하게 LOS B를 판단하였다.

• ETRI Journal
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• 제45권5호
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• pp.768-780
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• 2023

The application of unmanned aerial vehicles (UAVs) has recently attracted considerable interest in various areas. A three-dimensional multiple-input multiple-output concentric two-hemisphere model is proposed to characterize the scattering environment around a vehicle in an urban UAV-to-vehicle communication scenario. Multipath components of the model consisted of lineof-sight and single-bounced components. This study focused on the key parameters that determine the scatterer distribution. A time-variant process was used to analyze the nonstationarity of the proposed model. Vital statistical properties, such as the space-time-frequency correlation function, Doppler power spectral density, level-crossing rate, average fade duration, and channel capacity, were derived and analyzed. The results indicated that with an increase in the maximum scatter radius, the time correlation and level-crossing rate decreased, the frequency correlation function had a faster downward trend, and average fade duration increased. In addition, with the increase of concentration parameter, the time correlation, space correlation, and level-crossing rate increased, average fade duration decreased, and Doppler power spectral density became flatter. The proposed model was compared with current geometry-based stochastic models (GBSMs) and showed good consistency. In addition, we verified the nonstationarity in the temporal and spatial domains of the proposed model. These conclusions can be used as references in the design of more reasonable communication systems.

• 전기학회논문지
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• 제60권9호
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• pp.1646-1650
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• 2011

SAIDI(System Average Interruption Duration Index) is the index that signifies the power quality of customers. SAIDI is also used to know how well utilities operate their systems. The annual interruption time in the areas that consists of widely distributed customers, is generally longer than that in the areas that consists of heavily concentrated customers. The Reliability index of huge system is not necessarily better or worse than that of small system, because SAIDI is irrelevant to the total amount of power sold or the total number of customers. This paper proposes a customer density very relevant to SAIDI. The proposed customer density is used to modify the existing SAIDI to more clearly express the service level of power supply. A modified WSAIDI(weighted SAIDI) can be a useful indicator helping utilities improve the reliability of their systems and customers evaluate the service level of receiving power.

• 한국물환경학회지
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• 제22권2호
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• pp.264-270
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• 2006

In this research, volume reduction of activated sludge using electrolysis was studied to find an optimum condition using lab scale experiments. Wasted sludge was treated by electrolysis with controlling current density, chloride concentration, electrode distance, and reaction time. Volume of return sludge was reduced by 9.79% in average while maximum was 16.7%. Sludge volume reduction efficiency was affected by current density and reaction time. It was reversely proportional to the electrode distance. Especially current density was effective on the system performance significantly. Electric conductivity, salinity and COD were increased by electrolysis implying sludge disintegrated and converted to COD in part. An empirical equation for total solid removal efficiency by electrolysis was proposed by multiple linear regression analysis as: $TS_{rem}$(%) = 5.534 ${\times}$ current density (A/l) + 0.178 ${\times}$ reaction time (m) + 2.758.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3470-3493
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• 2019

IEEE 802.11s-based infrastructure Wireless Mesh Networks (iWMNs) are envisaged as a promising solution to provide ubiquitous wireless Internet access. The limited network capacity is a problem mainly caused by the medium contention between mesh users and the mesh access points (MAPs), which gets worst when the mesh clients employ the Transmission Control Protocol (TCP). To mitigate this problem, we use wireless network coding (WNC) in the MAPs. The aim of this proposal is to take advantage of the network topology around the MAPs, to alleviate the contention and maximize the use of the network capacity. We evaluate WNC when is used in MAPs. We model the formation of coding opportunities and, using computer simulations, we evaluate the formation of such coding opportunities. The results show that as the users density grows, the coding opportunities increase up to 70%; however, at the same time, the coding delay increments significantly. In order to reduce such delay, we propose to adaptively adjust the time that a packet can wait to catch a coding opportunity in an MAP. We assess the performance of moving-average estimation methods to forecast this adaptive sojourn time. We show that using moving-average estimation methods can significantly decrease the coding delay since they consider the traffic density conditions.