• 한국대기환경학회지
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• 제30권6호
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• pp.531-537
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• 2014

Terrestrial vegetation has been known as a main source of biogenic volatile organic compounds (BVOCs). Isoprene and monoterpene among the BVOCs are most abundant species emitted by forests, and have a significant impact on atmospheric chemistry. Abundancy of these species could lead to an increase or decrease in the production of natural tropospheric ozone in forests, depending on the nitric oxide (NO) concentration. Soil is the most significant source of natural NO. Understanding of NO emission from forest soil could be critical in evaluation of air quality in the forest area. Flux-gradient similarity theory (FGST) was applied for practical use to estimate forest soil NO emission at Mt. Taewha where is available micro-meteorological data near surface monitoring from flux tower. NO fluxes calculated by FGST were compared to flux results by flow-through dynamic chamber (FDC) measurement. Surface NO emission trends were shown between two different techniques, however their magnitudes were found to be different. NO emissions measured from FDC technique were relatively higher than those from theoretical results. Daily mean NO emissions resulted from FGST during Aug. 13, 14 and 15 were $0.28{\pm}8.45$, $2.17{\pm}15.55$, and $-3.18{\pm}13.65{\mu}gm^{-2}hr^{-1}$, respectively, while results from FDC were $2.26{\pm}1.44$, $5.11{\pm}3.85$, and $2.23{\pm}6.45{\mu}gm^{-2}hr^{-1}$. Trends of daily means were shown in similar pattern, which NO emissions were increasing during late afternoon ($r^2$=0.04). These emission trends could be because soil temperature and moisture influence importantly soil microbiology.

• 대한교통학회지
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• 제19권5호
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• pp.61-70
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• 2001

급변하는 교통환경 하에서 신뢰성 있는 기·종점통행량(O/D)를 구축하는 것은 매우 어려운 일이다. 특히, 시간과 비용의 제약하에서 교통계획을 수립해야 하는 경우라면 전통적인 O/D 구축방법인 O/D조사를 통해 O/D를 구축하는 것은 현실적으로 불가능한 일이다. 이로 인해 관측통행량을 이용하여 O/D를 추정하는 연구가 활발하게 이루어져 왔다. 그러나 현재까지 진행되어 온 연구들이 개별차량 O/D를 추정하는 대에만 국한되어 있어, 관측통행량으로 대중교통 O/D를 추정하는 연구는 거의 없는 실정이다. 본 연구는 이미 개별차량 O/D 추정에서 신뢰성이 검증된 Gradient방법을 대중교통 O/D 추정에 적용하여 그 신뢰성을 평가하는데 목적이 있다. 본 연구에서 대중교통 통행배정은 Spiess-Florian의 대중교통 통행배정규칙을 이용하였고, Gradient방법의 신뢰성을 평가하는 기준으로는 기본 O/D와 추정 O/D의 분포형태를 이용하였다.

• 스마트미디어저널
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• 제11권1호
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• pp.46-57
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• 2022

본 논문에서는 딥러닝을 기반으로 입력영상의 옵티컬 플로우(optical flow)와 그래디언트(gradient)를 이용하여 종단간 행동인식이 가능한 다중영역 기반 방사성 GCN(MRGCN: Multi-region based Radial Graph Convolutional Network) 알고리즘에 대해 기술한다. 이 방법은 데이터 취득이 어렵고 계산이 복잡한 스켈레톤 정보를 사용하지 않기 때문에 카메라만을 주로 사용하는 일반 CCTV 환경에도 활용이 가능하다. MRGCN의 특징은 입력영상의 옵티컬플로우와 그래디언트를 방향성 히스토그램으로 표현한 후 계산량 축소를 위해 6개의 특징 벡터로 변환하여 사용한다는 것과 시공간 영역에서 인체의 움직임과 형상변화를 계층적으로 전파시키기 위해 새롭게 고안한 방사형 구조의 네트워크 모델을 사용한다는 것이다. 또 데이터 입력 영역을 서로 겹치도록 배치하여 각 노드 간에 공간적으로 단절이 없는 정보를 입력으로 사용한 것도 중요한 특징이다. 30가지의 행동에 대해 성능평가 실험을 수행한 결과 스켈레톤 데이터를 입력으로 사용한 기존의 GCN기반 행동인식과 동등한 84.78%의 Top-1 정확도를 얻을 수 있었다. 이 결과로부터 취득이 어려운 스켈레톤 정보를 사용하지 않는 MRGCN이 복잡한 행동인식이 필요한 실제 상황에서 더욱 실용적인 방법임을 알 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.379-382
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• 1996

Evolution Strategy is used as an effective search algorithm in optimization problems and Sliding Mode Control is well known as a robust control algorithm. In this paper, we propose a Sliding Mode Control Method for robot manipulator using Evolution Strategy. Evolution Strategy is used to estimate Sliding Mode Control Parameters such as sliding surface gradient, continuous function boundary layer, unknown plant parameters and switching gain. Experimental results show the proposed control scheme has accurate and robust performances with effective search ability.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1994년도 FIFTH WESTERN PACIFIC REGIONAL ACOUSTICS CONFERENCE SEOUL KOREA
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• pp.746-751
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• 1994

The four-terminal transmission matrix method has been widely used to estimate the insertion-loss. However, the predictins using the equations in the four-terminal transmission matrix method do not reflect a practical phenomenon accurately, In this paper, the correction method to derive the insertion-loss for a constant sound pressure source is presented. The method of correction to the four-terminal transmission matrix method was proposed by rewriting the real and imaginary parts as they depend solely on the flow velocity. Then the result was compensated for by adding the component of the temperature gradient.

• 대한조선학회지
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• 제25권2호
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• pp.1-10
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• 1988

An axially marching numerical method is developed for the simulation of the internal waves produced by translation of a submersed vehicle in a density-stratified ocean. The method provides for the direct solution of the primitive variables [$\upsilon,\;p,\;\rho$] for the nonlinear and steady state three-dimensional Euler's equation with a non-constant density term in the vehicle-fixed cartesian co-ordinate system. By utilizing a known potential flow around the vehicle for an estimate of the axial velocity gradient, the present parabolic algorithm local upstreamwise disturbances and axial velocity variation.

• 한국통신학회논문지
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• 제33권1C호
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• pp.110-116
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• 2008

ML(Maximum Likelihood) 방법 기반의 도래각(Direction-of-Arrival, DOA) 추정은 본질적으로 다차원 비선형 비용 함수의 최적화 과정이다. 초기 추정치에 기울기(gradient) 기반 탐색을 적용하여 최종 추정치를 구하기 때문에, 초기 추청치의 정확성은 매우 중요하다. 본 논문은 균등한 전체탐색(uniform exhaustive search)과 개선된 전체탐색(improved exhaustive search)의 다차원 탐색 방법을 제안한다. 개선된 전체탐색 기법은 균등한 전체탐색의 기법에 비하여 정확성 측면과 계산량 측면에서 우수하다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.134-136
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• 1993

This paper presents a novel and efficient method to calculate the critical point of voltage collapse. Conjugate gradient and modified Newton-Raphson methods are employed to calculate two pairs of multiple load flow solutions for two operating conditions, i.e., both +mode and -mode voltages for two loading conditions respectively. Then these four voltage magnitude-load data sets of the bus which is most susceptible to voltage collapse, are fitted to third order polynomial using Lagrangian interpolation in order to represent approximate nose curve (P-V curve). This nose curve locates first estimate of the critical point of voltage collapse. The procedure described above is repeated near the critical point and the new estimate will be very close to the critical point. The proposed method is tested for the eleven bus Klos-Kerner system, with good accuracy and fast computation time.

• Kyungpook Mathematical Journal
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• 제61권3호
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• pp.631-644
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• 2021

In the present paper, we obtain gradient estimates for positive solutions to the following nonlinear parabolic equation under general geometric flow on complete noncompact manifolds $$\frac{{\partial}u}{{\partial}t}={\Delta}u+a(x,t)u^p+b(x,t)u^q$$ where, 0 < p, q < 1 are real constants and a(x, t) and b(x, t) are functions which are C² in the x-variable and C¹ in the t-variable. We shall get an interesting Harnack inequality as an application.

• 한국멀티미디어학회논문지
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• 제19권2호
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• pp.418-427
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• 2016

A smart parking management requires to track a vehicle in a indoor parking lot and to detect the place where the vehicle is parked. An advanced parking system watches all space of the parking lot with CCTV cameras. We can use these cameras for vehicles tracking and detection. In order to cover a wide area with a camera, a fisheye lens is used. In this case the shape and size of an moving vehicle vary much with distance and angle to the camera. This makes vehicle detection and tracking difficult. In addition to the fisheye lens, the vehicle headlights also makes vehicle detection and tracking difficult. This paper describes a method of realtime vehicle detection and tracking robust to the harsh situation described above. In each image frame, we update the region of a vehicle and estimate the vehicle movement. First we approximate the shape of a car with a quadrangle and estimate the four sides of the car using multiple histograms of oriented gradient. Second we create a template by applying a distance transform to the car region and estimate the motion of the car with a template matching method.