• Proceedings of the Acoustical Society of Korea Conference
• /
• 1998.06e
• /
• pp.11-14
• /
• 1998

근접 4점법을 이용하여 음원으로부터 측정점까지 음파가 전달되어 오는 공간상의 반사음 패턴을 구할 수 있다. 그러나 차량과 같이 협소한 공간에서는 반사음간의 시간차가 매우 작게 되고 따라서 단지 몇 개의 초기 반사음을 제외하고는 측정이 어렵게 된다. 본 연구에서는 측정에 사용된 스피커의 특성을 역필터링하여 차실 내의 펄스 반사음 자체 특성만을 추출함으로써 좁은 공간에서도 반사음 패턴의 측정이 가능하도록 하였다. 실내 반사음 패턴은 음파의 경로를 보여 주는 것이므로 본 측정법은 차량의 실내 음향 특성 파악과 음질 개선에 중요한 도구로 활용될 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2004.11a
• /
• pp.181-183
• /
• 2004

본 논문은 패킷 방식의 OFDM(orthogonal frequency division multiplexing) 시스템에서 등화기 출력과 비터비 복호기 출력을 이용한 잔존 주파수 옵셋 추정 법을 제안한다 패킷 방식의 OFDM에서는 패킷의 앞 부분의 훈련열을 이용하여 한번 추정하기 때문에 시간이 지남에 따라 추정 오차에 의한 위상 회전이 축적된다. 이러한 위상 회전의 축적을 막기 위해 등화기 출력과 비터비 복호기의 출력에서 잔존 주파수 옵셋을 추정하여 매 심볼마다 보상한다. 잔존 주파수 옵셋의 추정은 먼저 첫 번째 심복의 등화기 출력과 그것의 비터비 복호기 출력 사이에서 위상차를 구한다. 두 번째 심복의 위상차도 처음 심복과 같은 방법으로 구한다. 두 번째 구한 위상차는 이전 심볼의 위상차에서 잔존 주파수 옵셋의 영향이 더해져 있다. 이득 두개의 위상차의 차로부터 잔존 주과수 옵셋을 구할 수 있다. 이 방법은 전송된 데이터를 사용하여 추정하기 때문에 추가적인 훈련열을 사용하지 않고 매 심볼마다 보상을 할 수 있다는 장점이 있다.

• Journal of Korea Technology Innovation Society
• /
• v.16 no.3
• /
• pp.630-649
• /
• 2013

Korea Meteorological Administration has promoted the next generation urban and rural smart weather service project. The purpose of this project is to provide the necessary information to urban and rural districts by using the subdivided meteorological information. This study attempts to assess the value of the next generation urban and rural smart weather service project by using contingent valuation method. According to estimating result, annual mean willingness to pay per household for the next generation urban and rural smart weather service project is 2,947 won.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.39 no.3
• /
• pp.399-405
• /
• 2010

After Gomchui tea was prepared from leaves of Ligularia fischeri (Ledeb.) Turcz by blanching method, the antioxidant activity of major compounds in Gomchui tea was assessed. On-line HPLC-ABTS analysis revealed that caffeoylquinic acids (chlorogenic acids), such as 5-O-caffeoylquinic acid (5-CQA), 3,4-di-O-caffeoylquinic acid (3,4-DCQA), 3,5-di-O-caffeoylquinic acid (3,5-DCQA) and 4,5-di-O-caffeoylquinic acid (4,5-DCQA), were the major antioxidant compounds in Gomchui tea. The extraction efficiency of these compounds were examined in the various conditions such as extraction temperature, time and solvent. The results demonstrated that the extraction amount with water increased in proportion to extraction time (1~10 min) and temperature ($8{\sim}80^{\circ}C$). These active compounds were also extracted with water even at $8^{\circ}C$ (60% of $80^{\circ}C$), indicating that water is very good extraction solvent for extraction of these antioxidant constituents. However, the extraction efficiency of these compounds decreased when ethanol percentage in water increased. The extraction efficiency between Gomchui powder (no blanching) and tea was significantly different, and 60% of total antioxidant compounds in tea was removed from fresh leaves into water in blanching process, especially 3,5-DCQA (over 90%). Meanwhile, the sonication method didn't affect the extraction of these compounds in all solvents. These results suggest that Gomchui tea can be a good candidate for the tea beneficial to human health.

• Korean Journal of Soil Science and Fertilizer
• /
• v.31 no.2
• /
• pp.114-119
• /
• 1998

Intensity and stability of the blue color of phospho-molybdate complex in P analysis are known to be influenced by the matrix, reducing regent and acidity of the extractants. Objective of this research was to compare the efficiency of the color-developing reagents for P concentrations in distilled water and extracts of Lancaster, Mehlich II, and Mehlich III methods. Efficiencies on which to base this study were evaluated by the optimum ranges of P, reproducibility of calibration curve and stability of the developed color. Color-developing reagents employed were ammonium molybdate-1,2,4- aminonaphtholsulfonic acid (ANS), ammonium molybdate-ascorbic acid-bismuth subcarbonate (AB), and ammonium molybdate-ascorbic acid-antimony potassium tartarate (AA). The ANS revealed the lowest sensitivity but the widest ranges for P concentrations in color development. On the other hand, the AA bore the narrowest color-developing ranges and its sensitivity was similar to AB. However, at P concentrations lower than $0.5mg\;L^{-1}$, AA was more sensitive than AB. Based on the data on the ranges of calibration curve, stability of color and reproducibility of analytical data. AA reagent was considered to be suitable for the determination of P in distilled water and AB reagent was practically recommendable for soil P analysis in extracts by Lancaster, Mehlich II, and Mehlich III procedures.

• Journal of KIISE:Databases
• /
• v.31 no.5
• /
• pp.479-491
• /
• 2004

Location information of mobile objects is applied to vehicle tracking, digital battlefields, location based services, and telematics. Their location coordinates are periodically measured and stored in the application systems. The linear function is mainly used to estimate the location information that is not in the system at the query time point. However, a new method is needed to improve uncertainties of the location representation, because the location estimation by linear function induces the estimation error. This paper proposes an application method of the cubic spline interpolation in order to reduce deviation of the location estimation by linear function. First, we define location information of the mobile object moving on the two-dimensional space. Next, we apply the cubic spline interpolation to location estimation of the proposed data model and describe algorithm of the estimation operation. Finally, the precision of this estimation operation model is experimented. The experimentation comes out more accurate results than the method by linear function, although the proposed location estimation function uses the small amount of information. The proposed method has an advantage that drops the cost of data storage space and communication for the management of location information of the mobile objects.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.8
• /
• pp.37-45
• /
• 2002

A two-dimensional unsteady, inviscid flow solver has been developed for the simulation of airfoil-vortex interactions on unstructured dynamically adapted meshes. The Euler solver is based on a second-order accurate implicit time integration using a point Gauss-Seidel relaxation scheme and a dual time-step subiteration. A vertex-centered, finite-volume discretization is used in conjunction with the Roe's flux-difference splitting. An unsteady solution-adaptive dynamic mesh scheme is used by adding and deleting mesh points to take account of both spatial and temporal variations of the flow field. The effect of vortex interaction on the aeroelastic displacement of an airfoil attached to the idealized two degree-of-freedom spring system is investigated.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.11 no.5
• /
• pp.70-77
• /
• 2012

Dial-a-ride is the most widely available transit service for disabled persons or seniors in the United States and Europe. This paper studies a static dial-a-ride problem considering multiple depots, heterogeneous vehicles, and soft time windows. In this paper, we apply a heuristic based on clustering first-routing second(HCR) to a real-world large dial-a-ride problem from Maryland Transit Administration(MTA). MTA's real operation is compared with the results of developed heuristic for 24 cases. The objective function of the proposed model is to minimize the total cost composed of the service provider's cost and the customers' inconvenience cost. For the comparison, the objective function values of HCR do not include waiting cost, delay cost, and excess ride cost. The objective function values from HCR are better than those from MTA's operation for all cases. This result shows that our heuristic method can make the real operation better and more efficient.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.1841-1844
• /
• 2009

일반 하천에서의 유량측정 방법은 하천 조건에 따라 다르다. 전통적인 방법으로는 구조물에 의한 방법, 유속계 측정에 의한 유속-면적법, 부자에 의한 방법, 그리고 희석법 등이 있다. 그러나 이러한 방법들은 측정 위험성을 가지고 있다. 홍수시 발생되는 고유속과 심한 난류, 거대한 부유물질들은 하천 접근에 어려움을 가져오고, 측정 기기의 파손 위험성뿐만 아니라 인명피해까지 발생시킬 가능성이 있다. 최근 기존 방법들의 문제점을 해결하기 위하여 음파, 초음파, 레이더 등을 이용한 유량 측정 방법과 장비들이 개발되었다. 본 연구에서 사용한 레이더 유속계는 하천의 표면유속을 측정하는 비접촉식 센서로 홍수기 전 미리 유속 측정 단면 측량을 실시한다면 홍수시에도 비교적 신속하고 안전하게 유속을 측정할 수 있다. 따라서 본 연구에서는 레이더 유속계를 충청북도 괴산군 달천에 위치한 수전교에 설치하여 괴산댐 방류량 및 동시유량 측정 성과와 비교하였다. 2007년 7월부터 2008년 8월까지 $36m^3/s\;\sim\;821m^3/s$의 사상에서 총 10회 측정한 결과, 레이더 유속계를 사용하여 측정한 유량의 상대오차는 댐방류량 대비 -3.3% $\sim$ 27.5%로 나타나 평균11.8%의 상대오차를 보였다. 레이더 유속계 측정과 동시에 실시한 유속-면적법 측정, ADCP법 측정의 상대오차는 각각 평균 5.7%, 6.5%로 나타난 것과 비교한다면 다소 높은 오차를 보였다. 그러나 측정 시간의 경우 수위에 따라 다소 차이는 있지만 레이더 유속계를 이용하면 30분 정도의 시간이 소요되었으며, 유속면적법은 1시간 이상, ADCP법은 40분의 시간이 소요되었다. 이와 같이 레이더 유속계는 다른 방법에 비해 정확성은 다소 떨어지지만 측정 속도와 안정성 면에서는 우수하다고 판단된다. 문제점으로 지적되는 정확도 측면의 경우 레이더 유속계로 측정되는 표면유 속과 평균 유속 사이의 보정계수 문제를 보완한다면 보다 정확한 측정이 가능할 것으로 판단된다.

• Geophysics and Geophysical Exploration
• /
• v.24 no.4
• /
• pp.164-170
• /
• 2021

Frequency-domain and time-domain induced polarization methods can provide spectral information about subsurface media. Analysis of spectral characteristics has been studied mainly in the frequency-domain, however, time-domain induced polarization research has recently become popular. In this study, assuming a homogeneous half-space model, an inversion method was developed to extract Cole-Cole parameters from the measured secondary potential or electrical resistivity. Since the Cole-Cole parameters of chargeability, time constant, and frequency index are not independent of each other, various problems, such as slow convergence rate, initial model problem, local minimum problem, and divergence, frequently occur when conventional nonlinear inversion is applied. In this study, we developed an effective inversion method using the initial model close to the true model by introducing a grid search method. Finally, the validity of the developed inversion method was verified using inversion experiments.