• 제어로봇시스템학회논문지
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• 제19권8호
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• pp.682-687
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• 2013

Navigation is a crucial capability for all types of manned or unmanned vehicles. However, vehicle navigation in underwater environments still remains a challenging problem since GPS signals for position fixes are not available in the water. Terrain-referenced underwater navigation is an alternative navigation technique that utilizes geometric information of the subsea terrain to correct drift errors due to dead-reckoning or inertial navigation. Terrain-referenced navigation requires the description of an undulating terrain surface as a mathematical function or table, which often leads to a highly nonlinear estimation problem. Recently, PFs (Particle Filters), which do not require any restrictive assumptions about the system dynamics and uncertainty distributions, have been widely used for nonlinear filtering applications. However, PF has considerable computational requirements which used to limit its applicability to problems of relatively low state dimensions. This study proposes the use of a Rao-Blackwellized particle filter that is computationally more efficient than the standard PF for terrain-referenced underwater navigation involving a moderate number of states, and its performance is compared with that of the extended Kalman filter algorithm. The validity and feasibility of the proposed algorithm is demonstrated through numerical simulations.

• 한국농공학회논문집
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• 제58권4호
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• pp.85-95
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• 2016

PBT (Plate Bearing Test) is a commonly used compaction estimation used to provide basal support for embankments. This study presents the results from experimental evaluations PBT, LWDT (Light Drop Weight Tester) test and Geogauge test with embankment materials which consist in sandy soil, crushed stone and rock. The results of this study indicate that the regression analyze results (r) from test results between Young's modulus and $k_{30}$, $E_v$ are 0.385 and 0.111~0.496, estimated very lack of correlation. The Geogauge is frequency vibration from machine to underground. Geogauge can not measure to accuracy test results when it is used on ground of the rock or crushed stone. The regression analyze results (r) from $E_v$ and Dynamic modulus are 0.502~0.847, different estimated by calculate method, as it were, when calculate $E_v$, least square method are appeared more accuracy than gradient of secant.

• 대한조선학회지
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• 제9권1호
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• pp.1-6
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• 1972

To contribute towards more accurate estimation of the virtual coefficient for the vertical vibration of the chine-type ship, experimentally obtained three-dimensional correction factors, J, of added mass of prismatic beams having cross section shape of hypotrocoid characters, slightly concaved Lewis form and elliptic form are investigated in connection with the applicability of an approximate analytical calculation method compared to that proposed by T. Kumai[6] for the Lewis form cylinders, and synthetically in compared with the experimental works on various cross section shapes of the other type by L.C. Burril et al[8] and the analytical works on the ellipsoid of revolution by F.M. Lewis[1] and J.L. Taylor[2]. The experimental results show that the aforementioned analytical method gives, unlike that for the Lewis form cylinders, considerably larger J-values for the chine-type cylinders, and that the influence of the character of the cross section shape on J-values is not remarkable in practical sense. Finally, considering in synthesis the experimental results on prismatic beams, the Burril's works on palabolic plan form and elliptic plan form, and that the chine-type ship usually has a hull form of transom stern, it is fairly safe to say, at the present stage, that adoptation of the Taylor's J-values will not results in any large error in estimation of the virtual inertia coefficients of the chine-type ships.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.575-582
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• 2000

The flat Dilatometer test(flat DMT) has been known as an in-situ testing method which is simple and robust to use, and reliable for site stratification and evaluation of soil properties. It was designed and proposed by Marchetti in 1975 to characterize the properties of soils. There are many researches that have been done to evaluate the horizontal coefficient of consolidation from the dissipation test results of flat DMT on normally consolidated and slightly overconsolidated clays. The representative estimation methods of estimating the horizontal consolidation coefficient are DMT-C method which uses a C-reading dissipation curve and DMT-A method which uses a A-reading dissipation curve. This paper represents a comparison analysis of those two methods in obtaining the horizontal coefficients of consolidation. The reference values are also obtained by CPTU and other laboratory tests. The applicability of using flat DMT to characterize the consolidation behavior is also reviewed for two sites. According to the results, DMT-A method is not suitable for silty clays possibly because of the compressibility characteristics. As for the normally consolidated and slightly overconsolidated clays, the results obtained from the two methods are comparable with each other as well as with the laboratory test results.

• 한국해양학회지:바다
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• 제5권3호
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• pp.177-185
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• 2000

자료동화기법의 하나인 adjoint 방법은 제약조건으로서 모델의 기본방정식을 만족시키는 동시에 모델 결과와 관측자료 차이의 함수인 비용함수의 크기를 최소화시키는 모델변수를 찾아냄으로서 모델 결과를 향상시키는 기법이다. 본 연구에서는 수평방향 2차원 선형 조석모델과 adjoint 모델로 구성된 adjoint 꾸러미를 수립하고, 이를 임의로 설정한 직사각형 모델영역에 적용하였다. 조석모델로부터의 조위 모델 결과를 관측자료로 삼아 개방경계조건인 조위의 진폭을 역 추정하는 수치실험을 실시하여 자료 가중치에 대한 반응, 모델변수 초기 추정치의 중요성 및 지형 변화에 대한 반응 등을 살펴보았다 특히, adjoint꾸러미 적용시 대부분 경험적으로 설정되어왔던 가중치의 선정방법을 제시하였다.

• Environmental Analysis Health and Toxicology
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• 제16권4호
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• pp.189-196
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• 2001

Octanol/water partition coefficients of 52 chemicals were calculated using RP-HPLC estimation method and predicted by computer program, PCHEM. The result showed relationship between literature values and RP-HPLC observed values (relative coefficient r$^2$＝0.916), but the relationship of PCHEM values with literature values was lower than RP-HPLC value (relative coefficient r$^2$＝0.795). The average difference in partition coefficient between the RP-HPLC method and flask-shaking method was log Kow＝0.54, while the average difference between the values predicted form the computer program and flask- shaking method was log Kow = 0.36 Compared to octanol/water partition coefficients by 3 methods (Flask-shaking, RP-HPLC, computer prediction), the octanol/water partition coefficient values based on the flask-shaking method were very similar to the literature values, while the octanol/water partition coefficient values by RP-HPLC method without to consider the dead time, and computer prediction values did not significantly differ with the literature values.

• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.483-492
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• 2004

This paper presents an efficient algorithm for the estimation of damage location and severity in bridge structures using Probabilistic Neural Network (PNN). Generally, the Back Propagation Neural Network (BPNN)-based damage detection methods need a lot of training patterns for neural network learning process and the optimum architecture of a BPNN is selected by trial and error. In this paper, the PNN instead of the conventional BPNN is used as a pattern classifier. The modal properties of damaged structure are somewhat different from those of undamaged one. The basic idea of proposed algorithm is that the PNN classifies a test pattern which consists of the modal characteristics from damaged structure, how close it is to each training pattern which is composed of the modal characteristics from various structural damage cases. In this algorithm, two PNNs are sequentially used. The first PNN estimates the damage location using mode shape and the results of the first PNN are put into the second PNN for the damage severity estimation using natural frequency. The proposed damage assessment algorithm using the PNN is applied to a cable-stayed bridge to verify its applicability.

• 대한토목학회논문집
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• 제31권1B호
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• pp.63-70
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• 2011

횡월류위어를 천변저류지 등의 유입부에 설치하기 위해서는 정확한 월류량을 산정하는 것이 선행되어야 한다. 본 연구에서는 실제 하천에 적용성이 높을 것으로 판단되는 사다리꼴 수로의 광정횡월류위어에 대한 수리실험을 실시하였고, 유량계수산정을 위하여 상류 Froude수, 위어높이, 위어길이, 본류수로폭, 수로경사 등을 고려하였다. 분석결과 광정횡월류위어에서 $h/y_u$, $L/y_u$, $Fr_u$의 중요도가 큰 것을 확인하였고, 다중회귀분석을 통해 유량계수식을 제시하였다. 또한 기존 연구자들의 실험자료와 본 실험의 연구자료를 비교하였으며, 측정된 월류량과 계산된 월류량을 비교하여 유량계수식의 적용성을 확인하였다.

• Smart Structures and Systems
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• 제14권4호
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• pp.699-718
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• 2014

The indirect displacement estimation using acceleration and strain (IDEAS) method is extended to various types of beam structures beyond the previous validation on the prismatic or near-prismatic beams. By fusing different types of responses, the IDEAS method is able to estimate displacements containing pseudo-static components with high frequency noise to be significantly reduced. However, the concerns to the IDEAS method come from possible disagreement of the assumed sinusoidal mode shapes to the actual mode shapes, which allows the IDEAS method to be valid only for simply-supported prismatic beams and limits its applicability to real world problems. In this paper, the extension of the IDEAS method to the general types of beams is investigated by the mathematical formulation of the modal mapping matrix only for the monitored substructure, so-called monitoring span. The formulation particularly considers continuous and wide beams to extend the IDEAS method to general beam structures that reflect many real bridges. Numerical simulations using four types of beams with various irregularities are presented to show the effectiveness and accuracy of the IDEAS method in estimating displacements.

• 소음진동
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• 제9권1호
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• pp.60-69
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• 1999

In the first paper of this research$^{(1)}$. a new time series method. directional ARMAX (dARMAX) model-based approach. was proposed for rotordynamics identification. The dARMAX processes complex-valued signals, utilizing the complex modal testing theory which enables the separation of the backward and forward modes in the two-sided frequency domain and makes effective modal parameter identification possible. to account for the dynamic characteristics inherent in rotating machinery. In this second part. an evaluation of its performance characteristics based on both simulated and experimental data is presented. Numerical simulations are carried out to show that the method. a complex time series method. successfully implements the complex modal testing in the time domain. and it is superior in nature to the conventional ARMAX and the frequency-domain methods in the estimation of the modal parameters for isotropic and weakly anisotropic rotor systems. Experiments are carried out to demonstrate the applicability and the effectiveness of the dARMAX model-based approach, following the proposed fitting strategy. for the rotordynamics identification.