• 대한수학회지
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• 제58권3호
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• pp.723-740
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• 2021

Design and maintenance of large span roof structures require an analysis of their static and dynamic behavior depending on the physical parameters defining the structures. Therefore, it is highly desirable to estimate the parameters from observations of the system. In this paper we study the parameter estimation problem for damped shallow arches. We discuss both symmetric and non-symmetric shapes and loads, and provide theoretical and numerical studies of the model behavior. Our study of the behavior of such structures shows that it is greatly affected by the existence of critical parameters. A small change in such parameters causes a significant change in the model behavior. The presence of the critical parameters makes it challenging to obtain good estimation. We overcome this difficulty by presenting the Parameter Estimation Algorithm that identifies the unknown parameters sequentially. It is shown numerically that the algorithm achieves a successful parameter estimation for models defined by arbitrary parameters, including the critical ones.

• Journal of Welding and Joining
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• 제13권4호
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• pp.85-102
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• 1995

Weld quality of GMA welding processes is closely related to arc stability. Although many researches on arc stability have been performed, real-time estimation of arc stability has not been attempted. For instance, Mita proposed a off-line statistical method in which short circuiting and arcing time, and voltage and current wave forms were sampled to assess arc stability. But this method is not suitable to assess arc stability for GMA welder which employ inverter power source due to its controlled current and voltage wave forms. In this paper, the relationship between are stability and wire feed rate fluctuation is analyzed to propose new criterion for inverter power source. When arc voltage and arc current and arcing time are analyzed, we can assess arc stability only for short circuit transfer mode. When wire feed rate is analyzed, we can estimate arc stability udner the condition of spray transfer mode as well. Hence, the wire feed rate is chosen for monitoring process variable to cover possible metal transfer modes in GMAW. Through this research, it has been identified that arc stability in GMA welding processes is closely related to wire fed rate. When inverter power source is used, conventional statistical method of estimating arc stability, such as Mita index, is no longer valid due to its controlled voltage and current wave forms. Arc stability has been also examined in phase plane diagram.

• Structural Engineering and Mechanics
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• 제11권1호
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• pp.1-16
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• 2001

This paper discusses the elastic stability of unbraced frames under non-proportional loading based on the concept of storey-based buckling. Unlike the case of proportional loading, in which the load pattern is predefined, load patterns for non-proportional loading are unknown, and there may be various load patterns that will correspond to different critical buckling loads of the frame. The problem of determining elastic critical loads of unbraced frames under non-proportional loading is expressed as the minimization and maximization problem with subject to stability constraints and is solved by a linear programming method. The minimum and maximum loads represent the lower and upper bounds of critical loads for unbraced frames and provide realistic estimation of stability capacities of the frame under extreme load cases. The proposed approach of evaluating the stability of unbraced frames under non-proportional loading has taken into account the variability of magnitudes and patterns of loads, therefore, it is recommended for the design practice.

• 한국응용과학기술학회지
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• 제12권1호
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• pp.1-11
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• 1995

In this outline, the stability of solid/liquid dispersion was theoretically investigated the matter from all angles by using the modified DLVO theory. The stability was handled various considerations such as a production and characteristics of electrical double layer, total interaction$(V_T)$ that consisting of attractive force$(V_A)$ and repulsion$(V_R)$. coagulation, the stability ratio(W), critical flocculation concentration (cfc) and zeta potential$(\zeta)$ etc. It was possible for us to examine with the stability ratio(W), critical flocculation concentration (cfc) and zeta potential$(\zeta)$ that may estimation of stability of solid/liquid dispersion experimentally.

• 한국대기환경학회지
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• 제6권2호
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• pp.168-175
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• 1990

Pasquill stability class (PSC) was evaluated with Monin-Obukhov length (L) using the data observed at a height of 213m meteorological tower in Tsukuba, Japan. PSC was determined with wind speed and insolation (net radiation at night), and L was calculated with the heat flux and the friction velocity obtained at 25m by the eddy correlation method. To evaluate PSC with L, for every class of Pasquill stability (from A to F class), percentiles and median of L were used. Results show that for every class of Pasquill stability, L varies so widely that PSC does not adequately represent the atmospheric stability conditions. The scheme which estimates L using air temperature at two levels and wind speed at single level was developed. Comparison between estimated L by the scheme and observed L reveals that the scheme is better than PSC. Furthermore, the scheme is more advantageous than PSC because it uses air temperature at two levels instead of insolation which is more difficult to observe in the field than air temperature.

• Journal of Information Processing Systems
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• 제15권4호
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• pp.820-832
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• 2019

Estimation of accurate blood volume flow in ultrasound Doppler blood flow spectrograms is extremely important for clinical diagnostic purposes. Blood volume flow measurements require the assessment of both the velocity distribution and the cross-sectional area of the vessel. Unfortunately, the existing volume flow estimation algorithms by ultrasound lack the velocity space distribution information in cross-sections of a vessel and have the problems of low accuracy and poor stability. In this paper, a new robust ultrasound volume flow estimation method based on multigate (RMG) is proposed and the multigate technology provides detail information on the local velocity distribution. In this method, an accurate double iterative flow velocity estimation algorithm (DIV) is used to estimate the mean velocity and it has been tested on in vivo data from carotid. The results from experiments indicate a mean standard deviation of less than 6% in flow velocities when estimated for a range of SNR levels. The RMG method is validated in a custom-designed experimental setup, Doppler phantom and imitation blood flow control system. In vitro experimental results show that the mean error of the RMG algorithm is 4.81%. Low errors in blood volume flow estimation make the prospect of using the RMG algorithm for real-time blood volume flow estimation possible.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1091-1094
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• 2005

This paper formulates the parameter estimation of cornering behavior of a vehicle. Especially some vehicle parameter is very important on stability control of chassis by ECU, but some parameter is so hard to get by sensor which parameter is included the nonlinear characteristic of tire cornering force. So we need to deduce that parameter from used signal and numerical method. In this study, we propose a estimation method and present the simulation by parameter estimation technique.

• 한국기계가공학회지
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• 제9권3호
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• pp.49-55
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• 2010

In this paper, the stability of cracked cantilever T-beams subjected to subtangential follower force is investigated. Also, the effect of subtangential coefficient and crack on the natural frequency of T-beams is presented. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations. The values of critical follower force and the stability maps of cantilever T-beams are obtained according to the subtangential coefficient and crack severity. The results of this study will contribute to the safety testing and the stability estimation of cracked T-beams subjected to follower force.

• Geomechanics and Engineering
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• 제21권2호
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• pp.123-132
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• 2020

Due to the various restrictions and problems related to the construction of new roads in urban areas, underground road construction has been receiving a great deal of attention in the field of tunnel engineering. In this study, a double-deck road tunnel with a diverging section was analyzed for the evaluation of its stability. Both numerical analysis and scale model tests were performed, the results were used to develop a stability evaluation method for double-deck tunnels with diverging sections constructed in rocks by NATM. From regression analyses conducted on the results of the numerical analysis, an equation and a chart were derived, these tools allow us to obtain the strength/stress ratio (SSR) for double-deck road tunnels with a diverging tunnel in various diverging conditions quickly and accurately. These tools have great potential to help engineers evaluate the stability of double-deck tunnels in the preliminary design stage.

• 한국정밀공학회지
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• 제22권10호
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• pp.129-136
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• 2005

The demand on thermos furnace of Al molten metal has recently been getting higher and higher according to the increase in use of Al and Al alloys. This study considers the estimation of the thermal and mechanical stability in the thermos furnace for Al casting. It is executed through the analysis of heat transfer on the refractory material and heat stress on each steel shell. Also, the estimation of structural stability was appraised through the strength analysis of the lower structure. In result, the temperature of steel shell rose to 320.15K and its elastic deformation was about 1.5mm. The elastic deformation of the lower structure was about 0.66mm. As a result of it, the data obtain from the analysis in this study are regarded as stable value on considering that the size of the furnace is 2500mm.