• Structural Engineering and Mechanics
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• v.34 no.6
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• pp.779-799
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• 2010

In order to consider high-order effects on the actual limit state function, a new response surface method is proposed for structural reliability analysis by the use of high-order approximation concept in this study. Hermite polynomials are used to determine the highest orders of input random variables, and the sampling points for the determination of highest orders are located on Gaussian points of Gauss-Hermite integration. The cross terms between two random variables, only in case that their corresponding percent contributions to the total variation of limit state function are significant, will be added to the response surface function to improve the approximation accuracy. As a result, significant reduction in computational cost is achieved with this strategy. Due to the addition of cross terms, the additional sampling points, laid on two-dimensional Gaussian points off axis on the plane of two significant variables, are required to determine the coefficients of the approximated limit state function. All available sampling points are employed to construct the final response surface function. Then, Monte Carlo Simulation is carried out on the final approximation response surface function to estimate the failure probability. Due to the use of high order polynomial, the proposed method is more accurate than the traditional second-order or linear response surface method. It also provides much more efficient solutions than the available high-order response surface method with less loss in accuracy. The efficiency and the accuracy of the proposed method compared with those of various response surface methods available are illustrated by five numerical examples.

• Journal of Nutrition and Health
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• v.49 no.4
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• pp.213-222
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• 2016

Purpose: Coffee is the most frequently consumed food item in South Korea after rice and cabbage. Coffee contains various substances, including caffeine, cafestol, kahweol, chlorogenic acid, and many other known and unknown ingredients with some health benefits. Especially, cumulative evidence has shown that regular coffee use is associated with lower risk of type 2 diabetes, although limited and inconsistent data are available regarding metabolic syndrome. Methods: This study reviewed all available scientific and epidemiologic evidence on coffee consumption, metabolic syndrome, and the association between them. Most epidemiologic research regarding this association was of a cross-sectional design, and a few case-control and cohort studies were available. We conducted meta-analysis with 11 observational studies investigated in Europe, America, and Asia. Summary odds ratios (OR) were calculated using a random-effects model. Results: The overall OR of metabolic syndrome was 0.90 (95% Confidence Interval (CI), 0.81-0.99) for the highest category of coffee intake compared with the lowest intake category. These associations were stronger in populations of US and Europe (OR 0.84, 95% CI 0.76-0.94), whereas no association was observed in the Asian population (OR 1.00, 95% CI 0.81-1.23). Conclusion: The review results indicate that frequent coffee consumption may be beneficial to metabolic syndrome, but the association between coffee consumption and metabolic syndrome may differ by nations or continents.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.2
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• pp.141-157
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• 2012

For the application TBM tunneling method, Both tunnel design standard and case study designed & constructed in domestic and foreign have been conducted. According to the study, the number of lane and inner shape (single or duplex) vary depending on the volume of traffic. Also extra space located in the top and bottom of tunnel is used for a multipurpose such as ventilation, disaster prevention, maintenance and administration. To find area ratio according to the components of road TBM tunnel, a standard section was considered as a two-lane road. Then, the analysis of area ratio of this section which consists of components for clearance, extra space in upper and lower tunnel was carried on two widths of shoulder. In addition, after a structural analysis, a thickness requirement of lower slab which is essential for road tunnel was derived on a few supporting types. Through correlation analysis, the ranges of available cross-sectional area between slab thickness and lower extra space of the tunnel was presented.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.3975-3984
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• 2022

Distributed control system architecture is adopted for I&C systems of Prototype Fast Breeder Reactor, where the geographically distributed control systems are connected to centralized servers & display stations via switched Ethernet networks. TCP/IP communication plays a significant role in the successful operations of this architecture. The communication tasks at control nodes are taken care by TCP/IP offload modules; local area switched network is realized using layer-2/3 switches, which are finally connected to network interfaces of centralized servers & display stations. Safety, security, reliability, and fault tolerance of control systems used for safety-related applications of nuclear power plants is ensured by indigenous design and qualification as per guidelines laid down by regulatory authorities. In the case of commercially available components, appropriate suitability analysis is required for getting the operation clearances from regulatory authorities. This paper details the proposed approach for the suitability analysis of TCP/IP communication nodes, including control systems at the field, network switches, and servers/display stations. Development of test platform using commercially available tools and diagnostics software engineered for control nodes/display stations are described. Each TCP link behavior with impaired packets and multiple traffic loads is described, followed by benchmarking of the network switch's routing characteristics and security features.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.7
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• pp.702-710
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• 2008

In this paper, the observability of the INS/GPS integrated system for a land vehicle is analyzed on measurements and different filters with respect to the measurements are designed. In the stationary case, it is shown that horizontal accelerometer biases and vertical attitude errors and gyro biases are unobservable. An 8-state filter is designed based on the observability analysis. When GPS signal is available, a 15-state filter is used with position and velocity measurements. To estimate the INS errors even in the case that GPS signal is blocked a filter is designed in consideration of the non-holonomic constraints of a land vehicle. In this case, the horizontal position and velocity errors and vertical attitude error are unobservable. However, a 12-state filter including the velocity states is designed to estimate the accelerometer biases. When GPS signal recovers, a 9-state filter is used excluding the sensor biases. This paper presents a multi-dimensional filter that switches the four filters according to the usable measurements and maneuver environments. A simulation is carried out to verify the performance of the proposed filter.

• Interaction and multiscale mechanics
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• v.5 no.3
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• pp.211-228
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• 2012

This paper reports the development of a generalized inverse analysis formulation for the parameter estimation of four-parameter Burger model. The analysis is carried out by formulating the problem as a mathematical programming formulation in terms of identification of the design vector, the objective function and the design constraints. Thereafter, the formulated constrained nonlinear multivariable problem is solved with the aid of fmincon: an in-built constrained optimization solver module available in MatLab. In order to gain experience, a synthetic case-study is considered wherein key issues such as the determination and setting up of variable bounds, global optimality of the solution and minimum number of data-points required for prediction of parameters is addressed. The results reveal that the developed technique is quite efficient in predicting the model parameters. The best result is obtained when the design variables are subjected to a lower bound without any upper bound. Global optimality of the solution is achieved using the developed technique. A minimum of 4-5 randomly selected data-points are required to achieve the optimal solution. The above technique has also been adopted for real-time settlement of four oil refineries with encouraging results.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.4
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• pp.58-67
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• 1998

A sectional analysis of sheet metal forming process with an arbitrary tool shape is proposed in the present work. To improve the numerical convergence in the conventional membrane sectional analysis, the Bending Energy Augmented Membrane (BEAM) elements had been developed. The BEAM elements particularly improve the stability and convergence of the finite element method for the case of deep drawing. In this work, the FERGUBON spline (C$^2$-continuous) was used to fit the deformed mesh to smooth the given curves and calculate the local curvature of the deformed sheet. The fittings of the deformed sheet and tool surface profile ensure the stability and the convergence of the finite element analysis of highly nonlinear stamping processes. A center floor section and front fender section are analyzed to show the accuracy and robustness of the approach. The results obtained by the proposed approach are compared with the available experimental data.

• Structural Engineering and Mechanics
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• v.43 no.5
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• pp.583-605
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• 2012

This paper presents a spatial catenary cable element for the nonlinear analysis of cable-supported structures. An incremental-iterative solution based on the Newton-Raphson method is adopted for solving the equilibrium equation. As a result, the element stiffness matrix and nodal forces are determined, wherein the effect of self-weight and pretension are taken into account. In the case of the initial cable tension is given, an algorithm for form-finding of cable-supported structures is proposed to determine precisely the unstressed length of the cables. Several classical numerical examples are solved and compared with the other available numerical methods or experiment tests showing the accuracy and efficiency of the present elements.

• Korean Journal of Construction Engineering and Management
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• v.10 no.4
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• pp.87-100
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• 2009

The quality of early cost estimates is critical to the feasibility analysis and budget allocation decisions for public capital projects. Various researches have been attempted to develop cost prediction models in the early stage of a construction project. However, existing studies are limited on its applicability to actual projects because they focus primarily on a specific phase as well as utilize restricted information while the amount of information collectable differs from one another along with the project stages. This research aims to develop two-staged cost estimation model for the schematic planning and preliminary design process of a construction projects, considering the available information of each phase. In the schematic planning stage where outlined information of a project is only available, the Case-Based Reasoning model is used for easy and rapid elicitation of a project cost based on the extensive database of more than 90 actual highway construction projects. Then, the representing quantity-based model is proposed for the preliminary design stage where more information on the quantities and unit costs are collectable based on the alternative routes and cross-sections of a highway project. Real case studies are used to demonstrate and validate the benefits of the proposed approach. Through the two-stage cost estimation system, users are able to hold a timely prospect to presume the final cost within the budge such that feasibility study as well as budget allocation decisions are made on effectively and competitively.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.6
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• pp.253-260
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• 2015

In this study, using the FDS as the fire simulation and evacuation simulations of the Pathfinder, set the main control room of the building to the fire point fire safety assessment studies were carried out. At first the quantitative result such as distribution of visibility as time passing, distribution of temperature, distribution of CO density produced results using fire-simulation and evacuation-simulation was carried out based on the result that produced the final safety evaluation result as being calculated of evacuation time. As the risk increased with the distribution of visibility at the result of fire-simulation, evacuation-simulation was carried out using the result. Finally the result was made 127.9 sec that everyone could evacuate. The numerical results are analyzed in case of the places in the building required safe egress time for safety a as the analysis to be no more than available safe egress time was analyzed to be secured. The results of this safety evaluation represent that more smooth evacuation safety performance can be secured by linking the event of fire firefighting equipment as a result of simulating the worst conditions.