• International conference on construction engineering and project management
• /
• 2022.06a
• /
• pp.640-648
• /
• 2022

In the United States, the Safety Rest Areas (SRAs) were introduced as highway roadside infrastructures in the early 1900s. The State Departments of Transportation (DOTs) operate/maintain their SRAs using different methods. The Washington DOT used the in-house workforce method for over 20 years, whereas some states moved to Performance-Based Contracting (PBC) from the in-house workforce to save cost primarily. Several existing studies claimed that using the PBC approach saved costs on several highway assets. Thus, the principal objective of this study is to compute and compare the unit operating/maintenance cost of SRAs using the in-house workforce method (in Washington state) with the PBC approach (in other states). The findings of this study show that the average annual cost using the PBC approach was much more than the average annual cost using the in-house workforce approach. The findings also show that in Washington state, the 'Labor Cost' category was a key expenditure, which is statistically higher than other categories. The 'Labor Cost' was followed by the 'Other Services', and then 'Materials and Supplies' and 'Equipment.' The study's findings indicated that outsourcing does not always save costs for agencies. The study findings may help transportation construction/maintenance professionals select a cost-effective approach for their future planning.

• Journal of Families and Better Life
• /
• v.20 no.5
• /
• pp.137-147
• /
• 2002

Purpose of this study is to find the research direction to solve the housing problems for the elderly which based on approaches and issues in related studies. Research method was interpretative analysis of the articles issued from 1976 to 2002. Each approach (rationalistic approach, ecological approach, micro-sociological approach, typological approach, environment-psychological approach, welfare approach) produced helpful information and had relative merits. But the researchers must regard housing for the elderly as a social problem in macroscopic view to solve the housing problems for older people with welfare approach. As a result, to solve the housing problems with welfare approach for the elderly who live in their own place with community care, studies about lifetime home, care and repair, and management of housing for the elderly might be needed. And research about existing services, transfer system of services, financial problems, man power to manage the system might be needed to spread out the services to the middle class elderly.

• Water Engineering Research
• /
• v.5 no.4
• /
• pp.177-183
• /
• 2004

This paper introduces an eigenvalue method of transforming the hyperbolic partial differential equations of a particular unsteady friction water hammer model into characteristic form. This method is based on the solution of the corresponding one-dimensional Riemann problem that transforms hyperbolic quasi-linear equations into ordinary differential equations along the characteristic directions, which in this case arises as the eigenvalues of the system. A mathematical justification and generalization of the eigenvalues method is provided and this approach is compared to the traditional characteristic method.

• Journal of the Korean Data and Information Science Society
• /
• v.14 no.2
• /
• pp.209-216
• /
• 2003

Contingent valuation method (CVM) is a main evaluation method of nonmarket goods for which markets either do not exist at all or do exist only incompletely; an example is environmental good. A dichotomous choice approach, the most popular type of CVM in environmental economics, employs binary discrete choice models as statistical estimation models. In this paper, we propose a semiparametric dichotomous choice CVM method using local linear model of Fan and Gijbels (1996) in which probability distribution of error term is specified parametrically but latent structural function is specified nonparametrically. The computation procedures of the proposed method are illustrated with a simple design of simulations.

• Journal of the Korean Data and Information Science Society
• /
• v.9 no.2
• /
• pp.219-225
• /
• 1998

The parameters in linear models with censored normal responses are usually estimated by the iterative maximum likelihood and least square methods. However, the iterative least square method is simple but hardly has theoretical justification, and the iterative maximum likelihood estimating equations are complicatedly derived. In this paper, we justify these methods via Wedderburn (1974)'s quasi-likelihood approach. This provides an explicit justification for the iterative least square method and also directly the iterative maximum likelihood method for estimating the regression coefficients.

• East Asian mathematical journal
• /
• v.35 no.5
• /
• pp.597-612
• /
• 2019

In this study, we propose a new logarithmic barrier approach to solve linear programming problem using the projective method of Karmarkar. We are interested in computation of the direction by Newton's method and of the step-size using minorant functions instead of line search methods in order to reduce the computation cost. Our new approach is even more beneficial than classical line search methods. We reinforce our purpose by many interesting numerical simulations proved the effectiveness of the algorithm developed in this work.

• Bulletin of the Korean Mathematical Society
• /
• v.26 no.2
• /
• pp.127-134
• /
• 1989

This paper proposes a deformation method for solving practical nonlinear programming problems. Utilizing the nonlinear parametric programming technique with Quasi-Newton method [6,7], the method solves the problem by imbedding it into a suitable one-parameter family of problems. The approach discussed in this paper was originally developed with the aim of solving a system of structural optimization problems with frequently appears in various kind of engineering design. It is assumed that we have to solve more than one structural problem of the same type. It an optimal solution of one of these problems is available, then the optimal solutions of thel other problems can be easily obtained by using this known problem and its optimal solution as the initial problem of our parametric method. The method of nonlinear programming does not generally converge to the optimal solution from an arbitrary starting point if the initial estimate is not sufficiently close to the solution. On the other hand, the deformation method described in this paper is advantageous in that it is likely to obtain the optimal solution every if the initial point is not necessarily in a small neighborhood of the solution. the Jacobian matrix of the iteration formula has the special structural features [2, 3]. Sectioon 2 describes nonlinear parametric programming problem imbeded into a one-parameter family of problems. In Section 3 the iteration formulas for one-parameter are developed. Section 4 discusses parametric approach for Quasi-Newton method and gives algorithm for finding the optimal solution.

• Journal of the Society of Naval Architects of Korea
• /
• v.48 no.5
• /
• pp.426-434
• /
• 2011

Accurate weight prediction methods are an essential of the ship design in both ship cost managements and performance satisfactions. When no parent or similar ships are available, an adequate method of the ship weight estimating is required. In this study, there was carried out to develop the ship weight estimating method for the preliminary design phase. The weight estimating methods were first surveyed by the references and summarized their characteristics. The weight estimation method by statistical approach was developed for the container ship because the containerized transportation markets is gradually growing and ship's size and loading capacity are rapidly enlarged. The correlation analysis and the multiple regression analysis were used for developing the weight estimating method. As a results of evaluating the developed method, the error ratio of the variation between estimated weight and ship's data was about 5%. And it was only 1% difference with the calculating weight of conceptual design results by shipyard design team that the estimating weight of ultra-large container ship was predicted by the developed method.

• Structural Engineering and Mechanics
• /
• v.73 no.4
• /
• pp.455-462
• /
• 2020

The hybrid method using the extended finite element method (XFEM) and the forward Euler approach is widely employed to predict the fatigue life of plate structures. Due to the accuracy of the forward Euler approach is determined by a small step size, the performance of fatigue life prediction of the hybrid method is not agreeable. Instead the forward Euler approach, a prediction method using midpoint method and support vector regression (SVR) is presented to evaluate the stress intensity factors (SIFs) and the fatigue life. Firstly, the XFEM is employed to calculate the SIFs with given crack sizes. Then use the history of SIFs as a function of either number of fatigue life cycles or crack sizes within the current cycle to build a prediction model. Finally, according to the prediction model predict the SIFs at different crack sizes or different cycles. Three numerical cases composed by a homogeneous plate with edge crack, a composite plate with edge crack and center crack are introduced to verify the performance of the proposed method. The results show that the proposed method enables large step sizes without sacrificing accuracy. The method is expected to predict the fatigue life of complex structures.

• Journal of Chest Surgery
• /
• v.50 no.1
• /
• pp.36-40
• /
• 2017

Background: Surgical treatment of thoracic outlet syndrome (TOS) is necessary when non-surgical treatments fail. Complications of surgical procedures vary from short-term post-surgical pain to permanent disability. The outcome of TOS surgery is affected by the visibility during the operation. In this study, we have compared the complications arising during the supraclavicular and the transaxillary approaches to determine the appropriate approach for TOS surgery. Methods: In this study, 448 patients with symptoms of TOS were assessed. The male-to-female ratio was approximately 1:4, and the mean age was 34.5 years. Overall, 102 operations were performed, including unilateral, bilateral, and reoperations, and the patients were retrospectively evaluated. Of the 102 patients, 63 underwent the supraclavicular approach, 32 underwent the transaxillary approach, and 7 underwent the transaxillary approach followed by the supraclavicular approach. Complications were evaluated over 24 months. Results: The prevalence of pneumothorax, hemothorax, and vessel injuries in the transaxillary and the supraclavicular approaches was equal. We found more permanent and transient brachial plexus injuries in the case of the transaxillary approach than in the case of the supraclavicular approach, but the difference was not statistically significant. Persistent pain and symptoms were significantly more common in patients who underwent the transaxillary approach (p<0.05). Conclusion: The supraclavicular approach seems to be the more effective technique of the two because it offers the surgeon better access to the brachial plexus and a direct view. This approach for a TOS operation offers a better surgical outcome and lower reoperation rates than the transaxillary method. Our results showed the supraclavicular approach to be the preferred method for TOS operations.