• Wind and Structures
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• v.9 no.2
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• pp.125-146
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• 2006

Stonecutters Bridge of Hong Kong is a cable-stayed bridge with two single-column pylons each 298 m high and an aerodynamic twin deck. The total length of the bridge is 1596 m with a main span of 1018 m. The top 118 m of the tower will comprise structural steel and concrete composite while the bottom part will be of reinforced concrete. The bridge deck at the central span will be of steel whilst the side spans will be of concrete. Stonecutters Bridge has adopted a twin-girder deck design with a wide clear separation of 14.3 m between the two longitudinal girders. Although a number of studies have been conducted to investigate the aerodynamic performance of twin-girder deck, the actual real life application of this type of deck is extremely limited. This therefore triggered the need for conducting the present studies, the main objective of which is to investigate the performance of Stonecutters Bridge against flutter at its in-service stage as well as during construction. Based on the flutter derivatives obtained from the 1:80 scale rigid section model experiment, flutter analysis was carried out using 3-D finite element based single parameter searching method developed by the second author of this paper. A total of 6 finite element models of the bridge covering the in-service stage as well as 5 construction stages were established. The dynamic characteristics of the bridge associated with these stages were computed and applied in the analyses. Apart from the critical wind speeds for the onset of flutter, the dominant modes of vibration participating in the flutter vibration were also identified. The results indicate that the bridge will be stable against flutter at its in-service stage as well as during construction at wind speeds much higher than the verification wind speed of 95 m/s (1-minute mean).

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.93-101
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• 2012

Bridge deck has a role in a comfortable and safe passage of vehicles. At the same time, it preserves upper structure against the abrasion and shearing due to impact of traffic loads in bridges or has a role to protect the plate from off adverse effect of climatic process as rain, chemicals. Currently, the total number of inspected bridges is 6,248 in the general national road and to maintain effectively, Introduction of GPR system mounted in the vehicle has been considered. In this research, the comparison and analysis of bridge deck condition on general national road has been performed with major variations of superstructure type, span lengths, located region and ages by using 'the current status of road bridge and tunnel' that is provided by MLTM(Ministry of Land, Transport and Maritime Affairs). As a result, Condition assessment grade, superstructure type, age and length were derived as a major factor to determine priority for the condition assessment.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.43 no.2
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• pp.131-138
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• 2010

This study determined the optimum microalgae species and concentration for the brackish water flea, Diaphanosoma celebensis, in individual and community cultures by feeding it several different diets. Six single trials (Tetraselmis suecica, Isochrysis galbana, marine Chlorella ellipsoidea, freshwater Chlorella vulgaris, Scenedesmus sp., Selenastrum sp.) were conducted at 10 psu and $30^{\circ}C$. The community and individual cultures of the water flea were performed in 1-L beakers and 3-mL vessels (12-well culture plates), respectively. In the community cultures, the maximum density and specific growth rate were highest for water fleas fed T. suecica, reaching 60.0 individuals (ind.)/mL and 0.40, respectively. In the individual cultures, the most offspring and greatest life span of females were 56.9 ind. and 24.3 days, respectively, in the T. suecica trial. By contrast, diets of Scenedesmus sp. and Selenastrum sp. resulted in poor growth rates. In the T. suecica experiments examining a range of 10 to $200\times10^3$ cells/indl. the specific growth rate of the water flea tended to increase with the amount of supplement, while the life span decreased. The maximum density and number of offspring of females was highest at 53.5 ind./mL and 38.8 ind. respectively, at 40,000 cells/ind. These results suggest that the best microalgae species for the mass culture of D. celebensis is T. suecica and the optimum concentration is 40,000 cells per individual.

• Korean Journal of Agricultural Science
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• v.39 no.2
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• pp.227-242
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• 2012

Accurate estimation of milk production cost is very important for dairy farmers in establishing strategies for business management (e.g. planning a program for milk production, deciding the size of business and investment, determining the milk price for sale). Since the estimated cost of milk production is used as an important index to determine the basal price of milk in Korea, there has been much interest and debate on the method used to estimate milk production cost among the stakeholder. This study was thus carried out to identify problems in the current methodology for estimating cost of milk production, and to find a better way to improve it. We propose several alternatives and better ways to improve the current method for estimating cost of milk production. Estimation of the income and cost per head should be based on the number of cattle converted to grown cows. Cost estimation per liter of milk should be made for both whole milk and 3.4% milk fat corrected milk. The value of purchased cows and raised replacement heifers should be the same as their market value. The productive life span of cows should be less 4 years, and the terminal or salvage value of cows needs to be 30 to 40% less than her initial value. When calculating depreciation of cows over the productive life span, however, the salvage value should be 0 or 1 Korean won. On calculating labor costs, the farm labor wage corresponding to the average wage of nonfarm industrial workers should be assumed. Beside of these, better estimation procedures for other items are also given. The proposed methods from this study should improve the accuracy of estimation of milk production cost and help to achieve consensus among the stakeholder.

• The Journal of Korean Medicine
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• v.26 no.1 s.61
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• pp.1-10
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• 2005

Objective: We examined the antimetastatic effect of Curcuma zedoaria Roscoe (CZ) on pulmonary metastasis of B 16 cells. Methods: For 6 weeks, Zedoariae Rhizoma made from dried CZ were dissolved in distilled water and administered to mice 2 weeks before they were injected with B]6 melanoma cells. Mice were given CZ at doses of 250 and 500 mg/kg, and were compared for lung weight, survival days, and NO production. Results: Intake of CZ throughout the experiment extended the average survival time. Intake after B16 cell injection slightly prolonged survival time, but intake before B]6 cell injection did not influence life span. We examined the effect of CZ on macrophage function by measuring NO production. After the macrophages were given CZ for 6 weeks, the amount of NO generated by the macrophages stimulated with LPS in culture medium increased. NO generated by the macrophages also served as a cytotoxic factor against B16 melanoma cells. B16 melanoma-conditioned medium reduced NO production by macrophages. However, CZ treatment reversed the reduction in NO production by the conditioned medium significantly. Conclusion : These findings may suggest that macrophage function-modulating activity by CZ appears to underlie its antimetastatic activity, which leads to a decrease in the number of lung metastatic surface nodules and the extension of life span.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.179-188
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• 1995

SFRC overcomes brittleness of concrete and has increases strength due to the action of confmement, crack arrestmg mechan~sm and pull out resistances of steel f~bers ~ n s ~ d e the concrete. These lead also to the increased strength and ductility under the shear stress. It has been reported that the secondary remforcement effect of steel fibers IS more pronounced In shear than flexure. Addition of hooked stee!, fibers into the cementitious materials enhanced shear resistance and consequently improves structural behavior and shear strength of Reinforced Hooked-Steel-Fiber Concrete Ream(RHSFCI3) under the shear forces. Experimental observations were made on the main parameters effecting structural behavior of RHSFCB in this study. The volume fractions of fibers, shear span to depth ratios, and spaclngs of stlrrups were taken into account as the mam parameters. Some eyuatlons reported in the literatures, regardmg the predict~ons of the shear strength of RHSFCB have been evaluated stdtlst~cdlly based on the tot a1 number of 95 test results on RHSFCB faded In shear on shear flexu~al mode.

• Journal of Information Science Theory and Practice
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• v.5 no.2
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• pp.62-74
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• 2017

This study examined the mechanical engineering research output from India, Japan, and South Korea on different parameters including growth, collaboration indices, and activity index. The purpose of the study is to understand the overall development of mechanical engineering through analytical approaches applied on the scholarly outcome of the countries considered for the study. The study focuses on analysing the articles published by India, Japan, and South Korea, and is restricted to articles indexed in the Science Citation Index - Web of Science for the period 2000 to 2014. The ratios of number of paper to citations for India, Japan, and Korea are 20,836: 1,97,679; 24,494: 2,04,393; and 30,578: 2,66,902 respectively for the period 2000-2014. The findings show that there is a decline in Japanese publications in mechanical engineering, whereas other two countries have recorded an increasing trend. While India has tripled its publications in a span of 15 years, South Korea, on the other hand, has doubled its publications in the same span of time. There has been an increasing trend towards collaboration in almost all fields of science and technology. However, the extent of collaboration and their rate of growth varied for one subject to another, one branch to another branch of the same subject, and from one country to another country. The present study analyses the growth of research publications of the mechanical engineering domain including authorship distribution, collaboration indices, prominent journals, and activity index.

• Smart Structures and Systems
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• v.23 no.5
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• pp.449-466
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• 2019

Cable-stayed bridges are attractive due to their beauty, reducing material consumption, less harm to the environment and so on, in comparison with other kinds of bridges. As a massive structure with long period and low damping (0.3 to 2%) under many dynamic loads, these bridges are susceptible to fatigue, serviceability disorder, damage or even collapse. Tuned Mass Damper (TMD) is a suitable controlling system to reduce the vibrations and prevent the threats in such bridges. In this paper, Multi Tuned Mass Damper (MTMD) system is added to the Ahvaz cable stayed Bridge in Iran, to reduce its seismic vibrations. First, the bridge is modeled in SAP2000 followed with result verification. Dead and live loads and the moving loads have been assigned to the bridge. Then the finite element model is developed in OpenSees, with the goal of running a nonlinear time-history analysis. Three far-field and three near-field earthquake records are imposed to the model after scaling to the PGA of 0.25 g, 0.4 g, 0.55 g and 0.7 g. Two MTMD systems, passive and active, with the number of TMDs from 1 to 8, are placed in specific points of the main span of bridge, adding a total mass ratio of 1 to 10% to the bridge. The parameters of the TMDs are optimized using Genetic Algorithm (GA). Also, the optimum force for active control is achieved by Fuzzy Logic Control (FLC). The results showed that the maximum displacement of the center of the bridge main span reduced 33% and 48% respectively by adding passive and active MTMD systems. The RMS of displacement reduced 37% and 47%, the velocity 36% and 42% and also the base shear in pylons, 27% and 47%, respectively by adding passive and active systems, in the best cases.

• Structural Engineering and Mechanics
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• v.80 no.6
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• pp.749-765
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• 2021

Suspension bridges bear large eccentric live loads in rush hours when most vehicles travel in one direction on the left or right side of the bridge. With the increasing number and weight of vehicles and the girder widening, the eccentric live load effect on the bridge behavior, including bending and distortion of the main girder, gets more pronounced, even jeopardizing bridge safety. This study proposes an analytical algorithm based on multi-catenary theory for predicting the suspension bridge responses to eccentric live load via the nonlinear generalized reduced gradient method. A set of governing equations is derived to solve the following unknown values: the girder rigid-body displacement in the longitudinal direction; the horizontal projection lengths of main cable's segments; the parameters of catenary equations and horizontal forces of the side span cable segments and the leftmost segments of middle span cables; the suspender tensions and the bearing reactions. Then girder's responses, including rigid-body displacement in the longitudinal direction, deflections, and torsion angles; suspenders' responses, including the suspender tensions and the hanging point displacements; main cables' responses, including the horizontal forces of each segment; and the longitudinal displacement of the pylons' tower top under eccentric load can be calculated. The response of an exemplar suspension bridge with three spans of 168, 548, and 168 m is calculated by the proposed analytical method and the finite element method in two eccentric live load cases, and their results prove the former's feasibility. The nonuniform distribution of the live load in the lateral direction is shown to impose a greater threat to suspension bridge safety than that in the longitudinal direction, while some other specific features revealed by the proposed method are discussed in detail.

• Journal of the Korea Society of Computer and Information
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• v.27 no.12
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• pp.277-284
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• 2022

In this paper, we proposes a method of optimizing the processing order of skids to minimize the span time in a conveyor environment of the shipbuilding subassembly process. The subassembly process consists of a series of fixed tasks where the required work time is varied according to the skid type. The loading order of skids on a conveyor which determines the span time should be properly optimized and the problem size exponentially increases with the number of skids. In this regard, we propose a novel method called UniDev by defining a measure of the mean-absolute-deviation about the time difference among simultaneously processed tasks and iteratively improving it. Through simulations with various numbers of skids and processes, it was observed that our proposed method can efficiently reduce the overall work time compared with the multi-start and the 2-OPT methods.