• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.191-195
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• 2009

After developing the pre-crack to simulate a damaged reinforced concrete beam, fatigue test was conducted on the beam repaired by GFRP Bar and GSP embedded method. In the result of fatigue test, most residual displacement and crack of the experimental beams occurs in the early loading cycle and an increasing rate of these due to number of cycles were insignificant. Comparing with a non-repaired beam, a static strength of the repaired beam greatly increased, but fatigue strength decreased. In S-N curves, fatigue strength of the beam repaired by GFRP Bar and GSP was 58%, 52% of the static strength respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1041-1048
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• 2006

The pulley is one of core mechanical elements in the power steering system for vehicles. The pulley operates under both the compressive loading and the torque. Therefore, to assure the safety of the power steering system, it is very important to investigate the durability and the optimization of the pulley. In this study, the applied stress distribution of the pulley under high tension and torsion loads was obtained by using finite element analysis. Based on these results the fatigue life of the pulley with the variation of the fatigue strength was evaluated by a durability analysis simulator. The results at 50% and 1% for the failure probability were compared with respect to the fatigue life. In addition to the optimum design for the fatigue life is obtained by the response surface method. The response function utilizes the function of the life and weight factors. Within range for design life condition the minimization of the weight, one of the formulation, is obtained by the optimal design. Moreover the optimum design by considering its durability and validity is verified by the durability test.

• Journal of the Korean Applied Science and Technology
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• v.32 no.1
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• pp.56-61
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• 2015

In this study, the current-voltage curves for the SCM440 steel by the addition of an organic corrosion inhibitor triethanolamine(TEA) was measured using the conventional three electrodes of cyclic voltammetry. As a result, the C-V characteristics of SCM440 steel were to be for an irreversible process due to the oxidation current from the cyclic voltammetry. Diffusion coefficient according to the twice increasing the concentration of TEA in the corrosion inhibitor from $2.5{\times}10^{-4}M$ to $5.0{\times}10^{-4}M$, the diffusion coefficient was found to be a good corrosion-inhibiting effect is reduced by 1.5 times, so for each $2.561{\times}10^{-6}cm^2s^{-1}$ to $1.707{\times}10^{-6}cm^2s^{-1}$. When according to the electrolyte concentration and the effect is to increase the electrolyte concentration to 1.0 N at 0.5 N, the diffusion coefficient is $2.56{\times}10^{-6}cm^2s^{-1}$ to $5.12{\times}10^{-6}cm^2s^{-1}$, each 2 times decrease in the use of the electrolyte of 1.0 N, because this was more appropriate.

• Journal of Environmental Policy
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• v.10 no.4
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• pp.3-37
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• 2011

This paper investigates the existence of the environmental Kuznets curve (EKC) for carbon dioxide $CO_2$ emissions and its causal relationships with economic growth and openness by using time series data (1971-2006) from China (an emerging market), Korea (a newly industrialized country), and Japan (a developed country). The sample countries span a whole range of development stages from industrialized to newly industrialized and emerging market economies. The environmental consequences according to openness and economic growth do not show uniform results across the countries. Depending on the national characteristics, the estimated EKC show different temporal patterns. China shows an N-shaped curve while Japan has a U-shaped curve. Such dissimilarities are also found in the relationship between $CO_2$ emissions and openness. In the case of Korea, and Japan it represents an inverted U-shaped curve while China shows a U-shaped curve. We also analyze the dynamic relationships between the variables by adopting a vector auto regression or vector error correction model. These models through the impulse response functions allow for analysis of the causal variable's influence on the dynamic response of emission variables, and it adopts a variance decomposition to explain the magnitude of the forecast error variance determined by the shocks to each of the causal variables over time. Results show evidence of large heterogeneity among the countries and variables impacts.

• Journal of Animal Science and Technology
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• v.46 no.4
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• pp.503-508
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• 2004

This study was conducted to estimate the growth curve parameters of crossbreds between Korean native boars and Landrace sows and their relationships with meat qualities. The data used were weight-age data and carcass data from 131 males and 122 females raised at N.L.R.I in Korea. Growth curve parameters were estimated from nonlinear regression using Gompertz model individually. Average mature weight(A), average maturing rate(k), and average inflection point(u) showing maximum growth rate estimated were 179.54${\pm}$6.06kg, 0.3154${\pm}$0.0059, and 5.50${\pm}$0.11 months in females, and 179.84${\pm}$6.33kg, 0.3049${\pm}$0.0061, and 5.24${\pm}$0.13 months in males, respectively. For the growth curve parameters and derived statistics, the phenotypic correlations of maturing rate with gain rate at inflection, mature weight, and inflection point were - .30, - .77, and - .93 in male, and - .31, - .78 and - .94 in female, respectively. Matrure weight was positively correlated to the inflection point as + .89 in both male and female, indicating that late maturing pigs with lower k had longer maturing period with increasing gain rate and reached point of inflection later than early maturing pigs with higher k, and grew to larger mature weight. Backfat thickness and erode fat contents were correlated with mature weight positively in male and negatively in female, and correlated with gain rate at inflection point positively in both male and female, of which coefficients were as high as .42 and .50 in male, respectively.

• Journal of KIISE:Software and Applications
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• v.26 no.12
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• pp.1404-1417
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• 1999

웹과 같은 분산 환경에서는, 웹 브라우저 상에서 SQL 형식의 공간 질의를 수행시키는 것과 또한 서버로부터 그 질의 결과를 보는 것이 가능하다. 그러나, 격자 이미지(raster image)와 같은 대용량 공간 데이타를 포함하는 질의 결과를 웹 브라우징할 때 발생하는 많은 문제점들 중에서, 사용자 응답 시간의 지연은 매우 중요한 문제이다. 본 논문에서는 사용자의 재요청(callback) 접근 패턴이 공간적 근접성(spatial locality)을 따른다는 가정하에서의, 사용자 응답 시간을 최소화하기 위한 새로운 프리페치(prefetch) 전략에 대해서 서술한다. 본 논문의 프리페치 전략은 다음과 같이 요약될 수 있다. 첫째, 프리페치 알고리즘은 사용자의 접근 패턴을 잘 반영하는 힐버트 곡선(Hilbert-curve) 모델을 바탕으로 한다. 둘째, 프리페치 전송 비용을 줄이기 위해서 사용자의 재요청 시간 간격(think time)을 이용한다. 본 논문에서는, 힐버트 곡선을 이용한 프리페치 전략의 성능 평가를 위해서 다양한 실험을 하였으며, 그 결과로 프리페치를 하지 않는 방식보다 높은 성능 향상이 있음을 보인다.Abstract In distributed environment(e.g., WWW), it would be possible for the users to submit SQL-like spatial queries and to see their query results from the server on the Web browser. However, of many obstacles which result from browsing query results including large spatial data such as raster image, the delay of user response time is very critical. In this paper we present a new prefetch policy which can alleviate user response time on the assumption that user's callback access pattern has spatial locality. Our prefetch policy can be summerized as follows: 1) our prefetch algorithm is based on the Hibert-curve model which well replects user's access pattern, and 2) it utilizes user's callback interval to reduce prefetch network transmission cost. In this paper we conducted diverse experiments to show that our prefetch policy achieves higher performance improvement compared to other non-prefetch methods.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.10 no.2
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• pp.137-143
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• 1977

A study has been made to find out a new method of calculating the survival rate of a fish population from length composition and growth equation. 1. In the steady state of the fish population, let the total mortality rate be z, the age of complete recruitment $\alpha$, and the number of $\chi$ year class $N_\chi$. Then ire obtain $$N\chi=N\alpha\;\exp\;{-z(\chi-\alpha)}$$ Let the oldest age in the catch be h, the average age between the age of complete recruitment and the oldest age in the catch $U\chi$. Then we have $$U\chi=\frac{a-b\;\exp\;(-z(b-a))}{1-\exp\;(-z(b-a))}+\frac{1}{z}....(1)$$ and then let be infinite. Then we obtain $$Z=\frac{1}{U\chi-\alpha....(2)$$ 2. Calculating numerical value of $U\chi$ from age composition table and growth equation and substitute in (1) or (2) for it, we may obtain the value of s and $\varrho^{-z}$. 3. This method is applied t a case of yellow croaker in the Yellow Sea and the East China Sea. The results are as follows: Total mortality rate 0.82595 Survival rate 0.43782 95 percent confidence interval 0.43767-0.43797.

• Journal of the Korean Chemical Society
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• v.54 no.3
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• pp.283-286
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• 2010

A sensitive and reproducible method for the flotation-spectrophotometric determination of zirconium is reported. The method is based on the complex formation zirconium and xylenol orange (XO) which is floated in the interface of aqueous phase and n-hexane by vigorous shaking. By discarding the aqueous solution and n-hexane, the adsorbed complex on to the wall of a separating funnel was dissolved in a small volume of methanol solvent and its absorbance was measured at 429 nm. The effect of different parameters such as pH, concentrations of HCl, and XO, and volume of n-hexane flotation dissolvent, standing and shaking time were studied. The calibration curve was linear in the range of 7-120 ng $mL^{-1}$ of zirconium with a correlation coefficient of 0.9991. The limit of detection (LOD) was 5.8 ng $mL^{-1}$. The relative standard deviation (RSD) for seven replicate measurements of 50 and 110 ng $mL^{-1}$ of zirconium were 4.4 and 3.0%, respectively. The method was successfully applied to the determination of zirconium in water samples.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.3 no.3
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• pp.154-160
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• 1970

The present paper deals with the growth of yellow croaker by scale age reading. This study is based on material from 596 specimens caught by the Danish seine in the Yellow Sea during the period from June 1967 to April 1968. Ring marks of the scale were formed from April to July, corresponding to the spawning season of the fish reported by Bae (1960). Growth rate of each radius of the ring was approximately 0.73. The relationship between the total length and radius of scales, and the relationship between the body weight and total length are represented by the following equations respectively: L=61.350R+50.184 $$W=4.298L^{3.227}\times10^{-3}$$ Maximum total length calculated by the diagram of Walford's growth transformation, $$L_{n+1}=0.6866L_n+10.8730$$, was 346.9mm. Growth curve of the fish can be expressed by the following von Bertalanffy's equation : $$L_t=346.9(1-e^{-0.376(t+0.609)})$$

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.49-55
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• 2011

In order to analyze feasibility of replacing a conventional 6-mm Ti bar with a 5-mm bar, a series of rotating bending fatigue tests were carried out on Ti-6Al-4V bars by strengthening the fatigue performance using a special technique called UNSM (Ultrasonic Nanocrystal Surface Modification). The results of S-N curves clearly showed that the performance of the 5-mm titanium specimen was similar to that of the 6-mm specimen when the UNSM treatment was applied. The 5-mm treated specimen converged with small scattering band into the linear line of the non-treated 6-mm one. Below the fatigue life of $10^5$ cycles, the UNSM treatment did not show any significant superiority in the bending stress and fatigue life. However, over the fatigue life of $10^5$ cycles, the effect of UNSM was superior for each fatigue life, and the bending stress became longer and higher than that of the untreated one. In the case of 6-mm Ti-bar with UNSM, the fatigue limit was about 592 MPa, and there was fatigue strength increase of about 30.7% at the fatigue life of $10^4$ cycles compared to the untreated 6-mm bar. Therefore, the compressive residual stress made by the UNSM in Ti-6Al-4V increased the fatigue strength by more than 30%.