• 동력기계공학회지
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• 제18권1호
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• pp.91-98
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• 2014

In this investigation, the effect of crack orientation on spatial randomness of fatigue crack growth rate (FCGR) in friction stir welded (FSWed) 7075-T651 aluminum alloy joints has been statistically analyzed by Weibull distribution. The fatigue crack growth tests are conducted under three different constant stress intensity factor range (SIFR) control at room temperature with R = 0.1 and frequency 10Hz on compact tension (CT) specimen machined at base metal (BM) and weld metal (WM). The experimental fatigue crack growth rate data were obtained for two types of specimens having LT and TL orientations. LT specimens both base metal and weld metal showed higher fatigue crack growth rate as compared to TL specimens. In the lower SIFR region, FCGR were found to be almost 3 times higher in higher SIFR region. The shape parameter of Weibull both LT and TL orientation for FCGR was increased with increasing SIFR, the scale parameter was also increased with increasing SIFR. The smallest value of the shape parameter was shown in weld metal specimens having LT orientation at lower SIFR region.

• 한국항공운항학회지
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• 제31권1호
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• pp.92-98
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• 2023

This paper used the golf course visitors' data in Jeju region to forecast the growth of inbound air traveler to Jeju. This is because the golf course visitors were proven to bring the highest economic and production inducement effect to the Jeju region. Based on such a data, this paper forecast the short-term growth rate of inbound air traveler using ARIMA to the Jeju until December 2025. According to ARIMA (0,1,0) (0,1,1) model, it was analyzed that the monthly number of golf course visitors to Jeju has been increasing steadily even since COVID-19 pandemic and the number is expected to grow until the end of 2025. Applying the same parameters of ARIMA (0,1,0) (0,1,1) to inbound air travel data, it was found the growth rate of inbound air travelers would be higher than the growth rate of 2019 shortly without moderate variation even though the monthly number of inbound travelers to Jeju had been dropped during COVID-19 pandemic.

• 한국항만경제학회지
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• 제17권2호
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• pp.61-87
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• 2001

The purpose of this paper is to analyze the location, population growth. and cargo concentration of Korean port-cities. In the location theory, Sommer (1976) and McGee (1967) models are newly introduced, as are the Rimmer (1967), Bird (1965), Hoyle (1981) models. which were already introduced in previous studies from Korea. Analysis of population growth in the Korean port-cities is conducted using data from 1966 to 1998. Rimmer and Hoyle's concentration models are used to measure cargo concentration from 1966 to 2000. The main results of this paper are as follows: First, Korean ports are concentrated on the East Sea, the Southern Sea, and the West Sea. Their locations are closely related with the hinterland. the inland city, and growth of port-cities. In considering the foreign countrys' cases, Korean port-cities are similar to the models of Bird and Hoyle. Second, the populations of Ulsan and Pohang grew at the fastest rate in 1966-1998, while the port cities in the Honam and Jeiu region grew at much lower ratios. Most port cities are located near large industrial complexes. Third the growth rates of Gwangyang, Daesan, Pohang, Pyungtaeg, and Samchunpo increased, while those of Busan. Mukho, Masan, Mogpo, Yeosu, and Sokcho declined. Of particular note, the growth rate of Busan remained negative after the late 1980s. Fourth. empirical results using the Rimmer (1967) model indicate that Gwangyang, Daesan, Pyungtag, and Pohang have shown the concentration. But the deconcentration was shown from the Busan, Mukho, Janghang, Gunsan, Mogpo, Yeosu, Masan, Sokcho. and Jeju. Fifth, the concentration of ports located in West coast region has shown the mixed results between concentration and deconcentration except the concentration of early 1970s and 1990s. The concentration of ports located in East coast region has shown the concentration before the middle of 1980s. And deconcentration after the middle of 1980s have appeared. The Southern coast region has shown the continuous deconcentration except the partial concentration of early 1986. and 1991. Planners of Korean ports should find out the factors of concentration and deconcentration of each ports and should determine factors such as investment priority level. size and scope in order to ensure the balanced development of regional ports and port-cities.

• 원예과학기술지
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• 제18권4호
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• pp.499-502
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• 2000

의성 지역에서 재배하기 적합한 국내 한지형 마늘을 선발하고자 '의성', '예천', '단양', '정선' 및 '용인' 등 한지형 마늘 5종을 공시하여 생육특성과 수량성을 조사하였고, 난지형 마늘의 재배 적합성을 검증하기 위해 '남도' 마늘을 동시에 공시하였다. 국내 지방 재배종 마늘의 생장특성은 생태형에 따라 차이를 보여 난지형인 '남도'가 초기생장과 숙기가 빨랐던 반면, 한지형 지방종간에는 뚜렷한 차이가 없었다. 추대 현상에 있어서는 '정선'과 '용인'이 추대율이 낮았고 불완전 추대가 많았던 반면, '예천'과 '의성'은 추대율이 높고 '의성'은 2차생장률이 낮았다. 의성지방에서 재배된 한지형 마늘 중에 '예천'의 수량이 높았으며 생장 최성기에 타 품종에 비하여 작물생장률도 높았다. 의성 지역에서 재배된 '정선', '용인' 및 '단양'은 '의성'에 비하여 생산성이 낮은 것으로 평가되었다.

• 한국안전학회지
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• 제14권2호
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• pp.3-10
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• 1999

Fatigue crack growth rates in commercial plate of high strength Al 7075-T651 were investigated for the T-L direction in air, water and sea water. In this paper the effect of cyclic load wave-form(trapezoid and triangle) on fatigue crack growth rates in air, water and sea water environments were investigated using standard LEFM testing procedures. It was founded that the fatigue crack growth behaviors were not affected by cyclic load wave-forms. In region II (stable crack growth region), the fatigue crack growth behaviors were insensitive to cyclic load wave-forms and were sensitive to environment i.e. fatigue crack growth behaviors were higher in sea water than in air for all cyclic load wave-form. The result of fractographical morphology in air, water and sea water by SEM showed obvious dimple rupture and typical striation in air, but transgranular fracture surface in water and sea water. The values m are not affected by corrosion environments but C are different values.

• 산학경영연구
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• 제22권2호
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• pp.35-59
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• 2009

관광개발을 통한 국가발전을 도모하기위한 전략은 모든 국가들의 공통된 사안이다. 특히 경제적으로 안정된 선진국보다는 개발도상국이나 미개발국가에서 매우 선호되는 국가성장대안이 된다. 특히 인문자원보다는 자연자원을 활용하여 관광개발을 추진하려는 국가에서는 매우 신중한 개발전략 모색이 요구되며, 관광개발의 효과를 극대화하기위한 방안들이 수립되어지고 있다. 본 연구는 미개발국의 성장동력을 관광개발로 지정하고, 모든 가용자원을 접적화하여, 미래의 생존전략을 모색하기위한 방안을 강구하기위한 실증분석을 목적으로 한다. 이를 위해 아프리카 카메룬의 관련 전문가들을 중심으로 설문과 면접을 통해 국가성장동력으로의 관광산업을 지속가능하게 추진할 있는 전략을 제시하였다.

• Animal Bioscience
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• 제35권7호
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• pp.989-998
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• 2022

Objective: This study investigated the effects of intrauterine growth restriction (IUGR) during late pregnancy on the cell growth, proliferation, and differentiation in ovine fetal thymuses. Methods: Eighteen time-mated Mongolian ewes with singleton fetuses were allocated to three groups at d 90 of pregnancy: restricted group 1 (RG1, 0.18 MJ ME/body weight [BW]^0.75/d, n = 6), restricted group 2 (RG2, 0.33 MJ ME/BW^0.75/d, n = 6) and control group (CG, ad libitum, 0.67 MJ ME/BW^0.75/d, n = 6). Fetuses were recovered at slaughter on d 140. Results: The G0/G1 phase cell number in fetal thymus of the RG1 group was increased but the proliferation index and the expression of proliferating cell nuclear antigen (PCNA) were reduced compared with the CG group (p<0.05). Fetuses in the RG1 group exhibited decreased growth hormone receptor (GHR), insulin-like growth factor 2 receptor (IGF-2R), and their mRNA expressions (p<0.05). For the RG2 fetuses, there were no differences in the proliferation index and PCNA expression (p>0.05), but growth hormone (GH) and the mRNA expression of GHR were lower than those of the CG group (p<0.05). The thymic mRNA expressions of cyclin-dependent protein kinases (CDKs including CDK1, CDK2, and CDK4), CCNE, E2-factors (E2F1, E2F2, and E2F5) were reduced in the RG1 and RG2 groups (p<0.05), and decreased mRNA expressions of E2F4, CCNA, CCNB, and CCND were occurred in the RG1 fetuses (p<0.05). The decreased E-cadherin (E-cad) as a marker for epithelial-mesenchymal transition (EMT) was found in the RG1 and RG2 groups (p<0.05), but the OB-cadherin which is a marker for activated fibroblasts was increased in fetal thymus of the RG1 group (p<0.05). Conclusion: These results indicate that weakened GH/IGF signaling system repressed the cell cycle progression in G0/G1 phase in IUGR fetal thymus, but the switch from reduced E-cad to increased OB-cadherin suggests that transdifferentiation process of EMT associated with fibrogenesis was strengthened. The impaired cell growth, retarded proliferation and modified differentiation were responsible for impaired maturation of IUGR fetal thymus.

• 한국작물학회지
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• 제68권4호
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• pp.285-293
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• 2023

한반도 남부지방(진주)에서 콩 생태형에 따라 생육단계별 생육일수를 적산온도로 환산하여 한반도 북방지역 7개 농업기후지대의 콩 생육예측을 실시하였다. 그 결과는 아래와 같다. 1. 수양산 이남, 수양산 이북, 동해 남부, 중부 내륙, 북부내륙 지역들은 모든 생태형에서 정상적인 생육과 수확이 가능할 것으로 예측되었다. 2. 북부 고산지대는 모든 생태형에서 정상적인 생육이 불가능한 것으로 나타났고, 동해 북부지역은 조생종, 중생종은 정상적인 생육이 가능하지만 중만생종은 생육일수가 부족한 것으로 나타났다. 3. 파종 한계기는 수양산 이남, 수양산 이북, 동해 남부 지역은 생태형에 따라 6월 6일~26일까지, 중부 내륙 6월 2일~17일, 북부 내륙은 5월 24~6월 12일, 동해 북부는 5월 16일~6월 7일경인 것으로 조사되었다. 그러나 북부고산지대는 9℃기준인 4월 30일 파종하여도 생육일수가 부족한 것으로 나타났다.

• 한국세라믹학회지
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• 제33권2호
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• pp.203-213
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• 1996

In this study the subcritical crack growth behavior in an Al2O3-SiCw composite has been investigated using in situ fracture technique of applied moment double cantilever beam (AMDCB) specimens indside an SEM. This technique allows the detailed observation of whisker and grain bridging in the crack wake region. The experimental results indicated that the KI-a curve was deviated from the conventional powder law form and that the existed a region where the rate of microcrack growth was decreased with increasing the externally applied stress intensity factor. This behavior could be explained by arising crack growth resistance i.e. R-curve behavior which was associated with crack shielding due to whisker and grain bridging. The R-curve was also analyzed from the KI-a curve data in order to quantify the bridging effect in the Al2O3-SiCw composite.

• 한국결정성장학회지
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• 제18권1호
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• pp.1-4
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• 2008

The growth of composite-structured Nd:$GdVO_4$ single crystal rods by the double die EFG method is reported. Two crucibles are combined with an outer and inner die for ascending of different melt. The composite-structured Nd:$GdVO_4$ single crystal rods with a length of 50 mm and an outer diameter of 5 mm including of inner Nd-doped core region with diameter 3 mm were grown successfully. Nd distribution in the, radial direction has graded profile from result of EPMA. Absorption coefficient in the core region at 808 nm was $42cm^{-1}$. Finally, we demonstrated the laser oscillation using our composite crystal and 2-W output was obtained.