• Advances in concrete construction
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• 제3권4호
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• pp.253-268
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• 2015

This paper investigates the influence of various mix design parameters on the characteristics of concrete containing recycled coarse aggregates and Nano-Silica using Taguchi method. The present study adopts Water-cement ratio, Recycled Coarse Aggregate (%), Maximum cement content and Nano-Silica (%) as factors with each one having three different levels. Using the above mentioned control parameters with levels an Orthogonal Array (OA) matrix experiments of L9 (34) has selected and nine number of concrete mixes has been prepared. Compressive Strength, Split Tensile Strength, Flexural Tensile Strength, Modulus of Elasticity and Non-Destructive parameters are selected as responses. Experimental results are analyzed and the optimum level for each response is predicted. Analysis of 28 days CS depicts that NS (%) is the most significant factor among all factors. Analysis of the tensile strength results indicates that the effect of control factor W/C ratio is ranked one and then NS (%) is ranked two which suggests that W/C ratio and NS (%) have more influence as compared to other two factors. However, the factor that affects the modulus of elasticity most is found to be RCA (%). Finally, validation experiments have been carried out with the optimal mixture of concrete with Nano-Silica for the desired engineering properties of recycled aggregate concrete. Moreover, the comparative study of the predicted and experimental results concludes that errors between both experimental and predicted values are within the permissible limits. This present study highlights the application of Taguchi method as an efficient tool in determining the effects of constituent materials in mix proportioning of concrete.

• 한국대기환경학회지
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• 제15권4호
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• pp.385-392
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• 1999

This study was carried out to investigate the constituents of inorganic ions of precipitation in Mokpo and Yeochon area from Jan. 1996 to Dec. 1997. The volume-weighted mean pH of precipitation was 5.7(4.8~7.8) at Mokpo, and 5.6(5.1~7.4) at Yeochon area, respectively. The non-seasalt(nss) anion concentrations were found in order of $nss-SO^{2-}_4>NO^-_3>nss-Cl^-$ at two areas. The portion of $nss-SO^{2-}_4;and;NO^-_3$ was 71~84% out of anions. The the non-seasalt cation concentrations were found in order of $NH^+_4>nss-Ca^{2-}>nss-Mg^{2+}>nss-K^-$ at two areas. The portion of $NH^+_4;and; nss-Ca^{2+}$ was 85~92% out cations. Compared regionally the year concentraton of $nss-SO^{2-}_4$, the result of Yeochon was 3 times higher than that of Mokpo in 1996, while the results of two regions were almost similar in 1997. The reason was that Yeochon was restricted area of the use of 0.5% sulfur B-C oil, controlled air pollution emission area, controlled semitotal amounts of air pollution emission area and partial operating of factories in 1997. There were no ions having high correlation with $H^+,;but;nss-SO^{2-}_4,;NO^-_3,;NH^+_4;and;nss-Ca^{2+}$ showed high correlation coefficient each other. It seems that these ions have little correlation with $H^+$ because they are washed out on binding state. Factor analysis showed that the first factor was complicated factor containing anthropogenic and soil resource, the second factor was sea-salt resource and the third factor was independent behavior of hydrogen at Mokpo. While, the first factor was complicated factor containing anthropogenic and sea-salt resource, the second factor was $Ca(NO_3)_2$ salt and the third factor was $NH^+_4;and;SO^{2-}_4$ synergied by resource and combination at Yeochon.

• 한국해안·해양공학회논문집
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• 제20권4호
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• pp.421-428
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• 2008

부산 신항 개발사업으로 형성된 용원수로는 좁고 긴 형태로 해수흐름이 정체되어 환경악화가 우려되는 지역이다. 본 연구에서는 2003년부터 2007년까지의 월별 관측 자료를 이용하여 용원수로의 수질변화 양상을 분석하였다. 추정된 연평균 농도와 오차범위를 분석한 결과 용원수로 내부가 용원수로 입구에 비하여 전반적으로 뚜렷하게 수질이 악화되어 있는 것으로 파악되었다. 수로 입구의 수질농도를 기준으로 수로 내부의 수질농도는 COD, TN, TP 항목의 경우 각각 1.34배, 2.08배, 1.80배로 높은 것으로 파악되었다. 한편, Mann-Kendall 방법을 이용한 오염물질 농도변화의 추세검정 결과, 일반적으로 사용되는 95% 신뢰수준에서 추세를 가지는 경우는 SW-26 지점 TP 항목(증가추세)을 제외하고는 모두 뚜렷한 변화 추세는 없는(엄밀한 통계적인 용어로는 "있지 않은") 것으로 파악되었다.

• 한국문헌정보학회지
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• 제42권2호
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• pp.87-108
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• 2008

본 연구의 핵심 내용은 장애인을 위한 도서관서비스의 강화를 위해 국내 도서관의 장애인서비스 현황 및 요구에 대한 조사 분석과 국제도서관연맹(IFLA), 미국도서관협회 (ALA) 등 외국기관들이 장애인을 대상으로 제정한 각종 지침과 정책 등에 대한 조사 분석을 통해 국내 도서관들이 장애인서비스를 실시할 때 길잡이 역할을 할 수 있는 장애 유형별 지침과 기준의 구성요소를 도출하는 것이다. 도출된 구성요소는 도서관내외부의 물리적 접근성 및 이동권 보장, 접근 가능 장서 구축, 서비스와 프로그램, 보조공학기기, 웹 접근성과 유니버설 디자인, 인력자원의 개발과 활용, 국내외 유관기관과의 협력 등의 일곱 가지로 유형화시켰으며, 각 요소별로 기준 및 지침에 포함되어야 할 주요 내용도 명시하였다.

• 한국융합학회논문지
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• 제11권6호
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• pp.269-279
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• 2020

리더는 기업에서 없어서는 안 될 역할을 가지고 있다. 본 논문에서는 변혁적 리더를 검토 대상으로 하여 직원의 직무 만족도와 직무 성과 변수를 도입하였다. 변혁적 리더십이 직원의 직무성과와 직무만족도에 미치는 영향을 탐색하고, 또한 변혁적 리더십이 종업원의 직무성과에 영향을 미치는 요인을 찾고자 하였다. 본 연구에서는 설문 조사 방법을 채택하여 378개의 설문결과를 이용, SPSS23.0으로 조사 결과를 분석하였다. 연구결과에 의하면 변혁적 리더의 네 가지 구성변수는 직무성과와 직무만족도에 각각 서로 다른 영향을 미치는 것으로 나타났다. 기업의 리더는 리더십 스타일의 선택에 주의를 기울여야하며 직원의 업무 태도에 각별한 관심을 기울여야 한다. 본 연구는 기업의 인적 자원 관리 업무를 수행하는데 유익한 시사점을 제공한다. 본 연구에서는 직무만족도가 변혁적 리더십과 직무성과 사이의 중개 역할을 하는지는 검증되지 않았으며, 향후 연구에서 보완해야 할 필요가 있다.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.13-17
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• 2015

In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with delamination problem of multi-layered CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal cycling. The CC tape might also experience cyclic loading due to the energizing scheme (on - off) during operation. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in REBCO CC tapes becomes critical. In this study, transverse tensile tests were conducted under different loading conditions using different size of upper anvils on the GdBCO CC tapes. The mechanical and electromechanical delamination strength behaviors of the CC tapes under transverse tensile loading were examined and a two-parameter Weibull distribution analysis was conducted in statistical aspects. As a result, the CC tape showed similar range of mechanical delamination strength regardless of cross-head speed adopted. On the other hand, cyclic loading might have affected the CC tape in both upper anvil sizes adopted.

• 대한화학회지
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• 제26권4호
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• pp.229-234
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• 1982

용액법을 이용하여 황화광석중 황을 X-선 형광분광법에 의하여 간접적으로 정량하였다. 시료를 B$r_2$와 HN$O_3$의 혼합용액으로 녹여서 황을 S$O^4_{2-}$상태로 산화시켰고 주성분인 Si$O_2$는 HF로 처리하여 날려 보냈다. 이 용액에 여분의 일정량 B$a^{2+}$용액을 가하여 BaS$O_4$로 침전시키고 거른 다음 거른액과 씻은액중의 Ba의 형광 X-선세기를 측정하여 역계산으로 황을 정량하였다. 무게분석법에 의한 결과와 비교하여 보면 함량 $20{\sim}40%$ 범위에서 ${\pm}1.7%$의 평균차이를 나타낸다. 정광시료의 표준편차는 0.69로서 좋은 재현성을 나타냈다.

• 산업경영시스템학회지
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• 제39권2호
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• pp.119-128
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• 2016

Use of ICT in Government has ability to improve service delivery to its citizens, and yet many developing countries have lagged behind in the implementation of e-Government. Many e-Government initiatives also failed to achieve their objectives in developing countries. This paper therefore aims to identify critical failure or success factors in Kenya, using Heeks' Factor Model. A survey questionnaire was developed and data were collected and analyzed from officials and interested citizens. The analysis results enabled to highlight seven specific success and failure factors, and their constituent elements in Kenya. The Kenyan overall e-Government implementation score belongs to the Zone of Improvement (3.52 of total 5.0), which means partial success or failure. The enablers of e-Government projects are good strategy formulation, and internal and external drive, whereas main failures of e-Government are weak ICT infrastructure. The areas for improvement are project management, design, competencies and funding. Data analysis highlights both strengths and weaknesses for each factor or variable. In particular, Kenyan government excels at the drive for change by top to bottom government officers as well as external stakeholders, while the government officers who are using e-Government are satisfied with the availability of vision, strategy and plan of e-Government implementation. Both technologies and e-transactions laws were the worst of all the variables in e-Government implementation. Two areas should be improved using immediate corrective action. In-depth study reveals that government officers and citizens can't fully use their laptop and mobile devices due to the lack of both ICT network and its operating technology, and legal system associated with the transaction of business information. Finally, the study ends up with recommendations for policy makers to shape the future of e-Government system in both developing and developed countries.

• 한국환경과학회지
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• 제11권12호
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• pp.1205-1215
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• 2002

To evaluate the change for water quality after the water gate operation in Shiwha lake, in situ survey were conducted on september in 2000 and January, march, jane in 2001. Chemical characteristics and eutrophication level was estimated from the survey data. The water quality of the Shihwa lake was greatly affected by pollutant load from rainfall, and formation of stratification in summer and winter was increased to effect on nutrient release from sediment. Especially, high concentration of chlorophyll-a was occurred in autumn, due to increased nutrient, high water temperature and low salinity after rainfall runoff. The mean concentration of DIN, DIP were 0.346mg/L, 0.0217mg/L in surface water and 0.826mg/L, 0.0415mg/L in bottom water, respectively, which were over III grade of seawater standard. Also high percentage of ammonia nitrogen to DIN in bottom water for autumn and winter was affected by released nutrient from sediment. Correlation analysis of chlorophyll-a versus TSS was shown that organic matter was affected by autochthonous organic matter stem from the algae, these factor showed reverse correlation about salinity. Closely correlations among to the water quality constituent in continuity survey was appeared. The results of eutrophication index estimation showed the high potentiality of red tide occurrence in Shiwha lake, particularity in summer or fall. Overall water quality was greatly improve to compared with measuring data during 1997~1998 at the beginning water gate operation, which reported by KORDI. Therefore, to improve of water quality in Shiwha lake, we need to establish of management plan about nutrient release from sediment, rainfall runoff, maximum of seawater exchange.

• Earthquakes and Structures
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• 제15권4호
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• pp.369-382
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• 2018

A free vibration analysis and wave propagation of functionally graded porous beams has been presented in this work using a high order hyperbolic shear deformation theory. Unlike other conventional shear deformation theories, a new displacement field that introduces indeterminate integral variables has been used to minimize the number of unknowns. The constituent materials of the beam are assumed gradually variable along the direction of height according to a simple power law distribution in terms of the volume fractions of the constituents. The variation of the pores in the direction of the thickness influences the mechanical properties. It is therefore necessary to predict the effect of porosity on vibratory behavior and wave velocity of FG beams in this study. A new function of the porosity factor has been developed. Hamilton's principle is used for the development of wave propagation equations in the functionally graded beam. The analytical dispersion relationship of the FG beam is obtained by solving an eigenvalue problem. Illustrative numerical examples are given to show the effects of volume fraction distributions, beam height, wave number, and porosity on free vibration and wave propagation in a functionally graded beam.