• Earthquakes and Structures
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• 제16권2호
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• pp.221-234
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• 2019

Today, many important concrete face rockfill dams (CFRDs) have been built on the world, and some of these important structures are located on the strong seismic regions. In this reason, examination and monitoring of these water construction's seismic behaviour is very important for the safety and future of these dams. In this study, the nonlinear seismic behaviour of Ilısu CFR dam which was built in Turkey in 2017, is investigated for various reservoir water heights taking into account 1995 Kobe near-fault and far-fault ground motions. Three dimensional (3D) finite difference model of the dam is created using the FLAC3D software that is based on the finite difference method. The most suitable mesh range for the 3D model is chosen to achieve the realistic numerical results. Mohr-Coulomb nonlinear material model is used for the rockfill materials and foundation in the seismic analyses. Moreover, Drucker-Prager nonlinear material model is considered for the concrete slab to represent the nonlinearity of the concrete. The dam body, foundation and concrete slab constantly interact during the lifetime of the CFRDs. Therefore, the special interface elements are defined between the dam body-concrete slab and dam body-foundation due to represent the interaction condition in the 3D model. Free field boundary condition that was used rarely for the nonlinear seismic analyses, is considered for the lateral boundaries of the model. In addition, quiet artificial boundary condition that is special boundary condition for the rigid foundation in the earthquake analyses, is used for the bottom of the foundation. The hysteric damping coefficients are separately calculated for all of the materials. These special damping values is defined to the FLAC3D software using the special fish functions to capture the effects of the variation of the modulus and damping ratio with the dynamic shear-strain magnitude. Total 4 different reservoir water heights are taken into account in the seismic analyses. These water heights are empty reservoir, 50 m, 100 m and 130 m (full reservoir), respectively. In the nonlinear seismic analyses, near-fault and far-fault ground motions of 1995 Kobe earthquake are used. According to the numerical analyses, horizontal displacements, vertical displacements and principal stresses for 4 various reservoir water heights are evaluated in detail. Moreover, these results are compared for the near-fault and far-faults earthquakes. The nonlinear seismic analysis results indicate that as the reservoir height increases, the nonlinear seismic behaviour of the dam clearly changes. Each water height has different seismic effects on the earthquake behaviour of Ilısu CFR dam. In addition, it is obviously seen that near-fault earthquakes and far field earthquakes create different nonlinear seismic damages on the nonlinear earthquake behaviour of the dam.

• 농촌계획
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• 제24권4호
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• pp.147-155
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• 2018

The purpose of this study was to identify vulnerable area of emergency medical care. In the existing method, the emergency medical vulnerable area is set as an area that can not reach the emergency room within 30 minutes. In this study, we set up an area that can not reach within 30 minutes including the accessibility of 119 emergency center. To accomplish this, we obtained information on emergency room and 119 emergency center through Open API and constructed road network using digital map to perform accessibility analysis. As a result, 509 emergency room are located nationwide, 78.0% of them are concentrated in the region, 1,820 emergency center are located, and 61.0% of them are located in rural areas. The average access time from the center of the village to the emergency room was analyzed as 15.3 minutes, and the average access time considering the 119 emergency center was 21.8 minutes, 6.5 minutes more. As a result of considering the accessibility of 119 emergency center, vulnerable areas increased by 2.5 times, vulnerable population increased by 2.0 times, and calculating emergency medical care vulnerable areas, which account for more than 30% of the urban unit population, it was analyzed that it increased from 17 to 34 cities As a further study, it will be necessary to continuously monitor and research the real-time traffic information, medical personnel, medical field, and ambulance information to reflect the reality and to diagnose emergency medical care in the future.

• Earthquakes and Structures
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• 제15권6호
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• pp.667-685
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• 2018

In eccentrically braced steel frames (EBFs), the links are fuse members which enter inelastic phase before other structure members and dissipate the seismic energy. Based on the force-based seismic design method, damages and plastic deformations are limited to the links, and the main structure members are required tremendous sizes to ensure elastic with limited or no damage. Force-based seismic design method is very common and is found in most design codes, it is unable to determine the inelastic response of the structure and the damages of the members. Nowadays, methods of seismic design are emphasizing more on performance-based seismic design concept to have a more realistic assessment of the inelastic response of the structure. Links use ordinary steel Q345 (the nominal yielding strength $f_y{\geq}345MPa$) while other members use high strength steel (Q460 $f_y{\geq}460MPa$ or Q690 $f_y{\geq}690MPa$) in eccentrically braced frames with high strength steel combination (HSS-EBFs). The application of high strength steels brings out many advantages, including higher safety ensured by higher strength in elastic state, better economy which results from the smaller member size and structural weight as well as the corresponding welding work, and most importantly, the application of high strength steel in seismic fortification zone, which is helpful to popularize the extensive use of high strength steel. In order to comparison seismic behavior between HSS-EBFs and ordinary EBFs, on the basis of experimental study, four structures with 5, 10, 15 and 20 stories were designed by PBSD method for HSS-EBFs and ordinary EBFs. Nonlinear static and dynamic analysis is applied to all designs. The loading capacity, lateral stiffness, ductility and story drifts and failure mode under rare earthquake of the designs are compared. Analyses results indicated that HSS-EBFs have similar loading capacity with ordinary EBFs while the lateral stiffness and ductility of HSS-EBFs is lower than that of EBFs. HSS-EBFs and ordinary EBFs designed by PBSD method have the similar failure mode and story drift distribution under rare earthquake, the steel weight of HSS-EBFs is 10%-15% lower than ordinary EBFs resulting in good economic efficiency.

• 기술혁신학회지
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• 제21권4호
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• pp.1366-1385
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• 2018

최근 정부의 벤처기업 정책 지원은 창업 초기 중기의 벤처기업에 대한 R&D 지원에 초점을 두고 있다. 그러나 정보의 비대칭성 문제로 인한 역선택 가능성, 즉, 정부 R&D가 과연 성장 잠재력이 높은 창업 초기 중기 기업에게 지원되고 있는가에 대한 우려도 제기되고 있다. 특히 창업 중기는 죽음의 계곡으로 인해 벤처기업의 생존율이 크게 낮아지는 구간이기 때문에, 정책효과가 클 것으로 예상되는 우수 벤처기업을 선정하여 지원하는 것이 매우 중요하다. 이에 따라 본 연구는 2015년 벤처기업정밀실태조사 결과를 활용, 기술집약적 제조업 내 중기 벤처기업을 정부 R&D 지원 수혜기업(이하 수혜기업)과 비수혜 기업으로 나누고, 이들의 경영효율성 및 기술 재무성과를 비교하였다. 분석결과, 기술집약적 제조업 내 수혜기업은 비수혜 기업에 비해 경영효율성이 낮았으며, 이러한 경향은 중고위기술 제조업에서 더욱 크게 나타났다. 한편, 기술 및 재무성과 분석 결과, 수혜기업은 기술성은 우수하였으나, 성장성, 수익성, 안정성은 열위에 있음을 확인하였다. 특히 이러한 경향은 중고위기술 제조업 내 세부산업 전반에서 발견되었다. 이는 벤처기업에 대한 정부 R&D 지원 시, 역선택 문제가 우려됨을 시사한다. 따라서 향후 정부는 수혜기업 선정 시 경영효율성 및 재무성과를 중요 평가 기준으로 고려해야할 것이다. 또한 기술성이 뛰어난 기업의 경영효율성 및 재무성과를 제고하기 위한 정책과 함께, 경영효율성이 뛰어난 벤처기업을 정부 R&D 지원에 유인하기 위한 방법도 마련해야할 것이다.

• 기술혁신학회지
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• 제22권1호
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• pp.119-157
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• 2019

3D 프린팅 산업의 종사자들이 3D 프린터의 도입을 결정하는 의사 결정에 어떤 인자들이 영향을 주고, 인자들의 역할을 파악하는 것이 중요하다. 이를 통해 국내 기업 등에서 활용되는 3D 프린터의 활용 증대 및 관련 산업 투자 증가로, 국내 3D 프린팅 산업의 발전에 기여할 수 있는 방안을 찾고자 한다. 3D 프린터는 기술의 발전, 대중의 관심, 투자의 활성화에 따라 급속한 발전을 이룩하고 있다. 외국은 장비, 소재, S/W, 산업 활용 등에서 괄목할 발전을 거두고 있으나, 국내에서는 예상보다 저조하다. 3D 프린터 산업의 활성화 및 저변 확대를 위해 원활한 3D 프린터의 도입이 필요하나, 실제 도입 및 현장적용에는 상당히 미흡한 실정이다. 문헌조사를 통해 경제성, 기술성, 환경성을 대표하는 독립변수들을 선정하였고, 3D 프린팅 산업에 대한 사회환경융합형 통합기술수용모델을 제안하여, 독립변수들이 3D 기술 수용의도에 어떤 영향을 미쳤는지를 독립변수 상관분석법, 무상관 회귀분석법 등을 통해 조사하였다. 본 연구를 통해 기업이 3D 프린팅 기술 및 장비의 도입을 위해 출력단가와 같은 경제성 요인과 정부지원, 3D 컨텐츠 같은 환경성 요인들이 유기적으로 확대 발전해야 한다는 점을 확인하였다. 이는 정부의 체계적이고 실효적인 지원이 필요하고, 사용자인 기업이 직접 체감할 수 있는 경제적 지원과 관련 법령, 제도 등의 개선이 필요하다. 경제적, 기술적 시간적 투자가 진행되어야 국내의 3D 프린팅 산업이 발전되고 이를 토대로 3D 프린팅 산업을 4차산업혁명의 핵심 동력으로 삼아야 할 것이다.

• 한국응용과학기술학회지
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• 제36권1호
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• pp.355-361
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• 2019

Serratia marcescens 2354(ATCC 25419) 균주로부터 추출한 붉은 색소는 prodigiosin (PG)이었고, 이를 methanol에 녹여 자외선 및 가시광선 흡수 스펙트라를 측정한 결과 537 nm의 최대흡수파장 (${\lambda}_{max}$)을 갖는 산성용액에서의 전형적인 PG의 흡수 스펙트라이었다. 또한 methanol 용액에서 PG의 농도를 $1.0{\times}10-5M$에서 $9.0{\times}10-5M$로 증가시키면, 537 nm의 흡수강도는 증가하고 467 nm의 흡수강도는 감소하였으며, 500 nm에서 isosbestic point가 관측되었다. 이러한 현상은 537 nm와 467 nm가 각각 산과 염기용액에서의 PG 흡수대이고, 500 nm의 isosbestic point 등을 고려하면 가역적 산-염기 평형반응에 의한 결과라고 볼 수 있다. 한편 pH, 4.75의 acetic acid 완충용액에서 PG의 농도를 $6.0{\times}10^{-4}M$에서 $1.0{\times}10^{-4}M$로 감소시키면 500 nm에서 ${\lambda}_{max}$를 가지는 새로운 흡수대가 나타난다. 이 흡수대는 pH 4.75의 수용액에서만 나타나는 것으로 같은 pH의 순수한 methanol 용액에서는 나타나지 않는다. 이는 PG 분자가 $H_2O$에 의해 ${\alpha}$-이성질체에서 ${\beta}$-이성질체로의 전환에 기인하는 것이다. 즉 PG의 색변화는 용액의 농도 및 용매의 특성에 의해서도 일어날 수 있음을 확인하였다.

• Wind and Structures
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• 제28권4호
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• pp.255-270
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• 2019

Aerodynamic configurations of bridge decks have significant effects on the aerostatic torsional divergence and flutter forsuper long-span bridges, which are onset for selection of suitable bridge decksfor those bridges. Based on a cable-stayed bridge with double main spans of 1500 m, considering typical twin-box, stiffening truss and closed-box section, which are the most commonly used form of bridge decks and assumed that the rigidity of those section is completely equivalent, are utilized to investigate the effects of aerodynamic configurations of bridge decks on aerodynamic instability performance comprised of the aerostatic torsional divergence and flutter, by means of wind tunnel tests and numerical calculations, including three-dimensional (3D) multimode flutter analysis and nonlinear aerostatic analysis. Regarding the aerostatic torsional divergence, the results obtained in this study show twin-box section is the best, closed-box section the second-best, and the stiffening truss section the worst. Regarding the flutter, the flutter stability of the twin-box section is far better than that of the stiffening truss and closed-box section. Furthermore, wind-resistance design depends on the torsional divergence for the twin-box and stiffening truss section. However, there are obvious competitive relationships between the aerostatic torsional divergence and flutter for the closed-box section. Flutter occur before aerostatic instability at initial attack angle of $+3^{\circ}$ and $0^{\circ}$, while the aerostatic torsional divergence occur before flutter at initial attack angle of $-3^{\circ}$. The twin-box section is the best in terms of both aerostatic and flutter stability among those bridge decks. Then mechanisms of aerostatic torsional divergence are revealed by tracking the cable forces synchronous with deformation of the bridge decksin the instability process. It was also found that the onset wind velocities of these bridge decks are very similar at attack angle of $-3^{\circ}$. This indicatesthat a stable triangular structure made up of the cable planes, the tower, and the bridge deck greatly improves the aerostatic stability of the structure, while the aerodynamic effects associated with the aerodynamic configurations of the bridge decks have little effects on the aerostatic stability at initial attack angle of $-3^{\circ}$. In addition, instability patterns of the bridge depend on both the initial attack angles and aerodynamic configurations of the bridge decks. This study is helpful in determining bridge decksfor super long-span bridges in future.

• Structural Engineering and Mechanics
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• 제70권1호
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• pp.67-80
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• 2019

Strengthening with near surface mounted carbon fibre reinforced polymers (NSM-CFRP) is a strengthening technique that have been used for several decades to increase the load carrying capacity of reinforced concrete members. In Iraq, many concrete buildings and bridges were subjected to a wide range of damage as a result of the last war and many other events. Accordingly, there is a progressive increase in the strengthening of concrete structures, bridges in particular, by using CFRP strengthening techniques. Near-surface mounted carbon fibre polymer has been recently proved as a powerful strengthening technique in which the CFRP strips are sufficiently protected against external environmental conditions especially the high-temperature rates in Iraq. However, this technique has not been examined yet under repeated loading conditions such as traffic loads on bridge girders. The main objective of this research was to investigate the effectiveness of NSM-CFRP strips in reinforced concrete beams under repeated loads. Different parameters such as the number of strips, groove size, and two types of bonding materials (epoxy resin and cement-based adhesive) were considered. Fifteen NSM-CFRP strengthened beams were tested under concentrated monotonic and repeated loadings. Three beams were non-strengthened as reference specimens while the remaining were strengthened with NSM-CFRP strips and divided into three groups. Each group comprises two beams tested under monotonic loads and used as control for those tested under repeated loads in the same group. The experimental results are discussed in terms of load-deflection behavior up to failure, ductility factor, cumulative energy absorption, number of cycles to failure, and the mode of failure. The test results proved that strengthening with NSM-CFRP strips increased both the flexural strength and stiffness of the tested beams. An increase in load carrying capacity was obtained in a range of (1.47 to 4.49) times that for the non-strengthened specimens. Also, the increase in total area of CFRPs showed a slight increase in flexural capacity of (1.02) times the value of the control strengthened one tested under repeated loading. Increasing the total area of CFRP strips resulted in a reduction in ductility factor reached to (0.71) while the cumulative energy absorption increased by (1.22) times the values of the strengthened reference specimens tested under repeated loading. Moreover, the replacement of epoxy resin with cement-based adhesive as a bonding material exhibited higher ductility than specimen with epoxy resin tested under monotonic and repeated loading.

• Membrane and Water Treatment
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• 제10권3호
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• pp.207-212
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• 2019

Non-aqueous solvents (NASs) are generally known to be barely miscible, and reactive with polar compounds, such as water. However, water can interact with some NASs, which can be used as a new means for water recovery from saline water. This study explored the fate of water and salt in NAS, when saline water is mixed with NAS. Three amine solvents were selected as NAS. They had the same molecular formula, but were differentiated by their molecular structures, as follows: 1) NAS 'A' having the hydrophilic group ($NH_2$) at the end of the straight carbon chain, 2) NAS 'B' with symmetrical structure and having the hydrophilic group (NH) at the middle of the straight carbon chain, 3) NAS 'C' having the hydrophilic group ($NH_2$) at the end of the straight carbon chain but possessing a hydrophobic ethyl branch in the middle of the structure. In batch experiments, 0.5 M NaCl water was blended with NASs, and then water and salt content in the NAS were individually measured. Water absorption efficiencies by NAS 'B' and 'C' were 3.8 and 10.7%, respectively. However, salt rejection efficiency was 98.9% and 58.2%, respectively. NAS 'A' exhibited a higher water absorption efficiency of 35.6%, despite a worse salt rejection efficiency of 24.7%. Molecular dynamic (MD) simulation showed the different interactions of water and salts with each NAS. NAS 'A' formed lattice structured clusters, with the hydrophilic group located outside, and captured a large numbers of water molecules, together with salt ions, inside the cluster pockets. NAS 'B' formed a planar-shaped cluster, where only some water molecules, but no salt ions, migrated to the NAS cluster. NAS 'C', with an ethyl group branch, formed a cluster shaped similarly to that of 'B'; however, the boundary surface of the cluster looked higher than that of 'C', due to the branch structure in solvent. The MD simulation was helpful for understanding the experimental results for water absorption and salt rejection, by demonstrating the various interactions between water molecules and the salts, with the different NAS types.

• 접착 및 계면
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• 제22권2호
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• pp.63-68
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• 2021

Unsaturated Polyester Resin (UPR)은 유리섬유와 같은 강화제와 함께 사용되어 복합재료로 사용된다. 열경화성 수지인 UPR은 복합재료의 다양한 성형법 중 생산성이 우수하고 대량생산에 유리한 sheet molding compound (SMC) 성형법으로 산업에서 사용되고 있다. UPR을 기지재로 하는 섬유강화복합재료는 가볍고, 물성이 뛰어난 장점이 있지만 충격에 약하여 깨지기 쉽고, 경화 이후에는 부피가 감소하는 단점이 있기 때문에 강인성과 유연성을 부여할 수 있는 폴리올과 캡핑제를 달리하는 폴리우레탄 4종을 합성하여 첨가하여 그 단점을 극복하고자 하였다.