• 한국물환경학회지
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• 제20권6호
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• pp.670-675
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• 2004

Humic acids are macromolecules originated from natural water, soil, and sediment. The characteristics of humic acid enable it to change the distribution of metals as well as many kinds of organic contaminants and to determine the sorption of them from soil solution. To see the effect of humic acid on the removal rate of organic contaminants and heavy metals, batch-scale experiments were performed. As a natural geosorbent, black shale was used as a sorbent media, which showed hight sorption capacity of trichloroethylene (TCE), lead, cadmium and chromium. The effect of sorption-desorption, pH, ionic strength and the concentration of humic acid was taken into consideration. TCE sorption capacity by black shale was compared to natural bentonite and hexadecyltrimethylammonium (HDTMA) modified bentonite. The removal rate was good and humic acid also sorbed onto black shale very well. The organic part of humic acid could effectively enhance the partition of TCE and it act as an electron donor to reduce Cr(VI) to Cr(III). Cationic metal of Pb(II) and Cd(II) also removed from the water by black shale. With 3 mg/L of humic acid, both Pb(II) and Cd(II) were removed more than without humic acid. That could be explained by sorption and complexation with humic acid and that was possible when humic acid could change the hydrophobicity and solubility of heavy metals. Humic acid exhibited desorption-resistivity with black shale, which implied that black shale could be an alternative sorbent or material for remediation of organic contaminants and heavy metals.

• Structural Engineering and Mechanics
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• 제35권6호
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• pp.677-697
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• 2010

This paper focuses on geometrically non-linear static analysis of a simply supported beam made of hyperelastic material subjected to a non-follower transversal uniformly distributed load. As it is known, the line of action of follower forces is affected by the deformation of the elastic system on which they act and therefore such forces are non-conservative. The material of the beam is assumed as isotropic and hyperelastic. Two types of simply supported beams are considered which have the following boundary conditions: 1) There is a pin at left end and a roller at right end of the beam (pinned-rolled beam). 2) Both ends of the beam are supported by pins (pinned-pinned beam). In this study, finite element model of the beam is constructed by using total Lagrangian finite element model of two dimensional continuum for a twelve-node quadratic element. The considered highly non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. In order to use the solution procedures of Newton-Raphson type, there is need to linearized equilibrium equations, which can be achieved through the linearization of the principle of virtual work in its continuum form. In the study, the effect of the large deflections and rotations on the displacements and the normal stress and the shear stress distributions through the thickness of the beam is investigated in detail. It is known that in the failure analysis, the most important quantities are the principal normal stresses and the maximum shear stress. Therefore these stresses are investigated in detail. The convergence studies are performed for various numbers of finite elements. The effects of the geometric non-linearity and pinned-pinned and pinned-rolled support conditions on the displacements and on the stresses are investigated. By using a twelve-node quadratic element, the free boundary conditions are satisfied and very good stress diagrams are obtained. Also, some of the results of the total Lagrangian finite element model of two dimensional continuum for a twelve-node quadratic element are compared with the results of SAP2000 packet program. Numerical results show that geometrical nonlinearity plays very important role in the static responses of the beam.

• 항공우주정책ㆍ법학회지
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• 제23권1호
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• pp.3-32
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• 2008

In proportion to recent developments in aviation technology and growth of the air transport market, the risk of damages to third parties caused by aircrafts and the likelihood of unlawful interference on an aircraft in flight has grown larger. The war risk insurance market was paralyzed by the 9/11 terror event. And if another event on the scale of 9/11 occurs, compensations for third party damages will be impossible. Recognizing the need to modernize the existing legal framework and the absence of a globally accepted authority that deals with third party liability and compensation for catastrophic damage caused by acts of unlawful interference, the ICAO and various countries have discussed a liability and compensation system that can protect both third party victims and the aviation industry for the 7 years. In conclusion, in order to provide adequate protection for victims and the appropriate protection for air transport systems including air carriers, work on modernizing the Rome Convention should be continued and the new Convention should be finalized in the near future. Korea has not ratified the relevant international treaties, i.e. Rome Convention 1933, 1952 and 1978, and has no local laws which regulate the damage caused by aircraft to third parties on land. Consequently, it has to depend on the domestic civil tort laws. Most of the advanced countries in aviation such as the United States, England, Germany, France and even China, have incorporated the International Conventions to their national air law and governed carriers third party liability within their jurisdiction. The Ministry of Justice organized the Special Enactment Committee for Air Transport chapter under Commercial Law. The Air Transport chapter, which currently includes third party liability, is in the process of instituting new legislation. In conclusion, to settle such problems through local law, it is necessary to enact as soon as possible domestic legislation on the civil liability of the air carrier which has been connected with third party liability and aviation insurance.

• 대한토목학회논문집
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• 제41권5호
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• pp.601-608
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• 2021

최근 건설공사에서 근로기준법의 개정, 이상 기후의 증가로 인한 작업가능일수의 감소와 비작업일수의 증가에도 불구하고 이를 반영한 표준 건설공사기간이 마련되어 있지 않다. 이로 인해 현장에서 적정공사기간을 산정하더라도 예기치 못한 상황에 의해 공기지연이 발생하고 있는 실정이다. 따라서 본 연구에서는 기존의 방식에 건설 제반여건의 변화와 기후변화를 반영한 철도 교량공사의 비작업일수 산정방법을 제시하고, 이 산정방법을 철도 교량공사에 반영하여 전국의 지역별·월별 비작업일수를 산정하였다. 그 결과, 국내의 지역별·월별 비작업일수를 도출하였고, 이를 통해 지역적 특성과 공종별 특성을 반영한 정확한 공사기간의 규정 및 기준의 필요성을 제시했다.

• 한국지반환경공학회 논문집
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• 제19권12호
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• pp.33-39
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• 2018

본 연구에서는 토목섬유-점토의 접촉면 압밀 전단거동 평가를 위하여 상재하중 및 해수와 담수를 이용해 토목섬유-점토의 경계면에 대한 중요 특성인자를 규명하였다. 또한 폐기물 매립으로 바다에 매립공간을 확보하고 폐기물 처리 및 향후 토지이용 등 새롭게 필요 공간으로 변모가 가능하다. 토목섬유-점토의 접촉면에 거동특성을 분석한 결과 표준 압밀시험기를 이용하여 분석한 경우 해수보다 담수에서 압밀응력이 크게 증가하는 경향을 보였고, 동적 접촉면 전단 시험기를 이용하여 분석한 경우 해수와 담수 두 개의 조건에서 모두 동일하게 하부모듈에 가까운 와이어게이지일수록 변위값이 증가하고, 담수보다 해수의 조건에서 전단파괴가 급격히 일어나는 경향을 볼 수 있다. 따라서 토목섬유-점토의 접촉면에 작용하는 해수와 담수, 차수시설 설치여부(토목섬유)는 차수 시설 동적설계인자에 반드시 필요한 중요 변수로써 고려하여야 한다.

• Advances in concrete construction
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• 제13권1호
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• pp.71-81
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• 2022

Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.

• Structural Engineering and Mechanics
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• 제80권6호
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• pp.701-709
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• 2021

The paper aims at improving the understanding and mitigating the effects of tunnel fires that may breakout due to the burning fuel and/or explosion within the tunnel. This study particularly focuses on the behavior of the commonly used horse shoe geometry of tunnel systems. The problem has been obtained using an adequate well-established program incorporating the Lagrangian approach. A transient-thermo-coupled static structural analysis is carried out. The effects of radiation and convection to the outer walls of the tunnel is studied. The paper also presents the impact of the hazard on the structural integrity of the tunnel. A methodology is proposed to study the tunnel fire using a model which uses equivalent steel sheet to represent the presence of reinforcements to improve the computational efficiency with adequate validation. A parametric study has been carried out and the effect of suitable lining property for mitigating the fire hazard is arrived at. Detailed analysis is done for the threshold limits of the properties of the lining material to check if it is acceptable in all aspects for the integrity of the tunnel. The study may prove useful for developing insights for ensuring tunnel fire safety. To conduct such studies experimentally are tremendously costly but are required to gain confidence. But, scaled models, as well as loading and testing conditions, cannot be studied by many trials experimentally as the cost will shoot up sharply. In this context, the results obtained from such computational studies with a feasible variation of various combinations of parameters may act as a set of guidelines to freeze the adequate combination of various parameters to conduct one or two costly experiments for confidence building.

• 대한토목학회논문집
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• 제43권4호
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• pp.525-533
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• 2023

산지가 많은 부산시의 지형적 특성상 가용토지가 부족한 상황에서 경부선 철도까지 도심을 가로지르고 있어 생활권의 단절과 도심발전을 저해하고 있다. 이에 토지 확보를 위하여 입체개발의 필요성이 제기되고 있으며, 최근에는 경부선 철도의 지하화로 양분화 된 도시를 연결하고 토지를 효율적으로 사용할 수 있도록 하는데 관심이 증가하고 있다. 본 연구에서는 토지의 입체개발의 사례를 통해 개발유형을 분석하고, 부산시내 경부선 철도의 지하화 사업 시 메인이 되는 4개 권역(사상역, 구포역, 가야역, 부산진역)의 입체개발로 발생하는 가용토지에 효과적인 활용을 위한 시민인식조사 결과를 바탕으로 입체개발 유형별 개발방향 설정하였다. 또한 대상지 지역이 가지고 있는 지역적 특성과 현재 진행되고 있는 도시재생사업을 반영하여 철도에 의해 양분된 지역생활권의 단절 해소 및 철도시설 부지의 효율적 토지이용을 통한 입체적인 개발을 통해 철도 부지의 수평적, 수직적 공간활용의 설계방안을 제시하고자 한다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.462-462
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• 2022

Wetlands are one of the most vital natural habitats on the planet. India is incredibly blessed to have a number of multifunctional wetland ecosystems. Wetlands, in addition to their functional importance, can act as sources or sinks for greenhouse gases (GHGs) depending on their intrinsic factors. Carbon (CO2) and Methane (CH4) are the major greenhouse gases (GHG's) emitted in wetlands. It is demonstrated that, despite having 4.6 percent of its area covered by natural or man-made wetlands, being home to a large number of wetlands, and being the world's second largest cultivator of paddy, India's wetlands, including paddy fields that are intermittently flooded as typical wetlands, have been very poorly studied in terms of GHG emissions. The purpose of this paper is to examine the status of Indian wetlands and wetlands in terms of CH4 and CO2 emissions. The present study also reviews various literature to provide the equations, parameters that are required for estimating carbon and methane and some of the best strategies for conserving carbon in wetlands. The findings suggest that both non-manipulative and manipulative measures can be used to improve Carbon Sequestration (CS). Non-manipulative measures aim to improve CS by increasing the spatial extent of wetlands, whereas manipulative measures aim to change the characteristics of specific wetland components that influence CS. Uncertainty in carbon dynamics projections under changing environmental conditions is caused by a number of Knowledge gaps: i) There is a lack of knowledge on how organic matter mineralizes and partitions into carbon dioxide, methane, and dissolved organic carbon, ii) With the notable exception of methane dynamics, models that represent the dynamic interaction of processes and their controls have yet to be established. As a result, more research is needed to fully understand the importance of wetlands in terms of GHG emissions and carbon sequestration in India.

• 대한토목학회논문집
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• 제43권6호
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• pp.865-871
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• 2023

국내 도시철도 운영기관은 6대 광역지자체 산하기관인 도시철도 운영공기업과 민간투자법에 의해 설립되어 주로 경전철을 운영하는 민간운영사로 구성되어 있다. 도시철도 운영기관 중 경험, 실적, 인력, 공공성을 가지고 있는 도시철도 운영공기업 여러 곳이 해외사업을 추진하기 위해 노력하고 있다. 따라서 본 연구에서는 해외 철도 및 도시철도 사업 전망을 조사하고, 국내외 도시철도 운영공기업의 해외사업 접근법 및 해외사업 특성에 대한 문헌 및 자료 조사와 비교 분석을 통해 국내 도시철도 운영공기업의 해외사업 접근법에 대한 시사점을 도출하였고 국내 도시철도 운영공기업이 해외사업을 추진하는 방향에 대한 제언을 제시하였다. 이를 통해 국내 공공 및 민간 도시철도 운영기관이 기업별 특성에 맞는 준비 과정과 추진계획 및 방향성을 가지고 해외사업을 추진하는데 도움이 되기를 기대한다.