• Computers and Concrete
• /
• 제10권4호
• /
• pp.391-407
• /
• 2012

Utilization of supplementary cementing materials (SCM) by the cement industry, as a highly promising solution of sustainable cement development aiming to reduce carbon dioxide emissions, necessitates a more thorough evaluation of these types of materials on concrete durability. In this study a comparative assessment of the effect of SCM on concrete durability, of every cement type as defined in the European Standard EN 197-1 is taking place, using a software tool, based on proven predictive models (according to performance-related methods for assessing durability) developed and wide-validated for the estimation of concrete service life when designing for durability under harsh environments. The effect of Type II additives (fly ash, silica fume) on CEM I type of cement, as well as the effect of every Portland-composite type of cement (and others) are evaluated in terms of their performance in carbonation and chloride exposure, for a service life of 50 years. The main aim is to portray a unified and comprehensive evaluation of the efficiency of SCM in order to create the basis for future consideration of more types of cement to enter the production line in industry.

• Steel and Composite Structures
• /
• 제43권4호
• /
• pp.419-429
• /
• 2022

In response to the sustainability requirements set in the EU Commission's "Green Deal" towards reduction of the greenhouse gas emissions, it is estimated that the structural design for deconstruction is going to contribute considerably to the sustainable development of the built environment. The demountability of multi-material structural systems basically depends on the shear connectors used in the structural system. This paper focuses on a type of demountable injected shear connector with an injected steel-reinforced resin (iSRR) which consists of spherical steel particles embedded in a resin. Its application to steel-to-concrete and steel-to-Fiber Reinforced Polymer (FRP) decks is presented along with its benefits. In parallel, an overview of the experimental and numerical research on the evaluation of the mechanical properties of the demountable bolted connectors with iSRR is discussed. Last, detailed finite element (FE) models and a parametric study are performed to quantify the confinement level of the SRR material influenced by the oversized hole diameter.

• 한국자원식물학회지
• /
• 제35권6호
• /
• pp.820-824
• /
• 2022

Ecologically sustainable means of development is the point to support environmental homeostasis. One of our roles is to find bio-degradable resources that can be substituted for petroleum-based products to effectively abide by the natural viability. To counter the issues of deforestation and preserve biodiversity, it is necessary to produce a non-wood crop that can fulfill the requirement for raw material from which several products can be produced. Kenaf (Hibiscus cannabinus), a member of the family Malvaceae, is showing sufficient potentiality along this road-map. Due to its rich fiber content, it has been used extensively in various fields for long, probably as early as 4,000 BC. At present, kenaf has been used as provider of paper, plastics, fiber glass, biofuel, activated carbon and epoxy composite. This obviously catch one's attention towards its capability to replace petroleum-based products as a whole. Moreover, the plant shows considerable relevance in decreasing pollutants by virtue of its enormous absorption capacity. These multiple applications of kenaf justify its credibility to be the best resource for the better world. The paper presents an overview on its numerous uses reported in the literature that we have investigated and its great potential as a valuable multipurpose crop.

• 한국수소및신에너지학회논문집
• /
• 제25권1호
• /
• pp.19-27
• /
• 2014

Mg hydride has a high hydrogen capacity (7.6%), at high temperature, and is a lightweight and low cost material, thus it a promising hydrogen storage material. However, its high operation temperature and very slow reaction kinetics are obstacles to practical application. In order to overcome these disadvantages of Mg hydride, graphene powder was added to it. The addition of graphene has been shown to reduce the operating temperature of dehydrogenation. Moreover, in this report the environmental aspects of $MgH_x$-Graphene composites are investigated by means of the environmental life cycle assessment (LCA) method. $MgH_x$-Graphene mixture was prepared by hydrogen induced mechanical alloy (HIMA). The synthesized powder was characterized by XRD(X-ray Diffraction). The hydrogenation behaviors were evaluated by using a Sievert's type automatic PCT apparatus. Such evaluation of Materials also conducted in the LCA. From the result of P-C-T(Pressure-Composition-Temperature) curves, the $MgH_x$-3wt.% graphene composite was evaluated as having a 5.86wt.% maximum hydrogen storage capacity, at 523K. From absorption kinetic testing, the $MgH_x$-7wt.% graphene composite was evaluated as having a maximum 6.94wt.%/ms hydrogen absorption rate, at 573K. Environment evaluation results for the $MgH_x$-graphene composites and other materials indicated environmental impact from the electric power used and from the materials themselves.

• 한국수자원학회논문집
• /
• 제39권11호
• /
• pp.935-946
• /
• 2006

본 연구에서는 도시하천의 건천화 방지를 위한 지속가능한 수자원계획을 수립하기 위한 절차를 Heathcote가 제안한 다음과 같은 7단계를 토대로 제시하였다. 단계별 절차는 (1) 유역의 물순환 관련 요소 파악, (2) 문제점 도출 및 우선순위의 결정, (3) 분명하고 구체적인 목표의 설정, (4) 모든 대안의 제시, (5) 가능한 대안의 선별, (6) 선별된 대안의 효과분석, (7) 최종대안의 수립으로 이루어져 있다. 대상 유역의 정량적인 평가를 위한 건천화 지수 산정(2단계)과 대안의 효과 평가(7단계)에 지속가능한 개발 개념인 PSR 모형을 사용하여 각각의 인자를 결정할 것을 제안하였으며, 정량적인 평가에는 복합계획법의 사용을 제안하였다. 구체적인 목표 설정(3단계)을 위해 국내에서 이수관리를 위해 고시하고 있는 하천유지유량을 PHABSIM과 갈수량 산정방식을 이용하여 결정하도록 하였으며, 대안들의 효과 분석(6단계)에는 정확한 연속유출모의뿐만 아니라 토지이용 변화, 저수지 건설 및 운영 등의 대안을 모의할 수 있는 SWAT과 같은 정밀한 수문모형을 제안하였다. 제안된 절차는 다음 논문을 통해서 안양천 중상류 유역에 적용될 것이다.

• 한국수소및신에너지학회논문집
• /
• 제18권1호
• /
• pp.26-31
• /
• 2007

Hydrogen has a high potential to be a renewable substitute for fossil fuels, because of its high gravimetric energy density and environment friendliness. In particular, Magnesium have attracted much interest since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve the kinetic is addition of metal oxide. In this paper, the effect of $Fe_2O_3$ concentration on the kinetics of Mg hydrogen absorption reaction was investigated. $MgH_x-Fe_2O_3$ composites have been synthesized by hydrogen induced mechanical alloying. The powder synthesized was characterized by XRD, SEM and simultaneous TG, DSC analysis. The hydrogenation behaviors were evaluated by using a sievert's type automatic PCT apparatus. Absorption and desorption kinetics of Mg catalyzed with 5,10 mass% $Fe_2O_3$ are determined at 423, 473, 523, 573, 623K.

• Steel and Composite Structures
• /
• 제49권3호
• /
• pp.307-323
• /
• 2023

In this research, the study of the thermoelastic flexural analysis of silicon carbide/Aluminum graded (FG) sandwich 2D uniform structure (plate) under harmonic sinusoidal temperature load over time is presented. The plate is modeled using a simple two dimensional integral shear deformation plate theory. The current formulation contains an integral terms whose aim is to reduce a number of variables compared to others similar solutions and therefore minimize the computation time. The transverse shear stresses vary according to parabolic distribution and vanish at the free surfaces of the structure without any use of correction factors. The external load is applied on the upper face and varying in the thickness of the plates. The structure is supposed to be composed of "three layers" and resting on nonlinear visco-Pasternak's-foundations. The governing equations of the system are deduced and solved via Hamilton's principle and general solution. The computed results are compared with those existing in the literature to validate the current formulation. The impacts of the parameters (material index, temperature exponent, geometry ratio, time, top/bottom temperature ratio, elastic foundation type, and damping coefficient) on the dynamic flexural response are studied.

• 자원ㆍ환경경제연구
• /
• 제12권3호
• /
• pp.487-513
• /
• 2003

환경의 지속가능한 개발을 평가하기 위해서는 환경정보의 통합이 이루어져야 하며, 그 구체적인 수단으로 환경지표와 지수의 개발이 선행되어야만 한다. 해양환경 종합지수의 작성은 해양환경계정의 기초작업으로서 의의를 가지며, 해양국가인 우리 나라에 있어 매우 유용한 연구가 될 수 있다. 또한 지수의 형태에 있어서도 국내 해양환경의 전반적인 환경상태를 나타내는 해양환경 종합지수와 각 해양부문별 상태를 나타내는 부문해양환경지수의 개발이 적절하다. 따라서 본 연구에서는 1991년부터 2001년까지의 우리나라의 해양환경 종합지수를 도출해 보고자 한다. 해양환경 종합지수는 압력-상태-대응(pressure-sate-response PSR)체계를 따르며, 지수의 각 항목 및 가중치의 도출은 다속성 효용이론(multi-attribute utility theory : MAUT)을 적용한다. 본 연구에서 작성한 해양환경 종합지수는 해양환경에 대한 연도별 압력지수, 상태지수, 대응지수와 동해, 남해, 서해의 해역별 상태지수를 제공한다.

• 멤브레인
• /
• 제33권4호
• /
• pp.158-167
• /
• 2023

환경 오염과 천연 자원의 고갈에 대한 증가하는 우려는 환경적으로 지속 가능한 기술의 개발을 촉진했습니다. 퍼바포레이션은 낮은 에너지 소비, 환경 영향 및 성능 효율로 인해 최근 수십 년 동안 주목을 받아 왔습니다. 이 방법은 막이 원하는 선택도를 충족하도록 미세 조정될 수 있기 때문에 화학 종을 분리하고 유기 용매를 탈수하는 데 사용되었습니다. 역삼투 및 증류와 같은 여러 분리 공정은 실험 환경 및 산업 응용 분야에서 모두 활용되고 있습니다. 그러나 퍼바포레이션은 작동 압력 및 온도가 낮고 거부율이 높은 등 여러 이점이 있습니다. 그럼에도 불구하고, 현재 막 기술의 상태만으로는 실용적인 응용에 대한 요구를 충분하게 할 수 없습니다. 반면, 복합막은 유기 물질과 무기 물질의 장점을 모두 활용할 수 있습니다. 많은 연구들이 현재 한계를 해결하기 위해 그래핀 산화물(GO) 및 MXene (MX)과 같은 무기 나노 물질을 고분자 막에 효과적으로 통합했습니다. 이 검토는 투과증발에서의 2D 복합막의 최근 발전을 조사하고 성능 향상을 평가합니다.

• Geomechanics and Engineering
• /
• 제8권6호
• /
• pp.859-872
• /
• 2015

Pebble matrix filtration (PMF) is a water treatment technology that can remove suspended solids in highly turbid surface water during heavy storms. PMF typically uses sand and natural pebbles as filter media. Hand-made clay pebbles (balls) can be used as alternatives to natural pebbles in PMF treatment plants, where natural pebbles are not readily available. Since the high turbidity is a seasonal problem that occurs during heavy rains, the use of newly developed composite clay balls instead of pure clay balls have the advantage of removing other pollutants such as natural organic matter (NOM) during other times. Only the strength properties of composite clay balls are described here as the pollutant removal is beyond the scope of this paper. These new composite clay balls must be able to withstand dead and live loads under dry and saturated conditions in a filter assembly. Absence of a standard ball preparation process and expected strength properties of composite clay balls were the main reasons behind the present study. Five different raw materials from industry wastes: Red Mud (RM), Water Treatment Alum Sludge (S), Shredded Paper (SP), Saw Dust (SD), and Sugar Mulch (SM) were added to common clay brick mix (BM) in different proportions. In an effort to minimize costs, in this study clay balls were fired to $1100^{\circ}C$ at a local brick factory together with their bricks. A comprehensive experimental program was performed to evaluate crushing strength of composite hand-made clay balls, using uniaxial compression test to establish the best material combination on the basis of strength properties for designing sustainable filter media for water treatment plants. Performance at both construction and operating stages were considered by analyzing both strength properties under fully dry conditions and strength degradation after saturation in a water bath. The BM-75% as the main component produced optimum combination in terms of workability and strength. With the material combination of BM-75% and additives-25%, the use of Red Mud and water treatment sludge as additives produced the highest and lowest strength of composite clay balls, with a failure load of 5.4 kN and 1.4 kN respectively. However, this lower value of 1.4 kN is much higher than the effective load on each clay ball of 0.04 kN in a typical filter assembly (safety factor of 35), therefore, can still be used as a suitable filter material for enhanced pollutant removal.