• Journal of Korean Society of Rural Planning
• /
• v.21 no.4
• /
• pp.187-196
• /
• 2015

Among the factors of living environment, the one that is the most closely related with our living is the building. It is one of the biggest reasons for energy consumption as it forms 36% of the total energy consumption. Technologies equipped with excellent energy performance can hardly be applied to rural areas that are relatively poorer. Still, 89.8% rural residents are living in detached houses, and backward houses increase their financial burden and result in reduced insulation performance. Accordingly, this study is going to review the latest research written after 2000 dealing with rural houses and their insulation. The purpose of this study is to analyze the factors of insulation and how to improve insulation performance, conduct field research to find out how to apply low energy technologies applicable to houses with the subjects of experimental houses, the passive houses located in Jecheon City, Hongcheon Saldun zero energy houses, and energy independence villages, and find out how to perform follow-up research on insulation for rural houses. According to the findings, the latest research on insulation for rural houses is mostly focused on walls as well as windows and doors. Also, as ways to improve insulation performance, it suggests us to use high performance insulators, introduce new regeneration energy technology, and secure hermeticity. In addition, through field research, this author could find out low energy technologies applicable to houses such as solar energy facilities and heat recovery systems. Advanced research on insulation for rural houses has been focused on how to use materials or new regeneration energy, so follow-up research will have to consider the types of farming area or the residents' mode of living.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.11 no.4
• /
• pp.13-21
• /
• 2001

Electrorheological(ER) fluid is a kind of smart material with variable shear stress and dynamic viscosity under various electric field intensity. Electric field can control the damping characteristics of ER damper. The objective of this study is the analysis of the performance of ER damper and its application to shock absorber. Idealized nonlinear Bingham plastic shear flow model is used to predict the velocity profile between electrodes. Cylindrical dashpot ER damper with moving electrode is constructed and tested under various electric fields. The analytic and experimental results for damping force are compared and discussed. Drop test system using ER damper is prepared to identify transient vibration characteristics. The rebound is eased as the applied electric field increases. When semi-active control algorithm is applied, rebound phenomenon disappears and vibration energy level decays faster than the case of zero electric field.

• Transactions of the Korean hydrogen and new energy society
• /
• v.32 no.6
• /
• pp.573-584
• /
• 2021

Hydrogen is evaluated as one of the new energy sources that can overcome the limitations and pollution problems of conventional fossil fuels. Although hydrogen is CO₂-free, attention is required in NO_x emission and flame stability in order to use hydrogen in existing gas fuel system. However, use of electric grids is an unrealistic strategy for decarbonization for residential and commercial heating. Instead, use of H₂ that utilizes city gas grid is suggested as a reasonable alternative in terms of compatibility with existing systems, economic feasibility, and accessibility. In this study, the thermal efficiency and NO_x performance of the boiler according to the H₂ mixture ratio and vapor humidified ratio are reviewed for a humidified NG-H₂ boiler that vapor humidity to combustion air. Mixed fuel with H₂ (20%) is almost similar to NG in terms of efficiency, flame temperature, and pollution performance. Thus, it is expected to be directly compatible with the existing NG system. If the exhaust temperature of the H₂ boiler is lowered to around 60℃ at a humidified ratio of 15-20%, the NO_x emission concentration can be suppressed to about 5-10 ppm. The level of efficiency reaches 87% of the rated load efficiency, which is equivalent to the highest grade achievable.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2000.10a
• /
• pp.81-88
• /
• 2000

The elastic wave equation is solved using the finite-difference method in 3D space to simulate the seismic wave propagation. It is based on the velocity-stress formulation of the equation of motion on a staggered grid. The nonreflecting boundary conditions are used to attenuate the wave field close to the numerical boundary. To satisfy the stress-free conditions at the free-surface boundary, a new formulation combining the zero-stress formalism with the vacuum one is applied. The effective media parameters are employed to satisfy the traction continuity condition across the media interface. With use of the moment-tensor components, the wide range of source mechanism parameters can be specified. The numerical experiments are carried out in order to test the applicability and accuracy of this scheme and to understand the fundamental features of the wave propagation under the generalized elastic media structure. Computational results show that the scheme is sufficiently accurate for modeling wave propagation in 3D elastic media and generates all the possible phases appropriately in under the given heterogeneous velocity structure. Also the characteristics of the ground motion in an sedimentary basin such as the amplification, trapping, and focusing of the elastic wave energy are well represented. These results demonstrate the use of this simulation method will be helpful for modeling the ground motion of seismological and engineering purpose like earthquake hazard assessment, seismic design, city planning, and etc..

• Wind and Structures
• /
• v.17 no.4
• /
• pp.361-377
• /
• 2013

Wall functions have been widely used in computational fluid dynamics (CFD) simulations and can save significant computational costs compared to other near-wall flow treatment strategies. However, most of the existing wall functions were based on the asymptotic characteristics of near-wall flow quantities, which are inapplicable in complex and non-equilibrium flows. A modified wall function is thus derived in this study based on flow over a plate at zero-pressure gradient, instead of on the basis of asymptotic formulations. Turbulent kinetic energy generation ($G_P$), dissipation rate (${\varepsilon}$) and shear stress (${\tau}_{\omega}$) are composed together as the near-wall expressions. Performances of the modified wall function combined with the nonlinear realizable k-${\varepsilon}$ turbulence model are investigated in homogeneous equilibrium atmosphere boundary layer (ABL) and flow around a 6 m cube. The computational results and associated comparisons to available full-scale measurements show a clear improvement over the standard wall function, especially in reproducing the boundary layer flow. It is demonstrated through the two case studies that the modified wall function is indeed adaptive and can yield accurate prediction results, in spite of its simplicity.

• Journal of Environmental Policy
• /
• v.8 no.3
• /
• pp.181-206
• /
• 2009

The purpose of this paper is to analyze economic adequacy by estimating the benefit-cost for bird eco-park, eco-center, eco-river, and eco-waterway, which will be built in the new town of Kimpoo, Yangchon. This paper attempts an economic analysis for the development of an eco-friendly new town. The rates of B/C (benefit-cost) in all scenarios are over one. Especially, the B/C rate of the eco-center is the most efficient of the four eco-facilities by 5.02 - 3.75. In addition, the construction costs of the five eco-facilities are assumed to be 50 percent higher, though their economic soundness is maintained. This paper implies that providing ecological variety is one of the core components in constructing housing complexes and suggests that the construction of housing be harmonized with zero-carbon and energy efficient methods.

• Computers and Concrete
• /
• v.32 no.1
• /
• pp.61-74
• /
• 2023

This article investigates the wave propagation analysis of the imperfect functionally graded (FG) sandwich plates based on a novel simple four-variable integral quasi-3D higher-order shear deformation theory (HSDT). The thickness stretching effect is considered in the transverse displacement component. The presented formulation ensures a parabolic variation of the transverse shear stresses with zero-stresses at the top and the bottom surfaces without requiring any shear correction factors. The studied sandwich plates can be used in several sectors as areas of aircraft, construction, naval/marine, aerospace and wind energy systems, the sandwich structure is composed from three layers (two FG face sheets and isotropic core). The material properties in the FG faces sheet are computed according to a modified power law function with considering the porosity which may appear during the manufacturing process in the form of micro-voids in the layer body. The Hamilton principle is utilized to determine the four governing differential equations for wave propagation in FG plates which is reduced in terms of computation time and cost compared to the other conventional quasi-3D models. An eigenvalue equation is formulated for the analytical solution using a generalized displacements' solution form for wave propagation. The effects of porosity, temperature, moisture concentration, core thickness, and the material exponent on the plates' dispersion relations are examined by considering the thickness stretching influence.

• Journal of the Korea Institute of Building Construction
• /
• v.12 no.6
• /
• pp.615-623
• /
• 2012

Humanity is facing a number of serious issues associated with increased energy consumption and environmental pollution. Various studies/guidelines concerning sustainable building construction have suggested solutions to these disastrous problems, including: net-zero energy buildings, the green building certification system, and others. Sustainability pursues three expected effects: environmental, social, and economic merits. Korean Green Building Council (K-GBC) has also announced the Korean Green Building Certification System (K-GBCS) since 2003 based on sustainability. Some positive social and environmental aspects of the K-GBCS have already been reported. However, it is somewhat difficult to verify its economic merits, which are crucial to ensuring the validity of the K-GBCS. This research aims to verify the economic merits of the eco-friendly Korean-style condominiums accredited by K-GBCS. Following this, the expected economic effectiveness of K-GBCS will be examined in terms of sustainability. The underlying assumption is that the potential economic effect should reflect the actual economic merits, and should reflect the value of the housing in particular. According to the analysis of the variance, it can be concluded the value of green certified buildings is statistically higher than the value of non-certified buildings. Furthermore, it was also observed that this tendency was more dominant in Gyeonggi Province than in the City of Seoul. This may be caused by one of the variables: the proximity to downtown. In future studies, this variable should be studied in greater detail.

• Journal of Korea Water Resources Association
• /
• v.31 no.4
• /
• pp.439-448
• /
• 1998

There are many methods to calculate steady-state flowrate in a large water distribution system. Linear method which analyzes continuity equations and energy equations simultaneously is most widely used. Though it is theoretically simple, when it is applied to a practical water distribution system, it produces a very sparse coefficient matrix and most of its diagonal elements are to be zero. This sparsity characteristic of coefficient matrix makes it difficult to analyze pipe flow using the linear method. In this study, a graph theory is introduced to water distribution system analysis in order to prevent from producing ill-conditioned coefficient matrix and the technique is developed to produce positive-definite matrix. To test applicability of developed method, this method is applied to 22 pipes and 142 pipes system located nearby Taegu city. The results obtained from these applications show that the method can calculate flowrate effectively without failure in converage. Thus it is expected that the method can analyze steady state flowrate and pressure in pipe network systems efficiently. Keywords : pipe flow analysis, graph theory, linear method.

• Advances in environmental research
• /
• v.9 no.2
• /
• pp.97-107
• /
• 2020

The indiscriminate growth in global population poses a threat to the world in handling and disposal of Municipal solid waste. Rapid urban growth increases the production, consumption and generation of Municipal solid waste which leads to a drastic change in the environment. The methane produced from the Municipal Solid waste accounts for up to 11% global anthropogenic emissions, which is a major cause for global warming. This study reports the methane emission estimation using IPCC default, TNO, LandGEM, EPER and close flux chamber from open dump yards at Perungudi and Kodungaiyur in Chennai, India. The result reveals that the methane emission using close flux chamber was in the range of 8.8 Gg/yr-11.3 Gg/yr and 6.1Gg/yr to 9.1 Gg/yr at Kodungaiyur and Perungudi dump yard respectively. The per capita waste generation was estimated based on waste generation and population. The waste generation potential was projected using linear regression model for the period 2017-2050. The trend of CH₄ emission in the actual field measurement were increased every year, similarly the emission trend also increased in IPCC default method (mass balance approach), EPER Germany (zero order decay model) where as TNO and Land GEM (first order decay model) were decreased. The present study reveals that Kodungaiyur dump yard is more vulnerable to methane emission compared to Perungudi dump yard and has more potential in waste to energy conversion mechanisms than compare to Perungudi dump yard.