• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.1
• /
• pp.112-119
• /
• 2021

The failure mode of piping systems due to seismic loads is the low-cycle fatigue failure with ratcheting, and it was found that the element in which nonlinear behavior is concentrated and damage occurs is the elbow. In this study, to quantitatively express the failure criteria for a pipe elbow of SCH40 3-inch carbon steel under low-cycle fatigue, the limit state was defined as leakage, and the in-plane cyclic loading test was conducted. For the carbon steel pipe elbow, which is the vulnerable part to seismic load of piping systems, the damage index was represented using the moment-deformation angle relationship, and it was compared and analyzed with the damage index calculated using the force-displacement relationship. An attempt was made to quantitatively express the limit state of the carbon steel pipe elbow involving leakage using the damage index, which was based on the dissipated energy caused by repeated external forces.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.6
• /
• pp.303-309
• /
• 2012

Energy expenditure values were estimated based on the voice signals and body activities. Voice signals and body activities were obtained using PVDF contact vibration sensor and 3-axis accelerometer, respectively. Vibration caused by voices, activity signals, and actual energy consumption were acquired using data acquisition system and gas analyzer. With the use of power values from the voice signals and weight as independent variables, R-square of 0.918 appeared to show the highest value. For activity outputs, use of signal vector magnitude, body mass index, height, and age as independent variables revealed to provide the highest correlation with actual energy expenditure. Estimation of energy expenditure based on voice and activity provides more accurate results than based on activity only.

• KIEAE Journal
• /
• v.16 no.2
• /
• pp.17-22
• /
• 2016

Purpose: Sensitivity analysis offers a good guideline for designing energy conscious buildings, which is fitted to a specific building configuration. Sensitivity analysis is, however, still too expensive to be a part of regular design process. The One-at-a-time (OAT) is the most common and simplest sensitivity analysis method. This study aims to propose a reasonable ground that the OAT can be an alternative method for the variance-based method in some early design scenarios, while the variance-based method is known adequate for dealing with nonlinear response and the effect of interactions between input variables, which are most cases in building energy simulations. Method: A test model representing the early design phase is built in the DOE2 energy simulations. Then sensitivity ranks between the OAT and the Variance-based methods are compared at three U.S. sites. Result: Parameters in the upper rank by the OAT do not much differ from those by the Main effect index. Considering design practices that designers would chose the most energy saving design option first, this rank similarity between two methods seems to be acceptable in the early design phase.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.6
• /
• pp.57-65
• /
• 2014

Solar energy has attracted wide attention as a promising renewable energy source. The goal of this paper is to estimate the dynamic performance of solar flat plate collector system according to the weather conditions and the capacity of heat storage tank. This study provides a detailed description of the modeling methods and materials of the system. The effects of the daily clearness index and the volume of the heat storage tank on the hourly and daily performances of the system are numerically investigated. Special attention is focused on the important system variables including the solar insolation on the collector surface, useful energy, heat loss at the collector, and collector efficiency.

• Journal of Energy Engineering
• /
• v.24 no.1
• /
• pp.137-148
• /
• 2015

So far, the phenomenon of "electrification" has been deepened in Korean industry and especially direct heating energy which accounted for 44.0%(2010) of total energy consumed in Korean manufacturing has been significantly electrified. This paper decomposed electricity consumption for direct heating in Korean manufacturing from 1992 to 2012 using LMDI(Log Mean Divisia Index). This paper includes 4 different factors such as electricity proportion effect, direct heating proportion effect, energy intensity effect and added value effect. And this paper compared the consumption pattern by business type. As results, electricity proportion effect had contributed the most to the increase of electricity consumption for direct heating in Korean manufacturing. And Petrol-Chemical and Iron & Steel had the most electrification of direct heating.

• ETRI Journal
• /
• v.30 no.6
• /
• pp.853-855
• /
• 2008

This paper presents an energy-efficient spatial join algorithm for multiple sensor networks employing a spatial semijoin strategy. For optimization of the algorithm, we propose a GR-tree index and a grid-ID-based spatial approximation method, which are unique to sensor networks. The GR-tree is a distributed spatial index over the sensor nodes, which efficiently prunes away the nodes that will not participate in a spatial join result. The grid-ID-based approximation provides great reduction in communication cost by approximating many spatial objects in simpler forms. Our experiments demonstrate that the algorithm outperforms existing methods in reducing energy consumption at the nodes.

• KIEAE Journal
• /
• v.13 no.4
• /
• pp.49-54
• /
• 2013

released by IEA, 2010, indicated that Korea's GDP, of 8 countries surveyed-Korea, Frans, Germany, Italy, Japan, the UK, the USA, and Australia-was the lowest, but the electric consumption per head was third, following America and Australia. Thus, our government has been striving to reduce energy usage and especially to lessen the energy used in buildings, proposing a variety of road maps such as 'building energy efficiency rating' and 'energy saving design standards of buildings'. Accordingly, this study investigated the effect of the items of machine part among EPI items on the energy saving rate. I measured energy usage by ECO2 program, for simulation program, that is used for the building energy efficiency rating. Result showed that items concerning control of pumps and fans had much more saving rate than the ones concerning efficiency of heater and cooler that had bigger scores assigned among EPI items. Result showed that items concerning control of pumps and fans had much more saving rate than the ones concerning efficiency of heater and cooler that had bigger scores assigned among EPI items. Therefore, I think that grades assigned to items in energy performance index need to be corrected.

• Environmental and Resource Economics Review
• /
• v.18 no.4
• /
• pp.557-586
• /
• 2009

Although energy demand management policy attracts attention internationally and domestically, the importance of local government in this policy is not so much as central government. But local government can do a role with regard to this policy because it is close to energy consumers not like central government. So local energy plan should be based on the understanding local energy consumption characteristics to activate local energy demand management policy. This paper tries to analyze energy characteristics of 16 local governments by decomposing energy consumption into population, production and intensity factors. The result of index decomposition analysis shows that energy intensity improvement has offset the increase of energy consumption caused by economic growth in the metropolitan cities, while it couldn't offset in the other provinces because of industrialization based on the manufacturing. In conclusion, this paper suggests that it will be necessary to switch to low energy society by carrying out concrete energy efficiency improvement projects in the metropolitan cities while it will be helpful to make a local development plan for low energy intensive industrialization in the other provinces.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2331-2336
• /
• 2005

This paper proposes a new haptic device using a parallel mechanism with gimbal type actuators. This device has three legs actuated by 2-DOF gimbal mechanisms, which make the device simple and light by fixing all the actuators to the base. Three extra sensors are placed at passive joints to obtain a unique solution of the forward kinematics problem. The proposed haptic device is developed for an operator to use it on a desktop in due consideration of the size of an average Korean. The proposed haptic device has a small workspace for on operator to use it on a desktop and more sensitivity than a serial type haptic device. Therefore, the motors of the proposed haptic device are fixed at the base plate so that the proposed haptic device has a better dynamic bandwidth due to a low moving inertia. With this conceptual design, optimization of the design parameters is carried out. The objective function is defined by the fuzzy minimum of the global design indices, global force/moment isotropy index, global force/moment payload index, and workspace. Each global index is calculated by a SVD (singular value decomposition) of the force and moment parts of the jacobian matrix. Division of the jacobian matrix assures a consistency of the units in the matrix. Due to the nonlinearity of this objective function, Genetic algorithms are adopted for a global optimization.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.57 no.6
• /
• pp.107-115
• /
• 2015

The objective of the this study is to find the breakage index and changes in permeability of Bottom ash from thermoelectric power plants in Korea. Bottom ash was crushed by compaction according to compaction energy from 0 to $1661.4\;kN/m^2$. The particle size distribution was estimated by sieve analysis. The various breakage indexes were used for analyzing the change in particle size distribution and effect of compaction energy. In the result, breakage indexes were increased as compaction energy and initial upper 4.75 mm diameter ratio, but values and tendencies of breakage indexes appeared in different as calculation method of breakage indexes. The coefficient of permeability was decreased with particle breakage, but decreasing ratio of permeability was very small. Bottom ash has a higher permeability than the weathered soil and it is considered high usability as a permeable materials.