• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.685-688
• /
• 2008

Concrete is strong on the compressive property, but weak on the tensile and flexural properties. To improve these problems, the reinforcing bar is used in concrete. But porous concrete with steel fiber has a weak point when exposed to air, because porous concrete has the vast continuous void on its inside and steel fiber is easily rusted by air. For these reasons, this study investigated the void ratio, compressive strength, bending strength and bending toughness as steel fiber mixing ratio and target void ratio. From test results, actual void ratio and strength properties increased as the mixing ratio of steel fiber increase. In case the mixing ratio of steel fiber over the fixed ratio, strength is decreased. And from the toughness evaluation, compared to the porous concrete which isn't mixed with steel fiber, the deflection variation efficiency is remarkably improved. Consequently we can confirm the possibility of porous concrete with steel fiber for the secondary product and pavement material to improve strength and bending resistance efficiency.

• Nuclear Engineering and Technology
• /
• v.52 no.2
• /
• pp.279-286
• /
• 2020

In this article, we develop a reactive distillation (RD) column configuration for the production of hydrogen. This RD column is in the HI decomposition section of the sulphur - iodine (SI) thermochemical cycle, in which HI decomposition and H₂ separation take place simultaneously. The section plays a major role in high hydrogen production efficiency (that depends on reaction conversion and separation efficiency) of the SI cycle. In the column simulation, the rigorous thermodynamic phase equilibrium and reaction kinetic model are used. The tuning parameters involved in phase equilibrium model are dependent on interactive components and system temperature. For kinetic model, parameter values are adopted from the Aspen flowsheet simulator. Interestingly, there is no side reaction (e.g., solvation reaction, electrolyte decomposition and polyiodide formation) considered aiming to make the proposed model simple that leads to a challenging prediction. The process parameters are determined on the basis of optimal hydrogen production as reflux ratio = 0.87, total number of stages = 19 and feeding point at 8th stage. With this, the column operates at a reasonably low pressure (i.e., 8 bar) and produces hydrogen in the distillate with a desired composition (H₂ = 9.18 mol%, H₂O = 88.27 mol% and HI = 2.54 mol%). Finally, the results are compared with other model simulations. It is observed that the proposed scheme leads to consume a reasonably low energy requirement of 327 MJ/kmol of H₂.

• Korean Journal of Applied Biomechanics
• /
• v.21 no.5
• /
• pp.585-593
• /
• 2011

The purpose of this study was to analyze, from a kinematical point of view, the high jump techniques of three women's high jump winners at the IAAF World Championships, Daegu 2011. The trends for the techniques of the world's top high jumpers were examined, with a view toward adapting these techniques to the physical characteristics of Korean women's high jumpers. It was valuable that Di Martino, who was the shortest in height, was able to win a medal by using a single arm swing take-off technique, along with a half flexed leading leg swing to attain a deep arch and clear the bar. This showed that the world's top athletes used jumping techniques with no decrease in the run-up velocity at the take-off. Furthermore, It appeared that the knee joint angle at take-off had a direct effect on the body position at take-off (H1).

• Journal of Korean Society of Steel Construction
• /
• v.14 no.1
• /
• pp.79-85
• /
• 2002

Recently, prestressed H-Beam bridges with external unbonded Tendons are increasingly built. The mechanical behavior of prestressed steel H-beams is different from that of normal bonded PSC beams in a point of the slip of tendons at deviators and the change of tendon eccentricity that occurs, when service load are applied in external unbonded steel H-beams. The concept of prestressing steel structures has been widely considered, in spite of long and successful history of prestressing concrete members. In the study, The flexural test on prestressed steel H-beams has been performed in the various aspects of prestressed H-beam including the tendon type and profile. The load was plotted against the deflection and the strain respectively in the steel beam and prestressing bars. The value expected with the equation of internal force equilibrium and compatibility between the deflection of the bars and the H-beam was found to correlate well with the measured data.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.40 no.1
• /
• pp.60-64
• /
• 2004

The reason of the loss for the plastic sea-eel pots were estimated as crew's mistake, strong current, bad weather, rough seabed, artificial reef and other boats' fishing. Especially, pot loss happened on the fishing could make some additional catch, loss of the catches and ghost fishing because there are baits and alive fish in the lost pot. Quantity of the lost pots was estimated as 2~4 times of the ordinary usage. On the result of investigation to analyze the possibility of sustainable ghost fishing for the lost pot to feed the fishes at anytime because there were blenny, silver whiting, bar-tailed flathead and shrimp including sea-eel in the lost pot. In the bioeconomic point, ghost fishing is competitive with the general fishing. Accordingly, usage of biodegradable plastic material for the plastic sea-eel pot will be better to reduce ghost fishing

• Journal of Institute of Control, Robotics and Systems
• /
• v.17 no.6
• /
• pp.566-572
• /
• 2011

In recent semiconductor and FPD (Flat Panel Display) manufacturing processes, high clean-class delivery operation is required more and more for short working time and better product quality. Traditionally SLIM (Single-sided Linear Induction Motor) is widely used in the liner drive applications because of its simplicity in the rail structure. A magnetically levitated (Maglev) unmanned vehicle with SLIM traction, which is powered by a CPS (Contactless Power Supply) can be a high precision delivery solution for this industry. In this paper unmanned FPD-carrying vehicle, which can levitate without contacting the rail structure, is suggested for high clean-class FPD delivery applications. It can be more acceptable for the complex facilities composed with many processes which require longer rails, because of simple rail structure. The test setup consists of a test vehicle and a rounded rail, in which the vehicle can load and unload products at arbitrary position commanded through wireless communications of host computer. The experimental results show that the suggested vehicle and rail have reasonable traction servo and robust electromagnetic suspensions without any contact. The resolution of point servo errors in the SLIM traction system is accomplished under 1mm. The maximum gap error is ${\pm}0.25mm$ with nominal air gap length of 4.0mm in the electromagnetic suspensions. This type of automated delivery vehicle is expected to have significant role in the clean delivery like FPD glass delivery.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.45 no.6
• /
• pp.60-67
• /
• 2008

At present, RFID system is highly welcomed as a substitute system with its bar code recognition system and self recognition equipment. Consequently, the system has multi applications and can be complementing to its security. In particular, RFID system is significantly related with electronic transaction equipments : transportation card, ID card in check point, attendance sheet. Based upon these characteristic, the system is becoming extremely popular in the field of logistics, harbor and stock management, animal control and product circulation & distribution. In this dissertation, I would like to present a more efficient and stable remote entry control system with the network-based TCP/IP. It is a simple example of ubiquitous computing function. Above all, approved protocol system should be applied to the remote entry control function. Its efficient function with the applied approval protocol based-remote entry control system should be confirmed. Therefore, a preliminary test should be prerequisite in automatic entrance function with the embedded and TCP/IP-based RFID system.

• Journal of the Korean housing association
• /
• v.20 no.4
• /
• pp.131-142
• /
• 2009

High-rise and high-density apartment complexes have been built and supplied on a large scale in the 1st period of the New Town project in metropolitan areas since the late 1980s. Now It has become necessary to improve those apartment complexes, which have serious deterioration problems for aging more than about 20 years accompanying simultaneity and a large scale. The purpose of this research is to develop the evaluating indicators to measure the level of deterioration of apartments inclusively and practically in order to regenerate apartments as sustainable residential environments. This study is composed of the following four parts; (a) establishing the conceptual model of evaluation of apartment deterioration, (b) selecting evaluation items, (c) constituting evaluation measurement, and（ｄ)weighting evaluation indicators. First, deterioration of apartments was conceptualized by physical. social, and economical aspects in terms of sustainable development and proposed the conceptual model of hierarchy structure of evaluation of apartment deterioration by literature reviews. Second, evaluating items were selected based on literature reviews of existing indicators and preceding studies about apartments of Korea and foreign countries. The evaluating indicators were identified as a total of 77 evaluating items which were composed of three dimensions and 9 attributes on the basis of the conceptual model. They cover comprehensive scope of the apartment such as unit, building, complex, and site. Third, as the measurement, the 5 point ordinal scale measure was suggested. The evaluating measurement including measure standards, measure methods, and measure contents were developed by each evaluating items. Lastly, the weighting of evaluating indicators was analyzed by AHP method conducted by survey on the expert group. Items were identified as high contributors or low contributors. The weighting of these items could suggest several evaluations according to the situation. The evaluation of the level of deterioration can be done by both total evaluation and a specific field of evaluation. In addition, it is easy to grasp deteriorated attributes or dimensions by providing a radar and bar chart showing evaluation results. These evaluating indicators could be a useful tool to grasp actual methods for the regeneration of apartments.

• The Korean Journal of Community Living Science
• /
• v.26 no.3
• /
• pp.499-509
• /
• 2015

Efforts to have children consume milk continue across the world for the sufficient supply of calcium and protein. This study examines the frequency and amount of dairy milk and the recognition, acceptability, and knowledge of milk and dairy products by considering fifth- and sixth-graders in Hwaseong, Korea. The acceptability of milk and dairy products measured based on a five-point Likert-type scale was assessed to determine its correlations with breakfast frequency, the frequency of milk intake, and milk knowledge. According to descriptive statistics, 47% and 53% of the subjects were fifth- and sixth-graders, respectively, 53% and 47% were male and female, respectively, 45.3% and 51.2% had mothers in their thirties and forties, respectively, and 57% had working mothers. Breakfast frequency was 5.2 and 5.3 times per week, and milk and dairy intake was 4.6 times. The milk knowledge score was 5.3 out of 10 points. The average daily intake of milk was a cup (55.1%), and a vast majority preferred white milk (68.6%). Ice cream bar type (4.49 points) and cone type (4.48 points) showed the highest acceptability, and breakfast frequency was positively correlated with white milk and cheddar cheese (p<0.01). Daily milk intake frequency was positively correlated with white milk and fortified milk. Milk knowledge was positively correlation with white milk, fortified milk, functional yogurt (p <0.05), fermented milk, and cheese (p<0.01). The higher the breakfast frequency, the more likely the intake of white milk (p<0.01). An increase in milk intake increased milk knowledge (p<0.05). The higher the level of knowledge, the more likely the intake of fortified milk and the frequency of milk intake. These results suggest that school lunch milk may increase awareness and milk intake through continuing education in milk knowledge. High acceptability scores for white milk, fortified milk, and fermented milk indicate their suitability for school milk consumption.

• Structural Engineering and Mechanics
• /
• v.65 no.3
• /
• pp.291-302
• /
• 2018

Rigid body spring method (RBSM) is an effective tool to simulate the cracking process of structures, and has been successfully applied to investigate the behavior of reinforced concrete (RC) members. However, the theoretical researches and engineering applications of this method mainly focus on two-dimensional problems as yet, which greatly limits its applications in actual engineering projects. In this study, a three-dimensional (3-D) RBSM for RC structures is proposed. In the proposed model, concrete, reinforcing steels, and their interfaces are represented as discrete entities. Concrete is partitioned into a collection of rigid blocks and a uniform distribution of normal and tangential springs is defined along their boundaries to reflect its material properties. Reinforcement is modeled as a series of bar elements which can be freely positioned in the structural domain and irrespective of the mesh geometry of concrete. The bond-slip characteristics between reinforcing steel and concrete are also considered by introducing special linkage elements. The applicability and effectiveness of the proposed method is firstly confirmed by an elastic T-shape beam, and then it is applied to analyze the failure processes of a Z-type component under direct shear loading and a RC beam under two-point loading.