• Resources Recycling
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• v.29 no.1
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• pp.53-61
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• 2020

This study aimed to develop a foam concrete material for a ground repair system that has low strength and low fluidity by using an eco-friendly binder, which substitutes industrial by-products for more than 90% of cement. Basic properties were evaluated after substituting a small amount of calcium sulfo aluminate (CSA) for the binder to improve the sinking depth rate and volume change, commonly found when it had a large amount of industrial by-products. The substitution rates of CSA for the eco-friendly binder used for the foam concrete were 2.5, 5, and 10%. Fresh properties, hardened properties, pore structure, and hydrates were analyzed. Experimental results showed that using only 2.5% of CSA could improve the deep sinking depth which occurred when using an eco-friendly binder. As a result, the weight difference between the upper, middle, and lower parts of cast specimens was improved even after being hardened. The addition of CSA also contributed to the formation of small, uniformly sized closed pores and improved initial strength. However, when the proportion of CSA increased, the long-term strength decreased. However, it satisfied the target strength when 5% or less of CSA was used. The results of this study revealed that it was possible to manufacture foam concrete with low strength and high fluidity for repairing ground satisfying target qualities by adding 2.5% of CSA to the eco-friendly binder containing a large amount of industrial by-products.

• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.4
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• pp.99-107
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• 1979

In order to investigate the utilization of industrial waste and briquette ash for concrete production, briquette ash was used as fine aggregate for mortar production and three different kinds mortars were produced by mixing carbide and bottom aches with cement. These products were compared with mortar, produced by standard sand, in the respects of compressive, tensil and bending strengths. Further study on the economic aspect of utilization of briquette ash is needed but the results obtained from our preliminary study are summarized as follows : 1. The compressive strengths at the age of seven days of mortars, made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash and(cement+bottom ash) to briquette ash were 70%, 61% and 58%, respectively, of the mortar made of standard sand. The compressive strengths of those mortars at the age of 28 days were 56%, 49% and 48% of the mortar made standard sand. 2. The compressive strengths at the age of seven days of the mortar made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash and (cement+bottom ash) to briquette ash were 84%, 73%, and 70% of the mortar which was produced according to Korean Standard Value. The compressive strengths of those mortars at the age of 28 days were 85%, 73% and 73% of the mortar of the Korean Standard value. 3. The tensil strengths at the age of seven days of the mortars made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash, and (cement+bottom ash) to briquette ash were 64%, 36%, and 36%, respectively, of the mortar of standard sand. The tensil strengths of those mortars at the age of 28 days were 70%, 47%, and 39%, respectively, of the standard mortar. The mortars made of one to two ratios of cement to briquette ash at the age of seven and 28 days were higher than the mortars of Korean Standard. The other mortars were 61 to 62% at the age of seven days and 75 to 90% at the age of 28 days of the Korean Standard mortar, respectively. 4. The bending strengths at the age of seven days of mortar made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash, and (cement+bottom ash) to briquette ash were 46%, 53% and 50% of the mortar of standard sand. The bending strengths of those mortars at the age of 28 days were 90%, 77% and 69%, respectively of the mortar of standard sand. 5. The mortar of briquette ash which was lower in strengths compared with the mortar of cement have shown possibility of its secondary products of cement and concrete. The uses of briquette ash and industrial waste as construction materials would contribute toward solving various pollution problems caused by industrial wastes and saving labor costs needed to cleaning up. Furthermore, the effective use of briquette ash would greatly save the aggregate resources.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.58-68
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• 2010

This paper proposes a novel design of auto light control system with high efficiency using RS-485 to save lighting energy in new and existing buildings. The proposed system consists of ALSU(Auto Light Sensor Unit) which is connected with RS-485 to control lighting appliances, ALS(Auto Light Unit), and Hi-FACS which is a monitoring system using communication interface. lighting appliances are automatically controlled by ALSU which detects moving objects. The total system is designed to be controlled by either manual or auto mode by using the ALS. In addition, the monitoring system receives the information on the state of the lighting appliances from ALSU and ALS to control the proposed system We compared the proposed system with the conventional one in functionality and energy saving point of view. Through some experimental results, the proposed system shows better performance in various circumstances.

• Korean Journal of Construction Engineering and Management
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• v.12 no.1
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• pp.133-140
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• 2011

Recently, the demolition industry is becoming more important than ever for formulating reuse and recycling of a construction waste with the current trend in pursuing a sustainable development. As considering the situation of a domestic housing construction and an existing house, a scale of a demolition market is expected to increase continually. Therefore, for a sustainable development, it is needed to forecast and manage rightly the demolition waste producted in a demolition phase. But, because most of a demolition company is very small and the investment in a technology development is not enough, the effort to develope a system and to make a standard for managing righly a demolition waste is also not sufficient. Therefore, this study develops a system to automatize quantifying a demolition waste. This system makes it possible to manage the planning of demolition works and the quantifying, disposal, reusing and recycling of a demolition waste in one system by integrating all the activities related with demolition works. 3D drawings of each element for demolition works will manage by being linked to its schedule for visualizing 3D object. Also, this study presents methods for quantifying easily a demolition waste by using 3D object.

• Journal of Korean Association for Spatial Structures
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• v.8 no.5
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• pp.67-74
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• 2008

Multi-layered stone masonry monuments, such as stone pagoda can be modeled as a multi-degrees of freedom system. The dynamic behavior of these structures are mainly influenced by contour condition of contacting surface of stones. In this case the mass of the system can be easily estimated, mean while the estimation of stiffness at junction is not simple. In this paper a method for estimating the spring constant at the contacting surface of stone in proposed. This paper describes a method of computational modelling technique for structural analysis of stone pagodas using measurement of natural frequency and eigenvalue analysis. For this purpose Five story stone pagoda in Cchongnimsa site was selected as a model.

• Journal of the Korean Wood Science and Technology
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• v.32 no.4
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• pp.46-51
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• 2004

The objective of this study was to evaluate the applicability of high temperature drying to pitch pine (Pinus rigida) lumber, especially intended for use as lamina of structural glued laminated timber (glulam), to enhance the efficient utilization and provide added-value to that species. The high temperature schedule and drying procedures utilized were shown to be reasonable for drying glulam lamina due to the occurrence of small moisture gradients, minimal residual drying stress, and low warpage. Through preliminary tests, it was confirmed that residual resin at lamina surfaces did not adversely affect the gluing process. However, quantitative analysis of resin is required for developing a method to constrain the occurrence of pitch trouble with respect to decreasing long-term adhesive and finish durability of glulam in use after manufacturing. The final moisture content of high temperature dried lamina was much lower than target moisture content and discoloration was more severe than anticipated. In a further study, it will be necessary to determine the optimal drying conditions, such as temperature, humidity, drying time, and top load restraint level, which could best control discoloration, warpage, and moisture content of the lamina, while minimizing fuel expense.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.3-9
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• 2015

The wireless communication system adopts an appropriate retransmission scheme on each system protocol layer to improve reliability of data transmission. In each system protocol layer, the retransmission scheme operates in independently other layers and operates based on the parameters without reference to end-to-end performance of wireless communication system. For this reason, it is difficult to design the optimal system parameters that satisfy the QoS requirements for each service class. Thus, the performance analysis of wireless communication system is needed to design the optimal system parameters according to the end-to-end QoS requirements for each service class. In this paper, we derive the mathematical model to formulate the end-to-end performance of wireless communication system. We also evaluate the performance at the MAC and transport layers in terms of average spectral efficiency and average transmission delay. Based on the results of performance evaluations, we design the optimal system parameters according to the QoS requirements of service classes. From the results, the HARQ combined with AMC is appropriate for the delay-sensitive service and the ARQ combined with AMC is appropriate for a service that is insensitive to transmission delay. Also, the TCP can be applied for the delay-insensitive service only.

• Journal of the Korea Society for Simulation
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• v.27 no.2
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• pp.35-48
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• 2018

The study of air defense against North Korean tactical ballistic missiles (TBM) should consider the rapidly changing battlefield environment. The study for target re-designation for intercept missiles enables effective operation of friendly defensive assets as well as responses to dynamic battlefield. The researches that have been conducted so far do not represent real-time dynamic battlefield situation because the hit probability for the TBM, which plays an important role in the decision making process, is fixed. Therefore, this study proposes a target re-designation algorithm that makes decision based on hit probability which considers real-time field environment. The proposed method contains a trajectory prediction model that predicts the expected trajectory of the TBM from the current position and velocity information by using random forest and moving window. The predicted hit probability can be calculated through the trajectory prediction model and the simulator of the intercept missile, and the calculated hit probability becomes the decision criterion of the target re-designation algorithm for the missile. In the experiment, the validity of the methodology used in the TBM trajectory prediction model was verified and the superiority of using the hit probability through the proposed model in the target re-designation decision making process was validated.

• The korean journal of orthodontics
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• v.37 no.5
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• pp.376-385
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• 2007

Esthetic brackets which resemble the color of natural teeth have been widely used. But the frictional resistance of ceramic brackets, a typical esthetic bracket, is greater than that of metal brackets. The purpose of this study was to measure the frictional resistance of the new calcium phosphate brackets (CPB) which were recently developed and to evaluate its clinical usability by comparing the frictional differences of CPB with metal brackets and metal slot inserted ceramic brackets. Methods: Experimental groups were CPB (Hyaline II, Tomy, Tokyo, Japan), metal bracket (Kosaka, Tomy, Tokyo, Japan) and metal slot inserted ceramic bracket (Clarity, 3M Unitek, Monrovia, CA, USA). All of the brackets had 0.022-inch slot sizes. The brackets were tested with $0.019\;{\times}\;0.025$ inch stainless steel wire (3M Unitek, Monrovia, CA, USA). A biologic model was used to simulate the situation which would occur during orthodontic treatment with fixed appliances. Retraction force was applied at a speed of 5 mm/min for 30 seconds. The frictional resistance was measured on a universal testing machine (Instron 4467, Instron, Norwood, MA, USA). Results: CPB showed significantly higher friction than metal brackets (p < 0.05) and lower friction than metal slot inserted ceramic brackets (p < 0.01). Conclusions: CPB can be considered to be a useful orthodontic esthetic bracket with respect to frictional resistance, as its friction is remarkably lower than that of metal slot inserted ceramic brackets.

• Analytical Science and Technology
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• v.22 no.6
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• pp.514-518
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• 2009

Coenzyme $Q_{10}$($CoQ_{10}$), a vitamin E-like substance, represents a components of the complex antioxidant system of the human organism. $CoQ_{10}$ levels in human plasma were determined by high performance liquid chromatography (HPLC) with UV detection. It was dissociated from lipoproteins by methanol and extracted into n-hexane with liquid-liquid extraction procedure, after centrifugation, the supernatant was dried under nitrogen gas stream. The residue was dissolved in the absolute ethanol. Determination of $CoQ_{10}$ was performed on a $C_{18}$ reversed-phase analytical column with ultraviolet detection at 275 nm and the mobile phase containing 15% (v/v) ethanol in methanol at a flow rate of 1.7 mL/min. The low limit of quantitation was 0.02 mg/L (S/N=10), the linearity between the concentration and peak height is from 0.1 to 2.0 mg/L. Twenty-four randomly selected plasma samples from apparently healthy, 27 to 44 year old individuals (males and females) were analyzed for total $CoQ_{10}$. The average level in these subjects was $0.62{\pm}0.13mg/L$ with the range of 0.41-0.98 mg/L. This method has a specific and a sufficient limit of quantitation (LOQ) for analysis of $CoQ_{10}$ in human plasma in both a clinical study and research at laboratories.