• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.46-51
• /
• 1999

Mass concrete structures have many critical points in service. The cracks caused by the heat of hydration is the most serious problem, so that many method ot control cracks(precooling, postcooling, etc) have been applied to construction. But cooling methods take high cost and many installation and limits of field. Therefore it is useful to use the low heat hydration cements for low cost. This paper describes the characteristics of a low heat cement mixing the ternary components of cement(portland cement, blast furnace slag, fly ash) recently developed for mass concrete, belite cement, low heat slag cement(belite base) and fly ash cement (belite base). The objective of this paper is to study on low heat cement about initial compressive strength and hydration heat.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07b
• /
• pp.873-877
• /
• 2005

Recent developments in Dual Select Diode (DSD) AMLCD technology are described. They include a novel array design and drive method with shared select lines, which leads to higher aperture ratio and a further reduction of module cost. A Color-On-Array DSD process and pixel layout compatible with In-Plane-Switching is also proposed.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.11
• /
• pp.2237-2244
• /
• 2002

This research develops a low-cost and high accuracy kinematic calibration method based on the following principles: 1) the platform locations are accurately measured by a constrained movement to inspect a calibration target; 2) the constrained movement is chosen to guarantee the parameter observability; 3) the mechanical fixture to constrain the movement and the sensor to check the constrained movement are implemented by low-cost and high-accuracy devices; 4) the calibration is easily done at an industrial environment. The kinematic parameters calibrated with respect to a single plane aren't influenced due to the misalignment of the plane. A parameter observability is successfully obtained even through one planar constraint, which guarantees that all kinematic parameters are estimated by minimizing the cost function.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.521-526
• /
• 2001

This research develops a low-cost and high accurate kinematic calibration method for a parallel typed machining center tool. A planar table is used for a mechanical fixture restricting the platform to place at the constrained pose and a low-cost and high accurate digital indicator is employed for a device checking if the constrained movement is satisfied within the established range. The kinematic parameters calibrated with respect to a single plane aren't influenced from the misalignment of the plane. A parameter observability is successfully obtained even through one planar constraint, which guarantees that the kinematic parameters is estimated by minimizing the cost function.

• Industrial Engineering and Management Systems
• /
• v.3 no.1
• /
• pp.59-62
• /
• 2004

The number of tunnel has fast increased with the rapid expansion of highway network. Tunnel should be designed to provide for drivers both safety and pleasant driving conditions. In this perspective, the design for tunnel lightning is very important in order to provide its safety, pleasantness, and cost-efficiency of maintenance, all of which should be considered and analyzed for a better tunnel lighting. This paper attempts to compare the low-pressure sodium lamp, which have usually been used for tunnel lighting, with the fluorescent lamp, which we consider as an alternative for the former. In an effort to determine the number of lamps to meet the required illuminance in the tunnel, this research employs a simulation technique which would allow us to conjecture, with the aid of basic model, the life cycle cost for illumination per each tunnel. This analysis is expected to provide a basic method and related information for tunnel development and design.

• Journal of the Korean Society of Safety
• /
• v.27 no.5
• /
• pp.95-98
• /
• 2012

There are many high-rise apartment building construction in Korea. There was an accident to pass through worker head by rebar dropped from height place. Therefore, low cost-high effectiveness method to prevent this type of accident should be revised and applied into the construction site. This study is to find out which method could be effectively applied to a site with low cost. Practical field test at 4th floor, 10th floor of apartment building site using re-bar diameter D10, D13, D16, D19, D22 with a length of 1 m, 1.5 m, 2 m, 2.5 m, 3 m which are common by used in a site. The test has also been done with a cover of styrofoam thickness 4.5 cm and thickness 9cm on field drop preventing net. One sheet of styrofoam thickness 45 mm has approximately two times stronger than only prevention net, It is found. Also, Two sheets have approximately two times stronger than one sheet of it.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.10
• /
• pp.654-661
• /
• 2008

Our government will make a plan regulating the cooling limit temperature of the summer season to 26 degree and the heating limit temperature of the winter season to 20 degree for energy saving. Where, the key point of this politic pursuit can be the charge system on heating and cooling cost. Currently, the heating and cooling cost are charged as much as the volume or heat flow rate regardless of the high and low room temperature. However, we have suggested new cost estimating methodology as a worth method in the precedent study, and preformed the worth evaluation and cost allocation of electricity and heat on various cogenerations. In this study, we applied the suggested worth method to four kind of warm air, and preformed the worth evaluation and cost allocation of each warm air. As a result, the more energy a customer saved, the more heating unit cost decreased, and the more energy a customer consumed, the more heating unit cost increased. From this analysis, we hope that the suggested worth methodology can offer a theoretical basis to the politic pursuit of government, and induce the spontaneous energy saving of consumers.

• Safety and Health at Work
• /
• v.10 no.4
• /
• pp.452-460
• /
• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.12
• /
• pp.265-271
• /
• 2018

This paper presents a method for detecting damage to a structure at low cost using its impedance. The impedance technique is a typical method to detect local damage for structural health monitoring. This is a common technique for estimating damage by monitoring the electro-mechanical admittance signal of the structure. To apply this technique, an expensive impedance analyzer is generally used. On the other hand, it is necessary to develop a low-cost variant to effectively disseminate the technique. In this study, a method based on the transfer impedance using a function generator and digital multimeter, which are generally used in the laboratory instead of an impedance analyzer, was developed. That is, this technique estimates the damage by comparing the damage index using the amplitude ratio of the output voltage measured in the healthy and damaged state. A transfer impedance test was carried out on a steel specimen. By comparing the damage index, the presence of damage could be assessed reasonably. This study is a basic investigation of an impedance-based low-cost damage detection method that can be used effectively for structural health monitoring if supplemented with future research to estimate the damage location and severity.

• KIEAE Journal
• /
• v.12 no.6
• /
• pp.63-68
• /
• 2012

The aim of this study is to evaluate current policies and suggest the way of overcome financial impediments to the energy efficiency function of residential buildings. Based on this analysis the paper enumerates policy recommendations for enhancing how energy efficiency is addressed in building codes and other policies for residential buildings. For achieving this goal, this study conducts the cost-benefit analysis to measure total energy savings and associated total cost. The results of study shows that the cost is greater than the benefit from 1st to 4th year but the benefit will be greater than the cost for the rest of the year. In addition, this study designs a financial support method and an implementation mechanism. Investment from the capital market will take place with the government's interest subsidy. Home retrofit will be undertaken with low interest rate with 2.5% and the return will be paid by a monthly energy bill. The results of this study provides some useful insights for the policy design, including the importance of developing information tools for providing appropriate information to households.