• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.1295-1298
• /
• 2004

Selective Laser Sintering(SLS) method is one of Rapid Prototyping(RP) technologies. It is used to fabricate desirable part to sinter powder and stack the fabricated layer. To develop this SLS machine, it needs effective scanning path and the development of scanning device. This paper shows how to make fast scanning path with respect to scan spacing, laser beam size and scanning direction from 2-dimensional sliced file generated in commercial CAD/CAM software. Also, we develop the scanning device and its control algorithm to precisely follow the generated scanning path. Scanning path affects precision and total machining time of the final fabricated part. Sintering occurs using infrared laser which has high thermal energy. As a result, shrinkage and curling of the fabricated part occurs according to thermal distribution. Therefore, fast scanning path generation is needed to eliminate the factors of quality deterioration. It highly affects machining efficiency and prevents shrinkage and curling by relatively lessening the thermal distribution of the surface of sintering layer. To generate this fast scanning path, adaptive path generation is needed with respect to the shape of each layer, and not simply x, y scanning, but the scanning of arbitrary direction must be enabled. This paper addresses path generation method to focus on fast scanning, and development of scanning system and control algorithm to precisely follow generated path.

• Journal of Biosystems Engineering
• /
• v.28 no.2
• /
• pp.107-116
• /
• 2003

One of the major obstructing factors against managing dairy farm in Korea has been a shortage of roughage supply. The shortage of roughage caused excessive use of concentrate feed increase of production cost and deterioration of cattle quality. In order to solve this problem for the dairy farm, use of fallow paddy field in the winter was feasible to produce barley and rye forage during the winter season after harvesting of in. And many desirable effects of raising cattle productivity, saving dollars for importing feeds and providing huge ground for manure spreading are expected by enlarged local roughage production. Through analysing the forage producing process, a mechanized operation model was developed for dairy farms in Korea. Its model consists of seeding models(till, no-till model) and harvesting models(wrap silage, traditional silage, hay model). Currently, the government policies are being executed to urge producing winter cereal wrap silage in the fallow paddy field with various supporting programs. Ant with enlarged local forage production, it is possible to make a new huge market fur forage producing machine.

• Architectural research
• /
• v.7 no.1
• /
• pp.49-54
• /
• 2005

Conventional studies have focused on the reduction in the water-cement ratio, the use of various admixtures, etc., to ensure the durability of reinforced concrete structures against such deterioration factors as carbonation and chloride attack. However, improvement in the concrete quality alone is not considered sufficient or realistic for meeting the recent demand for a service life of over 100 years. This study intends to improve the durability of reinforced concrete structures by improvement in the reinforcing steel, which has remained untouched due to cost problems, through subtle adjustment of the steel components to keep the cost low. As a fundamental study on the performance of Cr-bearing rebars in steel reinforced concrete structures exposed to corrosive environments, The test specimens were made by installing 8 types of rebars in concretes with a chloride ion content of 0.3, 0.6, 1.2, 2.4 and $24kg/m^3$. Corrosion accelerated curing were then conducted with them. The corrosion resistance of Cr-bearing rebars was examined by measuring crack widths, half-cell potential, corrosion area and weight loss after 155 cycles of corrosion-accelerating curing. The results of the study showed that the corrosion resistance increased as the Cr content increased regardless of the content of chloride ions, and that the Cr-bearing rebars with a Cr content of 5% and 9% showed high corrosion resistance in concretes with a chloride ion content of 1.2 and $2.4kg/m^3$, respectively.

• Journal of Korean Neurosurgical Society
• /
• v.42 no.3
• /
• pp.228-231
• /
• 2007

The intracranial hemorrhage in regions remote from the site of initial operations is unusual but may present as fatal surgical complication. We report a rare case of multiple, sequential, remote intracranial hematomas after cranioplasty in a patient who did not have any prior risk factors. A 51-years-old man was transferred to the hospital after a head trauma. The brain computed tomography (CT) revealed acute subdural hemorrhage on the right hemisphere with prominent midline shifting. After performing decompressive craniectomy and hematoma removal, the patient recovered without any complications. However, the patient showed neurological deterioration immediately after cranioplasty, which was done three months after the first surgery. There was extensive hemorrhage in the posterior fossa remote from the site of the initial operation site. The brain CT taken soon after removing this hematoma evacuation displayed large epidural hematoma on the left hemisphere. This case represents posterior fossa hemorrhage after supratentorial procedure and sequential delayed hematoma on the contralateral supratentorial region thus seems very rare surgical complications. Despite several possible pathogenetic mechanisms for such remote hematomas, there are usually no clear cut relationships with each case as in our patient. However, for the successful outcome, prompt evaluation and intensive management seem mandatory.

• 제어로봇시스템학회:학술대회논문집
• /
• 2005.06a
• /
• pp.2175-2178
• /
• 2005

Selective Laser Sintering(SLS) method is one of Rapid Prototyping(RP) technologies. It has been used to fabricate desirable part to sinter powder and stack the fabricated layer. Since the sintering process occurs using infrared laser having high thermal energy, shrinkage and curling of the fabricated part occurs according to thermal distribution. Therefore, the fast scanning path generation is necessary to eliminate the factors of quality deterioration. In case of fabricating larger size parts, the unique scanning device and scanning path generation should be considered. In this paper, the development of SLS machines being capable of large size fabrication(800${\times}$1000${\times}$800 mm, W${\times}$D${\times}$H) will be addressed. The dual laser system and the unique scanning device have been designed and built, which employ CO2 lasers and dynamic 3-axis scanners. The developed system allows scanning a larger planar surface with the desired laser spot size. Also, to generate the fast scanning paths, adaptive path generation is needed with respect to the shape of each layer, and not simply x, y scanning, but the scanning of arbitrary direction should be enabled. To evaluate the suggested method, the complex part will be used for the experiment fabrication.

• Journal of the Korean housing association
• /
• v.17 no.5
• /
• pp.87-95
• /
• 2006

Building components have been deteriorated by various factors such as location, a building type, a surrounding environment and so on. In addition, each component has a peculiar characteristics, compared with other components in properties of matter an used part. Building components would be required to maintain its function and performance to provide the resident with a decent living condition. It is important to decide the repair time, scope and a required cost in repair plan, considering the each component's characteristics. In this parer, it aimed at providing the economic repair pattern to analyze the relation of the time-elapse and the cumulative repair cost in the apartment housing using 3rd quadratic function. Results of the study are as follows: First, the shape of the function for the economic repair is classified into two type. One is the continuous increase type of the cumulative cost which properly means the iterative repair type after built. The other is that the function has the maximum state at a point which means one-repair after its repair would be delayed to a scheduled time. Second, the iterative repair pattern would include window, roof proof, lighting and water supply pipe. The other repair pattern would include the paintings, heating pipe and sign board.

• Advances in pediatric surgery
• /
• v.13 no.1
• /
• pp.1-12
• /
• 2007

Biliary atresia (BA) is the result of fibrosing destructive inflammatory process affecting intrahepatic and extrahepatic bile ducts, which lead to cirrhosis and portal hypertension. Kasai portoenterostomy has been the standard operative procedure in biliary atresia. Recently, there has been remarkable increase in the survival rate in cases of BA. However, long-term survivors are not clearly evaluated in Korea. To define long-term prognosis factors of patients who underwent surgery for BA, a retrospective study was undertaken of 10 (37 %) patients surviving more than 10 years among 27 patients who underwent one of Kasai procedures between 1981 and 1995. Hepatomegaly was present in 4 and splenomegaly in 7 patients. Serum bilirubin was normalized at 1 year after operation. Aspartate aminotransferase (AST, GOT), Alanine aminotransferase(ALT, GPT) were normalized at 12 years and alkaline phosphatase(ALP) was normalized at 13.5 years. Cholangitis developed mainly within 5 years after operation so close follow up is needed. Life long follow-up is needed because of progressive deterioration of liver function even after 10 years.

• Research in Community and Public Health Nursing
• /
• v.27 no.4
• /
• pp.388-398
• /
• 2016

Purpose: To compare the changes in activities of daily living (ADLs) in older adults with stroke in different modalities of long term care (LTC) services, which include home care and institutional care. Methods: This is a comparative study using secondary data from the Korean national LTC insurance. Home care (HC) services users (n=3,494) and institutional care (IC) users (n=1,428) were extracted and compared in terms of ADLs and changes in ADLs to investigate the effects of HC and IC services in LTC. Results: All of the ADLs and LTC services benefit levels for 2 years had improved in both HC and IC services. The ADLs of older adults with stroke who received HC improved, while those who received IC experienced deterioration. The LTC services benefit levels of the HC and IC groups were significantly different after 2 years. Conclusion: The study has found that HC services may lead ADLs better for older adults with stroke. We recommend LTC policy makers to further develop HC and IC service programs to deliver quality LTC services.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.961-964
• /
• 2008

Fire safety is one of the important factors to be examined when applying ECC to actual concrete structures. The purpose of this study is to confirm whether the fire resistance of ECC satisfies the fire resistant requirements in order to use the fire protection material in concrete structures. Employed temperature curve are HC and RABT criterion, which are severe in various criterion of fire temperature in concrete structures. The test results show that ECC did not undergo any deterioration of fire resistance nor cause explosive spalling, which had been anticipated due to the presence of organic fibers. With comparison of current concrete and fire-resistance materials, the experimental results of ECC shows the better fire resistance performance than the other.

• Journal of the Korea Institute of Building Construction
• /
• v.9 no.1
• /
• pp.81-87
• /
• 2009

The purpose of this study is to investigate the sulfate attack resistance of concrete using the EAF(electric arc furnace) Slag as fine aggregate. In order to figure out the effects of magnesium sulfate solution on the durability of concrete using the EAF Slag as fine aggregate, the experiments for the immerging test in the 10% magnesium sulfate solution was executed by selecting factors such as aging processes, replacement ratio(0, 10, 20, 30, 50%), and duration of immerging. The specimens were made with various EAF slag replacements for fine aggregates and with W/C ratio fixed 0.45. compressive strength and S.D.F(Sulfate Deterioration Factor), weight change, and SEM(Scanning Electron Microscope) were tested. From the test results, EAF slag aggregate treated with accelerated aging is better than treated with air aging. The compressive strength and resistance to the sulfate attack is slightly improved with an increase in the EAF slag aggregate treated with accelerated aging replacement for aggregate.