• Journal of Welding and Joining
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• v.34 no.1
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• pp.26-34
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• 2016

Automotive today has been transforming to an electronic product by adopting a lot of convenience and safety features, suggesting that joining materials and their mechanical reliabilities are getting more important. In this study, a Sn-Cu-Cr-Ca solder composition having a high melting temperature ($>230^{\circ}C$) was fabricated and its joint properties and reliability was investigated with an aim to evaluate the suitability as a joining material for electronics of engine room. Furthermore, mechanical properties change under complex environment were compared with several existing solder compositions. As a result of contact angle measurement, favorable spreadability of 84% was shown and the average shear strength manufactured with corresponding composition solder paste was $1.9kg/mm^2$. Also, thermo-mechanical reliability by thermal shock and vibration test was compared with that of the representative high temperature solder materials such as Sn-3.5Ag, Sn-0.7Cu, and Sn-5.0Sb. In order to fabricate the test module, solder balls were made in joints with ENIG-finished BGA and then the BGA chip was reflowed on the OPS-finished PCB pattern. During the environmental tests, resistance change was continuously monitored and the joint strength was examined after tests. Sn-3.5Ag alloy exhibited the biggest degradation rate in resistance and shear stress and Sn-0.7Cu resulted in a relatively stable reliability against thermo-mechanical stress coming from thermal shock and vibration.

• Journal of Environmental Health Sciences
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• v.30 no.5 s.81
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• pp.432-439
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• 2004

Korean certification regulation for particulate filtering respirators requires inward leakage (IL) test as European Standards (EN) and the standard levels of regulation are the same as those of EN. This study was conducted to evaluate particulate filtering respirators being commercially used in the market by using IL and assess the characteristics of IL. The study began with discussing the concept of IL, comparison of IL with fit test, and IL measurement method. Three brands of half masks and 10 brands of filtering facepieces (two top class, four 1st class and four 2nd class), total 13 brands respirators, and 10 test panels (subjects) who were classified in 9 facial grids in accordance with face length and lip length, were selected for IL test. IL tests were conducted in the laboratory of 3M Innovation Center which was established by EN standard. As expected ILs of half masks were lower than those of filtering facepiece mask. ILs of half masks and some filtering facepieces were significantly different in manufacturers. ILs of 1st class filtering facepieces were found to be much more than those of 2nd class and thus the result would cause wearers to get confused to select a mask. Four of six brands being no compliance with standards were thought that they should be tested again for certification because of a lot of differences from standards. There were no significant differences among ILs of five exercises. In 6 out of 13 brands lognormal distribution of ILs may be a better fit distribution and in 7 brands both lognormal and normal distributions were rejected. The result indicates that geometric mean may be better than arithmetic mean to establish standard.

• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.276-282
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• 2007

The purpose of this study is to assess the accurate state of the following: total welding fumes versus welding fumes in the air, respirable particulate mass, and exposure of dockyard welders to heavy metals. In addition, this study provides basic data for proposing improvements to create efficient and appropriate welding environments and to prevent occupational diseases. The subjects of this study were 94 laborers who worked at the block construction sites of large-scale dockyards located in Gyeongnam Province from March 2005 to June 2005. In order to collect samples on total welding fumes in the air and respirable particulate mass from the welders, Methods 0500 and 0600, established by the National Institute for Occupational Safety and Health (NIOSH), were used. The metals within the welding fumes were also analyzed using Inductively Coupled Plasma (ICP) under Method 7300 from NIOSH. The results of this research are summarized below. The geometric mean concentration of total welding fumes and that of respirable particulate mass were $4.11\;mg/m^3\;and\;3.53\;mg/m^3$, respectively. As a result of comparing the two measurement methods, there were significant differences (p<0.05) between the two groups for Ca, Cu, Cr, and Ni; however, there were no differences in Fe, Mg, Zn, Mg, Pb, and Cd. As a result of the analysis, the correlation between Mn and the concentration of heavy metals in the total welding fumes and respirable particulate mass was found to be -0.29, a significant negative correlation. The correlation between other heavy metals, however, was low. Finally, in the same total welding fumes, the correlation of Fe and Mg was high.

• Journal of the Korean Institute of Gas
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• v.16 no.5
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• pp.41-46
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• 2012

The flash point the lowest temperature at which the concentration of vapor of the substance in the air reaches the lower flammability limit(LFL), and is one of the most important physical properties used to determine the potential for fire and explosion hazards of industrial materials. The most published flash point data was for pure components and the flash points of the binary solutions that have flammable components, appear to be scarce in the literature. In the present study, the flash points of tert-pentanol+n-decane system were measured by Tag open-cup tester. The measured data were compared with the values calculated by the Raoult's law and the optimization methods based on the Wilson and NRTL equations. The calculated values by optimization methods were found to be better than those based on the Raoult's law.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.1-8
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• 2007

Loran-C of ground transmitting station base that can prevent confusion of country navigation system and give BACK-UP function about electric wave navigation comparing utilization incapability state about GPS(Global Positioning System) infra that user is spreading rapidly over our society whole such as sea/aviation safety, vehicles navigation, minuteness agriculture, minuteness measurement in this treatise practical use of Loran-C navigation propose. Executed ASF(Additional Secondary Phase Factor) production and an application experiment Loran-C by location error improvement way to enhance practical use value. By the result Loran-C in conclusion that can improve location error 100~400m remarkably by 10~65m reach. Also, production extent is latitude when go composition medium and bends cotton at ASF revision table utilization of land area, this smell is judged to be suitable hardness 10 minutes. And notable location error improvement and numeric of GPS BACK-UP function are judged to be possible at a ASF revision table application to Korea Peninsula whole area hereafter.

• Journal of Korean Neurosurgical Society
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• v.53 no.2
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• pp.102-107
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• 2013

Objective : The Leksell Gamma Knife$^{(R)}$ (LGK) is based on a single-fraction high dose treatment strategy. Therefore, independent verification of the Leksell GammaPlan$^{(R)}$ (LGP) is important for ensuring patient safety and minimizing the risk of treatment errors. Although several verification techniques have been previously developed and reported, no method has ever been tested statistically on multiple LGK target treatments. The purpose of this study was to perform and to evaluate the accuracy of a verification method (modified variable ellipsoid modeling technique, MVEMT) for multiple target treatments. Methods : A total of 500 locations in 10 consecutive patients with multiple brain tumor targets were included in this study. We compared the data from an LGP planning system and MVEMT in terms of dose at random points, maximal dose points, and target volumes. All data was analyzed by t-test and the Bland-Altman plot, which are statistical methods used to compare two different measurement techniques. Results : No statistical difference in dose at the 500 random points was observed between LGP and MVEMT. Differences in maximal dose ranged from -2.4% to 6.1%. An average distance of 1.6 mm between the maximal dose points was observed when comparing the two methods. Conclusion : Statistical analyses demonstrated that MVEMT was in excellent agreement with LGP when planning for radiosurgery involving multiple target treatments. MVEMT is a useful, independent tool for planning multiple target treatment that provides statistically identical data to that produced by LGP. Findings from the present study indicate that MVEMT can be used as a reference dose verification system for multiple tumors.

• Journal of Korean Neurosurgical Society
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• v.54 no.3
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• pp.175-182
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• 2013

Objective : Intracavitary injection of beta-emitting radiation source for control of cystic tumors has been tried with a benefit of localized internal radiation. The authors treated cystic brain tumor patients with Holmium-166-chitosan complex (Ho-166-chico), composed of a beta-emitting radionuclide Holmium-166 and biodegradable chit polymer, and evaluated the safety and effective measurement for response. Methods : Twenty-two patients with recurrent cystic brain tumor and/or located in a deep or eloquent area were enrolled in this pilot study. The cyst volume and wall thickness were determined on CT or MRI to assess radiological response. The activity of Ho-166-chico injected via Ommaya reservoir was prescribed to be 10-25 Gy to the cyst wall in a depth of 4 mm. Results : There was neither complications related to systemic absorption nor leakage of Ho-166-chico in all 22 patients. But, two cases of oculomotor paresis were observed in patients with recurrent craniopharyngioma. Radiological response was seen in 14 of 20 available follow-up images (70%). Seven patients of 'evident' radiological response experienced more than 25% decrease of both cyst volume and wall thickness. Another 7 patients with 'suggestive' response showed decrease of cyst volume without definitive change of the wall thickness or vice versa. All patients with benign tumors or low grade gliomas experienced symptomatic improvement. Conclusion : Ho-166-chico intracavitary radiation therapy for cystic tumor is a safe method of palliation without serious complications. The determination of both minimal effective dosage and time interval of repeated injection through phase 1 trial could improve the results in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.40-45
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• 2018

Intelligent monitoring and diagnosis of production processes based on multivariate statistical methods has been one of important tasks for safety and quality issues. This is due to the fact that faults and unexpected events may have serious impacts on the operation of processes. This study proposes a diagnostic scheme based on effective representation of process measurement data and is evaluated using simulation process data. The effects of utilizing a preprocessing step and nonlinear statistical methods are also tested using fifteen faults of the simulation process. Results show that the proposed scheme produced more reliable results and outperformed other tested schemes with none of the filtering step and nonlinear methods. The proposed scheme is expected to be robust to process noises and easy to develop due to the lack of required rigorous mathematical process models or expert knowledge.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.3
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• pp.447-456
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• 2018

Elemental carbon (EC) and organic carbon (OC) thermal/optical methods for the analysis of ambient particulate matter were used to analyze twenty-two $PM_{2.5}$ samples along collected from May 28 to June 20 of 2016 at the Anmyeon measurement site ($36.32^{\circ}N$; $126.19^{\circ}E$). The three laboratory OCEC protocols, which are the National Institute of Occupational Safety and Health (NIOSH5040), the Interagency Monitoring of Protected Visual Environments_A(IMPROVE_A), and European Supersites for Atmospheric Aerosol Research2 (EUSAAR2), were utilized for the aerosol characterization experiment as in intercomparisons between three protocols. There are excellent agreement for total carbon (i.e. sum of EC and OC), but statistically significant differences were observed in the split between the measured EC and OC. IMPROVE_A EC values were always larger than both NIOSH5040 and EUSAAR2 protocols. These methods exhibited significantly different temperature-distributions based on thermogram analysis, which is normalized to total carbon. In this study, a protocol for carbonaceous analysis is suggested for the Korean Peninsula.

• Biomedical Science Letters
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• v.22 no.4
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• pp.199-206
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• 2016

Pesticides are widely used to prevent loss of agricultural production but extensive exposure can induce health problems to pesticide operators. This study was performed to evaluate the health risk of highly produced pesticides used in fruit growing farm land by comparison of estimated exposure level with AOEL using KO-POEM program. AOEL was driven based on NOAEL of each pesticide evaluated by JMPR, EFSA or KRDA. In calculation of exposure level, types of formulation, dilution factors, spraying duration and motor type and exposure protection device were allocated according to actual condition of use. Dermal absorption rate was differently applied among EFSA default values (25% or 75%), general default value (10%) or real test result values to know the plausibility of default values and safety of pesticide to operators in outline. Twenty pesticide ingredients (fungicides and insecticides) were produced more than 30 tons per year, which were mancozeb, chlorothalonil, imidaclopirid and etc in order. Dermal absorption rates obtained from studies were various from 0.07 to 81% but mostly under 10%. The estimated exposure levels showed big differences more than 10 times higher when using EFSA default rate and up to 5 times higher when using general rate of 10% comparing using rates of test results. Mancozeb, chlorthalonil, diazinon and chlorpyrifos presented still higher exposure level than AOEL even when using test absorption rate from study, which suggests that re-evaluation of AOEL or dermal exposure absorption rate or strict management are required for health protection of operators who use those four pesticides in farm land.