• Journal of Korean Society for Quality Management
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• v.27 no.2
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• pp.201-217
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• 1999

Industrial Measuring Instrument is a general name of equipments or tools for measuring and weighing. Inaccurate measuring instruments produce inferior goods in spite of excellent experts, good materials and wonderful equipments. Three characteristics are important for measuring instruments: choosing the proper instruments for measuring, using them properly and managing them to keep accuracy and precision. The purpose of this thesis is to develope the management standard for effective control of measuring instruments by analysing the problems and the management conditions of 100 PPM certified companies out of the domestic small and medium manufacturing industry, which steadily carry out quality control.

• Safety and Health at Work
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• v.6 no.3
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• pp.159-173
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• 2015

The hand coordinate systems for measuring vibration exposures and biodynamic responses have been standardized, but they are not actually used in many studies. This contradicts the purpose of the standardization. The objectives of this study were to identify the major sources of this problem, and to help define or identify better coordinate systems for the standardization. This study systematically reviewed the principles and definition methods, and evaluated typical hand coordinate systems. This study confirms that, as accelerometers remain the major technology for vibration measurement, it is reasonable to standardize two types of coordinate systems: a tool-based basicentric (BC) system and an anatomically based biodynamic (BD) system. However, these coordinate systems are not well defined in the current standard. Definition of the standard BC system is confusing, and it can be interpreted differently; as a result, it has been inconsistently applied in various standards and studies. The standard hand BD system is defined using the orientation of the third metacarpal bone. It is neither convenient nor defined based on important biological or biodynamic features. This explains why it is rarely used in practice. To resolve these inconsistencies and deficiencies, we proposed a revised method for defining the realistic handle BC system and an alternative method for defining the hand BD system. A fingertip-based BD system for measuring the principal grip force is also proposed based on an important feature of the grip force confirmed in this study.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.46-52
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• 2001

This study describes the precision control of the torque standard machine using a self-tuning fuzzy controller. The torque standard machine should generate the accurate torque for calibrating a torque sensor. In order to reduce the relative expanded uncertainty of the torque standard machine, when a weight is hanged to the end of the torque arm for generating the torque, the sloped torque arm should be accurately controlled to the horizontal level. If the slope of the torque arm is larger from the inaccurate control, the uncertainty of the torque standard machine due to control will be larger. This applies the inaccurate torque to a torque sensor to calibrate, and the measuring error of the torque sensor generate from it. Therefore the torque arm of the torque standard machine is accurately controlled. In this paper, the self-tuning fuzzy controller was designed using a fuzzy theory, and the torque arm of the torque standard machine was accurately controlled. The control gain of the fuzzy controller, that is the membership function size of the error, the membership function size of the error change and the membership function size of the controller were determined from the self-tuning. The control results of the torque standard machine were the overshoot within 0.0076mm, the rise time within 16.70sec and the steady state error within 0.0076mm.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.1
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• pp.88-94
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• 1999

This paper presents an accuracy evaluation method for muzzle velocity measurement systems. Among various measuring techniques, the solenoid coil scheme and the doppler radar scheme are considered due to their popularity in applications. The error sources are first identified and their effects on the accuracy of the measuring systems are quantified using mathmatical equations. The theoritic accuracy limits are then verified through comparison with experimental results. From the accuracy point of view, they turn out to be standard velocity measuring systems.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.1
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• pp.59-65
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• 2016

As modern electronic devices get smaller and smaller, high-resolution, large Field-Of-View (FOV), fast, and cost-effective 3-dimensional (3-D) measurement is requested more and more. In particular, defect inspection machines using machine-vision technology nowadays require 3-D inspection as well as the conventional 2-D inspection. Phase Measuring Profilometry (PMP) is one of the fast non-contact 3-D shape measuring methods currently being extensively investigated in the electronic component manufacturing industry. The PMP system is well known and is successfully applied to measuring complex surface profiles with varying reflectance properties. However, for highly reflective surfaces, such as Ball Grid Arrays (BGAs), it has difficulty accurately measuring 3-D shapes. In this paper, we propose a new fast optical system that can eliminate the highly reflective saturated regions in BGA ball images. This is achieved by utilizing four Low Intensity Grating (LIG) images together with the conventional High Intensity Grating (HIG) images. Extensive experiments using BGA samples show a repeatability of under ${\pm}20um$ in standard deviation, which is suitable for most 3-D shape measurements of BGAs.

• Journal of the Korea Management Engineers Society
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• v.23 no.4
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• pp.73-86
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• 2018

Most electric products produced during the manufacturing process are produced after design and mass production under a given control standard. In particular, the development phase should present the criteria for the production process by setting appropriate limits based on the performance being targeted. Even if the standard of performance is set considering the performance of the process, measuring the performance of the product after actual production results will cause nonconformities with the expected results. Among the performance of electrical products, Energy standards represented by energy consumption efficiency continue to be of importance, and are mandatory standards that correspond to national standards in most countries. Therefore, statistical quality control of these standards shall basically have a large number of test equipment for each product, ensure sufficient test time and continuous sampling of product samples. In the end, companies that produce and sell electric appliances are striving to control mass production at a great cost, but this is not acceptable. This study presents basic characteristics of the energy efficiency of electrical products and proposes and conducts a case study on statistical production control methods for performance variation across products under the standards about domestic and international regulations.

• Journal of the Korean Society of Safety
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• v.34 no.4
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• pp.22-31
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• 2019

The flammable liquid conductivity is an important factor in determining the generation of electrostatic in fire and explosion hazardous areas, so it is necessary to study the physical properties of flammable liquids. In particular, the relevant liquid conductivity in the process of handling flammable liquids in relation to the risk assessment and risk control in fire and explosion hazard areas, such as chemical plants, is classified as a main evaluation item according to the IEC standard, and it is necessary to have flammable liquid conductivity measuring devices and related data are required depending on the handling conditions of the material, such as temperature and mixing ratio for preventing the fire and explosion related to electrostatic. In addition, IEC 60079-32-2 [Explosive Atmospheres-Part 32-2 (Electrostatic hazards-Tests)] refers to the measuring device standard and the conductivity of a single substance. It was concluded that there is no measurement data according to the handling conditions such as mixing ratio of flammable liquid and temperature together with the use and measurement examples. We have developed the measurement reliability by improving the structure, material and measurement method of measuring device by referring to the IEC standard. We have developed a measurement device that is developed and manufactured by itself. The test results of flammable liquid conductivity measurement and the data of the NFPA 77 (Recommended Practice on Static Electricity) Annex B Table B.2 Static Electric Characteristic of Liquids were compared and verified by conducting the conductivity measurement of the flammable liquid handled in the fire and explosion hazardous place by using Measuring / Data Acquisition / Processing / PC Communication. It will contribute to the prevention of static electricity related disaster by taking preliminary measures for fire and explosion prevention by providing technical guidance for static electricity risk assessment and risk control through flammable liquid conductivity measurement experiment. In addition, based on the experimental results, it is possible to create a big data base by constructing electrostatic physical characteristic data of flammable liquids by process and material. Also, it is analyzed that it will contribute to the foundation composition for adding the specific information of conductivity of flammable liquid to the physical and chemical characteristics of MSDS.

• Korean journal of food and cookery science
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• v.15 no.2
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• pp.171-177
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• 1999

The purpose of this study was to serve a standard of the good quality control and shelf-life of food and beverage served from the vending machines. So it was performed to examine the temperature (internal & external environmental, food itself), pH, Aw, POV and microbiological quality of Adlay tea and Wheat noodles served from the vending machines based on storage time in the machines. They were assessed to find the critical control point(CCP) during each of the production, delivery, purchasing phases from the vending machines. The result of this study can be summarized as follows: 1. The temperature of foods inside the vending machines was ranged from 4$0^{\circ}C$ to 45$^{\circ}C$. It was in the range of dangerous zone. The average temperature of food showed 71$^{\circ}C$ for Adlay tea and 74$^{\circ}C$ for Wheat noodles. As a result of measuring pH and Aw, they had potential danger. 2. Even though POV was low, it increased as the time passed. 3. As a result of microbial analysis, it showed that the amount of total plate count and coliforms were increased ten times after 1 day respectively. Wheat noodles' coliform and total plate counts exceeded standard value in 1 day. As a result of food poisoning bacteria, it was negative in sample against Vibrio parahaemolyticus, Salmonella, Staphylococcus aureus.

• Korean Journal of Veterinary Service
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• v.43 no.3
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• pp.147-154
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• 2020

Standard samples were prepared for this study, and applied for BactoScan^TM and BactoCount^TM in order for quality control evaluation for total bacterial count in raw milk. Accordingly, the preparation of two lots of standard samples for quality control were lyophilized, which contain Lactobacillus lactis. The standard samples were prepared into three different levels of bacterial counts, those were Low 30,000~40,000, Medium 70,000~90,000, High 150,000~220,000 CFU/mL, respectively. Then, the proficiency tests were performed in total 19 laboratories for measuring total bacterial counts. The total bacterial counts in the standard samples showed 37~42, 82~105, 214~240 CFU/mL in the first lot, and it showed 30~36, 67~75, 131~163 CFU/mL in the second lot in low, medium and high levels, respectively. Based on these results, the absolute values of z-scores of six standard samples in 18 laboratories were ≤2, which means the samples are satisfactory. However, z-score in one laboratory was ≤3, which means the sample is questionable. Using two standard samples, the correlation between BactoScan^TM and BactoCount^TM was 0.9982, which means the results of total bacterial count measurement of both equipment were equivalent. Therefore, the standard samples manufactured in this study for quality control of total bacterial count using BactoScan^TM and BactoCount^TM in the raw milk could be applied to proficiency tests.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1173-1182
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• 2001

Recent noticeable advances of CNC machine tools have considerably improved productivity and precision in manufacturing processes. However, in the respect of productivity some defects still remain because selection of machining conditions entirely depends on the experiences of programmers. Usually, machining conditions such as feed rate and spindle speed have been selected conservatively by considering the worst cases, and it has brought the loss of machining efficiency. Thus, the improvement of cutting force controller has been done to regulate cutting force constantly and to maximize feedrate simultaneously in case that machining conditions change variously. In this study, sliding mode control with boundary layer is applied to milling process for cutting force regulation and in a commercial CNC machining center data transfer between PC and PMC (programmable machine controller) of CNC machine is done using a standard interface method. And in the cutting force measurement, an indirect cutting force measuring system using current signal of AC servo is adopted in order not to use high-priced equipment like tool dynamometer. The purpose of this study is to maximize the productivity in milling process, thus its results can be applied to cases such as rough cutting process.