• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.98-107
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• 1995

The in-process detection of drill wear and breakage is one of the most importnat technical problems in unmaned machining system. In this paper, the monitoring system is developed to monitor abnormal drilling states such as drill breakage, drill wear and unstable cutting using motor current. Drill breakage is detected by level monitoring. Tool wear is classified by fuzzy pattern recognition. The key feature for classification of tool wear is the estimated flank wear which is calculated by the proposed flank wear model. The characteristic of the model is not sensitive to the variation of cutting conditions but is sensitive to drill wear state. Unstable cutting states due to the unsmooth chip disposal and the overload are monitored by the variance/mean ratio of spindle motor current. Variance/mean ratio also includes the information about the prediction of drill wear and drill breakage. The evaluation experiments have shown that the developed system works very well.

• Toxicological Research
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• v.17
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• pp.11-16
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• 2001

The development of the central nervous system is a continuous process during the embryonic and fetal periods. For a better understanding of congenital anomalies of central nervous system, three major events of normal development, i.e., neurulation (3 to 4 weeks), brain vesicle formation (4 to 7 weeks) and mantle formation (over 8 weeks) should be kept in mind. The first category of anomalies is neural tube defect. Neural tube defects encompass all the anomalies arise in completion of neurulation. The second category of central nervous system anomalies is disorders of brain vesicle formation. This is anomaly that applies for "the face predicts the brain". Holoprosencephaly covers a spectrum of anomalies of intracranial and midfacial development which result from incomplete development and septation of midline structures within the forebrain or prosencephalon. The last category of central nervous system malformation is disorders involving the process of mantle formation. In the human, neurons are generated in two bursts, the first from 8 to 10 weeks and next from 12 to 14 weeks. By 16 weeks, most of the neurons have been generated and have started their migration into the cortex. Mechanism of migration disorders are multifactorial. Abnormal migration into the cortex, abnormal neurons, faulty neural growth within the cortex, unstable pial-glial border, degeneration of neurons, neural death by exogenous factors are some of the proposed mechanism. Agyria-pachygyria are characterized by a four-layerd cortex. Polymicrogyria is gyri that are too numerous and too small, and is morphologically heterogeneous. Cortical dysplasia is characterized by the presence Q[ abnormal neurons and glia arranged abnormally in focal areas of the cerebral cortex. Neuroglial malformative lesions associated with medically intractable epilepsy are hamartia or hamartoma, focal cortical dysplasia and microdysgenesis.ysgenesis.

• Journal of the Korean Ceramic Society
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• v.35 no.2
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• pp.163-171
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• 1998

Continuously contacting with camshaft the face of Valve Lifter made of cast iron brings about abnormal wear such as unfairwear or earlywear because it is heavily loaded in the valve train systems as the engine gets more powered. This abnormal wear becomes a defet namely over-clearance when the valve is lifting so that the fuel gas imperfectly combusted by unsuitable open or close aaction of the engine valve in the combustion chamber. The imperfect combustion in the end results in the major cause of air pollution and combustion chamber. The imperfectly combusted by unsuitable open or close action of the engine valve in the combustion chamber. The imperfect combustion in the end results in the major causes of air pollution and decrease of the engine output. Consequently to prevent this wear this study was to develop the valve lifter which is joined by brazing process with SCM435H and a tip by manufacturing the face as a superhardened which is joined by brazing process with SCM435H and a tip by manufacturing the face as a superhardened ceramics alloy which has high wear resistance. Having the excellent surface hardness with Hv1100-1200 the sintered body developed with superhardened alloy(WC) can endure the severe face loading in the valve train system. We experienced with various brazing alloys and obtained the excellent joining strength to the joint had 150MPa shear strength. Interface analysis and microstructure in a joint were examined through SEM & EDS Optical microscope. Also 2,500 hours high speed(3,000-4,000 rpm) and continuous (1step 12hr) engine dynamo testing was carried out to casting valve liter and ceramics-metal joint valve lifter so that the abnormal wears were compared and evaluated.

• Ocean and Polar Research
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• v.31 no.4
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• pp.339-347
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• 2009

It is possible to obtain accurate temperature and salinity profiles of the oceans using a SBE 911plus CTD and accompanying data conversion packages. To obtain highly accurate results, CTD data needs to be carefully processed in addition to proper and regular maintenance of the CTD itself. Since the manufacturer of the CTD provides tools that are necessary for post processing, it is possible to conduct proper processing without too much effort. Some users, however, are not familiar with all of the processes and inadvertently ignore some of these processes at the expense of data quality. To draw attention to these and other similar issues, we show how it is possible to improve data quality by utilizing a few extra processes to the standard or default data process procedures with CTD data obtained from the equatorial Eastern Pacific between 2001 and 2005, and 2007. One easy step that is often ignored in the standard data process procedure is "wild edit", which removes abnormal values from the raw data. If those abnormal values are not removed, the abnormality could spread vertically during subsequent processes and produce abnormal salinity in a range much wider than that of the raw data. To remove spikes in salinity profiles the "align CTD" procedure must be carried out not with the default values included in the data processing software but with a proper time constant. Only when "cell thermal mass" correction is conducted with optimal parameters, we can reduce the difference between upcast and downcast, and obtain results that can satisfy the nominal accuracy of the CTD.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.625-631
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• 2000

In this study, the characteristics and sinterablities of TiO2 powders which were fabricated on sol-gel process and supercritical fluid process were examined. The powders fabricated on sol-gel process were amorphous. The particle size and shape were changed with the amount of water used for hydrolysis of titanium ethoxide. The powders were changed from amorphous to crystalline by heating at 400℃. The crystalline anatase TiO2 powders were directly prepared in ethanol supercritical fluid condition that temperature was 270±3℃ and pressure was 7.3 MPa. It's primary crystalline size was 20 nm and agglomerated as spherical shape whose size was 0.7∼1㎛. The powders prepared on sol-gel process were not sintered densely at 900℃ because of abnormal grain growth. However, the powders which prepared on supercritical fluid process were sintered densely at the comparatively low temperature of 800℃ by ideal growth of grain, which are fired at 900℃.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.148-154
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• 1999

This study was carried out to verify grinding performance of dental diamond bur and investigate the possibility of AE application in dentistry field. Workpieces were made of acryl and bovine respectively for the experiments in this study. Grinding test was conducted to get the data of grinding resistance and specific grinding energy of four different types of diamond bur by using tool dynamometer. AE signal was acquired to verify grinding process in the AE measuring system. Tool wear was observed to find parameters about grinding characteristics of diamond bur by means of SEM picture. It was found that the wear of dental diamond bur could be detected with polishing of grinding material, removal of adhesive parts, wear of particles neighboring cutting nose, loss of material and elevation of temperature. The wear of B, C, D type diamond bur is due to wear and fracture of grain size. Abnormal state can be found through the behavior of AE signal in the grinding working. As a result, it is expected that forecast of abnormal state is possible using AE equipments under real time process.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.451-456
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• 2021

In order to improve the cell capacitance and scale down in capacitors of semiconductor memory devices, a stacked ONO structure has been introduced as a dielectric layer and thinning of these layers has been attempted continuously. However, many problems have emerged in the manufacturing process. In this study, L/L LPCVD system was used to suppress the growth of natural oxide film of about 10 Å, which was able to secure the capacitance of 3fF / cell. In addition, we investigated the effect of thinning of the dielectric film on the abnormal oxidation of the nitride film, and proposed a stable process control method for forming the dielectric film to ensure oxidation resistance.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.289-299
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• 2024

In the Pedestrian Dead Reckoning (PDR)/Global Positioning System (GPS)/Wi-Fi-integrated navigation system for indoor/outdoor continuous positioning of pedestrians, the process of detecting outliers in measurements is very important. When accurate location information from measurements is used, reliable correction data can be generated during the fusion filtering process. However, abnormal measurements may occur in certain situations, such as indoor/outdoor transitions, which can degrade filter performance and lead to significant errors in the estimated position. To address this issue, this paper proposes a method for detecting outliers in measurements based on Rényi Divergence (RD). When the deviation of the RD value is large, the measurements are considered outliers, and positioning is performed using only pure PDR. Based on experiments conducted with real data, it was confirmed that outliers were effectively detected for abnormal measurements, leading to an improvement in the performance of pedestrian navigation.

• Proceedings of the Korean Society for Quality Management Conference
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• 2007.04a
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• pp.302-309
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• 2007

To conduct statistical process control needs the assumption that the process data are independent. However, most of chemical processes, like a semi-conduct processes do not satisfy the assumption because of autocorrelation. It causes abnormal out of control signal in the process control and misleading process capability. In this study, we introduce that Shore's method to solve the problem and to find the optimal subgroup size to estimate variance for AR(l) model. Especially, we focus on finding an actual subgroup size for small samples using simulation. It may be very useful for statistical process control to analyze process capability and to make a Shewhart chart properly.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.2
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• pp.103-111
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• 2002

Out of all metal-cutting process, the hole-making process is the most widely used. It is estimated to be more than 30% of the total metal-cutting process. It is therefore desirable to monitor and detect drill wear during the hole-drilling process. One important aspect in controlling the drilling process is monitoring drill wear status. There are two systems, Basic system and Online system, to detect the drill wear. Basic system comprised of spindle rotational speed, feed rates, thrust torque and flank wear measured by tool microscope. Outline system comprised of spindle rotational speed feed rates, AE signal, flank wear area measured by computer vision, On-line monitoring system does not need to stop the process to inspect drill wear. Backpropagation neural networks (BPNs) were used for on-line detection of drill wear. The output was the drill wear state which was either usable or failure. This paper deals with an on-line drill wear monitoring system to fit the detection of the abnormal tool state.