• Journal of Korean Neurosurgical Society
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• v.30 no.7
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• pp.849-854
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• 2001

Delayed cerebral infarction after resection of craniopharyngioma is a uncommon entity, but leads to high morbidity and mortality. We present 3 such cases and discuss the etiology and pathogenesis with review of pertinent literatures. In our cases, delayed deterioration of consciousness was observed in all cases. All of them expired. The cause may be multifactorial and the surgical approach may contribute to the pathogenesis of delayed cerebral infarction. We suspect vasospasm might be the major mechanism of pathogenesis. Vessels were primed to spasm during operation due to blood in the cistern or mechanical injury. Vasoactive materials may have been liberated from the pituitary stalk or injured hypothalamus, either at the time of surgery, or later, after portions of tumor have undergone necrosis. The high degree of suspicion to detect vasospasm should be done in the case of the delayed deterioration of mental status at an early stage of craniopharyngioma surgery. Possible mechanism underlying this delayed cerebral infarction are discussed.

• Journal of Conservation Science
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• v.35 no.1
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• pp.19-31
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• 2019

To study the cleaning effects and post-treatment stability assessment of various methods of cleaning textiles with metal thread, six naturally-soiled historical textiles with metal thread were investigated at the Metropolitan Museum of Art, New York. Prior to the cleaning of fabricated gold, silver, and copper thread that had been glued onto a paper substrate, the artificial deterioration was carried out in a controlled environment with light(UV and daylight), and temperature and humidity factors which would weaken and damage the samples. A synthetic soil mixture was applied to the samples to imitate soil found on the historic and archaeological textiles with metal thread; the cleaning effect and post-treatment assessment were investigated by use of three textile cleaning methods: mechanical cleaning, wet cleaning, and solvent cleaning. While investigating the naturally-soiled textiles with metal thread, it was determined that the soil colors and sizes of contaminating particles of each textile were different due to the diversity of original environmental factors and conditions. After cleaning with kneaded rubber, Stoddard solvent, n-decane or n-hexane, a bright, clean effect was apparent. Kneaded rubber was successful in picking up both large and small particles, but its stickiness caused some of the metal leaf to peel off. Stoddard solvent produced a good cleaning effect, but after use of n-hexane and n-decane in the cleaning process, a white layer of residue remained on the textile's surface. Wet cleaning was not effective and the rapid humidity changes between wet and dry conditions caused the edges of the paper substrate to lose their original shape.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.161-167
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• 2020

In the process of cutting large aircraft parts, the tool may be abnormally worn or damaged due to various factors such as mechanical vibration, disturbances such as chips, and physical properties of the workpiece, which may result in deterioration of the surface quality of the workpiece. Because workpieces used for large aircrafts parts are expensive and require strict processing quality, a maintenance plan is required to minimize the deterioration of the workpiece quality that can be caused by unexpected abnormalities of the tool and take maintenance measures at an earlier stage that does not adversely affect the machining. In this paper, we propose a method to indirectly monitor the tool condition that can affect the machining quality of large aircraft parts through real-time monitoring of the current signal applied to the spindle motor during machining by comparing whether the monitored current shows an abnormal pattern during actual machining by using this as a reference pattern. First, 30 types of tools are used for machining large aircraft parts, and three tools with relatively frequent breakages among these tools were selected as monitoring targets by reflecting the opinions of processing experts in the field. Second, when creating the CNC machining program, the M code, which is a CNC auxiliary function, is inserted at the starting and ending positions of the tool to be monitored using the editing tool, so that monitoring start and end times can be notified. Third, the monitoring program was run with the M code signal notified from the CNC controller by using the DAQ (Data Acquisition) device, and the machine learning algorithms for detecting abnormality of the current signal received in real time could be used to determine whether there was an abnormality. Fourth, through the implementation of the prototype system, the feasibility of the method proposed in this paper was shown and verified through an actual example.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.465-466
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• 2002

In any mechanical system consisting of gears, shafts and/or bearings, the majority of metallic particles deposited into and carried by the lubrication system originate from the deterioration of oil-wetted working surfaces, even in proper lubrication system, due to failure mechanism (s) such as wear, fatigue and fretting corrosion. Determination of the point at which transition from normal to abnormal or to actual damage occurs has become a focus of attention in research activities for years, because it has been recognized that reliable, economic operation can be achieved through appropriate preventative measures. Known collectively from 'all size wear debris analysis' as early failure detection, the methods of testing for damage differ considerably, range from a micron or a submicron size debris analysis to Magnetic Chip Detector (MCD) ferrous debris analysis. This paper will be focused on the utilization of the low-cost analysis techniques for evaluation of industrial machinery condition.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.82.2-82.2
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• 2010

The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.

• Resources Recycling
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• v.16 no.2 s.76
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• pp.17-22
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• 2007

The report of an investigation into the performance of mortar specimens made with recycled fine aggregate (RA) exposed to sodium sulfate solution for 360 days is presented in this paper. Mechanical properties of mortar specimens such as visual examination, compressive strength, expansion and mass loss were periodically monitored. From the test results, it was found that mortar specimens with higher replacement levels of Rh exhibited poor performance in sodium sulfate solution. However, compared to mortar specimens without RA, those with lower replacement levels of RA (up to 50% by mass) was more resistant to sulfate attack. Through the x-ray diffraction analysis, it was confirmed that the main products causing sulfate deterioration in RA mortar specimens were the formation of gypsum and thaumasite.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.22-27
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• 2002

The existing compressor steel seal used in automotive air-conditioner has the problem of oil leakage and the deterioration in shielding performance, due to the abrasion and the corrosion of the material. A new type of polymer resin seal is studied in the research. The polymer resin seal has the characteristics of high anti-abrasiveness and anti-corrosiveness, which can overcome the deflects of the steel seal. In addition, the seal needs lower manufacturing cost and is appropriate to mass production, because it is made by the injection molding method requiring no mechanical processing. The profile generation program for seal mold has been developed using the gradient method, and the molding characteristics of the seal have analyzed through the flow analysis and the warpage analysis. The program has been verified by comparing the analysis results with the measured data of the test product. The research might be said to provide the basic method to produce the polymer resin seals with various types and dimensions.

• Journal of the Korean Society of Industry Convergence
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• v.1 no.2
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• pp.49-54
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• 1998

In the catalytic combustor, combustion characteristic and deterioration of catalysts were affected by non-uniformity of pre-mixed gas, Therefore, formation of uniform pre-mixed gas is one of important subjects. In this study, the effect of uniformity and non-uniformity of pre-mixed gas supplied to the catalyst was examined to clarify reaction acceleration and combustion characteristic of the catalytic combustion. It was clarified that static mixer or vaporizer tube length of about 150mm and weak swirl to a combustion air were effictive expedient to make uniform pre-mixed gas. And catalystic inlet temperature needs more than $600^{\circ}C$ with rich pre-mixed gas to active reaction.

• Journal of KSNVE
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• v.10 no.3
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• pp.474-479
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• 2000

Piston slap is not only one of the major sources of noise and vibration in internal combustion engines but also a cause of the deterioration of engine performance. The basic mechanism associated with the piston slap seems to be quite simple but the phenomenon is in fact complicated with regard to many mechanical elements associated, First of all the impact force of piston slap must be identified to estimate engine block surface vibration, In this paper model of collision point is proposed to calculate the impact force when slap surface vibration. In this paper model of collision point is proposed to calculate the impact force when slap occurs. The parameters of the model are estimated by employing the concept of point mobility, . The predicted and experimentally observed vibration results confirm that the proposed method is practically useful.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.1
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• pp.61-70
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• 2004

Generally, ceramics are very difficult-to-cut materials because of its high strength and hardness. The machining process of ceramics can be characterized by cracking and brittle fracture. In the machining of ceramics, edge chipping and crack propagation are the principal reasons to cause surface integrity deterioration. Such phenomenon can cause not only poor dimensional and geometric accuracy, but also possible failure of the ceramic parts. Ceramics can be machined with traditional method such as grinding and polishing. However, such processes are generally cost-expensive and have low material removal rate. Thus, in this paper, to overcome these problems. BN powder, which gives good cutting property, is added for the fabrication of machinable ceramics by volume of 5,10,15,20,25 and 30%. And, mechanical properties, R-curve behavior and machining tests are carried out to evaluate the machining properties of the manufactured machinable ceramics.