• Journal of Korea Multimedia Society
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• v.20 no.2
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• pp.134-143
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• 2017

Machine fault diagnosis recovers all the studies that aim to detect automatically faults or damages on machines. Generally, it is very difficult to diagnose a machine fault by conventional methods based on mathematical models because of the complexity of the real world systems and the obvious existence of nonlinear factors. This study develops an automatic machine fault diagnosis system that uses pattern recognition techniques such as principal component analysis (PCA) and artificial neural networks (ANN). The sounds emitted by the operating machine, a drill in this case, are obtained and analyzed for the different operating conditions. The specific machine conditions considered in this research are the undamaged drill and the defected drill with wear. Principal component analysis is first used to reduce the dimensionality of the original sound data. The first principal components are then used as the inputs of a neural network based classifier to separate normal and defected drill sound data. The results show that the proposed PCA-ANN method can be used for the sounds based automated diagnosis system.

• Journal of the Korean Society of Clothing and Textiles
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• v.29 no.6
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• pp.783-792
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• 2005

The purpose of this research is to develop appropriate Insole according to foot characteristics of female adults. This research concentrates on proving the effectiveness of Insole on resolving foot discomforts by analyzing the differences between the fitting and foot pressure before and after wearing Insole. Among 216 female testers of previous research, six testers wear selected and placed into six different groups classified according to foot discomforts and foot characteristics. After wearing Insole, the results indicates that the entire groups represented the improvement of fitting and the mitigation of foot discomfort. The results of foot pressure experiment shows that the maximum pressure of foot spreads out evenly after wearing Insole, which indicates the effectiveness of Insole. This efficacy works particularly well for foot testers of second and sixth group. The results indicate that group 6, which consist of the flat-footed and the old, have more noticeable effects derived from Insole, whereas group 3 and 5 do not, due to its constitution of people with fairly normal feet. Furthermore, it was evident that maximum pressure played a major role in proving the beneficial effects of Insole, one of which is to scatter the maximum pressure of heel away and lessen the foot pressure of plantar.

• Journal of Dental Rehabilitation and Applied Science
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• v.32 no.3
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• pp.202-208
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• 2016

The progressive attrition of teeth is a normal process by aging. However, excessive tooth wear with decreased vertical dimension of occlusion and collapse of occlusal plane may cause pathologic pulpal condition, occlusal disharmony and functional disorders. In this case, a patient with severely worn dentition was treated. Diagnostic wax-up was performed at the increased vertical dimension. After evaluation of provisional restorations for 12 weeks, final restorations were fabricated with zirconia crown and routine clinical assessments were made. Esthetically and functionally satisfactory results were obtained.

• International Journal of Reliability and Applications
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• v.3 no.1
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• pp.1-16
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• 2002

In reliability engineering, the bathtub-shaped hazard rates play an important role in survival analysis and many other applications as well. For the bathtub-shaped, initially the hazard rate decreases from a relatively high value due to manufacturing defects or infant mortality to a relatively stable middle useful life value and then slowly increases with the onset of old age or wear out. In this paper, we present a new two-parameter lifetime distribution function, called the Loglog distribution, with Vtub-shaped hazard rate function. We illustrate the usefulness of the new Vtub-shaped hazard rate function by evaluating the reliability of several helicopter parts based on the data obtained in the maintenance malfunction information reporting system database collected from October 1995 to September 1999. We develop the S-Plus add-in software tool, called Reliability and Safety Assessment (RSA), to calculate reliability measures include mean time to failure, mean residual function, and confidence Intervals of the two helicopter critical parts. We use the mean squared error to compare relative goodness of fit test of the distribution models include normal, lognormal, and Weibull within the two data sets. This research indicates that the result of the new Vtub-shaped hazard rate function is worth the extra function-complexity for a better relative fit. More application in broader validation of this conclusion is needed using other data sets for reliability modeling in a general industrial setting.

• Journal of the Korean Home Economics Association
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• v.37 no.11
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• pp.75-83
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• 1999

To develope an efficient fire fighter’s uniform for the fire fighting work and body protection, this study examined the regulations of fire lighter’s uniform and surveyed the actual wearing conditions, satisfaction degree, preferred color and design others. The results are as follows; 1. As for the satisfaction degree, the degree was normal in ordinary, low in working uniform and heat-proof uniform and very low in water-proof uniform about its design, size, color and materials. 2. As for the color, red was preferred for the working uniform and water-proof uniform. Blue, yellow and green was preferred next for corking uniform and yellow and blue for water-proof uniform. 3. As for the design, fire fighters wanted partial revision of the present uniform. They preferred stretchy training wear style and overact style in order. For the water-proof uniform, they preferred hip-length suit and pants and next to it they liked flee-length suit, waist belt and overact in order. 4. As for the regulations of the uniform, they wanted some addition in casual uniform, water-proof pants and water-proof gloves, and some deletion in the thermal barrier of water-proof uniform and ordinary uniform. 5. As for the distribution of the uniforms, the use of coupons was highly preferred.

• Tribology and Lubricants
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• v.31 no.6
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• pp.287-293
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• 2015

Laser surface texturing (LST), a surface engineering modification, has been considered as one of the new processes used to improve tribological characteristics of materials by creating artificially patterned microstructure on the contact surface of mechanical components. In LST technology, the laser is optimized to obtain or manufacture the dimples with maximum precision. The micro-dimples reduce the coefficients of friction and also improve the wear resistance of materials. This study investigates the effect of dimple density is investigated. For this purpose, a ball-on-disc type tester is used with AISI 52100 bearing steel as the test material. Discs are textured with a 5% and 10% dimple density. Experimental work is performed with normal loads of 5 N, 10 N, and 15 N under a fixed speed of 150 rpm at room temperature. The effect of the textured surface is compared to that of the untextured one. Experimental results show that the textured surface yields lower friction coefficients compared to those of untextured surfaces. Specifically, the 10% dimple density textured surface shows better friction reduction behavior than the 5% dimple density textured sample, and has an 18% improvement in friction reduction compared with the untextured samples. Microscopic observation using a scanning electron microscope (SEM) shows that the major friction mechanisms of the AISI 52100 bearing steel are adhesion, plastic deformation, and ploughing.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.1
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• pp.50-62
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• 1988

An experimental investigation of the machining characteristics of compact vermicular cast iron whose matrix were formulated under two kinds of annealing conditions has been conducted. The various characteristics of the machinability of CA cast iron depending upon its matrix and cutting condition have been obtained from the experiment. The results are as follow. As depth of cut increases, the shear stress slightly decreases in order $P_1, \P_2, \P_3$ which are classified by ferrite matrix of CV cast iron. As depth of cut increases, the normal stress increases, and annealing effect in heavy cutting is smaller than that in light cutting. The cutting energy slightly decreases, as depth of cut increases and the effect of annealing on cutting energy in light cutting is higher than that in heavy cutting. The cutting equation in this study are as follow. $P_1\:\2{\phi}\ + \1.49({\beta} - {\alpha} )=84^{\circ}$ $P_2\:\2{\phi}\ + \1.36({\beta} - {\alpha} )=82^{\circ}$ $P_3\:\2{\phi}\ + \1.34({\beta} - {\alpha} )=79^{\circ}$ Machining constants in this study for $P_1, P_2, P_3$give $74^{\circ} , 66^{\circ}, 61^{\circ}$ Tool wear increases as depth of cut increases, and decreases as ferrit matrix increases.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.677-684
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• 2010

Backlashes of gears provide gears for good lubrication and for removal of the interference between teeth by the wear and manufacturing errors. The backlash is the strong nonlinear factor to gears. This study deals with nonlinear modeling of helical gears with backlash. Excitation of helical gears comes from torque variation, the tooth surface error, and the periodical change of mesh stiffness. To study the effect of torque fluctuation, equation of motion for the single degree of freedom torsional model of helical gears with the periodical change of mesh stiffness and the backlash was derived. The Newmark beta method and the Newton-Raphson method were used to obtain the nonlinear behaviors of mesh forces of helical gears. All excitation frequencies initially caused the tooth separation and single-sided impacts of the gear pair and eventually led to the normal tooth contact. However, some special excitation frequencies caused the single-sided impacts in the entire time as well as the initial time. Damping increase reduced the duration of single-sided impacts, and the backlash increase caused those in the entire time domain.

• Journal of the Korean Society for Railway
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• v.15 no.3
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• pp.224-230
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• 2012

The wearing slider of the rail motor car's pantograph is considerable changed by the type and the material properties. Especially, precipitation and arc influences are main factors decided to life time of wearing slider and contact wire. This study is wearing phenomenon analysis of Cu-type wearing slider with high electric conductivity and resistance arc through experiment by running train. Author observed that wearing phenomenon of Cu-type wearing slider with normal and abnormal wearing characteristics and comparatively analysis precipitation, mileage and weight influences of exchanged Cutype and Fe-type wearing sliders. In this paper result showed that necessity for the application which is the Fe-type of wearing slider had superior wear resisting capacity etc., through tribology approach.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.584-589
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• 2006

In this paper, a test apparatus for reliability evaluation of a rotary compressor has been suggested with a short-cycle concept. $CO_2$ refrigerant is adopted for this cycle to avoid phase change during cycle operation. Evaporator is not necessary in short-cycle. Utilizing a short-cycle, the test apparatus was built on the purpose of evaluating the reliability of each rotary compressor on the conveyer belt of the factory. The primary validation of the test apparatus is discussed by analyzing the experimental heat balance data. Additional validation was performed through the overload continuous operation test where the wear rate of the $CO_2$ short-cycle was found to similar to that of the R22 normal-cycle. The reliability evaluation test apparatus with a short-cycle in present investigation was found simple and efficient in the view of reducing sample numbers, costs, and test time in analyzing the reliability of rotary compressors.