• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.973-976
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• 2009

Digital signal processing technique use to variety fields including communication. For these signal processing, FIR digital filter is representative. And for FIR digital filter designing, the window function is used to reduce the Gibbs phenomenon which occurs in the coefficient cutting process of the ideal filter. Therefore, in this paper to improve performance of digital filter, a high-order window function was applied. In this simulation, we compared a peak side-lobe and a transient characteristics with the existing window function.

• Journal of Korean Society for Quality Management
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• v.31 no.4
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• pp.150-163
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• 2003

The purpose of this paper is to propose an interactive method using the concept of Signal­to­Noise (SN) ratios and cutting ranges for selecting the most preferred alternatives of Multiple­attribute Decision­Making(MADM) with the­smaller­the­better or the­larger­the­better characteristics. In this method the decision makers could make a grouping of attributes by their priorities. This research is based on the assumption of an equality between the attributes of MADM with the characteristics of Taguchi method. As a result, this interactive method could transform the characteristic value of Taguchi method into the size of SN ratios which are relatively easy to understand by decision makers.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.4
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• pp.23-28
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• 2003

This paper describes the machining characteristics of a developed micro grooving machine. Experiments have been conducted on the various grooving condition such as spindle revolution speed, feed rate and depth of groove. V and U-shaped blade tool and STD11 workpiece was used in this study. To evaluate the developed micro grooving machine, AE signal obtained from each experimental condition was analyzed, and cutting stability was compared with the surface state. As a result this study presented the process to optimize grooving condition and possibility of application of AE technique in groove machining.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.62-69
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• 2010

Internal lathe machining with a boring bar is weak with respect to vibration because the bar is long and slender. Therefore, it is important to study the dynamic characteristics of a boring bar. The purpose of this study was to identify the effects of overhang and cutting conditions on the dynamic response characteristics of a boring bar. For an efficient experiment, an $L_g(3^3)$ orthogonal array was applied and the results were quantitatively analyzed by ANOVA. Overhang, feed per revolution, and depth of cut were selected as independent variables. Meanwhile, dynamic stiffness, damping ratio, damping coefficient, and acceleration were chosen as dependent variables. The vibration signal was obtained from an accelerometer attached to the boring bar, followed by visualization by a signal analyzer. The effect of overhang was found to have a significant effect on the dynamic stiffness, damping ratio, and damping coefficient, but the other variables did not. As the length of the overhang increased, the dynamic stiffness decreased and the damping ratio increased. In addition, the damping coefficient increased until the length of the overhang was 4D (where D is the shank diameter), after which it remained constant. The acceleration decreased until the overhang length was 4D, and then increased sharply when the overhang was increased further. From these results, the behavioral trend of the damping characteristics changed when its overhang length was 4D. Consequently, there is a critical point that the dynamic characteristics of boring bar change.

• Transactions of the Korean Society of Mechanical Engineers
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• v.8 no.2
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• pp.104-110
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• 1984

An electro-hydraulic copying system is developed and its performance is experimentally investigated. As compared with a mechanical hydraulic coping system, this system has a basic difference in that; (1) the stylus movement is converted into an electrical signal via a position transducer. (2)the actuator displacement is also measured by a position sensing element, which serves as a feedback signal. Since the system parameters affect the control performance, the response characteristics such as percentage overshoot, rise time, settling time and steady state error are experimentally obtained under variation of these variables. The system parameter include supply pressure, servo amplifier gain and feedback gain. The experimental result shows that the cutting tool follows a stylus input motion to a desirable accuracy. The implication of this result indicates that the developed system can enhance the copying accuracy of the conventionally used mechanical type of hydraulic copying system.

• 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.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.5
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• pp.430-435
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• 2013

This study is investigation of the characteristics for acoustic emission signal generated by destruction on glass fiber bundles and specimen that was machined composite materials surrounding the outside of GFRP cylinder. The Amplitude of acoustic emission signal gets bigger as the cutting angle of knife increases. Accordingly, the number of hits in destruction of composite materials specimen have more in longitudinal direction (longitudinal direction to the glass fiber) than in hoop direction (horizontal direction to the glass fiber) while the amplitude of signals were bigger in hoop direction than longitudinal direction. It was found out that the amplitude of the glass fiber breakage is more than 40 dB and that the amplitude of signal for matrix crack was less than 40 dB because matrix crack signal was not observed when threshold value is 40 dB and matrix crack signal suddenly appered when threshold value is 32 dB. The slope of the amplitude is related to the acoustic emission source and the slope of the amplitude of the horizontal and vertical directions are 0.16 and 0.08. In particular, The slope of the amplitude of longitudinal direction breakage appear similar to the glass fiber breakage and therefore Acoustic emission source of longitudinal direction breakage is estimated the glass fiber breakage.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.4
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• pp.277-283
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• 2006

As the products such as HDD, Notebook, PDA, and Mobile Phone become smaller and thinner, the radius of threads as well as holes for assembling those products become smaller, even down to 1mm. To produce such small holes and thread efficiently, multi tapping is highly necessitated. However the multi tapping characteristics is not well known because its complicated cutting mechanism and thus the quality of the produced holes and threads is not well studied yet. In this paper, experiments have been conducted for small-radius threads using M2 and M2.6 and M3 cold forming tap to investigate multi tapping process using several useful signal such as torque and Z-axis encoder pulse. The surface and profile of the machined threads have been magnified and observed through a SEM.

• Journal of Korean Society of Transportation
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• v.25 no.4
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• pp.89-98
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• 2007

Nowadays, aggressive driving is a common driving behavior and it is raised as a dangerous factor for both drivers and passengers. However, it is hard to find studies on aggressive driving in Korea, and even the definition of aggressive behavior is not clearly explained. In this study, the term "aggressive behavior" is defined based on previous studies, and the significance of several psycho-social factors which affect aggressive driving were verified with the 'habit' factor from the Theory of Planned Behavior (TPB). In the pilot study, domestic drivers reported that aggressive behaviors included speeding, traffic light signal violation, and improper passing (cutting drivers off when passing). In this study, controlling the demographic characteristics of these three aggressive behaviors, the authors explored the relationship of the behaviors with TPB factors such as the habit factor. Consequently, in the case of drivers' intentions for speeding and traffic light signal violations, subjective norm, perceived behavioral controllability, and habit were significant factors. In the case of intentions for improper passing, only perceived behavioral controllability and habit were significant. In speeding behavior and traffic light signal violations, only habit was significant besides intention; however, in improper passing, both perceived behavioral controllability and habit were significant besides intention. The authors also tested an alternative model including TPB and habit factors for three types of aggressive driving. Finally, there are several implications for a possible intervention program for aggressive driving, though there are some limitations of the study.

• Journal of Ginseng Research
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• v.32 no.4
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• pp.332-336
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• 2008

Red ginseng is classified according to outer form and the quality of internal tissue, and red ginseng below third grade can't be sold. Also there are many differences in price according to grade. So if inferior Red ginseng is sold, economic loss and claim take place. This research is done conducted to investigate the possibility of the non-destruction internal tissue investigation of red ginseng. It is observed and compared that MR image after getting MR image agrees with real cutting side in 10-13% water content of red ginseng. The MR image can be obtained to see the internal section of red ginseng with equal condition of time, temperature and slice thickness in spin echo pulse sequence. The MR signal of red ginseng is very weak, because it contains low water density. So it takes about 30 minutes with the measurement of single point image (SPI). But the suitable time to distinguish internal tissues is about 9 seconds in TE (Echo Time) 2.23 ms, TR (Repetition Time) 150ms. The image to discriminate internal tissues in 9 seconds can be obtained when slice thickness is 10 mm with changes of 3, 5, 10 mm. The image obtained after 30 minutes' boiling of 55 degrees has clearer image than that of normal temperature. It is thought that MR signal is stronger through active motion of water particles as temperature increases. With this method MR image of red ginseng can be obtained and characteristics of internal tissues can be observed in such a short time.