• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1996.10a
• /
• pp.187-193
• /
• 1996

This paper presents a new approach to modify the traditional method for sampling inspectionby variables to suit undesired measurement conditions. On the basis of a systematic analysis of the effects of measurement errors on different types of acceptance schemes this paper gives two modified equations for revising the sampling size η and the acceptability constant $textsc{k}$ to form a new acceptance scheme (η'$textsc{k}$) under undesired measurement conditions. It has proved that the new method is suitable to different types of sampling inspection by variables including that for mean value and that for percent defective. The new acceptance scheme based on the proposed technique provides an engineering feasibility to replace the traditional scheme to suit undesired measurement conditions.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.129-137
• /
• 2001

As the rotational speed and the track density are increased, the vibration of disk/spindle system becomes critical issue. In this work, we propose a simple inclined air bearing(20mm${\times}$20mm) system which is positioned very near to the rotating disk especially compact disc(CD) as a flexible disk, and we investigate suppressing effect about disk mode (0,0) both experimentally and numerically. We find dynamic stiffness and damping coefficients of bearing and apply to the disk vibration. The results show about 10 percent errors comparing to the experimental results. Also we investigate experimentally the reduction of disk vibration and power consumption with two different kinds of inclined bearing for normal disk drive system, which has tray and cover. We find inclined air bearing can decrease about 30 percents of the original disk vibration amplitude.

• Journal of the Korean Society of Safety
• /
• v.16 no.4
• /
• pp.182-187
• /
• 2001

This paper examines the effects on human reaction time and mental fatigue of changes in the intensity of physical activity. A treadmill-equipped instrument and perception tester were used to attain several levels of physical activity. In this paper, in order to determine the individual levels of physical activity of subjects, Borg-RPE scale, Heart Rate(HR) and Respiratory Quotient(RQ) were used. Also, a reaction test in whole-body activity on treadmill-equipped instrument and an addition test as an indicator of mental fatigue were performed. In the above experiments, the scores obtained in addition test administered before and after Physical activity at each intensity level used. Restricted within the limits of this paper, the results of these tests showed that mental fatigue decreased after physical activity.

• Journal of the Korea Safety Management & Science
• /
• v.9 no.4
• /
• pp.49-56
• /
• 2007

It is known that human factors account for 80 percent of all railway accidents. To reduce human errors must be the most efficient shortcut to railway safety. For public transportation employees like railway, the more delicate safety management should be executed in individual level. However, there are rarely efforts to improve safety performance of workers who are the subject operating the railway system. This paper develops a hierarchy model to evaluate the human safety performance in railway industry. To evaluate the model, AHP (Analytic Hierarchy Process) methodology is adopted. The hierarchy model is composed of four levels which are objective, two criteria, specific factors of criteria, and rating scales. In addition, since employees for evaluation are over 10, the pairwise comparisons for rating scales are carried out by the absolute measurement. We explore the applicability of AHP to the performance evaluation of railway safety workers by an example and also investigate the changes of alternatives that are railway employees according to the changes of human characteristic which is one of criteria.

• Journal of Biosystems Engineering
• /
• v.25 no.3
• /
• pp.233-240
• /
• 2000

A commercially available Doppler radar was modified and evaluated for on-board monitoring of ground speed. The radar output was corrected for pitch angle of aircraft based on the output of an electrolytic tilt sensor. The effects of aircraft speed, height and mounting angle on error in the ground speed were evaluated. The speed error decreased with an increase of the mounting angle since the radar contact angle with respect to the ground approached to the mounting angle. The error increased with an increase of the nominal aircraft speed. The altitude insignificantly affected the speed error. The Doppler radar provided acceptable percent errors within 5% in most measurements. The error can be reduced within ${\pm}$1.5% by increasing the mounting angle ($43^{\circ}$). The error of -3.8% at the mounting angle of $29^{\circ}$could be reduced by adjusting the mounting angle with respect to the radar contact angle.

• International Journal of Automotive Technology
• /
• v.6 no.5
• /
• pp.475-481
• /
• 2005

This paper deals with the algorithm of estimating the longitudinal speed of a braking vehicle using measurements from an accelerometer and a standard wheel speed sensor. We evolve speed estimation algorithms of increasing complexity and accuracy on the basis of experimental tests. A final speed estimation algorithm based on a Kalman filtering is developed to reduce measurement noise of the wheel speed sensor, error of the tire radius, and accelerometer bias. This developed algorithm can give peak errors of less than 3 percent even when the accelerometer signal is significantly biased.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.375-378
• /
• 2005

Voice Coil Motor is used linear motion actuator system that require precision positioning control. In order to control precision positioning of voice coil motor, Mathematical model of voice coil motor is needed. Mathematical model is obtained by combining voice coil motor's equation of motion with the equation of circuit and characteristic of voice coil motor. The induced model can predict output displacement according to duty ratio and amplitude. The model is verified by experimental test. Simulated results have tracking errors of less than 10 percent of experimental results.

• Radiation Oncology Journal
• /
• v.7 no.2
• /
• pp.279-285
• /
• 1989

Central axis depth dose data for 6 MV X-rays, including tissue maximum ratios, were measured for wedge fields according to Tatcher's equation. In wedge fields, the differences in magnitude which increased with depth, field size, and wedge thickness increased when compared with the corresponding open field data. However, phantom scatter correction factors for wedge fields differed less than $1\%$ from the corresponding open field factors. The differences in central axis percent depth dose between two types of fields indicated beam hardening by the wedge filter The deviation of percent depth doses and scatter correction factors between the effective wedge field and the nominal wedge field at same angle was negligible. The differences were less than $3.20\%$ between the nominal or effective wedge fields and the open fields for percent depth doses to the depth 7cm in $6cm{\times}6cm$ field. For larger $(10cm{\times}10cm)$ field size, however, the deviation of percnet depth doses between the nominal or effective wedge fields and the open fields were greater-dosimetric errors were $3.56\%$ at depth 7cm and nearly $5.30\%$ at 12cm. We suggest that the percent depth doses of individual wedge and wedge transmission factors should be considered for the dose calculation or monitor setting in the treatment of deep seated tumor.

• Korean Journal of Veterinary Research
• /
• v.38 no.3
• /
• pp.544-552
• /
• 1998

A random study of 574 dairy farms in Gyeongnam area was designed to determine 1) management factors that may be associated with the occurrence of drug residues; 2) the dairy farmer's attitudes and knowledge about residues; 3) how these variables influence the occurrence of residues in dairy cattle. Management factors perceived as having the greatest influence on drug residues in milk were insufficient knowledge about withdrawal periods, errors due to hired help, insufficient identification and record of animals treated for mastitis, dry cow treatment for mastitis, and metritis treatment. Seventy-one percent of farms with residues problem used mixed own feeds compared with twenty-nine percent of farms with premedicated feeds. Factors significantly associated with the occurrence of residues were herd size, increased number of hired persons, increased frequency of use of mixed-own feeds, category of medicated feed, and producer's attitude toward the public health significance of residues. Our findings suggest that residue occurrence was mainly associated with errors due to hired help, insufficient knowledge about withdrawal periods, poor animal identification and records of treatment animals and use of medicated feeds. Any residue avodiance educational program needs to stress how to deal with these factors. This educational program should be directed to dairy farmers and employees, especially temporary employees. In addition, Dairy farmer's attitudes and knowledge about drug residues need to be improved. More evidence on the public healths significance of residues should be available to them. Because belife in importance of public healths concerns was related to successful residue avidance and because 81.3% of the dairy farmers with residue problem thought public healths concerns were less important than economic ones, it would be helpful to provide educational programs specifically directed to this issue. it may be useful to provide programs not only for the dairy farmers but also change of their concerns about on the public healths.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.37 no.3_4
• /
• pp.34-47
• /
• 1995

It is experienced fact as a regular annual event that the structure to he designed on unreasonable flood for the agricultural structures including reservoirs have been brought not only loss of lives, but also enormous property damage. For the solution of this problem at issue, this study was conducted to develop an optimal runoff hydrograph model by comparison of the peak flows and time to peak between observed and simulated flows derived by linear time-invariant and linear time-variant models under the condition of having a short duration of heavy rainfall with uniform rainfall intensity at nine small watersheds which are within the range of 55.9 to 140.7 square kilometers in area in Han, Geum, Nagdong and Yeongsan Rivers. The results obtained through this study can be summarized as follows. 1. Storage constants and Gamma function arguments were calculated within the range of 1.2 to 6.42 and of 1.28 to 8.05 respectively by the moment method as the parameters for the analysis of runoff hydrograph based on linear time-invariant model. 2. Parameters for both linear time-invariant and linear time-variant models were calibrated with nine gaged watershed data, using a trial and error method. The resulting parameters including Gamma function argument, N and storage constant, K for linear time-invariant model were related statistically to watershed characteristic variables such as area, slope, length of main stream and the centroid length of the basin. 3. Average relative errors of the simulated peak discharge of calibrated runoff hydrographs by using linear time-variant and linear time-invariant models were shown to be 0.75 and 5.42 percent respectively to the peak of observed runoff hydrographs. Correlation coefficients for the statistical analysis in the same condition were shown to be 0.999 and 0.978 with a high significance respectively. Therefore, it can be concluded that the accuracy of a linear time-variant model is approaching more closely to the observed runoff hydrograph than that of a linear time-invariant model in the applied watersheds. 4. Average relative errors of the time to peak of calibrated runoff hydrographs by using linear time-variant and linear time-invariant models were shown to be 16.44 and 19.89 percent respectively to the time to peak of observed runoff hydrographs. Correlation coefficients in the same condition were also shown to be 0.999 and 0.886 with a high significance respectively. 5. It can be seen that the shape of simulated hydrograph based on a linear time- variant model is getting closer to the observed runoff hydrograph than that of a linear time-invariant model in the applied watersheds. 6. Two different models were verified with different rainfall-runoff events from data for the calibration by relative error and correlation analysis. Consequently, it can be generally concluded that verification results for the peak discharge and time to peak of simulated runoff hydrographs were in good agreement with those of calibrated runoff hydrographs.