• Journal of the Society of Naval Architects of Korea
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• v.31 no.2
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• pp.29-37
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• 1994

In this paper the modelling procedure and analysis technique for the prediction of accurate critical speeds of marine propeller shafts are suggested. As a solution method the transfer matrix method is employed to calculate the critical speeds, which are correspond to natural frequencies of the shaft in lateral vibration, and whirling responses. Furthermore, in order to check the validity of the simple prediction formulae, such as Jasper's formula and Panagopulos's formula, numerical calculations were performed. From the numerical results it was found that the critical speed of the propeller shaft is sensitive to the position and the supporting conditions of journal bearings.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.31-39
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• 1996

In this paper, the error and its sources in manufacturing of bourdon tube pressure gage was studied, and the method to reduce such errors was discussed. In more detail, the effects of parallelism of rollers, spring back, uniformity of radius curvature and the ratio of circumferential speeds of rollers were invesrti- gated. As a reselt, we could find out that the aprallelism of roller affected to the displacement error at the free end of gage and that the amount of spring back was closely related with the ratio of circumferential speeds of rollers. The uniformity of curvature radius was determined by the distance between bending rollers and it was comparatively uniform in the range above 30 .deg. C from the both sides of tube. Also, the ratio of circumfer-ential speeds of rollers was finded out as a very important factor giving severe influence on the creep or the hysteresis of bourdon tube.

• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.105-115
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• 2006

The purpose of this study is to elucidate the mechanical characteristics of lower extremity joint movements at different walking speeds in obese people and suggest the very suitable exercise for obese person's own body weight and basic data for clinical application leading to medical treatment of obesity. This experimental subjects are all males between the ages of 20 and 30, who are classified into two groups according to Body Mass Index(BMI): one group is 15 people with normal body weight and the other 15 obese people. Walking speed is analysed at 3 different speeds ($1.5^m/s$, $1.8^m/s$, $2.1^m/s$) which is increased by $0.3^m/s$ from the standard speed of $1.5^m/s$. We calculated joint moments of lower extremity during stance phase through video recording and platform force measurement.Two-way ANOVA(Analysis of Variance, Mix) is applied to get the difference of moments according to walking speeds between normal and obese groups. Pearson's Correlation Analysis is applied to look into correlation between walking speeds and joint moments in both groups. Significance level of each experiment is set as ${\alpha}=.05$. As walking speed increases maximum ankle plantar flexion moment in the stance phase is smaller in obese group than in normal group, which is suggestive of weak toe push-off during terminal stance in obese group, and the highest maximum ankle plantar flexion moment in obese group during the middle speed walking($1.8^m/s.$). Maximum ankle dorsal flexion moment in obese group is relatively higher than in normal group and this is regarded as a kind of compensatory mechanism to decrease the impact on ankle when heel contacts the floor. Maximum knee flexion and extension moments are both higher in normal group with an increase tendency proportional to walking speed and maximum hip flexion and extension moments higher in obese group. In summary, maximum ankle plantar flexion moment between groups(p<.025), maximum knee moment not in flexion but in extension(p<.001) within each group according to increasing walking speed, and maximum hip flexion and extension moment(p<.001 and p<.004, respectively according to increasing walking speed are statistically significant but knee and hip moments between groups are not. Pearson correlation are different: high correlation coefficients in maximum knee flexion and extension moments, in maximum hip extension moment but not hip flexion, and in maximum ankle dorsal flexion moment but not ankle plantar flexion, in each group. We suspect that equilibrium imbalance develops when the subject increases walking speed and the time is around which he takes his foot off the floor.

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1395-1406
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• 2022

This study investigated the effects of the urban forest and street trees on flow and temperature distribution in the Daegu National Debt Redemption Movement Memorial Park. For this, we implemented tree-drag and tree-cooling parameterization schemes in a computational fluid dynamics (CFD) model and validated the simulated wind speeds, wind directions, and air temperatures against the measured ones. We used the wind speeds, wind directions, air temperatures predicted by the local data assimilation and prediction system (LDAPS) as the inflow boundary conditions. To investigate the flow and thermal characteristics in the presence of trees in the target area, we conducted numerical experiments in the absence and presence of trees. In the absence of trees, strong winds and monotonous flows were formed inside the park, because there were no obstacles inducing friction. The temperature was inversely proportional to the wind speed. In the presence of trees, the wind speeds(temperatures) were reduced by more than 40 (5)% inside the park with a high planting density due to the tree drag (cooling) effect, and those also affected the wind speeds and temperatures outside the park. Even near the roadside, the wind speeds and temperatures were generally reduced by the trees, but the wind speeds and air temperatures increased partly due to the change in the flow pattern caused by tree drag.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.903-906
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• 1987

The digital private line network provides synchronous data communications over dedicated facilities at several speeds. This service became available to several major metropolitan areas in 1986 with speeds of 4800, 9600, 56000 b/s. The network is expected to grow to include many city areas. In this paper, synchronization plan for the network is proposed.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.30 no.1
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• pp.95-103
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• 1998

Many new technologies and developments designed to increase paper machine speeds and improve paper printability have emerged in recent years. These improvements have changed the structure of paper and given winder manufacturers new challenges, especially as the requirements of printing presses have also changed. Ever-increasing roll widths and diameters are needed. Along with faster press speeds and shorter acceleration times, the unwinding of roils in the press room has become a true test of paper strength and roll structure, In the following we will review the special winding features of coated papers and discuss a selection of the winder type to meet a mill's specific needs.

• Journal of Korean Society of Transportation
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• v.10 no.1
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• pp.21-40
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• 1992

We examine primarily the existing study procedures for freeway weaving section by comparing speed estimates. Most methods have poor predictions because of neglecting the weaving vehicle influ-ence. In this study we develop the speed prediction equation considering the weaving influence area i.e, weaving box. Assuming that speeds outside weaving box are similar to speeds in freeway basic sec-tions we develop speed equation in box based on the field data. Moreover level of service criteria and weaving analysis precedure are proposed under the new speed prediction equation.

• Journal of the Korean Institute of Intelligent Systems
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• v.4 no.2
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• pp.13-23
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• 1994

This study proposed a method of accessment for traffic flow on roads based on the driver's decision making. In order to, an attempt is carried out to express driving speeds through driver's congnitive language theoretically and experimentally. Membership function is derived to express driver's congnitive language about driving speed through a fuzzy set theory and examines the applicability for speed evaluation. As a resul, the membership function of the recognized as medium by drivers almost agrees with the frequency distribution of speeds on roads constrtained at 50km/h.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.10a
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• pp.85-90
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• 1996

In order to detect and suppress chatter in turning processes a stability control methodology was studied through manipulation of spindle speeds regarding to chatter frequencies. The chatter frequency was identified by monitoring and signal processing of sound pressure during turning on a lathe. The stability control methodology can select stable spindle speeds without knowing a prior knowledge of machine compliances and cutting dynamics. Teliability of the developed stability control methodology was verified through turning experiments on an engine lathe. Experimental results show that a microphone is an excellent sensor for chatter detection and control

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.282-291
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• 2000

In this paper, the dynamics of automated guideway transit vehicles with rubber tires are studied. Two different AGT models are considered: the bogie system and the steering system . It is found that the bogie system is stable at all possible operating speeds, whereas it is not true fur the steering system. To investigate the dynamic stability of steering systems, the critical speeds are investigated and the dynamics of the closed-loop steering control system are numerically simulated.