• Journal of the Korean Society of Industry Convergence
• /
• v.23 no.2_2
• /
• pp.245-254
• /
• 2020

This study investigated the so far little-researched characteristics of the behaviors of rock slopes at the time of an earthquake. For the selection of the rock block, a proper model was formed by applying the similarity in consideration of the roughness and strength of the rock slope(10m) on the site, and shaking table tests were carried out according to seismic excitement acceleration, and seismic waves. In the case of the inclination angle of the joint plane of 20°, the long period wave at 0.3g or more at the time of the seismic excitement surpassed the length of 100mm, the permissible displacement (0.01H, H:slope height), which brought about the collapse of the rock; the short period wave surpassed the permissible displacement at 0.1g, which caused the collapse of the slope. The rock slope was close to a rigid block and a structure more vulnerable to the long period wave than to the short period wave. It collapsed in the short period wave even at the seismic amplitude smaller than the maximum design acceleration in Korea.

• Journal of Biosystems Engineering
• /
• v.34 no.1
• /
• pp.1-7
• /
• 2009

In order to evaluate environmental comfort of tractor cabs, temperature, relative humidity and noise within the cab were taken from 31 tractors during plowing and rotovating operations. The temperature and humidity were evaluated with regard to the comfort zone of KS B ISO 14269-2 and PMV of ISO 7730. The noise was evaluated with regard to the permissible sound level of OSHA for daily exposure of 8 hours. The collected data indicated that thermal environment of the cabs was out of the comfort zone, which meant tractor operators worked under uncomfortable thermal conditions. Difference in the thermal comfort by tractor power and maker, and type of works was not found. However, 25% of the studied tractors showed PMV in a range of -0.5 to +0.5, which indicated their operators worked under the comfort criteria. PMV was improved when the cab was air-conditioned. Levels of measured cab noise were lower than the permissible criteria, and 76.7% of the studied tractors had cab noise ranged from 75 to 85 dBA. There was a tendency that high powered tractors, rotovating operations and locally-made tractors had greater cab noise levels. However, their differences were insignificant.

• Structural Engineering and Mechanics
• /
• v.17 no.3_4
• /
• pp.379-391
• /
• 2004

This paper deals with the development of h-version adaptive mesh refinement and recovery strategy using variable-node elements and its application to various engineering field problems with 2D quadrilateral and 3D hexahedral models. The variable-node elements which have variable mid-side nodes on edges or faces are effectively used in overcoming some problems in connecting the different layer patterns of the transition zone between the refined and coarse mesh. A modified recovery technique of gradients adequate for variable-node elements and proper selection of error norms for each engineering field problems are proposed. In the region in which the error is greater than the permissible refinement error, the mesh is locally refined by subdivision. Reversely, in some parts of the domain having the error smaller than the permissible recovery error, the mesh is locally recovered (coarsened) by combination. Hierarchical structures (e.g. quadtrees and octrees) and element-based storage structures are composed to perform this adaptive process of refinement and recovery. Some numerical examples of a 3D heat conduction analysis of the concrete with hydration heat and a 2D flow analysis of vortex shedding show effectiveness and validity of the proposed scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.7 no.4
• /
• pp.353-362
• /
• 1996

In this paper, SAR distribution is calculated according to the rabbit's head using approximation of its medium three layers model. Our experiment was classified 5 groups dependent on the power intensity of 2,450MHz microwave to measure EEG(Electroencephalograph) of rabbit, which was checked in left frontal lobe before and after irradiation of microwave. In results, mean total power of EEG was slightly decreased and mean composition percentages of $\theta$, $\delta$ and $\beta$ wave were increased after irradiation in observation. It means to decrease of elect- rophysiologic activity and trend of fast wave in brain after irradiation of its microwave. We analyzed the electrophysiological effect of the biobody quantitatively using measured EEG and estimated MPE (Maximum Permissible Exposure).

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.4
• /
• pp.325-333
• /
• 2004

It is investigated that the relation between the response time of DVR(Dynamic Voltage Restorer) and the possible compensation range of voltage dip by the DVR system which protects the 3-phase phase-controlled rectifier from voltage dip. As a result, the permissible range of voltage dip is presented in the 3-phase phase-controlled rectifier, and it is presented that the range of voltage dip which can be compensated according to the DVR s response time. when the DVR compensates voltage dip, Using the proposed method, the DVR s response time can be determined from the parameters of 3-phase phase-controlled rectifier and the possible compensation range of voltage dip, and it is possible to use the control system which have an appropriate speed. Therefore, the use of excessively fast device can be avoided, and the stability of the overall system is improved. Also the reliance of DVR about the 3-phase phase-controlled rectifier can be verified.

• Journal of the Korean Wood Science and Technology
• /
• v.43 no.5
• /
• pp.548-557
• /
• 2015

This study investigated environmental assessments of leachate containing formaldehyde from medium density fiberboard (MDF) disposed in laboratory-scale simulated landfills. Environmental impact assessment of leachate was conducted by measuring formaldehyde, toxicity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), bacterial enumeration, and pH. Amount of formaldehyde in leachate from MDF in soil decreased to the level of soil only treatment by 28 days, and toxicity decreased as the amount of formaldehyde decreased. BOD and COD levels in leachate from the treatments containing MDF exceeded permissible discharge levels of BOD or COD throughout the experimental period. The pH levels of all treatment were within permissible discharge range except on day 0. Fewer bacteria were observed in leachate from MDF in soil treatment than other treatments (MDF only, cured UF resin in soil, and soil only). Consequently, the leachate from disposal of MDF in soil detrimentally affect on environment. However, soil buffered formaldehyde leaching and pH on leachate in this study. Waste MDF may be required the pre-water soaking treatment for leaching formaldehyde to reclaim on land.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2003.11a
• /
• pp.8-12
• /
• 2003

To protect digital communications and broadcasting that are expected to be increasingly used at frequencies above 1GHz, there is a need to determine permissible disturbance limits for frequency bands above 1GHz according to indicates that better correlates with interference level in digital systems. The quality of digital communications is expressed in terms of bit error rate(BER) or throughput. In this regard, it has been reported that degradation of BER or throughput can be estimated from the amplitude probability distribution (APD) of disturbance amplitude. Therefore, if the APD can simply be measured with a high accuracy, APD will be an optimal index for the assessment of interference in digital communications. In this paper, we show that a measurement method using statistic model of APD has compatibility about performance reduction estimation of WLAN. And through approach of this inspection, we propose numeral models about interference effects of peak value and time rate of spurious.

• Tribology and Lubricants
• /
• v.31 no.4
• /
• pp.170-176
• /
• 2015

As a continuation of Part I, which developed a design formula of the minimum corner radius (R_min) for restraining tribological failures, Part II investigates design parameters such as material properties and contact force. As design examples, Al 7075-T651, SST 304 and HT-9 are chosen for the materials and 1, 10 and 100 kN are used for the forces. The results show that the difference in R_min decreases as either the elastic modulus increases or the contact force decreases. Given the same material and force, the permissible R_min decreases as the flat region increases and vice versa. Because the R_min values obtained from the examples are very small, the dimensions of the corner radius normally designed in engineering structures are regarded acceptable. The von Mises stress evaluated for a typical example, which is far below the yield strength, confirms this interpretation. Nevertheless, the present work can provide a design criterion as well as a guideline for quality control in the manufacturing of, in particular, contact corners, which has not been attempted before to the best of the author’s knowledge. In addition, this paper considers the problem of a step that may be formed in the contact contour by using a similar approach. The result shows that no size of the step is permissible.

• Journal of KSNVE
• /
• v.7 no.2
• /
• pp.247-254
• /
• 1997

In the case of a precision equipment, it requires a vibration free environment to provide its proper function. Especially, lithography and inspection devices, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved giga class semiconductor wafers. This high technology equipments require very strict environmental vibration standard in proportion to the accuracy of the manufacturing, inspecting devices. The vibration criteria are usually obtained either by the real vibration exciting test on the equipment or by the analytical calculation. This paper proposes a new method to solve this problem at a time. The permissible vibration level to a precision equipment can be easily obtained by analyzing a process of Frequency Response Function. This paper also demonstrates its effectiveness by applying the proposed method to finding the vibration criteria of a Computer Hard Disk Driver by Impact Test.

• Geomechanics and Engineering
• /
• v.3 no.2
• /
• pp.117-130
• /
• 2011

The methods of design available for geocell-supported embankments are very few. Two of the earlier methods are considered in this paper and a third method is proposed and compared with them. In the first method called slip line method, plastic bearing failure of the soil was assumed and the additional resistance due to geocell layer is calculated using a non-symmetric slip line field in the soft foundation soil. In the second method based on slope stability analysis, general-purpose slope stability program was used to design the geocell mattress of required strength for embankment. In the third method proposed in this paper, geocell reinforcement is designed based on the plane strain finite element analysis of embankments. The geocell layer is modelled as an equivalent composite layer with modified strength and stiffness values. The strength and dimensions of geocell layer is estimated for the required bearing capacity or permissible deformations. These three design methods are compared through a design example. It is observed that the design method based on finite element simulations is most comprehensive because it addresses the issue of permissible deformations and also gives complete stress, deformation and strain behaviour of the embankment under given loading conditions.