• Computers and Concrete
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• v.32 no.1
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• pp.15-26
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• 2023

In order to study the anti-seismic performance of full light-weight concrete utility tunnel, EL Centro seismic waves were input, and the seismic simulation shaking table test was carried out on the four utility tunnel models. The dynamic characteristics and acceleration response of the system consisting of the utility tunnel structure and the soil, and the interlayer displacement response of the structure were analyzed. The influence law of different construction methods, haunch heights and concrete types on the dynamic response of the utility tunnel structure was studied. And the experimental results were compared with the finite element calculation results. The results indicated that with the increase of seismic wave intensity, the natural frequency of the utility tunnel structure system decreased and the damping ratio increased. The assembling composite construction method could be equivalent to replace the integral cast-in-place construction method. The haunch height of the assembling composite full light-weight concrete utility tunnel was increased from 30 mm to 50 mm to enhance the anti-seismic performance during large earthquakes. The anti-seismic performance of the full light-weight concrete utility tunnel was better than that of the ordinary concrete utility tunnel. The peak acceleration of the structure was reduced by 21.8% and the interlayer displacement was reduced by 45.8% by using full light-weight concrete. The finite element simulation results were in good agreement with the experimental results, which could provide reference for practical engineering design and application.

• Geomechanics and Engineering
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• v.29 no.2
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• pp.133-143
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• 2022

The catastrophic earthquake-induced failure of slopes concentrically distributed at near-fault area, which indicated the special features of near-fault ground motions, i.e. horizontal pulse-like motion and large vertical component, should have great effect on these geo-disasters. We performed shaking table tests to investigate the effect of both horizontal pulse-like motion and vertical component on dynamic response of slope. Both unidirectional (i.e., horizontal or vertical motions) and bidirectional (i.e., horizontal and vertical components) motions are applied to soft rock slope model, and acceleration at different locations is reordered. The results show that the horizontal acceleration amplification factor (AAF) increases with height. Moreover, the horizontal AAF under unidirectional horizontal pulse-like excitations is larger than that subject to ordinary motion. The vertical AAF does not show an elevation amplification effect. The seismic response of slope under different bidirectional excitations is also different: (1) The horizontal AAF is roughly constant under horizontal pulse-like excitations with and without vertical waves, but (2) the horizontal AAF under ordinary bidirectional ground motions is larger than that under unidirectional ordinary motion. Above phenomena indicate that vertical component has limited effect on seismic response when the horizontal component is pulse-like ground motion, but it can greatly enhance seismic response of slope under ordinary horizontal motion. Moreover, the vertical AAF is enhanced by horizontal motion in both horizontal pulse-like and ordinary motion. Thence, we should pay enough attention to vertical ground motion, especially its horizontal component is ordinary ground motion.

• Geomechanics and Engineering
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• v.3 no.4
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• pp.291-321
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• 2011

The paper describes a simple numerical FLAC model that was developed to simulate the dynamic response of two instrumented reduced-scale model reinforced soil walls constructed on a 1-g shaking table. The models were 1 m high by 1.4 m wide by 2.4 m long and were constructed with a uniform size sand backfill, a polymeric geogrid reinforcement material with appropriately scaled stiffness, and a structural full-height rigid panel facing. The wall toe was constructed to simulate a perfectly hinged toe (i.e. toe allowed to rotate only) in one model and an idealized sliding toe (i.e. toe allowed to rotate and slide horizontally) in the other. Physical and numerical models were subjected to the same stepped amplitude sinusoidal base acceleration record. The material properties of the component materials (e.g. backfill and reinforcement) were determined from independent laboratory testing (reinforcement) and by back-fitting results of a numerical FLAC model for direct shear box testing to the corresponding physical test results. A simple elastic-plastic model with Mohr-Coulomb failure criterion for the sand was judged to give satisfactory agreement with measured wall results. The numerical results are also compared to closed-form solutions for reinforcement loads. In most cases predicted and closed-form solutions fall within the accuracy of measured loads based on ${\pm}1$ standard deviation applied to physical measurements. The paper summarizes important lessons learned and implications to the seismic design and performance of geosynthetic reinforced soil walls.

• Journal of the Korean Wood Science and Technology
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• v.17 no.2
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• pp.34-64
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• 1989

Corner block with anchor bolt(CBA) joint method used in knock-down type table furniture manufacturing can reduce the packing and transporting cost. Unfortunately. it also has the disastrous defect to be loosend and unstable during the service life mainly due to fatigue and creep(repeated and prolonged loading). So 22 joint groups constructed were tested to evaluate the effect of some design factors related to the size of side rail(apron). block attachment to side rail. and the number of anchor bolt as well as the effect of the type of corner block(mitered type vs. rectangular type) Usable strength from the stiffness coefficients of each joint group were analysed with SPSS /PC+ and described as the criteria of CBA joint construction. The conclusions were as follows: The height of side rail(50, 75 and 100 mm) and the addition of polyvinyl acetate(PVAc) emulsion in the corner block attactment to side rail had the effect on raising the usable strength of CBA joint with remarkable high significance. And the effect of 2 - anchor bolts was also superior to that of 1 - bolt significantly. However. the thickness of side rail(22 mm vs. 25 mm) had no effect on the strengthening the table joint rigidity. Mitered type corner block joint appeared to he recommendable for CBA jointed table construction rather than the rectangular type one regardless of the method of block attachment to side rail. The best result identified from Duncan's multiple comparison was in the construction with 25 mm thick and 100 mm height of side rail fastened using 2 - anchor bolts in mitered type corner block. But it would be reasonable to use 22 mm thick & 75 mm high side rail and mitered corner block with PVAc emulsion & 2 bolts considering the productivity and production cost down in the MDF furniture manufacturing industries.

• Journal of Wetlands Research
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• v.2 no.1
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• pp.95-107
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• 2000

The population dynamics of Salix nipponica and S. koreensis and the sediment factors were investigated in the wetland of the Nam-River. Chinju. Gyongsangnam-do, Korea. Each population of S. nipponica and S. koreensis was divided into four stages during the riverbed sedimentation: the first stage of establishment by S. nipponica, the second stage of coexistence by S, nipponica and S. koreensis, the third stage of dominated by S. koreensis, while S. nipponica was decreased during the increase of the water table in the sediment, and the fourth stage of the climax by S. koreensis, while S. nipponica almost died when the water table was twice to the third stage. Tree height, age, and density of S. nipponica were decreased, while S. koreensis increased along the sedimentation. And the composition of understory species showed no differences in each stage. The water table and the clay content affected on the distribution of Salix spp. in each stage, according to the PCA. The water table and the clay content increased during the sedimentation, while the other factors were almost the same.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.2
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• pp.1-9
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• 2003

We develop an experimental system to inspect a metal mask and, in this paper, introduce its inspection algorithm. This system is composed of an ASC(Area Scan Camera) and a belt type xy-table. The whole area of the metal mask is divided into several inspection blocks. The area of each block is equal to FOV(Field of View). For each block, the camera image is compared to the reference image. The reference image is made by gerber file. The rotation angle of the metal mask is calculated through the linear equation that is substituted two end points of horizontal boundary of a specific hole in a camera image. To calculate the position error caused by the belt type xy-table, HT(Hough-Transform) using distances among the holes in two images is used. The center of the reference image is moved as much as the calculated Position error to be coincided with the camera image. The information of holes in each image, such as centroid, size, width and height, are calculated through labeling. Whether a holes is mado correctly by laser machine or not, is judged by comparing the centroid and the size of hole in each image. Finally, we build the experimental system and apply this algorithm.

• Journal of Korean Society of Forest Science
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• v.4 no.1
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• pp.24-25
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• 1965

A statistical study was made on the size of sample plot to be used in the preparation of a yield table. This has always been an important problem needing solution in Korea. For this purpose, 3 replications of Korean white pine plantings with block size of $80m{\times}80m$ were established in the Kwangneung Experimental Forest. A location map was prepared of the pines in the blocks and the heights and the breast height diameters measured. Then those blocks were divided into 64, 64, 16, 16, 4, 4, and 1 standed $40m{\times}80m$ and $80m{\times}80m$ each. After these divisions, the average heights, average breast height diameters, standard deviations and coefficient of variations were computed for the plots and averaged according to plot size. As the results of these computations, it was shown that the standard deviation and the coefficient of variation suddenly increased with the beginning of an increase in plot size. However, these indicated an approximately constant value at a certain limit. Although the average value decreases with the initial increase in plot size, it also indicates an approximately constant value at a certain limit. This limit was between $20m{\times}40m$ and $40m{\times}40m$. With the purpose of evaluating these facts, the average height and the average diameter were computed for the number of standing trees in the $10m{\times}10m$ plots. A negative (minus) relationship was found between the number of standing trees and the average value. As a result of above evaluation, it was found that when the size of plot area was small, a larger estimated value, was obtained as well as a smaller standard deviation and coefficient of variation. It is possible, therefore, that an incorrect value might be used in the evalution of data as the stand structure could appear to be uniform when the plot size was small. In general, when the size of plot area is larger than $40m{\times}40m$, the probability of the difficulty occurring mentioned above is estimated to be small.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1824-1827
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• 2003

The sheet metal shearing process is normally used in the precision elements such as semi-conductor components. In precision elements, burrs usually reduce the quality of machined parts and cause interference, jamming and misalignment during assembly procedures and because of their sharpness, they can be safety hazard to personnel. Furthermore, not only burrs are hard to predict and avoid, but also deburring, the process of removing burrs, is time-consuming and costly. In order to get the burr-free parts, therefore, we developed the precise burr measuring system using the laser. The laser burr measuring system consists of the laser probe, the photo detector, the achromatic doublet lens, and the rotary ＆ the X-Y table. In previous reports, we used simple vertical measuring method. But, as we used relatively bigger laser spot diameter and had the limited reflection angle, it was difficult to obtain the precise measuring results. So called, the spot size effect makes the profile of burr measured distorted and the burr height measured smaller. By introducing the novel laser measuring method which employing the achromatic lens system and the tilting mechanism, we could make the spot size smaller and get the appropriate beam direction angle. Through the experiments, the accuracy of the developed system is proved. The burr height measured during the punching process can be used for automatic deburring and in-situ aligning.

• Journal of Korean Society of Forest Science
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• v.109 no.4
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• pp.477-483
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• 2020

We constructed a stand yield table for Chamaecyparis obtusa based on data from an actual forest. The previous stand yield table had a number of disadvantages because it was based on actual forest information. In the present study we used data from more than 200 sampling plots in a stand of Chamaecyparis obtusa. The analysis included theestimation, recovery and prediction of the distribution of values for diameter at breast height (DBH), and the result is a valuable process for the preparation ofstand yield tables. The DBH distribution model uses a Weibull function, and the site index (base age: 30 years), the standard for assessing forest productivity, was derived using the Chapman-Richards formula. Several estimation formulas for the preparation of the stand yield table were considered for the fitness index, and the optimal formula was chosen. The analysis shows that the site index is in the range of 10 to 18 in the Chamaecyparis obtusa stand. The estimated stand volume of each sample plot was found to have an accuracy of 62%. According to the residuals analysis, the stands showed even distribution around zero, which indicates that the results are useful in the field. Comparing the table constructed in this study to the existing stand yield table, we found that our table yielded comparatively higher values for growth. This is probably because the existing analysis data used a small amount of research data that did not properly reflect. We hope that the stand yield table of Chamaecyparis obtusa, a representative species of southern regions, will be widely used for forest management. As these forests stabilize and growth progresses, we plan to construct an additional yield table applicable to the production of developed stands.

• The Korean Journal of Food And Nutrition
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• v.1 no.1
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• pp.41-46
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• 1988

The purpose of this study was to evaluate the relation of nutrients intake and copper status between nonvegetarian female college students and lacto-ovo-vegetarian female college students. The height, weight and serum copper concentrations were determined. Food nutrients analysis procedure was made by computer using food composition table. The results was summarized as followed; 1) Mean values of weight & height were respectively 53.581$\pm$1.68kg.157.051$\pm$1.43cm in nonvegetarians and 51.23$\pm$1.45kg.156.65$\pm$1.24cm in facto-ovo-vegetarians. 2) The average intakes of protein, fat, carbohydrate, fiber, Ca, P, Fe and Vit. C were above the RDA in the two groups, but those of calories was below the RDA in non-vegetarians. Especially, fiber and icon intakes were significant in the two groups(p< 0.01, p< 0.05). 3) The percentage of iron absorption was 7.64% in nonvegetarians and 5% in facto-ovo-vegetarians. 4) Mean serum copper values of nonvegetarian and vegetarian were 107.08$\pm$14.39ug/100m1 and 113.31$\pm$20.86ug/100ml, respectively.