• Structural Engineering and Mechanics
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• v.19 no.4
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• pp.381-399
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• 2005

Base isolation technologies have been proven to be very efficient in protecting structures from seismic hazards during experimental and theoretical studies. In recent years, there have been more and more engineering applications using base isolators to upgrade the seismic resistibility of structures. Optimum design of the base isolator can lessen the undesirable seismic hazard with the most efficiency. Hence, tracing the nonlinear behavior of the base isolator with good accuracy is important in the engineering profession. In order to predict the nonlinear behavior of base isolated structures precisely, hundreds even thousands of degrees-of-freedom and iterative algorithm are required for nonlinear time history analysis. In view of this, a simple and feasible exact formulation without any iteration has been proposed in this study to calculate the seismic responses of structures with base isolators. Comparison between the experimental results from shaking table tests conducted at National Center for Research on Earthquake Engineering in Taiwan and the analytical results show that the proposed method can accurately simulate the seismic behavior of base isolated structures with elastomeric bearings. Furthermore, it is also shown that the proposed method can predict the nonlinear behavior of the VCFPS isolated structure with accuracy as compared to that from the nonlinear finite element program. Therefore, the proposed concept can be used as a simple and practical tool for engineering professions for designing the elastomeric bearing as well as sliding bearing.

• Smart Structures and Systems
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• v.24 no.1
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• pp.127-139
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• 2019

Residual drifts after an earthquake can incur huge repair costs and might need to replace the infrastructure because of its non-reparability. Proper functioning of bridges is also essential in the aftermath of an earthquake. In order to mitigate pounding and unseating damage of bridges subjected to earthquakes, a self-adaptive Ni-Ti shape memory alloy (SMA)-cable-based frictional sliding bearing (SMAFSB) is proposed considering self-adaptive centering, high energy dissipation, better fatigue, and corrosion resistance from SMA-cable component. The developed novel bearing is associated with the properties of modularity, replaceability, and earthquake isolation capacity, which could reduce the repair time and increase the resilience of highway bridges. To evaluate the super-elasticity of the SMA-cable, pseudo-static tests and numerical simulation on the SMA-cable specimens with a diameter of 7 mm are conducted and one dimensional (1D) constitutive hysteretic model of the SMAFSB is developed considering the effects of gap, self-centering, and high energy dissipation. Two types of the SMAFSB (i.e., movable and fixed SMAFSBs) are applied to a two-span continuous reinforced concrete (RC) bridge. The seismic vulnerabilities of the RC bridge, utilizing movable SMAFSB with the constant gap size of 60 mm and the fixed SMAFSBs with different gap sizes (e.g., 0, 30, and 60 mm), are assessed at component and system levels, respectively. It can be observed that the fixed SMAFSB with a gap of 30 mm gained the most retrofitting effect among the three cases.

• Tribology and Lubricants
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• v.35 no.3
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• pp.183-189
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• 2019

The driver seat of an automobile is in direct contact with the driver and provides the driver with a safe and comfortable ride. The seat consists of a frame, a rail, and many recliners. In recent years, strength and operating force measurement testing of the recliner have become vital for designing car seats. However, performance evaluation requires expensive testing equipment, numerous seat products, and considerable time. Therefore, the trend is to reduce experimentation through interpretation. This study examines the lubrication of solid lubricant for automotive seat recliners and confirms the friction and wear performance. In this study, the lubrication behavior of solid lubricants for car seat recliners is investigated to ascertain the friction and wear performance and to provide accurate values for the strength analysis. The friction material consists of a pin and a plate made from steel, which is widely used in recliners. The friction and wear under lubrication conditions are measured by a reciprocating friction wear tester. The friction coefficient is obtained according to the load and speed. Based on the obtained results, it is possible to achieve a reduction in the error of the test value and the analysis by providing the friction coefficient and wear of the lubricant. The results can be applied to the analysis of automobile seat design.

• Geomechanics and Engineering
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• v.32 no.4
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• pp.375-385
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• 2023

There are many joint fissures distributed in the engineering rock mass. In the process of geological history, the underground rock mass undergoes strong geological processes, and undergoes complex geological processes such as fracture breeding, expansion, recementation, and re-expansion. In this paper, the damage-stick-slip process (DSSP), an analysis model used for rock mass failure slip, was established to examine the master control and time-dependent mechanical properties of the new and primary fractures of a multi-fractured rock mass under the action of stress loading. The experimental system for the recemented multi-fractured rock mass was developed to validate the above theory. First, a rock mass failure test was conducted. Then, the failure stress state was kept constant, and the fractured rock mass was grouted and cemented. A secondary loading was applied until the grouted mass reached the intended strength to investigate the bearing capacity of the recemented multi-fractured rock mass, and an acoustic emission (AE) system was used to monitor AE events and the update of damage energy. The results show that the initial fracture angle and direction had a significant effect on the re-failure process of the cement rock mass; Compared with the monitoring results of the acoustic emission (AE) measurements, the master control surface, key blocks and other control factors in the multi-fractured rock mass were obtained; The triangular shaped block in rock mass plays an important role in the stress and displacement change of multi-fracture rock mass and the long fissure and the fractures with close fracture tip are easier to activate, and the position where the longer fractures intersect with the smaller fractures is easier to generate new fractures. The results are of great significance to a multi-block structure, which affects the safety of underground coal mining.

• Journal of Korean Society of Forest Science
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• v.88 no.2
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• pp.255-265
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• 1999

This study deals with forest soil characteristics and their effects on the trafficability of logging vehicles. The study area is the national experimental forest located in Kwangnung. This site has 20m length and is equally divided by 5 surveying ranges with 4m width, on which a tractor(FIATAGRI) attached with logging boogie can drive in 4 driving types, namely 1time-return unload, 1time-return with load of 780-790kg weight of 3 logs, 5 and 10times-return with same load. After one driving type on all surveying ranges, the soil hardness is surveyed 5 times with 3 several type tools, SHM-1 type, lang penetrometer(L-PNTM), and clegg impact soil tester(CIST). A disturbed degree of cover vegetation and sliding conditions of vehicle are also observed. As results, the soil type of the test site was SC by USCS and dry brown forest soil. The cover vegetation is gotten trambled under driving after 3-5 times-return, shrubs leaves are fully fallen and their bark are peeled, and after 10 times-return the cover vegetations were nearly disappeared. The test vehicle has neither slided nor was overthrown. The wheel tracks in the 1-3 ranges, of which unit weight(gd, gt) is high and soil moisture content(MC) is low, were only 1-2cm deep, but those in the 4-5 ranges, of which the gd, gt is low and the MC is high, were 5-7cm deep. In the soil hardness test, which was established in 5 test ranges by types of driving, the more driving times, the higher the hardness. The soil hardness surveyed by L-PNTM has changed slowly and that surveyed by SHM-1 type has risen sharply. In the ranges with higher specific gravity(Gs), higher unit weight, lower MC and higher liquid limit(LL) and plasticity index(PI) was the soil hardness high and the trafficability was good. In the ranges with opposite conditions, also in the ranges of the lower soil hardness, the trafficability must be not good, because the wheel track may be deep. The results from CIST attached with 4kg hammer was not better than expected. So it is recommended to use CIST with 2.5kg or 0.5kg hammer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.705-710
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• 2017

This paper proposes an estimation method of populations of Grapholita molestas using object segmentation and an SVM classifier in the moth images. Object segmentation and moth classification were performed on images of Grapholita molestas moth acquired on a pheromone trap equipped in an orchard. Object segmentation consisted of pre-processing, thresholding, morphological filtering, and object labeling process. The classification of Grapholita molestas in the moth images consisted of the training and classification of an SVM classifier and estimation of the moth populations. The object segmentation simplifies the moth classification process by segmenting the individual objects before passing an input image to the SVM classifier. The image blocks were extracted around the center point and principle axis of the segmented objects, and fed into the SVM classifier. In the experiments, the proposed method performed an estimation of the moth populations for 10 moth images and achieved an average estimation precision rate of 97%. Therefore, it showed an effective monitoring method of populations of Grapholita molestas in the orchard. In addition, the mean processing time of the proposed method and sliding window technique were 2.4 seconds and 5.7 seconds, respectively. Therefore, the proposed method has a 2.4 times faster processing time than the latter technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.352-360
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• 2008

Recently Task Group (TG) 4 of the Institute of Electrical and Electronics Engineers (IEEE) 802.15a has been recommended a system with ranging capability in existence of multiple Simultaneous operating piconets (SOPs) as well as low-cost, low-power. According to the ranging service, coherent and non-coherent based ranging schemes using ternary code have been adopted as a standard. However it is hard to estimate an accurate time of arrival (TOA) in case of using direct sequence based TOA estimation method because pulse repetition interval (PRI) offered by TG is more limited than the maximum excess delay (MED) of channel. To mitigate inter pulse interference (IPI) problem, this paper proposes a non-coherent TOA estimation scheme using non-periodic transmission (NPT) pattern. The proposed receiver is based on a non-coherent energy detection considering with motivation of low rate wireless personal area network (LR-WPAN). TOA information is estimated via proper comparison with a prescribed threshold after the sliding correlation and search back window (SBW) process for reducing TOA error. To verify the performance of proposed ranging scheme, two distinct channel models approved by IEEE 802.15.4a TG are considered. According to the simulation results, we could conclude that the proposed scheme have performed better performance than the conventional method on the existence of multiple SOPs.

• The Journal of Korean Society for Radiation Therapy
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• v.17 no.1
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• pp.19-31
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• 2005

Purpose : To supply the information of EPID system and to analyze the possibility of substitution EPID for film dosimetry. Materials & Methods : With amorphous silicon(aSi) type EPID and liquid filled lonization chamber(LC) type EPID, the reproducibility according to focus detector distance(FDD) change and gantry rotation was analyzed, and also the possible range of image acquisition was analyzed with Alderson Rando phantom. The resolution and the contrast of aSi type EPID image were analyzed through Las Vegas phantom and water phantom. DMLC image was analyzed with X-Omat V film and EPID to see wether it could be applied to the qualify assurance(QA) of IMRT. Results : The reproducibility of FDD position was within 1mm, but the reproducibility of gantry rotation was ${\pm}2,\;{\pm}3mm$ respectively. The resolution and the contrast of EPID image were affected by dose rate, image acquisition time, image acquisition method and frame number. According to the possible range of image acquisition of EPID, it is verified that the EPID is easier to use than film. There is no difference between X-Omat V film and EPID images for the QA of IMRT. Conclusion : Through various evaluation, we could obtain lots of useful information about the EPID. Because the EPID has digital data, also we found that the EPID is more useful than film dosimerty for the periodical Qualify Assurance of IMRT. Especially when it is difficult to do point dose measurement with diode or ionization chamber, the EPID could be very useful substitute. And we found that the diode and ionization chamber are difficult to evaluate the sliding window images of IMRT, but the EPID was more useful to do it.

• Journal of Korean Physical Therapy Science
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• v.9 no.3
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• pp.31-49
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• 2002

The purpose of this study was to investigate discomforts and sexual life and to identify the relation between the discomforts and sexual life with low back pain. The data were collected from March 2 through July 31, 2001. Four hundred forty-two questionnaires were returned (response rate=88.0%). Analysis of the data was done with SPSS PC+ and use descriptive statistics, $x^2$-test, t-test, ANOVA. regression. The statistics shows that over than 80% of the adults experienced lumbago at least one time in their life, and Back pain is known as one of the most common complaints made by the patients of all ages in the general hospital or local medical clinics throughout. However, in certain case it leads to a chronic condition which can cause a great deal of problems in management and in financial burden to individuals and society. The result of this study was summarized as follows: 1) It appeared that regarding the distribution of gender, male was the higher(63.6%) then that of female, the portion of forties was 28.5%. Sitting for long time was 23.1% in men and 21.7% in women. Unknown reason including sexual behaviour was 12.9% in men and 15.5% in women. Patients treated medicine and physical therapy were 36.4%. In level of educational background, the rate of high school was 31.0%, technical college was 28.5%. The highest proportion by occupation was 18.3% of office workers, occupation posture was 41.9% of sitting. 2) Men(26.0%) and most of women(34.8%) were not satisfied in the explanation satisfaction rate of sex life concerned disease. 23.8% in men and 23.6% in women considered flexibility of waist good. Man(33.3%) and most of woman(35.0%) considered that Health education is necessary. 32.7% in men and 27.3% in women did't mind educator is whoever. Preventing of lower back pain(LBP) and proper Health education of sex life are demanded in daily life. 3) 58.0% of man and 64.0% of woman mostly had a posture which is man over woman. 28.5% in men and 27.8% in women considered that proper information finding of LBP and sex life was very few and few. 37.7% in men and 42.7% in women have acquired information about sex life flung their friends. 4) The number of sex life was decreased from 2.96 0.98 to 2.61 1.63 and also the time of sex life was decreased from 3.65 1.89 to 226 1.64. The satisfaction rate of sex life changed from 3.60 0.86 to 2.77 1.10. In the number of sex life, The non correct group was 2.62 1.91 and the correct group was higher in 2.68 1.65. In the time of sex life, The non correct group was 2.02 1.47 and the correct group was higher in 229 1.65. The satisfaction rate of sex life was 2.76 0.86 in non correct group and 2.88 1.10 in correct group. So there was a difference. 5) In the satisfaction rate of sex life, Men who have a lower back pain were higher than women and no attack group was higher than attack group. As they had many sex life, the satisfaction rate was higher significantly in statistics. As the time of sex life was short, the satisfaction rate was lower significantly in statistics. As the age was low, the demand rate of Health education was high and as means of patient who had a lower back pain was high, the demand rate of Health education was high. As the patient who had a lower back pain had a long married life, the demand rate of Health education was high and as education level was high, the demand rate of Health education was high. It is necessary to provide patients with conservative treatment, educational teaching, and training to prevent further injuries in the future. In general, it is important to educate the public how to prevent back injuries and how to treat themselves in an onset period to prevent further injuries sliding into a chronic state. Sexuality is an integral part of normal and healthy relationships, but patients are unable to enjoy sex because they are riot able to get into a comfortable position due to back pain. Many conditions of the spine can make certain positions uncomfortable. Health educator should make the education program of the discomforts and the sexual pattern for low back pain in workplace and/or hospital. Further study Is needed on how to integrate the educational program on sexuality into the total rehabilitation program.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.151-165
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• 2019

In this study, the four types of improvement methods (increase self weight and reducing sliding force etc.) were proposed depending on install location with compaction grouting to improve seismic performance of existing port structure and optimal methods by analyzing the effects of improvement (stability, constructability and economy) by theoretical and numerical methods. From the dynamic time history analysis for artificial seismic waves, the results indicated that the horizontal displacement after improvement decreased compared to before improvement, however the displacement reduction effect among improvement methods was not significantly different. Slope stability based on the strength reduction method and the limit equilibrium analysis method, it is confirmed that the passive pile method is more safe than other methods. It is due to the shear strength at the failure surface is increased. In addition, the analysis of constructability and economy showed that the reduction of earth pressure method (type 02) and the passive pile method (type 03) are excellent. However, in the case of the passive pile method is concerned that there is a shortage of design cases and the efficiency can be reduced depend on various constraints such as ground conditions.