• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.4
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• pp.415-428
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• 2015

With increase of the extension of long tunnels and urban tunnelling, demands on the new tunnelling technologies are raised. Currently, drilling and blasting tunnel construction method is mostly used, however, because of sever blast vibration for some occasions, complaints from local residents and rock damages are inevitable. Accordingly, TBM tunnelling is more efficient and effective for such conditions. Nevertheless, tunnel construction costs of TBM cannot compete that of the drill and blasting method in Korea. To overcome such limitations, various TBM equipments and construction technologies are required. In addition, continuous revision of the design standard and specification are required. In this study, a detailed explanation regarding the revised version of TBM section in the tunnel standard specification at 2015 is shown.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.2
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• pp.101-111
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• 2004

In order to guarantee the stability of a tunnel and its optimum design, it is very important to obtain enough ground investigation data. In realty, however, it is not the case due to the limitation of measuring spatially distributed data and economical reasons. Especially, there are regions where drilling is impossible due to civil appeal and mountainous topology, and it is also difficult to estimate rock mass classes quantitatively with only geophysical exploration data. In this study, therefore, 3 dimensional multiple indicator kriging (3D-MI kriging), which can incorporate geophysical exploration data and drill core data off a tunnel center line, is proposed to cope with such problems. To this end, two dimensional mutiple indicator kriging, which is one of the geostatistical techniques, is extended for three dimensional analysis. Also, the proposed 3D-MI kriging was applied to determine the rock mass classes by RMR system for the design of a Kyungbu express rail way tunnel.

• Journal of the Korean Home Economics Association
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• v.43 no.5 s.207
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• pp.43-55
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• 2005

This research was designed to investigate and compare the characteristics of preferred clothing textiles for slacks and skirt of college students. One hundred five subjects majoring in fashion design were surveyed and the subjects selected three favorite materials among 120 samples presented in a swatch book. The subject's weighted frequencies were added tv order of preference. The results of this study were as follows: 1. In the spring and fall seasons, black twill cotton drill was preferred foremost as a textile for slacks, and medium gray basket weaved cotton pinhead with stripe pattern was preferred as a textile for skirts. 2. In summer, dark bluish gray plain linen crash was the most preferred material for slacks, and pale yellow plain linen tropical cloth was preferred for skirts. 3. In winter, olive gray cotton corduroy was the most favorite textile for slacks, and moderate brown twill wool hound check was preferred for the skirt. 4. In thickness and weight, textiles for winter were thicker and heavier than those chosen for other seasons, and textiles for skirts showed various thicknesses and weights as compared with those of slacks. 5. In fiber content, natural fibers such as cotton and wool were preferred for an seasons. 6. In the weave of textiles, twiu we,3ve was preferred for spring, fall and winter season, and plain weave was preferred for summer. 7 The most preferred colors for slacks were B and PB, and those for the skirts were YR and PB. For color characteristics, solid fabrics were generally preferred, and patterned fabrics were preferred for skirts as compared with slacks.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.12
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• pp.46-55
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• 2014

PCB design technology for high-speed transmission line has been developed continuously. Adapting to the high capacity of the communication system, switch fabric interface used for backplane is being standardized to accommodate more than 10Gbps serial interface. In this paper, various computer simulations are performed to compare the performance of each transmission line per length according to PCB material, and also to analyze the effect from via stub length and crosstalk, for the purpose of applying 11.5Gbps serial interface as a switch fabric interface in tera-bit switching system. As a result of the simulation, important design issues, such as PCB material of each board supporting 8dB improvement in transmission loss using low loss PCB, maximum available stub length on transmission line via, whether or not to apply the backdrill process to the via, and the clearance of the differential pair between transmission lines, are determined. The most efficient system architecture which could be applied 11.5Gbps serial interface in all switch fabric interfaces is defined from the simulation results.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.35-48
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• 2019

Domestic hydraulic drifters till now have been developed by benchmarking products from overseas leading companies. However, they do not have excellent impact performance as they are not suitable for characteristics (large flow rate and low pressure) of Korean hydraulic drill power pack, and therefore, research on the optimum design has not made much headway. This study performs multi-objective function optimization for hydraulic drifters whose capacity has been redesigned to deal with the large flow rate, and also with the help of this function, it aims to improve impact power and reduce supply and surge pressure. A summary of the research study is as follows: First, we set goals for improving impact power, supply pressure, and surge pressure, and then perform multi-objective function optimization on them. After that, we secure the reliability of the optimized analytical model by comparing the test results of the prototype built by the optimized design with the analysis results of the analytical model. This study used SimulationX, that is the hydraulic system analysis software, and EasyDesign, which is a multi-objective function optimization program. Through this research, we have achieved the results that satisfy the goal of developing high power drifters suitable for Korean type hydraulic drills.

• Journal of Biosystems Engineering
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• v.33 no.2
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• pp.83-93
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• 2008

In order to save labor and cost, direct seeding has been considered as an important alternative to the machine transplanting in rice cultivation. Current direct seeding machines for rice in Korea drill irregularly under various operating conditions. This study was conducted to develope a precision seeder which enables the accurate, even-spaced in row placement of rice seeds at uniform depths of 3-4 cm on dry paddy. Design, construction and performance evaluation of the precision seeder were carried out. The tractor rear-mounted type 8-rows precision seeder which performs seeding in addition to fertilizing, ditching, and rotary tilling works on dry paddy was developed. Main components of the seeder were ditcher and leveller, rotary tiller, powered roller type furrow opener, seeding device, powered roller type furrow covering and firming device, hydraulic unit, seeding speed control system, power transmission system, hitch and frame. Ditching, furrow opening, and seed covering and firming performances were good and seeding depths of 2-4 cm could be maintained. Planting accuracies and planting precisions were within 13.6%, and 31.2%, respectively, for planting space of 15 cm, and seeding velocity of 0.5 m/s. These mean variations of average planting space were within 2.1 cm, and 90% of seeds in a hill were seeded within 4.7 cm of hill length, respectively. Error ratios between setting planting space and measured average planting space were shown within 6.7%. Therefore the seeder showed good planting performance up to seeding velocity of 0.5 m/s in field tests. And field capacity of the seeder was about 0.28 ha/hour.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.1
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• pp.1-12
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• 2017

The purpose of this study was to identify the effects of a hands-on training regarding maritime safety including abandon ship and fire-fighting as related to sea survival, fire-fighting knowledge and emergency response leadership in seafarers engaged on a seagoing ship. The study was conducted with a nonequivalent control group pre-posttest design. Two hundred-sixty-six participants were assigned to either the experimental group(128) or control group(138). The hands-on training regarding maritime safety included sea survival and fire fighting drill, and it was implemented with the experimental group for two days from July 1, 2015 to June 30, 2016. Data was analyzed using chi-square, t-test and ANCOVA by using IBM SPSS Statistics(version 24) program. The experimental group who had the hands-on training showed significantly higher sea survival knowledge(F=902.32, p<.001), shipboard fire-fighting knowledge(F=1013.76, p<.001) and emergency response leadership(F=1802.62, p<.001) for maritime safety compared with the control group who had traditional education. The results indicate that a hands-on training is an effective teaching method to improve sea survival, fire-fighting knowledge and emergency response leadership in seafarers engaged. Further study is needed to identify the effect of a hands-on training regarding maritime safety according to the environmental changes of seafarers.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.378-386
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• 2005

Jook-Ryung roadway tunnel was constructed by drill-blast after pilot tunnelling by 2 TBMS. nis report analyzes the data for TBM performance in the total length of 7.3 km for the two pilot tunnels. Net penetration rates were recorded as high as 2.3 m/h and 2.0 m/h for the two different directions while degrees of operation were $31.4\%$ and $33.3\%$, respectively. The cutter lives for No.2 tunnel were evaluated $200\~280\;m^3/c$ and around 400 m/set as high as for Meraker 10 km tunnel in Norway. The relationship between net penetration rate and characteristics of rock mass which were obtained by RMR and TSP measurement, coincides with the prior studies. This kind of evaluation is expected to be used to design TBM tunnelling and to help to perform the TBM operation effectively

• Geomechanics and Engineering
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• v.23 no.1
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• pp.61-69
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• 2020

The uniaxial compressive strength (UCS) of rock is a basic parameter in underground engineering design. The disadvantages of this commonly employed laboratory testing method are untimely testing, difficulty in performing core testing of broken rock mass and long and complicated onsite testing processes. Therefore, the development of a fast and simple in situ rock UCS testing method for field use is urgent. In this study, a multi-function digital rock drilling and testing system and a digital core bit dedicated to the system are independently developed and employed in digital drilling tests on rock specimens with different strengths. The energy analysis is performed during rock cutting to estimate the energy consumed by the drill bit to remove a unit volume of rock. Two quantitative relationship models of energy analysis-based core drilling parameters (ECD) and rock UCS (ECD-UCS models) are established in this manuscript by the methods of regression analysis and support vector machine (SVM). The predictive abilities of the two models are comparatively analysed. The results show that the mean value of relative difference between the predicted rock UCS values and the UCS values measured by the laboratory uniaxial compression test in the prediction set are 3.76 MPa and 4.30 MPa, respectively, and the standard deviations are 2.08 MPa and 4.14 MPa, respectively. The regression analysis-based ECD-UCS model has a more stable predictive ability. The energy analysis-based rock drilling method for the prediction of UCS is proposed. This method realized the quick and convenient in situ test of rock UCS.

• Journal of Engineering Education Research
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• v.11 no.4
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• pp.19-33
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• 2008

The purpose of this study is to find out the effects of the use of Chatting Method(with AI Chatting robot: Chatterbot) and Computer Interest Levels on Teaching & Learning. The major findings of the study are as follows. Firstly, the chatting activities using the chatterbot method and computer Interest Levels were not effective in the academic achievement. Secondly, the chatting activities using the chatterbot method and computer Interest Levels were effective in improving the learning motivation. Thirdly, According to the result of post-feedback analysis, the benefits of chatterbot method was 'the new', 'transcends time and space', 'drill and practice learning' and was some of the drawbacks 'response fixed', lack of emotional transactions. and the proposal 'PBL' was reached(1. strength: new experience, 2. weakness: be tired, 3. proposal: PBL approach). Fourthly, the relationship between the academic achievement, learning motivation, post-feedback was no correlation. Based on these results, the study suggests that the chatterbot method was need for multiple instructional design strategy.