• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.543-561
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• 2020

This paper is the result of the study on the effect of the support structure of the tunnel steel rib. In tunnel excavation, the top and bottom half excavation methods result in subsidence of steel rib reinforcement due to insufficient support of steel rib reinforcement when the ground is poor after excavation. The foundation of the steel rib installed in the upper half excavates the bottom part of the base, causing the subsidence to occur due to various effects such as internal load and lateral pressure. As a result, the tunnel is difficult to maintain and its safety is problematic. To solve these problems, steel rib support structures have been developed. For the purpose of verification, the behavior of the supporting structure is verified by model experiments reduced to shotcrete and steel rib material similarity, the numerical analysis of ΔP and ΔP generated by bottom excavation by Terzaghi theoretical equation. As a result, it was found that the support structure of 20.100~198.423 kN is required for the 10~40 m section of the depth for each soil of weathered soil~soft rock. In addition, as a result of the reduced model experiment, a fixed level of 50% steel rib deposit of steel rib support structure was installed. The study shows that the installation of steel rib support structures will compensate for uncertainties and various problems during construction. It is also thought that the installation of steel rib support structure will have many effects such as stability, economy, and air reduction.

• Korean Journal of Culture and Social Issue
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• v.24 no.2
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• pp.221-250
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• 2018

The purpose of this study is to find out the causes of turnover, the causes of stay, and the effects of turnover of college graduates with early careers, based on the concept of job embeddedness and their stances. For this study, semi-structured interviews were conducted with 20 college graduates with early careers and the interviews were analyzed with phenomenological analytic research. The result of the study shows that the cause of turnover intention includes fit and link which are components of job embeddedness. More specifically, turnover intention of the interviewee is affected by fit which includes whether their ability and talent are used properly and whether their vision and culture fit well those of their organization, also affected by link which includes the formal or informal mutual relationship with coworkers and superiors. Stay intention, on the other hand, includes fit which contains satisfaction about work and organization, long-term career management. Stay intention also includes sacrifice which are anxiety about uncertain future and satisfaction about being employed. As an aspect of the effect of turnover, the satisfaction and fulfillment about work which are experienced after turnover by the interviewees and the satisfaction about coworkers and the team in which the interviewees are included offset the negative effect of turnover. The result also shows that organization should consider their workers' satisfaction about the first work, their amicable relationship, and turnover cost, to improve working and living standard of colleges graduates with early careers and to prevent them from turnover.

• The Journal of the Korea Contents Association
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• v.8 no.10
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• pp.309-316
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• 2008

In a study on effect of service education and training for tour conductors upon customer orientation and satisfaction it was shown that in view of insufficient service of education and training for tour conductors and increased number of population travelling by utilizing travel firms and their call for satisfying diverse demand there is need for customer oriented tour conductors to induce customer satisfaction through diverse role playing by tour conductors. It was indicated that such efforts lead to customer satisfaction and also has impact on improving image of company and on creating new customer. In view of such factors there is need for well planned, persistent education and training for service to heighten satisfaction of customer through well organized operation of service education and training program for tour conductors and through its continuous practice and experience.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.391-397
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• 2010

Performance tests of a liquid-oxygen pump were carried out using liquid nitrogen (LN2) as a working fluid in a cryogenic turbopump test facility in Korea Aerospace Research Institute (KARI). The tests were performed at 30-55% of the design rotational speed, and the results were compared with those from a water test. The experimental results confirmed the similarity of the hydraulic performance, which allows the prediction of the pump performance at a design rotational speed of 20,000 rpm. The overall cavitation performance of the pump in the cryogenic environment was better than that in the water environment for all ranges of flow rates and rotational speeds. Critical cavitation number at the design flow rate was determined as 0.012 from the cryogenic test, and as 0.024 from the water test. The improved cavitation performance is due to the thermodynamic effect in cryogenic fluids.

• The Journal of the Korea Contents Association
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• v.20 no.6
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• pp.705-716
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• 2020

The aim of this article is to examine the relationships between authentic leadership and job satisfaction and to test the moderating effects of co-workers undermining on that relationship. Data were collected from 24th companies in Korea. The sample included 490 employees chosen randomly. Moderated hierarchical regression was used to examine the moderating role of co-workers undermining on the authentic leadership and job satisfaction relationship. The results show that authentic leadership is positively and significantly correlated with job satisfaction. In addition, the results of the hierarchical multiple regression analyses support the moderating effects of perceived employee co-workers undermining with regard to the relationship between authentic leadership and job satisfaction. This study contributes to suggesting the role of co-worker's undermining as a key moderator of their relationship. The theoretical as well as practical implications of the results were discussed with the suggestion for future research.

• Journal of the Korea Convergence Society
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• v.7 no.3
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• pp.15-24
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• 2016

The purpose of this converged study was to examine the influencing factors on occupational stress in Korean workers. Data were collected with a convenience sample of 207 male workers living in Jeollanam-do region. The structured questionnaires measured the general and job-related factors, social support, and occupational stress. The results were as follows. (1) About half of participants had higher scores in occupational stress. (2) The annual income, supervisors' support, and coworkers' support were statistically significant variables predicting the level of occupational stress among Korean workers, accounting for 36% of the variability. The results of the study indicate that it is necessary to establish strategic workforce planning for workers to reduce occupational stress.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.338-348
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• 2004

The present study is conducted to investigate the effect of rib arrangements on an impingement/effusion cooling system with initial crossflow. To simulate the impingement/effusion cooling system, two perforated plates are placed in parallel and staggered arrangements with a gap distance of 2 times of tile hole diameter. Initial crossflow passes between the injection and effusion plates, and the square ribs (3mm) are installed on the effusion plate. Both the injection and effusion hole diameters are 10mmand Reynolds number based on the hole diameter and hole-to-hole pitch are fixed to 10,000 and 6 times of the hole diameter, respectively. To investigate the effects of rib arrangements, various rib arrangements, such as 90$^{\circ}$transverse and 45$^{\circ}$angled rib arrangements, are used. Also, the effects of flow rate ratio of crossflow to impinging jets are investigated. With the initial crossflow, locally low transfer regions are formed because the wall jets are swept away, and level of heat transfer rate get decreased with increasing flow rate of crossflow. When the ribs are installed on the effusion plate, the local distributions of heat/mass transfer coefficients around the effusion holes are changed. The local heat/mass transfer around the stagnation regions and the effusion holes are affected by the rib positions, angle of attack and rib spacing. For low blowing ratio, the ribs have adverse effects on heat/mass transfer, but for higher blowing ratios, higher and more uniform heat transfer coefficient distributions are obtained than the case without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. Average heat transfer coefficients with rib turbulators are approximately 10% higher than that without ribs, and the higher values are obtained with small pitch of ribs. However, the attack angle of the rib has little influence on the average heat/mass transfer.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.949-956
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• 2005

In this paper, a new CPW-fed cross shape fractal antenna having a self-affinity is presented. This novel configuration, which has anisotropic scaling symmetry, makes smaller profile characteristic compared to the fractal antenna using a self-similarity. Increase of the iteration coefficient, which leads to decrease of the fundamental resonant frequency, shows a good impedance matching condition and multi-band characteristics due to new surface current paths. The radiation patterns are similar to those of monopole antennas. In the K3 stage of iteration, the proposed antenna shows a measured maximum gain 2.27 dBi at 940 MHz. A commercially available software based on the FDTD algorithm has been used to obtain the predicted results. In addition, an RT/Duroid 5880 substrate has been employed for the experimental results.

• Journal of the Korean Society of Groundwater Environment
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• v.2 no.1
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• pp.14-21
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• 1995

Colloids such as exogenous biocolloids in a bioremediation operation can enhance the transport of contaminant in ground water by reducing retardation effects. Because of their colloidal size and favorable surface conditions in addition to their low density, bacteria can act as efficient contaminant carriers. When mobile bacteria are present in a subsurface environment, the system can be treated as consisting of three phases: water phase, bacterial phase, and the stationary solid matrix phase. In this work, a mathematical model based on mass balances is developed to describe the facilitated transport and fate of a contaminant in a porous medium. Bacterial partition between the bulk solution and the stationary solid matrix, and the contaminant partition among the three phases are represented by the equilibrium relationships. Solutions were obtained to provide estimates of contaminant and bacterial concentrations. A dimensionless analysis of the transport model was utilized to estimate model parameters from the experimental data. The model results matched with experimental data of Jenkins and Lion (1993). The presence of mobile bacteria enhances the contaminant transport. However, bacterial consumption of the contaminant which serves as a bacterial nutrient, can attenuate the contaminant concentration.

• Food Science and Preservation
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• v.12 no.3
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• pp.204-208
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• 2005

This study was conducted to investigate the effects of temperature and packaging on the quality characteristics of hot-water extract from Acanthopanax senticosus. The herb samples, ground and sifted($8{\sim}20$ mesh), were extracted by a boiling($100^{\circ}C$) water under the atmospheric pressure for 2 hrs. The extract was packed with out nylon PE(0.08 mm) pouch and kept under the condition(40 and $60^{\circ}C$) for 10 days. The reduction of turbidity, pH, polyphenol amount and DPPH radical scavenging activity of extract were retarded by packaging under the low temperature. Titratable acidity was increased with packaging at high temperature. Soluble solid content was not affected by packaging and temperature condition. The changes of quality characteristics followed the first-order reaction rate. Arrhenius equation was applied to determine the effects of temperature on the reaction rate constant, showing high $R^2$. These results suggested that packaging under lower temperature can be utilized for maintaining the quality of A senticosus extract.