• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.12
• /
• pp.1076-1083
• /
• 2017

This paper discusses the error estimation in radar measurement data obtained while tracking a launch vehicle. It is known that typical radar measurement data consist of the true positional or orientation information on the vehicle being tracked, random noise and a deterministic bias due to radio refraction. Unlike previous research works, this paper proposes a tracking-error (mainly bias) estimation method solely based on the single radar measurement with no aid of other measurement such as GPS. The proposed method has been verified with real measurement data obtained while tracking the KSLV-I launch vehicle.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09b
• /
• pp.61-67
• /
• 2010

Thick soft clay deposits which are generally located at the west and south coast of the Korean peninsula have complicated characteristics according to their orientation and formation history. Thus, several geotechnical problems could possibly occur when those soft clay deposits are used as foundations for marine structures. Deep cement mixing (DCM) method is one of the most widely used soft soil improvement method for various marine structures, nowadays. DCM method injects binders such as cement into the soft ground directly and mixes with the in-situ soil to improve the strength and other geotechnical properties sufficiently. However, the natural impacts induced by dynamic motions such as ocean waves, wind, typhoon, and tusnami give significant influences on the stability of marine structures and their underlaying foundations. Thus, the dynamic properties become important design criteria to insure the seismic stability of marine structures. In this study, the dynamic behavior of cemented Busan clay is evaluated. Laboratory unconfined compression test and resonant column test are performed on natural in-situ soil and cement mixed specimens to confirm the strength and strain-dependent dynamic behavior variation induced by cement mixing treatment. Results show that the unconfined compressive strength and shear modulus increase with curing time and cement content increment. Finally, the optimized cement mixing ratio for sufficient dynamic stability is obtained through this study. The results of this study are expected to be widely used to improve the reliability of seismic design for marine structures.

• Physical Therapy Rehabilitation Science
• /
• v.13 no.1
• /
• pp.18-25
• /
• 2024

Objective: This study is a single-group pre-post experimental study to determine the effects of simulation-based practice education on nursing students' self-efficacy, performance confidence, and educational satisfaction. Design: Single-group pre-post experimental studies Methods: This study was conducted from September 1, 2023 to November 30, 2023 for nursing undergraduate students in a simulation based practical education program. The subjects were provided with learning materials about an acute myocardial infarction case with chest pain for preliminary learning. After that, they were divided into teams of 6 people and asked to do self-study for 2 hours per team, twice a week, before conducting simulation practice. For the simulation based practical education, the participants were divided into 9 teams of 6 people each, and each team had 10 minutes for orientation, 15 minutes for scenario operation, and 50 minutes for debriefing. Results: After the simulation based practical education, self-efficacy increased statistically significantly from a mean of 3.51 before training to a mean of 3.80 after training (t=-2.12, p=0.038). However, there was no significant difference in performance confidence. There was a significant positive correlation between self-efficacy and performance confidence (r=0.62, p<0.001) and training satisfaction (r=0.67, p<0.001) after the simulation based practical education. Self-confidence was also significantly correlated with educational satisfaction (r=0.76, p<0.001). Conclusions: The results of this study showed that utilizing simulation-based practical education can increase nursing students' self-efficacy, which positively affects their performance confidence and educational satisfaction. Therefore, simulation-based practical education is an effective nursing education method that can improve nursing students' practical skills.

• The Journal of Engineering Geology
• /
• v.15 no.2 s.42
• /
• pp.213-227
• /
• 2005

This study aims to assess the problems with investigation method and to suggest the complementary solutions by comparing the predicted data from surface investigation with the outcome data from underground cavern. In the study area, one(NE-1) of 6 fracture zones predicted during the surface investigation was only confirmed in underground caverns. Therefore, it is necessary to improve the confidence level for prediction. In this study, the fracture classification criteria was quantitatively suggested on the basis of the BHTV images of NE-1 fracture zone. The major orientation of background fractures in rock mass was changed at the depth of the storage cavern, the length and intensity were decreased. These characteristics result in the deviation of predieted predicted fracture properties and generate the investigation bias depending on the bore hole directions and investigated scales. The evaluation of hydraulic connectivity in the surface investigation stage needs to be analyze by the groundwater pressures and hydrochemical properties from the monitoring bore hole(s) equipped with a double completion or multi-packer system during the test bore hole is pumping or injecting. The hydraulic conductivities in geometric mean measured in the underground caverns are 2-3 times lower than those from the surface and furthermore the horizontal hydraulic conductivity in geometric mean is six times lower than the vertical one. To improve confidence level of the hydraulic conductivity, the orientation of test hole should be considered during the analysis of the hydraulic conductivity and the methodology of hydro-testing and interpretation should be based on the characteristics of rock mass and investigation purposes.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.8
• /
• pp.881-887
• /
• 2012

CFRP composite materials have been widely used in various fields of engineering because of their excellent properties. They show high specific stiffness and specific strength compared with metallic materiasl. Woven CFRP composite materials are fabricated from carbon fibers with two orientation angles ($0^{\circ}/90^{\circ}$), which influences the mechanical properties. Therefore, woven CFRP composite materials show different types of fracture behavior according to the load direction. Therefore, the fracture behavior of these materials needs to be evaluated according to the load direction when designing structures using these materials. In this study, we evaluate the fracture strength of plain-woven CFRP composite materials according to the load direction. We performed tests for six different angles (load direction: $0^{\circ}/90^{\circ}$, $30^{\circ}/-60^{\circ}$, $+45^{\circ}/-45^{\circ}$) and estimated the fracture strength for an arbitrary fiber angle by using the modified Tan's theory and harmonic function.

• Journal of Distribution Research
• /
• v.12 no.3
• /
• pp.69-90
• /
• 2007

This study is set out to investigate the factors that influence customers' behavior of choice and switching between online and offline channels, separating the purchase decision into two stages, i.e., information search and purchase. Factors influencing channel choice are found to differ from stage to stage. The main results of this study are as follows. At the information search stage, customers' channel knowledge had impacts on the choice of the channel. Customers are more likely to visit offline bookstores when they have hedonic shopping orientation and higher involvement level with books. On the contrary, customers are more apt to search online when they have a lot of online shopping experiences. At the purchase stage, the results varied according to the search channel. When customers search for information online, the following variables lead to online purchases: online shopping experiences with books, price-focused shopping orientation, and time availability for shopping. Perceived risk made customers purchase offline even though they searched online. In case of offline searching, customers with more convenience-focused, hedonic-focused shopping orientation and less tim availability purchased offline.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.102-111
• /
• 2016

This study aims to identify the characteristics of the regional innovation system(RIS) and the determinants of innovation performance of SMEs. Data were collected from a questionnaire survey on 64 SMEs in the Daejeon and Chungcheong regions to uncover the relationship between capabilities, regional innovation capacities and innovation performance. The moderating effects of regional innovation capacities on the relationship between firms' innovation capabilities and performance were also tested. Empirical results revealed that R&D, marketing and entrepreneurial orientation had positive effects. The moderating effect of regional innovation capabilities on the relationship between entrepreneurial orientation (risk taking) and performance was also confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.481-487
• /
• 2019

Additive manufacturing is a state-of-the-art manufacturing process technology in which three-dimensional structures are fabricated by laminating two-dimensional sections of a structure using various materials such as plastic, ceramics, and metals. The additive manufacturing technology has the advantage of high design freedom, while the surface property (roughness) of the finished product varies depending on the process conditions, which necessitates performing a post-process after the products are manufactured. In this study, the surface roughness of a structure made of polyamide 12, which was manufactured by SLS (Selective Laser Sintering) and MJF (Multi Jet Fusion) process was compared. The processing condition was classified by the building orientation of structure as 0, 45, and 90 degrees, which is the angle between the analytical surface and the horizontal plane of the fabrication platform. Structures with a hole of various diameters ranging from 1mm to 10mm were manufactured and the hole characteristics (ratio of hole depth to diameter) and results of the specimens were compared. As a result of the surface characteristics analysis, the surface roughness value of the specimens manufactured with a building orientation of $45^{\circ}$ was the highest in both technologies. In the case of the through-hole structure fabrication, the shape was maintained with 5mm and 10mm diameter holes regardless of the building orientation, although the hole forming was difficult for the smaller holes.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.18 no.2
• /
• pp.141-156
• /
• 2023

The advancement of Information and Communication Technology (ICT), along with the expansion of government and private investment in startup discovery and funding, has led to the emergence of startups seeking to generate outstanding results based on innovative ideas. As successful startups serve as role models, the number of aspiring entrepreneurs preparing to launch their own startups continues to increase. However, unlike entrepreneurs who challenge themselves with serial entrepreneurship after experiencing success, early-stage startups face various challenges such as team building, technology development, and fundraising. Accelerators play a dual role of mentor and investor by providing education, mentoring, consulting, network connection, and initial investment activities to help startups overcome various challenges they face and facilitate their growth. This study investigated whether there is a correlation between the characteristics of startups and their entrepreneurial performance, and analyzed whether accelerators mediate the relationship between startup characteristics and entrepreneurial performance. A total of 11 hypotheses were proposed, and a survey was conducted on 302 startup founders and employees located across the country, including the metropolitan area, for empirical research. SPSS 23.0 and Amos 23.0 were used for statistical analysis. Through this study, it was found that factors such as innovation, organizational culture, financial characteristics, and learning orientation among the characteristics of startups, rather than having a direct impact on entrepreneurial performance, are linked to entrepreneurial performance through the role of accelerators. By analyzing the impact factors of startup characteristics on entrepreneurial performance, this study presents research on the role of accelerators and provides institutional improvements. It is expected to contribute to the expansion of investment and differentiated acceleration programs, enabling startups to seize the market and grow stably in the market.

• Journal of Engineering Education Research
• /
• v.21 no.1
• /
• pp.3-13
• /
• 2018

The purpose of this study is to propose a teaching and learning model that can effectively manage convergence education, which is one of the concerns of university education, at the level of course. The pre-collaborative instructional design stage is to prepare the operation of the convergence project course. It shares the common goal and establishes a team of relevant professors to set up the actual convergence project topic and establishes cooperation relationships with industry or community as needed. In the convergence project activity, students will be able to understand the learning objectives, learning activities, evaluation methods, and explain the subject of the convergence project by proceeding with the whole orientation. Students organize teams of interest and conduct learning and design activities on convergence technologies and present their results. In the educational improvement activities, professors will share the lesson process and results and discuss improvements through the improvement seminar. As a result of analyzing the effectiveness of the proposed convergence project based teaching and learning model, the convergence project experience has improved the cooperative self - efficacy for the learners and the results were confirmed that students perceived to achieve the expected learning goal and satisfied with their experience.