• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.44 no.3
• /
• pp.247-255
• /
• 2016

The purpose of this study is to investigate unsteady-state characteristics of a pintle thruster with various pintle speed. Based on steady state experimental results, non-linear pintle stroke equation is obtained and applied to the unsteady state experimental system. For the unsteady state experiments, three different pintle speeds are used: 3.10 mm/s, 5.65 mm/s, 10.83 mm/s, respectively. Results show that backward pintle stroke results in faster convergence time because of high chamber pressure during backward pintle stroke sequence. During the forward and backward process, thrust curve shows singular points. These phenomenons is caused by variation of mass flow rate, which is mainly due to changes of both chamber pressures and nozzle throat area. This behavior becomes distinctive for a faster pintle speed case.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.7 no.3
• /
• pp.151-162
• /
• 2011

This study defined acceptance of high-tech new product as user's active using the product such as utilizing application software rather than purchasing it. As exploring factors to effect on customer's acceptance, usefulness expectancy was examined from product side and application side. When investigating the exogenous variables to influence on usefulness expectancy from the product side, customer's product knowledge and social influences are put forward to support the hypothesis. From the application side, customer's knowledge about the application and its trust are put to explain usefulness expectancy of the application. Smart phone users were good subjects for this study and most hypotheses were tested using structural equation model and the results are followings. First usefulness expectancy of the product and of application significantly effect on customer's intention to use high-tech new product and also usefulness expectancy of the product positively effects on which of the application. Second customer's perceived knowledge about the product and social influences impact usefulness expectancy of the product. But third customer's perceived trust toward application didn't any positive impact usefulness expectancy of the application. Through the result, there will be several implications. First, from both of side; product and application, customer's usefulness expectancy should be satisfied to be successful in high-tech products market. Second, customer should be Ieant about advantages of the product and knowledge about the application as well, and then trigger their usefulness expectancy.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.2
• /
• pp.15-22
• /
• 2006

This paper presents a novel signal tracking algorithm for GNSS receivers using a MLE technique. In order to perform a robust signal tracking in severe signal environments, e.g., high dynamics for navigation vehicles or weak signals for indoor positioning, the MLE based signal tracking approach is adopted in the paper. With assuming white Gaussian additive noise, the cost function of MLE is expanded to the cost function of NLSE. Efficient and practical approach for Doppler frequency tracking by the MLE is derived based on the assumption of code-free signals, i.e., the cost function of the MLE for carrier Doppler tracking is used to derive a discriminator function to create error signals from incoming and reference signals. The use of the MLE method for carrier tracking makes it possible to generalize the MLE equation for arbitrary codes and modulation schemes. This is ideally suited for various GNSS signals with same structure of tracking module. This paper proposes two different types of MLE based tracking method, i.e., an iterative batch processing method and a non-iterative feed-forward processing method. The first method is derived without any limitation on time consumption, while the second method is proposed for a time limited case by using a 1st derivative of cost function, which is proportional to error signal from discriminators of conventional tracking methods. The second method can be implemented by a block diagram approach for tracking carrier phase, Doppler frequency and code phase with assuming no correlation of signal parameters. Finally, a state space form of FLL/PLL/DLL is adopted to the designed MLE based tracking algorithm for reducing noise on the estimated signal parameters.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.290.1-290.1
• /
• 2013

The electrical characterization of Au islands on TiO2 at nanometer scale (as a Schottky nanodiode) has been studied with conductive atomic force microscopy in ultra-high vacuum. The diverse sizes of the Au islands were formed by using self-assembled patterns on n-type TiO2 semiconductor film using the Langmuir-Blodgett process. Local conductance images showing the current flowing through the TiN coated AFM probe to the surface of the Au islands on TiO2 was simultaneously obtained with topography, while a positive sample bias is applied. The boundary of the Au islands revealed a higher current flow than that of the inner Au islands in current AFM images, with the forward bias presumably due to the surface plasmon resonance. The nanoscale Schottky barrier height of the Au/TiO2 Schottky nanodiode was obtained by fitting the I-V curve to the thermionic emission equation. The local resistance of the Au/TiO2 nanodiode appeared to be higher at the larger Au islands than at the smaller islands. The results suggest that conductive atomic force microscopy can be used to reveal the I-V characterization of metal size dependence and the electrical effects of surface plasmon on a metal-semiconductor Schottky diode at nanometer scale.

• Journal of the Korea Society of Computer and Information
• /
• v.24 no.7
• /
• pp.53-60
• /
• 2019

With the gradual in-depth use of social elements, music social networking has attracted more and more attention and discussion in the industry. Therefore, starting from the user experience theory and purchase intention theory, this paper explores the mechanism of user social experience and purchase intention in mobile music applications, and adds the mediating role of brand attachment on the basis of literature research. Based on previous studies on user experience measurement of social network and evaluation report of mobile music applications in the industry, and combined with in-depth interviews of users, whether the user experience of mobile music applications, which pays more and more attention to social elements, has an impact on purchase intention or not? What specific social experience can help form purchase intention? Are mediating variables at work? In practice, a total of 398 formal questionnaires were collected to obtain first-hand data. Later, reliability analysis, factor analysis and structural equation model test were carried out successively to verify the hypothesis. According to the results of empirical research, firstly, content experience, atmosphere experience and interactive experience in users' social experience of mobile music applications have a significant impact on brand attachment, secondly, atmosphere experience has a significant impact on purchase intention, and thirdly, brand attachment has a significant impact on users' purchase intention. Fourthly, brand attachment plays an intermediary role in the relationship between users' atmosphere experience and content experience and purchase intention. Based on the above research conclusions, the author puts forward corresponding marketing strategy Suggestions, which have certain guiding significance for mobile music applications to improve users' purchase intention, and have certain reference significance for the development of mobile music applications and the expansion of business model.

• Journal of the Korea Society of Computer and Information
• /
• v.26 no.1
• /
• pp.69-76
• /
• 2021

Recentlly neural network approach for solving a singular perturbed integro-differential boundary value problem have been researched. Especially the model of the feed-forward neural network to be trained by the back propagation algorithm with various learning algorithms were theoretically substantiated, and neural network models such as deep learning, transfer learning, federated learning are very rapidly evolving. The purpose of this paper is to study the approaching method for developing a neural network model with high accuracy and speed for solving singular perturbed problem along with asymptotic methods. In this paper, we propose a method that the simulation for the difference between result value of singular perturbed problem and unperturbed problem by using neural network approach equation. Also, we showed the efficiency of the neural network approach. As a result, the contribution of this paper is to show the possibility of simple neural network approach for singular perturbed problem solution efficiently.

• Journal of the Korea Society of Computer and Information
• /
• v.26 no.2
• /
• pp.169-176
• /
• 2021

The purpose of this study is to find out whether smartphone overdependence serves as a significant mediating effect in the relationship of anxiety and school life adjustment to prevent and reduce problems of anxiety and smartphone overdependence among university students and to seek alternatives to improve school life adjustment. For this purpose, a structural equation model analysis was conducted on male and female university students attending a four-year university located in Gwangju Metropolitan City to verify the mediated effect. As the result of the analysis, The mediating effects of smartphone overdependence were statistically significant and presented as a partial medium, showing the direct effect of anxiety directly affecting school life adjustment and the indirect effect of anxiety on school life adjustment by means of smartphone overdependence. Based on these findings, the significance of the study and its implications were discussed, and suggestions were put forward for further study.

• Korea Trade Review
• /
• v.42 no.2
• /
• pp.77-96
• /
• 2017

This paper attempts to analyze the influences of Korean global retailer's service marketing mix on local customers' satisfaction and their loyalty behaviors. Based on a literature review, three hypotheses are putting forward. The data from 139 customers in Weihai, China were used to test these hypotheses. This paper used Structural Equation Modeling to identify the relationship among the service marketing mix, the customer satisfaction and the customer loyalty behaviors. According to the empirical analysis, this study showed satisfactory data-fit of the proposed model and supported two of the three hypotheses. The empirical results indicated that the service marketing mix factors except the promotion factor take significant effect on the local customer satisfaction, and this in turn have influence on the customer loyalty behaviors. The result shows that Korean global retailers will need to leverage service marketing mix strategically when entering China. Practical implications of these findings needs to be considered for the global retailer to establish an effective marketing strategy.

• Korea Trade Review
• /
• v.41 no.5
• /
• pp.285-304
• /
• 2016

e-Commerce in Small and Medium-sized Enterprises(SMEs) provides a platform for fair competition between SMEs and large enterprises, and brings economic benefits to SMEs. Thus in the recent years, the e-Commerce in SMEs developed rapidly. However, the overall proportion of e-Commerce in SMEs in China remains low, and many SMEs' decision-makers tend to feel that their business is relatively weak in terms of information construction of scale and financial management, thus they keep the 'wait and see' attitude about the e-Commerce development decisions. Therefore, SMEs are facing three puzzles about e-Commerce application. First, if the companies need to implement e-Commerce, what are the e-Commerce adoption decision factors. Second, what are the successful implementation factors of e-Commerce. And how about the relationship between them. The third is how to measure the implementation effect of e-Commerce. What is the performance evaluation factors of e-Commerce. In this paper, the theoretical and empirical exploration and research are conducted towards these SMEs. Considering the actual situation of SMEs, this paper builds a theoretical model, then puts forward relevant hypothesis. This paper analyzes present influencing factors based on enormous research papers, and finally discovers the critical successful factors in doing business with e-Commerce in SMEs by conducting Structural Equation Modeling. Five critical factors are verified by cases of enterprise by demonstration study. Lastly, we can draw a conclusion that the innovation ability of leaders, the IT support of leaders and e-Commerce strategies are the success factors of e-Commerce for Chinese SMEs.

• The Journal of Asian Finance, Economics and Business
• /
• v.9 no.3
• /
• pp.95-103
• /
• 2022

This study aimed to find the mediating impact of entrepreneurial education during COVID-19 on entrepreneurial intention among university students from major cities of Pakistan. Majority of businesses shifted to online from offline mode as a result of COVID-19 pandemic. This created a great opportunity for university students to become entrepreneurs without much investment during COVID-19. Primary data for this study was collected with the help of an adopted questionnaire from previous studies. An online survey was considered appropriate due to the COVID-19 situation in the country. The number of data samples collected from the major cities of Pakistan was 460. The research hypothesis was tested with the help of SmartPLS by using least square structural equation modeling. Findings revealed there is full mediation of entrepreneurial education during COVID-19 between the self-efficacy, subjective norms, and attitude towards entrepreneurship for entrepreneurial intention during COVID-19 among university students. Therefore, the research confirmed the application of the theory of planned behavior among university students in Pakistan with regards to factors such as self-efficacy, subjective norms, attitude towards entrepreneurship and entrepreneurial intention. The present study also concludes that all students regardless of their area of study such as Business and Engineering look forward to become entrepreneurs during COVID-19. The students opting for entrepreneurship had either formal or informal entrepreneurial education during COVID-19.