• The Journal of the Acoustical Society of Korea
• /
• v.33 no.6
• /
• pp.392-399
• /
• 2014

The underwater acoustic communication is characterized by doubly spread channels, which are the delay spread due to multiple paths and the doppler spread due to environmental fluctuations or a moving platform. An equalizer is used to remove the inter-symbol interferences that the delay spread causes, but an equalizer doesn't use an acoustic environment such as a multipath. However, a passive time-reversal mirror is simpler than an equalizer because a matched filter is implemented numerically at the receiver structure along with one-way propagation. In this paper, a passive time-reversal mirror is applied to remove interferences due to a multipath in sea-going experimental data in East Sea in Oct. 2010 and improved communication performance is confirmed. The performance is verified by comparing the signal-to-interference plus noise ratio before/after passive time-reversal mirror. It is also performed independently of the passive time-reversal mirror and adaptive equalizer and the bit error rate is compared to verify the performance of underwater acoustic communication.

• Environmental and Resource Economics Review
• /
• v.29 no.2
• /
• pp.171-194
• /
• 2020

We revisit the impact of oil shocks on the Korean economy and examine how this impact varies depending on a business cycle. First, we estimate the probability of a recession through a logistic probability distribution, and correct the probability to match business cycles announced by the Korea National Statistical Office. We set up a STVAR model to analyze the response of macroeconomic variables to oil shocks according to business cycles. We find that oil shocks during the recession have a negative effect on GDP in the mid- and long-term, but during the expansion, GDP does not show a statistically significant response to oil shocks. We presume that this finding is associated with the factors of both the increase in demand for consumption and the increase in current account during the economic boom. Also, we find that the impact of oil shocks on the price level was also observed differently in terms of the persistence of inflation by business cycle. These results highlight the importance of an application of a regime switching model, which has been widely used in energy economics in recent years.

• The Journal of Korea Robotics Society
• /
• v.6 no.3
• /
• pp.197-209
• /
• 2011

This paper presents a localization system using ceiling images in a large indoor environment. For a system with low cost and complexity, we propose a single camera based system that utilizes ceiling images acquired from a camera installed to point upwards. For reliable operation, we propose a method using hybrid features which include natural landmarks in a natural scene and artificial landmarks observable in an infrared ray domain. Compared with previous works utilizing only infrared based features, our method reduces the required number of artificial features as we exploit both natural and artificial features. In addition, compared with previous works using only natural scene, our method has an advantage in the convergence speed and robustness as an observation of an artificial feature provides a crucial clue for robot pose estimation. In an experiment with challenging situations in a real environment, our method was performed impressively in terms of the robustness and accuracy. To our knowledge, our method is the first ceiling vision based localization method using features from both visible and infrared rays domains. Our system can be easily utilized with a variety of service robot applications in a large indoor environment.

• The Journal of the Korea Contents Association
• /
• v.16 no.12
• /
• pp.480-491
• /
• 2016

This study aims to determine the factors associated with preparation for turnover in youth employees, using a data from the Youth Panel 2007-2013. Study population were composed by 17,037 employees and a generalized estimating equations (GEE) using panel logit model was performed. It was identified that socioeconomic(age, sex, level of education, monthly income and type of employment) and work-related factors(perception of difficulties in performing tasks compared to level of education, perception on the Job-Major match, stabilization of employment, autonomy and empowerment of jobs, peer relationship in workplace) were statistically significant variables. Based on the analysis, dissatisfaction on working environment or condition might lead to employees prepare to turnover and it is a series of activities that to improve welfare and find a suitable job for oneself.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.13 no.6
• /
• pp.698-703
• /
• 2003

This paper presents analog secure communication system about safe speech transmission using chaotic signals. We applied various conditions that happen in actuality communication environment modifying chaotic synchronization and chaotic communication schemes and analyzed restoration performance of speech signal to computer simulation. In transmitter, we made the chaotic masking signal which is added voice signal to chaotic signal using PC(Pecora ＆ Carroll) and SFB(self-feedback) control techniques and transmitted encryption signal to noisy communication channel And in order to calculate the degree of restoration performance, we proposed the definition of analog average power of recovered error signals in receiver chaotic system. The simulation results show that feedback control techniques can certify that restoration performance is superior to quantitative data than PC method about masking degree, susceptibility of parameters and channel noise. We experimentally computed the table of relation of parameter fluxion to restoration error rate which is applied the encryption key values to the chaotic secure communication.

• Geophysics and Geophysical Exploration
• /
• v.12 no.4
• /
• pp.355-360
• /
• 2009

This paper presents mobile robot based down-scale mineral resources exploration test system for the USN (Ubiquitous Sensor Network) based exploration. The system emulates the actual exploration environment. Underneath the metal free test plate, a metal object is attached. A magneto-meter mounted mobile robot runs around on the plate to find the metal. The measured magneto-meter values are transferred to the host PC via wireless network. The system enables to improve the reliability of simulation as well as to help efficient exploration system design. Metal-detecting experiments were carried out to illustrate the efficiency of the proposed system.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.9 no.3
• /
• pp.155-164
• /
• 2009

Digital Content Marketplace based on Interactive Media is defmed as the marketplace for content service between contents supplier and consumer through iDTV environment. This Marketplace is increasing interest to u-Life service with Digital Environment. To Interactive Media, it can contribute to enhance its effectiveness by developing various contents and service model in the initial phase of broadcasting-communication convergence. This study designed metadata using Digital Content marketplace based on Interactive Media. Specially the matadata designing include recommendation-tag for supply supplementary content. It can support self-directed action. Through basic metadata with weight value, it is designed to support supplementary content customer to want on the marketplace. Recommendation-System can be built by many method and to recommend the service content including explicit properties using collaborative filtering method can solve limitations in existing content recommendation.

• The Journal of Korean Association of Computer Education
• /
• v.15 no.2
• /
• pp.1-8
• /
• 2012

General form of the programing education is finding and realizing algorithm to solve problems faster and more efficiently. In other words, it is based on convergent thinking. However, the programming education must have different characteristics to education targets. For elementary school students, it is needed to provide various experience-centered investigation environments. They should learn how to find the most efficient problem solving method by themselves. This study had adopted divergent thinking strategy where divergent thinking and convergent thinking can be repeated at the same time to suit a programming education with great importance of convergent thinking to elementary school leaners, and analyzed its effects. This study was applied to 5th graders, and 12 times of experimental measure classes were conducted by dividing them into the control group that conducted general programming class and the experimental group that conducted a programming class including divergent thinking of CPS model. As a result, CPS model had significant effect on the subordinate elements of creative problem solving skills, self-assurance, independence, and divergent thinking.

• Journal of Digital Convergence
• /
• v.14 no.12
• /
• pp.85-93
• /
• 2016

This study attempts to understand the Facebook advertising diffusion behavior in the situation of increasing consumer activeness. Especially, this study focuses on the influence of motives for using Facebook on Facebook advertising diffusion behavior. -Survey for 243 university students was executed after preliminary interview for extracting question items of motives for using Facebook.- This study finds that the experiencer of Facebook advertising diffusion behavior shows stronger motives for using Facebook than non-experiencer of Facebook advertising diffusion behavior. Logistic regression analysis was conducted to find out the impact of verified variables on Facebook advertising diffusion behavior. It was found that 'self-expression motive' influences on the all Facebook advertising diffusion behavior significantly. Based on the results, academic and practical implications are discussed.

• Journal of The Korean Association of Information Education
• /
• v.4 no.1
• /
• pp.57-71
• /
• 2000

Generally, Web Based Instruction has been deployed through whole studies, but the characteristic that is suit various WBI materials to a course of study is a important problem of instructional practice and it also has not to overlook. Therefore, Today's problem that is application of learning materials about the regional autonomy for Web Based Instruction, A plan that it can be solved in the social studies is propelling in this paper. Each of the whole country's region, the learning about the regional autonomy with centering around text, it is a text book, 'Social Investigation', that is developed specially is teaching until now, but developmental model of learning materials about the regional autonomy for Web Based Instruction is proposed by the efforts for improve this problem. Various learning materials about the regional autonomy for Web Based Instruction applied to learn our regional cultural life through the school homepage with based on this proposal. As a result of this study, By sloughing off old sensibility with centering around text, Student's Ability of self directed learning and solving problem is expanded with the dynamic multimedia regional Webpage's environment