• Journal of the Institute of Electronics Engineers of Korea SD
• /
• 제38권8호
• /
• pp.43-53
• /
• 2001

Wavelength conversion devices are essential to build an expanding all-optical network, and various types of wavelength conversion techniques are being researched. Among them, wavelength conversion based on the cross phase modulation in a directionally coupled semiconductor optical amplifier has been introduced and the concept has been experimentally proved. In this paper, a split-step method is applied to properly model the mentioned wavelength converter in the time-domain and various characteristics have been analyzed. It is shown that the present modeling approach can explain the results of the reported experimental results. Furthermore the wavelength conversion is shown to be well performed when the input signal wave and the converted wave travels in the opposite direction. The simulation shows that the positive and negative chirping appear simultaneously at both the leading and trailing of edges of the optical pulse.

• Journal of Intelligence and Information Systems
• /
• 제21권1호
• /
• pp.119-142
• /
• 2015

With the explosive growth in the volume of information, Internet users are experiencing considerable difficulties in obtaining necessary information online. Against this backdrop, ever-greater importance is being placed on a recommender system that provides information catered to user preferences and tastes in an attempt to address issues associated with information overload. To this end, a number of techniques have been proposed, including content-based filtering (CBF), demographic filtering (DF) and collaborative filtering (CF). Among them, CBF and DF require external information and thus cannot be applied to a variety of domains. CF, on the other hand, is widely used since it is relatively free from the domain constraint. The CF technique is broadly classified into memory-based CF, model-based CF and hybrid CF. Model-based CF addresses the drawbacks of CF by considering the Bayesian model, clustering model or dependency network model. This filtering technique not only improves the sparsity and scalability issues but also boosts predictive performance. However, it involves expensive model-building and results in a tradeoff between performance and scalability. Such tradeoff is attributed to reduced coverage, which is a type of sparsity issues. In addition, expensive model-building may lead to performance instability since changes in the domain environment cannot be immediately incorporated into the model due to high costs involved. Cumulative changes in the domain environment that have failed to be reflected eventually undermine system performance. This study incorporates the Markov model of transition probabilities and the concept of fuzzy clustering with CBCF to propose predictive clustering-based CF (PCCF) that solves the issues of reduced coverage and of unstable performance. The method improves performance instability by tracking the changes in user preferences and bridging the gap between the static model and dynamic users. Furthermore, the issue of reduced coverage also improves by expanding the coverage based on transition probabilities and clustering probabilities. The proposed method consists of four processes. First, user preferences are normalized in preference clustering. Second, changes in user preferences are detected from review score entries during preference transition detection. Third, user propensities are normalized using patterns of changes (propensities) in user preferences in propensity clustering. Lastly, the preference prediction model is developed to predict user preferences for items during preference prediction. The proposed method has been validated by testing the robustness of performance instability and scalability-performance tradeoff. The initial test compared and analyzed the performance of individual recommender systems each enabled by IBCF, CBCF, ICFEC and PCCF under an environment where data sparsity had been minimized. The following test adjusted the optimal number of clusters in CBCF, ICFEC and PCCF for a comparative analysis of subsequent changes in the system performance. The test results revealed that the suggested method produced insignificant improvement in performance in comparison with the existing techniques. In addition, it failed to achieve significant improvement in the standard deviation that indicates the degree of data fluctuation. Notwithstanding, it resulted in marked improvement over the existing techniques in terms of range that indicates the level of performance fluctuation. The level of performance fluctuation before and after the model generation improved by 51.31% in the initial test. Then in the following test, there has been 36.05% improvement in the level of performance fluctuation driven by the changes in the number of clusters. This signifies that the proposed method, despite the slight performance improvement, clearly offers better performance stability compared to the existing techniques. Further research on this study will be directed toward enhancing the recommendation performance that failed to demonstrate significant improvement over the existing techniques. The future research will consider the introduction of a high-dimensional parameter-free clustering algorithm or deep learning-based model in order to improve performance in recommendations.

• The Journal of Korean Academic Society of Nursing Education
• /
• 제15권1호
• /
• pp.32-43
• /
• 2009

Purpose: The purpose of this study was to identify the trend of nursing research by analyzing the doctoral dissertations in one college of nursing in Korea. Method: The areas of research, the methodological characteristics, and theories used in the research were explored in all doctoral dissertations (n=120) published from 1989 to 2006. Result: Mainly "Nursing" has been studied (44.9%) among four meta-paradigms of nursing science. The "client" domain (46.7%) and the "practice" domain (41.7%) were most frequently studied in type of nursing knowledge. The main purpose of the thesis was to develop nursing interventions and examine the effectiveness of the practice (40.8%) in quantitative research. Almost all (94.7%) of the qualitative dissertation studies were to explore phenomena in the nursing field. Almost half of the dissertations (43.9%) were an experimental design, 34.7% were a model construction, and 15.8% were a qualitative design. The majority of dissertations (83.3%) were to apply the specific theory and almost half (43.8%) studied borrowed theories from other fields. Conclusion: It is necessary to develop more rigorous and various research designs such a longitudinal design, or randomized controlled trial and this will lead to expanding the body of nursing knowledge.

• Journal of Intelligence and Information Systems
• /
• 제23권4호
• /
• pp.77-110
• /
• 2017

Recently, the diversification and individualization of consumption patterns through the web and mobile devices based on the Internet have been rapid. As this happens, the efficient operation of the offline store, which is a traditional distribution channel, has become more important. In order to raise both the sales and profits of stores, stores need to supply and sell the most attractive products to consumers in a timely manner. However, there is a lack of research on which SKUs, out of many products, can increase sales probability and reduce inventory costs. In particular, if a company sells products through multiple in-store stores across multiple locations, it would be helpful to increase sales and profitability of stores if SKUs appealing to customers are recommended. In this study, the recommender system (recommender system such as collaborative filtering and hybrid filtering), which has been used for personalization recommendation, is suggested by SKU recommendation method of a store unit of a distribution company that handles a homogeneous brand through a plurality of sales stores by country and region. We calculated the similarity of each store by using the purchase data of each store's handling items, filtering the collaboration according to the sales history of each store by each SKU, and finally recommending the individual SKU to the store. In addition, the store is classified into four clusters through PCA (Principal Component Analysis) and cluster analysis (Clustering) using the store profile data. The recommendation system is implemented by the hybrid filtering method that applies the collaborative filtering in each cluster and measured the performance of both methods based on actual sales data. Most of the existing recommendation systems have been studied by recommending items such as movies and music to the users. In practice, industrial applications have also become popular. In the meantime, there has been little research on recommending SKUs for each store by applying these recommendation systems, which have been mainly dealt with in the field of personalization services, to the store units of distributors handling similar brands. If the recommendation method of the existing recommendation methodology was 'the individual field', this study expanded the scope of the store beyond the individual domain through a plurality of sales stores by country and region and dealt with the store unit of the distribution company handling the same brand SKU while suggesting a recommendation method. In addition, if the existing recommendation system is limited to online, it is recommended to apply the data mining technique to develop an algorithm suitable for expanding to the store area rather than expanding the utilization range offline and analyzing based on the existing individual. The significance of the results of this study is that the personalization recommendation algorithm is applied to a plurality of sales outlets handling the same brand. A meaningful result is derived and a concrete methodology that can be constructed and used as a system for actual companies is proposed. It is also meaningful that this is the first attempt to expand the research area of the academic field related to the existing recommendation system, which was focused on the personalization domain, to a sales store of a company handling the same brand. From 05 to 03 in 2014, the number of stores' sales volume of the top 100 SKUs are limited to 52 SKUs by collaborative filtering and the hybrid filtering method SKU recommended. We compared the performance of the two recommendation methods by totaling the sales results. The reason for comparing the two recommendation methods is that the recommendation method of this study is defined as the reference model in which offline collaborative filtering is applied to demonstrate higher performance than the existing recommendation method. The results of this model are compared with the Hybrid filtering method, which is a model that reflects the characteristics of the offline store view. The proposed method showed a higher performance than the existing recommendation method. The proposed method was proved by using actual sales data of large Korean apparel companies. In this study, we propose a method to extend the recommendation system of the individual level to the group level and to efficiently approach it. In addition to the theoretical framework, which is of great value.

• The Journal of the Korea Contents Association
• /
• 제16권3호
• /
• pp.52-60
• /
• 2016

Many hidden aspects of society around the world that has been lurking as risk factors have been ultimately connected to disasters. Such connection did not just stop with massive damages to properties and loss of lives but became a serious social issue. Especially in the case for Korea, because the country has gone through abrupt economic growth which has resulted in rapid urbanization and expansion of economic scale, Korea has been caught in a vicious cycle of experiencing human and social calamities repeatedly. Due to the seriousness of such problem, there's been continued research in various fields for managing disasters, and the domain of knowledge has been expanding with complexity. The following study went beyond the perspectives of disaster prevention study, disaster prevention engineering and social sciences suggested from previous research directions in disaster and disaster prevention, and attempted an alternative research method by approaching from a service design perspective. During the process, the paper looked over the summary on disaster and service design. By applying it on disaster prevention projects, the research sets forth and discusses effective and practical disaster prevention service design. Through specific case studies, the research methodology applied was verified, and the purpose of the study was carried out in the perspective of real world applications different from textbook type discussions. It is expected that through the disaster prevention service design process and platform that were discovered during the research result, defining and understanding disaster prevention service design will be made apparent. Additionally, the research is expected to be used as a basic building block for building a visualized plan for tangible and intangible factors related to disasters before the disaster process through such proposed disaster prevention service design.

• Journal of Korean Society for Geospatial Information Science
• /
• 제23권1호
• /
• pp.3-14
• /
• 2015

As buildings in the downtown area, such as the complex building connected to the skyscraper and the underground facility, have become large and complex, the range of target domain of the space information service is rapidly expanding to the interior space; it is considered that this change will create various demands of service such as the indoor geospatial information base safety, the management of facility, and the interior navigation in the future, along with spread of mobile devices and development of IT technology. As for the indoor geospatial information, however, there is no certification standard of the established indoor geospatial information data quality, so preparing the certification standard is urgent. Thus, this study reviewed foreign and domestic research cases and prepared measures for quality verification of the indoor geospatial information to conduct a verification test of the Yeongdeungpo Station indoor geospatial information, established in 2014. As a result, through the verification test of the method and standard of the indoor geospatial information quality certification suggested by this research, it was identified that the uniform and higher quality data could be classified, and the types of error high frequently occurring could be investigated. These results are expected to be utilized as the basic data for establishing quality certification system for the indoor geospatial information in the future.

• Journal of Science and Technology Studies
• /
• 제18권3호
• /
• pp.217-255
• /
• 2018

Bitcoin, which appeared in 2008, was merely a conceptual virtual currency, but it now enjoys the status as actual money. Bitcoin is an electronic money system that can be traded directly without a central trust institution. Thanks to the popularization of Bitcoin, blockchain technology has become a widespread concern. That technology is expanding not only the currency mechanism, but also a variety of other services. The possibility of a blockchain in relation to actual currency is ongoing. This paper investigates the technological characteristics and social construction of the blockchain by comparing the cases of Bitcoin, Namecoin, and MediBloc among blockchain applications. Namecoin emerged in 2013 is an attempt to replace the centralized Internet Domain Name System(DNS). There has been controversy over that current system for a long time, but replacing the already established system is not easy. Nevertheless, Namecoin has potential as an alternative. Meanwhile, MediBloc is an application that involves distributed management of medical data in South Korea. MediBloc claims that the key producers of medical data are patients themselves. This is to challenge to the question who is a knowledge producer of medical data. Through these three cases, it has discussed that blockchain technology does supports to form more democratic decision-making or simply provide a technical solution as automation. As a citizen, we can intervene in the realization of blockchains by presenting social agenda. This will be a method of the social construction of technology.

• 한국노년학
• /
• 제40권2호
• /
• pp.269-289
• /
• 2020

The purpose of this study was to analyze the policy and programs of the Seoul50Plus Foundation and to propose policies and programs to promote active aging of middle-aged and elderly people. A single case study was utilized as a research method. The analysis framework of case was approached with four frameworks: the context of policy and program, ideology-goal analysis of policy and program, supplier and customer analysis of policy and program, and process and domain analysis of policy and program. The analysis data included the homepage content of the Seoul50Plus Foundation, related 50+ policy and program data, active aging research papers at home and abroad, and presentation and meeting materials. The results of the research showed that the policy and program background and environment were essential elements for responding to environmental changes in the aging society. In terms of the philosophy-goal, job creation, social participation, and approach to life design were systematically carried out for the ideology of 'creating a new life vision' and promoting active aging. In terms of subject-target, the subject of policy implementation is systematically composed of three stages: 50+ foundation, 50+ campus, and 50+ center. The target was limited to 50+ generations(age 50~64) and had a problem that is limited to applicants. In the process-area analysis, programs such as educational support, work and entrepreneurship support, counseling information, and new-age cultural creation activities were designed to increase added value according to the characteristics of the middle-aged people. In conclusion, the future Seoul50Plus Foundation's policy and lifelong learning programs need to be systematically promoted through cooperation with businesses and universities, expanding the target audience, matching the characteristics of the middle-aged and elderly, and linkage among programs.

• Journal of the Korea institute for structural maintenance and inspection
• /
• 제18권4호
• /
• pp.50-58
• /
• 2014

Due to the cost burden of new construction, the necessity of repair and retrofitting of aged structures is sharply increasing as the domain of repair and retrofitting construction is expanding. Because of the necessity, new technologies for repair and retrofitting are continuously studied in Korea and foreign countries. Steel adhesive method, fiber reinforced plastic (FRP) surface adhesive method, and external prestressing method are used to perform the repair and retrofitting works in Korea. In order to consider a repair method using steel mesh reinforced cement mortar (SMCM), 3-point flexural member test was conducted considering repair area and layer number of SMCM. Five types of specimens including ordinary reinforced concrete (RC) specimen with dimensions of $1400{\times}500{\times}200$ (mm) were cast for testing the deflection measurement, a LVDT was installed at the top center of the specimens. Also, a steel strain gauge and a concrete strain gauge were placed at the center of the specimens. A steel strain gauge was also installed on the shear reinforcement. The 3 point flexural member test results showed that the maximum load of SMCM reinforced specimen was higher than that of basic RC specimen in all of the load-displacement curves. Also, the results showed that, when the whole lower part of the basic RC specimen was reinforced, the maximum load and strain were 1.18 and 1.37 times higher than that of the basic RC specimen, respectively. Each specimen showed a slightly different failure behavior where the difference of the results was caused by the difference in the adhesive level between SMCM and RC. Particularly, in SM-B1 specimen, SMCM spalled off during the experiment. This failure behavior showed that the adhesive performance for RC must be improved in order to utilize SMCM as repair and retrofitting material.

• Journal of Korean Society of Archives and Records Management
• /
• 제1권1호
• /
• pp.37-52
• /
• 2001

1. establishment and development of China archives science: With the centuries-old history of archives and archives management, early China archives science came into being in 1930s, and the research pushed forward by archives enterprise has made great achievements since then. 1.1 Expanding research fields: Foundation