• The Korean Journal of Applied Statistics
• /
• v.25 no.2
• /
• pp.279-291
• /
• 2012

When fitting a Cox proportional hazards model with missing covariates, it is inefficient to exclude observations with missing values in the analysis. Furthermore, if the missing-data mechanism is not Missing Completely At Random(MCAR), it may lead to biased parameter estimation. Many approaches have been suggested to handle the Cox proportional hazards model when covariates are sometimes missing, but they are based on the selection model. This paper suggest an approach to handle Cox proportional hazards model with missing covariates by using the pattern-mixture model (Little, 1993). The pattern-mixture model is expressed by the joint distribution of survival time and the missing-data mechanism. In the pattern-mixture model, many models can be considered by setting up various restrictions, and different results under various restrictions indicate the sensitivity of the model due to missing covariates. A simulation study was conducted to show the sensitivity of parameter estimation under different restrictions in a pattern-mixture model. The proposed approach was also applied to mouse leukemia data.

• Journal of Intelligence and Information Systems
• /
• v.11 no.3
• /
• pp.129-139
• /
• 2005

The rapid growth of IT technologies enables the quality of human's daily life to be improved dramatically, Contrasting to the services in previous computing environment directed by user's request, the services in ubiquitous computing era of new IT technology are provided through recognizing users intention and utilizing context-aware information suited to the user. According to the contextual information, agents need to set a dynamic goal to achieve and work collaboratively with other agents. Agents that take control over their behaviors with capability of communicating with other agents become a thrust in this up-coming computing environment. This work focuses on building ontologies, shared knowledge bases among agents, to improve semantical interoperability among agents. More attention is given to the construction and effective management of ontology repository along with its requirement and organization. Ontology agent suggested takes an initiative role to manage the repository in a distributed manner and to facilitate the use of ontology in a multi-agent environment.

• The Journal of the Korea Contents Association
• /
• v.12 no.4
• /
• pp.76-85
• /
• 2012

Through opinion mining, we can analyze the degree of positive or negative sentiments that customers feel about important entities or attributes in online customer reviews. But, the limit of the opinion mining techniques is to provide only simple functions in analyzing the reviews. In this paper, we proposed novel techniques that can analyze the online customer reviews multi-dimensionally. The novel technique is to modify the existing OLAP techniques so that they can be applied to text data. The novel technique, that is, multi-dimensional analytic model consists of noun, adjective and document axes which are converted into four relational tables in relational database. The multi-dimensional analysis model would be new framework which can converge the existing opinion mining, information summarization and clustering algorithms. In this paper, we implemented the multi-dimensional analysis model and algorithms. we recognized that the system would enable us to analyze the online customer reviews more complexly.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.3
• /
• pp.193-198
• /
• 2012

Long term changes in winter time(JFM) sea surface temperature(SST) and marine ecosystem of different Korean waters during last five to six decades were illustrated. Fishing intensity with climate-ocean variability(e.g. SST) have been increasing since 1970s in all of the Korean marine waters. Winter SST around Korean waters went to colder regime in early 1980s and after the late 1980s increased gradually. After 1988/89 CRS all of the waterbody started warmer regime and well coincided with the CRS phenomena. Large predatory, small pelagic and crustacean and mollusks abundance were well coincided by the warmer SST regime after 1988/89 CRS and changed the fishery from demersal fishery to pelagic fishery. Ecosystem parameter of Mean Trophic Level(MTL) showed continuous decreasing trend since mid of 1970s which was mostly affected by the increasing of lower trophic level species. Fishing in balance(FIB) index showed increasing pattern since early 1970s to the late of 1970s and from early 1980s it was almost stable until now. Finally wasp-waist population of anchovy and Japanese sardine have a greater impact to the whole MTL since early 1970s.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.7
• /
• pp.258-264
• /
• 2018

This paper presents application of a differential search (DS) meta-heuristic optimization algorithm for optimal operation of a micro grid system. The DS algorithm simulates the Brownian-like random-walk movement used by an organism to migrate. The micro grid system consists of a wind turbine, a diesel generator, a fuel cell, and a photovoltaic system. The wind turbine generator is modeled by considering the characteristics of variable output. Optimization is aimed at minimizing the cost function of the system, including fuel costs and maximizing fuel efficiency to generate electric power. The simulation was applied to a micro grid system only. This study applies the DS algorithm with excellence and efficiency in terms of coding simplicity, fast convergence speed, and accuracy in the optimal operation of micro grids based on renewable energy resources, and we compared its optimum value to other algorithms to prove its superiority.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.3
• /
• pp.1337-1345
• /
• 2012

The principle of Effective Based Operation applied to the Korean Theater resulted in measurable effects to win the minimum battle. Based on the finding, this study recommends the effect analysis methodology under the V-C interoperability system to acquire a weapon system. This method is followed as below; to confirm the effect data on the organized weapon system, to set MOE, MOP and effect considering the purpose of the analysis, to apply the appropriate operational concept and scenario on the weapon system, and then the available C Model is after action reviewed, adjusted, and given feedback. The V-C interoperability system enables to perform the real-time combat experiment under the virtual synthesized battlefield circumstances. The defensive battle organization and displacement of the future anti-tank guided weapon system was considered in the modeling process. Scenario was written, which encompasses company-level units and the battalion-level operation. Then the available AWAM was embodied and effect-analyzed, which formed the foundation of SBA.

• Proceedings of the Korea Contents Association Conference
• /
• 2007.11a
• /
• pp.386-390
• /
• 2007

In this paper we present an Ontology Instance Management Tool. OntoManager is a user-friendly interactive ontology Instance management tool with webpage annotation tool and an image annotation tool. It supports the user with the task of creating and maintaining ontology-based OWL-markup, creating of OWL-instances, attributes and relationships. It include an ontology browser for the exploration of the ontology and instances and a HTML browser that will display the annotated parts of the text. And OntoManager is an image annotation tool that allows users to markup regions of an image with respect to concepts in an ontology. It provides the functionality to import images, ontologies, instance bases, perform markup, and export the resulting annotations to disk or the Web.

• Journal of KIISE:Software and Applications
• /
• v.36 no.4
• /
• pp.329-334
• /
• 2009

The ontology alignment has two kinds of major problems. First, the features used for ontology alignment are usually defined by experts, but it is highly possible for some critical features to be excluded from the feature set. Second, the semantic and the structural similarities are usually computed independently, and then they are combined in an ad-hoc way where the weights are determined heuristically. This paper proposes the modified parse tree kernel (MPTK) for ontology alignment. In order to compute the similarity between entities in the ontologies, a tree is adopted as a representation of an ontology. After transforming an ontology into a set of trees, their similarity is computed using MPTK without explicit enumeration of features. In computing the similarity between trees, the approximate string matching is adopted to naturally reflect not only the structural information but also the semantic information. According to a series of experiments with a standard data set, the kernel method outperforms other structural similarities such as GMO. In addition, the proposed method shows the state-of-the-art performance in the ontology alignment.

• Convergence Security Journal
• /
• v.12 no.6
• /
• pp.61-67
• /
• 2012

Accordingly the number of smart-phone-based malicious codes is also increasing and their techniques for malicio us purpose are getting more clever and evolved. Among them, the malicious codes related to Android take the major portion and it can be estimated that they are based on open source so that the access to the system is easy. Intent is a technique to support the communication between application's components by transmitting message subjects in Android. Intent provides convenience to developers, but it can be utilized as security vulnerability that allows the developer with a malicious purpose to control the system as intended. The vulnerability of intent security is that personal information can be accessed using discretionally its proper function given to application and smart phone's functions can be maliciously controlled. This paper improves with the Intent security vulnerability caused by the smart phone users' discretional use of custom kernel. Lastly, it verifies the malicious behaviors in the process of installing an application and suggests a technique to watch the Intent security vulnerability in realtime after its installation.

• Convergence Security Journal
• /
• v.12 no.6
• /
• pp.25-30
• /
• 2012

As the network composed of numerous sensor nodes, sensor network conducts the function of sensing the surrounding information by sensor and of the sensed information. Our military has also developed ICT(Information and Communication Technology) along with the methods for effective war by sharing smooth information of battlefield resources through network with each object. In this paper, a sensor network is clustered in advance and a cluster header (CH) is elected for clusters. Before deployment, a certificate is provided between the BS and the sensor nodes, and after clustering, authentication is done between the BS and the sensor nodes. Moreover, inter-CH authentication technique is used to allow active response to destruction or replacement of sensor nodes. Also, because authentication is done twice, higher level of security can be provided.