• The Korean Journal of Applied Statistics
• /
• v.28 no.6
• /
• pp.1209-1216
• /
• 2015

Competing-risks events are often observed in a clustered clinical study such as a multi-center clinical trial. We propose a joint modelling approach via a shared frailty term for competing risks survival data from a cluster. For the inference we use the hierarchical likelihood (or h-likelihood), which avoids an intractable integration. We derive the corresponding h-likelihood procedure. The proposed method is illustrated via the analysis of a practical data set.

• Journal of the Korean Operations Research and Management Science Society
• /
• v.16 no.2
• /
• pp.49-64
• /
• 1991

In this paper, we present a stepwise design methodology for relational databases using a new conceptual data model, the MAO(Multiple Aspects-based Object) model. Our methodology consists two steps : first, data requirements are conceptualized using the MAO model with concepts such as objects types and aspect types : second, the MAO model is transformed into the third normal form inn the relational model supported by commercial DBMs. A top-down approach is used for the MAO modelling in the first, step, and the transformation process in the second step can be automated. Our methodology supports easier and more database design of real world than other methodologies using existing data models.

• Journal of the Korean Data and Information Science Society
• /
• v.22 no.3
• /
• pp.605-612
• /
• 2011

In multi-center randomized clinical trial the treatment eect may be changed over centers. It is thus important to investigate the heterogeneity in treatment eect between centers. For this, uncorrelated random-eect models assuming independence between random-eect terms have been often used, which may be a strong assumption. In this paper we propose a correlated frailty modelling approach of investigating such heterogeneity using the hierarchical-likelihood method when the outcome is time-to-event. In particular, we show how to construct a proper prediction interval for frailty, which explores graphically the potential heterogeneity for a treatment-by-center interaction term. The proposed method is illustrated via numerical studies based on data from the design of a multi-center clinical trial.

• The Transactions of the Korea Information Processing Society
• /
• v.7 no.4
• /
• pp.1050-1061
• /
• 2000

This paper presents a new object model, LOM(Lightweight Object Model) and an implementation method for the distributed trader in heterogeneous distributed computing environment including mobile network. Trader is third party object that enables clients to find suitable servers, which provide the most appropriate services to client in distributed environment including dynamic reconfiguration of services and servers. Trading service requires simpler and more specific object model than genetic object models which provide richer multimedia data types and semantic characteristics with complex data structures. LOM supports a new reference attribute type instead of the relationship, inheritance and composite attribute types of the general object oriented models and so LOM has simple data structures. Also in LOM, the modelling step includes specifying of the information about users and the access right to objects for security in the mobile environment and development of the distributed storage for trading service. Also, we propose and implementation method of the distributed trader, which integrates the LOM-information object model and the OMG (object Management Group) computational object model.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.6 no.2
• /
• pp.94-106
• /
• 2004

Determining those gaps in agricultural and other information to improve agrometeorological analyses for agriculture is a large task. The effective integration of appropriate data systems, including remote sensing systems, with agricultural systems modelling capability is described as a worthy outcome in this endeavour. Data issues, including those associated with data length, quality, maintenance, and archiving remain serious issues to be addressed. The role of remote sensing and geographic information systems in agrometeorology is important and is explored here. The value of simulation models to provide the synthesis for future agrometeorological requirements is further elucidated.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
• /
• 2009.04a
• /
• pp.49-53
• /
• 2009

In this study, point gravity was measured to achieve terrestrid gravity data and the gravity is important element in precise geoid modelling. Surveys the relative gravity of 56 stations on 1st level route. In addition, it calculates gravity values, analysis gravity survey results using tidal correction, drift correction, datum-free adjustment. These point gravity data could be contribute in development of precise geoid model.

• Journal of electromagnetic engineering and science
• /
• v.16 no.1
• /
• pp.1-6
• /
• 2016

Computer simulations were conducted to demonstrate the generation of microwave-induced thermoacoustic signal. The simulations began with modelling an object with a biological tissue characteristic and irradiating it with a microwave pulse. The time-varying heating function data at every particular point on the illuminated object were obtained from absorbed electric field data from the simulation result. The thermoacoustic signal received at a point transducer at a particular distance from the object was generated by applying heating function data to the thermoacoustic equation. These simulations can be used as a foundation for understanding how thermoacoustic signal is generated and can be applied as a basis for thermoacoustic imaging simulations and experiments in future research.

• Proceedings of the Korea Technology Innovation Society Conference
• /
• 2017.11a
• /
• pp.1321-1321
• /
• 2017

Recently the attention to the 4th industrial revolution has been increasing. In the 4th industrial revolution era, the boundaries of physical space, digital space, and biological space are becoming blurred since the active convergence between various fields There are a lot of issues on the 4th industrial revolution such as artificial intelligence, internet of thing, big data, and cyber physical system. Accordingly, this study aims to analyse the main issues of the 4th industrial revolution. Data mining such as topic modelling method is used for the analysis. This study is expected to be helpful for the researcher and policy maker of the 4th industrial revolution.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.11 no.3
• /
• pp.281-291
• /
• 1999

A computer code based on a node equation method has been developed for the analysis of pipe network. Both data structure and object-oriented programming technique are used for pipe and node modelling, in which simplification process is applied to complicated and large pipe network. The semi-direct solver, ILU-CGS, improves greatly both the accuracy and the rate of convergence. The computational result of high-pressure pipe network of city gas in Taegu shows the good agreement with the real data.

• Korean Journal of Computational Design and Engineering
• /
• v.7 no.4
• /
• pp.262-268
• /
• 2002

Octree representation has the advantage of being able to represent complex shapes approximately through the repetition of simple primitive shapes. Due to this reason, octree representation together with VRML(Virtual Reality Modelling Language) is usually used for approximating 3D shapes. Since the data size of octree representation increases rapidly as 3D shape to be represented is more and more complicated, its transmission time also increase. In this paper, provided is the new octree representation and encoding/decoding scheme for real-time transmission through the internet in order to visualize 3D geometric data of large size approximately.