• Korean Journal of Mathematics
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• v.22 no.1
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• pp.85-89
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• 2014

A bounded linear Hilbert space operator T is said to be k-quasi-class A operator if it satisfy the operator inequality $T^{*k}{\mid}T^2{\mid}T^k{\geq}T^{*k}{\mid}T{\mid}^2T^k$ for a non-negative integer k. It is proved that if T is a k-quasi-class A contraction, then either T has a nontrivial invariant subspace or T is a proper contraction and the nonnegative operator $D=T^{*k}({\mid}T^2{\mid}-{\mid}T{\mid}^2)T^k$ is strongly stable.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1195-1200
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• 2004

We introduce an introductory engineering education course for engineering majors and non-engineering majors. This course does not require any previous knowledge and experience on engineering. It requires strong curiosities and imaginations on current and future society we live in, where technology is inseparable ingredient. Course encourages attendees to explore fundamental issues of engineering: what is proper technology and what are proper ways of exercising engineering, issues dealt in soft engineering. Since course topics cover many aspects of technology, traditional learning methods fail to be successful and efficient. Various efficient learning methods have been proposed and implemented. We utilize various interactive tangible media, which include simulated thought experiments and physical media experiences. About 20 episodes in short film format are produced based on scenario written according to related issues selected. Physical media like interactive robots are introduced for attendees' stimulated experiences. We summarize our exciting experiments on interactive teaching experiences at Pusan National University which include on/off-line interactions, assignments, projects, and evaluations.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.160-163
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• 2003

For the purpose of rolling hard metals such as silicon steel and non-ferrous metals, the backup roll driven-type mill has been widely used in cold rolling industry. Since the backup roll drive results in horizontal bending of the work rolls and therefore exerted reciprocal action on the roll gap contour, the selection of slim work rolls is very restricted. In this paper, we present an analytic equation based scheme to determine a proper horizontal position of work roll minimizing the horizontal force subject to mechanical constraints.

• Journal of the Korean Society of Tobacco Science
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• v.1 no.1
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• pp.21-32
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• 1979

This experiment was carried out to fond out the proper transplanting time of burley tobacco since the transplanting dates In Jeonla Do varied from early April to late June. In this experiment , the first transplanting was lone on April 10 and continued until June, 20 with the total of 7 Plantings. The results of experiment from 1977 to 1978 showed no significant differences on value per kg (won /kg ) from April 10 to May 10 whether the plants were grown with mulching or non -mulching The yield and price per 10a were highest with May, 10 transplanting . The proper transplanting date obtained by regression analysis, however, was between May, 1 to May 5.

• Structural Engineering and Mechanics
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• v.62 no.5
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• pp.537-550
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• 2017

Structural sizing is a rewarding task due to its non-convex constrained nature in the design space. In order to provide both global exploration and proper search refinement, a hybrid method is developed here based on outstanding features of Evolutionary Computing and Teaching-Learning-Based Optimization. The new method introduces an observer phase for memory exploitation in addition to vector-sum movements in the original teacher and learner phases. Proper integer coding is suited and applied for structural size optimization together with a fly-to-boundary technique and an elitism strategy. Performance of the proposed method is further evaluated treating a number of truss examples compared with teaching-learning-based optimization. The results show enhanced capability of the method in efficient and stable convergence toward the optimum and effective capturing of high quality solutions in discrete structural sizing problems.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.9
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• pp.84-93
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• 1996

This paper describes the development of new feature positioning method which embedded into the top-down assembly modeling system supporting conceptual design. In this work, the user provides the geometric constraints representing the position and size of features, then the system calculates their proper solution. The use of geometric constraints which are easy to understand intuitively enables the user to represent his design intents about geometric shapes, and enables the system to propagate the changes automatically when some editing occurs. To find the proper solution of given constraints, the Selective Solving Method in which the redundant or conflict equations are detected and discarded is devised. The validity of feature shapes satisfying the constraints can be maintained by this technique, and under or over constrained user-defined constraints can also be estimated. The problems such as getting the initial guess, controlling the multiple solutions, and dealing with objects of rotational symmetry are also resolved. Through this work, the feature based modeling system can support more general and convenient modeling method, and keeps the model being valid during modifying models.

• Tribology and Lubricants
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• v.22 no.1
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• pp.20-25
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• 2006

The stress behavior analysis of a-rings and packing for a LPG filling unit has been presented using a finite element analysis technique by non-linear MSC/MARC program. The sealing performance and endurance of a-rings and packing are affected by working conditions such as filling pressure, friction coefficient, compression ratio, and material properties. The elastomeric polymers of O-rings and packing are nitrile butadiene rubber (NBR) and polytetrafluoroethylene (PTFE), which are selected as proper materials of a-rings and packing based on the stress analysis results. The calculated FEM results showed that the proper material of O-ring is NBR as a secondary sealing component and the recommended material of packing is PTFE as a primary sealing unit during a LPG filling process.

• Journal of the Optical Society of Korea
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• v.13 no.3
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• pp.367-372
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• 2009

In this paper we propose an electronic domain timing phase selection scheme for the optical communication systems suffering from inter-symbol-interference (ISI) distortion due to chromatic dispersion (CD) or polarization mode dispersion (PMD). In the presence of CD/PMD a proper timing phase selection is important for discrete time domain equalizers, since different timing phases produce different nonlinear ISI channels of different severity. The proposed timing phase recovery scheme based on dispersion minimization (DM) practically approximates the optimal minimum mean squared error (MMSE) timing phase without training signals which reduces overall throughput substantially, especially in time-varying channels such as PMD. The simulation results show that the proposed DM timing agrees with MMSE timing phase, under proper normalization of the received signals, for various dispersion and OSNR.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.147-154
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• 1999

This paper presents a procedure for the frequency-domain analysis of a non-proportionally damped structure subjected to stationary seismic loads and for the finding of proper damper locations through simple analysis procedure without iteration. The shear areas of the dampers are decided in proportion to the magnitude of the components of the primary mode shape vector and to the root mean square values of the story drifts, The root-mean-squear responses are obtained using a power spectral density function for the ground acceleration. the results are compared with those obtained from damper placement decided in sequency based on the maximum story drift. According to the results the reliability of the proposed method turns out to be satisfactory compared to the methods which required iteration.

• Korean Journal of Community Nutrition
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• v.9 no.4
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• pp.501-510
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• 2004

This study was carried out to investigate the dietary attitudes, nutrition knowledge, nutrient intake, eating-related characteristics of dancing major and non-major female university students. The survey was conducted from October 1 to November 10, 2003 by questionnaires and data analyzed by SPSS program. The results are summarized as follows: 25.5% of the underweight group, 53.6% of the normal weight group, 12.5% of the overweight group and 66.7% of the obese group had correct perception about their body image. Eighty-one point three percent of the dancing majors and 77.2% of the non-majors were concerned about weight control, and 71.3% of the dancing majors and 64.5% of the non-majors had weight control experiences. There were no significant differences in nutrition knowledge scores and dietary attitude scores between dancing majors and non-majors. There were no significant differences in ‘predisposition to obesity scores’ between dancing majors and non-majors, and the scores were low. ‘Predisposition to anorexia’ scores and ‘uncontrollable urges to eat’ scores were significantly higher in the dancing majors compared to the non-majors. Intakes of the nutrients were lower than those of the Korean recommended dietary allowances (RDAs), except vitamin C in the dancing majors. Intakes of calories, calcium and iron were lower than those of the RDAs in the non-majors. Dietary attitude was positively correlated with nutrition knowledge but was negatively correlated with ‘uncont-rollable urges to eat’. In the dancing majors, ‘predisposition to obesity’ showed significantly positive correlation with obesity rate and ‘uncontrollable urges to eat’ and was negatively correlated with nutrition knowledge and dietary attitude. In the non-majors, obesity rate showed positive correlation with ‘predisposition to obesity’ and ‘uncontrollable urges to eat’. Therefore proper nutritional education program and recommended dietary allowances are required for dancing majors to improve their nutritional status.