• Journal of Korean Institute of Industrial Engineers
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• v.29 no.1
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• pp.78-89
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• 2003

Ordering is performed to reduce the amount of fill-ins of the Cholesky factor of a symmetric positive definite matrix. This paper proposes a new ordering algorithm that reduces the fill-ins of the Cholesky factor iteratively by elimination tree rotations and clique separators. Elimination tree rotations have been used mainly to reorder the rows of the permuted matrix for the efficiency of storage space management or parallel processing, etc. In the proposed algorithm, however, they are repeatedly performed to reduce the fill-ins of the Cholesky factor. In addition, we presents a simple method for finding a minimal node separator between arbitrary two nodes of a chordal graph. The proposed reordering procedure using clique separators enables us to obtain another order of rows of which the number of till-ins decreases strictly.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.65-70
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• 1992

The hindered internal rotation effect of methyl group on chemical reaction was studied for cis-trans isomerization reaction of 1-bromopropene system using RRKM technique. A comparative study of the isomerization rates was also performed between the rigid and allowed internal rotations. The calculated rate of rigid cis-trans isomerization of 1-bromopropene was shown to be three times higher than its other halogenated propene homologues with its internal rotations and found to be in good agreement with experimental observations. These findings could be explained reasonably well in terms of the differences of the rotational barrier heights among halogenated propenes and correlated with the relatively low internal rotation barrier of cis-1-bromopropene, 230 cal/mol, compared to those of other cis-1-halopropenes, 700-800 cal/mol, and trans-1-halopropenes, 2.0-2.4 kcal/mol.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.165-166
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• 2009

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.213-222
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• 1999

Elastic-plastic methods have been used for the better prediction of the actual behavior of continuous-composite plate girder bridges in the overload and maximum load analysis. The structural evaluation using ALFD(Alternate Load Factor Design) uses the elastic-plastic analysis. The plastic rotations that remain after the load is removed can be occurred by the yielding locations of the maximum moment section. This situation can occur due to the residual stresses even if the moment is below the theoretical yield moment. The local yielding causes positive automoments that assure elastic behavior under subsequent overloads. In this study, the automoments at the piers occurred due to the unit plastic rotations and other locations were calculated by the conjugate-beam method and three-moment equation, using the nine design span with progressively smaller pier sections. The automoments were determined by the developed computer programs in this study in which the moments and plastic rotations from the continuity and moment-inelastic rotation relationships must be equal. And also the ratings of 3-span continuous composite plate girder bridges with non-compact section were carried out according to the Korean Highway Bridge Specification.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.61-70
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• 2010

This study presents free vibration analyses of perforates steel plates with various cutouts. Four different parameters (shape, size, curvature radius ratio, and rotation of cutouts) were considered to investigate the effects of those parameters on the free vibration characteristics, such as natural frequencies of the perforated steel plates. Three different shapes of cutouts are circle, square, and triangle, and the considered sizes are 5, 10, 15, 20, and 25 mm. For the triangular and square cutouts, the characteristic radii of the inscribed circles of those cutouts were defined. In addition, the curvature radius ratio was defined as the ratio of curvature radius of bluntness and the characteristic radius. Then, total seven different curvature radius ratios (0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1) were considered. To investigate the rotation effect of the cutouts, it was considered four rotations ($0^{\circ}$, $15^{\circ}$, $30^{\circ}$, and $45^{\circ}$) for the square cutouts and three rotations (0, 15, and 30) for the triangular cutouts. All the free vibration analyses were conducted using a general purpose finite element program. From the analyses we found that the most influential parameter for the free vibration response of the perforated plates is the size of cutout. The other factors such as the shape, curvature radius ratio, and rotation are minors; they mainly change the natural frequency as long as the size effect is accompanied.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.153-165
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• 1999

In order to trace the lateral-torsional post-bucking behaviors of thin-walled space frames with non-symmetric cross sections, a geometrically non-linear finite element formulation is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for non-symmetric thin-walled cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, tangent stiffness matrices of thin-walled space frame element are derived by using the Hermition polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines and incremental member forces.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1446-1452
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• 2009

The behavior of bubbles in a centrifugal fluidized bed with a 340mm inner diameter, 195mm high was observed by photographs using 10.5${\mu}m$and 21.5${\mu}m$mean diameter of $Al_2O_3$particles as bed materials at each of 400rpm, 600rpm, 800rpm, and 1000rpm number of rotations of the rotor. At these experimental ranges, the experimental results clearly proved the effect of number of rotations of the rotor on the behavior of bubbles in the centrifugal fluidized bed. As the number of rotations of the rotor increased, the gas velocity at which bubbles begin to be formed also increased but diameter of bubbles decreased. And sizes of the bubbles were relatively small.

• Earthquakes and Structures
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• v.26 no.5
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• pp.349-361
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• 2024

Excessive torsional behaviour is one of the major reasons for failure of buildings, as inferred from past earthquakes. Numerous seismic codes across the world specify a displacement-based or drift-based criterion for classifying buildings as torsionally irregular. In recent years, quite a few researchers have pointed out some of the inherent deficiencies associated with the current codal guidelines on torsional irregularity. This short communication paper aims to envisage the need for a revision of the displacement-based guidelines on torsional irregularity, and further highlight the appropriateness of a rotation-based criterion. A set of 6 reinforced concrete building models with asymmetric shear walls are analysed using ETABS v18.0.2, by varying the number of stories from 1 to 9, and the torsional irregularity coefficient of various stories is calculated using the displacement-based formula. Since rotation about the vertical axis is a direct indication of the twist experienced by a building, the calculated torsional irregularity coefficients of all stories are compared with the corresponding floor rotations. The conflicting results obtained for the torsional irregularity coefficients are projected through five categories, namely mismatch with floor rotations, inconsistency in trend, lack of clarity in incorporation of negative values, sensitivity to low values of displacement and error conceived in the mathematical formulation. The findings indicate that the irregularity coefficient does not accurately represent the torsional behaviour of buildings in a realistic sense. The Indian seismic code-based values of 1.2 and 1.4, which are used to characterize buildings as torsionally irregular are observed to be highly sensitive to the numerical values of displacements, rather than the actual degree of rotation. The study thus emphasizes the revision of current guidelines based on a more relevant rotation-based or eccentricity-based approach.

• Journal of Technologic Dentistry
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• v.30 no.1
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• pp.121-130
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• 2008

The purpose of this research project is to assess students' stress during clinical rotations and to suggest strategies for enhancing professional skills as well as the quality of clinical rotations among the students of dental technology. The participants included 200 sophomores and juniors from dental laboratory college located in Daegu and Jeju. Data was collected December 7, 2007, and March 7, 2008, by survey samplings. A total of 185 completed surveys were obtained and analyzed for this study. Findings from the study are summarized below. When age and stress were compared, it was found that younger students had higher levels of stress related to their environment, role, and activities. Regarding grade level and stress, students in lower levels were slightly (p<.01) more likely to have stress (Sophomore =2.91, junior =2.49). When the stress level was compared with students' satisfaction with their major, the less students were satisfied, the higher their level of stress was. The study found a slight (p<.05) difference between groups [satisfaction group (M=2.44), group in between satisfaction and dissatisfaction (M=2.58), and dissatisfaction (M=2.82)) in the relationship between satisfaction with the major and overall stress. Again, it appears that stress levels increase as satisfaction with the chosen major decreases. Third, the intensity of stress was affected by the environment in which students practiced, classmate relationships, roles, goals and values, and activities, and areas of performance. It showed that the groups unsatisfied and in-between with the quality of practice have more intensified stress than the group with satisfaction. The study showed a slight (p<.01) difference amongst groups [(satisfaction group (M=2.17), group in between satisfaction and dissatisfaction (M=2.68), and dissatisfaction (M=2.96)) in the relationship between satisfaction with the quality of the clinical rotation and overall stress. It appeared that higher levels of stress were seen with lower satisfaction with the major. Overall, students' level of stress was correlated with age and grade level, level of satisfaction in the major and the quality of the clinical rotation. Furthermore, schools need to focus on improving the environment where students practice, classmate relationships, roles, goals and values, and activities, and areas of performance. Dental laboratory colleges should concentrate on the basic case with the quality of clinical rotation and the chosen major. More skillful teaching and properly assigned clinical rotations and classes, along with a strong practical knowledge base applicable to clinical rotations will be needed in order to address these sources of dissatisfaction.

• ETRI Journal
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• v.30 no.6
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• pp.868-870
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• 2008

The rotation-based transformation (RBT) for privacy preserving data mining is vulnerable to the independent component analysis (ICA) attack. This paper introduces a modified multiple-rotation-based transformation technique for special mining applications, mitigating the ICA attack while maintaining the advantages of the RBT.