• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.191-196
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• 2010

Power system restoration following a massive or complete blackout starts with energizing the primary restorative transmission system. During this primary restoration process, unexpected overvoltage may happen due to nonlinear interaction between the unloaded transformer and the transmission system. In the case of the Myanmar electric power system, there are so many wide outage experiences, including complete blackout cases, caused by 230kV line faults and so on. Consequently, Myanmar's system operators have been well trained to deal with wide blackouts. Howver, system blackout restoration has been conducted by relying on the experience of only a few specialists. So, more scientific analysis is required to meet the requirements necessary to ensure fast and reliable system restoration. This paper presents analytical results on the primary restorative transmission system of Myanmar, focusing on the problems during the early restoration process. Methodologies are presented that handle load pick-up, terminal voltage and the reactive capability limitation of black-start generators to compensate the Ferranti effect. Static and dynamic simulation with the PSSolution and EMTDC programs respectively for the six cases are performed in order to select the primary restorative transmission lines.

• Computers and Concrete
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• v.25 no.4
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• pp.355-367
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• 2020

This paper proposed a numerical investigation based on finite elements analysis (FEA) in order to study the punching shear behavior of reinforced concrete (RC) flat slabs using ABAQUS and SAP2000 programs. Firstly, the concrete and the steel reinforcements were modeled by hexahedral 3D solid and linear elements respectively, and the nonlinearity of the used materials was considered. In order to validate this model, experimental results considered in literature were compared with the proposed FE model. After validation, a parametric study was performed. The parameters include the slab thickness, the flexure reinforcement ratios and the axial membrane loads. Then, to reduce the time of FEA, a simplified modelling using 3D layered shell element and shear hinge concept was also induced. The effect of the footings settlement was studied using the proposed simplified nonlinear model as a case study. Results of numerical models showed that increase of the slab thickness by 185.7% enhanced the ultimate load by 439.1%, accompanied with a brittle punching failure. The punching failure occurred in one of the tested specimens when the tensile reinforcement ratio increased more than 0.65% and the punching capacity improved with increasing the horizontal flexural reinforcement; it decreased by 30% with the settlement of the outer footings.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.129-138
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• 2021

Due to the active progress in space programs for various types of ground and space missions, the high agile spacecraft maneuverability is also required. To meet the requirement of the given space missions, the Control Moment Gyros (CMG) for the alternatives of the classical reaction wheels can release the attitude maneuverability restrictions. In addition, the angular rates of the spacecraft is constrained due to the limited actuator characteristics. In this paper, a sliding mode control technique for the attitude control of the spacecraft equipped with the pyramid type of CSCMG(Constant Speed CMG) is designed, and the stability of the control system is guaranteed by using the Lyapunov stability theory. Finally, the control law proposed is analyized by numertical simulations.

• Journal of Korea Multimedia Society
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• v.12 no.7
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• pp.903-912
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• 2009

There are still many difficulties in developing techniques for modifying or transforming the flickering of motion capture data or in modifying motion capture data in such a way that suits the animation timing sheet. There is a problem in the existing method of modifying motion capture data. It requires almost same time as in the key frame animation work by a very skilled animator or even more time in modifying. It is believed that this kind of problem can be a basis for a more effective problem-solving method through creating the key animation data node and direct blend layer and replacement layer nodes. This study presents a new method which enables to modify animation data in a nonlinear way without modifying the existing animation data by creating an animation layer node for a direct connection to the animation node. 'Maya' API will be utilized in order to realize this method and the research range will be limited to 'Maya' 3D software which is generally used in motion picture and animation films. According to the results of this study, the new method is much more intuitive than the nonlinear one and does not require the preceding working of making animation clips. In addition, it has enabled to modify flickering and to extract key frames, and due to the compatibility with other programs, it has been possible to modify motion capture data by creating a direct layer node. Finally, in this study, the existing method of modifying animation will be examined, compared and analyzed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.822-831
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• 2021

Although programs have been developed to evaluate the risk of dragging anchors, it is practically difficult for VTS(vessel traffic service) operators to calculate and evaluate these risks by obtaining input factors from anchored ships. Therefore, in this study, the gross tonnage (GT) that could be easily obtained from the ship by the VTS operators was set as an independent variable, and linear and nonlinear regression analyses were performed using the input factors as the dependent variables. From comparing the fit of the polynomial model (linear) and power series model (nonlinear), the power series model was evaluated to be more suitable for all input factors in the case of container ships and bulk carriers. However, in the case of tanker ships, the power supply model was suitable for the LBP(length between perpendiculars), width, and draft, and the polynomial model was evaluated to be more suitable for the front wind pressure area, weight of the anchor, equipment number, and height of the hawse pipe from the bottom of the ship. In addition, all other dependent variables, except for the front wind pressure area factor of the tanker ship, showed high degrees of fit with a coefficient of determination (R-squared value) of 0.7 or more. Therefore, among the input factors of the dragging anchor risk assessment program, all factors except the external force, seabed quality, water depth, and amount of anchor chain let out are automatically applied by the regression analysis model formula when only the GT of the ship is provided.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.629-636
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• 2011

It has been suggested that buildings designed for strong ground motions will also have improved resistance to air blast loads. As an initial attempt to quantify this behavior, the responses of a ten story steel building, designed for the 1994 building code, with lateral resistance provided by perimeter moment frames, is considered. An analytical model of the building is developed and the magnitude and distribution of blast loads on the structure are estimated using available computer software that is based on empirical methods. To obtain the relationship between pressure, time duration, and standoff distance, these programs are used to obtain an accurate model of the air blast loading. A hemispherical surface burst for various explosive weights and standoff distances is considered for generating the air blast loading and determining the structural response. Linear and nonlinear analyses are conducted for these loadings. Air blast demands on the structure are compared to current seismic guidelines. These studies present the displacement responses, story drifts, demand/capacity ratio and inelastic demands for this structure.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.10 no.2
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• pp.1-10
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• 2015

This study examines the relationships between export intensity and knowledge search activities of Korea SME manufacturers. Using 2,145 firm data from the 2011 SME Technology Statistics Survey, we focused on the nonlinear relationships of export intensity and internal and external knowledge search activities. The results show that there are U-shaped relationships between export intensity and both of internal and external knowledge search activities. Local market-oriented or global market-oriented SMEs than the middle-level of exporters have more search activities both internally and externally. This study extends our understandings on the relationships between export intensity and knowledge search activities. There are some policy implications to develop supporting programs differing in knowledge search activities according to the acceleration of export or globalization of Korean SME manufacturers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.718-723
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• 2017

When structural analysis modelling methods of practical fields are investigated, a slab is generally modeled by a finite element mesh using plate elements and a shear wall is modeled using a shell element or wall element for 3-D structural analysis. The point worthy of notice in this practice is that a shear wall is modelled using only one wall or shell element divided by floors and column lines to produce structural models. The modeling method like this can cause analysis errors according to the type of computer programs in use, and these errors reduce the reliability of the analysis results. Therefore, to secure the reliability of structural analysis, studies of the causes of errors and finding reasonable modeling methods are necessary. In this study, the causes of analysis errors according to the modelling methods of a shear wall, which are used in practical fields, were investigated and some considering matters for modelling a shear wall are presented to reduce the analysis errors on these analysis results.

• Computational Structural Engineering
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• v.7 no.2
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• pp.89-99
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• 1994

The nonlinear dynamic behaviors of guardrail established on the local or high way have been investigated using BARRIER VII program with respect to four design variables such as section type of beams and posts, impact angle, impact velocity and vehicle weight. Computer simulation programs are sophisticated analytical models for analyzing dynamic vehicle/barrier interactions and provide a relatively inexpensive alternative to full scale crash testing. This study has been focused on the structural adequacy, occupant risk, and vehicle trajectory. For this purpose, the maximum defection and impact force have been calculated to design the clear zone and to analyze effect of impact attenuation. Also, the acceleration of vehicle and exit angle after collision have been computed to estimate the occupant risk. From this study, it is suggested that we should strengthen the design criteria of guardrail to prevent from disastrous traffic accidents.

• Korean Journal of Computational Design and Engineering
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• v.3 no.1
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• pp.57-67
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• 1998

Genetic programming (GP) is an extension of a genetic algoriths paradigm, deals with tree structures representing computer programs as individuals. In recent, there have been many research activities on applications of GP to various engineering problems including system identification, data mining, function approximation, and so forth. However, standard GP suffers from the lack of the estimation techniques for numerical parameters of the GP tree that is an essential element in treating various engineering applications involving real-valued function approximations. Unlike the other research activities, where nonlinear optimization methods are employed, I adopt the use of a weighted linear associative memory for estimation of these parameters under GP algorithm. This approach can significantly reduce computational cost while the reasonable accurate value for parameters can be obtained. Due to the fact that the GP algorithm is likely to fall into a local minimum, the GP algorithm often fails to generate the tree with the desired accuracy. This motivates to devise a group of additive genetic programming trees (GAGPT) which consists of a primary tree and a set of auxiliary trees. The output of the GAGPT is the summation of outputs of the primary tree and all auxiliary trees. The addition of auxiliary trees makes it possible to improve both the teaming and generalization capability of the GAGPT, since the auxiliary tree evolves toward refining the quality of the GAGPT by optimizing its fitness function. The effectiveness of this approach is verified by applying the GAGPT to the estimation of the principal dimensions of bulk cargo ships and engine torque of the passenger car.