• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.313-315
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• 2005

In a power system, an out-of-step condition causes a variety of risk such as serious damage to system elements, tripping of loads and generators, mal-operation of relays, etc. Therefore, it is very important to detect the out-of-step condition and take a proper measure. Several out-of-step detection methods have been employed in relays until now Mo,;t common method used for an out-of-step detection is based on the transition time through the blocking impedance area in R-X diagram. Also, the R-R dot out-of- step relay, the out-of-step prediction method and the adaptive out-of-step relay using the equal area criterion (EAC) and Global Positioning Satellite (GPS) technology have been developed. This paper presents the out-of-step detection algorithm using the time variation of the complex power. The complex power is calculated and the mechanical power of the generator is estimated by using the electrical power, and then the out-of-step detection algorithm, which is based on the complex Power and the estimated mechanical power, is presented. This algorithm, may detect the instant when the generator angle passes the Unstable Equilibrium Point (UEP). The proposed out-of-step algorithm is verified and tested by using Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP) MODELS.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.843-850
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• 2002

Linear transformation theory has been effectively used in the design and analysis of prestressed concrete structures. The underlying assumptions of the theory, which were often overlooked, are investigated in the respect of equivalent load method. As a result, it is found that the same equivalent loading system is produced for all the cases of the linear transformation by the assumptions of the conventional equivalent load method. On the other hand, equivalent loading systems in a strict and accurate sense do not satisfy the classical theories of the linear transformation. Also, it is shown that a little different equivalent loading system from the conventional one is obtained for each linear transformation according to the proposed equivalent load method that is derived from the self-equilibrium property of the tendon-induced forces. Therefore, it can be concluded that the linear transformation theory is valid only when referring to the conventional approximate equivalent load method. The discussions are further extended to the eccentrically located circumferential tendon in the wall of containment structures, where the problem of eccentricity is analyzed also from the view point of the linear transformation.

• Journal of Korean Society of Steel Construction
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• v.14 no.1
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• pp.79-85
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• 2002

Recently, prestressed H-Beam bridges with external unbonded Tendons are increasingly built. The mechanical behavior of prestressed steel H-beams is different from that of normal bonded PSC beams in a point of the slip of tendons at deviators and the change of tendon eccentricity that occurs, when service load are applied in external unbonded steel H-beams. The concept of prestressing steel structures has been widely considered, in spite of long and successful history of prestressing concrete members. In the study, The flexural test on prestressed steel H-beams has been performed in the various aspects of prestressed H-beam including the tendon type and profile. The load was plotted against the deflection and the strain respectively in the steel beam and prestressing bars. The value expected with the equation of internal force equilibrium and compatibility between the deflection of the bars and the H-beam was found to correlate well with the measured data.

• Physical Therapy Korea
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• v.6 no.3
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• pp.11-21
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• 1999

Human balance is maintained through a complex process involving sensory detection of body motions, integration of sensorimotor information within the central nervous system, and execution of appropriate musculoskeletal responses. The basic task of balance is to position the body center of gravity (COG) over some portion of the support base. When the COG extends beyond the base of support, the person has exceeded the limits of stability (LOS). At this point, a step or stumble is required to prevent a fall. Automatic postural responses operate to keep the COG over the base of support. They are a set of functionally organized, long-loop responses that act to keep the body in a state of equilibrium. There are four commonly identified automatic postural responses, or strategies. These are ankle strategy, hip strategy, suspensory (knee) strategy, and stepping strategy. Thus, the purpose of this study was to evaluate the LOS using various knee strategies. Forty subjects participated in this study. The subjects were comprised of 20 males and 20 females who were without neurologic, orthopaedic or balance performance impairments. The LOS was measured with a Balance Performance Monitor (BPM) Dataprint Software Version 5.3. The results of this study were as follows: 1) Knee joint angle which is to increase stability of standing balance with using knee strategy was at mid-range. 2) There were statistically significant differences in anteroposterior LOSs according to the knee strategy. 3) There were no statistically significant differences in mediolateral LOSs according to the knee strategy. 4) There were statistically significant differences of anteroposterior LOSs with using knee strategy according to gender. 5) There were no statistically significant differences in mediolateral LOSs with using knee strategy according to gender.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.74-80
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• 2009

In this study, the static and modal analyses to find the characteristic of eigenvalues for a towed cable were with a free boundary condition at the bottom end carried out with numerical study. The resulting numerical code with finite element method was used to study sample problems for a cable with towing speeds. After tracing the equilibrium state with a towing speed through the static analysis, modal analysis on the basis of static results was performed. The static top tension for a critical towing speed is nearly 50 percent of what it was for a free hanging pipe. From static analyses, it is found that towing speed has a noticeable effect on top tension of a towed pipe. At a high towing speed, differences between the first and second periods become larger. Compared to the fundamental period for a free hanging pipe, that for a towed pipe with a critical towing speed is approximately 1.4 times larger. This result is very important point in that the lock in condition and tension of the towed cable system with top excitation can be predicted. The corrected close form solution to solve natural periods for a towed cable was presented in this study. The code is validated by comparison of the results of theoretical and numerical studies. Two results were in very good agreement. This study can contribute to predicting the lock-in condition and tension for a towed cable or pipe with top excitation.

• International Journal of Control, Automation, and Systems
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• v.2 no.2
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• pp.247-255
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• 2004

The majority of real-world problems encountered by engineers involve simultaneous optimization of competing objectives. In this case instead of single optima, there is a set of alternative trade-offs, generally known as Pareto-optimal solutions. The use of evolutionary algorithms Pareto GA, which was first introduced by Goldberg in 1989, has now become a sort of standard in solving Multiobjective Optimization Problems (MOPs). Though this approach was further developed leading to numerous applications, these applications are based on Pareto ranking and employ the use of the fitness sharing function to maintain diversity. Another scheme for solving MOPs has been presented by J. Nash to solve MOPs originated from Game Theory and Economics. Sefrioui introduced the Nash Genetic Algorithm in 1998. This approach combines genetic algorithms with Nash's idea. Another central achievement of Game Theory is the introduction of an Evolutionary Stable Strategy, introduced by Maynard Smith in 1982. In this paper, we will try to find ESS as a solution of MOPs using our game model based co-evolutionary algorithm. First, we will investigate the validity of our co-evolutionary approach to solve MOPs. That is, we will demonstrate how the evolutionary game can be embodied using co-evolutionary algorithms and also confirm whether it can reach the optimal equilibrium point of a MOP. Second, we will evaluate the effectiveness of our approach, comparing it with other methods through rigorous experiments on several MOPs.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.425.1-425.1
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• 2014

Thermal transport in nanomaterials is not only scientifically interesting but also technological important for various future electronic, bio, and energy device applications. Among the various computation approaches to investigate lattice thermal transport phenomena in nanoscale, the atomistic nonequilibrium Green's function approach based on first-principles density functional theory calculations appeared as a promising method given the continued miniaturization of devices and the difficulty of developing classical force constants for novel nanoscale interfaces. Among the nanometerials, carbon atomic chains, namely the cumulene (all-doulble bonds, ${\cdots}C=C=C=C{\cdots}$) and polyyne (alternation of single and triple bonds, ${\cdots}C{\equiv}C-C{\equiv}C{\cdots}$) can be considered as the extream cases of interconnction materials for nanodevices. After the discovery and realization of carbon atomic chains, their electronic transport properties have been widely studied. For the thermal transport properties, however, there have been few literatures for this simple linear chain system. In this work, we first report on the development of a non-equilibrium Green's function theory-based computational tool for atomistic thermal transport calculations of nanojunctions. Using the developed tool, we investigated phonon dispersion and transmission properties of polyethylene (${\cdots}CH2-CH2-CH2-CH2{\cdots}$) and polyene (${\cdots}CH-CH-CH-CH{\cdots}$) structures as well as the cumulene and polyyne. The resulting phonon dispersion from polyethylene and polyene showed agreement with previous results. Compared to the cumulene, the gap was found near the ${\Gamma}$ point of the phonon dispersion of polyyne as the prediction of Peierls distortion, and this feature was reflected in the phonon transmission of polyyne. We also investigated the range of interatomic force interactions with increase in the size of the simulation system to check the convergence criteria. Compared to polyethylene and polyene, polyyne and cumulene showed spatially long-ranged force interactions. This is reflected on the differences in phonon transport caused by the delicate differences in electronic structure.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.3
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• pp.329-336
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• 2009

In this paper, we propose the design of an optimized fuzzy cascade controller for rotary inverted pendulum system by means of Hierarchical Fair Competition-based Genetic Algorithms (HFCGA) which is a kind of parallel genetic algorithms. The rotary inverted pendulum system is the system for controlling the inclination of pendulum axis through the adjustment of rotating arm. The control objective of the system is to control the position of rotating arm and to make the pendulum maintain the unstable equilibrium point of vertical position. To control rotary inverted pendulum system, we designs the fuzzy cascade controller scheme consisted of two fuzzy controllers and optimizes the parameters of the designed controller by means of HFCGA. A comparative analysis between the simulation and the practical experiment demonstrates that the proposed HFCGA based fuzzy cascade controller leads to superb performance in comparison with the conventional LQR controller as well as HFCGA based PD cascade controller.

• Journal of Korean Association for Spatial Structures
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• v.5 no.2 s.16
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• pp.73-79
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• 2005

Tensegrity is a relatively new structural system based on the use of continuous tension-discontinuous compression. Of course, a much more detailed structural investigation would be necessary, but at least in order to achieve the intended purpose, it is essential to understand the structural principles and the fundamental forces of tensegrity. Once this point is established, the applications of them to architecture are described, as well as the characteristics of these structures. Then, in spite of the controversial definitions to explain these systems, several examples of tensegrity prototypes or modules constructed in iESD(Institute of Environmental Structure Design) are presented to illustrate the feasibility of tensegrity as a lightweight structure. In this work, consequently, the reformability and application of tensegrity modules have also been researched in architecture, after the patterns of basic module as well as fundamental definition are introduced.

• Journal of the Korean Chemical Society
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• v.45 no.5
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• pp.401-412
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• 2001

The geometrical parameters, vibrational frequencies, and dissociation energies for $H_{2n+1}^+$ (n=1~6) clusters have been investigated using high level ab initio quantum mechanical techniques with large basis sets. The equilibrium geometries have been optimized at the self-consistent field (SCF), the single and double excitation configuration interaction (CISD), the coupled cluster with single and double excitation (CCSD), and the CCSD with connected triple excitations [CCSD(T)] levels of theory. The highest levels of theory employed in this study are TZ2P+d CCSD(T) up to $H^+_g$ and TZ2P CCSD(T) for $H_{11}^+$ and $H_{13}^+$. Harmonic vibrational frequencies are also determined at the SCF level of theory with various basis sets and confirm that all the optimized geometries are true minima. The dissociation energies, $D_e$, for $H_{2n+1}^+$ (n=26) have been predicted using energy differences at each optimized geometry and zero-point vibrational energies(ZPVEs) have been considered to compare with experimental dissociation energies, $D_0$.