• Proceedings of the KSR Conference
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• 2011.10a
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• pp.836-842
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• 2011

The lateral stability of bridge foundations against train moving load, emergency stopping load, earthquakes, and so on is very important for a railway bridge foundation. A borehole test is much more accurate than laboratory tests since it is possible to minimize the disturbance of ground conditions on the test site. The representative borehole test methods are Dilatometer, Pressuremeter and Lateral Load Tester, which usually provide force-resistance characteristics in elastic range. In order to estimate P-y curves using those methods, the non-linear characteristics of soil which is one of the most important characteristics of the soil cannot be obtained. Therefore, P-y curves are estimated usually using elastic modulus ($E_O$, $E_R$) of lateral pressure-deformation ratio obtained within the range of elastic behavior. Even though the pile foundation is designed using borehole tests in field to increase design accuracy, it is necessary to use a higher safety factor to improve the reliability of the design. A Large Displacement Borehole Testmeter(LDBT) is developed to measure nonlinear characteristics of the soil in this study. P-y curves can be directly achieved from the developed equipment. Comparisons between measured P-y curves the LDBT developed equipment, theoretical methods based on geotechnical investigations, and back-calculated P-y curves from field tests are shown in this paper. The research result shows that the measured P-y curves using LDBT can be properly matched with back-calculated P-y curves from filed tests by applying scale effects for sand and clay, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.413-418
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• 2018

In this paper, we describe the development of a non-enzymatic glucose sensor based on copper nanocubes(Cu NCs) electroplated laser induced graphene(LIG) electrodes which can detect a certain range of glucose concentrations. $CO_2$ laser equipment was used to form LIG electrodes on the PI film. This fabrication method allows easy control of the LIG electrode size and shape. The Cu NCs were electrochemically deposited on the LIG electrodes to improve electron transfer rates and thus enhancing electrocatalytic reaction with glucose. The average sheet resistances before and after electroplating were $15.6{\Omega}/{\Box}$ and $19.6{\Omega}/{\Box}$, respectively, which confirmed that copper nanocubes were formed on the laser induced graphene electrodes. The prepared electrode was used to measure the current according to glucose concentration using an electrochemical method. The LIG electrodes with Cu NCs demonstrated a high degree of sensitivity ($1643.31{\mu}A/mM{\cdot}cm^2$), good stability with a linear response to glucose ranging from 0.05 mM to 1 mM concentration, and a limit of detection of 0.05 mM. In order to verify that these electrodes can be used as flexible devices, the electrodes were bent to $30^{\circ}$, $90^{\circ}$, and $180^{\circ}$ and cyclic voltammetry measurements were taken while the electrodes were bent. The measured data showed that the peak voltage was almost constant at 0.42 V and the signal was stable even in the flexed condition. Therefore, it is concluded that these electrodes can be used in flexible sensors for detecting glucose in the physiological sample like saliva, tear or sweat.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.214-220
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• 2012

Deformation behaviour of rock mass around an opening measured during tunnel excavation is very important in order to assess the stability of the tunnel. Unfortunately displacement measured only after the installation of displacement measuring device can be acquired, which results in inevitably excluding the pre-displacement occurred and accumulated before the displacement measuring devices are installed. So it is very important to consider the pre-displacement based on the elapsed time before zero reading after deformation behaviour started. In this study, the accuracy of total estimated displacement depending on the distance between face and measurement position is calculated by statistical non-linear fitting on measurable displacement data. Besides, the influence of the unavoidable measurement error is considered by using Monte-Carlo simulation. As a result, the faster the initial reading started and the smaller the measurement error is, the higher the accuracy of estimating total displacement is obtained.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.10
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• pp.1383-1389
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• 2013

There were telecommunication noise and malfunctions of the electronic devices occurred over a wide area due to the high harmonic voltage and/or current levels of the Back-to-back converter in the DFIG wind power system even though the magnitude of all harmonics is within the international standards. The triangular carrier signals of the PWM used in the power converter system is related to the telecommunication noise because they are in the range of audible frequencies and amplified by a variety of the standing waves that were excited by harmonic voltage sources in the weak grid system such as a long distance distribution transmission lines. This paper describes the characteristics of the harmonics in the wind turbine-generator, numerical analysis and simulation of the harmonics resonance phenomena in the distribution lines as well as measuring induced voltage of the telecommunication lines in parallel with power lines in order to verify the root cause of the telecommunication noise. These noise problems can occur in a wind turbine power system with a non-linear converter at any time, as well as photovoltaic power system. So, the preliminary review of suitable filter devices and switching frequencies of the PWM have to be required by considering the stability of the controller at the design stage but as part of the measures the effect of the telecommunication cable shields was analyzed by comparing the measured data between multi-conductor with/without shields so as to attenuate the sources of the harmonics voltage induced into the telecommunication lines and to apply the most cost-effective measures in the field.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.10
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• pp.826-832
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• 1998

In this study the thin films with the structure of Si+SiO$_2$+TiN are made by RF supttering method. TiN, which has small diffusion coefficient and low resistivity, is evaporated between SiO$_2$ and Al layers. It investigates the V-R characteristics depending on the thickness of SiO$_2$ which is used as insulation layer and researches its effects on voltage stability of thin film and varistor. These films show very small resistance valus in negative(-) voltage and large and large value in positive voltage band, and with the increase of voltage, resistance value is rapidly reduced and the satisfactory characteristic of varistor is shown at +1[V]. It is found that resistance value of TiN thin film is small and also TiN thin film has more current than the thin film which is not evaporated by TiN thin film. When Al electrode is evaporated of SiO$_2$ thin film, spiking occurs, but the spiking can be prevented with evaporation of TiN between SiO$_2$ and Al layers and this thin films in made easily because of its good attachment. With the increase of voltage, the resistance is changed into non-linear pattern and the bidirectional varistor characteristic is shown and then its theory can be verified by this experiment. Accordingly, when TiN is evaporated of Si Wafer(n-100), it obtains better voltage-resistance than thin film which is not evaporated and also when varistor character is used electrically to automatic control element such as elimination of flame, power distribution arrestor and constant voltage compensation, satisfactory reproducibilities are expected.

• Computational Structural Engineering
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• v.10 no.4
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• pp.205-216
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• 1997

In order to trace the lateral post-buckling behaviors of thin-wafled space frames, a geometrically nonlinear 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 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 the thinwalled space frame element with 7 degrees of freedom including the restrained warping for each node 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 of the frame element due to rigid body rotations and incremental member forces from pure deformations. Finite element solutions for the spatial buckling and post-buckling analysis of thin-walled space frames are presented and compared with available solutions and other researcher's results.

• Journal of Electrical Engineering and Technology
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• v.5 no.2
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• pp.179-190
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• 2010

This paper describes a new stochastic heuristic algorithm in engineering problem optimization especially in power system applications. An improved particle swarm optimization (PSO) called adaptive particle swarm optimization (APSO), mixed with simulated annealing (SA), is introduced and referred to as APSO-SA. This algorithm uses a novel PSO algorithm (APSO) to increase the convergence rate and incorporate the ability of SA to avoid being trapped in a local optimum. The APSO-SA algorithm efficiency is verified using some benchmark functions. This paper presents the application of APSO-SA to find the optimal location, type and size of flexible AC transmission system devices. Two types of FACTS devices, the thyristor controlled series capacitor (TCSC) and the static VAR compensator (SVC), are considered. The main objectives of the presented method are increasing the voltage stability index and over load factor, decreasing the cost of investment and total real power losses in the power system. In this regard, two cases are considered: single-type devices (same type of FACTS devices) and multi-type devices (combination of TCSC, SVC). Using the proposed method, the locations, type and sizes of FACTS devices are obtained to reach the optimal objective function. The APSO-SA is used to solve the above non.linear programming optimization problem for better accuracy and fast convergence and its results are compared with results of conventional PSO. The presented method expands the search space, improves performance and accelerates to the speed convergence, in comparison with the conventional PSO algorithm. The optimization results are compared with the standard PSO method. This comparison confirms the efficiency and validity of the proposed method. The proposed approach is examined and tested on IEEE 14 bus systems by MATLAB software. Numerical results demonstrate that the APSO-SA is fast and has a much lower computational cost.

• Genomics & Informatics
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• v.20 no.1
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• pp.11.1-11.20
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• 2022

Vibrio harveyi belongs to the Vibrio genus that causes vibriosis in marine and aquatic fish species through double-stranded DNA virus replication. In humans, around 12 Vibrio species can cause gastroenteritis (gastrointestinal illness). A large amount of virus particles can be found in the cytoplasm of infected cells, which may cause death. Despite these devastating complications, there is still no cure or vaccine for the virus. As a result, we used an immunoinformatics approach to develop a multi-epitope vaccine against most pathogenic hemolysin gene of V. harveyi. The immunodominant T- and B-cell epitopes were identified using the hemolysin protein. We developed a vaccine employing three possible epitopes: cytotoxic T-lymphocytes, helper T-lymphocytes, and linear B-lymphocyte epitopes, after thorough testing. The vaccine was developed to be antigenic, immunogenic, and non-allergenic, as well as having a better solubility. Molecular dynamics simulation revealed significant structural stiffness and binding stability. In addition, the immunological simulation generated by computer revealed that the vaccination might elicit immune reactions in the actual life after injection. Finally, using Escherichia coli K12 as a model, codon optimization yielded ideal GC content and a higher codon adaptation index value, which was then included in the cloning vector pET2+ (a). Altogether, our experiment implies that the proposed peptide vaccine might be a good option for vibriosis prophylaxis.

• Journal of Korean Association for Spatial Structures
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• v.22 no.3
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• pp.25-32
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• 2022

In this paper, the instability of the domed spatial truss structure using wood and the characteristics of the buckling critical load were studied. Hexagonal space truss was adopted as the model to be analyzed, and two boundary conditions were considered. In the first case, the deformation of the inclined member is only considered, and in the second case, the deformation of the horizontal member is also considered. The materials of the model adopted in this paper are steel and timbers, and the considered timbers are spruce, pine, and larch. Here, the inelastic properties of the material are not considered. The instability of the target structure was observed through non-linear incremental analysis, and the buckling critical load was calculated through the singularities and eigenvalues of the tangential stiffness matrix at each incremental step. From the analysis results, in the example of the boundary condition considering only the inclined member, the critical buckling load was lower when using timber than when using steel, and the critical buckling load was determined according to the modulus of elasticity of timber. In the case of boundary conditions considering the effect of the horizontal member, using a mixture of steel and timber case had a lower buckling critical load than the steel case. But, the result showed that it was more effective in structural stability than only timber was used.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.83-96
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• 2024

This paper suggests an analytical approach to investigate the free vibration and stability of functionally graded (FG) beams with both perfect and imperfect characteristics using a quasi-3D higher-order shear deformation theory (HSDT) with stretching effect. The study specifically focuses on FG beams resting on variable elastic foundations. In contrast to other shear deformation theories, this particular theory employs only four unknown functions instead of five. Moreover, this theory satisfies the boundary conditions of zero tension on the beam surfaces and facilitates hyperbolic distributions of transverse shear stresses without the necessity of shear correction factors. The elastic medium in consideration assumes the presence of two parameters, specifically Winkler-Pasternak foundations. The Winkler parameter exhibits variable variations in the longitudinal direction, including linear, parabolic, sinusoidal, cosine, exponential, and uniform, while the Pasternak parameter remains constant. The effective material characteristics of the functionally graded (FG) beam are assumed to follow a straightforward power-law distribution along the thickness direction. Additionally, the investigation of porosity includes the consideration of four different types of porosity distribution patterns, allowing for a comprehensive examination of its influence on the behavior of the beam. Using the virtual work principle, equations of motion are derived and solved analytically using Navier's method for simply supported FG beams. The accuracy is verified through comparisons with literature results. Parametric studies explore the impact of different parameters on free vibration and buckling behavior, demonstrating the theory's correctness and simplicity.