• Structural Engineering and Mechanics
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• v.91 no.3
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• pp.291-300
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• 2024

This paper predicts the combined resonance behavior of the truncated conical shells (TCSs) under transverse and parametric coupled excitation. The motion governing equation is formulated in the framework of high-order shear deformation theory, von Kármán theory and Hamilton principle. The displacements and boundary conditions are characterized by a set of displacement shape functions with double Fourier series. Subsequently, the method of varying amplitude (MVA) is utilized to derive the approximate analytical solution of system response of TCSs. A comparative analysis is conducted to verify the accuracy of the current computational method. Additionally, the interaction mechanism of combined resonance, parametric resonance and primary resonance is examined. And the effect of damping coefficient, the external excitation, initial phase, axial motion speed, temperature variation, humidity variation, material properties and semi-vortex angle on the vibration mechanism are analyzed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.6
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• pp.360-364
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• 2015

Electronic systems based on solid state devices have changed to be more complicated and miniaturized as the electronic systems developed. If the electronic systems are exposed to HPEM (high power electromagnetics), the systems will be destroyed by the coupling effects of electromagnetic waves. Because the HPEM has fast rise time and high voltage of the pulse, the semiconductors are vulnerable to external stress factor such as the coupled electromagnetic pulse. Therefore, we will discuss about malfunction behavior and DFR (destruction failure rate) of the semiconductor caused by amplitude and repetition rate of the pulse. For this experiment, the pulses were injected into the pins of general purpose IC due to the fact that pulse injection test enables the phenomenon after the HPEM is coupled to power cables. These pulses were produced by pulse generator and their characteristics are 2.1 [ns] of pulse width, 1.1 [ns] of pulse rise time and 30, 60, 120 [Hz] of pulse repetition rate. The injected pulses have changed frequency, period and duty ratio of output generated by Timer IC. Also, as the pulse repetition rate increases the breakdown threshold point of the timer IC was reduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.67-67
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• 2009

Due to the scaling down of the dielectrics thickness, the leakage currents arising from electron tunneling through the dielectrics has become the major technical barrier. Thus, much works has focused on the development of high k dielectrics in both cases of memories and CMOS fields. Among the high-k materials, $Al_2O_3$ considered as good candidate has been attracting much attentions, which own some good properties as high dielectric constant k value (~9), a high bandgap (~2eV) and elevated crystallization temperature, etc. Due to the easy control of ion energy and flux, low ownership and simple structure of the inductively coupled plasma (ICP), we chose it for high-density plasma in our study. And the $BCl_3$ was included in the gas due to the effective extraction of oxygen in the form of BClxOy compound. In this study, the etch characteristic of ALD deposited $Al_2O_3$ thin film was investigated in $BCl_3/N_2$ plasma. The experiment were performed by comparing etch rates and selectivity of $Al_2O_3$ over $SiO_2$ as functions of the input plasma parameters such as gas mixing ratio, DC-bias voltage and RF power and process pressure. The maximum etch rate was obtained under 15 mTorr process perssure, 700 W RF power, $BCl_3$(6 sccm)/$N_2$(14 sccm) plasma, and the highest etch selectivity was 1.9. We used the x-ray photoelectron spectroscopy (XPS) to investigate the chemical reactions on the etched surface. The Auger electron spectroscopy (AES) was used for elemental analysis of etched surface.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.68-86
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• 2016

Understanding the frictional properties of rock discontinuities is crucial to ensure the stability of underground structures. In particular, the frictional behavior at depth depends on the complex interaction among mechanical, hydraulic, thermal and chemical characteristics and their coupled effects. In this study, a series of shear tests were carried out in a triaxial compression chamber to investigate the shearing behavior of saw-cut granite surface and rough shear surface of synthetic rocks. The test results were analyzed using Coulomb's shear strength criterion. The frictional behavior of saw-cut granite surface showed little variation at different confining, water pressures and temperature conditions, however in case of synthetic rocks, the frictional behavior showed different trend depending on normal stress level. In addition, the variation of stiffness and dilation at different testing conditions were analyzed, and the stiffness and dilation showed little variation at different water pressures and temperature conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.309-316
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• 2011

Canoes are usually made from wood or FRP. However, today environment-friendly materials are preferred, and hulls made of FRP are prohibited in some countries. Polyethylene can be recycled and so is suitable for synthetic canoe construction. We used 3D Boat-Design to determine the hydrostatic properties of the canoe. Flow-structure coupled analysis was performed using ANSYS Workbench R12.1. The hull pressure and passenger weight were considered as canoe loading factors. The key parameters for the canoe are the design variables. The constraints are as follows: (1) The maximum stress must not exceed 50% of the polyethylene yield stress; and (2) the canoe weight must not exceed 50 kg. The optimal structural conditions were obtained by the response optimization process. The components of the canoe hull were manufactured from polyethylene pipes and joined by thermal fusion methods. Tests showed that the polyethylene canoe had better performance than existing canoes.

• Journal of Korean Association for Spatial Structures
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• v.7 no.4
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• pp.73-78
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• 2007

The surrounding ground was much transformed by the lateral movement on the soft ground, and consequently the stake basis was damaged. In this case the installed stake is ratted the passive stake, and is actively being researched. When the unevenly distributed load was applied on the stake, and thus the lateral ground pressure was operated, and then the lateral movement was occurred, and consequently the structure is influenced. However, prediction and mechanism for the relationship of piles and abutment deformation is not sufficient. In this paper, coupled three-dimensional finite element analysis, which can be described solid, plate and frame elements at the same time, is developed by the authors. The lateral movement of bridge abutment for the aspect ratio of steel piles on soft clay is clarified by using developed numerical analysis.

• Journal of the Korean Chemical Society
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• v.24 no.4
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• pp.315-321
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• 1980

A steady-state kinetic study on a dye-coupled cytoplasmic polyol dehydrogenase from G. melanogenus was carried by the initial velocity measurements in the direction of the polyol oxidation and the product inhibition by D-fructose. For the initial rate experiments, D-mannitol and D-sorbitol were employed as the specific polyol substrates and 2,6-dichlorophenolin-dophenol (DPIP) as the specific cofactor substrate for the enzyme. When the polyol and DPIP were examined by varying one of substrates and by fixing the second, the corresponding reciprocal plots showed the typical parallel pattern. This suggests that the enzyme from G. melanogenus proceeds by a Ping Pong Bi-Bi mechanism in which the polyol may account as the first reactant-in, and the ketose formed as the first product-out, respectively. The product inhibition patterns obtained by D-fructose (one no-inhibition, one non-competitive, and two competitive) may also provide an additional conformatory evidence for the above mechanism. Based on the kinetic parameters obtained, it was also suggested that the rate-limiting step in the direction of polyol oxidation is associated with the release of the ketose from the Enzyme${\cdot}$Polyol complex.

• Journal of the Semiconductor & Display Technology
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• v.8 no.4
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• pp.65-69
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• 2009

Carbon nanotubes (CNTs) were coated with undoped zinc oxide (ZnO) or 5 wt% gallium-incorporated ZnO (GZO) using various deposition conditions. The CNTs were directly grown on conical-type tungsten substrates at $700^{\circ}C$ using inductively coupled plasma-chemical vapor deposition. The pulsed laser deposition technique was used to deposit the ZnO and GZO thin films with very low stress. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy were used to monitor the variations in the morphology and microstructure of CNTs prior to and after ZnO or GZO coating. The formation of ZnO and GZO films on CNTs was confirmed using energy-dispersive x-ray spectroscopy. In comparison to the as-grown (uncoated) CNT emitter, the CNT emitter that was coated with a thin (10 nm) GZO film showed remarkably improved field emission characteristics, such as the emission current of $325\;{\mu}A$ at 1 kV and the threshold field of $1.96\;V/{\mu}m$ at $0.1\;{\mu}A$, and it also exhibited the highly stable operation of emission current up to 40 h.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.17-24
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• 2001

Two-dimensional binary-phase diffraction gratings which can be employed to fabricate two- and three-dimensional periodic structures are designed and analyzed using rigorous coupled-wave analysis. These gratings serve as phase-masks which generate several diffracted waves from a normally incident beam and thus can produce a periodic interference pattern in space via nearfield holography. The properties of the diffracted beams can be controlled by varying the polarization and wavelength of the incident beam, surface-profile, groove depth and duty cycle of the mask. For the two-dimensional structure, optimum results can be obtained when the diffraction efficiency of the zero-order beam is minimized while that of the first-order maximized. On the other hand, when the diffraction efficiency of the zero-order is appreciable or even greater than other orders, we can obtain a variety of three-dimensional interference patterns which may be used to fabricate photonic crystals of tetragonal-body-centered and hexagonal structures in a submicron scale. scale.

• International Journal of Highway Engineering
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• v.20 no.1
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• pp.9-18
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• 2018

PURPOSES : In this research, the initiation and development of corrugation on a gravel road with certain wheel and boundary conditions were evaluated using a coupled discrete-element method (DEM) with multibody dynamics (MBD). METHODS : In this study, 665,534 particles with a 4-mm diameter were generated and compacted to build a circular roadbed track, with a depth and width of 42 mm and 50 mm, respectively. A single wheel with a 100-mm diameter, 40-mm width, and 0.157-kg mass was considered for the track. The single wheel was set to run slowly on the track with a speed of 2.5 rad/s so that the corrugation was gradually initiated and developed without losing contact between the wheel and the roadbed. Then, the shape of the track surface was monitored, and the movement of the particles in the roadbed was tracked at certain wheel-pass numbers to evaluate the overall corrugation initiation and development mechanism. RESULTS : Two types of corrugation, long wave-length and short wave-length, were observed in the circular track. It seems that the long wave-length corrugation was developed by the longitudinal movement of surface particles in the entire track, while the short wave-length corrugation was developed by shear deformation in a local section. Properties such as particle coefficients, track bulk density, and wheel mass, have significant effects on the initiation and development of long-wave corrugation. CONCLUSIONS : It was concluded that the coupled numerical method applied in this research could be effectively used to simulate the corrugation of a gravel road and to understand the mechanism that initiates and develops corrugation. To derive a comprehensive conclusion for the corrugation development under various conditions, the driver's acceleration and deceleration with various particle gradations and wheel-configuration models should be considered in the simulation.