• Journal of the Korean Geotechnical Society
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• v.22 no.9
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• pp.23-36
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• 2006

This study presents the development of a new closed-form analytical solution for the ultimate bearing capacity of an embedded wall in a granular mass. The closed-form analytical solution consists of upper and lower bound solutions (UB and LB). The calculated values from these bound solutions were compared with the author's two-dimensional laboratory wall model loading test and finite element analysis in the plastic region. The comparison showed that ultimate bearing loads from both the model test and finite element analysis are located between UB and LB. In particular, the ultimate bearing load from LB showed good agreement with the ultimate bearing load values from both the model test and finite element analysis. However, the calculated value from the conventional empirical form subjected to plane-strain conditions was shown to be much smaller than the LB.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.66.3-67
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• 2021

Low-mass stars form by the gravitational collapse of dense molecular cores. Observations and theories of low-mass protostars both suggest that accretion bursts happen in timescales of ~100 years with high accretion rates, so called episodic accretion. One mechanism that triggers accretion bursts is infalling fragments from the outer disk. Such fragmentation happens when the disk is massive enough, preferentially activated during the embedded phase of star formation (Class 0 and I). Most observations and models focus on the gas structure of the protostars undergoing episodic accretion. However, the dust and ice composition are poorly understood, but crucial to the chemical evolution through thermal and energetic processing via accretion burst. During the burst phase, the surrounding material is heated up, and the chemical compositions of gas and ice in the disk and envelope are altered by sublimation of icy molecules from grain surfaces. Such alterations leave imprints in the ice composition even when the temperature returns to the pre-burst level. Thus, chemical compositions of gas and ice retain the history of past bursts. Infrared spectral observations of the Spitzer and AKARI revealed a signature caused by substantial heating, toward many embedded protostars at the quiescent phase. We present the AKARI IRC 2.5-5.0 ㎛ spectra for embedded protostars to trace down the characteristics of accretion burst across the evolutionary stages. The ice compositions obtained from the absorption features therein are used as a clock to measure the timescale after the burst event, comparing the analyses of the gas component that traced the burst frequency using the different refreeze-out timescales. We discuss ice abundances, whose chemical change has been carved in the icy mantle, during the different timescales after the burst ends.

• Advances in nano research
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• v.9 no.3
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• pp.133-145
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• 2020

In this study, nonlinear vibrations and dynamic instabilities of a smart embedded micro shell conveying varied fluid flow and subjected to the combined electro-thermo-mechanical loadings are investigated. With the aim of designing new hydraulic sensors and actuators, the piezoelectric materials are employed for the body and the effects of applying electric field on the stability of the system as well as the induced voltage due to the dynamic behavior of the system are studied. The nonlocal piezoelasticity theory and the nonlinear cylindrical shell model in conjunction with the energy approach are utilized to mathematically modeling of the structure. The fluid flow is assumed to be isentropic, incompressible and fully develop, and for more generality of the problem both steady and time dependent flow regimes are considered. The mathematical modeling of fluid flow is also carried out based on a scalar potential function, time mean Navier-Stokes equations and the theory of slip boundary condition. Employing the modified Lagrange equations for open systems, the nonlinear coupled governing equations of motion are achieved and solved via the state space problem; forth order numerical integration and Bolotin's method. In the numerical results, a comprehensive discussion is made on the dynamical instabilities of the system (such as divergence, flutter and parametric resonance). We found that applying positive electric potential field will improve the stability of the system as an actuator or vibration amplitude controller in the micro electro mechanical systems.

• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.2
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• pp.61-70
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• 2012

This paper describes terrain-adaptive attitude controller for a hybrid mobile platform which operates in wheel & track mode. The wheel mode of the hybrid mobile platform allows quick driving performance in the flatland, while the track mode provides adaptive movement in the rough ground or stairway. The switching of the platform between two modes is automatically controlled by attitude controller algorithm. In addition, in the track mode, the platform automatically adjusts its attitude angle to overcome the obstacles in front. This paper demonstrates the attitude controller for the aforementioned wheel-track hybrid mobile platform in order to overcome terrain obstacles by using an adaptive method. The driving performance of the hybrid mobile platform has been tested and verified in various surrounding environments in both wheel and track mode. Further, this paper presents the experiments by using the track structure of mobile platform on forming adaptive attitude under various types of obstacles. The practicability and effectiveness of the proposed attitude controller of the platform has been demonstrated in urban building and a test-bed.

• IEMEK Journal of Embedded Systems and Applications
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• v.12 no.5
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• pp.343-350
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• 2017

Underwater glider with a single buoyancy engine could generally obtain propulsive forces by moving the center of buoyancy and gravity. Futhermore, The hull and internal structure of underwater glider are designed according to the purpose of long-time operation, high speed and a wide variety of payloads (sensors, communications and etc.). In this paper, Ray-type underwater glider featuring flatfish is considered in view of hydrodynamics. The hull design is especially performed by the analysis of fluid resistance and dynamic performance. The resistance performance is analyzed using the Computational Fluid Dynamics (CFD). In addition, a simulation program is implemented in order to verify the validity of dynamics modeling and dynamic performances.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.4
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• pp.165-172
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• 2006

In this paper we present a technique for detecting cross-reference points that allows improving watermark detect-ability. In general, Harris detector is commonly used for finding salient points. Harris detector is a kind of combined corner and edge detector which is based on neighboring image data distribution, therefore it has some limitation to find accurate salient points after watermark embedding or any kinds of digital attacks. The new method proposed in this paper used not data distribution but geometrical structure of a normalized image in order to avoid pointing error caused by the distortion of image data. After normalization, we constructed pre-specified number of virtual lines from top to bottom and left to right, and several of cross points were selected by a random key. These selected points specify almost same positions with the accuracy more than that of Harris detector after digital attacks. These points were arranged by a random key, and blocks centered in these points were formed. A reference watermark is formed by a block and embedded in the next block. Because same alteration is applied to the watermark generated and embedded blocks. the detect-ability of watermark is improved even after digital attacks.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.397-404
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• 1999

It is essential to measure load transfer mechanism of pile to check the appropriateness of assumptions made for design purpose and to continuously monitor the behavior of pile foundation. Through many attempts to monitor the behavior of super-structure in civil engineering area using several optical fiber sensors have been made, application of optical fiber sensor technology on pile foundation has not been tried up to now. Load transfer of model piles during compression loading was measured by optical fiber sensors and compared with the measurement by strain gauges. Fiber Bragg Grating(FBG) sensor system was used since it has many advantages, such as easy multiplexing, high sensitivity, and simple fabrication. Besides the model pile tests, uniaxial tension test of steel bar and compression tests of mortar specimen were carried out to evaluate the performance of FBG sensors in embedded environments. The shift of refilming wavelength due to the strain in FBG sensor is converted to the strain at sensor location and the dependence between them is 1.28 pm/${\mu}$ strain. FBG sensors embedded in model pile showed a better survivability than strain gauges. Measured results of load transfer by both FBG sensors and strain gauges were similar, but FBG sensors showed a smoother trend than those by strain gauge. Based on the results of model pile test, it was concluded that the use of FBG sensor for strain measurement in pile has a great potential for the analysis of pile load transfer.

• Journal of Oral Medicine and Pain
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• v.8 no.1
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• pp.33-41
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• 1983

The authors observed the ultrastructure of oral leukoplakia simplex of gingiva, buccal mucosa, tongue and alveolar ridge. For the purpose of clearly defining the lesions under investigation in this study, leukoplakias were cinsidered to be any white patches on the oral mucous membranes that could not be removed by rubbing and could not be classified clinically or microscopically as another diagnosable disease. The tissue to be examined were embedded in paraffin for light microscopic study. The tissue to be examined under the electronomicroscope were fixed in 2.5% glutaraldehyde in 0.1M cacodylate buffer and 1% osmic acid in 0.1M cacodylate buffer, dehydrated with guaded alchol, and treated with propylene oxide, and embedded in Epon.Ultrathin sections were obtained by LKB III ultrotome, stained with uranyl acetate/lead citrate, and examined with Corinth 500EM. The results were as follows : 1. Epithelium of leukoplakia consisted of stratum basale, stratum spinosum, stratum granulosum and stratum corneum. 2. There was hyperorthokerotosis or hyperparakeratosis. 3. Granular cells contained a lot number of membrane coating granule showing lamellar structure, clearing ot codensation, and a lot of keratohyaline granule varied in size. 4. An increased concentration of tonofilaments and an increased number of desmosomes were found in the stratum spinosum. 5. Basal lamina generally showed its continuity, but in some locatoins, its interreption and multiplication appeared.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.79-79
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• 2013

Quantum-structures with nanoparticles have been attractive for various electronic and photonic devices [1,2]. In recent, nonvolatile memories such as nano-floating gate memory (NFGM) and resistance random access memory (ReRAM) have been studied using silicides, metals, and metal oxides nanoparticles [3,4]. In this study, we fabricated nonvolatile memories with silicides (WSi2, Ti2Si, V2Si) and metal-oxide (Cu2O, Fe2O3, ZnO, SnO2, In2O3 and etc.) nanoparticles embedded in polyimide matrix, and photovoltaic device also with SiC nanoparticles. The capacitance-voltageand current-voltage data showed a threshold voltage shift as a function of write/erase voltage, which implies the carrier charging and discharging into the metal-oxide nanoparticles. We have investigated also the electrical properties of ReRAM consisted with the nanoparticles embedded in ZnO, SiO2, polyimide layer on the monolayered graphene. We will discuss what the current bistability of the nanoparticle ReRAM with monolayered graphene, which occurred as a result of fully functional operation of the nonvolatile memory device. A photovoltaic device structure with nanoparticles was fabricated and its optical properties were also studied by photoluminescence and UV-Vis absorption measurements. We will discuss a feasibility of nanoparticles to application of nonvolatile memories and photovoltaic devices.

• Structural Engineering and Mechanics
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• v.34 no.4
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• pp.449-474
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• 2010

A smart hollow cylinder consisting of a host functionally graded elastic core layer and two surface homogeneous piezoelectric layers is presented in this paper. The bonding between the layers can be perfect or imperfect, depending on the parameters taken in the general linear spring-layer interface model. The effect of such weak interfaces on free vibration and steady-state response is then investigated. Piezoelectric layers at inner and outer surfaces are polarized axially or radially and act as a sensor and an actuator respectively. For a simply supported condition, the state equations with non-constant coefficients are obtained directly from the formulations of elasticity/piezoelasticity. An approximate laminated model is then introduced for the sake of solving the state equations conveniently. It is further assumed that the hollow cylinder is embedded in an elastic medium and is simultaneously filled with compressible fluid. The interaction between the structure and its surrounding media is taken into account. Numerical examples are finally given with discussions on the effect of some related parameters.