• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.525-528
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• 1997

In this study, Eu(TTA)$_3$(phen) was synthesized and its films were prepared by vapor deposition method. Its films were characterized by UV-Vis absorption spectroscopy, Atomic Force Microscopy(AFM) and Photoluminescence(PL) measurements. Their electroluminescent(EL) characteristics were investigated by PL measurements, where a cell structure of glass substrate/ITO/Eu(TTA)$_3$(phen)/Al was employed. It was found that its films were well prepared without any decomposition and the film thickness could be controlled by adjusting the amount of Eu(TTA)$_3$(phen) in a boat. The EL spectrum of these films was almost the same as that of PL spectrum of these films.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1705-1706
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• 2006

Ferroelectric PZT (70/30) thick films were fabricated by the screen printing method. And the PZT (30/70) precusor solution were infiltrated by the spin-coating method on the PZT thick films to obtain a densification. All PZT thick films were sintered at $1050^{\circ}C$ for 10 min. Structural properties, such as crystalline structure, microstructures and compositional ratio, of PZT thick films were investigated with the variation of the number of sol coatings using XRD, SEM and EDS, respectively. All PZT thick films exhibited a perovskite polycrystalline structure without a pyrochloer phase. The thickness of PZT thick films, 4-times screen-printed, was approximately $60{\mu}m$. And the densification of the PZT thick films increased with increasing the number of sol coatings.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.4
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• pp.344-348
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• 2002

As microelectronics technology continues to progress, there is also a continuous demand on highly integration and miniaturization of systems. For example, it is desirable to package several integrated circuits together in multilayer structure, such as multichip modules, to achieve higher levels of compactness and higher performance. Passive components (i.e., capacitors, resistors, and inductors) are very important fort many MCM applications. In addition, the low-temperature co-fired ceramic (LTCC) process has considerable potential for embedding passive components in a small area at a low cost. In this paper, we investigate a method of statistically modeling integrated passive devices from just a small number of test structures. A set of LTCC inductors is fabricated and their scattering parameters (s-parameters) are measured for a range of frequencies from 50MHz to 5GHz. An accurate model for each test structure is obtained by using a building block based modeling methodology and circuit parameter optimization using the HSPICE circuit simulator.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.158-165
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• 1999

It has been established that a crack has an important effect on the dynamic behavior of a structure. This effect depends mainly on the location and depth of the crack. To identify the location and depth of a crack in a structure, a method is presented in this paper which uses hybrid neuro-genetic technique. Feed-forward multilayer neural networks trained by back-propagation are used to learn the input)the location and dept of a crack)-output(the structural eigenfrequencies) relation of the structural system. With this neural network and genetic algorithm, it is possible to formulate the inverse problem. Neural network training algorithm is the back propagation algorithm with the momentum method to attain stable convergence in the training process and with the adaptive learning rate method to speed up convergence. Finally, genetic algorithm is used to fine the minimum square error.

• International Journal of Advanced Culture Technology
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• v.10 no.4
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• pp.555-560
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• 2022

In this study, the insertion loss and phase delay according to the multi-layer structure radome parameters were analyzed using the boundary value solution approach, and the multi-layer structure and hexa mesh structures with low-loss electrical characteristics for the Ku-band transmission/reception frequency of 10.7 ~ 14.5 GHz were designed and manufactured. A hexa mesh was applied to minimize radio wave transmission and scattering, which lowered the transmittance refractive index according to the radio incident angle and minimized dielectric loss through high-density foam. Similar to the simulation result, the transmission loss obtained the gain in a specific receiving frequency band, and in the transmission frequency band, an excellent low loss characteristic was obtained with an insertion loss of 0.8dB or less. The results of this study can be used in radio transmission radomes of low-weight, low-cost end-system protection devices.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.50 no.1
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• pp.13-26
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• 2024

Objectives: The aim of this study was to perform a comparative analysis of the ultrastructural and chemical composition of sialoliths, tonsilloliths, and antroliths and to describe their growth pattern. Materials and Methods: We obtained 19 specimens from 18 patients and classified the specimens into three groups: sialolith (A), tonsillolith (B), and antrolith (C). The peripheral, middle, and core regions of the specimens were examined in detail by histology, micro-computed tomography (micro-CT), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy, and transmission electron microscopy (TEM). Results: In the micro-CT, group A showed alternating radiodense and radiolucent layers, while group B had a homogeneous structure. Group C specimens revealed a compact homogeneous structure. Histopathologically, group A showed a laminated, teardrop-shaped, globular structure. Group B demonstrated degrees of immature calcification of organic and inorganic materials. In group C, the lesion was not encapsulated and showed a homogeneous lamellar bone structure. SEM revealed that group A showed distinct three layers: a peripheral multilayer zone, intermediate compact zone, and the central nidus area; groups B and C did not show these layers. The main elemental components of sialoliths were O, C, Ca, N, Cu, P, Zn, Si, Zr, F, Na, and Mg. In group B, a small amount of Fe was found in the peripheral region. Group C had a shorter component list: Ca, C, O, P, F, N, Si, Na, and Mg. TEM analysis of group A showed globular structures undergoing intra-vesicular calcification. In group B, bacteria were present in the middle layer. In the outer layer of the group C antrolith, an osteoblastic rimming was observed. Conclusion: Sialoliths had distinct three layers: a peripheral multilayer zone, an intermediate compact zone and the central nidus area, while the tonsillolith and antrolith specimens lacked distinct layers and a core.

• Journal of the Korean Statistical Society
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• v.30 no.2
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• pp.179-192
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• 2001

When a statistical model has a hierarchical structure such as multilayer perceptrons in neural networks or Gaussian mixture density representation, the model includes distribution with unidentifiable parameters when the structure becomes redundant. Since the exact structure is unknown, we need to carry out statistical estimation or learning of parameters in such a model. From the geometrical point of view, distributions specified by unidentifiable parameters become a singular point in the parameter space. The problem has been remarked in many statistical models, and strange behaviors of the likelihood ratio statistics, when the null hypothesis is at a singular point, have been analyzed so far. The present paper studies asymptotic behaviors of the maximum likelihood estimator and the Bayesian predictive estimator, by using a simple cone model, and show that they are completely different from regular statistical models where the Cramer-Rao paradigm holds. At singularities, the Fisher information metric degenerates, implying that the cramer-Rao paradigm does no more hold, and that he classical model selection theory such as AIC and MDL cannot be applied. This paper is a first step to establish a new theory for analyzing the accuracy of estimation or learning at around singularities.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.315-318
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• 1998

Organic light-emitting diodes(OLEDs) or electroluminescent devices have attracted much attention because of their possible application as large-area light-emitting displays. Their structure was based on employing a multilayer device structure containing an emitting layer and a carrier transporting layer of suitable organic materials. In this study, several Tb complexes such as Tb(ACAC)$_3$(Phen), Tb(ACAC)$_3$(Phen-Cl) and Tb(TPB)$_3$(Phen) were synthesized and the photoluminescence(PL) and electroluminescence (EL) characteristics of their thin films were investigated by fabricating the devices having a structure of anode/HTL/terbium-oomplex/ETL/cathode, where TPD was used as an hole transporting and Alq$_3$ and TAZ-Si were used as an electron transporting materials. It was found that the photoluminescence(PL) and electroluminescence(EL) characteristics of these terbium complexes were dependent upon the ligands coordinated to terbium metal. Details on the explanation of electrical transport phenomena of the structure with I-V characteristics of the OLEDs using the trapped-charge-limited current(TCLC) model will be discussed.

• Smart Structures and Systems
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• v.33 no.3
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• pp.177-188
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• 2024

The fatigue-induced sequential failure of a structure having structural redundancy requires system-level analysis to account for stress redistribution. System reliability-based design optimization (SRBDO) for preventing fatigue-initiated structural failure is numerically costly owing to the inclusion of probabilistic constraints. This study incorporates the Branch-and-Bound method employing system reliability Bounds (termed the B³ method), a failure-path structural system reliability analysis approach, with a metaheuristic optimization algorithm, namely grey wolf optimization (GWO), to obtain the optimal design of structures under fatigue-induced system failure. To further improve the efficiency of this new optimization framework, an additional bounding rule is proposed in the context of SRBDO against fatigue using the B³ method. To demonstrate the proposed method, it is applied to complex problems, a multilayer Daniels system and a three-dimensional tripod jacket structure. The system failure probability of the optimal design is confirmed to be below the target threshold and verified using Monte Carlo simulation. At earlier stages of the optimization, a smaller number of limit-state function evaluation is required, which increases the efficiency. In addition, the proposed method can allocate limited materials throughout the structure optimally so that the optimally-designed structure has a relatively large number of failure paths with similar failure probability.

• Journal of the Semiconductor & Display Technology
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• v.9 no.4
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• pp.13-18
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• 2010

Extreme ultraviolet (EUV) lithography using 13.5 nm wavelengths is expected to be adopted as a mass production technology for 32 nm half pitch and below. One of the new issues introduced by EUV lithography is the shadowing effect. Mask shadowing is a unique phenomenon caused by using mirror-based mask with an oblique incident angle of light. This results in a horizontal-vertical (H-V) biasing effect and ellipticity in the contact hole pattern. To minimize the shadowing effect, a refilled mask is an available option. The concept of refilled mask structure can be implemented by partial etching into the multilayer and then refilling the trench with an absorber material. The simulations were carried out to confirm the possibility of application of refilled mask in 32 nm line-and-space pattern under the condition of preproduction tool. The effect of sidewall angle in refilled mask is evaluated on image contrast and critical dimension (CD) on the wafer. We also simulated the effect of refilled absorber thickness on aerial image, H-V CD bias, and overlapping process window. Finally, we concluded that the refilled absorber thickness for minimizing shadowing effect should be thinner than etched depth.