• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.417-420
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• 2006

The composition and structure of dendrite phase within $Zr_{76.11}Ti_{4.20}Cu_{4.51}Ni_{3.16}Be_{1.49}Nb_{10.53}$ bulk metallic glass (BMG) were confirmed by using an EPMA, XRD and TEM, respectively. The chief elements of dendrite phase were Zr-Ti-Nb and had a BCC structure. The thermal properties of this BMG have been then subsequently investigated by using a differential scanning calorimeter (DSC). The glass transition and crystallization onset temperatures were determined as $339.7^{\circ}C$ and $375.8^{\circ}C$ for this alloy, respectively. Mechanical properties have also been examined by conducting a series of uniaxial compression tests at various temperatures within supercooled liquid region under the strain rates between $10^{-4}/s$ and $3{\times}10^{-2}/s$. The deformation behavior of BMG composite within supercooled liquid region is similar to one of Vit-1 exhibiting amorphous single phase alloy. The flow stresses of BMG composite, however, are entirely higher than those of Vit-1 because dendrite phases are interfere with moving of atoms.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.432-441
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• 2008

In this study, the control performance of a Tuned Liquid Mass Damper(TLMD) manufactured to reduce the orthogonal bi-directional responses of building structures was experimentally evaluated. the TLMD using only one control device reduce bi-directional responses of building structures by making the TLMD behave as TMD and TLCD to the strong and weak axial direction of building structures. first, the control performance was evaluated by forcing sinusoidal waves to a test model that the TLMD is installed on the scale-downed building structure. Second, the real-time hybrid shaking table test was performed to evaluate the performance of the vibration control system made up of numerical part as a scale-downed building structural model and a physical experimental part as a TLMD. the superiority of bi-directional vibration control performance of the manufactured TLMD was verified by comparing the uncontrolled and controlled results of these tests.

• Journal of the Korean Vacuum Society
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• v.13 no.4
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• pp.182-188
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• 2004

Previous studies on the liquid Gallium ion sources used an electro-chemically etched tungsten wire with a coil-type heater. Such a structure requires excessive power consumption in the course of heating the liquid metal. In this work, a new structure is proposed that replaces the coil-type heater. It uses a Gallium reservoir made of six pre-etched 250$\mu\textrm{m}$ tungsten wires that surround the needle electrode. Gallium trading at the reservoir is observed to be much more stable, resulting in an improved beam stability.

• Journal of the Korean Chemical Society
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• v.11 no.4
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• pp.143-149
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• 1967

The Transient State Theory of Significant Liquid Structure is applied to a binary liquid solution of benzene and carbon tetrachloride, which gives slightly positive deviation from Raoults law. The partition function for the solution is derived according to the proposed theory. The various thermodynamic properties such as total and partial vapor pressures, molar volumes, entropies of mixing, and compressibilities are calculated at three different temperatures, 298.15^{\circ}K$, 313.15^{\circ}K$ and 343.1515^{\circ}K$. The calculated values agree satisfactorily with experimental data.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.279-285
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• 1999

Retinoids in anti-wrinkle cosmetics are widely used for the treatment of the photoaging skin these days, but very unstable in the presence of water. Multilamellar liquid crystal vesicles consisted of $poly(oxyethylene)_{15}oleyl$ ether $(POE_{15}OE)$ or $poly(oxyethylene)_{15}stearyl$ ether $(POE_{15}SE)$, cetostearyl alcohol (CSA) and cholesterol or oils were prepared to increase the stability of retinyl acetate or retinyl palmitate. $POE_{15}SE-CSA-Water$ systems were more unstable than $POE_{15}SE-CSA-Water$ systems due to the bended structure of oleyl groups. For the modification of vesicles, cholesterol was added. The enthalpy values were decreased reaching to zero and the water permeability of systems was decreased, but the stabilizaton of retinyl acetate was not greatly improved. The stability of retinyl acetate may depend on its location in the structure. Various oils were added for further stabilization and isopropyl myristate was most effective. In practice, retinyl palmitate showed better stability in the same vesicle than retinyl acetate, and the improved vesicles could be used for the anti-wrinkle cosmetics

• Journal of the Korean Chemical Society
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• v.10 no.1
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• pp.18-24
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• 1966

In formulating the Transient State Theory of Significant Liquid Structure it is assumed that there exist holes of molecular size in liquids and that the liquid state is partitioned in three states, namely, solid-like state, representing the molecules apart from holes; gas-like state, representing the molecules jumping into the holes; and the transient state, representing the molecules in a possible state of jumping into the holes by aquiring the strain energy due to the holes. It is found that the partition function derived according to the proposed theory can be applied to the liquids of argon, nitrogen, benzene, chloroform, and carbon disulfide with good accuracy.

• Macromolecular Research
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• v.12 no.3
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• pp.251-257
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• 2004

The nature of the nematic liquid crystal (LC) alignment induced by the rubbed polyimide (PI) alignment layers (ALs) and the electro-optical (EO) properties of the LC cells are expected to depend on the chemical and physical features of the PI. By employing five pyromellitic dianhydride (PMDA)-type PIs having different functionalities, we have studied the effects of the PI's structure and chemistry on the alignment characteristics and the cell's EO properties. Increasing the flexibility of the PI increases the pretilt angle and tends to improve the alignment stability. On the other hand, the rigid, fluorinated PI displays poor stability for LCs and induces a less stable/uniform LC alignment and, subsequently, a small pre tilt angle. It also transpired that fluorination of the PI deteriorated the voltage-transmittance characteristics and the voltage holding ratio; increasing the flexibility of the PI structure improves these EO properties. The finding that the qualitative trends for the PI's functionalities are similar for both the alignment and EO properties suggests that the EO properties are closely related to the alignment characteristics, which are determined by short-range interactions between LC and PI molecules.

• Composites Research
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• v.34 no.3
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• pp.180-185
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• 2021

Due to the formation of random three dimensional network structure, which cause a lot of scattering of phonons, the thermal conductivity is low when the liquid crystalline epoxy is cured with amine-based curing agent. This problem is solved by using a cationic initiator that can make mesogen groups to be stacked structure. In this experiment, the thermal stability is compared by investigating the activation energy of isothermal decomposition through TGA of an epoxy using an amine-based curing agent and a cationic initiator. As a result, the energy of the activation of the epoxy using a cationic initiator is high. Compared with the previous experiments, the thermal stability is similar to the thermal conductivity.

• Korean Journal of Materials Research
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• v.31 no.6
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• pp.331-338
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• 2021

Ti-Al-Si target and Cr-Si target are sputtered alternately to develop a multi-layered nitride coating on a steel mold to improve die-casting lifetime. Prior to the multi-layer deposition, a CrN layer is developed as a buffer layer on the mold to suppress the diffusion of reactive elements and enhance the cohesive strength of the multi-layer deposition. Approximately 50 nm CrSiN and TiAlSiN layers are deposited layer by layer, and form about three ㎛-thickness of multi-layered coating. From the observation of the uncoated and coated steel molds after the acceleration experiment of liquid metal injection casting, the uncoated mold is severely eroded by the adhesion of molten metallic glass. On the other hand, the multi-layer coating on the mold prevents element diffusion from the metallic glass and mold erosion during the experiment. The multi-layer structure of the coating transforms the nano-composite structured coating during the acceleration test. Since the nano-composite structure disrupts element diffusion to molten metallic glass, despite microstructure changes, the coating is not eroded by the 1,050 ℃ molten metallic glass.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.150-152
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• 2022

In this work, we propose a model that considers the behavior and synaptic plasticity of sensory neurons based on Liquid Time-constant Network (LTC). The neuron connection structure was experimented with four types: the increasing number of neurons, the decreasing number, the decreasing number, and the decreasing number. In this study, we experimented using a time series prediction dataset to see if the performance of the changed model improved compared to LTC. Experimental results show that the application of modeling of sensory neurons does not always bring about performance improvements, but improves performance through proper selection of learning rules depending on the type of dataset. In addition, the connective structure of neurons showed improved performance when it was less than four layers.