• International Journal of Aeronautical and Space Sciences
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• 제11권4호
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• pp.360-365
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• 2010

Three phase composite materials are widely used in the shipbuilding industry. When reinforced with fiber and particle, the physical and mechanical properties of polymer composite materials are improved. This paper presents the bending analysis of a three phase composite plate with an epoxy matrix, reinforced glass fiber and titanium oxide particles including creep effect when shear stress is taken into account. The obtained results indicate that creep strains lead to compression in the composite material. Introducing reinforced fibers and particles reduces the plate's deflection, when increasing the stretch coefficient allows the calculation of creep deflection during a long loading period.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 추계학술대회 논문집
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• pp.50-53
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• 1988

Lead titanate powders were prepared by mixed-oxide and sol-gel method. O-3 composites were prepared with these powders using Eccogel polymer. According to the volume percent of the PbTiO$_3$ powders, dielectric, piezoelectric properties and poling conditions were investigated. Relative dielectric constants were exponentially increased with volume percent of PbTiO$_3$. Piezoelectric strain coefficients (d$_{33}$ ) were increased with volume percent of PbTiO$_3$. Figure of merit (d$_{h}$.g$_{h}$) for the O-3 composites prepared by the mixed-oxide and sol-gel method were 2728(x10$^{-15}$ $m^2$/N) and 3100(x10$^{-15}$ $m^2$/N) at 70 volume percent of PbTiO$_3$, respectively.ely.

• 약학회지
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• 제43권5호
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• pp.635-641
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• 1999

In this study, we investigated the immunopotent activities of lepidan, a water soluble proteoglycan from Lentinus lepideus. To examine whether lepidan may affect nonspecific immune responses, we determined the effect on the production of nitric oxide (NO). Lepidan effectively increased the NO production in IFN-${\gamma}$ and LPS triggered RAW 264.7 cells. To further demonstrate the evidence that lepidan activates various immune cells, we determined the alkaline phosphatase activity, plaque-forming cell number and secretion of interleukine-4 (IL-4) and granulocyte/macrophage-colony stimulating factor (GM-CSF) after lepidan treatment in murine splenocytes. The results showed that lepidan increased alkaline phosphatase activity and the number of plaque-forming cells, which indicates that lepidan can lead B lymphocytes to late stage of differentiation. Also, when the splenocytes were cultured with lepidan for 48 hr, the level of IL-4 and GM-CSF in the supernatant dramatically increased. Taken together, these data suggest that lepidan is a biological response modulator that is able to activate immune responses.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1531-1532
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• 2006

Recently, the natural environment changes drastically, and the frequency of occurrence for lightning has gradually been increased. Such lightning delivers high volume of energy along the power line and communication line to the equipment in use. The high volume of energy arising from the lightning surge develops in fast velocity to destroy the facilities in power source and many other facilities in operation in sequential destruction with vast energy. In this thesis, the analysis on the change of clamping voltage characteristics by the contact resistance and lead inductance by using several case studies through the application of element for preventing the short circuit of Metal Oxide Varistor for ZnO.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.249.1-249.1
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• 2015

Quantum dots (QDs) are attracting growing attention for photovoltaic device applications because of their unique electronic, optical and physical properties. Lead sulfide (PbS) QDs are one of the most widely studied materials for the devices and known to have size-tunable properties. In this context, we investigated the relationship between the size of PbS QDs and two synthesizing conditions, a concentration of ligand, oleic acid in this work, and injection temperature. The inverted colloidal quantum dot solar cells based on the heterojunction of n-type zinc oxide layer and p-type PbS QDs were also fabricated. The size of the QDs and cell properties were observed to depend on both the QD synthesizing conditions, and hence the overall efficiency of the cell could vary even though the size of QDs used was same. The QD synthesizing conditions were finally optimized for the maximum cell efficiency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1434-1435
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• 2011

In this study, NKN-LST ceramics were prepared by a conventional mixed oxide method and their structure and piezoelectric properties were investigated with the variations of sintering temperature. It was observed that the various sintering temperatures influenced the electrical properties and structural properties of the NKN-LST ceramics. It was found that the piezoelectric properties of NKN-LST ceramic sintered at $1080^{\circ}C$ for 4h has a piezoelectric constant and a planar electromechanical coupling coefficient of 161pC/N and 0.311% respectively. This ceramics look very promising as possible, practicable, lead-free replacements for lead zirconate titanate.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.721-723
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• 1992

The electrical resistivity and piezoelectric properties have been studied for Lead Zirconate-Titanate(PZT) with $Nb_2O_5$ dopant, fabricated from conventional mixed-oxide powders and molten salt synthesis. The resistivity and electromechanical coupling factor(Kp) were increased with increasing Nb contents. The reason for increasing of the electrical resistivity below the Curie Temperature(Tc), It is believed that the p-type electrical conduction in PZT is caused by the lead vacancies. The electromechanical coupling factor(Kr) and piezoelectric constant $d_{33}$ were improved by Nb additives. This behavior can be explained as a compensation effect and $Nb^{5+}$ can serve as a donar and contribute electrons to the conduction process. As a result, the optimized $Nb_2O_5$ dopants on the PZT specimens were 0.75 wt%.

• 한국분말재료학회지
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• 제21권2호
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• pp.142-146
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• 2014

Fundamental experiences have been studied for development of pre-treatment process of Sn by-products such as solders. Dry and wet separation/recovery processes were considered by the differences of physical properties. The by-products, which are analyzed by solder metal and oxides. The metal and oxide were simply separated by dry ball-milling process for 12 hours, after that recovery metal powder might be reusable as lead or lead-free solders. In terms of wet separation process, samples were dissolved in $HNO_3+H_2O_2$ and the precipitation were analyzed by $SnO_2$. Overall efficiency of recovery might be increasing via developing simple pre-treatment process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1992년도 춘계학술대회 논문집
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• pp.133-136
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• 1992

Electrical resistivity and piezoelectric properties were investigated in Lead Zirconate-Titante(PZT) with Nb$_2$O$\sub$5/dopant, fabricated from conventional mixed-oxide powders and molten salt synthesis. The resistivity and electromechanical coupling factor(K$\sub$p/) were increased with increasing Nb content. The reason for increasing of the electrical resistivity below the Curie Temperature(TC). It is believed that the Curie Temperature(Tc). It is believed that the p-type electrical conduction in PZT is due to lead vacancies. The electromechanical coupling factor(K$\sub$p/) and piezoelectric constant d$\sub$33/ were improved. This behavior can be explained as a compensation effect and Nb$\^$5+/ can serve as a donar and contribute electrons to the conduction process. As a result, the optimized Nb$_2$O$\sub$5/ dopants on the PZT specimens were 0.75 wt%.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1642-1651
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• 2021

In this study, isophtalic neopentyl glycol polyester (NPG-PES) based composites with different loading ratios of pure tungsten metal (W), tungsten (VI) oxide (WO₃), tungsten boron (WB) and tungsten carbide (WC) composites were prepared as alternative shielding materials for ionizing electromagnetic radiation (IEMR) shielding. Structural characterizations of the composites were done. Gamma spectrometric analysis of composites for 80-2000 keV energy range was performed and their usability as IEMR shielding was discussed. As a result, the produced composites showed a shielding performance of 60-100% of the lead (the most widely used IEMR shielding material) depending on the reinforcement material, reinforcement loading rate and experimental conditions. Thus, it was reported that produced composites could be an alternative to lead shieldings that have several disadvantages as toxic properties, difficulty of processing and inelasticity.