• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.89-94
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• 2022

Thermoelectric materials can directly convert a temperature gradient to an electrical energy and vice-versa, and their performance is determined by the electrical conductivity, Seebeck coefficient, and thermal conductivity. However, it is difficult to establish an effective strategy for enhancing performance since electrical conductivity, Seebeck coefficient, and thermal conductivity are strongly dependent on the composition, crystal structure, and electronic structure of the material, and show a correlation with each other. Herein, based on the understanding of the formulas related to the performance of thermoelectric materials, we provide a methodology to establish feasible defect engineering strategies of thermal conductivity reduction for improving the performance of thermoelectric materials in connection with the experimental results.

• Advances in materials Research
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• v.13 no.1
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• pp.55-62
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• 2024

Cu-based sulfides have recently emerged as promising thermoelectric (TE) materials due to their low cost, non-toxicity, and abundance. In this research, point defect structure of Cu_2-xZnSnS₄ (x=0.1, 0.2, 0.3) samples were synthesized by the mechanical alloying method. Mixed powders of Cu, Zn, Sn and S were milled using high energy ball milling at a rotation speed of 300 rpm in Ar atmosphere. The milled Cu_2-xZnSnS₄ powders were heat-treated at 723 K for 24 h, and subsequently consolidated using spark plasma sintering (SPS) under an applied pressure of 60 MPa for 15 min. The thermal conductivity of the sintered Cu_2-xZnSnS₄ samples was evaluated. A well-defined Cu_2-xZnSnS₄ powders were successfully formed after milling for 16 h, with the particle sizes mostly distributed in the range of 60-100 nm. The lattice constants of aand cdecreased with increasing composition value x. The thermal conductivity of sintered x=0.1 sample exhibited the lowest value and attained 0.93 W/m K at 673 K.

• Clinical and Experimental Pediatrics
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• v.49 no.9
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• pp.917-929
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• 2006

Over the last several decades there has been a remarkable change in the therapeutic strategy of congenital heart disease. Development of new tools and devices, accumulations of experience, technical refinement have positively affected the outcome of interventional treatment. Many procedures including atrial septostomy, balloon valvuloplasty, balloon dilation of stenotic vessel with or without stent implantation, transcatheter occlusion of abnormal vascular structure, transcatheter closure of patent arterial duct and atrial septal defect, are now performed as routine interventional procedures in many institutes. In diverse conditions, transcatheter techniques also provide complementary and additive role in combination with surgery. Intraoperative stent implantation on stenotic vessels, perventricular device insertion, and hybrid stage 1 palliative procedure for hypoplastic left heart syndrome have been employed in high risk patients for cardiac surgery with encouraging results. Transcatheter closure of ventricular septal defect has been performed safely showing comparable result with surgery. Investigational procedures such as percutaneous valve insertion and valve repair are expected to replace the role of surgery in certain group of patients in the near future. Continuous evolvement in this field will contribute to reduce the risk and suffering from congenital heart disease, while surgery will be still remained as a gold standard for significant portion of congenital heart disease.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.211.2-211.2
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• 2015

In order to investigate the effect of front channel in DAL (dual active layer) TFT (thin film transistor), we successfully fabricated DAL TFT composed of ITZO and IGZO as active layer using the solution process. In this structure, ITZO and IGZO active layer were used as front and back channel, respectively. The front channel was changed from 0.05 to 0.2 M at fixed 0.3 M IGZO of back channel. When the mol concentration of front channel was increased, the threshold voltage (VTH) was increased from 2.0 to -11.9 V and off current also was increased from 10-12 to 10-11. This phenomenon is due to increasing the carrier concentration by increasing the volume of the front channel. The saturation mobility of DAL TFT with 0.05, 0.1, and 0.2 M ITZO were 0.45, 4.3, and $0.65cm2/V{\cdot}s$. Even though 0.2 M ITZO has higher carrier concentration than 0.05 and 0.1 M ITZO, the 0.1 M ITZO/0.3 M IGZO DAL TFT has the highest saturation mobility. This is due to channel defect such as pores and pin-holes. These defect sites were created during deposition process by solvent evaporation. Due to these defect sites, the 0.1 M ITZO/0.3 M IGZO DAL TFT shows the higher saturation mobility than that of DAL TFT with front channel of 0.2 M ITZO.

• Archives of Reconstructive Microsurgery
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• v.22 no.2
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• pp.52-56
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• 2013

Purpose: We had proceeded seven iIpsilateral dorsalis pedis vascularized pedicle flaps in the distal leg and foot to cover the restricted size defects and followed-up average for 5 years and 9 months to evaluate the survival rate, neurosensory function and cosmesis in final results. Materials and Methods: From January 1999 through October 2012, we have performed iIpsilateral dorsalis pedis vascularized pedicle flaps in the distal leg and foot to cover the restricted size defect (average around $3.6{\times}2.4cm$) in 7 cases and average age was 41.6 years (21.5 to 59.0 years). Lesion site was posterior heel in 4 cases, distal anterior leg in 3 cases. Donor structure was the dorsalis pedis artery and the first dorsal metatarsal vessel and deep peroneal nerve in 3 cases and the dorsalis pedis artery and the first dorsal metatarsal vessel in 4 cases. Results: Seven cases (100%) were survived and defect area was healed with continuous dressing without skin graft. The sensory function in the neurovascular flap was restored to normal in 3 cases. Cosmesis was good and fair in 7 cases (85.7%). Conclusion: Ipsilateral dorsalis pedis vascularized pedicle flap in the distal leg and foot is one of the choice to cover the exposed bone and soft tissues without microsurgical procedure.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.7-16
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• 2010

In this study, wire was used as the filler material for the laser repair welding, and the phenomenon in which the supplied filler material was melted and beaded down into the specimen was examined with varying laser powers and welding speeds. The optimal processing condition was found to be the laser power of 1,300 W, the welding speed and feed wire supply speed of 0.5 ml/in and the defocused distances of +2mm. At this time, the heat input(E) was $65{\sim}75\;J/mm^2$, and no internal defect occurred. When repair welding was carried out as the optimal processing for the part that had an external defect with the radius of 2mm, the filler metal was melted, resulting in the volume smaller than the defect part and thus causing the part unfilled. Therefore, it was found to be necessary to carry out repair welding two to three times by multiple passes rather than does it only once by single pass.

• Archives of Plastic Surgery
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• v.32 no.2
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• pp.255-258
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• 2005

The nasopalatine duct cyst, known as the incisive canal cyst, is the most common nonodontogenic cyst in the maxillofacial area. It is believed to arise from epithelial remnants of the embryonic nasopalatine duct. Nasopalatine duct cysts are most often detected in patients between forties and sixties. The trauma, bacterial infection, or mucous retention has been suggested as etiological factors. The cysts often present as asymptomatic swelling of the palate but can present with painful swelling or drainage. Radiologic findings include a well demarcated cystic structure in a round, ovoid or heart shape presenting with a well-defined bone defect in the anterior midline of the palate between and posterior to the central incisors. Most of them are less than 2cm in size. On MRI, the cyst is identified as a high-intensity, well-marginated lesion, which indicates that it contains proteinaceous material. We experienced a case of a 61-year-old female patient who had a $2.3{\times}2.6{\times}1.7cm$ sized nasopalatine duct cyst. The bony defect after a surgical extirpation was restored with hydroxyapatite. So we report a good results with some reviews of the literatures.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1380-1383
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• 2007

The secondary electron emission coefficient (${\gamma}$) of the cathode is an important factor for improving the discharge characteristics of AC-PDP, because of its close relationship to discharge voltage. In this experiment, we have investigated the electronic structure of the energy band in the MgO layer responsible for the high ${\gamma}$. We used three kinds of MgO pellet that have another component, and each MgO layers have been deposited by electron beam evaporation method. The work-functions of MgO layer have been investigated from their ion-induced secondary electron emission coefficient (${\gamma}$), respectively, using various ions with different ionization energies in a ${\gamma}-FIB$ (Focused Ion Beam) system. We have compared work-function with ${\gamma}-FIB$ system current signal for measurement defect energy level in MgO layer. MgO-A in the three types has lowest work-function value (4.12eV) and there are two defect energy levels.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.353-356
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• 2014

We fabricated organic photovoltaic (OPV) based on ZnO ripple structure on indium tin oxide as electron-collecting layers and PTB7-F20 as donor polymer. In addition, atomic layer deposition (ALD) was used for preparing additional ZnO layers on rippled ZnO. Addition of 2 nm-thick ALD-ZnO resulted in enhanced initial OPV performance and stability. Based on photoluminescence results, we suggest that ALD-ZnO layers reduced number of surface defect sites on ZnO, which can act as electron-hole recombination center of OPV, and increased resistance of ZnO towards surface defect formation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.267-272
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• 1999

Micro-defects in the undoped and MgO-doped $LiNbO_3$ single crystals, which were grown from a congruent melting composition (48.6 mol% $Li_2$O) by the CZ (Czochralski) method, were analyzed using microscopic techniques such as optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Effects of the dopant and g value (the fraction solidfied) on the domain structure and micro-defect were investigated to build a corelationship with a growth condition of crystal. It was observed that the micro-defect concentrated near the domain wall is caused by high stress. Especially, the micro-defect was observed to be biased toward a certain side of the domain wall.