• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.406-406
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• 2016

To get high efficiency n-type crystalline silicon solar cells, passivation is one of the key factor. Tunnel oxide (SiO2) reduce surface recombination as a passivation layer and it does not constrict the majority carrier flow. In this work, the passivation quality enhanced by different chemical solution such as HNO3, H2SO4:H2O2 and DI-water to make thin tunnel oxide layer on n-type crystalline silicon wafer and changes of characteristics by subsequent annealing process and firing process after phosphorus doped amorphous silicon (a-Si:H) deposition. The tunneling of carrier through oxide layer is checked through I-V measurement when the voltage is from -1 V to 1 V and interface state density also be calculated about $1{\times}1012cm-2eV-1$ using MIS (Metal-Insulator-Semiconductor) structure . Tunnel oxide produced by 68 wt% HNO3 for 5 min on $100^{\circ}C$, H2SO4:H2O2 for 5 min on $100^{\circ}C$ and DI-water for 60 min on $95^{\circ}C$. The oxide layer is measured thickness about 1.4~2.2 nm by spectral ellipsometry (SE) and properties as passivation layer by QSSPC (Quasi-Steady-state Photo Conductance). Tunnel oxide layer is capped with phosphorus doped amorphous silicon on both sides and additional annealing process improve lifetime from $3.25{\mu}s$ to $397{\mu}s$ and implied Voc from 544 mV to 690 mV after P-doped a-Si deposition, respectively. It will be expected that amorphous silicon is changed to poly silicon phase. Furthermore, lifetime and implied Voc were recovered by forming gas annealing (FGA) after firing process from $192{\mu}s$ to $786{\mu}s$. It is shown that the tunnel oxide layer is thermally stable.

• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.63-70
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• 2009

This study is part of an ongoing research project on the development of a sound-absorbing lightweight foamed concrete manufactured by a hydro-thermal reaction between silica and calcium. As the silica source, pulverized bottom ash was used, and as several cementitious powders of ordinary portland cement, alumina cement and calcium hydroxide were used. Manufacture of foamed concrete was accomplished using the pre-foaming method to make a continuous pore system, which is the method of making the foam by using a foaming agent, then making the slurry by mixing the foam, water, and powders. The experiment factors are W/B, foam agent dilution ratio, and foam ratio, and test items are compressive strength, dry density, void ratio, and absorption rate, as evaluated by NRC. The experiment results showed that the sound absorption of lightweight foamed concrete satisfied NRC requirements for the absorbing materials in most of the experiments. It is thus concluded that foam ratio was the most dominant factor, and significantly affected all properties of lightweight foamed concrete in this study. W/B rarely affected total void ratio and continuous void ratio as well as compressive strength, and dry density and foam agent dilution ratio also had little effect onalmost all properties. The analysis of the correlation between NRC, absorption time, continuous void ratio, and absorption time showed that the interrelationship of the continuous void ratio was high.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.3 s.32
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• pp.1-7
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• 2004

Tin plating on component finishes may grow whiskers under certain conditions, which may cause failures in electronics equipment. To protect the environment, 'lead-free' among component finishes is being promoted worldwide. This paper presents the evaluation results of whiskers on two kinds of lead-free plating materials at the plating temperature and under the reliability test. The rising plating temperature caused increasing the size of plating grain and shorting the growth of whisker. The whisker was grown under the temperature cycling the bent type in matt Sn plating and striated type in malt Sn-Bi. The whisker growth in Sn-Bi plating was shorter than that in Sn plating. In FeNi42 leadframe, the $7.0{\~}10.0{\mu}m$ diameter and the $25.0{\~}45.0{\mu}m$ long whisker was grown under 300 cycles. In the 300 cycles of Cu leadframe, only the nodule(nuclear state) grew on the surface, and in the 600 cycles, a $3.0{\~}4.0{\mu}m$ short whisker grew. After 600 cycles, the ${\~}0.34{\mu}m$ thin $Ni_3Sn_4$ formed on the Sn-plated FeNi42. However, we observed the amount of $0.76{\~}1.14{\mu}m$ thick $Cu_6Sn_5$ and ${\~}0.27{\mu}m$ thin $Cu_3Sn$ intermetallics were observed between the Sn and Cu interfaces. Therefore, the main growth factor of a whisker is the intermetallic compound in the Cu leadframe, and the coefficient of thermal expansion mismatch in FeNi42.

• Journal of Acupuncture Research
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• v.30 no.5
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• pp.51-64
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• 2013

Objectives : This study is performed to develop the oriental medical rating scale of knee pain and to assess its validity. Methods : 250 knee pain patients completed the previously accepted rating scale of knee pain(VAS, WOMAC(pain, function, stiffness), 6 minute walk test(number of steps, distance)) and oriental medical rating scale of knee pain which was developed by Hwang et al at 2012, before and after the 6 weeks acupuncture treatment. Comparing these results, we assessed the validity of oriental medical rating scale. Results : Comparing oriental medical rating scale of knee pain before acupuncture treatment with VAS, WOMAC(pain, function, stiffness) and 6 minute walk test(number of steps, distance), oriental medical rating scale showed correlation with VAS, WOMAC(pain, function, stiffness) and showed the highest correlation with WOMAC(function). Comparing the change of oriental medical rating scale of knee pain after 6 weeks of acupuncture treatment with the change of VAS, WOMAC(pain, function, stiffness) and 6 minute walk test(number of steps, distance) after 6 weeks, change of oriental medical rating scale showed correlation with the change of VAS, WOMAC(pain, function, stiffness) and showed the highest correlation with the change of WOMAC(function). Through factor analysis of oriental medical rating scale items, 4 factors(pain, swelling, deformation of the knee, thermal sense of the knee), 17 items were extracted. Conclusions : Oriental medical rating scale of knee pain reflected the patient's pain, functional limitation and stiffness well. And oriental medical rating scale reflected the patient's functional improvement after the treatment well.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.27-35
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• 2008

This work proposes a 14b 150MS/s 0.13um CMOS ADC for SDR systems requiring simultaneously high resolution, low power, and small size at high speed. The proposed ADC employs a calibration-free four-step pipeline architecture optimizing the scaling factor for the input trans-conductance of amplifiers and the sampling capacitance in each stage to minimize thermal noise effects and power consumption at the target resolution and sampling rate. A signal- insensitive 3-D fully symmetric layout achieves a 14b level resolution by reducing a capacitor mismatch of three MDACs. The proposed supply- and temperature- insensitive current and voltage references with on-chip RC filters minimizing the effect of switching noise are implemented with off-chip C filters. The prototype ADC in a 0.13um 1P8M CMOS technology demonstrates a measured DNL and INL within 0.81LSB and 2.83LSB, at 14b, respectively. The ADC shows a maximum SNDR of 64dB and 61dB and a maximum SFDR of 71dB and 70dB at 120MS/s and 150MS/s, respectively. The ADC with an active die area of $2.0mm^2$ consumes 140mW at 150MS/s and 1.2V.

• Korean Journal of Materials Research
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• v.21 no.5
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• pp.243-249
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• 2011

To reduce manufacturing costs of crystalline silicon solar cells, silicon wafers have become thinner. In relation to this, the properties of the aluminium-back surface field (Al-BSF) are considered an important factor in solar cell performance. Generally, screen-printing and a rapid thermal process (RTP) are utilized together to form the Al-BSF. This study evaluates Al-BSF formation on a (111) textured back surface compared with a (100) flat back surface with variation of ramp up rates from 18 to $89^{\circ}C$/s for the RTP annealing conditions. To make different back surface morphologies, one side texturing using a silicon nitride film and double side texturing were carried out. After aluminium screen-printing, Al-BSF formed according to the RTP annealing conditions. A metal etching process in hydrochloric acid solution was carried out to assess the quality of Al-BSF. Saturation currents were calculated by using quasi-steady-state photoconductance. The surface morphologies observed by scanning electron microscopy and a non-contacting optical profiler. Also, sheet resistances and bulk carrier concentration were measured by a 4-point probe and hall measurement system. From the results, a faster ramp up during Al-BSF formation yielded better quality than a slower ramp up process due to temperature uniformity of silicon and the aluminium surface. Also, in the Al-BSF formation process, the (111) textured back surface is significantly affected by the ramp up rates compared with the (100) flat back surface.

• Journal of Sericultural and Entomological Science
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• v.34 no.2
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• pp.41-51
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• 1992

In this thesis, both soap and enzymatic degumming method were adopted and the optimum degumming conditions were obtained. Difference between the two degumming methods in silk fiber state was investigated and analyzed on the basis of the results of physical testings, polarizing microscopy, scanning electron microscopy, viscosity measurement, (${\alpha}$＋$\varepsilon$) amino group contents measurement, birefringence measurement, amino acid analysis, thermal analysis, infrared spectroscopy and x-ray diffraction analysis. The results obtained were summarized as follows; Physical test results of the degummed silk fiber showed that the tenacity and the elongation of enzymatic degummed silk fiber were lower than those of soap degummed fiber. But SEM observation and amino acid analysis showed almost the same tendency in the two degumming methods. The viscosity of enzymatic degummed silk fiber was lower than that of soap degummed fiber, but (${\alpha}$＋$\varepsilon$) amino group contents was higher in the enzymatic degummed fiber. It can be suggested that the enzymatic degummed silk fibroin was more degraded than the soap degummed fibroin. The birefringence, endothermic temperature of DSC spectrum, IR crystallinity and X-ray lateral order factor of enzymatic degummed silk fiber were higher than those of soap degummed fiber. It seems that the enzymatic degummed silk fiber has the higher crystallinity than that of soap degummed one according to the above results. However, it can be inferred that these differences between soap and enzymatic degummed fiber would be lessened if pretreatment and aftertreatment were included in the enzymatic degumming process.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.168-175
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• 1997

In greenhouse, data on evapotranspiration or water consumption is important for the rational water management, irrigation planning, thermal environment analysis, and watering automation. But little investigations have been attempted to make clear the characteristics of water consumption in greenhouse. In this paper, evapotransplrations of lettuce and cucumber by cropping systems were investigated. And the correlations among evapotranspiration, pan evaporation, solar radiation, mean air temperature, and minimum relative humidity were analyzed. Experimental cropping systems of lettuce were soil culture and NFT system. Those of cucumber were soil culture, perlite culture, and rockwool culture. Total water consumption of lettuce was 2.62$\ell$/plant in soil culture and 1.71$\ell$/plant in NFT system. That of cucumber was 45.22$\ell$/plant in soil culture, 27.45$\ell$/plant in rockwool culture and 29.06$\ell$/plant in perlite culture. Therefore total water consumption of soil culture showed higher than soilless culture.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.97-107
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• 1994

The objective of this study is to develop polymer-impregnated concrete(PIC), which is a newly developed composite material made by impregnating polymer impregnanls into hardened normal concrete, and to develop analytical techniques for its proper applications. Crystalline methyl methacrylate(MMA) is chosen as a monomer of polymer impregnants. The corrlpositions of polymer impregnants and producing processes are developed by analyzing the effects of penetration, polymerization, thermal safety, and strengthening characteristics. On t he basis of experimental results of this study, various strength characteristics and stress strain constitutive relations are formulated in terms of the compressive strength of normal concrete and the polymer loadings, which can be applied for analysis and design of PIC members. In order to provide a model for fracture analysis of flexural members, fracture toughness, fracture energy, critical crack width, and tension softening relations near crack tip are also formulated in terms of member depth, initial notch depth, and the flexural strength of normal concrete. The structural analysis procedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. The accuracy and effectiveness of the developed computer program is examined by comparing the anal ytical results with the experimental results. Therefore, it is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1621-1625
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• 2015

Power quality has always been a concern of power engineers. Certainly an argument can be successfully made that most parts of power engineering have the ultimate objective to improve power quality. AC motors were widely used in industrial and domestic applications. Generally, AC motors were of two types: Induction and Synchronous motors. In motor many parameters like different load cycling, switching, working in hot weather and unbalances creates harmonics which creates major reasons for temperature rise of the motors. Due to high peak value of voltage, harmonics can weaken insulation in cables, windings and capacitors and different electronic components. Higher value of harmonics increase the motor current and decrease the power factor which will reduce the life time of the motor and increase the overall rating of all electrical equipments. Harmonics reduction of all the motors in India will save more power. Coating of windings of the motor with nano fillers will reduce the amount of harmonics in the motor. Based on the previous project works, actions were taken to use the enamel filled with various nano fillers for the coating of the windings of the different AC motors. Ball mill method was used to convert the micro particles of Al₂O₃, SiO₂, TiO₂, ZrO₂ and ZnO into nano particles. SEM, TEM and XRD were used to augment the particle size of the powder. The synthesized nano powders were mixed with the enamel by using ultrasonic vibrator. Then the enamel mixed with the nano fillers was coated to the windings of the several AC motors. Harmonics were measured in terms of various indices like THD, VHD, CHD and DIN by using Harmonic analyzer. There are many other measures and indices to describe power quality, but none is applicable in all cases and in many instances, these indices may hide more than they show. Sometimes power quality indices were used as a basis of comparison and standardization. The efficiency of the motors was increased by 5 – 10 %. The thermal withstanding capacity of the motor was increased by 5º to 15º C. The harmonics of the motors were reduced by 10 – 50%.