• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.155-155
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• 2011

반도체 양자링은 양자점과 같이 효율이 높은 광학 소자 및 전자 소자에 응용 가능할 뿐 아니라, 양자점과는 다른 흥미로운 현상 연구가 가능하기 때문에 지속적으로 연구되고 있는 양자 구조이다. 특히, 반도체 양자링은 다양한 양자 구조를 형성하기 위한 기초 구조로 사용될 수 있으므로, 반도체 양자링 구조의 형성 메카니즘을 연구하는 것 또한 중요하다. 본 연구에서는 Molecular Beam Epitaxy (MBE)를 이용하여 N-type (100) GaAs 기판 위에 GaAs 양자 구조를 형성하였다. As4 분압의 영향, 즉 3-5 ratio가 표면 양자 구조 변화에 미치는 영향을 관찰하기 위해 3족과 5족을 분리하여 성장하는 전형적인 성장 방식인, droplet epitaxy mode를 사용하였다. 성장 온도, Ga metal droplet 밀도 등의 조건을 고정하고 Arsenic 분압을 1e-5 torr부터 3e-8 torr로 감소시켰을 때 표면 이미지를 AFM과 SEM으로 관찰하였다. As4 분압이 1e-5 torr일 때 양자점의 표면 형상을 보여주다가 As4 분압을 줄여갈수록 양자점의 크기가 증가하면서 As4 분압 1e-6 torr에서는 SEM 이미지 상으로도 분명한 양자링을 관찰할 수 있었다. 특히 주목할 것은 As4 분압 1e-6 torr에서 더 줄여갈수록 양자링 중앙 부분의 낮은 부분이 점점 넓어졌다는 점이다. 이것은 As4 분압 1e-6 torr 이상의 조건이 As4와 Ga atom이 결합하여 GaAs 양자점을 형성하는데 적절한 3-5 ratio의 조건인 반면, 그보다 적은 As4 분압에서는 As4와 결합하지 못한 Ga atom의 표면 migration에 의한 driving force로 인해 양자링이 형성되었다고 추측할 수 있다. 이렇게 형성된 양자링을 열처리 후 macro-PL 측정을 통해 광학적 특성을 보고자 하였다. 그 결과 같은 조건에서 열처리되어 PL 측정한 양자점의 에너지에 비해 peak position이 blue shift한 것을 볼 수 있었다. 이것은 As4를 제외한 같은 조건에서 성장된 양자 구조에서 양자링의 경우 양자점에 비해 그 높이가 낮음을 추측해 볼 수 있다. 양자 구조의 모양과 광학 특성의 관계를 밝히기 위해 추후 추가 측정 및 분석이 필요할 것이다.

• Journal of Navigation and Port Research
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• v.34 no.3
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• pp.235-242
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• 2010

In recent years, the busan port is now facing a serious crisis. Exterally, though worldwide economics depression is a serious factor, cuttthroat competition between north port and new port since new port open lead to decrease terminal profitability and busan port image. The essential cause is crowed with terminal operators. therefore, This paper empirically analyze the container terminal integration factor solving busan port problem affecting the competitiveness performance. According to research results, integration between operators will be to acomplish global terminal, and so, contribute to increase service power, port productivity, cargoes and to be hub-port at the north-east asia. These results show political suggestions for importance of repid integration to improve busan port's competitiveness.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.04a
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• pp.916-919
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• 2017

최근 딥러닝의 발달로 인해 Sentiment analysis분야에서도 다양한 기법들이 적용되고 있다. 이미지, 음성인식 분야에서 높은 성능을 보여주었던 Convolutional Neural Networks (CNN)은 최근 자연어처리 분야에서도 활발하게 연구가 진행되고 있으며 Sentiment analysis에도 효과적인 것으로 알려져 있다. 기존의 머신러닝에서는 lexicon을 이용한 기법들이 활발하게 연구되었지만 word embedding이 등장하면서 이러한 시도가 점차 줄어들게 되었다. 그러나 lexicon은 여전히 sentiment analysis에서 유용한 정보를 제공한다. 본 연구에서는 SemEval 2017 Task4에서 제공한 Twitter dataset과 다양한 lexicon corpus를 사용하여 lexicon을 CNN과 결합하였을 때 모델의 성능이 얼마큼 향상되는지에 대하여 연구하였다. 또한 word embedding과 lexicon이 미치는 영향에 대하여 분석하였다. 모델을 평가하는 metric은 positive, negative, neutral 3가지 class에 대한 macroaveraged F1 score를 사용하였다.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.220-225
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• 2020

Hair is made of proteins containing various amino acids. Ultraviolet (UV) radiation is believed to be responsible for the most damaging effects of sunlight, and also plays an important role in hair aging. The purpose of this study was to investigate the changes in morphological and chemical structures after ultraviolet B (UVB) irradiation of human hair. The UVB-irradiated hair showed characteristic morphological and structural changes, compared to those of the normal hair. The result from a scanning electron microscope (SEM) equipped with an energy dispersive X-ray diffractometer (EDX) showed that the scale of UV-irradiated hair appeared to be rough and the amount of oxygen element was higher than that of the normal hair. Fluorescence and three dimensional (3D) topographical images were obtained by a confocal laser scanning microscope (CLSM). In 3D images, the green emission intensity of normal hair was much higher than that of fluorescing UVB-irradiated hair. The intensity of green emission reflects the intrinsic fluorescence of hair protein. Also, a fluorescent imaging method using fluorescamine reagent was used to identify the free amino groups resulting from a peptide bond breakage in UVB-irradiated hair. Strong blue fluorescence of UVB-irradiated hair, which indicates a very high level of amino groups, was observed by CLSM. Therefore, the fluorescamine as an extrinsic fluorescence could provide a useful tool to identify the peptide bond breakage in UVB-irradiated hair. Infrared image mapping was also employed to assess the cross-sections of normal and UVB-irradiated specimens to examine the oxidation of disulfide bonds. The degree of peak areas with strong absorbance for the disulfide mono-oxide was spread from the outside to the inside of hair. The spectroscopic techniques used alone, or in combination, launch new possibilities in the field of hair cosmetics.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.48-59
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• 2021

In this study, experiments were conducted to investigate the compressive·flexural performances of single fiber-reinforced mortar (FRM) using only steel fiber or carbon fiber which has different material properties as well as hybrid FRM using a mixture of steel and carbon fibers. The mortar specimens incorporated steel and carbon fibers in the mix proportions of 1+0%, 0.75+0.25%, 0.5+0.5%, 0.25+0.75% and 0+1% by volume at a total volume fraction of 1.0%. Their mechanical performance was compared and examined with a plain mortar without fiber at 28 days of age. The experiments of mortar showed that the hybrid FRM using a mixture of 0.75% steel fibers + 0.25% carbon fibers had the highest compressive and flexural strength, confirming by thus the synergistic reinforcing effect of the hybrid FRM. On the contrast, in the case of hybrid FRM using a mixture of 0.5% steel fibers + 0.5% carbon fibers witnessed the highest flexural toughness, suggesting as a result the optimal fiber mixing ratio of hybrid FRM to improve the strength and flexural toughness at the same time. Moreover, the fracture surface was observed through a scanning electron microscope (SEM) for image analysis of the FRM specimen. These results were of great help for images analysis of hybrid reinforcing fibers in cement matrix.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.165-172
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• 2021

The purpose of this study is to investigate the carbon capture capacity of various inorganic materials. For this purpose, the change in property of ordinary Portland cement (OPC), blast furnace slag fine powder (GGBS), and circulating fluidized bed boiler ash (CFBC) due to carbonation were analyzed. Carbonation curing was performed on all specimens through the accelerated carbonation experiment, and the amount of carbon capture was quantitatively analyzed by thermogravimetric analysis according to the age of carbonation. From the results, it is confirmed that the carbon capture capacity was shown in all specimens. The carbon capture amount was shown in the order of CFBC, OPC, and GGBS. The 28-day carbon capture of CFBC, OPC, and GGBS was 3.9%, 1.3%, and 9.4%, respectively. Carbon capture reaction occurred rapidly at the beginning of carbonation, and occurred slowly with increasing age. SEM image analysis revealed that an additional product generated by carbonation curing in all specimens was calcium carbonate.

• Journal of the Korean Applied Science and Technology
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• v.40 no.5
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• pp.1043-1054
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• 2023

Amidst the rapid growth of the vegan cosmetics market, consumer orientation towards environmental and ethical values has been intensifying. However, research on this subject remains limited. This study delves into the relationship between consumer value perception, environmental motivations, and perceived barriers influencing the purchase intentions of vegan cosmetics. Conducting a PLS-SEM analysis on a sample of 300 women with experience using vegan cosmetics, it was discerned that monetary value, social value, brand value, emotional value, quality value, and environmental knowledge play significant roles in influencing purchase intentions. The moderating effect analysis highlighted image barriers and value barriers as crucial factors. Through Importance-Performance Map Analysis, emotional value emerged as a pivotal element in strategizing to strengthen the purchasing intentions for vegan cosmetics. This research contributes both theoretically and practically to enhancing the competitive edge of the vegan cosmetics market and promoting sustainable consumption behavior.

• Membrane Journal
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• v.27 no.4
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• pp.350-357
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• 2017

In this study, we used TIPS (thermally induced phase separation) for the application of water treatment membrane, and observed the change in morphology of separation membrane due to the change of solidification temperature and heat capacity. For manufactured membrane, PVDF and silica with excellent mechanical properties and chemical resistance were used, and DOP (dioctyl phthalate), DBP (dibutyl phthalate) were used as the diluent. Using the SEM (scanning electron microscope), the morphology of each different coagulation solutions of heat capacity change was observed. As the heat capacity increased, the crystallization rate of PVDF was decreased and showed large pore. In contrast, It also confirmed that the smaller heat capacity, the faster the crystallization rate and make smaller pores.

• Journal of IKEEE
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• v.26 no.2
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• pp.232-239
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• 2022

We analyzed the effect of post-annealing on lithium phosphate (Li₃PO₄) solid-state thin-film. Li₃PO₄ thin films were deposited by radio frequency (RF) sputtering, with subsequent annealing of the films at 200-400 ℃. SEM imaging of the sample surfaces showed no significant difference in morphology between the annealed and non-annealed samples. XRD analysis indicated that the samples consist of an amorphous-like structure. Post-annealing changes in binding energy were confirmed by XPS analysis, while the leakage current density at -6 V was measured to be about 7.15 times lower in a device that had been annealed at 400 ℃ vs a non-annealed device. It was confirmed that the leakage current decreased with increasing post-annealing temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.509-515
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• 2012

In this study, ${\gamma}-Al_2O_3$ nanoparticles were synthesized by using coflow hydrogen diffusion flames. The synthesis conditions were varied with using several oxygen concentrations in the oxidizing air. The particle characteristics of the flame-synthesized $Al_2O_3$ nanoparticles were determined by examining the crystalline structure, shape, and specific surface area of the nanoparticles. The measured maximum centerline temperature of the flames ranged from 1507.8 K to 1998.7 K. The morphology and crystal structure of the $Al_2O_3$ nanoparticles were determined from SEM images and XRD analyses, respectively. The particle sizes were calculated from measured BET specific surface areas and ranged from 25 nm to 52 nm. From XRD analyses, it was inferred that a large number of the synthesized nanoparticles were ${\gamma}-Al_2O_3$ nanoparticles including ${\theta}-Al_2O_3$ nanoparticles.