• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.194-194
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• 2006

Polymer light-emitting diodes(PLEDs) have great potential application in large area flat panel displays and general lighting so intense academic and industrial research, and impressive scientific and technological progress has been achieved in this field. However, the efficiency and stability of PLEDs till need to be improved in order to fully realize the advantages of low cost and ease of fabrication provided by organic materials. Here, we report our effort to enhance the PLED' s performance in two approaches : 1) Utilizing nano-structured materials such as nano particles, clay, nano porous silica in active layer 2) Modifying the device structure in nano scale to improve not only the device efficiency but also its stability.

• Journal of Welding and Joining
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• v.18 no.3
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• pp.60-67
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• 2000

In this study, we constructed a preview-sensing visual sensor system for weld seam tracking in GMA welding. The visual sensor consists of a CCD camera, a diode laser system with a cylindrical lens and a band-pass-filter to overcome the degrading of image due to spatters and/or arc light. To obtain weld joint position and edge points accurately from the captured image, we compared Hough transform method with central difference method. As a result, we present Hough transform method can more accurately extract the points and it can be applied to real time weld seam tracking. Image processing is carried out to extract straight lines that express laser stripe. After extracting the lines, weld joint position and edge points is determined by intersecting points of the lines. Although a spatter trace is in the image, it is possible to recognize the position of weld joint. Weld seam tracking was precisely implemented with adopting Hough transform method, and it is possible to track the weld seam in the case of offset angle is in the region of $\pm15^{\circ}$.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.82-90
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• 2005

Recently, the in-line vision inspection has become the subject of growing research area in the visual control systems and robotic intelligent fields that are required exact three-dimensional pose. The objective of this article is to study the pc based in line visual inspection with the hand-eye structure. This paper suggests three dimensional structured light measuring principle and design method of laser sensor header. The hand-eye laser sensor have been studied for a long time. However, it is very difficult to perform kinematical analysis between laser sensor and robot because the complicated mathematical process are needed for the real environments. In this problem, this paper will propose auto-calibration concept. The detail process of this methodology will be described. A new thinning algorithm and constrained hough transform method is also explained in this paper. Consequently, the developed in-line inspection module demonstrate the successful operation with hole, gap, width or V edge.

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.458-465
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• 2022

Interest in the use of semiconductor-based photocatalyst materials for the degradation of organic pollutants in a liquid phase has grown, due to their excellent performance and response to the light source. Herein, we fabricated a NiO-SiC-TiO₂ ternary structured photocatalyst which had reduced bandgap energy, with strong activation under UV-light irradiation. The synthesized samples were examined using XRD, SEM, EDX, TEM, DRS, EIS techniques and photocurrent measurement. The results confirmed that the two types of metal oxides were well bonded to the SiC fiber surface. The junction of the new photocatalyst exhibited a large number of photoexcited electrons and holes. The holes tended to oxidize the water and form a hydroxyl radical, which promoted the decomposition of methylene blue. The close contact between the 2D SiC fiber and metal oxide semiconductors expanded the scope of absorption wavelength, and enhanced the usability of the ternary photocatalyst for the degradation of methylene blue. Among three synthesized samples, the NiO-SiC-TiO₂ showed the best photocatalytic effect, and was considered to have excellent photoelectron transfer due to the synergy effect between the metal oxide and SiC.

• International Journal of Korean Welding Society
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• v.1 no.2
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• pp.23-29
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• 2001

In this study, a preview-sensing visual sensor system is constructed far weld seam tracking in GMA welding. The visual sensor system consists of a CCD camera, a diode laser system with a cylindrical lens, and a band-pass-filter to overcome the degrading of image due to spatters and/or arc light. Among the image processing methods, Hough transform method is compared with the central difference method from a viewpoint of the capability for extracting the accurate feature position. As a result, it was revealed that Hough transform method can more accurately extract the feature positions and it can be applied to real time weld seam tracking. Image processing which includes Hough transform method is carried out to extract straight lines that express laser stripe. After extracting the lines, weld joint position and edge points are determined by intersecting the lines. Even though the image includes a spatter trace on it, it is possible to recognize the position of weld joint. Weld seam tracking was precisely implemented with adopting Hough transform method, and it is possible to track the weld seam in the case of offset angle is in the region of $\pm$ $15^{\circ}$.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.69-72
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• 2020

In this study, the inverted structured electroluminescence (EL) devices were fabricated with double electron transport layers (ETLs). The conduction band minimum (CBM) of TiO₂ NPs is lower than SnO₂ NPs. Therefore, it is expected that inserting TiO₂ NPs between the SnO₂ layer and the emission layer (EML) will reduce the energy barrier and transport electrons smoothly. The quantum dot light emitting diodes (QLEDs) with double ETLs showed the enhanced emission characteristics than those with only SnO₂ layer.

• KSBB Journal
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• v.15 no.1
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• pp.14-21
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• 2000

In this study, algae cultivation using the photobioreactor has been applied to remove the nitrogen and phosphorus compounds in the wastewater of the livestock industry. The optimal ratio of nitrate and ortho-phosphate concentration was found for the enhancement of removal efficiency. To achieve the high density culture of algae, the photobioreactor consisted of optical fibers wes developed to get the sufficient light intensity. The light could be illuminated uniformly from light source to the entire reactor by the optical fibers. The structured kinetic model was proposed to describe the growth rate, consumption rate of nitrates and ortho-phosphates in algae culture. The self-organizing fuzzy logic controller incorporated with genetic algorithm was constructed to control the semi-continuous wastewater treatment system. The proposed fuzzy logic controller was applied to maintain the nitrated concentration at the given set-point with the control of wastewater feeding rate. The experimental results showed that the self-organizing fuzzy logic controller could keep the nitrate concentration and enhance algae growth.

• Korean Journal of Materials Research
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• v.31 no.6
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• pp.353-366
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• 2021

In this study, photocatalytic degradation of ammonia in petrochemical wastewater is investigated by solar light photocatalysis. Two-dimensional ultra-thin atomic layer structured MoS₂ are synthesized via a simple hydrothermal method. We examine all prepared samples by means of physical techniques, such as SEM-EDX, HRTEM, FT-IR, BET, XRD, XPS, DRS and PL. And, we use fullerene modified MoS₂ nanosheets to enhance the activity of photochemically generated oxygen (PGO) species. Surface area and pore volumes of the MoS₂-fullerene samples significantly increase due to the existence of MoS₂. And, PGO oxidation of MB, TBA and TMST, causing its concentration in aqueous solution to decrease, is confirmed by the results of PL. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and the PGO effect increase in the case with modified fullerene. The experimental results show that this heterogeneous catalyst has a degradation of 88.43% achieved through visible light irradiation. The product for the degradation of NH₃ is identified as N₂, but not NO^2- or NO^3-.

• Journal of Korean Elementary Science Education
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• v.41 no.2
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• pp.283-294
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• 2022

Although the concept of light is important in the elementary school curriculum, substantial research suggests that students and teachers have difficulties in understanding it. Therefore, it is necessary to analyze the reasons for these difficulties-whether it is due to the content or due to the presentation method of contents, structure, and expression. The national curriculum and textbooks of Korea, the US, China, and Japan were comparatively analyzed from the following perspectives: 1) key concepts of light, 2) structure of light units in the textbook, 3) materials, light sources, and optics used in light units. Consequently, there were differences between countries in their inclusion of the concept of light in the curriculum. In particular, the Korean curriculum studies the concept of refraction by a convex lens, whereas the concept of light, light source, and vision is not introduced. Furthermore, countries also differed in their structuring of units. The Korean curriculum was presented segmentally by concept rather than structured according to core ideas or perspectives, and the connection between concepts was unclear. In addition, there were differences between the countries in materials, light sources, and optical instruments to explain key concepts. On using light, the US curriculum provides a purpose and uses light to achieve it, and China and Korea understand the concept. It was divided into the method of using the material to deepen. Based on the results of this analysis, the implications for the elementary science curriculum in Korea were derived as follows. First, it is necessary to introduce concepts sequentially and organize them so that the connection between concepts is well expressed. Second, it is necessary to introduce light and light sources as the predominant concepts. Third, it is necessary to include the principle of seeing objects. Fourth, it is necessary to adjust the material and content level of the refraction concept included in the light and lens unit. Fifth, an integrated approach is required because light has a deep connection with various concepts included in the elementary science curriculum.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.65-65
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• 2015

In this talk, I will introduce two topics. The first topic is the polymer light emitting diodes (PLEDs) using graphene oxide quantum dots as emissive center. More specifically, the energy transfer mechanism as well as the origin of white electroluminescence in the PLED were investigated. The second topic is the facile synthesis of eco-friendly III-V colloidal quantum dots and their application to light emitting diodes. Polymer (organic) light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nanomaterial without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence (EL) from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. (Sci Rep., 5, 11032, 2015). New III-V colloidal quantum dots (CQDs) were synthesized using the hot-injection method and the QD-light emitting diodes (QLEDs) using these CQDs as emissive layer were demonstrated for the first time. The band gaps of the III-V CQDs were varied by varying the metal fraction and by particle size control. The X-ray absorption fine structure (XAFS) results show that the crystal states of the III-V CQDs consist of multi-phase states; multi-peak photoluminescence (PL) resulted from these multi-phase states. Inverted structured QLED shows green EL emission and a maximum luminance of ~45 cd/m2. This result shows that III-V CQDs can be a good substitute for conventional cadmium-containing CQDs in various opto-electronic applications, e.g., eco-friendly displays. (Un-published results).