Effect of low processing rate on homogeneous microstructural evolution of polyacrylonitrile‑based carbon fibers

Doo‑Won Kim,Dae Ho Kim,Sung Ryong Kim,Bo‑Hye Kim,Yun Hyuk Bang,Duck Joo Yang,Go Bong Choi,Yoong Ahm Kim,Kap Seung Yang 한국탄소학회 2019 Carbon Letters Vol.29 No.5

This study demonstrates that low processing rate for producing polyacrylonitrile (PAN)-based carbon fiber is a critical to obtain a homogeneous radial microstructure with high resistance to oxidation, thereby resulting in their improved mechanical strength. The dry-jet wet spun PAN organic fibers were processed (e.g., stabilized and then carbonized) utilizing two different rates; one is 1.6 times longer than the other. The effect of processing rate on the microstructural evolutions of carbon fibers was analyzed by scanning electron microscopy after slow etching in air, as well as Raman mapping after graphitization. The rapidly processed fiber exhibited the multilayered radial structure, which is caused by the radial direction stretching of the extrusion in the spinning. In case of the slowly processed fiber, the layered radial structure formed in the spinning process was changed into a more homogeneous radial microstructure. The slowly processed fibers showed higher oxidation resistance, higher mechanical properties, and higher crystallinity than the rapidly processed one. Raman mapping confirmed that the microstructure developed during spinning was sustained even though fiber was thermally treated up to 2800 °C.

Laparoscopy vs. laparotomy for embryo transfer to produce transgenic goats (Capra hircus)

Sang Tae Shin,Sung Keun Jang,Hong Suk Yang,Ok Keun Lee,Yhong Hee Shim,Won Il Choi,Doo Soo Lee,Gwan Sun Lee,Jong Ki Cho,Young Won Lee 대한수의학회 2008 JOURNAL OF VETERINARY SCIENCE Vol.9 No.1

This study was performed to produce transgenic Korean native goat (Capra hircus) by laparoscopic embryo transfer (ET) to overcome the limitations of ET performed by laparotomy. Transgenic embryos were produced by DNA pronuclear microinjection of in vivo zygotes. The recipient goats were synchronized for estrus by using an introvaginal progesterone devices as a controlled internal drugreleasing insert (CIDR) for 13 days and injection of 400 IU PMSG 48 h before removal of the insert. Embryos were transferred on day 3 and 4 after removal of the insert. Recipient goats were deprived of feed for 48 h, then suspended in a laparotomy cradle at an angle of 45o. After obtaining a sufficient pneumoperitoneum, the laparoscope and forceps were inserted abdominally through 5 mm trocar sleeves. Examination of the ovaries and uterus was performed and then 213 embryos were transferred into the oviducts via the infundibula of 76 recipient goats. To compare pregnancy rates, ET was also performed by laparotomy in 82 recipient goats. The pregnancies in the recipient goats were diagnosed by ultrasound on day 30 after embryo transfer. The pregnancy rate with laparoscopic ET was significantly higher than with ET performed by laparotomy (46.1% vs. 28.6%, p < 0.05). In addition, the pregnancy rates were compared between ovulated and non-ovulated ovaries of the recipient goats in the laparoscopic ET group. No significant difference was observed between the pregnancy rates of ovulated and non-ovulated ovaries (41.3% vs. 33.3%, p < 0.05) suggesting that ET may also be possible in non-ovulated recipients through artificial rupture of Graafian follicles. These results suggest that laparoscopic ET is a highly efficient method for the transfer of goat embryos. This study was performed to produce transgenic Korean native goat (Capra hircus) by laparoscopic embryo transfer (ET) to overcome the limitations of ET performed by laparotomy. Transgenic embryos were produced by DNA pronuclear microinjection of in vivo zygotes. The recipient goats were synchronized for estrus by using an introvaginal progesterone devices as a controlled internal drugreleasing insert (CIDR) for 13 days and injection of 400 IU PMSG 48 h before removal of the insert. Embryos were transferred on day 3 and 4 after removal of the insert. Recipient goats were deprived of feed for 48 h, then suspended in a laparotomy cradle at an angle of 45o. After obtaining a sufficient pneumoperitoneum, the laparoscope and forceps were inserted abdominally through 5 mm trocar sleeves. Examination of the ovaries and uterus was performed and then 213 embryos were transferred into the oviducts via the infundibula of 76 recipient goats. To compare pregnancy rates, ET was also performed by laparotomy in 82 recipient goats. The pregnancies in the recipient goats were diagnosed by ultrasound on day 30 after embryo transfer. The pregnancy rate with laparoscopic ET was significantly higher than with ET performed by laparotomy (46.1% vs. 28.6%, p < 0.05). In addition, the pregnancy rates were compared between ovulated and non-ovulated ovaries of the recipient goats in the laparoscopic ET group. No significant difference was observed between the pregnancy rates of ovulated and non-ovulated ovaries (41.3% vs. 33.3%, p < 0.05) suggesting that ET may also be possible in non-ovulated recipients through artificial rupture of Graafian follicles. These results suggest that laparoscopic ET is a highly efficient method for the transfer of goat embryos.

Green Fabrication of Superhydrophobic Surfaces Using Laser Surface Texturing Without Toxic Chemicals: A Review

Won-Shik Chu,Malik Muhammad Shehroze,Ngoc Giang Tran,The-Hung Dinh,Sung-Tae Hong,Doo-Man Chun 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.25 No.5

This review study provides an overview of superhydrophobic surface fabrication techniques based on laser surface texturing that are environmentally friendly. There are many prospective applications for superhydrophobic surfaces, including self-cleaning, anti-icing, oil–water separation, anti-corrosion, and anti-biofouling. Except for hydrophobic nanoparticle coating procedures, superhydrophobic surface manufacturing methods have not been sufficiently developed or commercialized. Among the various fabrication techniques, laser surface texturing is an important process that is different from superhydrophobic surface coating processes. This technique can be used to fabricate superhydrophobic surfaces in an eco-friendly manner and can process selected regions without the use of a mask. This review study is intended to improve our understanding of these laser surface texturing technologies for fabricating superhydrophobic surfaces and to open up new research areas. In this review, procedures, materials, and parameters for creating superhydrophobic surfaces using laser processing and environmentally friendly post-processing are analyzed and summarized. Because they involve the use of hazardous chemicals, common laser processes with fluorination or silanization coatings were not included. Finally, we provide an overview of the study trends and offer conclusions based on this review.

A Culture-Based Study of the Bacterial Communities within the Guts of Nine Longicorn Beetle Species and their Exo-enzyme Producing Properties for Degrading Xylan and Pectin

Doo-Sang Park,Hyun-Woo Oh,Won-Jin Jeong,Hyangmi Kim,박호용,배경숙 한국미생물학회 2007 The journal of microbiology Vol.45 No.5

In this study, bacterial communities within the guts of several longicorn beetles were investigated by a culture-dependent method. A total of 142 bacterial strains were isolated from nine species of longicorn beetle, including adults and larvae. A comparison of their partial 16S rRNA gene sequences showed that most of the bacteria constituting the gut communities can typically be found in soil, plants and the intestines of animals, and approximately 10% were proposed as unreported. Phylogenetic analysis demonstrated that the bacterial species comprised 7 phyla, and approximately half were Gammaproteobacteria. Actinobacteria were the second most populous group (19%), followed by Firmicutes (13%) and Alphaproteobacteria (11%). Betaproteobacteria, Flavobacteria, and Acidobacteria were minor constituents. The taxonomic compositions of the isolates were variable according to the species of longicorn beetle. Particularly, an abundance of Actinobacteria existed in Moechotypa diphysis and Mesosa hirsute, which eat broadleaf trees; however, no Actinobacteria were isolated from Corymbia rubra and Monochamus alternatus, which are needle-leaf eaters. Considerable proportions of xylanase and pectinase producing bacteria in the guts of the longicorn beetles implied that the bacteria may play an important role in the digestion of woody diets. Actinobacteria and Gammaproteobacteria were the dominant xylanase producers in the guts of the beetles.

[구연17]Possible role of undifferentiated bone marrow cells from ROSA26 mice to contribute for forming molar tooth; understanding for tooth transplantation

Sung-Won Cho,Jae-Young Kim,Heui-Jung Hwang,Chae-Sun Im,Doo-Hwa Kang,Tae-Joon Gil,Hun-Moo Yang,Han-Sung Jung 대한체질인류학회 2004 대한체질인류학회 학술대회 연제 초록 Vol.47 No.-

Interleaved Soft-Switching Boost Converter for Photovoltaic Power-Generation System

Doo-Yong Jung,Young-Hyok Ji,Sang-Hoon Park,Yong-Chae Jung,Chung-Yuen Won IEEE 2011 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.26 No.4

<P>In this paper, a interleaved soft switching boost converter (ISSBC) for a photovoltaic (PV) power-generation system is proposed. The topology used raises the efficiency for the dc/dc converter of the PV power conditioning system (PVPCS), and it minimizes switching losses by adopting a resonant soft-switching method. A detailed mode analysis of the proposed topology is presented. The feasibility of the proposed topology is experimentally verified for a 1.2-kW prototype. The experimental results imply that 97.28% efficiency is achieved under the full-load condition. Consequently, it is confirmed that the overall efficiency is increased by about 1.5% compared with the conventional hard switching interleaved boost converter.</P>

A New Edible Pod Kidney Bean Cultivar, "Noghyeob 1" with Green Pod Color

Doo Chull Shin,Sung Taek Kang,Won Young Han,In Youl Baek,Myoung Gun Choung,Keum Yong Park,Seong Hyu Shin,Young Hyun Hwang,Jong Min Ko,Duck Yong Suh,Ho Yeong Kim 한국육종학회 2007 한국육종학회지 Vol.39 No.3

A new kidney bean cultivar, “Noghyeob 1” was developed at the Yeongnam Agricultural Research Institute (YARI) in 2005. “Noghyeob 1” was selected from a cross between KLG50074 and KLG50063. It has determinate growth habit, white flower, green pod color, oval shape of crossed section of pod at the harvesting time for edible pod, white seed coat and middle seed size (21.1 grams per 100 seeds). The average yield of edible pod of “Noghyeob 1” was 24.25 M/T per hectare in the yield trials which were carried out at the green house in spring and autumn in 2005. It was 7 percent higher than that of the check cultivar “Kangnangkong 1”.

High Temperature during Summer Lowers Sugar Concentration in Fruit Juice of Satsuma Mandarin

Doo Khil Moon,Jae Woong Byun,Chi Won Chae,Sang Wook Ko,Chang Myung Kim 한국원예학회 2006 한국원예학회 기타간행물 Vol.- No.-

Investigation of Firing Conditions for Optimizing Aluminum-Doped p<SUP>+</SUP> -layer of Crystalline Silicon Solar Cells

Sang Hee Lee,Doo Won Lee,Eun Gu Shin,Soo Hong Lee 한국태양광발전학회 2016 Current Photovoltaic Research Vol.4 No.1

Screen printing technique followed by firing has commonly been used as metallization for both laboratory and industrial based solar cells. In the solar cell industry, the firing process is usually conducted in a belt furnace and needs to be optimized for fabricating high efficiency solar cells. The printed-Al layer on the silicon is rapidly heated at over 800°C which forms a layer of back surface field (BSF) between Si-Al interfaces. The BSF layer forms p-p<SUP>+</SUP> structure on the rear side of cells and lower rear surface recombination velocity (SRV). To have low SRV, deep p<SUP>+</SUP> layer and uniform junction formation are required. In this experiment, firing process was carried out by using conventional tube furnace with N₂ gas atmosphere to optimize Voc of laboratory cells. To measure the thickness of BSF layer, selective etching was conducted by using a solution composed of hydrogen fluoride, nitric acid and acetic acid. The Voc and pseudo efficiency were measured by Suns-Voc to compare cell properties with varied firing condition.

Review of Conductive Copper Paste for c-Si Solar Cells

Sang Hee Lee,Doo Won Lee,Soo Hong Lee 대한금속재료학회(구 대한금속학회) 2017 대한금속·재료학회지 Vol.55 No.9

Abstract: In the photovoltaic industries, the main technique of metallization is screen printing with silver pastes, due to its simple and quick process. However, the high price of silver paste is one of the barriers to the producing of low cost solar cells. Consequently, a primary target in photovoltaic research is to reduce consumption of silver paste or substitute silver with other lower cost materials. As a proper candidate, copper has been extensively investigated for that purpose by many institutes and companies, since it is less expensive than silver with similar conductivity. The plating technique has been actively researched to apply copper as a contact for solar cells. However, copper paste, which was originally developed for integrated circuit applications, has been recently attracted attention. Initially, copper paste was applied for a low temperature annealing process since copper tends to oxidize easily. Recently, a firing type copper paste was also developed which involves coating of the copper particles with a barrier layer. This paper reviews recent developments of copper pastes for the application to solar cells, and its appropriate annealing conditions for better electrical properties. Also, the light I-V characteristics of copper paste on the solar cells reported in the literature are summarized. The 20.7% of the conversion efficiency of a PERT (passivated emitter and rear totally diffused) structure solar cell demonstrates the potential of copper paste as a promising future metallization material. (Received May 11, 2017; Accepted May 23, 2017)