• Carbon letters
• /
• v.11 no.3
• /
• pp.176-183
• /
• 2010

PAN precursor fibers were produced via wet-spinning process, and effects of polymerization and spinning processes, especially the stretching process, were investigated on mechanical properties and micro-morphologies of precursor fibers. An increase in molecular weight, dope solid and densification and a decrease in surface defects were possible by controlling polymerization temperature, the number of heating rollers for densification and the jet stretch ratio, which improved the mechanical properties of precursor fibers. The curves for strength, modulus, tensile power and diameter as a function of stretch ratio can be divided into three stages: steady change area, little change area and sudden change area. With the increase of stretch ratio, the fiber diameter became smaller, the degree of crystallization increased and the structure of precursor fibers became compact and homogeneous, which resulted in the increase of strength, modulus and tensile power of precursor fibers. Empirical relationship between fiber strength and stretch ratio was studied by using the sub-cluster statistical theory. It was successfully predicted when the strengths were 0.8 GPa and 1.0 GPa under a certain technical condition, the corresponding stretch ratio of the fiber were 11.16 and 12.83 respectively.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.9 no.4
• /
• pp.527-536
• /
• 2014

In this paper, the 50kW aerogenerator which is applicable to the microgrid was designed and analyzed by using commercial simulation program Maxwell 2D. Particularly, the suggested PMSG to reduce the cogging torque introduced the offset and skew concept. The suggested optimal value of offset and skew was decided by 2mm and 60 degree of electric angle. The simulation results of the PMSG when load operation condition showed the average harmonic distortion 1.3%, voltage 322.41V, current 94.95A, and iron loss 9.73W, eddy current loss 73.68W, copper loss 3.52kW. The capacity of aerogenerator calculated 61.56kW, and the suggested design process can be applied to higher capacity generator.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.5
• /
• pp.280-288
• /
• 2016

Microelectronic product consumers may already be expecting another paradigm shift with smarter phones over smart phones, but the current status of microelectronic manufacturing engineering education (MMEE) in universities hardly makes up the pace for such a fast moving technology paradigm shift. The purpose of MMEE is to educate four-year university graduates to work in the microelectronics industry with up-to-date knowledge and self-motivation. In this paper, we present a comprehensive curriculum for a four-year university degree program in the area of microelectronics manufacturing. Three hands-on experienced-based courses are proposed, along with a methodology for undergraduate students to acquire hands-on experience, towards integrated circuits (ICs) design, fabrication and packaging, are presented in consideration of manufacturing engineering education. Semiconductor device and circuit design course for junior level is designed to cover how designed circuits progress to micro-fabrication by practicing full customization of the layout of digital circuits. Hands-on experienced-based semiconductor fabrication courses are composed to enhance students’ motivation to participate in self-motivated semiconductor fab activities by performing a series of collaborations. Finally, the Microelectronics Packaging course provides greater possibilities of mastered skillsets in the area of microelectronics manufacturing with the fabrication of printed circuit boards (PCBs) and board level assembly for microprocessor applications. The evaluation of the presented comprehensive curriculum was performed with a students’ survey. All the students responded with “Strongly Agree” or “Agree” for the manufacturing related courses. Through the development and application of the presented curriculum for the past six years, we are convinced that students’ confidence in obtaining their desired jobs or choosing higher degrees in the area of microelectronics manufacturing was increased. We confirmed that the hypothesis on the inclusion of handson experience-based courses for MMEE is beneficial to enhancing the motivation for learning.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.05a
• /
• pp.88-92
• /
• 2003

In this paper, the characteristics of the ZnO films deposited on AI bottom electrode and the temperature effects on the ZnO film growth are presented along with the fabrication and their evaluation of the film bulk acoustic wave resonator (FBAR) devices. All the films used in this work were deposited using a radio-frequency (RF) magnetron sputtering technique. Growth characteristics of the ZnO films are shown to have a strong dependence on the deposition temperatures ranged from room temperature to 35$0^{\circ}C$ regardless of the RF power applied for sputtering the ZnO target. In addition, according to the growth characteristics of the distinguishably different micro-crystal structures and the degree of the c-axis preferred orientation, the deposition temperatures can be divided into 3 temperature regions and 2 critical temperatures in-between. Overall, the ZnO films deposited at/below 20$0^{\circ}C$ are seen to have columnar grains with a highly preferred c-axis orientation where the full width at half maximum (FWHM) of X-ray diffraction rocking curve is 14$^{\circ}$. Based on the experimental findings, several FBAR devices were fabricated and measured. As a result, the FBAR devices show return loss of ~19.5dB at resonant frequency of ~2.05GHz.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.159.1-159.1
• /
• 2011

Partial oxidation reformer was fabricated and operated using commercial transportation fuels. Fuel injector and heating coil were used for fuel atomization and startup, respectively. The reformer was designed to produce syngas for $150{\sim}200W_e$ class solid oxide fuel cell. The reformer was operated in the $O_2$/C range between 0.6 and 0.8 while the capacity was fixed at $150W_e$. The temperature range in catalyst bed was between $500^{\circ}C$ and $900^{\circ}C$. Only 83% fuel was converted to $H_2$, CO, $CO_2$ and $CH_4$ at the operating conditions. The lowest temperature increase to $700^{\circ}C$ when the reformer was operated at $200W_e$, Although the temperature profiles was improved, fuel conversion was 88%. On the other hand, fuel was completely converted when micro-reactor operated at the same condition. This difference maybe due to aromatic compounds formation at homogeneous region. In addition, a significant amount of coke deposition was observed at vent line. Homogeneous reaction depends on the degree of mixing. For this purpose, two fluid nozzle and Ultra sonic injector were compared to investigate the effect of atomization. Sauter mean diameter(SMD) of Ultra sonic injector was lower than two-fluid nozzle at test condition. However, conversion efficiency and fuel conversion were not improved by using two-fluid nozzle. these results imply that the temperature of homogeneous reaction region should be controlled to prevent coke formation.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.29 no.4
• /
• pp.360-367
• /
• 2009

The acoustic emission(AE) behavior of reinforced concrete slab under flexural loading was investigated to assess the integrity. This study was aimed at identifying the characteristics of AE response associated with damage development. By applying cyclic loading in various load steps, it was able to differentiate each AE source such as distributed micro crack initiation, friction, flexural crack and localized diagonal tension crack. The secondary peak and the change of AE hit rate gave valuable criteria fur assessment. From the analysis of the felicity ratio, furthermore, it was shown that this values can be used for evaluating the degree of concrete damage. Based on the experimental results, this approach for practical AE application may provide a promising method for estimating the level of damage and distress in concrete structures.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.27 no.2
• /
• pp.212-224
• /
• 2013

This study intends to clarify how Sayeok-tang(here in after reffered to SYT) affect C57BL/10 mice whose osteoarthritis was induced by papain. Osteoarthritis was induced by injecting papain in the knee joint of 3 groups(n=6) of mice. Normal group was non-treatment group and was not injected papain, whereas control mice were orally administered with $200{\mu}{\ell}$ of physiological saline. Positive comparison group was medicated with 100 mg/kg of Joins$^{(R)}$ mixed with $200{\mu}{\ell}$ of physiological saline. Experimental group was medicated with 400 mg/kg of SYT mixed with $200{\mu}{\ell}$ of physiological saline. Both Positive and experimental comparison groups were orally medicated once per day for 4 weeks. After the experiment, the functions of liver and kidney, inflammation cytokine values within serum, degree of revelation for inflammation cytokine genes, immune cells within blood, metabolism of arachidonic acid and amount of cartilage were measured and histopathological changes in the knee joint structures were observed. As results, SYT had no significant effect on the liver and kidney functions. Interleukin-$1{\beta}$(IL-$1{\beta}$), interleukin-6(IL-6), monocyte chemo attractant protein-1(MCP-1) and tumor necrosis factor-${\alpha}$(TNF-${\alpha}$) were significantly decreased. Inflammation cytokines in joints were all significantly decreased. Prostaglandin $E_2(PGE_2)$, thromboxane $B_2(TXB_2)$ were significantly decreased. Destruction of cartilage on micro computed tomography(CT)-arthrography was meaningfully decreased. In terms of histopathology, infiltration of inflammation, proliferation of synovial membrane, subsidence of cartilage and bone due to penetration of excessive formation of synovial cell and destruction of cartilage were small. Based on all results mentioned above, Sayeok-tang(SYT) is believed to be meaningful for suppressing the progress of osteoarthritis and its treatments because of its anti-inflammatory effects and alleviation of pain with histopathological effective efficacy.

• Economic and Environmental Geology
• /
• v.39 no.6 s.181
• /
• pp.771-786
• /
• 2006

Imha lake has a high turbid water which keeps up during a few months, as comparing to other dams. Origins of the high turbid water derive from suspended materials which compose of micro particles of clay and rock-forming minerals. They are the weathered products from surface rocks that relate with particular geology in drainage field of the Imha dim. Accordingly we have fundamentally surveyed the kinds, properties, distribution and structures of general geology, found a few particular geology that source clay materials, and traced the passage that their weathered products enter the dam. We have suggested the basic origins of increase in turbid degree from detecting kinds and behavior of the suspended materials cause high turbid water in the Imha lake.

• The Journal of the Korea Contents Association
• /
• v.17 no.7
• /
• pp.222-235
• /
• 2017

The purpose of this study is to analyze the perception of Korean universities' education specialists and seek direction for the development of MOOCs. To investigate this, 64 Korean university education specialists were surveyed about the educational goals of MOOCs and their perception of micro and macro issues. As a result, Korean university education specialists recognized MOOCs' educational goals as an innovation of education methods. Also, negative acknowledgment that issuance of certificates would cause confusion in the degree system, which is interpreted as a tendency to recognize MOOCs as a complementary material. On a macroscopic level, overall outlook was negative for K-MOOC. However, since K-MOOC is highly perceived to be subversive, it is necessary to discuss the possibility of using MOOCs. Accordingly, it suggested the institutional improvement for the utilization of K-MOOC and the possibility of joint development between universities.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.8 no.3
• /
• pp.166-170
• /
• 1975

Six kinds of canned processed fish-balls were collected from the local market of Korea in April, 1975 and frozen section was prepared with the fish-balls at $-25^{\circ}C$ , coincidently stained with PAS, sudan III, carbol-thionine and light green for histochemical observation on evaluation of materials and quality of the porducts. The results tased on morphological analysis were summarized as follows. Protein contents were showed the lowest level, ranging about $2.7-9.0\%$, while carbohydrate was contained from $58.1\%\;to\;75.2\%$ of the highest degree. Fat contents had a great variety depending upon the quality of porducts, showing $1.4-17.6\%$, and air bubble was contained from $14.4\%\;to\;21.1\%$, tended to a large quantity. In sample No. 6, the micro-organism3 were observed around the denaturated prtotein, carbohydrate, and air bubbles in canned fish-ball. When the other samples were incubated for 4 days at $37^{\circ}C$, bacterial colony was also formed around the denaturated protein, carbohydrate, and air bubbles in cavities.