• Korea-Australia Rheology Journal
• /
• v.19 no.1
• /
• pp.17-25
• /
• 2007

In liquid composite molding (LCM), composites are produced by impregnation of a dry preform with liquid resin. The resin flow through the preform is usually described by Darcy's law and the permeability tensor must be obtained for filling analysis. While the resin flow in the thickness direction can be neglected for thin parts, the resin flow in the transverse direction is important for thicker parts. However, the transverse permeability of the preform has not been investigated frequently. In this study, the transverse permeability was measured experimentally for five different fiber preforms. In order to verify the experimental results, the measured transverse permeability was compared with numerical results. Five different fiber mats were used in this study: glass fiber woven fabric, aramid fiber woven fabric, glass fiber random mat, glass fiber braided preform, and glass/aramid hybrid braided preform. The anisotropic braided preforms were manufactured by using a three dimensional braiding machine. The pressure was measured at the inlet and outlet positions with pressure transducers.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.3
• /
• pp.227-231
• /
• 2013

Electrodeionization is a hybrid separation process of electrodialysis and ion exchange to produce high purity water under electric field. This article provides a fabrication result of hole patterned metal electrode for elecrodeionization system. The hole patterns have been fabricated by nanosphere lithography (NSL). The technique utilizes the self-assembled nanospheres as lens-mask patterns and collimated laser beam source. The hole patterns have a periodic array structure. The images of hole pattern on metal electrode prepared were observed by SEM. We believe that the periodic hole patterned metal electrode structure is a useful device applicable for metal mat electrode in electrodeionization system.

• Korean Journal of Materials Research
• /
• v.6 no.4
• /
• pp.428-435
• /
• 1996

초미립 SiC분말과 SiC platelet을 2차성으로 Si3N4에 첨가하여 SiC/Si3N4 하이브리드 복합체를 가압소결로 제조한 후 2차상의 영향을 조사한 결과핫프레스법을 이용한 경우 SiC platelet은 Si3N4 기지 복합채의 치밀화를 저해하지 않고 초미립의 SiC 첨가는 Si3N4의 입성장을 효과적으로 억제하여 미세한 $\beta$-Si3N4의 grain을 형성함을 관찰하였다. 초미립 SiC첨가를 통한 복합체의 강도 증진은 상대적으로 $\beta$-Si3N4입자의 미세화에 의한 인성의 저하를 유도하나 SiC platelet을 첨가하여 급격한 강도 저하 없이 높은 인성을 갖는 하이브리드 복합체를 제조할 수 있었으며 SiC/Si3N4 하이브리드 복합체의 인성증진은 elongated $\beta$-Si3N4와 platelet SiC의 debonding에 의한 grain pull-out 영향임을 알 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.4
• /
• pp.1638-1654
• /
• 2018

The heterogeneous network (HetNet) has been one of the key technologies in Long Term Evolution-Advanced (LTE-A) with growing capacity and coverage demands. However, the introduction of femtocells has brought serious co-layer interference and cross-layer interference, which has been a major factor affecting system throughput. It is generally acknowledged that the resource allocation has significant impact on suppressing interference and improving the system performance. In this paper, we propose a hybrid-clustering algorithm based on the $Mat{\acute{e}}rn$ hard-core process (MHP) to restrain two kinds of co-channel interference in the HetNet. As the impracticality of the hexagonal grid model and the homogeneous Poisson point process model whose points distribute completely randomly to establish the system model. The HetNet model based on the MHP is adopted to satisfy the negative correlation distribution of base stations in this paper. Base on the system model, the spectrum sharing problem with restricted spectrum resources is further analyzed. On the basis of location information and the interference relation of base stations, a hybrid clustering method, which takes into accounts the fairness of two types of base stations is firstly proposed. Then, auction mechanism is discussed to achieve the spectrum sharing inside each cluster, avoiding the spectrum resource waste. Through combining the clustering theory and auction mechanism, the proposed novel algorithm can be applied to restrain the cross-layer interference and co-layer interference of HetNet, which has a high density of base stations. Simulation results show that spectral efficiency and system throughput increase to a certain degree.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.2
• /
• pp.926-936
• /
• 2017

The nonlinear behavior and the high performance requirement are the main problems that appear in the design of manipulator robots and their controllers. For that reason, the simulation, real-time execution and comparison of the performance of controllers applied to a robot with three degrees of freedom are presented. Five controllers are prepared to test the robot's dynamic model: predictive; hyperbolic sine-cosine; sliding mode; hybrid composed of a predictive + hyperbolic sine-cosine controller; and adaptive controller. A redundant robot, a communication and signal conditioning interface, and a simulator are developed by means of the MatLab/Simulink software, which allows analyzing the dynamic performance of the robot and of the designed controllers. The manipulator robot is made to follow a test trajectory which, thanks to the proposed controllers, it can do. The results of the performance of this manipulator and of its controllers, for each of the three joints, are compared by means of RMS indices, considering joint errors according to the imposed trajectory and to the controller used.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.27 no.4
• /
• pp.470-479
• /
• 1982

Researches on industrial crops in Korea before 1962 were concentrated on fiber crops such as cotton, kenaf, hemp, ramie and flax. Then research works on oil crops, sugar crops and other high income crops were followed. However, no land is shared for the production of kenaf, flax, sugar beet, sweet sorghum and sunflower at present in Korea, while the cultivation of cotton, hemp, ramie and mat rush is decreasing continuously to the marginal point. At present researches are emphasized on oil crops such as seasame, peanut and perilla and high income medicinal herbs of which cultivating acreages are increasing. Numerous varieties were released as a result of active breeding works on industrial crops since 1962, i.e. 3 sesame varieties including "Suweon 21", 3 peanut varieties including "Seoduntangkong", and 6 rape varieties including "Yudal" in oil crops, one cotton variety "Mokpo 7", one hemp variety "MS4-1", and one kenaf variety "Suweon 2" in fiber crops, and two stevia varieties "Suweon 2" and "Suweon II" in sugar crops. Quality improvement of rape seeds and development of hybrid rapes utilizing male sterile lines are the most significant results of breeding works, while the establishment of vinyl mulching cultivation of sesame and peanut are the most successful results in agronomic researches during the last 20 years.re the most successful results in agronomic researches during the last 20 years.

• The Korean Journal of Mycology
• /
• v.37 no.1
• /
• pp.86-90
• /
• 2009

The C. militaris belongs to entomopathogenic fungi, which have their specific sequences in internal transcribed spacer regions (ITS1 and ITS2) depending on species. In this study, to identify the phylogenetic relationship of the strain hybrided by mating of C. militaris, we compared DNA sequences of ITS regions and 5.8S ribosomal DNA (rDNA) repeat unit of hybrid strain and its parental strains. The result revealed that hybrid strains are C. militaris species. In addition, cordycepins produced by hybrid strains and other strains of C. militaris were analyzed by HPLC with 20mM $KH_2PO_4$ of mobile phase and C-18 columns. The result indicated that the strain hybrided by mating produce higher concentration of phytochemical cordycepin than other C. militaris strains.

• Journal of the Korean Wood Science and Technology
• /
• v.44 no.5
• /
• pp.750-759
• /
• 2016

The $MnO_2$ electrodeposited on the surface of the carbon nanofiber mats ($MnO_2$-LCNFM) were prepared from electrospun lignin-g-PAN copolymer via heat treatments and subsequent $MnO_2$ electrodeposition method. The resulting $MnO_2$-LCNFM was evaluateed for its potential use in a supercapicitor electrode. The increase of $MnO_2$ electric deposition time was revealed to increase diameter of carbon nanofibers as well as $MnO_2$ content on the surface of carbon nanofiber mats as confirmed by scanning electon microscope (SEM) analysis. The electrochemical properties of $MnO_2$-LCNFM electrodes are evaluated through cyclic voltammetry test. It was shown that $MnO_2$-LCNFM electrode exhibited good electrochemical performance with specific capacitance of $168.0mF{\cdot}cm^{-2}$. The $MnO_2$-LCNFM supercapacitor successfully fabricated using the gel electrolyte ($H_3PO_4$/Polyvinyl alcohol) showed to have the capacitance efficiency of ~90%, and stable behavior during 1,000 charging/discharging cycles.

• Korean Journal of Materials Research
• /
• v.31 no.2
• /
• pp.75-83
• /
• 2021

To cope with automobile exhaust gas regulations, ISG (Idling Stop & Go) and charging control systems are applied to HEVs (Hybrid Electric Vehicle) for the purpose of improving fuel economy. These systems require quick charge/discharge performance at high current. To satisfy this characteristic, improvement of the positive electrode plate is studied to improve the charge/discharge process and performance of AGM(Absorbent Glass Mat) lead-acid batteries applied to ISG automotive systems. The bonding between grid and A.M (Active Material) can be improved by applying the Sand-Blasting method to provide roughness to the surface of the positive grid. When the Sand-Blasting method is applied with conditions of ball speed 1,000 rpm and conveyor speed 5 M/min, ideal bonding is achieved between grid and A.M. The positive plate of each condition is applied to the AGM LAB (Absorbent Glass Mat Lead Acid Battery); then, the performance and ISG life characteristics are tested by the vehicle battery test method. In CCA, which evaluates the starting performance at -18 ℃ and 30 ℃ with high current, the advanced AGM LAB improves about 25 %. At 0 ℃ CA (Charge Acceptance), the initial charging current of the advanced AGM LAB increases about 25 %. Improving the bonding between the grid and A.M. by roughening the grid surface improves the flow of current and lowers the resistance, which is considered to have a significant effect on the high current charging/discharging area. In a Standard of Battery Association of Japan (SBA) S0101 test, after 300 A discharge, the voltage of the advanced AGM LAB with the Sand-Blasting method grid was 0.059 V higher than that of untreated grid. As the cycle progresses, the gap widens to 0.13 V at the point of 10,800 cycles. As the bonding between grid and A.M. increases through the Sand Blasting method, the slope of the discharge voltage declines gradually as the cycle progresses, showing excellent battery life characteristics. It is believed that system will exhibit excellent characteristics in the vehicle environment of the ISG system, in which charge/discharge occurs over a short time.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.44 no.3
• /
• pp.34-40
• /
• 2012

In this study, new antibacterial materials were developed to manufacture a functional corrugated board. Sulfur solution, a new antibacterial solution made from inorganic sulfur in the laboratory, and other antibacterial mat erials were adopted to treat the surface of a linerboard. We measured the antibacteriocidal and bacteriostatic activities, as well as the fungal resistance of the surface-treated linerboards, to identify the antibacterial properties. The mechanical properties of the surface-treated linerboard were also determined in order to identify the effects of the antibacterial materials on linerboard properties. Linerboard treated with sulfur solution, PVOH, and sodium metasulfite showed the highest antibacterial activity, while linerboard treated with sulfur solution and nano sulfur showed the highest fungal resistance. It was identified that sulfur solution has effective antibacterial properties. The antibacterial materials did not affect the mechanical properties of the surface-treated linerboard, but the binder showed significant effects in terms of the burst strength, the compressive strength, and the stiffness of the linerboard.