• Journal of Korean Society of Water and Wastewater
• /
• v.30 no.3
• /
• pp.343-350
• /
• 2016

Membrane distillation (MD) is a novel separation process that have drawn attention as an affordable alternative to conventional desalination processes. However, membrane fouling and pore wetting are issues to be addressed prior to widespread application of MD. In this study, the influence of ultrasonic irradiation on fouling and wetting of MD membranes was investigated for better understanding of the MD process. Experiments were carried out using a direct contact membrane distillation apparatus Colloidal silica was used as a model foulants in a synthetic seawater (35,000 mg/L NaCl solution). A vibrator was directed attached to membrane module to generate ultrasonic waves from 25 kHz (the highest energy) to 75 kHz (the lowest energy). Flux and TDS for the distillate water were continuously monitored. Results suggested that ultrasonic irradiation is effective to retard flux decline due to fouling only in the early stage of the MD operation. Moreover, wetting occurred by a long-term application of ultrasonic rradiation at 75 kHz. These results suggest that the conditions for ultrasonic irradiation should be carefully optimized to maximize fouling control and minimize pore wetting.

• Applied Chemistry for Engineering
• /
• v.4 no.2
• /
• pp.240-253
• /
• 1993

Silicon alkoxides are used as a raw materials of silica fibers, coating films and fine ceramics. Specially, the alkoxides have been confirmed the best raw material for VLSI thin film of computors in recent years. Because, the impotance of silicon alkoxides are increasing more and more now a days. And so, in thls report the synthetic methods, reaction mechanism, application fields of silicon alkoxides are summerized. Also, the results of our research and technical problems of silicon alkoxide preparation are introduced briefly.

• Structural Engineering and Mechanics
• /
• v.37 no.2
• /
• pp.131-147
• /
• 2011

The logarithmic decrement method has been long used to estimate damping ratios in systems with only one modal component such as linear single degree of freedom (SDOF) mechanical systems. This paper presents an application of a methodology that uses joint time-frequency distribution (JTFD) as input, instead of the raw signal, to systems with several vibration modes. A most important feature of the present approach is that it can be applied to a system with time-varying damping ratio. Initially the precision and robustness of the method is determined using a synthetic model with multiple harmonic components, one of them displaying a time-varying damping ratio, subsequently the results obtained from experiments with a reduced model are presented. A comparison is made between the results obtained with this methodology and those using the classical technique of Least Squares Complex Exponential Method (LSCE) in order to highlight the advantages of the former, such as, good precision, robustness and excellent performance in extreme cases, e.g., when very low frequency components and time varying damping ratio are present.

• The Journal of the Korean dental association
• /
• v.48 no.4
• /
• pp.275-279
• /
• 2010

Dental implant restoration in partial or full edentulous state has become the standard treatment in recent years. Bone graft with guided bone regeneration technique has been regarded as one of the most reliable methods to restore the bone defect area due to periodontal disease or dental trauma. Bone graft materials and membrane are the essential component of guided bone regeneration; however, a variety of bone graft materials confuse us in implant dentistry. Autogenous bone is the recognized standards in implant dentistry owing to its osteogenesis potential. Despite of its disadvantages, grafting autogenous bone is the most reliable methods. Even though the development of new bone grafts materials, autogenous bone is useful in exposed implant thread and total lack of buccal or lingual bone. Allogenic, xenogenic and synthetic bone have the osteoconductive and osteoinductive potential. These materials could be used successfully in self-contained cavity such as sinus cavity and three-wall defects. In this article, application of bone graft material is suggested according to the function of bone graft materials.

• Solar Energy
• /
• v.18 no.4
• /
• pp.1-10
• /
• 1998

Polymer induced turbulent drag reduction in a rotating disk apparatus was investigated using four different molecular weights of poly(ethylene oxide)(PEO) in a synthetic seawater solution for the purpose of potential application to the cold water piping in the Ocean Thermal Energy Conversion(OTEC) system. To apply drag reduction to the OTEC we measured the temperature dependence on the drag reduction efficiency. From this study, it was found that the drag reduction efficiency increases with the temperature and the concentration. To measure the drag reduction efficiency during the operation period, the drag reduction behavior was detected as a function of time and the results obtained from the experiment was compared to the Brostow's model equation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.12 no.1
• /
• pp.125-135
• /
• 2001

A 8$\times$4 microstrip antenna array is designed at 5.3 GHz and its characteristics are investigated with respect to the application in dual polarized synthetic aperture radars. The design is focused on the achievement of a wide bandwidth, a high polarization purity, a low loss, a good isolation and some mechanical requirements suitable for the application. The antenna is fed by a -3 dB tapered feed network, and is composed of dual polarized SSFIP (Strip-Slot-Foam-Inverted Patch) elements with honeycomb and shielding plane. Simulation results for the antenna array are presented and compared with measurements. It is observed that the antenna shows a bandwidth of 80 MHz, a polarization isolation better than 20 dB, an isolation of 40 dB, and good mechanical characteristics.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2001.11a
• /
• pp.163-168
• /
• 2001

This study examinated the application in construction field and the development of waterproofing material system by the spray water-soluble rubber asphalt to solve the problems of synthetic polymer sheet and gio membrane(A mat sheet of Bentonite) that had been used domestic waterproofing material in advance. As the result of study, characters of study water-souble rubber asphalt are the follows; 1) The amount of water absorption was '0.06'g and the seepage quantity was '0'g in result. 2) The tensile strength was about 30.7kgf/$cm^2$ and the elongation was about 72.4% in result. 3) After reliance of temperature test had been ended, the tensile strength was about 72.4kg/$cm^2$ in low temperature and about 30.7kgf/$cm^2$ in normal temperature. 4) After acid and alkaline treatment had been ended, the tensile strength was about 19.7kgf/$cm^2$ and about 21.9kgf/$cm^2$ in result. 5) After chlorine ion treatment had been ended, the tensile strength was 28.5kgf/$cm^2$ and the elongation was 250% in result. So, this study can propose the spray water-soluble rubber asphalt to satisfy the security and durability of waste filled land.

• Journal of Electrical Engineering and Technology
• /
• v.2 no.2
• /
• pp.274-279
• /
• 2007

This study focuses on the enhancement of maskless photolithography as well as the peptide synthesis application with single crystalline silicon micromirrors. A single crystalline silicon micromirror array has been designed and fabricated in order to improve its application to the peptide synthesis. A micromirror rotates about ${\pm}\;9^{\circ}$ at the pull-in voltage, which can range from 90.7 V to 115.1 V. A $210\;{\mu}m-by-210\;{\mu}m$ micromirror device with $270\;{\mu}m$ mirror pitch meets the requirements of an adequately precise separation for peptide synthesis. Synthetic 16 by 16 peptide array corresponds to the same number of micromirrors. The large size of peptide pattern and the separation facilitate biochip experiments using fluorescence assay. The peptide pattern has been synthesized on the GPTS-PEG200 surface with BSA-blocking and thereupon the background was acetylated to reject non-specific bindings. Hence, an averaged slope at the pattern edge has been distinguishably improved in comparison to patterning results from an aluminum micromirror.

• Geophysics and Geophysical Exploration
• /
• v.13 no.2
• /
• pp.159-168
• /
• 2010

Recent trend in petroleum/gas exploration is an application of 3D seismic exploration technique. Unlike the conventional 2D seismic data processing, 3D seismic data processing is considered as the one which requires expensive commercial software systems and high performance computer. This paper propose a practical 3D seismic processing methodology on a personal computer using public domain software such as SU, SEPlib, and SEPlib3D. The applicability of the proposed method has been demonstrated by successful application to a well known realistic 3D synthetic data, SEG/EAGE 3D salt model data.

• Journal of Information Processing Systems
• /
• v.16 no.4
• /
• pp.750-759
• /
• 2020

The wide application of various integrated location-based services (LBS social) and tourism application (app) has generated a large amount of trajectory space data. The trajectory data are used to identify popular tourist attractions with high density of tourists, and they are of great significance to smart service and emergency management of scenic spots. A hot spot analysis method is proposed, based on spatial clustering of trajectory stop points. The DBSCAN algorithm is studied with fast clustering speed, noise processing and clustering of arbitrary shapes in space. The shortage of parameters is manually selected, and an improved method is proposed to adaptively determine parameters based on statistical distribution characteristics of data. DBSCAN clustering analysis and contrast experiments are carried out for three different datasets of artificial synthetic two-dimensional dataset, four-dimensional Iris real dataset and scenic track retention point. The experiment results show that the method can automatically generate reasonable clustering division, and it is superior to traditional algorithms such as DBSCAN and k-means. Finally, based on the spatial clustering results of the trajectory stay points, the Getis-Ord Gi* hotspot analysis and mapping are conducted in ArcGIS software. The hot spots of different tourist attractions are classified according to the analysis results, and the distribution of popular scenic spots is determined with the actual heat of the scenic spots.