• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.3
• /
• pp.264-270
• /
• 2010

Waste activated sludge from sewage treatment plants mainly consisted of flocs of bacterial cell, and thus hard to be stabilized anaerobically due to rigid cell walls. One of the pretreatment methods to overcome this barrier is the venturi cavitation system (VCS) adopting hydrodynamic cavitation. This research was conducted to investigate the effects of the pretreatment of waste activated sludge by VCS on the anaerobic digestibility. Depending on the pretreatment period with the VCS, methane production, COD removal and VS removal efficiency increased 41%~45%, 36.5%~43.1% and 18.4~24.1%, respectively, compared to the control case. The increase in methane production from digester was 3.3~4.2 times higher than the theoretical methane potential of the increased SCOD after the VCS pre-treatment. This suggests that the VCS pre-treatment not only increases SCOD but also improves the digestibility of solid fractions. The energy mass balance indicated that the energy consumed for sludge pre-treatment could be recovered by the increased methane production after pre-treatment, suggesting the high potential for field application.

• Journal of Korean Ophthalmic Optics Society
• /
• v.15 no.4
• /
• pp.329-337
• /
• 2010

Purpose: The surfaces and compositions of rigid gas permeable (RGP) contact lenses were analyzed with the consistent methods, and the basic informations for the composition design of lens materials were suggested. Methods: The bulk structures were analyzed by using Fourier infrared spectroscopy (FTIR), the compositions of surface components were observed by using x-ray photoelectron spectroscopy (XPS), the surface morphology and roughness were observed using atomic force microscopy (AFM), and the wettabilities were estimated by the surface wetting angles. The relations and trends of those results were analyzed. Results: The high oxygen permeability RGP lenses showed the trend that the fluorine decreases and the silicon increases. As the silicon and fluorine contents increased, the carbon and oxygen contents of RGP lens materials decreased at a constant ratio. The decreasing ratio of the carbon contents was three times larger than the decreasing ratio of oxygen contents. The composition of the surface treated lens was far from these tendency line. When the silicon contents increased, the rough surface was formed with the cohered particles. When the fluorine contents increased, the rough surface was formed with the deep flaws. The surface roughness increased and then wettabilities decreased as the silicon and fluorine contents increased. For the surface roughness changes, the increasing ratio of the silicon contents was two times larger than the increasing ratio of fluorine contents. The surface of RGP lens materials appeared the hydrophobic character of which the wettabilities decreased when the roughnesses increased. Conclusions: The surfaces and compositions of RGP contact lenses were measured by the same methods. Those results and relationships were compared and analysed. It is considered that these research results will be applied with the basic data for the composition design of lens materials.

• Resources Recycling
• /
• v.22 no.2
• /
• pp.62-70
• /
• 2013

Electric arc furnace slag is made in ironworks during steel refining, it is been increasing chemical and physical resistibility using ageing method of unstable state of melting steel slag for using concrete's fine aggregates. Which is been changing stable molecular structure of aggregates, it restrains moving of ion and molecule. In Korea, KS F 4571 has been prepared for using the electric arc furnace slag to concrete aggregates. In this study, Electric arc furnace slag is used in the PMC(Polymer Modified Concrete) which is applied a bridge pavement of rehabilitation, largely. In that case, this study evaluates the structural safety about increasing the specific weight. The 4-type bridges(RC slab bridge, RC rigid-frame bridge, PSC Beam bridge, Steel box girder bridge) pavement's increasing the total dead load is in 1 ~ 2%. Design moments in a load combination are increased less then 2%. safety factor is decreased less than 3%. Therefore, the structural safety has no problem for applying the electric arc furnace slag within PMC in bridge.

• Journal of rehabilitation welfare engineering & assistive technology
• /
• v.5 no.1
• /
• pp.47-52
• /
• 2011

The functional loot orthoses, when wearing shoes, are in the direct contact with bottom of foots to improve and recover the correctness of abnormal lower limb musculoskeletal imbalance and the primary role of foot and also, it can act to keep the balance and weight of body and support the weakened region, so that it is very helpful to keep body balance for the standing position. In this paper, it was researched that foot orthoses which is accommodable for the function of impact absorption including the gait stability affect on the balanced performances of body in according to the formation and the material of foot part. Taking into account the balanced performances by using the sway velocity, the estimation and comparison of the effects on the balanced performances by each formation and material for foot orthoses was evaluated into significant values(p<0.006) in only the eye-opening posture with Firm state, In this posture, the static process performed by each foot formation reveals in order of normal foot(p<0.010), flat foot(p<0.000) and hollow foot(p<0.003) and then, on the base of each formation of foot part, the result that analyze the effects of the materials of foot orthoses on the balance performance appeared showing that soft materials is more effective on the normal foot and, on the other hand, rigid materials is more effective in balancing on flat foot and hollow foot.

• International Journal of Highway Engineering
• /
• v.13 no.4
• /
• pp.117-122
• /
• 2011

Asphalt concrete pavement can be widely seen on urban streets, highways, parking lots, and bike trails. Asphalt concrete pavement is relatively temperature sensitive materials due to the viscoelastic behavior, which can be defined as flexible performance in summer and rigid performance in winter. In terms of maintenance, it can be fixed quite easily if damaged. In addition, asphalt concrete pavement is generally found to be black and grey in color. However, several colors can be adopted to change the appearance of plain old boring, black and grey. Generally, there are two types of color systems in hot mix asphalt concrete materials. One system uses colored cementitious material that is applied to pavement surface through coating the surface of the asphalt pavement. The major disadvantage to this system requires a careful skill set to be used on the construction site in order to prevent taking off the cementitious material. The other coloring system colors the asphalt hot mixtures through using color additives. The main advantage to this system is that the asphalt pavement layer is colored using the same techniques that are already used in paving. The disadvantage is that the colors are limited to mainly reds and browns. In this study, a suggested color additive was evaluated, based on rutting, moisture sensitivity, and fatigue cracking performance.

• Journal of Chest Surgery
• /
• v.29 no.10
• /
• pp.1090-1094
• /
• 1996

From February 1980 to September 1995, 31 children between 2 months and 15 years of age with mitral valve disease have undergone mitral valve replacement(MVR) at Yonsei Cardiovascular Center and com- plete follow-up has been obtained on 28 patients. There were 10 males and 18 females whose weight ranged from 4.9kg to 56kg. Two patients died early postopeiatively and the overall hospital mortality rate was 7.1%. These two were infants but there were no statistically significant difference in overall mortality among the age groups(p=0.13). The valve related complication rate was 57.1% in children younger than 5 years of age, which showed higher complication rate compared to older patients(p< 0.05). The bioprosthetic valve have been applied in 7 patients, and its 5-year valve failure-free survival rate was 50% . No mechanical valve failu e had occurred in 21 patients. In considering high re-replacement rate of bioprosthetic valve, mechanical valve is recommended despite its possibility of bleeding and thromboembolic complications. However, the consequences of increasing body size and long-term interposition of a rigid prosthesis in a growing heart will require second valve replacement. En conclusion, mitral valve replacement can be performed tilth satisfactory long-term survival in children, although younger mean age of the children has an important influence on early mortality and com- plication rate. And therefore mitral valve replacement in children younger than 5 years of age needs special consideration.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.30 no.4
• /
• pp.301-307
• /
• 2004

The flap considered at first for the reconstruction of large maxillary defect, especially mid-face defect, is scapular free flap, because it provides ample composite tissue which can be designed 3-dimensionally for orbital, facial and oral reconstruction. In case of maxillary defect involving hard palate, however, this flap has some limitations. First, its bulk prevents oral function and physio-anatomic reconstruction of nasal and oral cavity. Second, mobility and thickness of cutaneous paddle covering the alveolar area reduce retention of tissue-supported denture and give rise to peri-implantitis when implant is installed. Third, lateral border of scapula that is to reconstruct maxillary arch and hold implants is straight, not U-shaped maxillary arch form. To overcome these problems, new concept of step prefabrication technique was provided to a 27-year-old male patient who had been suffering from a complete hard palate and maxillary alveolar ridge defect. In the first stage, scapular osteomuscular flap was elevated, tailored to fit the maxillary defect, particulated autologous bone was placed subperiosteally to simulate U-shaped alveolar process, and then wrapped up with split thickness skin graft(STSG, 0.3mm thickness). Two months later, thus prefabricated new flap was elevated and microtransferred to the palato-maxillary defect. After 6 months, 10 implant fixtures were installed along the reconstructed maxillary alveolus, with following final prosthetic rehabilitation. The procedure was very successful and patient is enjoying normal rigid diet and speech.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.16 no.1
• /
• pp.1-12
• /
• 2012

In this paper, the reduction factors to calculate the site coefficients of an embedded foundation are estimated, considering the effect of a poor backfill for the seismic design of a building built on an embedded foundation. This is determined by utilizing in-house finite element software, P3DASS, which has the capability of horizontal pseudo 3D seismic analysis with nonlinear soil. The 30m thick soil on stiff rock was assumed to be homogeneous, elastic, viscous and isotropic, and equivalent circular rigid foundations with radii of 10-70m were assumed to be embedded 0, 10, 20, and 30 m in the soil. Seismic analyses were performed with 7 bedrock earthquake records de-convoluted from the outcrop records; the scaling of the peak ground accelerations were to 0.1 g. The study results show that the site coefficients of a poor-backfilled foundation are gradually reduced as the foundation embedment ratio increases, except in the case of a small foundation embedded deeply in the weak soft soil. In addition, it was found that the deviation of the site coefficients due to the foundation size was not significant. Therefore, the typical reduction factors of an embedded foundation with poor backfill are proposed in terms of the shear wave velocity and site class. This is in order to find the site coefficients of an embedded foundation by multiplying the reduction factor by a site coefficient of a surface foundation specified in the design code. They can then be interpolated to determine the intermediate shear wave velocity.

• The Journal of the Convergence on Culture Technology
• /
• v.3 no.3
• /
• pp.7-19
• /
• 2017

Korean standard poetry with a fixed form are Rated Sijo. These Rated Sijos can be found in the 24 number of Gosijos. Then, why should Korean standard poetry be Rated Sijo? This is because only the Rated Sijo has a fixed form frame. Rated Sijo naturally tailored by a rigid framework is the best representation of Koreans' unique breath and temperament. Also, Rated Sijo is superior to general sijo or poem in terms of literary therapeutic utility for human body. If Haiku omits the end of narrative with the rated number of sounds and invites different imaginations to each reader, the Rated Sijo presents a certain frame to the direction of the human's rated signal by constructing the essence of the narrative with the rated number of sounds. Thus, the Rated Sijo suggests the way of human harmony and communication by inducing different imagination of readers cooperating in a certain direction. So, the famous poem of Korea, Rated Sijo, presents our future as a framework of literature that can contribute to the improvement of human communication and quality of life. Therefore, research to preserve and develop the value of the Rated Sijo should now be initiated and continued.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.3
• /
• pp.285-292
• /
• 2016

In this study, FE-BE direct coupling methods of 1D and 2D problems are considered for the pontoon-type floating structure and the difference of the modeling dimensions is investigated for the hydroelastic response. The modeling dimensions are defined as the 1D problem consisting 1D beam-2D fluid coupling and the 2D problem consisting 2D plate-3D fluid coupling with zero-draft assumption. For case studies, hydroelastic responses of the 1D Problem are compared to those of the 2D Problem for a wide range of aspect ratio and regular waves. It is shown that the effects of the elastic behavior are increased by decreasing the incident wavelength, whereas the effects of the rigid behavior are increased by increasing the incident wavelength. In 2D problem, the incident wave angle can be considered, and slightly more accurate results can be obtained, but the computational efficiency is lower. On the other hand, in 1D problem with plate-strip condition, the incident wave angle cannot be considered, but when the aspect ratio is large, the overall responses can be analyzed through a simplified model, and the computational efficiency can be improved.