• Applied Biological Chemistry
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• v.41 no.2
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• pp.181-186
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• 1998

The effects of sewage treatment on characteristics of sludge as a composting material were investigated for a year during the initial operation at the full-scale Chunan sewage treatment plant. Due to the shortage of design capacity of belt press, a sludge dewatering unit, non-volatile solids were recirculating and concentrating in the treatment plant, resulting in an increase of MLSS and a decrease in F/M ratio at the activated sludge system. Special attention is required for long term operations since the increase of non-volatile solids in the plant would deteriorates the treatment efficiency. The sewage sludge of the Chunan sewage treatment plant showed 79.5% of water content, 11.6% of organic content, and C/N ratio of 6.1, and contained As 1.8 mg/kg, Cd 27 mg/kg, Hg <0.1 mg/kg, Pb 54 mg/kg, T-Cr 370 mg/kg, and Cu 1,100mg/kg of heavy metals. In order to be used as raw material for optimum composting, the sewage sludge requires bulking agents for moistrure/porosity control and a carbon source for adjusting C/N ratio. However, the sewage sludge is not adequate as a soil conditioner after composing due to a high content of heavy metals. If the sewage sludge has to he used as a soil conditioner after composting, it as required to identify and remove tire industrial wastewater portions in tire influent of the plant since heavy metals in the influent were mostly concentrated in dewatered sludge.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.984-997
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• 2015

Chang'e-3 consisting of a lunar lander and exploration rover was launched on December 1, 2013 aboard a Long March 3B rocket flying from Xichang space launch center. Chang'e-3 was inserted into the lunar orbit after about a 5-day transit to the Moon and landed on the targeted landing site after orbiting around the Moon for 8 days. The successful landing of the Chang'e-3 gives a lot of help to analyze the future needs of the subsystem technologies and to figure out the trajectory from launch to lunar landing as well as operation sequences in the development of Korean lunar exploration is scheduled. Therefore, the configuration and analysis of overall mission of Chang'e-3 is performed based on the public information from the press and website. As a result, overall mission trajectory is reconstructed by solving boundary condition and then estimating control variable. Visibility status and eclipse status also analyzes so communication and power charge condition is as good as to operate lunar lander. Mass budget of the lander is derived using ${\Delta}V$ according to specific impulse.

• Geomechanics and Engineering
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• v.21 no.1
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• pp.63-71
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• 2020

Strength anisotropy is a typical feature of thin-bedded rock masses and their strength will be degraded subjected to water immersion effect. Such effect is crucial for the operation of hydropower plant because the impoundment lifts the water level of upstream reservoir and causes the rock mass of nearby slopes saturated. So far, researches regarding mechanical property of natural thin-bedded rock masses and their strength variation under water immersion based on field test method are rarely reported. This paper focuses on a thin-bedded stratified rock mass and carries out field test to investigate the mechanical property and strength variation characteristics. The field test is highlighted by samples which have a large shear dimension of 0.5 m*0.5 m, representing a more realistic in-situ situation than small size specimen. The test results confirm the anisotropic nature of the concerned rock mass, whose shear strength of host rocks is significantly larger than that of bedding planes. Further, the comparison of shear strength parameters of the thin-bedded rock mass under natural and saturated conditions show that for both host rocks and bedding planes, the decreasing extent of cohesion values are larger than friction values. The quantitative results are then adopted to analyze the influence of reservoir impoundment of a hydropower plant on the surrounding rock mass stability of diversion tunnels which are located in the nearby slope bank. It is evaluated that after reservoir impoundment, the strength degradation induced incremental deformations of surrounding rock mass of diversion tunnels are small and the stresses in lining structure are acceptable. It is therefore concluded that the influences of impoundment are small and the stability of diversion tunnels can be still achieved. The finings regarding field test method and its results, as well as the numerical evaluation conclusions are hoped to provide references for rock projects with similar concerns.

• Archives of Plastic Surgery
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• v.38 no.4
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• pp.438-444
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• 2011

Purpose: Adipose-derived stromal cells (ASCs) are readily harvested from lipoaspirated tissue or subcutaneous adipose tissue fragments. The stromal vascular fraction (SVF) is a heterogeneous set of cell populations that surround and support adipose tissue, which includes the stromal cells, ASCs, that have the ability to differentiate into cells of several lineages and contains cells from the microvasculature. The mechanisms that drive the ASCs into the osteoblast lineage are still not clear, but the process has been more extensively studied in bone marrow stromal cells. The purpose of this study was to investigate the osteogenic capacity of adipose derived SVF cells and evaluate bone formation following implantation of SVF cells into the bone defect of human phalanx. Methods: Case 1 a 43-year-old male was wounded while using a press machine. After first operation, segmental bone defects of the left 3rd and 4th middle phalanx occurred. At first we injected the SVF cells combined with demineralized bone matrix (DBM) to defected 4th middle phalangeal bone lesion. We used P (L/DL)LA [Poly (70L-lactide-co-30DL-lactide) Co Polymer P (L/DL)LA] as a scaffold. Next, we implanted the SVF cells combined with DBM to repair left 3rd middle phalangeal bone defect in sequence. Case 2 was a 25-year-old man with crushing hand injury. Three months after the previous surgery, we implanted the SVF cells combined with DBM to restore right 3rd middle phalangeal bone defect by syringe injection. Radiographic images were taken at follow-up hospital visits and evaluated radiographically by means of computerized analysis of digital images. Results: The phalangeal bone defect was treated with autologous SVF cells isolated and applied in a single operative procedure in combination with DBM. The SVF cells were supported in place with mechanical fixation with a resorbable macroporous sheets acting as a soft tissue barrier. The radiographic appearance of the defect revealed a restoration to average bone density and stable position of pharyngeal bone. Densitometric evaluations for digital X-ray revealed improved bone densities in two cases with pharyngeal bone defects, that is, 65.2% for 4th finger of the case 1, 60.5% for 3rd finger of the case 1 and 60.1% for the case 2. Conclusion: This study demonstrated that adipose derived stromal vascular fraction cells have osteogenic potential in two clinical case studies. Thus, these reports show that cells from the SVF cells have potential in many areas of clinical cell therapy and regenerative medicine, albeit a lot of work is yet to be done.

• Smart Structures and Systems
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• v.29 no.4
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• pp.625-640
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• 2022

Maglev rail joints are vital components serving as connections between the adjacent F-type rail sections in maglev guideway. Damage to maglev rail joints such as bolt looseness may result in rough suspension gap fluctuation, failure of suspension control, and even sudden clash between the electromagnets and F-type rail. The condition monitoring of maglev rail joints is therefore highly desirable to maintain safe operation of maglev. In this connection, an online damage detection approach based on three-dimensional (3D) convolutional neural network (CNN) and time-frequency characterization is developed for simultaneous detection of multiple damage of maglev rail joints in this paper. The training and testing data used for condition evaluation of maglev rail joints consist of two months of acceleration recordings, which were acquired in-situ from different rail joints by an integrated online monitoring system during a maglev train running on a test line. Short-time Fourier transform (STFT) method is applied to transform the raw monitoring data into time-frequency spectrograms (TFS). Three CNN architectures, i.e., small-sized CNN (S-CNN), middle-sized CNN (M-CNN), and large-sized CNN (L-CNN), are configured for trial calculation and the M-CNN model with excellent prediction accuracy and high computational efficiency is finally optioned for multiple damage detection of maglev rail joints. Results show that the rail joints in three different conditions (bolt-looseness-caused rail step, misalignment-caused lateral dislocation, and normal condition) are successfully identified by the proposed approach, even when using data collected from rail joints from which no data were used in the CNN training. The capability of the proposed method is further examined by using the data collected after the loosed bolts have been replaced. In addition, by comparison with the results of CNN using frequency spectrum and traditional neural network using TFS, the proposed TFS-CNN framework is proven more accurate and robust for multiple damage detection of maglev rail joints.

• Journal of Navigation and Port Research
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• v.46 no.4
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• pp.331-337
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• 2022

In 2021, the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP), a U.N. advisory research institute, cited container loss as one of six sources of marine litters in shipping. The sinking of the X-P ress Pearl in May 2021 caused a catastrophic environmental pollution accident in which the loaded containers were moved to the shore, and the plastic pellets were loaded inside covered the coast of Sri Lanka. With this history, the International Maritime Organization (IMO) will discuss prevention and follow-up measures for container loss during ship voyages, as an agenda at the 8th Sub Committee on Carriage of Cargoes and Containers meeting in September 2022. To establish Korea's response direction at the IMO meeting, this study identified major causes of container loss accidents, and considered the response through analysis based on the accident investigation report and related professional data. As a result, it was found that the major cause of container loss during voyages was the enlargement of container ships, bad weather, and poor loading of containers. In particular, the need to prepare countermeasures for the deterioration of the operational safety of large container ships due to bad weather was identified. Additionally, integrated monitoring of the implementation of international conventions is required, for the safe sea transportation of container cargo. In particular, in terms of preservation of the marine environment, it is necessary to supplement the system for the recovery of lost containers. Finally, it was found that it is necessary to establish systems that can complement each other in the shipbuilding and shipping industries, in terms of shipbuilding as well as ship operation, to fundamentally prevent container loss accidents at sea. It is judged that it is difficult to resolve the various factors of container loss at sea during voyages, by responding from an individual perspective.

• Membrane and Water Treatment
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• v.14 no.3
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• pp.129-140
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• 2023

The appropriate injection of H₂O₂ is essential to produce hydroxyl radicals (OH·) by mixing H₂O₂ quickly and exposing the resulting H₂O₂ solution to UV irradiation. This study focused on evaluating mixing device of H₂O₂ as a design factor of UV/H₂O₂ AOP pilot plant using a surface water. The experimental investigation involved both experimental and model-based analyses to evaluate the mixing effect of different devices available for the H₂O₂ injection of a tubular hollow pipe, elliptical type of inline mixer, and nozzle-type injection mixer. Computational fluid dynamics analysis was employed to model and simulate the mixing devices. The results showed that the elliptical type of inline mixer showed the highest uniformity of 95%, followed by the nozzle mixer with 83%, and the hollow pipe with only 18%, after passing through each mixing device. These results indicated that the elliptical type of inline mixer was the most effective in mixing H₂O₂ in a bulk. Regarding the pressure drops between the inlet and outlet of pipe, the elliptical-type inline mixer exhibited the highest pressure drop of 15.8 kPa, which was unfavorable for operation. On the other hand, the nozzle mixer and hollow pipe showed similar pressure drops of 0.4 kPa and 0.3 kPa, respectively. Experimental study showed that the elliptical type of inline and nozzle-type injection mixers worked well for low concentration (less than 5mg/L) of H₂O₂ injection within 10% of the input value, indicating that both mixers were appropriate for required H₂O₂ concentration and mixing intensity of UV/ H₂O₂ AOP process. Additionally, the elliptical-type inline mixer proved to be more stable than the nozzle-type injection mixer when dealing with highly concentrated pollutants entering the UV/H₂O₂ AOP process. It is recommended to use a suitable mixing device to meet the desired range of H₂O₂ concentration in AOP process.

• Smart Structures and Systems
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• v.30 no.5
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• pp.521-535
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• 2022

Efficient management of deteriorating civil infrastructure is one of the most important research topics in many developed countries. In particular, the remote displacement measurement of bridges using linear variable differential transformers, global positioning systems, laser Doppler vibrometers, and computer vision technologies has been attempted extensively. This paper proposes a remote displacement measurement system using closed-circuit televisions (CCTVs) and a computer-vision-based method for in-situ bridge bearings having relatively large displacement due to temperature change in long term. The hardware of the system is composed of a reference target for displacement measurement, a CCTV to capture target images, a gateway to transmit images via a mobile network, and a central server to store and process transmitted images. The usage of CCTV capable of night vision capture and wireless data communication enable long-term 24-hour monitoring on wide range of bridge area. The computer vision algorithm to estimate displacement from the images involves image preprocessing for enhancing the circular features of the target, circular Hough transformation for detecting circles on the target in the whole field-of-view (FOV), and homography transformation for converting the movement of the target in the images into an actual expansion displacement. The simple target design and robust circle detection algorithm help to measure displacement using target images where the targets are far apart from each other. The proposed system is installed at the Tancheon Overpass located in Seoul, and field experiments are performed to evaluate the accuracy of circle detection and displacement measurements. The circle detection accuracy is evaluated using 28,542 images captured from 71 CCTVs installed at the testbed, and only 48 images (0.168%) fail to detect the circles on the target because of subpar imaging conditions. The accuracy of displacement measurement is evaluated using images captured for 17 days from three CCTVs; the average and root-mean-square errors are 0.10 and 0.131 mm, respectively, compared with a similar displacement measurement. The long-term operation of the system, as evaluated using 8-month data, shows high accuracy and stability of the proposed system.