• Design & Manufacturing
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• v.16 no.3
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• pp.9-15
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• 2022

In order to reduce the manufacturing costs of the glass lens, it is necessary to manufacture a lens using a UV curable resin or a thermosetting resin, which is a curable material, in order to replace a glass lens. In the case of forming a lens using a thermosetting material, it is necessary to form several lenses at once using the wafer-level lens manufacturing technologies due to the long curing time of the material. When a lens is manufactured using a curable material, an error in the shape of the lens due to the shrinkage of the material during the curing process is an important cause of defects. The major factors for these shape errors and deformations are the shrinkage and the change of mechanical properties in the process of changing from a liquid material during curing to a solid state after complete curing. Therefore, it is necessary to understand the curing process of the material and to examine the shrinkage rate and change of physical properties according to the degree cure. In addition, it is necessary to proceed with CAE for lens molding using these and to review problems in lens manufacturing in advance. In this study, the viscoelastic properties of the material were measured during the curing process using a rheometer. Using the results, Rheological investigation of cure kinetics was performed. At the same time, The shrinkage of the material was measured and simple mathematical models were created. And using the results, the molding process of a single lens was analyzed using Comsol, a commercial S/W. In addition, the experiment was conducted to compare and verify the CAE results. As a result, it was confirmed that the shrinkage rate of the material had a great influence on the shape precision of the final product.

• Journal of Broadcast Engineering
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• v.27 no.5
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• pp.629-637
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• 2022

This study is an experiment on the use of RDW(Redirected Walking) technology, which helps users to hardly feel the difference of user movement in the limited physical space and the extended virtual space when the user moves while wearing the HMD in the real world. The RDW function installed in 3D space realization software such as Unity3D is used to induce the user's redirection by slightly distorting the virtual space according to the user's point of view. However, if the RDW distortion rate is used excessively, dissonance is highly likely to occur. In particular, it is easy to make errors that cause cybersickness of users. It is important to obtain the RDW data value in the virtual environment so that the user does not feel fatigue and cybersickness even after wearing the HMD for a long time. In this experiment, it was tested whether the user's RDW was safely implemented, and item and obstacle arrangement data were obtained through this experiment. The RDW data obtained as a result of the experiment were used for item placement and obstacle placement in the virtual space.

• Ocean Systems Engineering
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• v.12 no.2
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• pp.225-245
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• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• Geomechanics and Engineering
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• v.28 no.3
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• pp.283-298
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• 2022

Landslides triggered by the combination of heavy precipitation and anthropological disturbance in hilly areas cause severe damage to human lives, properties, and infrastructure constructions. A comprehensive investigation of the influencing factors and failure mechanisms of landslides are significant for disaster mitigation and prevention. This paper utilized the combination of detailed geological investigation, physical experimental testing as well as numerical modelling to determine the failure mechanism, and proposed a countermeasures of the Lantian landslide occurred on 2, July 2017. The results reveal that the Lantian landslide is a catastrophic reactivated slide which occurred in an active tectonic region in Southwest China. Because of the unique geological settings, the fully to highly weathered basalts in the study area with well-developed fractures favored the rainwater infiltration, which is the beneficial to slide reactivation. Engineering excavation and heavy precipitation are the main triggering factors to activate the slide motion. Two failure stages have been identified in the landslide. The first phase involves a shallow mass collapse originated at the upper slopes, which extends from the road to platform at rear part, which is triggered by excavation in the landslide region. Subjected to the following prolonged rainfall from 19 June to 2 July, 2017, the pore water pressure of the slope continually increased, and the groundwater table successively rise, resulting in a significant decrease of soil strength which leads to successive large-scale deep slide. Thereinto, the shallow collapse played a significant role in the formation of the deep slide. Based on the formation mechanisms of the landslide, detailed engineering mitigation measures, involving slope cutting, anchor cable frame, shotcrete and anchorage, retaining wall and intercepting ditch were suggested to reduce the future failure risk of the landslide.

• Korean Journal of Head & Neck Oncology
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• v.37 no.1
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• pp.33-37
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• 2021

Intraosseous hemangioma is a rare, benign vascular tumor of endothelial origin. It accounts for fewer than 1% of all hemangiomas, and very rarely occurs in the face. Intraosseous hemangioma usually presents as an asymptomatic lesion, but symptoms can occur due to the mass effect. The authors describe a case of intraosseous hemangioma of the zygoma with a review of the relevant literature. A 44-year-old man presented with a chief complaint of painless swelling on the left zygomatic region that had been slowly growing for the past year. On physical examination, a hard, non-movable mass in a deep layer was palpated. On computed tomography performed to evaluate its layers and extent, trabeculation was found inside the mass, but the lack of destruction of the surrounding bone suggested that the mass was benign. Complete surgical excision was performed under local anesthesia. After complete excision of the mass, slight erosions remained on the cortical bone of the zygoma, but because it was small enough not to cause a facial deformity such as depression or asymmetry, no additional reconstructive procedure was performed. There were no symptoms or recurrence during a 8-month follow-up period.

• Journal of People, Plants, and Environment
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• v.24 no.5
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• pp.469-483
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• 2021

Background and objective: If the Nelumbo nucifera spreads in a wetland at a high density, it can have considerable positive and negative ecological effects on habitats. For this reason, it is necessary to precisely investigate the impacts of its rapid proliferation. This study was conducted to propose the distribution and management of N. nucifera, which can cause the degradation of wildlife habitats due to the rapid spread of internal and external environmental factors that may affect the Junam wetland ecosystem. Methods: For the investigation and analysis of physical and ecological characteristics, factors of the abiotic environment such as general weather conditions, topography and water depth structure, and soil and water quality analysis, and bioenvironment characteristics such as changes in the N. nucifera community distribution were evaluated. To assess whether the differences in the soil depth and physicochemical characteristics between the N. nucifera community and the aquatic plant community are statistically significant, a One-way ANOVA was executed. Results: N. nucifera was presumably introduced in approximately 2007 and observed at a prevalence of only 0.8% in 2009, but had expanded to 11.1% in 2014. After that, the area was increased to 19.3% in 2015 and 40.0% in 2017, about twice that of the previous survey year. The rapid diffusion of an N. nucifera colony can have adverse effects on wildlife habitats and biodiversity at Junam Wetland. To solve these problems, four management methods can be proposed; water level management, mowing management, installation of posts and removal of lotus roots. Control of the N. nucifera community using these methods was judged to be suitable for cutting and water level management when considering expansion rate, water level variation, and wildlife habitat impacts. Conclusion: As the biotic and abiotic environmental factors are different for each wetland, it is necessary to determine the timing and method of management through a detailed investigation.

• Particle and aerosol research
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• v.18 no.4
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• pp.129-136
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• 2022

The line width of circuits in semiconductor devices continues to decrease down to a few nanometers. Since nanoparticles attached to the patterned wafer surface may cause malfunction of the devices, it is crucial to remove the contaminant nanoparticles. Physical cleaning that utilizes momentum of liquid for detaching solid nanoparticles has recently been tested in place of the conventional chemical method. Dropwise impaction has been employed to increase the removal efficiency with expectation of more efficient momentum exchange. To date, most of relevant studies have been focused on drop spreading behavior on a horizontal surface in terms of maximum spreading diameters and average spreading velocity of drop. More important is the local liquid velocity at the position of nanoparticle, very near the surface, rather than the vertical average value. In addition, there are very scarce existing studies dealing with microdroplet impaction that may be desirable for minimizing pattern demage of the wafer. In this study, we investigated the local velocity distribution in spreading liquid film under various impaction conditions through the CFD simulation. Combining the numerical results with the particle removal model, we estimated an effective cleaning diameter (ECD), which is a measure of the particle removal capacity of a single drop, and presented the predicted ECD data as a function of droplet's velocity and diameter particularly when the droplets are microns in diameter.

• Journal of Ecology and Environment
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• v.46 no.4
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• pp.282-291
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• 2022

Background: The Arctic permafrost stores enormous amount of carbon (C), about one third of global C stocks. However, drastically increasing temperature in the Arctic makes the stable frozen C stock vulnerable to microbial decomposition. The released carbon dioxide from permafrost can cause accelerating C feedback to the atmosphere. Soil organic matter (SOM) composition would be the basic information to project the trajectory of C under rapidly changing climate. However, not many studies on SOM characterization have been done compared to quantification of SOM stocks. Thus, the purpose of our study is to determine soil properties and molecular compositions of SOM in four different Arctic regions. We collected soils in different soil layers from 1) Cambridge Bay, Canada, 2) Council, Alaska, USA, 3) Svalbard, Norway, and 4) Zackenberg, Greenland. The basic soil properties were measured, and the molecular composition of SOM was analyzed through pyrolysis-gas chromatography/mass spectrometry (py-GC/MS). Results: The Oi layer of soil in Council, Alaska showed the lowest soil pH and the highest electrical conductivity (EC) and SOM content. All soils in each site showed increasing pH and decreasing SOC and EC values with soil depth. Since the Council site was moist acidic tundra compared to other three dry tundra sites, soil properties were distinct from the others: high SOM and EC, and low pH. Through the py-GC/MS analysis, a total of 117 pyrolysis products were detected from 32 soil samples of four different Arctic soils. The first two-axis of the PCA explained 38% of sample variation. While short- and mid-hydrocarbons were associated with mineral layers, lignins and polysaccharides were linked to organic layers of Alaska and Cambridge Bay soil. Conclusions: We conclude that the py-GC/MS results separated soil samples mainly based on the origin of SOM (plants- or microbially-derived). This molecular characteristics of SOM can play a role of controlling SOM degradation to warming. Thus, it should be further investigated how the SOM molecular characteristics have impacts on SOM dynamics through additional laboratory incubation studies and microbial decomposition measurements in the field.

• Journal of People, Plants, and Environment
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• v.23 no.6
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• pp.683-694
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• 2020

Background and objective: Cancer is the number one cause of death in Korea, and it affects any part of the body regardless of gender and age. Forest healing is a treatment that maximizes the effect of treatment and improves the quality of life. This study aims to provide basic data for the development and implementation of differentiated forest healing programs for cancer patients based on the survey on their interest and needs for the programs. Methods: The subjects were those diagnosed with cancer from October 2018 to April 2019, and this study used 144 copies of the questionnaire retrieved. The sample size of this study (n = 144) was the appropriate size required by G-Power, and the collected responses were analyzed using SPSS 25.0. Results: In the frequency analysis on the interest in forest healing, 79.2% of the subjects had no experience participating in forest healing, but 87% were aware of it, and 82.6% showed the intention to participate in forest healing programs. This indicates that even though not many of them have experience participating in forest healing, they showed high interest and needs for participation. They preferred to participate in spring (29.9%) and fall (27.8%), in programs carried out for 1.5-2 hours in the morning on weekdays. Conclusion: This study has implications for the analysis on forest healing needs of cancer patients, and it is necessary to plan, develop, and implement differentiated forest healing programs that meet the needs of the cancer patients depending on their characteristics. There is also a need to plan forest healing program that can promote both psychological stability and physical health of cancer patients and verify and evaluate their effects based on specialized training of forest healing instructors.

• Archives of Plastic Surgery
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• v.49 no.2
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• pp.184-194
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• 2022

The face and the external nose define an individual's physical appearance. Nasal deformities can cause facial disfigurement along with unwanted psychological repercussions. Nasal deformities range in severity, with the most severe cases being indications for a rhinectomy, due to the complexity of the nasal defect. According to published literature, there is no consensus among otolaryngologists and plastic surgeons on which technique or flap use is preferred in terms of complications, aesthetic outcome, or patient satisfaction. The goal of this study is to provide a comprehensive analysis of published studies on nasal reconstruction following rhinectomy. Using the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols guidelines for writing systematic reviews, a systematic review was conducted. Four databases were searched using a search strategy. These articles were then imported into the COVIDENCE software and went screening and thorough article review. After screening 2,237 articles, 23 studies were then extracted for data collection analysis. We collected data from 12 case series, 4 case studies, 1 prospective case series, and 4 retrospective chart review studies. The most commonly reported flaps were forehead flaps, superior extended nasal myocutaneous island, forearm free flaps, anterolateral thigh (ALT) free flap, medial femoral condyle free flap (n = 8), and zygomaticus implants (n = 6), and retained nasal prosthesis. Although not specifically indicated by a certain number, the most common indication for the rhinectomy was malignancy, followed by traumas, postsurgical complications, radionecrosis, and congenital nasal malformations.