• Korean Journal of Optics and Photonics
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• v.30 no.5
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• pp.193-196
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• 2019

The design and control of thermal flow is important for the operation of high-power laser diodes (LDs). It is necessary to analyze and improve the thermal bottleneck near the active layer of an LD. As the error in prediction of the thermal resistance of an LD is large, typically due to the hyperbolic increase and saturation to linear increase of the thermal resistance as a function of thickness, it is helpful to use a simple, modified divergence model for the improvement and optimization of thermal resistance. The characteristics of LDs are described quite well, in that the values for simulated thermal resistance curves and the thermal cross section followed are almost the same as the values from the model function. Also, the thermal-cross-section curve obtained by differentiating the thermal resistance is good for identifying thermal bottlenecks intuitively, and is also fitted quite well by the model proposed for both a typical LD structure and an improved LD with thin capping and high thermal conductivity.

• Geophysics and Geophysical Exploration
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• v.6 no.4
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• pp.171-179
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• 2003

In land and marine seismic survey, we generally set receivers with equal interval suppose that sampling interval Is too narrow. But the cost of seismic data acquisition and that of data processing are much higher, therefore we should design proper receiver interval. Spatial aliasing can be occurred on seismic data when sampling interval is too coarse. If we Process spatial aliasing data, we can not obtain a good imaging result. Trace interpolation is used to improve the quality of multichannel seismic data processing. In this study, we applied the Spitz algorithm which is widely used in seismic data processing. This algorithm works well regardless of dip information of the complex underground structure. Using prediction filter and original traces with linear event we interpolated in f-x domain. We confirm our algorithm by examining for some synthetic data and marine data. After interpolation, we could find that receiver intervals get more narrow and the number of receiver is increased. We also could see that continuity of traces is more linear than before Applying this interpolation algorithm on seismic data with spatial aliasing, we may obtain a better migration imaging.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.411-418
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• 2021

In order to experimentally investigate the effect of Ni or Cu addition on microstructure and mechanical properties of high Si Solution Strengthened Ferritic Ductile cast Iron (SSF DI), a series of lab-scale sand casting experiment were conducted by changing initial concentration of Ni up to 3.0wt% or Cu up to 0.9wt% in the alloy. It was found that increase in Ni or Cu content in the alloy leads to increase in strength properties and hardness as well as decrease in ductility. The higher Ni or Cu content the SSF DI has, the higher fraction of pearlite was observed. At similar levels of Ni or Cu contents in the alloy, higher pearlite area fraction was observed in the Cu-containing SSF DI than that in the Ni-containing SSF DI. When the effect of the microstructure on the mechanical properties of Ni-containing SSF DI was considered, Ni-containing SSF DI was found to have excellent strength and hardness as well as good elongation when the pearlite fraction was controlled less than 10%. As the pearlite fraction in the Ni-containing SSF DI exceeds 10%, however, it shows drastic decrease in elongation. Meanwhile, gradual increase in strength and hardness, and decrease in elongation with respect to increase in pearlite fraction were observed in Cu-containing SSF DI. The different microstructure-mechanical property relationships between Ni-containing and Cu-containing SSF DI were due to the combined effect of the relatively weak pearlite stabilizing effect of Ni compared to that of Cu in high Si SSF DI, and matrix strengthening effect caused by the different amounts of those alloying elements required for similar pearlite fraction.

• Journal of the Korea Convergence Society
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• v.12 no.12
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• pp.145-151
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• 2021

This study aimed to investigate the efficient conduct of HA coating on Ti Gr4 for the practical use of medical device. Ti Gr4 alloy specimens measuring 𝜱 25mm × 1mm were sprayed with hydroxyapatite using thermal spray according to ASTM F1185-88. The surface was evaluated at #120, #400, #1,000 sandpaper and barrel finishing. Each coating properties was analyzed using SEM, UTS 20,000psi cap. and in vitro cytotoxicity. Surface morphology consists of well molten particles with very little resolidified or unmolten areas. The average Ca/P ratio is 1.74 which is in good agreement with theoretical value of 1.67. The average roughness Ra is very representative of roughness of specimen. The coatings are dense and well adhered to the substrate. The average bond strength was 61.74 MPa with a standard deviation of 4.06 which indicates fairly reliable results for ASTM 633 type tests. Variations in results from jig design, epoxy used, crosshead speeds etc. in vitro cytotoxicity result had a Grade 3. The results of the study are expected to be helpful in osseointegration and plasma-spray HA coated Ti Gr4 are more satisfactory in HA coating thickness elevation which is preferable to any other system.

• 한국사회정책
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• v.25 no.3
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• pp.3-35
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• 2018

This article critically reviews the arguments that deny the financial feasbility and effectiveness of universal basic income as an alternative to existing social security systems and makes some suggestions to design effective and efficient basic income schemes. Regarding the financial feasibility of universal basic income, I argue that replacement of the existing regressive tax expenditures with universal basic income without raising tax rates can effectively reduce tax burden or provide income support to a majority of people except the rich. Addition of basic income to the tax base and reduction of the number of beneficiaries of public assistance and the amount of cash payment for them can further help save money. Regarding the redistributive effect, I note that the targeting ability of the existing social security systems is not good and that "the paradox of redistribution" that universal-type programs tend to be more redistributive than selective programs applies to universal basic income as well. I demonstrate significant redistributive effect of a hypothetical revenue-neutral basic income scheme and reviews several empirical studies done in Korea and abroad to show that basic income can be more effective in redistribution than social insurances or public assistance programs. Lastly, I emphasize the need to construct a reliable tax-benefit microsimulation model to help researchers to study redistributive effects of basic income schemes and other taxes and social policies.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.21-28
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• 2018

Despite a number of studies on consolidation behavior that have been carried out in the Nakdong River estuary in Busan, these are focused on the prediction of final settlement during ground improvement process, and there is almost no research on the long-term settlement occurring after that. For the practical study on the long-term settlement, the field monitored settlement data that measured over 10 years in the Busan new port facilities area were used, and the final settlement and predicted time-settlement line were constituted by hyperbolic function. As a result, the measured settlements depend on the thickness of clayey soils, and the pattern were similar to each other and good agreement with the predicted time-settlement line using hyperbolic method. Also, the settlement in the lower non-improved layer occupied 62-76% of total settlement. Information about above results would be quite helpful to understand the long-term settlement behaviors as well as the non-improved layer's settlement is more careful consideration needed at design phase.

• 재활복지
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• v.17 no.4
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• pp.245-265
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• 2013

The purpose of this study is to investigate 1) the perception of special school teachers on the significant skills required by students with intellectual disabilities(ID) for gaining and maintaining employment. For this study, a mixed method design including quantitative survey method and qualitative in-depth interview were utilized. First, through quantitative survey method, the perception on significant skills of students with ID for gaining and maintaining employment was investigated. At the same time, to overcome the limitation of a quantitative survey study, in-depth interviews with special school teachers were implemented. Through in-depth interviews, difficulties keeping students with ID from maintaining employment and significant skills for gaining & maintaining employment were investigated. Many students with ID have had difficulties in maintaining their employment for reasons such as behavioral problems, lack of social skills, or lack of diligence. Thus, many special teachers perceived the importance of educating the significant skills for maintaining their employment as well as gaining employment. For successful vocational transition, daily living skills, occupational skills, and personnel-social skills are significant. However, students' personal-social skills are more important than daily living skills and occupational skills. Among personal-social skills, students' sincerity, diligence, good-hearted personality, social skills, and ability for following directions of a supervisor are significant characteristics for gaining and maintaining employment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.65-70
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• 2019

The purpose of this study is to understand the college students' needs for software curriculum which based on surveys from educational satisfaction of the software lecture evaluation, as well as to find out the improvement plan by applying the text content analysis method. The research method used the text content analysis program to calculate the frequency of words occurrence, key words selection, co-occurrence frequency of key words, and analyzed the text center and network analysis by using the network analysis program. As a result of this research, the decent points of the software education network are mentioned with 'lecturer' is the most frequently occurrence after then with 'kindness', 'student', 'explanation', 'coding'. The network analysis of the shortage points has been the most mention of 'lecture', 'wish to', 'student', 'lecturer', 'assignment', 'coding', 'difficult', and 'announcement' which are mentioned together. The comprehensive network analysis of both good and shortage points has compared among key words, we can figure out difference among the key words: for example, 'group activity or task', 'assignment', 'difficulty on level of lecture', and 'thinking about lecturer'. Also, from this difference, we can provide that the lack of proper role of individual staff at group activities, difficult and excessive tasks, awareness of the difficulty and necessity of software education, lack of instructor's teaching method and feedback. Therefore, it is necessary to examine not only how the grouping of software education (activities) and giving assignments (or tasks), but also how carried out group activities and tasks and monitored about the contents of lectures, teaching methods, the ratio of practice and design thinking.

• Asian Spine Journal
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• v.12 no.6
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• pp.1060-1068
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• 2018

Study Design: Retrospective study. Purpose: Lumbar intervertebral disc degeneration is an important cause of low back pain. Overview of Literature: Spinal fusion is often reported to have a good course for adolescent idiopathic scoliosis (AIS). However, many studies have reported that adjacent segment degeneration is accelerated after lumbar spinal fusion. Radiography is a simple method used to evaluate the orientation of the vertebral column. magnetic resonance imaging (MRI) is the method most often used to specifically evaluate intervertebral disc degeneration. The Pfirrmann classification is a well-known method used to evaluate degenerative lumbar disease. After spinal fusion, an increase in stress, excess mobility, increased intra-disc pressure, and posterior displacement of the axis of motion have been observed in the adjacent segments. Methods: we retrospectively secured and analyzed the data of 15 patients (four boys and 11 girls) with AIS who underwent a spinal fusion surgery. We studied the full-length view of the spine (anterior-posterior and lateral) from the X-ray and MRI obtained from all patients before surgery. Postoperatively, another full-length spine X-ray and lumbosacral MRI were obtained from all participants. Then, pelvic tilt, sacral slope, curve correction, and fused and free segments before and after surgery were calculated based on X-ray studies. MRI images were used to estimate the degree to which intervertebral discs were degenerated using Pfirrmann grading system. Pfirrmann grade before and after surgery were compared with Wilcoxon signed rank test. While analyzing the contribution of potential risk factors for the post-spinal fusion Pfirrmann grade of disc degeneration, we used generalized linear models with robust standard error estimates to account for intraclass correlation that may have been present between discs of the same patient. Results: The mean age of the participant was 14 years, and the mean curvature before and after surgery were 67.8 and 23.8, respectively (p<0.05). During the median follow-up of 5 years, the mean degree of the disc degeneration significantly increased in all patients after surgery (p<0.05) with a Pfirrmann grade of 1 and 2.8 in the L2-L3 before and after surgery, respectively. The corresponding figures at L3-L4, L4-L5, and L5-S1 levels were 1.28 and 2.43, 1.07 and 2.35, and 1 and 2.33, respectively. The lower was the number of free discs below the fusion level, the higher was the Pfirrmann grade of degeneration (p<0.001). Conversely, the higher was the number of the discs fused together, the higher was the Pfirrmann grade. Conclusions: we observed that the disc degeneration aggravated after spinal fusion for scoliosis. While the degree of degeneration as measured by Pfirrmann grade was directly correlated by the number of fused segments, it was negatively correlated with the number of discs that remained free below the lowermost level of the fusion.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.105-113
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• 2018

In this study, the engineering properties including bearing capacity of subgrades stabilized with a binder are analyzed by laboratory and field experiments. The main components of the binder are CaO and $SO_3$. After the binder was mixed with a low plasticity clay, the passing rates were relatively decreased as the sieve mesh size increased. Not only did the soil type change to silty sand, but engineering properties, such as the plasticity index and modified California bearing ratio (CBR), were improved for the subgrade. A comparison of the compaction curves of the stabilized subgrade and field soil compacted with the same energy demonstrated an increase of approximately 6% in the maximum dry unit weight, slight decrease in optimum moisture content, and considerable increase improvement in grain size. In the modified CBR test, the effect of unit weight and strength increase of the modified soil (with a specific amount of binder) was remarkably improved. As the proportion of granulated material increased after the addition of binder, the swelling was reduced by 3.3 times or more during initial compaction and 6.5 times by final compaction. The unconfined compressive strength of the specimens was maintained at the homogeneous value with a constant design strength. The stabilized subgrade was validated by applying it in the field under the same conditions; this test demonstrated that the bearing capacity coefficients at all six sites after one day of compaction exceeded the target value and exhibited good variability.