• Journal of Ocean Engineering and Technology
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• v.26 no.2
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• pp.20-25
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• 2012

During drilling, the precipitation velocity of cuttings within an annulus depends on the density and configuration of the cuttings, and on the density, viscosity, and rheological characteristics of the drilling fluid. In directional drilling in particular, it is difficult to adjust and control the cuttings. In contrast to vertical drilling, it is very important to evaluate the flow characteristics of a drilling flow field. However, research on the transfer features of cuttings is inadequate. In this study, in order to identify transfer features of cuttings, an experiment was performed under wide-ranging conditions by constructing a slim hole annulus ($44mm{\times}30mm$) device. In this experiment, the particle volume fraction were influenced by particle size, particle concentration within the flow, pipe rotation, flow volume, and inclination of the annulus. In addition, a mathematical formula for volumetric concentration was deduced and compared to the test results and behavior of cuttings under the other drilling condition was made to be predicted. Therefore, this study can provide meaningful data for vertical and horizontal drilling, and for directional drilling.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.225-234
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• 2001

This paper represents the vector fields, three dimensional mean velocities, the turbulent intensities, the turbulent kinetic energy, and the Reynolds shear stresses in the X-Y plane of gas swirl burner with a cone type baffle plate measured by using X-probe from hot-wire anemometer system. This experiment is carried out at flow rates 350 and 450ℓ/min respectively, which are equivalent to the combustion air flow rate necessary for heat release 15,000 kcal/hr in gas furnace, in the test section of subsonic wind tunnel. The vector plot shows that the maximum axial mean velocity component exists in the narrow slits situated radially on the edge of gas swirl burner, for that reason, there is some entrainment phenomena of ambient air in the outer region of burner. Moreover, mean velocities in the initial region are largely distributed near the outer region of burner at Y/R≒0.97, but they diffuse and develop into the center flow region of burner according to the increase of axial distance. The turbulent intensities and the turbulent kinetic energy due to large inclination of mean velocity and swirl effect show that the maximum value in the initial region of burner is formed in the narrow slits situated radially on the edge of gas swirl burner and large values are mainly formed in the entire region of burner after X/R=2.4358, hence, the combustion reaction is anticipated to occur actively near this region. And the Reynolds shear stresses are also largely distributed from slite to vanes of gas swirl burner in the intial region, but their values largely disappear after X/R=3.2052.

• Current Photovoltaic Research
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• v.3 no.4
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• pp.121-125
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• 2015

BIPV system is one of the best ways to harness PV module. The BIPV system not only produces electricity, but also acts as a building envelope. Thus, it has the strong point of increasing the economical efficiency by applying the PV modules to the buildings. Bifacial solar cells can convert solar energy to electrical energy from both sides of the module. In addition, it is designed as 3 busbar layout which is the same with ordinary mono-facial soalr cells. Therefore, many of the module manufacturers can easily produce the bifacial solar cells without changing their manufacturing equipment. Moreover, bifacial BIPV system has much potential in building application by utilizing glass to glass structure. However, the performance of bifacial solar cells depends on a variety of factors, ranging from the back surface to surrounding conditions. Therefore, in order to apply bifacial solar cells to buildings, an analysis of bifacial PV module performance should be carried out that includes a consideration of various design elements, and reflects a wide range of installation conditions. As a result it found that the white insulation reflector type can improve the performance of the bifacial BIPV system by 16%, compared to the black insulation reflector type. The performance of the bifacial BIPV was also shown to be influenced by inclination angle, due to changes in both the amount of radiation captured on the front face and the radiation transmitted to the rear face through the transparent space. In this study is limited design condition and installation condition. Accordingly follow-up researches in this part need to be conducted.

• The korean journal of orthodontics
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• v.49 no.6
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• pp.381-392
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• 2019

Objective: The objective of this two-arm parallel trial was to compare the type of tooth movement during en masse retraction of the maxillary anterior teeth using labial versus lingual biocreative therapy. Methods: Twenty-eight subjects were randomized in a 1 : 1 ratio to either the labial or lingual group. En masse anterior retraction was performed using labial biocreative therapy in group A and lingual biocreative therapy in group B. Cone beam computed tomography scans were taken before and after retraction and the primary outcome was the type of tooth movement during anterior retraction. Data were analyzed using paired t-tests for comparisons within each group and independent-sample t-test for comparison of the mean treatment changes between the two groups. Results: Significant differences were found between the two groups in relation to the type of tooth movement (labiolingual inclination of the central incisor; mean difference, $5.85{\pm}1.85^{\circ}$). The canine showed significant distal tipping in the lingual group (mean difference, $6.98{\pm}1.25^{\circ}$). The canine was significantly more intruded in the lingual group (mean difference, $1.67{\pm}0.49mm$). Good anchorage control and significant soft tissue changes occurred in both groups. No serious adverse effects were detected. Conclusions: With a 10-mm retraction hook, the labial biocreative technique with the reverse curve overlay provided anterior retraction with good torque control, while in the lingual group, anterior retraction occurred with controlled tipping movement with significant distal tipping and intrusion of the canine (trial registration: The trial was registered at ClinicalTrials.gov [NCT03239275]).

• Journal of Fashion Business
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• v.23 no.1
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• pp.116-126
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• 2019

The purpose of this study is to objectify the shape of curvature and average change rate of angular and arched eyebrow makeup. The data for the analysis were the final 336 pieces for the cosmetology students in the whole country. SPSS 20.0 program was used for the collected data, frequency analysis, factor analysis, reliability analysis, and crossover analysis were performed. First, the frequency of the average change rate of eyebrow makeup (angular and arcuate) was analyzed. As a result, the eyebrows suitable for the angled type showed the highest level of 'A-2' and the arched eyebrows had the highest level of 'B-2'. Second, to analyze the important factors of eyebrow makeup, frequency of eyebrows was the most important, followed by the inclination of eyebrows and eyebrow tail. Third, factor analysis and reliability analysis were conducted to examine each dimension of eyebrow makeup perception, and it was derived from three factors including acceptability, aggressiveness, and playability. Fourth, in order to analyze the difference of important factors in the form of the standard eyebrow makeup, the cross - analysis was performed with chi - square test, and it was confirmed that the angular eyebrow makeup showed the most objectivity when the average change rate was 0.29 and the curvature was 0.67. Fifth, arcuate eyebrow makeup showed the most objectivity when the average change rate was 0.57 and curvature was 0.56. The results of this analysis can be used as objective data of aesthetic criteria when designing the eyebrow shape.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.146-152
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• 2022

Information collected from temperature, humidity, inclination, and pressure sensors using Raspberry Pi or Arduino is used in automatic constant temperature and constant humidity systems. In addition, by using it in the agricultural and livestock industry to remotely control the system with only a smartphone, workers in the agricultural and livestock industry can use it conveniently. In general, temperature and humidity are expressed in a line graph, etc., and the change is monitored in real time. The technology to visually express the temperature has recently been used intuitively by using an infrared device to test the fever of Corona 19. In this paper, the information collected from the Raspberry Pi and the DHT11 sensor is used to predict the temperature change in space through intuitive visualization and to make a immediate response. To this end, an algorithm was created to effectively visualize temperature and humidity, and data representation is possible even if some sensors are defective.

• Structural Engineering and Mechanics
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• v.83 no.4
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• pp.415-433
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• 2022

Eighteen (18) (120×300×2200 mm) beams were prepared and tested to evaluate the shear strength of Glass Fiber Reinforced Concrete (GFRC) beams with no shear reinforcement, and evaluate the effectiveness of various innovative strengthening systems to increase the shear capacity of the GFRC beams. The test variables are the amount of discrete glass fiber (0.0, 0.6, and 1.2% by volume of concrete) and the type of longitudinal reinforcement bars (steel or GFRP), the strengthening systems (externally bonded (EB) sheet, side near-surface mounted (SNSM) bars, or the two together), strengthening material (GFRP or steel) links, different configurations of NSM GFRP bars (side bonded links, full wrapped stirrups, side C-shaped stirrups, and side bent bars), link spacing, link inclination angle, and the number of bent bars. The experimental results showed that adding the discrete glass fiber to the concrete by 0.6%, and 1.2% enhanced the shear strength by 18.5% and 28%, respectively in addition to enhancing the ductility. The results testified the efficiency of different strengthening systems, where it is enhanced the shear capacity by a ratio of 28.4% to 120%, and that is a significant improvement. Providing SNSM bent bars with strips as a new strengthening technique exhibited better shear performance in terms of crack propagation, and improved shear capacity and ductility compared to other strengthening techniques. Based on the experimental shear behavior, an analytical study, which allows the estimation of the shear capacity of the strengthened beams, was proposed, the results of the experimental and analytical study were comparable by a ratio of 0.91 to 1.15.

• Korean Journal of Materials Research
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• v.33 no.5
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• pp.205-213
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• 2023

This paper reports the results of an experimental examination using X-rays to test annealing materials for lapped bearing steel (STB2), to confirm the validity of the weighted averaging analysis method. The distribution behavior for the α_𝜓-sin²𝜓 diagram and the presence or absence of differences in the peak method, half-value breadth method, and centroid method were investigated. When lapping the annealed bearing steel (STB2) material, a residual stress state with a non-directional steep gradient appeared in the surface layer, and it was found that the weighted averaging analysis method was effective. If there is a steep stress gradient, the sin²𝜓 diagram is curved and the diffraction intensity distribution curve becomes asymmetric, resulting in a difference between the peak method, half-value breadth method, and centroid method. This phenomenon was evident when the stress gradient was more than 2~3 kg/mm²/㎛. In this case, if the position of the diffraction line is determined using the centroid method and the weighted averaging analysis method is applied, the stress value on the surface and the stress gradient under the surface can be obtained more accurately. When the stress gradient becomes a problem, since the curvature of the sin²𝜓 diagram appears clearly in the region of sin²𝜓 > 0.5, it is necessary to increase the inclination angle 𝜓 as much as possible. In the case of a lapping layer, a more accurate value can be obtained by considering 𝜎₃ in the weighted averaging analysis method. In an isotropic biaxial residual stress state, the presence or absence of 𝜎₃ can be determined as the presence or absence of strain for sin²𝜓≈0.4.

• Safety and Health at Work
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• v.13 no.4
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• pp.440-447
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• 2022

Background: Agricultural handle equipment is present on all production areas' farms. They are handy and portable; however, excessive use can lead to acute traumas or accidental injuries. Repetitive movements, awkward postures, and hand-arm vibrations predispose them to pain and work-related musculoskeletal disorders. The purpose of this study was to observe the interaction of handle equipment in terms of electromyographic activity and analyze the postural work-related alterations. Materials and methods: Twenty male agricultural operators, mean age 24±1.54 years, underwent the electromyographic analysis testing their muscular activities with a brushcutter, electric saw, and hedge trimmer in four different test conditions. Results: The brushcutter proved to be the agricultural handle equipment with the higher mean frequency (3.37±0.38 Hz) and root mean square (5.25±1.24 ms^-2). Furthermore, the digital postural analysis showed a general asymmetry of the main arm and the respective side of the trunk. The head resulted right inclined in the anterior frontal plane by 5.7°±1.2°; the right scapula lower than the left in the posterior frontal plane (8.5°±1.8°), and a working trunk inclination of 34.15°±5.7°. Conclusions: Vibrations of handle equipment and awkward working postures represent a risk for agricultural operators. Preventive measures are required to avoid young operators from experiencing musculoskeletal disorders all lifelong.

• The korean journal of orthodontics
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• v.53 no.4
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• pp.264-275
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• 2023

Objective: To investigate the effects of maxillary orthodontic expansion on the alveolar bone tissue in adult patients treated with aligners by using cone-beam computed tomography. Methods: Thirty patients (22 females and 8 males; mean age: 36.3 years) were treated with Invisalign^® aligners. Cone-beam computed tomography and digital models were obtained before (T0) and after (T1) upper arch expansion. The bone thicknesses in the cervical, middle, and apical areas of the incisors, canines, premolar, and first molars were buccally and palatally measured, totaling 96 areas and 2,880 measurements. The buccolingual inclinations and transverse measurements of the teeth were obtained from digital models to correlate them with the bone changes. The statistical tests used were Student's t-test, analysis of variance, and Pearson's correlation tests (p < 0.05). Results: From the 96 areas evaluated, 84 revealed an increase or stability in the alveolar bone thickness and twelve displayed significant bone loss. Bone changes did not correlate with the tooth inclination and transverse measurements. Conclusions: Within the limitation of the present study, mild levels of upper arch expansion obtained with Invisalign^® aligners in adult patients did not result in any clinically significant loss of alveolar bone thickness.