• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.7
• /
• pp.52-60
• /
• 2019

The control circuit of the CPP applied to FFX Batch-I and LST-II may be capable of generating a backward pitch even when the grounding phenomenon occurs in the other system. The purpose of this study was to improve the CPP control circuit to maintain the pitch even in the event of grounding. Since the CPP control circuit changes the propeller angle with the voltage difference input, it has a design structure that can be vulnerable if the input voltage fluctuates instantaneously. In order to solve the above problem, a terminating resistor is applied to the end of the control wire and a signal converter is applied between the control wires, as a way to improve the CPP control circuit design. In order to verify that there is no problem in improving the CPP control circuit design, the CPP pitch change control was tested in the actual sailing commissioning with LST-II. Since the command pitch value and the feedback pitch value are very similar to each other, it is confirmed that the CPP control circuit is suitable for the control signal transmission because there is no problem in transmitting the control signal.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.46 no.2
• /
• pp.173-182
• /
• 2019

Vertical facial growth triggers the rotation of mandible to move the chin point to the downward and backward direction, which showed remarkably effective result making the less prominent chin. Recently, the intraoral removable appliance utilizing class III elastic demonstrated the vertical growth trigger mechanism. The treatment change was very fast and wearing was quite easy, compared to extraoral appliances. The purpose of this study was to verify the duration of the treatment on class III malocclusion using intraoral removable appliances, which designed to accelerate vertical facial growth. 56 patients were selected with the complaint of the protruded mandible and class III malocclusion (overjet : -3 - 0 mm, overbite : 0 - 4 mm). Information like; age at start, duration of the treatment events, type of the treatment, overjet, overbite etc. was collected and calculated. The average age of the patients delivering the initial brace was $8.75{\pm}1.10year$. Most of the anterior crossbite was resolved within 6 months. The total treatment period was $21.79{\pm}10.73months$ with the additional procedures like the alignment of anterior teeth and torque control using additional removable and fixed orthodontic appliances. The correlation study showed that patient's cooperation (p = 0.000) and the use of fixed appliance (p = 0.032) were significantly influenced on treatment duration.

• Journal of the Korea Computer Graphics Society
• /
• v.27 no.3
• /
• pp.55-63
• /
• 2021

This study proposes an interface for providing mobile interaction suitable for mobile virtual reality (VR) and analyzes it through comparative experiments. The proposed interface is premised on not using additional equipment except for the mobile head-mounted display(HMD) in consideration of accessibility and usability. And the interface that controls the movement interaction using the user's gaze is designed in two phases. The key is to minimize the occurrence of negative factors such as VR sickness that can be caused by straight line movement in virtual reality. To this end, two phases are designed: an interface composed of forward/backward buttons to move the gaze toward the ground, and an interface composed of left and right buttons on the front in consideration of the gaze change in real walking motion. An application that can compare and analyze movement interactions through the proposed interface is produced, and a survey experiment is conducted to analyze the user's satisfaction with the interface experience and the negative impact on the movement process. It was confirmed that the proposed movement interaction reduced negative effects such as VR sickness along with a satisfactory interface experience for users.

• Particle and aerosol research
• /
• v.15 no.3
• /
• pp.91-104
• /
• 2019

In this study, hourly measurements of $PM_{2.5}$ and its major chemical constituents such as organic and elemental carbon (OC and EC), and ionic species were made between January 15 and February 10, 2018 at the air pollution intensive monitering station in Gwangju. In addition, 24-hr integrated $PM_{2.5}$ samples were collected at the same site and analyzed for OC, EC, water-soluble OC (WSOC), humic-like substance (HULIS), and ionic species. Over the whole study period, the organic aerosols (=$1.6{\times}OC$) and $NO_3{^-}$ concentrations contributed 26.6% and 21.0% to $PM_{2.5}$, respectively. OC and EC concentrations were mainly attributed to traffic emissions with some contribution from biomass burning emissions. Moreover, strong correlations of OC with WSOC, HULIS, and $NO_3{^-}$ suggest that some of the organic aerosols were likely formed through atmospheric oxidation processes of hydrocarbon compounds from traffic emissions. For the period between January 18 and 22 when $PM_{2.5}$ pollution episode occurred, concentrations of three secondary ionic species ($=SO{_4}^{2-}+NO_3{^-}+NH_4{^+}$) and organic matter contributed on average 50.8 and 20.1% of $PM_{2.5}$, respectively, with the highest contribution from $NO_3{^-}$. Synoptic charts, air mass backward trajectories, and local meteorological conditions supported that high $PM_{2.5}$ pollution was resulted from long-range transport of haze particles lingering over northeastern China, accumulation of local emissions, and local production of secondary aerosols. During the $PM_{2.5}$ pollution episode, enhanced $SO{_4}^{2-}$ was more due to the long-range transport of aerosol particles from China rather than local secondary production from $SO_2$. Increasing rate in $NO_3{^-}$ was substantially greater than $NO_2$ and $SO{_4}^{2-}$ increasing rates, suggesting that the increased concentration of $NO_3{^-}$ during the pollution episode was attributed to enhanced formation of local $NO_3{^-}$ through heterogenous reactions of $NO_2$, rather than impact by long-range transportation from China.

• Journal of Environmental Analysis, Health and Toxicology
• /
• v.21 no.4
• /
• pp.281-291
• /
• 2018

Recently, long-range atmospheric transport (LRAT) from China is regarded as a major reason for elevated levels of particulate matter (PM) in Korea. However, local emissions also play an important role in PM pollution, especially in large-scale industrial cities. In this study, PM samples were collected at suburban, residential, and industrial sites in Ulsan, Korea. Polycyclic aromatic hydrocarbons (PAHs) and heavy metals were analyzed, and a potential human health risk assessment was conducted. The concentrations of PAHs and heavy metals in total suspended particles (TSP) increased during high $PM_{10}$ episodes, and backward trajectory analysis verified the influence of LRAT from China during the high episodes. Furthermore, the concentrations of PAHs and heavy metals in $PM_{2.5}$ and $PM_{10}$ at the industrial site were higher than those at the residential site. The risk assessment of PAHs and heavy metals in $PM_{2.5}$ suggested no significant health effects. The highest levels of PAHs were measured in the particle size of $0.32{\sim}0.56{\mu}m$ at the residential site, and those of heavy metals were detected in the particle size of 1.8~5.6 and $>18{\mu}m$, reflecting different major emissions sources for both groups. On the basis of this preliminary study, we are planning long-term monitoring and modeling studies to quantitatively evaluate the influence of industrial activities on the PM pollution in Ulsan.

• Korean Journal of Optics and Photonics
• /
• v.32 no.3
• /
• pp.120-125
• /
• 2021

We have developed a linearly polarized high-power Yb-doped fiber laser in the master oscillator power amplifier (MOPA) scheme for efficient spectral beam combining. We modulated the phase of the seed laser by pseudo-random binary sequence (PRBS), with the bit length optimized to suppress stimulated Brillouin scattering (SBS), and subsequently amplified seed power in a 3-stage amplifier system. We have constructed by coiling the polarization-maintaining (PM) Yb-doped fiber, with core and cladding diameters of 20 ㎛ and 400 ㎛ respectively, to a diameter of 9-12 cm for suppression of the mode instability (MI). Finally, we obtained an output power of 1.004 kW with a slope efficiency of 83.7% in the main amplification stage. The beam quality factor M² and the polarization extinction ratio (PER) were measured to be 1.12 and 21.5 dB respectively. Furthermore, the peak-intensity difference between the Rayleigh signal and SBS signal was observed to be 2.36 dB in the backward spectra, indicating that SBS is successfully suppressed. In addition, it can be expected that the MI does not occur because not only there is no decrease in slope efficiency, but also the beam quality for each amplified output is maintained.

• Journal of Biomedical Engineering Research
• /
• v.42 no.3
• /
• pp.71-79
• /
• 2021

Currently, the naked eyes-based diagnosis of bone metastases on CT images relies on qualitative assessment. For this reason, there is a great need for a state-of-the-art approach that can assess and follow-up the bone metastases with quantitative biomarker. Radiomics can be used as a biomarker for objective lesion assessment by extracting quantitative numerical values from digital medical images. In this study, therefore, we evaluated the clinical applicability of non-invasive and objective bone metastases computer-aided diagnosis using radiomics-based biomarkers in CT. We employed a total of 21 approaches consist of three-classifiers and seven-feature selection methods to predict bone metastases and select biomarkers. We extracted three-dimensional features from the CT that three groups consisted of osteoblastic, osteolytic, and normal-healthy vertebral bodies. For evaluation, we compared the prediction results of the classifiers with the medical staff's diagnosis results. As a result of the three-class-classification performance evaluation, we demonstrated that the combination of the random forest classifier and the sequential backward selection feature selection approach reached AUC of 0.74 on average. Moreover, we confirmed that 90-percentile, kurtosis, and energy were the features that contributed high in the classification of bone metastases in this approach. We expect that selected quantitative features will be helpful as biomarkers in improving the patient's survival and quality of life.

• Journal of the Institute of Convergence Signal Processing
• /
• v.21 no.1
• /
• pp.21-28
• /
• 2020

In this paper, a new type of electric wheelbarrow is proposed and developed. The developed electric wheelbarrow is equipped with an attitude reference system(ARS) sensor, which consists of 3-axis acceleration sensor and 2-axis Gyro sensor so that it can estimate pitch angle and roll angle. When an operator tilts the wheelbarrow up and down, the pitch angle is detected. The sign of the pitch angle is interpreted as the operator's intention for moving the wheelbarrow forward or backward and the controller drives the wheel of the wheelbarrow with the velocity according to the magnitude of the detected pitch angle. A cargo box of the wheelbarrow is designed to rotate and is controlled to maintain level always, so an operator can handle the electric wheelbarrow easily and safely. The wheelbarrow consists of an in-wheel motor, a DC motor, motor drives, an ARS sensor considering economical use in industrial field. Three experiments are performed to verify the feasibility and stability of the electric wheelbarrow.

• The Journal of Korean Academy of Sensory Integration
• /
• v.19 no.1
• /
• pp.24-38
• /
• 2021

Objective : This study aimed to create a Korea translation of the Evaluation in Ayres Sensory Integration (EASI) and to then test the adapted version for construct validity. Methods : The translation and content validation process were conducted in accordance with a four-step process, namely translation, integration, content validity examination, and backward translation. The construct validity of the translated version was evaluated using the EASI for children aged 3~12 years with and without sensory integration problems, comparing the two groups as well as preschool and school-aged groups. The group comparison was analyzed using the Mann-Whitney U test in SPSS. Results : In terms of content validity, all 20 items averaged more than 3.17 points. Of the four EASI categories, there was a difference in Sensory Perception (p=0.044) between the typical and sensory integration groups, and there was a statistical difference between tactile and vestibular sensations. Between the preschool and school-aged children, statistical difference was observed in two categories, namely Praxis and Ocular-Postural-Bilateral Motor Integration. Conclusion : Based on its construct validity, the Korean version of EASI is suitable for use in research. The construct validity study highlighted items that explain differences between typical and diagnostic children and items that explain those differences by age. Our findings could therefore be considered when interpreting EASI results.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.3
• /
• pp.537-542
• /
• 2022

There is a limit to the current indoor air quality (IAQ) monitoring method using fixed sensors and devices. A mobile robot for IAQ monitoring was developed by mounting IAQ monitoring sensors on a small multi-legged robot to minimize vibration and protect the sensors from vibration while robot moves. The developed mobile robot used a simple gait mechanism to enable the robot to move forward, backward, and turns only with the combination of forward and reverse rotation of the two DC motors. Due to the simple gait mechanism, not only IAQ data measurements but also gait motion control were processed using a single Arduino board. Because the mobile robot has small number of electronic components and low power consumption, a relatively low-capacity battery was mounted on the robot to reduce the weight of the battery. The weight of mobile robot is 1.4kg including links, various IAQ sensors, motors, and battery. The gait and turning speed of the mobile robot was measured at 3.75 cm/sec and 14.13 rad/sec. The maximum height where the robot leg could reach was 33 mm, but the mobile robot was able to overcome the bumps up to 24 mm.