• Journal of the Korea Computer Graphics Society
• /
• v.27 no.5
• /
• pp.63-71
• /
• 2021

Among drone autonomous flight technologies, obstacle avoidance is a very important technology that can prevent damage to drones or surrounding environments and prevent danger. Although the LiDAR sensor-based obstacle avoidance method shows relatively high accuracy and is widely used in recent studies, it has disadvantages of high unit price and limited processing capacity for visual information. Therefore, this paper proposes an obstacle avoidance algorithm for drones using camera-based PPO(Proximal Policy Optimization) reinforcement learning, which is relatively inexpensive and highly scalable using visual information. Drone, obstacles, target points, etc. are randomly located in a learning environment in the three-dimensional space, stereo images are obtained using a Unity camera, and then YOLov4Tiny object detection is performed. Next, the distance between the drone and the detected object is measured through triangulation of the stereo camera. Based on this distance, the presence or absence of obstacles is determined. Penalties are set if they are obstacles and rewards are given if they are target points. The experimennt of this method shows that a camera-based obstacle avoidance algorithm can be a sufficiently similar level of accuracy and average target point arrival time compared to a LiDAR-based obstacle avoidance algorithm, so it is highly likely to be used.

• The Journal of the Korea Contents Association
• /
• v.22 no.6
• /
• pp.69-77
• /
• 2022

Physical experiment through MBL has been used in many schools for a long time since students can check the experiment results immediately and conduct the experiment easily. However, conducting the experiment, not knowing the principle of the device or simply concentrating on the derived data has been raised as the problem of MBL experiment. To supplement this problem, this study measured the acceleration of gravity with the picket fence method, which is often used in MBL experiment, utilizing Arduino, calculated the error rate through a comparison to the actual acceleration of gravity and discussed the educational application of the experiment to measure it. As a result of the experiment, the error rate between the acceleration of gravity calculated by the experiment and the actual acceleration of gravity was about 1%, so it turned out that relatively accurate measurements were possible. Also, the sample mean of the experimental value was included in the confidence interval of 95%, so it could be concluded that it was a significant experiment. In addition, this study showed the possibility of the educational application of the experiment to measure it through the following: It can supplement the structural disadvantages of MBL; it can consider the interaction between Physics and Math; it is possible to converge with information course in STEAM education; and it is inexpensive to be equipped with the equipment. Hopefully, the physical experiment utilizing Arduino will further be revitalized in science gifted education based on this study.

• Korean Chemical Engineering Research
• /
• v.60 no.4
• /
• pp.473-477
• /
• 2022

In this study, candidate technologies for lithium recovery from the process waste liquid generated in the waste battery recycling process were reviewed, and technologies applicable to the process from the commercialization point of view were reviewed from a qualitative point of view. The evaporation method is difficult to apply because it requires a large-scale land and shows a low recovery rate due to the loss of Li during the concentration process. In the case of precipitation, a commercially available technology shows a high recovery rate due to the high Li/Na selectivity of phosphoric acid, but there are disadvantages in that the process is complicated due to the use of expensive phosphoric acid, requiring a recovery step, and continuous operation is impossible because solids are handled in the Li concentration process. In the case of solvent extraction, if we find an inexpensive extractant with high Li/Na selectivity, continuous operation is possible with the method used in extraction of other metals in the previous step, and when Li is concentrated, continuous operation is possible because it is in a liquid state. If it shows a similar recovery rate compared to precipitation technology, commercialization will be the most likely.

• Journal of the Korean Wood Science and Technology
• /
• v.32 no.2
• /
• pp.73-81
• /
• 2004

To develope of the inexpensive anti-stain chemicals, it was conducted to investigate the inhibitory effectiveness of mycelial growth and anti-mold effectiveness against test fungi causing surface mold of wood, iron corrosivity and hygroscopicity of six fluoride-based chemicals made from industrial by- product.Among the six chemicals. RNF-3 and RNF-4 were the most effective with respect to a mycelial growth control and anti-mold effectiveness. For the wood treatment with these chemicals, the optimum concentration was about 2% and there was no difference in the effectiveness of chemicals between wood species. The wood treated with synthesized chemicals showed a relatively high iron corrosion rate for corrosive F component whereas, in the treatment with RNF-3 and RNF-4, there was no difference from the untreated wood when the concentration was less than 2%. The hygroscopic property of wood was not effected by treatment of these chemicals. To prove the feasibility for practical using of RNF-3 and RNF-4 chemicals, it is necessary to test of anti-mold effectiveness in the sawmill by field test.

• Composites Research
• /
• v.35 no.6
• /
• pp.371-377
• /
• 2022

Triboelectric nanogenerator (TENG) devices have generated a lot of interest in recent decades. TENG technology, which is one of the technologies for harvesting mechanical energy among the energy wasted in the environment, is obtained by the dual effect of electrostatic induction and triboelectric charging. Recently, a multilayer thin film stacking method (or layer-by-layer (LbL) self-assembly technique) is being considered as a method to improve the performance of TENG and apply it to new fields. This LbL assembly technology can not only improve the performance of TENG and successfully overcome the thickness problem in applications, but also present an inexpensive, environmentally friendly process and be used for large-scale and mass production. In this review, recent studies in the accomplishment of LbL-based materials for TENG devices are reviewed, and the potential for energy harvesting devices reviewed so far is checked. The advantages of the TENG device fabricated by applying the LbL technology are discussed, and finally, the direction and perspective of this fabrication technology for the implementation of various ultra-thin TENGs are briefly presented.

• Wind and Structures
• /
• v.34 no.1
• /
• pp.127-136
• /
• 2022

In this work a multi-fidelity non-intrusive polynomial chaos (MF-NIPC) has been applied to a structural wind engineering problem in architectural design for the first time. In architectural design it is important to design structures that are safe in a range of wind directions and speeds. For this reason, the computational models used to design buildings and bridges must account for the uncertainties associated with the interaction between the structure and wind. In order to use the numerical simulations for the design, the numerical models must be validated by experi-mental data, and uncertainties contained in the experiments should also be taken into account. Uncertainty Quantifi-cation has been increasingly used for CFD simulations to consider such uncertainties. Typically, CFD simulations are computationally expensive, motivating the increased interest in multi-fidelity methods due to their ability to lev-erage limited data sets of high-fidelity data with evaluations of more computationally inexpensive models. Previous-ly, the multi-fidelity framework has been applied to CFD simulations for the purposes of optimization, rather than for the statistical assessment of candidate design. In this paper MF-NIPC method is applied to flow around a rectan-gular 5:1 cylinder, which has been thoroughly investigated for architectural design. The purpose of UQ is validation of numerical simulation results with experimental data, therefore the radius of curvature of the rectangular cylinder corners and the angle of attack are considered to be random variables, which are known to contain uncertainties when wind tunnel tests are carried out. Computational Fluid Dynamics (CFD) simulations are solved by a solver that employs the Finite Element Method (FEM) for two turbulence modeling approaches of the incompressible Navier-Stokes equations: Unsteady Reynolds Averaged Navier Stokes (URANS) and the Large Eddy simulation (LES). The results of the uncertainty analysis with CFD are compared to experimental data in terms of time-averaged pressure coefficients and bulk parameters. In addition, the accuracy and efficiency of the multi-fidelity framework is demonstrated through a comparison with the results of the high-fidelity model.

• Korean Chemical Engineering Research
• /
• v.61 no.2
• /
• pp.265-272
• /
• 2023

Lignocellulosic biomass is essential to pretreatment because of having rigid structures and a lot of lignin. Among methods of pretreatment, using THF solvents has the advantage of being easy to reuse. THF (Tetrahydrofuran) used as a co-solvent with water or ionic solvent that is inexpensive and can remove lignin over a wide range of reaction conditions. NaOH (Sodium hydroxide) has been demonstrated to preferentially solvate lignin from cellulose. Thus, NaOH was used as a pretreatment co-solvent for the fractionation of lignin by destroying the ether bond to amend for hydrolysis and expand the surface area of cellulose and hemicellulose. In this experiment, lignin was removed by the NaOH/THF co-solvent pretreatment process to characteristics for the pretreatment and obtain the optimal levulinic acid conversion yield through the acid catalyst conversion process. the NaOH/THF co-solvent system was conducted in various ratios of co-solvent under a total of 16 conditions. And the temperature was 180 ℃ during to 60 mins. The optimum condition of co-solvent is NaOH 5 wt%/THF 90:10(v/v%), 76.8% glucan content was obtained through this co-solvent pretreatment, and 90.1% lignin was removed. In the acid catalyst conversion process, which is a subsequent pretreatment process, the experiment was conducted under the conditions of 30 to 90 min of reaction time and 160 ℃ to 200 ℃ reaction temperature. The optimum condition of acid catalyst conversion process is 60min reaction time under of 180 ℃, and it obtained 84.7% of levulinic aicd conversion yield.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.2
• /
• pp.291-298
• /
• 2022

Recently developed drones are inexpensive and very convenient to operate. As a result, the production and utilization of spatial information using drones are increasing. However, most drones acquire images with a low-cost global navigation satellite system (GNSS) and an inertial measurement unit (IMU). Accordingly, the accuracy of the initial location and rotation angle elements of the image is low. In addition, because these drones are small and light, they can be greatly affected by wind, making it difficult to maintain a certain overlap, which degrades the positioning accuracy. Therefore, in this study, images are taken at different times in order to analyze the positioning accuracy according to changes in certain exterior orientation parameters. To do this, image processing was performed with Pix4D Mapper and the accuracy of the results was analyzed. In order to analyze the variation of the accuracy according to the exterior orientation parameters in detail, the exterior orientation parameters of the first processing result were used as meta-data for the second processing. Subsequently, the amount of change in the exterior orientation parameters was analyzed by in a strip-by-strip manner. As a result, it was proved that the changes of the Omega and Phi values among the rotation elements were related to a decrease in the height accuracy, while changes in Kappa were linked to the horizontal accuracy.

• Resources Recycling
• /
• v.32 no.3
• /
• pp.9-17
• /
• 2023

Efforts are currently underway to develop a method for efficiently recovering lithium from the cathode material of waste lithium iron phosphate batteries (LFP). The successful application of lithium battery recycling can address the regional ubiquity and price volatility of lithium resources, while also mitigating the environmental impact associated with both waste battery material and lithium production processes. The isomorphic substitution leaching process was used to recover lithium from spent lithium iron phosphate batteries. Lithium was leached by the isomorphic substitution of Fe²⁺ in LFP using a relatively inexpensive ferric chloride etching solution as a leaching agent. In the study, the leaching rate of lithium was compared using the ferric chloride etching solution at various multiples of the LFP molar ratio: 0.7, 1.0, 1.3, and 1.6 times. The highest lithium leaching rate was shown at about 98% when using 1.3 times the LFP molar ratio. Subsequently, to eliminate Fe, the leachate was treated with NaOH. The Fe-free solution was then used to synthesize lithium carbonate, and the harvested powder was characterized and validated. The surface shape and crystal phase were analyzed using SEM and XRD analysis, and impurities and purity were confirmed using ICP analysis.

• Journal of Practical Engineering Education
• /
• v.14 no.3
• /
• pp.593-600
• /
• 2022

Various sensors such as lidar, radar, and camera are fused and used in autonomous vehicles. Rider and radar sensors are difficult to popularize because they are expensive equipment. In order to popularize autonomous vehicles, research that can replace expensive equipment is continuously being conducted. In this paper, we use a single camera that is inexpensive and can be easily mounted. We propose a method for detecting the wheels and adjacent lanes of a front-side vehicle of a driving vehicle and estimating distances. Our proposed method detects lanes and wheels from frame images after frame extraction via input images. In addition, the distance is measured and compared with the actual distance measured in the actual road environment. The distance could be calculated relatively accurately within the error range of ± 3 cm. Through this, it is expected that the camera can be used as an alternative means when the cost of autonomous vehicles is reduced or when the lidar or radar sensor fails.