• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.3
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• pp.193-198
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• 2013

In general, boron recovery of 40-90% could be achieved by Reverse Osmosis (RO) membranes in neutral pH condition. As an emerging technology, Forward Osmosis (FO) membrane has attracted growing interest in wastewater treatment and desalination. The objective of this study is to evaluate the possibility of the boron removal in radioactive liquid waste by FO. In this study, the performance of FO was investigated to remove boron in the simulated liquid waste as the factors such as pH, osmotic pressure, ionic strength of solution, etc. The pH of feed solution is a major operating parameter which strongly influences to the permeation of boron and more than 80% of boron content can be separated when conducted at pH values less than 7. The water flux is not influenced but the boron flux and permeation rate tends to decrease in the low salt concentration of 1,000 mg/L. The boron flux increases linearly, but the permeation ratio of reducing boron is nearly constant even with changes in the draw solution concentration.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1786-1795
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• 2011

The trajectory control for omni-directional mobile robot is not easy. Especially, the tracking control which system uncertainty problem is included is much more difficult. This paper develops trajectory controller of 3-wheels omni-directional mobile robot using fuzzy multi-layered algorithm. The fuzzy control method is able to solve the problems of classical adaptive controller and conventional fuzzy adaptive controllers. It explains the architecture of a fuzzy adaptive controller using the robust property of a fuzzy controller. The basic idea of new adaptive control scheme is that an adaptive controller can be constructed with parallel combination of robust controllers. This new adaptive controller uses a fuzzy multi-layered architecture which has several independent fuzzy controllers in parallel, each with different robust stability area. Out of several independent fuzzy controllers, the most suited one is selected by a system identifier which observes variations in the controlled system parameter. This paper proposes a design procedure which can be carried out mathematically and systematically from the model of a controlled system; related mathematical theorems and their proofs are also given. Finally, the good performance of the developed mobile robot is confirmed through live tests of path control task.

• Journal of KIISE:Software and Applications
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• v.32 no.7
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• pp.663-673
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• 2005

An analysis model for the dynamics information of two-dimensional time-series patterns is described. In the proposed model, two novel transforms that visualize the dynamic characteristics are proposed. The first transform, referred to as speed equalization, reproduces a time-series pattern assuming a constant linear velocity to effectively model the temporal characteristics of the signing process. The second transform, referred to as velocity transform, maps the signal onto a horizontal vs. vertical velocity plane where the variation oi the velocities over time is represented as a visible shape. With the transforms, the dynamic characteristics in the original signing process are reflected in the shape of the transformed patterns. An analysis in the context of these shapes then naturally results in an effective analysis of the dynamic characteristics. The proposed transform technique is applied to an online signature verification problem for evaluation. Experimenting on a large signature database, the performance evaluated in EER(Equal Error Rate) was improved to 1.17$\%$ compared to 1.93$\%$ of the traditional signature verification algorithm in which no transformed patterns are utilized. In the case of skilled forgery experiments, the improvement was more outstanding; it was demonstrated that the parameter set extracted from the transformed patterns was more discriminative in rejecting forgeries

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.574-583
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• 2021

Predicting shipping markets is an important issue. Such predictions form the basis for decisions on investment methods, fleet formation methods, freight rates, etc., which greatly affect the profits and survival of a company. To this end, in this study, we propose a shipping freight rate prediction model for container ships using gated recurrent units (GRUs) and long short-term memory structure. The target of our freight rate prediction is the China Container Freight Index (CCFI), and CCFI data from March 2003 to May 2020 were used for training. The CCFI after June 2020 was first predicted according to each model and then compared and analyzed with the actual CCFI. For the experimental model, a total of six models were designed according to the hyperparameter settings. Additionally, the ARIMA model was included in the experiment for performance comparison with the traditional analysis method. The optimal model was selected based on two evaluation methods. The first evaluation method selects the model with the smallest average value of the root mean square error (RMSE) obtained by repeating each model 10 times. The second method selects the model with the lowest RMSE in all experiments. The experimental results revealed not only the improved accuracy of the deep learning model compared to the traditional time series prediction model, ARIMA, but also the contribution in enhancing the risk management ability of freight fluctuations through deep learning models. On the contrary, in the event of sudden changes in freight owing to the effects of external factors such as the Covid-19 pandemic, the accuracy of the forecasting model reduced. The GRU1 model recorded the lowest RMSE (69.55, 49.35) in both evaluation methods, and it was selected as the optimal model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.181-189
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• 2019

In this study, a triple-band antenna that can be used in WLAN(Wireless Local Area Network) at 2.4 GHz, 5.8 GHz, and 5G at 3.5 GHz is fabricated. The proposed antenna uses a parasitic element to show the triple band, and the reflector is used at a distance of ${\lambda}/4$ from the antenna to reduce the Specific Absorption Rate(SAR). Its dimensions are $100{\times}75{\times}1.6mm^3$ and each parameter value is optimized for better performance and a lower SAR value. As a result, we obtained a bandwidth of 540 MHz(2.02~2.56 GHz), 390 MHz(3.39~3.78 GHz), and 1,210 MHz(5.56~6.77 GHz) based on the reflection loss factor of -10 dB. In addition, the SAR values of the antenna with reflector are observed to reduce below the SAR value of international standard.

• Korean Journal of Clinical Laboratory Science
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• v.50 no.4
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• pp.399-405
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• 2018

The platelet count in clinical laboratories is essential for the diagnosis and treatment of hemostasis abnormalities, and accurate platelet counting in the low count range is of prime importance for deciding if a platelet transfusion is needed and for monitoring after chemotherapy. Quality control is designed to reduce and correct any deficiencies in the internal analytical process of a clinical laboratory prior to the release of patient results. Fragmented erythrocytes are the major confusing factors for platelet counting because of their similar size to platelets. The authors found that the low range QC values were out of 2SD with a Sysmex automatic analyzer in internal quality control process. Thus far, there has been little discussion on the relationship between hemolysis and the platelet parameters. Therefore, this study focused on the performance of automated platelet counts, including the PLT-F, the PLT-I, and PLT-O methods at the low platelet range using the low level QC materials and compared the 5 platelet parameters with the hemolyzed samples. The results showed that the CV was the smallest with PLT-F and P-LCR increased from 18.4 to 31.9% in the hemolysis samples. These results indicate that a more accurate estimation of the platelet counts can be achieved using the PLT-F method than the PLT-I method at the low platelet range. The use of the PLT-F system improves the confidence of results in low platelets samples in a routine hematology laboratory. The results suggest that P-LCR is a new parameter in assessing samples when the specimen is suspected of hemolysis and deterioration. Nevertheless, further studies will be needed to establish the relationship with P-LCR and hemolysis using human blood specimens.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.343-348
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• 2019

In this paper, a dual-band antenna is proposed for the autonomous vehicle as well as omni-directional. The proposed antenna operates in the 4G/LTE band (1,710~2,170MHz) and 5G/NR band (3,400~3,700MHz). In order to obtain the dual-band operation, the planar monopole antenna is proposed as the novel structure with single port of the 50ohm. To give the properties of dual-band, an additional antenna element with slit was added to the planar monopole antenna, and then a structural adjustment parameter was optimized for achieving the target performance in bands. The planar monopole antenna in the LTE band acts as the coupled feed for the added parasitic radiator in the 5G NR band. The proposed antenna has $38.5{\times}36.0{\times}1.0[mm^3]$ on a ground with diameter of 96mm. From the fabrication and measurement results, the impedance bandwidth (VSWR<2) of the proposed antenna covers 1,480~2,260MHz (LTE band: 1,710~2,170MHz) and 3,310~3,930MHz (5G NR band: 3,400~3,700MHz). The proposed planar monopole antenna also obtained the measured gain and radiation pattern of omni-directional radiation pattern in the anechoic chamber.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.1
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• pp.29-33
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• 2019

With shrinking form factor and improving performance of electronic packages, high input/output (I/O) density is considered as an important factor. Fan out wafer-level packaging (FO-WLP) has been paid great attention as an alternative. However, FO-WLP is vulnerable to warpage during its manufacturing process. Minimizing warpage is essential for controlling production yield, and in turn, package reliability. While many studies investigated the effect of process and design parameters on warpage using finite element analysis, they did not take uncertainty into consideration. As parameters, including material properties, chip positions, have uncertainty from the point of manufacturing view, the uncertainty should be considered to reduce the gap between the results from the field and the finite element analysis. This paper focuses on the effect of uncertainty of Young's modulus of chip on fan-out wafer level packaging warpage using finite element analysis. It is assumed that Young's modulus of each chip follows the normal distribution. Simulation results show that the uncertainty of Young's modulus affects the maximum von Mises stress. As a result, it is necessary to control the uncertainty of Young's modulus of silicon chip since the maximum von Mises stress is a parameter related to the package reliability.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.543-551
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• 2020

In this paper, we introduce a method to improve the accuracy of the length estimation of targets using a radar. The HRRP (High Resolution Range Profile) obtained from a received radar signal represents the one-dimensional scattering characteristics of a target, and peaks of the HRRP means the scattering centers that strongly scatter electromagnetic waves. By using the extracted scattering centers, the downrange length of the target, which is the length in the RLOS (Radar Line of Sight), can be estimated, and the real length of the target should be estimated considering the angle between the target and the RLOS. In order to improve the accuracy of the length estimation, parametric estimation methods, which extract scattering centers more exactly than the method using the HRRP, can be used. The parametric estimation method is applied after the number of scattering centers is determined, and is thus greatly affected by the accuracy of the number of scattering centers. In this paper, in order to improve the accuracy of target length estimation, the number of scattering centers is estimated by using AIC (Akaike Information Criteria), MDL (Minimum Descriptive Length), and GLE (Gerschgorin Likelihood Estimators), which are the source number estimation methods based on information theoretic criteria. Using the ESPRIT algorithm as a parameter estimation method, a length estimation simulation was performed for simple target CAD models, and the GLE method represented excellent performance in estimating the number of scattering centers and estimating the target length.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.42-48
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• 2021

Zn and Al added LiNi0.85Co0.15O2 cathode materials were synthesized to improve electrochemical properties and thermal stability using a solid-state route. Crystal structure, particle size and surface shape of the synthesized cathode materials was measured using XRD (X-ray diffraction) and SEM (scanning electron microscopy). CV (cyclic voltammetry), first charge-discharge profiles, rate capability, and cycle life were measured using battery cycler (Maccor, series 4000). Strong binding energy of Al-O bond enhanced structure stability of cathode material. Electrochemical properties were improved by preventing cation mixing between Li+ and Ni2+. Large ion radius of Zn+ increased lattice parameter of NC cathode material, which meant unit-cell volume was expanded. NCZA25 showed 80% of capacity retention at 0.5 C-rate during 100 cycles, which was 12% higher than that of NC cathode. The discharge capacity of NCZA25 showed 104 mAh/g at 5 C-rate. NCZA25 achieved 36 mAh/g more capacity than that of NC cathod. NCZA25 cathode material showed excellent rate capability and cycling performance.