• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1138-1145
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• 2007

In wireless communications, chaotic communications have been a field of interest due to its low complexity in hardware implementation and low power consumption in chaotic signal generation. Among the modulation schemes using the chaotic signal, Differential Chaos Shift Keying (DCSK) is a robust non coherent technique. As in the conventional communication systems, chaos-based systems are required to provide reasonable bit error performance in the presence of a narrow-band signal coming from any other systems. The frequency band of this foreign narrow band signal may lie within the bandwidth of the chaos-based systems. This situation may occur when chaotic signal transmission is done in the presence of other conventional communication system. This paper has evaluated the performance of the non coherent differential chaos shift keying (DCSK) system under the presence of conventional non-chaotic transmit reference system. Both systems are assumed to have same data rates. The mathematical expressions for the bit error rate (BER) are derived with computer simulations to verify the analytical results.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.12
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• pp.63-73
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• 2021

This study investigates the key determinants of exchange rate (RER) misalignment for the period 1991 to 2020. The BEER technique has been used to estimate the degree of the equilibrium exchange rate. To explore the actual exchange rate misalignment and to assess the behavior of variables that are different in different regimes of undervaluation and overvaluation, the nonlinear technique of Markov regime-switching (MSM) was applied. The mean and variance of each regime are highly significant and show that undervaluation episodes have a low mean (116.139) and more volatility (1.229) while overvaluation episodes have a high mean (126.732) with less volatility (0.871). The findings show that MSM accurately identifies exchange rate misalignment in both regimes as separate incidents of overvaluation and undervaluation. Results further depict that misalignment of the RER is affected by terms of trade, net foreign assets, interest differential, government investment, and consumption decision. Results recommend that if policymakers want to use the exchange rate as a policy tool, they must first consider the drivers of the equilibrium exchange rate. As a result, any deliberate actions to address exchange rate misalignment must focus on the underlying fundamentals that drive the exchange rate.

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.28-33
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• 2021

With the recent growing interest in eco-friendly cars, as interest in eco-friendly cars increases, interest and purchase of hydrogen fuel cell vehicles that do not emit pollutants are increasing. Recently, the government is supporting the expansion of hydrogen charging station and localization of core parts according to the government's hydrogen energy dissemination policy. In this study, the flow characteristics of the hydrogen flow control valve were investigated. As the differential pressure increases, the mass flow rate and flow coefficient tend to be different from the volume flow rate. And it was confirmed that it affects the hydrogen temperature due to the nozzle effect in the bottleneck section, and the change in density affects the mass flow rate.

• The KIPS Transactions:PartC
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• v.10C no.3
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• pp.305-310
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• 2003

The performance of various GFR implementations has been recently studied due to the interest to provide bandwidth guarantees with a simpler implementation than ABR in ATM networks. One of the important factors is buffer management for guaranteeing QoS in GFR service. An efficient buffer management algorithm is necessary to guarantee MCR for untagged cell in ATM switch. In this paper, we propose and evaluate a buffer management scheme to provide the GFR service guarantees. The proposed scheme can control the cell discarding for fairness in each VC, and compared with Double-EPD and DFBA. Our results show that the proposed buffer management with per-VC queuing achieves significant enhancement on goodputs and fairness index than those of existing methods.

• Journal of Mechanical Science and Technology
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• v.16 no.12
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• pp.1719-1724
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• 2002

A previously designed capillary viscometer with measuring differential pressure was modified to measure the viscosity of non-Newtonian fluids including unadulterated blood continuously over numerous shear rates in a single measurement. Because of unavoidable experimental noise and a limited number of data, the previous capillary viscometer experienced an inaccuracy and could not directly determine a viscosity without an iterative calculation. However, in the present measurement there are numerous data available near the point of interest so that the numeric value of the derivative, d(In Q)/d(In Q$\sub$w/), is no longer sensitive to the method of differentiation. In addition, relatively low and wide shear rate viscosity measurements were possible because of the present precision pressure-scanning method with respect to time. For aqueous polymer solutions, excellent agreement was found between the results from the pressure-scanning capillary viscometer and those from a commercially available rotating viscometer. In addition, the pressure-scanning capillary viscometer measured the viscosity of unadulterated whole blood without adding any anticoagulants.

• Journal of Digestive Cancer Research
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• v.12 no.1
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• pp.31-37
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• 2024

Pancreatic cancer is a highly fatal malignancy with a 5-year survival rate of < 10%. Endoscopic ultrasound (EUS) is a useful noninvasive tool for differential diagnosis of pancreatic malignancy and treatment decision-making. However, the performance of EUS is suboptimal, and its accuracy for differentiating pancreatic malignancy has increased interest in the application of artificial intelligence (AI). Recent studies have reported that EUS-based AI models can facilitate early and more accurate diagnosis than other preexisting methods. This article provides a review of the literature on EUS-based AI studies of pancreatic malignancies.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.441-445
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• 2005

In the resent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. But, no detailed researches between the thermo-dynamic property in Nitinol alloy have been done yet. In this study, the thermal property of high temperature Nitinol shape memory alloy were evaluated using differential scanning calorimeter(DSC). The structure property was investigated using X-ray diffraction(XRD). A dynamic mechanical analyzer(DMA) with three point bending mode was used to study storage and loss modulus of shape memory alloy according to the thirteen frequencies in the temperature range between 30 and $200^{\circ}C$. The effects of the temperature heating/cooling rate, the frequency on the damping capacity have been systematically investigated. Such a frequency and temperature changes also influenced significantly to the damping behavior of the shape memory alloy. It was also found that Nitinol exhibited high damping capacity during phase transformation.

• Journal of Wetlands Research
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• v.15 no.2
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• pp.179-189
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• 2013

The Haean basin is a unique geographical feature formed by differential erosion and it borders the military demarcation line. Recently the basin has become an interest of civilians due to security tour, highland vegetables and wetland. After the civil war, the population decreased but it has increased since 2007. The annual mean air temperature in the basin has increased with a rate of $+0.016^{\circ}C/yr$ and the annual precipitation also has increased with a rate of +10.41 mm/yr. The precipitation occurring in June~August (wet season) occupied most of the total precipitation increase. In addition, recently the number of groundwater wells and its use have gradually increased and most of them are for agriculture including cultivation of rice and highland vegetables. If the air temperature further increases in the future according to the climate change scenarios, the highland vegetables cultivation will be difficult. Furthermore, if the rainstorm in the summer will be enforced, the groundwater recharge and water management will be aggravated. Therefore, an evaluation for sustainable groundwater development in the basin and a reform of the current agriculture (change of cultivating crops) depending on much water are essentially required.

• Journal of the Korean Electrochemical Society
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• v.27 no.1
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• pp.15-31
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• 2024

The antimalarial drug hydroxychloroquine sulphate (HCQ) has taken much attention during the first COVID-19 pandemic phase for the treatment of severe acute respiratory infection (SARI) patients. Hence it is interest to study the electrochemical properties and photocatalytic degradation of the HCQ drug. Copper oxide (CuO) nanoparticles, graphene oxide (GO) and CuO/GO NC (nanocomposite) modified carbon paste electrodes (MCPE) are used for the detection of HCQ in an aqueous medium. Electrochemical behaviour of HCQ (20 μM) was observed using CuO/MCPE, GO/MCPE and CuO/GO NC/MCPE in 0.1 M phosphate buffer at pH 7 with a scan rate of 20 to 120 mV s^-1 by cyclic voltammetry (CV). Differential pulse voltammetry (DPV) of HCQ was performed for 0.6 to 16 μM HCQ. The CuO/GO NC/MCPE showed a reasonably good sensitivity of 0.33 to 0.44 μA μM cm^-2 with LOD of 69 to 92 nM for HCQ. Furthermore, the CuO/GO NC was used as a catalyst for the photodegradation of HCQ by monitoring its UV-Vis absorption spectra. About 98% was degraded in about 34 min under visible light and after 4 cycles it was 87%. The improved photocatalytic activity may be attributed to decrease in bandgap energy and enhanced ability for the electrons to migrate. Thus, CuO/GO NC showed good results for both sensing and degradation applications as well as reproducibility.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.12
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• pp.746-755
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• 2014

Compressive sensing (CS) has drawn much interest as a new sampling technique that enables signals to be sampled at a much lower than the Nyquist rate. By noting that the block-based compressive sensing can still keep spatial correlation in measurement domain, in this paper, we propose a novel encoding technique for measurement data obtained in the block-based CS of natural image. We apply discrete wavelet transform (DWT) to decorrelate CS measurements and then assign a proper quantization scheme to those DWT coefficients. Thus, redundancy of CS measurements and bitrate of system are reduced remarkably. Experimental results show improvements in rate-distortion performance by the proposed method against two existing methods of scalar quantization (SQ) and differential pulse-code modulation (DPCM). In the best case, the proposed method gains up to 4 dB, 0.9 dB, and 2.5 dB compared with the Block-based CS-Smoothed Projected Landweber plus SQ, Block-based CS-Smoothed Projected Landweber plus DPCM, and Multihypothesis Block-based CS-Smoothed Projected Landweber plus DPCM, respectively.