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In this study, we propose an explicit adaptive finite difference method (FDM) for the Cahn-Hilliard (CH) equation which describes the process of phase separation. The CH equation has been successfully utilized to model and simulate diverse field applications such as complex interfacial fluid flows and materials science. To numerically solve the CH equation fast and efficiently, we use the FDM and time-adaptive narrow-band domain. For the adaptive grid, we define a narrow-band domain including the interfacial transition layer of the phase field based on an undivided finite difference and solve the numerical scheme on the narrow-band domain. The proposed numerical scheme is based on an alternating direction explicit (ADE) method. To make the scheme conservative, we apply a mass correction algorithm after each temporal iteration step. To demonstrate the superior performance of the proposed adaptive FDM for the CH equation, we present two- and three-dimensional numerical experiments and compare them with those of other previous methods.

In this paper, we present a detailed derivation and numerical investigation of an indicator function for front-tracking methods. We use the discrete Dirac delta function to construct an indicator function from a set of Lagrangian points and solve the resulting discrete Poisson equation with the zero Dirichlet boundary condition using an iterative method. We present several computational tests to investigate the effect of parameters such as distance between points, uniformity of the distance, and types of the Dirac delta functions on the indicator function.

In this article, we present a Monte Carlo simulation (MCS) to estimate the total cost required to control the spread of the COVID-19 pandemic by financial incentives. One of the greatest difficulties in controlling the spread of the COVID-19 pandemic is that most infected people are not identified and can transmit the virus to other people. Therefore, there is an urgent need to rapidly identify and isolate the infected people to avoid the further spread of COVID-19. To achieve this, we can consider providing a financial incentive for the people who voluntarily take the COVID-19 test and test positive. To prevent the abuse of the financial incentive policy, several conditions should be satisfied to receive the incentive. For example, an incentive is offered only if the recipients know who infected them. Based on the data obtained from epidemiological investigations, we calculated an estimated total cost of financial incentives for the policy by generating various possible infection routes using the estimated parameters and MCS. These results would help public health policymakers implement the proposed method to prevent the spread of the COVID-19 pandemic. In addition, the incentive policy can support various preparations such as hospital bed preparation, vaccine development, and so forth.

In this study, we propose a time-dependent susceptible-unidentified infected-confirmed (tSUC) epidemic mathematical model for the COVID-19 pandemic, which has a time-dependent transmission parameter. Using the tSUC model with real confirmed data, we can estimate the number of unidentified infected cases. We can perform a long-time epidemic analysis from the beginning to the current pandemic of COVID-19 using the time-dependent parameter. To verify the performance of the proposed model, we present several numerical experiments. The computational test results confirm the usefulness of the proposed model in the analysis of the COVID-19 pandemic.

In this study, we present an unconditionally stable positivity-preserving numerical method for the Fisher–Kolmogorov–Petrovsky–Piskunov (Fisher–KPP) equation in the one-dimensional space. The Fisher–KPP equation is a reaction-diffusion system that can be used to model population growth and wave propagation. The proposed method is based on the operator splitting method and an interpolation method. We perform several characteristic numerical experiments. The computational results demonstrate the unconditional stability, boundedness, and positivity-preserving properties of the proposed scheme.

In this study, we consider a robust optimal parameter estimation method for the Susceptible-Unidentified infected-Confirmed (SUC) epidemic dynamics model. One of the problems in determining parameter values associated with epidemic mathematical models is that the optimal parameter values are very sensitive to the initial guess of parameter values. To resolve this problem, we fix the value of one parameter and solve an optimization problem of finding the other parameter values which best fit the confirmed population. The fixed parameter value can be obtained using data from epidemiological surveillance systems. To demonstrate the robustness and accuracy of the proposed method, we perform various numerical experiments with synthetic and real-world data from South Korea, the United States of America, India, and Brazil. The computational results confirm the potential practical application of the proposed method.

This study demonstrates the characteristics of a hybrid-type transparent electrode for touch screen panels, which was fabricated by coating carbon nanotubes (CNTs) via electrophoretic deposition (EPD) on copper (Cu)-meshes. The surface morphologies, visible-range transmittance and reflectance, and chromatic properties, such as yellowness and redness, of the fabricated CNTs-coated Cu mesh electrodes were characterized as functions of their dimensions (line-to-line spacing, line width, and electrode thickness) and compared with those of the Cu-mesh electrodes without coating of CNTs. The experimental results showed that the coating of CNTs substantially reduced the reflectance of the Cu-mesh electrodes and also improved their chromatic properties with their transmittance and sheet resistance only slightly changed, subsequently indicating that the CNTs-coated Cu-mesh electrodes possessed desirable characteristics for touch screen panels.

This study demonstrates hybrid-type transparent electrodes for touch screen panels. The hybrid-type electrodes were fabricated by coating silver (Ag) meshes with carbon nanotubes (CNTs). Thin Ag films were deposited on glass substrates using the sputtering method, and were then patterned via photolithography to obtain mesh structures with a 10 μm line width and 300 μm line-to-line spacing. The Ag meshes were coated with CNTs using two different methods: spray coating and electrophoretic deposition (EPD). For the samples of Ag meshes with no CNT coating as well as of CNT-coated Ag meshes, the visible-range transmittance and reflectance as well as the surface morphology were characterized and compared. The change in sheet resistance due to long-term exposure to air with an 85 °C temperature and 85% humidity was also measured. The experimental results indicated that the reflectance of the Ag mesh electrodes was substantially reduced by the CNT coating. Especially, the Ag mesh electrodes with EPD-coated CNTs showed excellent properties, such as higher than 80% transmittance, lower than 8% reflectance, and better stability.

This study presents a flexible recession forecast model where predictive variables and model coefficients can vary over time. In an application to US recession forecasting using pseudo real-time data, we find that time-varying logit models lead to large improvements in forecast performance, beating the individual best predictors as well as other popular alternative methods. Through these results, we also demonstrate the following features of the forecast models: (i) substituting roles between the two key features of predictor switching and coefficient change, (ii) considerable variations in the model size (i.e., the number of predictors used) over time, and (iii) substantial changes in the role/importance of major individual predictors over business cycles.

Hybrid-type transparent conductive electrodes (TCEs) were fabricated by coating copper (Cu) meshes with carbon nanotube (CNT) via electrophoretic deposition, and with nickel (Ni) via electroplating. For the fabricated electrodes, the effects of the coating with CNT and Ni on their transmittance and reflectance in the visible-light range, electrical sheet resistance, and chromatic parameters (e.g., redness and yellowness) were characterized. Also, an oxidation stability test was performed by exposing the electrodes to air for 20 d at 85 °C and 85% temperature and humidity conditions, respectively. It was discovered that the CNT coating considerably reduced the reflectance of the Cu meshes, and that the Ni coating effectively protected the Cu meshes against oxidation. Furthermore, after the coating with CNT, both the redness and yellowness of the Cu mesh regardless of the Ni coating approached almost zero, indicating a natural color. The experiment results confirmed that the hybrid-type Cu meshes with combined Ni-CNT coating improved characteristics in terms of reflectance, sheet resistance, oxidation stability, and color, superior to those of the primitive Cu mesh, and also simultaneously satisfied most of the requirements for TCEs.

This study attempted to investigate the characteristics of Phonation Threshold Pressure and Phonation Threshold Airflow of Patients who have Functional voice disorder. 50 subjects participated in study (32 subjects were patients who had functional voice disorders and 20 subjects were normal adults). The PAS (Phonatory aerodynamic system, model 6600, KAY electronics, Inc.) was used to measure the data and to do the analysis. Data from the Phonation Threshold Pressure was measured using voicing efficiency of the PAS protocol. Data from the Phonation Threshold Airflow was measured using Maximum Sustained Phonation of the PAS protocol. Those were used because of the ease of phonation. The results of this study showed that the differences in Phonation Threshold Pressure and Phonation Threshold Airflow between patients who had functional voice disorder and normal adults could be significant index. Patients who had functional voice disorder showed more higher figures than normal adults. These results suggest that Phonation Threshold Pressure and Phonation Threshold Airflow are very useful in diagnosing the voice disorder. The measured data also provided useful information for diagnosing patients with vocal fold diseases.

This study compared the aerodynamic multiparameters of whispers and phonation in patients with muscle misuse dysphonia(MMD) to evaluate the voice aerodynamic analysis for discrimination between whispers and phonation. Eleven patients with muscle misuse dysphonia were examined. Whispers were shorter with a maximum phonation time(MPT; p.05). The ROC analysis showed that the threshold of 23.83 ppm for PE achieved a good classification for whispers, with the perfect sensitivity(100%) and specificity(100%). Those results indicate PE reliably distinguished between whispers and phonation. The results also suggest that PE may provide a useful tool for studying the laryngeal source.

This paper decomposes and estimates trend/cyclical components of some key macro variables?GDP, inflation, and interest rate, using a simple DSGE model along with flexible trend specification. The extracted cyclical components of output and interest rate are similar to HP-filtered counterparts, despite some differences in persistence and volatility, while inflation resembles that from BK filtering. This implies that the usual practice of applying a single filtering method to the data of interest may be problematic. When the baseline model is extended to incorporate consumption habit and price indexation, habit turns out to be important in explaining the persistence of business cycles. Comparison of several alternative models shows that the usual practice of estimation of DSGE model using filtered data leads to biased results. Finally, various sensitivity analyses illustrate that (1) allowing for correlation between structural cyclical shocks and trend shocks and (2) including irregular components (in inflation rate) may deliver interesting/important implication for gap estimates.

In this study, the effects of coating with nano-structured carbon materials, such as carbon nanotube (CNT) and graphene, on the characteristics of transparent conductive electrodes based on copper (Cu) meshes, particularly on the visibility related to their color properties, were examined. The electrical sheet resistance of the Cu meshes remained almost unchanged regardless of the coating with CNT and graphene. Through the electrophoretic deposition method, the CNT and graphene layers were selectively used to coat only the regions where Cu mesh patterns had been formed, which helped minimize the transmittance loss caused by the coating with CNT and graphene. The reflectance of the Cu mesh was substantially reduced by the coating with CNT and graphene, meaning that the CNT or graphene coating layer played the role of suppressing the visible light reflected from the Cu mesh. In addition, the reflectance reduction effect was greater when the Cu mesh was coated with CNT rather than with graphene, which was at...