Almost periodic solutions of periodic linear partial functional differential equations

We study conditions for the abstract periodic linear functional differential equation $\dot{x}=Ax+F(t)x_t+f(t)$ to have almost periodic with the same structure of frequencies as $f$. The main conditions are stated in terms of the spectrum of the monodromy operator associated with the equation and the frequencies of the forcing term $f$. The obtained results extend recent results on the subject. A discussion on how the results could be extended to the case when $A$ depends on $t$ is given.Comment: 17 page

Exploring Dynamic Delegated Corridors and 4D Required Navigation Performance Trajectory to Enable UAM Aircraft to Integrate into the Existing Airspace System

Increased traffic congestion on urban road networks has impacted the travel time for commuters in highly populated urban centers. Urban Air Mobility (UAM) is recognized as a system that transports the passenger and air cargo from any location to any destination within a metropolitan area. UAM may offer a solution to the problematic issue of automobile urban surface transportation congestion. However, the predicted significant growth in the demand for integration of UAM operations into the existing airspace system in the next 20 years and beyond may exceed the capacity of current air traffic control (ATC) system resources, particularly the ATC workload. Many organizations in the aviation industry, academia, and government have conducted extensive studies on the issue of UAM airspace integration. Many of these proposed solutions involve high-level frameworks for managing UAM operations. In this paper, we describe the combination of the Dynamic Delegated Corridors (DDCs) and full four-dimensional (4D) Required Navigation Performance (RNP) trajectories to enable UAM aircraft to integrate into the existing airspace system. Experiments were conducted to measure and compare the ATC workload before and after the installation of DDCs and 4D RNP trajectories in the terminal control area (TCA) of an airport. This new approach is expected to help reduce the workload of ATC dramatically and contribute to the viability of UAM airspace integration into the existing airspace system to operate at low altitudes in the terminal controlled airspace together with other airspace users safely and efficiently

Dynamic Delegated Corridors and 4D Required Navigation Performance for Urban Air Mobility (UAM) Airspace Integration

Increased traffic congestion on urban road networks has impacted the travel time for commuters in highly populated urban centers. Urban Air Mobility (UAM) is recognized as a system that transports the passenger and air cargo from any location to any destination within a metropolitan area. UAM may offer a solution to the problematic issue of automobile urban surface transportation congestion. However, the predicted significant growth in the demand for integration of UAM operations into the existing airspace system in the next 20 years and beyond may exceed the capacity of current air traffic control (ATC) system resources, particularly the ATC workload. Many organizations in the aviation industry, academia, and government have conducted extensive studies on the issue of UAM airspace integration. Many of these proposed solutions involve high-level frameworks for managing UAM operations. In this paper, the combination of the Dynamic Delegated Corridors (DDCs) and full four-dimensional (4D) Required Navigation Performance (RNP) trajectories are proposed to enable UAM aircraft to integrate into the existing airspace system. Experiments will be conducted to measure and compare the ATC workload before and after the installation of DDCs and 4D RNP trajectories in the terminal control area (TCA) of an airport. The proposed approach in this paper is expected to help reduce the workload of ATC dramatically and contribute to the viability of UAM airspace integration into the existing airspace system to operate at low altitudes in the terminal controlled airspace together with other airspace users safely and efficiently

Ethical Issues of Vietnamese Auditors: Applying the Fraud Triangle Model

Purpose: The article analyzes the impact of the factors affecting the fraud of Vietnamese auditors applying the fraud triangle model, providing more empirical evidence on the factors affecting the fraud of the auditors. Vietnam.   Theoretical framework: This paper uses the the fraud triangle model.   Design/methodology/approach: Research method using questionnaire survey of managers and auditors of Vietnamese auditing firms, the survey results collected 250 questionnaires. After eliminating invalid questionnaires due to There are many blank cells, the author chooses to use 236 questionnaires. Quantitative research was carried out with SPSS 25 software.   Findings: Research results show that pressure perception factor has higher standardized Beta coefficient (0.390) than all other factors. The normalized Beta coefficients of the remaining factors are: Perception of opportunity (0.289), Rationalization (0.267)   Research, Practical   &   Social   implications: Based on the research results, the author has proposed recommendations to minimize the negative impact of these pressures in order to limit the occurrence of violations of professional ethics of Vietnamese auditors.   Originality/value:This study fills the gap in the Ethical issues of Vietnamese auditors: applying the fraud triangle model

Performance Evaluation of Pre-foamed Ultra-lightweight Composites Incorporating Various Proportions of Slag

This research examines the feasibility of using a mixture of cement, fly ash, ground granulated blast-furnace slag, and river sand to manufacture pre-foamed ultra-lightweight composite (PULC). Four PULC specimens were prepared with the substitution of cement by slag at 0, 10, 20, and 30 % by weight. The engineering properties of PULC samples were evaluated through the tests of compressive strength, dry density, water absorption, drying shrinkage, and thermal conductivity. Besides, numerical simulation of heat transfer through the PULC brick wall and the microstructure observation were performed. The performance of PULC mixtures incorporating slag showed higher effectiveness than merely used cement. The substitution of 20 % cement by slag resulted in the highest compressive strength as well as the lowest value of water absorption of the PULC samples. Also, the efficiency of the thermal conductivity was in inverse proportion with the density of PULC specimens and it was right for water absorption and drying shrinkage. Moreover, numerical simulations showed that the temperature distribution values in the wall made by PULC material were smaller than in the wall made by the normal clay brick in the same position. Besides, the microstructure analysis revealed that the existence of slag generated a more dense structure of PULC samples with the addition of calcium-silicate-hydrate (C-S-H) gel, especially for a mix containing 20 % slag. Thus, the results of this study further demonstrated that a 20 % slag was the optimal content for the good engineering properties of the PULC samples

An Early-age Evaluation of Thermal Cracking Index of Heavy Concrete Applying for Airport Pavement

Industrial waste management has been an integral part of many countries in the world, including in Vietnam. In which, bottom ash (BA) has been used as a pozzolanic additive in compositions of the heavy concrete applying for airport concrete pavement (ACP), which allows reducing the hydration heat, the cost, and the thermal cracking of the concrete during the construction process. The purpose of this study is to summarize the experimental laboratory results of the heavy concrete samples containing 35 % BA sourced from a thermal power plant in Vietnam. The mechanical and thermal properties of the heavy concrete samples were determined at different curing ages. Besides, the heat of cement hydration during the preparation of the heavy concrete in the laboratory was measured using a "TAM AIR" isothermal calorimeter. Moreover, the Midas civil computer software based on the finite element method was used to analyze the temperature field and thermal cracking index of the ACP at the early ages. As the results, the heavy concrete had the respective thermal conductivity and the average of specific heat of 1.1 W/(m.°C) and 878.35 J/(kg.°C). Moreover, the value of thermal cracking index indicates that no cracking occurred on the ACP at the early ages. Furthermore, the results of the present study can be considered as a useful reference source for future projects that are associated with the construction of the ACP

NONLINEAR CHARACTERISTICS OF SQUARE SOLID-CORE PHOTONIC CRYSTAL FIBERS WITH VARIOUS LATTICE PARAMETERS IN THE CLADDING

Nonlinear characteristics of fused silica, solid-core photonic crystal fibers (PCFs) with a square array of air holes are studied numerically. We present a novel design that emphasizes the difference in air hole diameters in the photonic cladding. These PCFs have the advantages of flat dispersion, high nonlinearity, and low attenuation. Based on simulation results, three optimal structures, denoted #F1, #F2, and #F3, having anomalous and all-normal dispersions in the near-infrared range are selected to investigate characteristic properties at the pump wavelength. Such PCFs open up many possibilities for nonlinear optical applications, especially supercontinuum generation

INFLUENCE OF STRUCTURAL PARAMETERS ON OPTICAL CHARACTERISTICS OF PHOTONIC CRYSTAL FIBERS WITH CIRCULAR LATTICE

We demonstrate in this study that near-zero, ultra-flattened chromatic dispersion can be achieved over a wide range of wavelengths in photonic crystal fibers (PCFs) by means of slight variations in the geometrical parameters of the cladding. To do that, a new solid-core circular PCF design with various air hole diameters and lattice constants is presented, and the design features are numerically analyzed in detail. After 40 simulations, we determined three structures that possess optimal dispersion with the following lattice constants (Ʌ) and filling factors for the first ring (d1/Ʌ): Ʌ = 0.8 µm, d1/Ʌ = 0.45 for #F1, Ʌ = 0.9 µm, d1/Ʌ = 0.45 for #F2, and Ʌ = 1.0 µm, d1/Ʌ = 0.45 for #F3. High nonlinearity and low attenuation are outstanding features of our model. With these advantages, the proposed fibers are targeted for smooth flat broadband supercontinuum generation for near-infrared applications