A distributionally robust index tracking model with the CVaR penalty: tractable reformulation

We propose a distributionally robust index tracking model with the conditional value-at-risk (CVaR) penalty. The model combines the idea of distributionally robust optimization for data uncertainty and the CVaR penalty to avoid large tracking errors. The probability ambiguity is described through a confidence region based on the first-order and second-order moments of the random vector involved. We reformulate the model in the form of a min-max-min optimization into an equivalent nonsmooth minimization problem. We further give an approximate discretization scheme of the possible continuous random vector of the nonsmooth minimization problem, whose objective function involves the maximum of numerous but finite nonsmooth functions. The convergence of the discretization scheme to the equivalent nonsmooth reformulation is shown under mild conditions. A smoothing projected gradient (SPG) method is employed to solve the discretization scheme. Any accumulation point is shown to be a global minimizer of the discretization scheme. Numerical results on the NASDAQ index dataset from January 2008 to July 2023 demonstrate the effectiveness of our proposed model and the efficiency of the SPG method, compared with several state-of-the-art models and corresponding methods for solving them

Design of four rotor aircraft with obstacle avoidance

The system uses TM4C123G as the core of quadrotor autonomous vehicle control, which consists of flight control module, power supply module, motor speed control module, optical flow sensing module, and target tracking identification module. The flight control module includes angle sensor, gyroscope, and TLS1401-LF module. The flight control processes the collected data through the chip (TM4C123G), and processes the data with PID control algorithm, while solving the PWM increment and decrement needed for the corresponding motor, adjusting the motor in time and adjusting the flight attitude. The binocular camera identifies the color of the pole tower and measures the distance, so that the distance between the aircraft and the nearest point of the pole tower is kept within 50±10cm. After detecting the red (green) tower as the center, fly around the tower clockwise (counter) for one week (top view). Finally, the OV7725 camera is used to identify the solid black circle mark of the landing point and land smoothly and accurately in the target area, thus realizing an efficient robot around the barrier

The Impact of International Trade on Economic Growth in Vietnam 1990 - 2015

The study examines the impact of exports, imports, gross capital formation, and exchange rate on the economic growth of Vietnam. The empirical analysis is conducted by using time series data from 1990-2015. The study employed regression analysis as the method of analysis using cointegration and vector error correction techniques (VECM) to find the long-run relationship between growth rate of the gross domestic product, exports, imports, gross capital formation, and exchange rate. The estimated results show that there is a long-run equilibrium relationship among dependent variables and independent variables. The results also indicate that the import and gross capital formation has a positive and significant influence on the economy of Vietnam, the exchange rate has positive and insignificant on economic growth. Meanwhile, import has a negative impact on economic growth. It concludes that international trade can play a major role in boosting Vietnam's economic growth. Keywords: Exports, imports, gross capital formation, exchange rate, and economic growt

The Impact of Foreign Direct Investment on Economic Growth: A Case Study in Vietnam 1990 – 2015

Over the past 20 years, the role of FDI in the Vietnamese economy has been important. FDI is one of the essential factors for the domestic economic growth. FDI not only increases the supply of investment capital but also promotes technology transfer, human capital accumulation, which promotes long-term economic growth. This paper employs time series techniques to analyses the effect of the foreign direct investment on economic growth in Viet Nam. The study uses annual data over the period 1990 - 2015. The gross domestic product (GDP) is the dependent variable, and foreign direct investment (FDI), gross fixed capital formation, real exchange rate, real interest rate, and inflation rate are the explanatory variables. Keywords: Gross domestic product, foreign direct investment, gross fixed capital formation

A one-dimensional extremely covalent material: monatomic carbon linear chain

Polyyne and cumulene of infinite length as the typical covalent one-dimensional (1D) monatomic linear chains of carbon have been demonstrated to be metallic and semiconductor (Eg = 1.859 eV), respectively, by first-principles calculations. Comparing with single-walled carbon nanotubes, the densities are evidently low and the thermodynamic properties are similar below room temperature but much different at the high temperature range. Polyyne possesses a Young's modulus as high as 1.304 TPa, which means it is even much stiffer than carbon nanotubes and to be the superlative strong 1D material along the axial direction. The Young's modulus of cumulene is estimated to be 760.78 GPa. In addition, polyyne is predicted to be as a one-dimensional electronic material with very high mobility

Evolutionary Analysis of Structural Protein Gene VP1 of Foot-and-Mouth Disease Virus Serotype Asia 1

Foot-and-mouth disease virus (FMDV) serotype Asia 1 was mostly endemic in Asia and then was responsible for economically important viral disease of cloven-hoofed animals, but the study on its selection and evolutionary process is comparatively rare. In this study, we characterized 377 isolates from Asia collected up until 2012, including four vaccine strains. Maximum likelihood analysis suggested that the strains circulating in Asia were classified into 8 different groups (groups I–VIII) or were unclassified (viruses collected before 2000). On the basis of divergence time analyses, we infer that the TMRCA of Asia 1 virus existed approximately 86.29 years ago. The result suggested that the virus had a high mutation rate (5.745 × 10−3 substitutions/site/year) in comparison to the other serotypes of FMDV VP1 gene. Furthermore, the structural protein VP1 was under lower selection pressure and the positive selection occurred at many sites, and four codons (positions 141, 146, 151, and 169) were located in known critical antigenic residues. The remaining sites were not located in known functional regions and were moderately conserved, and the reason for supporting all sites under positive selection remains to be elucidated because the power of these analyses was largely unknown

Analysis of synonymous codon usage in Hepatitis A virus

<p>Abstract</p> <p>Background</p> <p>Hepatitis A virus is the causative agent of type A viral hepatitis, which causes occasional acute hepatitis. Nevertheless, little information about synonymous codon usage pattern of HAV genome in the process of its evolution is available. In this study, the key genetic determinants of codon usage in HAV were examined.</p> <p>Results</p> <p>The overall extent of codon usage bias in HAV is high in <it>Picornaviridae</it>. And the patterns of synonymous codon usage are quite different in HAV genomes from different location. The base composition is closely correlated with codon usage bias. Furthermore, the most important determinant that results in such a high codon bias in HAV is mutation pressure rather than natural selection.</p> <p>Conclusions</p> <p>HAV presents a higher codon usage bias than other members of <it>Picornaviridae</it>. Compositional constraint is a significant element that influences the variation of synonymous codon usage in HAV genome. Besides, mutation pressure is supposed to be the major factor shaping the hyperendemic codon usage pattern of HAV.</p