Global Stabilization of High-Order Time-Delay Nonlinear Systems under a Weaker Condition

Under the weaker condition on the system growth, this paper further investigates the problem of global stabilization by state feedback for a class of high-order nonlinear systems with time-varying delays. By skillfully using the homogeneous domination approach, a continuous state feedback controller is successfully designed, which preserves the equilibrium at the origin and guarantees the global asymptotic stability of the resulting closed-loop system. A simulation example is given to demonstrate the effectiveness of the proposed design procedure

Examinees’ Affective Preference for Online Speaking Assessment: Synchronous VS Asynchronous

With technological advancement and the COVID pandemic, online speaking assessment is increasingly used in language teaching. Two modes are developed: online synchronous testing (direct human-to-human interview) and online asynchronous testing (semi-direct human-to-machine interview). Ample literature has explored how each of the two online modes differs from traditional face-to-face speaking assessments. However, few studies have investigated the differences between the two modes, especially in terms of examinees’ affective preferences. This study, therefore, compares the extent to which each mode is accepted and favored by test takers and explores why such an affective preference emerges. The participants are 46 college students enrolled in an Elementary Chinese course. They completed a survey that investigates their level of motivation, self-confidence, and anxiety in the two types of online speaking tests. An open-ended question item solicited further explanations from test-takers. Results showed a strong affective preference for synchronous assessment, as manifested by a higher level of motivation and self-confidence and a lower level of anxiety. Possible reasons are discussed based on students’ written responses. The study is theoretically significant as it identifies factors on student experience and performance in online speaking assessments. It also provides practical guidance for language teachers in optimizing online oral tests

Streamflow stationarity in a changing world

Whether river flows remain stationary is of great concern to hydrologists, water engineers, and society in general, yet is subject to substantial debate. Here we provide the first comprehensive assessment of the long-term stationarity of annual streamflow for 11 069 catchments globally. Our observation-based evidence shows that the long-term annual streamflow remains stationary in 79% of catchments with minimal human disturbance, indicating that historical climate change alone has not led to non-stationarity in annual streamflow series in most catchments. In direct contrast, we found streamflow has remained stationary in only 38% of those catchments where substantial human interventions have occurred. These results demonstrate the scale of the human impact on the freshwater system, and highlight the ongoing need for dealing with the impacts of direct human interventions to ensure successful water management into the future.This study is financially supported by the Ministry of Science and Technology of China (Grant No. 2019YFC1510604), the National Natural Science Foundation of China (Grant Nos. 42041004, 42071029, 41890821) and the Qinghai Department of Science and Technology (Grant No. 2019-SF-A4). M L R and T R M acknowledge support from the Australian Research Council (CE170100023)

The management of scientific research projects in local universities

With the increasing development of science and technology, and state and local governments paying more attention to the power of science and technology, many local universities are faced with a series of innovative management environment, such as, the growing amount of scientific research projects substantially, the improving level, the wide areas involved, which put forward some new requests in projects management for local universities. According to this question ,the scientific research projects management in local universities are ought to make the thinking correct, the essential captured , the supervision strengthen, the distinguishing feature stand out .And local universities should, in the links of research project application, project initation, project inspection, projiect accepting and the use of funds strengthen the management, improving the quality projects management, enhancing the comprehensive strength of scientific research

Photonics-based real-time ultra-high-range-resolution radar with broadband signal generation and processing

Abstract Real-time and high-resolution target detection is highly desirable in modern radar applications. Electronic techniques have encountered grave difficulties in the development of such radars, which strictly rely on a large instantaneous bandwidth. In this article, a photonics-based real-time high-range-resolution radar is proposed with optical generation and processing of broadband linear frequency modulation (LFM) signals. A broadband LFM signal is generated in the transmitter by photonic frequency quadrupling, and the received echo is de-chirped to a low frequency signal by photonic frequency mixing. The system can operate at a high frequency and a large bandwidth while enabling real-time processing by low-speed analog-to-digital conversion and digital signal processing. A conceptual radar is established. Real-time processing of an 8-GHz LFM signal is achieved with a sampling rate of 500 MSa/s. Accurate distance measurement is implemented with a maximum error of 4 mm within a range of ~3.5 meters. Detection of two targets is demonstrated with a range-resolution as high as 1.875 cm. We believe the proposed radar architecture is a reliable solution to overcome the limitations of current radar on operation bandwidth and processing speed, and it is hopefully to be used in future radars for real-time and high-resolution target detection and imaging

Scientometric Analysis of The Relationship between a Built Environment and Cardiovascular Disease

The prevention and treatment of cardiovascular disease (CVD) are necessary to improve patient quality of life and to reduce the burden of medical and other social problems. Reducing the impact of CVD through environmental intervention was hailed as the most economical approach and research into such interventions is becoming key. The purpose of this article is to summarize the research topics and developments in the field of the built environment and CVD between 2000 and 2021 using scientometric analysis. In total, 1304 records retrieved from the Web of Science core database were analyzed using CiteSpace software, and the results were displayed using knowledge mapping. The number of publications and conferences relating to the built environment and CVD showed an upward trend over the study period, with the United States taking the lead. Physical activity and the food environment were used as mediators and entry points to map the relationship between the built environment and CVD. Walkability, residence characteristics, the food environment, and greenness were key research topics. Research shifted over the period to incorporate quantitative analyses of subjective feelings while focusing on decreasing sedentary behavior. Understanding the variability in the built environment is critical to improving the generalizability of the findings presented in the individual studies. Inter-disciplinary and multi-disciplinary research is conducive to innovation and ensuring the integration of real environmental elements. This study provides an overview and valuable guidance for researchers relating to how the built environment impacts CVD

Broadband LFM Radar Imaging System Based on Microwave Photonic I/Q De-chirping

We propose a novel scheme of broadband LFM radar imaging system based on microwave photonic I/Q de-chirping. In the transmitter, a broadband linear frequency modulated signal is generated by photonic frequency-doubling. In the receiver, echoes reflected from the target are simultaneously sent to a couple of modulators in two polarization states. After the bias voltage of the corresponding modulator is adjusted to introduce a 90° phase difference, photonic I/Q de-chirping reception of radar echoes is achieved. The proposed radar is capable of real-time high-resolution detection and can distinguish the target on both sides of a reference point. The range ambiguity problem caused by image interference in current radar with photonic de-chirping reception is solved. In this study, first, the necessity of I/Q de-chirping is demonstrated. Then, the structure and principle of the proposed photonic-based radar are introduced. A K-band radar with a bandwidth of 8 GHz is established, and an experiment on target detection and inverse synthetic aperture radar imaging is conducted. Results show that the system can effectively suppress the interference from image frequencies