Elastic loading enhanced NH3 sensing for surface acoustic wave sensor with highly porous nitrogen doped diamond like carbon film

We proposed a surface acoustic wave (SAW) NH3 gas sensor based on nitrogen doped diamond like carbon (N-DLC) film. The N-DLC film, prepared using a microwave electron cyclotron resonance plasma chemical vapor deposition (ECR-PECVD) method, is highly porous and physically and chemically stable, and have active polar groups on its surface, which can selectively absorb polar NH3 gas molecules. These features of the film lead to the high sensitivity, low noise and excellent stability of the sensor. The sensor can achieve capabilities of in-situ monitoring NH3 in a concentration range from 100 ppb to 100 ppm with fast response (∼5 s) and recovery (∼29 s) at room temperature. The NH3 sensing mechanism is attributed to the decreased porosity of the N-DLC film caused by adsorbed NH3 molecules on its polar groups, which leads an increase of the elastic modulus of the film

Sedimentary ancient DNA reveals past ecosystem and biodiversity changes on the Tibetan Plateau: Overview and prospects

Alpine ecosystems on the Tibetan Plateau are being threatened by ongoing climate warming and intensified human activities. Ecological time-series obtained from sedimentary ancient DNA (sedaDNA) are essential for understanding past ecosystem and biodiversity dynamics on the Tibetan Plateau and their responses to climate change at a high taxonomic resolution. Hitherto only few but promising studies have been published on this topic. The potential and limitations of using sedaDNA on the Tibetan Plateau are not fully understood. Here, we (i) provide updated knowledge of and a brief introduction to the suitable archives, region-specific taphonomy, state-of-the-art methodologies, and research questions of sedaDNA on the Tibetan Plateau; (ii) review published and ongoing sedaDNA studies from the Tibetan Plateau; and (iii) give some recommendations for future sedaDNA study designs. Based on the current knowledge of taphonomy, we infer that deep glacial lakes with freshwater and high clay sediment input, such as those from the southern and southeastern Tibetan Plateau, may have a high potential for sedaDNA studies. Metabarcoding (for microorganisms and plants), metagenomics (for ecosystems), and hybridization capture (for prehistoric humans) are three primary sedaDNA approaches which have been successfully applied on the Tibetan Plateau, but their power is still limited by several technical issues, such as PCR bias and incompleteness of taxonomic reference databases. Setting up high-quality and open-access regional taxonomic reference databases for the Tibetan Plateau should be given priority in the future. To conclude, the archival, taphonomic, and methodological conditions of the Tibetan Plateau are favorable for performing sedaDNA studies. More research should be encouraged to address questions about long-term ecological dynamics at ecosystem scale and to bring the paleoecology of the Tibetan Plateau into a new era

Distributed Constraint Optimization with Flocking Behavior

This paper studies distributed optimization having flocking behavior and local constraint set. Multiagent systems with continuous-time and second-order dynamics are studied. Each agent has a local constraint set and a local objective function, which are known to only one agent. The objective is for multiple agents to optimize a sum of the local functions with local interaction and information. First, a bounded potential function to construct the controller is given and a distributed optimization algorithm that makes a group of agents avoid collisions during the evolution is presented. Then, it is proved that all agents track the optimal velocity while avoiding collisions. The proof of the main result is divided into three steps: global set convergence, consensus analysis, and optimal set convergence. Finally, a simulation is included to illustrate the results

Analysis and Detection Method for Machining Error of Globoidal Indexing Cam Profile

The profile of globoidal indexing cam is spatial undevelopable surface. It needs special CNC machine tool to finish batch production. The machining quality of the profile of globoidal indexing cam could be affected by the movement error of each part of machine tool and the clamped positioning error of workpiece. Firstly, this paper analyses the systematic error of the special machine tool of globoidal cam, derives the error transfer matrix, establishes the mathematical model of the globoidal cam profile which including all machining system errors through multi-body system theory primarily. Secondly, this method improves the measuring speed and avoids the probe radius compensation, and evaluates the tolerance of the profile greed of globoidal cam equidistant model directly. Finally, the feasibility of the measurement method is verified by experiments, and the experimental results are analysed and processed. It lays the foundation for the design, process and measurement of globoidal cam mechanism and provides a theoretical basis and key technology for developing the online rapid detection system of the globoidal indexing cam profile

High-frequency feedback robust control for flocking of multi-agent system with unknown parameters

In this paper, a kind of high-frequency feedback robust control for flocking of a multi-agent system with unknown parameters is put forward in detail. Firstly, a high-frequency feedback robust control scheme is proposed for the flocking problem of a multi-agent system with unknown parameters. Secondly, through the employment of Lyapunov stability theory, it's proved that velocity error is gradually stabilized and collisions between agents are also avoided. In addition, the high-frequency feedback robust control for flocking of a multi-agent system with unknown parameters is further proved. Finally, it is verified with the help of numerical simulation