Soil carbon balances and stock changes under different cropping and management systems

The project aimed to explore and identify practical management systems that enhance the soil organic carbon content in cropping systems. It includes effects of using perennial green manure, catch crops and animal manure in cropping systems and converting arable land to semi-natural grasslan

Soil carbon balances and stock changes under different cropping and management systems

The project aimed to explore and identify practical management systems that enhance the soil organic carbon content in cropping systems. It includes effects of using perennial green manure, catch crops and animal manure in cropping systems and converting arable land to semi-natural grasslan

Condensation of Eigen Microstate in Statistical Ensemble and Phase Transition

In a statistical ensemble with $M$ microstates, we introduce an $M \times M$ correlation matrix with the correlations between microstates as its elements. Using eigenvectors of the correlation matrix, we can define eigen microstates of the ensemble. The normalized eigenvalue by $M$ represents the weight factor in the ensemble of the corresponding eigen microstate. In the limit $M \to \infty$, weight factors go to zero in the ensemble without localization of microstate. The finite limit of weight factor when $M \to \infty$ indicates a condensation of the corresponding eigen microstate. This indicates a phase transition with new phase characterized by the condensed eigen microstate. We propose a finite-size scaling relation of weight factors near critical point, which can be used to identify the phase transition and its universality class of general complex systems. The condensation of eigen microstate and the finite-size scaling relation of weight factors have been confirmed by the Monte Carlo data of one-dimensional and two-dimensional Ising models.Comment: 9 pages, 16 figures, accepted for publication in Sci. China-Phys. Mech. Astro

Decentralized formation control with connectivity maintenance and collision avoidance under limited and intermittent sensing

A decentralized switched controller is developed for dynamic agents to perform global formation configuration convergence while maintaining network connectivity and avoiding collision within agents and between stationary obstacles, using only local feedback under limited and intermittent sensing. Due to the intermittent sensing, constant position feedback may not be available for agents all the time. Intermittent sensing can also lead to a disconnected network or collisions between agents. Using a navigation function framework, a decentralized switched controller is developed to navigate the agents to the desired positions while ensuring network maintenance and collision avoidance.Comment: 8 pages, 2 figures, submitted to ACC 201

Feasibility Study of a Campus-Based Bikesharing Program at UNLV

Bikesharing systems have been deployed worldwide as a transportation demand management strategy to encourage active modes and reduce single-occupant vehicle travel. These systems have been deployed at universities, both as part of a city program or as a stand-alone system, to serve for trips to work, as well as trips on campus. The Regional Transportation Commission of Southern Nevada (RTCSNV) has built a public bikesharing system in downtown Las Vegas, approximately five miles from the University of Nevada, Las Vegas (UNLV). This study analyzes the feasibility of a campus-based bikesharing program at UNLV. Through a review of the literature, survey of UNLV students and staff, and field observations and analysis of potential bikeshare station locations, the authors determined that a bikesharing program is feasible at UNLV

Stationary Cycling Induced by Switched Functional Electrical Stimulation Control

Functional electrical stimulation (FES) is used to activate the dysfunctional lower limb muscles of individuals with neuromuscular disorders to produce cycling as a means of exercise and rehabilitation. However, FES-cycling is still metabolically inefficient and yields low power output at the cycle crank compared to able-bodied cycling. Previous literature suggests that these problems are symptomatic of poor muscle control and non-physiological muscle fiber recruitment. The latter is a known problem with FES in general, and the former motivates investigation of better control methods for FES-cycling.In this paper, a stimulation pattern for quadriceps femoris-only FES-cycling is derived based on the effectiveness of knee joint torque in producing forward pedaling. In addition, a switched sliding-mode controller is designed for the uncertain, nonlinear cycle-rider system with autonomous state-dependent switching. The switched controller yields ultimately bounded tracking of a desired trajectory in the presence of an unknown, time-varying, bounded disturbance, provided a reverse dwell-time condition is satisfied by appropriate choice of the control gains and a sufficient desired cadence. Stability is derived through Lyapunov methods for switched systems, and experimental results demonstrate the performance of the switched control system under typical cycling conditions.Comment: 8 pages, 3 figures, submitted to ACC 201

An improved RCSA for identifying the spindle-holder taper joint dynamics

Spindle-holder taper joint is one of the most crucial joints of high speed spindle system (HSS). Dynamic behavior of this taper joint is critical for predicting tool point frequency response function (FRF) and evaluating the cutting process stability. To identify the spindle-holder taper joint dynamic behavior precisely and rapidly, a novel identification technology is presented in this paper. Firstly, receptance coupling substructure analysis (RCSA) is improved to save the computing time without sacrificing the calculation precision. Secondly, instead of extracting the joint coefficients by complex fitting methodology, a receptance matrix is identified to represent the spindle-holder taper joint dynamic characteristics. Finally, the joint receptance matrix is used, coupling with the analytical model of arbitrary holder with varying overhang length and diameter, to predict FRF at the free end of spindle-holder assembly. The results show good agreements between predictions and experimentations. And it is validated that the presented identification technology is feasible. Comparing to the previous literatures, the proposed approach is less time-consuming and more accurate to reflect the nonlinear characteristics of spindle-holder taper joint