Positivity and stability of mixed fractional‐order systems with unbounded delays: Necessary and sufficient conditions

This article provides a comprehensive study on quantitative properties of linear mixed fractional‐order systems with multiple time‐varying delays. The delays can be bounded or unbounded. We first obtain a result on existence and uniqueness of solutions to these systems. Then, we prove a necessary and sufficient condition for their positivity. Finally, we provide a necessary and sufficient criterion to characterize asymptotic stability of positive linear mixed fractional‐order systems with multiple time‐varying delays.     

Micro cam system driven by electrostatic comb-drive actuators based on SOI-MEMS technology

Microsystem Technologies - This paper reports a design and fabrication process of a micro cam system (MCS) with a flat-faced translating follower. The cam rim with cover diameter of 2.4 mm...     

Pseudo‐predictor feedback control of discrete‐time linear systems with a single input delay

This paper studies the problems of stabilization of discrete‐time linear systems with a single input delay. By developing the methodology of pseudo‐predictor feedback, which uses the (artificial) closed‐loop system dynamics to predict the future state, memoryless state feedback control laws are constructed to solve the problem. Necessary and sufficient conditions are obtained to guarantee the stability of the closed‐loop system in terms of the stability of a class‐difference equations. It is also shown that the proposed controller achieves semi‐global stabilization of the system if its actuator is subject to either magnitude saturation or energy constraints under the condition that the open‐loop system is only polynomially unstable. Numerical examples have been worked out to illustrate the effectiveness of the proposed approaches. Copyright © 2015 John Wiley & Sons, Ltd.     

H∞ Control with Transients for Singular Systems

In this paper, the problem of a generalized type of H_∞ control is investigated for continuous‐time singular systems, which treats a mixed attenuation of exogenous inputs and initial conditions. First, a performance measure that is essentially the worst‐case norm of the regulated outputs over all exogenous inputs and initial conditions is introduced. A necessary and sufficient condition is obtained to ensure the singular system to be admissible and the performance measure to be less than a prescribed scalar. Based on the criterion a sufficient condition for the existence of a state‐feedback controller is established in terms of linear matrix inequalities. Moreover, the relationship between the performance measure and the standard H_∞ norm of the system is provided. Two numerical examples are given to demonstrate the properties of the obtained results.     

A scalable, self-analyzing digital locking system for use on quantum optics experiments

Digital control of optics experiments has many advantages over analog control systems, specifically in terms of the scalability, cost, flexibility, and the integration of system information into one location. We present a digital control system, freely available for download online, specifically designed for quantum optics experiments that allows for automatic and sequential re-locking of optical components. We show how the inbuilt locking analysis tools, including a white-noise network analyzer, can be used to help optimize individual locks, and verify the long term stability of the digital system. Finally, we present an example of the benefits of digital locking for quantum optics by applying the code to a specific experiment used to characterize optical Schr?dinger cat states.     

Operation of a full-scale pumped flow biofilm reactor (PFBR) under two aeration regimes

A novel technology suitable for centralised and decentralised wastewater treatment has been developed, extensively tested at laboratory-scale, and trialled at a number of sites for populations ranging from 15 to 400 population equivalents (PE). The two-reactor-tank pumped flow biofilm reactor (PFBR) is characterised by: (i) its simple construction; (ii) its ease of operation and maintenance; (iii) low operating costs; (iv) low sludge production; and (v) comprising no moving parts or compressors, other than hydraulic pumps. By operating the system in a sequencing batch biofilm reactor (SBBR) mode, the following treatment can be achieved: 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS) reduction; nitrification and denitrification. During a 100-day full-scale plant study treating municipal wastewater and operating at 165 PE and 200 PE (Experiments 1 and 2, respectively), maximum average removals of 94% BOD5, 86% TSS and 80% ammonium-nitrogen (NH4-N) were achieved. During the latter part of Experiment 2, effluent concentrations averaged: 14 mg BOD5/l; 32 mg COD(filtered)/l; 14 mg TSS/l; 4.4 mg NH4-N/l; and 4.0 mg NO3-N/l (nitrate-nitrogen). The average energy consumption was 0.46-0.63 kWh/m3(treated) or 1.25-1.76 kWh/kg BOD5 removed. No maintenance was required during these experiments. The PFBR technology offers a low energy, minimal maintenance technology for the treatment of municipal wastewater.     

A Stochastic Vehicle Routing Problem with Travel Time Uncertainty: Trade-Off Between Cost and Customer Service

On-time shipment delivery is critical for just-in-time production and quick response logistics. Due to uncertainties in travel and service times, on-time arrival probability of vehicles at customer locations can not be ensured. Therefore, on-time shipment delivery is a challenging job for carriers in congested road networks. In this paper, such on-time shipment delivery problems are formulated as a stochastic vehicle routing problem with soft time windows under travel and service time uncertainties. A new stochastic programming model is proposed to minimize carrier’s total cost, while guaranteeing a minimum on-time arrival probability at each customer location. The aim of this model is to find a good trade-off between carrier’s total cost and customer service level. To solve the proposed model, an iterated tabu search heuristic algorithm was developed, incorporating a route reduction mechanism. A discrete approximation method is proposed for generating arrival time distributions of vehicles in the presence of time windows. Several numerical examples were conducted to demonstrate the applicability of the proposed model and solution algorithm.     

Development of a Weather Forecasting Code: A Case Study

Computational science is increasingly supporting advances in scientific and engineering knowledge. The unique constraints of these types of projects result in a development process that differs from the process more traditional information technology projects use. This article reports the results of the sixth case study conducted under the support of the Darpa High Productivity Computing Systems Program. The case study aimed to investigate the technical challenges of code development in this environment, understand the use of development tools, and document the findings as concrete lessons learned for other developers' benefit. The project studied here is a major component of a weather forecasting system of systems. It includes complex behavior and interaction of several individual physical systems (such as the atmosphere and the ocean). This article describes the development of the code and presents important lessons learned.     

A decision support system for environmental effects monitoring

The Environmental Effects Monitoring (EEM) Statistical Assessment Tool (SAT) Decision Support System (DSS) has been developed to provide a user-friendly data analysis, display and decision support tool for Canada's federal environmental effects monitoring program for the pulp and paper and mining industries. The target users include industries, consultants, regional EEM coordinators, National EEM Office and scientists involved in EEM-related research. The tool allows the assessment of the effects of effluent from industrial or other sources on fish and benthic populations. Effect endpoints, which are used as indicators of potentially important effluent effects, are measured at effluent-exposed sites and are compared statistically to measures at reference sites, in order to determine if changes have occurred and the magnitude of the changes. The main driver of the EEM-SAT DSS is its rule-based expert system. The results are used in assessing the adequacy of existing regulations for protecting aquatic environments.     

Experiences in developing and applying a software engineering technology testbed

A major problem in empirical software engineering is to determine or ensure comparability across multiple sources of empirical data. This paper summarizes experiences in developing and applying a software engineering technology testbed. The testbed was designed to ensure comparability of empirical data used to evaluate alternative software engineering technologies, and to accelerate the technology maturation and transition into project use. The requirements for such software engineering technology testbeds include not only the specifications and code, but also the package of instrumentation, scenario drivers, seeded defects, experimentation guidelines, and comparative effort and defect data needed to facilitate technology evaluation experiments. The requirements and architecture to build a particular software engineering technology testbed to help NASA evaluate its investments in software dependability research and technology have been developed and applied to evaluate a wide range of technologies. The technologies evaluated came from the fields of architecture, testing, state-model checking, and operational envelopes. This paper will present for the first time the requirements and architecture of the software engineering technology testbed. The results of the technology evaluations will be analyzed from a point of view of how researchers benefitted from using the SETT. The researchers just reported how their technology performed in their original findings. The testbed evaluation showed (1) that certain technologies were complementary and cost-effective to apply; (2) that the testbed was cost-effective to use by researchers within a well-specified domain of applicability; (3) that collaboration in testbed use by researchers and the practitioners resulted comparable empirical data and in actions to accelerate technology maturity and transition into project use, as shown in the AcmeStudio evaluation; and (4) that the software engineering technology testbed’s requirements and architecture were suitable for evaluating technologies and accelerating their maturation and transition into project use.