Prescribed-time containment control with prescribed performance for uncertain nonlinear multi-agent systems

The existing studies on prescribed-time control cannot directly deal with nonlinear functions which don’t satisfy Lipschitz growth conditions. No results are available for prescribed-time containment control of pure-feedback UNMASs with prescribed performance. Therefore, completely unknown nonlinear function, prescribed-time tracking of system states and prescribed performance of containment errors are simultaneously considered in this paper. Fuzzy logic systems are utilized to approximate completely unknown nonlinear function. Prescribed-performance function is introduced and further incorporated into a novel speed function. Combining the proposed speed function and barrier Lyapunov function, this article presents a novel adaptive fuzzy prescribed-time containment control method which can guarantee, under prescribed performance, all followers converge to a convex formed by dynamic leaders in a prescribed time. Moreover, all tracking errors converge to predefined regions in a prescribed time. The effectiveness of the proposed prescribed-time containment control method are confirmed by strict proof and simulation.     

Novel model reference adaptive control laws for improved transient dynamics and guaranteed saturation constraints

In classical model reference adaptive control (MRAC), the adaptive rates must be tuned to meet multiple competing objectives. Large adaptive rates guarantee rapid convergence of the trajectory tracking error to zero. However, large adaptive rates may also induce saturation of the actuators and excessive overshoots of the closed-loop system’s trajectory tracking error. Conversely, low adaptive rates may produce unsatisfactory trajectory tracking performances. To overcome these limitations, in the classical MRAC framework, the adaptive rates must be tuned through an iterative process. Alternative approaches require to modify the plant’s reference model or the reference command input. This paper presents the first MRAC laws for nonlinear dynamical systems affected by matched and parametric uncertainties that constrain both the closed-loop system’s trajectory tracking error and the control input at all times within user-defined bounds, and enforce a user-defined rate of convergence on the trajectory tracking error. By applying the proposed MRAC laws, the adaptive rates can be set arbitrarily large and both the plant’s reference model and the reference command input can be chosen arbitrarily. The user-defined rate of convergence of the closed-loop plant’s trajectory is enforced by introducing a user-defined auxiliary reference model, which converges to the trajectory tracking error obtained by applying the classical MRAC laws before its transient dynamics has decayed, and steering the trajectory tracking error to the auxiliary reference model at a rate of convergence that is higher than the rate of convergence of the plant’s reference model. The ability of the proposed MRAC laws to prescribe the performance of the closed-loop system’s trajectory tracking error and control input is guaranteed by barrier Lyapunov functions. Numerical simulations illustrate both the applicability of our theoretical results and their effectiveness compared to other techniques such as prescribed performance control, which allows to constrain both the rate of convergence and the maximum overshoot on the trajectory tracking error of uncertain systems.     

Perspective Paper: Assessing Air Quality as Part of a Physical Therapy Plan of Care

Purpose: The purposes of this clinical perspective paper are (1) to expand physical therapists’ awareness to the topic of air quality as a health priority when providing professional services; and (2) to provide templates for screening the indoor clinical environments and patient profiles to avert respiratory exacerbations, especially in persons with asthma. Summary of Key Points: The location where a physical therapist practices determines the air quality indices to which a person is exposed. Poor indoor air quality can expose a person to even greater compromise of respiration (ie, Sick Building Syndrome) than outdoor air quality secondary to an array of factors like building materials, the ventilation exchange rate of an enclosed space, chemicals used in cleaning, and humidity. Statement of Conclusions: Extrinsic (ie, environmental) and intrinsic (eg, pre-disposition to airway hypersensitivity) factors must be accounted for by physical therapists to safeguard their patients and themselves from experiencing respiratory compromise and/or distress as a result of a treatment session or their place of employment. Recommendations: Efforts to screen indoor environments for potential triggers and patient risk profiles for abnormal airway reactivity should routinely be undertaken. Individualized Action Plans should be prospectively prepared and readied for implementation when warranted.Key Words: asthma, Sick Building Syndrome, indoor air quality, respiratory impairment     

Bowling ball dynamics revealed by miniature wireless MEMS inertial measurement unit

This paper presents a novel sensor technology to deduce the dynamics of a bowling ball. The sensor, a miniature wireless inertial measurement unit (IMU), incorporates MEMS accelerometers and angular rate gyros, a microcontroller, a low power RF transceiver, and a rechargeable battery. When embedded in a bowling ball, the IMU transmits the acceleration and angular velocity data that define the dynamics of the ball starting with the bowler’s delivery and its motion in the lane. Example results from professional bowlers illustrate how this technology can be used to assess bowler skill and ball performance. For instance, the IMU accurately measures the spin dynamics of the ball which are crucial to develop the ball “hook.” An analysis of ball dynamics in the lane is distilled to a measurable “hook potential” metric for further assessing bowler skill. Finally, the sensor presented herein is believed to be the world’s smallest, wireless IMU. This highly miniaturized and wireless design will enable parallel training systems for many sports, including basketball, baseball, crew, cricket, golf, fly fishing, soccer, softball, tennis, rowing, among others.     

面向个性化推荐的快速关联规则挖掘算法

关联规则挖掘是解决电子商务推荐问题的重要方法之一.针对传统关联规则挖掘算法在解决移动电子商务环境个性化推荐问题时反复扫描数据库,频繁项挖掘效率低,关联规则挖掘准确率低以及规则大量冗余等不足,提出一个基于事务矩阵和用户兴趣度的关联规则挖掘算法(Matrix-and-Interestingness-based Association Rules Mining,MIbARM).该算法仅需扫描一次数据库,并在挖掘过程中不断缩小算法搜索空间以避免生成冗余候选项,同时避免了冗余规则挖掘,从而提高了挖掘效率.最后,在四组人工数据和160种参数组合的数值实验环境下,引入Apriori、CBAR 及BitTableFI算法对MIbARM进行对比验证.结果表明,在不减少有趣规则的前提下,MIbARM不但可有效避免冗余候选项集的产生,而且大幅减少了冗余规则数量,极大提高了算法的搜索效率,同时提升了个性化推荐的质量,更适用于移动电子商务环境下的个性化推荐问题.     

Myeloperoxidase in Chronic Kidney Disease

Numerous lines of evidence implicate a role of myeloperoxidase (MPO) in the pathogenesis of cardiovascular disease (CVD). It is a well accepted fact that patients with chronic kidney disease (CKD) are at an increased risk for CVD. MPO is a pro-oxidant enzyme which could be involved in the increased susceptibility of these patients to CVD. Hence, the levels of plasma MPO was determined in healthy controls as well as in patients with CKD [stratified with the level of their kidney failure as CKD stages II–V (end stage renal disease)]. Plasma MPO was assayed by a spectrophotometric method. Serum urea and creatinine were estimated on a clinical chemistry analyzer using standard laboratory procedures. The mean plasma MPO levels were significantly lower with advancing stages of renal failure (P < 0.001). There was a positive correlation between MPO and GFR (r = +0.89, P < 0.001) and a negative correlation with urea (r = −0.85, P < 0.001) and creatinine (r = −0.82, P < 0.001). While an inverse association was observed between plasma MPO and urea in CKD patients, such an association was not observed in control subjects (P = 0.43). In conclusion, the decline in plasma MPO levels may be due to the inhibitory effect of uraemic toxins on the enzyme.     

The Jatropha biofuels sector in Tanzania 2005-2009: Evolution towards sustainability?

Biofuel production has recently attracted much attention. Some anticipate substantial social and environmental benefits, while at the same time expecting sound profitability for investors. Others are doubtful, envisaging large trade-offs between the pursuit of social, environmental and economic objectives, particularly in poor countries in the tropics. The paper explores these issues in Tanzania, which has been an African forerunner in the cultivation of a bio-oil shrub called Jatropha curcas L. We trace how isolated Jatropha biofuel experiments developed since early 2005 towards a sectoral production and innovation system, and we investigate to what extent that system has been capable of developing and maintaining sustainable practices and producing sustainable outcomes. The application of evolutionary innovation theory allows us to view the developments in the sector as a result of evolutionary variation and selection on the one hand, and revolutionary contestation between different coalitions of stakeholders on the other. Both these processes constitute significant engines of change. While variation and selection are driven predominantly by localised technical and agronomic learning, the conflict-driven dynamics are highly globalised and occur primarily as a result of reflexive learning about problematic sustainability impacts. The sector is found to have moved some way towards a full sectoral innovation and production system, but it is impossible to predict whether a viable sector with a strong “triple bottom line” orientation will ultimate emerge, since many issues surrounding the social, environmental and financial sustainability still remain unresolved, especially relating to local and global governance.     

“Follow the Water”: Steve Squyres and the Mars Exploration Rovers

Steve Squyres was responsible for assembling the team of scientists, engineers and instruments that formed the Mars Exploration Rovers (MER). Squyres developed a vision that small-scale observations made by a robotic geologist on Mars would be the key for resolving the mystery of water on Mars. Prior to the MER missions, planetary scientists were divided between groups holding that ancient fluvial-like surface features on Mars were formed by water and those holding that the erosive and depositional forces were tied to liquid and gaseous CO₂. At issue was a fundamental understanding not only of early Martian geological processes and early solar luminosity, but also the possibility of life on Mars. To resolve these questions, Squyres and his team developed a new breed of rovers that were capable of identifying minerals and collecting textural observations. The resulting twin rovers, Opportunity and Spirit, have successfully resolved the single most important question about Mars that scientists have been debating for the past 30 years, providing compelling evidence for the action of water on the Martian surface. Squyres and the MER team have also initiated a new era in planetary exploration and inspired a new generation of students to become scientists and explorers. Steve Squyres and the MER team produced fundamental insights into the geology and climatology of Mars. These have resulted in major advances in our understanding of the potential for life on other planets and of life’s evolution on Earth. For the discovery and elucidation of water on Mars through the “robotic geologists” of the Mars Exploration Rovers, Steve Squyres was awarded the 2007 Benjamin Franklin Medal in Earth and Environmental Science.     

Demand articulation in emerging technologies: Intermediary user organisations as co-producers?

User involvement is assumed to be beneficial to innovation processes. Intermediary user organisations contribute to articulating societal demands for innovations. However, the learning processes inside these organisations are still not understood well. Therefore, this paper empirically investigates intermediaries using an event history approach. It yields characteristic learning mechanisms, e.g. concerning the management of expectations or actively building a case. If intermediaries overcome challenges regarding positioning, representation and the level of proactivity, they can play a precarious role in demand articulation in the context of new technologies.