Fixed-time sliding mode observer-based controller for a class of uncertain nonlinear double integrator systems

This paper investigates a fixed-time convergence issue using the sliding mode observer-based controller for a class of uncertain nonlinear double integrator systems. This observer-based controller is designed assuming that only the first state measurement is available and there is no information about external disturbances and modeling uncertainties. A new form of sliding mode observer in combination with a sliding mode controller is designed to estimate unmeasured state and unknown disturbances and uncertainties as well as provide the estimated data in the control law. A novel form of sliding surfaces for the robust observer-based controller is proposed for which fixed-time convergence is guaranteed to achieve trajectory tracking. In the proposed fixed-time scheme, the bound on the settling time is user-defined using design parameters regardless of the system's initial conditions. The control law and observer law are designed such that the chattering issue is alleviated in the control signal. The stability analysis of the closed-loop system using the observer-based controller is established via the Lyapunov theory. The validity of the controller design is tested by applying and simulating an example of a robot manipulator in Simulink/MATLAB. The superiority of the proposed method is demonstrated by comparing it with two other methods from the relevant literature.     

Politics and Science: A Combustible Mixture. Comment.

Comments on the article by Crosby et al (see record 2003-03405-003) in which psychological research is brought to bear on an examination of the policy of affirmative action. In their article, Crosby and colleagues cite the current author's paper "The Role of Value in the World of Psychology" (1999; see record 1999-11644-004) to support their contention that "science can never be fully free of values". The current author states that Crosby and colleagues misinterpreted his position. Specifically, the author believes that the question of whether science is value-loaded or value-free is pointless because the scientific enterprise consists of a variety of independent activities. Discussion centers on the implications of the fact/value dichotomy, science and politics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adaptive coordination in cardiac anaesthesia: a study of situational changes in coordination patterns using a new observation system

Patient care in hospital settings requires coordinated team performance. Studies in other industries show that successful teams adapt their coordination processes to the situational task requirements. This prospective field study aimed to test a new observation system and investigate patterns of adaptive coordination within operating room teams. A trained observer recorded coordination activities during 24 cardiac surgery procedures. The study tested whether different patterns occur during different phases of and between different types of surgical procedures (two-way multivariate ANOVA with repeated measure). A statistically significant increase was found in clinical and coordination activities in phases of the operation with high task interdependence. The highest level of 'coordination via the work environment' (i.e. an implicit coordination mechanism) was recorded during the actual procedure on the beating heart. These findings prove the sensitivity of the observation system developed and evaluated in this study and provide insight into patterns of adaptive coordination in cardiac anaesthesia. This study furthers our understanding of adaptive coordination as a cornerstone of effective team performance in complex work environments. Using a new observation system, it describes patterns employed by health care professionals in response to changing task demands in an acute patient care setting.     

A hybrid Branch-and-Bound and evolutionary approach for allocating strings of applications to heterogeneous distributed computing systems

Providing efficient workload management is an important issue for a large-scale heterogeneous distributed computing environment where a set of periodic applications is executed. The considered shipboard distributed system is expected to operate in an environment where the input workload is likely to change unpredictably, possibly invalidating a resource allocation that was based on the initial workload estimate. The tasks consist of multiple strings, each made up of an ordered sequence of applications. There is a quality of service (QoS) minimum throughput constraint that must be satisfied for each application in a string, and a maximum utilization constraint that must be satisfied on each of the hardware resources in the system. The challenge, therefore, is to efficiently and robustly manage both computation and communication resources in this unpredictable environment to achieve high performance while satisfying the imposed constraints. This work addresses the problem of finding a robust initial allocation of resources to strings of applications that is able to absorb some level of unknown input workload increase without rescheduling. The proposed hybrid two-stage method of finding a near-optimal allocation of resources incorporates two specially designed mapping techniques: (1) the Permutation Space Genitor-Based heuristic, and (2) the follow-up Branch-and-Bound heuristic based on an Integer Linear Programming (ILP) problem formulation. The performance of the proposed resource allocation method is evaluated under different simulation scenarios and compared to an iteratively computed upper bound.     

Thermodynamic properties of the liquid Sn−Ge and Sn−Au systems by mass spectrometry

The activities and partial molar heats of mixing have been determined for the liquid Sn?Ge system at 1773 K and the liquid Sn?Au system at 1873 K. The experimental technique consisted of analyzing Knudsen cell effusates with a TOF mass spectrometer. The ion current ratios for the monomeric vapor species were measured as a function of temperature and composition and the thermodynamic properties calculated using a modified form of the Gibbs-Duhem equations. In addition to exhibiting very slight positive deviation from ideal behavior, the Sn?Ge system displayed parabolic solution behavior over the entire composition range. The results for the excess partial molar free energies and partial molar heats of mixing for the Sn?Ge system can be represented by $$G_1^E = 3.06X_2^2 kJ/g \cdot mol$$ and $$H_1^M = 5.86X_2^2 kJ/g \cdot mol$$ at 1773 K. The Sn?Au system exhibited negative deviation from ideal behavior and the results can be partially represented by $$\begin{gathered} \log _{10} \gamma Au = - 0.388 - 0.650 X_{Sn}^2 (0.00 \leqslant X_{Au} \leqslant 0.30) \hfill \\ \log _{10} \gamma Sn = 0.658 - 2.63 X_{Au}^2 (0.00 \leqslant X_{Sn} \leqslant 0.25) \hfill \\ \end{gathered} $$ and $$H_1^M = - 61.7 X_2^2 kJ/g \cdot mol$$ at 1873 K. Comparison of the results with other investigations indicates the heat of mixing for the system becomes more exothermic with increasing temperature above 1100 K. An experimental technique is presented for determining the effect of dissociative ionization of molecular species on the activity coefficient. The effect of dissociative ionization of the molecular species present in the Knudsen cell effusate was determined to be negligible.     

Sufficient and necessary conditions: Misused terms.

Notes that although the terms sufficient and necessary are absolute in nature and allow no counterexamples, psychologists inappropriately apply them to probabilistic outcomes. Misuse of the terms leads to confusion and the creation of pseudoissues, as illustrated in the argument over whether therapist warmth is a necessary or sufficient condition in behavioral desensitization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of the iterative application of makespan heuristics on non-makespan machines in a heterogeneous parallel and distributed environment

Heterogeneous computing (HC) is the coordinated use of different types of machines, and networks to process a diverse workload in a manner that will maximize the combined performance and/or cost effectiveness of the system. Heuristics for allocating resources in an HC system are based on some optimization criterion. A common optimization criterion is to minimize the completion time of the machine that finishes last (makespan). In this study, we consider an iterative approach that repeatedly runs a mapping heuristic to minimize the makespan of the considered machines and tasks. For each successive iteration, the makespan machine of the previous iteration and the tasks assigned to it are removed from the set of considered machines and tasks. This study focuses on understanding the different mathematical characteristics of resource allocation heuristics that cause them to behave differently when combined with this iterative approach. This paper has three main contributions. The first contribution is the study of an iterative technique used in conjunction with resource allocation heuristics. The second contribution is the definition and mathematical characterization of “iteration invariant” heuristics. The third contribution is to determine the characteristics of a heuristic that will cause the mapping to change across iterations.     

N-Terminal Modification of Gly-His-Tagged Proteins with Azidogluconolactone

Site-specific protein modifications are vital for biopharmaceutical drug development. Gluconoylation is a non-enzymatic, post-translational modification of N-terminal HisTags. We report high-yield, site-selective in vitro α-aminoacylation of peptides, glycoproteins, antibodies, and virus-like particles (VLPs) with azidogluconolactone at pH 7.5 in 1 h. Conjugates slowly hydrolyse, but diol-masking with borate esters inhibits reversibility. In an example, we multimerise azidogluconoylated SARS-CoV-2 receptor-binding domain (RBD) onto VLPs via click-chemistry, to give a COVID-19 vaccine. Compared to yeast antigen, HEK-derived RBD was immunologically superior, likely due to observed differences in glycosylation. We show the benefits of ordered over randomly oriented multimeric antigen display, by demonstrating single-shot seroconversion and best virus-neutralizing antibodies. Azidogluconoylation is simple, fast and robust chemistry, and should accelerate research and development.     

On the Merits of Clinical Judgment: Comment.

Comments on the article by D. Westen and J. Weinberger (see record 2004-19091-002), which criticized academic clinical psychologists for being cynical about clinical judgment and clinical practice. In our view, it seems unlikely that more than a few academic clinical psychologists believe that they have little to learn from clinical practice or experience. In this comment, we examine the arguments about clinical judgment made by Westen and Weinberger (2004). Westen and Weinberger (2004) conflate the effect of training with the effect of experience. Westen and Weinberger (2004) do not mention that the value of training in psychology has been well-supported by research. While Westen and Weinberger (2004) make positive comments about the types of feedback that clinicians receive, for a number of reasons, including the Barnum effect, psychologists can be misled by feedback. Westen and Weinberger (2004) also argue that "psychotherapists tend to have much more direct and immediate feedback than most other medical practitioners, who may prescribe a medication or perform a procedure and not see the patient again for a year" (p. 603). But when psychologists make a diagnosis or describe a personality trait, they frequently do not receive "direct and immediate feedback" on whether they are right or wrong. In contrast, physicians often receive highly valid feedback. Finally, in discussing the value of ratings made by clinicians, Westen and Weinberger (2004) observe that "empirically, we have found surprisingly little evidence of theory-driven observational bias in using clinician-report methods" (p. 601). The issue is important because Westen and Weinberger argue in favor of using clinician ratings to construct diagnostic criteria. If clinicians' ratings are biased, then the criteria will be biased. (PsycINFO Database Record (c) 2010 APA, all rights reserved)