Germanium-antimony-selenium-tellurium thin films: Clusters formation by laser ablation and comparison with clusters from mixtures of elements

Quaternary germanium-antimony-selenium-tellurium (Ge-Sb-Se-Te) thin films deposited from Ge_19.4Sb_16.7Se_63.9−xTe_x (x = 5, 10, 15, and 20) glass-ceramics targets by radio frequency magnetron sputtering were studied using laser ablation quadrupole ion trap time of flight mass spectrometry. Binary, ternary, and quaternary Ge_aSb_bSe_cTe_d clusters were formed and their stoichiometry was determined. By comparison of the clusters obtained from quaternary Ge-Sb-Se-Te thin films and those from ternary Ge-Sb-Te materials, we found that Ge-Te species are not detected from the quaternary system. Furthermore, Ge-Se and Se-Te species are missing in mass spectra generated from Ge-Sb-Se-Te thin films. From the Ge-Sb-Se-Te thin films, 16 clusters were detected while ternary Ge-Sb-Se glasses yielded 26 species. This might be considered as a signal of higher stability of Ge-Sb-Se-Te thin films which is increasing with a higher content of Te. The missing (Se₂⁺, Ge_aSb⁺ (a = 1–4), and GeSe_c⁺ (c = 1, 2)) and new (Ge⁺ and Sb_bTe⁺ (b = 1–3)) clusters may indicate that some of the structural features of the films (Ge₂Se_6/2 and Se₂Sb-SbSe₂) were replaced by (GeSe_4−xTe_x and SbSe_3−xTe_x) ones. In addition, when comparing the stoichiometry of clusters formed from Ge-Sb-Se-Te thin films with those from the mixtures of the elements, only Sb₃⁺ and SbSe⁺ were observed in both cases. The knowledge gained concerning clusters stoichiometry contributes to the elucidation of the processes proceeding during plasma formation used for the chalcogenide thin films deposition.     

Control problems in super-articulated mechanical systems

Control of super-articulated mechanical systems (SAMS: controlled mechanical system in which the dimension of the configuration space exceeds the dimension of the control input space) is studied. As a starting point, a graphical characterization of general SAMS is developed in which a so-called control flow diagram (CFD) is constructed to represent the interaction forces among the degrees of freedom of the system; three types of structure, namely, the chain structure, the tree structure and isolated points, are identified; degree of complexity of the system is defined based on the structure of the system. A systematic backstepping type controller design is proposed for systems with a chain structure to achieve global asymptotic stability and trajectory tracking. Such a controller design itself illustrates the sufficient conditions for the existence of smooth feedback control such that the systems with a chain structure can be globally asymptotically stabilized. The connection of the authors' control algorithm with existing results is discussed     

Control and Communication Challenges in Networked Real-Time Systems

A current survey of the emerging field of networked control systems is provided. The aim is to introduce the fundamental issues involved in designing successful networked control systems, to provide a snapshot assessment of the current state of research in the field, to suggest useful future research directions, and to provide a broad perspective on recent fundamental results. Reflecting the goals of the Special Issue itself, this paper surveys relevant work from the areas of systems and control, signal processing, detection and estimation, data fusion, and distributed systems. We discuss appropriate network architectures, topics such as coding for robustly stable control in the presence of time-varying channel capacity, channels with fixed versus adaptively variable data width, issues in data rate problems in nonlinear feedback problems, and problems in routing for stability and performance. In surveying current research on networked control systems, we find that recent theoretical advances and target applications are intimately intertwined. The common goal of papers in the Special Issue which follows is to describe key aspects of this relationship. We also aim to provide a bridge between networked control systems and closely related contemporary work dealing with sensor networks and wireless communication protocols     

Robust quantization for digital finite communication bandwidth (DFCB) control

The problem of digital finite communication bandwidth (DFCB) control has come to the attention of the research community in connection with a growing interest in the development of distributed and/or networked control systems. In these systems, actuators, sensors, and other components are connected via data-rate constrained links such as wireless radio, etc. In this paper, we consider a scalar model of DFCB control that accommodates time-varying data-rate constraints, such as might occur with intermittent network congestion, and asynchronism of sampling and control actuation. Because of the possibly unpredictable fluctuation of the data-rate, we are interested in feedback control designs that will tolerate significantly constrained data-rates on feedback loops, while providing acceptable performance when such data-rate constraints are not in force. In light of a very basic notion of acceptable performance, we show that control designs with different number of quantization levels tolerate constrained data-rates differently. This leads to the conclusion that binary control represents the most robust control quantization under data-rate constraints imposed by time-varying congestion on the feedback communication channel. The advantage margin of binary control is further investigated numerically with and without the sampling-control asynchronism being considered. We show that the advantage margin is more substantial when the sampling-control asynchronism is significant. A design of quantized (binary) feedback with side channel information is proposed, and stability properties are discussed. We conclude the paper by examining performance limitations of our binary coding in the presence of noise.     

Effect of prepartum maternal energy density on the growth performance, immunity, and antioxidation capability of neonatal calves

This study investigated the effect of prepartum diets differing in energy density on growth performance, immunity, and antioxidation capability of neonatal calves. Thirty Holstein dairy cows were allocated at random into 3 groups: low energy group [L; net energy of lactation (NE(L))=5.25 MJ/kg of dry matter (DM)]; medium energy group (M; NE(L)=5.88 MJ/kg of DM); and high energy group (H; NE(L)=6.48 MJ/kg of DM) at d 21 prepartum. Plasma was sampled for analysis of glucose, total protein, β-hydroxybutyrate, and nonesterified fatty acids at 21, 14, and 7 d before parturition. After calving, birth weight and measurements of the calves in each group were recorded, and blood samples were collected for analysis of CD4, CD8, CD21, IL-2, IL-4, IL-6, total antioxidant capacity, superoxide dismutase, glutathione peroxidase, and maleic dialdehyde. The results indicated that although maternal weight did not differ among L, M, and H groups at 21, 14, and 7 d before parturition, the concentrations of glucose and β-hydroxybutyrate at 14 and 7 d in the L group were decreased compared with that in the H group. In addition, nonesterified fatty acids concentrations increased significantly in the L group at 14 and 7 d before parturition compared with that in the M and H groups. Birth weight, body height, body length, abdominal circumference, thoracic girth, umbilical girth, and levels of CD4, CD4:CD8, IL-2, IL-4, total antioxidant capacity, and superoxide dismutase were decreased in calves of the L group compared with those of the H group. For the M group, CD4, CD4:CD8, and superoxide dismutase were decreased; and in the L group glutathione peroxidase and maleic dialdehyde levels were significantly increased compared with those of the H group. Reducing the maternal energy density during the last 21 d before parturition had a negative effect on growth and development, immunity, and antioxidation capability of neonatal calves.