Exponential stability analysis and impulsive tracking control of uncertain time-delayed systems

In this paper, we study exponential stability and tracking control problems for uncertain time-delayed systems. First, sufficient conditions of exponential stability for a class of uncertain time-delayed systems are established by employing Lyapunov functional methods and algebraic matrix inequality techniques. Furthermore, tracking control problems are investigated in which an uncertain linear time-delayed system is used to track the reference system. Sufficient conditions for solvability of tracking control problems are obtained for the cases that the system state is measurable and non-measurable, respectively. When the state is measurable, we design an impulsive control law to achieve the tracking performance. When the state information is not directly available from measurement, an impulsive control law based on the measured output will be used. Finally, numerical examples are presented to illustrate the effectiveness and usefulness of our results

Analysis of Pile-Soil Dynamic Interaction by Combination of BEM and FEM

A hybrid method, in which soil media is modeled by 3-D boundary elements and the pile by 1-D finite elements, for an analysis of dynamic pile-soil interaction is investigated. A new series of equations and an efficient method to deal with singularity of integrals are presented. Several effects including pile length, stiffness of the pile and surrounding soil on dynamic response are studied. Finally, the characteristics of impaired and intact piles are investigated and compared; and some case studies are presented

Behavior of Double-row Pile Retaining Structure for Deep Excavation in Soft Clay

An excavation of 10.5m deep and 110m x 70m in plane with double-row pile retaining structure in soft clay has been completed, which is of severa1 advantages, such as elimination of lateral deflection and ground surface settlement, low cost and short duration of excavation. This paper presents tile design considerations, procedure of construction and excavation, behavior of this type of retaining structure. The FEM analysis has been carried for prediction of lateral deflection and stress, the results from FEM method conformed well with field measurement, some conclusions drawn from the design and construction Mil be valuable for future construction in similar engineering

Demystifying Developers' Issues in Distributed Training of Deep Learning Software

Deep learning (DL) has been pervasive in a wide spectrum of nowadays software systems and applications. The rich features of these DL based software applications (i.e., DL software) usually rely on powerful DL models. To train powerful DL models with large datasets efficiently, it has been a common practice for developers to parallelize and distribute the computation and memory over multiple devices in the training process, which is known as distributed training. However, existing efforts in the software engineering (SE) research community mainly focus on issues in the general process of training DL models. In contrast, to the best of our knowledge, issues that developers encounter in distributed training have never been well studied. Given the surging importance of distributed training in the current practice of developing DL software, this paper fills in the knowledge gap and presents the first comprehensive study on developers' issues in distributed training. To this end, we extract and analyze 1,054 real-world developers' issues in distributed training from Stack Overflow and GitHub, two commonly used data sources for studying software issues. We construct a fine-grained taxonomy consisting of 30 categories regarding the fault symptoms and summarize common fix patterns for different symptoms. Based on the results, we suggest actionable implications and research avenues that can potentially facilitate the future development of distributed training

Responses of the field-aligned currents in the plasma sheet boundary layer to a geomagnetic storm

Geomagnetic storms can result in large magnetic field disturbances and intense currents in the magnetosphere and even on the ground. As an important medium of momentum and energy transport among the solar wind, magnetosphere, and ionosphere, field-aligned currents (FACs) can also be strengthened in storm times. This study shows the responses of FACs in the plasma sheet boundary layer (PSBL) observed by the Magnetospheric Multiscale (MMS) spacecraft in different phases of a large storm that lasted from May 27, 2017, to May 29, 2017. Most of the FACs were carried by electrons, and several FACs in the storm time also contained sufficient ion FACs. The FAC magnitudes were larger in the storm than in the quiet period, and those in the main phase were the strongest. In this case, the direction of the FACs in the main phase showed no preference for tailward or earthward, whereas the direction of the FACs in the recovery phase was mostly tailward. The results suggest that the FACs in the PSBL are closely related to the storm and could be driven by activities in the tail region, where the energy transported from the solar wind to the magnetosphere is stored and released as the storm is evolving. Thus, the FACs are an important medium of energy transport between the tail and the ionosphere, and the PSBL is a significant magnetosphere–ionosphere coupling region in the nightside

Evaluation of Heat Generation in Unidirectional Versus Oscillatory Modes During K‐Wire Insertion in Bone

Heat generation during insertion of Kirschner wires (K‐wires) may lead to thermal osteonecrosis and can affect the construct fixation. Unidirectional and oscillatory drilling modes are options for K‐wire insertion, but understanding of the difference in heat generation between the two modes is lacking. The goal of this study was to compare the temperature rise during K‐wire insertion under these two modes and provide technical guidelines for K‐wire placement to minimize thermal injury. Ten orthopedic surgeons were instructed to drill holes on hydrated ex vivo bovine bones under two modes. The drilling trials were evaluated in terms of temperature, thrust force, torque, drilling time, and tool wear. The analysis of variance showed that the oscillatory mode generated significantly lowered peak bone temperature rise (13% lower mean value, p = 0.036) over significantly longer drilling time (46% higher mean time, p < 0.001) than the unidirectional mode. Drilling time had significant effect on peak bone temperature rise under both modes (p < 0.001) and impact of peak thrust force was significant under oscillatory mode (p < 0.001). These findings suggest that the drilling mode choice is a compromise between peak temperature and bone exposure time. Shortening the drilling time was the key under both modes to minimize temperature rise and thermal necrosis risk. To achieve faster drilling, technique analysis found that “shaky” and intermittent drilling with moderate thrust force are preferred techniques by small vibration of the drill about the K‐wire axis and slight lift‐up of the K‐wire once or twice during drilling. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1903–1909, 2019Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151349/1/jor24345_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151349/2/jor24345.pd

Role of G-protein coupled receptors in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death globally, with CVDs accounting for nearly 30% of deaths worldwide each year. G-protein-coupled receptors (GPCRs) are the most prominent family of receptors on the cell surface, and play an essential regulating cellular physiology and pathology. Some GPCR antagonists, such as β-blockers, are standard therapy for the treatment of CVDs. In addition, nearly one-third of the drugs used to treat CVDs target GPCRs. All the evidence demonstrates the crucial role of GPCRs in CVDs. Over the past decades, studies on the structure and function of GPCRs have identified many targets for the treatment of CVDs. In this review, we summarize and discuss the role of GPCRs in the function of the cardiovascular system from both vascular and heart perspectives, then analyze the complex ways in which multiple GPCRs exert regulatory functions in vascular and heart diseases. We hope to provide new ideas for the treatment of CVDs and the development of novel drugs