Efficient parallel graph trimming by arc-consistency

The Journal of Supercomputing - Given a large data graph, trimming techniques can reduce the search space by removing vertices without outgoing edges. One application is to speed up the parallel...     

Hybrid Nanovehicles: One Machine,Two Engines

Nanomotors have emerged as promising and versatile nanorobotic tools in a variety of medical, sensing, decontamination, and manufacturing applications due to their unique ability to operate and perform task at small scales. This review focuses on the current progress and future perspectives of hybrid nanomotors based on two power sources, with a special highlight on their distinct advantages, unique propulsion behaviors, adaptive operation, and potential applications. Such incorporation of multiple engines into a single nanoscale vehicle addresses certain limitations of nanomotors based on a single propulsion mode and adds new dimensions for advanced motion management. These attractive capabilities of hybrid nanoscale vehicles are discussed along with the challenges and opportunities when coupling several propulsion modes into a single device. With continuous innovations, it is expected that hybrid nanomotors will have a profound impact upon the field of nanorobotics.     

On the long-term use of visual gui testing in industrial practice: a case study

Visual GUI Testing (VGT) is a tool-driven technique for automated GUI-based testing that uses image recognition to interact with and assert the correctness of the behavior of a system through its GUI as it is shown to the user. The technique’s applicability, e.g. defect-finding ability, and feasibility, e.g. time to positive return on investment, have been shown through empirical studies in industrial practice. However, there is a lack of studies that evaluate the usefulness and challenges associated with VGT when used long-term (years) in industrial practice. This paper evaluates how VGT was adopted, applied and why it was abandoned at the music streaming application development company, Spotify, after several years of use. A qualitative study with two workshops and five well chosen employees is performed at the company, supported by a survey, which is analyzed with a grounded theory approach to answer the study’s three research questions. The interviews provide insights into the challenges, problems and limitations, but also benefits, that Spotify experienced during the adoption and use of VGT. However, due to the technique’s drawbacks, VGT has been abandoned for a new technique/framework, simply called the Test interface. The Test interface is considered more robust and flexible for Spotify’s needs but has several drawbacks, including that it does not test the actual GUI as shown to the user like VGT does. From the study’s results it is concluded that VGT can be used long-term in industrial practice but it requires organizational change as well as engineering best practices to be beneficial. Through synthesis of the study’s results, and results from previous work, a set of guidelines are presented that aim to aid practitioners to adopt and use VGT in industrial practice. However, due to the abandonment of the technique, future research is required to analyze in what types of projects the technique is, and is not, long-term viable. To this end, we also present Spotify’s Test interface solution for automated GUI-based testing and conclude that it has its own benefits and drawbacks.     

Fundamental Operation of Rectifiers with Thyristor AC Power Control

The dc output of low-voltage diode rectifiers can be adjusted economically and efficiently by thyristor ac power controllers on the ac side of the rectifier transformer. This method of obtaining voltage control has been used for a number of years. This paper presents an analysis of the various modes of operation, the waveforms, control characteristics, and various other parameters and observations of interest for some commonly employed circuits. In particular the sixpulse bridge rectifier with delta-wye transformer (ASA-23) and the six-pulse double-wye interphase rectifier with delta-double wye transformer (ASA-45) have been studied theoretically as well as experimentally. Attention has been given to the problem of transformer saturation, and the associated requirements for gating accuracy was found to be less stringent than one would expect. It was further discovered that these circuits have some pronounced advantages over the corresponding six-pulse phase controlled converters when comparing dc ripple and reactive power consumption from the line.     

Design and implementation of a new teleoperation control mode for differential drive UGVs

In this paper, we propose and implement a new control mode for teleoperated unmanned ground vehicles (UGVs), that exploits the similarities between computer games and teleoperation robotics. Today, all teleoperated differential drive UGVs use a control mode called Tank Control, in which the UGV chassis and the pan tilt camera are controlled separately. This control mode was also the dominating choice when the computer game genre First Person Shooter (FPS) first appeared. However, the hugely successful FPS genre, including titles such as Doom, Half Life and Call of Duty, now uses a much more intuitive control mode, Free Look Control (FLC), in which rotation and translation of the character are decoupled, and controlled separately. The main contribution of this paper is that we replace Tank Control with FLC in a real UGV. Using feedback linearization, the orientation of the UGV chassis is abstracted away, and the orientation and translation of the camera are decoupled, enabling the operator to use FLC when controlling the UGV. This decoupling is then experimentally verified. The developments in the gaming community indicates that FLC is more intuitive than Tank Control and reduces the well known situational awareness problem. It furthermore reduces the need for operator training, since literary millions of future operators have already spent hundreds of hours using the interface.     

Surface properties and biocompatibility of cellulose acetates

The article describes some properties of cellulose acetates (CAs) with different substitution degrees. The hydrophilic/hydrophobic properties, morphological aspects, and interface properties with red blood cells and platelets are affected by the substitution degree, synthesis conditions, history of the formed films from solutions in acetone/water nonsolvent/nonsolvent mixtures, and low pressure plasma treatment. The results obtained are useful in biomedical applications, including evaluation of bacterial adhesion onto surfaces, or utilization of CA for semipermeable membranes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Engineering Biomaterials for Myocardial Regeneration and Repair

Augmentation of myocardial tissue regeneration processes in injured hearts represents a major challenge in cardiology as current therapeutic approaches do not regenerate the myocardial tissue. Herein, we describe three emerging biomaterial-based strategies to treat heart injuries, as stand-alone therapies or in combination with regeneration-inducing signals and/or cells. One strategy relies on the injection of acellular biomaterials, at an early stage after myocardial infarction (MI); these materials replace the damaged extracellular matrix, maintain left ventricular (LV) thickness, and prevent the negative LV remodeling and progression to heart failure. This strategy is currently being investigated in advanced clinical trials using a novel alginate-based biomaterial. The second strategy employs engineered biomaterials, spatially presenting multiple regeneration-inducing factors, to promote myocardial tissue regeneration in chronic infarcted hearts. The recent attempts to understand the “natural capacity” of the myocardium to heal and the factors involved in these processes are promising to advance this therapy. The third strategy applies biomaterials to promote cardiac tissue engineering and create a pre-vascularized cardiac patch to replace damaged or missing myocardial tissue. Collectively, this review emphasizes the increasing importance of biomaterials in cardiology, describes the engineering schemes used in their fabrication, and their implementation in various therapeutic strategies aimed at cardiac tissue regeneration and repair. It mainly highlights the contribution of our group in developing these strategies.     

Stress-induced structural changes in La-doped BiFeO3–PbTiO3 high-temperature piezoceramics

High-temperature piezoelectric polycrystalline ceramics of the system (1 ? x)(Bi_1?yLa_y)FeO₃-xPbTiO₃ (BF–PT), which are mixed phase in their consolidated state, have been investigated by in situ neutron diffraction during the application of uniaxial compressive stress. It is suggested that the achievable strain in BF–PT is largely generated by straining of the rhombohedral phase. The results of the neutron diffraction measurements are compared and discussed with respect to the measured macroscopic ferroelastic constitutive behavior for various compositions of BF–PT.