Encoder based online motion planning and feedback control of redundant manipulators

This paper proposes and investigates an online motion planning and feedback control (OMPFC) scheme for redundant manipulators via techniques of quadratic programming and rotary encoder. The proposed OMPFC scheme is performed on a planar six degrees-of-freedom (DOF) manipulator. This robotic scheme incorporates the feedback of task-space position error. The joint state is obtained in real time via rotary encoders equipped on the physical manipulator. The original scheme is finally reformulated as a unified quadratic program (QP). The QP is solved online during the joint motion by employing an efficient numerical algorithm. Simulation and experimental results validate the physical realizability, online property, and efficacy of the proposed OMPFC scheme (including the employed numerical algorithm).     

Multidisciplinary methods (co-precipitation,ultrasonic, microwave,reflux and hydrothermal) for synthesis and characterization of CaMn3O6 nanostructures and its photocatalytic water splitting performance

Production of hydrogen and oxygen from water splitting reaction under visible light is a simple method for conversion of solar-to-hydrogen energy and it is a hopeful clean and renewable method for H₂ fuel generation. However, there is still a lack of potential materials with significant activity under visible light. Because of safety, chemical inertness, low cost, stability and other characteristics, transition metal oxide semiconductors have been widely applied as photocatalysts for hydrogen generation. Albeit, wide usage of semiconductor photocatalysts were prevented by its inability to exploit solar energy of visible region. Here we show synthesis of a nano-sized mixed metal oxide (MMO) Ca₃MnO₆ through wet-chemistry methods such as co-precipitation, ultrasonic, microwave, reflux, and hydrothermal methods. The nano-sized Ca₃MnO₆ has initially selected based on morphology and respective particle diameters. The selected sample shows a well-defined single crystal, free from any impurities, complete structural formation, and a band gap energy (E_g) of around 5.3 eV. The best product synthesized in ultrasonic method which shows the best morphology, purity and the highest efficiency for splitting of water to hydrogen and oxygen. Irrespective of preparation methods and morphologies, all samples split water into hydrogen and oxygen, as confirmed from their respective photocatalytic analysis. When the selected sample combined with (NH₄)₂Ce(NO₃)₆, the single-crystal Ca₃MnO₆ nanoparticles split water into hydrogen and oxygen more efficiently under visible light. Our findings demonstrate the importance of nanostructured Ca₃MnO₆ single-crystal photocatalysts in solar water splitting.     

Understanding mass and charge transports to create anion-ionomer-free high-performance alkaline direct formate fuel cells

The disadvantage of anion ionomer that possesses low hydroxide conductivity, and thermal and chemical instability hinders the development of the high-performance anion-exchange membrane direct liquid fuel cells. Instead of adding additional base and synthesizing high-conductivity ionomer material, by gaining insight into species transports, herein, we propose an anion-ionomer-free anion-exchange membrane direct formate fuel cell (AEM DFFC). Experimental result reveals that this conceptual anion-ionomer-free AEM DFFC can operate stably within a 6-h constant-current discharge at 10 mA cm⁻², mainly because formate hydrolysis renders a high OH⁻ conductivity. It was also found that the anion-ionomer-free AEM DFFC yields a peak power density as high as 41 mW cm⁻² at 40 °C, 40% higher than that of the conventional quaternary ammonia polysulfone anion-ionomer AEM DFFC. This can be attributed to the fact that the OH⁻-containing formate solution facilitates the mass and charge transports, thereby enlarging the triple-phase boundary for both anodic formate oxidation reaction and cathodic oxygen reduction reaction.     

Prediction of the impact of network switch utilization on application performance via active measurement

Although one of the key characteristics of High Performance Computing (HPC) infrastructures are their fast interconnecting networks, the increasingly large computational capacity of HPC nodes and the subsequent growth of data exchanges between them constitute a potential performance bottleneck. To achieve high performance in parallel executions despite network limitations, application developers require tools to measure their codes’ network utilization and to correlate the network’s communication capacity with the performance of their applications.This paper presents a new methodology to measure and understand network behavior. The approach is based in two different techniques that inject extra network communication. The first technique aims to measure the fraction of the network that is utilized by a software component (an application or an individual task) to determine the existence and severity of network contention. The second injects large amounts of network traffic to study how applications behave on less capable or fully utilized networks. The measurements obtained by these techniques are combined to predict the performance slowdown suffered by a particular software component when it shares the network with others. Predictions are obtained by considering several training sets that use raw data from the two measurement techniques. The sensitivity of the training set size is evaluated by considering 12 different scenarios. Our results find the optimum training set size to be around 200 training points. When optimal data sets are used, the proposed methodology provides predictions with an average error of 9.6% considering 36 scenarios.     

Influence of cooling rate and annealing on the DSC Tg of an epoxy resin

Glass transition temperature (Tg) is a key epoxy property and often being monitored in the production by the differential scanning calorimeter (DSC) method in the printed circuit board (PCB) industry. The dual-effect of cooling rate and annealing on the endothermic peak in the DSC scan of CE-688 epoxy resin plays a big role in the DSC Tg evaluation. An improved DSC program was developed in order to minimize/eliminate the influence of endothermic peak. Meanwhile, the curing pressure also shows distinct effect on the Tg of the epoxy resin.     

Violence detection using Oriented VIolent Flows

Nowadays, with so many surveillance cameras having been installed, the market demand for intelligent violence detection is continuously growing, while it is still a challenging topic in research area. Therefore, we attempt to make some improvements of existing violence detectors. The primary contributions of this paper are two-fold. Firstly, a novel feature extraction method named Oriented VIolent Flows (OViF), which takes full advantage of the motion magnitude change information in statistical motion orientations, is proposed for practical violence detection in videos. The comparison of OViF and baseline approaches on two public databases demonstrates the efficiency of the proposed method. Secondly, feature combination and multi-classifier combination strategies are adopted and excellent results are obtained. Experimental results show that using combined features with AdaBoost+Linear-SVM achieves improved performance over the state-of-the-art on the Violent-Flows benchmark.     

Development of a practical foolproof system using ultrasonic local positioning

The objective of this research is to develop a prototype for practical foolproof system which can be used in manual assembly processes. For this purpose, a high-performance and low-cost ultrasonic system is proposed to measure 3D positions of an indoor mobile object. Composed of an ultrasonic sender and a receiver, the system employs ultrasonic time-of-flight (TOF) and trilateration to estimate the positions of the object with an accuracy of few centimeters. To calculate three TOFs, ultrasonic signals are processed full-digitally with a low-cost FPGA, which provides high design flexibility keeping both high performance and low noise. Proposed system is autonomous, so there is no need of an external PC and the system development cost becomes low. As an improved thresholding method to calculate the TOFs, this paper proposes a debounce module, designed in the FPGA, to remove the pulse noises generated during the thresholding. The resulting time delay from the debounce is compensated by a microprocessor for calculating actual TOFs. Lastly, the positions of the mobile object are calculated from the TOFs values by trilateration in the microprocessor. In order to remove measurement noises, both moving average filters and Kalman filters are adopted in calculating the TOFs and positions.     

A mobile crowd sensing ecosystem enabled by CUPUS: Cloud-based publish/subscribe middleware for the Internet of Things

Mobile crowd sensing (MCS) is a novel class of mobile Internet of Things (IoT) applications for community sensing where sensors and mobile devices jointly collect and share data of interest to observe phenomena over a large geographic area. The inherent device mobility and high sensing frequency has the capacity to produce dense and rich spatiotemporal information about our environment, but also creates new challenges due to device dynamicity and energy constraints, as well as large volumes of generated raw sensor data which need to be processed and analyzed to extract useful information for end users. The paper presents an ecosystem for mobile crowd sensing which relies on the CloUd-based PUblish/Subscribe middleware (CUPUS) to acquire sensor data from mobile devices in a flexible and energy-efficient manner and to perform near real-time processing of Big Data streams. CUPUS has unique features compared to other MCS platforms: It enables management of mobile sensor resources within the cloud, supports filtering and aggregation of sensor data on mobile devices prior to its transmission into the cloud based on global data requirements, and can push information of interest from the cloud to user devices in near real-time. We present our experience with implementation and deployment of an MCS application for air quality monitoring built on top of the CUPUS middleware. Our experimental evaluation shows that CUPUS offers scalable processing performance, both on mobile devices and within the cloud, while its data propagation delay is mainly affected by transmission delay on wireless links.     

Image authentication and tamper localization based on relative difference between DCT coefficient and its estimated value

Digital images are increasingly transmitted over non-secure channels such as Internet, therefore image authentication techniques have recently gained great attention due to their importance for a large number of multimedia applications. To protect the authenticity of images, several approaches have been proposed. These approaches include conventional cryptography, semi-fragile watermarking and digital signatures. In this paper, we propose two techniques of the same type based on what we call characteristic data digest. Both techniques can blindly detect and localize malicious tampering, while maintaining reasonable tolerance to conventional content-preserving manipulations. The characteristic data is derived from the relative difference between each pair of selected DCT coefficient, AC for one technique and DC for another technique, in a central block and its counterpart estimated by the center block and its adjacent blocks. In order to maintain the relative difference relationship when the image undergoes legitimate processing, we make a pre-compensation for the coefficients. Experimental results show that our techniques are significantly superior to semi-fragile techniques under the condition of the same image fidelity, especially in tolerance range of legitimate processing, and/or the ability to detect and localize the tampered area. Due to the simplicity of the algorithms, our techniques can be used in video frame authentication, and even other digital media. In addition, this kind of proposed techniques can be extended to use other characteristic data, such as high-level moment, statistical data of images, and so on.

     

Synthesis,electrochemical and electrochromic properties of novel 2,4,6-Tri(pyridine-4-yl)pyridilium derivatives

Four star-shaped like fused heterocyclic compounds multi-electrochromic materials 2,4,6-Tri(pyridine-4-yl)pyridilium derivatives (TPPDs) were successfully synthesized and characterized by NMR, Solid IR spectra, APCI-MS, and UV–vis spectroscopy. The electrochemical properties, electrochromic behavior, electro-optical properties, and electrochromic mechanism were investigated by thermogravimetric analysis, cyclic voltammetry and UV–vis absorption spectra. Electrochromic devices based on these compounds were fabricated with an active area of 3 cm × 4 cm and their electrochromic performances were further studied. It was found the ECDs presented a stable as well as multicolor electrochromic change from colorless to blue, then violet-blue and finally black-blue between 0 V and +4.0 V. In addition, the prepared electrochromic materials had high coloration efficiency, low switching time, and nice redox stability. This type of multi-electrochromic materials would thus be promising candidates for applications in electrochromic devices.