Obtaining high catalytic activity and cycling stability of electrodes play a crucial role in vanadium redox flow batteries (VRFBs). However, some limitations, such as cost and required multiple synthesis procedures force us as an alternative solution; polypyrrole–sulfur-doped graphenes (PPy–SGs) are synthesized with a user-friendly electrochemical method and applied as a positive electrode for VRFB for the first time in the literature. Polypyrrole and sulfur-doped graphenes are formed on the graphite electrodes simultaneously in a 0.001 M pyrrole and 1.0 M H2SO4 solution at room temperature by a single-step cyclic voltammetry (CV) process. The electrode surface modification parameters such as the amount of S-doping, defect, and functionality rate of polymers and graphene are controlled by changing the cycle numbers at the scanned in a specific potential range. FTIR, Raman, XPS, SEM, and CV methods show the formation of PPy and sulfur-doped graphene layers on graphite electrode surfaces. The effects of PPy–SGs were investigated in VRFB for VO+2/VO2+ redox reactions. The electrochemical measurements of the PPy–SGs are carried out by CV and electrochemical impedance spectroscopy (EIS) analysis. According to CV results, PPy–SG20 demonstrates the best performance as a positive electrode material of the VRFB. This can be attributed to the significant improvement in the electrochemical kinetics by polypyrrole decorating graphene and enhancing active sites.
In this paper, microwave heating treatment process and fluorine addition over Co-B-F catalyst was applied to produce hydrogen via the hydrolysis of NaBH4. The effects of microwave heating treatment time, microwave heating treatment power, microwave inert gases and temperature on the catalyst were studied. X-ray absorption spectrometer, scanning electron microscopy coupled to energy-dispersive spectroscopy, nitrogen adsorption analyzer and infrared spectrometer were performed for the chemical characterization of the catalysts. It was found that Co-B-F and microwave-treated Co-B-F catalysts exhibited excellent catalytic activity to produce hydrogen. The rates of the maximum hydrogen production for untreated and microwave-treated Co-B-F catalysts are 1868 and 3400?mL/g/min, respectively. 相似文献
Chronic wounds are a major health concern and they affect the lives of more than 25 million people in the United States. They are susceptible to infection and are the leading cause of nontraumatic limb amputations worldwide. The wound environment is dynamic, but their healing rate can be enhanced by administration of therapies at the right time. This approach requires real‐time monitoring of the wound environment with on‐demand drug delivery in a closed‐loop manner. In this paper, a smart and automated flexible wound dressing with temperature and pH sensors integrated onto flexible bandages that monitor wound status in real‐time to address this unmet medical need is presented. Moreover, a stimuli‐responsive drug releasing system comprising of a hydrogel loaded with thermo‐responsive drug carriers and an electronically controlled flexible heater is also integrated into the wound dressing to release the drugs on‐demand. The dressing is equipped with a microcontroller to process the data measured by the sensors and to program the drug release protocol for individualized treatment. This flexible smart wound dressing has the potential to significantly impact the treatment of chronic wounds. 相似文献
This article introduces a new method entitled multi-objective feasibility enhanced partical swarm optimization (MOFEPSO), to handle highly-constrained multi-objective optimization problems. MOFEPSO, which is based on the particle swarm optimization technique, employs repositories of non-dominated and feasible positions (or solutions) to guide feasible particle flight. Unlike its counterparts, MOFEPSO does not require any feasible solutions in the initialized swarm. Additionally, objective functions are not assessed for infeasible particles. Such particles can only fly along sensitive directions, and particles are not allowed to move to a position where any previously satisfied constraints become violated. These unique features help MOFEPSO gradually increase the overall feasibility of the swarm and to finally attain the optimal solution. In this study, multi-objective versions of a classical gear-train optimization problem are also described. For the given problems, the article comparatively evaluates the performance of MOFEPSO against several popular optimization algorithms found in the literature. 相似文献
A stereolithography‐based bioprinting platform for multimaterial fabrication of heterogeneous hydrogel constructs is presented. Dynamic patterning by a digital micromirror device, synchronized by a moving stage and a microfluidic device containing four on/off pneumatic valves, is used to create 3D constructs. The novel microfluidic device is capable of fast switching between different (cell‐loaded) hydrogel bioinks, to achieve layer‐by‐layer multimaterial bioprinting. Compared to conventional stereolithography‐based bioprinters, the system provides the unique advantage of multimaterial fabrication capability at high spatial resolution. To demonstrate the multimaterial capacity of this system, a variety of hydrogel constructs are generated, including those based on poly(ethylene glycol) diacrylate (PEGDA) and gelatin methacryloyl (GelMA). The biocompatibility of this system is validated by introducing cell‐laden GelMA into the microfluidic device and fabricating cellularized constructs. A pattern of a PEGDA frame and three different concentrations of GelMA, loaded with vascular endothelial growth factor, are further assessed for its neovascularization potential in a rat model. The proposed system provides a robust platform for bioprinting of high‐fidelity multimaterial microstructures on demand for applications in tissue engineering, regenerative medicine, and biosensing, which are otherwise not readily achievable at high speed with conventional stereolithographic biofabrication platforms. 相似文献
Introduction Not only anemia, but also erythropoiesis stimulating agent (ESA)s for treating anemia may adversely affect prognosis of chronic hemodialysis patients. Various features of naturally (with no ESA usage) nonanemic patients may be useful for defining several factors in the pathogenesis of anemia. Methods Data, retrieved from the European Clinical Database (EuCliD)‐Turkey on naturally nonanemic prevalent chronic hemodialysis patients (n: 201) were compared with their anemic (those who required ESA treatment) counterparts (n: 3948). Findings Mean hemoglobin values were 13.5 ± 0.8 and 11.5 ± 0.9 g/dL in nonanemic and anemic patients, respectively (P < 0.001). Nonanemia status was associated with younger age, male gender, longer dialysis vintage, nondiabetic status, more frequent hepatitis‐C virus seropositivity and more frequent arteriovenous fistula usage. Serum ferritin and CRP levels and urea reduction ratio were higher in ESA‐requiring patients. One (99%) and two (95.3%) years survival rates of the “naturally nonanemic” patients were superior as compared to anemics (91.0% and 82.6%, respectively), (P < 0.001). Discussion “Naturally nonanemic” status is associated with better survival in prevalent chronic hemodialysis patients; underlying mechanisms in this favorable outcome should be investigated by randomized controlled trials including large number of patients. 相似文献
The percutaneous catheterization of central veins is increasingly used in nephrological practice as a temporary or permanent vascular access. Some mechanical complications may occur during insertion of catheter such as misplaced catheter. In this report, we present a case that was misplaced the catheter in esophagus and to analyze the reason of catheter malposition during percutaneous tunneled hemodialysis catheter insertion. 相似文献
The paper examines the validation of prediction models of acceptance of academic placement offers by students in the context of international applications at a large metropolitan Australian University using data mining techniques. Earlier works in enrolment management have examined various classification problems such as inquiry to enrol, persistence and graduation. The data and settings from different institutions are often different, which implies that in order to find out which models and techniques are applicable at a given university, the dataset from that university needs to be used in the validation effort. The whole dataset from the Australian university comprised 24,283 offers made to international applicants from the year 2008 to 2013. Every year around 2000–2500 new international students who accept offers of academic placement commence their studies. The important predictors for the acceptance of offers were as follows: the chosen course and faculty, whether the student was awarded any form of scholarship, and also the visa assessment level of the country by the immigration department. Prediction models were developed using a number of classification methods such as logistic regression, Naïve Bayes, decision trees, support vector machines, random forests, k-nearest neighbour, neural networks and their performances compared. Overall, the neural network prediction model with a single hidden layer produced the best result. 相似文献
Recent technological advances have motivated large-scale deployment of RFID systems. However, a number of critical design issues relating to efficient detection of tags remain unresolved. In this paper, we address three important problems associated with tag detection in RFID systems: (i) accurately detecting RFID tags in the presence of reader interference (reader collision avoidance problem); (ii) eliminating redundant tag reports by multiple readers (optimal tag reporting problem); and (iii) minimizing redundant reports from multiple readers by identifying a minimal set of readers that cover all tags present in the system (optimal tag coverage problem). The underlying difficulties associated with these problems arise from the lack of collision detection mechanisms, the potential inability of RFID readers to relay packets generated by other readers, and severe resource constraints on RFID tags. In this paper we present a randomized, distributed and localized Reader Collision Avoidance (RCA) algorithm and provide detailed probabilistic analysis to establish the accuracy and the efficiency of this algorithm. Then, we prove that the optimal tag coverage problem is NP-hard even with global knowledge of reader and tag locations. We develop a distributed and localized Redundant Reader Elimination (RRE) algorithm, that efficiently identifies redundant readers and avoids redundant reporting by multiple readers. In addition to rigorous analysis of performance and accuracy, we provide results from elaborate simulations for a wide range of system parameters, demonstrating the correctness and efficiency of the proposed algorithms under various scenarios. 相似文献
Reduced machining time and increased accuracy for a sculptured surface are both very important when producing complicated
parts, so, the step-size and tool-path interval are essential components in high-speed and high-resolution machining. If they
are too small, the machining time will increase, whereas if they are too large, rough surfaces will result. In particular,
the machining time, which is a key factor in high-speed machining, is affected by the tool-path interval more than the step
size. The present paper introduces a ‘system software’ developed to reduce machining time and increased accuracy for a sculptured
surface with Non-Uniform Rational B-Spline (NURBS) patches. The system is mainly based on a new and a powerful artificial
intelligence (AI) tool, called artificial immune systems (AIS). It is implemented using C programming language on a PC. It can be used as stand alone system or as the integrated module
of a CNC machine tool. With the use of AIS, the impact and power of AI techniques have been reflected on the performance of the tool path optimization system. The methodology
of the developed tool path optimization system is illustrated with practical examples in this paper. 相似文献