Low-bandwidth communication channels are used to support the information exchange between a microgrid centralized controller and local controllers in the secondary frequency control of an islanded ...microgrid. However, the impact of the inherent time delay in these communication channels on the microgrid performance has not been taken into account when the secondary frequency controller is designed. This paper investigates the effect of the communication delays on the secondary frequency control of an islanded microgrid with multiple distributed generators. A small-signal model-based method is introduced for the microgrid to find delay margins below which the microgrid can remain stable. By performing a series of trial studies, the relationships between secondary frequency control gains and delay margins are obtained. A gain scheduling approach is also proposed to compensate the effect of the communication delay on the secondary frequency control. Results from the Canadian urban distribution system have verified that communication delays can adversely affect the microgrid secondary frequency control, and the proposed gain scheduling approach can improve the robustness of the microgrid secondary frequency controller to communication delays.
Sosyal medya kullanımı gün geçtikçe artmakta ve beraberinde birçok yeni problemi de getirmektedir. Kişilerin düşünce, duygu ve fikirlerini kolaylıkla paylaşabildiği bu ortamlarda aşağılayıcı ve ...rencide edici saldırılarda bulunan hesaplara son zamanlarda sıkça rastlanmaya başlanmıştır. Siber zorbalık (cyberbullying) olarak adlandırılan bu durum ve eylemi yapan trol hesapların insanların bireysel ve sosyal yaşantılarına verdiği zararların engellenmesi bir ihtiyaç haline gelmiştir. Bu tür kullanıcıların mesajları insanları rahatsız etmekte ve sayıları takip edilemeyecek miktarlara ulaştığı durumlarda yazılımlar ile tespit edilmesi, gerektiğinde engellenmesi ve sınırlandırılması gerekmektedir. Biz bu çalışma ile Twitter üzerinde trol davranışları sergileyen kullanıcı hesaplarını tespit etmek için makine öğrenmesi yöntemlerini kullandık. Support Vector Machine (SVM), Logistic Regression (LR) ve Random Forest Regression (RFR) ile Twitter üzerinden topladığımız veriler ile trol kullanıcıların mesajları üzerinden çıkardığımız özellikler (features) ile kapsamlı deneyler gerçekleştirdik. Elde ettiğimiz sonuçlarda %93.93’lere varan oranlarda trol hesaplarını tespit etmeyi ve engellemeyi başardık.
To enable the broad adoption of wearable robotic exoskeletons in medical and industrial settings, it is crucial they can adaptively support large repertoires of movements. We propose a new ...human-machine interface to simultaneously drive bilateral ankle exoskeletons during a range of "unseen" walking conditions and transitions that were not used for establishing the control interface. The proposed approach used person-specific neuromechanical models to estimate biological ankle joint torques in real-time from measured electromyograms (EMGS) and joint angles. We call this "neuromechanical model-based control" (NMBC). NMBC enabled six individuals to voluntarily control a bilateral ankle exoskeleton across six walking conditions, including all intermediate transitions, i.e., two walking speeds, each performed at three ground elevations. A single subject case-study was carried out on a dexterous locomotion tasks involving moonwalking. NMBC always enabled reducing biological ankle torques, as well as eight ankle muscle EMGs both within (22% torque;12% EMG) and between walking conditions (24% torque; 14% EMG) when compared to non-assisted conditions. Torque and EMG reductions in novel walking conditions indicated that the exoskeleton operated symbiotically, as an exomuscle controlled by the operator.s neuromuscular system. This opens new avenues for the systematic adoption of wearable robots as part of out-of-the-lab medical and occupational settings.
•Zebra mussels were exposed to four toxicants independently and as binary mixtures.•Each mixture was assessed for synergistic, antagonistic, or additive interaction.•Mixtures of Clam-Trol CT-2 or ...EarthTec QZ with niclosamide were most synergistic.•Mixtures including potassium chloride were found to be additive to antagonistic.•Mixtures hold promise for more effective zebra mussel management.
Researchers most often focus on individual toxicants when identifying effective chemical control agents for aquatic invasive species; however, toxicant mixtures may elicit synergistic effects. Synergistic effects may decrease required concentrations and shorten exposure durations for treatments. We investigated four toxicants (EarthTec QZ, Clam-Trol CT-2, niclosamide, and potassium chloride) that have been considered to control invasive zebra mussels (Dreissena polymorpha Pallas, 1771). We determined the toxicity of binary mixtures for five different mixture ratios to adult mussels. We compared our observations to predictions made with concentration addition and independent action paradigms, as based on the dose-response relationships of each individual toxicant. We calculated the model deviation ratio for each combination at the LC50 and LC90 and identified three possible interactions: synergy, antagonism, and additivity. We found that mixtures of niclosamide and Clam-Trol CT-2 were the most synergistic while mixtures that included potassium chloride were largely additive to antagonistic. The use of synergistic combinations has potential to decrease the overall volume and concentration of individual toxicants required for dreissenid mussel treatments, thereby decreasing cost.
The task space contouring performance is significant for the machining accuracy of industrial robotic manipulators, but the contouring control of end-effector which is important in the industry has ...received scant attention. In this letter, a novel task space contouring error estimation and control scheme is developed to address the end-effector precision contouring problem of robotic manipulators. In order to quantify manipulator contouring performance, a 6-DOF synchronized contouring error is defined in the task space. Based on the definition, an optimization problem is constructed and solved to achieve high precision contouring error estimation. The proposed method shows excellent estimation accuracy even under extreme contouring conditions, which is the prerequisite for accurate contouring control. Then the solved contouring error is iteratively compensated into the end-effector reference in a feedforward way to achieve contouring error reduction. The effectiveness of the proposed method is derived theoretically under the assumption of small error and nonsingularity. Comparative experiments are conducted on an industrial manipulator. Quantitative results on different extreme trajectories demonstrate that the proposed control scheme not only has advantages in control stability and implementation simplicity, but also outperforms traditional joint space iterative learning control and cross-coupled iterative learning control on the end-effector contouring accuracy. The proposed method actually provides a practical solution to high-precision contouring applications for industrial manipulators.
Device-to-device (D2D) technology has been widely used to address the mobile traffic explosion problem due to its ability of direct communications between proximal devices. In practice, the available ...spectrum is often limited. With the rapid increase of D2D users and cellular users, the efficiency of resource allocation would be dramatically reduced. To overcome the above limitations, this paper proposes a spiking mean field reinforcement learning framework (S-MFRL) to optimize the resource allocation of D2D networks. Firstly, spiking neural network (SNN) cooperated with deep reinforcement learning is trained for channel selection and power control. Secondly, spatio-temporal backpropagation is adopted to accelerate the SNN training. Thirdly, mean field multi-agent reinforcement learning (MFRL) is applied to approximate interactions among D2D users. By this means, the optimization process of resource allocation becomes tractable as the number of D2D users increases, which solves the problem of exponential growth of user interactions. Two algorithms are implemented under the S-MFRL framework by integrating MFRL into spiking actor-critic (S-AC) and spiking proximal policy optimization (S-PPO), which are named S-MFAC and S-MFPPO, respectively. Experimental results show that our designed S-MFAC and S-MFPPO outperform both AC and PPO in terms of convergence rate, access rate, time-averaged overall throughput, and collision probability. Besides, further simulations have been conducted to verify the effectiveness of the proposed algorithm in the case of larger action space and hundreds of D2D users.
The final step of photosynthetic electron transfer from ferredoxin to NADP+ is catalysed by ferredoxin: NADP+ oxidoreductase (FNR). Localization of the FNR on the chloroplastic membrane is attained ...both, by the dynamic interaction via thylakoid rhodanese-like protein (TROL) and with the lasting interaction with the Tic62 protein. In such interactions, FNR forms a homodimeric complex in the presence of the FNR interacting domain from either TROL or Tic62 protein. Starting from crystal structure of FNR homodimeric complex, various systems consisting of the FNR proteins and/or the FNR binding domains from TROL and Tic62 proteins at the different pH were subjected to molecular dynamics simulations. Results of simulations enabled identification of the most important regions of non-covalent interactions between involved proteins and their detailed mapping. In silico mutations were introduced and simulated to investigate their influence to the structural properties, dynamics and stability of the protein complex. The interface regions between the FNR proteins, consisting mostly of hydrophobic interactions, were identified and shown to be under strong influence of the ITEPs conserved prolines and serines (PPSS region). Five functionally important hydrogen bond networks that span over the major structural elements of the involved proteins were identified and characterized. Three of them show pH dependence and might serve as the pH regulated switches for conformational changes of the protein complex. Presented computational results provide strong base for in vitro experiments on TROL, Tic62 and FNR proteins that should enable understanding of their behavior in the fluctuating environmental conditions.
Display omitted
•Molecular dynamics (MD) simulations of ferredoxin:NADP + oxidoreductase (FNR).•PH dependence of FNR complex formations with ITEP domain.•Detailed analysis of non-covalent interactions of FNR with TROL and Tic62 proteins.•Identification of five functionally important hydrogen bond networks.•Three pH dependent H-bond networks that migh be switches for conformational changes.
Robot-assisted minimally invasive surgery (MIS) has received increasing attention, both in the academic field and clinical operation. Master/slave control is the most widely adopted manipulation mode ...for surgical robots. Thus, sensing the force of the surgical instruments located at the end of the slave manipulator through the main manipulator is critical to the operation. This study mainly addressed the force detection of the surgical instrument and force feedback control of the serial surgical robotic arm. A measurement device was developed to record the tool end force from the slave manipulator. An elastic element with an orthogonal beam structure was designed to sense the strain induced by force interactions. The relationship between the acting force and the output voltage was obtained through experiment, and the three-dimensional force output was decomposed using an extreme learning machine algorithm while considering the nonlinearity. The control of the force from the slave manipulator end was achieved. An impedance control strategy was adopted to restrict the force interaction amplitude. Modeling, simulation, and experimental verification were completed on the serial robotic manipulator platform along with virtual control in the MATLAB/Simulink software environment. The experimental results show that the measured force from the slave manipulator can provide feedback for impedance control with a delay of 0.15 s.
En Internet, el término trol hace referencia a una persona cuya intención es alterar las conversaciones de los demás con acciones provocativas, sin sentido u ofensivas. Tras una perspectiva general ...del origen del término y de la literatura científica relacionada con diferentes entornos, el artículo analiza los usos de la palabra y sus derivados dentro de un grupo de Facebook, La Gastrite di Shy. En particular, se centra en los contextos en los que tanto el insulto como acusación de trolling ocurren al mismo tiempo. Los resultados de la encuesta, correspondientes a un momento concreto de la actividad de la comunidad, confirman en su conjunto los resultados de los estudios sobre el tema: la acción y la percepción de los trolls son contextuales y difíciles de generalizar. Existe, en efecto, un uso del término que responde a la necesidad de delimitar los límites (ideológicos, lingüísticos, culturales) de un grupo, de reafirmar o regular sus criterios de inclusión y exclusión. La aparición de un troll, real o aparente, puede ser el efecto de una provocación evidente o bien un reflejo de las dificultades que encuentra una comunidad para manejar la disidencia.
PDF
