Improvement of Power System Stability by Using New Switching Technique in Bridge-type Fault Current Limiter

The bridge-type fault current limiter has the capability of controlling the fault current by controlling the DC reactor current. This fault current limiter is mainly composed of a diode bridge rectifier and a DC reactor. To achieve this capability, a resistor parallel with a semiconductor switch has been used in series with a DC reactor. For this fault current limiter, a control scheme is proposed that uses the DC reactor current as a control variable to improve transient stability of the model power system without measuring any parameters of system. In this article, an analytical and simulation study was conducted on a one-machine infinite-bus system including a bridge-type fault current limiter and the proposed control scheme. Simulation results show that by controlling the turn-on and turn-off times of the switch, i.e., the switching technique, the proposed fault current limiter can not only limit the fault current but also absorb the accelerating energy of the generator, thereby improving power system transient stability. The rotor velocity, maximum output power of the generator, and critical fault clearing time are studied in this article to evaluate the effects of the proposed fault current limiter on power system transient stability.     

Thermal Buckling of Piezolaminated Plates Subjected to Different Loading Conditions

A thermal buckling analysis is presented for simply supported rectangular laminated composite plates that are covered with top and bottom piezoelectric actuators, and subjected to the combined action of thermal load and constant applied actuator voltage. The thermomechanical properties of composite and piezoelectric materials are assumed to be linear functions of the temperature. The formulations of the equations are based on the higher-order laminated plate theory of Reddy and using the Sanders nonlinear kinematic relations. The closed-form solutions for the buckling temperature are obtained through the Galerkin procedure and solving the resultant eigenvalue problem, which are convenient to be used in engineering design applications. Numerical examples are presented to verify the proposed method. The effects of the plate geometry, fiber orientation in composite layers, lay-up configuration, different utilized piezoelectric materials, temperature dependency of material properties, thermal conductivity, and energy generation on the buckling load are investigated.     

Learning active fusion of multiple experts' decisions: an attention-based approach

In this letter, we propose a learning system, active decision fusion learning (ADFL), for active fusion of decisions. Each decision maker, referred to as a local decision maker, provides its suggestion in the form of a probability distribution over all possible decisions. The goal of the system is to learn the active sequential selection of the local decision makers in order to consult with and thus learn the final decision based on the consultations. These two learning tasks are formulated as learning a single sequential decision-making problem in the form of a Markov decision process (MDP), and a continuous reinforcement learning method is employed to solve it. The states of this MDP are decisions of the attended local decision makers, and the actions are either attending to a local decision maker or declaring final decisions. The learning system is punished for each consultation and wrong final decision and rewarded for correct final decisions. This results in minimizing the consultation and decision-making costs through learning a sequential consultation policy where the most informative local decision makers are consulted and the least informative, misleading, and redundant ones are left unattended. An important property of this policy is that it acts locally. This means that the system handles any nonuniformity in the local decision maker's expertise over the state space. This property has been exploited in the design of local experts. ADFL is tested on a set of classification tasks, where it outperforms two well-known classification methods, Adaboost and bagging, as well as three benchmark fusion algorithms: OWA, Borda count, and majority voting. In addition, the effect of local experts design strategy on the performance of ADFL is studied, and some guidelines for the design of local experts are provided. Moreover, evaluating ADFL in some special cases proves that it is able to derive the maximum benefit from the informative local decision makers and to minimize attending to redundant ones.     

Optimal placement of PMUs to maintain network observability using a modified BPSO algorithm

This paper presents a novel approach to optimal placement of Phasor Measurement Units (PMUs) for state estimation. At first, an optimal measurement set is determined to achieve full network observability during normal conditions, i.e. no PMU failure or transmission line outage. Then, in order to consider contingency conditions, the derived scheme in normal conditions is modified to maintain network observability after any PMU loss or a single transmission line outage. Observability analysis is carried out using topological observability rules. A new rule is added that can decrease the number of required PMUs for complete system observability. A modified Binary Particle Swarm Optimization (BPSO) algorithm is used as an optimization tool to obtain the minimal number of PMUs and their corresponding locations while satisfying associated constraint. Numerical results on different IEEE test systems are presented to demonstrate the effectiveness of the proposed approach.     

Patterned wafer inspection by high resolution spectral estimation techniques

A new self-reference signal processing technique is proposed for detecting the location of irregularities and defects in a periodic two-dimensional signal or image. Using high-resolution spectral estimation algorithms, the proposed technique first extracts the period and structure of repeated patterns from the image. Then a defect-free reference image for comparison with the actual image is produced. Since the technique acquires all the information needed from a single image (in contrast to most existing methods), there is no need for a database image, a scaling or alignment procedure or any a priori knowledge about the repetition period of the patterns.Potential application fields for the proposed method range from the area of wafer and mask defect inspection, which includes inspection of memory chips, shift registers, switched capacitors, CCD arrays, and LCD displays to other areas that deal with repeated structures, such as crystallography. Some results of applying the proposed technique to real images from microlithography are presented.     

Direct and Residual Effects of Water Deficit Stress,Different Sources of Silicon and Plant-Growth Promoting Bacteria on Silicon Fractions in the Soil

Silicon - Silicon (Si) and plant growth promoting bacteria (PGPB) can effectively reduce the negative effects of water deficit stress and augment plant growth. Few studies have simultaneously...     

MXene Free Standing Films: Unlocking the Impact of Flake Sizes in Microwave Resonant Structures in Humid Environments

Microwave communication devices necessitate elements with high electrical conductivity, a property which was traditionally found in metals (e.g., copper). However, in applications such as satellite communications, metals prevent the payload from achieving lightweight and flexible characteristics. Here, we demonstrate the development of MXene film microwave resonators, leveraging MXene's high electrical conductivity and unique mechanical properties. To investigate resonant performance in humid conditions and study the effects of MXene's processing and treatment, MXene films with different flake sizes are prepared and exposed to cyclic humidity. For the large- and small-flake Ti₃C₂ MXene films in cyclic humidity, the large-flake film demonstrates higher electrical conductivity, higher resonance quality factor (150 and 35 as unloaded, and loaded), and less fluctuation of performance (≈1.7% total shift in resonance frequency). Further, by implementing MXene films of two different diameters, the correlation between film size and resonant frequency is demonstrated. By introducing an active resonant configuration, the effect of MXene degradation and microwave losses can be compensated. This active feedback loop demonstrates a ≈300 times increase in the quality factor of MXene resonators. As a building block for terrestrial and satellite communication modules, MXene resonators potentiate the replacement of metals in achieving unique electrical and mechanical properties.     

Impacts of alginate–basil seed mucilage–prebiotic microencapsulation on the survival rate of the potential probiotic Leuconostoc mesenteroides ABRIINW.N18 in yogurt

We aimed at improving probiotic survival, stability and release in digestive settings during yogurt storage. Alginate–basil seed mucilage was formulated with various concentrations of prebiotics (inulin, fructooligosaccharides and fenugreek) and selected for microencapsulation. When compared with uncapsulated probiotic cells, all examined formulations had high encapsulation effectiveness of over 98.2% and a viable potential probiotic cell survival (62%) when studied under simulated settings. These findings indicate the use of home-grown-based gums such as basil seed adhesive and fenugreek in combination with alginate are good media for probiotic encapsulation.     

Toward “E-Ring-Free” Lamellarin Analogues: Synthesis and Preliminary Biological Evaluation

Since the discovery of anticancer properties of a naturally occurring hexacyclic marine alkaloid Lamellarin D, the attempts have been made to prepare its synthetic analogues and elucidate the effects of each structural component on their activity profile. While F-ring-free, A-ring-free and B-ring-open lamellarins are known, E-ring-free analogues have never been investigated. In this work, we developed a facile and straightforward synthetic method toward E-ring-free lamellarin analogues based on the [3+2]-cycloaddition. For the first time, we prepared several pentacyclic lamellarin analogues without E-ring in their structure and assessed their cytotoxicity in a panel of cancer cell lines in comparison with several hexacyclic lamellarins. E-ring-free lamellarins were devoid of cytotoxicity due to their poor solubility in cellular environment.