Advanced wound-rotor machine model with saturation and high-frequency effects

Nowadays, the doubly–fed induction generator (DFIG) is perhaps the most common type of generator used in onshore wind turbines. With the thriving development of wind energy, there is a high demand for precisely predicting the dynamic performance of the DFIG. Due to the involvement of power electronics, massive high–frequency harmonics are injected into the machine leading to high–frequency effects such as parasitic currents. As the core of DFIGs, the wound–rotor induction machine must be well modeled to capture these significant phenomena in the operation of wind turbines. However, the T–equivalent model, which is currently the most widely used model in machine dynamic studies and controller designs, is incapable to simulate machine behaviors in the high–frequency range. The aim of this research is to develop a novel model of a wound–rotor induction machine, which incorporates magnetic saturation of the main flux path and high–frequency effects. The model’s experimental parameterization procedure is described in detail. This consists of standstill frequency response tests, and a test for determining the machine’s magnetizing characteristic and turns ratio. Time–domain simulations are used to highlight the capabilities of the proposed model, and to compare its predictions with those of a classical model at both transient and steady states. The results show that the proposed model can better capture the dynamic performance with the consideration of magnetic saturation. What is more, the high–frequency current ripples, which are caused by common–mode ground currents can also be simulated in the proposed model

Experimental Study on Hygrothermal Deformation of External Thermal Insulation Cladding Systems with Glazed Hollow Bead

This research analyzes the thermal and strain behavior of external thermal insulation cladding systems (ETICS) with Glazed Hollow Beads (GHB) thermal insulation mortar under hygrothermal cycles weather test in order to measure its durability under extreme weather (i.e., sunlight and rain). Thermometers and strain gauges are placed into different wall layers to gather thermal and strain data and another instrument measures the crack dimensions after every 4 cycles. The results showed that the finishing coat shrank at early stage (elastic deformation) and then the finishing coat tends to expand and become damaged at later stage (plastic deformation). The deformation of insulation layer is similar to that of the finishing coat but its variation amplitude is smaller. Deformation of substrate expanded with heat and contracted with cold due to the small temperature variation. The length and width of cracks on the finishing coat grew as the experiment progressed but with a decreasing growth rate and the cracks stopped growing around 70 cycles

Parity Splitting and Polarized-Illumination Selection of Plasmonic Higher-Order Topological States

Topological states, originated from interactions between internal degree of freedoms (like spin and orbital) in each site and crystalline symmetries, offer a new paradigm to manipulate electrons and classical waves. The accessibility of spin degree of freedom has motivated much attention on spin-related topological physics. However, intriguing topological physics related to atomic-orbital parity, another binary degree of freedom, have not been exploited since accessing approaches on atomic orbitals are not well developed. Here, we theoretically discover spectral splitting of atomic-orbital-parity-dependent second-order topological states on a designer-plasmonic Kagome metasurface, and experimentally demonstrate it by exploiting the easy controllability of metaatoms. Unlike previous demonstrations on Hermitian higher-order topological insulators, radiative non-Hermicity of the metasurface enables far-field access into metaatomic-orbital-parity-dependent topological states with polarized illuminations. The atomic-orbital parity degree of freedom may generate more intriguing topological physics by interacting with different crystalline symmetries, and promise applications in polarization-multiplexing topological lasing and quantum emitters.Comment: 19 pages, 4 figure

Cobalt Nickel Boride Nanocomposite as High-Performance Anode Catalyst for Direct Borohydride Fuel Cell

Similar to MXene, MAB is a group of 2D ceramic/metallic boride materials which exhibits unique properties for various applications. However, these 2D sheets tend to stack and therefore lose their active surface area and functions. Herein, an amorphous cobalt nickel boride (Co–Ni–B) nanocomposite is prepared with a combination of 2D sheets and nanoparticles in the center to avoid agglomeration. This unique structure holds the 2D nano-sheets with massive surface area which contains numerous catalytic active sites. This nanocomposite is prepared as an electrocatalyst for borohydride electrooxidation reaction (BOR). It shows outstanding catalytic activity through improving the kinetic parameters of BH4− oxidation, owing to abundant ultrathin 2D structure on the surface, which provide free interspace and electroactive sites for charge/mass transport. The anode catalyst led to a 209 mW/cm2 maximum power density with high open circuit potential of 1.06 V at room temperature in a miniature direct borohydride fuel cell (DBFC). It also showed a great longevity of up to 45 h at an output power density of 64 mW/cm2, which is higher than the Co–B, Ni–B and PtRu/C. The cost reduction and prospective scale-up production of the Co–Ni–B catalyst are also addressed

The efficacy and neural mechanism of acupuncture therapy in the treatment of visceral hypersensitivity in irritable bowel syndrome

Irritable Bowel Syndrome (IBS) is a complex functional gastrointestinal disorder primarily characterized by chronic abdominal pain, bloating, and altered bowel habits. Chronic abdominal pain caused by visceral Hypersensitivity (VH) is the main reason why patients with IBS seek medication. Significant research effort has been devoted to the efficacy of acupuncture as a non-drug alternative therapy for visceral-hyperalgesia-induced IBS. Herein, we examined the central and peripheral analgesic mechanisms of acupuncture in IBS treatment. Acupuncture can improve inflammation and relieve pain by reducing 5-hydroxytryptamine and 5-HT3A receptor expression and increasing 5-HT4 receptor expression in peripheral intestinal sensory endings. Moreover, acupuncture can also activate the transient receptor potential vanillin 1 channel, block the activity of intestinal glial cells, and reduce the secretion of local pain-related neurotransmitters, thereby weakening peripheral sensitization. Moreover, by inhibiting the activation of N-methyl-D-aspartate receptor ion channels in the dorsal horn of the spinal cord and anterior cingulate cortex or releasing opioids, acupuncture can block excessive stimulation of abnormal pain signals in the brain and spinal cord. It can also stimulate glial cells (through the P2X7 and prokinetic protein pathways) to block VH pain perception and cognition. Furthermore, acupuncture can regulate the emotional components of IBS by targeting hypothalamic-pituitary-adrenal axis-related hormones and neurotransmitters via relevant brain nuclei, hence improving the IBS-induced VH response. These findings provide a scientific basis for acupuncture as an effective clinical adjuvant therapy for IBS pain

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Advanced wound-rotor machine model with saturation and high-frequency effects

Nowadays, the doubly–fed induction generator (DFIG) is perhaps the most common type of generator used in onshore wind turbines. With the thriving development of wind energy, there is a high demand for precisely predicting the dynamic performance of the DFIG. Due to the involvement of power electronics, massive high–frequency harmonics are injected into the machine leading to high–frequency effects such as parasitic currents. As the core of DFIGs, the wound–rotor induction machine must be well modeled to capture these significant phenomena in the operation of wind turbines. However, the T–equivalent model, which is currently the most widely used model in machine dynamic studies and controller designs, is incapable to simulate machine behaviors in the high–frequency range. The aim of this research is to develop a novel model of a wound–rotor induction machine, which incorporates magnetic saturation of the main flux path and high–frequency effects. The model’s experimental parameterization procedure is described in detail. This consists of standstill frequency response tests, and a test for determining the machine’s magnetizing characteristic and turns ratio. Time–domain simulations are used to highlight the capabilities of the proposed model, and to compare its predictions with those of a classical model at both transient and steady states. The results show that the proposed model can better capture the dynamic performance with the consideration of magnetic saturation. What is more, the high–frequency current ripples, which are caused by common–mode ground currents can also be simulated in the proposed model.</p