Modal Analysis of Induction Generator Based Wind Farm Connected to Series-compensated Transmission Line and Line Commutated Converter High-Voltage DC Transmission Line

This article presents a comprehensive analysis of the potential of sub-synchronous resonance in induction generator based wind farms connected to a line commutated converter based high-voltage DC transmission line. Since series-compensated lines are also known to cause sub-synchronous resonance in induction generator based (Type 1) wind farms, this study also considers a series-compensated line in parallel with the high-voltage DC line for the investigation of sub-synchronous resonance potential. The CIGRE benchmark high-voltage DC system and the IEEE first benchmark system are considered as the study system components. A linearized state-space model of the study system is developed for eigenvalue analysis followed by participation factor analysis. A sensitivity study of the sub-synchronous resonance modes with respect to variation in different model parameters, such as rectifier firing angle, DC line power flow, and series compensation level, is also reported. It is found that the high-voltage DC rectifier station current regulator does not interact with any of the sub-synchronous modes of the wind farm. However, in the event that the high-voltage DC line is blocked during a contingency, the wind farm will operate radially with the series-compensated line and may experience sub-synchronous resonance oscillation due to the induction generator effect.     

Synthesis and characterization of soluble narrow band gap conducting polymers based on diketopyrrolopyrrole and propylenedioxythiophenes

A series of novel electro-active conjugated polymers containing 2,5-dialkyl-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-diones (DPPs) and 3,4-dihydro-3,3-dialkyl-2H-thieno[3,4-b][1,4]dioxepines (dialkyl-ProDOTs) were synthesized using Stille coupling reaction in presence of CuO. The molecular weights of the synthesized polymers were found to be in the range of 18,000–45,000. Incorporation of the electron deficient DPP units and the electron rich dialkyl-ProDOT units in the conjugated backbone leads to low band gap polymers. All the polymers were found to be highly soluble in most chlorinated organic solvents as well THF and toluene with excellent film forming properties. From the UV–vis spectra, the band gap of the polymers was determined as 1.40–1.42 eV which is lower than the poly(dialkylProDOT)s. From the electrochemical study, highest occupied molecular orbital (HOMO) energy levels of the synthesized polymers were found to be in the range of 5.54–5.51 eV. Because of such high HOMO level, the resulting polymers were found to be more oxidatively stable. Polymers are thermally stable till 325–346 °C with only 5% weight loss which was confirmed from thermogravimetric analysis (TGA). The polymers were found to be moderately conducting with maximum conductivity up to 0.2–6.0 S/cm.     

Numerical and experimental study on the three-dimensional extrusion of square section from square billet through a polynomial shaped curved die

The geometry of die profile plays a major role in reducing the extrusion pressure and ensuring the smooth flow of material. In general, the extrusion process is mostly affected by billet geometry, die geometry, and interface frictional force at the die billet geometry. In the present investigation, an analysis using three-dimensional upper bound method using fifth-order die profile function has been carried out for extrusion of square sections from square billet. The extrusion pressure and optimum die length have been computed by multivariable optimization technique. The present die shape profile is found to be superior to many other profiles. The results obtained will help in design of optimum die profile and investigation of its performance.     

A Flexi-PEGDA Upconversion Implant for Wireless Brain Photodynamic Therapy

Near-infrared (NIR) activatable upconversion nanoparticles (UCNPs) enable wireless-based phototherapies by converting deep-tissue-penetrating NIR to visible light. UCNPs are therefore ideal as wireless transducers for photodynamic therapy (PDT) of deep-sited tumors. However, the retention of unsequestered UCNPs in tissue with minimal options for removal limits their clinical translation. To address this shortcoming, biocompatible UCNPs implants are developed to deliver upconversion photonic properties in a flexible, optical guide design. To enhance its translatability, the UCNPs implant is constructed with an FDA-approved poly(ethylene glycol) diacrylate (PEGDA) core clad with fluorinated ethylene propylene (FEP). The emission spectrum of the UCNPs implant can be tuned to overlap with the absorption spectra of the clinically relevant photosensitizer, 5-aminolevulinic acid (5-ALA). The UCNPs implant can wirelessly transmit upconverted visible light till 8 cm in length and in a bendable manner even when implanted underneath the skin or scalp. With this system, it is demonstrated that NIR-based chronic PDT is achievable in an untethered and noninvasive manner in a mouse xenograft glioblastoma multiforme (GBM) model. It is postulated that such encapsulated UCNPs implants represent a translational shift for wireless deep-tissue phototherapy by enabling sequestration of UCNPs without compromising wireless deep-tissue light delivery.     

Design of a Compressive Sensing Based Fall detection System for Elderly Using WSN

Wireless Personal Communications - Recent researches have pointed out that one third persons are aged 65 and above requires special health care. As the number of elderly person is increasing, home...     

In-plane compression porometry of battery separators

We have designed equipment that measures, by means of capillary flow porometry, the pore structure of sheet materials. The equipment measures the influence of superimposed compressive stress on pore structure as well. The bubble point pressure, mean flow pressure, and flow distribution of a battery separator have been measured, and the influence of compressive stresses on these parameters have been observed. Our results demonstrate that the pore structure for in-plane flow is considerably different from that for flow in the perpendicular direction, and the effect of superimposed compressive stress is appreciable.     

Non-functionalized soluble diketopyrrolopyrrole: Simplest p-channel core for organic field-effect transistors

We report the synthesis, characterization and behavior in field-effect transistors of non-functionalized soluble diketopyrrolopyrrole (DPP) core with only a solubilizing alkyl chain (i.e. –C₁₆H₃₃ or –C₁₈H₃₇) as the simplest p-channel semiconductor. The characteristics were evaluated by UV–vis and fluorescence spectroscopy, X-ray diffraction, cyclic voltammetry (CV), thermal analysis, atomic force microscopy (AFM) and density functional theory (DFT) calculation. For top-contact field-effect transistors, two types of active layers were prepared either by a solution process (as a 1D-microwire) or thermal vacuum deposition (as a thin-film) on a cross-linked poly(4-vinylphenol) gate dielectric. All the devices showed typical p-channel behavior with dominant hole transports. The device made with 1D-microwiress of DPP-R18 showed field-effect mobility in the saturation region of 1.42 × 10^?2 cm²/V s with I_ON/I_OFF of 1.82 × 10³. These findings suggest that the non-functionalized soluble DPP core itself without any further functionalization could also be used as a p-channel semiconductor for low-cost organic electronic devices.     

用流动孔隙测量术设计复合型过滤介质

为使过滤材料在使用中达到令人满意的性能 ,要求过滤介质具有适宜的孔径尺寸、孔径分布、孔体积、孔表面积及渗透性。在本项调研中 ,将过滤介质用流动孔隙测量术进行了特征化处理 ,然后用预先特征化处理过的过滤介质设计复合型过滤介质 ,并用流动孔隙测量术测试复合型过滤介质。测量并分析通过干样品和湿样品的气体压力和流量 ,由此得出最大孔径尺寸、孔径分布及渗透性。数据表明 ,具有独特特征的复合型过滤介质可以通过合理挑选预先特征化处理过的过滤介质来制备。