A fault-tolerant strategy based on SMC for current-controlled converters

The sliding mode control (SMC) is used to control variable structure systems such as power electronics converters. This paper presents a fault-tolerant strategy based on the SMC for current-controlled AC–DC converters. The proposed SMC is based on three sliding surfaces for the three legs of the AC–DC converter. Two sliding surfaces are assigned to control the phase currents since the input three-phase currents are balanced. Hence, the third sliding surface is considered as an extra degree of freedom which is utilised to control the neutral voltage. This action is utilised to enhance the performance of the converter during open-switch faults. The proposed fault-tolerant strategy is based on allocating the sliding surface of the faulty leg to control the neutral voltage. Consequently, the current waveform is improved. The behaviour of the current-controlled converter during different types of open-switch faults is analysed. Double switch faults include three cases: two upper switch fault; upper and lower switch fault at different legs; and two switches of the same leg. The dynamic performance of the proposed system is evaluated during healthy and open-switch fault operations. Simulation results exhibit the various merits of the proposed SMC-based fault-tolerant strategy.     

Thermomechanical investigation of hydroxyl-terminated polybutadiene-based linear polyurethane elastomers

The present work describes the trend of linear polyurethane elastomers for its thermal and mechanical behavior. The linear polyurethane elastomers have been synthesized in two different series by changing the composition of the polymers. Both series have common macrodiol of hydroxyl-terminated polybutadiene and butanediol while they vary in the presence of diisocyanate. One of the series, contain an aromatic diisocyanate, toluene diisocyanate (TDI), and the other consist of 1,6-hexamethylene diisocyanate (HDI) as an aliphatic diisocyanate. For linear structure, ratio of OH and NCO group has been maintained 1.0. The hydrogen bonding index is determined from Fourier transform infrared to calculate the extent of interchain hydrogen bonding which manifest the microphase separation. Young's modulus (5.79 MPa) and tensile strength (1.14 MPa) are recorded for HDI-derived elastomers, while Young's modulus varies from 1.14 to 1.63 MPa for TDI-based elastomers which also resulted in higher thermal stability. Thermogravimetric curves exhibit two-step degradation with the stability of 300 °C. HDI-based polyurethane elastomers show better tensile properties and HDI but poor thermal stability as compared to TDI-based elastomers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47289.     

Representation and Reasoning with Multi-Point Events

Allen's Interval Algebra (IA) and Vilain & Kautz's Point Algebra (PA) consider an interval and a point as basic temporal entities (i.e., events) respectively. However, in many situations we need to deal with recurring events that include multiple points, multiple intervals or combinations of points and intervals. In this paper, we present a framework to model recurring events as multi-point events (MPEs) by extending point algebra. The reasoning tasks are formulated as binary constraint satisfaction problems. We propose a polynomial time algorithm (based on van Beek's algorithm) for finding all feasible relations. For the problem of finding a consistent scenario, we propose a backtracking method with a local search heuristic. We also describe an implementation and a detail empirical evaluation of the proposed algorithms. Our empirical results indicate that the MPE-based approach performs better than the existing approaches.     

Uterine myomata and outcome of assisted reproduction

BACKGROUND: Open lung biopsy (OLB) has long been considered the gold standard for the diagnosis of parenchymal lung disease. With recent advances in computed tomographic imaging and diagnostic techniques (eg, bronchoscopy), we thought it necessary to reevaluate the role of OLB in the management of patients with interstitial lung disease. METHODS: We carried out a retrospective analysis of 103 OLBs performed at Hadassah University Hospital, Jerusalem, and Carmel Medical Center, Haifa, between 1980 and 1994. Data gathered included demographic information, underlying condition, indications for biopsy, diagnosis before biopsy, final diagnosis, change in therapy, and mortality. "Benefit" was defined as a change in therapy resulting in survival. RESULTS: There were 45 immunocompetent patients (group 1), 39 immunocompromised patients (group 2), and 26 children (group 3), 7 of whom were included in group 2 for analysis. Overall, a diagnosis was reached after OLB in 85% of patients. An unexpected diagnosis was reached in 52%, and a change in therapy was instituted in 46%. The overall mortality rate was 20%. In group 1, the mortality rate was 13%, and "benefit" from OLB was reached in only 18%. In group 2, the mortality rate was 39%, and "benefit" was achieved in 46%, and in group 3, the mortality rate was 12% and "benefit", 50%. CONCLUSIONS: Open lung biopsy is an excellent diagnostic technique. In immunocompetent patients, the "benefit" is relatively low, as therapy (corticosteroids) is frequently used after biopsy. In immunocompromised patients, therapy changes substantially after OLB, but mortality is high. Therefore, OLB should be reserved for patients in whom the diagnosis is likely to lead to a change in therapy and in patients in whom the underlying condition has a reasonable prognosis according to the clinical impression by the attending physician.     

Simplified method of determining fetal brain weight in utero

Analysis of autopsy data shows that, from the 26th through the 38th gestational weeks, fetal brain weight (BrW) is a function of the 3.124 power of the largest head circumference (HC). Because there is excellent correlation between prenatal ultrasound measurement and postnatal tape measurement of the HC, it is possible to determine fetal BrW in utero. An alteration of the BrW:somatic weight (SW) relationship is an important physical stigma of asymmetric intrauterine growth retardation (IUGR). The value of longitudinal studies of fetal BrW and SW as a means of discriminating between normal and asymmetric growth is tested in a population at risk for IUGR.     

Transport properties of trivalent substituted Li-ferrites

The electrical resistivity and thermoelectric power of Li_0.5Fe_2.5–x R _x O₄ (R = Al, La, Sm and Gd; x = 0.0 and 0.1) are studied. The distribution of the substituted ions over the different lattice sites is determined from IR spectra. The electrical resistivity is found to have a direct relation with the ionic radius of the substituted R ions. Meanwhile, the absolute value of thermoelectric power decreased with increasing ionic radius.     

X-CleLo: intelligent deterministic RFID data and event transformer

Recently, passive Radio Frequency Identification (RFID) systems have received an increased amount of attention as researchers have worked to implement a stable and reliable system. Unfortunately, despite vast improvements in the quality of RFID technology, a significant amount of erroneous data is still captured in the system. Currently, the problems associated with RFID have been addressed by cleaning algorithms to enhance the data quality. In this paper, we present X-CleLo, a means to intelligently clean and transform the dirty data into high-level events using Clausal Defeasible Logic. The extensive experimental study we have conducted has shown that the X-CleLo method has several advantages over currently utilised cleaning techniques and achieves a higher cleaning and event discovery rate.     

Ranking the key parameters of immersion precipitation process and modeling the resultant membrane structural evolution

Key parameters coupling with the instantaneous nucleation concept (ie, the Big Bang analogy) was used to model immersion precipitation process. The merits of the acquired model were verified via comparing its predictions with experimental results of two well‐prepared and characterized cellulose acetate (CA) and polyacrylonitrile (PAN) membranes. A morphology predictable map, ΔPη^?1 versus ?₁, was constructed, where ΔP, η and ?₁ are osmotic pressure difference between nonsolvent and dope solution, dope viscosity and intruded nonsolvent volume fraction into the dope, respectively. The phase separation map, ΔPη^?1 (proportional with apparent system diffusivity with the unit of time^?1) versus ?₁ showed three regimes which, at least qualitatively, depicted the correct morphological evolution trends of the studied systems. Phase separation in regime one of CA membrane with the longest delayed time or lowest ΔPη^?1, led to bead‐like morphology. CA membrane with the shortest elapsed time or highest ΔPη^?1, separated to finger‐like morphology in regime three. Finally, phase separation in the intermediate regime of CA membrane, ended up to sponge‐like morphology. Phase separation time scales of the PAN membranes versus intruded nonsolvent into the dope solution were located in finger‐like region of the CA membrane, which its downward transition lowered the fingers population. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Improved phenol adsorption from aqueous solution using electrically conducting adsorbents

The electrically conducting and partially porous graphite based adsorbent (called NyexTM 2000) was tested for its adsorption capacity and electrochemical regeneration ability for the removal of phenol from aqueous solution. Nyex? 2000 was tested in comparison with Nyex? 1000, which is currently being used for a number of industrial waste water treatment applications. Nyex? 1000 exhibited small adsorption capacity of 0.1 mg g^?1 for phenol because of having small specific surface area of 1 m² g^?1. In contrast, Nyex? 2000 with specific surface area of 17 m² g^?1 delivered an adsorption capacity of 0.8 mg g^?1, which was eight-fold higher than that of Nyex? 1000. Nyex? 2000 was successfully electrochemically regenerated by passing a current of 0.5 A, charge passed of 31 C g^?1 for a treatment time of 45 minutes. These electrochemical parameters were comparable to Nyex? 1000 for which a current of 0.5 A, charge passed of 5 C g^?1 for a treatment time of 20 minutes were applied for complete oxidation of adsorbed phenol. The comparatively high charge density was found to be required for Nyex? 2000, which is justified with its higher adsorption capacity. The FTIR results validated the mineralization of adsorbed phenol into CO₂ and H₂O except the formation of few by-products, which were in traces when compared with the concentration of phenol removed from aqueous solution. The electrical energy as required for electrochemical oxidation of phenol adsorbed onto Nyex? 1000 & 2000 was found to be 214 and 196 J mg^?1, respectively. The comparatively low energy requirement for electrochemical oxidation using Nyex? 2000 is consistent with its higher bed electrical conductivity, which is twice that of Nyex? 1000.