Parameter Estimation from Near Stall Flight Data using Conventional and Neural-based Methods

The current research paper is an endeavour to estimate the parameters from near stall flight data of manned and unmanned research flight vehicles using conventional and neural based methods. For an aircraft undergoing stall, the aerodynamic model at these high angles of attack becomes non linear due to the influence of unsteady, transient and flow separation phenomena. In order to address these issues the Kirchhoff’s flow separation theory was used to incorporate the nonlinearity in the aerodynamic model in terms of flow separation point and stall characteristic parameters. The classical Maximum Likelihood (MLE) method and Neural Gauss-Newton (NGN) method have been employed to estimate the nonlinear parameters of two manned and one unmanned research aircrafts. The estimated static stall parameter and the break point, for the flight vehicles under consideration, were observed to be consistent from both the methods. Moreover the efficacy of the methods is also evident from the consistent estimates of post stall hysteresis time constant. It can also be inferred that the considered quasi steady model is able to adequately capture the drag and pitching moment coefficients in the post stall regime. The confidence in these estimates have been significantly enhanced with the observed lower values of Cramer-Rao bounds. Further the estimated nonlinear parameters were validated by performing a proof of match exercise for the considered flight vehicles. Interestingly the NGN method, which doesn’t involve solving equations of motion, was able to perform on a par with the MLE method

Carbon-related defects in Si:C/silicon heterostructures assessed by deep-level transient spectroscopy

This paper reports on a Deep-Level Transient Spectroscopy (DLTS) study of the electrically active defects in similar to 100 nm Si: C stressors, formed by chemical vapor deposition on p-type Czochralski silicon substrates. In addition, the impact of a post-deposition Rapid Thermal Annealing (RTA) at 850 degrees C on the DLT-spectra is investigated. It is shown that close to the surface at least two types of hole traps are present: one kind exhibiting slow hole capture, which may have a partial extended defect nature and a second type of hole trap behaving like a point defect. RTA increases the concentration of both hole traps and, in addition, introduces a point defect at EV + 0.35 eV in the depletion region of the silicon substrate at some distance from the Si: C epi layer. This level most likely corresponds with CiOi-related centers. Finally, a negative feature is found systematically for larger reverse bias pulses, which could point to a response of trap states at the Si: C/silicon hetero-interface

N-(2-Acetyl­phen­yl)benzene­sulfonamide

In the title compound, C14H13NO3S, the phenyl ring makes a dihedral angle of 81.5 (1)° with the benzene ring. The mol­ecular structure is stabilized by an intra­molecular N—H⋯O hydrogen bond and weak C—H⋯O inter­actions. In the crystal structure, mol­ecules are linked by weak inter­molecular C—H⋯O and C—H⋯π inter­actions

1,3-Dimethyl-5-(2-methyl­benzyl­idene)pyrimidine-2,4,6(1H,3H,5H)-trione

In the title compound, C14H14N2O3, the dihedral angle between the pyrimidine and benzene rings is 14.9 (1)°. The mol­ecular structure is stabilized by weak intra­molecular C—H⋯O inter­actions and the crystal structure exhibits a weak inter­molecular π–π inter­action [centroid–centroid distance = 3.575 (3) Å]

(4-Bromo­phen­yl)(1-phenyl­sulfonyl-1H-indol-2-yl)methanone

In the title compound, C21H14BrNO3S, the indole ring system forms dihedral angles of 65.64 (8) and 59.30 (8)°, respectively, with the phenyl and bromo­phenyl rings. In the crystal, mol­ecules are connected by a C—H⋯O hydrogen bond, forming a chain along [101]. The chains are further connected by weak inter­molecular C—H⋯π inter­actions, forming a layer parallel to the ac plane

Study of electrically active defects in epitaxial layers on silicon

Electrically active defects in silicon-based epitaxial layers on silicon substrates have been studied by Deep-Level Transient Spectroscopy (DLTS). Several aspects have been investigated, like, the impact of the pre-epi cleaning conditions and the effect of a post-deposition anneal on the deep-level properties. It is shown that the pre-cleaning thermal budget has a strong influence on the defects at the substrate/epi layer interface. At the same time, a post-deposition Forming Gas Anneal can passivate to a large extent the active defect states. Finally, it is shown that application of a post-deposition anneal increases the out-diffusion of carbon from a Si:C stressor layer into the p-type CZ substrate

7-Phenyl­sulfonyl-7H-benzofurano[2,3-b]carbazole

In the title compound, C24H15NO3S, the dihedral angle between the phenyl ring and the carbozole system is 74.91 (6)°. The S atom exhibits a distorted tetra­hedral geometry [N—S—C = 104.85 (8)°; O—S—O = 119.59 (9)°]. The crystal structure is established by weak inter­molecular π–π inter­actions [centroid–centroid distances = 3.583 (2)–3.782 (2) Å]

7H-1-Benzofuro[2,3-b]carbazole

In the title compound, C18H11NO, the carbazole and benzofuran rings are almost co-planar, making a dihedral angle of 3.31 (3)°. The crystal structure is stabilized by weak C—H⋯π inter­actions

1,3-Dimethyl­benzo[b]dibenzothio­phene

The molecule of the title compound, C18H14S, is approximately planar (r.m.s. deviation = 0.029 Å). The crystal packing is stabilized by weak inter­molecular C—H⋯π inter­actions

Piezo1 channel activation mimics high glucose as a stimulator of insulin release

Glucose and hypotonicity induced cell swelling stimulate insulin release from pancreatic β-cells but the mechanisms are poorly understood. Recently, Piezo1 was identified as a mechanically-activated nonselective Ca2+ permeable cationic channel in a range of mammalian cells. As cell swelling induced insulin release could be through stimulation of Ca2+ permeable stretch activated channels, we hypothesised a role for Piezo1 in cell swelling induced insulin release. Two rat β-cell lines (INS-1 and BRIN-BD11) and freshly-isolated mouse pancreatic islets were studied. Intracellular Ca2+ measurements were performed using the fura-2 Ca2+ indicator dye and ionic current was recorded by whole cell patch-clamp. Piezo1 agonist Yoda1, a competitive antagonist of Yoda1 (Dooku1) and an inactive analogue of Yoda1 (2e) were used as chemical probes. Piezo1 mRNA and insulin secretion were measured by RT-PCR and ELISA respectively. Piezo1 mRNA was detected in both β-cell lines and mouse islets. Yoda1 evoked Ca2+ entry was inhibited by Yoda1 antagonist Dooku1 as well as other Piezo1 inhibitors gadolinium and ruthenium red, and not mimicked by 2e. Yoda1, but not 2e, stimulated Dooku1-sensitive insulin release from β-cells and pancreatic islets. Hypotonicity and high glucose increased intracellular Ca2+ and enhanced Yoda1 Ca2+ influx responses. Yoda1 and hypotonicity induced insulin release were significantly inhibited by Piezo1 specific siRNA. Pancreatic islets from mice with haploinsufficiency of Piezo1 released less insulin upon exposure to Yoda1. The data show that Piezo1 channel agonist induces insulin release from β-cell lines and mouse pancreatic islets suggesting a role for Piezo1 in cell swelling induced insulin release. Hence Piezo1 agonists have the potential to be used as enhancers of insulin release