7,355 research outputs found
Aerodynamic Design of a Tailless Aeroplan
The paper presents an aerodynamic analysis of a one-seat ultralight (UL) tailless aeroplane named L2k, with a very complicated layout. In the first part, an autostable airfoil with a low moment coefficient was chosen as a base for this problem. This airfoil was refined and modified to satisfy the design requirements. The computed aerodynamic characteristics of the airfoils for different Reynolds numbers (Re) were compared with available experimental data. XFOIL code was used to perform the computations. In the second part, a computation of wing characteristics was carried out. All calculated cases were chosen as points on the manoeuvring and gust envelope. The vortex lattice method was used with consideration of fuselage and winglets for very complicated wing geometry. The PMW computer program developed at IAE was used to perform the computations. The computed results were subsequently used for structural and strength analysis and design
An interior-point method for mpecs based on strictly feasible relaxations.
An interior-point method for solving mathematical programs with equilibrium constraints (MPECs) is proposed. At each iteration of the algorithm, a single primaldual step is computed from each subproblem of a sequence. Each subproblem is defined as a relaxation of the MPEC with a nonempty strictly feasible region. In contrast to previous approaches, the proposed relaxation scheme preserves the nonempty strict feasibility of each subproblem even in the limit. Local and superlinear convergence of the algorithm is proved even with a less restrictive strict complementarity condition than the standard one. Moreover, mechanisms for inducing global convergence in practice are proposed. Numerical results on the MacMPEC test problem set demonstrate the fast-local convergence properties of the algorithm
Network Model of the CPE
Analysis of fractal systems (i.e. systems described by fractional differential equations) necessitates to create an electrical analog model of a crucial subsystem called Constant Phase Element (CPE). The paper describes a possible realization of such a model, that is quite simple and in spite of its simplicity makes it possible to simulate the properties of ideal CPEs. The paper also deals with the effect of component tolerances on the resultant responses of the model and describes several typical model applications
Aerodynamic Analysis of Turboprop Engine Air Intake
The objective of this paper is to present CFD computation of a LET L-410 engine nacelle equipped with a Walter M-601E turboprop engine. The main purpose is to estimate the air intake fluid characteristics of different air intake geometries. The results of these computations are part of an optimisation process focused on increasing the performance and reducing the losses in the ‘engine - nacelle` system. A problem with flow separation in the input section was observed. This project is supported by Ministry of Industry and Trade of the Czech Republic
High rate locally-correctable and locally-testable codes with sub-polynomial query complexity
In this work, we construct the first locally-correctable codes (LCCs), and
locally-testable codes (LTCs) with constant rate, constant relative distance,
and sub-polynomial query complexity. Specifically, we show that there exist
binary LCCs and LTCs with block length , constant rate (which can even be
taken arbitrarily close to 1), constant relative distance, and query complexity
. Previously such codes were known to exist
only with query complexity (for constant ), and
there were several, quite different, constructions known.
Our codes are based on a general distance-amplification method of Alon and
Luby~\cite{AL96_codes}. We show that this method interacts well with local
correctors and testers, and obtain our main results by applying it to suitably
constructed LCCs and LTCs in the non-standard regime of \emph{sub-constant
relative distance}.
Along the way, we also construct LCCs and LTCs over large alphabets, with the
same query complexity , which additionally have
the property of approaching the Singleton bound: they have almost the
best-possible relationship between their rate and distance. This has the
surprising consequence that asking for a large alphabet error-correcting code
to further be an LCC or LTC with query
complexity does not require any sacrifice in terms of rate and distance! Such a
result was previously not known for any query complexity.
Our results on LCCs also immediately give locally-decodable codes (LDCs) with
the same parameters
Frequency Shifts and Linewidth Changes of Infrared-Active Phonons in Double-Layered High-Temperature Superconductors
We calculate frequency shifts and changes in linewidths of infrared-active
phonons within a shell model for the bare phononic system coupled to an
electronic double-layer structure with inter-layer charge transfer. The
theoretical concept is applied to YBaCuO yielding a good description of
experimental results in the normal state as well as at the transition to the
superconducting state.Comment: 8 pages, LaTex, SISSA-CM-93-00
An Asp—Asn substitution in the proteolipid subnit of the ATP-synthase from Escherichia coli leads to a non-functional proton channel
Topological and functional aspects of the proton conductor, F, of the Escherichia coli ATP-synthase
The isolated H conductor, F , of the Escherichia co1i ATP-synthase consists of three subunits, a, b, and c. H -permeable liposomes can be reconstit~ted with F and lipids; addition of F-ATPase reconstitutes a functional ATP-synthase. Mutants with altered or misslng F subunits are defective in H conduction. Thus, all three subunits are necessary for the expression of H conduction. The subunits a and b contain binding sites for F• Computer calculations, cross-links, membrane-permeating photo-reactive labels, and proteases were used to develop tentative structural models for the individual F subunits
Impaired Induction of Adhesion Molecule Expression in Immortalized Endothelial Cells Leads to Functional Defects in Dynamic Interactions With Lymphocytes
Immortalization should overcome the problem of short lifespan and difficult culture of endothelial cells that limited their use in functional studies. We used four different immortalized endothelial cell lines to study dynamic interactions with lymphocytes. Surprisingly, tumor necrosis factor (TNF)α-stimulated human umbilical vein endothelial cells (HUVECs) or human dermal microvascular endothelial cells (HDMECs) readily supported rolling and binding of lymphocytes, whereas none of the immortalized cell lines did. As rolling interactions are primarily mediated by selectins and vascular cell adhesion molecule (VCAM)-1, the endothelial cells were analyzed regarding expression of selectins and other adhesion molecules. Interestingly, cell surface expression of E-selectin could only be detected on HUVEC and HDMEC. Immunocytochemistry showed that some immortalized endothelial cells expressed E-selectin intracellularly following TNFα stimulation, suggesting translation but defective post-translational processing or transport of the molecule. In contrast, other immortalized cell lines did not have detectable levels of E-selectin mRNA, suggesting impaired transcription. VCAM-1 could only be induced on normal and human placental microvascular endothelial cell-A2 endothelial cells, whereas all cell lines expressed intercellular adhesion molecule-1 following TNF stimulation. The immortalized endothelial cells tested here have lost functions that are required for dynamic interactions with immune cells and that are common to primary endothelial cells
- …