Search results for "element"

Multiobjective muffler shape optimization with hybrid acoustics modelling

2011

This paper considers the combined use of a hybrid numerical method for the modeling of acoustic mufflers and a genetic algorithm for multiobjective optimization. The hybrid numerical method provides accurate modeling of sound propagation in uniform waveguides with non-uniform obstructions. It is based on coupling a wave based modal solution in the uniform sections of the waveguide to a finite element solution in the non-uniform component. Finite element method provides flexible modeling of complicated geometries, varying material parameters, and boundary conditions, while the wave based solution leads to accurate treatment of non-reflecting boundaries and straightforward computation of the …

Inf-sup conditions on convex cones and applications to limit load analysis

2019

The paper is devoted to a family of specific inf–sup conditions generated by tensor-valued functions on convex cones. First, we discuss the validity of such conditions and estimate the value of the respective constant. Then, the results are used to derive estimates of the distance to dual cones, which are required in the analysis of limit loads of perfectly plastic structures. The equivalence between the static and kinematic approaches to limit analysis is proven and computable majorants of the limit load are derived. Particular interest is paid to the Drucker–Prager yield criterion. The last section exposes a collection of numerical examples including basic geotechnical stability problems.…

Optimization of the domain in elliptic variational inequalities

1986

Stability of Local Out-of-Plane Deformations of Orthotropic Sheet : Numerical Approach

2018

Reliable computation and local mesh adaptivity in limit analysis

2019

The contribution is devoted to computations of the limit load for a perfectly plastic model with the von Mises yield criterion. The limit factor of a prescribed load is defined by a specific variational problem, the so-called limit analysis problem. This problem is solved in terms of deformation fields by a penalization, the finite element and the semismooth Newton methods. From the numerical solution, we derive a guaranteed upper bound of the limit factor. To achieve more accurate results, a local mesh adaptivity is used. peerReviewed

Quadratic least-squares formulation for a local active noise control with stochastic domain and noise source

2012

A local active noise control method that uses stochastic numerical acoustical modeling is introduced. The frequency domain acoustical simulations are performed by a sequence solutions to Helmholtz equations approximated by FEM. The proposed ANC method maps microphone measurements linearly to the output signals of antinoise actuators. The matrix defining the linear mapping is optimized for each frequency to minimize expected value of the noise. The paper concentrates on defining the quadratic least-squares optimization problem for the minimization of the sound pressure field in the silet region. The formulation leads to a robust and accurate noise control in stochastic domains that has a sto…

Dažas transformācijas elementārā ģeometrijā

1935

Referāts nolasīts matēmatisko zinātņu darbinieku kongresā, 25. aprīlī 1935. gadā. Izdots Rīgā, 1936. Izdevusi Matēmatisko zinātņu darbinieku biedrība. Autors Cand. math. E. Grünbergs

Pirmsskolas vecuma bērna ritma izjūtas attīstība elementāras muzicēšanas procesā

2018

Darba nosaukums: Pirmsskolas vecuma bērna ritma izjūtas attīstība elementārās muzicēšanas procesā. Darba mērķis ir teorētiski analizēt un praktiski pārbaudīt bērna ritma izjūtas attīstību elementārās muzicēšanas procesā. Darbā tika apkopotas un analizētas pedagogu un psihologu atziņas par ritmu, ritma izjūtu un tās attīstību bērniem elementārās muzicēšanas procesā. Tika aprakstītas muzikālās darbības pirmsskolā. Veikts praktiskais pētījums, izmantojot muzikālās darbības un apstiprināti apgalvojumi – bērna ritma izjūtas attīstība tiek sekmēta elementārās muzicēšanas procesā. Darbam ir divas nodaļas. Pirmajā nodaļā tika apskatīts ritma un ritma izjūtas jēdzienu skaidrojums no pedagogu un psih…

Crystal structures of allyltriphenyl-phosphonium halogenocuprates(I)

2013

Alternating-current electrochemical synthesis is used to obtain for the first time halogenocuprates of an allyl derivative of phosphonium of the composition (CH2=CHCH2(C6H5)3P)CuX2 (X = Br (I), Cl (II)). Compound I crystallizes in the space group P21, a = 9.6341(3) A, b = 12.4167(4) A, c = 9.9618(4) A, β = 117.484(5)°, Z = 2. Compound II crystallizes in the space group P21/n, a = 9.9725(5) A, b = 15.4586(8) A, c = 13.7557(5) A, β = 90.429(4)°, Z = 4. In the structures of I and II quasilinear CuX 2 − anions are held by C-H…X hydrogen bonds inside a framework formed by the stacking of phenyl groups from CH2=CHCH2(C6P5)3P+ cations. Allyl groups are not involved in coordination with copper(I) a…

Intra-individual variability in TSH levels of healthy women during the first half of pregnancy

2017

TSH is the parameter most widely accepted to assess thyroid function, especially in pregnant women. The aim of this current study was to analyze intra-individual changes in TSH during the first half of pregnancy in women with TSH levels higher than 2.5mIU/L in early pregnancy.An observational, prospective study was conducted on 243 healthy pregnant women in the first trimester of pregnancy. Thyroid function was assessed by testing TSH and free T4 levels. A subgroup of women with TSH levels2.5mIU/L underwent additional tests (TSH, free T4, peroxidase antibodies). Information on dietary iodine intake and/or iodine supplements was also recorded.Mean TSH level was 1.89mIU/L (range 0.024-6.48mIU…