Effective speed of sound in phononic crystals

A new formula for the effective quasistatic speed of sound $c$ in 2D and 3D periodic materials is reported. The approach uses a monodromy-matrix operator to enable direct integration in one of the coordinates and exponentially fast convergence in others. As a result, the solution for $c$ has a more closed form than previous formulas. It significantly improves the efficiency and accuracy of evaluating $c$ for high-contrast composites as demonstrated by a 2D example with extreme behavior.Comment: 4 pages, 1 figur

Explicit asymptotic modelling of transient Love waves propagated along a thin coating

The official published version can be obtained from the link below.An explicit asymptotic model for transient Love waves is derived from the exact equations of anti-plane elasticity. The perturbation procedure relies upon the slow decay of low-frequency Love waves to approximate the displacement field in the substrate by a power series in the depth coordinate. When appropriate decay conditions are imposed on the series, one obtains a model equation governing the displacement at the interface between the coating and the substrate. Unusually, the model equation contains a term with a pseudo-differential operator. This result is confirmed and interpreted by analysing the exact solution obtained by integral transforms. The performance of the derived model is illustrated by numerical examples.This work is sponsored by the grant from Higher Education of Pakistan and by the Brunel University’s “BRIEF” research award

Interfacial stresses in bimaterial composites with nanosized interface relief

The paper compares analytical and numerical solutions for two-dimensional solid mechanics problems of elastic bimaterial composites with a nanosized interface relief that arises on a boundary between two bulk layers and on an interface of a nearly circular inclusion. It is supposed that the uniform stress state takes place at infinity. Here, we use Gurtin–Murdoch model in which interphase domains are represented as negligibly thin layers ideally adhering to the bulk phases. Static boundary conditions at the interface are formulated according to the generalized Laplace–Young law. To solve corresponding boundary value we use first-order boundary perturbation method based on Goursat–Kolosov complex potentials. To examine the perturbation results, we use a finite element calculations

The Structure of Martian Magnetosphere at the Dayside Terminator Region as Observed on MAVEN Spacecraft

We analyzed 44 passes of the MAVEN spacecraft through the magnetosphere, arranged by the angle between electric field vector and the projection of spacecraft position radius vector in the YZ plane in MSE coordinate system (${\theta}$ E ). All passes were divided into 3 angular sectors near 0{\deg}, 90{\deg} and 180{\deg} ${\theta}$ E angles in order to estimate the role of IMF direction in plasma and magnetic properties of dayside Martian magnetosphere. The time interval chosen was from January 17 through February 4, 2016 when MAVEN was crossing the dayside magnetosphere at SZA ~ 70{\deg}. Magnetosphere as the region with prevailing energetic planetary ions is always found between the magnetosheath and the ionosphere. 3 angular sectors of dayside interaction region in MSE coordinate system with different orientation of the solar wind electric field vector E = -1/c V x B showed that for each sector one can find specific profiles of the magnetosheath, the magnetic barrier and the magnetosphere. Plume ions originate in the northern MSE sector where motion electric field is directed from the planet. This electric field ejects magnetospheric ions leading to dilution of magnetospheric heavy ions population, and this effect is seen in some magnetospheric profiles. Magnetic barrier forms in front of the magnetosphere, and relative magnetic field magnitudes in these two domains vary. The average height of the boundary with ionosphere is ~530 km and the average height of the magnetopause is ~730 km. We discuss the implications of the observed magnetosphere structure to the planetary ions loss mechanism.Comment: 24 pages, 13 figure

Observation of a Chiral State in a Microwave Cavity

A microwave experiment has been realized to measure the phase difference of the oscillating electric field at two points inside the cavity. The technique has been applied to a dissipative resonator which exhibits a singularity -- called exceptional point -- in its eigenvalue and eigenvector spectrum. At the singularity, two modes coalesce with a phase difference of $\pi/2 .$ We conclude that the state excited at the singularity has a definitiv chirality.Comment: RevTex 4, 5 figure

Laparoscopic management of pancreatic lesions in children

Background. This review is the representation of our experience of laparoscopic approach to various pancreatic lesions in series of paediatric patients. Material and methods. 45 children aged from 1 month to 16 years diagnosed with congenital anomalies and acquired lesion of the pancreas underwent surgical treatment with the use of laparoscopic techniques. The following laparoscopic procedures were carried out: excision of gastric ectopic pancreas (n-19); external drainage, fenestration or Roux-en-Y cystojejunostomy of pancreatic cyst (n-8); excision of gastric duplication cyst of the pancreas, pancreatic lymphangioma or pancreatic hytatid cyst (n-4); spleen-preserving distal pancreatectomy or central pancreatectomy with distal pancreaticogastrostomy for solid pseudopapillary tumor (n-4); lateral pancreatojejunostomy for chronic relapsing pancreatitis and pancreatic ductal dilatation (n-3); enucleation of insulinoma (3); 95% near total pancreatectomy for congenital hyperinsulinism (3). Results. In 44 (97,7%) patients the undertaken laparoscopic procedures were successfully completed with no intraoperative complications occurred. The conversion to open distal pancreatic resection was required in 1(2,2%) case when laparoscopic dissection was very much complicated due to massive inflammatory changes in the peripancreatic tissue. Postoperatively, 1 (2.2%) patient developed small bowel obstruction due to Rouxen-Y anastomosis kinking which necessitated open anastomotic reconstruction. In 2 (4,4%) patients pancreatic fistula occurred after insulinoma enucleation and were successfully managed with ocreotide treatment. The rest 41 (91,1%) patients made prompt and uneventful recovery. At follow up, no evidence of recurrent pancreatitis or any associated gastrointestinal symptoms were recorded. Conclusion. Laparoscopic surgery for congenital anomalies and acquired lesions of the pancreas in children is feasible and safe if performed by skilled laparoscopic surgeon who should be experienced in the open complex operations on the pancreas