Identification of temperature profile and heat transfer on a dielectric membrane for gas sensors by `COSMOS' program simulation

The application of commercial 3-D software `COSMOS' for the design and thermal analysis of the low power consumption test structures with dielectric membrane for gas microsensors is presented. Within this work, the simulation provides the estimation of the temperature profile on the active area and the whole membrane including the four bridges and the heating efficiency in the temperature range 20-500 °C. Unravelling of the heat loss mechanisms in terms of radiation, convection, conduction by air and solid materials during heat transfer on the dielectric membrane is reported for the first time as a mean to evaluate by 3-D simulation the contribution of technological processes and lay-out design to the total heat losses

Positive Semidefiniteness and Positive Definiteness of a Linear Parametric Interval Matrix

We consider a symmetric matrix, the entries of which depend linearly on some parameters. The domains of the parameters are compact real intervals. We investigate the problem of checking whether for each (or some) setting of the parameters, the matrix is positive definite (or positive semidefinite). We state a characterization in the form of equivalent conditions, and also propose some computationally cheap sufficient\,/\,necessary conditions. Our results extend the classical results on positive (semi-)definiteness of interval matrices. They may be useful for checking convexity or non-convexity in global optimization methods based on branch and bound framework and using interval techniques

Image preprocessing for artistic robotic painting

Artistic robotic painting implies creating a picture on canvas according to a brushstroke map preliminarily computed from a source image. To make the painting look closer to the human artwork, the source image should be preprocessed to render the effects usually created by artists. In this paper, we consider three preprocessing effects: aerial perspective, gamut compression and brushstroke coherence. We propose an algorithm for aerial perspective amplification based on principles of light scattering using a depth map, an algorithm for gamut compression using nonlinear hue transformation and an algorithm for image gradient filtering for obtaining a well-coherent brushstroke map with a reduced number of brushstrokes, required for practical robotic painting. The described algorithms allow interactive image correction and make the final rendering look closer to a manually painted artwork. To illustrate our proposals, we render several test images on a computer and paint a monochromatic image on canvas with a painting robot

Thermal modelling of a porous silicon-based pellistor-type catalytic flammable gas sensor with two supporting beams

A three-dimensional transient thermal mathematical model of a porous silicon based pellistor with two supporting beams was developed. The model was numerically solved using the implicit alternating-direction finite difference method. A computer program written in ANSI C and run on a VAX/VMS computer was utilized to study the influence of the power consumption and the main geometrical dimensions (membrane, beam and heater size) of the pellistor mentioned above on its transient and steady-state thermal behaviour. It was found that considerable improvement in the thermal behaviour of the pellistor could be achieved by reducing the membrane size (length and width). The optimal beam length was determined as 100 μm. By comparing the main sources of energy dissipation it was found that energy was lost predominantly through the heat conduction into the supporting beams

Early perioperative res ults in 53 cases of locally rec urrent colorectal cancer

Purpose: The objective of this study was to analyze retrospectively the early perioperative results in a cohort of 53 patients with localy reccurent colorectal cancer (CRC).Material and methods: The study covered 53 patients with CRC 21 males and 32 females at a mean age of 62 years treated in the Clinic of Liver, Biliary, Pancreatic and General Surgery, Tokuda Hospital of Sofia, during the period from January 2007 to March 2013. Any necessary diagnostic and surgical methods were applied.Results: The locally recurrent CRC is a challenge for the surgeon because of the fact that in most cases it engages adjacent anatomical structures and organs, on the one hand, and it is accompanied by complications, on the other hand.Conclusion: Achievement of good late results in patients with recurrent CRC is due to radicality of the interventions. Most often, they should be multivisceral resections. The presence of intestinal obstruction of varying degree and of synchronous peritoneal and liver metastases commonly limit the possibilities for surgical interference with the disease. Particular attention should be paid to possible neoadjuvant treatment capable of reducing the stage of diasease and improving the perioperative outcomes. Therapeutic behaviour should be strictly individual and consider any possible options. The experience of the surgical team is extremely important, too

The curvature of semidirect product groups associated with two-component Hunter-Saxton systems

In this paper, we study two-component versions of the periodic Hunter-Saxton equation and its $\mu$-variant. Considering both equations as a geodesic flow on the semidirect product of the circle diffeomorphism group \Diff(\S) with a space of scalar functions on $\S$ we show that both equations are locally well-posed. The main result of the paper is that the sectional curvature associated with the 2HS is constant and positive and that 2$\mu$HS allows for a large subspace of positive sectional curvature. The issues of this paper are related to some of the results for 2CH and 2DP presented in [J. Escher, M. Kohlmann, and J. Lenells, J. Geom. Phys. 61 (2011), 436-452].Comment: 19 page

Multivisceral ‘en-bloc` resections of colorectal tumours - milestones in the surgical techniques

Purpose: Colorectal tumours (CRT) consisting mainly of colorectal cancer (CRC) are diagnosed sometimes at an advanced T4 stage, i. e. local involvement of neighbouring organ/organs and anatomical structure/ structures. Aggressive surgical approach preceded and/or followed by neo-adjuvant/adjuvant therapy is advocated because of proven benefit for the patient. The aim of this study was to carry out a literature survey, on the one hand, and to analyze the cases from the authors` institutional experience, on the other hand, in an attempt to submit for consideration the milestones of the multivisceral en-block resections in cases of locally advanced CRTs, i.e. to describe the specific surgical approaches depending on different tumour location and peritumoural involvement of adjacent structures and organs.Material and methods: A retrospective analysis of 154 cases of CRT was performed, all of them operated in the Clinic of Liver, Biliary, Pancreatic and General Surgery, Tokuda Hospital of Sofia, from January 1, 2007 to March 31, 2013. All the patients were diagnosed in an advanced T4-stage and received multivisceral en-bloc resections. Three main groups of methods that had been used were analyzed: 1) preoperative diagnosis, giving a hint of multivisceral en-bloc resection; 2) intraoperative assessment - gross tumour appearance, frozen sections (?), final histological examinations, and 3) surgical methods.Results: Early morbidity and mortality rates were 22,6% and 5,8%, respectively, without any significant difference when compared with ‘simple` colon and rectum resections and with literature data available.Conclusion: Multivisceral en-bloc resection for CRCs has been performed in more than 10% of the cases. It benefits the long-term prognosis. Tumour location and number of resected organs are essential characteristics of these procedures and they are independently associated with the quantity of intraoperative blood loss, higher early morbidity rates and more frequent local recurrence

Locally advanced adenocarcinoma of the supramesocolic part of the colon . Feat ures of surgical treatment and challenges

Purpose: The objective of the present study was to analyze the early results from the surgical treatment of locally advanced carcinoma of the colon in its transverse section and the two flexures.Material and methods: The study covered 36 patients with locally advanced colonic carcinoma, 19 males and 17 females at a mean age of 65,6 years, treated in the Clinic of Liver, Biliary, Pancreatic and General Surgery, Tokuda Hospital of Sofia during the period from January 2007 to March 2013. Any necessary diagnostic and surgical methods were applied.Results: Multivisceral resections were commonly performed in order to achieve a radical surgery in cases of locally advanced disease. Great surgeon`s experience in liver, biliary and pancreatic interventions is obligatorily required. In this paper we share our experience in the treatment of this disease for a period of 6 years.Conclusion: Our application of the multivisceral resections results in surgical radicality along with acceptable levels of perioperative morbidity and mortality rates when compared to other studies in in the foreign literature available