Search results for "Guide"
showing 10 items of 1478 documents
A method of variation of boundaries for waveguide grating couplers
2008
We describe a method for calculating the solution of the electromagnetic field in a non-rectilinear open waveguide by using a series expansion, starting from the field of a rectilinear waveguide. Our approach is based on a method of variation of boundaries. We prove that the obtained series expansion converges and we provide a radiation condition at infinity in such a way that the problem has a unique solution. Our approach can model several kinds of optical devices which are used in optical integrated circuits. Numerical examples will be shown for the case of finite aperiodic waveguide grating couplers.
Evaluation of time domain electromagnetic fields radiated by constant velocity moving particles traveling along an arbitrarily shaped cross-section w…
2012
[1] A technique for the accurate computation of the time domain electromagnetic fields radiated by a charged distribution traveling along an arbitrarily shaped waveguide region is presented. Based on the transformation (by means of the standard Fourier analysis) of the time-varying current density of the analyzed problem to the frequency domain, the resulting equivalent current is further convolved with the dyadic electric and magnetic Green’s functions. Moreover, we show that only the evaluation of the transverse magnetic modes of the structure is required for the calculation of fields radiated by particles traveling in the axial direction. Finally, frequency domain electric and magnetic f…
Highly efficient full-wave electromagnetic analysis of 3-D arbitrarily shaped waveguide microwave devices using an integral equation technique
2015
A novel technique for the full-wave analysis of 3-D complex waveguide devices is presented. This new formulation, based on the Boundary Integral-Resonant Mode Expansion (BI-RME) method, allows the rigorous full-wave electromagnetic characterization of 3-D arbitrarily shaped metallic structures making use of extremely low CPU resources (both time and memory). The unknown electric current density on the surface of the metallic elements is represented by means of Rao-Wilton-Glisson basis functions, and an algebraic procedure based on a singular value decomposition is applied to transform such functions into the classical solenoidal and nonsolenoidal basis functions needed by the original BI-RM…
An integrated structural health monitoring system based on electromechanical impedance and guided ultrasonic waves
2015
We propose a structural health monitoring (SHM) paradigm based on the simultaneous use of ultrasounds and electromechanical impedance (EMI) to monitor waveguides. Methods based on the propagation of guided ultrasonic waves (GUWs) are increasingly used in all those SHM applications that benefit from built-in transduction, moderately large inspection ranges, and high sensitivity to small flaws. Meantime, impedance-based SHM promises to adequately assess locally the structural integrity of simple waveguides and complex structures such as bolted connections. As both methods utilize piezoelectric transducers bonded or embedded to the structure of interest, this paper describes a unified SHM para…
Setting standards and implementing quality improvement in trauma care
1996
Setting standards and implementing quality improvement in trauma care needs consideration of the definitions of standards, guidelines, recommendations and the present quality of trauma care. Essential factors for consideration are the chain of survival and different intervals which may decide on patient outcome: (a) the trauma (occurrence) to trauma recognition interval which has, until now, not been taken into consideration with regard to morbidity and mortality; (b) the scene time is part of the total prehospital time which comprises rescuing the entrapped patient, preparation of the patient for treatment, and transfer to a rescue vehicle. The medical part of the scene time, however, repr…
Endometrial biopsy: Indications, techniques and recommendations. An evidence-based guideline for clinical practice
2023
This practice guideline provides updated evidence for the gynecologist who performs endometrial biopsy (EB) in gynecologic clinical practice. An international committee of gynecology experts developed the recommendations according to AGREE Reporting Guideline. An adequate tissue sampling is mandatory when performing an EB. Blind methods should not be first choice in patients with suspected endometrial malignancy. Hysteroscopy is the targeted-biopsy method with highest diagnostic accuracy and cost-effectiveness. Blind suction techniques are not reliable for the diagnosis of endometrial polyps. In low resources settings, and in absence of the capacity to perform office hysteroscopy, blind tec…
German Survey on EUS-Guided Diagnosis and Management of Gastrointestinal Stromal Tumors (GISTs) - Evidence or "Gut-Feeling"?
2015
To examine practice patterns of endosonographers in diagnosing and managing gastrointestinal stromal tumors (GISTs) in Germany.A modified published survey (Ha et al., Gastrointest Endosc 2009) was sent to endosonographic ultrasound (EUS) customers in Germany. The survey was also publicized on the homepage of an EUS interest group. To avoid duplicate opinions, participants were asked to return one survey per institution.142 centers of roughly 850 German EUS centers responded. 25 % were from University hospitals and 74 % from community hospitals. 61 % performed 2 EUS scans for suspected subepithelial lesions/week. Although 97 % of respondents believed that tissue acquisition with CD117 immuno…
Diagnostic performance of endoscopic ultrasound through‐the‐needle microforceps biopsy of pancreatic cystic lesions: Systematic review with meta‐anal…
2020
Objectives Endoscopic ultrasound through-the-needle biopsy (EUS-TTNB) is a useful tool for differential diagnosis among pancreatic cystic lesions (PCLs). Cystic fluid cytology (CFC) is recommended by guidelines, but its diagnostic accuracy is about 50%. The aim of this meta-analysis is to assess the clinical impact of EUS-TTNB in terms of technical success (TS), histological accuracy (HA) and diagnostic yield (DY). Methods Original studies in English language on EUS-TTNB were searched in MEDLINE and EMBASE until October 2019. Diagnostic accuracy of EUS-TTNB for identification of mucinous PCLs was calculated using individual diagnostic data of patients who underwent CFC and surgery. Results …
The reflection coefficient of a flared microstrip line radiating in an infinite parallel-plate waveguide
1993
In this article the reflection coefficient of a tapered microstrip line radiating in an infinite parallel-plate conducting waveguide is calculated. The reflection coefficient at the feed line is evaluated by using the aperture admittance of the horn and the scattering matrix of the continuous taper. The theoretical behavior of the aperture admittance is shown and the reflection coefficient of a microstrip horn radiating in the parallel-plate region of a bootlace lens is measured in order to verify the model. © 1993 John Wiley & sons, Inc.
Uncertainty evaluation in the measurements for the electric power quality analysis
2013
The paper deals with the uncertainty estimation in the measurements performed to assess the electric power quality. In a first steps, according to the 'ISO - Guide to Expression of the Uncertainty in Measurements' all the error sources, which give a significant contribution to the combined uncertainty associated to the measurement results, are identified. Successively, in order to analyze how the errors propagate through the measurement chain, a Monte Carlo based approach is proposed. The method exploits an ad-hoc developed simulator of the measurement process, which takes into account the particular way of propagation of all the identified error sources. Eventually, with the aim of validat…