A Robust Approach for the Derivation of Closed-form Green's Functions

Cataloged from PDF version of article.Spatial-domain Green’s functions for multilayer, planar geometries are cast into closed forms with two-level approximation of the spectral-domain representation of the Green’s functions. This approach is very robust and much faster compared to the original one-level approximation. Moreover, il does not require the investigation of the spectral-domain behavior of the Green’s functions in advance to decide on the parameters of the approximation technique, and it can be applied to any component of the dyadic Green’s function with the same ease

Closed form Greens functions for general sources and stratified media

Cataloged from PDF version of article.The closed-form Green's functions of the vector and scalar potentials in the spatial domain are presented for the sources of horizontal electric, magnetic, and vertical electric, magnetic dipoles embedded in general, multilayer, planar media. First, the spectral domain Green's functions in an arbitrary layer are derived analytically from the Green's functions in the source layer by using a recursive algorithm. Then, the spatial domain Green's functions are obtained by adding the contributions of the direct terms, surface waves, and complex images approximated by the Generalized Pencil of Functions Method (GPOF). In the derivations, the main emphasis is to put these closed-form representations in a suitable form for the solution of the mixed potential integral equation (MPIE) by the method of moments in a general three-dimensional geometry. The contributions of this paper are: 1) providing the complete set of closed-form Green's functions in spectral and spatial domains for general stratified media; 2) using the GPOF method, which is more robust and less noise sensitive, in the derivation of the closed-form spatial domain Green's functions; and 3) casting the closed-form Green's functions in a form to provide efficient applications of the method of moments. © 1995 IEE

Fine-Grain Checkpointing with In-Cache-Line Logging

Non-Volatile Memory offers the possibility of implementing high-performance, durable data structures. However, achieving performance comparable to well-designed data structures in non-persistent (transient) memory is difficult, primarily because of the cost of ensuring the order in which memory writes reach NVM. Often, this requires flushing data to NVM and waiting a full memory round-trip time. In this paper, we introduce two new techniques: Fine-Grained Checkpointing, which ensures a consistent, quickly recoverable data structure in NVM after a system failure, and In-Cache-Line Logging, an undo-logging technique that enables recovery of earlier state without requiring cache-line flushes in the normal case. We implemented these techniques in the Masstree data structure, making it persistent and demonstrating the ease of applying them to a highly optimized system and their low (5.9-15.4\%) runtime overhead cost.Comment: In 2019 Architectural Support for Programming Languages and Operating Systems (ASPLOS 19), April 13, 2019, Providence, RI, US

Kardiyak cerrahide miyokardiyal koruma açısından intermittant antegrad kardiyopleji ile antegrad/retrograd sürekli kardiyoplejinin karşılaştırılması

Amaç: Bu çalışmada kardiyak cerrahide miyokardiyal koruma açısından intermittant antegrad kardiyopleji ile antegrad/retrograd sürekli kardiyopleji karşılaştırıldı. Ça­lış­ma­pla­nı:­ Ekim 2010 - Ocak 2011 tarihleri arasında kliniğimizde kardiyak cerrahi ameliyatı uygulanan 106 hasta çalışmaya alındı. Hastalar, intermittant antegrad kardiyopleji uygulananlar (grup 1; 18 kadın, 14 erkek) ve antegrad/retrograd sürekli kardiyopleji uygulananlar (grup 2; 16 kadın, 58 erkek) olmak üzere iki gruba ayrıldı ve ameliyat sonrası elde edilen sonuçlar karşılaştırıldı. İşlem sürecinde troponin-I, kreatin kinaz-miyokard bandı (CK-MB) düzeyleri, kardiyopulmoner baypas (KPB) ve kros klemp süreleri, kardiyopleji toplam miktarları ve potasyum kullanımı değerlendirildi. Bul gu lar: Bulgularımıza göre, ortalama troponin-I ve CK-MB değerleri grup 1’de grup 2’den daha yüksekti. Ancak bu farklılık istatistiksel olarak anlamlı değildi. Grup 1’de troponin-I ve CK-MB değerleri kros-klemp ve KPB süresi ile korele iken, grup 2’de troponin-I ve CK-MB değerleri kros-klemp ve KPB süresi ile korele değildi. So­nuç:­ Troponin-I, CK-MB düzeyleri ile KPB ve kros-klemp zamanları arasında anterograd/retrograd sürekli kardiyopleji uygulanan grupta korelasyon bulunmadı. Buna göre, antegrad/ retrograd sürekli kardiyopleji ile efektif miyokardiyal koruma sağlandığında, troponin-I ve CK-MB değerleri etkilenmedi ve miyokardiyal koruma daha iyiydi. Anterograd/retrograd sürekli kardiyopleji daha iyi miyokardiyal koruma sağlasa da anterograd kardiyopleji sırasında aort basıncı istenen düzeylerde tutulabilmesi için monitörize edilmeli ve retrograd kardiyopleji sırasında da retrograd kanül doğru yerde tutulmalıdır. Anah­tar­söz­cük­ler: Kardiyopleji, koroner baypas cerrahi, miyokardiyal yaralanma, miyokardiyal koruma.Background:­ This study aims to compare intermittent antegrade cardioplegia and antegrade/retrograde continuous cardioplegia in terms of myocardial protection in cardiac surgery. Methods: Hundred six patients who underwent cardiac surgery in our clinic between October 2010 and January 2011 were included in the study. Patients were divided into two groups as patients who received intermittent antegrade cardioplegia (group 1; 18 females, 14 males) and who received antegrade/retrograde continuous cardioplegia (group 2; 16 females, 58 males), and postoperative results were compared. Troponin-I, creatine kinase-myocardial band (CK-MB) levels, durations of cardiopulmonary bypass (CPB) and cross-clamping, total amounts of cardioplegia, and potassium utilization during the process were evaluated. Results:­ According to our results, mean troponin-I and CK-MB levels were higher in group 1 than group 2. However, this difference was not statistically significant. While troponin-I and CK-MB values were correlated to durations of cross-clamping and CPB in group 1, troponin-I and CK-MB values were not correlated to durations of cross-clamping and CPB in group 2. Conclusion:­ No correlation was detected between troponin I, CK-MB levels, and durations of CPB and cross-clamping in the group which received anterograde/retrograde continuous cardioplegia. Therefore, troponin-I and CK-MB levels were not affected and myocardial protection was better once effective myocardial protection was obtained by antegrade/retrograde continuous cardioplegia. Although antegrade/retrograde continuous cardioplegia provides better myocardial protection, aortic pressure must be monitored to be kept between desired levels during antegrade cardioplegia, and the retrograde cannula must be kept in the appropriate place during retrograde cardioplegia

Spurious radiation from microstrip interconnects

Cataloged from PDF version of article.The level of spurious radiation from microstrip interconnects, which are modeled here as either single or asymmetric parallel microstrip lines terminated by arbitrary complex load impedances, is investigated in this paper. The calculation of the spurious radiation requires a knowledge of the current distributions on the microstrip lines, and the first step is to compute these distributions efficiently. This is carried out here by using the method of moments in conjunction with closedform spatial domain Green’s functions that circumvent the need for time-consuming evaluation of Sommerfeld integrals. Once the current distributions on the etches have been obtained, the level of spurious radiation, which is defined as the radiated power crossing the plane parallel to the plane of interconnects, is calculated. The dependence of the spurious radiation on the lengths of the lines and on the termination impedances of the etches is also studie

Electromagnetic scattering solution of conducting strips in layered media using the fast multipole method

Cataloged from PDF version of article.The fast multipole method (FMM) is applied to the solution of the electromagnetic scattering problems in layered media for the first time. This is achieved by using closedform expressions for the spatial-domain Green’s functions for layered media. Until now, the FMM has been limited to the homogeneous-medium problems. An integral equation based on the two-dimensional scalar Helmholtz equation is solved to compute the electromagnetic scattering from sample geometries of conducting strips in layered media in order to demonstrate the accuracy and the efficiency of the new method

An efficient method for electromagnetic characterization of 2-D geometries in stratified media

Cataloged from PDF version of article.A numerically efficient technique, based on the spectral-domain method of moments (MoM) in conjunction with the generalized pencil-of-functions (GPOF) method, is developed for the characterization of two-dimensional geometries in multilayer planar media. This approach provides an analytic expression for all the entries of the MoM matrix, explicitly including the indexes of the basis and testing functions provided that the Galerkin’s MoM is employed. This feature facilitates an efficient modification of the geometry without the necessity of recalculating the additional elements in the MoM matrix. To assess the efficiency of the approach, the results and the matrix fill times are compared to those obtained with two other efficient methods, namely, the spatial-domain MoM in conjunction with the closed-form Green’s functions, and a fast Fourier transform algorithm to evaluate the MoM matrix entries. Among these, the spectral-domain MoM using the GPOF algorithm is the most efficient approach for printed multilayer geometries

The Limited Integrator Model Regulator And its Use in Vehicle Steering Control

Unexpected yaw disturbances like braking on unilaterally icy road, side wind forces and tire rupture are very difficult to handle by the driver of a road vehicle, due to his/her large panic reaction period ranging between 0.5 to 2 seconds. Automatic driver assist systems provide counteracting yaw moments during this driver panic reaction period to maintain the stability of the yaw dynamics of the vehicle. An active steering based driver assist system that uses the model regulator control architecture is introduced and used here for yaw dynamics stabilization in such situations. The model regulator which is a special form of a two degree of freedom control architecture is introduced and explained in detail in a tutorial fashion whereby its integral action capability, among others, is also shown. An auxiliary steering actuation system is assumed and a limited integrator version of the model regulator based steering controller is developed in order not to saturate the auxiliary steering actuator. This low frequency limited integrator implementation also allows the driver to take care of low frequency steering and disturbance rejection tasks. Linear simulation results are used to demonstrate the effectiveness of the proposed method

A numerically efficient technique for the analysis of slots in multilayer media

Cataloged from PDF version of article.A numerically efficient technique for the analysis of slot geometries in multilayer media is presented using closed-form Green's functions in spatial domain in conjunction with the method of moments (MoM). The slot is represented by an equivalent magnetic-current distribution, which is then used to determine the total power crossing through the slot and the input impedance. In order to calculate power and current distribution, spatial domain closed form Green's functions are expanded as power series of the radial distance rho, which makes the analytical evaluation of the spatial domain integrals possible, saving a considerable amount of computation time