Inverse Algorithm Method Research Articles

Comparison of myocardial depolarization spreading after resynchronization with left bundle branch area pacing versus biventricular pacing

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Left bundle branch area pacing (LBBAP) is an emerging new method of cardiac resynchronization therapy (CRT) in patients with left bundle branch block (LBBB). Studies comparing LBBAP with standard biventricular pacing (BiV) have shown similar post-operative shortening of QRS duration and left ventricular activation times. Calculation of equivalent dipole (ED) trajectories from 12-lead high-resolution ECG (hrECG) provides additional insight into myocardial depolarization and may be used for further assessment of left ventricular activation. Purpose The aim of this study was to determine myocardial depolarization patterns with assessment of ED trajectories in patients undergoing CRT with LBBAP or BiV and to compare them to myocardial depolarization patterns of healthy controls. Methods Twenty-five heart failure patients in sinus rhythm and LBBB with indication for CRT were randomized in LBBAP or BiV pacing group. Five-minute supine 12-lead hrECG recordings before and one month after implantation were assessed. LBBAP group was compared to BiV group and both groups were compared to the control of healthy subjects with normal surface ECG. The QRS duration was measured manually by two independent electrophysiologists and averaged. ED trajectories were constructed with the use of inverse algorithm method. The length of ED trajectory was defined as a line between the start and the end of the ED trajectory and its orientation with azimuth and elevation angles. (Figure 1). Results Eleven patients received LBBAP and 14 BiV. There were no differences in baseline characteristics (72% male, 64% non-ischemic cardiomyopathy) between groups. The average baseline QRS duration was 174±20 ms in LBBAP and 180±17 ms in BiV group (p=0.42). QRS duration decreased to 134±14 ms after LBBAP (p<0.01) and 137±11 ms after BiV pacing (p<0.01) and was comparable in both groups (p=0.59). There was also no difference in absolute (p=0.72) or relative (p=0.72) QRS shortening. The absolute and relative ED shortening did not differ (p=0.43 and p=0.38, respectively). At follow-up, analysis of ED trajectories showed a significant difference in elevation angle in both groups (p<0.01). The elevation angle in LBBAP group (6±30°) was significantly different from the angle in BiV group (-44±33°) (p < 0.01), pointing more toward apex of the heart (Figure 2). Furthermore, elevation angle in LBBAP was more similar (absolute difference 49°) to healthy subjects than the elevation angle in BiV group (absolute difference 103°) (p<0.01). There was no intergroup difference in azimuth angle (p=0.07). Conclusion Compared to BiV pacing, resynchronization with LBBAP produces significantly different ED trajectory orientation, which was more comparable to orientation in healthy controls. While both resynchronization methods result in similar QRS narrowing, LBBAP may provide more physiological depolarization of the left ventricle in comparison to BiV.

Estimation of pore aspect ratio and capillary pressure coefficient to predict S-wave velocity based on rockphysics modeling in orthorhombic anisotropic reservoirs

Accurate prediction of S-wave velocity is of great significance in many aspects, such as inversion, migration, brittleness index calculation, etc. Under normal circumstances, the more types of known input parameters there are, the more accurate the rock’s specific situation, and the more accurate the predicted S-wave velocity. However, considering the actual situation, the types of parameters obtained through logging curves are relatively limited. Some parameters cannot be measured and calculated, which limits the accuracy of S-wave prediction. Therefore, if the parameters can be predicted, a more accurate underground situation is able to described by these parameters. Through rockphysical analysis, the pore aspect ratio and capillary pressure coefficient can affect the velocity. In this way, a new orthorhombic (ORT) rockphysical modeling process considering the pore aspect ratio and capillary pressure coefficient is proposed. The model consists of VTI anisotropy from compaction or textural alignment of minerals, and HTI anisotropy from high-angle fractures caused by stratum pressure, thus showing ORT anisotropy. The inputs of the model can be multiple minerals. And the pore structure and the modulus of the mixed fluids in the pores are considered. We use inverse theory (quantum genetic algorithms) to obtain the pore aspect ratio and capillary pressure coefficient and finally calculate the S-wave velocity through the above parameters. The calculation results in a shale reservoir show that the predicted S-wave velocity is in good agreement with the real logging data. This shows that the proposed rockphysical modeling process and inverse algorithm method are effective.

A Method of the Inverse Evaluation for Heat Transfer Coefficient between Al-Cu Alloys and Cooling Water

The heat transfer coefficient between the alloys and cooling water is affected by a lot of factors and hard to measure, a new method was investigated with a self-designed system ultilizing SP-15 high-frequency inductive heating unit. Based on measured temperature curves and Fourier heat transfer model, quantitative correlation between heat transfer coefficient and temperature was obtained by inverse algorithm method of iterative simulation and automatic optimization. The results showed that in submerged water-cooling process, the heat transfer coefficient reached to a peak value at the beginning and then decreased with increasing temperature. A decrease of cooling water temperature increased the peak value of the heat transfer coefficient, but did not change temperature range of the peak value from 200°C to 225°C . The heat transfer coefficient was mainly dependent of interfacial temperature between the Al-Cu alloys and the cooling water.The temperatures range from 200°C to 225°C gave the highest heat flux transfer.

Estimation of Unknown Boundary Heat Flux in Laminar Circular Pipe Flow Using Functional Optimization Approach: Effects of Reynolds Number

An inverse forced convection problem was studied in this paper. The unknown space-dependent heat flux at the outer boundary of a circular pipe was identified from the temperature measurements within the flow using the algorithm based on an improved conjugate gradient method, which is a combination of the modified inverse algorithm proposed by Ozisik et al. (Huang and Ozisik, 1992, “Inverse Problem of Determining Unknown Wall Heat Flux in Laminar Flow Through a Parallel Plate Duct,” Numer. Heat Transfer, Part A 21, pp. 2615–2618) and the general inverse algorithm based on the conjugate gradient method. The effects of the convection intensity, the number of thermocouples, the location of the thermocouples, and the measurement error on the performance of the modified inverse algorithm method and the improved inverse algorithm were studied thoroughly through three examples. It is shown that the improved inverse algorithm can greatly improve the solution accuracy in the entire computation domain. The accuracy and stability of both the modified inverse algorithm method and the improved inverse algorithm are strongly influenced by the Reynolds number and the shape of the unknown heat flux. Those functions, which contain more high-frequency components of Fourier series, are more sensitive to the increase in the Reynolds number.

Construction of refractive-index profile of single mode fiber from the near-field technology with an inverse algorithm method

In this paper, the refractive-index profile (RIP) of single-mode fiber is reconstructed from the measured transmitted near-field (NF) intensity combined with an inverse algorithm method, which can improve the conventional NF method to avoid the troubles introduced by multiple measurements and iteration smoothing in the processing of measuring the RIP without influencing the accuracy of the results. The method used here has the advantages of convenient operation and accurate results for the characterization of single-mode optical fiber; it can also be applied to the RIP measurement of graded index fibers, single-mode planar waveguides, and channel waveguides.

Spectroscopic ellipsometric characterization of transparent thin film amorphous electronic materials: integrated analysis

Silicon dioxide and silicon oxynitride thin films deposited on crystalline silicon substrates were characterized by phase modulated spectroscopic ellipsometry in the UV-visible range. The thickness and the refractive index of the films were calculated by assuming an ambient/film/substrate system with three different approaches: modeling the dielectric function with Cauchy's dispersion formula, using the Bruggeman effective medium approximation and using a direct inversion algorithm method. The comparison of the results obtained by these approaches along with the subsequent qualitative study of possible weak absorption and depth inhomogeneities in the samples allows us to evaluate the accuracy of the experimental data as well as the reliability of the model and results.