Photoacoustic Imaging using Combination of Eigenspace-Based Minimum Variance and Delay-Multiply-and-Sum Beamformers: Simulation Study

Delay and Sum (DAS), as the most common beamforming algorithm in Photoacoustic Imaging (PAI), having a simple implementation, results in a low-quality image. Delay Multiply and Sum (DMAS) was introduced to improve the quality of the reconstructed images using DAS. However, the resolution improvement is now well enough compared to high resolution adaptive reconstruction methods such as Eigenspace- Based Minimum Variance (EIBMV). We proposed to integrate the EIBMV inside the DMAS formula by replacing the existing DAS algebra inside the expansion of DMAS, called EIBMV-DMAS. It is shown that EIBMV-DMAS outperforms DMAS in the terms of levels of sidelobes and width of mainlobe significantly. For instance, at the depth of 35 mm, EIBMV-DMAS outperforms DMAS and EIBMV in the term of sidelobes for about 108 dB, 98 dB and 44 dB compared to DAS, DMAS, and EIBMV, respectively. The quantitative comparison has been conducted using Full-Width-Half-Maximum (FWHM) and Signal-to-Noise Ratio (SNR), and it was shown that EIBMV-DMAS reduces the FWHM about 1.65 mm and improves the SNR about 15 dB, compared to DMAS.Comment: Submitted in 24th Iranian Conference on Biomedical Engineering (ICBME 2017

Imam Sajad's View on Lifestyle: Acting against Deviations and Promoting Virtues

The term lifestyle was first introduced in social sciences in 1908 by Simmel. This was given individual and social dimensions and was considered as a major index of discerning the individual and social identities. The introduction of lifestyle issue in Iranian academia brought about its pros and cons. Some Muslim theorists tried to localize it and set about finding its associative concepts through investigating Islamic scientific heritage an Muslim scholars' ideas. By focusing on the term Islamic lifestyle, they produced texts in that field. Now, this new discourse is flourishing. The present article is centering upon and elaborating on Imam Sajad's view on lifestyle specifications, with the aim of contributing to the existing literature. Some of the specifications achieved are; compassion, actualizing one's instructions, and maintaining a constant relation with the Supreme God, all as practical methods in acting against deviations and promoting virtues. The research method has been descriptive/ analytical. The procedure includes selecting and analyzing Imam's Sahifa- al Sajadia and sayings, and then profiting from other related Ayas and traditions

New algorithm for evaluation of electric fields due to indirect lightning strike

Evaluation of electric field due to indirect lightning strike is an interesting subject. Calculation of electric and magnetic fields in time domain with the consideration of ground conductivity effect in the shortest possible time is an important objective. In this paper, using dipole method, Maxwell's equation and Cooray-Rubinstein formula, a new method for calculation of electric field in time domain is proposed. In addition, this proposed algorithm can also be used to evaluate the effect at the far distance cases of observation point from lightning channel

Considering on return stroke current wave shape for tall objective cases

The return stroke current along the lightning channel for striking of the lightning to tall objective case is different from ground surface case with many factors affect this phenomenon. This study considers the engineering related to return stroke current models where the general equations are expressed and different models are generated. The results obtained will be compared and discussed

New approach in time domain for evaluation of electric and magnetic fields near the lightning channel

The electric and magnetic fields due to lightning channel can be estimated by many methods such as Finite Difference Time Domain (FDTD) and dipole methods. Estimation of electric fields in time domain by dipole method for a realistic return stroke current along the lightning channel is very complex. On the other hand, the FDTD is an appropriate method for a close distance problem but it consumes high memory for the computer to process the result. This paper presents the combination of the FDTD and dipole methods for evaluation the magnetic fields at any observation points with less difficulty and less memory consumption. In addition, the use of the FDTD method provides the ability to evaluate the fields for the case of non-perfect ground conductivity. Hence, by applying the dipole and FDTD methods with the Caligaris et.al's algorithm, extended from Cooray-Rubinstein formula, the approach and formulation of electric and magnetic fields in time domain is proposed, with the consideration of the non-perfect ground conductivity effect. Results obtained from this new approach are compared with the measurements data published in literatures

Effect of soil resistivity on the value of lightning induced voltage

In this paper, lightning induced voltages on a distribution line associated with a lightning channel with reflection at the channel base were evaluated and compared with the corresponding values from a normal channel. Moreover, the effect of soil resistivity on the value of the lightning induced voltage and also lightning current and induced voltage behaviours versus soil resistivity changes were considered and the results discussed accordingly. The results showed that the reflected currents along channel can be strangely effective on the values of electromagnetic field and also lightning induced voltage. Therefore, in order to set proper protection on the distribution lines, the local information about electrical soil parameters should be taken into account

On the behaviour of lightning current for the case of striking to tall strature

In this paper, the behaviour of lightning current wave shapes at different heights along a tall tower are studied and the simulated current compared to the corresponding measured current obtained from a real tall structure. Further, the effects of ground reflection and also the tower top reflection factors on the peak values of current and current peak time at different heights along a tower are studied and the results discussed accordingly

Considering on charge density along return stroke lightning channel

Prediction of return stroke current wave shape along lightning channel is an important subject in evaluating the electromagnetic fields and induced overvoltage due to lightning channel at observation point and power line. This paper reviews the different return stroke current models, with the engineering current models is selected as the leading model, and evaluates the their current behaviors along the lightning channel. A comprehensive result on the charge density for each model will then be presented to conclude the findings