A Single-Step Method for Over-the-Horizon Geolocation Using Importance Sampling

This paper investigates the geolocation for an over-the-horizon (OTH) transmitter observed by widely separated arrays. We propose a maximum likelihood (ML) based direct position determination (DPD) method to directly locate the transmitter in a single step by exploiting the position information embedded in azimuth angles. The Monte Carlo importance sampling (IS) technique is employed to find an approximate global solution to this DPD problem, where the importance function analogous to Gaussian distribution is derived. This enables the transmitter to be precisely located with low complexity in a noniterative manner. Additionally, we derive the Cramér–Rao bound (CRB) expression for the investigated problem. The simulation results corroborate the superior localization performance of the proposed method with respect to the conventional two-step approaches and the iterative DPD method.

Role of Astrocytes in Central Nervous System, Disease Implications and New Physiological Implications in Memory and Learning

Inside Central Nervous System (CNS) appears neurons and glia cells. There are more glial cells than neurons and have more functions than neurons. Glia name represents different kind of cells, ones from neural origin (astrocytes, radial glia, and oligodendroglia), and others from blood monocytes (microglia). During ontogeny, neurons appear first (rat fetal 15th) and after astrocytes (rat fetal 21th) indicating a bigger importance function in the CNS. Also, during the phylogeny, reptiles have less astrocytes compared to neurons and in humans, astrocytes are double in number than neurons. This data, perhaps means that astrocytes are more special cells and work in memory and learning? Astrocytes have an important role in different mechanisms protecting CNS across the production of antioxidant and anti-inflammatory proteins, cleaning extracellular medium and helping neurons to communicate with each other correctly. Inflammatory mediators production are important to prevent changes in normal physiology. But, excessive or continue production leads to many diseases, such as Alzheimer's disease (AD), Sclerosis Lateral Amyotrophic (ELA), Multiple sclerosis (MS), and neurodevelopment diseases, like Bipolar disorder, Schizophrenia, and Autism's symptomatology. Different drugs and thecniques can reverse oxidative stress and/or inflammatory excess. This review is intended to serve as an approximation to the field.

A Study on the Korean Conversation Speech Level and Spectrum in Sound-Treated Environment

Purpose: Several studies have reported the differences between Korean and other countries’ speech in long-term average speech spectrum (LTASS) and band importance function. Authors tried to identify the conversational speech level, the resulting spectrum, and the LTASS for Korean. The purpose of this study was to support the production of a Korean-type hearing aid fitting formula to effectively improve the sound quality of hearing aids and the communication abilities with hearing aids, and to standardize the sound stimuli required to measure the performance of hearing aids. Methods: A total of 73 participants with normal hearing and with no specific voice and language deficits was voluntarily recruited from capital, Gyeongsang and Jeolla areas. The conversational speech level was measured by vocalizing ‘soft,’ ‘moderate,’ ‘raised,’ and ‘loud’ at a distance of 1.0 m from the speaker. And LTASS was measured by vocalizing it at a distance of 0.2 m from the speaker. Results: There was a difference in the mean of males and females in the conversation level, but no significant regional differences were shown. The conversational speech level corresponding to 30th, 65th, and 99th percentiles was 59.67, 64.74, and 79.07 dB sound pressure level, respectively. And the speech spectrum of 30th, 65th, and 99th percentile and LTASS showed in different forms from the international speech test signal. Conclusion: The results of this study should help to calculate the Korean type hearing aid fitting formula and should be used as the basic data to determine the characteristics of the sound stimuli when measuring the performance of the hearing aid.

Real-time subsurface scattering with single pass variance-guided adaptive importance sampling

In real-time applications, it is difficult to simulate realistic subsurface scattering with differing degrees translucency. Burley's reflectance approximation by empirically fitting the diffusion profile as a whole makes it possible to achieve realistic looking subsurface scattering for different translucent materials in screen space. However, achieving a physically correct result requires real-time Monte Carlo sampling of the analytic importance function per pixel per frame, which seems prohibitive to achieve. In this paper, we propose an approximation of the importance function that can be evaluated in real-time. Since subsurface scattering is more pronounced in certain regions (e.g., with light gradient change), we propose an adaptive sampling method based on temporal variance to lower the required number of samples. We propose a one phase adaptive sampling pass that is unbiased, and able to adapt to scene changes due to motion and lighting. To further improve the quality, we explore temporal reuse with a guiding pass prior to the final temporal anti-aliasing (TAA) phase that further improves the quality. Our local guiding pass does not constrain the TAA implementation, and only requires one additional texture to be passed between frames. Our proposed variance-guided algorithm has the potential to make stochastic sampling algorithm effective for real-time rendering.