A Phase Change Material Technology Review Paper in Solar Energy Uses and Storage

The rapidly rising issue of declining the non-renewable resources available has focused the world attention on how renewable resources can be better used and harvested. Solar energy is one of the essential sources of renewable energy. Solar energy is a source of renewable energy for various applications in the world today. The present study is regarded as a summary of early studies on utilizing phase-change material in the use and storage of solar power. Due to its high thermal density, the isothermal nature and the easy power, the late thermosetting with the material is an advantageous way to store thermal energy. This paper summarizes how thermal energy can be efficiently stored via PCM in thermal energy storage systems of solar collectors. PCMs are isothermal, have higher density energy storage and are capable of operating in varying temperature environments. Therefore, an attempt was made in this paper to summarize an analysis of the various applications of phase change material (PCM), even solar collection device integrating PCMs

Theoretical Measuring for Negative Chromatic Dispersion Curves of Photonic Crystal Fiber by Gaussian Function

Negative dispersion curves in a typical type of high negative chromatic dispersion photonic crystal fiber(PCF) have been investigated in this paper. The depended class of (PCF) has double-core structure (core- region: which has inner core and outer core) with a honeycomb photonic lattice in the cladding region. Negative dispersion curves deviated from core-region of this type of fibers will be investigated. The investigation has depended an estimation process using an approximation function to create a mathematical model that enables us to measure negative dispersion curves. The influence of inner-core parameters (dcore d1 and d2) on dispersion curves has been investigated by varying the values of these parameters.  Negative dispersion curves that were introduced by a previous study using finite-difference frequency-domain (FDFD)method for this class of(PCFs) are directly included in this work in order  to measure matching ratio with our results.   Gaussian approximation function has been considered to estimate our mathematical model. Keywords: Photonic crystal fiber, Theoretical model, Negative chromatic dispersion, Gaussian function

Single channel electroencephalogram feature extraction based on probability density function for synchronous brain computer interface

Over recent years, there has been an explosive growth of interest in Electroencephalogram (EEG) based-Brain Computer Interface (BCI). Technically any architecture of a BCI is designed to have the ability of extracting out a set of features from brain signal. This paper demonstrated the extraction process based on Probability Density Function (PDF).A shared control scheme was developed between a mobile robot and subject. In general, subjects were required to synchronously imagine a star rotating and mind relaxation at specific time and direction. The imagination of a star would trigger a mobile robot suggesting that there is an object at certain direction. The mobile robot was then looking for a target based on probability value assigned to it. The result shows that 95 of theta activity was concentrated at target\x92s direction (during star imagination) and reduced when there is no target (during mind relaxation)

Comparison Mechanical Properties of Two Types of Light Weight Aggregate Concrete

This paper presents the behavior of concrete properties by replacing the conventional coarse aggregate used in the concrete mixture by two types of lightweight aggregate; Expanded Perlite Aggregate (EPA) and Volcanic Pumice (VP). To fulfill this aim; three laboratory tests were applied; density, compressive strength, and abrasion resistance, that conducted to extrapolate the range of the changes in the properties of concrete with existence those types of aggregate in the mixture. Also, the volumetric proportion adopted as a strategy for replacing the coarse aggregate by EPA or VP in the concrete mixture. Then, the volumetric proportion ranged from 10% to 50% with the variation step was 10%. Therefore, ten concrete mixtures are prepared and divided into two groups; each group contains five concrete mixes to represent the volumetric replacement (10-50)% of conventional coarse aggregate by EPA or VP. On the other hand, one extra mixture designed by using conventional aggregate (coarse and fine aggregate) without any inclusion of EPA or VP to be considered as a reference mixture. The obtained laboratory results of this study proved that the density, compressive strength, and abrasion resistance readings of concrete decreased at any volumetric proportion replacement of coarse aggregate by EPA or VP. The decrease in density and compressive strength of concrete readings amounted the peak level at 50% replacing of coarse aggregate by EPA, which were 38.19% and 77.37%, respectively than the reference mixture. Additionally, the compressive strength is an important factor affecting the abrasion resistance of concrete mixture, and loss of abrasion decreased as compressive strength increased

The impact of unloading stresses on post-caldera magma intrusions

Calderas represent morphological depressions several kilometers in diameter, and the unloaded crustal stresses they produce can form rapidly (e.g. Pinatubo, 1990) or slowly (e.g. Hawaii, 2018). Active calderas are known as sites of persistent magma intrusions, and yet the dynamics of their shallow plumbing system is not well constrained. We use scaled laboratory experiments to study how experimental intrusions are created beneath a caldera by injecting dyed water (magma analogue) into the base of an elastic gelatin solid (crust analogue) with a cylindrical cavity in its surface to mimic a caldera-like topography. The evolving dike geometry and stress field were qualitatively determined using polarized light, and digital image correlation allowed the incremental and total strain to be quantified by tracking passive-tracer particles in the gelatin that fluoresced in a thin 2D vertical laser sheet. Our results show that the unloaded stress field from a caldera can cause a divergence of vertical dikes, and leads to circumferential dikes and cone sheets. When the caldera was large the initially vertical dike became arrested, then grew laterally via circumferentially-propagating en echelon segments; these eventually joined to complete a cone sheet that was parallel to, but extended outside and beneath, the large caldera. When the caldera was small, a circumferential dike erupted, producing a short fissure which was outside, but parallel to, the caldera. We suggest that the distinct curved geometry, velocity, strain and stress characteristics of circumferential dikes and cone sheets can be used to interpret the origin and growth of post-caldera magmatism and the likelihood of eruption in caldera systems

The role and safety of endobronchial ultrasound-guided transbronchial needle aspiration in the diagnosis and management of infected bronchogenic mediastinal cysts in adults

Bronchogenic and other duplication cysts are congenital abnormalities that can present at any age including adulthood years. They are usually asymptomatic and discovered incidentally on radiological imaging of the chest. They are commonly treated by surgical resection. Recently, endobronchial ultrasound has been used to assist in diagnosis when radiologic imaging is not definitive. Endobronchial ultrasound has been used rarely to drain infected cysts, a rare complication of the bronchogenic cyst. We present a unique case of an infected large bronchogenic cyst treated with endobronchial ultrasound drainage combined with conservative medical therapy. We also review the scarce available literature describing such an approach and its potential complications and add recommendations based on our experience in managing these anomalies

Reaction kinetics of carbon dioxide with aqueous solutions of l-Arginine, Glycine & Sarcosine using the stopped flow technique

The use of amino acids as potential solvents for carbon dioxide (CO2) capture has been considered by a number of researchers. However, very little is known about the kinetics and mechanism of amino acids-CO2 reactions. In this work, we investigate the reactions of three amino acids (l-Arginine, Glycine and Sarcosine) with CO2 in aqueous media using stopped-flow conductivity technique. The experiments were performed at temperatures between 293 and 313K and amino acids concentrations were in the range of 0.05–0.2 molar. The overall rate constants (kov) was found to increase with increased amino acid concentration and solution temperature. Both zwitterion and termolecular mechanisms were used to model and interpret the data. However, the Zwitterion mechanism was found to be the preferred one. From the stopped-flow results at pH around 6, we found that neutral l-Arginine, Glycine and Sarcosine react with CO2(aq) with k(M−1s−1)=2.81×1010exp(−4482.9T(K)), k(M−1s−1)=3.29×1013exp(−8143.7T(K)) and k(M−1s−1)=3.90×1013exp(−7991.0T(K)) respectively. The corresponding activation energies are 37.28kJmol−1, 67.71kJmol−1 And 66.44kJmol−1 respectively. A comparison between the kinetics of the three amino acids showed that Arginine exhibits highest reaction rate with CO2 followed by Sarcosine and then Glycine. The technique and results obtained from this work can be used as strong tools in the development of efficient new solvents for the removal of CO2 from flue and industrial gases.This paper was made possible by an NPRP Grant # 7-1154-2-433 from the Qatar National Research Fund (a member of Qatar Foundation)

“Many people have no idea”: a qualitative analysis of healthcare barriers among Yazidi refugees in the Midwestern United States

Background: The COVID-19 pandemic has shed new light on inequities in healthcare access faced by immigrant and refugee communities. To address ongoing disparities, there is an urgent need for ecological approaches to better understand the barriers that hinder and resources that facilitate access to healthcare. This study investigates barriers to healthcare system access faced by Yazidi refugees in the Midwestern United States. Methods: Informed by the Interpretative Phenomenological Approach, three focus group meetings with a community advisory board were conducted between September 2019 and January 2020. The nine-member focus group included social workers, healthcare providers, and members of the Yazidi community. Meeting recordings were transcribed into English, coded for themes, and validated. Results: We describe themes related to specific barriers to healthcare access; analyze the influence of relational dynamics in the focus group; explore experiential themes related to healthcare access in the Yazidi community, and finally interpret our findings through a social-ecological lens. Conclusion: Community agencies, healthcare organizations, policymakers, and other stakeholders must work together to develop strategies to reduce systemic barriers to equitable care. Community representation in prioritysetting and decision-making is essential to ensure relevance, acceptability, and utilization of developed strategies