Emissions of air pollutants from non-conventional sources have been on the rise in the North Texas area over the past decade. These include primary pollutants such as volatile organic compound (VOC) and oxides of nitrogen (NOx) which also act as precursors in the formation of ozone. Most of these have been attributed to a significant increase in oil and gas production activities since 2000 within the Barnett Shale region adjacent to the Dallas-Fort Worth metroplex region. In this study, air quality concentrations measured at the Denton Airport and Dallas Hinton monitoring sites operated by the Texas Commission on Environmental Quality (TCEQ) were evaluated. VOC concentration data from canister-based sampling along with continuous measurement of oxides of nitrogen (NOx), ozone (O3), particulate matter (PM2.5), and meteorological conditions at these two sites spanning from 2000 through 2014 were employed in this study. The Dallas site is located within the urban core of one of the fastest growing cities in the United States, while the Denton site is an exurban site with rural characteristics to it. The Denton Airport site was influenced by natural gas pads surrounding it while there are very few natural gas production facilities within close proximity to the Dallas …

The addition of hexagonal boron nitride (h-BN) has introduced a comprehensive reinforcing effect to the mechanical and electrochemical properties of commercial concrete, including fiber reinforced concrete (FRC) and steel fiber reinforced concrete (SFRC). Although this has been proven effective and applicable, further investigation and study is still required to optimize the strengthen result which will involve the exfoliation of h-BN into single-layered nano sheet, improving the degree of dispersion and dispersion uniformity of h-BN into concrete matrix. There is currently no direct method to test the degree of dispersion of non-conductive particles, including h-BN, in concrete matrix, therefore it is necessary to obtain an analogous quantification method like SEM, etc. The reinforcing mechanism on concrete, including FRC and SFRC is now attracting a great number of interest thanks to the huge potential of application and vast demand across the world. This study briefly describes the reinforcing mechanism brought by h-BN. In this study, different samples under varied conditions were prepared according to the addition of h-BN and dispersant to build a parallel comparison. Characterization is mainly focused on their mechanical properties, corrosive performance and SEM analysis of the cross-section of post-failure samples.

The coronary heart disease kills more than 350,000 persons/year and it costs $108.9 billion for the United States each year, in spite of significant advancements in clinical care and education for public, cardiovascular diseases (CVD) are leading cause of death and disability to the nation. A cardiovascular disease involves mainly heart or blood vessels (arteries, veins and capillaries) or both, and then mainly occurs in selected regions and affects heart, brain, kidney and peripheral arteries. As a surgical interventions, stent implantation is deployed to cure or ameliorate the disease. However, the high failure rate of stents used in patients with peripheral artery diseases has lead researchers to give special attention towards analyzing stent structure and characteristics. In this research, the mechanical properties of a stent based on the rhombus structure were analyzed and verified by means of analytical and numerical approaches. Theoretical model based on the beam theory were developed and numerical models were used to analyze the response of these structures under various and complex loading conditions. Moreover, the analysis of the stent inflation involves a model with large deformations and large strains, nonlinear material properties need to be considered to accurately capture the deformation process. The maximum stress …

For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn …