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Renewable Energy, Samuel A. Vigil

Civil and Environmental Engineering

No abstract provided.

Water Conservation And Wastewater Treatment, Samuel A. Vigil

Civil and Environmental Engineering

No abstract provided.

Comprehensive Analysis Of The Relationship Between Real-Time Traffic Surveillance Data And Rear-End Crashes On Freeways, Anurag Pande, Mohamed Abdel-Aty

Civil and Environmental Engineering

Rear-end collisions are the single most frequent type of crash on freeways. Their impact on freeway operation is also most noticeable because almost all of them occur during periods of medium to heavy demand. Preliminary explorations of average traffic speeds before a crash measured at loop detector stations surrounding the crash location showed that rear-end crashes can be placed into two mutually exclusive groups: first, those that occur under extended congestion and, second, those that occur with relatively free-flow conditions prevailing 5 to 10 min before the crash. With loop detector data preceding these two groups of rear-end crashes contrasted …

Critical Hypersonic Aerothermodynamic Phenomena, John J. Bertin, Russell M. Cummings

Aerospace Engineering

The challenges in understanding hypersonic flight are discussed and critical hypersonic aerothermodynamics issues are reviewed. The ability of current analytical methods, numerical methods, ground testing capabilities, and flight testing approaches to predict hypersonic flow are evaluated. The areas where aerothermodynamic shortcomings restrict our ability to design and analyze hypersonic vehicles are discussed, and prospects for future capabilities are reviewed. Considerable work still needs to be done before our understanding of hypersonic flow will allow for the accurate prediction of vehicle flight characteristics throughout the flight envelope from launch to orbital insertion.

Continuing Evolution Of Aerodynamic Concept Development Using Collaborative Numerical And Experimental Evaluations, Russell M. Cummings, Scott A. Morton

Aerospace Engineering

Traditionally, computational predictions and experimental evaluations of aerodynamic concepts have been conducted separately, with little collaboration other than post priori comparisons of results. This has led to distrust and even antagonism between the computational and the experimental communities. These difficulties probably began when early computational fluid dynamic practitioners boasted that wind tunnels would become secondary in aerodynamic concept development within a few short years, a prediction that has not come true. On the contrary, it is believed that a great deal of synergy can be cultivated when computational and experimental evaluations are conducted in an integrative fashion. A variety of …

Heat Pump Cooling And Greenhouse Microclimates In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh

BioResource and Agricultural Engineering

The purpose of this study was to determine and compare the performances of conventional and heat pump systems for cooling open and closed loop (confined) greenhouse systems. A dynamic simulation model was developed and validated to predict energy and mass exchanges in a greenhouse as a function of dynamic environmental factors. The model has options to evaluate the effects of location, time of the year, orientation, single and double polyethylene glazings, conventional and heat pump heating and cooling systems, CO₂ enrichment, ventilation, variable shading, and the use of night curtains in open and confined greenhouse environments. Variable shading, ventilation …

Dynamic Modeling Of Microclimate And Environmental Control Strategies In A Greenhouse Coupled With A Heat Pump System, Ilhami Yildiz, D. P. Stombaugh

BioResource and Agricultural Engineering

The purpose of this study was to develop and validate a dynamic simulation model to be employed in accurate prediction of microclimate in a greenhouse as a function of dynamic environmental factors. The model has options to evaluate the effects of location, time of the year, orientation, single and double polyethylene glazings, conventional and heat pump heating and cooling systems, open and confined greenhouse systems, CO₂ enrichment, variable shading, and the use of night curtains. Conventional gas furnace and evaporative cooling, respectively, provided heating and cooling in the conventional system. In the heat pump systems, gas-fired heat pump units …

Simulated Performances Of A Heat Pump System For Energy And Water Conservation In Open And Confined Greenhouse Systems, Ilhami Yildiz, D. P. Stombaugh

BioResource and Agricultural Engineering

The purpose of this study was to determine and compare the performances of conventional and heat pump systems for energy and water conservation in open and confined greenhouse systems. Conventional gas furnaces and evaporative cooling, respectively, provided heating and cooling in the conventional system. In the heat pump systems, gas-fired heat pump units provided both heating and cooling. The greenhouse with heat pump units also had an option to be operated as a completely confined system, using one of the heat pump units as a dehumidifier. Average energy consumption in winter was 56.9, 23.5, and 11.3 MJ/day.m² in the conventional, …

The Effect Of Reflow Profile On Snpb And Snagcu Solder Joint Shear Strength, Jianbiao Pan, Brian J. Toleno, Tzu-Chien Chou, Wesley J. Dee

Industrial and Manufacturing Engineering

Purpose –The purpose of this work is to study the effect of the reflow peak temperature and time above liquidus on both SnPb and SnAgCu solder joint shear strength.

Design/methodology/approach –Nine reflow profiles for Sn3.0Ag0.5Cu and nine reflow profiles for Sn37Pb have been developed with three levels of peak temperature (230°C, 240°C, and 250°C for Sn3.0Ag0.5Cu; and 195°C, 205°C, and 215°C for Sn37Pb) and three levels of time above solder liquidus temperature (30, 60, and 90 s). The shear force data of four different sizes of chip resistors (1206, 0805, 0603, and 0402) are compared across the different …

A Simplified Model For Ploughing Forces In Turning, Daniel Waldorf

Industrial and Manufacturing Engineering

This paper aims to provide experimental data in support of a modified theoretical model for quantifying the effect of cutting tool edge geometry on machining forces. A previously published slip-line model is simplified and extended to the case of turning. Several sets of machining experiments were run with custom-fabricated cutting inserts of varying edge hone radius and chamfer geometry. Cutting forces were measured using a dynamometer during cutting. Results show that varying edge geometry can have a major effect on cutting forces. The developed model effectively captures the edge phenomenon and its effect on cutting forces and also offers a …