The Presence of Birth Parents and Students’ Mathematics Achievement

This paper discusses the relationship between the presence of birth parents in a student’s home life and their grade last semester in mathematics. Our[1] study consisted of two sets of rosters from two different urban high schools in a large metropolitan district. The 238 students involved are currently enrolled in either AP Calculus AB, Pre-calculus, Applied Statistics, Algebra II, Honors Geometry, or Geometry. The research showed that 30.8% of students who live with only their birth mother received an A or a B for the semester while 17.5% percent failed their mathematics course. In contrast, 58.4% percent of students who live with both of their birth parents earned an A or a B and only 10.1% of them failed their mathematics course for the semester. I was able to conclude at a 1 percent significance level that students living with both of their birth parents are more likely to earn an A or a B in their mathematics course than students living with just one of their birth parents. Furthermore, at a 10 percent significance level, there is sufficient evidence to draw the conclusion that it is less likely for a student who lives with both of their birth parents to fail their mathematics course than it is for a student who lives with just their birth mother. Therefore, the data seems to imply a definite correlation between the presence of birth parents in the homes of students and the students’ grades. [1] This study was completed with one other person, Cailyn Rowan

Simulation of surface roughness during the formation of thermal spray coatings

The formation of a thermal spray coating was analyzed to identify methods to reduce the surface roughness of the coating. A new methodology was developed which uses a string of equally spaced node points to define the shape of the coating surface and to track the shape change as the thermal spray mass is deposited. This allows the calculation of arbitrary shapes for the coating surface which may be very complex. The model simulates the stochastic deposition of a large number of thermal spray droplets, where experimental data is used for the mass flux distribution on the target surface. This data shows that when the thermal spray mass impinges on the target surface, a large fraction of it (over-spray) splashes off the target and is re-deposited with a small spray angle, resulting in a large coating roughness. This analysis was used in a parameter study to identify methods for reducing the coating roughness. Effect of the shape of the profile for the pre-roughened substrate was found to be small. Decreasing the droplet size by a factor of 2 decreased the roughness by 13%. Increasing the spray angle for the over-spray by a factor of 2 decreased the roughness by 50%, and decreasing the amount of over- spray by a factor of 2 decreased the roughness by 51%

A capillary valve for microfluidic systems.

Microfluidic systems are becoming increasingly complicated as the number of applications grows. The use of microfluidic systems for chemical and biological agent detection, for example, requires that a given sample be subjected to many process steps, which requires microvalves to control the position and transport of the sample. Each microfluidic application has its own specific valve requirements and this has precipitated the wide variety of valve designs reported in the literature. Each of these valve designs has its strengths and weaknesses. The strength of the valve design proposed here is its simplicity, which makes it easy to fabricate, easy to actuate, and easy to integrate with a microfluidic system. It can be applied to either gas phase or liquid phase systems. This novel design uses a secondary fluid to stop the flow of the primary fluid in the system. The secondary fluid must be chosen based on the type of flow that it must stop. A dielectric fluid must be used for a liquid phase flow driven by electroosmosis, and a liquid with a large surface tension should be used to stop a gas phase flow driven by a weak pressure differential. Experiments were carried out investigating certain critical functions of the design. These experiments verified that the secondary fluid can be reversibly moved between its 'valve opened' and 'valve closed' positions, where the secondary fluid remained as one contiguous piece during this transport process. The experiments also verified that when Fluorinert is used as the secondary fluid, the valve can break an electric circuit. It was found necessary to apply a hydrophobic coating to the microchannels to stop the primary fluid, an aqueous electrolyte, from wicking past the Fluorinert and short-circuiting the valve. A simple model was used to develop valve designs that could be closed using an electrokinetic pump, and re-opened by simply turning the pump off and allowing capillary forces to push the secondary fluid back into its stowed position

Weld pool dynamics and the formation of ripples in 3D gas metal arc welding

© 2008, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 InternationalThis article studies the transient weld pool dynamics under the periodical impingement of filler droplets that carry mass, momentum, thermal energy, and species in a moving 3D gas metal arc welding. The complicated transport phenomena in the weld pool are caused by the combined effect of droplet impingement, gravity, electromagnetic force, plasma arc force, and surface tension force (Marangoni effect). The weld pool shape and the distributions of temperature, velocity, and species in the weld pool are calculated as a function of time. The phenomena of ‘‘open and close-up” for a crater in the weld pool and the corresponding weld pool dynamics are analyzed. The commonly observed ripples at the surface of a solidified weld bead are, for the first time, predicted by the present model. Detailed mechanisms leading to the formation of ripples are discussed.http://dx.doi.org/10.1016/j.ijheatmasstransfer.2007.07.04

Performance characterization of a hydrogen catalytic heater.

This report describes the performance of a high efficiency, compact heater that uses the catalytic oxidation of hydrogen to provide heat to the GM Hydrogen Storage Demonstration System. The heater was designed to transfer up to 30 kW of heat from the catalytic reaction to a circulating heat transfer fluid. The fluid then transfers the heat to one or more of the four hydrogen storage modules that make up the Demonstration System to drive off the chemically bound hydrogen. The heater consists of three main parts: (1) the reactor, (2) the gas heat recuperator, and (3) oil and gas flow distribution manifolds. The reactor and recuperator are integrated, compact, finned-plate heat exchangers to maximize heat transfer efficiency and minimize mass and volume. Detailed, three-dimensional, multi-physics computational models were used to design and optimize the system. At full power the heater was able to catalytically combust a 10% hydrogen/air mixture flowing at over 80 cubic feet per minute and transfer 30 kW of heat to a 30 gallon per minute flow of oil over a temperature range from 100 C to 220 C. The total efficiency of the catalytic heater, defined as the heat transferred to the oil divided by the inlet hydrogen chemical energy, was characterized and methods for improvement were investigated

Parameter study of a vehicle-scale hydrogen storage system.

Sandia National Laboratories has developed a vehicle-scale prototype hydrogen storage system as part of a Work For Others project funded by General Motors. This Demonstration System was developed using the complex metal hydride sodium alanate. For the current work, we have continued our evaluation of the GM Demonstration System to provide learning to DOE's hydrogen storage programs, specifically the new Hydrogen Storage Engineering Center of Excellence. Baseline refueling data during testing for GM was taken over a narrow range of optimized parameter values. Further testing was conducted over a broader range. Parameters considered included hydrogen pressure and coolant flow rate. This data confirmed the choice of design pressure of the Demonstration System, but indicated that the system was over-designed for cooling. Baseline hydrogen delivery data was insufficient to map out delivery rate as a function of temperature and capacity for the full-scale system. A more rigorous matrix of tests was performed to better define delivery capabilities. These studies were compared with 1-D and 2-D coupled multi-physics modeling results. The relative merits of these models are discussed along with opportunities for improved efficiency or reduced mass and volume