Critical Radius of Insulation

The critical radius of insulation is a counterintuitive concept within the study of heat transfer. The theory states that adding insulation to a cylindrical or spherical object will increase the rate of heat loss rather than decrease it, if the radius (thickness) of the insulation is at its “critical” value. The Critical Radius of Insulation Senior Project is designed to demonstrate this phenomenon to Heat Transfer students via a portable apparatus. The concept will be demonstrated with a cylindrical object which is heated by way of a separate voltage source. Thermocouples will display the temperature of the cylinder while insulation is added along with ambient air temperature, showing a distinct decrease in temperature caused by the addition of insulation. The design team conducted preliminary experiments using 1Ω, 2Ω, and 10Ω power resistors in an attempt to demonstrate the critical radius theory and evaluate the viability of using power resistors as the heated cylinder. The experiments were unsuccessful in demonstrating the critical radius theory but showed that the prototype setup was a viable design that could demonstrate this theory if the insulation material, insulation thickness, and power resistor diameter were properly modified. Based on the preliminary testing and analysis, a conceptual prototype model was developed. After further testing, the team determined that power resistors would take too long to reach steady state temperatures for a short classroom demonstration and that the diameters of the resistors were too large to demonstrate this theory with the appropriate experimental margin. Other studies were conducted using different heated cylinders starting with Calrod® heating elements. Testing was conducted with these heaters and 3D printed PLA insulation with great success. The heat loss for this setup was greater with the insulation than without, so the team used this heater and insulation combination to create a functioning structural prototype. Once the structural prototype was constructed and thoroughly tested, the team was able to successfully create a portable demonstration apparatus that physically shows the critical radius of insulation theory at work. This document details the iterative design process used to achieve the final design, the final design description, the manufacturing process used to build the final design, the verification and testing process, and conclusions about the overall project and the teams experience. The team’s overall objectives for this project are to first understand the concept of the critical radius of insulation and the experimental variables and assumptions that are important to proving it. The next step is to design and build an apparatus that can be used as a classroom demonstration and test this apparatus to ensure it is safe, easy to use, and clearly demonstrates critical radius theory. A supplemental handout also needs to be created to simply describe the theory to Heat Transfer students that will be witnessing this demonstration

X-ray image reconstruction from a diffraction pattern alone

A solution to the inversion problem of scattering would offer aberration-free diffraction-limited 3D images without the resolution and depth-of-field limitations of lens-based tomographic systems. Powerful algorithms are increasingly being used to act as lenses to form such images. Current image reconstruction methods, however, require the knowledge of the shape of the object and the low spatial frequencies unavoidably lost in experiments. Diffractive imaging has thus previously been used to increase the resolution of images obtained by other means. We demonstrate experimentally here a new inversion method, which reconstructs the image of the object without the need for any such prior knowledge.Comment: 5 pages, 3 figures, improved figures and captions, changed titl

Chronicles of Oklahoma

Article narrates the encounters and experiences the author had while participating in a boat ride to the Great Raft, one of the biggest water highways into Indian Territory, aboard the Belle of the Red River

High-resolution ab initio three-dimensional X-ray diffraction microscopy

Coherent X-ray diffraction microscopy is a method of imaging non-periodic isolated objects at resolutions only limited, in principle, by the largest scattering angles recorded. We demonstrate X-ray diffraction imaging with high resolution in all three dimensions, as determined by a quantitative analysis of the reconstructed volume images. These images are retrieved from the 3D diffraction data using no a priori knowledge about the shape or composition of the object, which has never before been demonstrated on a non-periodic object. We also construct 2D images of thick objects with infinite depth of focus (without loss of transverse spatial resolution). These methods can be used to image biological and materials science samples at high resolution using X-ray undulator radiation, and establishes the techniques to be used in atomic-resolution ultrafast imaging at X-ray free-electron laser sources.Comment: 22 pages, 11 figures, submitte

The Iron Assimilatory Protein, FEA1, from Chlamydomonas reinhardtii Facilitates Iron-Specific Metal Uptake in Yeast and Plants

We demonstrate that the unique green algal iron assimilatory protein, FEA1, is able to complement the Arabidopsis iron-transporter mutant, irt1, as well as enhance iron accumulation in FEA1 expressing wild-type plants. Expression of the FEA1 protein reduced iron-deficient growth phenotypes when plants were grown under iron limiting conditions and enhanced iron accumulation up to fivefold relative to wild-type plants when grown in iron sufficient media. Using yeast iron-uptake mutants, we demonstrate that the FEA1 protein specifically facilitates the uptake of the ferrous form of iron. Significantly, the FEA1 protein does not increase sensitivity to toxic concentrations of competing, non-ferrous metals nor facilitate their (cadmium) accumulation. These results indicate that the FEA1 protein is iron specific consistent with the observation the FEA1 protein is overexpressed in cadmium stressed algae presumably to facilitate iron uptake. We propose that the FEA1 iron assimilatory protein has ideal characteristics for the iron biofortification of crops and/or for facilitated iron uptake in plants when they are grown in low iron, high pH soils, or soils that may be contaminated with heavy metals