Determining thermal properties via parameter estimation of a one-dimensional, analytical model

“In thermal applications, thermal conductivity is used to predict how well a material conducts heat. The accuracy of the magnitude of the thermal conductivity becomes increasingly essential to optimize part geometry. Thermal conductivity can vary significantly from the nominal value due to post-processing. The ASTM standards available to measure thermal conductivity are challenging to reproduce because of the insulated and prescribed temperature boundary conditions that are needed. The research introduces two new methods for estimating thermal conductivity that deliver the same accuracy as the existing ASTM standards and are easier to implement. The methods account for losses in the heating to enable a better estimation of thermal conductivity. This research is directly applicable to estimating the thermal conductivity of additively manufactured materials. Additive manufacturing (AM) is being increasingly used for thermal applications; However, additive manufacturing can significantly affect thermal conductivity”--Abstract, page iv

Data on the Validation to Determine the Material Thermal Properties Estimation Via a One-Dimensional Transient Convection Model

These data were acquired to estimate the parameters of a closed form solution of a one-dimensional transient convection heat diffusion PDE. The purpose was to demonstrate that the model could be used to determine the thermal conductivity. The system was tested for a wide range of thermal conductivity, 15-400 W/mK, in order to verify that the method was applicable for various materials. The data reported here refer to the study in the research articles, Material Thermal Properties Estimation Via a One-Dimensional Transient Convection Model [1] and Influence of porosity on the thermal, electrical, and mechanical performance of selective laser melted stainless steel [2]. The dataset contains the raw data obtained from the temperature acquisition system as well as the processed results from a Python program to determine the thermal conductivity from a forced convection, transient one-dimensional heat diffusion equation

Data on the Validation to Determine the Material Thermal Properties Estimation via a One-Dimensional Transient Convection Model

These data were acquired to estimate the parameters of a closed form solution of a one-dimensional transient convection heat diffusion PDE. The purpose was to demonstrate that the model could be used to determine the thermal conductivity. The system was tested for a wide range of thermal conductivity, 15-400 W/mK, in order to verify that the method was applicable for various materials. The data reported here refer to the study in the research articles, “Material Thermal Properties Estimation Via a One-Dimensional Transient Convection Model” and “Influence of porosity on the thermal, electrical, and mechanical performance of selective laser melted stainless steel”. The dataset contains the raw data obtained from the temperature acquisition system as well as the processed results from a Python program to determine the thermal conductivity from a forced convection, transient one-dimensional heat diffusion equation

The proteomic response in the crustacean molting gland of land crab Gecarcinus lateralis in response to artificially induced molting throughout its molting cycle.

Molting in crustaceans is a highly complex physiological process involving negative regulation by two paired endocrine glands, the X-organ/sinus gland complex (XO/SG) and the Y-organ (YO). The XO/SG complex is responsible for making molt-inhibiting hormone (MIH) which negatively regulates synthesis of molting hormones (ecdysteroids) by the YO. Eyestalk ablation (ESA) removes the source of MIH and provides an experimental means to manipulate and induce molting, although the physiological effects of ESA on the YO have not been fully characterized. Analysis of gene expression in the XOs and YOs has lead to the development of a proposed molecular signaling pathway which regulates ecdysteroidogenesis and subsequent molting (ecdysis) in crustaceans. Results presented depict the changes in significantly different protein abundances in the YO over the course of the molting cycle (early, mid and late premolt) in crabs where 5 or more walking legs were lost, termed multiple leg autotomy (MLA). Proteins were characterized using two-dimensional gel electrophoresis and Delta2D software for statistical analysis. Future analysis will determine whether ESA can effectively mimic premolt conditions in the YO compared to the natural molting progression through protein identification by MALDI-TOF mass spectrometry. This will further resolve the metabolic and physiological changes associated with the transitions experienced by the YO throughout the molting stages. Determining the efficacy of ESA as a means to induce molting and determining molecular regulation of crustacean molting has broad economic impacts for crustacean fisheries as industry demands increase

Movements of House Sparrows Captured at an Experimental Grain Station in Fargo, North Dakota

From 2 August through 1 October 1993 we banded and leg flagged 362 house sparrows (126 adults, 236 juveniles) captured in a decoy trap at an experimental grain station on the campus of North Dakota State University, Fargo (NDSU). We documented sightings of leg-flagged birds between 3 August 1993 and 14 December 1994. Over this period, 56 (66%) of the total 76 observations of leg-flagged birds were on the NDSU campus; 21 (28%) of the 76 observations occurred between March and December 1994, a minimum of 5 months after the leg flags were attached and following the 1993-1994 winter. Of the 21 observations in 1994, 16 (76%) occurred on campus. The farthest sighting of a leg-flagged bird was 6.5 km (4 mi.) from the trap site. The data indicated that we captured and marked a localized population. A concerted effort based on trapping could reduce house sparrow damage on the small, experimental plots of cereal grains and sunflower grown at the station

Bandgap Change of Carbon Nanotubes: Effect of Small Tensile and Torsional Strain

We use a simple picture based on the $\pi$ electron approximation to study the bandgap variation of carbon nanotubes with uniaxial and torsional strain. We find (i) that the magnitude of slope of bandgap versus strain has an almost universal behaviour that depends on the chiral angle, (ii) that the sign of slope depends on the value of $(n-m) \bmod 3$ and (iii) a novel change in sign of the slope of bandgap versus uniaxial strain arising from a change in the value of the quantum number corresponding to the minimum bandgap. Four orbital calculations are also presented to show that the $\pi$ orbital results are valid.Comment: Revised. Method explained in detai

Ab initio molecular dynamics using density based energy functionals: application to ground state geometries of some small clusters

The ground state geometries of some small clusters have been obtained via ab initio molecular dynamical simulations by employing density based energy functionals. The approximate kinetic energy functionals that have been employed are the standard Thomas-Fermi $(T_{TF})$ along with the Weizsacker correction $T_W$ and a combination $F(N_e)T_{TF} + T_W$. It is shown that the functional involving $F(N_e)$ gives superior charge densities and bondlengths over the standard functional. Apart from dimers and trimers of Na, Mg, Al, Li, Si, equilibrium geometries for $Li_nAl, n=1,8$ and $Al_{13}$ clusters have also been reported. For all the clusters investigated, the method yields the ground state geometries with the correct symmetries with bondlengths within 5\% when compared with the corresponding results obtained via full orbital based Kohn-Sham method. The method is fast and a promising one to study the ground state geometries of large clusters.Comment: 15 pages, 3 PS figure

Density-functional-based predictions of Raman and IR spectra for small Si clusters

We have used a density-functional-based approach to study the response of silicon clusters to applied electric fields. For the dynamical response, we have calculated the Raman activities and infrared (IR) intensities for all of the vibrational modes of several clusters (SiN with N=3-8, 10, 13, 20, and 21) using the local density approximation (LDA). For the smaller clusters (N=3-8) our results are in good agreement with previous quantum-chemical calculations and experimental measurements, establishing that LDA-based IR and Raman data can be used in conjunction with measured spectra to determine the structure of clusters observed in experiment. To illustrate the potential of the method for larger clusters, we present calculated IR and Raman data for two low-energy isomers of Si10 and for the lowest-energy structure of Si13 found to date. For the static response, we compare our calculated polarizabilities for N=10, 13, 20, and 21 to recent experimental measurements. The calculated results are in rough agreement with experiment, but show less variation with cluster size than the measurements. Taken together, our results show that LDA calculations can offer a powerful means for establishing the structures of experimentally fabricated clusters and nanoscale systems

The strain energy and Young's Moduli of single-wall Carbon nanotubules calculated from the electronic energy-band theory

The strain energies in straight and bent single-walled carbon nanotubes (SWNTs) are calculated by taking account of the total energy of all the occupied band electrons. The obtained results are in good agreement with previous theoretical studies and experimental observations. The Young's modulus and the effective wall thickness of SWNT are obtained from the bending strain energies of SWNTs with various cross-sectional radii. The repulsion potential between ions contributes the main part of the Young's modulus of SWNT. The wall thickness of SWNT comes completely from the overlap of electronic orbits, and is approximately of the extension of $\pi$ orbit of carbon atom. Both the Young's modulus and the wall thickness are independent of the radius and the helicity of SWNT, and insensitive to the fitting parameters. The results show that continuum elasticity theory can serve well to describe the mechanical properties of SWNTs.Comment: 12 pages, 2 figure

Surface reconstruction induced geometries of Si clusters

We discuss a generalization of the surface reconstruction arguments for the structure of intermediate size Si clusters, which leads to model geometries for the sizes 33, 39 (two isomers), 45 (two isomers), 49 (two isomers), 57 and 61 (two isomers). The common feature in all these models is a structure that closely resembles the most stable reconstruction of Si surfaces, surrounding a core of bulk-like tetrahedrally bonded atoms. We investigate the energetics and the electronic structure of these models through first-principles density functional theory calculations. These models may be useful in understanding experimental results on the reactivity of Si clusters and their shape as inferred from mobility measurements.Comment: 9 figures (available from the author upon request) Submitted to Phys. Rev.