DESIGN OPTIMIZATION OF SPACE SYSTEM COMPONENTS USING ADDITIVE MANUFACTURING

While launch costs have decreased in the past decade, the desire to minimize mass for space systems persists. Previous research has identified several design optimization techniques centered around the use of additive manufacturing, but no way of combining these techniques into an efficient workflow has been developed yet. This thesis explores the feasibility of combining several design optimization techniques and assessing their performance to develop workflows that allow for rapidly optimizing components for use in aerospace systems. In this research, a rocket’s structural bracket was chosen as the component to be optimized. Various types of topology optimization techniques were applied to the bracket and were assessed on structural performance. A lattice design optimization was then conducted and evaluated. Afterward, a combination of multiple optimization techniques were then experimented with. The results of these experiments then had their performances evaluated as well. Through direct comparison of each model, it was found that a workflow centered around a lattice design produced the fastest and cheapest results. A workflow involving a topology optimization produced better results at higher expense. The best results came from combining a topology optimization with a lattice design optimization, but was the most computationally expensive. These results provide insight into the appropriate design and optimization workflow that will best support a system’s requirements.Distribution Statement A. Approved for public release: Distribution is unlimited.Ensign, United States Nav

Using activities to correct the Henderson-Hasselbalch equation

The Henderson-Hasselbalch equation is central in chemistry teaching and has many practical applications. The equation, however, has many inherent approximations which limit its application. Here, we focus on one particular approximation, the use of concentrations instead of activities. We show that this can be easily corrected for in a modification which extends the useful range of the equation to moderately strong electrolytes (I < 0.5). Without this correction, the calculated pH of a typical phosphate buffer is too high by up to 0.4. The correction can be easily automated in a spreadsheet and is straightforward to implement into the chemistry and biochemistry teaching and laboratory curriculum. It introduces students to the concept of activities in thermodynamic equilibrium, and to the Debye-Hückel equation. It further emphasizes the importance of using activities instead of concentrations when the ionic strength exceeds 0.005 M, in contrast to the approach found in textbooks where activities are introduced, but then ignored 'for the sake of simplicity', even in example calculations where the use of concentrations is clearly not appropriate. In this contribution we intend also to stimulate discussions about how to teach chemical equilibria, Brønsted-Lowry acid-base reactions and titrations, buffer solutions, the concept of activity and the concept and definition of pH

Discovery of a stellar companion to the nearby solar-analogue HD 104304

Sun-like stars are promising candidates to host exoplanets and are often included in exoplanet surveys by radial velocity (RV) and direct imaging. In this paper we report on the detection of a stellar companion to the nearby solar-analogue star HD 104304, which previously was considered to host a planetary mass or brown dwarf companion. We searched for close stellar and substellar companions around extrasolar planet host stars with high angular resolution imaging to characterize planet formation environments. The detection of the stellar companion was achieved by high angular resolution measurements, using the "Lucky Imaging" technique at the ESO NTT 3.5m with the AstraLux Sur instrument. We combined the results with VLT/NACO archive data, where the companion could also be detected. The results were compared to precise RV measurements of HD 104304, obtained at the Lick and Keck observatories from 2001-2010. We confirmed common proper motion of the binary system. A spectral type of M4V of the companion and a mass of 0.21 M_Sun was derived. Due to comparison of the data with RV measurements of the unconfirmed planet candidate listed in the Extrasolar Planets Encyclopaedia, we suggest that the discovered companion is the origin of the RV trend and that the inclination of the orbit of approximately 35 degrees explains the relatively small RV signal.Comment: 4 pages, 4 PNG figures, use aa.cls, accepted for publication in Astronomy & Astrophysic

Cavity-Enhanced Raman Spectroscopy in the Biosciences: In situ, Multicomponent and Isotope Selective Gas Measurements to Study Hydrogen Production and Consumption by Escherichia coli

Recently we introduced cavity-enhanced Raman spectroscopy (CERS) with optical feedback cw-diode lasers as a sensitive analytical tool. Here we report improvements made on the technique and its first application in the biosciences for in situ, multicomponent, and isotope selective gas measurements to study hydrogen production and consumption by Escherichia coli. Under anaerobic conditions, cultures grown on rich media supplemented with D-glucose or glycerol produce H2 and simultaneously consume some of it. By introducing D2 in the headspace, hydrogen production and consumption could be separated due to the distinct spectroscopic signatures of isotopomers. Different phases with distinctly different kinetic regimes of H2 and CO2 production and D2 consumption were identified. Some of the D2 consumed is converted back to H2 via H/D exchange with the solvent. HD was formed only as a minor component. This reflects either that H/D exchange at hydrogenase active sites is rapid compared to the rate of recombination, rapid recapture of HD occurs after the molecule is formed, or that the active sites where D2 oxidation and proton reduction occur are physically separated. Whereas in glucose supplemented cultures, addition of D2 led to an increase in H2 produced, while the yield of CO2 remained unchanged; with glycerol, addition of D2 led not only to increased yields of H2, but also significantly increased CO2 production, reflecting an impact on fermentation pathways. Addition of CO was found to completely inhibit H2 production and significantly reduce D2 oxidation, indicating at least some role for O2-tolerant Hyd-1 in D2 consumption

The Impact of Adaptive Optics on Star Formation Research

In this paper, we discuss the benefits of ground-based, adaptive optics (AO) aided observations for star formation research. After outlining the general advantages, we present results obtained during the ALFA science demonstration programme in 1999. These results underline the absolute necessity of AO assistance for almost any kind of observations regarding star formation regions.Comment: 10 pages, 8 figures (partially converted to bitmap), to appear in SPIE Proceedings 4007, Astronomical Telescopes and Instrumentation 2000, Munich, German

PYRAMIR: Calibration and operation of a pyramid near-infrared wavefront sensor

The concept of pyramid wavefront sensors (PWFS) has been around about a decade by now. However, there is still a great lack of characterizing measurements that allow the best operation of such a system under real life conditions at an astronomical telescope. In this article we, therefore, investigate the behavior and robustness of the pyramid infrared wavefront sensor PYRAMIR mounted at the 3.5 m telescope at the Calar Alto Observatory under the influence of different error sources both intrinsic to the sensor, and arising in the preceding optical system. The intrinsic errors include diffraction effects on the pyramid edges and detector read out noise. The external imperfections consist of a Gaussian profile in the intensity distribution in the pupil plane during calibration, the effect of an optically resolved reference source, and noncommon-path aberrations. We investigated the effect of three differently sized reference sources on the calibration of the PWFS. For the noncommon-path aberrations the quality of the response of the system is quantified in terms of modal cross talk and aliasing. We investigate the special behavior of the system regarding tip-tilt control. From our measurements we derive the method to optimize the calibration procedure and the setup of a PWFS adaptive optics (AO) system. We also calculate the total wavefront error arising from aliasing, modal cross talk, measurement error, and fitting error in order to optimize the number of calibrated modes for on-sky operations. These measurements result in a prediction of on-sky performance for various conditions

Shack-Hartmann wave front measurements in cortical tissue for deconvolution of large three-dimensional mosaic transmitted light brightfield micrographs

We present a novel approach for deconvolution of 3D image stacks of cortical tissue taken by mosaic/optical-sectioning technology, using a transmitted light brightfield microscope. Mosaic/optical-sectioning offers the possibility of imaging large volumes (e.g. from cortical sections) on a millimetre scale at sub-micrometre resolution. However, a blurred contribution from out-of-focus light results in an image quality that usually prohibits 3D quantitative analysis. Such quantitative analysis is only possible after deblurring by deconvolution. The resulting image quality is strongly dependent on how accurate the point spread function used for deconvolution resembles the properties of the imaging system. Since direct measurement of the true point spread function is laborious and modelled point spread functions usually deviate from measured ones, we present a method of optimizing the microscope until it meets almost ideal imaging conditions. These conditions are validated by measuring the aberration function of the microscope and tissue using a Shack-Hartmann sensor. The analysis shows that cortical tissue from rat brains embedded in Mowiol and imaged by an oil-immersion objective can be regarded as having a homogeneous index of refraction. In addition, the amount of spherical aberration that is caused by the optics or the specimen is relatively low. Consequently the image formation is simplified to refraction between the embedding and immersion medium and to 3D diffraction at the finite entrance pupil of the objective. The resulting model point spread function is applied to the image stacks by linear or iterative deconvolution algorithms. For the presented dataset of large 3D images the linear approach proves to be superior. The linear deconvolution yields a significant improvement in signal-to-noise ratio and resolution. This novel approach allows a quantitative analysis of the cortical image stacks such as the reconstruction of biocytin-stained neuronal dendrites and axons

High-resolution spectroscopy of triplet states of Rb2 by femtosecond pump-probe photoionization of doped helium nanodroplets

The dynamics of vibrational wave packets in triplet states of rubidium dimers (Rb2) formed on helium nanodroplets are studied using femtosecond pump-probe photoionization spectroscopy. Due to fast desorption of the excited Rb2 molecules off the droplets and due to their low internal temperature, wave packet oscillations can be followed up to very long pump-probe delay times >1.5ns. In the first excited triplet state (1)^3\Sigma_g^+, full and fractional revivals are observed with high contrast. Fourier analysis provides high-resolution vibrational spectra which are in excellent agreement with ab initio calculations