Total and dissolved organic nitrogen analysis in an urban watershed

Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Includes bibliographical references (p. 60-61).by Matthew S. Orosz.M.Eng

The science and politics of increasing nitrogen pollution from human activity : case study of the Aberjona watershed

Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2006.Includes bibliographical references (p. 56-60).The biogeochemical cycling of nitrogen has critical implications for all life on earth. The Haber-Bosch process (1909) paved the way for the industrial fixation of NH3 from unreactive atmospheric dinitrogen, a phenomenon previously restricted to the enzyme nitrogenase and to a lesser extent lightning. Perhaps the most profoundly catalytic invention of the 20th century, Haber-Bosch has greatly increased the global anthropogenic throughput of nitrogen that now rivals the 160 million metric tons fixed annually via nitrogenase. Notably 40% of the world's 6 billion people alive today owe their body's kilogram of nitrogen to synthetic fertilizer created via the Haber-Bosch process (Smil 2001). The intensification of agriculture and the growth of urban centers during the 20th century has also resulted in substantive increases in nitrogen loads to the environment. Nitrogen transported by surface and groundwater is ultimately concentrated in rivers and coastal areas, with consequences such as eutrophication and the "dead zones" of hypoxia found throughout the world. Microbial metabolism of nitrogen via the nitrification and denitrification pathways also produces N20, a potent greenhouse gas currently responsible for 5% of total atmospheric radiative forcing.(cont.) This thesis examines the environmental implications of increased nitrogen throughput and the regulatory frameworks that are evolving to cope with nitrogen pollution. A case study of the Aberjona river, draining a heavily polluted urban watershed north of Boston, is examined in terms of the correlation between urban intensity and nitrogen yields (r2=0.79), the internal processing of nitrogen via major biological pathways, and the role of legacy pollutants as a source of nitrogen. The high fraction of organic nitrogen (34% of TOT N export) suggests that the effects of urban intensification are not limited to the export of inorganic species, and should be included in urban nitrogen budgets for effective watershed management.by Matthew Orosz.S.M

ThermoSolar and photovoltaic hybridization for small scale distributed generation : applications for powering rural health

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 213-223).The problem of provisioning a remote health clinic or school with electricity, heating and cooling (trigeneration) is considered from an engineering design and optimization standpoint. A baseline technical-economic review of existing options is performed, and a novel alternative is proposed: micro-Concentrating Solar Power (CSP), featuring an Organic Rankine Cycle (ORC) using repurposed HVAC scroll compressors as expanders. The design of the [mu]-CSP technology is informed by a semi-empirical steady state multi-physics sizing and performance model (SORCE) which predicts system output, efficiency, and specific costs as a function of geoposition. Empirical validation of key mechanical and electrical components is performed to parameterize the model. On a levelized cost basis, ,-CSP is shown to outperform standard equipment for trigeneration applications at remote sites. Scroll expander development is identified as an opportunity for enhanced performance, and a computationally efficient method for selecting optimal thermo-mechanical geometries for a scroll expander is described. Tradeoffs between concentration ratio, power block size and thermal storage are examined, and the key role of thermal capacity in the system is highlighted. A semi-dynamic version of SORCE is developed to support optimization amongst system components in a simulated operating environment including insolation and thermal transients; this offers preliminary insights into control decisions that influence cost and performance, such as timing and power management of ORC operation. Finally, the concept of synergies between concentrating solar photovoltaic (CPV) and CSP architecture is explored. A semi-empirical diode model is developed using experimental data from commercially available a-SI and c-Si solar cells and incorporated into PV-SORCE (where the [mu]-CSP thermal absorber is replaced with a PV heat collection element). Optimization of design parameters influencing figures of merit (system efficiency and specific costs) indicates that an optimal configuration is highly sensitive to the PV properties; as such, further optimization of the hybrid system parameters is recommended. This research also involved lab and field (Lesotho, southern Africa) prototyping of small solar ORC units. Relevant design parameters and further development of the [mu]-CSP concept is discussed in the context of field experiences.by Matthew S. Orosz.Ph.D

Geometric Design of Scroll Expanders Optimized for Small Organic Rankine Cycles

The application of organic Rankine cycles (ORCs) for small scale power generation is inhibited by a lack of suitable expansion devices. Thermodynamic and mechanistic considerations suggest that scroll machines are advantageous in kilowatt-scale ORC equipment, however, a method of independently selecting a geometric design optimized for high-volume-ratio ORC scroll expanders is needed. The generalized 8-dimensional planar curve framework (Gravesen and Henriksen, 2001, “The Geometry of the Scroll Compressor,” Soc. Ind. Appl. Math., 43, pp. 113–126), previously developed for scroll compressors, is applied to the expansion scroll and its useful domain limits are defined. The set of workable scroll geometries is: (1) established using a generate-and-test algorithm with inclusion based on theoretical viability and engineering criteria, and (2) the corresponding parameter space is related to thermodynamically relevant metrics through an analytic ranking quantity fc (“compactness factor”) equal to the volume ratio divided by the normalized scroll diameter. This method for selecting optimal scroll geometry is described and demonstrated using a 3 kWe ORC specification as an example. Workable scroll geometry identification is achieved at a rate greater than 3 s⁻¹ with standard desktop computing, whereas the originally undefined 8-D parameter space yields an arbitrarily low success rate for determining valid scroll mating pairs. For the test case, a maximum isentropic expansion efficiency of 85% is found by examining a subset of candidates selected the for compactness factor (volume expansion ratio per diameter), which is shown to correlate with the modeled isentropic efficiency (R² = 0.88). The rapid computationally efficient generation and selection of complex validated scroll geometries ranked by physically meaningful properties is demonstrated. This procedure represents an essential preliminary qualification for intensive modeling and prototyping efforts necessary to generate new high performance scroll expander designs for kilowatt scale ORC systems.United States. Environmental Protection Agency (SU 83436701

Kepler eclipsing binary stars. VII. the catalogue of eclipsing binaries found in the entire Kepler data set

The primary Kepler Mission provided nearly continuous monitoring of ~200,000 objects with unprecedented photometric precision. We present the final catalog of eclipsing binary systems within the 105 deg2 Kepler field of view. This release incorporates the full extent of the data from the primary mission (Q0-Q17 Data Release). As a result, new systems have been added, additional false positives have been removed, ephemerides and principal parameters have been recomputed, classifications have been revised to rely on analytical models, and eclipse timing variations have been computed for each system. We identify several classes of systems including those that exhibit tertiary eclipse events, systems that show clear evidence of additional bodies, heartbeat systems, systems with changing eclipse depths, and systems exhibiting only one eclipse event over the duration of the mission. We have updated the period and galactic latitude distribution diagrams and included a catalog completeness evaluation. The total number of identified eclipsing and ellipsoidal binary systems in the Kepler field of view has increased to 2878, 1.3% of all observed Kepler targets

The Blue Straggler RS CVn Star S1082 in M67: A Detailed Light Curve and the Possibility of a Triple

We present a picture of the very unusual blue straggler S1082 in the old open cluster M67 whose light is the sum of a close binary (P = 1.0677978 d) and another cluster member. We provide a complete V-band light curve for the system, and show a number of unusual features including brightness variations at the 0.01-0.03 mag level from month to month at all phases, and a narrow primary and broad secondary eclipses. We use spectra from several sources to constrain the temperatures of the three known components, the relative flux contributions, rotational velocities, and radial velocities. The data clearly show that the brightest star (narrow-line component) seen in the spectrum is on an orbit with period P = 1189 +/- 7 d and eccentricity e = 0.57 +/- 0.08, although we cannot prove that there is a dynamical link between it and the close binary. Our models of the system indicate that the cooler component of the close binary lies on the main sequence near the cluster turn-off, while the hotter component lies near an extension of the main sequence blueward of the turn-off, and thus qualifies as a blue straggler by itself. The reduction of the masses of the stars in the close binary compared to previous models indicates that it is possible that the more massive component of the close binary formed from a merger of just two turnoff-mass stars.(abridged)Comment: 48 pages, 9 figures, AASTeX, accepted for A

Masses, radii, and orbits of small Kepler planets : The transition from gaseous to rocky planets

We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurements, along with high-resolution imaging and spectroscopy, Doppler spectroscopy, and (for 11 stars) asteroseismology, we establish low false-positive probabilities (FPPs) for all of the transiting planets (41 of 42 have an FPP under 1%), and we constrain their sizes and masses. Most of the transiting planets are smaller than three times the size of Earth. For 16 planets, the Doppler signal was securely detected, providing a direct measurement of the planet's mass. For the other 26 planets we provide either marginal mass measurements or upper limits to their masses and densities; in many cases we can rule out a rocky composition. We identify six planets with densities above 5 g cm-3, suggesting a mostly rocky interior for them. Indeed, the only planets that are compatible with a purely rocky composition are smaller than 2 R ⊕. Larger planets evidently contain a larger fraction of low-density material (H, He, and H2O).Peer reviewedFinal Accepted Versio

TOI-1338 : TESS' first transiting circumbinary planet

Funding: Funding for the DPAC has been provided by national institutions, in particular, the institutions participating in the Gaia Multilateral Agreement. W.F.W. and J.A.O.thank John Hood Jr. for his generous support of exoplanet research at SDSU. Support was also provided and acknowledged through NASA Habitable Worlds grant 80NSSC17K0741 and NASA XRP grant 80NSSC18K0519. This work is partly supported by NASA Habitable Worlds grant 80NSSC17K0741. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program under grant No.(DGE-1746045). A.H.M.J.T. has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 803193/BEBOP) and from a Leverhulme Trust Research Project grant No. RPG-2018-418. A.C. acknowledges support by CFisUC strategic project (UID/FIS/04564/2019).We report the detection of the first circumbinary planet (CBP) found by Transiting Exoplanet Survey Satellite (TESS). The target, a known eclipsing binary, was observed in sectors 1 through 12 at 30 minute cadence and in sectors 4 through 12 at 2 minute cadence. It consists of two stars with masses of 1.1 M⊙ and 0.3 M⊙ on a slightly eccentric (0.16), 14.6 day orbit, producing prominent primary eclipses and shallow secondary eclipses. The planet has a radius of ∼6.9 R⊕ and was observed to make three transits across the primary star of roughly equal depths (∼0.2%) but different durations—a common signature of transiting CBPs. Its orbit is nearly circular (e ≍ 0.09) with an orbital period of 95.2 days. The orbital planes of the binary and the planet are aligned to within ∼1°. To obtain a complete solution for the system, we combined the TESS photometry with existing ground-based radial-velocity observations in a numerical photometric-dynamical model. The system demonstrates the discovery potential of TESS for CBPs and provides further understanding of the formation and evolution of planets orbiting close binary stars.Publisher PDFPeer reviewe