| 1. |
- Leisawitz, David, et al.
(författare)
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The origins space telescope
- 2019
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 11115
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Konferensbidrag (refereegranskat)abstract
- The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid-and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 1/2 year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8-20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25-588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ∼ 300, and pointed observations at R ∼ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins' natural backgroundlimited sensitivity.
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| 2. |
- Leisawitz, David, et al.
(författare)
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The Origins Space Telescope: Mission concept overview
- 2018
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 10698
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Konferensbidrag (refereegranskat)abstract
- Downloading of the abstract is permitted for personal use only. The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.
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| 3. |
- Grasby, Katrina L., et al.
(författare)
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Estimating Classroom-Level Influences on Literacy and Numeracy: A Twin Study
- 2020
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Ingår i: Journal of Educational Psychology. - : AMER PSYCHOLOGICAL ASSOC. - 0022-0663 .- 1939-2176. ; 112:6, s. 1154-1166
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Tidskriftsartikel (refereegranskat)abstract
- Classroom-level influences on literacy skills in kindergarten through Grade 2, and on literacy and numeracy skills in Grades 3. 5, 7, and 9. were examined by comparing the similarity of twins who shared or did not share classrooms with each other. We analyzed two samples using structural equation modeling adapted for twin data. The first, Study 1, was of Australia-wide tests of literacy and numeracy, with 1,098; 1,080; 790, and 812 complete twin pairs contributing data for Grades 3, 5, 7, and 9, respectively. The second, Study 2, was of literacy tests from 753 twin pairs from kindergarten through Grade 2, which included a sample of United States and Australian students and was a reanalysis and extension of Byrne et al. (2010). Classroom effects were mostly nonsignificant; they accounted for only 2-3% of variance in achievement when averaged over tests and grades. Although the averaged effects may represent a lower-bound figure for classroom effects, and the design cannot detect classroom influences limited to individual students, the results are at odds with claims in public discourse of substantial classroom-level influences, which are mostly portrayed as teacher effects.
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| 4. |
- Wu, Desheng Dash, et al.
(författare)
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Green supply chain management under capital constraint
- 2019
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Ingår i: International Journal of Production Economics. - : Elsevier BV. - 0925-5273 .- 1873-7579. ; 215, s. 3-10
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Tidskriftsartikel (refereegranskat)abstract
- To determine how carbon emissions reduction affects supply chain operations and financing decisions, this paper examines a green supply chain, which consists of one manufacturer (playing the leading role) and one capital-constrained retailer; in this supply chain, bank financing and trade credit financing are viable. This research explores the retailer's optimal order quantity, the manufacturer's optimal wholesale price, the optimal level of carbon emissions (for both bank financing and trade credit financing), and the design of the contract to coordinate the supply chain. We find that the supply chain achieves a win-win outcome in terms of production quantity and emissions reduction when the manufacturer invests in emissions reduction. In addition, we find that a supply chain with a contract outperforms a non-contract supply chain in production quantity and emissions reduction. Furthermore, the effect is more remarkable when trade credit financing is viable.
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| 5. |
- Olson, A. L., et al.
(författare)
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A concise review of glycerol derivatives for use as fuel additives
- 2023
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 9:1
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Forskningsöversikt (refereegranskat)abstract
- Due to renewable fuel mandates worldwide, the increase in biodiesel production has caused an oversupply of low-cost glycerol on the markets, which can negatively affect the sustainability of the biodiesel industry as a whole. In order to avoid that scenario, the transformation of glycerol into value-added products has been investigated, and the production of additives for internal combustion engine fuels is one good example of glycerol valorization. The present work presents a summary of the literature describing the most important chemical pathways through which glycerol can be converted into fuel additives, to be subsequently mixed with either gasoline, biodiesel, or diesel fuel. The focus is on the three major categories, namely glycerol acetals/ketals, ethers, and esters (acetates). Moreover, the effectiveness of the different glycerol-derived compounds is illustrated through several examples from the literature. Finally, a few research gaps on the topic are identified and suggestions for future work are described.
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| 6. |
- Olson, André L., et al.
(författare)
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A Review of Isobutanol as a Fuel for Internal Combustion Engines
- 2023
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Ingår i: Energies. - 1996-1073. ; 16:22
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Forskningsöversikt (refereegranskat)abstract
- Isobutanol, one of the four isomers of butanol (C4H9OH), possesses some favorable properties that make it an attractive fuel for internal combustion engines. For instance, when compared to ethanol, isobutanol features a higher heating value and lower hygroscopicity (which prevents corrosion and enables it to be transported via pipelines). Moreover, its addition to gasoline does not distort the fuel blend’s vapor pressure to the same extent as ethanol does. All of this while having a high octane rating. Those advantages over ethanol suggest that isobutanol has the potential to be used as a gasoline oxygenate or even as a neat fuel. Furthermore, the advances made in biotechnology have enabled isobutanol to be produced from biomass more efficiently, allowing it to be used in compliance with existing renewable energy mandates. This article reviews some of the relevant literature dedicated to isobutanol as a motor fuel, covering its merits and drawbacks. Several studies on its combustion characteristics are also discussed. Most of the included literature refers to the use of isobutanol in spark-ignition (SI) engines, as its properties naturally lend themselves to such applications. However, isobutanol’s utilization in diesel engines is also addressed, along with a couple of low-temperature combustion examples.
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| 7. |
- Olson, André L., et al.
(författare)
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Experimental Investigation of Glycerol Derivatives and C1–C4 Alcohols as Gasoline Oxygenates
- 2024
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Ingår i: Energies. - 1996-1073. ; 17:7
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Tidskriftsartikel (refereegranskat)abstract
- Certain oxygenated compounds, when blended with gasoline, have the ability to inhibit the occurrence and decrease the intensity of engine knock, helping improve engine efficiency. Although ethanol has had widespread use as an oxygenate, higher alcohols, such as butanol, exhibit superior properties in some respects. Besides alcohols, glycerol derivatives such as glycerol tert-butyl ether (GTBE), among others, also have the potential to be used as gasoline oxygenates. This work provides a direct comparison, performed on a modified Waukesha CFR engine, of C1–C4 alcohols and the glycerol derivatives GTBE, solketal, and triacetin, all blended with a gasoline surrogate in different concentrations. The tests focused on how these oxygenated compounds affected the knocking behavior of the fuel blends, since it directly impacts engine efficiency. The test matrices comprised spark-timing sweeps at two different compression ratios, at stoichiometric conditions and constant engine speed. The results showed that, in general, the C1–C4 alcohols and the glycerol derivatives were effective in decreasing knock intensity. n-Butanol and solketal were the noteworthy exceptions, due to their demonstrated inferior knock-inhibiting abilities. On the other hand, isopropanol, isobutanol, and GTBE performed particularly well, indicating their potential to be used as gasoline oxygenates for future engines, as alternatives to ethanol.
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| 8. |
- Olson, André L., et al.
(författare)
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Experimental Investigation of Glycerol Derivatives as Low-Concentration Additives for Diesel Fuel
- 2023
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Ingår i: SAE Technical Papers.
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Konferensbidrag (refereegranskat)abstract
- The worldwide adoption of renewable energy mandates, together with the widespread utilization of biofuels has created a sharp increase in the production of biodiesel (fatty acid alkyl esters). As a consequence, the production of glycerol, the main by-product of the transesterification of fatty acids, has increased accordingly, which has led to an oversupply of that compound on the markets. Therefore, in order to increase the sustainability of the biodiesel industry, alternative uses for glycerol need to be explored and the production of fuel additives is a good example of the so-called glycerol valorization. The goal of this study is therefore to evaluate the suitability of a number of glycerol-derived compounds as diesel fuel additives. Moreover, this work concerns the assessment of low-concentration blends of those glycerol derivatives with diesel fuel, which are more likely to conform to the existing fuel standards and be used in unmodified engines. The various blends described in this article were tested on a heavy-duty diesel engine converted to single-cylinder operation. The overall behavior and the impact of the fuel blends on the engine's combustion, performance, and emissions were investigated. The results showed that the additives caused a modest decrease in engine-out soot concentrations along with slightly reduced hydrocarbon and carbon monoxide emissions. In addition, the blends appeared to have a positive impact on the soot-NOx trade-off. Finally, as expected, volumetric fuel consumption was slightly increased with the oxygenated blends, due to their lower heating values. In conclusion, even though the use of the glycerol derivatives in low concentrations did not produce dramatic outcomes, the results showed that they can nevertheless be used as a means to decrease fossil fuel usage in the transportation sector.
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| 9. |
- Wu, Desheng D., et al.
(författare)
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A Decision Support Approach for Accounts Receivable Risk Management
- 2014
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Ingår i: IEEE Transactions on Systems, Man & Cybernetics. Systems. - 2168-2216 .- 2168-2232. ; 44:12, s. 1624-1632
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Tidskriftsartikel (refereegranskat)abstract
- Financial disasters in private firms led to increased emphasis on various forms of risk management, to include market risk management, operational risk management, and credit risk management. Financial institutions are motivated by the need to meet increased regulatory requirements for risk measurement and capital reserves. This paper describes and demonstrates a model to support risk management of accounts receivable. We present a decision support model for a large bank enabling assessment of risk of default on the part of loan recipients. A credit scoring model is presented to assess account creditworthiness. Alternative methods of risk measurement for fault detection are compared, and a logistic regression model selected to analyze accounts receivable risk. Accuracy results of this model are presented, enabling accounts receivable managers to confidently apply statistical analysis through data mining to manage their risk.
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