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| 2. |
- Betoule, M., et al.
(författare)
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Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples
- 2014
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 568, s. A22-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We present cosmological constraints from a joint analysis of type la supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z < 0.1), all three seasons from the SDSS-11 (0.05 < z < 0.4), and three years from SNLS (0.2 < z < 1), and it totals 740 spectroscopically confirmed type la supernovae with high quality light curves. Methods. We followed the methods and assumptions of the SNLS three-year data analysis except for the following important improvements: I) the addition of the full SDSS-II spectroscopically-confirmed SN la sample in both the training of the SALT2 light-curve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN la light curves. Results. We produce recalibrated SN la light curves and associated distances for the SDSS-II and SNLS samples. The large SOSS-II sample provides an effective, independent, low -z anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the low -z SN sample. For a flat ACDM cosmology, we find Omega(m), = 0.295 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8 sigma (stat+sys) different than the previously published result of SNLS three-year data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant dark energy equation of state parameter omega = -1.018 +/- 0,057 (sral+sys) for a fiat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: omega = 59 -1.027 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.
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| 3. |
- Fu, Yifeng, 1984, et al.
(författare)
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Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 24:12, s. 1576-1581
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Tidskriftsartikel (refereegranskat)abstract
- A template-assisted method that enables the growth of covalently bonded three-dimensional carbon nanotubes (CNTs) originating from graphene at a large scale is demonstrated. Atomic force microscopy-based mechanical tests show that the covalently bonded CNT structure can effectively distribute external loading throughout the network to improve the mechanical strength of the material.
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| 4. |
- Sun, S., et al.
(författare)
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Thermal performance characterization of nano thermal interface materials after power cycling
- 2012
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Ingår i: Proceedings - Electronic Components and Technology Conference. - 0569-5503. - 9781467319669 ; , s. 1426-1430
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Konferensbidrag (refereegranskat)abstract
- The need for faster, smaller, and more reliable and efficient products has resulted in increase of heat generated in microelectronic components. The removal of the heat generated is an important issue in electronic packaging. A novel Nano-TIM was developed to improve the heat dissipation of electronics packaging. This paper aims at studying the heat dissipation performance of a new class of nano-structured polymer-metal composite film (Nano-TIM) after power cycling. The new Nano-TIM uses metal to provide continuous thermal pathways while using nano-polymer to control the elasticity of the TIM. Through semiconductor processing and RTD principle, chips including 5*5, 10*10, 20*20, 30*30 (mm 2), were developed to study different size's influence on heat dissipation effect of the Nano-TIM. Additional parameters studied include power effect. RTD is used respectively to measure the junction temperature, and then the R thJC (Junction-to-Case Thermal Resistance) is calculated afterwards. The Transient thermal resistances of the Nano-TIM were also tested by T3Ster method to further study heat dissipation effect of Nano-TIM. The morphologies and interaction between the Nano-TIM and chips were carefully studied using X-ray Scanning Microscope to analyze heat flow path. The result shows that Nano-TIMs can be used to 30 mm in chip length as the thermal interface material.
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| 5. |
- Wang, Xiaofeng, et al.
(författare)
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Evidence for type ia supernova diversity from ultraviolet observations with the hubble space telescope
- 2012
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 749:2, s. 126-
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Tidskriftsartikel (refereegranskat)abstract
- We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This data set provides unique spectral time series down to 2000 angstrom. Significant diversity is seen in the near-maximum-light spectra (similar to 2000-3500 angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminositiesmeasured in the uvw1/F250W filter are found to correlate with the B-band light-curve shape parameter Delta m(15)(B), but with much larger scatter relative to the correlation in the broadband B band (e.g., similar to 0.4 mag versus similar to 0.2 mag for those with 0.8 mag < Delta m(15)(B) < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by similar to 0.9 mag and similar to 2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.
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| 6. |
- Zhang, L., et al.
(författare)
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Study on the adhesion strength of new nano-structured polymer-metal composite for thermal interface material (Nano-TIM) under different pressures
- 2011
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Ingår i: Proceedings - 12th International Conference on Electronic Packaging Technology and High Density Packaging, ICEPT-HDP 2011, Shanghai, 8-11 August 2011. - 9781457717680 ; , s. 426-429
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Konferensbidrag (refereegranskat)abstract
- With the continual increase in cooling demand for microprocessors, the microelectronics industry has been increasingly focused on the development of thermal solutions. Thermal Interface Material (TIM) plays a key role in reducing the thermal resistance of packaging and the thermal resistance between the electronic device and the external cooling components. Nano-TIM, a new type of thermal interface material, was developed to improve the heat dissipation of electronic devices. This paper describes work undertaken to research the reliability of Nano-TIM. Pull tests were used to investigate the shear strength of samples with Nano-TIM of different thicknesses coalesced between two PCBs with Sn coating made under different pressure. Scanning Electron Microscopy (SEM) analysis techniques were used to determine the morphology of the shear fracture section after pull tests and observe the structure of the cross section of Nano-TIM coalesced between two PCBs with Sn coating.
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| 7. |
- Carlberg, Björn, 1983, et al.
(författare)
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Polymer-metal nanofibrous composite for thermal management of microsystems
- 2012
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Ingår i: Materials Letters. - : Elsevier BV. - 1873-4979 .- 0167-577X. ; 75, s. 229-232
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, a composite structure based on a porous electrospun polyimide structure infiltrated with indium aimed at thermal interface material applications is presented. A porous nanofibrous structure was prepared by electrospinning of polyimide. An interfacial nanocomposite layer of silver nanoparticles partially or fully embedded in the polyimide matrix was synthesized on the fiber surfaces, followed by autocatalytic deposition of a uniform silver coating (using the interfacial layer as an anchored seed layer) serving as a reactive wetting layer for the infiltrating melt. The thermal performance of the composite was evaluated and the thermal conductivity was determined to be 27 W/mK, accompanied by low contact resistance of the metallurgical bond (
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| 8. |
- Carlberg, Björn, 1983, et al.
(författare)
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Polymer nanofiber based continuous metal phase composite for thermal management applications
- 2010
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Ingår i: 3rd Electronics System Integration Technology Conference, ESTC 2010; Berlin; Germany; 13 September 2010 through 16 September 2010. - 9781424485536 ; , s. Art. no. 5642950-
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Konferensbidrag (refereegranskat)abstract
- A new composite design approach for thermal interface materials is presented. A porous electro spun nanofiber network composed of temperature stable poly imide was infiltrated with liquid phase indium at a pressure of 30 MPa. The polymer phase defmes composition and geometry, while the continuous metal phase gives binding to surfaces and high thermal conductivity. The composite was characterized by assembly of tri-layer copper/TIM/copper sandwich structures and subsequent xenon flash measurements extracting the thermal properties of the intermediate TIM layer. The interfacial contact resistance was found to be 8 Kmm2/W and the thermal conductivity was 28 W/mK, indicating the potential for use in thermal management applications.
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| 9. |
- Carlberg, Björn, 1983, et al.
(författare)
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Surface-Confined Synthesis of Silver Nanoparticle Composite Coating on Electrospun Polyimide Nanofibers
- 2011
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:21, s. 3057-3066
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Tidskriftsartikel (refereegranskat)abstract
- A methodology for fabricating hierarchical nanostructures by surface-confined synthesis of silver nanoparticles on electrospun polyimide nanofibers is reported. Through surface-confined imide cleavage at the dianhydride domain via immersion in an aqueous KOH solution, potassium polyamate coatings of accurately defined thickness are formed (at a rate of 25 nm h(-1)). By utilizing the ion-exchange capability of the polyamate resin, silver ions are introduced through immersion in an aqueous AgNO(3) solution. Subsequent reduction of the metal ion species leads to the formation of nanoparticles at the fiber surface. Two modes of reduction, chemical and thermal, are investigated in the report, each leading to distinct morphologies of the nanoparticle coatings. Via thermal reduction, a composite surface layer consisting of monodisperse silver nanoparticles (average diameter 5.2 nm) embedded in a re-imidized polyimide matrix is achieved. In the case of chemical reduction, the reduction process occurs preferentially at the surface of the fiber, leading to the formation of silver nanoparticles anchored at the surface, though not embedded, in a polyamic acid matrix. By regulating the modification depth, control of the particle density on the fiber surface is established. In both reduction approaches, the polyimide nanofiber core exhibits maintained integrity.
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| 10. |
- Ingason, Haukur, et al.
(författare)
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The Metro Project: Final Report
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The report compiles the results from the METRO-project. The different parts of the project; design fires, evacuation, integrated fire control, smoke control, extraordinary strain on constructions and fire- and rescue operations are presented separately. The most complicated and expensive part of the project was the performance of the large scale fire and explosion tests in the Brunsberg tunnel. The maximum heat release rates measured from the metro carriage was 77 MW. The maximum ceiling gas temperatures was 1118 °C. These values are high, and should be put into a perspective of the situation and the type of carriages used. The project is not recommending the highest values as the design fire, but values reflected in conditions. The egress study confirm that one of the major issues related to fire evacuation in underground transportation systems is that people often are reluctant to initiate an evacuation. New data show that participants moved with an average of 0.9 meters per second in the smoke filled environment (average visibility of 1.5–3.5 meters). A way-finding installation at the emergency exit, which consisted of a loudspeaker, was found to perform particularly well in terms of attracting people to the door. Two smoke control systems were simulated for a single exit metro station. The systems consisted of a pressurizing supply air system and mechanical exhaust ventilation system with and without platform screen doors. The results show that both the pressurizing supply air system and the mechanical exhaust air system provide effective smoke control for one exit metro station. The significance of the platform screen doors was shown to be important in relation to smoke control. Experiments and simulations have provided increased confidence in ability to simulate explosion scenarios to determine the pressure inside and outside a carriage and to be able to study variations of conditions such as carriage geometry and window designs. The explosion test performed show that an explosion with a relatively minor charge can significantly change the conditions for both evacuees and the rescue service. The results show that the conditions for evacuation and rescue operations can change dramatically as a result of a relatively minor explosion. Evaluation of methods and fire and rescue tactics in metros is given. Mapping of IR imaging as a tactical resource at tunnel fires was presented.
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