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排序方式: 共有193条查询结果,搜索用时 31 毫秒
31.
Amanda J. Gregory Jonathan P. Atkins Daryl Burdon Michael Elliott 《European Journal of Operational Research》2013
The purpose of this paper is to learn from Complex Adaptive Systems (CAS) theory to inform the development of Problem Structuring Methods (PSMs) both in general and in the specific context of marine management. The focus on marine management is important because it is concerned with a CAS (formed through the interconnection between natural systems, designed systems and social systems) which exemplifies their particularly ‘wicked’ nature. Recognition of this compels us to take seriously the need to develop tools for knowledge elicitation and structuring which meet the demands of CAS. In marine management, chief among those tools is the DPSIR (Drivers – Pressures – State Changes – Impacts – Responses) model and, although widely applied, the extent to which it is appropriate for dealing with the demands of a CAS is questionable. Such questioning is particularly pertinent in the context of the marine environment where there is a need to not only recognise a broad range of stakeholders (a question of boundary critique) but also to manage competing knowledge (economic, local and scientific) and value claims. Hence this paper emphasises how a CAS perspective might add impetus to the development of a critical perspective on DPSIR and PSM theory and practice to promote a more systemic view of decision-making and policy development. 相似文献
32.
Ryan Atkins 《Journal of luminescence》2008,128(9):1463-1470
We have completed a study of the optical properties of SrY2O4:Eu3+ under vacuum ultraviolet (VUV) excitation. Reflectance measurements on the undoped material yield a calculated band gap of about 6.1 eV. Studies on the doped material indicate that Eu3+ occupies the Y(1) and Y(2) sites in this host. Host-to-activator energy transfer calculations indicate a preference for transfer to Eu3+ at the Y(2) site. Modeling of the transfer efficiency data leads us to estimate that about 35% of absorbed radiation is lost to the surface under excitation near the band edge. 相似文献
33.
The optical absorption spectrum and the 400-nm photoluminescence (PL) of a 1.4-mol. % Ge photosensitive optical fiber preform subjected to high fluence of 193-nm ArF and 248-nm KrF excimer-laser irradiation are measured. The largest absorption increases occur near 200 nm in both cases, but a small net bleaching of absorption is obtained near the laser wavelength for KrF irradiations. The blue PL decreases during ArF exposure but increases with the KrF laser. In similarly excited 9-mol. % Ge fiber preforms the blue PL always decreases. A study of the PL intensity as a function of irradiating laser light intensity shows no evidence of multiple photon absorption effects. 相似文献
34.
C McConville RM Kalin D Flood 《Rapid communications in mass spectrometry : RCM》1999,13(13):1339-1345
Current methods for stable oxygen isotopic (delta (18)O) analysis of soil water rely on separation of water from the soil matrix before analysis. These separation procedures are not only time consuming and require relatively large samples of soil, but also have been shown to introduce a large potential source of error. Current research at Queen's University Belfast is focused on using direct equilibration of CO(2) with the pore water to eliminate this extraction step using the automated Multiprep system and a Micromass Prism III isotope ratio mass spectrometer (IRMS). The findings of this research indicate the method is less time consuming, more reliable, and reproducible to within accepted limits (+/-0.1% per thousand delta (18)O). In this study the direct equilibration method is used to analyse delta (18)O tracer profiles in the unsaturated zone of field soils, concurrently with chloride tracer profiles, which can be used to assess infiltration rates and mechanisms through the unsaturated zone. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
35.
RD Harris WS Baker Van Stipdonk MJ RM Crooks EA Schweikert 《Rapid communications in mass spectrometry : RCM》1999,13(14):1374-1380
A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
36.
E. D. T. Atkins M. J. Hill N. A. Jones S. J. Cooper 《Journal of Polymer Science.Polymer Physics》1998,36(13):2401-2412
Chain-folded lamellar crystals of nylon 2 4 have been prepared from dilute solution by addition of poor solvent. Two crystal structures are observed at room temperature: a monoclinic form I, precipitated at elevated temperature, and a less-defined, orthorhombic form II, precipitated at room temperature. The unit cell parameters for both forms are similar to those reported for its isomer, nylon 3. Nylon 2 4 form II is a liquid–crystal-like or disordered phase, consisting of hydrogen-bonded sheets in poor register in the hydrogen bond direction. Form I crystals have two characteristic interchain spacings of 0.41 nm and 0.39 nm at room temperature and on heating, exhibit a structural transformation and a Brill temperature (250°C) characteristic of many other even–even nylons. Nylon 2 4 is a member of the nylon 2 Y and nylon 2N 2(N+1) families, and the form I crystals show behavior commensurate with both. We propose they contain a proportion of intersheet hydrogen bonds at room temperature, similar to that for the nylon 2 Y family, and the short dimethylene alkane segments mean that the structure consists of hydrogen-bonded a-sheets, with an amide unit in each fold, similar to that of nylon 4 6. The fold geometry and sheet structure is compared with chain-folded apβ-sheet polypeptides and nylon 3. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2401–2412, 1998 相似文献
37.
V. Vijayasundaram V. Ramasamy PL. RM. Palaniappan 《Journal of Thermal Analysis and Calorimetry》2009,98(1):183-188
The paper presents the changes in the thermal properties of control, arsenic exposed and DMSA treated Labeo rohita bones by using thermo analytical techniques. The result shows that the mass loss due to the thermal decomposition occurs
in three distinct steps due to loss of water, organic and inorganic materials. The arsenic exposed bones present a different
thermal behaviour compared to the control bones. The residue masses are increased due to arsenic exposure, while the DMSA
treatment reduces the residue mass level. These thermal characteristics can be used as a qualitative method to check the metal
accumulation in samples. 相似文献
38.
Abazov VM Abbott B Acharya BS Adams M Adams T Alexeev GD Alkhazov G Alton A Alverson G Alves GA Aoki M Askew A Åsman B Atkins S Atramentov O Augsten K Avila C BackusMayes J Badaud F Bagby L Baldin B Bandurin DV Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bazterra V Bean A Begalli M Belanger-Champagne C Bellantoni L Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatnagar V Blazey G Blessing S Bloom K Boehnlein A Boline D Boos EE 《Physical review letters》2012,108(18):181803
We study WW and WZ production with ?νqq (?=e,μ) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb(-1) of integrated luminosity from pp collisions at sqrt[s]=1.96 TeV. Assuming the ratio between the production cross sections σ(WW) and σ(WZ) as predicted by the standard model, we measure the total WV (V=W,Z) cross section to be σ(WV)=19.6(-3.0)(+3.2) pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure σ(WW)=15.9(-3.2)(+3.7) pb and σ(WZ)=3.3(-3.3)(+4.1) pb, which is consistent with the standard model predictions. 相似文献
39.
Abazov VM Abbott B Acharya BS Adams M Adams T Alexeev GD Alkhazov G Alton A Alverson G Aoki M Askew A Åsman B Atkins S Atramentov O Augsten K Avila C BackusMayes J Badaud F Bagby L Baldin B Bandurin DV Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bazterra V Bean A Begalli M Belanger-Champagne C Bellantoni L Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatia S Bhatnagar V Blazey G Blessing S Bloom K Boehnlein A Boline D Boos EE 《Physical review letters》2012,108(13):131802
We present a search for Kaluza-Klein (KK) particles predicted by models with universal extra dimensions (UED) using a data set corresponding to an integrated luminosity of 7.3 fb(-1), collected by the D0 detector at a pp center-of-mass energy of 1.96 TeV. The decay chain of KK particles can lead to a final state with two muons of the same charge. This signature is used to set a lower limit on the compactification scale of R(-1)>260 GeV in a minimal UED model. 相似文献
40.
Abazov VM Abbott B Acharya BS Adams M Adams T Alexeev GD Alkhazov G Alton A Alverson G Aoki M Askew A Åsman B Atkins S Atramentov O Augsten K Avila C Badaud F Bagby L Baldin B Bandurin DV Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bazterra V Bean A Begalli M Belanger-Champagne C Bellantoni L Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatia S Bhatnagar V Blazey G Blessing S Bloom K Boehnlein A Boline D Boos EE Borissov G Bose T 《Physical review letters》2012,108(15):151804
We present a measurement of the W boson mass using data corresponding to 4.3 fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron pp collider. With a sample of 1,677,394 W → eν candidate events, we measure M(W) = 80.367 ± 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1 fb(-1) of integrated luminosity, to yield M(W) = 80.375 ± 0.023 GeV. 相似文献