37,171 research outputs found
Letter from X. N. Steeves to Carl Hayden
No full textLetter from X. N. Steeves to Carl T. Hayden describing road conditions around the Grand Canyon National Par
Letter from Carl Hayden to X. N. Steeves
No full textLetter with red pencil corrections from Carl T. Hayden to X. N. Steeves about the construction of an approach road to the canyo
A 2 h periodic variation in the low-mass X-ray binary Ser X-1
No full textSpectroscopy of the low-mass X-ray binary Ser X-1 using the Gran Telescopio Canarias have revealed a ?2 h periodic variability that is present in the three strongest emission lines. We tentatively interpret this variability as due to orbital motion, making it the first indication of the orbital period of Ser X-1. Together with the fact that the emission lines are remarkably narrow, but still resolved, we show that a main-sequence K dwarf together with a canonical 1.4 M? neutron star gives a good description of the system. In this scenario, the most likely place for the emission lines to arise is the accretion disc, instead of a localized region in the binary (such as the irradiated surface or the stream-impact point), and their narrowness is due instead to the low inclination (?10°) of Ser X-1
Using performance assessment in secondary school mathematics: an empirical study in a Singapore classroom
No full textThis article reports an exploratory study on using performance assessment in mathematics instruction in a high-performing secondary school in Singapore. An intact mathematics class participated in the study, and received chapter-based performance tasks as intervention during regular mathematics lessons for about one and a half school years. The performance tasks used included authentic and/or open-ended tasks. The students’ academic achievements and attitudes in mathematics were compared with a comparison class that did not receive the intervention. Both quantitative and qualitative data were collected, mainly through questionnaire surveys, performance task tests, conventional school exams, and interviews with students and teachers. The results suggest that the students receiving the intervention performed significantly better than their counterparts in solving conventional exam problems, and in general they also showed more positive changes in attitudes towards mathematics and mathematics learning. The students from the experimental class also expressed positive views about the benefits of using performance tasks in promoting their ability in higher order thinking, though no statistically significant difference was detected between the two classes of students in solving unconventional tasks before and after intervention. Overall, the results appear to support teachers’ using contextualised problems in real life situations and open-ended investigations in students’ learning of mathematic
Periacma simaoensis Li, Wang & Yan 1996
No full textPeriacma simaoensis Li, Wang & Yan, 1996 (Figure 14) Periacma simaoensis Li, Wang & Yan, 1996: 205. Wing expanse: 16.5 mm. Material examined: Holotype: „, Simao (22 ° 48 9 N, 100 ° 58 9 E), Yunnan Province, 1325 m, 24 April 1995, coll. Guangyun Yan. Distribution: China (Yunnan). Remarks: This species resembles P. fengxianensis, but can be distinguished from the latter by the uncus not dilated apically, the sacculus heavily sclerotized distally, and the aedeagus with distal 1/6 divided into two parts.Published as part of Wang, S. X. & Li, H. H., 2006, Review of the genus Periacma Meyrick (Lepidoptera, Oecophoridae) from China, with descriptions of four new species, pp. 2371-2393 in Journal of Natural History 40 (41 - 43) on page 2382, DOI: 10.1080/00222930601088123, http://zenodo.org/record/523174
Energy-absorption characteristics of tube-reinforced absorbent honeycomb sandwich structure
No full textNomex honeycombs are widely used in lightweight structures due to their unique porous structure. By adding an absorbent agent to Nomex honeycomb wall and filling carbon fiber reinforced polymer (CFRP) tube, a novel tube-reinforced absorbent honeycomb sandwich structure was proposed. Its compressive properties and energy absorption characteristics were studied experimentally and numerically. Compared with empty absorbent honeycomb, the normalized elastic modulus E, peak stress and energy absorption of tube-reinforced absorbent honeycomb can be increased by 55.74%, 621.69% and 327.86% respectively. Moreover, the energy absorption of the tube-reinforced absorbent honeycomb was increased by 30.34%, compared with the sum of empty absorbent honeycomb and CFRP tube tested separately. The interaction effects and enhancement mechanism between absorbent honeycomb and CFRP tube were also discussed. The excellent electromagnetic absorption and mechanical properties make this novel honeycomb sandwich structure much more competitive not only in electromagnetic wave stealth application but also in load-carry structures
Relations between x-ray timing features and spectral parameters of galactic black hole x-ray binaries
Get PDFWe present a study of correlations between spectral and timing parameters for a sample of black hole X-ray binary candidates. Data are taken from GX
339-4, H 1743-322, and XTE J1650-500, as the Rossi X-ray Timing Explorer
(RXTE) observed complete outbursts of these sources. In our study we investigate outbursts that happened before the end of 2009 to make use of the high-energy coverage of the HEXTE detector and select observations that
show a certain type of quasi-periodic oscillations (type-C QPOs). The spectral parameters are derived using the empirical convolution model simpl to model the Comptonized component of the emission together with a disc blackbody for the emission of the accretion disc. Additional spectral features, namely a reflection component, a high-energy cut-off, and excess emission at 6.4 keV, are taken into account. Our investigations confirm the known positive
correlation between photon index and centroid frequency of the QPOs and reveal an anti-correlation between the fraction of up-scattered photons and the QPO frequency. We show that both correlations behave as expected in the “sombrero”
geometry. Furthermore, we find that during outburst decay the correlation between photon index and QPO frequency follow a general track, independent of individual outbursts
Measurement of the differential and double-differential Drell-Yan cross sections in proton-proton collisions at root s=7 TeV
Get PDFMeasurements of the differential and double-differential Drell-Yan cross sections are presented using an integrated luminosity of 4.5 (4.8) fb−1 in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at s√ = 7 TeV. The measured inclusive cross section in the Z-peak region (60–120 GeV) is σ(ℓℓ) = 986.4 ± 0.6 (stat.) ± 5.9 (exp. syst.) ± 21.7 (th. syst.) ± 21.7 (lum.) pb for the combination of the dimuon and dielectron channels. Differential cross sections dσ/dm for the dimuon, dielectron, and combined channels are measured in the mass range 15 to 1500 GeV and corrected to the full phase space. Results are also presented for the measurement of the double-differential cross section d2σ/dm d|y| in the dimuon channel over the mass range 20 to 1500 GeV and absolute dimuon rapidity from 0 to 2.4. These measurements are compared to the predictions of perturbative QCD calculations at next-to-leading and next-to-next-to-leading orders using various sets of parton distribution functions
Olecryptotendipes exilis Yan, Wang & Bu 2012
No full textOlecryptotendipes exilis Yan, Wang & Bu, 2012 Olecryptotendipes exilis Yan, Wang & Bu, 2012: 43 Specimens examined. Type material: Holotype and Paratype. 2♂♂. CHINA: Hainan Province, Ledong Li Nationality Autonomous County, Jianfengling Nature Conservation area, 18°14'45.96"N, 109°30'42.69"E, 21.iv.1985, X. Wang. Diagnostic characters. Thorax and legs without blackish brown spots. Anal tergite bands Y-shaped, superior volsella apically with a partially sclerotized beak-like protrusion and a slender spur-like posterolateral projection, anal tergite with posterolateral weak lobes and anal point parallel-sided. Gonostylus swollen at base, curved inwards and slender to apex. Distribution. Oriental China (Hainan province).Published as part of Yan, Chuncai, Liu, Ting, Zhao, Guangjun, Shi, Yafeng & Wang, Xinhua, 2017, A new species of Olecryptotendipes Zorina from China (Diptera, Chironomidae), pp. 291-296 in Zootaxa 4299 (2) on page 294, DOI: 10.11646/zootaxa.4299.2.10, http://zenodo.org/record/83590
Corrigendum: Liu W-B, Wang C-Y, Tang Y-N, Wang Y, Pei W-X, Yan C-C (2024) Six new species of Cryptochironomus Kieffer (Diptera, Chironomidae) from the Nearctic region. ZooKeys 1200: 275–302. doi: 10.3897/zookeys.1200.119225
Get PDFCorrigendum: Liu W-B, Wang C-Y, Tang Y-N, Wang Y, Pei W-X, Yan C-C (2024) Six new species of Cryptochironomus Kieffer (Diptera, Chironomidae) from the Nearctic region. ZooKeys 1200: 275–302. https://doi.org/10.3897/ zookeys.1200.11922
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