Brightness variability investigation of BD+61°154     

J. N. Chkhikvadze 《Astronomische Nachrichten》1994,315(3):253-258

Photoelectric ubvyHαHβ observations of the Herbig Ae/Be star BD+61°154 are presented. The observational data are analyzed proceeding from the simple hypothesis that the light variation is mainly due to temperature changes of gaseous envelope.  相似文献   

INTEGRAL REPRESENTATIONS AND REGULARIZATIONS FOR A DIVERGENT SERIES SOLUTION OF A BEAM SUBJECTED TO SUPPORT MOTIONS     

J. T. CHEN  H.-K. HONG  C. S. YEH  S. W. CHYUAN 《地震工程与结构动力学》1996,25(9):909-925

Derived herein is the integral representation solution of a Rayleigh-damped Bernoulli–Euler beam subjected to multi-support motion, which is free from calculation of a quasi-static solution, and in which the modal participation factor for support motion is formulated as a boundary modal reaction, thus making efficient calculation feasible. Three analytical methods, including (1) the quasi-static decomposition method, (2) the integral representation with the Cesàro sum technique, and (3) the integral representation in conjunction with Stokes' transformation, are presented. Two additional numerical methods of (4) the large mass FEM simulation technique and (5) large stiffness FEM simulation technique are easily incorporated into a commercial program to solve the problem. It is found that the results obtained by using these five methods are in good agreement, and that both the Cesàro sum and Stokes' transformation regularization techniques can extract the finite part of the divergent series of the integral representation. In comparison with the Mindlin method and Cesàro sum technique, Stokes' transformation is the best way because it is not only free of calculation of the quasi-static solution, but also because it can obtain the convergence rate as rapidly as the mode acceleration method can.  相似文献   

The demographics of energy and mobility poverty: Assessing equity and justice in Ireland,Mexico, and the United Arab Emirates     

《Global Environmental Change》2023

Energy and mobility poverty limits people’s choices and opportunities and negatively impinges upon structural economic and social welfare patterns. It also hampers the ability of planners to implement more equitable and just decarbonization pathways. Research has revealed that climate policies have imposed a financial burden on low-income and other vulnerable groups by increasing food and energy prices, leading as well to global inequality. Similarly, researchers have warned that in developing countries, emission mitigation policies could increase poverty rates and even frustrate progress towards universal access to clean energy. This research explores whether low-income social groups experience a 'double energy vulnerability', a situation that simultaneously positions people at heightened risk of transport and energy poverty. We investigate this 'double vulnerability' through original data collection via three nationally representative surveys of Mexico (N = 1,205), the United Arab Emirates (N = 1,141), Ireland and Northern Ireland (N = 1,860). We draw from this original data to elaborate on the sociodemographic attributes, expenditure and behaviour emerging from energy and transport use, focusing on themes such as equity, behaviour and vulnerability. We propose energy and transport poverty indexes that allow us to summarize the key contributing factors to energy and transport poverty in the countries studied and uncover a strong correlation between these two salient forms of poverty. Our results suggest that energy and transport poverty are common issues regardless of the very different national, and even sub-national, contexts. We conclude that energy and transport poverty requires target policy interventions suitable for all segments of society, thus enabling contextually-tailored, just energy transitions.  相似文献   

IPCC emission scenarios: How did critiques affect their quality and relevance 1990–2022?     

《Global Environmental Change》2022

Long-term global emission scenarios enable the analysis of future climate change, impacts, and response strategies by providing insight into possible future developments and linking these different climate research elements. Such scenarios play a crucial role in the climate change literature informing the Intergovernmental Panel on Climate Change’s (IPCC) Assessment Reports (ARs) and support policymakers. This article reviews the evolution of emission scenarios, since 1990, by focusing on scenario critiques and responses as published in the literature. We focus on the issues raised in the critiques and the possible impact on scenario development. The critique (280) focuses on four areas: 1) key scenario assumptions (40%), 2) the emissions range covered by the scenarios and missing scenarios (25%), 3) methodological issues (24%), and 4) the policy relevance and handling of uncertainty (11%). Scenario critiques have become increasingly influential since 2000. Some areas of critique have decreased or become less prominent (probability, development process, convergence assumptions, and economic metrics). Other areas have become more dominant over time (e.g., policy relevance & implications of scenarios, transparency, Negative Emissions Technologies (NETs) assumptions, missing scenarios). Several changes have been made in developing scenarios and their content that respond to the critique.  相似文献   

Chronology of the Paleolithic site of Xibaimaying in the Nihewan Basin,North China,inferred from optical dating of fine-grained quartz     

《Quaternary Geochronology》2022

The Paleolithic site of Xibaimaying (XBMY), once considered the youngest flake tool site within the Nihewan Basin, North China, is an ideal archive to study the chronological relationship between flake tool and microblade industries in the Nihewan Basin during the Upper Palaeolithic, but the previous ages obtained for the site remain controversial. From 2015 to 2019, three areas at two archaeological localities (XBMY-I and XBMY-II) of the site were excavated, and well-preserved fossils and flake tools were unearthed. In this study, a total of 26 samples were collected from the three areas for optically stimulated luminescence (OSL) dating using a single-aliquot regenerative-dose (SAR) protocol on fine-grained quartz. A shared ‘Standardized growth curve’ (SGC) for a section was constructed to reduce the time required for D_e estimation. The long-term weighted average water contents of the samples during their burial period were estimated based on the in-situ water contents of continuous samples from a nearby borehole. All the OSL ages were modelled via Bayesian statistics using the OxCal software, modifying the OSL ages with stratigraphic constraints in each section. The results show that the cultural layer bearing flake tool assemblages falls within the period of 122–36 ka, indicating that the flake tool industry of the Xibaimaying site is comparable to that of the Youfangbei (108–86 ka), Banjingzi (∼86 ka) and Xinmiaozhuang (75–63 ka) sites, rather than the youngest one in the Nihewan basin, which explains why the Xibaimaying site is characterized as pure flake tool culture without any ‘advanced’ trait. The OSL dating results also shed new light on the study of sedimentary processes in the Xibaimaying site area. The different deposition rates (0.01–1.61 mm/a) for the sediments at the three newly excavated areas imply complex geomorphologic processes in the site area.  相似文献   

Chronology of Early to Mid-Pleistocene sediments in the northern North Sea: New evidence from amino acid and strontium isotope analyses     

《Quaternary Geochronology》2022

Sediments deposited during glacial-interglacial cycles through the Early to Mid-Pleistocene in the North Sea are chronologically poorly constrained. To contribute to the chronology of these units, amino acid racemization (AAR) and strontium (Sr) isotope analyses have been performed on samples from four shallow borings and one oil well along a transect in the northern North Sea. D/L Asp (aspartic acid) values obtained through reverse-phase liquid chromatography in the benthic foraminiferal species Elphidium excavatum is focused on because of consistent results and a good stratigraphic distribution of this benthic species. For the Early Pleistocene, an age model for the well 16/1–8, from the central part of the northern North Sea based on Sr ages allows for dating of the prograding wedges filling the pre-Quaternary central basin. A regional calibration curve for the racemization of Asp in Elphidium excavatum is developed using published ages of radiocarbon-dated samples and samples associated with the previously identified Bruhnes/Matuyama (B/M) paleomagnetic boundary and a Sr age from this study. Based on all the available geochronological evidence, samples were assigned to marine oxygen isotope stages (MIS) with uncertainties on the order of 10–70 ka.Sr ages suggest a hiatus of <2 million years (Ma) possibly due to non-deposition or low sedimentation between the Utsira Formation (Pliocene) and the Early Pleistocene. An increase in sedimentation rates around 1.5 ± 0.07 Ma (∼MIS 51) may partly be due to sediment supply from rivers from the south-east and partly due to the extension of ice sheet around 1.36 ± 0.07 Ma from the Norwegian coast to the central North Sea. A possible basin-wide glaciation occurred around 1.1 Ma (∼ MIS 32) (upper regional unconformity/top of unit Q4 in this study), resulting in erosion and regional unconformity. Two interglacials in the Norwegian Channel have been dated: the Radøy Interglacial to 1.07 ± 0.01 Ma (possibly MIS 31, the ‘super interglacial’), and the Norwegian Trench Interglacial to 0.50 ± 0.02 Ma (possibly MIS 13). A massive till unit identified at the same stratigraphic level in all shallow borings may partly represent an extensive MIS 12 glaciation. This study shows that the combined use of amino acid racemization data and Sr isotope chronology can refine the chronological ambiguities of Quaternary North Sea sediments related partly to the impact of glacial processes.  相似文献   

拓扑分子格中ST_-1、ST₀及ST₁的分离性          下载免费PDF全文

冯玉英  周伟灿 《大气科学学报》2000,23(4):611-615

在拓扑分子格中进一步讨论了ST_-1的性质,引进了ST₀、ST₁分离性概念,并研究了其相应的性质。  相似文献