749 research outputs found
Economic Analysis of Power Grid Interconnections Among Europe, North-East Asia, and North America With 100% Renewable Energy Generation
In this paper, we investigate whether the interconnection of power grids with 100% renewable energy generation can bring greater economic benefits now that the technology exists for high power, long distance Ultra High Voltage Direct Current transmission. Based on multi-year historical weather data and demand series, this study compares eight interconnection schemes for three regional grids in Europe, North-East Asia, and North America where there is around 8-hour time difference between any of the two regions. Sensitivity analyses are presented with respect to infrastructure capital cost and different weather year which show that interconnection yields a reduction of approximately 18% in the total annual system cost. The results in this paper also indicate that the regional levelized cost of electricity (LCOE) drops by 31%, 10%, and 10% for Europe, North-East Asia and North America, respectively. It is concluded that there is a strong incentive through both annual cost saving and regional LCOE drop in favour of full long-distance interconnections between the three regions in the context of the international drive towards a net-zero strategy
Global Electricity Interconnection With 100% Renewable Energy Generation
Under the United Nations ‘Net-Zero 2050’ target, transition towards a 100% renewable energy (RE) sourced power grid has become an ever more attractive pathway. However, the inherent fluctuations and intermittency of RE generation, particularly wind and solar, would inevitably pose great technical and economic barriers to their massive integration into the energy supply. A global interconnected electricity grid to utilize the complementarity of diverse demand patterns and RE sources provides an appealing solution. With detailed datasets, this paper is therefore to assess the economic benefits of such a global electricity grid with 100% RE generation using the state-of-the-art Ultra High Voltage Direct Current transmission technologies. The global electricity grid is split into 14 regions with 20 potential interconnection routes and regional geographical centroid is treated as equivalent node for inter-regional distance calculation. Global hourly meteorological re-analysis data of up to seven years with spatial resolution of (approximate ) is used to generate regional representative generation power series. With the minimum annual system cost for meeting demand in 2050, an integrated planning and power dispatch model is presented to determine the additional regional capacities of RE sources, storage systems, and the interconnectors from 2030, and in which load curtailment is incorporated and ‘ -1’ security are much stricter than those traditionally applied. The paper provides a comprehensive analysis with 24 cases based on different supply portfolios which show a 20% cost saving through specific global interconnections thereby lending support to the concept of a Global Electricity Grid
Dressing preserving the fundamental group
In this note we consider the relationship between the dressing action and the
holonomy representation in the context of constant mean curvature surfaces. We
characterize dressing elements that preserve the topology of a surface and
discuss dressing by simple factors as a means of adding bubbles to a class of
non finite type cylinders.Comment: 36 pages, 1 figur
Self-Avoiding Gonihedric Srting and Spin Systems
We classify different theories of self-intersecting random surfaces assigning
special weights to intersections. When self-intersection coupling constant
tends to zero, then the surface can freely inetrsect and it is
completely self-avoiding when tends to infinity. Equivalent spin
systems for this general case were constructed. In two-dimension the system
with is in complete disorder as it is in the case of 2D gauge
Ising system.Comment: Preprint CRETE-TH-21, October 1993,8 pages,Late
On the Brightening Propagation of Post-Flare Loops Observed by TRACE
Examining flare data observed by TRACE satellite from May 1998 to December
2006, we choose 190 (151 M-class and 39 X-class) flare events which display
post-flare loops (PFLs), observed by 171 \AA and 195 \AA wavelengths. 124 of
the 190 events exhibit flare ribbons (FRs), observed by 1600 \AA images. We
investigate the propagation of the brightening of these PFLs along the neutral
lines and the separation of the FRs perpendicular to the neutral lines. In most
of the cases, the length of the FRs ranges from 20 Mm to 170 Mm. The
propagating duration of the brightening is from 10 to 60 minutes, and from 10
minutes to 70 minutes for the separating duration of the FRs. The velocities of
the propagation and the separation range from 3 km/s to 39 km/s and 3 km/s to
15 km/s, respectively. Both of the propagating velocities and the separating
velocities are associated with the flare strength and the length of the FRs. It
appears that the propagation and the separation are dynamically coupled, that
is the greater the propagating velocity is, the faster the separation is.
Furthermore, a greater propagating velocity corresponds to a greater
deceleration (or acceleration). These PFLs display three types of propagating
patterns. Type I propagation, which possesses about half of all the events, is
that the brightening begins at the middle part of a set of PFLs, and propagates
bi-directionally towards its both ends. Type II, possessing 30%, is that the
brightening firstly appears at one end of a set of PFLs, then propagates to the
other end. The remnant belongs to Type III propagation which displays that the
initial brightening takes place at two (or more than two) positions on two (or
more than two) sets of PFLs, and each brightening propagates bi-directionally
along the neutral line.Comment: 13 pages, 11 figures, APJ in pres
Integral field near-infrared spectroscopy of II Zw 40
We present integral field spectroscopy in the near-infrared of the nearby
starburst galaxy IIZw40. Our new observations provide an unprecedented detailed
view of the interstellar medium and star formation of this galaxy. The
radiation emitted by the galaxy is dominated by a giant HII region, which
extends over an area of more than 400 pc in size. A few clusters are present in
this area, however one in particular appears to be the main source of ionizing
photons. We derive the properties of this object and compare them with those of
the 30 Doradus cluster in the Large magellanic cloud (LMC). We study the
spatial distribution and velocity field of different components of the
inetrstellar medium (ISM), mostly through the Bracket series lines, the
molecular hydrogen spectrum, and [FeII]. We find that [FeII] and H2 are mostly
photon excited, but while the region emitting [FeII] is almost coincident with
the giant HII region observed in the lines of atomic H and He, the H2 has a
quite different distribution in space and velocity. The age of the stellar
population in the main cluster is such that no supernova (SN) should be present
yet so that the gas kinematics must be dominated by the young stars. We do not
see, in the starbursting region, any geometrical or dynamical structure that
can be related to the large scale morphology of the galaxy.Comment: Accepted for publication on A&
Cancellation of Global Anomalies in Spontaneously Broken Gauge Theories
We discuss the generalization to global gauge anomalies of the familiar
procedure for the cancellation of local gauge anomalies in effective theories
of spontaneously broken symmetries. We illustrate this mechanism in a recently
proposed six-dimensional extension of the standard model.Comment: 5 pages; v2: version to appear in Phys. Rev.
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White matter microstructure associations with episodic memory in adults with Down syndrome: a tract-based spatial statistics study.
BACKGROUND: Nearly all persons with Down syndrome will show pathology of Alzheimer's disease in their 40s. There is a critical need for studies to identify early biomarkers of these various pathological changes of Alzheimer's disease in the Down syndrome population and understand the relationship of these biomarkers to cognitive symptoms in order to inform clinical trials. Although Alzheimer's disease is often considered a disease of gray matter, white matter degeneration has been documented during the preclinical stage of Alzheimer's disease. The current study examined the association between diffusion tensor imaging (DTI) measures of white matter microstructure and episodic memory performance in 52 adults with Down syndrome. METHODS: Seventy (N = 70) participants (M = 40.13, SD = 7.77 years) received baseline scans as part of the Neurodegeneration in Aging Down Syndrome (NiAD) study at two imaging facilities (36 at the University of Wisconsin-Madison [UW-Madison] and 34 at the University of Pittsburgh Medical Center [UPMC]). All participants had genetically confirmed trisomy 21. Fifty-two (N = 52) participants remained after QC. The DTI measures, fractional anisotropy (FA) and mean diffusivity (MD), were calculated for each participant. A combined measure of episodic memory was generated by summing the z-scores of (1) Free and Cued Recall test and (2) Rivermead Behavioural Memory Test for Children Picture Recognition. The DTI data were projected onto a population-derived FA skeleton and tract-based spatial statistics analysis was conducted using the FSL tool PALM to calculate Pearson's r values between FA and MD with episodic memory. RESULTS: A positive correlation of episodic memory with FA and a negative correlation of episodic memory and MD in the major association white matter tracts were observed. Results were significant (p < 0.05) after correction for chronological age, imaging site, and premorbid cognitive ability. CONCLUSION: These findings suggest that white matter degeneration may be implicated in early episodic memory declines prior to the onset of dementia in adults with Down syndrome. Further, our findings suggest a coupling of episodic memory and white matter microstructure independent of chronological age
Three‐dimensional MHD simulation of a flux rope driven CME
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94917/1/jgra16823.pd
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