835 research outputs found
Using Nyquist or Nyquist-Like Plot to Predict Three Typical Instabilities in DC-DC Converters
By transforming an exact stability condition, a new Nyquist-like plot is
proposed to predict occurrences of three typical instabilities in DC-DC
converters. The three instabilities are saddle-node bifurcation (coexistence of
multiple solutions), period-doubling bifurcation (subharmonic oscillation), and
Neimark bifurcation (quasi-periodic oscillation). In a single plot, it
accurately predicts whether an instability occurs and what type the instability
is. The plot is equivalent to the Nyquist plot, and it is a useful design tool
to avoid these instabilities. Nine examples are used to illustrate the accuracy
of this new plot to predict instabilities in the buck or boost converter with
fixed or variable switching frequency.Comment: Submitted to an IEEE journal in 201
Cost-efficient wireless mobile backhaul topologies: an analytical study
Proceedings of: 2010 IEEE Global Telecommunications Conference (GLOBECOM 2010), 6-10 December 2010, Miami, Florida, USAWireless communication technologies such as microwave radios are used to provide high-speed mobile backhaul
connectivity for radio access networks in cases in which wirebased
alternatives, e.g. cable or fiber, are not readily available
and cannot be deployed in an economic or timely manner.
Current mobile backhauls are predominantly deployed in tree
or ring topologies, which simplify traffic management. Yet, with
the increasing demand on backhaul capacity and the immense
cost pressure on mobile backhaul solutions, meshed wireless
mobile backhauls have been identified as a promising evolution.
While traffic management in wireless mesh networks have been
studied extensively in the literature, so far there is no quantitative
analysis comparing the different topology options, i.e. mesh, ring
and tree, regarding network performance and deployment cost.
This paper fills this gap by studying the minimum cost problem
of connecting a set of base station/gateway sites using different
topologies while supporting both time- and space-varying traffic
demands. Furthermore, we consider the additional constraint
of resilience to single link failures. The evaluation results show
that meshed wireless backhaul topologies are a cost-effective
alternative to trees and rings, in particular in the face of spatial
and temporal fluctuation of traffic demand and protection against
link failuresEuropean Community's Seventh Framework ProgramPublicad
Nonhomogeneous seawater Sr isotopic composition in the coastal oceans : a novel tool for tracing water masses and submarine groundwater discharge
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 12 (2011): Q05002, doi:10.1029/2010GC003372.Here we present high-precision (2σ = ±3 ppm) 87Sr/86Sr measurements in coastal waters, together with salinity, to evaluate water mass mixing and the influence of submarine groundwater discharge (SGD) in coastal waters and marginal seas. Nonhomogeneous Sr isotopic variations in water columns were documented in the Southern Okinawa Trough (SOT), South China Sea, and Kao-ping Canyon (KPC), where seawater 87Sr/86Sr varied up to 70 ppm. Seawater Sr isotopic composition changes only slightly in the upper 200 m of the SOT but was detectable and highly correlated with salinity, indicating a mixing between radiogenic North Pacific Tropical Water (high 87Sr/86Sr and high salinity) at 100–150 m and a less radiogenic component with low 87Sr/86Sr and low salinity at ∼200 m. Vertical profiles of seawater 87Sr/86Sr along the KPC show significant variations, suggesting dynamic mixing affected by continental inputs (i.e., river runoff and SGD) in this region. These results highlight the potential use of seawater Sr isotopes as a powerful tracer for determining mixing ratios and the dynamic mixing of oceanic water masses, especially in coastal and marginal seas.This
research was supported by a postdoctoral fellowship from Top
University (NCKU), Taiwan, to K.‐F. Huang and funds from
NSC and MOE, Taiwan, to C.‐F. You
Feasibility of Bispectral Index-Guided Propofol Infusion for Flexible Bronchoscopy Sedation: A Randomized Controlled Trial
There are safety issues associated with propofol use for flexible bronchoscopy (FB). The bispectral index (BIS) correlates well with the level of consciousness. The aim of this study was to show that BIS-guided propofol infusion is safe and may provide better sedation, benefiting the patients and bronchoscopists.After administering alfentanil bolus, 500 patients were randomized to either propofol infusion titrated to a BIS level of 65-75 (study group) or incremental midazolam bolus based on clinical judgment to achieve moderate sedation. The primary endpoint was safety, while the secondary endpoints were recovery time, patient tolerance, and cooperation.The proportion of patients with hypoxemia or hypotensive events were not different in the 2 groups (study vs. control groups: 39.9% vs. 35.7%, p = 0.340; 7.4% vs. 4.4%, p = 0.159, respectively). The mean lowest blood pressure was lower in the study group. Logistic regression revealed male gender, higher American Society of Anesthesiologists physical status, and electrocautery were associated with hypoxemia, whereas lower propofol dose for induction was associated with hypotension in the study group. The study group had better global tolerance (p<0.001), less procedural interference by movement or cough (13.6% vs. 36.1%, p<0.001; 30.0% vs. 44.2%, p = 0.001, respectively), and shorter time to orientation and ambulation (11.7±10.2 min vs. 29.7±26.8 min, p<0.001; 30.0±18.2 min vs. 55.7±40.6 min, p<0.001, respectively) compared to the control group.BIS-guided propofol infusion combined with alfentanil for FB sedation provides excellent patient tolerance, with fast recovery and less procedure interference.ClinicalTrials. gov NCT00789815
Double migration of the endangered Tricyrtis formosana (Liliaceae) in Japan
別経路で二度来訪していた絶滅危惧植物 --世界遺産地域における生物多様性の成立過程--. 京都大学プレスリリース. 2024-01-26.The Ryukyu Islands of Japan are a biodiversity hotspot due to geographical and historical factors. Tricyrtis formosana is a perennial herbaceous plant that commonly found in Taiwan. But only a few populations have been identified in a limited habitat on Iriomote Island, while populations of unknown origin occur near human settlements in an area on the main island of Okinawa. To better understand these populations of the phylogenetic uniqueness and intrinsic vulnerability, we conducted comparative analyses including (1) phylogeny and population structure with MIG-seq data, (2) photosynthesis-related traits of plants grown under common conditions and (3) transcriptome analysis to detect deleterious variations. Results revealed that T. formosana was split into two clades by the congeners and that Iriomote and Okinawa populations independently derived from ancestral Taiwanese populations in each clade. Photosynthetic efficiency was lowest in the Iriomote population, followed by Okinawa and Taiwan. Transcriptome analysis showed that the Iriomote population accumulated more deleterious variations, suggesting intrinsic vulnerability. These results indicate that each T. formosana population in Japan is phylogenetically unique and has been independently dispersed from Taiwan, and that the Iriomote population presents a high conservation difficulty with a unique photosynthesis-related characteristic and a larger amount of deleterious variations
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