1,982 research outputs found
A new schedule-based transit assignment model with travel strategies and supply uncertainties
This paper proposes a new scheduled-based transit assignment model. Unlike other schedule-based models in the literature, we consider supply uncertainties and assume that users adopt strategies to travel from their origins to their destinations. We present an analytical formulation to ensure that on-board passengers continuing to the next stop have priority and waiting passengers are loaded on a first-come-first-serve basis. We propose an analytical model that captures the stochastic nature of the transit schedules and in-vehicle travel times due to road conditions, incidents, or adverse weather. We adopt a mean variance approach that can consider the covariance of travel time between links in a space–time graph but still lead to a robust transit network loading procedure when optimal strategies are adopted. The proposed model is formulated as a user equilibrium problem and solved by an MSA-type algorithm. Numerical results are reported to show the effects of supply uncertainties on the travel strategies and departure times of passengers.postprin
The reliability-based stochastic transit assignment problem with elastic demand
This paper examines the reliability-based stochastic transit assignment problem with elastic demand. A Variational Inequality (VI) model for this problem is developed. The VI model considers capacity, waiting time and in-vehicle travel time as stochastic variables, and includes Spiess and Florian’s (1989) and de Cea and Fernández’s (1993) models as special cases. A reliability-based stochastic user equilibrium condition is defined to capture the route choice behavior of passengers. To illustrate the properties of the VI model, numerical studies were conducted on de Cea and Fernández’s (1993) network. The studies also show that Spiess and Florian’s and de Cea and Fernández’s models can overestimate the system performance substantially.postprin
Design and analysis of magnet proportioning for dual-memory machines
published_or_final_versio
Multi-Constellation GNSS Multipath Mitigation Using Consistency Checking
In a typical urban environment, a mixture of multipath-free,
multipath-contaminated and non-line-of-sight
(NLOS) propagated GNSS signals are received. The
errors caused by multipath-contaminated and NLOS
reception are the dominant source of reduced consumer-grade
positioning accuracy in the urban environment.
Many conventional receiver-based and antenna-based
techniques have been developed to mitigate either
multipath or NLOS reception with mixed success.
Nevertheless, the positioning accuracy can be maximised
based on the simple principle of selecting only those
signals least contaminated by multipath and NLOS
propagation to form the navigation solution. The advent
of multi-constellation GNSS provides the opportunity to
realise this technique that is potentially low-cost and
effective for consumer-grade devices. It may also be
implemented as an augmentation to other multipath
mitigation techniques.
The focus of this paper is signal selection by consistency
checking, whereby measurements from different satellites
are compared with each other to identify the NLOS and
most multipath-contaminated signals. The principle of
consistency checking is that multipath-contaminated and
NLOS measurements produce a less consistent navigation
solution than multipath-free measurements. RAIM-based
fault detection operates on the same principle.
Three consistency-checking schemes based on single-epoch
least-squares residuals are assessed: single sweep,
recursive checking and a hybrid version of the first two.
Two types of weighting schemes are also considered:
satellite elevation-based and signal C/N0-based weighting.
The paper also discussed the different observables that
may be used by a consistency-checking algorithm for
different applications and their effect on detection
sensitivity.
Test results for the proposed algorithms are presented
using data from both static positioning and stand-alone
dynamic positioning experiments. The static data was
collected using a pair of survey-grade multi-constellation
GNSS receivers using both GPS and GLONASS signals
at open sky and urban canyon locations, while the
dynamic data was collected using a consumer-grade
GPS/GLONASS receiver on a car in a mixed urban
environment. Significant improvements in position
domain are demonstrated using the weighted recursive
methods in the open environments. However in the urban
environments, there are insufficient directly received
signals for the conventional RAIM-based signal selection
to be effective all the time. Both positioning
improvements and risky outliers are demonstrated. More
advanced techniques have been identified for
investigation in future research
Lhx1/5 control dendritogenesis and spine morphogenesis of Purkinje cells via regulation of Espin
published_or_final_versio
Nel positively regulates the genesis of retinal ganglion cells by promoting their differentiation and survival during development
Peer reviewedPublisher PD
Climate Variability and Hemorrhagic Fever with Renal Syndrome Transmission in Northeastern China
Background: The transmission of hemorrhagic fever with renal syndrome (HFRS) is influenced by climatic variables. However, few studies have examined the quantitative relationship between climate variation and HFRS transmission. ---------- Objective: We examined the potential impact of climate variability on HFRS transmission and developed climate-based forecasting models for HFRS in northeastern China. ---------- Methods: We obtained data on monthly counts of reported HFRS cases in Elunchun and Molidawahaner counties for 1997–2007 from the Inner Mongolia Center for Disease Control and Prevention and climate data from the Chinese Bureau of Meteorology. Cross-correlations assessed crude associations between climate variables, including rainfall, land surface temperature (LST), relative humidity (RH), and the multivariate El Niño Southern Oscillation (ENSO) index (MEI) and monthly HFRS cases over a range of lags. We used time-series Poisson regression models to examine the independent contribution of climatic variables to HFRS transmission. ----------- Results: Cross-correlation analyses showed that rainfall, LST, RH, and MEI were significantly associated with monthly HFRS cases with lags of 3–5 months in both study areas. The results of Poisson regression indicated that after controlling for the autocorrelation, seasonality, and long-term trend, rainfall, LST, RH, and MEI with lags of 3–5 months were associated with HFRS in both study areas. The final model had good accuracy in forecasting the occurrence of HFRS. ---------- Conclusions: Climate variability plays a significant role in HFRS transmission in northeastern China. The model developed in this study has implications for HFRS control and prevention
Transgenic expression of the dicotyledonous pattern recognition receptor EFR in rice leads to ligand-dependent activation of defense responses
Plant plasma membrane localized pattern recognition receptors (PRRs) detect extracellular pathogen-associated molecules. PRRs such as Arabidopsis EFR and rice XA21 are taxonomically restricted and are absent from most plant genomes. Here we show that rice plants expressing EFR or the chimeric receptor EFR::XA21, containing the EFR ectodomain and the XA21 intracellular domain, sense both Escherichia coli- and Xanthomonas oryzae pv. oryzae (Xoo)-derived elf18 peptides at sub-nanomolar concentrations. Treatment of EFR and EFR::XA21 rice leaf tissue with elf18 leads to MAP kinase activation, reactive oxygen production and defense gene expression. Although expression of EFR does not lead to robust enhanced resistance to fully virulent Xoo isolates, it does lead to quantitatively enhanced resistance to weakly virulent Xoo isolates. EFR interacts with OsSERK2 and the XA21 binding protein 24 (XB24), two key components of the rice XA21-mediated immune response. Rice-EFR plants silenced for OsSERK2, or overexpressing rice XB24 are compromised in elf18-induced reactive oxygen production and defense gene expression indicating that these proteins are also important for EFR-mediated signaling in transgenic rice. Taken together, our results demonstrate the potential feasibility of enhancing disease resistance in rice and possibly other monocotyledonous crop species by expression of dicotyledonous PRRs. Our results also suggest that Arabidopsis EFR utilizes at least a subset of the known endogenous rice XA21 signaling components
Quantitative comparison of myocardial fiber structure between mice, rabbit, and sheep using diffusion tensor cardiovascular magnetic resonance
<p>Abstract</p> <p>Background</p> <p>Accurate interpretations of cardiac functions require precise structural models of the myocardium, but the latter is not available always and for all species. Although scaling or substitution of myocardial fiber information from alternate species has been used in cardiac functional modeling, the validity of such practice has not been tested.</p> <p>Methods</p> <p>Fixed mouse (n = 10), rabbit (n = 6), and sheep (n = 5) hearts underwent diffusion tensor imaging (DTI). The myocardial structures in terms of the left ventricular fiber orientation helix angle index were quantitatively compared between the mouse rabbit and sheep hearts.</p> <p>Results</p> <p>The results show that significant fiber structural differences exist between any two of the three species. Specifically, the subepicardial fiber orientation, and the transmural range and linearity of fiber helix angles are significantly different between the mouse and either rabbit or sheep. Additionally, a significant difference was found between the transmural helix angle range between the rabbit and sheep. Across different circumferential regions of the heart, the fiber orientation was not found to be significantly different.</p> <p>Conclusions</p> <p>The current study indicates that myocardial structural differences exist between different size hearts. An immediate implication of the present findings for myocardial structural or functional modeling studies is that caution must be exercised when extrapolating myocardial structures from one species to another.</p
- …