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161.
An acoustic vector sensor (AVS) can capture more information than a conventional acoustic pressure sensor (APS). As a result, more output channels are required when multiple AVS are formed into arrays, making processing the data stream computationally intense. This paper proposes a new algorithm based on the propagator method for wideband coherent sources that eliminates eigen-decomposition in order to reduce the computational burden. Data from simulations and lake trials showed that the new algorithm is valid: it resolves coherent sources, breaks left/right ambiguity, and allows inter element spacing to exceed a half-wavelength. 相似文献
162.
To evaluate the clinical outcome, effectiveness and safety of the surgical management of traumatic lumbar spondylolisthesis
with transforaminal lumbar interbody fusion (TLIF) with short segmental instrumentation fixation. A retrospective review of
a consecutive series of 24 patients with traumatic lumbar spondylolisthesis treated with TLIF procedure was carried out. Intraoperative
spinal cord monitoring was used to confirm the peripheral neural function intact during the reduction of the spondylolisthesis.
Preoperative clinical and radiographic evaluation of all cases were originally collected prospectively. Data regarding blood
loss, operative time, duration of hospital stay, radiographic fusion, instrumentation failure and clinical result were collected
and observed at regular follow-up periods. All patients were engaged in high-energy accidents in the lower back and 16 patients
had concomitant injuries. The mean operative time was 124 min, mean blood loss was 350 mL, and mean hospital stay was 6.5
days. There were no complications such as incision infection, cerebrospinal fluide (CSF) leakage and nerve root injury and
so on. All patients demonstrated a solid lumbar interbody fusion within 4 months, and no evidence of spondylolisthesis correction
loss, instrumentation failure and loosing. They all were completely asymptomatic, with normal neurologic findings, and had
resumed their previous level of physical activities on the final follow-up. Meticulous clinical examination and careful imaging
assessment could assist an early diagonosis in cases of traumatic lumbar spondylolisthesis. Performing open reduction and
the TLIF procedure as soon as possible could restore segmental stability and painless function. The TLIF procedure was a safe,
effective technique to treat traumatic lumbar spondylolisthesis. 相似文献
163.
Face recognition via adaptive image combination 总被引:1,自引:0,他引:1
于威威 《上海交通大学学报(英文版)》2010,15(5):600-603
Dimension reduction and manifold learning are the two most popular feature extraction methods. The two methods focus on spatial
locality as a guiding principle to find a low-dimensional basis for describing high-dimensional data, but no bases or features
are more spatially localized than the original image pixels. So, adaptive image combination is presented to represent a class
by a combined sample. The combined sample is a linear combination of original samples in the same class. Adaptive image combination
(AIC) find the best combination coefficients by minimizing the intrapersonal distance and maximizing the interpersonal distance.
Experimental results show that AIC is effective. 相似文献
164.
There is a growing literature that promotes the presence of a mix of compensatory and semi-compensatory processing strategies
in the way that individuals evaluate packages of attributes in real or hypothetical markets, and make choices. This paper
proposes a specification for the utility form in a choice model to test if, given a pair of attributes with a common-metric
(e.g., components of travel time or cost), the attribute with the dominating level defines the marginal (dis)utility that
is assigned to both attributes. We refer to this processing strategy as a parameter transfer rule. We use a stated choice
data set, in the context of car driving individuals choosing between tolled and non-tolled routes, to estimate a mixed logit
model which incorporates the presence of the parameter transfer rule and the conventional fully compensatory rule, both existing
up to a probability. We find that if this parameter transfer heuristic is part of the mix, the WTP is more than 30% higher,
on average, than when only a fully compensatory rule is imposed. We also contrast the parameter transfer rule with other semi-compensatory
heuristics which have been investigated in other papers, and show that the finding adds further support to the accumulating
evidence that a semi-compensatory attribute processing rules tend to result in higher mean WTP estimates compared to the fully
compensatory attribute processing rule. 相似文献
165.
Runyu Wang 《WMU Journal of Maritime Affairs》2011,10(2):143-165
Since the 1980s, the precautionary principle has been drawing more and more international attention. This became particularly
clear during the series of Conferences on the Protection of the North Sea, which addressed marine environmental protection,
and initiated the application of the principle into maritime affairs. Although a unified concept of the precautionary principle
is lacking, some typical formulations have been concluded in regional treaties and international documents, and components
of the principle can be summarised (Part I and Part II). The precautionary principle has been adopted by international documents
involving different fields of law of the sea, and been addressed by international courts and tribunals (Part III). While the
precautionary principle is still not part of customary international law (Part IV), its increasing level of worldwide acceptance
suggests that it will become a customary international law in the future. 相似文献
166.
This paper documents the efforts to operationalize the conceptual framework of MIcrosimulation Learning-based Approach to
TRansit Assignment (MILATRAS) and its component models of departure time and path choices. It presents a large-scale real-world
application, namely the multi-modal transit network of Toronto which is operated by the Toronto Transit Commission (TTC).
This large-scale network is represented by over 500 branches with more than 10,000 stops. About 332,000 passenger-agents are
modelled to represent the demand for the TTC in the AM peak period. A learning-based departure time and path choice model
was adopted using the concept of mental models for the modelling of the transit assignment problem. The choice model parameters
were calibrated such that the entropy of the simulated route loads was optimized with reference to the observed route loads,
and validated with individual choices. A Parallel Genetic Algorithm engine was used for the parameter calibration process.
The modelled route loads, based on the calibrated parameters, greatly approximate the distribution underlying the observed
loads. 75% of the exact sequence of transfer point choices were correctly predicted by the off-stop/on-stop choice mechanism.
The model predictability of the exact sequence of route transfers was about 60%. In this application, transit passengers were
assumed to plan their transit trip based on their experience with the transportation network; with no prior (or perfect) knowledge
of service performance. 相似文献
167.
This paper establishes a link between an activity-based model for the Greater Toronto Area (GTA), dynamic traffic assignment,
emission modelling, and air quality simulation. This provides agent-based output that allows vehicle emissions to be tracked
back to individuals and households who are producing them. In addition, roadway emissions are dispersed and the resulting
ambient air concentrations are linked with individual time-activity patterns in order to assess population exposure to air
pollution. This framework is applied to evaluate the effects of a range of policy interventions and 2031 scenarios on the
generation of vehicle emissions and greenhouse gases in the GTA. Results show that the predicted increase of approximately
2.6 million people and 1.3 million jobs in the region by 2031 compared to 2001 levels poses a major challenge in achieving
meaningful reductions in GHGs and air pollution. 相似文献
168.
In an attempt to reduce CO2 emissions from motorized transport, the Taiwanese government introduced an idling stop policy for vehicles in early 2007.
This paper seeks to quantify the environmental benefits of the policy based on a stated preference analysis. Motorcyclists
were surveyed at urban intersections in Taiwan, to identify the amount of time they would be willing to turn off their engines
while waiting at traffic lights (the WTO). A contingent valuation framework based on stated preference questions was designed
to determine the WTO. Results obtained from the Spike model showed that the average motorcyclist’s WTO is 82 s. In another
analysis, in which other variables were taken into consideration, such as the possibility that the policy will be enacted
as legislation, the expected WTO increased to 101 s. In both cases, an idling stop policy would have positive environmental
effects, reducing gasoline usage by 1021 L per hour and reducing CO2 emissions by 0.56 metric tons per hour at the intersection studied during peak periods. 相似文献
169.
This paper examines the location choice associated with discretionary activities (in-home vs. out-of-home). These substitution
patterns are important in terms of travel demand as in-home activities do not necessitate travel while out-of-home activities
incur travel. Mixed logit models are estimated using an activity dataset (2003 CHASE data) to analyze the factors associated
with this choice at the individual activity-level. Results suggest that the attributes of an activity significantly contribute
to understanding the likelihood of engaging in out-of-home activities. Activity type interaction terms reveal the varying
influence that socio-demographics, activity attributes and travel have over four different activity types modeled. The results
reveal that the location choice (in-home vs. out-of-home) is sensitive to travel characteristics. As the travel time and cost
increases, an individual is less likely to engage in an activity out-of-home. Compared to passive and social activities, the
location of active activities is more sensitive to changes in travel attributes. 相似文献
170.
Reliability in cost estimates in publicly funded projects is more important today than ever with increased governmental funding
to infrastructure projects and associated accountability requirements, but surface transportation projects, large and small,
in the United States have a legacy of cost overruns. The problems with these overruns start with the cost estimation process
before projects begin. Studies have shown that early cost estimations reflect best-case scenarios rather than realistic expectations,
and have attributed technical, economic, psychological, and political reasons for underestimation. The primary objectives
of this research were to determine how costs have been presented and updated in environmental impact statements, to identify
endemic technical problems with cost estimation during the environmental review of surface transportation projects, and to
develop recommendations for improving cost estimation and disclosure. Cost estimation methods were analyzed from the documents
of 100 projects, including draft environmental impact statements, final environmental impact statements, and records of decision.
The study concluded that the lack of guidance on how to include cost estimation in environmental review revealed itself in
the level of detail and attention given to estimating costs. Agencies omitted or included various aspects of cost estimation
randomly. Professional organizations should fill the gap of the need for specific guidance to cost estimation for environmental
review so it can evolve as a state of the practice. 相似文献