Long-Term Effectiveness of Radar Speed Display Signs in a University Environment

Vehicular speeds are of particular interest in areas with a high number of pedestrians due to the fact that 14-percent of all fatal crashes involve pedestrians. This study investigated the effect of a radar speed display sign placed for an extended period of time, at a location frequented by law enforcement on a road segment entering a university campus with a high number of pedestrians and vehicle speed violations. The statistical analysis included a comparison between AM peak, PM peak, and midday speeds collected one year apart. The data suggested that radar speed display signs can remain effective over a long period of time;causing drivers to decelerate when warned of a speeding violation. While other studies have examined long-term impacts of similar technologies, none have included a road entering a University campus. Thus, these findings support that other similar locations entering university campuses could see long-term benefits to stationary radar speed display signs.

A new coupled map car-following model considering drivers' steady desired speed

Based on the pioneering work of Konishi et al., in consideration of the influence of drivers＇ steady desired speed ef/ect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis.

An improved wind speed algorithm for “Jason-1” altimeter under tropical cyclone conditions

Rain effect and lack of in situ validation data are two main causes of tropical cyclone wind retrieval errors. The National Oceanic and Atmospheric Administration＇s Climate Prediction Center Morphing technique （CMORPH） rain rate is introduced to a match-up dataset and then put into a rain correction model to remove rain effects on ＂Jason-1＂ normalized radar cross section （NRCS）; Hurricane Research Division （HRD） wind sPeed, which integrates all available surface weather observations, is used to substitute in situ data for establishing this relationship with ＂Jason-l＂ NRCS. Then, an improved ＂Jason-l＂ wind retrieval algorithm under tropical cyclone conditions is proposed. Seven tropical cyclones from 2003 to 2010 are studied to validate the new algorithm. The experimental results indicate that the standard deviation of this algorithm at C-band and Ku-band is 1.99 and 2.75 m/s respectively, which is better than the existing algorithms. In addition, the C-band algorithm is more suitable for sea surface wind retrieval than Ku-band under tropical cyclone conditions.

Study on Spatial and Temporal Distribution Characteristics of Wind Energy Resource and Preservation in Central and West Hexi Corridor

[Objective] The aim was to explore the spatial and temporal distribution characteristics of wind energy resource and preservation in central and west area of Hexi Corridor. [Method] By dint of the wind speed data from 1955 to 2007 in ten meteorological observation station in central and west area of Hexi Corridor,and special wind tower fine data from January to December in 2007,the distribution and reserves of the region＇s wind energy resources were studied. [Result] The results showed that environmental wind speed was relatively stable in central and west Hexi Corridor. There were no distinct changes in climate characteristics distribution. There were regional differences in the distribution of wind energy,and there was a large numerical area of wind energy in Gazhou County and Yumen City; Wind energy in the region generally was higher. The wind energy density was above 100 w/m2 in the 10 m layer,around 140 w/m2 in most places,and was more than 200 w/m2 in the large number area. The wind grew in vertical direction along with the linear growth of height. Each 10 m high wind increased to 15 w/m2 averagely,50m layer wind energy was greater than the general 240 w/m2 and there were obvious changes on daily and annual with wind energy in central and west area of Hexi Corridor. The duration from March to May was a wind energy-intensive stage,10m height from the ground in the wind around 10：00 in low-value. After growing from 11：00,it met the day largest number at 18：00,and then reduced gradually. Effective wind speed hours in the region in general were more than 6 200 h,and the value in the large areas was close to 7 600 h. [Conclusion] The study laid basis for the development and application of wind energy in central and west area of Hexi Corridor.

Theoretical analysis of the conical premixed flame response to upstream velocity disturbances considering flame speed development effects

The effect of upstream velocity pertuibations on the response of a premixed flame was investigated in terms of the flame transfer function dependency on excitation frequency.In this study,the assumption of constant flame speed was extended and the effect of flame speed development was considered;i.e.,the flame speed would grow with the time after ignition or with the distance from a flame-holder.In the present study,the kinematics of a conical flame was investigated by linearization of the front tracking equation of flame to uniform and convected fluctuations of the flow velocity and the response was compared with that of a V-shaped flame and the experimental data in the previous studies.The results show that the effect of flame speed development could influence a decreasing gain and increase the phase of the flame response to the uniform velocity oscillations in low and moderate frequencies.Comparing the variations in the gain of flame response upon normalized frequency,show that a conical flame has lower values than the V-flame.In other woods,these flames might be less susceptible to combustion instabilities than the V-flames.Furthennore,the variations in phase of the V-flames responses,which show a quasi-linear behavior with normalized frequency,have higher values than the saturated behavior in phase of the conical flame responses.Also,considering that the flame speed development induces an increase in the gain and phase of the conical flame response to the convected velocity oscillations in certain frequencies;because the developed flame front has longer length in comparison to the flame front in constant flame speed model.Therefore,the flame length may be longer than convective wavelength and the heat release would be generated in different points of the flame;consequently the flow oscillations might exert a stronger impact on the unsteady heat release fluctuations.

WIND SPEED DISTRIBUTION REGULARITY AND WIND REDUCTION EFFECT OF SHELTER NET

Wind speed distribution regularities in a shelter mesh (S. M.) have been deduced from the wind speed distribution in the sheltered area of a single shelter beh (S. B.).The components of a wind vector in a mesh follow the error function distribution model or the logarithmic model of 2-variable power function.The wind vector itself follows the vector composition model of these models.We can calculate the wind speed distribution and wind reduction effect of a mesh under the conditions of any shelter-belt characteristics, any size and shape of a mesh and any wind inclination angle with this model. The results of our field model experiment are in better agreement with the theoretically calculated results.