Search

Evaluating arterial operational performance plays a pivotal role in arterial system management and enhancement. As a fundamental reference guide for traffic engineers, the Highway Capacity Manual (HCM) provides a series of analysis methodologies for evaluating multimodal operations on urban streets, highways, freeways, and off-street pathways. However, the efficient use of the performance evaluation methodology of urban street facilities for motorized vehicles in the HCM can be restricted by a large amount of traffic volume collections at signalized and access point intersections, roadway segment geometric data inputs, and complicated calculation procedures on urban street segments. Further, the use of alternative tools, such as vehicle trajectory data, remains to be explored to supplement the urban street facility calculation framework in the HCM. To bridge the gap, this research utilizes vehicle trajectory data as an alternative tool and proposes a combined vehicle trajectory data and HCM calculation framework to implement and assess the existing performance evaluation methodology of urban street facilities for motorized vehicles in the HCM 7th Edition. A case study was carried out on three major signalized arterials in Sparks, Nevada, for HCM methodology implementation and performance evaluation. Based on evaluation results, it was found that vehicle trajectory data can be utilized as an alternative tool to implement the performance evaluation methodology of urban street facilities for motorized vehicles in the HCM 7th Edition. It is recommended to combine arterial through-vehicle trajectories, the time-space diagram, arterial level of service (LOS), and the poorest segment LOS for arterial operational performance evaluation and further enhancement. The proposed automobile traveler perception score (ATPS) in the HCM was found to be insensitive to reflecting traveler’s perception of service quality. Additional traveler perception-based factors are recommended to be included for further ATPS development and enhancement. [ABSTRACT FROM AUTHOR]

Emergency vehicle preemption (EVP), a common traffic signal preemption in urban areas, is used to prioritize the right-of-way to emergency vehicles at signalized intersections by terminating active signal timing plans and running preemption plans. However, such mandatory signal changes can disrupt arterial signal coordination when an emergency vehicle travels through a well-coordinated signalized arterial. The research need has emerged to evaluate and minimize such disruptions to arterial signal coordination. Therefore, this research summarizes EVP operations along with preemption modules in North America Econolite Cobalt signal controllers (EOS software version) and investigates five available EVP exit strategies to minimize disruptions: return to defined phases, return to coordinated operations, return to free operations, return to first skipped phase, and return to the most delayed phase. The impacts of five exit strategies on arterial signal coordination are evaluated and compared on a signalized arterial through hardware-in-the-loop simulation (HILS) in four different simulation scenarios. From simulation results, it is found that EVP tends to worsen arterial and intersection operations for all five EVP exit strategies by increasing the arterial travel times and the total vehicle movement delay at preempted coordinated intersections. The performance of different EVP exit strategies is influenced by the route of the emergency vehicle and the EVP activation point. Furthermore, the selection of an EVP exit strategy depends on different operational objectives after EVP. When recovering arterial signal progression becomes the primary objective, the return to coordinated operations exit strategy is recommended to be selected at intersections to minimize disruptions. The return to the free operations exit strategy is recommended to avoid queue spillover and phase split failure issues at intersections when improving the intersection-level performance turns out to be the overarching goal. [ABSTRACT FROM AUTHOR]

For diagnosing deformation fault and latent loosing status of winding, this study proposed a state diagnosis method of transformer winding deformation based on fusing vibration and reactance parameters. The wavelet energy – matrix norm transformation method and reactance identification method were proposed to extract vibration and reactance parameters. The multi‐information collection system of transformer winding deformation state was designed. Aiming at the S‐11‐M‐500/35 transformer, short circuit current impact experiment was made and three deformation fault windings were designed. Status database of multi‐information for normal, loosing, deformation and specific fault types of winding were established. State diagnosis experiment on normal winding, loosing winding after short circuit current impact and deformation fault winding was made. Per unit value‐space vector transformation method was proposed to fuse vibration and reactance parameters, fusing eigenvector was established, and the winding deformation state was diagnosed by extracting fusing feature. On the basis of the above research, regarding deformation fault state winding, fault types were diagnosed based on the relevance vector machine. Results indicated that latent loosing, deformation fault and three deformation fault types of winding can be diagnosed accurately. Fusing diagnosis method proposed in this study was superior to the single vibration or reactance parameter diagnosis method. [ABSTRACT FROM AUTHOR]

Na0.5Bi0.5TiO3 (NBT) is a kind of excellent lead-free ferroelectric material. However, during the preparation of the NBT thin film by the chemical methods, the non-NBT phase is easier to be formed, which has a negative effect on the ferroelectric properties. In this paper, the Sr-doped NBT (SNBT) films were prepared by metal--organic solution deposition. The effects of Sr-doping amount, annealing temperature and duration on the appearance of non-NBT phase, and the relationship between the amount of non-NBT phase and the ferroelectric properties of the thin film was studied in detail. The results show that the appearance of the non-NBT phase in the SNBT is mainly because of the excessive amount of the doped ions or the excessive evaporation of Bi caused by long annealing duration. The excessive amount of the non-NBT phase will weaken the remanent polarization of the thin films. Using excessive 20% of Bi and reducing the annealing duration are the effective method for suppressing the non-NBT phase and improving the ferroelectricity of NBT-based film. [ABSTRACT FROM AUTHOR]

Presents a study on the gas flow properties of self extinguishing type circuit breakers (SECB) during current interruption. Structure of SECB; Mathematical model used in the study; Results and conclusions.

The morphology, composition and mechanism of the non-NBT phase in the Sr-doped NBT [SNBT, (Na0.5Bi0.5)1-xSrxTiO3] thin films by chemical method were investigated using XRD, SEM, crystallization analysis and thermodynamics analysis. The results showed that the non-NBT phase is the porphyroblastic grains in the matrix and looks like a plate-shaped polyhedron. The mechanism of the non-NBT phase formation is that the Sr2+ and Na+ combined with to form initial simple titanate, such as SrTiO3, Na2TiO3, or NBT phase decomposed because of the volatilization of Bi under a higher annealing temperature or longer annealing duration, and then transform into the secondary simple titanates (Sr2+,2Na+)TiO3 or (Sr,Na)xTiyOz. Moreover, the NBT phase disappeared for the SNBT films annealing at temperatures higher than 600°C and for 15 min. [ABSTRACT FROM AUTHOR]