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The concept of level of service (LOS) is meant to reflect user perception of the quality of service provided by a transportation facility or service. Although the LOS of bus rapid transit (BRT) has received considerable attention, the number of levels of service of BRT that a user can perceive still remains unclear. Therefore, this paper addresses this issue using fuzzy clustering of user perception. User perception is a six-dimension vector including perceived arrival time, perceived waiting time, bus speed perception, passenger load perception, perceived departure time, and overall perception. The research team developed a smartphone-based transit travel survey system to conduct the user perception surveys in three BRT systems in China. Fuzzy C-means clustering, improved using a simulated annealing genetic algorithm, was adopted to partition user perception into 2-10 clusters. Seven cluster validity indices were used to determine the appropriate number of LOS categories. The results indicate that users can perceive two to four levels of service. [ABSTRACT FROM AUTHOR]

The concept of level of service (LOS) is meant to reflect user perception of the quality of service provided by a transportation facility or service. Although the LOS of bus rapid transit (BRT) has received considerable attention, the number of levels of service of BRT that a user can perceive still remains unclear. Therefore, this paper addresses this issue using fuzzy clustering of user perception. User perception is a six-dimension vector including perceived arrival time, perceived waiting time, bus speed perception, passenger load perception, perceived departure time, and overall perception. The research team developed a smartphone-based transit travel survey system to conduct the user perception surveys in three BRT systems in China. Fuzzy C-means clustering, improved using a simulated annealing genetic algorithm, was adopted to partition user perception into 2 to 10 clusters. Seven cluster validity indices were used to determine the appropriate number of LOS categories. The results indicate that users can perceive two to four levels of service. [ABSTRACT FROM AUTHOR]

The thermal expansion and phase transition of unpoled and poled [0 0 1]-oriented 0.69Pb(Mg1/3Nb2/3)O3-0.31PbTiO3 crystals are investigated using thermomechanical analysis, domain evolution, and dielectric measurement. Results of thermomechanical analysis show that the unpoled crystal exhibits negative thermal expansion at a temperature range from 30 °C to 120 °C, and the lattice parameter c of the tetragonal (T) phase is larger than those of the rhombohedral (R) and cubic (C) phases, i.e., cT > cR and cT > cC. Two additional structural modifications near 50 °C and 125 °C are detected in the unpoled crystal. Compared with that of the poled crystal, the T → C phase transition temperature of the unpoled crystal is relatively higher. An increase in temperature causes the unpoled crystal to undergo R → T → C phase transition, whereas R → M → T → C phase transition sequences are observed in the poled crystal. The phase transition behaviors are further verified by domain evolution and dielectric measurement. The significant differences between poled and unpoled crystals are attributed to the differences in their domain structures. [ABSTRACT FROM AUTHOR]

Background: The objective of this pilot study was to evaluate cartilage T1ρ and T2 relaxation times and knee mechanics during walking and drop-landing for individuals with anterior cruciate ligament reconstruction (ACL-R). Methods: Nine patients (6 men and 3 women, age 35.8 ± 5.4 years, BMI 23.5 ± 2.5 kg/m2) participated 1.5 ± 0.8 years after single-bundle two-tunnel ACL reconstruction. Peak knee adduction moment (KAM), flexion moment (KFM), extension moment (KEM), and peak varus were calculated from kinematic and kinetic data obtained during walking and drop-landing tasks. T1ρ and T2 times were calculated for medial femur (MF), and medial tibia (MT) cartilage and compared between subjects with low KAM and high KAM. Biomechanical variables were compared between limbs. Results: The high KAM group had higher T1ρ for MT(p= 0.01), central MT (p = 0.05), posterior MF (p = 0.04), posterior MT (p = 0.01); and higher T2 for MT (p = 0.02), MF (p = 0.05), posterior MF (p = 0.002) and posterior MT (p = 0.01). During walking, ACL-R knees had greater flexion at initial contact (p = 0.04), and lower KEM (p = 0.02). During drop-landing, the ACL-R knees had lower KAM (p = 0.03) and KFM (p = 0.002). Conclusion: Patients with ACL-R who have higher KAM during walking had elevated MR relaxation times in the medial knee compartments. These data suggest that those individuals who have undergone ACL-R and have higher frontal plane loading, may be at a greater risk of knee osteoarthritis. [ABSTRACT FROM AUTHOR]

Background: The purpose of this investigation is to evaluate the T1ρ relaxation times of articular cartilage surrounding focal defects in the tibiofemoral joint. Methods: Quantitative cartilage assessment was performed using 3 T MRI with T1ρ mapping in 19 healthy individuals and 44OApatients. Sagittal T2-weighted fast spin echo (FSE) imageswere acquired for lesion assessment. Differences were determined using analysis of variance (ANOVA). Results: Cartilage lesions were found in 37% of controls, and 93% of OA patients. Meniscal tears were found in 16% of controls and 57% of OA patients. We observed no difference in T1ρ relaxation times when comparing cartilage immediately surrounding a focal defect, and the remaining cartilage within that compartment. The medial femoral condyle (MFC) had the highest incidence of cartilage defects. MFC and medial meniscus posterior horn T1ρ were higher in subjects having multiple focal lesions (p=0.048, pb0.001 respectively) and extensive full thickness lesions (p=0.009, pb0.001 respectively) compared to subjects with no MFC defects. Significant elevations in T1ρ of the adjacent compartment (medial tibia) and medial meniscus were observed in subjects with MFC lesions. Conclusion: Increased relaxation times in the involved compartment as well as the adjacent compartment and associated meniscus underscore the interdependence of these structures at bearing load. However, no differences in cartilage composition immediately surrounding a defect were noted. Finally, an association was observed between cartilage defects and meniscal damage in advanced disease. Clinical Relevance: Cartilage defects were not associated with degeneration in the immediately adjacent cartilage. [ABSTRACT FROM AUTHOR]