Analysis on circumferential natural frequencies of stator in permanent magnet synchronous motor

Accurate calculation on circumferential natural frequencies of stator structure in permanent magnet synchronous motor (PMSM) is very important for predicting the vibration and noise of PMSM. The analytical modal formula for the stator structure in PMSM is proposed, starting from the mathematical displacement model of cylindrical shell, then deriving the analytical formula for the stator structure. Firstly, finite element method (FEM) is applied to analyze the circumferential natural frequencies of cylindrical shells with different length, wall thickness, mean diameter, diameter-thickness ratio, size and installation position of terminal box. The influences on circumferential natural frequencies of cylindrical shells are studied. Furthermore, a new analytical formula considering diameter-thickness ratio for calculating circumferential natural frequencies of cylindrical shells is developed. Compared with the results of FEM, the correctness of the analytical formula is verified. Then, novel analytical formulas considering stiffness errors are proposed to calculate the circumferential natural frequencies of stator core and motor case. Compared with the results of FEM, the effectiveness of analytical method is validated. Finally, a new analytical formula considering diameter-thickness ratio, stiffness errors, existence of terminal box and mutual constraints is presented to calculate the circumferential natural frequencies of stator structure. Compared with the results of FEM and experimental method, the relative errors are respective within |4.43 %| and |3.38 %|. The validity of analytical formula is confirmed

Experimental analysis on noise characteristics of surface-mounted permanent magnet synchronous motors

Starting with the analysis on sound pressure level (SPL) spectrum of surface-mounted permanent magnet synchronous motors (SMPMSMs), the reasons for producing main peaks are investigated. According to different causes, different methods for reducing noise are proposed. Firstly, the SPL spectrum of SMPMSMs is obtained by experiment under the conditions of 2000 rpm rated speed, full load and 4 kHz switching frequency. Meanwhile, the frequencies corresponding to main peaks are found out. Secondly, the reasons for generating peaks in the SPL spectrum are researched from three aspects, namely, force sources, natural frequencies, coefficient of relative sound intensity. Then, on the basis of different causes for generating noise, different measures for decreasing noise are presented, namely, single cutting of two end rabbets of motor case in single clamping, waveform reconstruction of radial electromagnetic force density, enhancing of switching frequency, changing of natural frequency and decreasing of the length-diameter ratio of stator. Furthermore, the effectiveness for these methods is studied. Finally, a comprehensive method is proposed to decrease noise. The noise value of SMPMSMs is reduced by 4.7 dB(A) at the rated speed of 2000 rpm, full load and switching frequency of 4 kHz. In addition, the sharpness and loudness are respectively decreased by 0.522 acum and 6.97 sone at no load. The study provides references for the design of SMPMSMs with low noise

No. 14: The Impact of Proximity to Wet Markets and Supermarkets on Household Dietary Diversity in Nanjing City, China

Existing studies suggest that despite the proliferation of supermarkets, traditional wet markets have persisted in many countries and have been playing an important role in people’s daily food access. Yet, studies investigating the issue of food access and its influences on food security have mainly focused on food deserts and the proximity to supermarkets, with limited focus on wet markets and other food outlets. This study investigates the influence of the proximity to wet markets and supermarkets on urban household dietary diversity in Nanjing. Based on the data collected through a citywide survey in 2015 and the map data of wet markets and supermarkets, the Poisson regression model was deployed to examine the correlations between geographical proximity to supermarkets and wet markets and household dietary diversity. The results show that the coefficients for the distance to the nearest wet market are not statistically significant. Although the coefficients for the distance to nearest supermarket are statistically significant, they were too minor to be of practical importance. We argue, however, that the insignificant correlations reflect exactly the high physical accessibility to food outlets and the extensive spatially dense food supply network constituted by wet markets, supermarkets and small food stores in Nanjing. This is verified by the survey data that more than 90% of households purchased fresh food items within their neighbourhoods or in walking distance. In addition to the densely distributed food outlets, various other factors contributed to the non-significant influence of the distance to the nearest wet market and supermarket, including the many small food stores within or close to residential communities, the prevalence of three-generation extended households and high household income. This study highlights the importance of allowing mixed land use for food outlets with residential land and integrating wet markets into urban infrastructure planning

No. 24: Achieving Urban Food Security through a Public-Private Hybrid Food Provisioning System: A Case Study of Nanjing, China

Private and public markets are two models of urban food retailing governance. This paper examines the public-private hybrid model of urban food provisioning system and its governance in Nanjing, China. Based on data from surveys, non-structured interviews, and bibliographical material analysis, we examine the public-private hybrid model and its linkages with urban food security. Our analysis shows that the public-private hybrid model of food markets and its governance ensures a relatively high-level urban food security in Nanjing. We argue that the hybrid food market governance system effectively integrates public and private capital into a government-supported and regulated, small-business-based system in both food wholesale and retailing sectors. In the public-private hybrid system, wholesale markets and wet markets provide a physical “marketplace” for small-scale private food vendors to operate their business, while the private capital-based supermarkets is also integrated into the system of urban food provisioning. The paper reveals how the “crawling peg” policy and the regulation on the usage of marketplaces have ensured that the development of wet markets keeps pace with population growth. While the public-private hybrid system helps avoid market failure and government failure in food provisioning, it faces challenges such as reliance on fiscal inputs

No. 24: Achieving Urban Food Security Through a Public-Private Hybrid Food Provisioning System: A Case Study of Nanjing, China

Private and public markets are two models of urban food retailing governance. This paper examines the public-private hybrid model of urban food provisioning system and its governance in Nanjing, China. Based on data from surveys, non-structured interviews, and bibliographical material analysis, we examine the public-private hybrid model and its linkages with urban food security. Our analysis shows that the public-private hybrid model of food markets and its governance ensures a relatively high-level urban food security in Nanjing. We argue that the hybrid food market governance system effectively integrates public and private capital into a government-supported and regulated, small-business-based system in both food wholesale and retailing sectors. In the public-private hybrid system, wholesale markets and wet markets provide a physical “marketplace” for small-scale private food vendors to operate their business, while the private capital-based supermarkets is also integrated into the system of urban food provisioning. The paper reveals how the “crawling peg” policy and the regulation on the usage of marketplaces have ensured that the development of wet markets keeps pace with population growth. While the public-private hybrid system helps avoid market failure and government failure in food provisioning, it faces challenges such as reliance on fiscal inputs

Municipal sewage sludge compost promotes Mangifera persiciforma tree growth with no risk of heavy metal contamination of soil

Application of sewage sludge compost (SSC) as a fertilizer on landscaping provides a potential way for the effective disposal of sludge. However, the response of landscape trees to SSC application and the impacts of heavy metals from SSC on soil are poorly understood. We conducted a pot experiment to investigate the effects of SSC addition on Mangifera persiciforma growth and quantified its uptake of heavy metals from SSC by setting five treatments with mass ratios of SSC to lateritic soil as 0%:100% (CK), 15%:85% (S15), 30%:70% (S30), 60%:40% (S60), and 100%:0% (S100). As expected, the fertility and heavy metal concentrations (Cu, Zn, Pb and Cd) in substrate significantly increased with SSC addition. The best performance in terms of plant height, ground diameter, biomass and N, P, K uptake were found i n S30, implying a reasonable amount of SSC could benefit the growth of M. persiciforma. The concentrations of Cu, Pb and Cd in S30 were insignificantly different from CK after harvest, indicating that M. persiciforma reduced the risk of heavy metal contamination of soil arising from SSC application. This study suggests that a reasonable rate of SSC addition can enhance M. persiciforma growth without causing the contamination of landscaping soil by heavy metals

Nitrogen-doped micropores binder-free carbon-sulphur composites as the cathode for long-life lithium-sulphur batteries

Nitrogen-doped micropores-contained carbon nanofibres (NMCNFs) were prepared by carbonizing ZIF-8 grown in liquid-phase along with electrospinning. When NMCNFs act as sulphur host materials in lithium–sulphur batteries, NMCNFs can retard the shuttle effect and dissolution of polysulfides through the synergic action of effective physical confinement to micropores and nitrogen surface chemical absorption. NMCNFs show a capacity up to 636 mAh g−1 after 500 cycles against Li anode

Epithelial Neoplasia Coincides with Exacerbated Injury and Fibrotic Response in the Lungs of \u3cem\u3eGprc5a\u3c/em\u3e-Knockout Mice Following Silica Exposure

Exposure to crystalline silica is suggested to increase the risk for a variety of lung diseases, including fibrosis and lung cancer. However, epidemiological evidences for the exposure-risk relationship are ambiguous and conflicting, and experimental study from a reliable animal model to explore the relationship is lacking. We reasoned that a mouse model that is sensitive to both lung injury and tumorigenesis would be appropriate to evaluate the exposure-risk relationship. Previously, we showed that, Gprc5a-/- mice are susceptible to both lung tumorigenesis and endotoxin-induced acute lung injury. In this study, we investigated the biological consequences in Gprc5a-/- mouse model following silica exposure. Intra-tracheal administration of fine silica particles in Gprc5a-/- mice resulted in more severe lung injury and pulmonary inflammation than in wild-type mice. Moreover, an enhanced fibrogenic response, including EMT-like characteristics, was induced in the lungs of Gprc5a-/- mice compared to those from wild-type ones. Importantly, increased hyperplasia or neoplasia coincided with silica-induced tissue injury and fibrogenic response in lungs from Gprc5a-/- mice. Consistently, expression of MMP9, TGFβ1 and EGFR was significantly increased in lungs from silica-treated Gprc5a-/- mice compared to those untreated or wild-type ones. These results suggest that, the process of tissue repair coincides with tissue damages; whereas persistent tissue damages leads to abnormal repair or neoplasia. Thus, silica-induced pulmonary inflammation and injury contribute to increased neoplasia development in lungs from Gprc5a-/- mouse model

An economic and disease transmission model of human papillomavirus and oropharyngeal cancer in Texas

In 2017, 46,157 and 3,127 new oropharyngeal cancer (OPC) cases were reported in the U.S. and Texas, respectively. About 70% of OPC were attributed to human papillomavirus (HPV). However, only 51% of U.S. and 43.5% of Texas adolescents have completed the HPV vaccine series. Therefore, modeling the demographic dynamics and transmission of HPV and OPC progression is needed for accurate estimation of the economic and epidemiological impacts of HPV vaccine in a geographic area. An age-structured population dynamic model was developed for the U.S. state of Texas. With Texas-specific model parameters calibrated, this model described the dynamics of HPV-associated OPC in Texas. Parameters for the Year 2010 were used as the initial values, and the prediction for Year 2012 was compared with the real age-specific incidence rates in 23 age groups for model validation. The validated model was applied to predict 100-year age-adjusted incidence rates. The public health benefits of HPV vaccine uptake were evaluated by computer simulation. Compared with current vaccination program, increasing vaccine uptake rates by 50% would decrease the cumulative cases by 4403, within 100 years. The incremental cost-effectiveness ratio of this strategy was $94,518 per quality-adjusted life year (QALY) gained. Increasing the vaccine uptake rate by 50% can: (i) reduce the incidence rates of OPC among both males and females; (ii) improve the quality-adjusted life years for both males and females; (iii) be cost-effective and has the potential to provide tremendous public health benefits in Texas