890 research outputs found

    DEMAND FOR HEALTHY FOOD IN THE UNITED STATES

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    This study investigates the demand for selected healthy food groups in the United States. The original linear approximate almost ideal demand system (LA/AIDS) is modified by the use of a Laspeyres index and a normalization in order to compute demand elasticities identically to the AIDS model. The results of this study suggest that poultry is the most price elastic while cereals are the least price elastic. Fresh fruits and fresh vegetables are more price elastic than processed fruits and processed vegetables. Increasing income would induce the increases in the consumption of fresh vegetables and fruits more than that of cereals and bakery products, while increasing health risk concerns would induce the decreases in the consumption of bakery products and poultry but the increases in the consumption of fresh vegetables and cereals. The demographic variables exhibit certain effects on the demand for some healthy food groups and seasonal fluctuations statistically exist in the consumption of all food groups under study.AIDS model, elasticity, healthy food, household demand, United States, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,

    Enhancement of Multimodal Traffic Safety in High-Quality Transit Areas

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    Numerous extant studies are dedicated to enhancing the safety of active transportation modes, but very few studies are devoted to safety analysis surrounding transit stations, which serve as an important modal interface for pedestrians and bicyclists. This study bridges the gap by developing joint models based on the multivariate conditionally autoregressive (MCAR) priors with a distance-oriented neighboring weight matrix. For this purpose, transit-station-centered data in Los Angeles County were used for model development. Feature selection relying on both random forest and correlation analyses was employed, which leads to different covariate inputs to each of the two jointed models, resulting in increased model flexibility. Utilizing an Integrated Nested Laplace Approximation (INLA) algorithm and various evaluation criteria, the results demonstrate that models with a correlation effect between pedestrians and bicyclists perform much better than the models without such an effect. The joint models also aid in identifying significant covariates contributing to the safety of each of the two active transportation modes. The research results can furnish transportation professionals with additional insights to create safer access to transit and thus promote active transportation

    Thermal performance analysis of a solar energy storage unit encapsulated with HITEC salt/copper foam/nanoparticles composite

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    HITEC salt (40 wt. % NaNO2, 7 wt. % NaNO3, 53 wt. % KNO3) with a melting temperature of about 142 °C is a typical phase change material (PCM) for solar energy storage. Both aluminum oxide (Al2O3) nanopowder and metal foam were used to enhance pure HITEC salt, so as to retrieve the limitation of composite PCMs with single enhancement. The morphologies and thermo-physical properties of the composites were firstly characterized with Scanning Electron Microscope, Fourier-transform Infrared spectroscopy and Differential Scanning Calorimeter, respectively. A pilot test rig with a heater of 380 W located in the inner pipe was built, which was encapsulated with HITEC salt, nano-salt (HITEC salt seeded with 2 wt. % Al2O3 nanopowder) and salt/copper foam composite seeded with 2 wt. % Al2O3 nanopowder as storage media. Then heat storage and retrieval tests of the energy storage system were conducted both for pure HITEC salt and composite PCMs at various heating temperatures. The temperature evolutions and distributions of the PCMs at different locations were measured, including radial, angular, and axial locations, and the energy and volumetric mean powers during heat storage/retrieval processes were calculated subsequently. The results show that metal foam is generally compatible with the nano-salt. The maximum deviation of the melting/freezing phase change temperatures of the nano-salt/copper foam composite is 3.54 °C, whereas that of the nano-salt/nickel foam composite is 3.80 °C. The specific heats of the nano-salt are apparently enhanced with the addition of Al2O3 nanopowder both in solid and liquid states. The system encapsulated with the nano-salt/copper foam composite can be considerably enhanced, e.g. the time-duration of heat storage process at the heating temperature of 160 °C can be reduced by about 58.5%, compared to that of pure salt. The volumetric mean power of heat storage for the nano-salt/copper foam composite at the heating temperature of 180 °C increases to 109.32 kW/m3, compared with 53.01 kW/m3 of pure HITEC salt. The information will be helpful for solar system design, construction and application using molten salt for solar energy storage

    Recursive Importance Sketching for Rank Constrained Least Squares: Algorithms and High-order Convergence

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    In this paper, we propose a new {\it \underline{R}ecursive} {\it \underline{I}mportance} {\it \underline{S}ketching} algorithm for {\it \underline{R}ank} constrained least squares {\it \underline{O}ptimization} (RISRO). As its name suggests, the algorithm is based on a new sketching framework, recursive importance sketching. Several existing algorithms in the literature can be reinterpreted under the new sketching framework and RISRO offers clear advantages over them. RISRO is easy to implement and computationally efficient, where the core procedure in each iteration is only solving a dimension reduced least squares problem. Different from numerous existing algorithms with locally geometric convergence rate, we establish the local quadratic-linear and quadratic rate of convergence for RISRO under some mild conditions. In addition, we discover a deep connection of RISRO to Riemannian manifold optimization on fixed rank matrices. The effectiveness of RISRO is demonstrated in two applications in machine learning and statistics: low-rank matrix trace regression and phase retrieval. Simulation studies demonstrate the superior numerical performance of RISRO

    Plant C, N, P Stoichiometry Was Effected with Nitrogen Deposition on the Loess Plateau, China

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    The mass ratio of C:N:P (Carbon: Nitrogen: Phosphorus) in plant tissue can reflect the utilization efficiency of these basic elements (Piao et al. 2005). Additionally, the N:P ratio in plant tissue can be used to detect nutrient limita-tions as N, P or both are most often the driving force for ecosystem development and change (Koerselman and Meuleman 1996). N deposition has been increasing dramatically and it has great influence on the productivity, stability and nutrient supply conditions in the terrestrial and aquatic ecosystem in recent years (Wang and Yu 2008). Many scholars have focused on the C:N:P stoichiometry of individual plant or the whole plant communities which were based on weighted average of important key species and their element contents, rather than by collecting bio-mass samples of all the plants in the community level. Moreover, less is known of the effects of N deposition on C:N:P stoichiometry characteristics of plant communities, especially the grasslands of the Loess Plateau. An experiment was set to study the effects of N deposition on C, N,P stoichiometry characteristics by simulating N deposition by way of N addition

    Results of a cluster randomized controlled trial to promote the use of respiratory protective equipment among migrant workers exposed to organic solvents in small and medium-sized enterprises

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    Background: Existing evidence shows an urgent need to improve respiratory protective equipment (RPE) use, and more so among migrant workers in small and medium-sized enterprises (SMEs). The study aimed to assess the effectiveness of a behavioral intervention in promoting the appropriate use of RPE among internal migrant workers (IMWs) exposed to organic solvents in SMEs. Methods: A cluster randomized controlled trial was conducted among 1211 IMWs from 60 SMEs in Baiyun district in Guangzhou, China. SMEs were deemed eligible if organic solvents were constantly used in the production process and provided workers with RPE. There were 60 SMEs randomized to three interventions on a 1:1:1 ratio, namely a top-down intervention (TDI), a comprehensive intervention, and a control group which did not receive any intervention. IMWs in the comprehensive intervention received a module encompassing three intervention activities: An occupational health education and training component (lectures and leaflets/posters), an mHealth component in the form of messages illustrative pictures and short videos, and a peer education component. The TDI incorporated two intervention activities, namely the mHealth and occupational health education and training components. The primary outcome was the self-reported appropriate RPE use among IMWs, defined as using an appropriate RPE against organic solvents at all times during the last week before measurement. Secondary outcomes included IMWs’ occupational health knowledge, attitude towards RPE use, and participation in occupational health check-ups. Data were collected and assessed at baseline, and three and six months of the intervention. Generalized linear mixed models were performed to evaluate the effectiveness of the trial. Results: Between 3 August 2015 and 29 January 2016, 20 SMEs with 368 IMWs, 20 SMEs with 390 IMWs, and 20 SMEs with 453 IMWs were assigned to the comprehensive intervention, the TDI, and the control group, respectively. At three months, there were no significant differences in the primary and secondary outcomes among the three groups. At six months, IMWs in both intervention groups were more likely to appropriately use RPE than the control group (comprehensive intervention: Adjusted odds ratio: 2.99, 95% CI: 1.75–5.10, p < 0.001; TDI: 1.91, 95% CI: 1.17–3.11, and p = 0.009). Additionally, compared with the control group, the comprehensive intervention also improved all three secondary outcomes. Conclusions: Both comprehensive and top-down interventions were effective in promoting the appropriate use of RPE among IMWs in SMEs. The comprehensive intervention also enhanced IMWs’ occupational health knowledge, attitude, and practice. Trial registration: ChiCTR-IOR-15006929. Registered on 15 August 2015.The study was funded by National Science Foundation of China (81402767), the Medical Science and Technology Research Fund of Guangdong Province (WSTJJ20140116510124198504200421), China Medical Board (13-175) and Sun Yat-sen University (15ykpy08). The sponsors are not involved in study design; in the collection, analysis, and interpretation of data; in the writing of the report and in the decision to submit the paper for publication.https://doi.org/10.3390/ijerph1617318716pubpub1
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