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排序方式: 共有183条查询结果,搜索用时 15 毫秒
41.
Báez A Padilla H García R Torres Mdel C Rosas I Belmont R 《The Science of the total environment》2003,302(1-3):211-226
Carbonyl compounds in air were measured at two houses, three museums, and two offices. All sites lacked air-conditioning systems. Although indoor and outdoor air was measured simultaneously at each site, the sites themselves were sampled in different dates. Mean concentrations were higher in indoor air. Outdoor means concentrations of acetone were the highest in all sites, ranging from 12 to 60 microg m(-3). In general, formaldehyde and acetaldehyde had similar mean concentrations, ranging from 4 to 32 and 6 to 28 microg m(-3), respectively. Formaldehyde and acetone mean indoor concentrations were the highest, ranging from 11 to 97 and 17 to 89 microg m(-3), respectively, followed by acetaldehyde with 5 to 47 microg m(-3). Formaldehyde and acetaldehyde had the highest mean concentration in the offices where there were smokers. Propionaldehyde and butyraldehyde concentrations did not show definite differences between indoor and outdoor air. In general, the highest outdoor and indoor hourly concentrations were observed from 10:00 to 15:00 h. Mean indoor/outdoor ratios of carbonyls exceeded 1. Formaldehyde and acetaldehyde risks were higher in smoking environments. 相似文献
42.
Escobar-Rodríguez Tomás Bonsón-Fernández Rocío 《Information Systems and E-Business Management》2017,15(3):599-622
Information Systems and e-Business Management - The importance of e-commerce continues to grow in retail, providing companies with a tool to improve commercial and marketing strategies. In this... 相似文献
43.
Omar Francisco Montes Rocío Saldaña Garcés Felipe A. Reyes Reyes Patricia del Carmen Zambrano Robledo Francisco H. Estupiñán López Facundo Almeraya Calderón 《Welding International》2018,32(10):651-659
ABSTRACTAPI X70 steels are used for manufacturing and constructing pipes for transporting hydrocarbons; however, they deteriorate over time due to the environment to which they are exposed; influencing the rate and type of corrosion on the surfaces of the base metal (BM), heat-affected zone (HAZ) and fusion zone (FZ). In order to find out and evaluate the susceptibility to corrosion in joints made from API X70 steel subjected to different corrosive media, various tests were carried out using the process of double submerged arc welding, which were immersed in different electrolytes: sodium chloride (3.5% NaCl) and water (H2O) at ambient temperature in order to find out about behaviour. Electrochemical noise techniques and cyclic polarization curves were used to obtain the rate and type of corrosion produced in each of the analysed samples, including the three zones: BM, HAZ and FZ. In addition, characterization techniques such as optical microscopy and scanning electron microscopy were used for surface analysis. Most welds show mixed corrosion, with higher corrosion rates in 3.5% NaCl. 相似文献
44.
Ganem-Quintanar A Silva-Alvarez M Alvarez-Román R Casas-Alancaster N Cázares-Delgadillo J Quintanar-Guerrero D 《Journal of nanoscience and nanotechnology》2006,6(9-10):3235-3241
Naproxen-loaded nanoparticles were used to prepare, in a one-step process, unilaminar films of Eudragit E-100 (EE-100), avoiding the use of organic solvents and assuring the homogeneity and molecular dispersion of the drug. Nanoparticle films (NP-F) and conventional films (CV-F, prepared by casting of methanolic solutions onto a Teflon disc) were assayed by their mechanical properties, skin adhesivity, and calorimetric studies to compare their behavior. Different proportions of plasticizer (triacetin) were included to evaluate the quality of the films. Film characterization included in vitro drug release studies through a cellulose membrane using Franz-type cells, and in vivo stratum corneum penetration experiments by the tape stripping technique. The results showed that NP-F were semi-transparent to transparent, suggesting a good compatibility between naproxen and EE-100. Differential calorimetric studies (DSC) confirmed a molecular dispersion of naproxen in the EE-100 matrix. Taking into account the mechanical properties of the films, a 20% triacetin concentration can be considered as optimal for both types of films. The in vitro release data obtained from both systems (NP-F and CV-F) followed the Higuchi's model for matrix systems, with the Fickian diffusion (t(0.5)) being the main release mechanism. Concerning the in vivo penetration studies, no statistical differences were found for the penetrated amount of naproxen across the stratum corneum and the depth of penetration for the two films and between the three contact times (2, 4, and 6 h). The films formulated from nanoparticle dispersions (NP-F) were shown to be effective for the transdermal administration of naproxen, and can be considered as an interesting alternative for the preparation of films with several technological advantages. 相似文献
45.
Rocío Fernández‐Vázquez Carla M. Stinco Dolores Hernanz Francisco J. Heredia Isabel M. Vicario 《International Journal of Food Science & Technology》2013,48(9):1861-1867
This study was aimed to analyse the impact of the debittering process (DP) in the overall sensory properties of orange juice (OJ) (Citrus sinensis L. Var. Salustiana). The fresh industrial squeezed orange juice (FOJ) and the corresponding OJ after the DP (DOJ) were taken. No significant differences were found in acidity, pH and total soluble solids. Colour was evaluated by image analysis (DigiEye System). Hue and lightness were lower (more reddish and darker) after debittering (P < 0.001). Odour profile (limonene, α‐pinene, ethyl butanoate, octanal, linalool, citral and terpineol) decreased significantly (from 16% to 61% on average) as well as total phenolic compounds measured by Folin–Ciocalteu (P < 0.05). The influence of the debittering on the perceived colour, smell and taste was evaluated by paired comparison tests. The naïve panellists found significant differences not only in taste but also in colour and aroma between FOJ and DOJ; however, preference was not clear. 相似文献
46.
Morillo E Maqueda C Reinoso R Undabeytia T 《Environmental science & technology》2002,36(20):4319-4325
The influence of two organic amendments on norflurazon sorption-desorption processes in four soils with very different physicochemical characteristics was studied in laboratory experiments to evaluate the potential leaching of this pesticide through organic fertilized soils. Sorption-desorption experiments were performed on original soils and on a mixture of these soils with urban waste compost (SUW) and a commercial amendment from olive-mill wastes (OW), at a rate of 6.25% (w/w). These mixtures were used immediately after preparation and after aging for 2 months. Norflurazon was analyzed by using a HPLC method. Norflurazon retention in original soils was related not only to the organic matter (OM) content but also to mineral surfaces present in soils. Norflurazon sorption increases largely after amendment in soils with low OM content, but the addition of exogenous OM to soils with medium OM content and/or other available adsorptive surfaces did not significantly affect norflurazon sorption. Even in some cases pesticide sorption decreases, due to the blocking of the mineral and organic soil surfaces with the amendment added. Transformation of exogenous OM during incubation depends both on the amendment added and on the type of soil and can affect sorption-desorption behavior of the soils surfaces in different manner, due to the modification of their hydrophobic-hydrophilic characteristics. Norflurazon desorption from original soils showed hysteresis in all cases, but it was not affected or even decreased in amended soils. It was a nonexpected behavior, especially in sandy soil, since it is generally assumed that a higher sorption always implies a lower mobility in soils. Norflurazon sorption must be taking place on very low affinity sites on exogenous OM through weak bindings, from which the pesticide can be easily desorbed. The application to soils of the organic amendments used in the present study could not be accepted to reduce norflurazon losses due to leaching processes. 相似文献
47.
This paper reviews methodological approaches to the design (or redesign) of the supply chain (SC), including comprehensive approaches (proposals concerning the entire process of designing the SC) and those that deal with four specific aspects of the process (definition of the SC objectives, reverse SC, finance, and generation and use of scenarios) that have a decisive influence on the whole design of the SC. The comprehensive approaches include those based on typologies of products, markets and SCs and those that propose a succession of the stages to follow through the design process. The discussion shows that the use of typologies is not adequate to face SC design and that the methods proposing a succession of stages may suit, provided that they are developed and presented in a manner appropriate to their use for practitioners. The discussion leads also to suggest several research lines. 相似文献
48.
Kavitha Rani Balmuri Srinivasa Rao Madala Parameshachari Bidare Divakarachari Rocío Pérez de Prado Jaroslav Frnda 《Asian journal of control》2023,25(4):3015-3028
In Brain Computer Interface (BCI), achieving a reliable motor-imagery classification is a challenging task. The set of discriminative and relevant feature vectors plays a crucial role in classification. In this article, an enhanced optimization technique is implemented for selecting active feature vectors to enhance motor-imagery classification using Electroencephalography (EEG) signals. After collecting the input EEG signals from BCI competition III-4a and IV-2a databases, the 6th-order butter-worth filter is employed for eliminating base-line wander noise from the raw EEG signals. Further, the Variational Mode Decomposition technique is applied for separating the important signal components from the composite EEG signals, and then, the Higher Order Statistic, kurtosis, skewness, standard deviation, and entropy are utilized for feature extraction. The high-dimensional feature values are given to the Enhanced Grasshopper Optimization Algorithm for optimum feature selection, which are given to the Extreme Learning Machines (ELM) classifier for motor-imagery classification. Finally, in the resulting section, the optimized ELM model achieved 99.48% and 99.12% of accuracy on the BCI competition III-4a and IV-2a databases, where the achieved results are maximum compared to the traditional deep learning models. 相似文献
49.
Retrieval of leaf chlorophyll content in field crops using narrow-band indices: effects of leaf area index and leaf mean tilt angle 总被引:1,自引:0,他引:1
Xiaochen Zou Rocío Hernández-Clemente Priit Tammeorg Clara Lizarazo Torres Frederick L. Stoddard Pirjo Mäkelä 《International journal of remote sensing》2013,34(24):6031-6055
Reliable estimation of leaf chlorophyll-a and -b content (chl-a + b) at canopy scales is essential for monitoring vegetation productivity, physiological stress, and nutrient availability. To achieve this, narrow-band vegetation indices (VIs) derived from imaging spectroscopy data are commonly used. However, VIs are affected by canopy structures other than chl-a + b, such as leaf area index (LAI) and leaf mean tilt angle (MTA). In this study, we evaluated the performance of 58 VIs reported in the literature to be chl-a + b-sensitive against a unique measured set of species-specific leaf angles for six crop species in southern Finland. We created a large simulated canopy reflectance database (100,000 canopy configurations) using the physically based PROSAIL (coupling of PROSPECT and SAIL (Scattering by Arbitrarily Inclined Leaves) radiative transfer models) model. The performance of model-simulated indices was compared against airborne AISA Eagle II imaging spectroradiometer data and field-measured chl-a + b, LAI, and MTA values. In general, LAI had a positive effect on the strength of the correlation between chl-a + b and VIs while MTA had a negative effect in both measured and simulated data. Three indices (REIP (red edge inflection point), TCARI (transformed chlorophyll absorption ratio index)/OSAVI (optimized soil-adjusted vegetation index), and CTR6 (Carter indices)) showed strong correlations with chl-a + b and similar performance in model-simulated and measured data set. However, only two (TCARI/OSAVI and CTR6) were independent from LAI and MTA. We consider these two indices robust proxies of crop leaf chl-a + b. 相似文献
50.