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排序方式: 共有381条查询结果,搜索用时 15 毫秒
1.
Juhee Lee Sarah A. Willett Casimir C. Akoh Silvana Martini 《Journal of the American Oil Chemists' Society》2022,99(2):141-151
The purpose of this research was to determine the effect of high-intensity ultrasound (HIU) on physical properties, degree of oxidation, and oxidative stability of structured lipids (SLs). Caprylic acid (C) and stearic acid (S) were incorporated into menhaden oil using Lipozyme® 435 lipase to obtain five samples: (1) LC 20 (menhaden oil with 20% of C), (2) LC 30 (menhaden oil with 30% C), (3) LS 20 (menhaden oil with 20% S), (4) LS 30 (menhaden oil with 30% S), and (5) Blend C (menhaden oil with 16.24% C and 13.04% S). Samples were crystallized for 90 min at the following temperatures: (1) LC 20 at 15.5°C, (2) LC 30 at 17.5°C, (3) LS 20 at 24°C, (4) LS 30 at 30°C, and (5) Blend C at 18.0°C, and HIU was applied at the onset of crystallization. Physical properties, degree of oxidation, and oxidative stability were evaluated in sonicated and nonsonicated samples. All SLs had statistically higher G′ after sonication. Sonicated LS 30, LC 30, and Blend C had a higher melting enthalpy than the nonsonicated ones, while enthalpy values in sonicated LS 20 and LC 20 samples were not statistically different than the nonsonicated ones. No significant difference between sonicated and nonsonicated samples was observed in peroxide values (1.2 ± 0.1 meq/kg, p > 0.05) and in the oxidative stability index (6.3 ± 0.2 h, p > 0.05). These results showed that HIU was effective at changing physical properties without affecting the oxidation of the samples. 相似文献
2.
Emilio Marengo Valentina Longo Elisa Robotti Marco Bobba Fabio Gosetti Orfeo Zerbinati Silvana Di Martino 《应用聚合物科学杂志》2008,109(6):3975-3982
Principal component regression (PCR), partial least squares (PLS), StepWise ordinary least squares regression (OLS), and back‐propagation artificial neural network (BP‐ANN) are applied here for the determination of the propylene concentration of a set of 83 production samples of ethylene–propylene copolymers from their infrared spectra. The set of available samples was split into (a) a training set, for models calculation; (b) a test set, for selecting the correct number of latent variables in PCR and PLS and the end point of the training phase of BP‐ANN; (c) a production set, for evaluating the predictive ability of the models. The predictive ability of the models is thus evaluated by genuine predictions. The model obtained by StepWise OLS turned out to be the best one, both in fitting and prediction. The study of the breakdown number of samples to be included in the training set showed that at least 52 experiments are necessary to build a reliable and predictive calibration model. It can be concluded that FTIR spectroscopy and OLS can be properly employed for monitoring the synthesis or the final product of ethylene–propylene copolymers, by predicting the concentration of propylene directly along the process line. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
3.
M. Penco M. A. Pastorino E. Occhiello F. Garbassi R. Braglia G. Giannotta 《应用聚合物科学杂志》1995,57(3):329-334
Rubbers of different kind were tested as toughening agents of poly(ethylene terephthalate) (PET), noting significant morphological and mechanical differences. In particular, good results were obtained by using an ethylene–ethyl acrylate–glycidyl methacrylate copolymer. The resulting blend evidenced good particle distribution, and the latter was related to chemical interactions between the rubber epoxy groups and PET terminal groups, including the effect of low molecular weight and polymeric amine catalysts, and to extrusion conditions. © 1995 John Wiley & Sons, Inc. 相似文献
4.
Binary and m-ary encoding in applications of tree-based genetic algorithms for QoS routing 总被引:1,自引:1,他引:0
Vincenzo Maniscalco Silvana Greco Polito Antonio Intagliata 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2014,18(9):1705-1714
Ubiquitous and Pervasive Computing (UPC) applications often have Quality of Service (QoS) requirements. These become constraints for the UPC network infrastructure. In this paper, we refer to Mobile ad Hoc Networks, one of the most important technologies supporting UPC, and investigate on Genetic Algorithms (GAs) for QoS routing. GAs are part of the soft computing paradigm and can solve the NP search of QoS routes with multiple constraints. We elaborate on tree-based GAs, which represent the set of paths from source to destination as a tree and encode them through the crossed junctions. While their most well-known applications use m-ary encoding representing single paths in the chromosomes, in this paper we discuss a binary encoding with the objective of improving the convergence speed. The binary encoding represents classes of paths in the chromosomes and allows local search on classes of paths. These classes are both collectively exhaustive and mutually exclusive. Simulation results compare convergence speed and scalability of GA applications with binary and m-ary encoding in networks with an increasing number of nodes and links per node. As the per-class processing is reason of additional computational cost, an hybrid GA application that uses both binary and m-ary encoding is introduced. 相似文献
5.
Silvana?Martini Constantin?Bertoli Maria?Lidia?Herrera Ian?Neeson Alejandro?MarangoniEmail author 《Journal of the American Oil Chemists' Society》2005,82(5):305-312
An ultrasonic technique was developed to study the crystallization process of edible fats on-line. A chirp wave was used instead
of the conventional pulser signal, thus achieving a higher signal-to-noise ratio. This enabled measurements to be made in
concentrated systems [≈20% solid fat content (SFC)] through a 8.11-cm thick sample without significant signal loss. Fat samples
were crystallized at 20, 25, and 30°C at a constant agitation rate of 400 rpm for 90 min. The crystallization process was
followed by ultrasonic spectroscopy and a low-resolution pulsed nuclear magnetic resonance spectrometer. Specific relationships
were found between ultrasonic parameters [integrated response, time of flight (TF), and full width half maximum] and SFC.
TF, which is an indirect measurement of the ultrasonic velocity (v), was highly correlated to SFC (r
2>0.9) in a linear fashion (v=2.601 SFC+1433.0). 相似文献
6.
A Dagianti A Varveri L Sgorbini M Penco F Fedele 《Canadian Metallurgical Quarterly》1998,43(7):711-715
To date, the "warm-up" phenomenon in patients has been evaluated by ECG and symptom analysis. We investigated the warm-up phenomenon with supine bicycle stress echocardiography in patients with coronary artery disease documented by angiography and positive stress echocardiography. Sixteen coronary artery disease patients (54 +/- 9 years), who were off treatment throughout the study, were enrolled. Each of them underwent two consecutive exercise tests (25 W/2 min) with a 10-min recovery to reestablish baseline conditions. At the end of each stage of exercise and at peak exercise, when wall motion abnormalities (WMA), 1 mm ST depression and angina occurred, and at each minute, for the first 6 min of recovery, a 12-lead ECG was recorded and rate-pressure product was calculated. Time of onset and duration of 1 mm ST depression, WMA and angina, were also determined. Peak WMA, peak wall motion score index, duration of exercise and severity of angina were also evaluated. Exercise time duration and peak rate-pressure product were greater during the second than the first test (p = 0.02, p = 0.03 respectively); the second test also showed a longer delay of the onset of 1 mm ST depression and WMA (p = 0.01, p = 0.01 respectively) and higher rate--pressure product values (p = 0.04, p = 0.03 respectively). On the contrary, wall motion score index during the first and the second test was similar. Time to angina onset was longer during the second test (p = 0.03); the recovery period of ST depression and WMA was shorter during the second test (p = 0.02). In conclusion, these preliminary data show that patients tolerated the second period of ischemia better than the first, consistent with the presence of the warm-up phenomenon. However, the similarity of values of wall motion score index and WMA did not support a reduction in the ischemic area during the second test. This is in contrast with a possible modification of myocardial metabolism which typically underlies the ischemic preconditioning. 相似文献
7.
The execution of workflow processes requires authorizations for enforcing the assignment of tasks to agents, either human or automated, according to the security policy of the organization. This paper presents a workflow authorization framework based on roles and organizational levels, and on authorization constraints. To facilitate the assignment of tasks to agents, roles and organizational levels are organized into hierarchies. Authorization constraints are introduced to specify instance-dependent, time-dependent, and history-dependent authorizations. Authorization constraints are specified in terms of active rules, used also for authorization management. The Workflow Management System determines authorized agents on the basis of the contents of an authorization base maintained through the active rules defined in the system. 相似文献
8.
In this paper we generalize Rudeanu’s results from [13] to Post algebras. We give a necessary and sufficient condition for the existence of a Post function f such that the set of solutions of equation f(x) = 0 is a given interval. We also prove that every Post transformation is the parametric solution of some consistent Post equation. 相似文献
9.
Joao Sarraipa Catarina Marques-Lucena Silvia Baldiris Ramón Fabregat Silvana Aciar 《Journal of Intelligent Manufacturing》2016,27(1):83-99
Nowadays, it is commonly known that information systems need an agile capability of handling knowledge. To accomplish this, systems have to have a formal knowledge representation ability supported by specific and advanced reasoning features. This research work proposes a knowledge management approach with the purpose to gather, model and consume community knowledge for specific recommendation commitments. Such approach is accomplished by a semantic lexicon alignment between the various community knowledge assets, to facilitate collaborations establishment between people and systems in an interoperable fashion. Thus, a knowledge base supported by a thesaurus able to represent all the metadata needed to represent and characterize the various community stakeholders’ resources is proposed. The thesaurus represents the lexicon in the domain, which in the ALTER-NATIVA systems is mostly used to support the various e-Learning elements (e.g. courses) and users categorization, sustained by synchronization features to facilitate a constant update of its information. A set of services designed to recommend specific resources in relation to a determined profile of user is provided. Additionally, a discussion about how the ALTER-NATIVA knowledge management approach can be applied to industrial environments is presented. 相似文献
10.
Ultrafiltration based purification strategies for surfactin produced by Bacillus subtilis LB5A using cassava wastewater as substrate 下载免费PDF全文