A Numerical Approach to Stability of Multiclass Queueing Networks

The Multi-class Queueing Network (McQN) arises as a natural multi-class extension of the traditional (single-class) Jackson network. In a single-class network subcriticality (i.e. subunitary nominal workload at every station) entails stability, but this is no longer sufficient when jobs/customers of different classes (i.e. with different service requirements and/or routing scheme) visit the same server; therefore, analytical conditions for stability of McQNs are lacking, in general. In this note we design a numerical (simulation-based) method for determining the stability region of a McQN, in terms of arrival rate(s). Our method exploits certain (stochastic) monotonicity properties enjoyed by the associated Markovian queue-configuration process. Stochastic monotonicity is a quite common feature of queueing models and can be easily established in the single-class framework (Jackson networks); recently, also for a wide class of McQNs, including first-come-first-serve (FCFS) networks, monotonicity properties have been established. Here, we provide a minimal set of conditions under which the method performs correctly. Eventually, we illustrate the use of our numerical method by presenting a set of numerical experiments, covering both single and multi-class networks

Chemical composition and temperature influence on the rheological behaviour of honeys

The purpose of this work was to examine the viscoelastic properties of Spanish honeys with various sugar contents [fructose (32 42 g/100 g honey), glucose (24 35 g/100 g honey), sucrose (0.0 3.4 g/100 g honey)]; concentrations (79 83 ◦Brix), and moisture levels (16 19 g/100 g honey) at different temperatures (5, 10, 15, 20, 25, 30, and 40◦C). Honey showed Newtonian behaviour, presenting a highly viscous part (loss modulus was much greater than the elastic modulus). The loss modulus (G ) and viscosity increased with moisture content and a decrease with temperature. Exponential and power law models were applied to fit loss modulus and viscosity data. Polynomial models were proposed to describe the combined effect of temperature, fructose, glucose, sucrose content, other sugars, non-sugar substance, and moisture content.Oroian, MA.; Amariei, S.; Escriche Roberto, MI.; Leahu, A.; Damian, C.; Gutt, G. (2014). Chemical composition and temperature influence on the rheological behaviour of honeys. International Journal of Food Properties. 17(10):2228-2240. doi:10.1080/10942912.2013.791835S222822401710Kaya, A., Ko, S., & Gunasekaran, S. (2008). Viscosity and Color Change During In Situ Solidification of Grape Pekmez. Food and Bioprocess Technology, 4(2), 241-246. doi:10.1007/s11947-008-0169-4Bhandari, B., D’Arcy, B., & Chow, S. (1999). Rheology of selected Australian honeys. Journal of Food Engineering, 41(1), 65-68. doi:10.1016/s0260-8774(99)00078-3CHEN, Y.-W., LIN, C.-H., WU, F.-Y., & CHEN, H.-H. (2009). RHEOLOGICAL PROPERTIES OF CRYSTALLIZED HONEY PREPARED BY A NEW TYPE OF NUCLEI. Journal of Food Process Engineering, 32(4), 512-527. doi:10.1111/j.1745-4530.2007.00227.xYanniotis, S., Skaltsi, S., & Karaburnioti, S. (2006). Effect of moisture content on the viscosity of honey at different temperatures. Journal of Food Engineering, 72(4), 372-377. doi:10.1016/j.jfoodeng.2004.12.017Saravana Kumar, J., & Mandal, M. (2009). Rheology and thermal properties of marketed Indian honey. Nutrition & Food Science, 39(2), 111-117. doi:10.1108/00346650910943217Oroian, M., Amariei, S., Escriche, I., & Gutt, G. (2011). Rheological Aspects of Spanish Honeys. Food and Bioprocess Technology, 6(1), 228-241. doi:10.1007/s11947-011-0730-4Oroian, M. (2012). Physicochemical and Rheological Properties of Romanian Honeys. Food Biophysics, 7(4), 296-307. doi:10.1007/s11483-012-9268-xCohen, I., & Weihs, D. (2010). Rheology and microrheology of natural and reduced-calorie Israeli honeys as a model for high-viscosity Newtonian liquids. Journal of Food Engineering, 100(2), 366-371. doi:10.1016/j.jfoodeng.2010.04.023Witczak, M., Juszczak, L., & Gałkowska, D. (2011). Non-Newtonian behaviour of heather honey. Journal of Food Engineering, 104(4), 532-537. doi:10.1016/j.jfoodeng.2011.01.013Gómez-Díaz, D., Navaza, J. M., & Quintáns-Riveiro, L. C. (2005). Rheological behaviour of Galician honeys. European Food Research and Technology, 222(3-4), 439-442. doi:10.1007/s00217-005-0120-0Gómez-Díaz, D., Navaza, J. M., & Quintáns-Riveiro, L. C. (2012). Physicochemical characterization of Galician Honeys. International Journal of Food Properties, 15(2), 292-300. doi:10.1080/10942912.2010.483616Mora-Escobedo, R., Moguel-Ordóñez, Y., Jaramillo-Flores, M. E., & Gutiérrez-López, G. F. (2006). The Composition, Rheological and Thermal Properties of Tajonal (Viguiera Dentata) Mexican Honey. International Journal of Food Properties, 9(2), 299-316. doi:10.1080/10942910600596159Bhandari, B., D’Arcy, B., & Kelly, C. (1999). Rheology and crystallization kinetics of honey: Present status. International Journal of Food Properties, 2(3), 217-226. doi:10.1080/10942919909524606Mossel, B., Bhandari, B., D’Arcy, B., & Caffin, N. (2003). Determination of Viscosity of Some Australian Honeys Based on Composition. International Journal of Food Properties, 6(1), 87-97. doi:10.1081/jfp-120016626Zaitoun, S., Ghzawi, A. A.-M., Al-Malah, K. I. M., & Abu-Jdayil, B. (2001). RHEOLOGICAL PROPERTIES OF SELECTED LIGHT COLORED JORDANIAN HONEY. International Journal of Food Properties, 4(1), 139-148. doi:10.1081/jfp-100002192Yoo, B. (2004). Effect of temperature on dynamic rheology of Korean honeys. Journal of Food Engineering, 65(3), 459-463. doi:10.1016/j.jfoodeng.2004.02.006Abu-Jdayil, B., Al-Majeed Ghzawi, A., Al-Malah, K. I. ., & Zaitoun, S. (2002). Heat effect on rheology of light- and dark-colored honey. Journal of Food Engineering, 51(1), 33-38. doi:10.1016/s0260-8774(01)00034-6Mossel, B., Bhandari, B., D’Arcy, B., & Caffin, N. (2000). Use of an Arrhenius Model to Predict Rheological Behaviour in some Australian Honeys. LWT - Food Science and Technology, 33(8), 545-552. doi:10.1006/fstl.2000.0714Küçük, M., Kolaylı, S., Karaoğlu, Ş., Ulusoy, E., Baltacı, C., & Candan, F. (2007). Biological activities and chemical composition of three honeys of different types from Anatolia. Food Chemistry, 100(2), 526-534. doi:10.1016/j.foodchem.2005.10.010Giner, J., Ibarz, A., Garza, S., & Xhian-Quan, S. (1996). Rheology of clarified cherry juices. Journal of Food Engineering, 30(1-2), 147-154. doi:10.1016/s0260-8774(96)00015-5Ibarz, A., Pagán, J., & Miguelsanz, R. (1992). Rheology of clarified fruit juices. II: Blackcurrant juices. Journal of Food Engineering, 15(1), 63-73. doi:10.1016/0260-8774(92)90040-

Stratégies de promotion de la vaccination : Les effets des normes sociales sur l’intention de se faire vacciner contre le COVID-19

La pandémie de COVID-19 a eu un impact majeur sur la santé publique, l'économie et la société. Cette crise mondiale a souligné l'importance de la vaccination comme moyen de prévention et de lutte contre la propagation du virus. La vaccination est reconnue comme l'un des moyens les plus efficaces pour réduire la transmission du virus, protéger la santé publique et mettre fin à la pandémie (OMS, 2021a). La présente étude vise à explorer les facteurs influençant l'intention de se faire vacciner contre le COVID-19. L'hypothèse principale suppose que les normes sociales seraient positivement associées à l'intention de se faire vacciner, et que cette intention serait également liée aux mécanismes d’influence sociale ainsi qu’à l’efficacité perçue du vaccin. Les résultats obtenus suggèrent que les normes sociales, l'efficacité perçue ainsi que l’influence sociale informationnelle jouent un rôle important dans l'intention de se faire vacciner contre le COVID-19. </p

Monitoring of Fruit and Vegetable Waste Composting Process: Relationship between Microorganisms and Physico-Chemical Parameters

The aim of this study was to investigate and evaluate the composting potential of fruit and vegetable waste with sawdust in different combinations and to establish the relationship between microorganisms and physico-chemical parameters. Three samples were made with the C/N ratios of 50 (sample 1), 45 (sample 2), and 30 (sample 3) by adding fruit waste (apple, banana, orange, and kiwi peels) and vegetable waste (cabbage leaves, potato and carrot peels). The total amount of fruit and vegetable waste was approximately 2 kg in each sample to which different quantities of sawdust were added (1.23, 0.14, and 0.203 kg) in order to obtain the C/N ratios proposed and to limit the odor. Composting process was monitored over 70 days, while physico-chemical and microbiological analyses were performed. Results showed that in the first week pH is acidic and electrical conductivity values are high for all three samples, and then the pH values increase during the composting process, while electrical conductivity values decrease. The nitrogen content is low in all samples and will decrease during the first five weeks of the composting process, then begin to increase slightly. Cr, Cu, Ni, and Zn values in the all three compost samples are below threshold values. During the composing process the microbial communities are constantly changing. The compost was successfully obtained and meets the requirement standards for agricultural use. It can be concluded that there is statistically significant association between the microorganisms and physico-chemical indicators

Life cycle assessment of fermented milk: yogurt production

Yogurt is a fermented milk product, resulted through milk acidification by lactic acid bacteria, highly appreciated worldwide. In this study, life cycle assessment (LCA) methodology was applied for modelling of environmental impacts associated with yogurt production. The system boundaries include the following activities: milk processing, transport, solid waste and wastewater treatments. Functional unit set for this study is 1 kg of produced yogurt. The input and output data were collected from various sources like reports, databases, legislation. All these data were used further in the impact assessment stage performed with GaBi software which includes LCA methods like CML2001 - Jan. 2016, ReCiPe 1.08, UBP 2013, EDIP 2003 and others. Results showed that the global warming potential (GWP) determined for yogurt was 2.92 kg CO2 eq. per kg of yogurt, while acidification potential (AP) was approximately 0.014 kg SO2 eq. per kg of yogurt. It was observed that the main contributor to all impact categories is consumption of electricity during the yogurt production, mainly in the pasteurization, evaporation and cooling stages. 61.4% of the emissions resulted from transportation of raw materials contributes to GWP, while 38.3% to photochemical ozone creation potential (POCP). Emissions from wastewater treatment are contributing especially to the eutrophication potential (EP), while emission from solid waste landfilling are contributing mainly to POCP

STUDY ON THE ACCEPTABILITY OF YOGHURT WITH CARROT JUICE

In this paper we focus on the results of a study regarding the evaluation of the sensory characteristics and consumers’ acceptance of unsweetened yoghurt with carrot juice. The yoghurts were obtained considering three carrot juice levels (10%, 20% and 30%, respectively) and two starter cultures. Carrot yoghurt was prepared in the laboratory by adding carrot juice to milk and inoculated with a 3% yoghurt culture. The effects of the carrot juice on the sensory quality and consumers’ aceptance of the yoghurt samples were determined. The data obtained on various parameters were statistically analyzed

Rheological, Textural, and Sensorial Characterization of Walnut Butter

The rheological properties of six formulated walnut semi-solid pastes with 0.5, 1.5, and 2.0% w/w xanthan gum, maple syrup, and Jerusalem artichoke powder were characterized using the Mars 40 rheometer (Thermo Haake, Karlsruhe, Germany). The butter samples’ textural behavior and color parameters (CIE L*, a*, and b*) were analyzed. Sensory evaluation and consumer acceptance were also analyzed. Walnut kernels were roasted at an optimized temperature (120 °C) and time (30 min) and subsequently made into walnut butter (WB). Maple syrup has an appreciable influence on the rheological properties of walnut butter. The prepared butter exhibited non-Newtonian shear thinning behavior and showed excellent stability. The results showed that sample S3 (3% maple syrup and 2% xanthan gum) had a bright color with the highest L* values (47.31 ± 0.32), the lowest a* values (2.72 ± 0.04) and the highest b* values (20.54 ± 0.08). In comparison, sample S6 (5% Jerusalem artichoke powder and 2.0% xanthan gum) had a darker color, with the following mean values obtained: 44.67 ± 0.05 for L*, 6.70 ± 0.09 for a* and 18.34 ± 0.07 for b*. The addition of maple syrup even in combination with xanthan gum (2%) S3 to the walnut butter led to a decrease in the viscosity of the butter samples. The hardness and firmness of the walnut butter samples were affected by the type of sweetener used; thus, the nut butter with xanthan gum and Jerusalem artichoke powder had significantly higher hardness values than the samples with added maple syrup. Therefore, based on consumer preferences, we obtained new formulations of walnut butter with a high sensory quality, suitable for those with allergies to peanut butter

THE INFLUENCE OF INULIN AND PSYLLIUM ADDITION TO ICE-CREAM AND ITS EFFECTS ON THE SENSORIAL PROPERTIES

The objective of this research was to investigate the effect of substituting fructose by different levels of inulin (3 and 6%) and the addition of psyllium fibers (3 and 6%) on the quality attributes of lingonberry ice cream. Five formulations comprised of the control sample using fructose and the other four samples applying inulin and psyllium fibers, respectively, were examined to determine: pH, total acidity, sugar content, viscosity, water activity, color analysis, and sensory properties in order to find their optimum ratios. A positive linear correlation between psyllium fibers addition and apparent viscosity of the lingonberry ice cream was observed. Supplementation of inulin fibers revealed that lingonberry ice cream with 3 % inulin had the most appealing sensory characteristics. The results suggest that the addition of inulin and psyllium fibers as fiber-enriching agents can be used in the ice cream industry in order to fortify the diet

Plant-Based Milks: Alternatives to the Manufacture and Characterization of Ice Cream

This study investigated the potential use of dietary fibers (psyllium and pectin fibers added in different proportions of 0–10%) to improve the rheological, textural, and sensory characteristics of vegetable ice cream using vegetable milk (almond and hemp milk). Hemp milk was obtained from the peeled seeds of the industrial hemp plant, which includes varieties of Cannabis sativa, which have a low content of the psychotropic substance tetrahydrocannabinol (THC) and are grown for food. The rheological characteristics of the mix and ice cream were determined by using the Haake Mars rheometer. Compared with the control sample, the viscosities of the mix in all samples analyzed were enhanced with the addition of dietary fibers, due to the occurrence of interactions and stabilizations. The viscoelastic modules G′ G″ were determined on ice cream samples at a temperature of −10 °C. The elastic and viscous modulus showed high values with the increase of the addition of 6% dietary fibers. The textural characteristics were assessed by the shear strength of a layer of ice cream at a temperature of −4 °C. Hardness, firmness, and adhesiveness were influenced by the size of their ice crystals, the fat content, and the percentage of dietary fibers added. The sensory analysis of the ice cream showed higher overall scores for the almond milk ice cream, because the sweet taste was appreciated with a maximum score, while the hemp milk ice cream was evaluated for flavor and taste