International survey of Cronobacter sakazakii and other Cronobacter spp. in follow up formulas and infant food

A coordinated survey for Cronobacter and related organisms in powdered infant formula, follow up formula and infant foods was undertaken by 8 laboratories in 7 countries in recognition of and in response to the data needs identified in an FAO/WHO call for data in order to develop global risk management guidance for these products. The products (domestic and imported) were purchased from the local market and were categorised according to their principle ingredients. A total of 290 products were analysed using a standardised procedure of pre-enrichment in 225 ml Buffered Peptone Water (BPW), followed by enrichment in Enterobacteriaceae Enrichment (EE) broth, plating on the chromogenic Cronobacter Druggan–Forsythe–Iversen (DFI) agar and presumptive identification with ID 32 E. Presumptive Cronobacter isolates were identified using 16S rRNA gene sequence analysis. Aerobic plate counts (APC) of the products were also determined on nutrient agar. Fourteen samples had APC > 105 cfu/g, 3 of which contained probiotic cultures. C. sakazakii was isolated from 27 products; 3/91 (3%) follow up formulas (as defined by Codex Alimentarius Commission), and 24/199 (12%) infant foods and drinks. Hence C. sakazakii was less prevalent in follow up formula than other foods given to infants over the same age range. A range of other bacteria were also isolated from follow up formulas, including Acinetobacter baumannii, Enterobacter cloacae, Klebsiella pneumoniae, Citrobacter freundii, and Serratia ficaria. There was significant variation in the reconstitution instructions for follow up formulas. These included using water at temperatures which would enable bacterial growth. Additionally, the definition of follow up formula varied between countries

Avatar design types and user engagement in digital educational games during evaluation phase

Avatar design types can range from human representations to abstract representations. In digital educational games (DEGs), avatars are frequently used to encourage users to play the game. However, the role of avatar design types and their engagement in digital games are still unclear and empirically under research. Therefore, a bespoke digital educational game in geography was developed and validated by six expert users. Then forty-five users participated in the evaluation phase to investigate engagement and avatar types on digital educational games using the user engagement scale (UES). The results reported aesthetics and satisfaction factors somehow influenced the avatar design types, but none of the UES subscales was influenced by preferred avatar design types. Moreover, the human-cartoon avatar, which was not entirely human and cartoonish, was the most popular avatar design type among young adults. Other issues discussed for future developers and research included incorporating more avatar design selections into the study, integrating social interaction features into the game, using the same drawing style for avatars and provide easy access to the bespoke game during data collection

The effect of model updating of crash box structures with trigger mechanisms towards the crashworthiness output of the structures

This paper would focus on the structure of aluminium alloy spot welded crash box with the trigger mechanism as the structure are widely studied for its crashworthiness as well as the location of the structure itself at the car chassis which are subjected to dynamic loading of the car. Aluminium alloy is broadly used in the car body-in-white due to the properties of sufficient strength, better formability, light weight as well as good crashworthiness properties while welded joints are also extensively used as a joining of car components. As this study use both approach of finite element and experimental, in order to validate the finite element analysis (FEA) data, it would be correlated with the experimental approach and further optimization of the finite element (FE) modelling would be made to reduce the discrepancies of data. In this study, the model updating method which update the most sensitive modal parameters would be used towards the crashworthiness analysis to observe for any significant difference with the initial crashworthiness analysis. Finite element modal analysis would be done for the crash box structure and the data would then be correlated with experiment modal analysis (EMA). The same finite element modelling would also be used for the finite element crashworthiness analysis. For modal analysis of both approach, model updating was done to reduce the discrepancies and the sensitive modal parameters were identified and it were used in the new crashworthiness analysis. From the study, it could be observed that the crashworthiness output of the crash box structure with the updated model were different from the initial crashworthiness output in term of its total energy absorbed

Structural model updating of bolted joints in dissimilar material structure

This paper focusing on the joint modelling techniques of Finite Element (FE) to model a light dissimilar structure with bolted joints made up of bolts and nuts. The usage of a model update strategy is employed to improve the FE model's dynamic behaviour. In the FE model, a joint strategy is constructed using three different types of element connectors: CBAR, CBEAM, and CFAST. The modal parameters of a bolted joint structure made of dissimilar materials AZ31B and AA6061 were determined using Finite Element Analysis (FEA) and Experimental Modal Analysis (EMA) in this research (natural frequencies, damping ratio, and mode shapes). The number of elements, number of nodes, and total percentage errors of respectively initial FE model, when compared to EMA results, were evaluated. In comparison to the others, the CBAR element was chosen to represent a fastener joint for the updating process due to its accurate prediction of mode shapes and inclusion of updating parameters. Sensitivity analysis is performed before the updating process to choose the most sensitive parameter for updating purposes. In the FE model updating procedure, MSC Nastran's optimization technique is applied. Therefore, the discrepancies between FEA and EMA have been decreased. When compared to the measured equivalent, the percentage of error for the modified CBAR model drops from 4.37 percent to 2.71 percent. As a result, it is discovered that updating the FE model is a systemic and efficient technique in conducting the appropriate FE model in recreating the genuine structure

Strategies of finite element modeling for spot welded joints and its modal correlation with experimental data

In building many complex engineering structures, there are many types of joining methods such as welding and fasteners that can be implemented. Modeling for joints in finite elements can be challenging as it sometimes has limiting factors that cause the prediction of the dynamic behaviour of the actual joints to be less accurate. This study aims to demonstrated several approaches of finite element modeling for spot-welded joints ad to analyse its accuracy through the correlation of modal data from experimental modal analysis. These modeling approaches are created by creating and manipulating the elements at the associated location of the spot weld joint on a top-hat beam structure. Four different approaches of spot weld modeling that uses the modeling strategies performed in other studies were created. The spot weld models are validated by comparing the modal properties of the tested structure which are obtained through finite element analysis and experiments. Model updating was performed on all models in order to observe the ability of model improvement in those different modelling approaches. The findings show that the model that uses solid elements has the lowest error compared to the model that uses beam elements. The model that uses multiple-beam elements shows the ability to be improved the most. The model that uses the simplest modeling approach using a single beam has the highest error and shows the lowest improvement after model updating. It was found that solid element is more suitable to model spot weld and the application of solid element for spot weld joints should be investigated in more types of analyses

Variance analysis of dynamic properties for multiple top-hat section crash box structure

Vehicle design is the most significant factor in determining and decreasing the impact of accidents and improving road safety. Therefore, studies on the safety components of vehicles should be focused primarily on crash boxes. This study is focusing on the crash box structures that straightforwardly experience the vibrational phenomena. This project was conducted to determine the modal property such as natural frequencies of car crash box structure by performing the Experimental Modal Analysis (EMA) on several specimens. Impact hammer test applied and the analysis using ME’Scope VES to identify the modal properties. For this purpose, the experimental modal test setup has been established. An impact hammer test made it possible to obtain Frequency Response Function (FRF). The FRF were curve fitted in order to obtain the mode shapes and natural frequencies. The modal parameters found from both numerical analysis and experimental testing methods are compared. The modal behaviour of the crash box structure would be analysed for nine different pieces with different fabrication through same process of manufacturing applied towards the crash box structures which is the aluminium alloy 6061 that is commonly used in automotive industry. These nine-sample result will be analysed from the deviation of the result of the modal properties

Correlation of numerical and experimental analysis for dynamic behaviour of a 3 blade propeller structure

In pursuance of deciding the dependability of data gathered by testing a finite element modal in the software version, experimental data is frequently used for validation. On account of finite element analysis, it can sometimes be considered as inaccurate particularly when applied to the complex structure, for example, a propeller blade. This is because of challenges that may happen in the modelling of joints, boundary conditions, and damping of the structure. In this research, a procedure of correlation and validation of the model-based test plan with modal testing results was conducted. Modal properties (normal frequencies, mode shapes, and damping ratio) of a propeller blade structure were resolved by using both test experimental modal analysis (EMA) and finite element analysis (FEA). Correlation of both sets of data was performed for validation. It created the impression that there was a noticeable estimation of error between those two sets of data. Small discrepancies of percentage error of obtained natural frequency for FEA and EMA makes both of the methods can be applied to determine the dynamic characteristic of the propeller structure

Investigation on vibration analysis of beam structure with different types of joints

Modal analysis is widely used in order to identify the dynamic behaviour which are natural frequencies and mode shapes of a structure through the approach of experimental as well as finite element analysis. Beam which is commonly used in the industries of construction had gained the interest as the topic of research. This project intended to investigate the vibration analysis on dissimilar cantilever beam structure with different joints which will be conducted through finite element analysis (FEA). In FEA, cantilever beam structure is modelled by using dissimilar materials which is stainless steel 304 and aluminium 6061. Two types of element connector which are bar element (CBAR) and beam element (CBEAM) are modelled in FEA and applied to replicate real connections (welded joint and riveted joint). Besides, several element sizes are computed for mesh convergence analysis and the presence of crack is modelled and analyzed. Finite element modal analysis is simulated to determine modal properties. Natural frequencies of element connectors and real connections are compared to the equivalent rigid body method. From the FEA, it is found that the discrepancies of errors that occurred between CBAR with theoretical welded joint and CBEAM with theoretical riveted joint have proved that such joint element strategy best in representing real connectors. Thus, CBAR and CBEAM are compatible to resemble the real connection in the beam structure. The best element size is observed as well as the comparison between uncrack and crack beam structure is carried out