Changes In Process Conditions Research Articles

Enhanced Foamability with Shrinking Microfibers in Linear Polymer.

Strain hardening has important roles in understanding material structures and polymer processing methods, such as foaming, film forming, and fiber extruding. A common method to improve strain hardening behavior is to chemically branch polymer structures, which is costly, thus preventing users from controlling the degree of behavior. A smart microfiber blending technology, however, would allow cost-efficient tuning of the degree of strain hardening. In this study, we investigated the effects of compounding polymers with microfibers for both shear and extensional rheological behaviors and characteristics and thus for the final foam morphologies formed by batch physical foaming with carbon dioxide. Extensional rheometry showed that compounding of in situ shrinking microfibers significantly enhanced strain hardening compared to compounding of nonshrinking microfibers. Shear rheometry with linear viscoelastic data showed a greater increase in both the loss and storage modulus in composites with shrinking microfibers than in those with nonshrinking microfibers at low frequencies. The batch physical foaming results demonstrated a greater increase in the cell population density and expansion ratio with in situ shrinking microfibers than with nonshrinking microfibers. The enhancement due to the shrinkage of compounded microfibers decreasing with temperature implies that the strain hardening can be tailored by changing processing conditions.

Cellulose II aerogels: a review

Cellulose II aerogels are light-weight, open pores materials with high specific surface area. They are made in the same way as bio-aerogels based on other polysaccharides, via dissolution-(gelation)-solvent exchange-drying with supercritical CO2. Gelation step is often omitted as cellulose allows keeping 3D shape during solvent exchange (which leads to cellulose coagulation) and drying. Drying in supercritical conditions preserves the porosity of “wet” (coagulated) cellulose. There are numerous ways to vary cellulose II aerogel morphology and properties by changing processing conditions and cellulose type. Together with chemical and physical modifications of cellulose and possibility of making hybrid and composite materials (organic–inorganic and organic–organic), it opens up a huge variety of aerogel properties and applications. On one hand, they are similar to those of classical aerogels, i.e. can be used for absorption and adsorption, as catalysts and catalysts support and in electro-chemistry when pyrolysed. On the other hand, because the preparation of cellulose aerogels may not involve any toxic compounds, they can be used in life science applications such as pharma, bio-medical, food and cosmetics. The review makes an overview of results reported in literature on the structure and properties of cellulose II aerogels and their applications. The reader may be surprised finding more questions than answers and clear trends. The review shows that several fundamental questions still remain to be answered and applications to be explored.

Long-term investigation of microbial community composition and transcription patterns in a biogas plant undergoing ammonia crisis.

SummaryAmmonia caused disturbance of biogas production is one of the most frequent incidents in regular operation of biogas reactors. This study provides a detailed insight into the microbial community of a mesophilic, full‐scale biogas reactor (477 kWh h−1) fed with maize silage, dried poultry manure and cow manure undergoing initial process disturbance by increased ammonia concentration. Over a time period of 587 days, the microbial community of the reactor was regularly monitored on a monthly basis by high‐throughput amplicon sequencing of the archaeal and bacterial 16S rRNA genes. During this sampling period, the total ammonia concentrations varied between 2.7 and 5.8 g l−1 [NH 4 +–N]. To gain further inside into the active metabolic pathways, for selected time points metatranscriptomic shotgun analysis was performed allowing the quantification of marker genes for methanogenesis, hydrolysis and syntrophic interactions. The results obtained demonstrated a microbial community typical for a mesophilic biogas plant. However in response to the observed changing process conditions (e.g. increasing NH 4 + levels, changing feedstock composition), the microbial community reacted highly flexible by changing and adapting the community composition. The Methanosarcina‐dominated archaeal community was shifted to a Methanomicrobiales‐dominated archaeal community in the presence of increased ammonia conditions. A similar trend as in the phylogenetic composition was observed in the transcription activity of genes coding for enzymes involved in acetoclastic methanogenesis and syntrophic acetate oxidations (Codh/Acs and Fthfs). In accordance, Clostridia simultaneously increased under elevated ammonia concentrations in abundance and were identified as the primary syntrophic interaction partner with the now Methanomicrobiales‐dominated archaeal community. In conclusion, overall stable process performance was maintained during increased ammonia concentration in the studied reactor based on the microbial communities’ ability to flexibly respond by reorganizing the community composition while remaining functionally stable.

Color assessment of freeze‐dried mushrooms using Photoshop and optimization with genetic algorithm

AbstractAn image analysis and optimization technique exploiting Photoshop software coupled with genetic algorithm (GA) for a food processing application has been explored. Color characteristics (L*, a*, b*, change in color, hue, and chroma) for freeze‐dried mushrooms were determined. Mathematical models for predicting color characteristics of dried mushrooms with change in processing conditions were obtained using second order polynomials. Freeze‐drying (FD) conditions were optimized by an evolutionary algorithm. Results indicated that the temperature of primary and secondary drying cycles during FD have a significant impact on color. The search for optimum process conditions manifesting minimum color variation in the dried product as compared with fresh mushroom samples was done. Optimized response for color change and chroma were obtained as 4.58 and 9.78, respectively, after a 10 h drying cycle. The models developed can be used to determine the drying time for desired product color and processing conditions of FD.Practical applicationsConsumer preference for color is often a concern for food processing industries. Color detection of food materials in bulk needs to be performed rapidly and at low costs, which cannot be easily achieved using sophisticated color detection devices. The use of image acquisition system coupled with imaging software and modeling and optimization tools could provide a simple solution for the identification of superior food products based on image analysis.

ANALYSIS OF THE FLAME PULSATION SIGNALS USING A SHORT-TIME FOURIER TRANSFORM

The main aim of the diagnostics of combustion process is ensuring its stability and efficiency. The most important aspect related to the monitoring of the combustion process is a non-invasive acquisition of information from flame and subsequently subjecting it for further processing. Such method of research allows to evaluate the course of the process and determine the characteristic conditions under which the combustion process is stable or not. The article presents the application of short-time Fourier transform for the analysis of flame pulsation signals. The aim of the research was to find an area especially sensitive to the change of combustion process conditions.

Hydrogen solubility in donor-doped SrTiO3 from first principles

Hydrogen contamination of strontium titanate (STO) during processing and usage is a known problem. However, it is relatively little-studied due to the difficulty in quantifying the amount of hydrogen that dissolves in the lattice. Here, we use hybrid exchange-correlation density functional theory calculations as input to a grand canonical thermodynamics framework to estimate hydrogen solubility and site preferences in donor-doped STO. Our results provide clear theoretical evidence that hydrogen contamination in donor-doped STO occurs at a low enough level to essentially ignore. But, this simple conclusion belies hydrogen's rich behavior; unlike many dopants, it is able to easily change its incorporation site in response to changes in processing conditions. Overall, the findings are consistent with prevailing wisdom and suggest that the presented first principles approach could be used for systematic exploration of hydrogen's impact as a function of doping and processing in this and other wide bandgap materials.

Different formulations in gluten-free bread production: A review

Studies in recent years have shown that the market demand for gluten-free products is considerably increasing to fulfill celiac patients’ needs. Celiac disease is a food allergenic disease in humans induced by gluten in wheat, barley, rye, kamut, spelt and hybrids like triticale. For individuals with this disease, the one and only cure is to keep away from gluten-containing foods for perpetuity. Because of this reason, production and development of gluten-free bakery products, particularly bread because it is a basic food consumed daily in the world, have become popular and have been improved by the addition of different cereals, flours and starches, dough treatment or changing processing conditions and the method of baking. It needs to improve gluten-free bakery products’ quality because the absence of gluten is a big problem for the quality of dough and bread. For example, a bread made from gluten free flour has lower volume, weaker texture and aroma than the traditionally ones . However the increase of gluten-free market, there are still some problems such as their high prices, limited variety, and availability and low nutritional quality. This review focuses on the finding suitable alternatives for gluten free bread to improve their baking and sensory quality and nutritional properties.

Molecular footprint of co-solvents in hydrothermal liquefaction (HTL) of Fallopia Japonica

The influence of co-solvents on hydrothermal liquefaction (HTL) of Fallopia Japonica was studied as a function of temperature. Combination of low and high-resolution mass spectrometry with multi-layered data mining strategy resulted in a comprehensive characterization of the reaction products, mostly water-soluble organics (WSO) with a broad spectrum of chemical functionalities. The non-targeted analysis revealed the presence of a core composition in the samples independent of the process conditions and consisting of hydroxycarboxylic acids, imids, lactones, lactams, phenolics, various short-chain oxygenated aliphatics, and cyclohexane derivatives. Changes in process conditions did not affect those species showing that a part of the HTL product is not susceptible to process tailoring by addition of co-solvents. The findings indicated that the effect of tetralin is a combination of solubilization and scavenging resulting in an increased abundance of monomeric aromatics. For acetone, the results pointed to the promotion of retro-aldol splitting yielding low molecular weight oxygenates.

Multi-scale digital image correlation for detection and quantification of matrix cracks in carbon fiber composite laminates in the absence and presence of voids controlled by the cure cycle

Digital image correlation is applied to the images of a deforming composite to obtain strain maps at three length scales: micro-scale (ply level, hundreds of micrometers), meso-scale (laminate level, millimeters), and macro-scale (specimen level, tens of millimeters). The images are acquired in-situ with optical cameras and an electron microscope. The strain mapping at the macro- and meso-scales allows semi-automatic detection of matrix cracks and quantification of their density evolution in function of the applied strain. The micro-scale examination provides additional insights into the failure mechanisms. The technique is developed and then applied to characterize transverse cracking in cross-ply carbon fiber/epoxy composites in the absence and presence of manufacturing defects (including voids). Laminates with defects were produced by lowering the autoclave pressure and the cure temperature, intentionally. The strain for cracking onset and the saturation crack density are found to be different in the inner and outer transverse plies of both types of laminates. The change in processing conditions that led to the presence of voids and incomplete matrix cure resulted in a lower strain for cracking onset and up to 3.5 times increase of the crack density in comparison with the reference material without defects.

ВИРТУАЛЬНОЕ ФОРМООБРАЗОВАНИЕ ОБРАБАТЫВАЕМОЙ ПОВЕРХНОСТИ ПРИ КРУГЛОМ НАРУЖНОМ ШЛИФОВАНИИ С ОСЕВОЙ ПОДАЧЕЙ

PURPOSE. The paper deals with the model of shaping a processed surface in the operation of external cylindrical grinding with a traverse feed performed in an automatic cycle on CNC machines. The developed model of surface formation allows to conduct a step-by-step calculation of the current values of the actual radial in-feed and radii sizes in the different sections of the machined surface and predict the values of grinding surface dimensions throughout the whole grinding cycle for the given processing conditions. METHODS. The basis for the creation of computer-aided design systems serve the data presented in the regulatory literature that makes their use inefficient for the development of cycles for CNC machines. Existing engineering techniques also based on the recommendations of regulatory literature or on particular empirical data do not take into account the changes in variable processing conditions. RESULTS AND THEIR DISCUSSION. The paper discusses the simulation features of grinding cycles along the length of the machined part surface, shows a calculation scheme that establishes the relationship between the graphs of the accumulated software (tп k,i,z ) and actual (tф k,i,z ) feeds, tension (tн k,i,z ), elastic strain (у k,i,z ) of the technological system with the radii of the machined surface (R k,i,z ) when grinding a non-circular workpiece with the maximum radius (Rзаг max ), original workpiece radii (Rзаг k ) and initial radial run-out, which is calculated by formulas. CONCLUSIONS. Presented in the article formation model of the grinding surface in the operation of external cylindrical grinding with a traverse feed performed on a CNC machine allows to predict the actual dimensions of the machined surface for a given cycle and technological conditions of machining as well as to construct a model of the machined surface.

Optimisation of energy usage in ceramic kiln using pinch technique

The Pinch technology is one of the most advanced methodologies for energy saving in processes and total sites based on thermodynamic principles. In ceramic industry, energy distribution in kiln is very complex. The pinch analysis was used to minimise energy levels for ceramic kiln during operation at Phuoc Du Long ceramic company in Vietnam. Using Pinch technology, it was possible to identify appropriate changes in the core process conditions that could have an impact on energy savings. After the heat and material balance was established, targets for energy saving could be set prior to the design of the heat exchanger network in ceramic kiln. The results showed that the efficiency of the heat exchanger in the flue heat exchanger network had been determined. This also indicated that at the optimisation conditions, the heat loss was at a minimum. The heat and material balance were established in ceramic kiln. From the basic heat and material balance inside the old type of ceramic kiln, the energy lost via flue gas emission and heat transfer was found to be about 600 kJ. The Pinch point at 820 °C was determined to give a chance for energy saving.

Meeting new challenges in food science technology: The development of complex systems approach for food and biobased research

Abstract Current societal challenges and recent knowledge acquisition now provide the conditions for the renewal of our collective vision of food science and technology. To meet increasingly complex challenges, it obvious that current reductionist approaches in food science must give way to a knowledge-intensive framework for function-driven research and innovation. This implies a need for more in-depth, multiscale characterization of bioresources, leading to the detailed description of functional entities (molecules, macromolecules, substructures and assemblies etc.) and the development of new transformation technologies. These must provide the underpinning knowledge to devise specific transformations, using minimal energy and water inputs, and generate the targeted end-user products. We should thus consider food manufacturing as a complex systems problem, dealing with heterogeneous product matrices (agents), changing processing conditions (environmental context), non-linear behaviour (phase changes), novel functional properties (emerging phenomena), etc. Accordingly, we propose a new research methodology and innovation agenda, hereby utilizing the knowledge that we have gained in the past decade and described in this Special Issue.

Comparison of residence time models for pharmaceutical twin-screw-extrusion processes

Twin-Screw-Extrusion is an emerging and focused method with several applications in the pharmaceutical field. With respect to the desired process conditions, three different types of extrusion can be utilized such as Hot-Melt-, Wet- or Cold-Extrusion. For all of them the residence time and the residence time distribution are crucial process parameters determining the duration of thermal and mechanical stress to the processed material.Several approaches describing the residence time of extrusion processes are known and the most commonly applied models (Axial-Dispersion-, Tanks-in-Series- and Two-Compartment-Model) and functions (Zusatz-Function) were investigated. Therefore, experimental data representing different process conditions was applied from literature. The residence time distribution models were implemented and the least squares method was used to obtain the characteristic model parameters.The numerically calculated results were compared and evaluated based on the deviations to the experimental data overall, in crucial sections of the residence time plots and the comprehensibility of the model variables with respect to the interpretation for a process optimization. Moreover, the correlations between the characteristic parameters to those parameters of the different other tested models as well as their physical meaning have been revealed. Based on the results, a new model explicitly for twin-screw-extrusion was developed. This Twin-Dispersion-Model respects two independent mixing processes. Regarding to the parameters' comprehensibility and insight in process condition changes as well as deviations of the model fit to the experimental data, it was superior to all other tested models.

Optimization of Processing Conditions of Traditional Cured Tuna Loins–Muxama

Muxama is a traditional highly-valued food product prepared from dry-cured tuna loins in southern Portugal and Spain. The production procedure has seen little change over the last centuries. The muxama’s stability is due to reduced water activity. In addition, the drying method has secondary effects on characteristics of flavor, color, and the nutritional value of the product. Our objectives were to describe the dynamics of important physicochemical parameters such as moisture content, water activity (aW), NaCl concentration (as water–phase salt, ZNaCl), pH and color, during the salting and drying stages of muxama production, and to test the effect(s) of changes in the traditional processing conditions followed in southern Portugal, aiming at optimizing the production procedure. The lowest values of moisture and aW and highest ZNaCl obtained after drying tuna loins for seven days at 20 °C exceeded the values reported for commercial products and have impact on the appearance (color) of the product. Therefore, drying tuna loins at lower temperatures (ca. 14 °C) is probably more appropriate. The results obtained in this study could be used in the design of future experiments at other conditions and to assess other quality parameters, e.g., total volatile base nitrogen (TVB-N), thiobarbituric acid reactive substances (TBA-RS), microorganism abundance and sensory attributes, and subsequent validation trials.

Hot spinning formability of aluminum alloy tube

Spinning is a processing method in which a metal material such as a plate or pipe is pressed against a roller tool while rotating material with a forming die. Hot spinning processing is used for the production of high pressure hydrogen storage container. As an aluminum liner material for a high pressure hydrogen storage container, an Al-Mg-Si alloy is used from the viewpoint of hydrogen embrittlement resistance and strength. However, wrinkles and cracks generated during the formation of the liner material by hot spinning may cause breakage of the container. In this study, hot spinning is performed on Al-Mg-Si (A6063) alloy by changing processing conditions and processing temperature. After that, the effect of processing conditions and processing temperature on surface texture and wall thickness change was investigated. The results are followings, if the number of passes is large, the unevenness of the inner surface is small, but the length of the processed portion increases and the wall thickness decreases. On the other hand, when the temperature is high, the unevenness on the inner surface become large, the length of the worked portion hardly increases, and the wall thickness increases.

Optimisation of extrusion variables for the production of corn snack products enriched with defatted hemp cake

The effects of defatted hemp cake added to corn grits (at ratios of 0, 5, and 10% DM), the moisture content of the mixtures (15, 20, and 25%) and the temperature in the extruder ejection zone (150, 165, and 180°C) on the physical properties of extruded products have been investigated. Statistical optimization of investigated extrusion conditions using the response surface methodology was performed. The hemp cake was completely defatted by means of a supercritical CO2 extraction. The extrusion was performed on a laboratory single screw extruder and regulated by the following parameters: temperature in the dosing and compression zone (120 and 150°C), screw compression ratio (4 : 1), round die (4 mm). The change of extrusion process conditions significantly affected the physical properties of produced snacks. The expansion ratio ranged between 1.38 and 3.11, bulk density between 0.14 and 0.49 g/cm3, hardness between 18.15 and 70.62 N, fracturability from 3.65 to 10.38 mm, and the total colour change between 3.25 and 24.73.

In situ shrinking fibers enhance strain hardening and foamability of linear polymers

The strain hardening behavior of polymers has important roles in processing such as foaming, film formation, and fiber spinning. The most common method to enhance strain hardening is to introduce a long-chain branching structure on the backbone of a linear polymer, but this method is costly and challenging to tailor the behavior. We hypothesized that in situ shrinking fibers can increase the strain hardening of linear polymers, and the degree can be efficiently controlled. In this study, we show that heat-activated shrinking fibers compounded in linear polypropylene enhance strain hardening and foamability. Moreover, changing processing conditions, such as temperature, can amplify the degree of enhancement. Rheological measurements and physical foaming tests are shown to support our hypothesis.

Efficient implementation of multiple drive-in steps in thermal diffusion of phosphorus for PERC solar cells

N-type phosphorus diffusion in silicon using phosphorus oxychloride, POCl3, has been widely used in the production of p-type silicon solar cells. The thermal diffusion process in a furnace generally involves two steps: pre-deposition and drive-in. The phosphorous doping by thermal diffusion often shows high surface concentrations, leading to an increase in charge recombination, which should be inhibited in order to fabricate high efficiency silicon solar cells. In this study, we investigate the influence of 3 drive-in steps at sequentially increasing temperatures during the POCl3 diffusion on the emitter performance. As a result, it was found that the kink region was made shorter while maintaining surface concentration for a good metal contact without losing its passivation quality. This result is attributed to the higher active dopant concentration of the 3 drive-in step samples, leading to a lower series resistance and higher fill factor in the PERC solar cells. The results show that slight changes in the PSG process conditions can contribute to the improvement of high efficiency solar cells.

Grafting dual polar monomers onto hydroperoxidized polypropylene with the assistant of supercritical carbon dioxide

A hydroperoxidized polypropylene (HPP) was obtained by oxidizing PP porous particle in solid phase, followed by impregnating dual polar monomers of pentaerythritol triacrylate (PETA) and styrene (St) into the HPP with the aid of supercritical carbon dioxide (scCO2). Then, HPP was used as polymerization initiators and PETA/St were grafted onto microporous PP backbone in water medium. Effects of hydroperoxidation temperature, time, oxidant dosage and PP diameter on hydroperoxides concentration and Gp and Ge were illustrated systematically. Besides, effects of scCO2 swell time, pressure, monomers concentration and ratio, grafting reaction time and temperature on Gp and Ge were also examined. Results showed that Gp can be easily controlled by changing process conditions; Ge was observed to be greater than 90% in most of the cases. Gel content of grafted samples was also determined. The structures and thermal properties of grafted copolymers were characterized through FTIR, SEM, TGA and DSC.

Investigation of the cause of the chatter and physical behavior of a work roll in compact endless rolling

Mechanical devices that contain many rotating elements such as rolling mills inevitably generate vibrations. Vibrations not only cause unnecessary loads but also affect the quality of the manufactured product. Therefore, it is important to identify the causes of vibration in such mechanical devices and control them appropriately. In this study, the various causes of vibration in a rolling process were investigated, and the vibration types present in a compact endless-rolling mill (CEM) process were analyzed and compared. Three typical causes of vibration were analyzed. Based on these results, the cause of the vibrations that occur during changes in the processing conditions in a CEM can be inferred. More specifically, numerical analysis was conducted to study the physical behavior of work rolls (WRs) according to changes in the rolling process conditions. Using these analysis results, a mechanism to produce vibrations similar to those occurring in a CEM was proposed. The results of tracking the center position of a work roll showed that the direct effects of contact pressure on vibration were minimal, and changes in the lubrication type for the physical interaction between a WR and the contact strip were identified as a cause of vibration.