Variation of Intumescent Coatings Revealing Different Modes of Action for Good Protection Performance

Thermal insulation and mechanical resistance play a crucial role for the performance of an intumescent coating. Both properties depend strongly on the morphology and morphological development of the foamed residue. Small amounts (4 wt%) of fiberglass, clay and a copper salt, respectively, are incorporated into an intumescent coating to study their influence on the morphology and performance of the residues. The bench scale fire tests were performed on 75 × 75 × 2 mm³ coated steel plates according to the standard time–temperature curve in the Standard Time Temperature Muffle Furnace⁺ (STT Mufu⁺). It provided information about foaming dynamics (expansion rates) and thermal insulation. Adding the copper salt halved the expansion height, whereas the clay and fiberglass change the height of the residue only moderately. The time to reach 500°C was improved by 31% for clay and 15% for the other two fillers. Nondestructive micro computed tomography is used to assess the inner structure of the residues. A transition of the residue from a black, carbonaceous foam with closed cells into an inorganic, residual open cell sponge occurs at high temperatures. This transition is due to a loss of carbon; the change in microstructure is analyzed by scanning electron microscopy. Additional mechanical tests are performed and interpreted with respect to the results of the morphology analysis. Adding clay or copper salt improved the mechanical resistance tested by a factor 4. The additives significantly influence the thickness and foaming dynamics as well as the inner structure of the residues, whereas their influence on insulation performance is moderate. In conclusion, different modes of action are observed to achieve similar insulation performance during the fire test.     

Locomotion characteristics of dairy cows walking on pasture and the effect of artificial flooring systems on locomotion comfort

The locomotion comfort of dairy cows depends on the floor of the walking alleys. Optimal locomotion comfort is given when cows walk on pasture, allowing freedom from discomfort and pain and the expression of normal behavior. This study examined the characteristics of locomotion behavior on pasture (gold standard with optimal locomotion comfort) and compared it with behaviors of cows walking on mastic asphalt or solid rubber mats before and after a routine claw trimming session. Our hypotheses were (1) that gait variables were different on pasture versus mastic asphalt and on mastic asphalt versus rubber, and (2) that claw trimming had an effect on gait variables of cows walking on mastic asphalt. Twenty-four dairy cows kept in a tiestall facility were enrolled in this experimental trial. The pedogram was measured using 2 standalone 3-dimensional accelerometers (400 Hz), attached to the metatarsus of both hind limbs. The extracted pedogram variables included temporal events (kinematic outcome = gait cycle and stance-phase and swing-phase durations) and peaks (kinetic outcome = foot load, toe-off). The cows were further video-recorded to calculate walking speed and stride length. Locomotion score was performed on mastic asphalt to enroll only nonlame cows (locomotion score <3). For comparison between different floor types, repeated-measures ANOVA was performed with the cow as a subject variable, session time of measurement as within-subject variable, and flooring type as a fixed effect. Three separate analyses were performed: pasture versus mastic asphalt (analysis I), solid rubber versus mastic asphalt (analysis II), and the effect of claw trimming on the kinematic and kinetic variables on mastic asphalt (analysis III). All tested gait variables were significantly different between pasture and mastic asphalt floor. The optimal characteristics of locomotion comfort on pasture included shorter duration of gait cycle, longer stance-phase duration, shorter swing-phase duration, higher walking speed, longer stride length, and higher peaks of foot load and toe-off. However, gait variables of cows walking on rubber mats did not show any significant difference compared with the mastic asphalt floor; only stride length tended to be longer on rubber mats. In addition, the stance- and swing-phase durations significantly improved shortly after trimming. The left–right differences of the stance- and swing-phase durations tended to decrease after claw trimming when cows walked on asphalt floor. The results of this study show that solid rubber flooring does not result in significant improvement of the evaluated variables of locomotion comfort compared with mastic asphalt.     

Differential effects of monensin and a blend of essential oils on rumen microbiota composition of transition dairy cows

In response to oral application, monensin alters the rumen microbiota, increasing ruminal propionate production and energy availability in the animal. Data from different studies indicate that the susceptibility of rumen bacteria to monensin is mainly cell-wall dependent but tracing its activity to specific microbial groups has been challenging. Several studies have shown a similar effect for essential oils but results are inconsistent. To investigate the influence of monensin and a blend of essential oils (BEO, containing thymol, guaiacol, eugenol, vanillin, salicylaldehyde, and limonene) on the rumen microbiome, rumen liquid samples were collected orally on d 56 postpartum from cows that had either received a monensin controlled-release capsule 3 wk antepartum, a diet containing a BEO from 3 wk antepartum onward, or a control diet (n = 12). The samples were analyzed for pH, volatile fatty acid, ammonia, and lipopolysaccharide concentrations and protozoal counts. A 16S rRNA gene fingerprinting analysis (PCR–single-strand conformation polymorphism) and sequencing revealed that the BEO treatment had no effect on the rumen microbiota, whereas monensin decreased bacterial diversity. Twenty-three bacterial species-level operational taxonomic units were identified for which monensin caused a significant decrease in their relative abundance, all belonging to the phyla Bacteroidetes (uncultured BS11 gut group and BS9 gut group) and Firmicutes (Lachnospiraceae, Ruminococcaceae, and Erysipelotrichaceae). Ten bacterial operational taxonomic units belonging to the phyla Actinobacteria (Coriobacteriaceae), Bacteroidetes (Prevotella), Cyanobacteria (SHA-109), and Firmicutes (Lachnospiraceae and Ruminococcaceae) increased in relative abundance due to the monensin treatment. These results confirm the hypothesis that varying effects depending on cell-wall constitution and thickness might apply for monensin sensitivity rather than a clear-cut difference between gram-negative and gram-positive bacteria. No effect of monensin on the archaea population was observed, confirming the assumption that reported inhibition of methanogenesis is most likely caused through a decrease in substrate availability, rather than by a direct effect on the methanogens. The data support the hypothesis that the observed increase in ruminal molar propionate proportions due to monensin may be caused by a decrease in abundance of non-producers and moderate producers of propionate and an increase in abundance of succinate and propionate producers.     

Food Allergens: Is There a Correlation between Stability to Digestion and Allergenicity?

Food allergy is a major health problem in the Western countries, affecting 3–8% of the population. It has not yet been established what makes a dietary protein a food allergen. Several characteristics have been proposed to be shared by food allergens. One of these is resistance to digestion. This paper reviews data from digestibility studies on purified food allergens and evaluates the predictive value of digestibility tests on the allergenic potential. We point out that food allergens do not necessarily resist digestion. We discuss how the choice of in vitro digestibility assay condition and the method used for detection of residual intact protein as well as fragments hereof may greatly influence the outcome as well as the interpretation of results. The finding that digests from food allergens may retain allergenicity, stresses the importance of using immunological assays for evaluating the allergenic potential of food allergen digestion products. Studies assessing the allergenicity of digestion products, by either IgE-binding, elicitation or sensitizing capacity, shows that digestion may abolish, decrease, have no effect, or even increase the allergenicity of food allergens. Therefore, the predictive value of the pepsin resistance test for assessing the allergenic potential of novel proteins can be questioned.     

Chemical Degradation of Cathode Linings in Hall-Héroult Cells—An Autopsy Study of Three Spent Pot Linings

Cathode autopsies are used frequently in the aluminum industry to investigate pot failure and the degradation of the cathode lining. The materials observed in spent pot lining (SPL) has so far been assumed to reflect the sequence of layers from the cathode to the nonreacted refractory lining as present during the operation of the cell. Here, we demonstrate that the thermal gradient in the lining is reversed during cooling and that the physical appearance of the SPL is caused both by processes taking place during operation and cooling of the shutdown cell. X-ray diffraction and microscopy of the SPL from three shutdown cells revealed that sodium metal is the main component responsible for the chemical degradation of the refractory lining. Two distinct reaction fronts were identified in the three SPL showing that sodium is penetrating deeper down into the lining than the molten fluorides from the electrolyte. The mechanisms for the transport of sodium and bath components in the refractory lining are proposed based on the experimental observations. The sodium penetration is inhibited by the formation of a viscous barrier as suggested previously, but the current findings suggest that the barrier retards diffusion of O^2– and F^– anions rather than Na⁺ as proposed previously.     

超低碳钢连铸过程中Ti和P对水口结瘤的影响

浇注含Ti超低碳钢时,浸入式水口内产生结瘤,严重影响生产效率,同时对产品质量造成危害。根据企业生产的经验,随着超低碳钢中Ti和P含量的增加,水口结瘤的问题越来越严重。通过深入分析实际生产过程的试样和实验室研究,阐明浇注超低碳钢时Ti和P对水口结瘤的影响。分析了含Ti含P的超低碳钢水口结瘤物的成分,结果表明结瘤物的主要成分是氧化铝(>90%),Ti含量较少(0.58%～3.58%)。采用脉冲分布解析原子发射光谱法(OES-PDA)测得氧化夹杂物的大小随Ti含量的增加而变小。采用液滴法测定了溶质Ti和P对钢液/Al2O3体系的润湿性影响,结果表明Ti和P使体系接触角和钢液表面张力降低,其中Ti能够降低体系的接触角只是在其具有反应湿润性的情况下。研究表明Ti和P对产生结瘤的作用有显著区别:只要形成的表层界面具有润湿性,Ti就可以降低Al2O3夹杂物的大小,而氧化铝夹杂物颗粒越小,越容易结瘤。为了不产生结瘤就必须控制好Al脱氧的时间和Ti的加入时间。P可以增加Fe-Ti-P三元体系的润湿性是因为P可以增加Ti的活度,降低钢液的粘度。与Ti相比,P对产生结瘤的影响较小。     

Dimensional Changes in CFRP/PMI Foam Core Sandwich Structures

A sandwich structure was observed from the beginning of life—starting at the vacuum assisted manufacturing process up to several environmental in service conditions. Strain variations due to curing process at the manufacturing, well as thermal fluctuations and humidity environments in service were detected and reviewed by their influence on the overall dimensional stability. The CFRP/PMI foam core sandwich structure was checked for an application as a primary structure in commercial aviation with its specific environmental requirements.     

Two-colour Dynamic Light Scattering

Abstract

The design, alignment and operation of improved two-colour dynamic light scattering equipment which effectively suppresses multiple scattering and allows the study of the Brownian dynamics of optically turbid samples is described. The technique operates by cross-correlating scattered light of two different colours. With the appropriate scattering geometry, only singly scattered light contributes to the time-dependent part of the measured intensity cross-correlation function thus allowing straightforward interpretation of the data. To demonstrate the performance of the instrument we have studied various colloidal suspensions. Although dilute enough that free diffusion of the particles can be assumed, the samples ranged from quite transparent to distinctly turbid. We have confirmed that the measured cross-correlation functions accurately reflect only single scattering even in the presence of strong multiple scattering.     

Electron microscopy investigations of metal-support interaction effects in M/Y2O3 and M/ZrO2 thin films (M=Cu,Ni)

Model systems of the clean and pure oxides Y₂O₃ and ZrO₂, as well as Cu/Cu₂O and Ni/NiO particles embedded in the respective oxides have been used to study the reduction behavior of the oxides and the eventually associated metal-support interaction effects in oxide-supported systems. Particular emphasis has also been given to the influence of the phase transformation in ZrO₂-containing systems on metal-support interaction. Whereas Y₂O₃ has been found to be an outstandingly structurally and thermally stable oxide even upon reduction in hydrogen up to 1073 K, ZrO₂ was found to undergo a series of phase transformations from amorphous ZrO₂ to polycrystalline tetragonal ZrO₂ (∼673 K) and subsequently to monoclinic ZrO₂ (above 873 K). Both phase transformations were found to be basically dependent on gas partial pressure and annealing rate. However, substantial reduction of the oxides did not take place during the phase transformations. In turn, both Cu- and Ni-containing systems were not observed to be substantially affected by any (strong) metal-support interaction effects such as encapsulation by sub-stoichiometric oxides or reductive formation of intermetallic phases, at least up to temperatures of 1073 K. Equally, for the ZrO₂-containing systems, also the phase transformations occurring at elevated temperatures did not cause structural or thermo-chemical alterations of the Cu or Ni-particles. Differences in the metal-support interaction between Cu- and Ni-particles have only been obtained in the structural “reference” systems, that is, if supported on SiO₂. Whereas Cu/Cu₂O particles on SiO₂ are basically unaffected by the reductive treatment at elevated temperatures, a Ni₃Si₂ intermetallic phase is formed if SiO₂-supported Ni/NiO particles are treated in hydrogen at 673 K and above.     

Designing training for process control simulators: a review of empirical findings and current practices

Although simulators have been widely used as training environments in different industries (e.g. oil and nuclear power), there is little rigorous empirical work evaluating the effectiveness of the training methods employed. This article examines the use of simulator training in process control environments. The results of an exploratory field study are reported and the current practices of simulator training are described. The study revealed that simulator training varied considerably across organisations, often with little theoretical or empirical work to guide training design. To evaluate the utility and effectiveness of different methods of simulator training in process control environments, the article also presents a literature review of the research on laboratory- and field-based training. Several training methods are identified as having particular potential for temporal and adaptive transfer and are to be empirically tested in future studies.