Home About us Contact
|
Home About us Contact | ||
|
|
||
Penetration Resistance (penetration + resistance)
Selected AbstractsFailure Waves and their Possible Roles in Determining Penetration Resistance of GlassINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2010Stephan J. Bless 1 High-velocity impact can produce failure waves in glass. Failure waves limit the speed at which a glass target can become comminuted. The resulting time dependence of strength is likely to influence resistance to ballistic penetration. [source] Assessment and demarcation of trail degradation in a nature reserve, using GIS: case of Bukit Timah Nature ReserveLAND DEGRADATION AND DEVELOPMENT, Issue 5 2007K. Chatterjea Abstract With a significant rise in popularity of nature areas, particularly in urban settings like Singapore, Nature Reserves are being increasingly opened for public recreational use. In the Bukit Timah Nature Reserve (BTNR), the only remnant primary rain forest reserve in Singapore, trail networks are being expanded to meet this growing public demand. The physical condition of the present trail networks was assessed by monitoring the changes in surface compaction, soil moisture, infiltration rates, soil organic matter content, root density, litter cover and rill development. These parameters were compared with similar data obtained from undisturbed forested slopes to analyse the degree of changes brought about by trail usage. Significant changes occurred in all measured parameters, indicating observable degradation of the trails, particularly on vulnerable slopes. These changes are due to the heavy and increased use of the forest by visitors. Penetration resistance and shear strength of the top surface layers of the trails are important indicators of trail degradation status and these have been plotted, using GIS, to demarcate trails under different levels of stress. This field monitoring provides a relevant local assessment of trail conditions. It has potential for use in decision-making in future planning and forest management under similar site conditions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Soil structure and pedotransfer functionsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2003Y.A. Pachepsky Summary Accurate estimates of soil hydraulic properties from other soil characteristics using pedotransfer functions (PTFs) are in demand in many applications, and soil structural characteristics are natural candidates for improving PTFs. Soil survey provides mostly categorical data about soil structure. Many available characteristics such as bulk density, aggregate distribution, and penetration resistance reflect not only structural but also other soil properties. Our objective here is to provoke a discussion of the value of structural information in modelling water transport in soils. Two case studies are presented. Data from the US National Pedon Characterization database are used to estimate soil water retention from categorical field-determined structural and textural classes. Regression-tree estimates have the same accuracy as those from textural class as determined in the laboratory. Grade of structure appears to be a strong predictor of water retention at ,33 kPa and ,1500 kPa. Data from the UNSODA database are used to compare field and laboratory soil water retention. The field-measured retention is significantly less than that measured in the laboratory for soils with a sand content of less than 50%. This could be explained by Rieu and Sposito's theory of scaling in soil structure. Our results suggest a close relationship between structure observed at the soil horizon scale and structure at finer scales affecting water retention of soil clods. Finally we indicate research needs, including (i) quantitative characterization of the field soil structure, (ii) an across-scale modelling of soil structure to use fine-scale data for coarse-scale PTFs, (iii) the need to understand the effects of soil structure on the performance of various methods available to measure soil hydraulic properties, and (iv) further studies of ways to use soil,landscape relationships to estimate variations of soil hydraulic properties across large areas of land. [source] Effects of tractor wheeling on root morphology and yield of lucerne (Medicago sativa L.)GRASS & FORAGE SCIENCE, Issue 3 2008Summary The purpose of this study was to determine the effect of soil compaction on the herbage yield and root growth of lucerne (Medicago sativa L.). A field experiment was conducted on a silty loam Mollic Fluvisols soil in 2003,2006. Herbage yield and root morphology, in terms of root length density, mean root diameter, specific root length and distribution of dry matter (DM) in roots, were measured. Four compaction treatments were applied three times annually by tractor using the following number of passes: control without experimental traffic, two passes, four passes and six passes. The tractor traffic changed the physical properties of the soil by increasing bulk density and penetration resistance. Soil compaction also improved its water retention properties. These changes were associated with changes in root morphology and distribution of the DM in roots. Soil compaction resulted in higher proportions of the DM in roots, especially in the upper, 0,10 cm, soil horizon. Decreases in the root length density were observed in a root diameter range of 0·1,1·0 mm. It was also found that roots in a more compacted soil were significantly thicker. An effect of the root system of lucerne on soil compaction was observed. The root system of lucerne decreased the effects of soil compaction that had been recorded in the first and the second year of the experiment. An increase in the number of passes resulted in a decrease in the DM yield of herbage in the second and third harvests each year. [source] Influence of Microsilica Content on the Slag Resistance of Castables Containing Porous Corundum,Spinel AggregatesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2008Wen Yan Corrosion of five corundum,spinel castables containing the same porous aggregates and different matrices by converter slag (C/S=3) was conducted using the static crucible test through the counting pixels method, XRD, SEM, EDAX, and so on. It was found that the corrosion and penetration resistance depend on the microsilica content. Microsilica content strongly affects liquid phase formation in the matrix, changes the porosity, pore size distribution of matrix, and viscosity of slag penetrated, and thus affects its corrosion and penetration resistance. Increasing microsilica, decreasing the porosity, or increasing the viscosity of the penetrating slag improves, whereas increasing the pore size or liquid content reduces the penetration and corrosion resistance. The penetration resistance increased abruptly with an increase of the microsilica content from 0.65 to 1.95 wt%, but changed slightly with increase of the microsilica content from 1.95 to 3.90 wt%. The corrosion resistance increased with an increase of the microsilica content from 0 to 2.60 wt%, but slightly decreased with a further increase of the microsilica content to 3.90 wt%. 1.95,2.60 wt% microsilica leads to a compromise between low corrosion and low penetration. [source] Evaluation of a combined penetrometer for simultaneous measurement of penetration resistance and soil water contentJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2004Yurui Sun Abstract A combined penetrometer is an appropriate tool to measure the soil cone resistance and the water-content profile. As a relatively new technique, a combined capacitance-penetrometer for the simultaneous measurement of cone index and soil water content was developed at the Department of Agricultural Engineering of Bonn University in 2002. The objective of this study was the evaluation of the effectiveness and applicability of the innovated penetrometer with a focus on three aspects: (1) A capacitance sensor with two electrode configurations was calibrated for silt loam, sandy loam, and sand. The calibration results show that both electrode configurations have sufficient water-content sensitivity, but soil-specific calibrations seem necessary. (2) Under laboratory conditions, the dynamic resolution and response of the capacitance-penetrometer were validated, and its radius of influence was determined. (3) The field measurement results demonstrate that this measurement technique can be used to improve the interpretation quality of soil cone index data. Bewertung eines Penetrometers zur gleichzeitigen Bestimmung von Eindringwiderstand und Bodenfeuchte Für die Ermittlung von Bodenprofilen für den Eindringwiderstand und die Bodenfeuchte erscheint die Kombination aus Penetrometer und Bodenfeuchtesensor als geeignete Lösung. Ein solcher Kombinationssensor wurde im Jahr 2002 am Institut für Landtechnik der Universität Bonn für die simultane Messung des Eindringwiderstandes und der Bodenfeuchte entwickelt. In diesem Beitrag wird die Tauglichkeit und Anwendbarkeit für Feldmessungen in folgenden Schritten dargestellt: (1) Ein kapazitiver Sensor mit zwei Elektrodenkonfigurationen wurde für die drei Bodenarten schluffiger Lehm, sandiger Lehm und Sand kalibiriert. Die Kalibrationsgleichungen zeigen, dass beide Elektrodenanordnungen über ausreichende Empfindlichkeit zur Bodenfeuchtemessung verfügen. Es sind aber bodenartspezifische Kalibrierungen notwendig. (2) Die dynamische Auflösung und das Ansprechverhalten des Feuchtesensors wurden für beide Elektrodenanordnungen untersucht, und die Ausbreitung des dielektrischen Feldes wurde bestimmt. (3) Die Ergebnisse der Messungen im gewachsenen Boden zeigen, dass die Messmethode zur Verbesserung der Interpretation der Konus-Indexwerte herangezogen werden kann. [source] EFFECT OF LACTIC ACID AND LACTIC ACID BACTERIA TREATMENT ON MYOFIBRILLAR PROTEIN DEGRADATION AND DYNAMIC RHEOLOGY OF BEEFJOURNAL OF TEXTURE STUDIES, Issue 3 2007M. SIGNORINI ABSTRACT Lactic acid has been used as an efficient decontaminant in meats aimed for direct consumption or product fabrication. However, reports on the functionality of proteins extracted from lactic acid-treated meat are scattered. The objective of this work was to study the degradation and gelling ability of myofibrillar protein extracts obtained from beef treated with lactic acid of chemical and microbial origins, stored at 4 and 20C. The gelling ability was considerably reduced by lactic acid treatment as a result of protein denaturation in acid conditions at both storage temperatures. Scanning electron microscopy showed loose structures resulting in low penetration resistance and storage modulus. Treatments with lactic acid or lactic acid bacteria (LAB) had similar effect on tan,, affecting gel rigidity but not elasticity. Penetration in gels obtained from LAB-treated meat was highly correlated with myosin degradation. Lactobacillus carnis -treated meat produced compact gels with high penetration resistance and storage modulus, although the structure became looser with storage time. LAB treatment, although not as efficient as lactic acid as a meat preservative, is a milder process causing less severe changes in meat structure rheology. PRACTICAL APPLICATIONS The potential of lactic fermentation by selected strains is somewhat limited as compared to lactic acid preservation of meat substrates, regarding pH reduction and its consequence on pathogens and spoilage microorganism population reduction. However, lactic acid bacteria (LAB) treatments are milder; therefore, changes in protein structure and rheology are less severe. Lactic acid in its chemical form promotes protein changes, whereas LAB does not. As myofibrillar protein configuration is responsible for most meat functional properties, such as gel and emulsion formation, it is important that protein structure remains unchanged as much as possible. Using nonproteolytic strains, protein degradation can only be altered by endogenous or bacteria-produced enzymes, which can be inhibited by several means. Meat preservation by lactic fermentation with selected strains can be an alternative when keeping meat protein functional properties unaltered. [source] Mechanisms involved in control of Blumeria graminis f.sp. hordei in barley treated with mycelial extracts from cultured fungiPLANT PATHOLOGY, Issue 5 2002H. Haugaard Treatment with mycelial extracts, prepared from liquid cultures of Bipolaris oryzae, Pythium ultimum and Rhizopus stolonifer, protected barley (Hordeum vulgare) against powdery mildew disease caused by the fungus Blumeria graminis f.sp. hordei. The mechanisms of this protection were studied using histopathological methods and molecular analysis. Germination and appressorial formation of B. graminis were generally reduced after treatment with mycelial extracts. Although this reduction (between 12 and 62% depending on treatment and experiment) was inconsistent and only occasionally significantly different from the water-treated control, it indicated a direct antifungal effect of the extracts. In situations where the fungus succeeded in forming an appressorium, penetration efficiency and haustorium formation from these appressoria was not affected , no enhanced penetration resistance associated with papilla formation was detected. However, a post-penetration effect was observed, as B. graminis colonies on mycelial extract-treated leaves produced 50% fewer hyphae than on controls. Northern blot analyses showed earlier accumulation of defence-related gene transcripts following treatment with B. oryzae and P. ultimum mycelial extracts, and to a lesser extent R. stolonifer mycelial extract, compared with water-treated leaves. It is suggested that the protection mechanism of the mycelial extracts involves direct antifungal effects and possible induced resistance for the B. oryzae and P. ultimum mycelial extracts. [source] Transcriptional regulation by an NAC (NAM,ATAF1,2,CUC2) transcription factor attenuates ABA signalling for efficient basal defence towards Blumeria graminis f. sp. hordei in ArabidopsisTHE PLANT JOURNAL, Issue 6 2008Michael K. Jensen Summary ATAF1 is a member of a largely uncharacterized plant-specific gene family encoding NAC transcription factors, and is induced in response to various abiotic and biotic stimuli in Arabidopsis thaliana. Previously, we showed that a mutant allele of ATAF1 compromises penetration resistance in Arabidopsis with respect to the non-host biotrophic pathogen Blumeria graminis f. sp. hordei (Bgh). In this study, we have used genome-wide transcript profiling to characterize signalling perturbations in ataf1 plants following Bgh inoculation. Comparative transcriptomic analyses identified an over-representation of abscisic acid (ABA)-responsive genes, including the ABA biosynthesis gene AAO3, which is significantly induced in ataf1 plants compared to wild-type plants following inoculation with Bgh. Additionally, we show that Bgh inoculation results in decreased endogenous ABA levels in an ATAF1 -dependent manner, and that the ABA biosynthetic mutant aao3 showed increased penetration resistance to Bgh compared to wild-type plants. Furthermore, we show that ataf1 plants show ABA-hyposensitive phenotypes during seedling development and germination. Our data support a negative correlation between ABA levels and penetration resistance, and identify ATAF1 as a new stimuli-dependent attenuator of ABA signalling for the mediation of efficient penetration resistance in Arabidopsis upon Bgh attack. [source] Recovery of sandy beach and maritime forest vegetation on Phuket Island (Thailand) after the major Indian Ocean tsunami of 2004APPLIED VEGETATION SCIENCE, Issue 2 2009D. Hayasaka Abstract Question: How rapidly has the sandy beach and maritime forest vegetation on Phuket recovered and regenerated after the impact of the major Indian Ocean tsunami of 2004? What are the characteristics of sandy beach species for regenerating their populations and the invasion patterns of originally non-sandy beach species or other newcomers after the tsunami? Location: Phuket Island, southern Thailand. Methods: Species composition of beaches was studied on the same research plots 6 months before and 9 months after the tsunami. The changes in individual species cover before and after the tsunami were determined by ,2 tests. Change in community composition was analysed by detrended correspondence analysis. The relationship between species and environmental factors was analysed by canonical correspondence analysis. Results: The sites disturbed by the tsunami were often invaded by annuals, especially grasses and asteraceous plants, rather than by perennials. In contrast, species with clonal growth by stolons decreased significantly. Factors determining the species habitat differences were soil hardness (penetration resistance of sandy soil), per cent silt content, soil water content and beach management. Habitat differences among originally non-sandy beach herbaceous species that expanded their population or moved to the coast after the disaster were defined by sand accretion or erosion caused by the tsunami. Many sandy beach herbaceous communities changed into Dactyloctenium aegyptium communities because of the tsunami were originally constituted by non-sandy beach D. aegyptium with Cenchrus echinatus. Although the forest floors of most maritime forests were invaded by originally non-sandy beach Tridax procumbens, Eleusine indica or D. aegyptium because of the tsunami, this did not result in a change in the vegetation unit, because species' loss was restricted to the understorey. In time, these forests will recover their previous community composition. Conclusions: Our results suggest that originally non-sandy beach native species invaded the disturbed beaches rapidly after the tsunami but their habitats differ. Sites where sand accumulated on a beach because of the tsunami were invaded by D. aegyptium and E. indica, whereas soil erosion permitted invasion by Digitania adscendens. Tridax procumbens establishes rapidly on wet sites with hard soil, high per cent silt content and low beach management pressure. Sandy beach species with subterranean long rhizomes are strongly tolerant of such disasters. We concluded that the species composition of the beaches disturbed by a temporary large disaster is determined by dormancy and growth forms, with radicoid form being influential. [source] | |||||||||||||