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Carbonized Bamboo Culm-Based Composite Materials: Mechanical and Frictional Performance for Brake Pad Applications
Get PDFThis study examines the development and application of composite materials based on dry and carbonized bamboo culm particles for friction material applications, particularly as a potential replacement for asbestos-based materials. Due to the environmental and health risks associated with asbestos, sustainable, high-performance alternatives are essential. Carbonized bamboo particles offer excellent thermal stability, while bamboo culm enhances strength. The development involved selecting bamboo culm composites, carbonizing, drying, and integrating them with other materials to achieve the desired friction properties. The composite materials were developed in a laboratory setting, and mechanical and thermal experiments were used to characterize the materials' properties. A systematic experimental design approach, including the Taguchi method, was employed to optimize the formulation and processing parameters. Test results show that the developed composite material has high mechanical strength, with an average tensile strength of 10.31 ±0.21 MPa, a modulus of elasticity of 80.07 ±1.60 MPa, an impact strength of 0.6912 J/mm, and a Vickers hardness of 107 HV. Thermal stability was further confirmed during testing, with a maximum temperature of 950℃ at a heating rate of 10℃/min. The developed composite material also performed well in friction material tests, with a friction coefficient of 0.378 and a wear rate of 0.15 mm3/Nm. Thermogravimetric analysis showed that optimized carbonized bamboo brake pads had lower temperature degradation than commercial ones. Results indicated that dry and carbonized bamboo culm composite materials are effective for friction applications, performing comparably to commercial brake pads
Shrinkage Limit Determination of Soils Using Hydrophobic Compounds
Get PDFShrinkage limit is one of the important parameters among the Atterberg limits used to classify fine-grained soils and to express its volume stability. Conventional method to determine volume of wet and dry shrinkage pats to evaluate shrinkage limit involves the usage of mercury, which is highly toxic and hazardous to health. Recently various methods have been proposed by different researchers which do have certain shortcomings. The present study proposes a simple and alternate method to determine the volume of dry shrinkage pat with the use of hydro-phobic compound and water submersion method, which is required to calculate the shrinkage limit of soils, thereby overcoming the various shortcomings of the alternate methods proposed by different researchers in the recent past. Three hydrophobic compounds, namely Vaseline, hydrophobic liquid, and hydropho-bic glue were used to coat the dry shrinkage pats with a thin layer of these compounds and make them hydrophobic, and hence, determine their volume with water submersion. The results of shrinkage limits of soils used in this study obtained using all these three hydrophobic compounds are within the acceptable range as suggested by ASTM standard D427-04 (Test method for shrinkage factors of soils by the mercury method, ASTM International, West Conshohocken, 2004. https:// doi. org/ 10. 1520/ d0427-04) and ASTM standard D4943-02 (Standard test method for shrinkage factors of soils by the wax method, ASTM International , West Conshohocken, 2008. https:// doi. org/ 10. 1520/ d4943-08) for any two results obtained from two different tests of the same type, for multi-laboratory determinations. The proposed alternate method of determining the shrinkage limit is not only simple but also reliable. It can be verified by various researchers before it can find universal acceptance as a standard and alternate method of determining the shrinkage limit of soils
Latitude as a Factor Influencing Variability in Vegetational Development in Northeast England During the First (Preboreal) Holocene Millennium
Get PDFIn the North Atlantic region, the transition from the very cold Lateglacial Stadial (GS-1) to the temperate Holocene was abrupt, with a rapid increase in temperature of several degrees, after which the low-stature, cold-tolerant Stadial vegetation was replaced through the immigration and rapid succession of tall herb, heath, and shrub communities towards Betula woodland of varying density. In northeast England, pollen diagrams on a south to north transect between mid-Yorkshire and the Scottish border show that there was considerable variation in the rate at which postglacial woodland was established in the first Holocene millennium. In mid-Yorkshire’s Vale of York, the development of closed Betula woodland was swift, whereas in north Northumberland, near the Scottish border, Betula presence was low for the first several centuries of the Holocene, with open vegetation persisting and with shrub vegetation dominated mostly by Juniperus. Intermediate locations on the transect show there was a gradient in post-Stadial vegetation development in northeast England, with latitude as a major factor, as well as altitude. Transitional locations on the transect have been identified, where vegetation community change occurred. Vegetation development in the first Holocene millennium in northeast England was spatially complex and diverse, with the climatic effects of latitude the main controlling environmental variable
Varieties of Political Ethnography: Caring for the Far Right?
Get PDFOver the past decades political science has produced varied examples of ethnographic approaches. These approaches have tackled epistemological dilemmas but they have also exposed a second, methodological dimension, which is not so systematically explicated: the relations of researchers to their research participants. In this article, we focus on this second dimension of ethnographic practice. We use emblematic texts in political science, especially in comparative politics, to develop a four-fold typology of political ethnographies that takes into account the emotional dynamics between researchers and participants. We use this typology to analyze various gradations through which these emotional dynamics develop in fieldwork. Focusing on the navigation between distance and proximity that these dynamics entail, we propose the concept of "emotional proximity" to capture relations between the researcher and the participant. We investigate the validity of this novel typology by applying it to ethnographic studies of Far Right actors. The political distance separating researchers and participants in these studies allows us to investigate the methodologies of disconnecting political from emotional dynamics across this four-fold schema of ethnographic varieties. We argue that the "infidelity" of emotional distance (instead of proximity) is not an objectivist epistemological necessity but an indispensable methodological tool to the practice of participant observation
Star formation and stellar & AGN feedback in the absence of accretion, not gas stripping, set the quenching time-scale in satellite galaxies
Get PDFA Procedure to Estimate Dose and Time of Exposure to Ionizing Radiation from the γ-H2AX Assay
Get PDFAccurately estimating the radiation dose received by an individual is essential for evaluating potential damage caused by exposure to ionizing radiation. Most retrospective dosimetry methods require the time since exposure to be known and rely on calibration curves specific to that time point. In this work, we introduce a novel method tailored to the γ-H2AX assay, which is a protein-based biomarker for radiation exposure, that enables the estimation of both the radiation dose and the time of exposure within a plausible post-exposure interval. Specifically, we extend calibration curves available at two distinct time points by incorporating the biological decay of foci, resulting in a model that captures the joint dependence of foci count on both dose and time. We demonstrate the applicability of this approach using both real-world and simulated data
A Novel LoS/NLoS Identification-Assisted Positioning Method for 6G Indoor MIMO Communications
Get PDFIndoor positioning is an important application of integrated sensing and communication technology in the sixth generation (6G) wireless communications. To address the limitations of existing fingerprint-based positioning methods (FPMs) under severe multipath effects, a novel channel state information (CSI)-based channel fingerprint structure and a novel line-of-sight (LoS)/non-LoS (NLoS) identification-assisted positioning method (IAPM) is proposed for 6G indoor multiple-input multiple-output (MIMO) communications. The proposed channel fingerprint structure uses the proposed maximum received power path to enhance the feature discrimination. The proposed IAPM incorporates a LoS/NLoS identification module and an improved weighted random forest (IWRF) positioning algorithm for accurate positioning. Evaluations on both channel measurement data and channel synthetic data generated by ray tracing demonstrate that the proposed method achieves superior accuracy and robustness compared with widely used FPMs
Stagnation in peat profiles controls organic matter transformation in different mire types
Get PDFDecomposition of organic compounds in peat soils requires atmospheric oxygen, which is limited when water fills soil pore spaces. We examined the thermodynamics of organic matter decomposition in Austrian peatlands and predicted greater thermodynamic constraints deeper in the soil profile where pore spaces are water filled. For mire types with stagnant water we hypothesize that thermodynamic closure of the pore space will occur deeper in the soil profile and there will be a greater extent of organic matter transformation. In this study peat cores from eight different peatlands were collected and analysed for their Gibbs free energy of formation (ΔGf), carbon oxidation state (Cox), and degree of unsaturation (Ω). The experimental design included bogs and fens, as well as natural and degraded sites. The study showed that decomposition of organic matter was greater in fens and degraded sites than in bogs and undisturbed sites, respectively, and there was a consistent increase in Ω with depth that marked an evolution away from cellulose-dominated compositions and toward lignin-dominated compositions at depth. These results support our study hypothesis that greater water stagnation in sites results in less transformation and shows that peatlands can be distinguished between the stable and unstable, and by relative recalcitrance
Regularity of the stationary density for systems with fast random switching
Get PDFWe consider the piecewise-deterministic Markov process obtained by randomly switching between the flows generated by a finite set of smooth vector fields on a compact set. We obtain Hörmander-type conditions on the vector fields guaranteeing that the stationary density is: Ck whenever the jump rates are sufficiently fast, for any k<∞; unbounded whenever the jump rates are sufficiently slow and lower semicontinuous regardless of the jump rates. Our proofs are probabilistic, relying on a novel application of stopping times
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