Exponential Decay Equation Research Articles

Study on the skid resistance decay of submerged asphalt pavements based on texture parameters

AbstractIt is well known that prolonged rainwater erosion can adversely affect the surface texture of asphalt pavements, leading to a rapid decline in their skid resistance. This study utilized a small-scale accelerated loading device, a high-precision 3D scanner, and digital image processing technology to investigate the surface texture wear process and skid resistance decay trends of basalt asphalt pavement and steel slag asphalt pavement under water erosion and traffic load. The results indicate that under submerged conditions, the skid resistance (BPN) of asphalt pavement declines rapidly during the first 500,000 load cycles, and the rate of decline gradually stabilizes after 500,000 cycles. After 1.2 million load cycles, the BPN of basalt pavement decreased by 28.10%, while that of steel slag pavement decreased by 21.18%, indicating that the skid resistance of steel slag pavement is significantly better than that of basalt pavement. Texture parameters—namely, root mean square height, peak material volume, core material volume, void volume of the core, and valley void volume—exhibited the same decay trend as BPN. The average correlation coefficients between BPN and texture parameters were 0.846, 0.848, 0.898, and 0.916, respectively, indicating that texture parameters can be used as evaluation indicators for skid resistance decay. Finally, the decay of pavement skid resistance was predicted using an exponential decay equation.

Evaluation of lightning‐induced overvoltage on a 10 kV distribution line based on electromagnetic return‐stroke model using finite‐difference time‐domain

AbstractAccurate simulation of lightning‐induced overvoltage for overhead distribution lines is helpful to prevent lightning trip accidents. An electromagnetic return‐stroke model was used to represent lightning and then a 3D finite‐difference time‐domain (FDTD) method was adopted to simulate the lightning‐induced overvoltage on a distribution line without a field‐line coupling model. How lightning‐induced overvoltage behave for different ground conductivity and varying distance between the distribution line and the lightning channel was analysed. The results showed that the overvoltage waveforms at the centre point of the line corresponding to lightning strikes on the lossy ground and an ideal ground (σ = ∞) were similar; however, the peak amplitudes of the waveform were affected by soil conductivity at a close distance. The relationship between magnitude of the overvoltage and distance can be described by a second‐order exponential decay equation. Finally, the overvoltage calculated using the proposed model was compared with those obtained based on Agrawal's model and measurements made using the newly developed intelligent insulator on site. From these comparisons, it could be concluded that the FDTD method with the electromagnetic return‐stroke model produces reasonably accurate results of the attenuated oscillation waveform, which can better reproduce the overvoltage on operational distribution lines.

Reduction and Removal Mechanism of Cr(VI) by a Novel Penicillium Rubens LR6

Bioreduction of Cr(VI) is an efficient and environmentally friendly remediation method. In this study, we isolated and screened a strain of Penicillium rubens LR6 that could tolerate to Cr(VI) and investigated its mechanism for removing Cr(VI). We ascertained the factors affecting the ability of strain to remove Cr(VI) through batch experiments. The results revealed that the strain could effectively remove high concentrations of Cr(VI) and exhibit excellent removal efficiency under different environmental conditions. The removal of Cr(VI) by the strain could be accurately explained by the exponential decay equation, where approximately 9.45% of the Cr was immobilized on the microorganisms. We further investigated the ability of different cell fractions to remove Cr(VI) and found that bioreduction was the primary mechanism involved. This was supported by SEM and TEM analyses, which showed the presence of Cr on the surface and inside the cells. Additionally, XPS analysis confirmed the presence of both Cr(VI) and Cr(III) on the cell surface, and FTIR analysis suggested the involvement of amino, carboxyl, and hydroxyl groups in the reduction and fixation of Cr(VI) on the cell surface. The findings offer a novel technique for bioremediation of Cr(VI)-contaminated wastewater in weakly acidic to weakly alkaline and high salinity environments, providing potential solutions for remediating chromium-contaminated environments.

Early Post-Infusion Clearance of High-Dose Methotrexate Predicts Delayed Methotrexate Elimination and Acute Kidney Injury

Introduction High-dose methotrexate (HDMTX) is used for the treatment of hematologic malignancies but its use may be limited by delayed methotrexate elimination and acute kidney injury (AKI). Current guidelines for glucarpidase recommend administration between 48-60 hours following the start of a 24-hour HDMTX infusion based on methotrexate concentration at 36-, 42-, or 48-hours [Ramsey 2016]. However, this may be too late to prevent permanent toxicities in cases where significant AKI develops early during infusion. Recent evidence from pig models have shown that early methotrexate measurements can predict the development of AKI [Buddington 2023]. The aim of this study is to determine whether early elimination of methotrexate (soon after completion of the infusion) is a useful “early clearance biomarker” of delayed methotrexate elimination and AKI in humans. Methods Retrospective data from two sites in Spain that collected two or more early measurements of methotrexate levels from the end of HDMTX infusion were analyzed from a larger HDMTX registry. Methotrexate half-life was calculated employing exponential decay equations and the slope of a line connecting two out of three early time points; each combination was tested, and the best performing pair is reported. Early levels were tagged according to visual exploration and k-means cluster analysis (Figure 1). Delayed methotrexate elimination was defined as a concentration above 1 μmol/L after 42-hours from the start of infusion (micromolar criterion) or above 2 standard deviations (SD) from the population mean modeled using MTXPK.org at 42- or 48-hours from the start of infusion (SD criterion). Receiver operating characteristic (ROC) curves were fitted, with their respective area under the curve (AUC) and confidence intervals for delayed methotrexate elimination and AKI. Additionally, a logistic regression model was employed to predict AKI using a base model with covariates (age, sex, HDMTX dose, and first course) plus early methotrexate clearance. Results Data from 144 patients who received 453 HDMTX courses were included. Patient characteristics were as follows: 41% females, age ranged from 1.2 to 81.5 years at the time of HDMTX infusion; diagnoses included acute lymphoblastic leukemia, 79%; non-Hodgkin lymphoma, 21%. Median methotrexate dose was 4,856.9 mg/m 2 [IQR 2,871.7 - 4,985.0], with 88% of the courses infused over 24 hours and 12% over 4 hours. Delayed methotrexate elimination was found in 41% and 6.6% of the courses according to the micromolar criterion and SD criterion, respectively. AKI developed in 29.6% of courses. Median time for the first, second and third measurements were 0.25 [IQR 0.00 - 0.71], 6.32 [IQR 5.86 - 6.69] and 12 [IQR 11.68 - 12.50] hours, respectively. Half-life estimation between the second and third early time-points predicted delayed methotrexate elimination by the micromolar criterion with an ROC AUC of 0.81 [CI95 0.76 - 0.87] or SD criterion with an ROC AUC of 0.84 [CI95 0.68 - 1.00] (Fig. 2) and any grade AKI with an ROC AUC of 0.62 [CI95 0.55 - 0.69]. After adjusting for age, sex, HDMTX dose, and first course, half-life remained statistically significant in the logistic regression model, with an odds ratio of 1.4 [CI95 1.1 - 1.8] (p < 0.01). The addition of half-life to the base model improved the overall performance (ANOVA, p < 0.01). Conclusions The half-life of methotrexate elimination soon after completing the HDMTX infusion defines an early clearance biomarker that predicts delayed methotrexate elimination and AKI. It requires only the measurement of 2 early methotrexate levels soon after completing the infusion, and thus represents a practical and applicable method to identify patients at risk who may need pre-emptive interventions like increased hydration or glucarpidase.

Decomposition and nitrogen mineralization of <em>Gliricidia sepium</em> leaf green manure under diverse nutrient management strategies in irrigated lowland rice cropping systems in Sri Lanka

The utilization of green manure has become an essential strategy for enhancing soil fertility and substituting synthetic fertilizers. The decomposition and release of nutrients through mineralization processes are influenced by soil microbial activity, which in turn depends on the nutrient management practices employed. depending on nutrient management approaches. The study aimed to investigate the decomposition and N mineralization of Gliricidia sepium leaf green manure in an irrigated lowland rice ecosystem under different nutrient management systems (NMS), for a duration of eight weeks. Litterbags were placed at two soil depths, namely the topsoil, and subsoil, within three NMS; 100% Department of Agriculture (DOA) recommended inorganic fertilizer application (CNM), 50% of DOA recommended inorganic fertilizer combined with the organic fertilizer application (INM), and 100% organic fertilizer application (ONM). The treatments were arranged in a randomized complete block design and litterbags were retrieved weekly to determine dry mass, total N content, and total organic carbon content remaining in the leaves. The rate of decomposition and nutrient release was estimated using an exponential decay equation and analysis of variance was carried out using the repeated measures MIXED model. A consistent biphasic pattern of decomposition and mineralization was observed across all NMS treatments and soil depths, characterized by an initial rapid phase followed by a slower phase. However, significant differences (p<0.05) were observed among the treatments. The ONM treatment combined with topsoil placement exhibited a shorter time for 50% and 80% reduction in biomass and nitrogen content. Approximately 80% of the nitrogen content was released into the soil solution within 4-5 weeks of green manure incorporation, regardless of the nutrient management system employed. These findings suggest that with proper application rates and appropriate depth of placement, Gliricidia sepium green manure can effectively replace a significant portion of mineral nitrogen fertilizer, thereby enhancing nutrient use efficiency in lowland rice-based systems.

Physical and hydrological characteristics and modelling of the soil water retention curve in the brazilian semi-arid region

Semiarid regions are characterised by water scarcity, a limiting factor on plant growth and development. The Sertão Canal was built in the semiarid region of Brazil, more specifically in the state of Alagoas, with the aim of making year-round irrigation possible. However, for the best water management, a physical and hydrological knowledge of the soils is necessary. As such, the aim of this study was to determine the physical and hydrological characteristics of three different types of soil (Argisol, Quartzarenic Neossol and Regolithic Neossol) under native vegetation (Caatinga) and agricultural systems in the semiarid region of Alagoas, as well as to adjust the soil water retention characteristic curves. Soil samples were collected at depths of 0-10, 10-20 and 20-30 cm in the municipalities of Inhapi, Delmiro Gouveia and Pariconha, in the state of Alagoas. The points of the moisture characteristic curve were determined by the Richards method, at pressures of 33, 100, 500, 1000 and 1500 kPa. Retention curves were modelled using the exponential decay equation and compared using the van Genuchten equation, modelled with the help of the RETC computer software. Particle size varied according to the textural classification of the different soils, from Sand to a Sandy Clay Loam. The retention curve fluctuated due to the particle size of the soil, with the Red-Yellow Argisol (Inhapi) having a greater capacity for water retention. Extremely sandy soils, such as those in the Delmiro Gouveia region, had a low capacity for retaining water. For each soil sample, the exponential decay equation gave the best fit, with values for R2adjust of greater than 0.93. When the measured soil moisture levels were compared with the levels estimated by the RETC model, some of the treatments were unable to estimate accurately the moisture levels obtained with the soil water retention curves.

Study of cyclic cataluminescence virtual sensor array for gasoline quality monitoring

The addition of methyl tert-butyl ether (MTBE) can increase the octane number of gasoline to improve the combustion efficiency of gasoline. Because of the health effects on the population exposed to MTBE, limiting the addition of MTBE in gasoline will be thefuture development tendency. Here, a cyclic cataluminescence (CCTL) sensor array was utilized to monitor the addition of MTBE in gasoline. CCTL sensor obtained multistage signals (In) on a single catalyst, which realized the function of the sensor array. MTBE trigger-CCTL reaction on 4 kinds of catalysts was investigated. Three brands (No. 92, 95, and 98) of gasoline triggered the CCTL reaction to obtain In which conforms to the exponential decay equation (EDE). CCTL sensor was used to detect the volume ratio of MTBE to gasoline according to A and τ-values. The In was applied to normalize and distinguish gasoline through linear discriminate analysis (LDA) and hierarchical cluster analysis (HCA). The τ-values of gasoline on 4 catalysts generated a digital code to differentiate each gasoline. CCTL virtual sensor arrays own the sensor array function and provide a promising technology for gasoline quality analysis.

Comparison of Callery pear (Pyrus calleryana, Rosaceae) leaf decomposition rates with those of the invasive shrub Amur honeysuckle (Lonicera maackii, Caprifoliaceae) and two native trees, red maple (Acer rubrum, Sapindaceae) and American sycamore (Platanus occidentalis, Platanaceae)1

Invasive plants can alter nutrient cycling rates, because the leaves of many invasive species decay more quickly than those of native plants. Pyrus calleryana (Callery pear) is a relatively new woody invader in the eastern USA that rapidly colonizes open and disturbed areas. Invasive woody plants can alter forest nutrient cycling, yet the leaf decomposition rates of P. calleryana have not been previously determined. In this study, Pyrus calleryana leaf decomposition rates were compared against two widely distributed native trees, Acer rubrum (red maple) and Platanus occidentalis (American sycamore), with different levels of nitrogen (N), carbon (C):N, lignin, and lignin:N. It was also compared to that of the invasive shrub Amur honeysuckle (Lonicera maackii), which is known to have very fast decomposition rates. Litter bags were placed in four locations in a Callery pear-dominated stand in northern Kentucky in November 2014 and sampled at 3, 90, 12, and 18 mo. Dry weight and %N measurements were fit to a single exponential decay equation. Mass and N loss of P. calleryana leaf litter were both similar to those of A. rubrum, and they were lower than those of L. maackii; however, lignin and lignin:N levels were most similar to L. maackii. Platanus occidentalis decayed very slowly and immobilized rather than mineralized N. Pyrus calleryana is thus not predicted to greatly alter leaf litter decomposition in invaded forests, although litter decomposition dynamics might be different in mixtures with native species and in other locations.

Calculations of the magnitude of responsivities in pH-, temperature- and ion- responsive hydrogels

Stimuli-responsive hydrogels (SRHs) were prepared by thermal free radical redox polymerization in the aqueous solution of N-isopropyl acrylamide (NIPAAm), acrylamide (AAm) with any weak organic acid (such as propenoic acid, cis-butenedioic acid, crotonic acid, methacrylic acid, methylfumaric acid, itaconic acid, aconitic acid in the presence of N,N′-methylene bisacrylamide. DSC thermograms were taken to find the transition zone parameters of SRHs. Swelling studies were carried out to determine the effects of stimuli such as temperature, pH, and ionic strength on the swelling-shrinkage behavior of SRHs and to calculate the magnitude of the stimuli. A sigmoidal equation was used to calculate the parameters such as transition point, the magnitude of the stimulus, minimum and maximum swelling, the amplitude of the transition zone, etc. of the temperature or pH transition zones of SRHs, while the exponential decay equation was used to calculate the parameters of the swelling-ionic strength relationship of the same gels. With the idea that SRHs can be used as a biomaterial, swelling values of SRHs at the pH values of the body fluids at 37 °C were calculated with the help of these sigmoidal equation parameters. Similarly, swelling values of SRHs in hypertonic, isotonic, and hypotonic saline solutions were determined with the help of these exponential decay equation parameters.In conclusion, calculating the responsivity magnitude with the sigmoidal equation or exponential decay equation approach can be a useful tool for chemists, chemical engineers, bioengineers, biomedicine, biomaterials, polymer, and plastic scientists to find the transition zone parameters of stimuli-responsive hydrogels.

Remaining Capacity Estimation of Lead-acid Batteries Using Exponential Decay Equations

The precise capacity estimation of batteries can extend their lifespan and is necessary to ensure reliability and safety of operation. Many methods have been developed with this objective in the last decades. However, there is still research for more accurate and less complex methods in order to estimate the state of charge of operating batteries. This article presents exponential decay equations that model the behavior of the battery capacity drop with the discharge current. Experimental data for different application batteries showed that these equations have a superior accuracy compared to the empirical Peukert equation. Their parameters are dimensionally coherent and make the characterization and categorization of batteries possible, besides, they give insights about the behavior of the electrodes under different discharge rates. Due to the low complexity and easy adaptability to the currently employed methods, these equations can be easily employed in battery management systems without the need for great computational power. DOI: http://dx.doi.org/10.17807/orbital.v13i5.1555

Cornstalk biochar promoted the denitrification performance and cellulose degradation rate of Burkholderia sp. CF6

A strain Burkholderia sp. CF6 with denitrification and cellulose degradation ability was isolated. When sodium carboxymethyl cellulose (CMC-Na) dosage was 5 g L−1, the nitrate removal efficiency reached 96.48% after 48 h and the nitrite accumulation was only 0.07 mg L−1. The exponential decay equation was used to match the kinetics of denitrification and the correlation coefficient (R2) was higher than 0.940. The denitrification and cellulose degradation capabilities were promoted by cornstalk biochar. Through the comparison of nitrogen balance of different biochars, biochar of 400 ℃ (BC400) had the highest gaseous nitrogen conversion efficiency (83.31%). BC400 can accelerate the nitrate removal rate (from 0.08 to 0.32 mg L−1 h−1) and shorten the peak time of cellulase activity (from 48 to 24 h). The fourier transform infrared spectroscopy (FTIR) manifested that the BC400 assisted biological denitrification was achieved through phenolic and quinone groups. From the results of three-dimensional excitation-emission matrix (3D-EEM), it can be concluded that soluble microbial by-product and aromatic protein have a significant correlation with the effect of BC400 on the biological process of strain CF6. This research will provide new insights for agricultural waste utilization to treat low carbon to nitrogen (C/N) ratio wastewater.

Multifunctional MgO/HKUST-1 Composite for Capture, Catalysis, and Cyclic Cataluminescence Detection of Esters All-In-One to Rapidly Identify Scented Products.

The integration of metallic oxide and metal-organic frameworks has attracted considerable attention as obtained composite materials because they show synergistic effects in applications of catalysis and sensing. Herein, we developed the hybrid MgO and HKUST-1 for efficient capture, catalysis, and cyclic cataluminescence (CCTL) detection of esters all-in-one to rapidly identify scented products. The multifunctional MgO/HKUST-1 composite with high CCTL activity was synthesized and characterized. The multifunctional MgO/HKUST-1 composite acts as an enrichment material for ester capture and serves as a catalyst, assisting the analyte to trigger multistage signals. The multistage signals of ester-containing scented products also satisfy the exponential decay equation with a certain τ-value. The τ-values obtained by the CCTL system were applied to identify the brands of essential oils. The working temperature served as the sensor element to obtain various τ-values. The τ-values constituted a digital code to label the different brands of cigarettes with the same aroma type. The multistage signals could be used to distinguish the origin regions of essential oils and tobacco. This work combines the CCTL strategy with the sample pretreatment, opening up a new direction to develop CCL and providing a new platform to rapidly identify ester-containing scented products.

Physicomechanical properties and water resistance of heat-modified moso bamboo (Phyllostachys pubescens) as a function of density

The effects of treatment temperature on the physicomechanical properties and dimensional stability during water immersion of moso bamboo were investigated as a function of density. The results indicated that most of the physical and flexural properties and dimensional instability significantly decreased when the temperature increased to 220 °C. Additionally, the flexural properties of untreated and heat-treated bamboo showed a positive relationship with the apparent density, while their water absorption (WA) increased with decreasing apparent density. Furthermore, despite the treatment temperatures, the modulus of elasticity and WA for all the bamboo samples were better described using linear relationships and exponential decay equations, respectively.

Modeling Alleviative Effects of Ca, Mg, and K on Cu-Induced Oxidative Stress in Grapevine Roots Grown Hydroponically.

The aim of this study was to determine the pattern of alleviation effects of calcium (Ca), magnesium (Mg), and potassium (K) on copper (Cu)-induced oxidative toxicity in grapevine roots. Root growth, Cu and cation accumulation, reactive oxygen species (ROS) production, and antioxidant activities were examined in grapevine roots grown in nutrient solutions. The experimental setting was divided into three sets; each set contained a check (Hoagland solution only) and four treatments of simultaneous exposure to 15 μM Cu with four cation levels (i.e., Ca set: 0.5, 2.5, 5, and 10 mM Ca; Mg set: 0.2, 2, 4, and 8 mM Mg; K set: 0.6, 2.4, 4.8, and 9.6 mM K). A damage assessment model (DAM)-based approach was then developed to construct the dose-effect relationship between cation levels and the alleviation effects on Cu-induced oxidative stress. Model parameterization was performed by fitting the model to the experimental data using a nonlinear regression estimation. All data were analyzed by a one-way analysis of variance (ANOVA), followed by multiple comparisons using the least significant difference (LSD) test. The results showed that significant inhibitory effects on the elongation of roots occurred in grapevine roots treated with 15 μM Cu. The addition of Ca and Mg significantly mitigated phytotoxicity in root growth, whereas no significant effect of K treatment on root growth was found. With respect to oxidative stress, ROS and malondialdehyde (MDA) contents, as well as antioxidant (superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX)) activities, were stimulated in the roots after exposure to 15 μM Cu for three days. Moreover, H2O2 levels decreased significantly as Ca, Mg, and K concentrations increased, indicating that the coexistence of these cations effectively alleviated Cu-induced oxidative stress; however, alleviative effects were not observed in the assessment of the MDA content and antioxidant enzyme activities. Based on the DAM, an exponential decay equation was developed and successfully applied to characterize the alleviative effects of Ca, Mg, and K on the H2O2 content induced by Cu in the roots. In addition, compared with Mg and K, Ca was the most effective cation in the alleviation of Cu-induced ROS. Based on the results, it could be concluded that Cu inhibited root growth and Ca and Mg absorption in grapevines, and stimulated the production of ROS, lipid peroxidation, and antioxidant enzymes. Furthermore, the alleviation effects of cations on Cu-induced ROS were well described by the DAM-based approach developed in the present study.

Application of Gamma Ray-Responsive Genes for Transcriptome-Based Phytodosimetry in Rice.

Transcriptome-based dose–response curves were recently applied to the phytodosimetry of gamma radiation in a dicot plant, Arabidopsis thaliana, as an alternative biological assessment of genotoxicity using DNA damage response (DDR) genes. In the present study, we characterized gamma ray-responsive marker genes for transcriptome-based phytodosimetry in a monocot plant, rice (Oryza sativa L.), and compared different phytodosimetry models between rice and Arabidopsis using gamma-H2AX, comet, and quantitative transcriptomic assays. The transcriptome-based dose–response curves of four marker genes (OsGRG, OsMutS, OsRAD51, and OsRPA1) were reliably fitted to quadratic or exponential decay equations (r2 > 0.99). However, the single or integrated dose–response curves of these genes were distinctive from the conventional models obtained by the gamma-H2AX or comet assays. In comparison, rice displayed a higher dose-dependency in the comet signal and OsRAD51 transcription, while the gamma-H2AX induction was more dose-dependent in Arabidopsis. The dose-dependent transcriptions of the selected gamma-ray-inducible marker genes, including OsGRG, OsMutS, OsRAD51, and OsRPA1 in rice and AtGRG, AtPARP1, AtRAD51, and AtRPA1E in Arabidopsis, were maintained similarly at different vegetative stages. These results suggested that the transcriptome-based phytodosimetry model should be further corrected with conventional genotoxicity- or DDR-based models despite the high reliability or dose-dependency of the model. In addition, the relative weighting of each gene in the integrated transcriptome-based dose–response model using multiple genes needs to be considered based on the trend and amplitude of the transcriptional change.

Exponential decay: an approach to model nutrient uptake rates of macrophytes

One of the challenges of integrating phytoremediation into a waste treatment system is the sensitivity of plant species to fluctuations in environmental conditions and the difficulty in estimating subsequent changes to their rates of uptake. In this study, we examine a method using the exponential decay equation to approximate the median uptake rate (MUR) of nutrients for three aquatic macrophyte species, Salvinia molesta, Spirodela polyrhiza, and Lemna minor. These MUR values were then used to directly evaluate the phytoremediation performance between species and at varying levels of salinity stress. The results of this study indicate that an exponential decay relationship produced the most accurate models of the nutrient uptake profile for each species, with highest correlation values in 74.1% of tests for the three species at increasing salinity over a period of 14 d. S. polyrhiza and L. minor began to show significant reductions in nutrient uptake and growth at salinity concentration above 10 g/L. Using MUR, direct comparisons can be made between species in a time and mass-independent manner, allowing for the rapid assessment of phytoremediation performance under conditions of increasing salinity stress. Novelty statement In this study, we propose the use of an exponential decay model and the use of median uptake rate (MUR) obtained from the model coefficients as a method for directly comparing species performance under different conditions. Subsequently, we show how the use of MUR values obtained from three species of aquatic macrophytes allows for the direct comparison of species performance under increasing salinity stress. The method proposed in this study would improve the ability for easy comparison between species performance under varying environmental conditions. Future works could further build on the parameters proposed in this study and optimize the performance of phytoremediation systems developed for nutrient-affected wastewater management. This study is especially beneficial to phytoremediation researchers and environmental engineers who are implementing or designing macrophyte phytoremediation systems.

Laboratory investigations on wave attenuation characteristics of Rhizophora Mucronata poir using physical models with bottom friction

Species specific hydrodynamic characterization is essential for assessing the suitability of various types of mangroves in coastal protection as the dissipation of wave energy within the mangroves is governed primarily by various aspects which are specific to the species to which they belong. In the present study a specific mangrove species was selected and its wave attenuation characteristics were studied with the help of scaled physical models under controlled wave and vegetation conditions in a laboratory wave flume. The plant was initially identified as Rhizophora Mucronata and the scaled models prepared had the same biomechanical properties as that of the parent plant. Effect of root soil was incorporated in scaled models as bottom friction. Wave heights were measured after the forest models to evaluate the wave attenuation. It was found that wave heights were following the exponential decay equation of Kobayashi et al. (1993) except for the cases which have incorporated bottom friction. For such cases exponential decay equation was modified by incorporating a new parameter ‘d/D50’. Drag coefficients (CD), characteristic of the species were also determined without incorporating and with incorporating the effect of bottom friction of root soil. It is seen that drag coefficients are following an inverse relation with non-dimensional numbers (Re and KC). Empirical relations were developed between CD and a modified Keulegan Carpenter number (modified considering mangrove root submergence and mean particle size) for predicting the drag coefficients specific to Rhizophora Mucronata species for a variety of wave and water level conditions.

Effects of Ti Addition on Microstructure and Tribological Properties of In Situ Composite Carbide Coating WC-TiC/FeNi Fabricated by Plasma Transferred Arc Metallurgical Reaction

The effects of Ti addition on the microstructure and tribological properties of in situ composite carbide WC-TiC/FeNi coating were studied using XRD, SEM, EDS, and friction and dry sliding wear tests. The results show that the composite carbide WC-TiC was successfully in situ synthesized in the coating, and with Ti addition increased by 0.1 from 0.1 to 0.4 wt.%, the in situ carbide TiC increased from 3.4 to 24.4 vol.%, while the carbide WC decreased from 32.5 to 24.2 vol.%, and the coating hardness increased from 1027 to 1196 HV4.9. The friction and dry sliding wear tests show that for WC-TiC/FeNi composite coating, the addition of Ti can not only reduce the friction coefficient, the mass loss of both the coatings and its counterpart but also improve the friction stability, service life, and wear rate (WR). The relationship between the Ti addition and the coating wear rate fits the exponential decay equation WR = 10.6 − 0.089 $$\times$$ e (Ti/0.098). The main wear mechanisms of in situ WC-TiC/FeNi composite carbide coating are abrasive wear, oxidative wear, and micro-plow wear.

A Novel Method to Quantify Conditioner-to-Conditioner Variation and Predict Conditioner Lifetime and Process Failure Mode in Chemical Mechanical Planarization (CMP) Environment

In this study, we have developed a method to quantify inherent conditioner-to-conditioner variation using a mathematical model. Quantification of the lifetime of pad and conditioner in a chemical mechanical planarization (CMP) process using the model is also elucidated. Three conditioner types are selected based on their aggressiveness, and conditioning experiments are performed with five different conditioners of the same type to quantify the variation. Assuming exponential decay equation for pad wear rate (PWR), a simple model is developed and the model parameters, K and ${\lambda }$ , are derived in numeric form. K, a measure of conditioner aggressiveness, can be used as a metric to assess conditioner-to-conditioner variation, while ${\lambda }$ is a measure of conditioner lifetime. K and ${\lambda }$ values are also used to predict the failure mode of a CMP process (conditioner or pad failure mode). Pad groove depth and PWR curves of five different conditioners of the same type as a function of time are plotted along with upper and lower limits. The limiting factor (low PWR due to conditioner decay or excess pad removal) is identified to predict the failure mode. An example for each failure mode (A122 and 8031C1 conditioners for conditioner and pad failure modes, respectively) is presented.

Study on enthalpy relaxation of glassy polystyrene using Kohlrausch, Davidson-Cole and Havriliak-Negami distribution functions

The heat capacity data of PS after cooling at different rates were analyzed using heterogeneous kinetic model by combining exponential decay equation with various relaxation time distribution functions instead of the conventional method of combining the stretched relaxation function with Boltzmann superposition. It is found that the shape of the calculated heat capacity peak is highly correlated to the shape of the relaxation time distribution function. The fitting quality of the Davidson-Cole distribution function is worse compared with that of Kohlrausch distribution function. When the mirror functions of Kohlrausch and Davidson-Cole are used, the fitting quality improved greatly. The result indicates that relaxation kinetic of polymer may be described better by combining appropriate relaxation time spectrum with relaxation time model. This approach affords the possibility of taking the temperature and structure dependence of Kohlrausch exponent into consideration in the kinetic study of polymer in non-isothermal relaxations.