Actual Removal Research Articles

Optimising Nutrient Cycles to Improve Food Security in Smallholder Farming Families—A Case Study from Banana-Coffee-Based Farming in the Kagera Region, NW Tanzania

In East Africa, soil nutrient depletion and low yields jeopardise the food security of smallholder farming families and exacerbate poverty. The main reasons for the depletion of soil nutrients are overuse due to population growth, limited land, and increasing uncertainty in agricultural production caused by climate change. This study aims to analyse and optimise nutrient flows and stocks in the homegardens of smallholder banana-coffee-based farming systems in the Kagera region in NW Tanzania. The plant nutrients nitrogen (N), phosphorus (P), and potassium (K) in plant-based biomass and organic farm waste are under investigation. We used data from a farm household survey (150 households) and from focus group discussions with 22 trainers who had been training about 750 farm households in sustainable land management (SLM) at a local farmer field school. In total, we identified six farm household types and calculated a nutrient balance (NB) for the homegardens of each household type. The NB was calculated for the following five management scenarios: S0: business as usual; S1: the use of 80% of the available human urine; S2: the incorporation of 0.5 t yr−1 of the herbaceous legume species Crotalaria grahamiana into the soil; S3: the production of 5 m3 yr−1 CaSa-compost (human excreta and biochar) and its application on 600 m2 land; and S4: a combination of S1, S2, and S3. The results show that the NB varies considerably depending on whether farmers have implemented the SLM training, apply nutrient-preserving manure collection and storage methods, and purchase fodder (imported nutrients), or whether they do not collect manure or do not purchase fodder. Trained farm households are more likely to have a positive NB than untrained households because they have already improved the nutrient management of their farms through the successful implementation of SLM practices. Untrained households would improve the NB in their homegardens under all management scenarios. However, the NB depends on labour-intensive manure collection and compost production, labour shortages, prolonged dry seasons, and socio-economic imbalances. As long as these constraints remain, nutrient deficiencies will not be overcome with mineral fertilisers alone, because soils have to be further enriched with organic matter first. In this paper, we also emphasise the importance of the system boundary, because only a complete NB can give an estimate of actual nutrient removal and the resulting nutrient demand (including removals by fodder and trees). Further improvements in the SLM training may be achieved by (i) measuring the current nutrient status of soils, (ii) analysing the need for the coexistence of free-range livestock on the grassland and zero-grazing in trained households, and (iii) conducting an in-depth analysis of the socio-economic differences between successful and unsuccessful households. In conclusion, if smallholder farmers were to integrate further improved SLM training and optimised nutrient management (S1 to S4), we assume that the NB would turn positive. Last but not least, the SLM training by the farmer field school may serve as a best-practice example for training and policy recommendations made by government institutions.

Comparative Study Between Metronidazole Residues Disposal by Using Adsorption and Photodegradation Processes onto MgO Nanoparticles

The photodegradation and adsorption processes of metronidazole (MNZ) was conducted utilizing the batch reactor onto magnesium oxide nanoparticles (MgO NP) as the catalyst surface affected by UV radiation, initial concentration of MNZ, pH, catalyst loading, inorganic salts addition, time, and temperature. Chemical composition and morphological properties of the prepared MgO NP can also be portrayed by several techniques such as XRD, EDX, SEM, and TEM, while GC–MS analysis was used to monitor the photodegradation pathway for MNZ molecules. The results indicated that the actual removal of 93.2% of 80 mg/L MNZ present in 25 mL of a solution containing 0.1 mg/L of MgO NP could be distributed as 35.7% for maximum adsorption and 57.5% for degradation efficiency during 180 min. The degradation process is mainly of two steps; dark adsorption experiment, and photocatalytic degradation performance. Hence, Kinetic analyses indicate that adsorption constant estimated in dark conditions is smaller than the adsorption equilibrium constant derived from the Langmuir–Hinshelwood kinetic model through photodegradation of MNZ that follows pseudo-first-order kinetic. The adsorption isotherm result specified that the adsorption nature is chemisorption and fit Langmuir model, as well as thermodynamic results indicated that it is a nonspontaneous and endothermic reaction.

Adsorption of Cr (VI) onto Attapulgite/UiO-66-NH2 Composites from Aqueous Solution

A new attapulgite/UiO-66-NH2 composites adsorbent was prepared via solvothermal method and utilized to remove the Cr(VI) in the aqueous solution. The attapulgite/UiO-66-NH2 composites were detected by XRD, FTIR and SEM. The adsorption properties of the new adsorbent were investigated by batch experiments. The actual maximum removal efficiency was 96.31% at the optimal pH of 2 in 10 min, and the removal rate was directly proportional to the square of Cr ions concentration. Moreover, compared with UiO-66-NH2 and attapulgite, the attapulgite/UiO-66-NH2 composites adsorbent demonstrated an outstanding adsorption for Cr(VI). These results manifested that the attapulgite/UiO-66-NH2 composites were a latent adsorbent for the efficient removal of Cr(VI) in wastewater.

Broken words, furious wasps. How should we translate the sonic materiality of Araweté ritual singing?

In Araweté ritual singing, the performance of oporahẽ songs is an exercise in downplaying referential meaning without the actual removal of the sounds of the language. These songs are performed in a way that effectively break words into syllables, which are recombined to form unusual and “meaningless” words. Phrased differently, a good amount of these songs’ “meaning” is not in the things to which they are referring. By looking at the effect of this displacement of syllables in the performance and in the written rendering of the Araweté’s oporahẽ songs, this paper addresses the role of translation in anthropological practice when referential meaning is not easy to access. Following recent approaches in linguistic anthropology, the paper argues that an attention to the materiality of sound and voice in Araweté ritual singing provides a framework for understanding the performance and translation of songs in indigenous Amazonia.

Effects of Depth of Cutting on Damage Interferences during Double Scratching on Single Crystal SiC

In this work, the damage interference during scratching of single crystal silicon carbide (SiC) by two cone-shaped diamond grits was experimentally investigated and numerically analyzed by coupling the finite element method (FEM) and smoothed particle hydrodynamics (SPH), to reveal the interference mechanisms during the micron-scale removal of SiC at variable Z-axis spacing along the depth of cutting (DOC) direction. The simulation results were well verified by the scratching experiments. The damage interference mechanism of SiC during double scratching at micron-scale was found to be closely related to the material removal modes, and can be basically divided into three stages at different DOCs: combined interference of plastic and brittle removal in the case of less than 5 µm, interference of cracks propagation when DOC was increased to 5 µm, and weakened interference stage during the fracture of SiC in the case of greater than 5 µm. Hence, DOC was found to play a determinant role in the damage interference of scratched SiC by influencing the material removal mode. When SiC was removed in a combined brittle-plastic mode, the damage interference occurred mainly along the DOC direction; when SiC was removed in a brittle manner, the interference was mainly along the width of cutting; and more importantly, once the fragment of SiC was initiated, the interference was weakened and the effect on the actual material removal depth also reduces. Results obtained in this work are believed to have essential implications for the optimization of SiC wafer planarization process that is becoming increasingly important for the fabrication of modern electronic devices.

Effect of Missing Vines on Total Leaf Area Determined by NDVI Calculated from Sentinel Satellite Data: Progressive Vine Removal Experiments

Remote Sensing (RS) allows the estimation of some important vineyard parameters. There are several platforms for obtaining RS information. In this context, Sentinel satellites are a valuable tool for RS since they provide free and regular images of the earth’s surface. However, several problems regarding the low-resolution of the imagery arise when using this technology, such as handling mixed pixels that include vegetation, soil and shadows. Under this condition, the Normalized Difference Vegetation Index (NDVI) value in a particular pixel is an indicator of the amount of vegetation (canopy area) rather than the NDVI from the canopy (as a vigour expression), but its reliability varies depending on several factors, such as the presence of mixed pixels or the effect of missing vines (a vineyard, once established, generally loses grapevines each year due to diseases, abiotic stress, etc.). In this study, a vine removal simulation (greenhouse experiment) and an actual vine removal (field experiment) were carried out. In the field experiment, the position of the Sentinel-2 pixels was marked using high-precision GPS. Controlled removal of vines from a block of cv. Cabernet Sauvignon was done in four steps. The removal of the vines was done during the summer of 2019, matching with the start of the maximum vegetative growth. The Total Leaf Area (TLA) of each pixel was calculated using destructive field measurements. The operations were planned to have two satellite images available between each removal step. As a result, a strong linear relationship (R2 = 0.986 and R2 = 0.72) was obtained between the TLA and NDVI reductions, which quantitatively indicates the effect of the missing vines on the NDVI values.

In situ nitrogen removal processes in intertidal wetlands of the Yangtze Estuary

Estuarine and intertidal wetlands are important sites for nitrogen transformation and elimination. However, the factors controlling nitrogen removal processes remain largely uncertain in the highly dynamic environments. In this study, continuous-flow experiment combined with 15N isotope pairing technique was used to investigate in situ rates of denitrification and anaerobic ammonium oxidation (anammox) and their coupling with nitrification in intertidal wetlands of the Yangtze Estuary. The measured rates varied from below the detection limit to 152.39 µmol N/(m2·hr) for denitrification and from below the detection limit to 43.06 µmol N/(m2·hr) for anammox. The coupling links of nitrogen removal processes with nitrification were mainly dependent on nitrate, organic carbon, sulfide, dissolved oxygen and ferric iron in the estuarine and intertidal wetlands. Additionally, it was estimated that the actual nitrogen removal processes annually removed approximately 5% of the terrigenous inorganic nitrogen discharged into the Yangtze Estuary. This study gives new insights into nitrogen transformation and fate in the estuarine and intertidal wetlands.

Effects of tree retention and woody biomass removal on bird and small mammal communities

Contemporary forest management is increasingly focused on maintaining ecosystem function and services including biodiversity conservation. As a result, harvest guidelines related to retention of live trees and woody biomass (fine and coarse residue arising from harvesting) have been developed to provide benefits for wildlife, but there is much uncertainty on the effectiveness of these guidelines depending on stage of succession, retention levels, and focal taxa. We used an operational-scale, fully replicated factorial experiment to determine the effects of both tree retention (none, dispersed, aggregated) and woody residue harvesting (no removal, 20% retention, all removed) on breeding bird and small mammal communities in aspen forests 7–8 years after harvest. Bird community metric responses showed a clear and consistent positive response to tree retention; both tree retention configurations resulted in higher total abundance, increased diversity, and higher species richness compared to stands with no tree retention. There was no difference in community metrics between the retention configurations and no evidence that early successional species were negatively affected by tree retention. Total abundance of small mammals was lower in clear-cuts compared to tree retention treatments; moreover, clear-cut stands had lower species diversity compared to stands with the aggregated tree retention. There were limited effects of biomass harvest treatments on small mammal communities, likely because actual biomass removal was much lower than experimental targets. Overall, our results provide conclusive evidence on the continued benefits of tree retention on wildlife communities se0ven and eight years post-harvest in regenerating aspen forests.

A simple kinetic model applied to anaerobic digestion of cow manure

ABSTRACT A simple model of anaerobic degradation in a continuous stirred digester is presented. The hydrolysis of cow manure was modelled as consisting of two fractions, one rapidly degradable and the other more slowly degradable, and both processes were represented by first-order kinetics in a two-substrate first-order (TSFO) model. The fractions were separated by water flushing. Biomethane potential (BMP) tests were performed to determine the hydrolysis constant and biodegradability of each fraction. The hydrolysis constants of the rapidly and slowly degradable fractions were 0.278 and 0.069 d−1, respectively. Coupled with a simple anaerobic digestion model, the TSFO model was used to simulate the digester behaviour and predict methane production. Experiments in a 3.0 L digester were used to determine the decay constant and yield values and to validate the model. Two solid loads (2.9 and 4.4 gVS/L.d) were applied to the digester, and the dynamics of both biodegradable fractions, the non-biodegradable fraction and the microorganism concentration were reproduced by the model. These results approximate the actual biodegradable solids removal to within 85%. A parametric sensitivity study was performed, and the results show that the hydrolysis constant mainly influences the biodegradable fractions and that the decay and yield parameters mainly influence the microorganism concentration.

Experimental and Numerical Study of Crater Volume in Wire Electrical Discharge Machining.

Wire Electrical Discharge Machining (WEDM) is a popular non-conventional machining technology widely used in high-added value sectors such as aerospace, biomedicine, and the automotive industry. Even though the technology is now ready to meet the requirements of the most complex components, certain fundamental aspects related to the discharge process and gap conditions are not yet fully explained and understood. Combining single discharge experiments with numerical simulation represents a good approach for obtaining a deeper insight into the fundamentals of the process. In this paper, a fundamental study of the WEDM through single discharge experiments and numerical simulation is presented. WEDM single discharge experiments are described with the aim of identifying the relation between crater dimensions, discharge gap, and part surface roughness. A thermal transient numerical model of the WEDM process is presented, and correlation with actual industrial material removal rates (MRR) is analyzed. Results from single discharge WEDM experiments show that crater volume is as much as 40% lower when discharging on a rough surface than when the discharge occurs on a flat surface. The proposed thermal numerical model can predict actual removal rates of industrial machines with great accuracy for roughing cuts, deviations with experimental values being below 10%. However, lager deviations have been observed for other WEDM conditions, namely trim cuts, thus confirming the need for future research in this direction.

A Study of Influence of Servo-Control Strategy on Machining Efficiency in Micro-EDM

Micro-electrical discharge machining (micro-EDM) is a non-contact manufacturing technology that is based upon the erosion effect of a spark. It is a significant method for machining hard-to-cut materials and fabricating micro-scale structures. However, the traditional servo-control strategy, which is widely used in micro-EDM, tends to make the process unstable due to the tiny pulse discharge energy, high pulse discharge frequency, and complex discharge state. As a result, the effective discharge ratio and processing efficiency are low, which increases the cost and so limits the application of this technology. To solve this problem, a simulation model is established in this paper to analyze the negative influence on machining efficiency by traditional servo-control strategy. Then, a self-adaptive servo-control strategy is proposed to adjust the feed speed to match up with the actual material removal rate. Simulation and experimental studies are undertaken to verify the effectiveness and validity of the proposed strategy. The results demonstrate that feed speed can converge gradually under the self-adaptive servo-control strategy and the effective discharge ratio and processing efficiency are significantly improved.

Cryogel-based Ag°/Ag2O nanocomposites for iodide removal from water

In this study novel silver-modified cryogels were synthesized and applied for the removal of iodide from aqueous solutions. The co-allylamine-methacrylic acid-DMAAm-BisAAm (AAC) and co-allylamine-2-acrylamido-2-methyl-1-propansulfonic acid-DMAAm-BisAAm (SAC) cryogels were decorated with silver by one-step ion-exchange technique and characterized by TEM/EDS, SEM/EDS, FT-IR, XRD and zeta potential measurements. The silver loading was up to 159 and 98 mg/g for AAC and SAC cryogel nanocomposites, respectively. The silver is found in the structure of cryogels in the form of Ag2O and Ag° nanoparticles and the formation of metallic silver is attributed to in situ reduction of silver by the functional groups of the cryogels. The nanocomposites showed rapid kinetics and high adsorption capacity towards iodide. The equilibrium studies showed that in some samples the removal of iodide is higher than the theoretically expected based on the Ag:I molar ratio of 1:1. The analysis of the surface of the cryogels confirmed the theoretical Ag:I molar ratio and a study of the solution phase revealed that small amounts of leached Ag+ from the cryogels resulted in the formation of AgI colloids which, under the conditions of the experiments, exhibit Ag:I molar ratios lower than the theoretical value explaining the discrepancies between the theoretical and actual iodide removal rates.

Removal of MS‐2 coliphage in full‐scale reverse osmosis systems

AbstractRecent activity in the potable reuse field will incorporate reverse osmosis (RO) processes that will be required to provide pathogen removal. The California State Water Resources Control Board has implemented a 12‐10‐10 log removal value (LRV) requirement for viruses, Giardia, and Cryptosporidium for groundwater recharge projects. Depending on the details of a Surface Water Source Augmentation Project, new regulations in 2018 specify an additional log reduction requirement up to a total of 14‐12‐12. Regulatory requirements that specify a treatment technique (e.g., RO) and establish log removal requirements for treatment trains are being implemented. Surrogate indicators such as electrical conductivity (EC) and total organic carbon (TOC) reduction are currently being used as online indicators to determine compliance of RO systems. The actual virus removal through a full‐scale operating system is something that has not been extensively characterized. Most of the information that exists for testing with viruses is associated with bench‐ or pilot‐scale evaluations. Evaluations of permeate from full‐scale RO systems operating with wastewater effluent as the source water indicate that viruses are not present; however, concerns remain about the potential loss of integrity through the RO system. Under the regulatory criteria established in the US Environmental Protection Agency Membrane Filtration Guidance Manual for drinking water, bulk surrogate indicators such as EC or TOC lack the sensitivity to accurately measure the actual log reduction for pathogens. It is generally recognized that the feed water quality matrix can be variable in composition, which can also affect the measurement. Bulk surrogate indicators do not satisfy the criteria for being discretely quantifiable, a term that is synonymous with the indicator having a specific molecular weight or defined composition. While alternative chemical markers such as fluorescence compounds, sulfate, or strontium yield higher LRVs, the methods are not easily implemented. An underlying issue with these indicators is that, because of their small size, they will also diffuse through the membrane and understate the pathogen removal that is occurring. An article presented in Journal AWWA proposes that the results of a conductivity profile can be used to increase the sensitivity and calculate a higher LRV. Using the dilution model as the underlying approach, the technique differentiates conductivity that would be associated with diffusion from conductivity that would be associated with a defect. Literature review of prior work with MS‐2 challenge studies has been limited to small‐scale pilot evaluations. Information regarding the removal of MS‐2 coliphage in a typical production system was not present in literature. Conceptually, there should be no difference in MS‐2 removal between a pilot‐ and a full‐scale system; however, loss of rejection due to membrane aging may be a consideration. This article provides the challenge test results of MS‐2 bacteriophage (virus) through a full‐scale RO train operating in a water recycling facility. Challenge testing was performed at various operating conditions and includes the conductivity profiling results to characterize removal under integral, as well as intentionally compromised, conditions.

774. A New Outpatient Parenteral Antimicrobial Therapy (OPAT) Management Program Reduces Excess Antimicrobial Days of Therapy and Expedites Timely Central Line Removal

BackgroundPatients discharged on parenteral antimicrobials often require in-person follow-up to determine antimicrobial discontinuation and coordination of central line (CL) removal at the end of therapy. Without close attention to timing of follow-up, antimicrobial courses may be extended beyond a planned end date until scheduled follow-up, leading to excess antimicrobial days of therapy (DOT) and CL retention. Excess DOT can result in increased cost of medication and CL supplies, antimicrobial exposure, and risk of CL-associated bloodstream infections or thrombosis. We sought to assess the impact of the University of Virginia (UVA) OPAT program on excess antimicrobial DOT and excess CL days.MethodsThis was a retrospective chart review of patients enrolled in the OPAT program at UVA between August 2018 and April 2019. The UVA OPAT program was started in August 2018. Quality improvement (QI) practice changes were implemented in February 2019 for improving follow-up and stopping antimicrobials at the projected end date. Patients were therefore divided into 2 cohorts – August through January 2018 and February through April 2019. Data collected included projected end date of therapy (EOT), actual EOT, actual removal date of CL, and follow-up date. Excess antimicrobial DOT and excess CL days were calculated by the difference in projected vs. actual dates. For continuous data, Student t-test was used.Results248 patients enrolled in OPAT from August 2018 through April 2019. After implementation of QI efforts, mean time from projected EOT to follow-up appointment decreased from 10.0 days to 4.3 days for those with appointments after projected EOT. Mean excess antimicrobial DOT decreased from 2.8 ± 4.53 SD days to 1.6 ± 2.75 SD days (P = 0.026), and mean excess CL days decreased from 3.2 ± 4.63 SD days to 2.0 ± 2.89 SD days (P = 0.035).ConclusionThe involvement of an OPAT program with close attention to outpatient follow-up and cessation of antimicrobials decreased the excess antimicrobial DOT and CL days and reduced variability in care. Reduction in antimicrobial overuse and CL overuse is expected to reduce cost and decrease the risk of medication- and CL-related collateral damage.Disclosures All authors: No reported disclosures.

Optimal port call adjustment for liner container shipping routes

Container shipping companies usually alter their shipping networks in response to the seasonally changing shipping demand and freight rate. Rather than redesigning their shipping networks from scratch, they often choose to make small adjustments to the shipping routes by skipping some ports or adding additional calls to several ports. Inspired by above industrial practice in shipping network alteration, this study solves the port call adjustment problem (PCAP) to determine which port calls should be removed and which should be inserted for each route of a shipping network under the new shipping market patterns. A two-phase solution method is developed for the PCAP. In Phase 1, the candidate port calls for removal and insertion operations in each shipping route are determined. In Phase 2, the port call adjustment strategy is obtained by solving a mixed integer linear programming (MILP) model to select the port calls from these candidates identified in Phase 1 for actual removal and insertion operations. Considering the difficulties in solving the MILP model efficiently, two heuristic methods are also proposed to give near-optimal solutions in an acceptable computational time. Numerical experiments demonstrate that the proposed two-phase method is able to find a port call adjustment strategy that significantly reduces the operating cost.

On the effect of grain structure in micro-cutting of polycrystalline aluminate magnesium spinel (PAMS) crystals

This paper studies the anisotropic effect induced by the grain structure of polycrystalline aluminate magnesium spinel (PAMS) on the mechanism of surface generation in the micro-cutting process. The critical depth of cut for ductile–brittle transition (DBT) of PAMS is estimated from 81 to 163 nm by plunge-cutting tests. In the cutting tests with constant cutting depths from 250 nm to 1.5 µm, an apparent regional distribution of crack features is clearly observed and it implies that the randomly oriented crystal grains with different slip systems play an important role in brittle-regime surface generation and fractures evolution. An effective way to obtain a ductile-regime machined surface is to decrease the cutting depth to 50 nm, and a flawless surface can be obtained when the cutting depth is as shallow as 30 nm. With such a low cutting depth, the material is mainly removed by the ploughing effect. Finite element method (FEM) model has been developed to simulate the cutting process crossing a grain boundary of two adjacent grains with different anisotropy material properties. The simulation result supports that the subsurface damage and boundary fractures can be evoked ahead of the actual material removal process by the cutting stress propagating from the precedingly machined grain. Different crack-patterns are shown on the finished surfaces of the two adjacent grains of different orientations.

Comparison of Laser Milling Performance against Difficult-To-Cut Alloys: Parametric Significance, Modeling and Optimization for Targeted Material Removal.

During laser milling, the objective is not always to maximize the material removal rate (MRR). Milling of new material with targeted MRR is challenging without prior knowledge and established sets of laser parameters. The laser milling performance has been evaluated for three important aerospace alloys, i.e., titanium alloy, nickel alloy and aluminum alloy using the response surface method experimental plan (54 experiments for each alloy). Parametric effects of five important laser parameters, statistical analysis (main effects, interaction effects, strength and direction of effects), mathematical modeling and optimality search is conducted for the said alloys. Under the non-optimized laser parameters, the actual MRR significantly varies from the targeted MRR. Variation in the aluminum alloy is at the top as compared to the other two alloys. Among other significant terms, three terms have the largest effect on MRR in the case of TiA, two terms in the case of NiA, and five terms in the case of AlA. Under the optimized sets of laser parameters, the actual material removal highly close to the desired level (100%) can be achieved with minimum variation in all the three alloys. Mathematical models proposed here have the capability to well predict material removal prior to the actual machining of Ti6Al4V, Inconel 718 and AA 2024.

Controlling the material removal and roughness of Inconel 718 in laser machining

ABSTRACTNickel alloys including Inconel 718 are considered as challenging materials for machining. Laser beam machining could be a promising choice to deal with such materials for simple to complex machining features. The machining accuracy is mainly dependent on the rate of material removal per laser scan. Because of the involvement of many laser parameters and complexity of the machining mechanism it is not always simple to achieve machining with desired accuracy. Actual machining depth extremely varies from very low to aggressively high values with reference to the designed depth. Thus, a research is needed to be carried out to control the process parameters to get actual material removal rate (MRRact) equals to the theoretical material removal rate (MRRth) with minimum surface roughness (SR) of the machined surfaces. In this study, five important laser parameters have been used to investigate their effects on MRR and SR. Statistical analysis are performed to identify the significant parameters with their strength of effects. Mathematical models have been developed and validated to predict the machining responses. Optimal set of laser parameters have also been proposed and confirmed to achieve the actual MRR close to the designed MRR (MRR% = 100.1%) with minimum surface roughness (Ra = 2.67 µm).

Scratching-induced surface characteristics and material removal mechanisms in rotary ultrasonic surface machining of CFRP

Rotary ultrasonic machining has been successfully explored in surface machining of carbon fiber reinforced plastic (CFRP) composites. It has been proven to be an effective and efficient CFRP machining method. Both theoretical and experimental investigations have been conducted with the assumption that the CFRP is removed by brittle fracture removal mode. However, in brittle material machining, ductile flow phenomenon still exists. Ductile scratching marks are also observed on the machined CFRP surfaces. It is still unknown that what actual material removal modes are under different machining variables. To investigate the material removal mechanisms in rotary ultrasonic surface machining (RUSM) of CFRP, single abrasive scratching tests were conducted. The scratching induced characteristics and scratching forces were analyzed. Both the ductile removal mode and the brittle fracture removal mode were observed and identified in both carbon fiber layers and epoxy resin layers on the machined marks by using scanning electron microscopy (SEM) imaging. With the increase of scratching depth, the material removal mode of CFRP was changed from the ductile removal mode to the brittle fracture mode. From the analysis of kinematic trajectory of diamond grain, the scratching cutting forces were decreased in the tests with the assistance of ultrasonic vibration under the same machining variables. The generation mechanisms of the delamination were analyzed and discussed.

Effects of reaction conditions and liquid property on degradation of phenol by RGO/α-FeOOH supported on Al-MCM catalyst in heterogeneous photo-Fenton system

This study focused on investigating the effect of reaction conditions (catalyst and H2O2 dosage, light source under different pH) and liquid property on degradation of phenol over RGO/α-FeOOH supported on Al-MCM catalyst in heterogeneous photo-Fenton system. Batch experiments were conducted under specific operating conditions. It was found that with the increase of catalyst and H2O2 dosage, the phenol and COD removal efficiency went up to reach a maximum (at Cata/H2O2 mass ratio was 1.471) and then decreased. The reactions all fitted pseudo first order model. The phenol were degraded apparently by RGO/α-FeOOH-Al-MCM catalyst at different light source irradition or not when pHs ranged from 4.0 to 8.0. The solar irradiation not only dramatically accelerated the rate of Fenton-based reactions, but also extended the operating pH for the Fenton reaction (from 4.0 to 8.0). Higher initial phenol concentrations inhibited the rate of phenol degradation although actual phenol removal amount increased, which may be due to the fact that more intermediates produced at higher phenol concentration competed with phenol for the active sites. The addition of anions (Cl−, SO42−, NO3−, HCO3−, HPO42−), small molecule organic acids (CA, OA, TA) and natural organic matter (HA, FA) caused inhibition effect on phenol degradation.