Optimal Density Research Articles

Experimental Studyof M20 Grade Concrete Using Packing Density Method

Packingdensitymethodof mixdesign of concreteisnewmethodtodesigndifferent types of concrete. The mix design obtained from the packing density method hassuitableworkability,maximumpackingdensityandminimumvoidsratio.Thegeometrical characteristics like shape, size and proportion of fine aggregate and coarseaggregate affect packing density. The objective of this research is to study the mix designof concrete using packing density method anddevelop thecorrelation between bulkdensity, packing density and voids ratio. In this work large number of trail to decide theproportion of aggregate for that optimum bulk density and packing density calculated fordifferentvaryingproportionof20mm:12.5mmcoarseaggregate(i.e.90:10,80:20,70:30,65:35,60:40and50:50)andforvaryingproportioncoarse aggregate:fine aggregate (i.e. 90:10, 80:20, 70:30, 60:40, 55:45 and50:50). To finalize the mix designusing packing density method also varies the percentage of excess cement paste (i.e. 5%,7%, 9%, 10%, 11% and 12%). Tests were performed for the properties of fresh concretelike workability test (Slump cone) and hardened concrete like compressive strength, split-tensilestrength,pull-outtest,reboundhammerandflexuralTestetc.testsweredetermined at 7, 14 and 28 days. The obtained results for above mentioned test usingpackingdensitymethodat9%ofexcesscementpastearesatisfyingthestandardresults.

A bioinspired water oxidation catalyst that is ∼1/10th as active as the photosystem II oxygen evolving center at pH 7: a study of activity and stability factors.

The activity and stability of a heterogeneous water oxidation catalyst inspired by the Photosystem II - Oxygen Evolving Center (PSII-OEC) is reported. Ca-doped birnessite MnOx supported on a liquid crystalline reduced graphene oxide (LCrGO) substrate exhibited unprecedented performance for an abiological catalyst at pH 7, including an exceedingly low onset overpotential of 0.52 V (vs. 0.48 V reported for the PSII-OEC, 0.75 V for Pt, and 0.72 V for birnesite MnOx) and remarkably high activity per unit area at 0.56 V overpotential (∼10% that of a hypothetical, closely-packed monolayer of OEC sites at their optimum density of 1014 sites per cm2).

Effects Density and Salinity of Artificial Brackish Water on the Growth and Physiological Perfomance of Whiteleg Shrimp (Litopenaeus vannamei Boone, 1931)

The increase in shrimp culture causes problems with the quality of seawater which is a source of water for whiteleg shrimp culture it self. The use of artificial brackish water as a culture medium is an effort to increase the availability of water sources for whiteleg shrimp culture. This study aims to (1) determine the optimum stocking density of whiteleg shrimp culture using artificial brackish water salinity based on carrying capacity, (2) determine mineral content (Mg, Ca, Na and K) in artificial brackish water, (3) study the effect of salinity on the growth and blood glucose concentration of whiteleg shrimp cultivated in artificial brackish water, (4) examine the effect of salinity on hemolymph osmolarity of whiteleg shrimp cultivated in artificial brackish water. This study used an experimental method consisting of two stages. Each stage was arranged using a completely randomized design (CRD). Obtained stocking densities of SD-50% (20 shrimps/50L), SD (40 shrimps/50L) and SD+50% (60 shrimps/50L). The best growth and performance were obtained in the treatment of 20 individuals, namely survival (SR) 87%, specific growth rate (SGR) 3.26%/day and hemolymph glucose concentration of 30.73 mg/dl. In the next stage of the research, the salinity treatments tested were seawater, 10 ppt, 15 ppt, 20 ppt and 25 ppt. The best shrimp performance was obtained in treatment 20 shrimps/50 L, namely survival rate 70.00%, specific growth rate (SGR) 1.55%/day, feed conversion ratio (FCR) 1.72, glucose haemolymp 73.44 mg/dl. The optimal osmotic work level (OWL) value is obtained at a salinity of 15-20 ppt.

Application of Ultrasonic Methods in Super POD Thickness Measurement Examination

NDT is a scientific field of engineering that includes testing and inspection of materials and equipment which is useful for evaluating a condition, finding deficiencies and defects, and also extending the useful life of the infrastructure used. The main difference between non-destructive testing and other forms of material evaluation is that non-destructive testing allows evaluation or inspection of parts on site without having to permanently modify or damage the part. In maintaining the credibility of the company's services, the company adopting NDT/NDE testing techniques in carrying out regular inspections or checks on the tools used, one of which is the application of the ultrasonic method on the Super POD (Programmable Optimum Density). Based on this background, the author chose the theme of the study to write a scientific paper entitled “Application of Ultrasonic Methods in Super POD Thickness Measurement Examination”. The SBF-624 Super POD (programmable optimum density, POD) is a trailer-mounted fracturing service blender that can blend and pump up to 120 barrels per minute of fracturing slurry. The Super POD computers precisely control the solid-to-liquid ratio of the prop pant at design values in either ramp or stair-step mode. The results of observations of objects that have been inspected using the ultrasonic method, namely measuring the thickness of the Super POD SBF 624, from the good results without any defects being detected, and cleaned in surface condition so it can be said that the machine has shown good effective results and can meet the standards for using tools for the company.

General Properties of Commingled Materials for Mix Designs

Tailings volumes continue to collectively increase worldwide, leading to larger dams and tailings management facilities. With numerous high-profile dam failures in the past decade, the risks of these management practices are also growing. A potential shift to waste management practices at mineral mines is to commingle waste rock and dewatered tailings. This blended material should have superior physical strength properties provided by the waste rock together with improved chemical stability characteristics associated with the low permeability of the tailings. Ideally, commingled tailings and waste rock can be used to construct various mined earth landforms that are both physically and chemically stable, which will enhance operational performance and ultimately provide for the sustainable decommissioning and closure of the mining facility. To study these materials, the University of Alberta Geotechnical Centre is working with global industry partners to test commingled materials from several mine sites with varying ore and host rock types and climate regimes. The first stage of this study is described here and is focused on the optimum density, saturated hydraulic conductivity, and soil–water characteristic curves of various blend ratios, performed at laboratory scale.

Enhanced energy storage performance in Na(Nb,Ta)O3-doped Ba(Ti,Ca)O3-based ceramics through bidirectional optimization strategy

(1-x)(0.9Ba1.003Ti0.97Ca0.03O3–0.1(Bi0.51Na0.47)0.94Ba0.06TiO3)-xNa(Nb0.85Ta0.15)O3 (x = 0.03–0.15) ceramics were designed and fabricated through a bidirectional optimization strategy using traditional solid reaction method. The results revealed that the introduction of Na(Nb0.85Ta0.15)O3 increased the vacancy concentration at the A site, conducing to improved polarization and reduced grain size. The substitution at the B site disrupted the long-range ordered ferroelectric domains and generated polar nanodomains, leading to enhanced relaxation behavior. The optimum energy storage density of 3.57 J/cm3 and efficiency of 87.5% were simultaneously achieved under the electric field of 220 kV/cm in the sample with x = 0.09. Moreover, it also exhibits extremely high-power density (∼57 MW/cm3), ultrafast discharge time (∼103 ns), high discharge density (1.35 J/cm3), along with excellent temperature (30‒120 °C) and frequency stability (1‒100 Hz) under the equivalent electric field of 120 kV/cm. This novel design strategy provides theoretical guidance for the development of advanced electrical energy storage devices.

Electrochemical Polymerization of a Novel Thiophene-Derived Monomer and Its Use as Support Material for Methanol Oxidation

This research, conductive polymer supported modified electrode system which was prepared for usage in direct methanol fuel cells. To test the behavior of these electrode system for methanol oxidation, cyclic voltammetry (CV), chronoamperometry (CHR) and electrochemical impedance spectroscopy (EIS) methods were used as electrochemical methods. As the working electrode, pencil graphite electrode (PGE) was preferred because of its porous structure, good ion conductivity, practicality in application and ease of preparation and obtaining. Thiophene derivative 4,4')-2,2'-(diazen-1,2 diylbis(4,1 phenylene))bis(4 (thiophene-2-ylmethylene) oxazol-5(4H)-one), (DiAzBiPhBiTyOx) monomer was prepared and electrochemically polymerized by CV method in 0.01M TBAP and 0.05 HClO4 containing ACN solution on the surfaces of PGE. The spectroscopic characterization of the synthesized monomer was performed by NMR spectroscopy. Optimum polymerization conditions of monomer was determined according to scanning rate, potential range and acid density. The obtained modified electrode system (PGE/PDiAzBiPhBiTyOx) was doped with chloroplatinic acid hexahydrat-Pt2Cl6.6H2O (Pt) at different densities and the optimum catalyst density was determined as 3.25mM (PGE/3.25mMPt@PDiAzBiPhBiTyOx). The methanol oxidation performances of conductive polymer film, platinum and conductive polymer supported platinum catalyst systems were investigated separately. While the methanol oxidation responses of the conductive polymer film and platinum are almost similar, the methanol oxidation response of the platinum doped conductive polymer film catalyst system is higher. The modified electrode characterization was performed by CV, CHR and EIS methods. Furtheremore obtained modified electrode systems were characterized by FESEM/EDS, XRD to confirm the structures and morphologies. Also, the theoretical values such as electrochemical surface area (ECSA) and specific capacitance (Cs) were calculated in aqueous acidic solution with and without methanol. Cs values of the PGE/3.25mMPt@PDiAzBiPhBiTyOx electrode in aqueous acidic solution with and without methanol were 3.861 and 3x10-4Fg-1 respectively. Also, the electrochemical surface area values of the same electrode in aqueous acidic solution with and without methanol were 196.437 and 21.150m2g-1 respectively.

The effects of stocking density on growth, morphological development, behavior, and welfare parameters in pheasants (Phasianus colchicus).

In pheasants, which are generally raised in large flocks, stocking density is important for their growth and development, normal behavior and welfare. But there is still a lack of information on the optimum stocking density for game birds. This research was conducted on a total of 200 pheasants to examine the effects of low (5 pheasant/m2) and high (10 pheasant/m2) stocking density rearing practices on body weight, morphological development, behavioral characteristics and welfare parameters such as foot-pad dermatitis and plumage quality. When we look at the study results, it was determined that the density of stocking did not make a difference in the first 13 weeks of age, but pheasants reared at low density at the ages of 14-16 weeks reached higher body weight. In terms of body weight at 14, 15, and 16 weeks, the low stocking density group had an average of approximately 41, 71, and 94 g higher than the high stocking density group, respectively (p<0.05). It had been found that low density provides better morphological development. The low group was found to be significantly higher than the high group in terms of ornithological size, wingspan, back length, tail length, head length and head width, 5.9 cm, 2 cm, 1.3 cm, 7.6 cm, 1.7 mm and 1 mm, respectively (p<0.05). Since the animals in the low group had more individual space, they had the opportunity to perch and therefore exhibit more passive behavior. On the other hand, pheasants in the low group exhibited higher levels of aggressive behavior (p<0.05). More foraging behavior was observed in the higher group and the low-density group consumed more feed in the 14th week (p<0.05). But no significant differences were detected between groups in terms of feed consumption in other weeks (p>0.05). A 1.12 point higher score was calculated in the low group compared to the high group, especially in terms of tail feather quality, and as a result, pheasants reared in low stocking density had better plumage quality (p<0.05). It had been determined that as the stocking density decreases in the rearing of pheasants, they exhibit easier flight and roosting behaviors and therefore they were less affected by feather pecking behavior and had better feather quality. In addition, it had been determined that pheasants grow and develop better in this group, which had more rest opportunities. In conclusion, rearing at low stocking density is recommended for better fattening performance and better welfare conditions.

Characterization of runs of Homozygosity revealed genomic inbreeding and patterns of selection in indigenous sahiwal cattle.

Runs of homozygosity (ROH) are contiguous genomic regions, homozygous across all sites which arise in an individual due to the parents transmitting identical haplotypes to their offspring. The genetic improvement program of Sahiwal cattle after decades of selection needs re-assessment of breeding strategy and population phenomena. Hence, the present study was carried out to optimize input parameters in PLINK for ROH estimates, to explore ROH islands and assessment of pedigree and genome-based inbreeding in Sahiwal cattle. The sliding window approach with parameters standardized to define ROH for the specific population under study was used for the identification of runs. The optimum maximum gap, density, window-snp and window-threshold were 250Kb, 120Kb/SNP, 10, 0.05 respectively and ROH patterns were also characterized. ROH islands were defined as the short homozygous genomic regions shared by a large proportion of individuals in a population, containing significantly higher occurrences of ROH than the population specific threshold level. These were identified using the -homozyg-group function of the PLINK v1.9 program. Our results indicated that the Islands of ROH harbor a few candidate genes, ACAD11, RFX4, BANP, UBA5 that are associated with major economic traits. The average FPED (Pedigree based inbreeding coefficient), FROH (Genomic inbreeding coefficient), FHOM (Inbreeding estimated as the ratio of observed and expected homozygous genotypes), FGRM (Inbreeding estimated on genomic relationship method) and FGRM0.5 (Inbreeding estimated from the diagonal of a GRM with allele frequencies near to 0.5) were 0.009, 0.091, 0.035, -0.104 and -0.009, respectively. Our study revealed the optimum parameter setting in PLINK viz. maximal gaps between two SNPs, minimal density of SNPs in a segment (in kb/SNP) and scanning window size to identify ROH segments, which will enable ROH estimation more efficient and comparable across various SNP genotyping-based studies. The result further emphasized the significant role of genomics in unraveling population diversity, selection signatures and inbreeding in the ongoing Sahiwal breed improvement programs.

Ultrahigh sensitive SERS film of silver nanorods grown on nanohole array template by oblique angle deposition

To develop a highly sensitive silver nanorod (AgNR) array SERS film, anodic aluminum oxide (AAO) nanohole array templates were employed as seed substrates for oblique angle deposition (O.A.D.) by thermal evaporation. By pore broadening process, precise hole arrays of various diameters were fabricated from preliminarily prepared nanoholes of 30 nm diameter comprising equilateral triangle unit cells whose side length is 100 nm. Aligned silver nanorods of ∼1 μm length were fabricated on the several kinds of seed templates. The optical properties of the AgNR films were measured using thiophenol self-assembled monolayers on the film surfaces and a micro-Raman spectrometer employing a 785 nm pump laser. Out of the AgNR array samples, the AgNR array deposited on an 80-nm hole array substrate showed the highest SERS activity. The highest surface enhancement factor (E.F.) of Raman signal measured in this experiment was ∼7·107, which is ∼7 times higher than that of the AgNR array fabricated on a flat substrate. The main role of the nanopore array substrate was found to decrease the density of the grown nanorods, which is the key parameter determining the E.F. values of the AgNR arrays. From this and previous works, the optimum nanorod density is anticipated to be 8–9 rods/μm2, where E.F. of > 109 could be obtained. The nanorod density of the optimum AgNR array in this experiment was ∼10/μm2. The origin of the key role conducted by the nanorod density cannot be explained by hot spot effect and waits for understanding in the future studies. The ultrahigh sensitive AgNR array SERS film obtained in this work can be a very powerful medium for various chemical and biological sensors.

Optimizing sludge dewatering efficiency with ultrasonic Treatment: Insights into Parameters, Effects, and microstructural changes

Sludge dewatering plays a critical role in the efficient and cost-effective management of wastewater treatment plants. Ultrasonic treatment has emerged as a promising technique for improving dewatering processes. This study aims to evaluate the impact of ultrasonic treatment on sludge dewatering characteristics. A series of experiments were conducted to evaluate the dewatering characteristics of sludge under ultrasonic treatment. Experimental data was collected, and the effects of ultrasonic parameters on dewatering efficiency were analyzed. Ultrasound has the capacity to disintegrate sludge flocs, liberate tightly bound water, and enhance sludge dewatering capabilities. The application of ultrasound leads to the breakdown of sludge flocs, which facilitates a substantial amount of organic acids or carbonates. This, in turn, modifies the pH value of the sludge. Additionally, ultrasound induces instantaneous high temperature and pressure within the liquid phase, consequently elevating the temperature of the sludge slurry. Optimum ultrasound energy density and duration of ultrasound treatment exist. For the sludge samples analyzed in this investigation, it was determined that the optimal ultrasonic energy density is 9.8 W, while the optimal duration of ultrasound treatment is 30 s. Excessively escalating the sound energy density or prolonging the duration of ultrasound may yield unfavorable outcomes in terms of sludge dewatering effectiveness. To enhance sludge dewatering, it is crucial to select appropriate ultrasonic energy density and duration of ultrasonic treatment. This study demonstrates the positive impact of ultrasonic treatment on the dewatering characteristics of sludge. The findings provide valuable insights into the potential of ultrasonic technology for enhancing sludge dewatering.

Effects of plant density on alfalfa (Medicago sativa L.) seed yield in western Heilongjiang areas.

Alfalfa (Medicago sativa L.) is known as the "king of forages". The aim of the current study is to determine the optimum planting density as the key cultivation technique for high yield of alfalfa seed. Alfalfa variety (Longmu 801) was planted in experimental fields from 2014 to 2017. In the planting density test, the row spacing was 65, 80, and 95 cm, and the plant spacing was 30, 45, 60, 75, and 90 cm. The seed yield and yield components in the row spacing and plant spacing tests were measured. On the basis of 3 years average of the experimental data, the highest seed yield of 225.49 kg ha-1 was obtained with row spacing vs plant spacing of 65 and 60 cm, respectively. Correlation analysis showed a significant positive correlation between the racemes per stem, pods per raceme, pods per stem, seeds per pod, and the seed yield. These results suggested that Longmu 801 should be cultivated with 65 cm row spacing and 60 cm plant spacing to maximize seed yields in western Heilongjiang areas.

Low temperature sintering of [formula omitted] nanoceramics as an LTCC material, synthesized through combustion route, and a study on the influence of copper in their structural and dielectric behaviour

Nano size Zn2−xCuxV2O7(x=0∼2) ceramics, prepared through a single step modified combustion method has been sintered at a relatively lower temperature for the first time. The thermodynamics of phase transition of the as prepared samples with respect to temperature was studied using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The powder X-ray diffraction (XRD) analysis of the samples along with Rietveld refinement of the data confirmed that the compositions crystalized in monoclinic structure despite increasing x from 0 to 2. Raman spectroscopic analysis carried out in the powders also corroborated the XRD analysis. The High Resolution Transmission Electron Microscopy (HRTEM), shows that the annealed powders have a particle size of around 43 nm. A systematic study on the densification behaviour of the cylindrical pellets was conducted in the range 6800C-7800C to obtain optimal density. The microstructural study of the pellets sintered to the optimum density was conducted using Scanning Electron Microscopy (SEM). The electrical properties of the polished samples were measured using an Impedance Analyzer in the range 100Hz–1MHz at different temperatures from 50°C to 500°C. On varying x from 0 to 2, the dielectric constant of Zn2V2O7 ceramic showed a gradual increase from 7.9 to 15.9 at 10kHz at room temperature. The Zn2V2O7 ceramics showed a conductivity range from 4.10×10−9Scm−1 to 4.56×10−7Scm−1 between 300°C and 450°C .The present study confirmed the suitability of the ceramics as potential substrate material for LTCC applications.

Designing Reaction Coordinate for Ion-Induced Pore-Assisted Mechanism of Halide Ions Permeation through Lipid Bilayer by Umbrella Sampling.

Ion permeation mechanism through lipid membranes helps to understand cellular processes. We propose new reaction coordinates that allow ions to permeate according to their water affinity and interaction with the hydrophilic layer. Simulations were done for three different halides (F-, Cl-, and I-) in two different lipid bilayers, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dinervonoyl-sn-glycero-3-phosphocholine (DNPC). It is found that the involvement of the water molecules decreases the free energy barrier. The ions were found to follow different pathways for permeation. Formation of proper pores required a collaboration effort of the hydration shell water molecules and the hydrophilic lipid layer, which was favored in the case of Cl- ions. The optimum charge density and good water affinity of Cl- with respect to F- and I- ions helped to form the pore. The effect was prominently seen in the case of DNPC membrane because of its higher hydrophobic thickness. The umbrella sampling results were compared with other methods such as the Markov state model (MSM) and well-tempered metadynamics (WT-metaD).

Study on the optimisation of cement and binder content to develop a sustainable high-performance concrete

According to ACI concrete terminology, “High Performance concrete (HPC) is defined as a concrete meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices”. It is a new generation of concrete that has been evolved recently and are well received for its exceptional performance of strength and durability. Due to these characteristics, HPC are utilized in the construction of bridges, hydropower structures, pavements, mass concrete projects etc. HPC is a cementitious composite material composed of an optimized gradation of granular constituents, a water-to-binder ratio of less than 0.3, a high percentage of discontinuous internal fiber reinforcement and HPC can hold compressive strength of more than 60 MPa. HPC considered in this study is made with high-strength steel fibers, fine sand, cement, mineral and chemical admixtures and water. The conventional mix design used for normal concrete cannot be adopted for HPC because of the high compressive strength to be achieved. The main objective is to develop a sustainable HPC mix with optimum particle packing density to achieve the desired strength with the lowest cement and binder content. As part of the investigation, the impact of different constituents of HPC such as cement content and binder content on the compressive strength were examined. Also, the optimum particle packing density of mixes with different amount of cement and binder content were studied using EMMA software. From the results it is observed that the increase in cement or binder content beyond a particular level will have minimal impact on the compressive strength.

TINJAUAN KARAKTERISTIK ARUS LALU LINTAS DENGAN MENGGUNAKAN 3 MODEL PADA JALAN LUAR KOTA (STUDI KASUS RUAS JALAN TGH LOPAN LABUAPI KABUPATEN LOMBOK BARAT)

The growth in the number of vehicles that is not proportional to the provision of transportation infrastructure will cause transportation problems. The number of these vehicles continues to increase, causing many complex problems. One way to overcome this problem is to understand traffic behavior by creating mathematical and graphical relationships between traffic flow (flow), speed and density.The research was carried out on the TGH Lopan Labuapi Road section, West Lombok Regency with the aim of finding out the relationship between volume, speed and density of traffic using 3 models, namely the Greenshields, Greenberg and Underwood models, so that the most suitable model among the three models can be identified and also to know traffic characteristics including maximum volume, free flow speed, optimum speed and optimum density.From the analysis results, the best model is the Greenshields model so that the speed-density relationship model (Us-D) is Us = -0.431 D + 54.394, flow-Density (V-D) is V = -0.430 D² + 54.393 D -0.019 and flow-speed (V-Us) is V = -2.326 Us² + 126.487 Us . Based on the best model, namely the Greenshields model, the traffic flow characteristics obtained are maximum volume (Vm) of 1719.92, free flow speed (Uf) = 54.3 km/hour, optimal speed (Um) = 27.1 km/hour and Optimum Density (Dm) = 63.2 pcu/km

Derivation of Optimum Outfit Density for Surface Warships based on the Analysis of Variations in Work Content and Workforce Density and Productivity with Ship Size

The potential impact of a ship’s outfit density on the labor hours required for production, sustainment, and upgrade has been discussed within the domain of warship design for decades. For fixed ship mission, systems capabilities, crew size, specification complexity and maturity, other producibility characteristics, and work schedule, as a ship’s size varies, required production labor hours are impacted in two ways—first by a change in work content and second by a change in worker productivity with available space. Because these impacts are inversely related, there exists an optimum ship size and outfit density that minimizes required labor hours. This paper describes an analysis of optimum outfit density to minimize production labor hours for complex modern surface combatants. The key relationship between available space and worker productivity is defined based on data from multiple industries. This relationship is then used along with knowledge of surface combatant design and shipbuilding processes and production labor requirements to identify an optimum range of overall outfit density to target during ship design. This derived optimum range is validated with other related research and reference to the outfit densities of existing modern surface combatants and what is known about their ease of build. Also discussed are 1) alternative ship design and production paradigms that might allow for ships with higher outfit densities while maintaining efficient production, maintenance, and upgrade and 2) implications of the relationship between available worker space and worker productivity for shipyard planning and work execution.

Ultrasound assisted electrochemical oxidation of synthetic dye wastewater

ABSTRACT This study reports the treatment of synthetic dye wastewater in a sono-electrochemical reactor. The influence of three different supporting electrolytes (Na2SO4, NaCl, and Na2NO3) on % decolorisation was studied and higher decolorisation was observed with NaCl. The increase in applied current density (0.25, 0.5, 0.75, 1, 1.25 A/dm2) enhanced the color removal and the optimum current density arrived was 1.25 A/dm2. The % decolorisation was studied at three different pH (3, 7 & 11), and about 95.7% decolorisation was observed at pH 3. The inter electrode distance of 1 cm gave highest decolorisation. The addition of Na2SO4 and Na2NO3 in the sonolyzer bath did not influence the % decolorisation significantly. The sono-electrochemical process gave 99.16% decolorisation and 91.15% COD reduction while the electrochemical process gave 94.79% decolorisation and 76.82% COD reduction. The optimum electrolyte concentration, current density, pH and electrode distance of 0.5 g/L, 1.25 A/dm2, 3, and 1 cm, respectively gave highest decolorisation. The reaction kinetics of the sono-electrochemical oxidation treatment was also investigated. The higher mineralisation rate at a lower residence time indicates that the combined treatment is promising for degrading recalcitrant compounds present in wastewater.

Synthesis, characterization and insights into the supercapacitive and electrocatalytic (OER) bi-functional properties of nitrogen-doped reduced graphene oxide using dicyandiamide precursor

A facile methodology to synthesize the nitrogen-doped reduced graphene oxide (NG) via a solvothermal process exhibiting a substantial content of either pyrrolic-N or pyridinic N, is demonstrated. In the synthesis of NG, different amounts of dicyandiamide (DCDA) with a constant (1 g) amount of graphene oxide have been taken in DMF (solvent). This approach produced the nanosheets of N-doped graphene (NG-2) which possess optimum defect density and 10.58 % total nitrogen. Nitrogen within this NG material predominantly manifests in four distinct bonding configurations, with the most prevalent being pyrrolic-N. The solvothermally synthesized N-doped reduced graphene oxide exhibited good charge storage characteristics. Three electrode testing of NG-2 shows high specific capacitance (865.82 F/g at a particular current density of 0.5 A/g) and a high energy density (76.96 Wh/kg) in acidic conditions. This sample showed poor electrocatalytic activity for oxygen evolution reaction (OER). However, the material prepared with very high amount of DCDA (NG-4) showed a total N-content of 29 % with high contribution of pyridinic N, demonstrated good electrocatalytic activity for OER following the four-electron path. The Tafel slope of NG-4 sample is around 140 mV/dec which implies the facile conversion of OH− into O2, at relatively low overpotential within an alkaline system. Consequently, the synthesized dual-functional N-doped reduced graphene oxide material holds characteristics for the advancement of carbon-based energy storage materials, and simultaneously be utilized as catalyst for OER.

Investigation and optimization of load characteristics of a multi-stage load-reduction structure for vehicles during high-speed vertical water entry

Vehicles are subjected to intense impact loads during water entry at high speed, so some appropriate measures are taken to reduce the impact response of the structure. In this paper, a multi-stage load-reduction structure composed of foam aluminum and cavitation structure is designed to improve the load characteristics of high-speed vehicles. Its three-dimensional numerical model is established based on the Coupled Euler-Lagrange (CEL) method. The accuracy of the numerical simulation was verified by comparison with various experimental results of the sphere and AUV head section, and irrelevant grids were obtained. The simulation of a vehicle with and without a multi-stage load-reduction structure was carried out to study the load characteristics under the influence of different parameters such as vertical velocity and relative density of foam aluminum. Researches were also carried out to select the optimal parameters. The results show that the impact acceleration and the optimal density increase synchronously with the initial velocity. The installation of the multi-stage structure transforms the single impact of direct water entry into three reduced acceleration peaks, and finally realizes the load reduction. When the velocity is 100, 200 or 300 m/s, the load reduction rates under the optimum density are up to 84.6%, 83.7% and 79.3%.