Optimal Ratio Research Articles

RSM based optimization of lambda and mixed fuel concentration parameters of an LTC mode engine

In this study, the effects of lambda and premixed ratio (PR) parameters on the response parameters of an engine operating in LTC (low temperature combusiton) mode is investigated and optimized using a hybrid method. RSM (response surface method), which is a combination of experimental and statistical method, is used as hybrid method. Depending on the variable parameters of lambda and PR, an experimental set was created with CCD (central composite design) and experiments were performed. The effects of the variable parameters on the response parameters were investigated and evaluated in detail on the generated counter graphs, optimization of the variable parameters was carried out. As lambda increased, a decrease in engine torque and thermal efficiency values, and improvements in CO2 and NOx emissions were observed. As PR increased, thermal efficiency and specific fuel consumption values worsened. The optimum premixed ratio was determined as 33.619 % and lambda value as 2.576. At these conditions, the values of response parameter were obtained as torque 12.115 Nm, BSFC 346.764 g/kWh, ITE 21.447 %, CA10 3.503, CA50 8.005, CO 0.169 %, HC 191.467 ppm, CO2 5.301 %, NOx 404.564 ppm and soot 12.687 %. The optimization desirability value was determined as 0.665 and strengthened the goodness of the optimization.

Strength and Acid Resistance of Mortar with Different Binders from Palm Oil Fuel Ash, Slag, and Calcium Carbide Residue

This study deals with the use of ground palm oil fuel ash (GPOFA) in combination with ground granulated blast furnace slag (GGBFS) and ground calcium carbide residue (GCR) to produce the binary and ternary binders-based alkali activated mortar. The appropriate content of materials in each binder type was determined as a function of compressive strength. The results revealed that both GPOFA:GGBFS and GPOFA:GCR binders had an optimum blending ratio of 70:30 wt%, while the GPOFA:GGBFS:GCR binder was 55:30:15 wt%. An alkaline catalyst of NaOH was admixed to the best mixture in each binder type to stimulate the mortar's compressive strength. The sulfuric acid (H2SO4) resistance of the mortar in terms of weight change was also examined. The addition of 1M NaOH in both binary and ternary binders could enhance the compressive strength and H2SO4 resistance of the mortar. The highest compressive strength and lowest weight change due to soaking in H2SO4 solution were found in the ternary binder mortar with a 1 M NaOH. The mortar with GCR immersed in H2SO4 solution resulted in an increased weight, which was different from that of the mortar without GCR. The microstructural analysis of the alkali-activated pastes indicated more reaction products than in the case of the pastes without alkali activator. However, a higher concentration of 2 M NaOH resulted in a poor microstructure, which had a negative effect on the compressive strength and H2SO4resistance. Doi: 10.28991/CEJ-2024-010-07-08 Full Text: PDF

Soft nanotechnology: Used as a functional coating on a nanostructured germicidal surface

Bacterial contamination has emerged as a significant threat to human health over the past century. Initially, antibiotics were seen as the solution to this problem, but their overuse has led to the development of drug resistance and the rise of superbugs. These superbugs are resistant to most, if not all, conventional antibiotics, making them particularly difficult to treat. Interestingly, research has shown that the wings of dragonflies and cicadas possess natural nanopillar structures that are capable of inhibiting bacterial growth. These nanopillars puncture bacterial cell membranes, leading to bacterial death. This discovery has opened up new avenues for combating bacterial contamination. Recent advancements in soft nanotechnology have introduced innovative antibacterial coatings that are crucial for combating these antibiotic-resistant superbugs. These coatings work by mimicking the nanopillar structures found on the wings of dragonflies and cicadas. Understanding the interaction between bacteria and these nanoantibacterial coatings is essential for achieving effective bactericidal outcomes. Different bacteria require varying optimum aspect ratios, which can be achieved through various formation methods. Therefore, this paper elucidates the principles of soft nanocoating, with a focus on comparing aspect ratios obtained through different preparation techniques and, according to the different aspect ratio, determining the corresponding applicable sterilization scene. It also explores the practical application of nanostructure bactericidal surface coatings to address the growing threat of antibiotic resistance and enhance public health. Moreover, as an emerging field, this paper examines the challenges in soft nanocoating applications and the directions that can be improved in the future. The versatility and potential of soft nanotechnological coatings seems to apply to various industries, promising enhanced performance and safety standards. This is a crucial step towards creating a safer and healthier future for all.

NON-FIRED LATERITE SOIL BRICKS WITH NA-BASED STABILIZER ADDITION FOR SUSTAINABLE DEVELOPMENT

Fired bricks are widely used, but they are energy-intensive and non-eco-friendly. Non-fired bricks with chemical stabilisers can be the alternative solution, which is a low-energy-intensive and environmentally friendly manufacturing product. Laterite soil can be the raw material for the synthesis of non-fired clay brick in sodium hydroxide solution and sodium silicate solution. However, it may have been mixed with other laterite soils with different optimum moisture contents and grain sizes during extraction. Thus, the mixing ratio of laterite soil, Na-based stabilisers, and water for non-fired brick production is determined. Besides, two types of laterite soil, LAT 1 and LAT 2, from different locations were prepared, and another type of laterite soil, LAT 3, was prepared by mixing LAT 1 and LAT 2. Both three are compared primarily in terms of compressive strength and water absorption, which are mixed with the Na2SiO3/NaOH ratio. As a result, the new mixing ratio with increased water content was determined based on the optimum moisture content of the soil. Besides, the optimum mixing ratio of each type of brick was determined. Overall, based on the Malaysian standard, all types of brick samples from each ratio could be used as load-bearing class 1 and internal wall bricks. Additionally, LAT 2 and LAT 3-based bricks with a ratio of 1.5 Na2SiO3/NaOH ratio can be used as load-bearing brick class 2.

Self-Supervised Learning Improves Accuracy and Data Efficiency for IMU-Based Ground Reaction Force Estimation.

Recent deep learning techniques hold promise to enable IMU-driven kinetic assessment; however, they require large extents of ground reaction force (GRF) data to serve as labels for supervised model training. We thus propose using existing self-supervised learning (SSL) techniques to leverage large IMU datasets to pre-train deep learning models, which can improve the accuracy and data efficiency of IMU-based GRF estimation. We performed SSL by masking a random portion of the input IMU data and training a transformer model to reconstruct the masked portion. We systematically compared a series of masking ratios across three pre-training datasets that included real IMU data, synthetic IMU data, or a combination of the two. Finally, we built models that used pre-training and labeled data to estimate GRF during three prediction tasks: overground walking, treadmill walking, and drop landing. When using the same amount of labeled data, SSL pre-training significantly improved the accuracy of 3-axis GRF estimation during walking compared to baseline models trained by conventional supervised learning. Fine-tuning SSL model with 1-10% of walking data yielded comparable accuracy to training baseline model with 100% of walking data. The optimal masking ratio for SSL is 6.25-12.5%. SSL leveraged large real and synthetic IMU datasets to increase the accuracy and data efficiency of deep-learning-based GRF estimation, reducing the need for labeled data. This work, with its open-source code and models, may unlock broader use cases of IMU-driven kinetic assessment by mitigating the scarcity of GRF measurements in practical applications.

Starch vs. tannin as biodegradable reagents for ultrafine hematite depression

Enrichment of ultrafine liberated valuable minerals from their associated gangue phases is one of the emerging investigation topics within mineral processing and recycling. Using green flotation reagents and turning processes into eco-friendly systems is also one of the challenges in the green transition of ore beneficiation plants. Starch and Tanin as biodegradable depressants for hematite depression have been commercially used in various iron ore processing plants. However, their depression effects on ultrafine particles were not systemically assessed and compared. To fill this gap, this investigation examined the effects of starch, tannin, their mixtures (different ratios), and their different conditioning sequence on the floatability of ultrafine quartz and hematite (− 15 µm). Since the macromolecular polymer of these biodegradable depressants can bind particles together and flocculate them, turbidity analyses were used to assess their optimum ratio for hematite depression without affecting quartz floatability. Turbidity analyses provided a mixture of tannin and starch might enhance the flotation separation of quartz from hematite. Starch could flocculate ultrafine hematite particles, while tannin could disperse ultrafine quartz particles. Floatability experiments indicated that starch had the highest performance in hematite depression (lowest effect on quartz particles) compared to other conditions. Surface analyses (zeta potential and FTIR) proved floatability outcomes and highlighted starch had stronger adsorption on the hematite surface than tannin.

Efficacy of almond gum for coacervation with whey protein isolate- optimization, functionality and characterization: A comparison with high-methoxyl pectin

Complex coacervates of whey protein isolate (WPI) and two polysaccharides (almond gum (AG) and high methoxyl pectin (HMP)) under the different pHs (2.5–6.0) and biopolymer mass ratios (1:1–6:1) were prepared to achieve the maximum coacervate yield (CY). The optimum pH and mixing ratio to obtain the maximum CY of WPI-AG (75.93 %) and WPI-HMP (53.0 %) coacervates were 4.3 and 2:1, and 3.5 and 3:1, respectively. Although higher serum layers in emulsions stabilized by WPI-AG/HMP coacervates were detected at the 90 °C, remarkable heat stability under processing temperatures was obtained in ex-situ emulsions with both complex coacervates. Significantly more cold-storage and ionic stabilities were observed for emulsions formulated with WPI-AG than WPI-HMP. Peak shifts in FTIR spectra in the WPI-AG coacervate compared to the individual WPI and AG biopolymers revealed strong electrostatic interactions between these biopolymers. The absence of crystalline peaks for AG and HMP in X-ray diffraction (XRD) spectra confirmed the complexation of AG and HMP with WPI. Thermogravimetric and microstructural analyses showed that porous, loose mesh-like WPI-AG coacervates had superior thermal stability and structural integrity compared to WPI-HMP coacervates and individual biopolymers, which evidenced a more gradual weight loss pattern. WPI-AG coacervates would be promising for efficient emulsion-based delivery systems.

Experimental study on fiber-reinforced cement tailings sand-based grouting material preparation and factors influencing the grouting effect

To address the problem of permeation of tailings pond initial dams rockfill dams, fiber-reinforced cement tailings sand-based grouting (FRCTG) material, which can be used for rockfill dam reinforcement, was prepared by selecting ordinary portland cement (OPC), iron tailings sand (ITS), basalt fiber (BF), fly ash (FA) and water as the raw materials. Orthogonal tests were used to investigate the effects of the water-binder ratio (w/b) and material mass fraction on the rheological and mechanical properties of FRCTG and determine the optimum mixing ratio. Comparative analyses were performed of the grouting effect of FRCTG and pure OPC grouting materials based on concrete self-compacting tests and COMSOL simulations. Combined X-ray diffraction (XRD) and scanning electron microscopy-energy spectroscopy (SEM-EDS) microstructural characterization were used to reveal the factors influencing FRCTG mechanical properties. The results showed that when the water-binder ratio (w/b) was 0.5, ITS substitution percentage for OPC was 10 %, BF dosage was 0.2 %, BF length was 6 mm, and FA substitution percentage for OPC was 8 %, FRCTG had better rheological properties and flexural strength than pure OPC grouting materials. In addition, FRCTG self-compacting concrete also had stronger compressive strength and splitting strength. FRCTG showed a better filling capacity and diffusion effect, which preliminarily verified the feasibility of rockfill dam grouting. ITS inhibited the hydration reaction of the cementitious material and prolonged the setting time of the slurry. The interlocking structure formed by FA and hydration products indirectly enhanced the flexural strength of the grouting material. BF not only provided FRCTG reinforcement but also acted as the hydration product skeleton. FRCTG demonstrated better economic and environmental performance than traditional cement material while effectively utilizing ITS and FA solid waste.

A self-assembled surfactant for efficient flotation of cassiterite: Experimental study and DFT calculation

Surfactants of different kinds are important in the flotation of metal oxide ores. In this paper, a combined organic surfactant was formed through self-assembly of salicylhydroxamic acid (SHA) and isopropanolamine dodecylbenzenesulfonate (DBIA). The effects of SHA and DBIA on the flotation behavior of cassiterite were investigated. Density functional theory (DFT) calculations were used to clarify the microscopic adsorption mechanism of SHA and DBIA on the cassiterite surface. The flotation performance of the combined surfactant was investigated to determine the optimum ratio. Subsequently, the self-assembly behavior of the surfactants in aqueous solutions was examined using surface tension tests and molecular dynamics simulations. Flotation experiments and zeta potential, X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), contact angle, and adsorption capacity analyses were used to explore the flotation behavior and adsorption mechanism at the solid–liquid–gas boundary. The maximum flotation recovery of cassiterite were 45.73 % and 71.25 % when SHA and DBIA were used alone. By contrast, with the developed combined surfactant, the flotation recovery at the same reagent concentration was 84.92 %. The SHA/DBIA surfactant co-adsorbed at the aqueous solution interface, which decreased the surface tension of the solution to 4.943 × 10−4 mol/L and resulted in formation of a stable foam layer. These effects altered the surface properties of cassiterite and enhanced its surface hydrophobicity. Overall, this study provides valuable mechanistic insights into the enhanced chelation complexation of self-assembled surface collectors with metal oxides.

A wide-band high gain beamsteerable variable patch reflectarray antenna for THz applications

This article proposed a compact size, high gain, wideband reflectarray antenna for THz and 6 G applications. To enhance the aperture efficiency and gain, a single layer L-shape delay line-based unit cell with a size of 0.45λ0 is adopted. The λ0 is the free space wavelength at 1.35 THz. The SiO2 substrate is sandwiched between L- shape delay line and the ground plane of gold. The unit cell, equivalent parallel RLC circuit modelled with gap coupled capacitance is also presented which is validated through the Ansys-High Frequency Structure Simulator (HFSS) and Advanced Design System (ADS). The dimension of the RA is 3 mm having 610 elements. It is excited by the pyramidal horn antenna at an optimum distance (F/D =1.21). The optimum ratio (F/D) is calculated with the help of the cosq model at −10 dB edge taper. The operating bandwidth is obtained 46.15 % from 1 to 1.6 THz. The reflection phase and magnitude are 500° and 3.93 dB at 1.35 THz. It is adjusted by varying the length of the delay line. The maximum aperture efficiency and realized gain are 35 % and 28 dBi respectively. The Side lobe level is −15.5 dB and the Co-Cross polarization level is below −30 dB.

Revealing the catalytic ability of 5%Rh–5%Pt–5%Al2O3–85%CeO2 for CH4-based mixing fuel gases operating at 550 °C

With the work temperature of solid oxide fuel cells (SOFCs) lower to 400–600 °C, the use of CH4-based fuel gas needs to be pre-reformed into synthesis gas (H2 and CO) to mitigate anode carbon deposition. Although lots of catalysts have been widely studied for methane conversion, the development of low temperatures (below 550 °C) catalyst for efficient methane reforming reactions remains a challenge. Here, we proposed a nanosize 5%Rh–5%Pt–5%Al2O3–85%CeO2 composite catalyst (RPAC-550), which demonstrates excellent reforming reactions for CH4-based mixing fuel gases operating at 550 °C. In this work, the reforming process of RPAC-550 catalyst for dry CH4, CH4/H2O and CH4/CO2/H2O atmospheres in different ratios and operating at 550 °C were systematically studied. Then the obtained reforming gases and carbon deposition were studied thoroughly to get the optimum ratio of mixed fuel gases for SOFCs. At last, the designed RPAC-550 catalyst achieves a CH4 conversion rate as high as 60% with water-methane ratio in 0.6. Herein, the ratio of H2 and CO as reforming gases can be controlled precisely by adjusting the intake amount of oxidant CO2 and H2O into CH4, which is beneficial for customizing fuel gases. In addition, the RPAC-550 catalyst exhibits remarkable catalytic stability and anti-coking ability under 600 h continue test. This work provides new insights for the rational design of efficient catalysts to reform methane-based fuel gas at 550 °C.

Study on Enhancement of Acid Production by Combination Fermentation of Caproic Acid-producing Bacteria and Lactic Acid-producing Bacteria

A new caproic acid bacteria 20-5 (Caproicibacterium sp.) was newly screened in the laboratory, and several high-quality lactic acid bacteria A2-3 ( Sporolactobacillus fermentans ), GCB-3 ( Pediococcus acidilactici ), KR-4 ( Lactiplantibacillus plantarum ), LY-5 ( Levilactobacillus brevis ), B2-1 ( Lactiplantibacillus plantarum ) were used for exploratory compound fermentation experiments. The compound fermentation was a caproic acid bacteria (20-5) alone plus four lactic acid bacteria ( A2-3, GCB-3, KR-4, LY-5, B2-1 ), the experimental ratio was set up four groups of compound ratio of 1 : 2,1 : 1,5 : 1,10 : 1. The optimum ratio of 20-5 to B2-1 was 10 : 1, and the total acid yield reached 26.75 g / L. The best caproic acid production capacity after compounding was the 10: 1 group of 20-5 and B2-1, and the caproic acid yield was 7.22 g / L. The average lactic acid content in the fermentation broth was 4.52 g / L after compounding. After compounding, the acid production of the 1 : 1 and 5 : 1 groups of 20-5 : A2-3 and the 10 : 1 group of 20-5 : B2-1 increased compared with that of single bacteria. In the other compound groups, the acid production capacity decreased after the compound operation, and the lactic acid production generally decreased, but the caproic acid production increased, indicating that caproic acid bacteria can use lactic acid as a carbon source for fermentation and acid production activities, so that caproic acid bacteria can produce caproic acid.

Optimal design of offshore jacket platform using enhanced colliding bodies optimization algorithm

Given the considerable volume of materials used in jacket platforms, structural optimization of these structures is always of interest. In the design optimization of offshore jacket platforms, the objective function is iteratively evaluated through a number of complex and time-consuming analyses making the optimization process computationally expensive. To reduce the computational costs, therefore, it is imperative to investigate efficient optimization algorithms with a high convergence rate to achieve optimal solutions for offshore jacket structures as a large-scale and complex problem. Accordingly, this research studies the application of a novel metaheuristic algorithm called Enhanced Colliding Bodies Optimization (ECBO) for the design optimization of a real jacket platform, SPD19A. The optimization constraints comprise stress and buckling in the members, horizontal displacements at the working point, and structural adequacy control of connections. The optimization results are subsequently compared to a design optimized by the Genetic Algorithm (GA), as an example, to evaluate the efficiency of the ECBO algorithm for the offshore jacket structure. The outcomes indicate that ECBO optimizes the jacket more effectively by 15%, while the optimization ratio of GA is 11%. Hence, the results confirm that ECBO has great and favorable efficiency and can potently escape from local optima to reach a better design for the jacket structure.

A new pavement crack repair sealant with two-way shape memory effect

To address the challenge of sealant debonding due to cyclic temperature variations, a new pavement crack repair sealant which can achieve two-way shape memory deformation is developed. The developed crack sealant is a shape memory liquid crystal elastomer (SMLCE), designed to exhibit the deformation characteristics of heat contraction and cold expansion. First, the material composition and preparation process of the developed SMLCE are given. Thermodynamic properties, phase transition temperatures and molecular structures are analyzed based on DSC and FITR. The effects of the crosslinker and chain extender ratios and the key preparation processes on the two-way shape memory deformation and mechanical performance of SMLCE are systematically analyzed. Based on the analysis, the optimum ratio of SMLCE is determined to be 1:15 and the optimum secondary crosslinking preparation process is 150% orientation stretching. Under the optimal solution, the developed SMLCE can achieve the multiple two-way shape memory reversible deformation with a maximum 46% deformation in the temperature range of -20°C∼120°C. At the same time, the developed SMLCE has excellent mechanical properties, with a tensile strength of 20.7Mpa and an elongation at break of 322%. It also exhibits good low-temperature deformation capabilities at -10°C and above. Finally, the suitability and application potential of the developed two-way SMLCE as a pavement crack sealant are assessed. The developed SMLCE has good adaptability in most climate zones, which indicates its great potential as a pavement crack sealant. This research provides a new way for the pavement crack repair.

Investigation and Utilization of Alkali-Activated Grouting Materials Incorporating Engineering Waste Soil and Fly Ash/Slag

The alkali-activated composites technique is a promising method for the in situ preparation of cavity filling/grouting materials from engineering waste soil. To investigate the feasibility of engineering waste soil utilization by the alkali activation process, the macroscopic and microscopic properties of the fly ash/slag-based alkali-activated composites, after solidification/stabilization (S/S) with sandy clay excavated at Baishitang Station of Shenzhen Metro, were studied. The unconfined compressive strength (UCS) test was conducted to evaluate the S/S effect of alkali-activated composites. The results show that the optimum quality ratio of slag and fly ash correspond to 7:3, the modulus of alkaline activator to 1.3, and the alkalinity of alkaline activator to 10%. The alkali-activated composite’s strength under these parameters can reach 45.25 MPa at 3 days, 49.85 MPa at 7 days, and 62.33 MPa at 28 days. A maximum 3-day UCS of 21.71 MPa, 75% of the 28-day UCS, was achieved by an engineering waste soil and alkali-activated composites mass ratio of 5:5, slaked lime content of 4.5%, and a water-to-solid ratio of 0.26, and it can also meet the required fluidity and setting time for construction well. Fluidity is primarily affected by the soil-to-binder ratio, which decreases as the ratio decreases, while the water-to-solid ratio increases fluidity. Slaked lime has minimal impact on fluidity. The setting time is mainly influenced by the soil-to-binder ratio, followed by slaked lime content and water-to-solid ratio, with setting time shortening as the soil-to-binder ratio and slaked lime content increase, and lengthening as the water-to-solid ratio increases. Through Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS) tests, microscopic analysis showed that loose granular units are firmly cemented by alkali-activated composites. Based on the results of on-site grouting tests in karst caves, the alkali-activated grout materials reached a strength of 5.2 MPa 28 days after filling, which is 162.5% of the strength of cement grouting material, satisfying most of the requirements for cavity filling in Shenzhen.

A Novel Continuously Variable Transmission with Circumferentially Arranged Disks (CAD CVT)

This paper presents a novel Continuous Variable Transmission (CVT) design. CVT is highly beneficial for actuators with rotary output as it can improve the energy efficiency of the actuators by providing an optimum transmission ratio. This property of CVT is highly beneficial for fossil-fuel-based vehicles, electric vehicles, wind turbines, industrial robots, etc. With the exception of Spherical CVT and DH CVT, all known CVTs like push belt CVTs, toroidal CVTs, Milner CVTs, etc., require additional gear sets and clutches for direction reversal and neutral gear ratio. However, Spherical CVT and DH CVT have low torque capacity due to a single traction point constraint. Foregoing in view, a new CVT named CAD CVT has been developed. The paper presents the design conception, the operating principle, the transmission ratio, the torque capacity, frictional losses, and experimental verification of the basic functionality by manufacturing a Proof of Concept (PoC). The proposed CVT is the only CVT capable of independent direction reversal and high torque capacity as it can transmit torque through multiple traction points. The new CVT will significantly impact high-torque applications in different engineering applications, especially land transport consisting of heavy vehicles like trucks, buses, and trailers.

A capacitive humidity sensor based on nanodiamond/silver nanoparticles (ND/Ag) nanocomposite with high stability and rapid response for respiratory monitoring

In this work, a high-performance capacitive humidity sensor based on nanodiamond/silver nanoparticles (ND/Ag) nanocomposite is proposed. The influence of silver nanoparticles with different content in nanodiamond is investigated, and the optimum ratio of 5 wt% Ag in the composite shows the maximum humidity sensing performance, which is three times than that of the pure nanodiamond based humidity sensor. Moreover, the proposed sensor exhibits a superior repeatability, ultrafast response time (<2 s) and recovery time (<1 s). More importantly, the sensor can maintain a good repeatability and rapid response speed when exposure to high humidity for a long time, demonstrating the excellent stability of the proposed sensor. Furthermore, complex impedance spectroscopy was applied to account for the underlying sensing mechanisms of the ND/Ag composite film humidity sensor. Finally, we design a circuit to realize non-contact breathing control by using the fabricated humidity sensor, which demonstrate that the fabricated humidity sensor could be applied to some auto-control systems by human-breath. This work demonstrated that ND/Ag composite film is an ideal candidate material for constructing high-performance humidity sensors for respiratory applications.

Morphological, TGA, and FTIR on Rigid Polyurethane Composite Laminated with Untreated and Treated Bamboo Fiber Roof Insulation

The performance of roof insulation such as polyurethane decreased due to problems such as insufficient absorption and poor thermal insulation performance, especially during rainstorms. The aims of this study are to investigate the physical property and its potential reinforced material such as rigid polyurethane doped with treated and untreated bamboo fiber composite (RPU-BF) at different ratios of 0, 25, 30, 35, and 40% of bamboo fibers as an insulation material for roof applications. The bamboo fibers were treated by using silane coupling agent treatment. The rigid polyurethane composite samples were prepared and then laminated bamboo fiber to overcome the sound problem in roofs. The physical characterization was investigated by Water Contact Angle (WCA), the morphological by Scanning Electron Microscopy (SEM), Thermo-gravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) Analysis. The results showed that the treated bamboo fiber had a 192.5° water contact angle as a super hydrophobic property due to the presence of the chemical bonds Si-O-Si and Si-O-C in the silane coupling agent treatment. The morphology showed that 30% ratios of RPU-BF-T30 give the smallest pore diameter size. The peak of thermal degradation temperature of untreated and treated bamboo fiber was increased from 320°C to 350 °C with a weight loss of 80% to 50%. The treated bamboo fiber exhibited peaks at 3010–3040 cm-1 were associated with stronger Si-O-Si bonding, indicating the formation of new chemical bonds between bamboo fiber and silane coupling agent due to the ester bond from the cellulose, lignin, and hemicellulose. Thus, there was a similar trend peak in the functional chemical group in the FTIR spectrum of the RPU-BF composite. This result shows that RPU-BF composite had the potential of the optimum ratio of bamboo fiber as an insulation material for local communities and beneficial to the bamboo industry.

An optimization strategy for improving the aspect ratio of screen printing electronic paste based on rheological properties

The wide application of electronic pastes in the field of information electronics puts forward higher requirements for printability. As a key component to determine printability, there are few researches on the effect of organic vehicle components on printability of electronic paste. The purpose of the investigation was to explore the effects of different component contents on the properties of organic vehicles and then on the properties of electronic pastes. Experiments on the wettability of organic solvents to silicon wafers and solubility of adhesives were applied to screen organic solvents. The rheological properties of organic vehicles and electronic pastes in the optimization process were evaluated by the combined method of three interval thixotropy test (3ITT), oscillation amplitude sweep test and NMR relaxation time measurement. And the optimum ratio of adhesive, dispersant and coupling agent and the influence on rheological properties of electronic paste were determined. The optimized silver-aluminum paste as front-side paste was screen-printed and sintered to give a height/width (H/W) ratio of 0.4505 and an average resistivity of 5.06×10−6 Ω cm for the silver grid lines. The paste formulations developed in the investigation provide a new idea for the preparation and development of electronic pastes with excellent performance.

Research on Layered Steel Fiber Reinforced Concrete Mix Ratio Design Based on Orthogonal Test

The aim of this study was to investigate the effect of different mix ratios on the mechanical properties of steel fiber-reinforced concrete (LSFRC) and to determine an optimum mix ratio. The effects of four factors, namely, fly ash content, volume fraction of steel fibers, water–cement ratio, and sand rate, on the mechanical properties of LSFRC were investigated through orthogonal experiments. The microstructure of LSFRC at different mix ratios was analyzed using scanning electron microscopy (SEM), and an optimal mix ratio was derived. The results showed that the water–cement ratio and the volume fraction of steel fibers were the main factors affecting the mechanical properties of LSFRC. When the water–cement ratio was 0.38 and 0.42, the combined mechanical properties of concrete were superior. Steel fiber content between 0.6% and 1% had a significant effect on the splitting tensile strength of concrete. The effect of sand rate on compressive and splitting tensile strengths was consistent, with a significant effect on both at a sand rate of 40%. In terms of microstructure, 20% fly ash content promotes the hydration of concrete. The optimum LSFRC mix ratio determined was 0.42 water–cement ratio, 0.6% steel fiber content, 40% sand rate, and 20% fly ash content. Experimental verification using this mix ratio showed that the compressive, flexural, and split tensile strengths were increased by 3%, 19%, and 33%, respectively, when compared to ordinary concrete.