Rapid preparation of ceramic moulds for medium-sized superalloy castings with magnesia-phosphate-bonded bauxite-mullite investments

Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI), a series of experiments were conducted, including modifciation of the workable time of slurry by liquid(mL)/powder(g)(L/P) ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP) as strengthening agent, and adjustment of bauxite (g)/mullite(g)(B/M) ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.

Experimental seismic behavior of squat shear walls with precast concrete hollow moulds

This study proposes an innovative precast shear wall system, called an EVE precast hollow shear wall structure (EVE-PHSW). Precast panels in EVE-PHSW are simultaneously precast with vertical and horizontal holes. Noncontact lap splices of rebars are used in vertical joints connecting adjacent precast panels for automated prefabrication and easy in situ erection. The seismic behavior of EVE walls was examined through a series of tests on six wall specimens with aspect ratios of 1.0~1.3. Test results showed that EVE wall specimens with inside cast-in situ concrete achieved the desired “strong bending and weak shear” and failed in shear mode. Common main diagonal cracks and brittle shear failure in squat cast-in situ walls were prevented. Inside cast-in situ concrete could signifi cantly improve the shear strength and stiff ness of EVE walls. The details of boundary elements (cast-in situ or prefabricated) and vertical joints (contiguous or spaced) had little eff ect on the global behavior of EVE walls. Noncontact lap splices in vertical joints could enable EVE walls to exhibit stable load-carrying capacity through extensive deformations. Evaluation on design codes revealed that both JGJ 3-2010 and ACI 318-14 provide conservative estimation of shear strength of EVE walls, and EVE walls achieved shear strength reserves comparative to cast-in situ walls. The recommended eff ective stiff ness for cast-in situ walls in ASCE 41-17 appeared to be appropriate for EVE walls.

Modeling of unsteadiness of fluid flows and level fluctuations in thin slab continuous casting moulds

Unsteady fluid flows and level fluctuations in a thin slab continuous casting mould have significant influence on product quality. In this study, the phenomena concerning transient flow features and free surface motions were analyzed by means of the large eddy simulation （LES） software with the smagorinsky SGS model--VisualCast （VCast） II, where the Simpler algorithm on a body-fitted mesh was used to resolve governing equations. A series of water analog experiments on the fluid flow and the surface wave in the moulds of thin slab continuous casting were also performed. The results of fluid regions, middle of vortex and level fluctuation from digital simulations were identical with the results of the water analog experiments.

The Comparison Between Finite Element Analysis and Experimental Results of the Cooling of Injection Moulds with Hot Runner System

In an injection moulding process, the mould cooling s ystem is very important as an efficient and uniform cooling effect can improve b oth the productivity and part quality. Due to the complexity of the process, muc h research on the mould cooling analysis and cooling design optimization has bee n focused on the core and the cavity, excluding other systems of injection mould s. However, the runner system introduces a considerable amount of heat into the mould. In recent years, more and more hot runner systems are being applied in th e moulding industry to save material and decrease losses of injection pressure. This raises the need to include the hot runner system in the cooling analysis. I n this paper, a photo frame part was studied. The mould was built with a hot run ner system. Two thermal sensors were installed: one measures the temperature of lateral surface of hot runner nozzle; the other measures the plastic temperature from the core side. A pressure sensor was also installed to measure the pressur e of the core impression. Cooling analysis was performed using ABAQUS, ananalysi s software based on the Finite Element Method (FEM). The assembly including core , cavity and plastic part was modeled. Heat conduction from hot runner to cavity and from polymer melt to the mould and force convection on the cooling channel surfaces were studied. The natural convection between the ambient air and the ex terior mould surface was ignored. The simulations were adjusted with the experim ental results to find out the heat input from hot runner and its influence on mo uld cooling. Finally, the optimal cooling design and optimal injection condition were obtained.

Study of Compound Polishing Process on SnSb Alloy Moulds

The characteristic of metallographic structure of the SnSb alloy moulds is that hard particles are distributed on the soft metal matrix. Great difference of the hard particles and the soft metal matrix’hardness makes moulds’polishing become difficult. When a rigid grindstone is used to polish the surface of the SnSb alloy mould, the hard abrasives fall off and are embed in the soft matrix of SnSb alloy and while the process, the grinding chips are able to block the gap on the grindstone surface and enable the grindstone to blunt, which brings about the polished area on the surface of the mould is seriously squeezed and deformed and the crystal lattice of SnSb alloys is seriously distorted, and the work hardening takes place. At the same time, the rigid grindstone is easy to scratch the surface of the SnSb alloy mould. Owing to the above reasons, it is difficult to reduce surface roughness and improve the surface quality of SnSb alloy moulds. Taking use of the CAD/CAM technique and the complex processing of combining electrolyzing polishing and mechanical polishing with the magnetic force, mould’s polishing automation is realized on the numerical control machine tool. This complex processing is finished under a comprehensive action as the following: 1. Electrolyzing polishing action Under the electric field, the electrolyte between the elastic grind wheel and the mould is ionized, which electrolyzes the metal of the mould’s surface. The electrolyzing speed of convex peak on the mould’s surface is faster than that of concave valley, which levels the mould’s surface. 2. Mechanical Polishing action During electrolyzing, a dense passive film of low hardness is formed on the mould’s surface. While polishing, soft grinding wheel scraps the passive film on the conven peak easily, and the new metal surface is exposed, then, a new passive film is formed again, going round and round, the conven peak on the mould’s surface is leveled quickly. 3. Magnetic force action The charged particles in electric field will be acted by the Lorentz force in magnetic field. The field plays a stirring part on electrolyte and reduces electrochemical polarization and concentration polarization, and accelerates the electrochemical reaction. The complex polishing process is not only of high efficiency, but also of good surface quality and provides a good effective method for the non-ferrous metal polishing. When the mould is polished, a speed-raising tool system is used and it can increase the grinding wheel spindle’s speed up to five times. This paper describes the SnSb alloy moulds’polishing steps, grinding wheel speed-raising tool system, polishing principle and the results.

Application of Standardization for Initial Design of Plastic Injection Moulds

Today, the time-to-market for plastic products ar e getting shorter, thus the lead-time for making the injection mould is decreasin g. There is potential in timesavings in the mould design stage because the design process that is repeatable for every mould design can be standardized. T he preliminary work of any final plastic injection mould design is to always pro vide an initial design of the mould assembly for product designers (customers) p rior to receiving the final product CAD data. Traditionally and even up till no w, this initial design is always created using 2D CAD packages. The information used for the initial design is based on the technical discussion checklist, in which most mould makers have their own standards. This checklist is also being used as a quotation since the most basic information of the mould in the particu lar project is being recorded in it. The basic information in this checklist in cludes the number of cavities, the type of mould base to be used, the moulding m achine to be used for the moulding, the type of gating system, the type of resin material used and its shrinkage value etc. Information on special requirements such as the number of sliders or lifters to be used is also listed in the check list. At this stage, there is still no information on the cooling and ejection design since they are greatly dependent on the final product CAD data. This res earch focuses on the methodology of providing the initial design in 3D solid bas ed on the technical discussion checklist, which takes the role of the overall st andard template since every sub-design has its own standard template. An examp le of a sub-design that has its own standard template is the cavity layout desi gn. The cavity layout for plastic injection moulds can be designed by controlli ng the geometrical parameters using a standardization template. The standardiza tion template for the cavity layout design consists of configurations for the po ssible layouts. Each configuration of the layout design has its own layout desi gn table of all the geometrical parameters. This standardization template is pr e-defined in the layout design level of the mould assembly design. This ensure s that the required configuration can be loaded into the mould assembly design v ery quickly without having the need to redesign the layout. This makes it usefu l for technical discussions between the product designers and mould designers pr ior to the manufacture of the mould. Changes can be made to the 3D cavity layou t design immediately during the discussions thus the savings in time and avo idance of miscommunications.

Application of transparent casting moulds prepared by additive manufacturing technology in hydraulic simulation

Hydraulic simulation is one of the critical methods to research the filling mechanism of molten metal in the casting process.However,it only performs on test pieces with relatively simple structures due to the limitation of the preparation method.In this study,the method of photocuring additive manufacturing was used to prepare the complex casting mould from transparent photosensitive resin.The pouring test was carried out under different centrifugal conditions,and the filling process of the gating system,support bars and other positions in the vertical direction was recorded and analyzed.The experimental results show that the internal liquid level and the filling process of the test piece prepared by this method can be observed clearly.The angle between the liquid surface and the horizontal plane in the test piece gradually increases as the centrifugal rotational speed increases,which means the filling process is carried out from outside to inside at high rotational speed.The velocity of the fluid entering the runner increases with the increase of rotational speed,but the filling speeds is less affected by the centrifugal speed at other positions.The liquid flow is continuous and stable during the forward filling process,without splashing or interruption of liquid droplets.

Agile Manufacturing of Complex Moulds For Punch Devices

This paper focuses on agile manufacturing of complex moulds for punch devices and a decision analysis for the key link of agile manufacturing resources integration—the virtual company in a multivariate criterion universe of discourse. On the basis of presenting an agile manufacturing model of complex moulds for punch devices, we give a fuzzy decision method of two level judgment space of synthetic decision and several key problems which the production of complex moulds for punch devices must face under the architecture hierarchy of agile manufacturing. We give a fuzzy decision method of two level judgment space of synthetic decision and several key problems which the production of complex parts must face under the architecture hierarchy of agile manufacturing.

Efflux seems to be a general mechanism to resist tetracycline in the yeasts and possibly the moulds

Objective:To isolate yeasts and moulds from selected natural systems and study the effect of tetracycline(Tet)on them so as to generate comprehensive data for further elucidation of transfer or evolutionary development of Tet resistance in general and in these lower eukaryotes in particular.Methods:A total of 139 natural yeasts have been isolated from various ecosystems on potato dextrose agar medium.These along with model yeasts and selected natural and model moulds have been tested for their responses to Tet at various concentrations added to the growth media.The effluxed materials were obtained by vortexing and centrifugation of cells and tested against sensitive bacterium.Results:It was found that Tet efflux was a general feature of natural yeasts and filamentous fungi(moulds)could resist Tet upto a concentration of 5 mg/mL.However,at a very high concentration(10 mg/mL)neither the yeasts nor the moulds could grow indicating that Tet is toxic for these eukaryotes at very high concentrations.The presence of Tet in the medium exaggerates filamentation in all the hyphal forming yeasts.Conclusions:The results suggest efflux as the general mechanism of Tet-resistance in yeasts and moulds possibly acquired from bacteria via horizontal transfer.

STM Manipulation of Molecular Moulds on Metal Surfaces

Molecular Landers are a class of compounds containing an aromatic board as well as bulky side groups which upon adsorption of the molecule on a surface may lift the molecular board away from the substrate.Different molecular Landers have extensively been studied as model systems for nanomachines and the formation of molecular wires,as well as for their function as“molecular moulds”,i.e.,acting as templates by accommodating metal atoms underneath their aromatic board.Here,we investigate the adsorption of a novel Lander molecule 1,4-bis(4-(2,4-diaminotriazine)phenyl)-2,3,5,6-tetrakis(4-tert-butylphenyl)benzene(DAT,C_(64)H_(68)N_(10))on Cu(110)and Au(111)surfaces under ultrahigh vacuum(UHV)conditions.By means of scanning tunneling microscopy(STM)imaging and manipulation,we characterize the morphology and binding geometries of DAT molecules at terraces and step edges.On the Cu(110)surface,various contact configurations of individual DAT Landers were formed at the step edges in a controlled manner,steered by STM manipulation,including lateral translation,rotation,and pushing molecules to an upper terrace.The diffusion barrier of single DAT molecules on Au(111)is considerably smaller than on Cu(110).The DAT Lander is specially designed with diamino-triazine side groups making it suitable for future studies of molecular self-assembly by hydrogen-bonding interactions.The results presented here are an important guide to the choice of substrate for future studies using this compound.

Comparative antimicrobial activity of Moricin(naturally produced by silk worm,Bombyx mori larvae)against clinically important pathogens

With the emergence and spread of antimicrobial resistance(AMR)it becomes pertinent to search for an antimicrobial alternative to cater for the imminent need to control total drug-resistant(TDR)and multiple-drug-resistant(MDR)infections.Antimicrobial peptides(AMPs)have shown some promise and this study was designed to evaluate antimicrobial activity of Moricin(a naturally produced AMP by silkworm,Bombyx mori larvae)against 276 microbial strains of 83 species.Only two(Erwinia amylovora 1,Hafnia alvei 1)strains were classified as susceptible to Moricin at a concentration≤8μg/mL.If susceptibility criteria were set at MIC equivalent to≤128μg/mL then Moricin inhibited 17 strains.All of the Bacillus species strains and majority of the strains of Acinetobacter,Aeromonas,Enterococcus,Erwinia,Raoultella,and Serratia species were significantly(p<0.05)more often resistant(MIC>512μg/mL)to Moricin than strains belonging to Alacligenes,Bacillus,Escherichia,Klebsiella,Pantoea,Pasteurella,Salmonella,Staphylococcus and Streptococcus species.Susceptibility of different bacteria not only varied significantly to Moricin but also to most of the commonly used antibiotics.The susceptibility of microbes not only affected by their type but also by their source of origin.The study concluded that Moricin has a wide spectrum but limited potential to inhibit clinically important microbial strains belonging to different species and genera.

An Improved Elite Slime Mould Algorithm for Engineering Design

The Swarm intelligence algorithm is a very prevalent field in which some scholars have made outstanding achievements.As a representative,Slime mould algorithm(SMA)is widely used because of its superior initial performance.Therefore,this paper focuses on the improvement of the SMA and the mitigation of its stagnation problems.For this aim,the structure of SMA is adjusted to develop the efficiency of the original method.As a stochastic optimizer,SMA mainly stimulates the behavior of slime mold in nature.For the harmony of the exploration and exploitation of SMA,the paper proposed an enhanced algorithm of SMA called ECSMA,in which two mechanisms are embedded into the structure:elite strategy,and chaotic stochastic strategy.The details of the original SMA and the two introduced strategies are given in this paper.Then,the advantages of the improved SMA through mechanism comparison,balance-diversity analysis,and contrasts with other counterparts are validated.The experimental results demonstrate that both mechanisms have a significant enhancing effect on SMA.Also,SMA is applied to four structural design issues of the welded beam design problem,PV design problem,I-beam design problem,and cantilever beam design problem with excellent results.

Hyperspectral Remote Sensing Image Classification Using Improved Metaheuristic with Deep Learning

Remote sensing image(RSI)classifier roles a vital play in earth observation technology utilizing Remote sensing(RS)data are extremely exploited from both military and civil fields.More recently,as novel DL approaches develop,techniques for RSI classifiers with DL have attained important breakthroughs,providing a new opportunity for the research and development of RSI classifiers.This study introduces an Improved Slime Mould Optimization with a graph convolutional network for the hyperspectral remote sensing image classification(ISMOGCN-HRSC)model.The ISMOGCN-HRSC model majorly concentrates on identifying and classifying distinct kinds of RSIs.In the presented ISMOGCN-HRSC model,the synergic deep learning(SDL)model is exploited to produce feature vectors.The GCN model is utilized for image classification purposes to identify the proper class labels of the RSIs.The ISMO algorithm is used to enhance the classification efficiency of the GCN method,which is derived by integrating chaotic concepts into the SMO algorithm.The experimental assessment of the ISMOGCN-HRSC method is tested using a benchmark dataset.

Optimal Deep Transfer Learning Based Colorectal Cancer Detection and Classification Model

Colorectal carcinoma(CRC)is one such dispersed cancer globally and also prominent one in causing cancer-based death.Conventionally,pathologists execute CRC diagnosis through visible scrutinizing under the microscope the resected tissue samples,stained and fixed through Haematoxylin and Eosin(H&E).The advancement of graphical processing systems has resulted in high potentiality for deep learning(DL)techniques in interpretating visual anatomy from high resolution medical images.This study develops a slime mould algorithm with deep transfer learning enabled colorectal cancer detection and classification(SMADTL-CCDC)algorithm.The presented SMADTL-CCDC technique intends to appropriately recognize the occurrence of colorectal cancer.To accomplish this,the SMADTLCCDC model initially undergoes pre-processing to improve the input image quality.In addition,a dense-EfficientNet technique was employed to extract feature vectors from the pre-processed images.Moreover,SMA with Discrete Hopfield neural network(DHNN)method was applied for the recognition and classification of colorectal cancer.The utilization of SMA assists in appropriately selecting the parameters involved in the DHNN approach.A wide range of experiments was implemented on benchmark datasets to assess the classification performance.A comprehensive comparative study highlighted the better performance of the SMADTL-CDC model over the recent approaches.

Effect of Disinfection Time on Microbial Content and Quality of Cold Fresh Chicken

[Objective] The aim was to provide reference for the production technolo- gy of cold fresh chicken. [Method] Lactic acid was used as the disinfectant in cooling water, so as to study the effect of disinfection time on the microbial content and quality of cold fresh chicken. [Result] With disinfection of 20 min, the removal rates of the total colonies, coliforms and moulds reached over 95%. As the disinfec- tion time was further extended, it had no significant effect on the removal effects of the microbial content and could affect the tenderness and color of cold fresh chick- en. [Cendusion] The study provides references for the design and optimization of the production process of cold fresh chicken.

Microstructure and mechanical properties of Mg-Gd-Y-Zr alloy cast by metal mould and lost foam casting

The microstructure and mechanical properties of Mg-10.1Gd-3.74Y-0.25Zr （mass fraction, %） alloy （GW104 alloy） cast by metal mould casting （MMC） and lost foam casting （LFC） were evaluated, respectively. It is revealed that different forming modes do not influence the phase composition of as-cast alloy. In the as-cast specimens, the microstructures are similar and composed of α-Mg solid solution, eutectic compound of α-Mg＋Mg 24 （Gd, Y） 5 and cuboid-shaped Mg 5 （Gd, Y） phase; whereas the average grain size of the alloy produced by metal mould casting is smaller than that by lost foam casting. The eutectic compound of the alloy is completely dissolved after solution treatment at 525 ℃for 6 h, while the Mg 5 （Gd, Y） phase still exists after solution treatment. After peak-ageing, the lost foam cast alloy exhibits the maximum ultimate tensile strength of 285 MPa, and metal mould cast specimen 325 MPa at room temperature, while the tensile yield strengths of them are comparable. It can be concluded that GW104 alloy cast by lost foam casting possesses similar microstructure and evidently lower mechanical strength compared with metal mould cast alloy, due to slow solidification rate and proneness to form shrinkage porosities during lost foam casting process.

Production of carbon anodes by high-temperature mould pressing

Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.

Microstructure and crystal growth direction of Al-Cu alloy

The microstructures and crystal growth directions of permanent mould casting（PMC） and directionally solidified（DS） Al-Cu alloys with different contents of Cu were investigated. Simultaneously, the effects of pouring temperature on the microstructure and crystal growth direction of permanent mould casting pure Al were also discussed. The results indicate that the α（Al） crystals in the pure Al do not always keep common columnar grains, but change from the columnar grains to columnar dendrites with developed arms as the pouring temperature rises. The growth direction also varies with the change of pouring temperature. Cu element has similar effects on the microstructures of the PMC and DS casting Al-Cu alloys and the α（Al） crystals gradually change from columnar crystals in turn to columnar dendrites and developed equiaxed dendrites as the Cu content increases. The crystal growth direction in the PMC alloys gradually approaches （110） orientation with increasing Cu content. But the resulting crystals with growth direction of （110） do not belong to feathery grains. There are also no feathery grains to form in all of the DS Al-Cu alloys.

Rapid Non-destructive Detection for Molds Colony of Paddy Rice Based on Near Infrared Spectroscopy

Near infrared spectrometer technology under a wavelength range of 918-1045 nm was used to rapidly detect paddy rice that was stored at 5℃, 15℃ and 25℃. A total of 121 paddy rice samples were collected from artificial infection with moulds to build the calibration models to calculate the total number colony of moulds based on the principal component regression method and multiple linear regression method. The results of statistical analysis indicated that multiple linear regression method was applicable to the detection of the total number colony of moulds. The correlation of calibration data set was 0.943. The correlation of prediction data set was 0.897. Therefore, the result showed that near infrared spectroscopy could be a useful instrumental method for determining the total number colony of moulds in paddy rice. The near infrared spectroscopy methodology could be applied for monitoring mould contamination in postharvest paddy rice during storage and might become a powerful tool for monitoring the safety of the grain.