bluuebunny/crossref_metadata_2025 huggingface dataset:
Tofu’s Liquid waste treatment by continuous vermibiofilter column-type reactor
Authors: Persulessy A E , Rosmalina R T , Hartati E , Putra R D
Published: June 2020

The demands of tofu as food constantly increase in Indonesia, a large amount of clean water for production process of this food enhance significantly and resulting amount of liquid waste discharging goes to the sewer system increase and finally arrive into the streams or rivers in almost all big cities in Indonesia. Currently, only view of tofu makers which have waste water treatment plant however far from the standard which is expected for treating this liquid waste. Sampling of this liquid waste from centre of tofu maker were not comply the ministry of environment and forestry regulation (PerMenLH No.5 Tahun 2014). Therefore, in this study we have used vermibiofilter column-type reactor for treating Tofu’s liquid waste for reducing the concentration of pollutant. Vermibiofilter has chosen since this technique is regarded as simply way for treating the tofu’s liquid waste and also will provide a benefit for earthworm farmer in which this tofu’s liquid waste is food stuff for earthworm. The Species of earthworm we have used was Lumbricus rubellus that is an endemic earthworm in Indonesia. Usage of earthworm in biofilter column-type reactor shown that the removal efficiency of turbidity, TSS, COD, and BOD are 99.2 %, 66.19 %, 80.77 % and 81.05 % respectively and for column-type reactor without having earthworm (biofilter) as a control, the removal efficiency for Turbidity, TSS, COD and BOD are 98.4 %, 41.93 %, 66.77 % and 66.7 % respectively. This result showed that earthworm Lumbricus rubellus plays significant role for degrading organic matter, producing the microorganism decomposer and also absorbing organic matter.
Biohythane from organic waste: An overview
Authors: Priantoro E A , Sriwuryandari L , Sembiring T
Published: June 2020

Organic wastes considered as a common problem in Indonesia, especially from agricultural waste, such as fruits and vegetables waste. However, these organic wastes can also converted into biogas. Biohydrogen and biomethane play important roles for future economical energy sources due to clean, CO2 neutral and environmentally friendly. Biohythane is a mixture of methane and hydrogen that produced in two separated bioreactor. The total energy recovered from two stages fermentation considered higher than single stage bioreactor. The short hydraulic retention time applied in the first stage is enough to separate acidogenesis from methanogenesis; however the pretreatment is also needed for lignocellulosic waste. Temperature application in the first or both reactors are effective to improve the yield of biohythane from the organic waste; meanwhile it needs more energy rather than mesophilic condition. Bioreactor utilization by considering types of fermentation should become attention in the case we have to choose between solid or liquid organic waste. The range results from two stages are methane 45-55 %, hydrogen 11-15 %, and carbon dioxide 30-35 %, respectively.
Wastewater management strategies planning of Cimahi city based on 2018 city sanitation strategy guideline
Authors: Yasya H R , Juwana Iwan
Published: June 2020

Cimahi City is one of the developing cities in Indonesia that has low service sanitation condition, especially in domestic wastewater management. In 2016, the coverage of domestic wastewater services in the city only reached 68.17 %. It shows that 31.83 % of Cimahi region is not yet served with wastewater systems. In consequences, some communities discharging their wastewater to the stream. This matter could lead to water pollution that will indirectly affecting public health, potentially waterborne diseases. Based on these problems, this research was carried out to calculate the level of risk in each urban village of Cimahi. The risk level is stated in the form of scores 1-4 with a description of 1 is very low risk; 2 is low risk; 3 is high risk; 4 very high risk. The risk calculation considers the determinants (exposure and impact) which consist of the percentage of wastewater service, risk index based on the EHRA study, perceptions of related regional organizations, population, population density, poverty rates, and regional categories. The results obtained from the calculation of the risk of domestic wastewater in Cimahi show that the Pasirkaliki, Cibabat, Citeureup, Cipageran, Baros, and Cibeber have a very low risk; Cimahi and Utama are at low risk; Karangmekar, Cigugur Tengah and Cibeureum are at high risk; while Padasuka, Setiamanah, Leuwigajah and Melong have a very high risk, respectively.
Solid-state fermentation and formulation of non-sterile palm oil processing waste using Rhizopus azygosporus UICC 539
Authors: Sari M R , Oetari A , Sjamsuridzal W
Published: June 2020

This study reported the ability ofRhizopus azygosporusUICC 539 to utilize non-sterile slurry and palm kernel cake (PKC) through solid-state fermentation, preparation of the fungus and non-sterile waste mixture as a formula for animal feed, and analysis of nutrient content of the formula. Fungal culture in PSB at 30 and 40 °C for 5 days was prepared and wet weight biomass was used as inoculum for animal feed formula. Solid-state fermentation (SSF) was carried out on the mixtures of non-sterile slurry and PKC (3:1) at 30 and 40 °C for 5 days and the fermented waste mixtures were dried at 60°C for 5 days. The results showed that during SSF there were presence of colonies of other fungi and bacteria from the waste mixture besidesR. azygosporus. The total cell number ofR. azygosporusand other fungi were decreased after SSF. Changes in nutrient content in the formula were observed by comparing the treatment and control. Formula prepared at 40 °C showed an increase of carbohydrate content and total calorie, while formula prepared at 30 °C showed an increase only at carbohydrate content. A decrease of protein, water content, ash content, total fat, and energy from fat, was observed in formulas prepared at both temperatures.
Synthesis of polyelectrolyte complex (PEC) membrane chitosan-polystyrene sulfonate (PSS) from styrofoam waste as adsorbents of Cd(II) and Pb(II) ions
Authors: Opier R D A , Siswanta D
Published: June 2020

The adsorption of Cd(II) ions and Pb(II) ions has been studied using a chitosan polystyrene sulfonate (PSS) from styrofoam waste polyelectrolyte complex (PEC) membrane adsorbent. Chitosan-PSS PEC membrane was characterized by FTIR and SEM. The adsorption experiment was performed under various conditions such as weight ration of PSS and chitosan as adsorbent, pH, contact time, and different initial Cd(II) and Pb(II) concentrations. The data showed that the optimum ratio of PSS and chitosan was 60:40 for Cd(II) and Pb(II) ions. The optimum pH value was found to be 4 for Cd(II) ions and 5 for Pb(II) ions. The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data of Cd(II) and Pb(II) ions. The data fitted well to the pseudo-second order kinetic model. The experimental data of adsorption Cd(II) and Pb(II) ions also were fitted to Freundlich isotherms.
Solid-state fermentation of sterile slurry and palm kernel cake (PKC) mixture using Rhizopus azygosporus UICC 539
Authors: Arsy S L , Oetari A , Sjamsuridzal W
Published: June 2020

This study described solid-state fermentation of sterile slurry and palm kernel cake (PKC) mixtures by Rhizopus azygosporus UICC 539, preparation of the fungus and waste mixture as a formula for animal feed, and analysis of nutrient content of the formula. Preparation of inoculum (v/v) in Potato Sucrose Broth (PSB) was carried out at 30 and 40 °C for 5 days. Wet weight biomass was used as inoculum for solid-state fermentation (SSF) using sterile slurry and PKC (3:1) mixtures and SSF was carried out in flat trays (20×20×5 cm) at 30 and 40 °C for 5 days. The fermented waste mixture was dried at 60 °C for 5 days. Changes in nutrient content of the formula were observed by comparing the treatment and control. Formula prepared at 30 °C showed an increase in carbohydrate, protein and moisture content. A decrease was observed in total fat and ash content, calorie from fat and total calorie. Formula prepared at 40 °C showed an increase in protein and ash content. A decrease was observed in carbohydrate, moisture and total fat content, calorie from fat, and total calorie. Rhizopus azygosporus UICC 539 was able to grow and utilize the palm oil processing waste and improved the nutrient content of the formula.
Low-cost modified reactor to produce biochar and clamshell as alternative materials from acid mine drainage problem solving
Authors: Wibowo Y G , Sudibyo  , Muhammad D , Naswir M , Muljadi B P
Published: June 2020

Industrial activities and the natural oxidation of metallic sulphide-ores produce sulphate-rich waters with low pH and high heavy metals content generally termed Acid Mine Drainage (AMD). This is of great environmental concern, as some heavy metals are highly toxic. Within several possibilities, biochar and clamshell is an attractive option to treat AMD and to recover metals. This study aims to describe a simple method to utilized waste of both. Pyrolysis of waste material used to change waste to biomaterial biochar and clamshell. This research showed that biochar and clamshell are potentials material to reduce AMD impacts. This research will help and acceptable for rural areas to solve AMD problems.
A review on biogas purification through hydrogen sulphide removal
Authors: Andriani D , Rajani A , Kusnadi  , Santosa A , Saepudin A , Wresta A , Atmaja T D
Published: June 2020

Biogas has been recognized as a clean and renewable form of energy that is produced from biodegradable organic materials via an anaerobic digestion. In fact, biogas has been well expected to substitute current conventional sources of energy. The main composition of biogas includes methane (CH4) and carbon dioxide (CO2), which is accompanied by different contaminants in varied quantities such as ammonia (NH3), water vapour (H2O), hydrogen sulphide (H2S), methyl siloxanes, nitrogen (N2), oxygen (O2), halogenated volatile organic compounds (VOCs), carbon monoxide (CO) and hydrocarbons. Biogas has been widely utilized as either engine fuel or starting material for chemicals, hydrogen and/or synthesis gas productions. For certain applications, a certain purity degree of biogas is required. Technically, the presence of trace components in biogas has been known to negatively affect engine performance. Therefore, a removal of contaminants, particularly H2S and CO2, is expected to significantly improve biogas quality, thus enhancing its performance in various applications. Besides, the removal is performed to meet standardized gas specifications for its usage as vehicle fuel or being injected into a natural gas grid. In practices, different methods for biogas cleaning and upgrading have been recognized, in which differ in terms of functions, efficiency, and required quality of input gas. This study, therefore, aims at reviewing various H2S removal-based biogas cleaning techniques during and after digestion process.
Pyrethroid analysis in fresh tea leaves: preliminary study in building the low volume extraction
Authors: Pitoi M M , Gunawati R D , Ariyani M , Koesmawati T A , Yusiasih R , Maulana H
Published: June 2020

Low volume extraction using rotary agitator was used in order to develop method analysis for simultaneous determination of five pyrethroids (lambda-cyhalothrin, permethrin, cypermethrin, fenvalerate, and deltamethrin) in fresh tea leaves. The application of n-hexane, n-hexane with some modifications, acetonitrile, and ethyl acetate were tested to extract the pyrethroids before being injected to gas chromatography coupled with electron capture detector. The experiment was conducted in spike-experiment where known amount of pyrethroids were fortified into the fresh tea leaves and the results were compared to the no-spike-experiment where no pyrethroids were added. Result showed that n-hexane was able to extract all target pyrethroids from fresh tea leaves but the recovery values were low. Meanwhile, acetonitrile and ethyl acetate were able to extract pyrethroids with higher recovery values compare to n-hexane but only acetonitrile gave recovery values that were in the range suggested by European Union. Therefore acetonitrile is suggested as a solvent for low volume extraction of pyrethroids from fresh tea leaves.
The optimization of pyrethroid simultaneous analysis in tropical soil of Indonesian tea plantation: Preliminary study
Authors: Ariyani M , Pitoi M M , Yusiasih R , Maulana H , Koesmawati T A
Published: June 2020

The preliminary study for the simultaneous analysis of five synthetic pyrethroids (lambda-cyhalothrin, permethrin, cypermethrin, fenvalerate, and deltamethrin) in tropical soil of tea plantation has been performed. The objective of this study is to perform an optimum condition for simple method development, based on green analytical chemistry. The concentrations of 0.1 μg.g-1 for all pyrethroids were evaluated using ultrasonic and microwave-assisted extraction. The quantification was performed using gas chromatography-electron capture detection (GC-ECD). Based on the experiment, the 0.5 mm soils size particles and 30 minutes sonication times were set as optimal condition for ultrasonic-assisted extraction with the best recovery yields of spiked soils were from 80 to 105 % for each pyrethroid and repeatability represent by the relative standard deviation (RSD, %) ranging of 1.1 – 4.8 %. Results were comparable with those found by microwave-assisted extraction. The result shows that the reproducibility, which is represented by recoveries obtained, ranged from 151 – 276 %, and were unacceptable because the value was beyond the specific range that was proposed by the Association of Analytical Communities (AOAC) International. The ultrasonic-assisted extraction was applicable for pyrethroids analysis in the real sample, with concentration found was 0.01 to 0.12 μg.g−1.
Determination of volatile fatty acids in tofu wastewater by capillary gas chromatography with flame ionization detection: A Comparison of extraction methods
Authors: Rosmalina R T , Widyarani  , Hamidah U , Sintawardani N
Published: June 2020

Volatile fatty acids (VFA) are intermediate products during the anaerobic digestion process of complex waste. Accurate quantification of VFA is a useful measurement of the process. This study evaluated two extraction methods for gas chromatography determination of the following VFA: acetic acid, propionic acid, butyric acid, and valeric acid to find a simple and efficient preparation approaching on Green Analytical Chemistry methods. Tofu wastewater was used as the sample. The extraction was performed using diethyl ether and carried out either by vortex mixing or shaken by hand. The measurement was performed using gas chromatography with HP-INNOWax column and flame ionization detector. The linearity, precision, accuracy, limit of detection and limit of quantification were evaluated. VFA determination was linear at the concentration range of 5-500 μg/mL for all VFA. The precision of 2.59-12.63 % was obtained for both methods. The recovery of the fortified sample (10 µg-VFA/mL) was 75.33-98.31 % for vortex extraction and 99.81 to 103.80 % for shaken by hand extraction. Limits of detection and quantification of vortex extraction were 0.38-2.78 µg/mL and 1.06-3.03 µg/mL, respectively. Limits of detection and quantification using hand shaken extraction were 0.09-1.13 µg/mL and 0.55-1.61 µg/mL, respectively. Based on the high recovery and low limits of detection and quantification, shaken by hand extraction method can be used for rapid and accurate quantification of VFA.
Comparative study of different sorbents for clean-up for pyrethroid analysis in cocoa powder by GC-ECD: A preliminary study
Authors: Yusiasih R , Endah E S , Ariyani M , Koesmawati T A , Pitoi M M
Published: June 2020

Three types of solvents and 13 combinations of sorbents were tested to extract pyrethroids (lambda-cyhalothrin, permethrin, cypermethrin, fenvalerate, and deltamethrin) from cocoa powder and to remove interferences during clean-up step before being quantified by gas chromatography coupled with electron capture detector (GC-ECD). The result was analysed based on recovery study by spiking the cocoa powder with known amount of targeted pyrethroids. Acetonitrile, methanol, and n-hexane were compared as the solvents and the result showed that acetonitrile is relatively better in extracting pyrethroids. Moreover, 13 treatments, singly or combination of primary secondary amine (PSA), graphitized carbon black (GCB), C18, and florosil, were tested for clean-up step. The clean-up study shows that only combination of PSA and GCB; combination of C18 and Florisil; and combination of GCB and florisil comply the recovery guideline suggested by AOAC and EU, thus are suggested for clean-up for pyrethroid analysis in cocoa powder.
Integrated water quality modelling for spatial planning
Authors: Susilowati Y , Kumoro Y , Nur W H
Published: June 2020

The main objectives of spatial planning is to ensure that the utilization of land resources is planned and implemented in an organized manner to meet the needs of present and future generation. The aim of this study is to develop an integrated water quality modelling for spatial planning. Study area is Ciliwung watershed, in the middle of Jakarta Coastal watershed. This area is ideal for such a study. Jakarta is the capital city of the Republic of Indonesia, the most-populous national capital, incorporating one of the world’s largest coastal cities. The environmental condition of Ciliwung River is very poor. In this area exist a spatial distribution of socio-economic activities and related land uses such as urban area, industry, mining, agriculture, forestry, aquaculture and fisheries, commerce, transportation, and all the human activities that generate the associated manmade pollution and other environmental issues. Water quality modelling of Ciliwung River has been used to analyse the correlation of water quality in the river body with the land use in that area. Water quality modelling was performed using the QUAL2K public domain free software. Eutrophication models were used to determine the fate and transport of organic pollutants. Correlation analysis was carried out in term of to design the optimal land use planning. Optimizing land use was intended to obtain maximum economic benefits without causing environmental pollution. Several scenario analysis was applied in this area. Based on the water quality modelling, it is can be identified, the main pollution problem in Ciliwung system is in the downstream area, due to the high load of non-point source pollutants in the area. Pollution control in the downstream of Ciliwung is very crucial in term of the sustainability of Ciliwung water resources. Ciliwung pollutant load control can be done by land use planning and build a waste treatment plant. Spatial planning is needed in this areas to get the area with minimal pollutant loads.
A Fast Solving Method for Curve Profile of Suspension Bridge Catwalk System in Plane
Authors: Xiaoping Zhang , Zhuo Zeng , Zengzeng Li
Published: June 2020

With increasing demands of in plane suspension bridge for mountainous area of P. R. China in recent year, rapid erection of catwalk system has become the researching hotspot for constructors, wherein curve profile is one of the key factors that matter. In this paper, a nonlinear optimization method is introduced for fast solving curve profile of catwalk system. To achieve the goal, statics fundaments and compliant characteristics of general catenary is firstly analyzed. Structural detailing of catwalk system is then described so that segmentation prior to computation can be made as per loads types or requirements of obtaining finer curve coordinates. In addition, nominal curve profile of catwalk system is derived according to segmentation of main cable, based on which the actual catwalk curve profile solving problem is afterwards formulated as an unconstrained nonlinear programming in terms of external penalty parameter and solved by using Levenberg-Marquardt (L-M) algorithm. Finally, a study case is shown to illustrate the effectiveness of proposed method.
The School-building Model of the Church Schools in Nanjing, China before the 20th Century——Taking the Huiwen Academy as an Example
Authors: Wang Hechi
Published: June 2020

Church school is a special type of school in old China. After the first Opium War, Western churches have come to China to preach. Missionaries open churches, schools, and hospitals in China. This paper selects the largest church school in Nanjing in the late Qing Dynasty(before 1911) as an example. Based on the historical data of archival materials and the research methods of on-site mapping, the initial campus construction model of Nanjing Church School is summarized. The article first introduces the background of the school in China, the reasons for the establishment of the school, the history of the school; then analyzes the location, construction process, campus planning and architectural characteristics of the school; further analyzes the reasons why the western church replicates the western campus construction model; Finally, through the development of educational buildings, the contributions of church schools in the history of modern education in China are summarized. The article shows the development of large-scale educational buildings that are rare in the history of modern Chinese education. It not only clearly clarifies the history of the development of church schools in China, but also has important guiding significance for the heritage protection of today's historical buildings. At the same time, it also has important reference value for the protection of educational building heritage and campus construction in China and even in the world.
Research on Adaptive Facade Renovation Design of Industrial Architectural Heritage: A Case Study of Nanjing Hutchison Factory
Authors: Wu Yanming , Zhou Qi
Published: June 2020

The pst-industrial era witnesses the gradual decline or transformation of China’s traditional industrial industry. Meanwhile, the original facade design of most of the existing industrial architectural heritage can no longer keep up with the pace of the times, which left a lot of issues that need to be considered and studied urgently in the renovation of industrial architectural heritage.

In this article, the adaptive facade renovation design of industrial architectural heritage was studied and effective design strategies were summarized. Firstly, the research background of adaptive renovation of industrial architectural heritage and the research objects in this article were outlined and discussed, and then the relevant concepts and materials of facade renovation of industrial architectural heritage were summarized. Secondly, the renovation of Nanjing Hutchison Factory was cited here as an example for specific analysis. Finally, based on the analysis and summary of the case, corresponding design strategies and methods for the adaptive facade renovation were summarized, and the future research direction was put forward. This article is not only of great guidance and promotion to the renovation of Hutchison, but also of certain reference value to similar facade renovation projects of architectural heritages in China and even in the world.
Experimental Investigation for Moment Redistribution in Continuous RC Beams Top Strengthened with CFRP and Steel Plates
Authors: Ibrahim Amr , Salem Shady , Khalil Ayman , El-Kateb Mahmoud
Published: June 2020

An experimental study was conducted on eight T-section continuous reinforced concrete beams top strengthened with CFRP and steel plates. The beams had a constant cross section and flexural steel reinforcement which was designed to prevent brittle failure due to crushing of concrete before steel yielding. The plates were installed on both sides of the slab above the beam web as near surface mounted or externally bonded to investigate the effect of different plating techniques on the moment redistribution in reinforced concrete beams. The number of plates in each specimen was changed. Steel stirrups were used and designed so that no premature shear failure occurs. The experimental results show that the steel plating can cause up to 40 % redistribution of moments from the sagging to the hogging regions compared to the control specimen as well as a significant increase in the loading capacity of the beams. The results also revealed that the application of CFRP plates can lead to substantial amounts of moment redistribution when they are installed as near surface mounted plates, but without enhancing the load carrying capacity.
Study on Working Behavior of Cage-type Flexible Retaining Wall
Authors: Jie Liu , Yanyu Chen , Yehan Geng , Kaixuan Li
Published: June 2020

Cage-type flexible retaining wall is a new type of anti-seepage structure with broad market prospects due to its low cost and convenient installation. In order to study the working behavior of flexible cage-type retaining wall in flood control during the flood season, a three-dimensional finite element model of the structure was established, and the stress and deformation characteristics of the structure were analyzed. The results show that the maximum tensile stress is 17.1MPa, the maximum compressive stress is 12.6MPa, and the maximum structural deformation is 0.35mm, which are less than the allowable value, meaning the stress and deformation of the structure can meet the requirements of engineering construction. The reliability of the structure is verified by the full-scale model water retaining test. The vertical flow frame on the backwater side is a relatively weak part of the structure. When designing the structure, the cross-sectional dimensions of the vertical flow frame on the upstream side and the downstream flow frame can be reduced appropriately, while the cross-sectional dimensions of the vertical flow frame on the backwater side can be increased appropriately, so as to give better play to the material characteristics and save project cost.
Water Permeability Properties of Concrete made from Recycled Brick Concrete as Coarse Aggregate
Authors: Ahmad Syed Ishtiaq , Rahman Md. Shafiqur , Alam Md. Shahrior
Published: June 2020

Water Permeability characteristic of concrete made from recycled brick concrete as coarse aggregate was investigated and compared with concrete made from crushed virgin clay brick and natural stone aggregate. For this, concrete samples of three different compressive strengths 17.2, 20.6 and 24.1 MPa were prepared as per ACI mix design methods from each of these aggregates. These concrete samples were then tested for compressive strength and water permeability using the AT 315 machine as per BS EN 12390-8: “Depth of Penetration of Water under Pressure”. Apart from these, porosity and bulk density were also measured in hardened concrete. Compressive strength of concrete produced from virgin brick and recycled brick concrete was found to be lower than the design strength at 28th day. Coefficient of water permeability of concrete made from recycled brick concrete as coarse aggregate was found to be higher than that of virgin brick and natural stone aggregate concrete of equivalent strength by 350 to 400%. Water permeability was found to be directly related to compressive strength and porosity in hardened concrete.
Investigation of the Significance of Factors Affecting Long-Term Creep of Concrete using Screening Designs
Authors: Daou H , Raphael W
Published: June 2020

Creep has a main role in predicting delayed strain in concrete members and in estimating losses in prestressed concrete, such as nuclear containment vessels, bridges girders, etc. For that, the interest in studying creep has grown significantly. This study aims to investigate the significance of different factors affecting creep of concrete using the Northwestern University (NU) creep database. Experiments have been carried out at different conditions of water-cement ratio (w/c), aggregate-cement ratio (a/c), cement content (c), cement type (R or RS), admixtures, mean compressive strength (fcm), volume-surface ratio (v/s), relative humidity (RH), age at loading (t0) and stress level (sigma). In order to determine the significance of these factors, three statistical methods have been used: Daniel Plot, Lenth Plot and Bayesian screening. The results of this analysis can be used to build accurate computational models to predict creep of concrete by considering the major effects identified.
Effect of Humidity on Concrete Creep Predictions
Authors: Zgheib E H , Raphael W E
Published: June 2020

An accurate estimation of creep strains is mandatory to maintain the stability and integrity of concrete structures. Different parameters and conditions affect concrete creep predictions more precisely the relative humidity. To study its effect, a large database coming from international laboratories and research centers was applied to compare the experimental measurements to the theoretical values predicted by Eurocode 2 model. An inaccurate estimation was detected; therefore, an amelioration of the Eurocode 2 model was elaborated according to the relative humidity parameter. These calculations allow to predict accurately concrete creep and to avoid prejudicial consequences in structures due to creep phenomenon.
Obtaining Chitin/Chitosan-Melanin Complexes from Black Soldier Fly Hermetia Illucens
Authors: Khayrova Adelya , Lopatin Sergei , Varlamov Valery
Published: June 2020

Chitosan, obtained by deacetylation reaction of chitin, is a regular biopolymer with unique properties, including high biological and sorption activities. Melanin is considered as a natural photo and radio protector. Depending on the source and the isolation method, melanin possesses various physicochemical properties that can complement the radioprotective activity of chitosan and be used to solve important scientific and practical issues. Insects are relatively understudied natural sources of chitin-melanin complexes, whereas these components are linked by strong covalent bonds. This study developed a technology for the production of this natural conjugate, based on which its deacetylated derivative, the chitosan-melanin complex, was obtained, taking the black soldier fly as an example.
Influence of Surface Modification of BaTiO3 Nanoparticles by Sodium Oleate and Chitosan on their Optical Properties and Agglomeration in Aqueous Solutions
Authors: Roldan Lopez J A , Angelats-Silva L M , León-León H , Céspedes-Vásquez R , Aldama-Reyna C W , Emelianov N A
Published: June 2020

Spherical titanium barium nanoparticles with an average size about 100 nm in the tetragonal crystal phase were obtained by peroxide synthesis. To prevent their agglomeration and reduce the toxic effect, the surface of nanoparticles was chemically modified with sodium oleate and chitosan. Influence of surface modification by these compounds on agglomeration of nanoparticles in aqueous solutions, their spectral features, as well as generation of the second optical harmonic were investigated.
Comparing mesoscopic models for dendritic growth
Authors: Tourret D , Sturz L , Viardin A , Založnik M
Published: June 2020

We present a quantitative benchmark of multiscale models for dendritic growth simulations. We focus on approaches based on phase-field, dendritic needle network, and grain envelope dynamics. As a first step, we focus on isothermal growth of an equiaxed grain in a supersaturated liquid in three dimensions. A quantitative phase-field formulation for solidification of a dilute binary alloy is used as the reference benchmark. We study the effect of numerical and modeling parameters in both needle-based and envelope-based approaches, in terms of their capacity to quantitatively reproduce phase-field reference results. In light of this benchmark, we discuss the capabilities and limitations of each approach in quantitatively and efficiently predicting transient and steady states of dendritic growth. We identify parameters that yield a good compromise between accuracy and computational efficiency in both needle-based and envelope-based models. We expect that these results will guide further developments and utilization of these models, and ultimately pave the way to a quantitative bridging of the dendrite tip scale with that of entire experiments and solidification processes.
Reduced order models for welding and solidification processes
Authors: Mendez P F
Published: June 2020

This paper reviews the foundations of modelling of materials processing and methodologies of analysis outside the traditional discretization of the domain (e.g. finite elements, finite volume, etc.). It starts with a review of the mathematical framework with a focus on dimensional analysis and characteristic values. The methodology of minimal representation and correction factor is discussed with emphasis on computational methods to obtain the minimal representation and on the methodology of blending to obtain the correction factors. Welding on a thin plate with surface heat losses is used as a case study, and the results obtained are validated against published data for many materials, processes, and researchers.
Columnar-to-equiaxed transition in a laser scan for metal additive manufacturing
Authors: Yuan L , Sabau A S , StJohn D , Prasad A , Lee P D
Published: June 2020

In laser powder bed fusion additive manufacturing (LPBFAM), different solidification conditions, e.g., thermal gradient and cooling rate, can be achieved by controlling the process parameters, such as laser power and laser speed. Tailoring the behaviour of the columnar to equiaxed transition (CET) of the printed alloy during fabrication can facilitate the production of highly customized microstructures. In this study, effective analytical solutions for both thermal conduction and solidification are employed to model solidifying melt pools. Microstructure textures and solidification conditions are evaluated for numerous combinations of laser power and laser speed under bead-on-plate conditions. This analytical-based high-throughput tool was demonstrated to select specific process parameters that lead to desired microstructures. Two selected process conditions were examined in detail by a highly parallelized microstructural solidification model to reveal both nucleation and grain growth. Both numerical solutions agree well with experiments that are performed based on bead-on-plate conditions, indicating that these numerical models aid evaluation of the nucleation parameters, providing insights for controlling CET during the LPBFAM processing.
Thermomechanical modeling of additively manufactured structural parts - different approaches on the macroscale
Authors: Thorborg J , Esser P , Bayat M
Published: June 2020

Modeling the metal additive manufacturing process can be done on different length scales depending on the field of interest. However, due to the moving heat source and the narrow heat affected zone, a fine mesh and fine time resolution are required to analyze detailed information on various length scales. In this paper, the focus is on macro-scale temperature, deformation and residual stresses. The inherent strain method is applied layer by layer on the full part, to include the thermal contraction and inelastic strains generated by the moving heat source. The inherent strain components are mapped from the mesoscale simulations, where different boundary conditions can be used to resemble different regions from the macroscale. As an alternative to the inherent strain method and to include the thermal simulation on macroscale without simulating the moving heat source, a layer-by-layer approach is proposed and applied in the paper. The price to pay is the loss in detail of the thermal load. However, for the suggested layer-by-layer approach, the energy corresponds to the energy delivered from the laser. The proposed and implemented methods are applied to two examples and compared to measurements. Finally, large structural parts are simulated to evaluate the application on new trends in the automotive industry.
Study of thermoelectric magnetohydrodynamic convection on solute redistribution during laser additive manufacturing
Authors: Kao A , Gan T , Tonry C , Krastins I , Pericleous K
Published: June 2020

Melt pools formed in laser additive manufacturing (AM) are subject to large thermal gradients, resulting in the formation of thermoelectric currents due to the Seebeck effect. When in the presence of an external magnetic field, a Lorentz force is formed which drives fluid flow in the melt pool. This Thermoelectric Magnetohydrodynamics (TEMHD) phenomenon, can have a significant impact on the melt pool morphology and can alter the microstructural evolution of the solidification process. By coupling steady-state mesoscopic melt pool calculations to a microscopic solidification model, predictions of the resulting microstructure for multiple deposited layers have been obtained. The results indicate that the magnetic field can have a transformative effect on the microstructure and solute redistribution. This study highlights the theoretical potential for using magnetic fields as an additional control system to tailor AM microstructures.
Effect of evaporated gas flow on porosity and microstructure of IN718 parts produced by LPBF-processes
Authors: Jakumeit J , Huang C , Laqua R , Zielinski J , Schleifenbaum J H
Published: June 2020

Laser Powder Bed Fusion (LPBF) is the most widely used metal additive manufacturing (AM) process. A laser beam melts metal powder and partly the underlying solid metal to add metal layer by layer in selected regions. Temperatures up to the boiling temperature are reached resulting in a violent gas stream which affects solidification and can lead to porosity. Due to the small size of the melting zone, a detailed experimental analysis of the process is very difficult and simulation is an important tool to understand the manufacturing process and the influence of process parameter on the quality of components. In this work a three-phase melting and solidification simulation methodology has been used to investigate the melting, evaporation and solidification in a LPBF process. The methodology, originally developed to model casting processes, was extended by a model to calculate the heating of the metal powder by the laser beam and a metal evaporation model to include the effect of the evaporated metal gas on the total gas flow. The methodology was applied to analyse the melting, evaporation and solidification of single track experiments with IN718 powder. The simulation results were validated by comparing the calculated melt pool depth with the experimental findings. High laser power combined with slow laser speed leads to high energy densities at the melt pool, which result in a deep keyhole and increased porosity. The simulations revealed that evaporation of melt leads to a violent gas flow with velocities up to 100 m/s.
Part-scale mechanical modelling of LPBF including microstructural evolution effects
Authors: De Baere D , Bayat M , Mohanty S , Hattel J H
Published: June 2020

Due to its nature as a layer-by-layer production technique, the stresses and subsequent deformation from laser-based powder bed fusion are different from the ones observed in other manufacturing techniques. Additionally, because of the cyclic heating and cooling, the material undergoes significant microstructural changes during the process. Especially for the material Ti-6Al-4V, this microstructural change is pronounced, since the microstructure changes from β to α+β during the LPBF process. In this work, two models are coupled together in a novel way. First, a reduced-fidelity part-scale thermo-mechanical model will predict the stresses and deformation. This model uses both the meta-layer concept, and flash heating as methods for decreasing the computational cost. Secondly, a Johnson-Mehl-Avrami-Kolmogorov-based non-isothermal microstructural model is implemented as a state variable to estimate the change in phase fraction of the constituting phases. The results show that the part is made up mostly of a mix of α and α’ phases, and that the microstructural change only leads to a small change in the residual stress after the LPBF process.
Columnar-equiaxed transition in continuous casting based on a micro-macro solidification model with long-range solutal mixing
Authors: Uddagiri M , Spee J , Hubig S , Steinbach I
Published: June 2020

A novel model is proposed to describe the columnar to equiaxed transition (CET) in continuous casting. The model bases on Rappaz and Thevoz’s solute diffusion model for equiaxed dendritic growth, combined with a 1-Dimensional solidification model normal to the slab surface. The unique feature of the proposed model is the combination with a mixing term between interdendritic and extradendritic melt, representing long-range solutal mixing by convection. The model can also be applied to predict equiaxed to columnar transition (ECT), i.e. the chill zone thickness. The model consists of modules such as nucleation, growth kinetics, solute and heat balance, and a solute mixing module. Nucleation is considered with a fixed nucleation undercooling. The growth kinetics of the dendrites are treated according to the LGK model. A finite difference scheme is employed for solving 1-Dimensional heat transfer equations and finally, volume averaged solute balance equations are solved in a staggered scheme. Mixing of inter- and extradendritic liquid is, as a first step, treated ideally fast. When applied to Fe-C binary system with the thermo-physical properties obtained from literature and CALPHAD simulations, the model successfully predicts recalescence, phase fraction evolution, and concentration profiles in different phases. Realistic boundary conditions of the continuous casting process are obtained from macroscopic FEM simulation.
Simulation of longitudinal surface defect in steel continuous casting
Authors: Zappulla M L S , Thomas B G
Published: June 2020

Cracks and depressions in steel continuous casting often start during initial solidification in the mold and evolve later in the process. To understand the mechanism(s) of formation of these defects, a finite-element model of transient thermal-mechanical behavior during steel solidification has been developed and applied to simulate longitudinal depressions. The thermal model features a detailed analysis of heat transfer across the interfacial gap, which is fully coupled with a thermal-mechanical elastic-viscoplastic finite-element model that calculates the evolving size and shape of surface depressions. The results are compared with analysis of a sample with a longitudinal surface depression and crack from a commercial continuously cast slab. In this scenario, a thermal event caused a local drop in heat transfer, followed by frictional tension on the domain due to slab shrinkage, led to shell necking and the formation of a localized U-shaped depression. Finally, a new visualization methodology has been developed to better reveal defect formation in real time, such as longitudinal depressions, which persist as they move down the mold at the casting speed.
Integrated numerical simulation of the industrial continuous casting process
Authors: Fainberg J , Hepp E , Schäfer W , Krafthöfer C
Published: June 2020

The production of a continuously cast strand involves a large number of coupled phenomena involving flow, heat transfer, solidification and thermo-mechanics. In this paper, different approaches are described for the numerical modelling of industrial continuous casting processes at different levels of detail, dependent on the questions to be investigated. In the simplest case to obtain a rough estimate of the process conditions, the solidification of the strand is considered with a prescribed convective flux profile in the strand body based on the withdrawal speed. In the most complicated case, the process phase of filling of the empty mould is first calculated, followed by the phase of the withdrawal of the strand including consideration of the flow in both strand and tundish.
A meshless thermomechanical travelling-slice model of continuous casting of steel
Authors: Mavrič B , Dobravec T , Vertnik R , Šarler B
Published: June 2020

The travelling slice approximation of continuous casting process is widely used in industrial practice to model the heat transfer and solidification. Short computational times that are possible due to the reduction from three to two dimensions compensate for lower accuracy introduced by the approximation. In the same spirit, the travelling slice approximation is also used for the thermomechanical model in the present paper. The model includes contributions from metallostatic pressure, thermal contraction and viscoplastic deformation to describe the stress in the material slice. It incorporates simple models to predict the hot tearing and cracking. The model is solved with a novel strong-form meshless method. It allows flexible adaptive node distribution to accurately describe the behaviour in the solidifying region. In this paper we focus on the two-way coupling of the heat transfer and deformation of the strand to model the air-gap formation in the initial stage of the casting process and to study the emergent behaviour that is the result of this coupling. We find that the inclusion of the air-gap model significantly changes the stress distribution in the corners of the strand because of the reheating caused by the reduced heat-transfer.
Performance of turbulence models for flow prediction in a mould of continuous steel caster
Authors: Gregorc J , Kunavar A , Šarler B
Published: June 2020

The flow of molten steel in a mould during continuous casting process is nowadays most often studied using numerical approach. With such an approach, appropriate numerical tools have to be selected to achieve physically sound results. Within this work we focus on performance of different turbulence models for the case of casting of steel billets with single SEN port oriented in vertical, downward direction. Only fluid dynamics aspect of the casting process is considered, while all other phenomena are disregarded at this stage. Simulations were performed with commercial CFD package ANSYS Fluent with k-ε, k-ω and SAS turbulent models. The geometric model, material properties and process conditions are closely matched to those from our experimental water model studies, which is typically not done. Hence, the difference between the experiments and the numerical simulation originates only due to turbulence model performance. The experimental PIV data from the water model experimental system is used to benchmark the performance of various turbulence models. The models are compared based on lateral dispersion of the liquid jet exiting submerged entry nozzle (SEN) and formation of recirculation zones around the SEN. The results show that while all three models are capable of capturing general flow features, only the SAS model predicts finer turbulent structures and reasonably captures the flow behaviour in temporal domain.
Multiphase-field modelling of hydrogen pore evolution during alloy solidification
Authors: Zhang A , Guo Z , Wang Q , Xiong S
Published: June 2020

Gas porosity is recognized as one of the most common defects that can severely deteriorate the mechanical properties of solidified materials. Simulating the gas porosity in castings is challenging due to intricate multiphase interaction. In this work, a multiphase-field model is developed to simulate the evolution of both solid phase and hydrogen pore during solidification in the Al-Cu alloy. The driving forces for the solid-liquid and liquid-gas transitions are the undercooling and pressure difference respectively. Results show that the presence of hydrogen pore substantially changes the dendrite network. The Cu element accumulates near the solid-liquid interface due to solute partition. The pore causes a local hydrogen reservoir and Cu vacuum region, which elevates the average hydrogen content and retards the dendrite growth by blocking Cu diffusion.