bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Properties of Spider Silk for Use As a Biomaterial: Molecular Dynamics Investigations
Authors: Rawal Atul , Rhinehardt Kristen L. , Mohan Ram V. 
Published: February 2021

Abstract
Even though silkworm are the most dominant type of silk fibers used for commercial applications, spider silk has a definitive role in biomedical applications due to its biocompatibility and excellent mechanical properties as biomaterials. In recent years, recombinant production of the silk proteins at a larger scale has found new interest. Spider silk composites with a combination of a variety of other biomaterials have also been used to improve properties such as bio-compatibility, mechanical strength and controlled degradation. [1] A major constituent of spider silk fibers, are spidroin proteins. These are made up of repetitive segments flanked by conserved non-repetitive domains. The fiber proteins consist of a light chain and a heavy chain that are connected via a single disulfide bond. [2] Present paper employed steered molecular dynamics (SMD) as the principal method of investigating the mechanical properties of these nanoscale spider silk protein 3LR2, with a residual count of 134 amino acids. [3]. SMD simulations were performed by pulling on β-chain of the protein in the x-direction, while holding the other fixed. The focus of this paper is to investigate the mechanical properties of the nanoscale spider silk proteins with lengths of about 4.5nm in a folded state, leading to understanding of their feasibility in bio-printing of a composite spider silk biomaterial with a blend of various other biomaterials such as collagen. An in-depth insight into the fraying and tensile deformation and structural properties of the spider silk proteins are of innovative significance for a multitude of biomedical engineering applications. A calculated Gibbs free energy value of 18.59 kCal/mol via umbrella sampling corresponds with a complete separation of a single chain from a spider silk protein in case of fraying. Force needed for complete separation of the chain from the spider silk protein is analyzed, and discussed in this paper. It is found that the protein molecule undergoes a tensile stretch at strain rates of ≅ 11.65. An elastic modulus of 20.136 GPa, calculated via simple SMD simulations by subjecting the silk β-chain to a tensile stretch is also presented.
Energy Analysis and Waste Valorization in a Kraft Paper Plant
Authors: Antunes Pedro , Ferreira Manuel Eduardo , Vilarinho Maria Cândida , Teixeira José Carlos 
Published: February 2021

Abstract
Paper production is an energy intensive industry but due to the wastes of its process (black liquor, waste biomass, sludge) has the capacity to generate most of its energy internally. Central to this balance are cogeneration units that guarantee the internal production of heat and electricity. These are sized for the company’s thermal load, with excess electricity injected into the grid.
The efficient use of endogenous resources is a major route for improving the energy and environmental efficiency of the plant. Some of the waste materials include biomass wastes, sludges and other industrial wastes such as plastics.
The present work aims to identify the opportunity of introducing a waste biomass gasification plant and the use of the produced synthesis gas, replacing the natural gas currently used in the turbine included in the company’s cogeneration unit.
In this scenario, one of the cogeneration units in its current configuration has two steam boilers (one biomass; one black liquor) and a gas turbine whose waste heat feeds a recovery boiler to produce steam.
The work involved several steps: the energy balance of the unit, the characterization of biomass residues (mixing bark, pine bark, eucalyptus bark, and refuse fibers), the test experimental analysis of residual biomass gasification and the characterization of the synthesis gas produced.
In the electric and thermal energy producing units, gas turbines have a working efficiency above 35% while the steam turbines is considerably lower (15%). The efficiency of the chemical recovery boiler (79.5%) is lower than that of the biomass boiler (89.5%).
From the experimental analysis of biomass it was found that most of them have a carbon and hydrogen content higher than 48 % and 5 %, respectively. In terms of higher calorific value (HHV), for the biomass where it was possible to determine it, the value is between 19.3 and 23.6 MJ/kg. These properties reveal that the selected biomasses from within the company, have potential as fuels. The limitation on its use may be due to the ash content, which tends to exceed 10 %.
A gasification test (90 % eucalyptus biomass and 10 % mixture biomass) was also carried out to produce syngas and further characterization. The calorific value of the gas produced was 18 MJ/kg, with an absolute density of 1.17 kg/m3.
It can thus be seen that for a gas turbine with a 35.8 % efficiency with a workload of 29.9 MWe 4.6 kg/s of syngas is required.
Build Time Analysis of Additive Manufacturing for Next Generation SLS Systems
Authors: Machado Michael , Fangueiro Raul , Barros Daniel , Nobre Luís , Bessa João , Cunha Fernando , Silva João , Sousa João 
Published: February 2021

Abstract
With the recent advances in the additive manufacturing (AM) production technologies, AM is becoming more common in today’s industry, nowadays is a normal practice to use this solution either to test a new prototype or to manufacture a functional product. The increase application is mainly due to significant developments in the production solutions of the AM. These recent developments are resulting in an increase search for new and more efficient production solutions. This search is always focused in producing more efficiently, with a greater variety of materials and produce part with better quality and proprieties. From an industrial point of view, one of the types of additive manufacturing that is increasing the percentage of use is the selective laser sintering (SLS) technologies. Although this process was first used in the mid-80’s, it has shown great developments in the recent years. This evolution of the process allowed it to become a solid solution even if it is highly time consuming, especially when compared with other types of addictive manufacturing.
From the several aspects that make the SLS a robust solution is the fact that it offers a consistent solution to produce high complex part with good mechanical properties, and also the ability to use many core materials, from polymers, metal alloy, ceramics or even composites materials. Due to the fact that the production of part using SLS technologies takes a long time, shows the relevance to study the entire process in order to quantify the time spent in each stage a very important step.
This study can be conducted with two major goals, in one hand to be able to predict the build time needed to complete a predetermined task, and in other hand, to improve the overall efficiency of the process based on the knowledge acquired in the previous analysis. These two aspects are important because they allow the machine operator to choose the production plan more carefully and also to know all the parameters of the process to make it more efficient.
In this paper will be presented a survey of the major stages of a SLS process in order to quantify the time consumed in each one of the stages, and if possible, determine solution to reduce the time spent. To better understand the topic the paper will be divided according to the proprieties and time consumed in each of the elements of the process. In other words, it will be divided accordingly to a machine, laser and material point of view. Furthermore, this paper will be focused in the SLS process and the productions based in a polymeric powder, therefore also containing aspects related to the power source used.
Multidisciplinary Optimization-Enabled Design Automation and Optimization for Blowout Preventer Pipe Rams
Authors: Song Fei , Li Ke , Stephan Rivas Caroline , Bieneman Konstantin , Yap Thomas 
Published: February 2021

Abstract
A blowout preventer (BOP) is a large valve that encases an oil well on the surface. The valve may be closed while drilling if overpressure from a reservoir causes formation fluids such as oil and natural gas to back up within the wellbore and endanger the rig. A pipe ram is one of the critical components in the BOP system, which is designed to seal around a drill pipe, restricting the flow in the annulus between the outside of the drill pipe and the wellbore. The pipe ram design family, which contains hundreds of pipe ram designs, intends to cover different configurations to suit a variety of dill pipe sizes. To assure their structural integrity under service loads, these pipe rams need to be designed to meet the stress requirements per the American Petroleum Institute (API) Specification 16A and ASME (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code Section VIII, Division 2. With a conventional manual design workflow, it would take a significant amount of time and effort to complete all the designs for the product family with code compliance. Therefore, a scalable solution is highly desirable for delivery of customer-needed ram blocks with much shorter lead time. MDO (Multi-Disciplinary Optimization) involves multi-code integration, CAE (Computer-Aided Engineering) workflow automation, design space exploration, and optimization. MDO-enabled, automated design optimization is becoming increasingly popular in both scientific and engineering communities.
In this paper, a methodology for integration of CAD (Computer Aided Design), FEA (Finite Element Analysis), cost, and optimization packages to enable FEA automation and design optimization is presented. A BOP pipe ram is adopted as the use case. The ram block geometry was parameterized before being imported into an FEA package. The FEA workflow was automated such that once a set of geometric parameters are given, the preprocessing, solving, and postprocessing steps can be automatically completed. As part of the FEA postprocessing, stress linearization analysis per the API and ASME BPVC codes has also been automated, which had never been done in the past. A manufacturing cost analysis package can also be used to consume the parameterized geometry for automatic manufacturability assessment and cost predictions. The stress analysis and cost analysis workflows are conducted separately but also orchestrated by an MDO package. Reports that contain the analysis results are sequentially generated for various design permutations. The MDO-enabled automated design and cost analysis approach could substantially enhance efficiency and consistency in performing FEA and cost studies and producing analysis reports. It is also the backbone for automated design optimization, which could significantly improve the product performance and reliability and, meanwhile, minimize the development and product cost.
Mast System Design for Autonomous Tick Collection Robot
Authors: Harrison Moretto Caroline “Niki” , Dong Janet , Qiu Yesiliang 
Published: February 2021

Abstract
This paper discusses the design and testing of a mast system constructed to collect ticks from rugged terrain in remote areas via a mobile robot. The goal of this project is to develop a robotic tick collection mast that can be used to collect ticks in diverse tick habitats, such as shrubs, weeds, and grass of various heights, and in different environmental conditions. The project focuses on locating the ideal design of the mast system, including materials and dimensions, types of mounting fixtures, and a center of gravity that ensures maximum tick collection without causing robot instability. The design was tested in the field and through simulations.
The optimum design uses a mast system with two fixtures, a drag mast and a flag mast, made from t-slotted aluminum. The drag mast holds strips lower to the ground to collect ticks from the short grass, and the flag mast holds strips in the air, along the side of the robot, to collect ticks from taller grass and shrubs. The mast system design does not impact the robot’s ability to traverse challenging terrain, cause the robot to lose traction, frequently become permanently entangled in the brush, or have any other detrimental effect on robot mobility.
The drag and flag mounts are two separate fixtures that are removable and adjustable along the horizontal and vertical axes to accommodate various terrain types. The strip attachment points are also adjustable horizontally to allow the rearrangement of strips for optimum tick collection in different tick habitats.
The strength and stability of the mast system were evaluated using stress and center of gravity simulations. The design’s performance was also analyzed in the field using three types of tests: flagging and dragging, traversing uneven ground, and ascending and descending hills. The flagging and dragging test ran the robot along the side of taller foliage to test for tangling or breakage. The uneven ground test examined the robot’s performance over the ground that was pitted and dimpled to assess stability. The angled ground test studied the robot’s ability to ascend and descend hills to ensure it did not tip in any direction.
A robotic solution with a mast system and flagging and dragging mounts protects humans from being infected with potential illnesses from bugs and insects carrying disease pathogens, injuries from traveling across rough ground, and harm due to exposure to the elements. Productivity is also increased, as a robot can remain in the field for an extended period. The mast system design captures ticks despite adverse conditions, is easily interchangeable, and does not hinder tick collection.
Instability Study of Repetitive Nanosecond Pulsed Discharge Plasma in a Plasma Assisted Burner
Authors: Zare Saeid , Askari Omid 
Published: February 2021

Abstract
High velocity flows, as in aerospace applications require special techniques to stabilize and ignite diffusion flames. Some techniques focus on changing parameters like geometry, conditions of the flow, or fuel composition, but these techniques are usually too expensive or impossible due to major changes in the system. On the other hand, some techniques focus on generating a region of charged/excited species and active radicals upstream of the flame. That can substantially enhance the flame stability even under high strain rate or at lean-limit-flammability conditions. Repetitive nanosecond pulsed (RNP) discharge plasma is a nonthermal plasma technique with some remarkable potential to improve stability and ignitability of high velocity diffusion flames. This technique was used in previous papers in a plasma assisted coaxial inverse diffusion burner and showed some promising results by reducing the lift-off height and delaying detachment and blowout conditions. This burner is prepared to employ the discharges at the burner nozzle and simulate a single element of a multi-element methane burner. However, effectiveness of high-voltage high-frequency RNP plasma was limited by the mode of the discharge. During the tests, three different modes were observed at different combinations of plasma and flow conditions. These three modes are low energy corona, uniformly distributed plasma, and high-energy point-to-point discharge. Among these three, only well-distributed plasma significantly improved the flame. In other cases, plasma deployment was either ineffective or in some cases adversely affected the flame by producing undesirable turbulence advancing blow out. As a result, a comprehensive study of these modes is required. In this work, the transition between these three modes in a jet flame was discussed. It has been expressed as a function of plasma conditions, i.e. peak discharge voltage and discharge frequency. It was shown that increasing flow speed delays increases the voltage and frequency at which transition occurs from low-energy corona discharge to well distributed plasma discharge. Subsequently, the effective plasma conditions are thinned. On the other hand, by increasing the frequency of nanosecond discharges, the chance of unstable point-to-point discharges is decreased. In contrast, the discharge peak voltage causes two different consequences. If it is too low, the pulse intensity is too week that the system will experience no visible plasma discharges or the discharges will not pass the low-energy corona, no matter how high the frequency is. If too high, it will enhance the chance of point-to-point discharges and limits the stabilization outcome of the system. Therefore, an optimal region is found for peak discharge voltage.
Experimental and Numerical Investigation of Natural Convection Heat Transfer From Horizontal Rectangular Plate Fin Pin Fin Arrays
Authors: Dingare Sunil V. , Sane Narayan K. , Kulkarni Ratnakar R. 
Published: February 2021

Abstract
Fins are commonly employed for cooling of electronic equipment, compressors, Internal Combustion engines and for heat exchange in various heat exchangers. In short fin (length to height ratio, L/H = 5) arrays used for natural convection cooling, a stagnation zone forms at the central portion and that portion is not effective for carrying away heat. An attempt is made to modify plate fin heat sink geometry (PFHS) by inserting pin fins in the channels formed between plate fins and a plate fin pin fin heat sink (PFPFHS) is constructed to address this issue. An experimental setup is developed to validate numerical model of PFPFHS. The three-dimensional elliptic governing equations were solved using a finite volume based computational fluid dynamics (CFD) code. Fluent 6.3.26, a finite volume flow solver is used for solving the set of governing equations for the present geometry. Cell count based on grid independence and extended domain is used to obtain numerical results. Initially, the numerical model is validated for PFHS cases reported in the literature. After obtaining a good agreement with results from the literature, the numerical model for PFHS is modified for PFPFHS and used to carry out systematic parametric study of PFPFHS to analyze the effects of parameters like fin spacing, fin height, pin fin diameter, number of pin fins and temperature difference between fin array and surroundings on natural convection heat transfer from PFPFHS. It is observed that it is impossible to obtain optimum performance in terms of overall heat transfer by only concentrating on one or two parameters. The interactions among all the design parameters must be considered. This thesis presents Experimental and Numerical study of natural convection heat transfer from horizontal rectangular plate fin and plate fin pin fin arrays. The parameters of study are fin spacing, temperature difference between the fin surface and ambient air, fin height, pin fin diameter, number of pin fins and method of positioning pin fins in the fin channel. Experimental set up is validated with horizontal plate standard correlations. Results are generated in the form of variation in average heat transfer coefficient (ha), base heat transfer coefficient (hb), average Nusselt number (Nua) and base Nusselt number (Nub).
Total 512 cases are studied numerically and finally an attempt is made to correlate the Nusselt Number (Nu), Rayleigh Number (Ra), increase in percentage by inserting pin fins (% Area), ratios like spacing to height (S/H) and L/H obtained in the present study.
Experimental Validation of Mushy Zone Constant for Modeling of Solidification/Melting for Thermal Energy Storage Applications
Authors: Prabhu Vinit V. , Languri Ethan , Nawaz Kashif 
Published: February 2021

Abstract
The thermal energy storage (TES) systems use phase change materials (PCM’s) for storage and release of thermal energy. A lot of research is being conducted in recent times for fast, efficient storage and release of thermal energy using phase change materials in order to utilize the vast amount of latent heat available at constant temperature during phase change process. The numerical modeling for solidification and melting of PCM is employed in various commercial software and applied for different applications which include the solidification or melting. In the numerical simulation of phase change process, the solidification and melting are modelled using enthalpy-porosity method developed some researchers previously. The mushy zone constant is an important factor in this method which is used in the governing equations as a source term to model the melt front. The aim of this study is to determine the role of mushy zone constant on the solidification/melting behavior of phase change material numerically and validate the results with the experiments. The melting behavior of PCM is studied in this paper. The experimental setup consisting of a cubical container of dimensions 3″ × 3″ × 3″ filled with PCM was considered. The box was heated from one side and insulated from other sides so that the heat supplied is transferred to the PCM to melt it completely. The melting behavior of PCM was observed by capturing images at specific time intervals with the help of a camera. The camera was placed in such a way with minimum parallax error. These results are validated with previous numerical study in which the mushy zone constant was varied from 104 to 106 to determine the optimum value. The PCM used in this study is a paraffin wax material having a melting point of 48 °C. The propagation of melt front is plotted at different time steps and validated with the numerical results. The propagation of melt front is observed to be different for each of the mushy zone constant values. It was observed that the melting for higher values of mushy zone constant is observed to be similar to the experiment for the initial part of melting. Also, the melting rate speeds up and is observed to be similar to melting in the lower values of mushy zone constant. This paper aims to be a starting point to determine the optimum mushy zone constant for different factors affecting the melting behavior such as different materials, temperature difference.