bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Aspects of a Convergent Shock Wave Impinging a Perturbed Density Interface
Authors: Proano Erik S. , Rollin Bertrand , Seo Dongeun
Published: January 2019

The detailed characterization of a fluid flow following a convergent shock wave impinging a perturbed density interface is an extremely complex task as this flow combines geometry effects, compressibility effects and turbulence. Nonetheless, more understanding is necessary to be able to develop models that help accurately predict the flow behavior when occurring in engineering applications. Such an application is Inertial Confinement Fusion (ICF), where turbulent mixing induced by the interaction of the shock wave with the fuel pellet is detrimental to the fusion process. This interaction triggers mixing due to baroclinic vorticity deposition at the density interface in a phenomenon known as the Richtmyer-Meshkov Instability (RM). Next, the Rayleigh-Taylor Instability (RT) is driving the final growth of the mixing layer limited by secondary instabilities such as the Kelvin-Helmholtz Instability (KH). These classical hydrodynamic instabilities (HI) trigger the mixing process that leads ultimately to a highly-mixed fluid layer. For this study, we simulate a cylindrical Sulfur hexafluoride (SF6) target immersed into an air medium. The incident shock wave is regarded as a Chisnell-type converging shock wave impinging into a perturbed cylindrical density discontinuity generated with a wave-like spatial perturbation spectra. Parameters of interest are the growth rate and width of the mixing layer at the density discontinuity. This study aims at describing and quantifying relevant aspects of these flows coupling mixing layer growth with perturbation modes.
Micro-Mechanical Model for Thermo-Oxidative Aging of Elastomers
Authors: Mohammadi Hamid , Dargazany Roozbeh
Published: January 2019

In this study, a micro-mechanical model for constitutive behavior of elastomers subjected to thermo-oxidative aging is proposed. The model is based on the network decomposition concept and lies within the framework of continuum mechanics. It is assumed that the aging process leads to the formation of a new network with tighter chains. Accordingly, the strain energy of the system is constituted of two independent sources, the energy of the original soft network and the one of the reformed network. These strain energies were computed by integration of entropic energy of polymer chains in each direction of a micro-sphere. The model demonstrates good agreement with different experimental data on relaxation and intermittent tests.
Atomistic Simulations of Mechanical Properties of Circular and Collapsed Carbon Nanotubes With Covalent Cross-Links
Authors: Thapa Arun B. , Volkov Alexey N.
Published: January 2019

Stretching properties of single-walled carbon nanotubes (CNTs) of large diameters are studied in atomistic simulations. The simulations are performed based on the AIREBO empirical interatomic potential for three types of CNTs: Nanotubes with circular cross section, permanently collapsed nanotubes with “dog-bone”-shaped cross sections, and collapsed nanotubes with intra-tube covalent cross-links. In the last case, the cross-links between parallel quasi-planar parts of the nanotube wall are assumed to be formed by interstitial carbon atoms. The calculated equilibrium shape of collapsed nanotubes and the threshold diameter for permanently collapsed CNTs are found to agree with existing literature data. Elastic modulus, maximum stress, and strain at failure are calculated for zigzag CNTs with the equivalent diameter up to 6.27 nm in the temperature range from 5 K to 500 K. The simulations show that these mechanical properties only moderately depend on the diameter of circular CNTs. For collapsed CNTs with and without cross-links, the mechanical properties are practically independent of the CNT diameter for nanotubes with diameters larger than 4.7 nm. The elastic modulus and maximum stress of collapsed nanotubes are found to be smaller than those for the equivalent circular CNTs. The intra-tube cross-linking increases the elastic modulus and strength of collapsed CNTs in up to 50% compared to corresponding collapsed CNTs without cross-links, but reduces the breaking strain. Thermal softening of CNTs with increasing temperature in the range from 100 K to 500 K induces a decrease in the elastic modulus and maximum stress in about 12–33%.
Assessing the Impact of Using Educational Videos in Teaching Engineering Courses
Authors: Zaneldin Essam , Ahmed Waleed
Published: January 2019

Traditional ways of delivering lectures in classrooms proved to be inadequate and inefficient. Recently, the education sector is witnessing a dramatic progress and is undergoing a major shift. This shift has been influenced largely by technological and pedagogical trends and the greater worldwide access to the Internet. Videos were seen to be a major contributor to the shift in the educational landscape, acting as a powerful agent that adds value and enhances the quality of the learning experience. To be an effective player, videos continue to have a dramatic impact on higher education challenging the traditional way of delivering course content. While some lecturers may be embracing the use of videos in teaching, there are still lecturers who are reluctant to integrate this technology into their teaching methodology or do not have the skills to do so. This paper highlights the use of videos in teaching undergraduate courses in an international institution in order to boost students’ knowledge and enhance their learning experience. Findings of this study will be analyzed and discussed to address the main advantages of this promising initiative.
Three-Dimensional Cephalometric Analysis Using Computed Tomographic Imaging
Authors: Sanatkhani Soroosh , Menon Prahlad G.
Published: January 2019

Successful outcomes from the use of orthodontic devices are underpinned on their effective anchorage and the loading that they apply to the underlying facial structures. Anchorage plays an important role in determining the point of application of the corrective forces and subsequently the orientation of the resultant of these forces, which in-turn governs the outcome of treatment. Therefore, patient-specific design of anchors and their placement may benefit significantly from personalization using patient-specific and three-dimensional (3D) cephalometry. 3D cephalometry is therefore a first step to personalization of orthodontic treatment. In this feasibility study, we demonstrate the viability a novel image processing and surface analysis pipeline to quantify facial symmetry about the mid-sagittal facial plane, which may offer insight into optimal placement and orientation for implantation of orthodontic anchors, starting with patient-specific cone beam computed tomography (CBCT) images. Typical assessments of geometrical features/attributes of face include size, position, orientation, shape, and symmetry. Using 3D CBCT images in the DICOM image format, skull images were first segmented using a basic iso-contouring approach. To quantify symmetry, we split the skull along the mid-sagittal plane and used an iterative closest point (ICP) approach in order to rigidly co-register the left and right sides of the skull, optimizing for rotation, translation and scaling, after reflection of one half across the mid-sagittal plane. This was accomplished using an in-house plugin is developed for the open-source visualization toolkit (VTK) based 3D visualization tool, Paraview (Kitware Inc.). Finally, using a signed regional distance mapping plugin we were able to assess the regional asymmetry of regions of the skull (e.g. upper and lower jaw – specific targets for therapy) using colormaps of regional asymmetry (in terms of left-v/s-right side surface distance) and visualized the same as vector glyphs. The direction of these vectors is synonymous with anticipated regional forces required in order to achieve left-right symmetry, which in-turn may have value in surgical planning for orthodontic implantation. In sum, we demonstrate a workflow for computer-aided cephalometry to assess the symmetry of the skull, which shows promise for personalized orthodontic anchor design.
Modeling Tensile-Torsion Response of Double Twisted Helical Yarns
Authors: Dargazany Roozbeh , Lin Jiaqi , Mohammadi Hamid , Morovati Vahid
Published: January 2019

Multi-level helical twisted structures represent an example of how natural design achieved an optimized approach for creating a tough and strong fiber from often weak and soft microscale yarns through a hierarchical architecture. In this work, a constitutive model is presented to describe the load transfer within a double twisted helical structures in large deformation regime. The model aims to establish the torsion-tensile properties of fibers as an assembly of twisted yarns and filaments. The model associates the fiber response to the mechanics and the geometry of yarns in the deformed state. In this work, we mainly focus on elastic response of the material and thus inelastic damages were not considered. We modeled the inter-yarn forces that can cause friction. By considering the deformation induced changes in the geometry of constituents, the model describes the influence of the fiber composition parameters such as helical angel of the filaments, prestretch, pretwist of the yarns and the inter-yarn frictions, on the mechanical response of fibers. The model provides a detailed outlook into load transfer within fibers which helps us understand how to design fibers with certain performance.
A Novel Approach for Satellite Attitude Control by Using Solar Sailing
Authors: Li Ni , Arguelles Paolo , Chaput Kevin , Kenan Stephen L. , Kim Salla , Li Dongling , Vazquez Yosuar , Viveros Dennis , Nye Ted , Salinas Karl
Published: January 2019

Solar sailing is a new satellite propulsion technology using radiation pressure exerted by sunlight on a large mirrored surface. Since it does not need propellants, it is increasingly being considered by both the European Space Agency and the National Aeronautics and Space Administration for future science missions. An attitude control system is essential for a sail craft to maintain a desired orientation. IKAROS, launched in 2010, practically proved the possibility of using a solar sail as a propulsion system. However, it also showed the current sail orientation system could change the attitude very slowly, about 1 degree per day. In contrast to the existing single solar sail design, a new distributed four-sail configuration is proposed in this paper and the coordinated motion of the four sails is used to control the attitude pointing of a satellite. The feasibility and efficiency of this proposed design were assessed and concluded that it is possible to steer a CubeSat up to 1 degree in 60 seconds for either the roll or pitch axes.
Dynamic Model and Control Design for a Nonlinear Hydraulic Actuator
Authors: Borrás Pinilla Carlos , Sarmiento José Luis , Ortiz Juan Felipe
Published: January 2019

Industrial hydraulic systems are complex, and show nonlinear dynamic behavior because of their nature. When it is not easy to deal with the nonlinear models, hydraulic systems are usually described by linear or linearized models around operating points. In this work a nonlinear dynamic and mathematic model for the position control of a double rod hydraulic actuator was developed.

Three control strategies were implemented: PID control, optimal control (LQR) and control by Feedback Linearization. For the PID control and optimal control (LQR) strategies a linearized model of the hydraulic actuator was developed around a specific operating point, contrary to the Feedback Linearization control that have a wide operation range and the nonlinear model was used.

These mathematical models were represented on Simulink environment, in order to compare and analyze the response and dynamic behavior. The optimal control (LQR) shows better settling time than the PID control, both without overshoot; and the Feedback Linearization show the best dynamic performance in terms of settling time with a little overshoot and disturbance tolerance.
Frequency Effect of Torsion on Rotating Bending Fatigue Behavior of Gas Tungsten Arc (GTA) Welded AISI 1018 and AISI 4140 Welded Joints
Authors: Aziz Saad , Eren Ahmet , Wahab Muhammad A.
Published: January 2019

Fatigue failures of welded structure are subjected to occur due to multiaxial fatigue load and torsion. In the current research work, the frequency effect of torsion on rotating bending fatigue load is analyzed on AISI 1018 steel and AISI 4140 steel. To perform rotating bending torsional fatigue test of welded and un-welded specimens, a unit was designed and manufactured. Gas Tungsten Arc (GTA) welding was carried out on round bar of AISI 1018 steel and AISI 4140 steel welded using ER70-S2 filler metal for welded specimen. Later, the influence of torsional frequency on rotating bending with torsion is analyzed on both base metal and welded structures. The frequency of torsion was applied on the specimens were - 500 cycle, 1000 cycle, 1500 cycle, 2000 cycle and 2500 cycle. From the analysis, fatigue life of AISI 1018 and AISI 4140 base metal specimens (rotating bending and torsion) were not affected when torsion was applied at different frequencies. However, fatigue behavior of welded AISI 1018 and AISI 4140 specimens were highly affected by the frequency of torsion. For torsion applied at every 500 cycles, 83.8% reduction of fatigue life was observed for AISI 1018 welded specimen with respect to AISI 1018 base metal specimens. In addition, torsion applied for every 1000, 1500, 2000, and 2500 cycles; 81.9%, 80%, 77.1%, and 72.4% reduction on fatigue life were observed for AISI 1018 welded specimen compare to AISI 1018 base metal specimens, respectively. Welded AISI 4140 specimens experienced less change in fatigue life compare to welded AISI 1018 specimens. For torsion applied at every 500 cycles, 73.9% fatigue life reduction was observed for welded AISI 4140 specimens compare to AISI 4140 base metal specimens. For torsion applied at every 1000, 1500, 2000, and 2500 cycles; 65.2%, 60.8%, 50%, and 43.5% fatigue life reduction occurred on welded AISI 1018 specimen. Moreover, hardness measurements for welded specimens of AISI 4140 and AISI 1018 were performed longitudinally. For welded AISI 1018 specimen, 14.8% and 9.7% hardness decrease was observed longitudinally compare to AISI 1018 base metal specimen at heat-affected zone (HAZ) and from heat-affected zone through weld zone, respectively. For welded AISI 4140 specimen, 26.3% reduction of hardness value was observed compare to AISI 4140 base metal through heat-affected zone for longitudinal analysis. Moreover, fracture surface analysis was performed on the welded and non-welded specimens to understand the fracture behavior.
Nuclear Storage Cask Inspection Robotics As a Case Study in System Design Challenges
Authors: Bracken Jennifer , Brennan Sean , Van Sant Ian , Lissenden Clifford , Reichard Karl
Published: January 2019

Spent nuclear fuel, after cooling within a pool storage system, is generally stored in stainless steel dry storage casks. Some dry storage casks have been in regular use for decades, causing increasing interest in technologies to inspect these units. This work presents a case study on the design and prototyping challenges of a robotic inspection system known as PRINSE. PRINSE is designed for in-use dry nuclear waste storage casks, and its development was motivated by a recently completed multi-university NEUP study to develop, deploy, and test sensor systems enabling novel inspection capabilities. The field deployment situation presented particular design challenges not commonly seen in robotics for three reasons: geometric constraints to enter the in-situ cask environment, severe operational temperatures within the cask inspection area, and a high-radiation environment requiring stand-off human tele-operation and remote actuation of the robot from outside the cask. From a design standpoint, project hurdles included the teaming across multiple universities, the need to rapidly develop new prototype systems, and the novel design constraints which had to be managed carefully with the technology development process. This paper presents the specific mechanical engineering design challenges related to this complex system built to inspect dry storage casks. Additionally, it presents insights gained during the completion of the project, with specific focus on the challenges and methods used to achieve design coordination across sub-teams. Key experiences from this project are presented in a design-centric analysis of the management of technical constraints and how these constraints were distributed among the sub-teams.
User Centered Design Applied to the Improvement of Fine Motor Skills
Authors: Castro Alarcon Carolina , Castillo Cadena Santiago , Haro Mendoza Daniel , Vega Bello Jessica Daniela , Borja Ramírez Vicente , Ramírez-Reivich Alejandro , Escalera Matamoros Yesica , Treviño Arizmendi Arturo
Published: January 2019

This paper reports the development of a method to improve practical skills. The developed method arises from the observations made to the second-year students of Medicine degree at the National Autonomous University of Mexico (UNAM) in order to improve the learning of practical skills used in the “Introduction to Surgery” course.

However, the results obtained can be extrapolated to any profession that requires the usage of manual tools or fine and precise movements of hands. In the case of engineering, the proposed method can be applied to basic courses in electronics, technical drawing, manufacturing engineering, among others. As well as it can be used for specialized training in tasks such as welding, conventional machining, handling of hazardous materials or any other manual activity that requires precision. As a result, a methodology is presented to improve the learning of fine motor skills in a person, this allows developing of his/her professional activities in a fast and accurate way.
Low Cost Robotic Arm Manipulator Controller With Single Stage Fluid Valves
Authors: Campana Claudio , Tatoglu Akin
Published: January 2019

Piston pumps use a mechanism to create a reciprocating motion along an axis which then builds pressure in the barrel to force fluid through the pump. In general, pressure in the chamber is controlled by a heavy linear actuator to manipulate the valves at both suction and discharge points. While hydraulic actuators are strong enough to handle heavy payloads, they are not much suitable to drive arm manipulators mounted on mobile robots due to their heavy weight. To simplify the control logic more suitable for mobile robotics applications and to reduce the overall weight, we have used a smaller pump and utilized two simple trigger valves to control the stroke displacement of the extender. Since valves can only be in on and off states, a pulse width modulation (PWM) with duty cycle control is adopted. End manipulator position and velocity actuation are driven by a PI controller and maximum displacement accuracy, minimal rise time with minimum overshoot cases are studied. Experimental setup of the fluid valve control logic is explained. Both open and closed loop cases are discussed. It is shown that duty cycle control of valves can reach to a reasonable accuracy compared to the traditional linear control system with a lower weight and a simpler control logic.
Scalability Considerations in the Design of Microgrids to Support Socioeconomic Development in Rural Communities
Authors: Suk Hailie , Yadav Abhishek , Hall John
Published: January 2019

The interaction between technology and people is characterized by sociotechnical models. In the context of design, these types of systems are analyzed to increase productivity. The level of productivity is expected to increase as the technology evolves. Still, a lack of focus on adaptive design hinders the success of sociotechnical systems. The problem is evident in the relationship between microgrid technology and the residents of developing communities. An analysis of this type of sociotechnical system is analyzed in this paper. Rural villages in the developing world often lack access to the power grid. However, microgrids can provide electrical power in these locations. Power can be harnessed from renewable resources such as wind, solar, geothermal, and hydropower. Large batteries are used to store energy and buffer the electrical supply with the demand. The system powers security lighting, water pumps, and purification systems. Microgrids also power small machines that sustain agriculture in developing communities. The access to energy uplifts the developing community socially and economically. Still, as the community evolves, energy demand increases and the microgrid is unable to provide sufficient energy. A challenge in microgrid design involves the scalability of the system. Currently, there is no method for adapting the microgrid system to the increases in demand that occur over time. Accordingly, a mathematical framework is needed to support design decisions that could otherwise support adaptability. A demand model to predict the energy use for a composite rural village is presented. The predicted demand requirements are configured using a design optimization simulation model. These configurations are studied, and adaptive design techniques are devised through the process. The outcome of this study identifies a basic design methodology for microgrid design that is cognizant of scalability. Moreover, it identifies key attributes and relationships for the mathematical framework that supports the overarching goal of adaptable design.
On Self-Driving Car Safety: Occupancy Map Modification With Rapid Emergency Vehicle Detection
Authors: Tatoglu Akin , King Eoin , Lagler Jarrett
Published: January 2019

Unmanned ground vehicles (UGV) and self-driving cars utilize visual sensors including cameras, Lidars and radars not only for localization and obstacle avoidance purposes but also to generate a 3D map of the surroundings. When an emergency vehicle — such as a fire truck or an ambulance — is approaching, self-driving cars are required to modify their path plan and find a safe spot rapidly. However early detection of a fast approaching emergency vehicle in urban environment is challenging with a visual perception system since it requires direct view without an obstacle in between. To improve the safety of self-driving cars, a localization algorithm is required to maximize the path modification time constraint as well as to minimize location and direction detection time, especially at an intersection in urban environments. To overcome this challenge, we mounted a transducer array on top of a mobile robot and applied beam forming algorithms to predict the location and velocity vector of the remote dynamic vehicle. Even with high uncertainty, this strategy improved time requirement of occupancy grid update which marks all possible unsafe areas to avoid a collision. Two experimental setups of controlled and uncontrolled environments were prepared. Followed by preliminary transducer characteristic analysis in an anechoic chamber, an outdoor experiment with two mobile robots are executed to benchmark the capability of signal processing techniques while both source and observer are in motion.
Raising Inlet Air Temperature for a Hybrid-Cooled Server Retrofitted With Liquid Cooled Cold Plates
Authors: Chowdhury Uschas , Siddarth Ashwin , Sahini Manasa , Agonafer Dereje
Published: January 2019

In typical data centers, the servers and IT equipment are cooled by air and almost half of total IT power is dedicated to cooling. Hybrid cooling is a combined cooling technology with both air and water, where the main heat generating components are cooled by water or water-based coolants and rest of the components are cooled by air supplied by CRAC or CRAH. Retrofitting the air-cooled servers with cold plates and pumps has the advantage over thermal management of CPUs and other high heat generating components. In a typical 1U server, the CPUs were retrofitted with cold plates and the server tested with raised coolant inlet conditions. The study showed the server can operate with maximum utilization for CPUs, DIMMs, and PCH for inlet coolant temperature from 25–45 °C following the ASHRAE guidelines. The server was also tested for failure scenarios of the pumps and fans with reducing numbers of fans and pumps. To reduce cooling power consumption at the facility level and increase air-side economizer hours, the hybrid cooled server can be operated at raised inlet air temperatures. The trade-off in energy savings at the facility level due to raising the inlet air temperatures versus the possible increase in server fan power and component temperatures is investigated. A detailed CFD analysis with a minimum number of server fans can provide a way to find an operating range of inlet air temperature for a hybrid cooled server. Changes in the model are carried out in 6SigmaET for an individual server and compared to the experimental data to validate the model. The results from this study can be helpful in determining the room level operating set points for data centers housing hybrid cooled server racks.
A Computational Model of Continuous Hollow Cerebrovascular Arterioles Using a Fractal L-System
Authors: Cuitino Nicolas S. , Johannesson Benjamin , Pelegri Assimina A.
Published: January 2019

There is a need for better 3-D model representations of cerebrovasculature particularly on the order of arterioles. Such a model would have many applications and could be a useful tool for those conducting studies involving the brain and its function. The load bearing effects of the vasculature can be better studied with such a model, such as in the case of large strains. In addition, by having a continuous hollow structure, studies involving flow properties can be conducted at a whole scale rather than in a segmented view. Such studies are critical to the advancement of knowledge about the brain and its mechanics which can lead to advancements in preventative and curative care, as well as preventative safety measures. The model developed in this paper could serve as a tool in such studies. A fractal L-system is used to define the branching nature of the model. As such a growing tree structure is developed and characterized by its bifurcation at the end of a vessel segment. The index of bifurcation, α, is a parameter that controls the behavior of the two generated daughter vessels. The model presented here grows from a single parent branch into a bifurcation each of which then bifurcates as many times as specified. The length and diameter of the two daughter vessels will be a function of the respective parent’s length and diameter as well as a value α. The branching angle of the two daughter vessels will be entirely controlled by α. The hollow continuous nature of the model allows for it to be used as a representation of the arteriole structures in the brain. There is also use for such a model in other areas of the body, however, this study will focus on the representation of the cerebrovasculature. The end result is a branching tree model generated in Abaqus which is continuous, hollow and capable of extensive generation with uses in modeling complex cerebrovascular mechanics.
Experimental Investigation of an R134a Loop Thermosiphon for Shaft Cooling
Authors: Li Fajing , Gao Jianmin , Jiang Guangwei , Xu Liang , Liang Feng
Published: January 2019

Shaft cooling based on a loop thermosiphon is an ideal method for cooling of motorized spindles since it transfers heat with high efficiency and does not require an external power supply. In this study, an experiment was conducted on an R134a single-loop thermosiphon when the evaporation and condensation sections were on the same pipe. Results indicated that the single-loop thermosiphon was still operational with a minimum average thermal resistance of 0.51 W/°C when the filling ratio (FR) was 40%. The temperature distribution of the test specimen was determined predominantly by the amount of heating power, and not the mode. The optimum liquid filling ratio was 40% – 60% under this special condition, and both the thermal resistance and the heat transfer limit increased with the increase of FR in this range. The maximum temperature of the 150SD motorized spindle decreased 29% with the use of the R134a shaft cooling structure.
Settling Characteristics of Polymeric Additives in Dodecane
Authors: Singh Gurjap , Pitts Stephen , Lopes Elio , Ratner Albert
Published: January 2019

Recent studies have shown that adding polymeric additives to hydrocarbon-based fuels can lead to suppression of their splashing behavior, as well as enhance their burning rates. However, there is a lack of objective data on polymeric additives settling times in these fuels. Choosing Dodecane as a representative of diesel-based fuels, present research experimentally investigates the settling behavior of polymeric additives (graphene) when mixed in with Dodecane, and the effects of various surfactants on such behavior. Methodology for experimental setup, data collection and data analysis is presented. Various concentrations of additives and surfactants are analyzed, and trends for settling times are shown.
Investigation of Temperature Effect on Cracked Pressurized Pipes
Authors: Egab Karim , Oudah Saad K. , Nassar Ameen A. , Hassan Hassan R. , Bhuiyan Yeasin
Published: January 2019

Pipes carrying heated-pressurized fluid have numerous manufacturing defects that resulted from thermal loadings. Therefore, study the thermal loading effect on the cracked pipes is important to decrease the risks of pipe fracture during their operation. In this work, the effect of the thermal stress distribution on the cracked pipes has been studied numerically. The “mode I” type of crack has been considered for the study. The results have been validated with an available analytical solution for a pristine cylinder. The temperature and stress distribution for different crack length ratio has been studied. The influence of surface’s temperature and fluid’s temperature on radial stress, tangential stresses are discussed. The J-integral and stress intensity factor in analyzed for various thermal conditions. In addition, the radial and tangential stress variations of the various pressurized fluids which have various temperature have been investigated. The stress intensity factor and the J-integrals were calculated for different crack length ratios. In addition, the effect of surface temperature has been studied. It was found that the surface and fluid’s temperature affects the stress distributions and J-integral values. The results show that the J-integral and the stress intensity factor increases as the surface temperature of the pipe increases while their values decrease with increase the surface temperature.
Effect of Particle Parameters on Erosion Wear and Performance of Screw Centrifugal Pump
Authors: Shen Zhengjing , Chu Wuli
Published: January 2019

Sediment erosion is recognized as a serious engineering problem in slurry handling such as screw centrifugal pump, which has wide efficiency region and non-plugging performance. In the present study, the screw centrifugal pump was simulated based on the Euler-Lagrange method. The Mclaury model was adopted for the erosion prediction of flow passage components. By analyzing the correlation factor functions contained in the erosion model and performing some preliminary research with a simplified model, particle velocity, particle shape factor and particle concentration were selected as the influencing factors to analysis the quantitative relationship among particle parameters, erosion wear and performance of screw centrifugal pump. The results show that the erosion of volute casing is higher than impeller, and the erosion rate of suction side is higher than pressure side. The particles velocity is positively correlated with erosion wear and pump performance reduction rate. While the increase of particles shape factor shows the opposite trend. Erosion rate is found to be increases sharply and then slowly when particles concentration increases, because of the adhesion effect of sand particles in the volute casing inhibits the total erosion wear. The increase of erosion rate promoted the reduction rate of pump performance, and the pump efficiency decreased more significantly when the erosion rate increased to a certain extent. The results of this study are of great significance for further optimization of hydraulic design and structural design for screw centrifugal pump.
Comparison of Ablation Volume Produced With Multi-Tine Dry Type and Wet Type Electrodes During Radio Frequency Ablation: An In Vitro Study
Authors: Singh Sundeep , Repaka Ramjee
Published: January 2019

The present in vitro study aims at comparing the ablation volume obtained with commercially available RITA’s StarBurst® XL (dry type) and StarBurst® Xli-e (wet type) multi-tine electrodes during radiofrequency ablation (RFA) procedure. The experiments have been conducted on polyacrylamide based tissue-mimicking phantom gel whose thermo-electric properties are similar to that of the soft tissues. A temperature-controlled RFA has been performed utilizing AngioDynamics RITA 1500X® radiofrequency generator. The maximal longitudinal and maximal transverse dimensions of the coagulated phantom gels have been measured from which the derived ablation volume has been calculated. Further, the temperature distribution and power delivered with the dry type and wet type electrodes have been compared. The in vitro study revealed that the efficacy of wet type electrode is more pronounced as compared to the dry type electrode. Moreover, it has been found that both the electrodes are capable enough of producing ablation volume up to 5 cm in diameter.
Estimation and Comparison of Welding Performances Using MRA and GMDH in P-GMAW for SS 316L Material
Authors: Addamani Rudreshi , Venkatadas Ravindra Holalu , Gonchikar Ugrasen , Chethan Y. D.
Published: January 2019

The Pulsed Gas Metal Arc Welding (P-GMAW) process is used in high-technology industrial applications and it is one of the most significant arc welding processes. The quality, productivity and cost of welding will be affected by the P-GMAW welding input process parameters and are considered to the most important factors. It is necessary to determine the input and output relationship of the welding processes in order to understand and control the P-GMAW welding process parameters. P-GMAW is widely used process, especially in thin sheet metal industries. It offers an improvement in quality and productivity over regular Gas Metal Arc Welding (GMAW). The process enables stable spray transfer with low mean current and low net heat input. This paper describes the estimation and comparison of welding process parameters viz., current, gas flow rate and wire feed rate on ultimate tensile strength, yield strength, percentage of elongation and hardness. Experiments have been performed based on Taguchi’s L27 standard orthogonal array. Estimation of welding performances have been carried out using sophisticated mathematical models viz., MRA and GMDH, and, compared. The GMDH algorithm is designed to learn the process by training the algorithm with the experimental data. Three different criterion functions, viz., regularity, unbiased and combined criterions were considered for estimation in GMDH. Different GMDH models can be obtained by varying the percentage of data in the training set and the best model can be selected from these, viz., 50%, 62.5% and 75%. Estimation and comparison of welding performances were carried out using MRA and GMDH techniques.
Mathematical Model to Predict Tensile Strength of Underwater Friction Stir Welded (UFSW) on 5052 Aluminium Alloys
Authors: Paramaguru Dhanis , Pedapati Srinivasa Rao , Awang Mokhtar , Mohebbi Hamed
Published: January 2019

In this study, AA5052 joints are fabricated by underwater friction stir welding and the process parameters are optimized for maximum UTS value by utilizing a developed mathematical model. The experiments are conducted by using Taguchi’s L9 orthogonal array, and polynomial regression analysis is applied to generate the model. Statistical tools such as analysis of variance (ANOVA), coefficient of determination is applied to check the adequacy of the developed model at 95% confidence level. Type of welding tools is identified as the most influencing factor on deciding the mechanical properties of the joint, followed by tool rotational speed and tool welding speed. The optimum process parameters are identified by the Taguchi parametric design method. The results indicated that the optimum process parameters combinations for better mechanical properties is attained at tool rotational speed of 1500 rpm and tool welding speed of 100 mm/min, using taper threaded cylindrical tool. A maximum UTS value of 225.48 MPa is obtained and it is verified by confirmation test.
A Dynamic Escape Problem of Molecular Motors
Authors: Culver Dean , Glaz Bryan , Stanton Samuel
Published: January 2019

Animal skeletal muscle exhibits very interesting behavior at near-stall forces (when the muscle is loaded so strongly that it can barely contract). Near this physical limit, the actinmyosin cross bridges do more work than their energy releasing molecules, Adenosine TriPhosphate (ATP) suggest they can. It has been shown that the advantageous utilization of thermal agitation is a likely source for this increased capacity. Here, we propose a spatially two-dimensional mechanical model to illustrate how thermal agitation can be harvested for useful mechanical work in molecular machinery without rate functions or empirically-inspired spatial potential functions. Additionally, the model accommodates variable lattice spacing, and it paves the way for a full three dimensional model of cross-bridge interactions where myosin II may be azimuthally misaligned with actin binding sites. With potential energy sources based entirely on realizable components, this model lends itself to the design of artificial, molecular-scale motors.
Numerical Analysis of Breakwaters Turbulence Under Coastal Wave Actions
Authors: Ouyang Huanrong , Hantz Joshua , Nguyen Tam , Harrington Amy , Zhang Ning
Published: January 2019

Due to the coastal wave actions, Louisiana coastline has been experiencing serious depletion of wetlands over decades. The loss of wetlands is threating the environment and the economic development of Louisiana. Therefore, breakwaters are designed to protect the coastline from coastal erosion and wetland losses by dissipating the energy of waves and changing the transport of sediment which is brought by the waves. The objective of this research was to give a numerical analysis of 2-dimensional breakwaters under wave actions and 3-dimensional breakwaters turbulence characteristics under coastal wave actions using CFD simulation. In this research, three breakwater structures are tested: a solid panel with no holes, a panel with three holes, and a panel with eight holes. The breakwater designs aim to allow sediment pass through the holes, to deposit and accumulate sediment at target areas, and to reduce wave actions. There were three different cases simulated with wave actions and without wave actions in this study, each case using a different panel design. The results of this study were mainly compared with the 2-dimensional CFD simulation analysis conducted previously to prove the accuracy.
Heat Built Up During Dynamic Mechanical Analysis (DMA) Testing of Rubber Specimens
Authors: Esmaeeli Roja , Nazari Ashkan , Aliniagerdroudbari Haniph , Hashemi Seyed Reza , Alhadri Muapper , Zakri Waleed , Farhad Siamak
Published: January 2019

The viscoelastic properties of rubbers play an important role in dynamic applications and are commonly measured and quantified by means of Dynamic Mechanical Analysis (DMA) tests. The rubber properties including the static and dynamic moduli are a function of temperature; and an increase in the temperature leads to a decrease in both moduli of the rubber. Due to the heat generation inside the rubber during the DMA test and the possible change of the rubber properties it is important to quantify the amount of temperature rise in the rubber specimen during the test. In this study, a Finite Element Analysis (FEA) model is used to predict the heat generation and temperature rise during the rubber DMA tests. This model is used to identify the best shape of the specimen to achieve the minimum increase in temperature during the test. The double sandwich shear test and the cyclic compression tests are considered in this study because these two tests are mostly used in industry to predict the rubber viscoelastic properties.
Heat Transfer Modeling of Nanoparticle Packings on a Substrate
Authors: Yuksel Anil , Yu Edward T. , Cullinan Michael , Murthy Jayathi
Published: January 2019

The temperature evolution of nanoparticle packings on a substrate under high laser power is investigated both experimentally and via numerical simulations. Numerical modeling of temperature distributions in copper nanoparticle packings on a glass substrate is performed and results are compared with experiment under 2.6 kW/cm2 laser power. A coupled electromagnetic-heat transfer model is implemented to understand the nanoparticle temperature distribution. Very good agreement between the coupled electromagnetic-heat transfer model and the experimental results is obtained by matching the interfacial thermal conductance, G, between the nanoparticles using the experimental result in the coupled electromagnetic-heat transfer model.
New Design Method for Spiral Casings Considering the Properties of the Impeller and Spiral Casing at Design and Off-Design Conditions and Numerical Verification With CFD
Authors: Epple Philipp , Fritsche Manuel , Steppert Michael , Steber Michael
Published: January 2019

Radial fans for industrial applications are very commonly operated with a spiral casing, also called volute. The function of the volute is to collect the air from the impellers outlet and to transport it to the fans outlet. In the volute the tangential velocity component of the impeller is transformed in a straight velocity component at the volute’s outlet. In the volute the static pressure is increased according to the cross sectional area of the volute. When the flow exits the impeller the flow rate is given basically by the radial velocity component times the outlet area of the impeller. In the volute, however, the flow rate is basically given by the tangential velocity component at the impeller exit and in the volute considering the conservation of angular momentum. Hence, there is only one operating point, i.e. the design point of the volute, where the flow rate in the impeller matches the flow rate in the volute. In the literature the design of the volute is performed at the design point only and the cross sectional area of the volute is usually computed distributing the flow rate linearly from the tongue to the exit of the volute.

In this work an extended theoretical approach was developed considering the design point flow rate and off design flow rates. At the design point, the properties of the specific impeller, i.e. it’s radial and its tangential velocity components at the impeller’s exit are considered to design the volute. Furthermore, also the off-design characteristics of the impeller, i.e. its radial and tangential velocity components are considered in the design process of the volute. The flow rates in the impeller and in the volute match only at the design point, at off-design points the flow rates in the impeller and in the volute are different. This has an important impact on the design process of impeller – volute units. Each volute has also to be matched to the specific impeller.

In the numerical part a usual volute was designed considering the properties of a particular impeller. The performance of the volute and of complete fan was investigated with the commercial Navier–Stokes Solver ANSYS CFX. A detailed analysis of the results and the flow conditions in volute as well as in the impeller-volute unit and a comparison with the results predicted by the new volute theory is given.
Outcomes of the Student Mentoring and Research Training (SMART) Program
Authors: Islam Nazmul , Weimer Amy A.
Published: January 2019

Engaging undergraduate students in research not only improves discipline-specific knowledge and skillsets, but also exposes them to increased research-related career paths, and motivates their pursuit of graduate study. With an interest in increasing these outcomes among students, the University of Texas Rio Grande Valley (UTRGV) developed the Student Mentoring and Research Training (SMART) program. The primary objective of the program was to provide an increasing number of undergraduate student (UG) research opportunities by building triadic teams comprised of (1) a faculty mentor, (2) a graduate student assistant, and (3) at least three undergraduate students. By utilizing graduate student mentors, in collaboration with faculty researchers, an increased number of undergraduates could benefit from participation in these experiential learning opportunities. SMART also encouraged graduate student professional development as each graduate student oversaw a research project and was responsible for mentoring the UGs over a five-week period of employment. Three professional development workshops were implemented for graduate mentors. Workshops focused on teaching graduate students best practices in teaching of research skills, and building motivation, teamwork, and leadership. Pre- and post-test surveys were used to assess program effectiveness. Findings are reported on SMART program outcomes, which include analyses of quantitative and qualitative data collected from undergraduate student mentees and graduate student mentors during the first year of program implementation.
Optimal Design of a Segmented Tube With Side Branches for Noise Reduction
Authors: Belegundu Ashok D. , Grissom Michael D.
Published: January 2019

Acoustic filters, or mufflers, are used in a number of applications for suppression or attenuation of sound. These mufflers use pipes with side branches and/or Helmholtz resonators thus routing the flow through a number of passages wherein the waves are partially reflected resulting in sound power attenuation. With the idea of using a pipe for active noise cancellation to reduce cabin noise in propeller aircraft, we define an objective function that maximizes sound pressure (or other criteria) at a given frequency f0 while minimizing (attenuating) the pressure at other harmonics m1 f0, m2 f0 etc. within the frequency band. Thus, the device can be used to generate anti-noise at the first harmonic, while attenuating noise at higher harmonics. A design tool is developed here using an optimization technique. Plane wave propagation is assumed. A choice of objective functions can be user-specified. Details of the design parameters and objective functions are given followed by acoustic analysis details. Test results are then given which show that the code can be used as a valuable design tool for noise reduction.