bluuebunny/crossref_metadata_2025 huggingface dataset:
Gait Analysis in the Assessment of Patients Undergoing a Total Hip Replacement
Authors: Regazzoni Daniele , Vitali Andrea , Colombo Zefinetti Filippo , Rizzi Caterina
Published: January 2020

Nowadays, healthcare centers are not familiar with quantitative approaches for patients’ gait evaluation. There is a clear need for methods to obtain objective figures characterizing patients’ performance. Actually, there are no diffused methods for comparing the pre- and post-operative conditions of the same patient, integrating clinical information and representing a measure of the efficiency of functional recovery, especially in the short-term distance of the surgical intervention.

To this aim, human motion tracking for medical analysis is creating new frontiers for potential clinical and home applications. Motion Capture (Mocap) systems are used to allow detecting and tracking human body movements, such as gait or any other gesture or posture in a specific context. In particular, low-cost portable systems can be adopted for the tracking of patients’ movements. The pipeline going from tracking the scene to the creation of performance scores and indicators has its main challenge in the data elaboration, which depends on the specific context and to the detailed performance to be evaluated.

The main objective of this research is to investigate whether the evaluation of the patient’s gait through markerless optical motion capture technology can be added to clinical evaluations scores and if it is able to provide a quantitative measure of recovery in the short postoperative period.

A system has been conceived, including commercial sensors and a way to elaborate data captured according to caregivers’ requirements. This allows transforming the real gait of a patient right before and/or after the surgical procedure into a set of scores of medical relevance for his/her evaluation.

The technical solution developed in this research will be the base for a large acquisition and data elaboration campaign performed in collaboration with an orthopedic team of surgeons specialized in hip arthroplasty. This will also allow assessing and comparing the short run results obtained by adopting different state-of-the-art surgical approach for the hip replacement.
Optimizing Pulse Combustion Parameters in Carbon Anode Baking Furnaces for Aluminum Production
Authors: Tajik Abdul Raouf , Shamim Tariq , Ghoniem Ahmed F. , Abu Al-Rub Rashid K.
Published: January 2020

Pulsating flame jets have been widely used in open-top carbon anode baking furnaces for aluminum electrolysis. Reducing energy consumption and pollutant emissions are still major challenges in baking (heat-treatment) carbon anode blocks. It is also of immense significance to bake all the anodes uniformly irrespective of their position in the furnace. Baking homogeneity can be enhanced noticeably by optimizing anode baking operational, geometrical, and physical parameters. In the present study, CFD simulations are combined with a response surface methodology to investigate and optimize the effects of pulse pressure, pulse frequency, and mainstream inlet oxygen concentration and mainstream inlet temperature. Two-levels half fractional factorial design with a center point is employed. It is perceived that pulse combustion with short pulse time and high momentum results in significant enhancement of the anode baking furnace energy efficiency. The temperature homogeneity is also significantly improved. It is found that the oxygen concentration is statistically the most significant parameter on NOx and soot formations, followed by the fuel flow rate. For NOx formation, air inlet oxygen concentration has a strong interaction with pulse duration. Coupling CFD models with the response surface methodologies demonstrated great potential in multi-objective optimization of the anode baking process with enhanced energy efficiency and baking uniformity.
Investigating Effects of Different Flue-Wall Deformation Modes on the Performance of Anode Baking Furnaces for Aluminum Electrolysis
Authors: Tajik Abdul Raouf , Zaidani Mouna , Shamim Tariq , Abu Al-Rub Rashid K.
Published: January 2020

In carbon anode baking furnaces, temperature and quality of carbon anodes are significantly affected by the deformation of the flue-walls, where the flue-gases flow and combustion occur. Flue-walls aging gives rise to non-homogeneous baking of the carbon anodes and results in deterioration of the anode quality, which eventually causes instabilities in aluminum reduction cells and overconsumption of anodes and energy. It is imperative to develop a fully coupled 3D multi-physics computational model which takes into account a large number of physical phenomena that play vital roles in the baking process and are affected by the flue-wall deformation mode. In the present study, the effects of flue-wall deformation modes on flue-wall cavity gas flow and anode temperature distribution are investigated. The pressure and flow distributions for different levels of flue-wall deformation are demonstrated. It is perceived that a 100 mm convex mode of flue-wall deformation leads to under-baking of anodes by almost 20 degC. For the concave mode of deformation, since the packing coke thickness reduces, overbaking of anode occurs. The methodology and results presented in the present research can be employed effectively by the aluminum industry in modifying the furnace geometrical and operational parameters to enhance baking uniformity after flue-wall is deformed.
Novel Electro-FSI Model of Trabecular Network in the Brain Sub Arachnoid Space
Authors: Teimoori Khashayar , Sadegh Ali M. , Paneri Bhaskar
Published: January 2020

The brain is encased in the skull and suspended and supported by a series of three fibrous tissue layers: Dura mater, Arachnoid and Pia matter, known as the Meninges. Arachnoid trabeculae are strands of collagen tissues located in a space between the arachnoid and the pia matter known as the subarachnoid space (SAS). The SAS trabeculae play an important role in damping and reducing the relative movement of the brain with respect to the skull. The SAS is filled with cerebrospinal fluid (CSF), which is a colorless fluid that surrounds all over the brain inside the subarachnoid spaces. This fluid stabilizes the shape and position of the brain during head movements.

To address normal and pathological SAS functions, under conditions where an electrical stimulation is applied, this study proposes a novel fully-coupled electro-Fluid-Structure Interaction (eFSI) modeling approach to investigate the response of the system of SAS-CSF under the applied electric current, which is provided by the transcranial Direct Current Stimulation (tDCS) technique according to the following steps. First, a two-dimensional channel model of the brain SAS with several trabecular morphologies is numerically simulated using the finite element (FE) method. The channel model is then subjected to a specific electric field intensity by applying a 1∼2mA direct current. COMSOL Multiphysics v. 5.3a software is used to perform the coupled eFSI numerical simulation in order to investigate the effects of the applied electric field on the flow of the CSF, thereby showing the deflection of the trabeculae inside the channel model.

The results of this study demonstrate that the induced electric field causes less deflection of the trabeculae by exacerbating the velocity profile of the cerebrospinal fluid flow and decreasing the flow pressure applied on each trabecula inside the trabecular SAS channel. This electro-mechanostructural modeling approach is significant because of the applied current on the channel walls that can directly affect the CSF flow. In fact, the results of this study can open up a new horizon for future research on disorders like hydrocephalus, which involves an unusual production rate of the CSF inside the brain. This disorder may be controlled by applying an electric current in the brain, using one of the available brain stimulation techniques, i.e. tDCS. By using an electrical stimulation technique, one might control the dynamics of brain function and, therefore, regulate dysfunctionality through the first eFSI multiphysics modeling approach proposed in this study. Briefly, the brain SAS may be considered as a novel region for electrotherapeutic and electromechanical neuromodulation.
Deck Lid Surround Fit Correlation Study Between Dimensional Variation Simulation and Physical Vehicle
Authors: Zhongwu Han , Min Hu , Zhenhai Ma , Xiaoxu Niu , Ni Cao
Published: January 2020

During vehicle development process, dimensional variation simulation has been applied to evaluate fit performance of build variation widely, including front end area, rear end area, interior and chassis. Both product and process variation are simulated based on rigid assumptions in traditional variation simulation model, but many components are not rigid and deformed after assembled on physical vehicle, which make the variation simulation model result not correlate with physical build well. Deck lid is kinetic and easy to be elastic deformed that is caused by torque rod and seal force, which would affect deck lid surround fit, especially for deck lid to body side outer flush, but these situations are not considered in traditional variation simulation model. In order to improve the correlation between dimensional variation simulation and physical vehicle variation, in this paper, deck lid deformation is considered in new variation simulation model.

Compared with traditional method, the correlation between new variation simulation model and build variation on physical vehicle improved by 17%. This calculation method and result are closer to physical build than traditional variation simulation, limit of this study is seal margin variation, striker and bumper adjustment are not considered in FEA model. In future study, need to improve the correlation by considering all these factors. This study could be applied to identify actual vehicle fit risk in product development phase, it could also save tooling change cost in build period.
Enabler Study for Plan View Cutline Styling of Front End Based on Variation Simulation
Authors: Siyuan Jin , Min Hu , Yabin Chen
Published: January 2020

In current automobile market, plan view outline styling between hood and front fascia is very popular and customers are sensitive to this styling. How to assure high aesthetic quality with low cost is very important for automotive engineers. In this paper, the variation simulation model of the usual and a new method is established and compared by 3DCS software. The development method with a new locating strategy and installation process for fascia center bracket is presented to optimize product development and process enablers. Finally, the validity of the proposed method is verified on physical model.
Finite-Element Analysis of the Load Factor and Design for Bolted Circular Flange Joints Consisting of Dissimilar Clamped Parts Under Tensile Loadings
Authors: Sawa Shunichiro , Sekiguchi Yasuhisa , Sawa Toshiyuki
Published: January 2020

The load factor for bolted circular flange joints where two dissimilar material (steel-aluminum) of circular flanges are clamped by a lot of bolts and nuts under external tensile loadings is examined newly using Finite Element analysis. Furthermore, the effects of the bolt pitch circle diameter D and number of tightened bolts N on the load factor and a load when the interfaces start to separate are examined. The value of the load factor for steel-aluminum circular flange joint is a little bit larger than that for steel-steel circular flange joints and it increases as the value of D decreases. In addition, it decreases as the value of N increases. A maximum bending stress is also found newly about 5% larger than the bolt stress due to the load factor. The experiments to measure the load factor, the maximum bending bolt stress and a load when the interfaces start to separate were carried out. The FEM results are fairly coincided with the experimental results. Finally, based on the obtained load factor, a design method for bolted joints with dissimilar circular flanges is demonstrated for determining the nominal bolt diameter and the bolt strength grade and the effect of bolt number N is examined. It is found that the contact stress at the bearing surfaces of aluminum circular flange is critical and it is shown that washers are needed in some cases.
Developing a Cost-Effective and Functional Prosthetic Foot for Below Knee Amputees Using Topology Optimization and 3D Printing
Authors: Kamel Hisham , Harraz Omar , Attia Tamer
Published: January 2020

This paper presents the results of an investigative study on the development of an affordable and functional prosthetic foot for below knee amputees. A prototype was successfully manufactured using 3D printing technology. This continuously evolving technology enables the rapid production of prosthetics that are individually customized for each patient. Our prototype was developed after conducting a topology optimization study that interestingly converged to the shape of the biological human foot. Afterwards, a design was envisioned where a simple energy storage and release mechanism was implemented to replace the Achilles tendon, which minimizes the metabolic energy cost of walking. Our mechanism can successfully manage 70% of the energy compared to a normal person during each walking step. A finite element (FE) model of the prosthetic was developed and validated using experimental tests. Then, this FE model was used to confirm the safe operation of the prosthetic through simulating different loading scenarios according to the ISO standard. Our study clearly showed that customizable prosthetics could be produced at a fraction 1/60 of the cost of the commercially sold ones.
Deformation Mechanics of Tube in Variation of Process Sequence During Low Pressure Tube Hydroforming
Authors: Nikhare Chetan P.
Published: January 2020

Tube hydroforming is the successful manufacturing process to create a variety of shapes using fluid pressure. In this process, the tube was filled with the fluid and further pressurized to deform to various shapes. Tube hydroforming is categorized into three types: higher pressure, pressure sequencing and low-pressure tube hydroforming. Ferrous and non-ferrous metals are formed using these processes. Due to uniform thinning in the formed part, the parts can be lower weight and thus proven to be the technology to create lightweight parts for automotive and aerospace industries. This process has gained popularity due to its many advantages such as part consolidation, quality of the formed part and the possibility of unique shapes with indents or angles. This paper focuses on low-pressure tube hydroforming. In low-pressure tube hydroforming, during the closing of the die the tube is marginally pressurized to a fixed volume. The focus of this paper is to investigate the deformation mechanics of the tube due to variation in the process sequence during low-pressure tube hydroforming. The circular tube was formed in a square shape. The four sides of die edges were considered as individual edges and the motion of these edges will be varied to achieve the final shape. The deformation mechanics in each condition was presented and analyzed. The thickness and strain distribution were studied. The change of tube profile pattern from the start to the end of the process were presented and compared.
Improving Cutting Path on Custom 3D-Printed Surgical Guides for Bone-Tumor Resection
Authors: Helguero Carlos G. , Castro Juan , Ochoa César , Maldonado Fausto , Ramírez Emilio A. , Amaya Jorge L.
Published: January 2020

Custom three-dimensional (3D) printed guides are being used in the operative room as an aid to surgeons for increasing the accuracy of their cutting and resection techniques. In terms of bone-tumor resection, the cutting path printed in the custom jig is significantly important for two main purposes: first, the required fit for the implant that will replace the resected bone section and, second, the interaction between the remaining, healthy bone and the new implant in terms of forces, stresses and deformation.

Bone tumor resection has posed a challenge in orthopedic oncology, specifically due to a high level of difficulty in performing a limb-sparing surgery with negative margins on the remaining bone. A straight cutting path is usually used in clinical procedures due to the type of tooling available inside the operative room. 3D printed cutting path guides offer the possibility to evolve from a straight to a different path, e.g. a tapered path, and overcome fitting problems during surgery.

This work investigates the current straight cutting path used for typical bone tumor resection and compares it to a proposed tapered cutting path in terms of both implant fitting and stress analysis. Finite element analysis software is used to simulate a compression force exerted over the femur bone. Different taper cut angles are studied and results are reported to obtain an ideal angle for resection. Results are presented to evidence the need to evolve from the current resection technique in order to minimize the number of revision surgeries and for a better quality of life of patients under this type of surgical procedure.
Analysis of a Vertical-Axis Spherical Turbine for Energy Harvesting in Urban Water Supply Systems
Authors: Valencia Adriana S. , Jativa Cervantes Hugo , Castillo Eduardo , Garavitto Oguier A. , Soriano Guillermo E. , Castro Livingston D.
Published: January 2020

Fast-growing cities are a challenge for its current energy demand, especially in developing countries. Replacement of micro-turbines instead of dropping pressure valves in urban-water pipelines may assist in supplying energy to the electrical grid. The understanding of turbine design and its operational characteristics can help for efficient energy harvesting in these cities. The aim of this work is to design a cheap and versatile hydrokinetic vertical axis spherical turbine for extracting energy from water pipelines of 800 mm in diameter. The turbine runner is based on a NACA0018 airfoil. Performance prediction is obtained by implementing a double multiple stream tube (DMST) based model. Computational fluid dynamics (CFD) and finite element analysis are used for performance and design improvements. Based on the analysis, the turbine can generate an output power of approximately 1.71 kW with a dropping pressure head of 0.4 m and an internal flow velocity of 2.07 m/s with an efficiency of approximately 42.7%. The proposed method allows determining the available energy of 390 kW in the city of Guayaquil, Ecuador.
The Role of Higher Education Institutions Regarding Climate Change: The Case of Escuela Superior Politécnica del Litoral and its Carbon Footprint in Ecuador
Authors: Criollo Nancy P. , Ramirez Angel D. , Salas Daniel A. , Andrade Rafael
Published: January 2020

A case study of a university campus in a tropical area has been analyzed. Escuela Superior Politécnica del Litoral (ESPOL), one of the leading public polytechnic higher education institutions in Ecuador, is located in Guayaquil in the Guayas province. ESPOL has around 12300 students and 1740 faculty members and administrative staff. The climatic conditions are defined as dry tropical forest and have two main seasons, one with rain and high humidity and one that is dry. Average day temperature is 28°C. Air conditioning is required throughout the whole year. The carbon footprint (CF) has been calculated for the university campus as prescribed by the ISO 14064 International Standard for greenhouse gases (GHG) Emission and the Greenhouse Gas Protocol by the World Business Council for Sustainable Development (WBCSD) and World Resources Institute (WRI). Results indicate that the major contributor to the CF of the ESPOL campus is electricity generation off–campus with 66%. The CF per student is 0.406 tons CO2e which in comparison with information of other higher education institutions (HEIs) campuses is low. This is mostly associated with the CF of the electricity generated in Ecuador which is above 80% renewable. Additionally, a comparison of HEI cases based on their CF has been done. Further mitigation of GHG emissions is possible by energy efficiency measures at the building and transportation level.
Experimental Evaluation of Microclimate Cooling Garments Under Controlled Ambient Conditions
Authors: Baghirzade Mammadbaghir , Burns Samuel , Sun Hongwei , Sobkowicz-Kline Margaret , Johnston Stephen , Mack J. Hunter
Published: January 2020

A testing chamber was designed to evaluate the performance of microclimate cooling systems, which are used to extend human performance duration in heat stress environments by flowing fluids through flexible tubing in a conforming garment, carrying excess heat away from the wearer. The flexible experimental system accommodates changes in materials and garment design. In this study, one side of a chamber was able to output heat at a rate equivalent with that of human; a second, opposed chamber controls ambient conditions experienced by the garment. Temperature changes in both the interior and exterior sides of the chamber were measured. The cooling garment was tested at different conditions, transient and non-transient styles, with and without flowing fluid, and at various wattage densities (367.3 W/m2 and 576.8 W/m2). The designed testing chamber was validated for proper functionality. It was observed that, having a flowing fluid through the garment was more effective at higher body temperatures (∼45 °C) carrying away the excess amount of heat from the body.
Activity Coefficient of Different Salt Solutions for Reverse Electrodialysis Application
Authors: Emdadi Arash , Emdadi Simin , Zenouzi Mansour , Kowalski Gregory
Published: January 2020

Renewable energy sources and related conversion technologies are considered as the main solution for resolving the current issues related to global warming and environmental protection. Salinity gradient energy (SGE) is a source of renewable energy which can be defined as the Gibbs Energy of mixing when two solutions with different salinities mix together. The difference in the salinity of salt solutions is the main driving force of energy production by the SGE conversion technologies. One of the main conversion technologies of SGE is reverse electrodialysis (RED). In this technology the gradient between the concentrated and diluted salt solutions, the ions with a negative charge (anion) and positive charge (cation) pass through selective ion exchange membranes known as anion exchange membrane and cation exchange membrane. The driving force for diffusion of the ions is a function of the concentration gradient. The chemical potential of the salt solution is a function of the concentration of the salt solution and plays an important role in the Gibbs energy of mixing. The chemical potential of the salt solution is a thermodynamic property which is a function of the concentration and activity coefficient of the salt solution. The activity coefficient of the salt solution is a unique parameter which depends on the ionic strength of the solution and the type of ions in the salt solution. The salts with higher activity coefficient have a higher potential to be used in the SGE conversion process due to higher released Gibbs Energy during the mixing process. In this paper the thermodynamic model presented by Bromley [1], is used to calculate activity coefficient of 20 salts at different concentrations (0.01–6 molal). Two dimensionless parameters, Φ and Ψ, are defined as the ratio of activity coefficient and concentration between the concentrated and diluted solutions in 6 and 0.5 molal respectively. Using the dimensionless parameters, the theoretical open circuit voltage (OCV) of salt solutions in a RED cell is calculated. The salts are screened and ranked based on the activity coefficients and the theoretical open circuit voltage (OCV). The best salts are selected for use in a RED cell based on the activity coefficients and theoretical OCV. These alts could have potential for developing SGE storage systems in combination with renewable energy devices.
A Biphasic Viscoelastic Constitutive Model for Brain Tissue
Authors: Hosseini Farid Mohammad , Ramzanpour Mohammadreza , Ziejewski Mariusz , Karami Ghodrat
Published: January 2020

In this study, a rate-dependent biphasic model will be introduced to account for phenomenological behavior of brain tissue. For this purpose, a poro-hyper viscoelastic constitutive model is developed. The tissue is treated as a fluid-saturated porous medium, modeled as biphasic matter constituting of a solid matrix and interstitial liquids fill the porous spaces. The interactions between the two phases are assumed to be governed by Darcy’s law. This suggested model is calibrated with the experimental results of the bovine brain tissue, tested under high deformation rates (10, 100, 1000 mm/sec). The model will successfully take care of the detailed mechanical responses for solid and fluid phases, and their contributions to morphological behavior of this biological tissue. The material parameters of the model have been examined to agree well (R2 ≥ 0.96, where R is the coefficient of determination) with various deformation rates. In addition to representing the complete mechanical response and deformation of the solid phase, this biphasic model demonstrates the flow and diffusion of the liquid through the tissue networks.
Achieving Climate Control With Renewable Energy
Authors: Bower D. , Bielski M. , Mangan E. , Schell D. , Ghahremani K. , Gee D.
Published: January 2020

The purpose of this project was to explore the feasibility of powering a climate control system solely from a renewable energy source. The off-the-shelf cooling system components were taken from a ca. 1986 R-12 residential refrigerator and then reassembled onto a custom enclosure which was constructed to serve as the climate-controlled compartment. The enclosure design was purposefully simple: a rectangular shaped box constructed out of plywood and mounted on wheels together with a plexiglass door which was substituted for the front face. The overall design provided for enhanced mobility while also allowing for easy observation of the interior temperature via an interior-mounted, digital, commercial residential thermostat integrated into the control system. The system, nominally, is triggered by incident solar radiation; the initial set-point temperature was 21 °C. Compressor power was derived solely from renewable energy. Specifically, a pair of 100W 12V monocrystalline silicon photovoltaic solar panels was used to generate electricity which was subsequently stored in a deep-cycle battery. Under steady-state AC operation, the compressor draws approximately 2.1A. Due to system inefficiencies, the corresponding DC current draw is necessarily higher and approaches 22.3A. For a compressor duty cycle ranging from 50–100%, the current draw over a model 9 hr day would range from between 100.1–200.3 A-H. The lower limit is within the energy storage capacity for the fully-charged system, as currently designed.
Dynamic Behavior of Discretely Bonded Cross Tube With Functionally Graded Cellular Structure
Authors: Jenson Sean , Ohioma Eboreime , Ali Muhammad , Alam Khairul
Published: January 2020

Thin walled members are commonly used in vehicle’s frontal chassis to provide protection and damage attenuation to the passenger cabin in the case of an impact loading. These structural members undergo progressive deformation under axial loading. The type of deformation mode is critical as it defines the overall configuration of force-displacement curve. There are different types of deformation modes for cross tubes under axial loading. Likewise, the cellular structures exhibit distinct deformation modes under in-plane loading. The work presented here investigates the effects of bonding of cellular core structure on deformation modes of cross tubes under axial loading. The results show that partial, or discrete bonding of cellular core with the tube has significant effect on progressive deformation of tubes and therefore, presents an opportunity to re-configure force-displacement curve for improved protection of automobile structures under impact loading.
3D Flow Simulations of Fan Enclosure Concepts for a Novel Heat and Moisture Exchanger
Authors: Costa-Greger Justin , Wang Hailei
Published: January 2020

As the single most energy-intensive system in buildings, heating, ventilation, and air conditioning (HVAC) units consume on average 40 percent of total building energy in the United States. For regions with hot and humid climates, building loads due to HVAC systems increase significantly as a large portion of the electric load is used to condense moisture in the air. To improve building energy efficiency, energy recovery ventilators (ERV) have played an increasingly important role. They essentially rely on a membrane-based heat and moisture exchanger (HME) to reduce the latent heat load. A novel energy recovery ventilator was recently developed to improve ERV performance and advance building design. It combines a HME, two impeller fans and air enclosures into a single unit. In this work, two enclosure concepts were investigated, both of which have each fan placed in the enclosure of the HME inlet. Computational fluid dynamics (CFD) was used to model air flow inside the enclosure. The simulation results provided important information on the distribution of air flow across the inlets of the HME, which is expected to improve the enclosure design to meet the ERV performance target. A grid refinement study was conducted which showed that the medium grid refinement produced results within 3% of the asymptotic solution and had significantly less computation time compared to the fine grid. The first concept had a velocity uniformity of 86% at the HME inlet, while the second concept showed undesirable, reversed flow in the upper channels. The study indicates placing the fan at the outlet of the HME, rather than the inlet, would lead to more uniform air flow into the HME.
Period-1 Motions to Chaos With Varying Excitation Frequency in a Parametrically Driven Pendulum
Authors: Guo Yu , Luo Albert C. J.
Published: January 2020

In this paper, with varying excitation frequency, period-1 motions to chaos in a parametrically driven pendulum are presented through period-1 to period-4 motions. Using the implicit discrete maps of the corresponding differential equations, discrete mapping structures are developed for different periodic motions, and the corresponding nonlinear algebraic equations of such mapping structures are solved for analytical predictions of bifurcation trees of periodic motions. Both period-1 static points to period-2 motions and period-1 motions to period-4 motions are illustrated. The corresponding stability and bifurcations are studied. Finally, numerical illustrations of various periodic motions on the bifurcation trees are presented in verification of the analytical prediction.
Effects of Axial Compression Load, Borehole Clearance, and Contact Force Using Axial-Lateral Fluid Coupled Drill String Vibration Model
Authors: Chodankar Abhijeet D. , Seibi Abdennour
Published: January 2020

Drill string vibrations have resulted in an increase in non-productive time, drilling cost, and a need for drill string system optimization in the oil and gas industry. Higher vibrations can lead to washout, blow-out phenomena, and a rapid wear and tear of drill string components. An in-depth understanding of the root causes of the drill string vibrations is of utmost importance. The effects of mass imbalance, bottom hole assembly (BHA) design, weight on bit, hole angle, hole size, RPM, drilling fluid viscosity, bit and formation type on drill string vibrations have been studied in the past. The main objective of this paper is to propose a novel drill string vibration model taking into consideration the effects of axial compression load, borehole clearance, and contact force in conjunction with Euler-Bernoulli, Rayleigh, and Shear beam theories. The proposed model studies the effects of axial compression load, borehole clearance, and stiffness on the natural frequency and frequency response of drill string. The drill string is considered as a cantilever beam with a circular cross-sectional area in a horizontal drilling condition, while the fluid (water) around it is considered as a spring and dashpot model. Drill string vibrations are modeled based on a distributed system approach. The forces acting on the cantilever beam element are axial compression load, shear forces, bending moment, fluid stiffness and damping forces. A fourth order partial differential equation is derived and the solution is obtained based on the assumed modes approach to obtain the characteristic equation and mode shapes. Natural frequency is determined using the eigen values obtained from the characteristic equation. The orthogonality conditions are further derived to decouple the derived equation. The drill string is initially assumed unbounded, hence the amount of contact force required to restrict the drill string within the borehole is determined. An iterative process is employed to restrict the drill string deflection within the borehole with a corresponding increase in the stiffness of the drill string system. This will help in determining the experienced down hole contact forces and the stiffness requirements of the bottom hole assembly. Dominant frequencies are identified, compared with field results, further guiding the operator to avoid rotating the drill string at particular frequencies. A detailed study of the effects of contact forces, borehole clearances, and axial compression load will provide comprehensive guidelines in BHA design of drill string assembly. To conclude, this paper proposed an accurate model to identify dominant frequencies and provides a thorough BHA design guidelines for the drill string design manufacturers and field operators leading to a reduction in drilling cost and unproductive time, and environmentally friendly drilling operations.
A Magnetic and Shape Memory Alloy Actuated Gripper for Surgical Applications
Authors: Cooke Ian , DeClerck Brendon , Hallett Jesse , Miller Tyler , Mitchell Alexis , Rashidi Reza
Published: January 2020

This paper presents the development of a novel shape memory alloy (SMA) actuated gripper for use in the biomedical applications. The use of SMA in surgical forceps can allow a surgical robot to accurately and repeatedly apply a force and grip small objects or perform minor surgeries that are less invasive and allow for quicker recovery times. Current designs of thermally actuated grippers use SMAs as the gripping parts, which limits their application due to the transfer of heat to the object being gripped. The design of the gripper illustrated in this paper isolates the SMA coil from the gripping jaws to maintain a constant surface temperature at the gripping end and prevent thermal contamination of soft tissues. Isolating the SMA from the grippers also simplifies automated surgical robots by centralizing all heating elements. A magnetic field exerted between a pair of permanent magnets is used to restore the SMA coil upon cooling. The gripper housing and jaws were fabricated using a 3-D printer to allow for modeling of small features with little down time. A Nitinol SMA wire with a transition temperature of 45°C was wrapped into a 2.5mm diameter coil and heat treated to set the predefined shape. The SMA coil and other parts were assembled to form the gripper. The gripper was successfully tested using an Interlink Electronics Force Sensor and data acquisition card (DAQ), and the forces between the gripper jaws as well as the response time to close and open the jaws were recorded. The gripper produced a force of 0.9N when reaching the transition temperature. The response time for the gripper to close and open the jaws was measured to be approximately 0.16 s and 0.12 s, respectively. It was found that the magnetic field had a faster actuation on the coil than the shape memory alloy force during opening and closing jaws.
Fast Colored Point Feature Histograms Global Registration
Authors: Liu Xingjie , Wang Guolei , Zhang Simin , Chen Ken
Published: January 2020

We present an algorithm for fast global registration on colored dense point clouds. We combine CIELAB color information with fast point feature histograms for better correspondence and use color difference score to delete wrong pairs. The optimization is based on a method from Intel Labs that does not update correspondence or query closest-point during optimization. Experiments are taken on real partial overlapped data obtained from Kinect V2. The algorithm achieves a precise alignment with no initialization and cost little time. It can be extended to real-time robotics application for further study.
Research on Dynamic Characteristics of Complex Gap Combined Rotor of Large Generator
Authors: Li Yuan , Li Chen , Li Hui , Qi Shemiao , Liu Yi , Liu Heng
Published: January 2020

In this paper, a large generator rotor with complex clearance is taken as the research object, and the dynamic analysis model of this rotor is established. This study focuses on the prediction of the contact stiffness of its widely distributed contact interface and the cross-scale interstitial stiffness of the rotor. Furthermore, the dynamic characteristics of torsional under typical rotor state are studied, and the combined rotor of large generator is tested and verified. Through theoretical analysis and experimental study, the influence mechanism of clearance on dynamic characteristics of large generator rotor is revealed.
Mutual Information-Based Sensing Optimization for In-Process Quality Inspection of Multi-Station Assembly Processes
Authors: Liu Yinhua , Hu Xiaolei , Yue Xiaowei
Published: January 2020

To increase productivity and satisfy diverse customer demands, many assembly processes have been converted from single-model lines to flexible assembly lines. Conventional fixed-location sensing approaches cannot be used to inspect a broad mixture of different quality features for multiple product models effectively. The in-process dimensional quality inspection systems with robot-mounted optical gauging have been becoming increasingly popular for flexible multi-station assembly processes. These new systems enable more powerful quality inspection for various designs and provide more flexibility for dimensional monitoring and diagnosis. Meanwhile, they bring new challenges to sensing efficacy and efficiency because in-process cycle time for quality inspection is limited in dozens of seconds. This paper focuses on sensing optimization problem for multi-station assembly processes. We propose a novel data-driven sensing optimization approach based on in situ quality inspection data, for the purpose of improving variation detection of subsequent assemblies. Based on the dimensional inspection datasets, a mutual information-based model is proposed to measure the correlation relationships among components, intermediate subassemblies and final products. An objective function considering the maximum relevance and the minimum redundancy is developed, and then an optimization algorithm is applied to obtain the optimal sensors. A case study in auto body assembly process is used to show the performance of the proposed method.
A Natural Evolution Based Numerical Optimisation Framework to Develop and Enhance Airfoil-Slat Arrangement
Authors: Kumar Sushrut , Gupta Priyam , Singh Raj Kumar
Published: January 2020

Leading Edge Slats are popularly being put into practice due to their capability to provide a significant increase in the lift generated by the wing airfoil and decrease in the stall. Consequently, their optimum design is critical for increased fuel efficiency and minimized environmental impact. This paper attempts to develop and optimize the Leading-Edge Slat geometry and its orientation with respect to airfoil using Genetic Algorithm. The class of Genetic Algorithm implemented was Invasive Weed Optimization as it showed significant potential in converging design to an optimal solution. For the study, Clark Y was taken as test airfoil. Slats being aerodynamic devices require smooth contoured surfaces without any sharp deformities and accordingly Bézier airfoil parameterization method was used. The design process was initiated by producing an initial population of various profiles (chromosomes). These chromosomes are composed of genes which define and control the shape and orientation of the slat. Control points, Airfoil-Slat offset and relative chord angle were taken as genes for the framework and different profiles were acquired by randomly modifying the genes within a decided design space. To compare individual chromosomes and to evaluate their feasibility, the fitness function was determined using Computational Fluid Dynamics simulations conducted on OpenFOAM. The lift force at a constant angle of attack (AOA) was taken as fitness value. It was assigned to each chromosome and the process was then repeated in a loop for different profiles and the fittest wing slat arrangement was obtained which had an increase in CL by 78% and the stall angle improved to 22°. The framework was found capable of optimizing multi-element airfoil arrangements.
The Interaction Problem Between a Crack and a Wedge Disclination Dipole With Irwin Plastic Zone Correction
Authors: Cao Meigen , Fan Mu , Min Hequn
Published: January 2020

In this work, the multiple defects interaction problem is studied. A crack located near an inclusion is influenced by a wedge disclination dipole. Stress field induced by the disclination affects the crack tip field and yield behavior of the crack. With varying the wedge disclination dipole properties, including strength, position to the crack tip, arm length, etc., the plastic zone size (PZS), the crack tip opening displacement (CTOD) and the stress intensity factor (SIF) are estimated with the generalized Irwin model. Numerical results showed that the wedge disclination dipole arm length and strength can significantly increase or decrease the values of the CTOD and PZS, depending the disclination dipole positions. The maximum values of the CTOD and the PZS were explored with the change of disclination position.
Wettability Gradients on Graphene to Drive Bubble Motion
Authors: Yu Hongyang , Zhao Yu , Sha Jingjie , Chen Yunfei
Published: January 2020

The molecular dynamics (MD) method is employed to simulate thermal bubble nucleation processes confined in graphene nanochannels. It is found that nucleation sites depend strongly on the different solid-liquid interfacial properties in various systems. In this work, the thermal bubble nucleates on the graphene surface, on which the interaction between liquid molecules and channel wall is weak relatively. It is demonstrated that the hydrophobic surface would make thermal bubble to initiate easier. A conceptual design about surface wettability gradient was proposed, which can break the equilibrium state of a bubble and induce its unidirectional movement on the surface. Moreover, MD simulation showed that through a continuous gradient of surface wettability, the direction of movement is under control. These findings provide us with a method in device design for applications of self-controlling motion of bubble down to nanoscale and other wettability-enabled actuators.
Study on Fracture Mechanism and Fatigue Life Prediction for Cutting In-Situ TiB2/7050Al MMCs
Authors: Xiong Yi-feng , Wang Wen-hu , Lin Kun-yang , Liu Xiao-fen , Jiang Rui-song , Deng Chu-quan
Published: January 2020

For machined parts, the surface roughness and profile would have a significant impact on the fatigue life and fracture mechanism. At present, a lot of research have been carried out on the cutting mechanism, modeling and machining performance of particle reinforced Al-based metal matrix composites. However, the study of fatigue life and fracture mechanism of machined parts after cutting particle reinforced Al-based metal matrix composites is rarely reported. In this paper, the fatigue life and fatigue fracture morphology of in-situ TiB2/7050Al MMCs were studied by high cycle fatigue test under different loading stresses. It was found that the surface roughness influenced the fatigue life greatly. With surface roughness decreasing, the fatigue life of machined parts increased exponentially. The fracture mechanism of cutting in-situ TiB2/7050Al MMCs was found to be brittle fracture due to the existence of fine particles. Besides, a fatigue life prediction model was established based on the machined surface roughness. With validation, the relative errors between prediction model and experiment were smaller than 11% indicating that the proposed fatigue life prediction model of machined in-situ TiB2/7050Al MMCs parts was of good reliability and accuracy.
Delamination Detection in Composite Plates Using Linear and Nonlinear Ultrasonic Guided Waves
Authors: Shen Yanfeng , Cen Mingjing
Published: January 2020

This paper presents a delamination detection strategy for composite plates using linear and nonlinear ultrasonic guided waves via the wave field imaging and signal processing based on Scanning Laser Doppler Vibrometry (SLDV). The anisotropic elastodynamics in composite plates is first studied. Two numerical methods are deployed to analyze the wave mechanics within the composite plates. The Semi-analytical Finite Element (SAFE) method is utilized to obtain the dispersion curves and mode shapes for a carbon fiber composite plate by bonding two quasi-isotropic carbon fiber composite panels together. The Local Interaction Simulation Approach has been employed to investigate the wave propagation and interaction with the delamination. Contact Acoustic Nonlinearity (CAN) between the delamination interfaces during wave damage interaction is presented as a potential mechanism for delamination detection. After developing an in-depth understanding of the wave propagation and wave damage interaction mechanism, active sensing experiments are conducted using the Piezoelectric Wafer Active Sensors (PWAS) and the Scanning Laser Doppler Vibrometry (SLDV). Two delamination imaging methodologies are presented. The first one utilizes the total wave energy to detect the delamination, taking advantage of the trapped modes within the delaminated area. The second one adopts the nonlinear second harmonic imaging algorithm, highlighting the nonlinear interaction traces at the delamination region. The damage detection images are finally compared and fused to provide detailed diagnostic information of the delamination. The damage imaging technique presented in this paper possesses great potential in material evaluation and characterization applications. This paper finishes with summary, concluding remarks, and suggestions for future work.
Comparative Energy and Exergy Analysis of Proposed Gas Turbine Cycle With Simple Gas Turbine Cycle at Same Operational Cost
Authors: Khan M. N. , Alarifi Ibrahim M. , Tlili I.
Published: January 2020

Environmentally friendly and effective power systems have been receiving increased investigation due to the aim of addressing global warming, energy expansion, and economic growth. Gas turbine cycles are perceived as a useful technology that has advanced power capacity. In this research, a gas turbine cycle has been proposed and developed from a simple and regenerative gas turbine cycle to enhance performance and reduce Specific fuel consumption. The impact of specific factors regarding the proposed gas turbine cycle on thermal efficiency, net output, specific fuel consumption, and exergy destruction, have been inspected. The assessments of the pertinent parameters were performed based on conventional thermodynamic energy and exergy analysis. The results obtained indicate that the peak temperature of the Proposed Gas Turbine Cycle increased considerably without affecting fuel consumption. The results show that at Pressure Ratio (rp = 6) the performance of the Proposed Gas Turbine Cycle is much better than Single Gas Turbine Cycle but the total exergy destruction of Proposed Gas Turbine Cycle higher than the SGTC.