bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimated Fluid Force and Damping Characteristics of a Thin Film Damper Comparison Between Closed-Form Solutions and Numerical Analysis
Authors: Cook Jason T.
Published: January 2020

Analytical solutions of thin film dampers are useful for determining critical speeds and stability of rotor systems. Most thin film dampers in use are of short axial length, and closed-form solutions to the Reynolds equations exist for estimating pressure, forces, and damping for these types of dampers. This article compares the fluid film forces and damping estimated by the short film bearing model form of the Reynolds equations to the calculated forces and damping of a transient computational fluid dynamic simulation. For this comparison, the fluid was assumed to be incompressible, laminar, and isoviscous. The fluid film forces and damping are calculated from integrating the pressure distribution over the surface of the damper due to small amplitude motions about a steady state static off-center circular orbit. In this case, no cavitation is assumed, and the journal has no angular velocity, so direct stiffness cannot be calculated from the closed-form solution. Radial clearance, journal length, and journal eccentricity have a significant effect on fluid force and damping within a thin film damper. Fluid density does not affect fluid force or damping substantially, while fluid viscosity does. Both the closed-form solutions and computational fluid dynamics simulation compare well with each other and reflect these trends.
Cryogenic Material Properties of Polycaprolactone
Authors: Sagar Amrit , Nehme Christopher , Saigal Anil , James Thomas P.
Published: January 2020

In pursuit of research to create a synthetic tissue scaffold by a micropunching process, material properties of Polycaprolactone (PCL) in liquid nitrogen were determined experimentally. Specimens were prepared using injection molding and tested under compression to determine the stress-strain relationship of PCL below its glass transition temperature. Cryogenic conditions were maintained by keeping the PCL specimens submerged in liquid nitrogen throughout the loading cycle. Specimens of two different aspect ratios were used for testing. Yield Strength, Strength Coefficient, and Strain Hardening Exponent were determined for different specimen aspect ratios and extrapolated for the case with zero diameter to length ratio. Material properties were also determined at room temperature and compared against results available in the literature. Results demonstrate that PCL behaves in a brittle manner at cryogenic temperatures with more than ten times increase in Young’s modulus from its value at room temperature. The results were used to predict punching forces for the design of microscale hole punching dies and for validation of a microscale hole punching model that was created with a commercially available finite element software package, DEFORM 3D. The three parameters Yield Strength, Strength Coefficient, and Strain Hardening Exponent used in Ludwik’s equation to model flow stress of PCL in DEFORM 3D were determined to be 94.8 MPa, 210 MPa, and 0.54, respectively.
Optimum Synthesis of Rigid Mechanisms Using a Dynamic Ant-Search Method With Sensitivity Analysis
Authors: Diab Nadim , Itani Omar , Smaili Ahmad
Published: January 2020

Four-bar linkages are commonly used mechanisms in various mechanical systems and components. Several techniques for optimum synthesis of planar mechanisms have been suggested in literature such as the Genetic, Tabu, Simulated Annealing, Swarm-Based and many other algorithms. This paper covers optimization of four-bar mechanisms with path generation tasks using a Dynamic Ant Search (DAS) algorithm. Unlike the Modified Ant Search (MAS) technique where ants unanimously moved between the exploration and exploitation phases, in the proposed algorithm, each ant is free to travel between the two aforementioned phases independent of other ants and as governed by its own pheromone intensity level. Moreover, sensitivity analysis is conducted on the design parameters to determine their corresponding neighborhood search boundaries and thus improve the search while in the exploitation mode. These implemented changes demonstrated a remarkable impact on the optimum synthesis of mechanisms for path generation tasks. A briefing of the MAS based algorithm is first presented after which the proposed modified optimization technique and its implementation on four-bar mechanisms are furnished. Finally, three case studies are conducted to evaluate the efficiency and robustness of the proposed methodology where the performances of the obtained optimum designs are benchmarked with those previously reported in literature.
A Process Plant for Producing Rocket Fuel From Lunar Ice
Authors: Carrato Peter , Demitz Jack , Mueller Rob , Gulen John , Benz August
Published: January 2020

One of, if not the most, valuable resources on the Moon is ice. Since the late 1990’s evidence has been accumulating that supports the presence of water ice at both the north and south lunar poles. Although consumption of water is critical to sustaining human life, water can also serve as a feedstock to produce rocket fuel. Water may be broken down into hydrogen and oxygen which, when liquified, serves as a propellant for space travel. This paper investigates the process and energy demand for producing liquid hydrogen and oxygen from lunar ice. A preliminary flow sheet and discussion of unit operations for a lunar rocket fuel plant are provided. Sources of energy on the Moon, as well as design of structures, systems and components for the facility are considered.
Nanoparticles EOR Aluminum Oxide (Al2O3) Used As a Spontaneous Imbibition Test for Sandstone Core
Authors: Samba Mohammed A. , Hassan Hafsa A. , Munayr Mahjouba S. , Yusef Moataz , Eschweido Abdelkareem , Burkan Hamed , Elsharafi Mahmoud O.
Published: January 2020

There are three types of oil production energy operations, primary recovery, secondary recovery and enhanced oil recovery (EOR). EOR consider as the last period for production operations. Where the EOR classify into many types such as thermal injection, gas injection, microbial EOR and chemical flooding.

Chemical flooding classified into many types such as polymer, surfactant, alkaline and nanoparticles (NP). NP can be classified into many types such as Iron Oxide (Fe2O3), Aluminum Oxide (Al2O3) and Magnesium Oxide (MgO) etc. In this study NP Aluminum oxide (Al2O3) were used to enhance the oil recovery.

The main objective of this study is to use the Nanoparticles EOR (Al2O3) and know it is effect on increasing the extraction of oil from cores. The big motivation of using Al2O3 that it is easy to extract it from raw clay. However, the raw clay is available in Libya and using it will be more economic than using other method of chemical EOR.

Nanoparticles EOR Aluminum oxide (Al2O3) used as a spontaneous imbibition test for sandstone core samples after saturated by crude oil. A spontaneous imbibition test consisting of two scenarios of nanoparticle solution (Al2O3) with change temperature and compared with one scenario of distilled water. The spontaneous imbibition test was performed in this study at room temperature to oven temperature (30C°, 40C°, 50C°, 60C°, 70C°).

The results shown that the oil recovery increases with the increase of the concentration of nanoparticle (Al2O3) and increase the temperature. The higher oil recovery was 76.04% at NP (Al2O3) concentration 1%. Finally, oil swelling and adsorption (NP (Al2O3) with oil drops) have been noticed during the extraction of oil. Thus, the gravity force will be higher than the capillary force.
Steam Generation for EHOR Using PTC System Modeled in SAM
Authors: Gharbia Yousef , Fayed Mohamed , Anany Mohammed
Published: January 2020

Kuwait’s oil reserves include approximately 13 bn barrels of heavy oil, primarily located in the northern region of the country. The Lower Fars (LF) heavy oil development project aims to extract heavy oil from the Ratqa oil field. The US$7 bn project is being developed in phases, with the first phase expected to start in 2019 with a production rate of 60,000 Barrel of Oil Per Day (BOPD). This amount is planned to ramp up to 270,000 BOPD by 2030. The steam required for the Enhanced Heavy Oil Recovery (EHOR) process can be either generated by using conventional fuels or renewable energy resources, such as solar energy. The amount of steam required to recover a certain quantity of heavy oil depends on the value of Steam to Oil Ratio (SOR).

The aim of this work was to determine the specifications of a parabolic trough collector field required to produce steam with the right properties to recover 270,000 BOPD from Lower Fars reservoir. The Industrial Process Heat (IPH) model of the System Advisor Model (SAM) software, developed by the National Renewable Energy Laboratory (NREL), was used for this purpose. The capital cost and the running cost of the project, as well as the Levelized Cost of Heat (LCOH), were also determined. The simulation was implemented on EuroTrough ET150 trough collectors and Schott PTR 70 receiving tubes. Different plant designs with different types of heat transfer fluids (HTF) including Therminol VP-1, Therminol 59, Therminol 66, Dowtherm Q, Dowtherm RP, and Caloria HT43 have been investigated.
Forming Technology and Microstructure Distribution of Automobile Oil Pump Shaft by Extruded Cross Wedge Rolling
Authors: Shu Xue-Dao , Chen Tai-Zhu , Chang Ying , Zhu Ying , Gong Wen-Wei
Published: January 2020

In order to improve the material utilization ratio of automobile oil pump shaft, the extrusion wedge cross rolling process was developed to form automobile oil pump shaft, the results show that the volume of the blank head produced by extrusion cross wedge rolling is reduced by about 75% compared with that produced by traditional cross wedge rolling, and the material utilization ratio can be increased to about 95%. The microstructure distribution of automobile oil pump shaft formed by this process was studied systematically by fem simulation and experiment, get the forming process can make the grain size of oil pump shaft rolling parts refine continuously, and finally obtain fine and uniform grain structure. The average grain size measured by the experiment is in good agreement with the simulation results. The research results lay a theoretical foundation for reducing oil pump cost and improving life.
Analysis of Cornering Strength of Steel Wheels Including the Effects of Disc and Rim Interference Assembly
Authors: Dang Bin , Shan Yingchun , Liu Xiandong , Wang Xiaoran , Zhang Yue , Zeng Xianyu
Published: January 2020

The cornering fatigue test of commercial vehicle steel wheel is modeled and simulated by finite element method in this paper. The influence of interference stress between wheel disc and rim on the simulation results is analyzed. The interference stress is taken as predefined fields to superimpose with the stress generated by the bending load. Then the influence of two different superposition methods defining the interference stress as the average stress and the predefined fields on the stress in dangerous area of the wheel is compared. The results show that the interference stress has a significant effect on the stress state of the wheel and increases the amplitude of symmetric cyclic stress, which directly affects the prediction of fatigue life of the wheel. Therefore, the interference stress must be taken into consideration in the simulation analysis of cornering fatigue test. The influence of different interference stress superposition methods on the stress variation in the dangerous area is obviously different. The method which superimposes interference stress as predefined fields with the stress generated by the bending load is more consistent with the actual assembling and loading process of the wheel. Therefore, this paper provides a reasonable method for the simulation of cornering fatigue test, which can provide more accurate stress simulation results for the prediction of cornering fatigue life of the wheel.
A Study of Fast Charging of Li-Ion Battery With Pulsed Current
Authors: Liu Yu , Xu Meng , Xu Zhibang , Wang Xia
Published: January 2020

To fast charge lithium ion batteries while achieving higher capacity and limiting temperature rise, a constant current plus pulse current (CCPC) charging protocol is proposed. Parametric study for the CCPC design parameters including the current level, cut-off voltage, and pulse duration is performed experimentally. Taguchi method is adopted to search an optimal charging pattern. Experimental results show that the pulse charge current has the greatest effect on the charging time and temperature rise, while the pulse discharge current has the least effect on both. The optimal pattern from the Taguchi method is able to charge the cylindrical cell 15.6% faster than the traditional constant current constant voltage (CCCV) charging protocol. An electrochemical and thermal coupled model is developed to reveal the working principle of the CCPC. The modeling results show that the CCPC charging protocol reduces the concentration polarization with more uniform lithium ion distribution than the CCCV, thus accelerating the charging process.
Effects of Braking Pressure Distribution on Temperature Field and Stress Field During Braking
Authors: Zeng Xianyu , Liu Yu , Liu Xiandong , Shan Yingchun , Zhang Yue , Wang Xiaoran
Published: January 2020

The braking performance of the vehicle directly affects the driving safety. Because of the different number of brake pistons and the wear of the brake pads, the distribution of braking pressure will be uneven, which will affect the distribution of temperature field and stress field during braking, then affect the thermal fatigue life of brake discs. Therefore, in this paper, the static tensile and compressive tests of gray cast iron HT200 samples cut from vehicle brake discs are carried out at −25°C, room temperature (25°C) and 500°C, and the stress-strain curves are analyzed to obtain mechanical properties such as strength limit, elastic modulus and so on at the temperature. Based on these parameters, the finite element software ABAQUS is used to simulate the single emergency braking condition. The thermal-structural coupling simulation of brake disc is carried out to study the influences of uneven brake pressure distribution on the temperature and stress fields of brake disc, which lays a foundation for the thermal fatigue life evaluation of brake disc.
Design and Analysis of Epoxy Based Cable Terminations for Marine Cables
Authors: Prakash Raghu V. , Vibhu Padmanabhan G.
Published: January 2020

Synthetic fibers like Kevlar and Vectran are used as load carrying members in Electro-mechanical cables for marine applications. These cables have high strength, high modulus and very low water absorption rate which make them suitable materials for marine applications. The flexible electromechanical cables carry tensile load and electrical power along with data signals. Terminations are used to connect these cables to another cable or terminal. An efficient termination will ensure a load carrying capacity that is almost equal to the breaking load of the strength member of the cable. The presence of stress concentrators due to large diametrical difference between termination body and the braided fiber diameter as well as degradation in material properties reduces the strength and results in failure.

This study focuses on a chemical potting method of termination, where an epoxy compound is poured into a socket containing the Vectran™ synthetic fibers. The basic design of epoxy based termination, which has a cylindrical outer shell which secures the epoxy-fiber matrix, was selected for this study. The outer shell has two cylindrical inner surfaces of different diameters connected by a tapered region. Material property for static and fatigue loading was evaluated. Finite element analysis was carried out to understand the maximum stress profile developed in the termination and to improve the design. Baseline data on mechanical properties obtained from experiments was used as input in FE analysis. Results of the finite element analysis suggest a reasonable correlation with experiments.
Composite Overwrapped Pipe Burst Test: Modeling and Experimentation
Authors: Littlefield Andrew , Smith Lucas , Macri Michael , Root Joshua
Published: January 2020

With the emphasis on lightweighting, composites are being turned to help reduce weight while still maintaining strength and stiffness. However, composites tend to be linear elastic to failure so there is often no warning of failure unlike in metallic components. For this research, a pipe section was fabricated from an Inconel 718 liner with a carbon composite overwrap. The pipe was then subjected to increasing internal pressure until failure. The results from this experiment were used to assist in the creation and validation of a finite element model of the experiment. The model makes use of advanced numerical techniques to predict when failure will occur. This paper will present the fabrication, testing and modeling of this effort.
Influence of the Form of Pulse of Excitation on the Speed and Power Parameters of the Linear Pulse Electromechanical Converter of the Induction Type
Authors: Bolyukh Vladimir F. , Katkov Igor I.
Published: January 2020

Linear pulse electromechanical converters (LPEC) of induction type allow providing a high speed of the actuating element in the short active section and creating powerful power impulses with its insignificant movement. One of the ways to improve the electromechanical indicators of LPEC is the formation of current excitation pulses in the inductor using electronic power supply circuits containing a capacitive energy storage device. This publication is a continuation of our previous work on the influence of different parameters and conditions on the performance of LPEC.

Using the developed chain mathematical model, recurrent relations are obtained for calculating the interconnected electromagnetic, mechanical and thermal parameters of LPEC. It has been established that the speed and power electromechanical indicators of LPEC with aperiodic excitation pulse are better than those of LPEC with unipolar excitation, but worse than those of LPEC with oscillating-damped excitation pulse. LPEC with a unipolar excitation pulse, by the end of the working cycle, the smallest temperatures of the inductor and the armature are observed, while for LPEC with a oscillating-damped excitation pulse, the greatest efficiency is ensured, being 24.88%. The highest speed and power electromechanical indicators are provided at LPEC with a step-aperiodic excitation pulse.

Experimental studies of LPEC were conducted when operating as an electromechanical accelerator and a shock-power device. In studies of LPEC, a piezoelectric transducer was used as a shock-power device, which converted mechanical vibrations arising from the impact of the striker on the impact plate into electrical signals. In studies of LPEC, a displacement sensor was used as an electromechanical accelerator. It was established experimentally that the movement of the armature begins with a delay relative to the moment of occurrence of the current pulse and is almost linear in the initial part of the acceleration.
Effect of Grid-Generated Turbulence on the Dynamics of a Flexible Filament Hanging in Cross-Flow
Authors: Silva-Leon Jorge , Cioncolini Andrea
Published: January 2020

This paper describes preliminary experiments carried in a wind tunnel to study the effect of different turbulence intensities (nominally Tu = 0.6, 0.8 and 1.0%) on the dynamics of a flexible silicone filament (length to diameter ratio L/D = 83) hanging in crossflow in the range of reduced velocities of 7 < U* < 108. The turbulence intensity inside the wind tunnel was modified by employing two different grids (porosity β = 0.563 and 0.026). At low reduced velocities the filament was statically reconfigured but remained mostly rectilinear along its length. As the reduced velocity was further increased the filament started vibrating, and beyond a certain critical reduced velocity large-amplitude limit-cycle oscillation motions were observed. It is suggested that the turbulence intensity (shear velocity) affects the onset of the flapping motions and the amplitude of these. However, this behavior also depends on the turbulence integral length scale.
An Experimental Investigation of Electrorheological Fluid Damper Recoil System Used in Heavy Duty Application
Authors: Patil Santosh R. , Krishna S. , Gawade S. S. , Desavale R. G.
Published: January 2020

In this paper, a detailed analysis of a recoil system of an artillery gun has been carried out with a view to minimize recoil length by absorbing the thrust produced due to firing and bring the gun barrel to its original position for the next round of fire. In many structural and defense applications, minimization of recoil length is one of the major concerns. A lot of research work has been carried out on the recoil mechanism of an artillery gun to improve its mobility in the hilly region. The effect of recoil mass displacement and high fire rate to improve the overall efficiency of an artillery gun has been studied. In this work, the performance of an artillery gun recoil system is studied by using a damper with electrorheological (ER) fluid. Experimental and numerical studies are carried out to evaluate the performance of the recoil system in terms of recoil length and total recoil time at different elevation angles of firing, ranging from 0 to 80°. It is seen that the use of developed ER damper in the gun recoil system improves its dynamic performance.
Emergent Behavior in a Population of Thermostatically Controlled Loads With Peer-to-Peer Communication
Authors: Schwartz Ryan , Gardner John F.
Published: January 2020

Thermostatically controlled loads (TCLs) are often considered as a possible resource for demand response (DR) events. However, it is well understood that coordinated control of a large population of previously un-coordinated TCLs may result in load synchronization that results in higher peaks and large uncontrolled swings in aggregate load. In this paper we use agent based modeling to simulate a number of residential air conditioning loads and allow each to communicate a limited amount of information with their nearest neighbors. As a result, we document emergent behavior of this large scale, distributed and nonlinear system. Using the techniques described here, the population of TCLs experienced up to a 30% reduction in peak demand following the DR event. This behavior is shown to be beneficial to the goals of balancing the grid and integrating increasing penetration of variable generators.
Hybrid BCI Controller for a Semi-Autonomous Wheelchair
Authors: Nandikolla Vidya K. , van Leeuwen Travis K. , Hartman Amiel
Published: January 2020

Smart wheelchairs with semi or fully autonomous functions, can greatly improve the mobility of physically impaired persons. However, most are controlled using inputs that require physical manipulation (e.g. joystick controllers) and for persons with severe physical impairments this method of control can be too demanding. A noninvasive brain-computer interface (BCI) technology-based controller could bridge between the smart wheelchairs users and physically impaired persons with severe conditions. Current BCI controlled wheelchairs rely on detecting steady-state visually evoked potential (SSVEP) responses as these typically have the greatest data transfer rate. However, this method requires the user to focus on a screen for an extended period of time. This causes strain on the user and takes their attention away from their surroundings, which could be dangerous in a scenario that requires navigation around multiple moving objects. The focus of this project is to design a hybrid BCI controller using an electroencephalogram (EEG) headset to detect hand motor imagery (MI) and jaw electromyography (EMG) signals to control a smart wheelchair in conjunction with its semi-autonomous capabilities. A controller of this kind is well-known to have low data transfer rates, and therefore has lower accuracy and longer response times as compared to other controllers. However, a properly structured controller hierarchy between the BCI controller and semi-autonomous system is developed to compensate the limitations of the controller’s accuracy.
The Use of Qualitative Data Analysis for the Evaluation of Design Ethnography Training Among Undergraduate Engineering Students
Authors: Lai Heather L. , Eaton Tara
Published: January 2020

While qualitative data analysis (QDA) is an established method in education research, QDA is less common in engineering research and may be a challenge for engineering faculty not formally trained in qualitative methods to apply it in engineering education. The following describes the collaborative effort between an engineering design instructor and an anthropologist who used QDA to evaluate the implementation of design ethnography training in a third-year biomedical engineering design course. In their partnership, the study investigators examined student perspectives regarding design ethnography training and how such training in an engineering curriculum may prepare students for careers in biomedical design.

Data for the study consisted of reflective essays (N = 42) that the students completed following two primary exercises dedicated to design ethnography skills training. Investigators input typed and anonymized text files of the student essays into ATLAS.ti X7, a qualitative data analysis software program, for qualitative content analysis. QDA was conducted using the constant comparison method to inductively identify pertinent themes. Throughout the QDA process, the investigators routinely met to discuss, merge and interpret themes as needed. Upon the finalization of themes, researchers re-reviewed the data using the finalized codebook (a list of themes and their definitions) for coding reliability. This regular contact was invaluable for the engineering instructor, providing instruction on the process necessary for proper application of QDA.

The unique partnership between investigators offered the engineering design instructor the opportunity to evaluate engineering student perceptions of a new curriculum implementation in an in-depth manner not commonly attempted in engineering education. Results from the QDA showed that the incorporation of design ethnography skills training into an engineering design curriculum increased student awareness of the value of ethnography in understanding user environments while offering engineering students the opportunity to develop better observation skills. This study was successful not only in demonstrating efficacy of design ethnography training among undergraduate engineering students, but it also serves as an example of how QDA may be applied by engineering instructors for the evaluation of student experience and work in engineering education.
Determination of Future Robust Product Features for Modular Product Family Design
Authors: Greve Erik , Rennpferdt Christoph , Hartwich Tobias , Krause Dieter
Published: January 2020

Modular product architecture design allows product variants to be derived with little effort and cost. An essential part of designing modular product architectures is fulfilling customer-relevant product features, which represent the differentiating aspects for the customer and, thus, stand for the economic success of a product variant. However, product features are not only subject to high fluctuations due to changing environmental influences, but are also of varying relevance to customers over time. Not considering these aspects in the development phase can lead to costly changes in the product architecture later on. To counteract this, these two perspectives are merged and a methodical approach is introduced that identifies new product features and analyses their future development in the context of customer benefit. For this purpose, the current and future relevance to customers as well as uncertainties are calculated using Adaptive Conjoint Analysis and a Monte Carlo simulation. The results are consolidated in a visualization and the product features are classified according to their future implementation in robust product architecture. The procedure is explained using the example of a product family of vacuum cleaning robots.
Influence of Pocket Wear on the Dynamic Characteristics of High-Speed Ball Bearing Cage
Authors: Li Hui , Li Chen , Li Yuan , Qi Shemiao , Liu Yi , Liu Heng
Published: January 2020

Aiming at the problem of wear on the cage-pocket during the operation of high speed rolling bearing, a dynamic model of high-speed ball bearing was established considering the wear loss of the ball-pocket, and the simulation was carried out to research on the interaction among the balls, the inner ring, the outer ring and the cage with different wear loss of the ball-pocket. The effect of the pocket wear on the trajectory of the cage’s mass center and the skidding ratio of cage was obtained. It was found out that the mass-center trajectory of the cage presents two vibration modes with different amplitudes which emerges alternatively. Moreover, the wear loss of the ball-pocket has little effect on the average skidding ratio of the cage, however, the fluctuation amplitude would become larger as the wear increase. This study can provide theoretical guidance for the design of bearing cage pocket size.
Robust Control-Oriented Modeling of a Feedback-Linearized Powered Pediatric Lower-Limb Orthosis
Authors: Laubscher Curt A. , Sawicki Jerzy T.
Published: January 2020

Linear robust control techniques such as μ-synthesis can be used to design controllers for linear systems to guarantee specified performance criteria in the presence of modeling uncertainties, disturbances, and sensor noise. However, these techniques are rather uncommon in robotics due to the nonlinear nature of the plant where direct application would require large model uncertainties and therefore may only create a satisfactory controller if using lenient performance criteria. The inclusion of feedback linearization can rectify this by effectively converting the plant from a nonlinear system to a linear one, resulting in smaller model uncertainties.

This paper proposes the use of feedback linearization to enable the use of linear robust control techniques on nonlinear systems. This approach is applied to a provisional version of a powered pediatric lower-limb orthosis. Sine sweep experiments are conducted to determine frequency response data for the system with and without feedback linearization. Models are identified to match the recorded data using optimization for both cases. Uncertainties are manually applied such that they encapsulate the observed measurements. The amount of uncertainties in the two models are quantified and a comparison shows that the uncertainties in the feedback-linearized system are smaller than in the system without feedback linearization.
Dynamics of Compound Droplet Passing Through a Conical CTC Microfilter
Authors: Chang Pengliang , Hashem Mohammad Abul , Chen Xiaolin , Tan Hua
Published: January 2020

Circulating tumor cells (CTCs) are important biomarkers which can be used for early-stage cancer detection and treatment. Developing an efficient approach to detect CTCs from peripheral blood is a challenging problem due to their extreme rarity. The CTC microfiltration provides a good solution as a critical method based on the physical property of CTCs. In this study, we employed a compound droplet model to investigate the transport behavior of a CTC squeezing through a conical-shaped microfilter. The compound droplet model of CTC is composed of a cortical membrane, cytoplasm and the nucleus. Numerically, we used the octree-based Adaptive-Mesh-Refinement (AMR) to analyze the deformable CTC flowing through a microfilter with non-uniform cross-sections. We investigated the pressure-deformability behavior of the cell with different nuclear to cytoplasmic ratio (N/C ratio). Our study revealed that the nucleus smaller than the filter pore did not affect the pressure behaviors significantly. However, when the nucleus is larger than the filter pore size, the pressure behaviors are greatly affected. We also studied the effects of the flow rate on the cell squeezing process. We found that the critical pressure increases significantly with the flow rate. Our study can provide valuable information about cell transport behavior in conical-shaped microfilters.
Stability Analysis of Demand Response Systems Utilizing Locally Communicating Thermostatically Controlled Loads
Authors: Kuwada Jason , Gardner John F.
Published: January 2020

Thermostatically Controlled Loads (TCLs) have shown great potential for Demand Response (DR) events. However, it has been commonly seen that DR events using TCLs may cause load synchronization and unwanted oscillatory effects, especially in homogeneous populations. In an attempt to mitigate the negative impacts of DR events, a decentralized method is proposed that modifies each thermostat behavior based on the activity of nearby TCLs. This feedback introduces the possibility of instability in the aggregate behavior. A stability analysis is performed on a model of the aggregate system and the results of that analysis compared to simulation results. Several populations were considered, varying population size, communication topology, thermostat deadband and heterogeneity of the population. While the linearized analysis failed to accurately predict instabilities in the aggregate system, it did provide insight into global behavior.
Design Resilience of Demand Response Systems Utilizing Locally Communicating Thermostatically Controlled Loads
Authors: Kuwada Jason , Mehrpouyan Hoda , Gardner John F.
Published: January 2020

Thermostatically Controlled Loads (TCLs) have shown great potential for Demand Response (DR) events. The focus of this study is to investigate the effects of adding communication throughout a population of TCLs on the resilience of the system. A Metric for resilience is calculated on varying populations of TCLs and verified with agent based modeling simulations. At the core of this study is an added thermostat criterion created from the combination of a proportional gain and the average compressor operating state of neighboring TCLs. Differing connection architectures are also analyzed. Resilience of the systems under different connection topologies, are calculated by analyzing algebraic connectivity at varying population sizes. The resilience analysis was verified through simulation. Results of the analysis show the effect of on delay schemes and connection architecture on stability limit of each system. Good concurrence was found between predicted and observed resilience for smaller dead-band sizes. Simulations showed varying results on the effect of a simulated attack based on location of the attack within the population.
Modeling Prestress-Driven Buckling Behavior of Elastic Lamina in the Aortic Media
Authors: Tamura Atsutaka , Kato Yuya
Published: January 2020

Mathematical modeling of the thoracic aorta is important for understanding the development and progression of various cardiovascular diseases, helping to detect extraordinary stress distributions of the hypertensive aortic wall, even in early stages. However, it is difficult to ensure the biofidelity of biological materials in formulating a mathematical model. In a freshly isolated aortic media, composed mainly of smooth muscle cell layers (SMLs) and elastic laminae (ELs), circumferential EL waviness and longitudinal EL undulation are often observed because of the structural “buckling” of ELs. This is considered to be closely associated with residual stresses of SMLs and ELs in the aortic wall but the mechanism underlying such EL buckling behavior remains unclear. In the present study, a series of numerical simulations were designed to identify effective mechanical parameters to reproduce EL buckling in the aortic media. We found that prestress initially administered to ELs in the circumferential and axial directions, and the predefined internodal distance, which couples the SML and EL, are essential to computationally reconstruct the circumferential EL waviness and the longitudinal EL undulation in an unloaded state. We also proposed a set of equations based on the numerical results and successfully predicted EL buckling behaviors of the aorta in vitro.
Energetic and Exergetic Performance Comparison of an Ejector Refrigeration System Using Modern Low GWP Refrigerants
Authors: Mwesigye Aggrey , Dworkin Seth B.
Published: January 2020

In this study, a novel model is used to precisely predict the performance of an ejector refrigeration system utilizing modern environmentally benign working fluids in both the critical and subcritical modes of operation. Energetic and exergetic performance of low global warming potential and non-ozone depleting HCFO and HFO refrigerants: R1233zd(E), R1224yd(Z), R1225ye(Z), hydrocarbon refrigerants: Isobutane and Isopentane and RE245cb2 is compared with that of conventional refrigerants: R141b and R245fa. The model takes the ejector area ratios, generator pressure, and evaporator pressure into account in the determination of the ejector loss coefficients. A program written in Engineering Equation Solver (EES) was used to obtain solutions of the developed mathematical model. In the analysis, ejector area ratios between 6.44 and 12.76, evaporator temperatures between 4 and 16°C, condenser temperatures between 25 and 50°C as well as generator temperatures between 70 and 110°C were used. Results show that Isobutane and R1225ye(Z) have the greatest performance, giving an over 150% increase in the coefficient of performance (COP) compared to R245fa. The increase in the COP with isopentane, RE245cb2, R1224yd(Z) and R1233zd(E) were as high as 22%, 32%, 16% and 14%, respectively at the lowest area ratio. Results further show that the ejector contributes the highest exergy losses (up to 55%, depending on the evaporator, condensing and generator temperatures) compared to the other components. The contribution of the condenser to the total exergy loss is up to 28%, for the generator it is up to 34% and up to 12% for the evaporator. The pump and the throttle valve give values lower than 0.5 and 9%, respectively for all the refrigerants.
Study on Velocity Distribution Estimation Using Blood Pressure Data Based on the Coupled Wave Theory of Elastic Pipes and Fluids
Authors: Tokunaga Takeshi , Mori Koji , Kadowaki Hiroko , Saito Takashi
Published: January 2020

Cardiovascular disease that is one of Non-Communicable Disease accounts for about 25% of death in Japan. Prevention of arteriosclerosis that is a main cause of cardiovascular disease is important. Since an early lesions of arteriosclerosis progress as functional change of an endothelial cell that is uniformly distributed on the luminal surface of a blood vessel, an accurate evaluation of the endothelial cell function is important as prevention of the arteriosclerosis. Although Flow-Mediated Dilation (FMD) is widely used as a diagnosis of the endothelial cell function in clinic, it is an evaluation method that uses a static diameter of a blood vessel. Moreover, it isn’t possible to take into account individual difference of a wall shear stress on the endothelial cell. In previous study, it is found that an evoked hyperemic wall shear stress is a major correlate of %FMD. In order to accurately measure the endothelial cell function, it is necessary to simply assess the hyperemic shear stress during FMD. However, it is difficult to non-invasively measure the hyperemic shear stress on the endothelial cell in clinic. In this study, we focused on a blood pressure data that is obtained non-invasively and formulated a relationship between the pressure and a flow velocity based on the coupled wave theory. And we estimated a hyperemic shear stress by using a blood pressure data that is obtained by a tonometry method in experiment that simulate FMD. As a result of estimating the hyperemic shear stress, it reflected characteristics of blood flow in clinic. It may be necessary to consider the hyperemic pressure fluctuation that is waves including low frequency components. Moreover, the hyperemic pressure fluctuation should not be treated as a waveform that has individually different a static pressure in estimation of the hyperemic wall shear stress.
Advanced Packaging Solution for High Density FCCSP Molding Warpage
Authors: Liu Shuai-Lin , Ye Ward , Wang Yu-Po , Wang Long-Yuan , Lin Fred
Published: January 2020

In recent years, the IC industry continues to drive demand in the consumer market, and more global sales of smart-phones, smart-watches and tablets have continued to grow. In order to continuously enhance high performance computing, the consumer products pursued began to integrate HBM (High Bandwidth Memory) and AI (Artificial Intelligence) to strong and powerful mainstream market.

With the shrinking use space pursued by consumer products, it is necessary to continuously develop lighter and thinner products, and under such product conditions, it seems that the risks and difficulties of advanced packaging technology will be expected. Due to the ministration application, the warpage issue is the most influential factor in the following development of packaging technology. In this paper, we would like to overcome the poor strip warpage, not only to choose the EMC material form CTE property, but to think about improving the warpage from the machine process. The residual stress generated by the molding process of thermosetting resins exerts serious influences upon the mechanical properties, so we use Laser area beam processing to reheat the EMC and use the vacuum suction to reshape the warpage deformation. In this case, we verify the laser radiation time and peak temperature control of different strip types (including molded, thermal taped and ball attached molded strip) and EMC wafer form. We succeed to improve the maximum strip warpage from 17 um to 1um; wafer form from 13um to 3.5um. This laser beam reshape technology is proven to solve the warpage significantly for high density assembly.
A Convenient and Reliable Method of Manufacturing Inclined Bulk Graphite for Measuring Thermal Conductivity With TDTR
Authors: Zhao Yu , Yu Hongyang , Sha Jingjie , Chen Yunfei
Published: January 2020

In this work, in order to study the thermal transport along arbitrary direction in bulk graphite, we develop a simple and convenient method to manufacture inclined bulk graphite applying Focused Ion beam (FIB). Then, we measure the thermal conductivity of inclined bulk graphite with the time-domain thermoreflectance (TDTR) technique and the measured results show that our processing method is reliable. Based on the TDTR measurement of inclined bulk graphite with a tilt angle of 90°, the in-plane thermal conductivity is on the order of 2030 Wm−1 K−1 and the cross-plane thermal conductivity is on the order of 5.5 Wm−1 K−1 at room temperature, which is close to the previously reported results. Our processing and measurement methods provide a new perspective on the study of the intrinsic mechanism of anisotropic thermal transport in anisotropic layered materials.
Optimizing Material Parameters for Better Formability of DQ Steel Pipe
Authors: Memon Shabbir , Mohammed Obaidur Rahman , Koppisetty D. V. Suresh , Lankarani Hamid M.
Published: January 2020

As Pipelines are subjected to bursting failure, the prediction of the burst capacities of corroded pipelines is of significant relevance to the pipeline industry. The Single mode deformation processes, most commonly used in laboratory evaluations like tensile test, may not realistically predict formability performance. Therefore, limit strains tests that use multiple deformation stages would better simulate actual material performance hence bulge test is widely used in pipeline industry for analyzing formability. The tube bulge test is an advanced testing material in which the tube is placed in a die cavity and is sealed from both the ends, the water is injected from the hole inside the sealing punch and hydraulic pressure is increased and the tube gets deformed at the center. The objective of this work is to utilize Taguchi coupled finite element computational methodology to determine the optimum material parameters to attain better formability without necking-splitting failure. To evaluate the dependence of the slope of the forming limit diagram on the material parameters, the simulation under various combinations of strain-hardening exponent (n), plastic strain ratio (r) and thickness of tube (t) is carried out and using thickness gradient criterion, the occurrence of necking i. e. forming limit strains during tube bulging is examined. By observing the optimum condition obtained for maximum plain strain it is concluded that higher the n, r and t more the limit strains will be. It is also observed that among n, r and t, n is the most prominent factor contributing on limit strains followed by r and t. The verification of optimum process parameters obtained through Taguchi technique is carried out using additive model and it is found that the observed value is well in agreement with the predicted value, the extra validation simulation is carried out to validate the Taguchi results.
An Assessment of the Validity of Quasi-Steady Analysis of Pressure Relief Valves
Authors: Doyle Christopher , Dempster William , Taggart Steven
Published: January 2020

In this paper, the validity of the commonly used quasi-steady design approach to pressure relief valves (PRV) is examined by comparing detailed steady state conditions of valve behavior directly with transient conditions. To achieve this, a PRV conforming to ASME VIII standards was modelled using the commercial computational fluid dynamics (CFD) package ANSYS FLUENT to account for transient fluid-structure interaction processes. Detailed steady state CFD simulations were conducted using quasi-steady assumptions and compared to high fidelity transient moving mesh simulations to allow the piston forces to be examined. The results indicated that noticeably different magnitudes can occur between steady state and transient simulations; highlighting the possibility of significant differences occurring between quasi steady designed valves and their ultimate performance. In this paper, a single operating condition is examined, using air at 10.3 barg, for a 5231BX refrigeration valve supplied by the Henry Group to highlight the main issues. Analysis has indicated that the differences in performance are generated by temporal, short lived vortices at the piston surface which influences the bulk flow features as the disc accelerates and decelerates; altering the net disc forces when compared to steady state conditions.