bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Time-Frequency Control of Permanent Magnet Synchronous Motors
Authors: Wang Xin , Suh C. Steve
Published: February 2017

Permanent magnet synchronous motors are essential components in a wide range of applications in which their unique benefits are explored. However, in order for a permanent magnet synchronous motor to achieve satisfactory performance, particular control frameworks are essential. After all, permanent magnet synchronous motor is an AC machine, which is characterized by its complex structure and strongly coupled system states. Therefore, in order for it to achieve satisfactory dynamic performance, advanced control techniques are the only solution. This paper presents a precise speed control of permanent magnet synchronous motors using the nonlinear time-frequency control concept. The novel aspect of this nonlinear time-frequency control, which is an integration of discrete wavelet transformation and adaptive control, is its ability in analyzing the fundamental temporal and spectral qualities inherent of a permanent magnet synchronous motor and exerting control signals accordingly. Simulation results verifies that the proposed nonlinear time-frequency control scheme is feasible for alleviating the nonlinear behavior of the permanent magnet synchronous motor which hampers the tracking of speed with desired precision.
Combat Helmet Design Incorporating Multiple Ballistic Threats, Brain Functional Areas and Injury Considerations
Authors: Matic Peter , Moser Alex E. , Saunders Robert N.
Published: February 2017

Combat helmet protection zone parametric design is presented for small arms and explosive device ballistic threat notional spatial distributions. The analysis is conducted using a computer aided design software application developed to evaluate ballistic threats, helmet design parameters, and a standard set of common brain injuries associated with head impacts. The analysis helps to define the helmet trade space, facilitates prototyping, and supports helmet design optimization.

Direct head impacts and helmet impacts, with and without helmet back face contact to the head, are tabulated. Head strikes are assumed to produce critical or fatal penetrating injuries. Helmet back face deflections and impact generated projectile-helmet-head motions are determined. Helmet impact obliquity is accounted for by attenuating back face deflection. Head injury estimates for ten common focal and diffuse head injuries are determined from the back face deflections and the head injury criteria. These, in turn, are related to the abbreviated injury score and associated radiographic dimensional diagnostic criteria and loss of consciousness diagnostic criteria from the trauma literature.
Optical Diagnostics for Energetic Materials Research
Authors: Hargather Michael J. , Smith Joshua L. , Anderson James , Winter Kyle
Published: February 2017

Optical diagnostics including schlieren, shadowgraphy, and background-oriented schlieren (BOS) are used to visualize shock waves and compressible flow phenomena present in energetic and explosive events. These techniques visualize refractive index variations to obtain a range of qualitative and quantitative information. A one-dimensional explosively-driven shock tube facility is used with schlieren imaging to measure shock wave propagation speeds from explosive-thermite mixtures. The schlieren imaging visualizes turbulent flow structures in the expanding product gas region. An imaging spectrometer is paired with the schlieren imaging to quantify the mixing of the explosive product gases with the ambient environment. Shadowgraphy is applied to image field-scale explosive tests. The shadowgraph images reveal shock waves, fragment motion and speed, and the motion of product gases. BOS is a modern technique for visualizing refractive fields via their distortion of a background pattern. Here the technique is applied to image field-scale explosive events using the ambient background of the test pad. The BOS images clearly show shock wave propagation and reflection from surfaces, which is not clearly visible in the raw high-speed digital images.
1-D Thermoreflectance Measurement Technique for Freestanding Micro/Nano Cantilever Beams
Authors: Elahi Mirza M. , Ghasemi Baboly Mohammadhosein , Leseman Zayd C.
Published: February 2017

Pump-probe thermoreflectance is a well-known non-contact optical measurement technique for thermal property analysis of thin film materials on a semi-infinite substrate. Two laser lines are commonly used, one of which is used to heat the structure (the pump) and the other is used to measure the change in reflectivity (the probe) to infer thermal properties of the material/structure. This work extends the technique to freestanding cantilever beams. The pump beam applies a constant flux to the free end of the cantilever thereby inducing a thermal gradient along its length which is measured by the probe beam. Measurement of the thermal gradient allows for determination of the thermal conductivity of the material. Convective and radiative heat losses are minimized by performing the experiment at high vacuum and removing the substrate underneath the beam. We demonstrate the technique by measuring the thermal conductivity for four Si cantilever beams that are 1.29 μm thick. The average thermal conductivity for the beams was measured to be 96.9 ± 1.76 Wm−1K−1.
FEM Analysis on Creep Deformation and Axial Bolt Force Change in Threaded Fasteners at Elevated Temperature
Authors: Omiya Yuya , Watanabe Tadatoshi , Fujii Masahiro , Yamamoto Haruka
Published: February 2017

In this study, the creep deformation in the threaded joint are discussed using a finite element method, and evaluated the influence of the dimensions of bolt and clamped parts. The stress and creep strain distributions are calculated using the Finite Element Analysis. The occurrence and the propagation of the creep deformation and influence of the creep deformation on the axial bolt force were discussed. It was found that the creep deformation occurred at the bearing surfaces and the engagement screw thread mainly at the elevated temperature. The creep deformation was a cause of the reduction in axial bolt force.
Nonlinear Time-Frequency Control of Electromagnetic Solenoid Valve
Authors: Southern Jacob D.
Published: February 2017

The main objective of this study is to prove that an electromagnetic solenoid valve can be controlled accurately and have a rapid response time while not having to linearize the system. An electromagnetic solenoid valve can neither be slow nor have large amounts of error due to the small distances between the pressure ports and the accuracy of the system they are used to control. The valve modeled for this study was an automotive transmission solenoid valve. The solenoid valve has three ports: supply, exhaust, and controlled pressure. For simplification, this model only considers moving the spool to a specific port location, which will be user specified. The controller used for this system was a nonlinear time-frequency controller that uses Daubechies-3 wavelets for signal transformation. Once, the controller was optimized it was able to control the system accurately and with a rapid response time. The system is able to reach the desired input and maintain zero error in two tenths of a second with out greatly over shooting the desired input. Overall, this system is physically possible to control the way the simulation predicts because all of the parameters used in the simulation are from a real solenoid valve.
Study on Model Parameters of Focal Cooling Device Using a Peltier Element for a Living Body
Authors: Uehara Kenyu , Miyago Kentaro , Mori Koji , Saito Takashi
Published: February 2017

Cooling treatment is known as one of the effective treatment for injury. It has an optimum cooling temperature level depending on a symptom or an injury. Hence a highly precise temperature control function is required for a cooling device for this kind of treatment. A mathematical model of cooling device using a Peltier element is necessary to realize its functions. In this paper, we examined the characteristics of model parameters by identification experimentally and comparison of its values. Three cooling devices (A, B and C) were used. A Peltier element of device A and device B were the same size with different cooling performance respectively. Whereas a Peltier element of device C was bigger than the two devices. Effects of devices size and cooling performance on the model parameters were investigated. It is shown that most of the parameter values were increased in the device C. The Seebeck coefficient and the internal resistance had little dependent relation with the device size while the other heat conductances were strongly dependence upon the size. From these results, the characteristics of each parameters became mostly evident by comparison of three devices of different sizes and cooling performances. However, it is required to analyze more and utilize different devices to carry out the development of cooling device by using this model.
Musculoskeletal System for Bio-Inspired Robotic Systems Based on Ball and Socket Joints
Authors: Wu Lianjun , Tadesse Yonas
Published: February 2017

Musculoskeletal system is the fundamental structure that allows complex mobility of biological systems. A lot of efforts have been made in the past to mimic this structure using synthetic materials for use in robotic systems. Development challenges for this technology include design and manufacturing, system integration, control methods and energy usage. One of the key elements of musculoskeletal system is artificial muscles or actuators used in this system. Actuators presented in the literature do not match the performance of natural muscles in most of the metrics such as force generation, strain output, frequency, power density, ease of control and repeatability. This paper briefly describes the recently introduced Twisted and Coiled Polymer (TCP) muscles integrated into a ball and socket joint made of ABS plus® material. The proposed structure consists of a class of ball-and-socket joint that incorporates TCP muscles and silicone to generate multidimensional actuation. Most traditional joint-and-actuator assemblies include passive rotary joints actuated by servomotors via gears transmission. Our proposed ABS based 3D printed joint is actuated by artificial muscles without any complex mechanical transmission system. In comparison with other such assemblies, the proposed joint system is a promising solution to the diverse applications in robotics, especially where soft actuators and cost effective solutions are needed.
Thermal Predictions of the AGR-3/4 Experiment Using PIE-Measured Time Varying Gas Gaps
Authors: Hawkes Grant L. , Sterbentz James W. , Maki John T. , Pham Binh T.
Published: February 2017

A thermal analysis was performed for the Advanced Gas Reactor test experiment (AGR-3/4) with Post Irradiation Examination (PIE) measured time varying gas gaps. The experiment was irradiated at the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL). Several fuel irradiation experiments are planned for the AGR Fuel Development and Qualification Program which supports the development of the Very-High-Temperature gas-cooled Reactor (VHTR) under the Next-Generation Nuclear Plant (NGNP) project.

AGR-3/4 combines two tests in a series of planned AGR experiments to test tri-structural-isotropic (TRISO)-coated, low-enriched uranium oxy-carbide fuel. The AGR-3/4 test was designed primarily to assess fission product transport through various graphite materials. The AGR-3/4 test irradiation in the ATR started in December 2011 and finished in April 2014. Forty-eight (48) TRISO fueled compacts were inserted into twelve separate capsules for the experiment (four compacts per capsule).

The purpose of this analysis was to calculate the temperatures of each compact and graphite layer to obtain daily average temperatures using PIE-measured time (fast neutron fluence) varying gas gaps and to compare with experimentally measured thermocouple data. PIE-measured experimental data was used for the graphite shrinkage versus fast neutron fluence. Heat rates were input from a detailed physics analysis using the Monte Carlo N-Particle (MCNP) code for each day during the experiment. Individual heat rates for each non-fuel component were input as well. A steady-state thermal analysis was performed for each daily calculation. A finite element model was created for each capsule using the commercial finite element heat transfer and stress analysis package ABAQUS. The fission and neutron gamma heat rates were calculated with the nuclear physics code MCNP. ATR outer shim control cylinders and neck shim rods along with driver fuel power and fuel depletion were incorporated into the daily physics heat rate calculations. Compact and graphite thermal conductivity were input as a function of temperature and fast neutron fluence with the field variable option in ABAQUS. Surface-to-surface radiation heat transfer along with conduction heat transfer through the gas mixture of helium-neon (used for temperature control) was used in these models. Model results are compared to thermocouple data taken during the experiment.
On the Effective Properties of 3D Metamaterials
Authors: Abdelhamid Mohamed , Czekanski Aleksander
Published: February 2017

A continuum-based model is developed for the octet-truss unit cell in order to describe the effective mechanical properties (elastic modulus) of the lattice structure. This model is to include different geometric parameters that impact the structural effects; these parameters are: lattice angle, loading direction, thickness to diameter ratio, diameter to length ratio, and ellipticity. All these geometric parameters are included in the stiffness matrix, and the impact of each parameter on the stiffness tensor is investigated. Specifically, the effect of the lattice angle on the elastic moduli is discussed, and the loading direction of the highest elastic modulus is investigated for different lattice angles. Furthermore, the Gurtin-Murdoch model of surface elasticity is used to include the size effect in the stiffness tensor, as well as anisotropy of this model is investigated.
Application of Non-Convex Analytic and Geometric Tools to a PLIC-VOF Method
Authors: López J. , Gómez P. , Zanzi C. , Faura F. , Hernández J.
Published: February 2017

An efficient approach to handle either convex or non-convex arbitrary polytopes is applied to volume truncation and volume conservation enforcement operations involved in volume of fluid (VOF) methods. A comparison between the proposed approach and conventional procedures based on convex decomposition is carried out for different tests, demonstrating that the proposed tools represent a substantial improvement in computational efficiency. A speedup of around one order of magnitude is achieved for the reconstruction of several interfacial shapes. The non-convex tools have been used to implement a highly accurate volume of fluid (VOF) method based on a multidimensional advection scheme with edge-matched flux polyhedra and a piecewise linear interface calculation (PLIC) method. A preliminary analysis of the accuracy, computational efficiency and volume conservation properties of the implemented PLIC-VOF method is carried out.
Direct Sensing of Wing Flapping and Rotation Parameters for a Hawkmoth-Sized Flapping Wing Micro Air Vehicle
Authors: Sahai Ranjana
Published: February 2017

Many insights can still be gained from the flapping flight of nature’s flyers, particularly from how they can effortlessly transition between flight modes and maneuver in obstacle-strewn environments. Furthermore, they are able to do this without the typical control surfaces found in manmade vehicles. Many theories have been postulated on how this is accomplished and they often involve control of individual wing position and stroke velocity. As such, direct sensing of wing motion both in flapping and in rotation would be desirable. In this work, we look at implementing wing motion sensing through the use of optical sensors. We develop sensing designs for both the transmissive and reflective sensor types, present design reasoning, and discuss the advantages and disadvantages of their use. Finally, we employ the sensors on the wing of a flapping wing MAV capable of power autonomous flight and demonstrate successful sensor tracking of general wing motion.
Understanding the Influence of Turbine Geometry and Atmospheric Turbulence on Wind Turbine Wakes
Authors: Gu Ping , Kuo Jim Y. J. , Romero David A. , Amon Cristina H.
Published: February 2017

A wind turbine wake is divided into two regions, near wake and far wake. In the near wake region, the flow is highly turbulent and is strongly influenced by the rotor geometry. In the far wake region, the influence of rotor geometry becomes less important as atmospheric effects become dominant. However, how turbine geometry and atmospheric condition affect the two wake regions is not well studied. In this work, the influence of atmospheric turbulence and the blade aerodynamic forces on wake development is studied using computational fluid dynamics (CFD) models. The CFD simulation results are based on an actuator disk model and an k–ε turbulence model. The effects of blade geometry are captured by prescribing aerodynamics forces exerted by a LM8.2 blade on an actuator disk, and are compared with that of an equivalent uniform normalized force, under two atmospheric turbulence conditions. The finding shows that the length of the near wake region is strongly affected by atmospheric turbulence, with the wake becoming fully developed as far as 2.5 rotor diameters downstream of the rotor under low turbulence conditions. Furthermore, the velocity profile in the far wake region is independent of the blade profile. In other words, in the cases studied, an actuator disk with an equivalent uniform force will produce nearly identical velocity profiles in the far wake region as one with nonuniform aerodynamic force profiles. These findings have implications on existing wake models where the far wake is the region of interest. Specifically, the beginning of the far wake region should be properly defined for each scenario, and that it is not necessary to provide detailed rotor geometry for far wake simulations.
Numerical Modeling and Optimization of a Natural Gas and Coke Oven Gas Mixing Flow Field
Authors: Liu Xiang , Wu Bin , Tang Guangwu , Chen Yuchao , Silaen Armin K. , Zhou Chenn Q.
Published: February 2017

Coke oven gas (COG) is a by-product of the coke making process. In the steelmaking industry, COG is often injected along with natural gas as fuel into blast furnace to replace coke for cost reduction. For an integrated steel plant, NG is always more expensive than COG. Especially, NG is purchased externally, and COG is generated internally. To lower the total fuel cost, the operators always try to maximize COG usage and only use NG as supplement for thermal control. However, it is found that such simple concept could not be implemented successfully. Every time, as NG flow rate increases, the COG flow rate decreases automatically. As a result, total fuel supply is short than expected, and the blast furnace finally loses thermal stability. A comprehensive investigation was conducted. Computational fluid dynamics (CFD) was used to model the COG and NG pipeline system. It is identified that mixing of COG and NG has a critical impact. In the existing pipeline system, COG and NG is simply mixed at a joint where COG and NG meet. CFD simulation identified that the current mixing of COG and NG is not adequate, causing COG flow out of control as NG flow varies. A new design of COG and NG joint is developed by adding baffles to ensure the COG flow can be adjusted as needed.
Effect of Cure Temperature and Pressure on Autoclave-Bonded Polycarbonate Single Lap Joints
Authors: Nassar Sayed A. , Jagatap Shraddha , Tardito Marcello
Published: February 2017

This study investigates the effect of cure temperature and pressure on the mechanical performance of autoclave-bonded single lap joints (SLJ). Joint load transfer capacity (LTC) and failure mode analysis are provided. Test joints are made of two polycarbonate lexan adherends that are autoclave-bonded together using aliphatic polyether (Polyurethane) film adhesive (Huntsman PE399). Two levels of cure pressure and cure temperature are investigated, for their effect on joint load transfer capacity and failure. Data analysis and discussion are provided.
Analysis of the Quality Factor and Response Time of Resonant Biosensor
Authors: Hassanpour Pezhman A.
Published: February 2017

The relationship between the overall damping and response time of resonant biosensors is investigated in this paper. The governing equation of motion is derived using a single degree-of-freedom model of the resonator considering the dynamic effect of adsorption of the measured parameter. It is shown that the adsorption leads to a damping force on the resonant sensor. If not taken into account, this damping force results in misinter-pretation of the sensor readings.
Self-Aligned Carbon Nanotube Yarns for Multifunctional Optoelectronic Applications
Authors: Uddin M. Jasim , Grissom Glenn , Leal Miguel , Galvez Veronica , Trad Tarek , Touhami Ahmed , Islam Nazmul , Parsons Jason , Moore H. Justin
Published: February 2017

In this work, the morphology and electrocatalytic features of carbon nanotube yarns at the structural level allow for enhanced photoconversion efficiency. The energy conversion of electron-hole pairs within the carbon nanotube yarn (CNY) due to the functionalization with nanostructured photoactive TiO2 phases is remarkable. A well oriented anatase TiO2 thin layer (approximately 100 nm) forms at the interfaces of CNY and TiO2 mesoporous film when the sample is precoated and annealed at 350°C. Field Emission Scanning Electron Microscopy (FESEM) images show the integrity and homogeneity of the TiO2 surface, which is indicative of the overall durability of the CNY-based dye sensitized solar cell (DSSC); Coating TiO2 on self-aligned carbon nanotube yarns provides several benefits from their high chemical stability, excellent functionality, nontoxicity and relatively low cost. The maximum photon to current conversion efficiency (ηAM1.5) achieved was 3.1%.
Optimization of an Electrokinetic Orthogonal Electrode Pattern for Multifunctional System
Authors: Guduru Rakesh , Uddin Mohammed , Islam Nazmul
Published: February 2017

One of the most notable methods for improving microflows is the design of an orthogonal electrode pair that accentuates the non-uniformity in the electric field and, as a result produces stronger net flows at lower voltages. Orthogonal electrodes also have been reported to produce high velocity fluid flow when excited by AC signals, showing potential for micro-pumping applications. Breaking the symmetry of electric fields in the electrode pair produces a unidirectional flow [1] which is salubrious for pumping. As many research groups believe that the Manipulation of microfluidics and particles can be effectively done by AC electrokinetic (ACEK) technique, the current research work in our lab involves in designing a multifunctional system to manipulate the particles to improve the binding process and the fluid flow. This research also explicates the AC electrokinetic processes such as capacitive electrode polarization, Faradic polarization and the AC electrothermal effect, to better explain the directional flow patterns and their role in manipulating the microfluidics. Different flow patterns were obtained by varying the level and frequency of AC potential.
Nano Heat Pipe: Nonequilibrium Molecular Dynamics Simulation
Authors: Moulod Mohammad , Hwang Gisuk
Published: February 2017

A heat pipe has been known as a thermal superconductor utilizing a liquid-vapor phase change, and it has drawn significant attentions for advanced thermal management systems. However, a challenge is the size limitation, i.e., the heat pipe cannot be smaller than the evaporator/condenser wick structures, typically an order of micron, and a new operating mechanism is required to meet the needs for the nanoscale thermal management systems. In this study, we design the nanoscale heat pipe employing the gas-filled nanostructure, while transferring heat via ballistic fluid-particle motions with a possible returning working fluid via surface diffusions along the nanostructure. The enhanced heat flux for the nano heat pipe is demonstrated using the nonequilibrium molecular dynamics simulations (NEMDS) for the argon gas confined by the 20 nm-long Pt nanogap with a post wall with the temperature difference between the hot and cold surfaces of 20 K. The predicted results show that the maximum heat flux through the gas-filled nanostructure (heat pipe) nearly doubles that of the nanogap without the post wall at 100 < T < 140 K. The optimal operating conditions/material selections are discussed. The results for the nanogap agree with those obtained from the kinetic theory, and provide insights into the design of advanced thermal management systems.
Numerical Study of Cruciform Specimens for Biaxial Tensile Tests
Authors: Puente Medellín Luis F. , Balvantin Antonio , Diosdado-De la Peña J. A.
Published: February 2017

This paper presents a numerical study of different geometries of cruciform specimens for biaxial tensile tests. The aim of these specimens is to be used on fixtures for biaxial tests mounted in universal testing machines. For the study, a model of isotropic material for steel sheet metal specimens was considered. Thus, only the mechanical properties of the sheet metal in the rolling direction were considered in the simulations. In this numerical analysis, the normal stress distribution and the consequent shear stress were studied. Additionally, the effect of the inclusion of multiple slots as well as a thickness reduction on the normal and shear stresses were assessed. Hence, a specimen in which a uniform normal stress distribution with zero shear stress, is necessary. The results of the analysis show that a specimen with features, multiple slots and a thickness reduction in the central area, provides a better performance in the simulations than dismissing any of these characteristics. Finally, a specimen model suitable for the mentioned test is proposed according to the obtained numerical results and the feasibility of manufacture of the experimental sample-test.
Weldment Analysis of a Diesel Engine Exhaust Manifold
Authors: Mojtahed Masoud , Le Nganh , DeSoto Jerry Wayne
Published: February 2017

The Exhaust Manifold is an increasingly important component of industrial turbocharged diesel engines. It can be a key factor to increase the efficiency of any engine, in this case a power plant diesel engine. Analysis of the various structural and thermal loading of the liquid-cooled manifolds is of vital importance to increase the components efficiency and overall engine performance. In this analysis, problems such as thermal stress issues causing manifold failure are identified and redesigned to meet performance requirements and environmental regulations. These manifolds are of complicated shapes and contain many weld joints to attach several integral parts. The weld regions are identified to be sensitive to thermal stresses and most likely prone to failure. The welds were added to the model in ANSYS® Workbench. Computational Fluid Dynamics (Fluent) and Finite Element Analysis (FEA) were used to analyze the welded model. The main outcome was to understand the welds behavior using the ANSYS software and its powerful tools and to determine whether the areas containing welds are likely to fail under the given conditions. A simple double pipe model was also created and congruently analyzed to validate the results and the techniques used in analyzing the manifold model.
Experimental Investigation of Liquid Carry-Over in GLCC© Separators for 3-Phase Flow
Authors: Kolla Srinivas Swaroop , Mohan Ram S. , Shoham Ovadia
Published: February 2017

Prediction of the Operational Envelope (OPEN) for liquid carry-over is essential for optimized performance of Gas-Liquid Cylindrical Cyclone (GLCC©1) compact separators. This study extends the previous GLCC liquid carry-over studies from 2-phase flow to 3-phase gas-oil-water flow incorporating pressure and level control configurations. A series of experiments were conducted to evaluate the performance of a 3″ diameter GLCC in terms of OPEN for liquid carry-over. Both light oil and heavy oil were utilized, with watercuts ranging from 0 to 100%. The liquid level was controlled at 6″ below the GLCC inlet. A significant effect of watercut on the OPEN for liquid carry-over for three-phase flow was observed. As the watercut reduces, the OPEN for liquid carry-over reduces too. Also, the OPEN for heavy oil reduces as compared to light oil, which could be primary due to the effect of viscosity. Finally, the annular mist velocity increases with the increment of watercut and viscosity.
Development of a Solid-State Inflation Balloon Deorbiter
Authors: Roddy Morgan , Huang Adam
Published: February 2017

In this paper we report on the current development of the Solid State Inflation Balloon (SSIB), a simple, reliable, low-cost, non-propulsive deorbit mechanism for the full range of small satellites (<180kg). Small satellites typically rely on aerodynamic drag to deorbit within the FAA’s 25 year requirements. The SSIB will enhance aerodynamic drag by inflating a balloon at the end-of-life of a satellite mission. This technology will provide a scalable and non-existing capability, low-cost deorbit, for applications in the full-range of smallsats, from CubeSats to MicroSats. The proposed SSIB system is composed of three major components: a Micro-Electro-Mechanical Systems (MEMS) Solid-State Gas Generator (SSGG) chip, a balloon structure made of thin metallized polyimide films such as Kapton® HN composed of multiple lenticular gores which will form a spherical balloon, and a subsystem package suitable for spacecraft integration. The SSGG is composed of a 2D addressable array of Sodium Azide (NaN3) crystals on a glass substrate. The crystals are contained in wells formed by a thick-film of epoxy polymer (SU-8). Under each well is a resistive heater that is selectively addressed using Metal-Insulator-Metal (MIM) diode networks. When heated to above 350 °C, the NaN3 spontaneously decomposes to generate N2 gas in time scales on the order of 10 milliseconds. Each well can be designed with a typical volume of 10−15 m3 to 10−6 m3 of NaN3. The SSIB system has built-in redundancy due to the fact that the SSGG is a scalable chip design and can incorporate as many gas generating wells as a mission may dictate. Additionally, the SSIB can mitigate balloon leaks by sequential deployment of additional gas wells and can thereby maintain the inflated state of the balloon. The SSIB system will be low power (< 1 W) and have low mass (mass is proportional to the size of the required balloon). Initial simulations have shown that the SSIB can deorbit small satellites from above 1000 km within 25 years.
Direct Writing on Phosphate Glass Using Atomic Force Microscopy for Rapid Fabrication of Nanostructures
Authors: Barna Shama F. , Jacobs Kyle E. , Mensing Glennys A. , Ferreira Placid M.
Published: February 2017

Rapid and cost effective fabrication of nanostructures is critical for experimental exploration and translation of results for commercial development. While conventional techniques such as E-beam or Focused Ion beam lithography serve some prototyping needs for nano-scale experimentations, cost and rate considerations prohibit use for manufacturing. Specialized lithographic processes [e.g. nanosphere lithography or interference lithography] are also powerful tools in creating nanostructures but provide limited shapes, positioning and size control of nanostructures. In this work, we demonstrated a liquid-free and mask-less electrochemical writing approach using atomic force microscopy (AFM) that is capable of making arbitrary shapes of silver nanostructures in seconds on a solid state super-ionic (AgI)x (AgPO3)(1−x) glass. Under ambient conditions. silver is extracted selectively on super-ionic (AgI)x (AgPO3)(1−x) glass surface by negatively biasing an AFM probe relative to an Ag film counter electrode.

Both voltage controlled and current controlled writings demonstrated localized extraction of silver. The current controlled approach is shown to be the preferred writing approach to make repeatable and uniform patterns of silver on (AgI)x AgPO3(1−x), where x represents the mole fraction of AgI in the mixture and the control parameter that tunes the conductivity of the sample. We demonstrated current controlled printing of silver on two different compositions of the material (i.e. (AgI)0.125 (AgPO3 )0.875 and (AgI)0.25(AgPO3)0.75 ). Depending on the magnitude of the constant current and tip speed, line-width of the silver pattern can be ∼150 nm. The length of these patterns are limited to the maximum distance the tip can be moved using the AFM position controls. The substrate being optically transparent allows the use of this writing technique for rapid prototyping plasmonic devices. By using the patterned substrate as a template for replica molding of soft materials such as polydimethylsiloxane (PDMS), this writing technique can also be utilized for high throughput nano-channel fabrication in biofluidics and microfluidics devices.
Experimental Investigation on Tags Placement Affecting the Efficient Encoding of Multiple Passive UHF RFID Tags With Unique Identifiers
Authors: Yi Zhou , Phua Zi Qin , N. B. Rangel Vitor , Parker Johné M.
Published: February 2017

Recently, the Internet of things (IoT) has emerged as a promising solution for several industrial applications. One of the key components in IoT is passive radio frequency identification (RFID) tags which do not require a power source for operations. Specifically, ultra-high frequency (UHF) tags are studied in this paper. However, due to factors such as tag-to-tag interference and inaccurate localization, RFID tags that are closely spaced together are difficult to detect and program accurately with unique identifiers. This paper investigates several factors that affect the ability to encode a specific tag with unique information in the presence of other tags, such as reader power level, tag-to-antenna distance, tag-to-tag distance and tag orientation. ANOVA results report reader power level and tag spacing, along with effect interactions power level*tag space and tag space*tag orientation to be significant at the levels investigated. Results further suggest a preliminary minimum tag-to-tag spacing which enables the maximum number of tagged items to be uniquely encoded without interference. This finding can significantly speed up the process of field programming in item-level tagging.
Numerical Simulation of Insulin Depot Formation in Subcutaneous Tissue Comparing Different Cannula Geometries
Authors: Zedelmair Michael M. , Mukherjee Abhijit
Published: February 2017

In this study, the impact of the cannula geometry on the formation of the depot in subcutaneous tissue is investigated when injecting insulin using an insulin pump. The simulations have been conducted using the Computational Fluid Dynamics (CFD) software ANSYS Fluent. The study is focusing on rapid acting insulin analogues typically used in insulin pump therapy, which enter the bloodstream very shortly after administration. A previously developed 2-dimensional simulation has been transferred into a 3-dimensional case in order to simulate cases with non-axisymmetric geometries. The tissue has been modeled as a homogeneous anisotropic porous media by the use of different porosity values in the parallel and perpendicular direction with respect to the skin surface. The process of absorption is implemented into the model by the use of a locally variable species sink term. The basic case, simulated with a solid cannula, has been compared to other cannula geometries in order to evaluate if the delivery of insulin in the tissue can be improved. The geometries under consideration are the addition of circumferential holes in the wall of the cannula as well as using an array of cannulas instead of a single cannula. The depot formation is analyzed simulating a standard bolus injection of 0.05ml of insulin using an injection time of 25 seconds. It is observed that the addition of multiple holes in the wall of the cannula or using an array of cannulas can alter the shape of the depot quite significantly. The impact of the depot shape on the diffusion of insulin in the tissue has been evaluated by measuring the total volume of the depot after injection.
Optimization of the Thermal Request Profiles of Buildings Connected With a Large District Heating Network
Authors: Verda Vittorio , Guelpa Elisa , Barbero Giulia , Brundu Francesco , Acquaviva Andrea , Patti Edoardo
Published: February 2017

Thermal storage is very important in modern district heating networks in order to increase the share of waste heat and heat produced through renewable sources and cogeneration. The role of thermal storage is even more important in the case of Mediterranean areas, where climate and user behavior cause high peak requests in the morning. Nevertheless the installation of large storage volumes is not always feasible, especially in dense urban areas, therefore alternative options are investigated. One of these options is virtual storage. This consists in proposing changes to the thermal request profiles of some of the connected buildings, in order to obtain a peak shaving, which is an effect similar to that obtained using storage. To perform such approach there are two crucial elements: 1) an advanced ICT solution able provide real time information about the thermal request of the buildings and the thermodynamic conditions at the thermal substations; 2) a detailed thermo fluid-dynamic model of the district heating network able to simulate the temperature evolution along the network as the function of time. Using physical models it is possible to examine the effects, obtained by modifying the thermal request of users, on the total load of the thermal plants feeding the network. In particular, the model is applied to the analysis of changes in the start-up time of the buildings as well as possible pauses during the day. The start-up strategy should not produce significant effects on the building temperatures, so that acceptable comfort standard can be guaranteed. This is checked using a compact model of the buildings which parameters are obtained through data measured at the thermal substations.

These changes in the request profiles usually involve a larger heat request. Nevertheless, peak shaving is accompanied by a reduction in heat generation of boilers and an increase in the thermal production of efficient systems, such as cogeneration units. This results in a significant reduction in the primary energy consumption. The goal of the analysis is to find the optimal start-up strategy in order to minimize the primary energy consumption at the thermal plants.

An application to the Turin district heating network, which is the largest network in Italy, is presented. In particular, a subnetwork connecting the main transport network to about 100 buildings located in the central area of the town is considered. The analysis if performed in selected days where the optimization was conducted the day before on the basis of weather forecasts and then applied to the network. Despite the changes in the request profiles could be applied only to a limited number of buildings, the analysis show that the peak request can be reduced. Simulations performed considering the application of changes to a larger number of buildings show that reduction in the primary energy consumptions of the order of 1.25% can be obtained.
Numerical Study of Convective Heat Transfer From Expanding Annular Pipe Flows
Authors: Hammad Khaled J.
Published: February 2017

Convective heat transfer from suddenly expanding annular pipe flows are numerically investigated within the steady laminar flow regime. A parametric study is performed to reveal the influence of the annular diameter ratio, k, the Prandtl number, Pr, and the Reynolds number, Re, over the following range of parameters: k = {0, 0.5, 0.7}, Pr = {0.7, 1, 7, 100}, and Re = {25, 50, 100}. Heat transfer enhancement downstream of the expansion plane is only observed for Pr > 1. Peak wall-heat-transfer-rates always appear downstream of the flow reattachment point, in the case of suddenly expanding round pipe flows, i.e. k = 0. However, for suddenly expanding annular pipe flows, i.e., k = 0.5 and 0.7, peak wall-heat-transfer-rates always appear upstream of the flow reattachment point. The observed heat transfer augmentation is more dramatic for suddenly expanding annular flows, in comparison with the one observed for suddenly expanding pipe flows. For a given annular diameter ratio and Reynolds number, increasing the Prandtl number, always results in higher wall-heat-transfer-rates downstream the expansion plane.
Photovoltaic-Thermoelectric Systems for Building Cooling Applications: A Preliminary Study
Authors: Bhargava Akshay , Najafi Hamidreza
Published: February 2017

Thermal comfort in buildings using energy efficient methods has attracted lots of attentions during last few decades. In the present paper, the feasibility of using thermoelectric (TE) modules to provide cooling for a residential building located in Melbourne, FL is studied. It is assumed that photovoltaic (PV) panels are used to provide necessary power for TE operation. The building roof is covered with PV panels and an air channel is installed on the bottom of the panels. The TE modules are located inside the air channel and are attached to a metal sheet from the bottom which constructs the ceiling of the building. The metal sheet on the ceiling cools down in summer to provide space cooling through natural convection and radiation. A mathematical model is developed to simulate the system in MATLAB. The simulation results include transient temperature values through each layer of the system and heat removal/rejection rates from thermoelectric modules. A specific temperature is defined for thermal comfort and the number of TE modules that is required to maintain the temperature below the limit is determined. The results suggest that TE modules can be successfully used for building cooling applications. Further investigation and experiments are required for a comprehensive design of the system.
Influencing Factors and Scaling Law of Bubble Detachment at a Submerged Orifice
Authors: Wang Yiwei , Huang Chenguang , Wu Xiaocui
Published: February 2017

Bubble formation and detachment are important in the drag reduction of underwater vehicle by using gas injection, which are involved in the integrated scaling law considering bubbles coalescence. The parameters of influencing factors are theoretically derived by dimensionless analysis on this issue. Then the effects are shown by analyzing results with various parameters. Results indicate that, the viscous force can be neglected near the default condition, and the bubble is difficult to detach if the viscosity is very large. Surface tension is the major constraint force in the default condition, which is also sensitive. The bubble easily crushes if the surface tension is small, while the neck of bubble can hardly break up if the surface tension is large. For the contact angle, the bubble profile significantly exceeds the orifice boundary if the wall surface is hydrophobic, which makes detachment period becomes larger.
Two-Phase Spray Cooling With Water/2-Propanol Binary Mixture: Investigation of Mass Diffusion Resistance
Authors: Obuladinne Sai Sujith , Bostanci Huseyin
Published: February 2017

Two-phase spray cooling has been an emerging thermal management technique offering high heat transfer coefficients (HTCs) and critical heat flux (CHF) levels, near-uniform surface temperatures, and efficient coolant usage that enables to design of compact and lightweight systems. Due to these capabilities, spray cooling is a promising approach for high heat flux applications in computing, power electronics, and optics. The two-phase spray cooling inherently depends on saturation temperature-pressure relationships of the working fluid to take advantage of high heat transfer rates associated with liquid-vapor phase change. When a certain application requires strict temperature and/or pressure conditions, thermophysical properties of the working fluid play a critical role in attaining proper efficiency, reliability, or packaging structure. However, some of the commonly used working fluids today, including refrigerants and dielectric liquids, have relatively poor properties and heat transfer performance. In such cases, utilizing binary mixtures to tune working fluid properties becomes an alternative approach.

This study aimed to conduct an initial investigation on the spray cooling characteristics of practically important binary mixtures and demonstrate their capability for challenging high heat flux applications. The working fluid, water/2-propanol binary mixture at various concentration levels, specifically at x1 (liquid mass fraction of 2-proponal in water) of 0.0 (pure water), 0.25, 0.50, 0.879 (azeotropic mixture) and 1.0, represented both non-azeotropic and azeotropic cases. Tests were performed on a closed loop spray cooling system using a pressure atomized spray nozzle with a constant liquid flow rate at corresponding 20°C subcooling conditions and 1 Atm pressure. A copper test section measuring 10 mm × 10 mm × 2 mm with a plain, smooth surface simulated high heat flux source. Experimental procedure involved controlling the heat flux in increasing steps, and recording the steady-state temperatures to obtain cooling curves in the form of surface superheat vs heat flux. The obtained results showed that pure water (x1 = 0.0) and 2-propanol (x1 = 1.0) provide the highest and lowest heat transfer performance, respectively. At a given heat flux level, the HTC values indicated strong dependence on x1, where the HTCs depress proportional to the concentration difference between the liquid and vapor phases. The CHF values sharply decreased at x1≥ 0.25.
Skull Deformation Has No Impact on the Variation of Brain Intracranial Pressure
Authors: Rezaei Asghar , Sarvghad-Moghaddam Hesam , Eslaminejad Ashkan , Ziejewski Mariusz , Karami Ghodrat
Published: February 2017

Skull deformation and vibration has been hypothesized to be an injury mechanism when the human head undergoes an impact scenario. The extent that skull deformation may increase the risk of traumatic brain injury, however, is not well understood. This computational study explains whether skull deformation has any impact on the variation of intracranial pressure (ICP). To this end, a finite element head model including major anatomical components of the human head was employed. The head model has been validated against ICP variations on the brain. The impact simulations were carried out using a rigid cylindrical impactor. The scenarios were frontal impacts with the impactor hitting the forehead of the head model at two impact severity levels. In order to examine the effect of skull elasticity on the stress wave propagation inside the cranium under an external applied force, the skull was also taken as a rigid body with the same density as the elastic one, and the result were compared with those obtained with the deformable skull. For the two cases, the variation of ICPs at the coup and countercoup sites were recorded and compared. The results of the study showed that, for the case studies presented here, the deformation of skull didn’t increase the level of ICP inside the brain. It was concluded that the skull rapid body motion might be responsible for brain injuries.