bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Design and Initial Performance Testing of an Apple-Picking End-Effector
Authors: Davidson Joseph R. , Mo Changki
Published: March 2016

The fresh market apple industry currently relies on manual labor for all harvesting activities. The lack of mechanical harvesting technologies is a serious concern because of rising labor costs and increasingly uncertain labor availability. Researchers have been working for several decades to develop mechanical harvesters for tree fruit. The two fruit removal methods considered include mass mechanical harvesters and selective harvesting with robotics technology. Whereas mass mechanical harvesters have demonstrated unacceptable damage rates, robotic systems have been limited by insufficient speed and robustness. This paper describes the design and analysis of a novel underactuated end-effector fabricated for the robotic harvesting of tree fruit. The device has been optimized around a set of target tasks, the most critical being speed, low complexity, suitability for a highly variable field environment, and the replication of hand picking so as to minimize fruit damage. Development of the end-effector has been facilitated by a thorough study of the dynamic forces involved during the manual harvesting of apples. The end-effector produces a spherical power grasp with a normal force distribution and picking sequence replicating selected human patterns. An underactuated, tendon-driven device with compliant flexure joints has been adopted to improve system performance in the presence of position errors as well as enhance robustness to variable fruit size, shape, and orientation. The prototype end-effector also uses minimal sensors and incorporates open-loop control to reduce complexity and improve picking speed. This paper presents the theoretical analysis of the end-effector kinematics and discusses the selection of key geometric parameters. Experiments have been conducted to determine the normal forces developed during grasping of the apple. Results indicate that open-loop, feedforward control can be used to produce optimal normal force patterns.
CFD Simulation of Smoke Spread Through Elevator Shafts During Fires in High Rise Buildings
Authors: He Qize , Ezekoye Ofodike A. , Tubbs Beth , Baldassarra Carl
Published: March 2016

Smoke spread through the elevator shafts of high rise buildings has been numerically investigated using the Fire Dynamics Simulator (FDS), which is a computational fluid dynamics (CFD) program suitable for fire induced heat and mass transfer. A model of a high rise building was developed and a fire was set at the first level. The smoke spread process through the elevator shafts was evaluated. The process can be divided into two phases. In the first phase, the smoke gradually fills the shafts, and the gas temperature and pressure in the shafts are transient. After this phase, the smoke fully fills the shafts, the temperature and pressure in the shaft are almost steady, which suggests that the smoke inflow rate equals the outflow rate. Throughout the process, the spatial distributions of temperature and pressure in the elevator shaft under fire situations were reported. The hot fire product gases entering the shaft causes a stack effect, which transports smoke to the upper levels. A method of partially enclosing the elevator lobbies was also investigated by the CFD simulation. The results were compared with the unenclosed situation, and showed that enclosing lobbies not only increases the time needed for the smoke to fully fill the shafts, but also reduces the temperature and pressure differences in the shafts.
Experimental Investigations on the Performance of a Cross Flow Air Heated Humidifier
Authors: Khalid K. A. , Yassen A. S. , Salaudeen S. A. , Antar M. A.
Published: March 2016

A horizontal cross flow air heated humidifier is designed for three modes of heating. It is tested to investigate its performance in terms of its ability to effectively humidify air. The system investigated in this study has both the humidifier and the heater(s) integrated in one unit. Special low pressure-drop nozzles are used to spray water such that they provide a fine mist, thus they break a liquid to tiny droplets to increase the surface area for better heat and mass transfer between the hot air and sprayed water. Several attempts to improve system performance are made. For example, the effect of adding packing material to further increase heat and mass transfer surface area is attempted. Another attempt is by having an inter-stage heating such that a heating coil (basically a heat exchanger where hot water is circulated in a closed loop) is placed after a first-stage sprayer to heat the air again such that its ability to absorb more moisture increases as it is passed through a second-stage sprayer. A mist eliminator is placed at the exit of the humidifier to make sure water droplets are not allowed to leave the humidifier with the exit humid air stream. Performance parameters used in the analysis include the temperature and humidity of the exit air stream in addition to the humidifier effectiveness that is considered one of the crucial parameters in designing a HDH desalination system. A comparison between different modification to the humidifier are made to select the mode that results in the closest exit air stream to saturation condition and the highest humidifier effectiveness. Adding the packing material showed insignificant improvement to the humidifier performance. On the other hand, the inter-stage heating is believed to be effective in increasing the unit effectiveness.
Numerical and Experimental Study of Turbulent Flows Around Clark Y-14 Aerofoil
Authors: Vadake Kshitij , Cui Jie
Published: March 2016

Experimental Fluid Dynamics (EFD) and Computational Fluid Dynamics (CFD) have been instrumental in Fluid Mechanics to help solve scientific and engineering problems. This research attempts to use both techniques to perform a parametric study of turbulence flow around airfoil ClarkY-14 at various velocity and angle of attack (AoA).

Clark Y-14 airfoil was designed in the 1920’s. It demonstrated good overall performance at low and moderate Reynolds numbers. With the progress in the aviation field, its performance was sub-optimal for newer aircraft designs. However, with the advent of RC airplanes and model aircrafts, there is a renewed interest in this airfoil. Various research projects have been conducted using this airfoil, but there hasn’t been a combined EFD and CFD study of the performance characteristics of the airfoil itself, which still finds real world applications today. One important aspect of this research included the investigation of the effects of a Force Measurement Device/Sensor, which is typically used in scaled/full-size wind tunnels to mount the test model as well as measure the forces/moments acting on it during the testing. The presence of such a device could affect the quality of the data obtained from the wind tunnel testing when compared to a real world application scenario where the aforementioned device may not be present. To the best of the author’s knowledge, no detailed study has been published on the effects of such devices.

In this study, the results with and without the measuring device were generated by using CFD simulations. The results were then compared to see to what extent the inclusion of these devices will affect the results. The methodology used for this research was experimental as well as computational. In the present research, a commercially available CFD software STAR-CCM+ was employed to simulate the flows around airfoil Clark Y-14. The experimental data was obtained from wind tunnel tests using AEROLAB Educational Wind Tunnel (EWT) and compared with the simulation data from the CFD. The two data sets were in good agreement. Both experimental and simulation results were used to understand the effects of the measurement device/sensor used in the scaled wind tunnel on the lift and drag coefficients of the airfoil.

Two separate CFD simulation setups were designed to model the presence and absence of the measurement device/sensor. These setups replicated the wind tunnel setup. The airfoil was tested and simulated at different speeds as well as different AoA. The comparative study gave a useful insight on the accuracy of the CFD simulations in relation to the actual testing. The analysis of results concluded that the force measurement device/sensor had insignificant effects on the accuracy and quality of data collected through wind tunnel testing.
Study of Buckling of Cracked Plate Reinforced in Compression
Authors: Cherif Sadek Salem , Tamine Tawfik
Published: March 2016

The objective of this paper is to numerically analyze the buckling of reinforced structures (stiffened plate) cracked under compressive stress by considering the evolution of cracks and its orientation. Numerical modeling and calculation by the finite element method, estimated the critical load for compression panel. The work presented in the article was inspired by several publications that related to this field. Brighenti have studied the behavior of elastic buckling of rectangular cracked thin plate for different boundaries conditions. Following these calculations, a calibration function was derived to estimate the load ratio Ψ to the compression function of the crack length and its inclination. We found that the variation of the critical stress is proportional to the crack dimensions. In buckling, a transverse crack is more stable than a longitudinal crack.
Concentration Measurements of OH and CH Radicals in Laminar Partially Premixed and Prevaporized Jet A / Palm Methyl Ester Blend Flames
Authors: Balakrishnan Arun , Parthasarathy Ramkumar N. , Gollahalli Subramanyam R.
Published: March 2016

Palm methyl ester (PME) is an attractive alternate fuel that is becoming popular in Asia and has the potential for a wider application. In this study, the near-burner flame characteristics in the laminar partially premixed flames of Jet A, PME and their blends (25%, 50% and 75% by volume) were investigated. Planar laser-induced fluorescence (PLIF) technique was used to determine the relative concentration of OH and CH radicals in the near-burner region of the flames. The fuel was prevaporized by injecting into a hot air stream and passed through a 9.5 mm stainless steel tube which served as the injector. The burner exit equivalence ratios of 2, 3 and 7, were selected to simulate a wide range of (high to low) partially premixed modes of combustion that exist in practical combustors. The PLIF measurements indicated that the OH and CH concentrations closely followed the temperature profiles at the equivalence ratio of 2. The blend-fuel flames had higher OH and CH concentrations than the neat fuel flames at equivalence ratios of 2 and 3. At the equivalence ratio of 7, a significant reduction in OH concentration was observed in the near-burner region of the flames having biofuel content, and the CH concentration was comparatively higher than OH concentration of corresponding flames. The presence of high CH concentration in the region of peak NO concentration indicated that the NO formation at this condition was likely through the Fenimore mechanism. The concentration measurements of OH and CH radicals revealed a non-monotonic variation with the proportion of biofuel in the fuel blend and suggested a complex competition between the growth and oxidation of poly aromatic hydrocarbons (PAH) and soot particles, and the formation of combustion products.
Development of New Backwashing Air Amplifying Device for Bag Filter
Authors: Ebisuzaki Ryo , Mukai Eijiro , Nakazato Youichi , Jitsukawa Masaru , Monden Kenji
Published: March 2016

Bag filters are used to prevent dust exposure in many environments. They require maintenance to retain their filtration efficiency. The typical maintenance approach is pulse jet backwashing, but this method is not entirely effective for maintaining filters in all environments as its reverse air pressure is insufficient for some applications. Hence, there has been a recognized need to amplify the backwashing air.

A new type of device was recently developed on the basis of the Coandă effect, which amplifies the backwashing air and results in greater efficiency. However, it still does not offer sufficient performance (particularly when multiple devices are connected, as happens under actual use conditions), and its actuating mechanism is unclear. In this study, we investigated fluid behavior in the device and attempted to improve its design using computation fluid dynamics (CFD). We found that the Coandă effect injector does indeed improve efficiency by inducing more outer air into the device and forming a negative pressure area via overexpansion of sonic flow. We also developed an improved device that has 1.2 times higher reverse air cleaning efficiency. Our improved device improves the nozzle angle and the wall shape of the device to smoothen the supersonic flow attachment to the wall.

The CFD analysis further established that tapering to a square pipe is effective for providing a uniform supply of compressed air to multiple connected amplifying devices. In addition, this shape shortens the time to onset of amplification, and compressed air can be more effectively used. These effects were experimentally confirmed.
MEMS Wind Speed Sensor: Large Deflection of Curved Micro-Cantilever Beam Under Uniform Horizontal Force
Authors: Changizi M. Amin , Abolfathi Ali , Stiharu Ion
Published: March 2016

Micro-cantilever beams are currently employed as sensor in various fields. Of main applications, is using such beams in wind speed sensors. For this purpose, curved out of plane micro-cantilever beams are used. Uniform pressure on such beams causes a large deflection of beam. General mechanics of material theory deals with small deflection and thus cannot be used for explaining this deflection. Although there are a body of works on analysing of large deflection [1], nonlinear deflection, of curved beams [2], yet there is no research on large deflection of curved beam under horizontal uniform distributed force.

Theoretically, the wind force is applying horizontally on curved micro-cantilever beam. Here, we neglect the effect of moving weather from beam sides.

We first aim how to drive the governed equation. A curved beam does not have a calculable centroid. Also large deflection of beam changes its curvature which would change the centroid of beam consciously. The variation of centroid makes very though calculating the bending moment of each cross section in the beam. To address this issue, an integral equation will be used. The total force will be considered as a single force applied at the centroid.

The second challenge is solving the governed nonlinear ordinary differential equation (ODE). Although there are several methods to solve analytically nonlinear ODE, Lie symmetry method, with all its complication, is a general method for this kind of equations. This approach covers all current methods in analytical solving nonlinear ODEs. In this method, an infinitesimal transformation should be calculated. All transformations under one parameter creates a group that called Lie group. A value of parameter which transfers the equation onto itself is called invariant of ODE. One can calculate canonical coordinates ODEs by the invariant. Solving the canonical coordinates ODEs yields to calculating the canonical coordinates. Canonical coordinate are used to reduce the order of nonlinear ODE [3]. By repeating this method one can solve high order ODEs.

Our last question is how to do numerical solution of ODE. The possible answer will help to explain the phenomena of deflection clearly and compare the analytical solution with numerical results. Small dimensions of beam, small values of applied force from one side and Young modules value from the other side, will create a stiff ODE. Authors experience in this area shows that the best method to sole these kind of equations is LSODE. This method can be used in Maple.

Here, primary calculations show that the governed equation is second order nonlinear ODE and we propose two possible invariants to solve ODE. Overall, the primary numerical solution has shown perfect match with the exact solution.
Material Characterization of Ultrasonically Consolidated Laminated Ti-Al Composites (UC-LMC)
Authors: Kaya İrfan , Cora Ömer Necati , Koç Muammer
Published: March 2016

Ultrasonic consolidation (UC) is an additive manufacturing process where thin and dissimilar metallic layers are bonded through the action of ultrasonic oscillation energy with low energy consumption. The surface oxide layer and the other contaminations between two surfaces are broken up with ultrasonic oscillation improving the bonding strength. This study aimed for investigating the mechanical behavior of laminated metal composite (LMC) blanks that consist of several layers of commercially pure titanium (CP-1) and pure aluminum (AA 1100) foils with different number of layers. The LMC blanks were ultrasonically consolidated on a thick aluminum substrate with three different numbers (1, 3, 5) of bi-layers. Each bi-layer consists of UC bonded one AA 1100 and one Ti foils. Both uniaxial (tensile) and biaxial (hydraulic bulge) tests were carried out under two strain rates and four different temperature levels to reveal the mechanical response of LMCs with different conditions. Increase in number of bi-layers resulted in higher overall strength of LMC’s as titanium content in LMC is increased. Delamination of layers was observed for 1-bilayer LMC’s at room temperature while curling was noted at higher temperature tests. The results obtained from tensile and hydraulic bulge tests were compared to observe significant differences in UTS values and elongation. The effect of temperature, loading condition, and strain rate on the material responses were discussed on the basis of test results. At low temperature, the strain and strength values of bulge samples were higher than the values of tensile samples. However, at high temperatures, lower strain and lower strength were obtained from bulge test. The maximum strain of 0.46 was obtained at 300°C test temperature for 5 bi-layer both parallel rolling direction sample in the all LMCs from tensile test.
Interdisciplinary System Architecture for Intelligent Technical Systems
Authors: Westermann Thorsten , Anacker Harald , Dumitrescu Roman , Frank Ursula , Hessenkämper Axel
Published: March 2016

Nowadays, mechanical engineering products change from mechatronic products, characterized by the close interplay of mechanics, electronics, control and software engineering to Intelligent Technical Systems (ITS). Intelligent Technical Systems are mechatronic systems with inherent partial intelligence. Mechanical engineering products will be a symbiosis of information technology and mechanical parts. This will entail a rising complexity of technical systems and its development. Therefore we introduce an approach to improve system architectures of mechanical engineering products to realize Intelligent Technical Systems. Our approach meets the following challenges: creating a domain-spanning description of the system with Model-Based Systems Engineering (MBSE); designing an interdisciplinary and modular system architecture by using the technological concept of Intelligent Technical Systems; identifying and implementing solution elements as reusable modules. Validated by a separator, our results clarify the benefits of MBSE and the technological concept of ITS to improve system architectures of mechanical engineering products to realize Intelligent Technical Systems.
Smoke Barrier Design for Tilted Tunnels With Scale Modeling Experiments
Authors: Yeung W. S. , Chow W. K.
Published: March 2016

As pointed out in previous research papers, smoke barriers commonly used for horizontal tunnels cannot block smoke if installed in a tilted tunnel inclined at a large angle to the horizontal. Six new smoke barrier designs were proposed for a tilted tunnel with their performance evaluated by scale modeling experiments. A tilted tunnel model was constructed with the inclined angle adjusted up to 35° to the horizontal. All smoke barrier prototypes were made by 3-D printing. A small 200 W propanol pool fire was used as the testing heat source. Smoke pellets were burnt for generating smoke. Smoke movement patterns observed in the six designs were compared. The time when smoke started to fall to 50% of the tunnel height along the whole tunnel was measured to evaluate the performance of the barrier.
Introducing Entropy for the Statistical Energy Analysis of an Artificially Damped Oscillator
Authors: Tufano Dante A. , Sotoudeh Zahra
Published: March 2016

The purpose of this paper is to introduce the concept of entropy for a main resonator attached to a “fuzzy structure”. This structure is described explicitly using the Lagrangian method, and is treated as a layer of discrete resonators. A generic entropy formulation is then developed for the layer of resonators, which is used to determine the individual oscillator entropies. The combined entropy of the linear resonator system is then determined and compared numerically to the sum of the individual oscillator entropies. The entropy behavior of the system is then related to the energy behavior of the system and explained in regards to the the “artificial damping” of the main resonator.
Validation of Equilibrium-Based, One-Dimensional, Two-Phase Pipe Flow Models With Transient, Three-Dimensional, CFD Simulations for Horizontal Flows
Authors: Popa Florentina , Filippov Andrey , Houchens Brent C.
Published: March 2016

One-dimensional (1D), equilibrium-based mechanistic model predictions are compared to three-dimensional (3D) transient computational fluid dynamics results for horizontal two-phase, gas-liquid pipe flow. The 3D regions of interest include both those expected to be in equilibrium conditions and those where transitions between flow regimes occur. Equilibrium simulations, such as those for stratified flow in a horizontal pipe, allow crucial validation of the equilibrium-based closure relations by means of numerical experiments. In the transitional regions, fully 3D, time-dependent numerical simulations provide a means to estimate the error in the equilibrium-based models and suggest how reasonable approximations can be made in these regions.
Conceptual Design and Numerical Modeling of Prototype Counterflow Cooling Tower With Forced Draft for Geothermal Applications
Authors: González Pedraza Oskar J. , Pacheco Ibarra J. Jesús , Rubio Maya Carlos , Galván González Sergio R.
Published: March 2016

Cooling towers are widely used in temperature control in industrial processes and electricity generation processes by conventional and renewable energy methods. In this paper, it is presented an integral design of a counterflow cooling tower with forced draft for geothermal applications. The conceptual design was done in SolidWorks® software and the numerical simulation of the fluid through the tower was performed in Fluent® software. In the conceptual design were made both structural and tower elements design of the counterflow tower with forced draft. Besides, it was designed a self-drive sprinkler which distributes the water flow to be cooled inside the tower. In the mathematical model the velocity and temperature profiles were analyzed under different turbulence models that allow to increase their accuracy, as a result of this, it was able to calculate the heat transfer in the boundary layer between the walls packing and circulating air inside the tower. As a consequence could be estimate the coefficient of convective heat transfer.
3D Measurements of Nano-Particle Transport in Complex 2.5D Micro-Models
Authors: Upadhyay Jagannath , Park Daniel S. , Thompson Karsten E. , Nikitopoulos Dimitris E.
Published: March 2016

A confocal Micro-Particle Image Velocimetry (C-μPIV) technique along with associated post image processing algorithms is established to quantify three dimensional distributions of nano-particle velocity and concentration at the micro-scale (pore-scale) in 2.5D porous media designed from a Boise rock sample. In addition, an in-situ, non-destructive method for measuring the geometry of the micro-model, including its depth, is described and demonstrated. The particle experiments use 900 nm fluorescence labeled polystyrene particles at a flow rate of 10 nLmin−1 and confocal laser scanning microscopy (CLSM), while in-situ geometry measurements use regular microscope along with Rhodamine dye and a depth-to-fluorescence-intensity calibration. Image post-processing techniques include elimination of background noise and signal from adsorbed nano-particle on the inner surfaces of the micro-model. In addition, a minimization of depth of focus technique demonstrates a capability of optically thin slice allowing us to measure depth wise velocity in 2.5D micro-model. The mean planar components of the particle velocity of the steady-state flow and particle concentration distributions were measured in three dimensions. Particle velocities range from 0.01 to 122 μm s−1 and concentrations from 2.18 × 103 to 1.79 × 104 particles mm−2. Depth-wise results show that mean velocity closer to the top wall is comparatively higher than bottom walls, because of higher planar porosity and smooth pathway for the nano-particles closer to the top wall. The three dimensional micro-model geometry reconstructed from the fluorescence data can be used to conduct numerical simulations of the flow in the as-tested micro-model for future comparisons to experimental results after incorporating particle transport and particle-wall interaction models.
Phase-Change Material to Thermally Regulate Photovoltaic Panels to Improve Solar to Electric Efficiency
Authors: Rosenthal Andrew H. , Gonçalves Bruna P. , Beckwith J. A. , Gulati Rohit , Compere Marc D. , Boetcher Sandra K. S.
Published: March 2016

This paper investigates the use of phase-change material (PCM) for temperature regulation of a rack-mounted photovoltaic (PV) solar panel. PV panels exhibit a significant decrease in electrical efficiency as temperature trends higher. Current PV panels are approximately 10–16% efficient at harnessing incident solar irradiation into effective electrical power. The remaining solar irradiation that is not converted to electricity will heat the PV panel and decrease efficiency. Using PCM for temperature regulation and temporary heat storage in photovoltaic/thermal systems (PVT) is an emerging technology that has attracted attention recently. The PCM absorbs heat and regulates peak temperature, which allows the PV panel to operate at lower temperatures during peak solar conditions. Further, the waste heat stored in the PCM can be used for other applications. The main focus of this paper is to experimentally evaluate the heat dissipation of four different PCM containment configurations from a simulated PV panel.
Energy Ships and Plug-In Hybrid Electric Vehicles: Are They the Key for a Rapid Transition to an Emission-Free Economy?
Authors: Platzer M. F. , Sarigul-Klijn N.
Published: March 2016

In this paper a novel method is presented to store energy in order to overcome the intermittent power supply problems caused by the use of conventional wind turbines. This novel method is based on the recognition that the winds over the oceans can be harnessed by means of sailing ships equipped with hydrokinetic turbines whose electric output can be used to charge electric batteries or to convert the seawater into hydrogen. It is shown that small off-grid communities can be supplied with stable year-round power by means of a small fleet of remotely controlled ships which operate in high-wind ocean areas. A prelimina1y cost analysis indicates that this energy ship concept is economically competitive with land-based wind-hydrogen systems. Also, it is shown that the Hawaiian Islands can be provided with stable year-round power by the use of large-scale energy ships operating in high-wind areas to produce hydrogen and by the use of energy ships operating in Hawaiian waters to charge the batteries of plug-in hybrid electric vehicles.
Prediction of Thermal Conductivity of Two-Dimensional Superlattices of Graphene and Boron Nitride by Equilibrium Molecular Dynamics
Authors: Saiz Fernan , da Silva Carlos , Amon Cristina H.
Published: March 2016

Graphene is a promising material to design faster microprocessors given its exceptionally high thermal conductivity. However, due to its null electronic band gap, graphene must be combined with high-electric conductivity materials such as boron nitride to manufacture competitive alternatives to traditional semiconductors. Thus, the goal of this study is to determine the thermal conductivities and heat capacities of two-dimensional superlattices of graphene and boron nitride as a function of the secondary periodicity and interface orientation. We apply the Green-Kubo method to atomic trajectories calculated with Molecular Dynamics to determine the thermal conductivities of superlattices with periodicities between one and five in the armchair and zigzag orientations at 300 K. Results show that conductivities increase with decreasing periodicity, in good agreement with predictions made with Harmonic Lattice Dynamics. Thermal conductivities parallel to the interface are significantly higher than those perpendicular to the interface in the armchair configuration and vice versa in the zigzag orientation. Moreover, the heat capacities are practically independent of the periodicity and interface orientation up to 1500 K.
Toward a Systematic Design Process for Apparel
Authors: Zhao Yu , He Dong , Lin Y. , Zhang W. J.
Published: March 2016

This paper first provides a critical review of the literature regarding the contemporary apparel (product) design process, and then proposes a new apparel design process. Apparel is a general term for products which covers dress, skirt, etc. The new apparel design process applies a so-called systematic design approach well known to field of design. The systematic design approach classifies a design into four phases, namely, task classification, conceptual design, embodiment design, and detail design. The four phases are then tailored to apparel design. The new apparel design process is thus more rational and systematic. The paper uses a gown (a type of apparel) design as a case to illustrate the benefit of this new apparel design process, i.e., improved potentials to make apparel design more creative and efficient.
Novel Use of Semiconductive Conjugated Polymer With Optimized Scintillator for Betavoltaic Applications
Authors: Sharma Ashish , Melancon Justin , Bailey Sheila , Zivanovic Sandra
Published: March 2016

The ongoing advanced space exploration requires the novel energy sources that can generate power for extreme duration without need of refill. The long duration betavoltaic devices are presented using conjugated polymer with scintillators. The Monte Carlo simulations are used to study the interaction of electron beam with two different scintillators, Cerium doped Yttrium Aluminum Garnet (Ce:YAG) and Thallium doped Cesium Iodide (CsI:Tl). The catholuminescence profiles from simulation showed that CsI:Tl is more-efficient to generate photons when hit by electron beam compared to Ce:YAG. The semiconductive conjugated polymer device stack of ITO/PEDOT:PSS/P3HT:ICBA/Al are then fabricated and tested with Ce:YAG and CsI:Tl scintillators under different electron beam energies. The electrical current is successfully extracted from these betavoltaic devices when illuminated with electron beams. As expected, the betavoltaic devices with CsI:Tl scintillator performed better compared with Ce:YAG. The maximum power conversion efficiency (PCE) of 0.24% is obtained at 10 kV electron beam with CsI:Tl, while PCE in device with Ce:YAG is 0.16%. The short circuit current in devices with CsI:Tl is about 57%, greater than in devices with Ce:YAG. The experimental result showed that output electrical power increased with increase in incident electron beam energy.
Study of Waste Heat Driven Adsorption Cooling System Employing Doped MiL-101(Cr) and Water as Adsorbent Adsorbate Pair
Authors: Chakraborty Anutosh , Muztuza Ali Syed , Teo How Wei Benjamin
Published: March 2016

This article presents the dynamic behaviors of two bed adsorption chiller utilizing the composite adsorbent “immobilization of NH2, -NO2, -OH groups to MiL-101(Cr)” as adsorbent and water as adsorbate, which is based on the experimentally confirmed adsorption isotherms and kinetics data. The experimentally measured MOFs + water based isotherms and kinetics data are fitted with adsorption isotherm models and linear driving force kinetics equations. Compared with the experimental data of conventional adsorption chiller based on zeolites/silica gel-water system, we found that the newly working pair provides better cooling capacity and performances in terms of COP and adsorption bed size. From numerical simulation, it is also found that the cooling capacity can be increased up to 20 percent of the parent silica gel-water adsorption chiller and the COP can be improved up to 25% more at optimum conditions.
Study of the Effect of Impeller Side Clearance on the Centrifugal Pump Performance Using CFD
Authors: Ayad A. Farid , Abdalla H. M. , Abou El-Azm A.
Published: March 2016

Centrifugal pumps (CP) are probably among the most often used machinery in industrial facilities as well as in common practice. Compared to other types of rotating pumps, CP yield higher efficiency. In aerospace application reducing the weight of the CP impeller has the advantage of reducing mechanical stresses and enable using the CP at high number of revolution. In order to minimize the impeller weight the requirements to study and develop the CP with semi-open impeller appears. Using this type of impeller results in clearance between the impeller blades and the casing which degrade the centrifugal pump performance. The impact of this side clearance has not been deeply investigated in open literature.

The present paper is devoted to reveal more details about the impact of CP side clearance on its performance. This is done by numerically investigating the influence of the variation of the CP side clearance width (0:0.2 impeller width) on the CP performance parameters at different flow rates (0:5 Liter/s). These CP performance parameters include the pump head, efficiency, slip factor, blades loads and the internal flow structure.

3-D steady numerical simulation has been carried out using commercial software, ANSYS® CFX. The computational domain consists of four zones: inlet, side gab, impeller and volute with outlet. They are defined by means of the multi-reference frame technique. The impeller is situated in the rotating reference frame, while the inlet, side gab and outlet zones are in the fixed reference frame, and they are related to each other through the “frozen rotor” interface. The meshes of four computational domains are generated separately after performing mesh sensitivity analysis. The boundary conditions are set as total pressure at inlet and the mass flow at outlet. A no-slip condition is imposed at the wall boundary defined at the blade and casing. A turbulent, incompressible flow solver has been adapted using SST k–ω turbulent model.

The numerical simulation has been compared with own experimental results and a published empirical formulas to verify the numerical solution. The CFD results show an acceptable agreement with the results of the experimental work and the empirical formulas. It has been shown that the impeller side clearance have a great regression effect on the centrifugal pump performance. An explanation to the performance regression has been proposed based on the flow field feature. Performance regression could be attributed to the drop in the pressure difference between the impeller inlet and outlet. And the redistribution of the velocity inside the impeller channel and the side clearance.
Feature Extraction of Leaks Signals in Plastic Water Distribution Pipes Using the Wavelet Transform
Authors: Butterfield Joseph D. , Collins Richard P. , Beck Stephen B. M.
Published: March 2016

The location of leaks in water distribution pipes are traditionally identified by cross correlating two vibro-acoustic signals measured with accelerometers either side of the leak, but this method provides little information about the features of the signal (such as the leak flow rate) and does not differentiate between the leak signal and background noise. Due to its capability to provide time and frequency information, wavelet analysis can be used to extract features about the leak. However one of the greatest challenges is the selection of the mother wavelet, and there has been limited studies investigating how varying the mother wavelet can produce alternate results in the context of leaks in water distribution systems. This study demonstrates the potential of the wavelet transform to distinguish between the different features composed in the signal, including the leak noise, ambient noise, pump noise and leak type on plastic pipe when applied to data from a test rig. Variables such as the influence of pressure or distance from the leak are also included in order to demonstrate the efficacy of the wavelet transform in providing information about the signal. Moreover, this research gains an understanding of how the choice of different mother wavelet can influence the information provided by the leak signal. The results demonstrate that an appropriate mother wavelet can be identified and that the wavelet transform can localise features of the signal, including pump noise, background noise and the leaks characteristics.
Multiscale Modeling of the Effect of Nanoscale Defects on Al2O3 Mechanical Behavior
Authors: Zamani Seyed Mohammad Mahdi , Iacobellis Vincent , Behdinan Kamran
Published: March 2016

This study presents a multiscale framework to simulate the effect of nanovoids on the mechanical response of α-Al2O3 at finite temperatures. The bridging cell method, which divides the system into three domains (atomistic, bridging and continuum) and incorporates a finite element method throughout the system, was performed for the simulations. Two important crystal orientations of basal and prismatic planes of α-Al2O3’s hexagonal crystal structure were selected. The simulations were conducted at room temperature, 300K, and fire temperature, 1400K, based on the variety of in-service temperatures alumina is being applied in. The results were compared with respect to deformation behavior, stress distribution and ultimate tensile strength. Results showed different failure mechanism and tensile strength for the two crystal orientations. In addition, the magnitude of stresses and material’s deformation were increased at higher temperatures, where the ultimate tensile strength slightly reduced.
Ranking and Optimization of CAC and HAC Leakage Using Pressure Controlled Models
Authors: Alissa Husam A. , Nemati Kourosh , Sammakia Bahgat , Ghose Kanad , Seymour Mark , King David , Tipton Russell
Published: March 2016

In cold aisle containment (CAC) the supply of cold air is separated within the contained volume. The hot air exhaust leaves the IT and increases the room’s temperature before returning to the cooling unit. On the other hand, hot aisle containment (HAC) generates a cooler environment in the data center room as a whole by segregating hot air within the containment. Hot air is routed back to the cooling unit return by a drop ceiling or a chimney. Each system has different characteristics and airflow paths. For instance, leakage introduces different effects for CACs and HACs since the hot and cold aisles are switched.

This article utilizes data center measurements and containment characterization carried out circa April 2015 in the ES2 Data Center lab at Binghamton University. Details on the containment model include leakages at below racks, above racks, below CAC doors, between doors, and above doors. The model deploys the experimentally obtained flow curves approach for flow-pressure correlation.

Data center operators rely on the pressure differential to measure how much the IT is provided. Hence, in this study the level of provisioning was expressed in terms of pressure differentials between the hot and cold aisles. In this manner the model reflected real-life DC thermal management practices. This was done by integrating a pressure differential based controller to the cooling unit model. Leakages in each system are quantified and ranked based on a proposed LIF (Leakage Impact Factor) metric.

The LIF describes the transport contribution each leakage location has. This metric can be used by containment designers and data center operators to prioritize their sealing efforts or consider deploying the containment solution differently. Finally, a systematic approach is shown in which containment models can be used to optimize operations at the real-life site.
Sensing Cyclic Load, Damage Extent and Location in Carbon Nanotube-Epoxy Composite via Electrical Conductivity
Authors: Ardebili Mahmoud K. , Ikikardaslar Kerim T. , Loi Daniel , Delale Feridun
Published: March 2016

Carbon nanotube epoxy resin composite coupons were subjected to either cyclic tensile loading or crack-like damage while their electrical resistivity was monitored. The main objective of the study was to utilize piezoresistivity of the composite as means of strain and/or damage detection. Volume resistivity was obtained using Kelvin in-line four-probe resistance measurement technique. The technique minimizes contact resistance between electrodes and the composite, which could be orders of magnitude larger than the material resistance being measured. In the cyclic tensile loading study an MTS machine was employed to load the sample to 15 MPa tensile stress and then cycle it between 5 to 15 MPa with a period of 100 seconds. In damage detection part of the study, a CNC mill was used to insert two different types of damages to the sample. The first was a cut along the 25-mm width of the sample, with depth variation of 0.25 to 2.0 mm. The second damage was through thickness cuts that started from one side of the sample and its length changed from 1 to 12 mm. The results of cyclic load tests showed a strong correlation between applied stress and the resistivity changes. The obtained data indicate that resistivity changes may be used as a possible replacement for strain gauges. The damage detection results provide the capability of determining location and quantification of significant damages. Application of these techniques can be useful tools for real time structural health monitoring of composites.
Mixture Model for Graphite Flake Orientation Distribution in a Used Rotor
Authors: Rajput Sandeep , Paliwal Manish , Mahajan Ajay
Published: March 2016

We analyze the deformation of the substrate matrix and the shear forces it is exposed to through the geometry of graphite flakes in the substrate from samples already subjected to breaking pressure applications up to 30 bar. Microscopic Images of the cross-section of the brake pad polished to a 0.1 μm scale were examined. Statistical analysis was conducted, state vectors and variance-co-variance matrix were defined, and considered every state as a distribution. Parameters for each “shear deformation stage” were estimated using Expectation-Maximization algorithm. Finally, a mixture model was identified for the distribution of graphite flakes across the rotor thickness.
Synthesis and Processing of Solution Spun Cellulose Acetate Fibers Reinforced With Carbon Nanotubes
Authors: Sultana Quazi Nahida , Absar Saheem , Hulsey Stephanie , Schanz Hans , Khan Mujibur
Published: March 2016

We report the fabrication of Cellulose Acetate (CA) based fibers reinforced with Multi-Walled Carbon Nanotubes (MWCNTs) using a solution spinning process. The motivation of this work is to produce high performance fibers based on sustainable natural materials as an alternative to synthetic fibers for structural applications. A 30 wt% solution of CA in a binary solvent system of N, N-dimethylacetamide (DMAc) and Acetone (3:7 v/v) was used for the solution spinning of CA fibers. Both neat and CNT-loaded CA fibers were produced. The CNT loading with respect to the polymer was at 0.5 wt%. For CA-MWCNT spinning solutions, the MWCNTs were initially dispersed in the solvent and then CA is added and mixed together. The mixing temperature kept 40–45°C. The viscosity of the CA solution was 8,000 cP. Addition of MWCNT increased the viscosity of the CA solution to 32,000 cP. A lab-scale solution spinning line consisting of a constant torque high temperature gear pump and heated extrusion channels was used to produce both neat and CA-MWCNT fibers. The solution was pumped through a spinneret at the end of the extrusion channel with an orifice as a viscous gel-like filament which was passed through a spool placed in a coagulation bath and then it formed as fiber. The fibers are collected to a takeup roll at a draw ratio of 8.0. Characterization studies of both neat and MWCNT loaded fibers were performed differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). DSC analysis of fibers showed reduction in crystallinity of CA upon inclusion of 0.5 wt% MWCNT. TGA analysis showed improvement of thermal stability in CA-MWCNT fibers compared to neat CA. Cross-sections of neat CA fibers showed smooth surfaces with no significant defects, while CA-MWCNT showed formation of micro-voids and irregular features. Longitudinal views of outer surface of both neat CA and CA-MWCNT fibers showed no indication of surface defects or protrusions.
Computational Simulation of the Tethered Undersea Kites for Power Generation
Authors: Ghasemi Amirmahdi , Olinger David J. , Tryggvason Gretar
Published: March 2016

The dynamic motion of tethered undersea kites (TUSK) is studied using numerical simulations. TUSK systems consist of a rigid-winged kite moving in an ocean current. The kite is connected by tethers to a platform on the ocean surface or anchored to the seabed. Hydrodynamic forces generated by the kite are transmitted through the tethers to a generator on the platform to produce electricity. TUSK systems are being considered as an alternative to marine turbines since the kite can move in high speed motions to increase power production compared to conventional marine turbines. The two-dimensional Navier-Stokes equations are solved on a regular structured grid that comprises the ocean current flow, and an immersed boundary method is used for the rigid kite. A two-step projection method along with Open Multi-Processing (OpenMP) is employed to solve the flow equations. The reel-out and reel-in velocities of the two tethers are adjusted to control the kite angle of attack and the resultant hydrodynamic forces. A baseline simulation was studied where a high net power output was achieved during successive kite power and retraction phases. System power output, vorticity flow fields, tether tensions, and hydrodynamic coefficients for the kite are determined. The power output results are in good agreement with established theoretical results for a kite moving in two dimensions.
Tip-Over Simulation of Degraded Dry Storage Structures
Authors: Dehghani Champiri Masoud , Attar Arezou , Hanifehzadeh Mohammad , Willam Kaspar J. , Gencturk Bora
Published: March 2016

Concrete dry cask structures may be degraded due to environmental aging before they are encountered to hypothetical events. In this paper, first long term behavior of dry cask structures including creep and shrinkage is investigated numerically using COMSOL. Subsequently, the findings of the first part of the study are implemented into LS-DYNA to perform a crash analysis. Two cases including full bond and no bond between concrete cask and steel liner are compared. The results show shear transfer and significant damage in the interfacial region of the concrete cask and steel liner in the case of full bond, and large inelastic deformations far beyond the strain level for tensile cracking and compressive crushing of concrete.