bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of an Extended-Duct Air Delivery System in Tall Spaces Conditioned by Rooftop Units
Authors: Kennett Ryan , Hwang Yunho , Radermacher Reinhard
Published: February 2017

Mixing ventilation in high bay buildings conditioned by rooftop units involves supplying and returning air near the ceiling. Several problems occur in tall spaces, such as higher return air temperatures in the summer and excessive stratification in the winter. A novel air delivery strategy is investigated that involves supplying and returning air at different heights depending on the season. In the summer, air is supplied low and returned just above the occupied zone in order to cool the occupied zone directly, letting the upper zone stratify. In the winter, air is supplied high and returned low in order to draw warm air down from the ceiling, thus promoting destratification. This system’s performance was investigated in a full-scale experiment using measured temperature profiles and utility bills. A calibrated EnergyPlus model used measured temperature profiles as an input to a room-air model to study the effects of stratification on building energy consumption. The EnergyPlus model predicts 19% yearly HVAC electricity savings when considering the additional pressure drop of extended ducting and 37% yearly HVAC electricity savings without considering extra pressure drop. A utility bill analysis of the test facility shows a yearly 28.8% reduction in HVAC electricity consumption.
In-Furnace Sulfur Capture by Co-Firing Coal With Alkali-Based Sorbents
Authors: Rokni Emad , Chi Hsun Hsien , Levendis Yiannis A.
Published: February 2017

Over the last quarter of a century, since the 1990 US Clean Air Act Amendments were enacted the gaseous sulfur emission, in the form of sulfur dioxide, have been reduced [1] by a factor of 4, by switching to lower sulfur content coals, installation of flue gas desulfurization (FGD) sorbents or switching altogether to natural gas as a fuel. Penetration of alternative energy generation also has had a positive impact. However, current emissions of sulfur dioxide are still voluminous, amounting to 3,242,000 short tons annually in the USA [2]. As wet flue gas desulfurization is both real-estate- and capital-intensive, infurnace dry sorbent injection has been considered over the years to be a viable alternative. However there is still uncertainty on the best selection of the sorbents for particular coals and furnace operating conditions. This is particularly the case when it is economically attractive for the power-plant operator to burn locally-sourced high-sulfur coal, such as the case of Illinois bituminous coals. This manuscript presents experimental results on the reduction of sulfur oxide emissions from combustion of a high-sulfur content pulverized bituminous coal (Illinois #6 Macoupin). The coal particles were in the size range of 90–125 μm and were blended with dry calcium-, sodium-, potassium-, and magnesium-containing powdered sorbents at different proportions. The alkali/S molar ratios were chosen to be at stoichiometric proportions (Ca/S = 1, Mg/S = 1, Na2/S = 2, and K2/S = 2) and the effectiveness of each alkali or alkali earth based sorbent was evaluated separately. Combustion of coal took place in a drop-tube furnace, electrically-heated to 1400 K under fuel-lean conditions. The evolution of combustion effluent gases, such as NOx, SO2 and CO2 were monitored and compared among the different sorbent cases. The use of these sorbents helps to resolve the potential of different alkali metals for effective in-furnace sulfur oxide capture and possible NOx reduction. It also assesses the effectiveness of various chemical compounds of the alkalis, such as oxides, carbonates, peroxides and acetates.
Impulse Force as an Additional Safety Criterion for Improving the Injury Prevention Performance of Impact Attenuation Surfaces in Children’s Playgrounds
Authors: Eager David , Hayati Hasti , Chapman Chris
Published: February 2017

More than four decades has passed since introducing safety standards for Impact Attenuation Surfacing (IAS) used in children’s playgrounds. Falls in children’s playgrounds is a major source of injuries and IAS is one of the best safety interventions deployed to reduce the incidence and severity of these injuries. Currently there are two criteria that measure the injury prevention performance of IAS, namely: Head Injury Criteria (HIC); and maximum acceleration (Gmax). Based on the ASTM playground safety standard F1292 the thresholds of HIC and Gmax are 1000 and 200g respectively. If the playground IAS complies with this Standard the number and severity of fall-related injuries in playgrounds should be decreased. However after implementing these standards a high number of children continue to be hospitalized due to fall-related playground injuries In this paper we tested ten samples based on ASTM F1292 standard to propose the introduction of an additional criterion to HIC and Gmax which can filter and remove hazardous IAS that technically comply with the current 1000 HIC and 200g safety thresholds. The proposed criterion is called the impulse force criterion (If) and combines the change of the momentum and the impact duration. The Gmax, HIC and If results are presented graphically and numerically.
Dynamic Response Mechanism of Rotary Type Ultrasonic Motor Under High Impact Load
Authors: Sun D. , Wang X. J. , Chen C. , Wang J. , Liu Y. F.
Published: February 2017

To analyze structural dynamic response of rotary ultrasonic motor under high impact load, a theoretical model is established in this paper. A rotary ultrasonic motor includes two main components: stator and rotor. According to structure form and movement principle, they can be simplified as annular plates. When the system is imparted an impact load, dynamic displacement response of stator and rotor can be obtained. The damage to stator and rotor is analyzed in theory. It gave agreement with simulation and experimental result. Finally, influence of various structure parameters on the deformation of stator and rotor is analyzed and some suggestions on improving performance of rotary type ultrasonic motor are proposed.
Thermal Modeling and Design Analysis of a Hybrid Microdevice for Continuous-Flow PCR Using One Heater
Authors: Bin Perwez Usama , Aziz Imran , Akhtar Imran , Zaidi Tahir
Published: February 2017

In microfluidic devices, polymerase chain reaction (PCR) is a biomedical technique with great potential for on-site evidence collection system of various pathology and food samples. Although microfluidics has exhibited the ability to miniaturize and automate many laboratory procedures, an essential comprehension of the thermofluidic modeling tools is ultimately critical to streamline the design process of microfluidic device. One of the main obstacles for device miniaturization and process simplification of continuous-flow PCR (CF-PCR) device is employing two or more heaters which lead to process complexity. To overcome these complexities, a novel metal alloy assisted hybrid microdevice (polydimethylsiloxane and glass) for CF-PCR employing one heater is considered. In this paper, a two-step conjugate thermal model, solid domain and one pass model, is developed to optimize the thermal efficiency of a hybrid CF-PCR device using one heater. The effects of heat transfer on temperature distribution and thermal gradients in hybrid CF-PCR device are analyzed using ANSYS CFX 15. For optimized design of PCR chip, parameters, such as protrusion length (3 cm, 4 cm, and 5 cm), metal alloy thickness (1 mm, 2 mm, and 3 mm) and boundary conditions are varied to analyze the effect on temperature distribution in a microchannel. The proposed schemes pave the way for system integration and minimizing the accessories, realizing a portable microfluidic device applicable for on-site and direct field uses.
Optimization of Joined Conical Shells Based on Free Vibration
Authors: Karimi Mahabadi Rayehe , Bakhtiari-Nejad Firooz
Published: February 2017

This work aims at utilizing genetic algorithm (GA) to pursue the optimization of joined conical shells based on free vibration. Semi-vertex angles of cones and fibre orientation of the laminated composite are considered as design variables. First, the model is simulated in ABAQUS, the model is validated by comparing its results to other obtained from the literature. Then the first non-zero natural frequency of isotropic joined conical shell is maximized by changing the two semi-vertex angles of cones. Last the fibre orientation of laminated joined shells are optimized to achieve the maximum natural frequency.
On the Dynamics of Vibro-Impacting Tapered Cantilever With Tip Mass
Authors: Vyas Vishal , Gandhi Prasanna
Published: February 2017

Vibro-impact situations in beams arise in several applications including turbine blades, vibration energy harvesting, etc This paper presents dynamic analysis of vibro-impacting tapered beam having tip mass and impacting against two stops. It is well known in the literature that typical frequency response of a uniform cantilever impacting against single stop shows resonance frequency shift along with hysteretic jump and drop phenomena. This paper investigates interesting perturbations in the frequency response curves on account of addition of another stop for a tapered counterpart. A piecewise linear modeling is used to consider spring-damper model for impact and tapered beam mode shapes are obtained using differential transform method. It is demonstrated both experimentally and theoretically that more taper in the beam in general increases the peak amplitude ratio and two stops play important role in enhancement of peak amplitude ratio while keeping the frequency shift the same.
Closed-Loop Control of Photovoltage for Photovoltaic-Electrostatic Driven Servo System
Authors: Wang X. J. , Lu F. , Huang J. H.
Published: February 2017

It is experimentally confirmed that the response speed of photo-induced deformation lags far behind the photovoltage and it is difficult to control the magnitude of the photo-induced electric field in PLZT ceramic due to the serious residual photovoltage. The primary purpose of this article is to control the photovoltage of PLZT for a photovoltaic-electrostatic driven servo system proposed in this paper. The control equations of photovoltage for photovoltaic-electrostatic driven servo system are derived based on the mathematical model of PLZT with coupled multi-physics fields. Parameters of photovoltage of PLZT ceramic during the illumination phase and light off phase are identified through the static experiment. Based on simple on-off control strategy, real-time switching the UV light via an optical shutter is adopted to achieve the desired photovoltage. Then, the closed-loop photovoltage control experiments for photovoltaic-electrostatic driven servo system based on PLZT ceramic are carried out. The experimental results show that the photovoltage can be successfully controlled at the target degree by switching the UV light with an optical shutter. The control strategy can be applied in the photovoltaic-electrostatic driven servo system to achieve the target degree of angular or displacement deflection.
Acquiring Embodied Knowledge Through Practice: A Wisdom Engineering Approach
Authors: Fukuda Shuichi
Published: February 2017

Although remarkable progress has been made in the field of explicit knowledge, research about tacit knowledge is still very few. This paper takes up embodied knowledge such as bicycle riding, as one kind of tacit knowledge. As embodied knowledge cannot be articulated and verbalized, it has to be transferred to another person through practice. But how we can acquire embodied knowledge more effectively through practice is still the question at issue.

Indeed, there are works to help a learner to acquire embodied knowledge by showing the videos or through OJT. But since features or control points are not explicit, it is very difficult for a learner to acquire a good sense for judgments and for decisions to cope with the changing situations.

Although there are many approaches to multivariate analysis, there are very few approaches which provide a holistic perspective. In this sense, pattern-based approach is better than other approaches.

This paper points out that pattern-based Recognition Taguchi (RT) approach in Mahalanobis Taguchi System (MTS) is expected to be a very promising and versatile tool to help a learner acquire embodied knowledge because it allows us to take the differences of body behavior from person to person in addition to providing the holistic perspective.
Wind Power Forecasting Model Fusion Evaluation Based on Comprehensive Weights
Authors: Tian Jianyan , Liu Tingting , Banerjee Amit , Wei Aixue , Yang Shengqiang , Gao Wei
Published: February 2017

Studies show that fusion modeling can improve the forecasting accuracy of wind power. Fusion modeling is the process of selective use of information from individual forecasting models. The reasonable evaluation of the individual models is the premise and basis of model optimization so that the individual models with high forecasting accuracy can be selected to establish the fusion model. Because the results of a single index model evaluation may not be comprehensive, the multi-index fusion evaluation method based on maximizing deviations and subjective correction is proposed. The method is applied to the selection of short-term wind power forecasting models. Firstly, this method establishes the individual model base of wind power forecasting model. Secondly, it establishes the more comprehensive evaluation index system. Thirdly, it combines maximizing deviations with the subjective correction coefficient to determine the comprehensive weight of each model, which is used to calculate the fusion evaluation value and get the evaluation order to achieve the model optimization. Finally, based on five years of data from a wind power plant in Shanxi Province, the validated experiments by multiple sets of forecasting data have been done using MATLAB in this paper. The simulation results demonstrate that the evaluation based on the proposed fusion evaluation method is more comprehensive and stable compared to evaluation using a single index. More importantly, it can effectively guide the model optimization with simple operating steps.
Framework to Quantify Uncertainties in Piezoelectric Energy Harvesters
Authors: Ruiz Rafael O. , Meruane Viviana
Published: February 2017

The interest of this work is to describe a framework to propagate uncertainties in piezoelectric energy harvesters (PEHs). The uncertainties are related to the random error associated to the mathematical model adopted, incomplete knowledge of the model parameters and the randomness nature of the excitation. The framework presented could be employed to conduct Prior and Posterior Robust Stochastic predictions. The prior analysis assumes a known Probability Density Function (PDF) for the uncertain variables while the posterior analysis calculates this PDF by adopting a Bayesian updating technique. The framework is particularized to evaluate the behavior of the Frequency Response Functions (FRFs) in PEHs while its implementation is illustrated by the use of a unimorph PEH. Results reveal the importance to include the model parameters uncertainties in the estimation of the FRFs. In that sense, the present framework constitutes a powerful tool in the robust design and prediction of PEH’s performance.
An Experimental and Numerical Study of Convective Boiling of Nanoemulsion Inside Mini-Channels Heat Exchanger
Authors: Poudel Naresh , Acar Musa , Tran Thanh , Xu Jiajun
Published: February 2017

In this paper, both experimental and numerical studies have been performed on the convective boiling heat transfer of the Ethanol-in-Polyalphaolefin (PAO) Nanoemulsions inside a heat exchanger of twelve 1mm diameter mini-channels that was subjected to a uniform heat flux at its outer surface. The heat transfer characteristics and the pressure drop of the Ethanol/PAO nanoemulsion was studied experimentally, meanwhile, the volume of fraction (VOF) model with Pressure-Velocity coupling based Semi Implicit Method for Pressure Linked Equations (SIMPLE) iterative algorithm is employed to simulate the same experimental conditions numeircally. The results reveal that the convective boiling heat transfer coefficient of the nanoemulsion can be greatly enhanced upon the nucleation of ethanol nanodroplets inside, in which a maximum 50% enhancement compared to pure PAO base fluid can be achieved under current test conditions. However, the thermal conductivity and viscosity of the nanoemulsions has an insignificant effect on convective boiling heat transfer coefficient based on the experimental results. The ANSYS FLUENT simulation results also agree well with the experimental data. The Ethanol-in-PAO nanoemulsion could function as a good alternative conventional working fluid in two phase heat transfer applications.
A Numerical Study of the Effect of Triangular Waves on Natural Convective Heat Transfer From an Upward Facing Heated Horizontal Isothermal Surface
Authors: Oosthuizen Patrick H.
Published: February 2017

A numerical study of natural convective heat transfer from an upward facing, heated horizontal isothermal surface imbedded in a large flat adiabatic surface has been undertaken. On the heated surface is a series of triangular shaped waves. Laminar, transitional, and turbulent flow conditions have been considered. The flow has been assumed to be two-dimensional and steady. The fluid properties have been assumed constant except for the density change with temperature giving rise to the buoyancy forces. This was with treated using the Boussinesq approach. The numerical solution has been obtained using the commercial CFD solver ANSYS FLUENT©. The k-epsilon turbulence model with full account being taken of buoyancy force effects has been employed. The heat transfer rate from the heated surface expressed in terms of a Nusselt number is dependent on the Rayleigh number, the number of waves, the height of the waves relative to the width of the heated surface, and the Prandtl number. This study obtained results for a Prandtl number of 0.74 which is effectively the value for air. An investigation of the effect of the Rayleigh number, the dimensionless height of the surface waves, and the number of surface waves on the Nusselt number has been undertaken.
Thermal Gradient on Hybrid Composite Propellant Tank Materials at Cryogenic Temperatures
Authors: Avila Raudel O. , Islam Md S. , Prabhakar Pavana
Published: February 2017

Cryogenic tanks are devices that are commonly used to store extremely low temperature fluids, usually in their liquid state. Cryogenic fuel tanks carry cryogenic propellants such as liquid oxygen, liquid methane or liquid hydrogen, at subfreezing temperatures in its condensed form in order to generate highly combustible liquids. This type of tank is exposed to an extremely cold temperature in its interior and to ambient temperature on its external surface resulting in large temperature gradient across the thickness of the wall. In this paper, hybrid textile composites with carbon and Kevlar® fabric are explored as means to reduce the influence of thermal gradient in order to enhance the material performance when cryogenic propellant fuels are stored in spacecraft applications.

Previous initial studies of tensile and flexural tests have indicated that carbon and Kevlar® textile composites are suitable materials for cryogenic temperatures. The pristine mechanical properties of carbon composites changed within a maximum of 3–4% after initial cryogenic exposure during the fueling stage, while 17% for Kevlar® composites. Computational models of hybrid carbon-Kevlar® composites were subjected to cryogenic temperature (77 K) to investigate the effect of exposure for extended periods and to aid in the design of optimum layups for the same. Six optimal combinations were selected that resulted in low interface stresses and lower number of peak stresses through the thickness of the laminate. These layups were deduced to perform better compared to other layups due to lesser susceptibility to delamination type failure upon cryogenic exposure. Experimental investigation of the chosen hybrid composites has revealed few optimum combinations for use in tanks. As a next step, computational analysis of cryogenic exposure to only one surface of hybrid composites was performed to simulate the composite wall containing the liquid fuel. Based on the suggestions from the computational models, experiments to determine optimum designs of the composite wall were conducted. An ABS plastic insulating holder was computationally designed and 3D printed to hold the specimens such that only one surface is exposed to LN2. A total of eight composite layups were exposed to liquid nitrogen using the plastic holder to study their response to thermal gradient cryogenic exposure. Based on the results obtained computationally and supported by experiments, optimum hybrid layups of composites to sustain cryogenic exposure were determined.
A Non-Orthogonal Constitutive Material Model for Advanced Woven Fabrics Based on a Mesoscale Unit Cell
Authors: Erol Ozan , Powers Brian M. , Keefe Michael
Published: February 2017

Advanced woven fabrics can provide a wide range of mechanical properties since the yarns can be arranged in different architectural patterns thus allowing the fabric structure to be tuned based on the specific needs. This adjustable nature makes them an attractive material choice for applications where versatility is highly desired. Hence, there is an increasing interest in woven fabrics in the recent years. They have been used in various applications such as deployable structures, protective garments, medical scaffolds and composites. With the increased interest, there is a need for efficient and accurate computational tools to investigate the mechanical behavior and deformation of woven fabrics for specific applications. Although there are several computational models in the literature that can model uniaxial and biaxial behavior of woven fabrics, there are not any commonly accepted material models for woven fabrics due to the complex interaction of trellising and deformation. Here, we propose an easy to implement constitutive material model based on a mesoscale unit cell of the woven fabrics. The proposed model utilizes the two prominent deformation mechanisms affecting the mechanical response at the mesoscale level: (1) Yarn stretching, and (2) shearing. These mesoscale mechanisms are mechanistically implemented within an unit cell by using truss and rotational springs to generate the mechanical response of the woven fabric. The yarns’ nonlinear mechanical behavior is modeled with non-linear trusses and assumed to be pin-jointed at the center of the unit cell. The truss elements are allowed to rotate at the pin-joint reproducing the yarns’ relative rotational motion during shearing. The fabric’s shear resistance involves two components: yarn-to-yarn relative rotation/sliding and yarn locking due to the yarn transverse compression. These components of the fabric shear resistance are modeled as a non-linear rotational spring located at the pin-joint which generates a moment resisting the shear deformation. The developed forces and moments from the trusses and rotational spring within the unit cell structure are then used to determine the continuum stress state of the material point. The material properties and parameters defined in the proposed model are easy to obtain from uniaxial tensile and shear tests on fabrics. To validate the material model, plain weave Kevlar KM2 fabric is modeled by replicating the standard uniaxial tensile and bias extension tests. The results obtained show that the material model provides a good description of the in-plane deformation and mechanical response.
Cup Forming: A Study in Quasi-Automatic Strain Based Control
Authors: Srinath Suchethan M. , Emblom William J.
Published: February 2017

Force-based closed-loop control of stamp forming processes have in the past been investigated in order to improve the formability of sheet metal when forming automotive body panels. Previous researchers have controlled local forces and wrinkling using active draw beads and variable blank holder forces. However, it has been recognized that strain-based control in critical locations may be more effective. This study is an initial examination of strain-based control. In order to simplify the problem of strain control, cup forming was utilized and a quasi-automatic proportional control system was utilized. Both finite element analysis and experimental results were examined. It was demonstrated that control at the punch nose resulted in better strain control than at the die shoulder. For this study, two approaches were considered for control. For the first approach, if the effective strains were within +/−0.005 of the target strain, the process was said to be in control while the second approach used a factor of 10% deviation from the target strain to be in control. It was shown that the second method resulted in improved control. However, a third approach, which was a synthesis of the first two approaches resulted in very close agreement between the target strains and the strains from the controlled simulations.
Numerical Investigation on the Rotating Stall Characteristics in a Three-Blade Centrifugal Impeller
Authors: Lei Cao , Zhengwei Wang , Yexiang Xiao , Yongyao Luo
Published: February 2017

When a pump operates in part-load conditions, it is apt to form flow separations and even stall cells at the blade surfaces. In some conditions, stall cells may circumferentially propagate among the blade channels, known as rotating stall, which can affect the rotor system dynamic stability. Conventionally it is believed that the formation and circumferential propagation of stall cells is attributed to the nonuniformity of the flow state in front of the impeller inlet. In recent decades, many investigations indicate that the uneven flow field at the impeller outlet related to the asymmetric volute casing is also an important factor to induce rotating stalls. Thus the formation and propagation mechanism of rotating stalls is complex and has not been clearly understood so far. In addition, previous studies mainly focused on the rotating stalls in vaned diffusers, while it is more difficult to figure out rotating stalls in impellers for which little studies has been done. In this paper, numerical simulations are conducted for a three-blade centrifugal pump with a flow rate of 0.75Qd where Qd is the design flow rate. The SST-SAS model with a curvature correction is applied to predict the unsteady internal flows. The time-averaged pump head, efficiency and axial power agree well with the experimental results from a previous test. From the numerical results, a special rotating stall is detected in this condition. In order to verify the effect of the volute casing, a contrast simulation is also conducted without the volute casing domain. It shows that rotating stalls always occur whether there is a volute casing or not, but the distribution and motion of the stall cells are changed by the existence of the volute casing. It indicates that the nonuniform flow distribution at the impeller outlet is not an essential factor for the formation of rotating stall but accelerates the variation of stall cells. Based on the whole-flow-passage result, a stall cell in one blade channel disappears for about 2/15T (T is the duration of one revolution) when the downstream blade runs across the tongue, and the same phenomenon recurs in the upstream blade channel after 1/3T, which is unusual and worthy of investigation. The pressure fluctuations within the whole flow passage are intensified by the rotating stall more or less, especially at the middle region of pressure surface of blades, around the tongue and in the beginning of the discharge passage.
Geometry Design and Contact Ratio Analysis for Circular Arc Parallel-Axis Helical Gears
Authors: Chen Z. , Lei B. , Zhao Q.
Published: February 2017

Based on space curve meshing theory, in this paper, we present a novel geometric design of a circular arc helical gear mechanism for parallel transmission with convex-concave circular arc profiles. The parameter equations describing the contact curves for both the driving gear and the driven gear were deduced from the space curve meshing equations, and parameter equations for calculating the convex-concave circular arc profiles were established both for internal meshing and external meshing. Furthermore, a formula for the contact ratio was deduced, and the impact factors influencing the contact ratio are discussed. Using the deduced equations, several numerical examples were considered to validate the contact ratio equation. The circular arc helical gear mechanism investigated in this study showed a high gear transmission performance when considering practical applications, such as a pure rolling process, a high contact ratio, and a large comprehensive strength.
The Nonlinear Inplane Behavior and Progressive Damage Modeling for Laminate by Peridynamics
Authors: Yu Yin , Liu Su-Su , Zhao Shu-Li , Yu Zhefeng
Published: February 2017

The modeling method of fiber-reinforced composites by state-based peridynamics was studied. The one-parameter nonlinear constitutive model was used to get the nonlinear relationship between force vector state and deformation vector state. Then the governing equation for laminate with nonlinear inplane behavior was built. A compensation modification method was also proposed to reduce the surface effects. A scalar function was introduced in the equation of force vector state in order to describe the damage. After the proposed compensation modification method was verified to reduce strain energy error of particles in the boundary region effectively, both unidirectional and orthotropic composite panels under uniaxial tension load were modeled. The resulting stress-strain curves fit well with the test data. Also, progressive damage analysis of composite panels with a center-hole was carried out, and the corresponding damage results agreed well with the experimental and simulating results of a relevant published research.
A Numerical Study of the Convective Heat Transfer From the Inner Surface of a Recessed Window Covered by a Double-Layer Honeycomb Top Down-Bottom Up Blind
Authors: Oosthuizen Patrick H. , Mansouri Neda
Published: February 2017

The purpose of the present work was to investigate numerically the effect of the top and/or bottom blind openings on the convective heat transfer from a window fitted with a double-layered top down-bottom up honeycomb blind system. Top down-bottom up systems that utilize so-called honeycomb (or cellular) blinds can be opened at the top and/or the bottom. When a honeycomb blind is fully closed there are two or more vertical blind portions and a series of horizontal or nearly horizontal blind portions which join the vertical portions and form a column of cells. This gives the blind system its honeycomb or cellular structure. When opening a honeycomb blind the vertical portions of the blind bend or fold allowing the overall height of the blind to decrease. A double-layered honeycomb blind is constructed with three vertical blind portions and two columns of cells. A recessed window has been considered in the present study and only the convective heat transfer from the window to the surrounding room has been investigated. The surfaces of the blind are assumed to offer no resistance to heat transfer. The commercial CFD solver ANSYS FLUENT© has been used to obtain the solution. Over the range of parameters considered in this study, both laminar and turbulent flow can occur. The k-ε turbulence model has been used in obtaining the solutions. The convective heat transfer rate from the inner surface of the window, expressed in terms of a mean Nusselt number based on the window height and the difference between the window and the air temperatures, will depend on the Rayleigh number, also based on the window height, and the difference between the window and the air temperatures, the dimensionless top and bottom blind openings, and the dimensionless window recess depth. Variations of the mean Nusselt number with Rayleigh number for various values of these other parameters have been obtained and the results used to study how these other parameters affect the window heat transfer rate.
Reverse Osmosis Desalination Module: Three Dimensional, Transient Analyses
Authors: Anqi Ali E. , Usta Mustafa , Alrehili Mohammed , Alkhamis Nawaf , Oztekin Alparslan
Published: February 2017

The desalination process using reverse osmosis membrane is used around the globe to produce fresh water. In the present paper, simulations are conducted to examine steady and transient nature of the flow inside a three dimensional desalination module containing cylindrical spacers. Navier-Stokes and mass transport equations are solved to determine the flow and concentration field in the feed channel for Reynolds number of 800. The spiral wound membrane is treated as a functional surface where the solution-diffusion model is applied. The flow and the concentration field are strongly three dimensional and transient in nature. The present authors demonstrated that the momentum mixing induced by the presence of spacers enhances the flux performance of the membrane. It is also shown that transient effects and the secondary flows induced by three dimensional flow transitions are mitigating the concentration polarization and fouling/scaling that occurs along the surface of the membrane.
Utilization of Modal Test Techniques for Quality Control of Mass Manufactured Parts
Authors: Gençoğlu Caner , Gürel Aslı Arife , Koç Ege Can
Published: February 2017

Bringing a high tech product to the market as soon as possible has never been so critical. Quality control of critical parts manufactured in large quantities is a problem to solve in many industries ranging from aerospace to automotive. If there are precision parts with very tight dimensional tolerances in the assembly, each and every dimension of every part must be measured. Otherwise parts with dimensions out of tolerances will create more trouble in the later steps of the assembly. Measuring the dimensions of precision parts using high precision coordinate measurement machines (CMM) is time consuming and can be quite cumbersome. Also the initial investment to be made in order to acquire a precise CMM is quite expensive. An alternative solution to this quality assurance (QA) problem is utilizing the vibrational characteristics of the manufactured part. A quality acceptance criterion using those characteristics of the part can be developed. Natural frequencies and mode shapes of the part are the key parameters to be measured when deciding the part to fail or pass. For this purpose, a test setup with the ability of automated modal testing is required. In this study, such a system is designed and developed named as the modal test robot (MTR). The MTR consists of an automated modal test hammer to excite the modes of test part, a mechanism to support the hitting hammer and a heavy granite table to secure the part. By using finite element (FE) analysis, the natural frequency range for the acceptable test part is determined. High fidelity FE analysis models are utilized to ensure good agreement between analysis and test results. Three different parts called the spool; the four arm star and the blade are examined as case studies. In case studies, relationship between part dimension and the natural frequency of the part is calculated by utilizing parametric FE model for each part. Using this relationship, fail or pass criterion is developed according to a specific natural frequency of the part. Natural frequencies of the part are measured on the MTR. Since modal test is carried out by using the MTR, repeatability and coherence of the test results are increased. By this procedure, a technician can make a quick decision whether the measured part passes of fails by just checking the natural frequency. Utilizing the vibrational characteristics as a fail or pass criterion for parts instead of a dimensional measurements is a fast and cheap method that can be employed in QA processes. By implementing this methodology, QA cycle times for manufactured parts reduces 90% and higher number of parts can be controlled in a limited inspection time.
Effects of Intrinsic Strain on the Structural Stability and Mechanical Properties of Phosphorene Nanotubes
Authors: Liao Xiangbiao , Chen Xi
Published: February 2017

Using molecular dynamics (MD) simulations, we explore the structural stability and mechanical integrity of phosphorene nanotubes (PNTs), where the intrinsic strain in the tubular PNT structure plays an important role. It is proposed that the atomic structure of larger-diameter armchair PNTs (armPNTs) can remain stable at higher temperature, but the high intrinsic strain in the hoop direction renders zigzag PNTs (zigPNTs) less favorable. The mechanical properties of PNTs, including the Young’s modulus and fracture strength, are sensitive to the diameter, showing a size dependence. A simple model is proposed to express the Young’s modulus as a function of the intrinsic axial strain which in turns depends on the diameter of PNTs. In addition, the compressive buckling of armPNTs is length-dependent, whose instability modes transit from column buckling to shell buckling are observed as the ratio of diameter/length increases.
Analytical Bifurcation Trees of a Periodically Excited Pendulum
Authors: Guo Yu , Luo Albert C. J.
Published: February 2017

In this paper, the bifurcation trees of a periodically excited pendulum are investigated. Implicit discrete maps for such a pendulum are developed to construct discrete mapping structures. Bifurcation trees of the corresponding periodic motions are predicted semi-analytically through the discrete mapping structure. The corresponding stability and bifurcation analysis are carried out through eigenvalue analysis. Finally, numerical illustrations of various periodic motions are given to verify the analytical prediction. The accurate periodic motions in the periodically forced pendulum are predicted for the first time through the implicit mapping systems, and the corresponding bifurcation trees of periodic motion to chaos are obtained.
Image Guided Automation of Endovascular Robotic Surgery
Authors: Ashammagari Aditya Reddy , Sankaran Naveen Kumar , Chembrammel Pramod , Chollangi Ravikiran , Siddiqui Adnan , Snyder Kenneth , Kesavadas Thenkurussi
Published: February 2017

Interventional cardiologists and neurosurgeons are exposed to X-ray radiations while performing surgery. A few tele-robotic systems currently in the market require tedious tele-control using an external input device. In this paper we propose to automate such interventional surgeries using a robotic system using image guided intervention. After image processing of x-ray fluoroscope image and applying new machine learning techniques based on Markov Decision process, our new robotic system is capable of reaching aortic arch, which is the first step in cardiac and neuro-interventional procedures. Further, we explain the algorithm and demonstrate the proposed system implementation on an endovascular simulator.
Manufacturability of Overhang Structures Fabricated by Binder Jetting Process
Authors: Yang Fan , Tang Yunlong , Zhao Yaoyao Fiona
Published: February 2017

Due to the superior mechanical properties of metals and the inherent capability of additive manufacturing (AM) to fabricate complex structures, metal AM reveals a promising future in the industrial fields. Compared with other metal AM processes, Binder Jetting (BJ) process has potential of producing overhang structures without additional supports. This advantage of BJ process significantly enlarges the design freedom of complex metal parts with intricate overhang structures. However, it should be noted that there is still a certain manufacturing limitation of overhang structures for BJ process. Without the support of loose powder after the depowdering process, the green part is vulnerable to the inevitable external loads, such as self-weight. In this paper, a theoretical model has been proposed to evaluate the self-support capability of printed green parts after the depowdering process. A set of experiments has been designed to find the maximum normal stress that printed green parts can withstand. This proposed theoretical model can be used to predict manufacturability of overhang structure of any arbitrary shape. Based on this model, some design guidelines and future work are summarized at the end of this paper.
Numerical Studies of the Effectiveness of Electrodes With Conductive Dots in Flow Batteries
Authors: Zhang Xuyang , Luo Song , Liu Hongtan , Wang Conghua
Published: February 2017

In flow batteries generally the entire surface of the electrodes are conductive. Due to the highly corrosive nature of the electrolytes of many types of flow batteries there exists a dilemma in choosing electrode materials: highly corrosion resistant materials have very high cost and low cost materials have low corrosion resistance and thus low durability. To overcome this difficulty, a novel design of electrodes with conductive dots and corrosion resistant film is proposed [1]. Such electrodes can be made of low-cost base metals covered with corrosion resistant film and evenly distributed conductive dots, which can be made of highly corrosion resistance material such as gold, titanium, etc. Since the area covered by the highly corrosion resistance metals can be only a small percentage of the total electrode area the cost of the electrode can be relatively low. In this study, numerical simulations have been performed to study the effectiveness of such a design. In this work, lead-acid flow batteries are used as a model for redox flow batteries. The results from the electrode with conductive dots are compared with those from conventional electrodes. When conventional electrodes are used, the entire electrode surface is active for electrochemical reactions. When redox reactions occur under charging and discharging cycles, the redox species are consumed very fast and the electrolyte concentrations on the electrode surface decrease sharply from those in the bulk flow, leading to sharp decrease in reaction rate along the flow direction. When electrodes with conductive dots are used, though the active area is much smaller, reaction rates in the down-stream are similar to those in the upstream. This is due to the recovery of electrolyte concentrations in the non-active area surrounding the conductive dots, mainly from diffusion. The more uniform reaction rates from the upstream to the downstream results in much higher average current density per unit active area. Thus, even though the active area of the electrode with conductive dots is much smaller, the total reaction rate per unit apparent electrode area is not much lower. The modeling results show that the electrodes with conductive dots are highly effective even when the area covered by the conductive dots is only a few percent of the total electrode area.
Design of a Rooftop Wind Harnessing System With Smart Wind Deflecting Structure
Authors: Rashidi Majid , Kadambi J. R. , Suren Scott
Published: February 2017

This work presents a novel design for a rooftop wind tower system; the system is primarily intended for areas of low natural wind speeds. The relatively low natural wind is increased by a factor of about 1.6 times via a wind deflecting structure to reach the cut-in speed of typical rooftop wind turbines which is approximately 3 m/s. The system additionally responds to relatively high wind velocity, above 20 m/s, in a way that eliminates its wind speed amplification attributes; this will protect the wind turbines against exposure to high wind speeds that could be harmful to the turbines and to the mast structure that supports the turbine/generator. In case of high natural wind speed, above 20 m/s, passively controlled trap-doors, that are parts of the wind deflecting structure, allow wind to pass through the wind deflecting structure, thereby eliminating wind speed amplification of the deflecting structure. The design disclosed in this work comprises of a half cylinder wind deflecting structure that includes a plurality of spring loaded trap-doors; when closed, they form the wind deflecting structure up to a prescribed maximum natural wind speed. As the natural wind speed increases beyond its prescribed maximum, the spring loaded trap doors open as the result of the pressure exerted upon them by the wind. The design presented in this work increases the range of cut-in and cut-out wind speeds for a typical rooftop wind turbine.
Combustion Characteristic of Flow Through a Low Swirl Injector
Authors: Deng Yangbo , Zheng Luohan , Su Fengmin , Ma Chenshuo
Published: February 2017

An experimental study was carried out in order to provide a better understanding of the combustion characteristics of a low swirl injector (LSI). The swirl vanes angles are respectively 37°, 42° and 50°, and the swirl numbers are varied in a wide range. The fuel gases used in the experiment include propane, methane and methane with hydrogen. The results show: (1) the lean premixed propane, methane, methane with hydrogen and air flow through the LSI can sustain steady combustion at a lower swirl number; (2) the LSIs can generate a blue lift-off “W” type flames surrounding a long yellow pulsating flame and the blue flame consists of four clusters blue flames connected together along circumferential direction; (3) the flame structure converts the “W” type flame into the “broom” type flame with the pulsating yellow flame, and the distance between the front of the flame and the nozzle shortens with increasing swirl number in the same vane angle case; (4) the spectroscopic of the flame shows the yellow flames are emitted by diatomic carbon.
Numerical Study of the Effect of the Upstream Object on Flow Control of the Downstream Object
Authors: Zheng Z. Charlie , Liu Yangliu , Huang Diangui
Published: February 2017

Flow behaviors of the downstream object, such as a cylinder or an airfoil, can be influenced significantly by an upstream object in close proximity. Examples include tandem cylinders and cylinder-airfoil interactions. In this study, numerical simulations are carried out to investigate several parameters that affect the flow around the downstream object, such as the relative location, size, and motion of the upstream object. Particularly, the flow separation and the related lift and drag behavior are studied.