bluuebunny/crossref_metadata_2025 huggingface dataset:
An Automated Procedure for the Optimization of Suspension Damping of Road Racing Motorcycles
Authors: Leonelli Luca , Mancinelli Nicolò
Published: April 2014

The suspension systems generally installed in road racing motorcycles make it possible to fine tune the damping characteristics through a wide range of adjustments, so that the amount of force delivered for low and high suspension shaft speed, in both compression and rebound states, can be independently set by the user. Nevertheless, the optimal choice of suspension tuning parameters is a difficult task, normally affecting the vehicle dynamic behavior and its handling characteristics, and technical literature lacks procedures being developed and adopted in practice for this purpose. In this paper a handling-oriented algorithm for the optimization of the suspension damping parameters of a passively suspended racing motorcycle is presented. An optimization function is proposed for two significant maneuvers in road racing, such as high lean angle cornering and braking. The related objective functions are based on the minimization of the fluctuating component of the vertical front tire-ground force, allowing the tire to maximize the friction contact actions, that is maximizing the vehicle’s ability to accelerate. The above maneuvers are simulated by means of a multibody motorcycle model where the suspensions non-linearity is taken into account. The experimental damping force versus suspension shaft speed relationship is modeled by means of a non-parametric B-spline piecewise function, whose coefficients are determined by a mixed interpolation-approximation procedure, and their choice and values are restrained by manufacturability constraints. This makes it possible to properly model the effects of the tuning control parameters and of the dry friction with a minimum number of parameters. Moreover, it is shown that a computationally efficient optimization can be performed using this properly designed B-spline coefficients as optimization variables.
Vibration Analysis and Transformation of Hyper Compressor Pipeline for LDPE Plants
Authors: Bai W. J. , Li Y. Q. , Duan Q.
Published: April 2014

Excessive pipe vibration brings a series of serious problems, especially for hyper compressors used by LDPE production. Therefore, the pipeline vibration issues should be handled with care as the process gas reaches pressures up to 350 MPa (50,000 psi). This paper focuses on how to analyze the hyper compressor pipe vibration during operation and maintenance. Taking the outlet pipe vibration of an ultra-high pressure ethylene compressor for example, firstly the vibration level was assessed by the site measurement and signal processing. Then the acoustical analysis was executed based on the plane wave theory and the finite element theory. After that, the modal analysis of pipelines was made with the finite element method. Finally the analyses of all the obtained results made it possible to identify the true reason for pipeline vibration — gas pulsation with large amplitude instead of gas column resonance and structure resonance. Based on the integrated analyses of the results, the retrofit measures were proposed and verified.
Hydraulic Characteristics of the New Type Bulb Turbine With Micro-Head
Authors: Li Lingyu , Zheng Yuan , Zhou Daqing , Mi Zihao
Published: April 2014

The head of low-head hydropower stations is generally higher than 2.5m in the world, while micro-head hydropower resources which head is less than 2.5m are also very rich. In the paper, three-dimensional CFD method has been used to simulate flow passage of the micro-head bulb turbine. The design head and unit flow of the turbine was 1m and 3m3/s respectively. With the numerical simulation, the bulb turbine is researched by analyzing external characteristics of the bulb turbine, flow distribution before the runner, pressure distribution of the runner blade surface, and flow distribution of the outlet conduit under three different schemes. The turbine in second scheme was test by manufactured into a physical model. According to the results of numerical simulation and model test, bulb turbine with no guide vane in second scheme has simpler structure, lower cost, and better flow capacity than first scheme, which has traditional multi-guide vanes. Meanwhile, efficiency of second scheme has just little decrease. The results of three dimensions CFD simulation and test results agree well in second scheme, and higher efficiency is up to 77% which has a wider area with the head of 1m. The curved supports in third scheme are combined guide vanes to the fixed supports based on 2nd scheme. By the water circulations flowing along the curved supports which improve energy transformation ability of the runner, the efficiency of the turbine in third scheme is up to 82.6%. Third scheme, which has simpler structure and best performance, is appropriate for the development and utilization of micro-head hydropower resources in plains and oceans.
Droplet Spreading on Textured Surface Based on SPH Method
Authors: Meng Shuai , Zhao Zhen , Wang Qian , Yang Rui
Published: April 2014

Droplet spreading occurs when a water drop hits the surfaces in a relatively low speed, which is a very important process in many applications (for example printing technologies and especially observation of diffusion of liquid state contaminant). This paper is aimed at analyzing contact angle and roughness, the two main factors’ effect on droplet spreading using SPH (smoothed particle hydrodynamics) method. When fluid-fluid and fluid-solid particle-particle interaction is added according to Alexandre Tartakovsky and Paul Meakin, surface tension and contact angle can be simulated. Line-shaped projections of different height are applied here as rough surfaces. The result shows two main effects of textured surface with different contact angle: unequal spreading in different direction and capillary phenomenon in the gap formed by the line-shaped projections.
Robust Design of North American Power Grid to Mitigate Cascading Failures
Authors: Piacenza Joseph R. , Tumer Irem Y. , Fields John J. , Bozorgirad Mir Abbas , Hoyle Christopher
Published: April 2014

Catastrophic cascading system failures such as the August 13th Blackout of 2003 highlight the vulnerability of the North American power grid, and emphasize the need for research to mitigate failure events. The incorporation of robust design, the insensitivity of system performance in the presence of noise (or uncertainty) from both internal and external sources, into existing and future power grid design strategies can increase system reliability. This paper presents a high-level topological network approach to power grid robust optimization as a solution for designing against cascading system failure. A mathematical model was created representing a standard power grid network consisting of generation and demand nodes, as well as node connections based on actual topological transmission line relationships. Each node possesses unique power generation or demand attributes, and various network connection configurations are examined based on system demand requirements. In this model, failure events are initiated by the removal of a single network connection, and remaining loads are redistributed throughout the system. Cascading failure effects are captured when the existing network configuration cannot support the resulting demand load, and transmission line failures continue propagate until the system again reaches a steady state, based on remaining nodes and connections. The primary goal of this research is to facilitate an understanding of design trade-offs between system robustness and performance objectives. In this research, robustness is defined as the resilience to initiating faults, where a robust network has the ability to meet system generation requirements despite propagating network failures. Primary performance objectives are total system cost and the ability to satisfy network demand after a failure, while robustness is represented as the lack of variability in the amount of demand which is satisfied after a failure. By understanding network reactions due to cascading failures, as well as performance trade-offs required to mitigate these failures, reliability in power grid systems can be increased.
Computational Study of Lateral Impact Behavior of Pressurized Pipelines
Authors: Dou Yangqing , Liu Yucheng
Published: April 2014

This paper presents a computational study to investigate the crash responses and collapse mechanisms of pipelines subjected to lateral impact. Influence of internal pressure of the pipelines on their lateral impact behavior is revealed through a serious of numerical crashworthiness analysis. FEA software package, LS-DYNA, is used to model the pressurized pipelines and perform the crashworthiness analysis. The simulation results provide a substantial background for the future experimental study to completely investigate dynamic responses and failure modes of pipelines subjected to low-velocity lateral impact. The results presented in this paper also have potential benefits on research of safety and reliability of civil pipelines and development of advanced pipelines materials.
Experimental and Numerical Study of the Effects of Asymmetric Micro Ratchets on Pool Boiling Performance
Authors: Brumfield Lance , Park Sunggook
Published: April 2014

Nucleate boiling is an attractive method for achieving high heat flux at low superheat temperatures. It is frequently used for industrial applications such as heat exchangers and is being considered to cool advanced central processing units (CPU) which produce heat fluxes on the order of 1 MW/m2 and are becoming increasingly less efficient to cool via forced conduction of air. The issues with implementing nucleate boiling as a cooling mechanism lies in the difficulty of quantifying the complex and numerous mechanisms which control the process.

A comprehensive nucleate boiling model has yet to be formulated and will be required in order to safely and reliably cool high performance electronics. Spatially periodic systems with localized asymmetric surface structures (ratchets) can induce directed transport of matter (liquid/particles) in the absence of net force. It was hypothesized that ratchets may enhance pool boiling heat transfer by aiding in the removal of vapor which forms on the heated surface. Therefore, experiments on pool boiling using asymmetric micro ratchets of various geometries, with FC-72 as the working fluid, were investigated. Additionally, various numerical pool boiling simulations were performed using FLUENT to better understand the underlying physical principles behind pool boiling.
A Modified Disjoining Pressure Model for Thin Film Evaporation of Water
Authors: Azarkish Hassan , Behzadmehr Amin , Frechette Luc G. , Sheikholeslami Tahereh Fanaei , Sarvari Seyyed Masoud Hosseini
Published: April 2014

In the present work, a modified model to predict the disjoining pressure for thin film evaporation of water is presented. There has been some controversy about disjoining pressure modeling, especially for the case of polar liquids such as water. The conventional models for prediction of disjoining pressure, such as non-polar, logarithmic and exponential models, lead to different values of pressure and physically invalid thicknesses of the thin film near the non-evaporating region. In the present work, a modified disjoining pressure model is introduced based on multiplying a stretching function with the van der Waals component of disjoining pressure to consider the other intermolecular and surface effects such as structural forces and hydrogen bonds. Comparison of the present model with conventional ones shows that it can account for the effect of water molecules polarity over the entire extended meniscus. Also, the non-evaporating region thickness can be appropriately evaluated by this model, unlike the conventional ones. Moreover, the simple formulation of this model makes it suitable for analytical investigations of water thin film evaporation. Finally the effects of superheat, wall temperature and far field meniscus radius on the heat and mass transfer and fluid flow characteristic of thin film region are investigated and compared for the different disjoining pressure models.
Analysis and Life Testing for Design of Cryogenic Bearing Assemblies on the James Webb Space Telescope Optical Telescope Element
Authors: Evans John W. , Barto Allison , Gallagher Benjamin , Finley Paul , Samuel Mat , Burke Jacob
Published: April 2014

The James Webb Space Telescope is NASA’s next generation space based telescope. The Optical Telescope Element (OTE) is an infrared system designed to operate at cryogenic temperatures. Its primary mirror consists of 18 segments; each segment is controlled by a series of actuators mounted on the back of each mirror segment. Mission success depends vitally on the actuators, specifically the critical bearing assembly of each actuator’s gear motor. This paper details the methodology employed by NASA and Ball Aerospace to evaluate the lifetime of the bearings and to design life tests which quantitatively offset risk at the system level, in a cost effective manner. The life prediction methodology utilized the Lundberg-Palmgren rule to estimate life, employing a cryogenic service factor developed from consideration of fracture toughness changes expected at cryogenic temperatures. This approach showed the capacity of the bearing system to have significant margin and reliability necessary to endure the requirements of OTE operations, over the life of JWST, under the estimated loads. Baseline test designs were subsequently developed with targets designed to show adequate risk reduction during life testing. Tests were subsequently executed at cryogenic temperatures and targets were shown to be met for the required system level risk tolerance.
Simulation of the High Strain Rate Deformation Behavior of Titanium Based Alloy for Biomedical Applications
Authors: Ocran Emmanuel , Aina Johnson , Odoh Daniel
Published: April 2014

Human body functions as a network of mechanically coupled parts (components) that work together to form a complete system; these body components can experience failure when in service. Specifically, failure such as arthritis may be caused by articulations at the hip and knee joints. One of such solutions to this failure is the total hip replacement. Materials used in this prosthesis, therefore play an important role in the success of the implant. One of the most commonly used implant material in modern day arthroplasty is the Ti6Al4V alloy, because of its excellent resistance to wear and corrosion in the human body environment. In reality, such implant in service may be subjected to impact loading (at a velocity of about 250–1000m/s), leading to deformation. Typical, examples include an implanted patient involved in an automobile crash and a golf ball hitting an implanted patient at the point of implantation. In this study, the wear and tear resistance property of Ti6Al4V alloy is determined by performing simulation on the high strain rate deformation behavior of IN718 super alloy material and Ti6Al4V plated Inconel material. The maximum stress localized within the plated Inconel material is lesser than that in the unplated material. This shows that Ti6Al4V alloy prevents the localization of stress in the parent Inconel material and is therefore a good wear prevention material, under impact conditions. Also, the impact characterization behavior of Ti6Al4V material is performed in this research in order to determine the maximum stress allowable in the titanium alloy before ultimate failure. Simulation of the high strain rate behavior of the Ti6Al4V alloy is performed at velocities in the range 9–20m/s. It is observed that the localized stress within the Ti6Al4V alloy increases with increased impact velocity. A maximum localized stress is observed in the material beyond which the Ti6Al4V alloy experiences failure. The result of the simulation process helps in determining the maximum impact which an implanted patient can therefore be exposed to and the preventive measures that can be taken in order to guarantee safety of the implanted patient.
A Discrete-Time Model for Lotka-Volterra Equations With Preserved Stability of Equilibria
Authors: Nguyen-Van Triet , Hori Noriyuki
Published: April 2014

A Lotka-Volterra differential equation is discretized using a method proposed recently by the same authors for nonlinear autonomous systems and the stability of equilibrium points of the resulting discrete-time model is investigated. It is shown that when Jacobian matrix of the nonlinear equation is invertible, the equilibrium points of the model are identical to those of the original continuous-time system, and their asymptotic stability and instability are retained for any sampling period. While the method can be applied to any Lotka-Volterra types, simulation results are presented for a competitive-type example, where the continuous-time system and their discrete-time models obtained by the forward-difference, Mickens’, Kahan’s, and the proposed methods are compared. They illustrate that, in general, the proposed model performs better than other discrete-time models.
Effect of Process Parameters on the Microstructure Homogeneity of AA6082 Aluminum Alloy Deformed by Twist Extrusion
Authors: Senthil Kumar V. S. , Mohammed Iqbal U.
Published: April 2014

Twist extrusion is a severe plastic deformation in which the rectangular shaped work piece is extruded through a die with a twist channel. In this work the twist extrusion process of AA6082 T6 aluminum samples were carried out to investigate the effects of process parameters like temperature and deformation passes on the microstructure homogeneity. The results indicate that the grain refinement of AA 6082 T6 aluminum alloy leads to inhomogeneous microstructure after one twist extrusion pass. On further extrusion passes the inhomogeneity in the microstructure is found to be disappeared. The homogeneity of the distribution of the deformation was confirmed by micro hardness testing. Finite element modeling has been performed in DEFORM 3D software for determining the homogeneity of the effective strain distribution which agreed well with the experimental values.
Effect of Build Orientation on Mechanical Properties of Rapid Prototyping (Fused Deposition Modelling) Made Acrylonitrile Butadiene Styrene (ABS) Parts
Authors: Ashtankar K. M. , Kuthe A. M. , Rathour Bechu Singh
Published: April 2014

Prototyping is the process of building pre-production models of a product to test various aspects of its design. Fused deposition modeling (FDM) is a process for developing rapid prototype (RP) objects by depositing fused layers of material according to numerically defined cross sectional geometry. The quality of FDM produced parts is significantly affected by various parameters used in the process. This paper aims to study the effect of one such parameter i.e., build orientation, on mechanical properties (mainly tensile and compressive strength) of FDM processed parts. In rapid prototyping (FDM), the orientation of the parts during fabrication is critical as it can affect part strength such as tensile and compressive strength. Specimens are prepared for tensile/compression test as per ASTM standards. It was found that the build orientation of the specimen has more of an impact on strength. The layering build process of rapid prototyping creates a variance in strength depending on the build orientation.

The D695 standard allows for stable compression testing and is used for compression testing. Several geometries are allowed for tension specimens under the D638 standard. We chose the type I specimen as it is the most commonly used and best fit our mechanical testing equipment. From the tensile test result, it is found that when build orientation is increasing from 0° to 90°, ultimate tensile strength decreases. It is maximum at 0° orientation i.e., 15.2 MPa and minimum at 90° orientation i.e., 11.6 MPa. The tensile stress at 0° (i.e. axial direction) is 23.68 % higher than transverse direction (i.e., 90°). From the compressive test results, it is found that, when sample orientation is increasing from 0° to 90°, the ultimate compressive strength decreases. It is maximum at 0° orientation i.e., 26.66 MPa and minimum at 90° orientation i.e., 22.22 MPa. The compressive stress at 0° (i.e. axial direction) is 16.65 % higher than transverse direction (i.e. 90°).
Fatigue Crack Growth Analysis of Mild Steel Plate Welded by Friction Stir Welding
Authors: Pandey K. N. , Gupta Saurabh Kumar
Published: April 2014

Parts and structures are often welded together in different ways, as it is cost and weight effective in comparison to conventional bolted and riveted joints. Steel followed by aluminum alloys, are the most frequently welded metal. Welding results in inhomogeneous and different materials near the joint which may lead to defects. These defects may be the cause of initiation and development of cracks as a result of cyclic loading. In the present work fatigue crack growth rate of a mild steel plate welded by friction stir welding (FSW) has been studied under constant amplitude load with different values of R-ratio. Hardness in the base metal was found to be low in comparison to thermo-mechanically affected and weld nugget zone. Grain size of weld zone was much smaller to base metal and it was the same to heat affected zone and base metal. A C-T specimen with notch at welded and non welded region was tested to get the behavior of Fatigue Crack Growth (FCG) at different zones. It has been found that the fatigue crack growth rate in welded material is lower as compared to base material.
Investigation of Single Phase Models for Predicting Pressure Drop in Nanofluid Flow in Circular Pipes
Authors: Göktepe Sinan , Atalık Kunt , Ertürk Hakan
Published: April 2014

Macroscopic modeling of hydrodynamic behavior of nanofluid flow in a uniformly heated circular pipe is considered. Single-phase models with Brownian and dispersion viscosity models are evaluated by comparing predicted pressure drop and apparent friction factor with experimental and two-phase Eulerian-Eulerian model results from literature. Single-phase models are capable of predicting heat transfer of nanofluids better when dispersion models are used. However, they fail to accurately predict pressure drop when used with standard viscosity models. Two-phase models on the other hand, can accurately predict both thermodynamic and hydrodynamic field at the expense of computational time. A new viscosity model, which is based on dispersion viscosity, is proposed to increase accuracy of single-phase models in predicting hydrodynamic field of nanofluid flow. Results suggest that single-phase dispersion viscosity model is the most accurate single-phase model.
A Novel Energy Flow Model for High-Frequency Vibration Analysis of Beams in a Thermal Environment
Authors: Zhang Wenbo , Chen Hualing , Zhu Danhui , Kong Xiangjie
Published: April 2014

As an exceedingly important issue in vibro-acoustic community, the thermal effects can significantly affect the dynamic behaviors of the structures. The previous studies are mainly performed using the deterministic methods which are infeasible at high frequencies. Energy flow analysis (EFA) is a recent method for high-frequency structural analysis. However, until now the thermal effects are neglected in EFA studies. In this paper, a novel EFA model is developed to predict the high-frequency response of beams in a thermal environment. The wavenumber related with the axial membrane force arising from thermal stresses is considered in the derivation, and then the thermal stress effect is incorporated in the EFA governing equation in terms of effective damping loss factor. In addition, the effect of temperature-dependent material properties is included in the EFA formulation. The proposed EFA model is validated against the modal analysis for a simply supported beam for various frequencies and damping loss factors, and good agreements are found. The results indicate that the thermal effects can affect spatial distributions and levels of the energy density, and the vibrational response of beam increases with temperature.
Characteristics of Flame Bases for V-Gutters Stabilized Premixed Flames
Authors: Gong Fan , Huang Yong
Published: April 2014

The objective of this work is to investigate the flame stabilization mechanism and the impact of the operating conditions on the characteristics of the steady, lean premixed flames. It’s well known that the flame base is very important to the existence of a flame, such as the flame after a V-gutter, which is typically used in ramjet and turbojet or turbofan afterburners and laboratory experiments. We performed two-dimensional simulations of turbulent premixed flames anchored downstream of the heat-conducting V-gutters in a confined passage for kerosene-air combustion. The flame bases are symmetrically located in the shear layers of the recirculation zone immediately after the V-gutter’s trailing edge. The effects of equivalence ratio of inlet mixture, inlet temperature, V-gutter’s thermal conductivity and inlet velocity on the flame base movements are investigated. When the equivalence ratio is raised, the flame base moves upstream slightly and the temperature gradient dT/dx near the flame base increases, so the flame base is strengthened. When the inlet temperature is raised, the flame base moves upstream very slightly, and near the flame base dT/dx increases and dT/dy decreases, so the flame base is strengthened. As the V-gutter’s thermal conductivity increases, the flame base moves downstream, and the temperature gradient dT/dx near the flame base decreases, so the flame base is weakened. When the inlet velocity is raised, the flame base moves upstream, and the convection heat loss with inlet mixture increases, so the flame base is weakened.
Improved Bed Support for Molecular Sieve Dehydrators and Adsorbers
Authors: Thomas Cyrus R. , Cartwright Gordon T. , Norell Robert G. , Diwakar Philip M.
Published: April 2014

Adsorbent beds supported by a support grid traditionally use ceramic rope packing to fill an expansion gap between the vessel shell and the bed support grid. This gap allows the bed support grid to move under thermal expansion. The bed support grid would be constricted from thermal expansion without this gap, causing it to buckle or fail during process heating operations. An unobstructed expansion gap is critical for proper performance of the bed support grid. Preventing molecular sieve granules and fines from filling around the rope packing is crucial to long-term bed support performance in molecular sieve dehydrators. Granules and fines converge into an incompressible mass once they are in the expansion gap, preventing bed support grid expansion upon heating. An annular mesh screen or bolted cover plate typically covers the rope packing as the primary sealing mechanism. Nevertheless, gaps between the vessel shell and the annular mesh screen or bolted cover plate allow fines and granules into the expansion gap. Thermally cycled adsorbent beds, such as molecular sieve dehydrators beds, continue to be plagued by bed support grid damage due to the failure of these traditional sealing methods to prevent migration of fines and granules into the expansion gap.

This paper provides details of an improved adsorbent bed support design that utilizes a superior sealing mechanism which features a fixed hold down ring design. The fixed hold down ring design provides an innovative method of sealing the expansion gap that will effectively eliminate the pathway by which molecular sieve granules and fines enter the expansion gap. This is accomplished by welding the hold down ring directly to the vessel shell above the bed support grid. Additionally, the rope packing is moved from the expansion gap to the gap between the hold down ring and the top of the bed support grid. A relief gap is provided in the bottom of the banding around the periphery of the bed support grid to allow expulsion of fines from the expansion gap. These features provide an expansion gap sealing mechanism that eliminates the chronic failures experienced by conventional bed support grid sealing mechanisms. While the fixed hold down ring design has been specifically developed to resolve the thermal expansion issues associated with molecular sieve dehydrators, it can be used for many types of packed beds requiring modified bed support designs.
A Local Refinement Technique for B-Spline Finite Element Shell Modeling
Authors: Carminelli Antonio , Catania Giuseppe
Published: April 2014

This paper presents a refinement technique for a B2-spline degenerate isoparametric shell finite element model for the analysis of the vibrational behavior of thin and moderately thick-walled structures. Complex structures to be refined are modeled by means of FE B-spline patches assembled with C0 continuity as usual in FE technique. The model refinement was performed by adding, on the domain of the selected patch, a tensorial set of polynomial B-spline functions, defined on local clamped knot vectors, and normalizing all the functions so that the resulting displacement field remain polynomial and continuous overall the domain except on the boundaries of the refined subdomain. A degrees of freedom trasformation, based on the knot-insertion algorthim, is adopted in order to guarantee the C0 continuity of the displacement field on the boundaries of the refined subdomain. Two numerical examples are presented in order to test the proposed approach. The natural frequencies of two structures, computed by means of the proposed modelling technique, are compared with reference results available in the literature or computed by means of reference standard FE models. Strengths and limits of the approach are finally discussed.
Solar Water Heater Design for Houses in Arid Zones
Authors: Vega Ramses , Campbell Hector E. , Ocampo Juan de Dios , Bonilla G. Diego R.
Published: April 2014

This paper shows the simulation and design of a flat plate solar collector system, used to feed hot water to a typical home located in the city of Mexicali, Baja California, México. The system consists of a solar collector, a storage tank, a water pump and accessories and special tools that allow its proper operation. Analyzing the consumption and end use of water in a typical House, a demand profile is established, which combined with the weather information of the region, constitutes the input parameters required for the simulation of the system, which is performed with the software package TRNSYS. Mexicali, due to its location (latitude 32 °, longitude 114 °) and semi-desert condition presents high temperatures in the summer and low in winter, so the design and operation of such systems require special features, not always considered in the conventional ratings. This paper presents methods for simulation and design oriented to optimize the dimensioning and operation of this type of solar heaters in regions with extreme temperature conditions.
Blast Overpressure Measured on a Bare vs. Helmeted Rigid Headform
Authors: Baumer Timothy , Rapo Mark A. , Wong Jessica M. , Powell Brian J. , Juhas Brett D. , Chan Philemon C. , MacKiewicz James F.
Published: April 2014

There is significant concern that blast overpressure can cause mild traumatic brain injury (mTBI). An accurate understanding of the blast flow and overpressure event as well as it’s interaction with the head and helmet system is a necessary first step in establishing loading conditions to the head. It also provides a means for model validation and other predictive capabilities. A custom-designed Blast Overpressure Bust (BOB) containing 22 surface pressure sensors was rigidly mounted in a live-fire blast event. The blast field tests were conducted in an open field using 4 lbs. of cylindrical C4 charges suspended 48″ above the pad. The BOB was mounted to a torso surrogate and positioned 92″ from the hanging charge. The BOB was oriented at blast impact angles of 0 (front-facing), 45, 90, and 180 degrees. The BOB was tested in both bare and helmeted configurations. Data recorded across a bare headform at each angle established a baseline for the pressure trace at each sensor location. Two helmeted cases were investigated: Advanced Combat Helmet (ACH) with the sling suspension system and ACH with Team Wendy pads. Results showed peak pressures on exposed surfaces normal to the blast were ∼1200kPa with side-on pressures of ∼400kPa. The addition of a helmet did not alter the peak normal pressures, but showed slight to moderate increases in pressure beneath the helmet based on the amount of cushioning present. The sling suspension, which leaves an open gap between the head and helmet, resulted in several recorded amplification points beneath the helmet with the peaks reaching ∼800kPa. The Team Wendy pads trials, which effectively fill the gap between the head and helmet, showed amplifications with peaks of ∼500kPa. An additional set of tests was conducted using an ingress barrier positioned between the head and helmet at the brim. Results showed pressures under the helmet that were lower than the bare headform trials. While it was shown that adding a helmet did in fact increase pressures relative to the bare headform case, these amplifications were still far less than the peak pressure exerted on the exposed surfaces of the headform. The data presented herein is the most robust data set to date for pressures exerted on a helmeted headform and is considered applicable to the first 3–5ms of an unconstrained system, during which time motion is minimal.
Improvement on the Analysis of a Finite Element Composites Model
Authors: Atanasov Atanas A. , Wright Thomas J. , Parmigiani John P.
Published: April 2014

Finite element models are increasingly being utilized in composite materials design; thus, an increase in the accuracy of the model analysis and a decrease in computational cost are of paramount importance. This study investigates the effects of a particular add-on, Helius:MCT (Firehole Technologies, Inc.), onto the Abaqus (Dassault Systèmes) software package. Unlike the stand-alone Abaqus software, Helius:MCT embodies a solver, which analyzes the composite structure by separating the fiber and matrix into constituent parts. Treating the fiber and matrix as separate, yet linked entities, allows for a more accurate depiction of the formations of stress and strain within the composite. Furthermore, Helius:MCT utilizes a method called Intelligent Discrete Softening (IDS), a feature not present within Abaqus, to increase solver robustness and convergence probability. An Abaqus finite element (FE) model of a notched, carbon-fiber panel loaded in bending was used in this study. Six different laminate combinations were tested with six variations of the Abaqus model. Three of the variations used Helius:MCT with Abaqus and three the stand-alone Abaqus package. The combinations were composed of either 20 or 40 plies with 10, 30, or 50 percent all zero ply orientations. All the FE analysis results were compared to experimental values for a plate of the exact configuration as that of the model. The most accurate results were obtained using Helius:MCT. The configuration with the greatest accuracy utilizes Helius:MCT and deviates an average of 1.7 percent from experimental values for maximum flexural strength. A single run takes an average of 7 hours to complete. Conversely, the most accurate configuration obtained without the use of Helius:MCT deviates an average of 10 percent from the experimental values and takes over 80 hours to run. Helius: MCT increases the accuracy and decreases the computational costs of the analyses of composite models in Abaqus. The improvements in analyses while using Helius: MCT may allow for a substantial savings in experimental costs and in valuable time.
Data Center Transient Flow Analysis Using Proper Orthogonal Decomposition
Authors: Song Zhihang , Murray Bruce T. , Sammakia Bahgat
Published: April 2014

Real-time analysis of the transient temperature distribution and flow field in a data center is not possible using well-resolved computational fluid dynamics (CFD) simulations. Reduced order models must be used to predict the optimum operating and control conditions to achieve better energy-efficiency. Here, the proper orthogonal decomposition (POD) method is used to model transient behavior of a simple hot aisle/cold aisle data center configuration. Verified CFD simulation results were used to generate snapshots for building a reduced order POD model corresponding to transient variation of the computer room air conditioner (CRAC) operating conditions. Good agreement is achieved between the CFD and reduced order model predictions for the evolving flow structure over a range of CRAC supply operating conditions. Once constructed, the computational time required to obtain the POD results for the transient response is considerably reduced compared to the CFD simulations. The advantages and disadvantages of the POD method for this type of transient behavior are discussed, and recommendations are made on using this type of compact modeling approach to develop a real-time predictive tool for data center design and control to enhance energy efficiency.
Wire-Electric Gyroscope
Authors: Avrutov Vadym
Published: April 2014

The wire-electric gyroscope (WEG) is a new type of the angular rate sensor. The basic principle of the WEG is based on the hypothesis of invariance of the electric current speed for the same wire (coil). It is similar to the Sagnac effect for the speed of light.

The method of angular rate determination is described. The voltage difference between two wire coils with different line coupling can be expressed in applied rotation (angular) rate and velocity of electric current. The scale factor depends on the magnitude of the current, number of the coil turns, the coil’s radius, the cross-section area of the wire and specific (unit) resistance of the wire. WEG can be produced cost-effectively and can be a good choice for low-cost applications.
Experimental Evaluation of Impeller Surface Geometry Effect on the Performance of a Centrifugal Pump
Authors: Das Susanta K. , Ali M. Firoz
Published: April 2014

An experimental investigation is carried out to document the impeller surface geometry effects on the performance of a centrifugal pump. Total three types of impeller surface geometries are investigated in this study. All the experiments were performed on the PumpLabTM, a self contained centrifugal-flow pump demonstrator made by the Turbine Technologies. This system offers a clear visualization of pump performance and operating characteristics including a see-through flow circuit from the point of reservoir pickup to reservoir return. Inlet and outlet valves were manually adjusted for the creation of pump performance curves. The pump’s rpm were varied remotely through computer control to create the system resistance curves. The rpm and flow rates of the pump were varied via installed flow rotameter in order to obtain pressure data. Using the experimental data, the pump performance curves, pump head (ΔH), and system curves were calculated for each impeller surface geometry. The pump’s performance and system curves were then plotted at four different speeds. The results show that the pump performance varies significantly based on impeller surface geometry. The results help to understand how to determine appropriate operating points for different impeller surface geometries by optimizing the pump performance.
The Effect of Bench Arrangements on the Natural Ventilation of a Multispan Greenhouse
Authors: Kruger Sunita , Pretorius Leon
Published: April 2014

In this paper, the influence of various bench arrangements on the microclimate inside a two-span greenhouse is numerically investigated using three-dimensional Computational Fluid Dynamics (CFD) models. Longitudinal and peninsular arrangements are investigated for both leeward and windward opened roof ventilators. The velocity and temperature distributions at plant level (1m) were of particular interest. The research in this paper is an extension of two-dimensional work conducted previously [1]. Results indicate that bench layouts inside the greenhouse have a significant effect on the microclimate at plant level. It was found that vent opening direction (leeward or windward) influences the velocity and temperature distributions at plant level noticeably.

Results also indicated that in general, the leeward facing greenhouses containing either type of bench arrangement exhibit a lower velocity distribution at plant level compared to windward facing greenhouses. The latter type of greenhouses has regions with relatively high velocities at plant level which could cause some concern. The scalar plots indicate that more stagnant areas of low velocity appear for the leeward facing greenhouses. The windward facing greenhouses also display more heterogeneity at plant level as far as temperature is concerned.
An Experimental Study of Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry in a Coil Heat Exchanger
Authors: Kong Minsuk , Alvarado Jorge L. , Languri Ehsan M.
Published: April 2014

The use of microencapsulated phase change material (MPCM) slurry as an enhanced heat transfer fluid is considered to be very promising for saving energy in thermal energy systems. However, little is known how MPCM may exhibit enhanced heat transfer performance in coil heat exchanger. Coil heat exchangers are extensively used in industrial applications including heating, ventilating and air conditioning (HVAC) systems because of their superior heat transfer performance and compactness. In this study, the heat transfer characteristics of MPCM slurry in a coil heat exchanger have been investigated experimentally. Thermal properties of MPCM slurry were measured using a differential scanning calorimeter. Pressure drop, overall heat transfer coefficient and heat transfer effectiveness in a coil heat exchanger were determined by considering different flow rates. It was found that heat transfer characteristics were positively affected by the phase change process of the phase change material in MPCM, even though MPCM exhibit reduced turbulence and increased pressure drop. The overall heat transfer coefficient for MPCM slurry is in the range of 5,000 to 9,000 W/m2-K over a Dean number range from 1,600 to 4,000 (equivalent Reynolds number range of 6,000 to 15,000). The enhancement in heat transfer performance is about 17% when compared to that for water. In addition, durability tests of MPCM slurry were conducted to evaluate the MPCM’s ability to withstand continuous pumping conditions, which is critically important in the implementation of MPCM slurry in industrial applications.
Airflow and Heat Transfer in a Room With a Large Opening
Authors: Park David , Battaglia Francine
Published: April 2014

Natural ventilation is an effective method to save energy required to condition buildings and to improve indoor air quality. Computational fluid dynamics (CFD) software was used to model single-sided buoyancy-driven natural ventilation in a single room with a heater and door. The velocity and temperature profiles at the doorway agreed fairly well with published literature that includes an experimental [1] and numerical study [2]. The CFD models predicted the neutral level with a difference of 1.5 % compared to experimental results. Using solutions at the doorway, heat transfer rates were calculated. More realistic situations were modeled by considering conduction through walls. The heat loss through the wall was measured and the solutions at the doorway were compared to the case with an adiabatic wall condition. The effect of heat transfer coefficients and the ambient temperature on heat loss through wall, room temperature, and airflow in the room were studied.
Pressure Drop in Mini-Scale Coiled Tubing
Authors: Ghobadi M. , Muzychka Y. S.
Published: April 2014

In the present study, laminar, steady state flow in mini-scale coiled tubes was studied experimentally. Three different tube diameters: 1.6 mm, 1.27 mm and 1.016 mm with different lengths of 1 m and 0.5 m were coiled with different radius of curvature to provide data over a wide range of Reynolds numbers from 5 to 2300. A simple empirical model is developed based on the experimental results to predict the pressure drop increase based on Dean number. The results and simple model are also compared to a well-known existing model for circular tubing. The coiled tube lengths used in this study were long enough to consider the flow to be fully developed. The effects of varying curvature and tube length are also studied. The pitch of the coils is restricted to the diameter of the tube to minimize the effect of coiling. Dean number is used instead of Coiled number (modified Dean number) which allows the results to be expanded to spiral and curved tubing.
Performance Assessment of Blends of CO2 With Eco-Friendly Working Fluids for Heat Pump Applications
Authors: Fan Xiaowei , Zhang Xianping , Wei Xinli , Wang Fang , Zhang Xiaojing
Published: April 2014

Since pure CO2 as refrigerant has some disadvantages failing to meet requirements, binary blends of CO2 (or R744) with other eco-friendly working fluids, R290, R1270, R170, RE170 and HFC134a are proposed in this paper to be used for medium temperature heat pump systems. The eco-friendly refrigerant mixtures can reduce the heat rejection pressure as that for pure CO2, and meanwhile suppress the flammability, explosivity as that for pure HCs or RE170. Based on the pinch point of heat transfer, the numerical models of heat pump cycle using CO2-based mixture are developed. With a comprehensive consideration of heating coefficient of performance (COPh), optimum heat rejection pressure, volumetric heating capacity, discharge temperature, the binary mixture CO2/R290 is determined as the most suitable working fluid for the given heat pump application. Compared to pure CO2, the optimum heat rejection pressure of mixture for 95/5, 90/10, 85/15 and 80/20 is decreased by 0.82, 0.94, 1.06 and 1.86MPa respectively for heat sink outlet temperature of 65°C. The experimental testrig is designed and set up for the transcritical heat pump system. The experimental study with different CO2 mass fraction has been carried out, which conducts a study on the variations of heat pump performance, component’s mass fraction and working fluid charge. The experimental results validated the CO2/R290 natural mixture proposed in theory. The experimental results provide useful references on the optimization and improvement of CO2/R290 heat pump testrig.
Interpreting Microscopic Magnetic Resonance Elastography Measurements Using Finite Element Analysis
Authors: Liu Yifei , Yasar Temel , Royston Thomas J.
Published: April 2014

Microscopic Magnetic Resonance Elastography (μMRE) could be useful in estimating the shear stiffness of biological or other samples of small dimension. In this study, a silicon rubber phantom shell with liquid inside of it was measured using μMRE. A parametric simulation study of a simplified axisymmetric shell model was performed in order to interpret the wave propagation and how it is affected by the material parameter values.
Differences Among an Expert and a Non Expert in the Behavior for Chucking in the Lathe
Authors: Sirisuwan Porakoch , Koshino Tetsushi , Narita Chieko , Yoshikawa Takashi
Published: April 2014

The expert worker (85 years old) has worked for 70 years and the non expert (16 years old) has worked 1 year of experience for the lathe processing. The subjects were compared the difference in the waist, the shoulder and the fore arm movement between the two worker while they were chucking on the lathe machine. Determination used the same parts and the same type of lathe machine for investigated. There were 4 main categories that related three stances position alignment and two hands position on the key chuck.

Using the 6 infrared cameras and 2 video cameras captured the position of each marker. All markers position data which synchronization was taken by a motion analysis system (sampling rate: 100Hz). As a results show the balance movement both the waist and the shoulder during the chucking that had significantly greater in the expert worker than the non expert worker.