bluuebunny/crossref_metadata_2025 huggingface dataset:
Design Concept of a CFRP External Trailing Edge for Ailerons
Authors: Gozluklu Burak , Oncul Gulsen , Koseoglu Ugur
Published: April 2014

The most recent civil aircraft dominantly use composite structures such as in the ailerons. However, airworthiness authorities raise concerns about lightning strike damage and repairability if the aileron is made of composite material. Today, aerodynamic profiles of aircraft wings become more complex and challenging for designers who need adequate space to fit conventional “torque box” designs inside the wing surfaces. The aero-surfaces may become too shallow and curved in the trailing edge side of the wing which is highly exposed to edge impact and lightning strike damages. This paper presents a new design concept for Carbon Fiber Reinforced Plastic (CFRP) External Trailing Edge (CETE) structure for the trailing edge of the ailerons. CETE is attached to the main aileron torque box where the main load carrying composite spar, ribs and panels are located. The design objective of the CETE combines various important features such as better strength characteristics against lightning strike and edge impact, and easier repairability with a lighter aileron. This paper also discusses recurring and non-recurring costs and monetary benefits of the new design concept. The CETE concept is as simple as creating a secondary torque box on the trailing edge side of the aileron with two C-section parts; inner and outer parts of CETE. The inner part of CETE provides a secondary spar to the aileron to sustain the main torque box force flows and support the trailing edge panels. The main structural feature of CETE is to form a low loaded zone by its outer part which is located at the outermost region of the trailing edge where mechanical edge impact and lightning strike damages are frequently encountered. It is revealed during the lightning strike tests that, the resulting damages can be catastrophic and located at the trailing edge line where the metallic strips are located. In case of lightning strike damage on the CETE, the aileron is able to carry loads since the flows in the main torque box is minimally disturbed as the inner part of CETE is still intact while the outer part is damaged. Similarly, the damage after edge impact is trapped at the outer section of the CETE where the loads are minimized by CETE design. In case of a larger damage, CETE can be replaced easily instead of replacing the whole aileron which is cost effective in long term although the initial costs seem higher than the conventional designs.
A Study of Spatially-Resolved Non-Equilibrium in Laser-Irradiated Graphene Using Boltzmann Transport Equation
Authors: Vallabhaneni Ajit K. , Loy James , Singh Dhruv , Ruan Xiulin , Murthy Jayathi
Published: April 2014

Raman spectroscopy is typically used to characterize graphene in experiments and also to measure properties like thermal conductivity and optical phonon lifetime. The laser-irradiation processes underlying this measurement technique include coupling between photons, electrons and phonons. Recent experimental studies have shown that e-ph scattering limits the performance of graphene-based electronic devices due to the difference in their timescales of relaxation resulting in various bottleneck effects. Furthermore, recently published thermal conductivity measurements on graphene are sensitive to the laser spot size which strengthens the possibility of non-equilibrium between various phonon groups. These studies point to the need to study the spatially-resolved non-equilibrium between various energy carriers in graphene. In this work, we demonstrate non-equilibrium in the e-ph interactions in graphene by solving the linearized electron and phonon Boltzmann transport equations (BTE) iteratively under steady state conditions. We start by assuming that all the electrons equilibrate rapidly to an elevated temperature under laser-irradiation and they gradually relax by phonon emission and reach a steady state. The electron and phonon BTEs are coupled because the e-ph scattering rate depends on the phonon population while the rate of phonon generation depends on the e-ph scattering rate. We used density-functional theory/density-functional perturbation theory (DFT/DFPT) to calculate the electronic eigen states, phonon frequencies and the e-ph coupling matrix elements. We calculated the rate of energy loss from the hot electrons in terms of the phonon generation rate (PGR) which serve as an input for solving the BTE. Likewise, ph-ph relaxation times are calculated from the anharmonic lattice dynamics (LD)/FGR. Through our work, we obtained the spatially resolved temperature profiles of all the relevant energy carriers throughout the entire domain; these are impossible to obtain through experiments.
Experimental Vehicles Program Aides in Innovative Hands-On Learning Experiences
Authors: Foroudastan Saeed , Thompson Brigette
Published: April 2014

The Experimental Vehicles Program (EVP) was created in 2004 as an umbrella program for five different undergraduate experimental vehicle design teams. These projects consist of the Solar Vehicle, Moonbuggy, Baja SAE, Formula SAE, and Solar Boat. The goal of the EVP is to foster undergraduate student development through hands-on construction of experimental vehicles with the guidance of faculty mentors and partnerships with both national and international industry leaders.

Each EVP project performs a vital function in the professional development of students. The projects provide a forgiving environment in which students can test their classroom knowledge in a real-world setting and learn important skills such as leadership, effective communication, and working as a team member. Furthermore, the students in the EVP develop highly versatile and qualified skill sets that will allow them to fill various positions within the workplace. In the past 90% of EVP graduates have been able to obtain highly regarded national and international positions upon graduation due to their real-world hands-on experience gained throughout their involvement in the EVP. Each year the EVP sponsors up to sixty interdisciplinary students that come together in peer-led teams to combine and expand upon their classroom knowledge in building innovative vehicles. The successes of the MTSU EVP have been recognized by becoming the national model for hands-on engineering education; helping engineering students take classroom knowledge and apply it to real-world situations. Students work in teams to annually design, construct, and test novel vehicle designs for participation in national and international competitions. Due to the competitive nature of each of the events, students must use cutting edge technology and design methods in order to create the best entries possible. Often times this means creating partnerships with industry leaders who help mentor the students from the design conception, the fabrication, through the manufacturing of each vehicle. These partnerships benefit both the students and the companies; students are able to create real-world contacts and gain a working knowledge of the industry that they cannot learn in the classroom. Furthermore, the students are able to use the contacts to garner equipment like solar panels and wheels. Likewise, the companies are able to receive recognition at national and international competition as program sponsors are advertised on the competition vehicles. Moreover the industries are able to build relationships with future employees who have real-world experience and who have become intimately involved with specialized technology such as “green energy”.
Electrode Separation and Operating Orientation: Mechanisms for Maximizing Performance of Cu/Cu2+ Aqueous Thermogalvanic Cells
Authors: Li Hechao , Gunawan Andrey , Phelan Patrick E. , Buttry Daniel A. , Mujica Vladimiro , Taylor Robert A. , Prasher Ravi S.
Published: April 2014

Aqueous thermogalvanic cells have been studied since 1825, and have largely been explored in the past two decades because of their potential to convert low-temperature waste heat to electricity [1, 2]. However, even though these cells have long been known in the electrochemistry community, they have not received much attention from the thermal transport community. This is surprising given that their performance is highly dependent on controlling both thermal and mass (ionic) transport.
Deployment Driving Analysis of Deployable Structure Considering Imperfections
Authors: Guo Hongwei , Liu Rongqiang , Deng Zongquan
Published: April 2014

The strain energy present in the structure due to manufacturing imperfections as initial strains are considered and the method for investigating the effects of strain energy due to manufacturing imperfections is developed. The strain energy restored in the structures produced by the initial strains is optimised to find the worst case set of imperfections. The methods proposed are validated by applying to one freedom truss structure. Then the case of a truss is considered with the worst set of imperfections for strain energy, peak force value and work input determined. The worst case set of imperfections contributes maximum strain energy in the truss with different configuration angles is found and driving force values and work input due to presence of changing strain energy through deployment are determined, the worst case set of imperfections are also found by optimisation of these quantities. The methods developed in this paper can be extended to all planar deployable truss structures.
Simple, Fast, and Low Cost Fabrication Methods of Microchannels for Manipulation of Living Cells
Authors: Alazzam Anas , El-Khasawneh Bashar , Abutayeh Mohammad
Published: April 2014

This work details simple non-cleanroom fabrication techniques to build hermetic microchannels using laboratory available material and equipment. Four different methods are presented for fast fabrication of microchannels at low cost. The microchannels are to be used for the manipulation of living cells. These methods of fabrication of microfluidics devices have previously been used and documented as reactors, fluid mixer, and for fluids transportation and inspection. In this work, all methods were used for manipulation of living cells. Each method, its advantages and disadvantages for this particular application are reported. The microfluidic device built using the first method includes a polymer-based part and a glass substrate with a layer of patterned electrodes. The Polymer-based microchannel is made outside the cleanroom facility using a simple mold made from adhesive tape. Moreover, the fabrication of a non-polymer microchannel made from double-sided tape is described. The microchannel height is about 50 μm while the width varies between 100 μm to a few hundred microns. The third method of fabrication is made by a 3D printer. The master molds for the polymer-based microfluidic device are fabricated by 3D printing of biocompatible material on glass substrate. The fourth method is a simple embossing of a male die in plastic or polymer substrate. A computer numerical control (CNC) machine was used to fabricate the embossing mold in stainless steel, brass, and aluminum. Microchannels were created by stamping the mold in a Cyclic Olefin Copolymer (COC) substrate.
Optimisation of Conjugate Elliptical Cooling Channels With Internal Heat Generation
Authors: Olakoyejo Olabode Thomas , Bello-Ochende Tunde , Meyer Josua Petrus
Published: April 2014

This paper presents the development of the three-dimensional flow architecture of conjugate cooling channels in forced convection with internal heat generation within the solid for an elliptical cooling channel configuration. The main objective was to optimise the configuration in such a way that the peak temperature was minimised subject to the constraint of the fixed global volume of solid material. The cooling fluid was driven through the channels by the pressure difference across the channel.

The structure had three degrees of freedom as design variables: elemental volume, channel hydraulic diameter and channel-to-channel spacing. The shape of the channel is allowed to morph to determine the best configuration that gave the lowest thermal resistance. A gradient-based optimisation algorithm was applied in order to search for the best optimal geometric configuration that improved thermal performance by minimising thermal resistance for a wide range of dimensionless pressure difference. The effect of porosities, applied pressure differences and heat generation rate on the optimal geometry was reported. There are unique optimal design variables for a given pressure difference. Results obtained show that the effects of dimensionless pressure drop on minimum thermal resistance were consistent with those obtained in the open literature.
On Development of a Semi-Mechanistic Wall Boiling Model
Authors: Das Saurish , Punekar Hemant
Published: April 2014

In modern cooling systems the requirement of higher performance demands highest possible heat transfer rates, which can be achieved by controlled nucleate boiling. Boiling based cooling systems are gaining attention in several engineering applications as a potential replacement of conventional single-phase cooling system. Although the controlled nucleate boiling enhances the heat transfer, uncontrolled boiling may lead to Dry Out situation, adversely affecting the cooling performance and may also cause mechanical damage due to high thermal stresses. Designing boiling based cooling systems requires a modeling approach based on detailed fundamental understanding of this complex two-phase heat and mass transfer phenomenon. Such models can help analyze different cooling systems, detect potential design flaws and carry out design optimization.

In the present work a new semi-mechanistic wall boiling model is developed within commercial CFD solver ANSYS FLUENT. A phase change mechanism and wall heat transfer augmentation due to nucleate boiling are implemented in mixture multiphase flow framework. The phase change phenomenon is modeled using mechanistic evaporation-condensation model. Enhancement of wall heat transfer due to nucleate boiling is captured using 1D empirical correlation, modified for 3D CFD environment. A new method is proposed to calculate the local suppression of nucleate boiling based on the flow velocity, and hence this model can be applied to any complex shaped coolant passage. For different wall superheat, the wall heat fluxes predicted by the present model are validated against experimental data, in which 50-50 volume mixture of aqueous ethylene glycol (a typical anti-freeze coolant mixture) is used as working fluid. The validation study is performed in ducts of different sizes and shapes with different inlet velocities, inlet sub-cooling and operating pressures. The results are in good agreement with the experiments. This model is applied to a typical automobile Exhaust Gas Recirculation (EGR) system to study boiling heat transfer phenomenon and the results are presented.
Transition From Low Cycle to High Cycle in Uniaxial Fatigue
Authors: El-Sayed Mohamed E. M.
Published: April 2014

Fatigue is the most critical failure mode of many mechanical component. Therefore, fatigue life assessment under fluctuating loads during component development is essential. The most important requirement for any fatigue life assessment is knowledge of the relationships between stresses, strains, and fatigue life for the material under consideration. These relationships, for any given material, are mostly unique and dependent on its fatigue behavior.

Since the work of Wöhler in the 1850’s, the uniaxial stress versus cycles to fatigue failure, which is known as the S-N curve, is typically utilized for high-cycle fatigue. In general, high cycle fatigue implies linear elastic behavior and causes failure after more than 104 or 105 cycles. However. the transition from low cycle fatigue to high cycle fatigue, which is unique for each material based on its properties, has not been well examined. In this paper, this transition is studied and a material dependent number of cycles for the transition is derived based on the material properties. Some implications of this derivation, on assessing and approximating the crack initiation fatigue life, are also discussed.
Acoustically Augmented Flow and Transport in Supercritical Fluids
Authors: Hasan Nusair , Farouk Bakhtier
Published: April 2014

Acoustically augmented flow and transport in supercritical fluid (CO2) generated by standing wave in a cylindrical enclosure is simulated. The oscillatory flow field in the enclosure is created by the vibration of one of the end walls of the enclosure. A novel application of the acoustically augmented flow in membrane contactors used in supercritical fluid extraction process is demonstrated numerically. The predicted results from the present study can be utilized to enhance the transport mechanisms in these fluids. The geometric parameters and the frequency of the vibrating wall are chosen such that the lowest acoustic mode propagates along the enclosure. A real-fluid model for representing the thermo-physical and transport properties of the supercritical fluid is considered. The fully compressible form of the Navier–Stokes equations is used to model the flow fields and an implicit time-marching scheme is used to solve the equations. The formation of the acoustic field in the enclosure is computed and fully described and the acoustic boundary layer development is predicted. The interaction of the wave field with viscous effects and the formation of streaming structures are revealed by time-averaging the solutions over a given period. Due to diverging thermo-physical properties of supercritical fluid near the critical point, large scale oscillations are generated even for small sound field intensity. The effects of near-critical property variations and system pressure on the formation process of the streaming structures are also investigated.
Thermal and Optical Analysis of a Stacked Photobioreactor Design
Authors: Jain Aadhar , Jung Erica E. , Kalontarov Michael , Erickson David
Published: April 2014

In this work, we present thermal and optical analysis of a stacked photobioreactor design for growth of fuel producing photosynthetic cyanobacteria to achieve significantly higher volume and energy efficiency as compared to traditional photobioreactor designs. Our photobioreactor design incorporates racks of propagating slab waveguides [1], stacked over each other with spacing of a few hundred microns, in order to optimize light, fluid and gas delivery — the three essential ingredients for cyanobacterial growth — to the cyanobacteria growing in between the racks. The use of propagating slab waveguides provides a mechanism for efficient localized delivery of light to the cyanobacteria. However, it is important to analyze the light distribution of such waveguide systems in the photobioreactors to ensure they always remain within the optimal range for the bacteria. Further, the close packing of cyanobacteria in a closed system raises concerns regarding heat entrapment within the reactor, due to the heat produced as waste by the cyanobacteria. Higher temperatures can lead to a significant loss in efficiency in fuel producing and growth centers of the bacteria. Therefore it is important to design the reactor with appropriate thermal conditions for constraining the temperatures within optimal range for the bacteria. Here we attempt to simulate the thermal characteristics of such a system and estimate the temperature map of the system, and use these to dictate the design parameters and characteristics of the photobioreactor.
A Non-Dimensional Analysis to Characterize Thermomagnetic Convection of a Temperature Sensitive Magnetic Fluid in a Flow Loop
Authors: Karimi-Moghaddam Giti , Gould Richard D. , Bhattacharya Subhashish
Published: April 2014

This paper presents results from theoretical and numerical studies of a single-phase, temperature sensitive magnetic fluid operating under steady-state laminar flow conditions in a partially heated thermomagnetic circulation loop under the influence of an external magnetic field (created by a solenoid). A one-dimensional theoretical model has been developed using scaling arguments to characterize thermomagnetic circulation in this loop in terms of the geometric length scales, magnetic fluid properties, and strength of the imposed magnetic field. In parallel to this theoretical analysis, supporting numerical simulations using COMSOL Multiphysics simulation software have been undertaken to obtain data for use in this 1D model. A correlation for the non-dimensional heat transfer (Nusselt number) as a function of the appropriate magnetic Rayleigh number and a correlation for the mass flow rate based on the system’s properties are developed.
Novel Low Cost Powerless MEMS Based Ossicular System
Authors: Ganesan Adarsh Venkataraman , Ramanujam Ramdoss Varun Das , Kishore Kumar Deepan , Swaminathan S.
Published: April 2014

In this paper, the design of MEMS based implantable device is proposed which does not require electrical power for the device functioning. The device is designed to mimic the human ossicular system and is aimed at restoring hearing by implanting it in patients with a damaged or surgically removed ossicular chain. The model involves multiple micro-beams considering the low cost and easy fabrication processes needed to realize the device. The solid mechanical and acoustic analyses for the MEMS based ossicular system are performed in COMSOL Multiphysics. Here, the device specifications are evaluated for the hearing frequency range 20Hz–20000Hz. The device delivers the maximum pressure gain of 10 dB is obtained at 5500 Hz. Further, the total displacement of 14*10−6 mm is obtained at the oval window for sound pressure level of 90 dB, using this device. The maximum weight of the whole system is approximately 33.7 mg and is in relevance with the human ossicular system. The failure analysis is also done to assess the device’s strength at extreme sound pressure of 200 Pa i.e., when nearby jet airplane taking off. The results shown here demonstrate the potential of the MEMS actuators for application to middle-ear audio-prosthesis systems without power supply requirements.
Reliability-Centered Maintenance for Off-Highway Truck: Case Study of Sungun Copper Mine Operation Equipment
Authors: Moniri Morad Amin , Pourgol-Mohammad Mohammad , Sattarvand Javad
Published: April 2014

Surface mining equipment play an important role in capital investments and operating costs of mining industry. Improvement of the equipment performance leads to improvement of operation cost. Efficient operation and maintenance techniques centered on reliability are the methods of choice. Recent researches promote the necessity of utilization of optimal maintenance methods instead of traditional methods. This study aims in application of optimal maintenance methods for reduction of occurrence of sudden failures and equipment break down. Evaluation of reliability-centered maintenance is demonstrated on mining dump trucks operation and maintenance are utilized for Sungun copper mine. The operation data is used to quantify the failure and maintenance profile for each component required for reliability analysis. The modeling is done by using reliability block diagram and solved by Monte Carlo simulation for assessment of the dynamic behavior of the equipment. The reliability of the system is evaluated and importance of each component is estimated. The importance analysis is used to identify the items which have critical impact on reliability and availability of overall equipment for prioritizing the decision for improvements. The reliability importance measure is computed for the components by weighted importance method. Trend analysis is conducted to select proper model for the maintenance profile. Availability estimations demonstrate overall performance of the equipment on its life span.
Driveline Configuration and Terrain Effect on Slippage and Efficiency of a 6×6/6×4 Truck
Authors: Vantsevich Vladimir V. , Murphy Dennis , Bortolin Gianantonio , Farley Blair , Judd Gabriel
Published: April 2014

The power distribution between driving wheels has been shown to have a significant impact on vehicle energy efficiency, but there has only been limited research in this area. As shown in this paper, the wheel power distribution is largely dependent on the power dividing units (PDUs) which split/vector power between the driving wheels. The performance of a particular driveline system will also depend largely on the terrain conditions the vehicle encounters.

This paper presents an analysis of PDU configurations in 6×6/6×4 terrain trucks. The vehicle efficiency is evaluated in a wide variety of typical operating conditions including varying surface types, speeds and accelerations, and slope conditions. An analytical method is presented which can be used to determine the tire circumferential forces and slippages. Finally, an analysis of the effects of the driveline configuration, terrain, and surface type on truck transportation efficiency is presented for three PDU combinations.
Investigation of Vehicle Crash Pulse Severity Using Frontal New Car Assessment Program (NCAP) Test Data
Authors: Park Chung-Kyu , Kim Eun-Young , Kan Cing-Dao (Steve)
Published: April 2014

The severity of vehicle crash pulses of the frontal New Car Assessment Program (NCAP) tests is evaluated by existing metrics. The existing metrics can be categorized into four groups: metrics based on vehicle crash pulse only, metrics based on vehicle crash pulse with assumed occupant response, metrics based on vehicle crash pulse with actual occupant responses, and combined metrics. The paper discusses their evaluation results of frontal NCAP test data and their assessability of the crash pulse severity.
3D Packaging Materials Based on Graphite Nanoplatelet and Aluminum Nitride Nanocomposites
Authors: Lingamneni Srilakshmi , Marconnet Amy M. , Goodson Kenneth E.
Published: April 2014

Nanostructured composites with efficient percolation networks are promising candidates for packaging materials due to their high thermal conductivity. In this study, we investigate the thermal conductivity of composites consisting of a combination of exfoliated graphene nanoplatelet (xGNP) and aluminum nitride (AlN) particles in polyvinylidine fluoride (PVDF) matrix. The surfaces of the AlN particles are treated with silane to reduce the interfacial thermal resistance at particle-matrix boundary. Samples with 50 vol% AlN and 2 vol% xGNP showed an order of magnitude enhancement in thermal conductivity. AlN composites (with and with out xGNP) showed evidence of effective percolation pathways for AlN vol % over ∼40.
A CFD-Based Robust Design of Operating Conditions for an HVAC System
Authors: Arias Luis F. , Bula Silvera Antonio J. , Sanjuan Marco E.
Published: April 2014

HVAC systems are directly related to comfort (human health, productivity, etc.) and energy consumption. Depending on the application and geographical area, they may become a key disruptive and energy starving system. The research discussed in this paper describes a CFD-based approach for robust HVAC system design aimed at reducing variability in the conditioned area by adjusting operating parameters. Since robust design techniques aim at minimum variance (via S/N ratio), the solutions obtained allow the selection of operating parameters leading to more uniform distribution. Three variables were used: air velocity (to control energy transfer from people to the surrounding air), Unit usage (a ratio to consider the air conditioning system inertia compared to air conditioning requirements), and room temperature set point (representing the relation between the machine and the conditions room).

Embedded codes with field functions in the CFD software allow the simulation of a very basic operation strategy, and demonstrate a quasi-dynamic operation for different cooling capacities and air velocity. Results allow allocating operating parameters that lead to a more uniform temperature and relative humidity distributions, therefore, this approach can be adequately combined with statistical design of experiments for better conditions.
Particle Manipulation in Dielectrophoretic Devices
Authors: Gencoglu Aytug , Olney David , La Londe Alexandra , Koppula Karuna , Lapizco-Encinas Blanca H.
Published: April 2014

Microfluidic devices or lab-on-a-chip systems can make a significant impact in many fields where obtaining a rapid response is critical, particularly in analyses involving biological cells. Microfluidics has revolutionized the manner in which many different assessments/processes are carried out, since it offers attractive advantages over traditional bench-scale techniques. Some of the advantages are: small sample and reagent amounts, higher resolution and sensitivity, improved level of integration and automation, lower cost and much shorter processing times. There is a growing interest on the development of techniques that can be used in microfluidics devices. Among these, electrokinetic techniques have shown great potential due to their flexibility. Dielectrophoresis (DEP) is an electrokinetic mechanism that refers to the interaction of a dielectric particle with a spatially non-uniform electric field; this leads to particle movement due to polarization effects. DEP offers great potential since it can be carried out employing DC and AC electric fields, and neutral and charged particles can be manipulated. This work is focused on the use of insulator based DEP (iDEP), a novel dielectrophoretic mode that employs arrays of insulating structures to generate dielectrophoretic forces. Successful microparticle manipulation can be achieved employing iDEP, due to its unique characteristics that allow for great flexibility. In this work, microchannels containing arrays of cylindrical insulating posts were employed to concentrate, sort and separate microparticles. Mathematical modeling with COMSOL® was performed to identify optimal device configuration. Different sets of experiments were carried out employing DC and AC potentials. The results demonstrated that effective and fast particle manipulation is possible by fine tuning dielectrophoretic force and electroosmotic flow.
Performance Evaluation of an MR-Compatible Rotating Anode X-Ray Tube
Authors: Shin Mihye , Lillaney Prasheel , Hinshaw Waldo , Fahrig Rebecca
Published: April 2014

The key technical innovation needed for close proximity hybrid x-ray/MR (XMR) imaging systems is a new rotating anode x-ray tube motor that can operate in the presence of strong magnetic fields. In order for the new motor design to be optimized between conflicting design requirements, we implemented a numerical model for evaluating the dynamics of the motor. The model predicts the amount of produced torque, rotation speed, and time to accelerate based on the Lorentz force law; the motor is accelerated by the interaction between the magnetic moments of the motor wire loops and an external magnetic field. It also includes an empirical model of bearing friction and electromagnetic force from the magnetic field. Our proposed computational model is validated by experiments using several different magnitudes of external magnetic fields, which averagely shows an agreement within 0.5 % error during acceleration. We are using this model to improve the efficiency and performance of future iterations of the x-ray tube motor.
The Automation of Education: How Computers Will Take Over Most Teaching Jobs
Authors: Wasfy Hatem , Wasfy Tamer , Peters Jeanne , Mahfouz Riham
Published: April 2014

The cost of primary, secondary and higher education consumes large percentages of the incomes of families, states and even countries every year. In this paper, we describe how automation can not only greatly reduce the cost of education, but also create new learning paradigms that can increase the effectiveness of that education as compared to traditional classroom learning. Intelligent Tutoring Massively Open Online Courses (ITMOOCs) can seamlessly deliver entire curricula while ensuring that students achieve and maintain the required level of proficiency in every curriculum topic. This is achieved by organizing the curriculum into an ontology of interconnected topic nodes, and assessing the students’ performance after he/she covers every node. The Intelligent Tutoring System (ITS) continuously adapts the course’s delivery to the needs of each student by skipping over topics that the student demonstrates proficiency in, and reviewing topics that are determined to be the cause of assessment failures in downstream course nodes. The ITS can also ensure that students maintain the required level of proficiency in the topics they have learned throughout their educational and professional careers by assigning an expiration time to each curriculum node after which it is reassessed. The system allows each student to set unique educational goals by selecting the individual topics that he/she ultimately wants to learn.
Grasping Analysis of a Bio-Inspired UAV/MAV Perching Mechanism
Authors: Xie Pu , Ma Ou
Published: April 2014

This paper presents the grasping analysis of a bio-inspired UAV/MAV perching mechanism designed at New Mexico State University. The mechanism is composed of a cable-driven leg mechanism and two cable-driven underactuated three-digit feet. The mechanical design was based on the analysis of the anatomy of bird legs and feet. In this paper, the grasping stable condition of the mechanical foot is studied through a quasi-static analysis, which models the relationship between the actuated forces of a digit and the contact forces on each phalanx. Using this model, we can understand the foot’s stable grasping configuration regions. Furthermore, the contact behavior between each foot and the perched object is evaluated using the Hertz contact force model on SimMechanics. The static analysis conclusion and the contact analysis show that this paper has given a fundamental contribution for the designed artificial foot used in developing UAV/MAV perching technology.
Development of a Comprehensive Virtual Training Package for Power Plant Boiler
Authors: Li Fan , Shen Litao , Tang Guangwu , Wu Bin , Zhou Chenn Q. , Heim Joel E.
Published: April 2014

As one of the most important components in coal-fired power station, the operators and maintenance crews of boiler systems receive comprehensive training in unit operation procedures and emergency preparedness. Due to the inaccessibility of the field environment, the majority of the training sessions take place in a classroom using 2D presentation materials such as pictures, drawings, etc. In order to provide a more efficient training program, a software package for power plant boilers was developed through the integration of Computational Fluid Dynamics (CFD) and Virtual Reality (VR) visualization. Using numerical simulation data, the package creates a computer-generated boiler in which the users can observe the actual phenomenon in an easily-understood context. It also allows instructors and trainees to selectively explore various components, operating conditions and scenarios using the built-in Graphic User Interface (GUI). This training package enables people who are unfamiliar with boiler operations to gain better understanding in much less time.
Power Generation With Pressure Retarded Osmosis
Authors: Akram Waqas , Sharqawy Mostafa H.
Published: April 2014

Energy can be generated from two streams of different salt concentration using the osmotic pressure difference. Different methods have been proposed to harvest this energy. Pressure retarded osmosis (PRO) is investigated as a viable method and most promising technology. In PRO process, pure water permeates through a semi permeable membrane from the low hydrostatic pressure stream (feed solution) to the higher hydrostatic pressure stream (draw solution) due to the osmotic pressure difference. This increases the volume flow rate of the pressurized draw stream and energy is obtained by depressurizing the draw stream through a hydro turbine. In this study a one-dimensional computational model is developed to precisely estimate the power production under different operating conditions. Different feed and draw solution concentrations are used to estimate the power production from PRO. The maximum power density (power per unit membrane area), using available membrane characteristics, obtained from seawater–freshwater streams is 2.6 W/m2 and for the disposed brine–seawater streams is 9.1 W/m2. The performance of PRO process is very sensitive to the membrane characteristics in particular to the water permeability and PRO module configuration.
Infrared Image Evaluation on the Burning of Human Skin Caused by Laptop Computer
Authors: He Zhi Zhu , Xue Xu , Deng Zhong Shan , Liu Jing
Published: April 2014

Laptop computer has become increasingly popular over the past decade owing to its portable and high feature benefiting from the high integration chips densely packed inside. However, it also leads to intense heat generation, which will cause thermal discomfort even injury to human body. In fact, there are increasing cases reported regarding low temperature burning. This paper is aimed to demonstrate and evaluate the extreme thermal interaction between laptop computer and human body based on infrared (IR) imaging quantification. The whole surface temperatures of laptop were recorded and analyzed to detect the hot spot, which may cause potential thermal injury to the human skin. The maximum temperature of the exhaust air from the inner laptop was found to be up to 70.4°C for a double-cored laptop with full-loaded operation. This leads to a burning of hand skin even for short exposure time (5 minutes). Such injury would further be exacerbated by prolonged exposure time. In addition, a three dimensional simulation based on Pennes bioheat transfer model was used to investigate the temperature response of skin subject to thermal stimulation from desktop. The present study is expected to be valuable for a wide public concern regarding a better and safer laptop in the near future.
Hydrogen-Air Deflagration in the Presence of Longitudinal Concentration Gradients
Authors: Kudriakov S. , Kuznetsov M. , Studer E. , Grune J.
Published: April 2014

Hydrogen gathering at the top of the containment or reactor building may occur due to an interaction of molten corium and water followed by a severe accident of a nuclear reactor (like TMI, Chernobyl, Fukushima accidents). It accumulates usually in a containment of nuclear reactor as a stratified semi-confined layer of hydrogen-air mixture. Depending on the local concentration and/or presence and activation of mitigation devices, hydrogen may burn following different combustion regimes. Thus, there is a need to estimate the severity of a combustion process under given geometrical configuration, scale, ignition position, and uniformity and composition of combustible mixture. A series of experiments performed at Karlsruhe Institute of Technology (KIT) in the framework of the LACOMECO European project is devoted to flame propagation in an obstructed large scale cylinder vessel with vertical hydrogen concentration gradients. A 33 m3 volume divided in two sub-compartments, lower (21.6 m3) and upper (11.2 m3), separated by round duplex door of 1 m diameter with a metal structure with 6 layers of wooden plates reproduce real geometry of obstructions with a blockage ratio of 0.33–0.43. A sampling probes method is used to control real distribution of hydrogen. Practically linear positive and negative vertical concentration gradients in the range from 4 % to 13 % are created prior to ignition. Pressure sensors (PCB type), ion probes and thermocouples are used in the experiments to monitor dynamics of hydrogen combustion. The process of flame propagation is investigated depending on hydrogen concentration gradient and ignition positions. Critical conditions for flame acceleration-deceleration and quenching of the flame due to hydrogen concentration gradient are the main scopes of the work. The experimental data obtained during the project will be used for safety analysis, risk assessment and as benchmark experiments for CFD numerical codes validation.
Material Compatibility Study for Thermal Energy Storage Containment Structure With Phase Change Material
Authors: Qiu Songgang , Galbraith Ross
Published: April 2014

A desirable feature of concentrated solar power system is to provide electricity in a dispatchable manner during cloud transients and non-daylight hours. A Dish-Stirling concentrating solar power prototype demonstration system was built to incorporate a thermal energy storage (TES) module containing a phase-change material between the solar thermal receiver and the Stirling engine. This paper presents the results of a material compatibility study conducted to determine the suitability of two different metal alloys for use in the construction of the TES module. Key requirements of the materials include strength and corrosion resistance at elevated temperatures, commercial availability, and manufacturability using common fabrication methods. The TES module contains a NaCl/NaF eutectic salt, at temperatures ranging from local ambient to 700°C, where the salt is slightly superheated above its melt temperature. Sample containers made from SS316L and Inconel 625 were fabricated and thoroughly cleaned for compatibility studies based on an extensive literature review. Both the containers and the salt constituents were subjected to a bake-out cycle to drive off moisture, and permit outgassing of contaminants. The containers were filled with salt in a controlled-atmosphere glove box. Filled containers were crimped and sealed by electron-beam welding. The finished samples were placed in a furnace, heated, and held at 750°C. One of each sample container material was removed from the furnace at both 100 and 2500 hours. The containers were cut open to analyze and evaluate the material surface and cross-section. After 100 hours, both SS316L and Inconel 625 exhibited a very small amount of corrosion. The stainless steel suffered a shallow inter-granular grain boundary attack, on the order of 1–2 mm in depth. The Inconel 625 surface formed an oxide complex, which is resistant to dissolution into the molten salt. After 2500 hours, the surface morphology for both materials was largely unchanged, with the corrosion process having switched from an initial localized pattern, to a more uniform pattern. The corrosion depth measured at 2500 hours remained near 1–2 mm, suggesting that the corrosion rate decelerated. Both materials showed promise for compatibility with the chosen salt.
On the Computations of Flow Regimes and Thermal Patterns in Large Scale High Compute Density Data Centers
Authors: Khalil Essam E. , Aziz Mena H.
Published: April 2014

High power dissipation from microprocessors, support chips, memory chips and mass storage has resulted in large overall power dissipation from computer systems. The deployment of these computer systems in large numbers and in very dense configurations in a data center had resulted in very high power densities at room level. These computer systems are deployed in a rack. A standard 2-meter high rack can accommodate an equivalent of 34 thin desktop systems. If the maximum power dissipation from each system is 300W, a single rack in a data center can be assumed to dissipate 7.2 KW. A data center can have hundreds of these 7.2 KW racks. Due to such high heat loads, designing the air conditioning system in a data center using simple energy balance is no longer adequate. Moreover, the data center design cannot rely on intuitive design of air distribution. It is necessary to model the airflow and temperature distribution in a data center. In this paper, a computational fluid dynamics model of a prototype data center is presented to make the case for such modeling. The present paper is devoted to investigate the air flow patterns, temperatures and relative humidity in large compute density data centers. Computational fluid dynamics software is utilized to simulate the data center flow pattern. The paper used the simulation techniques as embedded in the commercially available CFD code (FLUENT 6.2). The CFD modelling techniques solved the continuity, momentum and energy conservation equations in addition to standard k–ε model equations for turbulence closure.
Thermal Transport at Carbon Nanotube-Graphene Junction
Authors: Park Jungkyu , Prakash Vikas
Published: April 2014

We present results of a molecular dynamics study to analyze thermal transport at carbon nanotube (CNT)-graphene junctions comprising of single layer graphene and (6,6) armchair single-walled carbon nanotubes (SWCNTs). Two possible junction types with different degrees of sp2 and sp3 hybridization are investigated. Reverse Non-Equilibrium Molecular Dynamics (RNEMD) simulations are used to obtain the thermal conductivities in these hybrid structures and also analyze the role of the interfacial thermal resistance at the SWCNT-graphene junctions in limiting thermal transport. The highest out-of-plane (along the SWCNT axis) thermal conductivity of a hybrid structure with a CNT-graphene junction was obtained to be 158.9±1.2 W/m-K when the junction comprised of only sp2 bonds with an interpillar distance of 15 nm and a pillar height of 200 nm. The highest in-plane thermal conductivity (along the graphene layer plane) with two CNT-graphene junctions was found to be 392.2±9.9 W/m-K with junctions comprising of only sp2 bonds and an interpillar distance of 20 nm and a pillar height of 25 nm. In all cases, junctions with mixed sp2/sp3 hybridization showed higher interfacial thermal resistance than junctions with pure sp2 bonds, and the thermal interfacial resistance was found to be weakly dependent on the length of CNT and the interpillar distance. The highest interfacial thermal resistance measured across the CNT-graphene junction was 3.10×10−6 K-cm2/W when the junction comprised of mixed sp2/sp3 bonds and with 15 nm interpillar distance and 50 nm pillar height.
Integrated Wastewater Recovery and Reuse via Waste Heat Utilization
Authors: Chudnovsky Yaroslav , Kozlov Aleksandr
Published: April 2014

A variety of industrial wastewater recovery technologies for different areas and applications has been developed over the years, including primarily thermal and membrane processes. The main thermal processes include atmospheric distillation, distillation with mechanical vapor compression, vacuum distillation, multi-stage flash distillation, multi-effect distillation with thermal vapor compression, etc. [1,2]. The membrane processes contain reverse osmosis, electrodialysis, and nanofiltration. The multi-stage flash distillation and reverse osmosis processes dominate in most applications. Wastewater recovery and re-use technologies have been expanding rapidly in recent decades. The market is also driven by the falling costs of wastewater recovery, which are due to the technological advances in the process. The costs of clean water produced by wastewater recovery process dropped considerably over the years as a result of reductions in price of equipment, reductions in power consumption and advances in system design and operating experiences. In this work state-of-the art and innovative wastewater recovery/re-use technologies are estimated and compared in their features and cost respects. The new technology is discussed that allows increasing in energy efficiency of the wastewater recycling and reduce electricity consumption associated with conventional methods. Successful development and implementation of the technology for food processing applications will provide large energy and water savings to the industry. These savings are tied to an energy efficiency increase and reduction in pumping power for process water supply. The ability to integrate waste heat recovery with wastewater reuse also leads to product cost reduction opportunities for producers.