bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and Comparison of Experimental Results Both of Wind Tunnel Test and Running Test for HEMU-400X Pantograph
Authors: Lee Yeongbin , Paik Jin-sung , Kwak Minho , Yoo Jinsun , Kim Kyu Hong , Lee Dongho , Kwon Hyeok-Bin
Published: July 2013

In this paper, experimental results both of wind tunnel test and running test for HEMU-400X pantograph were compared and were analyzed. In wind tunnel test, 1/4scale pantograph for HEMU-400X which is being developed for the maximum speed of 400km/h in Korea were tested to investigate the vertical lift force of pantograph at the operational speed of 250, 270, 300, 330, 360 and 400km/h using lift estimation from 1/4 scaled model results. In the running test of train, the contacting force of pantograph was measured to current operational speed of 300km/h. Finally, the results of vertical lift force of pantograph in wind tunnel test and contacting force for the running test were compared to analyze the aerodynamic characteristics of the pantograph for HEMU-400X.
SEPTA PTC Communications Systems
Authors: Monastero Michael J. , Weiss Stephen , Pretorius Francois , Burke Sheldon
Published: July 2013

The Southeastern Pennsylvania Transportation Authority (SEPTA), the 6th largest transit system in the U.S. by passenger miles travelled, is among the nation’s commuter rail agencies in the process of implementing Positive Train Control (PTC) that must be completed by the Federal mandate deadline of December, 2015.

SEPTA will be implementing ACSES (Advanced Civil Speed Enforcement System), originally introduced on Amtrak on portions of the Northeast Corridor (NEC), as an overlay system applied upon a base of Automatic Train Control (ATC) cab signaling. Every SEPTA train travels on Amtrak territory as a “tenant” at some time during its daily run, and consequently ACSES is required for interoperable PTC operation on Amtrak. The application of ACSES on SEPTA territory will be complemented by a simultaneous upgrading of existing and new ATC on SEPTA.

Among the many decisions faced by the SEPTA PTC design team, the PTC communications systems design has proven to be challenging. The communications systems include digital radios, communications managers, ground based networks, office systems, network management and network security. Some elements have been designed from the ground up, with few commercial “off the shelf” components available to meet the design requirements. Moreover, SEPTA had limited 220 MHz spectrum available for a PTC radio network in a relatively compact geographic area of dense commuter rail traffic. The radio network and communications managers, in particular, are breaking new ground for U.S. commuter rail operations with adoption of Time Division Multiple Access (TDMA) digital packet radios operating in the 220 MHz spectrum, under the control of communications managers.

This paper will present an overview of SEPTA’s PTC communications systems, and focus upon the design process, subsequent field testing, and the rationale behind key decisions reached by the design team, that led to the selection of the technologies and network topologies that will be utilized in meeting the implementation of PTC at SEPTA.
Salt Corrosion Prevention Measure for SHINKANSEN Viaducts
Authors: Yamaguchi Masaki , Shimizu Kenji
Published: July 2013

“SHINKANSEN” is the network of high speed railway lines in Japan.

The ITOIGAWA region of western Japan is the area where the HOKURIKU SHINKANSEN is in closest proximity to the Japan Sea coast. In this area, degradation and repair of many structures occur due to salt damage. Japan has never constructed SHINKANSEN structures requiring 100-year-durability in such a corrosive area. Therefore, severe salt corrosion prevention measures are adopted in this area, compared with normal structures. In this paper, we will first show the deterioration of structures due to salt damage. We will then introduce salt corrosion prevention measures adopted for structures in the ITOIGAWA region. As premises for not getting rusted for reinforcing bar in the concrete until after 100 years, the special concrete mix and use of cement were determined. On the other hand, salt corrosion prevention measures for the structures were adopted using three methods. These were adopted for each section taking into consideration the issue of cost. At the end, quality control during construction is stated.
RTCONTACT: An Efficient Wheel-Rail Contact Algorithm for Real-Time Dynamic Simulations
Authors: Bosso N. , Gugliotta A. , Zampieri N.
Published: July 2013

Determination of contact forces exchanged between wheel and rail is one of the most important topics in railway dynamics. Recent studies are oriented to improve the existing contact methods in terms of computational efficiency on one side and on the other side to develop more complex and precise representation of the contact problem. This work shows some new results of the contact code developed at Politecnico di Torino identified as RTCONTACT; this code, which is an improvement of the CONPOL algorithm, is the result of long term activities, early versions were used in conjunction with MBS codes or in Matlab® environment to simulate vehicle behaviour. The code has been improved also using experimental tests performed on a scaled roller-rig. More recently the contact model was improved in order to obtain a higher computational efficiency that is a required for the use inside of a Real Time process. Benefit of a Real Time contact algorithm is the possibility to use complex simulation models in diagnostic or control systems in order to improve their performances. This work shows several comparisons of the RTCONTACT contact code respect commercial codes, standards and benchmark results.
The Use of Packet-Switched vs. Circuit-Switched Networks for Data Transport in a Public Transit Environment
Authors: Fitzmaurice Michael
Published: July 2013

Ethernet has become the de-facto standard for providing data transport not just throughout the internet but for numerous private and industrial networks. Prior to Ethernet’s dominance, circuit-switched networks (or time-division multiplexed networks like SONET) were popular choices for applications that required flexible and reliable data transport. Over the past 10 years, packet-switched networks in general (and Ethernet in particular) have usurped the role formerly played by these circuit-switched networks but is this a good development given that not all applications that require data transport are created equal? In the public transit environment, data transport networks are often used for mission critical applications that directly support revenue service such as signaling and train control and are increasingly based upon packet-switched networks. This paper will explore the current trend of using packet-switched as opposed to circuit-switched networks in the context of providing data transport for rail-based public transit agencies and, after examining five case studies, draw conclusions that are relevant for public transit agencies.
Effects of Embankment Scenario on the Aerodynamic Coefficients of a Railway Vehicle Through Wind Tunnel Tests
Authors: Cheli F. , Fiocco F. , Giappino S. , Tomasini G.
Published: July 2013

Embankment is a typical layout for rail infrastructures and train aerodynamic coefficients in this scenario are necessary for the analysis of cross wind effects. Nevertheless wind tunnel tests on scale models with the embankment scenario presents difficulties in the reproduction of the boundary conditions, that is the simulation of a “pseudo-infinite” full scale embankment. To investigate this topic we have performed wind tunnel tests on an ETR500 1:45 scale model using a finite length embankment, with and without an upwind nose and a “pseudo-infinite” embankment, reproduced by the extension wall-to-wall of the scenario. The paper presents the tests results in terms of aerodynamic force coefficients and surface pressures. Guidelines for wind tunnel tests on embankment are than discussed.
National Train Bus and its Diagnostics
Authors: Lasak Petr , Zemlicka Michal , Lieskovsky Ales , Marek Stanislav , Myslivec Ivo
Published: July 2013

Modern trains must provide a certain level of control, diagnostic and information services. To satisfy it, rail vehicles have to be equipped with devices communicating over special networks. Nowadays, commonly used networks are described in the IEC 61375 and the UIC 556 standards.

The National Train Bus (NTB) is a train network standard created in parallel with IEC 61375. The main difference is that it can operate on lower speed than it is common in rail environment, while still keeping the time-critical character of communication in mind.

Therefore, it is suitable for rail vehicles, including refurbished ones, to avoid high requirements on installed hardware and software. It was successfully tested and it is being used in many different DMUs operated by Czech and Finnish Railways.

This article describes the main communication and diagnostic principles of NTB and shows the differences between the IEC 61375 solutions and NTB.
Laser-Based Measurement of Over Dimensional Freight Rail Shipments
Authors: Schlake Bryan W. , Daniel Brian S. , Voorheis Ron
Published: July 2013

In pursuit of improved safety, Norfolk Southern Corp. (NS) has partnered with Amberg Technologies to explore the potential benefits of a laser-based measurement system for measuring over dimensional freight rail shipments. Shipments that do not fall within a standard geometric envelope, denoted as Plate B in the Association of American Railroads (AAR) Open Top Loading Rules [1], are considered to be over dimensional, or High-Wide Loads (HWLs). Extending beyond the limits of the Plate B diagram, these loads are not permitted in unrestricted interchange service. Instead, they must be measured both at points of origin and at interchange points. For US Class I Railroads, the de facto method for measuring HWLs requires mechanical personnel to either climb on the equipment or use a ladder and physically measure the overall height and width of the load. Using a tape measure, plumb line, and 6-foot level, car inspectors, or carmen, must often make multiple measurements to determine the height or width of a critical point on the load. The summation of these measurements can be subject to mathematical human error. In addition to the inherent limitations with regards to accuracy and efficiency, this method of measurement presents considerable safety challenges.

The objective of the project was to develop a portable, cost-effective and accurate measurement system to improve the day-to-day operational process of measuring HWLs and reduce human exposure to railyard hazards. Norfolk Southern worked closely with Amberg Technologies to provide a clear overview of the current measuring methods, requirements, challenges and risks associated with HWLs. Amberg then developed a prototype system (with patent pending) and successful tests have been completed at both a point of origin for NS shipments and at a location where HWLs are received at interchange. The measuring system consists of a tripod mounted laser, a specially designed track reference target (TRT) and software designed specifically for HWL measurements. The system allows car inspectors to take measurements from a safe, strategic location away from the car. As a result, this system eliminates the need to climb on the equipment or a ladder and greatly reduces the amount of time spent on and around live tracks. In addition, initial tests indicate that this technology reduces the labor time required to measure HWLs by as much as one half while improving measurement accuracy. These tests have demonstrated that a laser-based system has the potential to greatly improve the safety, efficiency and accuracy associated with measuring HWLs.
Sustainability of Natural and Cultural Assets in an Urban Environment: A Responsible Approach to Tunneling Constructions
Authors: Belkaya Huseyin , Ozmen Haluk
Published: July 2013

The Marmaray Project provides a full upgrading of the existing commuter rail system in Istanbul connecting Europe to Asia with an immersed tunnel under the Istanbul Strait, and providing an uninterrupted modern high-capacity new railway system. The Marmaray Project, with a peak hour capacity of 75,000 passengers per direction, is urgently needed to ease traffic congestion in a metropolis of 15 million inhabitants. The immersed tunnel under the Istanbul Strait is the deepest built so far, and the Istanbul region will most likely experience a seismic event of up to M7.5 during the lifetime of the Project. Besides these technical challenges, the Project involves environmental challenges due to the outstanding and unique natural and historical assets of Istanbul. Preservation and rescuing of Historical Heritage forms a particular focus point. The challenge for Istanbul is to help develop a modern city whilst protecting its natural environment and historical heritage.
Axle Generator for Freight Car Electric Systems
Authors: Nagode C. , Ahmadian M. , Taheri S.
Published: July 2013

As the desire to implement more electronic devices such as measuring or tracking systems on freight cars grows, having a source of power to rely on becomes an issue. An innovative and practical solution to keep batteries charged is presented. Placed on the car axle, the system uses the rotation of the wheelset as input motion. Friction wheels roll on the outside of the car axle, transferring the power to a generator through a set of gears. Designed to be easily implemented, the system can be installed or removed conveniently and quickly.

The first laboratory tests showed that the system is capable of producing more than 100 Watts of power at a simulated 55 mph. A speed of only 20 mph is necessary to generate voltages high enough to charge a 12-Volt battery. A second series of tests proves that connecting the generator differently (in a “Y” configuration) improves the output voltages by about 70%, generating three times more power and requiring only 10mph to reach the voltage necessary for charging a common lead-acid battery.
Driver Behavior Analysis Using Vehicle Safety Systems’ Field Operational Test Data
Authors: Ngamdung Tashi , daSilva Marco
Published: July 2013

The United States Department of Transportation’s (US DOT) Research and Innovative Technology Administration’s John A. Volpe National Transportation Systems Center (Volpe Center), under the direction of the US DOT Federal Railroad Administration (FRA) Office of Research and Development (R&D), is leveraging the National Highway Traffic Safety Administration (NHTSA) sponsored Integrated Vehicle Based Safety System (IVBSS) Light Vehicle (LV) Field Operational Test (FOT) to collect and analyze drivers’ activities at or on approach to highway-rail grade crossings. Grade crossings in Michigan, Indiana, and Ohio were cross-referenced with IVBSS LV FOT research vehicle location to identify the time research vehicles were present at a crossing. The IVBSS LV FOT included 108 participants that took a total of 22,656 trips. Of the 22,656 total trips, 3,137 trips included a total of 4,215 grade crossing events.

The analysis was based of drivers’ activities at the 4,215 grade crossing events. Both looking behavior and distractions did not significantly differ based on gender. However when analyzed per age-group, younger drivers (between 20 to 30 years old) were significantly more likely to be distracted than middle-aged drivers (between 40 to 50 years old) or older drivers (between 60 to 70 years old). For looking behavior, the data revealed that older drivers are more likely to look at least one way at or on approach to highway-rail crossing (43.8 percent exhibited this behavior) than either middle-aged drivers (35.0 percent exhibited this behavior) or younger drivers (25.3 percent exhibited this behavior).
Measuring Concrete Crosstie Rail Seat Pressure Distribution With Matrix Based Tactile Surface Sensors
Authors: Rapp Christopher T. , Edwards J. Riley , Dersch Marcus S. , Barkan Christopher P. L. , Mediavilla Jose , Wilson Brent M.
Published: July 2013

A sustained increase in gross rail loads and cumulative freight tonnages, as well as increased interest in high and higher-speed passenger rail development in the United States, is placing an increasing demand on railway infrastructure. According to a railway industry survey conducted by the University of Illinois at Urbana-Champaign (UIUC), rail seat deterioration (RSD) was identified as one of the primary factors limiting concrete crosstie service life. Therefore, it can be seen that there is a need for infrastructure components with increased strength, durability, and ability to maintain the tighter geometric track tolerances under demanding loading conditions. Researchers have hypothesized that localized crushing of the concrete rail seat is one of five potential mechanisms that contribute to RSD. Therefore, to better understand this mechanism, UIUC is utilizing a matrix based tactile surface sensor (MBTSS) to quantify the forces acting at the interface between the bottom of the rail pad and the concrete tie rail seat. The MBTSS measures the forces and distribution of pressure as a load is applied to the rail seat. Preliminary laboratory testing has shown that higher modulus rail pads distribute forces poorer than lower modulus rail pads, leading to localized areas with high contact pressure and a higher probability of crushing. Testing has also shown that as the lateral/vertical (L/V) force ratio increases, the pressure on the field side of the rail seat also increases, possibly accelerating RSD. The objective of future field testing is to be able to validate the assumptions made from this preliminary laboratory data. Data collected and analyzed throughout this research project will provide valuable insight into developing future concrete crosstie and fastening system component designs that meet the operational and loading demands of high speed rail and joint passenger/freight corridors.
Mobile WiMAX Performance, Applications, and Deployment Considerations for North America’s Freight Railroad Industry
Authors: Shrestha Pradhumna Lal , Hempel Michael , Sharif Hamid , Mehrvarzi Shahram
Published: July 2013

With the anticipation of Positive Train Control (PTC), as well as many other advanced rail applications, a modern end-to-end communication network infrastructure has become an essential requirement for the North American railroad industry. One focus area is on wireless technologies for track-side and yard deployments. Among the available broadband technologies, Mobile WiMAX has emerged as the most favorable solution for deployment in such an environment. It provides high throughput, large coverage and the support for many diverse applications, with attractive features like seamless handover, Quality-of-Service (QoS), the recovery from packet loss through mechanisms like Hybrid-Automatic Repeat reQuest (H-ARQ) and vehicular mobility support.

In this paper, we provide an overview of our research endeavors in evaluating Mobile WiMAX. We discuss our design and implementation of Mobile WiMAX computer model based on Network Simulator 2 (NS-2), which can simulate sophisticated scenarios frequently encountered by the railcars. We describe our experience in setting up our WiMAX testbeds in Ashland, NE and Logan, IA, utilizing the infrastructure from BNSF and UP in those locations, respectively. Since our test beds serve as prototypes, similar design principles can be applied for the eventual large-scale nationwide network deployment by the railroad industry. Furthermore, we present laboratory and field test results that clearly validate our design principles and demonstrates the advantages of Mobile WiMAX deployments for railroad operations.
Developing a Framework to Address Performance and Security Protocol Concerns in Identity Management for Interoperable Positive Train Control Systems
Authors: Bandara Damindra S. , Bondi André B. , Goel Rajni , Pilapitiya Nalin , Wijesekera Duminda
Published: July 2013

The timely delivery, correctness, integrity, and authenticity of signaling messages sent to trains running under Positive Train Control (PTC) are necessary to ensure safe train operations and to prevent the insertion of malicious messages or the alteration of authentic ones in transit in train control traffic. Mutual authentication of trains and messages must occur when a train enters a zone under PTC from dark territory, when a train moves from one railroad company’s network to another’s, when a train communicates with a Wayside Interface Unit, or when it communicates with the head of a work crew on the railroad line. We describe concerns about performance requirements and protocol security related to this process, and develop a framework for defining use cases, performance models, and secure methods to meet them.
Improving Casting Integrity Through the Use of Simulation Software and Advanced Inspection Methods
Authors: Sowden Ike , Currier George
Published: July 2013

Casting integrity is essential for providing components that meet design criteria for strength and fatigue performance. As the leading method of manufacturing metal components in the rail industry, maintaining quality and consistency is a continuing struggle for car owners and builders. Internal shrinkage and voids due to insufficient metal flow are issues commonly found in casting molds which are not designed or utilized properly. Using casting simulation software, potential issues can be discovered upfront and robust mold designs can be created that offer a tolerance for the variance or variations in casting conditions that are present in the real world.

Strato, Inc. has extensively studied the effectiveness of these simulations in foundries through advanced inspection techniques. It is evident that casting simulations can not only locate, but also explain shrinkage cavities and voids through material density plots and inspection of directional solidification via critical fraction solid time plots. This approach is markedly more efficient than the traditional trial and error method, where mold makers rely on experience and destructive testing to develop acceptable mold designs.

With recent advances in simulation software, the labor and time-intensive ways of the past have been supplanted by a more scientific approach to the problem. Understanding the fluid dynamics and thermodynamics of the casting process provides a means of creating a stable, repeatable final product. This higher quality final product can be delivered faster to the customer and at a far less expense by identifying problem areas prior to the tooling and sampling processes. Case-studies explored by the Strato engineering team suggest that using this software decreases the fallout rate.
The Role of Railroads in Multimodal Woody Biomass Transportation in Michigan
Authors: Lautala Pasi , Pouryousef Hamed , Handler Robert , Chartier Stephen
Published: July 2013

Minimizing transportation costs is essential in the forest products industry, as the relatively low value and high weight of the products causes transportation to account for exceptionally high portion of the overall cost. The forest products such as logs, chips, and residues (woody biomass) are one of the major business sources in Michigan especially in Upper Peninsula of Michigan. Currently, truck transportation is used for the great majority of the trips, but it is believed that a more cost-efficient transportation chain might be achieved through use of multimodal approach by trucks and rail and in some cases water transportation.

This paper presents the three alternative transportation supply chain models for woody biomass transportation; 1) single mode, 2) multimodal and 3) intermediate storage. The paper uses data from three recent studies to describe the forest products transportation in the upper mid-west, including the typical distances for movements and the breakdown of cost elements for each alternative. It will discuss the potential benefits of increased use of rail as part of the transportation chain and address the perceived drawbacks and challenges caused by the shift. It will also present cost-gradient maps developed to highlight the capability of rail to expand the economical radius for obtaining feedstock and demonstrate how increasing fuel prices change the balance toward multimodal transportation. Finally, the paper will highlight the potential for gained efficiency in log truck operations through increased use of rail.
Train Power Converter Switching Surge Impact Studies
Authors: Ku Bih-Yuan , Ko Ming-Jan , Liu Jen-Sen
Published: July 2013

In this paper we address the issue of switching surges generated by power converters onboard a train impacting other trains and wayside equipment. We present two cases from both ac and a dc electrified railroad systems in Taiwan to manifest the seriousness of these surges if not properly mitigated. We conclude that this issue must be taken into consideration when commissioning new train power converters in a railroad system. Also corresponding standards need to be developed to ensure compatibility of new power converters with the existing trains and wayside equipment.
Comparing Geometry Correction Capability of AGGS and TGCS Tamper Control Systems on Amtrak’s Northeast Corridor
Authors: Wnek Jonathan M. , Chrismer Steven M.
Published: July 2013

One of Amtrak’s high-speed continuous action tampers has been fitted with TGCS (Track Geometry Control System) tamper control software to compare the quality and durability of geometry correction it provides with that of the existing tamper control system, AGGS. Comparison between the two systems is made by reviewing measured track geometry data from before and after maintenance, and by reviewing changes in ride quality accelerations of instrumented passenger cars. Although the testing program is in its early stages and the number of test locations so far is limited, results to date are very much in favor of TGCS.
Theoretical Considerations and Applications of Nonlinear Guided Waves for Nondestructive Assessment of Structures: A Railroad Track Case-Study
Authors: Nucera C. , Di Scalea F. Lanza , Fateh M. , Carr G.
Published: July 2013

Nonlinear guided wave propagation is a field that has received considerable attention in the last few decades mainly because the use of nonlinear features of elastic waves appears very promising for Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM) of several structures. Recent findings show that the characteristics of nonlinear wave propagation significantly enhance both sensitivity and efficiency compared to more traditional NDE/SHM approaches. Nonlinear features (in particular higher harmonics generation) may be very efficient indicators of some structural states that are difficult or even impossible to be detected by other means. The complex mathematical framework governing these phenomena is the main obstacle to the widespread diffusion of these techniques; in the past investigations pertaining to higher harmonic generation have been limited in applicability to structures with simple geometries where an analytical solution for the waveguide modes was available. In the present paper the classical Semi-Analytical Finite Element (SAFE) formulation (necessary to analyze complex geometries) is extended to the nonlinear regime and is implemented into a commercial code, exploiting all its capabilities. The resulting tool is able to efficiently study the nonlinear elastic wave propagation and the internal resonance conditions in a broad spectrum of structural systems. After a brief description of the theoretical background and the proposed algorithm, a railroad track is considered as case-study. The nonlinear analysis reveals optimal combinations of primary and secondary modes and also pinpoint “false positives” where internal resonance does not occur. It is emphasized how the knowledge of these ideal combinations of modes is pivotal for the application of any NDE/SHM technique relying on nonlinear features of elastic wave propagation; in light of this fact the formulation proposed in the present work appears very promising.
On the ERTMS/ETCS Level 2 Degraded Mode: Colored Petri Net Model for Discrete Point Positioning System
Authors: Dhahbi S. , Abbas-Turki A. , El Moudni A.
Published: July 2013

The main objective of the signalling system ERTMS/ETCS is to permit safe and interoperable operation of European railway traffic [6]. Safe traffic requires precise data about the position and the movement of trains. This paper focuses on the train positioning system of ERTMS/ETCS level 2. This system is based on the combination of the odometer and the electronic position markers (balises) that are detected by the trains during its travel. This paper describes how this positioning system works and derives the different causes of its failures. An elementary Coloured Petri Net model of the positioning system is presented. This model is validated through simulations. For safety reasons, the model shows that the train has to stop if it misses a balise or if there is a high risk of odometer errors. This confirms the recommendations of the Subset 026-3.
A Microscopic Locomotive Emission Model Study Based on Power Balance Framework
Authors: Hui Hu
Published: July 2013

A microscopic locomotive emission model based on power balance framework is deeply studied in this paper. First, on the basis of summarizing characteristics of diesel locomotive exhausts, relevant factors affecting emissions such as technology, operation and environment are discussed. Second, from perspective of emission production mechanism a systematic framework based on power balance is proposed and analyzed. Then, some specific formulas calculating energy consumption, fuel use, emissions are given in detail on the basis of train operation mode.. Finally, a simulation case is illustrated to evaluate the methods schematically compared to emission standard in China.
Optimizing Skip Stop Service in Passenger Rail Transportation
Authors: Sogin Samuel L. , Caughron Brennan M. , Chadwick Samantha G.
Published: July 2013

Two-track passenger rail lines typically operate with all trains serving every station. Without additional infrastructure, transit planners have limited options to improve travel times. Service could be improved by operating a skip-stop service where trains only serve a subset of all the station stops. A skip-stop pattern must find an optimal balance between faster passenger travel times and lower service frequencies at each station. A mixed integer formulation is proposed to analyze this tradeoff; however, the mixed integer formulation could not scale efficiently to analyze a large scale commuter line. A genetic algorithm is presented to search the solution space incorporating a larger problem scope and complexity. In a case study of a Midwest commuter line, overall passenger travel time could be decreased by 9.5%. Both analyses can give insights to transit operators on how to improve their service to their customers and increase ridership.
A High-Performance Solution-Processable Hybrid Thermoelectric Material
Authors: Yee Shannon K. , Coates Nelson , Urban Jeffrey J. , Majumdar Arun , Segalman Rachel A.
Published: July 2013

Thermoelectrics have the potential to become an alternative power source for distributed electrical generation as they could provide co-generation anywhere thermal gradients exist. More recent material and manufacturing advances have further suggested that thermoelectrics could independently generate primary power [1]. However, due to cost, manufacturability, abundance, and material performance, the full potential of thermoelectrics has yet to be realized. In the last decade, thermoelectric material improvements have largely been realized by diminishing thermal conductivities via nanostructuring without sacrificing performance in electrical transport [2]. An alternative approach is to decouple and optimize the electrical conductivity and thermopower using the unique properties of organic-inorganic interfaces [3]. One method to do this could leverage the electrical properties of a conducting polymer in combination with the thermoelectric proprieties of an inorganic semiconductor in such a way that the interaction between these materials breaks mixture theory. Furthermore, it is expected that the thermal conductivity of this hybrid material would be low due to the inherent vibration mode mismatch between polymers and inorganics. Previously, we have developed a method for producing a solution-processable thermoelectric material suitable for thin film applications using a hybrid polymer-inorganic systems consisting of crystalline tellurium nanowires coated in a thin layer of a conducting polymer (i.e., PEDOT:PSS) [4]. The interfacial properties could be realized in bulk and films demonstrate enhanced transport properties beyond those of either component. More recently, we have been able to significantly improve the thermoelectric properties of these materials by morphological and chemical modifications. Here, we present our methodology and experimental transport properties of this new material where the thermal conductivity, electrical conductivity, and thermopower predictably vary as a function of composition, size, and the structural conformation caused by the solvent. The mechanism for these improvements is currently under investigation, but experimental results suggest that transport is dominated by interfacial phenomena. Furthermore, experiments suggest that both the electrical conductivity and thermopower can be independently increased without appreciably increasing the thermal conductivity. These improvements, in concert with the solution processable nature of this material, make it ideal for new thermoelectric applications.
Electrokinetic Power Generation by Forward Osmosis
Authors: Hon Kar Cherng , Yang Chun , Low Seow Chay
Published: July 2013

In this paper, an innovative direct power generation technique from salinity gradient is proposed and demonstrated. The basis of this novel method encompasses forward osmosis (FO) and electrokinetic (EK) principles. Tapping the concentration difference between seawater and river fresh water, forward osmosis (FO) is utilized to allow for spontaneously transporting water across a semi-permeable membrane. The flow of water is then directed towards array of microchannels in the form of porous medium where power is produced from the electrokinetical streaming potential. Experimentally, NaCl solution and DI water were used to model as seawater and fresh river water, respectively. Both glass and polymer based porous media and commercial flat sheet FO membranes were employed herein. Results show power density could reach the order of 101W/m2. Having features of ease of fabrication, simple configuration and no mechanical moving parts, this method provides a feasible mean to harvest enormous energy from salinity gradient. Thus the proposed technique could contribute greatly to renewable energy and towards sustainable future.
Enhanced Thermal Conductivity of Water With Surfactant Encapsulated and Individualized Single-Walled Carbon Nanotube Dispersions
Authors: Harish S. , Ishikawa Kei , Einarsson Erik , Inoue Taiki , Chiashi Shohei , Shiomi Junichiro , Maruyama Shigeo
Published: July 2013

In the present work, the effective thermal conductivity of single walled carbon nanotube dispersions in water was investigated experimentally. Single-walled carbon nanotubes (SWNTs) were synthesized using the alcohol catalytic chemical vapour deposition method. The diameter distribution of the SWNTs was determined using resonance Raman spectroscopy. Sodium deoxycholate (SDC) was used as the surfactant to prepare the nanofluid dispersions. Photoluminescence excitation spectroscopy (PLE) reveals that majority of the nanotubes were highly individualized when SDC was employed as the surfactant. The nanofluid dispersions were further characterized using transmission electron microscopy, atomic force microscopy (AFM) and optical absorption spectroscopy (OAS). Thermal conductivity measurements were carried out using a transient hot wire technique. Nanotube loading of up to 0.3 vol% was used. Thermal conductivity enhancement was found to be dependent on nanotube volume fraction and temperature. At room temperature the thermal conductivity enhancement was found to be non-linear and a maximum enhancement of 13.8% was measured at 0.3 vol% loading. Effective thermal conductivity was increased to 51% at 333 K when the nanotube loading is 0.3 vol%. Classical macroscopic models fail to predict the measured thermal conductivity enhancement precisely. The possible mechanism for the enhancement observed is attributed to the percolation of nanotubes to form a three-dimensional structure. Indirect effects of Brownian motion may assist the formation of percolating networks at higher temperature thereby leading to further enhancements at higher temperature.
Phonon Transport in Carbon Nanotube Aerogels
Authors: Hu Lin , Chen Haibin , Coloyan Gabriella , McGaughey Alan J. H.
Published: July 2013

A carbon nanotube (CNT) aerogel is a low-density network of small diameter single-walled CNTs held together by van del Waals forces. Due to the excellent mechanical, thermal, and electrical properties of individual CNTs and the potential to fuse the junctions in the aerogel, CNT aerogels are candidates for ultralight structural media, radiation detectors, thermal insulators, and electrical conductors. Using molecular dynamics (MD) simulation, we predict the thermal conductance of the junction formed between two CNTs. To access the range of conditions present in the aerogel, we test the effects of different boundary conditions, the CNT lengths, and the rotational angle of the CNTs. A 3-D network model of the aerogel is built that will be used with the MD predictions to estimate the aerogel thermal conductivity.
Experimental Investigation of Two Phase Flow in Micro-Sized Circular Tubes
Authors: Lim Y. S. , Yu Simon C. M.
Published: July 2013

Single phase and two phase flow characteristics in micro-sized glass tubes with i.d. (inner diameter) of 300 and 500 μm have been examined experimentally. Single phase pressure drop measurements are found generally in good agreement with Poiseulle flow theory. Transitional flow is found to start earlier at Reynolds number about 1600 as compared to the onset of transitional flow at Reynolds number of 2300 for macro-scale tubes. In addition, these glass tubes are employed for the investigation of adiabatic two phase flow characteristic by introducing gas phase via a stainless steel tube inserted at the center of the glass tube. Real time flow visualization obtained under the same flow condition are analyzed by both cross sectional void fraction (one dimensional drift flux model) and volumetric void fraction (image processing method). The analysis shows that the void fraction estimated by drift flux model (DFM) agrees with homogeneous correlation (α = β) and Armand correlation (α = 0.833β). However image processing method seems to reveal that the slip ratio for the two phase flow is more significant and that the void fraction results are clustering between slip ratio of 3 and 7. Additionally, two phase frictional pressure losses are compared with the convention correlation for macro-sized tube (Lockhart-Martinelli model). It is found that measurements of the two phase frictional pressure drop can serve as a flow map to predict the flow patterns when the flow in the channel is not transparent.
Thermal Performance of an Open Loop Pulsating Heat Pipe With Ferrofluid (Magnetic Nano-Fluid)
Authors: Taslimifar Mehdi , Mohammadi Maziar , Saidi Mohammad Hassan , Afshin Hossein , Shafii Mohammad Behshad , Kazemzadeh Hannani Siamak
Published: July 2013

In the present research an experimental investigation is performed to explore the effects of working fluid, heat input, ferrofluid concentration, magnets location, and inclination angle on the thermal performance of an Open Loop Pulsating Heat Pipe (OLPHP). Obtained results show that using ferrofluid can improve the thermal performance and applying a magnetic field on the water based ferrofluid decreases the thermal resistance. It shows that at an inclination angle of the OLPHP to be zero, the thermal performance of the present OLPHP reduces. Best heat transfer capability was achieved at 67.5 degree relative to horizontal axis for all of working fluids. Variation of the magnets location leads to a different thermal resistance in the OLPHP charged with ferrofluid.
Thermoelectric Characterization of Ge2Sb2Te5 Films for Phase-Change Memory
Authors: Lee Jaeho , Kodama Takashi , Won Yoonjin , Asheghi Mehdi , Goodson Kenneth E.
Published: July 2013

While thermoelectric effects can strongly influence the performance of phase-change memory (PCM), the thermoelectric properties of phase-change materials for thin film structure have received little attention. This work reports the temperature and phase dependent Seebeck coefficient of 25 nm and 125 nm thick Ge2Sb2Te5 (GST) films. The Seebeck coefficient of crystalline GST films varies strongly with film thickness, due to changes in crystallization effect and grain boundary scattering. Electrothermal simulations demonstrate that the measured thermoelectric properties can strongly influence the temperature distribution and figures of merit for PCM devices. These data will facilitate cell optimization of novel phase-change memories.
Temperature-Dependent Thermal and Thermoelectric Properties of Single-Walled Carbon Nanotube Aerogels
Authors: Zhang Kejia , Yadav Abhishek , Kim Kyu Hun , Oh Youngseok , Islam Mohammad F. , Uher Ctirad , Pipe Kevin P.
Published: July 2013

Aerogels are ultraporous solids that have found a number of uses due to their very low density. Recently, aerogels based on single-walled carbon nanotubes (SWCNTs) have been fabricated and show significant potential for battery, supercapacitor, sensor, and thermal applications due to the electrical, mechanical, and thermal properties of SWCNTs as well as their capacity for functionalization. In this work we report temperature-dependent (100–300 K) measurements of thermal conductivity, electrical conductivity, and Seebeck coefficient for SWCNT aerogels synthesized through a critical point drying technique. Two types of aerogels are considered: an as-grown SWCNT aerogel and one that is coated with multiple graphitic layers (Gr-SWCNT) leading to significantly improved mechanical properties. Thermal conductivity and electrical conductivity were found to be significantly higher for SWCNT aerogels than for other aerogels, even though they have a much smaller density. Gr-SWCNT aerogels were found to have lower thermal conductivities than as-grown samples.
Three-Dimensional Analytical Model for Pressure-Driven Cross-Stream Diffusion in Microchannels With Arbitrary Aspect Ratios
Authors: Song Hongjun , Wang Yi , Pant Kapil
Published: July 2013

The utilization of cross-stream diffusion under laminar flow for precise analyte handling plays a critical role in microfluidic biochemical assays such as sample preparation, concentration gradient generation, and molecular interactions. The non-uniform velocity profile along the cross-section of a rectangular microchannel with arbitrary aspect ratio under pressure-driven flow results in unique, heterogeneous species transport including Taylor dispersion and position-dependent diffusion scaling law. Although numerical methods such as finite difference method, finite element method, the method of lines and lattice Boltzmann (LB) method have been used for quantitative study of the phenomena, they inherently suffer from several limitations, such as difficulty to provide direct, physical insight into the underlying transport mechanism and prohibitive computational cost to suppress the artificial numerical diffusion (ND). To address these issues, several analytical models have been proposed, which share several common assumptions such as large aspect ratio and neglecting depth-wise diffusion due to the non-uniform axial velocity in the 3D convection-diffusion equation, markedly limiting their utility. In this paper, we present a three dimensional (3D) analytical model to investigate the diffusion of analyte between two cross streams in rectangular microchannels with arbitrary aspect ratios under pressure-driven flow. The 3D convection-diffusion equation is solved in a Fourier series form using a double integral transformation method and associated eigensystem calculation. Therefore, the model for the first time is capable of capturing the non-uniform transport rate (i.e., the ‘butterfly effect’) and the position-dependent scaling-law of diffusion (1/3-power at the channel wall and 1/2-pwer at the half-depth plane) through an analytical solution. Our analytical model was extensively validated against both experimental and numerical data in terms of the concentration distribution, diffusion scaling law and the mixing efficiency with excellent agreement (the relative error is much less than 0.5% in various benchmark test cases.) Quantitative comparison between our analytical model and other prior analytical models in extensive parameter space was also performed, which convincingly demonstrates that our model accommodates much broader transport regimes and more practical microfluidic applications.
Digital Microfluidic Device for Hotspot Cooling in ICS Using Electrowetting on Dielectric
Authors: Bindiganavale Govindraj Shreyas , Moon Hyejin , You Seung Mun , Amaya Miguel
Published: July 2013

To meet the increasing demand of efficient cooling performance in small scale, this paper presents a digital microfluidics (DMF) microscale liquid cooling system which works on the principle of electrowetting on dielectric (EWOD). In EWOD DMF, fluids are handled drop-wise by external electric field.

When the dispensed liquid droplet arrives at the hotspot by EWOD DMF operation, it picks up heat and removes heat when it leaves. This process can be repeated for a series of droplets by using a completely automated LabVIEW controlled system connected to the PCB package. With the help of indium tin oxide (ITO) thin film resistance temperature detectors (RTD) and pre-calibrated temperature coefficient of resistance (TCR) data, the temperatures of the hotspot before and after the residence of liquid droplet (i.e., cooling) can be recorded for different frequencies (dwelling time period of droplet on the hotspot) of the drop motion and varying heater power. Future work will involve RTD resistance data collection to plot the heat flux and the temperature difference (before and after cooling) for different frequencies of drop motion.

Although the primary focus is to study single phase cooling, the DI water drop will experience considerable evaporation resulting in higher cooling performance. The single phase cooling studies will help in establishing a robust platform for future two-phase cooling analysis in which evaporation effects will be considered.
Intracellular Ice Formation (IIF) and Plasma Membrane Integrity During Freeze-Thaw Repetitions in a Micro-Thickness Medium Layer
Authors: Li Yuhui , Wang Hao
Published: July 2013

Intracellular ice formation (IIF) plays a critical role in cryobiology, though the underlying biophysical mechanisms are still not completely explicable. In this work, a directional freezing scheme integrated with microlayer cell culture was employed to allow directional freezing as well as high-power microscopic observation of IIF in a single optical plane. The initiation of IIF and its spreading within the cells were well observed. The fluorescent reagents were employed to label the cell membrane and nucleus. It was found that the cell membrane could keep intact even though the cell had undergone IIF, and the intact cells could have IIF again in the next freezing cycle until their membranes were finally disrupted. The results shed light on the relationship between IIF and the integrity of cell membrane.