bluuebunny/crossref_metadata_2025 huggingface dataset:
Brake Specific Fuel Consumption and Power Advantages for a Turbocharged Two-Stroke Direct-Injected Engine
Authors: Findlay Andrew , Harker Nicholas , Den Braven Karen R.
Published: August 2009

A turbocharged gasoline direct injection (GDI) two-stroke engine for use in snowmobile applications has been developed. Applying GDI to a two-stroke engine significantly reduces emissions of unburned hydrocarbons and improves fuel economy by reducing or eliminating the short-circuiting of fuel that occurs in conventional carbureted two-stroke engines. Performance is a high priority for recreational enthusiasts. Direct-injection also allows for further improvement in power and efficiency through the use of exhaust turbocharging. With the scavenging and fuel flows separated, turbocharging can efficiently increase the mass of air delivered to the engine. This increases specific power output and decreases specific fuel consumption. Results show that the brake specific fuel consumption (BSFC) of the turbocharged engine was improved over the entire engine operating range compared to the naturally aspirated engine. It was seen that a mild boost pressure of 5 psi could increase power by 40 brake-horsepower (bhp) at the peak engine speed and over 60 bhp at lower engine speeds. The results show that turbocharged direct injection is a viable option for high performance two-stroke engines.
Experimental Study of a Two-Phase Heat Transport Device Driven by Electrohydrodynamic Conduction Pumping
Authors: Pearson Matthew R. , Seyed-Yagoobi Jamal
Published: August 2009

Heat pipes are well-known as simple and effective heat transport devices, utilizing two-phase flow and the capillary phenomenon to remove heat. However, the generation of capillary pressure requires a wicking structure and the overall heat transport capacity of the heat pipe is generally limited by the amount of capillary pressure generation that the wicking structure can achieve. Therefore, to increase the heat transport capacity, the capillary phenomenon must be either augmented or replaced by some other pumping technique. Electro-hydrodynamic (EHD) conduction pumping has been demonstrated as an effective method for pumping liquid films by using DC electric fields and a dielectric working fluid. Beyond increased pumping capacity, EHD conduction pumping offers other advantages over capillary pumping, such as active control of the pumping capacity via the intensity of the applied electric field. This experimental study demonstrates the prospects of a macro-scale two-phase heat transport device that is driven by EHD conduction pumping. Various liquid film thicknesses are considered. In each case, the performance of the EHD-driven heat transport device at various electric field intensities is compared to the capabilities of the same device under gravity alone. The effect of tilt on the device is also considered.
A Multilayer Process for the Connection of Fine-Pitch-Devices on Molded Interconnect Devices (MIDs)
Authors: Leneke Thomas , Hirsch Soeren , Schmidt Bertram
Published: August 2009

A key factor for the propagation of technological applications is the miniaturization of respective components, subsystems and overall systems. To meet future requirements in such size decreasing environments the packaging and mounting technology needs new impulses. 3D-MIDs (three-dimensional molded interconnect devices) exhibit a high potential for smart packages and assemblies. A three-dimensional shaped circuit carrier allows the integration of various functional features (e.g. electrical connections, housing, thermal management, mechanical support). This combination makes a further system shrinking possible. Yet, the mounting of high-density area-array fine-pitch packaged semiconductors (BGA, CSP, MCM) or bare dies to 3D-MIDs is problematic. The lack of a three-dimensional multilayer technology makes a collision free escape routing for devices with a high I/O count difficult. Therefore a new 3D-MID multilayer process was developed and combined with an established 3D-MID metallization process. A demonstrator with three metallization layers, capable, e.g., for flip-chip mounting of area-array packages, is fabricated. The multilayer structure of the demonstrator is investigated with respect to the mechanical and electrical behavior.
Effects of Process Parameters on Shrinkage Uniformity and Birefringence of Injection-Compression Molded Parts
Authors: Huang Han-Xiong , Yang Can , Li Kun
Published: August 2009

Injection-compression molding (ICM) with greater flexibility than conventional injection molding (CIM) can produce parts with better quality. In this work, polystyrene (PS) parts were molded by ICM technology. The effects of seven dominating process parameters, including mold temperature, melt temperature, compression force, compression distance, compression speed, compression time, and delay time, on both shrinkage uniformity and birefringence of PS parts were investigated. The results showed that compression force is the most important parameter for part shrinkage uniformity. The position with a lowest shrinkage moved towards the gate with increased compression distance. There is a remarkable increase in birefringence with larger compression forces. There is certain relationship between shrinkage uniformity and birefringence results.
Performance Evaluation of HIC Component Testing Device With a Flexible Neck Using Computational Model
Authors: Thorbole Chandrashekhar K. , Lankarani Hamid M.
Published: August 2009

The Head Injury Criteria (HIC) compliance is an important aircraft interior furnishing certification. This certification confirms the compliance of the HIC requirement as per 14CFR 23.562 [1] and 14 CFR 25.562 [2]. Full scale crash sled tests are widely used destructive test method to show the required compliance of head injury criteria. This method is costly, time consuming and non repeatable. Factors such as sled pulse shape, belt slack, seating posture of the dummy results change in the dynamic conditions which ultimately affect the HIC value. This poses a significant challenge and high costs to the manufactures to show the compliance of aircraft interior furnishings for the certification process. These factors compel the development of alternative method to certify the cabin furnishings for HIC compliance without consuming aircraft seats, which is more repeatable and non time consuming. The laboratory HIC component tester is the device developed to duplicate the full scale crash HIC result. This device is capable to produce similar dynamic conditions upon impact with the test article resulting duplication of the full scale crash test result. The current model is developed with the rigid neck of polycarbonate unlike the flexible neck of Hybrid II part 572 ATD (Anthropomorphic Test Dummy). This study investigates the scope of improvement in dynamic characteristic of the HCTD (HIC Component Testing Device) with flexible neck. Flexible neck performance is evaluated using validated computational model of the HCTD. The computational model is used to simulate the correlation between the HCTD with rigid neck and HCTD with flexible neck with FSST (Full Scale Sled Test). The result demonstrates that HTCD correlates well with the FSST when flexible neck is used and provides conservative results with rigid neck.
Experimental Measurement of the Ski Boot Stiffness in Sagittal and Frontal Planes
Authors: Rossi Stefano , Cappa Paolo , Patane` Fabrizio
Published: August 2009

In the present paper a novel device and a post-processing procedure are proposed to evaluate the mechanical behavior of a ski boot stiffness. The originality of the methodology consists in the following elements: (1) the stiffness is evaluated not only in plantar/dorsi flexion direction, but also in inversion/eversion one; (2) the loads are applied automatically and along programmable paths; and (3) the stiffness is calculated as the full jacobian of the applied moments. The testing apparatus is a XY Cartesian robot equipped with two linear potentiometers, a 6-axes load cell and a cardanic/prismatic joint for resembling the behavior of the knee complex. The experiments consisted of a cyclic horizontal displacement applied to the knee, with a period of 1 s in variable directions, and the measurement of the consequent boot reaction force. The chosen directions of load were straight lines passing through the neutral position of the boot; the lines changed their angle in respect to the ski when three displacement cycles were completed. The range of variation of flexion and inversion angles were 7° and 5°, respectively. The device showed a high level of repeatability, in comparison with the level of accuracy typical for the biomechanical evaluations, that permitted estimation of the stiffness of the tested boot as a 3rd order polynomial. The results achieved could be useful for the estimation of the reaction forces corresponding to ankle joint angles measurable during the skiing.
Electrowetting of Nanofluids Containing Silver Nanoparticles
Authors: Laroque Leonard , Jain Abhishek , Wang Tie , Chinnathambi Karthik , Ramanath Ganapathiraman , Borca Tasciuc Theodorian
Published: August 2009

Application of voltage across a liquid-dielectric interface resulting in the change of fluid contact angle is known as electrowetting on dielectric (EWOD) effect [1]. EWOD actuation is one of the most preferred techniques to move liquid at microscale due to relatively low voltages, low currents and power consumption requirements, and the absence of electrolysis. Our recent work has shown that nanofluids containing semiconductor nanoparticles exhibit a very strong EWOD effect [2, 3]. In particular, in the tested voltage range of 0 to 60 V, nanofluids loaded with molecularly-capped bismuth telluride nanoparticles show enhanced stability and increased actuation range of contact angle change. Developing a fundamental understanding of the role of nanostructure inclusions in controlling and potentially enhancing the EWOD effect would pave the way for the efficient use of EWOD with nanofluids in a wide range or microfluidic applications. Here we extend the studies on the EWOD behavior of nanofluids, to a system containing noble metal nano particles. In this abstract we report the preliminary results of the electro-wetting studies on nanofluids containing silver nano particles.
Experimental Nonlinear Vibration Analysis of Piezoelectrically Actuated Microcantilevers
Authors: Mahmoodi S. Nima , Jalili Nader
Published: August 2009

With daily growth of using microcantilevers in microelectromechanical systems, comprehensive analysis on their dynamical behavior is necessary since they are mostly utilized as the main sensing device. In this paper, the out-of-plane vibrations of the piezoelectrically actuated microcantilever are experimentally investigated. The microcantilever is covered with a piezoelectric layer on its top surface through which it can be excited by applying the voltage to the piezoelectric actuator. The nonlinear frequency response of the microcantilever is studied and shift in natural frequency due to nonlinearity is examined. By observing the subharmonics of the fundamental frequencies at 2X and 3X, it is experimentally shown that there exist cubic and quadratic nonlinearities in the microcantilever. A mathematical model based on these experimental tests is then proposed and verified. The out-of-plane measurements provide the ability to observe both transversal and torsional modes. In addition, the modes in which the microcantilever acts like a plate are observed.
Numerical Simulation of Thermal Stress for a Liquid-Cooled Exhaust Manifold
Authors: Fu Dong , Huang Dui , Juma Ahmed , Schreiber Curtis M. , Wang Xiuling , Zhou Chenn Q.
Published: August 2009

Liquid-cooled exhaust manifolds are widely used in turbocharged diesel engines. The large temperature gradient in the overall manifold will cause remarkable thermal stress. The objective of the project is to modify the current design for preventing the high thermal stress and extending the life span of the manifold. To achieve the objective, the combination between Computational Fluid Dynamics (CFD) with Finite Element (FE) is introduced. Firstly, CFD analysis is conducted to obtain temperature distribution, providing boundary conditions of the thermal load on the FE mesh. Afterward, FE analysis is carried out to determine the thermal stress. The interpolation of the temperature data from CFD to FE is done by Binary Space Partitioning (BSP) tree algorithm. To accurately quantify the thermal stress, nonlinear material behavior is considered. The computational results are compared with that of Number of Transfer Units (NTU) method, and are further verified with industrial experiment data. All these comparisons indicate that present investigation reasonably predicts the thermal stress behavior. Based on the results, recommendations are given to optimize the manifold design.
Modeling of Thermal Hydraulics Aspects of Combined Top and Bottom Water Reflood Experiment PARAMETER-SF2 Using SOCRAT 2.1 Code
Authors: Vasiliev Alexander D.
Published: August 2009

The PARAMETER-SF2 test conditions simulated a severe LOCA (Loss of Coolant Accident) nuclear power plant sequence in which the overheated up to 1700÷2300K core would be reflooded from the top and the bottom in occasion of ECCS (Emergency Core Cooling System) recovery. The test was successfully conducted at the NPO “LUTCH”, Podolsk, Russia, in April 3, 2007 and was the second of two experiments to be performed in the frame of ISTC 3194 Project. PARAMETER facility of NPO “LUTCH”, Podolsk, is designed for studies of the VVER fuel assemblies behavior under conditions simulating design basis, beyond design basis and severe accidents. After the maximum cladding temperature of 1750K was reached in the bundle during PARAMETER-SF2 test, the top flooding (flow rate 40g/s) was begun and later approximately in 30 s the bottom flooding (flow rate 100g/s) was initiated. Two-phase (water and steam) flow determined the fuel assembly cooling conditions. The thermal hydraulic and SFD (Severe Fuel Damage) best estimate numerical complex SOCRAT 2.1 was used for the calculation of PARAMETER-SF2 experiment. Thermal hydraulics in PARAMETER-SF2 experiment played very important role and its adequate modeling is important for the thermal analysis. The results obtained by the complex SOCRAT 2.1 were compared with experimental data concerning different aspects of thermal hydraulics behavior including convective and radiative heat transfer in the bundle and the CCFL (counter-current flooding limitation) phenomenon during the reflood. The temperature experimental data were found to be in a good agreement with calculated results. It is indicative of the adequacy of modeling the complicated thermo-hydraulic behavior in the PARAMETER-SF2 test.
Effect of Radial Curvature in Rockets on Film Cooling Adiabatic Effectiveness and Jet Width
Authors: McCall Jonathan F. , Branam Richard D.
Published: August 2009

A computational study was performed to determine the effects of radial curvature on film cooling adiabatic effectiveness. This curvature is typically encountered in modern rocket combustion sections. Jet width and spanwise-averaged adiabatic effectiveness are observed to slightly decrease as radius of curvature decreases. This decrease impacts hole spacing requirements for adequate thermal management inside rocket combustors. Compound injection aggravates the effect so that the increased adiabatic efficiency usually associated is diminished due to a cradling effect of the radial curvature. The result is an increase in adia-batic efficiency immediately downstream of the hole and a decrease after 2 hole diameters, when compared to the flat plate. Furthermore, increasing the momentum ratio past 1 diminishes the effect of radial curvature on adiabatic effectiveness. Quantified understanding of radial curvature effects allow one to use flat plate effectiveness correlations for sizing of film cooling systems in internal flow situations, like rocket combustion chambers. This research is funded and supported by AFRL Propulsion Directorate.
Integral Transform Solutions for Diffusion in Heterogeneous Media
Authors: Naveira Carolina P. , Fudym Olivier , Cotta Renato M. , Orlande Helcio R. B.
Published: August 2009

The Generalized Integral Transform Technique is employed in the hybrid numerical-analytical solution of heat diffusion problems in heterogeneous media. The GITT is utilized to handle the associated eigenvalue problem with aribitrarily space variable coefficients, defining an eigenfunction expansion in terms of a Sturm-Liouville problem of known solution. The formal solution is first applied in solving an example of space variable thermophysical properties found in heat transfer analysis of functionally graded materials (FGM), validated by the exact solution obtained through classical integral transforms in the specific situation of exponentially varying coefficients. Then, it is challenged in handling a double-layered system with abrupt variation of properties, and critically compared against the exact solution obtained by the classical integral transform method with the adequate discontinuous multi-region eigenvalue problem. The convergence behavior of the proposed expansions is then critically inspected and numerical results are presented to demonstrate the applicability of the general approach.
Dynamic and Quasi-Static Grade Crossing Collision Tests
Authors: Mu¨hlanger Michelle , Llana Patricia , Tyrell David
Published: August 2009

To support the development of a proposed rule [1], a full-scale dynamic test and two full-scale quasi-static tests have been performed on the posts of a state-of-the-art (SOA) end frame. These tests were designed to evaluate the dynamic and quasi-static methods for demonstrating energy absorption of the collision and corner posts. The tests focused on the collision and corner posts individually because of their critical positions in protecting the operator and passengers in a collision where only the superstructure, not the underframe, is loaded. There are many examples of collisions where only the superstructure is loaded. For the dynamic test, a 14,000-lb cart impacted a standing cab car at a speed of 18.7 mph. The cart had a rigid striking surface in the shape of a coil mounted on the leading end that concentrated the impact load on the collision post. During the dynamic test the collision post deformed approximately 7.5 inches, and absorbed approximately 137,000 ft-lbs of energy. The SOA collision post was successful in preserving space for the operators and the passengers. For the quasi-static test of the collision post, the collision post was loaded in the same location and with the same fixture as the dynamic test. The post absorbed approximately 110,000 ft-lb of energy in 10 inches of permanent, longitudinal deformation. For the quasi-static test of the corner post, the post was loaded at the same height as the collision post, with the same fixture. The corner post absorbed 136,000 ft-lb of energy in 10 inches of permanent, longitudinal deformation. The series of tests was designed to compare the dynamic and quasi-static methods for measuring collision energy absorption during structural deformation as a measure of crashworthiness. When properly implemented, either a dynamic or quasi-static test can demonstrate the crashworthiness of an end frame.
A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 3—Applications to Predict Railroad Vehicle-Track Interaction Performance
Authors: Zaazaa Khaled E. , Martin Timothy P. , Whitten Brian , Marquis Brian , Curtis Erik , El-Sibaie Magdy , Tajaddini Ali
Published: August 2009

The dynamic response of a railroad vehicle traveling at speed over track deviations can be predicted by using multibody simulation codes. In this case, the solution of nonlinear equations of motion and extensive calculations based on the suspension characteristics of the vehicle are required. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to simulate contact forces between wheel and rail. In this paper, several applications to examine such issues as critical speed, curving performance at varying cant deficiencies, and wheel load equalization are presented to demonstrate the use of the multibody code. In addition, the application of the multibody code can be extended to train a neural network system. Neural network technology has the ability to learn relationships between a mechanical system input and output, and, once learned, give quick outputs for given input. The neural network can be combined with the use of a nonlinear multibody code to predict the performance of multiple railroad vehicle types in real time. In this paper, this system is briefly presented to shed light on the optimum use of the multibody code to prevent derailment.
Estimation of Rail Bending Stress From Real-Time Vertical Track Deflection Measurement
Authors: Greisen Curt , Lu Sheng , Duan Haoliang , Farritor Shane , Arnold Richard , GeMeiner Bill , Clark Dwight , Toth Tom , Hicks Kevin , Sussmann Ted , Fateh Mahmood , Carr Gary
Published: August 2009

High traffic volume, heavy axle loads, and high train speed can produce large rail bending stresses which contribute to increased track deterioration. Rail stress problems are further exacerbated by poor support conditions such as abrupt changes in vertical track modulus and poor track geometry. This paper summarizes the development of a measurement technique, based on a system being developed over the past few years at the University of Nebraska and sponsored by the Federal Railroad Administration, to determine the actual bending stress in the rail in real-time from a car moving at revenue speeds. The UNL system measures the rail height relative to the line created by the wheel/rail contact points. The system functions continuously over long distances and in revenue service. The system establishes three points of the rail shape beneath the loaded wheels and over a distance of ten feet. These points include the location of high bending stress below the loaded wheels. This direct measurement of the rail shape can then be mapped into rail stress through the curvature of the rail and beam theory. As verification of the UNL measurement system, results from tests conducted on the Union Pacific Railroad’s Yoder Subdivision are discussed. In these tests, bondable resistance strain gages were mounted to the lower flange of the rail at several locations. The track was then loaded by spotting the measurement car over the strain gages and by moving the car over the gages at various speeds. The loaded and unloaded rail profiles were measured using surveying equipment and the relationship between the UNL deflection measurement and the measured rail stress was explored. These early results suggest the UNL system is capable of measuring real-time bending stress in the rail.
Mechanical Properties of Tank Car Steels Retired From the Fleet
Authors: McKeighan Peter C. , Jeong David Y. , Cardinal Joseph W.
Published: August 2009

As a consequence of recent accidents involving the release of hazardous materials (hazmat), the structural integrity and crashworthiness of railroad tank cars have come under scrutiny. Particular attention has been given to the older portion of the fleet that was built prior to steel normalization requirements instituted in 1989. This paper describes a laboratory testing program to examine the mechanical properties of steel samples obtained from tank cars that were retired from the fleet. The test program consisted of two parts: (1) material characterization comprised of chemical, tensile and Charpy V-notch (CVN) impact energy and (2) high-rate fracture toughness testing. In total, steel samples from 34 tank cars were received and tested. These 34 tank cars yielded 61 different pre-1989 TC128-B conditions (40 shell and 21 head samples), three tank cars yielded seven different post-1989 TC128-B conditions (four shell and three head samples), and six tank cars yielded other material (A212, A515, and A285 steel) conditions (six shell and five head samples). The vast majority of the TC128-B samples extracted from retired tank cars met current TC128-B material specifications. Elemental composition requirements were satisfied in 97 percent of the population whereas the required tensile properties were satisfied in 82 percent of the population. Interpretation of the high-rate fracture toughness tests required dividing the pre-1989 fleet into quartiles that depended on year of manufacture or age, and testing three tank cars per quartile. Considering the high-rate fracture toughness results at 0°F for the pre-1989 fleet, 100 percent of the oldest two quartiles, 58 percent of the second youngest quartile, and 83 percent of the youngest quartile exhibited adequate or better fracture toughness (defined as toughness greater than 50 ksi√in). High-rate fracture toughness at –50°F was adequate for 83 percent of two quartiles (the youngest and second oldest), but the other two quartiles exhibited lower toughness with only 33 (2nd youngest) to 50 percent (oldest) exhibiting adequate properties.
Supplemental Pit Fire Control Deluge System: Spokane Regional Waste to Energy Facility
Authors: Taam Damon M. K. , Conklin Chuck
Published: August 2009

After sixteen years of operation, it became apparent that the pit fire protection system installed during construction of the Spokane Regional Waste to Energy (WTE) Facility (1989–1991) was inadequate. A risk analysis was performed by Creighton Engineering Inc., a fire protection consulting firm, hired by the Spokane Regional Solid Waste System (Regional System) and Wheelabrator Spokane Inc. With input from Spokane County Fire District 10 and the City of Spokane Fire Department, a replacement supplemental fire protection system was designed and ultimately installed. This paper will describe the problems with the once state of the art fire system and the planning, design and installation of the new system.
Emissions Performance of a Novel Combustor Burning Shredded Wood
Authors: Lindsey C. , Sawyer M. , Schmidt A. , Aubrey P. , Webster A.
Published: August 2009

The Air Force Research Laboratory, Airbase Technologies Division (AFRL/RXQ) is engineering and evaluating the Transportable Waste-to-Energy System (TWES). This trailer mounted system will convert military base waste and biomass waste streams to useful heat and power. The Department of Energy (DOE) Federal Energy Management Program (FEMP) is a TWES funding partner. The first stage of the project is a suspension-type combustor (furnace). The furnace has been built and tested. A key feature of the furnace system is its unique patented combustion coil design. The design is intended to maximize ablative heat transfer by increasing particle residence time near a radiant ignition source. The innovative features of the design are targeted at ensuring that the system can be highly fuel-flexible to convert a variety of biomass and other waste streams to energy while demonstrating very low emissions. In 2008, the unit underwent two days of emissions stack testing using established Environmental Protection Agency (EPA) testing protocols. During the testing, extensive real-time data were also collected. This paper presents the data and corresponding analysis of the recent emissions testing performed while utilizing dry wood chips as a control fuel. Detailed emission comparisons are presented using publicly available information from commercial units and from a similarly sized experimental system for small biomass combustion. Key combustion efficiency factors, such as carbon monoxide emissions and nitrogen oxide emissions are presented. The authors also provide commentary on the results for next generation units and the use of this mode of energy conversion for small scale systems.
RSCR® System to Reduce NOx Emissions From Boilers
Authors: Abrams Richard F. , Faia Robert
Published: August 2009

Babcock Power Environmental (BPE), a Babcock Power Inc. company, has developed a new, innovative, high-efficiency NOx reduction technology designed to greatly reduce the NOx emissions from waste to energy (WTE) boilers at relatively low cost. This “tail-end” system uses Selective Catalytic Reduction (SCR) to achieve the high reduction performance. Conventional SCR catalyst cannot be used in the traditional “high-dust” location, downstream of the economizer because constituents in the ash would poison the catalyst quickly, rendering it useless. Thus, the Regenerative Selective Catalytic Reduction (RSCR®) system is designed to operate at the end of the plant before the flue gas is discharged to the stack. The process utilizes a reactant (usually aqueous ammonia) to be added to the flue gas stream upstream of the RSCR to reduce NOx to harmless reaction products, N2 and H2O. The RSCR combines the efficient heat recovery, temperature control, reactant mixing, and catalyst into a single unit and provides the maximum NOx reduction and heat recovery practical. The paper will describe the overall predicted performance of a typical WTE boiler plant using this new technology. The paper will also provide actual operating data on the RSCR, which has been retrofitted to four biomass-fired units.
Controlled etching and regrowth of tunnel oxide for antenna-coupled metal-oxide-metal diodes
Authors: Tiwari Badri , Bean Jeffrey A. , Szakmány Gergő , Bernstein Gary H. , Fay Patrick , Porod Wolfgang
Published: August 2009

The authors have designed a new procedure for fabrication of infrared (IR) sensors. These sensors consist of a dipole antenna coupled with a metal-oxide-metal (MOM) (Al–AlOx–Pt) diode. The surface of electron beam evaporated Al, serving as one of the electrodes, is cleaned using an Ar plasma, followed by in situ controlled growth of the tunneling oxide, AlOx. The antenna, its leads, and the overlap of the Al and Pt electrodes that defines the MOM overlap area are all defined using electron beam lithography. The MOM overlap area of these devices is as small as 50×80 nm2. Features of our process include the use of dissimilar metals for the formation of the MOM diode, small MOM diode size, and controlled etching and regrowth of the tunneling oxide. A CO2 laser at 10.6 μm was used for the IR characterization of these sensors. Current-voltage and IR measurements are presented. The normalized detectivity (D∗) for these devices was found to be 2.13×106 cm Hz1/2 W−1.
Highly sensitive positive-working molecular resist based on new molecule
Authors: Hattori Shigeki , Yamada Arisa , Saito Satoshi , Asakawa Koji , Koshiba Takeshi , Nakasugi Tetsuro
Published: August 2009

A highly sensitive positive-working molecular resist based on a new molecule, 1,3,5-tris[p-(p-hydroxyphenyl)-phenyl]benzene (THTPPB), was designed and synthesized. THTPPB showed a high glass transition temperature (Tg) of 145°C. Some acid-leaving groups were attached to THTPPB to realize positive-working performance developed by an alkaline aqueous developer. 70nm line-and-space (1:1) positive tone pattern was fabricated with high sensitivity (<1μC∕cm2) by the exposure to a low-energy electron beam (5keV).
Does hydrogen change the fullerenelike structure in CNx thin films?
Authors: Roy Debdulal , Chhowalla Manish , Hellgren Niklas , Amaratunga G. A. J.
Published: August 2009

The authors have reported the structure of the nanoclusters in carbon nitride thin films before [D. Roy et al., Phys. Rev. B 70, 035406 (2004)]. In this work, effects of the addition of hydrogen in the deposition gas mixture on the structures of carbon nitride thin films prepared by magnetron sputtering were investigated using Raman spectroscopy. Raman measurements showed that the structures of carbon nanoclusters remained unaffected by the addition of hydrogen in the carbon nitride films. On the other hand, the structures of amorphous thin films were affected by the addition of hydrogen in the deposition gas mixture. These are explained in terms of changes in the ratios of the D-peak to the G-peak intensities and shifts in the G-peak centers.
Cu-plated through-wafer vias for AlGaN∕GaN high electron mobility transistors on Si
Authors: Chen K.-H. , Ren F. , Pais A. , Xie Huikai , Gila B. P. , Pearton S. J. , Johnson J. W. , Rajagopal P. , Roberts J. C. , Piner E. L. , Linthicum K. J.
Published: August 2009

A robust method for creating Cu-plated through-wafer vias for AlGaN∕GaN high electron mobility transistors on Si is reported. The initial 70μm deep vias with diameters of 50μm are created by deep Si reactive ion etching, followed by pulsed Cu electroplating and mechanical polishing to planarize the metal. This is an attractive approach for increasing the effective thermal conductivity of the composite substrate for very high power device applications.
Accuracy of Spencer‐Attix cavity theory and calculations of fluence correction factors for the air kerma formalism
Authors: La Russa D. J. , Rogers D. W. O.
Published: August 2009

EGSnrc calculations of ion chamber response and Spencer‐Attix (SA) restricted stopping‐power ratios are used to test the assumptions of the SA cavity theory and to assess the accuracy of this theory as it applies to the air kerma formalism for beams. Consistent with previous reports, the EGSnrc calculations show that the SA cavity theory, as it is normally applied, requires a correction for the perturbation of the charged particle fluence by the presence of the cavity. The need for corrections arises from the fact that the standard prescription for choosing the low‐energy threshold in the SA restricted stopping‐power ratio consistently underestimates the values of needed if no perturbation to the fluence is assumed. The use of fluence corrections can be avoided by appropriately choosing , but it is not clear how can be calculated from first principles. Values of required to avoid corrections were found to be consistently higher than values obtained using the conventional approach and are also observed to be dependent on the composition of the wall in addition to the cavity size. Values of have been calculated for many of the graphite‐walled ion chambers used by the national metrology institutes around the world and found to be within 0.04% of unity in all cases, with an uncertainty of about 0.02%.
Considering marker visibility during leaf sequencing for segmental intensity‐modulated radiation therapy
Authors: Zhao Bo , Dai Jianrong , Ling C. Clifton
Published: August 2009

Purpose:

Segmental intensity‐modulated radiation therapy (IMRT) delivers a sequence of segments to obtain a desired intensity distribution. Many leaf sequencing algorithms for segmental IMRT have been developed with the aim of reducing delivered monitor units (MUs) and (or) number of segments and, consequently, to reduce the total treatment delivery time. With the development of real‐time detection technology, it is useful to develop leaf sequencing algorithms that consider the detecting probability of markers implanted into or near the target volume.

Methods:

In this study, the authors defined the concept of marker visibility to denote the marker's detecting probability and proposed a new leaf sequencing algorithm based on the Kamath algorithm. The new algorithm first uses the Kamath algorithm to generate an initial leaf sequence and then performs a series of column transformations to obtain a new leaf sequence that is optimal in terms of MU efficiency and marker visibility. The authors evaluated the performance of the new algorithm with six artificial fields that had randomly generated intensity matrices and 15 clinical fields that had intensity matrices from the IMRT plans for three prostate cancer patients.

Results:

Compared to the Kamath algorithm, the new algorithm does not increase the total delivered intensity but increases the marker visibility. For the artificial fields, the marker visibility increased from 66.67% to 91.67% for small radiation fields, from 39.29% to 42.86% for medium size fields, and from 31.48% to 37.04% for large fields. For the clinical fields, the marker visibility increased 9%–20% for four fields, 20%–30% for three fields, 30%–40% for two fields, and more than 40% for one field. However, the marker visibility did not change for 4 out of 15 fields.

Conclusions:

The authors developed a new leaf sequencing algorithm for optimal MU efficiency and marker visibility and also rigorously proved its optimality.
Gamma Knife output factor measurements using VIP polymer gel dosimetry
Authors: Moutsatsos A. , Petrokokkinos L. , Karaiskos P. , Papagiannis P. , Georgiou E. , Dardoufas K. , Sandilos P. , Torrens M. , Pantelis E. , Kantemiris I. , Sakelliou L. , Seimenis I.
Published: August 2009

Purpose:

Water equivalent polymer gel dosimeters and magnetic resonance imaging were employed to measure the output factors of the two smallest treatment fields available in a Gamma Knife model C radiosurgery unit, those formed employing the 4 and 8 mm final collimator helmets.

Methods:

Three samples of the VIP normoxic gel formulation were prepared and irradiated so that a single shot of the field whose output factor is to be measured and a single shot of the reference 18 mm field were delivered in each one. Emphasis is given to the development and benchmarking of a refined data processing methodology of reduced uncertainty that fully exploits the 3D dose distributions registered in the dosimeters.

Results:

Polymer gel results for the output factor of the 8 mm collimator helmet are found to be in close agreement with the corresponding value recommended by the vendor ( versus 0.956, respectively). For the 4 mm collimator helmet, however, polymer gel results suggest an output factor 3% lower than the value recommended by the vendor ( versus 0.870, respectively).

Conclusions:

A comparison with corresponding measurements published in the literature indicates that output factor results of this work are in agreement with those obtained using dosimetric systems which, besides fine spatial resolution and lack of angular and dose rate dependence of the dosimeter's response, share with polymer gels the favorable characteristic of minimal radiation field perturbation.
An effective correction algorithm for off‐axis portal dosimetry errors
Authors: Bailey Daniel W. , Kumaraswamy Lalith , Podgorsak Matthew B.
Published: August 2009

Portal dosimetric images acquired for IMRT pretreatment verification show dose errors of up to 15% near the detector edges as compared to dose predictions calculated by a treatment planning system for these off‐axis regions. A method is proposed to account for these off‐axis effects by precisely correcting the off‐axis output factors, which calibrate the imager for absolute dose. Using this method, agreement between the predicted and the measured doses improves by up to 15% for fields near the detector edges, resulting in passing rate improvements of as much as 60% for gamma evaluation of , 3% within the collimator jaws.
Task Group 142 report: Quality assurance of medical acceleratorsa)
Authors: Klein Eric E. , Hanley Joseph , Bayouth John , Yin Fang‐Fang , Simon William , Dresser Sean , Serago Christopher , Aguirre Francisco , Ma Lijun , Arjomandy Bijan , Liu Chihray , Sandin Carlos , Holmes Todd
Published: August 2009

The task group (TG) for quality assurance of medical accelerators was constituted by the American Association of Physicists in Medicine's Science Council under the direction of the Radiation Therapy Committee and the Quality Assurance and Outcome Improvement Subcommittee. The task group (TG‐142) had two main charges. First to update, as needed, recommendations of Table II of the AAPM TG‐40 report on quality assurance and second, to add recommendations for asymmetric jaws, multileaf collimation (MLC), and dynamic/virtual wedges. The TG accomplished the update to TG‐40, specifying new test and tolerances, and has added recommendations for not only the new ancillary delivery technologies but also for imaging devices that are part of the linear accelerator. The imaging devices include x‐ray imaging, photon portal imaging, and cone‐beam CT. The TG report was designed to account for the types of treatments delivered with the particular machine. For example, machines that are used for radiosurgery treatments or intensity‐modulated radiotherapy(IMRT) require different tests and/or tolerances. There are specific recommendations for MLC quality assurance for machines performing IMRT. The report also gives recommendations as to action levels for the physicists to implement particular actions, whether they are inspection, scheduled action, or immediate and corrective action. The report is geared to be flexible for the physicist to customize the QA program depending on clinical utility. There are specific tables according to daily, monthly, and annual reviews, along with unique tables for wedge systems, MLC, and imaging checks. The report also gives specific recommendations regarding setup of a QA program by the physicist in regards to building a QA team, establishing procedures, training of personnel, documentation, and end‐to‐end system checks. The tabulated items of this report have been considerably expanded as compared with the original TG‐40 report and the recommended tolerances accommodate differences in the intended use of the machine functionality (non‐IMRT, IMRT, and stereotactic delivery).
Verification and source‐position error analysis of film reconstruction techniques used in the brachytherapy planning systems
Authors: Chang Liyun , Ho Sheng‐Yow , Chui Chen‐Shou , Du Yi‐Chun , Chen Tainsong
Published: August 2009

A method was presented that employs standard linac QA tools to verify the accuracy of film reconstruction algorithms used in the brachytherapy planning system. Verification of reconstruction techniques is important as suggested in the ESTRO booklet 8: “The institution should verify the full process of any reconstruction technique employed clinically.” Error modeling was also performed to analyze seed‐position errors. The “isocentric beam checker” device was used in this work. It has a two‐dimensional array of steel balls embedded on its surface. The checker was placed on the simulator couch with its center ball coincident with the simulator isocenter, and one axis of its cross marks parallel to the axis of gantry rotation. The gantry of the simulator was rotated to make the checker behave like a three‐dimensional array of balls. Three algorithms used in the ABACUS treatment planning system: orthogonal film, 2‐films‐with‐variable‐angle, and 3‐films‐with‐variable‐angle were tested. After exposing and digitizing the films, the position of each steel ball on the checker was reconstructed and compared to its true position, which can be accurately calculated. The results showed that the error is dependent on the object‐isocenter distance, but not the magnification of the object. The averaged errors were less than within the tolerance level defined by Roué et al. [“The EQUAL‐ESTRO audit on geometric reconstruction techniques in brachytherapy,” Radiother. Oncol. 78, 78–83 (2006)]. However, according to the error modeling, the theoretical error would be greater than if the objects were located more than away from the isocenter with a 0.5° reading error of the gantry and collimator angles. Thus, in addition to carefully performing the QA of the gantry and collimator angle indicators, it is suggested that the patient, together with the applicators or seeds inside, should be placed close to the isocenter as much as possible. This method could be used to test the reconstruction techniques of any planning system, and the most suitable one can be chosen for clinical use.
Uncertainties in effective dose estimates of adult CT head scans: The effect of head size
Authors: Gregory Kent J. , Bibbo Giovanni , Pattison John E.
Published: August 2009

Purpose: This study is an extension of a previous study where the uncertainties in effective dose estimates from adult CT head scans were calculated using four CT effective dose estimation methods, three of which were computer programs (CT‐EXPO, CTDOSIMETRY, and IMPACTDOSE) and one that involved the dose length product (DLP). However, that study did not include the uncertainty contribution due to variations in head sizes.

Methods: The uncertainties due to head size variations were estimated by first using the computer program data to calculate doses to small and large heads. These doses were then compared with doses calculated for the phantom heads used by the computer programs. An uncertainty was then assigned based on the difference between the small and large head doses and the doses of the phantom heads.

Results: The uncertainties due to head size variations alone were found to be between 4% and 26% depending on the method used and the patient gender. When these uncertainties were included with the results of the previous study, the overall uncertainties in effective dose estimates (stated at the 95% confidence interval) were 20%–31% (CT‐EXPO), 15%–30% (CTDOSIMETRY), 20%–36% (IMPACTDOSE), and 31%–40% (DLP).

Conclusions: For the computer programs, the lower overall uncertainties were still achieved when measured values of CT dose index were used rather than tabulated values. For DLP dose estimates, head size variations made the largest (for males) and second largest (for females) contributions to effective dose uncertainty. An improvement in the uncertainty of the DLP method dose estimates will be achieved if head size variation can be taken into account.
Evaluation of nonrigid registration models for interfraction dose accumulation in radiotherapy
Authors: Janssens Guillaume , Orban de Xivry Jonathan , Fekkes Stein , Dekker André , Macq Benoit , Lambin Philippe , van Elmpt Wouter
Published: August 2009

Purpose:

Interfraction dose accumulation is necessary to evaluate the dose distribution of an entire course of treatment by adding up multiple dose distributions of different treatment fractions. This accumulation of dose distributions is not straightforward as changes in the patient anatomy may occur during treatment. For this purpose, the accuracy of nonrigid registration methods is assessed for dose accumulation based on the calculated deformations fields.

Methods:

A phantom study using a deformable cubic silicon phantom with implanted markers and a cylindrical silicon phantom with MOSFET detectors has been performed. The phantoms were deformed and images were acquired using a cone‐beam CT imager. Dose calculations were performed on these CT scans using the treatment planning system. Nonrigid CT‐based registration was performed using two different methods, the Morphons and Demons. The resulting deformation field was applied on the dose distribution. For both phantoms, accuracy of the registered dose distribution was assessed. For the cylindrical phantom, also measured dose values in the deformed conditions were compared with the dose values of the registered dose distributions. Finally, interfraction dose accumulation for two treatment fractions of a patient with primary rectal cancer has been performed and evaluated using isodose lines and the dose volume histograms of the target volume and normal tissue.

Results:

A significant decrease in the difference in marker or MOSFET position was observed after nonrigid registration methods for both phantoms and with both methods, as well as a significant decrease in the dose estimation error ( for the cubic phantom and for the cylindrical) with both methods. Considering the whole data set at once, the difference between estimated and measured doses was also significantly decreased using registration ( for both methods). The patient case showed a slightly underdosed planning target volume and an overdosed bladder volume due to anatomical deformations.

Conclusions:

Dose accumulation using nonrigid registration methods is possible using repeated CT imaging. This opens possibilities for interfraction dose accumulation and adaptive radiotherapy to incorporate possible differences in dose delivered to the target volume and organs at risk due to anatomical deformations.