bluuebunny/crossref_metadata_2025 huggingface dataset:
A Real-Time Simulation System for Excavator Controller
Authors: Gong Wen , Wang Qing-Feng
Published: December 2010

In order to supply a reliable and low-cost method for testing excavator's controllers and evaluating the performance of strategies, an excavator real-time simulation system has been developed. The hardware-in-the-loop system, including dynamic model of the arms, dynamic model of the main hydraulic system and an 3D real-time display subsystem, is presented in this paper. The simulation results are also described at the end of the paper.
Hierarchic Particle Swarm Optimization Based Target Tracking
Authors: Niu Chang-Feng , Liu Yu-Shu
Published: December 2010

A target tracking algorithm based on particle swarm optimization (PSO) is proposed. Due to a premature convergence with PSO in multimodal problems, an improved PSO, i.e. hierarchic particle swarm optimization (HPSO), is proposed and utilized to track target. To maintain high diversity of particle swarm, dynamic propagation is utilized to generate new particles in tracking process. In addition, parameters in PSO are adaptively adjustment in iteration process, leading to a favorable performance in tracking applications. Experiment results demonstrate the proposed algorithm is accurate and effective.
Real-Time Visualization Method for Large-Scale Crowd Simulation
Authors: Xiao He , He Chunlin
Published: December 2010

Animating virtual crowds with a large number of autonomous agents are effective to enhance realism in virtual reality applications. In this paper we present some preliminary results concerning a real-time visualization methods for large crowds reside in virtual environments. Making good use of LOD, we adopt three resolution models as detailed, less detailed geometry and imposter to represent virtual agent. At the same time we divide virtual crowd into crowd, group, and agent. Then we continue to divide agent into leader- agent and general-agent. We only have to certain which model should be adopted for leader-agent in one group not for every agent for less time complexity. We demonstrate our methods through the manifest the large number of human crowd in the virtual environment.
Simulation and Agitation Characteristic Model of Screw Shaft in Bituminous Mixture Transfer Vehicle Based on PSO and L-M Algorithm
Authors: You Zhang-ping , Li Wan-li , Wang Peng-cheng , Li Zi-guang
Published: December 2010

To analyze agitation characteristic of screw shaft in Bituminous Mixture Transfer Vehicle (BMTV), a Neural Network (NN) model was established, based on helical blade radius, pitch and rotational speed of screw shaft used as input vector, while asphalt mixture segregation rate used as output vector. To solve the problems of the slow convergence rate and easily falling into local minimum in BP algorithm, PSO algorithm combined with Levenberg-Marquardt algorithm was employed as learning algorithm of the NN. Model of BMTV was designed and manufactured, and model experiment data was applied to simulation experiment of the screw shaft NN model. Simulation and experiment results indicate that the proposed approach not only can overcome the drawbacks of BP algorithm, but also has faster convergence and higher computational precision than original PSO. It also can be applied to building model for agitation characteristics of screw shaft in BMTV, and it is effective.
Research on the Barcode Positioning and Correction Method Based on Improved Convex Hull Algorithm for Mobile Phone
Authors: Liu Zhi , Yan Ruiyi , Lu Jian
Published: December 2010

It is inevitable that barcode images captured by mobile phone camera have some extent of tilting and distortion. In traditional method, the Hough Transform method is adopted to detect the L-shape in the barcode image of Data Matrix. However, with huge complexity and large storage space, it is not suitable for application on the mobile phone. In this paper, under Symbian OS in Nokia, an improved convex hull algorithm is adopted to exclude some invalid convex hull vertices through angle, length calculation filters. Then a fake quadrilateral is created to fit Data Matrix image contour. This approach can both shorten calculation time and ensure accurate positioning. It is suitable for mobile phone application. At the end of this paper, both the traditional method and the improved approach are tested on Nokia N73 for the comparison of the efficiency and effectiveness.
AAP and AAPM: Improved Prefetching Structures of the L2 Cache
Authors: Zheng Qiaoshi , Gao Deyuan , Chen Jie , Wang Chao
Published: December 2010

The push technique is an effective method of tolerating the Load-to-use latency. However, not every memory level can gain a sound performance improvement when the push technique is adopted. In this paper, we devise a quantitative approach to analyze workload on the bus. For balancing workload, we propose a novel architecture, which compounds the push and prefetching technique to serve different storage levels. Between the L1 and the L2 cache, we use the push technique. Between the L2 cache and memory, we utilize the prefetching technique. Focusing on the L2 cache prefetching, we propose AAP and AAPM, both of which meet the requirement of timeliness and bandwidth adaptability and can increase the IPC by 2% compared with SRP.
Comparison of Feed-Forward Schemes for Anti-Sway Control of Rotary Crane
Authors: Ahmad M. A. , Ismail R. M. T. Raja , Ramli M. S. , Samin R. E.
Published: December 2010

This paper presents investigations into the development of feed-forward control schemes for anti-swaying control of a rotary crane system. A nonlinear rotary crane system is considered and the dynamic model of the system is derived using the Euler-Lagrange formulation. An unshaped square-pulse torque input is used to determine the characteristic parameters of the system for design and evaluation of the feed-forward control techniques. Feed-forward control schemes based on input shaping and filtering techniques are to be examined. The proposed techniques are designed based on the properties of the system for anti-sway control. The responses of the rotary crane system to the shaped inputs are analyzed in time and frequency domains. Performances of the control schemes are examined in terms of sway angle reduction and time response specifications. Finally, a comparative assessment of the proposed control techniques is presented and discussed.
The Design and Realization of Wireless Sensor Network Gateway
Authors: Wu Jiaping , Shen Jianhua , Fan Wanyong
Published: December 2010

Aim at the gateway node of the wireless sensor network, this paper designs and implements a kind of wireless gateway. Inside the wireless sensor network, the data transferring is based on the Zigbee module; between the gateway node and the host, the transferring is based on the Wi-Fi module. Both the hardware scheme and the programming method of software are introduced. At the end, the performance of the gateway is tested, and the result shows that it can be used for general purposes.
Stabilization of Aerodynamic Unstable Missiles Using Linear and Nonlinear Approaches
Authors: Fan Jun-fang , Su Zhong
Published: December 2010

The challenge and control problem of static unstable missiles were presented. The steady-state benefits of static instability were illustrated, while the corresponding control challenge was described by the characteristic lag of airframe and the increment of necessary control usage. Control limitation led by unstable zero-pole pair was analyzed for preliminary design and evaluation. Linear control strategy was examined wherein the three loop acceleration autopilots was developed using an optimal control approach combined with frequency domain constraint. The weights selection and relation with system performance were detailed. Then the nonlinear backstepping recursive method was detailed. The results show that the actuator bandwidth is the crucial limiting factor for controlling a static unstable missile.
New H∞ Controllers Design for Networked Control System with Disturbance Based on Asynchronous Dynamical System
Authors: Wang Jihua , Dong Ling , Bai Yan
Published: December 2010

In this paper, a class of networked control system (NCS) with disturbance, time delay and packet dropout is converted into a discrete-time system which could be viewed as an asynchronous dynamical system with rate constraints. For the system, based on Lyapunov stability theory and LMI approach we present two new state feedback controllers which can make the closed-loop system exponentially stable and meet prescribed or optimal H∞ performance index. A numerical example is worked out in detail to illustrate our results.
Research on Image Recognition of Spores Based on BP Neural Network
Authors: Li Yang , Zhang Xiuhua , Yi Jinggang , Li Xin
Published: December 2010

Aiming at the shortcoming of manual recognition of spores, the paper proposes an auto-recognition method based on BP neural network. After pre-treatment of spore images and feature vector extraction, the BP neural network is set up for spore characteristics identification. The simulation results of MATLAB7.0 show that the auto-recognition method is able to identify the characteristics of spore images.
Artificial Neural Networks Based Recognition of Selected Palmprint Features
Authors: Altun Adem Alpaslan , Nooraliei Amir
Published: December 2010

Biometric recognition suggests a reliable solution to the problem of user authentication in our networked society. Among all biometrics, palmprint-based recognition is one of the most reliable personal identification methods. In this study, a new approach to the palmprint recognition phase is presented. 2D Gabor filters are used for feature extraction of palmprints. After Gabor filtering, standard deviations are computed in order to generate the palmprint feature vector. In addition, Genetic algorithm based feature selection is used to select the best feature subset from the palmprint feature set. Four different algorithms of Artificial Neural Networks are then applied to the feature vectors for recognition of the people. Recognition rate equal to 98 percent are obtained by using conjugate gradient algorithms.
Dynamic Cloth Simulation with Fast Self-Collision Detection
Authors: Shapri Nur Saadah Mohd , Bade Abdullah , Daman Daut
Published: December 2010

Dynamic cloth simulation becomes the most important issue in certain applications such as games, animation, virtual reality and medical which is the dynamic effect with fast self collision between cloth-to-cloth becomes the main problem to resolve. To achieve the reality cloth simulation, we use a mass-spring system, which is the universal model in cloth simulation. For the animation of the particles, we considered internal and external forces to create cloth to look more realistic. As cloth simulators, to handle the cloth self collision is more complicated. So, several methods have been suggested by numerous researchers. Furthermore, we discuss numerous methods for an efficient avoidance of self collision detection. So that the efficiency animation of cloth can be improves much.
Partitioning Large Database Using Irrelevant Attributes for Knowledge Discovery and Learning
Authors: Al Moghalis Mohamed A. , Imam Ibrahim F.
Published: December 2010

Learning systems are very effective tools for discovering knowledge from databases. Most symbolic learning systems face difficulties when discovering knowledge from large databases. Adapting the learning systems to cope with large databases is the traditional solution to overcome these limitations. This paper evaluates a new methodology for partitioning the representation space. The method selects an irrelevant attribute, determined by a utility function, to partition the representation space. Since irrelevant attributes are not needed to describe concepts learned from the original data, the knowledge discovered from all subspaces should be independent of such an attribute. If the representation space is partitioned by a relevant attribute, the knowledge discovered from all subspaces are combined simply using information about that attribute. The method is analyzed using C5 learning system, or See5.
Frequency Hopping Spread Spectrum Transceiver Implementation Using Floating-Point DSP
Authors: Ahmed Hossam E. , Zekry A. A. , Elhennawy Adel E. , Hassan Ayman M.
Published: December 2010

Mechanisms based on frequency hopping have been widely used in many applications such as the personal communications services and the wireless networks. In this paper, we describe, simulate and implement a frequency hopping spread spectrum transceiver. A baseband model for Bluetooth Frequency Hopping Transceiver is presented. Several modulation techniques, such as QPSK, 8-FSK and 16-QAM, are exploited to achieve a bit rate of 2Mbps, 3Mbps and 4Mbps respectively. We clacutate the bit error rate of the described transceiver model with the aid of Monte Carlo analysis technique. The proposed model is then implemented using the C6713 floating-point DSP. The functionality of the implemented system is tested via Real Time Data Exchange (RTDX).
Robot Path Planning Using Wavefront Approach with Virtual Wave HI
Authors: Nooraliei Amir , Nooraliei Hamed
Published: December 2010

This paper discusses about new way for motioning planning of robots in dynamic environments that they depend on wave expansion approach that avoids wave re-expansion in sudden obstacles case. Wave that is re-expansion in big measure environments takes an important amount of time and process. A new wave expansion algorithm about path finding, either abrupt obstacles are met or local minima, has been suggested as so-called virtual wave hill algorithm, which prevents re-expansion of wave. In addition the reflects of the simulation and its results reflects that how the performance has developed the current methods. By using the algorithm it's been tried to prevent the re-expansion of the wave.
Characterization of Color Devices by Polynomial Regression
Authors: Sun Bang-Yong , Zhou Shi-Sheng , Cao Cong-Jun , Yuan-Lin Zheng
Published: December 2010

As color devices may lose accuracy during a period of time, characterization should be made to calibrate them. A 4th order polynomials regression method is proposed for color characterization. In the experiment, different forms of polynomials are used to represent the relationship of RGB and L*a*b*, and the result shows the new proposed 4th order polynomials have smaller errors than other forms of polynomials. What's more, the 3D LUT and neural network method are also compared with our method, and the result suggested that all these three method have the error about 2 color difference units, which is far lower than the replicate threshold of 6. While our method takes up the least time in experiment, which is significant and may broaden its application in image processing.
Exploring the Potential of Using Augmented Reality Approach in Cultural Heritage System
Authors: Noh Zakiah , Ismail Ajune Wanis , Sunar Mohd Shahrizal
Published: December 2010

Nowadays, Augmented Reality (AR) has become well-accepted technology with realism as one of the major contribution in computer graphics. AR is a technology that superimposed virtual and real scene in the same space. This technology requires accurate registration between virtual and real world augmentation, be it geometric registration or illumination registration. Hence, a lot of efforts have been done to explore the elements in AR technology including features and challenging issues in AR that need to be highlighted in order to reconstruct AR system. In cultural heritage system, the accurate registration is important to produce realistic environment and to improve the user's experience. The culture heritage reconstruction is significance to preserve, protect and interpret our culture and history. This paper will present an overview on the potentials of AR approach in cultural heritage system that will improve the quality of the system.
Design, Simulation and Implementation of Asymmetric Digital Subscriber Line Modem on DSP Kit
Authors: Zayed Hossam Labib A. , Zekry A. A. , Elhenawy Adel Ezat , Hassan Ayman M.
Published: December 2010

In this paper, design, simulation and implementation of Asymmetric Digital Subscriber Line (ADSL) modem is presented which can be applied to different telephone networks. Lhe ADSL modem is modeled and simulated under the MATLAB version 7.3 (R2006b) environments by which the simulation is achieved for both the downstream and upstream directions of the modem. The ADSL modem with a transmission throughput between 640 kbps and 6 Mbps operating over most of existing telephone subscriber loops has been implemented on TI TMS320C6713 DSP for consumer multimedia applications. Except the Analog Front End, all the basic building blocks of the ADSL modem functionalities are implemented with DSP platform. We use Real-Time Data Exchange (RTDX) as a way to debug and test our DSP designs.
Research on Model of Waveform Selection in Cognitive Radar
Authors: Wang Bin , Wang Jinkuan , Song Xin , Yan Dongmei
Published: December 2010

Cognitive radar can be aware of its environment, utilize intelligent signal processing, provide feedback from the receiver to the transmitter for adaptive illumination and preserve the information contents of radar returns. In this paper, based on the analysis of the parameters of radar mesurements, range-Doppler resolution cell is built up. Then stochastic dynamic programming model of waveform selection in cognitive radar is proposed, which is viewed as an important part of cognitive radar. In simulation, the importance of adaptive waveform selection in cognitive radar is shown.
Study of Fault Detection Device Based on DSP in Distribution Networks
Authors: He Hongjiang , Song Linxia
Published: December 2010

Since currently in China the power supply distribution system adopts low current grounding system with indirect grounding of neutral, so the fault of single phase grounding in the system takes place frequently. With reference of actual conditions for single phase grounding fault, The paper designs a new realtime monitoring and fault diagnosis device, On the one hand, the device can measure some elementary power parameters, such as the three-phase voltages, current, power, frequency etc. on the other hand, it can really monitor system status. Results of operation show that this device computing speed quickly, strong anti-jamming capability, stable operation, has the good performance-to-price ratio, is very practical in the small current grounding and the grid.
An Intelligent and Interactive Control System Based on PDA for Digital Home
Authors: Xu Huaiyu , Su Ruidan , Zhuang Hao , Yu Xiangxiang , Kan Jilong
Published: December 2010

This paper introduces an intelligent and interactive control system (IICS) based on Personal Digital Assistant (PDA) with Windows Embedded Compact System (Windows CE). IICS can configure, monitor and control the wireless digital terminals of digital home. The system consists of a software platform, a controller on PDA and the wireless communication network. Also, Field Programming Gate Array (FPGA) is designed as microcontroller in hardware part to connect PDA and home appliances. In addition, a digital home server is proposed for remote control that PDA can link to the server by GPRS network outside. User interface of IICS provides an efficient way of operating all the appliances in the home. Finally, the experimental results demonstrate that IICS is of high performance for coordinating the home appliances.
Some Results on the Minimal Covering of Precomplete Sets in Partial Four-Valued Logic
Authors: Zhou Xiaoqiang , Liu Renren , Gu Sisi
Published: December 2010

The decision and constitution of the Sheffer function is one of the important problems in multi-valued logic theory. This problem can be reduced to the decision of the minimal covering of precomplete sets in the multi-valued logic function sets. According to the completeness theory in partial k-valued logic and the similar relationship theory among precomplete sets, the methods of determination on the minimal covering precomplete sets are found out, and the minimal covering members of function sets preserving full symmetric, simply separable and regularly separable relations in partial four-valued logic are decided.
Utilizing Information Extraction to Display Biographies on Google Earth
Authors: Xu Huaiyu , Cai Heng , Hou Xiaoyu , Cao Yingbin , Chen Mo
Published: December 2010

Due to the information explosion, web IE (information extraction) comes into being. Though people get used to inquiring information by 2-D text reading in traditional way, browsing words is not enough for users' acquiring knowledge today. Actually, people find that most information is geo-referenced especially after Digital Earth (DE) is proposed, which makes people can get information in a 3-D environment. Google Earth (GE) is such kind of one important product of DE. In order to make people get more information from GE's limited information recourses, we utilize IE to extract needed information from semi-structured web page biographies and map the information to corresponding places on GE. Also, how people read traditional 2-D text in a 3-D environment is studied. How the previous text biography is vividly presented on ‘our planet’ like a man's life trace is introduced in our work.
Research of Module-Based Airplane Configuration Management Technology
Authors: Yong Yu , Hu Lu , Younus Muhammad , Fan Yuqing
Published: December 2010

The increasing airplane diversification, complication, serialization, and customization needs an excellent configuration management and control system to guarantee the consistency, integrity, orderly and traceability of information data. In this paper, few key methods are proposed and analyzed to improve the airplane configuration management and control. Airplane configuration definition is optimized by classifying options and module. Management mode has been change from drawing-central to part-central management, and every part has been assigned a unique identification number. Airplane product structure is established by modules whereas Link-Module and Independent-Module are classified by relationship of modules and options. Effectivity is replaced on the module not on every part to simplified effectivity management. Improved hierarchical version control by two-level version tracking model has been introduced which provides the rules of changes about part number or version identification.
Simulation of electron beam lithography of nanostructures
Authors: Stepanova M. , Fito T. , Szabó Zs. , Alti K. , Adeyenuwo A. P. , Koshelev K. , Aktary M. , Dew S. K.
Published: December 2010

The authors report a numeric simulation tool that they developed for the modeling and analysis of electron beam lithography (EBL) of nanostructures employing a popular positive tone resist polymethylmethacrylate (PMMA). Modeling and process design for EBL fabrication of 5–50 nm PMMA structures on solid substrates is the target purpose of the simulator. The simulator is functional for exposure energies from 1 to 50 keV with arbitrary writing geometries. The authors employ a suite of kinetic models for the traveling of primary, secondary, and backscattered electrons in the resist, compute three-dimensional (3D) distributions of the yield of main-chain scission in PMMA, and convert these into the local volume fractions of fragments of various sizes. The kinetic process of development is described by the movement of the resist-developer interface with the rate derived from the mean-field theory of polymer diffusion. The EBL simulator allows the computation of detailed 3D distributions of the yield of main-chain scission in PMMA for various conditions of exposure, the corresponding volume fractions of small fragments, and the clearance profiles as functions of the development in time and temperature. This article describes the models employed to simulate the EBL exposure and development, reports examples of the computations, and presents comparisons of the predicted development profiles with experimental cross-sectional resist profiles in dense gratings.
Impact of the resist properties on the antisticking layer degradation in UV nanoimprint lithography
Authors: Francone A. , Iojoiu C. , Poulain C. , Lombard C. , Pépin-Donat B. , Boussey J. , Zelsmann M.
Published: December 2010

In this work, the authors evaluate the impact of chemical and mechanical properties of UV nanoimprint lithography resists on the durability of antisticking treatments applied on the quartz mold surface. To do this, three acrylate-based resists were formulated and characterized. Fourier transform infrared spectroscopy was used to investigate the degree of conversion of each formulation as a function of the exposure dose and electron spin resonance was used to investigate the chemical reactivity of each formulation with respect to a fluorinated antisticking layer (Optool DSX from Daikin Chemicals). The impact of resist mechanical properties on the mold surface treatment degradation was also studied. Elastic modulus and hardness were measured by nanoindentation as a function of the polymerization degree. Then, these resists were imprinted with a dummy quartz template treated beforehand with the antisticking layer. The release properties of the molds were monitored by measuring their free surface energy as a function of the chemical and mechanical properties of the imprinted resists. A detailed comparative study has shown that release properties degradation is more governed by a mechanical than by a chemical interaction.
Inspection of open defects in a thin film transistor-liquid crystal display panel by using a low-energy electron microcolumn
Authors: Oh Tae Sik , Kim Dae-Wook , Kim Young Chul , Ahn Seungjoon , Lee Gun-hee , Kim Ho Seob
Published: December 2010

The demand on the electron beam (e-beam) for the inspection of semiconductor devices or display panel is rapidly increasing since e-beam cannot only monitor the small structures but also has the potential of detecting electrical troubles or repairing the defects. However, the merit of e-beam is limited because of the high cost, low throughput, and the possible damage due to the high e-beam energy. A microcolumn is a strong candidate to solve these limitations as its size is extremely miniaturized (both column diameter and height can be reduced down to a few millimeters) and the output e-beam energy is as low as 100–1000 eV. In this work, the authors tried to test the inspection of defects by applying a low voltage microcolumn to liquid crystal display panel. In order to demonstrate the authors’ inspection method, they extracted a 7’’ thin film transistor-liquid crystal display (TFT-LCD) panel from the production line just after completing the pixel structures and used this panel as a test sample. On the selected panel, the authors intentionally made some defects such as open data or gate lines by cutting some points using a laser beam. They operated their microcolumn with a beam energy of 300 eV and obtained the scanning images of the panel while operating the panel with specific operation conditions. The operation parameters for the test TFT-LCD panel such as the voltages applied to the gate lines, data lines, and storage capacitors was fixed at two specific sets of values. Then, the image obtained by the secondary electron reflects the information on the electrical state of the pixels as well as the geometrical ones. By combining the two sets of data, the authors could explain the correlation between the irregular behavior in the image contrast and the open defects and the detailed results will be discussed.
Piezoresistive effect in the three-dimensional diamondlike carbon nanostructure fabricated by focused-ion-beam chemical vapor deposition
Authors: Kometani Reo , Yusa Kouki , Warisawa Shin’ichi , Ishihara Sunao
Published: December 2010

In this study, the electrical material characteristics of a three-dimensional (3D) diamondlike carbon (DLC) structure fabricated by focused-ion-beam chemical vapor deposition (FIB-CVD) were evaluated to realize functional 3D nano- and micromechanical devices based on the piezoresistive material. However, the DLC cantilever structure fabricated by FIB-CVD did not exhibit piezoresistive properties due to the incorporated gallium (Ga), which was implanted by Ga+ FIB irradiation. Therefore, a method for the modification of material characteristics was examined to introduce piezoresistive properties in the 3D DLC structure fabricated by FIB-CVD. Long-time annealing (12 h or more) at a low temperature (300 °C) was found to be an effective method to realize a 3D DLC structure with piezoresistive properties. Long-time annealing at low temperatures caused Ga elimination from the DLC without any change in the sp2/(sp2+sp3) ratio. The values of the gauge factor were in the range of 2–34. 3D nano- and microstructures with piezoresistive properties could be realized by FIB-CVD and annealing treatment.
Gas field ion source and liquid metal ion source charged particle material interaction study for semiconductor nanomachining applications
Authors: Tan Shida , Livengood Richard , Shima Darryl , Notte John , McVey Shawn
Published: December 2010

Semiconductor manufacturing technology nodes will evolve to the 22, 15, and 11 nm generations in the next few years. For semiconductor nanomachining applications, further beam spot size scaling is required beyond what is capable by present generation Ga+ focused ion beam technology. As a result, continued Ga+ beam scaling and/or alternative beam technology innovations will be required. In this work, several alternative ion beam technologies are explored and compared to Ga+ beam for key nanomachining and substrate interaction attributes. First, thorough Monte Carlo simulations were conducted with various ion species incident on silicon and copper. Additionally, silicon and copper substrates were experimentally exposed to ion beams of helium, neon, and gallium. These substrates were subsequently analyzed to determine the sputter yields and subsurface damage.
Nanoimprinted P3HT/C60 solar cells optimized by oblique deposition of C60
Authors: Yang Yi , Aryal Mukti , Mielczarek Kamil , Hu Walter , Zakhidov Anvar
Published: December 2010

Poly(3-hexylthiophene) (P3HT)-C60 organic photovoltaic devices with interpenetrating donor-acceptor interfaces were fabricated by oblique thermal deposition of C60 into the P3HT nanogratings. The uniformity and step coverage of C60 infiltration into the P3HT nanostructures, which can determine the device performance, were dependent on the C60 evaporation angle. It was also observed that the C60 deposition rate and thickness determine the efficiency. A 50% improvement in power conversion efficiency is observed due to the increased exciton dissociation rate at the larger area P3HT-C60 interface at optimal C60 deposition filling. With the proposed technique, a highly efficient organic solar cell using an insoluble acceptor has been fabricated.
High accuracy UV-nanoimprint lithography step-and-repeat master stamp fabrication for wafer level camera application
Authors: Kreindl G. , Glinsner T. , Miller R. , Treiblmayr D. , Födisch R.
Published: December 2010

Herein, the authors demonstrate the use of step-and-repeat nanoimprint lithography for the fabrication of wafer level lens master. Thereby, the authors will focus on so far unmet needs in regard to lateral lens to lens positioning, residual layer uniformities, as well as optic axis tilt control to enable the fabrication of high-end megapixel camera modules.
Alanine/EPR dosimetry applied to the verification of a total body irradiation protocol and treatment planning dose calculation using a humanoid phantom
Authors: Schaeken B. , Lelie S. , Meijnders P. , Van den Weyngaert D. , Janssens H. , Verellen D.
Published: December 2010

Purpose:

To avoid complications in total body irradiation (TBI), it is important to achieve a homogeneous dose distribution throughout the body and to deliver a correct dose to the lung which is an organ at risk. The purpose of this work was to validate the TBI dose protocol and to check the accuracy of the 3D dose calculations of the treatment planning system.

Methods:

Dosimetry based on alanine/electron paramagnetic resonance (EPR) was used to measure dose at numerous locations within an anthropomorphic phantom (Alderson®) that was irradiated in a clinical TBI beam setup. The alanine EPR dosimetry system was calibrated against water calorimetry in a Co‐60 beam and the absorbed dose was determined by the use of “dose‐normalized amplitudes”. The dose rate of the TBI beam was checked against a Farmer ionization chamber. The phantom measurements were compared to 3D dose calculations from a treatment planning system (Pinnacle®) modeled for standard dose calculations.

Results:

Alanine dosimetry allowed accurate measurements which were in accordance with ionization chamber measurements. The combined relative standard measurement uncertainty in the Alderson phantom was. The humanoid phantom was irradiated to a reference dose of 10 Gy, limiting the lung dose to 7.5 Gy. The ratio of the average measured dose midplane in the craniocaudal direction to the reference dose was 1.001 with a spread of ±4.7% (1 sd). Dose to the lung was measured in 26 locations and found, in average, 1.8% lower than expected. Lung dose was homogeneous in the ventral‐dorsal direction but a dose gradient of was observed in the craniocaudal direction midline within the lung lobe. 3D dose calculations (Pinnacle®) were found, in average, 2% lower compared to dose measurements on the body axis and 3% lower for the lungs.

Conclusions:

The alanine/EPR dosimetry system allowed accurate dose measurements which enabled the authors to validate their TBI dose protocol. Dose calculations based on a collapsed cone convolution dose algorithm modeled for regular treatments are accurate within 3% and can further be improved when the algorithm is modeled for TBI.
Comparison of radiation exposure and associated radiation‐induced cancer risks from mammography and molecular imaging of the breasta)
Authors: O'Connor Michael K. , Li Hua , Rhodes Deborah J. , Hruska Carrie B. , Clancy Conor B. , Vetter Richard J.
Published: December 2010

Purpose:

Recent studies have raised concerns about exposure to low‐dose ionizing radiation from medical imaging procedures. Little has been published regarding the relative exposure and risks associated with breast imaging techniques such as breast specific gamma imaging (BSGI), molecular breast imaging (MBI), or positron emission mammography (PEM). The purpose of this article was to estimate and compare the risks of radiation‐induced cancer from mammography and techniques such as PEM, BSGI, and MBI in a screening environment.

Methods:

The authors used a common scheme for all estimates of cancer incidence and mortality based on the excess absolute risk model from the BEIR VII report. The lifetime attributable risk model was used to estimate the lifetime risk of radiation‐induced breast cancer incidence and mortality. All estimates of cancer incidence and mortality were based on a population of 100 000 females followed from birth to age 80 and adjusted for the fraction that survives to various ages between 0 and 80. Assuming annual screening from ages 40 to 80 and from ages 50 to 80, the cumulative cancer incidence and mortality attributed to digital mammography, screen‐film mammography, MBI, BSGI, and PEM was calculated. The corresponding cancer incidence and mortality from natural background radiation was calculated as a useful reference. Assuming a 15%–32% reduction in mortality from screening, the benefit/risk ratio for the different imaging modalities was evaluated.

Results:

Using conventional doses of 925 MBq Tc‐99m sestamibi for MBI and BSGI and 370 MBq F‐18 FDG for PEM, the cumulative cancer incidence and mortality were found to be 15–30 times higher than digital mammography. The benefit/risk ratio for annual digital mammography was for both the 40–80 and 50–80 screening groups, but dropped to 3:1 for the 40–49 age group. If the primary use of MBI, BSGI, and PEM is in women with dense breast tissue, then the administered doses need to be in the range 75–150 MBq for Tc‐99m sestamibi and 35 MBq–70 MBq for F‐18 FDG in order to obtain benefit/risk ratios comparable to those of mammography in these age groups. These dose ranges should be achievable with enhancements to current technology while maintaining a reasonable examination time.

Conclusions:

The results of the dose estimates in this study clearly indicate that if molecular imaging techniques are to be of value in screening for breast cancer, then the administered doses need to be substantially reduced to better match the effective doses of mammography.
Evaluation of a multi‐atlas based method for segmentation of cardiac CTA data: a large‐scale, multicenter, and multivendor study
Authors: Kirişli H. A. , Schaap M. , Klein S. , Papadopoulou S. L. , Bonardi M. , Chen C. H. , Weustink A. C. , Mollet N. R. , Vonken E. J. , van der Geest R. J. , van Walsum T. , Niessen W. J.
Published: December 2010

Purpose:

Computed tomography angiography (CTA) is increasingly used for the diagnosis of coronary artery disease (CAD). However, CTA is not commonly used for the assessment of ventricular and atrial function, although functional information extracted from CTA data is expected to improve the diagnostic value of the examination. In clinical practice, the extraction of ventricular and atrial functional information, such as stroke volume and ejection fraction, requires accurate delineation of cardiac chambers. In this paper, we investigated the accuracy and robustness of cardiac chamber delineation using a multiatlas based segmentation method on multicenter and multivendor CTA data.

Methods:

A fully automatic multiatlas based method for segmenting the whole heart (i.e., the outer surface of the pericardium) and cardiac chambers from CTA data is presented and evaluated. In the segmentation approach, eight atlas images are registered to a new patient's CTA scan. The eight corresponding manually labeled images are then propagated and combined using a per voxel majority voting procedure, to obtain a cardiac segmentation.

Results:

The method was evaluated on a multicenter/multivendor database, consisting of (1) a set of 1380 Siemens scans from 795 patients and (2) a set of 60 multivendor scans (Siemens, Philips, and GE) from different patients, acquired in six different institutions worldwide. A leave‐one‐out 3D quantitative validation was carried out on the eight atlas images; we obtained a mean surface‐to‐surface error of and an average Dice coefficient of 0.93 was achieved. A 2D quantitative evaluation was performed on the 60 multivendor data sets. Here, we observed a mean surface‐to‐surface error of and an average Dice coefficient of 0.91 was achieved. In addition to this quantitative evaluation, a large‐scale 2D and 3D qualitative evaluation was performed on 1380 and 140 images, respectively. Experts evaluated that 49% of the 1380 images were very accurately segmented (below 1 mm error) and that 29% were accurately segmented (error between 1 and 3 mm), which demonstrates the robustness of the presented method.

Conclusions:

A fully automatic method for whole heart and cardiac chamber segmentation was presented and evaluated using multicenter/multivendor CTA data. The accuracy and robustness of the method were demonstrated by successfully applying the method to 1420 multicenter/multivendor data sets.
High‐rate x‐ray spectroscopy in mammography with a CdTe detector: A digital pulse processing approach
Authors: Abbene L. , Gerardi G. , Principato F. , Del Sordo S. , Ienzi R. , Raso G.
Published: December 2010

Purpose:

Direct measurement of mammographic x‐ray spectra under clinical conditions is a difficult task due to the high fluence rate of the x‐ray beams as well as the limits in the development of high resolution detection systems in a high counting rate environment. In this work we present a detection system, based on a CdTe detector and an innovative digital pulse processing (DPP) system, for high‐rate x‐ray spectroscopy in mammography.

Methods:

The DPP system performs a digital pile‐up inspection and a digital pulse height analysis of the detector signals, digitized through a 14‐bit, 100 MHz digitizer, for x‐ray spectroscopy even at high photon counting rates. We investigated on the response of the digital detection system both at low (150 cps) and at high photon counting rates (up to 500 kcps) by using monoenergetic x‐ray sources and a nonclinical molybdenum anode x‐ray tube. Clinical molybdenum x‐ray spectrum measurements were also performed by using a pinhole collimator and a custom alignment device.

Results:

The detection system shows excellent performance up to 512 kcps with an energy resolution of 4.08% FWHM at 22.1 keV. Despite the high photon counting rate (up to 453 kcps), the molybdenum x‐ray spectra, measured under clinical conditions, are characterized by a low number of pile‐up events. The agreement between the attenuation curves and the half value layer values, obtained from the measured spectra, simulated spectra, and from the exposure values directly measured with an ionization chamber, also shows the accuracy of the measurements.

Conclusions:

These results make the proposed detection system a very attractive tool for both laboratory research and advanced quality controls in mammography.
Acoustic radiation force contrast in MRI: Detection of calcifications in tissue‐mimicking phantoms
Authors: Mende Jessica , Wild Judith , Ulucay Deniz , Radicke Marcus , Kofahl Anna‐Lisa , Weber Bernd , Krieg Robert , Maier Karl
Published: December 2010

Purpose:

Mammography is a widely used tool for the screening of breast cancer, and calcifications are a common finding in most mammograms. The location, size, number, morphology, and distribution of calcifications are an important information to differentiate a benign lesion from probably malignant pathologies. Calcifications are not detectable with a standard dynamic contrast enhanced breast MRI. The authors present a novel method for the detection and imaging of calcifications in breast tissue without ionizing radiation or contrast agents.

Methods:

Measurements of localized tissue displacement in phantoms due to applied acoustic radiation force were performed. This displacement was imaged with a displacement sensitive spin‐echo MRI sequence. Pieces of eggshell that represent calcifications were embedded in tissue‐mimicking agarose phantoms. The sizes of the calcifications were, , and . The calcifications were scanned with ultrasound (U.S.) at 2.5 MHz and intensities up to . The U.S. beam was moved inside the phantom by a computer‐controlled three‐dimensional hydraulic positioning system. The U.S. beam was scanned over the two smaller calcifications with the displacement sensitivity of the MRI sequence parallel to the U.S. beam path. Grayscale coded maps of the displacement scans are presented. For the calcification, the U.S. intensities were varied. Finite element simulations were performed to verify if the experiments complied with theory.

Results:

The authors found that the displacement caused by the U.S. is increased at the position of the calcification. The area of increased displacement is at least twice as large as the calcification itself. The simulations show this increase in displacement and area at the position of the calcification. When changing the displacement sensitivity direction to perpendicular to the U.S. beam, a crossed black and white four‐leaf clover is visible at the position of the calcification.

Conclusions:

The U.S. is scattered and reflected by the calcifications. This leads to the increased displacement which is transmitted to the surrounding material because of the elastic coupling between the calcification and the agarose material. Due to the high differences in acoustic impedance and elastic properties between the surrounding tissue and the calcification, even the detection of pieces smaller than the resolution of the MRI scanner is possible. The acoustic radiation force contrast in MR phase‐difference images offers a positive signal for calcifications from a smooth background in phantoms. This method offers a possibility of differentiating qualitatively and quantitatively hard calcifications from stiffer inclusions such as tumors.
A novel off‐axis scanning method for an enlarged ellipse cone‐beam computed tomography field of view
Authors: Li Tianfang , Li Xiang , Yang Yong , Heron Dwight E. , Huq M. Saiful.
Published: December 2010

Purpose:

Current on‐board imaging systems commonly used by modern linear accelerators (LINACs) have a limited field of view (FOV) for a cone‐beam CT (CBCT) scan, which is typically less than 50 cm. Consequently, truncation artifacts often occur for large patients. The goal of this work is to investigate a novel method to increase the FOV for current on‐board CBCT systems.

Methods:

When a large patient is scanned with CBCT, any region outside the FOV is only partially sampled within a short range of projection angles, and at other angles no x‐ray beams may pass through that region. To increase the sampling rate for the region outside the FOV, we have designed a new source trajectory by shifting the center of rotation during a CBCT scan. This resulted in a reduced sampling rate at the central area and increased sampling rate at the edges. The tradeoff led to a more balanced sampling for an enlarged FOV. An iterative algorithm was also developed to reconstruct the CT image under the new sampling scheme using a compressed sensing technique.

Results:

The method was validated by numerical simulations mimicking a Varian Trilogy CBCT system, and it was found that artifact‐free images could be obtained with the FOV as large as 80 cm.

Conclusions:

The new CT scanning trajectory can be easily realized under current clinical setup with little modification of the control system, and this can be useful for treating obese patients.
Combining registration and active shape models for the automatic segmentation of the lymph node regions in head and neck CT images
Authors: Chen Antong , Deeley Matthew A. , Niermann Kenneth J. , Moretti Luigi , Dawant Benoit M.
Published: December 2010

Purpose:

Intensity‐modulated radiation therapy (IMRT) is the state of the art technique for head and neck cancer treatment. It requires precise delineation of the target to be treated and structures to be spared, which is currently done manually. The process is a time‐consuming task of which the delineation of lymph node regions is often the longest step. Atlas‐based delineation has been proposed as an alternative, but, in the authors' experience, this approach is not accurate enough for routine clinical use. Here, the authors improve atlas‐based segmentation results obtained for level II–IV lymph node regions using an active shape model (ASM) approach.

Methods:

An average image volume was first created from a set of head and neck patient images with minimally enlarged nodes. The average image volume was then registered using affine, global, and local nonrigid transformations to the other volumes to establish a correspondence between surface points in the atlas and surface points in each of the other volumes. Once the correspondence was established, the ASMs were created for each node level. The models were then used to first constrain the results obtained with an atlas‐based approach and then to iteratively refine the solution.

Results:

The method was evaluated through a leave‐one‐out experiment. The ASM‐ and atlas‐based segmentations were compared to manual delineations via the Dice similarity coefficient (DSC) for volume overlap and the Euclidean distance between manual and automatic 3D surfaces. The mean DSC value obtained with the ASM‐based approach is 10.7% higher than with the atlas‐based approach; the mean and median surface errors were decreased by 13.6% and 12.0%, respectively.

Conclusions:

The ASM approach is effective in reducing segmentation errors in areas of low CT contrast where purely atlas‐based methods are challenged. Statistical analysis shows that the improvements brought by this approach are significant.