Showing papers in "Physics Procedia in 2012"

Abstract: Selective Laser Melting (SLM) is an Additive Manufacturing (AM) technique in which a part is built up in a layer- by-layer manner by melting the top surface layer of a powder bed with a high intensity laser according to sliced 3D CAD data. In this work, mechanical properties like tensile strength, elongation, Young's modulus, impact toughness and hardness are investigated for SLM-produced AlSi10Mg parts, and compared to conventionally cast AlSi10Mg parts. It is shown that AlSi10Mg parts with mechanical properties comparable or even exceeding to those of conventionally cast AlSi10Mg can be produced by SLM.

Abstract: A free data-analysis framework for muSR has been developed. musrfit is fully written in C++, is running under GNU/Linux, Mac OS X, as well as Microsoft Windows, and is distributed under the terms of the GNU GPL. It is based on the CERN ROOT framework and is utilizing the Minuit optimization routines for fitting. It consists of a set of programs allowing the user to analyze and visualize the data. The fitting process is controlled by an ascii-input file with an extended syntax. A dedicated text editor is helping the user to create and handle these files in an efficient way, execute the fitting, show the data, get online help, and so on. A versatile tool for the generation of new input files and the extraction of fit parameters is provided as well. musrfit facilitates a plugin mechanism allowing to invoke user-defined functions. Hence, the functionality of the framework can be extended with a minimal amount of overhead for the user. Currently, musrfit can read the following facility raw-data files: PSI-BIN, MDU (PSI), ROOT (LEM/PSI), WKM (outdated ascii format), MUD (TRIUMF), NeXus (ISIS).

Abstract: Layerwise Laser Melting (LLM) is an Additive Manufacturing process which allows producing complex metallic parts by building parts layer by layer. Monitoring and control of the melting process is needed for further development of the process and future adoption of the process by industry since it allows to monitor the quality of the building process during the actual build job. Furthermore, melt pool monitoring enables a better and more fundamental understanding of the thermal behavior of the process. This paper describes a system for monitoring of the melt pool during LLM and a data processing algorithm to map the measured melt pool data in space. With this so called mapping approach the data interpretation can be significantly reduced. It will be shown that with this system a wide range of process failures can be detected during the process.

Abstract: In a repair process chain, damaged areas or cracks can be removed by milling and subsequently be reconditioned with new material deposition. The use of laser metal deposition has been investigated for this purpose. The material has been deposited into different groove shapes, using both stainless steel and Ti-6Al-4 V. The influence of welding parameters on the microstructure and the heat affected zone has been studied. The parameters have been modified in order to achieve low heat input and consequently low distortion as well as low metallurgical impact. Finally, an evaluation of the opportunities for an automatized repair process is made.

Abstract: Thin metal films have recently attracted large interest due to their practical application in photo-detectors, solar cells and quantum electronics. It is known that thin films of noble metals such as Au, Ag, and Cu have a maximum optical transmittance in the shorter part of spectrum. In our work, optical properties of thin metals films deposited by thermal evaporation and low pressure (1.33·10-5 - 1.33·10-4 Pa) DC plasma sputtering were investigated. Such low pressure is provided by triode sputtering method which supports a ballistic type of mass transfer between the sputtering target and the substrate. This method enables fine control of the film thickness and its density. Comparison of the films deposited by mentioned above two methods on glass substrates shows significant differences in their optical and electrical properties. Thin films of following metals: Sn, Al, V, Ti, Ni, Mo, Ta, W, Au, Ag, and Cu were deposited on glass and their optical and electrical properties were studied. The transmission spectra of thin films of various metals have significant differences. In our paper we discuss the causes of these differences.

Abstract: The median filtering algorithm has good noise-reducing effects, but its time complexity is not desirable. The paper proposed an improved median filtering algorithm. The algorithm uses the correlation of the image to process the features of the filtering mask over the image. It can adaptively resize the mask according to noise levels of the mask. The statistical histogram is also introduced in the searching process of the median value. Experimental results show that the algorithm reduces the noise and retains the details of the image. The complexity of the algorithm is decreased to O (N), and the performance of noise reduction has effectively improved.

Abstract: Laser melting of titanium material, e.g. Ti-6Al-4 V, offers great potential in manufacturing automotive components, lightweight structures and medical implants. In order to achieve required mechanical properties of laser melted components quality of powder materials is essential. Unmelted powder is recycled and reused in a subsequent process. Due to repeated recycling it is suggested that powder material changes. In this paper aging processes of Ti-6Al-4 V powder are studied. It was observed that powder particles coarsen and flowability increases. Comparing examined powder characteristics to bulk material properties it was noticed that there are significant effects of aged powder on laser melted components.

Abstract: This paper presents our recent progress on the applications of laser metal deposited (LMD) Ti6Al4 V parts. The microstructure of the fabricated parts shows prior columnar β grains consisting of acicular α’ martensite. The yield and ultimate tensile strengths of the fabricated parts are superior to those of cast and annealed wrought material, while the elongation is lower. On-line monitoring and control of the LMD process was performed by monitoring the pool area and feedback controlling the laser power in order to decrease heat accumulation. The substrate dilution is diminished and the decreased heat accumulation reduces its effects on the microstructure.

Abstract: The lack of dense, fast, energy efficient memory has been the main detractor for multiple superconducting digital projects in the past. Recently, fundamental physics research in superconductor-ferromagnet thin-film tunnel structures created a new opportunity to solve this long-standing problem. Superconductivity and ferromagnetism, two deeply antagonistic electronic properties, can co-exist in form of Magnetic Josephson Junctions (MJJs). The superconducting-ferromagnetic MJJs are electrically compatible with traditional superconductor-insulator-superconductor (SIS) Josephson junctions (JJs) used for digital energy-efficient single flux quantum (eSFQ/ERSFQ) circuits. Both MJJ and JJ circuits have similar fabrication process and can be integrated on a single chip. As a result, a combination of MJJs and JJs can be used to form addressable memory cells, energy-efficient memory periphery circuits and programmable logic elements. In this paper, we present the test results of superconductor-insulator-ferromagnet-superconductor (SIFS) MJJs showing their applicability for superconducting spintronic memory and digital circuits.

Abstract: Silicon Photomultipliers (SiPMs) have emerged as promising alternative to fast vacuum photomultiplier tubes (PMT). A fully digital implementation of the Silicon Photomultiplier (dSiPM) has been developed in order to overcome the deficiencies and limitations of the so far only analog SiPMs (aSiPMs). Our sensor is based on arrays of single photon avalanche photodiodes (SPADs) integrated in a standard CMOS process. Photons are detected directly by sensing the voltage at the SPAD anode using a dedicated cell electronics block next to each diode. This block also contains active quenching and recharge circuits as well as a one bit memory for the selective inhibit of detector cells. A balanced trigger network is used to propagate the trigger signal from all cells to the integrated time-to-digital converter. In consequence, photons are detected and counted as digital signals, thus making the sensor less susceptible to temperature variations and electronic noise. The integration with CMOS logic provides the added benefit of low power consumption and possible integration of data post-processing directly in the sensor. In this overview paper, we discuss the sensor architecture together with its characteristics with a focus on scalability and practicability aspects for applications in medical imaging, high energy- and astrophysics.

Abstract: In this paper we combine the largest minimum distance algorithm and the traditional K-Means algorithm to propose an improved K-Means clustering algorithm. This improved algorithm can make up the shortcomings for the traditional K-Means algorithm to determine the initial focal point. The improved K-Means algorithm effectively solved two disadvantages of the traditional algorithm, the first one is greater dependence to choice the initial focal point, and another one is easy to be trapped in local minimum [1] , [2] .

Abstract: Conditions of a layer-by-layer synthesis of 3D parts made of nitinol by a Selective Laser Melting (SLM) are studied. Full-density 3D parts from nitinol are manufactured by the SLM with preheating up to 500 °C. The effect of different laser parameters on the structure and an intermetallic phase composition of the melted samples is analyzed by the methods of optical metallography, microhardness measurement, SEM, X-ray and EDX analysis. Optimal SLM conditions for NiTi sample's fabrication and eventual biomedical applications are discussed.

Abstract: The Internet of Things (IOT) has been paid more and more attention by the academe, industry, and government all over the world. The concept of IOT and the architecture of IOT are discussed. The key technologies of IOT, including Radio Frequency Identification technology, Electronic Product Code technology, and ZigBee technology are analyzed. The framework of digital agriculture application based on IOT is proposed.

Abstract: This paper describes a laser-based process to join thermoplastics with metals thermally without the help of any additives. Using PA6.6 and DC01 the main process parameters were investigated with different joining strategies for laser-transparent and nontransparent thermoplastics. For both process variations a failure of the joint within the base material PA6.6 was achieved. It was also shown that there is no correlation between the standardized surface roughness parameter R a and the shear strength of the joining. The successfully performed joining of PA6 GF45 with DC01 underlines the potential of the described joining method for lightweight design and other industrial applications.

Abstract: In order to clarify the role of AdaBoost algorithm for feature selection, classifier learning and its relation with SVM, this paper provided a brief introduction to the AdaBoost which is used for producing a strong classifier out of weak learners firstly. The original adaptive boosting algorithm and its application in face detection and facial expression recognition are reviewed. In pattern classification domain, support vector machine has been widely used and shows promising performance. However, it is expensive in terms of time-consuming. A sort of cascaded support vector machines architecture is capable of improving the classification accuracy based on AdaBoost boosting algorithm, namely, AdaboostSVM. It applied boosting algorithm to feature selection and classifier learning for support vector machine classification and it has achieved approved performance through some researcher's pioneering work.

Abstract: The article starts with circular economy and the connotation of green supply chain, then analyzes the difference between green supply chain and traditional supply chain and elaborates the content of green supply chain management. On that basis, the approach to implement green supply chain management in china shall be put forward.

Abstract: We have designed and tested at high frequency an RSFQ-based Arithmetic-Logic Unit (ALU), the critical component of an 8-bit RSFQ processor datapath. The ALU design is based on a Kogge-Stone adder and employs an asynchronous wave-pipelined approach scalable for wide datapath processors. The 8-bit ALU circuit was fabricated with HYPRES’ standard 4.5 kA/cm2 process and consists of 7,950 Josephson junctions, including input and output interfaces. In this paper, we present chip design and high-speed test results for the 8-bit ALU circuit.

Abstract: Laser cladding has become an established technology for parts repair and surface modification for cost-intensive components. Due to ongoing improvements of laser sources, process technology and strategy, the range of applications for laser deposition processes is continuously increasing. Critical issues as well as performance and economic efficiency problems have been solved in recent years. Consequently big advances have been done in laser cladding, from micro to macro, from low- to high power as well as in hybrid processes.

Abstract: EASIROC, standing for Extended Analogue Si-pm Integrated ReadOut Chip is a 32 channels fully analogue front end ASIC dedicated to readout SiPM detectors. This low power and highly versatile ASIC was developed from the chip SPIROC[1] which has been designed for the Analogue Hadronic Calorimeter foreseen at the International Linear Collider. EASIROC integrates a 4.5 V range 8-bit DAC per channel for individual SIPM gain adjustment. A multiplexed charge measurement from 160 fC up to 320 pC is available thanks to 2 analogue outputs. These charge paths are made of 2 variable gain preamplifiers followed by 2 tuneable shapers and a track and hold. A trigger path integrates a fast shaper followed by a discriminator the threshold of which is set by an integrated 10-bit DAC. These 32 trigger outputs can be used for timing measurements. The power consumption is lower than 5 mW/channel and unused features can be powered OFF to decrease the power. The chip has been designed in AMS 0.35 μm SiGe technology and 4000 dies have been produced in 2010. Its versatility allows its use in many photo detector experiments and is already used for PEBS, MuRAY, J-PARC and medical imaging.

Abstract: Photovoltaic(PV) Module is indispensable of a stand-alone PV system. In this paper, a one-diode equivalent circuit-based versatile simulation model in the form of masked block PV module is proposed. By the model, it is allowed to estimate behavior of PV module with respect changes on irradiance intensity, ambient temperature and parameters of the PV module. In addition, the model is capable of function of Maximum Power Point Tracking (MPPT) which can be used in the dynamic simulation of stand-alone PV systems.

Abstract: Ahigh resolution(σ< 2 μm) beam telescope based on monolithic active pixel sensors (MAPS) was developed within the EUDET collaboration. EUDET was a coordinated detector R&D programme for the future International Linear Collider providing test beam infrastructure to detector R&D groups. The telescope consists of six sensor planes with a pixel pitch of either 18.4 μm or 10 μmand canbe operated insidea solenoidal magnetic fieldofupto1.2T.Ageneral purpose cooling, positioning, data acquisition (DAQ) and offine data analysis tools are available for the users. The excellent resolution, readout rate andDAQintegration capabilities made the telescopea primary beam tests tool also for several CERN based experiments. In this report the performance of the final telescope is presented. The plans for an even more flexible telescope with three differentpixel technologies(ATLASPixel, Mimosa,Timepix) withinthenew European detector infrastructure project AIDA are presented.

Abstract: A new algorithm GRPDBSCAN (Grid-based DBSCAN Algorithm with Referential Parameters) is proposed in this paper. GRPDBSCAN, which combined the grid partition technique and multi-density based clustering algorithm, has improved its efficiency. On the other hand, because the Eps and Minpts parameters of the DBSCAN algorithm were auto-generated, so they were more objective. Experimental results shown that the new algorithm not only can better differentiate between noises and discovery clusters of arbitrary shapes but also have more robust.

Abstract: The conventional histogram equalization algorithm is easy causing information loss. The paper presented an adaptive histogram-based algorithm in which the information entropy remains the same. The algorithm introduces parameter β in the gray level mapping formula, and takes the information entropy as the target function to adaptively adjust the spacing of two adjacent gray levels in the new histogram. So it avoids excessive gray pixel merger and excessive bright local areas of the image. Experiments show that the improved algorithm may effectively improve visual effects under the premise of the same information entropy. It is useful in CT image processing.

Abstract: From the connotation of green logistics management, we discuss the principles of green packaging, and from the two levels of government and enterprises, we put forward a specific management strategy. The management of green packaging can be directly and indirectly promoted by laws, regulations, taxation, institutional and other measures. The government can also promote new investment to the development of green packaging materials, and establish specialized institutions to identify new packaging materials, standardization of packaging must also be accomplished through the power of the government. Business units of large scale through the packaging and container-based to reduce the use of packaging materials, develop and use green packaging materials and easy recycling packaging materials for proper packaging.

Abstract: A direct laser metal deposition (DLMD) technology with co-axial powder injection is used to fabricate a complex functional graded structure (FGS) fabrication. The aim of the study is to demonstrate the possibility to produce intermetallic phases in the Ti-Al powder systems in the course of a single-step DMD process. Besides, relationships between the main laser cladding parameters and the intermetallic phase structures of the built-up objects have been studied. In our research we applied the optical microscopy, X-ray analysis, microhardness measurement and SEM with EDX analysis of the laser-fabricated intermetallics. The discussion of the mechanisms of Ti x Al y (x,y = 1.3) intermetallic transformations in exothermal reactions is also offered in the report.

Abstract: GET is an international program to develop a reconfigurable and scalable medium sized system to cover nuclear physics requirements for instruments with up to 30k electronic channels.

Abstract: We summarize our recent work, using all atom molecular dynamics simulation to study the role of poly(ethylene glycol) (PEG) in drug delivery. We have simulated the drug delivery liposome membrane, in both the Gel and Liquid crystalline states. The simulations of the PEGylated membrane have been carried out in the presence of a physiological concentration of NaCl, and two other salts encountered in physiological conditions, KCL and CaCl 2 . We also simulated targeting moieties on the PEGylated membrane, comparing the behavior of two targeting moieties. We also simulated PEG with three drug molecules for which it is used as a delivery aid: paclitaxel, piroxicam, and hematoporphyrin. We found that the specific properties of PEG, its solubility in both polar and non-polar solvents, and its acting as a polymer electrolyte, have a significant e_ect on its behavior when used in drug delivery.

Abstract: We demonstrate an economical and robust route to fabricate large-area microchannel plate (MCP) detectors which will open new opportunities in larger area MCP-based detector technologies. Using our newly developed bottom-up process flow, we have fabricated large area MCPs (8 x 8). We used Atomic Layer Deposition (ALD), a powerful and precise thin film deposition technique, to tailor the electrical resistance and secondary electron emission (SEE) properties of large area, low cost, borosilicate glass capillary arrays. The self limiting growth mechanism in ALD allows atomic level control over the thickness and composition of resistive and secondary electron emission (SEE) layers that can be deposited conformally on high aspect ratio capillary glass arrays. We have developed several robust and reliable ALD processes for the resistive coatings and SEE layers to give us precise control over the resistance in the target range for MCPs (106-109 Ω) and SEE coefficient (up to 8). The MCPs are tested in stacks of one or two plates and exhibit gains as high as 107 for a pair of MCPs. This approach allows the functionalization of microporous, insulating substrates to produce MCPs with high gain and low noise. These capabilities allow separation of the substrate material properties from the amplification properties. We studied the various MCP parameters such as gain, background counts, and resistance as a function of the ALD process parameters. Here we describe a complete process flow to produce fully functionalized working large area MCPs.

Abstract: Within a collaboration of American Superconductor, Siemens, Nexans and Southern California Edison one electrical phase of a resistive superconducting fault current limiter for the 115 kV transmission voltage level has been designed and manufactured. The active part of the limiter consists of 63 bifilar coils made of 12 mm wide steel-stabilized YBCO conductor and is housed in a cryostat operated at 5 bar and 74 K. The first phase was completely assembled and successfully subjected to power switching tests and high voltage tests. The basic design of the system and the test results are reported. The work was funded in part by US-DOE under Contract Number DE-FC26-07NT43243.

Abstract: To improve material structure analysis using thermal (cold) neutrons at several pulsed neutron sources, we have developed a new gas detector for neutrons that employs a gas electron multiplier (GEM) as the detector. For neutron detection, both surfaces of a single GEM foil are coated with boron, and to increase efficiency, several GEM foils are stacked in a chamber. A prototype chamber was constructed with 10 cm × 10 cm GEM foils, and several beam tests were performed at a research reactor in Japan and at pulsed neutron sources (Hokkaido University and the Japan Proton Accelerator Research Complex). We achieved a detection efficiency of 30% for 0.22-nm thermal neutrons and a position resolution of ∼0.5 mm. In addition, we demonstrate two applications.