363 research outputs found
Electrical Nanoprobing of Semiconducting Carbon Nanotubes using an Atomic Force Microscope
We use an Atomic Force Microscope (AFM) tip to locally probe the electronic
properties of semiconducting carbon nanotube transistors. A gold-coated AFM tip
serves as a voltage or current probe in three-probe measurement setup. Using
the tip as a movable current probe, we investigate the scaling of the device
properties with channel length. Using the tip as a voltage probe, we study the
properties of the contacts. We find that Au makes an excellent contact in the
p-region, with no Schottky barrier. In the n-region large contact resistances
were found which dominate the transport properties.Comment: 4 pages, 5 figure
MULTIPROCESSOR MODELING TECHNOLOGIES FOR THE APPLIED STATISTICAL TASKS
The work considers the multiprocessors technologies of modeling for Monte Carlo tasks. It is shown that only application of the modern super productive systems permitted the new way to realize the mechanism of corresponding partitioned computations. The calculating schemes that supply to provide the increase of productivity and calculations' speed effectiveness are shown. In this article the modified algorithm of parallel calculations is offered based on the Monte Carlo method. Here every calculator has its own random generator of numbers. Thus intermediate calculations come true independently on the different, separately taken blades of cluster, "calculators". The results are already processed on some separately taken master -blades ("analyzer"). This allows to get rid from the necessary presence of router-communicator between the random generator of numbers and "calculator". Obviously, that such decision allows to accelerate the process of calculations. It is shown that the parallel algorithms of the Monte Carlo method are stable to any input data and have the maximal parallel form and, thus, minimal possible time of realization using the parallel computing devices. If it is possible to appoint one processor to one knot of calculation. Thus the realization of calculations becomes possible in all knots of net area in parallel and simultaneously.The work considers the multiprocessors technologies of modeling for Monte Carlo tasks. It is shown that only application of the modern super productive systems permitted the new way to realize the mechanism of corresponding partitioned computations. The calculating schemes that supply to provide the increase of productivity and calculations' speed effectiveness are shown. In this article the modified algorithm of parallel calculations is offered based on the Monte Carlo method. Here every calculator has its own random generator of numbers. Thus intermediate calculations come true independently on the different, separately taken blades of cluster, "calculators". The results are already processed on some separately taken master -blades ("analyzer"). This allows to get rid from the necessary presence of router-communicator between the random generator of numbers and "calculator". Obviously, that such decision allows to accelerate the process of calculations. It is shown that the parallel algorithms of the Monte Carlo method are stable to any input data and have the maximal parallel form and, thus, minimal possible time of realization using the parallel computing devices. If it is possible to appoint one processor to one knot of calculation. Thus the realization of calculations becomes possible in all knots of net area in parallel and simultaneously
Electromechanical instability in suspended carbon nanotubes
We have theoretically investigated electromechanical properties of freely
suspended carbon nanotubes when a current is injected into the tubes using a
scanning tunneling microscope. We show that a shuttle-like electromechanical
instability can occur if the bias voltage exceeds a dissipation-dependent
threshold value. An instability results in large amplitude vibrations of the
carbon nanotube bending mode, which modify the current-voltage characteristics
of the system
Online Εvaluation of Earth Observation Derived Indicators for Urban Planning and Management
Extensive urbanization and growth of population density have acquired a paramount interest towards a sustainable urban development. Earth Observation (EO) is an important source of information required for urban planning and management. The availability of EO data provides the immense opportunity for urban environmental indicators development easily derived by remote sensors. In this study, the state of the art methods were employed to develop urban planning and management relevant indicators that can be evaluated by using EO data. The importance of this approach lies on providing alternatives for improving urban planning and management, without consuming time and resources in collecting field or archived data. The evaluated urban indicators were integrated into a Web‐based Information System that was developed for online exploitation. The results for three case studies are therefore available online and can be used by urban planners and stakeholders in supporting their planning decisions
Strong coupling between single-electron tunneling and nano-mechanical motion
Nanoscale resonators that oscillate at high frequencies are useful in many
measurement applications. We studied a high-quality mechanical resonator made
from a suspended carbon nanotube driven into motion by applying a periodic
radio frequency potential using a nearby antenna. Single-electron charge
fluctuations created periodic modulations of the mechanical resonance
frequency. A quality factor exceeding 10^5 allows the detection of a shift in
resonance frequency caused by the addition of a single-electron charge on the
nanotube. Additional evidence for the strong coupling of mechanical motion and
electron tunneling is provided by an energy transfer to the electrons causing
mechanical damping and unusual nonlinear behavior. We also discovered that a
direct current through the nanotube spontaneously drives the mechanical
resonator, exerting a force that is coherent with the high-frequency resonant
mechanical motion.Comment: Main text 12 pages, 4 Figures, Supplement 13 pages, 6 Figure
Complex 99mTc-PDA-DTPA for myocardial imaging
The 123I-labeled fatty acids such as 123I-Iodophenylpentadecanoic acid and 123I-Beta-methyliodophenylpentadecanoic acid are the agents used clinically for myocardial imaging. Fatty acids are the major source of energy for the normal myocardium. However, under ischemic conditions the myocardial cells switch to glucose metabolism for their energy needs. Fatty acids undergo prolonged metabolic stunning in patients with reversible ischemia, thereby helping in early diagnosis of coronary artery disease in highrisk patients. High cost andlimited availability of cyclotron-produced 123I, makes 99mTc-labeled fatty acids more desirable for the purpose. In diagnosis the dominant radionuclide is 99mTc. It is estimated that it is involved in about 85% of all imaging procedures in nuclear medicine. The method for preparation of new 99mTc-fatty chemical systems based on modified diethylene triamine pentaacetic acid (DTPA) molecule has been elaborated in this work . The main advantage using DTPA as chelate agent for radioactive label, is the molecule or it's derivative ability to form sufficiently stable complexes with different radioactive metals including technetium-99. Moiety of pentadecanoic acid addition gave the ability to prepare modified complex of DTPA. In a labeling procedure, freshly eluted Na99mTcO4 (20mCi) was added to a mixture of cysteine, stannous chloride, PDK-DTPA and ethanol in a vial. On keeping the reaction mixture at 90 0C for 30 min, [99mTc-PDK-DTPA] radiopharmaceutical was formed. Thereafter, the reaction mixture was cooled over ice and characterized by HPLC. The result of dynamic scintigraphic research showed, that after being injected, the substance is actively acumulated into myocardium. Eventually one can say that modified DTPA-moleculs are functionally suitable for myocardial imaging
RUSSIAN ENGINEERING TEACHERS AS AN IMPORTANT PART OF IGIP
The paper highlights the milestones of the history of the International Society for Engineering Pedagogy (IGIP) from 1972 until now. Professor A. Melezinek was a founder of the society; he developed its structure that survived to the present time. Now his pedagogical ideas are being developed and revised to reflect the changes in the goals and contents of engineering education, new methods, means of training and control, modern communication capabilities. Global challenges, problems of sustainable development and construction of the so-called “Resilient Society” were the main topics of the last Annual IGIP conferences. Globalization has led to the organization of the International Federation of Engineering Education Societies (IFEES). IGIP was one of its founders in 2006. We discuss different aspects of cooperation between Russian technical universities and IGIP, which began in 1995. Regional IGIP conferences and round tables are one of the aspects of such cooperation. The importance of this interaction for the Russian scientific school of engineering education is emphasized
Prediction of Bodyweight and Energy Expenditure Using Point Pressure and Foot Acceleration Measurements
Bodyweight (BW) is an essential outcome measure for weight management and is also a major predictor in the estimation of daily energy expenditure (EE). Many individuals, particularly those who are overweight, tend to underreport their BW, posing a challenge for monitors that track physical activity and estimate EE. The ability to automatically estimate BW can potentially increase the practicality and accuracy of these monitoring systems. This paper investigates the feasibility of automatically estimating BW and using this BW to estimate energy expenditure with a footwear-based, multisensor activity monitor. The SmartShoe device uses small pressure sensors embedded in key weight support locations of the insole and a heel-mounted 3D accelerometer. Bodyweight estimates for 9 subjects are computed from pressure sensor measurements when an automatic classification algorithm recognizes a standing posture. We compared the accuracy of EE prediction using estimated BW compared to that of using the measured BW. The results show that point pressure measurement is capable of providing rough estimates of body weight (root-mean squared error of 10.52 kg) which in turn provide a sufficient replacement of manually-entered bodyweight for the purpose of EE prediction (root-mean squared error of 0.7456 METs vs. 0.6972 METs). Advances in the pressure sensor technology should enable better accuracy of body weight estimation and further improvement in accuracy of EE prediction using automatic BW estimates
Coupling carbon nanotube mechanics to a superconducting circuit
The quantum behaviour of mechanical resonators is a new and emerging field
driven by recent experiments reaching the quantum ground state. The high
frequency, small mass, and large quality-factor of carbon nanotube resonators
make them attractive for quantum nanomechanical applications. A common element
in experiments achieving the resonator ground state is a second quantum system,
such as coherent photons or superconducting device, coupled to the resonators
motion. For nanotubes, however, this is a challenge due to their small size.
Here, we couple a carbon nanoelectromechanical (NEMS) device to a
superconducting circuit. Suspended carbon nanotubes act as both superconducting
junctions and moving elements in a Superconducting Quantum Interference Device
(SQUID). We observe a strong modulation of the flux through the SQUID from
displacements of the nanotube. Incorporating this SQUID into superconducting
resonators and qubits should enable the detection and manipulation of nanotube
mechanical quantum states at the single-phonon level
Photocurrent Imaging of p-n Junctions and Local Defects in Ambipolar Carbon Nanotube Transistors
We use scanning photocurrent microscopy (SPCM) to investigate the properties
of internal p-n junctions as well as local defects in ambipolar carbon nanotube
(CNT) transistors. Our SPCM images show strong signals near metal contacts
whose polarity and positions change depending on the gate bias. SPCM images
analyzed in conjunction with the overall conductance also indicate the
existence and gate-dependent evolution of internal p-n junctions near contacts
in the n-type operation regime. To determine the p-n junction position and the
depletion width with a nanometer scale resolution, a Gaussian fit was used. We
also measure the electric potential profile of CNT devices at different gate
biases, which shows that both local defects and induced electric fields can be
imaged using the SPCM technique. Our experiment clearly demonstrates that SPCM
is a valuable tool for imaging and optimizing electrical and optoelectronic
properties of CNT based devices.Comment: 5 pages, 5 figure
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