Version Of Source Research Articles

Characterization of a circular arc electron source for a self-neutralizing air-breathing plasma thruster

The paper presents an enhanced version of an arc electron source designed for air ionization applications in a self-neutralizing air-breathing plasma thruster. The arc electron source is specifically suited for the air-breathing plasma thruster, as it allows precise control of mean electron energy levels. This paper focuses on the ionization aspects of air-breathing thrusters through the development of axially magnetized arc electron sources. The sources consist of a circular and coaxial configuration of a metallic arc plasma source coupled with a positively biased grid to extract electrons and control mean electron energy. The average mean electron energy of electrons in the arc electron source is regulated by adjusting the bias voltage of the grid within the range of 0 V – 300 V. To investigate the behavior of ion current density and electron density concerning pressure and mean electron energy, the current probe and magnetic filter were utilized. It was demonstrated that the circular electron source leads to enhanced ionization of airflow by achieving plasma densities greater than 1018 m−3. By utilizing a high-speed camera for the circular arc electron source, the arc spot was seen to move azimuthally due to the magnetic field. Furthermore, scanning electron microscopy and a conductance measurement system were employed for the coaxial arc electron source to examine the deposition and conductance of the electron extraction grid. While the grid underwent deposition of about 600 microns, the conductance was observed to increase/saturate with time and bias voltage, indicating an electrically “self-healing material”.

A source- and channel-coding approach to the analysis and design of languages and ideographies.

Can we explain the advantage natural languages enjoy over ideographies in a way that enables us to attempt the design of an ideography that "works"? I deploy an adapted version of Shannon's source- and channel-coding partitioning of a communication system to explain the communicative dynamics and shortfalls of ideographies, and reveal ways in which entrenchable, generalist ideographies could be designed.

Goal-Oriented Quantization: Analysis, Design, and Application to Resource Allocation

In this paper, the situation in which a receiver has to execute a task from a quantized version of the information source of interest is considered. The task is modeled by the minimization problem of a general goal function $f(x;g)$ for which the decision $x$ has to be taken from a quantized version of the parameters $g$. This problem is relevant in many applications e.g., for radio resource allocation (RA), high spectral efficiency communications, controlled systems, or data clustering in the smart grid. By resorting to high resolution (HR) analysis, it is shown how to design a quantizer that minimizes the gap between the minimum of $f$ (which would be reached by knowing $g$ perfectly) and what is effectively reached with a quantized $g$. The conducted formal analysis both provides quantization strategies in the HR regime and insights for the general regime and allows a practical algorithm to be designed. The analysis also allows one to provide some elements to the new and fundamental problem of the relationship between the goal function regularity properties and the hardness to quantize its parameters. The derived results are discussed and supported by a rich numerical performance analysis in which known RA goal functions are studied and allows one to exhibit very significant improvements by tailoring the quantization operation to the final task.

Main magnetic focus ion source: Device with high electron current density

We discuss recent experiments performed with an upgraded version of the main magnetic focus ion source (MaMFIS) at the Joint Institute for Nuclear Research in Dubna. The device operates in the range of electron beam energies extended up to 40 keV. The achieved electron current densities are of the order of 10 kA cm−2. This assessment is consistent both with the very short ionization time and with the utmost ionization degree of the produced highly charged ions. Due to its high efficiency, the MaMFIS technology is especially promising for ionization of short-lived radionuclides and heavy elements. A new scheme for charge breeding is proposed.

Controllable Key Agreement With Correlated Noise

The problem of secret-key-based authentication under privacy and storage constraints on the source sequence is considered. Identifier measurement channels during authentication are assumed to be controllable via a cost-constrained action sequence. Inner and outer bounds for the key-leakage-storage-cost regions are derived for a generalization of the classic two-terminal key agreement model. Additions to the model are that the encoder observes a noisy version of a remote source, and this noisy output and the remote source output together with an action sequence are given as inputs to the measurement channel at the decoder. Thus, correlation is introduced between the noise components on the encoder and decoder measurements. The model with a key generated by an encoder is extended to the randomized models, where a key is embedded to the encoder. The results are relevant for several user and device authentication scenarios including physical and biometric identifiers with multiple measurements that provide diversity and multiplexing gains. Achievable (key, storage, cost) tuples are evaluated for binary identifiers and measurement channels represented as a mixture of binary symmetric subchannels. Significant gains from using an action sequence are illustrated to motivate the use of low-complexity transform-coding algorithms with cost-constrained actions.

Микроразмерные источники энергии для имплантируемых и носимых медицинских устройств

Важным направлением в области медицинской техники является создание имплантируемых устройств, поддерживающих функционирование организма. Многие из таких устройств требуют энергоснабжения, причем желательно, чтобы такие источники работали весь период имплантации, даже если речь идет о пожизненной установке импланта. Представлен обзор литературных данных по источникам энергии для питания имплантируемых и носимых медицинских устройств. Приведена сравнительная оценка характеристик биотопливных элементов как наиболее проработанного варианта имплантируемого источника энергии с другими возобновляемыми источниками электрической энергии на основе термо-, пьезо-, электростатических, магнито- и фотопреобразователей. Особое внимание уделено применению имплантируемых устройств, которые могут служить источником энергии для маломощных потребителей – микропомп, кардиостимуляторов, нейроимплантов и т.д.

Composite Ni@Ti nanoparticles produced in arrow-shaped gas aggregation source

A modified version of Haberland type gas aggregation source with an arrow-shaped aggregation chamber set with two magnetrons was used for the production of core@shell Ni@Ti nanoparticles. This configuration that had two separate magnetrons in one aggregation chamber gave the possibility to independently control the power to each magnetron and thus to control the structure of created nanoparticles. Furthermore, the chosen geometry resulted, under optimized conditions, in the suppression of the formation of single-material nanoparticles that is a common problem in the case of conventionally used planar arrangement of magnetrons in the aggregation chamber.

Ion source based on a circular anode layer plasma thruster.

A new version of pulsed ion source based on plasma thruster technology has been developed and tested. The ion source design uses a circular anode layer geometry in which the ion beam is extracted radially from the full circumference. The source has been tested for operation in argon, nitrogen, and air at a gas flow rate of up to 20 SCCM with discharge current and voltage measurements in low- and high-current modes. The source, having a simple design and open acceleration gap geometry for observation and photography, is suitable for the treatment of the inner surfaces of pipes and tubes.

MICROSIZE ENERGY SOURCES FOR IMPLANTABLE AND WEARABLE MEDICAL DEVICES

The creation of implantable devices that support the functioning of the body is an important area in the field of medical technology. Many of these devices require a power supply, and it is desirable that such sources work during the entire period of implantation, even in the case of a lifelong implant installation. The published data on energy sources for powering implantable and wearable medical devices is reviewed. A comparative assessment of the characteristics of biofuel cells as the most developed version of an implantable energy source with other renewable sources of electric energy based on thermo-, piezo-, electrostatic (ES), magneto-, and photo-converters is given. Particular attention is paid to the use of implantable devices that can serve as a source of energy for low-power systems: micropumps, pacemakers, neuroimplants, etc.

Implementation of the Omega (ω) Index to Detect Large-Scale Systematic Cheating

<p style="text-align:justify">Cheating detection is an important issue in standardized testing, especially in large-scale settings. Statistical approaches are often computationally intensive and require specialised software to conduct. We present a two-stage approach that quickly filters suspected groups using statistical testing on an IRT-based answer-copying index. We also present an approach to mitigate data contamination and improve the performance of the index. The computation of the index was implemented through a modified version of an open source R package, thus enabling wider access to the method. Using data from PIRLS 2011 (N=64,232) we conduct a simulation to demonstrate our approach. Type I error was well-controlled and no control group was falsely flagged for cheating, while 16 (combined n=12,569) of the 18 (combined n=14,149) simulated groups were detected. Implications for system-level cheating detection and further improvements of the approach were discussed.</p>

Simulation study of longitudinal injection scheme for HALS with a higher harmonic cavity system

Longitudinal injection is a promising on-axis injection scheme for diffraction-limited storage rings. In the latest version of the Hefei advanced light source (HALS), both the dynamic aperture and momentum aperture have been optimized. A longitudinal injection scheme was investigated on the HALS using a double-frequency radio frequency system. To evaluate the injection performance, various errors were considered. A series of tracking simulations were conducted, and the injection efficiency was obtained under different error levels.

Research Note: Low‐frequency pneumatic seismic sources

ABSTRACTPneumatic seismic sources, commonly known as airguns, have been serving us well for decades, but there is an increasing need for sources with improved low‐frequency signal and reduced environmental impact. In this paper, we present a new pneumatic source that is designed to achieve these goals by operating with lower pressures and larger volumes. The new source will release more air creating larger bubbles with longer bubble periods than airguns. The release of the air will be tuned so that the rise time will be longer and the sound pressure level and its slope will be lower. Certain engineering features will eliminate cavitation. Larger bubbles increase low‐frequency content of the signal, longer rise times decrease mid‐frequency content and the elimination of cavitation reduces high‐frequency content. We have not yet built a full‐scale version of the new source. However, we have manufactured a small‐scale low‐pressure source incorporating most of the engineering features, and tested it in a lake. Here, we present the lake data that, as expected, show a significant reduction in the sound pressure level, increase in rise time, decrease in slope and decrease in high‐frequency content while maintaining the same low‐frequency content when the source prototype is operated at low pressure compared with high pressure. Synthetic data produced by numerical modelling of the full‐scale proposed pneumatic source suggest that the new source will improve the low‐frequency content and can produce geophysically useful signal down to 1 Hz.

Off-Axis Ions Extraction Simulation in Tubular Electron String Ion Source (TESIS)

Tubular Electron String Ion Source (TESIS) – improved version of Electron String Ion Source (ESIS) aiming for nearly 200-fold increase in ion yield – is under development at JINR. TESIS advantages over ESIS are discussed and their characteristics are compared. Basic scheme of TESIS operation is presented. One of the crucial processes in TESIS – off-axis ion extraction – requires special confilguration of output electrodes providing steep potential gradient. Numerical simulations of ion extraction trajectories for two different electrode confilgurations are compared and the optimal one is discussed. The obtained results will be useful for TESIS design and construction.

Applications of Serpent 2 Monte Carlo Code to ITER Neutronics Analysis

Nuclear analysis supporting the design and licensing of ITER is traditionally performed using MCNP and the reference model C-Model; however, the complexity of C-Model has resulted in the geometry creation and integration process becoming increasingly time-consuming. Serpent 2 is still a beta code; however, recent enhancements mean that it could, in principle, be applied to ITER neutronics analysis. Investigations have been undertaken into the effectiveness of Serpent for ITER neutronics analysis and whether this might offer an efficient modeling environment.An automated MCNP-to-Serpent model conversion tool was developed and successfully used to create a Serpent 2 variant of C-Model. A version of the deuterium-tritium plasma neutron source was also created. Standard reference tallies in C-Model for the blanket and vacuum vessel heating were implemented, and comparisons were made between the two transport codes assessing nuclear responses and computer requirements in the ITER model. Excellent agreement was found between the two codes when comparing neutron and photon flux and heating in the ITER blanket modules and vacuum vessel.Comparing tally figures of merit, computer requirements for Serpent were typically three to five times that of MCNP, and memory requirements were broadly similar. While Serpent was slower than MCNP when applied to fusion neutronics, future developments may improve this, and Serpent offers clear benefits that will reduce analyst time, including support for meshed geometry, robust universe implementation that avoids geometry errors at the boundaries, and mixed geometry types. Additional work is proceeding to compare Serpent against experiment benchmarks relevant for fusion shielding problems. While further developments are needed to improve variance reduction techniques and reduce simulation times, this paper demonstrates the suitability of Serpent to some aspects of ITER analysis.

Electrical source of pseudothermal light

We describe a simple and compact electrical version of a pseudothermal light source. The source is based on electrical white noise whose spectral properties are tailored by analog filters. This signal is used to drive a light-emitting diode. The type of second-order coherence of the output light can be either Gaussian or Lorentzian, and the intensity distribution can be either Gaussian or non-Gaussian. The output light field is similar in all viewing angles, and thus, there is no need for a small aperture or optical fiber in temporal coherence analysis.

A 60 mA DC H− multi cusp ion source developed at TRIUMF

This paper describes the latest high-current multi cusp type ion source developed at TRIUMF, which is capable of producing a negative hydrogen ion beam (H−) of 60 mA of direct current at 140V and 90A arc. The results achieved to date including emittance measurements and filament lifetime issues are presented. The low current version of this ion source is suitable for medical cyclotrons as well as accelerators and the high current version is intended for producing large neutral hydrogen beams for fusion research. The description of the source magnetic configuration, the electron filter profile and the differential pumping techniques given in the paper will allow the building of an arc discharge H− ion source with similar properties.

Inverse Source Problems for Maxwell's Equations and the Windowed Fourier Transform

The inverse source problem for time-harmonic Maxwell's equations in three-dimensional free space is considered. Given far field observations of a wave radiated by a compactly supported volume current density at a single frequency, we generalize a qualitative reconstruction algorithm, recently developed in [R. Griesmaier, M. Hanke, and T. Raasch, SIAM J. Sci. Comput., 34 (2012), A1544--A1562], to this three-dimensional vector-valued setting. The method is based on the fact that a windowed Fourier transform of the far field data approximates an exponential transverse ray transform with a purely imaginary exponent of a smoothed version of the unknown source. Applying a filtered backprojection for the standard transverse ray transform to a suitably generalized squared absolute value of the windowed Fourier transform of the far field data, we recover information on the support of the volume current density. We analyze this algorithm, discuss its numerical implementation, and supplement our theoretical findings...

Travels in North America, 1832–1834: A Concise Edition of the Journals of Prince Maximilian of Wied. Edited by Marsha V. Gallagher. Translated by William J. Orr, Paul Schach, and Dieter Karch. Foreword by Jack F. Becker

The same press that produced The North American Journals of Prince Maximilian of Wied, 1832–1834 in three massive volumes between 2008 and 2012 has released a user-friendly one volume condensed version of this important eyewitness source. The Joslyn Art Museum curator/historian Marsha Gallagher, who co-edited the complete version with Stephen S. Witte, chose the selections, representing around 200,000 words, or approximately one-third of the complete version. In her own words, she provides the reader “a good overview and understanding of where Maximilian went in North America, what he saw, and what he thought was significant about both” (p. xiii). The text is supplemented with thirty-two color and sixteen black-and-white illustrations from Maximilian’s own hand, as well as from that of the Swiss artist Karl Bodmer. As in her previous work, Gallagher provides the reader with short biographies of the most frequently mentioned Cast of Characters who appear in Maximilian’s journals. These include a few of the principal Indian leaders met on the journey, as well as many non-Indian hosts and acquaintances representing men of science in Boston and Philadelphia as well as fur traders and clerks from St. Louis to Fort McKenzie, below present-day Great Falls, Montana.

Auralizations with loudspeaker arrays from a phased combination of the image source method and acoustical radiosity

In order to create a simulation tool that is well-suited for small rooms with low diffusion and highly absorbing ceilings, a new room acoustic simulation tool has been developed that combines a phased version of the image source with acoustical radiosity and that considers the angle dependence of the surface properties. The new tool is denoted PARISM, and here PARISM is used to create loudspeaker array-based auralizations. Different auralization techniques are compared, such as Ambisonics, vector-based panning, and the method of nearest loudspeaker. The implementations of the auralization techniques with PARISM are described and compared to implementations of auralizations with another geometrical acoustic simulation tool, i.e., ODEON and the LoRA toolbox that applies Ambisonics to ODEON simulations. In opposition to the LoRA toolbox, higher order Ambisonics are also applied to the late part of the PARISM impulse response, because more directional information is available with acoustical radiosity. Small rooms with absorbing surfaces are tested, because this is the room type that PARISM is particularly useful for.

The effect of reactions on the formation and readout of the gradient of Bicoid

During early development, the establishment of gradients of transcriptional factors determines the patterning of cell fates. The case of Bicoid (Bcd) in Drosophila melanogaster embryos is well documented and studied. There are still controversies as to whether SDD models in which Bcd is Synthesized at one end, then Diffuses and is Degraded can explain the gradient formation within the timescale observed experimentally. The Bcd gradient is observed in embryos that express a Bicoid-eGFP fusion protein (Bcd-GFP) which cannot differentiate if Bcd is freely diffusing or bound to immobile sites. In this work we analyze an SDID model that includes the Interaction of Bcd with binding sites. We simulate numerically the resulting full reaction–diffusion system in a cylindrical domain using previously determined biophysical parameters and a simplified version of the Bcd source. In this way we obtain solutions that depend on the spatial location approximately as observed experimentally and that reach such dependence at a time that is also compatible with the experimental observations. Analyzing the differences between the free and bound Bcd distributions we observe that the latter spans over a longer lengthscale. We conclude that deriving the lengthscale from the distribution of Bcd-GFP can lead to an overestimation of the gradient lengthscale and of the Hill coefficient that relates the concentrations of Bcd and of the protein, Hunchback, whose production is regulated by Bcd.