5,041 research outputs found
Shielded Micro-Coplanar CRLH TL Zeroth-Order Resonator Antenna: Critical Performance Evaluation
The attention of this paper is focused on the four unit cell zeroth-order resonator antenna (ZORA), manufactured on a shielded micro-coplanar composite right/left-handed (CRLH) transmission line structure. The antenna was designed to achieve a broadside patch-type radiation pattern. The dimensions of the antenna element follow: 15.6 x 9.35 x 3.1 mm (i.e. 0.27 x 0.16 x 0.05 λ0 at the measured zeroth-order resonance f0 = 5.14 GHz) with the shielded plane of the size of 60 x 40 mm (approx. 1.0 x 0.7 λ0). The measured gain and the antenna efficiency are equal to 4.6 dBi and 48 %, respectively. The performance of the proposed ZORA is subject to critical evaluation based on the comparison with the reference quarter-wavelength patch antenna (QWPA) that has the same dimensions. It has been found that ZORA provides comparable or even better parameters to those of QWPA, except of the bandwidth, which is much narrower in case of ZORA. In comparison to QWPA, the main advantage of the proposed ZORA might be then seen in the possibility to produce the entire ZORA structure by means of the integrated microstrip technology with air bridges. In contrary to it, the fabrication of the QWPA requires the use of either the foam substrate or plastic support pins or the application of ridged self-supporting metal plates
Microwave Drying of Textile Materials and Optimization of a Resonant Applicator
The principal aim of this work was to design and optimize the applicator for microwave drying. Our applicator is derived from the Fabry-Perrot resonator, which is an open type resonator.The whole system works at frequency 2.45 GHz and the magnetron that we used delivers power 800 W. This machine is intended for use in drying in factory production of fabrics. After identifying of the basic arrangement of the microwave drying machine, the next step in the design was the use of the electromagnetic field simulator. We determined the position of the magnetron and found the distribution of the electric field strength in drying textiles in this way. In parallel, we analyzed the drying system with analytical calculations. We created a diagram of the EM waves inside this structure and reached the resulting expression for use in calculating the strenght of the electric field in the plane of the drying textile. This quantity depends on the electrical characteristics of wet textiles, e.g. the permittivity and the loss factor. Measurements of these dielectric properties for the coburg is complicated, and this method makes it possible to solve our problem with dielectric parameters. We have SAR distribution results (by simulation and also by measurement), results of measurements of the moisture content in the dried textile with respect to time. These results are important for subsequent optimization of the efficiency of the whole machine.
The Bak-Sneppen Model on Scale-Free Networks
We investigate by numerical simulations and analytical calculations the
Bak-Sneppen model for biological evolution in scale-free networks. By using
large scale numerical simulations, we study the avalanche size distribution and
the activity time behavior at nodes with different connectivities. We argue the
absence of a critical barrier and its associated critical behavior for infinite
size systems. These findings are supported by a single site mean-field analytic
treatment of the model.Comment: 5 pages and 3 eps figures. Final version appeared in Europhys. Let
A Machine Learning Approach for Gearbox System Fault Diagnosis
This study proposes a fully automated gearbox fault diagnosis approach that does not require knowledge about the specific gearbox construction and its load. The proposed approach is based on evaluating an adaptive filter's prediction error. The obtained prediction error's standard deviation is further processed with a support-vector machine to classify the gearbox's condition. The proposed method was cross-validated on a public dataset, segmented into 1760 test samples, against two other reference methods. The accuracy achieved by the proposed method was better than the accuracies of the reference methods. The accuracy of the proposed method was on average 9% higher compared to both reference methods for different support vector settings
Assessment of the thermal tissue models for the head and neck hyperthermia treatment planning
Purpose: To compare different thermal tissue models for head and neck hyperthermia treatment planning, and to assess the results using predicted and measured applied power data from clinical treatments. Methods: Three commonly used temperature models from literature were analysed: “constant baseline”, “constant thermal stress” and “temperature dependent”. Power and phase data of 93 treatments of 20 head and neck patients treated with the HYPERcollar3D applicator were used. The impact on predicted median temperature T50 inside the target region was analysed with maximum allowed temperature of 44 °C in healthy tissue. The robustness of predicted T50 for the three models against the influence of blood perfusion, thermal conductivity and the assumed hotspot temperature level was analysed. Results: We found an average predicted T50 of 41.0 ± 1.3 °C (constant baseline model), 39.9 ± 1.1 °C (constant thermal stress model) and 41.7 ± 1.1 °C (temperature dependent model). The constant thermal stress model resulted in the best agreement between the predicted power (P = 132.7 ± 45.9 W) and the average power measured during the hyperthermia treatments (P = 129.1 ± 83.0 W). Conclusion: The temperature dependent model predicts an unrealistically high T50. The power values for the constant thermal stress model, after scaling simulated maximum temperatures to 44 °C, matched best to the average measured powers. We consider this model to be the most appropriate for temperature predictions using the HYPERcollar3D applicator, however further studies are necessary for developing of robust temperature model for tissues during heat stress.</p
The Brown Dwarf Kinematics Project (BDKP). III. Parallaxes for 70 Ultracool Dwarfs
We report parallax measurements for 70 ultracool dwarfs (UCDs). Using both
literature values and our sample, we report new polynomial relations between
spectral type and M. Including resolved L/T transition binaries in the
relations, we find no reason to differentiate between a "bright" (unresolved
binary) and "faint" (single source) sample across the L/T boundary. Isolating
early T dwarfs, we find that the brightening of T0-T4 sources is prominent in
M where there is a [1.2 - 1.4] magnitude difference. A similar yet
dampened brightening of [0.3 - 0.5] magnitude happens at M and a plateau
or dimming of [-0.2 - -0.3] magnitude is seen in M. Comparing with
evolutionary models that vary gravity, metallicity, and cloud thickness we find
that a near constant temperature of 1200 100 K along a narrow spectral
subtype of T0-T4 is required to account for the brightening and color magnitude
diagram of the L-dwarf/T-dwarf transition. Furthermore, there is a significant
population of both L and T dwarfs which are red or potentially "ultra-cloudy"
compared to the models, many of which are known to be young indicating a
correlation between enhanced photospheric dust and youth. For the low
surface-gravity or young companion L dwarfs we find that 8 out of 10 are at
least [0.2-1.0] magnitude underluminous in M and/or M compared to
equivalent spectral type objects. We speculate that this is a consequence of
increased dust opacity and conclude that low-surface gravity L dwarfs require a
completely new spectral-type/absolute magnitude polynomial for analysis.Comment: 65 pages, Accepted for publication to Ap
Biomic Specialization and Speciation Rates in Ruminants (Cetartiodactyla, Mammalia): A Test of the Resource-Use Hypothesis at the Global Scale
The resource-use hypothesis proposed by E.S. Vrba predicts that specialist species have higher speciation and extinction rates than generalists because they are more susceptible to environmental changes and vicariance. In this work, we test some of the predictions derived from this hypothesis on the 197 extant and recently extinct species of Ruminantia (Cetartiodactyla, Mammalia) using the biomic specialization index (BSI) of each species, which is based on its distribution within different biomes. We ran 10000 Monte Carlo simulations of our data in order to get a null distribution of BSI values against which to contrast the observed data. Additionally, we drew on a supertree of the ruminants and a phylogenetic likelihood-based method (QuaSSE) for testing whether the degree of biomic specialization affects speciation rates in ruminant lineages. Our results are consistent with the predictions of the resource-use hypothesis, which foretells a higher speciation rate of lineages restricted to a single biome (BSI = 1) and higher frequency of specialist species in biomes that underwent high degree of contraction and fragmentation during climatic cycles. Bovids and deer present differential specialization across biomes; cervids show higher specialization in biomes with a marked hydric seasonality (tropical deciduous woodlands and schlerophyllous woodlands), while bovids present higher specialization in a greater variety of biomes. This might be the result of divergent physiological constraints as well as a different biogeographic and evolutionary history
Adaptive multi-agent system for a washing machine production line
This paper describes the implementation of a multi-agent system in a real industrial washing machine production line aiming to integrate process and quality control, allowing the establishment of feedback control loops to support adaptation facing condition changes. For this purpose, the agent-based solution was implemented using the JADE framework, being the shared knowledge structured using a proper ontology, edited and validated in Protégé and posteriorly integrated in the multi-agent system. The solution was intensively tested using historical real production data and it is now being installed in the real production line. The preliminary results confirm the initial expectations in terms of improvement of process performance and product quality
A 10-micron Search for Inner-Truncated Disks Among Pre-Main-Sequence Stars With Photometric Rotation Periods
We use mid-IR (primarily 10 m) photometry as a diagnostic for the
presence of disks with inner cavities among 32 pre-main sequence stars in Orion
and Taurus-Auriga for which rotation periods are known and which do not show
evidence for inner disks at near-IR wavelengths. Disks with inner cavities are
predicted by magnetic disk-locking models that seek to explain the regulation
of angular momentum in T Tauri stars. Only three stars in our sample show
evidence for excess mid-IR emission. While these three stars may possess
truncated disks consistent with magnetic disk-locking models, the remaining 29
stars in our sample do not. Apparently, stars lacking near-IR excesses in
general do not possess truncated disks to which they are magnetically coupled.
We discuss the implications of this result for the hypothesis of
disk-regulated angular momentum. Evidently, young stars can exist as slow
rotators without the aid of present disk-locking, and there exist very young
stars already rotating near breakup velocity whose subsequent angular momentum
evolution will not be regulated by disks. Moreover, we question whether disks,
when present, truncate in the manner required by disk-locking scenarios.
Finally, we discuss the need for rotational evolution models to take full
account of the large dispersion of rotation rates present at 1 Myr, which may
allow the models to explain the rotational evolution of low-mass pre-main
sequence stars in a way that does not depend upon braking by disks.Comment: 20 pages, 4 figure
- …