586 research outputs found
Thermal analysis of induction and synchronous reluctance motors
In this paper, the thermal behavior of two induction motors (2.2 and 4 kW, four poles) and two synchronous reluctance motors [(SynRMs) transverse-laminated] are investigated and compared. Both motor types use the same stator but have different rotors. Using a lumped-parameter simulation program, a thermal analysis has been also carried out, and the obtained results have been compared with the experimental ones. A direct comparison of the thermal behavior of the two motor types has thus been made for constant load and constant average copper temperature conditions. Inasmuch as the SynRM has negligible rotor losses compared with the induction motor, it is capable of a larger rated torque, from 10% to more than 20%, depending on the relative size of end connections and motor lengt
Virtual Stiffness: A Novel Biomechanical Approach to Estimate Limb Stiffness of a Multi-Muscle and Multi-Joint System
In recent years, different groups have developed algorithms to control the stiffness of a robotic device through the electromyographic activity collected from a human operator. However, the approaches proposed so far require an initial calibration, have a complex subject-specific muscle model, or consider the activity of only a few pairs of antagonist muscles. This study described and tested an approach based on a biomechanical model to estimate the limb stiffness of a multi-joint, multi-muscle system from muscle activations. The âvirtual stiffnessâ method approximates the generated stiffness as the stiffness due to the component of the muscle-activation vector that does not generate any endpoint force. Such a component is calculated by projecting the vector of muscle activations, estimated from the electromyographic signals, onto the null space of the linear mapping of muscle activations onto the endpoint force. The proposed method was tested by using an upper-limb model made of two joints and six Hill-type muscles and data collected during an isometric force-generation task performed with the upper limb. The null-space projection of the muscle-activation vector approximated the major axis of the stiffness ellipse or ellipsoid. The model provides a good approximation of the voluntary stiffening performed by participants that could be directly implemented in wearable myoelectric controlled devices that estimate, in real-time, the endpoint forces, or endpoint movement, from the mapping between muscle activation and force, without any additional calibrations
Development and Experimentation of a CubeSat Magnetic Attitude Control System Testbed
For CubeSats requiring high pointing accuracy and slewing agility, ground-based hardware-in-the-loop simulations are strongly demanded to test and validate spacecraft subsystems and guidance, navigation, and control algorithms. In this article, a magnetic attitude control system (MACS) testbed for a CubeSat is developed utilizing a spherical air bearing and a Helmholtz cage. The design, development, and verification procedure of MACS is presented together with different test scenarios. To generate enough torque with the magnetorquer system in the dynamic testbed, the Helmholtz coil system of the testbed has driven to provide an augmented magnetic field. As an example of experimentation, the B-dot control algorithm was implemented to dissipate the angular momentum of the dynamic MACS testbed. The experimental results were compared with those of the numerical simulations
Dietary Lippia citriodora extract in rabbit feeding: effects on quality of carcass and meat
Abstract. Due to consumer demand, in recent years considerable attention has been focused on the use of natural compounds in animal feed. The aim of this study was to evaluate the effect of dietary natural extract from Lippia citriodora (commonly named "limoncina"), titrated in verbascoside, on quality, measured as oxidative stability, fatty acid composition, alpha-tocopherol and retinol content and sensory traits of rabbit meat. Forty-five New Zealand white rabbits were randomly assigned to three age- and body-weight-balanced feeding groups of 15 animals each in which a conventional pelleted diet (CON) was supplemented with 1 or 2 kg tâ1 (low natural-extract (LNE) and high natural-extract (HNE) groups, respectively) of Lippia citriodora extract for 55 days. No influence on carcass characteristics and the chemical composition of meat was observed. A trend for a positive effect on alpha-tocopherol tissue content (P = 0.07) and on thiobarbituric reactive substance (TBARS) values was observed (P = 0.063) in Longissimus Lumborum muscle from the HNE group. The fatty acid profile of the meat was affected by dietary treatment with a significant decrease (P = 0.001) in saturated fatty acids and an increase (P = 0.01) in polyunsaturated fatty acids in both treated groups compared to the CON group. The supplementation with natural extract at the highest dosage improved the tenderness and juiciness of meat, highlighting a better consistency than CON and LNE groups. In conclusion, this study shows that the natural extract used has the potential to improve rabbit meat in order to produce functional food, without altering the chemical and physical characteristics of meat
Dietary Lippia citriodora extract in rabbit feeding: Effects on quality of carcass and meat
Due to consumer demand, in recent years considerable attention has been focused on the use of natural compounds in animal feed. The aim of this study was to evaluate the effect of dietary natural extract from Lippia citriodora (commonly named "limoncina"), titrated in verbascoside, on quality, measured as oxidative stability, fatty acid composition, alpha-tocopherol and retinol content and sensory traits of rabbit meat. Forty-five New Zealand white rabbits were randomly assigned to three age- and body-weight-balanced feeding groups of 15 animals each in which a conventional pelleted diet (CON) was supplemented with 1 or 2 kg t-1(low natural-extract (LNE) and high natural-extract (HNE) groups, respectively) of Lippia citriodora extract for 55 days. No influence on carcass characteristics and the chemical composition of meat was observed. A trend for a positive effect on alpha-tocopherol tissue content (P = 0.07) and on thiobarbituric reactive substance (TBARS) values was observed (P = 0.063) in Longissimus Lumborum muscle from the HNE group. The fatty acid profile of the meat was affected by dietary treatment with a significant decrease (P = 0.001) in saturated fatty acids and an increase (P = 0.01) in polyunsaturated fatty acids in both treated groups compared to the CON group. The supplementation with natural extract at the highest dosage improved the tenderness and juiciness of meat, highlighting a better consistency than CON and LNE groups. In conclusion, this study shows that the natural extract used has the potential to improve rabbit meat in order to produce functional food, without altering the chemical and physical characteristics of meat
Liver contrast enhanced ultrasound perfusion imaging in the evaluation of chronic hepatitis C fibrosis: preliminary results
We wanted to determine whether liver contrast-enhanced ultrasound (CEUS)âderived peak signal
intensity (PSI) and peak signal intensity/time (PIT) predict liver fibrosis in chronic hepatitis C (CHC). Fortynine
patients with CHC (METAVIR classification) and 10 control subjects were included in the study. After a bolus
of 2.4 mL SonoVue (Bracco Imaging, Milan, Italy) solution was injected into a peripheral vein, the right lobe of
the liver containing the right portal vein was scanned in a transverse section. Two-dimensional sonography was
performed using the Philips iU22 ultrasound system (Philips Healthcare, Best, the Netherlands). A 1.0â5.0-MHz
(C5-1) wideband convex transducer was used, applying the following settings in all cases. Regions of interest
were manually drawn over the right liver lobe and over the portal vein (PV). Liver parenchyma PSI (LPpsi)
and PIT (LPpit), portal vein PSI (PVpsi) and PIT (PVpit) were automatically calculated. dPSI was defined as
the difference between PVpsi and LPpsi. A significant correlation was observed between PAPSI and fibrosis scores.
When patients were stratified according to their LPpsi, a significant difference was achieved only between patients
with fibrosis score 0â1 vs. 2â3 and 2 vs. 4. Statistically significant differences between all fibrosis scores, except 0 vs.
1 and 3 vs. 4 were observed when dPSI was used to stratify patients. Overall diagnostic accuracy of LPpsi and dPSI
measurement for severe fibrosis by area under the receiving operator characteristic curve analysis was, respectively,
0.87 and 0.88.We suggest that liver CEUS perfusion could have the potential to be used as a complementary
tool for the evaluation of liver fibrosis. However, further large-scale studies are required to accurately assess its
accuracy in the evaluation of liver fibrosis
Probiotic bacteria regulate intestinal epithelial permeability in experimental ileitis by a TNF-dependent mechanism
Background: We previously showed that the probiotic mixture, VSL#3, prevents the onset of ileitis in SAMP/YitFc (SAMP) mice, and this effect was associated with stimulation of epithelial-derived TNF. The aim of this study was to determine the mechanism(s) of VSL#3-mediated protection on epithelial barrier function and to further investigate the "paradoxical" effects of TNF in preventing SAMP ileitis. Methods: Permeability was evaluated in SAMP mice prior to the onset of inflammation and during established disease by measuring transepithelial electrical resistance (TEER) on ex vivo-cultured ilea following exposure to VSL#3 conditioned media (CM), TNF or VSL#3-CM + anti-TNF. Tight junction (TJ) proteins were assessed by qRT-PCR, Western blot, and confocal microscopy, and TNFRI/TNFRII expression measured in freshly isolated intestinal epithelial cells (IEC) from SAMP and control AKR mice. Results: Culture with either VSL#3-CM or TNF resulted in decreased ileal paracellular permeability in pre-inflamed SAMP, but not SAMP with established disease, while addition of anti-TNF abrogated these effects. Modulation of the TJ proteins, claudin-2 and occludin, occurred with a significant decrease in claudin-2 and increase in occludin following stimulation with VSL#3-CM or TNF. TNF protein levels increased in supernatants of SAMP ilea incubated with VSL#3-CM compared to vehicle, while IEC-derived TNFR mRNA expression decreased in young, and was elevated in inflamed, SAMP versus AKR mice. Conclusions: Our data demonstrate that the previously established efficacy of VSL#3 in preventing SAMP ileitis is due to direct innate and homeostatic effects of TNF on the gut epithelium, modulation of the TJ proteins, claudin-2 and occludin, and overall improvement of intestinal permeability. © 2012 Corridoni et al
NaNet: a Low-Latency, Real-Time, Multi-Standard Network Interface Card with GPUDirect Features
While the GPGPU paradigm is widely recognized as an effective approach to
high performance computing, its adoption in low-latency, real-time systems is
still in its early stages.
Although GPUs typically show deterministic behaviour in terms of latency in
executing computational kernels as soon as data is available in their internal
memories, assessment of real-time features of a standard GPGPU system needs
careful characterization of all subsystems along data stream path.
The networking subsystem results in being the most critical one in terms of
absolute value and fluctuations of its response latency.
Our envisioned solution to this issue is NaNet, a FPGA-based PCIe Network
Interface Card (NIC) design featuring a configurable and extensible set of
network channels with direct access through GPUDirect to NVIDIA Fermi/Kepler
GPU memories.
NaNet design currently supports both standard - GbE (1000BASE-T) and 10GbE
(10Base-R) - and custom - 34~Gbps APElink and 2.5~Gbps deterministic latency
KM3link - channels, but its modularity allows for a straightforward inclusion
of other link technologies.
To avoid host OS intervention on data stream and remove a possible source of
jitter, the design includes a network/transport layer offload module with
cycle-accurate, upper-bound latency, supporting UDP, KM3link Time Division
Multiplexing and APElink protocols.
After NaNet architecture description and its latency/bandwidth
characterization for all supported links, two real world use cases will be
presented: the GPU-based low level trigger for the RICH detector in the NA62
experiment at CERN and the on-/off-shore data link for KM3 underwater neutrino
telescope
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