Development of a Solid State Transformer for HEMP/GMD Common Mode Current Mitigation
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Donnelly, Timothy James↗
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Spatiotemporal Filtering Using Principal Component Analysis and Karhunen-Loeve Expansion Approaches for Regional GPS Network Analysis
Spatial filtering is an effective way to improve the precision of coordinate time series for regional GPS networks by reducing so-called common mode errors, thereby providing better resolution for detecting weak or transient deformation signals. The commonly used approach to regional filtering assumes that the common mode error is spatially uniform, which is a good approximation for networks of hundreds of kilometers extent, but breaks down as the spatial extent increases. A more rigorous approach should remove the assumption of spatially uniform distribution and let the data themselves reveal the spatial distribution of the common mode error. The principal component analysis (PCA) and the Karhunen-Loeve expansion (KLE) both decompose network time series into a set of temporally varying modes and their spatial responses. Therefore they provide a mathematical framework to perform spatiotemporal filtering.We apply the combination of PCA and KLE to daily station coordinate time series of the Southern California Integrated GPS Network (SCIGN) for the period 2000 to 2004. We demonstrate that spatially and temporally correlated common mode errors are the dominant error source in daily GPS solutions. The spatial characteristics of the common mode errors are close to uniform for all east, north, and vertical components, which implies a very long wavelength source for the common mode errors, compared to the spatial extent of the GPS network in southern California. Furthermore, the common mode errors exhibit temporally nonrandom patterns.
displacement↗
High-Voltage-Input Level Translator Using Standard CMOS
proposed integrated circuit would translate (1) a pair of input signals having a low differential potential and a possibly high common-mode potential into (2) a pair of output signals having the same low differential potential and a low common-mode potential. As used here, "low" and "high" refer to potentials that are, respectively, below or above the nominal supply potential (3.3 V) at which standard complementary metal oxide/semiconductor (CMOS) integrated circuits are designed to operate. The input common-mode potential could lie between 0 and 10 V; the output common-mode potential would be 2 V. This translation would make it possible to process the pair of signals by use of standard 3.3-V CMOS analog and/or mixed-signal (analog and digital) circuitry on the same integrated-circuit chip. A schematic of the circuit is shown in the figure. Standard 3.3-V CMOS circuitry cannot withstand input potentials greater than about 4 V. However, there are many applications that involve low-differential-potential, high-common-mode-potential input signal pairs and in which standard 3.3-V CMOS circuitry, which is relatively inexpensive, would be the most appropriate circuitry for performing other functions on the integrated-circuit chip that handles the high-potential input signals. Thus, there is a need to combine high-voltage input circuitry with standard low-voltage CMOS circuitry on the same integrated-circuit chip. The proposed circuit would satisfy this need. In the proposed circuit, the input signals would be coupled into both a level-shifting pair and a common-mode-sensing pair of CMOS transistors. The output of the level-shifting pair would be fed as input to a differential pair of transistors. The resulting differential current output would pass through six standoff transistors to be mirrored into an output branch by four heterojunction bipolar transistors. The mirrored differential current would be converted back to potential by a pair of diode-connected transistors, which, by virtue of being identical to the input transistors, would reproduce the input differential potential at the output
Yager, Jeremy A.↗
Excitation of pressure modes in common envelopes
The excitation of oscillatory modes by a low-mass star orbiting inside a common envelope with a more massive star is investigated, with emphasis on adiabatic high spherical harmonic degree (l is much greater than 1) modes propagating outward in the envelope. The dominant oscillatory modes are those for which the spherical harmonic order is large, and thus the amplitudes are large close to the equatorial plane and small closer to the poles. A secondary of mass about 1 percent of the primary mass excites modes with relative surface amplitudes of a few x 10 percent. Even a Jupiter-like brown dwarf, when it is very deep in the envelope of an asymptotic giant branch star, can cause perturbations of relative surface amplitudes of about 10 percent near the equatorial plane. If mass loss is influenced by oscillation, then this mechanism can lead to higher mass loss in the equatorial plane. In case of an asymptotic giant branch primary, this might lead to the formation of an elliptical planetary nebula.
Soker, Noam↗
Common Cause Failures and Ultra Reliability
A common cause failure occurs when several failures have the same origin. Common cause failures are either common event failures, where the cause is a single external event, or common mode failures, where two systems fail in the same way for the same reason. Common mode failures can occur at different times because of a design defect or a repeated external event. Common event failures reduce the reliability of on-line redundant systems but not of systems using off-line spare parts. Common mode failures reduce the dependability of systems using off-line spare parts and on-line redundancy.
reliability↗
Switching power supply filter
A filter for a switching power supply. The filter includes a common mode inductor with coil configurations allowing differential mode current from a dc source to pass through but attenuating common mode noise from the power supply so that the noise does not reach the dc source. The invention also includes the use of feed through capacitors at the switching power supply input terminals to provide further high-frequency noise attenuation.
Kumar, Prithvi R.↗
Optimal Hairpin Winding Configuration for EV Traction Motors to Enhance Active CMV Cancellation Capability of NPL.X Inverter
Active common-mode voltage (CMV) cancellation in neutral-point-less (NPL.X) inverter is an effective approach for reducing common-mode electromagnetic interference and alleviating voltage stress associated with high-speed switching in EV traction drives. However, the existing hairpin winding configuration often exhibits impedance imbalance due to slot leakage inductance and manufacturing constraints, limiting the effectiveness of active CMV cancellation. This paper investigates symmetric hairpin winding configurations for a dual-three-phase EV traction machine to improve impedance symmetry. Considering the manufacturing constraints of six-layer hairpin windings, four feasible symmetric winding configurations are analyzed. Two-dimensional finite-element analysis is performed to extract the impedance parameters of each configuration. The extracted impedance parameters are used to quantify the impedance mismatch between complementary phase pairs and evaluate its influence on active CMV cancellation. The results show that the fully interleaved winding configuration achieves perfectly balanced phase impedances with 0 % mismatch, whereas the mismatch in the other configurations ranges from approximately 2.4 % to 0.8 %. Consequently, the resulting total CMV overshoot is significantly suppressed to near zero voltage under high-voltage and high switching frequency operating conditions, demonstrating the importance of winding symmetry for maximizing the active CMV cancellation capability of the NPL.X inverter.
Lee, Kangbeen [Purdue Univ., West Lafayette, IN (U↗
Test of the Equivalence Principle in an Einstein Elevator
The laboratory activity consisted in the construction of a laboratory prototype of a differential accelerometer. The laboratory prototype has been used to conduct key tests on the differential instrument. We demonstrated the ability to damp quickly transient oscillations by utilizing a resistive load in the feedback loops and then removing that load to reestablish a high quality factor of the detector. A rotating divide with tilt control was also built. This device was utilized to impart (through the Earth's gravity) common-mode perturbations to the differential accelerometer. These calibration disturbances have been used to trim the acceleration outputs of the individual proof masses in order to obtain a common-mode rejection factor better than 10(exp -4) in a sufficiently large frequency band centered at the spin frequency.
Shapiro, Irwin I.↗
Large-scale real-time signal processing in physics experiments: the ALICE TPC FPGA pipeline
For LHC Run 3, the ALICE Time Projection Chamber was upgraded to operate in continuous readout mode. Interaction rates of up to 50 kHz in Pb-Pb collisions require real-time processing of more than 3 TB s -1 of raw detector data. This requirement is met by a custom FPGA-based processing pipeline that performs the complete front-end data treatment fully in-stream, including common-mode correction, pedestal subtraction, ion-tail filtering, zero suppression, and dense data packing. A central element of the design is a highly parallel common-mode correction algorithm operating directly on the streaming data. It robustly identifies signal-free readout channels on a time-bin basis and applies pad-dependent scaling to compensate for local variations in capacitive coupling in the GEM readout. In combination with pedestal subtraction and ion-tail filtering, this enables accurate baseline restoration under extreme high-occupancy conditions, preventing signal loss while efficiently suppressing noise prior to zero suppression. The pipeline operates continuously at the full detector bandwidth and reduces the raw input rate of approximately 3 TB s -1 to about 900 GBps for Pb-Pb collisions at the target interaction rate. Overall, it represents a large-scale FPGA-based real-time signal-processing implementation for high-energy physics detector readout.
Digital signal processing (DSP)↗
Solar electric propulsion thrust beam interactive effects
Interactive effects between ion engine thrust beams and an SEP spacecraft and its science payload have been examined. AC electric contamination from thrust beam potential fluctuations of both 'common mode' and 'point-to-point' forms has been evaluated. Quenching of point-to-point E-fields by both thrust ion and charge exchange ion plasmas is expected. Reduction methods for AC electric contamination from common mode thrust beam potential fluctuations have been developed. Charged particle contamination of ambient space and plasma wave contamination may result from density magnitude and spatial extent of charge exchange plasma plumes. Reduction methods for cone of directions of high angle charge exchange ions have been examined.
Sellen, J. M., Jr.↗
Cryogenic Equivalence Principle Experiment
The purpose of this project is to test the equivalence of inertial and passive gravitational mass in an Earth-orbiting satellite. A ground-based experiment is now well developed. It consists of comparing the motions of two cylindrical test masses suspended in precision superconducting magnetic bearings and free to move along the horizontal (axis) direction. The masses are made of niobium and lead-plated aluminum. A position detector based on a SQUID magnetometer measures the differential motion between the masses. The periods of the masses are matched by adjustment of the position detector until the system is insensitive to common mode signals, and so that the experiment is less sensitive to seismic vibration. The apparatus is contained in a twelve inch helium dewar suspended in a vibration isolation stand. The stand achieves 30 db isolation from horizontal motions between 0.1 and 60 Hz, by simulating the motion of a 200 meter long pendulum with an air bearing. With this attenuation of seismic noise and a common mode rejection ratio of 10 to the 5th power in the differential mode, the ground based apparatus should have a sensitivity to equivalence principle violations of one part in 10 to the 13th power; the satellite version might have a sensitivity of one part in 10 to the 17th power.
Everitt, C. W. F.↗
Phase detector for three-phase power factor controller
A phase detector for the three phase power factor controller (PFC) is described. The phase detector for each phase includes an operational amplifier which senses the current phase angle for that phase by sensing the voltage across the phase thyristor. Common mode rejection is achieved by providing positive feedback between the input and output of the voltage sensing operational amplifier. this feedback preferably comprises a resistor connected between the output and input of the operational amplifier. The novelty of the invention resides in providing positive feedback such that switching of the operational amplifier is synchronized with switching of the voltage across the thyristor. The invention provides a solution to problems associated with high common mode voltage and enables use of lower cost components than would be required by other approaches.
Nola, F. J.↗
Optically isolated logarithmic nanoammeter capable of floating to 5 kilovolts
A logarithmic current-measuring instrument was developed to measure plasma coupling currents at a common mode voltage of 5 kilovolts. Positive or negative currents can be measured from 10 to the -9th power to .001 ampere direct current. Optical isolation is used to control input switching and to provide data referenced to ground potential. Analog meter readouts as well as zero to five volt outputs are provided for peripheral data collection. Six independent channels are provided. Three measure positive currents, and three measure negative currents. Although designed for vacuum operation, it can be used equally well in air to measure low currents at high common mode voltages.
Sturman, J. C.↗
Interferometer for Measuring Displacement to Within 20 pm
An optical heterodyne interferometer that can be used to measure linear displacements with an error <=20 pm has been developed. The remarkable accuracy of this interferometer is achieved through a design that includes (1) a wavefront split that reduces (relative to amplitude splits used in other interferometers) self interference and (2) a common-optical-path configuration that affords common-mode cancellation of the interference effects of thermal-expansion changes in optical-path lengths. The most popular method of displacement- measuring interferometry involves two beams, the polarizations of which are meant to be kept orthogonal upstream of the final interference location, where the difference between the phases of the two beams is measured. Polarization leakages (deviations from the desired perfect orthogonality) contaminate the phase measurement with periodic nonlinear errors. In commercial interferometers, these phase-measurement errors result in displacement errors in the approximate range of 1 to 10 nm. Moreover, because prior interferometers lack compensation for thermal-expansion changes in optical-path lengths, they are subject to additional displacement errors characterized by a temperature sensitivity of about 100 nm/K. Because the present interferometer does not utilize polarization in the separation and combination of the two interfering beams and because of the common-mode cancellation of thermal-expansion effects, the periodic nonlinear errors and the sensitivity to temperature changes are much smaller than in other interferometers
Zhao, Feng↗
Improvement of scanning radiometer performance by digital reference averaging
Most radiometers utilize a calibration technique in which measurements of a known reference are subtracted from measurements of an unknown source so that common-mode bias errors are cancelled. When a radiometer is scanned over a varying scene, it produces a sequence of outputs, each being proportional to the difference between the reference and the corresponding input. A reference averaging technique is presented that employs a simple digital algorithm which exploits the asymmetry between the time-variable scene inputs and the nominally constant reference input by averaging many reference measurements to decrease the statistical uncertainty in the reference value. This algorithm is, therefore, optimized by an asymmetric chopping sequence in which the scene is viewed for more than one-half of the duty cycle (unlike the analog Dicke technique). Reference averaging algorithms are well within the capabilities of small microprocessors. Although this paper develops the technique for microwave radiometry, it may be beneficial for any system which measures a large number of unknowns relative to a known reference in the presence of slowly varying common-mode errors.
Bremer, J. C.↗
Diverse toxins exhibit a common binding mode to the nicotinic acetylcholine receptors
Not Available
59 BASIC BIOLOGICAL SCIENCES↗
Tele-assistance for semi-autonomous robots
This paper describes a new approach in semi-autonomous mobile robots. In this approach the robot has sufficient computerized intelligence to function autonomously under a certain set of conditions, while the local system is a cooperative decision making unit that combines human and machine intelligence. Communication is then allowed to take place in a common mode and in a common language. A number of exception-handling scenarios that were constructed as a result of experiments with actual sensor data collected from two mobile robots were presented.
Rogers, Erika↗
EMI Filters for Low-Temperature Applications
Filters that suppress electromagnetic interference (EMI) on signal cables connected to cryogenic electronic equipment can be made from cores consisting of high-permeability materials. The basic principle of operation of these filters is the same as that of the ferrite-core common-mode EMI filters now commonly used on cables that connect computers with peripheral equipment. An inductive EMI filters blocks EMI due to its impedance to high frequency EMI signals. Since the impedance is proportional to the permeability, a material with high permeability forms the core of such a filter.
Chui, Talso↗