422 results about "Frequency filtering" patented technology

The present application relates to a switch cabinet discharge fault detection method, system, equipment and medium, belonging to the technical field of power equipment fault detection, the fault detection method includes: receiving real-time monitoring data of the switch cabinet to be monitored and aligning the timestamp; performing dynamic amplitude compensation on the electric field signal data based on the aligned current humidity data, generating the corrected electric field signal data and performing time-frequency domain analysis, extracting the discharge pulse density and high-frequency energy proportion; performing frequency filtering and waveform analysis on the vibration signal, calculating the impact intensity factor and the vibration energy entropy value; making abnormal judgments on the discharge pulse density and the impact intensity factor, and marking the abnormal discharge according to the abnormal judgment results; based on the synchronous change correlation of the high-frequency energy proportion and the impact intensity factor and the vibration energy entropy value, verifying the abnormal discharge marking result, and obtaining the discharge fault result. The present application can realize efficient detection and accurate diagnosis of switch cabinet discharge faults.

The invention provides a time sequence prediction method and system based on frequency filtering and multi-view modeling, and relates to the technical field of time sequence prediction. Comprising the following steps: acquiring historical time sequence data, filtering to obtain a filtered seasonal component, and performing multi-scale division to obtain a multi-scale sequence; in each scale sequence, introducing an embedding amount, performing cyclic translation in a time dimension, generating fragments of multiple view angles, and calculating cyclic attention of the multi-scale sequence; calculating the inter-segment attention of the current scale sequence and the lag differential attention between adjacent segments to obtain the residual attention of the multi-scale sequence; and further obtaining a feature representation corresponding to each scale sequence, and aggregating the feature representations of the multi-scale sequences to obtain a multi-scale comprehensive feature representation. According to the method, effective high-frequency details are reserved while noise is removed, periodic features and local dynamic changes in time sequence fragments are extracted, and the long-term dependency relationship between different time fragments is modeled.

The invention discloses a method for adaptively identifying the thickness of a black soil layer based on a variational mode decomposition method and a ground penetrating radar technology, and the method can directly measure the thickness of the black soil layer of a large-area black land through the ground penetrating radar technology, automatically filters ground penetrating radar signal clutters, and corrects the ground position. According to the technical scheme, on the basis of a center frequency method and a residual error method, variational mode decomposition parameters suitable for black land ground penetrating radar signals are automatically obtained, then modal components of variational mode decomposition are subjected to counting analysis, a spectrogram of original ground penetrating radar signals and the actual black soil layer thickness are compared, an empirical model based on the peak area proportion is established, and the calculation accuracy is improved. The automatic screening can be used for identifying the post-screening center frequency and frequency sweep width of the thickness of the black soil layer, and the position of the black soil layer is adaptively identified after frequency filtering, so that the thickness of the black soil layer can be quickly obtained, and the identification accuracy and efficiency are improved.

The invention provides an optical cable intrusion detection method and device based on distributed optical fiber vibration sensing, belongs to the technical field of optical fiber sensing and security monitoring, and solves the problems that existing optical cable security monitoring is high in false alarm rate, poor in real-time performance and difficult to meet long-distance optical cable security requirements. The method comprises the following steps: acquiring a first vibration signal in a preset amplitude range; performing frequency filtering processing on the first vibration signal to obtain a second vibration signal; performing feature extraction processing on the second vibration signal to obtain a high-dimensional feature vector; performing multi-scale time sequence classification processing on the high-dimensional feature vector to obtain classification data; and determining the vibration state of the optical cable according to the classification data. According to the scheme, long-distance security monitoring of the optical cable is realized, and the accuracy of a detection result is improved.

This application provides a system for generating a drive signal and a method for generating a drive signal for driving a two-in-one device integrating a first component capable of generating sound and a second component capable of generating vibration. The system includes an audio signal pre-processing module, configured to perform low-frequency filtering and acoustic effect processing on an input signal according to a high-pass filtering parameter to obtain an audio signal; a vibration signal generation module, configured to generate a vibration signal based on an acoustic characteristic of the audio signal or a preset vibration library; a signal synthesis module, configured to superpose the audio signal with the vibration signal to output the drive signal; and an amplitude-limiting control module, configured to determine whether the audio signal and the vibration signal exceeds a maximum allowable range when superposed, and attenuate the audio signal and / or the vibration signal.

The invention discloses a GIS ultrahigh frequency sensor ultrasonic cooperative detection system based on piezoelectric energization, and relates to the field of electric power detection, and the system comprises an excitation module which is used for transmitting a piezoelectric excitation signal with a specific frequency to a preset detection region in GIS equipment, so as to trigger the potential partial discharge acoustoelectric signal radiation of the region; the sensing module is used for receiving ultrahigh-frequency electromagnetic signals and ultrasonic vibration signals radiated by partial discharge in the GIS equipment; the excitation frequency, the filtering bandwidth and the sampling rate are dynamically optimized according to the detection result, the detection accuracy and efficiency are continuously improved, and reliable and effective guarantee is provided for safe operation and defect early warning of GIS equipment.

Aspects of the disclosure relate to wireless communication, and high-frequency filters with resonators. One aspect is a device including first and second busbars, and electrode fingers coupled between the busbars, with electrode fingers extending different distances toward an opposite busbar such that a second end of each of the electrode fingers collectively form wave shapes. The device further includes pluralities of gap reflectors positioned between the wave shapes and a nearest busbar.

The invention discloses a broadband wearable double-frequency filtering antenna with an independent and controllable radiation zero point, and the antenna employs a double-layer dielectric substrate structure, the upper layer is a Rogers4350B substrate, the lower layer is a flexible felt substrate, and a multi-structure coupling design of a T-shaped strip, a U-shaped groove, a rectangular groove and a parasitic strip is integrated through a rectangular radiation patch. And dual-frequency work and radiation zero independent regulation and control are realized. Wherein the T-shaped strip generates a dual-frequency characteristic and a first radiation zero point between two frequency bands; the U-shaped groove regulates and controls the low-frequency zero point and broadens the low- The rectangular groove introduces a second radiation zero point between two frequency bands and expands the high-frequency bandwidth; a high-frequency zero point and a new resonance point are introduced into the parasitic strip, and the high-frequency matching bandwidth is widened. The antenna has the flexible wearable characteristic, the broadband performance and the independent controllable characteristic of the radiation zero point, and is suitable for wireless communication scenes such as WiMAX / WLAN and the like.

The invention relates to the technical field of intelligent control, in particular to a specialty paper slitting and embossing process thickness detection system, which comprises an acquisition module used for determining a plurality of dynamic reference points at a preset position at the downstream of an outlet of an embossing roller, acquiring original displacement data in real time, constructing a dynamic polygon according to the dynamic reference points, and determining the thickness of the dynamic polygon; calculating a centroid offset and an area change rate, generating a dynamic adjustment coefficient, and calibrating the displacement original data through the dynamic adjustment coefficient to obtain calibrated displacement data; the filtering module is used for performing high-frequency filtering processing on the calibration displacement data to generate filtering displacement data; and the anti-interference module is used for performing anti-electromagnetic interference processing on the filtering displacement data to generate anti-interference displacement data. According to the invention, through accurate detection, anti-interference processing and real-time control of the whole link, high-precision monitoring and regulation of the thickness of the special paper in the slitting and embossing process are realized.

The invention discloses an AI-based high-fidelity audio coding and decoding algorithm adaptive to an auditory range and a compression optimization method, and the algorithm comprises an audio signal preprocessing module which is used for carrying out the preprocessing of an input audio signal, including but not limited to denoising, frequency filtering, gain adjustment, time domain / frequency domain transformation and the like, and carrying out the compression optimization of the audio signal; and the preprocessing module is used for performing feature extraction through a convolutional neural network (CNN) or an auto-encoder network so as to improve the signal-to-noise ratio of an audio signal and remove environmental noise, and generating optimized audio features. Through an AI-based auditory range adaptation algorithm, dynamic optimization can be performed according to individual auditory characteristics, so that the audio coding and decoding process is more in line with the perception characteristics of human ears, better balance is obtained between the compression ratio and the tone quality, higher audio experience is provided, and through the adaptive quantization and code rate control technology, the audio coding and decoding efficiency is improved. According to the method, on the premise of keeping the high-fidelity tone quality, the deep learning algorithm is utilized to optimize the allocation of computing resources, and the consumption of the computing resources is reduced.

A vehicle vibration extraction system according to the present disclosure includes: at least one memory configured to store instructions; and at least one processor configured, by executing the instructions, to acquire measurement data of vibration generated on a road from a sensing apparatus that measures vibration generated on the road by using an optical fiber buried in the road, and extract a vehicle vibration component from the measurement data by performing frequency filtering on the measurement data by using a band limiting filter having a passband associated to the road and a road surface state of the road.

The invention discloses an LLCL filter design method, and relates to the technical field of power electronics. The method comprises the following steps: acquiring an initial filter capacitance, an initial inverter side filter inductance, a power grid side filter inductance and a target frequency; calculating filtering branch inductance based on the filtering capacitance and the target frequency; calculating a positive harmonic peak frequency based on the filter capacitor, the inverter side filter inductor, the power grid side filter inductor and the filter branch inductor; calculating damping resistance, damping inductance and damping capacitance based on the positive harmonic peak frequency, the filter capacitance, the resonant frequency value constraint, the first value range constraint and the second value range constraint of the quality factor; and when the target parameter does not meet the grid-connected current harmonic standard, updating the filter capacitor and / or the inverter side filter inductance, and skipping to the step of calculating the filter branch inductance based on the filter capacitor and the target frequency so as to carry out iteration until the grid-connected current harmonic standard is met. According to the embodiment of the invention, the design optimization of the parameter value of the filter element in the LLCL filter is realized.

The invention discloses an intermediate frequency filter chip based on a gallium arsenide IPD process, which adopts the GaAs IPD process with three metal layers and comprises six resonators, twelve capacitors and three metalized grounding holes. The six resonators are composed of capacitors C1-C6 and inductors L1-L6 which are connected in series / in parallel, the inductors are all of self-built octagonal structures, and wiring is only conducted on the middle layer and the uppermost metal layer; a branch series capacitor Ca-Cc and a main parallel capacitor Cd-Cf respectively form six transmission zeros outside a low-frequency band and a high-frequency band. According to the invention, the characteristics of small size and wide band of the filter chip are realized, the loss is reduced, the in-band flatness is improved, and the filter chip has high frequency selectivity and high out-of-band rejection capability.

The invention discloses a software radio digital signal frequency conversion method and system and a medium. Relates to the technical field of digital signal processing. Comprises: acquiring an input signal; performing complex multiplication on the input signal and the carrier signal to obtain a frequency conversion signal; based on an adjustable filtering extraction module, performing integral multiple or rational multiple filtering extraction on the frequency conversion signal to obtain an output signal; wherein rational multiple filtering extraction is realized by a numerical control oscillator and an interpolation unit; according to the scheme, on the basis of the traditional technology of realizing the digital down converter on the FPGA, the method and the structure are improved, and on the basis of an adjustable filtering extraction module, integral multiple or rational multiple filtering extraction is carried out on a frequency conversion signal to obtain an output signal; free adjustment of the digital down-conversion multiple is achieved, and rational number multiple configuration of digital down-conversion is achieved based on the numerically controlled oscillator and the interpolation unit.

A system for beamforming and filtering. In some embodiments, the system includes an array of antenna elements; and a front-end circuit connected to the antenna elements, the front-end circuit including a plurality of delay elements. The delay elements may be configured to provide beam forming; and to operate as delay elements in a finite impulse response filter.

The invention discloses a signal high-frequency interference resisting device and method for electrical resistance tomography. A high-frequency filtering unit in the device comprises a magnetic ring, a coaxial shielding line, a first resistor and a second resistor; the coaxial shielding lines are connected between the corresponding detection electrodes and the signal sampling ends, and the first resistors are connected between the first ends of the signal lines in the corresponding coaxial shielding lines and the first ends of the signal lines in the next coaxial shielding lines. The second resistor is connected between the second end of the signal line in the corresponding coaxial shielding line and the second end of the signal line in the next coaxial shielding line; the first end of the signal line in the coaxial shielding line is also connected with the first end of the shielding layer in the next coaxial shielding line; the magnetic rings sleeve the outer layers of all the coaxial shielding wires and are tightly attached to the outer layers of the coaxial shielding wires, filtering on a transmission line is achieved, the twisted-pair coaxial shielding wire magnetic rings are combined to serve as transmission wire harnesses, a hardware coupling filter circuit between the wire harnesses is constructed, the suppression effect of common-mode interference is improved, sampling signals are more real, and imaging is clearer.

The invention discloses a rotary table angle data filtering method based on an adaptive cut-off frequency filter, relates to the technical field of signal data filtering, and aims to solve the problem of numerical value jumping caused by high-frequency noise interference on rotary table angle data. The method comprises the following steps: firstly, setting a minimum cut-off frequency and a speed coefficient for an adaptive cut-off frequency filter, obtaining rotary table angle data, calculating the change speed of filtered standard data, and dynamically adjusting the cut-off frequency of the filter; filtering the data for multiple times by using an exponential smoothing formula; and finally, updating the dynamic cut-off frequency according to a filtering result to obtain filter parameters. The filter is a low-pass filter, has the advantages of being easy and convenient to adjust parameters, high in adaptability and high in calculation efficiency, can effectively suppress noise, and meanwhile keeps sensitivity to fast change data. Experiments prove that the method has good performance in different speed data processing, and is suitable for an inertial navigation equipment turntable system.

The utility model relates to a split-phase inverter, and the inverter comprises a first filter circuit which comprises a filter capacitor CX1, a filter capacitor CX2, and a filter inductor LX employing a magnetic integrated filter inductor structure; the second filter circuit comprises a filter inductor L; the split-phase inverter circuit comprises a direct current bus DC +, a direct current bus DC-, a first switch network, a second switch network, a direct current filter capacitor C1 and a direct current filter capacitor C2, the direct current filter capacitor C1 and the direct current filter capacitor C2 are connected in series, and the first switch network and the second switch network are electrically connected with the filter inductor LX. The size and the cost of the high-frequency filter inductor are effectively reduced based on the magnetic integrated structure, and the filter performance is improved.

The invention provides an intelligent pulse ultrasonic fluid measurement method and device, and belongs to the field of pulse ultrasonic fluid measurement. The method comprises the following steps: starting and initializing an intelligent pulse ultrasonic fluid measuring device arranged on a pipeline needing to be measured; the method comprises the following steps: configuring and starting an ultrasonic transmitter and an ultrasonic receiver, then setting a sampling frequency and a sampling period, enabling the ultrasonic transmitter to output a constant-amplitude signal with a fixed frequency, and enabling the ultrasonic receiver to collect the constant-amplitude signal output by the ultrasonic transmitter; carrying out amplification and frequency-selecting filtering on the collected constant-amplitude signal output by the ultrasonic transmitter, and extracting a vortex frequency effective signal; and calculating the flow velocity and flow of the fluid, and outputting the calculated flow velocity and flow. The fluid flow velocity value is calculated through the pulse ultrasonic technology, corresponding analog or digital signals are displayed and output, and a high-precision and large-range-ratio measurement result is provided.

The invention discloses an intelligent electric power system remote monitoring device and a monitoring method thereof, relates to the technical field of electric power monitoring interference prevention, solves the problem that comprehensive and deep feature extraction is difficult to perform on complex waveforms, and provides an intelligent electric power system remote monitoring device and a monitoring method thereof through careful analysis of signal waveform features in a monitored line. A scientific characteristic value sequence recognition system is established; aiming at the standard waveform of each monitoring item, the characteristic value sequence of the standard waveform is accurately locked, and whether the signal waveform is interfered or not can be sensitively identified by virtue of change characteristic analysis and characteristic sequence matching; according to the method, the abnormal waveform points and the interference waveforms are accurately calibrated, a proportion value judgment method is applied, misjudgment caused by parameter numerical value fluctuation is effectively avoided, the interference recognition accuracy is greatly improved, frequency filtering is directly carried out on the waveforms which do not belong to monitoring items, and the filtering efficiency is improved; for the waveforms belonging to the monitoring item, the time of different waveforms is ingeniously adjusted by determining a time difference characteristic sequence.

The invention relates to an anti-interference array antenna host with variable array elements, which is composed of antenna characteristic modeling software and an array signal processing host, and is characterized in that the antenna characteristic modeling software is mainly used for modeling an antenna array and can set parameters including the number of array elements, array element spacing, array element positions, an antenna pattern and the like; the wave path difference of navigation and interference signals in different directions reaching different array elements of the array antenna and wavefront simulation parameters such as signal power, time delay and Doppler change values are calculated by taking the reference array element as the center, and the characteristics of different types of array antennas are flexibly simulated; the array signal processing host is mainly used for executing an anti-interference processing algorithm configured by a user, supporting a space-time / space-frequency filtering framework, an LMS / SMI / DMI / RLS inversion method, an LCMV / MMSE / MSINR constraint criterion, zeroing / wave beam and other combined strategies, and flexibly simulating the characteristics of different anti-interference processing modules.

The utility model relates to the technical field of equipment over-temperature protection, and discloses a protection circuit and an over-temperature protection device for a high-frequency filter capacitor of a photovoltaic inverter, a temperature protection module is introduced into a high-frequency filter module, and the temperature protection module acquires and monitors the temperature corresponding to the high-frequency filter module. Then the collected temperature signals are encoded and transmitted to a processing host corresponding to the photovoltaic inverter, the host decodes and analyzes the encoded temperature signals, intelligent monitoring of the current module temperature of the high-frequency filtering module is achieved, and when it is detected that the module temperature reaches the set early warning temperature, the high-frequency filtering module is started to perform early warning. The host generates a response control signal and transmits the response control signal to the temperature protection module, the temperature protection module executes matched temperature control operation according to the control signal, and then over-temperature early warning and / or over-temperature control of the high-frequency filtering module and / or the photovoltaic inverter are / is achieved.

The invention discloses a sequence recommendation method and system based on a wavelet enhanced adaptive frequency filter, and the method comprises the steps: constructing a user behavior sequence according to the interaction between a user and an article, mapping the article in the user behavior sequence into an embedded vector, and processing the embedded vector to obtain a sequence embedded representation; the sequence is embedded and expressed, global features and fine-grained features are obtained through dynamic frequency filtering and wavelet feature enhancement, and fusion time domain features are obtained through feature integration; and processing the fused time domain feature to obtain a final time domain feature, performing probability prediction on an output vector of the last time step in the final time domain feature and transposition of an article embedding matrix to obtain a recommendation probability, and performing sorting to obtain a sequence recommendation result. According to the method, personalized global information is extracted and fuzzy non-stationary signals and short-term fluctuation are enhanced through dynamic frequency filtering and wavelet features, and performance and efficiency optimization is realized in a long-sequence recommendation scene through cooperative work of the two modules.

The invention provides an audio missing fragment repairing method, which comprises the following steps of S1, performing short-time Fourier transform on a damaged audio signal to obtain an STFT amplitude spectrum, and converting the STFT amplitude spectrum into a Mel scale through a frequency filter bank to obtain a Mel spectrum of the damaged signal; s2, using the trained vector quantization variational auto-encoder to encode the Mel spectrum of the damaged signal into a potential spatial feature with a relatively low dimension; s3, applying a diffusion model method, taking the damaged potential spatial features as conditions, splicing sampled Gaussian noise, performing T-step denoising through the trained denoising network, and outputting predicted complete potential spatial features; and S4, decoding the predicted complete potential features through an auto-encoder to obtain a predicted complete Mel spectrum, repairing a signal phase by using a sensing HiFiGAN vocoder, and outputting a repaired voice signal. According to the invention, natural and coherent restoration of long voice missing segments is realized, and the robustness of the method in a noise environment is improved.

The invention discloses a frequency regulation optimization control method considering wind-fire storage cooperation, and belongs to the technical field of novel power system frequency regulation. Comprising the steps of establishing a wind power frequency modulation model, a thermal power and power grid frequency modulation model and a flywheel energy storage frequency modulation model; designing a frequency first-order low-pass filter, decomposing a frequency signal into a high-frequency signal and a low-frequency signal, and performing flywheel energy storage and wind power response respectively; a thermal power primary frequency modulation signal first-order filter is designed, a primary frequency modulation signal is decomposed into a high-frequency component and a low-frequency component, the high-frequency component is responded by a wind storage system in proportion and serves as compensation of respective frequency modulation instructions, and the low-frequency component is responded by a thermal power generating unit; designing a wind power frequency modulation control strategy and a flywheel energy storage charging and discharging control strategy considering the charge state; different scenes are set, and the frequency modulation effect and the thermal power fluctuation relieving performance are analyzed. Generator output fluctuation can be effectively reduced, frequency modulation pressure is shared for the thermal power generating unit, and safe and stable operation of the system is facilitated.

The invention discloses an anti-interference L-band microwave remote sensing radiometer, and the radiometer comprises a radio frequency receiving assembly which comprises a miniaturized array antenna, a single-pole three-throw switch, a band-pass filter, a low-noise amplifier, a frequency mixer, a local oscillation source, an intermediate-frequency filter, an intermediate-frequency amplifier, and a detector; a signal control and acquisition assembly; a calibration component; a data processing and transmitting component; the miniaturized array antenna is used for receiving a radio frequency noise signal in a target direction; the single-pole three-throw switch is used for respectively switching and receiving the radio frequency noise signal in the target direction, a radio frequency noise signal after heat source matching and a radio frequency noise signal after cold source matching; a radio frequency noise signal is processed through a band-pass filter, a low-noise amplifier, a frequency mixer, an intermediate-frequency filter, an intermediate-frequency amplifier and a detector in sequence, and a detection signal is combined with a calibration algorithm to complete noise temperature measurement in a target direction; the data processing and transmission assembly transmits the data to the platform. The radiometer provided by the invention has strong anti-interference capability and can be used for various scenes for retrieving environmental parameters.

The invention relates to the technical field of machine learning, in particular to a collaborative filtering recommendation method based on a spectrogram neural network. The method comprises the following steps: generating a graph embedded signal corresponding to a user-item interaction graph by using a spectrum GNN based on the user-item interaction graph, and specifically comprises the following steps: scaling an original filtering function by using a frequency signal scaling function based on the original filtering function of the spectrum GNN to generate a first filtering function; respectively using a monomial basis to approximate the first filtering function to train and generate a low-frequency filtering function and a high-frequency filtering function; and based on the user-item interaction diagram, respectively using a low-frequency filtering function and a high-frequency filtering function to generate a low-frequency diagram embedded signal and a high-frequency diagram embedded signal corresponding to the user-item interaction diagram. According to the collaborative filtering recommendation method based on the spectrogram neural network, the characteristics of the user item interaction diagram can be fully reserved, and homogenization of recommendation results is avoided.

The invention discloses a low-temperature filtering module and a quantum computer using the same. The low-temperature filtering module comprises a grounded shell; the filter main body is integrated in the shell, and the filter main body comprises a plurality of coaxially arranged metal cylinders to form an impedance conversion structure; the infrared wave-absorbing structure is integrated in the housing, and the infrared wave-absorbing structure wraps the filter main body. According to the invention, the low-pass filter and the infrared wave-absorbing structure are integrally designed through a coaxial discontinuous metal cylinder structure, and impedance conversion filtering and infrared quasi-particle absorption functions are realized in parallel in an integrated module, so that the high-frequency filtering performance of an original separation device is maintained, the number of devices is reduced through function integration, and the cost is reduced. The material cost and the occupied space of the mK temperature zone are remarkably reduced, the cooling capacity pressure of a refrigerator is relieved, meanwhile, the loss of a cascade connector is eliminated, the consistency of devices is improved, and a key solution is provided for space expansion and reliability optimization of a high-density superconducting bit system.

The invention relates to an audio decoding output stage circuit and audio equipment, the audio decoding output stage circuit comprises an I / V conversion module and a low-pass filtering module, and the I / V conversion module comprises a conversion circuit, a crossed diamond amplification circuit, an overcurrent protection circuit and a Roche network circuit; the conversion circuit comprises a JFET (Junction Field Effect Transistor) audio operational amplifier chip and an I / V (Input / Output) conversion resistor and is used for converting an input current into an analog voltage signal; the crossed diamond amplifying circuit can reduce the input offset voltage; the over-current protection circuit can carry out over-current protection; the rowbell network circuit can prevent high-frequency self-oscillation of the power output stage; and the low-pass filtering module comprises a filtering circuit and an ultrahigh frequency filtering circuit arranged at the output end of the audio decoding output stage circuit. The scheme can bring high-performance sound performance, and has the advantages of lower distortion, higher conversion rate, low output impedance and large pushing current.

A method of detecting an earthquake is described, comprising receiving a signal representative of measurements of three-dimensional acceleration of the device as a function of time; frequency filtering of the signal; determining, from the filtered signal, data representative of acceleration directions as a function of time; an earthquake being detected if a) the magnitude of the acceleration is greater than a first threshold and the directions of the acceleration are substantially collinear with one another for a first time interval; or b) the directions of acceleration are substantially collinear with one another during a second time interval, and the directions of acceleration are substantially collinear with one another during a third time interval subsequent to the second time interval, and the directions of acceleration of the second interval and the third interval are substantially orthogonal.