73 results about "Frequency generation" patented technology

The invention relates to the technical field of interference suppression, in particular to an electromagnetic compatibility optimization method and system for a ship shaft frequency converter, and the method comprises the steps: carrying out the term-by-term judgment of sensitive interference energy, current errors and switching loss after the discretization and jump limitation based on a frequency sequence, and screening out a boundary-crossing sequence, the genetic algorithm executes cross combination and amplitude superposition in the residual sequence, a new frequency set is formed through transformation and rearrangement, frequency points are distributed in a plurality of intervals to be reorganized, the switch state is predicted and updated one by one through Kalman filtering, observation residual errors are corrected in real time, and the frequency points are reorganized. The harmonic distortion rate, the radiation intensity and the instruction change amplitude are synchronously output by taking the time index as a sequence, the deviation is compensated at the amplitude and phase level, the harmonic index and the radiation index are controlled in an agreed range, the switching loss and the instruction change are within threshold values, and a complete closed loop covering frequency generation, harmonic correction and sequence updating is formed.

The invention discloses an image transmitting and displaying method and electronic equipment, and relates to the technical field of terminals. The electronic device comprises an SoC and a display screen, when a display drive of the SoC is not sent to display, after high-frequency TE is started, a TE signal is generated according to a second frequency, Vsync is generated according to a first frequency, and the second frequency is larger than the first frequency. The SoC generates the timestamp according to the first frequency based on the TE signal, so that the value of the calibration count can be normally increased, and the calibration counting of the Vsync signal and the TE signal is successfully completed.

The utility model relates to the technical field of alarms, in particular to a frequency-adjustable alarm module, which is characterized in that a master control module is respectively in communication connection with a frequency generation module and an alarm execution module, the frequency generation module is in communication connection with an infrared transceiver module, and the infrared transceiver module is in communication connection with the alarm execution module. And the power supply management module is respectively and electrically connected with the main control module, the infrared transmitting and receiving module and the alarm execution module. According to the utility model, different components in the alarm, the infrared transmitter and the wireless charging PCB are modularly divided according to functions and effects of the components; the functions of unlocking, multi-level alarming and frequency switching achieved based on the communication relation are highlighted, a more flexible and effective alarming mode is achieved, the defects of a traditional alarm are overcome, and high market application value is achieved.

The invention relates to the technical field of construction site management, in particular to a highway construction site Internet of Things positioning and tracking system which comprises a fundamental frequency calculation module, a parameter generation module, a central frequency generation module, a central frequency calculation module and a central frequency calculation module. The fundamental frequency calculation module collects engine rotating speed and angular speed signals and calculates engine vibration fundamental frequency by combining ignition factors. The dynamic filtering module is used for configuring the weighting coefficient as a difference equation parameter, blocking bandwidth energy through convolution filtering and generating a purification angular velocity; the trajectory tracking module is used for calculating the purification angular velocity and a zero deviation value, calling a Runge-Kutta algorithm for integral generation of a course angle, and generating a position coordinate in combination with a driving speed. According to the method, the vibration fundamental frequency is inversely calculated by collecting the rotating speed of the engine, the blocking bandwidth is dynamically constructed according to the interference frequency, the frequency characteristic is mapped to be a difference equation coefficient, vibration noise is accurately stripped, course drift is eliminated, and it is ensured that the positioning coordinates matched with the actual track are output.

This invention belongs to the field of analog integrated circuit technology, specifically relating to a frequency adaptive circuit for downhole detection. This invention utilizes a closed-loop adaptive feedback mechanism, employing multiple excitation frequencies generated by a frequency generator to continuously match and adapt to the transducer's resonant frequency. When a set of excitation frequencies achieves the highest matching degree with the resonant frequency, the echo energy reaches its peak. The frequency generator is adaptively adjusted based on the excitation frequency corresponding to the maximum peak signal obtained during the detection phase, and this optimal excitation frequency is used to generate the excitation signal in subsequent operations, thus completing the adaptation between the excitation frequency and the resonant frequency. This invention effectively avoids the influence of downhole temperature and pressure changes on the transducer's resonant frequency, and combines high automation, good real-time performance, and high imaging quality.

A scattering parameter measurement device based on microwave photonic mixing includes a microwave generation module 1, a signal loading module 2, a local oscillator frequency generation module 3, a multi-channel microwave photonic mixing module 4, an analog-to-digital converter (ADC) module 5, and a signal processing module 6. Along the signal output direction of the multi-channel microwave photonic mixing module 4, the ADC module 5 and the signal processing module 6 are sequentially arranged. This invention utilizes microwave photonic mixing technology and a local oscillator source with relatively small bandwidth to down-convert a high-frequency microwave signal to a fixed-frequency intermediate frequency (IF) signal. This reduces the bandwidth requirements of the receiver's electronic components and the sampling rate requirements of the ADC. It abandons the traditional superheterodyne structure and / or direct conversion structure, using a miniaturized continuous optical module as the light source for microwave photonic mixing, simplifying the system structure and reducing cost and power consumption.

The invention relates to a device for generating high-frequency currents for the cosmetic and / or therapeutic treatment of tissue by means of electrodes of the device, comprising: a high-frequency energy source for generating high-frequency currents and at least one first electrode pair having two electrodes for applying the high-frequency currents to the tissue, which electrodes are each connected to an output of the high-frequency energy source, which device is designed to generate the high-frequency currents at a plurality of different frequencies fj by means of the high-frequency energy source, characterised in that the device is designed to generate the currents at a plurality of different frequencies fj by means of the high-frequency energy source in a temporal sequence having sequence steps Sj where j=1, 2, …, M; M ∈ ℕ; at least one current generated in said sequence step Sj and having the frequency fj and a duration Tj for which the current at the frequency fj is generated in the sequence step Sj is assigned to each sequence step Sj, and at least one sequence of the frequencies fj is a random sequence. In addition, at least one of the following additional features is implemented: The current intensity of the currents lies between 100 mA and 2 A, preferably between 300 mA and 1 A. The frequencies fj lie in a frequency range between 0.1 MHz and 20 MHz, preferably between 0.1 MHz and 10 MHz, most preferably between 0.1 MHz and 3 MHz. The duration Tj is less than 100 ms, preferably less than 50 ms. The invention further relates to a corresponding treatment method, in particular a cosmetic treatment method.

The invention relates to the technical field of fan rotating speed detection, and particularly provides a fan rotating speed detection method and device and electronic equipment. The method comprises the steps that the total number of sampling points and the total number of high-level sampling points in a fan rotating speed detection period are counted; the total number of high-level sampling points refers to the number of high-level sampling points obtained by sampling frequency generation signals of the fan in a fan rotating speed detection period, and the high-level duty ratio in the fan rotating speed detection period is obtained according to the number of the high-level sampling points and the total number of sampling points; if it is determined that the frequency generation signal, obtained in the fan rotating speed detection period, of the fan is a normal signal according to the high-level duty ratio, the latest current fan rotating speed is determined based on the fan rotating speed detection period; and if it is determined that the fan frequency generation signal obtained in the fan rotating speed detection period is abnormal according to the high-level duty ratio, the specified fan rotating speed is determined as the latest current fan rotating speed. Therefore, the accuracy of fan rotating speed detection is improved.

A laser assembly and a method for generating continuous-wave (CW) light at approximately 193 nm (between 180 nm and 200 nm) and at a power of 1W or higher using two CW laser sources: one laser source generating first fundamental light that is twice frequency doubled or otherwise converted into first CW light having a first deep-ultraviolet (DUV) wavelength between 250 nm and 275 nm, the other laser source generating second CW light having an infrared (IR) wavelength between 1300 nm and 1700 nm. A resonant cavity receives the second CW light and generates enhanced CW light at 100 W or higher. A first non-linear optical (NLO) crystal mixes a first enhanced CW light portion and the first CW light to generate sum-frequency generation (SFG) light having a second DUV wavelength. A second NLO crystal mixes a second enhanced CW light portion and the SFG light to generate output CW light at approximately 193 nm.

A fluid filled fiber for a quasi-phase matched generator and a laser incorporating such a fluid filled fiber. The liquid filled fiber has charge transfer molecules dissolved in a solvent. In another embodiment, the liquid of the LF fiber comprises or consists essentially of highly polar liquids and / or charge transfer molecules having relatively high molecular dipole values. The liquid filled fiber is usable with a laser for differential frequency generation.

A multimodal hyperspectral vibrational sum-frequency generation (VSFG) platform and a method of tumor diagnosis are provided. The method employs the chemical-specific VSFG microscopy platform as a label-free imaging technique for tumor identification.

According to the frequency generation circuit, the chip and the electronic equipment provided by the embodiment of the invention, the calibration mode is introduced to the gain filtering module, and the calibration voltage is accessed when the gain filtering module is in the calibration mode, so that the offset voltage during gain is calibrated, the calibration state signal is obtained, whether calibration is completed or not can be intuitively indicated through the calibration state signal, and the calibration efficiency is improved. Under the condition that the calibration state signal indicates that calibration is completed, errors caused by offset voltage can be suppressed, the stability of the calibrated gain filtering module is higher, therefore, when the gain filtering module is switched to the filtering mode to filter the target voltage, the integral leakage phenomenon can be effectively reduced, and the stability of the gain filtering module is improved. Therefore, the stability of the target frequency signal generated by the subsequent oscillation module is improved.

This invention discloses a photonic terahertz communication system based on non-uniform probabilistic shaping, belonging to the field of terahertz communication. Specifically, it includes a transmitter and a receiver. The transmitter incorporates non-uniform probabilistic shaping and phase fuzzy encryption techniques, using photonic beat frequency generation to produce a terahertz signal. This signal is then transmitted wirelessly via single-mode fiber to the receiver, where it is mixed with a frequency-multiplied local oscillator signal to achieve down-conversion of the terahertz signal, obtaining an intermediate frequency (IF) signal. The IF signal is then sampled and input to an RX-DSP module for digital signal processing, ultimately obtaining the original data and calculating the bit error rate (BER). This invention improves the system's BER performance and significantly enhances the security of the photonic terahertz communication system.

A laser apparatus for generating a sub- 190 nanometer laser beam includes a deep-ultraviolet solid-state laser source to generate an initial deep-ultraviolet laser beam, at least one mid-infrared solid-state laser source to generate at least one respective mid-infrared laser beam, and at least one lithium triborate crystal to generate an output deep-ultraviolet laser beam from the initial deep-ultraviolet and mid-infrared laser beams via sum-frequency generation. Each mid-infrared solid- state laser source includes (a) a holmium-, thulium-, or chromium-doped gain crystal or gain fiber or (b) an optically-pumped semiconductor gain material to generate the respective mid-infrared laser beam. The laser apparatus may be configured for continuous-wave and pulsed operation, thus offering versatile solutions for applications requiring DUV laser radiation below 190 nanometers. Advantageously, the present approach relies on lithium triborate. Lithium triborate crystals can be grown with the quality and dimensions needed for industrial applications.

The application discloses a human body falling detection method and system based on acoustic signals. The method comprises the following steps: controlling a loudspeaker to generate ultrasonic waves at a set frequency, and collecting acoustic signals generated when a human body falls by using a microphone; performing shunting and denoising on the acoustic signals to obtain low-frequency signals generated by human body collision and high-frequency signals of human body reflected ultrasonic waves; detecting the starting point and ending point of human body activity in the low-frequency signals, and detecting the starting point and ending point of human body activity in the high-frequency signals, and then determining the starting point and ending point of the acoustic signals; performing feature extraction on the low-frequency signals and the high-frequency signals respectively to obtain low-frequency signal features and high-frequency signal features; inputting the low-frequency signal features and the high-frequency signal features into a pre-trained double-flow long short-term memory network classification model to obtain a falling detection result. The application can realize real-time falling monitoring, and has high recognition accuracy and low false alarm rate.

To provide a high-output high-frequency generator having a simple configuration.SOLUTION: The high frequency generator (10) is provided with a voltage generation part (12) for generating a voltage by the irradiation of feed light, a photodiode (11) for generating electrons by the photoelectric conversion of signal light and converting the electrons into a current by the voltage, and an antenna (13) for radiating radio waves on the basis of the current. The high frequency generation device may include a vacuum package (14), and the voltage generation unit, the photodiode, and the antenna may be provided in the vacuum package.SELECTED DRAWING: Figure 1

The invention provides an intelligent unmanned aerial vehicle-mounted ultrasonic insect repelling system and an insect repelling method thereof, and belongs to the technical field of physical prevention and control of agricultural pests. Comprising a main control module used for dual-mode frequency control and unmanned aerial vehicle linkage; the frequency generation module is used for generating a 20-60kHz signal through a 32-bit frequency tuning word; the power amplification module is used for amplifying the signal to 2.83-10V to drive an ultrasonic horn; the shell is of a double-layer damping structure, is provided with sound transmission holes and is fixed to the unmanned aerial vehicle through the bandage holes. An STC12C5A60S2 single chip microcomputer in the main control module is used for programming and combining with an AD9851 direct digital frequency synthesizer to send out an ultrasonic signal, and then a 1V sine wave of the AD9851 is amplified to 2.83-10V through a power amplification module (TDA2030A audio amplifier) to drive a PW5120 loudspeaker. The three-dimensional maneuverability of the unmanned aerial vehicle is combined, the terrain limitation is broken through, and large-area and dynamic insect expelling coverage is achieved; 2, a dual-mode frequency-adjustable technology (automatic circulation / key control) is adopted to cope with the pest resistance and the frequency sensitivity difference of different species;

The invention relates to a real-time vibration compensation device and method for a cold atom gravimeter. The device comprises a Raman laser, a rubidium atomic group, a reflector, an accelerometer, an optical phase-locked loop module, an analog-to-digital converter, a reference clock source, a heteronuclear FPGA, a direct frequency generation module and an upper computer. Two pairs of Raman lasers oppositely act on a rubidium atomic group in the vertical direction, the accelerometer and the reflector are in rigid connection, analog differential signals of the accelerometer enter the analog-digital converter, converted digital signals enter the heteronuclear FPGA for digital calculation, and the reference clock source serves as clock signals of the digital circuit. A signal calculated by the heteronuclear FPGA enters the direct frequency generation module and is output to the optical phase-locked loop to control the phase of the Raman laser, and the heteronuclear FPGA communicates with the upper computer through TCP connection. The vibration real-time compensation device for the cold atom gravimeter is fully digital, and has the advantages of large dynamic range, low noise and high-precision phase synchronization compensation capability.

This disclosure relates to the field of metal detection technology, providing a metal detector for multi-frequency detection, comprising: a balanced coil system including: a transmitting coil assembly including a low-frequency and a second transmitting coil; a first transmitting coil driving circuit including: a first signal generator generating a magnetic field generation signal time-division multiplexed by first and second frequencies; a first resonant circuit allowing switching of resonant frequencies between the first and second frequencies; a first signal switcher providing a frequency switching signal to the first resonant circuit; and a second transmitting coil driving circuit including: a second signal generator generating a magnetic field generation signal time-division multiplexed by third and fourth frequencies; a second resonant circuit allowing switching of resonant frequencies between the third and fourth frequencies; and a second signal switcher providing a frequency switching signal to the second resonant circuit; the two signal generators operate together to form a combination of alternating magnetic fields generated by each frequency. The increased number of frequencies generating alternating magnetic fields enhances detection strength and accuracy, expanding application scenarios.

The embodiment of the invention provides a frequency conversion device based on a lithium niobate ridge waveguide on an insulator and a preparation method, and belongs to the field of integrated optical, nonlinear optical and optoelectronic devices. The device comprises a silicon substrate layer, a silicon dioxide buffer layer, an x-cut lithium niobate film layer and a silicon dioxide cladding from bottom to top, a ridge waveguide with width periodically changing is arranged on the x-cut lithium niobate layer, and light in the waveguide is propagated in the y-axis direction. The waveguide with the width periodically changing is prepared on the lithium niobate film, quasi-phase matching is achieved, and therefore the second harmonic conversion efficiency is greatly improved. By changing the period of the waveguide, second-order nonlinear phase matching conditions under different wavelengths, such as phase matching conditions of second harmonic generation, sum frequency generation and difference frequency generation, can be met. Correspondingly, according to the preparation method, the waveguide structure with the periodically changed width can be formed through a single etching process, and a complex ferroelectric domain inversion step is not needed. The preparation method has the advantages of simple process, controllable morphology and flexible design.

The application discloses a kind of millimeter wave signal phase noise test methods based on super-stable laser, utilize common cavity Brillouin laser frequency stabilization technology to generate super-stable laser as carrier wave to carry out double sideband modulation to the millimeter wave signal to be measured, when utilizing optical fiber ring resonant cavity to excite Brillouin laser, two sidebands are different in frequency shift: the sideband of high frequency shifts down more, the sideband of low frequency shifts down less, the common cavity Brillouin laser generated is coupled with double optical sideband pump laser, separation is obtained different in frequency interval upper and lower double sideband optical signal, then beat frequency, mixed frequency generation to MHz order intermediate frequency signal, intermediate frequency signal noise characteristic directly carries the phase noise of signal to be measured, by phase noise analyzer, intermediate frequency signal is analyzed and quantitatively evaluated with noise spectral density, complete the phase noise test of millimeter wave signal to be measured, solve the cooperative optimization problem that reference source stability, system noise and signal noise to be measured are difficult to separate in super-high frequency signal noise test.

The invention relates to the field of optical communication and photon integrated circuits, in particular to an optical isolator and an optical isolation method. The optical isolator is based on a periodically poled lithium niobate (PPLN) waveguide, and non-reciprocal optical transmission is realized by using a difference frequency generation (DFG) effect. The whole structure integrates the Bragg grating, the beam combiner and the multimode interferometer so as to realize efficient wavelength conversion and optical isolation functions. In the working process, wavelength conversion is carried out on light propagating forwards in the PPLN waveguide through the DFG effect, and the light is transmitted to the output end with low loss. Meanwhile, the Bragg grating strongly inhibits light propagating in the back direction, so that it is ensured that one-way transmission of the light passes through the scheme, compact and reliable chip-level optical isolation can be achieved, dependence on traditional discrete components is reduced, and an efficient optical isolation method is provided for an integrated optical system and a photon integrated circuit. The invention is suitable for various optical communication and sensing applications.

The application discloses a device with obstacle avoidance decision function, and belongs to the field of non-electric variable control or regulation system. The application is used to solve the technical problems of high power consumption, large delay and being easily disturbed by self motion and environmental light of the existing obstacle avoidance scheme. The application comprises a modulated light source, an event-based sensor and a processing unit. The modulated light source generates light at a specific frequency and forms a three-dimensional space. The event-based sensor senses the change of light intensity in the three-dimensional space and outputs an event stream. The processing unit is configured to trigger an obstacle avoidance decision process if an object contour is detected according to the event stream. The application can be used for real-time obstacle avoidance of mobile robots, unmanned aerial vehicles or intelligent vehicles, and has the characteristics of low power consumption, small delay, high robustness and low cost.

To provide a smart volume controller that achieves superior audio fidelity or power efficiency.SOLUTION: A controller configured to control the sound generation module includes a volume control configured to determine a demodulation amplitude and a modulation amplitude corresponding to a target volume. The sound generation module includes a drive circuit and an air pulse generation device. The drive circuit generates a demodulated drive signal according to the demodulated amplitude and generates a modulated drive signal according to the modulated amplitude to drive the air pulse generation device. The air pulse generation device generates sound by generating a plurality of air pulses at an ultrasonic pulse rate.SELECTED DRAWING: Figure 5

The invention discloses a magnetic resonance radio frequency magnetic field enhancement device of a high dielectric ceramic metal composite periodic array, which comprises a plurality of composite resonance units, the plurality of composite resonance units are arranged in an array according to a preset period, and each composite resonance unit comprises a first metal sheet, a second metal sheet and a dielectric ceramic layer, the first metal sheet and the second metal sheet are arranged at an interval along the thickness direction, and the dielectric ceramic layer is located between the first metal sheet and the second metal sheet to enable the first metal sheet and the second metal sheet to form capacitive coupling. The multiple composite resonance units are configured to be suitable for generating passive resonance at the Larmor frequency of the magnetic resonance system. According to the magnetic resonance radio frequency magnetic field enhancement device of the high dielectric ceramic metal composite periodic array, passive magnetic field enhancement can be achieved, and the magnetic resonance radio frequency magnetic field enhancement device has the advantages of being simple in structure, low in cost, good in compatibility, easy to adjust parameters, easy to machine, good in enhancement effect and the like.

The application discloses a low-stray ultra-fast frequency agile source, and relates to the technical field of radar communication.The frequency source aims to solve the technical problem that the frequency source in the prior art is difficult to simultaneously consider low-stray, fine step and ultra-fast frequency agile.The frequency source comprises a first frequency generating module, a second frequency generating module, a frequency step refinement module and a final mixing and filtering module; the frequency step of a coarse step intermediate frequency signal provided by the second frequency generating module is refined step by step by at least two levels of frequency division-mixing-filtering processing of the frequency step refinement module, so that a fine step final intermediate frequency signal is obtained; and the final intermediate frequency signal is mixed and filtered with a high frequency local oscillator signal provided by the first frequency generating module, so as to output a target frequency signal.The application completely avoids DDS, so that the excellent performances of low-stray, fine step and ultra-fast frequency agile are simultaneously realized.

The application discloses a kind of wideband high-speed digital frequency hopping system and method based on direct frequency generation.The system includes FPGA, digital-analog converter and clock chip, wherein the FPGA has differential high-speed serial interface, is configured as JESD204B high-speed interface;The digital-analog converter captures entire spectrum at a time, built-in DDC digital frequency conversion and FIR filter, support up to 6GHz radio frequency frequency direct generation;The clock chip generates two-way 256MHz differential LVDS clock, and the working clock of FPGA and digital-analog converter is all used 256MHz clock.The method includes baseband IQ signal generation, baseband IQ signal interpolation filtering, odd-even sequence splitting, odd-even sequence digital frequency conversion, odd-even sequence merging sending, digital up-conversion and radio frequency output these steps.The application has high reliability, low cost, small volume, low power consumption, and has excellent anti-interference performance.

A frequency shifting device based on the Doppler effect, a noise bypass frequency shifting device based on the receiver, a composite noise reduction device, and a method are disclosed. The frequency shifting device based on the Doppler effect includes: a rotor module (101) with a noise port, the noise port including a first noise port (10101) and a second noise port (10102). The first noise port (10101) is connected to the second noise port (10102) on the noise propagation path. The first noise port (10101) is used to connect to a sound source or output frequency-shifted noise. The second noise port (10102) follows the rotor module (101) in a periodic motion relative to a reference frame, causing a Doppler effect due to the relative motion between the second noise port (10102) and the noise source. This results in a frequency shift in the transmission or reception frequency relative to the reference frame. The frequency shift of the second noise port (10102) relative to the reference frame is controlled by changing the speed of the periodic motion. The reference frame includes an inertial reference frame and a non-inertial reference frame. This invention addresses the technical deficiency of existing general-purpose silencer technology, which suffers from the invariability of silencing characteristics due to limitations in material properties or structural design. It realizes a new type of silencer with variable silencing characteristics, namely, a frequency shifting device, silencing equipment, and method based on the Doppler effect.

The invention belongs to the technical field of terahertz, and particularly relates to a tunable terahertz generation method based on a physical driving generative adversarial network and a topological metasurface, and the method comprises the steps: constructing a heterogeneous integrated topological metasurface unit comprising thin-film lithium niobate, an arrayed nano antenna, tungsten disulfide and a graphene layer; a physical driving generative adversarial network is utilized, Maxwell equation set constraints are introduced into a loss function, and a topological structure sequence meeting wave vector matching conditions is reversely designed; infrared laser is adopted as a pumping source, a difference frequency generation effect is utilized to excite the metasurface, and a continuous domain bound state effect is combined to enhance the local field intensity, so that high-power and continuously adjustable-frequency terahertz waves are generated. The terahertz full-band high-efficiency conversion and ultra-fast dynamic tuning are realized, the output power and the light beam quality are remarkably improved, and the physical feasibility of a design result is ensured.

This invention discloses a pulsating pressure generation and excitation system and method for high-pressure liquid pipelines. It employs an internal flow channel fixed within a main body structure. The internal flow channel is a transverse through-hole structure with vertical through-holes, the axis of which is perpendicular to the axis of the transverse through-holes. A rotor is nested within the vertical through-holes of the internal flow channel. The main body has rotor holes coaxial with the vertical through-holes of the internal flow channel. The transverse through-holes of the internal flow channel serve as liquid flow channels. Multiple cutting blades are circumferentially spaced on the rotor. By controlling the number of speed changes, the amount of change, and the duration of the change, a continuous change in pulsating pressure from one frequency to another is achieved, thereby generating frequency-sweeping pulsating pressure changes. The excited pressure pulsation amplitude is high, and the frequency of the pressure pulsation can be easily adjusted to generate high-frequency pressure pulsations. This invention features a simple structure, smooth fluid channels, continuous flow, and low energy loss.