Conventional Chopper Research Articles

Comparison of patient experiences and clinical outcomes between an illuminated chopper and a conventional chopper under a surgical microscope.

To compare patient experiences and cooperation and the clinical outcomes illuminated chopper vs conventional chopper during cataract surgery. 4 tertiary institutions in Korea. Prospective, randomized, paired-eye, controlled pilot study. 152 eyes of 76 patients who underwent bilateral cataract surgeries were enrolled in this study. The surgical method was randomly assigned to each patient's eye (1 eye using the illuminated chopper with a light source and the other using the conventional chopper under the microscope light). Patient suffering scores (the degree of strong light perception, glare, inability to fixate, anxiety, discomfort, and fear) from 0 to 10 (10 being the most severe level); cooperation score from 0 to 3 (3 being the best cooperation); operating time; and corneal endothelial cell density (ECD) preoperatively and postoperatively were compared between the 2 groups. The mean patient suffering score of all 6 parameters in the iChopper group was significantly smaller than those in the control group (all P < .05). The mean patient cooperation score of the iChopper group (2.3 ± 0.8) was significantly greater than that of the control (1.6 ± 0.9; P < .001). There was no significant difference in the mean operating time and corneal ECD at each visit between the groups, albeit the mean corneal ECD was significantly decreased from baseline to 1 month after cataract surgery in both groups. Phacoemulsification using the illuminated chopper provides less glare and anxiety and better cooperation during cataract surgery without increasing the operating time and damaging corneal endothelium compared with the conventional chopper.

A Discrete-Time MOS Parametric Amplifier-Based Chopped Signal Demodulator

This article presents a discrete-time parametric amplifier (DTPA) as the signal demodulator for chopper amplifier. Unlike the conventional chopper, the DTPA demodulator features noise-efficient gain augmentation while demodulating the chopped signal. The demodulator also enables low-frequency noise cancellation during the inherent track-and-hold (T/H) process of the charge parametrization. The positive feedback loop and the dc servo loop are implemented for applications requiring larger input impedance and dc input offset cancellation using a bandpass transfer function. Design considerations for the DTPA-based demodulator circuit and the merits and demerits of the chopper-DTPA amplifier are discussed as well. The proposed design has been fabricated in a standard 180-nm CMOS technology node. The complete design occupies 0.127 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of the die area and consumes 2.4-μW power from a 1.5 V of VDD. The measurement results show that the DTPA demodulator provides 8-dB gain enhancement while improving on the prior art of T/Hbased demodulator and the amplifier achieves input referred noise voltage of 2 μV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> in 143-Hz bandwidth.

Chopper-Stabilized Low-Noise Multipath Operational Amplifier With Dual Ripple Rejection Loops

This brief presents a chopper-stabilized low-noise multipath operational amplifier with dual ripple rejection loops. The multipath amplifier scheme has a lower noise and a wider bandwidth than the conventional chopper amplifiers. The dual ripple rejection loops are proposed to effectively attenuate the offset and low-frequency noise components. The dual ripple rejection loops are implemented using a feedback low-pass filter (LPF) for AC coupling and a floating high-pass filter (HPF) for additional low-frequency rejection with a fast common mode response. The amplifier is fabricated using a 0.18- ${\mu }\text{m}$ CMOS process with an active area of 4.92 mm2. The input referred noise level is 6.62 nV/ $\surd $ Hz, and the total current consumption is 117.2 ${\mu }\text{A}$ with a 1.8 V power supply.

Chopper Sugarcane Combine Harvester with Middle-Mounted Primary Extractor

Conventional chopper sugarcane combine harvesters had numerous drawbacks, including high center of gravity, easy clogging, and high trash rate. In order to resolve these problems, a chopper sugarcane combine harvester with shorter roller train and primary extractor installed in the middle was designed in the present study. The proposed harvester was equipped with the roller train and billet transporters. Moreover, the structure of the primary extractor was improved, and its position was selected to address the issues of chopper harvesters. Performing the field experiment shows that the average traveling speed of the proposed machine was 2 km/h, while the average feed capacity was 5.5 kg/s. Furthermore, it was found that the qualified rate of the cutting height, rate of the broken perennial ratoon, total loss, trash rate, and the qualified rate of cane billets were 90.1%, 9.6%, 3.1%, 4.4%, and 92.1%, respectively. Field experiment showed that the proposed machine harvested 2 × 104 kg of sugarcane per hour, where the average harvesting cost was about 45 RMB per 1000 kg of the cane. It was found that the operating efficiency was approximately 200 times higher than that of the manual harvesting, while the corresponding costs were reduced by 55%–70%. Moreover, it was concluded that the proposed machine was superior over AS60 and 4GZQ-260 in terms of the harvesting performance and almost reached the level of them in regard to the economic performance.

Research on Simulation of Electronic-Protection Circuit of Chopper Cascade Speed Control System

Firstly, according to the topology of conventional chopper cascade speed system to analyze the transient process of main loop during of contactor operation when device failure. Because the contactor action requires a longer time, Equipment is vulnerable to the impact of high voltage, high current during the contactor action, and cause damage to power electronic devices. For contactors drawbacks, the main circuit topology with electronic-protection circuit is designed. Then analyze transient process of chopper cascade speed control system with electronic-protection circuit under high-voltage power failure conditions. Finally, simulation model of chopper cascade speed control system with electronic-protection circuit is built respectively in Matlab. Simulation results show that electronic-protection circuits effectively solve the problem of high-voltage power failure under active inverter structure and inverter subversion.

Electric Energy Exchange and Applications of Superconducting Magnet in an SMES Device

A unified energy exchange system with an equivalent dc circuit topology is presented for superconducting magnetic energy storage (SMES) study. The principle and experimental prototype design have been carried out to study the dynamic energy exchange characteristics of SMES for both voltage sag and swell compensations, with a new bridge-type I/V chopper and relevant digital control method introduced and compared with the conventional chopper. The bridge-type I/V chopper has been demonstrated to be more suitable for low-voltage power applications because of its high energy storage and exchange efficiencies. The integrated SMES application solutions and characteristics in the modern power systems have also been discussed using two sample cases of daily load leveling and voltage fluctuation compensation presented.

Feasibility demonstration of a new Fermi chopper with supermirror-coated slit package

Abstract The efficiency of inelastic neutron scattering measurements using a chopper spectrometer can be markedly improved by utilizing multiple incident energies (Multi- E i method). However, in conventional chopper systems, optimization of the experimental condition for all incident energies is absolutely impossible. We developed a new Fermi chopper with a supermirror-coated slit package in order to overcome the problem and experimentally demonstrated that the full optimization of the experimental condition for multiple incident energies is nearly achieved.

Enhances in Crude Protein and Effects on Fermentation Profile of Corn and Forage Sorghum Silage with Addition of Cowpea

Abstract This study was conducted to assess nutritive value of corn ( Zea mays L.) and forage sorghum [ Sorghum bicolor (L.) Moench] silage when ensiled with different proportions of cowpea [ Vigna unguiculata (L.) Walp.]. Corn and forage sorghum were harvested at the ½ milk line and late dough stages of kernel maturity, respectively, and cowpea was harvested at a vegetative stage in two consecutive years at New Mexico State University (NMSU), Agricultural Science Center at Clovis. All three crops were chopped using a conventional chopper. The main crops, corn and forage sorghum, were mixed with cowpea at main crop:cowpea ratios of 100:0, 75:25, 50:50, 25:75, and 0:100%. For each mixture, 1.1 lb of fresh material was vacuum sealed in a plastic bag and fermented for an average of 127 days, four bags per mixture. In both crops, crude protein (CP) increased as proportion of cowpea increased in the mixture. In addition, pH, lactic acid, and total acids increased in both crops when cowpea was added. Silage with 100% cowpea had the highest pH and lowest lactic acid concentration. It is concluded that mixing cowpea with corn and forage sorghum for silage increased CP concentration of the mixture. Additional research is needed to assess mixtures that produce silage with more desirable fermentation characteristics.

AMATERAS: A Cold-Neutron Disk Chopper Spectrometer

AMATERAS is a new disk-chopper-type spectrometer installed at Materials and Life Science Experimental Facility (MLF) of J-PARC. AMATERAS is equipped with an extra chopper for pulse shaping at the upstream position, in addition to a monochromating chopper, which conventional chopper spectrometers at pulsed source have. Owing to the use of these choppers and the high peak intensity from a coupled moderator source at MLF, the AMATERAS design realizes high-intensity and high-energy-resolution measurements in quasielastic and inelastic neutron scattering experiments. The spectrometer had the first neutron beam in May 2009. During the course of commissioning, the performance of the spectrometer was confirmed by conducting test experiments. AMATERAS is now open to users and is producing scientific outputs.

Advanced MMIC Receiver for 94-GHz Band Passive Millimeter-Wave Imager

In this paper, we present the development of an advanced MMIC receiver for a 94-GHz band passive millimeter-wave (PMMW) imager. Our configuration is based on a Dicke receiver in order to reduce fluctuations in the detected voltage. By introducing an electronic switch in the MMIC, we achieved a high resolution millimeter-wave image in a shorter image collection time compared to that with a conventional mechanical chopper. We also developed an imaging array using MMIC receivers.

Conceptual Design Of Magic Chopper Used For 4SEASONS at J-PARC

4SEASONS is designed to utilize the multiple incident energies (MIE) selected by a special Fermi chopper and enhance the measurement efficiency. Chopper opening time determined by a conventional Fermi chopper is inevitably constant, and thus we cannot realize the optimal experimental condition for each incident energy. Therefore, a new concept of Fermi chopper is required for the success of MIE measurement at 4SEASONS. In this paper, we present a new concept of supermirror-coated Fermi chopper (MAGIC chopper) specialized for MIE measurement at 4SEASONS. MAGIC chopper increases the effective opening time at lower incident energies, and consequently the energy dependence of effective opening time gets close to that of moderator pulse width. In addition to the matching of experimental condition, MAGIC chopper also realizes almost constant energy resolution in the wide range of incident energy.

Cancellation of Amplifier Offset and &lt;formula formulatype="inline"&gt; &lt;tex&gt;$1/{f}$&lt;/tex&gt;&lt;/formula&gt; Noise: An Improved Chopper Stabilized Technique

In this brief, a theoretical analysis on the limits of conventional chopper stabilization technique is presented and a solution conceived to improve the amplifier performance is proposed. The expected replicas of the 1/f noise at the chopping frequency and its multiples are attenuated by a modified chopping control. Simulations done by using records of real 1/f noise outputs showed that, by following the proposed approach, the spectrum of the signal is not affected while the 1/f replicas are reduced by more than 40 dB with respect to conventional techniques. The required circuit for the generation of the chopping signal is also described. The resulting overhead with respect to conventional techniques is negligible and fully acceptable.

Spectroscopic investigations of photoinduced changes of the spatial distribution of charge carriers in modulation-doped quantum-well structures.

We investigated the photoinduced changes of the spatial distribution of the free holes in p-type modulation-doped GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterostructures by measuring the energy of the quantum-well luminescence, which is conditioned by the many-particle effect of band-gap renormalization and the excitonic interactions between the electrons and holes. A conventional chopper technique with millisecond time resolution permitted us to study the dynamics of the hole density variations in the quantum wells. The strength of excitonic effects on the luminescence signals could be estimated by application of a magnetic field oriented parallel to the growth direction of the samples. \textcopyright{} 1996 The American Physical Society.

Design and Performance of a Hadamard Transform Infrared Spectrometer with No Moving Parts

The development of an improved Hadamard transform infrared HT-IR) spectrometer with no moving optical parts is described. This spectrometer is based on a thermo-optic array for the stationary encoding of radiation (TOASTER) fabricated from Nichrome resistance wire. The TOASTER HT-IR instrument utilizes a reversed Czerny-Turner optical mount and relies on entrance focal plane modulation for operation. This design allows the dedispersion optics to be eliminated while still providing for a multiplex advantage. In addition, a conventional mechanical chopper is not needed in this instrument because the TOASTER is used as a natural modulator. The TOASTER HT-IR spectrometer can acquire an infrared spectrum in the range of 2.5 to 11 μm (4000 to 910 cm−1). Its spectral resolution is 0.07 μm (∼7 cm−1 at 1000 cm−1), and, for fifteen spectral resolution elements, the observation window is 0.5 μm (∼48 cm−1 at 1000 cm−1). In addition to the design of the instrument, this communication also examines the thermo-optic switching properties of the Nichrome wire used in the prototype TOASTER. Although the maximum switching speed of the Nichrome wire is governed by its thermal decay time, we show that the TOASTER can be operated faster than this limit by employing a preheating step.

A fast response, open path, infrared hygrometer, using a semiconductor source

Investigations were carried out as to the feasibility of using a semiconductor source in the design of a new rapid response, open-path hygrometer. A single-beam instrument was constructed employing an infrared light emitting diode (LED) as a source instead of the usual high energy, wideband filament. The spectral emission envelope encompassed the 1.87 μm water absorption band. Electronic modulation and thermoelectrical cooling of the diode eliminated the conventional chopper wheel and stabilized the peak wavelength emission. Path length was 200 mm. Over a water vapour concentration range of 0–16 g m−3, absorption varied by 2% in a linear fashion. At 10 Hz, the noise level was 0.1 g m−3 rms. Hygrometer resolution and stability are constrained by the detector noise level, the small source emission in the absorption band and low frequency drift in the optical filter. Despite these problems, the new instrument showed comparable performance characteristics to a commercial Lyman-α hygrometer. Latent heat fluxes measured with both instruments and a Kaijo-Denki, 3-D sonic anemometer agreed to within 4% over a range 0–350 W m−2. Further improvements in performance can be anticipated with advances in detector and LED technology.

An Ultra-Low Drift Amplifier Using a New Type of Series-Shunt MOSFET Chopper

A chopper amplifier of a new type is proposed for the amplification of nanovolt-order dc voltage. The chopper is built by connecting a shunt switch, which is driven at twice the chopper frequency, to the output terminals of a conventional and balanced-type series-shunt MOSFET chopper. The present chopper is free from offset voltage arising from spike voltages and has an input voltage offset temperature coefficient of less than 0.1 nV/°C for a signal source of less than 1 k?, and a long-term drift of 2 nV/18 h for signal source resistance of 6.1 ?.

Design and performance of a wide band chopper for neutron small angle scattering

Characterization of a wide band neutron chopper, which can provide a wide range of wavelengths of slow neutrons in a pulse, was performed by computer calculations to obtain the optimum value of the coefficient of neutron utilization. This was done after detailed examinations of neutron burst shapes and transmission probabilities for various shapes of slits of the rotor with the shapes of the slits determined in accordance with the neutron trajectories in the rotating rotor. In the calculations, the divergence angles of incident neutrons are fully taken into account. A wide band chopper designed on the basis of the characterization to provide polychromatic pulsed neutrons in the range of 2–10 A for neutron small angle scattering (NSAS) has been installed at Kyoto University Research Reactor. The manufacture of the rotor and the experimental tests for the rotor have satisfactorily been performed. As an application of the chopper to NSAS, precipitation phenomena in the Ti-Nb alloy aged at 643 K were successfully examined as a function of aging time by means of the time-of-flight technique. In the NSAS, scattering patterns were simultaneously provided for a wide range of the scattering vector. It has been demonstrated that the coefficient of neutron utilization by the present chopper is improved by about 57 times at λ = 2 A ̊ and 12 times at 5 Å, respectively, in comparison with the coefficient for a conventional chopper.

Accuracy of measurements of a neutron spectrum by means of a conventional and a correlation chopper

The accuracy of measurements performed by use of the correlation or the conventional chopper is considered. The new decoding method based on a calculated decoding sequence is used. In the calculations statistical and Monte-Carlo methods are employed. The influence of the background on the accuracy of the measurements is shown on graphs.

A new high performance computer d-c amplifier

A new computer d-c amplifier designed for very fast as well as for real-time analog/hybrid computation combines large bandwidth (30 MHz gain-bandwidth product) and high mid-band gain (68 dB at 10 KHz) with full ± 10V, 30mA output to 5.0 MHz, and low open-loop output im pedance (50 ohms at 10 KHz). High d-c gain (120 dB) and exceptionally low drift (50 pA/°C, 2.5 μV/°C ) is obtained with the aid of an inexpensive hot-substrate integrated- circuit preamplifier rather than with conventional chopper stabilization. A three-channel feedforward design employs an overcurrent-protected 30 mA class AB wideband output stage in the high-frequency channel, a feedback-equalized integrated-circuit operational amplifier as the intermedi ate-frequency channel, and the hot-substrate integrated differential amplifier stage as the low-frequency channel. Overcurrent protection makes the new amplifier short- circuit proof. Table 1 shows the performance of the new d-c amplifier.

A comparison of two detecting methods for time-of-flight measurements of thermal neutron spectra

Neutron spectra from the graphite reflector in the Norwegian reactor JEEP 1 have been measured by means of the conventional chopper technique. A comparison is made between the spectra obtained with a boron polyester scintillator respective a BF 3 detector placed at the end of the neutron flight path. Both detecting methods supplement each other at least for a straight slit chopper, as for a gamma sensitive detector the zero point of the time-of-flight scale automatically is given by the chopped gamma beam “peak”.