On-off System Research Articles

Photon statistics of single-mode zeros and ones from an erbium-doped fiber amplifier measured by means of homodyne tomography

We report measurement of the photon-number distributions of zeros and ones that emerge from an erbium-doped fiber amplifier (EDFA) in an on-off modulated communication system. Single-mode single-photon resolution was achieved by employing the method of optical homodyne tomography. The measured distributions agree with the quantum predictions of a Bose-Einstein distribution for the zeros and a Laguerre (noncentral negative binomial) distribution for the ones over a dynamic range up to 40 dB. The resulting noise figure of the amplifier compares well to that measured by an optical spectrum analyzer.

Error Rate Analysis of Optical Receivers with Fabry-Perot Optical Filter and Equalizing Postdetection Filtering

A complete analytic solution in form of the moment-generating function is presented for the statistical distribution of the decision variable of an on-off system with a Fabry-Perot optical filter. The results include ASE noise, photodetector shot noise and dark current together with thermal noise in the decision circuit. The influence of intersymbol interference is incorporated into the analysis and the optimal bandwidth of the optical filter is determined. It is shown that an equalizing electrical postdetection filter may make a significant improvement in performance. The analysis is extended to cover receivers with an arbitrary optical filter and arbitrary postdetection filtering by making use of a Gaussian approximation.

Regulation of the CYP1A1 promoter in transgenic mice: an exquisitely sensitive on-off system for cell specific gene regulation.

Mammalian cytochrome P-450s in the CYP1A gene family catalyse the oxidation of a wide range of drugs and foreign compounds resulting in their excretion. These enzymes are highly inducible by a range of compounds, including polycyclic aromatic hydrocarbons such as 3-methylcholanthrene (3-MC) and dioxins. Analysis of the CYP1A1 promoter has identified dioxin responsive enhancer elements which mediate the induction response. In order to evaluate this promoter as an in vivo regulatable expression system and to gain further insights into the tissue specific regulation of this gene, an 8.5 kb genomic fragment of the rat CYP1A1 promoter was cloned upstream of the lacZ reporter gene. This construct was used to generate transgenic mice and three independent lines were expanded for further study. The regulation of beta-galactosidase expression was determined in mock and 3-MC-treated mice in an extensive range of tissues. In untreated animals no transgene expression was detectable over non-transgenic controls. Treatment with 3-MC caused a profound increase in transgene expression (> 1,000-fold) in many tissues including liver, adrenal, kidney and intestine. Inducible transgene expression was also detectable in many of the other tissues including the spleen, lung, pancreas and the reproductive organs. Although the absolute levels of induction varied, no significant differences in the pattern of transgene expression were observed between the three different transgenic mouse lines. In addition, the pattern of transgene expression correlated closely with the reported regulation of CYP1A1 protein. These results indicate that the CYP1A1 promoter can drive expression of heterologous genes in a truly on/off manner in a variety of tissues and cell types which will allow the expression of other proteins to be controlled in vivo. This reporter system also provides a model for establishing the environmental and hormonal factors regulating the expression of the CYP1A1 gene.

Simulation in transient regime of a heat pump with closed-loop and on-off control

The present work introduces a mathematical model for a heat pump with a variable-speed compressor, driven by a d.c. servomotor, operating either in closed loop by a power law control action or by the traditional on-off basis. The resulting differential and algebraic equations are integrated in time for a specified period of simulation in both designs. The results show that the closed-loop system presents significant savings in energy consumption when compared with the on-off system, under the same environmental conditions.

How many ganglion cells are there to a foveal cone?

Published studies on humans and monkeys show discrepancies in the reported quantitative relationship between cones (C) and ganglion cells (G). Data on human foveal retina suggest that it cannot accommodate the midget on-off system in addition to other functional channels. Foveal cell densities along the vertical meridian (0-1.8 mm eccentricity) were estimated in one normal human retina using the disector method. Cell ratios were calculated from cumulative total numbers. G density peaked at 0.65 mm eccentricity and C density at the foveola. Cumulative cell numbers showed a more rapid increase in G than in C with increasing eccentricity. G/C ratios of 2.7-3.4 were found using lateral displacement data modified from macaque. Using one estimate of displacement from the sections, the G/C ratio was 3.0. This study shows that there are on average three ganglion cells per foveal cone in humans, as in monkeys.

Precision universal temperature ( −200°C to +200°C) controller with fast solid state on-off system

A simple, rugged, reliable, low cost temperature display-cum-controller has been designed and constructed using standard integrated circuits and a 3½ digit LED display. The controller, utilising semiconductor controlled rectifiers as fast solid state on–off switches capable of maintaining the set temperature constant within the temperature range -200°C to + 200°C with a resolution of ±0·05°C. A thermocouple (specifically, a copper-constantan type) sensor has been used because of its fast response time and tolerance of high magnetic fields.

SIMULATION OF A RICE DRYING SYSTEM

ABSTRACT A simulation model using SLAM II/PC was successfully developed and validated for an on-farm bin rice drying system. The effects of gas-modulating control as compared to a conventional on-off gas flow control, and air recirculation on the energy consumption, drying time, and drying cost were analyzed. Simulation results of the total rice drying energy in August for both types of controls were within one percent of the average from field tests. The simulated gas-modulating control system saved 25% of the total rice drying energy over the conventional on-off system in August, as compared to about 30% in field tests (Verma and Jacobsen, 1987). Air recirculation was not beneficial without dehumidification during summer in southwest Louisiana.

Characteristic patterns of feeding, drinking and motor activity under artificial twilight conditions in rats

Under natural circumstances,twilight is known to play an important role in behavioral and metabolic changes in mammals. Since experimental rooms are usually illuminated by on-off lighting system, an artificial twilight system was devised and its effect on feeding, drinking and motor activity was compared with those in on-off system. Following 10 days of on-off lighting (a 12:12 light-dark cycle), a twilight regimen was introduced. Illuminant intensity increased from 0 to 90 lumen during a 2 hr period of dawn and decreased reversely during same hour period of dusk. Three different types of twilight conditions were tested, i.e., (1) dawn: 0800-1000 hr and dusk: 1800-2000 hr, (2) dawn: 0600-0800 hr and dusk: 2000-2200 hr, (3) dawn: 0600-0800 hr and dusk: 1800-2000 hr. Total amount of 24-hr consumptions or activity was not influenced following the twilight conditions. Immediately after a period of dawn started, rats decreased food and water intake subsequent to their increase during the later periods of dark. During a dusk period, food and water intake increased markedly during twilight conditions in type 3. In type 1, however, such facilitated effects were not found.

A One-bit Memory Receiver for Channels with Memory

A receiver is investigated with one-bit memory for communication channels with memory. The memory of the channel is characterized by the statistical correlation of the received bits due to fading. An optimal solution to the problem is considered but is found to be quite complex to implement. Therefore, a suboptimal receiver having a decision-feedback structure is examined. The performance of the receiver is shown to be better than a receiver without memory. Binary on-off keying system is considered as an example and numerical results are obtained.

Comfort Control for Central Electric Heating Systems

Central electric heating systems typically consist of a number of low-mass heating elements. Due to this low mass, fast rates of temperature rise and fall will occur in the furnace. The end result can be large and uncomfortable temperature swings in the living space. In order to provide good comfort, the control system used must take into account the characteristics of an electric furnace. An analog computer study was conducted to determine the best method of controlling an electric central heating system. The analog computer optimized the thermostat design parameters to provide the required end result of homeowner comfort and long heat equipment life. Since mechanical thermostats have practical limitations on minimum switching differentials and only solid-state electronics could overcome this difficulty, the computer optimized controller was built using integrated circuit electronics. A field test compared the performance of a conventional ON-OFF mechanical thermostat system with the new solid-state controller. The conventional system produced excessive room temperature swings of 3°F, while the new controller produced small swings of less than 1°F.

Comparative Performance of Twin-Channel and Single-Channel Optical-Frequency Receivers

This paper describes a theoretical comparison of the noise immunity of direct-detection binary single-channel with direct-detection binary twin-channel optical digital communication systems. The conclusion is that a simple ON-OFF single-channel system is usually superior to twin-channel systems (such as polarization modulation and differentially coherent phase-shift systems) in noise immunity as well as simplicity. This result is quite different from the radio frequency case where twin-channel systems exhibit up to 6-dB advantage relative to single-channel systems.

A general approach for on-off control systems oscillations

A rigorous approach is presented for determining the forced or free oscillations of an on-off system whose linear part is of arbitrary order and whose non-linear part may have a dead zone, hysteresis and dissymetry. A graphical representation yields the solution as the intersections of a circle and a locus Г consisting of two portions which depend respectively on the characteristics of the non-linear component and on the transfer function of the linear part. Examples illustrate the procedure and show the influence of system parameters.

Performance of a Multiple Address RADA System

Potentialities and limitations are derived for a random access, discrete address (RADA) communication system in which addresses consist of time-frequency coded pulses and in which a higher order alphabet is realized by assigning many different addresses per person. The performance of such a multiple address RADA system is derived as a function of two parameters: the channel utilization and the size of the time-frequency matrix. The channel utilization is the ratio of the total information rate to the channel bandwidth. The size of the time-frequency matrix, in which addresses are formed, is a measure of the receiver complexity. If there is no limitation on matrix size, arbitrarily low probabilities of error can be obtained for any value of channel utilization below 70 percent by increasing the number of addresses per person. If both matrix size and channel utilization are fixed, a minimum error probability is achieved with an optimum number of addresses per person. The performance of a multiple address RADA system is shown to be generally superior to that of a single address ON-OFF RADA system.

Forced Oscillations and Convex Superposition in Piecewise-Linear Systems

Abstract : Several aspects of the theory of forced oscillations of piecewise-linear systems are considered. The general problem of determining such periodic solutions is formulated and the principal methods of solving the problem are described briefly. By way of illustration, forced periodic solutions of the simplest kind are determined for a second-order on-off system subject to a sinusoidal external force. Piecewise-linear systems are shown to possess a property of convex superposition with respect toANY SET OF RESPONSES (to different excitations) which are synchronous, i.e., are in phase as they switch from one linear branch of the piecewiselinear function to another. Finally, for sets of periodic responses which are almost synchronous, a conjecture is offered concerning approximate superposition; in this connection the example involving the second-order system is reconsidered. (Author)

光波干渉式の刻線機に用いる波長自動調節について

Presented in this paper is an automatic wavelength control used in the interferometric ruling machine for standard line scale. The machine has a fringe counting interferometer to control the positions to be ruled using the wavelength of Kr86 0.565μm line. The machine also has a Fizeau interferometer to control the wavelength used in the position-controlling interferometer in order to obtain an integral counting number of fringes for the scale line intervals of 1mm and to remove the errors caused by variation of the refractive index of surrounding air and thermal expansion of scale blanks. The Fizeau interferometer is set in a closed vessel and the interference fringes of five visible lines of Hg198 lamp are detected by photoeletric elements. The conditions are calculated for obtaining the maximum fringe signals from the Fizeau interferometer. The optimum values for the reflactance of the mirrors and the distance between them are found to be 50-60% and 67-80mm respectively. The air pressure in the vessel is controlled by the on-off system operated by the fringe signals of the Fizeau interferometer. The accuracy of the wavelength controlled by this method is found to be ±2×10-7. This accuracy can be kept even in long run test.

Predictive control of an on-off system with two control variables

This paper studies the optimum control of multi-variable systems by considering the behaviour of the two-variable on-off system described by the equation x ¨ + A x ˙ = u where u 1 , u 2 = ± 1. By the application of Pontryagin's maximum principle, it is shown how the number of switchings and the drive ratio u 1 /u 2 , for an optimum trajectory (minimum settling time criterion), depend on the nature of the matrix A. For the case when the interaction terms a 12 and a 21 have the same sign, the maximum number of switchings for an optimum trajectory is three, and the drive ratio u 1 /u 2 near the origin of the error phase space has the same sign as a 12 and a 21 . A predictive controller described in this paper finds the three switching times by an iterative process which involves the application of logical rules to the predicted behaviour of the system, computed in a fast analogue model. This realizable controller is optimum when the two-by-two matrix A has a 12 a 21 ≥ 0; and will also control systems where a 12 a 21 < 0, although not optimally. It is also shown that the problem of hunting may be overcome by confining the hunting to the fast model alone.

Null-zone envelope detection in binary systems

The effects of applying the null-zone decision mechanism to two types of envelope-detection systems are investigated, and comparisons are made with previous results for synchronous-detection systems. It is demonstrated conclusively that, just as for the synchronous system, null-zone reception offers a means of improving the information rate of a unidirectional system. Moreover, the relative behavior is about the same in all three cases, except that the asymmetry of the on-off system may present some additional difficulties.

CAS System and Some of Its Dynamic Characteristics

The Continuous Automated Spinning System developed by the Toyo Spinning Co., Ltd. is briefly described and some of its dynamic characteristics are discussed in this article. Each card is equipped with a reserve box which receives cotton in loose form and supplies it to the card without forming laps. Cards produce sufficiently uniform slivers without the aid of separate metering device, such as the piano motion. A uniform distribution of cotton to reserve boxes is insured by a simple on-off cotrol system on the unit hoppers and the branch coveyors. Super Auto Drawer (SAD) contains an automatic sliver-evening device which is essentially an open-loop control system. To get the best evening action, the proportional gain Kƒ and the memory time are set to the value given by the equations below. Kƒ=1 γ=(Memory time)-(Transportation time within the SAD)/(Servo time constant)=-0.6 Since the Sliver Reversing Drawer (SRD) cuts incoming slivers at constant intervals, SRD slivers contain stepwise changes in their weight, but such changes are perfectly smoothed out by the sliver-evening device in the SAD. The sliver-to-yarn Ultra High Draft (UHD) Ring Frame converts SAD slivers directly into yarns at a draft ratio of 360.

An Analytic Frequency-Response Solution for a Higher Order Servomechanism With a Nonlinear Control Element

On-off-type control systems designed on the basis of step-input response sometimes exhibit poor frequency-response characteristics. When subjected to periodic inputs, such systems may oscillate at subharmonics of the input frequencies under certain conditions. An example of subharmonic response of an on-off-type system is shown in Fig. 1(a). Fig. 1(b) shows the corresponding fundamental response. When an on-off system is designed with a proportional band, the frequency response of the system must be carefully investigated for the possibility of “jump resonance” and subharmonic oscillations. This is particularly necessary when the system is known to be subjected to occasional periodic inputs. This paper presents an effective method for evaluating the frequency response, both open-loop and closed-loop, for on-off-type feedback control systems with or without proportional bands. Fig. 2 shows one type of the system under discussion. The essential material presented follows the Laplace-transform method suggested by D. Kahn [1]. It is an extension of the work already reported by K. Ogata [2, 3].