Ideal Compression Research Articles

The application of m-sequences to bi-static active sonar

The m-sequences are ideal pulse compression signals that combine the energy of CW with the resolution of a pulse. Successful applications include numerous acoustic propagation experiments and the Global Positioning System. Yet, early attempts (circa 1960) to apply m-sequences to mono-static active sonar were unsuccessful. Through the years, Birdsall, Metzger and others have developed a body of theory, numerical methods and at-sea demonstrations that establish the feasibility of a novel bi-static approach—one that holds promise in high reverberation shallow water environs. An analysis is presented here. The approach includes (1) continuous transmission of long m-sequences; (2) synchronous sampling to form a CON (Complete Ortho-Normal) data set; (3) direct blast removal by HCCO (Hyperspace Cancellation by Coordinate Zeroing); and (4) a full range waveform Doppler search. Ultra-fast Hadamard Transforms speed up the direct waveform pulse m-sequence pulse compression and the inverse pulse waveform transform and thereby allow timely execution of the intensive computational burden. The result is a demonstrable approach that produces a gain of 30 dB over a simple pulse and 10 dB over other sonar signals. In the end, the approach requires continuous transmission and reception as opposed to ping and listen an awkward concept at first.

중간 냉각기가 있는 고압 다단 왕복동식 압축기에 관한 열역학적 해석

Simplified thermodynamic analysis of high pressure 4-stage reciprocating compressors with 4 inter-coolers has been investigated to predict a behavior of a compressor system for NGV(natural gas vehicles). A computer program has been developed to predict and estimate the performance of high pressure 4-stage reciprocating compressor system. Thermodynamic properties of compressed natural gas(CNG) were calculated by ideal gas theory and compression cycle was assumed as reversible adiabatic compression and expansion processes, and isobaric intake and discharge processes. Comparison between results predicted by calculation model and measured by experimental tests is presented.

The effect of hydrogen enrichment on exhaust emissions and thermal efficiency in a LPG fuelled engine

The concept of hydrogen enriched LPG fuelled engine can be essentially characterized as low emissions and reduction of backfire for hydrogen engine. The purpose of study is obtaining low-emission and high-efficiency in LPG engine with hydrogen enrichment. In order to determine the ideal compression ratio, a variable compression ratio single cylinder engine was developed. The objective of this paper is to clarify the effects of hydrogen enriched LPG fuelled engine on exhaust emission, thermal efficiency and performance. The compression ratio of 8 was selected to minimize abnormal combustion. To maintain equal heating value, the amount of LPG was decreased, and hydrogen was gradually added. In a similar manner, the relative air-fuel ratio was increased from 0.8 to 1.3 in increment of 0.1, and the ignition timing was controlled to be at MBT each case.

Thermodynamic Analyses of Wet Compression Process in the Compressor of Gas Turbine

Thermodynamic model of wet compression process is established in this paper. The topics of ideal wet compression process, actual wet compression process, water droplet evaporative rate, wet compression work, inlet evaporative cooling, concept of wet compression efficiency, aerodynamic breaking of water droplets etc. are investigated and discussed in this paper.

Analysis of the gas compressibility effects on the constant-entropy reversible processes of refrigerants and refrigerant mixtures

Thermally and calorically real gas modelling based on the Martin–Hou equation of state is assumed for pure and mixed refrigerants in the superheated vapour phase. It allows the constant-entropy reversible processes which take place within the work transfer components of ideal vapour compression cycles to be properly analysed. These processes, in fact, occur in a region of the Mollier diagram close to the saturated vapour curve where covolume and molecular forces alter the equation of state of an ideal gas. Thus, real gas effects are significant and cannot be ignored. They give a more accurate indication of the refrigerant end temperature associated with an isentropic compression as well as of the corresponding work exchanged and volumetric efficiency. In particular, it is shown that the gas compressibility effects play a ‘ favourable’ role during the isentropic compression processes since they allow the work transferred to be reduced up to 10% for HFC-refrigerant 134a, and HFC-refrigerant mixtures 407C and 410A. But, at the same time, they play an ‘ unfavourable’ role since they can reduce the compressor volumetric efficiency (i.e. refrigerant mass flow rate) and, consequently, the cooling (or heating) capacity of the vapour compression system up to 7%.

A generalized analysis for cascading single fluid vapor compression refrigeration cycles using an entropy generation minimization method

This paper focuses on cascading an ideal vapor compression cycle and determining the optimal intermediate temperatures based on the entropy generation minimization method. Only superheating and throttle losses of the cycle are considered since they are inherent to the ideal vapor compression refrigeration cycle. The second law equations have been developed in terms of specific heats and temperature ratios with the intent of reducing involved property modeling. Also the entropy generation was expressed in terms of a single independent variable and minimized to develop an advanced rule for selecting optimum intermediate temperatures. Results for a cascade system operating between reduced temperatures of 0.684 and 0.981 with R-134a as the working fluid are presented. The approximate method presented here predicted the optimum intermediate reduced temperature for a two-stage system to be 0.88, a difference of 2% from the optimum. The method presented was a much better predictor of the optimum temperature than the geometric mean method which was 0.82, a difference of 5% from the optimum. The entropy generation distribution of the optimum solution was investigated. For a two-stage system, the lower stage and higher stage entropy generation was 44% and 56%, respectively. In comparison to the single stage, the two-stage reduced losses by 78%.

An analysis of the efficacy of bag-valve-mask ventilation and chest compression during different compression–ventilation ratios in manikin-simulated paediatric resuscitation

The ideal chest compression and ventilation ratio for children during performance of cardiopulmonary resuscitation (CPR) has not been determined. The efficacy of chest compression and ventilation during compression–ventilation ratios of 5:1, 10:2 and 15:2 was examined. Eighteen nurses, working in pairs, were instructed to provide chest compression and bag-valve-mask ventilation for 1 min with each ratio in random on a child-sized manikin. The subjects had been previously taught paediatric CPR within the last 3 or 5 months. The efficacy of ventilation was assessed by measurement of the expired tidal volume and the number of breaths provided. The rate of chest compression was guided by a metronome set at 100/min. The efficacy of chest compressions was assessed by measurement of the rate and depth of compression. There was no significant difference in the mean tidal volume or the percentage of effective chest compressions delivered for each compression–ventilation ratio. The number of breaths delivered was greatest with the ratio of 5:1. The percentage of effective chest compressions was equal with all three methods but the number of effective chest compressions was greatest with a ratio of 5:1. This study supports the use of a compression–ventilation ratio of 5:1 during two-rescuer paediatric cardiopulmonary resuscitation.

VLSI design for high-speed LZ-based data compression

A simple real-time parallel architecture for CMOS VLSI implementation of a Ziv–Lempel data compression system is presented. This encoding system employs a linear systolic array to find concurrently the matches between each input data character and its corresponding dictionary, and can easily achieve ideal compression ratio by cascading the chips of the encoding cell. A new encoding architecture is proposed to improve the encoding speed and reduce hardware complexity for the encoding cells. In addition, the number of memory accesses is reduced to save power consumption for high-speed applications. The encoder codes one character (more than eight bits) per encoding cycle. The clock rate by Verilog simulator can be constrained below 15 ns using the Compass standard cell library for the 0.6 µm CMOS process.

Realization of dynamic range controllers on a digital signal processor for audio systems.

This paper describes a new design method of dynamic range controllers, such as compressor, limiter, expander and noise gate, on a DSP for digital audio systems. For the compressor, we have previously proposed an efficient implementing method on DSP by calculating the polynomial expression to approximate the power transformation. Based on the approximation algorithm, we extend the positive compression ratio to the negative compression ratio for the compressor. Then, we design an expander based on the facts that the ideal compression characteristic could be obtained by application of a polynomial expression. By defining an expansion (downward expansion) characteristic with two threshold levels, the gain for getting the expansion may be decomposed into a gain of an upward expansion with an integer expansion ratio, a gain of a compression and gain shift. By this method, the ideal input-output characteristic can be achieved by using seven-order polynomial expression for dynamic range control of 50dB. The digital signal processing on DSP is about 130 steps for the compressor, and 120 steps for the expander with a given expansion ratio equal to or smaller than 15.

Effects of longitudinal beam compression in a free-electron laser.

When the scaled growth rate of a free-electron laser (FEL) is plotted as a function of the scaled thermal velocity for the case of ideal beam compression, we find two distinct cases. If the FEL is in the energy-spread-dominated regime, the growth rate can be improved as a result of compression provided the scaled thermal velocity is less than unity. Surprisingly, we find that the growth rate is always improved if the FEL is in the emittance-dominated regime.

Packetized Video--Options for Interaction between the User, the Network and the Codec

In this paper we analyse the requirements that the user and a pocket network have of compressed video. From these, we produce a synthesis of the characteristics of an ideal video compression coding. Using this dialectic, we then examine the currently available compression schemes and determine which is closest to the ideal

Advances in Sclerotherapy Treatment of Varicose and Telangiectatic Leg Veins

Sclerotherapy as a treatment for varicose veins originated in the 1800s. Unfortunately, experience with this treatment modality has been fraught with complications and failures. Recent interest by the general public in this form of treatment has uncovered a lack of formal training and protocols within the medical establishment. Nevertheless, recent experience with sclerotherapy has been found to be more positive than previously realized. Three “advances” in sclerotherapy treatment for varicose and telangiectatic leg veins have occurred within the last 20 years. We term these “advances” not because they are new, but because they are newly popular—proper diagnosis prior to treatment; optimal choice of sclerosing solutions and concentrations; and ideal compression techniques to limit sclerophlebitis, recanalization and complications. These advances will be detailed in the following paper.

Advanced Fusion Fuel for Inertial Confinement Fusion

This paper reports that the realization of an ideal volume compression of laser-irradiated fusion pellets opens the possibility for an alternative to spark ignition; this has been proposed for many years for inertial confinement fusion. Using a detailed volume ignition computation of sources of reheat in deuterium-deuterium (D-D) reactions (alpha, proton, and tritium reheat), the result of the calculations show that D-D pellets can be utilized in the same way as in the deuterium-tritium reaction if higher compression can be achieved. Fusion gains of more than 80 are obtained with an initial temperature of only {approx}3.0 keV, input energies close to 2.4 GJ, and initial compression at 30,000 times the solid-state density.

Volume ignition of laser driven fusion pellets and double layer effects

The realization of an ideal volume compression of laser-irradiated fusion pellets (by C. Yamanaka) opens the possibility for an alternative to spark ignition proposed for many years for inertial confinement fusion. A re-evaluation of the difficulties of the central spark ignition of laser driven pellets is given. The alternative volume compression theory, together with volume burn and volume ignition (discovered in 1977), have received less attention and are re-evaluated in view of the experimental verification by Yamanaka, generalized fusion gain formulas, and the variation of optimum temperatures derived at self-ignition. Reactor-level DT fusion with MJ-laser pulses and volume compression to 50 times the solid-state density are estimated. Dynamic electric fields and double layers at the surface and in the interior of plasmas result in new phenomena for the acceleration of thermal electrons to suprathermal electrons. Double layers also cause a surface tension which stabilizes against surface wave effects and Rayleigh–Taylor instabilities.

Methods for comparing the performance of pure and mixed refrigerants in the vapour compression cycle

Methods of comparing pure and mixed refrigerants are considered by computing the coefficient of performance and the heating capacity for an ideal vapour compression cycle for R22/R11 aand R22/R11 mixtures. For comparisons based only on one characteristic condensation temperature and one evaporation temperature, the results depend entirely on how the characteristic temperatures are defined. A method specifying the heat transfer fluid temperatures and a total heat exchanger area per unit capacity is thought to offer a comparison applicable to both pure and mixed refrigerants. Using this method, the effects of compressor superheat, heat exchanger approach temperatures, and the match of refrigerant and heat transfer fluid temperatures are discussed.

Volume Ignition in Pellet Fusion to Overcome the Difficulties of Central Ignition

Since C. Yamanaka et al. demonstrated that the best fusion gains from laser irradiated pellets result only when central shocks are avoided and an ideal volume compression is achieved, the problems o f the central (spark) ignition with necessary densities of 1000 times the solid state may be overcome. Based on an analytical formula of volume ignition, the new conditions should provide reactor adequate laser fusion with compression to 50 to 100 times solid state.

A new pulse compression system for intense relativistic electron beams

A special 360° deflection magnet has been installed at the exit of the 150 MeV Geel Electron Linear Accelerator (GELINA). It consists of five sectors with zero gradient fields and is designed to accept a 50% electron energy spread in the beam of the accelerator. This beam enters the magnet with a pulse width (fwhm) of typically 10 ns and leaves it with a pulse width (fwhm) of 0.6 ns. The peak current rises by this charge conserving compression from originally 10 A to about 100 A at the exit of the magnet. The compression is made possible by the time correlated electron energy degression caused by beam loading in the accelerator. The magnetic field effectuates a phase space transformation, translating the energy dispersion into a time correlated spread of trajectory lengths. This results in a delayed arrival of the leading edge of the pulse at the exit of the magnet as compared with the corresponding arrival of the trailing edge, which means a pulse compression. The pulse shape transformation by the magnetic field and the conditions for ideal pulse compression are analysed. This is followed by a description of the magnet with its electron optics and by a communication about the results and the operational experience.

A Method for In-Process Failure Prediction in Cold Upset Forging

This paper addresses the prediction of plastic tensile instability and ductile fracture of a specimen undergoing a compression test (simple upsetting). The method used to predict failure is based primarily on Thomason’s approach for predicting tensile plastic instability in compression tests. However, to apply this method to in-process prediction, a means for calculating the flow stress-strain properties from in-process measurements is needed. A method is introduced that is derived from Bridgman’s correction factor for effective stress after necking occurs in the tensile test, but with a different approach that is suitable for compression specimens. The new correction factor enables one to correct the effective stress after barreling occurs, which eliminates the need for an ideal test (without barreling) to find the effective stress of a specimen. The results were in agreement with those derived from an ideal compression test. Stress data found using this correction factor was then used to predict failure using Thomason’s method.

体心立方金属の圧延板における表面集合組織形成のシミュレーション

It is well known that under conditions of high friction between rolls and material a unique texture called the surface texture, which is distinctly different from the center texture, appears in the surface layer of a rolled sheet.In this paper, the rolling process under conditions of high friction is regarded as the sheet compression between two parallel rough plates. Therefore, two types of shear mode of deformation having opposite shear-directions arise in the surface layer of sheet in addition to the ideal plane strain compression. From such a model, the development of the surface texture in rolled bcc polycrystalline metals is simulated as a function of rolling reduction on the basis of the theory already proposed by the authors, in which the final orientations of deformation textures in polycrystalline metals can be uniquely predicted. Also the variation of texture through the thickness of the sheet rolled under conditions of high friction between rolls and material is predicted by computer simulation. The simulated textures at various layers throughout the sheet thickness are in agreement with the experimental ones of cold-rolled niobium reported by Vandermeer and Ogle.

The melting performance of single screw extruders

AbstractA number of recent screw designs is analyzed for melting performance, using a simple analytical approach based on Tadmor's original work. The melting length for a screw with constant depth channel is used as reference. An ideal compression screw will have a melting length of one‐half the melting length of the reference screw. The Maillefer melt separation principle is discussed. The Maillefer screw melts in 2/3 of the length of the reference screw. Screws by Barr, by Dray and Lawrence and by Kim are shown to approach the ideal compression screw. A new design screw, using ideal compression and multiple channels and having a very large screw pitch, is shown to be a considerably more efficient melting device than any of the other, screws discussed.