Showing papers on "Compression ratio published in 1993"

Fractal image compression

Abstract: Fractals are geometric or data structures which do not simplify under magnification. Fractal Image Compression is a technique which associates a fractal to an image. On the one hand, the fractal can be described in terms of a few succinct rules, while on the other, the fractal contains much or all of the image information. Since the rules are described with less bits of data than the image, compression results. Data compression with fractals is an approach to reach high compression ratios for large data streams related to images. The high compression ratios are attained at a cost of large amounts of computation. Both lossless and lossy modes are supported by the technique. The technique is stable in that small errors in codes lead to small errors in image data. Applications to the NASA mission are discussed.

Data compression/decompression processor

Abstract: A data compression/decompression processor (a single-chip VLSI data compression/decompression engine) for use in applications including but not limited to data storage and communications The processor is highly versatile such that it can be used on a host bus or housed in host adapters, so that all devices such as magnetic disks, tape drives, optical drives and the like connected to it can have substantial expanded capacity and/or higher data transfer rate The processor employs an advanced adaptive data compression algorithm with string-matching and link-list techniques so that it is completely adaptive, and a dictionary is constructed on the fly No prior knowledge of the statistics of the characters in the data is needed During decompression, the dictionary is reconstructed at the same time as the decoding occurs The compression converges very quickly and the compression ratio approaches the theoretical limit The processor is also insensitive to error propagation

New diffraction grating pair with very linear dispersion for laser pulse compression

Abstract: The principle of operation of a new diffraction grating pair for laser pulse compression is described. This device, which exhibits a very linear group time delay variation against frequency around an inflection point, could be useful for very wide bandwidth laser pulse compression or very large compression ratios.

Combustion state-detecting system for internal combustion engines

Abstract: A combustion state-detecting system for an internal combustion engine is provided, which detects misfires occurring in the engine. A crank angle sensor generates a crank angle signal with a predetermined period shorter than a firing period of the engine whenever the crankshaft rotates through a predetermined angle. An ECU detects the rotational speed of the engine, based on the crank angle signal whenever the crank angle signal is generated to generate a rotational speed signal, and filters the rotational speed signal to extract a specific frequency component therefrom. A rate of variation in the extracted specific frequency component is calculated every first predetermined time period, and an average value of the rate of variation is calculated every second predetermined time period longer than the first predetermined time period. Further, the difference between the average value and the rate of variation is calculated, and absolute values of the difference is cumulated over the second predetermined time period to obtain a difference cumulative value. Then, the difference cumulative value is compared with a predetermined value, and it is determined that the engine is in a continuous degraded combustion state when the difference cumulative value has continued to exceed the predetermined value, and that the engine is in a sporadic degraded combustion state when the difference cumulative value once exceeds the predetermined value once and then becomes smaller than the predetermined value, before it again exceeds the predetermined value.

Variable compression piston

Abstract: In an internal combustion engine, an eccentric bearing (16) located between the connecting rod (14) and the piston pin (12) can be used to vary the compression ratio. In this invention the eccentric bearing is held in any position by a continuously variable hydraulic lock. The hydraulic lock is controlled by a valve assembly (30) which can fix or release the lock bar (18). When the lock bar is released the eccentric bearing can turn as a result of the upward or downward inertia and gas pressure forces on the piston (10). However, a check valve (34) in the valve assembly allows it to turn only in the direction set by the valve assembly until it reaches the new position and re-locks. Engine oil is provided at regulated pressures through oil passages in the connecting rod, eccentric bearing and piston pin to set the position of the valve assembly and to provide a supply for the hydraulic lock. The oil pressure is controlled by an engine-management computer and the position of the valve assembly is set by pressures which are varied within the normal operating limits of the engine. Advantages are continuous variability, little change to existing engine components, low parts count, relatively low addition to reciprocating weight, and no chance of failure due to partial engagement, impact or wear.

Jet engine performance enhancement through use of a wave-rotor topping cycle

Abstract: A simple model is used to calculate the thermal efficiency and specific power of simple jet engines and jet engines with a wave-rotor topping cycle. The performance of the wave rotor is based on measurements from a previous experiment. Applied to the case of an aircraft flying at Mach 0.8, the calculations show that an engine with a wave rotor topping cycle may have gains in thermal efficiency of approximately 1 to 2 percent and gains in specific power of approximately 10 to 16 percent over a simple jet engine with the same overall compression ratio. Even greater gains are possible if the wave rotor's performance can be improved.

Rotary engine with variable compression ratio

Abstract: A rotary engine in which two rotors having interleaving radial vanes (3,4,8,9) revolve inside a cylindrical cavity and are connected to a planetary output gear system which causes them to alternately speed up and slow down. An axial shaft (5) attached to one rotor and passing through the other rotor contains a thrust bearing (10) to prevent the rotors from moving apart. The rotor vanes and disk-shaped end plates (1,6) which contain cooling means divide the cylindrical cavity into four chambers in which intake, compression, explosion and exhaustion occur. A passageway (39,39') containing an adjustable, pressure-sensitive valve (40) vents the compression chamber to the intake chamber to allow the compression ratio to be varied and to provide for a greater compression ratio than expansion ratio.

A method and a device for changing the compression ratio in an internal combustion engine

Abstract: The invention relates to a process and a device for setting the compression ratio of an internal combustion engine by changing the relative distance between the rotational axis (7a) of the engine crankshaft (7) and the surface of the engine cylinder head (2) which delimits the end of each cylinder (4) in the engine. The process according to the invention is characterized in that the relative displacement between the rotational axis (7a) of the crankshaft (7) and the cylinder head (2) is carried out in such a manner that the rotational axis of the crankshaft is displaced both parallel to a plane containing the longitudinal axis of each of the engine cylinders (4), and perpendicular to said plane. The device according to the invention is characterized in that the crankshaft (7) is mounted for rotation in excentrically placed bearing openings (16) in circular adjustment discs (13), which are rotatably mounted in the bearing openings (19) in the engine block (1). Furthermore, a rotating device (31, 34, 35) is coupled to the adjustment discs (13) for simultaneous rotation thereof relative to the engine block (1).

Digital Image Compression Based on Visual Perception and Scene Properties

Abstract: Digital compression techniques have made impressive progress in recent years. Frequently, a reader of a paper on compression is left with the impression that one is getting something for nothing; however, compression can only be achieved by leaving out unnecessary information about the image. A compression ratio of 20:1 simply means that 95% of the information in the original image has been eliminated. There are only two types of information that can be removed without seeing degradation in image quality: information that can be accurately predicted or information that the human visual system cannot see. This article will discuss present compression techniques in terms of these two factors and show how even further compression can be obtained by developing a complete understanding of scene properties and those of visual perception. From an analysis based on present knowledge of visual perception and scene statistics, compression ratios in excess of 50:1 should be achievable without perceptible degradation.

Internal combustion engine air/fuel ratio regulation

Abstract: Internal combustion engine air/fuel ratio regulation in which closed-loop air/fuel ratio control responsive to a pre-converter oxygen sensor feedback signal is further regulated in accord with a feedback signal from a post-converter oxygen sensor signal operative under certain engine operating conditions to provide an average actual engine air/fuel ratio signal. A pre-converter oxygen sensor rich/lean threshold is adjusted in accord with the post-converter signal to drive or maintain such post-converter signal within a preferred range corresponding to an average engine air/fuel ratio of stoichiometry.

Internal combustion engine having high performance combustion chamber

Abstract: An internal combustion engine has a cylinder head with a combustion chamber defined by a depression in the head. The raised face surface of a piston extends into the combustion chamber in the cylinder head as the piston approaches top dead center, and creates turbulent squish currents within the chamber as closely matching surfaces on the piston face and on the walls of the combustion chamber in the head force gases out from between these surfaces. The turbulence helps to prevent autoignition and allows higher compression ratios than would otherwise be possible.

Pruning of the transform space in block-based fractal image compression

Abstract: A method for fractal image compression is presented which is an extension of A.E. Jacquin's (1990) algorithm. The proposed algorithm improves Jacquin's block-based algorithm by allowing irregularly shaped fractal transformations. The method for producing these transformations is to start with the block-based approach and then prune the transformations in the transform space. The results show a large improvement in compression ratio over Jacquin's system at the same signal-to-noise ratio. For high compression ratios the system has similar performance to the JPEG (Joint Photographic Experts Group) standard. >

An Investigation of Water as a Refrigerant

Abstract: This paper explores some of the basic thermodynamic and technical considerations involved in using water as a working fluid for refrigeration and heat pump cycles down to its freezing point of 0 C. It is first shown how the integration of the functions of refrigerant and heat transfer fluid can lead to energy savings, especially for the case of ice production. Next, the two fundamental requirements that the compressor must fulfill -- handling a very large volume flow and achieving a large compression ratio -- are described. A thermodynamic analysis of multistage compression follows to investigate the adiabatic head requirements and the large desuperheating irreversibility. It is concluded that a radically new type of vacuum compressor must be developed in order for water to be used as working fluid in vapor compression refrigeration cycles.

ECG data compression by modeling

Abstract: The paper presents a novel algorithm for data compression of single lead electrocardiogram (ECG) data. The method is based on parametric modeling of the discrete cosine transformed ECG signal. Improved high frequency reconstruction is achieved by separately modeling the low and the high frequency regions of the transformed signal. Differential pulse code modulation is applied on the model parameters to obtain a further increase in the compression. Compression ratios up to 1:40 were achieved without significant distortion.

General analysis of the mechanical efficiency of reciprocating heat engines

Abstract: This paper examines the mechanical efficiency of reciprocating heat engines in a general setting. From an abstract mathematical characterization of machines, the relation of the pressure-volume cycle of an engine and the characteristics of its mechanism to its useful work output is established. Using the ideal Stirling engine in conjunction with this relation, a functional upper bound on the mechanical efficiency of all engines is derived. This shows the existence of limits on compression ratio under conditions relating the level of performance of the mechanism to the ratio of engine operating temperatures. This has implications for the design of engines intended for operation from low grade sources, such as industrial waste heat or passive solar energy.

Variable compression internal combustion engine

Abstract: Controlled variation of piston .displacement and adjustment of compression ratio are achieved by an adjustment mechanism located between the vehicle crank shaft and the piston which changes the effective length of the piston rod. The piston rod is divided into upper and lower portions and the adjustment mechanism connected to both portions at the point of division. The adjustment mechanism allows controlled lateral displacement of the two parts of the piston rod from each other at the point of division while still transmitting energy of motion from the piston to the crank shaft.

Fuel injection device for multi cylinder two stroke engine

Abstract: A system for controlling the supply of fuel to a multiple cylinder, two cycle, crankcase compression, internal combustion engine wherein air flow is normally measured by a pressure sensor in the crankcase chamber of only one of the cylinders. When an abnormal condition is sensed, the supply of fuel to the cylinder associated with the pressure sensor is discontinued and in some embodiments, the control of the fuel to the other cylinders is accomplished by means other than pressure sensing.

Methods and devices for self-correcting video compression

Abstract: Self-correcting video compression procedures and devices for encoding and decoding and reduction of artifacts of digitized video images and thereby increasing the compression ratio and the efficiency of image storage and transmission by using a best fit surface encoding technique. Encoder accurately processes differential image encoding by computing copy of decoder frame and employing feedback methods.

Air-fuel ratio control apparatus for an internal combustion engine

Abstract: An apparatus for controlling an air-fuel ratio in a lean burn internal combustion engine, such that three different air-fuel ratio zones are set, the three zones being an ultra lean zone with a low load, a medium lean zone with a medium load, and a non-lean zone with a high load. When the engine is under low load conditions, a map FLEANPM is selected to obtain an ultra lean air-fuel ratio based on detected intake pressure PM values and engine speed NE. When the engine is under medium load conditions, a map FLEANTA is selected to obtain a medium lean air-fuel ratio based on a detected throttle opening values TA and engine speed NE. When the engine is under high load, conditions the lean correction control is canceled, thereby obtaining a theoretical air-fuel ratio or an air-fuel ratio smaller than the theoretical air-fuel ratio, and when the engine remains at a point in the medium lean zone, the air-fuel ratio decreases gradually toward the theoretical air-fuel ratio as time elapses.

The evolution of lossless data compression techniques

Abstract: Lossless data compression has suddenly exploded into a $300 million market Commercial examples are file compression software packages than can more than double the storage in disc files while the new CCITT V42bis standard can double the transmission rates in modems Applications will soon spread into digital image compression (HDTV), teleconferencing, wide area networks (WAN, ISDN), digital audio tapes (DAT) and brain-like databases (Autosopher) There are five competing methods each championed by different vendors and the battle for the best algorithm is far from being settled The old Huffman code was long a favorite of academics and mathematicians It may be used as an addition to other compression codes but is not commercially viable by itself The original Ziv-Lempel (1977) codes have a temporary headstart because of heavy promotions by Stac Electronics These codes already deliver slow file compression software or fast hardware compression using plug-in modules These codes will prove to be inferior in the long run The Ziv-Lempel-Welch (LZW) codes are now the most commonly used compression codes They may be superseded soon by combined fixed and dynamic learning networks The British Telecom Lempel-Ziv (BTLZ) code is the state of the art for dynamic libraries It is used in the V42bis compression modems The fixed library Autosophy networks offer the highest compression ratio and additional data encryption They do however require prior knowledge of the kind of data or language being compressed These networks may operate at extreme speed and without the danger of error propagation

Valve timing controller of internal combustion engine

Abstract: PURPOSE:To keep off the worsening of combustion at a light load area by checking the unnecessary drop in an effective compression ratio at the time of engine low temperature. CONSTITUTION:A variable valve timing mechanism(VVT) 23 consists of a timing pulley 24 and a step motor 25, making the on-off timing of an intake valve 9 variable in succession. A variable valve timing electronic control unit(ECU) 41 drives and controls the VVT 23 to control the on-off timing of the intake valve 9 so as to reduce any pumping loss in an engine 1 on the basis of the detected value of an engine speed sensor 30 or the like. In addition, the VVT electronic control unit 41 sets a control range of the VVT 23 so as to be the lower in the detected value of a water temperature sensor 32, the narrower in the on-off timing control range. Accordingly, at the time of low temperature, a difference between both upper and lower values of the on-off timing is controlled so as to become smaller, thus an effective compression ratio is checked to be unnecessarily lessened as securing a certain degree of a pumping loss reducing effect in the engine 1.

Process for the adaptive knock control of an internal combustion engine.

Abstract: A method for the adaptive knock control of an internal combustion engine serves for shifting the ignition angle of an internal combustion engine in the retard direction when knocking occurs and for subsequently carrying out a return of the ignition angle in the advance direction. At the same time, the internal combustion engine is to have sub-divided operating ranges, and a value of an ignition-angle retard, determined in a range during operation, is always stored when this range is left. At the same time, in particular an average of all the ignition angles outputted in a range or a retard value plotted by a digital low-pass filter is to be stored.

Auxiliary chamber type gas engine

Abstract: PURPOSE: To provide an auxiliary chamber type gas engine which is designed to provide an auxiliary chamber with a gas fuel chamber, prevent the occurrence of self-ignition through the increase of a compression ratio to a high value, and use natural gas as fuel. CONSTITUTION: The interior of an auxiliary chamber 2 is divided into two sections of the one being a gas fuel chamber 17 and the other being an air chamber 3 and an auxiliary chamber piston 6 to effect reciprocating movement is arranged. A spark plug 25 is arranged in a gas fuel chamber 17 and a gas fuel valve 23 is arranged to a gas fuel feed port 22 through which gas fuel is fed to the gas fuel chamber 17. During a period in which the auxiliary piston 6 is positioned at a large part 11, the gas fuel chamber 17 is communicated with a main chamber 1 through a communication hole 12 formed in the lower part of the auxiliary chamber 2. A given amount of gas fuel is feedable to the auxiliary chamber 2 and the compression strength of air in the main chamber is increased to a high value and beside lean combustion is practicable, and logic thermal efficiency is improved. COPYRIGHT: (C)1995,JPO

Internal plasma-combustion engine system

Abstract: An internal combustion engine system including an engine, timer/distributor device and a compliant electromagnetic device is disclosed. The engine may have one or more cylinders and includes an anode positioned above a cathodic piston whereby the anode delivers high intense short bursts of electrical energy through the combustion chamber and ignites fuel delivered by an injector. Each engine cylinder is connected to a distributor which sequences and delivers the high energy impulses from the compliant electromagnetic device to an individual cylinder when the piston is at or near top dead center. The compliant electromagnetic device includes an inductor, a power source and a field of material, i.e., the air/fuel mixture within the combustion chamber. The summed equivalence of the electromagnetic fields within the combustion chamber at any instant in time controls the intensity of the pulses and the quantity of pulses that are discharged by the anode. An alternative embodiment is provided which further improves performance by recirculating non-combusted gases and mixing them with high pressurized fuel and delivering the mixture to the combustion chamber where the fuel is fragmented, dissociated and combusted. The resulting internal combustion engine system has improved working efficiencies as well as a reduction in the emissions by the engine.

Combustion chamber for air compressing, self-igniting internal combustion engines

Abstract: A combustion chamber shape for air-compressing, self-igniting internal combustion engines is designed such that fuel injection jets ejected from a multiport injection valve positioned on the cylinder axis do not come into contact with the walls of the combustion chamber. For this purpose, the piston bottom is conically shaped whereby the slant of the conical surface is selected such that the piston bottom is adapted to the contour of the widening injected fuel jet. The cylinder head bottom is designed as a spherical segment, also with the goal that the fuel injection jet does not come into contact with the combustion chamber walls. The conically designed piston bottom may have radially extending depressions when the combustion chamber is very small in order to achieve high compression ratios. With the depressions it is ensured that despite the small distance between the piston bottom and the cylinder head bottom the injected fuel jet does not come into contact with the combustion chamber walls so that an incomplete combustion is prevented.

Internal combustion engine of variable compression ratio

Abstract: (57) [Abstract] [Purpose] To provide a variable compression ratio internal combustion engine capable of realizing stable and reliable control of the compression ratio without changing the basic structure of the connecting rod, the crankshaft, or the like and the supporting method thereof. [Structure] The crankcase 4 and the cylinder block 13 are not integrated, but are connected by two left and right compression ratio changing cam shafts 23 and 24. Both cam shafts 23, 24 are rotated by a small diameter portion 26 rotatably fitted to a cam holder 25 formed on the lower left and right ends of the cylinder block 13, and a cam holder 27 formed on the upper left and right ends of the crankcase 4. And a large diameter portion 28 that can be freely fitted. Both cam shafts 23, 24 are so-called eccentric cams, and the center of the small diameter portion 26 is horizontally and outwardly offset from the center of the large diameter portion 28. Therefore, when the cam shafts 23 and 24 rotate, the cylinder block 1 3 moves up and down with respect to the crankcase 4.

Variable cycle three-stroke engine

Abstract: A virtual three-stroke engine (1) with intake and compression strokes approximately one half of the power stroke of approximately 12 to one expansion ratio and with total firing cycle stroke lengths equal to approximately three expansion strokes to minimize engine throttling and frictional losses over the real world drive cycle and provide high torque from a one-to-one drive shaft RPM to engine firing cycle RPM provided by a cam type driver for controlling the piston motions and extracting the power from the piston.