Compression Ratio

In this paper, a novel image encryption scheme based on JPEG2000 is proposed, which encrypts only the code-blocks corresponding to some sensitive precincts. The proposed process encryption doesn’t introduce superfluous JPEG2000 markers in the protected codestream, i.e, the protected codestream format is compliant to JPEG2000 codestream one. It keeps file format and compression ratio unchanged and doesn’t degrade the original error robustness. The proposed scheme works with any standard ciphers and introduces negligible computational cost.

Data compression is one of the enabling technologies for the application of communication technology with ever growing Internet, explosive development of mobile communication and the ever-increasing impact of video communication to store the data in a compact way for minimum cost of storage and transmission. There are various compression techniques available which are capable of application specific large compression ratios.

We present the Nearest Sub-class Classifier (NSC), which is a classification algorithm that unifies the flexibility of the nearest neighbor classifier with the robustness of the nearest mean classifier. The algorithm is based on the Maximum Variance Cluster algorithm and as such it belongs to the class of prototype-based classifiers. The variance constraint parameter of the cluster algorithm serves to regularise the classifier, that is, to prevent overfitting. With a low variance constraint value the classifier turns into the nearest neighbor classifier and with a high variance parameter it becomes the nearest mean classifier with the respective properties. In other words, the number of prototypes ranges from the whole training set to only one per class. In the experiments, we compared the NSC with regard to its performance and data set compression ratio to several other prototype-based methods. On several data sets the NSC performed similarly to the k-nearest neighbor classifier, which is a well-established classifier in many domains. Also concerning storage requirements and classification speed, the NSC has favorable properties, so it gives a good compromise between classification performance and efficiency.

We present Angle-Analyzer, a new single-rate compression algorithm for trianglequad hybrid meshes. Using a carefully-designed geometry-driven mesh traversal and an efficient encoding of intrinsic mesh properties, Angle-Analyzer produces compression ratios 40% better in connectivity and 20% better in geometry than the leading Touma and Gotsman technique for the same level of geometric distortion. The simplicity and performance of this new technique is demonstrated, and we provide extensive comparative tests to contrast our results with the current state-of-the-art techniques.

In Image Compression, the researchers' aim is to reduce the number of bits required to represent an image by removing the spatial and spectral redundancies. Recently discrete wavelet transform and wavelet packet has emerged as popular techniques for image compression. The wavelet transform is one of the major processing components of image compression. The result of the compression changes as per the basis and tap of the wavelet used. It is proposed that proper selection of mother wavelet on the basis of nature of images, improve the quality as well as compression ratio remarkably. We suggest the novel technique, which is based on wavelet packet best tree based on Threshold Entropy with enhanced run-length encoding. This method reduces the time complexity of wavelet packets decomposition as complete tree is not decomposed. Our algorithm selects the sub-bands, which include significant information based on threshold entropy. The enhanced run length encoding technique is suggested provides better results than RLE. The result when compared with JPEG-2000 proves to be better.

The waveform data, which is gathered during digital simulation of large and complex systems easily fill up huge amounts of disk space on the simulation computer. This is specially true for many deep-submicron designs. Hence, we developed a set of algorithms and techniques which can be used to efficiently compress digital waveforms without losing any significant information from the original data. Experimental results show that compression ratios of up to 300 compared to a original VCD formatted file can be achieved.

Binary image compression is desirable for a wide range of applications, such as digital libraries, map archives, fingerprint databases, facsimile, etc. In this paper, we present a new highly efficient algorithm for lossless binary image compression. The proposed algorithm introduces a new method, direct redundancy elimination, to efficiently exploit the two-dimensional redundancy of an image, as well as a novel

This paper proposes a Hierarchical Evolutionary-Deterministic Algorithm (HEDA) for designing square grounding grids. This algorithm performs the design by means of a hierarchical coupling of a real coded evolutionary algorithm and the Hooke-Jeeves algorithm. The design of the grounding grid is here formalized as a min-max problem. The maximization part is the search of the most dangerous point for a given topological structure, the minimization part is the optimization of the topological parameter (compression ratio) of the grounding grid. The solution of the system of partial differential equations related to the spatial distribution of the current field is carried out by the Galerkin method. The program gives good results in terms of accuracy and computational complexity.

In this paper a wavelet-based steganographic method is proposed for robust short-message hiding. The message is embedded into the most significant wavelet coefficients of a cover image to provide invisibility and resistance against lossy transmission over cellular networks, compression or other distortion. The architecture consists of three modules. In the first module the initial message is enciphered by an encryption

In this paper, we present a hybrid chain coding based scheme for contours and binary image compression and reconstruction. The proposed scheme comprises of a lossless and a lossy parts. This scheme is designed in such a way to generate extensive number of replicate links in the contours that can be assembled according to our (n10, 5) rule that can be highly compressed. Furthermore, for the lossy part, we introduce a new line processing technique to smooth the contours while maintaining high image quality. The experimental results show that the proposed method surpasses all published chain coding methods including FCC, DCC, DCC-8, VCC, CRCC, and L&Z. In addition, this scheme produced significantly higher compression ratio than WinZip, G3, G4, JBIG1, and JBIG2 standards.

This paper introduces a real-time data compression and transmission algorithm between e-health terminals for a periodic ECGsignal. The proposed algorithm consists of five compression procedures and four reconstruction procedures. In order to evaluate the performance of the proposed algorithm, the algorithm was applied to all 48 recordings of MIT-BIH arrhythmia database, and the compress ratio (CR), percent root mean square difference (PRD), percent root mean square difference normalized (PRDN), rms, SNR, and quality score (QS) values were obtained. The result showed that the CR was 27.9:1 and the PRD was 2.93 on average for all 48 data instances with a 15% window size. In addition, the performance of the algorithm was compared to those of similar algorithms introduced recently by others. It was found that the proposed algorithm showed clearly superior performance in all 48 data instances at a compression ratio lower than 15:1, whereas it showed similar or slightly inferior PRD performance for a data compression ratio higher than 20:1. In light of the fact that the similarity with the original data becomes meaningless when the PRD is higher than 2, the proposed algorithm shows significantly better performance compared to the performance levels of other algorithms. Moreover, because the algorithm can compress and transmit data in real time, it can be served as an optimal biosignal data transmission method for limited bandwidth communication between e-health devices.

This paper presents an ECG compressor based on optimized quantization of Discrete Cosine Transform (DCT) coefficients. The ECG to be compressed is partitioned in blocks of fixed size, and each DCT block is quantized using a quantization vector and a threshold vector that are specifically defined for each signal. These vectors are defined, via Lagrange multipliers, so that the estimated entropy is minimized for a given distortion in the reconstructed signal. The optimization method presented in this paper is an adaptation for ECG of a technique previously used for image compression. In the last step of the compressor here proposed, the quantized coefficients are coded by an arithmetic coder. The Percent Root-Mean-Square Difference (PRD) was adopted as a measure of the distortion introduced by the compressor. To assess the performance of the proposed compressor, 2-minute sections of all 96 records of the MIT-BIH Arrhythmia Database were compressed at different PRD values, and the corresponding compression ratios were computed. We also present traces of test signals before and after the compression/decompression process. The results show that the proposed method achieves good compression ratios (CR) with excellent reconstruction quality. An average CR of 9.3:1 is achieved for PRD equal to 2.5%. Experiments with ECG records used in other results from the literature revealed that the proposed method compares favorably with various classical and state-of-the-art ECG compressors. 

In the effort to reduce pollutant emissions from diesel engines various solutions have been proposed, one of which is the use of natural gas as supplement to liquid diesel fuel, with these engines referred to as fumigated, dual fuel, compression ignition engines. One of the main purposes of using natural gas in dual fuel (liquid and gaseous one) combustion systems is to reduce particulate emissions and nitrogen oxides. Natural gas is a clean burning fuel; it possesses a relatively high auto-ignition temperature, which is a serious advantage over other gaseous fuels since then the compression ratio of most conventional direct injection (DI) diesel engines can be maintained high. In the present work, an experimental investigation has been conducted to examine the effects of the total air-fuel ratio on the efficiency and pollutant emissions of a high speed, compression ignition engine located at the authors' laboratory, where liquid diesel fuel is partially substituted by natural gas in various proportions, with the natural gas fumigated into the intake air. The experimental results disclose the effect of these parameters on brake thermal efficiency, exhaust gas temperature, nitric oxide, carbon monoxide, unburned hydrocarbons and soot emissions, with the beneficial effect of the presence of natural gas being revealed. Given that the experimental measurements cover a wide range of liquid diesel supplementary ratios without any appearance of knocking phenomena, the belief is strengthened that the findings of the present work can be very valuable if opted to apply this technology on existing DI diesel engines.

This paper investigates typical behaviors like damped oscillations in fractional order (FO) dynamical systems. Such response occurs due to the presence of, what is conceived as, pseudo-damping and meta-damping in some special class of FO systems. Here, approximation of such damped oscillation in FO systems with the conventional notion of integer order damping and time constant has been carried out using Genetic Algorithm (GA). Next, a multilayer feed-forward Artificial Neural Network (ANN) has been trained using the GA based results to predict the optimal pseudo and meta-damping from knowledge of the maximum order or number of terms in the FO dynamical system.

A process for the industrial production of magnesium hydride (MgH 2) based on a thermal equilibrium method and its application to portable hydrogen sources is proposed. Mg powders and tablets compressed with mechanically ground Mg ribbons were successfully hydrogenated in a 50-kg-batch furnace. The resultant MgH 2 showed a hydrogen yield of around 96% with good reproducibility. The compression ratio of Mg tablets was found to be an important factor in the hydrogenation yield. A hydrolysis technique using citric acid as an additive was employed to generate hydrogen under 373 K. Increasing the concentration of citric acid and the temperature accelerated the hydrolysis reactivity. A hydrogen reactor utilizing hydraulic head pressure was developed. It generated hydrogen continuously for 1 h at a flow rate of 100 ml min −1 with hydrolysis of 5 g of tablet-form MgH 2. The conversion yield was around 70%, regardless of the flow rate.

A piston motion controller for a free-piston internal combustion engine is presented. To improve dynamic performance in the control of the piston motion and engine compression ratio, the controller response is determined from a prediction of engine top dead centre error rather than the measured value from the previous cycle. The proposed control approach showed superior performance compared with that of standard PI feedback control known from the literature due to a reduced control action time delay. The manipulation of fuel injection timing to reduce in-cylinder pressure peaks and cycle-to-cycle variations was also studied, indicating that with the the piston motion estimation, the injection timing is a powerful control variable for this purpose.

A practical impossibility of prediction of signs of DCT coefficients is generally accepted. Therefore each coded sign of DCT coefficients occupies usually 1 bit of memory in compressed data. At the same time data of all coded signs of DCT coefficients occupy about 20-25% of a compressed image. In this work we propose an effective approach to predict signs of DCT coefficients in block based image compression. For that, values of pixels of already coded/decoded neighbor blocks of the image are used. The approach consist two stages. At first, values of pixels of a row and a column which both are the nearest to already coded neighbor blocks are predicted by a context-based adaptive predictor. At second stage, these row and column are used for prediction of the signs of the DCT coefficients. Depending on complexity of an image proposed method allows to compress signs of DCT coefficients to 60-85% from their original size. It corresponds to increase of compression ratio of the entire image by 3-9% (or up to 0.5 dB improvement in PSNR).

Future high resolution instruments planned by CNES to succeed SPOT5 will lead to higher bit rates because of the increase in both resolution and number of bits per pixel, not compensated by the reduced swath. Data compression is then needed, with compression ratio goals higher than the 2.81 SPOT5 value obtained with a JPEG like algorithm. Compression ratio should rise typically to 4-6 values, with artifacts remaining unnoticeable : SPOT5 algorithm performances have clearly to be outdone. On another hand, in the framework of optimized and low cost instruments, noise level will increase. Furthermore, the Modulation Transfer Function (MTF) and the sampling grid will be fitted together, to -at least roughly-satisfy Shannon requirements. As with the Supermode sampling scheme of the SPOT5 Panchromatic band, the images will have to be restored (deconvolution and denoising) and that renders the compression impact assessment much more complex. This paper is a synthesis of numerous studies evaluating several data compression algorithms, some of them supposing that the adaptation between sampling grid and MTF is obtained by the quincunx Supermode scheme. The following points are analyzed : compression decorrelator (DCT, LOT, wavelet, lifting), comparison with JPEG2000 for images acquired on a square grid, compression fitting to the quincunx sampling and on board restoration (before compression) versus on ground restoration. For each of them, we describe the proposed solutions, underlining the associated complexity and comparing them from a quantitative and qualitative point of view, giving the results of experts analyses.

This paper introduces a real-time data compression and transmission algorithm between e-health terminals for a periodic ECGsignal. The proposed algorithm consists of five compression procedures and four reconstruction procedures. In order to evaluate the performance of the proposed algorithm, the algorithm was applied to all 48 recordings of MIT-BIH arrhythmia database, and the compress ratio (CR), percent root mean square difference (PRD), percent root mean square difference normalized (PRDN), rms, SNR, and quality score (QS) values were obtained. The result showed that the CR was 27.9:1 and the PRD was 2.93 on average for all 48 data instances with a 15% window size. In addition, the performance of the algorithm was compared to those of similar algorithms introduced recently by others. It was found that the proposed algorithm showed clearly superior performance in all 48 data instances at a compression ratio lower than 15:1, whereas it showed similar or slightly inferior PRD performance for a data compression ratio higher than 20:1. In light of the fact that the similarity with the original data becomes meaningless when the PRD is higher than 2, the proposed algorithm shows significantly better performance compared to the performance levels of other algorithms. Moreover, because the algorithm can compress and transmit data in real time, it can be served as an optimal biosignal data transmission method for limited bandwidth communication between e-health devices.

A Flexible Representation of Quantum Images (FRQI) is proposed to provide a representation for images on quantum computers in the form of a normalized state which captures information about colors and their corresponding positions in the images. A constructive polynomial preparation for the FRQI state from an initial state, an algorithm for quantum image compression (QIC), and processing operations for quantum images are combined to build the whole process for quantum image processing on FRQI. The simulation experiments on FRQI include storing, retrieving of images and a detection of a line in binary images by applying quantum Fourier transform as a processing operation. The compression ratios of QIC between groups of same color positions range from 68.75 to 90.63% on single digit images and 6.67-31.62% on the Lena image. The FRQI provides a foundation not only to express images but also to explore theoretical and practical aspects of image processing on quantum computers.

This paper presents the determination of knock rating of gaseous fuels in a single cylinder engine. The first part of the work deals with an application of a standard method for the knock rating of gaseous fuels. The Service Methane Number (SMN) is compared with the standard Methane Number (MN) calculated from the standard AVL software METHANE (which corresponds to the MN measured on a Cooperative Fuel Research engine). Then, in the second part, the 'mechanical' resistance to knock of our engine is highlighted by means of the Methane Number Requirement (MNR). A single cylinder LISTER PETTER engine was modified to run as a spark ignition engine with a fixed compression ratio and an adjustable spark advance. Effects of engine settings on the MNR are deduced from experimental data and compared extensively with previous studies. Using the above, it is then possible to adapt the engine settings for optimal knock control and performances. The error on the SMN and MNR stands beneath^2 MN units over the gases and engine settings considered. q

One of the objectives of car manufacturers is to improve engine performance, reduce consumption and reduce emissions. To achieve this objective, it is important to understand the phenomena involved in the combustion chambers of engines. There are various factors that influence the engine performance such as compression ratio, atomization of fuel, fuel injection pressure, and quality of fuel, combustion rate, air fuel ratio, intake temperature and pressure and also based on piston design, inlet manifold, and combustion chamber designs etc. Geometrical design of intake manifold is one such method for the better performance of an I.C. Engine. Air swirl motion in CI engine influences the atomization and distribution of fuel injected in the combustion chamber. Intake manifolds provides Air motion to the chamber. So, to get the maximum output with the least input on Diesel engine researchers are experimentally and computationally working on construction of the intake manifold configurations for increase in engine performance and reduction of Exhaust Emissions. In this paper i have studied few papers and also gone through basics of my topic from various books to understand the phenomena.

When it comes to travelling by cars, mishaps and unwanted incidents such as tyre puncture, low air pressure in tyre are extremely common. A conventional carjacking system makes use of mechanical advantage to lift the cars. Despite the mechanical advantage jacking up a car is a very difficult task for many people especially women and elderly people. The objective of this project is develop a new carjacking system in order to make the operation easier, safer and more reliable in order to save individuals from unnecessary expenditure of energy and reduce health risks especially backache problems. In the context of this particular project, the newly developed scissor jack uses a 12 V DC motor as the prime mover which works using the car battery. The motor is connected to the lead screw of the jack through reduction gear, so as the motor starts, the pinion is rotates with a torque equal to the motor torque. Since the pinion is in mesh with the gear (double the number of teeths in pinion) in the lead screw, the driven gear starts rotating with a multiplied torque, thereby lifting the car. The developed system also has a provision for inflating the tyre, which is used when the air pressure in the tyre is lesser than ideal conditions. The system uses a reciprocating type compressor which works on the 12 V supply. The main advantage of this system is that we can use it whenever we requires.

Alcohols have been used as a fuel for engines since 19th century. Among the various alcohols, ethanol is known as the most suited renewable, bio-based and ecofriendly fuel for spark-ignition (SI) engines. The most attractive properties of ethanol as an SI engine fuel are that it can be produced from renewable energy sources such as sugar, cane, cassava, many types of waste biomass materials, corn and barley. In addition, ethanol has higher evaporation heat, octane number and flammability temperature therefore it has positive influence on engine performance and reduces exhaust emissions. In this study, the effects of unleaded gasoline (E0) and unleaded gasoline-ethanol blends (E50 and E85) on engine performance and pollutant emissions were investigated experimentally in a single cylinder four-stroke spark-ignition engine at two compression ratios (10:1 and 11:1). The engine speed was changed from 1500 to 5000 rpm at wide open throttle (WOT). The results of the engine test showed that ethanol addition to unleaded gasoline increase the engine torque, power and fuel consumption and reduce carbon monoxide (CO), nitrogen oxides (NO x ) and hydrocarbon (HC) emissions. It was also found that ethanol-gasoline blends allow increasing compression ratio (CR) without knock occurrence.

Advanced combustion strategies including premixed charge compression ignition, homogeneous charge compression ignition, and lifted flame combustion are promising approaches for meeting increasingly stringent emissions regulations and improving fuel efficiency in next generation powertrains. Variable valve actuation and closed-loop control promise to play a key role in the promotion and control of these advanced combustion modes. For example, modulation of intake valve closure timing dictates the effective compression ratio and influences the total amount of charge trapped inside the cylinder, and in so doing allows manipulation of the in-cylinder reactant concentrations and temperature prior to and during the combustion process. The effort described here uses data from, and an experimentallyvalidated simulation model for, a multi-cylinder engine with variable geometry turbocharging, cooled exhaust gas recirculation, and fully flexible variable valve actuation. This effort's intent is to determine the control authority over the gas exchange process and effective compression ratio when intake valve closure timing modulation is included on a modern turbocharged diesel engine, as well as to lay the groundwork for closed-loop control design for the promotion and control of advanced combustion modes. The engine testbed at Purdue provides a unique opportunity to pursue these objectives for turbocharged engines with exhaust gas recirculation, as it is the only such engine system in academia outfitted with multi-cylinder fully-flexible valve actuation. A method to estimate in-cylinder temperature at top dead centre is also described. Candidate control architectures for both steady state and transient operation are introduced.

The main purpose of this work was to develop a mathematical model and computer programs for ejector studies in refrigeration cycles. Version A of the program was written for optimal ejector design while Version B, with more built-in flexibility, was intended for simulation. The study is a one-dimensional analysis of compressible refrigerant flow, based on a forward marching technique of solution for the conservation equations. Refrigerant properties were evaluated using NIST [NIST Standard Reference Database 23, NIST Thermodynamics and Transport Properties of Refrigerants and Refrigerant Mixtures, 1998, REFPROP, Version 6.01] subroutines for equations of state solutions. The approach assesses the flow locally and provides the flexibility of returning upstream for correcting adjustments. Model validation against the R141b data of Huang et al. [Int. J. Refrig. 22 (1999) 354] has shown very good agreement under all conditions. Analysis with refrigerant R142b was performed for typical refrigeration conditions. The entrainment ratio x, the compression ratio P 6 /P 2 and geometric parameters such as diameters and axial dimensions were used to assess performance. Local distributions of pressure, temperature and Mach number were obtained for typical conditions and the mixing chamber was found to greatly impact operation and performance, by controlling the shock wave occurrence and intensity. Crown

We use the first and second laws of thermodynamics to analyze the behavior of an ideal jet engine. Simple analytical expressions for the thermal efficiency, the overall efficiency, and the reduced thrust are derived. We show that the thermal efficiency depends only on the compression ratio r and on the velocity of the aircraft. The other two performance measures depend also on the ratio of the temperature at the turbine to the inlet temperature in the engine, T 3 / T i. An analysis of these expressions shows that it is not possible to choose an optimal set of values of r and T 3 / T i that maximize both the overall efficiency and thrust. We study how irreversibilities in the compressor and the turbine decrease the overall efficiency of jet engines and show that this effect is more pronounced for smaller T 3 / T i .

The design and performance characteristics of a novel top-down uniflow scavenged gasoline direct-injection two-stroke engine are presented. The novelty of the engine lies in the cylinder head that contains multiple check valves that control scavenging airflow into the cylinder from a supercharged air plenum. When the cylinder pressure drops below the intake plenum pressure during the expansion stroke, air flows into the cylinder through the check valves. During compression the cylinder pressure increases to a level above the intake plenum pressure and the check valves close preventing back-flow into the intake plenum. The engine head design provides asymmetrical intake valve timing without the use of poppet valves and the associated valve-train. In combination with an external Roots-type supercharger that supplies the plenum and exhaust ports at the bottom of the cylinder wall, the novel head provides top-down uniflow air scavenging. Motoring tests indicated that the check valves seal and the peak pressure is governed by the compression ratio. The only drawback observed is that valve closing is delayed as the engine speed increases. In order to investigate the valve dynamics, additional tests were performed in an optically-accessible cold flow test rig that enabled the direct measurement of valve opening and closing time under various conditions.

This paper presents the results obtained of a compression ignition engine (modified to run on spark ignition mode) fuelled with hydrogen-ethanol dual fuel combination with different percentage substitutions of hydrogen (0-80% by volume with an increment of 20%) under variable compression ratio conditions (i.e. 7:1, 9:1 and 11:1) by varying the spark ignition timing at a constant speed of 1500 rpm. The various engine performance parameters studied were brake specific fuel consumption, brake mean effective pressure and brake thermal efficiency. It was found from the present study that for specific ignition timing the brake mean effective pressure and the brake thermal efficiency increases with the increase of hydrogen fraction in ethanol and all hydrogen substitutions showed the maximum increase in brake thermal efficiency and reduction in brake specific fuel consumption value at around 25 CA advanced ignition timing. The best operating conditions were obtained at a compression ratio of 11:1 and the optimum fuel combination was found to be 60-80% hydrogen substitution to ethanol.

The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO 2 emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed that hemp based NMT have compatible or even better strength properties as compared to conventional flax based thermoplastics. A value of 63 MPa for flexural strength is achieved at 64% fiber content by weight. Similarly, impact energy values (84 Á/154 J/m) are also promising. The carbon sequestration and storage by hemp crop through photosynthesis is estimated by quantifying dry biomass of fibers based on one metric ton of NMT. A value of 325 kg carbon per metric ton of hemp based composite is estimated which can be stored by the product during its useful life. An extra 22% carbon storage can be achieved by increasing the compression ratio by 13% while maintaining same flexural strength. Further, net carbon sequestration by industrial hemp crop is estimated as 0.67 ton/h/year, which is compatible to all USA urban trees and very close to naturally, regenerated forests. A comparative life cycle analysis focused on nonrenewable energy consumption of natural and glass fiber composites shows that a net saving of 50 000 MJ (Â/3 ton CO 2 emissions) per ton of thermoplastic can be achieved by replacing 30% glass fiber reinforcement with 65% hemp fiber. It is further estimated that 3.07 million ton CO 2 emissions (4.3% of total USA industrial emissions) and 1.19 million m 3 crude oil (1.0% of total Canadian oil consumption) can be saved by substituting 50% fiber glass plastics with natural fiber composites in North American auto applications. However, to compete with glass fiber effectively, further research is needed to improve natural fiber processing, interfacial bonding

With the continuous enhancement in the speed and architecture of mobile processors it has become possible to play even high resolution videos on them. However the compilers have lagged behind in taking full utilization of the processing capabilities of the underlying hardware. H.264, known for its high compression ratio and computational complexity, needs performance optimizations for a computationally constraint environment. Some of these techniques are described in this paper.

A three-stage metal hydride based hydrogen compressor prototype was built. It has been designed for a hydrogen production facility using a low-pressure alkaline electrolyser. The compression system should transfer heat recovered from the electrolyser into the hydride beds to allow hydrogen desorption flow. The three-stage compressor achieves a compression ratio of 20:1 atm. It performs a thermal cycling of three AB 5 hydrides between 20 and 80 • C. Its flow rate, for 25 g of each hydride bed, reaches about 20 l (NTP) of hydrogen per hour. The prototype is now operational. Some improvements in the heat transfer management system are also carried out before proceeding to the interconnection with the electrolyser and to the extent that the hydrogen produced satisfies the high purity requirement of the hydrides used in the compressor.

Shape memory is the property of a material to remember its original shape despite subsequent plastic deformation. The exposure to specific temperature profiles induces a shape memory effect on auxetic (negative Poisson's ratio) foam specimens, returning them to their initial dimensions. This behaviour is a one-way effect, and it is a property of the polyurethane (PU) constituent of the foam. The foam specimens were transformed from conventional Poisson's ratio to auxetic, returned to conventional and once again to auxetic under multiple mechanical and thermal loading. At each stage the foams were mechanically characterized under cyclic tensile and compressive loading. The manufacturing route adopted for the auxetic PU specimens involved a multiaxial compression of the native foam, heating of the compressed specimens above the T g of the foam polymer, and cooling under running water. Twenty specimens, divided equally between two varieties of PU-based foam, were fabricated. Two different compression ratios were used during auxetic conversion for both kinds of foam, and the same final temperature of 135°C was adopted. Tensile and compressive cyclic tests were performed in order to measure the tangent modulus (i.e. stiffness), Poisson's ratios and energy dissipated per unit volume. Remarkable differences before and after the memory effect took place were found, showing mechanical behaviour unique to each of these phases. The shape memory effect plays an important role in the mechanical behaviour of the auxetic foams.

Hydrogen-fuelled internal combustion engines are a possible solution to make transportation more ecological. Only emissions of oxides of nitrogen (NO x ) occur at high loads, being a constraint for power and efficiency optimization. A thermodynamic model of the engine cycle enables a cheap and fast optimization of engine settings. It needs to accurately predict the heat transfer in the engine because the NO x emissions are influenced by the maximum gas temperature. However, The existing engine heat transfer models in the literature are developed for fossil fuels and they have been cited to be inaccurate for hydrogen. We have measured the heat transfer inside a spark ignited engine with a thermopile to investigate the heat transfer process of hydrogen and to find the differences with a fossil fuel. This paper describes the effects of the compression ratio, ignition timing and mixture richness on the heat transfer process, comparing hydrogen with methane. A convection coefficient is used to separate the effect of the temperature difference between the gas and the wall from the influence of the gas movement and combustion. The paper shows that the convection coefficient gives more insight in the heat transfer process in a combustion engine despite the assumptions involved in its definition. The comparison between hydrogen and methane demonstrates, in contrast to what is believed, that the heat loss of hydrogen can be lower.

A previously developed one-dimensional model, based on a forward marching solution technique of the conservation equations has been used to study ejector operation and performance in a large range of refrigeration working conditions. Several important features of ejector operation characteristics were simulated. Global parameter values, their local distributions along the ejector including the temperature, the pressure and the Mach number were calculated for design and off design conditions. Operation parameters such as the entrainment ratio u, compression ratios P exit /P ev , P g /P exit and the geometric ratio (D/D c ) 2 were found to significantly affect performance. The impact of the generator, the evaporator, the condenser and related thermodynamic parameters, which have been assessed in this study, are summarized as: Fluid mixing conditions dictated by the fluid type, the mixing chamber geometry, the inlet and outlet constraints, may lead to off design operation with related stability and performance deterioration Internal superheat generation, due to inefficient mixing and normal shock waves is very important in off design operation Some degree of inlet superheat (around 5 8C) is necessary to prevent internal condensation but excess superheat is detrimental to the condenser efficiency at exit Generator pressure conditions and the evaporator temperature significantly affect ejector performance. Crown Impact des conditions de fonctionnement sur la performance d'un éjecteur supersonique dans une installation frigorifique

In this paper, a novel predictive-based lossless image compression algorithm is presented. Lossless compression must be applied when data acquisition is important and expensive, as in aerial, medical and space imaging. Besides requirements of high compression ratios as much as it is possible, lossless image coding algorithms must be fast. Proposed algorithm is developed for efficient and fast processing of 12-bit medical images. Comparison with standardized lossless compression algorithm, JPEG-LS is done on a set of 12-bit medical images with different statistical features. It is shown that proposed solution can achieve approximately same bitrates as JPEG-LS even though it is much simpler.

We propose a new still image coding technique which is a highly developed version of the renowned wavelet difference reduction (WDR). This new coder inherits the important properties from the original WDR, such as embeddedness, target compression ratio, region of interest support and the simplicity. The special treatment is performed in the significant pass by using context-based adaptable scanning order to predict the new significant coefficients. The prediction model is based on the compactness in subband coefficients and also the quadtree relation between the same orientation subbands. In binary mode, the coder is consistently better than SPIHT. A new conditional arithmetic coding (AC) using array of contexts is specifically designed for WDR-based coder. Rate-distortion results of the new coder in AC mode are superior to all other WDR-based coders in the literature and are very comparable to SPIHT-AC and JPEG2000, the best coders, at all bit rates for all images in the test set.

Free-piston engines are under investigation by a number of research groups worldwide due to their potential advantages in terms of fuel efficiency and engine emissions. Some prototypes have emerged, mainly aimed for vehicle propulsion, and have reported favourable performance compared to conventional technology. This paper describes the design of a modular compression ignition free-piston engine generator, applicable to electric power generation in large-scale systems. The development of a full-cycle engine simulation model is described, and extensive simulation results are presented, giving insight into engine operating characteristics and performance. The operating characteristics of the free-piston engine was found to differ significantly from those of conventional engines, giving potential advantages in terms of fuel efficiency and emissions formation due to fast power stroke expansion. Effects of varying engine stroke length and compression ratio were not found to give any large advantages.

Image compression has many applications. For example, it is an important step for distributed and network based pattern recognition. For real time object recognition or reconstruction, image compression can greatly reduce the image size, and hence increase the processing speed and enhance performance. Fractal image compression is a relatively recent image compression method. Its basic idea is to represent images as a fixed point of a contractive Iterated Function System (IFS). Spiral Architecture (SA) is a novel image structure on which images are displayed as a collection of hexagonal pixels. The efficiency and accuracy of image processing on SA have been demonstrated in many recently published papers. We have shown the existence of contractive IFS's through the construction of a Complete Metric Space on SA. The selection of range and domain blocks for fractal image compression is highly related to the uniform image separation specific to SA. In this paper, we will review the current research work on fractal image compression based on SA. We will compare the results obtained on SA and the traditional square structure in terms of compression ratio and PSNR.

Digital images have become an important source of information in the modern world of communication systems. In their raw form, digital images require a tremendous amount of memory. Many research efforts have been devoted to the problem of image compression in the last two decades. Two different compression categories must be distinguished: lossless and lossy. Lossless compression is achieved if no distortion is introduced in the coded image. Applications requiring this type of compression include medical imaging and satellite photography. For applications such as video telephony or multimedia applications, some loss of information is usually tolerated in exchange for a high compression ratio.

Decreasing the program size has become an important goal in the design of embedded systems target to mass production. This problem has led to a number of efforts aimed at designing processors with shorter instruction formats (e.g. ARM Thumb and MIPS16), or that can execute compressed code (e.g. IBM CodePack PowerPC). Much of this work has been directed towards RISC architectures though. This paper proposes a solution to the problem of executing compressed code on embedded DSPs. The experimental results reveal an average compression ratio of 75% for typical DSP programs running on the TMS320C25 processor. This number includes the size of the decompression engine. Decompression is performed by a state machine that translates codewords into instruction sequences during program execution. The decompression engine is synthesized using the AMS standard cell library and a 0.6m 5V technology. Gate level simulation of the decompression engine reveals minimum operation frequencies of 150MHz.

The existing techniques for electrocardiogram (ECG) data compression have been classified into three major categories, namely, direct data compression (DDC), transformation compression (TC) and parameter extraction compression (PEC). This paper deals with an efficient DDC algorithm, which has been developed over existing modified Amplitude Zone Time Epoch Coding (AZTEC) technique, named as improved modified AZTEC and tested on Common Standard for quantitative Electrocardiography (CSE) database. The performance has been evaluated on the basis of compression ratio (CR), percentroot-mean-square difference (PRD) and fidelity of the reconstructed signal. A comparison of the wavelet-derived features of compressed and original signals has been used for performance evaluation of the compressed signal. In this paper, the effect of length of least-square polynomial smoothing filters, i.e., parabolic filters, on the reconstructed signal has been analyzed. The use of 7-point parabolic filter has been found to improve the percent-root-mean-square difference (PRD), i.e. lower PRD, compared to reconstruction process of ECG signal without filter. It is also observed that the use of parabolic filters rejects high frequency noise, which is reflected in the form of reduced electromyographic noise.

The reserve of petroleum over the world is limited. It is very important to save petroleum fuels or find some substitutes. The oxygen enriched hydrogen-HHO gas was produced by the process of water electrolysis. Hydroxyl gas was produced by the electrolysis process of different electrolytes (KOH, NaOH, and NaCl) with various electrode designs in a leak proof Plexiglas reactor (hydrogen generator). This review paper presents the concern with the effectiveness of oxygen enriched hydrogen-HHO gas addition on performance and combustion characteristics of a SI engine with variable compression ratio. The effect will be shown on the SI engine of the brake thermal efficiency, un-burn hydrocarbon, NOx emission, carbon dioxide, and carbon monoxide with the use of HHO and a variable compression ratio.

The research on alternative fuels for internal combustion engine has become essential due to depletion of petroleum products and its major contribution for pollutants, where Natural gas is one of the most promising fuel alternatives for the future. Most of the BIOGAS fuelled vehicles in India are aftermarket retrofitted conversions from the existing SI engine vehicles. it is found that power produced by the BIOGAS engine is 8-14% less compare to Gasoline engine. To increase the performance of the Bi-fuel engine there are many parameter which can be optimized. One of them is ignition energy. BIOGAS because of high ignition temperature and low flame speed compare to gasoline for complete combustion higher ignition energy is required. The objective of this research is to improve engine performance and emissions of BIOGAS fuelled SI engine by optimize ignition energy. The Performance and emission both decreased when engine was made to run on BIOGAS instead of Petrol. The review of this study can contribute important data for the design and optimization of spark-ignited engine fuelled by BIOGAS for performance enhancement and emission reduction.

In this research, a gamma-type, low-temperature differential (LTD) solar Stirling engine with two cylinders was modeled, constructed and primarily tested. A flat-plate solar collector was employed as an in-built heat source, thus the system design was based on a temperature difference ...