Comparative Analysis of Equal and Unequal Grounding Grid Configurations by Compression Ratio and Least Square Curve Fitting Techniques

The primary aim of the power system grounding is to safeguard the person and satisfying the performance of the power systemtomaintain reliable operation.With equal conductor spacing grounding grid design,the distribution of the current in the grid is not uniform.Hence,unequal grid conductor span in which grid conductors are concentrated more at the periphery is safer to practice than equal spacing.This paper presents the comparative analysis of two novel techniques that create unequal spacing among the grid conductors:the least-square curve fitting technique and the compression ratio techniquewith equal grid configuration for both square and rectangular grids.Particle Swarm Optimization(PSO)is adopted for finding out one optimal feasible solution among many feasible solutions of equal grid configuration for both square and rectangular grids.Comparative analysis is also carried out between square and rectangular grids using the least square curve fitting technique as it results in only one unequal grid configuration.Simulation results are obtained by theMATLAB software developed.Percentage of improvement in ground potential rise,step voltage,touch voltage,and grid resistancewith variation in compression ratios are plotted.

Effect of compression ratio on microstructure evolution of Mg−10%Al−1%Zn−1%Si alloy prepared by SIMA process

A new Mg−10%Al−1%Zn−1%Si alloy with non-dendritic microstructure was prepared by strain induced melt activation(SIMA)process.The effect of compression ratio on the evolution of semisolid microstructure of the experimental alloy was investigated.The results indicate that the average size ofα-Mg grains decreases and spheroidizing tendency becomes more obvious with the compression ratios increasing from 0 to 40%.In addition,the eutectic Mg2Si phase in the Mg−10%Al−1%Zn−1%Si alloy transforms completely from the initial fishbone shape to globular shape by SIMA process.With the increasing of compression ratio,the morphology and average size of Mg2Si phases do not change obviously.The morphology modification mechanism of Mg2Si phase in Mg−10%Al−1%Zn−1%Si alloy by SIMA process was also studied.

Simulation Research on the Effect of Cooled EGR, Supercharging and Compression Ratio on Downsized SI Engine Knock

Knock in spark-ignition（SI） engines severely limits engine performance and thermal efficiency. The researches on knock of downsized SI engine have mainly focused on structural design, performance optimization and advanced combustion modes, however there is little for simulation study on the effect of cooled exhaust gas recirculation（EGR） combined with downsizing technologies on SI engine performance. On the basis of mean pressure and oscillating pressure during combustion process, the effect of different levels of cooled EGR ratio, supercharging and compression ratio on engine dynamic and knock characteristic is researched with three- dimensional KIVA-3V program coupled with pressure wave equation. The cylinder pressure, combustion temperature, ignition delay timing, combustion duration, maximum mean pressure, and maximum oscillating pressure at different initial conditions are discussed and analyzed to investigate potential approaches to inhibiting engine knock while improving power output. The calculation results of the effect of just cooled EGR on knock characteristic show that appropriate levels of cooled EGR ratio can effectively suppress cylinder high-frequency pressure oscillations without obvious decrease in mean pressure. Analysis of the synergistic effect of cooled EGR, supercharging and compression ratio on knock characteristic indicates that under the condition of high supercharging and compression ratio, several times more cooled EGR ratio than that under the original condition is necessarily utilized to suppress knock occurrence effectively. The proposed method of synergistic effect of cooled EGR and downsizing technologies on knock characteristic, analyzed from the aspects of mean pressure and oscillating pressure, is an effective way to study downsized SI engine knock and provides knock inhibition approaches in practical engineering.

A SPARSITY AND COMPRESSION RATIO JOINT ADJUSTMENT METHOD FOR COLLABORATIVE SPECTRUM SENSING

Spectrum sensing is the fundamental task for Cognitive Radio (CR). To overcome the challenge of high sampling rate in traditional spectral estimation methods, Compressed Sensing (CS) theory is developed. A sparsity and compression ratio joint adjustment algorithm for compressed spectrum sensing in CR network is investigated, with the hypothesis that the sparsity level is unknown as priori knowledge at CR terminals. As perfect spectrum reconstruction is not necessarily required during spectrum detection process, the proposed algorithm only performs a rough estimate of sparsity level. Meanwhile, in order to further reduce the sensing measurement, different compression ratios for CR terminals with varying Signal-to-Noise Ratio (SNR) are considered. The proposed algorithm, which optimizes the compression ratio as well as the estimated sparsity level, can greatly reduce the sensing measurement without degrading the detection performance. It also requires less steps of iteration for convergence. Corroborating simulation results are presented to testify the effectiveness of the proposed algorithm for collaborative spectrum sensing.

A numerical investigation into the effect of altering compression ratio, injection timing, and injection duration on the performance of a diesel engine fuelled with diesel-biodiesel-butanol blend

Using renewable fuels for diesel engines can reduce both air pollution and dependence on fossil fuels.A computer simulation was constructed to predict the performance,combustion characteristics,and NOx emissions of a diesel engine fuelled with diesel-biodiesel-butanol blends.The simulation was validated by comparing the modelling results against experimental data and a good agreement between the results was found.The fuels used for the validation were diesel(B0),biodiesel(B100),diesel-biodiesel blend(B50),and two diesel-biodiesel-butanol blends with 45%diesel-45%biodiesel-10%butanol(Bu10)and 40%diesel-40%biodiesel-20%butanol(Bu20)by volume.Experimental results showed that the addition of butanol reduced NOx emissions but deteriorated the engine performance.The aim of the current work was the numerical optimization of the different parameters to enhance the engine performance while using butanol to decrease NOx emissions.The engine compression ratio(CR)varied from 14 to 24,in increments of 2.Fuel injection timing(IT)was reduced from 30°before top dead centre(bTDC)to 5°bTDC in increments of 5°.Also,the fuel injection duration(IDur)was extended from 20°to 50°in increments of 10°.Results showed that the increase in the CR improved engine performance for the two investigated fuels,Bu10 and Bu20.The maximum engine brake power(BP),thermal efficiency(BTE),and minimum brake-specific fuel consumption(BSFC)of 1.46 kW,32.3%,and 0.273 kg/kWh respectively,were obtained when the Bu10 fuel was injected under the optimum conditions of 24 CR,15°bTDC IT,and 40°IDur.Under these optimum conditions,the BP,BTE,and BSFC improved by 3%-3.5%for Bu10 and Bu20 fuel blends compared with the base engine conditions of a CR of 22,30°IDur,and 10°bTDC IT.The heat release rate during the premixed phase increased when the IT was advanced,while the mixing-controlled combustion phase was enhanced when the IT was reduced.NOx emissions increased with increasing CR,while both an increase in IDur at constant IT and the reduction of the IT decreased the engine NOx emissions.Under the optimum conditions,the NOx emissions for Bu10 and Bu20 were further decreased by 2.2%and 0.9%,respectively,compared with the experimental results under base engine conditions.Reducing the IT from 15°to 5°bTDC at a CR of 24 and IDur of 40°caused the NOx emissions for Bu10 and Bu20 to decrease by 16%.When the IDur was increased from 20°to 50°at a CR of 24 and an IT of 15°bTDC,the NOx emissions for Bu10 and Bu20 decreased by 12.3%and 11.8%,respectively.The addition of butanol to the diesel-biodiesel blend under optimum conditions showed results that were comparable to those of pure diesel,with a decrease in NOx emissions.

Quantitative Comparative Study of the Performance of Lossless Compression Methods Based on a Text Data Model

Data compression plays a key role in optimizing the use of memory storage space and also reducing latency in data transmission. In this paper, we are interested in lossless compression techniques because their performance is exploited with lossy compression techniques for images and videos generally using a mixed approach. To achieve our intended objective, which is to study the performance of lossless compression methods, we first carried out a literature review, a summary of which enabled us to select the most relevant, namely the following: arithmetic coding, LZW, Tunstall’s algorithm, RLE, BWT, Huffman coding and Shannon-Fano. Secondly, we designed a purposive text dataset with a repeating pattern in order to test the behavior and effectiveness of the selected compression techniques. Thirdly, we designed the compression algorithms and developed the programs (scripts) in Matlab in order to test their performance. Finally, following the tests conducted on relevant data that we constructed according to a deliberate model, the results show that these methods presented in order of performance are very satisfactory:- LZW- Arithmetic coding- Tunstall algorithm- BWT + RLELikewise, it appears that on the one hand, the performance of certain techniques relative to others is strongly linked to the sequencing and/or recurrence of symbols that make up the message, and on the other hand, to the cumulative time of encoding and decoding.

Improvement of engine performance with high compression ratio based on knock suppression using Miller cycle with boost pressure and split injection

In theory,high compression ratio has the potential to improve the thermal efficiency and promote the power output of the SI engine.However,the application of high compression ratio is substantially limited by the knock in practical working process.The objective of this work is to comprehensively investigate the application of high compression ratio on a gasoline engine based on the Miller cycle with boost pressure and split injection.In this work,the specific optimum strategies for CR10 and CR12 were experimentally investigated respectively on a single cylinder DISI engine.It was found that a high level of Miller cycle with a higher boost pressure could be used in CR12 to achieve an effective compression ratio similar to CR10,which could eliminate the knock limits at a high compression ratio and high load.To verify the advantages of the high compression ratio,the fuel economy and power performance of CR10 and CR12 were compared at full and partial loads.The result revealed that,compared with CR10,a similar power performance and a reduced fuel consumption of CR12 at foil load could be achieved by using the strong Miller cycle and split injection.At partial load,the conditions of CR12 had very superior fuel economy and power performance compared to those of CR10.

Transmission ratio (T_n) in the radian direction normal to joints in 2-D compressional wave propagation in rock masses

The transmission ratio along the radian direction normal to the joints was studied in the Universal Distinct Element Code （UDEC）. The variation of the transmission ratio with the ratio of joint spacing to wavelength was generalized into a general curve, which was determined by two critical points. The relationship between the two critical points and the affecting factors, quantity of joints and the normalized normal stiffness of joints, were obtained. A prediction model of the transmission ratio in the radian direction normal to the joints was proposed. The proposed model was applied to a field explosion test. The estimated values of the peak particle velocity from the prediction model were compared with the field records. The comparisons showed that the prediction model of the transmission ratio in the direction normal to the joints in the process of 2-D compressional wave propagation through multiple parallel joints is reliable.

Application Research of Image Compression Technology in Monitoring System of Rape Crop in Areas of Qinling Mountains

[Objective] The aim was to present a proposal about a new image compression technology, in order to make the image be able to be stored in a smaller space and be transmitted with smaller bit rate on the premise of guaranteeing image quality in the rape crop monitoring system in Qinling Mountains. [Method] In the proposal, the color image was divided into brightness images with three fundamental colors, followed by sub-image division and DCT treatment. Then, coefficients of transform domain were quantized, and encoded and compressed as per Huffman coding. Finally, decompression was conducted through inverse process and decompressed images were matched. [Result] The simulation results show that when compression ratio of the color image of rape crops was 11.972 3∶1, human can not distinguish the differences between the decompressed images and the source images with naked eyes; when ratio was as high as 53.565 6∶1, PSNR was still above 30 dD,encoding efficiency achieved over 0.78 and redundancy was less than 0.22. [Conclusion] The results indicate that the proposed color image compression technology can achieve higher compression ratio on the premise of good image quality. In addition, image encoding quality and decompressed images achieved better results, which fully met requirement of image storage and transmission in monitoring system of rape crop in the Qinling Mountains.

基于XGBoost算法的v_(P)/v_(S)预测及其在储层检测中的应用

鄂尔多斯盆地碳酸盐岩地层蕴含着丰富的油气资源。在勘探实践中发现,大牛地气田马家沟组断层发育、断距小,类型多样且成因复杂,给勘探、开发带来了较多挑战。为了应对这些挑战,提高储层预测的精度变得至关重要。在分析大牛地气田敏感弹性参数的基础上,建立地震属性与储层纵横波速度比(v_(P)/v_(S))的关系,提出一种基于XGBoost算法的地震多属性v_(P)/v_(S)预测方法。为了进一步提升XGBoost算法的预测精度和泛化能力,采用贝叶斯算法对XGBoost算法的超参数进行优化,从而找到最佳的超参数组合,以确保模型在训练集和测试集上的性能均能得到提升。将XGBoost算法应用于Marmousi 2模型进行横波速度预测,预测值与实际值相关系数超过0.88,而均方误差、平均绝对百分比误差分别低于6.55×10^(-7)和4%,验证了该方法的准确性和可靠性。在鄂尔多斯盆地大牛地气田,应用该方法获得的v_(P)/v_(S)成功识别出含气储层,结果与实际钻井数据一致。理论模型和实际数据应用结果表明,XGBoost作为一种强大的机器学习算法预测精度较高,为直接由叠后地震属性预测v_(P)/v_(S)提供了一种有效的途径。

An underwater acoustic data compression method based on compressed sensing

The use of underwater acoustic data has rapidly expanded with the application of multichannel, large-aperture underwater detection arrays. This study presents an underwater acoustic data compression method that is based on compressed sensing. Underwater acoustic signals are transformed into the sparse domain for data storage at a receiving terminal, and the improved orthogonal matching pursuit(IOMP) algorithm is used to reconstruct the original underwater acoustic signals at a data processing terminal. When an increase in sidelobe level occasionally causes a direction of arrival estimation error, the proposed compression method can achieve a 10 times stronger compression for narrowband signals and a 5 times stronger compression for wideband signals than the orthogonal matching pursuit(OMP) algorithm. The IOMP algorithm also reduces the computing time by about 20% more than the original OMP algorithm. The simulation and experimental results are discussed.

Time Synchronized Velocity Error for Trajectory Compression

Nowadays,distance is usually used to evaluate the error of trajectory compression.These methods can effectively indicate the level of geometric similarity between the compressed and the raw trajectory,but it ignores the velocity error in the compression.To fill the gap of these methods,assuming the velocity changes linearly,a mathematical model called SVE(Time Synchronized Velocity Error)for evaluating compression error is designed,which can evaluate the velocity error effectively,conveniently and accurately.Based on this model,an innovative algorithm called SW-MSVE(Minimum Time Synchronized Velocity Error Based on Sliding Window)is proposed,which can minimize the velocity error in trajectory compression under the premise of local optimization.Two elaborate experiments are designed to demonstrate the advancements of the SVE and the SW-MSVE respectively.In the first experiment,we use the PED,the SED and the SVE to evaluate the error under four compression algorithms,one of which is the SW-MSVE algorithm.The results show that the SVE is less influenced by noise with stronger performance and more applicability.In the second experiment,by marking the raw trajectory,we compare the SW-MSVE algorithm with three others algorithms at information retention.The results show that the SW-MSVE algorithm can take into account both velocity and geometric structure constraints and retains more information of the raw trajectory at the same compression ratio.

A Novel Scheme for Compression of Cash Images

In the field of economy, there are more and more electronic scanning cash images, which need to be compressed in a higher compression ratio. This paper proposes a specific compression algorithm for cash images. First, according to cash image characteristics and standard JPEG （joint photographic experts group） compression, image re-ordering techniques are analyzed, and the method of modifying some blocks into single color blocks is adopted. Then, a suitable quantization table for cash images is obtained. Experimental results show that the method is effective.

Efficient Data Compression of ECG Signal Based on Modified Discrete Cosine Transform

This paper introduced an efficient compression technique that uses the compressive sensing(CS)method to obtain and recover sparse electrocardiography(ECG)signals.The recovery of the signal can be achieved by using sampling rates lower than the Nyquist frequency.A novel analysis was proposed in this paper.To apply CS on ECG signal,the first step is to generate a sparse signal,which can be obtained using Modified Discrete Cosine Transform(MDCT)on the given ECGsignal.This transformation is a promising key for other transformations used in this search domain and can be considered as the main contribution of this paper.A small number of wavelet components can describe the ECG signal as related work to obtain a sparse ECGsignal.Asensing technique for ECGsignal compression,which is a novel area of research,is proposed.ECG signals are introduced randomly between any successive beats of the heart.MIT-BIH database can be represented as the experimental database in this domain of research.TheMIT-BIH database consists of various ECG signals involving a patient and standard ECG signals.MATLAB can be considered as the simulation tool used in this work.The proposed method’s uniqueness was inspired by the compression ratio(CR)and achieved by MDCT.The performance measurement of the recovered signal was done by calculating the percentage root mean difference(PRD),mean square error(MSE),and peak signal to noise ratio(PSNR)besides the calculation of CR.Finally,the simulation results indicated that this work is one of the most important works in ECG signal compression.

A New Approach Based on Set Partitioning in Hierarchical Tree Algorithm for Image Compression

In this paper, the authors propose a new approach to image compression based on the principle of Set Partitioning in Hierarchical Tree algorithm （SPIHT）. Our approach, the modified SPIHT （MSPIHT）, distributes entropy differently than SPIHT and also optimizes the coding. This approach can produce results that are a significant improvement on the Peak Signal-to-Noise Ratio （PSNR） and compression ratio obtained by SPIHT algorithm, without affecting the computing time. These results are also comparable with those obtained using the Embedded Zerotree Wavelet （EZW） and Joint Photographic Experts Group 2000 （JPG2） algorithms.

Medical Image Compression Using Wrapping Based Fast Discrete Curvelet Transform and Arithmetic Coding

Due to the development of CT (Computed Tomography), MRI (Magnetic Resonance Imaging), PET (Positron Emission Tomography), EBCT (Electron Beam Computed Tomography), SMRI (Stereotactic Magnetic Resonance Imaging), etc. has enhanced the distinguishing rate and scanning rate of the imaging equipments. The diagnosis and the process of getting useful information from the image are got by processing the medical images using the wavelet technique. Wavelet transform has increased the compression rate. Increasing the compression performance by minimizing the amount of image data in the medical images is a critical task. Crucial medical information like diagnosing diseases and their treatments is obtained by modern radiology techniques. Medical Imaging (MI) process is used to acquire that information. For lossy and lossless image compression, several techniques were developed. Image edges have limitations in capturing them if we make use of the extension of 1-D wavelet transform. This is because wavelet transform cannot effectively transform straight line discontinuities, as well geographic lines in natural images cannot be reconstructed in a proper manner if 1-D transform is used. Differently oriented image textures are coded well using Curvelet Transform. The Curvelet Transform is suitable for compressing medical images, which has more curvy portions. This paper describes a method for compression of various medical images using Fast Discrete Curvelet Transform based on wrapping technique. After transformation, the coefficients are quantized using vector quantization and coded using arithmetic encoding technique. The proposed method is tested on various medical images and the result demonstrates significant improvement in performance parameters like Peak Signal to Noise Ratio (PSNR) and Compression Ratio (CR).

Investigation on Emission and Combustion with 100% Palm Kernel Methyl Ester as Fuel on VCR-DI-Diesel Engine

Methyl or ethyl esters of vegetable oils are the reliable alternative fuels for the petroleum diesel, because their properties are very nearer to the petroleum diesel. But the flash point and auto-ignition temperatures are very high for these esters. CR （compression ratio） is one of the parameter which influences the atomization and vaporization of fuel. It is also caused for improvement in the turbulence which leads to better combustion. In this work the single cylinder diesel engine was tested at different compression ratios i.e. 16.5：1, 17.5：1, 18.5：1, 19：1 with palm kernel methyl ester without modifications. On increasing compression ratio closeness of molecules of air increases and fuel is injected into that air caused for better combustion. The inbuilt oxygen of methyl or ethyl ester will participate in the combustion and causes for reduction of HC and CO. Better compression ratio for an engine with particular fuel provides satisfactory thermal efficiency and less environmental pollution. In the investigations, for palm kernel methyl ester, 18.5：1 compression ratio is preferable on single cylinder Dl-diesel engine.

长庆气田榆林区山2段砂岩气藏的AVO分析

AVO分析方法是利用地震反射波振幅与炮检距的关系来识别岩性、检测油气的一种地震技术。它充分利用地震采集中的多种信息 ,进行资料处理与分析 ,对于岩性勘探有很好的帮助。鄂尔多斯盆地上古生界下二叠统山西组含气砂岩主要属湖相三角洲平原分流河道沉积 ,是一种具低孔低渗和高阻抗特征的岩性气藏。在岩性处理解释上 ,很难区分含气砂岩和致密砂岩。引入AVO处理分析方法 ,利用不同岩性泊松比差异所形成的AVO特征响应 ,可以有效区分地震高阻抗层的岩性及含气性 ,部分避免了地震岩性解释上的陷阱。在长庆气田榆林区山西组山 2段高阻抗砂岩气藏的勘探开发中 ,应用高保真的CDP道集资料进行AVO处理分析 ,提高了天然气钻井的成功率 ,取得了较好的应用效果。

应用声波全波列测井计算裂缝性含气储层参数

裂缝性气层的解释目前仍存在许多困难 ,主要原因是测井特征微弱 ,不易识别。在文献总结的基础上 ,采用纵波首波幅度比值法、合成横波时差重叠法、纵横波速度比法、等效弹性模量差比法和三孔隙度重叠法等方法定性识别气层 ,其目的在于通过突出气层的测井特征来识别气层。引入弹性模量差比计算含气饱和度 ,并用一口井的核磁测井差谱结果进行了对比验证。没有横波资料的井 ,通过引入纵、横波地区经验关系来获得横波。应用提取的斯通利波也可以计算渗透率。某油田 7口井的处理结果与地质实际吻合 ,表明这种方法切实可行 ,可以全面评价裂缝性气层。

文安地震前后首都圈分区波速比时变特征

2006年7月4日在首都圈数字地震台网的中南部发生了河北文安MS5.1地震.此次地震为该数字地震台网2002年投入运行以来发生的最强地震事件.本文利用多台和达法,分析处理了首都圈107个数字地震台站2002—2007年判读的大量震相数据.为提高波速比计算的精度和稳定性,对波速比计算环境和条件进行了多方面限定.例如,地震发生位置相对集中,台站选取范围有限,参与计算到时数据在5个以上,以及线性拟合精度高、误差低等.经这些限定条件后的研究发现,文安地震前,在文安和唐山附近地区地震波速比出现正常—降低—恢复—发震的异常演变过程.震前1年,出现波速比较明显降低过程,异常持续时间1年左右;同期邢台、京西北、京西南、京津和北京地区波速比的变化则基本平稳.文安地震发生后,文安和唐山地区的波速比恢复正常的平稳变化状态.通过波速比计算结果的误差和稳定性分析认为,文安地震前在文安和唐山附近地区地震波速比异常是可信的.