Accelerated generation of holograms with ultra-low memory symmetrically high-compressed look-up table

Computer-generated holography technology has been widely applied,and as research in this field deepens,the demand for memory and computational power in small AR and VR devices continues to increase.This paper presents a hologram generation method,i.e.,a symmetrically high-compressed look-up table method,which can reduce memory usage by50%.In offline computing,half of the basic horizontal and vertical modulation factors are stored,halving the memory requirements without affecting inline speed.Currently,its potential extends to various holographic applications,including the production of optical diffraction elements.

A general purpose exact Rayleigh scattering look-up table for ocean color remote sensing

The current exact Rayleigh scattering calculation of ocean color remote sensing uses the look-up table （LUT）, which is usually created for a special remote sensor and cannot be applied to other sensors. For practical application, a general purpose Rayleigh scattering LUT which can be applied to all ocean color remote sensors is generated. An adding-doubling method to solve the vector radiative transfer equation in the plane-parallel atmosphere is deduced in detail. Compared with the exact Rayleigh scattering radiance derived from the MODIS exact Rayleigh scattering LUT, it is proved that the relative error of Rayleigh scattering calculation with the adding-doubling method is less than 0.25%, which meets the required accuracy of the atmospheric correction of ocean color remote sensing. Therefore, the adding-doubling method can be used to generate the exact Rayleigh scattering LUT for the ocean color remote sensors. Finally, the general purpose exact Rayleigh scattering LUT is generated using the adding-doubling method. On the basis of the general purpose LUT, the calculated Rayleigh scattering radiance is tested by comparing with the LUTs ofMODIS, SeaWiFS and the other ocean color sensors, showing that the relative errors are all less than 0.5%, and this general purpose LUT can be applied to all ocean color remote sensors.

Preliminary Study on Broadband Resonance of Shaking Table Based on the Compressibility of Gas

In order to improve the performance of the shaking table,a vibration-enhanced shaking table which exploited broadband resonance was constructed.The broadband resonance was realized by an adjustable stiffness mechanism which exploited gas compressibility.Different from the traditional device,a gas filled cylinder(GFC)was mounted between the shake table and the exciter,and a pressure regulator was designed to regulate the gas pressure of the GFC.The natural frequency of the designed shaking table can be adjusted based on the compressibility of gas during the test.The principle of stiffness adjustment was theoretically analyzed and a series of experiments were carried out to investigate the effects of regulating the natural frequency.The experimental results indicate that the amplitude can be twice amplified and the natural frequency can be regulated between 2 0 Hz and 6 0 Hz.

Fine Doppler shift acquisition algorithm for BeiDou software receiver by a look-up table

The BeiDou software receiver uses the fast Fourier transform(FFT)to perform the acquisition.The Doppler shift estimation accuracy should be less than 500 Hz to ensure satellite signals to enter a locked state in the tracking loop.Since the frequency step is usually 500 Hz or larger,the Doppler shift estimation accuracy cannot guarantee that satellite signals are brought into a stable tracking state.The straightforward solutions consist in increasing the sampling time and using zero-padding to improve the frequency resolution of the FFT.However,these solutions intensify the complexity and amount of computation.The contradiction between the acquisition accuracy and the computational load leads us to research for a more simple and effective algorithm,which achieves fine acquisition by a look-up table.After coarse acquisition using the parallel frequency acquisition(PFA)algorithm,the proposed algorithm optimizes the Doppler shift estimation through the look-up table method based on the FFT results to improve the acquisition accuracy of the Doppler shift with a minimal additional computing load.When the Doppler shift is within the queryable range of the table,the proposed algorithm can improve the Doppler shift estimation accuracy to 50 Hz for the BeiDou B1I signal.

Performance of global look-up table strategy in digital image correlation with cubic B-spline interpolation and bicubic interpolation

Global look-up table strategy proposed recently has been proven to be an efficient method to accelerate the interpolation, which is the most time-consuming part in the iterative sub-pixel digital image correlation （DIC） algorithms. In this paper, a global look-up table strategy with cubic B-spline interpolation is developed for the DIC method based on the inverse compositional Gauss-Newton （IC-GN） algorithm. The performance of this strategy, including accuracy, precision, and computation efficiency, is evaluated through a theoretical and experimental study, using the one with widely employed bicubic interpolation as a benchmark. The global look-up table strategy with cubic B-spline interpolation improves significantly the accuracy of the IC-GN algorithm-based DIC method compared with the one using the bicubic interpolation, at a trivial price of computation efficiency.

Research of NO_(2) vertical profiles with look-up table method based on MAX-DOAS

Obtaining the vertical distribution profile of trace gas is of great significance for studying the diffusion procedure of air pollution.In this article,a look-up table method based on multi-axis differential optical absorption spectroscopy(MAX-DOAS)technology is established for retrieving the tropospheric NO_(2) vertical distribution profiles.This method retrieves the aerosol extinction profiles with minimum cost function.Then,the aerosol extinction profiles and the atmospheric radiation transfer model(RTM)are employed to establish the look-up table for retrieving the NO_(2) vertical column densities(VCDs)and profiles.The measured NO_(2) differential slant column densities(DSCDs)are compared with the NO_(2) DSCDs simulated by the atmospheric RTM,and the NO_(2) VCDs,the weight factor of NO_(2) in the boundary layer,and the boundary layer height are obtained by the minimization process.The look-up table is established to retrieve NO_(2) VCDs based on MAX-DOAS measurements in Huaibei area,and the results are compared with the data from Copernicus Atmospheric Monitoring Service(CAMS)model.It is found that there are nearly consistent and the correlation coefficient R2 is more than 0.86.The results show that this technology provides a more convenient and accurate retrieval method for the stereoscopic monitoring of atmospheric environment.

冻土区桥梁桩基础抗震试验研究现状及展望

总结了现阶段冻土区桥梁桩基础抗震试验研究的主要任务,从试验的目的、优势、设计和不足等方面对冻土三轴压缩试验、桩-冻土体系拟静力试验和地震模拟振动台试验的研究现状进行了系统的总结与分析,提出了相应的改进措施和发展方向。考虑到室内试验中桥梁桩基础-冻土相互作用体系实施难度的问题,提出了采用子结构试验方法开展冻土区桥梁抗震试验的思路。

基于邻接比特压缩表的频繁闭项集挖掘算法

频繁闭项集(Frequent Closed Items,FCI)是一种表示事物之间关联关系的有效方式,它能克服频繁项集(Frequent Items,FI)信息冗余的缺点。FCI挖掘算法研究旨在以更优的时空效率,在原始数据集中找到所有的FCI。相关研究成果重在关注时间效率的提升,但空间效率欠佳。提出一种高空间压缩率数据结构——邻接比特压缩表(Compressed Adjacency Byte table,Cab-table),将项集与交易集压缩到剔除全部0之后的比特表中,使空间高度压缩。基于此数据结构的频繁闭项集挖掘算法(Cab-Miner),采用运算栈与检索栈来实现非递归方式的频繁闭项集挖掘,相较于之前普遍采用递归方式的算法,在理论上可使空间占用率由O(L*N+M)降为O(3N)。基于公开数据集与真实数据集的实验表明,上述算法在原始数据集压缩,以及运算内存消耗上,都有较优的表现,尤其在处理真实数据集时,空间表现极佳。另外在某些属性的数据集上也表现出优越的时间效率。

Fundamental Study on Response Properties of Structures Constructed on Lunar Regolith

The Artemis Program, for constructing the lunar base, is in progress. How to design and construct architectural and civil engineering structures in the lunar environment has become an important issue. The lunar surface is covered with soft sand, called regolith, and it is required to protect lunar bases and structures, as well as internal precision equipment, against vibrational disturbances such as moonquakes and meteorite collisions. Therefore, in this study, the static and cyclic triaxial compression tests of the regolith simulant were conducted. The reference strain and equivalent damping factor of the regolith simulant were smaller compared to sandy soil on Earth. In addition, a shaking table test using model specimens was conducted on the response properties of regolith ground alone and structures set on regolith ground. The buried foundation and pile foundation notably suppressed the horizontal response attributed to the rocking component compared to a direct foundation.

小型铅芯橡胶支座剪切性能试验研究

通过对小型铅芯橡胶支座(LRB)进行剪切试验,研究了支座剪应变、压应力和加载频率对支座等效水平刚度、屈服后刚度、屈服力和等效阻尼比的影响。结果表明:随着剪应变的增大,支座的等效水平刚度和屈服后刚度减小,屈服力增大,等效阻尼比呈线性减小;随着竖向压应力的增大,支座的等效水平刚度减小,屈服后刚度呈线性减小,屈服力和等效阻尼比呈线性增大;加载频率对支座的剪切性能基本没有影响,可以忽略;100%剪应变以内,施加的剪应变和压应力没有对隔震支座造成损伤;剪应变超过100%的大变形和大压应力会使支座进入塑性,造成支座部分永久性损伤。建议根据振动台试验的工况顺序及支座在振动台试验的最大实际变形设计拟静力试验的工况。提出日本规范等效水平刚度计算公式的修正系数,并与振动台试验实测值进行对照,证明了修正后的计算公式计算精度有所提高。

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.

Color Spatial Quantization and Compression Technique Based on Palette

The method of color quantization and the technique of color spatial quantization based onKohonen neural network are presented in this paper.The later is actually a method of matrixquantization.Using Kohonen NN a palette and a codebook for color spatial quantization canbe easily obtained.Image compression techniques for digital areonautical maps must be cho-sen to allow rapid decompression and display while maximizing the compression ratio and im-age quality.The palette-based compression technique uses a palette and a codebook based onpalette for color spatial quantization as double look-up -tables,making image decompressionand display just a quick and simple process of looking up the two tables.

振动台试验用小尺寸普通叠层橡胶支座性能试验研究

为研究振动台模型试验用小尺寸普通叠层橡胶支座力学性能,设计完成静力试验和振动台试验,分析加载频率、剪应变、压应力以及振动台模拟不同地震动对小尺寸普通叠层橡胶支座水平等效刚度和等效阻尼比的影响。试验数据表明,静力试验下,加载频率在0.02~0.3Hz内变化时,对支座性能影响较小;剪应变由10%增大至250%,水平等效刚度减小,等效阻尼比先降低后趋于基本稳定,剪应变大于100%后,支座性能会发生改变;压应力由0.5σ0增大至2.5σ0,小尺寸普通叠层橡胶支座水平等效刚度呈减小趋势,等效阻尼比呈增大趋势且幅度较大;动力试验下,在弹性范围内,支座水平等效刚度和等效阻尼比随剪应变的增大线性下降,与静力试验数据结果有一定差异,说明直接使用静力试验的数据结果来预估实际小尺寸支座的性能是不准确的。

光伏直驱压缩式制冷装置对多年冻土路基热稳定性的影响

针对工程扰动引起的多年冻土退化与路基热稳定性问题,基于光伏发电技术与制冷技术,开发一种用于防治多年冻土退化的光伏直驱压缩式制冷装置,并开展现场应用测试与数值模拟研究。研究结果表明:新装置能够适应多年冻土地区的严寒环境,实现自动化运行,且装置运行期间,制冷管管壁热流密度随太阳总辐射量的增大而增大,平均热流密度为-4.1~-6.3 W/m^(2)。与普通路基相比,制冷路基的热学稳定性得到显著提升,其中,冻土人为上限随着制冷管长度与管壁热流密度的增大而提高,随着制冷管埋置深度的增大先提高后降低,而冻土升温速率则随着制冷管长度、埋深与管壁热流密度的增大而降低。基于灰色关联理论分析可知,制冷功率对人为上限影响最显著,制冷管长度的影响次之,埋置深度的影响最小;而冻土升温速率对制冷管埋置深度最敏感,制冷功率次之,制冷管长度最小,建议设计施工时优先选择更为显著的因素加以调控。

基于变换域注意力机制的压缩伪影去除的方法

图像有损压缩过程往往会导致图像质量退化,使图像出现压缩伪影。针对现有基于深度学习的方法缺乏对联合图像专家组(Joint Photographic Experts Group,JPEG)压缩算法先验信息的利用,提出一种基于变换域注意力机制的去伪影方法。该方法利用卷积神经网络在像素域和离散余弦变换(discrete cosine transform,DCT)域分别提取特征,再将双域学习的特征信息进行融合。利用量化表设计了DCT注意力机制,该模块根据DCT系数的损失程度给予各频率系数不同的权值,使网络自适应补偿量化引起的误差。于此基础上,在像素域引入通道注意力机制,从而更好地利用量化表的先验信息。在主要数据集上,提出的去伪影方法以固定的模型参数对多种质量因子的压缩图像进行伪影去除实验。实验结果表明,所提出的方法在各评价指标和主观视觉上取得较好的效果。

The establishment of crystal position look-up table for positron emission tomography with block detectors

A method has been developed to establish the crystal position look-up table for positron emission tomography with block detectors. It is based on the principle that the counts in crystal position histogram obey the Gaussian mixture model (GMM). This method has taken full consideration of the characteristics of the GMM and the detector itself. The experimental results have proved that it is simple, reliable, and universal.

CRC Look-up Table Optimization for Single-Bit Error Correction

Many communication systems use the cyclic redundancy code （CRC） technique for protecting key data fields from transmission errors by enabling both single-bit error correction and multi-bit error detection. The look-up table design is very important for the error-correction implementation. This paper presents a CRC look-up table optimization method for single-bit error correction. The optimization method minimizes the address length of the pre-designed look-up table while satisfying certain restrictions. The circuit implementation is also presented to show the feasibility of the method in the application specific integrated circuit design. An application of the optimization method in the generic framing procedure protocol is implemented using field programmable gatearrays. The result shows that the memory address length has been minimized, while keeping a very simple circuit implementation.

Device and circuit analysis of a sub 20 nm double gate MOSFET with gate stack using a look-up-table-based approach

In this paper, we explore the possibility of mapping devices designed in TCAD environment to its modeled version developed in cadence virtuoso environment using a look-up table （LUT） approach. Circuit simu- lation of newly designed devices in TCAD environment is a very slow and tedious process involving complex scripting. Hence, the LUT based modeling approach has been proposed as a faster and easier alternative in ca- dence environment. The LUTs are prepared by extracting data from the device characteristics obtained from device simulation in TCAD. A comparative study is shown between the TCAD simulation and the LUT-based alternative to showcase the accuracy of modeled devices. Finally the look-up table approach is used to evaluate the perform- ance of circuits implemented using 14 nm nMOSFET.

Accurate and fast table look-up models for leakage current analysis in 65nm CMOS technology

Novel physical models for leakage current analysis in 65 nm technology are proposed. Taking into consideration the process variations and emerging effects in nano-scaled technology, the presented models are capable of accurately estimating the subthreshold leakage current and junction tunneling leakage current in 65 nm technology. Based on the physical models, new table look-up models are developed and first applied to leakage current analysis in pursuit of higher simulation speed. Simulation results show that the novel physical models are in excellent agreement with the data measured from the foundry in the 65 nm process, and the proposed table look-up models can provide great computational efficiency by using suitable interpolation techniques. Compared with the traditional physical-based models, the table look-up models can achieve 2.5X speedup on average on a variety of industry circuits.