数字水准仪标尺编码原理研究

数字水准仪的标尺编码规则直接影响其测量精度.基于现有几种数字水准仪标尺编码的特点,归纳出标尺条码的编码衡量指标:信息密度、分辨率和纠错能力.以条码的最大编码容量与单个码区长度之比值衡量其承载的信息密度;利用光学系统的点扩散函数研究条码图像的分辨率,即相邻边缘的相互影响,得出码元相邻边缘的间距相等时,影响最小的结论;用相关系数或编码所用函数本身的性质表征条码的纠错能力.依据编码指标建立一套新的标尺编码规则:以格雷码为数值码,固定宽度的码元为参考码,两者交替组合.分析表明,该种编码不但信息密度大,分辨率高,而且纠错能力强.     

基于SVG的地理信息编码与DOM交互解析实现

SVG作为新兴的基于XML的矢量图形描述规范，在很多方面与地理信息系统中的基本概念表述一致。在对地理信息进行SVG编码的基础上，利用DOM对地理信息SVG编码文档进行解析，实现了基于SVG的Web地理信息发布实例。实验表明，采用SVG技术的通用性好、矢量显示质量高、响应速度快的优点来开发地理信息的Web应用，也是顺应Web地理信息发布发展需要的。     

A simple test and predictive models for assessing swell potential of Ankara (Turkey) Clay

During the past three decades, damage due to swelling action of Ankara Clay has been observed more clearly in some parts of Ankara where rapid expansion of the city led to the construction of various kinds of structures. In this study, a comprehensive research program has been conducted (i) to investigate the effect of remoulding and desiccation on the swelling behavior of Ankara Clay and its swelling anisotropy, (ii) to estimate depth of active zone, (iii) to develop a simple technique in determining the magnitude of swelling based on water content of the soaked specimen after 24 and 72 h (w_max24,72), and (iv) to produce predictive models which could be used to estimate the swelling potential of Ankara Clay from its mineralogical and simply measured engineering characteristics. A laboratory testing program was carried out using both undisturbed, and remoulded and desiccated samples selected from 20 different locations. Montmorillonite was identified as being the main clay mineral present. Based on the moisture content variation with depth, the active expansive zone was considered to be about 2 m. The test results suggest that swelling pressure of the clay considerably decreases and/or dies out when the water content is greater than 30%. It is also noted that the measured lateral swelling is significantly in excess of the vertical equivalent indicating an anisotropy with respect to swelling. Statistical assessments indicate that a new parameter (w_max24,72) from a simple test, suggested in this study, is a very strong parameter for predicting swelling parameters of Ankara Clay. Based on 60 empirical predictive equations with coefficients of correlation between 0.96 and 0.66 from multiple regression analyses, w_max24,72, methylene blue value, liquid limit, dry unit weight and smectite content are the most important index and mineralogical properties to predict the swelling parameters of Ankara clay with small deviations from the measured values.     

Experimental investigation of tsunami bore impact pressure on a perforated seawall

Catastrophic failures of many tsunami barriers along the affected coasts during the 2011 Tohoku earthquake tsunami has prompted extensive investigation into improving and revising design codes for tsunami defence structures. To date, researchers and coastal engineers are investigating to understand the failure mechanisms and to find solutions so that the structures merely remain intact in the extreme event such as tsunami. Thus, the present work is motivated to experimentally study tsunami-induced bore pressures exerted on vertical seawalls; a solid vertical wall and a porous vertical seawall that consisted of a perforated front wall and a solid rear wall. Bores with various heights and velocities were generated by using the dam-break method. A porous seawall with 20% porosity of perforated front wall was used in this study. Bore pressures exerted on the solid rear wall and chamber oscillations that occurred in the experiments were also discussed. The experimental results showed that multiple peak pressures were observed during bore run-up phase in the time series of bore impacts. A predictive equation to estimate the maximum bore pressure on a perforated seawall was developed using multiple regression analysis. The proposed equation was also compared with previous empirical formulas.     

Predicting suitable habitat for the cold-water coral Lophelia pertusa (Scleractinia)

Ecological-niche factor analysis (ENFA) was applied to the reef framework-forming cold-water coral Lophelia pertusa. The environmental tolerances of this species were assessed using readily available oceanographic data, including physical, chemical, and biological variables. L. pertusa was found at mean depths of 468 and 480 m on the regional and global scales and occupied a niche that included higher than average current speed and productivity, supporting the theory that their limited food supply is locally enhanced by currents. Most records occurred in areas with a salinity of 35, mean temperatures of 6.2–6.7  °C and dissolved oxygen levels of 6.0–6.2 ml l⁻¹. The majority of records were found in areas that were saturated with aragonite but had low concentration of nutrients (silicate, phosphate, and nitrate). Suitable habitat for L. pertusa was predicted using ENFA on a global and a regional scale that incorporated the north-east Atlantic Ocean. Regional prediction was reliable due to numerous presence points throughout the area, whereas global prediction was less reliable due to the paucity of presence data outside of the north-east Atlantic. However, the species niche was supported at each spatial scale. Predicted maps at the global scale reinforced the general consensus that the North Atlantic Ocean is a key region in the worldwide distribution of L. pertusa. Predictive modelling is an approach that can be applied to cold-water coral species to locate areas of suitable habitat for further study. It may also prove a useful tool to assist spatial planning of offshore marine protected areas. However, issues with eco-geographical datasets, including their coarse resolution and limited geographical coverage, currently restrict the scope of this approach.     

新疆前兆震群ρ值的研究

研究新疆伊宁——乌鲁木齐和乌什——库尔勒1972年以来发生的49个震群的ρ值表明,ρ<0.55可作为前兆震群的判据指标。分析了ρ<0.55标准下的前兆震群的预测能力,认为,震群序列的ρ值具有一定的预报效能。     

PREDICTIVE ABILITY OF REGRESSION MODELS.PART Ⅰ:STANDARD DEVIATION OF PREDICTION ERRORS (SDEP)

The standard deviation of prediction errors(SDEP)is used to evaluate and compare the predictive abilityof some regression models,namely MLR,ACE and linear and non-linear PLS,the last being the bestone.The parameter is determined by a cross-validation approach as an average of several runs obtainedon forming groups in a random way.The variation in SDEP with the number of latent variables in PLSis also discussed.     

公主岭市西部水源地地下水系统初步研究

本文以公主岭市西部水源地为例,以地下水系统的观点,对该区进行了全面的系统化、模型化和最优化,建立了地下水系统的预报模型和管理模型,推求了各系统的资源量及水位、水质分布规律,最后得出了该区地下水最佳开采量和取水工程方案。     

栅格电子地图的无损压缩新方法

JBIG在压缩灰度或彩色图像时,需要将图像分解为多个位面,编解码效率低而且难以利用位面之间的相关性.文章提出了RBMA方法,首先将像素值转换为引用值,然后使用多重算术编码压缩引用值,避免了位面分解.实验表明,RBMA方法与JBIG相比不仅成倍提高了编解码效率,而且提高了约40％的压缩比.GIF以一维的形式编码像素,在处理相同颜色区域时存在字典条目长度增长缓慢的问题.本文提出的LZWB方法将具有相同颜色的区域特殊编码,只输出色块的颜色、色块宽度与高度.实验表明,LZWB提高了约20％的压缩比,解码速度约为GIF的3.7倍.