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1.
The parameters obtained from oedometric consolidation tests are commonly used in the development of constitutive modeling and for engineering practice. This paper focuses on the influence of the natural deposition plane orientation on oe- dometric consolidation behavior of three natural clays from the southeast coast of China. Oedometer tests were conducted on intact specimens prepared by sampling at a series of angles relative to the natural deposition plane. For each specimen, yield stress, compressibility indexes, secondary compression, and permeability coefficients were determined. The influence of the sampling angle on these properties was investigated, revealing that yield stress, compression index, swelling index, creep index, ratio of secondary compression coefficient to compression index （Cae/JCc） and permeability coefficient were all dependent to some extent on the sampling angle. These findings indicate the role of the anisotropy due to the natural deposition on the oedometric con- solidation behavior. 相似文献
2.
Model comparison is one useful approach in applications of structural equation modeling. Akaike’s information criterion (AIC) and the Bayesian information criterion (BIC) are commonly used for selecting an optimal model from the alternatives. We conducted a comprehensive evaluation of various model selection criteria, including AIC, BIC, and their extensions, in selecting an optimal path model under a wide range of conditions over different compositions of candidate set, distinct values of misspecified parameters, and diverse sample sizes. The chance of selecting an optimal model rose as the values of misspecified parameters and sample sizes increased. The relative performance of AIC and BIC type criteria depended on the magnitudes of the parameter misspecified. The BIC family in general outperformed AIC counterparts unless under small values of omitted parameters and sample sizes, where AIC performed better. Scaled unit information prior BIC (SPBIC) and Haughton's BIC (HBIC) demonstrated the highest accuracy ratios across most of the conditions investigated in this simulation. 相似文献
3.
The purpose of the current study is to examine the performance of four information criteria (Akaike's information criterion [AIC], corrected AIC [AICC] Bayesian information criterion [BIC], sample-size adjusted BIC [SABIC]) for detecting the correct number of latent classes in the mixture Rasch model through simulations. The simulation study manipulated various class-distinction features (percentages of class-variant items, magnitudes, and patterns of item difficulty differences) and mixing proportions, assuming that a mixture Rasch model with two latent classes was the true model. Unlike previous studies that showed BIC's superiority to other indices, our findings from this study suggested that the four information criteria had differential performance depending on the percentage of class-variant items and the magnitude and pattern of item difficulty differences under a two-class structure. Furthermore, the present study revealed that AICC and SABIC generally performed as good as or better than their counterparts, AIC and BIC, respectively, for the class-class structure with a sample of 3,000. 相似文献
4.
This study investigated the performance of fit indexes in selecting a covariance structure for longitudinal data. Data were simulated to follow a compound symmetry, first-order autoregressive, first-order moving average, or random-coefficients covariance structure. We examined the ability of the likelihood ratio test (LRT), root mean square error of approximation (RMSEA), comparative fit index (CFI), and Tucker–Lewis Index (TLI) to reject misspecified models with varying degrees of misspecification. With a sample size of 20, RMSEA, CFI, and TLI are high in both Type I and Type II error rates, whereas LRT has a high Type II error rate. With a sample size of 100, these indexes generally have satisfactory performance, but CFI and TLI are affected by a confounding effect of their baseline model. Akaike's Information Criterion (AIC) and Bayesian Information Criterion (BIC) have high success rates in identifying the true model when sample size is 100. A comparison with the mixed model approach indicates that separately modeling the means and covariance structures in structural equation modeling dramatically improves the success rate of AIC and BIC. 相似文献
5.
The accuracy of structural model parameter estimates in latent variable mixture modeling was explored with a 3 (sample size) × 3 (exogenous latent mean difference) × 3 (endogenous latent mean difference) × 3 (correlation between factors) × 3 (mixture proportions) factorial design. In addition, the efficacy of several likelihood-based statistics (Akaike's Information Criterion [AIC], Bayesian Information Ctriterion [BIC], the sample-size adjusted BIC [ssBIC], the consistent AIC [CAIC], the Vuong-Lo-Mendell-Rubin adjusted likelihood ratio test [aVLMR]), classification-based statistics (CLC [classification likelihood information criterion], ICL-BIC [integrated classification likelihood], normalized entropy criterion [NEC], entropy), and distributional statistics (multivariate skew and kurtosis test) were examined to determine which statistics best recover the correct number of components. Results indicate that the structural parameters were recovered, but the model fit statistics were not exceedingly accurate. The ssBIC statistic was the most accurate statistic, and the CLC, ICL-BIC, and aVLMR showed limited utility. However, none of these statistics were accurate for small samples (n = 500). 相似文献
6.
我国工业综合竞争力的省际空间差异及影响因子 总被引：2，自引：2，他引：0
我国各省区的工业显在竞争力、潜在竞争力和综合竞争力的空间格局呈现出典型的非均衡性,东西部地区之间差异非常显著。东部沿海地带工业竞争力较强,中西部地区则相对较弱。各省区的工业显在竞争力、潜在竞争力和综合竞争力在空间分布上具有相近的空间相关、空间集聚的特点。工业综合竞争力的空间格局与潜在竞争力的空间相关程度更高,二者相关系数达到0．86,说明工业潜在竞争力的空间差异对综合竞争力的影响更大。一些以重工业为主的老工业基地,尽管工业显在竞争力相对较高,但是相对于那些以资金、知识密集型的新兴产业为主的省区,潜在竞争力却非常弱。区域工业综合竞争力构成要素的因子影响程度的大小依次是：工业生产率因子、工业增加值率因子、工业产品销售率因子和工业生产要素占有率因子。 相似文献
7.
This research focuses on the problem of model selection between the latent change score (LCS) model and the autoregressive cross-lagged (ARCL) model when the goal is to infer the longitudinal relationship between variables. We conducted a large-scale simulation study to (a) investigate the conditions under which these models return statistically (and substantively) different results concerning the presence of bivariate longitudinal relationships, and (b) ascertain the relative performance of an array of model selection procedures when such different results arise. The simulation results show that the primary sources of differences in parameter estimates across models are model parameters related to the slope factor scores in the LCS model (specifically, the correlation between the intercept factor and the slope factor scores) as well as the size of the data (specifically, the number of time points and sample size). Among several model selection procedures, correct selection rates were higher when using model fit indexes (i.e., comparative fit index, root mean square error of approximation) than when using a likelihood ratio test or any of several information criteria (i.e., Akaike’s information criterion, Bayesian information criterion, consistent AIC, and sample-size-adjusted BIC). 相似文献
8.
INTRODUCTIONTheTianzilingwastelandfillbuiltin 1991toproperlydisposeofmunicipalsolidwaste(MSW)hasadesignedservicelifeof13years.Itwasfilledstagebystageatthebeginningoftheelevationof 50 .5m .Bynow ,thelandfillhasreachedthelevelof 10 2 .5m ,whichex ceedst… 相似文献
9.
改革开放三十多年来,东南沿海是中国经济发展最快、人口和财富最集中的地区,然而台风及由其引发的暴雨洪涝、滑坡/泥石流等灾害链时有发生,对区域安全构成严重威胁。尊重自然规律,与灾害风险共存的适应是以协调人类系统与自然系统关系为出发点,即人类要在充分尊重自然灾害的区域规律基础上,合理调适自身行为,实现"与风险共存"的可持续发展。具体的适应行为又可分为工程性和非工程两大类,工程性适应侧重防灾减灾工程(如海堤、水库)等能力建设,非工程性适应侧重减灾组织体系和运行机制建设(如分区分时的人员转移安置,灾害分级响应和纵横协调,多主体风险共担等)。综上各项工程和非工程性适应对策,有助于大大提升区域灾害风险防范和综合适应能力,有效减轻东南沿海台风灾害链损失。 相似文献
10.
西部大开发给西部民族地区的教育事业带来了前所未有的发展机遇,学校体育教育也随着基础教育的深化改革取得了长足的进步,但与沿海一带发达地区相比还存在着较大差距.其中,体育意识薄弱,体育经费不足,场地器材等体育设施缺乏,以及体育师资数量不足、专业水平较低等,是制约边疆民族地区中、小学体育教育发展的主要因素.笔者通过大量的碉研和实践,提出了在边疆民族地区中、小学体育教学中融入民族民间体育内容,以利用本地资源因地制宜的教学思路,以供大家参考. 相似文献
11.
尚东玲 《五邑大学学报(社会科学版)》2003,5(2):55-58
鸦片战争爆发后，清朝内外局势发生重大变化。以李鸿章为代表的洋务派认为，面对“变局”形势，中国应该大力开展以近代化海军与海防设施为中心的海防建设，其“变局”观的发展与清朝海防建设的实施有重要的因果关系。 相似文献
12.
选择内江市交通绿地（林地、灌丛、草地）为研究对象,通过对土壤干筛团聚含量、土壤机械组成、土壤水稳性指数（K值）、土壤抗蚀性指数S（％）等指标的测定和分析,研究了城市交通绿地土壤的抗蚀性能.结果表明,三种城市绿地土壤抗蚀性强弱不同,但都随时间的延长呈下降趋势,并且三种模式下土壤抗蚀指数都随浸水时间（t）呈三次函数曲线变化（R2＞0.9684）;其中相关分析得出水稳性指数与粘粒、物理性粘粒、＞0.25 mm粒径、2～5 mm粒径、5～7 mm粒径呈正相关关系,与粗粉粒、砂粒、0.25～0.5 mm粒径、0.5～1 mm粒径表现出负相关趋势,这说明土壤团聚体大粒径、机械组成粘粒和物理性粘粒含量越少,土壤水稳性指数越大,抗蚀性能越强.抗蚀性能强弱由大到小为：草地＞灌丛＞林地. 相似文献
13.
INTRODUCTIONSoftsoilsarewidelydistributedinChinasco-astalareas.The1985earthquakethatinflictedgreatdamagetoMexicoCitysitedonsoftsoilfounda-tionsgreatlyattractedattentionofresearchersandengineersandmovedthemtostudythedynamicpropertiesofsoftsoils.Manyresearcheshavebeendedicatedtothestudyofdynamicpropertiesofsoftsoils.InChina,deepcementmixingmethodshavebeenwidelyusedinthecoastalareas.Theme-chanicalpropertiesofthesecompositefoundationsoilsarenotthesameasthatofundisturbedsoftsoilsorotherkinds… 相似文献
14.
秦文淑 《广东轻工职业技术学院学报》2007,6(4):13-17
粘土矿物因其独特的性质而广泛应用于各个领域.通过不同方法对粘土进行改性,最大程度地利用其优异性能,可应用于环保、建材及医药等领域中.本文主要介绍了几类常见的粘土改性方法,并针对膨润土、凹凸棒石、海泡石、坡缕石等粘土矿物在环保及其他领域中的应用研究现状作了综述,对其潜在的研究前景作了讨论. 相似文献
15.
彭连清 《温州大学学报(社会科学版)》2008,21(5)
利用区域间投入产出表的基本流量数据,采用Miller-Round模型测算了东部沿海地区的区域内乘数效应及其与国内各区域相互溢出效应。结果显示,东部沿海对国内其他区域的溢出效应大,发挥着引领全国经济的火车头作用;从国内其他区域获得的溢出效应更大,在区际经济联系中得到更大的收益;外溢效应更多被中部和北部沿海、南部沿海地区所吸收,对经济落后的西北、西南区域的溢出效应较小,但是西北、西南区域对东部沿海地区的溢出效应却较大。 相似文献
16.
高等教育与区域发展-以"首都教育"为视角的考察 总被引：11，自引：0，他引：11
吴志攀 《北京大学教育评论》2003,1(4):68-77
高等教育与区域发展具有相关性 ,我国经济发展呈现区域化趋势 ,沿海地区展开教育资源竞争 ,以此带动人才战略、技术升级和产业换代及文化发展。在以知识为基础的经济背景下 ,教育被列入第三产业 ,高等教育的发展有可能也有必要与区域经济发展相结合 ,研究北京地区高教发展的有利与不利条件以及高教向边缘发展 ,向沿海发展 ,向企业教育和民办教育发展的趋势。高等教育发展正面临着新一轮资源配置 ,高等教育走廊和远距离校区就是资源重新配置的表现。可以看出高等教育与区域经济发展 ,以及与交通及通讯事业发展的相关性比以往任何时候都更加突出 相似文献
17.
将混沌现象和邻域细化搜索策略应用于实数编码遗传算法(RCGA)中,提出了一种改进的RCGA。并将该算法应用于连续函数优化求解。与其他方法相比,表明该算法可靠且算法效率更高。 相似文献
18.
The study of measurement invariance in latent profile analysis (LPA) indicates whether the latent profiles differ across known subgroups (e.g., gender). The purpose of the present study was to examine the impact of noninvariance on the relative bias of LPA parameter estimates and on the ability of the likelihood ratio test (LRT) and information criteria statistics to reject the hypothesis of invariance. A Monte Carlo simulation study was conducted in which noninvariance was defined as known group differences in the indicator means in each profile. Results indicated that parameter estimates were biased in conditions with medium and large noninvariance. The LRT and AIC detected noninvariance in most conditions with small sample sizes, while the BIC and adjusted BIC needed larger sample sizes to detect noninvariance. Implications of the results are discussed along with recommendations for future research. 相似文献
19.
Conclusion Novel polymer/clay nanocomposites can be prepared by varying two parameters; first by optimizing polymer to clay ratio and
second by varying the processing techniques. An exploration in making the polymer/clay nanocomposites with different clays,
surfactants and polymers is a continuing subject of research and interest to both academia and industry. 相似文献
20.
闫存庭 《伊犁师范学院学报》2007,1(4):36-40
一提到近代中国的海防和塞防,人们不禁会想到左宗棠和李鸿章。但是,对近代中国海防和塞防作出重大贡献的当属枢臣文祥。同治、光绪年间正值中国处于内忧外患之际,他既主张重视海防建设,同时又力挺左宗棠西征。建立了中国第一支近代意义上的海军,又顺利收复了新疆,维护了中国的主权和领土完整。 相似文献