一种测试不同温度下非饱和土土-水特征曲线的试验装置

研究目的：研制一种试验装置,以实现对非饱和土土-水特征曲线温度效应的有效测试。创新要点：1．研制了一种温控非饱和土三轴试验装置,包括加载系统、吸力控制系统和温度控制系统;2．利用研制的温控非饱和土三轴试验装置,对不同温度（25,40和60℃）以及不同应力（40100和200kPa）条件下的非饱和土土-水特征曲线进行了试验测定。研究方法：1．总结分析已有的温控三轴仪所采用的加热方式的优缺点,提出环向加热压力室内水体的方法;2．基于GDS非饱和土三轴仪,研制可实现温度控制功能的温控非饱和土三轴仪（图1、2）;3．开展不同温度及不同应力条件下非饱和土土水特征曲线的试验研究。重要结论：1．所研制的温控非饱和土三轴仪的实用效果得到验证;2．温度的升高将引起非饱和土持水性能的降低。     

蚀变岩在三向应力状态下的力学及变形特性研究

实际工程中的岩体总是处于三向应力状态下,研究三向应力状态下岩体强度和变形特性,对于岩土工程的设计施工具有重要意义。此次研究以某水电站工程项目为依托,对水电站左右坝肩的蚀变岩做了大量的常规三轴压缩试验。在此基础上,经过分析处理,得出了蚀变岩的抗剪强度指标与围压的相关关系,建立了应力-应变关系曲线的分阶段本构模型。在蚀变岩的力学特性研究方面进行了有益的探索,为工程设计和稳定性分析提供了重要的技术支撑。     

An investigation of a novel three-dimensional activity monitor to predict free-living energy expenditure

Abstract

The aim of this study was to assess the capability of the 3dNX? accelerometer to predict energy expenditure in two separate, free-living cohorts. Twenty-three adolescents and 14 young adults took a single dose of doubly labelled water and wore a 3dNX? activity monitor during waking hours for a 10-day period while carrying out their normal routines. Multiple linear regression with backward elimination was used to establish the strength of the associations between various indices of energy expenditure, physical activity counts, and anthropometric variables. 3dNX? output accounted for 27% and 35% of the variance in the total energy expenditure of the adolescent and young adult cohort, respectively. The explained variance increased to 78%, with a standard error of estimate of 7%, when 3dNX? output was combined with body composition variables. The 3dNX? accelerometer can be used to predict free-living daily energy expenditure with a standard error of estimate of 1.65 MJ in adolescents and 1.52 MJ in young adults. The inclusion of anthropometric variables reduces the error to approximately 1 MJ. Although it remains to cross-validate these models in other populations, early indications suggest that the 3dNX? provides a useful method of predicting energy expenditure in free-living individuals.     

分子点群的不可约表示

介绍了分子对称群（对称操作解）及其表示的一些基本性质，通过例子说明了群论在化学中的应用。     

RT3三轴加速度传感器测量多种类型身体活动效度研究

目的：：评价RT3三轴加速度传感器测量20种身体活动效度水平,验证其能耗预测模型精度,并试图推导精度更高的适合中国人群的能耗预测模型。方法：运用间接热量测定法,测试14名男性和16名女性共计20项活动能耗水平,测量项目包括：2mph步行、3mph步行、3mph 3%坡度斜坡行走、3mph 8%坡度斜坡行走、4mph快走、4mph 3%坡度斜坡快走、5mph慢跑、6mph中速跑、中速跳绳、快速跳绳、10mph骑自行车、13mph骑自行车、沿楼梯上楼、沿楼梯下楼、擦桌子、洗衣服、拖地、打乒乓球、上肢力量、下肢力量测试。结果：RT3三轴加速度传感器三轴矢量和、垂直轴、矢状轴、水平轴counts与实测MET的一元线性回归方程R2分别为0.63、0.62、0.59,0.46,表明RT3三轴counts对于活动均较为敏感,呈现一定程度同步变化。 RT3矢量和与垂直轴counts无论是测量步行,还是测量日常生活活动,与实测MET的一元线性回归方程的R2均一致。结论：使用三轴加速度传感器未体现明显优于单轴加速度传感器。 RT3自身能耗预测模型不适合中国人群。 RT3可以较好感应不同速度步行运动,但仍然无法感应坡度步行、上下楼运动,本研究推导的步行回归公式及常见活动回归公式预测能耗的准确度高于国外公式,但仍然存在一定误差。     

Experimental study of lightweight aggregate concrete under multiaxial stresses

Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A "plastic flow plateau" area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.