长白落叶松苗木质量与造林效果关系的比较

以苗高和地径为分级标准,将长白落叶松播种苗(1-0)分成2级:Ⅰ级苗和Ⅱ级苗,将移植苗(1-1)分成3级:特级苗、Ⅰ级苗和Ⅱ级苗,以苗龄和等级为试验因子进行了根生长潜力和造林效果试验。结果表明:①1 cm新根数量（TNR1）在苗龄之间和等级之间差异均显著,说明TNR1能代表不同苗龄和等级长白落叶松苗木的发根能力,可作为评价苗木质量的活力指标。②播种苗苗高和地径生长量均大于移植苗,所有处理中移植苗特级苗的生长量和生长率最低。造林成活率依次为:移植苗和播种苗的Ⅰ级苗移植苗Ⅱ级苗播种苗Ⅱ级苗和移植苗特级苗。通过逐步多元回归分析,得出苗木形态指标与根生长潜力及生长量之间存在很强的相关性,可以用形态指标预测长白落叶松苗木的活力状况和造林后的生长表现。从造林成活率和生长量两个方面来看,再考虑到培育周期和育苗成本,造林效果最好的是移植苗Ⅰ级苗,其次是播种苗Ⅰ级苗和移植苗Ⅱ级苗。      

抚育对北京低山侧柏游憩林灌草生物多样性的影响

该文研究低山厚土阳、阴坡侧柏游憩林抚育前和抚育1年后林下灌草生物多样性的变化情况。抚育措施包括清死枝、修活枝、割灌木等。结果表明:在阳坡侧柏游憩林内,抚育后灌木的Shannon指数、Shannon均匀度指数、Simpson指数、丰富度指数升高,提高幅度在0.6%～204.2%之间,且灌木优势种的优势地位减弱;而草本层的Shannon指数、Shannon均匀度指数、Simpson指数、丰富度指数都有所降低,降低幅度在9.0%～19.7%之间,且草本层中优势种的优势地位有所加强。在阴坡侧柏游憩林内,抚育后林下灌木的丰富度指数、Shannon指数和Simpson指数分别提高83.3%、32.4%和13.9%,且灌木优势种的优势地位减弱;而草本层的丰富度指数和Shannon指数增加18.7%和2.5%,且草本优势种的优势地位有所加强。研究认为,在北京低山侧柏游憩林内进行抚育是可行的。      

利用正义RNAi技术提高玉米直链淀粉含量效果的研究

为了研究利用正义RNAi技术提高玉米直链淀粉含量效果,用基因枪法将构建的sbeⅡb正义RNAi表达载体pBAC506和pBAC508(筛选标记基因分别为35S启动子及Adh1-intron1增强驱动的epsps和bar)导入玉米(Zea mays)自交系幼胚愈伤组织,经过筛选、分化和再生获得了44株转基因当代植株,经PCR扩增、PCR-Southern检测有30株为阳性.选择9株健壮的阳性植株进行基因组Southern-blotting分析,结果表明7株T0植株整合了目的基因,其中4株整合了1个转基因拷贝,2株整合了2个转基因拷贝,1株整合了3个转基因拷贝.这7株中有2株结实,直链淀粉含量分别为23.22%和24.60%,有一定的小幅提高.下一步要进行较大规模的基因枪转化,得到比较大的转基因群体,以对更多转基因后代进行鉴定,期望筛选出外源基因多拷贝插入和直链淀粉含量大幅提高的株系.     

Study on Vibration Performance of Engineered Wood Truss Joist Floors

In recent years wood trusses are widely used in buildings due to their excellent performance and ease of construction. As with solid lumber joists, however, the vibration of wood truss joist floors can cause occupants to feel discomfort. To understand the relationship between the vibration performance of wood truss joist floors and the perceptions of occupants, experimental and subjective evaluations were conducted on six truss joist floors. The results show there is close relationship between perceptions of occupants and the fundamental natural frequency, static deflection and vibration acceleration of truss joist floors. The installation of bracings and straps greatly improved the vibration performance of light truss joist floors. We suggest that two or more factors should be included in the design criteria for controlling wood floor vibration, such as static deflection and fundamental natural frequency. Peak acceleration can be adopted as a factor in the evaluation system of vibration performance of wood truss joist floors.     

Study on Softening Constitutive Model of Malan Loess

In this paper, based on the uniaxial compression tests, consolidated undrained shear tests,consolidation drainage shear tests of Malan loess with different water contents, and based on understanding deeply of peculiar physico mechanical property of Malan     

Research on Neural Network Applied in Heat Load Control of Heat Pump System

In recent years, lots of heat pump systems have been applied for district heating. In order to insure safe and efficient running of these systems, perfect load control methods are necessary. In this paper, the load matching problem between heat pump syst     

Early Warning of Risk for Transportation Infrastructure Projects under a PPP Model

Based on characteristics of transportation infrastructure projects under a PPP model, an early warning risk index system for the private sector was put forward. The system is comprised of 15 indexes from five aspects, including risks associated with politics and law, economics, credit, construction and operation. An early warning risk model was constructed by applying fuzzy set theory and matter element theory. The fuzzy set method helps calculate the weight and evaluation values for qualitative indexes, thereby avoiding the limitations of individual decisions. The matter element method can evaluate comprehensive risks by using the comprehensive relations, is easy to use, and directly gives results. Further empirical research was conducted that verifies this method is scientific and applicable.     

Energy Consumption Features for Large scale Public Office Buildings in Greater Guangzhou, P. R. China

The annual energy consumption of representative office buildings in Guangzhou, P. R. China, was surveyed over a three year period. Among the modern office buildings surveyed, two large scale office buildings were chosen to analyze the energy consumption features and monthly energy consumption trends. Based on the actual occupied area calculation, the total annual energy consumption of the two office buildings was 149.3 kWh/m2 and 115 kWh/m2, respectively. The air conditioning energy consumption in two office buildings accounted for 49.2% and 38.5% of the total energy consumption. The research results could be used as energy consumption sub databases or references for large scale public buildings in Guangzhou due to the accurate survey technique and representativeness of the survey objects. In addition, energy consumption in these office buildings was compared with levels described in other studies. Energy saving methods are proposed for buildings located in hot summer/warm winter climate zones.     

A 3D Visco elasto plastic Finite Element Analysis of the Asphalt Pavement Rutting Deformation

Based on the dynamic action between vehicles and pavement, a simplified model of vehicle dynamic loading caused by surface evenness was established. This research made it possible to find a Asphalt Pavement Rutting Prediction method based on the theory of visco elasto plasticity which is the basic theory of the dynamics, and finite element method (FEM). Asphalt pavement rutting was calculated and predicted, and the factors influencing rutting were analyzed and calculated. The good agreement between the calculation results and the testing road data indicate that the rutting prediction method is reasonable and reliable.     

Dynamic Properties of Saturated Clay and Undisturbed Silty Clay

The apparatus for static and dynamic universal triaxial and torsional shear soil testing was employed to perform stress-controlled cyclic torsional shear testing under isotropic consolidated conditions. We conducted a dynamic torsion test of a single hollow sample to obtain its dynamic property data at different effective confining pressures with saturated clay and disturbed silty clay. The results show that the maximum dynamic shear modulus Gmax and ξ obtained from single sample of the cyclic shear test approached those of the traditional method of dynamic torsional testing. We indicate that G/Gmax～ γ andξ/ξmax ～γ of the two soils are independent of confining pressure and testing methods. Each G and ξ can be obtained from the equations we provide. Furthermore, the single sample test method can diminish the differences between the samples during experimentation and effectively provide convenience with authentic experimental results.