INTERACTIVE EFFECTS OF ELEVATED CO2 AND SALINITY ON THREE

poster abstractAtmospheric carbon dioxide (CO2) has increased steadily since Pre-Industrial times. The need for a better understanding of the effects of ele-vated CO2 on plant physiology is clear, particularly in the context of other changes and stresses. Previous studies have focused on how plants are af-fected by either elevated CO2 or salinity, one of many plant stresses. How-ever, little is known about the interaction of these two factors on plant growth. In my project, plants were exposed to both elevated CO2 and salini-ty, so that the effects of either factor and the interaction of the two on common grass species could be examined. Three grass species were sub-jects for my experiment. Kentucky bluegrass (Poa pratensis L.) and red fes-cue (Festuca rubra L.), both C3 cool season grasses, as well as buffalo grass(Buchloe dactyloides (Nutt.)Engelm.), a C4 warm season grass, were studied. The CO2 levels were set to 400 μmol mol-1, close to the current concentration, or 760 μmol mol-1, projected to be reached by the end of this century. The salt concentrations were 0, 25, 50, 75, and 100 mM NaCl with CaCl2 added at lower rates (1% of each respective molarity for NaCl). Five replicates per treatment (a total of 150 pots) were grown for 100 days. My results demonstrated stimulated growth at elevated CO2 and inhibited growth with increasing salinity. Collection and statistical analysis of data for variance is being performed to determine which, if any, of the fixed factors had significant effects on the given parameters. My results will improve the understanding of plant responses to multiple environmental changes in the future

Calculation for Moment Capacity of Beam-to-Upright Connections of Steel Storage Pallet Racks

Steel storage pallet rack structures are three-dimensional framed structures, which are widely used to store different kinds of goods. For the easy accessibility to stored products, pallet racks are not usually braced in the down-aisle direction. The down-aisle stability is mostly provided by the characteristics of beam-to-upright connections, and the characteristics of upright base connections. In this paper, calculation for moment capacity of beam-to-upright connections is carried out. A mechanical model is presented firstly. Based on the model, moment capacity is related to the failure capacity, directly determined by the failure mode, of the topmost tab of the beam-end-connector and the corresponding upright wall. Different methods to predict the failure capacity are derived for two types of failure modes, i.e. crack of tab and crack of upright wall. The new method has shown a satisfactory agreement with experimental results demonstrating the reliability of the model in predicting the moment capacity of beam-to-upright connections

Relay Selection Considering Successive Packets Transmission in Cooperative Communication Networks

Relay selection has been regarded as an effective method to improve the performance of cooperative communication system. However, frequent operation of relay selection can bring enormous control message overhead and thereby decrease the performance of cooperative communication. To reduce the relay selection frequency, in this paper, we propose a relay selection scheme to choose the best relay with considering successive packets transmission. In this scheme, according to the length of data packet, data transmission rate and the estimated channel state information (CSI), the best relay is selected to maximize the number of successive packets transmission under the condition that the given symbol-error-rate (SER) is kept. Finally, numerical results show that the proposed relay selection scheme can support the operation of successive packets transmission in cooperative wireless networks and that the maximum number of successive packets transmission is affected by the different network parameters, i.e., data transmission rate, packet length and Doppler frequency at one relay node

Experimental Analysis of Beam-to-upright Connections in Cold-formed Steel Storage Pallet Racks

A research program is currently in progress at Department of Building Engineering of Tongji University with the aim of investigating the behavior of cold-formed steel storage pallet racks under static and dynamic loading. This paper presents preliminary experimental analysis on the monotonic behavior of beam-to-upright connections. In the experimentation, the set-up was specially designed to accommodate precise requirement of boundary conditions and the measurement method was refined from the general ones used in rack design codes. It is shown that deformation modes of the connections were similar before failure while the failure modes were different depending on the specific constructional details. Moment-rotation characteristic curves are obtained and compared. On the base of these curves, the main parameters controlling the stiffness and moment capacity of connections, such as thickness of upright section, depth of pallet beam section, construction of beam end connector (mainly the number of tabs) and the loading direction are discussed

Implication of Climate Change Induced Variation in Wind Extremes on Wind Farm in Mountainous Area of Central China—A Case Study of Hengshan

AbstractWind load is critical to the safety of wind turbines. Wind turbines are designed according to the referrence wind speed of 50-year recurrence interval. The climate change induced variation in extremes of wind could impact safety of wind turbines. Meteorological data from Hengshan weather station in central China is investigated. The wind data of 1973–1992 and 1992–2011 are utilized to estimate the extreme wind of 50-year recurrence interval using method of independent storm and generalized pareto distribution model. It is uncovered that although extreme wind of 50-year recurrence interval escalate a little during the two time spans, it will not affect the safety of wind turbines over there notably

Dynamic Response and Safety Control of Newly Poured Secondary Lining Concrete under Large Section Tunnel Blasting-A Case Study of Longnan Tunnel of Ganshen High-speed Railway

The age of newly poured concrete is short, the cementation between aggregates is weak. At this time, the vibration will affect its performance. The secondary lining concrete newly poured in the tunnel is close to the work face and is susceptible to blasting vibration during construction. In order to study the safety threshold of blasting vibration velocity of newly poured secondary lining concrete in tunnels, the finite element model is established in ANSYS with the large-section Longnan tunnel project as an example. The attenuation law of vibration velocity in three directions of secondary lining under blasting load was analyzed by combining field blasting monitoring with numerical simulation, and the reliability of numerical simulation was verified. Through the numerical simulation results, the vibration velocity and von mises stress distribution of the newly poured secondary lining concrete of the tunnel are analyzed; combined with the dynamic tensile strength theory of concrete, the safety threshold of vibration velocity of newly poured secondary lining concrete of tunnel based on numerical calculation is established; through the indoor vibration test, taking the compressive strength and acoustic velocity of concrete as the indexes, the safety threshold of blasting vibration velocity of newly poured secondary lining concrete of tunnel based on shaking table test is obtained. Combined with the results of numerical simulation and vibration test, the safety threshold of blasting vibration velocity of newly poured secondary lining concrete in large-section tunnels is obtained, and the standard in this field is improved