Dissertations / Theses on the topic 'LATERAL DRIFT'

Flazasulfuron is one of the newest sulfonylurea (SU) herbicides to be registered for use in the fine turf industry. Flazasulfuron is safe for use on bermudagrass (Cynodon dactylon), and zoysiagrass (Zoysia japonica) yet controls several grass, broadleaf, and sedge weeds. In fine turf, flazasulfuron controls cool-season grasses such as tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) without harming warm-season grasses. Although SU herbicides like flazasulfuron bring several potential benefits to turfgrass markets, there are also several concerns related to using these herbicides in turfgrass areas. For many plant species, SU herbicides can cause phytotoxicity or death at less than 1 g ai/ha-1indicating small quantities of active ingredient are required to cause problems if herbicide moves in the environment. Herbicide moves to nontarget plants either after it has been applied via lateral relocation or during application via spray drift. Trials were conducted to evaluate flazasulfuron and trifloxysulfuron sodium tracking, runoff and drift in turfgrass environments. Field trials were conducted at six locations across the US to evaluate effects of irrigation, herbicide treatment, nontreated buffer distance, and time of tracking on creeping bentgrass (Agrostis stolonifera) putting green response to dislodged herbicide residues. Although average turf injury did not exceed 2%, significant differences were noted when treated plots were irrigated prior to tracking. In addition, putting green injury was negatively correlated and normalized difference vegetative index was positively correlated with increasing buffer distance. Data indicate the importance of post treatment irrigation to reduce lateral relocation of SU herbicides like flazasulfuron and trifloxysulfuron sodium in turfgrass. In other studies, herbicides were applied to turfgrass on 7 to 11 % slopes and perennial ryegrass injury was assessed at various distances down slope following an irrigation or rainfall event. Herbicide movement in runoff water was indicated by perennial ryegrass discoloration as much as 18 m below treated plots when excessive herbicide rates were applied to saturated soils. Based on perennial ryegrass injury, flazasulfuron at the rates tested was equivalent or more mobile than trifloxysulfuron sodium and equivalent or less mobile than pronamide when subjected to irrigation or rainfall soon after application to saturated soils. To assess spray drift, a bioassay based on corn height reduction was conducted and corn plants were exposed to potential spray drift in field conditions using conventional turfgrass spray equipment. A sprayer was operated when wind speeds were between 6.4 and 9.6 km h-1 and sentry plants were placed various distances between 0 and 30 m down wind. Wind speeds and direction were confirmed with anemometers and neutrally-buoyant balloons. Herbicide drift was not detected beyond 4.6 m downwind of either herbicide application. Data suggest a 5- to 8-m nontreated buffer area should sufficiently protect neighboring cool-season turfgrasses and other plants against flazasulfuron drift, runoff, and tracking as long as product is not applied to saturated soils and irrigated prior to traffic.
Master of Science in Life Sciences

In a typical light metal building, the structural members are designed for the forces and moments obtained from the wind drift analysis, which assumes pinned connections at the base. The pinned connections provide no moment at the base and have zero rotational stiffness. However, in reality every connection provides some restraint and has some rotational stiffness. Hence, by considering a modeling assumption of pinned condition, the actual behavior of the connection is not captured and this results in overestimation of lateral drifts and appearance of larger moments at the knee of the gable frames. Since the structural components are designed on the basis of these highly conservative results, the cost of the project increases. This thesis investigates the real behavior of the column base connection and tries to reduce the above stated conservatism by developing a computer program or â wizardâ to calculate the initial rotational stiffness of any column base connection. To observe the actual behavior of a column base connection under different load cases, a number of finite element models were created in SAP2000. Each finite element model of the column base connection contained base plate, column stub, anchor bolts and in some cases grout as its components. The model was mainly subjected to three load cases, namely gravity, wind and gravity plus wind. After performing many analyses, the influence of flexibility of each component on the flexibility of the connection was observed and a list of parameters was created. These parameters are the properties of above mentioned components which characterizes any column base connection. These parameters were then used as inputs to model any configuration of the column base connection in the developed wizard. The wizard uses OpenSees and SAP2000 to analyze the modeled configuration of the connection and provides values of the initial rotational stiffness and maximum bearing pressure for the provided loads. These values can be further used in any structural analysis which is done to calculate the lateral drift of a frame under lateral loads. This will also help in getting results which are less conservative than the results which one gets on assuming pinned condition at the base.
Master of Science

During an earthquake, columns in a one-story building must support vertical gravity loads while undergoing large lateral drifts associated with deflections of the vertical seismic force resisting system and deflections of the flexible roof diaphragm. Analyzing the behavior of these gravity columns is complex since not only is there an interaction between compression and bending, but also the boundary conditions are not perfectly pinned or fixed. In this research, the behavior of steel columns that are square hollow structural sections (HSS) is investigated for stability using three design methods: elastic design, plastic hinge design, and pinned base design. First, for elastic design, the compression and flexural strength of the HSS columns are calculated according to the AISC specifications, and the story drift ratio that causes the interaction equation to be violated for varying axial force demands is examined. Then, a simplified design procedure is proposed; this procedure includes a modified interaction equation applicable to HSS column design based on a parameter, Pnh/Mn, and a set of design charts are provided. Second, a plastic hinge design is grounded in the concept that a stable plastic hinge makes the column continue to resist the gravity load while undergoing large drifts. Based on the available test data and the analytical results from finite element models, three limits on the width to thickness ratios are developed for steel square HSS columns. Lastly, for pinned base design, the detailing of a column base connection is schematically described. Using FE modeling, it is shown that it is possible to create rotational stiffness below a limit such that negligible moment develops at the column base. All the design methods are demonstrated with a design example
Master of Science
One-story buildings are one of the most economical types of structures built for industrial, commercial, or recreational use. During an earthquake, columns in a one-story building must support vertical gravity loads while undergoing large lateral displacements, referred to as story drift. Vertical loads cause compression forces, and lateral drifts produce bending moments. The interaction between these forces makes it more complex to analyze the behavior of these gravity columns. Moreover, since the column base is not perfectly fixed to the ground, there are many boundary conditions applicable to the column base depending on the fixity condition. For these reasons, the design for columns subjected to lateral drifts while supporting axial compressive forces has been a growing interest of researchers in the field. However, many researchers have focused more on wide-flange section (I-shape) steel columns rather than on tube section columns, known as hollow structural section (HSS) steel columns. In this research, the behavior of steel square tube section columns is investigated for stability using three design methods: elastic design, plastic hinge design, and pinned base design. First, for elastic design, the compression and flexural strength of the HSS columns are calculated according to current code equations, and the story drift that causes failure for varying axial force demands is examined. Then, a simplified design procedure is proposed including design charts. Second, a plastic hinge design is grounded in the concept that controlled yielding at the column base makes the column continue to resist the gravity load while undergoing large drifts. Based on the available test data and results from computational models, three limits on the width to thickness ratios of the tubes are developed. Lastly, for pinned base design, concepts for detailing a column base connection with negligible bending resistance is schematically described. Using a computational model, it is shown that the column base can be detailed to be sufficiently flexible to allow rotation. All the design methods are demonstrated with a design example.

Desembocaduras são ambientes bastante dinâmicos e sujeitos à complexa interação entre fatores estabilizadores e desestabilizadores. Dependendo dessa interação, desembocaduras podem apresentar a tendência de migração ao longo de barreiras arenosas. Um dos mecanismos mais eficientes de transporte de sedimento paralelo à costa, e conseqüentemente migração de canais, são as correntes longitudinais geradas pelas ondas se aproximando obliquamente a costa. A motivação do presente trabalho é entender o comportamento morfodinâmico do sistema de desembocadura do rio Itapocú, localizado no centro-norte de Santa Catarina, frente aos processos forçantes que atuam na sua migração ao longo da linha de costa. A morfologia dos pontais arenosos foi obtida a partir de levantamentos morfológicos com o uso de DGPS. Para analisar a refração de ondas foi utilizado o modelo numérico MIKE 21 - SW, sendo considerados como condições de contorno dados de ondas referentes ao ano de 2002 e dados de ondas previstos referentes ao período de coleta. Os dados de saída do modelo foram utilizados para estimar a deriva litorânea potencial na região. Os resultados morfológicos obtidos demonstraram uma migração da desembocadura para o norte durante o período analisado, sendo mais intenso durante o inverno e o verão. A refração de ondas incidentes do quadrante sul sofreram mais o fenômeno da refração e as ondas de leste apresentaram menor variação angular ao se aproximarem da costa. A deriva litorânea potencial anual para os dados de ondas de 2002 apresentou sentido norte-sul, com inversão de sentido durante o outono, sul-norte. A deriva litorânea potencial para os dados referentes ao período estudado apresentou sentido sul-norte, concordando com a migração observada. A deriva potencial em frente aos pontais apresentou direção para o norte durante todas as estações. Os dados de descarga fluvial não apresentaram influência na migração do canal, porém apresentaram uma relação com a largura do mesmo sazonalmente. Os dados de morfologia juntamente com os dados de deriva litorânea referentes às ondas de 2004/2005 mostraram claramente a migração do canal para o norte sendo a deriva a principal contribuinte para a migração da desembocadura.
Inlets are highly dynamic environments subjected to the complex interaction between stabilizing and destabilizing factors. Depending on this interaction, inlets have a tendency to migrate along sandy barriers. One of the most effective mechanisms for transporting sediment alongshore and consequently controlling the migration of inlets, are currents generated by waves approaching the coast at an angle. The motivation of this study is to better understand the morphodynamic behavior of the Itapocú inlet, at the northern Santa Catarina coast. The morphology of the sandy spits that enclose the inlet was obtained from morphological surveys conducted with the use of DGPS. To analyze the wave refraction the numerical model MIKE 21 SW has been applied to the region. Boundary conditions have been set based on a one-year long database (2002) and predicted waves for the studied period. The model output has been used to estimate the potential longshore drift in the region. Results show the migration of the inlet to the north during the analyzed period, with higher migration rates during winter and summer. Waves inciding from the south are the most influenced by the refraction process, while the less refracted waves are those coming from the east The net longshore drift obtained when using the 2002 database is southwards, presenting slight inversions during the year. When using the predicted wave data for the studied period, the potential longshore drift is dominated by northward direction, in agreement with the observed inlet migration. The Itapocú river discharge does not present any relation with the observed inlet migration rates, although there seems to be a relation with the seasonal channel width variability. The surveyed morphological evolution is well related to the potential longshore drift, indicating that during the monitored period, the northwards inlet migration is being controlled by the wave generated longshore drift.

The Vertically Oriented Interlocking Timber (VOIT) panel is a new solid wood panel similar to Interlocking Cross Laminated Timber (ICLT) and the more commonly known Cross Laminated Timber (CLT). Like ICLT, VOIT panels use timber connections instead of the adhesives or metal fasteners common to CLT. The difference of VOIT is the orientation of the layers. Where CLT and ICLT panels alternate the orientation of each layer, VOIT panels orient all the layers in the same direction. The vertically oriented layers are then attached to one another by smaller horizontal dovetail members.Two types of VOIT panels were provided to be tested for in-plane lateral loading. Type I had three rows of horizontal dovetail members connecting the layers and Type II had four rows of dovetail members as well as two diagonal members to provide stiffness. Two panels of each type were provided, measuring 8 ft. wide, 8 ft. tall, and 13.75 in. thick. Each panel was disassembled after monotonic lateral in-plane loading to determine possible failure modes. Testing results suggest the VOIT panels to be comparable in shear strength to other wood shear walls, including light frame, CLT, and ICLT walls. A two-part analytical model was created to determine the deflection of the wall when loaded as well as the shear strength of the wall. The model predicted deflection and wall strength reasonably well. Due to the small sample size, additional testing is necessary to confirm the results of the Type I and Type II VOIT panels. Additional testing with more variations of the panel and member geometries is also needed to validate the scope of the model.

Most of the older reinforced concrete (RC) buildings have columns that are deficient when the current code requirements are considered. Therefore, performance of the columns determines the performance of the structure under the effects of earthquake induced lateral loads. It is recognized that no provision is proposed in TEC2007 to estimate the failure type called flexure-shear. Behavior of columns having probability of failing in flexure-shear failure mode is mostly underestimated by TEC2007 procedures. In addition, failure type classification of columns performed according to the linear and nonlinear procedures of TEC2007 needs to be examined with respect to the test results to cover all failure types including flexure-shear failure in order to lead the engineers develop economical and realistic retrofit solutions. In this study, different methods are explored to obtain reliable estimates for the performance of code deficient shear critical RC columns. Special considerations are given to Axial-Shear-Flexure interaction (ASFI) approach due to its mechanical background. After examination of different approaches, ASFI method with proposed modifications was selected as the most reliable model and lateral load-displacement analyses were performed on a database of shear critical columns. Findings were compared with the estimations of the nonlinear procedure given in Turkish Earthquake Code (TEC2007) for database columns. In addition, drift capacity equations and simplified safe drift capacity equations are proposed in light of statistical studies on the selected column specimens. In the last part of the study, performance evaluation of columns according to nonlinear procedures of FEMA 356, TEC2007, ASCE/SEI 41 update supplement, and EUROCODE 8 were conducted.

This thesis is a study into the response and seismic safety of three-dimensional multi-storey concrete structures under concurrent orthogonal seismic excitations. It employs the nonlinear time-history method as its analysis tools. Time-history analyses rely heavily on their utilised earthquake records. Accordingly, this study examines the different approaches of selecting earthquake suites and develops a methodology of selecting representative earthquake scenarios. This methodology is credibly implemented in selecting a far- and a near field suites representative of the New Zealand seismic hazard. The study investigates the response of 6-, 9- and 12-storey concrete structures of different n-X-bays × m-Y-bays. Bidirectional responses of these considered structures are examined and consequently the current combination rules are scrutinised. Consequently this study strongly recommends the use of the 40-percent combination rule in lieu of the widely used 30-percent rule; and the use of time-history analysis in lieu of quasi/equivalent static and response modal analysis methods to avoid their strong dependence on combination rules. An intensive study is conducted employing the incremental dynamic analysis (IDA) technique to investigate structural demands of interstorey drifts, lateral storey drifts and storey accelerations. The study utilises the developed far-field suite and identifies the 50th and 90th percentile demands. Hence it provides easy-to-use expressions to facilitate rapid calculation of the structural demands and the effects of biaxial interactions. An implementation into the Demand and Capacity Factor Design (DCFD) format is presented that infers confidence in the performance levels of the considered structures. The study also draws attention to the importance of considering storey accelerations as their storey values reach as high as 10 × PGA. A sensitivity study is conducted by repeating the IDA investigation while using the developed near-field suite. Subsequently a comparison between the near- and the far-field results is conducted. The results were markedly similar albeit of less magnitudes until the (seismic hazard) intensity measure IM = Sa(T₁) = 0.4g when the near-field results show sudden flat large increase in demands suggesting a brittle collapse. This is attributed to the higher content of the higher mode frequencies contained in near-field ground motions. Finally, the study examines the (vectorial) radial horizontal shear demands in columns and beam-column joints of the previous far- and near-field studies. The combined radial shear demands in corner, edge and internal columns and joints are evaluated that roughly show a square-root proportional relationship with IM that exhibit somewhat brittle failure at IM ≥ 0.35g. Shears demands in the (4-way) internal columns and the (2-way) corner joints show highest magnitude in their respective class. The results suggest transverse joint shear reinforcement of 1.5, 1.0 and 0.5 of the longitudinal reinforcement of the neighbouring beam respectively for corner, edge and internal joints. An implementation of a proposed practical (and simpler) DCFD format shows satisfactory confidence in columns performance in shear up to IM = 0.35g, conversely to joints unsatisfactory performance in shear at the onset of inelastic behaviour (IM > 0.05g).

This article presents a simulation study into effects of compliant (flexible) components (such as the engine subframe and the lower control arm) and their deflections on the characteristics of a vehicle experiencing steering drift during straight-line braking. The vehicle front and rear suspension are modelled using multi-body dynamic analysis software. The front suspension model represents theMacPherson strut design of the vehicle and includes a rack and pinion steering system, brake system, engine subframe, and a powertrain unit. The model has been analysed under two steering control methods: fixed and free control. Suspension characteristics and the effect of deflections arising from the subframe and the lower control arm on these suspension characteristics have been analysed. The simulations confirmed that variation of component stiffness and interactions within components give rise to side-to-side deflections that could affect lateral drift during braking. It is concluded that side-to-side variation of suspension characteristics can have a detrimental effect on lateral drift during braking and that compliant components whose stiffness varies from side to side can cause different side-to-side deflections that can induce and influence variation in suspension characteristics such as toe steer angle that can lead the vehicle during braking.

碩士
國立勤益科技大學
電子工程系
106
Power semiconductor devices are commonly used in LED bulbs and computer transformers, and are also widely used in industrial equipment, automotive electronic ignition systems, mobile phone battery charging and communication equipment, so power semiconductors are often served as protective switches as the first goalkeeper for electrical appliances, and are also regarded as the main direction of future research in terms of miniature size. This paper mainly studies the thickness reduction of the epitaxial layer, and confirms that the component breakdown voltage range reaches 700 V or more, ensuring the safety of components. This study used the Synopsys TCAD simulation software pro Vided by the National Center for High-performance Computing (NCHC), which was paired with the National Nano Device Laboratories, Process parameters of NDL Semiconductor Manufacturing Machine, as well as machine process parameters that can be produced by academic laboratories. The power semiconductors simulated in this study reaches a static breakdown voltage of 765 V of bulk silicon, and a static breakdown voltage of 805 V of SOI with the silicon substrate of 15 μm thickness. In the discussion of the thickness reduction of the epitaxial layer, the static breakdown voltage of the structure of the SOI epitaxial layer thickness of 3 μm is 751 V, and the dynamic breakdown voltage can reach 704 V under the gate input 5 V. In the future, this power semiconductor component structure will be able to apply this structure to production.

碩士
雲林科技大學
光學電子工程研究所
99
Power devices are widely applied to power electronics owing to the development in semiconductor industry. Lateral Double-Diffused MOSFET (LDMOSFET) is one of the power devices. LDMOSFET is usually the driver component in high voltage integrated circuits. Basically, power devices have two figures of merits, which are high operating voltage and low turn-on resistance. RESURF (Reduced Surface Field) is one kind of power device. It has the same I-V characteristic with MOSFET. Applying the principles of RESURF, the integration of circuits can be realized by building power devices on a thin epitaxial layer. This thesis focuses on the structure and some process parameters of multiple-resistivity drift region and VLD (variation of lateral doping) drift region in LDMOSFET. And This study includes simulations of the structures of LDMOSFET with tools like TSUPREM4 and MEDICI to analyze the of breakdown voltage and on-resistance characteristics of the device. Methods of overcoming defects in the device and actual fabrication of a device of an optimal design are also discussed. Compared with the conventional, the specific on-resistance in multi-resistance drift region structure is 24.74 mΩ-cm2 (decrease 8.02%); in VLD drift region structure, the specific on-resistance is reduced to 24.13 mΩ-cm2 (decrease 10.29%),and the breakdown voltage is almost the same.

碩士
國立臺灣大學
土木工程學研究所
107
The seismic behavior of the high strength steel hollow box column (high strength HBC) under the high axial load was experimentally investigated. The parameters in this study included the width-to-thickness (b/t) ratio, axial load level and loading types. Full-size tests were carried out on six welded box-section columns fabricated from SM570MC (nominal yield strength 420 MPa~ 540 MPa). The HBC specimens were 290 to 400 mm in width and 4000 mm in height, with nominal b/t ratios varied from 11 to 21. The HBC specimens were tested under a constant axial load and the increasing cyclic loading (or near-fault loading). Experimental results indicate that smaller b/t ratio in HBC can delay the local buckling effectively, resulting in better ductility. Moreover, the width-thickness limit for HBC in Taiwanese specification, which is 21, can not apply to the cases under a high axial load. This means the smaller b/t requirement of highly ductile member (λhd=12.9) in AISC 341 (2016) should be used in the seismic design. Also, loading sequence for beam-to-column moment connections based on AISC 341 (2016) is stricter than the near-fault loading that we used in this work. All the design codes include AISC-LRFD(2016), AIJ(2010) and Taiwanese Code(2010) are conservative in predicting the flexural strength of high strength HBC. In this work, the backbone curve for hollow section steel column was proposed and compared with those proposed by ASCE 41 (2013) and NIST (2017). It shows that the backbone curves proposed by ASCE 41 (2013) and NIST (2017) will underestimate the flexural strength and the plastic rotation under a high axial load (40%Py). The backbone curve proposed by this work can give good accuracy in predicting the flexural strength and the plastic rotation of high strength HBC.