No description available.

No description available.

Weight reduction, increased fuel economy, and increased safety of structures in transportation applications has led to much interest in lightweight higher strength structural aluminum alloys. Suitable joining techniques to create such structures with aluminum sheets are required. Generally, similar and dissimilar sheet metals can be joined by adhesive bonding, welding, and mechanical fastening. Difficulty of welding and long processing times for adhesive bonding make mechanical fastening a process of much interest for joining of high strength aluminum sheets. Among the different mechanical fastening techniques available in manufacturing, clinching is a common method of joining by forming in which a punch and die are used to form a geometrical interlock. However, the process introduces surface steps on both sides of the joined sheets where one side consists of a protrusion and the other a pit. Also, clinch joining, a well-accepted and widely used process for joining ductile sheet metals, is more challenging for high strength lower ductility aluminum sheets such as AA7075. The current work aims at studying clinch-ability of high strength lower ductility AA7075 aluminum sheets of different tempers by conventional as well as a new clinching technique called "die-less" clinching. A new tooling was designed in order to conduct die-less clinches. The results showed that room temperature clinching is possible for the softer tempers namely solution treated and annealed states. However, the peak aged sheets failed to form a successful joint. A novel electrical resistance heating technique (ERH) to provide ductility to the joined sheets was used to obtain die-less clinched joints in AA7075-T6. ERH technique provides a large range of heating temperatures from room temperature to 270°C for a current duration of 3 sec. The AA7075-T6 sheets showed a superior joining by using ERH. The joint showed a metallurgical locking mechanism in addition to the commonly available form locking mechanism. / Thesis / Doctor of Philosophy (PhD) / Clinching is a common method of joining sheet metals by forming. A punch and die are used to form a permanent geometrical interlock. However, the process introduces surface steps on both sides of the joined sheets where one side consists of a protrusion and the other a pit. Clinch joining is a well-accepted and widely used process for joining ductile sheet metals. Joining of high strength lower ductility aluminum sheets such as AA7075 is more challenging. The current work aims at joining AA7075 aluminum sheets of different tempers by clinching using the conventional method as well as a new clinching technique called "die-less" clinching. The study includes a new tooling design in order to conduct die-less clinches. Also, a novel electrical resistance heating technique (ERH) to provide ductility to the joined sheets was used to obtain die-less clinched joints in the peak aged AA7075-T6. ERH technique provides a large range of heating temperatures from room temperature to 270°C for a current duration of 3 sec. The AA7075-T6 sheets showed a superior joining by using ERH.

Yes / This paper is about three working class women academics in their 40s, who are at different phases in their career. I take a reflexive, feminist, (Reay 2000, 2004, Ribbens and Edwards, 1998) life story approach (Plummer, 2001) in order to understand their particular narratives about identity, complicity, relationships and discomfort within the academy, and then how they inhabit care-less spaces. However unique their narratives, I am able to explore an aspect of higher education – women and their working relationships – through a lens of care-less spaces, and argue that care-less-ness in the academy, can create and reproduce animosity and collusion. Notably, this is damaging for intellectual pursuits, knowledge production and markedly, the identity of woman academics. In introducing this work, I first contextualise women in the academy and define the term care-less spaces, then move onto discuss feminist methods. I then explore and critique in some detail, the substantive findings under the headings of ‘complicity and faking it’ and ‘publishing and collaboration’. The final section concludes the paper by drawing on Herring's (2013) legal premise, in the context of care ethics, as a way to interrogate particular care-less spaces within higher education.

The less-than-truckload (LTL) transportation industry is highly competitive with low profit margins. Carriers in this industry strive to reduce costs and improve customer service to remain profitable. LTL carriers rely on a network of hubs and service centers to transfer freight. A hub is typically a cross docking terminal in which shipments from inbound trailers are unloaded and reassigned and consolidated onto outbound trailers going to the correct destinations. Freight handling in a hub is labor intensive, and workers must quickly transfer freight during a short time period to support customer service levels. Reducing shipment transfer time in hubs offers the opportunity to reduce labor costs, improve customer service, and increase competitive advantages for carriers. This research focuses on improving the efficiency of hub operations in order to decrease the handling costs and increase service levels for LTL carriers. Specifically, the following two decision problems are investigated: (1) assigning trailers to dock doors to minimize the total time required to transfer shipments from inbound trailers to destination trailers and (2) sequencing unloading and loading of freight to minimize the time required by dock employees. The trailer-to-door assignment problem is modeled as a Quadratic Assignment Problem (QAP). Both semi-permanent and dynamic layouts for the trailer-to-door assignment problem are evaluated. Improvement based heuristics, including pair-wise exchange, simulated annealing, and genetic algorithms, are explored to solve the trailer-to-door assignment problem. The freight sequencing problem is modeled as a Rural Postman Problem (RPP). A Balance and Connect Algorithm (BCA) and an Assign First and Route Second Algorithm (AFRSA) are investigated and compared to Balanced Trailer-at-a-Time (BTAAT), Balanced Trailer-at-a-Time with Offloading (BTAATWO), and Nearest Neighbor (NN). The heuristics are evaluated using data from two LTL carriers. For these data sets, both the total travel distance and the transfer time of hub operations are reduced using a dynamic layout with efficient freight sequencing approaches, such as the Balance and Connect Algorithm (BCA), the Balanced Trailer-at-a-Time with Offloading (BTAATWO), and the Nearest Neighbor (NN). Specifically, with a dynamic layout, the BCA reduces travel distance by 10% to 27% over BTAAT and reduces the transfer time by 17% to 68% over BTAAT. A simulation study is also conducted for hub operations in a dynamic and stochastic environment. The solutions from the door assignment and freight sequencing approaches are evaluated in a simulation model to determine their effectiveness in this environment. The simulation results further demonstrate that the performance measures of hub operations are improved using a dynamic layout and efficient freight sequencing approaches. The main contributions of this research are the integer programming models developed for the freight sequencing problem (FSP), based on the Rural Postman Problem (RPP). This is the first known application of the RPP for the FSP. Efficient heuristics are developed for the FSP for a single worker and for multiple workers. These heuristics are analyzed and compared to previous research using industry data. / Ph. D.

The less-than-truckload (LTL) industry is highly competitive, with recent average profit margins less than 3%. LTL shipments are routed through a network of service centers and hubs. The performance of the entire LTL distribution network is highly dependent on the speed and accuracy of the hub operations. The focus of this research effort is to improve hub operations in order to reduce costs and increase service performance levels. Specifically, new approaches are investigated for assigning trailers to dock doors and sequencing the unloading of shipments at hubs. This thesis reviews current industry practices and available research literature on hub operations. Solution approaches for the trailer-to-door assignment and freight sequencing problems are presented along with case study results. The main performance measures are bottleneck time, total labor time, and total travel distance. For the trailer-to-door assignment problem, also referred to as the hub layout problem, the three approaches investigated are the original approach, a semi-permanent approach, and a dynamic approach. For the freight sequencing problem, the five approaches evaluated are trailer-at-a-time, trailer-at-a-time with offloading, nearest neighbor within a group, nearest neighbor within a shared group, and nearest neighbor. The approaches are implemented in C++ and analyzed using data from a regional LTL carrier. The case study results indicate that the dynamic layout performs significantly better than the original and semi-permanent layout for total distance, total labor time, and bottleneck time. For total distance and total labor time, the dynamic layout with nearest neighbor sequencing is the preferred approach. For bottleneck time, the dynamic layout with trailer-at-a-time with offloading performs best, while the nearest neighbor sequencing approach performs almost as well. In general, the case study results indicate that a dynamic layout with either a trailer-at-a-time with offloading approach or a nearest neighbor approach offers the largest potential for improvement. The assumptions and results of the hub layout and freight sequencing approaches are further evaluated using a simulation model. The simulation model indicates that a dynamic layout with nearest neighbor sequencing offers the largest potential for improvement in a more realistic environment with probabilistic and dynamic events. The simulation results also indicate that the trailer-at-a-time with offloading approach may need to be modified to account for more realistic dock conditions. In summary, the approaches explored in this research offer significant opportunity to improve hub operations through reducing bottleneck time, total labor time, and total travel distance. / Master of Science

This thesis focuses on the design issues of the multiple-output boost full-bridge converter, which is constructed by cascading the boost regulator with the inductor-less full-bridge converter. The design of the boost regulator has been proposed briefly with component selection and compensator design. After that, the inductor-less full-bridge converter is analyzed extensively. In the first place, the operation principle of the inductor-less full-bridge converter is introduced. Later, the effect of parasitic resistance and inductance is analyzed in an L-R series circuit model as step-response, which relates the drop of output voltage to the load current. Then, the effects of the dc blocking capacitor for the unbalanced load condition and unbalanced duty cycle are tackled. The theoretical results are compared with the experimental results and the simulation results to verify the relationship between the output voltage drop and load current. The overall efficiency of the converter is tested under various conditions. The design of the planar transformer is critical to limit the profile of the converter and the leakage phenomenon. A planar transformer fit for the inductor-less full-bridge converter is designed and analyzed in 3D FEA software. An N-port transformer model is proposed to implement the inductance matrix into the leakage inductance matrix for circuit analysis. Based on this N-port model several measurements to extract the parameters in this model are proposed, where only the impedance analyzer is needed. Finally, the effects of trace layout and encapsulation on breakdown voltage in PCB are summarized from experimental results. / Master of Science

Die vorliegende Arbeit beinhaltet verschiedene Aspekte der Embryogenese des Pfeilschwanzkrebses Limulus polyphemus (Chelicerata, Xiphosura), darunter die frühe Neurogenese, die Axogenese, eine Analyse der "Kopf"segmentierung bei Cheliceraten und anderen Arthropoden, sowie das Expressionsmuster des Homöoboxgens Distal-less insbesondere in neuronalen Zusammenhängen. Darüber hinaus wurde eine neue Embryonalstadieneinteilung geleistet. Markierungen mit Phalloidin sowie weiterer neurospezifischer Marker ergaben, daß die frühe Neurogenese bei Limulus polyphemus durch die Immigration von Zellclustern erfolgt. Die Zellen nehmen eine flaschenförmige Gestalt annehmen, bevor sie sich aus dem ventralen Neuroektoderm lösen. Die Anzahl der Zellen pro Zellcluster steigt mit fortschreitender Entwicklung. Die Zellcluster konzentrieren sich in in Zentrum jedes Hemisegmentes, und in ihrem dorsalen Bereich beginnt die rasch voranschreitende Axogenese. Die Untersuchung der "Kopf"segmentierung mittels alpha-Tubulin-Markierungen bei Limulus polyphemus, Triops cancriformis (Crustacea) und Lepisma saccharina (Hexapoda) ergab sowohl bei der Entwicklung des circumoesophagealen Neuropilringes und der Innervierung der dazugehörigen Anhangspaare als auch hinsichtlich des Verlaufs des Stomatogastrischen Nervensystems beachtliche Übereinstimmungen, die entgegen der klassischen Auffassung den Schluß zulassen, daß das Deutocerebrum der Cheliceraten keineswegs reduziert wurde oder mit dem Tritocerebrum verschmolzen ist, sondern die Chelicere innerviert. Somit wäre das Chelicerenneuromer homolog zum Deutocerebrum der Crustacea und Hexapoda (1. Antenne). Der Vergleich des Expressionsmuster des Homöoboxgens Distal-less bei Limulus und Lepisma saccharina ergab neben den typischen Expressionen in auswachsenden Extremitäten- und andern Anhangsknospen bei beiden Vertretern Expressionen in neuronalen Zusammenhängen (im Lobus opticus, Ganglien bei Limulus oder in das ZNS umgebende Zellen bei Lepisma), an den verschiedensten Positionen späterer Sinnesorgane wie Mechano- oder Chemorezeptoren. Doppelmarkierungen mit Synorf-1 deuten darauf hin, daß es sich bei den Dll-positiven Zellen zum größten Anteil um Glia-Zellen handelt. / The following study contains different aspects of the embryology of the horseshoe crab Limulus polyphemus (Chelicerata, Xiphosura) with the main focus on early neurogenesis, axogenesis and the "head"segmentation in chelicerates and other arthropods. The expression pattern of the homeobox gene Distal-less was examined with main focus on neuronal correlations. In addition, a new staging was provided. Phalloidin stainings and other markers showed that the early neurogenesis in Limulus polyphemus happens via immigration of cell clusters. Cellclusters in the prosoma contain cells that become bottle shaped before they immigrate from the ventral neuroectoderm. The number of these cells increases during further development, and the cells concentrate in the middle of each hemisegment. Axogenesis starts at the dorsal edge of these concentrated cellclusters and progresses quite fast building the typical ladder like CNS of arthropods. The investigation of the "head"segmentation using alpha-tubulin stainings in Limulus polyphemus, Triops cancriformis (Crustacea), and Lepisma saccharina (Hexapoda) showed remarkable similarities in the development of the circumesophageal neuropil ring, the related appendages, and the course of the stomatogastric nerves. These results lead to the thesis that the deutocerebrum of chelicerates is neither completely reduced nor totally merged into the tritocerebrum but innervates the chelicerae which contradicts the classical view. According to these results the neuromer of the chelicerae would be homologous to the deutocerebrum of Crustaceans and Hexapods (first antennae). The expression pattern of the homeobox gene Distal-less was examined and compared in Limulus polyphemus and Lepisma saccharina. Beside the typical expression pattern in the developing appendages a participation of the gene in development of the nervous system was observed. Dll positve cells were found in or at least in direct contact with the CNS (optical lobe, ganglia in Limulus or surrounding the entire CNS including the brain of Lepisma), at different positions of later mechano- and chemoreceptors (lateral spines, bristles, flabellum, Johnstons organ etc.). Double stainings using Dll and Synorf-1 showed that at least most of these Dll-postive cells are most likely glia cells.

In this thesis, the problem of intercepting highly manoeuvrable threats using seeker-less interceptors that operate in the command guidance mode, is addressed. These systems are more prone to estimation errors than standard seeker-based systems. Several non-linear and optimal estimation and guidance concepts are presented in this thesis for interception of randomly maneuvering targets by seeker-less interceptors. The key contributions of the thesis can be broadly categorized into six groups, namely (i) an optimal selection of bank of lters in interactive multiple model (IMM) scheme to cater to various maneuvers that are expected during the end-game, (ii) an innovative algorithm to reduce chattering phenomenon and formulate effective guidance algorithm based on 'differential game guidance law' (modi ed DGL), (iii) IMM/DGL and IMM/modified DGL based integrated estimation/guidance (IEG) strategy, (iv) sensitivity and robustness analysis of Kalman lters and ne tuning of lters in filter bank using innovation covariance, (v) Performance of tuned IMM/PN, tuned IMM/DGL and tuned IMM/modi ed DGL against various target maneuvers, (vi) Performance comparison with realistic missile model. An innovative generalized state estimation formulation has been proposed in this the-sis for accurately estimating the states of incoming high speed randomly maneuvering targets. The IMM scheme and an optimal selection of lters, to cater to various maneu-vers that are expected during the end-game, is described in detail. The key advantage of this formulation is that it is generic and can capture evasive target maneuver as well as straight moving targets in a uni ed framework without any change of target model and tuning parameters. In this thesis, a game optimal guidance law is described in detail for 2D and 3D engagements. The performance of the differential game based guidance law (DGL) is compared with conventional Proportional Navigation (PN) guidance law, especially for 3D interception scenarios. An innovative chatter removal algorithm is introduced by modifying the differential game based guidance law (modified DGL). In this algorithm, chattering is reduced to the maximum extent possible by introducing a boundary layer around the switching surface and using a continuous control within the boundary layer. The thesis presents performance of the modified DGL algorithm against PN and DGL, through a comparison of miss distances and achieved accelerations. Simulation results are also presented for varying fiight path angle errors. Apart from the guidance logic, two novel ideas have been presented following the evolving "integrated estimation and guidance" philosophy. In the rst approach, an in-tegrated estimation/guidance (IEG) algorithm that integrates IMM estimator with DGL law (IMM/DGL), is proposed for seeker-less interception. In this interception scenario, the target performs an evasive bang-bang maneuver, while the sensor has noisy measure-ments and the interceptor is subject to an acceleration bound. The guidance parameters (i.e., the lateral acceleration commands) are computed with the help of zero e ort miss distance. The thesis presents the performance of the IEG algorithm against combined IMM with PN (IMM/PN), through a comparison of miss distances. In the second ap-proach, a novel modi ed IEG algorithm composed of IMM estimator and modi ed DGL guidance law is introduced to eliminate the chattering phenomenon. Results from both of these integrated approaches are quite promising. Monte Carlo simulation results re-veal that modi ed IEG algorithm achieves better homing performance, even if the target maneuver model is unknown to the estimator. These results and their analysis o er an insight to the interception process and the proposed algorithms. The selection of lter tuning parameters puts forward a major challenge for scien-tists and engineers. Two recently developed metrics, based on innovation covariance, are incorporated for determining the filter tuning parameters. For predicting the proper combination of the lter tuning parameters, the metrics are evaluated for a 3D interception problem. A detailed sensitivity and robustness analysis is carried out for each type of Kalman lters. Optimal and tuned Kalman lters are selected in the IMM con guration to cater to various maneuvers that are expected during the end-game. In the interception scenario examined in this thesis, the target performs various types of maneuvers, while the sensor has noisy measurements and the interceptor is subject to acceleration bound. The tuned IMM serves as a basis for synthesis of e cient lters for tracking maneuvering targets and reducing estimation errors. A numerical study is provided which demonstrates the performance and viability of tuned IMM/modi ed DGL based modi ed IEG strategy. In this thesis, comparison is also performed between tuned IMM/PN, tuned IMM/DGL and tuned IMM/modi ed DGL in integrated estimation/guidance scheme. The results are illustrated by an extensive Monte Carlo simulation study in the presence of estimation errors. Simulation results are also presented for end game maneuvers and varying light path angle errors . Numerical simulations to study the aerodynamic e ects on integrated estimation/ guidance structure and its e ect on performance of guidance laws are presented. A detailed comparison is also performed between tuned IMM/PN, tuned IMM/DGL and tuned IMM/modi ed DGL in integrated estimation/guidance scheme with realistically modelled missile against various target maneuvers. Though the time taken to intercept is higher when a realistic model is considered, the integrated estimation/guidance law still performs better. The miss distance is observed to be similar to the one obtained by considering simpli ed kinematic models.

No description available.