Computer aided design and analysis of cold formed sections

The work reported in this thesis is concerned with the improvement and expansion of the assistance given to the designer by the computer in the design of cold formed sections. The main contributions have been in four areas, which have consequently led to the fifth, the development of a methodology to optimise designs. This methodology can be considered an `Expert Design System' for cold formed sections. A different method of determining section properties of profiles was introduced, using the properties of line and circular elements. Graphics were introduced to show the outline of the profile on screen. The analysis of beam loading has been expanded to beam loading conditions where the number of supports, point loads, and uniform distributive loads can be specified by the designer. The profile can then be checked for suitability for the specified type of loading. Artificial Intelligence concepts have been introduced to give the designer decision support from the computer, in combination with the computer aided design facilities. The more complex decision support was adopted through the use of production rules. All the support was based on the British standards. A method has been introduced, by which the appropriate use of stiffeners can be determined and consequently designed by the designer. Finally, the methodology by which the designer is given assistance from the computer, without constraining the designer, was developed. This methodology gives advice to the designer on possible methods of improving the design, but allows the designer to reject that option, and analyse the profile accordingly. The methodology enables optimisation to be achieved by the designer, designing variety of profiles for a particular loading, and determining which one is best suited.

Failure analysis of cold-formed steel sections

The purlin-sheeting system has been the subject of numerous theoretical and experimental investigations over the past 30 years, but the complexity of the problem has led to great difficulty in developing a sound and general model. The primary aim of the thesis is to investigate the failure behaviours of cold-formed zed and channel sections for use in purlin-sheeting systems. Both the energy method and finite strip method are used to develop an approach to investigate cold-formed zed and channel section beams with partial-lateral restraint from the metal sheeting when subjected to a uniformly distributed transverse load. The stress analysis of cold-formed zed and channel section beams with partially-lateral restraint from the metal sheeting when subjected to a uniformly distributed transverse load is investigated firstly by using the analytical model based on the energy method in which the restraint actions of the sheeting are modelled by using two springs representing the translational and rotational restraints. The numerical results have showed that the two springs have significantly different influences on the stresses of the beams. The influence of the two springs has also been found to depend on the anti-sag bar and the position of the loading line. A novel method is presented for analysing the elastic local buckling behaviour of cold-formed zed and channel section beams with partial-lateral restraint from metal sheeting when subjected to a uniformly distributed transverse load, which is carried out by inputting the cross sectional stresses with the largest compressive stress into the finite strip analysis. By using the presented novel method, individual influences of warning stress, partially lateral restraints from the sheeting and the dimensions of the cross section and position of the loading line on the buckling behaviour are investigated.

Global optimisation of cold-formed steel sections

In this thesis, standard algorithms are used to carry out the optimisation of cold-formed steel purlins such as zed, channel and sigma sections, which are assumed to be simply supported and subjected to a gravity load. For zed, channel and sigma section, the local buckling, distortional buckling and lateral-torsional buckling are considered respectively herein. Currently, the local buckling is based on the BS 5950-5:1998 and EN 1993-1-3:2006. The distortional buckling is calculated by the direct strength method employing the elastic distortional buckling which is calculated by three available approaches such as Hancock (1995), Schafer and Pekoz (1998), Yu (2005). In the optimisation program, the lateral-torsional buckling based on BS 5950-5:1998, AISI and analytical model of Li (2004) are investigated. For the optimisation program, the programming codes are written for optimisation of channel, zed and sigma beam. The full study has been coded into a computer-based analysis program (MATLAB).

Gravity spun polycaprolactone fibers for applications in vascular tissue engineering:proliferation and function of human vascular endothelial cells

Poly(ε-caprolactone) (PCL) fibers produced by wet spinning from solutions in acetone under low-shear (gravity-flow) conditions resulted in fiber strength of 8 MPa and stiffness of 0.08 Gpa. Cold drawing to an extension of 500% resulted in an increase in fiber strength to 43 MPa and stiffness to 0.3 GPa. The growth rate of human umbilical vein endothelial cells (HUVECs) (seeded at a density of 5 × 104 cells/mL) on as-spun fibers was consistently lower than that measured on tissue culture plastic (TCP) beyond day 2. Cell proliferation was similar on gelatin-coated fibers and TCP over 7 days and higher by a factor of 1.9 on 500% cold-drawn PCL fibers relative to TCP up to 4 days. Cell growth on PCL fibers exceeded that on Dacron monofilament by at least a factor of 3.7 at 9 days. Scanning electron microscopy revealed formation of a cell layer on samples of cold-drawn and gelatin-coated fibers after 24 hours in culture. Similar levels of ICAM-1 expression by HUVECs attached to PCL fibers and TCP were measured using RT-PCR and flow cytometry, indicative of low levels of immune activation. Retention of a specific function of HUVECs attached to PCL fibers was demonstrated by measuring their immune response to lipopolysaccharide. Levels of ICAM-1 expression increased by approximately 11% in cells attached to PCL fibers and TCP. The high fiber compliance, favorable endothelial cell proliferation rates, and retention of an important immune response of attached HUVECS support the use of gravity spun PCL fibers for three-dimensional scaffold production in vascular tissue engineering. © Mary Ann Liebert, Inc.

Expert system design for cold form sections

The concept of an Expert System (ES) has been acknowledged as a very useful tool, but few studies have been carried out in its application to the design of cold rolled sections. This study involves primarily the use of an ES as a tool to improve the design process and to capture the draughtsman's knowledge. Its main purpose is to reduce substantially the time taken to produce a section drawing, thereby facilitating a speedy feedback to the customer. In order to communicate with a draughtsman, it is necessary to use sketches, symbolic representations and numerical data. This increases the complexity of programming an ES, as it is necessary to use a combination of languages so that decisions, calculations, graphical drawings and control of the system can be effected. A production system approach is used and a further step has been taken by introducing an Activator which is an autoexecute operation set up by the ES to operate an external program automatically. To speed up the absorption of new knowledge into the knowledge base, a new Learning System has been constructed. In addition to developing the ES, other software has been written to assist the design process. The section properties software has been introduced to improve the speed and consistency of calculating the section properties. A method of selecting or comparing the most appropriate section for a given specification is also implemented. Simple loading facilities have been introduced to guide the designer as to the loading capacity of the section. This research has concluded that the application of an ES is beneficial and with the activator approach, automated designing can be achieved. On average a complex drawing can be displayed on the screen in about 100 seconds, where over 95% of the initial section design time for repetitive or similar profile can be saved.

The Mechanics of the drawing of polygonal sections from round at elevated temperature

Economic factors such as the rise in cost of raw materials, labour and power, are compelling manufacturers of cold-drawn polygonal sections, to seek new production routes which will enable the expansion in the varieties of metals used and the inclusion of difficult-to-draw materials. One such method generating considerable industrial interest is the drawing of polygonal sections from round at elevated temperature. The technique of drawing mild steel, medium carbon steel and boron steel wire into octagonal, hexagonal and square sections from round at up to 850 deg C and 50% reduction of area in one pass has been established. The main objective was to provide a basic understanding of the process, with particular emphasis being placed on modelling using both experimental and theoretical considerations. Elevated temperature stress-strain data was obtained using a modified torsion testing machine. Data were used in the upper bound solution derived and solved numerically to predict drawing stress strain, strain-rate, temperature and flow stress distribution in the deforming zone for a range of variables. The success of this warm working process will, of course, depend on the use of a satisfactory elevated temperature lubricant, an efficient cooling system, a suitable tool material having good wear and thermal shock resistance and an efficient die profile design which incorporates the principle of least work. The merits and demerits of die materials such as tungsten carbide, chromium carbide, Syalon and Stellite are discussed, principally from the standpoint of minimising drawing force and die wear. Generally, the experimental and theoretical results were in good agreement, the drawing stress could be predicted within close limits and the process proved to be technically feasible. Finite element analysis has been carried out on the various die geometries and die materials, to gain a greater understanding of the behaviour of these dies under the process of elevated temperature drawing, and to establish the temperature distribution and thermal distortion in the deforming zone, thus establishing the optimum die design and die material for the process. It is now possible to predict, for the materials already tested, (i) the optimum drawing temperature range, (ii) the maximum possible reduction of area per pass, (iii) the optimum drawing die profiles and die materials, (iv) the most efficient lubricant in terms of reducing the drawing force and die wear.

Transducer diffraction theory and development of an ultrasonic tomogram

The work described in this thesis is the development of an ultrasonic tomogram to provide outlines of cross-sections of the ulna in vivo. This instrument, used in conjunction with X-ray densitometry previously developed in this department, would provide actual bone mineral density to a high resolution. It was hoped that the accuracy of the plot obtained from the tomogram would exceed that of existing ultrasonic techniques by about five times. Repeat measurements with these instruments to follow bone mineral changes would involve very low X-ray doses. A theoretical study has been made of acoustic diffraction, using a geometrical transform applicable to the integration of three different Green's functions, for axisymmetric systems. This has involved the derivation of one of these in a form amenable to computation. It is considered that this function fits the boundary conditions occurring in medical ultrasonography more closely than those used previously. A three dimensional plot of the pressure field using this function has been made for a ring transducer, in addition to that for disc transducers using all three functions. It has been shown how the theory may be extended to investigate the nature and magnitude of the particle velocity, at any point in the field, for the three functions mentioned. From this study. a concept of diffraction fronts has been developed, which has made it possible to determine energy flow also in a diffracting system. Intensity has been displayed in a manner similar to that used for pressure. Plots have been made of diffraction fronts and energy flow direction lines.

Effectiveness of nonpharmacologic treatments for acute seasonal allergic conjunctivitis

Objective - To investigate whether artificial tears and cold compress alone or in combination provide a treatment benefit and whether they were as effective as or could enhance topical antiallergic medication. Design - Randomized, masked clinical trial. Participants - Eighteen subjects (mean age, 29.5±11.0 years) allergic to grass pollen. Intervention - Controlled exposure to grass pollen using an environmental chamber to stimulate an ocular allergic reaction followed by application of artificial tears (ATs), 5 minutes of cold compress (CC), ATs combined with CC, or no treatment applied at each separate visit in random order. A subset of 11 subjects also had epinastine hydrochloride (EH) applied alone and combined with CC in random order or instillation of a volume-matched saline control. Main Outcome Measures - Bulbar conjunctival hyperemia, ocular surface temperature, and ocular symptoms repeated before and every 10 minutes after treatment for 1 hour. Results - Bulbar conjunctival hyperemia and ocular symptoms decreased and temperature recovered to baseline faster with nonpharmaceutical treatments compared with no treatment (P?of EH was enhanced by combining it with a CC (P?Cold compress combined with ATs or EH lowered the antigen-raised ocular surface temperature to less than the pre-exposure baseline. Artificial tear instillation alone or CC combined with ATs or EH significantly reduced the temperature (P?Cold compress combined with ATs or EH had a similar cooling effect (P?>?0.05). At all measurement intervals, symptoms were reduced for both EH and EH combined with CC than CC or ATs alone or in combination (P?of allergic conjunctivitis. A CC enhanced the use of EH alone and was the only treatment to reduce symptoms to baseline within 1 hour of antigenic challenge. Signs of allergic conjunctivitis generally were reduced most by a combination of a CC in combination with ATs or EH.

Effectiveness of nonpharmacologic treatments for acute seasonal allergic conjunctivitis

Objective To investigate whether artificial tears and cold compress alone or in combination provide a treatment benefit and whether they were as effective as or could enhance topical antiallergic medication. Design Randomized, masked clinical trial. Participants Eighteen subjects (mean age, 29.5±11.0 years) allergic to grass pollen. Intervention Controlled exposure to grass pollen using an environmental chamber to stimulate an ocular allergic reaction followed by application of artificial tears (ATs), 5 minutes of cold compress (CC), ATs combined with CC, or no treatment applied at each separate visit in random order. A subset of 11 subjects also had epinastine hydrochloride (EH) applied alone and combined with CC in random order or instillation of a volume-matched saline control. Main Outcome Measures Bulbar conjunctival hyperemia, ocular surface temperature, and ocular symptoms repeated before and every 10 minutes after treatment for 1 hour. Results Bulbar conjunctival hyperemia and ocular symptoms decreased and temperature recovered to baseline faster with nonpharmaceutical treatments compared with no treatment (P <0.05). Artificial tears combined with CC reduced hyperemia more than other treatments (P <0.05). The treatment effect of EH was enhanced by combining it with a CC (P <0.001). Cold compress combined with ATs or EH lowered the antigen-raised ocular surface temperature to less than the pre-exposure baseline. Artificial tear instillation alone or CC combined with ATs or EH significantly reduced the temperature (P <0.05). Cold compress combined with ATs or EH had a similar cooling effect (P > 0.05). At all measurement intervals, symptoms were reduced for both EH and EH combined with CC than CC or ATs alone or in combination (P <0.014). Conclusions After controlled exposure to grass pollen, CC and AT treatment showed a therapeutic effect on the signs and symptoms of allergic conjunctivitis. A CC enhanced the use of EH alone and was the only treatment to reduce symptoms to baseline within 1 hour of antigenic challenge. Signs of allergic conjunctivitis generally were reduced most by a combination of a CC in combination with ATs or EH. © 2014 by the American Academy of Ophthalmology.

Beyond the particular and universal:dependence, independence, and interdependence of context, justice, and ethics

This article reflects on context effects in the study of behavioral ethics and organizational justice. After a general overview, we review three key challenges confronting research in these two domains. First, we consider social scientific versus normative approaches to inquiry. The former aims for a scientific description, while the latter aims to provide prescriptive advice for moral conduct. We argue that the social scientific view can be enriched by considering normative paradigms. The next challenge we consider, involves the duality of morally upright versus morally inappropriate behavior. We observe that there is a long tradition of categorizing behavior dichotomously (e.g., good vs. bad) rather than continuously. We conclude by observing that more research is needed to compare the dichotomous versus continuous perspectives. Third, we examine the role of “cold” cognitions and “hot” affect in making judgments of ethicality. Historically speaking, research has empathized cognition, though recent work has begun to add greater balance to affective reactions. We argue that both cognition and affect are important, but more research is needed to determine how they work together. After considering these three challenges, we then turn to our special issue, providing short reviews of each contribution and how they help in better addressing the three challenges we have identified.

Collaborative filtering and deep learning based recommendation system for cold start items

Recommender system is a specific type of intelligent systems, which exploits historical user ratings on items and/or auxiliary information to make recommendations on items to the users. It plays a critical role in a wide range of online shopping, e-commercial services and social networking applications. Collaborative filtering (CF) is the most popular approaches used for recommender systems, but it suffers from complete cold start (CCS) problem where no rating record are available and incomplete cold start (ICS) problem where only a small number of rating records are available for some new items or users in the system. In this paper, we propose two recommendation models to solve the CCS and ICS problems for new items, which are based on a framework of tightly coupled CF approach and deep learning neural network. A specific deep neural network SADE is used to extract the content features of the items. The state of the art CF model, timeSVD++, which models and utilizes temporal dynamics of user preferences and item features, is modified to take the content features into prediction of ratings for cold start items. Extensive experiments on a large Netflix rating dataset of movies are performed, which show that our proposed recommendation models largely outperform the baseline models for rating prediction of cold start items. The two proposed recommendation models are also evaluated and compared on ICS items, and a flexible scheme of model retraining and switching is proposed to deal with the transition of items from cold start to non-cold start status. The experiment results on Netflix movie recommendation show the tight coupling of CF approach and deep learning neural network is feasible and very effective for cold start item recommendation. The design is general and can be applied to many other recommender systems for online shopping and social networking applications. The solution of cold start item problem can largely improve user experience and trust of recommender systems, and effectively promote cold start items.