Reinforced concrete poles are commonly used as street lighting and electrical transmission poles. Typical concrete lighting poles experience very little load due to torsion. The governing design loads are typically bending moments as a result of wind on the arms, fixtures, and the pole itself. The Canadian pole standard, CSA A14-07 relates the helical reinforcing to the torsion capacity of concrete poles. This issue and the spacing of the helical reinforcing elements are investigated. Based on the ultimate transverse loading classification system in the Canadian standard, the code provides a table with empirically derived minimum helical reinforcing amounts that vary depending on: 1) the pole class and 2) distance from the tip of the pole. Research into the minimum helical reinforcing requirements in the Canadian code has determined that the values were chosen empirically based on manufacturer’s testing. The CSA standard recommends two methods for the placement of the helical reinforcing: either all the required helical reinforcing is wound in one direction or an overlapping system is used where half of the required reinforcing is wound in each direction. From a production standpoint, the process of placing and tying this helical steel is time consuming and an improved method of reinforcement is desirable. Whether the double helix method of placement produces stronger poles in torsion than the single helix method is unknown. The objectives of the research are to analyze the Canadian code (CSA A14-07) requirements for minimum helical reinforcement and determine if the Canadian requirements are adequate. The helical reinforcement spacing requirements and the effect of spacing and direction of the helical reinforcing on the torsional capacity of a pole is also analyzed. Double helix and single helix reinforcement methods are compared to determine if there is a difference between the two methods of reinforcement. The Canadian pole standard (CSA A14-07) is analyzed and compared to the American and German standards. It was determined that the complex Canadian code provides more conservative spacing requirements than the American and German codes however the spacing requirements are based on empirical results alone. The rationale behind the Canadian code requirements is unknown. A testing program was developed to analyze the spacing requirements in the CSA A14-07 code. Fourteen specimens were produced with different helical reinforcing amounts: no reinforcement, single and double helical spaced CSA A14-07 designed reinforcement, and single helical specimens with twice the designed spacing values. Two specimens were produced based on the single helical reinforcement spacing. One specimen was produced with helical reinforcement wound in the clockwise direction and another with helical reinforcement in the counter clockwise direction. All specimens were tested under a counter clockwise torsional load. The clockwise specimens demonstrated the response of prestressed concrete poles with effective helical reinforcement whereas the counter clockwise reinforced specimens represented theoretically ineffective reinforcement. Two tip sizes were produced and tested: 165 mm and 210 mm. A sudden, brittle failure was noted for all specimens tested. The helical reinforcement provided no post-cracking ductility. It was determined that the spacing and direction of the helical reinforcement had little effect on the torsional capacity of the pole. Variable and scattered test results were observed. Predictions of the cracking torque based on the ACI 318-05, CSA A23.3-04 and Eurocode 2 all proved to be unconservative. Strut and tie modelling of the prestressing transfer zone suggested that the spacing of the helical steel be 40 mm for the 165 mm specimens and 53 mm for the 210 mm specimens. Based on the results of the strut and tie modelling, it is likely that the variability and scatter in the test results is due to pre-cracking of the specimens. All the 165 mm specimens and the large spaced 210 mm specimens were inadequately reinforced in the transfer zone. The degree of pre-cracking in the specimen likely causes the torsional capacity of the pole to vary. The strut and tie model results suggest that the requirements of the Canadian code can be simplified and rationalized. Similar to the American spacing requirements of 25 mm in the prestressing transfer zone, a spacing of 30 mm to 50 mm is recommended dependent on the pole tip size. Proper concrete mixes, adequate concrete strengths, prestressing levels, and wall thickness should be emphasized in the torsional CSA A14-07 design requirements since all have a large impact on the torsional capacity of prestressed concrete poles. Recommendations and future work are suggested to conclusively determine if direction and spacing have an effect on torsional capacity or to determine the factors causing the scatter in the results. The performance of prestressed concrete poles reinforced using the suggestions presented should also be further investigated. Improving the ability to predict the cracking torque based on the codes or reducing the scatter in the test results should also be studied.

This study is to analyze and test the extrusion process of a hollow spur gear and a solid helical product with magnesium alloy. In the hollow spur gear part, firstly, a design criterion to determine the forming parameters is proposed. Then, the Finite Element Analysis is used to simulate the flow pattern of the billet from separating channel, welding chamber to die bearing part. From a series of simulation results, the effect of separating channel length, mandrel entrance angle, welding chamber height, etc. on the radial filling ratio, welding pressure, extrusion load, etc. are found. By using the Taguchi Methods, we can find the most important parameters. Finally, a better die geometry is designed to obtain a sound product. In the helical product part, the Finite Element Analysis is used to get the understandings of radical filling ratio of magnesium alloy in the helical zone. Then, a better die geometry is designed from the results of analyses. Finally, hot extrusion experiments of a hollow spur gear and a solid helical product are conducted. The experimental values of the extrusion load and the product¡¦s dimension are compared with the analytic values to verify the validity of the analytic models.

The number of horizontal wells is increasing rapidly in all over the world with the growth of new technological developments. During horizontal well drilling, much more complex problems occur when compared with vertical well drilling, such as decrease in load transfer to the bit, tubular failure, tubular fatigue and tubular lock-up. This makes selection of appropriate tubular and making the right drill string design more important. As the total compression load on the horizontal section increases, the behavior of the tubular changes from straight to sinusoidal buckling, and if the total compression load continues to increase the behavior of the tubular changes to helical buckling. Determination of critical buckling loads with finite element method (FEM) in horizontal wells is the main objective of this study. Initially, a computer program (ANSYS) that uses FEM is employed to simulate different tubular and well conditions. Four different pipe sizes, four different wellbore sizes and three different torque values are used to model the cases. Critical buckling load values corresponding to significant variables are collected from these simulated cases. The results are classified into different buckling modes according to the applied weight on bit values and the main properties of the simulated model, such as modulus of elasticity, moment of inertia of tubular cross section, weight per unit length of tubular and radial clearance between the wellbore and the tubular. Then, the boundary equations between the buckling modes are obtained. The equations developed in this thesis by simulating the cases for the specific tubular sizes are used to make a comparison between the critical buckling load values from the models in the literature and this work. It is observed that the results of this work fit with literature models as the tubular size increases. The influence of torque on critical buckling load values is investigated. It is observed that torque has a slight effect on critical buckling load values. Also the applicability of ANSYS for buckling problems was revealed by comparing the ANSYS results with the literature models&amp / #8217 / results and the experimental study in the literature.

Protein-protein interactions are key to several biological processes that facilitate signal transduction and many other processes. These interactions are involved in pathways that are critical to many human diseases. Targeting specific protein-protein interactions is a challenging goal because protein-protein interactions are predominately through hydrophobic interactions. Antagonists of the protein-protein interactions need to be perfectly fit into the binding pockets to ensure the activity. The -helical domain of the proteins behaves as the recognition motifs for numerous protein-protein, and protein-nucleic acid interactions. Research has shown that pathways of many diseases contain protein-protein interactions involving -helical domains, e.g. neurological disorders, bacterial infections, HIV and cancer, etc. It is difficult yet very important to design small molecules to target the shallow binding areas of protein-protein interactions. So far the most successful one is Hamilton’s 1,4-terphenylene scaffold, which has been used to target the interactions between p53/MDM2, Bak/Bcl-xL etc. Inspired by this, we designed and synthesized three new scaffolds of non-pepditic -helical mimetics, mimicking the i, i + 4, i + 7 positions of an -helix. There are three basic principles that were leading our design. The side chains of our designed molecules should act as mimetics of the side chains of an -helix. Second, our molecules should possess improved water solubility. Third, the molecules should be easy to synthesize to generate a focused library. Some of our molecules, including the ones whose molecular weight are as low as 294, started to show some inhibition against p53/MDM2 interactions.

Advances in technology have placed a great emphasis on the design of broadband antennas as well as antenna miniaturization to cope with the demands of making electronic and handheld communication devices smaller and more efficient. In this thesis, the design and fabrication of a frequency independent antenna and a narrow-band planar microstrip Balun are presented. An analysis of frequency selective surfaces is also introduced in order to demonstrate their capability to miniaturize antenna thickness. Lastly, s-parameters measurements and efficiency characterization are performed to determine the radiation properties of surface mount chip inductors in order to determine the feasibility of using them as electrically small antennas.Two types of frequency independent antennas are considered due to their planar geometries, the Equiangular and Archimedean spiral antennas. Frequency independent antennas are radiating devices that have frequency independent impedance and pattern properties because their shape is specified only in terms of angles.The Balun is designed to meet the need of a feeding element for the Archimedean spiral antenna. A Balun is a three port device that connects an unbalanced transmission line such as a coaxial line to a balanced feed line such as the one required by two-arm spiral antennas. The Balun discussed in this work is designed to operate at 2.4 GHz with a 200 MHz bandwidth and to transform the antenna input impedance to a 50-ohm reference impedance. The main characteristics from this device that distinguish it from commercially available structures are its low cost, planarity, and compact footprint. The balancing capability of this Balun is shown by the close agreement between the measured and simulated results. Antennas can be potentially miniaturized in the z-direction by replacing the PEC ground plane separated from the antenna by a lambda /4 thick substrate with a frequency selective surface (FSS) structure that allows the ground plane conductor to be in close proximity to the antenna without affecting its radiation performance. The FSS layer operating at 2.4 GHz presented in this thesis is static (not tuned) and thus the overall bandwidth reduces approximately to the bandwidth obtained with the narrow-band Balun.

Dendritic encapsulation of poly(phenyleneethynylene)s or PPEs has been shown to enhance photoluminescent quantum efficiency and facilitate energy transfer by funneling photonic energy absorbed on the dendron periphery efficiently to the conjugated polymeric core. The research presented herein focuses on incorporating degradable dendron onto PPEs, examining whether or not similar benefits were conferred upon the proposed system and controlling polymer luminescence through the elimination of the insulating macromolecules. PPEs appended with disassembling dendrons of various generation sizes were synthesized and their optical properties studied. Polymer luminescence was then quenched via chemical degradation of the disassembling dendrons. Furthermore, the macromolecules resulting from disassembly exhibited tunable luminescence properties upon manipulation of pH. Consequently, it was determined that polymer luminescence could be controlled upon forming phenolic moieties along the PPE backbone. Tunable emission was later realized in the thin film as well through the integration of crosslinkable dendrons onto the polymer core.Recently, helical synthetic linear polymers have demonstrated the ability to facilitate stereoselective processes such as catalysis, recognition and separation. Consequently, it has become increasingly desirable to develop new platforms capable of imparting asymmetry. The work presented herein describes the synthesis of a series of polymers based upon chiral hydrobenzoin and the subsequent conformational analysis performed on these materials. It was envisioned that these polymeric materials might inherently possess conformational asymmetry and as result could be able to impart configurationally chirality by introducing a diastereomeric bias for the formation of one enantiomer over the other during the course of the reaction.

This Ph.D. thesis reports the discovery and study of several morphologies of ABC triblock copolymer assemblies in block selective solvents. One block copolymer self-assembled into helices (mostly double and some triple helices), and the other block copolymer formed a mixture of structures resembling hamburgers and striped cylinders. The helices, biomimmetic structures which are unusual from block copolymer self assembly, were prepared from the triblock copolymer poly(n-butyl methacrylate)-block-poly(2-cinnamoyloxyethyl methacrylate)-block-poly(tert-butyl acrylate) (PBMA-b-PCEMA-b-PtBA). They were formed spontaneously in several binary solvent mixtures including dichloromethane/methanol, tetrahydrofuran (THF)/methanol, and chloroform/methanol. They were formed in the composition ranges where the mixtures were good for the PtBA block, poor for the PCEMA block, and marginal for the PBMA block. The structure was studied and established by TEM, AFM, DLS and 1H NMR and by TEM tomography. The mechanism and kinetics of helix formation was examined. The Hamburger and striped cylinder structures were produced from poly(tert-butyl acrylate)-block-poly(2-cinnamoyloxyethyl methacrylate)-block-poly(succinated glyceryl monomethacrylate) or (PtBA-b-PCEMA-b-PSGMA) in mixtures of THF, (-)-sparteine and 1- or 2-propanol. Here THF solubilized all the blocks of the copolymer, while propanol was a precipitant for the middle block (PCEMA), and the chiral amine, (-)-sparteine, complexed with PSGMA and made it insoluble. Within the Hamburger-like structure, the “filling” was made of the complexed PSGMA chains and the "buns" were made of PCEMA. The striped cylinders were made of stacking alternating PCEMA and PtBA stubs. The PtBA chains were located on the outer surfaces of both of these structures. With the hamburger structures, after PCEMA crosslinking, we were able to remove the chiral amine by dialysis and make the PSGMA chains soluble again in solvents such as N, N dimethylformamide. The hamburgers were thus separated into two halves, with each half existing as a Janus particle, which had PtBA chains on one side and PSGMA chains on the other side. The Janus particles might have interesting applications, such as in Pickering emulsion stabilization. / Thesis (Ph.D, Chemistry) -- Queen's University, 2010-04-30 18:01:06.281

Background. Operative stabilisation of paediatric supracondylar elbow fractures is most commonly achieved through the use of percutaneous Kirschner wires. These implants are inert, cheap and simple to use. However, the requirement for removal and the possibility of pin site infection provides opportunity for the development of new techniques that eliminate these drawbacks. Bioabsorbable pins that remain in situ and allow definitive closure of skin at the time of surgery could provide such advantages. However, their ability to maintain fracture reduction and their effect on the growth plate has not been adequately evaluated. Hypotheses. The Acumed® Biotrak Helical Nail (a bioabsorbable fixation implant) has comparable strength to Kirschner wires and does not result in significant disruption of the growth plate or subsequent growth. Studies. Three complementary studies were performed. (1) A retrospective cohort analysis was performed to establish the prevalence of complications related to Kirschner wire fixation of paediatric supracondylar elbow fractures. (2) A saw-bone model was designed to compare the mechanical performance of the Helical Nail and Kirschner wires. (3) An ovine model was designed to assess the in vivo effects of the Helical Nail on limb growth and physeal morphology. The surgical practicalities of the device and its potential for use in the paediatric setting were evaluated. The primary outcome was femoral length six months after Helical Nail insertion. Micro-CT evaluation of growth plate thickness, percentage disruption and bony infiltration was undertaken – the first time this technique has been used in a large animal study. Traditional histopathological techniques complimented the Micro-CT analysis and offered comment on the microscopic appearance of the growth plate immediately adjacent to the bioabsorbable nails. Results. The infection rate within a large tertiary referral centre was 9.6%, which was marginally higher than previous cohort studies. Mechanical testing demonstrated that the Helical Nail had comparable strength in rotation, but inferior resistance to posterior translation, when compared to Kirschner wires. In the ovine model, the Helical Nail disrupted 3.4% of the physis. The nails had no effect on femoral growth during the six month study period. Micro-CT analysis of both the helical nail and Kirschner wire groups demonstrated multiple bony bridges, with two cases of physeal tethering in the Helical Nail group. There was no difference in physeal thickness or bony infiltration of the physis. Histopathology did not reveal any significant inflammatory or foreign body reaction adjacent to the nails. Conclusion. The Helical Nail demonstrated a number of encouraging attributes which indicate its potential. However, in its current state the device is not suitable for use in the stabilisation of paediatric supracondylar elbow fractures.

Na prática brasileira, usualmente a previsão da capacidade de carga de fundações por estacas é baseada em métodos semi-empíricos, por meio de correlações diretas da resistência de ponta e por atrito lateral ao longo da estaca com os valores de NSPT. Entretanto, no caso de fundações por estacas helicoidais, ainda utilizam-se métodos teóricos que necessitam de valores de parâmetros geotécnicos obtidos indiretamente a partir de correlações com os valores de NSPT (coesão, peso específico, ângulo de atrito, coeficiente de empuxo). Portanto, nesta dissertação foi desenvolvido um método semi-empírico para estimar a capacidade de carga à tração de fundações por estacas helicoidais profundas por meio de correlações diretas com o valor de NSPT do solo de instalação da estaca. Além disso, são apresentados no presente trabalho valores de fator de torque KT, obtidos por análise estatística, para a verificação da capacidade de carga à tração da estaca usando-se medidas do torque necessário para instalá-la no terreno. Nesta pesquisa dois diferentes modelos para estimativa da capacidade de carga foram desenvolvidos e analisados estatisticamente. O estudo das características das amostras de fundações por estacas helicoidais usadas nesta pesquisa permitiu a subdivisão em grupos (tipo de solo e quantidade de hélices) de modo a se obter modelos mais precisos. Com os resultados deste trabalho, foi possível elaborar recomendações para projeto e execução de estacas helicoidais, bem como desenvolver um modelo para estimar a capacidade de carga à tração de estacas helicoidais instaladas em solos similares aos das estacas usadas neste estudo. / The pile capacity in Brazil is usually predicted by semi-empirical methods based on direct correlations between SPT-N values and pile shaft and pile base resistance. However, the uplift capacity of helical piles is still calculated using theoretical methods based on soil parameters, as: cohesion, unit weight, friction angle, and lateral earth pressure coefficient. In this case, these parameters are obtained indirectly from correlations with values of SPT-N. This dissertation was inspired by the need of a more appropriate method to calculate the uplift capacity of helical piles, by correlating the capacity of the bearing plates directly with the soil type and SPT-N values. In this work, it was developed a semi-empirical method for estimating the pullout capacity of deep helical piles by using SPT test results, similarly to the other methods used for conventional piles. Also, this work presents some results of torque factor, obtained by statistical analysis, to the verification of the pile capacity by using the torque recorded at the end of pile installation. In this research, it was performed several statistical analysis to obtain appropriate models to estimate the uplift capacity of helical piles. The cases of helical piles used in this investigation are classified into groups according to the soil type and the number of helices. As a result, detailed evaluations and recommendations for improvement of helical pile design are presented. The proposed model is recommended to calculate the uplift capacity of helical piles installed in similar soils to that used in this study.

Made available in DSpace on 2014-10-09T12:53:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:44Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP / FAPESP:05/03612-0