Evaluation of an innovative joint design for the adjacent box beam bridges

Bridges constructed with adjacent precast prestressed concrete box beams have been in service for many years and provide an economical solution for short and medium span bridges. A recurring problem with this type of bridge is the cracking in the longitudinal joints between adjacent beams, resulting in reflective cracks forming in the asphalt wearing surface or concrete deck. AASHTO (2014) states that the differential shrinkage due to differences in age, concrete mix, environmental conditions etc., have been observed to cause internal force effects that are difficult to predict at the design phase. The objective of this research is to develop an innovative design of the connection used in adjacent precast concrete box beam bridges to eliminate cracking and leakage in the longitudinal joints between adjacent boxes. To meet the research goal, a comprehensive review of relevant specifications and technical literature from the past twenty years has been conducted to study the design and construction attributes influencing the long-term performance of the box beam bridge joint and identify the reasons that cause cracking in the joint between the adjacent box beams. A three step evaluation of joint was conducted on the material level, small scale level and full scale level. In each level of evaluation, both experimental and analytical evaluation were conducted. The results indicated that the innovative connection can create a crack-free joint without the utilization of a shear key nor transverse post-tensioning. Both experimental and analytical results indicate that the innovative joint showed good performance in resisting joint cracks in both the early-age and the long-term service life of the bridge. The “compression-dominate-joint” created by the expansive joint material combined with transverse reinforcing steel across the interface is expected to overcome the difficulties in predicting the early-age internal forces during the design phase stated by AASHTO (2014). To further investigate the performance of this joint detail, it is recommended that a field trial be completed. During this field trial, the bridge should be monitored and evaluated during early age concrete curing as well as for a period of at least two years following construction

On the influence of the Continental Slope on the Western Boundary Layer: The enhanced transport and recirculation

Quasi-geostrophic theory is used to study the effect of a continental slope on the Western Boundary Layer. The compression of the vortex tubes by the slope results in a strong northward boundary current called the Continental Slope Boundary Current (hereafter CSBC). On the β-plane, for a reasonably high slope, we find a strong barotropic recirculation which enhances the total transport of the Western Boundary Current significantly. The two-layer model further shows that the CSBC is trapped in the lower layer. In oceans with very deep lower layers, the CSBC transport increases dramatically. Consequently, even for a very weak lower layer incoming flow, we can still have a very strong barotropic CSBC transport compared to the Inertial Boundary Current. Additionally, for an ocean with a very deep lower layer, we can always have comparable total transport in both layers even when the lower layer incoming flow is very weak

An analog OP-amp IP-core using 0.18 micrometer CMOS technology.

This thesis presents a new design for a 0.18mum CMOS analog Operational Amplifier. The most difficult design challenge for a low-voltage operational amplifier is the design of a rail-to-rail input differential amplifier stage with a constant transconductance (gm). The main contribution in this thesis is the novel design methodology of a DC level shifter that enables the synthesis of a 0.18mum CMOS analog operational amplifier with a constant-gm implementation over a common-mode voltage range from 0 to 1.8V. The design of a 0.18mum CMOS low-voltage operational amplifier with constant overall transconductance gm, which allows for a rail-to-rail input swing without degrading the common-mode rejection ratio (CMRR) or causing the slew rate to vary, is developed in this thesis. The DC level shifter circuit design methodology optimizes all the transistors of the DC level shifter to improve the overlapping of p-pair and n-pair tail currents. The 1.8V CMOS operational amplifier has power consumption less than 178muw, a CMRR of 123.6 dB and a slew rate of 4V/mus. A total of 32 transistors were used in the final layout. The purpose of this design is to build the operational amplifier as an Intellectual Property (IP) core suitable for System-on-Chip (SOC) implementation. This IP core can be repeatedly used in future designs and should also be able to easily inserted into any vendor technology or design methodology. Source: Masters Abstracts International, Volume: 41-04, page: 1155. Adviser: W. C. Miller. Thesis (M.A.Sc.)--University of Windsor (Canada), 2002

The SYZ mirror symmetry and the BKMP remodeling conjecture

The Remodeling Conjecture proposed by Bouchard-Klemm-Mari\~{n}o-Pasquetti (BKMP) relates the A-model open and closed topological string amplitudes (open and closed Gromov-Witten invariants) of a symplectic toric Calabi-Yau 3-fold to Eynard-Orantin invariants of its mirror curve. The Remodeling Conjecture can be viewed as a version of all genus open-closed mirror symmetry. The SYZ conjecture explains mirror symmetry as $T$-duality. After a brief review on SYZ mirror symmetry and mirrors of symplectic toric Calabi-Yau 3-orbifolds, we give a non-technical exposition of our results on the Remodeling Conjecture for symplectic toric Calabi-Yau 3-orbifolds. In the end, we apply SYZ mirror symmetry to obtain the descendent version of the all genus mirror symmetry for toric Calabi-Yau 3-orbifolds.Comment: 18 pages. Exposition of arXiv:1604.0712

The Gerby Gopakumar-Mari\~no-Vafa Formula

We prove a formula for certain cubic $\Z_n$-Hodge integrals in terms of loop Schur functions. We use this identity to prove the Gromov-Witten/Donaldson-Thomas correspondence for local $\Z_n$-gerbes over \proj^1.Comment: 43 pages, Published Versio

A Review of Smart Materials in Tactile Actuators for Information Delivery

As the largest organ in the human body, the skin provides the important sensory channel for humans to receive external stimulations based on touch. By the information perceived through touch, people can feel and guess the properties of objects, like weight, temperature, textures, and motion, etc. In fact, those properties are nerve stimuli to our brain received by different kinds of receptors in the skin. Mechanical, electrical, and thermal stimuli can stimulate these receptors and cause different information to be conveyed through the nerves. Technologies for actuators to provide mechanical, electrical or thermal stimuli have been developed. These include static or vibrational actuation, electrostatic stimulation, focused ultrasound, and more. Smart materials, such as piezoelectric materials, carbon nanotubes, and shape memory alloys, play important roles in providing actuation for tactile sensation. This paper aims to review the background biological knowledge of human tactile sensing, to give an understanding of how we sense and interact with the world through the sense of touch, as well as the conventional and state-of-the-art technologies of tactile actuators for tactile feedback delivery