Mechanical performance of through thickness reinforcement for damage tolerant aircraft structurse

This thesis is focused on investigating the mechanical performance of Z-pin reinforced laminate under different loading conditions and the development of automatic Z-pin insertion machines. A versatile surface-based finite element modeling strategy is developed for the analysing of cohesive contact analysis. The modeling approach is developed based on bridging law and modified Coulomb friction law. This modeling method has been validated via comparing against the benchmark work, including the Double cantilever beam test, 4-point End-Notched Flexure test, Mixed-mode Bending test. The tensile fibre failure, modeled using the Weibull Failure criterion, verified through comparing the modeling results to an experimental tensile test result of unidirectional laminate coupon. The modeling approach carried forward to the analysis of the Z-pin reinforced laminate. A three-dimensional modeling approach was used in order to address the microstructural features of Z-pinned laminates. These features, including the presence of resin pockets surrounding Z-pin, stacking sequence, Internal splitting. The interface between Z-pin and laminate, as well as internal splitting, were described by customised surface-based cohesive contact. There are a few factors that significantly affect the modeling results, including Frictional coefficient, internal splitting, mode mixities, and each of them was discussed in the parametric study section. The modeling approach was used to justify the performance of Z-pins in resisting dynamic mode I and mode II delamination has been investigated at a high loading rate. It was found that the Z-pin efficiency in resisting mode I delamination decreased with increasing loading rate compared to the quasi-static loading case, and the loading rate in the mode II test did not significantly influence the maximum bridging force. Moreover, the FE result tends to delay the shift of the failure mode from pull-out to pin rupture. An automatic Z-pin insertion machine is proposed in the last chapter. Building based on a 3D-printer, the insertion machines able to move, heat, and insert Z-pins by the control of Commerical software LabView. Keywords: Bridging law, Surface-based, Benchmark work. Three-Dimensional FE model, Dynamic bridging, LabViewOpen Acces

The Impact of Hedging on Stock Return and Firm Value: New Evidence from Canadian Oil and Gas Companies

This paper analyzes the impact of hedging activities of large Canadian oil and gas companies on their stock returns and firm value. Differing from the existing literature this research finds that some of these relationships are nonlinear based on the framework of nonlinear generalized additive models. The research based on this more general methodology reveals some interesting findings on oil and gas hedging activities. The large Canadian oil and gas firms are able to use hedging to protect downside risk against the unfavorable oil and gas price changes. But oil hedging appears to be more effective in protecting stock returns than gas hedging is when downside risk presents. In addition, oil and gas reserves are more likely to play a positive (negative) role when the oil and gas prices are increasing (decreasing). Finally, hedging, in particular hedging on gas, together with profitability, investment and leverage, has certain impacts on firm value.oil; gas; hedging; return; firm value; general additive models ; Canada

Laser Cooling of 85Rb Atoms to the Recoil Temperature Limit

We demonstrate the laser cooling of 85Rb atoms in a two-dimensional optical lattice. We follow the two-step degenerate Raman sideband cooling scheme [Kerman et al., Phys. Rev. Lett. 84, 439 (2000)], where a fast cooling of atoms to an auxiliary state is followed by a slow cooling to a dark state. This method has the advantage of independent control of the heating rate and cooling rate from the optical pumping beam. We operate the lattice at a Lamb-Dicke parameter eta=0.45 and show the cooling of spin-polarized 85Rb atoms to the recoil temperature in both dimension within 2.4 ms with the aid of adiabatic cooling

Search for serendipitous TNO occultation in X-rays

To study the population properties of small, remote objects beyond Neptune's orbit in the outer solar system, of kilometer size or smaller, serendipitous occultation search is so far the only way. For hectometer-sized Trans-Neptunian Objects (TNOs), optical shadows actually disappear because of diffraction. Observations at shorter wave lengths are needed. Here we report the effort of TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June 2007 to October 2011. No definite TNO occultation events were found in the 334 ks data. We investigate the detection efficiency dependence on the TNO size to better define the sensible size range of our approach and suggest upper limits to the TNO size distribution in the size range from 30 m to 300 m. A list of X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA

Necessary Reform of Insurance Law in China after its WTO

This paper will include five parts: Part I will clearly examine China\u27s obligations under the General Agreement on Trade in Service and its WTO commitments through official WTO documents. Part II will briefly introduce the history of China\u27s insurance business and relevant legislation, discuss the recent rapid growth in the Chinese insurance market, and reveal that, although the legal reform in insurance law and related regulations has been initiated, other reforms are still necessary to back the continuing growth of the insurance market. Part III will examine whether the Insurance Law of 2002 and related regulations have conformed with all obligations and commitments that China owes the WTO and determine whether further amendments are needed. Part IV will compare China\u27s Insurance Law and other regulations with international standards to see if any disparity exists. This analysis will utilize guidelines, standards, and principles released by the International Association of Insurance Supervisors (IAIS). To cure any defect based on the IAIS standard, relevant legislation from two major insurance markets, the United States and the European Union, will be presented as guidance for the recommendation of further amendments to China\u27s Insurance Law. Finally, Part V will describe an optimal legal system of insurance laws and regulations in the post-WTO era

Bell's Inequality and Entanglement in Qubits

We propose an alternative evaluation of quantum entanglement by measuring the maximum violation of the Bell's inequality without performing a partial trace operation. This proposal is demonstrated by bridging the maximum violation of the Bell's inequality and the concurrence of a pure state in an $n$-qubit system, in which one subsystem only contains one qubit and the state is a linear combination of two product states. We apply this relation to the ground states of four qubits in the Wen-Plaquette model and show that they are maximally entangled. A topological entanglement entropy of the Wen-Plaquette model could be obtained by relating the upper bound of the maximum violation of the Bell's inequality to the concurrences of a pure state with respect to different bipartitions.Comment: 10 page

Grip Suppression using a Machine-Learned Technique

This publication describes techniques for grip suppression of a touchscreen display of a computing device using a machine-learned technique. When a user intentionally or unintentionally touches the display (e.g., with a hand or a finger), a Touch Manager of the computing device performs operations to determine a user intent associated with the touch input to prevent false triggering of the display (e.g., by a grip of a hand holding the device). A machine-learned (ML) model calculates the likeliness of an intentional touch input (e.g., a tap, a swipe, or a scroll of a hand or a finger to input or manage information on the device) by identifying and assigning weights to features of the touch input. A total weight is calculated for each touch input and compared to a default threshold (e.g., an accepted threshold associated with an intentional touch input), which may be adjusted to ensure accuracy of user-intent predictions. After the Touch Manager verifies the user-intent predictions using heuristic and/or hysteresis logic, the computing device may perform operations to suppress or enable the touch input

Causality in Quantiles and Dynamic Stock Return-Volume Relations

This paper investigates the causal relations between stock return and volume based on quantile regressions. We first define Granger non-causality in all quantiles and propose testing non-causality by a sup-Wald test. Such a test is consistent against any deviation from non-causality in distribution, as opposed to the existing tests that check only noncausality in certain moment. This test is readily extended to test non-causality in different quantile ranges, and the testing results enable us to identify the quantile range for which causality is relevant. In the empirical studies of 3 major stock market indices, we find that, while the conventional test suggests no causality in mean, there are strong evidences that lagged volume Granger causes return in all but some middle quantiles. In particular, the causal effects have opposite signs at lower and upper quantiles and are stronger at more extreme quantiles. These relations form (symmetric) V shapes across quantiles. They also show that the dispersion of the return distribution increases with volume so that volume has a positive effect on return volatility. It is also shown that the quantile causal effects of lagged return on volume are mainly negative.Granger non-causality in quantiles, quantile causal effect, quantile regression, return-volume relation, sup-Wald test