Search results

The purpose of this paper is to empirically examine the effect on US stock, bond and real estate investment trust (REIT) prices triggered by the US Federal Reserve Chairman Ben Bernanke’s announcement of a possible intent to unwind, or taper, quantitative easing (QE). In particular, the author assessed whether the effect of the “Taper Tantrum” was fundamental or financial on financial markets.

The methodology used to determine whether the effect of the “Taper Tantrum” was fundamental or purely financial is that suggested by French and Roll (1986) as extended by Tuluca et al. (2003). The analysis is based on daily data for large cap stocks, small cap stocks, long-term bonds and REITs for 18 months before Ben Bernanke’s announcement and for 18 months after the announcement.

The results show that the “Taper Tantrum” had a fundamental, rather than a financial effect on all asset classes, especially so for REITs.

The author also found that in the post-taper period following Ben Bernanke’s announcement the correlation of REITs with stocks decreased compared with pre-taper period, whereas the correlation of REITS with bonds increased substantially. In other words, the “Taper Tantrum” had a profound effect on the risk/return benefits of including REITs in the US mixed-asset portfolio.

This is the first paper to examine the effect of the “Taper Tantrum” on REITs.

The purpose of this study is to investigate the aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips.

In this work, wind tunnel tests were made to study the influence in aerodynamic characteristics over a typical low-to-moderate-aspect-ratio wing of a general aviation aircraft, equipped with sheared – swept and tapered planar – wing tips. An experimental parametric study of different wing tips was tested. Variations in its leading and trailing edge sweep angle as well as variations in wing tip taper ratio were considered. Sheared wing tips modify the flow pattern in the outboard region of the wing producing a vortex flow at the wing tip leading edge, enhancing lift at high angles of attack.

The induced drag is responsible for nearly 50% of aircraft total drag and can be reduced through modifications to the wing tip. Some wing tip models present complex geometries and many of them present benefits in particular flight conditions. Results have demonstrated that sweeping the wing tip leading edge between 60 and 65 degrees offers an increment in wing aerodynamic efficiency, especially at high lift conditions. However, results have demonstrated that moderate wing tip taper ratio (0.50) has better aerodynamic benefits than highly tapered wing tips (from 0.25 to 0.15), even with little less wing tip leading edge sweep angle (from 57 to 62 degrees). The moderate wing tip taper ratio (0.50) offers more wing area and wing span than the wings with highly tapered wing tips, for the same aspect ratio wing.

Although many studies have been reported on the aerodynamics of wing tips, most of them presented complex non-planar geometries and were developed for cruise flight in high subsonic regime (low lift coefficient). In this work, an exploration and parametric study through wind tunnel tests were made, to evaluate the influence in aerodynamic characteristics of a low-to-moderate-aspect-ratio, tapered, untwisted, unswept wing, equipped of sheared wing tips (wing tips highly swept and tapered).

This paper aims to present the capacitance characterization of tapered dielectrophoresis (DEP) microelectrodes as micro-electro-mechanical system sensor and actuator device. The application of DEP-on-a-chip (DOC) can be used to evaluate and correlate the capacitive sensing measurement at an actual position and end station of liquid suspended targeted particles by DEP force actuator manipulation.

The capability of both, sensing and manipulation was analysed based on capacitance changes corresponding to the particle positioning and stationing of the targeted particles at regions of interest. The mechanisms of DEP sensor and actuator, designed in DOC applications were energized by electric field of tapered DEP microelectrodes. The actual DEP forces behaviour has been also studied via quantitative analysis of capacitance measurement value and its correlation with qualitative analysis of positioning and stationing of targeted particles.

The significance of the present work is the ability of using tapered DEP microelectrodes in a closed mode system to simultaneously sense and vary the magnitude of manipulation.

The integration of DOC platform for contactless electrical-driven with selective detection and rapid manipulation can provide better efficiency in in situ selective biosensors or bio-detection and rapid bio-manipulation for DOC diagnostic and prognostic devices.

Tapered section can resist maximum stress at a single location while the stresses are considerably lower at the rest of the member; therefore, it could have higher structural efficiency compared to conventional section. It could also satisfy functional requirements while reducing weight and cost in many fields of civil construction. Perforation in the steel section also eases the integration of Mechanical and Electrical (M&E) services such as ventilation pipes and electrical cables within the structural depths of the beam. In this analysis, the structural efficiency of tapered steel section with perforation under lateral-torsional buckling behaviour is investigated.

A total of 81 models are analysed using LUSAS software and five variables are investigated which involved perforation sizes, perforation shapes, perforation layout, tapering ratio and flange and Web thickness. Buckling moment is obtained from the analysis results in LUSAS software, while self-weight and structural efficiency are manually calculated.

Perforation size of 0.75 D has the highest structural efficiency, although it can withstand a smaller buckling load. This is due to its lower self-weight compared to other perforation sizes. The square perforation shape also has the highest structural efficiency compared to circular perforation and diamond perforation. An increment of percentage in structural efficiency of the square perforation shape with 0.75 D is the highest at 3.07%. The circular perforation shape with 0.75 D (Open-Open-Open perforation layout) has the highest increment of percentage in structural efficiency which is 2.37%. The tapering ratio of 0.3 is the most efficient and an increment of percentage in structural efficiency is 114.36%. The flange thickness of 0.02 m and Web thickness of 0.015 m has the highest structural efficiency at 45.756 and 29.171, respectively.

In conclusion, a section should be able to resist the large buckling moment and has a lower self-weight to achieve high structural efficiency.

The purpose of this paper presents the effects of actively morphing root chord and taper on the energy of the flight control system (i.e. FCS).

Via regarding previously mentioned purposes, sophisticated and realistic helicopter models are benefitted to examine the energy of the FCS.

Helicopters having actively morphing blade root chord length and blade taper consume less control energy than the ones having one of or any of passively morphing blade root chord length and blade taper.

Actively morphing blade root chord length and blade taper can be used for cheaper helicopter operations.

The main originality of this paper is applying active morphing strategy on helicopter blade root chord and blade taper. In this paper, it is also found that using active morphing strategy on helicopter blade root chord and blade taper reasons less energy consumption than using either passively morphing blade root chord length plus blade taper or not any. This causes also less fuel consumption and green environment.

The purpose of this paper is to propose and optimize plastic optical fiber (POF) probe with macro-bending biconical tapered structure for the relative humidity (RH) sensing.

In this study, the principle is the evanescent wave power modulated by the ambient humidity. The probe is fabricated by using fused biconical taper and heat-setting method and then coated with a fluorescent moisture-sensitive film.

The probe’s sensing performance can be optimized by changing the probe’s curvature radius, biconical tapered transition length and taper waist diameter. The result shows that the sensitivity of the probe is up to 1.60 and 3.40 mV/ per cent, respectively, at low humidity (10-45 per cent) and high humidity (45-90 per cent). Also, this probe has good linearity, repeatability, photostability and long-term stability.

The proposed probe can improve the sensitivity and linearity of RH sensing without complex devices, which is necessary for mass production, remote measurement and convenient operation.

POF probe with macro-bending biconical tapered structure is investigated in this paper, which is proved to be effective in improving the sensitivity and linearity.

The purpose of this study is to examine the effect of passive and active morphing of blade root chord length and blade taper on the control effort of the flight control system (FCS) of a helicopter.

Physics-based helicopter models, which are functions of passive and active morphing, are created and applied in helicopter FCS design to determine the control effort.

Helicopters, having both passively and actively morphing blade root chord length and blade taper, experience less control effort than the ones having either only passively morphing blade root chord length or only blade taper or only actively morphing blade root chord length and blade taper.

Both passively and actively morphing blade root chord length and blade taper can be implemented for more economical autonomous helicopter flights.

Main novelty of our article is simultaneous application of passive and active morphing ideas on helicopter root chord length and blade taper. It is also proved in this study that using both passive and active morphing ideas on helicopter blade root chord and blade taper causes much less energy consumption than using either only passive morphing idea on helicopter blade root chord and blade taper or only active morphing idea on helicopter blade root chord and blade taper. This also reduces fuel consumption and also makes environment cleaner.

THE change from the parallel wings of the now obsolescent biplane to the tapered wings of the monoplane, usually fitted with flaps, raised a great number of problems, both aerodynamic and structural. Work on these has been pursued vigorously during the past few years, but the designer is still some considerable distance from having all his questions answered. For instance, further information is required as to the relation between wing thickness and profile drag before it can be decided what is the maximum thickness which can be used, taking both aero‐dynamical and structural considerations into account. This question is complicated by the fact that, so far as the tip sections are concerned,. the indications are that the thickness ratio has important effects on the nature of the stall, violent or gentle. So, too, will such factors as centre line camber and position of maximum ordinate affect the nature of the stall in greater or Jess degree. Added to these factors there is, of course, the important one of the taper itself, including—as is now realised—the question as to the way in which the tapering is done, that is, whether by sweeping the trailing edge forward or the leading edge back, or, as is more usual, a combination of the two.

THE fundamental problem of aerofoil theory is to predict accurately the characteristics of wings of various sections and plan form when the former may be any function of the latter. The vortex theory of aerofoils enables us to predict the chief properties of aerofoils below the stall. We are, however, interested also in the conditions obtaining at and above the stall. In the present state of the art we are obliged to rely on wind tunnel tests. The number and variety of wings that would have to be tested in order to give us at all a comprehensive survey of the possibilities of taper, aerodynamic twist and varying section are so great that wind tunnel tests can so far only be said to have touched the fringe of the problem.

The purpose of this paper is to study the resonance failure sensitivity analysis of straight-tapered assembled pipe conveying nonuniform axial fluid by an active learning Kriging (ALK) method.

In this study, first, the motion equation of straight-tapered assembled pipe conveying nonuniform fluid is built. Second, the Galerkin method is used for calculating the natural frequency of assembled pipe conveying nonuniform fluid. Third, the ALK method based on expected risk function (ERF) is used to calculate the resonance failure probability and moment independent global sensitivity analysis.

The findings of this paper highlight that the eigenfrequency and critical velocity of uniform fluid-conveying pipe are less than the reality and the error is biggest in first-order natural frequency. The importance ranking of input variables affecting the resonance failure can be obtained. The importance ranking is different for a different velocity and mode number. By reducing the uncertainty of variables with a high index, the resonance failure probability can be reduced maximally.

There are no experiments on the eigenfrequency and critical velocity. There is no experiments about natural frequency and critical velocity of straight tapered assembled pipe to verify the theory in this paper.

The originality of this paper lies as follows: the motion equation of straight-tapered pipe conveying nonuniform fluid is first obtained. The eigenfrequency of nonuniform fluid and uniform fluid inside the assembled pipe are compared. The resonance reliability analysis of straight-tapered assembled pipe is first proposed. From the results, it is observed that the resonance failure probability can be reduced efficiently.