Annular impinging jet with recirculation zone expanded by acoustic excitation

Flow visualization and mass transfer (naphthalene sublimation) experiments were performed on acoustically excited annular air jet with diameter ratio Di/Do=0.95. Two different regimes of the time-mean flow field were found, differing in the size of the central recirculation zone, with either the single stagnation point or the stagnation circle. The switching between the two regimes is accomplished by acoustic excitation, under identical geometry conditions. An effective stabilization of the large recirculation zone, as well as remarkable augmentation of average heat/mass transfer by 23%, have been achieved at the excitation Strouhal number Sh=0.94

Uniform task level definitions for robotic system performance comparisons

A series of ten task levels of increasing difficulty was compiled for use in comparative performance evaluations of available and future robotics technology. Each level has a breakdown of ten additional levels of difficulty to provide a layering of 100 levels. It is assumed that each level of task performance must be achieved by the system before it can be appropriately considered for the next level

A survey of adaptive control technology in robotics

Previous work on the adaptive control of robotic systems is reviewed. Although the field is relatively new and does not yet represent a mature discipline, considerable attention has been given to the design of sophisticated robot controllers. Here, adaptive control methods are divided into model reference adaptive systems and self-tuning regulators with further definition of various approaches given in each class. The similarity and distinct features of the designed controllers are delineated and tabulated to enhance comparative review

Enhancement of synthetic jets by means of an integrated valve-less pump Part II. Numerical and experimental studies

The paper studies the performance of the new fluid jet actuator based on the novel principle of the generation of fluid jet, which has been presented in [Z. Travnicek, A.I. Fedorchenko, A.-B. Wang, Enhancement of synthetic jets by means of an integrated valve-less fluid pump. Part I. Design of the actuator, Sens. Actuators A, 120 (2005) 232-240]. The fluid jet actuator consists of a synthetic jet actuator and a valve-less pump. The resulting periodical fluid jet is intrinsically non-zero-net-mass-flux, in contrast to the traditional synthetic jet. The numerical results have been compared with the laboratory experiments comprising phase-locked smoke visualization and time-mean velocity measurements. The results have confirmed the satisfactory performance of the actuator

A Re-Examination of the Border Effect

This paper reexamines the evidence on the border effect, the finding that the border drives a wedge between domestic and foreign prices. We argue that the border effect can be inflated by the volatility and persistence of the nominal exchange rate and by the cross-country heterogeneity in the distribution of within-country price differentials. We develop a simple framework to separate the border effect from these confounding factors. Using price data from Engel and Rogers (1996) and Parsley and Wei (2001), we show that after controlling for the confounding factors the border effect between the U.S. and Canada and the U.S. and Japan is negligible.

A Re-Examination of the Border Effect

This paper reexamines the evidence on the border effect, the finding that the border drives a wedge between domestic and foreign prices. We argue that the border effect can be inflated by the volatility and persistence of the nominal exchange rate and by the cross-country heterogeneity in the distribution of within-country price differentials. We develop a simple framework to separate the border effect from these confounding factors. Using price data from Engel and Rogers (1996) and Parsley and Wei (2001), we show that after controlling for the confounding factors the border effect between the U.S. and Canada and the U.S. and Japan is negligible.

No-moving-part hybrid-synthetic jet actuator

In contrast to usual synthetic jets, the “hybrid-synthetic jets” of non-zero timemean nozzle mass flow rate are increasingly often considered for control of flow separation and/or transition to turbulence as well as heat and mass transfer. The paper describes tests of a scaled-up laboratory model of a new actuator version, generating the hybrid-synthetic jets without any moving components. Self-excited flow oscillation is produced by aerodynamic instability in fixed-wall cavities. The return flow in the exit nozzles is generated by jet-pumping effect. Elimination of the delicate and easily damaged moving parts in the actuator simplifies its manufacture and assembly. Operating frequency is adjusted by the length of feedback loop path. Laboratory investigations concentrated on the propagation processes taking place in the loop

Computer simulation and design of a three degree-of-freedom shoulder module

An in-depth kinematic analysis of a three degree of freedom fully-parallel robotic shoulder module is presented. The major goal of the analysis is to determine appropriate link dimensions which will provide a maximized workspace along with desirable input to output velocity and torque amplification. First order kinematic influence coefficients which describe the output velocity properties in terms of actuator motions provide a means to determine suitable geometric dimensions for the device. Through the use of computer simulation, optimal or near optimal link dimensions based on predetermined design criteria are provided for two different structural designs of the mechanism. The first uses three rotational inputs to control the output motion. The second design involves the use of four inputs, actuating any three inputs for a given position of the output link. Alternative actuator placements are examined to determine the most effective approach to control the output motion