Airway sensors play an important role in control of breathing. Recently, it was found that pulmonary slowly adapting stretch receptors (SARs) cease after a brief excitation following sodium pump blockade by ouabain. This deactivation can be explained by overexcitation. If this is true, mechanical stimulation of the SARs should also lead to a deactivation. In this study, we recorded unit activity of the SARs in anesthetized, open-chest, and mechanically ventilated rabbits and examined their responses to lung inflation at different constant pressures. Forty-seven of 137 units had a clear deactivation during the lung inflation. The deactivation threshold varied from unit to unit. For a given unit, the higher the inflation pressure, the sooner the deactivation occurs. For example, the SARs deactivated at 3.0 +/- 0.3 and 4.8 +/- 0.4 s when the lungs were inflated to constant pressures of 30 and 20 cmH(2)O, respectively (n = 25, P < 0.0001). The units usually ceased after a brief intense discharge. In some units, their activity shifted to a lower level, indicating a pacemaker switching. Our results support the notion that SARs deactivate due to overexcitation.

An organic compound containing N, B and O was synthesised by reacting 3-hydroxymethyl-quinazolin-4-ones and formalin in 1, 4-dioxane solution, the resulting product then being reacted with butanol and boric acid in dimethylbenzene solution. The tribological performance of the novel compound when added to liquid paraffi n was evaluated using a four-ball tester and a ring-on-block machine. The relationship between performance and concentration was analysed, and the results showed that the compound possesses good anti-wear, friction-reducing and load-carrying properties. The mechanism of action of the additive was investigated using X-ray photoelectron spectroscopy. Surface analysis indicated the formation of a protective fi lm containing borate, Fe 3 O 4 , and an organonitrogen compound. This protective fi lm formed during sliding processes contributes to the increase in wear resistance.

Ionic polymer-metal composites (IPMC) are a class of electroactive polymers (EAP), and they currently attract numerous researchers to study their performance characteristics and applications. However, research on its start-up characteristics still requires more attention. In the IPMC start-up state (the moment of applying an actuation voltage at the very beginning), its mechanical performance is different in the stable working state (working for at least 10 min). Therefore, this paper focuses on three performance relationships of an IPMC strip between its maximal tip deformation and voltage, its maximal stress and voltage, as well as its maximal strain and voltage, both in the two states. Different from other reports, we found that they present nonlinear tendencies in the start-up state rather than linear ones. Therefore, based on the equivalent bimorph beam model, a finite element electromechanical coupling calculation module in the ANSYS software was utilized to simulate these characteristics. Furthermore, a test system is introduced to validate the phenomena. As a whole, these three relationships and the FEA method may be beneficial for providing control strategies effectively to IPMC actuators, especially in their start-up states.

In this paper, melamine was used as porogen to prepare porous polyimide film by in-situ polymerization. The mechanical properties, thermal properties, dielectric properties, oil content and friction and wear properties of polyimide films with different porosity were investigated. The tensile strength of porous films decreases obviously with increase of melamine content. It shows the lower thermal decomposition temperature and the faster decomposition speed compared with the non-porous film, indicating higher heat exchange rate due to holes in porous films. As the porogen content increases, the dielectric constant decreases significantly, and the film with melamine content of 20 wt.% has the lowest dielectric constant of 2.43. The holes lead to good oil storage performance and the wear rate and the friction coefficient decrease with the increase of porosity. Keywords: polyimide; porous; melamine; dielectric; friction

A visual tracking system based on ultrasonic motors is designed in view of shortcoming of traditional video surveillance system, which has a large volume, complicated structure. The pan-tilt can rotate in horizontal and vertical directions by using two ultrasonic motors served as the driving units. The image from video camera is processed and the target is identified and real-time tracked by rotating the pan-tilt which is controlled by ultrasonic motor. Compared with electromagnetic motor, the ultrasonic motor has advantages of high torque at low speed, quick response, high precision and self-locked, which makes the structure simpler and control more convenient. Experimental results show that the system can be stably tracking the selected target with fast response speed and relatively high tracking accuracy.