Optimal Design on Clearance of Piston Friction Pair for Water Hydraulic Pump

The optimal clearance formula of piston friction pair for water hydraulic pump was established based on thermal balance principle. Simulations and experimental research were carried out on its influence factors, results show that, a minimum thermal clearance exists in each of the piston friction pair and its initial clearance must be greater than this one, otherwise it will happen to death. Some effective measures can take to reduce the minimum thermal balance clearance as follows: decreasing the piston diameter or swash-plate tilt angle, choosing the appropriate couple material, reducing friction coefficient and fully running-in, etc.

Increased role of skeletal muscle in the calorigenic response to glucagon of cold-acclimated ducklings

The site of the calorigenesis observed in birds after glucagon was sought in control and cold-acclimated (CA) ducklings. Twenty-four 6-wk-old muscovy ducklings were reared either at thermoneutrality (TN) (25 degrees C) or in the cold (4 degrees C) from the age of 1 wk. Glucagon-induced calorigenesis (GIC) was estimated at 25 degrees C after a peritoneal glucagon injection (103 nmol/kg). Glucagon induced a higher increase in animal heat production (indirect calorimetry) and body temperature in CA (+45% and +1.1 degrees C) than in control ducklings (+30% and +0.4 degree C). In CA ducklings, the perfusion rate (thermal clearance method) and temperature of gastrocnemius increased (+130% and +1.0 degree C) shortly after glucagon, whereas tissue oxygenation (polarography) decreased (-34%). There was no significant effect of glucagon in TN controls. These changes, which peaked 45-60 min after glucagon injection, indicated a prolonged increase of muscle O2 consumption in CA ducklings. Leg muscle blood flow (radioactive microspheres) measured 45 min after glucagon was slightly increased in controls (+20%; P < 0.05), while in CA ducklings, the increase was larger (+76%; P < 0.05). The arteriovenous difference in O2 content was not markedly affected by glucagon in both groups. These parameters indicated an increase in leg muscle O2 uptake in response to glucagon of +29% in controls and +76% in CA ducklings. In controls, 28% of the GIC measured in vivo could be attributed to whole body skeletal muscles, compared with 53% in CA ducklings. The remaining part might be accounted for mostly by the liver.(ABSTRACT TRUNCATED AT 250 WORDS)