We consider an Mx /G/1 queueing system with N-policy and multiple vacations. As soon as the system empties, the server leaves for a vacation of random length V. When he returns, if the queue length is greater than or equal to a predetermined value N(threshold), the server immediately begins to serve the customers. If he finds less than N customers, he leaves for another vacation and so on until he finally finds at least N customers. We obtain the system size distribution and show that the system size decomposes into three random variables one of which is the system size of ordinary Mx /G/1 queue. The interpretation of the other random variables will be provided. We also derive the queue waiting time distribution and other performance measures. Finally we derive a condition under which the optimal stationary operating policy is achieved under a linear cost structure.

Prediction equations for the carbon monoxide diffusing capacity of the lung (DLCO) and diffusing capacity per liter of lung volume (DLCO/VA) were derived from 90 normal nonsmoking subjects (40 men and 50 women), using a standardized single-breath technique for determining carbon monoxide diffusing capacity.The results obtained are as follows: The mean values for DLCO and DLCO/VA were 28.05±5.07 ml/min/mmHg, 4.569±0.694 ml/min/mmHg/L for men and 20.79±4.03 ml/min/mmHg, 4.695±0.743 ml/min/mmHg/L for women, respectively.The values for DLCO and DLCO/VA disclosed significantly negative correlation with advancing age and positive correlation with height.Normal prediction formulas were obtained for diffusing capacity, using age and height. leftMen:DLCO=0.3504 H−0.2156 A−23.168leftDLCO/VA=−0.0205 H−0.0283A+9.0919leftWomen:DLCO=0.2491 H−0.1533 A−11.662leftDLCO/VA =0.0140 H− 0.0216 A+3.413

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