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121.
恒运电厂5号机抽汽供热改造 总被引:1,自引:0,他引:1
介绍半高压单缸凝汽式汽轮机改造为抽汽拱热式组的设计思路及施工改造过程,对改造中出现的新问题进行了分析并提出解决办法,改造后,机组抽气直接供给热网,社会效益和经济效益明显。 相似文献
122.
介绍了VLSI版图验证中电阻提取的基本原理和主要方法,给出了一种新颖的基于边界元法的电阻提取算法。该算法采用变节点单元,较好地解决了实际问题中经常出现的角点问题。通过应用该算法对几个实例进行提取,证明使用本文的算法不仅在精度上而且在占用CPU时间上都取得了令人满意的效果 相似文献
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HU Rothen B Sporre G Engberg G Wegenius M H?gman G Hedenstierna 《Canadian Metallurgical Quarterly》1995,82(4):832-842
BACKGROUND: Atelectasis, an important cause of impaired gas exchange during general anesthesia, may be eliminated by a vital capacity maneuver. However, it is not clear whether such a maneuver will have a sustained effect. The aim of this study was to determine the impact of gas composition on reappearance of atelectasis and impairment of gas exchange after a vital capacity maneuver. METHODS: A consecutive sample of 12 adults with healthy lungs who were scheduled for elective surgery were studied. Thirty minutes after induction of anesthesia with fentanyl and propofol, the lungs were hyperinflated manually up to an airway pressure of 40 cmH2O. FIO2 was either kept at 0.4 (group 1, n = 6) or changed to 1.0 (group 2, n = 6) during the recruitment maneuver. Atelectasis was assessed by computed tomography. The amount of dense areas was measured at end-expiration in a transverse plane at the base of the lungs. The ventilation-perfusion distributions (VA/Q) were estimated with the multiple inert gas elimination technique. The static compliance of the total respiratory system (Crs) was measured with the flow interruption technique. RESULTS: In group 1 (FIO2 = 0.4), the recruitment maneuver virtually eliminated atelectasis for at least 40 min, reduced shunt (VA/Q < 0.005), and increased at the same time the relative perfusion to poorly ventilated lung units (0.005 < VA/Q < 0.1; mean values are given). The arterial oxygen tension (PaO2) increased from 137 mmHg (18.3 kPa) to 163 mmHg (21.7 kPa; before and 40 min after recruitment, respectively; P = 0.028). In contrast to these findings, atelectasis recurred within 5 min after recruitment in group 2 (FIO2 = 1.0). Comparing the values before and 40 min after recruitment, all parameters of VA/Q were unchanged. In both groups, Crs increased from 57.1/55.0 ml.cmH2O-1 (group 1/group 2) before to 70.1/67.4 ml.cmH2O-1 after the recruitment maneuver. Crs showed a slow decrease thereafter (40 min after recruitment: 61.4/60.0 ml.cmH2O-1), with no difference between the two groups. CONCLUSIONS: The composition of inspiratory gas plays an important role in the recurrence of collapse of previously reexpanded atelectatic lung tissue during general anesthesia in patients with healthy lungs. The reason for the instability of these lung units remains to be established. The change in the amount of atelectasis and shunt appears to be independent of the change in the compliance of the respiratory system. 相似文献
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