This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Background:A low dose of ketamine can be an effective preemptive analgesic by preventing central sensitization when administered before surgical trauma. In this study, we assessed the preemptive analgesic effect of low-dose ketamine administered intravenously to patients undergoing arthroscopic rotator cuff repair with intra articular ropivacaine injection. Methods: This randomized, double-blinded study included fifty-six patients scheduled for elective arthroscopic rotator cuff repair. Normal saline (group C) or 0.5 mg/kg of ketamine (group K) was injected intravenously before the skin incision. An intra articular injection using 20 ml of 0.75% ropivacaine was performed in both groups just before wound closure by the surgeon at the end of the surgery. Postoperative pain was assessed by the numeric rating scale (NRS) in the post-anesthesia care unit (PACU) and at 12, 24, and 48 hours postoperatively. The total dose of fentanyl consumption and side effects were recorded. Results: There were no significant differences between the C and K groups for the NRS of pain in the PACU and at 12, 24, and 48 hours after the surgery. In addition, there was also no significant difference in total fentanyl consumption between the two groups. Conclusions: Preemptive ketamine did not reduce preemptive pain scores and fentanyl consumption in patients who underwent arthroscopic rotator cuff repair with intra articular local anesthetic injection. Therefore, more aggressive and multimodal pain control is required in patients undergoing arthroscopic shoulder surgery regardless of the use of preemptive intravenous ketamine injection.

Reactor coolant pump (RCP) is designed for the heat transfer of heat which is generated from reactor vessel to steam generators by circulating the coolant water. RCP is the only rotating equipment in the nuclear steam supply system (NSSS). Therefore, the problem of vibration has arisen caused by the hydraulic forces of the working fluid. These forces can drastically alter the critical speeds and stability characteristics and can act as significant destabilizing forces. So, vibration evaluation of RCP has been considered as a very important issue [1]. Among them, unbalance response caused by weight of unbalancing of rotating shaft could have serious effects on the entire rotor system. Thus, precise unbalance response spectrum analyses are required. In general, in order to evaluate the unbalance response characteristics for centrifugal pump, finite element analysis was performed according to the ISO 1940-1 standard. However, finite element analysis according to the ISO 1940-1 standard does not considering fluid flow effect. So, finite element analysis result and experimental results may be some differences. Vibration characteristics of RCP has affected by fluid flow effect induced from working fluid. Therefore, in order to understand vibration characteristics for the RCP shaft assembly considered in actual operating condition, rotor dynamic analysis should be performed considering the fluid flow effect. In this research, owing to accurately evaluate the vibration characteristics for the RCP considering hydro forces due to the fluid flow, we measured the bearing force and moment take into account the fluid-induced force. And then response spectrum analysis of RCP shaft assembly was performed considering fluid induced bearing radial forces which are measured values. Lastly, evaluate the vibration characteristics considering effect of fluid flow according to the number of revolution.

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