Jump and Pull-in Instability of a MEMS Gyroscope Vibrating System.

Jump and pull-in instability are common nonlinear dynamic behaviors leading to the loss of the performance reliability and structural safety of electrostatic micro gyroscopes. To achieve a better understanding of these initial-sensitive phenomena, the dynamics of a micro gyroscope system considering the nonlinearities of the stiffness and electrostatic forces are explored from a global perspective. Static and dynamic analyses of the system are performed to estimate the threshold of the detecting voltage for static pull-in, and dynamic responses are analyzed in the driving and detecting modes for the case of primary resonance and 1:1 internal resonance. The results show that, when the driving voltage frequency is a bit higher than the natural frequency, a high amplitude of the driving AC voltage may induce the coexistence of bistable periodic responses due to saddle-node bifurcation of the periodic solution. Basins of attraction of bistable attractors provide evidence that disturbance of the initial conditions can trigger a jump between bistable attractors. Moreover, the Melnikov method is applied to discuss the condition for pull-in instability, which can be ascribed to heteroclinic bifurcation. The validity of the prediction is verified using the sequences of safe basins and unsafe zones for dynamic pull-in. It follows that pull-in instability can be caused and aggravated by the increase in the amplitude of the driving AC voltage.

Complications of laparoscopic radical hysterectomy and pelvic lymphadenectomy--experience of 117 patients.

OBJECTIVE: To describe the combined surgical technique of laparoscopic radical hysterectomy and pelvic lymphadenectomy (LRH + LPL) for cervical cancers and summarize our experiences in prevention and treatment of complications, so as to provide strategies to prevent and appropriately manage the complications that may occur during these procedures. METHODS: A retrospective study was conducted on LRH + LPL in 117 cases of cervical cancer with International Federation of Gynecology and Obstetrics stages Ib (n = 96) and II a (n = 21) from August 1998 to December 2006. The intraoperative and postoperative complications were analyzed. RESULTS: The overall conversion rate was 1.7% (2/117). Four patients had vessel injuries, 3 of which were treated laparoscopically. One patient had a common iliac vein laceration that could not be controlled laparoscopically after failing to deal with the injured branch of common iliac vein. Cystotomy occurred in 5 patients. One case of stage IIa with a bladder laceration longer than 3 cm was converted to laparotomy during the early stages of the learning curve. The remaining 4 were managed laparoscopically. Postoperative complications occurred in 38.5% (n = 45) of the patients, including 38 patients with urinary retention who exhibited complete resolution within 6 months by intermittent training and catheterization, 4 with lymphocyst who underwent conservation treatment, 1 with ureteral fistula that was treated by cystoscopic placement of double-J ureteral stents, 1 with mild adynamic bowel obstruction who received conservative management, and 1 with vesicovaginal fistula that was closed by conservative treatment. CONCLUSIONS: With the continuous skilled laparoscopic technology, mastering the tips of prevention, and treatment of complications, LRH + LPL will be widely performed in the future.

Effects of delays on the basin boundary of attraction in a hopfield network of two delay-connecting neurons.

A continuous-time Hopfield neural network with two delay-connecting neurons is considered in this paper. Some sufficient conditions for the number and delay-independent stability of the equilibria in the network are given analytically. It is necessary to classify the attraction domains since multiple attractors coexist when the sufficient conditions are satisfied. Thus, effects of the delays on the boundary separating the basins of attraction of the stable equilibria are investigated analytically and numerically. The results show that the evolution of the boundary depends on the delays and is neither simple nor intuitive even if the delays do not affect the stability of attractors. The results provide also the possibility to design the network according to the memory pattern and storage.

A comparison of laparoscopic radical hysterectomy and pelvic lymphadenectomy and laparotomy in the treatment of Ib-IIa cervical cancer.

OBJECTIVE: To compare the feasibility, morbidity, and survival outcome of the laparoscopic radical hysterectomy and pelvic lymphadenectomy (LRH+LPL) with abdominal radical hysterectomy and pelvic lymphadenectomy (ARH+APL) for FIGO stage Ib-IIa cervical carcinoma. METHODS: The consecutive cases with FIGO Ib-IIa cervical cancer from August 1998 to December 2005 were documented, including 90 patients underwent LRH+LPL, and 35 patients underwent ARH+APL as control group. The clinic data of perioperative periods and survival were compared between groups. RESULTS: In laparoscopy group the operating time increased significantly (262.99+/-67.6 min vs. 217.2+/-71.56 min, P=0.001), and the recovery time of bowel decreased significantly (1.96+/-0.62 days vs. 2.40+/-1.06 days, P=0.025). No significant difference was found between groups when the blood loss during operation (369.78+/-249.94 ml vs. 455.14+/-338.05 ml, P=0.125), numbers of the pelvic lymph nodes resected (21.28+/-8.39 vs. 18.77+/-9.47, P=0.151), recovery time of bladder function and postoperative hospital stays were compared. All laparoscopic procedures were completed successfully except 2 cases converted to laparotomy. The median follow-up was 26 months (range 5 to 84 months). Ten and five cases lost to follow-up in laparoscopy and laparotomy group, respectively. Excluding the lost cases, the recurrence rate (13.75% vs. 12%, P>0.05) and the mortality rate (10% vs. 8%, P>0.05) between groups was similar. CONCLUSION: Our data demonstrated that cervical cancer could be treated successfully with LRH+LPL with similar efficacy and recurrence rates to ARH+APL. LRH+LPL is a safe and effective alternative to conventional abdominal surgery for stage Ib-IIa cervical cancer, and should be used if the surgeon is sufficiently trained. Its clinical value should be confirmed by multicenter randomized clinic trials.