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Active control of a flexible structure with time delay
Cai, Guo-Ping,Yang, Simon X. Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.2
Time delay exists inevitably in active control, which may not only degrade the system performance but also render instability to the dynamic system. In this paper, a novel active controller is developed to solve the time delay problem in flexible structures. By using the independent modal space control method, the differential equation of the controlled mode with time delay is obtained from the time-delay system dynamics. Then it is discretized and changed into a first-order difference equation without any explicit time delay by augmenting the state variables. The modal controller is derived based on the augmented system using the discrete variable structure control method. The switching surface is determined by minimizing a discrete quadratic performance index. The modal coordinate is extracted from sensor measurements and the actuator control force is converted from the modal one. Since the time delay is explicitly included throughout the entire controller design without any approximation, the system performance and stability are guaranteed. Numerical simulations show that the proposed controller is feasible and effective in active vibration control of dynamic systems with time delay. If the time delay is not explicitly included in the controller design, instability may occur.
( Ping Sheng ),( Yun-long Cheng ),( Chuan-chuan Cai ),( Wei-jin Guo ),( Ying Zhou ),( Ge Shi ),( Yi-ming Fan ) 대한피부과학회 2016 Annals of Dermatology Vol.28 No.6
Background: Although Becker`s nevus (BN) is a relatively common disease, the systematic studies of clinicopathological and immunohistochemical results are poorly reported. Objective: To investigate the clinicopathological features and immunohistochemical alterations of keratinocyte proliferation, melanocyte density, smooth muscle hyperplasia and nerve fiber distribution in BN. Methods: Clinical and pathological data were collected in 60 newly-diagnosed BN cases. Immunohistochemical stain of Ki-67, Melan-A, keratin 15, smooth muscle actin and protein gene product 9.5 was performed in 21 cases. Results: The median diagnostic and onset age was 17 and 12 years, respectively. Skin lesions usually appeared on the upper trunk and upper limbs. The pathological features included the rete ridge elongation and fusion and basal hyperpigmentation. Epidermal Ki-67, Melan-A and keratin 15 expression and dermal nerve fiber length were significantly higher in lesional and perilesional skin than in normal skin (p<0.05∼0.01), while smooth muscle actin expression was upregulated only in skin lesion (p<0.05). Conclusion: Although the clinical diagnosis of BN is often straightforward, histopathology is helpful to differentiate from other pigmentary disorders. The hyperproliferation of keratinocytes, melanocytes, arrector pili muscle and dermal nerve fibers could be involved in the patho-genesis of BN. (Ann Dermatol 28(6) 697∼703, 2016)
Ming-Zhou Gao,Guo-Ping Cai,Ying Nan 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.1
Based on the trajectory optimization, this article proposes an adaptive fault-tolerant H∞ compensationcontrol approach for a reentry vehicle with external disturbance and parameter uncertainty. The sensor and actuatorfaults are both considered to including loss of effectiveness, stuck and outage of actuator, and loss of effectivenessof sensor. Firstly, we set up the reentry model for the reentry vehicle and use computational fluid dynamics (CFD)to calculating the heating rate on the surface of the vehicle. Then we divide the vehicle into several isothermalregions appropriately according to the heating rate, and establish the corresponding database for the aerodynamiccharacteristics. When the database accomplished, more accurate control variables and flight path can be achievedby using the conjugate gradient method. And the aerodynamic heating rate on the surface of the reentry vehicle willbe improved considerably. Afterwards, an adaptive fault-tolerant H∞ compensation control method is introduced todeal with the external disturbance and parameter uncertainty of the reentry vehicle system based on the trajectoryoptimization. The Lyapunov functional is adopted to guarantee the stability of the system. The effectiveness ofsuch adaptive fault-tolerant H∞ compensation control method has been identified by numerous simulation results.
Ming-Zhou Gao,Guo-Ping Cai 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.1
In current study for wing flutter of reentry vehicle, the effect of input saturation to wing flutter is rarelyconsidered and few of the fault-tolerant control problem is taken into account. In this paper, we use the radial basisfunction neural network and the finite-time adaptive fault-tolerant control technique to deal with the wing flutterproblem, which is subject to input saturation, parameter uncertainties and external disturbances. Sensor and actuatorfaults are both considered in the control design. Firstly, an optimal flight trajectory of reentry vehicle is designedusing the conjugate gradient method, so as to decrease the aerodynamic heating rate and temperature on the surfaceof the reentry vehicle. Then based on the trajectory optimization, we ignore the effect of temperature, and buildup the motion equation of wing flutter. Finally, a finite-time H¥ adaptive fault-tolerant controller is introduced. Simulation results indicate that, the optimized trajectory designed may decrease the aerodynamic heating rate ofthe reentry vehicle; the designed fault-tolerant controller can effectively deal with the faults in the system and canpromptly suppress the wing flutter as well.
Tight sportswear and physiological function-Effect on muscle strength and EMG activity-
( Xiao Qun Dai ),( Yu Ping Li ),( Juan Juan Cai ),( A Ming Lu ),( Guo Dong Wang ) 복식문화학회 2013 服飾文化硏究 Vol.21 No.4
It has been reported that tight sportswear could have complicated influence on physiological function of human body. The purpose of this present study was to investigate the effect of wearing gradient compression tights (GCT) on muscle strength and EMG activity during repeated isokinetic muscle contractions. Four healthy male undergraduate students performed maximal voluntary isokinetic concentric muscle contractions on biomechanical test and training systems with GCT and loose pants as control (Cont) respectively. During each test, the peak torque of extensor and flexor contractions and the surface electromyography (sEMG) of the recrus femoris and medial gastrocnemius was recorded simultaneously, the peak torque was recorded as an indicator of muscle strength, and the average amplitude and mean power frequency of sEMO were calculated as indicators of EMG activity. The results showed that: the peak torque decreased gradually during continuous muscle contractions both when the Cont and GCT were worn. average sEMG and mean power frequency declined along with the repetitions of muscle contractions for both wearing conditions, and the change tendency was consistence with that of peak torque. There was no obvious, difference between the peak torque recorded wearing the Cont or wearing GCT, but when GCT were worn, average sEMG was lower and mean power frequency was higher than the Cont condition. In 24 samples obtained from four subjects, 80% of results showed the same trend. So we could make a conclusion that wearing ocr had no obvious effect on the improvement of muscle strength, but it would affect the EMO activity posiuvly.
Li, Shu-Hong,Guo, Zhi-Xing,Xiao, Cheng-Zuo,Wei, Wei,Shi, Ming,Chen, Zhi-Yuan,Cai, Mu-Yan,Zheng, Lie,Guo, Rong-Ping Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.8
Background: Prognostic factors of postoperative early and late recurrence in patients with hepatocellular carcinoma (HCC) undergoing curative resection remain to be clarified. The aim of this study was to identify risk factors for postoperative early (${\leq}$ 2 year) and late (> 2 year) intrahepatic recurrences in patients with single HCCs without macrovascular invasion. Methods: A total of 280 patients from December 2004 to December 2007 were retrospectively included in this study. Intrahepatic recurrence was classified into early (${\leq}$ 2 year) and late (> 2 year) and the Chi-Square test or Fisher's exact test and multivariate logistic regression analysis were performed to determine significant risk factors. Results: During the follow-up, 124 patients had intrahepatic recurrence, early and late in 82 and 42 patients, respectively. Multivariate logistic regression analysis showed that microvascular invasion (p=0.006, HR: 2.397, 95% CI: 1.290-4.451) was the only independent risk factor for early recurrence, while being female (p = 0.031, HR: 0.326, 95% CI: 0.118-0.901), and having a high degree of cirrhosis (P=0.001, HR: 2.483, 95% CI: 1.417-4.349) were independent risk factors for late recurrence. Conclusions: Early and late recurrence of HCC is linked to different risk factors in patients with single HCC without macrovascular invasion. This results suggested different emphases of strategies for prevent of recurrence after curative resection, more active intervention including adjuvant therapy, anti-cirrhosis drugs and careful follow-up being necessary for patients with relevant risk factors.