Decision–control mechanism for Markovian jump linear systems with Gaussian noise

This paper investigates the decision–control mechanism for Markovian jump linear systems with Gaussian noise. The mechanism here consists of two parts: decision to govern the mode transition rate matrix and output‐feedback controller to govern system state. Motivated by this, a joint index is put forward to evaluate system performance, which is a combination of traditional jump linear quadratic Gaussian cost and additional decision cost because extra expenses will be taken for adopting decision to mode transition rate matrix. For the minimization of joint index, the designing of optimal decision–control pair is deduced to the seeking of optimal decision. Meanwhile, the optimal decision can be obtained via an iterative with its convergence proved. Numerical examples illustrate the validity of the proposed mechanism. Copyright © 2015 John Wiley & Sons, Ltd.     

3D MRI quantification of femoral head deformity in Legg–Calvé–Perthes disease

The purpose of this study was to quantify femoral head deformity in patients with Legg–Calvé–Perthes disease (LCPD) using a novel three dimensional (3D) magnetic resonance imaging (MRI) reconstruction and volume based analysis. Bilateral femoral heads of 17 patients (mean age 9.9 ± 2.0 years; 12 boys, 5 girls) with LCPD were scanned 1–2 times (n = 33 LCPD heads, 20 normal heads) using a 1.5T MRI scanner. Fourteen patients had unilateral and three had bilateral LCPD with five hips in the Waldenström initial stage, 9 in the fragmentation stage, 14 in the reossification stage, and 5 in the healed stage. 3D digital reconstructions of femoral heads were created using MIMICS software. Deformity was quantified using a 3D volume ratio method based on reference hemisphere volume as well as two surface geometry methods. Intra‐observer analysis showed that 97% of the LCPD femoral heads were within 10% of the original value and test shapes had 99.6% accuracy. For normal femoral heads, the volume ratios of all except one were between 95 and 98% (n = 20) of a perfect hemisphere volume. For femoral heads affected with LCPD, the volume ratios ranged from 43% to 96% of a perfect hemisphere (n = 33). The volume ratio method and the two surface geometry comparison methods had high correlation (r = 0.89 and 0.96). In summary, the 3D MRI volume ratio method allowed accurate quantification and demonstrated small changes (<10%) of the femoral head deformity in LCPD. This method may serve as a useful tool to evaluate the effects of treatment on femoral head shape. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2051–2058, 2017.

     

New methods for the estimation of Takagi–Sugeno model based extended Kalman filter and its applications to optimal control for nonlinear systems

This paper describes new approaches to improve the local and global approximation (matching) and modeling capability of Takagi–Sugeno (T‐S) fuzzy model. The main aim is obtaining high function approximation accuracy and fast convergence. The main problem encountered is that T‐S identification method cannot be applied when the membership functions are overlapped by pairs. This restricts the application of the T‐S method because this type of membership function has been widely used during the last 2 decades in the stability, controller design of fuzzy systems and is popular in industrial control applications. The approach developed here can be considered as a generalized version of T‐S identification method with optimized performance in approximating nonlinear functions. We propose a noniterative method through weighting of parameters approach and an iterative algorithm by applying the extended Kalman filter, based on the same idea of parameters’ weighting. We show that the Kalman filter is an effective tool in the identification of T‐S fuzzy model. A fuzzy controller based linear quadratic regulator is proposed in order to show the effectiveness of the estimation method developed here in control applications. An illustrative example of an inverted pendulum is chosen to evaluate the robustness and remarkable performance of the proposed method locally and globally in comparison with the original T‐S model. Simulation results indicate the potential, simplicity, and generality of the algorithm. An illustrative example is chosen to evaluate the robustness. In this paper, we prove that these algorithms converge very fast, thereby making them very practical to use. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimal control of a water reservoir with expected value–variance criteria

The article presents how to solve a reservoir management problem, which has been formulated as a two‐criteria stochastic optimal control problem. Apart from the expected value of a performance index, its variance is also considered. Three approaches are described: a method based on the Lagrange function; a method based on the ordinary moment of the second order (finite time horizon); and a method based on linear programming (infinite time horizon). In the second part of the article, they are assessed in a case study concerning a reservoir in the southern part of Poland. Copyright © 2006 John Wiley & Sons, Ltd.     

A convex optimization procedure to compute ℋ︁2 and ℋ︁∞ norms for uncertain linear systems in polytopic domains

In this paper, a convergent numerical procedure to compute ??₂ and ??_∞ norms of uncertain time‐invariant linear systems in polytopic domains is proposed. The norms are characterized by means of homogeneous polynomially parameter‐dependent Lyapunov functions of arbitrary degree g solving parameter‐dependent linear matrix inequalities. Using an extension of Pólya's Theorem to the case of matrix‐valued polynomials, a sequence of linear matrix inequalities is constructed in terms of an integer d providing a Lyapunov solution for a given degree g and guaranteed ??₂ and ??_∞ costs whenever such a solution exists. As the degree of the homogeneous polynomial matrices increases, the guaranteed costs tend to the worst‐case norm evaluations in the polytope. Both continuous‐ and discrete‐time uncertain systems are investigated, as illustrated by numerical examples that include comparisons with other techniques from the literature. Copyright © 2007 John Wiley & Sons, Ltd.     

A trajectory‐based sampling strategy for sequentially refined metamodel management of metamodel‐based dynamic optimization in mechatronics

Dynamic optimization problems based on computationally expensive models that embody the dynamics of a mechatronic system can result in prohibitively long optimization runs. When facing optimization problems with static models, reduction in the computational time and thus attaining convergence can be established by means of a metamodel placed within a metamodel management scheme. This paper proposes a metamodel management scheme with a dedicated sampling strategy when using computationally demanding dynamic models in a dynamic optimization problem context. The dedicated sampling strategy enables to attain dynamically feasible solutions where the metamodel is locally refined during the optimization process upon satisfying a feasibility‐based stopping condition. The samples are distributed along the iterate trajectories of the sequential direct dynamic optimization procedure. Algorithmic implementation of the trajectory‐based metamodel management is detailed and applied on two case studies involving dynamic optimization problems. These numerical experiments illustrate the benefits of the presented scheme and its sampling strategy on the convergence properties. It is shown that the acceleration of the solution time of the dynamic optimization problem can be achieved when evaluating the metamodel that is lower than 90% compared to the computationally expensive model.     

Hybrid predictive control of a DC–DC boost converter in both continuous and discontinuous current modes of operation

Developing efficient and appropriate modeling and control techniques for DC–DC converters is of major importance in power electronics area and has attracted much attention from automatic control theory. Since DC–DC converters have a complex hybrid nature, recently several techniques based on hybrid modeling and control have been introduced. These techniques have shown better results as compared with conventional averaging‐based schemes with limited modeling and control abilities. But the current works in this field have not considered all possible dynamics of the converters in both continuous and discontinuous current modes (CCM, DCM) of operations. These dynamics are results of controlled and uncontrolled switching phenomena in DC–DC converters. This paper proposes a new switching scheme for modeling and controlling a DC–DC boost converter. The converter is represented as a hybrid automaton by considering the all three possible modes. The hybrid automaton is translated into the mixed logical dynamical (MLD) mathematical framework. The switching among these modes is generated by hybrid predictive control method which is calculated by Mixed Integer Quadratic Programming (MIQP). Using the exact model of the converter, the proposed switching algorithm can globally control the converter in all operation regimes, including CCM and DCM operations, considering all constraints in the physical plant, such as maximum inductor current and capacitor voltage limits. The switching algorithm is applied to a real converter circuit, modeled with various parasitic components. Simulation results are provided to show the advantages of the proposed control scheme. Copyright © 2010 John Wiley & Sons, Ltd.     

Improved microcirculation by low‐viscosity histidine– tryptophan–ketoglutarate graft flush and subsequent cold storage in University of Wisconsin solution: results of an orthotopic rat liver transplantation model

As previously shown in a model of isolated rat liver perfusion, the combined use of an initial graft flush with low‐viscosity histidine–tryptophan–ketoglutarate (HTK) solution followed by cold storage in University of Wisconsin (UW) solution markedly improved the preservation during an extended cold storage period. In this study, we aimed to transfer our results into an in vivo model of orthotopic rat liver transplantation, and to elucidate the potential mechanism of the improved preservation by focusing on the hepatic microcirculation. Livers were harvested from male Wistar rats. Aortic perfusion with a pressure of 100 cm H₂O was performed with either UW (group UW) or HTK (groups UW and HTK_UW), followed by additional back‐table perfusion with UW (group HTK_UW). After 20‐h cold storage at 4 °C, livers were orthotopically transplanted with reconstructing the hepatic artery. As measured by bile flow and liver enzymes, HTK flush followed by UW storage was superior compared to single use of either UW or HTK solution. The hepatic microcirculation was significantly improved, as shown by the increased percentage of reperfused sinusoids and reduced sinusoidal leucostasis. HTK and UW effectively reduce ischaemia‐reperfusion injury after liver transplantation. By combining the comparative advantages of both solutions, a cumulative effect resulting in an improved preservation was shown. Thus, this mechanism improves microcirculatory reperfusion.     

Constrained non‐smooth optimization in dead‐beat control of linear servosystems

Motivated by the polynomial approach to the dead‐beat ripple‐free control of a continuous linear servosystem, the paper presents a new effective algorithm for non‐smooth constrained optimization with design objectives applicable to both control and process variables. Constraints on closed‐loop poles are introduced and their role in optimization and rejection of a finite‐length continuous plant disturbances is examined. The solution is based on a new way of parametrization of the set of all admissible dead‐beat ripple‐free controllers and the constrained non‐smooth optimization profits from its linear programming formulation. Copyright © 2005 John Wiley & Sons, Ltd.     

A Case–Control Study of Betapapillomavirus Infection and Cutaneous Squamous Cell Carcinoma in Organ Transplant Recipients

We examined the association between betapapillomavirus (betaPV) infection and cutaneous squamous cell carcinoma (SCC) in organ transplant recipients. A total of 210 organ transplant recipients with previous SCC and 394 controls without skin cancer were included. The presence of 25 betaPV types in plucked eyebrow hairs was determined using a human papillomavirus (HPV) DNA genotyping assay, and antibodies for the 15 most prevalent betaPV types were detected using multiplex serology. We used multivariate logistic regression models to estimate associations between various measures of betaPV infection and SCC. BetaPV DNA was highly prevalent (>94%) with multiple types frequently detected in both groups. We found a significant association between SCC and the concordant detection of both antibodies and DNA for at least one betaPV type (adjusted OR 1.6; 95% CI 1.1;2.5). A borderline‐significant association with SCC was found for HPV36 (adjusted OR 2.4; CI 1.0;5.4), with similar associations for HPV5, HPV9 and HPV24. These data provide further evidence of an association between betaPV infection and SCC in organ transplant recipients. Confirmation of a betaPV profile predictive of risk for SCC may pave the way for clinically relevant pretransplant HPV screening and the development of preventive and therapeutic HPV vaccination.     

Gestational Age and the Risk of Maternal Breast Cancer: A Population‐Based Case–Control Study

There is limited evidence that the gestational age at delivery may influence the risk of maternal breast cancer. While extreme prematurity has been suggested to increase the risk, there seems to be no study available so far that investigates the due effects of a late delivery. This research aimed to identify the impact of both preterm and late deliveries on the risk of maternal breast cancer within a period of 5 years after birth. Our dataset was created by linking data from the Nevada Cancer Registry database (1995–2008) and the birth certificates issued by the Nevada State Health Division (1994–2003). The study cohort consisted of 213,250 women who gave birth from January 1, 1994 to December 31, 2003. We performed a nested population‐based case – control study on 126 Nevada mothers with a first lifetime breast cancer diagnosed from January 1, 1995 through December 31, 2003, and 504 Nevada cancer‐free mothers. Women with pregnancies who progressed beyond 40 weeks of gestation were at a significantly lower risk of developing breast cancer for the 5‐year period following a delivery, when compared to women who delivered at 37–40 weeks of gestation (OR: 0.33, 95% CI: 0.11–0.92) in a multivariate model. Additional pregnancy characteristics did not significantly predict the risk of maternal breast cancer. Pregnancies that extended beyond 40 weeks of gestation were strongly associated with a lower likelihood of premenopausal breast cancer. Biological plausibility for this association may correspond to the fact that as pregnancy develops into more advanced stages, mammary cells have more time to attain complete differentiation and maturation; a process that starts early in the third trimester.     

The Combination of icariin and constrained dynamic loading stimulation attenuates bone loss in ovariectomy‐induced osteoporotic mice

Osteoporosis is a disease characterized by low bone mass and progressive destruction of bone microstructure, resulting in increasing the risk of fracture. Icariin (ICA) as a phytoestrogen shows osteogenic effects, and the mechanical stimulation has been demonstrated the improving effect on osteoporosis. The objective of this study was to investigate the effect of ICA in combination with constrained dynamic loading (CDL) stimulation on osteoporosis in ovariectomized (OVX) mice. The serum hormone levels, bone turnover markers, trabecular architecture, ulnar biomechanical properties, and the expression of osteoblast‐related gene (alkaline phosphatase, ALP; osteocalcin, OCN; bone morphogenetic protein‐2, BMP‐2; Collagen I (α1), COL1; osteoprotegerin, OPG) and osteoclast‐related genes (receptor activators of NF‐κB ligand, RANKL; tartrate‐resistant acid phosphatase, TRAP) were analyzed. The results showed that ICA + CDL treatment could increase the osteocalcin (20.85%), estradiol levels (20.61%) and decrease the TRAP activity (26.27%) significantly than CDL treatment. The combined treatment attenuated bone loss and biomechanical decrease more than single use of CDL treatment. ICA + CDL treatment significantly up‐regulated the level of osteoblast‐related gene expression and down‐regulated the osteoclast‐related genes expression; moreover, the combined treatment increased the ratio of OPG/RANKL significantly compared to ICA (72.83%) or CDL (65.63%) treatment alone. The present study demonstrates that icariin in combination with constrained dynamic loading treatment may have a therapeutic advantage over constrained dynamic loading treatment alone for the treatment of osteoporosis, which would provide new evidence for the clinical treatment of osteoporosis. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1415–1424, 2018.

     

Robust LQG control of uncertain linear systems via simultaneous H2 and H∞ approach

This communication is concerned with an optimal linear quadratic control design with guaranteed stability for systems with real time-varying parameter uncertainties and unstructured unmodelled dynamics. It is shown that this problem can be converted into a mixed H₂ and H_∞ control problem. A simultaneous H₂ and H_∞ approach is then applied to solve the latter problem. A numerical example is presented to demonstrate the significance of the proposed technique. © 1997 John Wiley & Sons, Ltd.     

Protective influence of rosiglitazone against testicular ischaemia–reperfusion injury in rats

Testicular torsion is a urology urgent disease which causes testicular injury and potential sterility. In this study, we explored the protective influence of rosiglitazone on testicular ischaemia–reperfusion damage. There were 28 male Sprague Dawley rats in total, which were assigned randomly to four groups. Group A was blank control one; group B was testicular injury one; group C was rosiglitazone one; group D was rosiglitazone antagonist one. The testicles were counter‐rotated after 2 hr and then underwent orchiectomy 24 hr later. We found that testicular tissue structure of rats was seriously damaged in groups B and D. However, group C had better testicular architecture. Similar findings were also shown for lipid peroxidation by evaluating the MDA activity (p < .05). Unlike group B or group D, the levels of inflammation by evaluating the MPO activity, the levels of TNF‐a, IL‐1 and IL‐6 and the expressions of ICAM‐1 were prominently lower in group C (p < .05) as well. So our researches demonstrated that rosiglitazone significantly decreased the amount of responsive oxygen radical and regulated inflammatory responses. Rosiglitazone had a protective influence against testicular ischaemia–reperfusion injury in rats and possibly depended on its anti‐inflammatory and antioxidant traits.     

Characteristics of Epstein–Barr viraemia in adult liver transplant patients: A retrospective cohort study

Therapeutic immunosuppression following solid organ transplantation increases the risk of Epstein–Barr (EBV) viraemia, which is implicated in post‐transplant lymphoproliferative disease (PTLD). We retrospectively analysed the incidence of EBV viraemia and clinical outcomes in 98 liver transplant recipients. Patients underwent EBV DNA monitoring by whole‐blood PCR: EBV levels were correlated with clinical parameters and outcomes for a median of 249 days. 67% patients developed EBV viraemia (EBV DNA ≥100 copies/ml) and 30% had sustained viraemia. There was a trend towards higher hazard ratios for viraemia with exposure to aciclovir (HR 1.57, P = 0.12) or in recipients of a poorly HLA‐matched graft (HR 1.62, P = 0.10). These associations became significant in the subgroup with >90 days surveillance; HR 2.54 (P = 0.0015) for aciclovir and HR 1.99 (P = 0.03) for poorly matched grafts. The converse was true with ganciclovir (HR 0.56 P = 0.13). Viraemia was more prolonged in men (median duration 7 days vs 1; P = 0.01) and in those with lower UKELD scores (11 days vs 1 day; P = 0.001) but shortened with ganciclovir exposure (P = 0.06). Younger patients were more likely to have high peak viral loads (P = 0.07). No clinical signs or symptoms or adverse outcomes were associated with EBV reactivation.     

H∞ filter design for linear time‐invariant systems with polytopic uncertainties in finite frequency domain

This paper deals with the problem of finite frequency full‐order filter design for discrete‐time and continuous‐time linear systems, with polytopic uncertainties. Based on the generalized Kalman–Yakubovich–Popov lemma and a parameter‐dependent Lyapunov function, a set of sufficient conditions are established in terms of matrix inequalities, ensuring that the filtering error system is stable and the attenuation level, from disturbance to the estimation error, is smaller than a given value over a prescribed finite frequency domain of the external disturbances. Then, in order to linearize and relax the obtained matrix inequalities, we introduce a large number of slack variables by applying Finsler's lemma twice, which provides extra degrees of freedom in optimizing the guaranteed performance. This leads to performance improvement and reduction of conservatism in the solution. It is shown later that the robust filter gains can be obtained by solving a set of linear matrix inequalities. Numerical examples are given to illustrate the effectiveness and the less conservatism of the proposed approach in comparison with the existing methods. Copyright © 2016 John Wiley & Sons, Ltd.     

Design of ℋ︁∞ fuzzy controllers for nonlinear systems with random data dropouts

The problem of ??_∞ control of nonlinear networked control systems subject to random data dropout is concerned in this paper. The random data dropout, because of the limited bandwidth of the network channels, could exist in the communication channels both from the sensor to the controller and from the controller to the actuator simultaneously. The nonlinear plant is represented by the well‐known Takagi–Sugeno fuzzy model and the random data dropout is expressed by the Bernoulli random binary distribution. In the presence of random data dropout, two control schemes, state feedback and static output feedback, are proposed to design ??_∞ controllers such that the closed‐loop system is stochastically stable and preserves a guaranteed ??_∞ performance. The addressed controller design problem is transformed to an auxiliary convex optimization problem, which can be solved by a linear matrix inequality approach. Three examples are provided to illustrate the applicability and less conservativeness of the developed theoretical results. It is easy to see that our approach is simple but our results are much less conservative than the recently published results. Copyright © 2010 John Wiley & Sons, Ltd.     

High‐order maximum principles for the stability analysis of positive bilinear control systems

We consider a continuous‐time positive bilinear control system, which is a bilinear control system with Metzler matrices. The positive orthant is an invariant set of such a system, and the corresponding transition matrix is entrywise nonnegative for all time. Motivated by the stability analysis of positive linear switched systems under arbitrary switching laws, we define a control as optimal if it maximizes the spectral radius of the transition matrix at a given final time. We derive high‐order necessary conditions for optimality for both singular and bang–bang controls. Our approach is based on combining results on the second‐order derivative of a simple eigenvalue with the generalized Legendre‐Clebsch condition and the Agrachev–Gamkrelidze second‐order optimality condition. Copyright © 2015 John Wiley & Sons, Ltd.