This brief presents a nonlinear control design for a two-wheeled inverted pendulum robot, based on new analysis of the classical state-dependent Riccati equation (SDRE) scheme and a novel alternative ...strategy. The solvability of pointwise algebraic Riccati equations (AREs) corresponding to the nonunique state-dependent coefficients (SDCs) of the SDRE scheme is analyzed from a new perspective. This is formulated as a simple equivalence condition with reduced dimensionality, which circumvents the excessive online computational effort to check the solvability of classical SDRE. The condition is derived in a way to facilitate the generalization to all meaningful SDCs. Moreover, due to unsolvable AREs, all conflicts against the primary objective of posture balance of the robot are revealed and illustrated, with a connection to the robot physical parameters. At the system states that cause such conflicts and other unsolvable AREs, a simple analytical solution via alternative SDC constructions is suggested. More potential advantages of this SDC construction over the classical scheme are revealed in simulations, e.g., the maximum input/torque and total energy consumption.
Proteasomes are compartmentalized, ATP-dependent, N-terminal nucleophile hydrolases that play essentials roles in intracellular protein turnover. They are present in all 3 kingdoms. Pharmacological ...inhibition of proteasomes is detrimental to cell viability. Proteasome inhibitor rugs revolutionize the treatment of multiple myeloma. Proteasomes in pathogenic microbes such as Mycobacterium tuberculosis (Mtb), Plasmodium falciparum (Pf), and other parasites and worms have been validated as therapeutic targets. Starting with Mtb proteasome, efforts in developing inhibitors selective for microbial proteasomes have made great progress lately. In this review, we describe the strategies and pharmacophores that have been used in developing proteasome inhibitors with potency and selectivity that spare human proteasomes and highlight the development of clinical proteasome inhibitor candidates for treatment of leishmaniasis and Chagas disease. Finally, we discuss the future challenges and therapeutical potentials of the microbial proteasome inhibitors.
This article presents new analytical results that substantially improve the computational performance of the state-dependent Riccati equation (SDRE) scheme to control a nonlinear benchmark problem. ...The analysis formulates the equivalent applicability condition in a reduced-dimensional system space, which is in terms of the pointwise solvability of SDRE but generally deemed challenging/impossible. It starts with a unified coverage of the <inline-formula><tex-math notation="LaTeX">{\boldsymbol{\alpha }}</tex-math></inline-formula>-parameterization method, which has been widely utilized to exploit the flexibility of the state-dependent coefficient (SDC) matrix in the SDRE scheme. When specializing to a practically meaningful SDC, the analysis further sheds light on a much simpler equivalent condition by virtue of a novel categorization of the entire state space. This largely alleviates the dominant computational burden pointwise at each time instant or system state, which is supported by complexity analysis, and validated through simulations. In addition, it enlarges the domain of interest in the previous design, which was constrained due to the numerical implementation. Notably, the generality of the analytical philosophy also includes robustness to parameter values of this benchmark application, and a variety of nonlinear control systems within and beyond the SDRE design framework.
•An accurate and stable fluid-structure interaction scheme concerning heat transfer process is proposed for forced convection heat transfers from cylindrical structures under flow-induced ...vibration.•Coupling mechanisms among the flow patterns, cylinder vibrations and heat transfer features of an isolated circular cylinder and two tandem circular cylinders in laminar flow regime are analyzed.•For an isolated circular cylinder, large-scale vortex-induced vibration appearing in the “lock-in” regime increases the mean Nusselt number of the cylinder by up to 15%.•For two tandem circular cylinders, wake interference amplifies the flow-induced vibration of the downstream cylinder by up to 81.32%, leading to a maximum heat transfer amplification of 28.3%.
Flow-induced vibrations (FIVs) and forced convection heat transfers of two tandem circular cylinders in laminar flow with Re=150 and Pr=0.7 are investigated using fluid-structure interaction (FSI) simulation. The cylinder is heated, elastically supported and only allowed to vibrate in the transverse direction, with the mass ratio, damping ratio, centre-to-centre distance fixed respectively at m*=2, ζ=0, L/D=4 and the reduced velocity varied in Ur=1~20. The two-dimensional incompressible Navier-Stokes equations and energy equation are coupled with the vibrating equation of the spring-mass-damper model to describe FIV of two tandem cylinders involving forced convection heat transfer process. An FSI solver is proposed by combing the modified characteristic-based split scheme, dual-time stepping method, segment spring analogy method and loosely coupled partitioned approach, the accuracy and stability of which are validated using two benchmark models including the forced convection heat transfer from a fixed circular cylinder and FIV of an elastically supported circular cylinder. Using FSI simulation, characteristics of FIVs and their effects on forced convection heat transfers of two tandem circular cylinders are analyzed in detail. The obtained numerical results are insightful to the understanding of the heat transfer features of a group of cylindrical structures under FIVs, such as the tube bundles in heat exchangers and power plants, fuel rod bundles in nuclear reactors and riser system in offshore oil and gas platforms.
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Nanocarrier for augmenting the efficacy of reactive oxygen species (ROS) by tumor microenvironment (TME) has become an emerging strategy for cancer treatment. Herein, a smart biodegradable drug ...delivery nanoplatform with mitochondrial-targeted ability, pH-responsive drug release and enzyme-like catalytic function is designed. This efficient ROS-generating platform uses ultrasound with deeper penetration capability as excitation source for combined chemotherapy and sonodynamic therapy (SDT) of tumor. In vitro experiments show that the nanoplatform can co-load Ce6 and DOX and be degraded in slight acid environment, and the DOX release rate is 63.91 ± 1.67%. In vivo experiments show that the nanoplatform has extremely biosafety and can be enriched in tumor site and excluded from body after 24 h. More significantly, after combined treatment, the tumors are eliminated and the mice still survive healthily without recurrence after 60 d. This is because not only it can achieve mitochondrial targeting and use platinum particle to increase oxygen content in TME to enhance the effect of SDT, but also it can use weak acidic TME to accelerate drug release to achieve the combination of chemotherapy and SDT. The probe provides a new strategy for designing ROS-based nanoplatform for the treatment of malignant tumor.
Environmental friendly metal halides have become emerging candidates as energy downconverting emitters for lighting and X‐ray imaging applications. Herein, luminescent single crystals of ...tetramethylammonium manganese chloride (C4H12NMnCl3) and tetraethylammonium bromide ((C8H20N)2MnBr4) are synthesized via a facile room‐temperature evaporation method. C4H12NMnCl3 and (C8H20N)2MnBr4 with octahedrally and tetrahedrally coordinated Mn2+ have correspondingly exhibited red and green emission peaking at 635 and 515 nm both originating from 4T1–6A1 transition of Mn2+ with high photoluminescence quantum yield (PLQY) of 91.8% and 85.1% benefiting from their specific crystal structures. Thanks to their strong photoexcitation under blue light, high PLQY, tunable emission spectra, good environmental stability, the white light‐emitting diode based on blending of C4H12NMnCl3 and (C8H20N)2MnBr4 delivers an outstanding luminous efficacy of 96 lm W−1, approaching commercial level, and shows no obvious photoluminescence intensity degradation after 3000 h under operation. In addition, manganese halides also demonstrate interesting characteristics under X‐ray excitation, C4H12NMnCl3 and (C8H20N)2MnBr4 exhibit steady‐state X‐ray light yields of 50 500 and 24 400 photons MeV−1, low detectable limits of 36.9 and 24.2 nGyair s−1, good radiation hardness, and X‐ray imaging demonstration with high‐resolution of 5 lp mm−1. This work presents a new avenue for luminescent Mn‐based metal halides toward multifunctional light‐emitting applications.
Manganese halides C4H12NMnCl3 and (C8H20N)2MnBr4 have correspondingly exhibited red and green emission with high photoluminescence quantum yields over 85%. The white light‐emitting diode based on their mixture delivers a high luminous efficacy of 96 lm W−1 and 3000 h operational stability. Meanwhile, they exhibit high steady‐state X‐ray light yields of 50 500 and 24 400 photons MeV−1 as well as low detectable limits.
This article presents new analytical results that fundamentally ensure the applicability of the state-dependent Riccati equation (SDRE) scheme, for the three-degree-of-freedom helicopter control ...system that is of benchmark importance. The analysis removes any online time-consuming applicability check that is in terms of the pointwise solvability of SDRE, which leverages a series of equivalence transformations and dimension reductions. This largely improves the computational performance since the checking routine accounts for the dominant burden, which is endorsed by complexity analysis and practical validations. The analysis also categorizes the entire state space, where the newly discovered inapplicable subspace is efficiently resolved using an alternative SDRE design. As for the second/other computational load (pointwise SDRE-solving), we novelly introduce a state-of-the-art solver, provide a MATLAB-compatible implementation, and demonstrate performance advantages in computing time and accuracy. Notably, the simulations reveal more potential advantages as compared to the recent literature, including the control effort efficiency and robustness to model uncertainty. Moreover, the generality of the proposed theoretical results includes parameter robustness of this aerospace application and various control systems within the SDRE design framework and beyond.
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