Adaptive Control of Unknown Time Varying Dynamical Systems with Regret Guarantees

The study of online control of unknown time varying dynamical systems is a relatively under-explored topic. In this work, we present regret guarantee with respect to a stronger notion of system variability compared to \cite{minasyan2021online} and thus provide sub-linear regret guarantee for a much broader range of scenarios. Specifically, we give regret guarantee wtih respect to the number of changes compared to the average squared deviation of \cite{minasyan2021online}. The online control algorithm we propose continuously updates its estimate to track the changes and employs an online optimizer to simultaneously optimize the control policy. We show that our algorithm can achieve a sub-linear regret with respect to the number of changes under two settings: (i) matched disturbance system with general convex cost functions, (ii) general system with linear cost functions. Specifically, a regret of $\Gamma^{1/5}_TT^{4/5}$ can be achieved, where $\Gamma_T$ is the number of changes in the underlying system and $T$ is the duration of the control episode

Estimating 3D Uncertainty Field: Quantifying Uncertainty for Neural Radiance Fields

Current methods based on Neural Radiance Fields (NeRF) significantly lack the capacity to quantify uncertainty in their predictions, particularly on the unseen space including the occluded and outside scene content. This limitation hinders their extensive applications in robotics, where the reliability of model predictions has to be considered for tasks such as robotic exploration and planning in unknown environments. To address this, we propose a novel approach to estimate a 3D Uncertainty Field based on the learned incomplete scene geometry, which explicitly identifies these unseen regions. By considering the accumulated transmittance along each camera ray, our Uncertainty Field infers 2D pixel-wise uncertainty, exhibiting high values for rays directly casting towards occluded or outside the scene content. To quantify the uncertainty on the learned surface, we model a stochastic radiance field. Our experiments demonstrate that our approach is the only one that can explicitly reason about high uncertainty both on 3D unseen regions and its involved 2D rendered pixels, compared with recent methods. Furthermore, we illustrate that our designed uncertainty field is ideally suited for real-world robotics tasks, such as next-best-view selection

Top-down effects of filter-feeding fish and bivalves moderate bottom-up effects of nutrients on phytoplankton in subtropical shallow lakes: An outdoor mesocosm study

Biomanipulation has been widely used in the ecological restoration of eutrophic lakes for decades. However, biomanipulation is prone to failure if external nutrient loads are not reduced. In order to explore the importance of filter-feeding fish and bivalves on algal control, an outdoor mesocosm experiment was conducted using different nutrient concentrations. Four treatments simulating daily loads of nutrients in Lake Taihu were studied: current, two times, and three times average daily loads of nutrients with both fish (Aristichthys nobilis) and Asian clam (Corbicula fluminea) and as a control current daily loads without fish or bivalves. Results showed that stocking of filter-feeding fish and bivalves (80 g m-3 bighead carp; 200 g cm-2 clams) at two times daily nutrient loads could effectively control water column Chl a concentrations and phytoplankton biomass. At higher nutrient concentrations (TN & GE; 260 & mu;g L-1 d-1; TP & GE; 10 & mu;g L-1 d-1), top-down control of filter-feeding fish and bivalves was less effective and bottom-up effects resulted in significant increases of Chl a concentration. Thus, as phytoplankton biomass in freshwater ecosystems is determined by both the top-down effects of predators and the bottom-up effects of nutrients, external loadings should be controlled when filter-feeding fish and bivalves are used for algal control to ensure the efficacy of biomanipulation.A combination of filter-feeding fish and clams suppressed phytoplankton, which could not be affected by low-level nutrients.Bottom-up effects at high-level nutrients on phytoplankton overcome top-down effects, indicating that nutrient levels should be controlled to optimize the effect of the intervention.imag

Enhanced room-temperature Na+ ionic conductivity in Na4.92_{4.92}Y0.92_{0.92}Zr0.08_{0.08}Si4_{4}O12_{12}

Developing cost-effective and reliable solid-state sodium batteries with superior performance is crucial for stationary energy storage. A key component in facilitating their application is a solid-state electrolyte with high conductivity and stability. Herein, we employed aliovalent cation substitution to enhance ionic conductivity while preserving the crystal structure. Optimized substitution of Y3+ with Zr4+ in Na5YSi4O12 introduced Na+ ​ion vacancies, resulting in high bulk and total conductivities of up to 6.5 and 3.3 ​mS ​cm−1, respectively, at room temperature with the composition Na4.92Y0.92Zr0.08Si4O12 (NYZS). NYZS shows exceptional electrochemical stability (up to 10 ​V vs. Na+/Na), favorable interfacial compatibility with Na, and an excellent critical current density of 2.4 ​mA ​cm−2. The enhanced conductivity of Na+ ​ions in NYZS was elucidated using solid-state nuclear magnetic resonance techniques and theoretical simulations, revealing two migration routes facilitated by the synergistic effect of increased Na+ ​ion vacancies and improved chemical environment due to Zr4+ substitution. NYZS extends the list of suitable solid-state electrolytes and enables the facile synthesis of stable, low-cost Na+ ion silicate electrolytes

Antibacterial activity and antibacterial mechanism of flavaspidic acid BB against Staphylococcus haemelyticus

Abstract Background Staphylococcus haemolyticus (S. haemolyticus) is the main etiological factor in skin and soft tissue infections (SSTI). S. haemolyticus infections are an important concern worldwide, especially with the associated biofilms and drug resistance. Herein, we investigated the inhibitory effect of Flavaspidic acid BB obtained from plant extractions on clinical S. haemolyticus strains and their biofilms. Moreover, we predicted its ability to bind to the protein-binding site by molecular simulation. Since the combination of Hsp70 and RNase P synthase after molecular simulation with flavaspidic acid BB is relatively stable, enzyme-linked immunosorbent assay (ELISA) was used to investigate Hsp70 and RNase P synthase to verify the potential antimicrobial targets of flavaspidic acid BB. Results The minimum inhibitory concentrations (MIC) of flavaspidic acid BB on 16 clinical strains of S. haemolyticus was 5 ~ 480 µg/mL, and BB had a slightly higher inhibitory effect on the biofilm than MUP. The inhibitory effect of flavaspidic acid BB on biofilm formation was better with an increase in the concentration of BB. Molecular simulation verified its ability to bind to the protein-binding site. The combination of ELISA kits showed that flavaspidic acid BB promoted the activity of Hsp70 and inhibited the activity of RNase P, revealing that flavaspidic acid BB could effectively inhibit the utilization and re-synthesis of protein and tRNA synthesis, thus inhibiting bacterial growth and biofilm formation to a certain extent. Conclusions This study could potentially provide a new prospect for the development of flavaspidic acid BB as an antibacterial agent for resistant strains

Design of remote wireless monitoring system for coal mine main ventilator

The main ventilator room of coal mine is remote and difficultly covered by wired network, so as to cause main ventilator monitoring system falling into information island. For above problem, a design scheme of remote wireless monitoring system for coal mine main ventilator based on mobile platform was put forward. The system uses a GPRS DTU to communicate with PLC for collecting field monitoring data, and the data is uploaded to a cloud data sever through GPRS network. On the other hand, mobile client based on Android system accesses the cloud data sever by use of socket communication mode through 3G, 4G or WiFi wireless network, so that users can remotely monitor operation status of coal mine main ventilator anytime and anywhere. The test results verify feasibility of the system

Combining bivalve (Corbicula fluminea) and filter-feeding fish (Aristichthys nobilis) enhances the bioremediation effect of algae: An outdoor mesocosm study

In outdoor mesocosms, we experimentally studied the effect of combining two native filter feeders, bighead carp (Aristichthys nobilis) and Asian clam (Corbicula fluminea), to control nuisance cyanobacterial blooms. Four treatments - clam-only, fish-only, combined and controls - were used. In combination, bighead carp (80 g m(-3)) and Asian clam (260 g m(-2)), had a remarkable controlling effect on phytoplankton biomass and improved water quality. By the end of the experiment, the chlorophyll a (Chl a) concentration of the combined group was below 5 mu g L-1 compared with 36 mu g L-1 in the clam-only treatments and 31 mu g L-1 in the controls, whereas Chl a in the fish-only group had increased to 211 mu g L-1. Large-sized algae (Microcystis sp.) dominated in the control group and the clam-only group, whereas small-sized algae (Actinastrum hantzschii and Clamydomonas globose) dominated in the fish-only group. The concentrations of total nitrogen (TN) and total phosphorus (TP) in the water column were significantly reduced by clam stocking, regardless of the presence of fish. A 24-h laboratory experiment was conducted to verify whether the excrements produced by clams filtering small-sized algae could be eaten by bighead carp. At the end of the experiment, the density of Scenedesmus obliquus had decreased significantly in the clam-presentmesocosms, and the gut fullness index of bighead carp was significantly higher in the clam-present mesocosms than when clams were absent. Our results show that, under the selected experimental conditions and densities, water clarity improved when bighead carp and Asian clam occurred together, whereas Chl a concentrations and algae biomass increased in the fish-only mesocosms; in the clam-only mesocosms no significant effectswere observed. We suggest that the combination of filter-feeding fish and clams may enhance water clarity and it may therefore potentially be a useful restoration tool

A small omnivore fish (

Transplantation of submerged macrophytes has been widely used to improve water quality in restoring shallow lakes in China. However, in some lakes, small omnivorous fish predominated the fish assemblages and fed mainly on submerged macrophytes. Despite significant research examining grazing selectivity in herbivorous fishes, macrophyte feeding preferences of small omnivorous fishes are poorly understood. We conducted a mesocosm experiment to examine the effects of a prolific small omnivorous bitterling fish Acheilognathus macropterus on the relative growth rate (RGR) and biomass of submerged macrophytes (Ceratophyllum demersum, Myriophyllum spicatum, Vallisneria denseserrulata, and Hydrilla verticillata). Our results showed that the presence of A. macropterus significantly increased nutrient concentrations (e.g. total nitrogen and total phosphorus). The RGR of C. demersum in the bitterling-present treatment was significantly lower than the controls, in the presence of other macrophyte species. Further, total biomass of the four species of macrophytes in the fish-present mesocosms was markedly lower than in the fish-absent treatment, suggesting considerable consumption of macrophytes by bitterling. Moreover, the percent biomass of V. denserrulata and H. verticillata were significantly enhanced by the presence of bitterling. Our findings suggest that A. macropterus may increase nutrient concentrations through excretion and reduce the biomass and RGR of certain submerged macrophytes which may shift macrophyte community structure via selective grazing

Comparative Effectiveness of Different Combinations of Treatment Interventions in Patients with Stroke at the Convalescence Stage Based on the Markov Decision Process

Objective. The objective of this study was to compare the effectiveness of different combinations of interventions in patients with stroke at the convalescence stage based on the electronic health records (EHRs) by using the Markov decision process (MDP) theory and explore the feasibility of the Markov model in the real-world study (RWS). Methods. Screening was conducted for patients with stroke at the convalescence stage who were admitted to the Third Affiliated Hospital of Zhejiang Chinese Medical University from January 2012 to January 2017 based on the EHRs. The relevant clinical data were extracted, and the appropriate conversion was made (state-action-reward) according to the Markov model. The transformed data were analysed and solved by the MDP to obtain the best interventions for patients with various stroke recovery periods. Results. 926 patients with stroke at the convalescence stage were initially selected. And according to the inclusion exclusion criteria, 854 patients were screened. Through the MDP, we obtained the following results: (1)when the patients with stroke at the convalescence stage have a medical history, but no complications, and mild neurological impairment, ≥66-year- and 18–45-year-old patients are advised to choose acupuncture treatment. 46–65-year-old patients are advised to choose rehabilitation treatment. When patients with moderate to severe neurological impairment, patients are advised to choose rehabilitation, Chinese herbal decoction, and acupuncture combined therapy. (2) Without complications or medical history, patients who are ≥ 66 years old are recommended to choose rehabilitation treatment when the nerve function impairment is mild; rehabilitation and acupuncture treatment are recommended when moderate and severe injuries are caused. (3) The combination of rehabilitation, Chinese herbal decoction, and acupuncture treatment is recommended for patients with phlegm and blood stasis. Acupuncture treatment is recommended for patients with mild impairment of nerve function in qi deficiency and blood stasis type. Rehabilitation, Chinese herbal decoction, and acupuncture treatment are recommended for moderate-severe injuries. Conclusions. The MDP makes it possible to study the effectiveness of various treatment methods in stroke patients who are at the convalescence stage. Further exploratory studies using MDP theory in other areas in which complex interventions are common would be worthwhile