Circular Cascade Research Articles

Rapid RNA detection through intra-enzyme chain replacement-promoted Cas13a cascade cyclic reaction without amplification

The clinical methods to detect RNA viruses and disease-related RNAs suffer from time-consuming processes, high false-positive rates, or limited sensitivity. Here, we propose a strategy for rapid RNA detection through intra-enzyme chain replacement-mediated Cas13a cascade cyclic reaction without target amplification. A hairpin RNA mediator (a cleavage substrate for target-activated Cas13a) and a guiding RNA recognized by the cleavage product through intra-enzyme chain replacement were designed and optimized. Upon the recognition and binding of the target RNA to the Cas13a/CrRNA complex, Cas13a is initially activated to cleave the mediator, and the cleavage products recognize the corresponding Cas13a/CrRNA complex by intra-enzyme chain replacement and initiate the circular cascade of Cas13a cleavage and activation. The accumulated active Cas13a cleaves fluorescent reporter probe for achieving target RNA detection. This “mix & read” RNA detection at room temperature was performed in total 30 min. Using miRNA-21 as the target, the changes in fluorescence intensity were linearly correlated to the concentrations from 10 fM to 50 pM with the detection limit of 75 aM, while no significant changes in fluorescence intensity were detected for non-targets. This method applied to the clinical sputum respiratory syncytial virus-positive samples gave results consistent with those from the clinical fluorescence immunoassay. Thus, intra-enzyme chain replacement-promoted Cas13a cascade cyclic reaction for detection of RNA viruses in the “mix & read” mode at room temperature is rapid, simple, convenient, and efficient for RNA detection and can be adapted to point-of-care testing for high throughput screening of RNA virus infections.

Improvement of Unstable Flow in a Low Solidity Cascade Diffuser of Centrifugal Compressor by Multi-Objective Optimization

A compressor for turbochargers is commonly required improving efficiency and expanding the operating flow rate range. Though an aerofoil type diffuser shows better pressure recovery than conventional vaneless diffuser, it is difficult to design the aerofoil type diffuser under conditions of wide change of the flow angle. An innovative design of a Low Solidity circular cascade Diffuser (LSD) was proposed for flow range enhancement of cascade diffuser¸ and an interesting function of the LSD is introduced. At small flow rate conditions, low energy fluid near the diffuser side wall spread between the diffuser blade, and low energy fluid moves to the leading edge of the adjacent blade, then low energy fluid merged with main flow and suppress the flow separation. The phenomena spread to circumferential direction, and whole of the LSD blades show high stability for separation under a large angle of attack. In this study, LSD is designed for compressors of turbocharger by using a Genetic Algorithms (GA) with meta-model of an Artificial Neural Networks (ANN). The final goal of this study is to optimize the LSD with having secondary flow effect under low flow rate conditions.

Eucalyptus Bark as Source of Bio-oil or Phenolic Compounds

Background: Eucalyptus bark and scraps are generated in the production of mediumdensity fiberboard (MDF). An approach aiming to add value to such wastes was studied, following the concepts of circular economy and biomass cascade strategy. Bio-oil and phenolic resin were produced by pyrolysis from two types of biomass, Eucalyptus bark and MDF waste. As is well known, conventional phenolic resins are normally obtained from fossil resources. These products were obtained from the pyrolysis of two types of biomass to reduce environmental waste and dependence on petroleum-based products. Objective: The main objective of the present study was to produce phenolic resin from Eucalyptus wastes, aiming to reduce the fossil dependence on conventional resins used in the production line of MDF. Methods: Fast pyrolysis and slow pyrolysis were employed for bio-oil and phenolic resin production. The bio-oil and resins were characterized with standard lab analyses for their physicochemical properties, while their thermal properties were studied via thermogravimetric analysis (TGA). Results: The shear strength of the lap internal bonding of the phenolic resin binders with 19.8% of bio-oil was 2.09, 1.34, and 1.63 MPa under dry, boiler, and soaked conditions, respectively, which was acceptable for panel fabrication and can represent a significant saving in terms of fossil resins and cost reduction. Discussion: According to the results, 1 g medium fraction of bio-oils was equivalent to 1.35 g of conventional phenols, indicating those bio-oils as phenolic structures that could be used as binders. The bio-oil yields for bark and MDF were 40.9 and 25.1, respectively, which indicate a potential for replacing the conventional fossil-based phenolic resin. Conclusion: The results revealed the possibility of replacing conventional fossil-based chemicals with phenolic resin from renewable resources with similar overall properties, replacing about 1/3 of the conventional resin.

Numerical analysis of the aerodynamic performance and excitation forces in a transonic turbine cascade with flat-tip and squealer-tip blades

The purpose of this paper is to numerically investigate the effect of blade tip clearance and its structure on the turbine aerodynamic performance and excitation force on blades in a transonic turbine cascade. Hence, circular cascades with flat-tip and squealer-tip blades and eight different tip clearances based on the SNECMA transonic turbine were established and the rotational effect was taking into consideration. The simulations were performed by solving the RANS equations and the SST turbulence model was used. The results show that tip clearance and tip structure have a significant influence on the turbine efficiency and excitation forces. Smaller tip clearance and squealer tip structure can reduce the tip leakage flow and leads to higher turbine efficiency. The tangential blade force varies nonlinearly with tip clearance since the leakage flow significantly changes the static pressure distributions on blade surfaces. Further, the excitation force factor was also calculated and illustrated.

Compositional abstraction of large-scale stochastic systems: A relaxed dissipativity approach

In this paper, we propose a compositional approach for the construction of finite abstractions (a.k.a. finite Markov decision processes (MDPs)) for networks of discrete-time stochastic control subsystems that are not necessarily stabilizable. The proposed approach leverages the interconnection topology and a notion of finite-step stochastic storage functions, that describes joint dissipativity-type properties of subsystems and their abstractions, and establishes a finite-step stochastic simulation function as a relation between the network and its abstraction. To this end, we first develop a new type of compositionality conditions which is less conservative than the existing ones. In particular, using a relaxation via a finite-step stochastic simulation function, it is possible to construct finite abstractions such that stabilizability of each subsystem is not necessarily required. We then propose an approach to construct finite MDPs together with their corresponding finite-step storage functions for general discrete-time stochastic control systems satisfying an incremental passivability property. We also construct finite MDPs for a particular class of nonlinear stochastic control systems. To demonstrate the effectiveness of the proposed results, we first apply our approach to an interconnected system composed of 4 subsystems such that 2 of them are not stabilizable. We then consider a road traffic network in a circular cascade ring composed of 50 cells, and construct compositionally a finite MDP of the network. We employ the constructed finite abstractions as substitutes to compositionally synthesize policies keeping the density of the traffic lower than 20 vehicles per cell. Finally, we apply our proposed technique to a fully interconnected network of 500 nonlinear subsystems and construct their finite MDPs with guaranteed error bounds on the probabilistic distance between their output trajectories.

Compositional abstraction-based synthesis for networks of stochastic switched systems

In this paper, we provide a compositional approach for constructing finite abstractions (a.k.a. finite Markov decision processes (MDPs)) of interconnected discrete-time stochastic switched systems. The proposed framework is based on a notion of stochastic simulation functions, using which one can employ an abstract system as a substitution of the original one in the controller design process with guaranteed error bounds on their output trajectories. To this end, we first provide probabilistic closeness guarantees between the interconnection of stochastic switched subsystems and that of their finite abstractions via stochastic simulation functions. We then leverage sufficient small-gain type conditions to show compositionality results of this work. Afterwards, we show that under standard assumptions ensuring incremental input-to-state stability of switched systems (i.e., existence of common incremental Lyapunov functions, or multiple incremental Lyapunov functions with dwell-time), one can construct finite MDPs for the general setting of nonlinear stochastic switched systems. We also propose an approach to construct finite MDPs together with their corresponding stochastic simulation functions for a particular class of nonlinear stochastic switched systems. We show that for this class of systems, the aforementioned incremental stability property can be readily checked by matrix inequalities. To demonstrate the effectiveness of our proposed results, we first apply our approaches to a road traffic network in a circular cascade ring composed of 200 cells, and construct compositionally a finite MDP of the network. We employ the constructed finite abstractions as substitutes to compositionally synthesize policies keeping the density of the traffic lower than 20 vehicles per cell. We then apply our proposed techniques to a fully interconnected network of 500 nonlinear subsystems (totally 1000 dimensions), and construct their finite MDPs with guaranteed error bounds. We compare our proposed results with those available in the literature.

The effect of yeast supplementation on equine fecal microbial population dynamics following abrupt dietary changes

In this paper, we propose a compositional approach for the construction of finite abstractions (a.k.a. finite Markov decision processes (MDPs)) for networks of discrete-time stochastic control subsystems that are not necessarily stabilizable. The proposed approach leverages the interconnection topology and a notion of finite-step stochastic storage functions, that describes joint dissipativity-type properties of subsystems and their abstractions, and establishes a finite-step stochastic simulation function as a relation between the network and its abstraction. To this end, we first develop a new type of compositionality conditions which is less conservative than the existing ones. In particular, using a relaxation via a finite-step stochastic simulation function, it is possible to construct finite abstractions such that stabilizability of each subsystem is not necessarily required. We then propose an approach to construct finite MDPs together with their corresponding finite-step storage functions for general discrete-time stochastic control systems satisfying an incremental passivability property. We also construct finite MDPs for a particular class of nonlinear stochastic control systems. To demonstrate the effectiveness of the proposed results, we first apply our approach to an interconnected system composed of 4 subsystems such that 2 of them are not stabilizable. We then consider a road traffic network in a circular cascade ring composed of 50 cells, and construct compositionally a finite MDP of the network. We employ the constructed finite abstractions as substitutes to compositionally synthesize policies keeping the density of the traffic lower than 20 vehicles per cell. Finally, we apply our proposed technique to a fully interconnected network of 500 nonlinear subsystems and construct their finite MDPs with guaranteed error bounds on the probabilistic distance between their output trajectories.

Development of high-efficiency and low-cost unshrouded turbine runner for small scale hydropower plant

Facing a growing demand for low initial cost and high-efficiency small scale hydropower plants, a new type of Francis turbine was developed for Kazunogawa small hydropower plant with cooperation from industrial, governmental, and academic sectors. To reduce the cost of the turbine while increasing its efficiency, a prototype turbine with an unshrouded runner and a cylindrical casing was developed. The unshrouded runner was designed by Waseda University. Typically, the turbine runner for small scale hydropower is manufactured via a casting method; however, the unshrouded runner can be milled with a 5 axis CNC machine, thereby reducing cost and manufacturing lead time. A cylindrical casing has advantages of low fabrication cost and compact footprint. However, it had lower efficiency compared to a spiral casing with conventional design. Therefore, in this study, topology optimization based on CFD analysis was conducted on the casing and double circular cascade to improve efficiency. In addition, the axial thrust was estimated from CFD analysis to design the bearings and to determine the runner gap. Finally, a performance test was conducted on-site and peak efficiency of 91% was confirmed. This paper also reports the follow-up observation of the prototype turbine after commercial operation started.

Visualization of Flow Field in Circular Cascade Having Rotating Stall Suppressed by Tip Injection with PIV

Visualization of Flow Field in Circular Cascade Having Rotating Stall Suppressed by Tip Injection with PIV

Internal flow and loss mechanisms of specific speed 160 m-kW shroudless hydro turbine

High efficiency and low-cost hydro turbines are becoming more popular for medium and small-scale hydropower generation in underdeveloped locations. Because of this, a shroudless hydro turbine of medium specific speed 160 [m-kW] was developed based on a low specific speed 80 [m-kW] design concept previously studied in the author’s laboratory. We are aiming to develop an optimal design method and further improve performances of the medium- specific speed 160 [m-kW] shroudless hydro turbine. The most important factors are the internal flow and the loss mechanism of each flow path component. In this study, the internal flow and loss mechanisms were investigated and clarified by experimental and computational approaches. The main loss mechanisms in the double circular cascade is the high swirling strength vortices extending from the guide vane inlet to the outlet near the end wall of guide vanes. Furthermore, it has been found that the interference of the secondary flow and leakage flow, and the tip leakage vortex are the predominant loss mechanisms of the shroudless runner.

Global Search of a Three-dimensional Low Solidity Circular Cascade Diffuser for Centrifugal Blowers by Meta-model Assisted Optimization

A three-dimensional blade of a low solidity circular cascade diffuser in centrifugal blowers is designed by means of a multi-point optimization technique. The optimization aims at improving static pressure coefficient at a design point and at a small flow rate condition. Moreover, a clear definition of secondary flow expressed by positive radial velocity at hub side is taken into consideration in constraints. The number of design parameters for three-dimensional blade reaches to 10 in this study, such as a radial gap, a radial chord length and mean camber angle distribution of the LSD blade with five control points, control point between hub and shroud with two design freedom. Optimization results show clear Pareto front and selected optimum design shows good improvement of pressure rise in diffuser at small flow rate conditions. It is found that three-dimensional blade has advantage to stabilize the secondary flow effect with improving pressure recovery of the low solidity circular cascade diffuser.

Effect of Fluid Injection to a Leading Edge of Circular Cascade on Centrifugal Compressor Performance

Effect of Fluid Injection to a Leading Edge of Circular Cascade on Centrifugal Compressor Performance

低速回転時における円形翼列の旋回失速の可視化

低速回転時における円形翼列の旋回失速の可視化

多目的最適化による三次元小弦節比翼列ディフューザの設計

多目的最適化による三次元小弦節比翼列ディフューザの設計

1410 円形翼列翼前縁への噴流の運動量付加による旋回失速抑制(流体工学VIII)

1410 円形翼列翼前縁への噴流の運動量付加による旋回失速抑制(流体工学VIII)

Flow range enhancement by secondary flow effect in low solidity circular cascade diffusers

High-pressure ratio and wide operating range are highly required for compressors and blowers. The technical issue of the design is achievement of suppression of flow separation at small flow rate without deteriorating the efficiency at design flow rate. A numerical simulation is very effective in design procedure, however, cost of the numerical simulation is generally high during the practical design process, and it is difficult to confirm the optimal design which is combined with many parameters. A multi-objective optimization technique is the idea that has been proposed for solving the problem in practical design process. In this study, a Low Solidity circular cascade Diffuser (LSD) in a centrifugal blower is successfully designed by means of multi-objective optimization technique. An optimization code with a meta-model assisted evolutionary algorithm is used with a commercial CFD code ANSYS-CFX. The optimization is aiming at improving the static pressure coefficient at design point and at low flow rate condition while constraining the slope of the lift coefficient curve. Moreover, a small tip clearance of the LSD blade was applied in order to activate and to stabilize the secondary flow effect at small flow rate condition. The optimized LSD blade has an extended operating range of 114 % towards smaller flow rate as compared to the baseline design without deteriorating the diffuser pressure recovery at design point. The diffuser pressure rise and operating flow range of the optimized LSD blade are experimentally verified by overall performance test. The detailed flow in the diffuser is also confirmed by means of a Particle Image Velocimeter. Secondary flow is clearly captured by PIV and it spreads to the whole area of LSD blade pitch. It is found that the optimized LSD blade shows good improvement of the blade loading in the whole operating range, while at small flow rate the flow separation on the LSD blade has been successfully suppressed by the secondary flow effect.

125 PIVによる遠心送風機小弦節比翼列ディフューザの二次流れの計測

125 PIVによる遠心送風機小弦節比翼列ディフューザの二次流れの計測

207 2次元PIVによる円形翼列の動翼近傍における速度測定(流体工学II,学術講演)

207 2次元PIVによる円形翼列の動翼近傍における速度測定(流体工学II,学術講演)

Control of secondary flow in a low solidity circular cascade diffuser

According to the previous experimental works on the low solidity circular cascade diffuser (LSD), a pressure recovery of a centrifugal blower was improved by the LSD significantly in a wide range of flow rate, and the pressure recovery was improved further by the LSD with a tandem cascade in comparison with the LSD with a single-row cascade. In the present study, the flow behavior in the LSD with the tandem cascade has been analyzed numerically by using the commercial CFD code of ANSYS-CFX12. It was shown clearly that the higher pressure recovery was achieved by applying the LSD with the tandem cascade, and the high pressure recovery is based on the high pressure rise in the vaneless space upstream of the LSD and the high blade loading of the front blade of the LSD. The high pressure recovery in the LSD could be achieved by controlling the flow separation on the suction surface of the front blade and also on that of the rear blade due to formation of the favorable secondary flow and due to increase in mass flow passing through the slit section between the front and rear blades.

206 静止円形翼列におけるシンセティックジェットの影響(流体工学II,一般講演)

206 静止円形翼列におけるシンセティックジェットの影響(流体工学II,一般講演)