An impeller blade with a slot structure can affect the velocity distribution in the impeller flow passage of the centrifugal pump, thus affecting the pump’s performance. Various slot structure geometric parameter combinations were tested in this study to explore this relationship: slot position p, slot width b1, slot deflection angle β, and slot depth h with (3–4) levels were selected for each factor on an L16 orthogonal test table. The results show that b1 and h are the major factors influencing pump performance under low and rated flow conditions, while p is the major influencing factor under the large flow condition. The slot structure close to the front edge of the impeller blade can change the low-pressure region of the suction inlet of the impeller flow passage, thus improving the fluid velocity distribution in the impeller. Optimal slot parameter combinations according to the actual machining precision may include a small slot width b1, slot depth h of ¼ b, slot deflection angle β of 45°–60°, and slot position p close to the front edge of the blade at 20–40%.

A novel strategy for micro/nano-structural and/or water dispersible biochars and their potential application in new and traditional fields.

No abstract

A B S T R A C TUric acid (UA), a waste product of purine derivatives catabolism, is one of the main culprits of gout. In this paper, a simple and sensitive method for the simultaneous voltammetric detection of uric acid (UA) and the most common purine derivatives like guanine (G) and adenine (A) in human serum and lettuce samples was successfully realized using glassy carbon electrode (GCE) modified with the waterprocessable nanotubular composites consisting of both halloysite nanotubes (HNTs) and carboxyl-functionalized multi-walled carbon nanotubes (fMWCNTs) that were well dispersed by carboxymethyl cellulose (CMC). A water-processable HNTs hybrid nanotubes with fMWCNTs were successfully prepared using CMC assist, and the CMC-HNTs-fMWCNTs composites were characterized by scanning electron microscopy, fourier-transform infrared spectroscopy, transmission electron microscope, electrochemical impedance spectroscopy, cyclic voltammetry and chronocoulometry. CMC-HNTs-fMWCNTs/GCE displayed enhanced electrode stability in water, effective surface area, adhesive property and adsorption capacity, and electrocatalytic activity for the oxidation of UA, G and A, which could simultaneously detected three purine derivatives in linear ranges from 1 to 130 µM with a limit of detection (LOD) of 0.5 µM for UA, 0.05 to 9 µM with LOD of 0.018 µM for G, and 0.3 to 25 µM with LOD of 0.19 µM for A, respectively. The asfabricated sensor displayed high sensitivity, low detection limit, good sensing stability, remarkable feasibility, and satisfactory practicality. Keywords Electrochemical sensor · Purine derivatives · Nanotubes · Uric acid · Adenine · Guanine pairing liquid chromatography [8], flow injection-chemiluminescence [9] and capillary electrophoresis [10] have been established for the determination of biomolecules. Although they display unique advantages in accuracy and selectivity in mixtures with real samples, these methods still exist complex and time-consuming sample pretreatment, tedious sample purification steps, strong interference resulting from colored substances or impurities present in real samples, low sensitivity, and the high cost of equipment, reagent, and operator training. Sensors based on chemically modified electrode were employed for the electrochemical detection of purine derivatives, even further employed for the electrochemical detection of purine 4 derivatives in real samples. More and more literatures have been widely reported for the determination of purine derivatives due to the combination of superior properties of various materials (Table1[11-20]). Electrochemical sensors based on various nanocomposites have significantly enhanced synergistic effects in sensing performances like sensitivity, selectivity, accuracy due to the combination of nanomaterials[21]. Nanomaterials and their nanocomposites have recently been attracting considerable attention of scientists and engineers owing to their surface and interface effect, small size effect, quantum size effect, macroscopic quantum tunneling effect, thi...

We developed a novel method to address multicollinearity in linear models called average ordinary least squares (OLS)-centered penalized regression (AOPR). AOPR penalizes the cost function to shrink the estimators toward the weighted-average OLS estimator. The commonly used ridge regression (RR) shrinks the estimators toward zero, that is, employs penalization prior 𝛽 ∼ N(0, 1∕k) in the Bayesian view, which contradicts the common real prior 𝛽 ≠ 0. Therefore, RR selects small penalization coefficients to relieve such a contradiction and thus makes the penalizations inadequate. Mathematical derivations remind us that AOPR could increase the performance of RR and OLS regression. A simulation study shows that AOPR obtains more accurate estimators than OLS regression in most situations and more accurate estimators than RR when the signs of the true 𝛽s are identical and is slightly less accurate than RR when the signs of the true 𝛽s are different. Additionally, a case study shows that AOPR obtains more stable estimators and stronger statistical power and predictive ability than RR and OLS regression. Through these results, we recommend using AOPR to address multicollinearity more efficiently than RR and OLS