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The present study investigates the effects of secondary flow due to angled rib turbulators on the heat/mass transfer in the square channels with channel rotation and bleed flow. The angle of attack of the angled ribs was 45 deg. The bleed holes were located between the rib turbulators on either the leading or trailing surface. The tests were conducted under the conditions corresponding to various bleed ratios (BR = 0.0, 0.2, and 0.4) and rotation numbers (Ro =0.0, 0.2, and 0.4) at Re = 10,000. The results suggest that the heat/mass transfer characteristics were influenced by the Coriolis force, the decrement of the main flow rate, and the secondary flow. In the 90 deg angled ribbed channel, the heat/mass transfer reduced on the leading surface with an increment in the rotation number, but it increased on the trailing surface. However, it decreased on both surfaces in the 45 deg angled ribbed channel. As the bleed ratio increased, the Sherwood number ratios decreased on both the bleeding and nonbleeding surfaces for the 45 deg angled ribs but increased on the bleeding surface for the 90 deg angled ribs.

The present study investigates the effects of bleed flow on heat/mass transfer and pressure drop in a rotating channel with transverse rib turbulators. The hydraulic diameter([D.sub.h]) of the square channel is 40.0 mm. 20 bleed holes are midway between the rib turburators on the leading surface and the hole diameter (d) is 4.5 mm. The square rib turbulators are installed on both leading and trailing surfaces. The rib-to-rib pitch (p) is 10.0 times of the rib height (e) and the rib height-to-hydraulic diameter ratio (e/[D.sub.h]) is 0.055. The tests were conducted at various rotation numbers (0, 0.2, 0.4), while the Reynolds number and the rate of bleed flow to main flow were fixed at 10,000 and 10%, respectively. A naphthalene sublimation method was employed to determine the detailed local heat transfer coefficients using the heat/mass transfer analogy. The results suggest that for a rotating ribbed passage with the bleed flow of BR = 0.1, the heat/mass transfer on the leading surface is dominantly affected by rib turbulators and the secondary flow induced by rotation rather than bleed flow. The heat/mass transfer on the trailing surface decreases due to the diminution of main flow. The results also show that the friction factor decreases with bleed flow. [DOI: 10.1115/1.2720495]

Cholangiopathy is a diverse spectrum of chronic progressive bile duct disorders with limited treatment options and dismal outcomes. Scaffold‐ and stem cell‐based tissue engineering technologies hold great promise for reconstructive surgery and tissue repair. Here, we report a combined application of 3D scaffold fabrication and reprogramming of patient‐specific human hepatocytes to produce implantable artificial tissues that imitate the mechanical and biological properties of native bile ducts. The human chemically derived hepatic progenitor cells (hCdHs) were generated using two small molecules A83‐01 and CHIR99021 and seeded inside the tubular scaffold engineered as a synergistic combination of two layers. The inner electrospun fibrous layer was made of nanoscale–macroscale polycaprolactone fibers acting to promote the hCdHs attachment and differentiation, while the outer microporous foam layer served to increase mechanical stability. The two layers of fiber and foam were fused robustly together thus creating coordinated mechanical flexibility to exclude any possible breaking during surgery. The gene expression profiling and histochemical assessment confirmed that hCdHs acquired the biliary epithelial phenotype and filled the entire surface of the fibrous matrix after 2 weeks of growth in the cholangiocyte differentiation medium in vitro. The fabricated construct replaced the macroscopic part of the common bile duct (CBD) and re‐stored the bile flow in a rabbit model of acute CBD injury. Animals that received the acellular scaffolds did not survive after the replacement surgery. Thus, the artificial bile duct constructs populated with patient‐specific hepatic progenitor cells could provide a scalable and compatible platform for treating bile duct diseases. [ABSTRACT FROM AUTHOR]

Three-dimensional printing technology is widely being adopted in the manufacturing of oral appliances. The purpose of this study was to determine the most suitable method of manufacturing oral appliances by comparing the physical and mechanical properties of various 3D printing methods with the conventional method. Experimental groups consisted of six 3D-printed specimens via FDM, two polyjets, SLS, SLA, and DLP, and the milling methods. The control group consisted of an acrylic resin specimen made by the conventional manual method. The water absorption and solubility, color stability, flexural strength, and surface hardness were tested and statistically analyzed. The FDM, SLS, and DLP methods exhibited comparable water absorption and solubility with the control group, and only the SLA method exhibited significantly higher water solubility than the control group. In terms of the color stability, only the milling method met the requirements of the allowable clinical range. The FDM, SLA, and DLP methods exhibited comparable flexural strength with the control group. The surface hardness of the PJ-2, DLP, and milling methods was acceptable for replacing conventional manual method. Therefore, the most suitable method of manufacturing oral appliances among the experimental groups was the DLP method in terms of its water absorption and solubility, flexural strength, and surface hardness. [ABSTRACT FROM AUTHOR]

A reduced order time-delay control is derived and applied to the position control of a brushless DC motor with a highly simplified hardware configuration: use of six-step commutation without current control unit. In addition, the closed-loop stability has been analyzed by using the singular perturbation method. Throughout experimental studies, it is observed that reduced order time delay control effectively compensates for parameter variations and nonlinearities, which a conventional PID control cannot handle with adequate performances. This result shows that reduced order time-delay control enables an economical design without compromising performance. More importantly, the example establishes a case that: a good control method can compensate for the hardware deficiency in a given plant, and as a result it even enables a simpler design of plants at the design stage.

Motivated by the idea of the time delay estimation used in the Time Delay Control, Time Delay Observer (TDO) has been constructed. Owing to this idea, TDO does not require a model, and hence is easy to design for nonlinear systems in the phase variable form, even when the plant dynamics is not well known. Not including a model, TDO turned out to be robust to parameter variations and computationally efficient; yet achieved better accuracy. For this observer, the convergence property and the sensitivity to sensor noise have been analyzed. Then, in a simulation with a nonlinear plant, and in an experiment with a robot, TDO achieved an accuracy level similar to sliding observer and better than a Kalman filter. In an experiment on a pneumatic cylinder control, TDO reconstructed states much better than a numerical differentiator with low-pass filtering.