Comments on "Robust iterative learning control design is straightforward for uncertain LTI systems satisfying the robust performance condition"

For original paper see ibid., vol.48, p.101-6 (2003). The article comments on the result of the above paper. The authors of the original paper showed that Theorem 1 is only the sufficient condition of the convergence in the sense of the L/sub 2/-norm. In this note, Theorem 1 is proved to be the not only sufficient but also necessary condition using some mathematical manipulation.     

Structure Stability,Flame Retardancy,and Antimicrobial Properties of Polyurethane Composite Nanofibers Containing Tannic Acid and Boron-Doped Carbon Nanotubes

A polyurethane (PU) composite nanofiber with superior flame retardancy and antimicrobial property is developed through the simultaneous incorporation of boron-doped carbon nanotubes (CNTs) and tannic acid (TA), resulting in excellent thermal, mechanical, and eco-friendly flame-retardant properties. The tensile strength and peak heat-release rate of the composite nanofiber increase with increasing filler content, with the optimal performance (7.38 ± 1.04 MPa and 254 W g⁻¹) being achieved at 3 wt% filler. Using a series of analytical techniques, it is demonstrated that the nanostructure of the neat PU completely collapses upon heating, transforming into a film-like structure; in contrast, a higher loading of nanofiller leads to a higher heat-shielding capability, thereby facilitating preservation of the composite nanofiber structure. Finally, the antibacterial activity is shown to increase as a result of the synergic effect of the boron-doped CNTs and TA.     

Comparison of sintering behavior and mechanical properties between WC−8Co and WC−8Ni hard materials produced by high-frequency induction heating sintering

The sintering behavior and mechanical properties of WC-Co and WC-Ni hard materials produced by high-frequency induction-heating sintering (HFIHS) were compared using ultra fine WC, WC-Co, and WC-Ni powders. HFIHS allows very quick densification to near theoretical density and prohibits grain growth in nano-structured materials. Highly dense WC, WC-Co, and WC-Ni with a relative density of up to 99.2% could be obtained with simultaneous application of 60 MPa pressure and induced current within 2 min without significant change in grain size. The hardness and fracture toughness of the dense WC, WC-Co, and WC-Ni composites produced by HFIHS were also investigated.     

Integrative Magneto-Microfluidic Separation of Immune Cells Facilitates Clinical Functional Assays

Accurately analyzing the functional activities of natural killer (NK) cells in clinical diagnosis remains challenging due to their coupling with other immune effectors. To address this, an integrated immune cell separator is required, which necessitates a streamlined sample preparation workflow including immunological cell isolation, removal of excess red blood cells (RBCs), and buffer exchange for downstream analysis. Here, a self-powered integrated magneto-microfluidic cell separation (SMS) chip is presented, which outputs high-purity target immune cells by simply inputting whole blood. The SMS chip intensifies the magnetic field gradient using an iron sphere-filled inlet reservoir for high-performance immuno-magnetic cell selection and separates target cells size-selectively using a microfluidic lattice for RBC removal and buffer exchange. In addition, the chip incorporates self-powered microfluidic pumping through a degassed polydimethylsiloxane chip, enabling the rapid isolation of NK cells at the place of blood collection within 40 min. This chip is used to isolate NK cells from whole blood samples of hepatocellular cancer patients and healthy volunteers and examined their functional activities to identify potential abnormalities in NK cell function. The SMS chip is simple to use, rapid to sort, and requires small blood volumes, thus facilitating the use of immune cell subtypes for cell-based diagnosis.     

Characteristics of dynamic brittle fracture captured with peridynamics

Using a bond-based peridynamic model, we are able to reproduce various characteristics of dynamic brittle fracture observed in experiments; crack branching, crack-path instability, asymmetries of crack paths, successive branching, secondary cracking at right angles from existing crack surfaces, etc. We analyze the source of asymmetry in the crack path in numerical simulations with an isotropic material and symmetric coordinates about the pre-crack line. Asymmetries in the order of terms in computing the nodal forces lead to different round-off errors for symmetric nodes about the pre-crack line. This induces the observed slight asymmetries in the branched crack paths. A dramatically enhanced crack-path instability and asymmetry of the branching pattern are obtained when we use fracture energy values that change with the local damage. The peridynamic model used here captures well the experimentally observed successive branching events and secondary cracking. Secondary cracks form as a direct consequence of wave propagation and reflection from the boundaries.     

Consolidation of binderless nanostructured TiC by pulsed current activated sintering and its mechanical properties

A dense nanostructured TiC with a relative density of up to 98% was produced with simultaneous application of 80 MPa pressure and pulsed current of 2800 A using the nanopowder of TiC. The effect of the ball milling times on the sintering behavior, grain size and mechanical properties of binderless TiC was investigated.     

Iodine diffusion during iodine‐vapor curing and its effects on the morphology of polycarbosilane/silicon carbide fibers

Iodine‐vapor curing is used to produce continuous SiC fibers from polycarbosilane (PCS), but attempts to limit the uptake of oxygen during the curing process result in SiC fibers with different morphologies and pore types. The cause of this distinct transformation in the morphology of the fibers is determined in this study by tracing the distribution of iodine in PCS fibers cured either at a set temperature or for a given period. The results reveal that the final morphology of the fibers is dependent on the degree of iodine diffusion, or on the extent of their cross‐linked area. Using this knowledge, fibers with three distinct morphologies are produced by controlling the curing conditions. Optimization of this curing process is shown to inhibit the formation of pores and retard the incorporation of oxygen, while still allowing the fibers to retain their cylindrical shape. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42687.