On the stability of almost parallel boundary layer flows

The spatial stability of a two-dimensional boundary-layer flow along a flat plate, including its non-parallel character, is determined by means of a multiple scale approximation. This leads to inhomogeneous Orr-Sommerfeld equations for the corrections due to the non-parallel effect. These equations have been solved by the method of order reduction. A neutral curves of total amplifications have been calculated based on the kinetic energy of the disturbance. The non-parallel effect decreasesthe stability.     

Concrete Slabs Reinforced with FRP Grids. I: One-Way Bending

Currently, considerable interest exists in the use of fiber-reinforced polymer (FRP) reinforcement for concrete structures. Due to the generally lower modulus of elasticity of FRP in comparison with steel and the linear behavior of FRP, certain aspects of the structural behavior of RC members reinforced with FRP may be substantially different from similar elements reinforced with steel reinforcement. In this two-part paper the use of different types of FRP grid reinforcement for concrete slabs is investigated, presenting detailed experimental and analytical work. In the first part, the structural behavior in one-way bending is considered. This paper shows which structural measures are needed to ensure acceptable serviceability behavior. The presented analysis and discussion of test results covers the ultimate state and the ultimate limit state for bending, serviceability limit states, ductility, deformability, and ultimate to service load ratio.     

Efficient performance analysis of newly proposed sleep-mode mechanisms for IEEE 802.16m in case of correlated downlink traffic

There is a considerable interest nowadays in improving energy efficiency of wireless telecommunications. The sleep-mode mechanism in WiMAX (IEEE 802.16) and the discontinuous reception (DRX) mechanism of LTE are prime examples of energy saving measures. Recently, Samsung proposed some modifications on the sleep-mode mechanism, scheduled to appear in the forthcoming IEEE 802.16m standard, aimed at minimizing the signaling overhead. In this work, we present a performance analysis of this proposal and clarify the differences with the standard mechanism included in IEEE 802.16e. We also propose some special algorithms aimed at reducing the computational complexity of the analysis.     

Organizing the Web's Information Explosion to Discover Unknown Unknowns

This paper introduces the TORISHIKI-KAI project, which aims to construct a million-word-scale semantic network from the Web using state of the art knowledge acquisition methods. The resulting network can be browsed as a Web search directory, and we show that the directory is useful for finding “unknown unknowns” — in the infamous words of D.H. Rumsfeld: things “we don't know we don't know.” Because typically we have no way to look for information we don't even know is missing, a crucial characteristic of unknown unknowns is that they are very difficult to discover through keyword-based Web search. Some examples of the unknown unknowns we have found include unexpected troubles associated with commercial products, surprising new combinations of ingredients in new recipes, unexpected tools or methods for commiting suicide, and so on. We expect such information to be useful for risk management, innovation support, and the detection of harmful information on the Web.     

An evaluation of the impact of SG1 disproportionation and the addition of styrene in NMP of methyl methacrylate

A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate (MMA; nitroxide: N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 disproportionation (A = 1.4 10⁷ L mol^?1 s^?1; E_a = 23 kJ mol^?1) are reported, based on homopolymerization data accounting for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths (TCLs ≤ 300), this nonisothermicity is also relevant for NMP of MMA with a small amount of styrene. Parameter tuning to copolymerization data confirms a penultimate monomer unit effect for activation (s_a2 = k_a12/k_a22=6.7; 363 K; 1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene mass fraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the fractions of activation‐growth‐deactivation cycles with a given amount of monomer units and the copolymer composition distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2545–2559, 2018