Thermal conductivity of carbon nanofiber mats

The anisotropic thermal conductivity of novel vapor grown carbon nanofiber (VGCNF) based paper-like mats was measured for increasing volume fraction and at different stages of heat-treatment. These nanofiber mats were prepared to exhibit high in-plane and low through-plane thermal conductivities with the goal of assessing their potential as 2-D heat spreaders. The in-plane thermal conductivity of the mats varied from 12 W/m-K to 157 W/m-K for volume fractions of 0.067 and 0.462, respectively, while the corresponding through-plane thermal conductivities were measured to be 0.428 W/m-K and 0.711 W/m-K. Heat treatment to temperatures above 3000 °C increased the through-plane thermal conductivity of the mats by an order of magnitude. However, the in-plane thermal conductivity, at best, was only seen to double. A model is proposed to describe the arrangement of nanofibers in the mats, and analytical expressions were used to estimate the thermal conductivity of an individual nanofiber using experimental results. Thermal conductivities of approximately 1400 W/m-K and 1600 W/m-K were calculated for individual VGCNFs heat treated to temperatures of around 1100 °C and above 3000 °C, respectively.     

Implementation of an optical S-R flip-flop with polarization encoded light signal

A new method is proposed to implement an optical S-R flip-flop by polarization encoded light signal,necessary optical nonlinear material and half-wave plate.In this system the real time speed of operation can be achieved,and at the time of transmission the average power of a byte remains constant.This polarization encoded flip-flop can act as a memory cell.     

Estimation of power of heaters in a radiant furnace for uniform thermal conditions on 3-D irregular shaped objects

For uniform thermal conditions on 3-D irregular shaped design objects, this paper reports estimation of optimal power of the panel heaters placed along the walls of a 3-D radiant furnace. Hemispherical, cylindrical, conical, and a combination of cylindrical and conical, and finally a case study of a car body model are considered as the design objects (DOs). The entire surface areas of the furnace walls and that of the DO are divided into surface elements. The surface elements of the furnace walls are made of the panel heaters. In this boundary design problem, the objective function is developed as an error function of estimated and the desired heat fluxes on the surfaces of DO. The radiative exchange among the surface elements is computed using the radiation element method by ray emission model (REM²), and the objective function is minimized using the micro-genetic algorithm (MGA). Power of the panel heaters are estimated for different sizes of the DOs. Although the panel heaters have been placed along the furnace walls, for uniform thermal conditions, for a given DO, not all are required. Having known that not all are required, to ease the control, estimations have also been shown by grouping the heaters along the furnace walls. This study provides a guideline for a priori knowing the heater setting and their corresponding power requirement in heating of 3-D irregular shaped objects.     

Analyzing the adoption and diffusion of voice-enabled smart-home systems: empirical evidence from Thailand

Universal Access in the Information Society - The market for voice assistants (VAs) and other allied voice-based smart-home products is gradually emerging. The initial growth has been slower than...     

Thermodynamic optimization of solar flat-plate collector

Second-law modeling of flat-plate collectors is performed with the objective of describing collector performance when entropy generation is minimum. Effects of irreversibility are demonstrated. Factors mostly effecting the generation of entropy are discussed.     

Biomass gasification for decentralized power generation: The Indian perspective

This article attempts to highlight the technical and economical issues related to decentralized power generation in India using biomass gasification. Biomass-based energy has several distinct advantages such as wide availability and uniform distribution that puts it ahead among the renewable energy options for India. The estimated potential of power generation through renewable sources in India is 85 GW with biomass power contributing approximately 20 GW. Especially, in the remote areas and hilly terrains of India, biomass gasification-based power generation offers a highly viable solution for meeting energy demands of small villages and hamlets, which would not only make them independent but will also reduce burden on state electricity boards. This paper reviews various technical options for biomass gasification-based low-, medium- and large-scale power generation. We essentially discuss the merits and demerits (operational and other problems) of different systems. Further, we also deal with economics of these systems and discuss principal factors influencing the viability of the biomass-based power generation. Finally, we review some case studies of biomass-based power generation for meeting energy needs, both thermal and electrical.     

Identification of uncertain nonlinear systems for robust fuzzy control

In this paper, we consider fuzzy identification of uncertain nonlinear systems in Takagi-Sugeno (T-S) form for the purpose of robust fuzzy control design. The uncertain nonlinear system is represented using a fuzzy function having constant matrices and time varying uncertain matrices that describe the nominal model and the uncertainty in the nonlinear system respectively. The suggested method is based on linear programming approach and it comprises the identification of the nominal model and the bounds of the uncertain matrices and then expressing the uncertain matrices into uncertain norm bounded matrices accompanied by constant matrices. It has been observed that our method yields less conservative results than the other existing method proposed by S?krjanc et al. (2005) [11] and [12]. With the obtained fuzzy model, we showed the robust stability condition which provides a basis for different robust fuzzy control design. Finally, different simulation examples are presented for identification and control of uncertain nonlinear systems to illustrate the utility of our proposed identification method for robust fuzzy control.     

A lower bound method for quantum circuits

Quantum circuits, which are shallow, limited in the number of gates and additional workspace qubits, are popular for quantum computation because they form the simplest possible model similar to the classical model of a network of Boolean gates and capable of performing non-trivial computation. We give a new lower bound technique for such circuits and use it to give another proof that deterministic computation of the parity function cannot be performed by such circuits.     

Roles of quantified expressions of building performance assessment in facility procurement and management

This paper treats rational expressions of building performance in order to better support dialogues between stakeholders. These expressions are based on the notion of objectively quantifiable performance measures, which are introduced through a set of “performance indicators”. The indicators can be used to quantify expectations and fulfillments in structured dialogues between different stakeholders. The focus of the paper is on the introduction of two types of indicators: (1) based on normative models in biophysics and physiology and (2) based on empiricist models of Environment–Behavior studies. The treatment is positioned to support rational decision making during different stages of building delivery and use. The focus of this paper is specifically on informing decisions during design evolution, and facility and portfolio management phases of a building's lifecycle.