Measurement of high-temperature effective thermal conductivity of porous spheres

A new unsteady-state method for measuring the high temperature effective thermal conductivity of porous spheres is described. The method is based on moving a spherical body from an enclosure at a low temperature into one at a higher temperature and measuring the surface temperature with a recording radiation pyrometer. The thermal conductivity is evaluated using the known relations between the dimensionless surface temperature and time. The apparatus requirements are discussed in detail. The thermal conductivities of calcined dolomite/silicon metal mixtures, of the type used in the production of magnesium, were measured at 750 to 1150°C with compaction pressures of 67 to 185 MPa both before and after reaction.     

Development of n-type microcrystalline SiO<Subscript>x</Subscript>:H films and its application by innovative way to improve the performance of single junction µc-Si:H solar cell

Light trapping is one of the fundamental necessities of thin film based solar cell for its performance elevation. Back reflection of unused light of first pass is the key way to improve the light trapping phenomena. In this study we have reported the development of n-type hydrogenated microcrystalline silicon oxide (n-µc-SiO:H) layers of different characteristics. The deposition has been done by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. The detailed characterization of the films include the following: (1) electrical properties (2) optical properties like E₀₄ (3) structural studies which include crystalline fraction by Raman spectroscopy and grain size by X-ray diffraction measurement, FTIR spectroscopy, AFM and TEM studies. n-µc-SiO:H layer has been introduced as the n-layer of single junction p–i–n structure µc-Si solar cells. By various techniques the optimum use of n-µc-SiO:H layer for enhancing the performance of µc-Si:H solar cells has been done. It has been found that by using suitable bilayer of two different n-µc-SiO:H layers, it is possible to increase the solar cell performances. The maximum efficiency obtained without any back reflector is 8.44% that is about 8.9% higher than that obtained by using n-µc-Si:H layer as n-layer in the solar cells.     

Studies of reaction mechanisms during stabilization of electrospun polyacrylonitrile carbon nanofibers

Various reaction mechanisms such as cyclization, oxidation, dehydrogenation, and crosslinking are studied during stabilization of electrospun polyacrylonitrile nanofibers using different in situ techniques such as differential scanning calorimetry (DSC), shrinkage measurement, and dynamic mechanical analysis (DMA). DSC results show that oxidation preferentially occurs in cyclized structure. It is also found that the cyclization reaction has the highest activation energy followed by oxidation/dehydrogenation and crosslinking reactions. In situ shrinkage measurement and DMA data are used to study the extent of cyclization and cross‐linking reactions, respectively, in air. Comparing the in situ shrinkage measurement with DSC data, it is found that cyclization reaction in air progresses in two different mechanisms such as radical cyclization, which depends only on the temperature and ionic cyclization, which is limited by the rate of oxygen diffusion. It is found that complete cyclization time occurs at about 189 min for isothermal heat treatment at 260°C with 5°C/min ramp, while cross‐linking reaction becomes dominant at 132 min. POLYM. ENG. SCI., 58:1315–1321, 2018. © 2017 Society of Plastics Engineers     

Strategy for promotions and development of renewable technologies in Bangladesh: experience from Grameen Shakti

This paper discusses experiences from the renewable energy program of Grameen Shakti (GS), which is aimed to provide energy to rural areas. GS has already passed 3 years in marketing solar home system in rural Bangladesh. Within this short period, GS gathered a lot of experience in marketing the solar home system. Up to July 1999, GS had sold 1147 solar home systems and the installed capacity was 53.3 kWp. Customers use these systems for various purposes like, lighting houses, shops, offices, watching TV, operating computer and so on. The systems are functioning well. Some of the customers have enhanced income through PV systems by extending working hours and selling power to neighbors. There are various obstacles for expansion of PV program in rural Bangladesh, the main barrier being the high cost of PV module. To make the system affordable, customers need easier financing scheme. GS offers easier financing terms to the customers so that they can afford solar home system.     

An interactive multimedia system on “computer architecture,organization, and design”

The multimedia system described in this paper demonstrates the successful integration of multimedia into education and provides a clear example of how multimedia can be used to deliver computer engineering and computer science concepts to the often diverse student base. The paper describes an interactive, knowledge-based multimedia system that has been used to teach users about the basic aspects of computer architecture, organization, and design. The system is well suited for self-paced, student directed study, student review, and classroom presentation and discussion. The system allows learners to choose how information will be displayed, changing for example, among text, graphics, animation, and simulation. The hypermedia capabilities built into the system enables it to respond based on the dynamic evaluation of both the contexts of the human-computer collaboration and the knowledge base underlying the visible screen presentation. The system serves as a very useful aid to introduce and demonstrate some of the fundamental ideas of computer architecture and organization     

Modeling of the Oxygen Transfer Characteristics of a ‘See‐Saw’ Bioreactor

Animal cell line culture is difficult in the existing conventional bioreactors. A substantial amount of animal cells are destroyed by the impinging fan blades or entrapment inside the bubbles. An endeavor has been made to design and develop a new type of bioreactor suitable for animal cell culture. The bioreactor is named a ‘see‐saw’ bioreactor from its underlying principle of operation. In this paper, the oxygen transfer characteristics of the ‘see‐saw’ bioreactor are modeled and tried to be verified.     

The world photovoltaic scale: an international reference cell calibration program

This paper describes the World Photovoltaic Scale (WPVS) international reference cell calibration program. The WPVS provides a scale for PV performance measurements that has been established through round‐robin calibration of a group of primary monocrystalline Si reference cells and is traceable to Système International (SI) units. Procedures for recalibration of the reference cell group have been devised, along with procedures for admittance and calibration of new reference cells. A reference cell package has been designed that meets the unique needs of the WPVS. It is hoped that the existing WPVS group will eventually be replaced with cells of the new design that have passed a comprehensive acceptance‐test procedure. Copyright © 1999 John Wiley & Sons, Ltd.     

Synthesis of nanolayered ternary borides powders (MAB phases) by sustainable molten salt shielded synthesis/sintering (MS3) process

Journal of Materials Science - In this paper, we report the synthesis of Fe2AlB2, Mn2AlB2, and MoAlB powders by using molten salt shielded synthesis/sintering (MS3)—a sustainable processing...