Determination of the thermal transport properties of ammonia borane and its thermolysis product (polyiminoborane) using the transient plane source technique

Reliable thermal property data are necessary to improve the fidelity of chemical hydride thermal decomposition models. The thermal diffusivity and conductivity of ammonia borane (NH₃BH₃) and its partial thermolysis product (polyiminoborane) were measured at various packing densities using a transient plane source technique under ambient conditions. The particle size of the ammonia borane powder was between 200 and 600 μm, while the particle size of the polyiminoborane powder was between 10 and 30 μm. The thermal diffusivity and conductivity of the ammonia borane increased from 0.17 to 0.24 mm²/s and 0.19 to 0.44 W/m K (±10%), respectively, when its packing density was increased from 0.37 to 0.58 g/cm³. The increase in thermal conductivity is due to the increase in contact area between particles and the increase in the thermal diffusivity is related to an increase in density and volumetric heat capacity caused by compaction. The thermal conductivity of the polyiminoborane powder was approximately three times lower, likely due to its higher porosity. The thermal diffusivity and conductivity of this product changed from 0.21 to 0.12 mm²/s and 0.068 to 0.23 W/m K (±10%), respectively, when its packing density was increased from 0.13 to 0.96 g/cm³.     

Jatropha curcas: A potential biofuel plant for sustainable environmental development

Jatropha curcas L. (JCL) has been propagated as unique and potential tropical plant for augmenting renewable energy sources due to its several merits for which it deserves to be considered as sole candidate in the tangible and intangible benefits of ecology and environment. The species has been advocated for extensive plantations on degraded wasteland throughout the world. Our current knowledge of JCL is inadequate to understand their contribution in societal and environmental benefit. Presently, this species has received much attention because of its immense role in bio-diesel production an eco-friendly fuel, bio-degradable, renewable and non-toxic in nature compared to petro-diesel except few carcinogenic compounds found in oil cake. However, complete information on the multiple roles of JCL for eco-environmental benefits is lacking. Recent reports on various roles of JCL such as effective phytoremediator, carbon sequester, degraded land developer, and soil erosion controller have been discussed in this communication. Additionally, some of its contribution for medicinal and deriving as therapeutic uses are also highlighted. JCL related problems are also discussed. Further there is a controversial debate on its application, extension, and risks, which needs to be exploited well for its beneficial role in tropical environment. These issues are dealt herewith to observe its future scope to mitigate energy crisis, environmental management and sustainable productions.     

Analysis of vibration characteristics of one-axis heavy duty stages

This study focus on the dynamic characteristics of one-axis stages with its heavy duty top plate over 300 kg. A simplified modeling of one-axis heavy duty stages for machine tools is suggested to understand the characteristics of the vibration in the heavy duty stage. The equivalent finite element model for LM guide bearings is applied to analyze the dynamic characteristics of the precision stage. Moreover, the role of screw bolts which fasten the positions between LM guide rails and the main table is also discussed. The suggested modeling shows below 11.8 % error from the measured result values of the modal experiments.     

Model predictive control: Review of the three decades of development

Three decades have passed since milestone publications by several industrialists spawned a flurry of research and industrial / commercial activities on model predictive control (MPC). This article reviews major developments and achievements during the three decades and attempts to put a perspective on them. The first decade is characterized by the fast-growing industrial adoption of the technology, primarily in the refining and petrochemical sectors, which sparked much interest and also confusion among the academicians. The second decade saw a number of significant advances in understanding the MPC from a control theoretician’s viewpoint, which included state-space interpretations / formulations and stability proofs. These theoretical triumphs contributed to the makings of the second generation of commercial software, which was significantly enhanced in generality and rigor. The third decade’s main focus has been on the development of “fast MPC,” a term chosen to collectively describe the various efforts to bring orders-of-magnitude improvement in the efficiency of the on-line computation so that the technology can be applied to systems requiring very fast sampling rates. Throughout the three decades of the development, theory and practice supported each other quite effectively, a primary reason for the fast and steady rise of the technology.     

Divalent cation diffusion in calcium fluorapatite

The mechanisms by which calcium ions are transported through the fluorapatite lattice are investigated using computer simulations. Cation vacancy assisted pathways are considered and migration energy barriers are calculated using a nudged elastic band transition state search. Migration activation energies for a range of divalent cations, in addition to calcium are compared. Generally there is very little change in activation energy as cation radius increases. Furthermore, in all cases the lowest energy migration pathways occur parallel to the c-axis either associated with the central anion channel via Ca(2) sites or away from the channel and via Ca(1) sites.     

A higher‐order extended finite element method for dislocation energetics in strained layers and epitaxial islands

This paper presents a higher‐order method for modeling dislocations with the extended finite element method (XFEM). This method is applicable to complex geometries, interfaces with lattice mismatch strains, and both anisotropic and spatially non‐uniform material properties. A numerical procedure for computing the J‐integral around a dislocation core to determine the energy release rate for a virtual advance of the dislocation line is described. Several examples in three dimensions illustrate the applicability of this method to material interfaces and semiconductor heterostructures, specifically the computation of the energetics of systems of dislocations in SiGe islands deposited on pure Si substrates. Copyright © 2010 John Wiley & Sons, Ltd.     

Teaching entrepreneurship in senior design courses.

A senior design capstone course can provide students with the opportunity to develop communication, interpersonal, and design skills and to learn about the product development process and project management. It is an excellent tool for preparing students for careers in biomedical engineering, especially those interested in employment with medical device companies. The author suggests that educators and design instructors should provide the opportunity for students to develop the skills and acquire the knowledge needed for successful careers in biomedical engineering. This includes development of (i) communication, interpersonal, teamwork, and design skills, (ii) an understanding of the legal, regulatory, and economic aspects of healthcare and the medical industry and (iii) basic business literacy. For additional in-depth entrepreneurial education, a graduate management degree with concentration in entrepreneurship might be the best approach. In order to develop an entrepreneurial perspective in all biomedical engineering students, "teachable moments" that are themselves in many of these courses should be taken advantage of.     

Turbine Discharge Measurement by the Velocity-Area Method

Developing the head-power-discharge relationship for a low-head hydroelectric turbine requires accurate measurements of discharge through the unit. Discharge measurements are commonly determined using some type of velocity-area method. The German (DIN) code is used by many utilities. In this paper a densely spaced array of Ott meter data, collected according to the German code, are used to examine the accuracy of this approach. Field data, obtained near the intake entrance (i.e., stoplog guides) of a low-head hydroelectric generating station, show clearly the complex (i.e., nonfully developed) nature of the horizontal flow. Laboratory testing of a scale model suggest that metering the flow close to the entrance of an intake, according to the German code, where the flow is not yet fully developed, will overestimate the discharge by approximately 3%.