Energy absorption behaviours of CSM-based GFRC plates with hemispherical features

In the present study, the mechanical behaviour of CSM (chopped strand mat)-based GFRC (glass fibre-reinforced composite) plates with single and multiple hemispheres under compressive loads has been investigated both experimentally and numerically. The basic stress-strain behaviours arc identified with quasi-static tests on two-ply coupon laminates and short cylinders, and these are followed up with compressive tests in a UTM (universal testing machine) on single- and multiple-hemisphere plates. The ability of an explicit LS-DYNA solver in predicting the complex material behaviour of composite hemispheres, including failure, is demonstrated. The relevance and scalability of the present class of structural components as `force-multipliers' and `energy-multipliers' have been justified by virtue of findings that as the number of hemispheres in a panel increased from one to four, peak load and average absorbed energy rose by factors of approximately four and six, respectively. The performance of a composite hemisphere has been compared to similar-sized steel and aluminium hemispheres, and the former is found to be of distinctly higher specific energy than the steel specimen. A simulation-based study has also been carried out on a composite 2 x 2-hemisphere panel under impact loads and its behaviour approaching that of an ideal energy absorber has been predicted. In summary, the present investigation has established the efficacy of composite plates with hemispherical force multipliers as potential energy-absorbing countermeasures and the suitability of CAE (computer-aided engineering) for their design.

Loop Heat Pipes: A Review of Fundamentals, Operation, and Design

The loop heat pipe (LHP) is a passive two-phase heat transport device that is gaining importance as a part of spacecraft thermal control systems and also in applications such as in avionics cooling and submarines. A major advantage of a loop heat pipe is that the porous wick structure is confuned to the evaporator section, and connection between the evaporator and condenser sections is by smooth tubes, thus minimizing pressure drop. A brief overview of loop heat pipes with respect to basic fundamentals, construction details, operating principles, and typical operating characteristics is presented in this paper. Finally, the paper presents the current developments in modeling of thermohydraulics and design methodologies of LHPs.

Analysis and design of split-capacitor resistive-inductive passive damping for LCL filters in grid-connected inverters

Grid-connected inverters require a third-order LCL filter to meet standards such as the IEEE Std. 519-1992 while being compact and cost-effective. LCL filter introduces resonance, which needs to be damped through active or passive methods. Passive damping schemes have less control complexity and are more reliable. This study explores the split-capacitor resistive-inductive (SC-RL) passive damping scheme. The SC-RL damped LCL filter is modelled using state space approach. Using this model, the power loss and damping are analysed. Based on the analysis, the SC-RL scheme is shown to have lower losses than other simpler passive damping methods. This makes the SC-RL scheme suitable for high power applications. A method for component selection that minimises the power loss in the damping resistors while keeping the system well damped is proposed. The design selection takes into account the influence of switching frequency, resonance frequency and the choice of inductance and capacitance values of the filter on the damping component selection. The use of normalised parameters makes it suitable for a wide range of design applications. Analytical results show the losses and quality factor to be in the range of 0.05-0.1% and 2.0-2.5, respectively, which are validated experimentally.

PROTEIN DISULFIDE ANALYSIS AND DESIGN

The significant contribution of naturally occurring disulfide bonds to protein stability has encouraged development of methods to engineer non-native disulfides in proteins. These have yielded mixed results. We summarize applications of the program MODIP for disulfide engineering. The program predicts sites in proteins where disulfides can be stably introduced. The program has also been used as an aid in conformational analysis of naturally occurring disulfides in a-helices, antiparallel and parallel beta-strands. Disulfides in a-helices occur only at N-termini, where the first cysteine residue is the N-cap residue of the helix. The disulfide occurs as a CXXC motif and can possess redox activity. In antiparallel beta-strands, disulfides occur exclusively at non-hydrogen bonded (NHB) registered pairs of antiparallel beta-sheets with only 1 known natural example occurring at a hydrogen bonded (HB) registered pair. Conformational analysis suggests that disulfides between HB residue pairs are under torsional strain. A similar analysis to characterize disulfides in parallel beta-strands was carried out. We observed that only 9 instances of cross-strand disulfides exist in a non-redundant dataset. Stereochemical analysis shows that while tbe chi(square) angles are similar to those of other disulfides, the chi(1) and chi(2) angles show more variation and that one of tbe strands is generally an edge strand.

Organic photovoltaics: key photophysical, device and design aspects

Key aspects of Organic Photovoltaics (OPVs) have been reviewed in this tutorial. Issues pertaining to the choice of materials, fabrication processes, photophysical mechanisms, device characterization, morphology of active layers and manufacturing are discussed. Special emphasis has been given to recent developments in large-area modules. Current strategies in enhancing the performance using external optical engineering approaches have also been highlighted. OPVs as a technology combine low weight, flexibility, low cost, good form factor and high-throughput processing; making them a promising PV technology for the future.

Chemical Treatment Methods Pilot (CTMP) System for Treatment of Urban Runoff – Phase I. Feasibility and Design

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