Effect of vertical stress rest period on deformation behaviour of unbound granular materials: Experimental and numerical investigations

Repeated load triaxial test is used to assess the deformation behaviour of unbound granular materials (UGMs) in flexible road pavements. Repeated load pulse characteristics (i.e. shape, loading period and rest period) are the stress configurations used in the experimental set-up to simulate the passing axle loads. Some researchers and standard testing protocols suggest a rest period of varying durations after a loading phase. A thorough review of existing literature and practises has revealed that there is no agreement about the effect of the rest period of vertical stress pulse on the deformation behaviour of the UGMs. Therefore, the main objective of this study is to investigate the effect of repeated stress rest period on the deformation behaviour of UGMs experimentally. Experiments are conducted, both with and without rest period, using basalt and granite crushed rocks from Victoria, Australia. Furthermore, in order to gain insight into the effect of the rest period, finite element modelling is also developed. Both the experimental and modelling results show that the rest period has a noticeable effect on both resilient and permanent deformation behaviours of UGMs. It is, therefore, recommended to take extra precautions while adopting a particular standard testing protocol and to supplement the results by additional tests with different loading configurations.     

Optimal Crop Planning and Conjunctive Use of Water Resources in a Coastal River Basin

Due to increasing trend of intensive rice cultivation in a coastal river basin, crop planning and groundwater management areimperative for the sustainable agriculture. For effective management, two models have been developed viz. groundwater balance model and optimum cropping and groundwater management model to determine optimum cropping pattern and groundwater allocation from private and government tubewells according to different soil types (saline and non-saline), type of agriculture(rainfed and irrigated) and seasons (monsoon and winter). A groundwater balance model has been developed considering mass balance approach. The components of the groundwater balance considered are recharge from rainfall, irrigated rice and non-rice fields, base flow from rivers and seepage flow from surface drains. In the second phase, a linear programming optimization model is developed for optimal cropping and groundwater management for maximizing the economic returns. Themodels developed were applied to a portion of coastal river basin in Orissa State, India and optimal cropping pattern forvarious scenarios of river flow and groundwater availability wasobtained.     

A Novel Method Based on Capillary Suction Time (CST) for Assessment of Dispersion Characteristics of Suspensions

This paper presents the applicability of a simple and novel technique based on capillary suction time (CST) to characterize the dispersibility of suspension. The method is simple, rapid, and requires little experience. It has been shown to be extremely useful for comparing the dispersibility during preparation of a stable suspension of ceramic powder with high solids loading. The method has also been found to be suitable for obtaining homogeneous suspensions of maximum stability. The dispersibility of particles in any suspension has been assessed with respect to the condition at point of zero charge (pH_pzc). A quantitative measure of the dispersibility has been proposed in term of a dispersion ratio (DR). According to this proposition, the suspension is in a state of dispersion when the value of DR is more than unity, whereas it is in a flocculated state when the value of DR is less than unity.     

A review of the internal forced convective heat transfer characteristics of nanofluids: Experimental features,mechanisms and thermal performance criteria

In this review paper, we summarize important milestones in experimental studies that indicate the effects of volume fraction, nanoparticle size, operating temperature and pH on the internal forced convective heat transfer characteristics of nanofluids. In addition, many mechanisms for the enhancement of the convective heat transfer coefficient of nanofluids proposed by investigators are categorized into two dominant mechanisms. The first dominant mechanism is properties’ change of nanofluids such as thermal conductivity and viscosity. The other is the motion of nanoparticles in nanofluid flow due to Brownian motion, thermal dispersion and migration. Finally, the thermal performance criteria which can estimate whether nanofluids are useful in actual engineering systems, are summarized. Authors expect that the understanding of the convective heat transfer characteristics of nanofluids could help many thermal engineers to develop nanofluids which can be used in industrial applications.     

Structural biological composites: An overview

Biological materials are complex composites that are hierarchically structured and multifunctional. Their mechanical properties are often outstanding, considering the weak constituents from which they are assembled. They are for the most part composed of brittle (often, mineral) and ductile (organic) components. These complex structures, which have risen from millions of years of evolution, are inspiring materials scientists in the design of novel materials. This paper discusses the overall design principles in biological structural composites and illustrates them for five examples; sea spicules, the abalone shell, the conch shell, the toucan and hornbill beaks, and the sheep crab exoskeleton.     

Electrophoretic deposition of alumina on stainless steel from non-aqueous suspension

Electrophoretic deposition of alumina on stainless steel has been investigated. The influence of different organic media and deposition parameters such as solid concentration, applied voltage and time of deposition on deposit yield has been evaluated. Maximum deposit yield was obtained for solvent media that imparts highest magnitude of surface charge on alumina in suspension. The deposit yield increased linearly with concentration of alumina powder in suspension, and applied voltage following Hamakers law. A similar linearity in yield was observed at short deposition times, but a deviation in linearity was observed at higher time of deposition, which is attributed to the shielding effect of the deposited layers and accumulation of ions at the electrode, and depletion of powder in the suspension with progress in deposition.     

An Efficient Look-up Table-based Approach for Multiplication over GF(2 m ) Generated by Trinomials

In this paper, we present an efficient look-up table (LUT)-based approach to design multipliers for GF(2 ^m ) generated by irreducible trinomials. A straightforward LUT-based multiplication requires a table of size (m×2 ^m ) bits for the Galois field of degree m. The LUT size, therefore, becomes quite large for the fields of large degrees recommended by the National Institute of Standards and Technology (NIST). Keeping that in view, we have proposed a digit-serial LUT-based design, where operand bits are grouped into digits of fixed width, and multiplication is performed in serial/parallel manner. We restrict the digit size to 4 to store only 16 words in the LUT to have lower area-delay complexity. We have also proposed a digit-parallel LUT-based design for high-speed applications, using the same LUT as the digit-serial design, at the cost of some additional multiplexors and combinational logic for parallel modular reductions and additions. We have presented a simple circuit for the initialization of LUT content, which can be used to update the LUT in three cycles whenever required. The proposed digit-serial design involves less area-complexity and less time-complexity than those of the existing LUT-based designs. The proposed digit-parallel design offers nearly 28 % improvement in area-delay product over the best of the existing LUT-based designs. NIST has recommended five binary finite fields for elliptic curve cryptography, out of which two are generated by the trinomials Q(x)=x ²³³+x ⁷⁴+1 and Q(x)=x ⁴⁰⁹+x ⁸⁷+1. In this paper, we have designed a reconfigurable multiplier that can be used for both these fields. The proposed reconfigurable multiplier is shown to have a negligible reconfiguration overhead and would be useful for cryptographic applications.     

S.A.W. bandpass filter with ?50 dB sidelobes using unweighted i.d.t.s

The use of a resonantly loaded i.d.t. (r.l.i.d.t.) as an s.a.w. track changer in bandpass filter design is described. A filter with 3dB fractional bandwidth (f.b.w.) of 11.5% and ?50 dB sidelobes is realised using unweighted input/output i.d.t.s of 5? finger pairs each and a 7? finger pair r.l.i.d.t. as the s.a.w. track changer. The scheme is expected to be useful in realising low-shape-factor low-sidelobe bandpass filters using relatively short i.d.t.s.