Nano-Ammonium Perchlorate: Preparation,Characterization, and Evaluation in Composite Propellant Formulation

Nanomaterials are finding applications in explosives and propellant formulations due to their large surface area and high surface energy. This high surface energy is responsible for the low activation energy and increase in burning rate of the composition. Therefore, a successful attempt has been made to prepare nano-ammonium perchlorate using a nonaqueous method by dissolving ammonium perchlorate (AP) in methanol followed by adding the dissolved AP to the hydroxyl-terminated polybutadiene (HTPB), homogenization, and vacuum distillation of the solvent. The nano-AP thus formed was characterized using a NANOPHOX particle size analyzer (Sympatec, Germany), transmission electron microscopy (FEI, Hillsboro, OR), X-ray diffraction (PANalytical B.V., The Netherlands) and scanning electron microscopy (Ikon Analytical Equipment Pvt. Ltd., Mumbai, India) for particle size, purity, and morphology, respectively. The thermal behavior of nano-AP was also studied using differential thermal analysis–thermo gravimetric analysis (DTA-TGA). The data indicated that the particle size of the prepared AP was in the range of 21–52 nm and the thermal decomposition temperature was lower than that of coarse AP. Characterized nano-AP was subsequently used in composite propellant formulation up to 5% with 86% solid loading and studied for different properties. The results showed a 14% increase in burning rate in comparison to standard propellant composition with desired mechanical properties.     

Microalloyed Steel Bars and Forgings

This paper examines microalloyed steels—steels which develop their properties in the as-received condition without requiring further heat treatment, such as quenching and tempering. Microalloyed steel bars and forgings offer a clear cut potential for cost reduction and energy savings. The metallurgy for producing high strength microalloyed bars and forgings is in place. However, significant improvement in the notch toughness of these materials is necessary, and the metallurgy required to achieve this toughness improvement exists. With application of the necessary metallurgical techniques in rolling mills and forge shops, the utilization of high strength microalloyed steel bars and forgings will increase greatly.     

The political economy of metering agricultural tube wells in West Bengal,India

Unmetered electricity supply to agriculture has given rise to a unique and invidious water–energy–food nexus in India. Metering of agricultural consumers has been suggested as a way to break the nexus, but most states have not been able to meter farmers due to their opposition . The only exception is the state of West Bengal. Using primary data from a household survey conducted in 2010 when the metering process was still underway, this paper argues that farmers’ support for metering in West Bengal can be explained in terms of the economics of groundwater use and politics surrounding agriculture and groundwater in the state.     

Improved Algorithms for Uniform Partitions of Points

We consider the following one- and two-dimensional bucketing problems: Given a set S of n points in \reals ¹ or \reals ² and a positive integer b , distribute the points of S into b equal-size buckets so that the maximum number of points in a bucket is minimized. Suppose at most (n/b) + Δ points lie in each bucket in an optimal solution. We present algorithms whose time complexities depend on b and Δ . No prior knowledge of Δ is necessary for our algorithms. For the one-dimensional problem, we give a deterministic algorithm that achieves a running time of O(b ⁴ (Δ ² +log n) + n) . For the two-dimensional problem, we present a Monte Carlo algorithm that runs in subquadratic time for small values of b and Δ . The previous algorithms, by Asano and Tokuyama [1], searched the entire parameterized space and required Ω ( n ² ) time in the worst case even for constant values of b and Δ . We also present a subquadratic algorithm for the special case of the two-dimensional problem when b=2 .     

The distribution of osteocalcin, degree of mineralization, and mechanical properties along the length of Cyprinus carpio rib bone

This study examined the spatial distribution of selected biochemical and mechanical properties along the length of carp rib bone. Carp rib bone was chosen because of its unusually high osteocalcin content relative to other extractable proteins. The amount of osteocalcin was significantly lower (p<0.01) at the most distal section, relative to all other sections. The amount of phosphate (p<0.05) and the elastic modulus in the longitudinal plane (p<0.0001) were found to be significantly higher in the most distal section, relative to the most proximal section. There was no significant difference in the calcium distribution, molar Ca/P ratio, or elastic modulus in the transverse plane. It was speculated that the distal section contains less mature bone. The methods illustrate the potential usefulness of nanoindentation to characterize the mechanical properties of bone, relative to its biochemical composition. © 2001 Kluwer Academic Publishers     

Analysis and characterization of photo-plethysmographic signal

Qualitative assessment of the overall clinical status of the subject and characterization of complex cardiovascular dynamics from digital blood volume pulsations measured noninvasively using a photo-plethysmographic device is addressed. A novel concept is employed to detect the dominant nonsinusoidal periodicity embedded in the data series and to extract the associated periodic component. The detection and the extraction of periodic component is performed with moving window to accommodate the variations of the physiological oscillations. The covariance matrix formed by the gradually varying pattern is used as a simple measure of qualitative assessment. Further, the characterization of the underlying system in the light of nonlinear dynamical analysis is also presented. The stable subjects are shown to behave as a low-dimensional system whereas the diseased subjects exhibit comparatively high dimensional activity.     

Review on Metal-Filled Plastics. Part1. Electrical Conductivity

Plastic composites are members of both the oldest and the newest of materials. The first reinforced polymeric-based materials are recorded in Genesis and Exodus in the Bible as being used by the people of Babylonia and Mesopotamia around 4000–2000 B.C. These materials consisted of bitumen-based pitch for building products and bundles of papyrus reed embedded in a bitumen matrix for the construction of river boats [1]. The Hindu Vedas (written about 1000 B.C.) refers to the use of lac (a complex polymeric substance consisting of polyether and polyester chains) with fine sand for the manufacture of whetstones, which were known in India and China for several thousand years. There are a number of examples that could date back the origin of polymer composites into antiquity [1–3]. but the science of enhancing the properties of polymeric composites by the use of suitable fillers has been practiced extensively not earlier than the beginning of this century. For example, the tensile strength of polystyrene was modified by the incorporation of glass fillers only in the 1950s, half a century later than that predicted by Backeland in the early 1900s [2]. Carbon black is known to be a potential reinforcement for rubber for over 50 years. Although glass bead and glass fibers have been known for centuries, the use of these economical products in the plastic industry is relatively new [2].     

Fundamental Limits of Organic Packages and Boards and the Need for Novel Ceramic Boards for Next Generation Electronic Packaging

The system-on-a-package (SOP) paradigm proposes a package level integration of digital, RF/analog and opto-electronic functions to address future convergent microsystems. Two major components of SOP fabrication are sequential build-up of multiple layers (4–8) of conducting copper patterns with interlayer dielectrics on a board and multiple ICs flip-chip bonded on the top layer. A wide range of passives, wave-guides and other RF and opto-electronic components buried within the dielectric layers provide the multiple functions on a single microminiaturized platform.The routing of future nanoscale ICs with 10,000+ I/Os require multiple build-up layers of ultra fine board feature sizes of 10 m lines/space widths and 40 m pad diameters. Current FR4 boards cannot achieve this build-up technology because of dimensional instability during processing. These boards also undergo high warpage during the sequential build-up process which limits the fine-line lithography and also causes misalignment between the vias and their corresponding landing pads. In addition, the CTE mismatch between the silicon die and the board leads to IC-package interconnect reliability concerns, particularly in future fine-pitch assemblies where underfilling becomes complicated and expensive.This work reports experimental and analytical work comparing the performance of organic and novel ceramic boards for SOP requirements. The property requirements as deduced from these results indicate that a high stiffness and tailorable CTE from 2–4 ppm/C is required to enable SOP microminiaturized board fabrication and assembly without underfill. A novel ceramic board technology is proposed to address these requirements.