Determination of RDX and Keto-RDX in High-Explosive Mixtures by High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) has been used for separation and quantitation of components of high explosives...     

Optimal Spectrum Management of DSL With Nonstrictly Convex Rate Region

Recently, the problem of optimal spectral balancing (OSB) for digital subscriber lines (DSL) with constrained transmit power has been solved using Lagrange's dual optimization technique and a weighted sum rate maximization (WSRM) approach. In many cases, the total power constraint is not binding. Although, this means a huge computational complexity reduction, the algorithm fails to reach certain points on the rate region (RR). In this paper, an in-depth analytical view of the WSRM approach is provided, and it is shown that when the RR is not strictly convex, the WSRM approach fails to reach certain points on the RR. Moreover, using N-dimensional geometry, a novel iterative facet dividing algorithm (IFDA) capable of reaching any point on the RR is proposed. Analytical and simulation results show that our technique is much more reliable and considerably faster than current algorithms. Moreover, it can be used for a wide range of problems which use WSRM approach, including OSB in the general case.     

Trans-limonene dioxide,a promising bio-based epoxy monomer

Vast quantities of the natural terpene (R)-limonene can be collected from food waste. Epoxidation of its two double bonds provides limonene dioxide (LDO), a difunctional epoxy monomer. However, LDO is a mixture of four isomers, two of which (trans-LDO) are actually difunctional while the others (cis-LDO) have one epoxide group which is significantly less reactive, as revealed by Fourier transformed infrared spectroscopic analysis of formulations cross-linked with polyethylene imine. These results are also confirmed when preparing epoxy formulations using respectively cis or trans isomers. From DFT calculations, the reactivity of each epoxide group of LDO has been assessed in model reactions with primary and secondary amines, in the presence of amine or alcohol hydrogen-bond donors. The kinetics of cross-linking has also been probed by differential scanning calorimetry. As measured by dynamic mechanical analysis, the resulting epoxy resins based on trans isomers have a storage modulus of ca 1GPa at room temperature and a glass transition temperature (T_g) of 70°C. These results demonstrate that trans LDO is a promising bio-based epoxy monomer, which could be used as an alternative to petroleum-based epoxy monomers.     

Passive recruitment of circulating leukocytes into capillary sprouts from existing capillaries in a microfluidic system

Recent evidence implicating leukocytes in angiogenesis raises the question of whether leukocytes and other cells circulating with the blood in microvascular networks can home to capillary sprouts intraluminally. This study describes an investigation of leukocyte trafficking in sprouting capillaries fabricated using soft lithography. The leukocytes passing with whole blood through existing capillaries were able to enter microfabricated capillary sprouts of variable length and sprouting angle due to the mechanical interaction with red blood cells (RBCs) at the sprouting bifurcation, in spite of the complete absence of blood flow through the blind-ended sprouts or any chemoattractants. The RBCs formed "comet tails" (the densely packed cellular trains forming behind leukocytes as they move through narrow capillaries) and effectively pushed leukocytes into the microfabricated sprouts while bypassing them at the sprouting bifurcation. Individual sprouts filled with several leukocytes, as wells as RBCs and platelets, were observed. The results of this study suggest that (i) blood cells are likely present in capillary sprouts throughout their development, (ii) leukocytes and other circulating cells may use this mechanism to home to capillary sprouts intraluminally for direct engraftment, and (iii) tissues may use this phenomenon as another mechanism for local recruitment of leukocytes from the blood stream.     

Performance analysis of time-hopping spread-spectrum multiple-access systems: uncoded and coded schemes

An ultra-wide bandwidth time-hopping spread-spectrum code division multiple-access system employing a binary PPM signaling has been introduced by Scholtz (1993), and its performance was obtained based on a Gaussian distribution assumption for the multiple-access interference. In this paper, we begin first by proposing to use a practical low-rate error correcting code in the system without any further required bandwidth expansion. We then present a more precise performance analysis of the system for both coded and uncoded schemes. Our analysis shows that the Gaussian assumption is not accurate for predicting bit error rates at high data transmission rates for the uncoded scheme. Furthermore, it indicates that the proposed coded scheme outperforms the uncoded scheme significantly, or more importantly, at a given bit error rate, the coding scheme increases the number of users by a factor which is logarithmic in the number of pulses used in time-hopping spread-spectrum systems.     

Frequency equations for the in-plane vibration of orthotropic circular annular plate

Orthotropic circular annular plates have a lot of applications in engineering such as space structures and rotary machines. In this paper, frequency equations for the in-plane vibration of the orthotropic circular annular plate for general boundary conditions were derived. To obtain the frequency equation, first the equation of motion for the circular annular plate in the cylindrical coordinate is derived by using the stress-strain- displacement expressions. Helmholtz decomposition is used to uncouple the equations of motion. The wave equation is obtained by assumption a harmonic solution for the uncoupled equations. Using the separation of the variables leads to the general wave equation solution and the in-plane displacements in the r and θ directions. Finally, boundary conditions are exerted and the natural frequency is derived for general boundary conditions. The obtained results are validated by comparing with the previously reported and those from finite element analysis.     

Digital Textbooks

The traditional publishing industry is seeing the first signs of its own doom while desperately hanging on to the last few dollars of profit from selling pulped forest trees. The demise of paper-based publishing is as certain and as inevitable as the end of the use of stone hieroglyphics. It's likely that Generation X will be the last to support the traditional print-publishing industry. The rationale for this prediction is simple: there is absolutely no reason for high school students to carry around pounds of books in their backpack when almost everything else is now paperless. In the following paragraphs, I will explain why the extinction of paper-based textbook publishing is inevitable and why the strategies of the publishing industry to maintain its grip should be viewed as last-gasp efforts.     

A logical framework for visual information modeling and management

A unified semantic visual data-modeling framework is presented in the paper. In the proposed model, an extended conceptual graph is proposed as an annotation mechanism of a user's perceptual understanding of video objects, activities, and events. A precise definition of the term domain knowledge in visual information processing is presented. A conceptual structure, associated terms, visual feature extraction methods, and a set of constrains in feature extraction are considered as domain information. The proposed visual data model has six different abstraction layers. A higher level is more abstracted and more semantically summarized. A polygon-based bounding volume is used in video object approximation in space and time. We use a bounding volume in motion trajectory representation, rather than motion vectors. This model allows simultaneous access of both temporal and spatial information. The proposed model may be used as a referencing framework for various visual information management systems' developments.     

Intermolecular interaction of a neutral polymeric bonding agent containing N-Vinylpyrrolidone units with ammonium perchlorate and Keto-RDX

The interaction of a new neutral polymeric bonding agent (NPBA) containing N-Vinylpyrrolidone units with two types of oxidizers (ammonium perchlorate and Keto-RDX) was investigated by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). NPBA forms a layer of film on the surface of oxidizers. The paper gives hypothetical mechanisms for improving significantly mechanical properties by addition of the neutral polymeric bonding agent (NPBA).     

Electrocatalytic performance of Pt/Ru/Sn/W fullerene electrode for methanol oxidation in direct methanol fuel cell

In this work,fullerene was modified by platinum,ruthenium,tin and tungsten nanoparticles.The material was characterized by XRD,ICP-OES and TEM micrograph.The average nanoparticle size on fullerene was 5-8 nm.The application of this material was investigated as a catalyst for methanol oxidation in direct methanol fuel cell.A glassy carbon electrode was modified by Pt/Ru/Sn/W fullerene and electrocatalytic activity of the electrode toward methanol oxidation in basic medium has been demonstrated and investigated using cyclic voltammetry.The catalyst showed good reactivity for methanol oxidation.