Fluid flow in a screw pump oil supply system for reciprocating compressors

This work presents a mathematical analysis of an oil supply system for reciprocating compressors. The system is based on a single screw pump attached to the bottom end of the vertical rotating shaft immersed in the oil sump. The fluid flow in the pump was modeled with a semi-analytical approach based on the solution for the laminar fully developed oil flow in a screw extruder via the Generalized Integral Transform Technique. The screw pump model is coupled with that for the flow in the shaft region so as to provide an estimate of the oil flow rate and of the so-called ‘climbing-time’, i.e., the amount of time needed for a fluid particle to travel from the oil sump to the top of the shaft. The calculation method was verified against experimental data and Computational Fluid Dynamics modeling results.     

Natural Lignocellulosic Fibers as Engineering Materials—An Overview

Recent investigations on the tensile properties of natural cellulose-based fibers revealed an increasing potential as engineering materials. This is particularly the case of very thin fibers of some species such as sisal, ramie, and curaua. However, several other commonly used fibers such as flax, jute, hemp, coir, cotton, and bamboo as well as less known bagasse, piassava, sponge gourde, and buriti display tensile properties that could qualify them as engineering materials. An overview of the strength limits attained by these fibers is presented. Based on a tensile strength vs density chart, it is shown that natural fibers stand out as a relevant class of engineering materials.     

Pre-Hispanic ceramics analyzed using PIXE and radiographic techniques

Ceramics objects are the most common artifacts found during excavation of archaeological sites and often depicts cultural habits and manufacturing technologies of the culture. The determination of macroscopic and microscopic characteristics of the ceramic objects such as the ceramic porosity, addition of tempers in the clay, main chemical components and the trace elements present in the ceramic can reveal many aspects about the manufacturing processes used by the culture, its degree of development, the provenance of the raw materials and the exchange networks. Also the radiography can help to investigate the manufactured processes, the size of the tempers used and the conservation status of the artifacts. In this present work two non-destructive techniques, radiography and PIXE (Particle Induced X-ray Emission) were used to characterize one set of thirty-six pre-Hispanic ceramic pieces from the Chimu Culture conserved in the Museu de Arqueologia e Etnologia (MAE/USP). The PIXE analyses performed in the external beam setup at LAMFI (Laboratório de Análise de Materiais por Feixes Iônicos) allowed measure the principal chemical elements such as Al, Si, K, Ti, Fe and Ca, present in this group of pieces. X-ray imagings allowed identify the manufacture processes, the granularity of the tempers used, as well as the similarity and the differences between the pieces studied.     

Mass transfer kinetics and mathematical modelling of the osmotic dehydration of orange‐fleshed honeydew melon in corn syrup and sucrose solutions

A simple mathematical model to predict dehydration and impregnation process during osmotic dehydration of orange‐fleshed honeydew in sucrose and corn syrup solutions was proposed. Results showed low dispersion and a good fitting capability for WL and SG kinetics. Diffusivity values for WL ranged from 0.96 × 10^?10 to 2.22 × 10^?10 and 1.04 × 10^?10 to 3.10 × 10^?10 m² s^?1 in corn syrup and sucrose solutions, respectively. For SG, the obtained range was 0.72 × 10^?10 to 2.35 × 10^?10 and 0.71 × 10^?10 to 2.46 × 10^?10 m² s^?1 in corn syrup and sucrose solutions, respectively. The half‐life of dehydration rates (t_1/2) was from 30.9 to 71.2 min and from 19.4 to 57.5 min in corn syrup and sucrose solutions, respectively. Diffusivities values obtained according to the proposed model were close to the ones observed from diffusive model; t_1/2 was a promising criterion for the process time definition.     

Exact corotational shell for finite strains and fracture

The corotational method for frame-invariant elements is generalized to obtain a consistent large-strain shell element incorporating thickness extensibility. The resulting element allows arbitrary in-plane deformations and is distinct from the traditional corotational methods (either quadrature-based or element-based) in the sense that the corotational frame is exact. The polar decomposition operation is performed in two parts, greatly simplifying the linearization calculations. Expressions for the strain-degrees-of-freedom matrices are given for the first time. The symbolic calculations are performed with a well-known algebraic system with a code generation package. Classical linear benchmarks are shown with excellent results. Applications with hyperelasticity and finite strain plasticity are presented, with asymptotically quadratic convergence and very good benchmark results. An example of finite strain plasticity with fracture is solved successfully, showing remarkable robustness without the need of enrichment techniques.     

SWTRACK: An intelligent model for cargo tracking based on off-the-shelf mobile devices

Logistics represent the biggest cost for transportation companies. Companies are investing in monitoring and tracking systems aiming at improving services, reducing costs and ensuring the safety in cargos transports. This article presents an intelligent model to obtain the position of vehicles, using off-the-shelf mobile devices named SWTRACK. The proposal allows distributors companies to track loads and to have real-time information about their whereabouts during a travel. SWTRACK presents an automatic travel management to initialize and finish travels without user interaction. Furthermore, it provides a mechanism to monitor detours in planned routes and to send alarms notification through mobile devices. To build that mechanism, we studied the Geofence concept and existing techniques to prepare two solutions based on continuous monitoring. Those solutions were compared and discussed. We also conducted a model evaluation using off-the-shelf mobile devices. Moreover, we provide an impact analysis regarding GPS precision and battery power consumption. In the end, we show that the proposed model generates a reliable system for tracking vehicles.     

Deductive verification of cryptographic software

We apply state-of-the art deductive verification tools to check security-relevant properties of cryptographic software, including safety, absence of error propagation, and correctness with respect to reference implementations. We also develop techniques to help us in our task, focusing on methods oriented towards increased levels of automation, in scenarios where there are clear obvious limits to such automation. These techniques allow us to integrate automatic proof tools with an interactive proof assistant, where the latter is used off-line to prove once-and-for-all fundamental lemmas about properties of programs. The techniques developed have independent interest for practical deductive verification in general.     

Antibody responses of cows during an outbreak of neosporosis evaluated by indirect fluorescent antibody test and different enzyme-linked immunosorbent assays

Hairpin ribozymes with high cleavage activities were designed. An extra sequence was introduced at the 3'-end of the hairpin ribozyme to increase the binding to the substrate RNA, as compared to the wild-type hairpin ribozyme. A three-way junction (TWJ) was formed between the newly designed ribozyme and the substrate RNA. The complex with a solid TWJ showed less RNA cleavage activity than the wild-type hairpin ribozyme. However, the ribozyme with a TWJ with five unpaired bases or propandiol phosphate linkers had higher cleavage activity than the parent ribozyme without the TWJ. When a cis-cleavage system, in which the 5'-end of the substrate RNA was conjugated to the 3'-end of the ribozyme, was employed, the complex with the TWJ containing unpaired bases was also cleaved faster than the complex with the solid TWJ. This suggested that these differences in the cleavage activities were derived from the confirmation, and this was proven by nondenaturing gel electrophoresis. The TWJ hairpin ribozyme containing unpaired bases is able to bind strongly with substrate RNAs and to cleave them efficiently. Since the three-way ribozyme presented here is more active than the wild-type ribozyme, this type of ribozyme can serve as a more efficient tool to control RNA activities in vitro and in vivo.