Exploring isolated lignin material from oil palm biomass waste in green composites

Lignin obtained from oil palm biomass empty fruit bunches (EFB) fibers, has been used as curing agent in green epoxy composites. Epoxy–lignin composites, with varying lignin content (15%, 20%, 25% and 30%), reinforced with EFB fiber were prepared. The effect of EFB-based lignin on the mechanical, thermal and morphology properties of the composites were investigated and compared with the composites cured with isophorone diamine curing agent. The improved thermal stability and the observed microstructure of the fractured surface of the composites were attributed to good fiber–matrix interaction, induced by the curing agent. The epoxy composites cured with 25% lignin content proved to be a better matrix and gave optimum value compared with other formulations which was confirmed by its mechanical, thermal and morphological properties.     

Theoretical model for annular flow condensation in rectangular micro-channels

This study examines the pressure drop and heat transfer characteristics of annular condensation in rectangular micro-channels with three-sided cooling walls. A theoretical control-volume-based model is proposed based on the assumptions of smooth interface between the annular liquid film and vapor core, and uniform film thickness around the channel’s circumference. Mass and momentum conservation are applied to control volumes encompassing the liquid film and the vapor core separately. The model accounts for interfacial suppression of turbulent eddies due to surface tension with the aid of a new eddy diffusivity model specifically tailored to shear-driven turbulent films. The model predictions are compared with experimental pressure drop and heat transfer data for annular condensation of FC-72 along 1 × 1 mm² parallel channels. The condensation is achieved by rejecting heat to a counterflow of water. The data span FC-72 mass velocities of 248–367 kg/m² s, saturation temperatures of 57.8–62.3 °C, qualities of 0.23–1.0, and water mass flow rates of 3–6 g/s. The data are also compared to predictions of previous separated flow mini/micro-channel and macro-channel correlations. While some of the previous correlations do provide good predictions of the average heat transfer coefficient, they fail to capture axial variation of the local heat transfer coefficient along the channel. The new model accurately captures the pressure drop and heat transfer coefficient data in both magnitude and trend, evidenced by mean absolute error values of 3.6% and 9.3%, respectively.     

1 kWe sodium borohydride hydrogen generation system: Part II: Reactor modeling

Sodium borohydride (NaBH₄) hydrogen storage systems offer many advantages for hydrogen storage applications. The physical processes inside a NaBH₄ packed bed reactor involve multi-component and multi-phase flow and multi-mode heat and mass transfer. These processes are also coupled with reaction kinetics. To guide reactor design and optimization, a reactor model involving all of these processes is desired. A one-dimensional numerical model in conjunction with the assumption of homogeneous catalysis is developed in this study. Two submodels have been created to simulate non-isothermal water evaporation processes and pressure drop of two-phase flow through the porous medium. The diffusion coefficient of liquid inside the porous catalyst pellets and the mass transfer coefficient of water vapor are estimated by fitting experimental data at one specified condition and have been verified at other conditions. The predicted temperature profiles, fuel conversion, relative humidity and pressure drops match experimental data reasonably well.     

IFRS: An Indexed Face Recognition System Based on Face Recognition and RFID Technologies

Access control systems are in contact with humans in everyday life, it is used in buildings, smartphones, cars, and IoT. Access control systems became an active research area. The performance of an access control system is specified by its speed and accuracy. Biometric systems are powerful access control systems which use humans’ biological or physiological properties to provide access to the restricted data or area. From all of the many biometric system types, the face recognition system is the only type that is delivering the automatic property. Moreover, it is the most acceptable type of biometric systems to the humans. The main challenges in the face recognition system are the degradation of the speed and accuracy when the system database grew bigger. This is because the face recognition system is an identification system that adopts a one to many (1:M) relationship. As a result, there is a need to develop a system with one to one (1:1) relationship, which is a challenging process. Motivated by such challenge, this paper proposes a system called Indexed Face Recognition System (IFRS) which is based on the combination of face recognition technology and Radio Frequency Identification technology. IFRS uses Local Binary Pattern Histogram as a feature vector and Haar-cascade classifier for the face detection. Moreover, the system is enhanced with three pre-processing methods namely: Bilateral filter, Histogram Equalization, and applying Tan and Triggs’ algorithm. In addition, IFRS performs an image normalization processes before and after Face Detection phase to enhance images quality, these process are: Color Conversion and Image Cropping and Resizing. Two experiments were done. The first experiment was done on 400 images with 40 subjects (10 images per subject). The second experiment was done on 210 collected images for 21 subjects (10 images per subject) from University students as a real-life case study. The practical results demonstrates that 4?×?4 image divisions gives better results than 8?×?8 image divisions as far as recognition time, database access time, and storage capacity are concerned. The practical results show that IFRS can reach an accuracy of 100% with a very little amount of time delay that is negligible.     

Thermal Stresses in Spherical Shells

This paper presents an iterative finite-difference technique for the analysis of axisymmetric spherical shells with variable wall thickness. The formulation is based on thin elastic shell theory. One-dimensional finite-difference points are used to discretize the shell into strips along the meridian, and an iterative technique is employed to determine the normal and meridional displacements. The stress resultants and bending stresses are then evaluated. Unlike existing analytical and finite-difference techniques, the proposed method is applicable with ease to any variation in rigidity along the meridian, to general loading conditions, and to steep and shallow shells. Results are presented and compared with those of the finite-element method.     

Linear Programming Approach to Optimize Strategic Investment in the Construction Workforce

The construction industry in the United States and other parts of the world has been facing several challenges, including a shortage of skilled workers. A review of the relevant body of knowledge indicates that one of the key reasons for this problem is the absence of human resource management strategies for construction workers at project, corporate, regional, or industry levels. This paper addresses the issues of workforce training and allocation on construction projects. It presents a framework to optimize the investment in, and to make the best use of, the available workforce with the intent to reduce project costs and improve schedule performance. A linear program model, entitled the Optimal Workforce Investment Model, is built to provide an optimization-based framework for matching supply and demand of construction labor most efficiently through training, recruitment, and allocation. Given a project schedule or demand profile and the available pool of workers, the suggested model provides human resource managers a combined strategy for training the available workers and hiring additional workers. The input data to the proposed model consists of a certain available labor pool, cost figures for training workers in different skills, the cost of hiring workers, hourly labor wages, and estimates of affinities between the different considered skills. The objective of the model is to minimize labor costs while satisfying project labor demands. Results from application of the model to typical situations are presented, and recommendations for future developments are made.     

Application of nano-EBIC to the characterization of GaAs and InP homojunctions

High resolution electron-beam-induced current (EBIC) analyses were carried out on InP and GaAs substrates with a home-made atomic force microscope (AFM) combined with a scanning electron microscope (SEM). With this scanning nano-EBIC microscope, a sample can be conventionally imaged by SEM, its local topography investigated by AFM and nano-EBIC image simultaneously obtained. In this study, we report the utilization of nano-EBIC microscopy for imaging and characterizing GaAs and InP homojunctions. I-V characteristic measurements allow understanding of the electrical behavior of the AFM tip-sample contact. The electron probe intensity must be larger than about 100?pA to be able to generate an induced current because of the surface states which act as non-radiative recombination centers. The minority carrier diffusion length of InP and GaAs is measured and compared for different electron probe currents and it is shown that the measurements are not perturbed by photon recycling, i.e. the self-absorption of photons that gives rise to an extra generation of electron-hole pairs.     

One-Dimensional Model for Multi-Barge Flotillas Impacting Bridge Piers

Abstract:   The serious consequence of barge-bridge collisions necessitates the study of barge impact loadings on bridges. This article introduces an elastoplastic spring-mass model for the analysis of multi-barge flotillas colliding with bridge piers at zero angle of attack. The model accounts for the essential factors pertaining to barge/flotilla impacts, such as pier geometry and stiffness, and dynamic interaction between barges. A method to identify the elastoplastic behavior of barge crushing is also presented. The proposed method generates impact force time-histories for a multitude of flotilla configurations in a matter of minutes, which is especially valuable in probabilistic analysis requiring many collision simulations. The results from this study are compatible with the respective impact time-histories produced by exhaustive finite element simulations. A bridge pier impacted by a three-barge and a 15-barge flotilla is studied.