Investigation of the parameters that influence the accuracy of bond defect detection in CFRP bonded specimens using IR thermography

Infra-red (IR) testing has emerged as a promising non-destructive method (NDM) to detect and effectively observe bond defects in composite materials. This paper presents the findings of an investigation of carbon fiber-reinforced polymer (CFRP) fabrics and laminates externally bonded to concrete and steel members. Various kinds of artificial bond defects at the CFRP-substrate bond surface were investigated in specimens with single- as well as multi-layer CFRP fabrics. Particular emphasis was placed on the use of different heating modules in the IR nondestructive testing. This was implemented by generating different thermal waves within the CFRP-substrate bond surface. The results show that substrate material type and methods of surface preparation have a marked influence on the type of heating modules that produce the best detection capability. The results also show that the number of CFRP layers has a considerable effect on the effectiveness of bond identification and the accuracy of the IR images.     

Influence of Chemical Reaction on Heat and Mass Transfer in MHD Radiative Flow due to Non-Coaxial Rotations of Disk and Fluid at Infinity

Theoretical Foundations of Chemical Engineering - An exact solution of the problem regarding influence of chemical reaction and buoyant force on the heat and mass transfer in a radiative flow due...     

Place attachment assessment of a heritage place: A case study of the Roman amphitheater in downtown Amman,Jordan

This research investigated the place attachment of a heritage place, namely, the Roman amphitheater, by using a valid model, the Kyle, Graefe, and Manning (2005) model. This model presents three factors to reach place attachment: place identification, place dependence, and social bonding. Although the validity of the used model was proved, statistical tests were used to verify the validity of the collected data because the model was used on a heritage site. In accordance with the mentioned model, the sample was interviewed using the model questionnaire to evaluate people's attachment to the heritage place during rush hours. Along with other statistical tests, the exploratory factor analysis of the sample elaborated that the Kyle, Graefe, and Manning model is not completely valid for this study, because the results added a new effective factor, namely, spiritual value. The place attachment estimation was then examined using the new model. The nature of the place was found to affect the model used to evaluate its place attachment.     

BER Performance Using Linear Phase Orthogonal Binary Codes for Multi-users Mobile Communication

Wireless Personal Communications - Nowadays, modern wireless mobile communication systems attempt to increase the number of subscribers simultaneously, starting from the third to fifth generations....     

Ultrasonication as pretreatment for drying of tomato slices in a hot air–microwave hybrid oven

This study aims to investigate the effect of ultrasonic pretreatment on drying time and quality properties of tomato slices dried by microwave combined with hot air at 60°C. The influence of ultrasound pretreatment (0, 20, and 40?min) and microwave power (120, 150, and 180?W) on drying time, color, total phenolic content, lycopene, vitamin C, and rehydration capacity of dried slices of tomato was studied. Results showed that as the microwave power level increased, drying time decreased significantly (about 46.4%). Ultrasound pretreatment decreased the drying time by 7.38% only at 120?W microwave power and 40?min of pretreatment compared to those without ultrasound pretreatment at the same microwave power. Depending on drying conditions, vitamin C and lycopene contents reduced from 433.94 to 81.89?mg AA/100?g dry solids and 3920.57 to 415.40?mg/100?g dry solids, respectively. The change in total phenolic content was not severe as much as vitamin C contents. Rehydration capacity of pretreated samples was larger than nontreated samples. The color values of dried tomato slices were in the acceptable range. Both microwave power and ultrasound pretreatment affected the quality of the final product significantly.     

Conventional chiller performances simulation and field data

In most commercial buildings and industrial plants HVAC systems consume large amounts of energy, and usually offer the most significant potential for savings. Liquid conventional chillers play a very important role in providing these savings. Proper design, installation, and maintenance of these systems are therefore the key steps leading to improved efficiency which benefit both the customers and the utilities. To effectively materialize this concept two steps have been followed here. In the first section of this paper conventional chillers of different types have been modelled and simulated using a software (DOE2). The chillers are rated for a generic building and meteorological weather of San Diego. Performance parameters such as the part/full-load efficiencies, the number of occurrences during peak hours and load frequencies are then calculated. These results gave typical performance values (curves) which can be used to compare screw, centrifugal, and reciprocating chillers among each other within a predefined scope. In the following section the field data of 39 conventional chillers and the manufacturers specifications of some of them are collected and analysed. This gave an overall view of their actual field performance and their deviation from the manufacturers' specifications. Comparison of the simulated and collected data also provided better vision of the expected performances versus the actual performances, and pinpointed some major drawbacks in the design and sizing methodology. The results also led to important conclusions regarding the status quo and the possibilities in the immediate future. Preferred chiller types and methods of providing the required cooling energy recommended by the simulation results are compared with the existing ways of providing energy in order to conform the eventual promises and quantify the room for efficiency.     

Low Prandtl number chaotic convection in porous media with uniform internal heat generation

Using the theory of dynamical systems, this study investigated the effects of a uniform internal heat generation on chaotic behaviour in thermal convection in a fluid-saturated porous layer subject to gravity and heated from below for low Prandtl number. A low-dimensional, Lorenz-like model was obtained using Galerkin truncated approximation. The fourth-order Runge–Kutta method was employed to solve the nonlinear system. We found that there is an inverse proportional relation between the level of internal heat G and the scaled Rayleigh number R, and consequently the porous media gravity-related Rayleigh number Ra.     

Doping Nanoscale Graphene Domains Improves Magnetism in Hexagonal Boron Nitride

Carbon doping can induce unique and interesting physical properties in hexagonal boron nitride (h‐BN). Typically, isolated carbon atoms are doped into h‐BN. Herein, however, the insertion of nanometer‐scale graphene quantum dots (GQDs) is demonstrated as whole units into h‐BN sheets to form h‐CBN. The h‐CBN is prepared by using GQDs as seed nucleations for the epitaxial growth of h‐BN along the edges of GQDs without the assistance of metal catalysts. The resulting h‐CBN sheets possess a uniform distrubution of GQDs in plane and a high porosity macroscopically. The h‐CBN tends to form in small triangular sheets which suggests an enhanced crystallinity compared to the h‐BN synthesized under the same conditions without GQDs. An enhanced ferromagnetism in the h‐CBN emerges due to the spin polarization and charge asymmetry resulting from the high density of C? N and C? B bonds at the boundary between the GQDs and the h‐BN domains. The saturation magnetic moment of h‐CBN reaches 0.033 emu g^?1 at 300 K, which is three times that of as‐prepared single carbon‐doped h‐BN.