3D Finite-Element Analysis of Substandard RC Columns Strengthened by Fiber-Reinforced Polymer Sheets

Numerical analyses are performed to predict the stress–strain behavior of square reinforced concrete columns strengthened by fiber-reinforced polymer (FRP) sheet confinement. The research focuses on the contribution of FRP sheets to the prevention of elastic buckling of longitudinal steel bars under compression, in cases of inadequate stirrup spacing. A new Drucker–Prager-type plasticity model is proposed for confined concrete and is used in constructed finite-element model. Suitable plasticity and elasticity models are used for steel reinforcing bars and fiber-reinforced polymers correspondingly. The finite-element analyses results are compared against published experimental results of columns subjected to axial compression, to validate the proposed finite-element model. Stress concentrations in concrete core and on FRP jacket are investigated considering circular or square sectioned, plain or reinforced concrete columns. Geometry of the section as well as the presence of steel bars and stirrups affect remarkably the variation and magnitude of stress on FRP as percentage of its tensile strength.     

Substandard reinforced concrete members subjected to compression: FRP confining effects

The investigation focuses on the effectiveness of fiber-reinforced polymer (FRP) confinement in upgrading ductility and strength of reinforced concrete members under axial monotonic compression. An experimental program is presented that extends available database to address the behavior of old type members with square section, having extremely low concrete strength and potential longitudinal bars’ premature buckling. Reinforced concrete specimens were strengthened by carbon or glass FRP wraps while plain FRP confined concrete specimens were also constructed and tested to evaluate comparatively the confining effects of steel stirrups, FRP wraps, or of dual confinement. The achieved strength, ductility and energy absorption levels of the specimens were quantified to assess the effect of the longitudinal bars. Finally, a handy design-oriented empirical strength model is proposed. According to the proposed approach, no estimation of effective stress or strain at failure of FRP jacket is necessary. The satisfactory accuracy of the predictions of the proposed model is demonstrated through comparison against existing models and over a large database of results on uniform confinement as well as over presented specimens.     

Multi-RAT Aggregation Through Spectrum Reallocation for Future Wireless Networks

Wireless Personal Communications - Next generation wireless networks are becoming the main focus of the industry by putting efforts to launch beyond 4G (i.e. 5G) communication systems by 2020....     

Three dimensional modeling for steel-concrete composite bridges using systems of bar elements — Modeling of skewed bridges

A new improved way for modeling steel composite straight bridges has been presented (Vayas, 2009; Vayas, 2010). The proposed model is based on the representation of steel I-girders through the use of equivalent trusses. The concrete slab is suitably represented by a set of bar elements. Diaphragms and stiffeners may also be taken into account. In contrast to the grillage model, which is usually used for the analysis of bridges, the recommended three dimensional model allows for a more reliable prediction of deformations and internal forces. This paper discusses the extension of the model to skewed composite bridges. The presence of skew makes the analysis complicated and for this reason the grillage analysis is not always recommended. Phenomena like differential deflections of the main girders during concreting and lateral displacements of the flanges can be adequately predicted using the proposed model. The new way for modeling composite bridges, using a spatial system of beam-like structural elements, can also be used for stability analysis of skewed bridges. Worked examples are provided to illustrate the set up procedure of the proposed modeling and to compare the different ways of analysis.     

Graphitized filament plasma enhanced CVD deposition of nanocrystalline diamond

A novel approach to the deposition of polycrystalline diamond is presented. The technique is based on the hot filament chemical vapour deposition technique (HFCVD). While it is similar to a high plasma power “bias enhanced growth” HFCVD, it relies on a graphite filament rather than on a metal one. It was found that with an appropriate choice of the growth parameters, 4–9% CH₄ in H₂, filament temperature > 2200 °C, 25 mBar gas pressure, plasma power > 500 W, a long filament lifetime can be achieved, when a simultaneous deposition of graphitic carbon on the hot graphite filament and of nanocrystalline diamond on a substrate facing the filament assembly is realized. In this paper the growth of nanocrystalline diamond films and their characterization (SEM, XRD, AFM) are presented. While the technique is promising for low cost, large area deposition of nanocrystalline diamond films, also the growth of microcrystalline diamond has been observed.     

Short-acquisition-time JPRESS and its application to paediatric brain tumours

Objective

To develop and assess a short-duration JPRESS protocol for detection of overlapping metabolite biomarkers and its application to paediatric brain tumours at 3 Tesla.

Materials and methods

The short-duration protocol (6 min) was optimised and compared for spectral quality to a high-resolution (38 min) JPRESS protocol in a phantom and five healthy volunteers. The 6-min JPRESS was acquired from four paediatric brain tumours and compared with short-TE PRESS.

Results

Metabolite identification between the 6- and 38-min protocols was comparable in phantom and volunteer data. For metabolites with Cramer–Rao lower bounds > 50%, interpretation of JPRESS increased confidence in assignment of lactate, myo-Inositol and scyllo-Inositol. JPRESS also showed promise for the detection of glycine and taurine in paediatric brain tumours when compared to short-TE MRS.

Conclusion

A 6-min JPRESS protocol is well tolerated in paediatric brain tumour patients. Visual inspection of a 6-min JPRESS spectrum enables identification of a range of metabolite biomarkers of clinical interest.

     

A Low-Complexity PTS-based PAPR Reduction Technique for OFDM Signals without Transmission of Side Information

Increased peak-to-average power ratio (PAPR) imposes a design challenge for orthogonal frequency division multiplexing-based signals. An efficient technique to address the increased PAPR problem is the partial transmit sequences (PTS) approach. A significant drawback of PTS is the fact that it multiplies the transmitted symbol with weighting factors selected by the transmitter. Since the weighting factors are required for decoding, they are explicitly transmitted, in most cases. This paper proposes a new low-complexity technique for retrieving the weighting factors in the receiver. The proposed decoder uses the predefined values of pilot tones and explores all the permissible combinations of weighting factors in order to identify the factor combination employed by the transmitter. The proposed decoder requires no additional pilot tones or explicit transmission of side information, therefore no data rate loss is implied. Furthermore this paper presents a digital very large scale integration implementation of the proposed PTS decoder and demonstrates its low-power properties.     

Glucoamylases production of Aspergillus niger in solid state fermentation using a continuous counter-current reactor

This work presents the continuous production of fungal biomass and glucoamylase by solid state fermentation (SSF) in a counter-current reactor adapted for this purpose. Pre-germinated conidia of Aspergillus niger were used as an inoculum, and sugarcane bagasse, embedded with a nutritive solution, was the solid support. The solids residence time distribution (RTD) was carried out by feeding one impule of blue-coloured humidified bagasse and its RTD was fixed at 20 h. This study demonstrated that the values of the measured parameters (pH, moisture, biomass, glucoamylases production) were similar to those reported for batch SSF using the same solid support and micro-organism. A marked increase in biomass occurred from the progressive compartment (from compartment 1 to 9) into the reactor and the enzyme production was important (40 IU g⁻¹ dry exit solids). No mycelium damage or sporulation was observed by microscopy analysis. The above results confirmed that the continuous production of enzymes by SSF under no sterile conditions was successful. Inoculation with pre-germinated conidia shortened the processing time and allowed control of the age of the mycelium in each compartment. Aeration was accomplished by natural convection and moisture content had to be controlled. This process can be applied to the continuous production of fungal biomass and metabolites in SSF with industrial applications using environmental-friendly biotechnology.