Properties of hybrid fiber reinforced concrete under repeated impact loads

Steel, glass and polypropylene fiber reinforced concrete structures were investigated under repeated impact loads in this study. Twelve different concrete series prepared fiberless the one of all and the others reinforced polypropylene, glass, steel and hybrid fiber were produced. The polypropylene fibers in diameter of 50 mm, l/d (length/diameter) ratio of 400, glass fibers in diameter of 14 mm, l/d ratio of 857 and steel fibers in diameter of 0.75 mm, l/d ratio of 80 were used in concrete mixtures. The volumetric contents were 0.5, 0.75 and 1% in fiber reinforced concrete. The volumetric content was 0.1% in polypropylene and glass fiber reinforced concrete. Drop-weight test similar the method presented ACI 544.2R-89 was conducted using 28 days cured samples having dimensions of 100 × 100 × 100 mm and reduction of strength were determined by ultrasonic pulse velocity (UPV) test. Furthermore, initial crack formation and fracture numbers variation in samples were detected. In the present study, it was aimed to develop performance under repeated impact loads using fibers in concrete. As a result, especially impact performance was rather increased in steel fiber reinforced concrete, and hybrid fibers had also positive effect on the performance of concrete.     

A Hybrid Object-Oriented Very Low Bit Rate Video Codec

There are a large number of applications requiring the compression of video at Very Low Bit Rates (VLBR). Such applications include wireless video conferencing, video over the internet, multimedia database retrieval and remote sensing and monitoring. Recently, the MPEG-4 standardization effort has been a motivating factor to find a solution to this challenging problem. The existing approaches to this problem can generally be grouped into block-based, model-based, and object-oriented. Block-based approaches follow the traditional strategy of decoupling the image sequence into blocks, model-based approaches rely on complex 3-D models for specific objects that are encoded, and object-oriented approaches rely on analyzing the scene into differently moving objects. All three approaches exhibit potential problems. Block-based approaches tend to generate artifacts at the boundaries of the blocks, as well as to limit the minimum achievable bit-rate due to the fixed analysis structure of the scene. Model-based codecs are limited by the complex 3-D models of the objects to be encoded. On the other hand, object-oriented codecs can generate a significant overhead due to the analysis of the scene which needs to be transmitted, which in turn can be the limiting factor in achieving the target bit-rates. In this paper, we propose a hybrid object-oriented codec in which the correlations among the three information fields, e.g., motion, segmentation and intensity fields, are exploited both spatially and temporally. In the proposed method, additional intelligence is given to the decoder, resulting in a reduction of the required bandwidth. The residual information is analyzed into three different categories, i.e., occlusion, model failures, and global refinement. The residual information is encoded and transmitted across the channel with other side information. Experimental results are presented which demonstrate the effectiveness of the proposed approach.     

Design and implementation of a Secure Bandwidth Broker Discovery Protocol

Differentiated Services architecture definition lacks control level functionalities. One of the solutions proposed to fill this gap is Bandwidth Brokers (BB). Bandwidth Brokers are autonomous entities inside a network which is responsible for bandwidth management of the network along with other tasks. There is a lack of protocol for Bandwidth Brokers to discover other Bandwidth Brokers automatically. This study introduces a new Secure Bandwidth Broker Discovery Protocol (BBDP), which allows Bandwidth Brokers to automatically discover other Bandwidth Brokers. In this paper design principles, protocol details, working scenarios and implementation details of the BBDP protocol are presented.     

Buckling of symmetric cross-ply square plates with various boundary conditions

The buckling analysis of cross-ply laminated square plates subjected to three types of in-plane forces and various edge boundary conditions is presented on the basis of a unified five-degree-of-freedom shear deformable plate theory. The employment of the appropriate “shear deformation shape functions” in the theory leads to certain shear deformable plate theories developed previously, also, fulfills the requirement of the continuity conditions among the layers. The governing equations of buckling behaviour of completely simply supported cross-ply laminated plates are solved analytically. For the plates with different combinations of free, clamped and simply supported boundary conditions at their edges, the Ritz method is applied by assuming the displacement components as the double series of simple algebraic polynomials. The numerical results obtained on the basis of various plate theories for uniaxial, biaxial compression and compression–tension types of loading and different length-to-thickness ratios are presented and compared with the ones available in the literature.     

Effects of genotype and environment on β-glucan and dietary fiber contents of hull-less barleys grown in Turkey

In this study, the effects of cultivar and environment on β-glucan and total dietary fibre (TDF) contents and various quality characteristics of hull-less barley samples grown in Turkey were investigated. There were significant differences among the barley genotypes and different locations in terms of β-glucan and TDF content (p < 0.05). Significant correlations were found between β-glucan content and some quality criteria (sieve analysis and 1000 kernel weight). The correlations between TDF and grain yield, hectolitre weight, 1000 kernel weight and protein content were also generally significant. These results indicated that environmental and genetic factors are involved in the total β-glucan content of barley.     

Decolorisation of textile effluent using homogeneous photochemical oxidation processes

In this paper, the results of COD and colour removal from textile effluent using homogeneous photochemical oxidation processes in a batch mode are presented. The results show that the best result was obtained using a combined O₃/H₂O₂/UV process, with 97% removal for COD and 99% removal for colour. Optimum conditions for pH and hydrogen peroxide dosage for this process was determined as 3 and 25 mg/l, respectively. Both H₂O₂/UV and O₃/UV combinations were found to result in similar levels of COD and colour removal efficiencies (over 91% removal for COD and 96% for colour). In addition, the associated operating costs of the various advanced oxidation processes were determined in this study. Received: 21 February 2005; Accepted: 14 June 2005.     

Beitrag zum Verbundverhalten von bindemittelvergütetem bindigen Boden mit Polyvinylalkohol‐Geogittern

Contribution to the interaction performance of binder‐stabilized cohesive soil and PVA geogrids. The interaction behaviour between geosynthetics and soils is essential for the stability calculation of geosynthetic reinforced earth. It is important to analyse the parameters which are responsible for the state of failure of the composite construction and evaluate the interaction between the geosynthetic and the soil. Theoretic models are not suitable and not transparent enough to simulate the interaction behaviour out of many reasons. This is why interaction parameters are determined by shear and pull‐out tests. Most of the literatures available for these tests are based on cohesionless soils. Scientific analysis of geogrids embedded in cohesive soils is rare and fragmentary. Furthermore, analysis is almost not present for binder‐stabilized cohesive soils. The growing shortage of satisfactory granular soils with high friction and the availability of local cohesive soils have resulted in an increasing interest for such soils in the last years. This is one of the reasons why many shear and pull‐out tests were conducted at the TU Bergakademie Freiberg with the cooperation of HUESKER Comp. on cement and lime stabilised cohesive soils with high alkali resistant PVA geogrids. A newly developed testing device, which has proved itself with the adaptation of in‐situ boundary conditions and repro ducible test results, was taken into operation for these tests. The test results are very promising. The PVA geogrid tested has very high coefficients of interaction both in the shear and pull‐out mode, with certain synergetic effects occurring.     

Effects of hydrothermal aging on glass–fiber/polyetherimide (PEI) composites

The moisture absorption behavior and the influence of moisture on thermal and mechanical properties of glass–fiber/polyetherimide (PEI) laminates have been investigated. The laminates were exposed to hydrothermal aging at two different temperatures and high moisture rates. The properties of as-received and hydrothermally aged samples were compared. The hydrothermally aged laminates contained a large amount of moisture which caused decrease in the glass transition temperature and deterioration in mechanical properties (interlaminar shear strength, flexural modulus, bearing strength, etc.). Fractographic analysis revealed interfacial debonding as the dominant failure mechanism, indicating a strong influence of water degradation on fracture toughness results. Alterations in visco-elastic properties of glass/PEI composite which was exposed to hydrothermal aging were analyzed with the dynamic mechanical thermal analysis (DMTA) method. DMTA tests give evidence of plasticization of the PEI matrix.     

Dielectrical properties of food materials--1: factors affecting and industrial uses

The electrical properties of foods and biological products have been the most valuable factors in the novel food technology. They have been defined both from electromagnetic field concepts and from the electrical-circuit point of view. Recently, these properties are used to assess the characterization of the processes based on electrical methods: electromagnetic, electro-processes. This article is a review of dielectrical properties of food materials. It also includes factors affecting the dielectrical properties of foods and their industrial uses.