Workability of hybrid fiber reinforced self-compacting concrete

Compared to fiber reinforced concrete (FRC), self-compacting concrete (SCC) is a relatively new type of concrete with high flowability and good cohesiveness. It offers very attractive economical and technical benefits, which can be further extended when combined with FRC. In this article two different types of steel fibers were used, in combination, and the effects of fiber inclusion on the workability of hybrid fiber reinforced self-compacting concrete (HFR-SCC) is studied. The effects of fibers are quantified based on the fiber volume, length, and aspect ratios of the fibers. It was concluded that in addition to the above-mentioned quantifiable three properties, other properties of fibers such as shape and surface roughness are also found to be important but they cannot be quantified at this stage.     

Excavation and support design of the Dicle–Kralkizi water tunnel: an overview

Tunneling projects have their uniqueness in terms of engineering problems. The expertise gained from analyzing these projects establishes a sound basis for future application. This paper conveys experiences gained during the construction and support of the design of the Dicle–Kralkizi water tunnel, Turkey. Tunnel stability problems including overbreaks and surface subsidence are evaluated. An analysis of the breakdowns, factors controlling advance rate and the overall performance of tunnel are covered. The accumulated information presented here is believed to be useful and reliable for a successful tunnel excavation in similar formations.     

Effects of circumferential pick spacing on boom type roadheader cutting head performance

Effects of equal and unequal circumferential pick spacing on the performance of boom type roadheaders having cylindrical cutting heads are investigated. For this purpose, two experimental cutting heads with equal and unequal circumferential spacing are designed and manufactured. The cutting head with unequal circumferential spacing is specifically designed to prevent tool-holder overlap at the nose section. Manufacturing difficulties associated with equal circumferential pick spacing due to tool-holder overlap are discussed with solid modeling and practical applications. The heads are tested at Park Cayirhan Coal Mine in Turkey and their cutting performances are analysed. Although better cutting performance for equal circumferential spacing are predicted by force–balance analysis, in situ measurements of instantaneous (net) traversing speed and cutting rate, pick consumption rate and machine vibration show that no significant difference exists between the performances of the two cutting heads.     

Impacts of some building passive design parameters on heating demand for a cold region

In this study, the impact of passive design parameters such as building shape and orientation position on heating demand has been theoretically investigated. Therefore, a transient heat transfer problem in the building envelope with insulation and without insulation is solved by using the finite difference method. The considered buildings are placed on the ground with the azimuth angles from 0^°$0^{°}$ to 90^°${90}^{°}$. The heat loss per unit area of the buildings is computed by hour–hour and the yearly energy consumption of the buildings is also determined in the simulation model. The climatic data of Elazigˇ (38.4^°N)$(38.4^{°}\mathrm{N})$, a city located in a cold region of Turkey, are considered for the analysis. It is shown that buildings with a square shape have more advantages, and the most suitable orientation angles are 0^°$0^{°}$ and 80^°${80}^{°}$ for buildings having shape factors (the ratio of building length to building depth ) 2/1 and 1/2, respectively.     

Laser cutting of 7050 Al alloy reinforced with Al2O3 and B4C composites

In the present study, laser cutting of 7050 aluminum alloy sheets reinforced with Al₂O₃ and B₄C particles are carried out. The cut geometry is examined using scanning electron microscope and the optical microscope. The lump parameter analysis technique is used to formulate and determine the kerf width size. The predictions for kerf width are compared with experimental data. The percentage kerf width size variation along the cut edges is determined and the influence of the laser power level and duty cycle of the laser pulses on the percentage kerf width size variation is examined. It is found that 7050 aluminum alloy reinforced with 20% Al₂O₃ composite results in relatively large kerf width size as compared to its counter parts that corresponding to 7050 aluminum alloy reinforced with 20% B₄C composite. The kerf width size predicted agreed with the experimental data for both composites.     

A microwave method based on amplitude-only reflection measurements for permittivity determination of low-loss materials

A new method based on amplitude-only reflection measurements for complex permittivity determination of low-loss materials backed by a short-circuit termination is presented. There are two main advantages of the proposed method. First, it is insensitive to calibration plane shifts and phase uncertainties in reflection measurements of low-loss materials. Second, it does not require any additional test material with a thickness value different than that of the material under test. The disadvantage of the proposed method is that it is not convenient to apply for complex permittivity determination of dispersive low-loss materials. The method is validated by complex and amplitude-only scattering parameter measurements at X-band of a low-loss sample (polystyrene) fitted into a waveguide section. The method, as other non-resonant methods, can only provide a rough indication of the imaginary part of the permittivity for low-loss samples.     

Post-buckling behavior of carbon fiber epoxy composite plates

In this study, the pre-buckling and post-buckling behaviors of layered composite plates which were made of woven carbon fiber fabric with a circular hole in the middle were investigated experimentally and numerically. Firstly, load-displacement graphs of composite plates with different hole diameters were experimentally obtained under compressive load. Then the numerical load-displacement graphs of the plates were found with the ANSYS package program which used the finite element method. As a result, after linear buckling experimental and numerical results were found to be compatible with each other. In addition, damage behavior of plates after buckling with the aid of Tsai-Wu damage criterion was obtained similar to experimental results. The increase in hole diameter did not change the load-displacement behavior characteristics of the plates after buckling. However, it has reduced maximum damage load and maximum failure displacement. The stress at the perimeter of the hole increased significantly with the increase of the vertical displacement with immediately after the buckling but later was not significantly affected by this increase.

     

An extract of <i>Hypericum perforatum</i> induces wound healing through inhibitions of Ca²⁺ mobilizations,mitochondrial oxidative stress and cell death in epithelial cells: Involvement of TRPM2 channels

The wound is induced by several mechanical and metabolic factors. In the etiology of the wound recovery,excessive oxidative stress, calcium ion (Ca²⁺) influx, and apoptosis have important roles. Ca²⁺-permeable TRPM2 channel is activated by oxidative stress. Protective roles of Hypericum perforatum extract (HP) on the mechanical nerve injury-induced apoptosis and oxidative toxicity through regulation of TRPM2 in the experimental animals wererecently reported. The potential protective roles in HP treatment were evaluated on the TRPM2-mediated cellularoxidative toxicity in the renal epithelium (MPK) cells. The cells were divided into three groups as control, wound,and wound + HP treatment (75 µM for 72 h). Wound diameters were more importantly decreased in the wound+HPgroup than in the wound group. In addition, the results of laser confocal microscopy analyses indicated protectiveroles of HP and TRPM2 antagonists (N-(p-Amylcinnamoyl) anthranilic acid and 2-aminoethyl diphenylborinate)against the wound-induced increase of Ca²⁺ influx and mitochondrial ROS production. The wound-induced increaseof early (annexin V-FITC) apoptosis and late (propidium iodide) apoptosis were also decreased in the cells by the HPtreatment. In conclusion, HP treatment acted protective effects against wound-mediated oxidative cell toxicity andapoptosis through TRPM2 inhibition. These effects may be attributed to their potent antioxidant effect.     

Nash bargaining game model for two parallel stages process evaluation with shared inputs

Data envelopment analysis is a non-parametric technique for evaluating peer decision making units (DMUs) with using multiple inputs to produce multiple outputs. In the real world, DMUs usually have complex structures. One of these structures is a two-stage process with intermediate measures. In this structure, there are two stages and each stage uses inputs to produce outputs, separately where the outputs of the first stage are the inputs for the second stage. Cooperative model such as centralized model and non-cooperative model are game theoretic approaches to evaluate two-stage processes. Non-cooperative model supposes that one of the stages is the leader and another stage is the follower, whereas in the centralized model, both stages are evaluated simultaneously. In this paper, we propose a game theoretic model based on the Nash bargaining game to calculate weights when parallel stages with shared inputs compete to reach a high efficiency in the competitive strategy. Two data sets including the bank branches and thermal power plants in Iran are used to show the abilities of proposed model. This model can be applied in other processes such as supply chain, manufacturing and public service units.     

Exhaust Emissions from an Engine Fueled with Biodiesel from High-Oleic Soybeans

Biodiesel is a fuel comprising mono-alkyl esters of medium to long-chain fatty acids derived from vegetable oils or animal fats. Typically, engines operated on soybean-based biodiesel exhibit higher emissions of oxides of nitrogen (NOx) compared with petroleum diesel. The increase in NOx emissions might be an inherent characteristic of soybean oil’s polyunsaturation, because the level of saturation is known to affect the biodiesel’s cetane number, which can affect NOx. A feedstock that is mostly monounsaturated (i.e. oleate) helps to balance the tradeoff between cold flow and oxidative stability. Genetic modification has produced a soybean event, designated 335-13, with a fatty acid profile high in oleic acid (>85%) and with reduced palmitic acid (<4%). This high-oleic soybean oil was converted to biodiesel and run in a John Deere 4045T 4.5-L four-stroke, four-cylinder, turbocharged direct-injection diesel engine. The exhaust emissions were compared with those from conventional soybean oil biodiesel and commercial No. 2 diesel fuel. There was a significant reduction in NOx emissions (α = 0.05) using the high-oleic soybean biodiesel compared with regular soybean oil biodiesel. No significant differences were found between the regular and high-oleic biodiesel for unburned hydrocarbon and smoke emissions.