Modeling the behavior of longwall coal mine gate roadways subjected to dynamic loading

In order to characterize the behavior of a main gate during retreating of longwall faces and to evaluate the performances of five different support types, including rock bolts and steel sets, a total of 21 convergence and 18 floor-heave stations were installed. Consequently, about 11,500 convergence and 7200 floor-heave data points were obtained over a period of 14 months. In order to simulate the behavior of a supported main gate roadway, a convergence model, represented by an exponential function, was developed on the basis of statistical analyses. In addition to the convergence model, convergence–velocity and convergence–acceleration models were also derived and interpreted in terms of gate road behavior. It was determined that the convergence depends on the loading region, the time, the location of the upper and lower longwall faces, the support type and pattern, and the static and dynamic support loads. Convergence–velocity and acceleration curves provide better means to interpret the performance of supports and gate roadway behavior.     

Interesting faces: A graph-based approach for finding people in news

In this study, we propose a method for finding people in large news photograph and video collections. Our method exploits the multi-modal nature of these data sets to recognize people and does not require any supervisory input. It first uses the name of the person to populate an initial set of candidate faces. From this set, which is likely to include the faces of other people, it selects the group of most similar faces corresponding to the queried person in a variety of conditions. Our main contribution is to transform the problem of recognizing the faces of the queried person in a set of candidate faces to the problem of finding the highly connected sub-graph (the densest component) in a graph representing the similarities of faces. We also propose a novel technique for finding the similarities of faces by matching interest points extracted from the faces. The proposed method further allows the classification of new faces without needing to re-build the graph. The experiments are performed on two data sets: thousands of news photographs from Yahoo! news and over 200 news videos from TRECVid2004. The results show that the proposed method provides significant improvements over text-based methods.     

Lewis acid catalyzed diesel‐like fuel production from raw corn oil

The pyrolysis of raw corn oil in the absence and presence of Lewis acids was carried out at 500°C. The catalytic effect of AlCl₃ was better than that of FeCl₃. The physico‐chemical properties of diesel‐like fuels produced by Lewis acid catalyzed are close to that of commercial diesel fuel. The diesel‐like fuels obtained from catalytic runs can be evaluated as diesel fuels. Copyright © 2008 John Wiley & Sons, Ltd.     

Multi-objective optimization of transporting blood products by routing UAVs: the case of Istanbul

Since the blood is necessary for surgical operations, disease treatments, chronic disorders, and traumatic accidents, it is staminal to manage the flow in the supply chain of blood products from donors to patients that can save lives. Therefore, this paper focuses on transporting blood products from distribution centers to hospitals in cities by routing unmanned aerial vehicles (UAVs). The problem includes two objective functions as minimizing the used number of UAVs and their total travel distances, simultaneously by considering range, payload weight, and payload volume of UAVs. The problem also covers the blood product demands of hospitals and the supply capacities of distribution centers. A multi-objective integer programming (MOIP) model and three multi-objective metaheuristics are designed to solve the defined problem. To test the effectiveness of the proposed methods, real-life blood product demands of hospitals in Istanbul for the year 2019 are obtained from the Turkish Red Crescent and several scenarios are created as the case study. In scenarios, two types of vertical take-off and landing UAVs are considered, the MOIP is developed by using ILOG, solved via CPLEX, and the metaheuristics are coded in MATLAB. The results reveal that the proposed methods can find good solutions for the problem in acceptable CPU times.     

Synthesis and characterization of novel fluorine‐containing methacrylate copolymers: Reactivity ratios,thermal properties,and antimicrobial activity

The free‐radical‐initiated copolymerization of 2‐(4‐acetylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (AOEMA) and 2‐(4‐benzoylphenoxy)‐2‐oxoethyl‐2‐methylacrylate (BOEMA) with 2‐[(4‐fluorophenyoxy]‐2‐oxoethyl‐2‐methylacrylate (FPEMA) were carried out in 1,4‐dioxane solution at 65°C using 2,2′‐azobisisobutyronitrile as an initiator with different monomer‐to‐monomer ratios in the feed. The monomers and copolymers were characterized by FTIR and ¹H‐ and ¹³C‐NMR spectral studies. ¹H‐NMR analysis was used to determine the molar fractions of AOEMA, BOEMA, and FPEMA in the copolymers. The reactivity ratios of the monomers were determined by the application of Fineman‐Ross and Kelen‐Tudos methods. The analysis of reactivity ratios revealed that BOEMA and AOEMA are less reactive than FPEMA, and copolymers formed are statistically in nature. The molecular weights (M _w and M _n) and polydispersity index of the polymers were determined using gel permeation chromatography. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increase in the mole fraction of FPEMA in the copolymers. Glass transition temperatures of the copolymers were found to decrease with an increase in the mole fraction of FPEMA in the copolymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Motorcycle riders' perception of helmet use: complaints and dissatisfaction

In accidents which involve two-wheeled vehicles the helmet plays a life-saving role, but very little is known about the motorcycle rider's perception of the helmet. We evaluated the relationships between having been involved in an accident and dissatisfaction with the helmet, and between the perception of motorcycle riders and the objective features of the helmet. This was a case-control study: riders of motorized two-wheelers who had been involved in accidents (accident cases) were compared against a similarly interviewed sample of riders that had not been in accidents (control cases). Information about the driver, the vehicle and the helmet was collected in all interviews. To evaluate the relationships, logistic regressions were carried out. The majority of drivers were dissatisfied with their helmets, but no evidence was found to link this dissatisfaction with having been involved in an accident. The two most common complaints related to noisiness, followed by the helmet visor. Complaints did not seem to be statistically associated with physical features of the helmet.     

Interfacial strength and fracture energy of individual carbon nanofibers in epoxy matrix as a function of surface conditions

The interfacial shear strength (IFSS) and fracture energy of individual carbon nanofibers embedded in epoxy were obtained for different surface conditions and treatments by novel, MEMS-based, nanoscale fiber pull-out experiments. As-grown vapor grown carbon nanofibers (VGCNFs) with turbostratic surface and 5 nm peak-to-valley surface roughness exhibited high IFSS and interfacial fracture energy, averaging 106 ± 29 MPa and 1.9 ± 0.9 J/m², respectively. Subsequent high temperature heat treatment and graphitization resulted in drastically reduced IFSS of 66 ± 10 MPa and interfacial fracture energy of 0.65 ± 0.14 J/m². The smaller IFSS values and the reduced standard deviation were due to significant reduction of the fiber surface roughness to 1–2 nm, as well as a decrease in surface defect density during conversion of turbostratic and amorphous carbon to highly ordered graphitic carbon. For both grades of VGCNFs failure was adhesive with clear nanofiber surfaces after debonding. Oxidative functionalization of high temperature heat-treated VGCNFs resulted in much higher IFSS of 189 ± 15 MPa and interfacial fracture energy of 3.3 ± 1.0 J/m². The debond surfaces of functionalized nanofibers had signs of matrix residue and/or shearing of the outer graphitic layer of the VGCNFs, namely the failure mode was a combination of cohesive matrix and/or cohesive fiber failure which contributed to the high IFSS. For all three grades of VGCNFs the IFSS was independent of fiber length and diameter. The findings of this experimental study emphasized the critical role of nanofiber surface morphology and chemistry in determining the shear strength and fracture energy of nanofiber interfaces, and shed light to prior composite-level strength and fracture toughness measurements.     

Reversibility of electric-field-induced mechanical changes in soft tissues

Recently, ultrasound has been used to study the physiological-level electric-field-induced mechanical changes (EIMC) in general soft biological tissues. Here, we present the experimental results on the dependence of EIMC on the polarity of the applied electric field. We applied an ac voltage source to heart tissues and monitored the amplitude changes and time shifting of the ultrasound echoes. The shifting of the echoes was decomposed into a trend component and a fluctuation (feature) component. The changes in amplitude and the fluctuation component of the time shift, but not the trend component of the time shift, can be mostly reversed by reversing the polarity of the applied voltage. The polarity-dependence study reveals two different mechanisms underlying EIMC.