Dominant rock properties affecting the performance of conical picks and the comparison of some experimental and theoretical results

Conical picks are the essential cutting tools used especially on roadheaders, continuous miners and shearers and their cutting performance affects directly the efficiency and the cost of rock/mineral excavation. In this study, in order to better understand the effects of dominant rock properties on cutter performance, 22 different rock specimens having compressive strength values varying from 10 to 170 MPa are first subjected to a wide range of mechanical tests. Then, laboratory full-scale linear cutting tests with different depth of cut and cutter spacing values are realized on large blocks of rock specimens using one type of conical pick. Specific energy, cutting and normal force values for relieved and unrelieved cutting modes are recorded using a triaxial force dynamometer with capacity of 50 tonnes and a data acquisition system. Cutter force and specific energy values are correlated with rock properties and theoretical force and specific energy values obtained from widely used theoretical approaches.The results indicate that uniaxial compressive strength among the rock properties investigated is best correlated with the measured cutter performance values, which is in good agreement with previous studies. However, it is also emphasized in this study that Brazilian tensile strength, Schmidt hammer rebound values, static and dynamic elasticity modulus are also dominant rock properties affecting cutter performance.Theoretical specific energy defined by different researchers has a meaningful relationship with the experimental specific energy, which is an essential parameter for predicting the instantaneous cutting rates of mechanical excavation systems. It is also demonstrated that the experimental cutter forces obtained for 5 mm depth of cut are in good agreement with theoretical force values, if the friction angle between rock and cutting tool is included in the theoretical formulation. It is emphasized that, to some extend, laboratory tests can help to minimize high cost of a trial–error approach in the field.     

Fuzzy functions based ARX model and new fuzzy basis function models for nonlinear system identification

In this study, auto regressive with exogenous input (ARX) modeling is improved with fuzzy functions concept (FF-ARX). Fuzzy function with least squares estimation (FF-LSE) method has been recently developed and widely used with a small improvement with respect to least squares estimation method (LSE). FF-LSE is structured with only inputs and their membership values. This proposed model aims to increase the capability of the FF-LSE by widening the regression matrix with lagged input–output values. In addition, by using same idea, we proposed also two new fuzzy basis function models. In the first, basis of the fuzzy system and lagged input–output values are structured together in the regression matrix and named as “L-FBF”. Secondly, instead of using basis function, the membership values of the lagged input–output values are used in the regression matrix by using Gaussian membership functions, called “M-FBF”. Therefore, the power of the fuzzy basis function is also enhanced. For the corresponding models, antecedent part parameters for the input vectors are determined with fuzzy c-means (FCM) clustering algorithm. The consequent parameters of the all models are estimated with the LSE. The proposed models are utilized and compared for the identification of nonlinear benchmark problems.     

Effect of replacing disc cutters with chisel tools on performance of a TBM in difficult ground conditions

A summary of a research program covering a period of two years on the performance of a TBM in a very complex and difficult geology is presented in this study. The formations in the study area varied from alluvium, sludge, mudstone, shale and limestone to quartzite with strengths from soft to very hard. The dykes frequently intruded the sedimentary rocks resulting in different degrees of weathering and fracturing in the country rock causing tremendous delays in progress rate of the TBM. The disc cutters started cutting inefficiently in clayey medium strength ground with extreme water income, at where also excessive disc consumptions started due to insufficient friction between the disc cutters and very soft (sludgy) formation, and it was decided to replace all disc cutters with chisel tools (ripper, scraper). Before making this important decision that could affect totally the excavation efficiency and production rate, some theoretical estimations were performed using the Evans’ cutting theory after some modifications based on the previous experimental studies for relieved cutting mode and wear flat, front ridge and vee-bottom angles found in complex shapes of chisel tools to estimate deterministically the torque and thrust requirements of the TBM.Field measurements of the torque and thrust requirements of the TBM equipped with the chisel tools validated the theoretical considerations and the deterministic model used for predicting the performance. Statistical analysis indicated that the model could be used reliably for performance prediction. This study also gave a unique opportunity to compare the performance of disc cutters and chisel tools used on the same TBM at variety of grounds and to analyze the effect of replacing disc cutters with chisel tools on the performance of the TBM. The field measurements indicated that the chisel tools were superior to the disc cutters in especially soft to medium strength rocks.     

Assessment of odorous VOCs released from a main MSW landfill site in Istanbul-Turkey via a modelling approach

An air pollution modeling study was conducted to investigate the odorous effects of volatile organic compounds (VOCs) emissions from a sanitary landfill area on ambient air quality. The atmospheric dispersion of hydrogen sulfide (H₂S) and 22 VOCs was modeled. Industrial Source Complex v3 Short Term (ISCST3) model was used to estimate hourly concentrations of odorous VOCs over the nearest residential area. Odor thresholds of VOCs of interest were also found in the literature. Results showed that short-term averages of three odorous VOCs, namely ethyl mercaptan, methyl mercaptan and hydrogen sulfide, exceeded their odor thresholds, which are reported to be 0.022, 0.138 and 11.1 μg/m³, respectively, at several points within the domain. Their highest concentrations within Gokturk County were estimated to be 0.09387 μg/m³ for ethyl mercaptan, 0.07934 μg/m³ for methyl mercaptan and 6.315 μg/m³ for hydrogen sulfide. Short-term model results revealed the occasional odor problems being reported for Gokturk County. Hourly concentrations were used to obtain frequencies of odor episodes in Gokturk County via a probability analysis. The results showed that ethyl mercaptan concentrations did not exceed its odor threshold during more than 8.84% of the time. Similarly, the maximum odor episode frequencies for methyl mercaptan and hydrogen sulfide were 0.98% and 0.34% of the time, respectively.     

Disrupted temporal control in the R6/2 mouse model of Huntington’s disease.

Huntington’s disease is characterized by corticostriatal dysfunction and degeneration of the striatum with progressive loss of the medium spiny neurons. These circuits are important for instrumental responding, interval timing, and temporal control over motor output. We investigated the acquisition of timed operant responding in two R6/2 Huntington’s Disease models, differing in CAG repeat length and genetic background (115 and 250 CAG repeats, and a mixed CBAxC57 or pure C57 background) and their corresponding wild type controls using the peak procedure. Both mouse lines exhibited similar response control deficits. In unreinforced peak trials, mice either did not learn to terminate an ongoing response past reinforcement time or required more trials to acquisition compared to the wild type mice. While transgenic and wild type mice did not exhibit differences in temporal accuracy, response curves were flatter in transgenic mice, suggesting decreased temporal control over operant responding. The results are discussed in terms of the neurobiology of interval timing, instrumental responding, and the neuropathology of HD and R6/2 mice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Catalytic coating of virus particles with zinc oxide

We show that the rod-shaped Tobacco mosaic virus (TMV) can be coated with the wide band gap semiconductor zinc oxide by electroless deposition under mild reaction conditions. The process involves pretreatment with aqueous Pd(II), followed by nucleation of ZnO, directed to palladium centers formed on the surface of TMV. The mechanism is based on the local pH change due to the reduction of nitrate by dimethylamine borane at the palladium. Morphology and chemical composition have been analyzed by transmission electron microscopy (TEM) and by energy filtering TEM, respectively. The optical properties were elucidated by cathodoluminescence, which showed the desired near-band edge emission.     

Ultrastructure of male reproductive system of Eurydema ventrale Kolenati 1846 (Heteroptera: Pentatomidae)

The male reproductive system of Eurydema ventrale Kolenati 1846 is studied morphologically and histologically by using light, scanning and transmission electron microscopes. The reproductive system of the male E.ventrale consists of a pair of testis, a pair of vas deferens, a pair of seminal vesicles, accessory glands, a bulbus ejaculatorius, a pair of ectodermal sacs, and a ductus ejaculatorius. The testicular follicles have three different development zones (growth zone, maturation zone, and differentiation zone). The testes are connected to the seminal vesicles by the vas deferens that is a specialized in sperm storage. Sperm have an elongated head and a tail (flagellum) with an axonema and two mitochondrial derivatives. Vas deferens and seminal vesicles are fine, long, and cylindrical. The seminal vesicle is connected with bulbus ejaculatorius, which is balloon shaped and surrounded with accessory glands. The bulbus ejaculatorius is continuous with ductus ejaculatorius which is connected to the aedeagus. Microsc. Res. Tech. 78:643–653, 2015. © 2015 Wiley Periodicals, Inc.     

Oxidation Behavior of Bi(Pb,Ga) SrCaCuO System

A nominal compositions of BiSrCaCuO (3:2:2:3), (2:2:2:3), (4:3:3:4), and BiPbGaSrCaCuO (3:0.5:2:2:3), (3:0.3:0.3:2:2:3) have been prepared by conventional melt-quenching method. The oxidation behaviors of samples prepared were analyzed using a thermogravimetric analyser, TGA. Total mass gains of samples, average oxidation rates and maximum oxidation rates were calculated separately. TGA measurements of all samples were carried out under the normal atmosphere pressure.