Ege linyitleri işletmesi (ELİ) Eynez yeraltı ocağı mekanize uzunayak panosu tavan kömürü üretiminin sayısal modellemesi

Boren;DEMiR Export;et al;metso Expect results;Outotec;TMMOB Maden Muhendisleri Odasi23rd International Mining Congress and Exhibition of Turkey, IMCET 2013 -- 16 April 2013 through 19 April 2013 -- Antalya -- 105453Effective caving of top coal is the most critical factor in maintaining an efficient production in longwall with top coal caving method. During production of the top coal by caving, considerable amount of coal may be left in the goaf and in addition, the produced coal may be diluted with rock, consequently, decreasing the extraction ratio and production efficiency. In this study, numerical studies associated with numerical modelling of Eynez Underground Mine have been carried out. Firstly, the longwall panel was modelled by using a software called FLAC3D, developed based on finite difference technique. Secondary, the induced stresses developing around the longwall face have been determined. Finally, the most critical step of production that is top coal caving through the frames of shields has been modelled. In Eynez Underground Mine, top coal was sufficiently fractured but the marl at the roof was not fractured and there occurred a big opening after caving of top coal. In order to achieve efficient and quick production, the marl must be cracked in as uniformly sized pieces as possible

Determination of reactional cutting forces on a circular sawblade machine by using experimental studies and numerical modelling

WOS: 000300455700019Slab/strip production from blocks in natural stone processing plants is mostly carried out by using circular sawblade cutting machines. An efficient sawing operation can only be maintained by selecting proper cutting parameters. Experimental studies and numerical modelling methods are significant in terms of identifying the effective forces occurring during natural stone cutting with circular sawblades. In this study, experimental investigation was performed on real marble, known as Afyon White Marble, using a fully automatic circular sawblade stone cutting machine. Then, numerical modelling of circular sawing was performed with commercially available software called PFC3D. A discrete-element model of the sawing process was developed, and various numerical models were performed for different peripheral speeds and advance rates in compliance with the actual cutting operation being carried out in the laboratory. Finally, data obtained from the experimental studies were compared with the modelling data. A comparison indicates that the reactional cutting forces obtained by means of the numerical modelling are in good agreement with the results of the laboratory measurements. Consequently, the cutting operation can be determined quickly and economically. A literature review showed that, through this study, numerical modelling of the circular sawblade stone cutting process was successfully performed for the first time. It was envisaged that this would dynamically help in the examination of distinct factors in the area of natural stone processing by numerical modelling and in the illustration of the sawing mechanism.TUBITAK [104M384]This work was supported by the TUBITAK project [grant number 104M384], named Sawability Classification of Some Natural Stones with Circular Sawing and Numerical Modeling of Sawing Mechanism

Effect of Acidulated Phosphate Fluoride and Casein Phosphopeptide-Amorphous Calcium Phosphate Application on Shear Bond Strength of Orthodontic Brackets

Objective: To evaluate the effect of a recently introduced prophylactic agent, casein phospho-peptide-amorphous calcium phosphate (CPP-ACP), on shear bond strength of brackets and compare it with the effect of acidulated phosphate fluoride (APF). Materials and Methods: Forty-eight freshly extracted mandibular bovine incisors were used. Teeth were randomly divided into four groups (n = 12) as follows: group 1 served as control, and no pretreatment was performed on the enamel; group 2, enamel was treated with 1.23% APF and CPP-ACIP, respectively; group 3, enamel was treated with CPP-ACP; and group 4, enamel was treated with 1.23% APF for 4 minutes. In all groups, brackets were bonded using a conventional acid-etch and bond system (Transbond XT, 3M Unitek, Monrovia, Calif). Bonded specimens were first stored in deionized water at 37 degrees C for 24 hours, subjected to thermal cycling for 1000 cycles, and further stored in distilled water for 6 weeks before debonding procedures. After debonding, teeth and brackets were examined under a stereomicroscope at 10x magnification for any adhesive remaining, in accordance with the modified adhesive remnant index. Results: The shear bond strengths of all experimental groups were significantly higher than that of the control group (P .05). Conclusion: The use of CPP-ACP either alone or combined with APF could be considered as an alternative prophylactic application in orthodontic practice since it did not compromise bracket bond strength.WoSScopu