STATISTIČKA ANALIZA UTJECAJA KONTROLIRANIH I NEKONTROLIRANIH PARAMETARA NA RAD DIJAMANTNOM ŽIČNOM PILOM, PRIKAZ SLUČAJA

Nowadays, most mining and quarrying industries utilize a diamond wire saw machine for bench cutting operations. This method uses a metal wire or cable assembled by diamond beads to cut the hard stone into large blocks. Many parameters classified into controllable and uncontrollable parameters affect the performance of the diamond wire saw cutting method. The uncontrollable parameters are related to rock engineering properties, and controllable parameters are related to operational aspects and machine performance. The diamond wire sawing process’s production rate is one of the most critical parameters influencing the design optimization and quarrying cost estimation. The cutting rate and wear rate of diamond beads are the most important factors to evaluate quarries’ production performance. This study aims to determine the effects of different controllable and uncontrollable parameters on different quarries’ production rates. Rock engineering properties like strength, hardness, and abrasivity, and operational aspects, such as cutting angle and drive wheel diameters, are considered as the main factors affecting the production performance of the diamond wire saw method. To discover the influence of these parameters, a detailed investigation in ten quarry operations was carried out. The relation between cutting rate and diamond bead wear with different parameters is estimated. It was observed that different controllable and uncontrollable parameters could increase or decrease the cutting rate and diamond bead wearing. Furthermore, using simple and multiple regression analysis, performance prediction of the cutting rate and wearing of diamond beads was developed, and the best equations were proposed.Danas se u najvećemu broju rudnika i kamenoloma upotrebljava dijamantna žična pila za razne operacije na čelima radilišta. Uporabom metalne žice (ili kabela) na koju su dodani dijamantni zupci mogu se rezati veliki blokovi arhitektonsko-građevnoga kamena. Pri tomu rezanje ovisi o nizu parametara od kojih se neki mogu, a neki ne mogu kontrolirati. Oni koji se ne mogu kontrolirati jesu inženjerska svojstva stijena, a oni koji se mogu kontrolirati jesu operativne varijable i svojstva stroja. Iznos rezanja/proizvodnje najkritičnija je varijabla prema utjecaju na iznos proizvodnje. Svojstva stijena kao čvrstoća, tvrdoća i abrazivnost te operativne vrijednosti poput kuta rezanja, promjera pogonskoga kotača najvažnije su varijable koje utječu na proizvodnju žičnih pila. Procijenjen je odnos između brzine rezanja i trošenja dijamantnih zubaca i opaženo je kako različite varijable utječu na povećanje ili smanjivanje iznosa proizvodnje. Analizirane su metodama jednostavne i višestruke regresije, uključivši sve spomenute varijable, te su predložene jednadžbe kojima se opisuju opažene pojave

Si Waveguide Technology for High Performance Millimeter-Wave/Terahertz Integrated Systems

The terahertz (THZ) spectrum (0.3 – 3 THz) offers new opportunities to a wide range of emerging applications which demand high-quality THz sources, detectors, amplifiers, and integrated circuits. On-chip integration of planar transmission line passive components degrades their performance due to the conduction loss. Therefore, a hybrid integrated technology in which all of the high-quality passive components are implemented using a suitable off-chip planar integrated technology and the active devices are placed on-chip, has become the most promising approach. In this thesis, a low-cost and low-loss silicon-on-glass (SOG) integrated circuit technology is proposed for THz/millimeter-wave (mmW) applications. Highly-resistive intrinsic silicon (Si) is selected as the main guiding region due to its high transparency at mmW/THz frequency ranges and the maturity of Si-devices fabrication. In the proposed technology, all of the passive components and waveguide connections are made of highly-resistive Si on a glass substrate. The proposed technique leads to a high-precision and low-cost fabrication process, wherein the alignment between the sub-structures is automatically achieved during the fabrication process. This is performed by photolithography and dry etching of the entire integrated passive circuit layout through the Si layer of the SOG wafer. The SOG dielectric ridge waveguide, as the basic component of the SOG integrated circuit, is theoretically and experimentally investigated. A test setup is designed to measure propagation characteristics of the proposed SOG waveguide. Measured dispersion diagrams of the SOG dielectric waveguides show average attenuation constants of 0.63 dB/cm, 0.28 dB/cm, and 0.53 dB/cm over the frequency ranges of 55 – 65 GHz, 90 – 110 GHz, and 140 – 170 GHz, respectively. Extending the SOG platform toward the THz range is achieved by new SOG waveguide structures wherein the glass substrates below the Si channels are etched to reduce the effect of greater glass material loss at higher frequencies (i.e., > 200 GHz). To fabricate these structures, the glass substrate is etched in hydrophilic acid before bonding to the Si. Four new SOG configurations, called the suspended SOG, corrugated SOG, rib SOG, and U-SOG waveguides are proposed with their respective fabrication techniques for the THz range of frequencies. In the suspended SOG waveguide, a periodic configuration of Si beams supports the Si guiding channel over the etched grove on the glass substrate. Measurements of two suspended SOG waveguides show low attenuation constants of 0.031 dB/λ0 and 0.042 dB/λ0 (on average) over the frequency ranges of 350 - 500 GHz and 400 - 500 GHz, respectively. It is theoretically demonstrated that the rib SOG and U-SOG waveguides are promising candidates for THz high-density and low-loss integrated circuits. Rib SOG waveguide and U-SOG waveguide test devices are designed over the frequency bands of 0.8 – 0.9 THz and 0.9 – 1.1 THz. The proposed SOG waveguide technology can easily be extended to several THz with no limitations. A new mmW low-loss dielectric phase shifter integrated in the corrugated SOG platform is designed, fabricated, and measured. Phase shifts of 111 ° and 129 ° at frequencies of 85 GHz and 100 GHz, with maximum insertion losses of 0.65 dB and 2.5 dB, are achieved during measurements of the proposed phase shifter. Millimeter-wave integrated SOG tapered antennas are developed and implemented. The idea of a suspended SOG tapered antenna is demonstrated to enhance the radiation efficiency and the gain of the SOG tapered antenna over 110 – 130 GHz. The suspended SOG tapered antenna, which can function under two orthogonal mode excitations, shows measured efficiencies of higher than 90 % for the two vertical polarizations

Computational studies of history-dependence in nematic liquid crystals in random environments

Glassy liquid crystalline systems are expected to show significant history-dependent effects. Two model glassy systems are the RAN and SSS (sprinkled silica spin) lattice models. The RAN model is a Lebwohl-Lasher lattice model with locally coupled nematic spins, together with uncorrelated random anisotropy fields at each site, while the SSS model has a finite concentration of impurity spins frozen in random directions. Here Brownian simulation is used to study the effect of different sample histories in the low temperature regime in a three-dimensional (d=3) model intermediate between SSS and RAN, in which a finite concentration p<pc (pc the percolation threshold) of frozen spins interacts with neighboring nematic spins with coupling W. Simulations were performed at temperature T?TNI/2 (TNI the bulk nematic-isotropic transition temperature) for temperature-quenched and field-quenched histories (TQH and FQH, respectively), as well as for temperature-annealed histories (AH). The first two of these limits represent extreme histories encountered in typical experimental studies. Using long-time averages for equilibrated systems, we calculate orientational order parameters and two-point correlation functions. Finite-size scaling was used to determine the range of the orientational ordering, as a function of coupling strength W,p and sample history. Sample history plays a significant role; for given concentration p, as disorder strength W is increased, TQH systems sustain quasi-long-range order (QLRO) and short-range order (SRO). The data are also consistent with a long-range order (LRO) phase at very low disorder strength. By contrast, for FQH and p?0.1, only LRO and QLRO occur within the range of parameters investigated. The crossover between regimes depends on history, but in general, the FQH phase is more ordered than the AH phase, which is more ordered than the TQH phase. However, at temperatures close to the isotropic-nematic phase transition of pure samples we observe SRO for p=0.1 even for FQH. We detect also in the QLRO phase a domain-type structural pattern, consistent with ideas introduced by Giamarchi and Doussal [Phys. Rev. B 52, 1242 (1995)] on superconducting flux lattices. In the weak-disorder limit the orientational correlation length obeys the Larkin-Imry-Ma scaling ??D?2/(4?d)

Maksimiziranje efikasnosti rudarenja u kamenolomu, prikaz studije slučaja

Nowadays, the dimension stone industry performs a crucial role in the world economy. Accordingly, dimension stone quarries’ importance grows due to their different applications in various construction, building, and decorative industries. Some issues threaten this industry and provide a financial risk that should be taken into account to make the smallest possible risk for investment. The presence of discontinuities in the rock mass has a key function as far as it concerns the overall quality of in situ rock blocks. It impacts the feasibility of dimension stone quarries and overall mine exploitation efficiency. Therefore, it is recommended to survey discontinuities and rock blocks and estimate the average geometry of a rock block, including the shape and size, before mining the benches to maximize mining exploitation efficiency and minimize waste ore production. This investigation aims to survey the discontinuities of the limestone quarry mine located in Josheghan, Iran, to determine and calculate rock blocks’ suitable geometry and an extraction’s direction for active mine benches. For this purpose, the scanline method was applied to survey discontinuities in seven active benches. 3DEC software was used to indicate discontinuities and model the rock blocks for all active benches. It was concluded that the benches’ cutting line make a 13.14 degree with the discontinuities main’s direction. The result of this study proved that by changing the direction of mining and extraction for active mine benches, the unnecessary waste production would decrease. The production rate with the recommended extraction direction will increase by about 1.13% compared to the current extraction direction, which makes 13.14 degrees with the discontinuities main’s direction. Currently, bench seven recorded the minimum production rate, which is 97.60; by applying the new extraction’s direction, it is predicted that this bench will achieve a 99.83 production rate. Consequently, it is concluded by improving the production rate, exploitation efficiency would increase considerably.Danas industrija arhitektonsko-građevnoga kamena zauzima važno mjesto u svjetskoj ekonomiji. Time raste i važnost kamenoloma. Postoje također i rizici povezani s takvim aktivnostima, posebice financijski. Nazočnost pukotina u stijenskoj masi može biti glavni rizik među njima, jer one ruše kvalitetu kamena, a time utječu na iskoristivost kamenoloma. Stoga je vrlo važno istražiti pukotine, stijenske blokove, njihovu geometriju i dimenzije prije otkopavanja, kako bi se podigla iskoristivost i smanjila količina jalovine. Ovdje su izučene pukotine u kamenolomu vapnenca u Josheghanu, Iran. Izračunana je odgovarajuća geometrija stijenskih blokova važna za eksploataciju. Metodom Scanline predviđene su pukotine na sedam radilišta, a paketom 3DEC za cijeli kamenolom. Izračunano je kako se smjer otkopavanja treba projicirati s otklonom od 13,14 stupnjeva u odnosu na glavni smjer pružanja pukotina. Dokazano je kako se promjenom smjera rudarenja povećava i udjel jalovine. No, rudarenjem pod navedenim kutom povećat će se pridobivanje za 1,13 % u usporedbi s trenutačnim. Na radilištu broj sedam zabilježena je minimalna proizvodnja od 97,60, a primjenom ovih rezultata očekuje se dosizanje vrijednosti od 99,83. Na taj način moguće je znatno povećati proizvodnju i iskoristivost

History-Dependent Patterns in Randomly Perturbed Nematic Liquid Crystals

We study the characteristics of nematic structures in a randomly perturbed nematic liquid crystal (LC) phase. We focus on the impact of the samples history on the universal behavior. The obtained results are of interest for every randomly perturbed system exhibiting a continuous symmetry-breaking phase transition. A semimicroscopic lattice simulation is used where the LC molecules are treated as cylindrically symmetric, rod-like objects interacting via a Lebwohl-Lasher (LL) interaction. Pure LC systems exhibit a first order phase transition into the orientationally ordered nematic phase at T=Tc on lowering the temperature T. The orientational ordering of LC molecules is perturbed by the quenched, randomly distributed rod-like impurities of concentration p. Their orientation is randomly distributed, and they are coupled with the LC molecules via an LL-type interaction. Only concentrations below the percolation threshold are considered. The key macroscopic characteristics of perturbed LC structures in the symmetry-broken nematic phase are analyzed for two qualitatively different histories at T≪Tc. We demonstrate that, for a weak enough interaction among the LC molecules and impurities, qualitatively different history-dependent states could be obtained. These states could exhibit either short-range, quasi-long-range, or even long-range order

Fracture resistance of endodontically treated maxillary incisors restored with single or bundled glass fiber-reinforced composite resin posts

To compare the fracture resistance of endodontically treated maxillary incisors restored with single versus bundled glass fiber-reinforced composite resin posts (FRC). Twenty-four maxillary incisors underwent root canal preparation (1.5-mm-diameter pos