Concentration of K-feldspar from a pegmatitic feldspar ore by flotation

Abundant reserves of Na-feldspar (albite) and K-feldspar (orthoclase or microcline) are found in granites, syenite, tracite and pegmatites. As both feldspar minerals have similar chemical structure and physicochemical properties, their separation is challenging. Flotation is known to be the only technique to enable their separation. The fundamentals on the separation of these minerals were well documented in our earlier studies. In this study, a pegmatite ore with a K₂O/Na₂O (3.78:3.37) ratio of 1.12 was studied in a Denver flotation cell both at natural and acidic pH using HF and H₂SO₄. Because of the perthitic structure of the ore no significant separation is observed at natural pH. Interestingly, a selective separation was achieved at low pH using HF and H₂SO₄ (pH 2.5–2.8). The selectivity is induced by the addition of Na⁺ ions through depression of albite. Selective separation has been carried out by stagewise flotation using the tree technique. Accordingly, a pegmatite ore composed of 3.37% Na₂O and 3.78% K₂O is upgraded to 10.51% K₂O and 3.02% Na₂O with a K₂O/Na₂O = 3.48 in HF medium and to 2.55 in H₂SO₄ medium. It is shown that products recovered in other stages are also considered as commercially significant. Especially, quartz, which is recovered in the tailings in HF medium, is suitable for glass industry. The overall results show that commercial utilization of these results is possible.     

Experimental constraints on the volatility of germanium,zinc, and lithium in Martian basalts and the role of degassing in alteration of surface minerals

The surface of Mars is enriched in Cl and S which is linked to volcanic activity and degassing. Similarly, elevated Ge and Zn levels in Gale crater sedimentary bedrock indicate a magmatic source for these elements. To constrain the relative effects of Cl and S on the outgassing of these trace metals and chemical characteristics of primary magmatic vapor deposits incorporated to Martian surface, we conducted a set of degassing and fumarolic alteration experiments. Ge is found to be more volatile than Zn in all experiments. In S-bearing runs, the loss of Ge and Zn was less than any other experiments. In Cl-only runs, degassing of Zn was more than twice that of Ge within the first 10 min and percent loss increased for both elements with increasing time. In Cl + S runs, S-induced reduction of GeO₂ and ZnO to metallic Ge and Zn switches the preference of chloride formation from Zn to Ge. Up to 90% of Ge and Zn loss in the 1-h no volatile-added (NVA) experiments might be due to the small amounts of Cl contamination in NVA mixes via other oxides used for synthesis. Alteration experiments show different phases between 1-h and 24-/72-h runs. In 1-h runs, anhydrite and langbeinite dominate while in 24-/72-h runs halite and sylvite dominate the condensate assemblages. S-bearing phases form as the intermediate products of fumarolic deposition, while chlorides are common when the system is allowed to cool gradually. One-hour exposure was sufficient to form alteration phases and vapor deposits such as NaCl, KCl, CaSO₄, and langbeinites on the Martian analog minerals. These salts were identified in Martian meteorites and in situ measurements. Our results provide evidence that volcanic degassing along with fumarolic alteration could be a potential source for the enrichment and varying abundances of Cl, S, Fe, Zn, Ge in Martian surface, as well as a cause for Ge depletion in shergottites.     

Calculation of wave-induced turbulent flows in estuaries

The k-ε turbulence model which relates the eddy viscosity to turbulent kinetic energy, k, and to the rate of its dissipation, ε, and determines the distribution of these two quantities from modeled transport equations, is employed in calculating the vertical structure of wave-induced turbulent flows in two-dimensional estuaries. The empirical constants in this model are given the standard values cited in the literature and used successfully for calculating a large variety of steady flows; they are not tuned to the oscillating flows. The free surface elevation and the eddy-viscosity distribution are also calculated as a part of the solution. First, calculations performed for oscillatory laminar flows are compared with analytic solutions to ensure the proper performance of the numerical scheme. The turbulent flow in a laboratory-estuary model with one end closed, and in the Humber Estuary is simulated with the numerical model, and the results are compared with the corresponding flume and field measurements. The influence of frequency and roughness is thereby investigated. The results indicate that the time and space variation of the velocity field and the phase lag between the surface slope and the horizontal velocity can be predicted satisfactorily in wave-induced turbulent flows.     

Experimental and numerical studies on buckling restrained braces with posttensioned carbon fiber composite cables

There has been an increasing interest in using residual deformation as a seismic performance indicator for earthquake resistant building design. Self-centering braced structural systems are viable candidates for minimizing residual deformations following a major earthquake. Hence, this study proposes an alternative type of buckling restrained brace (BRB) with externally attached posttensioned (PT-BRB) carbon fiber composite cables (CFCCs). The steel core of the brace is used as an energy dissipator, whereas the CFCCs provide the self-centering force for minimizing residual story drifts. Three proof-of-concept specimens are designed, fabricated, and cyclically tested at different posttensioning force levels. The CFCC behavior to obtain cyclic response, including the anchorage system, is examined closely. A parametric study is also conducted to show the effect of the different configurations of PT-BRBs on the inelastic response. Furthermore, optimal brace parameters are discussed to realize design recommendations. The results indicated that the implementation of partially self-centering BRBs in building frames can lead to the target residual displacements. A stable behavior is obtained for the proposed PT-BRBs when subjected to the loading protocol specified in the American Institute of Steel Construction (AISC) 2016 Seismic Provisions.     

Evaluating Surface Runoff Responses to Land Use Changes in a Data Scarce Basin: a Case Study in Palas Basin,Turkey

Water Resources - In this study, hydrologic regimes of the Palas basin have been investigated with land use/land cover (LULC) change. To investigate the relationship between precipitation and...     

Spring tube braces for seismic isolation of buildings

A new low-cost seismic isolation system based on spring tube bracings has been proposed and studied at the Structural and Earthquake Engineering Laboratory of Istanbul Technical University. Multiple compression-type springs are positioned in a special cylindrical tube to obtain a symmetrical response in tension and compression-type axial loading. An isolation floor, which consists of pin-ended steel columns and spring tube bracings, is constructed at the foundation level or any intermediate level of the building. An experimental campaign with three stages was completed to evaluate the capability of the system. First, the behavior of the spring tubes subjected to axial displacement reversals with varying frequencies was determined. In the second phase, the isolation floor was assessed in the quasi-static tests. Finally, a ¼ scaled 3D steel frame was tested on the shake table using actual acceleration records. The transmitted acceleration to the floor levels is greatly diminished because of the isolation story, which effects longer period and higher damping. There are no stability and self-centering problems in the isolation floor.     

Boundary-layer development on circular cylinders

Mean-velocity measurements were made in the boundary layer on a smooth circular cylinder fitted with trip wires to model supercritical flow. The data are compared with the predictions of a boundary-layer calculation method to study the relative influence of surface curvature and low-Reynolds-number effects, and to assess the accuracy with which the location of separation can be determined. It is shown that the effects of surface curvature are most important close to separation while those of low Reynolds numbers are significant everywhere except near separation.     

An experimental model application of wavescreen: Dynamic pressure, water particle velocity, and wave measurements

This paper analyses the results of an application of a piled wavescreen. Experimental measurements were undertaken in the laboratory conditions for a given structural configuration under the attack of regular and irregular waves. Dynamic pressure distribution along and around the inclined piles was obtained employing pressure transducers. Using these data, in-line dynamic wave forces acting on piles were also determined. Water particle (orbital) velocities were measured at seaward and landward of the wavescreen using two acoustic Doppler velocimeters (ADV) simultaneously. Furthermore, wave data were collected using resistance type wave gauges at the seaward and landward of the structure. Based on those data, wave attenuation performance of the wavescreen was explored for two different depth values. Findings showed that piled wavescreen can provide effective shore protection as an environmentally friendly coastal structure.     

Elimination of effects of earthquake in monitoring crustal movement

Monitoring crustal movements is important in understanding the earth surface and in developing theories about plate tectonics. Plate tectonics describes earth crust which consists of a number of plates moving relative to one another. Global plate models suggest that plate movements are constant due to the fact that relative movements of plates were represented by averaged plate motion. However, if an earthquake occurs, the uniform movement of related plates does not follow the regular trend. In analysis by Kalman Filter, the effects of an earthquake occured within crustal movement monitoring period by geodetic method have been eliminated by a proposed approach, Fading Memory Filter. The proposed method was tested using a real/simulated data. The results of the test showed that the effect of a strong earthquake (M_w = 7.1) which had occurred in the Gulf of Eilat/Aqaba was eliminated. Consequently, the proposed method is capable of removing or eliminating a suddan effect in monitoring crustal movements in the analysis by using the Kalman Filter.