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H.T.B.M. Petrus Tsuyoshi Hirajima Yuji Oosako Moriyasu Nonaka Keiko Sasaki Takashi Ando 《International Journal of Mineral Processing》2011,98(1-2):15-23
Cenospheres recovery is one of the coal fly ash beneficiations, providing economic as well as environmental benefits. Current techniques, such as lagoon or other wet-separation processes, consume large amounts of water and add to water pollution due to leaching of toxic materials from fly ash. The other possible disadvantage is the need for a wide operational area, which is unsuitable for densely populated countries. As wet-separation processes have some disadvantages, an improved and/or sustainable alternative recovery technique is required. An air classifier is one of the alternative techniques. In this study, two types of air classifiers, namely a closed-type pneumatic separator and a micron separator, have been investigated. In terms of separation efficiency, it was found that the micron separator has the potential to be applied in cenospheres recovery from coal fly ash, giving a Newton's efficiency of 0.44, as compared to a value of about 0.26 for the closed-type pneumatic separator. The cenospheres recoveries of both pieces of equipment at their optimum Newton's efficiencies were similar at over 60 wt.%. The separation performance was further assessed from the particle distributions of the overflow and underflow products obtained from both pieces of equipment, as well as from SEM images. It was found that the lower Newton's efficiency of the closed-type pneumatic separator was due to the re-concentration of fine particles in the underflow product at air-flow rates higher than 2.2 m/s (the underflow product yield was about 55 wt.%).In order to further confirm the applicability of this technique, the micron separator, which had provided higher separation efficiency and cenospheres recovery, was deployed in a cenospheres recovery unit prior to the use of a wet-separation process (float and sink tank). About 80% of the cenospheres was recovered, with an 87.8% reduction in the total mass of fly ash to be separated in the float and sink tank. Consequently, much less water was needed for the process of cenospheres recovery. Moreover, it was also confirmed that the micron separator could yield higher quality fly ashes, that is, fly ash types I and II, from lower feed quality of fly ash type IV, which is the lowest category in commercial classification of fly ash according to JIS A6201. 相似文献
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Marked fluctuation of concentrations of90Sr and137Cs was observed in the bottom waters at the entrance of Wakasa Bay during 1987–1992, and the cause was investigated. The concentrations of90Sr and137Cs in the bottom waters were significantly low when the upper level of the Japan Sea Proper Water (JSPW) was high and covered the sampling depth, but high when the upper level of the JSPW was low. The cause of the fluctuation observed in the bottom waters is, therefore, suggested to be the vertical fluctuation of the upper level of the JSPW on the shelf slope, which has been little described before. 相似文献
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Transport measurement with a horizontal and a vertical pipe microphone in a mountain stream: taking account of particle saltation 
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下载免费PDF全文 The pipe microphone has been shown to be an effective means for monitoring bedload transport in mountain streams. It is commonly installed perpendicular to the flow direction on a stable river bed, such as that of a check dam. Acoustic pulses caused by bedload collisions with the pipe are detected by a microphone. However, bedload particles saltating over the pipe remain undetected. To overcome this disadvantage, we installed a horizontal as well as a vertical pipe microphone in the Ashi‐arai‐dani supercritical channel located in the Hodaka mountain range, Japan. The vertical pipe was installed on the wall of the channel and the horizontal pipe was installed on the channel bed. The acoustic response of the horizontal pipe is expected to be larger than that of the vertical pipe, because the bedload concentration decreases with increasing height above the bed. However, at high amplifications, the peak pulse value from the vertical pipe is higher than that from the horizontal pipe. We explain this observation as follows: under high bedload discharge conditions, the pulses of the horizontal pipe are saturated but those of the vertical pipe are not. We proposed a ratio (Rhv) between the pulses detected by these sensors, and applied this ratio for calibrating the contemporaneous pulses detected by a microphone located immediately upstream of a bedload slot sampler. Indeed the Rhv‐corrected pulses correlated well with the bedload discharge calculated from the sampler, supporting our explanation. We conclude that bedload monitoring using concomitant vertical and horizontal pipe microphones can be used to calibrate centrally located pipe microphones when the bedload concentration is approximately homogeneous laterally across the width of the channel cross‐section, and thereby represent bedload discharges more accurately than with only a single pipe microphone. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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Beraki Asmerom F. Morioka Yushi Engelbrecht Francois A. Nonaka Masami Thatcher Marcus Kobo Nomkwezane Behera Swadhin 《Climate Dynamics》2020,54(11):4775-4792
Climate Dynamics - The study examines the influence of external climate forcings, and atmosphere–ocean–sea–ice coupled interaction on the Southern Hemisphere (SH) atmospheric... 相似文献
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Episode 48 of the ongoing eruption of Kilauea, Hawai`i, began in July 1986 and continuously extruded lava for the next 5.5 years from a low shield, Kūpaianaha. The flows in March 1990 headed for Kalapana and inundated the entire town under 15–25 m of lava by the end of August. As the flows advanced eastward, they entered into Kaimū Bay, replacing it with a plain of lava that extends 300 m beyond the original shoreline. The focus of our study is the period from August 1 to October 31, 1990, when the lava buried almost 406,820 m2 of the 5-m deep bay. When lava encountered the sea, it flowed along the shoreline as a narrow primary lobe up to 400 m long and 100 m wide, which in turn inflated to a thickness of 5–6 m. The flow direction of the primary lobes was controlled by the submerged delta below the lavas and by damming up lavas fed at low extrusion rates. Breakout flows through circumferential and axial inflation cracks on the inflating primary lobes formed smaller secondary lobes, burying the lows between the primary lobes and hiding their original outlines. Inflated flow lobes eventually ruptured at proximal and/or distal ends as well as mid-points between the two ends, feeding new primary lobes which were emplaced along and on the shore side of the previously inflated lobes. The flow lobes mapped with the aid of aerial photographs were correlated with daily observations of the growing flow field, and 30 primary flow lobes were dated. Excluding the two repose periods that intervened while the bay was filled, enlargement of the flow field took place at a rate of 2,440–22,640 square meters per day in the bay. Lobe thickness was estimated to be up to 11 m on the basis of cross sections of selected lobes measured using optical measurement tools, measuring tape and hand level. The total flow-lobe volume added in the bay during August 1–October 31 was approximately 3.95 million m3, giving an average supply rate of 0.86 m3/s. 相似文献
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Interannual-to-decadal variations in the subtropical countercurrent (STCC) and low potential vorticity (PV) water and their
relations in the North Pacific Ocean are investigated on the basis of a 60-year-long hindcast integration of an eddy-resolving
ocean general circulation model. Although vertically coherent variations are dominant for STCC interannual variability, a
correlation analysis shows that an intensified STCC vertical shear accompanies lower PV than usual to the north on 25.5- to
26.1-σθ isopycnal surfaces, and intensified meridional density gradient in subsurface layers, consistent with Kubokawa’s theory (J
Phys Oceanogr 29:1314–1333, 1999). The low-PV signals appear at least 2 years before peaks of STCC, propagating southwestward from the subduction region. 相似文献
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Seasonal variations of the Hawaiian Lee Countercurrent induced by the meridional migration of the trade winds 总被引：1，自引：0，他引：1
Hideharu Sasaki Shang-Ping Xie Bunmei Taguchi Masami Nonaka Yukio Masumoto 《Ocean Dynamics》2010,60(3):705-715
Seasonal variations of the Hawaiian Lee Countercurrent (HLCC) are investigated using satellite observations of sea surface
height and wind stress as well as eddy-resolving ocean model simulations. The HLCC is strong from summer to winter and weak
in spring between the dateline and the Hawaiian Islands. In response to the seasonal migration of the northeast trade winds
in the meridional direction, the wind curl dipole lee of Hawaii varies in strength, exciting westward-propagating Rossby waves.
The analyses of both observations and simulations show that the propagation of Rossby waves south of the HLCC, driven by the
southern pole of the wind curl dipole in the lee of the islands, contributes the most to the seasonal variations of the HLCC.
Unlike the wind-driven seasonal variations, our analysis suggests that other mechanisms such as mode water intrusion or air–sea
interaction may cause the interannual variations of the HLCC. 相似文献
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Shigeki?HosodaEmail author Shang-Ping?Xie Kensuke?Takeuchi Masami?Nonaka 《Journal of Oceanography》2004,60(5):865-877
The North Pacific Central Mode Water (CMW) is a water mass that forms in the Kuroshio-Oyashio Extension (KOE) region with
characteristic low potential vorticity. Recent studies have suggested that the CMW, as low potential vorticity water, plays
an important role in the adjustment of the subtropical gyre and subsurface variability on decadal to interdecadal timescales.
We have forced a realistic ocean general circulation model (OGCM) with observed wind stress and sea surface temperature (SST)
forcing to investigate the decadal variations of the CMW. Associated with the large atmospheric changes after the mid-1970s
climate regime shift, the upper thermocline experiences a cooling as negative SST anomalies in the central North Pacific are
subducted and advected southward. In addition to this thermodynamic response, the CMW’s path shifts anomalously eastward in
response to anomalous Ekman pumping. This eastward shift of the core of the CMW produces a lowering of the isotherms, and
a consequent warming, on the path of the CMW core. This warming partially counteracts the cooling associated with subducted
surface anomalies, and it may be responsible for the reduced temperature variations at the climatological position of the
CMW when both anomalous wind and heat fluxes are given. Lateral induction across the sloping bottom of the winter mixed layer
in the KOE is critical to the formation of the low potential vorticity CMW. Coarse resolution models, which are widely used
in climate modeling, underestimate the horizontal gradient of the mixed layer depth and form only a weak CMW or none at all.
We have conducted a coarse resolution experiment with the same OGCM, showing that the subsurface response is much reduced.
In particular, there is no dynamic warming in the CMW and the thermodynamic response to the SST cooling dominates. The resultant
total response differs substantially from that in the finer resolution run where a strong CMW forms. This sensitivity to the
model resolution corroborates the important dynamical role that the CMW may play with its distinctive low potential vorticity
character and calls for its improved simulation. 相似文献