Flat Basin Research Articles

Effects of Pressure on Nitrogen Content and Solidification Structure during Pressurized Electroslag Remelting Process with Composite Electrode

The nitrogen content and solidification structure of the 1Mn18Cr18N ingots produced by the customized laboratory‐scale vacuum induction melting furnace and the pressure electroslag remelting furnace (PESR) with novel composite electrode under different pressure and the same power consumption are compared and studied. The results show that there are perfectly uniform radial chromium and nitrogen profiles during the PESR process. The nitrogen uptake reaction in the PESR process with composite electrode takes place on the liquid metal film on the electrode. Nitrogen uptake could be improved by increasing the nitrogen partial pressure. In addition, the basin depth at a pressure of 0.1 and 1.22 MPa is about 41 and 38 mm, the angle of the grains with respect to the vertical axis is 35° and 31°, respectively. The flat metal basin profile resulted from the thermal resistance at the slag–mold interface decreasing with increasing pressure. Primary and secondary dendritic arm spacing (PDAS and SDAS) variations exhibit an increasing and subsequently decreasing the trend as they move further away from the center in a horizontal direction. Both PDAS and SDAS decrease with increasing pressure from 0.1 to 1.22 MPa.

Testing the performance of tubular solar still with flat basin, cords wick basin, and various angle of inclinations

Freshwater scarcity is a growing concern due to population expansion and industrial development. Solar stills offer a solution for generating potable water, although production volumes are limited. This research aims to address this challenge by improving the yield, thermal efficiency, and cost-effectiveness of freshwater production in tubular solar stills (TSS). We propose a novel approach that incorporates wick materials within the TSS design. This method involves creating a specific number of cuts (cracks) in a secondary basin liner positioned 2.5 cm above the original liner within the still. The upper liner is extended with wick, and wicking cords are suspended from edges and openings of this liner. These cords continuously remove saltwater, ensuring a consistently moist wick surface. The design of the wick cords optimizes water utilization and minimizes energy waste. The cords extract precisely the amount of saline water needed for evaporation, eliminating the loss or overflow of hot water. This approach maximizes wick efficiency without sacrificing freshwater production. The study investigates the performance of the TSS using 32 wick cords in conjunction with jute wick material. This modification to the conventional TSS offers a simple and cost-effective method to enhance productivity. Additionally, the glass cover of the still is tilted at an angle to facilitate the collection of distilled water droplets. ICWTSS was used as a code name for the modified TSS. After that, three distinct inclination angles (2°, 4°, and 6°) were examined, and the effectiveness of ICWTSS at each angle was contrasted with that of CSS. With a 6° angle of inclination, the ICWTSS showed a 67 % thermal efficiency and a 257 % increase in production over CSS.

ТЕРМИЧЕСКАЯ ИСТОРИЯ ФОРМИРОВАНИЯ КРИОЛИТОЗОНЫ В ОСАДОЧНОМ РАЗРЕЗЕ ТЮМЕНСКОЙ СВЕРХГЛУБОКОЙ СКВАЖИНЫ СГ-6

The thermal evolution of the permafrost in the sedimentary section of the Tyumen superdeep SG-6 well has been numerically reconstructed using the ICE2020 software package, which is part of the GALO flat basin modeling system. The thermal evolution of the sedimentary strata in the last 3.5 My is considered as the final stage of the basin modeling, whose formation began with continental rifting in the Late Permian. Abrupt climate changes in the late Pliocene-Holocene led to a decrease in the rock temperature by 15-20°C in the upper 1-1.5 km of the SG-6 sedimentary section. The maximum thickness of the permafrost in the study area was about 711 m, reached 2.6 Mya. The maximum thickness of the permafrost for the last ice age (23-18 thous and years ago) was 412 m, reached about 14.5 thousand years ago. According to our modeling, the modern base of the permafrost is at the depth of 311 m and is degrading with the rate about 13 m/1000 y. The results of our calculations with a database of climatic data limited to the last 50 and 100 thousand years differ markedly from the modeling results with the complete database for the last 3.5 My.

Performance assessment of a novel solar distiller with a fountain-shaped basin design embedded with phase change materials enriched with copper oxide nano-additives: A detailed experimental investigation

This study uses a novel structure of a dome-shaped solar distiller (DSD) with a stepped conical absorbent basin with multi-trays instead of the typical flat absorbent basin solar stills to enhance the evaporation and exposure areas. Moreover, a fountain seawater feed supply system is also centrally integrated into the developed basin to reduce the saltwater film thickness on the stepped conical trays for enhancing the heating processes of seawater over the trays' surfaces. Meanwhile, a phase change material enriched with CuO nanoparticles (NCPCM) is also embedded inside the hollow multi-tray stepped conical basin to prolong the distiller's nightly yield. Three DSDs are piloted and investigated: a dome-shaped solar distillatory with a fountain feed supply and nanocomposite (DSD-FFS + NCPCM), a dome-shaped solar distillatory with a fountain feed supply (DSD-FFS), and reference dome-shaped solar distiller (RDSD). The findings showed that the daily product output was 7.21 kg/day/m2 for DSD-FFS + NCPCM and 6.84 kg/day/m2 for DSD-FFS. In contrast, the RDSD achieved a daily product output of 4.44 kg/day/m2. This represents a significant improvement of 62.38 % and 54.05 % for DSD-FFS + NCPCM and DSD-FSS, respectively, over RDSD. Furthermore, the daily energic efficacity for DSD-FFS + NCPCM and DSD-FFS was evaluated at 62.42 % and 60.40 %, respectively, indicating an augmentation rate of 59.61 % and 53.56 % over RDSD. More so, the distiller exergy efficiency for DSD-FFS + NCPCM and DSD-FFS reached 4.16 % and 3.59 %, respectively, signifying an increase percentage of 123.66 % and 98.39 % over RDSD. Additionally, the cost analysis revealed that the price per 1 kg of distillate of the DSD-FFS + NCPCM and DSD-FFS declined by 18.48 % and 16.13 % over RDSD.

Optimization and thermo-economic assessment of hemispherical solar distillers with a flat and concave basin: Experimental approaches

One of the challenging issues facing the world today is a lack of clean drinking water. The straightforward and efficient solution to this problem is the use of solar stills, which is one of the solar desalination methods that use renewable energy. The design selection of the solar stills is one of the strategies for distillate optimization, which aims to increase the productivity of solar distillates. To achieve this idea, this study deals with a comparative performance analysis of two solar stills with the same hemispherical cover, one contains a flat basin and the second contains a concave basin. Two hemispherical solar distillers, one of which has a flat basin (HSD-FB) and the other has a concave basin (HSD-CB) were designed and tested in El Oued, Algeria, under the same climatic conditions to get the better design of basin solar distillers. The results showed that the concave basin represents the best design that achieved the highest performance of hemispherical solar distillers. The daily productivity of the hemispherical solar distiller with a concave basin (HSD-CB) reached 5.50 kg/m3 with an improvement of 23.59% compared to HSD-FB. Also, with the utilization of the concave basin (HSD-FB), the daily thermal efficiency increased from 37.69% to 46.43% with an improvement of 23.19% compared to HSD-FB.

Interaction of planting system with radiation-use efficiency in wheat lines.

Radiation-useefficiency (RUE) is animportant trait for raising biomass and yield potential in plant breeding. However, the effect of the planting system (PS) on genetic variation in RUE has not been previously investigated. Our objectives were to quantify genetic variation in RUE, biomass and grain yield in raised-bed and flat-basin planting systems, and associations with canopy-architecture traits (flag-leaf angle and curvature). Twelve spring wheat (Triticum aestivum L.) cultivars were evaluated under irrigated conditions for 3 years in North West Mexico using raised-bed and flat-basin planting systems. Canopy architecture traits were measured at booting and anthesis + 7 days. Grain yield (10.6%), biomass (7.6%), and pre-grain-filling RUE (9.7%) were higher in raised beds than flat basins, while a significant planting system × genotype interaction was found for grain yield. Genetic variation in pre-grain-filling RUE was associated with biomass and grain yield in beds and basins. In flat basins, higher pre-grain-filling RUE was correlated with a more upright flag-leaf angle but not in raised beds. In raised beds, cultivars with less upright flag-leaf angle had greater fractional light interception pre-anthesis. Taller semi-dwarf cultivars intercepted relatively more radiation in the beds than the flats before anthesis, consistent with the taller cultivars showing relatively greater increases in yield in beds compared to flats. Our results indicated that the evaluation of genotypes for RUE and biomass in wheat breeding should take into account planting systems to capture genotype × PS effects. In addition, the results demonstrate how flag-leaf angle has a different effect depending on the planting system.

Employing a vertical wick, reflector, and Nano phase change material to improve the thermo-economic performance of a tubular solar still

There is an increasing lack of drinkable water as a result of increased industry and population expansion, which has prompted scientists to arise with creative solutions to this demand. Solar stills are capable of producing drinkable water; however, they don't produce a lot of it. The objective of this study is to augment the yield, improve the thermal performance, and lower the price of the distillate produced by a tubular solar still (TSS). The effects of three modifications on thermo-economic performance of TSS systems have been studied and compared with a conventional solar still (CSS). The TSS has first been tested using a flat basin absorber, which shows 47 % thermal efficiency and 85 % higher productivity (5750 ml/m2) than a CSS (3100 ml/m2). In a second test, vertical wick (VWTSS) was used in place of a flat basin. The VWTSS displayed a 57.3 % thermal efficiency and a 155 % better productivity (8300 ml/m2) than CSS (3250 ml/m2). Thirdly, a back reflector was used to test the VWTSS. The productivity of the VWTSS with mirror (9350 ml/m2) showed 183 % higher than that of CSS (3300 ml/m2). Therefore, using a backside mirror causes the VWTSS output to increase by 28 % compared to the VWTSS without mirror. And the VWTSS with mirror has a 61 % thermal efficiency. Finally, using Nano-PCM, the VWTSS with mirror has been put to the test. As a result, the VWTSS demonstrated 209 % greater productivity (9900 ml/m2) than CSS (3200 ml/m2). The use of Nano PCM increased VWTSS productivity with mirror by 26 % compared to the VWTSS with mirror. The environmental parameter of VWTSS with modifications is 34.8 tons CO2 per year. The cost of freshwater is 0.028 and 0.014 $/L for CSS and VWTSS with reflector and Nano-PCM, respectively.

From desiccation to wetlands and outflow: Rapid re-filling of Lake Victoria during the Latest Pleistocene 14–13 ka

Reconstructing hydrological variability is critical for understanding Lake Victoria’s ecosystem history, the evolution of its diverse endemic fish community, the dynamics of vegetation in the catchment, and the dispersal of aquatic and terrestrial fauna in the East African Rift system during Latest Pleistocene and Holocene times. Whereas consensus exists on widespread desiccation of Lake Victoria ∼18 – 17 ka, the re-filling history (16 – 13 ka) has remained highly controversial. Here, we present data from four new sediment cores along a depth transect. We use lithostratigraphic core correlation, sediment facies, XRF data, wetland vegetation analysis (Typha pollen), and 14C chronologies of unprecedented precision to document Latest Pleistocene lake-level variability. At our coring site in the central basin, local Typha wetlands existed >16.7 ka, alternating with periods of desiccation. Moisture increased slightly between ca. 16.7 – 14.5 ka and wetlands with permanent, shallow ponds established simultaneously in the center and the marginal, more elevated parts of the flat lake basin. After ca. 14.0 ka, lake levels increased; wetlands in the central basin were submerged and replaced by lacustrine environments and a >50 m deep lake established ca. 13.5 ka, likely with intermittent overflow most of the time. The lake reached modern or even above-modern levels around 10.8 ka. This lake-level history is consistent with regional terrestrial paleoenvironmental reconstructions, notably the expansion of Afromontane and rainforest. Our data suggest a complex picture of paleoclimatic conditions in Eastern Africa and teleconnections to the North-Atlantic and Indian Ocean domains.

Holocene seismic activity in south‐eastern Switzerland: Evidence from the sedimentary record of Lake Silvaplana

AbstractHigh‐Alpine regions are prone to a large variety of geohazards, among which earthquakes have the strongest impact on landscape and local population. Historic records indicate a moderate to high seismic activity in the northern, south‐western and central parts of Switzerland. In contrast, south‐eastern Switzerland has less historic earthquake chronicles due to the low population density, resulting in a poorly constrained seismic event catalogue. The aim of this study is to evaluate the palaeoseismic activity for south‐eastern Switzerland by using the sedimentary record of Lake Silvaplana in the Engadine Valley. A dense grid of high‐resolution two‐dimensional seismic profiles, high‐resolution bathymetry and a 10 m long sediment core from the deepest basin were used to investigate the stratigraphy of the lake sediments. The bathymetry reveals a flat basin, flanked by steep slopes to the north‐west and south‐east. The acoustic basement consists of four ridges, and gently‐dipping fans to the south‐west and north‐east. Expressions of slope failure can be identified in all domains of the lake floor and the subsurface data. Multiple coevally‐triggered chaotic mass‐flow deposits, overlain by megaturbidites with a coarse‐sand base, have been detected along ten horizons in the seismic data. The four most recent of these deposits are cored and radiocarbon dated to approximately 230, 310, 960 and 1330 cal yr bp, indicating four over‐regional seismic events that triggered large slope failures in Lake Silvaplana in the last 1400 years. Correlation with sediments of Lake Sils, Lake Como, Lake Iseo and Lake Ledro indicate within radiocarbon uncertainties a large earthquake around 1330 cal yr bp. Within their age ranges, the postulated earthquake at 310 cal yr bp (1640 ce) further correlates with a moment magnitude Mw ca 5.4 event in Ftan in 1622 ce, and the 960 cal yr bp (990 ce) earthquake correlates with a Mw ca 5.2 earthquake in Brescia in 1065 ce. Six mass‐movement deposits, also suggested to be caused by earthquakes, were not reached by the sediment core and have suggested ages between 7800 and 11 300 cal yr bp. Thus, Lake Silvaplana sediments provide the first reliable record of seismic activity for the mid and Late Holocene in this region, likely related to the neotectonic activity of the Engadine Line, a major fault zone running along the main valley.

Energy, exergy, and economic analyses of a modified hemispherical solar distiller augmented with convex absorber basin, wicks, and PCM

An innovative designed convex basin is utilized instead of the flat absorber basin to maximize the exposure and vaporization surface areas. Moreover, a jute cloth layer is used over the convex basin as a wicking material for promoting the vaporization rates inside the modified distiller. Additionally, the influences of using phase change material (PCM) thermal storage on the distiller performance was studied on the distiller thermo-economic performance are investigated. Three hemispherical distillers are designed and tested, namely, modified hemispheric distiller with a wick convex absorber basin (MHD-WCAB), modified distiller with a wick convex absorber basin and PCM (MHD-WCAB + PCM), and reference hemispheric distiller (RHD). The performance of three proposed hemispherical stills is performed based on economic, energetic, and exergetic points. The daily distilled product reached 7.95 and 6.90 kg/m2/day for the MHD-WCAB + PCM and MHD-WCAB, respectively, 4.25 kg/m2/day for RHD, achieving 87.06% and 62.35% improvement relative to the RHD. Furthermore, the daily energy efficiency of MHD-WCAB + PCM and MHD-WCAB is evaluated as 46.90% and 34.04%, respectively, representing an improvement rate of 85.67% and 61.74% compared to RHD. The daily exergy efficiency of MHD-WCAB + PCM and MHD-WCAB reached 3.88% and 3.39%, respectively, yielding an augmentation rate of 128.24%, and 99.41% over RHD.

Bioremediation Potential of Algae (Chlorella vulgaris) in Crude Oil Contaminated Sediment

Aim: To evaluate the bioremediation potential of algae (Chlorella vulgaris) in crude oil contaminated sediment.
 Study Design: The study employs three (3) experimental designs using flat rubber, statistical analysis of the data and interpretation makes up the study design.
 Place and Duration of Study: New Calabar River, Choba, Obio Akpor Local Government Area, Rivers State, Nigeria, was used for this study. New Calabar River lies between longitude 6°53.13E and latitude 4°53.52N in Choba. Bioremediation monitoring process lasted for 56 days; analyses were carried out at 14 days’ interval.
 Methodology: Three (3) experimental set up were employed using a using flat rubber basin, each set up contained 2500g of sediment and was contaminated with 250ml of Crude Oil except Control 1 uncontaminated sediment (Us). The set up was augmented with the Chlorella vulgaris (CHL) except the control 1 and 2 (Us and Cs). Sediment profile like Temperature, pH, Nitrogen, Phosphorus, Potassium, electrical conductivity, moisture content, total organic carbon, soil organic matter and total hydrocarbon content (THC) before contamination was determined using standard analytical methods while parameters like Temperature, pH, Nitrogen, Phosphorus, Potassium and Total Hydrocarbon Contents (THC) were monitored throughout the experimental period. Microalgae and Hydrocarbon utilizing algae (HUA) were monitored throughout the experimental period using standard microbiological methods. Percentage Bioremediation was estimated from amount of THC reduction from day 1 (initial) of monitoring. Statistical analysis was carried out for microbiological and physicochemical parameters when treated using Statistical ANOVA to ascertain significant difference of mean values between various treatments.
 Results: Results revealed the amount of hydrocarbon removed and % bioremediation efficiency after 56 days of monitoring with different treatment on the set up is given in a decreasing order as follows: (initial contamination value of 10525mg/kg) Cs+Chl (7700mg/kg; 73.15%) > control (Cs) contaminated without amendment of organisms (6345mg/kg 60.28%) > and Us uncontaminated sediment 1969.96 mg/kg. The total hydrocarbon content (THC) of the treated setup decreased from (10525mg/kg initial contamination value) at the start of bioremediation to Cs+Chl (7700mg/kg: 73.15%) at the end of bioremediation. The highest count of microalgae (log10cfu/g) for each set up during the monitoring were as follows; day 0 Us (7.65) day14 Cs (7.63) day28 Us (7.70) day42 Cs+Chl (7.60) day56 Cs (7.30). It was observed that peak count was on day28 (7.70) and a decline was on day56 (7.30). The highest Hydrocarbon Utilizing Algae (Log10cfu/g) count for each set up during the monitoring were as follows; day 0 Cs+Chl (5.23) day 14 Cs+Chl (5.30) day28 Cs (5.23) day42 Cs+Chl (4.77) > day56 Cs (5.07). Decline was observed on day 42 and peak count was on day 14.
 Conclusion: Results from the study revealed that Chlorella vulgaris is capable of degrading hydrocarbon components. There was a faster utilization of hydrocarbon by set up with Chlorella vulgaris than control. Though incomplete removal of crude oil was observed in THC concentration value. This suggests that an improvement in the process is required. Such improvement could include biostimulation of the polluted sample or some chemical pretreatment of the sample. From the study, bioremediation can be said to be a viable and effective response to sediment contamination with crude oil.

Spatiotemporal expansion modes of urban areas on the Loess Plateau from 1992 to 2021 based on nighttime light images

Long-term nighttime light data can effectively reflect the spatiotemporal evolution pattern of urban areas. Based on nighttime light data obtained from 1992 to 2021, the spatiotemporal expansion modes of urban areas on the Loess Plateau were investigated by remote sensing image band fusion processing, geospatial analysis, statistics and classification methods. Results show that the characteristics of the spatiotemporal expansion of urban areas were retained in the extraction boundaries. From the perspective of time scales, the urban areas have grown tripled to 11,481 km2. Four significant instances of urban areas increase occurred, with one large increase occurring almost every ten years. From the perspective of spatial scales, urban area expansion has two important features. First, the expansion speed of urban areas, which is based on three indicators, has large spatial dissimilarities. Five modes can be divided based on the expansion velocity of 44 cities/counties. Second, urban development increases uniquely, and can be described based on three expansion modes: Ring Extension, which mainly occurs in wide and flat basins of the main rivers; Linear Extension primarily arises on both banks of rivers in hilly and gully areas; and Point Extension mainly occurs in areas away from the main rivers. Our results highlight that the spatiotemporal expansion modes of urban areas on the Loess Plateau retain the significant influence of the geological environment, which can provide scientific guidance for the sustainable development of human-land relationships.

Novel Design of Double Slope Solar Distiller with Prismatic Absorber Basin, Linen Wicks, and Dual Parallel Spraying Nozzles: Experimental Investigation and Energic–Exergic-Economic Analyses

Increasing the evaporation zone inside the solar distiller (SD) is a pivotal method for augmenting its freshwater production. Hence, in this work, a newly designed prismatic absorber basin covered by linen wicks was utilized instead of the conventional flat absorber basin to increase the surface area of the vaporization zone in a double-slope solar distiller (DSSD). Meanwhile, for further enhancement of modified DSSD performance, dual parallel spraying nozzles are incorporated underneath the glass cover as a saltwater feed supply to minimize the thickness of the saltwater film on the wick, which enhances the heating process of the wick surface and, consequently, the evaporation and condensation processes are improved. Two double slope distillers, namely a double slope solar distiller with wick prismatic basin and dual parallel spraying nozzles (DSSD-WPB&DPSN) and a traditional double slope solar distiller (TDSSD), are made and tested in the outdoor summer conditions of Tanta, Egypt (31° E and 30.5° N). A comparative energic–exergic-economic analysis of the two proposed solar stills is also conducted, in terms of the cumulative distillation yield, daily energy efficiency, daily exergy efficiency, and cost per liter of distilled yield. The present results show that the cumulative distillation yield of the DSSD-WPB&DPSN was 8.20 kg/m2·day, which is higher than that of the TDSSD by 49.64%. Furthermore, the energy and exergy efficiencies were increased by 48.51% and 118.10%, respectively, relative to TDSSD. Additionally, the life cost assessment reveals that the cost per liter of the distilled yield of the DSSD-WPB&DPSN is decreased by 11.13% compared to the TDSSD.

DEM BASED COMPUTATION OF TOPOGRAPHIC SURFACE ROUGHNESS TO REVEAL INCISION IN GILGIT-BALTISTAN,PAKISTAN

This research investigates interrelationship between landscape evolution and neotectonics in the Gilgit-Baltistan (GB) region based on surface roughness (SR). We analyzed the topographic surface features such as flat area, surface area and surface ratio using Shuttle RadarTopographic Mission-Digital Elevation Model (SRTM DEM) with a spatial resolution of 90 meters. The objective is to make a SR map and to identify areas influenced by neotectonics. The DEM based spatial distribution of slope gradients and slope orientations along with the aspect map were combined to portray the vertical dissection. Lower values of vertical dissection indicate relatively flat topographic basins which generally mean a region of with intermediate slope gradient and slope orientation. Areas with high vertical dissection values correspond to sharp changes in the slope gradients and slope orientations, which could be due to abrupt scrap edges (possibly neotectonic or lithological control). Higher vertical dissection values in GB are wide spread and are oriented SE- NW in Ghanche, Skardu, Hunza, Gilgit and northern Ghizer districts along Karakorum, South Pamirs and Hindu-Kush ranges. While a few higher roughness values are aligned NE- SW in Diamir and Gilgit districts along the Raikot Fault. The surface roughness map is capable of identifying deeply incised valleys, tectonic uplifts and depressions.

DEM BASED COMPUTATION OF TOPOGRAPHIC SURFACE ROUGHNESS TO REVEAL INCISION IN GILGIT-BALTISTAN,PAKISTAN

This research investigates interrelationship between landscape evolution and neotectonics in the Gilgit-Baltistan (GB) region based on surface roughness (SR). We analyzed the topographic surface features such as flat area, surface area and surface ratio using Shuttle RadaTopographic Mission-Digital Elevation Model (SRTM DEM) with a spatial resolution of 90 meters. The objective is to make a SR map and to identify areas influenced by neotectonics. The DEM based spatial distribution of slope gradients and slope orientations along with the aspect map were combined to portray the vertical dissection. Lower values of vertical dissection indicate relatively flat topographic basins which generally mean a region of with intermediate slope gradient and slope orientation. Areas with high vertical dissection values correspond to sharp changes in the slope gradients and slope orientations, which could be due to abrupt scrap edges (possibly neotectonic or lithological control). Higher vertical dissection values in GB are wide spread and are oriented SE- NW in Ghanche, Skardu, Hunza, Gilgit and northern Ghizer districts along Karakorum, South Pamirs and Hindu-Kush ranges. While a few higher roughness values are aligned NE- SW in Diamir and Gilgit districts along the Raikot Fault. The surface roughness map is capable of identifying deeply incised valleys, tectonic uplifts and depressions.

Late Paleozoic Accumulation of Coal-Bearing Successions in the Wuhai Coalfield, Western North China: Back-Arc Basin Response to Southward Subduction of the Paleo-Asian Ocean

The Late Paleozoic is an important epoch of coal-bed accumulation in the North China, particularly in its western segment, where a world-class coal field has been found and exploited for three decades. Coal-bearing layers recorded rapid Late Carboniferous to Early Permian sea-level rise that led to the evolution of the shallow marine tidal flat basin, followed by regression that resulted in the formation of deltaic facies. However, little attention has been paid to the tectonic factors that assisted in the coal accumulation processes, which have been demonstrated worldwide to be pivotal. In this study, we evaluate the significant influence of southward subduction of the middle segment of the Paleo-Asian Ocean (PAO) during Carboniferous to Early Permian deposition of coal-bearing neritic to deltaic successions in the western North China Block (NCB). We pinpoint a direct link between basin-filling evolution of the northwestern Ordos Basin and the progressive uplift of the Inner Mongolia continental arc triggered by the south-dipping subduction of the Solonker ocean plate. Sedimentary facies variation and paleocurrent reconstruction indicate sedimentary routing from the north to northeast. The petrology and detrital zircon geochronology of sampled sandstones indicate evolving provenances from a dominated cratonic basement to a mixed orogen and continental arc. The Carboniferous samples are generally quartz arenites and contain a large number of Archean to Paleoproterozoic zircons with small amounts of Paleozoic arc pluton components, indicating sediment supply dominated by the western NCB Precambrian basement. In contrast, the youngest sample of the Shanxi Formation is sub-litharenite, the age spectrum of which is characterized by the dominance of ca. 450 and 270 Ma ages, indicative of a high influx of Paleozoic arc detritus. This shift in sandstone petrology, detrital zircon distribution, and depositional setting allows us to link the shoaling of the Ordos Basin with mountain building and the unroofing of the continental arc, which enhances our understanding of both the subduction of the PAO and coal accumulation in the NCB.

Thermo-economic performance improvement of hemispherical solar still using wick material with V-corrugated basin and two different energy storage materials

Solar still is a developing solar desalination method that has been introduced to face the shortage of freshwater with low energy consumption. However, this method is challenged by its low productivity. Therefore, the following work aimed to improve the freshwater productivity and reduce the produced water price. Herein, the performance of a hemispheric solar still equipped with four alternative combinations was experimentally studied; and its thermo-economic performance was assessed. The experimental work had four stages, firstly the distiller’s flat basin was replaced by a V-corrugated basin. Secondly, the corrugated basin was covered with a black cotton wick material. Thirdly, paraffin wax, as a phase change material (PCM), was contained under the wick-coated corrugated basin for latent thermal storage purpose. Finally, paraffin was replaced with sheep fat PCM. Each modified distiller was compared to a conventional one from 8 A.M. until 9 P.M. under the climate conditions of Suez City, Egypt lies at (29. 5825 °N, 32.5734°E) in terms of the thermal performance, daily productivity, and freshwater price. The four cases showed increasing in the daily productivity by ratios of 11 %, 25.7 %, 34.1 %, and 39.6 % respectively. The fourth case showed the best water productivity and thermal performance. It had daily productivity of 4737.5 mL/m2 and 45 % thermal efficiency. Furthermore, the thermal performance in terms of the thermal and exergy efficiencies improved by 39.75 % and 44.04 %, whereas the average total heat transfer coefficient increased by 5.5 %. Moreover, the freshwater price was 0.0137 $/L, likewise, 17.5 % cost reduction.

Experimental investigation and thermo-economic performance analysis of a modified solar distiller design with thermal storage material and v-corrugated absorber basin

A comparative experimental study is carried out to augment the freshwater productivity of a single-slope solar distiller. A v-corrugated basin is utilized to boost the evaporation area for effective heat transfer of saline water; meanwhile, a phase change material (PCM) is incorporated underneath the basin to extend the still's nocturnal distillate yield. Paraffin wax is utilized as a PCM, and longitudinal copper fins are embedded inside the paraffin container to improve the heat transfer processes of the wax. Besides, the proposed solar distillers are investigated under flat and v-corrugated basin configurations with and without PCM. Four distillers, namely; traditional flat basin solar distiller (TFBSD), flat basin solar distiller with rearward copper longitudinal fins immersed in the PCM container (FBSD-PCM&Fins), v-corrugated basin solar distiller without PCM (VBSD), and v-corrugated basin solar distiller integrated with PCM (VBSD-PCM) are tested at the climatic conditions of Tanta (30.47° N and 31° E), Egypt. A comparative thermo-economic analysis of the four solar distillers is also performed, including the daily energetic efficiency, freshwater production, and distillate yield cost. The present results indicate that the VBSD-PCM maximized both energo-economic performance and freshwater production among the investigated modifications. The accumulated water production and the daily energetic efficiency of the VBSD-PCM are improved by 63.57 % and 72.70 %, respectively, compared to the TFBSD. Furthermore, the economic assessment shows that the cost of freshwater production of the VBSD-PCM is reduced by 23.10 % compared to the TFBSD.

A NEW METHOD TO CONTROL THE REGIONAL STRATA MOVEMENT OF SUPER-THICK WEAK CEMENTATION OVERBURDEN IN DEEP MINING

In the western of china, the deep mining area with super-thick and weak cementation overburden is vast, sparsely populated and the ecological environment is extremely fragile. With the large-scale exploitation of deep coal resources, it is inevitable to face green mining problem, whose essence is the surface subsidence control. Therefore, it is necessary to study the control technology for the regional mining based on the evolution law of subsidence movement and energy-polling of super-thick and weak cementation overburden, and put forward the economically design scheme that can control strata movement and surface subsidence in a certain degree. Based on the key strata control theory, this paper puts forward the subsidence control scheme of partial filling -partial caving in multi-working face coordinated mining, and further studies its control mechanism through the numerical simulation and then analyzes the control effect of the strata movement and energy-polling in the fully caving mining, backfill mining, wide strip skip-mining and mixed filling mining method etc., the following conclusions are detailed as follows: (1) The maximum value of energy-polling occurs on the coal pillars or on both sides of goaf. With the width of goaf, the maximum value of energy-polling increases in a parabola. (2) In the partial filling-partial caving multiple working faces coordinated mining based on the main key stratum, the stress distribution of the composite backfill in the filling working face is parabolic, and it is high on both sides and low in the middle. Moreover, in the composite backfill, the stress concentration degree of a outside coal pillar is greater than that of the inside coal pillar. (3)The control mechanism of partial filling-partial caving harmonious mining based on main key layer structure is the double-control cooperative deformation system, formed by the composite backfill and the main and sub-key layers structure. They jointly control the movement and energy accumulation of overlying strata by greatly reducing the effective space to transmit upward, and absorb the wave subsidence trend of the overburden until it develops into a single flat subsidence basin. (4) Considering the recovery rate, pillar rate, area filling rate, technical difficulty and subsidence coefficient etc., the partial filling-partial caving multiple working faces coordinated mining based on the main key stratum is the most cost-effective mining method to control surface subsidence. This paper takes a guiding role in controlling the regional strata movement and surface subsidence of deep mining with super-thick and weak cementation overburden.

Assessing the Accuracy of a Borehole-Controlled P-Wave Velocity Model of Yucca Flat, Nevada Using Large-N Seismic Data

ABSTRACT With geologic data from over 950 boreholes, Yucca Flat basin, residing on the Nevada National Security Site, has excellent borehole control on stratigraphy. These data were used to create a Geologic Framework Model (GFM) of the basin. Of these boreholes, 188 have corresponding downhole seismic survey data, which were used to determine average P-wave velocities of the geologic units and create a GFM seismostratigraphic model (GFM-SS). With the acquisition of six new active-source large-N datasets in Yucca Flat, we can now quantitatively assess the accuracy of the GFM-SS previously controlled only by borehole data. For each of the six datasets, we subset the GFM to the region of interest and create a forward model of P-wave travel times for the GFM-SS given the large-N source-receiver geometries. We first made trial-and-error adjustments to the unit velocities (while keeping the layer geometry intact) to improve the travel-time residuals. We then implemented a simulated annealing approach to find the optimal velocity model for each dataset. Our results indicate that the borehole-controlled model overestimates alluvium velocities across Yucca Flat. This result persists even when we make smaller GFM-SS models that are local to individual large-N experiments. We hypothesize that this result is a combination of shorter ray paths and the resulting lack of interaction with large-scale features (such as faults), as well as less attenuation of high frequencies in the borehole data. Both the current GFM-SS and the updated model based on median velocities that we present here overgeneralize local unit velocities, which can be quite heterogeneous in Yucca Flat.