Impact of wetting-drying cycles and acidic conditions on the soil aggregate stability of yellow‒brown soil

Soil aggregate is the basic structural unit of soil,which is the foundation for supporting ecosystem functions,while its composition and stability is significantly affected by the external environment.This study was conducted to explore the effect of external environment(wetting-drying cycles and acidic conditions)on the soil aggregate distribution and stability and identify the key soil physicochemical factors that affect the soil aggregate stability.The yellow‒brown soil from the Three Gorges Reservoir area(TGRA)was used,and 8 wetting-drying conditions(0,1,2,3,4,5,10 and 15 cycles)were simulated under 4 acidic conditions(pH=3,4,5 and 7).The particle size distribution and soil aggregate stability were determined by wet sieving method,the contribution of environmental factors(acid condition,wetting-drying cycle and their combined action)to the soil aggregate stability was clarified and the key soil physicochemical factors that affect the soil aggregate stability under wetting-drying cycles and acidic conditions were determined by using the Pearson’s correlation analysis,Partial least squares path modeling(PLS‒PM)and multiple linear regression analysis.The results indicate that wetting-drying cycles and acidic conditions have significant effects on the stability of soil aggregates,the soil aggregate stability gradually decreases with increasing number of wetting-drying cycles and it obviously decreases with the increase of acidity.Moreover,the combination of wetting-drying cycles and acidic conditions aggravate the reduction in the soil aggregate stability.The wetting-drying cycles,acidic conditions and their combined effect imposes significant impact on the soil aggregate stability,and the wetting-drying cycles exert the greatest influence.The soil aggregate stability is significantly correlated with the pH,Ca^(2+),Mg^(2+),maximum disintegration index(MDI)and soil bulk density(SBD).The PLS‒PM and multiple linear regression analysis further reveal that the soil aggregate stability is primarily influenced by SBD,Ca^(2+),and MDI.These results offer a scientific basis for understanding the soil aggregate breakdown mechanism and are helpful for clarifying the coupled effect of wetting-drying cycles and acid rain on terrestrial ecosystems in the TGRA.

Effects of Serum Concentration, Synchronization Time and Confluence on the Cell-Cycle Synchronization Efficiency of Goat Fibroblasts

This study aims to evaluate the effect of serum concentration, synchronization time, and confluence degree on the synchronisation efficiency of goat fibroblast cycle. The results indicated that there was no difference in the percentage of nucleated fibroblasts in the G0/G1 stage between serum concentrations of 0.3% and 0.4% (83.89% and 82.69%, respectively, P > 0.05) as well as between serum concentrations of 0.2% and 0.5% (76.95% and 75.46%, respectively, P > 0.05). The percentage of nucleated fibroblasts in the G0/G1 stage was highest at the concentration of 0.3% and lowest in the control group (83.89% vs. 62.67%, P 0.05). The beneficial effect of high confluence was confirmed by the large percentage of nucleated fibroblasts at the G0/G1 stage. The 60% confluency was significantly lower than the 80% and 100% confluency (73.44%, 86.63%, and 87.17%, respectively, P < 0.05). The results indicate that the goat fibroblast cycle synchronization is the most effective at the serum concentration of 0.3%, 72 hours of synchronization and 100% confluency.

Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and Wetting-Drying

The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to repeated freezing-thawing and wetting-drying, which determines the possibility of changing their grain-size composition and structure. Experimental studies in laboratory conditions on the influence of cyclic freezing-thawing (FTC) and wetting-drying (WDC) on the quality indicators of lignites have been carried out, their granulometric (fractional) composition has been studied. Freezing-thawing cycle conditions are as follows (FTC): minimum exposure temperature: -20°C;maximum: +5°C;relative humidity: 30%;number of processing cycles: 3. Wetting-drying cycles are as follows (WDC): drying temperatures are +20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher yield of fine sizes (-6+0;-13+0 mm) than the cycles of freeze-thaw. Furthermore, it is found that the increase in the yield of fines depends on the heating temperature: coal disintegration proceeds more intensively at a higher temperature of drying.

Cycle Time Analysis of Open Pit Mining Dump Trucks

This study demonstrates a practical cycle time analysis of dump truck haulage system of “Ukhaa Khudag” open-pit coal mine located in Umnugobi Province, Mongolia. It examines the possibility of minimizing the cycle time of the haulage system as well as factors impacting the speed of the dump truck. The current study divides the open pit mine road for the dump trucks into five sections which are bench road, ramp, surface road, dump road uphill, and dump road. Meanwhile, it investigates the influence of the length, the grade, and the rolling resistance of the road section on the cycle time. The data is analyzed using mathematical regression methods via Microsoft Excel program. For each of the five road sections, we compare the statistical calculations of three regression models: linear, quadratic and exponential;thus, a total of thirty regression models are obtained in this research. Accordingly, the cycle time for each road section is predicted by the most accountable model. The loaded and empty direction of the movement is measured and calculated for each road section, and it appears that the difference between the calculated mean value and the actual cycle time of the models is 0.82 seconds with a relative error of 2.51 percent.

Analysis of Waste-Rock Transportation Process Performance in an Open-Pit Mine Based on Statistical Analysis of Cycle Times Data

In this paper, the performance of a waste rock transportation process in an open pit mine was assessed by using cycle time data. A computerized truck-excavator dispatch system was used to record the cycle times. The process was broken into seven steps (or components of the total cycle), durations of which were recorded for a period of 1 month, leading to N = 60,690 data points or dispatches. The open pit mine studied consisted of 12 waste types loaded by 14 excavators and hauled by 49 trucks (at a trucks-to-excavator ratio of 3.5:1) in 75 changing locations. The string-type data was coded using integers to allow a FORTRAN code to extract process performance parameters using statistical analysis. The study established a wide range of parameters including: the waste material generation rate (about 1.73 million t/month, 81% comprising waste rock), truck fill factor, f, total cycle time (Tct), production capacity, theoretical cycle time, non-productive cycle time Tnp, and cycle time performance ratio (CTPR), denoted as Tpr. The factors affecting the process performance include: truck model, excavator model, location (haul distance and road conditions) and material type. For a fixed material type and tonnage, the PDFs of the cycle time components were logarithmic in nature, capable of differentiating performance variations under different factors. It was concluded that the performance of the waste material transportation system in this mine was determined to be acceptable due to mean value of Tpr = 2.432 being closer to unity. Reduction measures were suggested to minimize the cycle time for the process bottlenecks determined from Pareto analysis (that is, full haul, empty haul and loading processes).

Analysis of Medical Waste Incinerator Performance Based on Fuel Consumption and Cycle Times

A detailed assessment of an incinerator based on fuel consumption and cycle time data is presented in this paper. The study was conducted at Temeke district hospital for 22 months consecutively covering 654 days of daily data collection on fuel consumption and cycle times. The composition for the medical waste incinerated varied between 15% and 35% for sharps waste and between 65% and 85% for other waste, with mean values of 25% and 75%, respectively. The results revealed poor performance of the incinerator due to higher fuel consumption (above 30 L/cycle). The incineration cycle times were observed to range between 2 and 4 hours, all of which were too high for the loading rates observed (55 - 214 kg). A strong dependency of diesel oil consumption on cycle time was observed due to lack of temperature control leading to continuous fuel flow into the burners. The incineration capacity was very low compared to other incinerators in terms of tons per year. This paper gives an insight on the factors affecting incinerator performance assessed based on diesel oil consumption and cycle times. It can be generalized that the incinerator performance was poor due to several factors ranging from poor incinerator design, operator skills, waste management practices, waste storage practices, etc. The hospital was advised to install a new incinerator with short incineration cycle time (30 - 40 minutes) and lower fuel consumption (10 L/cycle) at a loading rate of 200 kg/cycle.

Life Cycle Assessment Introduced by Using Nanorefrigerant of Organic Rankine Cycle System for Waste Heat Recovery

The use of nanorefrigerants in Organic Rankine Cycle(ORC)units is believed to affect the cycle environment performance,but backed with very few relevant studies.For this purpose,a life cycle assessment(LCA)has been performed for the ORC system using nanorefrigerant,the material and energy input,characteristic indicators and comprehensive index of environmental impact,total energy consumption and energy payback time(BPBT)of the whole life cycle of ORC system using Al_(2)O_(3)/R141b nanorefrigerant were calculated.Total environmental comprehensive indexes reveal that ECER-135 index decrease by 1.5%after adding 0.2%Al_(2)O_(3)nanoparticles to R141b.Based on the contribution analysis and sensitivity analysis,it can be found out ORC system manufacturing is of the most critical stage,where,the ECER-135 index of ORC component production is the greatest,followed by the preparation process of R141b,transportation phase,and that of Al_(2)O_(3)nanoparticles preparation is small.The retirement phase which has good environmental benefits affects the result significantly by recycling important materials.Meanwhile,the main cause and relevant suggestion for improvement were traced respectively.Finally,the environmental impacts of various power generations were compared,and results show that the power route is of obvious advantage.Among the renewable energy,ORC system using Al_(2)O_(3)/R141b nanorefrigerant with minimal environmental impact is only 0.67%of coal-fired power generation.The environmental impact of current work is about 14.34%of other nations’PV results.

A discrete-event model to simulate the effect of truck bunching due to payload variance on cycle time, hauled mine materials and fuel consumption

Data collected from truck payload management systems at various surface mines shows that the payload variance is significant and must be considered in analysing the mine productivity,energy consumption,greenhouse gas emissions and associated cost.Payload variance causes significant differences in gross vehicle weights.Heavily loaded trucks travel slower up ramps than lightly loaded trucks.Faster trucks are slowed by the presence of slower trucks,resulting in‘bunching’,production losses and increasing fuel consumptions.This paper simulates the truck bunching phenomena in large surface mines to improve truck and shovel systems’efficiency and minimise fuel consumption.The study concentrated on completing a practical simulation model based on a discrete event method which is most commonly used in this field of research in other industries.The simulation model has been validated by a dataset collected from a large surface mine in Arizona state,USA.The results have shown that there is a good agreement between the actual and estimated values of investigated parameters.

Cyclostratigraphy and paleoclimate analysis of the Lingshui Formation in Changchang Sag,Qiongdongnan Basin,China

The Qiongdongnan Basin,located in the sea between Hainan Island and the Xisha Islands,is a faulted Cenozoic basin on the northern continental margin of the South China Sea.The Changchang Sag,situated in the eastern part of the central depressional zone in the deepwater area of the Qiongdongnan Basin,exhibits a near EW-striking morphology and represents an important potential target for oil/gas exploration.However,the age of the interface of the Lingshui Formation remains controversial,which hinders a comprehensive understanding of the tectonic evolution and hydrocarbon accumulation pattern in the Changchang Sag.This study focuses on well A,located in the depositional center of the Changchang Sag,and employs cyclostratigraphic analysis to identify cyclic signals of the Milankovitch cycles recorded in the sedimentary strata.Spectral analysis of natural gamma logging data from this well reveals the presence of 405 kyr long eccentricity cycles,100 kyr short eccentricity cycles,39.3 kyr obliquity cycles,and 20.58 kyr age precession cycles.By employing astronomical tuning,a“floating”astronomical time scale of the Lingshui Formation spanning 5.483 million years(Myr)is established.The top interface of the Oligocene in the International Geological Time Scale 2020(GTS2020),with a geological age of 23.03 Ma,is used as the time anchor to establish a high-precision absolute astronomical age framework for the Lingshui Formation.The results indicate that the bottom interface of the first member of the Lingshui Formation is dated at 23.79 Ma,the bottom interface of the second member is dated at 25.08 Ma,and the bottom interface of the third member is dated at 28.51 Ma.Additionally,the average sedimentation rate during this period is estimated to be 9.261 cm/kyr.Furthermore,paleoclimate and paleoenvironmental reconstructions were carried out through quantitative analysis of spore and pollen assemblages,as well as foraminifera within the Lingshui Formation.These analyses suggest that the deposition of the Lingshui Formation occurred under warm and humid temperate climatic conditions.The results of paleoclimate proxy analysis and comparative fitting analysis of the astronomical time scale confirm that the climate evolution during this period was influenced by astronomical orbital forces,such as eccentricity and precession.

Research on Corrosion Effect of Sulfate Ions on Concrete Under Wetting-Drying Cycle

Saline soil is widely distributed in the marine sediments along the coast of the world and the arid-semi-arid areas of the Middle East and Iraq,and calcium sulfate erosion has become one of the important factors affecting the durability of concrete in this area.In order to clarify the mechanism of sulfate ion damage to concrete,this paper mainly takes saline soil with high sulfate content in coastal area as well as arid-semi-arid area as the research object,and uses indoor geotechnical test,field test and numerical simulation to study the influence of different dry-wet cycle times on the unconfined compressive strength of concrete test blocks,and puts forward the relationship between the erosion arrival depth and time of sulfate ion in concrete,so as to predict the long-term erosion depth by using the erosion depth of sulfate ion in concrete in short time.The results show that the shorter the erosion time when the erosion reaches a certain depth,and the larger the erosion reaches when the erosion time is the same,the faster the erosion reaches the depth with the increase of erosion time.Compared with rectangular section concrete,circular section concrete penetrates faster.The results of this study can provide a reference for the durability design of concrete in saline soil sites containing sulfate.

INFLUENCE OF DWELL TIME ON HIGH TEM-PERATURE LOW CYCLE FATIGUE (HTLCF) BEHAVIOR IN AN Nd-BEARING NEAR-α TITANIUM ALLOY

The influences of strain amplitude ranges and dwell time at peak strains on the low cycle fatigue (LCF) properties at 600℃ of a new near α high temperature titanium alloy containing rare earth Nd are investigated. The creep fatigue interaction behavior is discussed in this paper in terms of a creep fatigue interaction cumulative law and fatigue crack propagation model. The results show that the creep fatigue interaction is largely dependent on the strain amplitude range, and the tensile dwell periods, as well as compressive dwell periods, have a great influence on the LCF life of this alloy.

Independent Cycle Time Assignment for Min-max Systems

A variety of problems in digital circuits, computer networks, automated manufacturing plants, etc., can be modeled as min-max systems. The cycle time is an important performance metric of such systems. In this paper, we focus on the cycle time assignment of minimax systems which corresponds to the pole assignment problem in traditional linear control systems. For the min- max system with max-plus inputs and outputs, we show that the cycle time can be assigned disjointedly by a state feedback, if and only if the system is reachable. Furthermore, a necessary and sufficient condition for the cycle time to be assigned independently by a state feedback is given. The methods are constructive, and some numerical examples are given to illustrate how the methods work in practice.

Investigation of Excavator Performance Factors in an Open-Pit Mine Using Loading Cycle Time

This study presents the effect of excavator model, loading operation location, shift availability and truck-shovel combination on loading cycle time and productivity of an open-pit mine. The loading cycle time was used to assess the material loading system performance which is one of the key components of the total cycle time for material transportation in an open-pit mine. Loading is among the components of cycle time during which material is being handled. The data analyzed?was?collected from a computerized dispatch system at GGM from which 62,000 loading dispatches per month involving several shifts, 14 excavators and 49 trucks were loaded. About 4465 dispatches per excavator and 1276 dispatches per truck were assessed using loading cycle time data for each dispatch for a period of four months (between August and December). Under fixed tonnage loaded and waste type (33 t of non-acid forming waste rock),?it was observed that loading cycle time depends on excavator model, location and truck being loaded. Average cycle times, PDFS?and CDFS of loading cycle time series were used to identify differences in performance under different situations. It was concluded that shift availability for excavators, loading location, excavator model and truck-shovel combinations strongly affect the productivity during loading process in an open-pit mine.

Closed and Open Metabolic Cycles: Transition Time

A metabolic cycle can be viewed as a central core and its branches. The central core is here firstly considered as a pre-closed metabolic cycle (CMC), with a unique first substrate, but with no input or output of other components. By contrast, the metabolic cycles in nature are open metabolic cycles (OMC) with output and input of external substrates (through “metabolic branches”), modulating continuously the enzyme activities and the total concentration of their substrates thorough complex regulatory phenomena. In this work, the transition from a Closed to an Open metabolic cycle has been simulated by a consecutive entry and exit of two components through the catalytic action of two enzymes. It is known that after any alteration of the initial conditions, the cycles need a time to reach new equilibrium. We have measured the changes of transition time (T.T.) values in 81 models of CMC differing in Km or Vmax values. In general, the T.T. tends to be shorter in cycles with preponderant lower Km and higher Vmax values. Further, Mathematica refinement for the estimation of transition time from the data previously calculated can be obtained with the use of the command Interpolating Function.

Analysis of Temperature Profiles and Cycle Time in a Large-Scale Medical Waste Incinerator

Temperature profiles and cycle times in a large-scale medical waste incinerator installed in a referral hospital were used to assess the performance and functionality of incinerator. The study was conducted using data collected from 8 cycles per days for 67 days. For proper combustion and destruction of toxic components in the primary chamber and destruction of pollutants and toxic components in the flue gas, it is desired to reach the maximum temperature in the chambers faster and maintain this maximum temperature for an extended time interval. The primary and secondary temperatures T1 and T2, respectively, were recorded at an interval of one minute for different cycles. Different amounts of wastes with varying proportions of sharps and other wastes were loaded into the incinerator and temperature profiles recorded. The analysis shows that the incinerator works at primary temperature less than the required recommended by manufacturer while the secondary chamber operates between 600 and above 950℃, although higher temperatures up to 1020℃ were observed. The average load preparation time was observed to be 14.6 minutes, while the chamber preheating time before daily initial loading was 25.45 minutes. Both temperature profiles were observed to have similar shapes for all combustion cycles studied, except when incinerator malfunctioning occurred. The average cycle time was established to be 32.7 minutes and 28.97 minutes based on time to drop to 550℃ after the maximum temperature and loading time intervals, respectively, although longer cycle times were observed. Temperature drop in both combustion chambers as a result of waste charging was observed in the interval of 5 minutes. The chamber heating rate was observed to decrease exponentially with time during both preheating and incineration operation.

Key Dolerite Dyke Swarms of Amazonia:U-Pb Constraints on Supercontinent Cycles and Geodynamic Connections with Global LIP Events Through Time

High-resolution U–Pb(ID-TIMS,baddeleyite)ages are presented for mafic dykes from selected swarms in two important Amazonian regions:the Carajás Province in the east,and the Rio Apa block in the southwest–areas

Evaluation of deriving fire cycle of forested landscape based on time-since-fire distribution

Estimation of fire cycle has been conducted by using the negative exponential function as an approximation of time-since-fire distribution of a landscape assumed to be homogeneous with respect to fire spread processes. The authors imposed predefined fire cycles on a virtual landscape of 100 cell ×100 cell, and obtained a mosaic composing of patches with different stand ages (i.e. time since fire). Graphical and statistical methods (Van Wagner 1978; Reed et al. 1998) were employed to derive fire cycle from the virtual landscape. By comparing the predefined and the derived fire cycles, the two methods and tested the effects of sample size and hazard of burning (i.e., stand’s susceptibility to fire in relation to its stand age) were evaluated on fire cycle deviation. The simulation results indicated a minimum sample size of 10 times of the annual burnt area would be required for partitioning time-since-fire distribution into homogeneous epochs indicating temporal change in fire cycle. Statistically, there was significant difference among the imposed and the derived fire cycle, regardless of sample sizes with or without consideration of hazard of burning. Both methods underestimated the more recent fire cycle without significant difference between them. The results imply that deviation of fire cycle based on time-since-fire distribution warrants cautious interpretation, especially when a landscape is spatially partitioned into small units and temporal changes in fire cycle are involved.

Effect of cyclic wetting-drying on tensile mechanical behavior and microstructure of clay-bearing sandstone

The understanding of the weakening mechanism of tensile strength of rock subjected to cyclic wetting-drying is critical for rock engineering.Tensile strength tests were conducted on a total of 35 sandstone specimens with different wetting-drying cycles.The crack propagation process and acoustic emission characteristics of the tested samples were obtained through a high-speed camera and acoustic emission system.The results indicate that the tensile strength is observably reduced after cyclic wetting-drying,and the extent of the reduction is not only related to the number of wettingdrying cycle,but also closely related to the clay mineral content of the sample.In addition,as the cycles of wetting-drying increase,the effect of each single cycle on tensile strength get reduced until it becomes constant.Moreover,the crack initiation and penetration time is prolonged as the number of wetting-drying cycle increases,which indicates that cyclic wetting-drying weakens the rock stiffness and enhances the ductility of sandstone.Meanwhile,the acoustic emission characteristics of the tested samples further confirmed the ductile behaviour of the sandstone samples with increasing wetting-drying cycle.Furthermore,through the analysis of the microstructure and mineral composition of the samples with different wetting-drying cycles,it is concluded that the main weakening mechanisms of sandstones containing clay minerals are frictional reduction,chemical and corrosive deterioration.

Th–U cycle performance analysis based on molten chloride salt and molten fluoride salt fast reactors

The recent development of molten salt fast reactors has generated a renewed interest in them. As compared to traditional solid fuel fast neutron systems, it has many unique advantages, e.g., lower fissile inventory,no initial criticality reserve, waste reduction, and a simplified fuel cycle. It has been recognized as an ideal reactor for achieving a closed Th–U cycle. Based on the carrier salt, molten salt fast reactors could be divided into either a molten chloride salt fast reactor(MCFR) or a molten fluoride salt fast reactor(MFFR);to compare their Th–U cycle performance, the neutronic parameters in a breeding and burning(B&B) transition scenario were studied based on similar core geometry and power. The results demonstrated that the required reprocessing rate for an MCFR to achieve self-breeding was lower than that of an MFFR.Moreover, the breeding capability of an MCFR was better than that of an MFFR;at a reprocessing rate of 40 L/day,using LEU and Pu as start-up fissile materials, the doubling time(DT) of an MFFR and MCFR were 88.0 years and 48.0 years, and 16.5 years and 16.2 years, respectively.Besides, an MCFR has lower radio-toxicity due to lower buildup of fission products(FPs) and transuranium(TRU),while an MFFR has a larger, delayed neutron fraction with smaller changes during the entire operation.