Dynamic behaviors of water-saturated and frozen sandstone subjected to freeze-thaw cycles

In high-altitude cold areas,freeze-thaw(F-T)cycles induced by day-night and seasonal temperature changes cause numerous rock mass slope engineering disasters.To investigate the dynamic properties of rock in the natural environment of a high-altitude cold area,standard specimens were drilled from the slope of the Jiama copper mine in Tibet,and dynamic compression tests were performed on watersaturated and frozen sandstone with different numbers of F-T cycles(0,10,20,30,and 40)by the split Hopkinson pressure bar(SHPB)system with a cryogenic control system.The influence of water-saturated and frozen conditions on the dynamic performance of sandstone was investigated.The following conclusions are drawn:(1)With increasing strain rate,the attenuation factor(la)of water-saturated sandstone and the intensifying factor(li)of frozen sandstone linearly increase.As the number of F-T cycles increases,the dependence factor(ld)of water-saturated sandstone linearly decreases,whereas the ld of frozen sandstone linearly increases.(2)The prediction equation of the dynamic compressive strength of water-saturated and frozen sandstone is obtained,which can be used to predict the dynamic compressive strength of sandstone after various F-T cycles based on the strain rate.(3)The mesoscopic mechanism of water-saturated and frozen sandstone’s dynamic compressive strength evolution is investigated.The water softening effect causes the dynamic compressive strength of water-saturated sandstone to decrease,whereas the strengthening effect of pore ice causes it to increase.(4)The decrease in the relative dynamic compressive strength of water-saturated sandstone and the increase in the relative dynamic compressive strength of frozen sandstone can be attributed to the increased porosity.

Effect of rich R-TiO2 on the rate and cycle properties of Li4Ti5O12 as anode for lithium ion batteries

Li4Ti5012 (LTO) with rich R-TiO2 (17.06, 23.69, and 34.42 wt%), namely, R-TiO2@Li4Ti5O12 composites, were synthesized using the hydrothermal method and tetrabutyl titanate (TBT) as the precursor. Rietveld refinement of X-ray diffraction (XRD) results show that the proportion of Li occupying 16d sites is extraordinary low and the lattice constants of LTO and R-TiO2 change with the ritanium dioxide content. EIS measurements showed that with in creasing R-TiO2 content, both its charge transfer impedance (Rct) and lithium ion diffusion coefficient (DLi) decreased. The changes of Rct and DLi caused by the increase of titanium dioxide content have synergic-antagonistic effects on the rate and cycle properties of Li4Ti5012. The rate performance is positively related to DLi, while the cycle property is negatively correlated with Rct, indicati ng that the rate performs nee is mainly related to DLi, while Rct more significantly affects the cycle performance. LTO-RT-17.06% exhibited excellent rate properties, especially under a high current density (5.0 C, 132.5 mAh/g) and LTO-RT-34.42% showed superior long-term cycle performance (0.012% capacity loss per cycle) compared to that of LTO-RT-17.06% and LTO-RT-23.69%.

Low cycle fatigue behavior of the extruded AZ80 magnesium alloy under different strain amplitudes and strain rates

Low cycle fatigue behavior of extruded AZ80 magnesium alloy was investigated under uniaxial tension-compression at different strain amplitudes and strain rates.The results show that the extruded AZ80 magnesium alloy exhibits cyclic hardening at strain amplitudes ranging from 0.4%to 1.0%,the asymmetry of hysteresis loops becomes increasingly obvious when the strain amplitude increases.Higher strain rates correspond to higher stress amplitudes,high mean stresses and short fatigue life.{10–12}extension twins play a role in the cyclic deformation under higher strain amplitudes(0.8%,1.0%).The relationship between total strain energy density and fatigue life can be described by the modified Morrow model.The effect of strain rate on the fatigue life can also be predicted by the model.

IN SITU DAILY GROWTH RATE OF PROCHLOROCOCCUS AT THE CHLOROPHYLL MAXIMUM LAYER IN THE SOUTHERN SOUTH CHINA SEA:AN ESTIMATION FROM CELL CYCLE ANALYSIS

Prochlorococcus is the dominant population of the autotrophs in the oceanic area in theSouth China Sea; and contributes significantly to picoplanktonic (【2μm) carbon biomass. However, thereis no availabe data on its growth the and productivity so far. In the present study, the in situ populationgrowth rate of Prochlorococus at the chlorophyll maximum layer at 6 .3°N, 110°E in the South China

Improving Cyclic Stability and Rate Performance of Lithium Ion Batteries Using La^(3+)Modified LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)Cathode Materials

La_(4)NiLiO_(8)-coated NCM622 samples were prepared through a sol-gel method,and the electrochemical performance as cathode materials was investigated.It is revealed that part of the introduced La^(3+)ions produce a coating layer on the surface of NCM622 particles,while the rest occupy the 3b position of the lattice.The optimized sample exhibits a capacity retention of 96.54%after 100 cycles under 1C rate with a discharge specific capacity of 117.54 mAh·g^(-1)under 5C rate,much higher than those of the unmodified sample.The results show that the addition of La^(3+)ion can greatly improve the cyclic stability and the rate performance of NCM622.

Evaluation of Corrosion Product Activity in a Typical PWR with Extended Cycles and Flow Rate Perturbations

Effect of flow rate perturbations has been studied using the modified computer program CPAIR-P for time dependent corrosion rates in Pressurized Water Reactors (PWRs) having extended cycles. In these simulations, a decrease in the corresponding saturation values of corrosion product activity (CPA) is observed for higher pH values. Comparison of CPA’s behavior has been done for constant flow-rate case as well as for transients with elevated 10B levels (~40%) in dissolved boric acid in coolant in two operating cycles. When the flow rate is decreased in the first cycle, the saturation value of CPA attains new higher values. Also, in the second operating cycle, the saturation values are about 12% higher when compared with the values in the first cycle.

The Relationship between Corporate Real Estate and Economic Cycle

Studies on the relationship between corporate real estate(CRE)and economic cycles are very thin,especially from developing countries,such as South Africa.More,in practice,most firms hardly dedicate enough resources to CRE divisions.This leads to that management not fully maximises the wealth of shareholders.This study uses multi-linear regression to test how GDP,interest rate,and total corporate costs react to changes in CRE.The sample is made up of blue chip firms listed on the Johannesburg Stock Exchange(JSE).The results reveal mixed bag solutions-for certain firms;GDP,interest rate,and corporate costs are statistically significant and vice versa.More,this analysis can be replicated to other similar industries and indices around the world.

Correlation of crack growth rate and stress ratio for fatigue damage containing very high cycle fatigue regime

A model is proposed to correlate the crack growth rate and stress ratio containing very high cycle fatigue regime.The model is verified by the experimental data in literature.Then a formula is derived for the effect of mean stress on fatigue strength,and it is used to estimate the fatigue strength of a bearing steel in very high cycle fatigue regime at different stress ratios.The estimated results are also compared with those by Goodman formula.

Dynamic grey model of verification cycle and lifecycle of measuring instrument and its application

Two dynamic grey models DGM (1, 1) for the verification cycle and the lifecycle of measuring instrument based on time sequence and frequency sequence were set up, according to the statistical feature of examination data and weighting method. By a specific case, i.e. vernier caliper, it is proved that the fit precision and forecast precision of the models are much higher, the cycles are obviously different under different working conditions, and the forecast result of the frequency sequence model is better than that of the time sequence model. Combining dynamic grey model and auto-manufacturing case the controlling and information subsystems of verification cycle and the lifecycle based on information integration, multi-sensor controlling and management controlling were given. The models can be used in production process to help enterprise reduce error, cost and flaw.

ECONOMIC GROWTH AND CYCLES IN MODERN CHINA

If the theory of cyclical fluctuation can be applied to modern China, the economic development ofChina in this period can be seen as consisting of several stages. At each stage as well as in the wholeperiod, chosen index system is likely to help measure the growth rate. By vertical and horizontal com-parison, this paper will try to settle the disputes on China’s modern economic development.

3D hierarchically porous NiO/Graphene hybrid paper anode for long-life and high rate cycling flexible Li-ion batteries

With the rapid emergence of wearable devices, flexible lithium-ion batteries(LIBs) are much more needed than ever. Free-standing graphene-based composite paper electrodes with various active materials have appealed wide applications in flexible LIBs. However, due to the prone-to-restacking feature of graphene layers, a long cycle life at high current densities is rather difficult to be achieved. Herein, a unique threedimensional(3D) hierarchically porous NiO micro-flowers/graphene paper(fNiO/GP) electrode is successfully fabricated. The resulting fNiO/GP electrode shows superior long-term cycling stability at high rates(e.g., storage capacity of 359 mAh/g after 600 cycles at a high current density of 1 A/g). The facile 3D porous structure combines both the advantages of the graphene that is highly conductive and flexible to ensure rapid electrons/ions transfer and buffer the volume expansion of NiO during charge/discharge,and of the micro-sized NiO flowers that induces hierarchical between-layer pores ranging from nanomicro meters to promote the penetration of the electrolyte and prevent the re-stacking of graphene layers. Such structural design will inspire future manufacture of a wide range of active materials/graphene composite electrodes for high performance flexible LIBs.

Astronomical Cycles of the Late Permian Lopingian in South China and Their Implications for Third-Order Sea-Level Change

The late Permian(Lopingian)was a crucial climate transition period from the late Paleozoic Ice Age to the early Triassic of exceptionally high temperatures.However,the origins of the third-order sea-level changes during the Lopingian Epoch remain unclear.Here,we presented astronomically calibrated gamma-ray(GR)log and non-U GR(computed gamma ray or CGR)curves from the clastic and carbonate successions of well GFD-1 in the Pingle Depression of South China for studying the sea-level oscillations during the Lopingian.Spectral analyses of the 405 kyr-calibrated GR and CGR time data revealed periodicities close to about 405,about 100,about 44.2,about 35.1,about 21,and about 17.5 kyr,supporting the existence of Milankovitch forcing in the sedimentary records.A high-resolution astronomical time scale and high-resolution sedimentation rate curve of the Lopingian from well GFD-1 were constructed by cyclostratigraphic analysis.The eccentricity and obliquity amplitude modulation cycles suggested long periodicities of about 2.4 and about 1.2 myr,respectively.In the Wuchiapingian greenhouse of the Lopingian,the about 2.4 myr eccentricity oscillation controlled‘weak’glacio-eustasy and/or aquifer eustatic changes related to the global third-order sea-level changes and that a lowstand(W2)was initiated by an eccentricity oscillation minimum.In contrast,during the Changhsingian,which exhibited a cooling event,an about 1.2 myr obliquity cycle was probably strong,with the sea-level records highlighting the link between the‘icehouse’sea-level lowering(C2 and C1)and the obliquity nodes.Moreover,dynamic sedimentary noise model as an indicator of sea-level showed local third-order sea-level variations,the coevolution trends in the orbital power,global and local sea-level changes,and sedimentation rate had significant implications for establishing the global nature and synchronicity of these million-year-scale eustatic records and reconstructing the temporal depositional history at a regional scale.In addition,the volcanism and tectonism that continued into the early-middle Wuchiapingian probably led to a series of climate changes that drove the hydrological cycles not paced by the Milankovitch cycles.

Identification of Milankovitch Cycles and Calculation of Net Primary Productivity of Paleo-peatlands using Geophysical Logs of Coal Seams

Individual coal seams formed in paleo-peatlands represent sustained periods of terrestrial carbon accumulation and a key environmental indicator attributed to this record is the rate of carbon accumulation.Determining the rate of carbon accumulation requires a measure of time contained within the coal.This study aimed to determine this rate via the identification of Milankovitch orbital cycles in the coals.The geophysical log is an ideal paleoclimate proxy and has been widely used in the study of sedimentary records using spectral analysis.Spectral analyses of geophysical log from thick coal seams can be used to identify the Milankovitch cycles and to calculate the period of the coal deposition.By considering the carbon loss during coalification,the long-term average carbon accumulation rate and net primary productivity(NPP)of paleo-peatlands in coal seams can be obtained.This review paper presents the procedures of analysis,assessment of results and interpretation of geophysical logs in determining the NPP of paleo-peatlands.

Accelerating Effect of Wetting-Drying Cycles on Steel Bar Corrosion in Concrete

Raining and sun-shining processes in natural climate were simulated by water spraying and infrared lightshining alternately as wetting-drying cycles in accelerated durability test. The accelerating effects of the wet-ting-drying cycles and the variation of corrosion current density and corrosion potential of steel bar in concrete undersuch conditions were studied. The result shows that the main reason leading to accelerating corrosion of steel bar inconcrete is the wetting-drying cycles, which can cause the increase of corrosion potential difference between the an-ode and cathode of steel bar corrosion cell and the decrease of concrete resistance. Corrosion rate of the steel bar inconcrete under four typical conditions, including wetting-drying cycle, long time submerging in water, long time ex-posure to indoor and outdoor environment were measured and compared. The test results indicate that the corrosionrates under the four typical conditions are in the order of spraying and infrared light shining cycles, outdoor environ-ment, indoor environment, and submerging in water, respectively.

A two-parameter model to predict fatigue life of high-strength steels in a very high cycle fatigue regime

In this paper, ultrasonic(20 kHz) fatigue tests were performed on specimens of a high-strength steel in very high cycle fatigue(VHCF) regime. Experimental results showed that for most tested specimens failed in a VHCF regime, a fatigue crack originated from the interior of specimen with a fish-eye pattern, which contained a fine granular area(FGA) centered by an inclusion as the crack origin. Then,a two-parameter model is proposed to predict the fatigue life of high-strength steels with fish-eye mode failure in a VHCF regime, which takes into account the inclusion size and the FGA size. The model was verified by the data of present experiments and those in the literature. Furthermore, an analytic formula was obtained for estimating the equivalent crack growth rate within the FGA. The results also indicated that the stress intensity factor range at the front of the FGA varies within a small range, which is irrespective of stress amplitude and fatigue life.

Experiments on an Open-Loop Cycle Carbon Dioxide Refrigeration System

An open loop cycle carbon dioxide(CO2)refrigeration system is established,and the cooling performances of high-pressure CO2 under different storage conditions(25℃,30℃,and 35℃)are investigated.Moreover,the experimental mass flow rates of CO2 are compared with the theoretical values at different conditions and refrigeration capacities.The results indicate that the storage condition of CO2 has a significant impact on the refrigeration performance,and the mass flow rate of CO2 increases with the increasing storage temperature in a given refrigeration capacity.

China's economic growth and the inflation cycles since reform and opening to the outside world

This paper analyzes the cyclical characteristics of China’s economic growth and inflation since reform and opening-up, and explores the intrinsic link between the two.The study will be a guideline to keep a good balance between economic growth and inflation.

Melatonin improves the first cleavage of parthenogenetic embryos from vitrified-warmed mouse oocytes potentially by promoting cell cycle progression

Background:This study investigated the effect of melatonin(MT)on cell cycle(G1/S/G2/M)of parthenogenetic zygotes developed from vitrified-warmed mouse metaphase II(MII)oocytes and elucidated the potential mechanism of MT action in the first cleavage of embryos.Results:After vitrification and warming,oocytes were parthenogenetically activated(PA)and in vitro cultured(IVC).Then the spindle morphology and chromosome segregation in oocytes,the maternal mRNA levels of genes including Miss,Doc1r,Setd2 and Ythdf2 in activated oocytes,pronuclear formation,the S phase duration in zygotes,mitochondrial function at G1 phase,reactive oxygen species(ROS)level at S phase,DNA damage at G2 phase,early apoptosis in 2-cell embryos,cleavage and blastocyst formation rates were evaluated.The results indicated that the vitrification/warming procedures led to following perturbations 1)spindle abnormalities and chromosome misalignment,alteration of maternal mRNAs and delay in pronucleus formation,2)decreased mitochondrial membrane potential(MMP)and lower adenosine triphosphate(ATP)levels,increased ROS production and DNA damage,G1/S and S/G2 phase transition delay,and delayed first cleavage,and 3)increased early apoptosis and lower levels of cleavage and blastocyst formation.Our results further revealed that such negative impacts of oocyte cryopreservation could be alleviated by supplementation of warming,recovery,PA and IVC media with 10^(−9) mol/L MT before the embryos moved into the 2-cell stage of development.Conclusions:MT might promote cell cycle progression via regulation of MMP,ATP,ROS and maternal mRNA levels,potentially increasing the first cleavage of parthenogenetic zygotes developed from vitrified-warmed mouse oocytes and their subsequent development.

Impact of Serum Progesterone Levels in GnRH Antagonist Assisted Reproduction Cycles on Pregnancy Outcomes: A Prospective Cohort Study

Background: With controlled ovarian hyperstimulation (COH) with gonadotrophin releasing hormone (GnRH) antagonists, sometimes it is associated with incomplete luteolysis leading to elevated serum progesterone in early follicular phase. Persistence of this elevation might reduce the chance for clinical pregnancy. Objective: To assess the effect of elevated early and late follicular progesterone (P) levels during gonadotrophins releasing hormone (GnRH) antagonist cycles on pregnancy outcome. Design: Prospective single center study. Setting: North-western Military hospital, Kingdom of Saudi Arabia. Patients: 302 in vitro fertilization/intra-cytoplasmic sperm injection (IVF-ICSI) patients. Intervention(s): Recombinant follicle stimulating hormone (r-FSH), (150 - 300 IU) started daily from cycle day 2;GnRH antagonist treatment started on day 6 of the cycle. The serum progesterone (P) measured twice on cycle day 2 and human chorionic gonadotrophin (hCG) day. Main Outcome Measures: Clinical pregnancy and live birth rates per started cycle. Results: The incidence of elevated serum P on day 2 was (5.3%) and on hCG day was (17.5%), statistically significant differences in clinical pregnancy rate (32.3% versus 13.0%) and in live birth rate (23.4% versus 11.1%) were present between the normal and high serum progesterone groups on hCG day, but these differences were not statistically significant in the groups of elevated basal progesterone. Conclusion: Follicular phase progesterone rise either on day 2 or the day of hCG trigger was associated with lower clinical pregnancy and live birth rates. This impact was more prominent with trigger day elevation.

Second Law of Thermodynamics Formalism Applied to Finite Duration through Cycles of Living Dissipative Systems

A simple and general theory to describe basic irreversible thermodynamic aspects of aging in all dissipative living is presented. Any dissipative system during its operation continuously loses efficiency by the production of structural or functional defects because of the second law of thermodynamics. This continuous loss of efficiency occurs on all the dissipative systems through the realization of specific functional cycles, leading to a maximum action principle of any system involving the Planck’s constant during their total dissipative operation. We applied our theory to the calculation of men and women lifespans from basal metabolic rate per unit weight and to the calculation of a new aging parameter per cycle of some human organs or physiological functions. All microscopic theory of the aging of living beings should be consistent with the second law of the thermodynamics. In other words, the operation of the biological self-organized structures only implies a delay in which the dissipative biological systems outside of equilibrium approach inexorably to the thermodynamic equilibrium obeying the second law of the thermodynamics.