Mechanical anisotropy associated with beddings in shale under Brazilian test conditions:Insights from acoustic emission statistics

A comprehensive understanding of shale’s bedding anisotropy is crucial for shale-related engineering activities,such as hydraulic fracturing,drilling and underground excavation.In this study,seven Brazilian tests were conducted on shale samples at different bedding orientations with respect to the loading direction(0°,45°and 90°)and the disc end face(0°,45°and 90°).An acoustic emission(AE)system was employed to capture the evolution of damage and the temporal-spatial distribution of microcracks under splitting-tensile stress.The results show that the Brazilian tensile strength decreases with increasing bedding inclination with respect to the disc end face,while it increases with the angle between bedding and loading directions.Increasing the bedding inclination with respect to the end face facilitates the reduction in b value and enhances the shale’s resistance to microcrack growth during the loading process.Misalignment between the bedding orientation and the end face suppresses the growth of mixed tensile-shear microcracks,while reducing the bedding angle relative to the loading direction is beneficial for creating mixed tensile-shear and tensile cracks.The observed microscopic failure characteristics are attributed to the competing effects of bedding activation and breakage of shale matrix at different bedding inclinations.The temporal-spatial distribution of microcracks,characterized by AE statistics including the correlation dimension and spatial correlation length,illustrates that the fractal evolution of microcracks is independent of bedding anisotropy,whereas the spatial distribution shows a stronger correlation.The evolution features of correlation dimension and spatial correlation length could be potentially used as precursors for shale splitting failure.These findings may be useful for predicting rock mass instability and analyzing the causes of catastrophic rupture.

Mutual impact of true triaxial stress, borehole orientation and bedding inclination on laboratory hydraulic fracturing of Lushan shale

Unconventional resources like shale gas has been the focus of intense research and development for two decades. Apart from intrinsic geologic factors that control the gas shale productivity (e.g. organic matter content, bedding planes, natural fractures, porosity and stress regime among others), external factors like wellbore orientation and stimulation design play a role. In this study, we present a series of true triaxial hydraulic fracturing experiments conducted on Lushan shale to investigate the interplay of internal factors (bedding, natural fractures and in situ stress) and external factors (wellbore orientation) on the growth process of fracture networks in cubic specimens of 200 mm in length. We observe relatively low breakdown pressure and fracture propagation pressure as the wellbore orientation and/or the maximum in situ stress is subparallel to the shale bedding plane. The wellbore orientation has a more prominent effect on the breakdown pressure, but its effect is tapered with increasing angle of bedding inclination. The shale breakdown is followed by an abrupt response in sample displacement, which reflects the stimulated fracture volume. Based on fluid tracer analysis, the morphology of hydraulic fractures (HF) is divided into four categories. Among the categories, activation of bedding planes (bedding failure, BF) and natural fractures (NF) significantly increase bifurcation and fractured areas. Under the same stress regime, a horizontal wellbore is more favorable to enhance the complexity of hydraulic fracture networks. This is attributed to the relatively large surface area in contact with the bedding plane for the horizontal borehole compared to the case with a vertical wellbore. These findings provide important references for hydraulic fracturing design in shale reservoirs.

Anisotropic cyclic deformation behavior of an extruded Mg-3Y alloy sheet with rare earth texture

Mg-RE(magnesium-rare earth)alloys exhibit pronounced in-plane anisotropy of mechanical response under quasi-static monotonic loading resulting from the RE texture,as extensively reported.In this work,an obvious in-plane anisotropy of cyclic deformation behavior was observed in an extruded Mg-3Y alloy sheet during strain-controlled tension-compression low-cycle fatigue(LCF)at room temperature.The extrusion direction(ED)samples displayed better fatigue resistance with almost symmetrical hysteresis loops and longer fatigue life compared with the transverse direction(TD)samples.The influences of texture on the deformation modes,cracking modes,and mechanical behavior of Mg-Y alloy sheets under cyclic loading were studied quantitatively and statistically.The activation of various slip/twinning-detwinning systems was measured at desired fatigue stages via EBSD observations together with in-grain misorientation axes(IGMA)analysis.The results indicate that the activation of deformation modes in the TD sample was featured by the cyclic transition,i.e.,prismatic slip(at the tensile interval)→{10–12}tension twinning(at the compressive reversal)→detwinning+prismatic slip(at the re-tensile reversal).In the case of the ED sample,the cyclic deformation was dominated by the basal slip throughout the fatigue life.For cracking modes,intergranular cracking and persistent slip bands(PSB)cracking were the primary cracking modes in the ED sample while the TD sample showed a high tendency of{10–12}tension twinning cracking(TTW cracking).The underlying mechanisms influencing the activation of various slip/twinning-detwinning systems,as well as cracking modes and cyclic mechanical behavior,were discussed.

A Review of the Nutritional Health Effects of Roselle (Hibiscus sabdariffa L.) Calyces

Roselle ( Hibiscus Sabdariffa L.) is a tropical and subtropical plant.This paper reviewed the distribution of roselle in China,and the varieties of roselle grown in China.The main chemical components of roselle calyces were listed,and the nutritional health effects and the latest development and utilization of roselle calyx were summarized,in order to provide a reference for better promotion and cultivation of roselle.

Changes in behaviors of rats with sciatic nerve injury and expression of growth associated protein-43 in dorsal root ganglion

BACKGROUND： Neuropathic pain is closely related to neuroplasticity, and growth associated protein-43 （GAP 43） is a molecular marker for neuronal development and neuroplasticity. The expression of GAP-43 during the development of neuropathic pain should have its own characters. OBJECTIVE： To observe the changes in behaviors of rats with sciatic nerve injury and GAP-43 expression in dorsal root ganglion（DRG） affected ascribing to developing nerve transection and nerve crush, two types of neuropathic pain models. DESIGN： Randomized controlled animal experiment SETTING： Department of Anesthesiology in Second Hospital of Xiamen City and Second Affiliated Hospita of Shantou University Medical College. MATERIALS： Totally 250 adult Wistar rats of either gender, weighing 180 to 250 g, were involved in the study. The rats were randomized into 3 groups： nerve transection group （n =120）, nerve crush group （n =120）, and normal control group （n =10）. The rats in the nerve transection group and nerve crush group were subdivided separately into 6 groups,and were allowed to survive for 3, 7, 14, 21, 30 and 60 days after nerve injury （n =20）. Mouse anti-GAP-43 monoclonal antibody （Sigma Co.,Ltd.）, Supervision TM anti-mouse reagent （HRP, Changdao antibody diagnosis reagent Co.,Ltd., Shanghai）, DAB/H202 （Boster Co. Ltd, Wuhan）, and HMIAS-100 image analysis system （Qianping Image engineering Company, Tongji Medical University） were employed in this study. METHODS： This experiment was carried out in the Surgical Department and Pathological Laboratory, the Second Hospital Affiliated to Shantou Medical College during April 2004 to April 2005. （1） Grouping intervention： Animals were anesthetized and the sciatic nerve of the right side was exposed at thigh around ischial tuberosity. Sciatic nerves of rats in nerve transection group were transected at 1 cm below infrapiriform foramen, and those in nerve crush group were exposed as well as the nerve transection group, and crushed at 0.5 cm below infrapiriform foramen with hemostatic forceps for 10 s× 3 times. Rats in normal control group did not receive any treatments. （2） Behavioral observation： The behavioral changes were observed on the first day after sciatic nerve injury and spontaneous pain severity was measured with autotomy scores. One point was given for the removal of one nail, and the score was added 1 point for each distal digit affected, getting another point still suiting for each proximal digit, the maximum score permitted was 11 for each paw. （3） Detection of GAP-43： The DRG of L5 at right side was taken out respectively 3,7,14,21,30 and 60 days after nerve injury and made into sections. The expression of GAP-43 was detected with immunohistochemical method. T test was used for comparing the difference in the measurement data in clinical analysis. MAIN OUTCOME MEASURES ： （1） The severity of autotomy at the affected feet. （2） The expression of GAP-43 in the right DRG. RESULTS： Totally 250 rats entered the stage of result analysis. （1） Autotomy score： The percentage of autotomy caused by nerve injury pain of rats in the nerve transection group and crush group was increased with the elongation of survival time; The percentage of autotomy in nerve transection group was higher than that in the nerve crush group at each period after nerve injury. Eighty percent rats presented autotomy and forty percent bited digits in the nerve transection group 60 days after nerve injury. Whereas only one third of rats showed autotomy in the nerve crush group. The autotomy scores in the nerve transection group were higher than those in the nerve crush group at each period with nerve injury. The mean scores were 2.1 ±2.1 in the nerve transection group 60 days after nerve injury, while those were only 0.7±1.5 in the nerve crush group. （2）The GAP-43 expression in DRG： The GAP-43 expression in the nerve transection group reached the peak on 7 days after injury （0.614 ±0.004）, still presented 60 days after injury （0.515±0.004）. On the contrast, it reached the peak on 14 days in the nerve crush group （0.583 ±0.006）, sequently, it declined on 21 days （0.563±0.008） and basically recovered to normal level on 60 days after nerve injury （0.231±0.003）. The GAP-43 expression was only （0.225±0.005）in the normal control group. The GAP-43 expressions in both the nerve transection group and nerve crush group were oignificantly stronger than that in the normal control group （t =4.074-14.726, P 〈 0.05）; and the GAP-43 expression was significantly stronger in the nerve transection group in comparison with the nerve crush group （t =3.357-6.236, P 〈 0.05）. CONCLUSION： （1）Nerve transection is more easy to cause spontaneous pain than nerve crush. （2） The GAP-43 expression in DRG is stronger in the nerve transection than that in the nerve crush as the same period, namely, to reach the peak quicker and keep longer peak expression period. （3） The occurrence of neuropathic pain might be related to neuroplasticity.

Tailoring Texture to Highly Strengthen AZ31 Alloy Plate in the Thickness Direction via Pre-tension and Rolling-Annealing

Conventional wrought Mg alloys,such as AZ31 and ZK60 rolled plates,usually exhibit significantly low tensile yield strength in the thickness direction.This can be attributed to the high activity of{10-12}tension twinning due to the strong basal texture(<0001>//ND,normal direction).In this work,the tensile yield strength in the ND of the as-rolled(AR)AZ31 plate increased from 50 to 150 MPa(increased by 200%)via simple processing,i.e.,pre-tension and rolling-annealing(PTRA)treatment.The strong basal texture(<0001>//ND)of the AR plate was changed into a weakened fiber texture(<0001>⊥ND).The evolution of microstructures during PTRA treatment and the activated deformation modes during uniaxial tension were studied quantitatively and statistically by the means of intergranular misorientation(IM)and in-grain misorientation axes(IGMA)analysis.The results indicate that various twin variants,as well as{10-12}-{10-12}secondary twins,were activated during pre-tension and rolling,and most residual matrix was consumed by twins after annealing.The dominated deformation modes in tension changed from{10-12}tension twinning(the AR sample)to prismatic slip(the PTRA sample)in the early tensile deformation.The underlying formation mechanism of the fiber texture and corresponding strengthening mechanism were discussed.

The catalytic effect of both oxygen-bearing functional group and ash in carbonaceous catalyst on CH_(4)-CO_(2) reforming

A kind of new catalyst-carbonaceous catalyst-for CH_(4)-CO_(2) reformation has been developed in our laboratory.The effect of both oxygen-bearing functional group such as phenolic hydroxyl,carbonyl,carboxyl,and lactonic,and ash such as Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the carbonaceous catalyst on the CH_(4)-CO_(2) reforming has been investigated with a fixed-bed reactor.It has been found that the carbonaceous catalyst is an efficient catalyst on CO_(2)-CH_(4) reforming.With the decrease of oxygen-bearing functional group,the catalytic activity of carbonaceous catalyst decreases quickly.The oxygen-bearing functional groups play a significant role in the carbonaceous-catalyzed CO_(2)-CH_(4) reforming;the ash components in carbonaceous catalyst also have an important influence on the CO_(2)-CH_(4) reforming.Fe_(2)O_(3),Na_(2)CO_(3),and K_(2)CO_(3) in the ash can catalyze the CO_(2)-CH_(4) reforming reaction;CaO has little effect on CO_(2)-CH_(4) reforming reaction.CaO can catalyze the gasification between carbonaceous catalyst and CO_(2);Al_(2)O_(3) and MgO inhibit the CO_(2)-CH_(4) reforming.

Catalytic performance of Co-Mo-Ce-K/γ-Al_(2)O_(3) catalyst for the shift reaction of CO in coke oven gas

The catalytic performance of Co-Mo-Ce-K/γAl_(2)O_(3) catalyst for the shift reaction of CO in coke oven gas is investigated using X-ray diffraction(XRD)and temperature-programmed reduction(TPR).The results indicate that Ce and K have a synergistic effect on promoting the catalytic activity,and the Co-Mo-Ce-K/γAl_(2)O_(3) catalyst with 3.0 wt-%CeO2 and 6.0 wt-%K_(2)O exhibits the highest activity.CeO2 favors Co dispersion and mainly produces an electronic effect.TPR characterization results indicate that the addition of CeO2-K_(2)O in the Co-Mo-Ce-K/γ-Al_(2)O_(3) catalyst decreases the reduction temperature of active components,and part of octahedrally coordinated Mo6+transforms into tetrahedrally coordinated Mo6+,which has a close relationship with the catalytic activity.

Effect of carbon deposition over carbonaceous catalysts on CH_(4)decomposition and CH_(4)-CO_(2)reforming

An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH_(4)-CO_(2)reforming.Thermogravimetry(TG)and X-ray diffraction(XRD)were employed to study the characteristics of carbon deposition.It was found that the carbonaceous catalyst is an efficient catalyst in methane decomposition and CH_(4)-CO_(2)reforming.The trend of methane decomposition at lower temperatures is similar to that at higher temperatures.The methane conversion is high during the initial of stage of the reaction,and then decays to a relatively fixed value after about 30 min.With temperature increase,the methane decomposition rate increases quickly.The reaction temperature has significant influence on methane decomposition,whereas the carbon deposition does not affect methane decomposition significantly.Different types of carbon deposition were formed at different methane decomposition reaction temperatures.The carbon deposition Type I generated at 900℃ has a minor effect on CH_(4)-CO_(2)reforming and it easily reacts with carbon dioxide,but the carbon deposition Type II generated at 1000℃and 1100℃clearly inhibits CH_(4)-CO_(2)reforming and it is difficult to react with carbon dioxide.The results of XRD showed that some graphite structures were found in carbon deposition Type II.