Fabrication and Mechano-sensing Characteristics of Bending Polypyrrole Actuator

To prepare a conductive polymer actuator with decent performance,a self-built experimental platform for the preparation of polypyrrole film is employed.One of the essential goals is to examine the mechanical characteristics of the actuator in the presence of various combinations of process parameters,combined with the orthogonal test method of"four factors and three levels".The bending and sensing characteristics of actuators of various sizes are methodically examined using a self-made bending polypyrrole actuator.The functional relationship between the bending displacement and the output voltage signal is established by studying the characteristics of the actuator sensor subjected to various degrees of bending.The experimental results reveal that the bending displacement of the actuator tip almost exhibits a linear variation as a function of length and width.When the voltage reaches 0.8 V,the bending speed of the actuator tends to be stable.Finally,the mechanical properties of the self-assembled polypyrrole actuator are verified by the design and fabrication of the microgripper.

Near-infrared brain functional characteristics of mild cognitive impairment with sleep disorders

BACKGROUND Mild cognitive impairment(MCI)has a high risk of progression to Alzheimer’s disease.The disease is often accompanied by sleep disorders,and whether sleep disorders have an effect on brain function in patients with MCI is unclear.AIM To explore the near-infrared brain function characteristics of MCI with sleep disorders.METHODS A total of 120 patients with MCI(MCI group)and 50 healthy subjects(control group)were selected.All subjects underwent the functional near-infrared spec-troscopy test.Collect baseline data,Mini-Mental State Examination,Montreal Cognitive Assessment scale,fatigue severity scale(FSS)score,sleep parameter,and oxyhemoglobin(Oxy-Hb)concentration and peak time of functional near-infrared spectroscopy test during the task period.The relationship between Oxy-RESULTS Compared with the control group,the FSS score of the MCI group was higher(t=11.310),and the scores of Pittsburgh sleep quality index,sleep time,sleep efficiency,nocturnal sleep disturbance,and daytime dysfunction were higher(Z=-10.518,-10.368,-9.035,-10.661,-10.088).Subjective sleep quality and total sleep time scores were lower(Z=-11.592,-9.924).The sleep efficiency of the MCI group was lower,and the awakening frequency,rem sleep latency period,total sleep time,and oxygen desaturation index were higher(t=5.969,5.829,2.887,3.003,5.937).The Oxy-Hb concentration at T0,T1,and T2 in the MCI group was lower(t=14.940,11.280,5.721),and the peak time was higher(t=18.800,13.350,9.827).In MCI patients,the concentration of Oxy-Hb during T0 was negatively correlated with the scores of Pittsburgh sleep quality index,sleep time,total sleep time,and sleep efficiency(r=-0.611,-0.388,-0.563,-0.356).It was positively correlated with sleep efficiency and total sleep time(r=0.754,0.650),and negatively correlated with oxygen desaturation index(r=-0.561)and FSS score(r=-0.526).All comparisons were P<0.05.CONCLUSION Patients with MCI and sleep disorders have lower near-infrared brain function than normal people,which is related to sleep quality.Clinically,a comprehensive assessment of the near-infrared brain function of patients should be carried out to guide targeted treatment and improve curative effect.

Travelling characteristics of road vehicles on single-level rail-cum-road bridge under the dynamic and aerodynamic impact of travelling trains

Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibration system developed herein,this study examines the dynamic characteristics when road vehicles meet trains in this situation.The influence of load combination,vehicle type and vehicle location is analyzed.A method to obtain the aerodynamic load of road vehicles encountering the train at an arbitrary wind speed is proposed.The results show that due to the windproof facilities and the large line distance between the railway and highway,the aerodynamic and dynamic influence of trains on road vehicles is slight,and the vibration of road vehicles depends on the road roughness.Among the road vehicles discussed,the bus is the easiest to rollover,and the truck-trailer is the easiest to sideslip.Compared with the aerodynamic impact of trains,the crosswind has a more significant influence on road vehicles.The first peak/valley value of aerodynamic loads determines the maximum dynamic response,and the quick method is optimized based on this conclusion.Test cases show that the optimized method can produce conservative results and can be used for relevant research or engineering applications.

供应链金融对中小企业R&D投资效率的影响:基于融资约束视角

创新是中小企业保持竞争力、适应市场变化和实现可持续发展的关键。基于2016-2022年创业板中小企业相关数据,运用三阶段DEA分析、面板Tobit模型回归、二元Logistic回归等方法,探究供应链金融对中小企业R&D投资效率的影响。结果表明,供应链金融能够显著提高中小企业R&D投资效率,融资约束在二者间发挥遮掩效应。进一步分析发现,上述效应对供应链集中度较高的企业更为显著。结论可为发挥供应链金融筹资优势,促进供应链生态系统资源互补、信息共享的协同创新网络形成,进而支持中小企业创新活动提供理论支持。

Clinicopathological differences between patients with schistosomal appendicitis and non schistosomal appendicitis:A retrospectively study of past ten years

BACKGROUND Chronic schistosomiasis causes multiple organ and multiple system diseases,especially the digestive system.Schistosome eggs are mainly deposited in the stomach,liver and colorectal,but a few eggs are deposited in the appendix and cause disease.At present,there are few studies on schistosomal appendicitis.AIM To explore the differences in epidemiological,clinical and pathological characteristics between schistosomal appendicitis and non-schistosomal appendicitis over the past decade in order to assess the impact of schistosomiasis on appendicitis.METHODS The differences of general data,clinical data and laboratory examination data of patients with appendicitis from October 2013 to October 2023 were retrospectively analyzed.All patients were divided into two groups for analysis.There were 136 patients in schistosomal appendicitis group and 5418 patients in non-schistosomal appendicitis group.RESULTS Schistosomal appendicitis accounted for 2.45%of all patients with appendicitis,and the annual proportion in the past decade was 2.2%,2.9%,1.8%,1.9%,3.4%,3.1%,1.9%,1.6%,3%,2.6%,respectively.The prevalence of schistosomal appendicitis was middle-aged and elderly males,with an average age of 61.73±15.335 years.The main population of non-schistosomal appendicitis was middle-aged men,with an average age of 35.8±24.013 years(P<0.001).The distribution of pathological types of appendicitis was different between the two groups(P<0.001).The incidence of acute suppurative appendicitis in non-schistosomal appendicitis was higher than that in schistosomal appendicitis[odds ratio(OR)=0.504;95%confidence interval(CI):0.349-0.728;P<0.001].The proportion of acute attack of chronic appendicitis in schistosomal appendicitis was higher than that in non-schistosomal appendicitis(OR=2.614;95%CI:1.815-3.763;P<0.001).The proportion of schistosomal appendicitis patients complicated with colorectal cancer was higher than that of nonschistosomal appendicitis patients(OR=5.087;95%CI:1.427-18.132;P=0.012).There was no difference in clinical symptoms between the two groups.In the laboratory examination,there was a significant difference in white blood cells between schistosomal appendicitis and non-schistosomal appendicitis.The level of white blood cells in schistosomal appendicitis group was slightly higher than the upper limit of the normal range.Other statistically significant indicators were in the normal range.CONCLUSION Schistosomal appendicitis is a severe condition that is often associated with intestinal malignancies,potentially leading to a poor prognosis.Schistosomal appendicitis is more likely to be misdiagnosed and missed diagnosed in clinical work because of its nonspecific clinical manifestations and laboratory examination.It is crucial to differentiate schistosomal appendicitis in middle-aged and elderly male patients presenting with appendicitis,and to ensure early detection and treatment.

ALDH1、BCRP在乳腺癌组织中表达及与其临床病理特征的相关性分析

目的探讨乙醛脱氢酶1(ALDH1)、乳腺癌耐药蛋白(BCRP)在乳腺癌组织中表达及与其临床病理特征的关系。 方法选取88例乳腺癌患者作为研究对象,均行手术治疗,术中切除肿瘤的同时需采集癌旁正常组织一并送检,分析ALDH1、BCRP在乳腺癌组织及癌旁正常组织中的表达情况,并分析ALDH1、BCRP表达与患者年龄、肿瘤分期、淋巴结转移、绝经情况、肿瘤大小等病理特征的关系。 结果肿瘤组织内ALDH1阳性表达率、BCRP阳性表达率较癌旁正常组织高(P<0.05);肿瘤分期Ⅲ~Ⅳ期、有淋巴结转移、肿瘤大小≥3 cm患者ALDH1阳性表达率、BCRP阳性表达率高于肿瘤分期Ⅰ~Ⅱ期、无淋巴结转移、肿瘤大小<3 cm患者,有统计学差异(P<0.05)。 结论ALDH1、BCRP在乳腺癌组织内存在较高阳性表达,其高表达与肿瘤分期、淋巴结转移关系密切,参与肿瘤增殖及转移过程,或可指导临床治疗工作,增强抗肿瘤效果。

Morphological and biochemical characteristics associated with autophagy in gastrointestinal diseases

Autophagy is a cellular catabolic process characterized by the formation of double-membrane autophagosomes.Transmission electron microscopy is the most rigorous method to clearly visualize autophagic engulfment and degradation.A large number of studies have shown that autophagy is closely related to the digestion,secretion,and regeneration of gastrointestinal(GI)cells.However,the role of autophagy in GI diseases remains controversial.This article focuses on the morphological and biochemical characteristics of autophagy in GI diseases,in order to provide new ideas for their diagnosis and treatment.

Schistosomal appendicitis:A serious and often misdiagnosed condition

Schistosomal appendicitis(SA)is a rare but serious complication of schistosomiasis,a parasitic disease affecting over 250 million people worldwide.A recent retrospective study by Wang et al provides important insights into the clinicopathological characteristics of SA.The study compared 136 cases of SA to 5418 cases of non-SA over a ten-year period.Key findings include a higher average age of SA patients(61.73 years vs 35.8 years for non-SA),a higher proportion of acute on chronic appendicitis(33.1%vs 16%),and a significantly higher incidence of colorectal cancer(11.7%vs 2.2%).Despite these differences,SA remains a diagnostic challenge due to its nonspecific clinical presentation and lack of specific laboratory findings.The study also highlights the persistent prevalence of SA,accounting for 1.6%-3.4%of all appendicitis cases each year from 2013 to 2023.These findings underscore the need for enhanced awareness,early detection,and prompt treatment of SA in endemic regions.Given the association with colorectal cancer,patients with SA require thorough screening and follow-up.Further research into the pathogenesis and diagnostic markers of SA is warranted.As the global battle against schistosomiasis continues,targeted efforts to diagnose and manage SA can significantly improve patient outcomes.

Robust interface and excellent as-built mechanical properties of Ti–6Al–4V fabricated through laser-aided additive manufacturing with powder and wire

The feasibility of manufacturing Ti-6Al-4V samples through a combination of laser-aided additive manufacturing with powder(LAAM_(p))and wire(LAAM_(w))was explored.A process study was first conducted to successfully circumvent defects in Ti-6Al-4V deposits for LAAM_(p) and LAAM_(w),respectively.With the optimized process parameters,robust interfaces were achieved between powder/wire deposits and the forged substrate,as well as between powder and wire deposits.Microstructure characterization results revealed the epitaxial prior β grains in the deposited Ti-6Al-4V,wherein the powder deposit was dominated by a finerα′microstructure and the wire deposit was characterized by lamellar α phases.The mechanisms of microstructure formation and correlation with mechanical behavior were analyzed and discussed.The mechanical properties of the interfacial samples can meet the requirements of the relevant Aerospace Material Specifications(AMS 6932)even without post heat treatment.No fracture occurred within the interfacial area,further suggesting the robust interface.The findings of this study highlighted the feasibility of combining LAAM_(p) and LAAM_(w) in the direct manufacturing of Ti-6Al-4V parts in accordance with the required dimensional resolution and deposition rate,together with sound strength and ductility balance in the as-built condition.

Spatiotemporal deformation characteristics of Outang landslide and identification of triggering factors using data mining

Since the impoundment of Three Gorges Reservoir(TGR)in 2003,numerous slopes have experienced noticeable movement or destabilization owing to reservoir level changes and seasonal rainfall.One case is the Outang landslide,a large-scale and active landslide,on the south bank of the Yangtze River.The latest monitoring data and site investigations available are analyzed to establish spatial and temporal landslide deformation characteristics.Data mining technology,including the two-step clustering and Apriori algorithm,is then used to identify the dominant triggers of landslide movement.In the data mining process,the two-step clustering method clusters the candidate triggers and displacement rate into several groups,and the Apriori algorithm generates correlation criteria for the cause-and-effect.The analysis considers multiple locations of the landslide and incorporates two types of time scales:longterm deformation on a monthly basis and short-term deformation on a daily basis.This analysis shows that the deformations of the Outang landslide are driven by both rainfall and reservoir water while its deformation varies spatiotemporally mainly due to the difference in local responses to hydrological factors.The data mining results reveal different dominant triggering factors depending on the monitoring frequency:the monthly and bi-monthly cumulative rainfall control the monthly deformation,and the 10-d cumulative rainfall and the 5-d cumulative drop of water level in the reservoir dominate the daily deformation of the landslide.It is concluded that the spatiotemporal deformation pattern and data mining rules associated with precipitation and reservoir water level have the potential to be broadly implemented for improving landslide prevention and control in the dam reservoirs and other landslideprone areas.

Grain Yield,Biomass Accumulation,and Leaf Photosynthetic Characteristics of Rice under Combined Salinity-Drought Stress

Simultaneous stresses of salinity and drought often coincide during rice-growing seasons in saline lands,primarily due to insufficient water resources and inadequate irrigation facilities.Consequently,combined salinity-drought stress poses a major threat to rice production.In this study,two salinity levels(NS,non-salinity;HS,high salinity)along with three drought treatments(CC,control condition;DJ,drought stress imposed at jointing;DH,drought stress imposed at heading)were performed to investigate their combined influences on leaf photosynthetic characteristics,biomass accumulation,and rice yield formation.Salinity,drought,and their combination led to a shortened growth period from heading to maturity,resulting in a reduced overall growth duration.Grain yield was reduced under both salinity and drought stress,with a more substantial reduction under the combined salinity-drought stress.The combined stress imposed at heading caused greater yield losses in rice compared with the stress imposed at jointing.Additionally,the combined salinity-drought stress induced greater decreases in shoot biomass accumulation from heading to maturity,as well as in shoot biomass and nonstructural carbohydrate(NSC)content in the stem at heading and maturity.However,it increased the harvest index and NSC remobilization reserve.Salinity and drought reduced the leaf area index and SPAD value of flag leaves and weakened the leaf photosynthetic characteristics as indicated by lower photosynthetic rates,transpiration rates,and stomatal conductance.These reductions were more pronounced under the combined stress.Salinity,drought,and especially their combination,decreased the activities of ascorbate peroxidase,catalase,and superoxide dismutase,while increasing the contents of malondialdehyde,hydrogen peroxide,and superoxide radical.Our results indicated a more significant yield loss in rice when subjected to combined salinity-drought stress.The individual and combined stresses of salinity and drought diminished antioxidant enzyme activities,inhibited leaf photosynthetic functions,accelerated leaf senescence,and subsequently lowered assimilate accumulation and grain yield.

Clinical characteristics of acute non-varicose upper gastrointestinal bleeding and the effect of endoscopic hemostasis

BACKGROUND Acute non-variceal upper gastrointestinal bleeding(ANVUGIB)constitutes a prevalent emergency within Gastroenterology,encompassing 80%-90%of all gastrointestinal hemorrhage incidents.This condition is distinguished by its abrupt onset,swift progression,and notably elevated mortality rate.AIM To gather clinical data from patients with ANVUGIB at our hospital in order to elucidate the clinical characteristics specific to our institution and analyze the therapeutic effectiveness of endoscopic hemostasis.METHODS We retrospectively retrieved the records of 532 patients diagnosed with ANVUGIB by endoscopy at our hospital between March 2021 and March 2023,utilizing our medical record system.Data pertaining to general patient information,etiological factors,disease outcomes,and other relevant variables were meticulously collected and analyzed.RESULTS Among the 532 patients diagnosed with ANVUGIB,the male-to-female ratio was 2.91:1,with a higher prevalence among males.Notably,43.6%of patients presented with black stool as their primary complaint,while 27.4%had hematemesis as their initial symptom.Upon admission,17%of patients exhibited both hematemesis and black stool,while most ANVUGIB patients primarily complained of overt gastrointestinal bleeding.Urgent routine blood examinations at admission revealed that 75.8%of patients had anemia,with 63.4%experiencing moderate to severe anemia,and 1.5%having extremely severe anemia(hemoglobin<30 g/L).With regard to etiology,53.2%of patients experienced bleeding without a definitive trigger,24.2%had a history of using gastric mucosa-irritating medications,24.2%developed bleeding after alcohol consumption,2.8%attributed it to improper diet,1.7%to emotional excitement,and 2.3%to fatigue preceding the bleeding episode.Drug-induced ANVUGIB was more prevalent in the elderly than middle-aged and young individuals,while bleeding due to alcohol consumption showed the opposite trend.Additionally,diet-related bleeding was more common among the young age group compared to the middle-aged group.Gastrointestinal endoscopy identified peptic ulcers as the most frequent cause of ANVUGIB(73.3%),followed by gastrointestinal malignancies(10.9%),acute gastric mucous lesions(9.8%),and androgenic upper gastrointestinal bleeding(1.5%)among inpatients with ANVUGIB.Of the 532 patients with gastrointestinal bleeding,68 underwent endoscopic hemostasis,resulting in an endoscopic treatment rate of 12.8%,with a high immediate hemostasis success rate of 94.1%.

Research on the influences of motion characteristics of jetting projectile charge under water

Shaped charge warhead is important for enhancing the damage performance of underwater weapons.This paper used finite element analysis software and based on JPC water penetration experiments to examine the influence of liner parameters(wall thickness,material),charge aspect ratio,and stand-off distance on the movement characteristics of JPC in water.The findings reveal that the head diameter of the JPC increases and experiences significant erosion after entering the water,the effective length of the JPC in water undergoes two distinct phases:a growth phase and a decrease phase,with the velocity of the JPC decaying exponentially.Increasing the liner thickness,stand-off distance and the charge aspect ratio can improve the erosion resistance and the velocity retention capacity of the JPC.The optimal ranges for liner thickness and stand-off distance are 0.0363D_(k) to 0.0545D_(k)(D_(k) is the charge diameter),the stand-off distance should be within 1.0D_(k).After the charge aspect ratio higher than 1.25,the charge structure exerts minimal influence the movement characteristics of the JPC in water.Material density plays a crucial role in the velocity decay pattern of the JPC during penetration.JPC with higher densities exhibit superior velocity retention capabilities in water,with the velocity decay pattern converging if the densities are similar.Consequently,copper,tantalum and tungsten liners are deemed appropriate for underwater shaped charge warhead.Finally,the results will provide an important reference for the design of underwater shaped charge warhead.

Dynamic response mechanism and precursor characteristics of gneiss rockburst under different initial burial depths

To investigate the influence mechanism of geostress on rockburst characteristics,three groups of gneiss rockburst experiments were conducted under different initial geostress conditions.A high-speed photography system and acoustic emission(AE)monitoring system were used to monitor the entire rockburst process in real time.The experimental results show that when the initial burial depth increases from 928 m to 1320 m,the proportion of large fracture scale in rockburst increases by 154.54%,and the AE energy increases by 565.63%,reflecting that the degree and severity of rockburst increase with the increase of burial depth.And then,two mechanisms are proposed to explain this effect,including(i)the increase of initial geostress improves the energy storage capacity of gneiss,and then,the excess energy which can be converted into kinetic energy of debris ejection increases,consequently,a more pronounced violent ejection phenomenon is observed at rockburst;(ii)the increase of initial geostress causes more sufficient plate cracks of gneiss after unloading ofσh,which provides a basis for more severe ejection of rockburst.What’s more,a precursor with clear physical meaning for rockburst is proposed under the framework of dynamic response process of crack evolution.Finally,potential value in long term rockburst warning of the precursor obtained in this study is shown via the comparison of conventional precursor.

Experimental study of the damage characteristics of rocks containing non-penetrating cracks under cyclic loading

The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.

Deformation Characteristics of Hydrate-Bearing Sediments

The safe and efficient development of natural gas hydrate requires a deep understanding of the deformation behaviors of reservoirs.In this study,a series of triaxial shearing tests are carried out to investigate the deformation properties of hydrate-bearing sediments.Variations of volumetric and lateral strains versus hydrate saturation are analyzed comprehensively.Results indicate that the sediments with high hydrate saturation show dilative behaviors,which lead to strain-softening characteristics during shearing.The volumetric strain curves have a tendency to transform gradually from dilatation to compression with the increase in effective confining pressure.An easy prediction model is proposed to describe the relationship between volumetric and axial strains.The model coefficientβis the key dominating factor for the shape of volumetric strain curves and can be determined by the hydrate saturation and stress state.Moreover,a modified model is established for the calculation of lateral strain.The corresponding determination method is provided for the easy estimation of model coefficients for medium sand sediments containing hydrate.This study provides a theoretical and experimental reference for deformation estimation in natural gas hydrate development.

Experimental investigation on coal pore-fracture variation and fractal characteristics synergistically affected by solvents for improving clean gas extraction

Chemical solvents instead of pure water being as hydraulic fracturing fluid could effectively increase permeability and improve clean methane extraction efficiency.However,pore-fracture variation features of lean coal synergistically affected by solvents have not been fully understood.Ultrasonic testing,nuclear magnetic resonance analysis,liquid phase mass spectrometry was adopted to comprehensively analyze pore-fracture change characteristics of lean coal treated by combined solvent(NMP and CS_(2)).Meanwhile,quantitative characterization of above changing properties was conducted using geometric fractal theory.Relationship model between permeability,fractal dimension and porosity were established.Results indicate that the end face fractures of coal are well developed after CS2and combined solvent treatments,of which,end face box-counting fractal dimensions range from 1.1227 to 1.4767.Maximum decreases in ultrasonic longitudinal wave velocity of coal affected by NMP,CS_(2)and combined solvent are 2.700%,20.521%,22.454%,respectively.Solvent treatments could lead to increasing amount of both mesopores and macropores.Decrease ratio of fractal dimension Dsis 0.259%–2.159%,while permeability increases ratio of NMR ranges from 0.1904 to 6.4486.Meanwhile,combined solvent could dissolve coal polar and non-polar small molecules and expand flow space.Results could provide reference for solvent selection and parameter optimization of permeability-enhancement technology.

Characteristics of proppant transport and placement within rough hydraulic fractures

A three-dimensional reconstruction of rough fracture surfaces of hydraulically fractured rock outcrops is carried out by casting process,a large-scale experimental setup for visualizing rough fractures is built to perform proppant transport experiments.The typical characteristics of proppant transport and placement in rough fractures and its intrinsic mechanisms are investigated,and the influences of fracture inclination,fracture width and fracturing fluid viscosity on proppant transport and placement in rough fractures are analyzed.The results show that the rough fractures cause variations in the shape of the flow channel and the fluid flow pattern,resulting in the bridging buildup during proppant transport to form unfilled zone,the emergence of multiple complex flow patterns such as channeling,reverse flow and bypassing of sand-carrying fluid,and the influence on the stability of the sand dune.The proppant has a higher placement rate in inclined rough fractures,with a maximum increase of 22.16 percentage points in the experiments compared to vertical fractures,but exhibits poor stability of the sand dune.Reduced fracture width aggravates the bridging of proppant and induces higher pumping pressure.Increasing the viscosity of the fracturing fluid can weaken the proppant bridging phenomenon caused by the rough fractures.

Investigation of hydroxyl-terminated polybutadiene propellant breaking characteristics and mechanism impacted by submerged cavitation water jet

A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.

Modeling of the Soil-Water Characteristic Curve-Case Study in Bom Brinquedo Hill’s, Antonina, Brazil

In this paper,we present a modeling of the soil-water characteristic curve for residual and sedimentary soils of Bom Brinquedo Hill’s,located in Antonina,Brazil.This mountain range region is characterized as a natural disaster risk area,requiring continuous research related to the stability of the area.To obtain the soil-water characteristic curve,undisturbed samples of residual and sedimentary soil were collected,followed by suction testing using the filter paper method.Considering the bimodal characteristic presented by the soil,LABFIT software was employed for curve fitting using the generic formulation“Harris+C”.The results of the tests indicated that the phenomenon of hysteresis had a greater influence in situations with higher suction levels.When comparing the residual moisture values of the macropores between residual soil and sedimentary soil,the former exhibited the lower value.This suggests that the residual soil has a coarser grain size and larger pores,which facilitates the release of water retained in the soil’s macropores.