Pressure stimulated current in progressive failure process of combined coal-rock under uniaxial compression:Response and mechanism

Effective monitoring of the structural health of combined coal-rock under complex geological conditions by pressure stimulated currents(PSCs)has great potential for the understanding of dynamic disasters in underground engineering.To reveal the effect of this way,the uniaxial compression experiments with PSC monitoring were conducted on three types of coal-rock combination samples with different strength combinations.The mechanism explanation of PSCs are investigated by resistivity test,atomic force microscopy(AFM)and computed tomography(CT)methods,and a PSC flow model based on progressive failure process is proposed.The influence of strength combinations on PSCs in the progressive failure process are emphasized.The results show the PSC responses between rock part,coal part and the two components are different,which are affected by multi-scale fracture characteristics and electrical properties.As the rock strength decreases,the progressive failure process changes obviously with the influence range of interface constraint effect decreasing,resulting in the different responses of PSC strength and direction in different parts to fracture behaviors.The PSC flow model is initially validated by the relationship between the accumulated charges of different parts.The results are expected to provide a new reference and method for mining design and roadway quality assessment.

Experimental research on influence mechanism of loading rates on rock pressure stimulated currents

The study of pressure stimulated current(PSC)changes of rocks is significant to monitor dynamic disasters in mines and rock masses.The existing studies focus on change laws and mechanism of currents generated under the loading of rocks.An electrical and mechanics test system was established in this paper to explore the impacts of loading rates on PSCs.The results indicated that PSC curves of different rocks had different change laws under low/high loading rates.When the loading rate was relatively low,PSC curves firstly changed gently and then increased exponentially.Under high loading rates,PSC curves experienced the rapid increase stage,gentle increase stage and sudden change stage.The compressive strength could greatly affect the peak PSC in case of rock failure.The loading rate was a key factor in average PSC.Under low loading rates,the variations of PSCs conformed to the damage charge model of fracture mechanics,while they did not at the fracture moment.Under high loading rates,the PSCs at low stress didn’t fit the model due to the stress impact effects.The experimental results could provide theoretical basis for the influence of loading rates on PSCs.

Analysis on the Effect of Yiqi Huoxue Decoction Combined with Neuromuscular Electrical Stimulation in Improving ICU-Acquired Debility in Mechanically Ventilated Patients

Objective:To investigate the effect of Yiqi Huoxue decoction combined with neuromuscular electrical stimulation on improving intensive care unit(ICU)acquired debility in mechanically ventilated patients.Methods:50 patients who were admitted to the ICU and received mechanical ventilation treatment in our hospital from June 2022 to June 2023 and were complicated with ICU-acquired neurasthenia were selected,and randomly grouped using the randomized envelope method into two groups:control group with 25 patients who received neuromuscular electrical stimulation alone;observation group with 25 patients who received the traditional Chinese medicine Yiqi Huoxue decoction.Comparison indexes:treatment efficiency,degree of emotional recovery(APACHEⅡscore),muscle strength status(MRC score),motor status(FAC rating),and self-care ability(BI index score).Results:The treatment efficiency of patients in the observation group patients was higher as compared to those in the control group(P<0.05).There was no significant difference in the comparison of the results of the scores(ratings)of each index between the two groups before treatment(P>0.05).After the treatment,the APACHEⅡscores of patients in the observation group were significantly lower as compared to those in the control group,while the MRC scores,FAC ratings,and BI index scores were higher in the observation group than those of the control group patients(P<0.05).Conclusion:The combined application of Yiqi Huoxue decoction and neuromuscular electrical stimulation in the treatment of patients with ICU-acquired neurasthenia complicated by mechanical ventilation significantly enhanced the clinical efficacy,the patient’s muscle strength,motor status,and ability of self-care.Hence,it has high application value and is worthy to be popularized.

Impact of mechanical stimulation on the life cycle of horticultural plant

Mechanical stimulation technology is critical in agricultural crop production because it is constantly regarded as a developing green technology to regulate plants to meet people's need for green and healthy agricultural products. Various environmental mechanical stimulation impacts seed germination, seedling growth, flowering date, fruit quantity, and fruit quality throughout the life cycle of a horticultural plant. This study first outlines the basic characteristics of six types of common mechanical stimulation in nature:precipitation, wind, gravity,touch, sound, and vibration. The effects of various mechanical stimulation types on the seed, seedling, flowering, and fruit of horticultural plants throughout their whole life cycle are then presented, as reviewed in the recent 100 years of existing literature. Finally, potential future study directions are discussed. The main challenge in mechanical stimulation technology is to uncover its potential capabilities for regulating and controlling plant development and fruit quality in green agriculture instead of agricultural chemicals.

Biochemical and Physiological Responses of Arabidopsis thaliana Leaves to Moderate Mechanical Stimulation

Mechanical stimulation of plants can be caused by various abiotic and biotic environmental factors.Apart from the negative consequences,it can also cause positive changes,such as acclimatization of plants to stress conditions.Therefore,it is necessary to study the physiological and biochemical mechanisms underlying the response of plants to mechanical stimulation.Our aim was to evaluate the response of model plant Arabidopsis thaliana to a moderate force of 5 N(newton)for 20 s,which could be compared with the pressure caused by animal movement and weather conditions such as heavy rain.Mechanically stimulated leaves were sampled 1 h after exposure and after a recovery period of 20 h.To study a possible systemic response,unstimulated leaves of treated plants were collected 20 h after exposure alongside the stimulated leaves from the same plants.The effect of stimulation was assessed by measuring oxidative stress parameters,antioxidant enzymes activity,total phenolics,and photosynthetic performance.Stimulated leaves showed increased lipid peroxidation 1 h after treatment and increased superoxide dismutase activity and phenolic oxidation rate after a 20-h recovery period.Considering photosynthetic performance after the 20-h recovery period,the effective quantum yield of the photosystem II was lower in the stimulated leaves,whereas photochemical quenching was lower in the unstimulated leaves of the treated plants.Nonphotochemical quenching was lower in the stimulated leaves 1 h after treatment.Our study suggested that plants sensed moderate force,but it did not induce pronounced change in metabolism or photosynthetic performance.Principal component analysis distinguished three groups–leaves of untreated plants,leaves analysed 1 h after stimulation,while stimulated and unstimulated leaves of treated plants analysed 20 h after treatment formed together the third group.Observed grouping of stimulated and unstimulated leaves of treated plants could indicate signal transduction from the stimulated to distant leaves,that is,a systemic response to a local application of mechanical stimuli.

Mechanisms of repetitive transcranial magnetic stimulation for antidepression: Evidence from preclinical studies

This review summarizes the anti-depressant mechanisms of repetitive transcranial magnetic stimulation in preclinical studies,including anti-inflammatory effects mediated by activation of nuclear factor-E2-related factor 2 signaling pathway,anti-oxidative stress effects,enhancement of synaptic plasticity and neurogenesis via activation of the endocannabinoid system and brain derived neurotrophic factor signaling pathway,increasing the content of monoamine neurotransmitters via inhibition of Sirtuin 1/monoamine oxidase A signaling pathway,and reducing the activity of the hypothalamic-pituitary-adrenocortical axis.We also discuss the shortcomings of transcranial magnetic stimulation in preclinical studies such as inaccurate positioning,shallow depth of stimulation,and difficulty in elucidating the neural circuit mechanism up-and down-stream of the stimulation target brain region.

Repetitive transcranial magnetic stimulation in Alzheimer’s disease:effects on neural and synaptic rehabilitation

Alzheimer’s disease is a neurodegenerative disease resulting from deficits in synaptic transmission and homeostasis.The Alzheimer’s disease brain tends to be hyperexcitable and hypersynchronized,thereby causing neurodegeneration and ultimately disrupting the operational abilities in daily life,leaving patients incapacitated.Repetitive transcranial magnetic stimulation is a cost-effective,neuro-modulatory technique used for multiple neurological conditions.Over the past two decades,it has been widely used to predict cognitive decline;identify pathophysiological markers;promote neuroplasticity;and assess brain excitability,plasticity,and connectivity.It has also been applied to patients with dementia,because it can yield facilitatory effects on cognition and promote brain recovery after a neurological insult.However,its therapeutic effectiveness at the molecular and synaptic levels has not been elucidated because of a limited number of studies.This study aimed to characterize the neurobiological changes following repetitive transcranial magnetic stimulation treatment,evaluate its effects on synaptic plasticity,and identify the associated mechanisms.This review essentially focuses on changes in the pathology,amyloidogenesis,and clearance pathways,given that amyloid deposition is a major hypothesis in the pathogenesis of Alzheimer’s disease.Apoptotic mechanisms associated with repetitive transcranial magnetic stimulation procedures and different pathways mediating gene transcription,which are closely related to the neural regeneration process,are also highlighted.Finally,we discuss the outcomes of animal studies in which neuroplasticity is modulated and assessed at the structural and functional levels by using repetitive transcranial magnetic stimulation,with the aim to highlight future directions for better clinical translations.

Neuroprotective effects of repetitive transcranial magnetic stimulation on Alzheimer's disease: Undetermined therapeutic protocols and mechanisms

Alzheimer's disease(AD)is a prevalent neurodegenerative disorder characterized by gradual deterioration of cognitive functions,for which an effective treatment is currently unavailable.Repetitive transcranial magnetic stimulation(rTMS),a well-established noninvasive brain stimulation method,is utilized in clinical settings to address various neuropsychiatric conditions,such as depression,neuropathic pain,and poststroke dys-function.Increasing evidence suggests that rTMs may enhance cognitive abilities in individuals with AD.However,its optimal therapeutic protocols and precise mechanisms are currently unknown,impeding its clinical implementation.In the present review,we aimed to summarize and discuss the efficacy-related parameters in rTMs treatment,encompassing stimulus frequency,stimulus pattern,stimulus intensity,and the configuration of the stimulus coil.Furthermore,we reviewed promising rTMS therapeutic protocols involving various combinations of these factors,that were examined in clinical studies.Based on our analysis,we propose that a multisite high-frequency rTMS(HF-rTMS)regimen has value in AD therapy,and that promising single-site protocols,such as HF-rTMS,applied over the left dorsolateral prefrontal cortex,precuneus,or cerebellum are required to be validated in larger clinical studies.Lastly,we provide a comprehensive review of the potential mechanisms underlying the neuroprotective effects of rTMS on cognition in AD in terms of brain network modulation as well as cellular and molecular reactions.In conclusion,the interaction of diverse mechanisms may be responsible for the total therapeutic effect of rTMS on AD.This review provides theoretical and practical evidence for the future clinical application and scientific research of rTMS in AD.

Role of TGF-βl Signaling in Heart Valve Calcification Induced by Abnormal Mechanical Stimulation in a Tissue Engineering Model

A tissue engineering model of heart valve calcification induced in a bio-reactor was established to evaluate the calcification induced by abnormal mechanical stimulation and explore the underlying molecular mechanisms.Polyethylene glycol (PEG)-modified decellularized porcine aortic leaflets seeded with human valve interstitial cells (huVICs)were mounted on a Ti-Ni alloy frame to fabricate two-leaflet and three-leaflet tissue engineered valves.The two-leaflet model valves were exposed to abnormal pulsatile flow stimulation with null (group A),low (1000mL/min,group B),medium (2000mL/min,group C),and high velocity (3000mL/min,group D)for 14 days. Morphology and calcification were assessed by yon Kossa staining,alkaline phosphatase (ALP)content,and Runx2 immunostaining.Leaflet calcification and mRNA and protein expression of transforming growth factor (TGF)-β1,bone morphogenetic protein 2 (BMP2),Smadl,and MSX2 were measured at different time points.ALP content was examined in two-leaflet valves seeded with BMP2 shRNA plasmid-infected huVICs and exposed to the same stimulation conditions.The results showed that during 14 days of flow stimulation,huVICs on the leaflet surface proliferated to generate normal monolayer coverage in groups A,B,and C.Under mechanical stimulation,huVICs showed a parallel growth pattern in the direction of the fluid flow,but huVICs exhibited disordered growth in the high-velocity flow environment,yon Kossa staining,ALP measurement,and immunohistochemical staining for Runx2 confirmed the lack of obvious calcification in group A and significant calcification in group D.Expression levels of TGF-β1,BMP2, and MSX2 mRNA and protein were increased under fluid stimulation.ALP production by BMP2 shRNA plasmid-infected huVICs on model leaflets was significantly reduced.In conclusion,abnormal mechanical stimulation in a bioreactor induced calcification in the tissue engineering valve model.The extent of calcification correlated positively with the flow velocity,as did the mRNA and protein levels of TGF-β1,BMP2,and MSX2.These findings indicate that TGF-β1/BMP2 signaling is involved in valve calcification induced bv abnormal mechanical stimulation.

Screening for Resistance Mechanisms in Cowpea Genotypes on <i>Alectra vogelii</i>

Parasitic angiosperm Alectra vogelii Benth is a growing problem in Malawi, particularly with current emphasis on legumes. Therefore, two studies were set in order to understand the possible mechanisms of resistance in cowpea genotypes on their reaction to the parasitic weed. In the first experiment, Mkanakaufiti, IT99K-7-21-2-2XIT82E-16, Sudan 1 and IT82E-16 were grown in Alectra infested and non-infested pots. The experiment (2*4 factorial treatment combination) was arranged in an RCBD and replicated eight times. The second experiment, involved Petri-dish techniques where 4 genotype roots were assessed on their ability to stimulate the germination of A. vogelii as a proxy for germination stimulant production. The experiment was arranged in an RCBD and replicated five times. In the first experiment, data was collected on;the number of days to first Alectra emergence, Alectra shoot counts at 6, 8, 10, and 12 weeks after planting (WAP), Alectra attachment at 5 and 12 WAP, Alectra biomass at 12 WAP, cowpea biomass parameters at 5 and 12 WAP, yield and yield components per pot. While in the second experiment, number of germinated Alectra seeds per Petri dishes was recorded. The results indicated that IT82E-16 (33.25 days) and Sudan 1 (34.25 days) were earlier infested whilst late on IT99K-7-21-2-2XIT82E-16 (38 days) which correlated to the number of Alectra attachments. There were significant differences (p = 0.05) in weekly Alectra counts between cowpea varieties from 6 up to 10 WAP. Mkanakaufiti and IT99K-7-21-2-2XIT82E-16 were observed with no and few Alectra shoots infestation respectively which was an indicator of resistance mechanism in the study. Number of pods, grain weight (g) and harvest index per pot were significantly affected by inoculation protocol with lower yield on infested cowpea genotypes. The same trend was observed on cowpea varieties where Mkanakaufiti (21.9 g/pot) shown higher yield followed by IT82E-16 (12.5 g/pot) which is susceptible but with tolerance ability to the parasitic weed. The study has shown that resistance mechanisms can be categorized as no or few Alectra shoots, death of Alectra shoots and late infestation. In the Petri dishes, only 3 WAP grown Mkanakaufiti root media failed to induce the germination of Alectra seeds while the opposite occurred on IT82E-16, Sudan 1 and IT99K-7-21-2-2XIT82E-16. On the contrary, 4 WAP grown root media of the four genotypes stimulated Alectra germination which shed more light on the seed behaviour in the soil. This is worth exploring as more could be known to what causes termination of Alectra shoots on Mkanakaufiti. Still, intensifying resistant genotypes should be a goal in order to reduce Alectra seed banks in the soil, thereby, increasing cowpea yield.

Dynamic Fluid Flow Mechanical Stimulation Modulates Bone Marrow Mesenchymal Stem Cells

Osteoblasts are derived from mesenchymal stem cells （MSCs）, which initiate and regulate bone formation. New strategies for osteoporosis treatments have aimed to control the fate of MSCs. While functional disuse decreases MSC growth and osteogenic potentials, mechanical signals enhance MSC quantity and bias their differentiation toward osteoblastogenesis. Through a non-invasive dynamic hydraulic stimulation （DHS）, we have found that DHS can mitigate trabecular bone loss in a functional disuse model via rat hindlimb suspension （HLS）. To further elucidate the downstream cellular effect of DHS and its potential mechanism underlying the bone quality enhancement, a longitudinal in vivo study was designed to evaluate the MSC populations in response to DHS over 3, 7, 14, and 21 days. Five-month old female Sprague Dawley rats were divided into three groups for each time point： age-matched control, HLS, and HLS＋DHS. DHS was delivered to the right mid-tibiae with a daily ＂10 min on-5 min off-10 min on＂ loading regime for five days/week. At each sacrifice time point, bone marrow MSCs of the stimulated and control tibiae were isolated through specific cell surface markers and quantified by flow cytometry analysis. A strong time-dependent manner of bone marrow MSC induction was observed in response to DHS, which peaked on day 14. After 21 days, this effect of DHS was diminished. This study indicates that the MSC pool is positively influenced by the mechanical signals driven by DHS. Coinciding with our previous findings of mitigation of disuse bone loss, DHS induced changes in MSC number may bias the differentiation of the MSC population towards osteoblastogenesis, thereby promoting bone formation under disuse conditions. This study provides insights into the mechanism of time-sensitive MSC induction in response to mechanical loading, and for the optimal design of osteovorosis treatments.

Mechanical stimulation of the scalp improves the extra-and intracranial blood circulation in humans and mice

Background:Scalp combing,as an ancient method of health care,has been used for thousands of years in traditional Chinese medicine.Although this method is considered to be beneficial for the blood circulation of the head,the underlying mechanisms remain unclear.Methods:Both human participants and mice were used in this study.In participants,the scalp was stimulated by combing continuously for 5 min,and the temperature was measured using infrared thermal imaging before and after stimulation.In mice,the temperature was determined before and at 5,15,and 30 min after a 5-min scalp mechanical stimulation(SMS).Additionally,the vasculature of the mice was labeled with retro-orbital fluorescein isothiocyanate-dextran injection,and the capillaries were observed directly under a confocal microscope.Using in vivo CLARITY imaging and the spectrofluorometric detection of Evans Blue dye extravasation,the bloodebrain barrier permeability was assessed.Results:SMS increased the temperature of the left ear significantly in human(P=.0247)while can slightly increase the temperature of the right ear and the face without significant difference(P>.05).Moreover,SMS can significantly slow the decrease in the temperature of the external auditory canal at 5 min(P=.0153)and in body temperature at 15 min(P=.0295)after SMS whereas no significant difference in body temperature at 30 min(P>.05)compared with control mice.Furthermore,capillaries of the ear with a diameter of less than 8 mm were significantly dilated(P=.0006)following SMS and the number of dextran dots was higher at 15 min(P>.05)and 30 min(F=10.98,P=.037)after SMS intervention compared with control mice.Conclusion:Our study provides strong evidence to support the notion that scalp combing can improve extra-and intracranial blood circulation under healthy conditions.

Healing Wounds under Mechanical Stress: A Case Example

This paper challenges the concept that the essential element in wound healing is to offload pressure. We suggest a change in approach that recognizes the integumentary system as one which, like all other body systems, adapts to the stresses put upon it. We use a clinical case example to illustrate the use of intentional mechanical stress to promote wound healing and include a review of the relevant literature. The intent of this publication is to call for a new look at clinical practice regarding wound healing and to call for future research directed at investigation of this theory.

Studies on Stimulating Effect of Two Selective Insecticides on the Numbers of Laid Egg by Yellow Rice Borer,Tryporyza incertulas(Walker)and Their Effects on Biochemistry of Rice Plants

Buprofezin and imidacloprid are selective insecticides against Homoptera insects. This paper investigated stimulating effect of the two insecticides on the number of laid eggs by yellow rice borer, Tryporyza incertulas(Walker) of three generations in 20012002. The results showed that the reproductive rate of emergence months during the larvae feeding on the rice plants of Xiushui63 treated with the two insecticides was significantly higher than that of control, indicating that the numbers of laid eggs by the borer was stimulated following buprofezin and imidacloprid applications. However, there was no such effect for the larvae feeding on rice variety Zhendao2 which showed moderate resistance to the insect. In addition, the incidence of stimulating egg laid for the first instar treated with the two insecticides was greater than that for the third instar. Biochemical tests showed that oxalic acid concentration declined, and photosynthetic rate of rice leaves following the two insecticide applications declined significantly compared to control, whereas reducing sugar concentration increased significantly for all other treatments of two varieties except Xiushui63 treated with buprofezin. The level of glutathione-S-transferase varied with rice variety and insecticide.

Establish the Long-effective Mechanism of Food Security in China

In despite of fluctuation in recent years, the grain yield in China has been increasing, which relieves the conflict between supply and demand and turns the situation of food security good. However, because of the rapid increase in food consumption, the conflicts of food quality and structure in the supply and demand equilibrium has become more and more obvious and the long-effective mechanism of food security has not been estab-lished yet. It is found that the factors affecting food security in China include the scarcity and dissipation of resources, farmers’ low enthusiasm in planting grain crops and the inappropriateness of the emphasis and measures of macro-economic regulation and control. Therefore, the authors advance to optimize resources allocation, strengthen macro-economic regulation and control and policy stimulation and establish the mechanism of allocating grain production cost, to set up the long-effective mechanism of China food security and keep it stable in the long term.

Effects of bionic mechanical stimulation on the properties of engineered cartilage tissue

Tissue-engineered cartilage(TEC)remains a potential alternative for the repair of articular cartilage defects.However,there has been a significant different between the properties of TEC and those of natural cartilage.Studies have shown that mechanical stimulation such as compressive load can help regulate matrix remodelling in TEC,thus affecting its biomechanical properties.However,the influences of shear induced from the tissue fluid phase have not been well studied and may play an important role in tissue regeneration especially when integrated with the compressive load.Therefore,the aim of this study was to quantitatively investigate the effects of combined loading mechanisms on TEC in vitro.A bespoke biosimulator was built to incorporate the coupled motion of compression,friction and shear.The specimens,encapsulating freshly isolated rabbit chondrocytes in a hydrogel,were cultured within the biosimulator under various mechanical stimulations for 4 weeks,and the tissue activity,matrix contents and the mechanical properties were examined.Study groups were categorized according to different mechanical stimulation combinations,including strain(5-20%at 5%intervals)and frequency(0.25 Hz,0.5 Hz,1 Hz),and the effects on tissue behaviour were investigated.During the dynamic culture process,a combined load was applied to simulate the combined effects of compression,friction and shear on articular cartilage during human movement.The results indicated that a larger strain and higher frequency were more favourable for the specimen in terms of the cell proliferation and extracellular matrix synthesis.Moreover,the combined mechanical stimulation was more beneficial to matrix remodelling than the single loading motion.However,the contribution of the combined mechanical stimulation to the engineered cartilaginous tissue matrix was not sufficient to impede biodegradation of the tissue with culture time.

Oscillating Mechanical Stimulation of the Craniocervical Region as Physical Therapy for Chronic Migraine: A Pilot Trial

Objective: We conducted a prospective trial of oscillating mechanical stimulation (OS) of the craniocervical region as treatment for drug-refractory chronic migraine (CM). Methods: Ten patients (8 women, 2 men;mean age 47.0 &plusmn;15.1 years) were enrolled. The treatment was administered over an 8-week period to 13, 4, and 9 sites on the face and head, neck, and upper back, respectively, at 5- to 15-pound intensity. The primary outcome measure was the number of days patients suffered a migraine (hereafter “number of migraine days”), and the secondary outcome measures were the six-item Headache Impact Test (HIT-6) and Visual Analog Scale (VAS) scores for migraine pain intensity and the nine-item Patient Health Questionnaire (PHQ-9) and the seven-item Generalized Anxiety Disorder (GAD-7) scale scores. Results: Nine patients completed treatment. The number of migraine days remained unchanged, from a mean 21.7 &plusmn;11.6 days/month before treatment to 19.3 &plusmn;7.3 days/month upon completion of treatment. However, the HIT-6 scores improved from 67.0 &plusmn;8.2 to 61.4 &plusmn;7.1 (p = 0.007) after 3 weeks, 61.1 &plusmn;11.5 (p = 0.01) after 6 weeks, and 59.9 &plusmn;11.6 (p = 0.035) upon completion of treatment. Similarly, the VAS scores improved significantly from 7.3 &plusmn;1.7 to 5.7 &plusmn;3.1 (p = 0.018) at 6 weeks and 4.8 &plusmn;2.8 (p = 0.011) upon completion of treatment. The GAD-7, PHQ-9, and allodynia scale scores remained unchanged. Conclusion: Our data suggest that OS is well tolerated and may become a feasible form of treatment for drug-resistant CM.

Mechanisms of remaining oil formation by water flooding and enhanced oil recovery by reversing water injection in fractured-vuggy reservoirs

To get a deeper understanding on the formation mechanisms and distribution laws of remaining oil during water flooding, and enhanced oil recovery(EOR) mechanisms by reversing water injection after water flooding, 3D visualization models of fractured-vuggy reservoir were constructed based on the elements and configuration of fractures and vugs, and typical fracture-vug structures by using advanced CT scanning and 3D printing technologies. Then, water flooding and reversing water injection experiments were conducted. The formation mechanisms of remaining oil during water flooding include inadequate injection-production well control, gravity difference between oil and water, interference between different flow channels, isolation by low connectivity channel, weak hydrodynamic force at the far end. Under the above effects, 7 kinds of remaining oil may come about, imperfect well-control oil, blind side oil, attic oil at the reservoir top, by-pass residual oil under gravity, by-pass residual oil in secondary channel, isolated oil in low connectivity channel, and remaining oil at far and weakly connected end. Some remaining oil can be recovered by reversing water injection after water flooding, but its EOR is related to the remaining oil type, fracture-cavity structure and reversing injection-production structure. Five of the above seven kinds of remaining oil can be produced by six EOR mechanisms of reversing water injection: gravity displacement, opening new flow channel, rising the outflow point, hydrodynamic force enhancement, vertically equilibrium displacement, and synergistic effect of hydrodynamic force and gravity.

不同预时效挤压态Mg−Gd−Y−Zn−Zr合金的再结晶行为和强化机制

通过控制预时效时间制备3种不同状态的试样,研究不同预时效状态对挤压态Mg−9.5Gd−4Y−2.2Zn−0.5Zr(质量分数,%)合金的动态再结晶行为(DRX)和性能的影响。结果表明,欠时效挤压(UAE)样品的细晶体积分数为17.4%,而峰时效挤压(PAE)和过时效挤压(OAE)样品的细晶体积分数分别达到89.7%和50.4%。在晶粒内部和晶界处分布的致密、细小的β颗粒相通过粒子激发形核机制显著提高了形核位点和位错密度。然而,致密针状γ'相抑制位错滑移,延迟DRX形核。PEA和OAE样品中细小晶粒的差异归因于原始颗粒相的数量和尺寸的不同,而其拉伸性能的差异归因于不同的显微组织。由于晶界强化和析出强化机制的贡献更大,PAE样品具有更优异的拉伸性能。

结合对抗训练和特征混合的孪生网络防御模型

神经网络模型容易受到对抗样本攻击。针对当前防御方法侧重改进模型结构或模型仅使用对抗训练方法导致防御类型单一且损害模型分类能力、效率低下的问题,提出结合对抗训练和特征混合训练孪生神经网络模型(SS-ResNet18)的方法。该方法通过线性插值混合训练集样本数据,使用残差注意力模块搭建孪生网络模型,将PGD对抗样本和正常样本输入不同分支网络进行训练。在特征空间互换相邻样本部分输入特征以增强网络抗干扰能力,结合对抗损失和分类损失作为网络整体损失函数并对其进行标签平滑。在CIFAR-10和SVHN数据集上进行实验,该方法在白盒攻击下表现出优异的防御性能,黑盒攻击下模型对PGD、JSMA等对抗样本的防御成功率均在80%以上;同时,SS-ResNet18模型时间花销仅为子空间对抗训练方法的二分之一。实验结果表明,SS-ResNet18模型能防御多种对抗样本攻击,与现有防御方法相比,其鲁棒性强且训练耗时较短。