Background:Hospitals have reported that implementing rapid response system activation(RRS)activation has increased patient safety.As a result,there has been growing interest in identifying factors that lead to success...Background:Hospitals have reported that implementing rapid response system activation(RRS)activation has increased patient safety.As a result,there has been growing interest in identifying factors that lead to successful RRS activation.While introducing an automated RRS activation system has prompted nurses to be more vigilant about monitoring vital signs,it has not necessarily encouraged them to conduct thorough patient assessments to identify early signs of deterioration.Purpose:The current study aimed to assess nurses’attitudes towards RRS activation for clinically deteriorated patients in the clinical units of King Abdul-Aziz Hospital.Methods:A descriptive cross-sectional research design was utilised in the study,and 144 nurses working in the medical and surgical units of King Abdul-Aziz Hospital were recruited to participate using a convenient non-probability sampling technique.Results:The study’s findings reported that nurses have a positive attitude towards RRS benefits(Mean=3.70;SD=0.70).Their overall attitude towards RRS activation among clinically deteriorated patients is still low positive(Mean=2.71;SD=0.61).The nurses’attitudes towards RRS benefits significantly differ among nationalities and the clinical area/unit where they were assigned,with a P-value of 0.0194 and 0.000,respectively.Attitudes towards RRS barriers significantly differ among nationality(P-value=0.0037),education level(P-value=0.0032),area of assignment(P-value=0.020),and whether they have a good understanding of abnormal observations(P-value=0.0122).Regarding the nurses’attitude towards management belief,the significant result is only with the clinical area/unit of assignment with a P-value of 0.000.Conclusion:The current study found a low positive attitude towards RRS activation among ward nurses,especially given that monitoring vital signs is critical to their job.Nurses may fear being perceived as clinically inept for redundant activations caused by poor quality,but their attitude towards activating the RRS in clinical deterioration is still largely negative.This is because most RRSs rely on ward nurses to recognise clinical deterioration and manually alert responders through phone calls,hospital communication systems,or face-to-face communication.展开更多
Deterioration and loss of quality of vegetable oil is a big challenge in the food industry.This study investigated the synthesis of nickel ferrite(Ni Fe_(2)_(O4))via co-precipitation method and its use for the removal...Deterioration and loss of quality of vegetable oil is a big challenge in the food industry.This study investigated the synthesis of nickel ferrite(Ni Fe_(2)_(O4))via co-precipitation method and its use for the removal of free fatty acids(FFAs)in deteriorated vegetable oil.Ni Fe2 O4 was characterized using Fourier transformed infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermogravimetric(TG)analysis,Brunauer–Emm ett–Teller(BET)surface area,transmission electron microscopy(TEM),scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDX).Synthesis of Ni Fe_(2)_(O4)was confirmed by characterization,which revealed a BET surface area of 16.30 m^(2)·g^(-1)and crystallite size of 29 nm.Ni Fe_(2)_(O4)exhibited an adsorption capacity of 145.20 L·kg^(-1)towards FFAs with an 80.69%removal in a process,which obeys Langmuir isotherm and can be described by the pseudo-second-order kinetic model.The process has enthalpy(DH)of 11.251 k Jámolà1 and entropy(DS)of 0.038 k J·mol^(-1)K^(-1)with negative free energy change(DG),which suggests the process to be spontaneous and endothermic.The quantum chemical computation analysis via density functional theory further revealed the sorption mechanism of FFAs by Ni Fe_(2)_(O4)occurred via donor–acceptor interaction,which may be described by the lowest unoccupied molecular orbital(LUMO)and the highest occupied molecular orbital(HOMO).The study showed Ni Fe_(2)_(O4)to be a potential means that can remove FFAs from deteriorated vegetable oil.展开更多
This paper aims to present an effective method to partial deteriorated strength columns,and to investigate the mechanical behavior of the defect part. Five groups of 150×150 mm×mm plain square columns are ca...This paper aims to present an effective method to partial deteriorated strength columns,and to investigate the mechanical behavior of the defect part. Five groups of 150×150 mm×mm plain square columns are cast; each specimen has two different strengths,the lower strength in the middle segment and higher strength in both ends. The lower strength is to simulate the status of partial deteriorated region. Different layers of CFRP sheets have been wrapped just on the lower strength part to gain the reinforcement with CFRP sheets,and to verify the practicability of partial confinement. Specimens are subjected to monotonic axial compression until failure. Axial load,axial and transverse strains are measured to compare the different behaviors between the two parts. Experimental results show that partial confinement can significantly enhance the strength and the ductility of the deteriorated strength part,then,the load capacity of the whole column can be increased subsequently. Test data indicate that the ultimate load of the confined column is higher than that of the original column without deterioration; partial confinement on weakness is a feasible approach.展开更多
This paper considers a deteriorated multi-item economic order quantity (EOQ) problem, which has been studied in literature, but the algorithms used in the literature are limited. In this paper, we explore the optimal ...This paper considers a deteriorated multi-item economic order quantity (EOQ) problem, which has been studied in literature, but the algorithms used in the literature are limited. In this paper, we explore the optimal policy of this inventory problem by analyzing the structural properties of the model, and introduce a simple algorithm for generating the optimal solution to this problem. Numerical results are reported to show effi-cacy of the proposed method.展开更多
Water level fluctuations in the reservoir deteriorate soils and rocks on the bank landslides by drying-wetting(D-W)cycles,which results in a significant decrease in mechanical properties.A comprehensive understanding ...Water level fluctuations in the reservoir deteriorate soils and rocks on the bank landslides by drying-wetting(D-W)cycles,which results in a significant decrease in mechanical properties.A comprehensive understanding of deterioration mechanism of sliding-zone soils is of great significance for interpreting the deformation behavior of landslides.However,quantitative investigation on the deterioration characteristics of soils considering the structural evolution under D-W cycles is still limited.Here,we carry out a series of laboratory tests to characterize the multi-scale deterioration of sliding-zone soils and reveal the mechanism of shear strength decay under D-W cycles.Firstly,we describe the micropores into five grades by scanning electron microscope and observe a critical change in porosity after the first three cycles.We categorize the mesoscale cracks into five classes using digital photography and observe a stepwise increase in crack area ratio.Secondly,we propose a shear strength decay model based on fractal theory which is verified by the results of consolidated undrained triaxial tests.Cohesion and friction angle of sliding-zone soils are found to show different decay patterns resulting from the staged evolution of structure.Then,structural deterioration processes including cementation destruction,pores expansion,aggregations decomposition,and clusters assembly are considered to occur to decay the shear strength differently.Finally,a three-stage deterioration mechanism associated with four structural deterioration processes is revealed,which helps to better interpret the intrinsic mechanism of shear strength decay.These findings provide the theoretical basis for the further accurate evaluation of reservoir landslides stability under water level fluctuations.展开更多
In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical...In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.展开更多
The girder end restraint devices such as bearings and dampers on long span suspension bridge will deteriorate over time.However,it is difficult to achieve the quantitative assessment of the performance of the restrain...The girder end restraint devices such as bearings and dampers on long span suspension bridge will deteriorate over time.However,it is difficult to achieve the quantitative assessment of the performance of the restraint device through existing detection methods in actual inspections,making it difficult to obtain the impact of changes in the performance of the restraint device on the bridge structure.In this paper,a random vehicle load model is firstly established based on the WIM data of Jiangyin Bridge,and the displacement of girder end under the actual traffic flow is simulated by using finite element dynamic time history analysis.On this basis,according to the performance test data of the bearings and dampers,the performance degradation laws of the above two restraint devices are summarized,and the performance degradation process of the two restraint devices and the effects of different restraint parameters on the bridge structure are simulated.The results show that the performance degradation of the damper will significantly reduce the damping force at low speed,resulting in a significant increase in the cumulative displacement of the girder end;in the presence of longitudinal dampers,the increase in the friction coefficient caused by the deterioration of the bearing sliding plate has little effect on the cumulative displacement,but excessive wear of the bearing sliding plate adversely affects the structural dynamic performance.展开更多
Our study aims at developing compatible raw compositions of earth with building materials in the desert zones,for an adequate restoration.To arrive at our objective,we developed compositions of adobes in bases of the ...Our study aims at developing compatible raw compositions of earth with building materials in the desert zones,for an adequate restoration.To arrive at our objective,we developed compositions of adobes in bases of the local raw materials(red clay of Adrar,sand of dune,the black sand and the chopped straw).The results of the mineralogical characteristics(Rx),physical(density,the humidity and the grading analysis)used raw materials,showed successful and compatible characteristics with the building materials of the Saharan Ksour.The formulations are based on compositions witnesses as reference(1 Volume of clay+2 Volume of sand+water).The objective of this study,concerns the identification of the various mechanical characteristics(mechanical resistance in the flexion and in the compression),followed by an ultrasound study(mechanism of change in front of hydric behavior),of the compatible adobe with the local building materials.展开更多
Determining the high-temperature history of rocks and evaluating their associated deterioration levels are essential for the stable and efficient functioning of geological engineering projects.This research introduces...Determining the high-temperature history of rocks and evaluating their associated deterioration levels are essential for the stable and efficient functioning of geological engineering projects.This research introduces a precise,time-efficient,and cost-effective approach that integrates metal intrusion technology,backscattered electron(BSE)imaging,and the ResNet50 deep-learning algorithm to differentiate high-temperature histories.The damage characteristics in the microstructure of rocks subjected to different temperature treatments are successfully extracted.The results show that,compared to previously reported convolutional neural networks(CNN)training and classification methods,the proposed ResNet50 algorithm improves identification accuracy by over 10%,achieving up to 98%accuracy in classifying degraded sandstone treated at temperatures ranging from 25℃ to 1000℃.More importantly,through feature extraction of sandstone specimens after high-temperature deterioration,the ResNet50 algorithm demonstrates a superior ability to locate microscopic damage characteristics associated with different temperatures-an achievement rarely reported in previous research.For sandstone specimens exposed to 200℃-600℃,the extracted features primarily highlight the opening of primary pores and changes in rock particle morphology.In contrast,as the treated temperature exceeds 600℃,the extracted features predominantly reflect thermal damage fracture,whose area first diffuses and then concentrates,aligning closely with the thermal damage theory of rock.The findings of this study not only advance a deep learning-based approach for identifying rock deterioration after high-temperature exposure but also deepen the understanding of the relation between rock microstructural characteristics and high-temperature deterioration.展开更多
Food security has been an issue of global concern and this has attracted a lot of research interest. Cassava is an extremely popular crop and is becoming the cornerstone for addressing food security in many parts of t...Food security has been an issue of global concern and this has attracted a lot of research interest. Cassava is an extremely popular crop and is becoming the cornerstone for addressing food security in many parts of the world. The competing needs for cassava cuts across both human and animal consumption. It serves as a raw material in textile industry and is now one of the preferred materials for making biofuels. As the world’s population continues to grow, the demand for drought resistant crops such as cassava is increasing. The high demand for various forms of processed cassava will continue to increase cassava prices making it an attractive business venture. Several small-scale cassava farmers are making a fortune and additional income through this business. Preliminary investigations show that the profitable way for a farmer to market his cassava is to add value to it. Unfortunately, cassava undergoes post-harvest physiological deterioration (PPD) after three days of harvest. In order to make cassava farming even more profitable, there is a need to process it within the shelf life of 2 - 3 days after harvesting. One way to preserve cassava is by grating it into pulp and drying it into pellets or chips. In this study, an electrically powered multi-purpose cassava grating machine with grater blades inclined at two different tooth angles, 25˚ and 30˚ was designed, fabricated and its performance characteristics investigated. The results showed that the plate with a tooth angle of 30˚ resulted in higher grating efficiency. This was attributed to better grip on the cassava when perforations on the plate inclined at 30˚. The grating capacity was also significantly improved as very small amounts of cassava slipped out un-grated.展开更多
Utilizing the ballast layer with more durable and stable characteristics can help avoid significant expenses due to decreased maintenance efforts.Strengthening the ballast layer with different types of reinforcements ...Utilizing the ballast layer with more durable and stable characteristics can help avoid significant expenses due to decreased maintenance efforts.Strengthening the ballast layer with different types of reinforcements or substituting the stone aggregates with the appropriate granular materials could potentially help to achieve this goal by reducing the ballast deterioration.One of the exquisite and most effective solutions to eliminate these challenges is to use waste materials such as steel slag aggregates and useless tires.Utilizing these waste materials in the ballasted railway track will contribute to sustainable development,an eco-friendly system,and green infrastructure.So in a state-of-the-art insightful,the ballast aggregates,including a mixture of steel slag and stone aggregates,are reinforced with a novel kind of geo-grid made of waste tire strips known as geo-scraps.This laboratory research tried to explain the shear strength behavior of the introduced mixing slag-stone ballast reinforced with tire geo-scrap.To achieve this goal,a series of large-scale direct shear tests were performed on the ballast which is reinforced by tire geo-scrap and included various combinations of slag and stone aggregates.The concluded results indicate that the optimal mixing ratio is attained by a combination of 75%slag and 25%stone aggregates which is reinforced by tire geo-scrap at a placing level of 120 mm.In this case,the shear strength,internal friction angle,vertical displacement,and dilatancy angle of stone–slag ballast reinforced with geo-scraps exhibited average changes of+28%,+9%,-28%,and-15%,respectively.展开更多
Alzheimer’s disease(AD)is a slow,progressive neurodegenerative disease with clinical symptoms that typically emerge in the elderly,leading to deterioration of cognitive functions over time.Memory loss is the primary ...Alzheimer’s disease(AD)is a slow,progressive neurodegenerative disease with clinical symptoms that typically emerge in the elderly,leading to deterioration of cognitive functions over time.Memory loss is the primary symptom,eventually leading to significant declines in executive and cognitive functions,along with psychiatric and behavioral changes,and alterations in personality.展开更多
To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion condition...To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion conditions,the weakening characteristics,observable characteristics,softening characteristics of the dynamic parameters,dynamic failure characteristics,dynamic failure forms and dynamic microscopic characteristics were analyzed.Under each corrosion condition,the dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity tended to decrease with immersing time.The dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity exhibited an inverted U-shaped trend.Under dynamic impact,the failure process of acidly corroded samples can be divided into the following stages:the initial stage,elastic energy accumulation stage,local failure of coal and secondary rock crack expansion stage,coal fragment ejection stage,rock spalling stage and complete instability stage.Under dynamic impact,failure modes exist:coal crushing failure,rock fragmenting failure,rock splitting failure and full splitting failure.After impact failure,sample fragments are distributed in powder,granular,cone and block forms.Based on Zhu-Wang-Tang nonlinear viscoelastic properties,a model considering chemical corrosion and impact damage was proposed.The combined effects of chemical and impact-induced damage on the dynamic mechanical properties of coal-rock assemblages were systematically analyzed.展开更多
The rock masses in the hydro-fluctuation zone of reservoir banks sustain wettingdrying cycles(WDC),thereby affecting the stability of the reservoir bank slope.In this paper,rock masses with argillaceous siltstone and ...The rock masses in the hydro-fluctuation zone of reservoir banks sustain wettingdrying cycles(WDC),thereby affecting the stability of the reservoir bank slope.In this paper,rock masses with argillaceous siltstone and silty mudstone interbedded in Badong Formation were taken as the research object to investigate the variation of strength parameters of soft and hard interbedded rock masses with WDC and dip angle through laboratory experiments and numerical experiments.Some attempts were made to reveal the mechanical properties deterioration mechanism of interbedded rock masses by quantitatively analyzing the contribution of strength parameters deterioration of hard rocks,soft rocks,and bedding planes to the strength parameters deterioration of rock masses.The results indicate that the logarithmic function could be used to describe the deterioration of each strength parameter of both argillaceous siltstone and silty mudstone and bedding plane with the number of WDC.The strength parameters of interbedded rock masses decrease as the number of WDC increases,with the largest decrease after the first cycle and then slowing down in the later cycles.The strength parameters initially decrease and then increase as the dip angles increase.The impact of deteriorated strength parameters of bedding planes and rocks on the deterioration of strength parameters of interbedded rock masses differs significantly with the dip angle,which can be divided into four typical ranges of different controlling factors.展开更多
BACKGROUND Stress hyperglycemia(SH)is a common phenomenon that is present in about 50%of patients with acute ischemic stroke(AIS).It is thought to be a main risk factor for poor functional outcome among patients with ...BACKGROUND Stress hyperglycemia(SH)is a common phenomenon that is present in about 50%of patients with acute ischemic stroke(AIS).It is thought to be a main risk factor for poor functional outcome among patients with AIS undergoing intravenous thrombolysis(IVT).AIM To investigate the predictive value of glycemic indicators for early neurological outcomes(ENOs)in patients with AIS treated with IVT.METHODS We retrospectively reviewed a prospectively collected database of patients with AIS who underwent IVT at the Department of Neurology,Second Affiliated Hospital of Xuzhou Medical University,between January 2017 and June 2022.ENO included early neurological improvement(ENI)and early neurological deterioration(END),defined as a decrease or increase in the National Institutes of Health Stroke Scale(NIHSS)score between baseline and 24 hours after IVT.We analyzed the associations between glycemic indicators[including admission hyperglycemia(AH),fasting blood glucose(FBG),and SH ratio(SHR)]and ENO in all patients and in subgroups stratified by diabetes mellitus(DM).RESULTS A total of 819 patients with AIS treated with IVT were included.Among these,AH was observed in 329 patients(40.2%).Compared with patients without AH,those with AH were more likely to have a higher prevalence of DM(P<0.001)and hypertension(P=0.031)and presented with higher admission NIHSS scores(P<0.001).During the first 24 hours after IVT,END occurred in 208 patients(25.4%)and ENI occurred in 156 patients(19.0%).Multivariate mixed logistic regression analyses indicated that END was independently associated with AH[odds ratio(OR):1.744,95%confidence interval(CI):1.236-2.463;P=0.002].Subjects were classified into four groups representing quartiles.Compared with Q1,patients in the higher quartiles of SHR(Q2:OR:2.306,95%CI:1.342-3.960;P=0.002)(Q3:OR:2.284,95%CI:1.346-3.876;P=0.002)(Q4:OR:3.486,95%CI:2.088-5.820;P=0.001)and FBG(Q3:OR:1.746,95%CI:1.045-2.917;P=0.033)(Q4:OR:2.436,95%CI:1.476-4.022;P=0.001)had a significantly higher risk of END in the overall population.However,none of the glycemic indicators were found to be associated with ENI in patients with or without DM.CONCLUSION Our study demonstrated that glycemic indicators in patients with stroke treated with IVT were associated with the presence of END rather than ENI during the first 24 hours after admission.展开更多
Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints...Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.展开更多
This study investigates the compressive and tensile properties of basalt fiber-reinforced concrete (BFRC) after ultra-low-temperature freeze-thaw cycles. Scanning electron microscope (SEM) analysis was conducted to ex...This study investigates the compressive and tensile properties of basalt fiber-reinforced concrete (BFRC) after ultra-low-temperature freeze-thaw cycles. Scanning electron microscope (SEM) analysis was conducted to examine the deterioration mechanisms caused by freeze-thaw cycles and sulfate erosion. The results show that compressive and tensile strengths increase with basalt fiber dosage. The optimal dosage is 0.2%. With longer exposure to sulfate erosion, both strengths decline significantly. Basalt fibers effectively bridge cracks, control expansion, enhance compactness, and improve concrete performance. Ultra-low-temperature freeze-thaw cycles and sulfate erosion cause rapid crack growth. Sulfate erosion produces crystallization products and expansive substances. These fill cracks, create pressure, and damage the internal structure. Freezing and expansion forces further enlarge voids and cracks. This provides space for expansive substances, worsening concrete deterioration and reducing its performance.展开更多
Soft rock is one of the common geological conditions in coal mine underground water reservoir engineering.The cross-scale correlation analysis of water erosion soft lithology deterioration is very important for the sa...Soft rock is one of the common geological conditions in coal mine underground water reservoir engineering.The cross-scale correlation analysis of water erosion soft lithology deterioration is very important for the safety and stability of coal mine underground reservoir(CMUR)engineering.To address the issues of grain crowding and segmentation difficulties in cross-scale corelation analysis,as well as the limitations of traditional etching methods,this study proposes an image grain segmentation method based on deep learning algorithms,utilizing scanning electron microscopy and image process-ing techniques.The method successfully segments crowded grains and eliminates the interference from misplaced particles.In addition,indoor uniaxial compression tests were conducted to obtain the mechanical properties of sandstone samples with different water content.By quantitatively characterizing the macroscopic and microscopic deterioration degree of red sandstone samples with different water contents,the relationship between the strength changes of rock samples and the pet-rographic parameters such as grain size and grain shape is analyzed,and the influence law of soft lithology deterioration in CMUR engineering is revealed.The results indicate:(1)Water significantly weakens the mechanical properties and stability of soft rock.With increasing water content,the strength of sandstone samples continuously decreases,and the failure mode transitions from brittle to ductile failure.(2)The deterioration of micro-micro structures is the main cause of the decrease in mechanical properties of water-eroded soft rock.Grain size,grain area,and aspect ratio are negatively correlated with water content,indicating that hydrophilic minerals in soft rock dissolve under the action of water,leading to rock damage.(3)Grain size,area,and aspect ratio can serve as significant indicators for quantifying the strength changes of water-eroded soft rock.The research findings can be applied to stability assessment and disaster prevention in CMUR engineering.展开更多
We consider the preventive maintenance of a production system that is deteriorated by random shocks and the production process itself. The degree of deterioration is modeled by discrete and finite states. Shocks arriv...We consider the preventive maintenance of a production system that is deteriorated by random shocks and the production process itself. The degree of deterioration is modeled by discrete and finite states. Shocks arrive according to a Poisson process and deteriorate the system by random amounts. The system may deteriorate whenever it produces an item. The system is continuously monitored and repaired if the system state is at or above a predetermined level for maintenance. We analyze the lifetime, product quantity, average cost, and average profit considering revenue from the product and cost due to setup, operation, and repair. Assuming a structure of system parameters and costs, using numerical examples, we investigate the impact of production and shock arrivals on the average profit and the optimal maintenance level that maximizes the average profit. The proposed model is applicable to manufacturing tasks in which machines wear due to production, for example, press processes, milling, turning, punching, and drilling.展开更多
Different from oil and gas production,hydrate reservoirs are shallow and unconsolidated,whose mechanical properties deteriorate with hydrate decomposition.Therefore,the formations will undergo significant subsidence d...Different from oil and gas production,hydrate reservoirs are shallow and unconsolidated,whose mechanical properties deteriorate with hydrate decomposition.Therefore,the formations will undergo significant subsidence during depressurization,which will destroy the original force state of the production well.However,existing research on the stability of oil and gas production wells assumes the formation to be stable,and lacks consideration of the force exerted on the hydrate production well by formation subsidence caused by hydrate decomposition during production.To fill this gap,this paper proposes an analytical method for the dynamic evolution of the stability of hydrate production well considering the effects of hydrate decomposition.Based on the mechanical model of the production well,the basis for stability analysis has been proposed.A multi-field coupling model of the force state of the production well considering the effect of hydrate decomposition and formation subsidence is established,and a solver is developed.The analytical approach is verified by its good agreement with the results from the numerical method.A case study found that the decomposition of hydrate will increase the pulling-down force and reduce the supporting force,which is the main reason for the stability deterioration.The higher the initial hydrate saturation,the larger the reservoir thickness,and the lower the production pressure,the worse the stability or even instability.This work can provide a theoretical reference for the stability maintaining of the production well.展开更多
文摘Background:Hospitals have reported that implementing rapid response system activation(RRS)activation has increased patient safety.As a result,there has been growing interest in identifying factors that lead to successful RRS activation.While introducing an automated RRS activation system has prompted nurses to be more vigilant about monitoring vital signs,it has not necessarily encouraged them to conduct thorough patient assessments to identify early signs of deterioration.Purpose:The current study aimed to assess nurses’attitudes towards RRS activation for clinically deteriorated patients in the clinical units of King Abdul-Aziz Hospital.Methods:A descriptive cross-sectional research design was utilised in the study,and 144 nurses working in the medical and surgical units of King Abdul-Aziz Hospital were recruited to participate using a convenient non-probability sampling technique.Results:The study’s findings reported that nurses have a positive attitude towards RRS benefits(Mean=3.70;SD=0.70).Their overall attitude towards RRS activation among clinically deteriorated patients is still low positive(Mean=2.71;SD=0.61).The nurses’attitudes towards RRS benefits significantly differ among nationalities and the clinical area/unit where they were assigned,with a P-value of 0.0194 and 0.000,respectively.Attitudes towards RRS barriers significantly differ among nationality(P-value=0.0037),education level(P-value=0.0032),area of assignment(P-value=0.020),and whether they have a good understanding of abnormal observations(P-value=0.0122).Regarding the nurses’attitude towards management belief,the significant result is only with the clinical area/unit of assignment with a P-value of 0.000.Conclusion:The current study found a low positive attitude towards RRS activation among ward nurses,especially given that monitoring vital signs is critical to their job.Nurses may fear being perceived as clinically inept for redundant activations caused by poor quality,but their attitude towards activating the RRS in clinical deterioration is still largely negative.This is because most RRSs rely on ward nurses to recognise clinical deterioration and manually alert responders through phone calls,hospital communication systems,or face-to-face communication.
文摘Deterioration and loss of quality of vegetable oil is a big challenge in the food industry.This study investigated the synthesis of nickel ferrite(Ni Fe_(2)_(O4))via co-precipitation method and its use for the removal of free fatty acids(FFAs)in deteriorated vegetable oil.Ni Fe2 O4 was characterized using Fourier transformed infrared spectroscopy(FTIR),X-ray diffraction(XRD),thermogravimetric(TG)analysis,Brunauer–Emm ett–Teller(BET)surface area,transmission electron microscopy(TEM),scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDX).Synthesis of Ni Fe_(2)_(O4)was confirmed by characterization,which revealed a BET surface area of 16.30 m^(2)·g^(-1)and crystallite size of 29 nm.Ni Fe_(2)_(O4)exhibited an adsorption capacity of 145.20 L·kg^(-1)towards FFAs with an 80.69%removal in a process,which obeys Langmuir isotherm and can be described by the pseudo-second-order kinetic model.The process has enthalpy(DH)of 11.251 k Jámolà1 and entropy(DS)of 0.038 k J·mol^(-1)K^(-1)with negative free energy change(DG),which suggests the process to be spontaneous and endothermic.The quantum chemical computation analysis via density functional theory further revealed the sorption mechanism of FFAs by Ni Fe_(2)_(O4)occurred via donor–acceptor interaction,which may be described by the lowest unoccupied molecular orbital(LUMO)and the highest occupied molecular orbital(HOMO).The study showed Ni Fe_(2)_(O4)to be a potential means that can remove FFAs from deteriorated vegetable oil.
文摘This paper aims to present an effective method to partial deteriorated strength columns,and to investigate the mechanical behavior of the defect part. Five groups of 150×150 mm×mm plain square columns are cast; each specimen has two different strengths,the lower strength in the middle segment and higher strength in both ends. The lower strength is to simulate the status of partial deteriorated region. Different layers of CFRP sheets have been wrapped just on the lower strength part to gain the reinforcement with CFRP sheets,and to verify the practicability of partial confinement. Specimens are subjected to monotonic axial compression until failure. Axial load,axial and transverse strains are measured to compare the different behaviors between the two parts. Experimental results show that partial confinement can significantly enhance the strength and the ductility of the deteriorated strength part,then,the load capacity of the whole column can be increased subsequently. Test data indicate that the ultimate load of the confined column is higher than that of the original column without deterioration; partial confinement on weakness is a feasible approach.
文摘This paper considers a deteriorated multi-item economic order quantity (EOQ) problem, which has been studied in literature, but the algorithms used in the literature are limited. In this paper, we explore the optimal policy of this inventory problem by analyzing the structural properties of the model, and introduce a simple algorithm for generating the optimal solution to this problem. Numerical results are reported to show effi-cacy of the proposed method.
基金funding support from the NSFC Key Projects of International Cooperation and Exchanges (Grant No.42020104006)the National Key Research and Development Program of China (Grant No.2023YFC3007001)the National Natural Science Foundation of China (Grant No.42307227).
文摘Water level fluctuations in the reservoir deteriorate soils and rocks on the bank landslides by drying-wetting(D-W)cycles,which results in a significant decrease in mechanical properties.A comprehensive understanding of deterioration mechanism of sliding-zone soils is of great significance for interpreting the deformation behavior of landslides.However,quantitative investigation on the deterioration characteristics of soils considering the structural evolution under D-W cycles is still limited.Here,we carry out a series of laboratory tests to characterize the multi-scale deterioration of sliding-zone soils and reveal the mechanism of shear strength decay under D-W cycles.Firstly,we describe the micropores into five grades by scanning electron microscope and observe a critical change in porosity after the first three cycles.We categorize the mesoscale cracks into five classes using digital photography and observe a stepwise increase in crack area ratio.Secondly,we propose a shear strength decay model based on fractal theory which is verified by the results of consolidated undrained triaxial tests.Cohesion and friction angle of sliding-zone soils are found to show different decay patterns resulting from the staged evolution of structure.Then,structural deterioration processes including cementation destruction,pores expansion,aggregations decomposition,and clusters assembly are considered to occur to decay the shear strength differently.Finally,a three-stage deterioration mechanism associated with four structural deterioration processes is revealed,which helps to better interpret the intrinsic mechanism of shear strength decay.These findings provide the theoretical basis for the further accurate evaluation of reservoir landslides stability under water level fluctuations.
基金funding support from the National Natural Science Foundation of China(Grant No.12172019).
文摘In cold regions,rock structures will be weakened by freeze-thaw cycles under various water immersion conditions.Determining how water immersion conditions impact rock deterioration under freeze-thaw cycles is critical to assess accurately the frost resistance of engineered rock.In this paper,freeze-thaw cycles(temperature range of-20℃-20℃)were performed on the sandstones in different water immersion conditions(fully,partially and non-immersed in water).Then,computed tomography(CT)tests were conducted on the sandstones when the freeze-thaw number reached 0,5,10,15,20 and 30.Next,the effects of water immersion conditions on the microstructure deterioration of sandstone under freezethaw cycles were evaluated using CT spatial imaging,porosity and damage factor.Finally,focusing on the partially immersed condition,the immersion volume rate was defined to understand the effects of immersion degree on the freeze-thaw damage of sandstone and to propose a damage model considering the freeze-thaw number and immersion degree.The results show that with increasing freeze-thaw number,the porosities and damage factors under fully and partially immersed conditions increase continuously,while those under non-immersed condition first increase and then remain approximately constant.The most severe freeze-thaw damage occurs in fully immersed condition,followed by partially immersed condition and finally non-immersed condition.Interestingly,the freeze-thaw number and the immersion volume rate both impact the microstructure deterioration of the partially immersed sandstone.For the same freeze-thaw number,the damage factor increases approximately linearly with increasing immersion volume rate,and the increasing immersion degree exacerbates the microstructure deterioration of sandstone.Moreover,the proposed model can effectively estimate the freeze-thaw damage of partially immersed sandstone with different immersion volume rates.
基金supported by the National Key Research and Development Program of China(No.2022YFB3706704)the Academician Special Science Research Project of CCCC(No.YSZX-03-2022-01-B).
文摘The girder end restraint devices such as bearings and dampers on long span suspension bridge will deteriorate over time.However,it is difficult to achieve the quantitative assessment of the performance of the restraint device through existing detection methods in actual inspections,making it difficult to obtain the impact of changes in the performance of the restraint device on the bridge structure.In this paper,a random vehicle load model is firstly established based on the WIM data of Jiangyin Bridge,and the displacement of girder end under the actual traffic flow is simulated by using finite element dynamic time history analysis.On this basis,according to the performance test data of the bearings and dampers,the performance degradation laws of the above two restraint devices are summarized,and the performance degradation process of the two restraint devices and the effects of different restraint parameters on the bridge structure are simulated.The results show that the performance degradation of the damper will significantly reduce the damping force at low speed,resulting in a significant increase in the cumulative displacement of the girder end;in the presence of longitudinal dampers,the increase in the friction coefficient caused by the deterioration of the bearing sliding plate has little effect on the cumulative displacement,but excessive wear of the bearing sliding plate adversely affects the structural dynamic performance.
文摘Our study aims at developing compatible raw compositions of earth with building materials in the desert zones,for an adequate restoration.To arrive at our objective,we developed compositions of adobes in bases of the local raw materials(red clay of Adrar,sand of dune,the black sand and the chopped straw).The results of the mineralogical characteristics(Rx),physical(density,the humidity and the grading analysis)used raw materials,showed successful and compatible characteristics with the building materials of the Saharan Ksour.The formulations are based on compositions witnesses as reference(1 Volume of clay+2 Volume of sand+water).The objective of this study,concerns the identification of the various mechanical characteristics(mechanical resistance in the flexion and in the compression),followed by an ultrasound study(mechanism of change in front of hydric behavior),of the compatible adobe with the local building materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.52408271 and 52174092)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20230615).
文摘Determining the high-temperature history of rocks and evaluating their associated deterioration levels are essential for the stable and efficient functioning of geological engineering projects.This research introduces a precise,time-efficient,and cost-effective approach that integrates metal intrusion technology,backscattered electron(BSE)imaging,and the ResNet50 deep-learning algorithm to differentiate high-temperature histories.The damage characteristics in the microstructure of rocks subjected to different temperature treatments are successfully extracted.The results show that,compared to previously reported convolutional neural networks(CNN)training and classification methods,the proposed ResNet50 algorithm improves identification accuracy by over 10%,achieving up to 98%accuracy in classifying degraded sandstone treated at temperatures ranging from 25℃ to 1000℃.More importantly,through feature extraction of sandstone specimens after high-temperature deterioration,the ResNet50 algorithm demonstrates a superior ability to locate microscopic damage characteristics associated with different temperatures-an achievement rarely reported in previous research.For sandstone specimens exposed to 200℃-600℃,the extracted features primarily highlight the opening of primary pores and changes in rock particle morphology.In contrast,as the treated temperature exceeds 600℃,the extracted features predominantly reflect thermal damage fracture,whose area first diffuses and then concentrates,aligning closely with the thermal damage theory of rock.The findings of this study not only advance a deep learning-based approach for identifying rock deterioration after high-temperature exposure but also deepen the understanding of the relation between rock microstructural characteristics and high-temperature deterioration.
文摘Food security has been an issue of global concern and this has attracted a lot of research interest. Cassava is an extremely popular crop and is becoming the cornerstone for addressing food security in many parts of the world. The competing needs for cassava cuts across both human and animal consumption. It serves as a raw material in textile industry and is now one of the preferred materials for making biofuels. As the world’s population continues to grow, the demand for drought resistant crops such as cassava is increasing. The high demand for various forms of processed cassava will continue to increase cassava prices making it an attractive business venture. Several small-scale cassava farmers are making a fortune and additional income through this business. Preliminary investigations show that the profitable way for a farmer to market his cassava is to add value to it. Unfortunately, cassava undergoes post-harvest physiological deterioration (PPD) after three days of harvest. In order to make cassava farming even more profitable, there is a need to process it within the shelf life of 2 - 3 days after harvesting. One way to preserve cassava is by grating it into pulp and drying it into pellets or chips. In this study, an electrically powered multi-purpose cassava grating machine with grater blades inclined at two different tooth angles, 25˚ and 30˚ was designed, fabricated and its performance characteristics investigated. The results showed that the plate with a tooth angle of 30˚ resulted in higher grating efficiency. This was attributed to better grip on the cassava when perforations on the plate inclined at 30˚. The grating capacity was also significantly improved as very small amounts of cassava slipped out un-grated.
文摘Utilizing the ballast layer with more durable and stable characteristics can help avoid significant expenses due to decreased maintenance efforts.Strengthening the ballast layer with different types of reinforcements or substituting the stone aggregates with the appropriate granular materials could potentially help to achieve this goal by reducing the ballast deterioration.One of the exquisite and most effective solutions to eliminate these challenges is to use waste materials such as steel slag aggregates and useless tires.Utilizing these waste materials in the ballasted railway track will contribute to sustainable development,an eco-friendly system,and green infrastructure.So in a state-of-the-art insightful,the ballast aggregates,including a mixture of steel slag and stone aggregates,are reinforced with a novel kind of geo-grid made of waste tire strips known as geo-scraps.This laboratory research tried to explain the shear strength behavior of the introduced mixing slag-stone ballast reinforced with tire geo-scrap.To achieve this goal,a series of large-scale direct shear tests were performed on the ballast which is reinforced by tire geo-scrap and included various combinations of slag and stone aggregates.The concluded results indicate that the optimal mixing ratio is attained by a combination of 75%slag and 25%stone aggregates which is reinforced by tire geo-scrap at a placing level of 120 mm.In this case,the shear strength,internal friction angle,vertical displacement,and dilatancy angle of stone–slag ballast reinforced with geo-scraps exhibited average changes of+28%,+9%,-28%,and-15%,respectively.
基金supported by the National Natural Science Foundation of China(82120108010 and 81930028).
文摘Alzheimer’s disease(AD)is a slow,progressive neurodegenerative disease with clinical symptoms that typically emerge in the elderly,leading to deterioration of cognitive functions over time.Memory loss is the primary symptom,eventually leading to significant declines in executive and cognitive functions,along with psychiatric and behavioral changes,and alterations in personality.
基金supported by the National Natural Science Foundation of China(Nos.52034009 and 52174093)the Fundamental Research Funds for the Central Universities(Nos.2024ZKPYNY01,2023ZKPYNY03,and 2023YQTD02).
文摘To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion conditions,the weakening characteristics,observable characteristics,softening characteristics of the dynamic parameters,dynamic failure characteristics,dynamic failure forms and dynamic microscopic characteristics were analyzed.Under each corrosion condition,the dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity tended to decrease with immersing time.The dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity exhibited an inverted U-shaped trend.Under dynamic impact,the failure process of acidly corroded samples can be divided into the following stages:the initial stage,elastic energy accumulation stage,local failure of coal and secondary rock crack expansion stage,coal fragment ejection stage,rock spalling stage and complete instability stage.Under dynamic impact,failure modes exist:coal crushing failure,rock fragmenting failure,rock splitting failure and full splitting failure.After impact failure,sample fragments are distributed in powder,granular,cone and block forms.Based on Zhu-Wang-Tang nonlinear viscoelastic properties,a model considering chemical corrosion and impact damage was proposed.The combined effects of chemical and impact-induced damage on the dynamic mechanical properties of coal-rock assemblages were systematically analyzed.
基金supported by the Chinese National Key R&D Program(No.2022YFC3080200)the Chinese National Natural Science Foundation(No.42090054)。
文摘The rock masses in the hydro-fluctuation zone of reservoir banks sustain wettingdrying cycles(WDC),thereby affecting the stability of the reservoir bank slope.In this paper,rock masses with argillaceous siltstone and silty mudstone interbedded in Badong Formation were taken as the research object to investigate the variation of strength parameters of soft and hard interbedded rock masses with WDC and dip angle through laboratory experiments and numerical experiments.Some attempts were made to reveal the mechanical properties deterioration mechanism of interbedded rock masses by quantitatively analyzing the contribution of strength parameters deterioration of hard rocks,soft rocks,and bedding planes to the strength parameters deterioration of rock masses.The results indicate that the logarithmic function could be used to describe the deterioration of each strength parameter of both argillaceous siltstone and silty mudstone and bedding plane with the number of WDC.The strength parameters of interbedded rock masses decrease as the number of WDC increases,with the largest decrease after the first cycle and then slowing down in the later cycles.The strength parameters initially decrease and then increase as the dip angles increase.The impact of deteriorated strength parameters of bedding planes and rocks on the deterioration of strength parameters of interbedded rock masses differs significantly with the dip angle,which can be divided into four typical ranges of different controlling factors.
基金Supported by the Foundation of Jiangsu Provincial Commission of Health and Family Planning,No.QNRC2016353the Commission of Health and Family Planning Xuzhou,No.KC22206.
文摘BACKGROUND Stress hyperglycemia(SH)is a common phenomenon that is present in about 50%of patients with acute ischemic stroke(AIS).It is thought to be a main risk factor for poor functional outcome among patients with AIS undergoing intravenous thrombolysis(IVT).AIM To investigate the predictive value of glycemic indicators for early neurological outcomes(ENOs)in patients with AIS treated with IVT.METHODS We retrospectively reviewed a prospectively collected database of patients with AIS who underwent IVT at the Department of Neurology,Second Affiliated Hospital of Xuzhou Medical University,between January 2017 and June 2022.ENO included early neurological improvement(ENI)and early neurological deterioration(END),defined as a decrease or increase in the National Institutes of Health Stroke Scale(NIHSS)score between baseline and 24 hours after IVT.We analyzed the associations between glycemic indicators[including admission hyperglycemia(AH),fasting blood glucose(FBG),and SH ratio(SHR)]and ENO in all patients and in subgroups stratified by diabetes mellitus(DM).RESULTS A total of 819 patients with AIS treated with IVT were included.Among these,AH was observed in 329 patients(40.2%).Compared with patients without AH,those with AH were more likely to have a higher prevalence of DM(P<0.001)and hypertension(P=0.031)and presented with higher admission NIHSS scores(P<0.001).During the first 24 hours after IVT,END occurred in 208 patients(25.4%)and ENI occurred in 156 patients(19.0%).Multivariate mixed logistic regression analyses indicated that END was independently associated with AH[odds ratio(OR):1.744,95%confidence interval(CI):1.236-2.463;P=0.002].Subjects were classified into four groups representing quartiles.Compared with Q1,patients in the higher quartiles of SHR(Q2:OR:2.306,95%CI:1.342-3.960;P=0.002)(Q3:OR:2.284,95%CI:1.346-3.876;P=0.002)(Q4:OR:3.486,95%CI:2.088-5.820;P=0.001)and FBG(Q3:OR:1.746,95%CI:1.045-2.917;P=0.033)(Q4:OR:2.436,95%CI:1.476-4.022;P=0.001)had a significantly higher risk of END in the overall population.However,none of the glycemic indicators were found to be associated with ENI in patients with or without DM.CONCLUSION Our study demonstrated that glycemic indicators in patients with stroke treated with IVT were associated with the presence of END rather than ENI during the first 24 hours after admission.
基金financially supported by the National Natural Science Foundation of China (No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group (No.SNKJ2022A01-R26)funded by the China Scholarship Council (CSC No.202006220274)。
文摘Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.
文摘This study investigates the compressive and tensile properties of basalt fiber-reinforced concrete (BFRC) after ultra-low-temperature freeze-thaw cycles. Scanning electron microscope (SEM) analysis was conducted to examine the deterioration mechanisms caused by freeze-thaw cycles and sulfate erosion. The results show that compressive and tensile strengths increase with basalt fiber dosage. The optimal dosage is 0.2%. With longer exposure to sulfate erosion, both strengths decline significantly. Basalt fibers effectively bridge cracks, control expansion, enhance compactness, and improve concrete performance. Ultra-low-temperature freeze-thaw cycles and sulfate erosion cause rapid crack growth. Sulfate erosion produces crystallization products and expansive substances. These fill cracks, create pressure, and damage the internal structure. Freezing and expansion forces further enlarge voids and cracks. This provides space for expansive substances, worsening concrete deterioration and reducing its performance.
基金supported by the National Natural Science Foundation of China(51774196,52304093)China Postdoctoral Science Foundation(2023M741968)Shandong Provincial Natural Science Foundation(ZR2023ME086).
文摘Soft rock is one of the common geological conditions in coal mine underground water reservoir engineering.The cross-scale correlation analysis of water erosion soft lithology deterioration is very important for the safety and stability of coal mine underground reservoir(CMUR)engineering.To address the issues of grain crowding and segmentation difficulties in cross-scale corelation analysis,as well as the limitations of traditional etching methods,this study proposes an image grain segmentation method based on deep learning algorithms,utilizing scanning electron microscopy and image process-ing techniques.The method successfully segments crowded grains and eliminates the interference from misplaced particles.In addition,indoor uniaxial compression tests were conducted to obtain the mechanical properties of sandstone samples with different water content.By quantitatively characterizing the macroscopic and microscopic deterioration degree of red sandstone samples with different water contents,the relationship between the strength changes of rock samples and the pet-rographic parameters such as grain size and grain shape is analyzed,and the influence law of soft lithology deterioration in CMUR engineering is revealed.The results indicate:(1)Water significantly weakens the mechanical properties and stability of soft rock.With increasing water content,the strength of sandstone samples continuously decreases,and the failure mode transitions from brittle to ductile failure.(2)The deterioration of micro-micro structures is the main cause of the decrease in mechanical properties of water-eroded soft rock.Grain size,grain area,and aspect ratio are negatively correlated with water content,indicating that hydrophilic minerals in soft rock dissolve under the action of water,leading to rock damage.(3)Grain size,area,and aspect ratio can serve as significant indicators for quantifying the strength changes of water-eroded soft rock.The research findings can be applied to stability assessment and disaster prevention in CMUR engineering.
基金supported by the 2010 Hannam University Research Fund
文摘We consider the preventive maintenance of a production system that is deteriorated by random shocks and the production process itself. The degree of deterioration is modeled by discrete and finite states. Shocks arrive according to a Poisson process and deteriorate the system by random amounts. The system may deteriorate whenever it produces an item. The system is continuously monitored and repaired if the system state is at or above a predetermined level for maintenance. We analyze the lifetime, product quantity, average cost, and average profit considering revenue from the product and cost due to setup, operation, and repair. Assuming a structure of system parameters and costs, using numerical examples, we investigate the impact of production and shock arrivals on the average profit and the optimal maintenance level that maximizes the average profit. The proposed model is applicable to manufacturing tasks in which machines wear due to production, for example, press processes, milling, turning, punching, and drilling.
基金financially supported by the National Natural Science Foundation of China(Grant No.51890914)。
文摘Different from oil and gas production,hydrate reservoirs are shallow and unconsolidated,whose mechanical properties deteriorate with hydrate decomposition.Therefore,the formations will undergo significant subsidence during depressurization,which will destroy the original force state of the production well.However,existing research on the stability of oil and gas production wells assumes the formation to be stable,and lacks consideration of the force exerted on the hydrate production well by formation subsidence caused by hydrate decomposition during production.To fill this gap,this paper proposes an analytical method for the dynamic evolution of the stability of hydrate production well considering the effects of hydrate decomposition.Based on the mechanical model of the production well,the basis for stability analysis has been proposed.A multi-field coupling model of the force state of the production well considering the effect of hydrate decomposition and formation subsidence is established,and a solver is developed.The analytical approach is verified by its good agreement with the results from the numerical method.A case study found that the decomposition of hydrate will increase the pulling-down force and reduce the supporting force,which is the main reason for the stability deterioration.The higher the initial hydrate saturation,the larger the reservoir thickness,and the lower the production pressure,the worse the stability or even instability.This work can provide a theoretical reference for the stability maintaining of the production well.
