Objective:To investigate the clinical efficacy and cost-effectiveness of combined hemodialysis(HD)and hemoperfusion(HP)therapy in managing secondary hyperparathyroidism(SHPT)in patients undergoing maintenance hemodial...Objective:To investigate the clinical efficacy and cost-effectiveness of combined hemodialysis(HD)and hemoperfusion(HP)therapy in managing secondary hyperparathyroidism(SHPT)in patients undergoing maintenance hemodialysis(MHD).Methods:A total of 195 patients with MHD and SHPT at Deyang People's Hospital from April 2024 to April 2025 were enrolled.Patients were randomly assigned to a control group receiving standard HD treatment and an experimental group receiving HD combined with HP therapy.The experimental group underwent 1 year of observation(97 cases in the experimental group,98 cases in the control group).During treatment,changes in parathyroid hormone(PTH),serum calcium,serum phosphorus,and inflammatory factors were monitored,along with analysis of treatment-related economic benefits and safety.Results:The experimental group demonstrated significantly better reductions in PTH,serum phosphorus,and inflammatory factors compared to the control group(P<0.05).Although the total treatment cost was slightly higher,the unit cost per therapeutic effect was lower,resulting in a superior cost-effectiveness ratio.Conclusion:Combined HD and HP therapy can significantly improve SHPT-related indicators in MHD patients,demonstrating safety,controllability,and high cost-effectiveness,making it a clinically applicable and recommended treatment option.展开更多
To quantitatively identify the maintenance demand for each highway segments in the pavement maintenance scheme design,a mathematical model of uniform segment division was established and an approach of applying cluste...To quantitatively identify the maintenance demand for each highway segments in the pavement maintenance scheme design,a mathematical model of uniform segment division was established and an approach of applying cluster analysis theory to the uniform segment division and evaluation of pavement maintenance demand was proposed.The actual maintenance project of a highway carried out in Guangdong province was cited as an example to demonstrate the validity of the proposed method.It is proved that the cluster analysis can eliminate human factors in classification without being constrained by the quantities of samples,considering multiple pavement distress indexes and the continuity of samples.Thus it is evident that cluster analysis is an efficient analytical tool in uniform segment division and evaluation of maintenance demand.展开更多
Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is...Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.展开更多
The stoichiometric matrix of a simplified metabolic network inBacillus Subtillis was constructed from the flux balance equations,which were used for reconciliation of the measured rates anddetermination of the inner m...The stoichiometric matrix of a simplified metabolic network inBacillus Subtillis was constructed from the flux balance equations,which were used for reconciliation of the measured rates anddetermination of the inner metabolic rates. Thus more reliableresults of the true and empirical maintenance coefficients wereobtained. The true maintenance coefficient is linearly related to thespecific growth rate and changes with the P/O ratio. The measuredbiomass yield of adenosine triphosphate (ATP) is also linearlyrelated to the P/O ratio.展开更多
BACKGROUND The burden of chronic kidney disease(CKD)is rising rapidly globally.Fluid overload(FO),an independent predictor of mortality in CKD,should be accurately assessed to guide estimation of the volume of fluid t...BACKGROUND The burden of chronic kidney disease(CKD)is rising rapidly globally.Fluid overload(FO),an independent predictor of mortality in CKD,should be accurately assessed to guide estimation of the volume of fluid to be removed during haemodialysis(HD).Clinical score(CS)and bio-impedance analysis(BIA)have been utilized in assessment of FO and BIA has demonstrated reproducibility and accuracy in determination of fluid status in patients on HD.There is need to determine the performance of locally-developed CSs in fluid status assessment when evaluated against BIA.AIM To assess the hydration status of patients on maintenance HD using BIA and a CS,as well as to evaluate the performance of that CS against BIA in fluid status assessment.METHODS This was a single-centre,hospital-based cross-sectional study which recruited adult patients with CKD who were on maintenance HD at Kenyatta National Hospital.The patients were aged 18 years and above and had been on maintenance HD for at least 3 mo.Those with pacemakers,metallic implants,or bilateral limbs amputations were excluded.Data on the patients’clinical history,physical examination,and chest radiograph findings were collected.BIA was performed on each of the study participants using the Quantum®II bio-impedance analyser manufactured by RJL Systems together with the BC 4®software.In evaluating the performance of the CS,BIA was considered as the gold standard test.A 2-by-2 table of the participants’fluid status at each of the CS values obtained compared to their paired BIA results was constructed(either++,+-,--or-+for FO using the CS and BIA,respectively).The results from this 2-by-2 table were used to compute the sensitivity and specificity of the CS at the various reference points and subsequently plot a receiver operating characteristic(ROC)curve that was used to determine the best cut-off point.Those above and below the best CS cut-off point as determined by the ROC were classified as being positive and negative for FO,respectively.The proportions of participants diagnosed with FO by the CS and BIA,respectively,were computed and summarized in a 2-by-2 contingency table for comparison.McNemar’s chi-squared test was used to assess any statistically significant difference in proportions of patients diagnosed as having FO by CS and BIA.Logistic regression analysis was conducted to assess whether the variables for the duration of dialysis,the number of missed dialysis sessions,advisement by health care professional on fluid or salt intake,actual fluid intake,the number of anti-hypertensives used,or body mass index were associated with a patient’s odds of having FO as diagnosed by BIA.RESULTS From 100 patients on maintenance HD screened for eligibility,80 were recruited into this study.Seventy-one(88.75%)patients were fluid overloaded when evaluated using BIA with mean extracellular volume of 3.02±1.79 L as opposed to the forty-seven(58.25%)patients who had FO when evaluated using the CS.The difference was significant,with a P value of<0.0001(95%confidence interval:0.1758-0.4242).Using CS,values above 4 were indicative of FO while values less than or equal to 4 denoted the best cut-off for no FO.The sensitivity and specificity for the CS were 63%and 78%respectively.None of the factors evaluated for association with FO showed statistical significance on the multivariable logistic regression model.CONCLUSION FO is very prevalent in patients on chronic HD at the Kenyatta National Hospital.CS detects FO less frequently when compared with BIA.The sensitivity and specificity for the CS were 63%and 78%respectively.None of the factors evaluated for association with FO showed statistical significance on the multivariable logistic regression model.展开更多
Within this paper, the process of statistical safety analysis has been presented, which involves the following steps： formulation of basic principles of statistical safety analysis, initial events analysis, accident ...Within this paper, the process of statistical safety analysis has been presented, which involves the following steps： formulation of basic principles of statistical safety analysis, initial events analysis, accident sceneries progress analysis, risk calculation, and risk calculation results analysis. On this basis, it has been concluded that the bucket wheel excavator SRs 1200×24/4×0（400 kW）＋VR safety criteria is the mechanism for the hoist of rotor＇s arrow failure modes, because in that case whole bucket wheel excavator failure would necessarily happen （excavator falling down on counterweight）. Therefore, excavator units statistical safety analysis is accomplished preventively to obtain its effective maintenance management.展开更多
Taking the project of introducing reliability-centered maintenance( RCM) into maintenance decision in an AP1000 nuclear power plant( NPP) under construction as the research object,an improved RCM methodology was propo...Taking the project of introducing reliability-centered maintenance( RCM) into maintenance decision in an AP1000 nuclear power plant( NPP) under construction as the research object,an improved RCM methodology was proposed, and the application software and an RCM-based maintenance strategies management system were designed. In the pilot project,the RCMbased maintenance decision methodology had been applied to determining the maintenance strategies for two systems. Both the decision process and the results were described in this paper. The achievements of this project promoted the introduction and routinization of an advanced and effective maintenance decision mode in nuclear power field,which could provide valuable reference for new NPPs in China.展开更多
Most traditional assessment methods, which have complicated mathematic formulas,are difficult for calculation and application in system efficiency evaluation. A new approach to annual equipment maintenance system effi...Most traditional assessment methods, which have complicated mathematic formulas,are difficult for calculation and application in system efficiency evaluation. A new approach to annual equipment maintenance system efficiency assessment,the set pair analysis method( SPAM),has been proposed based on the principle of set pair analysis( SPA). Firstly,the evaluation index system of the annual equipment maintenance is proposed. Secondly,the evaluation model of the annual equipment maintenance efficiency based on the SPAM is built. Then the application processes of the SPAM are introduced. At the end of the paper,a real application example is given. The results of the application indicate that the proposed model is feasible and effective. It can give strong supports to improve the evaluation effect of the unit equipment maintenance support.展开更多
The instruments of regional automatic weather station are placed outside to measure daily changes of meteorological factors. Due to common influence of sun,wind,rain and other factors,it is very easy to cause various ...The instruments of regional automatic weather station are placed outside to measure daily changes of meteorological factors. Due to common influence of sun,wind,rain and other factors,it is very easy to cause various faults and damages of the instrument. The construction of regional automatic weather station network plays an important role in improving forecast accuracy,servicing local government and ecological civilization construction,providing scientific disaster prevention and relief decision-making basis for government department. In this paper,based on daily operation situation of regional automatic weather station in Shaoyang region,combining communication,hardware and software,fault situation of collector,temperature and humidity sensor,wind sensor and rainfall sensor in automatic weather station is analyzed in detail. Moreover,some common fault cases are listed and analyzed,some troubleshooting methods are summarized,and daily maintenance measures are proposed.展开更多
Motor vehicle inspection and maintenance (I/M) programs are designed to identify high-emitting vehicles and mitigate their impacts on air quality and climate. I/M programs have been traditionally ranked superior among...Motor vehicle inspection and maintenance (I/M) programs are designed to identify high-emitting vehicles and mitigate their impacts on air quality and climate. I/M programs have been traditionally ranked superior among various vehicle emission control measures by the results of cost-benefit analysis, based on the assumption that these programs will achieve the targeted emission reduction outcomes. However, the actual effects of I/M programs may be greatly uncertain and when this uncertainty is taken into account, these programs may become suboptimal. This study develops a new a cost-benefit analysis framework that links various program design consideration, such as program participation rate, identification rate and effective repair rate, to the public health benefits as well as costs of the programs. This framework helps decision makers to investigate minimum implementation requirements that at least ensure the benefits are greater than the costs of implementing the programs in order to improve the overall effectiveness of the I/M programs. To illustrate the applications of the framework, it was applied to a particulate matter oriented I/M program targeting all diesel-fueled vehicles in the city of Bangkok, Thailand, a large metropolitan area that has been suffering from severe ambient PM pollution mainly attributable to its wide use of diesel-fueled vehicles and motorcycles. It was found that the health benefits achieved from the program are sensitive to several key program design elements, including participation rate and problem vehicle identification rate, fraction of effective repairs and illegal operation rate. Other variables, such as the testing cut-points and vehicle population growth rate, only have modest effects on the overall emission reduction and consequent health benefits. Overall, the performance of multiple variables associated with I/M program design needs to be improved simultaneous in order to achieve the targeted benefits of the program.展开更多
Preventative maintenance (PM) measures for bridges are proactive maintenance actions which aim to prevent or delay a deterioration process that may lead to failure. This type of maintenance can be justified on economi...Preventative maintenance (PM) measures for bridges are proactive maintenance actions which aim to prevent or delay a deterioration process that may lead to failure. This type of maintenance can be justified on economic grounds since it can extend the life of the bridge and avoid the need for unplanned essential/corrective maintenance. Due to the high importance of the effective integration of PM measures in the maintenance strategies of bridges, the authors have developed a two-stage evolutionary optimization methodology based on genetic algorithm (GA) principles which links the probabilistic effectiveness of various PM measures with their costs in order to develop optimum PM strategies. In this paper, the sensitivity of the methodology to various key input parameters of the optimization methodology is examined in order to quantify their effects and identify possible trends in the optimum PM intervention profiles. The results of the sensitivity studies highlight the combined use of both proactive and reactive PM measures in deriving optimum strategy solutions. The precise mix and sequence of PM measures is clearly a function of the relative effectiveness and cost of the different available PM options as well as the various key parameters such as discount rate, target probability of failure, initial probability of failure and service life period examined. While the results highlight the need for more reliable data they also demonstrate the robustness and usefulness of the methodology;in the case where data is limited it can be used as a comparative tool to improve understanding of the effects of various strategies and enhance the decision making process.展开更多
In existing references,authors and companies have defined the maintenance variables over time;it is found that in some cases there are traditions,incorrect postulates or the inappropriate use of terminology,which lead...In existing references,authors and companies have defined the maintenance variables over time;it is found that in some cases there are traditions,incorrect postulates or the inappropriate use of terminology,which leads to a misinterpretation of the results when maintenance management is analyzed.Starting from a documentary and deductive methodology,in this article,the analysis of some authors is presented and,from its origin,the initial variables that allow the construction of adequate algorithms for the maintenance function and to obtain the correct information related to it are re-defined.In a simple way with mathematical models,to then apply statistical models which allows,subsequently,calculating the maintenance information and achieving that professionals,professors and students are incorporated into maintenance analysis processes with a higher cognitive level,producing continuous information and comprehensive to analyze and investigate industrial equipment based on a basic history.展开更多
Since the 21st century,China's economy has enjoyed rapid development and people's living standards have been improved.At the same time,the pursuit of beauty of people is getting increasingly higher and landsca...Since the 21st century,China's economy has enjoyed rapid development and people's living standards have been improved.At the same time,the pursuit of beauty of people is getting increasingly higher and landscaping of and design of gardens has been widely pursued by people.This paper has discussed and analyzed the design of flower border and maintenance of flower border in the later period,hoping to provide some help and support for the relevant technical workers.展开更多
This paper attempts to concentrate on the eight basic principles of reliability-centeredmaintenance, and discusses respectively the differences between old and new maintenanceconcepts in eight aspects, i.e., function ...This paper attempts to concentrate on the eight basic principles of reliability-centeredmaintenance, and discusses respectively the differences between old and new maintenanceconcepts in eight aspects, i.e., function of rework at hard time, potential failure and funcrionalfailure, function of preventive maintenance, change of failure consequence, determinarion ofpreventive maintenance work and formulation of initial preventive maintenance program, andperfection of preventive maintenance program.展开更多
We take Shunde District,Foshan City in Guangdong Province for example,to carry out SWOT analysis of urban greening maintenance and management.The strengths of greening management and maintenance in Shunde District are...We take Shunde District,Foshan City in Guangdong Province for example,to carry out SWOT analysis of urban greening maintenance and management.The strengths of greening management and maintenance in Shunde District are as follows:(i)The greening area and quality are continuously improved in the downtown of Shunde District;(ii)The management and maintenance work is carried out well;(iii)The management and maintenance level tends to be increasingly perfected.The weaknesses of greening management and maintenance are as follows:(i)The fees for greening management and maintenance are very low;(ii)There is corner as yet untouched in the junction of some town streets;(iii)The greening management and maintenance technicians are unprofessional;(iv)The greening management is not in place;(v)There is management vacancy phenomenon in the management and maintenance of regional green space;(vi)The design and construction phase is flawed.Finally,based on the analysis of strengths and weaknesses of greening,we put forth the recommendations for the development of management and maintenance in urban green space.展开更多
A situation maintenance-based cooperative guidance strategy is proposed to intercept a high-speed and high-maneuverability target via inferior missiles.Reachability and relative motion analyses are conducted to develo...A situation maintenance-based cooperative guidance strategy is proposed to intercept a high-speed and high-maneuverability target via inferior missiles.Reachability and relative motion analyses are conducted to develop and pursue virtual targets,respectively.A two-stage guidance strategy under nonlinear kinematics is developed on the basis of virtual targets.The first stage optimizes the coverage and collision situation by pursuing virtual targets under specific angular constraints.The second stage subsequently intercepts the superior target based on the handover condition optimized by the first stage.Numerical simulation results are provided to compare the effectiveness and superiority of the proposed strategy with those of the reachability-based cooperative strategy(RCS),coverage-based cooperative guidance(CBCG)and augmented proportional navigation(APN)under various maneuvering modes.展开更多
Railway systems are critical components of transportation networks requiring consistent maintenance.This paper proposes a novel data-driven approach to detect various maintenance needs of railway track systems using a...Railway systems are critical components of transportation networks requiring consistent maintenance.This paper proposes a novel data-driven approach to detect various maintenance needs of railway track systems using acceleration data obtained from a passenger train in operation.The framework contains four modules.Firstly,data pre-processing and cleansing are performed to extract useful data from the whole dataset.Then,condition-sensitive features are extracted from the raw data in three different domains of time,frequency,and time-frequency.In the third module,the best subset of measurement features that characterize the state of the tracks are selected using the analysis of variance(ANOVA)algorithm which eliminates irrelevant characteristics from the feature set of responses.Finally,a multilabel classification algorithm based on the cascade feed-forward neural network(CFNN)is used to classify the type of maintenance needs of the track.An open-access dataset from a field study in Pennsylvania,USA,is used in this study for validation of the proposed method.The results indicate that employing a CFNN can achieve 95%accuracy in identifying two maintenance activities,tamping and surfacing,using time-domain features.Moreover,an extensive analysis has been conducted to evaluate the influence of various feature extraction and selection methods,diverse classification algorithms,and different types of accelerometers(uni-axial and tri-axial)on the accuracy of the proposed method.展开更多
To maintain their capacity,transportation infrastructures are in need of regular maintenance and rehabilitation.The major challenge facing transportation engineers is the network-level policies to maintain the deterio...To maintain their capacity,transportation infrastructures are in need of regular maintenance and rehabilitation.The major challenge facing transportation engineers is the network-level policies to maintain the deteriorating roads at an acceptable level of serviceability.In this work,a quantitative transportation network efficiency measure is presented and then how to determine optimally network-level road maintenance policy depending on the road importance to the network performance has been demonstrated.The examples show that the different roads should be set different maintenance time points in terms of the retention capacities of the roads,because the different roads play different roles in network and have different important degrees to the network performance.This network-level road maintenance optimization method could not only save lots of infrastructure investments,but also ensure the service level of the existing transportation system.展开更多
As an effective means for improving system condition and reducing failures, a reasonable preventive maintenance scheduling guarantees the stability and safety of the system. This paper studies a consecutive maintenanc...As an effective means for improving system condition and reducing failures, a reasonable preventive maintenance scheduling guarantees the stability and safety of the system. This paper studies a consecutive maintenance scheduling problem for single-component systems with imperfect maintenance, and an optimum model with minimum reliability constraint for minimal cost rate is developed based on the renewal theory. The agebased and reliability-based maintenance strategies are modeled and compared according to a numerical example based on the degradation data of the actual system, which also verifies the optimality of the reliability-based strategy. At last, the influence of some key parameters is discussed by sensitive analysis.展开更多
The xanthan fermentation data in the stationary phase was analyzed using the black box and the metabolic network models. The data consistency is checked through the elemental balance in the black box model. In the met...The xanthan fermentation data in the stationary phase was analyzed using the black box and the metabolic network models. The data consistency is checked through the elemental balance in the black box model. In the metabolic network model, the metabolic flux distribution in the cell is calculated using the metabolic flux analysis method, then the maintenance coefficients is calculated.展开更多
基金supported by the Deyang City Science and Technology Planning Project[Grant Number 2023SZZ010].
文摘Objective:To investigate the clinical efficacy and cost-effectiveness of combined hemodialysis(HD)and hemoperfusion(HP)therapy in managing secondary hyperparathyroidism(SHPT)in patients undergoing maintenance hemodialysis(MHD).Methods:A total of 195 patients with MHD and SHPT at Deyang People's Hospital from April 2024 to April 2025 were enrolled.Patients were randomly assigned to a control group receiving standard HD treatment and an experimental group receiving HD combined with HP therapy.The experimental group underwent 1 year of observation(97 cases in the experimental group,98 cases in the control group).During treatment,changes in parathyroid hormone(PTH),serum calcium,serum phosphorus,and inflammatory factors were monitored,along with analysis of treatment-related economic benefits and safety.Results:The experimental group demonstrated significantly better reductions in PTH,serum phosphorus,and inflammatory factors compared to the control group(P<0.05).Although the total treatment cost was slightly higher,the unit cost per therapeutic effect was lower,resulting in a superior cost-effectiveness ratio.Conclusion:Combined HD and HP therapy can significantly improve SHPT-related indicators in MHD patients,demonstrating safety,controllability,and high cost-effectiveness,making it a clinically applicable and recommended treatment option.
基金Sponsored by the Scientific and Technological Project on Road Maintenance Management Mode in Guangdong Province(Grant No.200407132)the Launching Fund Project for Dr.in Guangdong Province(Grant No.05300135)
文摘To quantitatively identify the maintenance demand for each highway segments in the pavement maintenance scheme design,a mathematical model of uniform segment division was established and an approach of applying cluster analysis theory to the uniform segment division and evaluation of pavement maintenance demand was proposed.The actual maintenance project of a highway carried out in Guangdong province was cited as an example to demonstrate the validity of the proposed method.It is proved that the cluster analysis can eliminate human factors in classification without being constrained by the quantities of samples,considering multiple pavement distress indexes and the continuity of samples.Thus it is evident that cluster analysis is an efficient analytical tool in uniform segment division and evaluation of maintenance demand.
基金supported by the National Key R&D Program of China(Grant No.2018YFC0809300)the National Natural Science Foundation of China(Grant No.51806247)+2 种基金the Key Technology Project of Petro China Co Ltd.(Grant No.ZLZX2020-05)the Foundation of Sinopec(Grant No.320034)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462020YXZZ052)
文摘Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.
基金Supported by the Key Program of National Natural Science Foundation of China (No. 20036010) and the National Science Fund for Distinguished Young Scholars (No. 20028607).
文摘The stoichiometric matrix of a simplified metabolic network inBacillus Subtillis was constructed from the flux balance equations,which were used for reconciliation of the measured rates anddetermination of the inner metabolic rates. Thus more reliableresults of the true and empirical maintenance coefficients wereobtained. The true maintenance coefficient is linearly related to thespecific growth rate and changes with the P/O ratio. The measuredbiomass yield of adenosine triphosphate (ATP) is also linearlyrelated to the P/O ratio.
文摘BACKGROUND The burden of chronic kidney disease(CKD)is rising rapidly globally.Fluid overload(FO),an independent predictor of mortality in CKD,should be accurately assessed to guide estimation of the volume of fluid to be removed during haemodialysis(HD).Clinical score(CS)and bio-impedance analysis(BIA)have been utilized in assessment of FO and BIA has demonstrated reproducibility and accuracy in determination of fluid status in patients on HD.There is need to determine the performance of locally-developed CSs in fluid status assessment when evaluated against BIA.AIM To assess the hydration status of patients on maintenance HD using BIA and a CS,as well as to evaluate the performance of that CS against BIA in fluid status assessment.METHODS This was a single-centre,hospital-based cross-sectional study which recruited adult patients with CKD who were on maintenance HD at Kenyatta National Hospital.The patients were aged 18 years and above and had been on maintenance HD for at least 3 mo.Those with pacemakers,metallic implants,or bilateral limbs amputations were excluded.Data on the patients’clinical history,physical examination,and chest radiograph findings were collected.BIA was performed on each of the study participants using the Quantum®II bio-impedance analyser manufactured by RJL Systems together with the BC 4®software.In evaluating the performance of the CS,BIA was considered as the gold standard test.A 2-by-2 table of the participants’fluid status at each of the CS values obtained compared to their paired BIA results was constructed(either++,+-,--or-+for FO using the CS and BIA,respectively).The results from this 2-by-2 table were used to compute the sensitivity and specificity of the CS at the various reference points and subsequently plot a receiver operating characteristic(ROC)curve that was used to determine the best cut-off point.Those above and below the best CS cut-off point as determined by the ROC were classified as being positive and negative for FO,respectively.The proportions of participants diagnosed with FO by the CS and BIA,respectively,were computed and summarized in a 2-by-2 contingency table for comparison.McNemar’s chi-squared test was used to assess any statistically significant difference in proportions of patients diagnosed as having FO by CS and BIA.Logistic regression analysis was conducted to assess whether the variables for the duration of dialysis,the number of missed dialysis sessions,advisement by health care professional on fluid or salt intake,actual fluid intake,the number of anti-hypertensives used,or body mass index were associated with a patient’s odds of having FO as diagnosed by BIA.RESULTS From 100 patients on maintenance HD screened for eligibility,80 were recruited into this study.Seventy-one(88.75%)patients were fluid overloaded when evaluated using BIA with mean extracellular volume of 3.02±1.79 L as opposed to the forty-seven(58.25%)patients who had FO when evaluated using the CS.The difference was significant,with a P value of<0.0001(95%confidence interval:0.1758-0.4242).Using CS,values above 4 were indicative of FO while values less than or equal to 4 denoted the best cut-off for no FO.The sensitivity and specificity for the CS were 63%and 78%respectively.None of the factors evaluated for association with FO showed statistical significance on the multivariable logistic regression model.CONCLUSION FO is very prevalent in patients on chronic HD at the Kenyatta National Hospital.CS detects FO less frequently when compared with BIA.The sensitivity and specificity for the CS were 63%and 78%respectively.None of the factors evaluated for association with FO showed statistical significance on the multivariable logistic regression model.
文摘Within this paper, the process of statistical safety analysis has been presented, which involves the following steps： formulation of basic principles of statistical safety analysis, initial events analysis, accident sceneries progress analysis, risk calculation, and risk calculation results analysis. On this basis, it has been concluded that the bucket wheel excavator SRs 1200×24/4×0（400 kW）＋VR safety criteria is the mechanism for the hoist of rotor＇s arrow failure modes, because in that case whole bucket wheel excavator failure would necessarily happen （excavator falling down on counterweight）. Therefore, excavator units statistical safety analysis is accomplished preventively to obtain its effective maintenance management.
文摘Taking the project of introducing reliability-centered maintenance( RCM) into maintenance decision in an AP1000 nuclear power plant( NPP) under construction as the research object,an improved RCM methodology was proposed, and the application software and an RCM-based maintenance strategies management system were designed. In the pilot project,the RCMbased maintenance decision methodology had been applied to determining the maintenance strategies for two systems. Both the decision process and the results were described in this paper. The achievements of this project promoted the introduction and routinization of an advanced and effective maintenance decision mode in nuclear power field,which could provide valuable reference for new NPPs in China.
文摘Most traditional assessment methods, which have complicated mathematic formulas,are difficult for calculation and application in system efficiency evaluation. A new approach to annual equipment maintenance system efficiency assessment,the set pair analysis method( SPAM),has been proposed based on the principle of set pair analysis( SPA). Firstly,the evaluation index system of the annual equipment maintenance is proposed. Secondly,the evaluation model of the annual equipment maintenance efficiency based on the SPAM is built. Then the application processes of the SPAM are introduced. At the end of the paper,a real application example is given. The results of the application indicate that the proposed model is feasible and effective. It can give strong supports to improve the evaluation effect of the unit equipment maintenance support.
文摘The instruments of regional automatic weather station are placed outside to measure daily changes of meteorological factors. Due to common influence of sun,wind,rain and other factors,it is very easy to cause various faults and damages of the instrument. The construction of regional automatic weather station network plays an important role in improving forecast accuracy,servicing local government and ecological civilization construction,providing scientific disaster prevention and relief decision-making basis for government department. In this paper,based on daily operation situation of regional automatic weather station in Shaoyang region,combining communication,hardware and software,fault situation of collector,temperature and humidity sensor,wind sensor and rainfall sensor in automatic weather station is analyzed in detail. Moreover,some common fault cases are listed and analyzed,some troubleshooting methods are summarized,and daily maintenance measures are proposed.
文摘Motor vehicle inspection and maintenance (I/M) programs are designed to identify high-emitting vehicles and mitigate their impacts on air quality and climate. I/M programs have been traditionally ranked superior among various vehicle emission control measures by the results of cost-benefit analysis, based on the assumption that these programs will achieve the targeted emission reduction outcomes. However, the actual effects of I/M programs may be greatly uncertain and when this uncertainty is taken into account, these programs may become suboptimal. This study develops a new a cost-benefit analysis framework that links various program design consideration, such as program participation rate, identification rate and effective repair rate, to the public health benefits as well as costs of the programs. This framework helps decision makers to investigate minimum implementation requirements that at least ensure the benefits are greater than the costs of implementing the programs in order to improve the overall effectiveness of the I/M programs. To illustrate the applications of the framework, it was applied to a particulate matter oriented I/M program targeting all diesel-fueled vehicles in the city of Bangkok, Thailand, a large metropolitan area that has been suffering from severe ambient PM pollution mainly attributable to its wide use of diesel-fueled vehicles and motorcycles. It was found that the health benefits achieved from the program are sensitive to several key program design elements, including participation rate and problem vehicle identification rate, fraction of effective repairs and illegal operation rate. Other variables, such as the testing cut-points and vehicle population growth rate, only have modest effects on the overall emission reduction and consequent health benefits. Overall, the performance of multiple variables associated with I/M program design needs to be improved simultaneous in order to achieve the targeted benefits of the program.
文摘Preventative maintenance (PM) measures for bridges are proactive maintenance actions which aim to prevent or delay a deterioration process that may lead to failure. This type of maintenance can be justified on economic grounds since it can extend the life of the bridge and avoid the need for unplanned essential/corrective maintenance. Due to the high importance of the effective integration of PM measures in the maintenance strategies of bridges, the authors have developed a two-stage evolutionary optimization methodology based on genetic algorithm (GA) principles which links the probabilistic effectiveness of various PM measures with their costs in order to develop optimum PM strategies. In this paper, the sensitivity of the methodology to various key input parameters of the optimization methodology is examined in order to quantify their effects and identify possible trends in the optimum PM intervention profiles. The results of the sensitivity studies highlight the combined use of both proactive and reactive PM measures in deriving optimum strategy solutions. The precise mix and sequence of PM measures is clearly a function of the relative effectiveness and cost of the different available PM options as well as the various key parameters such as discount rate, target probability of failure, initial probability of failure and service life period examined. While the results highlight the need for more reliable data they also demonstrate the robustness and usefulness of the methodology;in the case where data is limited it can be used as a comparative tool to improve understanding of the effects of various strategies and enhance the decision making process.
文摘In existing references,authors and companies have defined the maintenance variables over time;it is found that in some cases there are traditions,incorrect postulates or the inappropriate use of terminology,which leads to a misinterpretation of the results when maintenance management is analyzed.Starting from a documentary and deductive methodology,in this article,the analysis of some authors is presented and,from its origin,the initial variables that allow the construction of adequate algorithms for the maintenance function and to obtain the correct information related to it are re-defined.In a simple way with mathematical models,to then apply statistical models which allows,subsequently,calculating the maintenance information and achieving that professionals,professors and students are incorporated into maintenance analysis processes with a higher cognitive level,producing continuous information and comprehensive to analyze and investigate industrial equipment based on a basic history.
文摘Since the 21st century,China's economy has enjoyed rapid development and people's living standards have been improved.At the same time,the pursuit of beauty of people is getting increasingly higher and landscaping of and design of gardens has been widely pursued by people.This paper has discussed and analyzed the design of flower border and maintenance of flower border in the later period,hoping to provide some help and support for the relevant technical workers.
文摘This paper attempts to concentrate on the eight basic principles of reliability-centeredmaintenance, and discusses respectively the differences between old and new maintenanceconcepts in eight aspects, i.e., function of rework at hard time, potential failure and funcrionalfailure, function of preventive maintenance, change of failure consequence, determinarion ofpreventive maintenance work and formulation of initial preventive maintenance program, andperfection of preventive maintenance program.
基金Supported by Scientific Research Project of Shunde Daliang Urban Administration Bureau in 2010
文摘We take Shunde District,Foshan City in Guangdong Province for example,to carry out SWOT analysis of urban greening maintenance and management.The strengths of greening management and maintenance in Shunde District are as follows:(i)The greening area and quality are continuously improved in the downtown of Shunde District;(ii)The management and maintenance work is carried out well;(iii)The management and maintenance level tends to be increasingly perfected.The weaknesses of greening management and maintenance are as follows:(i)The fees for greening management and maintenance are very low;(ii)There is corner as yet untouched in the junction of some town streets;(iii)The greening management and maintenance technicians are unprofessional;(iv)The greening management is not in place;(v)There is management vacancy phenomenon in the management and maintenance of regional green space;(vi)The design and construction phase is flawed.Finally,based on the analysis of strengths and weaknesses of greening,we put forth the recommendations for the development of management and maintenance in urban green space.
基金supported by the National Natural Science Foundation of China(Grant No.62203362)the Natural Science Basic Research Program of Shaanxi(Grant No.2023-JC-QN-0569)。
文摘A situation maintenance-based cooperative guidance strategy is proposed to intercept a high-speed and high-maneuverability target via inferior missiles.Reachability and relative motion analyses are conducted to develop and pursue virtual targets,respectively.A two-stage guidance strategy under nonlinear kinematics is developed on the basis of virtual targets.The first stage optimizes the coverage and collision situation by pursuing virtual targets under specific angular constraints.The second stage subsequently intercepts the superior target based on the handover condition optimized by the first stage.Numerical simulation results are provided to compare the effectiveness and superiority of the proposed strategy with those of the reachability-based cooperative strategy(RCS),coverage-based cooperative guidance(CBCG)and augmented proportional navigation(APN)under various maneuvering modes.
基金supported by Research Ireland under Grant No.20/FFP-P/8706.
文摘Railway systems are critical components of transportation networks requiring consistent maintenance.This paper proposes a novel data-driven approach to detect various maintenance needs of railway track systems using acceleration data obtained from a passenger train in operation.The framework contains four modules.Firstly,data pre-processing and cleansing are performed to extract useful data from the whole dataset.Then,condition-sensitive features are extracted from the raw data in three different domains of time,frequency,and time-frequency.In the third module,the best subset of measurement features that characterize the state of the tracks are selected using the analysis of variance(ANOVA)algorithm which eliminates irrelevant characteristics from the feature set of responses.Finally,a multilabel classification algorithm based on the cascade feed-forward neural network(CFNN)is used to classify the type of maintenance needs of the track.An open-access dataset from a field study in Pennsylvania,USA,is used in this study for validation of the proposed method.The results indicate that employing a CFNN can achieve 95%accuracy in identifying two maintenance activities,tamping and surfacing,using time-domain features.Moreover,an extensive analysis has been conducted to evaluate the influence of various feature extraction and selection methods,diverse classification algorithms,and different types of accelerometers(uni-axial and tri-axial)on the accuracy of the proposed method.
基金Project(71101155)supported by the National Natural Science Foundation of ChinaProject(2015JJ2184)supported by the Natural Science Foundation of Hunan Province,China
文摘To maintain their capacity,transportation infrastructures are in need of regular maintenance and rehabilitation.The major challenge facing transportation engineers is the network-level policies to maintain the deteriorating roads at an acceptable level of serviceability.In this work,a quantitative transportation network efficiency measure is presented and then how to determine optimally network-level road maintenance policy depending on the road importance to the network performance has been demonstrated.The examples show that the different roads should be set different maintenance time points in terms of the retention capacities of the roads,because the different roads play different roles in network and have different important degrees to the network performance.This network-level road maintenance optimization method could not only save lots of infrastructure investments,but also ensure the service level of the existing transportation system.
基金the National Natural Science Foundation of China(Nos.71571015 and 71621001)
文摘As an effective means for improving system condition and reducing failures, a reasonable preventive maintenance scheduling guarantees the stability and safety of the system. This paper studies a consecutive maintenance scheduling problem for single-component systems with imperfect maintenance, and an optimum model with minimum reliability constraint for minimal cost rate is developed based on the renewal theory. The agebased and reliability-based maintenance strategies are modeled and compared according to a numerical example based on the degradation data of the actual system, which also verifies the optimality of the reliability-based strategy. At last, the influence of some key parameters is discussed by sensitive analysis.
基金Supported by the National Natural Science Foundation of China(No.29776035).
文摘The xanthan fermentation data in the stationary phase was analyzed using the black box and the metabolic network models. The data consistency is checked through the elemental balance in the black box model. In the metabolic network model, the metabolic flux distribution in the cell is calculated using the metabolic flux analysis method, then the maintenance coefficients is calculated.
