An inverse analysis of fluid flow through granular media using differentiable lattice Boltzmann method

This study presents a method for the inverse analysis of fluid flow problems.The focus is put on accurately determining boundary conditions and characterizing the physical properties of granular media,such as permeability,and fluid components,like viscosity.The primary aim is to deduce either constant pressure head or pressure profiles,given the known velocity field at a steady-state flow through a conduit containing obstacles,including walls,spheres,and grains.The lattice Boltzmann method(LBM)combined with automatic differentiation(AD)(AD-LBM)is employed,with the help of the GPU-capable Taichi programming language.A lightweight tape is used to generate gradients for the entire LBM simulation,enabling end-to-end backpropagation.Our AD-LBM approach accurately estimates the boundary conditions for complex flow paths in porous media,leading to observed steady-state velocity fields and deriving macro-scale permeability and fluid viscosity.The method demonstrates significant advantages in terms of prediction accuracy and computational efficiency,making it a powerful tool for solving inverse fluid flow problems in various applications.

A review of methods,applications and limitations for incorporating fluid flow in the discrete element method

The past decade has witnessed the substantial growth in research interests and progress on the subject of coupled hydro-mechanical processes in rocks and soils,driven mainly by the surge of research in unconventional hydrocarbon reservoirs and associated hazards.Many coupling techniques have been developed to include the effects of fluid flow in the discrete element method(DEM),and the techniques have been applied to a variety of geomechanical problems.Although these coupling methods have been successfully applied in various engineering fields,no single fluid/DEM coupling method is universal due to the complexity of engineering problems and the limitations of the numerical methods.For researchers and engineers,the key to solve a specific problem is to select the most appropriate fluid/DEM coupling method among these modeling technologies.The purpose of this paper is to give a comprehensive review of fluid flow/DEM coupling methods and relevant research.Given their importance,the availability or unavailability of best practice guidelines is outlined.The theoretical background and current status of DEM are introduced first,and the principles,applications,and advantages and disadvantages of different fluid flow/DEM coupling methods are discussed.Finally,a summary with speculation on future development trends is given.

A new method for fluid identification and saturation calculation of low contrast tight sandstone reservoir

The resistivity difference between oil and gas layers and the water layers in low contrast tight sandstone reservoirs is subtle. Fluid identification and saturation calculation based on conventional logging methods are facing challenges in such reservoirs. In this paper, a new method is proposed for fluid identification and saturation calculation in low contrast tight sandstone reservoirs. First, a model for calculating apparent formation water resistivity is constructed, which takes into account the influence of shale on the resistivity calculation and avoids apparent formation water resistivity abnormal values.Based on the distribution of the apparent formation water resistivity obtained by the new model, the water spectrum is determined for fluid identification in low contrast tight sandstone reservoirs.Following this, according to the average, standard deviation, and endpoints of the water spectrum, a new four-parameter model for calculating reservoir oil and gas saturation is built. The methods proposed in this paper are applied to the low contrast tight sandstone reservoirs in the Q4 formation of the X53 block and X70 block in the south of Songliao Basin, China. The results show that the water spectrum method can effectively distinguish oil-water layers and water layers in the study area. The standard deviation of the water spectrum in the oil-water layer is generally greater than that in the water layer. The new four-parameter model yields more accurate oil and gas saturation. These findings verify the effectiveness of the proposed methods.

The Efficient Finite Element Methods for Time-Fractional Oldroyd-B Fluid Model Involving Two Caputo Derivatives

In this paper,we consider the numerical schemes for a timefractionalOldroyd-B fluidmodel involving the Caputo derivative.We propose two efficient finite element methods by applying the convolution quadrature in time generated by the backward Euler and the second-order backward difference methods.Error estimates in terms of data regularity are established for both the semidiscrete and fully discrete schemes.Numerical examples for two-dimensional problems further confirmthe robustness of the schemes with first-and second-order accurate in time.

The effect of intraoperative goal-directed fluid therapy in patients under anesthesia for gastrointestinal surgery

BACKGROUND Intraoperative fluid management is an important aspect of anesthesia mana-gement in gastrointestinal surgery.Intraoperative goal-directed fluid therapy(GDFT)is a method for optimizing a patient's physiological state by monitoring and regulating fluid input in real-time.AIM To evaluate the efficacy of intraoperative GDFT in patients under anesthesia for gastrointestinal surgery.METHODS This study utilized a retrospective comparative study design and included 60 patients who underwent gastrointestinal surgery at a hospital.The experimental group(GDFT group)and the control group,each comprising 30 patients,received intraoperative GDFT and traditional fluid management strategies,respectively.The effect of GDFT was evaluated by comparing postoperative recovery,com-plication rates,hospitalization time,and other indicators between the two patient groups.RESULTS Intraoperative blood loss in the experimental and control groups was 296.64±46.71 mL and 470.05±73.26 mL(P<0.001),and urine volume was 415.13±96.72 mL and 239.15±94.69 mL(P<0.001),respectively.The postoperative recovery time was 5.44±1.1 days for the experimental group compared to 7.59±1.45 days(P<0.001)for the control group.Hospitalization time for the experimental group was 10.87±2.36 days vs 13.65±3 days for the control group(P<0.001).The visual analogue scale scores of the experimental and control groups at 24 h and 48 h INTRODUCTION Gastrointestinal surgery is one of the most common procedures in the field of general surgery[1],involving the stomach,intestines,liver,pancreas,spleen,and other internal abdominal organs[2,3].With advancements in surgical technology and anesthesia methods,the safety and success rates of surgery have significantly improved[4,5].However,intraop-erative fluid management remains a critical challenge[6].Traditional fluid management strategies often rely on experience and basic physiological parameters,which may lead to excessive or insufficient fluid input,thereby affecting postoperative recovery and complication rates.Intraoperative goal-directed fluid therapy(GDFT)is an emerging fluid management strategy that dynamically adjusts fluid input volume by monitoring the patient's hemodynamic parameters in real-time to optimize the patient's physiological state[7,8].GDFT has shown superiority in many surgical fields;however,its application in gastrointestinal surgery requires further research and verification[9,10].The application of intraoperative GDFT in clinical settings has gradually increased in recent years[11,12].Studies have demonstrated that GDFT can optimize tissue perfusion and oxygenation by precisely controlling fluid input and reducing the occurrence of postoperative complications[13,14].For example,in cardiac and major vascular surgeries,GDFT significantly reduced the incidence of postoperative acute kidney injury and cardiovascular events[15,16].Similarly,in abdominal surgery,GDFT effectively reduced postoperative infections and expedited recovery[17].However,studies on the utilization of GDFT in gastrointestinal surgery are relatively limited and they are confounded by contradictory findings[18].Traditional fluid management strategies typically rely on estimating fluid input volume based on the patient's weight,preoperative status,and basic physiological parameters[19].However,this method lacks real-time dynamic adjustment,which may result in either insufficient or excessive fluid input,consequently affecting postoperative recovery.Insufficient fluid input can lead to hypovolemia and inadequate tissue perfusion,whereas excessive fluid input can cause tissue edema and postoperative complications,such as pulmonary edema and heart failure.GDFT involves dynamically adjusting fluid input volume by monitoring the patient's hemodynamic parameters in real-time,such as cardiac output,pulse pressure variability,and central venous pressure.Commonly used monitoring equipment include esophageal Doppler and pulse wave profile analyzers[20].These devices provide real-time hemo-dynamic data to assist anesthesiologists in tailoring fluid therapy to a patient's specific condition.Firstly,the patient's volume responsiveness is assessed by preloading fluid;secondly,fluid input volume is dynamically adjusted based on real-time monitoring data;finally,vasoactive and inotropic drugs are administered in combination to further optimize the patient’s hemodynamic status.Through personalized fluid management,GDFT can more accurately maintain intraop-erative hemodynamic stability and reduce complications[21].Gastrointestinal surgery involves procedures on multiple organs,often requiring prolonged operative times and extensive tissue trauma,which presents challenges for intraop-erative fluid management.Surgical procedures can lead to significant bleeding and fluid loss,requiring prompt and effective fluid replenishment.In addition,the slow recovery of gastrointestinal function after surgery and susceptibility to complications such as intestinal obstruction and delayed gastric emptying elevate the necessity for postoperative fluid management.

Effects of fluid therapy combined with a preoperative glucose load regimen on postoperative recovery in patients with rectal cancer

BACKGROUND Patients with rectal cancer undergoing radical resection often have poor post-operative recovery due to preoperative fasting and water deprivation and the removal of diseased tissue,and have a high risk of complications.Therefore,it is of great significance to apply appropriate rehydration regimens to patients un-dergoing radical resection of rectal cancer during the perioperative period to improve the postoperative outcomes of patients.AIM To analyze the effects of goal-directed fluid therapy(GDFT)with a preoperative glucose load regimen on postoperative recovery and complications in patients undergoing radical resection for rectal cancer.METHODS Patients with rectal cancer who underwent radical resection(n=184)between January 2021 and December 2023 at our hospital were randomly divided into either a control group or an observation group(n=92 in each group).Both groups received a preoperative glucose load regimen,and routine fluid replacement and GDFT were additionally implements in the control and observation groups,res-pectively.The operative conditions,blood levels of lactic acid and inflammatory markers,postoperative recovery,cognitive status,hemodynamic indicators,brain oxygen metabolism,and complication rates were compared between the groups.RESULTS The colloidal fluid dosage,total infusion,and urine volume,as well as time to first exhaust,time to food intake,and postoperative length of hospital stay,were lower in the observation group(P<0.05).No significant differences were observed between the two groups in terms of operation time,bleeding volume,crystalloid liquid consumption,time to tracheal extubation,complication rate,heart rate,or mean arterial pressure(P>0.05).Compared with the control group,in the ob-servation group the lactic acid level was lower immediately after the surgery(P<0.05);the Mini-Mental State Examination score was higher on postoperative day 3(P<0.05);the pulse pressure variability(PPV)was lower at 30 min after pneumoperitoneum(P<0.05),though the differences in the PPV of the two groups was not significant at the remaining time points(P>0.05);tumor necrosis factor-αand interleukin-6 levels were lower on postoperative day 3(P<0.05);and the left and right regional cerebral oxygen saturation was higher immediately after the surgery and 30 min after pneumoperitoneum(P<0.05).CONCLUSION GDFT combined with the preoperative glucose load regimen is a safe and effective treatment strategy for im-proving postoperative recovery and risk of complications in patients with rectal cancer undergoing radical re-section.

Evaluation of working fluids for organic Rankine cycles using group-contribution methods and second-law-based models

The group-contribution (GC) methods suffer from a limitation concerning to the prediction of process-related indexes, e.g., thermal efficiency. Recently developed analytical models for thermal efficiency of organic Rankine cycles (ORCs) provide a possibility of overcoming the limitation of the GC methods because these models formulate thermal efficiency as functions of key thermal properties. Using these analytical relations together with GC methods, more than 60 organic fluids are screened for medium-low temperature ORCs. The results indicate that the GC methods can estimate thermal properties with acceptable accuracy (mean relative errors are 4.45%-11.50%);the precision, however, is low because the relative errors can vary from less than 0.1% to 45.0%. By contrast, the GC-based estimation of thermal efficiency has better accuracy and precision. The relative errors in thermal efficiency have an arithmetic mean of about 2.9% and fall within the range of 0-24.0%. These findings suggest that the analytical equations provide not only a direct way of estimating thermal efficiency but an accurate and precise approach to evaluating working fluids and guiding computer-aided molecular design of new fluids for ORCs using GC methods.

The Study of English Teaching Methods in Secondary Vocational School Based on the Role Letter's Therapy

Secondary vocational school students is different from ordinary high school students and university students,especially in the aspect of English teaching and learning.In view of the special career orientation of secondary vocational school education.English teaching methods in secondary vocational schools should have more practical and targeted. Used the Role Letter's Therapy in English teaching can help students develop interest in learning English and learning initiative consciousness. In this paper I will talk about the important of the Role Letter's Therapy in English teaching of Secondary vocational school,and how to use it.

NUMERICAL STUDY OF TWO INTERFACE METHODS FOR COMPRESSIBLE MULTI-FLUID FLOWS

Two interface capturing methods are studied for multi fluid flows, governed by the stiffened gas equation of state. The mixture type interface capturing algorithm uses a simple volume fraction model Euler equations written in a quasi conservative form, which is solved by a standard high resolution piecewise parabolic method (PPM) with multi fluid Riemann solver. The level set interface capturing method uses a narrow band ghost fluid method (GFM) with no numerical smearing. Several examples are presented and compared for one and two dimensions, which show the feasibility of the two methods applied to various multi fluid problems.

MIXED COMPATIBLE ELEMENT AND MIXED HYBRID INCOMPATIBLE ELEMENT VARIATIONAL METHODS IN DYNAMICS OF VISCOUS BAROTROPIC FLUIDS

This paper presents and proves the mixed compatible finite element variationalprinciples in dynamics of viscous barotropic fluids. When the principles are proved, itis found that the compatibility conditions of stress can be naturally satisfied. The gene-rallzed variational principles with mixed hybrid incompatible finite elements are alsopresented and proved, and they can reduce the computation of incompatible elements indynamics of viscous barotropic flows.

Overview of the Analytical Lifecycle of Supercritical Fluid Chromatography Methods

In recent times, the overall interest over Supercritical Fluid Chromatography (SFC) is truly growing within various domains but especially for pharmaceutical analysis. However, in the best of our knowledge modern SFC is not yet applied for drug quality control in the daily routine framework. Among the numerous reported SFC methods, none of them could be found to fully satisfy to all steps of the analytical method lifecycle. Thereby, the present contribution aims to provide an overview of the current and past achievements related to SFC techniques, with a targeted attention to this lifecycle and its successive steps. The included discussions were therefore structured accordingly and emphasizing the analytical method lifecycle in accord with the International Conference on Harmonisation (ICH). Recent and important scientific outputs in the field of analytical SFC, as well as instrumental evolution, qualification strategies, method development methodologies and discussions on the topic of method validation are reviewed.

Influence of in vitro Methods, Receptor Fluids on Percutaneous Absorption and Validation of a Novel in vitro Method

In vitro experiment using excised skin has been valuable for studying the mechanism of percutaneous absorption. Based on previously established static diffusion cell system in this laboratory, a novel model-peifused glass diffusion cell system is desboed. The results of initial comporative study on percutaneous absorption between glass perfused diffusion cell and static diffusion cell, ih vitro and in vivo permeation as well as factors affecting permeation with seven radiolabelled chemicals are presented. The results demonstrate that the peifused diffusion cell system, which used a perfusion nuid betow the suiface of skin to take up the materials which penetrated the skin, is more similar to physiologic condition,convenient and automatic than that of the static cell. It well predicts the in vivo percutaneous absorption if appropriate areptor fluid is chosen. The results also show that the selection of receptor fluid is critical for in vitro permeation of chemicals with different soubility

SOME DEVELOPMENTS IN VISCOUS FLUID DYNAMICS AND ITS NUMERICAL METHODS

Viscous fluid flows contain abundant "physical phenomena and the viscous fluid dynamics is of wide applications in the fields of natural and engineering sciences. After the basic equations of viscousfluiddynamics (i.e., the Navier-Stokes equations) came out, one of the most important contributions to the discipline was the boundary layer (BL) theory and the BL equations presented by Prandtl

Role of oral-fluid based measles diagnostic methods for measles global elimination

Measles eradication is biologically feasible. There is an availability of a safe, effective and inexpensive vaccine; a proven elimination strategy; high Local demand; and an effective global partnership and initiative to support vaccination. Measles eradication is a cost-effective scenario and a good investment to avoid expensive epidemics and save those children die due to measles. Laboratory investigations are indispensable to monitor the progress of measles elimination. This role will require the development of more sensitive diagnostic methods suitable for diagnosis and surveillance, genetic analysis of measles strains and a technology which is transferable worldwide. Measles diagnosis relies increasingly on serological tests. The practical utility of oral-fluid methods(antibody and genetic) in evaluating and refining measles immunization programs would,additionally, provide support for a global surveillance initiative. The utility of in a population survey, in a vaccine sero-conversion study and application in molecular epidemiological use is demonstrated in this review. It is to be hoped that this review will assist in the wider uptake and acceptance of methodology in both developed and developing country situation. More research needed for further evaluation of a recently developed point-of-care test for measles diagnosis: detection of measles-specific Ig M antibodies and viral nucleic acid for wider use oral-fluid methodology. There is a strong case and imperative for the promotion of methods by World Health Organization in its global program of control/eradication of measles over the coming decade.

Effect of perioperative fluid therapy on early phase prognosis after liver transplantation

BACKGROUND: Although liver transplantation (LT) has made rapid progress, early pulmonary complications still occur. More attention should be paid to fluid therapy that may be an important factor leading to these complications. It is necessary to investigate the correlation between intraoperative and postoperative fluid therapy and early pulmonary complications after LT, then attempt to provide a reasonable fluid therapy in the perioperative period. METHODS: Sixty-two patients who had undergone Ff were enrolled and analyzed retrospectively. Based on early phase prognosis after LT, the 62 patients were divided into a non-pulmonary complication group and a pulmonary complication group. Twenty perioperative variables were analyzed in both groups to screen out several factors causing early pulmonary complications, then the parameters reflecting postoperative recovery were analyzed. RESULTS: The pulmonary complication group had 29 patients (46.77%), 3 (4.84%) of whom died during the perioperative period. Using monofactorial analysis for each variable, the two groups differed in the following variables: preoperative lung function, volume of intraoperative transfusion, volume of intraoperative bleeding, and volume of intraoperative net fluid retention and fluid balance (<=-500 ml) in >= 2 of the first 3 days after operation. Analysis of the relationship between multivariate factors and pulmonary complications after LT by logistic multivariate regression analysis showed that preoperative lung function, volume of intraoperative bleeding, and fluid balance (<=-500 ml) in >=-2 of the first 3 days after operation were influential factors. CONCLUSIONS: It is important to maintain fluid balance during the perioperative period of LT. If the hemodynamics are stable, appropriate negative fluid balance in the first 3 days after operation apparently decreases the incidence of early pulmonary complications after LT. These measures are associated with better postoperative recovery.

Quadrature-based moment methods for the population balance equation: An algorithm review

The dispersed phase in multiphase flows can be modeled by the population balance model(PBM). A typical population balance equation(PBE) contains terms for spatial transport, loss/growth and breakage/coalescence source terms. The equation is therefore quite complex and difficult to solve analytically or numerically. The quadrature-based moment methods(QBMMs) are a class of methods that solve the PBE by converting the transport equation of the number density function(NDF) into moment transport equations. The unknown source terms are closed by numerical quadrature. Over the years, many QBMMs have been developed for different problems, such as the quadrature method of moments(QMOM), direct quadrature method of moments(DQMOM),extended quadrature method of moments(EQMOM), conditional quadrature method of moments(CQMOM),extended conditional quadrature method of moments(ECQMOM) and hyperbolic quadrature method of moments(Hy QMOM). In this paper, we present a comprehensive algorithm review of these QBMMs. The mathematical equations for spatially homogeneous systems with first-order point processes and second-order point processes are derived in detail. The algorithms are further extended to the inhomogeneous system for multiphase flows, in which the computational fluid dynamics(CFD) can be coupled with the PBE. The physical limitations and the challenging numerical problems of these QBMMs are discussed. Possible solutions are also summarized.

Goal-directed therapy in intraoperative fluid and hemodynamic management

Intraoperative fluid management is pivotal to the outcome and success of surgery, especially in high-risk proce- dures. Empirical formula and invasive static monitoring have been traditionally used to guide intraoperative fluid management and assess volume status. With the awareness of the potential complications of invasive procedures and the poor reliability of these methods as indicators of volume status, we present a case scenario of a patient who underwent major abdominal surgery as an example to discuss how the use of minimally invasive dynamic monitoring may guide intraoperative fluid therapy.

DIFFERENTIAL QUADRATURE METHOD TO STABILITY ANALYSIS OF PIPES CONVEYING FLUID WITH SPRING SUPPORT

It is a new attempt to extend the differential quadrature method(DQM) to stability analysis of the straight and curved centerlinepipes conveying fluid. Emphasis is placed on the study of theinfluences of several parameters on the critical flow velocity.Compared to other methods, this method can more easily deal with thepipe with spring support at its boundaries and asks for much lesscomputing effort while giving ac- ceptable precision in the numericalresults.

Preparation of TiO_2-MoO_3 nano-composite photo-catalyst by supercritical fluid dry method

A series of TiO 2-MoO 3 nano-composite photocatalysts were prepared by supercritical fluid dry method(SCFD) and an impregnation technique with TiCl 4 and (NH 4) 6Mo 7O 24 ·4H 2O as the starting materials. The catalysts were characterized by the means of XRD, TEM and UV-Vis. Methyl orange was used as model compound for the evaluation of their catalytic activities. The results indicated that the photo-catalyst prepared by SCFD had the advantages of small size(12.84 nm), narrow distribution and good dispersivity. The presence of small amount of Mo in composite catalyst gives rise to the red shift of its absorbance wavelength, decrease of its energy gap and increase of the utility of visible light. Furthermore, higher surface acidity of the photo-catalyst was obtained as the result of the addition of MoO 3. Compared with pure TiO 2, the catalytic activity of the TiO 2-MoO 3 nano-composite photo-catalyst was improved significantly. As the doping concentration of the composite catalysts was controlled at 0.6%(molar percentage), 100% degradation of methyl orange was achieved with in 1.2 h irradiation time.