Semi-analytical solution for drained expansion analysis of a hollow cylinder of critical state soils

The expansion of a thick-walled hollow cylinder in soil is of non-self-similar nature that the stress/deformation paths are not the same for different soil material points.As a result,this problem cannot be solved by the common self-similar-based similarity techniques.This paper proposes a novel,exact solution for rigorous drained expansion analysis of a hollow cylinder of critical state soils.Considering stress-dependent elastic moduli of soils,new analytical stress and displacement solutions for the nonself-similar problem are developed taking the small strain assumption in the elastic zone.In the plastic zone,the cavity expansion response is formulated into a set of first-order partial differential equations(PDEs)with the combination use of Eulerian and Lagrangian descriptions,and a novel solution algorithm is developed to efficiently solve this complex boundary value problem.The solution is presented in a general form and thus can be useful for a wide range of soils.With the new solution,the non-self-similar nature induced by the finite outer boundary is clearly demonstrated and highlighted,which is found to be greatly different to the behaviour of cavity expansion in infinite soil mass.The present solution may serve as a benchmark for verifying the performance of advanced numerical techniques with critical state soil models and be used to capture the finite boundary effect for pressuremeter tests in small-sized calibration chambers.

FREEZE PROFILE AND HEAT BALANCE CALCULATION OF THE 160kA DRAINED CELL

A 2D full cell thermo-electric model of 160kA drained cell was set up using finiteelement code to calculate its freeze profile, then the drained cell model was modifiedaccording to the freeze profile computed and its heat balance was calculated. Comparedwith that of a 160kA conventional Hall-Heroult cell (H-H cell), though the melts vol-ume of the drained cell reduced greatly, the whole heat loss from it didn't drop downapparently, and an analysis was presented in the paper. On the other hand, the anode-cathode distance (ACD) of a drained cell was much less than that of a H-H cell, sothe voltage drop on it and heat produced decreased too, steps should be taken to keepa workable heat balance on a drained cell.

Visualization of drained rock volume(DRV) in hydraulically fractured reservoirs with and without natural fractures using complex analysis methods(CAMs)

The drainage areas(and volumes)near hydraulically fractured wells,computed and visualized in our study at high resolution,may be critically affected by the presence of natural fractures.Using a recently developed algorithm based on complex analysis methods(CAMs),the drained rock volume(DRV)is visualized for a range of synthetic constellations of natural fractures near hydraulic fractures.First,flow interference effects near a single hydraulic fracture are systematically investigated for a variety of natural fracture sets.The permeability contrast between the matrix and the natural fractures is increased stepwise in order to better understand the effect on the DRV.Next,a larger-scale model investigates flow interference for a full hydraulically fractured well with a variety of natural fracture sets.The time of flight contours(TOFCs)outlining the DRV are for all cases with natural fractures compared to a base case without any natural fractures.Discrete natural fractures,with different orientations,hydraulic conductivity,and fracture density,may shift the TOFC patterns in the reservoir region drained by the hydraulically fractured well,essentially shifting the location of the well’s drainage area.The CAM-based models provide a computationally efficient method to quantify and visualize the drainage in both naturally and hydraulically fractured reservoirs.

A method of determining and designing the drained slope in drained aluminum reduction cells

Based on principles of electromagnetic fluid dynamics the exerted forces and movement states of melted aluminum in the traditional reduction cells and the drained cells were compared and analyzed in this paper. And based on the theory of slow movement, a formula in respect of the drained angle was derived, i.e. θ≥(J zB x-J xB z)ρg-(J xB y-J yB x ). It can be seen that the drained slope can be decided by respectively multiplying the area current densities and magnetic induction intensities in three coordinate directions in aluminum reduction cells, and the drained slope is approximate to 0.6% derived from typical data based on measurement and calculation, which implies that the key parameter is obtained in designing of drained cells. The results can be used for a designing basis for drained cathodes.

Drained rock volume around hydraulic fractures in porous media:planar fractures versus fractal networks

This study applies the Lindenmayer system based on fractal theory to generate synthetic fracture networks in hydraulically fractured wells.The applied flow model is based on complex analysis methods,which can quantify the flow near the fractures,and being gridless,is computationally faster than traditional discrete volume simulations.The representation of hydraulic fractures as fractals is a more realistic representation than planar bi-wing fractures used in most reservoir models.Fluid withdrawal from the reservoir with evenly spaced hydraulic fractures may leave dead zones between planar fractures.Complex fractal networks will drain the reservoir matrix more effectively,due to the mitigation of stagnation flow zones.The flow velocities,pressure response,and drained rock volume(DRV)are visualized for a variety of fractal fracture networks in a single-fracture treatment stage.The major advancement of this study is the improved representation of hydraulic fractures as complex fractals rather than restricting to planar fracture geometries.Our models indicate that when the complexity of hydraulic fracture networks increases,this will suppress the occurrence of dead flow zones.In order to increase the DRV and improve ultimate recovery,our flow models suggest that fracture treatment programs must find ways to create more complex fracture networks.

Effect of Loading Rate on Lateral Pile-Soil Interaction in Sand Considering Partially Drained Condition

Reliable assessment of the lateral pile–soil interaction is of pronounced importance for the design of mono-pile foundations of offshore wind turbines. As the offshore engineering moves to deeper waters, the diameter of monopiles is getting larger, usually about 5 m and could be up to 8 m, which may lead to partially drained behaviors of sand in the vicinity of the pile and thus imply limitations of conventional design methods in which fully drained conditions were assumed. To shed light on this issue, a fully-coupled finite element model was established using an in-house developed finite element code DBLEAVES, incorporating a cyclic mobility constitutive model that is capable of describing the instantaneous contractive and dilative response of sands simultaneously. Triaxial and centrifuge model tests were conducted to calibrate the constitutive model and validate the pile–soil interaction model respectively. This is followed by a parametric study primarily focusing on the effects of loading rates. The initial stiffness of the p–y curve was found to increase with the loading rate whilst the bearing capacity showed the inverse,and the mechanism behind this phenomenon is examined in detail. Then an explicit model was developed to evaluate the development of excess pore pressure in the pile front upon lateral loading, and an upper boundary of normalized loading rate was identified to distinguish fully and partially drained conditions.

Vibration pore water pressure characteristics of saturated fine sand under partially drained condition

Vibration pore water pressure characteristics of saturated fine sand under partially drained condition were investigated through stress-controlled cyclic triaxial tests employed varied fine content of samples and loading frequency. In order to simulate the partially drained condition, one-way drainage for sample was implemented when cyclic loading was applied. The results show that the vibration pore water pressure's response leads the axial stress and axial strain responses, and is lagged behind or simultaneous with axial strain-rate's response for all samples in this research. In addition, the satisfactory linear relationship between vibration pore water pressure amplitude and axial strain-rate amplitude is also obtained. It means that the direct cause of vibration pore water pressure generation under partially drained conditions is not the axial stress or axial strain but the axial strain-rate. The lag-phase between pore water pressure and axial strain-rate increases with the increase of the fine content or the loading frequency.

Stress relaxation of warm frozen soil under drained or undrained conditions

To investigate the influence of drainage conditions on stress relaxation characteristics of warm frozen soil, a series of laboratory tests were carried out under drained and undrained conditions. The results indicate that confining pressure obviously influences the relaxation process of warm frozen soil. Under undrained condition, with increase in confining pressure, the critical relaxation du- ration tends to grow as well as instantaneous relaxation. But the relaxation rate is sensitive to confining pressure in the initial stage, and with further development, the effect tends to diminish. Under drained condition, the relaxation rate is greater than that under tmdrained condition in the initial stage but with the development of relaxation, the difference decreases. The volumetric defor- mation of warm frozen clay under drained condition is much larger than that under undrained condition.

DEM simulations of critical state behaviour of granular materials under various drained triaxial stress path tests

The present study investigates the critical state behaviour of granular assemblies composed of clumped particles under four different drained axisymmetric triaxial stress paths,using the discrete element method(DEM).A series of numerical samples were prepared at initial states with different density indexes(1D)and different initial confining pressures(ρ′0).These samples were sheared to large strains,at which constant stresses and volumes were maintained to reach the critical state.The evolution of stress ratio under the same loading mode(for the same intermediate principal stress ratio,b)is shown to yield an almost identical behaviour independent of stress paths,whereas the stress-strain response depends on the stress paths.Four different axisymmetric stress paths all share the same unique friction angle at critical state,indicating the Mohr-Coulomb failure criterion is the appropriate critical state strength criterion,which is at least true for the axisymmetric stress conditions.A unique coordination number(CN)is achieved at the critical state for a given po,which is independent of the stress path.The critical state CN is found to increase with the increase in po,which could be attributed to the decrease in the critical state void ratio(ec)as mean effective stress(ρ′0)increases.Interestingly,a unique linear functional relationship is found between the critical state values of cN and ec,and a unique polynomial functional relationship is found between the critical state values of CN andρ′.These functional relationships indicate no dependency on the stress paths or loading modes,thus characterizing unique features at critical states at both macroscopic and microscopic levels for a given type of granular material.

COMPARISON OF GRANULAR MATERIAL BEHAVIOUR UNDER DRAINED TRIAXIAL AND PLANE STRAIN CONDITIONS USING 3D DEM SIMULATIONS

Three dimensional （3D） DEM （discrete element method） simulations of drained triaxial compression and plane strain tests are presented for both dense and loose assemblies of polydisperse spheres using a periodic cell. In the work reported, drained tests were modelled by deforming the samples under constant mean stress conditions. The drained behaviour is shown to be qualitatively similar to published physical experimental results. The Bishop＇s formula for the estimation of the intermediate principal stress is evaluated. The existence of critical density is shown to be independent of initial packing densities and strain conditions. Different failure criteria have been compared based on the DEM simulation results, and the Lade criterion is found to be the most appropriate one. A new microscopic fabric parameter is introduced to give insight to structural anisotropy under general 3D fabric conditions. It is found that two parameters characterize the evolution of the stress and fabric respectively independent of strain conditions.

Modelling smear effect of vertical drains using a diameter reduction method

Vertical drains are used to accelerate consolidation of clays in ground improvement projects.Smear zones exist around these drains,where permeability is reduced due to soil disturbance caused by the installation process.Hansbo solution is widely used in practice to consider the effects of drain discharge capacity and smear on the consolidation process.In this study,a computationally efficient diameter reduction method(DRM)obtained from the Hansbo solution is proposed to consider the smear effect without the need to model the smear zone physically.Validated by analytical and numerical results,a diameter reduction factor is analytically derived to reduce the diameter of the drain,while achieving similar solutions of pore pressure dissipation profile as the classical full model of the smear zone and drain.With the DRM,the excess pore pressure u obtained from the reduced drain in the original un-disturbed soil zone is accurate enough for practical applications in numerical models.Such performance of DRM is independent of soil material property.Results also show equally accurate performance of DRM under conditions of multi-layered soils and coupled radial-vertical groundwater flow.

Special stent for draining the abdominal abscess respectively from colon and duodenum:A case report

BACKGROUND Postoperative abdominal infections are an important and heterogeneous health challenge.Many samll abdominal abscesses are resolved with antibiotics,but larger or symptomatic abscesses may require procedural management.CASE SUMMARY A 65-year-old male patient who suffered operation for the left hepatocellular carcinoma eight months ago,came to our hospital with recurrent abdominal pain,vomit,and fever for one month.Abdominal computed tomography showed that a big low-density dumbbell-shaped mass among the liver and intestine.Colonoscopy showed a submucosal mass with a fistula at colon of liver region.Gastroscopy showed a big rupture on the submucosal mass at the descending duodenum and a fistula at the duodenal bulb.Under colonoscopy,the brown liquid and pus were drained from the mass with“special stent device”.Under gastroscopy,we closed the rupture of the mass with a loop and six clips for purse stitching at the descending duodenum,and the same method as colonoscopy was used to drain the brown liquid and pus from the mass.The symptom of abdominal pain,vomit and fever were relieved after the treatment.CONCLUSION The special stent device could be effectively for draining the abdominal abscess respectively from colon and duodenum.

Palliative long-term abdominal drains vs large volume paracenteses for the management of refractory ascites in end-stage liver disease

BACKGROUND Long-term abdominal drains(LTAD)are a cost-effective palliative measure to manage malignant ascites in the community,but their use in patients with end-stage chronic liver disease and refractory ascites is not routine practice.The safety and cost-effectiveness of LTAD are currently being studied in this setting,with preliminary positive results.We hypothesised that palliative LTAD are as effective and safe as repeat palliative large volume paracentesis(LVP)in patients with cirrhosis and refractory ascites and may offer advantages in patients’quality of life.AIM To compare the effectiveness and safety of palliative LTAD and LVP in refractory ascites secondary to end-stage chronic liver disease.METHODS A retrospective,observational cohort study comparing the effectiveness and safety outcomes of palliative LTAD and regular palliative LVP as a treatment for refractory ascites in consecutive patients with end-stage chronic liver disease followed-up at our United Kingdom tertiary centre between 2018 and 2022 was conducted.Fisher’s exact tests and the Mann-Whitney U test were used to compare qualitative and quantitative variables,respectively.Kaplan-Meier survival estimates were generated to stratify time-related outcomes according to the type of drain.RESULTS Thirty patients had a total of 35 indwelling abdominal drains and nineteen patients underwent regular LVP.The baseline characteristics were similar between the groups.Prophylactic antibiotics were more frequently prescribed in patients with LTAD(P=0.012),while the incidence of peritonitis did not differ between the two groups(P=0.46).The incidence of acute kidney injury(P=0.014)and ascites/drain-related hospital admissions(P=0.004)were significantly higher in the LVP group.The overall survival was similar in the two groups(log-rank P=0.26),but the endpoint-free survival was significantly shorter in the LVP group(P=0.003,P<0.001,P=0.018 for first ascites/drain-related admission,acute kidney injury and drain-related complications,respectively).CONCLUSION The use of LTAD in the management of refractory ascites in palliated end-stage liver disease is effective,safe,and may reduce hospital admissions and utilisation of healthcare resources compared to LVP.

Experiment and simulation on degradation and burnout mechanisms of SiC MOSFET under heavy ion irradiation

Experiments and simulation studies on 283 MeV I ion induced single event effects of silicon carbide(SiC) metal–oxide–semiconductor field-effect transistors(MOSFETs) were carried out. When the cumulative irradiation fluence of the SiC MOSFET reached 5×10^(6)ion·cm^(-2), the drain–gate channel current increased under 200 V drain voltage, the drain–gate channel current and the drain–source channel current increased under 350 V drain voltage. The device occurred single event burnout under 800 V drain voltage, resulting in a complete loss of breakdown voltage. Combined with emission microscope, scanning electron microscope and focused ion beam analysis, the device with increased drain–gate channel current and drain–source channel current was found to have drain–gate channel current leakage point and local source metal melt, and the device with single event burnout was found to have local melting of its gate, source, epitaxial layer and substrate. Combining with Monte Carlo simulation and TCAD electrothermal simulation, it was found that the initial area of single event burnout might occur at the source–gate corner or the substrate–epitaxial interface, electric field and current density both affected the lattice temperature peak. The excessive lattice temperature during the irradiation process appeared at the local source contact, which led to the drain–source channel damage. And the excessive electric field appeared in the gate oxide layer, resulting in drain–gate channel damage.

Gunsight suture with subcutaneous vacuum drainage during enterostomy decreased the surgical site infection rate in obese rectal cancer patients:A retrospective study

Background:Surgical site infection(SSI)is the most common complication after stoma closure and is particularly common in obese patients.To reduce the incidence of SSI,various skin closure techniques have been proposed;however,the best technique is still under debate.The purpose of this study was to explore the effectiveness of subcutaneous vacuum drains(SVDs)after two surgical suture techniques following stoma reversal in obese patients. Methods:Data from 190 obese patients with rectal cancer who underwent stoma reversal for enterostomy between February 2012 and April 2023 at Jinxiang Hospital Affiliated to Jining Medical University were retrospectively analyzed.These patients were divided into two groups:gunsight suture(GS)with SVD and primary linear suture(PLS)with SVD.The GS group and PLS group included 90 and 100 patients,respectively.The clinical characteristics and short-term outcomes were compared between the two groups.Postoperative pain scores were analyzed using a generalized estimation equation. Results:Surgery was successfully performed in both groups.The rate of SSI in the GS group was significantly lower than that in the PLS group(2.2%vs 9.0%,P=0.046).Patients in the GS group had a significantly shorter wound healing time than did patients in the PLS group,as well as a significantly shorter postoperative fasting time(P<0.05).No significant differences were found between the groups in terms of the postoperative hospital stay,operative time,and estimated blood loss(P>0.05).The results of the generalized estimation equation analysis showed that the GS group had significantly lower pain scores at 12,24,48,and 72 h after surgery than the PLS group(P<0.05).Moreover,the GS group showed significantly better alleviation of wound pain between 12 and 72 h after surgery(P<0.05). Conclusions:The GS technique with SVD may be recommended for wound closure of a nonfunctioning stoma in obese patients.

A Ferroelectric Domain-Wall Transistor

On the basis of novel properties of ferroelectric conducting domain walls,the domain wall nanoelectronics emerges and provides a brand-new dimension for the development of high-density,high-speed and energy-efficient nanodevices.For in-memory computing,three-terminal devices with both logic and memory functions such as transistors purely based on ferroelectric domain walls are urgently required.Here,a prototype ferroelectric domain-wall transistor with a well-designed coplanar electrode geometry is demonstrated on epitaxial Bi Fe O_(3)thin films.For the logic function,the current switching between on/off states of the transistor depends on the creation or elimination of conducting domain walls between drain and source electrodes.For the data storage,the transistor can maintain nonvolatile on/off states after the write/erase operations,providing an innovative approach for the development of the domain wall nanoelectronics.

Single-event-transient effect in nanotube tunnel field-effect transistor with bias-induced electron–hole bilayer

The single event transient(SET)effect in nanotube tunneling field-effect transistor with bias-induced electron–hole bilayer(EHBNT-TFET)is investigated by 3-D TCAD simulation for the first time.The effects of linear energy transfer(LET),characteristic radius,strike angle,electrode bias and hit location on SET response are evaluated in detail.The simulation results show that the peak value of transient drain current is up to 0.08 m A for heavy ion irradiation with characteristic radius of 50 nm and LET of 10 Me V·cm^(2)/mg,which is much higher than the on-state current of EHBNTTFET.The SET response of EHBNT-TFET presents an obvious dependence on LET,strike angle,drain bias and hit location.As LET increases from 2 Me V·cm^(2)/mg to 10 Me V·cm^(2)/mg,the peak drain current increases monotonically from 0.015 mA to 0.08 mA.The strike angle has an greater impact on peak drain current especially for the smaller characteristic radius.The peak drain current and collected charge increase by 0.014 mA and 0.06 fC,respectively,as the drain bias increases from 0.1 V to 0.9 V.Whether from the horizontal or the vertical direction,the most sensitive hit location is related to wt.The underlying physical mechanism is explored and discussed.

Ambipolar performance improvement of the C-shaped pocket TFET with dual metal gate and gate–drain underlap

Dual-metal gate and gate–drain underlap designs are introduced to reduce the ambipolar current of the device based on the C-shaped pocket TFET(CSP-TFET).The effects of gate work function and gate–drain underlap length on the DC characteristics and analog/RF performance of CSP-TFET devices,such as the on-state current(I_(on)),ambipolar current(I_(amb)),transconductance(g_(m)),cut-off frequency(f_(T))and gain–bandwidth product(GBP),are analyzed and compared in this work.Also,a combination of both the dual-metal gate and gate–drain underlap designs has been proposed for the C-shaped pocket dual metal underlap TFET(CSP-DMUN-TFET),which contains a C-shaped pocket area that significantly increases the on-state current of the device;this combination design substantially reduces the ambipolar current.The results show that the CSP-DMUN-TFET demonstrates an excellent performance,including high I_(on)(9.03×10^(-4)A/μm),high I_(on)/I_(off)(~10^(11)),low SS_(avg)(~13 mV/dec),and low I_(amb)(2.15×10^(-17)A/μm).The CSP-DMUN-TFET has the capability to fully suppress ambipolar currents while maintaining high on-state currents,making it a potential replacement in the next generation of semiconductor devices.

Low switching loss and increased short-circuit capability split-gate SiC trench MOSFET with p-type pillar

A split-gate SiC trench gate MOSFET with stepped thick oxide, source-connected split-gate(SG), and p-type pillar(ppillar) surrounded thick oxide shielding region(GSDP-TMOS) is investigated by Silvaco TCAD simulations. The sourceconnected SG region and p-pillar shielding region are introduced to form an effective two-level shielding, which reduces the specific gate–drain charge(Q_(gd,sp)) and the saturation current, thus reducing the switching loss and increasing the short-circuit capability. The thick oxide that surrounds a p-pillar shielding region efficiently protects gate oxide from being damaged by peaked electric field, thereby increasing the breakdown voltage(BV). Additionally, because of the high concentration in the n-type drift region, the electrons diffuse rapidly and the specific on-resistance(Ron,sp) becomes smaller.In the end, comparing with the bottom p~+ shielded trench MOSFET(GP-TMOS), the Baliga figure of merit(BFOM,BV~2/R_(on,sp)) is increased by 169.6%, and the high-frequency figure of merit(HF-FOM, R_(on,sp) × Q_(gd,sp)) is improved by310%, respectively.

Abscess drain migration into the colon following laparoscopic cholecystectomy

Percutaneous abscess drainage is a procedure commonly performed by interventional radiologists to provide source control on infections using CT or ultrasound guidance.The interventionalist has many different sizes and shapes of catheters to treat abscesses of varying sizes and locations,but the general approach to each abscess is similar:provide a percutaneous route for purulence,bacteria,necrotic tissue,and other debris to escape the body.While generally considered a low-risk procedure,adverse events can occur due to operator error or other means.We present a unique case of an abscess drain placed into a right upper quadrant abscess that formed following laparoscopic cholecystectomy that perforated and entered the colon.Astute physicians,both in the emergency department and the radiology reading room,were able to rapidly rule out more common post-operative complications and make the correct diagnosis,likely preventing dangerous sequelae from developing in this patient.