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.

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.

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.

Control of Seepage through Earth Dams Based on Pervious Foundation Using Toe Drainage Systems

Many dangerous effects arise from seepage through earth dams based on pervious layer. Therefore, the dam embankment must be provided with seepage control measures to avoid such effects. In the present work, different control methods were used such as flat slopes, toe drainage systems, and a catch drain in the tail water. The hydraulic performance of each control measure was evaluated using the analytical solutions, previously developed, to estimate the seepage quantity (q), the height of seepage surface (h3), and the coordinates of the free surface (hx). Study was conducted on a physical model for a dam embankment having a top width (b) = 10.0 meter, height (Hd) = 30.0 meter, and slope factor (m) = 1.5. The obtained results were analyzed and presented in dimensionless charts. Results showed that, the used control measures possess a great effect on the characteristics of seepage through earth dams based on pervious foundations. A comparative study was conducted between the studied toe drainage systems to enable the designers the better choice for design purposes.

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.

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.

Recent evidence for subcutaneous drains to prevent surgical site infections after abdominal surgery:A systematic review and metaanalysis

BACKGROUND Surgical site infections(SSIs)increase mortality,hospital stays,additional medical treatment,and medical costs.Subcutaneous drains prevent SSIs in gynecological and breast surgeries;however,their clinical impact in abdominal surgery remains unclear.AIM To investigate whether subcutaneous drains were beneficial in abdominal surgery using a systematic review and meta-analysis.METHODS The database search used PubMed,MEDLINE,and the Cochrane Library.The following inclusion criteria were set for the systematic review:(1)Randomized controlled trial studies comparing SSIs after abdominal surgery with or without subcutaneous drains;and(2)Studies that described clinical outcomes,such as SSIs,seroma formation,the length of hospital stays,and mortality.RESULTS Eight studies were included in this meta-analysis.The rate of total SSIs was significantly lower in the drained group(54/771,7.0%)than in the control group(89/759,11.7%),particularly in gastrointestinal surgery.Furthermore,the rate of superficial SSIs was slightly lower in the drained group(31/517,6.0%)than in the control group(49/521,9.4%).No significant differences were observed in seroma formation between the groups.Hospital stays were shorter in the drained group than in the control group.CONCLUSION Subcutaneous drains after abdominal surgery prevented SSIs and reduced hospital stays but did not significantly affect seroma formation.The timing of drain removal needs to be reconsidered in future studies.

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.

The Elist Drain Retainer: A New Adherent Drain Retainer with Antibacterial Properties

Background: Surgical drains are used in at least half of all surgical operations world-wide. The gold standard for the fixation of drains to the skin is currently the “Roman garter” (RG) technique, which involves knotting a suture around the drain. Its disadvantages include the time to perform the technique, possible loosening and accidental removal, and bacterial infection with biofilm formation if left in place for weeks. Methods: The Elist Drain Retainer (EDR) has been developed, and it consists of a short plastic tube bent to 90° with a side slit for the drain, fixed to a mounting patch with adhesive and an antiseptic. Results: In a clinical trial comparing 25 drain attachments with the RG versus 25 drain attachments with the new EDR, the former took an average of five minutes and the EDR took an average of one minute to place. Loosening occurred in five (20%) drains and accidental removal occurred in four (16%) for the RG group versus no incidences of loosening or accidental removal in the EDR group. Self-removal of the EDR was possible for seven (28%) patients. Conclusion: The EDR demonstrated a clear advantage over the RG in all tested parameters. The lack of instruments and the possibility of self-removal of the EDR when a drain is needed are particularly advantageous features.

A new concept of backfll design—Application of wick drains in backflled stopes

Backflling represents an environmentally friendly mining waste disposal technique.It is increasingly used in underground mines all over the world.However,its primary purpose remains to improve ground stability and to reduce ore dilution.Previous investigations have shown that fll drainage plays a key role in backfll and barricade design.With a poor drainage system in the backflled stope,the required dimension of barricade,which is constructed at the base of the stope near the drift entrance,has to be increased.A poor backfll drainage system can also lead to a signifcant increase in drainage waiting time and further reduction in mining productivity.In this paper,the drainage of conventional backfll design in backflled stopes is briefly reviewed.For the frst time,the application of the wick drain is introduced in the backfll within mine stopes.The drainage improvement from the introduction of the wick drain is illustrated using numerical modeling.

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.

隧道涌水量基于MODFLOW中DRAIN模块水力传导系数取值探析

目前Visual Modflow已广泛地应用于隧道涌水的模拟,Drain模块中的水力传导系数是一个综合系数,但没有可参考的取值范围。从排水沟水力传导系数对隧洞涌水量引起的变化入手,通过C值的不同取值范围,利用模型计算出的涌水量与真实涌水量进行对比,发现当水力传导系数取值在一定范围内时计算出的涌水量最接近施工时隧道的真实涌水量,以此为Drain模块中水力传导系数的取值作一个经验参考。

Drainage Management Problems Evaluation: Case Study Baloza and EL-Farama Drains, North Sinai, Egypt

Drainage management activities aim at maintaining the performance of drainage networks by assessing the major drainage management problems regarding sedimentation, bank erosion, vegetation, water quality, and biodiversity, to find appropriate solutions for channel improvement in order to increase agricultural productivity and maintain agricultural land and the surrounding environment. In this research, we evaluate the drainage management problems to the surface drains Baloza and EL-Farama in the cultivated Tina Plain region (21,000 hectares) North Sinai, Egypt to provide an accurate data to help decision-makers to know the status of maintenance of the watercourses and the need for improvement. For this, Intensive field investigations were carried out regarding a hydrographic survey of the actual drains cross-section using total station and aqua sounder devices, visual stream bank erosion survey, and vegetation survey. In addition, monthly water samples from the drainage water were treated and analyzed for physical and chemical, bacteriological related indices. The results showed, the studied drains suffer from sedimentation, vegetation infection, and bank erosion in some reaches and need remedy. Estimated sedimentation in EL-Farama Drain was 34369 m3/year and in Baloza Drain 29153 m3/year;bank slope failures upstream and downstream pump stations were recorded;the average weed infection ratio for both drains was 30%. The results of water quality parameters showed acceptable concentrations for BOD, DO, NO3, and total coliform according to Egypt decree, 92/2013 for the protection of the Nile River and its waterways from pollution, except TDS (more than 10,000 mg/L). The drainage water was classified as high saline and it was unacceptable for irrigation. Therefore, the author recommends to remove sedimentation and vegetation every 2 years by mechanical methods, applying gabions lining to prevent bank erosion, and treating drainage water using wetland system and utilizing the treated wastewater in fish farming.

Prophylactic Wound Drainage in Orthopaedics: A Comparative Evaluation of Closed Suction Drainage versus No-Drainage in a Nigerian Teaching Hospital

Background: Surgical wound drainage is practiced routinely by many orthopaedic surgeons despite studies that challenge the practice. Among proponents, the advantages of drainage include prevention of haematoma and/or seroma formation which potentially reduces the chances for infection, prevention of wound swelling, prevention of compartment syndrome and improvement of the local wound environment. Opponents argue that prophylactic wound drainage confers no significant advantages, increases the risk of infection and the need for blood transfusion with the attendant risks of this therapy. Aim: To ascertain if prophylactic drainage of clean orthopaedic wounds confer any significant advantages by evaluating wound and systemic factors in two treatment groups. Patients and Methods: A prospective analysis of 62 patients was undergoing clean orthopaedic procedures. The patients were randomly assigned to a “No drain” (study) group and a “drain” (control) group. Each group had 31 patients. Surgeons were blinded to the randomization process and the evaluation of clinical outcomes. The parameters assessed included pain, superficial wound infection, the need for post-operative transfusion, wound leakage, dressing changes and the surgery-discharge interval. Data was analysed using SPSS statistics version 20 (IBM Corp., New York). Results: There were no significant differences in the demographic data. Femoral fractures were the commonest indication for surgery (43.55%), and plate and screw osteosynthesis was the commonest procedure (48.4% in the drain group and 67.7% in the no-drain group). There was a significantly higher need for post-operative transfusion in the drain group (22.6% against 0%) as well as a significantly prolonged capillary refill time (2.39 + 0.56 secs versus 2.03 + 0.41 secs). Although not statistically significant, there were four cases (12.8%) of superficial wound infection in the drain group and 1 case (3.2%) in the no-drain group. Conclusion: Prophylactic wound drainage confers no significant advantages over no drainage and may contribute to increased treatment costs through an increased post-operative transfusion requirements.

新型Drain Box设计与应用

本文首先介绍了目前国内海上油气田设施开排系统设计的工艺设计流程的原理及应用特点,随后通过对比分析介绍了一种新型DrainBox的设计与运用,最后对该新型DrainBox的创新点进行了分析和介绍,并对其推广与应用前景进行了展望。

Prophylactic intra-peritoneal drain placement following pancreaticoduodenectomy:A systematic review and metaanalysis

AIM:To conduct a meta-analysis comparing outcomes after pancreaticoduodenectomy(PD)with or without prophylactic drainage.METHODS:Relevant comparative randomized and nonrandomized studies were systemically searched based on specific inclusion and exclusion criteria.Postoperative outcomes were compared between patients with and those without routine drainage.Pooled odds ratios(OR)with 95%CI were calculated using either fixed effects or random effects models.RESULTS:One randomized controlled trial and four non-randomized comparative studies recruiting 1728patients were analyzed.Patients without prophylactic drainage after PD had significantly higher mortality(OR=2.32,95%CI:1.11-4.85;P=0.02),despite the fact that they were associated with fewer overall complications(OR=0.62,95%CI:0.48-0.82;P=0.00),major complications(OR=0.75,95%CI:0.60-0.93;P=0.01)and readmissions(OR=0.77,95%CI:0.60-0.98;P=0.04).There were no significant differences in the rates of pancreatic fistula,intraabdominal abscesses,postpancreatectomy hemorrhage,biliary fistula,delayed gastric emptying,reoperation or radiologic-guided drains between the two groups.CONCLUSION:Indiscriminate abandonment of intraabdominal drainage following PD is associated with greater mortality,but lower complication rates.Future randomized trials should compare routine vs selective drainage.

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.

Drainage by urostomy bag after blockage of abdominal drain in patients with cirrhosis undergoing hepatectomy

Abdominal drainage was previously recommended as a post-hepatectomy procedure for patients with cirrhosis.This report introduces a simple technique that prevents leakage of ascitic fluid after cirrhotic hepatectomy complicated by blockage of the abdominal drain.In 59 patients who had had cirrhotic hepatectomy complicated by leakage of ascites in the drain site after drainage removal between January 2001 and April 2011,31 underwent suture ligation(sutured group) and 28 were given urostomy bag at the abdominal drainage site(drainage group).The mean length of postoperative hospital stay in the drainage group was shorter than in the sutured group(16.11±2.61 vs 34.23±4.86 days,P=0.000).Meanwhile,the drainage group showed decreased postoperative complications,including leakage of ascites,wound infection,and collection of ascites.Drainage by urostomy bag can prevent prolonged leakage of ascitic fluid after the blockage of abdominal drains in patients undergoing cirrhotic hepatectomy.

Diagnostic value of drain amylase for detecting intrathoracic leakage after esophagectomy

AIM:To investigate the value of elevated drain amylase concentrations for detecting anastomotic leakage(AL) after minimally invasive Ivor-Lewis esophagectomy(MIILE).METHODS:This was a retrospective analysis of prospectively collected data in two hospitals in the Netherlands. Consecutive patients undergoing MI-ILE were included. A Jackson-Pratt drain next to the dorsal side of the anastomosis and bilateral chest drains were placed at the end of the thoracoscopic procedure. Amylase levels in drain fluid were determined in all patients during at least the first four postoperative days. Contrast computed tomography scans and/or endoscopic imaging were performed in cases of a clinically suspected AL. Anastomotic leakage was defined as any sign of leakage of the esophago-gastric anastomosis on endoscopy,re-operation,radiographic investigations,post mortal examination or when gastro-intestinal contents were found in drain fluid. Receiver operator characteristic curves were used to determine the cut-off values. Sensitivity,specificity,positive predictive value,negative predictive value,risk ratio and overall test accuracy were calculated for elevated drain amylase concentrations.RESULTS:A t o t a l o f 8 9 p a t ie n t s w e re in c lu d e d between March 2013 and August 2014. No differences in group characteristics were observed between patients with and without AL,except for age. Patients with AL were older than were patients without AL(P = 0.01). One patient(1.1%) without AL died within 30 d after surgery due to pneumonia and acute respiratory distress syndrome. Anastomotic leakage that required any intervention occurred in 15 patients(16.9%). Patients with proven anastomotic leakage had higher drain amylase levels than patients without anastomotic leakage [median 384 IU/L(IQR 34-6263) vs median 37 IU/L(IQR 26-66),P = 0.003]. Optimal cut-off values on postoperative days 1,2,and 3 were 350 IU/L,200 IU/L and 160 IU/L,respectively. An elevated amylase level was found in 9 of the 15 patients with AL. Five of these 9 patients had early elevations of their amylase levels,with a median of 2 d(IQR 2-5) before signs and symptoms occurred.CONCLUSION:Measurement of drain amylase levels is an inexpensive and easy tool that may be used to screen for anastomotic leakage soon after MI-ILE. However,clinical validation of this marker is necessary.

A CAD oriented quasi-analytical large-signal drain current model for 4H-SiC MESFETs

This paper reports that a 4H-SiC MESFET （Metal Semiconductor Field Effect Transistor） large signal drain current model based on physical expressions has been developed to be used in CAD tools. The form of drain current model is based on semi-empirical MESFET model, and all parameters in this model are determined by physical parameters of 4H-SiC MESFET. The verification of the present model embedded in CAD tools is made, which shows a good agreement with measured data of large signal DC I-V characteristics, PAE （power added efficiency）, output power and gain.