Clinical efficacy of endovascular revascularization combined with vacuum-assisted closure for the treatment of diabetic foot

BACKGROUND The diabetic foot is a common cause of disability and death,and comorbid foot infections usually lead to prolonged hospitalization,high healthcare costs,and a significant increase in amputation rates.And most diabetic foot trauma is complicated by lower extremity arteriopathy,which becomes an independent risk factor for major amputation in diabetic foot patients.AIM To establish the efficacy and safety of endovascular revascularization(ER)combined with vacuum-assisted closure(VAC)for the treatment of diabetic foot.METHODS Clinical data were collected from 40 patients with diabetic foot admitted to the Second Affiliated Hospital of Soochow University from April 2018 to April 2022.Diabetic foot lesions were graded according to Wagner’s classification,and blood flow to the lower extremity was evaluated using the ankle-brachial index test and computerized tomography angiography of the lower extremity arteries.Continuous subcutaneous insulin infusion pumps were used to achieve glycemic control.Lower limb revascularization was facilitated by percutaneous transluminal balloon angioplasty(BA)or stenting.Wounds were cleaned by nibbling debridement.Wound granulation tissue growth was induced by VAC,and wound repair was performed by skin grafting or skin flap transplantation.RESULTS Of the 35 cases treated with lower limb revascularization,34 were successful with a revascularization success rate of 97%.Of these,6 cases underwent stenting after BA of the superficial femoral artery,and 1 received popliteal artery stent implantation.In the 25 cases treated with infrapopliteal artery revascularization,39 arteries were reconstructed,7 of which were treated by drug-coated BA and the remaining 32 with plain old BA.VAC was performed in 32 wounds.Twenty-four cases of skin grafting and 2 cases of skin flap transplantation were performed.Two patients underwent major amputations,whereas 17 had minor amputations,accounting for a success limb salvage rate of 95%.CONCLUSION ER in combination with VAC is a safe and effective treatment for diabetic foot that can significantly improve limb salvage rates.The use of VAC after ER simplifies and facilitates wound repair.

Colon perforation with severe peritonitis caused by erotic toy insertion and treated using vacuum-assisted closure:A case report

BACKGROUND Colorectal foreign bodies are commonly encountered during surgery.They are frequently observed in men 20 to 90 years of age and have bimodal age distribution.Surgical management is necessary for cases of rectal perforation.However,surgical site infections are the most common complications after colorectal surgery.CASE SUMMARY We discuss a case of rectal perforation in a patient who presented to our hospital 2 d after its occurrence.The perforation occurred as a result of the patient inserting a sex toy in his rectum.Severe peritonitis was attributable to delayed presentation.CONCLUSION Vacuum-assisted closure was performed to treat the wound,which healed well after therapy.No complications were noted.

Micro-power negative pressure wound technique reduces risk of incision infection following loop ileostomy closure

BACKGROUND Prophylactic loop ileostomy is an effective way to reduce the clinical severity of anastomotic leakage following radical resection of rectal cancer.Incisional surgical site infection(SSI)is a common complication after ileostomy closure.AIM To evaluate the efficacy and safety of the micro-power negative pressure wound technique(MPNPWT)in preventing incisional SSI.METHODS This was a prospective,randomized controlled clinical trial conducted at a single center.A total of 101 consecutive patients who underwent ileostomy closure after rectal cancer surgery with a prophylactic ileostomy were enrolled from January 2019 to December 2021.Patients were randomly allocated into an MPNPWT group and a control group.The MPNPWT group underwent intermittent suturing of the surgical incision with 2-0 Prolene and was covered with a micro-power negative pressure dressing.The surgical outcomes were compared between the MPNPWT(n=50)and control(n=51)groups.Risk factors for incisional SSI were identified using logistic regression.RESULTS There were no differences in baseline characteristics between the MPNPWT(n=50)and control groups(n=51).The incisional SSI rate was significantly higher in the control group than in the MPNPWT group(15.7%vs 2.0%,P=0.031).However,MPNPWT did not affect other surgical outcomes,including intra-abdominal complications,operative time,and blood loss.Postoperative hospital stay length and hospitalization costs did not differ significantly between the two groups(P=0.069 and 0.843,respectively).None of the patients experienced adverse effects of MPNPWT,including skin allergy,dermatitis,and pain.MPNPWT also helped heal the infected incision.Our study indicated that MPNPWT was an independent protective factor[odds ratio(OR)=0.005,P=0.025)]and diabetes was a risk factor(OR=26.575,P=0.029)for incisional SSI.CONCLUSION MPNPWT is an effective and safe way to prevent incisional SSI after loop ileostomy closure.

Comparison of modified gunsight suture technique and traditional interrupted suture in enterostomy closure

BACKGROUND Prophylactic enterostomy surgery is a common surgical approach used to reduce the risk of anastomotic leakage in patients who have undergone partial intestinal resection due to trauma or tumors.However,the traditional interrupted suturing technique used in enterostomy closure surgery has several issues,including longer surgical incisions and higher incision tension,which can increase the risk of postoperative complications.To address these issues,scholars have proposed the use of a“gunsight suture”technique.This technique involves using a gunsight incision instead of a traditional linear incision,leaving a gap in the center for the drainage of blood and fluid to reduce the risk of infection.Building on this technique,we propose an improved gunsight suture technique.A drainage tube is placed at the lowest point of the incision and close the gap in the center of the gunsight suture,which theoretically facilitates early postoperative mobility and reduces the burden of dressing changes,thereby reducing the risk of postoperative complications.AIM To compare the effectiveness of improved gunsight suture technique with traditional interrupted suture in closing intestinal stomas.METHODS In this study,a retrospective,single-center case analysis was conducted on 270 patients who underwent prophylactic ileostomy closure surgery at the Department of Colorectal Surgery of Qilu Hospital from April 2017 to December 2021.The patients were divided into two groups:135 patients received sutures using the improved gunsight method,while the remaining 135 patients were sutured with the traditional interrupted suture method.We collected data on a variety of parameters,such as operation time,postoperative pain score,body temperature,length of hospital stays,laboratory indicators,incidence of incisional complications,number of wound dressing changes,and hospitalization costs.Non-parametric tests and chi-square tests were utilized for data analysis.RESULTS There were no statistically significant differences in general patient information between the two groups,including the interval between the first surgery and the stoma closure[132(105,184)d vs 134(109,181)d,P=0.63],gender ratio(0.64 vs 0.69,P=0.44),age[62(52,68)years vs 60(52,68)years,P=0.33],preoperative body mass index(BMI)[23.83(21.60,25.95)kg/m²vs 23.12(20.94,25.06)kg/m²,P=0.17].The incidence of incision infection in the improved gunsight suture group tended to be lower than that in the traditional interrupted suture group[(n=2/135,1.4%)vs(n=10/135,7.4%),P<0.05],and the postoperative hospital stay in the improved gunsight suture group was significantly shorter than that in the traditional interrupted suture group[5(4,7)d vs 7(6,8)d,P<0.05].Additionally,the surgical cost in the modified gunsight suture group was slightly lower than that in the traditional suture group[4840(4330,5138)yuan vs 4980(4726,5221)yuan,P>0.05],but there was no significant difference in the total hospitalization cost between the two groups.CONCLUSION In stoma closure surgery,the improved gunsight technique can reduce the incision infection rate,shorten the postoperative hospital stay,reduce wound tension,and provide better wound cosmetic effects compared to traditional interrupted suture.

New devices and techniques for endoscopic closure of gastrointestinal perforations

Gastrointestinal perforations,which need to be managed quickly,are associated with high morbidity and mortality. Treatments used to close these perforations range from surgery to endoscopic therapy. Nowadays,with the development of new devices and techniques,endoscopic therapy is becoming more popular. However,there are different indications and clinical efficacies between different methods,because of the diverse properties of endoscopic devices and techniques. Successful management also depends on other factors,such as the precise location of the perforation,its size and the length of time between the occurrence and diagnosis. In this study,we performed a comprehensive review of various devices and intro-duced the different techniques that are considered effective to treat gastrointestinal perforations. In addition,we focused on the different methods used to achieve successful closure,based on the literature and our clinical experiences.

DETERMINATION OF CLOSURE EFFECT IN FATIGUE CRACKING BY MEANS OF COMPLIANCE TECHNIQUE AND NUMERICAL METHOD

The crack tip strain gauge method in the compliance technique was used to determine the opening load of notched crack of axle steel,and the nonlinear finite element ADINA program, to which the cyclic stress-strain curve of axle steel was applied,was used to analyze the stress-strain field ahead of the crack tip and the opening load of notched crack.The results of both the compliance technique and the numerical method were in good agreement.In this pa- per,the concept of the sensitive point is proposed and the key to the determination of the crack opening load in the experiment is to place a strain gauge at sensitive point.It is certified by both experimental and numerical methods that the sensitive point has the best linear relation- ship character and the value of strain is much greater.

Assessment of the effect of wound closure technique on postoperative sequaele and complications after impacted mandibular third molar extraction

Aims and Objectives: The aim of the study was to compare the effect of complete and partial wound closures on postoperative sequelae and complications after surgical removal of impacted mandibular third molars. Patients and Methods: One hundred and twenty patients who required 121 surgical extractions of mandibular impacted third molars were included in the study. Patients were randomly divided into 2 groups based on wound closure after surgery. In group 1 (complete wound closure, n1 = 60) patients had their extraction sockets completely closed by mucosal flap while in group 2 (partial wound closure, n2 = 60) patients had their extraction sockets partially closed. Data collected included maximum inter-incisal distance (MID) and facial width which were recorded both preoperatively and postoperatively. What also recorded were postoperative pain intensity and postoperative complications. Results: There were 50 (41.7%) males and 70 (58.3%) females (male to female ratio of 1:1.4);age range was 18-40 years and the mean was 26 ± 10 years. The mean ages of patients in both groups showed no significant difference (group 1 = 26.5 ± 7.2;group 2 = 27.1 ± 8.1). The pain was maximal at the first postoperative day review and it gradually reduced in intensity towards the preoperative values for both groups. The pain perceptionsin patients in group 2 were however significantly lower than those of group 1 on days 1 and 3 but not statistically different on day 7. The mean difference in the postoperative and preoperative MID was greatest on the 1st postoperative day and gradually became smaller on the subsequent review days. Comparison of this mean difference between the 2 groups however showed a significant difference in the 2 groups only on day 7. Maximal swelling was noted in both groups on the third postoperative day. A comparison of the mean facial width between the two groups showed no statistically significant difference on all the review days. The postoperative complication rate was 5% in both groups. Conclusions: The results of the study indicate that there was a comparative reduction in postoperative sequelae namely pain and trismus after impacted mandibular third molar surgery when a partial wound closure technique was done. However, there was no significant difference in the postoperative complication rate between the two groups.

Polysorb^R(an absorbable lactomer) staples, a safe closure technique for distal pancreatic resection

AIM:To investigate twenty-year experience evaluated the use of the PolysorbR(an absorbable lactomer)staples for distal pancreatic resection.METHODS:The data on 150 patients[92 men,58women,mean age 52(24-72)years]who underwent distal pancreatectomy(DP)in the last 20 years were collected prospectively from an electronic database.The diagnosis was confirmed by endoscopic retrograde cholangiopancreatography,sonography,computed tomography and/or magnetic resonance imaging.The indications for DP were focal pancreatic necrosis,spontaneous pancreatic fistulas,abscesses,pseudocysts,segmental chronic obstructive pancreatitis in the tail,traumatic disruption,and benign(cystadenomas,insulinomas,or glucagonomas)or malignant tumours.The distal resections were performed without splenectomy in 29 of the 150 patients(19%).In the event of splenectomy,the splenic artery and vein were individually ligated,the TA-55 Auto Suture stapler,loaded with Premium PolysorbR 55 staples(5.5mm),was placed across the gland,and the trigger was pulled,the action of which produced two staggered absorbable suture lines.The gland distal to the stapler wasthen amputated with a scalpel on the TA-55 stapler and the two rows of staples were left in the proximal pancreatic stump.After the distal resection,a drainage tube was inserted into the pancreatic bed.RESULTS:The average duration of the operation was150 min(range:90-210 min)and no transfusion was indicated during the operation.After DP in one patient a type B fistula was diagnosed,which was treated successfully by conservative treatment comprising of 12-d octreotide medication(3×0.1 mg/d)and jejunal feeding.The incidence of postoperative pancreatic fistula was therefore0.6%.Another 2 patients suffered postoperative pancreatitis,which was also conservatively treated.Reoperations were performed in 2 patients on the first or second postoperative day,necessitated by bleeding from the retroperitoneal region.The morbidity was 3.3%(5 patients),but no mortality occurred in the postoperative period.Overall,the postoperative period was uneventful without any complications(pancreatic fistula,abscess,bleeding or wound infection)in 145 patients.The length of the postoperative stay ranged between 8 and 16 d.For the 145 patients who had no any postoperative complications,the hospital stay was 8 or 9 d.No mortality occurred in the follow-up period(6 or 12 mo postoperatively);but 6 mo after surgery one patient suffered a pseudocyst following recurrent pancreatitis and was treated with cystojejunostomy.CONCLUSION:Our clinical results demonstrated that the application of absorbable lactomer staples for distal pancreatic resection is a safe alternative to the standard closure technique.

Closure technique for the hybrid girder cable stayed bridge of Edong Bridge

Based on Edong Yangtze River Bridge, which is the second longest hybrid girder cable stayed bridge with 926 m long main span, the influencing factors and crucial techniques of the main span closure method for long span hybrid girder cable stayed bridge are studied. After theoretical analysis, numerical evaluation and practical test, the loading assistant closure method is employed in Edong Yangtze River Bridge. The loading assistant closure method, with better thermal adaptability and less influence on bridge line and the forced status, can meet the requirements of the unstressed state control method. Based on the mentioned advantages, the loading assistant closure method is applicable to long span hybrid girder cable stayed bridges. The conclusion can provide a reference for the further design of the similar brid^es.

Evaluation of Nasal and Temporal Anterior Chamber Angle with Four Different Techniques

Background: Anterior chamber angle (ACA) can be measured by many different techniques. In order for a technique to be a part of the routine eye examination, it has to be quick and easy in good agreement with gonioscopy both nasally and temporally. Aim: To investigate variation in ACA measurement between gonioscopy, van Herick technique, anterior segment optical coherence tomography (AS-OCT) and Sirius Scheimpflug-Camera both nasally and temporally. Method: The ACA of 50 eyes of 25 healthy subjects was measured with gonioscopy, van Herick technique, AS-OCT and Sirius Scheimpflug-Camera. The angle was measured both nasally and temporally. Results: No statistically significant difference could be found between gonioscopy, van Herick technique and AS-OCT either nasally or temporally. The Sirius Scheimpflug-Camera on the other hand showed statistically significant difference to gonioscopy (p < 0.0001) both nasally (p = 0.03, p = 0.001, p < 0.0001) and temporally (p = 0.0002, p = 0.001, p Conclusion: This study showed good agreement between three of the four techniques. ACA measurements obtained by the Sirius Scheimpflug-Camera should therefore not be considered interchangeable with those obtained by the remaining three methods.

改良式封闭负压辅助闭合技术联合湿性敷料在肠外瘘患者中的应用效果

目的:探讨改良式封闭负压辅助闭合技术联合湿性敷料在肠外瘘患者中的应用效果。方法:选取2018年12月—2021年12月于宜宾市第一人民医院普外科行手术治疗的91例肠外瘘患者作为研究对象,随机分为观察组(n=42)、对照组(n=49)。对照组采用常规对症治疗,观察组在对照组基础上采用改良式封闭负压辅助闭合技术联合湿性敷料治疗。比较两组瘘口周围皮炎发生情况、日均换药次数、自发性愈合率及瘘口愈合时间。结果:与对照组比较,观察组瘘口周围皮炎发生率更低、日均换药次数更少、瘘口自发性愈合率更高、自发愈合时间更短,差异均具有统计学意义(P<0.05)。结论:改良式封闭负压辅助闭合技术联合湿性敷料在肠外瘘患者中的应用效果良好,可有效控制患者瘘口周围皮炎的发生,减少换药次数,促进瘘口愈合。

马鞍山长江公铁大桥Z3号桥塔施工关键技术

巢马城际铁路马鞍山长江公铁大桥主航道桥为(112+392+2×1120+392+112)m三塔钢桁梁斜拉桥,Z3号桥塔为超高多肢钢-混组合塔,高308 m。上塔柱钢结构高87.5 m,分13个吊装节段,最重505 t;中、下塔柱混凝土结构高217.5 m,分38个节段液压爬模施工;钢-混结合段高3 m,内部采用PBL键+剪力钉+高强度钢锚杆+高强度混凝土结构形式。在中塔柱设置钢管临时横撑控制塔柱线形及应力;下横梁采用落地支架法分层施工,与对应塔柱同步浇筑;钢-混结合段混凝土采用C60细石补偿收缩混凝土+高强度灌浆料,保证了混凝土施工质量;采用工厂“2+1”立体匹配制造、“提升站+运输栈桥”钢塔节段转运等技术,并研制15000 t•m超大型塔吊,实现了钢塔柱大节段的制造、整体滩地运输和吊装;钢塔节段间采用栓焊组合连接形式,通过设置工艺隔板、双面坡口等措施控制了钢塔焊接变形;利用定位桁架临时锁定钢塔合龙段实现了钢塔的精确合龙,定位桁架受力及变形均满足要求。

手术区域全密闭技术在经皮同轴大通道内镜下腰椎融合术治疗退行性腰椎滑脱症中的应用

目的:探讨手术区域全密闭(full surgical area closure technique,FSAC)技术在经皮同轴大通道内镜下腰椎融合术(percutaneous coaxial large-channel endoscopic lumbar interbody fusion,PLE-LIF)治疗退行性腰椎滑脱症中的应用价值。方法:回顾性分析2020年1月~2023年1月因单节段退变性腰椎滑脱症在我院行PLE-LIF的83例患者,其中46例术中采用FSAC技术,纳入FSAC组;37例未采用FSAC技术,纳入N-FSAC组。两组患者性别、年龄、病程及住院时间等一般资料无统计学差异(P>0.05)。两组患者均规律随访1年。记录两组患者手术时间及并发症发生情况。记录两组患者术前1d、术后3d、术后3个月、术后1年的腰痛及下肢痛视觉模拟评分(visual analogue scale,VAS)及术前1d、术后3个月、术后1年的功能障碍指数(Oswestry disability index,ODI)。术后3个月复查腰椎X线片并采用Meyerding分级评估滑脱复位情况,术后1年复查CT并采用Brantigan标准评价两组椎间融合情况。结果:FSAC组手术时间较N-FSAC组更短(118.9±10.6min vs 130.6±16.3min,P<0.05)。两组术后各时间点腰痛和下肢痛VAS评分及ODI均较术前明显下降(P<0.05),两组间同时间点比较均无统计学差异(P>0.05)。N-FSAC组有2例发生下肢麻木,FSAC组无下肢麻木发生;N-FSAC组及FSAC组分别有4例和1例发生神经水肿性疼痛;两组均有1例发生cage移位,两组均无内固定松动、感染及硬膜囊撕裂发生,N-FSAC组术中并发症发生率较FSAC组更高(18.9%vs 4.3%)(P<0.05)。术后1年两组患者的滑脱程度较术前均明显改善(P<0.05),两组间无统计学差异(P>0.05);FSAC组42例椎间融合成功,N-FSAC组34例椎间融合成功,两组间的融合率(91.3%vs 91.9%)及椎间融合分级比较无统计学差异(P>0.05)。结论:采用FSAC技术的PLE-LIF治疗单节段退变性腰椎滑脱症时,能缩短手术时间,提高手术安全性。

改良全埋垂直褥式减张缝合与皮内连续缝合对儿童手术切口愈合以及瘢痕形成的影响

目的皮内连续缝合(intradermic continuous suture,ICS)是临床上常用的缝合方法之一,但因减张效果不足容易导致瘢痕增生;改良全埋垂直褥式减张缝合(modified fully buried vertical mattress suture,MFBVMS)在整形外科应用广泛,具有良好的减张效果;本研究旨在比较MFBVMS和ICS对伤口愈合以及瘢痕形成的影响。方法本研究为前瞻性研究,选择2022年1月至8月于上海交通大学医学院附属新华医院儿普外科行开放手术的70例患儿作为研究对象,使用信封法随机分为观察组和对照组,每组各35例;观察组采取MFBVMS,对照组采取ICS,比较两组患儿缝合时间、切口愈合等级、术后1个月、6个月所测量瘢痕宽度以及温哥华评估量表(vancouver scar scale,VSS)评分结果,观察两组患儿切口不良反应发生情况。结果观察组缝合时间(16.66±6.35)min,长于对照组的(7.20±3.48)min,差异有统计学意义(t=-7.729,P<0.001)。术后6个月观察组瘢痕宽度(1.13±0.53)mm,小于对照组的(2.49±1.03)mm,差异有统计学意义(t=6.920,P<0.001);VSS评分(3.69±1.13)分,小于对照组的(5.49±1.25)分,差异有统计学意义(t=6.352,P<0.001)。观察组手术后无一例切口不良反应发生,与对照组11.43%的切口不良反应率相比,差异有统计学意义(χ^(2)=4.242,P<0.05);观察组切口愈合时间(6.77±0.55)d,小于对照组的(7.83±2.47)d,差异有统计学意义(t=2.475,P<0.05)。结论MFBVMS应用于儿童手术能明显减少切口瘢痕形成,改善切口愈合质量。

双层软组织缝合封闭技术在下颌骨中早期药物相关性颌骨骨坏死患者手术治疗中的应用

目的:探究双层软组织缝合封闭技术在单纯应用抗骨吸收药物引起的发生在下颌骨的中早期药物相关性颌骨骨坏死(medication-related osteonecrosis of the jaw,MRONJ)患者手术治疗中的临床应用效果。方法:选择2021年10月至2022年9月于北京大学口腔医院四病区经手术治疗的中早期下颌骨MRONJ患者的病历资料进行回顾性分析,收集患者术前基线临床资料,包括原发疾病、伴发疾病、用药方案(药物种类、用药时长)、MRONJ分期、临床症状、影像学表现等,所有患者在手术中行下颌骨边缘切除术去除坏死骨,运用双层软组织缝合封闭技术关闭伤口,术后定期复查随访,评价双层软组织缝合封闭技术的治疗效果及并发症,并对患者进行疼痛评分和功能状态评价。结果:研究共纳入13例患者(女12例,男1例),年龄(66.69±13.14)岁。原发疾病包括骨质疏松7例,肺癌2例,乳腺癌3例,前列腺癌1例;2例伴发糖尿病,2例伴发心血管疾病,1例伴发干燥综合征。9例患者静脉注射唑来膦酸,平均用药时间(37.7±20.0)个月,7例患者同时服用了来曲唑片等其他药物;3例患者应用地舒单抗注射液,平均用药时间(10.3±11.9)个月;5例患者服用阿仑膦酸钠片,平均用药时间(55.20±27.20)个月,2例患者不同程度地服用醋酸泼尼松片或阿卡波糖片。MRONJ 1期4例,2期9例。13例患者均采用双层软组织缝合封闭技术关闭伤口,术后平均随访11.9个月(9~17个月),13例患者皆治愈,无溢脓等并发症发生。患者术前Karnofsky功能状态评分量表(Karnofsky performance status,KPS)评分为(68.46±14.05)分,术后评分为(82.31±15.36)分,差异有统计学意义(P<0.05)。患者术前疼痛评估视觉模拟评分量表(visual analogue scale,VAS)评分为(5.77±0.73)分,术后评分为(0.38±0.51)分,差异有统计学意义(P<0.001)。结论:双层软组织缝合封闭技术在中早期单纯使用抗骨吸收类药物的下颌骨MRONJ患者中可以取得良好的临床治疗效果,可为用药情况更加复杂的MRONJ患者提供临床治疗思路。

宜宾临港长江公铁大桥主桥超宽钢箱梁施工关键技术

宜宾临港长江公铁大桥主桥为主跨522 m的公铁同层双塔双索面钢箱梁斜拉桥,主桥钢箱梁宽63.9 m、高5 m,节段最大重量519.6 t。钢箱梁采用分部件加工、节段整体制作、场内预拼装方案制造。南岸钢箱梁采用边跨顶推+中跨单悬臂施工;北岸钢箱梁采用边跨存梁+双悬臂施工;中跨合龙段采用配切+顶推合龙。采用钢箱梁顶板与底板单元两拼工艺、钢箱梁锚固块体多工序组拼、预设反变形量的长线法总拼等制造技术,有效解决了超宽钢箱梁焊接变形量大的问题,大大提高了钢箱梁制造精度;南岸边跨钢箱梁利用中跨侧来梁进行顶推施工,解决了边跨运梁、吊梁施工难的问题,且避免了占用既有道路;北岸边跨钢箱梁利用枯水期预先存梁,解决了浅滩区钢箱梁施工受季节性水文影响大的问题,为双悬臂施工提供了先决条件;中跨合龙段采用现场配切+顶推施工,实现主跨钢箱梁精确合龙。

基于有限元技术的疲劳裂纹扩展方法研究进展

疲劳裂纹是引起工程结构断裂失效的重要因素之一.目前疲劳裂纹扩展的有限元仿真商业软件有ANSYS、ABAQUS、FRANC3D、ZENCRACK等,这些软件为疲劳裂纹扩展过程的研究提供了有力支撑.本文对目前疲劳裂纹扩展的有限元仿真方法进行了综述.阐明了疲劳裂纹的定义以及研究疲劳裂纹扩展行为的必要性;介绍了三种用于模拟疲劳裂纹扩展的有限元方法:扩展有限元法(XFEM)、内聚力模型(CZM)和虚拟裂纹闭合技术(VCCT);分别总结了三种方法的基本理论和核心思想,对三种方法的应用与发展进行了分类归纳;最后对三种有限元方法进行分析,指出每种方法各自的优势及目前存在的局限性,并对疲劳裂纹扩展有限元仿真技术的未来改进方向给出了建议.

黄茅海跨海通道高栏港大桥钢箱梁施工关键技术

黄茅海跨海通道高栏港大桥为(110+248+700+248+110)m全飘浮体系双塔双索面斜拉桥,主梁为分体式钢箱梁,标准梁段重约370 t、最大悬臂拼装梁段重约468 t,采用桥面吊机进行悬臂拼装,施工阶段抗风问题突出。通过设置塔梁三向临时锚固抵抗施工过程中的不平衡力及力矩,有限元计算结果表明塔梁三向临时锚固均满足受力需求;在边跨侧设置抗风临时墩,并依据受力分析结果确定抗风临时墩的钢管桩选用∅1200 mm×12 mm,平联、斜撑选用∅426 mm×6 mm,施工阶段安全渡台;通过设置横断面预拱度保证了钢箱梁成桥横坡;采用反力牛腿法在被吊装梁段和已安装梁段匹配侧施加成对反力有效减小匹配高差,保证了钢箱梁的顺利匹配安装;边、辅墩墩顶前一梁段的斜拉索二次张拉后再进行合龙,避免了施工期间边、辅墩支座出现负反力;中跨采用单边起吊加配重和自然温差配切的合龙方式。

基于VCCT理论的芯片多顶针剥离工艺参数优化

针对芯片在拾取过程中易碎裂的问题,采用虚拟裂纹闭合法对多顶针工艺拾取芯片的过程进行动力学建模和仿真。首先建立了芯片-胶层-蓝膜复合模型结构;然后进行了硅片-蓝膜单轴拉伸实验,确定了模型的关键参数;最后通过模拟不同工艺参数,包括顶针间距和胶层材料的变化,对剥离过程中芯片上的最大应力变化进行了深入的分析。仿真结果显示,在芯片剥离过程中,芯片中心区域出现了明显的应力集中。减小顶针间距可以有效缓解芯片中心区域的应力集中现象。此外,选择具有较低临界断裂能的胶层材料可以减小剥离过程中芯片所受的应力。最终结果为多顶针拾取芯片工艺的参数选择提供了参考价值,有助于提高芯片拾取的可靠性。

iRoot SP单尖法根管充填后桩道预备时机对根尖封闭效果的影响

目的研究iRootSP单尖法根管充填后不同桩道预备时机对根尖封闭效果的影响。方法收集单根管离体牙75枚,截冠,随机分9组,其中A1、A2、A3组采用AH-Plus+热牙胶充填,;B1、B2、B3组采用iRoot SP+单尖根充;A4组热牙胶根充;B4组单尖根充;C组只预备不充填。A1和B1组立即预备桩道,而A2和B2组则1周后延迟进行,A3、B3、A4、B4组不进行桩道预备。A4组和B4组为阳性对照组,C组为阴性对照组,运用染料微渗漏实验及扫描电镜观察评价根尖区微渗漏情况。结果各实验组及阳性对照组的染料均渗透入根尖,渗透深度分别为A1:(1.14±0.40)mm;A2:(1.32±0.14)mm;A3:(0.61±0.15)mm;A4:(4.75±0.16)mm;B1:(1.07±0.17)mm;B2:(1.22±0.19)mm;B3:(0.52±0.15)mm;B4:15 mm;C:0 mm。比较染料渗透深度,其中A1组与A3组、B1组与B3组、A2组与A3组、B2组与B3组间差异具有统计学意义(P<0.05)。其余各组之间的差异均无统计学意义(P>0.05)。iRootSP封闭性与AH-Plus相似,iRootSP单尖法充填后即刻、延迟桩道预备后根尖封闭性相似。结论iRoot SP单尖法根管充填与AH-Plus热牙胶连续波垂直加压根充比较,其根尖封闭效果相似,即刻、延迟桩道预备对iRoot SP单尖法根管充填根尖封闭效果无影响。