A novel efficient energy absorber with free inversion of a metal foam-filled circular tube

In this paper, a novel efficient energy absorber with free inversion of a metal foam-filled circular tube(MFFCT) is designed, and the axial compressive behavior of the MFFCT under free inversion is studied analytically and numerically. The theoretical analysis reveals that the energy is mainly dissipated through the radial bending of the metal circular tube, the circumferential expansion of the metal circular tube, and the metal filled-foam compression. The principle of energy conservation is used to derive the theoretical formula for the minimum compressive force of the MFFCT over free inversion under axial loading. Furthermore, the free inversion deformation characteristics of the MFFCT are analyzed numerically. The theoretical steady values are found to be in good agreement with the results of the finite element(FE) analysis. The effects of the average diameter of the metal tube, the wall thickness of the metal tube, and the filled-foam strength on the free inversion deformation of the MFFCT are considered. It is observed that in the steady deformation stage, the load-carrying and energy-absorbing capacities of the MFFCT increase with the increase in the average diameter of the metal tube, the wall thickness of the metal tube, or the filled-foam strength. The specific energy absorption(SEA) of free inversion of the MFFCT is significantly higher than that of the metal tube alone.

Comparison of decompression tubes with metallic stents for the management of right-sided malignant colonic obstruction

BACKGROUND Emergency surgical resection is a standard treatment for right-sided malignant colonic obstruction; however, the procedure is associated with high rates of mortality and morbidity. Although a bridge to surgery can be created to obviate the need for emergency surgery, its effects on long-term outcomes and the most practical management strategies for right-sided malignant colonic obstruction remain unclear.AIM To determine the appropriate management approach for right-sided malignant colonic obstruction.METHODS Forty patients with right-sided malignant colonic obstruction who underwent curative resection from January 2007 to April 2017 were included in the study.We compared the perioperative and long-term outcomes of patients who received bridges to surgery established using decompression tubes and those created using self-expandable metallic stents(SEMS). The primary outcome was the overall survival duration(OS) and the secondary endpoints were the diseasefree survival(DFS) duration and the preoperative and postoperative morbidity rates. Analysis was performed on an intention-to-treat basis.RESULTS There were 21 patients in the decompression tube group and 19 in the SEMS group. There were no significant differences in the perioperative morbidity rates of the two groups. The OS rate was significantly higher in the decompression tube group than in the SEMS group(5-year OS rate; decompression tube 79.5%,SEMS 32%, P = 0.043). Multivariate analysis revealed that the bridge to surgery using a decompression tube was significantly associated with the OS(hazard ratio, 17.41; P = 0.004). The 3-year DFS rate was significantly higher in thedecompression tube group than in the SEMS group(68.9% vs 45.9%; log-rank test,P = 0.032). A propensity score–adjusted analysis also demonstrated that the prognosis was significantly better in the decompression tube group than in the SEMS group.CONCLUSION The bridge to surgery using trans-nasal and trans-anal decompression tubes for right-sided malignant colonic obstruction is safe and may improve long-term outcomes.

Focused electron beam transport through a long narrow metal tube at elevated pressures in the forevacuum range

We present here our investigations of the features of focused electron beam transport in free space at elevated pressures of a few pascals.We have explored the effect of the beam accelerating voltage,operating gas pressure,and magnetic focusing upon the trajectory of beam electrons in the crossover region,in particular on the beam convergence and divergence angles.It is shown that for the forevacuum pressure range of 2-5 Pa explored,a distinctive feature of the propagation of a focused electron beam with a current of up to 20 mA at an accelerating voltage of 10-20 kV is the difference in the angles of convergence(before the focus)and divergence(after the focus).Whereas at a low pressure of 2 Pa the divergence angle is smaller than the convergence angle,as the pressure increases the divergence angle increases and for pressures greater than 5 Pa the divergence angle is greater than the convergence angle.The results obtained were used in experiments on electron beam transport through a long narrow metal tube with a diameter of 5.8-9.2 mm and length of 10-30 cm.We show that for a 30 cm long tube of 7.5 mm diameter,the focused beam transmission can exceed 70%.

Low-velocity impact of rectangular foam-filled fiber metal laminate tubes

Through theoretical analysis and finite element simulation,the low-velocity impact of rectangular foam-filled fiber metal laminate(FML)tubes is studied in this paper.According to the rigid-plastic material approximation with modifications,simple analytical solutions are obtained for the dynamic response of rectangular foam-filled FML tubes.The numerical calculations for low-velocity impact of rectangular foam-filled FML tubes are conducted.The accuracy of analytical solutions and numerical results is verified by each other.Finally,the effects of the metal volume fraction of FMLs,the number of the metal layers in FMLs,and the foam strength on the dynamic response of foam-filled tubes are discussed through the analytical model in details.It is shown that the force increases with the increase in the metal volume fraction in FMLs,the number of the metal layers in FML,and the foam strength for the given deflection.

Study on buffering performance of thin-walled metal tube with different angles

High frequency shock load is often generated during pyrotechnic device working, which is detrimental to spacecraft structures and electric devices. Therefore, it is valuable to reduce the shock load in pyrotechnic device design. Actually, there are several ways to decrease pyroshock loads, such as reduction of powder,installation of buffering structure, insulation of damageable devices, and so on. Considered assuring the function of pyrotechnic device and minimum of structure modification, shock absorbing structure is more propitious to be introduced in pyrotechnic device. In this paper, based on the method of thinwalled metal tube diameter-expanding, a thin-walled tube shock buffering structure was designed on a separate bolt. Built on the simplified structure of a separate bolt, the model of cone piston impacting thin-walled tube absorber was established, and the thin-walled tube shock absorbing characteristics and the relation between cone angles and absorber performance were analyzed. The results showed that the change of buffering force of thin-walled tube could be divided into four phases, and each phase was correspondent to the cone piston structure. In addition, as the cone angle increases, the max shock acceleration changes in the style of decrease-increase-decrease-increase, which is the result of coupled effects of cone piston max enter depth, buffering force and energy loss. In short, these results could establish the relationships between thin-walled tube absorbing performance and its structure, which is of significance to develop low-shock pyrotechnic device.

Effect of cyclotron resonance on ‘hot’ dispersion in a staggered double metallic grating sheet beam travelling wave tube

Based on the beam wave synchronous interaction in transverse and longitudinal directions at the same time and starting from Maxwell’s equation and linear Vlasov equation, the beam–wave interaction ‘hot’ dispersion equation considering both cyclotron resonance and Cherenkov resonance in a staggered double metallic grating traveling wave tube is deduced.Through the reasonable selection for geometric and electrical parameters, the numerical calculation and analysis of the ‘hot’ dispersion equation shows that the beam–wave interaction gain and frequency band with the cyclotron resonance enhancement effect are higher than those with only Cherenkov resonance radiation.

Forming of tubes and bars of alumina/LY12 composites by liquid extrusion process

Tube and bar products of aluminum alloy composites reinforced by alumina short fiber were formed in a single process with liquid extrusion technology. The microstructure verifies that the reinforcing effect is obvious in the deformation direction since fibers are distributed along this direction, which is resulted from the flow and crystallization under pressure of liquid metal and large plastic deformation of solidified metal in the process. The interface between fiber and matrix belongs to mechanical bonding. The fractograph demonstrates ductile mode. Liquid extrusion process opens up a new way for fabricating tube, bar and shaped products.

Metal stent combined with ileus drainage tube for the treatment of delayed rectal perforation: A case report

BACKGROUND Acute iatrogenic colorectal perforation(AICP)is a serious adverse event,and immediate AICP usually requires early endoscopic closure.Immediate surgical repair is required if the perforation is large,the endoscopic closure fails,or the patient's clinical condition deteriorates.In cases of delayed AICP(>4 h),surgical repair or enterostomy is usually performed,but delayed rectal perforation is rare.CASE SUMMARY A 53-year-old male patient underwent endoscopic submucosal dissection(ESD)at a local hospital for the treatment of a laterally spreading tumor of the rectum,and the wound was closed by an endoscopist using a purse-string suture.Unfortunately,the patient then presented with delayed rectal perforation(6 h after ESD).The surgeons at the local hospital attempted to treat the perforation and wound surface using transrectal endoscopic microsurgery(TEM);however,the perforation worsened and became enlarged,multiple injuries to the mucosa around the perforation and partial tearing of the rectal mucosa occurred,and the internal anal sphincter was damaged.As a result,the perforation became more complicated.Due to the increased bleeding,surgical treatment with suturing could not be performed using TEM.Therefore,the patient was sent to our medical center for follow-up treatment.After a multidisciplinary discussion,we believed that the patient should undergo an enterostomy.However,the patient strongly refused this treatment plan.Because the position of the rectal perforation was relatively low and the intestine had been adequately prepared,we attempted to treat the complicated delayed rectal perforation using a self-expanding covered mental stent(SECMS)in combination with a transanal ileus drainage tube(TIDT).CONCLUSION For patients with complicated delayed perforation in the lower rectum and adequate intestinal preparation,a SECMS combined with a TIDT can be used and may result in very good outcomes.

Decompression of Malignant Large-bowel Obstruction with a Self-expanding Metallic Stent or Transanal Drainage Tube

Objective To compare the outcomes after self-expanding metallic stent (SEMS) or transanal drainage tube (TDT) placement in patients with malignant large-bowel obstruction (MLBO). Methods Seventy-three patients with MLBO from the clinical unit underwent SEMS (n = 51) or TDT (n = 22) placement from 2012 to 2017. The success rates of placement, clinical outcomes after decompression, complications, the time to resuming enteral nutrition (EN), Karnofsky performance status (KPS) scoring and the following-up therapeutic options were investigated. Results Technical success were achieved in 100% of patients in both groups. The clinical success rates were 98.0%(50/51) for SEMS and 95.5%(21/22) for TDT. No perforation was found in any group, while 3.9%(2/51) in the SEMS and 18.2%(4/22) in TDT group experienced displacement (P = 0.26). It took 2.1 IQR (0~2) days and 3 IQR (2~5) days to resume EN in the SEMS and TDT groups, respectively (P < 0.001). The KPS scores were significantly higher in patients implanted with SEMS (70, IQR 50~80) than in those with TDT (35, IQR 30~50)(P < 0.001). In the SEMS group, 37.3%(19/51) of patients underwent stenting as a bridge to surgery, 9.8%(5/51) for chemotherapy only and 52.9%(27/51) for palliation, while 40.9%(9/22), 0 and 59.1%(13/22) underwent placement for these reasons in the TDT group, respectively. The majority (6/9) of the patients who underwent TDT placement as a bridge to surgery required stoma creation, while only 31.6%(6/19) of those in the SEMS group needed a stoma (P = 0.080). In addition, anastomotic leakage was only found in the TDT group (2/9)(P = 0.10). Conclusion Both SEMS and TDT placement could provide clinical relief for MLBO. However, SEMS placement is associated with earlier EN, fewer complications, and benefits for the postoperative quality-of-life.

Exfoliative esophageal bleeding caused by blind placement of a nasogastric tube:Two cases and a literature review

Transnasal intubation is a clinical operation usually performed blindly at the bedside.Mild adverse events,such as epistaxis and tube misplacement,are relatively common.Esophageal bleeding or perforation and other serious adverse events are rare.In the present study,two cases of severe diffuse esophageal bleeding caused by the blind placement of a nasogastric tube are described.These cases were successfully treated using a covered metal stent or Sengstaken-Blakemore tube.A review of the literature regarding the possible causes of such adverse events and the potential endoscopic treatments for severe hemorrhage are discussed.

微细金属管制造技术现状与研究进展

微细金属管具有微环境下的微通道封闭、定向导向、稳流导流等功能,被广泛应用于医疗、电工电子、传热、光学等领域。受加工工具小型化、尺寸效应对材料性能和摩擦行为的改变等限制,微细金属管的制备极具挑战性。总结了微细金属管常用制备技术的制备原理、特点、制造能力以及优缺点,包括热挤压成形、冷拔成形、无模拉拔成形以及电铸成形,并对微细金属管制造技术的未来发展趋势与研究重点进行了展望。

基于压电筒状叠堆的无线金属腐蚀探针设计及性能研究

基于压电筒状叠堆和压电阻抗技术提出了一种由压电筒状叠堆和金属杆组成的新型金属腐蚀探针。建立了多层结构探针纵向振动的传递矩阵模型,导出了电学阻抗方程,求得了第一阶谐振频率和反谐振频率,并与已有文献的特例结果进行了对比,验证了理论求解的正确性。此外,采用理论分析、人造定量腐蚀试验、温度敏感试验、加速腐蚀试验和无线阻抗测试试验系统地研究了探针的性能。研究结果表明:探针的第一阶谐振频率和反谐振频率随着杆长减小而增大,随着腐蚀天数的增加而增大,随着温度的增大而减小;无线阻抗系统测量的阻抗谱与传统阻抗分析仪的测量结果一致性较好。研究成果为开发无线定量测量的新型金属腐蚀探针提供重要参考。

MIL-101(Cr)吸附/热脱附-气相色谱-质谱法检测苯系和氯代VOCs

以金属有机骨架材料MIL-101(Cr)为填料构建了一种新型吸附采样管,将其与热脱附-气相色谱-质谱联用实现了15种典型苯系和氯代挥发性有机物(VOCs)的检测。结果显示,15种VOCs在0~100 ng范围内呈良好的线性关系,相关系数(r2)达到0.99以上,检出限为0.7~1.9 ng。在5、30、70 ng添加量下,15种VOCs的平均回收率分别为86.0%~126%、91.7%~133%和77.6%~135%,相对标准偏差(RSD)分别为6.6%~18%、2.9%~20%和1.3%~20%。MIL-101(Cr)填料吸附管测试稳定性和不同批次吸附管重复性的RSD分别为0.50%~14%和0.30%~18%。MIL-101(Cr)填料吸附管基于质量更少的填料实现了对苯系和氯代VOCs更高效的吸附、富集和热脱附,有助于降低吸附采样管的气体穿透风险。该研究拓展了MOFs材料在环境检测领域的实际应用场景。

大直径不锈钢管内旋压成形的金属流动堆积缺陷研究

采用Abaqus软件仿真分析大直径不锈钢管在内旋压成形过程中的金属流动堆积现象。采用单因素控制法讨论了壁厚分别为20 mm、12 mm和7 mm时Ф508 mm不锈钢管在三旋轮内旋压过程中的等效应变、金属流动及旋轧力的变化规律,并分析了不同厚度时层间金属质点的流动速度,进一步得出金属流动堆积的原因。结果表明:随着初始壁厚值的不断减小,壁厚为7 mm时,旋轮前方产生的金属堆积高度达到9 mm,接触区的等效应变值最大达到7.9,产生的旋轧力高达450 kN。可见,在相同工况下,钢管的壁厚越小,接触区的等效应变值越大,所需旋压力也越大,产生的金属堆积现象越严重。

双管板换热器管板平均金属温度确定方法研究

国家标准GB/T 151—2014《热交换器》中对于双管板换热器的计算,需要给出内外管板的平均金属温度,但标准未给出管板平均金属温度的确定方法,为此,借助FLUENT软件对双管板换热器管板及其邻近流体区域的传热进行了数值模拟研究,在理论传热公式和数值模型基础上,对换热器在不同介质和不同流速下的温度场进行数值模拟,给出了双管板换热器内外管板平均金属温度的确定方法和简易计算公式,研究结果可有助于双管板换热器的设计,同时便于工程应用。

Heat transfer characteristics of nanofluid through circular tube

Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.

Optimizing loading path and die linetype of large length-to-diameter ratio metal stator screw lining hydroforming

In order to meet the high temperature environment requirement of deep and superdeep well exploitation, a technology of large length-to-diameter ratio metal stator screw lining meshing with rotor is presented. Based on the elastic-plasticity theory, and under the consideration of the effect of tube size, material mechanical parameters, friction coefficient and loading paths, the external pressure plastic forming mechanical model of metal stator screw lining is established, to study the optimal loading path of metal stator lining tube hydroforming process. The results show that wall thickness reduction of the external pressure tube hydroforming(THF) is about 4%, and three evaluation criteria of metal stator screw lining forming quality are presented: fillet stick mold coefficient, thickness relative error and forming quality coefficient. The smaller the three criteria are, the better the forming quality is.Each indicator has a trend of increase with the loading rate reducing, and the adjustment laws of die arc transition zone equidistance profile curve are acquired for improving tube forming quality. Hence, the research results prove the feasibility of external pressure THF used for processing high-accuracy large length-to-diameter ratio metal stator screw lining, and provide theoretical basis for designing new kind of stator structure which has better performance and longer service life.

Fabrication of Porous Bulk Metallic Glass

An open-cell porous bulk metallic glass （BMG） with a diameter of at least 6 mm was fabricated by using an U-turn quartz tube and infiltration casting around soluble NaCI placeholders. The pore formation and glassy structure were examined by optical microscopy （OM）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results show that the pores or cells are connected to each other and the specimen is composed of a mostly glassy phase. This paper provides a suitable method for fabrication of porous BMG and BMG with larger size in diameter.

Heavy Metals Accumulation in Soil Irrigated with Industrial Effluents of Gadoon Industrial Estate, Pakistan and Its Comparison with Fresh Water Irrigated Soil

Wastewater mixed with industrial effluents is used for irrigation in Gadoon Industrial estate and thus contaminating soil. This soil was tested for heavy metal content by using atomic absorption spectrophotometer (perkin elmer 700) and compared with control soil irrigated with tube well water at seven selected spots. Accumulation of the toxic metal was significantly greater in the soil irrigated with industrial effluent than control soil (p < 0.05). Manganese (Mn) was the most significant pollutant, accumulated up to 9.95 ppm in the soil irrigated with industrial waste water. It was found that the samples were containing Zn in the range of 1.596 - 6.288, Cu 0.202 - 1.236, Co 0.074 - 0.115, Ni 0.0002 - 0.544, Cr 0.243 - 0.936, Mn 3.667 - 9.955 and Pb 0.488 - 1.259 ppm. No sample was containing the heavy metal above the critical level mentioned in typical and unsafe heavy metal levels in soil.