Fracture of two three-dimensional parallel internal cracks in brittle solid under ultrasonic fracturing

Similar to hydraulic fracturing(HF), the coalescence and fracture of cracks are induced within a rock under the action of an ultrasonic field, known as ultrasonic fracturing(UF). Investigating UF is important in both hard rock drilling and oil and gas recovery. A three-dimensional internal laser-engraved crack(3D-ILC) method was introduced to prefabricate two parallel internal cracks within the samples without any damage to the surface. The samples were subjected to UF. The mechanism of UF was elucidated by analyzing the characteristics of fracture surfaces. The crack propagation path under different ultrasonic parameters was obtained by numerical simulation based on the Paris fatigue model and compared to the experimental results of UF. The results show that the 3D-ILC method is a powerful tool for UF research.Under the action of an ultrasonic field, the fracture surface shows the characteristics of beach marks and contains powder locally, indicating that the UF mechanism includes high-cycle fatigue fracture, shear and friction, and temperature load. The two internal cracks become close under UF. The numerical result obtained by the Paris fatigue model also shows the attraction of the two cracks, consistent with the test results. The 3D-ILC method provides a new tool for the experimental study of UF. Compared to the conventional numerical methods based on the analysis of stress-strain and plastic zone, numerical simulation can be a good alternative method to obtain the crack path under UF.

An Efficient Three-Dimensional Coupled Normal Mode Model and Its Application to Internal Solitary Wave Problems

We present an efficient three-dimensional coupled-mode model based on the Fourier synthesis technique. In principle, this model is a one-way model, and hence provides satisfactory accuracy for problems where the forward scattering dominates. At the same time, this model provides an efficiency gain of an order of magnitude or more over two-way coupled-mode models. This model can be applied to three-dimensional range-dependent problems with a slowly varying bathymetry or internal waves. A numerical example of the latter is demonstrated in this work. Comparisons of both accuracy and efficiency between the present model and a benchmark model are also provided.

Assessment of internal quality of billets using ultrasonic three-dimensional layered characterization

To address the challenge of visualizing internal defects within castings, ultrasonic nondestructive testing technology has been introduced for the detection and characterization of internal defects in castings. Ultrasonic testing is widely utilized for detecting and characterizing internal defects in materials, thanks to its strong penetration ability, wide testing area, and fast scanning speed. However, traditional ultrasonic testing primarily relies on one-dimensional waveforms or two-dimensional images to analyze internal defects in billets, which hinders intuitive characterization of defect quantity, size, spatial distribution, and other relevant information. Consequently, a three-dimensional (3D) layered characterization method of billets internal quality based on scanning acoustic microscope (SAM) is proposed. The method starts with a layered focus scanning of the billet using SAM and pre-processing the obtained sequence of ultrasonic images. Next, the ray casting is employed to reconstruct 3D shape of defects in billets, allowing for characterization of their quality by obtaining characteristic information on defect spatial distributions, quantity, and sizes. To validate the effectiveness of the proposed method, specimens of 42CrMo billets are prepared using five different processes, and the method is employed to evaluate their internal quality. Finally, a comparison between the ultrasonic image and the metallographic image reveals a difference in dimensional accuracy of only 2.94%. The results indicate that the new method enables visualization of internal defect information in billets, serving as a valuable complement to the traditional method of characterizing their internal quality.

Role of three-dimensional endoanal ultrasound in assessing the anal sphincter morphology of female patients with chronic proctalgia

AIM To assess the role of three-dimensional endoanal ultrasound (3D-EAUS) for morphological assessment of the anal sphincter of female patients with chronic proctalgia (CP). METHODS In this unmatched case control study, 30 consecutive female patients with CP and 25 normal women (control group) were enrolled. 3D-EAUS was performed in all subjects. Thickness and length of internal anal sphincter (IAS), thickness of puborectalis muscle (PR), length of the external anal sphincter (EAS) plus PR, and puborectalis angle were measured and compared between the two groups. RESULTS Patients with CP had significantly shorter IAS length and greater PR thickness, as compared to those in normal individuals (26.28 +/- 3.59 mm vs 28.87 +/- 4.84 mm, P < 0.05 and 9.67 +/- 1.57 mm vs 8.85 +/- 0.97 mm, P < 0.05, respectively). No significant between-group differences were observed with respect to IAS thickness and the EAS plus PR length (P > 0.05). Puborectalis angle in the CP group was significantly decreased, both in resting (88.23 degrees +/- 1.81 degrees vs 89.94 degrees +/- 2.07 degrees in control group, P < 0.05) and straining (88.47 degrees +/- 3.32 degrees vs 90.72 degrees +/- 1.87 degrees in control group, P < 0.05) phases, which suggest the presence of paradoxical contraction of PR in patients with CP. In the CP group, no significant difference in puborectalis angle was observed between the resting and straining phases (88.23 degrees +/- 1.81 degrees vs 88.47 degrees +/- 3.32 degrees respectively, P > 0.05). CONCLUSION The association of greater PR thickness and paradoxical contraction of PR with CP suggest their potential value as markers of CP.

Shallow Water Modal Evolution Due to Nonlinear Internal Waves

Acoustic modal behavior is reported for an L-shape hydrophone array during the passage of a strong nonlinear internal wave packet. Acoustic track is nearly parallel to the front of nonlinear internal waves. Through modal decomposition at the vertical array, acoustic modes are identified. Modal evolution along the horizontal array then is examined during a passing internal wave. Strong intensity fluctuations of individual modes are observed before and during the internal waves packet passes the fixed acoustic track showing a detailed evolution of the waveguide modal behavior. Acoustic refraction created either uneven distribution of modal energy over the horizontal array or additional returns observable at the entire L-shape array. Acoustic ray-mode simulations are used to phenomenologically explain the observed modal behavior.

Convective heat and mass transfer effects in three-dimensional flow of Maxwell fluid over a stretching surface with heat source

Heat and mass transfer effects in three-dimensional flow of Maxwell fluid over a stretching surface were addressed.Analysis was performed in the presence of internal heat generation/absorption. Concentration and thermal buoyancy effects were accounted. Convective boundary conditions for heat and mass transfer analysis were explored. Series solutions of the resulting problem were developed. Effects of mixed convection, internal heat generation/absorption parameter and Biot numbers on the dimensionless velocity, temperature and concentration distributions were illustrated graphically. Numerical values of local Nusselt and Sherwood numbers were obtained and analyzed for all the physical parameters. It is found that both thermal and concentration boundary layer thicknesses are decreasing functions of stretching ratio. Variations of mixed convection parameter and concentration buoyancy parameter on the velocity profiles and associated boundary layer thicknesses are enhanced. Velocity profiles and temperature increase in the case of internal heat generation while they reduce for heat absorption. Heat transfer Biot number increases the thermal boundary layer thickness and temperature. Also concentration and its associated boundary layer are enhanced with an increase in mass transfer Biot number. The local Nusselt and Sherwood numbers have quite similar behaviors for increasing values of mixed convection parameter, concentration buoyancy parameter and Deborah number.

Research on Translation Strategies of Political Texts for International Publicity from the Perspective of Eco-Translatology

Eco-translatology provides a new perspective and methodology for the international publicity translation of political texts.This paper applies the viewpoint and methodology of eco-translatology,focuses on the three-dimensional transformation of language,culture,and communication,and discusses how translators can adapt to the eco-environment of political texts through the specific example of the keynote speech of China’s president at the opening ceremony of the Third Belt and Road Forum for International Cooperation and select suitable translation strategies and techniques to achieve an ecological balance of the target text in multiple dimensions.

Three-dimensional printing combined with open reduction and internal fixation versus open reduction and internal fixation in the treatment of acetabular fractures:A systematic review and meta-analysis

Purpose:This meta-analysis compared the clinical outcome of three-dimensional(3D)printing combined with open reduction and internal fixation(ORIF)to traditional ORIF in the treatment of acetabular fractures.Methods:We searched the Cochrane Library,PubMed,Embase,VIP database,CNKI,and Wanfang data-base with keywords"acetabular fracture","3D printing","three-dimensional printing","open reduction and internal fixation","Acetabulum","Acetabula"from January 2000 to March 2020.Two reviewers independently selected articles,extracted data,assessed the quality evidence and risk bias of included trials using the Cochrane Collaboration’s tools and/or Newcastle-Ottawa scale.When the two analysts had different opinions,they would ask the third analyst for opinion.Randomized controlled trials or retrospective comparative studies of 3D printing combined with ORIF(3D printing group)versus traditional ORIF(conventional group)in the treatment of acetabular fractures were selected.The data of operation time,intraoperative blood loss,intraoperative fluoroscopy times,incidence of complications,excellent and good rate of Matta score for reduction,and excellent and good rate of hip function score were extracted.Stata14.0 statistical software was used for data analysis.Results:Altogether 9 articles were selected,including 5 randomized controlled trials and 4 retrospective studies.A total of 467 patients were analyzed,250 in the conventional group,and 217 in the 3D printing group.The operation time in the 3D printing group was less than that in the conventional group and the difference was statistically significant(standardized mean difference(SMD)=-1.19,95%CI:-1.55 to-0.82,p<0.05).The intraoperative bleeding volume of the 3D printing group was significantly lower than that of the conventional group(SMD=-1.08,95%CI:-1.65 to-0.51,p<0.05).The fluoroscopy times were less in the 3D printing group than in the conventional group and the difference was statistically significant(SMD=-1.64,95%CI:-2.35 to-0.93,p<0.05).The total incidence of complications in the 3D printing group was significantly lower than that in the conventional group(OR=0.43,95%CI:0.24-0.79,p<0.05).There was no significant difference in the excellent and good rate of Matta score for reduction between the two groups(OR=0.60,95%CI:0.34-1.06,p>0.05).There was no significant difference in the excellent and good rate of hip function score at the end of postoperative follow-up between the two groups(OR=0.84,95%CI:0.46-1.56,p>0.05),but the follow-up time varies from 6 months to 40 months.Conclusion:Compared with traditional ORIF,3D printing combined with ORIF has certain advantages in terms that 3D printing not only helps surgeons to understand acetabular fractures more intuitively,but also effectively reduces operation time,intraoperative blood loss,intraoperative fluoroscopy times,and postoperative complications.However,there were no significant differences in the excellent and good rate of Matta score for reduction and the excellent and good rate of hip function score at the end of follow-up.

小额信贷国际经验及其启示

我国小额信贷正处在一个新的发展时期,但在发展政策和模式等方面还存在一定的争议,因此,学习和借鉴国外的发展经验就具有一定的理论和现实意义。在500多年的国际小额信贷发展历史进程中,各国对小额信贷大多采取鼓励发展的政策,选择适合自己国情的小额信贷发展模式,同时,强调小额信贷的商业化和可持续性发展,对小额信贷监管力度不断加强,注重小额信贷风险的控制。国际小额信贷的发展给我国小额信贷工作提供了有益启示,今后小额信贷要逐步实现从福利型向商业型转变,小额信贷的利率要遵循市场化原则,而且小额信贷机构要不断夯实自身发展基础,强调规范发展和加强监管。

小额信贷的目标偏移:来自国际数据的经验研究

利用MIX面板数据,采用固定效应二阶段最小二乘估计法验证了影响小额信贷机构目标偏移的有关命题。经验分析表明,交易成本、规模效应、累进贷款以及贷款模式对小额信贷机构的目标偏移具有预期影响。提出采取激励性财税政策、适度扩大规模、利用团体贷款或者村银行贷款技术等措施,以期望解决小额信贷机构的目标偏移问题。

从国际经验考察中国小额信贷的商业化进程

从国际经验考察中国小额信贷商业化进程,存在市场化运作不充分,垄断现象突出,金融开放政策不彻底等问题。基于我国国情与现实,未来我国小额信贷商业化应在创造多元有序竞争的金融环境、探索多层次农村资金批发零售机制、发展各种小额信贷商业合作创新机制、加强立法并重视NGOs等小额信贷机构商业化的要求等方面不断加强。

微型金融机构可持续发展能力的国际比较

微型金融作为一种有效的扶贫方式和金融服务手段在全球范围内快速发展。然而，微型金融的实践面临的一个主要挑战是如何在“扶贫”和“可持续发展”之间维持平衡。从可持续发展的经济含义出发，建立微型金融机构可持续发展能力评价指标体系，运用层次分析法，利用2000-2012年14个国家的财务和社会绩效数据，计算各国微型金融机构可持续发展能力得分。结果显示，我国微型金融机构可持续发展能力较弱。由此，从利率市场化、资金来源多元化、金融产品的多样化等几个方面提出了提高我国微型金融机构可持续发展能力的政策建议。

农村微型金融机构可持续发展的国际经验与借鉴

农村微型金融机构在弥补农村金融服务空白,解决城乡金融发展不平衡等方面发挥了积极作用。但由于我国微型金融发展较晚,其发展的可持续性值得关注。分析了微型金融机构在国外的发展经验,阐述了孟加拉国乡村银行和玻利维亚阳光银行可持续发展的原因,以此为借鉴,提出我国农村微型金融机构可持续发展的建议。

农村小额信贷可持续发展国际经验分析

文章以全新的视角,从国外可持续发展的农村小额信贷的典型模式,泰国农业和农村合作社银行、印尼人民银行农村信贷部和孟加拉乡村银行等三家银行经营业绩分析与农村小额信贷可持续发展国际经验分析三个方面,为农村小额信贷的实践和发展提供了思路。

水平二维内微肋管内凝结两相流的流型实验

通过实验研究，从工程应用角度和流型转变控制机理考虑，将水平二维内微肋管内的凝结流型分为三区即：环状流，分层流与间歇流。通过解析法得到流型转变的判。流型图。与作者所做实验数据吻合。

小额信贷公司内部审计研究

随着经济的快速发展,正规金融体系已经无力满足所有竞争主体对资金的需求,随之出现一些新型金融组织;小额贷款公司的出现,成为支持"三农"小企业获取资金的强有力补充。在分析小额贷款公司产生、发展以及内部审计必要性的基础上,指出在监督缺位情况下的内部审计独立性、内部审计人员素质、内部审计方法等多方面存在问题。针对这些问题,经深入调研分析,提出了转变审计观念,提升内部审计独立性;多方位提高内部审计人员素质;引入信息处理系统、改进审计方法和手段等三方面建议和措施。

Surgical treatment for both-column acetabular fractures using pre-operative virtual simulation and three-dimensional printing techniques

Background:Surgical treatment of both-column acetabular fractures is challenging because of the complex acetabular fracture patterns and the curved surface of the acetabulum.Seldom study has compared the application of three-dimensional(3D)printing technology and traditional methods of contouring plates intra-operatively for the surgical treatment of both-column acetabular fractures.We presented the use of both 3D printing technology and a virtual simulation in pre-operative planning for both-column acetabular fractures.We hypothesized that 3D printing technology will assist orthopedic surgeons in shortening the surgical time and improving the clinical outcomes.Methods:Forty patients with both-column acetabular fractures were recruited in the randomized prospective case-control study from September 2013 to September 2017 for this prospective study(No.ChiCTR1900028230).We allocated the patients to two groups using block randomization(3D printing group,n=20;conventional method group,n=20).For the 3D printing group,1:1 scaled pelvic models were created using 3D printing,and the plates were pre-contoured according to the pelvic models.The plates for the conventional method group were contoured during the operation without 3D printed pelvic models.The operation time,instrumentation time,time of intra-operative fluoroscopy,blood loss,number of times the approach was performed,blood transfusion,post-operative fracture reduction quality,hip joint function,and complications were recorded and compared between the two groups.Results:The operation and instrumentation times in the 3D printing group were significantly shorter(130.8±29.2 min,t=-7.5,P<0.001 and 32.1±9.5 min,t=-6.5,P<0.001,respectively)than those in the conventional method group.The amount of blood loss and blood transfusion in the 3D printing group were significantly lower(500[400,800]mL,Mann-Whitney U=74.5,P<0.001 and 0[0,400]mL,Mann-Whitney U=59.5,P<0.001,respectively)than those in the conventional method group.The number of the approach performed in the 3D printing group was significantly smaller than that in the conventional method group(pararectus+Kocher-Langenbeck[K-L]approach rate:35%vs.85%;x2=10.4,P<0.05).The time of intra-operative fluoroscopy in the 3D printing group was significantly shorter than that in the conventional method group(4.2±1.8 vs.7.7±2.6 s;t=-5.0,P<0.001).The post-operative fracture reduction quality in the 3D printing group was significantly better than that in the conventional method group(good reduction rate:80%vs.30%;x2=10.1,P<0.05).The hip joint function(based on the Harris score 1 year after the operation)in the 3D printing group was significantly better than that in the conventional method group(excellent/good rate:75%vs.30%;χ^2=8.1,P<0.05).The complication was similar in both groups(5.0%vs.25%;χ^2=3.1,P=0.182).Conclusions:The use of a pre-operative virtual simulation and 3D printing technology is a more effective method for treating bothcolumn acetabular fractures.This method can shorten the operation and instrumentation times,reduce blood loss,blood transfusion and the time of intra-operative fluoroscopy,and improve the post-operative fracture reduction quality.

三维内微肋水热管强化传热实验

首次报道了三维内微肋两相闭式热虹吸管的传热性能.在实验范围内,与光管相比,竖直放置时,平均沸腾换热系数可以提高50%~238%,平均凝结换热系数可以提高100%~222%;小倾角下,平均沸腾换热系数可以提高51%~171%,平均凝结换热系数可以提高42%~170%.三维内微肋结构能够大大强化热管的沸腾换热与凝结换热,有效地减小热管的内热阻.

Multi-slice spiral computed tomography in diagnosing unstable pelvic fractures in elderly and effect of less invasive stabilization

BACKGROUND Older people are more likely to experience pelvic fractures than younger people.Multi-slice spiral computed tomography(CT)uses three-dimensional(3D)reconstruction technology to generate 3D images that can clearly demonstrate the 3D space of fractures and detect fractures at a higher rate.AIM To investigate the clinical value of multi-slice spiral CT 3D reconstruction in the diagnosis of unstable pelvic fractures in the elderly as well as the effect of less invasive stabilization.METHODS A total of 86 patients with unstable pelvic fractures treated between March 2016 and March 2019 underwent femoral supracondylar bone traction before surgery.Pelvic radiography and multi-row spiral CT were performed successively once the patient’s vital signs and hemodynamic indices were stable.Secondary processing of the original data was performed to obtain 3D reconstruction images and determine the vertical displacement of the pelvis.After basic or complete reduction,minimally invasive internal fixation using hollow lag screws was performed.The detection rates of fracture location and classification by X-ray and CT reconstruction were compared.Patients were divided into two groups according to the presence or absence of preoperative 3D reconstruction to compare postoperative reduction,wound healing time,fracture healing time,hospitalization time,visual analog scale(VAS)score,poor internal fixation,and functional recovery.RESULTS The diagnostic coincidence rates of X-rays for pubic symphysis,ilium wing,sacroiliac periarticular,and sacral fractures were lower than those of CT reconstruction.The coincidence rate of CT reconstruction in the clinical classification of pelvic fractures was 100%,whereas 11 cases were misdiagnosed by X-ray;the total coincidence rate was 87.21%.The total excellent and good rates of postoperative reduction were significantly higher in the study group than in the control group(P<0.05).The wound healing,fracture healing,and hospitalization times were significantly shorter in the study group than in the control group(P<0.05).The VAS scores decreased in both groups postoperatively and were lower in the study group than in the control group(P<0.05).The total incidence of poor postoperative internal fixation was significantly lower in the study group than in the control group(P<0.05).The overall rate of postoperative functional recovery was significantly higher in the study group than in the control group(P<0.05).CONCLUSION Multi-slice spiral CT has high guiding significance for the diagnosis,classification,and treatment of unstable pelvic fractures in the elderly.Preoperative 3D reconstruction can effectively shorten the operation time and promote fracture healing,while minimally invasive internal fixation can effectively reduce pain and promote functional recovery of fracture sites,making it worthy of clinical application.

Analysis of Heat and Mass Transfer for a Single-Planar-Anode-Supported Solid Oxide Fuel Cell Considering Internal Reforming

The temperature uniformity and component concentration distributions in solid oxide fuel cells during operating processes can influence the cell electrochemical and thermal characteristics.A three-dimensional thermal-fluid numerical model including electrochemical reactions and water-gas-shift(WGS)reaction for a single channel solid oxide fuel cell was developed to study the steady-state characteristics,which include distributions of the temperature(T),temperature gradient((35)T/(35)x),and fuel utilization.It was shown that the maximum temperature(Tmax)changed with operating voltage and the maximum temperature gradient(((35)T/(35)x)max)occurred at the inlet of the channel of a solid oxide fuel cell by simulation.Moreover,the natural convection condition had a great influence on T and(35)T/(35)x.The thermal stress generated by temperature differences was the key parameter and increasing the convection heat-transfer coefficient can greatly reduce the thermal stress.In addition,the results also showed that there were lower temperature gradients and lower current density at high working voltage;therefore,choosing the proper operating voltage can obtain better cell performance.