Thread Length Research Articles

Application of spaghetti knotting technology in single-hole laparoscopic suturing instructional program on the basis of multi-directional stitching technology: a randomized controlled trial

BackgroundSpaghetti knotting technology is an emerging technique that can reduce the visual field restriction of the operator in laparo-endoscopic single site (LESS) surgery. Multi-directional stitching technology has been proved to improve the accuracy of suturing in clinical application of LESS surgery. Therefore, we conducted a study to evaluate the teaching efficacy and the operation workload of spaghetti knotting technology and conventional knotting technology in LESS suture teaching based on the multi-directional stitching technology.MethodsWe selected forty junior residents to learn the skill of knot tying with single-hole laparoscopic simulators. The forty students were randomly and equally divided into control group and experimental group. The control group was trained by the conventional knotting method, and the experimental group was trained by the spaghetti knotting technology. The grades were calculated before and after the training program, including operation score of suturing time, trhead length, needle insertion accuracy, knotting stability, tissue integrity, tissue tightness and the cognitive workload score of mental, physical and temporal demands, performance, effort and frustration.ResultsThere was no significant difference between two groups before training. After training, knotting skills and workload were significantly improved. There were significant differences between the two groups in knotting time (p = 0.001), thread length (p = 0.01), and tissue integrity(p = 0.003). The experiment group took less time, left longer thread and had higher tissue integrity. The workload of the experiment group was also accurately reduced. However, there was no significant difference between the two groups in needle insertion accuracy(p = 0.560), knotting stability(p = 0.059), and tissue tightness(p = 0.731).ConclusionIn LESS suture teaching based on the multi-directional stitching technology, the training of spaghetti knotting techniques significantly improved students’ learning efficacy and reduced their workload compared to training conventional knotting techniques. It suggested the combination of spaghetti knotting and multi-directional stitching technology could be a practicable method for laparoscopic skills teaching and a feasible clinical application value on spaghetti knotting technology in LESS surgery.

Study on the Process of Preparing Aluminum Foam Sandwich Panel Precursor by Friction Stir Welding

In recent years, high-performance lightweight and multifunctional aluminum foam sandwiches (AFSs) can be successfully applied to spacecraft, automobiles, and high-speed trains. Friction stir welding (FSW) has been proposed as a new method for the preparation of AFS precursors in order to improve the cost-effectiveness and productivity of the preparation of AFS. In this study, the AFS precursors were prepared using the FSW process. The distribution of foaming agents in the AFS precursors and the structure and morphology of AFS were observed using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS). The effects of the temperature and material flow on the distribution of the foaming agent during the FSW process were analyzed through experimental study and numerical simulation using ANSYS Fluent 19.0 software. The results show that the uniform distribution of the foaming agent in the matrix and excellent densification of AFS precursor can be prepared when the rotation speed is 1500 r/min, the travel speed is 25 mm/min, the tool plunge depth is 0.2 mm, and the tool moves along the retreating side (RS). In addition, the experimental and numerical simulations show that increasing the welding temperature improves the uniformity of foaming agent distribution and the area of AFS precursor prepared by single welding, shortening the thread length inhibits the foaming agent from reaching the upper sandwich plate and moving along the RS leads to a more uniform distribution of the foaming agent. Finally, the AFS with porosity of 74.55%, roundness of 0.97, and average pore diameter of 1.192 mm is prepared.

Experimental and numerical study on mounting force and withdrawal strength of self-threaded dowels in particleboard

Traditional and alternative joining techniques have been used for many years at the connection points of structural bearing systems. Especially, glued doweled and screwed type mechanical connections are widely used in wooden structures and furniture constructions. Although there are many studies related to the strength of dowel and screw joints, limited papers describe the practical use of self-threaded dowels (STDs) in the joints. In this study, thread geometry effect of the STDs in particleboard (PB) was investigated by determining the mounting force and withdrawal strength values. For this purpose, STDs including three different thread width (0,2 - 0,3 - 0,4 mm) and two different thread length (1 - 2 mm) were designed, produced and tested under static compressive and tensile forces. All STDs were produced with polylactic acid (PLA) by using Layer Plastic Deposition (LPD) method in 3D printing technology. Uniaxial compression tests were performed in order to determine the minimum mounting force while the tension tests were performed for determining the maximum withdrawal force required to put the STDs into the hole and pull out them, respectively. Numerical analysis (FEM) were used to analyze the contact pressures and stresses of the STD joints. Abaqus v6.13-1 software was utilized for the numerical analyses. In addition, multiple regression analysis was carried out to predict the mounting force and withdrawal strength of the STDs. Results showed that the predictive expressions developed provided reasonable estimates for mounting force and withdrawal strength of STDs. According to the statistical analyses; thread width, thread length and their interaction have significantly affected both mounting force and withdrawal strength of STDs. At the end of the experimental and numerical tests, STDs with 0,2 mm width and 2 mm length threads gave the lowest mounting force values, stresses and contact forces. However, the highest withdrawal strength values were obtained from the STDs with 0,3 mm width and 1 mm length threads. According to the results of the study, the optimum STD was the one with 0,3 mm thread width and 2 mm thread length. In conclusion, the STDs can be utilized as an alternative fastener to the conventional glued dowel type joints in PB. However, corner joints constructed of different kinds of wood-based composites and connected with the STDs should be investigated in the future studies.

Motion of a ball attached to a mass via a hole in a horizontal table

Abstract Measurements are presented of the circular motion of a ball on a table attached to another ball by a length of thread via a hole in the table. It is a standard problem often assigned to students, but the experimental results differ from predictions.

Formation of sodium-alginate droplets in an X-microdevice: Characterization of the pinching efficiency

Experiments and simulations are used jointly to gain a comprehensive insight into the pinching mechanism that generates alginate droplets in an X-microdevice operating in a hydrodynamic flow-focusing configuration. The X-microdevice is fed with an aqueous alginate solution into one inlet channel, while sunflower oil and Span80 are fed into the other two inlet channels. The use of the adaptive mesh refinement and volume of fluid method allows accurate tracking of the interface in numerical simulations. The sensitivities of numerical predictions to the contact angle and the surface tension are estimated through dedicated sets of simulations. Subsequently, numerical simulations and experiments are compared for different flow rates with a satisfactory agreement. We observe that the pinch-off mechanism may lead to the formation of several satellite drops in addition to the main droplet. A pinching performance indicator is suggested based on the amount of alginate that is encapsulated in the main droplet. The effect of operating conditions on the pinching efficiency, frequency, and droplet diameter is discussed to provide valuable information to optimize the droplets production. The pinching efficiency is closely related to the length and diameter of the liquid thread. At low flow rates, a short liquid thread is observed. This leads to the formation of few satellites and, thus, to high pinching efficiency but low droplet production. Increasing the dispersed-phase flow rate slightly reduces the efficiency but significantly increases the production.

A new approach for predicting seam strength

Owing to a high amount of stress, seam failure in workwear fabrics makes the fabric unsuitable although the fabric strength is high. It is therefore important to predict the seam strength to ascertain the performance of the garments during use and determine the required thread strength to match the required seam strength. An assembly is composed of a sewing thread and a fabric. The thread forming the seam undergoes several stresses during its passage from the sewing machine to the formation of the loop and when wearing the garment: these are mechanical stresses. Therefore, it is necessary to evaluate the strength of the seam. But, in the bibliography, most researchers have studied the strength of the seam concerning a single type of stitch. This work aimed to examine the seam's strength from the resistance to the loop of the thread for all types of stitches. In all of the earlier predictive equations, seam strength is predicted from thread loop strength with some multiplicative factors. The thread loop strength is measured without considering the stitch type. During the sewing process, threads loop differently from one stitch to another, therefore, the standard thread loop strength becomes unfit to predict the seam strength. In this paper, the effects of loop thread length and configuration are studied on thread loop strength and seam strength. The seam strengths predicted from the loop strength before and after considering the new loop configurations and the real seam strength are compared. So, new clamps for loop strength are configured and carried out. It is observed that there is a closer match between experimental and predicted seam strength with new loop configurations. The loop configuration has a significant effect on the thread loop strength and improves the accuracy of seam-strength prediction.

Investigating the biomechanical behaviour of tendon-loaded wrist joint using web-like kinematic network model

The complexity of wrist anatomy and mechanics makes it challenging to develop standardized measurements and establish a normative reference database of wrist biomechanics despite being studied extensively. Moreover, heterogeneity factors in both demographic characteristics (e.g. gender) and physiological properties (e.g. ligament laxity) could lead to differences in biomechanical behaviour even within healthy groups. We investigated the kinematic behaviour of the carpal bones by creating a virtual web-like network between the bones using electromagnetic (EM) sensors. Our objective was to quantify the changes in the carpal bones’ biomechanical relative motions and orientations during active wrist motion in the form of orb-web architecture. Models from five cadaveric specimens at different wrist positions: (1) Neutral to 30° Extension, (2) Neutral to 50° Flexion, (3) Neutral to 10° Radial Deviation, (4) Neutral to 20° Ulnar Deviation, and (5) Dart-Throw Motion – Extension (30° Extension/10° RD) to Dart-Throw Motion Flexion (50° Flexion/20° UD), in both neutral and pronated forearm have been analyzed. Quantification analyses were done by measuring the changes in the network thread length, as well as determining the correlation between the threads at different wrist positions. We observed similarities in the kinematic web-network patterns across all specimens, and the interactions between the network threads were aligned to the carpal bones’ kinematic behaviour. Furthermore, analyzing the relative changes in the wrist web network has the potential to address the heterogeneity challenges and further facilitate the development of a 3D wrist biomechanics quantitative tool.

Modern Electromagnetic-Radiation-Shielding Materials Made Using Different Knitting Techniques.

This paper summarizes the possibility of employing knitted textile barriers as a shield against electromagnetic fields to protect the human body from their negative impact. Ten variants of knitted fabrics made of electrically conductive yarns, steel, and copper wire that differed in stitch pattern, structural parameters, and raw material, were designed, manufactured, and tested. The knitted fabrics produced differed in structural parameters, including course and wale density, surface density, thickness, thread length in the loop, wale and course take-up, volume cover factor, and surface porosity. These parameters were examined in accordance with the research methodology used in knitting. Barrier measurements were taken in the direction of the wales and in the direction of the courses for two frequencies of electromagnetic fields: 2-4 GHz and 4-7 GHz. It was observed that the shielding effectiveness of the manufactured materials depends on the structural parameters of the fabric, the stiches applied, and the type of yarn.

Tensile behavior of TOBs bolted T-stub to circular steel tube with Reverse-Channel

The T-stub bolted to Circular Steel Tube strengthened by Reverse-Channel using Thread-fixed One-side Bolts (TOBs) under tension was studied in this paper. Through welding a reverse channel, the regular bolted flat endplate connection could be employed for the steel beam to circular steel tube column. At the same time, the reverse channel also strengthens the tube wall and extends the hole thread length. Four TOBs bolted T-stub to Circular Steel Tube strengthened by Reverse-Channel (CST-RC) specimens were designed and tested under tension. Critical parameters were determined as the outer diameter of the steel tube, the tube wall thickness, and the bolt gauge distance. Test results revealed three typical failure modes: complete yielding of the whale tube wall, thread shear failure, and complete yielding of the whole tube wall with the thread failure. As well as the tube wall thickness could effectively increase the load-bearing capacity of the connection, a larger bolt gauge distance could reduce the connection deformation. Finite Element Models (FEM) were developed to analyze the load carrying mechanism of TOBs bolted T-stubs to CST-RC. The connection deformation contour, the yield line patterns of tube wall, and the stress distribution on the threads were presented. The behavior of TOBs bolted T-stubs to CST-RC was compared to that of TOBs bolted T-stubs to Circular Steel Tube (CST), and that of TOBs bolted T-stubs to Square Steel Tube (SST). It was found that the reverse channel effectively reduces the circular tube wall deformation and increases connection load-bearing capacity.

Experimental investigation of uncertain factors on the mechanical properties of half-grouted sleeve connected with large-diameter high-strength reinforcement

The half-grouted sleeve connection (HGSC) is widely used to connect reinforcement in precast concrete (PC) structures. While some studies have examined the mechanical behavior of the HGSC, there is still a lack of research on uncertain factors with large-diameter high-strength reinforcement. To fill this gap, an extensive experimental study was conducted to investigate the mechanical properties of the HGSC under monotonic tensile loads. The impact of various uncertain factors, including the embedded length, water-binder ratio (w/b) of the grouting material, eccentricity of rebar, thread diameter, and thread length, was investigated. It was found that the HGS connected with large-diameter high-strength reinforcement has four damage modes, i.e., thread fracture, thread pullout, reinforcement fracture, and bond-slip failure. Notably, to obtain the target of equivalent reinforcement, the dispersion ratio of the w/b should be controlled within 0.3, the embedded length should be greater than 6d, and the thread diameter and the thread length should not be less than 1d. Based on the HGSC investigated in this paper, a model for predicting the axial force and circumferential confining strain was presented, and a method was provided to calculate the elastic and plastic lengths for the embedded reinforcement. This study provides valuable guidance for the application of large-diameter high-strength rebar in PC structures.

EXPERIMENTAL INVESTIGATION OF SECONDARY FLOW DURING THE DROPLET FORMATION IN THE FLOW-FOCUSING CHANNEL

In this study, we have investigated the complex dynamics of droplet formation in a flow-focusing channel. Experiment has been performed under micro-particle image velocimetry (μPIV). The growth of droplets has been observed at four stages: lagging, filling, necking, and detachment. The interaction of two immiscible fluids, de-aerated water and silicon oil, is used. Characteristics of the droplet thread have been analyzed. Length of dispersed thread and tip size decrease with increased flow rate ratio. Furthermore, the flow characteristics of the dispersed phase, the velocity fields, contour plots of vorticity (ω<sub>z</sub>) swirl strength (λ<sub>1</sub>), and circulation strength (Г/U<sub>d</sub>W) have been investigated. Vortex flow region is identified during the droplet formation in such flow conditions (Re ~ 1 and Ca < 0.01). The vortex flow region shrinks with increasing flow rate ratio. Our experimental methodology and results have illustrated the presence of a temporal vortex pair during droplet formation in dispersed phase, a phenomenon with potential to amplify the chaotic mixing of multiphase fluids in a microchannel.

The Use of Thread and Fabric in Feminist Zines

The Use of Thread and Fabric in Feminist Zines

Art Is Magic

Art Is Magic

Design research on the unmeshed thread section structure of engine conrod bolts

In the design standard for hexagonal flange bolts, the reliability of the bolt connection structure varies when different structural forms of bolts are selected. However, there are few studies on the design and selection of bolts with different structural forms, and the design law of the bolt connection structure cannot be summarized comprehensively. In this paper, a finite element model of conrod bolt tightening was established based on the mesh convergence criterion, and the model was verified by comparing the simulation curve of tightening torque-bolt preload with the theoretical curve. The influence of the length of unmeshed thread, the length of thin rod and the diameter of thin rod section on the stress and deformation of conrod bolt was studied, it is found that the increase of the three kinds of structural parameters will reduce the stress concentration and radial deformation at the first thread of engagement, which can guarantee the structural strength of the bolt. At the same time, the fatigue safety factor of the bolt easy-to-failure region was analyzed, and the reliability of different structural forms of bolts was evaluated comprehensively. The results show that when the structure of bolt conforms to the design standard of full thread hexagonal flange bolt, the length of unmeshed thread is 27 mm, the stress value and radial deformation of the first thread are the smallest, and the fatigue safety factor of the bolt easy-to-failure region is the largest, which is not easy to damage. In the design of hexagonal flange bolts, full thread hexagonal flange bolts are used as much as possible.

Heatwaves hinder mussel invasion by weakening byssus production

Heatwaves and bioinvasion are among the most pressing ecological issues worldwide. The highly invasive South American mussels (Mytella strigata) can construct extremely dense byssal mats in intertidal habitats they invade, causing serious threats to local biodiversity and ecosystems. Yet, little is known about whether intensifying heatwaves might facilitate their invasions. Here, we investigated how the byssus production of M. strigata responds to heatwaves scenarios that have frequently occurred in recent years in the South China Sea. Compared with those grown at ambient temperature, mussels exposed to simulation heatwaves secreted significantly lowered number, length, and diameter of byssal threads, and exhibited significant impairments in the adhesion of byssus. Differential expressions of key genes involved in byssus production (e.g., foot protein gene, cell apoptosis gene, extracellular matrix-receptor interaction gene, and neuroactive ligand-receptor interaction gene) offered deeper insights into heatwaves-induced physiological changes in byssal gland. These results can provide an improved understanding of responses of mussel byssus production to intensifying heatwaves and take a major leap forward in examining the dispersal of highly invasive species in a rapidly warming ocean.

Self-consistent equilibrium models of prominence thin threads heated by Alfvén waves propagating from the photosphere

The fine structure of solar prominences is composed of thin threads that outline the prominence magnetic field lines. Observations have shown that transverse waves of Alfvénic nature are ubiquitous in prominence threads. These waves are driven at the photosphere and propagate to prominences suspended in the corona. Heating due to Alfvén wave dissipation could be a relevant mechanism in the cool and partially ionised prominence plasma. In this work, we explore the construction of 1D equilibrium models of prominence thin threads that satisfy an energy balance condition between radiative losses, thermal conduction, and Alfvén wave heating. We assumed the presence of a broadband driver at the photosphere that launches Alfvén waves towards the prominence. An iterative method was implemented in which the energy balance equation and the Alfvén wave equation are consecutively solved. From the energy balance equation and considering no wave heating initially, we computed the equilibrium profiles along the thread of the temperature, density, ionisation fraction, and other relevant parameters. On these equilibrium profiles, we used the Alfvén wave equation to compute the wave heating rate, which was then put back in the energy balance equation to obtain new equilibrium profiles, and so on. The process was repeated until convergence to a self-consistent thread model heated by Alfvén waves was achieved. We obtained equilibrium models composed of a cold and dense thread, an extremely thin prominence-corona transition region, and an extended coronal region. We found that the length of the cold thread decreases with the temperature at the prominence core and increases with the Alfvén wave energy flux injected at the photosphere. However, computed equilibrium models for large wave energy fluxes are not possible when the wave heating rate inside the cold thread becomes larger than the radiative losses. The maximum value of the wave energy flux that allows for an equilibrium depends on the prominence core temperature. This constrains the existence of thread equilibria in realistic conditions.

Incomplete Screw Thread Engagement of Proximal Fragment: A Possible Failure Risk After Internal Fixation for Femoral Neck Fractures.

Background For successful internal fixation for femoral neck fracture, the sliding mechanism of the screw is important because it can induce inter-fragmental compression. The thread should penetrate the fracture line and be located within the proximal fragment. If screw thread engagement is incomplete and a part of the thread remains within the distal fragment, the screw sliding can be disturbed, potentially leading to fixation failure. We hypothesized that screw threadin the fracture is a risk of fixation failure. Methods We studied 133 hips that underwent internal fixation for femoral neck fracture using dual sliding and compression screws (DSCS) with 20 mm threads. The existence of incomplete thread engagement and fixation failure (cut out, perforation, pseudoarthrosis, or femoral neck shortening) were evaluated on anteroposterior hip radiography postoperatively. The distances from the thread end to the fracture line, screw head to the femoral head cortex, and femoral head diameter were measured to analyze their relationships with any incomplete thread engagement and fixation failure. Differences in evaluation data were assessed using Fisher's exact test, Student's t-test, and receiver operating characteristic (ROC) analysis. Results Forty-six cases had at least one screw with incomplete thread engagement, and the other 87 hips had a complete engagement. The failure rate in the group of hips with incomplete thread engagement was significantly higher (7/46, 15.2%) than that in the group of hips with complete thread engagement (3/87, 3.4%) (P = 0.032). Incomplete thread engagement was found in 59 out of 266 screws (22.2%), and a femoral head ≤ 43.9 mm in diameter was associated with an increased risk of incomplete thread engagement. Most incomplete thread engagement screws (81.4%) had < 5 mm thread length within the distal fragment. Conclusion A partially threaded screw is a significant risk of fixation failure after internal fixation for a femoral neck fracture. The smaller femoral head diameter increases the possibility of incomplete thread engagement. Shortening the thread length by 5 mm may help to avoid incomplete thread engagement.

Test on Compressive Performance of Hollow Concrete-Filled Sandwich Circular Steel Tubes Connected by Thread

The connection method of lengthening the steel tube of hollow concrete-filled sandwich circular steel tubes and threaded connections is proposed. The length, depth and position are the basic parameters. Twelve hollow concrete sandwich circular steel pipes with threaded connections were designed and subjected to axial compression tests. The axial compressive loading–longitudinal compressive displacement curves, axial compressive loading strain of steel tube curves and failure mode of the specimens are analyzed, and the effects of different parameters on the axial compressive-bearing capacity and stiffness of the specimens are studied. The results showed that within the range of parameters studied, the axial compression load–longitudinal compression displacement curves of the specimens were the linear elastic stage and the elastic–plastic stage, which can be divided into a yield-strengthening stage and a decreasing stage. The bearing capacity and strength of the lined threaded connection specimen are not inferior to those of the ordinary specimen or the welded specimen. The bearing capacity and strength of the specimen increase with the increase of the thread length. The bearing capacity and strength of the specimens connected with inner liner screws at the ends are higher than those connected with inner liner bolts at the middle.

Static behavior of TOBs bolted endplate connection to strengthened HSST with fixed thread length

Five thread-anchored one-side bolts connected endplate connections to Hollow Square Steel Tube (TOBEC-HSSTs) with various strengthening measures were tested to investigate the structural performance under monotonic loads. The thread anchored length was 1.2 times the bolt diameter for all specimens. The connection behaviour were influenced by the endplate thicknesses and the strengthening measures (i.e. the internal polygonal tube, the internal polygonal tube with infilled concrete, and the cross-H section stiffener with infilled concrete). The failure patterns, moment-rotation curves, and strain response of joints were obtained through tests. It was found that (1) 1.2 times the bolt diameter was taken as the safe thread assembled length, which can avoid the premature failure of hole threads not before the fracture of other components under monotonic loads. (2) The presence of the infilled concrete can improve the rigidity and strength of the connection by 84% and 23%, respectively, compared to the reference joint without the infilled concrete, and the thickness of the column wall can be reduced when the concrete was infilled into hollow steel tube. (3) For the connections with thin endplates, the cross-H section stiffener exhibited 8.8% and 3.5% higher preliminary stiffness and yield bending moment than the inner polygonal tube, but the cross-H section stiffener had 14.3% lower rotation capacity. (4) Thickening endplates can change the failure modes of the connections to beam plastic hinge formation, enhance the preliminary stiffness and yield bending moment of joints by 2.4% ∼11%, but decrease the rotation capacity of joints by 54% compared to thin endplates. Based on experimental results, the calculation methods of the bending moment bearing capacity for TOBEC-HSSTs considering the strengthening effect of internal stiffeners and infilled concrete under different failure patterns were proposed with errors no greater than 15%.

Do the miniscrews of the prefabricated systems for the “appliance first” protocol of miniscrew-assisted rapid palatal expansion have lengths that meet the palatal thickness of patients?

In the "appliance first" protocol of miniscrew-assisted rapid palatal expansion, the prefabricated shape of the expanders limits the potential locations for miniscrew placement. Considering the influence of palatal thickness on the selection of the optimal length of miniscrews, this study aimed to evaluate the thickness of both bone and mucosa of the palate of patients aged 6-65 years and suggest optimal lengths of miniscrews for this approach. Two hundred and eighty-two cone-beam computed tomography of patients of both sexes were divided into 3 groups according to age. The thicknesses of bone and mucosa were measured in the anterior and posterior regions of the palate. Males showed a greater thickness of palatal bone than females. The thickness of both bone and mucosa was greater in the anterior region of the palate. The young patients showed greater bone thickness than adults and mature adults. The mature adults showed thinner bone thickness in the posterior region of the palate and greater mucosal thickness along the palate than young patients and adults. Development of miniscrews with longer thread lengths is necessary. Miniscrews with a 3-mm thread length would prevent excessive extravasation in the posterior region of the palate. The thickness of both bone and mucosa of the palate is variable and influenced by sex and age. Manufacturing additional miniscrews with different lengths of thread is suggested to achieve bicortical anchorage in patients undergoing the "appliance first" protocol of miniscrew-assisted rapid palatal expansion.