Helical Screws Research Articles

Artificial Helical Screws of 2D Materials with Archimedean Spiral Arrangement

AbstractHelix structures, which are frequently observed in nature, act as versatile structural templates for complex functionalities with asymmetry and anisotropy. However, atomically thin 2D materials, including graphene, transition metal dichalcogenides (TMDs), and MXenes, do not have inherent chirality in their planar geometry and cannot easily form such a structure. This study presents the macroscopic self‐assembly of 2D materials for helical screws with an Archimedean spiral arrangement. The naturally triggered spontaneous rotation upon the 1D fiber assembly of 2D materials forms helical screws consisting of multiple helices and perversions. For a clear understanding of the morphological evolution of helical screws, variations in the helical pitch and angle are systematically analyzed considering thermodynamic and kinetic conditions. Subsequently, the influence of spontaneous helix formation on the properties of the 2D assembled fibers is investigated in terms of the solvent‐driven actuator performance and electrical and electrothermal properties. The suggested approach provides a new perspective on the directed self‐assembly of inherently achiral 2D materials toward chiral helix formation.

Design and development of an automated soy chaap making machine

AbstractSoy chaap is a novel textured soy protein, gaining popularity as the best plant‐based protein. Presently, few entrepreneurs are practicing manual techniques to prepare soy chaap using non‐scientific and inappropriate food standards. So far, no machine is available in the public domain for producing quality soy chaap. Therefore, an automated soy chaap making machine was designed and developed, which works based on the principle of simultaneous pulling, rotation, and longitudinal movement of the skewer. It consists of a gluten extractor, dough sheeter cum cutter, and soy chaap wrapping machine. The gluten extractor comprises two helical screws that develop the dough and separates the gluten. The dough sheeter cum cutter is fabricated to transform the dough into the sheet of a dimension required for the wrapping on the next machine. Finally, the soy chaap wrapping machine is used to wrap the sheet on the skewer to develop soy chaap, which is operated by a microcontroller. The developed machine was tested, and the capacity of the machine was found 5 kg/hr (89% efficiency). The energy requirement per hour for producing soy chaap in frozen and canned form was 2.632 and 3.824 kWh, respectively. The machine's total cost was 3,895.45 USD having the cost of production for frozen and canned chaap was found to be 1.35 and 1.75 USD per kg. The developed machine would be a boon for the micro, small, and medium enterprises and others to produce quality soy chaap while getting a better economic return.Practical ApplicationsThe present work can extend the utilization of the soybean in developing a novel product. It produces high‐quality soy chaap with high capacity by reducing dependency on inefficient and unhygienic manual methods. This machine development lays a pavement in setting up the micro, small, and medium enterprises and creates employment opportunities.

Kinematic Model of a Magnetic-Microrobot Swarm in a Rotating Magnetic Dipole Field

This letter describes how a rotating magnetic dipole field will manipulate the location and shape of a swarm of magnetic microrobots, specifically microrobots that convert rotation into forward propulsion, such as helical swimmers and screws. The analysis assumes a swarm that can be described by a centroid and a covariance matrix, with the swarm comprising an arbitrary and unknown number of homogenous microrobots. The result of this letter is a kinematic model that can be used as an a priori model for motion planners and feedback control systems. Because the model is fully three-dimensional and does not require any localization information beyond what could realistically be determined from medical images, the method has potential for in vivo medical applications. The model is experimentally verified using magnetic screws moving through a soft-tissue phantom, propelled by a rotating spherical permanent magnet.

COMSOL simulation and experimental validation of promoter geometries facilitating citric acid transport in electrodialysis

Citric acid transport facilitation in electrodialysis was investigated using different flow promoter geometries e.g. rod, twisted tape (TT), rectangular winglet (RW) shape vortex generator (VG) and helical screws at four different flow rates 5, 10, 15 and 20 LPH. Flow visualization of 39 promoters (shape, spacing and orientation) were performed using 3D simulation (COMSOL Multiphysics® 5.3a). Based on simulation results, 14 best promoters were selected for experimental determination of ion transport and power consumption from Sherwood number, Sh and Power number, Pn respectively. With increase in flow rate and reduced spacing, Sh increased along with Pn. Mesh type TT performed better than mono layer TT but pressure drop increased. Screw promoter placed parallel to flow showed higher Sh and Pn compared to rod, VG and TT. 50% rise in Sh was noted with helical screw (d/h=1.33, α=90°) relative to empty channel. 1.5 times rise in LCDs were noted with conducting TT compared to non-conducting TTs with barely 1.5% increase in Pn. LCDs with conducting TTs were 80% higher compared to empty channel.

Low Reynolds number swimming of helical structures in circular channels

Rotating helical structures are very effective in low Reynolds number swimming and propulsion. Helical rods are extensively studied theoretically and computationally with asymptotical methods, but the effects of the geometric variables in full-scale and the performance of other helical structures, such as ribbons and Archimedean screws, are also important for the understanding of swimming in confinements and design of micro swimming robots. In this study, a CFD model is developed to study swimming of helical rods, ribbons, screws and filaments, in circular channels under constant angular velocity or constant external torque. Effects of geometric parameters and the confinement radius on the swimming velocity and efficiency are demonstrated. Wavelength and amplitude of the helical wave, filament radius, thickness and width of ribbons, and eccentricity of tails are studied. Swimming performance of magnetically coated ribbons is compared with the ribbons with magnetic heads. Theoretical results in literature are used to validate the CFD results and to identify the role of hydrodynamic interactions between helical body and the channel wall.

Five Types of Ruled Helical Surfaces for Helical Conveyers, Support Anchors and Screws

The paper provides an overview of five types of ruled helical surfaces which can be used for helical conveyers, support anchors and screws. The geometry of helical surfaces has been well studied. Several available methods of strength analysis of helicoidal shells give one a choice in solving one-dimensional or two-dimensional problems. The basic problems considered in this paper include geometrical research and static analysis of right and developable helicoids. Several works dealing with stress-strain state of oblique, pseudo-developable helicoids, and pseudo-developable helicoid of general type are given in References.

Heat Transfer Performance through a Flat Tube Using Rotary Helical Screw-tape Inserts

Heat transfer characteristics and friction factor in the horizontal double pipes of a flat tube with full and varied spacer length helical screws at various rotational speeds are investigated for Reynolds numbers ranging from 580 to 1,582. The heat transfer and friction factor of the inserted tube are significantly increased compared to those of the plain tube. The Nusselt number, friction factors, and thermal enhancement efficiency were increased with decreasing spacer length at increasing rotational speed under the same operating conditions.

Dr DD Tanna – Story of a Legend

Dr DD Tanna – Story of a Legend

Vertical Uplift Capacity of a Group of Helical Screw Anchors in Sand

In this paper experimental investigations on the behavior of single, double and triple helical screw anchors under the influence of vertical uplift loads are presented. The testing program was conducted on three model anchors having single, double and triple helical screws installed in sand. The experimental setup was instrumented to measure the pullout load and the upward displacement of the anchor. It was observed that the pullout load varied significantly with the installation depth of the anchor and the number of anchors. A mathematical model was developed using the limit-equilibrium method of analysis. Based on experimental results, non-dimensional graphs were plotted normalizing the deformation and load axis both and simple equations are proposed correlating load and deformation. Using these equations an anchor foundation for a particular structure can be designed. Comparison of the pullout load values obtained from the theory developed and the present experimental results showed good agreement.

The effect of moment arm length on high angled femoral neck fractures (Pauwels’ III)

This study investigated loads among five fixation types (FT) [three cannulated screws (CS), dynamic hip screws with and without derotational screws (DHS-DS and DHS), and dynamic helical hip screws with and without derotational screws (DHHS-DS and DHHS)] across three fracture moment lengths (ML) in Pauwels’ Type III fractures. Methods: Seventy-five sawbones were tested (5 FT × 5 trials × 3 ML). The study hypothesis was that significant differences in axial loading to failure would be demonstrated when CS was compared with the other four FT at the three MLs. Each construct was exposed to an axial compressive load to failure. Construct failure was defined as 5 mm of migration at the fracture site or fixation failure. Shapiro-Wilk was used to test for data normality. Subsequently, independent t-tests with Bonferroni correction was used for paired comparisons. Results: At fracture Moments A and B there were no statistical differences between CS and the other FT. At fracture Moment C all four FT yielded significantly higher (p ≤ 0.001) loads compared with CS. Conclusions: for basicervical fractures CS is a suboptimal form of fixation compared with DHS and DHHS both with and without derotation screws.

Percutaneous Treatment of Mitral Regurgitation

Percutaneous mitral valve therapy became a reality more than 25 years ago with the first description of balloon valvuloplasty for rheumatic mitral stenosis.1 More recently, percutaneous closure of paravalvular leaks after surgical valve implantation has been shown to have a potential, but limited, role.2–4 However, valvular mitral regurgitation (MR) remains largely the purview of surgery. Recently, the potential for less invasively replicating these successful surgical procedures without the need for thoracotomy or cardiopulmonary bypass has generated considerable interest. For the most part, these new approaches are modeled after established surgical strategies. Percutaneous approaches to mitral repair can be broadly divided into procedures that address the various components of the mitral valve. For purposes of discussion, the mitral valve can be considered to have several component parts: leaflets, subvalvular apparatus (chordate tendinae and papillary muscles), annulus, left atrium, and left ventricle.5 All are integral to the normal function of the mitral valve and each is a potential avenue for repair. Although many such avenues may not lead to an effective surgical option, it may be unwise to dismiss the possibility that others will achieve some measure of success. We briefly review the current percutaneous therapies being developed and evaluated for the management of MR. The current status of various percutaneous therapies is presented in Table 1. View this table: Table 1. Current Status of Percutaneous Mitral Valve Repair Procedures ### Leaflet Repair Complex leaflet repair is currently beyond the reach of a percutaneous approach. However, the relatively simple but, in selected patients, effective “double-orifice” surgical repair initially described by Alfieri and coworkers6 can be reproduced. In the surgical procedure, the free edges of the mitral leaflets are sutured together in the mid portion creating 2 separated orifices. Generally, surgical leaflet repair is combined with implantation of an annuloplasty ring. The surgical literature …

A Novel Method of Percutaneous Mitral Valve Repair for Ischemic Mitral Regurgitation

This investigation sought to determine the feasibility of a novel method of a percutaneous mitral valve repair. Percutaneous mitral valve repair has emerged as an alternative therapy for patients with functional mitral regurgitation. However, current methods that rely on cannulation of the coronary sinus may not result in direct reduction of the mitral annulus area due to the superior relationship of the sinus to the annulus. A novel device, consisting of helical stainless steel screws connected by a biocompatible tether, was designed for percutaneous mitral valve repair. This device was implanted by implanting the helical screws directly into the myocardium at the posteromedial mitral annulus of 8 anesthetized pigs from the right internal jugular vein. Implantation of the device resulted in a 19.7 +/- 0.1% reduction in mitral annular area and an 18.8 +/- 0.1% decrease in the mitral anterior-posterior dimension (both p < 0.05 vs. baseline). This annular reduction persisted at 3-month follow-up. Both the coronary sinus and left circumflex coronary artery remained patent in all animals. There was no evidence of device migration, poor wound healing, or tissue thrombosis at the sites of device implantation. Percutaneous mitral valve repair targeting the ventricular myocardium from central venous access is feasible. By directly acting on the posteromedial mitral annulus, this methodology targets the mitral annular area most frequently affected by ischemic mitral regurgitation, lessens the risk of coronary artery impingement, promotes coronary sinus patency, and overcomes technical concerns that may arise when the coronary sinus lies significantly superior to the mitral annulus.

A seven-helix coiled coil

Coiled-coil proteins contain a characteristic seven-residue sequence repeat whose positions are designated a to g. The interacting surface between alpha-helices in a classical coiled coil is formed by interspersing nonpolar side chains at the a and d positions with hydrophilic residues at the flanking e and g positions. To explore how the chemical nature of these core amino acids dictates the overall coiled-coil architecture, we replaced all eight e and g residues in the GCN4 leucine zipper with nonpolar alanine side chains. Surprisingly, the alanine-containing mutant forms a stable alpha-helical heptamer in aqueous solution. The 1.25-A resolution crystal structure of the heptamer reveals a parallel seven-stranded coiled coil enclosing a large tubular channel with an unusual heptad register shift between adjacent staggered helices. The overall geometry comprises two interleaved hydrophobic helical screws of interacting cross-sectional a and d layers that have not been seen before. Moreover, asparagines at the a positions play an essential role in heptamer formation by participating in a set of buried interhelix hydrogen bonds. These results demonstrate that heptad repeats containing four hydrophobic positions can direct assembly of complex, higher-order coiled-coil structures with rich diversity for close packing of alpha-helices.

Modeling of the plasticating process in a single‐screw extruder: A fast‐track approach

AbstractA new mathematical model has been developed to analyze the entire flow field of a single screw extruder under steady‐state conditions. Intended as a rational design tool for practising engineers in the polymer processing industry, the model contains no partial differential equations and hence does not require the use of numerical solution techniques. To achieve generality, a generic approach is proposed and has been adopted in the derivation of governing algebraic equations from general conservation laws covering channel geometry, polymer flow speed, equivalent radius in a pipe, material properties, power consumption and heat transfer. The model makes no use of empirical factors or correlation. The validity of the new model has been assessed by comparison with published experimental results. Good agreement was achieved with respect to its ability to predict (a) the solid‐bed width profile; (b) the axial pressure profile and (c) the temperature and pressure of the melt pool at the extruder exit. Furthermore, the model can predict other information including the solid‐bed velocity in the axial direction and the power consumption. The work has demonstrated the potential of a fast track approach to designing helical extruder screws, while maintaining a level of accuracy comparable with more complex 3D models but without the penalty of computational efforts.

Computerized overwire (ball) measurement of tooth thickness of worms, screws and gears

The authors propose a general approach for computerized overwire (ball) measurement of tooth thickness for gears, worms and screws, with symmetrical and unsymmetrical location of two surfaces that form the space of the workpiece. The relation between the tolerance of tooth thickness and the variation of the measure M is determined. The basic idea of the proposed approach is based on the determination of points of tangency of the surface of a ball (wire) with the surface of the workpiece (the worm, the gear). The geometry of worms based on the existing methods of their generation has been analytically determined. The authors have developed algorithms and computer programs for numerical computations. The proposed approach is illustrated with examples of measurements of involute helical gears and screws.

A Concept of Micro-Robot Imitating Bacteria with Helical Flagella.

A concept of a micro robot is proposed. The robot is assumed to possess a spherical body and rotating helical screws as bacteria do. Formulations are conducted for describing the motion of the robot applying the resistive force theory of Stokes flow. The motions of the robot with two screws are numerically analyzed as an example. An on-off type control for rotation of the one screw is employed. When the two screws rotate in the same direction (mode 1), the robot swims almost straight. The body of the robot rotates in the opposite direction of screw rotation. When one of the screws is at a standstill and the other keeps rotation (mode 2), the robot moves along a helix. Alternating these two modes, the robot changes the direction of the motion. It is shown that the robot which can detect the distance from a destination can approach it according to a simple rule.

A Study on the Hydraulic Copying System : 2nd Report, Turning of Noncircular Cross Section

This paper deals with a special method of using the hydraulic copying system called polygon turning, namely turning of a noncircular cross section. Considering the relation between copying accuracy and the dynamic characteristics of the hydraulic copying system, the following results were obtained for estimation of error and improvement of the accuracy. (1) The error resulting from a simple polygon turning can be calculated from dynamic parameters, particularly from time constant, of the hyaraulic copying system and shape of model of a cross section for the turning. (2) The dynamic performance parameters of the copying system were suitably obtained from field measurement of frequency response using a plate cam as an input signal generator. (3) A method for modification of model shape to reduce the resultant output error was developed and applied to a polygon turning and a turning of helical shaft or screws. The validity of the method was confirmed by experiments.

Power requirement for the mixing of thixotropic liquids

A procedure has recently been proposed by Godfrey et al. [1] for the calculation of the variation of power consumption with time when a thixotropic liquid is agitated from rest using an impeller which rotates at constant speed. This procedure requires a knowledge of the power requirement for Newtonian and time-independent non-Newtonian liquids together with viscometric data for the thixotropic liquid obtained under constant shear rate conditions. Experimental work to test the procedure has been carried out in a 0.126-m-diameter cylindrical vessel with anchor, helical ribbon and helical screw impellers. Power consumption data were obtained for a range of Newtonian and time-independent non-Newtonian liquids and this was then used to make predictions of the measured power input to the thixotropic liquids: salad cream, tomato ketchup, yoghurt, paint and Laponite solutions. The agreement between experiment and theory was usually better than 10%. However, for the case of the helical screws rotating in Laponite it was observed that regions existed close to the vessel wall where there was no fluid circulation. In such cases, the predicted power input was greatly in excess of the measured value. This is not a serious limitation of the predictive procedure since efficient industrial mixers would keep the entire fluid in circulation.

Entrainment Patterns of Screw Hopper Dischargers

Helical Screws are commonly used to extract bulk solids from the outlet slots of hoppers. The manner in which material flows into the screw affects the flow characteristics of the hopper, residence periods of the contents in various locations, segregation, attrition and torque requirements of the screw. Regimes of motion of the solids in various sections of the equipment are outlined and a simple qualitative analysis enables predictions to be made based on material factors and screw dimensions. Consequential factors are discussed relevant to design and applications.