Helical Groove Research Articles

Grinding Analysis for Helical Groove of Micro Mill Based on Non-instantaneous-pole Envelope Principle

Grinding Analysis for Helical Groove of Micro Mill Based on Non-instantaneous-pole Envelope Principle

The histone chaperone sNASP binds a conserved peptide motif within the globular core of histone H3 through its TPR repeats.

Eukaryotic chromatin is a complex yet dynamic structure, which is regulated in part by the assembly and disassembly of nucleosomes. Key to this process is a group of proteins termed histone chaperones that guide the thermodynamic assembly of nucleosomes by interacting with soluble histones. Here we investigate the interaction between the histone chaperone sNASP and its histone H3 substrate. We find that sNASP binds with nanomolar affinity to a conserved heptapeptide motif in the globular domain of H3, close to the C-terminus. Through functional analysis of sNASP homologues we identified point mutations in surface residues within the TPR domain of sNASP that disrupt H3 peptide interaction, but do not completely disrupt binding to full length H3 in cells, suggesting that sNASP interacts with H3 through additional contacts. Furthermore, chemical shift perturbations from 1H-15N HSQC experiments show that H3 peptide binding maps to the helical groove formed by the stacked TPR motifs of sNASP. Our findings reveal a new mode of interaction between a TPR repeat domain and an evolutionarily conserved peptide motif found in canonical H3 and in all histone H3 variants, including CenpA and have implications for the mechanism of histone chaperoning within the cell.

Wideband Circularly Polarized Vortex Surface Modes on Helically Grooved Metal Wires

We report the characteristics of a right-handed helically grooved metal wire waveguide. For the helically grooved waveguide, the normal degenerate HE1 spoof surface plasmon polariton (SSPP) mode could be decomposed into two opposite circularly polarized modes, i.e., HE−1 and HE+1 SSPP modes, due to the chirality of helical grooves. The dispersion characteristics of the nondegenerate $\mathbf{HE}\pm\mathbf{1}$ SSPP modes were numerically obtained, and their spiral electromagnetic distributions were also presented. It was found that the $\mathbf{HE}\pm\mathbf{1}$ modes were circularly polarized; they were also vortex modes and possessed an orbit angular monument. In addition, the focusing characteristics of such waves near the waveguide end were investigated. The distinct advantages, such as a relatively long focusing length and the circular polarization of the chiral $\mathbf{HE}+\mathbf{1}$ SSPP modes, make the helically grooved metal wire waveguide a potential for near-field circular dichroism detection.

Design of modified Magnus wind rotors using computational fluid dynamics simulation and multi-response optimization

Concerns on climate change and dwindling fossil fuel supply have renewed interest on alternative ways of harnessing renewable energy. Using rotating cylinders to generate lift from a fluid stream, a Magnus rotor can produce up to 10 times more lift compared to an airfoil. However, it is also producing more drag. Recent studies have demonstrated improvement on the aerodynamic efficiency of a Magnus rotor through the application of surface modifications such as grooves, bumps, dimples, and even changing the shape of the cylinder into a frustum. However, it is unknown which is most desirable among those modifications; moreover, if some may be combined for even better performance. This present study seeks to fill the mentioned research gap with the aid of computer simulation tool ANSYS CFX. Simulation results showed that modifying cylinder shape into a frustum generates the most lift force. However, it is also increasing the drag on the cylinder. Interestingly, a helical groove may be employed around the frustum cylinder to mitigate the increase in drag, making the two modifications a promising combination. Multiple response surface analysis using desirability function was used to investigate the sensitivity of the rotor design to the different modifications. Furthermore, a new perspective is introduced wherein the rotor may be able to withstand more drag in exchange for more lift. For lift generation purposes, bumps are not desirable. Finally, the aerodynamic performances of the modified rotors are compared against other published results by means of a drag polar plot.

Modelling methods for end mill grooves based on different wheel geometries

Helical groove of end mill has great influence on its cutting performance. It is normally ground by disk wheels and the groove geometry varies with different wheel geometries. To improve the machining accuracy and reduce the cost of the groove machining process, establishing the groove model with the known wheel geometry and the wheel movement locus before the actual grinding is necessary. In this paper, according to the characteristics of wheel geometry, two different methods are introduced to build the groove model. One is based on the enveloping theory, taking into account the fact that the groove is generated by the enveloping movement of the wheel. Contact lines between the wheel and the groove are firstly deduced. Then, the expressions of the groove and the groove section lines are obtained. This method works well for wheels with straight generatrices. However, if the generatrix consists of quadric curves, a complex transcendental equation needs to be solved to satisfy the enveloping condition. Thus, the other modified graphical method is needed. The wheel is expressed in piecewise. During the grinding process, every part of the wheel will form a family of surfaces. By solving the intersections of these families and the end mill cross-section plane, a point set is obtained. Obviously, the outline of the set is the groove section line. Using this method, the result will be a set of points, but it has no wheel geometry limitation. The calculation procedures of these two methods are programmed with the MATLAB language and have good agreements with the Boolean result.

A GENERAL CAD/CAM MODEL FOR APT-LIKE ROTARY MILLING CUTTERS

This paper presents a general mathematical model for NC-machining an APT-LIKE rotating cutter. The design model of cutting-edge and helical groove is also developed by using the principles of differential geometry and kinematics. Based on the envelope condition, approaches for solving the inverse problems that are related to the manufacturing models are also presented. The velocities of the cutter in the radial and axial directions are then determined based on the gouging avoidance of grooves. The results of the numerical experiment indicate that the proposed systematic design method by using 2-axis NC machine setup is feasible and reliable.

Deep-subwavelength Guiding and Superfocusing of Spoof Surface Plasmon Polaritons on Helically Grooved Metal Wire

Deep-subwavelength guiding and superfocusing of spoof surface plasmon polaritons (SSPPs) realized on a helically grooved metal wire at microwave frequencies are presented in this paper. Two smooth bridges with gradient helical grooves decorated on the cylindrical and conical metal wire are proposed and designed, respectively. High-efficiency and broadband mode conversion from the traditional guided waves to the SSPPs and superfocusing of SSPPs are reported. Numerical simulations quantitatively show that the amplitudes of electric field at the tip of the conical wire with gradient helical grooves can be magnified 50 times more than that of the input signal in broadband. Moreover, the second transition structure ensures that the depth of helical groove can be tuned flexibly and arbitrarily, making it compatible with all kinds of N-type coaxial connectors. Strong field concentration and superfocusing of these two structures can be easily extended to terahertz (THz) frequencies by tuning the geometrical parameters and can find important applications in sensing, spectroscopy and near-field imaging in the microwave and THz frequencies.

Enhancement of performance of wire electrochemical micromachining using a rotary helical electrode

The inherent characteristics of wire electrochemical micromachining (WECMM) enable it to be a feasible alternative to machining micro structures with good surface integrity in difficult-to-machine materials. Efficient electrolyte renewal has been proven to be important to the process stability and material removal rate in the machining of high aspect ratio micro structures. This paper proposes a method of WECMM using a rotary helical electrode to enhance electrolyte refreshment in the machining depth direction gap. Simulations of the flow field indicate that when a helical electrode revolves at a high speed, the electrolyte in the machining gap is stirred drastically, and the helical groove on the electrode surface is conducive to electrolytic flow in the axial direction. In addition, a series of experiments verifies that the maximum electrode feedrate and the slit width uniformity in the depth direction are enhanced by using a rotary helical electrode. Finally, two complex micro structures are successfully produced using a rotary helical electrode at a spindle speed of 20000rpm.

Generation of Subwavelength Plasmonic Nanovortices via Helically Corrugated Metallic Nanowires.

We demonstrate that plasmonic helical gratings consisting of metallic nanowires imprinted with helical grooves or ridges can be used efficiently to generate plasmonic vortices with radius much smaller than the operating wavelength. In our proposed approach, these helical surface gratings are designed so that plasmon modes with different azimuthal quantum numbers (topological charge) are phase-matched, thus allowing one to generate optical plasmonic vortices with arbitrary topological charge. The general principles for designing plasmonic helical gratings that facilitate efficient generation of such plasmonic vortices are derived and their applicability to the conversion of plasmonic vortices with zero angular momentum into plasmonic vortices with arbitrary angular momentum is illustrated in several particular cases. Our analysis, based both on the exact solutions for the electromagnetic field propagating in the helical plasmonic grating and a coupled-mode theory, suggests that even in the presence of metal losses the fundamental mode with topological charge m = 0 can be converted to plasmon vortex modes with topological charge m = 1 and m = 2 with a conversion efficiency as large as 60%. The plasmonic nanovortices introduced in this study open new avenues for exciting applications of orbital angular momentum in the nanoworld.

Prediction of Residual Stresses for a Hollow Product in Cold Radial Forging Process

Radial forging is an open die forging process used for reducing the diameters of shafts, tubes, stepped shafts and axles and also for creating internal profiles such as rifling the gun barrels. The radial forging of tube is usually performed over a mandrel to create an internal profile and/or size the internal diameter. Most of the previous studies conducted on the radial forging process have used axisymmetric models. In this research, residual stresses of a short hollow tube in a cold radial forging process are investigated using 3-D finite element simulation. In this study, a mandrel with six helical grooves and two steps along its length is used. This kind of mandrel is innovated in this research. The workpiece is modeled as an elastic-plastic material and the commercial finite element software, ABAQUS is used to simulate of the process. The accuracy of the model is tested by comparing the predicted results with available experimental work and also validated by both slab and upper bound methods. Residual stresses in the radial forged product and the influence of the process parameters on stress distribution, such as workpiece motions, friction and percentage of reduction are studied to determine the optimized parameters of simulation and improve the condition of this process.

Formulating CAM parameters for surface patterning by grinding process based on unit pattern geometry

Grinding employs an abrasive product, usually a rotating wheel, which is brought into controlled contact with a workpiece surface. The grinding patterning process can be simulated using computer programming with specific user-defined parameters. To predict the surface pattern that will result from grinding with the grooved wheel, calculating the CAM parameters is very important. The intention of this research is to formulate CAM parameters for the generation of a surface pattern on a flat nominal surface by grinding with a wheel that has been prepared in a special way. A diamond dresser having a rounded tip is applied to prepare helical grooves on the conventional wheel’s surface. With the intention of extracting CAM parameters, a mathematical model is developed for a grinding patterning process, starting from the unit pattern geometry of the workpiece plate. The models are characterized by the process parameters of grinding patterning such as unit pattern geometry, dressing parameters, wheel geometry and grinding conditions, as well as work surface geometry. A computer program with a user interface is developed using Matlab according to the proposed mathematical model to predict surface pattern. In addition, several examples of simulation results of the 3D wheel geometry model and corresponding patterned surfaces have been displayed using the proposed CAM parameters as input. Formulated CAM parameters can be used to control the actual grinding process or predict the ground surface pattern.

Fluid Flow in the Oil Pumping System of a Hermetic Compressor

This work deals with the investigation of the oil pumping system in hermetic compressors for refrigeration application. The oil pump which is used for this study consists of two pumping areas: the lower pumping area with a pick-up tube and an eccentric bore, and the upper pumping area with a helical groove. This study focuses on the helical groove in the upper pumping area. To analyse the fluid flow in the helical groove, a numerical approach is introduced. In this approach the Navier-Stokes equations are adapted to the problem and are solved by using the finite volume method. Compared to analytical models, this method is able to obtain the flow field in the cross section of the helical groove at higher resolution. The higher geometrical resolution also enables the analysis of the flow in the small gap between the rotating crankshaft and the stationary wall. The present method is used to quantify different operating parameters on the oil mass flow rate.

Frequency-dependent circular-polarization of terahertz chiral spoof surface plasmon polariton on helically grooved metallic wire

Chiral spoof surface plasmon polaritons in the terahertz region, resulting from a coherent superposition of TM and HE modes, can be generated by normally exciting helically corrugated metal wire with a linearly polarized Gaussian light. The handedness of the chiral SPP depends on the handedness of the helical groove. The chirality of the surface wave causes a spiral spatial extent of average power whose period is determined by the difference in the wave vector between two modes. Simultaneously, highly circular polarization of a confined surface wave emerges from the chirality of the geometry. Moreover, the polarization state is heavily dependent on working frequency relative to the characteristic frequency of each mode. This type of chiral SPP, originating from the helical groove, makes helically corrugated metal wire useful for some special applications, such as circularly polarized sources for terahertz near-field microscopy or terahertz sensors for chiral biomolecules.

A Study on the General CAD Model for Rotary Milling Cutters

This paper presents a general mathematical model for NC-machining an APT-LIKE rotating cutter. The design model of cutting-edge and helical groove are also developed by using the principles of differential geometry and kinematics. The analytical solution for the resolution profile of helical groove has also been developed. The results of numerical experiment indicate that the proposed systematic design method by using 2-axis NC machine setup are feasible and reliable.

The fixity of prostate seed implants: The impact of the strand surface on its ability to migrate inside oil and gel medium.

Radioactive seed implants are widely used to treat cancer patients, most commonly those with prostate cancer. However, the seeds have a tendency to migrate after placement in patients, a phenomenon that can result in unfavorable outcomes. The ability of the seed strand to migrate was investigated by examining the impact of the strand surface on the velocity of its movement inside oil and gel media. We investigated the motion of smooth surface strands and strands with different grooved helical profiles after they were placed in oil and gel media. Three patterns of grooved helices were studied (60, 140, and 300 rotations per meter). The movement of the strands through a tube filled with the medium was recorded by the motion sensor, and the drag forces on the individual strands were calculated and compared for the oil and gel media. The strands with 60, 140, and 300 rotations/meter grooved helical surfaces demonstrated less mobility in both oil and gel than the strands with a smooth surface. The strand with the highest number of helical grooves per meter recorded the largest drag force and moved more slowly in both media. The differential in the motion of the smooth strand and the strands with grooved surfaces can be attributed to the increased surface area of the grooved strands. This finding is significant since it will impact, theoretically, the design, and thus the migration of seed implants that are used to treat cancer patients, particularly those with prostate cancer.

Forming mechanism of three-dimensional integral fin based on flat surface

To improve heat-transfer performance, a novel integral three-dimensional fin-structure on the plat surface was presented to increase the evaporation efficiency. The three-dimensional fin-structure is composed of a spiral micro-groove and multi radial micro-grooves. Both ploughing-extrusion (P-E) and stamping were used to form the integral-fins with a connection between radial and circumferential directions. Based on the SEM results, the relationships among P-E speed vP-E, rotational speed np and feed fp, and among interference length Li, stamping feed angle θc and stamping depth ac were analyzed. The effects of processing parameters on the groove morphology and the matching relationship between parameters were also discussed. The integral finned surface with micro-grooves and cracks can be obtained under such processing conditions: P-E depth ap=0.3 mm, ac=0.3 mm, the interval of helical groove dp=1.24 mm, θc=2° and np=50 r/min.

ROLL PASS DESIGN OF A BALL-ROLLING MILL. PART 2

In making balls for ball mils the metal is deformed in rolling balls in rolls with helical pass grooves. Insofar as the character of the deformation is concerned, the pass can be divided into the forming section, where the rolls bite the billet and reduce it gradually into the ball shape, and the finishing section where the ball is rolled to the final size and severed from the rest of the billet. A normal process of rolling is provided for by designing the forming section of the pass groove. In the article outcomes calculation roll pass design for rolling of balls. Calculation is made for roiling of ball of125 mm. Initial data for ball-rolling mill design are given.

Crystal structure of Hop2-Mnd1 and mechanistic insights into its role in meiotic recombination.

In meiotic DNA recombination, the Hop2−Mnd1 complex promotes Dmc1-mediated single-stranded DNA (ssDNA) invasion into homologous chromosomes to form a synaptic complex by a yet-unclear mechanism. Here, the crystal structure of Hop2−Mnd1 reveals that it forms a curved rod-like structure consisting of three leucine zippers and two kinked junctions. One end of the rod is linked to two juxtaposed winged-helix domains, and the other end is capped by extra α-helices to form a helical bundle-like structure. Deletion analysis shows that the helical bundle-like structure is sufficient for interacting with the Dmc1-ssDNA nucleofilament, and molecular modeling suggests that the curved rod could be accommodated into the helical groove of the nucleofilament. Remarkably, the winged-helix domains are juxtaposed at fixed relative orientation, and their binding to DNA is likely to perturb the base pairing according to molecular simulations. These findings allow us to propose a model explaining how Hop2−Mnd1 juxtaposes Dmc1-bound ssDNA with distorted recipient double-stranded DNA and thus facilitates strand invasion.

Verification of simulation of surface texturing on planar surface by grinding

Surface texturing is a means of pattern generation on a workpiece surface to provide functionality or for aesthetic reasons. Grinding is one of the various technology used for surface texturing. Compared with other methods (such as lasers, abrasive jet machining, mechanical cutting or rolling, and etching), grinding has some advantages for large-area texturing. In texturing by grinding, the grinding wheel needs particular shapes such as helical grooves on the peripheral surface of the wheel, depending on the shape of patterns to be generated on a workpiece. A grinding wheel with a helical groove generates patterns on the workpiece by the relative motion of the wheel and the workpiece. The pattern shapes are determined according to the combination of the grinding wheel speed and feed rate, as well as the geometry of the helical groove of the wheel. Before texturing, it is important to predict the textured patterns with a mathematical model. If the textured patterns are predictable, the shape of the grinding wheel and the grinding parameters can be determined. This paper proposes a mathematical model for the prediction of pattern generation, and verification of texturedpatterns based on the simulation resultsis given.

Visualizing the molecular recognition trajectory of an intrinsically disordered protein using multinuclear relaxation dispersion NMR.

Despite playing important roles throughout biology, molecular recognition mechanisms in intrinsically disordered proteins remain poorly understood. We present a combination of (1)H(N), (13)C', and (15)N relaxation dispersion NMR, measured at multiple titration points, to map the interaction between the disordered domain of Sendai virus nucleoprotein (NT) and the C-terminal domain of the phosphoprotein (PX). Interaction with PX funnels the free-state equilibrium of NT by stabilizing one of the previously identified helical substates present in the prerecognition ensemble in a nonspecific and dynamic encounter complex on the surface of PX. This helix then locates into the binding site at a rate coincident with intrinsic breathing motions of the helical groove on the surface of PX. The binding kinetics of complex formation are thus regulated by the intrinsic free-state conformational dynamics of both proteins. This approach, providing high-resolution structural and kinetic information about a complex folding and binding interaction trajectory, can be applied to a number of experimental systems to provide a general framework for understanding conformational disorder in biomolecular function.