Change In Radius Research Articles

Influence of tool-edge radius on the nano-cutting process of non-continuous surfaces in single-crystal silicon

Pore deformation and damage are caused by the compression of the cutting tool during the machining of porous materials. Tool-edge radius is a key factor in the nano-cutting of pores and significantly influences the resulting deformation and damage. In this paper, the molecular dynamics simulations were conducted to investigate nano-cutting process of the non-continuous surface in single-crystal silicon. Surface morphology, pore wall deformation, cutting forces, and subsurface damage were calculated and discussed under different tool-edge radii. The results indicated that the change of the tool-edge radius greatly affect the machining quality of non-continuous surface. Cutting forces and accumulated material above the pores increase with increasing tool-edge radius, and the side of the tool entering the pore is more susceptible to damage than the opposite side. Additionally, normal force was identified as the primary cause of damage on the side of the tool entering the pore. The longitudinal damage depth on the side of the tool entering the pore increases with the tool-edge radius. Comprehensive analysis of material distribution, pore wall deformation and damage indicates that a smaller tool-edge radius is more conducive to pore processing.

Developmental Anatomy of the Radial Bow in Pediatric Patients Using 3D Imaging.

While radial bow shape is well characterized in adults, its development in children is not well understood. Previous studies on the radial bow use radiographs, thus, rotational positioning of the forearm could alter bowing measurements. This study used 3D imaging to better assess the pediatric radial bow. Computed tomography scans from the New Mexico Decedent Image Database were obtained for ages 2 to 16 (females) and 18 (males) (n=152). 3D models were generated using Slicer and Rhino software. Length of the entire radial bow (bicipital tuberosity to sigmoid notch), maximum radial bow, location of the maximum radial bow (bicipital tuberosity to the point of maximum bowing), and distal, middle, and proximal third radial bows were measured. The length of the entire bow increased with age, with a strong correlation with age ( r =0.90, P <0.01). The maximum bow increased with age, with a strong correlation with age ( r =0.78, P <0.01). The maximum bow normalized to the length of the entire bow increased mildly with age, mean 0.059 ± 0.012 ( r =0.24, P =0.0024), but seems to plateau around age 8. The location of the maximum bow increased with age ( r =0.85, P <0.01). The normalized location of the maximum bow remained constant between ages, with a mean of 0.41 ± 0.10 ( r =0.12, P =0.14). The normalized distal third bow mildly increased with age ( r =0.34, P <0.01), the normalized middle third bow mildly increased with age ( r =0.25, P <0.01), and the normalized proximal third bow remained constant between ages ( r =0.096, P =0.24). Normalized values for maximum, distal third, and middle third radial bow increase with age, while normalized values for location and proximal third radial bow remain relatively constant, suggesting the proportional shape of the radius changes during development, although qualitatively plateaus after age 8. Retrospective comparative study, Level-III.

Influence of volume expansion in NaCl crystallization on the physical properties and molecular structure of asphalt: A MD simulation study

The pavement damage caused by salt-induced volume expansion is becoming increasingly noticeable. Molecular dynamics (MD) method was applied to evaluate the effects of varied volumes of NaCl crystals on physical properties and structure of asphalt. The effects of NaCl crystals on the compatibility between styrene–butadiene–styrene triblock copolymer (SBS) and asphalt, as well as the influence of SBS on the diffusion coefficient of NaCl crystals in the asphalt system, were investigated alongside their effects on the physical modulus and molecular structure of asphalt. The results show that the solubility parameter of the asphalt blends decreases as the volume of NaCl crystals increases. Specifically, the solubility parameter decreases by 52.5 % for the biaxial crystalline growth of NaCl and asphalt blends compared to the matrix asphalt. The analysis of the ion diffusion coefficient reveals that the primary disruption of NaCl crystals in asphalt blends is due to early Cl- and late Na+ diffusion. Furthermore, the rise in shear modulus of the asphalt blends suggests that the salt erosion process of SBS-modified asphalt is advantageous for its high temperature and shear resistance. The changes in peak radial distribution function and radius of gyration indicate that the inclusion of NaCl and SBS into asphalt is a physical aging process. In this case, SBS incorporation acts as a reinforcement to the asphalt to retard the erosion of NaCl.

Increasing planting density increases fruit mass and reduces the dispersal ability of a range‐expanding invasive plant, Mikania micrantha

AbstractAimInvasive plants may evolve a suite of distinctive traits during spread in the new range. Among these traits, dispersal ability is an important trait determining the invasion speed of exotic plants. There is evidence that higher dispersal ability is favoured at the invasion front, where population density may be low. However, no study has explicitly tested how planting density in a common garden affects the dispersal ability of invasive plants.LocationHainan island of China.MethodsIn this study, using 27 populations of an invasive plant, Mikania micrantha, which is expanding its range on Hainan island of China, we examine how three dispersal‐related traits (i.e. dispersal ability, fruit mass, and pappus radius) change with distance from invasion centre and field population density, and how planting density in a common garden affects dispersal traits.ResultsDispersal traits did not change with distance from the invasion centre and field population cover either in the natural environment or in the common garden. In the common garden, increasing planting density from one to five plants per pot increased fruit mass and decreased dispersal ability, indicating that the effect of density on dispersal traits could not be detected in the field. The relationship between dispersal ability in the natural environment and that in the common garden was positive but significant only under the five plants per pot treatment, possibly because dispersal traits in natural conditions were selected under high‐density growth conditions.Main ConclusionsOur results indicate that increasing population density may increase fruit mass and reduce the dispersal ability of range‐expanding invasive plants. We suggest that further studies exploring the patterns of dispersal traits in range‐expanding invasive plants in a common garden should consider intraspecific competition.

Neutron Star in Quantized Space-Time

We construct and analyze a model of a neutron star in a κ-deformed space-time. This is conducted by first deriving the κ-deformed generalization of the Einstein tensor, starting from the non-commutative generalization of the metric tensor. By generalizing the energy-momentum tensor to the non-commutative space-time and exploiting the κ-deformed dispersion relation, we then set up Einstein’s field equations in the κ-deformed space-time. As we adopt a realization of the non-commutative coordinates in terms of the commutative coordinates and their derivatives, our model is constructed in terms of commutative variables. Using this, we derive the κ-deformed generalization of the Tolman–Oppenheimer–Volkoff equation. Now, by treating the interior of the star as a perfect fluid as in the commutative space-time, we investigate the modification of the neutron star’s mass due to the non-commutativity of space-time, valid up to first order in the deformation parameter. We show that the non-commutativity of space-time enhances the mass limit of the neutron star. We show that the radius and maximum mass of the neutron star depend on the deformation parameter. Further, our study shows that the mass increases as the radius increases for fixed values of the deformation parameter. We show that maximum mass and radius increase as the deformation parameter increases. We find that the mass varies from 0.26M⊙ to 3.68M⊙ as the radius changes from 8.45 km to 18.66 km. Using the recent observational limits on the upper bound of the mass of a neutron star, we find the deformation parameter to be |a|∼10−44 m. We also show that the compactness and surface redshift of the neutron star increase with its mass.

Film Thickness Decay and Wear Behavior of Grease-Lubricated Point Contact under Cyclic Variable Loads

For wind turbine applications, there is a cyclic load-varying process between rolling elements and raceways in pitch bearings. This kind of motion can also lead to radial fretting. However, this is seldom addressed under grease-lubricated conditions in the literature. In this study, grease-lubricated point contact problems have been investigated experimentally under cyclic load-varying conditions. The findings revealed that as the load-varying range diminishes, the variation in grease film distribution becomes more subtle and the rate of discharge of thickener fiber clusters in the stick zone decelerates. This is due to the fact that the rate of change in the Hertz contact radius is reduced and the migration of grease is weakened during the unloading process. Due to the large apparent viscosity of grease with a high soap content, entrapped grease is not easily discharged during loading, and the thickness of the film in the stick zone progressively increases as the soap content of the grease is augmented. This also causes the variable load zone to wear out more easily. As the grease is subjected to repeated loading and unloading, there is a gradual reduction in film thickness, and larger thickener fiber clusters tear, resulting in a flattened form and shear thinning. Grease containing sulphur–phosphorus additives demonstrates a superior effect on reducing fretting wear within the large variable load range but generally proves effective for smaller load-varying ranges. This study may offer insights into the degradation of grease under variable load motion and methods to prevent radial fretting wear.

Current driven properties and the associated magnetic domain walls manipulation in U-shaped magnetic nanowires

Based on the extended Landau–Lifshitz–Gilbert method, the properties of current driven domain wall movement in U-shaped magnetic nanowires and the effect of spin wave assistance on their properties have been investigated. The results show that changes of the curvature radius of magnetic nanowire can cause the additional pinning action and the pinning action will weaken the speed of current driven domain wall movement. For U-shaped magnetic nanowires, the changes of curvature radius can be represented by the radius R at the bend. The results show that the decline of its speed non-monotonically increases with the decrease of the bending radius of magnetic nanowires. On the other hand, the assistance of applying spin waves not only enhances the movement of magnetic domain walls but also weakens the pinning action. Further research has shown that applying the appropriate spin waves at the bend changing point can completely eliminate the influence induced by bend changing, in order to ensure uniform and stable movement of current driven magnetic domain walls in U-shaped magnetic nanowires, and achieve the current driven three-dimensional racetrack memory technology.

Evaluation with a Coordinate-Measuring Machine of Dimensional Accuracy of the Abutment Duplication Technique in Cement- Retained Implant Restoration.

To evaluate the effectiveness and accuracy of a proposed duplication technique in terms of one- and three-dimensional discrepancies between an original abutment and polyurethane duplicates obtained through a conventional workflow in single-implant rehabilitation. A titanium, shoulderless abutment was chosen for a single-implant cemented rehabilitation. The master cast was made using a plastic-based die system, and the implant portion was separated. The implant section was consecutively duplicated eight times using a manual technique with polyvinyl siloxane and unfilled polyurethane resin as impression and die materials. The duplicates were analyzed with a coordinate-measuring machine (SmartScope Flash 200, Optical Gaging Products): one- and three- dimensional discrepancies were determined for each duplicate on 20 analysis points (A to T) located on the abutment surface. Changes in the abutment radius were also calculated to estimate the effects on cement thicknesses. One-dimensional discrepancies were -0.5 Å} 61.2 μm, -6.6 Å} 39.7 μm, and -19.4 Å} 47.8 μm on the X, Y, and Z axes, respectively; three-dimensional variation was -66.4 Å} 60.1 μm. Friedman test showed no significant difference between duplicates' one-dimensional variations on X (P = .059), Y (P = .156), or Z (P = .223) axes; a significant difference was found regarding three-dimensional changes (P < .001). Dunn test showed higher discrepancies on the X axis and on the abutment head. Mean variation of the abutment radius was -12.09 μm. The abutment duplication technique was shown to be an accurate and repeatable procedure for single cementable restorations.

Effect of cutting conditions on tool wear and wear mechanism in micro-milling of additively manufactured titanium alloy

This study investigated the effects of different cutting conditions, including dry, flooded, chilled air, and the minimum quantity lubrication (MQL), on cutting forces, burr width, tool wear, and surface roughness using constant cutting parameters. The results showed that the minimum cutting forces were obtained with MQL, while the cutting forces obtained with dry and chilled air were 97% and 80% higher, respectively. During dry cutting, the tool diameter decreased by 3.4%, whereas in MQL and flood cutting, the tool diameter reduction was 2.2%. The minimum corner and edge radius change were achieved in MQL-assisted cutting. At the beginning of the cutting process, the difference between the Sa values obtained for dry and flood cutting was more than 200%, while at the end of the cutting process, this difference was about 140%. It was observed that chilled air has a positive effect on surface roughness. There is an average difference of 21% in burr widths between up and down milling.

Convective flow generated in viscous liquid by isothermal and isoconcentration distribution in crown enclosure with novel aspects of inclined magnetic field

ABSTRACT Combined buoyancy shifts from temperature and concentricity gradients create double-diffusive convection. Complex Crown form enclosure with heat and mass source brings originality and practicality by enhancing use in a broad variety of technical, industrial, and geophysical operations. Current artifact is to explore thermosolutal diffusion in buoyantly driven flowing of viscid liquid contained in a crown enclosure with the installation of a uniformly heated and soluted circular cylinder. Novel physical characteristics of inclining magnetic field are introduced, and distributions affected by cylinder radius change are compared. Dimensionless PDEs are solved numerically using finite elements. Grid independence test ensures simulation mesh level. Hybrid meshing with triangular and rectangular components discretizes domain. Linear interpolating polynomials approximate pressure, whereas quadratic polynomials approach velocity, temperature, and concentricity. PARDISO solves a non-linear system of equations efficiently. Average Nusselt and Sherwood numbers are estimated by comparing relevant parameters to cylinder radius change. Heat transference rate rises to 40% and mass transport upsurges to 60% when radius of cylinder is increased from 0.1 to 0.2. Hartmann number tends to affect a decline in Nusselt and Sherwood quantities. Reduction in thermal and solutal boundary layers near surface of the cylinder is observed against the improve in radius of cylinder.

3D micromechanical modeling of orthogonal hole saw cutting on CFRP composites

In the interest of developing a comprehensive understanding of the drilling process using the hole saw tool, this article aims to build a three-dimensional (3D) micromechanical model representing the orthogonal cutting of CFRP using one tooth of the hole saw tool. For this purpose, a finite element model is developed using Abaqus Explicit code. The influence of various drilling parameters like rake angle, inclination angle and cutting-edge radius on the drilling quality is explored. Especially, chip formation mechanisms, cutting force and lateral damage are analyzed. Through finite element simulations and computational analyses, it is found that these outputs results are highly influenced by drilling parameters. When the fiber orientation angle is set to 0°, increasing the rake angle results in a change in the chip formation mechanism from buckling to bending. In contrast, with a fiber orientation angle of 90°, bending and shear governs the chip formation process, irrespective of the rake angle. In both cases, whether the fiber orientation angle is 0° or 90°, chips tend to fragment more favorably with increasing the inclination angle. Regarding the cutting-edge radius, when the fiber orientation angle is 0°, an increase in the cutting-edge radius leads to a transition in the chip-forming mechanism from buckling to bending. However, for a fiber orientation angle of 90°, the chip formation remains governed by bending even as the cutting-edge radius changes. Decreasing the rake angle, the inclination angle, and the cutting-edge radius contribute to a reduction of the cutting force. As the inclination angle and the cutting-edge radius increase, the lateral damage increases, while the rake angle has showed a negligible impact on the damage. These results provide a guidance on the appropriate hole saw tool parameters for a good drilling quality namely, a rake angle of 20°, an inclination angle of 5° and a cutting-edge radius of 0.03 mm.

Diagnostics of the airless wheel by the combined method

For construction and road machinery, tubeless tires made on the basis of elastic polyurethanes are being used more often. The diagnosis of airless tires made of elastic polymer materials in order to determine the conditions of their safe operation is becoming more and more relevant. The use of roller stands does not give accurate results, because the round support surface of the rollers introduces distortion. A method of obtaining basic parameters and characteristics on simple stands is proposed. Use their values for tire research and diagnostics in software environments such as Ansys, Solidworks, AutoCad. For the designed and manufactured sample of an airless wheel on the stands, the dependences of the change in the static radius of the wheel depending on the load and the change in the deflection of the wheel depending on the lateral force at different loads on the wheel were obtained. They became the basis for the initial parameters and characteristics of the wheel modeled in the Solidworks environment. Its properties were simulated for three cases of wheel rolling: “driven wheel”, “driving wheel” and “free wheel”. The obtained results show that the most difficult mode is the movement of the wheel on the deformable support base. In this mode, the opposite sides of the spokes work in tension and compression when blowing the spokes to a vertical state. The values of stress do not exceed the critical allowable ones during rupture or during compression for polyurethane. Therefore, it can be diagnosed that the wheel is in satisfactory condition.

Impact of the chimney junction radius on the air-flow characteristics inside a solar Chimney Power Plant

The chimney junction of solar chimney power plant was the main element coupled the solar collector to the chimney. It presents an important impact on the SCPP design, which is change the air-flow direction. The numerical code ANSYS Fluent was used in this study to investigate how the chimney Junction radius affected the local air-flow characteristics and the turbine site. Using test results from an experimental prototype constructed in Sfax, Tunisia, the numerical method was validated and verified. For four set-ups with various chimney connection radii, thermodynamic variables such as distributions of the total pressure, static temperature, static pressure, and magnitude velocity were examined. Also, the influence of these parameters on the air turbulence was analyzed through the transition zone. The results showed that the local air-flow characteristics and therefore, the SCPP efficiency were significantly impacted by changes in junction radius. Besides, the maximum velocity inside the chimney was varied and changes its location when the junction radius changed. These facts affect directly the overall turbine expenditure, which represented in terms of structure and power capacity.

The impact of low-velocity shock waves on the dynamic behaviour characteristics of nanobubbles.

Low-velocity shock wave-induced contraction and expansion of nanobubbles can be applied to biocarriers and microfluidic systems. Although experiments have been conducted to study the application effects, the dynamic behavior characteristics of nanobubbles remain unexplored. In this work, we utilize molecular dynamics (MD) simulations to investigate the dynamic behavior characteristics of nanobubbles influenced by low-velocity shock waves in a liquid argon system. The DBSCAN (Density-Based Spatial Clustering of Applications with Noise) machine learning method is used to calculate the equivalent radius of nanobubbles. Two statistical methods are then utilized to predict the time series changes in the equivalent radius of nanobubbles without rebound shock waves. The piston velocity is analyzed using the bisection method to obtain the critical impact states of the nanobubble. The results show that at the low velocity shock wave (piston velocity of 0.1 km s-1), the shock wave pressure is small, the non-vacuum nanobubbles contract and expand in a circular shape, and the gas particles inside the bubble are not dispersed. In contrast, the vacuum nanobubbles collapse directly. As the shock wave rebounds upon impact, it triggers periodic contraction and expansion of the nanobubbles. The predictions indicate that the equivalent radius will vary within a small range according to the pre-predicted values in the absence of the rebound shock wave. Nanobubbles are present in four critical impact states: dispersed gaps, multiple smaller bubbles, two split bubbles, and a concave bubble.

Correlating structural changes in thermoresponsive hydrogels to the optical response of embedded plasmonic nanoparticles.

Stimuli-responsive microgels, composed of small beads with soft, deformable polymer networks swollen through a combination of synthetic control over the polymer and its interaction with water, form a versatile platform for development of multifunctional and biocompatible sensors. The interfacial structural variation of such materials at a nanometer length scale is essential to their function, but not yet fully comprehended. Here, we take advantage of the plasmonic response of a gold nanorod embedded in a thermoresponsive microgel (AuNR@PNIPMAm) to monitor structural changes in the hydrogel directly near the nanorod surface. By direct comparison of the plasmon response against measurements of the hydrogel structure from dynamic light scattering and nuclear magnetic resonance, we find that the microgel shell of batch-polymerized AuNR@PNIPMAm exhibits a heterogeneous volume phase transition reflected by different onset temperatures for changes in the hydrodyanmic radius (RH) and plasmon resonance, respectively. The new approach of contrasting plasmonic response (a measure of local surface hydrogel structure) with RH and relaxation times paves a new path to gain valuable insight for the design of plasmonic sensors based on stimuli-responsive hydrogels.

Microfluidic extensional flow device to study mass transfer dynamics in the polymer microparticle formation process.

Polymer microparticles are often used to encapsulate drugs for sustained drug-release treatments. One of the ways they are manufactured is by using a solvent extraction process, in which the polymer solution is emulsified into an aqueous bulk phase using a surfactant as a stabilizing agent, followed by the removal of the solvent. The radius of a polymer drop decreases as a function of time until the polymer reaches the gelling point, after which it is separated and dried. Among the various operating parameters, the rate of solvent extraction is a critical step that affects the morphology and porosity, and consequently, the kinetics of drug release. But a fundamental mechanistic understanding of the solvent extraction dynamics as a function of shear is still unexplored. In this study, we have developed an experimental mass transfer model to predict the extraction by using the microfluidic extensional flow device (MEFD) to probe the shear and extraction dynamics at the level of a single drop in a linear extensional flow field. We used a computer-controlled feedback algorithm to manipulate the flow field and hydrodynamically trap a Hele-Shaw drop and observe the extraction process. For the polymer solution, we used a biocompatible polymer, poly-lactic-co-glycolic acid (PLGA) with ethyl acetate (EtOAc) as the solvent. Our experiments were conducted by varying the extensional rate (G) in the channel from ∼0.1 s-1 to ∼10 s-1, and using an analytical solution of the flow field, we captured the dissolution process and measured the change in drop radius (R) with time (t). Interestingly, we initially observed a short-time asymptote R ∼ t, and later the long-time asymptote of R = constant; both trends were physically explained. The transport model developed in this work can be used to predict extraction rates and polymer microparticle composition for any polymer-solvent system. This work is also an important contribution to the literature on convective mass transfer in partially miscible emulsions.

Mössbauer spectroscopy and its application to the chemical science

Mössbauer spectroscopy is a powerful tool to investigate the physical and chemical state of the solid material including Mössbauer nuclide. The mechanism of Mössbauer spectroscopy is nuclear energy is shifted and spit by the interaction of the nucleus and its surrounding electrons. Moreover, the hyperfine interaction reveals the chemical phenomena and physical states such as oxidation state, spin state, magnetic state, and nuclear radius change between ground and excited state using. Mössbauer spectroscopy could present basic chemical science including physics and environmental science of materials.

An in-silico approach to identify bioactive phytochemicals from Houttuynia cordata Thunb. As potential inhibitors of human glutathione reductase

Cellular infections are central to the etiology of various diseases, notably cancer and malaria. Counteracting cellular oxidative stress via the inhibition of glutathione reductase (GR) has emerged as a promising therapeutic strategy. Houttuynia cordata, a medicinal plant known for its potent antioxidant properties, has been the focus of our investigation. In this study, we conducted comprehensive in silico analyses involving the phytochemical constituents of H. cordata to identify potential natural GR inhibitors. Our methodological approach encompassed multiple in silico techniques, including molecular docking, molecular dynamics simulations, MMPBSA analysis, and dynamic cross-correlation analysis. Out of 13 docked phytochemicals, Quercetin, Quercitrin, and Sesamin emerged as particularly noteworthy due to their exceptional binding affinities for GR. Notably, our investigation demonstrated that Quercetin and Sesamin exhibited promising outcomes compared to the well-established pharmaceutical agent N-acetylcysteine (NAC). Molecular dynamics analyses provided insights into the ability of these phytochemicals to induce structural compaction and stabilization of the GR protein, as evidenced by changes in radius of gyration and solvent-accessible surface area. Moreover, MMPBSA analysis highlighted the crucial roles of specific residues, namely Gly27, Gly28, Ser51, His52, and Val61, in mediating essential interactions with these phytochemicals. Furthermore, an assessment of Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADME-Tox) profiles underscored the favourable drug-like attributes of these phytochemicals. Thus, the current findings underscore the immense potential of Houttuynia cordata phytochemicals as potent antioxidants with the capacity to combat a spectrum of maladies, including malaria and cancer. This study not only unveils novel therapeutic avenues but also underscores the distinctive outcomes and paramount significance of harnessing H. cordata phytochemicals for their efficacious antioxidant properties. Communicated by Ramaswamy H. Sarma

Protonation reaction at the air/water interface monitored by a bubble Fabry-Perot interferometer

A novel interferometric technique for studies of exothermal chemical reactions at the water surface is presented. The key feature of the technique is the use of an air bubble as the interface which hosts coating molecules and at the same time acts as a subnanometer-sensitive Fabry-Perot interferometer which follows the bubble radius change after a chemical reaction with coating molecules. As an example we report measurements of a protonation reaction with dodecyl-amine (DA). A monolayer of the DA surfactant is formed at the gas-liquid interface of a millimeter-sized bubble immersed in a 10.6 pH solution. After the monolayer formation, the residual DA is removed from the bulk by gentle rinsing. Interference with the DA bulk reaction is avoided. Protonation is induced by HCl injection. The reaction in the thin DA coating layer generates a non-trivial evolution of the bubble radius with amplitude oscillations of the order of 10−3 of the bubble radius with persisting time of a few hundred seconds. Measurements are performed at different DA coverages of the bubble surface, always below the maximum coverage. Control experiments with non-coated bubble show no amplitude radius oscillations. Formation and stability of the DA monolayer are precisely monitored by measurements of the lowest-frequency bubble capillary mode. A possible interpretation of the experiments is given in terms of heat effects, vapor production and surface modification. Molecular Dynamics simulations provide a mechanistic understanding of surface effects triggered by the protonation reaction which promotes desorption of positively charged DA micelles.

A Robust Model-Based Radius Estimation Approach for Helical Climbing Motion of Snake Robots

In this article, a radius estimation approach for snake robot's helical climbing motion is proposed, which enables a snake robot successfully implementing compliant helical climbing along pipes/trees with varying radius. More specifically, a mathematical model is first set up to describe the relationship between the helical rolling gait and the radius information. Based on the model, a robust radius estimation approach, consisting of two important stages of multistep calculation and curve fitting, is then proposed, which utilizes the measurements of joint angles as feedback to generate an accurate estimation for the radius of pipes/trees. Utilizing the estimation result, a control algorithm is then employed to make the robot climb along pipes/trees successfully, even when the radius changes over time. Some experimental results are collected and then analyzed to show the superior performance of the proposed robust model-based radius estimation approach.