Serpentine Curve Research Articles

Two-dimensional obstacle avoidance control algorithm for snake-like robot in water based on immersed boundary-lattice Boltzmann method and improved artificial potential field method

In order to study the adaptability of a multi-redundancy and multi-degree-of-freedom snake-like robot to underwater motion, a two-dimensional (2-D) obstacle avoidance control algorithm for a snake-like robot based on immersed boundary-lattice Boltzmann method (IB-LBM) and improved artificial potential field (APF) is proposed in this paper. Firstly, the non-linear flow field model is established under the framework of LBM, and the IB method is introduced to establish a fluid solid coupling of a 2-D soft snake-like robot. Then, the obstacle avoidance of a snake-like robot in a flow field is realized by optimizing the curvature equation of the serpentine curve and eliminating the local minimum in APF method. Finally, the effects by exerted different control parameters on a snake-like robot’s obstacle avoidance capability are analyzed via MATLAB simulation experiment, by which we can find the optimal parameter of the obstacle avoidance and testify the validity of the proposed control algorithm.

2D Underwater Obstacle Avoidance Control Algorithm Based on IB-LBM and APF Method for a Multi-Joint Snake-Like Robot

In order to study the rapidity and stability of multi-joint snake-like robots in underwater obstacle avoidance, a new underwater obstacle avoidance control algorithm for multi-joint snake-like robots based on the combination of IB-LBM (Immersed Boundary-Lattice Boltzmann Method) and APF (Artificial Potential Field) is proposed in this paper. Firstly, the IB-LBM is used to establish the non-linear flow field model and the fluid-structure coupling model of a multi-joint snake-like robot. Secondly, the 2-D Serpentine curve equation of motions of a multi-joint snake-like robot is improved, and APF method is added to each joint of the robot to control its motion direction, so as to achieve effective obstacle avoidance of the robot in the flow field. Then by MATLAB simulation experiment, influences of different control parameters on obstacle avoidance performance of a multi-joint snake-like robot are analyzed, and the best parameters suitable for obstacle avoidance of a robot are found to improve the rapidity and stability of the whole system. Finally, an underwater obstacle avoidance experiment of a multi-joint snake-like robot is carried out to verify the effectiveness of the proposed control algorithm in real environment.

A new statistical model for the Day Reconstruction Method.

The Day Reconstruction Method (DRM) is a method to measure one's subjective affective status by soliciting information in a questionnaire about the previous day's activities. We developed a new model to examine the association of daily activities, the friendliness of interacting partners, and time-of-day on net affect scores among 10,377 adults participating in the World Health Organization's Study on global ageing and adult health (SAGE). A multilevel regression was fitted and the time-of-day effect was modeled by restricted cubic spline. The net affect score was a serpentine curve; stable from 4a.m. to 6a.m., increased from 7a.m. to 12 noon, and became stable onwards. Participants had the highest net affect scores during religious activities (0.48, 95% confidence interval [CI]: 0.44, 0.53), and they enjoyed leisure activities, exercising, and household responsibilities more than work. Compared with events that lacked interacting partners, activities with very friendly interacting partners were associated with higher net affect scores (0.21, 95% CI: 0.19, 0.22), but events with slightly friendly interacting partners, slightly irritating or very irritating partners had lower net affect scores. To conclude, researchers using DRM for assessing well-being status across time should include the type of activities and the friendliness of the interacting partners.

GS0520 ポンプ水車特性に与えるガイドベーン開度の影響に関する数値シミュレーション

In order to clarify the instability phenomena when the pump-turbine stops in case of necessity, the experiment and the numerical simulation were performed. The past research shows that these phenomena occur when the characteristic curve observed is the serpentine curve. Also, the inlet height and the outlet height of the pump-turbine's runner has no effect on this result. Therefore, this research focuses on how the inlet and blade angle of the guide vanes affects the characteristic curve observed when the blade thickness of pump turbine's runner is changed. Three different inlet and blade angles are used for the experiment and the numerical simulation. As a result, they show that the instability of the pump turbine is decreased by the guide vanes. Besides, the numerical simulation shows the vortex occurs at the trading edge of the runner.

A new hyperchaotic map and its application in an image encryption scheme

Recently, the hyperchaotic maps have been investigated in order to develop more secure encryption schemes. In this paper we propose a new hyperchaotic map derived from parametric equations of the serpentine curve. Its complex behavior was proven theoretically and numerically, using Lyapunov exponents, bifurcation diagram and correlation dimension of the attractor. The proposed map is then used in a new image encryption scheme with a classic bi-modular architecture: a diffusion stage, in which the pixels of the plain image are shuffled using a random permutation generated with a new algorithm, and a confusion stage, in which the pixels are modified with a XOR-scheme based on the proposed map. The results of its statistical analysis show that the proposed image encryption scheme provides an efficient and secure way for image encryption.

Tunable pattern transitions in a liquid-crystal-monomer mixture using two-photon polymerization

Through two-photon lithographic processes, we report experimentally and numerically a series of photoinduced tunable polymerization patterns in shapes from straight channel, serpentine curve, to periodic grating when an ultrashort femtosecond laser pulse directly writes in a liquid-crystal-monomer mixture along a line for different scanning speeds. Laser beams with polarization perpendicular to the direction of writing and the alignment of liquid crystals, produce snake-shaped patterns at an intermediate scan rate.

Flexural Behavior of Prestressed UHPC Beams

Ultra High Performance Concrete (UHPC), which has very special properties that are remarkably different to the properties of normal and high performance concrete, is being increasingly used for the construction of structure. In this paper, an experimental program was formulated to investigate the characteristics of complete stress-strain curve of UHPC in uniaxial compression and flexural behaviors of prestressed UHPC beams. The particular focus was the influence of the partial prestress ratio and jacking stress on the flexural response of UHPC beams. The results show that UHPC is of good deformability, and a general form of the serpentine curve is proposed to represent the complete stress-strain relationship of UHPC in compression. The tests of beams demonstrated that the UHPC beams have an excellent behavior in load carrying capacity, crack distribution and deformability, their ultimate deflection can reach 1/34～1/70 of the span. Based on this investigation, theoretical correlations for the prediction structure response of UHPC beam are proposed.

Closing, and: Clara’s Vision

Closing, and: Clara’s Vision William Reichard (bio) Closing Two rooms away the workman screws down cement board, shores up the porch’s sagging floor. He has the radio on. Next to me, the old cat lies prone, hind legs paralyzed, speaking his last. All I can say in return is Yes, Yes. The radio drones on, all talk. I can’t discern words, just sounds, the cadence of speech familiar, but broken. The old cat’s words are not cries, but statements. Blessed are those graced with the gift of tongues. Yes. Yes. [End Page 131] Clara’s Vision (Appalachian Trail) We drove for hours across terrain I couldn’t recognize; through small towns with landscapes that read: church, church, feed store, church, past ramshackle houses that looked as if they’d been pulled from antique photographs: shoeless children running through yards, old-looking young women working stern-faced on front porches. We arrived near sunset, when the light was gently capping each ridge, cutting the edges of rocks in red, pink, gray. I didn’t know what heaven was, but perhaps this was it: clouds sweeping gravel paths; granite disappearing, then reappearing, in the mist; small peaks poking out of miniature white mountains within mountains. The air was thin. I thought I might faint. You pointed along the serpentine curve of the path and told me it went all the way up to Canada. How far was that? How many lifetimes would it take to traverse that distance? Since I’d met you, I’d only wondered, more and more, how one can come to be saved, I mean truly saved, not the down-on-your-knees, begging to be forgiven saved, but the kind where we each come to know ourselves [End Page 132] —radiance and repulsion aside— just simply to know ourselves. I thought you’d found that and I wanted it too. As the sun set, the path began to fade into an impenetrable darkness. You said we’d hike the trail one day and I believed you. Then, back to the truck for the long ride home. I didn’t know then what heaven was, but I wanted to believe you did. William Reichard William Reichard is the author of four collections of poetry, including Sin Eater and This Brightness (both with Mid-List Press). Reichard is a program director for the Higher Education Consortium for Urban Affairs and lives with his partner, James Cihlar, in Saint Paul, Minnesota. Copyright © 2010 University of Nebraska Press

SU‐FF‐T‐347: Utility of Serpentine Curve for Smoothing and Extrapolating Depth Dose Scans

Purpose: To smooth measured data to a function that will permit well behaved extrapolation beyond the limits of measurement. This is of particular interest in extrapolating typical ion chamber scans of depth dose profiles to surface dose for comparison with other results such as Monte Carlo calculations, extrapolation chambers, film, etc. Method and Materials: The serpentine curve was chosen as a potential function because it has a general shape in the first quadrant that is similar to a photon depth dose curve. However, it cannot be fit to the data with a simple scaling of axes. The method chosen for variable scaling was to convert the measured percent dose at each depth to a serpentine depth value. A polynomial fit of the relationship between serpentine depth and physical depth was obtained from a Microsoft Excel spreadsheet. The depth dose curve was recomputed based on the polynomial conversion of depth to serpentine depth. Results: Depth dose curves ranging from 1×1 to 40×40 cm were analyzed. For extrapolating to surface data up to 5 cm depth was used. Data less than a 5 mm depth was not used to avoid the distortions that occur as the ion chamber becomes only partially rather than fully submerged. Data from 5 cm to 35 cm was separately fit to permit extrapolation to 40 cm depth. The recomputed curves exactly overlay the measured data except for the noise in the measured data and a slight difference at the 5 cm point. They have well behaved extrapolation to surface and deep depth values that compare well with alternate measurements. Conclusion: A variable scaling of depth to serpentine depth yields excellent smoothing of data and yields well behaved extrapolation. It may also serve as a good method of interpolating sparse data.

Sensitive inspection of void defects using synchrotron refraction imaging with quantitative modelling of contrast enhancement

Few techniques are available to assess air inclusions in opaque plastic materials. This study showed a remarkable contrast gain for small air voids by synchrotron radiation imaging with refraction mode: comparing an absorption image, a 60-fold gain in contrast was observed for a 66 µm void. Minimally, a 24 µm inclusion was visualised using a detector with 6 µm × 6 µm resolution. The mechanism of contrast gain for small inclusions on refraction images cannot be explained by X-ray absorption, and X-ray refraction was proposed as its cause. In order to analyse the object-size dependency of contrast, the signal intensity profile due to refracted X-rays at the boundary was fitted by an analytical serpentine curve, which is one of the cubic curves. Calculation showed that signal intensity at the centre of an object increased with the decrease of an object size by the overlapping of X-rays refracted to the inside, and that the increase was steep for objects of 100 µm and smaller. As a conclusion, X-ray refraction produced an extremely high contrast gain for small air voids in synchrotron radiation imaging with refraction mode, and consequently, this imaging will be a sensitive technique for non-destructive detection and mapping of minute air inclusions.

The Normalistic Subject and Its Curves: On the Symbolic Visualization of Orienteering Data

First, a current discursive event that deserves to be called more than simply "molecular": on September 2, 2000, the (Springer) Bildzeitung headlined its issue with a downward-moving grey, white, and red serpentine curve that illustrated the rate of the euro from its beginning at $1.18 to its then current position at $.90. On the curve, three small golden-blue euros, in each of which a crack is forming, roll into the valley of the curve—at the bottom a large euro pathetically explodes into six fragments (after waiting undamaged and predominantly golden at the beginning of its ride in the upper left). The background is pitch black and carries the text: "So many men who introduced it failed in work and life"—and in the large bold print typical for the Bildzeitung: "Curse over the Euro?" Finally, we see four face portraits alongside the curve with block texts like "Shot himself dead;" "4 years imprisonment;" "Corruption, resignation;" and "Agonizing death from cancer." We are dealing with a discursive event to the extent that the Bildzeitung has for a long time resisted the general trend of the German and international print media of disseminating the "normalistic curve-landscape." In the following paper, I would like to follow this landscape with several thoughts. Only very recently did the Bildzeitung begin to publish selected economic data and popularity tests in the form of curves. For decades, other publications regularly disseminated the infographs of the agency Globus Kartendienst or those of other partly homespun productions. Since the 1990s at the latest, [End Page 47] Click for larger view The front page of the famous German "political tabloid" Bild shows the plunge of the euro during the year 2000. It asks: "Curse of the Euro?" showing the photos of four leading politicians committed to the creation of the single European currency who were jailed for corruption, committed suicide, or died. these presses published complex curve-landscapes in all of the economic pages at least, from which they spread out into other columns. Ernst Schulte-Holtey has shown that entirely new media like Focus and Die Woche originated in the nineties in Germany, and were consciously conceived—at least subdominantly—as "publications of curve-landscapes."1 If one inquires about the possible reasons for the reservation of the Bildzeitung, one could cite the traditional credo of many pop journalists more than reasons of cost. These journalists shun all statistics because of their mathematical connotations and because they believe that only large photos of individual people can make possible a heartfelt identification. Since its beginning in 1986, the surprising success of the American illustrated newspaper USA Today shows that this credo cannot certainly be absolute or even generally true: with this publication, we are dealing—very much like Focus and Die Woche—with a distinct publication of curve-landscapes with large infographics like the euro curve. These infographics appear [End Page 48] on the front page of almost every economics section and on many front pages of the general news. Hence, processes of subjective identification can also take place with curves that condense statistical knowledge, an idea that the editorial staff of the Bildzeitung was the last to grasp. Interestingly, this insight could have come through another field entirely, one apparently very far away from economics and politics: in any case, for some time now the Bildzeitung has also subscribed to the trend that originated in the United States of representing the horoscope in the form of a curve. Here, the curve (swinging simply between "+" and "-") shows one's relative degree of "happiness." Such a procedure naturally rests on the presupposition that the "normal" reader already lives "in a curve-form"—that is, the reader perceives its existential feeling like an economic rate between ups and downs. The euro curve is a regression curve, that is, a negative growth...

Analysis of Snake Movement Forms. 2nd Report. Comparison of the locomotive efficiencies for various movement forms of snake creep locomotion.

In this work, we compared the locomotive efficiencies for various creep movement curves of snake locomotion, by analyzing the power density function and the ratio of the tangential force to the mormal force. The results show that the proposed Serpentine curve (S. Ma, JSME Trans., Vol. # 62, No. # 593 (C), pp. # 230-236, 1996) is more valid as the snake creeping locomotion shape than the Clothoid and Serpenoid curves (S. Hirose, Biologically Inspired Robots, Oxford University Press, 1993).

Analysis of Snake Movement Forms. 1st Report. Standard Creep Movement Forms of Snake.

In this paper, we elucidate the standard creep movement forms (S-shaped curve) of a snake, which is the typical locomotive movement shown by snakes. Serpentine curve in the constant steady state velocity and ex-serpentine curve in the constant steady state acceleration are derived for the uniform creep locomotion of the snake, through analyzing physiologically its muscle characteristics, Muscular force is also discussed for these two types uniform locomotive curves. The results proposed here are demonstrated by computer simulation to agree with previously reported experimental results (Y. Umetani and S. Hirose, Trans. of the Society of Instrument and Control Engineers, 10-5 1974, 513-518, in Japanese).