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Last update: August 15, 2014.

1

Lower extremity joint loading during walking is strongly affected by the steepness of the slope and might cause pain and injuries in lower extremity joint structures. One feasible measure to reduce joint loading is the reduction of walking speed. Positive effects have been shown for level walking, but not for graded walking or hiking conditions. The aim of the study

Hermann Schwameder; Elke Lindenhofer; Erich Müller

2005-01-01

2

Join Edgar, the man, and Gigi, the dog on a walk through a wacky cut and paste world filled with drunk clowns, smoking grandmas, and sidewalk preachers. Who knows what may be down the next block, or what lies in store for Gigi and the end of the walk?This animated short was completed using Lightwave 5.6, blending 2D and 3D

2001-01-01

3

Gait abnormalities ... of how a person walks is called the gait. Different types of walking problems occur without a ... Some walking abnormalities have been given names: Propulsive gait -- a stooped, stiff posture with the head and ...

4

... daily activities, get around, and exercise. Having a problem with walking can make daily life more difficult. ... walk is called your gait. A variety of problems can cause an abnormal gait and lead to ...

5

NSDL National Science Digital Library

This site from Illuminations presents a lesson plan that requires students to use a gallery walk to share their mathematical conclusions. A gallery walk allows students to view the work of other students in the class and to explain their own work.

Illuminations

6

Walking Perception by Walking Observers

ERIC Educational Resources Information Center

People frequently analyze the actions of other people for the purpose of action coordination. To understand whether such self-relative action perception differs from other-relative action perception, the authors had observers either compare their own walking speed with that of a point-light walker or compare the walking speeds of 2 point-light…

Jacobs, Alissa; Shiffrar, Maggie

2005-01-01

7

A coyote walking in dry creek bed of streamside scrub vegetation dominated by the native plant, mule fat (Baccharis salidifolia), about 20 days before the fire. In their wildlife research, USGS scientists position camera traps along trails and dry creek beds, places that are likely to be travel rout...

8

ERIC Educational Resources Information Center

This article gives a brief history of fire-walking and then deals with the physics behind fire-walking. The author has performed approximately 50 fire-walks, took the data for the world's hottest fire-walk and was, at one time, a world record holder for the longest fire-walk (www.dwilley.com/HDATLTW/Record_Making_Firewalks.html). He currently…

Willey, David

2010-01-01

9

Walking Wellness. Student Workbook.

ERIC Educational Resources Information Center

This comprehensive student text and workbook, for grades four through eight, contains 16 workshop units focusing on walking field trips, aerobic pacing concepts, walking techniques, nutrition, weight control and healthy life-style planning. Co-ordinated homework assignments are included. The appendixes include 10 tips for walking, a calorie chart,…

Sweetgall, Robert; Neeves, Robert

10

Abstract—Biomechanical,tools were used to assess stability for 11 patients who, following the surgical amputation of one lower limb, required the assistance of a walking frame to ambulate. The Walker Tipping Index (WTI), as derived from the forces applied to the walking frame, was developed specifically for this study to examine the relationship between stability and walking frame height during ambulation,.

A. Barry Deathe; Richard D. Pardo; David A. Winter; Keith C. Hayes; Jennifer Russell-Smyth

11

ERIC Educational Resources Information Center

A generation ago, it was part of growing up for all kids when they biked or walked to school. But in the last 30 years, heavier traffic, wider roads and more dangerous intersections have made it riskier for students walking or pedaling. Today, fewer than 15 percent of kids bike or walk to school compared with more than 50 percent in 1969. In the…

Mason, Nick

2007-01-01

12

NASA Astrophysics Data System (ADS)

We investigate the dynamics of random walks on weighted networks. Assuming that the edge weight and the node strength are used as local information by a random walker. Two kinds of walks, weight-dependent walk and strength-dependent walk, are studied. Exact expressions for stationary distribution and average return time are derived and confirmed by computer simulations. The distribution of average return time and the mean-square displacement are calculated for two walks on the Barrat-Barthélemy-Vespignani (BBV) networks. It is found that a weight-dependent walker can arrive at a new territory more easily than a strength-dependent one.

Wu, An-Cai; Xu, Xin-Jian; Wu, Zhi-Xi; Wang, Ying-Hai

2007-02-01

13

Biomechanical tools were used to assess stability for 11 patients who, following the surgical amputation of one lower limb, required the assistance of a walking frame to ambulate. The Walker Tipping Index (WTI), as derived from the forces applied to the walking frame, was developed specifically for this study to examine the relationship between stability and walking frame height during ambulation. However, the WTI may be useful as a criterion of stability to assist clinicians in their evaluation of walker use in a variety of patient populations. Walker stability was examined as subjects, wearing their prostheses, completed 30-sec walking trials in each of the normal, high, and low walking frame height conditions. Adjusting the height of the walker to one setting (3 cm) above or below normal appears to redistribute the load of walking between the upper and lower extremities without adversely affecting stability. PMID:8868415

Deathe, A B; Pardo, R D; Winter, D A; Hayes, K C; Russell-Smyth, J

1996-02-01

14

The present study focuses on the intricate relationship between human body movement and music, in particular on how music may influence the way humans walk. In an experiment, participants were asked to synchronize their walking tempo with the tempo of musical and metronome stimuli. The walking tempo and walking speed were measured. The tempi of the stimuli varied between 50 and 190 beats per minute. The data revealed that people walk faster on music than on metronome stimuli and that walking on music can be modeled as a resonance phenomenon that is related to the perceptual resonance phenomenon as described by Van Noorden and Moelants (Van Noorden, L., & Moelants, D. (1999). Resonance in the perception of musical pulse. Journal of New Music Research, 28, 43-66). PMID:17910985

Styns, Frederik; van Noorden, Leon; Moelants, Dirk; Leman, Marc

2007-10-01

15

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required: It is possible to design robots that walk in a humanlike manner by providing them with motors to drive every joint and a computer that tells every joint what its angle should be. There are many successful robots of this ilk, but they are very complex and use far more energy than would a walking human. In his Perspective, Alexander discusses a different type of robot inspired by toys that walk passively downhill. These robots have much simpler control systems and use much less energy than conventional walking robots.

R. McNeill Alexander (University of Leeds;School of Biology)

2005-04-01

16

NSDL National Science Digital Library

In this fun group activity involving music and movement, learners are introduced to the idea that many insects walk by using their legs to create "alternating triangles." Learners sing the "Ants Go Marching" song and then study insect specimens. They make models of insects with six legs using Styrofoam and dowels or pencils and brainstorm ideas about how insects walk with all those legs. The most active part of The Bug Walk is when learners, in groups of five, pretend they are an insect's body and simulate an insect's movement. At the end, they discuss what it was like, what problems they had, and ideas for how their walk could have been easier.

Huff, Paula R.

2005-01-01

17

NASA Technical Reports Server (NTRS)

A walking boot assembly particularly suited for use with a positively pressurized spacesuit is presented. A bootie adapted to be secured to the foot of a wearer, an hermetically sealed boot for receiving the bootie having a walking sole, an inner sole, and an upper portion adapted to be attached to an ankle joint of a spacesuit, are also described.

Vykukal, H. C.; Chambers, A. B.; Stjohn, R. H. (inventors)

1977-01-01

18

Localization of Walking Robots

Proper navigation of walking machines in unstructured terrain requires the knowledge of the spatial position and orientation of the robot. There are many approaches for localization of mobile robots in outdoor environment, but their application to walking robots is rather rare. In particular, middle sized robots like LAURON III don’t provide the possibility to carry large or heavy sensors. Due

Bernd Gaßmann; Franziska Zacharias; Johann Marius Zöllner; Rüdiger Dillmann

2005-01-01

19

NSDL National Science Digital Library

The Solar Photon Random Walk Model simulates the path of photons in radiative transport as they escape from the Sun. Photons do not travel in a straight line, but rather collide with larger particles and get redirected. This simulation models that process using a random walk in polar coordinates. The random walk parameters are adjustable to match different models of the structure of the sun, or the user can input their own values. The Solar Photon Random Walk Model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_comp_phys_photon_random_walk.jar file will run the program if Java is installed.

Onken, Ew

2011-07-26

20

Walking patterns in pregnancy.

Women are encouraged to be active before, during and after pregnancy. However, most pregnant women do not engage in sufficient levels of physical activity. For women who experience gestational diabetes mellitus (GDM), physical activity recommendations are part of the standard management. Walking is the most common activity undertaken by women across the lifespan and often recommended by health professionals. Little research specifically exploring the patterns of walking before, during and after pregnancy has been undertaken. This study investigated patterns of walking undertaken by pregnant women, including those who experienced GDM. A sample of convenience was used to recruit pregnant or postpartum women in regional New South Wales, Australia. Women completed a self-report physical activity survey. The survey also included demographic questions, GDM diagnosis and physical activity advice received from health professionals. The respondents were divided into two groups; those with GDM (GDM) and those without GDM (NoGDM). In both groups, walking declined during pregnancy and returned to prepregnancy levels in the postpartum. This decline was similar to the decline observed in leisure-time physical activity. The GDM group walked more than the NoGDM group and a higher percentage of GDM reported being advised to engage in physical activity by health professionals. Even though walking is the most common activity undertaken for women across the lifespan, prepregnancy walking levels do not necessarily continue during pregnancy. Advice from health professionals may assist in maintaining walking levels during pregnancy. Encouraging pregnant women to continue their prepregnancy walking level may be a relatively simple strategy to increase participation in physical activity. PMID:24305070

Doran, Frances M; Buckley, Nellie A

2013-01-01

21

NASA Astrophysics Data System (ADS)

Based on the experience gathered from the walking robot Johnnie the new performance enhanced 25-DoF humanoid robot Lola was built. The goal of this project is to realize a fast, human-like walking. This paper presents different aspects of this complex mechatronic system. Besides the overall lightweight construction, custom build multi-sensory joint drives with high torque brush-less motors were crucial for reaching the performance goal. A decentralized electronics architecture is used for joint control and sensor data processing. A simulation environment serves as a testbed for the walking control, to minimize the risk of damaging the robot hardware during real world experiments.

Schwienbacher, Markus; Favot, Valerio; Buschmann, Thomas; Lohmeier, Sebastian; Ulbrich, Heinz

22

Normal and hemiparetic walking

NASA Astrophysics Data System (ADS)

The idea of a model-based control of rehabilitation for hemiparetic patients requires efficient models of human walking, healthy walking as well as hemiparetic walking. Such models are presented in this paper. They include 42 degrees of freedom and allow especially the evaluation of kinetic magnitudes with the goal to evaluate measures for the hardness of hemiparesis. As far as feasible, the simulations have been compared successfully with measurements, thus improving the confidence level for an application in clinical practice. The paper is mainly based on the dissertation [19].

Pfeiffer, Friedrich; König, Eberhard

2013-01-01

23

Quantum walks with history dependence

We introduce a multi-coin discrete quantum walk where the amplitude for a coin flip depends upon previous tosses. Although the corresponding classical random walk is unbiased, a bias can be introduced into the quantum walk by varying the history dependence. By mixing the biased walk with an unbiased one, the direction of the bias can be reversed leading to a

A P Flitney; D Abbott; N F Johnson

2004-01-01

24

ERIC Educational Resources Information Center

Edmund Peyson Weston's long and remarkable career as the father of walking speaks for the benefits of regular exercise through pedestrian activities and a simple life-style based on a moderate approach to eating and personal habits. (LH)

Matthews, George R.

1979-01-01

25

\\u000a Based on the experience gathered from the walking robot Johnnie the new performance enhanced 25-DoF humanoid robot Lola was built. The goal of this project is to realize a fast, human-like walking. This paper presents different aspects of this\\u000a complex mechatronic system. Besides the overall lightweight construction, custom build multi-sensory joint drives with high\\u000a torque brush-less motors were crucial for

Markus Schwienbacher; Valerio Favot; Thomas Buschmann; Sebastian Lohmeier; Heinz Ulbrich

2009-01-01

26

Walking School Bus Networks: A \\

Summary A Walking School Bus (WSB) is an alternative method for children to travel to and from school. Adult volunteers walk a set route to school, collecting children from designated stops along the way. In 2000, we trialed WSB \\

Carolyn O'Fallon; Charles Sullivan; Paul Cottam

27

Removing measurements from quantum walks

NASA Astrophysics Data System (ADS)

Quantum walks are very useful tools in designing quantum algorithms. Amplitude amplification is a key technique to increase the success probability of a quantum-walk-based algorithm, and it is quadratically faster than classical probabilistic amplification. However, amplitude amplification only applies to quantum walks with one-shot hitting time, where no measurements except a final one are performed, and not to quantum walks with concurrent hitting time, where measurements happen or absorbing boundaries exist at each step. In this paper, we propose a procedure to modify quantum walks with concurrent hitting time by removing measurements from them. This procedure enables us to use amplitude amplification to design algorithms based on the modified quantum walks which are faster than those based on the original walks with a concurrent hitting time and more robust than those based on the corresponding walks with a one-shot hitting time.

Ying, Shenggang; Ying, Mingsheng

2013-01-01

28

ERIC Educational Resources Information Center

Fay and Sam go for a walk. Sam walks along the left side of the street while Fay, who walks faster, starts with Sam but walks to a point on the right side of the street and then returns to meet Sam to complete one segment of their journey. We determine Fay's optimal path minimizing segment length, and thus maximizing the number of times they meet…

Bailey, Herb; Kalman, Dan

2011-01-01

29

Connectedness of random walk segmentation.

Connectedness of random walk segmentation is examined, and novel properties are discovered, by considering electrical circuits equivalent to random walks. A theoretical analysis shows that earlier conclusions concerning connectedness of random walk segmentation results are incorrect, and counterexamples are demonstrated. PMID:20714017

Cheng, Ming-Ming; Zhang, Guo-Xin

2011-01-01

30

Gait Evaluation of Overground Walking and Treadmill Walking Using Compass-Type Walking Model

NASA Astrophysics Data System (ADS)

A treadmill is a useful apparatus for the gait training and evaluation. However, many differences are reported between treadmill and overground walking. Experimental comparisons of the muscle activity of the leg and the heart rate have been carried out. However, the dynamic comparison has not been performed. The dynamic evaluation of the overground walking and the treadmill walking using a compass-type walking model (CTWM) which is a simple bipedal walking model, then their comparison is discussed. It is confirmed that the walking simulation using the CTWM can simulate the difference of that walk, it is clarified that there are the differences of the kick impulse on the ground and the turning impulse of the foot to the variation of the belt speed and then differences are the main factor of two walking.

Nagata, Yousuke; Yamamoto, Masayoshi; Funabiki, Shigeyuki

31

NSDL National Science Digital Library

This resource consists of a Java applet and descriptive text. The applet illustrates a random walk on a discrete time interval from 0 to n. The time n and the probability of a step to the right can be varied. The random variables of interest are the final position, the maximum position, and the time of the last zero.

Siegrist, Kyle

32

ERIC Educational Resources Information Center

In the Walking Out Graphs Lesson described here, students experience several types of representations used to describe motion, including words, sentences, equations, graphs, data tables, and actions. The most important theme of this lesson is that students have to understand the consistency among these representations and form the habit of…

Shen, Ji

2009-01-01

33

ERIC Educational Resources Information Center

Exploration of a specific use of Text Based Virtual Reality--not just as powerful communities for authentic communication and collaboration in language learning but exploiting role-playing and writing aspects. The "Walk on Ice" takes a group of adult English-as-a-Second-Language learners through the creation of imaginary characters who interact in…

Turner, Jane

1998-01-01

34

ERIC Educational Resources Information Center

Physical models in the classroom "cannot be expected to represent the full-scale phenomenon with complete accuracy, not even in the limited set of characteristics being studied" (AAAS 1990). Therefore, by modifying a popular classroom activity called a "planet walk," teachers can explore upper elementary students' current understandings; create an…

Schuster, Dwight

2008-01-01

35

Walking lessons from orangutans

NSDL National Science Digital Library

A group of scientists in the United Kingdom now have a different idea of how we came to walk on two legs. They got their idea from watching wild orangutans, who spend almost their whole lives in the trees of the rainforest.

American Association for the Advancement of Science (AAAS;)

2007-06-01

36

10 CFR 431.302 - Definitions concerning walk-in coolers and walk-in freezers.

Code of Federal Regulations, 2010 CFR

...concerning walk-in coolers and walk-in freezers. 431.302 Section 431.302... Walk-in Coolers and Walk-in Freezers Â§ 431.302 Definitions concerning walk-in coolers and walk-in freezers. Walk-in cooler and...

2010-01-01

37

[Walking abnormalities in children].

Walking is a spontaneous movement termed locomotion that is promoted by activation of antigravity muscles by serotonergic (5HT) neurons. Development of antigravity activity follows 3 developmental epochs of the sleep-wake (S-W) cycle and is modulated by particular 5HT neurons in each epoch. Activation of antigravity activities occurs in the first epoch (around the age of 3 to 4 months) as restriction of atonia in rapid eye movement (REM) stage and development of circadian S-W cycle. These activities strengthen in the second epoch, with modulation of day-time sleep and induction of crawling around the age of 8 months and induction of walking by 1 year. Around the age of 1 year 6 months, absence of guarded walking and interlimb cordination is observed along with modulation of day-time sleep to once in the afternoon. Bipedal walking in upright position occurs in the third epoch, with development of a biphasic S-W cycle by the age of 4-5 years. Patients with infantile autism (IA), Rett syndrome (RTT), or Tourette syndrome (TS) show failure in the development of the first, second, or third epoch, respectively. Patients with IA fail to develop interlimb coordination; those with RTT, crawling and walking; and those with TS, walking in upright posture. Basic pathophysiology underlying these condition is failure in restricting atonia in REM stage; this induces dysfunction of the pedunculopontine nucleus and consequently dys- or hypofunction of the dopamine (DA) neurons. DA hypofunction in the developing brain, associated with compensatory upward regulation of the DA receptors causes psychobehavioral disorders in infancy (IA), failure in synaptogenesis in the frontal cortex and functional development of the motor and associate cortexes in late infancy through the basal ganglia (RTT), and failure in functional development of the prefrontal cortex through the basal ganglia (TS). Further, locomotion failure in early childhood causes failure in development of functional specialization of the cortex through the spinal stepping generator-fastigial nucleus-thalamus-cortex pathway. Early detection of locomotion failure and early adjustment of this condition through environmental factors can prevent the development of higher cortical dysfunction. PMID:21068458

Segawa, Masaya

2010-11-01

38

NSDL National Science Digital Library

The famous Walking Tour series on WNET, New York's public television station went to Newark, New Jersey, for the first tour outside of New York. Visitors who missed the show, or prefer a more interactive experience, will definitely enjoy the walking tour via the website. The two hosts of the tour, historian Barry Lewis, and former morning show host David Hartman, give visitors a multimedia tour which starts with a video clip in the "About the Program" link. Visitors will find that the "History of Newark" link is divided into four time periods, including "Colonial Founding", "Industrial Revolution", and "The Riots". The "See the Sites" link offers a more interactive approach for visitors to get to know Newark. There are 360-degree virtual tours of "Penn Station Newark", "Trinity Church" and "Military Park" on the left hand side of the page, and a map with 21 hotspots on it of Newark's "best landmarks and areas".

39

Relativistic Weierstrass random walks.

The Weierstrass random walk is a paradigmatic Markov chain giving rise to a Lévy-type superdiffusive behavior. It is well known that special relativity prevents the arbitrarily high velocities necessary to establish a superdiffusive behavior in any process occurring in Minkowski spacetime, implying, in particular, that any relativistic Markov chain describing spacetime phenomena must be essentially Gaussian. Here, we introduce a simple relativistic extension of the Weierstrass random walk and show that there must exist a transition time t{c} delimiting two qualitative distinct dynamical regimes: the (nonrelativistic) superdiffusive Lévy flights, for t

Saa, Alberto; Venegeroles, Roberto

2010-08-01

40

Relativistic Weierstrass random walks

NASA Astrophysics Data System (ADS)

The Weierstrass random walk is a paradigmatic Markov chain giving rise to a Lévy-type superdiffusive behavior. It is well known that special relativity prevents the arbitrarily high velocities necessary to establish a superdiffusive behavior in any process occurring in Minkowski spacetime, implying, in particular, that any relativistic Markov chain describing spacetime phenomena must be essentially Gaussian. Here, we introduce a simple relativistic extension of the Weierstrass random walk and show that there must exist a transition time tc delimiting two qualitative distinct dynamical regimes: the (nonrelativistic) superdiffusive Lévy flights, for t

Saa, Alberto; Venegeroles, Roberto

2010-08-01

41

NSDL National Science Digital Library

Artist Bob Miller's "Light Walk" at the Exploratorium is always an eye-opening experience for students and teachers alike. His unique discoveries will change the way you look at light, shadow, and images. The author includes activities such as doing your own lightwalk, building a pinhole viewer, building a pinhole camera, and slide projector activities. The author also provides an additional bibliography that is accompanied by reading materials. External links to related internet resources are also provided.

Miller, Bob

2009-05-12

42

Selection pressures give composite correlated random walks Lévy walk characteristics.

Composite correlated random walks have been posited as a strong alternative to Lévy walks as models of multi-scale forager movement patterns. Here it is shown that if plastic then intrinsic composite correlated random walks will, under selection pressures, evolve to resemble optimal Lévy walks when foraging is non-destructive. The fittest composite correlated random walkers are found to be those that come closest to being optimal Lévy walkers. This may explain why such a diverse range of foragers have movement patterns that can be approximated by optimal Lévy walks and shows that the 'Lévy-flight foraging' hypothesis has a broad hinterland. The new findings are consistent with recent observations of mussels Mytilus edulis and the Australian desert ant Melophorus bagoti which suggest that animals approximate a Lévy walk by adopting an intrinsic composite movement strategy with different modes. PMID:23665359

Reynolds, A M

2013-09-01

43

Biomechanics of walking with snowshoes

Snowshoeing is a popular form of winter recreation due to the development of lightweight snowshoes that provide flotation, traction, and stability. The purpose of this study was to determine the effects of snowshoes on lower extremity kinematics during level walking. Twelve adults (6 males, 6 females, body mass = 67.5 ± 10.7 kg) completed six 3-minute level walking trials. Subjects walked overground without snowshoes and

Raymond C. Browning; Rebecca N. Kurtz; Hugo Kerherve

2012-01-01

44

Biomechanics of walking with snowshoes

Snowshoeing is a popular form of winter recreation due to the development of lightweight snowshoes that provide flotation, traction, and stability. The purpose of this study was to determine the effects of snowshoes on lower extremity kinematics during level walking. Twelve adults (6 males, 6 females, body mass = 67.5 ± 10.7 kg) completed six 3-minute level walking trials. Subjects walked overground without snowshoes and

Raymond C. Browning; Rebecca N. Kurtz; Hugo Kerherve

2011-01-01

45

Persistence of random walk records

NASA Astrophysics Data System (ADS)

We study records generated by Brownian particles in one dimension. Specifically, we investigate an ordinary random walk and define the record as the maximal position of the walk. We compare the record of an individual random walk with the mean record, obtained as an average over infinitely many realizations. We term the walk ‘superior’ if the record is always above average, and conversely, the walk is said to be ‘inferior’ if the record is always below average. We find that the fraction of superior walks, S, decays algebraically with time, S ? t??, in the limit t ? ?, and that the persistence exponent is nontrivial, ? = 0.382?258…. The fraction of inferior walks, I, also decays as a power law, I ? t??, but the persistence exponent is smaller, ? = 0.241?608…. Both exponents are roots of transcendental equations involving the parabolic cylinder function. To obtain these theoretical results, we analyze the joint density of superior walks with a given record and position, while for inferior walks it suffices to study the density as a function of position.

Ben-Naim, E.; Krapivsky, P. L.

2014-06-01

46

NSDL National Science Digital Library

The Physics Laboratory of the National Institute of Standards and Technology (NIST) provides A Walk Through Time, a site devoted to examining the question of how humans have measured time throughout history. In one example, Egyptians created the first timepiece (shadow clock or sundial) in the approximate year of 1500 BC to measure "hours." Nowadays, the Physics Laboratory develops and operates the "standards of time and frequency and coordinates them with other world standards." Those interested in timekeeping methods and an historical perspective on the evolution of time measurement will find this site fascinating.

47

NASA Technical Reports Server (NTRS)

Proposed agile walking robot operates over rocky, sandy, and sloping terrain. Offers stability and climbing ability superior to other conceptual mobile robots. Equipped with six articulated legs like those of insect, continually feels ground under leg before applying weight to it. If leg sensed unexpected object or failed to make contact with ground at expected point, seeks alternative position within radius of 20 cm. Failing that, robot halts, examines area around foot in detail with laser ranging imager, and replans entire cycle of steps for all legs before proceeding.

Larimer, Stanley J.; Lisec, Thomas R.; Spiessbach, Andrew J.; Waldron, Kenneth J.

1990-01-01

48

NASA Technical Reports Server (NTRS)

Proposed walking-beam robot simpler and more rugged than articulated-leg walkers. Requires less data processing, and uses power more efficiently. Includes pair of tripods, one nested in other. Inner tripod holds power supplies, communication equipment, computers, instrumentation, sampling arms, and articulated sensor turrets. Outer tripod holds mast on which antennas for communication with remote control site and video cameras for viewing local and distant terrain mounted. Propels itself by raising, translating, and lowering tripods in alternation. Steers itself by rotating raised tripod on turntable.

Larimer, Stanley J.; Lisec, Thomas R.; Spiessbach, Andrew J.

1990-01-01

49

Nonreversal and nonrepeating quantum walks

NASA Astrophysics Data System (ADS)

We introduce a variation of the discrete-time quantum walk, the nonreversal quantum walk, which does not step back onto a position that it has just occupied. This allows us to simulate a dimer and we achieve it by introducing a different type of coin operator. The nonrepeating walk, which never moves in the same direction in consecutive time steps, arises by a permutation of this coin operator. We describe the basic properties of both walks and prove that the even-order joint moments of the nonrepeating walker are independent of the initial condition, being determined by five parameters derived from the coin instead. Numerical evidence suggests that the same is the case for the nonreversal walk. This contrasts strongly with previously studied coins, such as the Grover operator, where the initial condition can be used to control the standard deviation of the walker.

Proctor, T. J.; Barr, K. E.; Hanson, B.; Martiel, S.; Pavlovi?, V.; Bullivant, A.; Kendon, V. M.

2014-04-01

50

Quantum walks on quotient graphs

A discrete-time quantum walk on a graph {gamma} is the repeated application of a unitary evolution operator to a Hilbert space corresponding to the graph. If this unitary evolution operator has an associated group of symmetries, then for certain initial states the walk will be confined to a subspace of the original Hilbert space. Symmetries of the original graph, given by its automorphism group, can be inherited by the evolution operator. We show that a quantum walk confined to the subspace corresponding to this symmetry group can be seen as a different quantum walk on a smaller quotient graph. We give an explicit construction of the quotient graph for any subgroup H of the automorphism group and illustrate it with examples. The automorphisms of the quotient graph which are inherited from the original graph are the original automorphism group modulo the subgroup H used to construct it. The quotient graph is constructed by removing the symmetries of the subgroup H from the original graph. We then analyze the behavior of hitting times on quotient graphs. Hitting time is the average time it takes a walk to reach a given final vertex from a given initial vertex. It has been shown in earlier work [Phys. Rev. A 74, 042334 (2006)] that the hitting time for certain initial states of a quantum walks can be infinite, in contrast to classical random walks. We give a condition which determines whether the quotient graph has infinite hitting times given that they exist in the original graph. We apply this condition for the examples discussed and determine which quotient graphs have infinite hitting times. All known examples of quantum walks with hitting times which are short compared to classical random walks correspond to systems with quotient graphs much smaller than the original graph; we conjecture that the existence of a small quotient graph with finite hitting times is necessary for a walk to exhibit a quantum speedup.

Krovi, Hari; Brun, Todd A. [Communication Sciences Institute, University of Southern California, Los Angeles, California 90089 (United States)

2007-06-15

51

NASA Astrophysics Data System (ADS)

We propose a new model of slow-roll inflation in string cosmology, based on warped throat supergravity solutions displaying 'walking' dynamics, i.e. the coupling constant of the dual gauge theory slowly varies over a range of energy scales. The features of the throat geometry are sourced by a rich field content, given by the dilaton and RR and NS fluxes. By considering the motion of a D3-brane probe in this geometry, we are able to analytically calculate the brane potential in a physically interesting regime. This potential has an inflection point: in its proximity we realize a model of inflation lasting sixty e-foldings, and whose robust predictions are in agreement with current observations. We are also able to interpret some of the most interesting aspects of this scenario in terms of the properties of the QFT dual theory.

Erdmenger, Johanna; Halter, Sebastian; Núñez, Carlos; Tasinato, Gianmassimo

2013-01-01

52

Constraining walking and custodial technicolor

We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level - custodial technicolor - and argue that these models cannot emerge from walking-type dynamics. We suggest that it is possible to have a very light spin-one axial (vector) boson. However, in the walking dynamics the associated vector boson is heavy while it is degenerate with the axial in custodial technicolor.

Foadi, Roshan; Frandsen, Mads T.; Sannino, Francesco [University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark); Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

2008-05-01

53

Walking Dynamics from String Duals

NASA Astrophysics Data System (ADS)

A large class of solutions of the background equations for a specific system of D5-branes shows many of the properties of a walking theory. The gauge coupling is almost constant over an intermediate range of energies, the coupling is strong, the theory confines, a condensate forms. We study the Wilson loops and the spectrum of scalar glueballs in these backgrounds, finding quite surprising results. This model, and possibly its extensions, provide a suitable laboratory in which to study the (strongly coupled) properties of walking dynamics, which lies at the core of walking technicolor. Note from Publisher: This article contains the abstract only.

Piai, Maurizio

2011-01-01

54

Physiological responses to nordic walking, walking and jogging

The goal of this study was to evaluate the physiological responses during incremental field tests (FT) in nordic walking (NW), walking (W) and jogging (J). Fifteen healthy middle-aged women participated in three FT. Heart rate (HR) and oxygen uptake \\u000a$${\\\\left( {\\\\ifmmode\\\\expandafter\\\\dot\\\\else\\\\expandafter\\\\.\\\\fi{V}{\\\\text{O}}_{2} } \\\\right)}\\u000a$$ were monitored continuously by portable analyzers. Capillary blood lactate (La) was analyzed at rest and after

Thorsten Schiffer; Axel Knicker; Uwe Hoffman; Brigitte Harwig; Wildor Hollmann; Heiko K. Strüder

2006-01-01

55

Analysis of absorbing times of quantum walks

Quantum walks are expected to provide useful algorithmic tools for quantum computation. This paper introduces absorbing probability and time of quantum walks and gives both numerical simulation results and theoretical analyses on Hadamard walks on the line and symmetric walks on the hypercube from the viewpoint of absorbing probability and time.

Tomohiro Yamasaki; Hirotada Kobayashi; Hiroshi Imai

2003-01-01

56

The excited random walk in one dimension

We study the excited random walk, in which a walk that is at a site that contains cookies eats one cookie and then hops to the right with probability p and to the left with probability q = 1 - p. If the walk hops onto an empty site, there is no bias. For the 1-excited walk on the half-line

Tibor Antal; S. Redner

2005-01-01

57

Qualitative Hybrid Control of Dynamic Bipedal Walking

We present a qualitative approach to the dynamical control of bipedal walking that allows us to combine the benefits of passive dynamic walkers with the ability to walk on uneven terrain. We demonstrate an online control strategy, synthesizing a stable walking gait along a sequence of irregularly spaced stepping stones. The passive dynamic walking paradigm has begun to establish itself

Subramanian Ramamoorthy; Benjamin Kuipers

2006-01-01

58

Neuronal control of Drosophila walking direction.

Most land animals normally walk forward but switch to backward walking upon sensing an obstacle or danger in the path ahead. A change in walking direction is likely to be triggered by descending "command" neurons from the brain that act upon local motor circuits to alter the timing of leg muscle activation. Here we identify descending neurons for backward walking in Drosophila--the MDN neurons. MDN activity is required for flies to walk backward when they encounter an impassable barrier and is sufficient to trigger backward walking under conditions in which flies would otherwise walk forward. We also identify ascending neurons, MAN, that promote persistent backward walking, possibly by inhibiting forward walking. These findings provide an initial glimpse into the circuits and logic that control walking direction in Drosophila. PMID:24700860

Bidaye, Salil S; Machacek, Christian; Wu, Yang; Dickson, Barry J

2014-04-01

59

Train to improve your lung, heart, and other muscle endurance while walking a progressive, measured distance. The Train Like an Astronaut project uses the excitement of exploration to challenge stu...

60

I introduce a continuous-time quantum walk on graphs called the quantum snake walk, the basis states of which are fixed-length paths (snakes) in the underlying graph. First, I analyze the quantum snake walk on the line, and I show that, even though most states stay localized throughout the evolution, there are specific states that most likely move on the line as wave packets with momentum inversely proportional to the length of the snake. Next, I discuss how an algorithm based on the quantum snake walk might potentially be able to solve an extended version of the glued trees problem, which asks to find a path connecting both roots of the glued trees graph. To the best of my knowledge, no efficient quantum algorithm solving this problem is known yet.

Rosmanis, Ansis [David R. Cheriton School of Computer Science and Institute for Quantum Computing, University of Waterloo, West Waterloo, Ontario, N2L 3G1 (Canada)

2011-02-15

61

... You don’t have to worry about walking miles and miles. Slow and steady wins the race! Wear the ... provider about your medications, symptoms, and health problems. Last Updated March 2006 © 2014 Health in Aging. All ...

62

Gallery Walk Questions on Karst

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about karst. The questions are organized according to the cognitive level at ...

63

Gallery Walk Questions on Rivers

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about rivers. The questions are organized according to the cognitive level ...

64

Correlated continuous time random walks

Continuous time random walks impose a random waiting time before each particle jump. Scaling limits of heavy-tailed continuous time random walks are governed by fractional evolution equations. Space-fractional derivatives describe heavy-tailed jumps, and the time-fractional version codes heavy-tailed waiting times. This paper develops scaling limits and governing equations in the case of correlated jumps. For long-range dependent jumps, this leads

Mark M. Meerschaert; Erkan Nane; Yimin Xiao

2009-01-01

65

Aging continuous time random walks

We investigate biased and nonbiased aging continuous time random walks (ACTRW), using fractal renewal theory. For example, a biased ACTRW process describes a Montroll-Weiss CTRW process which starts at time -ta and then at time t=0 a bias is added to the random walk (i.e., an external field is switched on). Statistical behaviors of the displacement of the random walker

Eli Barkai; Yuan-Chung Cheng

2003-01-01

66

Walking technipions at the LHC

NASA Astrophysics Data System (ADS)

We calculate technipion masses of the walking technicolor by explicitly evaluating nontrivial contributions from various possible chiral breaking sources in a concrete walking technicolor setting of the one-family model. Our explicit computation of the mass and the coupling in this concrete model setting reveals that the technipions are on the order of several hundred GeV in the region to be discovered at the LHC.

Jia, Junji; Matsuzaki, Shinya; Yamawaki, Koichi

2013-01-01

67

We analyze the potential of the Large Hadron Collider (LHC) to observe signatures of phenomenologically viable walking technicolor models. We study and compare the Drell-Yan and vector boson fusion mechanisms for the production of composite heavy vectors. We find that the heavy vectors are most easily produced and detected via the Drell-Yan processes. The composite Higgs phenomenology is also studied. If technicolor walks at the LHC, its footprints will be visible and our analysis will help in uncovering them.

Belyaev, Alexander; Foadi, Roshan; Frandsen, Mads T.; Jaervinen, Matti; Sannino, Francesco; Pukhov, Alexander [NExT Institute: School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, United Kingdom, and Particle Physics Department, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); High Energy Physics Center, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark); Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow 119992 (Russian Federation)

2009-02-01

68

Constraining walking and custodial technicolor

We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level---custodial technicolor---and argue that these models cannot emerge from walking-type dynamics. We suggest that it is possible to have a very light spin-one axial

Roshan Foadi; Mads T. Frandsen; Francesco Sannino

2008-01-01

69

Walkable Environments and Walking Activity

People who walk for transportation or pleasure face many challenges in the physical environment. Many people in the U.S. want to walk for utilitarian, health, or recreation purposes, but are discouraged from doing so, in part, by a lack of pedestrian facilities, an auto-dominated infrastructure (e.g., multi-lane roads that separate activity centers), and threats to their safety. While facilities for

Elizabeth Shay; Steven C. Spoon; Asad J. Khattak

70

Random walk through fractal environments.

We analyze random walk through fractal environments, embedded in three-dimensional, permeable space. Particles travel freely and are scattered off into random directions when they hit the fractal. The statistical distribution of the flight increments (i.e., of the displacements between two consecutive hittings) is analytically derived from a common, practical definition of fractal dimension, and it turns out to approximate quite well a power-law in the case where the dimension D(F) of the fractal is less than 2, there is though, always a finite rate of unaffected escape. Random walks through fractal sets with D(F)< or =2 can thus be considered as defective Levy walks. The distribution of jump increments for D(F)>2 is decaying exponentially. The diffusive behavior of the random walk is analyzed in the frame of continuous time random walk, which we generalize to include the case of defective distributions of walk increments. It is shown that the particles undergo anomalous, enhanced diffusion for D(F)<2, the diffusion is dominated by the finite escape rate. Diffusion for D(F)>2 is normal for large times, enhanced though for small and intermediate times. In particular, it follows that fractals generated by a particular class of self-organized criticality models give rise to enhanced diffusion. The analytical results are illustrated by Monte Carlo simulations. PMID:12636828

Isliker, H; Vlahos, L

2003-02-01

71

Quantum walks based on an interferometric analogy

There are presently two models for quantum walks on graphs. The ''coined'' walk uses discrete-time steps, and contains, besides the particle making the walk, a second quantum system, the coin, that determines the direction in which the particle will move. The continuous walk operates with continuous time. Here a third model for quantum walks is proposed, which is based on an analogy to optical interferometers. It is a discrete-time model, and the unitary operator that advances the walk one step depends only on the local structure of the graph on which the walk is taking place. This type of walk also allows us to introduce elements, such as phase shifters, that have no counterpart in classical random walks. Several examples are discussed.

Hillery, Mark; Bergou, Janos [Department of Physics, Hunter College of CUNY, 695 Park Avenue, New York, New York 10021, USA (United States); Feldman, Edgar [Department of Mathematics, Graduate Center of the City University of New York, 365 Fifth Avenue, New York, New York 10016, USA (United States)

2003-09-01

72

Characterizing walking activity in people with stroke.

Stroke is the leading cause of disability in the U.S. Many people with stroke have limited walking ability and are inactive. In this paper we describe a novel shoe based sensor, SmartShoe, and a signal processing technique to identify walking activity. The technique was validated with 6 people with walking impairment due to stroke. The results suggest that the SmartShoe is able to accurately identify walking activity. This device could be used to monitor walking activity as well as provide behavioral enhancing feedback to increase activity levels and walking ability in people with stroke for extended periods of time in the real world. PMID:22255512

Fulk, George D; Lopez-Meyer, Paulo; Sazonov, Edward S

2011-01-01

73

Mechanical design of walking machines.

The performance of existing actuators, such as electric motors, is very limited, be it power-weight ratio or energy efficiency. In this paper, we discuss the method to design a practical walking machine under this severe constraint with focus on two concepts, the gravitationally decoupled actuation (GDA) and the coupled drive. The GDA decouples the driving system against the gravitational field to suppress generation of negative power and improve energy efficiency. On the other hand, the coupled drive couples the driving system to distribute the output power equally among actuators and maximize the utilization of installed actuator power. First, we depict the GDA and coupled drive in detail. Then, we present actual machines, TITAN-III and VIII, quadruped walking machines designed on the basis of the GDA, and NINJA-I and II, quadruped wall walking machines designed on the basis of the coupled drive. Finally, we discuss walking machines that travel on three-dimensional terrain (3D terrain), which includes the ground, walls and ceiling. Then, we demonstrate with computer simulation that we can selectively leverage GDA and coupled drive by walking posture control. PMID:17148055

Arikawa, Keisuke; Hirose, Shigeo

2007-01-15

74

Noisy continuous time random walks.

Experimental studies of the diffusion of biomolecules within biological cells are routinely confronted with multiple sources of stochasticity, whose identification renders the detailed data analysis of single molecule trajectories quite intricate. Here, we consider subdiffusive continuous time random walks that represent a seminal model for the anomalous diffusion of tracer particles in complex environments. This motion is characterized by multiple trapping events with infinite mean sojourn time. In real physical situations, however, instead of the full immobilization predicted by the continuous time random walk model, the motion of the tracer particle shows additional jiggling, for instance, due to thermal agitation of the environment. We here present and analyze in detail an extension of the continuous time random walk model. Superimposing the multiple trapping behavior with additive Gaussian noise of variable strength, we demonstrate that the resulting process exhibits a rich variety of apparent dynamic regimes. In particular, such noisy continuous time random walks may appear ergodic, while the bare continuous time random walk exhibits weak ergodicity breaking. Detailed knowledge of this behavior will be useful for the truthful physical analysis of experimentally observed subdiffusion. PMID:24089728

Jeon, Jae-Hyung; Barkai, Eli; Metzler, Ralf

2013-09-28

75

NSDL National Science Digital Library

Each student has been given a packet of information on an energy topic. There are two articles that all the students will receive, on energy conservation and addiction to oil, and then several others on their specific topic. Each student will be instructed to become the classroom expert on their specific topic by reading the articles and being invited to look up more information. These steps are modified from Step by Step Instructions for Gallery Walk I learned this technique at a Cutting Edge workshop put on by the National Association of Geoscience Teachers called Designing Innovative and Effective Geoscience Courses in the summer of 2008. The steps to this lesson are: I have generated a list of questions around energy. The questions will be written on poster-sized paper, one question to each sheet. The questions will be posted in a foyer area. The students have been given general directions in the previous class, and more specific directions will be given the day of the event. The students have been prepared by reading packets of energy information, as described above in this document. They have also been advised on how the grading rubric and feedback will be used. The students will be put into groups of two, because the class is so small. Each group will have a different colored marker. If the groups were larger, roles would be assigned, like recorder, speaker, emissary, etc... That won't work with this small class. We will begin the gallery walk. Each team will start at a different chart, read the question, talk to each other, then document their response in their colored ink. They will be encouraged to write in a pithy bulleted format closest to the top of the chart. The teams will rotate to a new station after a period of time (to be determined!) They will rotate clockwise. Arriving at a new station, the students will read the question, the responses of the other groups who posted before them, and add their comments, sort of like a BLOG. The groups can switch recorders at each station to keep all members involved. I will monitor the students' progress. I may have to intervene to clarify a point or direct the students to think of something they may have overlooked. I will wander between groups, listening in, and asking "Socratic" guiding questions if needed. Once all groups have responded to all the posters, they can return to posters to read the other postings, and even add to their own comments. After the rotations and comment period, students will "report out", which each group synthesizes the comments for each question into a summary. The groups will then take turns making oral reports on the questions at hand. I may decide to have them do a written report instead, so that they create a document to refer to later in the course. I will be gauging student understanding throughout the report stage, to reinforce correctly expressed concepts and correct for errors or misconceptions. The questions my students had to answer were: What sources of energy (conventional and alternative-yet-to-be-brought-to-market) are appropriate powering motor vehicles? In detail, what are the advantages and disadvantages of each? What sources of energy (conventional and alternative) are appropriate for powering homes? (Heat, hot water, cooking, cooling, light, etc) In detail, what are the advantages and disadvantages? What are the most polluting energy sources, and what type of pollution do they produce? What are the least polluting energy sources, and why aren't we using them more? What are fifteen ways the average person can conserve energy? Do we need to conserve energy? Do developing nations need to? Why or why not? Should energy conservation be a legal mandate from the U.S. government for our citizens? Should the U.N. require international consensus on energy conservation? Would that be fair to developing nations? What are the reasons we can no longer depend on fossil fuels (both domestic and imported) to power the United States of America? What are the great issues at stake? Who will pay the price for energy decisions made (or not made) in the next few years? What do you anticipate that price might be?

Ellis, Katharine

76

NSDL National Science Digital Library

In this activity, learners will train to improve lung, heart, and other muscle endurance as they walk a progressive, measured distance. Learners measure out a course according to specific distances, walk/jog/run the distance, and record and graph their observations. This activity simulates how astronauts must train before missions in order to build up the endurance required to move in space. An embedded video on this page showcases the activity. Learners can complete this activity as part of NASA's Fit Explorer Challenge, in which learners train like astronauts, set goals, track their progress, and accumulate points to progress through Exploration Levels and earn certificates.

Center, Nasa J.

2012-06-26

77

Tracking Human Walking Using MARG Sensors.

National Technical Information Service (NTIS)

This thesis addresses modeling and simulation of the human lower extremities in order to track walking motion and estimate walking distance. The lower extremities are modeled as an articulated object, which consists of rigid bars connected to each other b...

I. Pantazis

2005-01-01

78

Quantum walks, quantum gates, and quantum computers

The physics of quantum walks on graphs is formulated in Hamiltonian language, both for simple quantum walks and for composite walks, where extra discrete degrees of freedom live at each node of the graph. It is shown how to map between quantum walk Hamiltonians and Hamiltonians for qubit systems and quantum circuits; this is done for both single-excitation and multiexcitation encodings. Specific examples of spin chains, as well as static and dynamic systems of qubits, are mapped to quantum walks, and walks on hyperlattices and hypercubes are mapped to various gate systems. We also show how to map a quantum circuit performing the quantum Fourier transform, the key element of Shor's algorithm, to a quantum walk system doing the same. The results herein are an essential preliminary to a Hamiltonian formulation of quantum walks in which coupling to a dynamic quantum environment is included.

Hines, Andrew P. [Pacific Institute of Theoretical Physics and Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, V6T 1Z1 (Canada); Pacific Institute for the Mathematical Sciences, 1933 West Mall, University of British Columbia, Vancouver, British Columbia, V6T 1Z2 (Canada); Stamp, P. C. E. [Pacific Institute of Theoretical Physics and Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, V6T 1Z1 (Canada)

2007-06-15

79

The Recovery of Walking in Stroke Patients: A Review

ERIC Educational Resources Information Center

We reviewed the literature on walking recovery of stroke patients as it relates to the following subjects: epidemiology of walking dysfunction, recovery course of walking, and recovery mechanism of walking (neural control of normal walking, the evaluation methods for leg motor function, and motor recovery mechanism of leg). The recovery of walking…

Jang, Sung Ho

2010-01-01

80

Claimed walking distance of lower limb amputees

Purpose: Walking ability in general and specifically for lower limb amputees is of major importance for social mobility and ADL independence. Walking determines prosthesis prescription. The aim of this study was to mathematically analyse factors influencing claimed walking distance of lower limb amputees of 500 m or more. Method: A total of 437 patients returned two questionnaires: the Groningen Questionnaire

JAN H. B. GEERTZEN; JOLINE C. BOSMANS; CEES P. VAN DER SCHANS; PIETER U. DIJKSTRA

2005-01-01

81

Restoring walking after spinal cord injury

One of the most obvious deficits following a spinal cord injury is the difficulty in walking, forcing many patients to use wheelchairs for locomotion. Over the past decade considerable effort has been directed at promoting the recovery of walking and to find effective treatments for spinal cord injury. Advances in our knowledge of the neuronal control of walking have led

Karim Fouad; Keir Pearson

2004-01-01

82

Online Trajectory Generation for Omnidirectional Biped Walking

This paper describes the online generation of tra- jectories for omnidirectional walking on two legs. The gait can be parameterized using walking direction, walking speed, and rotational speed. Our approach has a low computational complexity and can be implemented on small onboard computers. We tested the proposed approach using our humanoid robot Jupp. The competitions in the RoboCup soccer domain

Sven Behnke

2006-01-01

83

Developmental Continuity? Crawling, Cruising, and Walking

ERIC Educational Resources Information Center

This research examined developmental continuity between "cruising" (moving sideways holding onto furniture for support) and walking. Because cruising and walking involve locomotion in an upright posture, researchers have assumed that cruising is functionally related to walking. Study 1 showed that most infants crawl and cruise concurrently prior…

Adolph, Karen E.; Berger, Sarah E.; Leo, Andrew J.

2011-01-01

84

Humanlike walking with toe supporting for humanoids

A model of a walking pattern imitating human motion is presented. An accurate imitation of human motion and a robust bipedal walking motion are, however, hardly realized together. We therefore focus on only three charac- teristics of human walking motion: single toe support, knee stretching, and swing leg motion. Based on a conventional pattern generator, single toe support is added,

Kanako Miura; Mitsuharu Morisawa; Fumio Kanehiro; Shuuji Kajita; Kenji Kaneko; Kazuhito Yokoi

2011-01-01

85

Walk around the Block Curriculum.

ERIC Educational Resources Information Center

This curriculum packet contains two teacher-developed lesson plans for upper elementary students focusing on the built environment. The first lesson plan, "The Built Environment--An Integrating Theme" (Liesa Schroeder), offers suggestions for developing a walking tour around the school neighborhood, a historic area, or a city square. It finds that…

Center for Understanding the Built Environment, Prairie Village, KS.

86

Everyday Fitness Ideas from the National Institute on Aging at NIH www.nia.nih.gov/Go4Life Walking Safely in ... For more information, see the Go4Life tip sheet Fitness Clothes and Shoes . www.nia.nih.gov/Go4Life ...

87

Walk Through a Hydroelectric Project

NSDL National Science Digital Library

This site offers a virtual walk-through tour of a hydroelectric facility. The creation of hydroelectricity begins at the dam, where the power plant converts the force of falling water into electricity. It shows how dams operate and the equipment necessary for electrical generation.

88

We present the method of the quasi-random walk for the ap- proximation of functionals of the solution of second kind Fredholm integral equations. This deterministic approach eciently uses low discrepancy se- quences for the quasi-Monte Carlo integration of the Neumann series. The fast procedure is illustrated in the setting of computer graphics, where it is applied to several aspects of

Alexander Keller

89

Beam Walking in Special Education

ERIC Educational Resources Information Center

An experimental test on beam walking (for balance), administered to 189 minimally brain injured and 226 educable mentally retarded (EMR) 8- to 13-year-old children, yielded results such as reliability estimates for the mean of three trials were high and there was greater performance reliability for EMR children. (MC)

Broadhead, Geoffrey D.

1974-01-01

90

Random walking during quiet standing

NASA Astrophysics Data System (ADS)

During quiet standing, the human body continually moves about in an erratic, and possibly chaotic, fashion. Here we show that postural sway is indistinguishable from correlated noise and that it can be modeled as a system of bounded, correlated random walks. These novel results suggest that the postural control system incorporates both open-loop and closed-loop control mechanisms.

Collins, J. J.; de Luca, C. J.

1994-08-01

91

Walking ability following knee arthroplasty

Functional assessment of patients before and after prosthetic knee arthroplasty is based on clinical examination, which is usually summarized in various knee scores. The present study proposes a different and more subject orientated assessment for functional grading of these patients by measuring their maximal distance of walking ability, which is not apparent from the conventional outcome scores.Eighteen consecutive patients with

N. Rosenberg; G. Nierenberg; R. Lenger; M. Soudry

2007-01-01

92

Random Walks on Sensor Networks

We consider the mobile data gathering problem in large-scale wireless sensor networks with static sensor nodes and a mobile patrol node. Based on the assumptions that (a) the sensor positions are unknown and (b) the network may not be entirely connected, we formulate the problem as one of random walks in random geometric graphs and derive analytical bounds for the

Lu ´ isa; Lima Joao

93

Random Walks on Sensor Networks

We consider the mobile data gathering problem in large-scale wireless sensor networks with static sensor nodes and a mobile patrol node. Based on the assumptions that (a) the sensor positions are unknown and (b) the network may not be entirely connected, we formulate the problem as one of random walks in random geometric graphs and derive analytical bounds for the

Lu Isa Lima; Jo Ao Barros

2007-01-01

94

Toe Walking and Language Development

Neurodevelopmental markers that are present early in childhood may identify children at risk for later developmental disabilities. This paper attempts to clarify the relationship between one such proposed marker, toe walking, and language development in a general pediatric population. One hundred sixty-three children being seen for well-child visits were included in the study. Information from each child's caretaker was obtained

Pasquale Accardo; Jill Morrow; M. Susan Heaney; Barbara Whitman; Terry Tomazic

1992-01-01

95

Listening Walks and Singing Maps

ERIC Educational Resources Information Center

The Listening Walk by Paul Showers and illustrated by Aliki, and "It's My City: A Singing Map" by April Pulley Sayre with pictures by Denis Roche, provide two examples of texts that aid in building children's phonological awareness for reading and music. The author describes each narrative and discusses its function as a springboard to composition…

Cardany, Audrey Berger

2011-01-01

96

Objective: To determine whether 10 minutes of treadmill walking had a different effect on overground walking pattern compared with 10 minutes of overground walking in newly ambulatory stroke patients. Are any changes influenced by walking ability?Design: A within-participant, repeated measures experimental study was conducted. Each participant carried out 10 minutes of overground walking practice followed by 10 minutes of treadmill

Suzanne S Kuys; Sandra G Brauer; Louise Ada; Trevor G Russell

2008-01-01

97

Adaptive Walk on Fitness Soundscape

\\u000a We propose a new IEC for musical works based on an adaptive walk on a fitness landscape of sounds. In this system, there is\\u000a a virtual plane that represents the genetic space of possible musical works called fitness soundscape. The user stands on\\u000a the soundscape, and hears the multiple sounds that correspond to one’s neighboring genotypes at the same time.

Reiji Suzuki; Takaya Arita

98

Quantum walks with infinite hitting times

Hitting times are the average time it takes a walk to reach a given final vertex from a given starting vertex. The hitting time for a classical random walk on a connected graph will always be finite. We show that, by contrast, quantum walks can have infinite hitting times for some initial states. We seek criteria to determine if a given walk on a graph will have infinite hitting times, and find a sufficient condition, which for discrete time quantum walks is that the degeneracy of the evolution operator be greater than the degree of the graph. The set of initial states which give an infinite hitting time form a subspace. The phenomenon of infinite hitting times is in general a consequence of the symmetry of the graph and its automorphism group. Using the irreducible representations of the automorphism group, we derive conditions such that quantum walks defined on this graph must have infinite hitting times for some initial states. In the case of the discrete walk, if this condition is satisfied the walk will have infinite hitting times for any choice of a coin operator, and we give a class of graphs with infinite hitting times for any choice of coin. Hitting times are not very well defined for continuous time quantum walks, but we show that the idea of infinite hitting-time walks naturally extends to the continuous time case as well.

Krovi, Hari; Brun, Todd A. [Communication Sciences Institute, University of Southern California, Los Angeles, California 90089 (United States)

2006-10-15

99

Quantum walks with random phase shifts

We investigate quantum walks in multiple dimensions with different quantum coins. We augment the model by assuming that at each step the amplitudes of the coin state are multiplied by random phases. This model enables us to study in detail the role of decoherence in quantum walks and to investigate the quantum-to-classical transition. We also provide classical analog of the quantum random walks studied. Interestingly enough, it turns out that the classical counterparts of some quantum random walks are classical random walks with a memory and biased coin. In addition random phase shifts 'simplify' the dynamics (the cross-interference terms of different paths vanish on average) and enable us to give a compact formula for the dispersion of such walks.

Kosik, Jozef [Research Center for Quantum Information, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Quniverse, Liscie udolie 116, 841 04 Bratislava (Slovakia); Buzek, Vladimir [Research Center for Quantum Information, Slovak Academy of Sciences, Dubravska cesta 9, 845 11 Bratislava (Slovakia); Abteilung fuer Quantenphysik, Universitaet Ulm, 89069 Ulm (Germany); Hillery, Mark [Department of Physics, Hunter College of CUNY, 695 Park Avenue, New York, New York 10021 (United States)

2006-08-15

100

Quantum walks with random phase shifts

NASA Astrophysics Data System (ADS)

We investigate quantum walks in multiple dimensions with different quantum coins. We augment the model by assuming that at each step the amplitudes of the coin state are multiplied by random phases. This model enables us to study in detail the role of decoherence in quantum walks and to investigate the quantum-to-classical transition. We also provide classical analog of the quantum random walks studied. Interestingly enough, it turns out that the classical counterparts of some quantum random walks are classical random walks with a memory and biased coin. In addition random phase shifts “simplify” the dynamics (the cross-interference terms of different paths vanish on average) and enable us to give a compact formula for the dispersion of such walks.

Košík, Jozef; Bužek, Vladimír; Hillery, Mark

2006-08-01

101

What Changes in Infant Walking and Why

This study compared the relative contributions of growing body dimensions, age, and walking experience in the development of walking skill in 9- to 17-month-old infants (N 5 210), 5-6-year old kindergartners (N 5 15), and college students (N 5 13). Kinematic measures derived from participants' footprints showed characteristic improvements in walking skill. As children became bigger, older, and more experienced,

Karen E. Adolph; Beatrix Vereijken; Patrick E. Shrout

2003-01-01

102

Walk-Startup of a Two-Legged Walking Mechanism

NASA Astrophysics Data System (ADS)

There is a growing interest towards humanoid robots. One of their most important characteristic is the two-legged motion - walk. Starting and stopping of humanoid robots introduce substantial delays. In this paper, the goal is to explore the possibility of using a short unbalanced state of the biped robot to quickly gain speed and achieve the steady state velocity during a period shorter than half of the single support phase. The proposed method is verified by simulation. Maintainig a steady state, balanced gait is not considered in this paper.

Babkovi?, Kalman; Nagy, László; Krklješ, Damir; Borovac, Branislav

103

Walking with the Dead: The Place of Ghost Walk Tourism in Savannah, Georgia

Ghost-themed walking tours are increasingly popular in the United States and globally. Although walking tours are often perceived as structured with pre-determined direction and content, this study of ghost walk tours in Savannah, Georgia alludes to something strikingly different. Although the tours are not usually free-form, interviewed ghost walk tour guides speak openly about how the tour experience is often

Glenn W. Gentry

2007-01-01

104

NSDL National Science Digital Library

This site provides the description and instructions for as well as the link to "The Self-Avoiding Random Walk" applet. In the SAW applet, random walks start on a square lattice and then are discarded as soon as they self-intersect. If a random walk survives after N steps, we compute the square of the distance from the origin, sum it up, and divide by the number of survivals. This variable is plotted on the vertical axis of the graph, which is plotted to the right of the field where random walks travel.

Buldyrev, Sergey; Mcgath, Gary; Trunfio, Paul

2009-12-16

105

Quantum to classical transition for random walks.

We look at two possible routes to classical behavior for the discrete quantum random walk on the integers: decoherence in the quantum "coin" which drives the walk, or the use of higher-dimensional (or multiple) coins to dilute the effects of interference. We use the position variance as an indicator of classical behavior and find analytical expressions for this in the long-time limit; we see that the multicoin walk retains the "quantum" quadratic growth of the variance except in the limit of a new coin for every step, while the walk with decoherence exhibits "classical" linear growth of the variance even for weak decoherence. PMID:14525294

Brun, Todd A; Carteret, Hilary A; Ambainis, Andris

2003-09-26

106

Motor modules in robot-aided walking

Background It is hypothesized that locomotion is achieved by means of rhythm generating networks (central pattern generators) and muscle activation generating networks. This modular organization can be partly identified from the analysis of the muscular activity by means of factorization algorithms. The activity of rhythm generating networks is described by activation signals whilst the muscle intervention generating network is represented by motor modules (muscle synergies). In this study, we extend the analysis of modular organization of walking to the case of robot-aided locomotion, at varying speed and body weight support level. Methods Non Negative Matrix Factorization was applied on surface electromyographic signals of 8 lower limb muscles of healthy subjects walking in gait robotic trainer at different walking velocities (1 to 3km/h) and levels of body weight support (0 to 30%). Results The muscular activity of volunteers could be described by low dimensionality (4 modules), as for overground walking. Moreover, the activation signals during robot-aided walking were bursts of activation timed at specific phases of the gait cycle, underlying an impulsive controller, as also observed in overground walking. This modular organization was consistent across the investigated speeds, body weight support level, and subjects. Conclusions These results indicate that walking in a Lokomat robotic trainer is achieved by similar motor modules and activation signals as overground walking and thus supports the use of robotic training for re-establishing natural walking patterns.

2012-01-01

107

Walking for Mental Vitality: Some Psychological Benefits of Walking in Natural Settings

The benefits to society from walking are many (e.g., economic, social, environmental) and a variety of personal motives support walking including utilitarian travel, increased physical health, and the intrinsic benefits of recreation and social interaction. There is now emerging a new reason for walking which both benefits society and is motivating to the individual. It focuses on mental (attentional) restoration.

Raymond De Young

108

Annually, in Australia, 10–15% of all road-related fatalities involve pedestrians. Of those pedestrians fatally injured, approximately 45% were walking while intoxicated or ‘drink walking’. Drink walking is increasing in prevalence and younger persons may be especially prone to engage in this behaviour and, thus, are at heightened risk of being injured or killed. Presently, limited research is available regarding the

Rushmila Haque; Natalie Clapoudis; Melissa King; Ioni Lewis; Melissa K. Hyde; Patricia Obst

109

Topology of Minimal Walking Technicolor

NASA Astrophysics Data System (ADS)

We perform a lattice study of the topological susceptibility and instanton size distribution of the SU(2) gauge theory with two adjoint Dirac fermions (also known as Minimal Walking Technicolor), which is known to be in the conformal window. In the theory deformed with a small mass term, by drawing a comparison with the pure gauge theory, we find that topological observables are decoupled from the fermion dynamics. This provides further evidence for the infrared conformality of the theory. A study of the instanton size distribution shows that this quantity can be used to detect the onset of finite size effects.

Bennett, Ed; Lucini, Biagio

2013-05-01

110

Quantum Walks with Encrypted Data

NASA Astrophysics Data System (ADS)

In the setting of networked computation, data security can be a significant concern. Here we consider the problem of allowing a server to remotely manipulate client supplied data, in such a way that both the information obtained by the client about the server’s operation and the information obtained by the server about the client’s data are significantly limited. We present a protocol for achieving such functionality in two closely related models of restricted quantum computation—the boson sampling and quantum walk models. Because of the limited technological requirements of the boson scattering model, small scale implementations of this technique are feasible with present-day technology.

Rohde, Peter P.; Fitzsimons, Joseph F.; Gilchrist, Alexei

2012-10-01

111

NASA Astrophysics Data System (ADS)

Coherent transport of quantum particles in binary superlattices driven by an ac force can realize a kind of quantum walk (QW) that can be referred to as Bloch-Zener QW. In this regime, the particle wavepacket undergoes a sequence of Zener tunnelling events that mimic a discrete QW on a lattice, provided that the impulse of the ac force over one semi-cycle of oscillation is properly adjusted. In the Bloch-Zener QW, the coin states are related to the particle occupation of the two minibands, and thus it does not require any internal degrees of freedom of the particle.

Longhi, S.

2012-11-01

112

PURPOSE The purpose of this study was to compare the effects of a 24-week walking with poles rehabilitation program with a traditional 24-week walking program on physical function in patients with peripheral arterial disease (PAD). METHODS Patients with PAD (n=103, age = 69.7±8.9 years, ankle-brachial index <0.90 or evidence of calcified vessels) were randomized into a rehabilitation program of traditional walking (n=52) or walking with poles (n=51). Patients exercised 3 times per week for 24 weeks. Exercise endurance was measured by time walked on a constant workrate treadmill test at 6, 12, and 24 weeks. Perceived physical function was measured by the SF-36 and Walking Impairment Questionnaire. Tissue oxygenation was measured using near-infrared spectroscopy. RESULTS Patients assigned to the traditional walking group walked longer at 24 weeks than those assigned to the pole walking group (21.10±17.07 min and 15.02±12.32 respectively, P=.037). There were no differences between the groups in tissue oxygenation. However, there was a significant lengthening of time for which it took to reach minimum tissue oxygenation values (P <0.001) within the groups on the constant workrate test. There were no differences between the groups in perceived physical function as measured by the physical function subscale on the Short-Form 36 or perceived walking distance as measured by the walking distance subscale on the Walking Impairment Scale. CONCLUSIONS Traditional walking was superior to walking with poles in increasing walking endurance on a constant workrate treadmill test for patients with peripheral arterial disease.

Collins, Eileen G.; O'Connell, Susan; McBurney, Conor; Jelinek, Christine; Butler, Jolene; Reda, Domenic; Gerber, Ben S.; Hurt, Christopher; Grabiner, Mark

2012-01-01

113

Walking in circles: a modelling approach.

Blindfolded or disoriented people have the tendency to walk in circles rather than on a straight line even if they wanted to. Here, we use a minimalistic walking model to examine this phenomenon. The bipedal spring-loaded inverted pendulum exhibits asymptotically stable gaits with centre of mass (CoM) dynamics and ground reaction forces similar to human walking in the sagittal plane. We extend this model into three dimensions, and show that stable walking patterns persist if the leg is aligned with respect to the body (here: CoM velocity) instead of a world reference frame. Further, we demonstrate that asymmetric leg configurations, which are common in humans, will typically lead to walking in circles. The diameter of these circles depends strongly on parameter configuration, but is in line with empirical data from human walkers. Simulation results suggest that walking radius and especially direction of rotation are highly dependent on leg configuration and walking velocity, which explains inconsistent veering behaviour in repeated trials in human data. Finally, we discuss the relation between findings in the model and implications for human walking. PMID:25056215

Maus, Horst-Moritz; Seyfarth, Andre

2014-10-01

114

Planar bipedal walking with foot rotation

This paper addresses the key problem of walking with both fully-actuated and underactuated phases. The studied robot is planar, bipedal, and fully actuated in the sense that it has feet with revolute, actuated ankles. The desired walking motion is assumed to consist of three successive phases: a fully-actuated phase where the stance foot is flat on the ground, an underactuated

Jun Ho Choi; J. W. Grizzle

2005-01-01

115

Welly-Walks for Science Learning

ERIC Educational Resources Information Center

This article discusses how a regular walk in the wind or the rain can help develop science knowledge and skills. The author describes one "welly-walk" and links it to National Curriculum for England requirements so that readers can see how easy it is. (Contains 1 figure and 1 box.)

Fradley, Carol

2006-01-01

116

Efficient filtering using monotonic walk model

This paper proposes a nonlinear filter for estimating monotonic underlying trend from noisy observations. The filter computes maximum aposteriori probability (MAP) estimate using a monotonic walk model instead of the random walk model in standard linear filtering. The batch estimate is a solution of quadratic programming (QP) problem. This paper shows that the QP has a form of isotonic regression

Dimitry Gorinevsky

2008-01-01

117

Environment-dependent continuous time random walk

A generalized continuous time random walk model which is dependent on environmental damping is proposed in which the two key parameters of the usual random walk theory: the jumping distance and the waiting time, are replaced by two new ones: the pulse velocity and the flight time. The anomalous diffusion of a free particle which is characterized by the asymptotical

Fang Lin; Jing-Dong Bao

2011-01-01

118

Quantum walks with memory on cycles

NASA Astrophysics Data System (ADS)

We study the model of quantum walks on cycles enriched by the addition of 1-step memory. We provide a formula for the probability distribution and the time-averaged limiting probability distribution of the introduced quantum walk. Using the obtained results, we discuss the properties of the introduced model and the difference in comparison to the memoryless model.

Mc Gettrick, Michael; Miszczak, Jaros?aw Adam

2014-04-01

119

Decelerating Environmentally Destructive Lawn-Walking

ERIC Educational Resources Information Center

Three general strategies were used to generate six interventions to decrease lawn walking in a park. While none of the three strategies appeared generally superior, some interventions were more effective than others. Another intervention, designed independently by professional planners, was also evaluated and shown to increase lawn walking…

Hayes, Steven C.; Cone, John D.

1977-01-01

120

Random Walks in World Money Rates

Interest rate changes in major industrialized countries are examined and found to exhibit significant deviations from random walks. When measured over short horizons, interest rate changes demonstrate significant negative serial correlation. As the time horizon is extended, the negative dependencies decline and interest rate changes approach random walks. In general, the evidence suggests that short-term interest rate changes in major

Nan Ting Chou; William H. Dare; William Dukes; Christopher K. Ma

2008-01-01

121

Calcaneal loading during walking and running

GIDDINGS, V. L., G. S. BEAUPRE ´, R. T. WHALEN, and D. R. CARTER. Calcaneal loading during walking and running.Med. Sci. Sports Exerc., Vol. 32, No. 3, pp. 627- 634, 2000. Purpose: This study of the foot uses experimentally measured kinematic and kinetic data with a numerical model to evaluate in vivo calcaneal stresses during walking and running. Methods: External

VIRGINIA L. GIDDINGS; ROBERT T. WHALEN; DENNIS R. CARTER

2000-01-01

122

Mesonic spectroscopy of minimal walking technicolor

We investigate the structure and the novel emerging features of the mesonic nonsinglet spectrum of the minimal walking technicolor theory. Precision measurements in the nonsinglet pseudoscalar and vector channels are compared to the expectations for an IR-conformal field theory and a QCD-like theory. Our results favor a scenario in which minimal walking technicolor is (almost) conformal in the infrared, while

Luigi Del Debbio; Biagio Lucini; Agostino Patella; Claudio Pica; Antonio Rago

2010-01-01

123

Attitudes to urban walking in Tehran

There is a growing interest in increasing walking in urban areas, partly to reduce pollution and other problems related to transportation by cars, and partly to improve public health (through reasonable exercise such as walking). In this study several factors that influence the amount of pedestrian movement in Tehran (Iran) are explored. Data were collected through questionnaires and interviews, and

Seyed Mehdi Moeini

2012-01-01

124

Dead Reckoning Navigation For Walking Robots

Autonomous and teleoperated mobile robots require an accurate knowledge of their spatial location in order to acctrmplish many tasks. Many mobile robots make use of dead reckoning navigation because of its simplicity, low cost and robustness. Although dead reckoning navigation has been used for centuries for ships and wheeled vehicles, the application to a walking machine is novel. Since walking

Gerald P. Roston; Eric P. Krotkov

1992-01-01

125

Discrete Quantum Walks Hit Exponentially Faster

This paper addresses the question: what processes take polynomial time on a quantum computer that require exponential time classically? We show that the hitting time of the discrete time quantum walk on the n-bit hypercube from one corner to its opposite is polynomial in n. This gives the first exponential quantum-classical gap in the hitting time of discrete quantum walks.

Julia Kempe

2005-01-01

126

Quantum Random Walks Hit Exponentially Faster

We show that the hitting time of the discrete time quantum random walk on the n-bit hypercube from one corner to its opposite is polynomial in n. This gives the first exponential quantum-classical gap in the hitting time of discrete quantum random walks. We provide the framework for quantum hitting time and give two alternative definitions to set the ground

Julia Kempe

2002-01-01

127

Power Demand for Walking on the Treadmill

NSDL National Science Digital Library

This paper presents a mathematical model for walking on the treadmill that calculates the minimum power required for walking on the level at a constant speed and relates it to the pace length. The calculation includes both the horizontal and vertical moti

Hageseth, Gaylord T.

2000-02-01

128

Planar Bipedal Walking with Anthropomorphic Foot Action

This paper investigates the key problem of walking with both fully actuated and underactuated phases. The studied robot is planar, bipedal, and fully actuated in the sense that it has feet with revolute, actuated ankles. The desired walking motion is assumed to consist of three successive phases: a fully- actuated phase where the stance foot is flat on the ground,

Jun Ho Choi; J. W. Grizzle

2005-01-01

129

Land Use, Residential Density, and Walking

Background The neighborhood environment may play a role in encouraging sedentary patterns, especially for middle-aged and older adults. Purpose Associations between walking and neighborhood population density, retail availability, and land use distribution were examined using data from a cohort of adults aged 45 to 84 years old. Methods Data from a multi-ethnic sample of 5529 adult residents of Baltimore MD, Chicago IL, Forsyth County NC, Los Angeles CA, New York NY, and St. Paul MN, enrolled in the Multi-Ethnic Study of Atherosclerosis in 2000–2002 were linked to secondary land use and population data. Participant reports of access to destinations and stores and objective measures of the percentage of land area in parcels devoted to retail land uses, the population divided by land area in parcels, and the mixture of uses for areas within 200m of each participant's residence were examined. Multinomial logistic regression was used to investigate associations of self-reported and objective neighborhood characteristics with walking. All analyses were conducted in 2008 and 2009. Results After adjustment for individual-level characteristics and neighborhood connectivity, higher density, greater land area devoted to retail uses, and self-reported measures of proximity of destinations and ease of walking to places were each related to walking. In models including all land use measures, population density was positively associated with walking to places and with walking for exercise for more than 90 min/wk both relative to no walking. Availability of retail was associated with walking to places relative to not walking, having a more proportional mix of land uses was associated with walking for exercise for more than 90 min/wk, while self-reported ease of access to places was related to higher levels of exercise walking both relative to not walking. Conclusions Residential density and the presence of retail uses are related to various walking behaviors. Efforts to increase walking may benefit from attention to the intensity and type of land development.

Rodriguez, Daniel A.; Evenson, Kelly R.; Diez Roux, Ana V.; Brines, Shannon J.

2009-01-01

130

Go Naked: Diapers Affect Infant Walking

In light of cross-cultural and experimental research highlighting effects of childrearing practices on infant motor skill, we asked whether wearing diapers, a seemingly innocuous childrearing practice, affects infant walking. Diapers introduce bulk between the legs, potentially exacerbating infants’ poor balance and wide stance. We show that walking is adversely affected by old-fashioned cloth diapers, and that even modern disposable diapers—habitually worn by most infants in the sample—incur a cost relative to walking naked. Infants displayed less mature gait patterns and more missteps and falls while wearing diapers. Thus, infants’ own diapers constitute an on-going biomechanical perturbation while learning to walk. Furthermore, shifts in diapering practices may have contributed to historical and cross-cultural differences in infant walking.

Cole, Whitney G.; Lingeman, Jesse M.; Adolph, Karen E.

2013-01-01

131

Physiological responses to nordic walking, walking and jogging.

The goal of this study was to evaluate the physiological responses during incremental field tests (FT) in nordic walking (NW), walking (W) and jogging (J). Fifteen healthy middle-aged women participated in three FT. Heart rate (HR) and oxygen uptake (V(O)(2)) were monitored continuously by portable analyzers. Capillary blood lactate (La) was analyzed at rest and after every stage of the FT. The disciplines showed differences during stage 1.8 and 2.1 m s(-1) for V(O)(2) between NW and W (P < 0.05). The maximum value was measured at 1.8 m s(-1 )(8%). In accordance with La, V(CO)(2) was higher in NW compared with W during all stages (P < 0.05) and even higher in NW compared with J during 2.1 and 2.4 m s(-1). While there were higher HR for NW and W at 2.4 m s(-1) than in J (P < 0.01), there were increases for HR at fixed values of 2 (La2) and 4 (La4) mmol l(-1 )lactate for J compared with NW and W (P < 0.01). Although the speed of NW was slower than that of W at La2 and La4 (P < 0.05), there were no differences for the HR and the V(O)(2) Our results demonstrate that metabolic responses are a helpful instrument to assess the intensity during bipedal exercise. As NW speed at submaximal lactate levels is lower than in W and J, W and J test measures of HR and V(O)(2) are not suitable for NW training recommendations. Additionally, the V(O)(2) formed by performing NW is not as high as previously reported. PMID:16799817

Schiffer, Thorsten; Knicker, Axel; Hoffman, Uwe; Harwig, Brigitte; Hollmann, Wildor; Strüder, Heiko K

2006-09-01

132

Common muscle synergies for balance and walking

Little is known about the integration of neural mechanisms for balance and locomotion. Muscle synergies have been studied independently in standing balance and walking, but not compared. Here, we hypothesized that reactive balance and walking are mediated by a common set of lower-limb muscle synergies. In humans, we examined muscle activity during multidirectional support-surface perturbations during standing and walking, as well as unperturbed walking at two speeds. We show that most muscle synergies used in perturbations responses during standing were also used in perturbation responses during walking, suggesting common neural mechanisms for reactive balance across different contexts. We also show that most muscle synergies using in reactive balance were also used during unperturbed walking, suggesting that neural circuits mediating locomotion and reactive balance recruit a common set of muscle synergies to achieve task-level goals. Differences in muscle synergies across conditions reflected differences in the biomechanical demands of the tasks. For example, muscle synergies specific to walking perturbations may reflect biomechanical challenges associated with single limb stance, and muscle synergies used during sagittal balance recovery in standing but not walking were consistent with maintaining the different desired center of mass motions in standing vs. walking. Thus, muscle synergies specifying spatial organization of muscle activation patterns may define a repertoire of biomechanical subtasks available to different neural circuits governing walking and reactive balance and may be recruited based on task-level goals. Muscle synergy analysis may aid in dissociating deficits in spatial vs. temporal organization of muscle activity in motor deficits. Muscle synergy analysis may also provide a more generalizable assessment of motor function by identifying whether common modular mechanisms are impaired across the performance of multiple motor tasks.

Chvatal, Stacie A.; Ting, Lena H.

2013-01-01

133

Medical Aspects of Space Walking

NASA Technical Reports Server (NTRS)

Dr. Musgrave has acquired extensive experience during a distinguished and impressive career that includes flying as an astronaut on six Shuttle missions, participating in many hours of extravehicular activity, and contributing his myriad talents toward great public service, especially in the area of education. He has a unique perspective as a physician, scientist, engineer, pilot, and scholar. His interests and breadth of knowledge, which astound even the seasoned space enthusiast, have provided the space program an extraordinary scientific and technical expertise. Dr. Musgrave presented a personal perspective on space flight with particular emphasis on extravehicular activity (EVA or space walking), which was copiously illustrated with photographs from many space missions. His theme was two fold: the exacting and detailed preparations required for successful execution of a mission plan and a cosmic view of mankind's place in the greater scheme of things.

Musgrave, Story

1999-01-01

134

Directional genome walking using PCR.

We describe here a PCR-based "directional genome walking" protocol. The basic procedure for the amplification consists of two rounds of PCR. A primary PCR was performed, on the genomic DNA using a biotinylated primer specific to a known sequence in the genome along with four universal walker primers that were designed with partial degeneracy. The biotinylated primary PCR products were immobilized on streptavidin-linked paramagnetic beads. This step removed all nonspecific amplification products, and the purified template was used for the second PCR using a nested primer and the walker primer-2 to increase specificity. This technique is potentially useful for cloning promoter regions and has been successfully used to isolate 5'-flanking genomic regions of many cDNA clones previously isolated by us. PMID:12398192

Mishra, R N; Singla-Pareek, S L; Nair, S; Sopory, S K; Reddy, M K

2002-10-01

135

Symptoms of Parkinson's disease (PD) progress despite optimized medical treatment. The present study investigated the effects of a flexibility and relaxation programme, walking, and Nordic walking (NW) on walking speed, stride length, stride length variability, Parkinson-specific disability (UPDRS), and health-related quality of life (PDQ 39). 90 PD patients were randomly allocated to the 3 treatment groups. Patients participated in a 6-month study with 3 exercise sessions per week, each lasting 70?min. Assessment after completion of the training showed that pain was reduced in all groups, and balance and health-related quality of life were improved. Furthermore, walking, and Nordic walking improved stride length, gait variability, maximal walking speed, exercise capacity at submaximal level, and PD disease-specific disability on the UPDRS in addition. Nordic walking was superior to the flexibility and relaxation programme and walking in improving postural stability, stride length, gait pattern and gait variability. No significant injuries occurred during the training. All patients of the Nordic walking group continued Nordic walking after completing the study. PMID:21603199

Reuter, I; Mehnert, S; Leone, P; Kaps, M; Oechsner, M; Engelhardt, M

2011-01-01

136

Symptoms of Parkinson's disease (PD) progress despite optimized medical treatment. The present study investigated the effects of a flexibility and relaxation programme, walking, and Nordic walking (NW) on walking speed, stride length, stride length variability, Parkinson-specific disability (UPDRS), and health-related quality of life (PDQ 39). 90 PD patients were randomly allocated to the 3 treatment groups. Patients participated in a 6-month study with 3 exercise sessions per week, each lasting 70?min. Assessment after completion of the training showed that pain was reduced in all groups, and balance and health-related quality of life were improved. Furthermore, walking, and Nordic walking improved stride length, gait variability, maximal walking speed, exercise capacity at submaximal level, and PD disease-specific disability on the UPDRS in addition. Nordic walking was superior to the flexibility and relaxation programme and walking in improving postural stability, stride length, gait pattern and gait variability. No significant injuries occurred during the training. All patients of the Nordic walking group continued Nordic walking after completing the study.

Reuter, I.; Mehnert, S.; Leone, P.; Kaps, M.; Oechsner, M.; Engelhardt, M.

2011-01-01

137

Factors influencing whether children walk to school.

Few studies have simultaneously evaluated multiple levels of influence on whether children walk to school. A large cohort of 4338 subjects from 10 communities was used to identify the determinants of walking through (1) a one-level logistic regression model for individual-level variables and (2) a two-level mixed regression model for individual and school-level variables. Walking rates were positively associated with home-to-school proximity, greater age, and living in neighborhoods characterized by lower traffic density. Greater land use mix around the home was, however, associated with lower rates of walking. Rates of walking to school were also higher amongst recipients of the Free and Reduced Price Meals Program and attendees of schools with higher percentage of English language learners. Designing schools in the same neighborhood as residential districts should be an essential urban planning strategy to reduce walking distance to school. Policy interventions are needed to encourage children from higher socioeconomic status families to participate in active travel to school and to develop walking infrastructures and other measures that protect disadvantaged children. PMID:23707968

Su, Jason G; Jerrett, Michael; McConnell, Rob; Berhane, Kiros; Dunton, Genevieve; Shankardass, Ketan; Reynolds, Kim; Chang, Roger; Wolch, Jennifer

2013-07-01

138

Music walk, fractal geometry in music

NASA Astrophysics Data System (ADS)

In this study, sequences of musical notes from various pieces of music are converted into one-variable random walks (here termed ‘music walks’). Quantitative measurements of the properties of each musical composition are then performed by applying Hurst exponent and Fourier spectral analyses on these music-walk sequences. Our results show that music shares the similar fractal properties of a fractional Brownian motion (fBm). That is, music displays an anti-persistent trend in its tone changes (melody) over decades of musical notes; and music sequence exhibits generally the 1/f?-type spectrum (fractal property), with apparently two different ? values in two different temporal scales.

Su, Zhi-Yuan; Wu, Tzuyin

2007-07-01

139

[Walking assist robot and its clinical application].

The walking assist robot was developed to improve gait disturbance in patients with severe disabilities. The robot had a trunk supporter, power generator and operating arms which held patient's lower extremities and simulated walking, a control unit, biofeedback system, and a treadmill. We applied the robot-aided gait training to three patients with severe gait disturbance induced by stroke, axonal Guillan-Barré syndrome or spinal cord injury, and the walking assist robot turned out to be effective in improving the gait disturbance. PMID:19530565

Kakou, Hiroaki; Shitama, Hideo; Kimura, Yoshiko; Nakamoto, Yoko; Furuta, Nami; Honda, Kanae; Wada, Futoshi; Hachisuka, Kenji

2009-06-01

140

Random walks on ordered mixed binary lattices

NASA Astrophysics Data System (ADS)

We present results of random-walk simulations in ordered mixed binary two-dimensional lattices. We calculate the number of sites visited in an n-step walk and compare this to our previous work on random lattices. We also examine the effect of the mean free path of the random walker. We find a considerable difference, as walks in the ordered cases produce a greater efficiency than in the random ones. We rationalize this behavior with the use of the number of reflections on closed sites, which we also find to differ in these two cases. Suggestions for experimental situations are made.

Argyrakis, Panos

1983-01-01

141

Machines that walk: The adaptive suspension vehicle

NASA Astrophysics Data System (ADS)

The design and operation of statically stable fully terrain-adaptive walking machines are discussed, with an emphasis on the adaptive-suspension vehicle developed at Ohio State University (Waldron and McGhee, 1986). Chapters are devoted to a review of walking-machine development, gait analysis and gaits for level walking, gaits for irregular terrain, coordination, leg design by four-bar linkage synthesis, design of a pantograph leg, motion-controlled ankle design, and the Adaptive Suspension Vehicle. Diagrams, drawings, and graphs are provided.

Song, Shin-Min; Waldron, Kenneth J.

142

Mussels realize Weierstrassian L?vy walks as composite correlated random walks

Composite correlated random walks (CCRW) have been posited as a potential replacement for Lévy walks and it has also been suggested that CCRWs have been mistaken for Lévy walks. Here I test an alternative, emerging hypothesis: namely that some organisms approximate Lévy walks as an innate CCRW. It is shown that the tri-modal CCRW found to describe accurately the movement patterns of mussels (Mytilus edulis) during spatial pattern formation in mussel beds can be regarded as being the first three levels in a hierarchy of nested movement patterns which if extended indefinitely would correspond to a Lévy walk whose characteristic (power-law) exponent is tuned to nearly minimize the time required to form patterned beds. The mussels realise this Lévy walk to good approximation across a biologically meaningful range of scales. This demonstrates that the CCRW not only describes mussel movement patterns, it explains them.

Reynolds, Andy M.

2014-01-01

143

An Analysis of Absorbing Times of Quantum Walks

Quantum walks are expected to provide useful algorithmic tools for quantum computation. This paper introduces absorbing probability and time of quantum walks and gives both numerical simulation results and theoretical analyses on Hadamard walks on the line and symmetric walks on the hypercube from the viewpoint of absorbing probability and time.

Tomohiro Yamasaki; Hirotada Kobayashi; Hiroshi Imai

2002-01-01

144

The process of habituation to treadmill walking at different velocities

Eighteen young adult male subjects, who were naive to treadmill walking were walked for ten minutes on a motorised treadmill. The subjects were split into three groups with the six subjects in each group walking at a given relative speed. The use of relative speed factors out stature differences which are known to affect walking velocity. The relative speeds chosen

J. C. WALL; J. CHARTERIS

1980-01-01

145

Humanoid robot push recovery through walking phase modification

Push recovery is an important capability that needs to be included while developing a robust humanoid robot walking scheme. In this paper we propose an overall control system and a push recovery controller for humanoid robot walking. When the robot is pushed, the algorithm will modify the walking phase to maintain walking, while considering the practical constraints. 3D simulation results

A. H. Adiwahono; Chee-Meng Chew; Weiwei Huang; Van Huan Dau

2010-01-01

146

Walking and Eating Behavior of Toddlers at 12 Months Old

ERIC Educational Resources Information Center

Locomotive and eating behavior of 52 toddlers was observed at 12 months old in a nursery school and investigated in relation to the acquisition of independent walking. The toddlers who acquired walking ate more by themselves using the hands than the toddlers who did not start walking. This suggested that acquisition of walking was associated with…

Koda, Naoko; Akimoto, Yuko; Hirose, Toshiya; Hinobayashi, Toshihiko; Minami, Tetsuhiro

2004-01-01

147

A self-organizing model of walking patterns of insects

Insects generate walking patterns which depend upon external conditions. For example, when an insect is exposed to an additional load parallel to the direction in which it is walking, the walking pattern changes according to the magnitude of the load. Furthermore, even after some of its legs have been amputated, an insect will produce walking patterns with its remaining legs.

Shinichi Kimura; Masafuni Yano; Hiroshi Shimizu

1994-01-01

148

"I'm Just a'-Walking the Dog" correlates of regular dog walking.

Intrapersonal and environmental factors associated with dog walking (N = 483) were examined. A greater proportion of regular (80%) than irregular (59%) dog walkers met the recommended 150 minutes of physical activity per week. Owners who perceived greater social support and motivation from their dogs to walk, and who had access to a dog-supportive park within their neighborhood, were more likely to regularly walk with their dogs, even after adjustment for other well-known correlates of physical activity. The higher level of physical activity of regular dog walkers can be attributed to the additional walking these owners perform with their dogs. PMID:20010004

Christian nee Cutt, Hayley; Giles-Corti, Billie; Knuiman, Matthew

2010-01-01

149

Care and Operation of Walk-Ins.

ERIC Educational Resources Information Center

Problems of owners who use their walk-in coolers and freezers only part of the year demand special consideration. Proper techniques for startup, operation, and shutdown must be used to guarantee efficient, inexpensive operation. (Author)

Bauer, James M.

1979-01-01

150

Walking with coffee: Why does it spill?

NASA Astrophysics Data System (ADS)

In our busy lives, almost all of us have to walk with a cup of coffee. While often we spill the drink, this familiar phenomenon has never been explored systematically. Here we report on the results of an experimental study of the conditions under which coffee spills for various walking speeds and initial liquid levels in the cup. These observations are analyzed from the dynamical systems and fluid mechanics viewpoints as well as with the help of a model developed here. Particularities of the common cup sizes, the coffee properties, and the biomechanics of walking proved to be responsible for the spilling phenomenon. The studied problem represents an example of the interplay between the complex motion of a cup, due to the biomechanics of a walking individual, and the low-viscosity-liquid dynamics in it.

Mayer, H. C.; Krechetnikov, R.

2012-04-01

151

STP Random Walk 2D SAW Program

NSDL National Science Digital Library

The RandomWalkSAW program simulates a self-avoiding random walk in two dimensions. The walker has an equal probability of going in any direction, but cannot return to a site that has already been visited. The default number of initial walkers is 100 and the total number of steps N = 1024. RandomWalkSAW is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp RandomWalkSAW.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-10-10

152

The random walk model of intrafraction movement

NASA Astrophysics Data System (ADS)

The purpose of this paper is to understand intrafraction movement as a stochastic process driven by random external forces. The hypothetically proposed three-dimensional random walk model has significant impact on optimal PTV margins and offers a quantitatively correct explanation of experimental findings. Properties of the random walk are calculated from first principles, in particular fraction-average population density distributions for displacements along the principal axes. When substituted into the established optimal margin recipes these fraction-average distributions yield safety margins about 30% smaller as compared to the suggested values from end-of-fraction Gaussian fits. Stylized facts of a random walk are identified in clinical data, such as the increase of the standard deviation of displacements with the square root of time. Least squares errors in the comparison to experimental results are reduced by about 50% when accounting for non-Gaussian corrections from the random walk model.

Ballhausen, H.; Reiner, M.; Kantz, S.; Belka, C.; Söhn, M.

2013-04-01

153

Minimal walking technicolor: Setup for collider physics

Different theoretical and phenomenological aspects of the minimal and nonminimal walking technicolor theories have recently been studied. The goal here is to make the models ready for collider phenomenology. We do this by constructing the low energy effective theory containing scalars, pseudoscalars, vector mesons, and other fields predicted by the minimal walking theory. We construct their self-interactions and interactions with standard model fields. Using the Weinberg sum rules, opportunely modified to take into account the walking behavior of the underlying gauge theory, we find interesting relations for the spin-one spectrum. We derive the electroweak parameters using the newly constructed effective theory and compare the results with the underlying gauge theory. Our analysis is sufficiently general such that the resulting model can be used to represent a generic walking technicolor theory not at odds with precision data.

Foadi, Roshan; Frandsen, Mads T.; Ryttov, Thomas A.; Sannino, Francesco [CERN Theory Division, CH-1211 Geneva 23 (Switzerland); University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark); Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark)

2007-09-01

154

Gallery Walk Questions on Atmospheric Moisture

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about Atmospheric Mosture. The questions are organized according to the ...

155

NSDL National Science Digital Library

The RandomWalk2D program simulates a random walk in two dimensions. The default number of walkers is 1000, and the probability of going right, left up or down at any step is the same. RandomWalk2D is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp RandomWalk2D.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-10-10

156

NSDL National Science Digital Library

The RandomWalk1D program simulates a random walk in one dimension for steps of unit length and equal time intervals. The default number of steps is N = 16 and the probability of going right or left at any step is the same (the probability p of going to the right for a single step is 0.5). RandomWalk1D is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp RandomWalk1D.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-10-10

157

Random walks with self-similar clusters

We construct a random walk on a lattice having a hierarchy of self-similar clusters built into the distribution function of allowed jumps. The random walk is a discrete analog of a Lévy flight and coincides with the Lévy flight in the continum limit. The Fourier transform of the jump distribution function is the continuous nondifferentiable function of Weierstrass. We show that, for cluster formation, it is necessary that the mean-squared displacement per jump be infinite and that the random walk be transient. We interpret our random walk as having an effective dimension higher than the spatial dimension available to the walker. The difference in dimensions is related to the fractal (Hausdorff-Besicovitch) dimension of the self-similar clusters.

Hughes, Barry D.; Shlesinger, Michael F.; Montroll, Elliott W.

1981-01-01

158

William J. Glackens: "The Cedar Walk."

ERIC Educational Resources Information Center

Provides a lesson plan for primary grade-level students based on William J. Glackens' oil painting, "The Cedar Walk." The goal of the lesson is to introduce students to landscape/seascape painting. (JDH)

Davidson, Marilyn

1986-01-01

159

Random walks with self-similar clusters.

We construct a random walk on a lattice having a hierarchy of self-similar clusters built into the distribution function of allowed jumps. The random walk is a discrete analog of a Lévy flight and coincides with the Lévy flight in the continum limit. The Fourier transform of the jump distribution function is the continuous nondifferentiable function of Weierstrass. We show that, for cluster formation, it is necessary that the mean-squared displacement per jump be infinite and that the random walk be transient. We interpret our random walk as having an effective dimension higher than the spatial dimension available to the walker. The difference in dimensions is related to the fractal (Hausdorff-Besicovitch) dimension of the self-similar clusters. PMID:16593023

Hughes, B D; Shlesinger, M F; Montroll, E W

1981-06-01

160

Power Demand in Walking and Pace Optimization.

ERIC Educational Resources Information Center

Presents an elementary formulation of the work expenditure corresponding to walking, the most common physical exercise. The model described is included in a physics course for freshmen in physical education and physical therapy. (Author/JN)

Bellemans, A.

1981-01-01

161

Gallery Walk Questions on Map Reading

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about map reading. The questions are organized according to the cognitive ...

162

STP Random Walk 1D Continuous Program

NSDL National Science Digital Library

The RandomWalk1DContinuous program simulates a random walk in one dimension for steps of any length between 0 and 1. The default number of steps is N = 16 and the probability p of going to the right for a single step is 0.5. RandomWalk1DContinuous is part of a suite of Open Source Physics programs that model aspects of Statistical and Thermal Physics (STP). The program is distributed as a ready-to-run (compiled) Java archive. Double clicking the stp RandomWalk1DContinuous.jar file will run the program if Java is installed on your computer. Additional programs can be found by searching ComPADRE for Open Source Physics, STP, or Statistical and Thermal Physics.

Gould, Harvey; Tobochnik, Jan; Christian, Wolfgang; Cox, Anne

2008-10-10

163

Gallery Walk Questions on Earth's Radiation Balance

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about the Earth's Radiation Balance. The questions are organized ...

164

Purpose: Most studies on barefoot and shod walking have so far focused on leg muscle activity. However, footwear might also have an impact on the back and neck. The aim of the present study was to compare back and neck muscle activity as well as kinematic gait parameters during barefoot walking, conventional shod walking and walking in flexible shoes, commercially

Brigitte Wirth; Fabian Hauser; Roland Mueller

2011-01-01

165

Quantum random walks using quantum accelerator modes

We discuss the use of high-order quantum accelerator modes to achieve an atom optical realization of a biased quantum random walk. We first discuss how one can create coexistent quantum accelerator modes, and hence how momentum transfer that depends on the atoms' internal state can be achieved. When combined with microwave driving of the transition between the states, a different type of atomic beam splitter results. This permits the realization of a biased quantum random walk through quantum accelerator modes.

Ma, Z.-Y.; Burnett, K.; D'Arcy, M. B.; Gardiner, S. A. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8424 (United States); Department of Physics, University of Durham, Rochester Building, South Road, Durham DH1 3LE (United Kingdom)

2006-01-15

166

Standardized Questionnaires of Walking & Bicycling Database

This database contains questionnaire items and a list of validation studies for standardized items concerning walking and biking from multiple national and international physical activity questionnaires (PAQs). The purpose of this database is to provide easy access to a large number of items assessing duration and frequency of walking and bicycling in the non-disabled adult population. We also briefly review the results of validation studies identified for some of the PAQs.

167

Evaluating Walking in Patients with Multiple Sclerosis

Walking limitations are among the most visible manifestations of multiple sclerosis (MS). Regular walking assessments should be a component of patient management and require instruments that are appropriate from the clinician's and the patient's perspectives. This article reviews frequently used instruments to assess walking in patients with MS, with emphasis on their validity, reliability, and practicality in the clinical setting. Relevant articles were identified based on PubMed searches using the following terms: “multiple sclerosis AND (walking OR gait OR mobility OR physical activity) AND (disability evaluation)”; references of relevant articles were also searched. Although many clinician- and patient-driven instruments are available, not all have been validated in MS, and some are not sensitive enough to detect small but clinically important changes. Choosing among these depends on what needs to be measured, psychometric properties, the clinical relevance of results, and practicality with respect to space, time, and patient burden. Of the instruments available, the clinician-observed Timed 25-Foot Walk and patient self-report 12-Item Multiple Sclerosis Walking Scale have properties that make them suitable for routine evaluation of walking performance. The Dynamic Gait Index and the Timed Up and Go test involve other aspects of mobility, including balance. Tests of endurance, such as the 2- or 6-Minute Walk, may provide information on motor fatigue not captured by other tests. Quantitative measurement of gait kinetics and kinematics, and recordings of mobility in the patient's environment via accelerometry or Global Positioning System odometry, are currently not routinely used in the clinical setting.

Bennett, Susan

2011-01-01

168

One-Family Walking Techni-Pions

NASA Astrophysics Data System (ADS)

We compute masses of the techni-pions in the one-family walking Technicolor model by properly taking into account the characteristic walking features. We find the techni-pion masses are generally on the order of 300 - 500 GeV, to be accessible at the ongoing LHC experiments. The techni-pion cross sections are compared with the currently available LHC data.

Jia, Junji; Matsuzaki, Shinya; Yamawaki, Koichi

169

Leg Design for a Humanoid Walking Robot

The paper presents the leg design of the 22-DoF humanoid walking robot Lola. The goal of the project is to realize a fast, human-like walking motion. The robot is characterized by its lightweight construction, a modular, multi-sensory joint design with brushless motors and an electronics architecture using decentralized joint controllers and sensor data processing. Linear actuators are used for the

Sebastian Lohmeier; Thomas Buschmann; Markus Schwienbacher; Heinz Ulbrich; Friedrich Pfeiffer

2006-01-01

170

Generalized quantum walk in momentum space

NASA Astrophysics Data System (ADS)

We consider a new model of quantum walk on a one-dimensional momentum space that includes both discrete jumps and continuous drift. Its time evolution has two stages; a Markov diffusion followed by localized dynamics. As in the well known quantum kicked rotor, this model can be mapped into a localized one-dimensional Anderson model. For exceptional (rational) values of its scale parameter, the system exhibits resonant behavior and reduces to the usual discrete time quantum walk on the line.

Romanelli, A.; Auyuanet, A.; Siri, R.; Abal, G.; Donangelo, R.

2005-07-01

171

Walking technicolor signatures at hadron colliders

Aspects of the dynamics of walking technicolor models are expected to have important consequences for technihadron production at hadron colliders. Hard-mass enhancements characteristic of walking technicolor raise technipion (piT) masses relative to technirho (rhoT) masses so that the decays rhoT-->piTpiT are either suppressed or forbidden altogether. Thus, rhoT can be unusually narrow with unconventional decay modes. Large weak isospin breaking

M. V. Ramana

1991-01-01

172

Minimal walking technicolor: Setup for collider physics

Different theoretical and phenomenological aspects of the Minimal and\\u000aNonminimal Walking Technicolor theories have recently been studied. The goal\\u000ahere is to make the models ready for collider phenomenology. We do this by\\u000aconstructing the low energy effective theory containing scalars, pseudoscalars,\\u000avector mesons and other fields predicted by the minimal walking theory. We\\u000aconstruct their self-interactions and interactions with

Roshan Foadi; Mads T. Frandsen; Thomas A. Ryttov; Francesco Sannino

2007-01-01

173

Mesonic spectroscopy of minimal walking technicolor

We investigate the structure and the novel emerging features of the mesonic nonsinglet spectrum of the minimal walking technicolor theory. Precision measurements in the nonsinglet pseudoscalar and vector channels are compared to the expectations for an IR-conformal field theory and a QCD-like theory. Our results favor a scenario in which minimal walking technicolor is (almost) conformal in the infrared, while spontaneous chiral symmetry breaking seems less plausible.

Del Debbio, Luigi [SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Lucini, Biagio; Patella, Agostino [School of Physical Sciences, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Pica, Claudio [CP3-Origins, University of Southern Denmark, Odense, 5230 M (Denmark); Rago, Antonio [Department of Physics, Bergische Universitaet Wuppertal, Gaussstrasse 20, D-42119 Wuppertal (Germany)

2010-07-01

174

The first walking batch fabricated silicon micro-robot able to carry loads has been developed and investigated. The robot consists of arrays of movable robust silicon legs having a length of 0.5 or 1 mm. Motion is obtained by thermal actuation of robust polyimide joint actuators using electrical heating. Successful walking experiments have been performed with the 15x5 mm 2 sized

Thorbjörn Ebefors; Johan Ulfstedt Mattsson; Edvard Kälvesten; Göran Stemme

1999-01-01

175

Nordic walking improves mobility in Parkinson's disease

Nordic walking may improve mobility in Parkinson's disease (PD). Here, we examined whether the beneficial effects persist after the training period. We included 19 PD patients [14 men; mean age 67.0 years (range 58-76); Hoehn and Yahr stage range 1-3] who received a 6-week Nordic walking exercise program. Outcome was assessed prior to training (T1), immediately after the training period

Frank J. M. van Eijkeren; Ruud S. J. Reijmers; Mirjam J. Kleinveld; Angret Minten; Jan Pieter ter Bruggen; Bastiaan R. Bloem

2008-01-01

176

Convergence of quantum random walks with decoherence

In this paper, we study the discrete-time quantum random walks on a line subject to decoherence. The convergence of the rescaled position probability distribution p(x,t) depends mainly on the spectrum of the superoperator L{sub kk}. We show that if 1 is an eigenvalue of the superoperator with multiplicity one and there is no other eigenvalue whose modulus equals 1, then P(({nu}/{radical}(t)),t) converges to a convex combination of normal distributions. In terms of position space, the rescaled probability mass function p{sub t}(x,t){identical_to}p({radical}(t)x,t), x is an element of Z/{radical}(t), converges in distribution to a continuous convex combination of normal distributions. We give a necessary and sufficient condition for a U(2) decoherent quantum walk that satisfies the eigenvalue conditions. We also give a complete description of the behavior of quantum walks whose eigenvalues do not satisfy these assumptions. Specific examples such as the Hadamard walk and walks under real and complex rotations are illustrated. For the O(2) quantum random walks, an explicit formula is provided for the scaling limit of p(x,t) and their moments. We also obtain exact critical exponents for their moments at the critical point and show universality classes with respect to these critical exponents.

Fan Shimao; Feng Zhiyong; Yang, Wei-Shih [Department of Mathematics Temple University, Philadelphia, Pennsylvania 19122 (United States); Xiong Sheng [Department of Mathematics and Sciences Edward Waters College, Jacksonville, Florida 32209 (United States)

2011-10-15

177

Calcaneal loading during walking and running

NASA Technical Reports Server (NTRS)

PURPOSE: This study of the foot uses experimentally measured kinematic and kinetic data with a numerical model to evaluate in vivo calcaneal stresses during walking and running. METHODS: External ground reaction forces (GRF) and kinematic data were measured during walking and running using cineradiography and force plate measurements. A contact-coupled finite element model of the foot was developed to assess the forces acting on the calcaneus during gait. RESULTS: We found that the calculated force-time profiles of the joint contact, ligament, and Achilles tendon forces varied with the time-history curve of the moment about the ankle joint. The model predicted peak talocalcaneal and calcaneocuboid joint loads of 5.4 and 4.2 body weights (BW) during walking and 11.1 and 7.9 BW during running. The maximum predicted Achilles tendon forces were 3.9 and 7.7 BW for walking and running. CONCLUSIONS: Large magnitude forces and calcaneal stresses are generated late in the stance phase, with maximum loads occurring at approximately 70% of the stance phase during walking and at approximately 60% of the stance phase during running, for the gait velocities analyzed. The trajectories of the principal stresses, during both walking and running, corresponded to each other and qualitatively to the calcaneal trabecular architecture.

Giddings, V. L.; Beaupre, G. S.; Whalen, R. T.; Carter, D. R.

2000-01-01

178

Quantum walks with tuneable self-avoidance in one dimension.

Quantum walks exhibit many unique characteristics compared to classical random walks. In the classical setting, self-avoiding random walks have been studied as a variation on the usual classical random walk. Here the walker has memory of its previous locations and preferentially avoids stepping back to locations where it has previously resided. Classical self-avoiding random walks have found numerous algorithmic applications, most notably in the modelling of protein folding. We consider the analogous problem in the quantum setting - a quantum walk in one dimension with tunable levels of self-avoidance. We complement a quantum walk with a memory register that records where the walker has previously resided. The walker is then able to avoid returning back to previously visited sites or apply more general memory conditioned operations to control the walk. We characterise this walk by examining the variance of the walker's distribution against time, the standard metric for quantifying how quantum or classical a walk is. We parameterise the strength of the memory recording and the strength of the memory back-action on the walker, and investigate their effect on the dynamics of the walk. We find that by manipulating these parameters, which dictate the degree of self-avoidance, the walk can be made to reproduce ideal quantum or classical random walk statistics, or a plethora of more elaborate diffusive phenomena. In some parameter regimes we observe a close correspondence between classical self-avoiding random walks and the quantum self-avoiding walk. PMID:24762398

Camilleri, Elizabeth; Rohde, Peter P; Twamley, Jason

2014-01-01

179

Quantum walks with tuneable self-avoidance in one dimension

NASA Astrophysics Data System (ADS)

Quantum walks exhibit many unique characteristics compared to classical random walks. In the classical setting, self-avoiding random walks have been studied as a variation on the usual classical random walk. Here the walker has memory of its previous locations and preferentially avoids stepping back to locations where it has previously resided. Classical self-avoiding random walks have found numerous algorithmic applications, most notably in the modelling of protein folding. We consider the analogous problem in the quantum setting - a quantum walk in one dimension with tunable levels of self-avoidance. We complement a quantum walk with a memory register that records where the walker has previously resided. The walker is then able to avoid returning back to previously visited sites or apply more general memory conditioned operations to control the walk. We characterise this walk by examining the variance of the walker's distribution against time, the standard metric for quantifying how quantum or classical a walk is. We parameterise the strength of the memory recording and the strength of the memory back-action on the walker, and investigate their effect on the dynamics of the walk. We find that by manipulating these parameters, which dictate the degree of self-avoidance, the walk can be made to reproduce ideal quantum or classical random walk statistics, or a plethora of more elaborate diffusive phenomena. In some parameter regimes we observe a close correspondence between classical self-avoiding random walks and the quantum self-avoiding walk.

Camilleri, Elizabeth; Rohde, Peter P.; Twamley, Jason

2014-04-01

180

Quantum walks with tuneable self-avoidance in one dimension

Quantum walks exhibit many unique characteristics compared to classical random walks. In the classical setting, self-avoiding random walks have been studied as a variation on the usual classical random walk. Here the walker has memory of its previous locations and preferentially avoids stepping back to locations where it has previously resided. Classical self-avoiding random walks have found numerous algorithmic applications, most notably in the modelling of protein folding. We consider the analogous problem in the quantum setting – a quantum walk in one dimension with tunable levels of self-avoidance. We complement a quantum walk with a memory register that records where the walker has previously resided. The walker is then able to avoid returning back to previously visited sites or apply more general memory conditioned operations to control the walk. We characterise this walk by examining the variance of the walker's distribution against time, the standard metric for quantifying how quantum or classical a walk is. We parameterise the strength of the memory recording and the strength of the memory back-action on the walker, and investigate their effect on the dynamics of the walk. We find that by manipulating these parameters, which dictate the degree of self-avoidance, the walk can be made to reproduce ideal quantum or classical random walk statistics, or a plethora of more elaborate diffusive phenomena. In some parameter regimes we observe a close correspondence between classical self-avoiding random walks and the quantum self-avoiding walk.

Camilleri, Elizabeth; Rohde, Peter P.; Twamley, Jason

2014-01-01

181

NASA Technical Reports Server (NTRS)

Carnegie Mellon University's Autonomous Planetary Exploration Program (APEX) is currently building the Daedalus robot; a system capable of performing extended autonomous planetary exploration missions. Extended autonomy is an important capability because the continued exploration of the Moon, Mars and other solid bodies within the solar system will probably be carried out by autonomous robotic systems. There are a number of reasons for this - the most important of which are the high cost of placing a man in space, the high risk associated with human exploration and communication delays that make teleoperation infeasible. The Daedalus robot represents an evolutionary approach to robot mechanism design and software system architecture. Daedalus incorporates key features from a number of predecessor systems. Using previously proven technologies, the Apex project endeavors to encompass all of the capabilities necessary for robust planetary exploration. The Ambler, a six-legged walking machine was developed by CMU for demonstration of technologies required for planetary exploration. In its five years of life, the Ambler project brought major breakthroughs in various areas of robotic technology. Significant progress was made in: mechanism and control, by introducing a novel gait pattern (circulating gait) and use of orthogonal legs; perception, by developing sophisticated algorithms for map building; and planning, by developing and implementing the Task Control Architecture to coordinate tasks and control complex system functions. The APEX project is the successor of the Ambler project.

Whittaker, William; Dowling, Kevin

1994-01-01

182

Persistent random walk with exclusion

NASA Astrophysics Data System (ADS)

Modelling the propagation of a pulse in a dense milieu poses fundamental challenges at the theoretical and applied levels. To this aim, in this paper we generalize the telegraph equation to non-ideal conditions by extending the concept of persistent random walk to account for spatial exclusion effects. This is achieved by introducing an explicit constraint in the hopping rates, that weights the occupancy of the target sites. We derive the mean-field equations, which display nonlinear terms that are important at high density. We compute the evolution of the mean square displacement (MSD) for pulses belonging to a specific class of spatially symmetric initial conditions. The MSD still displays a transition from ballistic to diffusive behaviour. We derive an analytical formula for the effective velocity of the ballistic stage, which is shown to depend in a nontrivial fashion upon both the density (area) and the shape of the initial pulse. After a density-dependent crossover time, nonlinear terms become negligible and normal diffusive behaviour is recovered at long times.

Galanti, Marta; Fanelli, Duccio; Piazza, Francesco

2013-11-01

183

Does botulinum toxin A improve the walking pattern in children with idiopathic toe-walking?

Background Numerous recommendations have been made for treating idiopathic toe-walking (ITW), but the treatment results have been questioned. The purpose of this study was to investigate whether botulinum toxin A (BTX) improves the walking pattern in ITW as examined with 3-D gait analysis. Participants and methods A consecutive series of 15 children (aged 5–13 years) were enrolled in the study. The children underwent a 3-D gait analysis prior to treatment with a total of 6 units/kg bodyweight Botox® in the calf muscles and an exercise program. The gait analysis was repeated 3 weeks and 3, 6, and 12 months after treatment. A classification of toe-walking severity was made before treatment and after 12 months. The parents rated the perceived amount of toe-walking prior to treatment and 6 and 12 months after treatment. Results Eleven children completed the 12-month follow-up. The gait analysis results displayed a significant improvement, indicating decreased plantarflexion angle at initial contact and during swing phase and increased dorsiflexion angle during midstance at all post-treatment testing instances. According to the parents’ perception of toe-walking, 3/11 children followed for 12 months had ceased toe-walking completely, 4/11 decreased toe-walking, and 4/11 continued toe-walking. After 6–12 months, the toe-walking severity classification improved in 9 of the 14 children for whom data could be assessed. Conclusions A single injection of BTX in combination with an exercise program can improve the walking pattern in children with ITW seen at gait analysis, but the obvious goal of ceasing toe-walking is only occasionally reached.

Gutierrez-Farewik, Elena M.; Bartonek, Asa; Tedroff, Kristina; Orefelt, Christina; Haglund-Akerlind, Yvonne

2010-01-01

184

Code of Federal Regulations, 2010 CFR

...consumption of walk-in coolers and walk-in freezers. 431.304 Section 431.304 Energy...EQUIPMENT Walk-in Coolers and Walk-in Freezers Test Procedures Â§ 431.304 ...consumption of walk-in coolers and walk-in freezers. (a) Scope. This section...

2010-01-01

185

It has been suggested that aerobic training should be considered in stroke rehabilitation programs to counteract detrimental health effects and decrease cardiovascular risk caused by inactivity. Robot-assisted treadmill exercise (using a Lokomat device) has the potential to increase the duration of walking therapy relative to conventional overground therapy. We investigated whether exercise intensity during Lokomat therapy is adequate to elicit a training effect and how assistance during walking in the Lokomat affects this exercise intensity. Ten patients with stroke (age 54 +/- 9 yr) walked in both the Lokomat and in a hallway. Furthermore, 10 nondisabled subjects (age 43 +/- 14 yr) walked in the Lokomat at various settings and on a treadmill at various speeds. During walking, oxygen consumption and heart rate were monitored. Results showed that for patients with stroke, exercise intensity did not reach recommended levels (30% heart rate reserve) for aerobic training during Lokomat walking. Furthermore, exercise intensity during walking in the Lokomat (9.3 +/- 1.6 mL/min/kg) was lower than during overground walking (10.4 +/- 1.3 mL/min/kg). Also, different settings of the Lokomat only had small effects on exercise intensity in nondisabled subjects. PMID:23516057

van Nunen, Michiel P M; Gerrits, Karin H L; de Haan, Arnold; Janssen, Thomas W J

2012-01-01

186

Kardiorespiratorische Parameter verglichen zwischen nordic walking und walking in Höhen- und Tallage

Ziel der Untersuchung war es zum einen, Nordic Walking mit Walking bezüglich Ventilation, Sauerstoffaufnahme, Herzfrequenz, Energieverbrauch, Borg und Sauerstoffsättigung (V'e, Vo2, Hf, EE, Borg, SaO2) unter Feldtest Konditionen zu vergleichen und zum anderen, jene Parameter in Höhen- (1600m) und Tallage (600m) zu vergleichen.

Hannes Zischg; Georg Spazier

187

Nordic walking practice might improve plantar pressure distribution.

Nordic walking (NW), characterized by the use of two walking poles, is becoming increasingly popular (Morgulec-Adamowicz, Marszalek, & Jagustyn, 2011). We studied walking pressure patterns of 20 experienced and 30 beginner Nordic walkers. Plantar pressures from nine foot zones were measured during trials performed at two walking speeds (preferred and 20% faster), and under two walking conditions (NW vs. normal walking). In comparison to normal walking, NW experience led to a significant (p < .05) pressure reduction of about 50% on the central metatarsals. No significant increases were detected in other foot regions. The differences between experienced and beginners during normal walking including a 40% pressure reduction on the metatarsal area, suggests that regular NW practice might also have a beneficial effect on plantar pressure when walking without poles. PMID:22276400

Pérez-Soriano, Pedro; Llana-Belloch, Salvador; Martínez-Nova, Alfonso; Morey-Klapsing, G; Encarnación-Martínez, Alberto

2011-12-01

188

Localization of Discrete Time Quantum Walks on the Glued Trees

NASA Astrophysics Data System (ADS)

In this paper, we consider the time averaged distribution of discrete time quantum walks on the glued trees. In order to analyse the walks on the glued trees, we consider a reduction to the walks on path graphs. Using a spectral analysis of the Jacobi matrices defined by the corresponding random walks on the path graphs, we have spectral decomposition of the time evolution operator of the quantum walks. We find significant contributions of the eigenvalues $\\pm 1$ of the Jacobi matrices to the time averaged limit distribution of the quantum walks. As a consequence we obtain lower bounds of the time averaged distribution.

Ide, Yusuke; Konno, Norio; Segawa, Etsuo; Xu, Xin-Ping

2014-03-01

189

Myoelectric walking mode classification for transtibial amputees.

Myoelectric control algorithms have the potential to detect an amputee's motion intent and allow the prosthetic to adapt to changes in walking mode. The development of a myoelectric walking mode classifier for transtibial amputees is outlined. Myoelectric signals from four muscles (tibialis anterior, medial gastrocnemius (MG), vastus lateralis, and biceps femoris) were recorded for five nonamputee subjects and five transtibial amputees over a variety of walking modes: level ground at three speeds, ramp ascent/descent, and stair ascent/descent. These signals were decomposed into relevant features (mean absolute value, variance, wavelength, number of slope sign changes, number of zero crossings) over three subwindows from the gait cycle and used to test the ability of classification algorithms for transtibial amputees using linear discriminant analysis (LDA) and support vector machine (SVM) classifiers. Detection of all seven walking modes had an accuracy of 97.9% for the amputee group and 94.7% for the nonamputee group. Misclassifications occurred most frequently between different walking speeds due to the similar nature of the gait pattern. Stair ascent/descent had the best classification accuracy with 99.8% for the amputee group and 100.0% for the nonamputee group. Stability of the developed classifier was explored using an electrode shift disturbance for each muscle. Shifting the electrode placement of the MG had the most pronounced effect on the classification accuracy for both samples. No increase in classification accuracy was observed when using SVM compared to LDA for the current dataset. PMID:23708765

Miller, Jason D; Beazer, Mahyo Seyedali; Hahn, Michael E

2013-10-01

190

Vection in depth during treadmill walking.

Vection has typically been induced in stationary observers (ie conditions providing visual-only information about self-motion). Two recent studies have examined vection during active treadmill walking--one reported that treadmill walking in the same direction as the visually simulated self-motion impaired vection (Onimaru et al, 2010 Journal of Vision 10(7):860), the other reported that it enhanced vection (Seno et al, 2011 Perception 40 747-750; Seno et al, 2011 Attention, Perception, & Psychophysics 73 1467-1476). Our study expands on these earlier investigations of vection during observer active movement. In experiment 1 we presented radially expanding optic flow and compared the vection produced in stationary observers with that produced during walking forward on a treadmill at a 'matched' speed. Experiment 2 compared the vection induced by forward treadmill walking while viewing expanding or contracting optic flow with that induced by viewing playbacks of these same displays while stationary. In both experiments subjects' tracked head movements were either incorporated into the self-motion displays (as simulated viewpoint jitter) or simply ignored. We found that treadmill walking always reduced vection (compared with stationary viewing conditions) and that simulated viewpoint jitter always increased vection (compared with constant velocity displays). These findings suggest that while consistent visual-vestibular information about self-acceleration increases vection, biomechanical self-motion information reduces this experience (irrespective of whether it is consistent or not with the visual input). PMID:23964381

Ash, April; Palmisano, Stephen; Apthorp, Deborah; Allison, Robert S

2013-01-01

191

Random Walks in a Trapping Environment

NASA Astrophysics Data System (ADS)

We discuss the statistics of random walks in the presence of a trapping environment, that is, when the environment can act as a trap. This model is also referred as ideal chain or static random walks. Peculiar features arise for diffusion in this model due to the presence of rare events which, however, play a fundamental role in the determination of the asymptotic behaviour. Using a combination of analytical and numerical techniques, we show the origin and effect of this pathological behaviour which is a common feature in many models with disorder and its difference from the kinetic random walks on disorder without trapping. New results for many quantities of interest are derived and physically interpreted. An alternative approach, based on the properties of the spectrum of the transition (or diffusion) matrix is also shown to give consistent results. An exact calculation for an analytical solvable hierarchical model is shown to give different behaviour for the quantities of interest. Finally an improved and self-consistent real space renormalization group approach for random walks is presented. This approach allows the study of the complete phase diagram for the problem of a random walk in the presence of a surface or defects but without disorder. The approach is valid in any dimension and allows the determination of the phase diagram with an arbitrary degree of accuracy. Problems arising from the extension of this approach to disordered systems are also discussed.

Giacometti, Achille

192

Effects of load inversion in cockroach walking.

To examine how walking patterns are adapted to changes in load, we recorded leg movements and muscle activities when cockroaches (Periplaneta americana) walked upright and on an inverted surface. Animals were videotaped to measure the hindleg femoro-tibial joint angle while myograms were taken from the tibial extensor and flexor muscles. The joint is rapidly flexed during swing and extended in stance in upright and inverted walking. When inverted, however, swing is shorter in duration and the joint traverses a range of angles further in extension. In slow upright walking, slow flexor motoneurons fire during swing and the slow extensor in stance, although a period of co-contraction occurs early in stance. In inverted walking, patterns of muscle activities are altered. Fast flexor motoneurons fire both in the swing phase and early in stance to support the body by pulling the animal toward the substrate. Extensor firing occurs late in stance to propel the animal forward. These findings are discussed within the context of a model in which stance is divided into an early support and subsequent propulsion phase. We also discuss how these changes in use of the hindleg may represent adaptations to the reversal of the effects of gravity. PMID:7884685

Larsen, G S; Frazier, S F; Fish, S E; Zill, S N

1995-02-01

193

Nordic walking improves mobility in Parkinson's disease.

Nordic walking may improve mobility in Parkinson's disease (PD). Here, we examined whether the beneficial effects persist after the training period. We included 19 PD patients [14 men; mean age 67.0 years (range 58-76); Hoehn and Yahr stage range 1-3] who received a 6-week Nordic walking exercise program. Outcome was assessed prior to training (T1), immediately after the training period (T2) and-in a subgroup of 9 patients--5 months after training (T3). At T2, we observed a significant improvement in timed 10-m walking, the timed get-up-and-go-test (TUG), the 6-min walking test and quality of life (PDQ-39). All treatment effects persisted at T3. Compliance was excellent, and there were no adverse effects. These preliminary findings suggest that Nordic walking could provide a safe, effective, and enjoyable way to reduce physical inactivity in PD and to improve the quality of life. A large randomized clinical trial now appears justified. PMID:18816697

van Eijkeren, Frank J M; Reijmers, Ruud S J; Kleinveld, Mirjam J; Minten, Angret; Bruggen, Jan Pieter Ter; Bloem, Bastiaan R

2008-11-15

194

Coin state properties in quantum walks

Recent experimental advances have measured individual coin components in discrete time quantum walks, which have not received the due attention in most theoretical studies on the theme. Here is presented a detailed investigation of the properties of M, the difference between square modulus of coin states of discrete quantum walks on a linear chain. Local expectation values are obtained in terms of real and imaginary parts of the Fourier transformed wave function. A simple expression is found for the average difference between coin states in terms of an angle ? gauging the coin operator and its initial state. These results are corroborated by numerical integration of dynamical equations in real space. The local dependence is characterized both by large and short period modulations. The richness of revealed patterns suggests that the amount of information stored and retrieved from quantum walks is significantly enhanced if M is taken into account.

Andrade, R. F. S.

2013-01-01

195

Symmetries and noise in quantum walk

NASA Astrophysics Data System (ADS)

We study some discrete symmetries of unbiased (Hadamard) and biased quantum walk on a line, which are shown to hold even when the quantum walker is subjected to environmental effects. The noise models considered in order to account for these effects are the phase flip, bit flip, and generalized amplitude damping channels. The numerical solutions are obtained by evolving the density matrix, but the persistence of the symmetries in the presence of noise is proved using the quantum trajectories approach. We also briefly extend these studies to quantum walk on a cycle. These investigations can be relevant to the implementation of quantum walks in various known physical systems. We discuss the implementation in the case of NMR quantum information processor and ultracold atoms.

Chandrashekar, C. M.; Srikanth, R.; Banerjee, Subhashish

2007-08-01

196

Universal quantum computation by discontinuous quantum walk

Quantum walks are the quantum-mechanical analog of random walks, in which a quantum ''walker'' evolves between initial and final states by traversing the edges of a graph, either in discrete steps from node to node or via continuous evolution under the Hamiltonian furnished by the adjacency matrix of the graph. We present a hybrid scheme for universal quantum computation in which a quantum walker takes discrete steps of continuous evolution. This ''discontinuous'' quantum walk employs perfect quantum-state transfer between two nodes of specific subgraphs chosen to implement a universal gate set, thereby ensuring unitary evolution without requiring the introduction of an ancillary coin space. The run time is linear in the number of simulated qubits and gates. The scheme allows multiple runs of the algorithm to be executed almost simultaneously by starting walkers one time step apart.

Underwood, Michael S.; Feder, David L. [Institute for Quantum Information Science, University of Calgary, Calgary, Alberta T2N 1N4 (Canada)

2010-10-15

197

The dynamics of walking acquisition: a tutorial.

Tracking for developmental changes is at the heart of developmental psychology. The qualitative features of the variation of the center of mass (CoM) acceleration during a sequence of steps are revealed by first return maps, a tool taken from differential dynamics. The focus is put on the acceleration of the CoM along the antero-posterior and medio-lateral axes. Application is shown on data recorded from one infant followed up repeatedly during the first year of learning to walk. At a given experience in walking, the gait dynamics is exhaustively characterized by a specific enchainment of pendula and quasi-equilibria. The developmental process is revealed by the succession of dynamical structures, each determined at each walking experience. It shows a drift toward increasingly regular gait patterns, together with a clear asymmetry between an impulse foot and a regulatory foot. PMID:22721738

Bonneuil, Noël; Bril, Blandine

2012-06-01

198

Genome Walking by Next Generation Sequencing Approaches

Genome Walking (GW) comprises a number of PCR-based methods for the identification of nucleotide sequences flanking known regions. The different methods have been used for several purposes: from de novo sequencing, useful for the identification of unknown regions, to the characterization of insertion sites for viruses and transposons. In the latter cases Genome Walking methods have been recently boosted by coupling to Next Generation Sequencing technologies. This review will focus on the development of several protocols for the application of Next Generation Sequencing (NGS) technologies to GW, which have been developed in the course of analysis of insertional libraries. These analyses find broad application in protocols for functional genomics and gene therapy. Thanks to the application of NGS technologies, the original vision of GW as a procedure for walking along an unknown genome is now changing into the possibility of observing the parallel marching of hundreds of thousands of primers across the borders of inserted DNA molecules in host genomes.

Volpicella, Mariateresa; Leoni, Claudia; Costanza, Alessandra; Fanizza, Immacolata; Placido, Antonio; Ceci, Luigi R.

2012-01-01

199

Random walks of oriented particles on fractals

NASA Astrophysics Data System (ADS)

Random walks of point particles on fractals exhibit subdiffusive behavior, where the anomalous diffusion exponent is smaller than one, and the corresponding random walk dimension is larger than two. This is due to the limited space available in fractal structures. Here, we endow the particles with an orientation and analyze their dynamics on fractal structures. In particular, we focus on the dynamical consequences of the interactions between the local surrounding fractal structure and the particle orientation, which are modeled using an appropriate move class. These interactions can lead to particles becoming temporarily or permanently stuck in parts of the structure. A surprising finding is that the random walk dimension is not affected by the orientation while the diffusion constant shows a variety of interesting and surprising features.

Haber, René; Prehl, Janett; Hoffmann, Karl Heinz; Herrmann, Heiko

2014-04-01

200

Random Walk with Barycentric Self-interaction

NASA Astrophysics Data System (ADS)

We study the asymptotic behaviour of a d-dimensional self-interacting random walk ( X n ) n?? (?:={1,2,3,…}) which is repelled or attracted by the centre of mass Gn = n^{-1} sum_{i=1}n Xi of its previous trajectory. The walk's trajectory ( X 1,…, X n ) models a random polymer chain in either poor or good solvent. In addition to some natural regularity conditions, we assume that the walk has one-step mean drift {E}[X_{n+1} - X_n mid X_n - G_n = x] ??\\|x\\|^{-?}hat{ x} for ??? and ??0. When ?<1 and ?>0, we show that X n is transient with a limiting (random) direction and satisfies a super-diffusive law of large numbers: n -1/(1+ ?) X n converges almost surely to some random vector. When ??(0,1) there is sub-ballistic rate of escape. When ??0 and ??? we give almost-sure bounds on the norms ? X n ?, which in the context of the polymer model reveal extended and collapsed phases. Analysis of the random walk, and in particular of X n - G n , leads to the study of real-valued time-inhomogeneous non-Markov processes ( Z n ) n?? on [0,?) with mean drifts of the form {E}[ Z_{n+1} - Z_n mid Z_n = x ] ?? x^{-?} - frac {x}{n}, where ??0 and ???. The study of such processes is a time-dependent variation on a classical problem of Lamperti; moreover, they arise naturally in the context of the distance of simple random walk on ? d from its centre of mass, for which we also give an apparently new result. We give a recurrence classification and asymptotic theory for processes Z n satisfying (0.1), which enables us to deduce the complete recurrence classification (for any ??0) of X n - G n for our self-interacting walk.

Comets, Francis; Menshikov, Mikhail V.; Volkov, Stanislav; Wade, Andrew R.

2011-06-01

201

Idiopathic toe walking and sensory processing dysfunction

Background It is generally understood that toe walking involves the absence or limitation of heel strike in the contact phase of the gait cycle. Toe walking has been identified as a symptom of disease processes, trauma and/or neurogenic influences. When there is no obvious cause of the gait pattern, a diagnosis of idiopathic toe walking (ITW) is made. Although there has been limited research into the pathophysiology of ITW, there has been an increasing number of contemporary texts and practitioner debates proposing that this gait pattern is linked to a sensory processing dysfunction (SPD). The purpose of this paper is to examine the literature and provide a summary of what is known about the relationship between toe walking and SPD. Method Forty-nine articles were reviewed, predominantly sourced from peer reviewed journals. Five contemporary texts were also reviewed. The literature styles consisted of author opinion pieces, letters to the editor, clinical trials, case studies, classification studies, poster/conference abstracts and narrative literature reviews. Literature was assessed and graded according to level of evidence. Results Only one small prospective, descriptive study without control has been conducted in relation to idiopathic toe walking and sensory processing. A cross-sectional study into the prevalence of idiopathic toe walking proposed sensory processing as being a reason for the difference. A proposed link between ITW and sensory processing was found within four contemporary texts and one conference abstract. Conclusion Based on the limited conclusive evidence available, the relationship between ITW and sensory processing has not been confirmed. Given the limited number and types of studies together with the growing body of anecdotal evidence it is proposed that further investigation of this relationship would be advantageous.

2010-01-01

202

Intra-limb coordination while walking is affected by cognitive load and walking speed.

Knowledge about intra-limb coordination (ILC) during challenging walking conditions provides insight into the adaptability of central nervous system (CNS) for controlling human gait. We assessed the effects of cognitive load and speed on the pattern and variability of the ILC in young people during walking. Thirty healthy young people (19 female and 11 male) participated in this study. They were asked to perform 9 walking trials on a treadmill, including walking at three paces (preferred, slower and faster) either without a cognitive task (single-task walking) or while subtracting 1?s or 3?s from a random three-digit number (simple and complex dual-task walking, respectively). Deviation phase (DP) and mean absolute relative phase (MARP) values-indicators of variability and phase dynamic of ILC, respectively-were calculated using the data collected by a motion capture system. We used a two-way repeated measure analysis of variance for statistical analysis. The results showed that cognitive load had a significant main effect on DP of right shank-foot and thigh-shank, left shank-foot and pelvis-thigh (p<0.05), and MARP of both thigh-shank segments (p<0.01). In addition, the main effect of walking speed was significant on DP of all segments in each side and MARP of both thigh-shank and pelvis-thigh segments (p<0.001). The interaction of cognitive load and walking speed was only significant for MARP values of left shank-foot and right pelvis-thigh (p<0.05 and p<0.001, respectively). We suggest that cognitive load and speed could significantly affect the ILC and variability and phase dynamic during walking. PMID:24861632

Ghanavati, Tabassom; Salavati, Mahyar; Karimi, Noureddin; Negahban, Hossein; Ebrahimi Takamjani, Ismail; Mehravar, Mohammad; Hessam, Masumeh

2014-07-18

203

Quantum Random Walks with General Particle States

NASA Astrophysics Data System (ADS)

A convergence theorem is obtained for quantum random walks with particles in an arbitrary normal state. This unifies and extends previous work on repeated-interactions models, including that of Attal and Pautrat (Ann Henri Poincaré 7:59-104 2006) and Belton (J Lond Math Soc 81:412-434, 2010; Commun Math Phys 300:317-329, 2010). When the random-walk generator acts by ampliation and either multiplication or conjugation by a unitary operator, it is shown that the quantum stochastic cocycle which arises in the limit is driven by a unitary process.

Belton, Alexander C. R.

2014-06-01

204

Adaptive Walks and Extreme Value Theory

NASA Astrophysics Data System (ADS)

We study biological evolution in a high-dimensional genotype space in the regime of rare mutations and strong selection. The population performs an uphill walk which terminates at local fitness maxima. Assigning fitness randomly to genotypes, we show that the mean walk length is logarithmic in the number of initially available beneficial mutations, with a prefactor determined by the tail of the fitness distribution. This result is derived analytically in a simplified setting where the mutational neighborhood is fixed during the adaptive process, and confirmed by numerical simulations.

Neidhart, Johannes; Krug, Joachim

2011-10-01

205

Background Given the documented physical activity disparities that exist among low-income minority communities and the increased focused on socio-ecological approaches to address physical inactivity, efforts aimed at understanding the built environment to support physical activity are needed. This community-based participatory research (CBPR) project investigates walking trails perceptions in a high minority southern community and objectively examines walking trails. The primary aim is to explore if perceived and objective audit variables predict meeting recommendations for walking and physical activity, MET/minutes/week of physical activity, and frequency of trail use. Methods A proportional sampling plan was used to survey community residents in this cross-sectional study. Previously validated instruments were pilot tested and appropriately adapted and included the short version of the validated International Physical Activity Questionnaire, trail use, and perceptions of walking trails. Walking trails were assessed using the valid and reliable Path Environmental Audit Tool which assesses four content areas including: design features, amenities, maintenance, and pedestrian safety from traffic. Analyses included Chi-square, one-way ANOVA's, multiple linear regression, and multiple logistic models. Results Numerous (n = 21) high quality walking trails were available. Across trails, there were very few indicators of incivilities and safety features rated relatively high. Among the 372 respondents, trail use significantly predicted meeting recommendations for walking and physical activity, and MET/minutes/week. While controlling for other variables, significant predictors of trail use included proximity to trails, as well as perceptions of walking trail safety, trail amenities, and neighborhood pedestrian safety. Furthermore, while controlling for education, gender, and income; for every one time per week increase in using walking trails, the odds for meeting walking recommendations increased 1.27 times, and the odds for meeting PA recommendation increased 3.54 times. Perceived and objective audit variables did not predict meeting physical activity recommendations. Conclusions To improve physical activity levels, intervention efforts are needed to maximize the use of existing trails, as well as improve residents' perceptions related to incivilities, safety, conditions of trail, and amenities of the walking trails. This study provides important insights for informing development of the CBPR walking intervention and informing local recreational and environmental policies in this southern community.

2012-01-01

206

Having Kids Walk to School Comes with Risks, Benefits

... page, please enable JavaScript. Having Kids Walk to School Comes With Risks, Benefits Added physical activity is ... about letting their kids walk or bike to school. Motor vehicle crashes are the leading cause of ...

207

Random Walks With Reinforcement: As an Application of Exchangeability

In an effort to cover the topic of Random Walks With Reinforce- ment, we will first cover the basics, go over some simulations and my find- ings, then walk through the proof of partial exchangeability.

Paul Mollema

208

A Walk a Day Keeps Disability at Bay

... this page, please enable JavaScript. A Walk a Day Keeps Disability at Bay Study links greater mobility ... two groups. One group walked 20 minutes a day, while the other group received educational material about ...

209

Comparison of treadmill and over-ground Nordic walking

The purpose of this study was to compare the physiological responses of Nordic walking on a specially designed treadmill and Nordic walking on a level over-ground surface. Thirteen participants completed three 1-h Nordic walking training sessions. Following the training sessions, each participant performed two 1600-m over-ground Nordic walking trials at a self-selected pace. Each participant then completed two 1600-m Nordic

Gail Dechman; Jennifer Appleby; Mike Carr; Melanie Haire

2012-01-01

210

Comparison of treadmill and over-ground Nordic walking

The purpose of this study was to compare the physiological responses of Nordic walking on a specially designed treadmill and Nordic walking on a level over-ground surface. Thirteen participants completed three 1-h Nordic walking training sessions. Following the training sessions, each participant performed two 1600-m over-ground Nordic walking trials at a self-selected pace. Each participant then completed two 1600-m Nordic

Gail Dechman; Jennifer Appleby; Mike Carr; Melanie Haire

2011-01-01

211

Quantum Walk on a Line for a Trapped Ion

NASA Astrophysics Data System (ADS)

We show that a multistep quantum walk can be realized for a single trapped ion with an interpolation between a quantum and random walk achieved by randomizing the generalized Hadamard coin flip phase. The signature of the quantum walk is manifested not only in the ion’s position but also in its phonon number, which makes an ion-trap implementation of the quantum walk feasible.

Xue, Peng; Sanders, Barry C.; Leibfried, Dietrich

2009-10-01

212

Quantum walk on a line for a trapped ion.

We show that a multistep quantum walk can be realized for a single trapped ion with an interpolation between a quantum and random walk achieved by randomizing the generalized Hadamard coin flip phase. The signature of the quantum walk is manifested not only in the ion's position but also in its phonon number, which makes an ion-trap implementation of the quantum walk feasible. PMID:19905805

Xue, Peng; Sanders, Barry C; Leibfried, Dietrich

2009-10-30

213

Continuous-time quantum walks on star graphs

In this paper, we investigate continuous-time quantum walk on star graphs. It is shown that quantum central limit theorem for a continuous-time quantum walk on star graphs for N-fold star power graph, which are invariant under the quantum component of adjacency matrix, converges to continuous-time quantum walk on K{sub 2} graphs (complete graph with two vertices) and the probability of observing walk tends to the uniform distribution.

Salimi, S. [Department of Physics, University of Kurdistan, P.O. Box 66177-15175, Sanandaj (Iran, Islamic Republic of)], E-mail: shsalimi@uok.ac.ir

2009-06-15

214

Self-Attractive Random Walks: The Case of Critical Drifts

NASA Astrophysics Data System (ADS)

Self-attractive random walks (polymers) undergo a phase transition in terms of the applied drift (force): If the drift is strong enough, then the walk is ballistic, whereas in the case of small drifts self-attraction wins and the walk is sub-ballistic. We show that, in any dimension d ? 2, this transition is of first order. In fact, we prove that the walk is already ballistic at critical drifts, and establish the corresponding LLN and CLT.

Ioffe, Dmitry; Velenik, Yvan

2012-07-01

215

Integer Addition and Subtraction: Walking the Number Line (2)

NSDL National Science Digital Library

This Java applet, an adaption of "Integer Addition and Subtraction: Walking the Number Line" (cataloged separately) models the addition and subtraction of integers of example expressions by walking a character along a number line. A slider changes the example expression and the check boxes show or can hide the character's walking trail, hints and solutions for the example expressions.

Maine, Edc I.

2012-01-01

216

Optimal computation with non-unitary quantum walks

Quantum versions of random walks on the line and the cycle show a quadratic improvement over classical random walks in their spreading rates and mixing times respectively. Non-unitary quantum walks can provide a useful optimisation of these properties, producing a more uniform distribution on the line, and faster mixing times on the cycle. We investigate the interplay between quantum and

Viv Kendon; Olivier Maloyer

2008-01-01

217

Dynamic walking and running of the quadruped using neural oscillator

We attempt to induce a quadruped robot to walk dynamically on irregular terrain and run on flat terrain by using a nervous system model. For dynamic walking on irregular terrain, we employ a control system involving a neural oscillator network, a stretch reflex and a flexor reflex. Stable dynamic walking when obstructions to swinging legs are present is made possible

Hiroshi Kimura; Kazuaki Sakurama; Seiichi Akiyama

1998-01-01

218

Powered flight, child's play, silly wheels and walking machines

Recent theoretical and experimental studies of biped walking machines are reviewed. The author summarizes results in passive and pumped walking, and discuss issues arising for robot design. The fundamental idea is that a pair or pendula will walk just as naturally as a wheel will roll. It is shown that, as far as dynamics and control are concerned, use of

T. McGeer

1989-01-01

219

Pattern generation for bipedal walking on slopes and stairs

Uneven terrain walking is one of the key challenges in bipedal walking. In this paper, we propose a motion pattern generator for slope walking in 3D dynamics using preview control of zero moment point (ZMP). In this method, the future ZMP locations are selected with respect to known slope gradient. The trajectory of the center of mass (CoM) of the

Weiwei Huang; Chee-Meng Chew; Yu Zheng; Geok-Soon Hong

2008-01-01

220

HUMANOID ROBOT WALKING TRAJECTORY GENERATION AND HYBRID CONTROL

Past three decades witnessed a growing interest in biped walking robots because of their advantageous use in the human environment. However, their control is challenging because of their many DOFs and nonlinearities in their dynamics. Various trajector y generation and walking control approaches ranging f rom open loop walking to systems with many sensors and feedback loops have been reported

Ozan Ayhan; Kemalettin Erbatur

221

Walking and the Preservation of Cognitive Function in Older Populations

ERIC Educational Resources Information Center

Purpose: This cross-sectional study takes a unique look at the association between patterns of walking and cognitive functioning by examining whether older adults with mild cognitive impairment differ in terms of the community settings where they walk and the frequency, intensity, or duration of walking. Design and Methods: The sample was based on…

Prohaska, Thomas R.; Eisenstein, Amy R.; Satariano, William A.; Hunter, Rebecca; Bayles, Constance M.; Kurtovich, Elaine; Kealey, Melissa; Ivey, Susan L.

2009-01-01

222

Online Walking Pattern Generation for Biped Humanoid Robot with Trunk

This paper describes an online method generating walking patterns for biped humanoid robots having a trunk. Depending on the walking command, the motion patterns of the lower-limbs are created and connected to the prewalking patterns smoothly in online. For the stability of the biped robots, the trunk and the waist motion is generated by a walking stabilization control that is

Hun-ok Lim; Yoshiharu Kaneshimat; Atsuo Takanishi

2002-01-01

223

A new random walk model for PCS networks

This paper proposes a new approach to simplify the two-dimensional random walk models capturing the movement of mobile users in Personal Communications Services (PCS) networks. Analytical models are proposed for the new random walks. For a PCS network with hexagonal configuration, our approach reduces the states of the two-dimensional random walk from ( )t o , where is the layers

Ian F. Akyildiz; Yi-bing Lin; Wei-ru Lai; Rong-jaye Chen

2000-01-01

224

What mechanisms coordinate leg movement in walking arthropods?

The construction of artificial walking machines has been a challenging task for engineers for several centuries. Advances in computer technology have stimulated this research in the past two decades, and enormous progress has been made, particularly in recent years. Nevertheless, in comparing the walk of a six-legged robot with the walk of an insect, the immense differences are immediately obvious.

Holk Cruse

1990-01-01

225

Searching via walking: How to find a marked clique of a complete graph using quantum walks

NASA Astrophysics Data System (ADS)

We show how a quantum walk can be used to find a marked edge or a marked complete subgraph of a complete graph. We employ a version of a quantum walk, the scattering walk, which lends itself to experimental implementation. The edges are marked by adding elements to them that impart a specific phase shift to the particle as it enters or leaves the edge. If the complete graph has N vertices and the subgraph has K vertices, the particle becomes localized on the subgraph in O(N/K) steps. This leads to a quantum search that is quadratically faster than a corresponding classical search. We show how to implement the quantum walk using a quantum circuit and a quantum oracle, which allows us to specify the resources needed for a quantitative comparison of the efficiency of classical and quantum searches—the number of oracle calls.

Hillery, Mark; Reitzner, Daniel; Bužek, Vladimír

2010-06-01

226

Random walk centrality for temporal networks

NASA Astrophysics Data System (ADS)

Nodes can be ranked according to their relative importance within a network. Ranking algorithms based on random walks are particularly useful because they connect topological and diffusive properties of the network. Previous methods based on random walks, for example the PageRank, have focused on static structures. However, several realistic networks are indeed dynamic, meaning that their structure changes in time. In this paper, we propose a centrality measure for temporal networks based on random walks under periodic boundary conditions that we call TempoRank. It is known that, in static networks, the stationary density of the random walk is proportional to the degree or the strength of a node. In contrast, we find that, in temporal networks, the stationary density is proportional to the in-strength of the so-called effective network, a weighted and directed network explicitly constructed from the original sequence of transition matrices. The stationary density also depends on the sojourn probability q, which regulates the tendency of the walker to stay in the node, and on the temporal resolution of the data. We apply our method to human interaction networks and show that although it is important for a node to be connected to another node with many random walkers (one of the principles of the PageRank) at the right moment, this effect is negligible in practice when the time order of link activation is included.

Rocha, Luis E. C.; Masuda, Naoki

2014-06-01

227

Myths about the Country Walk Case

ERIC Educational Resources Information Center

The Country Walk case in Dade County, Florida was long considered a model for how to prosecute a multi-victim child sexual abuse case involving young children. In the past 10 years, however, a contrary view has emerged that the case was tainted by improper interviewing and was likely a false conviction. This is the first scholarly effort to assess…

Cheit, Ross E.; Mervis, David

2007-01-01

228

Asymmetric random walks and drift-diffusion

NASA Astrophysics Data System (ADS)

To obtain the drift-diffusion equation from an asymmetric random walk it has been required that the left and right jump probabilities are approximately equal. It is shown here that such a restriction is not needed. Using multiple scales the equation is derived, where the scales are based on the advection and diffusion scales.

Holmes, M.

2013-05-01

229

Coupled continuous time random walks in finance

Continuous time random walks (CTRWs) are used in physics to model anomalous diffusion, by incorporating a random waiting time between particle jumps. In finance, the particle jumps are log-returns and the waiting times measure delay between transactions. These two random variables (log-return and waiting time) are typically not independent. For these coupled CTRW models, we can now compute the limiting

Mark M. Meerschaert; Enrico Scalas

2006-01-01

230

On Linnik's continuous-time random walks

In many fields of applied physics, the phenomenology of the space-time phenomena to be understood (in general for prediction purposes) may be described in the following most simple way: events with random common positive amplitude occur randomly in time according to a continuous time random walk (CTRW) model; the prerequisite is therefore a statistical model for both the amplitude and

Thierry Huillet

2000-01-01

231

Coupled continuous time random walks in finance

Continuous time random walks (CTRWs) are used in physics to model anoma- lous diffusion, by incorporating a random waiting time between particle jumps. In finance, the particle jumps are log-returns and the waiting times measure delay be- tween transactions. These two random variables (log-return and waiting time) are typically not independent. For these coupled CTRW models, we can now compute

Mark M. Meerschaert; Enrico Scalas

2009-01-01

232

Anisotropic branching random walks on homogeneous trees

Symmetric branching random walk on a homogeneous tree exhibits a weak sur- vival phase: For parameter values in a certain interval, the population survives forever with positive probability, but, with probability one, eventually vacates every finite subset of the tree. In this phase, particle trails must converge to the geometric boundaryof the tree. The random subset3 of the boundary consisting

I. Hueter; S. P. Lalley

1999-01-01

233

Anisotropic branching random walks on homogeneous trees

. Symmetric branching random walk on a homogeneous tree exhibits a weak survival phase: For parameter values in a certain interval, the population survives forever with positive probability, but, with probability\\u000a one, eventually vacates every finite subset of the tree. In this phase, particle trails must converge to the geometric boundary? of the tree. The random subset ? of the

Irene Hueter; Steven P. Lalley

2000-01-01

234

The One-Dimensional Random Walk

NSDL National Science Digital Library

Created by authors Gary McGath and Paul Trunfio of Boston University's Center for Polymer Studies, this is the description and instructions for the One-Dimensional Random Walk applet. This Applet relates random coin-flipping to random motion. It strives to show that randomness (coin-flipping) leads to some sort of predictable outcome (the bell-shaped curve).

Mcgath, Gary; Trunfio, Paul

2008-12-30

235

Developmental implications of idiopathic toe walking

Objective: To determine whether children with persistent toe walking, without suspected developmental problems, and with normal results after neurologic examination, who were seen in an orthopedic clinic demonstrate delays in language development, gross or fine motor skills, visuomotor development, sensory integration function, or evidence of behavioral problems through a comprehensive multidisciplinary evaluation.Study design: A prospective, descriptive study of 13 children

Lisa H. Shulman; Debra A. Sala; Mary Lynn Y. Chu; Patricia R. McCaul; Bonnie J. Sandler

1997-01-01

236

Recognition of walking behaviors for pedestrian navigation

This paper presents a method for detecting and classifying walking behaviors based on acceleration measurements of a pedestrian, and is employed in an indoor navigation system currently being developed. The prototype navigation system uses a set of inexpensive and wearable sensors: a bi-axial accelerometer, a digital compass, and an infrared light detector. Using the measured acceleration data, the proposed method

Seon-Woo Lee; Kenji Mase

2001-01-01

237

Random Walk with Continuously Smoothed Variable Weights

Many current local search algorithms for SAT fall into one of two classes. Random walk algorithms such as Walksat\\/SKC, Novelty+ and HWSAT are very successful but can be trapped for long periods in deep local minima. Clause weighting algorithms such as DLM, GLS, ESG and SAPS are good at escaping local minima but require expen- sive smoothing phases in which

Steven David Prestwich

2005-01-01

238

Go Naked: Diapers Affect Infant Walking

ERIC Educational Resources Information Center

In light of cross-cultural and experimental research highlighting effects of childrearing practices on infant motor skill, we asked whether wearing diapers, a seemingly innocuous childrearing practice, affects infant walking. Diapers introduce bulk between the legs, potentially exacerbating infants' poor balance and wide stance. We show that…

Cole, Whitney G.; Lingeman, Jesse M.; Adolph, Karen E.

2012-01-01

239

Power grid analysis using random walks

This paper presents a linear-time algorithm for the DC analysis of a power grid, based on a random walk technique. Experimental results show that the proposed method is faster than existing approaches and has an acceptable error margin. It also has a desirable property of localizing computation, and can be extended to RC- network transient analysis. This method has been

Haifeng Qian; Sani R. Nassif; Sachin S. Sapatnekar

2005-01-01

240

Kinematical Analysis of Underwater Walking and Running

The purpose of this study was to determine kinematical characteristics of underwater locomotion and to compare them with those of land locomotion. Six male subjects performed walking and running on both conventional and underwater treadmills. Both treadmill speeds increased incrementally starting from 0.56 m s 1 to 3.33 m s 1, the maximum speed of the underwater treadmill. The motion

Takeru Kato; Shohei Onishi; Kaoru Kitagawa

2001-01-01

241

Assessment of a Solar System Walk

ERIC Educational Resources Information Center

The idea of sending students and the general public on a walk through a scale model of the solar system in an attempt to instill an appreciation of the relative scales of the sizes of the objects compared to the immense distances between them is certainly not new. A good number of such models exist, including one on the National Mall in…

LoPresto, Michael C.; Murrell, Steven R.; Kirchner, Brian

2010-01-01

242

Random Walk Method for Potential Problems

NASA Technical Reports Server (NTRS)

A local Random Walk Method (RWM) for potential problems governed by Lapalace's and Paragon's equations is developed for two- and three-dimensional problems. The RWM is implemented and demonstrated in a multiprocessor parallel environment on a Beowulf cluster of computers. A speed gain of 16 is achieved as the number of processors is increased from 1 to 23.

Krishnamurthy, T.; Raju, I. S.

2002-01-01

243

Random matrices, nonbacktracking walks, and orthogonal polynomials

NASA Astrophysics Data System (ADS)

Several well-known results from the random matrix theory, such as Wigner's law and the Marchenko-Pastur law, can be interpreted (and proved) in terms of nonbacktracking walks on a certain graph. Orthogonal polynomials with respect to the limiting spectral measure play a role in this approach.

Sodin, Sasha

2007-12-01

244

Random Walks and Sustained Competitive Advantage

Strategy is concerned with sustained interfirm profitability differences. Observations of such sustained differences are often attributed to unobserved systematic a priori differences in firm characteristics. This paper shows that sustained interfirm profitability differences may be very likely even if there are no a priori differences among firms. As a result of the phenomenon of long leads in random walks, even

Jerker Denrell

2004-01-01

245

Garden walking for depression: a research report.

This study was designed to determine the effect of garden walking and reflective journaling on adults who are 65 years old and older with depression. The Geriatric Depression Scale measured depression. Four themes emerged from the interview data collected from each participant. PMID:20706087

McCaffrey, Ruth; Hanson, Claire; McCaffrey, William

2010-01-01

246

Human Walking Analysis Assisted by DGPS

The recent advent of high sampling frequency GPS receivers opens new perspectives for the analysis of human walking pattern. Coupling satellite signal with tri- axial accelerometry gives important information on the step length of individuals. The stride length variability directly influences dead reckoning for on-foot navigation when the position cannot be computed by double integration of the antero-posterior acceleration. The

Quentin Ladetto; Vincent Gabaglio; Bertrand Merminod; Philippe Terrier; Yves Schutz

247

Random walks in a Dirichlet environment

This paper states a law of large numbers for a random walk in a random iid environment on ${\\\\mathbb Z}^d$, where the environment follows some Dirichlet distribution. Moreover, we give explicit bounds for the asymptotic velocity of the process and also an asymptotic expansion of this velocity at low disorder.

Nathanaël Enriquez; Christophe Sabot

2005-01-01

248

Coyote Walking Through Post-Wildfires

The next photo on the camera at 11:12 p.m. PST on Oct. 23, 2007, shows a coyote walking out of the wash at night, a day and a half after the fire, heading back in the direction from which the coyote was running on the early morning of Oct. 22, 2007. Photo credit: USGS...

249

A Random Walk on a Circular Path

ERIC Educational Resources Information Center

This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.

Ching, W.-K.; Lee, M. S.

2005-01-01

250

The walk and jump of Equisetum spores.

Equisetum plants (horsetails) reproduce by producing tiny spherical spores that are typically 50 µm in diameter. The spores have four elaters, which are flexible ribbon-like appendages that are initially wrapped around the main spore body and that deploy upon drying or fold back in humid air. If elaters are believed to help dispersal, the exact mechanism for spore motion remains unclear in the literature. In this manuscript, we present observations of the 'walks' and 'jumps' of Equisetum spores, which are novel types of spore locomotion mechanisms compared to the ones of other spores. Walks are driven by humidity cycles, each cycle inducing a small step in a random direction. The dispersal range from the walk is limited, but the walk provides key steps to either exit the sporangium or to reorient and refold. Jumps occur when the spores suddenly thrust themselves after being tightly folded. They result in a very efficient dispersal: even spores jumping from the ground can catch the wind again, whereas non-jumping spores stay on the ground. The understanding of these movements, which are solely driven by humidity variations, conveys biomimetic inspiration for a new class of self-propelled objects. PMID:24026816

Marmottant, Philippe; Ponomarenko, Alexandre; Bienaimé, Diane

2013-11-01

251

Biomechanics of walking, running, and sprinting

A biomechanical study of 13 runners which consisted of 2 male sprinters, 5 experienced joggers, and 6 elite long-distance runners were studied. We obtained hip, knee, and ankle joints motions in the sagittal plane and electromyographic data from specific muscle groups.As the speed of gait increased, the length of stance phase progressively decreased from 62% for walking to 31% for

Roger A. Mann; John Hagy

1980-01-01

252

Walking to School: Taking Research to Practice

ERIC Educational Resources Information Center

This article describes the results of a study that helped determine common barriers to active commuting to and from school, as well as the results of a Walking School Bus program that was implemented at two neighborhood elementary schools in Nebraska. While parental perceived barriers to active commuting may influence the travel choices of…

Heelan, Kate A.; Unruh, Scott A.; Combs, H. Jason; Donnelly, Joseph E.; Sutton, Sarah; Abbey, Bryce M.

2008-01-01

253

Pushing Random Walk Beyond Golden Ratio

We propose a simple modification of a well-known Random Walk algorithm for solving the Satisfiability problem and analyze its performance on random CNFs with a planted solution. We rigorously prove that the new algorithm solves the Full CNF with high probability, and for random CNFs with a planted solution of high density finds an assignment that differs from the planted

Ehsan Amiri; Evgeny S. Skvortsov

2007-01-01

254

Elementary Education: Elementary Students Simulate Moon Walk.

ERIC Educational Resources Information Center

Describes the project of a fourth- and fifth-grade class in simulating a moon walk. Teams consisted of the astronauts, the life support team, the flight program team, the communications team, the scientific team, and the construction team. Their visit to the Marshall Space Flight Center is also described. (SA)

Aviation/Space, 1980

1980-01-01

255

Sunspot random walk and 22-year variation

We examine two stochastic models for consistency with observed long-term secular trends in sunspot number and a faint, but semi-persistent, 22-yr signal: (1) a null hypothesis, a simple one-parameter random-walk model of sunspot-number cycle-to-cycle change, and, (2) an alternative hypothesis, a two-parameter random-walk model with an imposed 22-yr alternating amplitude. The observed secular trend in sunspots, seen from solar cycle 5 to 23, would not be an unlikely result of the accumulation of multiple random-walk steps. Statistical tests show that a 22-yr signal can be resolved in historical sunspot data; that is, the probability is low that it would be realized from random data. On the other hand, the 22-yr signal has a small amplitude compared to random variation, and so it has a relatively small effect on sunspot predictions. Many published predictions for cycle 24 sunspots fall within the dispersion of previous cycle-to-cycle sunspot differences. The probability is low that the Sun will, with the accumulation of random steps over the next few cycles, walk down to a Dalton-like minimum. Our models support published interpretations of sunspot secular variation and 22-yr variation resulting from cycle-to-cycle accumulation of dynamo-generated magnetic energy.

Love, Jeffrey J.; Rigler, E. Joshua

2012-01-01

256

Walking-Beam Solar-Cell Conveyor

NASA Technical Reports Server (NTRS)

Microprocessor-controlled walking-beam conveyor moves cells between work stations in automated assembly line. Conveyor has arm at each work station. In unison arms pick up all solar cells and advance them one station; then beam retracks to be in position for next step. Microprocessor sets beam stroke, speed, and position.

Feder, H.; Frasch, W.

1982-01-01

257

Walk Test Used to Monitor the Performance in the Health-Directed Nordic Walking

ERIC Educational Resources Information Center

Study aim: To assess the performance of subjects engaged in health-directed Nordic Walking training (with poles) and subjected to 2-km walk test (no poles). Material and methods: A total of 72 subjects, including 8 men and 32 women aged 23-73 years and 32 female students aged 19-25 years participated in the study. They were subjected twice to 2-km…

Kamien, Dorota

2008-01-01

258

Several economic and financial time series are bounded by an upper and lower finite limit (e.g., interest rates). It is not possible to say that these time series are random walks because random walks are limitless with probability one (as time goes to infinity). Yet, some of these time series behave just like random walks. In this paper we propose

2002-01-01

259

Federal Register 2010, 2011, 2012, 2013

...Period for Walk-In Coolers and Walk-in Freezers AGENCY: Office of Energy Efficiency...support document for walk-in coolers and freezers and a public meeting on May 14, 2010...document for walk-in coolers and walk-in freezers is to be re-opened from July 15,...

2010-07-15

260

IntroductionNordic pole walking (NW) has gained significant attention to increase caloric expenditure vs. conventional walking without poles. However data are pending regarding the hemodynamic response of Nordic pole walking vs. walking. We hypothesized that NW increases cardiac output stronger than conventional walking at a given perceived level of physical exertion in a field test.

Karsten Knobloch

2009-01-01

261

Based on a higher cardio-pulmonary and cardio-vascular benefit and a promised reduction of mechanical load of the musculoskeletal system Nordic Walking (NW) shows an increased market potential. The present study should investigate whether there are biomechanical differences between the locomotion patterns NW, walking and running. Moreover possible resultant load differences should be determined. Eleven subjects, who were already experienced with the NW-technique, participated in this experiment. The kinematic data were collected using two high-speed camera systems from posterior and from lateral at the same time. Simultaneously the ground reaction forces were recorded. The kinematic and the kinetic data reveal differences between the three analyzed locomotion patterns. For NW as well as walking the mechanical load of the lower extremity is lower compared to running. None of the kinematic parameters suggest a "physiological benefit" of NW compared to walking. Moreover NW shows higher vertical and horizontal forces during landing. Exclusively the lower vertical force peak during push off indicates a lower mechanical load for NW in comparison to walking. Consequently it is questionable is NW -- based on its promised "biomechanical benefits" compared to walking -- should be still recommended for overweight people and for people with existing musculoskeletal problems of the lower limb. PMID:16544213

Kleindienst, F I; Michel, K J; Schwarz, J; Krabbe, B

2006-03-01

262

Langevin Picture of Lévy Walks and Their Extensions

NASA Astrophysics Data System (ADS)

In this paper we derive Langevin picture of Lévy walks. Applying recent advances in the theory of coupled continuous time random walks we find a limiting process of the properly scaled Lévy walk. Next, we introduce extensions of Levy walks, in which jump sizes are some functions of waiting times. We prove that under proper scaling conditions, such generalized Lévy walks converge in distribution to the appropriate limiting processes. We also derive the corresponding fractional diffusion equations and investigate behavior of the mean square displacements of the limiting processes, showing that different coupling functions lead to various types of anomalous diffusion.

Magdziarz, Marcin; Szczotka, W?adys?aw; ?ebrowski, Piotr

2012-04-01

263

NetLogo Models Library: Random Walk 360

NSDL National Science Digital Library

Agent-based model produced using NetLogo that demonstrates random walks and diffusion. In this model the turtles engage in a "random walk." Each turtle walks one step away from its current location in a different random direction at each clock tick. This movement is known as walking a 360-gon "lattice." A lattice is a set of points on the plane (or in space) that form a grid on which turtles walk. As the simulation continues, one can expect the turtles to become more spread out. Will they ever return home (to their point of origin at 0 0)? Observe the kinds of patterns that develop as the turtles move.

Wilensky, Uri

264

Factors for Lower Walking Speed in Persons with Multiple Sclerosis

Objective. The purpose of this study was to analyze factors related to lower walking speed in persons with multiple sclerosis (PwMS). Methods. A cross-sectional survey was conducted. The study participants were 120 consecutive PwMS, who were able to walk, even with device assistance. Demographic and clinical data were collected. Walking speed was measured in 10 m walk test. Possible factors were assessed: disability, fatigue, visual functioning, balance confidence, physical activity level, walking impact, cognitive interference, and motor planning. A forward linear multiple regression analysis examined the correlation with lower speed. Results. Lower walking speed was observed in 85% of the patients. Fatigue (41%), recurrent falls (30%), and balance problems were also present, even with mild disability (average EDSS = 2.68). A good level of physical activity was noted in most of the subjects. Dual-task procedure revealed 11.58% of walking speed reduction. Many participants (69.57%) imagined greater walking speed than motor execution (mean ? 28.42%). Physical activity level was the only characteristic that demonstrated no significant difference between the groups (lower versus normal walking speed). Many mobility measures were correlated with walking speed; however, disability, balance confidence, and motor planning were the most significant. Conclusions. Disability, balance confidence, and motor planning were correlated with lower walking speed.

Nogueira, Leandro Alberto Calazans; dos Santos, Luciano Teixeira; Sabino, Pollyane Galinari; Alvarenga, Regina Maria Papais; Santos Thuler, Luiz Claudio

2013-01-01

265

Cardiovascular Responses Associated with Daily Walking in Subacute Stroke

Despite the importance of regaining independent ambulation after stroke, the amount of daily walking completed during in-patient rehabilitation is low. The purpose of this study is to determine if (1) walking-related heart rate responses reached the minimum intensity necessary for therapeutic aerobic exercise (40%–60% heart rate reserve) or (2) heart rate responses during bouts of walking revealed excessive workload that may limit walking (>80% heart rate reserve). Eight individuals with subacute stroke attending in-patient rehabilitation were recruited. Participants wore heart rate monitors and accelerometers during a typical rehabilitation day. Walking-related changes in heart rate and walking bout duration were determined. Patients did not meet the minimum cumulative requirements of walking intensity (>40% heart rate reserve) and duration (>10?minutes continuously) necessary for cardiorespiratory benefit. Only one patient exceeded 80% heart rate reserve. The absence of significant increases in heart rate associated with walking reveals that patients chose to walk at speeds well below a level that has meaningful cardiorespiratory health benefits. Additionally, cardiorespiratory workload is unlikely to limit participation in walking. Measurement of heart rate and walking during in-patient rehabilitation may be a useful approach to encourage patients to increase the overall physical activity and to help facilitate recovery.

Prajapati, Sanjay K.; Gage, William H.; McIlroy, William E.

2013-01-01

266

Comparison of elliptical training, stationary cycling, treadmill walking and overground walking.

The extent to which therapeutic, exercise or robotic devices can maximize gait function is a major unresolved issue in neurorehabilitation. Several factors may influence gait outcomes such as similarity of the task to overground walking, degree of coordination within and across limbs, and cycle-to-cycle variability in each device. Our objective was to compare lower extremity kinematics, coordination and variability during four locomotor tasks: overground walking, treadmill walking, elliptical training and stationary cycling in 10 non-disabled adults (6 male; mean age 22.7±2.9 yrs, range 20-29). All first performed four overground walking trials at self-selected speed with mean temporal-spatial data used to pace the other conditions. Joint positions, excursions, and the Gait Deviation Index (GDI) were compared across conditions to evaluate kinematic similarity. Time-series data were correlated within and across limbs to evaluate intralimb and interlimb coordination, respectively. Variability in cadence was quantified to assess how constrained the locomotor rhythm was compared to overground walking. Treadmill walking most closely resembled overground with GDI values nearly overlapping, reinforcing its appropriateness for gait training. Cycling showed the largest GDI difference from overground, with elliptical closer but still a significant distance from all three. Cycling showed greater hip reciprocation Cycling and elliptical showed stronger intralimb synergism at the hip and knee than the other two. Based on kinematics, results suggest that elliptical training may have greater transfer to overground walking than cycling and cycling may be more useful for enhancing reciprocal coordination. Further evaluation of these devices in neurological gait disorders is needed. PMID:21683599

Damiano, Diane L; Norman, Tracy; Stanley, Christopher J; Park, Hyung-Soon

2011-06-01

267

Environment-dependent continuous time random walk

NASA Astrophysics Data System (ADS)

A generalized continuous time random walk model which is dependent on environmental damping is proposed in which the two key parameters of the usual random walk theory: the jumping distance and the waiting time, are replaced by two new ones: the pulse velocity and the flight time. The anomalous diffusion of a free particle which is characterized by the asymptotical mean square displacement

Lin, Fang; Bao, Jing-Dong

2011-04-01

268

Holographic integral equations and walking technicolor

We study chiral symmetry breaking in the holographic D3-D7 system in a simple model with an arbitrary running coupling. We derive equations for the D7 embedding and show there is a light pion. In particular we present simple integral equations, involving just the running coupling and the quark self-energy, for the quark condensate and the pion decay constant. We compare these to the Pagels-Stokar or constituent quark model equivalent. We discuss the implications for walking technicolor theories. We also perform a similar analysis in the four-dimensional field theory whose dual is the nonsupersymmetric D3-D5 system and propose that it represents a walking theory in which the quark condensate has dimension 2+{radical}(3)

Alvares, Raul; Evans, Nick; Gebauer, Astrid; Weatherill, George James [School of Physics and Astronomy, Southampton University, Southampton, SO17 1BJ (United Kingdom)

2010-01-15

269

Random walks on finite lattices with traps

We consider dissipative processes involving both chemical reaction and physical diffusion in systems for which the influence of boundaries and system size on the dynamics cannot be neglected. We report the results of Monte Carlo simulations on an irreversible reaction in a confined system subject to two sorts of finite boundary conditions. The problem is posed in such a way as to take maximal advantage of two earlier studies: Montroll's work on random walks on d-dimensional periodic lattices with traps, and the work of Sanders, Ruijgrok, and ten Bosch on random walks on two-dimensional finite lattices with traps. Our results are used to discuss the concept of reduction of dimensionality as introduced by Adam and Delbrueck in their study of biological diffusion processes.

Hatlee, M.D.; Kozak, J.J.

1980-02-15

270

We discuss a possible experimental scheme for the implementation of a quantum walk. The scheme is based on the passage of an atom inside a high-Q cavity. The chirality is characterized by the atomic states and the displacement is characterized by the photon number inside the cavity. The quantum steps are described by appropriate interactions with a sequence of classical and quantized cavity fields.

Di Tiegang [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Hillery, Mark [Department of Physics, Hunter College of CUNY, 695 Park Avenue, New York, New York 10021 (United States); Zubairy, M. Suhail [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Department of Electronics, Quaid-i-Azam University, Islamabad (Pakistan)

2004-09-01

271

A random walk approach to quantum algorithms

The development of quantum algorithms based on quantum versions of random\\u000awalks is placed in the context of the emerging field of quantum computing.\\u000aConstructing a suitable quantum version of a random walk is not trivial: pure\\u000aquantum dynamics is deterministic, so randomness only enters during the\\u000ameasurement phase, i.e., when converting the quantum information into classical\\u000ainformation. The outcome

Vivien M. Kendon

2006-01-01

272

Walking technicolor and electroweak radiative corrections

We examine the effect of walking technicolor dynamics on the electroweak S-parameter and contrast it with the effect of QCD-like technicolor dynamics. Our main tools are the operator product expansion for the high-momentum behavior of the electroweak gauge boson vacuum polarizations and the analyticity of these polarizations which relate their low and high momentum behaviors. We show that whereas in

Raman Sundrum; Stephen D. H. Hsu

1993-01-01

273

Infrared dynamics of minimal walking technicolor

We study the gauge sector of minimal walking technicolor, which is an SU(2) gauge theory with nf=2 flavors of Wilson fermions in the adjoint representation. Numerical simulations are performed on lattices Nt×Ns3, with Ns ranging from 8 to 16 and Nt=2Ns, at fixed beta=2.25, and varying the fermion bare mass m0, so that our numerical results cover the full range

Luigi Del Debbio; Biagio Lucini; Agostino Patella; Claudio Pica; Antonio Rago

2010-01-01

274

Delayed Random Walks: Modeling Human Posture Control

NASA Astrophysics Data System (ADS)

We consider a phenomenological description of a noisy trajectory which appears on a stabiliogram platform during human postural sway. We hypothesize that this trajectory arises due to a mixture of uncontrollable noise and a corrective delayed feedback to an upright position. Based on this hypothesis, we model the process with a biased random walk whose transition probability depends on its position at a fixed time delay in the past, which we call a delayed random walk. We first introduce a very simple model (T. Ohira and J. G. Milton, Phys.Rev.E. 52), 3277, (1995), which can nevertheless capture the rough qualitative features of the two--point mean square displacement of experimental data with reasonable estimation of delay time. Then, we discuss two approaches toward better capturing and understanding of the experimental data. The first approach is an extension of the model to include a spatial displacement threshold from the upright position below which no or only weak corrective feedback motion takes place. This can be incorporated into an extended delayed random walk model. Numerical simulations show that this extended model can better capture the three scaling region which appears in the two--point mean square displacement. The other approach studied the autocorrelation function of the experimental data, which shows oscillatory behavior. We recently investigated a delayed random walk model whose autocorrelation function has analytically tractable oscillatory behavior (T. Ohira, Phys.Rev.E. 55), R1255, (1997). We discuss how this analytical understanding and its application to delay estimation (T. Ohira and R. Sawatari, Phys.Rev.E. 55), R2077, (1997) could possibly be used to further understand the postural sway data.

Ohira, Toru

1998-03-01

275

Baby Carriage: Infants Walking With Loads

Maintaining balance is a central problem for new walkers. To examine how infants cope with the additional balance control problems induced by load carriage, 14-month-olds were loaded with 15% of their body weight in shoulder-packs. Both symmetrical and asymmetrical loads disrupted alternating gait patterns and caused less mature footfall patterns. Walking was most severely compromised by back loads. Infants with

Jessie S. Garciaguirre; Karen E. Adolph; Patrick E. Shrout

2007-01-01

276

Walking Habits of Adults with Mental Retardation

ERIC Educational Resources Information Center

The walking activity of men and women with mental retardation residing in community settings was described. Participants were 38 women (M age = 0.7, SD = 9.5) and 65 men (M age = 35.9, SD = 11.2). They wore pedometers for 7 days. A 2 ? 2 factorial ANOVA indicated no significant gender differences in total step counts or between participants with…

Stanish, Heidi I.; Draheim, Christopher C.

2005-01-01

277

Early independent walking: a longitudinal study of load perturbation effects.

This study investigated infants' ability to adapt to experimentally induced changes in their body dimensions at walk onset, and how this ability is affected by increased walking experience. Fifteen infants were studied over their first 6 months of independent walking with a load perturbation design. They traversed a walkway with loads symmetrically placed around the shoulders, waist, or ankles, and without loading. At walk onset, infants fell more with shoulder and ankle loads than with waist or no loads. Shoulder loads further resulted in higher walking speed and longer steps, while waist loads resulted in increased walking speed and larger foot rotation. Ankle loads disrupted walking proficiency the most, as indicated by lower walking speed, shorter steps, larger foot rotation, and smaller step-to-step angle. Step width was not differentially affected by the conditions. With increased experience, walking proficiency increased across all conditions, but ankle loads lagged behind the other conditions. Loading effects are discussed with respect to walking experience and position of the loads on the body. PMID:19365798

Vereijken, Beatrix; Pedersen, Arve Vorland; Størksen, Jan Harry

2009-05-01

278

The variability problem of normal human walking.

Previous investigations have suggested considerable inter-individual variability in the time course pattern of net joint moments during normal human walking, although the limited sample sizes precluded statistical analyses. The purpose of the present study was to obtain joint moment patterns from a group of normal subjects and to test whether or not the expected differences would prove to be statistically significant. Fifteen healthy male subjects were recorded on video while they walked across two force platforms. Ten kinematic and kinetic parameters were selected and input to a statistical cluster analysis to determine whether or not the 15 subjects could be divided into different 'families' (clusters) of walking strategy. The net joint moments showed a variability corroborating earlier reports. The cluster analysis showed that the 15 subjects could be grouped into two clusters of 5 and 10 subjects, respectively. Five parameters differed significantly, so the group of 5 subjects was characterized by (1) a higher peak knee joint extensor moment, (2) more flexed knee joint angle at heel strike, (3) during the whole stance phase, (4) lower peak knee joint flexor moment and (5) lower ankle joint angle at flat foot position. Calculation of bone-on-bone forces in the knee joint showed a value of 64 N/kg body weight in the K+ group and 55 N/kg in the K- group (p<0.05). It is unknown if differences of similar magnitude contribute to early joint degeneration in some individuals while not in others. PMID:21852174

Simonsen, Erik B; Alkjær, Tine

2012-03-01

279

Random walk to a nonergodic equilibrium concept.

Random walk models, such as the trap model, continuous time random walks, and comb models, exhibit weak ergodicity breaking, when the average waiting time is infinite. The open question is, what statistical mechanical theory replaces the canonical Boltzmann-Gibbs theory for such systems? In this paper a nonergodic equilibrium concept is investigated, for a continuous time random walk model in a potential field. In particular we show that in the nonergodic phase the distribution of the occupation time of the particle in a finite region of space approaches U- or W-shaped distributions related to the arcsine law. We show that when conditions of detailed balance are applied, these distributions depend on the partition function of the problem, thus establishing a relation between the nonergodic dynamics and canonical statistical mechanics. In the ergodic phase the distribution function of the occupation times approaches a delta function centered on the value predicted based on standard Boltzmann-Gibbs statistics. The relation of our work to single-molecule experiments is briefly discussed. PMID:16486234

Bel, G; Barkai, E

2006-01-01

280

Gait Recognition and Walking Exercise Intensity Estimation

Cardiovascular patients consult doctors for advice regarding regular exercise, whereas obese patients must self-manage their weight. Because a system for permanently monitoring and tracking patients’ exercise intensities and workouts is necessary, a system for recognizing gait and estimating walking exercise intensity was proposed. For gait recognition analysis, ?? filters were used to improve the recognition of athletic attitude. Furthermore, empirical mode decomposition (EMD) was used to filter the noise of patients’ attitude to acquire the Fourier transform energy spectrum. Linear discriminant analysis was then applied to this energy spectrum for training and recognition. When the gait or motion was recognized, the walking exercise intensity was estimated. In addition, this study addressed the correlation between inertia and exercise intensity by using the residual function of the EMD and quadratic approximation to filter the effect of the baseline drift integral of the acceleration sensor. The increase in the determination coefficient of the regression equation from 0.55 to 0.81 proved that the accuracy of the method for estimating walking exercise intensity proposed by Kurihara was improved in this study.

Lin, Bor-Shing; Liu, Yu-Ting; Yu, Chu; Jan, Gene Eu; Hsiao, Bo-Tang

2014-01-01

281

Animal navigation: general properties of directed walks.

The ability to locomote is a defining characteristic of all animals. Yet, all but the most trivial forms of navigation are poorly understood. Here we report and discuss the analytical results of an in-depth study of a simple navigation problem. In principle, there are two strategies for navigating a straight course. One is to use an external directional reference and to continually reorient with reference to it. The other is to monitor body rotations from internal sensory information only. We showed previously that, at least for simple representations of locomotion, the first strategy will enable an animal or mobile agent to move arbitrarily far away from its starting point, but the second strategy will not do so, even after an infinite number of steps. This paper extends and generalizes the earlier results by demonstrating that these findings are true even when a very general model of locomotion is used. In this general model, error components within individual steps are not independent, and directional errors may be biased. In the absence of a compass, the expected path of a directed walk in general approximates a logarithmic spiral. Some examples are given to illustrate potential applications of the quantitative results derived here. Motivated by the analytical results developed in this work, a nomenclature for directed walks is proposed and discussed. Issues related to path integration in mammals and robots, and measuring the curvature of a noisy path are also addressed using directed walk theory. PMID:18781320

Cheung, Allen; Zhang, Shaowu; Stricker, Christian; Srinivasan, Mandyam V

2008-09-01

282

Efficacy of Nordic walking in obesity management.

The effects of a Nordic walking (NW) program compared to those of a walking (W) program on physiological and perceptual variables in obese middle-aged women were investigated. Subjects (n=12 NW group, n=11 W group) trained over 12 weeks 3 times.week (-1). Body mass, body mass index (BMI), body fat, heart rate (HR), resting blood pressure, peak oxygen consumption (V?O (2peak)) were measured before and after the training period. Moreover, HR, rating of perceived exertion (RPE) and adherence were recorded during all training sessions. After the training period body mass, body fat and diastolic blood pressure decreased in both groups (P<0.05) whereas V?O (2peak) increased in the NW group (+3.7?ml.min (-1).kg (-1); P=0.005). During the training sessions, mean HR (P=0.021), HR at preferred walking speed (P=0.020) and % of time at high intensity (P=0.031) were higher in NW than in the W group. Finally, RPE was not influenced by the modality of exercise and NW group showed a higher rate of adherence (91±19% vs. 81±29%; P=0.011). To conclude, NW activity in obese women allows an increase in exercise intensity and adherence to a training program without increasing the perception of effort leading to enhanced aerobic capacity. PMID:21472629

Figard-Fabre, H; Fabre, N; Leonardi, A; Schena, F

2011-06-01

283

Walking simulator for evaluation of ophthalmic devices

NASA Astrophysics Data System (ADS)

Simulating mobility tasks in a virtual environment reduces risk for research subjects, and allows for improved experimental control and measurement. We are currently using a simulated shopping mall environment (where subjects walk on a treadmill in front of a large projected video display) to evaluate a number of ophthalmic devices developed at the Schepens Eye Research Institute for people with vision impairment, particularly visual field defects. We have conducted experiments to study subject's perception of "safe passing distance" when walking towards stationary obstacles. The subject's binary responses about potential collisions are analyzed by fitting a psychometric function, which gives an estimate of the subject's perceived safe passing distance, and the variability of subject responses. The system also enables simulations of visual field defects using head and eye tracking, enabling better understanding of the impact of visual field loss. Technical infrastructure for our simulated walking environment includes a custom eye and head tracking system, a gait feedback system to adjust treadmill speed, and a handheld 3-D pointing device. Images are generated by a graphics workstation, which contains a model with photographs of storefronts from an actual shopping mall, where concurrent validation experiments are being conducted.

Barabas, James; Woods, Russell L.; Peli, Eli

2005-03-01

284

Genome walking by next generation sequencing approaches.

Genome Walking (GW) comprises a number of PCR-based methods for the identification of nucleotide sequences flanking known regions. The different methods have been used for several purposes: from de novo sequencing, useful for the identification of unknown regions, to the characterization of insertion sites for viruses and transposons. In the latter cases Genome Walking methods have been recently boosted by coupling to Next Generation Sequencing technologies. This review will focus on the development of several protocols for the application of Next Generation Sequencing (NGS) technologies to GW, which have been developed in the course of analysis of insertional libraries. These analyses find broad application in protocols for functional genomics and gene therapy. Thanks to the application of NGS technologies, the original vision of GW as a procedure for walking along an unknown genome is now changing into the possibility of observing the parallel marching of hundreds of thousands of primers across the borders of inserted DNA molecules in host genomes. PMID:24832505

Volpicella, Mariateresa; Leoni, Claudia; Costanza, Alessandra; Fanizza, Immacolata; Placido, Antonio; Ceci, Luigi R

2012-01-01

285

Gait recognition and walking exercise intensity estimation.

Cardiovascular patients consult doctors for advice regarding regular exercise, whereas obese patients must self-manage their weight. Because a system for permanently monitoring and tracking patients' exercise intensities and workouts is necessary, a system for recognizing gait and estimating walking exercise intensity was proposed. For gait recognition analysis, ?? filters were used to improve the recognition of athletic attitude. Furthermore, empirical mode decomposition (EMD) was used to filter the noise of patients' attitude to acquire the Fourier transform energy spectrum. Linear discriminant analysis was then applied to this energy spectrum for training and recognition. When the gait or motion was recognized, the walking exercise intensity was estimated. In addition, this study addressed the correlation between inertia and exercise intensity by using the residual function of the EMD and quadratic approximation to filter the effect of the baseline drift integral of the acceleration sensor. The increase in the determination coefficient of the regression equation from 0.55 to 0.81 proved that the accuracy of the method for estimating walking exercise intensity proposed by Kurihara was improved in this study. PMID:24714057

Lin, Bor-Shing; Liu, Yu-Ting; Yu, Chu; Jan, Gene Eu; Hsiao, Bo-Tang

2014-04-01

286

The purpose of this study was to compare the effects of Nordic walking with conventional walking and band-based resistance exercise on functional fitness, static balance and dynamic balance in older adults. Volunteers (n = 65) were divided into four groups: Nordic walking (NW), conventional walking (CW), resistance (RES), and control. Each group performed activity 50-70 min·day(-1) (warm-up 10-15 min, main exercise 30-40, and cool down 10-15 min), 3 days·week(-1) (NW and CW) or 2 day·week(-1) (RES) for 12 wks. Upper-body strength improved (p < 0. 05) in the RES (22.3%) and the NW (11.6%) groups compared to the CW and control groups. Cardio- respiratory fitness improved more in the NW (10.9%) and CW (10.6%) groups compared to the RES and control groups. Upper- and lower-body flexibility also improved in all exercise groups compared to the control group. There were no improvements in balance measures in any group. While all modes of exercise improved various components of fitness, Nordic walking provided the best well-rounded benefits by improving upper-body strength, cardiovascular endurance, and flexibility. Therefore, Nordic walking is recommended as an effective and efficient mode of concurrent exercise to improve overall functional fitness in older adults. Key PointsNordic walking, conventional walking, and resistance training are beneficial for older adults.Nordic walking and conventional walking both improve cardio-respiratory fitness while resistance training does not.Nordic walking provides additional benefits in upper-body muscular strength compared to conventional walking.Nordic walking is an effective and efficient mode of exercise to improve overall fitness in older adults. PMID:24149147

Takeshima, Nobuo; Islam, Mohammod M; Rogers, Michael E; Rogers, Nicole L; Sengoku, Naoko; Koizumi, Daisuke; Kitabayashi, Yukiko; Imai, Aiko; Naruse, Aiko

2013-01-01

287

Finding Structural Anomalies in Star Graphs Using Quantum Walks

NASA Astrophysics Data System (ADS)

We develop a general theory for a quantum-walk search on a star graph. A star graph has N edges each of which is attached to a central vertex. A graph G is attached to one of these edges, and we would like to find out to which edge it is attached. This is done by means of a quantum walk, a quantum version of a random walk. This walk contains O(?N ) steps, which represents a speedup over a classical search, which would require O(N) steps. The overall graph, star plus G, is divided into two parts, and we find that for a quantum speedup to occur, the eigenvalues associated with these two parts in the N?? limit must be the same. Our theory tells us how the initial state of the walk should be chosen, and how many steps the walk must make in order to find G.

Cottrell, Seth; Hillery, Mark

2014-01-01

288

Barriers and facilitators for walking in individuals with intermittent claudication.

This study aimed to identify barriers and facilitators associated with walking for exercise among people who experience intermittent claudication. Fifteen individuals (7 men and 8 women) participated in 3 focus groups that were tape-recorded and content analyzed. A social-cognitive framework was used to categorize barriers and facilitators as those related to the person, to the activity, or to the environment. Variables identified included those specific to intermittent claudication and those common among the general population. Barriers to walking included irregular or graded walking surfaces, uncertainty about the outcome of walking, ambiguity regarding pain, the need to take rest breaks, and the presence of leg pain. Facilitating factors included availability of a resting place, use of cognitive coping strategies, companionship support, and availability of a treadmill-walking program. Findings are interpreted in light of current research on exercise determinants and encourage prospective examinations of the predictive validity of these factors for walking. PMID:18212396

Galea, Melissa N; Bray, Steven R; Ginis, Kathleem A Martin

2008-01-01

289

Adaptive walks on correlated fitness landscapes with heterogeneous connectivities

NASA Astrophysics Data System (ADS)

We propose a model for studying the statistical properties of adaptive walks on correlated fitness landscapes which are established in genotype spaces of complex structure. The fitness distribution on the genotype space follows either the bivariate Gaussian distribution or the bivariate exponential distribution. In both cases the degree of correlation of the fitness landscape can be tuned by using a single parameter. To perform the adaptive walks two distinct rules are applied: the random adaptation walk (RAW) and the gradient adaptation walk (GAW). While for the RAW the mean walk length, \\bar {L} , is a monotonic increasing function of the connectivity of the genotype space, for the GAW \\bar {L} is a one-humped function. The RAW produces longer adaptive walks compared to the GAW, though its performance is slightly poorer and thereby the local maxima reached by the GAW algorithm are usually closer to the global optimum of the fitness landscape.

de Lima Filho, J. A.; Moreira, F. G. B.; Campos, P. R. A.; de Oliveira, Viviane M.

2012-02-01

290

Depressive Symptoms, Social Support, and Walking Among Hispanic Older Adults

Objectives Depressive symptoms and physical inactivity are health risks among minority older adults. This study examined whether social support moderated the relationship of depressive symptoms to walking behavior among 217 community-dwelling, Hispanic older adults. Method Cross-sectional analyses were used to test whether different forms of social support interacted with depressive symptoms to affect both likelihood and amount of walking. Results Analyses showed a significant interaction between depressive symptoms and instrumental support related to the likelihood of walking and a marginally significant interaction between depressive symptoms and instrumental social support related to the amount of walking. Depressive symptoms were associated with a lower likelihood and lower amount of walking among participants receiving high levels of instrumental social support (e.g., help with chores) but not low instrumental support. Emotional and informational support did not moderate the depression to walking relationship. Conclusion Receiving too much instrumental support was related to sedentary behavior among depressed older adults.

Perrino, Tatiana; Brown, Scott C.; Huang, Shi; Brown, C. Hendricks; Gomez, Gianna Perez; Pantin, Hilda; Szapocznik, Jose

2013-01-01

291

Background Using two different measures of park area, at three buffer distances, we sought to investigate the ways in which park area and proximity to parks, are related to the frequency of walking (for all purposes) in Australian adults. Little previous research has been conducted in this area, and results of existing research have been mixed. Methods Residents of 50 urban areas in metropolitan Melbourne, Australia completed a physical activity survey (n = 2305). Respondents reported how often they walked for ?10 minutes in the previous month. Walking frequency was dichotomised to ‘less than weekly’ (less than 1/week) and ‘at least weekly’ (1/week or more). Using Geographic Information Systems, Euclidean buffers were created around each respondent’s home at three distances: 400metres (m), 800 m and 1200 m. Total area of parkland in each person’s buffer was calculated for the three buffers. Additionally, total area of ‘larger parks’, (park space???park with Australian Rules Football oval (17,862 m2)), was calculated for each set of buffers. Area of park was categorised into tertiles for area of all parks, and area of larger parks (the lowest tertile was used as the reference category). Multilevel logistic regression, with individuals nested within areas, was used to estimate the effect of area of parkland on walking frequency. Results No statistically significant associations were found between walking frequency and park area (total and large parks) within 400 m of respondent’s homes. For total park area within 800 m, the odds of walking at least weekly were lower for those in the mid (OR 0.65, 95% CI 0.46-0.91) and highest (OR 0.65, 95% CI 0.44-0.95) tertile of park area compared to those living in areas with the least amount of park area. Similar results were observed for total park area in the 1200 m buffers. When only larger parks were investigated, again more frequent walking was less likely when respondents had access to a greater amount of park area. Conclusions In this study we found that more park area in residential environments reduced the odds of walking more frequently. Other area characteristics such as street connectivity and destinations may underlie these associations by negatively correlating with park area.

2012-01-01

292

The study investigated the effect of varying pole weights on energy expenditure, upper limb muscle activation and on forces\\u000a transmitted to the poles during Nordic walking (NW). Twelve women [age = 21 (2) years, body mass = 60.8 (6) kg, height = 1.71\\u000a (0.06) m] participated in five 7-min walking tests randomly chosen without poles (W), with normal NW poles (NW) or with added\\u000a masses of 0.5 kg (NW + 0.5) 1.0 kg

Thorsten Schiffer; Axel Knicker; Melissa Montanarella; Heiko K. Strüder

2011-01-01

293

Stabilizing biped walking on rough terrain based on the compliance control

In this paper, we propose a control system that changes the compliance based on the walking speed to stabilize biped walking on rough terrain. The proposed system does not use the inclination of the terrain. Instead, the system changes walking modes depends on its walking speed. In the downhill terrain, when the walking speed is increased, the stiffness of the

Masaki Ogino; Hiroyuki Toyama; Minoru Asada

2007-01-01

294

Realization of dynamic biped walking stabilized by trunk motion on a sagittally uneven surface

The authors introduce a control method for dynamic biped walking stabilized by trunk motion on a sagitally uneven surface, that is for a biped walking robot which has a trunk to stabilize its walking, and its effectiveness as supported by walking experiments using a biped walking robot. This control method is based on the introduction of a new concept called

Atsuo Takanishi; Hun-ok Lim; Masayuki Tsuda; Ichiro Kato

1990-01-01

295

AutoGait: A mobile platform that accurately estimates the distance walked

AutoGait is a mobile platform that autonomously discovers a user's walking profile and accurately estimates the distance walked. The discovery is made by utilizing the GPS in the user's mobile device when the user is walking outdoors. This profile can then be used both indoors and outdoors to estimate the distance walked. To model the person's walking profile, we take

Dae-Ki Cho; Min Mun; Uichin Lee; Williams J. Kaiser; Mario Gerla

2010-01-01

296

A symmetric walking cancellation algorithm of a foot-platform locomotion interface

This paper describes a symmetric walking cancellation algorithm for generating smooth motions on the foot-platform locomotion interface. This solves the problem of the asymmetric walking velocity profile of the swing and stance feet in the existing constant-velocity walking cancellation method. The proposed symmetric walking cancellation method cancels the stance foot motion with the opposite swing foot motion. Walking simulations, experiments,

Jungwon YoonI; Jeha Ryu

2008-01-01

297

Entropy rate of message sources driven by quantum walks

NASA Astrophysics Data System (ADS)

The amount of information generated by a discrete time stochastic processes in a single step can be quantified by the entropy rate. We investigate the differences between two discrete time walk models, the discrete time quantum walk and the classical random walk, in terms of entropy rate. We develop analytical methods to calculate and approximate it. This allows us to draw conclusions about the differences between classical stochastic and quantum processes in terms of the classical information theory.

Kollár, B.; Koniorczyk, M.

2014-02-01

298

COORDINATED WALKING OF STICK INSECTS ON A MERCURY SURFACE

SUMMARY Adult stick insects walk on a mercury surface at step frequencies in the range 1-4 Hz with a coordination similar to that found in free-walking adults at their maximum step frequency of 3 Hz. The amplitude of leg movement covers the same range as that found in free-walking animals. The use of a mercury substrate effectively removes mechanical interactions

D. GRAHAM; H. CRUSE

1981-01-01

299

A New Family of Solvable Pearson-Dirichlet Random Walks

An n-step Pearson-Gamma random walk in R d starts at the origin and consists of n independent steps with gamma distributed lengths and uniform orientations. The gamma distribution of each step length has a shape parameter q>0. Constrained random walks of n steps in R d are obtained from the latter walks by imposing that the sum of the step

Gérard Le Caër

2011-01-01

300

A New Family of Solvable Pearson-Dirichlet Random Walks

An n-step Pearson-Gamma random walk in ?\\u000a d\\u000a starts at the origin and consists of n independent steps with gamma distributed lengths and uniform orientations. The gamma distribution of each step length has\\u000a a shape parameter q>0. Constrained random walks of n steps in ?\\u000a d\\u000a are obtained from the latter walks by imposing that the sum of the step

Gérard Le Caër

2011-01-01

301

On the non-equivalence of two standard random walks

NASA Astrophysics Data System (ADS)

We focus on two models of nearest-neighbour random walks on d-dimensional regular hyper-cubic lattices that are usually assumed to be identical-the discrete-time Polya walk, in which the walker steps at each integer moment of time, and the Montroll-Weiss continuous-time random walk in which the time intervals between successive steps are independent, exponentially and identically distributed random variables with mean 1. We show that while for symmetric random walks both models indeed lead to identical behaviour in the long time limit, when there is an external bias they lead to markedly different behaviour.

Bénichou, O.; Lindenberg, K.; Oshanin, G.

2013-09-01

302

Connecting the discrete- and continuous-time quantum walks

Recently, quantized versions of random walks have been explored as effective elements for quantum algorithms. In the simplest case of one dimension, the theory has remained divided into the discrete-time quantum walk and the continuous-time quantum walk. Though the properties of these two walks have shown similarities, it has remained an open problem to find the exact relation between the two. The precise connection of these two processes, both quantally and classically, is presented. Extension to higher dimensions is also discussed.

Strauch, Frederick W. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8423 (United States)

2006-09-15

303

Open Quantum Walks: Microscopic Derivation and Generalised Master Equation

NASA Astrophysics Data System (ADS)

Recently, a formalism for discrete time open quantum walks was introduced [S. Attal et al., J. Stat. Phys., 147 (2012) 832; S. Attal, F. Petruccione, I. Sinayskiy, Phys. Lett. A, 376 (2012) 1545]. This formalism is exclusively based on the non-unitary dynamics induced by the environment. This approach rests upon the implementation of appropriate completely positive maps. Open quantum walks include the classical random walk and through a realization procedure a connection to the Hadamard quantum walk is established. Open quantum walks allow for an unravelling in terms of quantum trajectories. It was shown [I. Sinayskiy and F. Petruccione, QIP 11 (2012) 1301] that open quantum walks can perform universal quantum computation and can be used for quantum state engineering. Here, we present the microscopic derivation of open quantum walks. A walk on a graph is considered and transitions between vertices are mediated by the interaction of the walker with a shared bosonic environment. The reduced dynamics of the walker is shown to be described in terms of a generalised Markovian master equation. The time discretization of the master equation gives raise to an open quantum walk. Based on the class of microscopic models considered here possible physical implementations are discussed.

Petruccione, Francesco; Sinayskiy, Ilya

2013-03-01

304

Walking control of small size humanoid robot: Hajime Robot 18

NASA Astrophysics Data System (ADS)

HAJIME ROBOT 18 is a fully autonomous biped robot. It has been developed for RoboCup which is a worldwide soccer competition of robots. It is necessary for a robot to have high mobility to play soccer. High speed walking and all directional walking are important to approach and to locate in front of a ball. HAJIME ROBOT achieved these walking. This paper describes walking control of a small size humanoid robot 'HAJIME ROBOT 18' and shows the measurement result of ZMP (Zero Moment Point). HAJIME ROBOT won the Robotics Society of Japan Award in RoboCup 2005 and in RoboCup 2006 Japan Open.

Sakamoto, Hajime; Nakatsu, Ryohei

2007-12-01

305

Spectral analysis of walking with shoes and without shoes.

This study analyzes the walking balance of young students based on 1/f fluctuations using auto-regressive (AR) modeling. There was more good walking balance than bad, influenced positively or negatively by the students' shoes. After the subjects understood their own walking condition, based on 1/f fluctuation, and had received suitable rehabilitation and shoes, their walking balance became better. This study provides a useful new method of medical evaluation in rehabilitation and physical fitness, and a means for subjects to maintain a state of well being. PMID:17945938

Tsuruoka, Masako; Tsuruoka, Yuriko; Shibasaki, Ryosuke; Yasuoka, Yoshifumi

2006-01-01

306

FRACTAL DIMENSION RESULTS FOR CONTINUOUS TIME RANDOM WALKS

Continuous time random walks impose random waiting times between particle jumps. This paper computes the fractal dimensions of their process limits, which represent particle traces in anomalous diffusion.

Meerschaert, Mark M.; Nane, Erkan; Xiao, Yimin

2013-01-01

307

Walking on a Graph with a Magnifying Glass: Stratified Sampling via Weighted Random Walks

Our objective is to sample the node set of a large unknown graph via crawling, to accurately estimate a given metric of interest. We design a random walk on an appropriately defined weighted graph that achieves high efficiency by preferentially crawling those nodes and edges that convey greater information regarding the target metric. Our approach begins by employing the theory

Maciej Kurant; Minas Gjoka; C. T. Butts; Athina Markopoulou

2011-01-01

308

Nordic Walking Verletzungen - Der Nordic-Walking-Daumen als neue Verletzungsentität

Background: Nordic pole Walking (NW) as trend sport is asso- ciated with beneficial effects on the cardiovascular system. Data regarding the injury and overload injury rates are pending. Methods: 137 athletes (74 % females, 53 ± 12 years, weight 73 ± 13 kg, height 169 ± 11 cm) were prospectively ask using a two-sided questionnaire. Mean NW experience was 212.8

K. Knobloch; P. M. Vogt

2006-01-01

309

Walking the Walk: The Association Between Community Environmentalism and Green Travel Behavior

Problem: Reducing gasoline consumption could sharply curtail greenhouse gas emissions. Ongoing research seeks to document factors associated with green travel behavior, like walking and transit use.Purpose: We seek to determine whether green beliefs and values are associated with green travel behavior. We measure whether residents of communities with environmentalist attributes drive less, consume less gasoline, and are more likely to

Matthew E. Kahn; Eric A. Morris

2009-01-01

310

Vertical engine for walk behind lawn mower

This patent describes a lawn mower or other similar walk behind type of implement that is designed to be operated in a normally erect position and which is tilted to the side for servicing. An engine is provided for the lawn mower having an output shaft rotatable about a vertically extending axis. The engine includes a lubricating system incorporating a crankcase in which the engine output shaft rotates and a crankcase ventilating system. The crankcase ventilating system is designed so as to prevent lubricant from flowing into the induction system when the engine is tilted on its side.

Isaka, Y.; Oguri, K.

1988-03-01

311

Planning strategies for the Ambler walking robot

NASA Technical Reports Server (NTRS)

A hierarchy of planning strategies is proposed and explained for a walking robot called the Ambler. The hierarchy decomposes planning into levels of trajectory, gait, and footfall. An abstraction of feasible traversability allows the Ambler's trajectory planner to identify acceptable trajectories by finding paths that guarantee footfalls without specifying exactly which footfalls. Leg and body moves that achieve this trajectory can be generated by the Ambler's gait planner, which incorporates pattern constraints and measures of utility to search for the best next move. By combining constraints from the quality and details of the terrain, the Ambler's footfall planner can select footfalls that insure stability and remain within the tolerances of the gait.

Wettergreen, David; Thomas, Hans; Thorpe, Chuck

1990-01-01

312

Pier Walk '97: The Electronic Version

NSDL National Science Digital Library

Pier Walk, hosted by the Navy Pier in Chicago, is the world's largest outdoor sculpture exhibition, showcasing the talents of 110 artists from 7 countries. This site offers a virtual tour in two formats: a text based index, essentially a slide show in five parts, and a pictorial index with thumbnails and some basic information about each artist. There is also a pop-up shortcut Java menu without text. Another feature is a modest collection of links to other sculpture sites, a nice resource as paintings seem to dominate the current world of virtual exhibitions.

1997-01-01

313

Light dilaton in walking gauge theories

We analyze the existence of a dilaton in gauge theories with approximate infrared conformal symmetry. To the extent that these theories are governed in the infrared by an approximate fixed point (walking), the explicit breaking of the conformal symmetry at these scales is vanishingly small. If confinement and spontaneous chiral-symmetry breaking set in at some infrared scale, the resultant breaking of the approximate conformal symmetry can lead to the existence of a dilaton with mass parametrically small compared to the confinement scale, and potentially observable at the LHC.

Appelquist, Thomas [Department of Physics, Sloane Laboratory, Yale University, New Haven, Connecticut 06520 (United States); Bai Yang [Theoretical Physics Department, Fermilab, Batavia, Illinois 60510 (United States)

2010-10-01

314

Quantum-walk-based search and centrality

We study the discrete-time quantum-walk-based search for a marked vertex on a graph. By considering various structures in which not all vertices are equivalent, we investigate the relationship between the successful search probability and the position of the marked vertex, in particular, its centrality. We find that the maximum value of the search probability does not necessarily increase as the marked vertex becomes more central, and we investigate an interesting relationship between the frequency of the successful search probability and the centrality of the marked vertex.

Berry, Scott D.; Wang, Jingbo B. [School of Physics, The University of Western Australia, Perth, WA 6009 (Australia)

2010-10-15

315

NSDL National Science Digital Library

In the previous lesson, students learned about the issue of bycatching by fisheries and how it affects marine habitats. Dolphins are one of the main species affected by bycatching. Dolphins use echolocation to identify the location of objects in the water, but they have difficulty identifying nets, and thus can be caught accidentally. Students will learn how echolocation works, why certain animals use it to determine the size, shape, and distance of objects, and how humans can potentially take advantage of dolphins' echolocation ability when developing bycatch avoidance methods. In this activity the students will experience a simulation of echolocation and use it to walk along a path while blindfolded.

Engineering K-Ph.d. Program

316

Thermodynamical asymmetries in whirling, jumping and walking

NASA Astrophysics Data System (ADS)

We analyze, from the thermodynamical point of view, mechanical systems in which there is the production of mechanical energy due to an internal source of energy, and compare that analysis with a similar one for the ‘symmetric’ motion that occurs with energy dissipation. The analysis of the energetic asymmetries is instructive to put in evidence the role of thermodynamics even in the discussion of mechanical aspects. We illustrate the discussion with the well-known example of a person on a rotating platform outstretching and contracting his or her arms, and also with other common situations such as jumping and walking.

Güémez, J.; Fiolhais, M.

2014-05-01

317

ERIC Educational Resources Information Center

These two case studies assessed technology-based programs for promoting walking fluency and improving foot-ground contact during walking with a man and a woman with multiple disabilities, respectively. The man showed breaks during walking and the woman presented with toe walking. The technology used in the studies included a microprocessor with…

Lancioni, Giulio E.; Singh, Nirbhay N.; O'Reilly, Mark F.; Sigafoos, Jeff; La Martire, Maria L.; Oliva, Doretta; Groeneweg, Jop

2012-01-01

318

Federal Register 2010, 2011, 2012, 2013

...Standards for Walk-In Coolers and Freezers; Correction AGENCY: Office of...procedure for walk-in coolers and freezers. The correction addresses an erroneous...temperature condition for walk-in freezers. DATES: Effective Date:...

2011-06-02

319

Behavioral and neural correlates of imagined walking and walking-while-talking in the elderly.

Cognition is important for locomotion and gait decline increases the risk for morbidity, mortality, cognitive decline, and dementia. Yet, the neural correlates of gait are not well established, because most neuroimaging methods cannot image the brain during locomotion. Imagined gait protocols overcome this limitation. This study examined the behavioral and neural correlates of a new imagined gait protocol that involved imagined walking (iW), imagined talking (iT), and imagined walking-while-talking (iWWT). In Experiment 1, 82 cognitively-healthy older adults (M?=?80.45) walked (W), iW, walked while talking (WWT) and iWWT. Real and imagined walking task times were strongly correlated, particularly real and imagined dual-task times (WWT and iWWT). In Experiment 2, 33 cognitively-healthy older adults (M?=?73.03) iW, iT, and iWWT during functional magnetic resonance imaging. A multivariate Ordinal Trend (OrT) Covariance analysis identified a pattern of brain regions that: (1) varied as a function of imagery task difficulty (iW, iT and iWWT), (2) involved cerebellar, precuneus, supplementary motor and other prefrontal regions, and (3) were associated with kinesthetic imagery ratings and behavioral performance during actual WWT. This is the first study to compare the behavioral and neural correlates of imagined gait in single and dual-task situations, an issue that is particularly relevant to elderly populations. These initial findings encourage further research and development of this imagined gait protocol as a tool for improving gait and cognition among the elderly. Hum Brain Mapp 35:4090-4104, 2014. © 2014 Wiley Periodicals, Inc. PMID:24522972

Blumen, Helena M; Holtzer, Roee; Brown, Lucy L; Gazes, Yunglin; Verghese, Joe

2014-08-01

320

Only 25-35% of Canadian children and youth regularly engage in active transportation (AT; e.g., non-motorized travel modes such as walking and cycling) to/from school. Previous research shows that distance between home and school is the strongest barrier to AT. Based on social ecological theory, we describe several strategies to overcome this barrier. At the individual level, children and youth could engage in AT to/from destinations such as parks, shops, friends' and family members' residence, and sport fields which may be located closer than their school. Parents who drive their kids to/from school could drop them within a "walkable" distance so that they can walk for the remainder of the trip. Partnerships could be developed between schools and other nearby institutions that would allow cars and buses to use their parking lot temporarily so that children could do a portion of the school trip on foot. Developing a well-connected network of sidewalks along low traffic streets can also facilitate AT. At the policy level, decisions regarding school location have a direct influence on distance. Finally, social marketing campaigns could raise awareness about strategies to incorporate AT into one's lifestyle, and encourage parents to reconsider what constitutes a "walkable" distance. PMID:24495826

Larouche, Richard; Barnes, Joel; Tremblay, Mark S

2013-01-01

321

The 1991-1992 walking robot design

NASA Technical Reports Server (NTRS)

The University of Maryland Walking Machine team designed and constructed a robot. This robot was completed in two phases with supervision and suggestions from three professors and one graduate teaching assistant. Bob was designed during the Fall Semester 1991, then machined, assembled, and debugged in the Spring Semester 1992. The project required a total of 4,300 student hours and cost under $8,000. Mechanically, Bob was an exercise in optimization. The robot was designed to test several diverse aspects of robotic potential, including speed, agility, and stability, with simplicity and reliability holding equal importance. For speed and smooth walking motion, the footpath contained a long horizontal component; a vertical aspect was included to allow clearance of obstacles. These challenges were met with a leg design that utilized a unique multi-link mechanism which traveled a modified tear-drop footpath. The electrical requirements included motor, encoder, and voice control circuitry selection, manual controller manufacture, and creation of sensors for guidance. Further, there was also a need for selection of the computer, completion of a preliminary program, and testing of the robot.

Azarm, Shapour; Dayawansa, Wijesurija; Tsai, Lung-Wen; Peritt, Jon

1992-01-01

322

Improving the accuracy of walking piezo motors

NASA Astrophysics Data System (ADS)

Many application areas require ultraprecise, stiff, and compact actuator systems with a high positioning resolution in combination with a large range as well as a high holding and pushing force. One promising solution to meet these conflicting requirements is a walking piezo motor that works with two pairs of piezo elements such that the movement is taken over by one pair, once the other pair reaches its maximum travel distance. A resolution in the pm-range can be achieved, if operating the motor within the travel range of one piezo pair. However, applying the typical walking drive signals, we measure jumps in the displacement up to 2.4 ?m, when the movement is given over from one piezo pair to the other. We analyze the reason for these large jumps and propose improved drive signals. The implementation of our new drive signals reduces the jumps to less than 42 nm and makes the motor ideally suitable to operate as a coarse approach motor in an ultra-high vacuum scanning tunneling microscope. The rigidity of the motor is reflected in its high pushing force of 6.4 N.

den Heijer, M.; Fokkema, V.; Saedi, A.; Schakel, P.; Rost, M. J.

2014-05-01

323

Random walk with priorities in communicationlike networks

NASA Astrophysics Data System (ADS)

We study a model for a random walk of two classes of particles (A and B). Where both species are present in the same site, the motion of A's takes precedence over that of B's. The model was originally proposed and analyzed in Maragakis [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.77.020103 77, 020103(R) (2008)]; here we provide additional results. We solve analytically the diffusion coefficients of the two species in lattices for a number of protocols. In networks, we find that the probability of a B particle to be free decreases exponentially with the node degree. In scale-free networks, this leads to localization of the B's at the hubs and arrest of their motion. To remedy this, we investigate several strategies to avoid trapping of the B's, including moving an A instead of the hindered B, allowing a trapped B to hop with a small probability, biased walk toward non-hub nodes, and limiting the capacity of nodes. We obtain analytic results for lattices and networks, and we discuss the advantages and shortcomings of the possible strategies.

Bastas, Nikolaos; Maragakis, Michalis; Argyrakis, Panos; ben-Avraham, Daniel; Havlin, Shlomo; Carmi, Shai

2013-08-01

324

Improving the accuracy of walking piezo motors.

Many application areas require ultraprecise, stiff, and compact actuator systems with a high positioning resolution in combination with a large range as well as a high holding and pushing force. One promising solution to meet these conflicting requirements is a walking piezo motor that works with two pairs of piezo elements such that the movement is taken over by one pair, once the other pair reaches its maximum travel distance. A resolution in the pm-range can be achieved, if operating the motor within the travel range of one piezo pair. However, applying the typical walking drive signals, we measure jumps in the displacement up to 2.4 ?m, when the movement is given over from one piezo pair to the other. We analyze the reason for these large jumps and propose improved drive signals. The implementation of our new drive signals reduces the jumps to less than 42 nm and makes the motor ideally suitable to operate as a coarse approach motor in an ultra-high vacuum scanning tunneling microscope. The rigidity of the motor is reflected in its high pushing force of 6.4 N. PMID:24880408

den Heijer, M; Fokkema, V; Saedi, A; Schakel, P; Rost, M J

2014-05-01

325

Elastic coupling of limb joints enables faster bipedal walking.

The passive dynamics of bipedal limbs alone are sufficient to produce a walking motion, without need for control. Humans augment these dynamics with muscles, actively coordinated to produce stable and economical walking. Present robots using passive dynamics walk much slower, perhaps because they lack elastic muscles that couple the joints. Elastic properties are well known to enhance running gaits, but their effect on walking has yet to be explored. Here we use a computational model of dynamic walking to show that elastic joint coupling can help to coordinate faster walking. In walking powered by trailing leg push-off, the model's speed is normally limited by a swing leg that moves too slowly to avoid stumbling. A uni-articular spring about the knee allows faster but uneconomical walking. A combination of uni-articular hip and knee springs can speed the legs for improved speed and economy, but not without the swing foot scuffing the ground. Bi-articular springs coupling the hips and knees can yield high economy and good ground clearance similar to humans. An important parameter is the knee-to-hip moment arm that greatly affects the existence and stability of gaits, and when selected appropriately can allow for a wide range of speeds. Elastic joint coupling may contribute to the economy and stability of human gait. PMID:18957360

Dean, J C; Kuo, A D

2009-06-01

326

Elastic coupling of limb joints enables faster bipedal walking

The passive dynamics of bipedal limbs alone are sufficient to produce a walking motion, without need for control. Humans augment these dynamics with muscles, actively coordinated to produce stable and economical walking. Present robots using passive dynamics walk much slower, perhaps because they lack elastic muscles that couple the joints. Elastic properties are well known to enhance running gaits, but their effect on walking has yet to be explored. Here we use a computational model of dynamic walking to show that elastic joint coupling can help to coordinate faster walking. In walking powered by trailing leg push-off, the model's speed is normally limited by a swing leg that moves too slowly to avoid stumbling. A uni-articular spring about the knee allows faster but uneconomical walking. A combination of uni-articular hip and knee springs can speed the legs for improved speed and economy, but not without the swing foot scuffing the ground. Bi-articular springs coupling the hips and knees can yield high economy and good ground clearance similar to humans. An important parameter is the knee-to-hip moment arm that greatly affects the existence and stability of gaits, and when selected appropriately can allow for a wide range of speeds. Elastic joint coupling may contribute to the economy and stability of human gait.

Dean, J.C.; Kuo, A.D.

2008-01-01

327

Contextual learning and obstacle memory in the walking cat

Synopsis Animals in their natural environments display a remarkably diverse variety of walking patterns. Although some of this diversity is generated by alterations in feedback from the moving limbs, animals can modify their walking in many ways that cannot be directly attributed to this sensory feedback. For example, animals and humans can learn to associate a particular environment with disturbances

D. A. McVea; K. G. Pearson

2007-01-01

328

Promoting Discussion in the Science Classroom Using Gallery Walks

NSDL National Science Digital Library

A gallery walk is a discussion technique that gets students out of their chairs and actively involved in synthesizing important science concepts, writing, and public speaking. The technique also cultivates listening and team-building skills. This paper provides guidance for conducting, managing, and assessing gallery walks.

Francek, Mark

2006-09-01

329

Weak Ergodicity Breaking in the Continuous-Time Random Walk

The continuous-time random walk (CTRW) model exhibits a nonergodic phase when the average waiting time diverges. Using an analytical approach for the nonbiased and the uniformly biased CTRWs, and numerical simulations for the CTRW in a potential field, we obtain the nonergodic properties of the random walk which show strong deviations from Boltzmann-Gibbs theory. We derive the distribution function of

G. Bel; E. Barkai

2005-01-01

330

Asymptotic properties of multistate random walks. I. Theory

A calculation is presented of the long-time behavior of various random walk properties (moments, probability of return to the origin, expected number of distinct sites visited) formultistate random walks on periodic lattices. In particular, we consider inhomogeneous periodic lattices, consisting of a periodically repeated unit cell which contains a finite number of internal states (sites). The results are identical to

J. B. T. M. Roerdink; K. E. Shuler

1985-01-01

331

Continuous time random walks and south Spain seismic series

Lévy flights were introduced through the mathematical research of thealgebra or random variables with infinite moments. Mandelbrot recognizedthat the Lévy flight prescription had a deep connection toscale-invariant fractal random walk trajectories. The theory of ContinuousTime Random Walks (CTRW) can be described in terms of Lévydistribution functions and it can be used to explain some earthquakecharacteristics like the distribution of waiting

A. Posadas; J. Morales; F. Vidal; O. Sotolongo-Costa; J. C. Antoranz

2002-01-01

332

The Theory of Ordered Spans of Unrestricted Random Walks.

National Technical Information Service (NTIS)

The spans of an n-step random walk on a simple cubic lattice are the sides of the smallest rectangular box, with sides parallel to the coordinate axes, that contains the random walk. Daniels first developed the theory in outline and derived results for th...

G. H. Weiss R. J. Rubin

1975-01-01

333

Energy-Efficient Trajectory Planning for Biped Walking Robot

For the researches of biped walking robot, energy-efficiency is an important issue. We have proposed an optimal trajectory planning method based on a function approximation method, and applied it for 2D biped walking model. With this method, we obtained the solution of minimal square integration value of the input torque. Before that, this method only includes equality state constraint, but

Qingjiu Huang; Takamasa Hase

2006-01-01

334

Children's Physical Activity: The Contribution of Playing and Walking

ERIC Educational Resources Information Center

This paper draws on research in which 200 children were fitted with motion sensors and asked to keep travel and activity diaries. The findings show that walking and playing away from home can contribute significantly to children's volume of physical activity, with consequent implications for their health. Not only do both playing and walking…

Mackett, Roger L.; Paskins, James

2008-01-01

335

Validity of the Nike+ device during walking and running.

We determined the validity of the Nike+ device for estimating speed, distance, and energy expenditure (EE) during walking and running. Twenty trained individuals performed a maximal oxygen uptake test and underwent anthropometric and body composition testing. Each participant was outfitted with a Nike+ sensor inserted into the shoe and an Apple iPod nano. They performed eight 6-min stages on the treadmill, including level walking at 55, 82, and 107 m x min(-1), inclined walking (82 m x min(-1)) at 5 and 10% grades, and level running at 134, 161, and 188 m x min(-1). Speed was measured using a tachometer and EE was measured by indirect calorimetry. Results showed that the Nike+ device overestimated the speed of level walking at 55 m x min(-1) by 20%, underestimated the speed of level walking at 107 m x min(-1) by 12%, but closely estimated the speed of level walking at 82 m x min(-1), and level running at all speeds (p<0.05). Similar results were found for distance. The Nike+ device overestimated the EE of level walking by 18-37%, but closely estimated the EE of level running (p<0.05). In conclusion the Nike+ in-shoe device provided reasonable estimates of speed and distance during level running at the three speeds tested in this study. However, it overestimated EE during level walking and it did not detect the increased cost of inclined locomotion. PMID:20027538

Kane, N A; Simmons, M C; John, D; Thompson, D L; Bassett, D R; Basset, D R

2010-02-01

336

The metabolic transition speed between backward walking and running

Although the metabolic transition speed for forward exercise has already been determined, the walk–run transition speed for backward exercise has not been investigated before. The aim of this study was to determine the speed at which it becomes metabolically more efficient to run backwards than to walk backwards. Eighteen healthy volunteers, who successfully completed three backward exercise practice sessions, participated

Elmarie Terblanche; Werner A. Cloete; Pieter A. L. du Plessis; Jacques N. Sadie; Annemie Strauss; Marianne Unger

2003-01-01

337

External rotation as morphological bootstrapping for emergence of biped walking

Many researchers are interested in the onset and learning of bipedal walking, but still not much is known how a human (and even a robot) can acquire the ability. In this paper, we hypothesize that external rotation of the hip joint plays an essential role for emergence of bipedal walking in human infancy. We build an infant robot “Pneu-born 13”

Koh Hosoda; Yoichiro Ishii

2010-01-01

338

Linearly Bounded Liars, Adaptive Covering Codes, and Deterministic Random Walks

We analyze a deterministic form of the random walk on the integer line called the {\\\\em liar machine}, similar to the rotor-router model, finding asymptotically tight pointwise and interval discrepancy bounds versus random walk. This provides an improvement in the best-known winning strategies in the binary symmetric pathological liar game with a linear fraction of responses allowed to be lies.

Joshua N. Cooper; Robert B. Ellis

2009-01-01

339

Factors of the physical environment associated with walking and bicycling

PURPOSE: The purpose of this study was to identify factors of the physical environment that may influence time spent on walking and bicycling. METHODS: Demographic factors and time spent on walking and bicycling (during leisure time and for commuting purposes) were assessed with a self-administered questionnaire. GIS databases were used to objectively measure the total square area of green space

G. C. WANDA WENDEL-VOS; A. JANTINE SCHUIT; RAYMOND DE NIET; HENDRIEK C. BOSHUIZEN; WIM H. M. SARIS; DAAN KROMHOUT

2004-01-01

340

Humanoids Walk with Feedforward Dynamic Pattern and Feedback Sensory Reflection

Since a biped humanoid inherently suffers from instability and always risks tipping over, ensuring high stability and reliability of walking is one of the most important goals. The paper proposes a walk control consisting of a feedforward dynamic pattern and a feedback sensory reflex. The dynamic pattern is a rhythmic and periodic motion, which satisfies the constraints of dynamic stability

Qiang Huangh; Yoshihiko Nakamura; Tetsunari Inamura

2001-01-01

341

Slip observer for walking on a low friction floor

This paper presents a slip observer towards stabilizing biped walks on a low friction floor. Although biped humanoid robots are expected to easily adapt to environments designed for human, in fact they tend to tip over easily on real environments. For a practical use, it is one of important issues to stabilize a biped walking on an unexpected slippery floor

Kenji Kaneko; Fumio Kanehiro; Shuuji Kajita; Mitsuharu Morisawa; Kiyoshi Fujiwara; Kensuke Harada; H. Hirukawa

2005-01-01

342

Angular momentum primitives for human walking: biomechanics and control

Towards the goal of developing stable humanoid robots and leg prostheses, we present a biologically motivated control strategy for walking where system angular momentum is explicitly controlled. Using human kinematic gait data, we calculate the distribution of spin angular momentum throughout the human body at slow and self-selected walking speeds. Principal component analysis reveals three angular momentum primitives that explain

Marko Popovic; Amy Englehart

2004-01-01

343

Modular Architecture for Humanoid Walking Pattern Prototyping and Experiments

In this paper we describe the use of design patterns as a basis for creating a Humanoid Walking Pattern Generator Software having a modular architecture. This architecture made possible the rapid porting of several novel walking algorithms on a full size humanoid robot HRP-2. The body of work currently available allows extracting a general software architecture usable with inter-exchange between

Olivier Stasse; Björn Verrelst; Pierre-Brice Wieber; Bram Vanderborght; Paul Evrard; Abderrahmane Kheddar; Kazuhito Yokoi

2008-01-01

344

New trends in the control of walking robots

Presents some new trends for the control of climbing and walking robots (CLAWAR). In the first part some paradigms concerning the soft computing approach for the control of walking robots are illustrated. Then some considerations concerning the fuzzy control of the robot ROBINSPEC, the self-learning strategy adopted to analyze collective behaviour of the piezo light intelligent flea microrobots and the

P. Arena; G. Muscato; M. Lavorgna; R. Caponetto

1998-01-01

345

Alterations in muscle activation patterns during robotic-assisted walking

Objective. The goal of this study was to compare the muscle activation patterns in various major leg muscles during treadmill ambulation with those exhibited during robotic-assisted walking. Background. Robotic devices are now being integrated into neurorehabilitation programs with promising results. The influence of these devices on altering naturally occurring muscle activation patterns utilized during walking have not been quantified. Methods.

Joseph M. Hidler; Anji E. Wall

2005-01-01

346

Alterations in EMG patterns during robotic assisted walking

Robotic devices are being developed for gait rehabilitation with promising results. This study focuses on the effectiveness of one such device: the Lokomat, a robotic gait orthosis. Muscle activations patterns (EMG) generated in normal subjects while walking on a treadmill were compared to those exhibited during Lokomat walking. Eight of the major leg muscles were chosen for measurement. For each

A. E. Wall; J. M. Hidler

2004-01-01

347

The effect of hospital unit layout on nurse walking behavior.

Objective: To confirm a new method for the research question, "How do different hospital unit layouts affect nurses' walking behavior and distance?"Background: Concern is renewed regarding nurses' long walking distances because of the trend toward larger patient rooms with family areas inside, resulting in a larger overall unit size. Studies have found unit design characteristics that support nurses' efficient walking, but few have done it in units designed for patient- and family-centered care. To examine the effect of unit design on nurses' walking behavior, the authors propose a new method of observing a specific task.Methods: The authors observed nurses during the task of medication administration.Results: Contrary to their hypotheses, results showed: (1) Experienced nurses had more unnecessary stops and longer walking distances than new nurses because of interactions; and (2) nurses in the smaller wing of the unit walked more than those in the larger wing of the same unit. The authors posit that the closeness between the nurses' path to the medication supply room and the central nurses' station affected the frequency of interactions and prompted a deviation from the shortest and most efficient path during medication administration.Conclusion: Observing a specific task to identify the effect of unit layout was effective, determining that overall unit shape or unit layout type might not be a good predictor of nurses' walking behavior; instead the characteristics of the path that connects functional spaces such as patient room and medication area might better predict nurses' walking behavior. PMID:23224843

Yi, Lu; Seo, Hyun-Bo

2012-01-01

348

On the hitting times of quantum versus random walks

The hitting time of a classical random walk (Markov chain) is the time required to detect the presence of - or equivalently, to find - a marked state. The hitting time of a quantum walk is subtler to define; in particular, it is unknown whether the detection and finding problems have the same time complexity. In this paper we define

Frédéric Magniez; Ashwin Nayak; Peter C. Richter; Miklos Santha

2009-01-01

349

Random walks on graphs to model saliency in images

We formulate the problem of salient region detection in images as Markov random walks performed on images represented as graphs. While the global properties of the image are extracted from the random walk on a complete graph, the local properties are extracted from a k-regular graph. The most salient node is selected as the one which is globally most isolated

Viswanath Gopalakrishnan; Yiqun Hu; Deepu Rajan

2009-01-01

350

Adaptive L?vy Walks in Foraging Fallow Deer

Background Lévy flights are random walks, the step lengths of which come from probability distributions with heavy power-law tails, such that clusters of short steps are connected by rare long steps. Lévy walks maximise search efficiency of mobile foragers. Recently, several studies raised some concerns about the reliability of the statistical analysis used in previous analyses. Further, it is unclear whether Lévy walks represent adaptive strategies or emergent properties determined by the interaction between foragers and resource distribution. Thus two fundamental questions still need to be addressed: the presence of Lévy walks in the wild and whether or not they represent a form of adaptive behaviour. Methodology/Principal Findings We studied 235 paths of solitary and clustered (i.e. foraging in group) fallow deer (Dama dama), exploiting the same pasture. We used maximum likelihood estimation for discriminating between a power-tailed distribution and the exponential alternative and rank/frequency plots to discriminate between Lévy walks and composite Brownian walks. We showed that solitary deer perform Lévy searches, while clustered animals did not adopt that strategy. Conclusion/Significance Our demonstration of the presence of Lévy walks is, at our knowledge, the first available which adopts up-to-date statistical methodologies in a terrestrial mammal. Comparing solitary and clustered deer, we concluded that the Lévy walks of solitary deer represent an adaptation maximising encounter rates with forage resources and not an epiphenomenon induced by a peculiar food distribution.

Focardi, Stefano; Montanaro, Paolo; Pecchioli, Elena

2009-01-01

351

Guiding Students through Expository Text with Text Feature Walks

ERIC Educational Resources Information Center

The Text Feature Walk is a structure created and employed by the authors that guides students in the reading of text features in order to access prior knowledge, make connections, and set a purpose for reading expository text. Results from a pilot study are described in order to illustrate the benefits of using the Text Feature Walk over…

Kelley, Michelle J.; Clausen-Grace, Nicki

2010-01-01

352

Torsional Directed Walks, Entropic Elasticity, and DNA Twist Stiffness

DNA and other biopolymers differ from classical polymers because of their torsional stiffness. This property changes the statistical character of their conformations under tension from a classical random walk to a problem we call the ``torsional directed walk.'' Motivated by a recent experiment on single lambda-DNA molecules [Strick, T. R., Allemand, J.-F., Bensimon, D., Bensimon, A. & Croquette, V. (1996)

J. David Moroz; Philip Nelson

1997-01-01

353

Optimal On-Line Walking Pattern Generation for Biped Robots

A new 2D walking pattern generation method is proposed for biped robots in this paper. The key feature of the proposed method is to obtain an optimal walking pattern on-line with the largest stability in the sense of zero moment point (ZMP) subject to the constraints of torque and velocity of the joint actuators. With the aids of a 3-link

Hao Chen; Shuwen Pan; Rong Xiong; Jun Wu

2010-01-01

354

Blind Walking of a Planar Bipedal Robot on Sloped Terrain

Simple intuitive c ontrol strategies can b e used to compel bipedal robots to walk over s loped terrain. We describe an a lgorithm for walking d ynamically and steadily over sloped terrain with unknown slope gradients and transition locations. The algorithm is developed ba sed on geometric c onsiderations. The overall algorithm is very simple and does not require

Chee-meng Chew; Jerry E. Pratt; Gill A. Pratt

1999-01-01

355

Chinese City Children and Youth's Walking Behavior

ERIC Educational Resources Information Center

Purpose: Although walking has been demonstrated as one of the best forms for promoting physical activity (PA), little is known about Chinese city children and youth's walking behavior. The purpose of this study was therefore to assess ambulatory PA behavior of Chinese city children and youth. Method: The daily steps of 2,751 children and…

Quan, Minghui; Chen, Peijie; Zhuang, Jie; Wang, Chao

2013-01-01

356

Automatic vs hand-controlled walking of paraplegics.

A rule-based control and its application in functional electrical stimulation (FES) assisted walking of subjects with paraplegia are described in this paper. The design of rules for control comprises the following two steps: (1) determination of muscle activation patterns by using a fully customized spatial (3D) model of paraplegic walking, and (2) learning of rules, that is, correlation between the muscle activation patterns and kinematics of walking by means of an artificial neural network. The adopted FES system activated eight muscle groups with surface electrodes. The only joints allowing movement in the coronal plane were the hips, and externally controlled joints in sagittal plane were ankles, knees and hips. The simulation minimized the tracking error of the joint angles and the total activation of all eight muscles being stimulated. A radial-basis function artificial neural network was applied for learning of rules. Three automatically controlled modes (slow, near-normal, and near-ballistic) and hand-controlled walking were evaluated in six subjects with a complete spinal cord lesion (T8-T10). The performance of walking was assessed by the following: (1) energy consumption based on oxygen uptake, (2) physiological cost index, (3) maximum speed of walking, and (4) a questionnaire. The results showed that all modes of walking are achievable and that automatic control leads to more efficient and faster walking. The speed of walking achieved by automatic control was almost three times bigger compared with the speed of hand-controlled walking. The energy cost and rate decreased significantly when automatic control was applied; yet, they were still much bigger than the values measured in able-bodied subjects. The objective outcome measures suggest that the near-ballistic walking was the most effective, yet a questionnaire shows that most subjects preferred slow walking. The most likely reason for the preference of lower efficiency walking over the faster end energy efficient near-ballistic walking was that paraplegic patients had difficulties in synchronizing the voluntary movement of the trunk and arms to the artificially controlled movements of legs. PMID:12485787

Popovi?, Dejan; Radulovi?, Milovan; Schwirtlich, Laszlo; Jaukovi?, Novak

2003-01-01

357

Random walk in dynamically disordered chains: Poisson white noise disorder

Exact solutions are given for a variety of models of random walks in a chain with time-dependent disorder. Dynamic disorder is modeled by white Poisson noise. Models with site-independent (global) and site-dependent (local) disorder are considered. Results are described in terms of an affective random walk in a nondisordered medium. In the cases of global disorder the effective random walk contains multistep transitions, so that the continuous limit is not a diffusion process. In the cases of local disorder the effective process is equivalent to usual random walk in the absence of disorder but with slower diffusion. Difficulties associated with the continuous-limit representation of random walk in a disordered chain are discussed. In particular, the authors consider explicit cases in which taking the continuous limit and averaging over disorder sources do not commute.

Hernandez-Garcia, E.; Pesquera, L.; Rodriguez, M.A.; San Miguel, M. (Universitat de les Illes Balears, Palma de Mallorca (Spain))

1989-06-01

358

Checklist and Pollard Walk butterfly survey methods on public lands

Checklist and Pollard Walk butterfly survey methods were contemporaneously applied to seven public sites in North Dakota during the summer of 1995. Results were compared for effect of method and site on total number of butterflies and total number of species detected per hour. Checklist searching produced significantly more butterfly detections per hour than Pollard Walks at all sites. Number of species detected per hour did not differ significantly either among sites or between methods. Many species were detected by only one method, and at most sites generalist and invader species were more likely to be observed during checklist searches than during Pollard Walks. Results indicate that checklist surveys are a more efficient means for initial determination of a species list for a site, whereas for long-term monitoring the Pollard Walk is more practical and statistically manageable. Pollard Walk transects are thus recommended once a prairie butterfly fauna has been defined for a site by checklist surveys.

Royer, R. A.; Austin, J. E.; Newton, W. E.

1998-01-01

359

Spectral analysis of walking improvement utilizing AR modeling.

This study analyzes the walking improvement based on 1/f fluctuations and impulse responses utilizing Auto-Regressive (AR) modeling. Once subjects were aware of the correct posture, the fluctuation of subject's both sides of the hip while walking was improved more rhythmic. The analysis of impulse response utilizing AR modeling provided clear results for the evaluation of improvement to walking stability. After the subjects understood their own walking condition, based on 1/f fluctuation, and had received suitable rehabilitation and shoes, their walking stability improved satisfactorily. This study provides a useful method of medical evaluation in rehabilitation and physical fitness, and a means for subjects to maintain a state of well being. PMID:19163860

Tsuruoka, Masako; Tsuruoka, Yuriko

2008-01-01

360

Radar walk detection in the apartments of elderly.

Seniors want to live more independent lifestyles. This comes with some risks including dwindling health and major injuries due to falling. A factor that has been studied and seen to have a correlation to fall risk is change in gait speed. Our goal is to create a passive system that monitors the gait of elderly so that assessments can be given by caregivers if gait changes do occur. This paper will cover a method of using pulse-Doppler radar to detect when walks occur. In unscripted living environments, we are able to detect valid walks. The system does miss walks during the day, but when walks are detected, they are actually valid walks 91.8% of the time using a large data base of radar signals captured in living environments. PMID:23367262

Phillips, Calvin E; Keller, James; Popescu, Mihail; Skubic, Marjorie; Rantz, Marilyn J; Cuddihy, Paul E; Yardibi, Tarik

2012-01-01

361

Field testing of physiological responses associated with Nordic Walking.

This study compared the physiological responses (oxygen consumption and energy expenditure) of Nordic Walking to regular walking under field-testing conditions. Eleven women (M age = 27.1 years, SD = 6.4) and 11 men (M age = 33.8 years, SD = 9.0) walked 1,600 m with and without walking poles on a level, 200-m track. For women, Nordic Walking resulted in increased oxygen consumption (M = 14.9 ml x kg(-1) x min(-1), SD = 3.2 vs. M = 1 7.9 ml x kg(-1) min(-1), SD = 3.5; p < .001), caloric expenditure (M = 4.6 kcal x min(-1), SD = 1.2 vs. M = 5.4 kcal x min(-1), SD = 1.2; p < .001), and heart rate (M = 113.7 bpm, SD = 12.0 vs. M = 118.7 bpm, SD = 14.8; p < .05) compared to regular walking. For men, Nordic Walking resulted in increased oxygen consumption (M = 12.8 ml x kg(-1) min(-1), SD = 1.8 vs. M = 15.5, SD =3.4 ml x kg(-1) min(-1); p < .01), caloric expenditure (M = 5.7 kcal x min(-1), SD = 1.3 vs. M = 6.9 kcal x min(-1), SD = 1.8; p < .001), and heart rate (M = 101.6 bpm, SD = 12.0 bpm vs. M = 109.8 bpm, SD = 14.7; p < .01) compared to regular walking. Nordic Walking, examined in the field, results in a significant increase in oxygen use and caloric expenditure compared to regular walking, without significantly increasing perceived exertion. PMID:12230336

Church, Timothy S; Earnest, Conrad P; Morss, Gina M

2002-09-01

362

Historical documents, original and archival photos, and MS Publisher software were used to develop and promote a two mile guided walking trail incorporating the Martin Luther King, Jr. National Voting Rights Walk, Selma Antebellum Historic District and Bloch Park. The aim is to promote learning about Alabama history while enhancing fitness, as a planned activity of a programme to prevent

Brian F. Geiger; Karen A. Werner

2009-01-01

363

Based on a higher cardio-pulmonary and cardio-vascular benefit and a promised reduction of mechanical load of the musculoskeletal system Nordic Walking (NW) shows an increased market potential. The present study should investigate whether there are differences in joint loading of lower extremities using an inverse dynamics approach between NW and Walking. In this experiment 15 subjects participated, who were already

F. I. Kleindienst; F. Stief; F. Wedel; S. Campe; B. Krabbe

364

This study aimed to investigate any differences between the motor skills and sensory processing abilities of children between the ages of 4 and 8, who do and do not have an idiopathic toe walking gait. Children in each cohort were tested with a number of norm referenced assessments. A total of 60 children participated, 30 within each cohort. Those with an idiopathic toe walking gait were found to have different Sensory Profile quadrant scores (P = .002), poorer performance on the Bruininks-Oseretsky Test of Motor Proficiency (P ? .001), a lower vibration perception threshold (P = .001), and poorer performance on the Standing Walking Balance subtest of the Sensory Integration and Praxis Test (P = .047), compared with non-toe walking peers. Although this research does not give a causative factor for toe walking gait, it provides a number of theories as to why this gait may not be idiopathic in nature. PMID:23349518

Williams, Cylie M; Tinley, Paul; Curtin, Michael; Wakefield, Suzanne; Nielsen, Sharon

2014-01-01

365

Prediction of Falls Using a 3-m Zigzag Walk Test

[Objective] This study investigated the applicability of a 3-m zigzag walk test for the prediction of falls and examined the relationships among fall history, the 3-m zigzag walk test, 10-m walk, and age. [Subjects] A total of 50 elderly individuals (23 males and 27 females) aged 65 and over, who were able to walk independently, were studied. [Methods] Four poles made of PET bottles were placed on a 3-m walkway in a straight line to create a zigzag course, and the time needed to walk it was measured. The best results on days 1 and 2 were adopted for the fall and no-fall groups, and intra-rater reproducibility was evaluated by calculating the intra-class correlation coefficient and performing the paired t-test. For comparison of the time needed to walk the zigzag between the 2 groups, the unpaired t-test was performed. The relationships between the times needed to walk the 3-m zigzag and 10?m and age were analyzed by calculating the correlation coefficient with fall history as the dependent variable, in multiple logistic regression analysis with the times needed to walk the 3-m zigzag and 10?m and age as independent variables. For the optimal classification of the fall and no-fall groups, cutoffs were calculated based on the ROC curve. [Results] The paired t-test results did not show differences between measurements, and the ICC was 0.97 in the fall, and 0.94 in the no-fall groups. The fall group needed significantly more time than the no-fall group to walk the 3-m zigzag. Further, the Pearson product-moment correlation coefficient revealed a significant correlation between the times needed to walk the 3-m zigzag and 10?m, while no correlation was observed between the time needed to walk the 3-m zigzag and age (r=0.225). The time needed to walk the 3-m zigzag was extracted as a factor associated with fall history in multiple logistic regression analysis, with an odds ratio of 0.377. Its significance as a variable was p<0.01. In the Hosmer-Lemeshow test of the study model, the rate of discrimination between the predicted and actual values was 82.0%. [Conclusion] The cutoff time to walk the 3-m zigzag was estimated to be 10.5 seconds, suggesting that this model may be a valid index for the prediction of falls.

Masuda, Suzuka; Suganuma, Kazuo; Kaneko, Chika; Hoshina, Kazuo; Suzuki, Taeko; Serita, Toru; Sakakibara, Ryoko

2013-01-01

366

Using built environment characteristics to predict walking for exercise

Background Environments conducive to walking may help people avoid sedentary lifestyles and associated diseases. Recent studies developed walkability models combining several built environment characteristics to optimally predict walking. Developing and testing such models with the same data could lead to overestimating one's ability to predict walking in an independent sample of the population. More accurate estimates of model fit can be obtained by splitting a single study population into training and validation sets (holdout approach) or through developing and evaluating models in different populations. We used these two approaches to test whether built environment characteristics near the home predict walking for exercise. Study participants lived in western Washington State and were adult members of a health maintenance organization. The physical activity data used in this study were collected by telephone interview and were selected for their relevance to cardiovascular disease. In order to limit confounding by prior health conditions, the sample was restricted to participants in good self-reported health and without a documented history of cardiovascular disease. Results For 1,608 participants meeting the inclusion criteria, the mean age was 64 years, 90 percent were white, 37 percent had a college degree, and 62 percent of participants reported that they walked for exercise. Single built environment characteristics, such as residential density or connectivity, did not significantly predict walking for exercise. Regression models using multiple built environment characteristics to predict walking were not successful at predicting walking for exercise in an independent population sample. In the validation set, none of the logistic models had a C-statistic confidence interval excluding the null value of 0.5, and none of the linear models explained more than one percent of the variance in time spent walking for exercise. We did not detect significant differences in walking for exercise among census areas or postal codes, which were used as proxies for neighborhoods. Conclusion None of the built environment characteristics significantly predicted walking for exercise, nor did combinations of these characteristics predict walking for exercise when tested using a holdout approach. These results reflect a lack of neighborhood-level variation in walking for exercise for the population studied.

Lovasi, Gina S; Moudon, Anne V; Pearson, Amber L; Hurvitz, Philip M; Larson, Eric B; Siscovick, David S; Berke, Ethan M; Lumley, Thomas; Psaty, Bruce M

2008-01-01

367

Older adults and those with increased fall risk tend to walk slower. They may do this voluntarily to reduce their fall risk. However, both slower and faster walking speeds can predict increased risk of different types of falls. The mechanisms that contribute to fall risk across speeds are not well known. Faster walking requires greater forward propulsion, generated by larger muscle forces. However, greater muscle activation induces increased signal-dependent neuromuscular noise. These speed-related increases in neuromuscular noise may contribute to the increased fall risk observed at faster walking speeds. Using a 3D dynamic walking model, we systematically varied walking speed without and with physiologically-appropriate neuromuscular noise. We quantified how actual fall risk changed with gait speed, how neuromuscular noise affected speed-related changes in fall risk, and how well orbital and local dynamic stability measures predicted changes in fall risk across speeds. When we included physiologically-appropriate noise to the 'push-off' force in our model, fall risk increased with increasing walking speed. Changes in kinematic variability, orbital, and local dynamic stability did not predict these speed-related changes in fall risk. Thus, the increased neuromuscular variability that results from increased signal-dependent noise that is necessitated by the greater muscular force requirements of faster walking may contribute to the increased fall risk observed at faster walking speeds. The lower fall risk observed at slower speeds supports experimental evidence that slowing down can be an effective strategy to reduce fall risk. This may help explain the slower walking speeds observed in older adults and others. PMID:23659911

Roos, Paulien E; Dingwell, Jonathan B

2013-06-21

368

Treadmill walking of the pneumatic biped Lucy: Walking at different speeds and step-lengths

Actuators with adaptable compliance are gaining interest in the field of legged robotics due to their capability to store\\u000a motion energy and to exploit the natural dynamics of the system to reduce energy consumption while walking and running. To\\u000a perform research on compliant actuators we have built the planar biped Lucy. The robot has six actuated joints, the ankle,\\u000a knee

B. Vanderborght; B. Verrelst; R. Van Ham; M. Van Damme; R. Versluys; D. Lefeber

2008-01-01

369

Disordered quantum walks in one lattice dimension

NASA Astrophysics Data System (ADS)

We study a spin-12-particle moving on a one-dimensional lattice subject to disorder induced by a random, space-dependent quantum coin. The discrete time evolution is given by a family of random unitary quantum walk operators, where the shift operation is assumed to be deterministic. Each coin is an independent identically distributed random variable with values in the group of two-dimensional unitary matrices. We derive sufficient conditions on the probability distribution of the coins such that the system exhibits dynamical localization. Put differently, the tunneling probability between two lattice sites decays rapidly for almost all choices of random coins and after arbitrary many time steps with increasing distance. Our findings imply that this effect takes place if the coin is chosen at random from the Haar measure, or some measure continuous with respect to it, but also for a class of discrete probability measures which support consists of two coins, one of them being the Hadamard coin.

Ahlbrecht, Andre; Scholz, Volkher B.; Werner, Albert H.

2011-10-01

370

The subtle nature of financial random walks

NASA Astrophysics Data System (ADS)

We first review the most important ``stylized facts'' of financial time series, that turn out to be, to a large extent, universal. We then recall how the multifractal random walk of Bacry, Muzy, and Delour generalizes the standard model of financial price changes and accounts in an elegant way for many of their empirical properties. In a second part, we provide empirical evidence for a very subtle compensation mechanism that underlies the random nature of price changes. This compensation drives the market close to a critical point, that may explain the sensitivity of financial markets to small perturbations, and their propensity to enter bubbles and crashes. We argue that the resulting unpredictability of price changes is very far from the neoclassical view that markets are informationally efficient.

Bouchaud, Jean-Philippe

2005-06-01

371

The QWalk simulator of quantum walks

NASA Astrophysics Data System (ADS)

Several research groups are giving special attention to quantum walks recently, because this research area have been used with success in the development of new efficient quantum algorithms. A general simulator of quantum walks is very important for the development of this area, since it allows the researchers to focus on the mathematical and physical aspects of the research instead of deviating the efforts to the implementation of specific numerical simulations. In this paper we present QWalk, a quantum walk simulator for one- and two-dimensional lattices. Finite two-dimensional lattices with generic topologies can be used. Decoherence can be simulated by performing measurements or by breaking links of the lattice. We use examples to explain the usage of the software and to show some recent results of the literature that are easily reproduced by the simulator. Program summaryProgram title: QWalk Catalogue identifier: AEAX_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAX_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public Licence No. of lines in distributed program, including test data, etc.: 10 010 No. of bytes in distributed program, including test data, etc.: 172 064 Distribution format: tar.gz Programming language: C Computer: Any computer with a C compiler that accepts ISO C99 complex arithmetic (recent versions of GCC, for instance). Pre-compiled Windows versions are also provided Operating system: The software should run in any operating system with a recent C compiler. Successful tests were performed in Linux and Windows RAM: Less than 10 MB were required for a two-dimensional lattice of size 201×201. About 400 MB, for a two-dimensional lattice of size 1601×1601 Classification: 16.5 Nature of problem: Classical simulation of discrete quantum walks in one- and two-dimensional lattices. Solution method: Iterative approach without explicit representation of evolution operator. Restrictions: The available amount of RAM memory imposes a limit on the size of the simulations. Unusual features: The software provides an easy way of simulating decoherence through detectors or random broken links. In the two-dimensional simulations it also allows the definition of permanent broken links, besides calculation of total variation distance (from the uniform and from an approximate stationary distribution) and the choice between two different physical lattices. It also provides an easy way of performing measurements on specific sites of the 2D lattice and the analysis of observation screens. In one-dimensional simulations it allows the choice between three different lattices. Both one- and two-dimensional simulations facilitates the generation of graphics by automatically generating gnuplot scrips. Additional comments:An earlier version of QWalk was first presented in [1]. The simulator generates gnuplot scripts that can be used to make graphics of the output data. Several examples of input files are provided. Running time: The simulation of 100 steps for a two-dimensional lattice of size 201×201 took less than 2 seconds on a Pentium IV 2.6 GHz with 512 MB of RAM memory, 512 KB of cache memory and under Linux. It also took about 15 minutes for a lattice of size 1601×1601 on the same computer. Optimization option -O2 was used during compilation for these tests. References: [1] F.L. Marquezino, R. Portugal, QWalk: Simulador de caminhadas quânticas, in: Proceedings of 2nd WECIQ, Campina Grande, Brazil, IQuanta, 2007, pp. 123-132.

Marquezino, F. L.; Portugal, R.

2008-09-01

372

Random time averaged diffusivities for Lévy walks

NASA Astrophysics Data System (ADS)

We investigate a Lévy walk alternating between velocities ±v0 with opposite sign. The sojourn time probability distribution at large times is a power law lacking its mean or second moment. The first case corresponds to a ballistic regime where the ensemble averaged mean squared displacement (MSD) at large times is ?x2? ? t2, the latter to enhanced diffusion with ?x2? ? t?, 1 < ? < 2. The correlation function and the time averaged MSD are calculated. In the ballistic case, the deviations of the time averaged MSD from a purely ballistic behavior are shown to be distributed according to a Mittag-Leffler density function. In the enhanced diffusion regime, the fluctuations of the time averages MSD vanish at large times, yet very slowly. In both cases we quantify the discrepancy between the time averaged and ensemble averaged MSDs.

Froemberg, D.; Barkai, E.

2013-07-01

373

Excursion set theory for correlated random walks

NASA Astrophysics Data System (ADS)

We present a new method to compute the first crossing distribution in excursion set theory for the case of correlated random walks. We use a combination of the path integral formalism of Maggiore & Riotto, and the integral equation solution of Zhang & Hui and Benson et al. to find a numerically and convenient algorithm to derive the first crossing distribution. We apply this methodology to the specific case of a Gaussian random density field filtered with a Gaussian smoothing function. By comparing our solutions to results from Monte Carlo calculations of the first crossing distribution we demonstrate that approximately it is in good agreement with exact solution for certain barriers, and at large masses. Our approach is quite general, and can be adapted to other smoothing functions and barrier function and also to non-Gaussian density fields.

Farahi, Arya; Benson, Andrew J.

2013-08-01

374

Critical Scaling in Standard Biased Random Walks

NASA Astrophysics Data System (ADS)

The spatial coverage produced by a single discrete-time random walk, with an asymmetric jump probability p?1/2 and nonuniform steps, moving on an infinite one-dimensional lattice is investigated. Analytical calculations are complemented with Monte Carlo simulations. We show that, for appropriate step sizes, the model displays a critical phenomenon, at p=pc. Its scaling properties as well as the main features of the fragmented coverage occurring in the vicinity of the critical point are shown. In particular, in the limit p?pc, the distribution of fragment lengths is scale-free, with nontrivial exponents. Moreover, the spatial distribution of cracks (unvisited sites) defines a fractal set over the spanned interval. Thus, from the perspective of the covered territory, a very rich critical phenomenology is revealed in a simple one-dimensional standard model.

Anteneodo, C.; Morgado, W. A. M.

2007-11-01

375

Random walks on the mental number line.

The direction of influence between conceptual and motor activation, and its relevance for real-life activities, is still unclear. Here, we use the frequently reported association between small/large numbers and left/right space to investigate this issue during walking. We asked healthy adults to generate random numbers as they made lateral turns and found that (1) lateral turn decisions are predicted by the last few numbers generated prior to turning; (2) the intention to turn left/right makes small/large numbers more accessible; and (3) magnitude but not order of auditorily presented numbers influences the listener's turn selection. Our findings document a bidirectional influence between conceptual and motor activation and point to a hierarchically organized conceptual-motor activation. PMID:24091774

Shaki, Samuel; Fischer, Martin H

2014-01-01

376

The subtle nature of financial random walks.

We first review the most important "stylized facts" of financial time series, that turn out to be, to a large extent, universal. We then recall how the multifractal random walk of Bacry, Muzy, and Delour generalizes the standard model of financial price changes and accounts in an elegant way for many of their empirical properties. In a second part, we provide empirical evidence for a very subtle compensation mechanism that underlies the random nature of price changes. This compensation drives the market close to a critical point, that may explain the sensitivity of financial markets to small perturbations, and their propensity to enter bubbles and crashes. We argue that the resulting unpredictability of price changes is very far from the neoclassical view that markets are informationally efficient. PMID:16035906

Bouchaud, Jean-Philippe

2005-06-01

377

Discrete time quantum walks on percolation graphs

NASA Astrophysics Data System (ADS)

Randomly breaking connections in a graph alters its transport properties, a model used to describe percolation. In the case of quantum walks, dynamic percolation graphs represent a special type of imperfections, where the connections appear and disappear randomly in each step during the time evolution. The resulting open system dynamics is hard to treat numerically in general. We shortly review the literature on this problem. We then present our method to solve the evolution on finite percolation graphs in the long time limit, applying the asymptotic methods concerning random unitary maps. We work out the case of one-dimensional chains in detail and provide a concrete, step-by-step numerical example in order to give more insight into the possible asymptotic behavior. The results about the case of the two-dimensional integer lattice are summarized, focusing on the Grover-type coin operator.

Kollár, Bálint; Novotný, Jaroslav; Kiss, Tamás; Jex, Igor

2014-05-01

378

Non-equilibrium transition from dissipative quantum walk to classical random walk

NASA Astrophysics Data System (ADS)

We have investigated the time evolution of a free particle in interaction with a phonon thermal bath, using the tight-binding approach. A dissipative quantum walk can be defined and many important non-equilibrium decoherence properties can be investigated analytically. The non-equilibrium statistics of a pure initial state have been studied. Our theoretical results indicate that the evolving wave-packet shows the suppression of Anderson’s boundaries (ballistic peaks) by the presence of dissipation. Many important relaxation properties can be studied quantitatively, such as von Neumann’s entropy and quantum purity. In addition, we have studied Wigner’s function. The time-dependent behavior of the quantum entanglement between a free particle—in the lattice—and the phonon bath has been characterized analytically. This result strongly suggests the non-trivial time dependence of the off-diagonal elements of the reduced density matrix of the system. We have established a connection between the quantum decoherence and the dissipative parameter arising from interaction with the phonon bath. The time-dependent behavior of quantum correlations has also been pointed out, showing continuous transition from quantum random walk to classical random walk, when dissipation increases.

Nizama, Marco; Cáceres, Manuel O.

2012-08-01

379

Lower and upper extremity loading in nordic walking in comparison with walking and running.

Nordic walking (NW) was compared with walking (W) and running (R) with respect to upper and lower limb injury risks. 24 NW-instructors performed W, NW, and R trials on a runway covered with artificial turf at controlled speeds. Foot pronation and ground reaction forces were measured as well as shock wave transmission to the right wrist. Comparison of NW and W shows similar results for all of the four chosen velocities (5 km/h, 7 km/h, 8 km/h, 8.5 km/h). Except for the 2nd peak of the vertical ground reaction force, NW results in higher loading rates and horizontal forces as well as higher pronation and pronation velocity values as compared with W. Wrist acceleration values up to 7.6 times gravitational acceleration were recorded in NW. Compared with R at the same speeds (8 km/h and 8.5 km/h), NW can be recommended as low impact sport with 36% lower loading rates and 59% lower pronation velocities. However, the high wrist accelerations in NW reveal that the upper extremities are exposed to considerable repetitive shocks, which may cause overuse injuries of the upper extremities. Thus, additional preventive exercises for the upper limb muscles are recommended as well as using shock absorbing walking poles. PMID:21451179

Hagen, Marco; Hennig, Ewald M; Stieldorf, Peter

2011-02-01

380

Molecular motors: thermodynamics and the random walk.

The biochemical cycle of a molecular motor provides the essential link between its thermodynamics and kinetics. The thermodynamics of the cycle determine the motor's ability to perform mechanical work, whilst the kinetics of the cycle govern its stochastic behaviour. We concentrate here on tightly coupled, processive molecular motors, such as kinesin and myosin V, which hydrolyse one molecule of ATP per forward step. Thermodynamics require that, when such a motor pulls against a constant load f, the ratio of the forward and backward products of the rate constants for its cycle is exp [-(DeltaG + u(0)f)/kT], where -DeltaG is the free energy available from ATP hydrolysis and u(0) is the motor's step size. A hypothetical one-state motor can therefore act as a chemically driven ratchet executing a biased random walk. Treating this random walk as a diffusion problem, we calculate the forward velocity v and the diffusion coefficient D and we find that its randomness parameter r is determined solely by thermodynamics. However, real molecular motors pass through several states at each attachment site. They satisfy a modified diffusion equation that follows directly from the rate equations for the biochemical cycle and their effective diffusion coefficient is reduced to D-v(2)tau, where tau is the time-constant for the motor to reach the steady state. Hence, the randomness of multistate motors is reduced compared with the one-state case and can be used for determining tau. Our analysis therefore demonstrates the intimate relationship between the biochemical cycle, the force-velocity relation and the random motion of molecular motors.

Thomas, N.; Imafuku, Y.; Tawada, K.

2001-01-01

381

Course 8: Statistics of Knots and Entangled Random Walks

NASA Astrophysics Data System (ADS)

Contents 1 Introduction 2 Knot diagrams as disordered spin systems 2.1 Brief review of statistical problems in topology 2.2 Abelian problems in statistics of entangled random walks and incompleteness of Gauss invariant 2.3 Nonabelian algebraic knot invariants 2.4 Lattice knot diagrams as disordered Potts model 2.5 Notion about annealed and quenched realizations of topological disorder 3 Random walks on locally non-commutative groups 3.1 Brownian bridges on simplest non-commutative groups and knot statistics 3.2 Random walks on locally free groups 3.3 Analytic results for random walks on locally free groups 3.4 Brownian bridges on Lobachevskii plane and products of non-commutative random matrices 4 Conformal methods in statistics of random walks with topological constraints 4.1 Construction of nonabelian connections for ?2 and PSL(2, Z ) from conformal methods 4.2 Random walk on double punctured plane and conformal field theory 4.3 Statistics of random walks with topological constraints in the two-dimensional lattices of obstacles 5 Physical applications. Polymer language in statistics of entangled chain-like objects 5.1 Polymer chain in 3D-array of obstacles 5.2 Collapsed phase of unknotted polymer 6 Some "tight" problems of the probability theory and statistical physics 6.1 Remarks and comments to Section 2 6.2 Remarks and comments to Sections 3 and 4 6.3 Remarks and comments to Section 5

Nechaev, S.

382

Sampling frequency impacts measurement of walking activity after stroke.

The purpose of this study was to examine the effect of sampling epoch on total time spent walking and number of walking bouts per day in persons with stroke. Ninety-eight persons with average age of 63.8 yr and average time poststroke of 43.6 mo participated. Participants wore a StepWatch Activity Monitor for 3 to 5 consecutive days. The number of strides taken was collected in consecutive 5 s epochs and down sampled into 10, 20, 30, and 60 s epochs. Total time walking and total number of walking bouts were determined for each day. Low activity days were defined as days below the 25th percentile of total steps per day and high activity days as days above the 75th percentile of total steps per day. Total time walking and total number of bouts were different for each sampling epoch (p < 0.001 for all). The 5 s sampling epoch resulted in calculation of ~40% of the walking time and ~6 times as many bouts as a 60 s sampling epoch. Differences were greater for low activity days (p < 0.001 for all). Sampling epoch affects daily step activity variables whose calculation depends on time, especially during low activity days. Sampling epoch must be carefully considered when designing studies aimed at understanding patterns of daily walking activity. PMID:24458896

Knarr, Brian; Roos, Margaret A; Reisman, Darcy S

2013-01-01

383

Survey of Korean pedestrians' natural preference for walking directions.

The primary objective of this study was to investigate the stereotypes of Koreans regarding preferred walking directions when encountering various public walking facilities, and to provide useful information to pedestrians and traffic policy legislators. To this end, this study was conducted in two phases. In the first phase, we conducted observational research on pedestrians' walking directions in ten different situations. In the second phase, six hundred Korean male and female subjects were selected to investigate the various statistics about their preferred walking directions and their employment characteristics in diverse walking facilities. The results showed that 59.3% abided by the Left-side Traffic rule while 40.7% abided by the Right-side rule. On the contrary, 73.7% of respondents showed preferences to the Right-side Traffic rule. Moreover, right-handed people showed strong tendencies to walk on the right side of the road and vice versa, hence suggesting that the direction people naturally prefer in walking should be a crucial determinant when regulating traffic policies. PMID:23664206

Jung, Hwa S; Jung, Hyung-Shik

2013-11-01

384

Changes in corticospinal excitability following adaptive modification to human walking.

Locomotor adaptations to a novel environment can be measured through changes in muscle activity patterns and lower limb kinematics. The location and mechanisms underlying these adaptive changes are unknown. The purposes of the current study were (1) to determine whether corticospinal tract (CST) excitability is altered by resisted walking and (2) to ascertain whether changes in cortical excitability are muscle specific. Forty healthy participants walked with a robotic gait device (Lokomat) that applied a velocity-dependent resistance against hip and knee movements during walking. CST excitability was assessed by quantifying motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation immediately before and after baseline and resisted walking. MEPs were measured in either the biceps femoris (BF) or the rectus femoris (RF). Recruitment curves were collected by stimulating in 5 % increments from 105 to 145 % of active motor threshold. Results demonstrated a significant increase in MEP amplitude in the BF following baseline walking in the Lokomat. The RF did not demonstrate these changes. There was no further change in MEP size following resisted walking in either muscle group. These results suggest that locomotion increases CST excitability in a muscle-specific fashion. As such, it may be important for determining how to enhance the central nervous system's ability to integrate adaptive strategies during walking. PMID:23494384

Zabukovec, J R; Boyd, L A; Linsdell, M A; Lam, T

2013-05-01

385

Visual control of foot placement when walking over complex terrain.

The aim of this study was to investigate the role of visual information in the control of walking over complex terrain with irregularly spaced obstacles. We developed an experimental paradigm to measure how far along the future path people need to see in order to maintain forward progress and avoid stepping on obstacles. Participants walked over an array of randomly distributed virtual obstacles that were projected onto the floor by an LCD projector while their movements were tracked by a full-body motion capture system. Walking behavior in a full-vision control condition was compared with behavior in a number of other visibility conditions in which obstacles did not appear until they fell within a window of visibility centered on the moving observer. Collisions with obstacles were more frequent and, for some participants, walking speed was slower when the visibility window constrained vision to less than two step lengths ahead. When window sizes were greater than two step lengths, the frequency of collisions and walking speed were weakly affected or unaffected. We conclude that visual information from at least two step lengths ahead is needed to guide foot placement when walking over complex terrain. When placed in the context of recent research on the biomechanics of walking, the findings suggest that two step lengths of visual information may be needed because it allows walkers to exploit the passive mechanical forces inherent to bipedal locomotion, thereby avoiding obstacles while maximizing energetic efficiency. PMID:23750964

Matthis, Jonathan S; Fajen, Brett R

2014-02-01

386

Preferred step frequency minimizes veering during natural human walking.

In the absence of visual information, humans cannot maintain a straight walking path. We examined the hypothesis that step frequency during walking affects the magnitude of veering in healthy adults. Subject walked at a preferred (1.77 ± 0.18 Hz), low (0.8 × preferred, 1.41 ± 0.15 Hz), and high (1.2× preferred, 2.13 ± 0.20 Hz) step frequency with and without a blindfold. We compared the absolute differences between estimated and measured points of crossing a target line after 16 m of forward walking at the three step frequencies. There was no significant difference in veering when subjects walked at the different frequencies without a blindfold. However, the magnitude of veering was the smallest at the preferred (mean ± SE=91.6 ± 33.6 cm) compared with the low (204.3 ± 43.0 cm) and high (112.7 ± 34.0 cm) frequency gaits with a blindfold. Thus, walking at a preferred step frequency minimizes veering, which occurs in the absence of visual information. This phenomenon may be associated with the previously reported minimization of movement variability, energy cost, and attentional demand while walking at a preferred step frequency. PMID:22051522

Uematsu, Azusa; Inoue, Koh; Hobara, Hiroaki; Kobayashi, Hirofumi; Iwamoto, Yuki; Hortobágyi, Tibor; Suzuki, Shuji

2011-11-21

387

Behavior Change Techniques Used to Promote Walking and Cycling

Objective: Evidence on the effectiveness of walking and cycling interventions is mixed. This may be partly attributable to differences in intervention content, such as the cognitive and behavioral techniques (BCTs) used. Adopting a taxonomy of BCTs, this systematic review addressed two questions: (a) What are the behavior change techniques used in walking and cycling interventions targeted at adults? (b) What characterizes interventions that appear to be associated with changes in walking and cycling in adults? Method: Previous systematic reviews and updated database searches were used to identify controlled studies of individual-level walking and cycling interventions involving adults. Characteristics of intervention design, context, and methods were extracted in addition to outcomes. Intervention content was independently coded according to a 26-item taxonomy of BCTs. Results: Studies of 46 interventions met the inclusion criteria. Twenty-one reported a statistically significant effect on walking and cycling outcomes. Analysis revealed substantial heterogeneity in the vocabulary used to describe intervention content and the number of BCTs coded. “Prompt self-monitoring of behavior” and “prompt intention formation” were the most frequently coded BCTs. Conclusion: Future walking and cycling intervention studies should ensure that all aspects of the intervention are reported in detail. The findings lend support to the inclusion of self-monitoring and intention formation techniques in future walking and cycling intervention design, although further exploration of these and other BCTs is required. Further investigation of the interaction between BCTs and study design characteristics would also be desirable.

Bird, Emma L.; Baker, Graham; Mutrie, Nanette; Ogilvie, David; Sahlqvist, Shannon; Powell, Jane

2013-01-01

388

Perception, planning, and control for walking on rugged terrain

NASA Technical Reports Server (NTRS)

The CMU Planetary Rover project is developing a six-legged walking robot capable of autonomously navigating, exploring, and acquiring samples in rugged, unknown environments. To gain experience with the problems involved in walking on rugged terrain, a full-scale prototype leg was built and mounted on a carriage that rolls along overhead rails. Issues addressed in developing the software system to autonomously walk the leg through rugged terrain are described. In particular, the insights gained into perceiving and modeling rugged terrain, controlling the legged mechanism, interacting with the ground, choosing safe yet effective footfalls, and planning efficient leg moves through space are described.

Simmons, Reid; Krotkov, Eric

1991-01-01

389

Analysis of the two-particle controlled interacting quantum walks

NASA Astrophysics Data System (ADS)

We have recently proposed the two-particle controlled interacting quantum walks for building quantum Hash schemes (Li et al. Quantum Inf Proc, 2012. doi:10.1007/s11128-012-0421-8). In this paper, we adopt the mutual information, the measurement-induced disturbance and the quantum mutual information to measure the classical correlation, the quantum correlation and the total correlation between two particles respectively. Our conclusion is that the correlation between the particles of the two-particle controlled interacting quantum walks is similar to that of the two-particle interacting quantum walks. It is superb for keeping the quantum Hash scheme safe.

Li, Dan; Zhang, Jie; Ma, Xiu-Wen; Zhang, Wei-Wei; Wen, Qiao-Yan

2013-06-01

390

Decoherence in a one-dimensional quantum walk

In this article we study decoherence in the discrete-time quantum walk on the line. We generalize the method of decoherent coin quantum walk, introduced by Brun et al. [Phys. Rev. A 67, 32304 (2003)]. Our analytical expressions are applicable for all kinds of decoherence. As an example of the coin-position decoherence, we study the broken line quantum walk and compare our results with the numerical one. We also show that our analytical results reduce to the Brun formalism when only the coin is subjected to decoherence.

Annabestani, Mostafa; Abolhassani, Mohamad Reza [Department of Physics, Basic Sciences Faculty, Tarbiat Modarres University, Tehran (Iran, Islamic Republic of); Akhtarshenas, Seyed Javad [Department of Physics, University of Isfahan, Isfahan (Iran, Islamic Republic of); Quantum Optics Group, University of Isfahan, Isfahan (Iran, Islamic Republic of)

2010-03-15

391

Biomechanical effects of rockers on walking in a plaster cast.

Rockers are applied to lower limb casts to assist walking but there is little information on their biomechanical effects. The performances of 10 commercially available rockers were compared. They were applied to a below-knee cast worn by a normal subject who was also tested walking in the cast alone. Gait analysis was used to evaluate kinematic and kinetic data. The design of rocker had no effect upon the kinematics of walking. However, using new criteria for kinetic assessment of rocker function (tibial floor angular velocity and centre of pressure progression), most designs had a deleterious effect on the biomechanics of gait. Only two rockers approached the ideal kinetic criteria. PMID:1991786

Hullin, M G; Robb, J E

1991-01-01

392

On a treadmill, humans switch from walking to running beyond a characteristic transition speed. Here, we study human choice between walking and running in a more ecological (non-treadmill) setting. We asked subjects to travel a given distance overground in a given allowed time duration. During this task, the subjects carried, and could look at, a stopwatch that counted down to zero. As expected, if the total time available were large, humans walk the whole distance. If the time available were small, humans mostly run. For an intermediate total time, humans often use a mixture of walking at a slow speed and running at a higher speed. With analytical and computational optimization, we show that using a walk–run mixture at intermediate speeds and a walk–rest mixture at the lowest average speeds is predicted by metabolic energy minimization, even with costs for transients—a consequence of non-convex energy curves. Thus, sometimes, steady locomotion may not be energy optimal, and not preferred, even in the absence of fatigue. Assuming similar non-convex energy curves, we conjecture that similar walk–run mixtures may be energetically beneficial to children following a parent and animals on long leashes. Humans and other animals might also benefit energetically from alternating between moving forward and standing still on a slow and sufficiently long treadmill.

Long, Leroy L.; Srinivasan, Manoj

2013-01-01

393

Treadmill Adaptation and Verification of Self-Selected Walking Speed: A Protocol for Children

ERIC Educational Resources Information Center

Walking is a common activity of daily life and researchers have used the range 3-6 km.h[superscript -1] as reference for walking speeds habitually used for transportation. The term self-selected (i.e., individual or comfortable walking pace or speed) is commonly used in the literature and is identified as the most efficient walking speed, with…

Amorim, Paulo Roberto S.; Hills, Andrew; Byrne, Nuala

2009-01-01

394

Assessment of Walking Speed and Distance in Subjects With an Incomplete Spinal Cord Injury

Background. The 10-meter walk test and 6-minute walk test are increasingly used to evaluate the recovery of walking in patients with incomplete spinal cord injury. So far, there is no evidence whether the application of different walking dis- tances provides complementary information about ambula- tory capacity in patients with incomplete spinal cord injury. Studies about testing preferred and maximum speeds

Hubertus J. A. van Hedel; Volker Dietz; Armin Curt

395

Identifying Belief-Based Targets for the Promotion of Leisure-Time Walking

ERIC Educational Resources Information Center

Walking is the most common type of physical activity (PA) and the likely target of efforts to increase PA. No studies, however, have identified the belief-level correlates for walking using the theory of planned behavior. This study elicits salient beliefs about walking and evaluates beliefs that may be most important for walking-promotion…

Rhodes, Ryan E.; Blanchard, Chris M.; Courneya, Kerry S.; Plotnikoff, Ronald C.

2009-01-01

396

The Effects of a 12-Week Walking Program on Community-Dwelling Older Adults

ERIC Educational Resources Information Center

Walking is a popular and easily accessible form of physical activity. However, walking instruction for older adults is based on the evidence gathered from younger populations. This study evaluated walking conditions, strength, balance, and subjective health status after a 12-week walking-training program in community-dwelling adults greater than…

Cheng, Shun-Ping; Tsai, Tzu-I; Lii, Yun-Kung; Yu, Shu; Chou, Chen-Liang; Chen, I-Ju

2009-01-01

397

Experimental approach for high speed walking of biped robot MARI-1

In this paper, a biped robot MARI-1 developed in our laboratory, which is light and for the purpose of fast walking, is introduced. The hardware including the robot frame, actuators, sensors, and control system are described. The method of walking pattern generation is presented. For the aim of fast walking, walking pattern modification with ZMP feedback, two control approaches of

Chi Zhu; Mikio Okamura; Atsuo Kawamura; Yoshihito Tomizawa

2004-01-01

398

Predictors of 6-minute walk test and 12-minute walk/run test in obese children and adolescents.

The purpose of this study was to identify predictors of the distance achieved during a 6-minute walk test and a 12-minute walk/run test (Cooper test) in obese children and adolescents and to evaluate the influence of a residential treatment on the association of these predictors with the distance. A search of the Revalidation Centre Zeepreventorium (De Haan, Belgium) medical records database of all children and adolescents (age 10 to 18 yrs) treated for obesity between September 2003 and February 2006, revealed 65 charts with all relevant data (anthropometrical, maximal graded exercise, lung function, 6-minute walk test and 12-minute walk/run test) at admission as well as after 3 months treatment. The multidisciplinary treatment has a positive influence on anthropometrical variables, endurance capacity, vital capacity, and residual volume (p < 0.05). The distance covered during the 6-minute walk test and the 12-minute walk/run test is correlated with all anthropometrical data and peak VO2 (p < 0.05). After 3 months of treatment, bivariate correlation was stronger for almost every parameter compared to admission. Following a stepwise regression, BMI z-score is a dominant predictor of both field tests at admission and after 3 months treatment. VO2peak contributes only significantly in the 12-minute walk/run test at admission. Conclusion: In obese children and adolescents BMI z-score is the most dominant predictor of the variability in performances on the 6-minute walk test and the 12-minute walk/run test at admission as well as after 3 months of treatment. PMID:17726615

Calders, Patrick; Deforche, Benedicte; Verschelde, Sabine; Bouckaert, Jacques; Chevalier, Frederic; Bassle, Eddy; Tanghe, Ann; De Bode, Patrick; Franckx, Hilde

2008-05-01

399

Abstract There is lack of data on the physiological characteristics of over ground walking and walking recommendations for Chinese young adult. The purpose of the study was to measure walking-related energy expenditure during field testing, to identify step-rate cut-point associated with moderate and vigorous intensity, and to translate physical activity (PA) guidelines into walking goals for Chinese young adults. Design Cross-sectional analytic study. Setting Two communities from Beijing and Shanghai in China. Participants A sample of 226 Chinese adults (117 men, 109 women) with a mean age of 21.7 (±0.2) years, volunteered to participate in the study. All Participants were recreationally active without orthopaedic limitations, free of chronic diseases, not taking any medications that affect metabolism and non-smokers. Outcome measures All the participants completed four 6?minincremental over ground walking at different speeds of 3.8, 4.8, 5.6 and 6.4?km/h, respectively. Indirect calorimeter was used to measure energy expenditure at each speed. Receiver operating characteristic curves were used to determine the step-rate cut-points associated with moderate and vigorous intensity activity. Results At the same walking speed, step counts per minute were higher in women than in men. No significant differences were found in VO2 per weight (ml/kg/min) between women and men. Step-rate cut-point associated with walking at 3 metabolic equivalents (METs) and 6METs were 105 and 130?step/min when analysing men and women together. There were slight differences on the cut-points between women and men if data were analysed separately. Conclusions In order to meet PA guidelines, Chinese young adult should walk 30?min with at least 105 step/min or 3150 steps or 2?km with the same step-rate per day. Walking at a higher speed of 130 step/min might provide additional health benefit.

Wang, Huan; Zhang, Yan-feng; Xu, Liang-liang; Jiang, Chong-min

2013-01-01

400

Recurrences in three-state quantum walks on a plane

NASA Astrophysics Data System (ADS)

We analyze the role of dimensionality in the time evolution of discrete-time quantum walks through the example of the three-state walk on a two-dimensional triangular lattice. We show that the three-state Grover walk does not lead to trapping (localization) or recurrence to the origin, in sharp contrast to the Grover walk on the two-dimensional square lattice. We determine the power-law scaling of the probability at the origin with the method of stationary phase. We prove that only a special subclass of coin operators can lead to recurrence, and there are no coins that lead to localization. The propagation for the recurrent subclass of coins is quasi-one dimensional.

Kollár, B.; Štefa?ák, M.; Kiss, T.; Jex, I.

2010-07-01

401

72. View looking SE down pedestrian walking away from bridge ...

72. View looking SE down pedestrian walking away from bridge towards Brooklyn. Jet Lowe, photographer, 1982. - Brooklyn Bridge, Spanning East River between Park Row, Manhattan and Sands Street, Brooklyn, New York, New York County, NY

402

Relation between coined quantum walks and quantum cellular automata

Motivated by the recent work of Patel et al., this paper clarifies a connection between coined quantum walks and quantum cellular automata in a general setting. As a consequence, their result is naturally derived from the connection.

Masatoshi Hamada; Norio Konno; Etsuo Segawa

2004-01-01

403

11. LAUREL POOL, LOOKING NORTHWEST FROM HAZEL WALK Photocopy of ...

11. LAUREL POOL, LOOKING NORTHWEST FROM HAZEL WALK Photocopy of photograph, 1930s National Park Service, National Capital Region files - Dumbarton Oaks Park, Thirty-second & R Streets Northwest, Washington, District of Columbia, DC

404

10. CLIFTON HILL, LOOKING NORTHWEST ACROSS STREAM FROM HAZEL WALK ...

10. CLIFTON HILL, LOOKING NORTHWEST ACROSS STREAM FROM HAZEL WALK Photocopy of photograph, 1930s National Park Service, National Capital Region files - Dumbarton Oaks Park, Thirty-second & R Streets Northwest, Washington, District of Columbia, DC

405

9. CLIFTON HILL, LOOKING NORTHEAST ACROSS STREAM FROM HAZEL WALK ...

9. CLIFTON HILL, LOOKING NORTHEAST ACROSS STREAM FROM HAZEL WALK Photocopy of photograph, 1930s National Park Service, National Capital Region files - Dumbarton Oaks Park, Thirty-second & R Streets Northwest, Washington, District of Columbia, DC

406

Simple Approximate Solutions to Continuous-Time-Random-Walk Transport.

National Technical Information Service (NTIS)

This paper presents a procdure for obtaining simple approximate solutions to the continuous-time random walk (CTRW) as it applies to charge transport in amorphous materials. Application of this procedure to a particularly simple trial function leads to an...

F. B. McLean G. A. Ausman

1976-01-01

407

Continuous-time quantum walks with defects and disorder

NASA Astrophysics Data System (ADS)

With the advent of physical implementations of quantum walks, a general theoretical and efficient numerical framework is required for the study of their interactions with defects and disorder. In this paper, we derive analytic expressions for the eigenstates of a one-dimensional continuous-time quantum walk interacting with a single defect, before investigating the effects of multiple diagonal defects and disorder, with emphasis on its transmission and reflection properties. Complex resonance behavior is demonstrated, showing alternating bands of zero and perfect transmission for various defect parameters. Furthermore, we provide an efficient numerical method to characterize quantum walks in the presence of diagonal disorder, paving the way for selective control of quantum walks via the optimization of position-dependent defects. The numerical method can be readily extended to higher dimensions and multiple interacting walkers.

Izaac, J. A.; Wang, J. B.; Li, Z. J.

2013-10-01

408

Hierarchical random-walk algorithms for power grid analysis

This paper presents a power grid analyzer that combines a divide-and-conquer strategy with a random-walk engine. A single-level hierarchical method is first described and then extended to multi-level and \\

Haifeng Qian; Sachin S. Sapatnekar

2004-01-01

409

The experimental study on the contact process of passive walking

NASA Astrophysics Data System (ADS)

The passive dynamic walking is a new concept of biped walking. Researchers have been working on this area with both theoretical analysis and experimental analysis ever since McGeer. This paper presents our compass-like passive walking model with a new set of testing system. Two gyroscopes are used for measuring the angles of two legs, and ten FlexiForce sensors are used for measuring the contact forces on the feet. We got the experimental data on the passive walking process with the validated testing system. A great emphasis was put on the contact process between the feet and the slope. The contact process of the stance leg was divided into four sections, and differences between the real testing contact process and the classic analytical contact process with no bouncing and slipping were summarized.

Qi, Feng; Bi, Lai-Ye; Wang, Tian-Shu; Li, Jun-Feng

2012-08-01

410

Gallery Walk Questions on Weathering and Mass Wasting

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about weathering and mass wasting. The questions are organized according to ...

411

Walking Could Be Key Step Against Kidney Disease

... the Clinical Journal of the American Society of Nephrology , Taiwanese researchers found that regular walks helped kidney ... SOURCE: Clinical Journal of the American Society of Nephrology , news release, May 15, 2014 HealthDay Copyright (c) ...

412

6. FORSYTHIA WALK AFTER WIDENING Photocopy of photograph, date unknown ...

6. FORSYTHIA WALK AFTER WIDENING Photocopy of photograph, date unknown National Park Service, National Capital Region files - Dumbarton Oaks Park, Thirty-second & R Streets Northwest, Washington, District of Columbia, DC

413

Adiabatic Quantum Computing and Quantum Walks: Algorithms and Architectures.

National Technical Information Service (NTIS)

During the period of this grant, there were a many significant results on quantum adiabatic algorithms and quantum walks. On the adiabatic front, there were papers showing how to design error correcting codes specifically for these Hamiltonian based algor...

E. Farhi

2011-01-01

414

Determination of stresses in below-knee walking casts.

Glass fibre bandages are now commonly used for definitive below-knee walking casts, in preference to plaster of Paris, since they are better able to withstand the stresses imposed upon them. This paper describes a technique for recording the cast strains in glass fibre bandages and shows typical stress levels in patient and volunteer casts. A typical map of the stress variations in walking casts during gait in a volunteer has been produced. The study shows that the high stresses recorded along the medial and lateral borders of the foot by the strain gauge technique are confirmed by clinical experience, since this is where failure is most commonly seen in below-knee walking casts. It is concluded that the current generation of polyurethane impregnated glass fibre splinting bandages are too brittle in many cases for below-knee walking casts and that a more flexible fabric would reduce the incidence of cast breakdown. PMID:23916106

Wytch, R; Mitchell, C G; Gaffron, I D; Neil, G; Wardlaw, D

1990-02-01

415

Gallery Walk Questions on the Hydrosphere and Cryosphere

NSDL National Science Digital Library

created by Mark Francek, Central Michigan University The following are potential questions that could be used in a gallery walk activity about the hydrosphere and cryosphere. The questions are organized according ...

416

Generic quantum walk using a coin-embedded shift operator

NASA Astrophysics Data System (ADS)

The study of quantum walk processes has been widely divided into two standard variants, the discrete-time quantum walk (DTQW) and the continuous-time quantum walk (CTQW). The connection between the two variants has been established by considering the limiting value of the coin operation parameter in the DTQW, and the coin degree of freedom was shown to be unnecessary [F. W. Strauch, Phys. Rev. A 74, 030301(R) (2006)]. But the coin degree of freedom is an additional resource which can be exploited to control the dynamics of the QW process. In this paper we present a generic quantum walk model using a quantum coin-embedded unitary shift operation UC . The standard version of the DTQW and the CTQW can be conveniently retrieved from this generic model, retaining the features of the coin degree of freedom in both variants.

Chandrashekar, C. M.

2008-11-01

417

Improving walking assessment in subjects with an incomplete spinal cord injury: responsiveness

Study design:Prospective longitudinal study.Objectives:To investigate the responsiveness of the Walking Index for Spinal Cord Injury II (WISCI II), 6-Min Walk (6MWT) and 10-Meter Walk Tests (10MWT) for the assessment of walking capacity in incomplete spinal cord injury (iSCI) and to validate these tests with the lower extremity motor score (LEMS).Setting:European Multicenter Study of Human Spinal Cord Injury.Methods:The walking tests of

H J A van Hedel; M Wirz; A Curt; HJA van Hedel

2006-01-01

418

A Robust Quadruped Walking Gait for Traversing Rough Terrain

Abstract-Legged locomotion excels when terrains become too rough for wheeled systems or open-loop walking pattern gen-erators to succeed, i. e., when accurate foot placement is of pri-mary importance in successfully reaching the task goal. In this paper we address the scenario where the rough terrain is trav-ersed with a static walking gait, and where for every foot place-ment of a

Dimitris Pongas; Michael Mistry; Stefan Schaal

2007-01-01

419

Walking with Increased Ankle Pushoff Decreases Hip Muscle Moments

In a simple bipedal walking model, an impulsive push along the trailing limb (similar to ankle plantar flexion) or a torque at the hip can power level walking. This suggests a tradeoff between ankle and hip muscle requirements during human gait. People with anterior hip pain may benefit from walking with increased ankle pushoff if it reduces hip muscle forces. The purpose of our study was to determine if simple instructions to alter ankle pushoff can modify gait dynamics and if resulting changes in ankle pushoff have an effect on hip muscle requirements during gait. We hypothesized that changes in ankle kinetics would be inversely related to hip muscle kinetics. Ten healthy subjects walked on a custom split-belt force-measuring treadmill at 1.25 m/s. We recorded ground reaction forces and lower extremity kinematic data to calculate joint angles and internal muscle moments, powers and angular impulses. Subjects walked under three conditions: Natural Pushoff, Decreased Pushoff and Increased Pushoff. For the Decreased Pushoff condition, subjects were instructed to push less with their feet as they walked. Conversely, for the Increased Pushoff condition, subjects were instructed to push more with their feet. As predicted, walking with increased ankle pushoff resulted in lower peak hip flexion moment, power, and angular impulse as well as lower peak hip extension moment and angular impulse (p<0.05). Our results emphasize the interchange between hip and ankle kinetics in human walking and suggest that increased ankle pushoff during gait may help compensate for hip muscle weakness or injury and reduce hip joint forces.

Lewis, Cara L.; Ferris, Daniel P.

2008-01-01

420

Continuous-Time Random Walks, Fractional Calculus and Stochastic Integrals

Continuous-time random walks are pure-jump processes with several applications in physics, but also in insurance, finance and economics. Based on heuristic considerations, a definition is given for the stochastic integral driven by continuous-time random walks. The martingale properties of the integral are investigated. It is shown how the definition can be used to easily compute the stochastic integral by means

E. Scalas; G. Germano; M. Politi; R. L. Schilling

2009-01-01

421

Generalized master equations for continuous-time random walks

An equivalence is established between generalized master equations and continuous-time random walks by means of an explicit relationship between psi(t), which is the pausing time distribution in the theory of continuous-time random walks, and phi(t), which represents the memory in the kernel of a generalized master equation. The result of Bedeaux, Lakatos-Lindenburg, and Shuler concerning the equivalence of the Markovian

V. M. Kenkre; E. W. Montroll; M. F. Shlesinger

1973-01-01

422

Generalized master equations for continuous-time random walks

An equivalence is established between generalized master equations and continuous-time random walks by means of an explicit relationship between?(t), which is the pausing time distribution in the theory of continuous-time random walks, andf(t), which represents the memory in the kernel of a generalized master equation. The result of Bedeaux, Lakatos-Lindenburg, and Shuler concerning the equivalence of the Markovian master equation

V. M. Kenkre; E. W. Montroll; M. F. Shlesinger

1973-01-01

423

Six-minute walk test in Chagas cardiomyopathy

We studied systematically, for the first time, the utility of the six-minute walk test (6MWT) in Chagas disease. The walked distance at 6MWT correlated negatively with the increased circulating levels of monocyte chemoattractant protein (MCP-1, r=?0.358, p=0.04) and natriuretic peptide type B (BNP, r=?0.349, p=0.04), as well as positively with ejection fraction deterioration (r=0.451, p=0.004), indicating that submaximal functional capacity

Lidiane Sousa; Fernando Antônio Botoni; Raquel R. Britto; Manoel Otávio da Costa Rocha; Antonio Lúcio Teixeira; Mauro Martins Teixeira; Adelina M. Reis; Bráulio Muzzi R. Oliveira; Antonio L. Ribeiro

2008-01-01

424

Gate imperfection in the quantum random-walk search algorithm

NASA Astrophysics Data System (ADS)

We study how imperfect quantum gates affect the quantum random-walk search algorithm. We find that systematic errors in phase inversions result in the reduction of the maximum probability of the marked state and lower the algorithm efficiency with an increasing degree of inaccuracy. The size of the database should be limited due to the inevitable errors. Finally, we compare the phase noise caused by such errors in the random-walk search algorithm with that in the Grover search algorithm.

Li, Yun; Ma, Lei; Zhou, Jie

2006-07-01

425

Muscle compensatory mechanisms during able-bodied toe walking

The purpose of this study was to use muscle-actuated forward dynamic simulations to quantify individual muscle contributions to body support (vertical ground reaction force) and propulsion (horizontal ground reaction force) and the mechanical energetics of the body segments during toe and heel-toe walking performed by able-bodied subjects to identify possible compensatory mechanisms necessary to toe walk. The simulations showed that

Kotaro Sasaki; Richard R. Neptune; Judith M. Burnfield; Sara J. Mulroy

2008-01-01

426

The melting phenomenon in random-walk model of DNA

The melting phenomenon in a double-stranded homopolypeptide is considered. The relative distance between the corresponding monomers of two polymer chains is modeled by the two-dimensional random walk on the square lattice. Returns of the random walk to the origin describe the formation of hydrogen bonds between complementary units. To take into account the two competing interactions of monomers inside the chains, we obtain a completely denatured state at finite temperature T{sub c}.

Hayrapetyan, G. N.; Mamasakhlisov, E. Sh.; Papoyan, Vl. V., E-mail: vpap@theor.jinr.ru [Yerevan State University (Armenia); Poghosyan, S. S. [Joint Institute for Nuclear Research (Russian Federation)

2012-10-15

427

System Design and Control of Anthropomorphic Walking Robot LOLA

This paper presents the 25-DOF full-size humanoid robot LOLA . Our goal is to realize fast and human-like walking. Furthermore, we want to increase the robot's autonomous, vision-guided walking capabilities. LOLA is characterized by a redundant kinematic configuration, an extremely lightweight design, joint actuators with brushless motors and an electronics architecture using decentralized joint control. Special emphasis was put on

Sebastian Lohmeier; Thomas Buschmann; Heinz Ulbrich

2009-01-01

428

Elasticity and movements of the cockroach tarsus in walking

Anatomical, kinematic and ablation studies were performed to evaluate the contribution of elasticity in use of the cockroach\\u000a tarsus (foot) in walking. The distal tarsus (claws and arolium) engages the substrate during the stance phase of walking by\\u000a the action of a single muscle, the retractor unguis. Kinematic and ablation studies demonstrated that tarsal disengagement\\u000a occurs at the end of

S. F. Frazier; G. S. Larsen; D. Neff; L. Quimby; M. Carney; R. A. DiCaprio; S. N. Zill

1999-01-01

429

Lectures on walking technicolor, holography and gauge\\/gravity dualities

Dynamical electro-weak symmetry breaking is an appealing, strongly-coupled alternative to the weakly-coupled models based on an elementary scalar field developing a vacuum expectation value. In the first two sections of this set of lectures, I summarize the arguments, based on low-energy phenomenology, supporting walking technicolor as a realistic realization of this idea. This pedagogical introduction to walking technicolor, and more

Maurizio Piai

2010-01-01

430

Alterations in muscle activation patterns during robotic-assisted walking

Objective. The goal of this study was to compare the muscle activation patterns in various major leg muscles during treadmill ambulation with those exhibited during robotic-assisted walking.Background. Robotic devices are now being integrated into neurorehabilitation programs with promising results. The influence of these devices on altering naturally occurring muscle activation patterns utilized during walking have not been quantified.Methods. Muscle activity

Joseph M. Hidler; Anji E. Wall

2005-01-01

431

Walking performance in people with diabetic neuropathy: benefits and threats

Aims\\/hypothesis Walking is recommended as an adjunct therapy to diet and medication in diabetic patients, with the aim of improving physical fitness, glycaemic control and body weight reduction. Therefore we evaluated walking activity on the basis of capacity, performance and potential risk of plantar injury in the diabetic population before it can be prescribed safely.Subjects, materials and methods Twenty-three subjects with diabetic

R. V. Kanade; R. W. M. van Deursen; K. Harding; P. Price

2006-01-01

432

Data-Centric Routing in Sensor Networks using Biased Walk

We present spiral, a data-centric routing algorithm for short-term communication in unstructured sensor networks. Conventional data-centric routing algorithms are based on flooding or random walk. Flooding returns the shortest route but has a high search cost; random walk has a lower search cost but returns a sub-optimal route. Spiral offers a compromise between these two extremes - it has a

Huilong Huang; John H. Hartman; Terril N. Hurst

2006-01-01

433

Functional CLT for random walk among bounded random conductances

We consider the nearest-neighbor simple random walk on $\\\\Z^d$, $d\\\\ge2$, driven by a field of i.i.d. random nearest-neighbor conductances $\\\\omega_{xy}\\\\in[0,1]$. Apart from the requirement that the bonds with positive conductances percolate, we pose no restriction on the law of the $\\\\omega$'s. We prove that, for a.e. realization of the environment, the path distribution of the walk converges weakly to that

Marek Biskup; Timothy M. Prescott

2007-01-01

434

MODELING BILL'S GAIT: ANALYSIS AND PARAMETRIC SYNTHESIS OF WALKING SOUNDS

This paper presents algorithms and systems for automatic analysis and parametric synthesis of walking and other (gesture-rate) periodically modulated noisy sounds. A recording of walking is analyzed, extracting the gait (tempo and left\\/right asymmetries), heel-toe events, etc. Linear prediction is used to extract the basic resonances. Wavelet decomposition is performed, and a high frequency-subband is used to calculate statistics for

PERRY R. COOK

2002-01-01

435

Kinematic characteristics of elite men's 50 km race walking.

Race walking is an endurance event which also requires great technical ability, particularly with respect to its two distinguishing rules. The 50 km race walk is the longest event in the athletics programme at the Olympic Games. The aims of this observational study were to identify the important kinematic variables in elite men's 50 km race walking, and to measure variation in those variables at different distances. Thirty men were analysed from video data recorded during a World Race Walking Cup competition. Video data were also recorded at four distances during the European Cup Race Walking and 12 men analysed from these data. Two camcorders (50 Hz) recorded at each race for 3D analysis. The results of this study showed that walking speed was associated with both step length (r=0.54,P=0.002) and cadence (r=0.58,P=0.001). While placing the foot further ahead of the body at heel strike was associated with greater step lengths (r=0.45,P=0.013), it was also negatively associated with cadence (r= -0.62,P<0.001). In the World Cup, knee angles ranged between 175 and 186° at initial contact and between 180 and 195° at midstance. During the European Cup, walking speed decreased significantly (F=9.35,P=0.002), mostly due to a decrease in step length between 38.5 and 48.5 km (t=8.59,P=0.014). From this study, it would appear that the key areas a 50 km race walker must develop and coordinate are step length and cadence, although it is also important to ensure legal walking technique is maintained with the onset of fatigue. PMID:23679143

Hanley, Brian; Bissas, Athanassios; Drake, Andrew

2013-01-01

436

The melting phenomenon in random-walk model of DNA

NASA Astrophysics Data System (ADS)

The melting phenomenon in a double-stranded homopolypeptide is considered. The relative distance between the corresponding monomers of two polymer chains is modeled by the two-dimensional random walk on the square lattice. Returns of the random walk to the origin describe the formation of hydrogen bonds between complementary units. To take into account the two competing interactions of monomers inside the chains, we obtain a completely denatured state at finite temperature T c .

Hayrapetyan, G. N.; Mamasakhlisov, E. Sh.; Papoyan, Vl. V.; Poghosyan, S. S.

2012-10-01

437

On the Hitting Times of Quantum Versus Random Walks

The hitting time of a classical random walk (Markov chain) is the time required to detect the presence of—or equivalently, to find—a marked state. The hitting time of a quantum walk is subtler to define; in particular, it is unknown whether the detection\\u000a and finding problems have the same time complexity. In this paper we define new Monte Carlo type

Frederic Magniez; Ashwin Nayak; Peter C. Richter; Miklos Santha

2008-01-01

438

Reduced plantar sensation causes a cautious walking pattern

The aim of this study was to investigate the influence of reduced plantar sensation on gait patterns during walking in 20 healthy subjects (25.9±1.2 years, 61.6±11.5kg, 178±9.5cm) with no history of sensory disorders. Force plate measurements, electromyography (EMG) measurements and a three-dimensional movement analysis were performed simultaneously during barefoot walking before and after reduction of plantar sensation using an ice

Eric Eils; Susann Behrens; Oliver Mers; Lothar Thorwesten; Klaus Völker; Dieter Rosenbaum

2004-01-01

439

One-Dimensional Quantum Walks with One Defect

NASA Astrophysics Data System (ADS)

The CGMV method allows for the general discussion of localization properties for the states of a one-dimensional quantum walk, both in the case of the integers and in the case of the nonnegative integers. Using this method we classify, according to such localization properties, all the quantum walks with one defect at the origin, providing explicit expressions for the asymptotic return probabilities to the origin.

Cantero, M. J.; Grünbaum, F. A.; Moral, L.; Velázquez, L.

440

Physical Motion Analysis of Nordic Walking (P77)

Recent years have seen a worldwide increase in people participating in Nordic Walking with a heavy concentration in Northern\\u000a Europe. This trend has led to abundant research in Nordic Walking and to reports that this type of exercise is effective in\\u000a reducing load on the lower limbs. At the same time, there has been no comprehensive experimental study to our

Takayuki Koizumi; Nobutaka Tsujiuchi; Masaki Takeda; Yusuke Murodate

441

Physical Motion Analysis Of Nordic Walking (P77)

Recent years have seen a worldwide increase in people participating in Nordic Walking with a heavy concentration in Northern\\u000a Europe. This trend has led to abundant research in Nordic Walking and to reports that this type of exercise is effective in\\u000a reducing load on the lower limbs. At the same time, there has been no comprehensive experimental study to our

Takayuki Koizumi; Nobutaka Tsujiuchi; Masaki Takeda; Yusuke Murodate

442

Biped walking control based on hybrid position\\/force control

This paper describes a real-time walking control system developed for the biped robots JOHNNIE and LOLA. Walking trajectories are planned on-line using a simplified robot model and modified by a stabilizing controller. The controller uses hybrid position\\/force control in task space based on a resolved motion rate scheme. Inertial stabilization is achieved by modifying the contact force trajectories. The paper

Thomas Buschmann; Sebastian Lohmeier; Heinz Ulbrich

2009-01-01

443

fNIRS Study of Walking and Walking While Talking in Young and Old Individuals

Background. Evidence suggests that gait is influenced by higher order cognitive and cortical control mechanisms. However, less is known about the functional correlates of cortical control of gait. Methods. Using functional near-infrared spectroscopy, the current study was designed to evaluate whether increased activations in the prefrontal cortex (PFC) were detected in walking while talking (WWT) compared with normal pace walking (NW) in 11 young and 11 old participants. Specifically, the following two hypotheses were evaluated: (a) Activation in the PFC would be increased in WWT compared with NW. (b) The increase in activation in the PFC during WWT as compared with NW would be greater in young than in old participants. Results. Separate linear mixed effects models with age as the two-level between-subject factor, walking condition (NW vs WWT) as the two-level repeated within-subject factor, and HbO2 levels in each of the 16 functional near-infrared spectroscopy channels as the dependent measure revealed significant task effects in 14 channels, indicating a robust bilateral increased activation in the PFC in WWT compared with NW. Furthermore, the group-by-task interaction was significant in 11 channels with young participants showing greater WWT-related increase in HbO2 levels compared with the old participants. Conclusions. This study provided the first evidence that oxygenation levels are increased in the PFC during WWT compared with NW in young and old individuals. This effect was modified by age suggesting that older adults may underutilize the PFC in attention-demanding locomotion tasks.

Mahoney, Jeannette R.; Izzetoglu, Meltem; Izzetoglu, Kurtulus; Onaral, Banu; Verghese, Joe

2011-01-01

444

Neural decoding of treadmill walking from noninvasive electroencephalographic signals.

Chronic recordings from ensembles of cortical neurons in primary motor and somatosensory areas in rhesus macaques provide accurate information about bipedal locomotion (Fitzsimmons NA, Lebedev MA, Peikon ID, Nicolelis MA. Front Integr Neurosci 3: 3, 2009). Here we show that the linear and angular kinematics of the ankle, knee, and hip joints during both normal and precision (attentive) human treadmill walking can be inferred from noninvasive scalp electroencephalography (EEG) with decoding accuracies comparable to those from neural decoders based on multiple single-unit activities (SUAs) recorded in nonhuman primates. Six healthy adults were recorded. Participants were asked to walk on a treadmill at their self-selected comfortable speed while receiving visual feedback of their lower limbs (i.e., precision walking), to repeatedly avoid stepping on a strip drawn on the treadmill belt. Angular and linear kinematics of the left and right hip, knee, and ankle joints and EEG were recorded, and neural decoders were designed and optimized with cross-validation procedures. Of note, the optimal set of electrodes of these decoders were also used to accurately infer gait trajectories in a normal walking task that did not require subjects to control and monitor their foot placement. Our results indicate a high involvement of a fronto-posterior cortical network in the control of both precision and normal walking and suggest that EEG signals can be used to study in real time the cortical dynamics of walking and to develop brain-machine interfaces aimed at restoring human gait function. PMID:21768121

Presacco, Alessandro; Goodman, Ronald; Forrester, Larry; Contreras-Vidal, Jose Luis

2011-10-01

445

Stance and swing phase costs in human walking

Leg swing in human walking has historically been viewed as a passive motion with little metabolic cost. Recent estimates of leg swing costs are equivocal, covering a range from 10 to 33 per cent of the net cost of walking. There has also been a debate as to whether the periods of double-limb support during the stance phase dominate the cost of walking. Part of this uncertainty is because of our inability to measure metabolic energy consumption in individual muscles during locomotion. Therefore, the purpose of this study was to investigate the metabolic cost of walking using a modelling approach that allowed instantaneous energy consumption rates in individual muscles to be estimated over the full gait cycle. At a typical walking speed and stride rate, leg swing represented 29 per cent of the total muscular cost. During the stance phase, the double-limb and single-limb support periods accounted for 27 and 44 per cent of the total cost, respectively. Performing step-to-step transitions, which encompasses more than just the double-support periods, represented 37 per cent of the total cost of walking. Increasing stride rate at a constant speed led to greater double-limb support costs, lower swing phase costs and no change in single-limb support costs. Together, these results provide unique insight as to how metabolic energy is expended over the human gait cycle.

Umberger, Brian R.

2010-01-01

446

Response inhibition during avoidance of virtual obstacles while walking.

While walking, one often has to suppress and adjust a planned step in order to avoid a fall. Given that steps are preprogrammed this requires some form of motor inhibition. Motor inhibition is commonly tested in hand function and only recently attempts have been made to evaluate inhibition in the lower limbs, during step initiation. As adequate motor inhibition might play a role in avoiding falls a test to assess response inhibition during walking would be valuable. We developed a task in which subjects walked on a treadmill by stepping on projected patches of light, which could suddenly change color forcing the subjects to avoid it by shortening or lengthening their steps. The difficulty level was manipulated in 4 conditions by changing the distance available to respond. We hypothesized that larger demands on motor inhibition during walking would produce more failures and tested the performance of young adults (n=12) in order to establish the protocol for use in older adults. The failure rate on the walking test was analyzed. Reducing the available response distance by 150 mm from the easiest condition resulted in a significant increase in failure rates from 15.6% to 65.1%. Therefore, results indicate this novel test can be used to assess the level of motor inhibition during walking. Additionally, in comparison to previous literature on obstacle avoidance, our experiment shows that changing a precise aiming movement is considerably more challenging than changing the same movement executed automatically. PMID:23968973

Potocanac, Zrinka; Hoogkamer, Wouter; Carpes, Felipe P; Pijnappels, Mirjam; Verschueren, Sabine M P; Duysens, Jacques

2014-01-01

447

Human Body Detection that Uses Electric Field by Walking

NASA Astrophysics Data System (ADS)

For a method for detecting the human body, such factors that no blind corner should exist, subjects other than human beings will not be erroneously detected. In this paper, a new method for detecting a human body wherein attention is focused on the human characteristics of walking will be studied. It had been known that a human body is electrified by walking, thus forming an electrical field around the human body. It was considered from walking waveforms in which human walking was reflected that a human body could be detected more advantageously. The measuring method is not affected by vibrations, etc. In addition, detection is possible with a simple electrode, which is advantageous in terms of cost. In this study, electrification on the human body in which components of actions of both feet are superimposed will be measured at a remote place, under an assumed living environment, and by using an algorithm that remotely detects walking characteristics based on the waveforms in which movements of both feet are reflected. Walking of 10 subjects including infants was actually measured, and a system, which is capable of detecting the number of steps at an accuracy of approximately 99.4% was shown.

Takiguchi, Kiyoaki; Wada, Takayuki; Toyama, Shigeki

448

Current-reinforced random walks for constructing transport networks

Biological systems that build transport networks, such as trail-laying ants and the slime mould Physarum, can be described in terms of reinforced random walks. In a reinforced random walk, the route taken by ‘walking’ particles depends on the previous routes of other particles. Here, we present a novel form of random walk in which the flow of particles provides this reinforcement. Starting from an analogy between electrical networks and random walks, we show how to include current reinforcement. We demonstrate that current-reinforcement results in particles converging on the optimal solution of shortest path transport problems, and avoids the self-reinforcing loops seen in standard density-based reinforcement models. We further develop a variant of the model that is biologically realistic, in the sense that the particles can be identified as ants and their measured density corresponds to those observed in maze-solving experiments on Argentine ants. For network formation, we identify the importance of nonlinear current reinforcement in producing networks that optimize both network maintenance and travel times. Other than ant trail formation, these random walks are also closely related to other biological systems, such as blood vessels and neuronal networks, which involve the transport of materials or information. We argue that current reinforcement is likely to be a common mechanism in a range of systems where network construction is observed.

Ma, Qi; Johansson, Anders; Tero, Atsushi; Nakagaki, Toshiyuki; Sumpter, David J. T.

2013-01-01

449

Neural decoding of treadmill walking from noninvasive electroencephalographic signals

Chronic recordings from ensembles of cortical neurons in primary motor and somatosensory areas in rhesus macaques provide accurate information about bipedal locomotion (Fitzsimmons NA, Lebedev MA, Peikon ID, Nicolelis MA. Front Integr Neurosci 3: 3, 2009). Here we show that the linear and angular kinematics of the ankle, knee, and hip joints during both normal and precision (attentive) human treadmill walking can be inferred from noninvasive scalp electroencephalography (EEG) with decoding accuracies comparable to those from neural decoders based on multiple single-unit activities (SUAs) recorded in nonhuman primates. Six healthy adults were recorded. Participants were asked to walk on a treadmill at their self-selected comfortable speed while receiving visual feedback of their lower limbs (i.e., precision walking), to repeatedly avoid stepping on a strip drawn on the treadmill belt. Angular and linear kinematics of the left and right hip, knee, and ankle joints and EEG were recorded, and neural decoders were designed and optimized with cross-validation procedures. Of note, the optimal set of electrodes of these decoders were also used to accurately infer gait trajectories in a normal walking task that did not require subjects to control and monitor their foot placement. Our results indicate a high involvement of a fronto-posterior cortical network in the control of both precision and normal walking and suggest that EEG signals can be used to study in real time the cortical dynamics of walking and to develop brain-machine interfaces aimed at restoring human gait function.

Presacco, Alessandro; Goodman, Ronald; Forrester, Larry

2011-01-01

450

Effects of Walking Direction and Cognitive Challenges on Gait in Persons with Multiple Sclerosis

Declines in walking performance are commonly seen when undergoing a concurrent cognitive task in persons with multiple sclerosis (MS). The purpose of this study was to determine the effect of walking direction and simultaneous cognitive task on the spatiotemporal gait parameters in persons with MS compared to healthy controls. Ten persons with MS (Median EDSS, 3.0) and ten healthy controls took part in this pilot study. Participants performed 4 walking trials at their self-selected comfortable pace. These trials included forward walking, forward walking with a cognitive task, backward walking, and backward walking with a cognitive task. Walking performance was indexed with measures of velocity, cadence, and stride length for each testing condition. The MS group walked slower with significantly reduced stride length compared to the control group. The novel observation of this investigation was that walking differences between persons with MS and healthy controls were greater during backward walking, and this effect was further highlighted during backward walking with added cognitive test. This raises the possibility that backward walking tests could be an effective way to examine walking difficulties in individuals with MS with relatively minimal walking impairment.

Wajda, Douglas A.; Sandroff, Brian M.; Pula, John H.; Motl, Robert W.; Sosnoff, Jacob J.

2013-01-01

451

The limits of agency in walking humans.

An important principle of human ethics is that individuals are not responsible for actions performed when unconscious. Recent research found that the generation of an action and the building of a conscious experience of that action (agency) are distinct processes and crucial mechanisms for self-consciousness. Yet, previous agency studies have focussed on actions of a finger or hand. Here, we investigate how agents consciously monitor actions of the entire body in space during locomotion. This was motivated by previous work revealing that (1) a fundamental aspect of self-consciousness concerns a single and coherent representation of the entire spatially situated body and (2) clinical instances of human behaviour without consciousness occur in rare neurological conditions such as sleepwalking or epileptic nocturnal wandering. Merging techniques from virtual reality, full-body tracking, and cognitive science of conscious action monitoring, we report experimental data about consciousness during locomotion in healthy participants. We find that agents consciously monitor the location of their entire body and its locomotion only with low precision and report that while precision remains low it can be systematically modulated in several experimental conditions. This shows that conscious action monitoring in locomoting agents can be studied in a fine-grained manner. We argue that the study of the mechanisms of agency for a person's full body may help to refine our scientific criteria of self-hood and discuss sleepwalking and related conditions as alterations in neural systems encoding motor awareness in walking humans. PMID:20144893

Kannape, O A; Schwabe, L; Tadi, T; Blanke, O

2010-05-01

452

Monitoring Butterfly Abundance: Beyond Pollard Walks

Most butterfly monitoring protocols rely on counts along transects (Pollard walks) to generate species abundance indices and track population trends. It is still too often ignored that a population count results from two processes: the biological process (true abundance) and the statistical process (our ability to properly quantify abundance). Because individual detectability tends to vary in space (e.g., among sites) and time (e.g., among years), it remains unclear whether index counts truly reflect population sizes and trends. This study compares capture-mark-recapture (absolute abundance) and count-index (relative abundance) monitoring methods in three species (Maculinea nausithous and Iolana iolas: Lycaenidae; Minois dryas: Satyridae) in contrasted habitat types. We demonstrate that intraspecific variability in individual detectability under standard monitoring conditions is probably the rule rather than the exception, which questions the reliability of count-based indices to estimate and compare specific population abundance. Our results suggest that the accuracy of count-based methods depends heavily on the ecology and behavior of the target species, as well as on the type of habitat in which surveys take place. Monitoring programs designed to assess the abundance and trends in butterfly populations should incorporate a measure of detectability. We discuss the relative advantages and inconveniences of current monitoring methods and analytical approaches with respect to the characteristics of the species under scrutiny and resources availability.

Pellet, Jerome; Bried, Jason T.; Parietti, David; Gander, Antoine; Heer, Patrick O.; Cherix, Daniel; Arlettaz, Raphael

2012-01-01

453

Random-walk model of homologous recombination

NASA Astrophysics Data System (ADS)

Interaction between two homologous (i.e., identical or nearly identical) DNA sequences leads to their homologous recombination in the cell. We present the following stochastic model to explain the dependence of the frequency of homologous recombination on the length of the homologous region. The branch point connecting the two DNAs in a reaction intermediate follows the random-walk process along the homology (N base-pairs). If the branch point reaches either of the homology ends, it bounds back to the homologous region at a probability of ? (reflection coefficient) and is destroyed at a probability of 1-?. When ? is small, the frequency of homologous recombination is found to be proportional to N3 for smaller N and a linear function of N for larger N. The exponent of the nonlinear dependence for smaller N decreases from three as ? increases. When ?=1, only the linear dependence is left. These theoretical results can explain many experimental data in various systems. (c) 1995 The American Physical Society

Fujitani, Youhei; Kobayashi, Ichizo

1995-12-01

454

Entangling power of disordered quantum walks

NASA Astrophysics Data System (ADS)

We investigate how the introduction of different types of disorder affects the generation of entanglement between the internal (spin) and external (position) degrees of freedom in one-dimensional quantum random walks (QRWs). Disorder is modeled by adding another random feature to QRWs, i.e., the quantum coin that drives the system's evolution is randomly chosen at each position and/or at each time step, giving rise to dynamic, fluctuating, or static disorder. The first one is position independent, with every lattice site having the same coin at a given time; the second has time- and position-dependent randomness; and the third one is time independent. We show for several levels of disorder that dynamic disorder is the most powerful entanglement generator, followed closely by fluctuating disorder. Static disorder is the less efficient entangler, being almost always less efficient than the ordered case. Also, dynamic and fluctuating disorder lead to maximally entangled states asymptotically in time for any initial condition, while static disorder has no asymptotic limit and, similarly to the ordered case, has a long-time behavior highly sensitive to the initial conditions.

Vieira, Rafael; Amorim, Edgard P. M.; Rigolin, Gustavo

2014-04-01

455

Infrared dynamics of minimal walking technicolor

We study the gauge sector of minimal walking technicolor, which is an SU(2) gauge theory with n{sub f}=2 flavors of Wilson fermions in the adjoint representation. Numerical simulations are performed on lattices N{sub t}xN{sub s}{sup 3}, with N{sub s} ranging from 8 to 16 and N{sub t}=2N{sub s}, at fixed {beta}=2.25, and varying the fermion bare mass m{sub 0}, so that our numerical results cover the full range of fermion masses from the quenched region to the chiral limit. We present results for the string tension and the glueball spectrum. A comparison of mesonic and gluonic observables leads to the conclusion that the infrared dynamics is given by an SU(2) pure Yang-Mills theory with a typical energy scale for the spectrum sliding to zero with the fermion mass. The typical mesonic mass scale is proportional to and much larger than this gluonic scale. Our findings are compatible with a scenario in which the massless theory is conformal in the infrared. An analysis of the scaling of the string tension with the fermion mass toward the massless limit allows us to extract the chiral condensate anomalous dimension {gamma}{sub *}, which is found to be {gamma}{sub *}=0.22{+-}0.06.

Del Debbio, Luigi [SUPA, School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Lucini, Biagio; Patella, Agostino [School of Physical Sciences, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Pica, Claudio [CP-Origins, University of Southern Denmark, Odense, 5230 M (Denmark); Rago, Antonio [Department of Physics, Bergische Universitaet Wuppertal, Gaussstrasse 20, D-42119 Wuppertal (Germany)

2010-07-01

456

Walking capabilities of Gregor controlled through Walknet

NASA Astrophysics Data System (ADS)

Locomotion control of legged robots is nowadays a field in continuous evolution. In this work a bio-inspired control architecture based on the stick insect is applied to control the hexapod robot Gregor. The control scheme is an extension of Walknet, a decentralized network inspired by the stick insect, that on the basis of local reflexes generates the control signals needed to coordinate locomotion in hexapod robots. Walknet has been adapted to the specific mechanical structure of Gregor that is characterized by specialized legs and a sprawled posture. In particular an innovative hind leg geometry, inspired by the cockroach, has been considered to improve climbing capabilities. The performances of the new control architecture have been evaluated in dynamic simulation environments. The robot has been endowed with distance and contact sensors for obstacle detection. A heading control is used to avoid large obstacles, and an avoidance reflex, as can be found in stick insects, has been introduced to further improve climbing capabilities of the structure. The reported results, obtained in different environmental configurations, stress the adaptive capabilities of the Walknet approach: Even in unpredictable and cluttered environments the walking behaviour of the simulated robot and the robot prototype, controlled through a FPGA based board, remained stable.

Arena, Paolo; Patané, Luca; Schilling, Malte; Schmitz, Josef

2007-06-01

457

Monitoring butterfly abundance: beyond Pollard walks.

Most butterfly monitoring protocols rely on counts along transects (Pollard walks) to generate species abundance indices and track population trends. It is still too often ignored that a population count results from two processes: the biological process (true abundance) and the statistical process (our ability to properly quantify abundance). Because individual detectability tends to vary in space (e.g., among sites) and time (e.g., among years), it remains unclear whether index counts truly reflect population sizes and trends. This study compares capture-mark-recapture (absolute abundance) and count-index (relative abundance) monitoring methods in three species (Maculinea nausithous and Iolana iolas: Lycaenidae; Minois dryas: Satyridae) in contrasted habitat types. We demonstrate that intraspecific variability in individual detectability under standard monitoring conditions is probably the rule rather than the exception, which questions the reliability of count-based indices to estimate and compare specific population abundance. Our results suggest that the accuracy of count-based methods depends heavily on the ecology and behavior of the target species, as well as on the type of habitat in which surveys take place. Monitoring programs designed to assess the abundance and trends in butterfly populations should incorporate a measure of detectability. We discuss the relative advantages and inconveniences of current monitoring methods and analytical approaches with respect to the characteristics of the species under scrutiny and resources availability. PMID:22859980

Pellet, Jérôme; Bried, Jason T; Parietti, David; Gander, Antoine; Heer, Patrick O; Cherix, Daniel; Arlettaz, Raphaël

2012-01-01

458

75 FR 55067 - Energy Conservation Program: Test Procedures for Walk-In Coolers and Walk-In Freezers

Federal Register 2010, 2011, 2012, 2013

...to ASTM C1303 Methodology 6. Heat Transfer Through Concrete a. Floorless...Alternatives to ASTM C1303. (8) Heat transfer through concrete. (9) U-factor...walk-in equipment resulting from the heat transfer performance of the...

2010-09-09

459

This study aimed to compare physiological and perceptual responses to Nordic walking (NW) in obese women to those of walking\\u000a (W), and to assess if these responses were modified by a learning period of NW technique. Eleven middle-aged obese women completed\\u000a exercise trials (5 min each) at 4 km\\/h, inclinations of ?5, 0 and +5%, with and without poles. Ventilation $$ \\\\left(

H. Figard-Fabre; N. Fabre; A. Leonardi; F. Schena

2010-01-01

460

In this paper, the authors introduce an anthropomorphic dynamic biped walking robot adapting to the humans' living floor. The robot has two systems: 1) a special foot system to obtain the position relative to a landing surface and the gradient of the surface during its dynamic walking; 2) an adaptive walking control system to adapt to the path surfaces with

J. Yamaguchi; N. Kinoshita; A. Takanishi; I. Kato

1996-01-01

461

The walking energy cost test (WECT) is a useful tool when measuring ambulatory function in children with motor disorders. However, data on the reliability of this test in Duchenne muscular dystrophy (DMD) is not available. In this study we established the reliability of the WECT and the commonly used six-minute walk test (6MWT) in 19 boys with DMD, aged 6-12years. Participants performed the WECT and 6MWT twice within three weeks. Reliability was determined for walking distance (D, m) and gross energy cost (EC, Jkg(-1)m(-1)), using the intraclass correlation coefficient (ICC2,1) and smallest detectable change (SDC). Reliability for walking distance was good, with an ICC of 0.92 [95% CI: 0.81-0.97] and 0.83 [CI: 0.53-0.94] for the 6MWT and WECT, respectively, and an ICC of 0.85 [CI: 0.64-0.94] for gross EC. SDCs were 12.2% for D6MWT, 12.7% for DWECT and 18.5% for gross EC. In conclusion, in young boys with DMD, the reliability of both the WECT and 6MWT for assessing walking distance is adequate. Gross EC, as assessed with the WECT is also reliable and sufficiently sensitive to detect change in walking strain following interventions at group level. PMID:24365209

Kempen, J C E; Harlaar, J; van der Kooi, A J; de Groot, I J M; van den Bergen, J C; Niks, E H; Verschuuren, J J G M; Brehm, M A

2014-03-01

462

Stride-time variability and sensorimotor cortical activation during walking.

The time it takes between consecutive foot contacts from the same leg is referred to as the stride-time interval. Several investigations have shown that the variations that are present in the stride time intervals are linked to walking balance. In this study, functional near infrared spectroscopy (fNIRS) was utilized to evaluate whether activation in the medial sensorimotor cortices reflects the amount of variations seen in the stride-time intervals. Thirteen healthy adults (Age=23.7 ± 1.4 yrs.) walked forwards and backwards on a programmable treadmill. Each walking condition consisted of two sessions, with each being comprised of five alternating blocks of standing still or walking at 0.45 m/s. Activation in the medial sensorimotor cortices was measured using an fNIRS system, which consisted of a 4 × 4 grid of infrared optode emitter/detector pairs. The optodes were positioned on the participant's head using the International 10/20 system with Cz located beneath the center of the front two rows of optodes. We evaluated the block-wise changes in the amount of oxygenated (oxyHb) and deoxygenated hemoglobin (deoxyHb) in the channels that were located over the supplementary motor area, pre-central gyrus, post-central gyrus and superior parietal lobule. Throughout the experiment, a footswitch system was used to concurrently measure the amount of variation present in the stride-time intervals. Our results showed that oxyHb was greater in the supplementary motor area, pre-central gyrus, and superior parietal lobule when participants walked backwards rather than forwards, which suggests that backward walking presents more of a challenge to the nervous system as it controls the stepping pattern. Additionally, there was a significant decrease in the amount of deoxyHb present in the supplementary motor area while walking backward. Consistent with previous investigations, we noted that the amount of variability present in the stride-time intervals was greater during backward walking compared to forward walking. In addition, the amount of variation in the stride-time intervals while walking forward was positively correlated with the maximum oxyHb response found in the pre-central gyrus and supplementary motor area, which has not been previously shown. This neurobehavioral relationship supports the notion that the subtle variations found in the stride-time intervals are partly associated with processing demands by the motor cortices for regulating the forward temporal kinematics. PMID:21920441

Kurz, Max J; Wilson, Tony W; Arpin, David J

2012-01-16

463

Inverse dynamic analysis of the lower extremities during nordic walking, walking, and running.

Compared with walking (W), Nordic walking (NW) exhibits greater cardiopulmonary and cardiovascular benefits. Some authors conjecture that compared with W or running (R), NW imposes smaller mechanical loads on the musculoskeletal system. The purpose of the current study was to quantify any differences in joint loading of the lower extremities among NW, W, and R. Fifteen experienced adults participated. Kinematic and force measurements were combined using an inverse dynamics approach to yield joint moments. The results showed no biomechanical benefit of NW. Instead, NW involved greater knee joint loading just after heel strike compared with W. This was due to the longer steps and the higher sole angle during the first part of the stance phase. The sagittal and frontal plane moments were smaller for NW compared with R, but in the transverse plane, the ankle moments were greater in NW than in W or R. Based on these results, NW is not recommended as an exercise for persons who seek to reduce biomechanical loading of the lower extremities. PMID:19075304

Stief, Felix; Kleindienst, Frank I; Wiemeyer, Josef; Wedel, Florian; Campe, Sebastian; Krabbe, Berthold

2008-11-01

464

Hip flexor fatigue limits walking in Charcot-Marie-Tooth disease

Charcot–Marie–Tooth (CMT) disease results in distal lower limb weakness that affects walking. In this study we assess the role of the hip flexors in compensating for distal weakness while walking and the effects of prolonged walking on these putative compensatory strategies. Eighteen subjects with CMT disease were compared with 14 matched controls while they walked on a treadmill to a predetermined point of perceived effort. A significant reduction was observed in peak hip flexor velocity during walking and hip flexor maximal voluntary contraction. In a second session following selective fatigue of the hip flexors, hip flexor velocity decreased immediately on walking, and walking duration was greatly reduced. This study suggests that hip flexors compensate for distal weakness and that fatigue in the hip flexors can limit walking duration. Treatments directed toward improving proximal muscle strength may therefore help to delay onset of hip flexor fatigue and thus prolong walking duration.

RAMDHARRY, GITA M.; DAY, BRIAN L.; REILLY, MARY M.; MARSDEN, JONATHAN F.

2013-01-01

465

Unobtrusive assessment of walking speed in the home using inexpensive PIR sensors

Walking speed and activity are important measures of functional ability in the elderly. Our earlier studies have suggested that continuous monitoring may allow us to detect changes in walking speed that are also predictive of cognitive changes. We evaluated the use of passive infrared (PIR) sensors for measuring walking speed in the home on an ongoing basis. In comparisons with gait mat estimates (ground truth) and the results of a timed walk test (the clinical gold standard) in 18 subjects, we found that the clinical measure overestimated typical walking speed, and the PIR sensor estimations of walking speed were highly correlated to actual gait speed. Examination of in-home walking patterns from more than 100,000 walking speed samples for these subjects suggested that we can accurately assess walking speed in the home. We discuss the potential of this approach for continuous assessment.

Hagler, Stuart; Austin, Daniel; Kaye, Jeffrey; Pavel, Misha

2010-01-01

466

Walking reduces sensorimotor network connectivity compared to standing

Background Considerable effort has been devoted to mapping the functional and effective connectivity of the human brain, but these efforts have largely been limited to tasks involving stationary subjects. Recent advances with high-density electroencephalography (EEG) and Independent Components Analysis (ICA) have enabled study of electrocortical activity during human locomotion. The goal of this work was to measure the effective connectivity of cortical activity during human standing and walking. Methods We recorded 248-channels of EEG as eight young healthy subjects stood and walked on a treadmill both while performing a visual oddball discrimination task and not performing the task. ICA parsed underlying electrocortical, electromyographic, and artifact sources from the EEG signals. Inverse source modeling methods and clustering algorithms localized posterior, anterior, prefrontal, left sensorimotor, and right sensorimotor clusters of electrocortical sources across subjects. We applied a directional measure of connectivity, conditional Granger causality, to determine the effective connectivity between electrocortical sources. Results Connections involving sensorimotor clusters were weaker for walking than standing regardless of whether the subject was performing the simultaneous cognitive task or not. This finding supports the idea that cortical involvement during standing is greater than during walking, possibly because spinal neural networks play a greater role in locomotor control than standing control. Conversely, effective connectivity involving non-sensorimotor areas was stronger for walking than standing when subjects were engaged in the simultaneous cognitive task. Conclusions Our results suggest that standing results in greater functional connectivity between sensorimotor cortical areas than walking does. Greater cognitive attention to standing posture than to walking control could be one interpretation of that finding. These techniques could be applied to clinical populations during gait to better investigate neural substrates involved in mobility disorders.

2014-01-01

467

Bone-on-bone forces during loaded and unloaded walking.

Joint moments and bone-on-bone forces in the ankle, knee and hip joint were studied in 7 healthy male subjects during unloaded and loaded walking. The subjects walked across a force platform while they were filmed at 200 Hz. Loaded walking was examined at 10 and 20 kg load carried symmetrically in the hands. Peak joint moments and peak bone-on-bone forces increased from unloaded to loaded walking for the ankle and hip joint (p < 0.05). The lowest bone-on-bone forces were found at the ankle joint (3,318 +/- 390 N) during unloaded walking and the highest at the hip joint (6,399 +/- 1,517 N) during 20 kg loading. Expressed relative to body weight (BW) these values corresponded to 4.2 +/- 0.50 and 8.0 +/- 1.78 BW). However, the individual values showed that 2 of the 7 subjects differed remarkably from the other 5, especially with respect to the hip joint loadings. During loaded walking (20 kg) these 2 subjects showed 14.4 and 15.1 BW peak compression force in the hip joint while the remaining subjects were all below 6.3 BW, which could be explained by the 2 subjects' low ankle joint moments and higher knee and hip joint moments. Apparently, a total 'leg moment' formed by the three major joints is required to support the body and maintain the locomotion, although the relative contribution from each joint can differ among individuals. The peak joint moments were the most dominant contributor to the peak bone-on-bone forces. Therefore, it is concluded that interindividual differences in walking style can lead to pronounced differences in peak bone-on-bone forces. It remains unclear how these interindividual differences are related to joint degradation. PMID:7660757

Simonsen, E B; Dyhre-Poulsen, P; Voigt, M; Aagaard, P; Sjøgaard, G; Bojsen-Møller, F

1995-01-01

468

Roll-over characteristics of human walking on inclined surfaces.

Roll-over characteristics of able-bodied human subjects walking on ramped surfaces were examined in this study. Ten subjects walked at their normal self-selected speed on a level surface, a 5-deg ramp, and a 10-deg ramped surface. Ramps were designed such that ground reaction forces and center of pressure of the ground reaction forces could be measured on their surfaces. This set-up facilitated calculation of the effective rockers that the ankle-foot (AF) and knee-ankle-foot (KAF) systems conformed to during single-limb stance (contralateral toe off to contralateral heel contact). Since our original "roll-over shapes" were characterized between heel contact and opposite heel contact, we label the shapes found during single-limb stance as "truncated roll-over shapes". We hypothesized that the ankle-foot system would adapt to the various surfaces, creating a roll-over shape that would change in orientation with different levels of inclination. The truncated AF roll-over shapes supported this hypothesis for uphill walking but did not support the hypothesis for downhill walking. However, truncated roll-over shapes of the KAF system did adjust their orientation to match both the positive and negative levels of surface inclination. In general, the ankle appears to be the main adapting joint when walking up inclined surfaces while the knee becomes important for the overall adaptation in downhill walking. Knowledge of physiological lower-limb roll-over characteristics on ramped surfaces may help in the development of biomimetic prostheses and orthoses that will automatically adapt to changes in walking surface inclination. PMID:15664674

Hansen, Andrew H; Childress, Dudley S; Miff, Steve C

2004-12-01

469

Effects of volitional walking control on postexercise changes in motor cortical excitability.

To explore the effects of qualitative or quantitative changes in walking on motor cortical excitability, a transcranial magnetic stimulation procedure was used to examine the alterations of motor-evoked potential (MEP) amplitude following walking. Eight healthy participants completed a series of two walking tasks on a treadmill at 2 km/h. The ratio of the left stance duration to the right stance duration was 1 : 2 in the asymmetrical walking task and 1 : 1 in the symmetrical walking task. In each task, walking for 10 min followed by MEP measurement for ?4 min was repeated three times. MEP measurements were also performed before a walking task as a baseline and continued every 10 min for a further 30 min after the completion of the walking task. During slight voluntary contraction of the left tibialis anterior muscle, MEP measurements were conducted four times. Although a significant MEP depression was found after the asymmetrical walking task with increasing amount of walking, no significant decrease in MEP below baseline was observed after the symmetrical walking task throughout all measurement sessions. This MEP depression was the prominent response to the asymmetrical walking task compared with the symmetrical walking task. These findings indicate that the intentional control of walking pattern has both temporal and task-specific influences on excitability changes in the cerebral cortex, and suggest that motor cortical excitability may be altered by controlling the amount of central commands to the legs even during gait exercise. PMID:24157703

Ito, Tomotaka; Tsubahara, Akio; Shinkoda, Koichi; Suzuki, Keita; Yoshimura, Yosuke; Kobara, Kenichi; Osaka, Hiroshi; Watanabe, Susumu

2014-01-01

470

Give your ideas some legs: The positive effect of walking on creative thinking.

Four experiments demonstrate that walking boosts creative ideation in real time and shortly after. In Experiment 1, while seated and then when walking on a treadmill, adults completed Guilford's alternate uses (GAU) test of creative divergent thinking and the compound remote associates (CRA) test of convergent thinking. Walking increased 81% of participants' creativity on the GAU, but only increased 23% of participants' scores for the CRA. In Experiment 2, participants completed the GAU when seated and then walking, when walking and then seated, or when seated twice. Again, walking led to higher GAU scores. Moreover, when seated after walking, participants exhibited a residual creative boost. Experiment 3 generalized the prior effects to outdoor walking. Experiment 4 tested the effect of walking on creative analogy generation. Participants sat inside, walked on a treadmill inside, walked outside, or were rolled outside in a wheelchair. Walking outside produced the most novel and highest quality analogies. The effects of outdoor stimulation and walking were separable. Walking opens up the free flow of ideas, and it is a simple and robust solution to the goals of increasing creativity and increasing physical activity. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:24749966

Oppezzo, Marily; Schwartz, Daniel L

2014-07-01

471

Recurrence properties of unbiased coined quantum walks on infinite d -dimensional lattices

NASA Astrophysics Data System (ADS)

The Pólya number characterizes the recurrence of a random walk. We apply the generalization of this concept to quantum walks [M. Štefa?ák , Phys. Rev. Lett. 100, 020501 (2008)] which is based on a specific measurement scheme. The Pólya number of a quantum walk depends, in general, on the choice of the coin and the initial coin state, in contrast to classical random walks where the lattice dimension uniquely determines it. We analyze several examples to depict the variety of possible recurrence properties. First, we show that for the class of quantum walks driven by Hadamard tensor-product coins, the Pólya number is independent of the initial conditions and the actual coin operators, thus resembling the property of the classical walks. We provide an estimation of the Pólya number for this class of quantum walks. Second, we examine the two-dimensional Grover walk, which exhibits localization and thus is recurrent, except for a particular initial state for which the walk is transient. We generalize the Grover walk to show that one can construct in arbitrary dimensions a quantum walk which is recurrent. This is in great contrast with classical walks which are recurrent only for the dimensions d=1,2 . Finally, we analyze the recurrence of the 2D Fourier walk. This quantum walk is recurrent except for a two-dimensional subspace of the initial states. We provide an estimation of the Pólya number in its dependence on the initial state.

Štefa?ák, M.; Kiss, T.; Jex, I.

2008-09-01

472

Walking vs running for hypertension, cholesterol, & diabetes risk reduction

Background To test whether equivalent energy expenditure by moderate-intensity (e.g., walking) and vigorous-intensity exercise (e.g., running) provides equivalent health benefits. Methods and Results We used the National Runners’ (n=33,060) and Walkers’ (n=15,945) Health Study cohorts to examine the effect of differences in exercise mode and thereby exercise intensity on coronary heart disease (CHD) risk factors. Baseline expenditure (METhr/d) was compared to self-reported, physician-diagnosed incident hypertension, hypercholesterolemia, diabetes and CHD during 6.2 years follow-up. Running significantly decreased the risks for incident hypertension by 4.2% (P<10-7), hypercholesterolemia by 4.3% (P<10-14), diabetes by 12.1% (P<10-5), and CHD by 4.5% per METh/d run (P=0.05). The corresponding reductions for walking were 7.2% (P<10-6), 7.0% (P<10-8), 12.3% (P<10-4), and 9.3% (P=0.01). Relative to <1.8 METh/d, the risk reductions for 1.8 to 3.6, 3.6 to 5.4, 5.4 to 7.2, and ? 7.2 METh/d were: 1) 10.1%, 17.7%, 25.1% and 34.9% from running and 14.0%, 23.8%, 21.8% and 38.3% from walking for hypercholesterolemia; 2) 19.7%, 19.4%, 26.8% and 39.8% from running and 14.7%, 19.1%, 23.6% and 13.3% from walking for hypertension; 3) 43.5%, 44.1%, 47.7% and 68.2% from running and 34.1%, 44.2%, and 23.6% from walking for diabetes (too few cases for diabetes for walking >5.4 METh/d). The risk reductions were not significantly greater for running than walking for diabetes (P=0.94) or CHD (P=0.26), and only marginally greater for walking than running for hypertension (P=0.06) and hypercholesterolemia (P=0.04). Conclusion Equivalent energy expenditures by moderate (walking) and vigorous (running) exercise produced similar risk reductions for hypertension, hypercholesterolemia, diabetes, and CHD, but there is limited statistical power to evaluate CHD conclusively.

Thompson, Paul D.

2013-01-01

473

Interactive cueing with walk-Mate for Hemiparetic Stroke Rehabilitation

Background Many techniques that compensate for locomotion problems in daily life using externally controlled stimulation have recently been reported. These techniques are beneficial for effortlessly supporting patients’ locomotive functions, but the users of such devices must necessarily remain dependent on them. It is possible that some individuals with gait impairment may be prevented recovering locomotive function. From a rehabilitation viewpoint, it may therefore be supposed that ideally, devices that can be used in daily life to improve the locomotive functions of the body itself should be proposed. Methods We evaluate the effectiveness of Walk-Mate, which has been used mainly as a gait compensation device, as a gait rehabilitation training device by analyzing improvement in locomotion before, during and after rehabilitation in hemiparetic patients and comparing it with a previous gait training method. Walk-Mate generates a model walking rhythm in response to a user’s locomotion in real time, and by indicating this rhythm using auditory stimuli, provides a technology that supports walking by reducing asymmetries and fluctuations in foot contact rhythm. If patients can use the system to learn a regulated walking rhythm, then it may also be expected to fulfil the functions of a gait rehabilitation training device for daily life. Results With regard to asymmetry, significantly improvements were seen for compensatory movement during training using Walk-Mate, but improvements were not retained as rehabilitative results. Regarding fluctuations in the foot contact period, significant improvement was observed for compensatory movement during training and these significant improvements were retained as rehabilitative results. In addition, it became clear that such improvement could not be adequately obtained by the previously proposed training technique utilizing constant rhythmic auditory stimulation. Conclusions Walk-Mate effectively compensated for locomotion problems of hemiparetic patients by improving gait rhythm both during and after training, suggesting that locomotive function can be effectively recovered in some patients. The interactive mechanism of Walk-Mate may be capable of simultaneously achieving the aims of gait compensation and gait rehabilitation training methods previously developed under individual frameworks. Walk-Mate is a promising technology for assisting the reintegration of disabled persons into society.

2012-01-01

474

EMG patterns during assisted walking in the exoskeleton.

Neuroprosthetic technology and robotic exoskeletons are being developed to facilitate stepping, reduce muscle efforts, and promote motor recovery. Nevertheless, the guidance forces of an exoskeleton may influence the sensory inputs, sensorimotor interactions and resulting muscle activity patterns during stepping. The aim of this study was to report the muscle activation patterns in a sample of intact and injured subjects while walking with a robotic exoskeleton and, in particular, to quantify the level of muscle activity during assisted gait. We recorded electromyographic (EMG) activity of different leg and arm muscles during overground walking in an exoskeleton in six healthy individuals and four spinal cord injury (SCI) participants. In SCI patients, EMG activity of the upper limb muscles was augmented while activation of leg muscles was typically small. Contrary to our expectations, however, in neurologically intact subjects, EMG activity of leg muscles was similar or even larger during exoskeleton-assisted walking compared to normal overground walking. In addition, significant variations in the EMG waveforms were found across different walking conditions. The most variable pattern was observed in the hamstring muscles. Overall, the results are consistent with a non-linear reorganization of the locomotor output when using the robotic stepping devices. The findings may contribute to our understanding of human-machine interactions and adaptation of locomotor activity patterns. PMID:24982628

Sylos-Labini, Francesca; La Scaleia, Valentina; d'Avella, Andrea; Pisotta, Iolanda; Tamburella, Federica; Scivoletto, Giorgio; Molinari, Marco; Wang, Shiqian; Wang, Letian; van Asseldonk, Edwin; van der Kooij, Herman; Hoellinger, Thomas; Cheron, Guy; Thorsteinsson, Freygardur; Ilzkovitz, Michel; Gancet, Jeremi; Hauffe, Ralf; Zanov, Frank; Lacquaniti, Francesco; Ivanenko, Yuri P

2014-01-01

475

Walk-off correction with AFB nonlinear composites

NASA Astrophysics Data System (ADS)

Beam walk-off in uniaxial and biaxial crystals occurs when the phase normal of the propagating electromagnetic wave deviates from the direction of the Poynting vector. This beam walk-off limits frequency conversion efficiency and restricts the OPO tuning range. The beam walk-off angle in nonlinear single crystals can be alleviated by bonding similar non-linear crystals rotated by 180° with respect to each other. An even number of twisted twins of single crystals is formed that is stress-free and has negligible loss at the AFB® (Adhesive-Free Bond) interfaces. Since no adhesive is employed and the bonding force consists primarily of Van der Waals attractive forces, there is no adverse effect or absorption at the bond interface. The theory of walk-off angles as a function of orientation for uniaxial and biaxial crystals is derived. Correcting beam walk-off by producing an AFB® composite configuration results in more efficient frequency conversion and thereby allows the generation of higher power output of frequency converted radiation for a given input power. Beam correction is demonstrated experimentally for zinc germanium phosphide (ZGP) as representative of a uniaxial nonlinear crystal, and on biaxial KTP crystals. AFB® composites of ZGP with inactive ends of gallium phosphide have been produced in an effort to further improve damage resistance of a ZGP optical parametric oscillator for frequency conversion into the mid-IR range.

Lee, H.-C.; Meissner, H. E.

2007-05-01

476

EMG patterns during assisted walking in the exoskeleton

Neuroprosthetic technology and robotic exoskeletons are being developed to facilitate stepping, reduce muscle efforts, and promote motor recovery. Nevertheless, the guidance forces of an exoskeleton may influence the sensory inputs, sensorimotor interactions and resulting muscle activity patterns during stepping. The aim of this study was to report the muscle activation patterns in a sample of intact and injured subjects while walking with a robotic exoskeleton and, in particular, to quantify the level of muscle activity during assisted gait. We recorded electromyographic (EMG) activity of different leg and arm muscles during overground walking in an exoskeleton in six healthy individuals and four spinal cord injury (SCI) participants. In SCI patients, EMG activity of the upper limb muscles was augmented while activation of leg muscles was typically small. Contrary to our expectations, however, in neurologically intact subjects, EMG activity of leg muscles was similar or even larger during exoskeleton-assisted walking compared to normal overground walking. In addition, significant variations in the EMG waveforms were found across different walking conditions. The most variable pattern was observed in the hamstring muscles. Overall, the results are consistent with a non-linear reorganization of the locomotor output when using the robotic stepping devices. The findings may contribute to our understanding of human-machine interactions and adaptation of locomotor activity patterns.

Sylos-Labini, Francesca; La Scaleia, Valentina; d'Avella, Andrea; Pisotta, Iolanda; Tamburella, Federica; Scivoletto, Giorgio; Molinari, Marco; Wang, Shiqian; Wang, Letian; van Asseldonk, Edwin; van der Kooij, Herman; Hoellinger, Thomas; Cheron, Guy; Thorsteinsson, Freygardur; Ilzkovitz, Michel; Gancet, Jeremi; Hauffe, Ralf; Zanov, Frank; Lacquaniti, Francesco; Ivanenko, Yuri P.

2014-01-01

477

How many animals really do the Lévy walk?

Lévy walks (LW) are superdiffusive and scale-free random walks that have recently emerged as a new conceptual tool for modeling animal search paths. They have been claimed to be more efficient than the "classical" random walks, and they also seem able to account for the actual search patterns of various species. This suggests that many animals may move using a LW process. LW patterns look like the actual search patterns displayed by animals foraging in a patchy environment, where extensive and intensive searching modes alternate, and which can be generated by a mixture of classical random walks. In this context, even elementary composite Brownian walks are more efficient than LW but may be confounded with them because they present apparent move-length-heavy tail distributions and superdiffusivity. The move-length "survival" distribution (i.e., the cumulative number of moves greater than any given threshold) appears to be a better means to highlight a LW pattern. Even once such a pattern has been clearly identified, it remains to determine how it was actually generated, because a LW pattern is not necessarily produced by a LW process but may emerge from the way the animal interacted with the environment structure through more classical movement processes. In any case, emergent movement patterns should not be confused with the processes that gave rise to them. PMID:17824427

Benhamou, Simon

2007-08-01

478

Random walks of colloidal probes in viscoelastic materials

NASA Astrophysics Data System (ADS)

To overcome limitations of using a single fixed time step in random walk simulations, such as those that rely on the classic Wiener approach, we have developed an algorithm for exploring random walks based on random temporal steps that are uniformly distributed in logarithmic time. This improvement enables us to generate random-walk trajectories of probe particles that span a highly extended dynamic range in time, thereby facilitating the exploration of probe motion in soft viscoelastic materials. By combining this faster approach with a Maxwell-Voigt model (MVM) of linear viscoelasticity, based on a slowly diffusing harmonically bound Brownian particle, we rapidly create trajectories of spherical probes in soft viscoelastic materials over more than 12 orders of magnitude in time. Appropriate windowing of these trajectories over different time intervals demonstrates that random walk for the MVM is neither self-similar nor self-affine, even if the viscoelastic material is isotropic. We extend this approach to spatially anisotropic viscoelastic materials, using binning to calculate the anisotropic mean square displacements and creep compliances along different orthogonal directions. The elimination of a fixed time step in simulations of random processes, including random walks, opens up interesting possibilities for mod