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1

Walk Score®  

PubMed Central

Background Walk Score® is a nationally and publicly available metric of neighborhood walkability based on proximity to amenities (e.g., retail, food, schools). However, few studies have examined the relationship of Walk Score to walking behavior. Purpose To examine the relationship of Walk Score to walking behavior in a sample of recent Cuban immigrants, who overwhelmingly report little choice in their selection of neighborhood built environments when they arrive in the U.S. Methods Participants were 391 recent healthy Cuban immigrants (M age=37.1 years) recruited within 90 days of arrival in the U.S., and assessed within 4 months of arrival (M=41.0 days in the U.S.), who resided throughout Miami-Dade County FL. Data on participants’ addresses, walking and sociodemographics were collected prospectively from 2008 to 2010. Analyses conducted in 2011 examined the relationship of Walk Score for each participant’s residential address in the U.S. to purposive walking, controlling for age, gender, education, BMI, days in the U.S., and habitual physical activity level in Cuba. Results For each 10-point increase in Walk Score, adjusting for covariates, there was a significant 19% increase in the likelihood of purposive walking, a 26% increase in the likelihood of meeting physical activity recommendations by walking, and 27% more minutes walked in the previous week. Conclusions Results suggest that Walk Score is associated with walking in a sample of recent immigrants who initially had little choice in where they lived in the U.S. These results support existing guidelines indicating that mixed land use (such as parks and restaurants near homes) should be included when designing walkable communities. PMID:23867028

Brown, Scott C.; Pantin, Hilda; Lombard, Joanna; Toro, Matthew; Huang, Shi; Plater-Zyberk, Elizabeth; Perrino, Tatiana; Perez-Gomez, Gianna; Barrera-Allen, Lloyd; Szapocznik, Jose

2013-01-01

2

Quantum Walks  

NASA Astrophysics Data System (ADS)

This tutorial article showcases the many varieties and uses of quantum walks. Discrete time quantum walks are introduced as counterparts of classical random walks. The emphasis is on the connections and differences between the two types of processes (with rather different underlying dynamics) for producing random distributions. We discuss algorithmic applications for graph-searching and compare the two approaches. Next, we look at quantization of Markov chains and show how it can lead to speedups for sampling schemes. Finally, we turn to continuous time quantum walks and their applications, which provide interesting (even exponential) speedups over classical approaches.

Reitzner, Daniel; Nagaj, Daniel; Bužek, Vladimír

2011-12-01

3

Gallery Walk  

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

4

Lévy walks  

E-print Network

Random walk is a fundamental concept with applications ranging from quantum physics to econometrics. Remarkably, one specific model of random walks appears to be ubiquitous across many research fields as a tool to analyze non-Brownian dynamics exhibited by different systems. The L\\'evy walk model combines two key features: a finite velocity of a random walker and the ability to generate anomalously fast diffusion. Recent results in optics, Hamiltonian many-particle chaos, cold atom dynamics, bio-physics, and behavioral science, demonstrate that this particular type of random walks provides significant insight into complex transport phenomena. This review provides a self-consistent introduction into the theory of L\\'evy walks, surveys its existing applications, including latest advances, and outlines its further perspectives.

V. Zaburdaev; S. Denisov; J. Klafter

2014-10-19

5

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

6

Walk Score  

NSDL National Science Digital Library

If you're looking for a walkable community, is there a way to determine which neighborhood might be best for you? Interested parties might use the Walk Score to get a basic sense of nearby amenities, such as grocery stores, parks, restaurants, and so on. Visitors can type in a street address or neighborhood, and they can find out the location's cumulative Walk Score. Also, visitors can use the site to find out about potential nearby rental properties, if they are so inclined. This site is compatible with all operating systems.

2012-04-27

7

Earth Walk  

NSDL National Science Digital Library

In this hands-on and feet-on excursion, learners take a science walk to visualize the planet's immense size and numerous structures, without the usual scale and ratio dimensions found in most textbooks. Learners also compare their body's height to a scaled-down Earth.

Muller, Eric

1995-01-01

8

Quantum random walks without walking  

SciTech Connect

Quantum random walks have received much interest due to their nonintuitive dynamics, which may hold the key to a new generation of quantum algorithms. What remains a major challenge is a physical realization that is experimentally viable and not limited to special connectivity criteria. We present a scheme for walking on arbitrarily complex graphs, which can be realized using a variety of quantum systems such as a Bose-Einstein condensate trapped inside an optical lattice. This scheme is particularly elegant since the walker is not required to physically step between the nodes; only flipping coins is sufficient.

Manouchehri, K.; Wang, J. B. [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley WA 6009 (Australia)

2009-12-15

9

Nature Walk  

NSDL National Science Digital Library

In this activity, learners take an indoor nature walk and discover various objects that have been brought in from the outdoor environment. In preparation for the activity, an educator places natural and man-made items around a room for learners to discover. Learners examine what they find and make notes about what they see and smell, how they (the learners) feel, and what each item looks like (including sketches). Then the group addresses the topic of "Leave No Trace" as it applies to a real nature walk. This would be a great activity before a field trip to a park, arboretum, or other outdoor environment, and can be done with one learner, a class, or even a large group at a family science event.

National 4-H Council

2009-01-01

10

JOIN THE WALK! HANDLEMAN WALK FOR AUTISM  

E-print Network

JOIN THE WALK! HANDLEMAN WALK FOR AUTISM a fundraiser to support Douglass Developmental is the Handleman Walk for Autism? The WALK is a fun family event with: Live music, food, moon bouncing, face garden on Rutgers Campus. The event raises funds for children and adults with autism and celebrates

Cheng, Mei-Fang

11

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

12

Quantum Walks Norio Konno  

E-print Network

Quantum Walks Norio Konno Yokohama National University Two types of quantum (random) walks, discrete-time (coined) or continuous- time, were introduced as the quantum mechanical extension of the corresponding classical random walks in connection with quantum computing and have been extensively studied over

Schürmann, Michael

13

Walk This Way  

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

14

Driven quantum walks.  

PubMed

We introduce the concept of a driven quantum walk. This work is motivated by recent theoretical and experimental progress that combines quantum walks and parametric down-conversion, leading to fundamentally different phenomena. We compare these striking differences by relating the driven quantum walks to the original quantum walk. Next, we illustrate typical dynamics of such systems and show that these walks can be controlled by various pump configurations and phase matchings. Finally, we end by proposing an application of this process based on a quantum search algorithm that performs faster than a classical search. PMID:25192097

Hamilton, Craig S; Kruse, Regina; Sansoni, Linda; Silberhorn, Christine; Jex, Igor

2014-08-22

15

Driven Quantum Walks  

NASA Astrophysics Data System (ADS)

We introduce the concept of a driven quantum walk. This work is motivated by recent theoretical and experimental progress that combines quantum walks and parametric down-conversion, leading to fundamentally different phenomena. We compare these striking differences by relating the driven quantum walks to the original quantum walk. Next, we illustrate typical dynamics of such systems and show that these walks can be controlled by various pump configurations and phase matchings. Finally, we end by proposing an application of this process based on a quantum search algorithm that performs faster than a classical search.

Hamilton, Craig S.; Kruse, Regina; Sansoni, Linda; Silberhorn, Christine; Jex, Igor

2014-08-01

16

Enhanced: Walking Made Simple  

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

17

6.EE Morning Walk  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Sierra walks her dog Pepper twice a day. Her evening walk is two and a half times as far as her morning walk. At the end of the week she tells her mom,...

18

Private Mineral Gallery Walk  

NSDL National Science Digital Library

Students make and display posters of the mineral they researched throughout the semester. The instructor and TA review the posters while students answer questions as they walk around and examine each other's posters.

Perkins, Dexter

19

What is Gallery Walk?  

NSDL National Science Digital Library

Gallery Walk is a discussion technique that gets students out of their chairs and into a mode of active engagement. The advantage of the method is its flexibility and the variety of benefits for students and ...

20

BIOPHYSICS: Myosin Motors Walk the Walk  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. Myosin molecular motors move along actin filaments to drive, for example, muscle contraction or the intracellular trafficking of vesicles. However, it has not been clear whether myosin V moves along actin filaments in a hand-over-hand or inchworm fashion. In their Perspective, Molloy and Veigel explain new work (Yildiz et al.) that provides evidence in support of the hand-over-hand model for how myosin V walks along actin.

Justin E. Molloy (National Institute for Medical Research;Division of Physical Biochemistry); Claudia Veigel (National Institute for Medical Research;Division of Physical Biochemistry)

2003-06-27

21

Walks on SPR neighborhoods.  

PubMed

A nearest-neighbor-interchange (NNI)-walk is a sequence of unrooted phylogenetic trees, T1, T2, . . . , T(k) where each consecutive pair of trees differs by a single NNI move. We give tight bounds on the length of the shortest NNI-walks that visit all trees in a subtree-prune-and-regraft (SPR) neighborhood of a given tree. For any unrooted, binary tree, T, on n leaves, the shortest walk takes ?(n²) additional steps more than the number of trees in the SPR neighborhood. This answers Bryant’s Second Combinatorial Challenge from the Phylogenetics Challenges List, the Isaac Newton Institute, 2011, and the Penny Ante Problem List, 2009. PMID:23702562

Caceres, Alan Joseph J; Castillo, Juan; Lee, Jinnie; St John, Katherine

2013-01-01

22

Walking Tips for Older Adults  

MedlinePLUS

... A Print Share Glossary previous page Related Topics Balance Problems Falls Prevention Foot Problems Related Documents PDF Walking Tips for Older Adults Download Join our e-newsletter! Resources Walking Tips ...

23

Walking with a Slower Friend  

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

24

Walking Out Graphs  

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

25

Take a Planet Walk  

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

26

The walking robot project  

NASA Technical Reports Server (NTRS)

A walking robot was designed, analyzed, and tested as an intelligent, mobile, and a terrain adaptive system. The robot's design was an application of existing technologies. The design of the six legs modified and combines well understood mechanisms and was optimized for performance, flexibility, and simplicity. The body design incorporated two tripods for walking stability and ease of turning. The electrical hardware design used modularity and distributed processing to drive the motors. The software design used feedback to coordinate the system and simple keystrokes to give commands. The walking machine can be easily adapted to hostile environments such as high radiation zones and alien terrain. The primary goal of the leg design was to create a leg capable of supporting a robot's body and electrical hardware while walking or performing desired tasks, namely those required for planetary exploration. The leg designers intent was to study the maximum amount of flexibility and maneuverability achievable by the simplest and lightest leg design. The main constraints for the leg design were leg kinematics, ease of assembly, degrees of freedom, number of motors, overall size, and weight.

Williams, P.; Sagraniching, E.; Bennett, M.; Singh, R.

1991-01-01

27

Correlated random walks  

SciTech Connect

We present a new approach to the calculation of first passage statistics for correlated random walks on one-dimensional discrete systems. The processes may be non-Markovian and also nonstationary. A number of examples are used to demonstrate the theory.

de la Selva, S.M.T.; Lindenberg, K.; West, B.J.

1988-10-01

28

Passive walking with knees  

Microsoft Academic Search

It is shown that passive dynamic walking, a phenomenon originally described for bipeds having straight legs, also works with knees. Thus, giving only a downhill slope as a source of energy, a human-like pair of legs will settle into a natural gait generated by the passive interaction of gravity and inertia. No muscular input is required. The physics is much

T. McGeer

1990-01-01

29

Quantum Random Walks , F. Petruccione  

E-print Network

science [3], economics [4] and biology [5]. Basically, the trajectory of a random walk consistsOpen Quantum Random Walks S. Attal 1 , F. Petruccione 2 , C. Sabot 1 and I. Sinayskiy 2 1 Universit Physics University of KwaZulu-Natal Durban 4001, South Africa Abstract A new model of quantum random walks

Attal, Stéphane

30

Men's meaning of walking engagement  

Microsoft Academic Search

Understanding men's perceptions and beliefs about physical activity could help us improve the effectiveness of health promotion walking programs. This study explores men's perceptions and beliefs about a structured walking program, including what hinders and what enhances their engagement. Qualitative methods were used to explore men's lived experiences of engaging in a walking program over a one-year period.Focus groups and

Elisabeth Lord; Robert Bush

2012-01-01

31

[Walking abnormalities in children].  

PubMed

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

32

A Walk Through Newark  

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".

33

Relativistic Weierstrass random walks.  

PubMed

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 tt{c} . Implications of this crossover between different diffusion regimes are discussed for some explicit examples. The study of such an explicit and simple Markov chain can shed some light on several results obtained in much more involved contexts. PMID:20866862

Saa, Alberto; Venegeroles, Roberto

2010-08-01

34

Water-walking devices  

Microsoft Academic Search

We report recent efforts in the design and construction of water-walking machines inspired by insects and spiders. The fundamental\\u000a physical constraints on the size, proportion and dynamics of natural water-walkers are enumerated and used as design criteria\\u000a for analogous mechanical devices. We report devices capable of rowing along the surface, leaping off the surface and climbing\\u000a menisci by deforming the

David L. Hu; Manu Prakash; Brian Chan; John W. M. Bush

2007-01-01

35

Take a Planet Walk  

NSDL National Science Digital Library

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 environment where students generate questions based on their prior knowledge; and challenge students to think critically about the accuracy and limitations of a scale model of our solar system.

Schuster, Dwight

2008-09-01

36

Curve walking in crayfish  

PubMed

Curve walking of crayfish Astacus leptodactylus was investigated by exploiting their optomotor response. The animal walked while spatially fixed on a motor-driven treadmill and turning behaviour was induced by an optical stimulus, a pattern consisting of vertical stripes moving in a horizontal direction. In this open-loop situation, the crayfish maintains the same step frequency for the legs on both sides of the body for low and intermediate turning speeds, but increases the step amplitude of the outer legs 2, 3 and 4 by shifting the posterior extreme position (PEP) of these legs in a posterior direction and reduces the step amplitude of inner leg 5 by shifting the PEP of this leg in an anterior direction. Furthermore, the main movement direction of the legs can change relative to the body. This was observed for outer leg 5 and also, at higher turning speeds, for outer leg 2. As coordinating influences between contra- and ipsilateral legs were found directly to influence only the anterior extreme position of the legs, these results indicate that the mechanisms controlling curve walking may be different from those controlling normal leg coordination. PMID:9319377

Cruse; Saavedra

1996-01-01

37

Biomechanics of walking with snowshoes  

Microsoft Academic Search

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

38

Biomechanics of walking with snowshoes  

Microsoft Academic Search

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

39

Quantum walks of correlated particles  

E-print Network

Quantum walks of correlated particles offer the possibility to study large-scale quantum interference, simulate biological, chemical and physical systems, and a route to universal quantum computation. Here we demonstrate quantum walks of two identical photons in an array of 21 continuously evanescently-coupled waveguides in a SiOxNy chip. We observe quantum correlations, violating a classical limit by 76 standard deviations, and find that they depend critically on the input state of the quantum walk. These results open the way to a powerful approach to quantum walks using correlated particles to encode information in an exponentially larger state space.

Alberto Peruzzo; Mirko Lobino; Jonathan C. F. Matthews; Nobuyuki Matsuda; Alberto Politi; Konstantinos Poulios; Xiao-Qi Zhou; Yoav Lahini; Nur Ismail; Kerstin Wörhoff; Yaron Bromberg; Yaron Silberberg; Mark G. Thompson; Jeremy L. O'Brien

2010-06-24

40

Three movies Who we are Randomness Random walks Number walks base four Seeing walks on numbers References Seeing Things by Walking on Real Numbers  

E-print Network

Three movies Who we are Randomness Random walks Number walks base four Seeing walks on numbers on real numbers www.carma.newcastle.edu.au/walks #12;Three movies Who we are Randomness Random walks" 1 Three movies Three movies of numbers 2 Who we are The current team 3 Randomness What is Pi? What

Borwein, Jonathan

41

BBC: Walking with Beasts  

NSDL National Science Digital Library

This BBC Web site comes loaded with interactive multimedia features on evolution and the animal kingdom. Users can view 3-D images as well as video and audio clips of prehistoric creatures, play an interactive evolution game, and much more. The Web site also includes dozens of comprehensive, downloadable lessons plans and worksheets for students age 7-14 (click on Teachers to access these materials). The lesson plans encourage offline investigation and problem solving, but also provide links to relevant features within the Walking with Beasts Web site. The use of certain online features, with their engaging visuals and interactive design, should make these lesson plans especially appealing to students.

42

Agile Walking Robot  

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

43

Rugged Walking Robot  

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

44

a walking tour of ALONG THE OLIVE WALK  

E-print Network

a walking tour of Caltech ALONG THE OLIVE WALK #12;2 The California Institute of Technology Medal of Technology. Welcome to Caltech! Caltech offers an unparalleled undergraduate education and research experience through joint programs with City of Hope, Huntington Memorial Hospital, Children

Stoltz, Brian M.

45

Walking Out and On ARE YOU A WALK OUT?  

E-print Network

to consciously carry with us the values and practices that feel essential. What have we learned, what do we and preserve it at all costs. This is what we'll most need as we walk out and walk on to give birth their formal leadership to champion values and practices that respect people, that rely on people's inherent

Sheridan, Jennifer

46

RANDOM WALK IN MARKOVIAN ENVIROMENT  

Microsoft Academic Search

We prove a quenched central limit theorem for random walks with bounded increments in a randomly evolving environment on Zd. We assume that the transition probabilities of the walk depend not too strongly on the environment and that the evolution of the environment is Markovian with strong spatial and temporal mixing properties.

DMITRY DOLGOPYAT; GERHARD KELLER; CARLANGELO LIVERANI

47

Night Walk II Gabriele Peters  

E-print Network

Night Walk II Gabriele Peters FernUniversit¨at in Hagen Fakult¨at f¨ur Mathematik und Informatik.peters@fernuni-hagen.de 1 Topic of the Artwork This photograph shows a figure walking at night along a street in an acient of the original pho- tograph by stylistic devices such as coarse grain, artificial colorization, and motion blur

Peters, Gabriele

48

RANDOM WALK AND HYPERPLANE ARRANGEMENTS  

Microsoft Academic Search

LetC be the set of chambers of a real hyperplane arrangement. We study a random walk on C introduced by Bidigare, Hanlon, and Rockmore. This includes various shu†ing schemes used in computer science, biology, and card games. It also includes random walks on zonotopes and zonotopal tilings. We flnd the stationary distributions of these Markov chains, give good bounds on

Kenneth S. Brown; Persi Diaconis

1998-01-01

49

Random Walks on Complex Networks  

Microsoft Academic Search

We investigate random walks on complex networks and derive an exact expression for the mean first-passage time (MFPT) between two nodes. We introduce for each node the random walk centrality C, which is the ratio between its coordination number and a characteristic relaxation time, and show that it determines essentially the MFPT. The centrality of a node determines the relative

Jae Dong Noh; Heiko Rieger

2004-01-01

50

Quantum walks on quotient graphs  

SciTech Connect

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

Water-walking devices  

NASA Astrophysics Data System (ADS)

We report recent efforts in the design and construction of water-walking machines inspired by insects and spiders. The fundamental physical constraints on the size, proportion and dynamics of natural water-walkers are enumerated and used as design criteria for analogous mechanical devices. We report devices capable of rowing along the surface, leaping off the surface and climbing menisci by deforming the free surface. The most critical design constraint is that the devices be lightweight and non-wetting. Microscale manufacturing techniques and new man-made materials such as hydrophobic coatings and thermally actuated wires are implemented. Using high-speed cinematography and flow visualization, we compare the functionality and dynamics of our devices with those of their natural counterparts.

Hu, David L.; Prakash, Manu; Chan, Brian; Bush, John W. M.

2007-11-01

52

Water-walking devices  

NASA Astrophysics Data System (ADS)

We report recent efforts in the design and construction of water-walking machines inspired by insects and spiders. The fundamental physical constraints on the size, proportion and dynamics of natural water-walkers are enumerated and used as design criteria for analogous mechanical devices. We report devices capable of rowing along the surface, leaping off the surface and climbing menisci by deforming the free surface. The most critical design constraint is that the devices be lightweight and non-wetting. Microscale manufacturing techniques and new man-made materials such as hydrophobic coatings and thermally actuated wires are implemented. Using highspeed cinematography and flow visualization, we compare the functionality and dynamics of our devices with those of their natural counterparts.

Hu, David L.; Prakash, Manu; Chan, Brian; Bush, John W. M.

53

Renormalization Group for Quantum Walks  

NASA Astrophysics Data System (ADS)

A renormalization group (RG) treatment of quantum walks holds significant promise for insights into quantum transport phenomena and search algorithms for quantum computing. The generality of this approach has a good chance to elucidate salient characteristics of quantum walks on higher-dimensional lattices which at this point are unobtainable with other methods and are even difficult to study numerically. Key questions concern the scaling properties of (unitary) quantum evolution depending on the lattice type. Is there a single exponent describing the mean-square displacement of quantum walks, similar to the scenario observed in ordinary random walks, or is there a spectrum of modes, each with their own exponent? Does quantum interference ensure that these exponents are always smaller than for the respective classical random walks? To what extend do translational invariance and other lattice properties matter? Generally, what is the nature of universality in quantum walks? Our preliminary results on effectively one-dimensional lattices demonstrates how RG can be used to study quantum random walks and their asymptotic behavior.

Falkner, Stefan; Boettcher, Stefan; Portugal, Renato

2013-03-01

54

Fault-Tolerant Quantum Walks  

E-print Network

Quantum walks are expected to serve important modelling and algorithmic applications in many areas of science and mathematics. Although quantum walks have been successfully implemented physically in recent times, no major efforts have been made to combat the error associated with these physical implementations in a fault-tolerant manner. In this paper, we propose a systematic method to implement fault-tolerant quantum walks in discrete time on arbitrarily complex graphs, using quantum states encoded with the Steane code and a set of universal fault tolerant matrix operations.

S. D. Freedman; Y. H. Tong; J. B. Wang

2014-08-06

55

Quantum snake walk on graphs  

SciTech Connect

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

56

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 ...

57

Adaptive walk on complex networks.  

PubMed

We investigate the properties of adaptive walks on an uncorrelated fitness landscape which is established in sequence spaces of complex structure. In particular, we perform numerical simulations of adaptive walks on random graphs and scale-free networks. For the former, we also derive some analytical approximations for the density of local optima of the fitness landscape and the mean length walk. We compare our results with those obtained for regular lattices. We obtain that the density of local optima decreases as 1/z, where z is the mean connectivity, for all networks we have investigated. In random graphs, the mean length walk L reaches the asymptotic value e - 1 for large z, which corresponds to the result for regular networks. Although we could not find an exact estimate, we derive an underestimated value for L. Unlike random graphs, scale-free networks show an upper asymptotic value of L. PMID:16089779

Campos, Paulo R A; Moreira, F G Brady

2005-06-01

58

Bouchaud walks with variable drift  

E-print Network

In this paper we study a sequence of Bouchaud trap models on $\\mathbb{Z}$ with drift. We analyze the possible scaling limits for a sequence of walks, where we make the drift decay to 0 as we rescale the walks. Depending on the speed of the decay of the drift we obtain three different scaling limits. If the drift decays slowly as we rescale the walks we obtain the inverse of an \\alpha$-stable subordinator as scaling limit. If the drift decays quickly as we rescale the walks, we obtain the F.I.N. diffusion as scaling limit. There is a critical speed of decay separating these two main regimes, where a new process appears as scaling limit. This critical speed is related to the index $\\alpha$ of the inhomogeneity of the environment.

Parra, Manuel Cabezas

2010-01-01

59

Random Walks in Cellular Automata.  

National Technical Information Service (NTIS)

The topological defects or phase boundaries discerned in a number of one-dimensional cellular automata appear to perform random walks as well as simpler motions. We analyze their properties rigorously using probabilistic and graph theoretic methods. This ...

K. Eloranta

1992-01-01

60

Walking Robot Locomotion System Conception  

NASA Astrophysics Data System (ADS)

This work is a brief analysis on the application and perspective of using the walking robots in different areas in practice. The most common characteristics of walking four legs robots are presented here. The specific features of the applied actuators in walking mechanisms are also shown in the article. The experience of Institute of Mechanics - BAS is illustrated in creation of Spiroid and Helicon1 gears and their assembly in actuation of studied robots. Loading on joints reductors of robot legs is modelled, when the geometrical and the walking parameters of the studied robot are preliminary defined. The obtained results are purposed for designing the control of the loading of reductor type Helicon in the legs of the robot, when it is experimentally tested.

Ignatova, D.; Abadjieva, E.; Abadjiev, V.; Vatzkitchev, Al.

2014-09-01

61

Walking and jumping spores  

NASA Astrophysics Data System (ADS)

The Equisetum plants, more commonly called ``horsetail,'' emit 50-microns spores that are spherical in shape and present four hygroscopic arms. Under high humidity, the arms are retracted. But under lower humidity, less than 70%, the four arms deploy beautifully. With time-lapse image recordings, we show that under repeated cycles of dry and high humidity, the spores behave as random walkers, since they move by about their size in a different direction at every cycle. The process is apparently stochastic because of the complex shape of the arms and hysteretic friction of the arms on the ground. For some spores, a decrease in humidity level results in very fast jumps, the spores taking off at a typical velocity of a meter per second, as recorded on high-speed camera. With these jumps, they reach centimetric elevations, much larger than their size. The physical mechanism at the root of these ``Levy-flight'' jumps is still under investigation. The walking and jumping phenomena thus provide motility, which we believe is helpful for the understanding of the biological dispersion of the spores. It could also bring biomimetic inspiration to engineer new motile elastic structures.

Marmottant, Philippe

2012-02-01

62

Walking with Prehistoric Beasts  

NSDL National Science Digital Library

Nope, it's not about dinosaurs but it is just as fascinating! "Walking with Prehistoric Beasts is the Discovery Channel's new television series on the creatures that inhabited Earth after the dinosaurs disappeared 65 million years ago (mya). The program's companion Website offers fabulous graphics and games, with a little bit of informative text mixed in, about such beasts as Gastornis, a meat-loving bird the size of a tall human, Propalaeotherium, a 43 million year old cat-sized horse, and Andrewsarchus, a furry, land-dwelling ancestor of the whale. Facts on pronunciation, etymology, geologic time range, body size, diet, geographic range and closest living relative are given for every animal in the Beast Gallery. When visiting this site you should not miss the How do We Know section, housing audio recordings of paleontologists answering your e.mail questions (Real/Windows Media) or the Changing Worlds game in which players control a map of Earth showing vegetation, mammal life and ocean currents from 65 mya to present. Plus, you can test your beast-mastery with the Beastly Quiz.

2001-01-01

63

Correlated continuous time random walks  

Microsoft Academic Search

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

64

Random walk models in biology.  

PubMed

Mathematical modelling of the movement of animals, micro-organisms and cells is of great relevance in the fields of biology, ecology and medicine. Movement models can take many different forms, but the most widely used are based on the extensions of simple random walk processes. In this review paper, our aim is twofold: to introduce the mathematics behind random walks in a straightforward manner and to explain how such models can be used to aid our understanding of biological processes. We introduce the mathematical theory behind the simple random walk and explain how this relates to Brownian motion and diffusive processes in general. We demonstrate how these simple models can be extended to include drift and waiting times or be used to calculate first passage times. We discuss biased random walks and show how hyperbolic models can be used to generate correlated random walks. We cover two main applications of the random walk model. Firstly, we review models and results relating to the movement, dispersal and population redistribution of animals and micro-organisms. This includes direct calculation of mean squared displacement, mean dispersal distance, tortuosity measures, as well as possible limitations of these model approaches. Secondly, oriented movement and chemotaxis models are reviewed. General hyperbolic models based on the linear transport equation are introduced and we show how a reinforced random walk can be used to model movement where the individual changes its environment. We discuss the applications of these models in the context of cell migration leading to blood vessel growth (angiogenesis). Finally, we discuss how the various random walk models and approaches are related and the connections that underpin many of the key processes involved. PMID:18426776

Codling, Edward A; Plank, Michael J; Benhamou, Simon

2008-08-01

65

Neuronal control of Drosophila walking direction.  

PubMed

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

66

Energy Gallery Walk  

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

67

Random Walks in Noninteger Dimension  

E-print Network

One can define a random walk on a hypercubic lattice in a space of integer dimension $D$. For such a process formulas can be derived that express the probability of certain events, such as the chance of returning to the origin after a given number of time steps. These formulas are physically meaningful for integer values of $D$. However, these formulas are unacceptable as probabilities when continued to noninteger $D$ because they give values that can be greater than $1$ or less than $0$. In this paper we propose a random walk which gives acceptable probabilities for all real values of $D$. This $D$-dimensional random walk is defined on a rotationally-symmetric geometry consisting of concentric spheres. We give the exact result for the probability of returning to the origin for all values of $D$ in terms of the Riemann zeta function. This result has a number-theoretic interpretation.

Carl M. Bender; Stefan Boettcher; Lawrence R. Mead

1993-11-10

68

Walking the history of healthcare.  

PubMed

The history of healthcare is complex, confusing and contested. In Walking London's medical history the story of how health services developed from medieval times to the present day is told through seven walks. The book also aims to help preserve our legacy, as increasingly former healthcare buildings are converted to other uses, and to enhance understanding of the current challenges we face in trying to improve healthcare in the 21st century. Each walk has a theme, ranging from the way hospitals merge or move and the development of primary care to how key healthcare trades became professions and the competition between the church, Crown and City for control of healthcare. While recognising the contributions of the 'great men of medicine', the book takes as much interest in the six ambulance stations built by the London County Council (1915) as the grandest teaching hospitals. PMID:18193703

Black, Nick

2007-12-01

69

After Talking the Talk, Now Walk the Walk  

ERIC Educational Resources Information Center

In this article, the author describes what his students are doing following the ATM Easter conference in Telford, where he was inspired by a workshop entitled "Vitamin D Maths," conducted by Jocelyn D'Arcy. He describes an activity that allows his Year 11 students to walk through angles drawn on the floors. This topic will now literally be given a…

Vukovic, Paul

2011-01-01

70

Limit of random walks of random trees  

E-print Network

Limit of random walks and of random trees ------------------------------ Elements phenomenons (quantum physics, magnetism, polymer, DNA, genealogical tree, random walk, Markov chain, etc, statistical physics, biology, a lot of objects hav­ ing a discrete nature appear for various reason

Marckert, Jean-François

71

Quantum walks, quantum gates, and quantum computers  

SciTech Connect

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

72

Walking: A Step in the Right Direction  

MedlinePLUS

... Adobe Acrobat Reader Walking…A Step in the Right Direction What are the benefits of walking? Do ... with the other leg. Leg Curl Pull your right foot toward your buttocks with your right hand. ...

73

Stable and robust walking with compliant legs  

Microsoft Academic Search

Bipedal walking could be implemented into a robot by mimicking spring-like leg behaviour. The fundamental model, describing human-like leg function in walking is the bipedal spring-mass model which was investigated in this study. We identified several types of walking patterns, e.g. symmetric and asymmetric walking, that accounts for high variability of gait. The aim of this study is the identification

Juergen Rummel; Yvonne Blum; Horst Moritz Maus; Christian Rode; André Seyfarth

2010-01-01

74

KidsWalk-to-School: A Guide To Promote Walking to School.  

ERIC Educational Resources Information Center

This guide encourages people to create safe walking and biking routes to school, promoting four issues: physically active travel, safe and walkable routes to school, crime prevention, and health environments. The chapters include: "KidsWalk-to-School: A Guide to Promote Walking to School" (Is there a solution? Why is walking to school important?…

Center for Chronic Disease Prevention and Health Promotion (DHHS/CDC), Atlanta, GA.

75

The effect of walking speed and avatars on Redirected Walking Master Thesis  

E-print Network

The effect of walking speed and avatars on Redirected Walking Master Thesis Fakultät Informatik in combination with Redirected Walking 11 1.1.5 Studying human behavior while walking 11 1.1.6 Avatars in virtual 48 4.2 Concepts: Extending redirection with avatar distractors 49 4.2.1 Support of existing

76

A Random Walk to Capacitance  

E-print Network

A Random Walk to Capacitance Dianne P. O'Leary My high school physics teacher told us that we didn't have the `capacicity' to understand the subject, since we hadn't had calculus. In this case study, we and for a pair of parallel plates. The cube, though, is a shape for which no formula is known. In this case study

O'Leary, Dianne P.

77

Looperased random walks Richard Kenyon  

E-print Network

Loop­erased random walks Richard Kenyon Universit'e de Paris­Sud May 31, 1999 [summary by Cyril Kenyon, we know that domino tiling (the so called two dimensional lattice dimer model, a model which has. Kenyon won't use representations theory, but a ``discrete Laplacian'', from which he gets the full

Banderier, Cyril

78

Water-Walking Submitted by  

E-print Network

Water-Walking Submitted by David L. Hu, Brian Chan, and John W. M. Bush, Massachusetts Institute of Technology The water strider Fig. 1 is an insect of characteristic length 1 cm and weight 10 dynes of hairs that render its legs effectively nonwetting.1 The water strider propels itself by driving its

Bush, John W.M.

79

Random Walks in Random Environments  

E-print Network

Random walks provide a simple conventional model to describe various transport processes, for example propagation of heat or diffusion of matter through a medium. However, in many practical cases the medium is highly irregular due to defects, impurities, fluctuations etc., and it is natural to model this as random environment. In the random walks context, such models are referred to as Random Walks in Random Environments (RWRE). This is a relatively new chapter in applied probability and physics of disordered systems, initiated in the 1970s. Early interest was motivated by some problems in biology, crystallography and metal physics, but later applications have spread through numerous areas. After 30 years of extensive work, RWRE remain a very active area of research, which has already led to many surprising discoveries. The goal of this article is to give a brief introduction to the beautiful area of RWRE. The principal model to be discussed is a random walk with nearest-neighbor jumps in independent identically distributed (i.i.d.) random environment in one dimension, although we shall also comment on some extensions and generalizations. The focus is on rigorous results; however, heuristics is used freely to motivate the ideas and explain the approaches and proofs. In a few cases, sketches of the proofs have been included, which should help the reader to appreciate the flavor of results and methods.

L. V. Bogachev

2007-07-20

80

Random Walks in Random Environments  

E-print Network

Random walks provide a simple conventional model to describe various transport processes, for example propagation of heat or diffusion of matter through a medium. However, in many practical cases the medium is highly irregular due to defects, impurities, fluctuations etc., and it is natural to model this as random environment. In the random walks context, such models are referred to as Random Walks in Random Environments (RWRE). This is a relatively new chapter in applied probability and physics of disordered systems, initiated in the 1970s. Early interest was motivated by some problems in biology, crystallography and metal physics, but later applications have spread through numerous areas. After 30 years of extensive work, RWRE remain a very active area of research, which has already led to many surprising discoveries. The goal of this article is to give a brief introduction to the beautiful area of RWRE. The principal model to be discussed is a random walk with nearest-neighbor jumps in independent identica...

Bogachev, L V

2006-01-01

81

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.

82

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

83

A Walk to the Well.  

ERIC Educational Resources Information Center

During a walk, an outdoor education teacher reflects on the status of outdoor education in Ottawa (Canada) and importance of maintaining a close relationship with nature. He looks for signs of an old log home site, observes a hawk's flight, discovers remains of a plastic bag in an owl pellet, and realizes that everyone is working on survival. (LP)

Weir, Phil

1994-01-01

84

Successful Statewide Walking Program Websites  

ERIC Educational Resources Information Center

Statewide Extension walking programs are making an effort to increase physical activity levels in America. An investigation of all 20 of these programs revealed that 14 use websites as marketing and educational tools, which could prove useful as the popularity of Internet communities continues to grow. Website usability information and an analysis…

Teran, Bianca Maria; Hongu, Nobuko

2012-01-01

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

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

87

Humanlike walking with toe supporting for humanoids  

Microsoft Academic Search

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

88

Walking Analysis using an Acceleration Sensor  

Microsoft Academic Search

It is important to evaluate walking stability to improve people's health. There are many cases of unstable walking even if people think they are in good health. A small, light acceleration sensor was attached to subjects' center of gravity to measure the acceleration displacement while the subjects were walking. By using the seasonal adjustment model it was possible to predict

Yuriko Tsuruoka; Ryosuke Shibasaki

2007-01-01

89

Limit Theorems for the Fibonacci Quantum Walk  

E-print Network

We study the discrete-time quantum walk in one-dimension governed by the Fibonacci transformation .We show localization does not occur for the Fibonacci quantum walk by investigating the stationary distribution of the walk, in addition, we obtain the weak limit theorem.

Clement Ampadu

2011-08-25

90

Walking analysis using an acceleration sensor.  

PubMed

It is important to evaluate walking stability to improve people's health. There are many cases of unstable walking even if people think they are in good health. A small, light acceleration sensor was attached to subjects' center of gravity to measure the acceleration displacement while the subjects were walking. By using the seasonal adjustment model it was possible to predict the periodic fluctuations observed, decomposing the original data into factors representing stability and instability. We suggest the walking stability of each subject using the ratio of the variance of instability to the variance of stability. This study provides useful information for understanding walking systems in preventive medicine and rehabilitative medicine. PMID:18003126

Tsuruoka, Yuriko; Shibasaki, Ryosuke

2007-01-01

91

Walk-Startup of a Two-Legged Walking Mechanism  

Microsoft Academic Search

\\u000a There is a growing interest towards humanoid robots. One of their most important characteristic is the two-legged motion –\\u000a walk. Starting and stopping of humanoid robots introduce substantial delays. In this paper, the goal is to explore the possibility\\u000a of using a short unbalanced state of the biped robot to quickly gain speed and achieve the steady state velocity during

Kalman Babkovic; László Nagy; Damir Krkljes; Branislav Borovac

2010-01-01

92

Spatial search by quantum walk  

NASA Astrophysics Data System (ADS)

Grover’s quantum search algorithm provides a way to speed up combinatorial search, but is not directly applicable to searching a physical database. Nevertheless, Aaronson and Ambainis showed that a database of N items laid out in d spatial dimensions can be searched in time of order N for d>2 , and in time of order Npoly(logN) for d=2 . We consider an alternative search algorithm based on a continuous-time quantum walk on a graph. The case of the complete graph gives the continuous-time search algorithm of Farhi and Gutmann, and other previously known results can be used to show that N speedup can also be achieved on the hypercube. We show that full N speedup can be achieved on a d -dimensional periodic lattice for d>4 . In d=4 , the quantum walk search algorithm takes time of order Npoly(logN) , and in d<4 , the algorithm does not provide substantial speedup.

Childs, Andrew M.; Goldstone, Jeffrey

2004-08-01

93

Lattice walks by long jumps  

NASA Astrophysics Data System (ADS)

Diffusion on surfaces has in the past been modeled as a random walk in continuous time between nearest-neighbor sites on a lattice. In order to allow tests for the possible participation of long jumps in actual diffusion processes, we examine the properties of random walks in which transitions are not limited to jumps between nearest-neighbor sites. Two features of such walks are of special interest: (a) the moments of the displacements, which are directly related to the diffusivity and the statistical uncertainties in its determination; (b) the distribution function governing the probability of displacements, which is an important indicator of the contributions from long jumps. The techniques used to develop expressions for these quantities are illustrated for random walks in one dimension, with transitions allowed between neighbors up to three spacings removed. The appropriate probability generating function is derived starting from the Kolmogoroff equation. This is then manipulated to yield both the moments and the distribution of displacements in terms of the jump rates to first-, second-, and higher-nearest neighbors. Inasmuch as this approach to the distance distribution is not universally feasible, the latter is also evaluated directly as a combinatorial problem for diffusion by single and double jumps. Generating function techniques are then used to describe two-dimensional diffusion with contributions from long jumps on the (110) plane of the bcc lattice. Atomic jumps of different lengths are allowed along the close-packed directions, and jumps along the Cartesian coordinates are considered as well. The most challenging problem is to describe diffusion on the (111) plane of the fcc lattice, on which atoms can be bound at two different types of positions, one surrounded by the other, so that double jumps are no longer uncorrelated with single jumps. Lower moments of the displacements are developed from rather complicated generating functions, but combinatorial methods have to be used to derive the complete distribution function governing displacements.

Wrigley, John D.; Twigg, Mark E.; Ehrlich, Gert

1990-08-01

94

2-D pointing while walking  

Microsoft Academic Search

A frequent assertion in wearable computer discussions is that WIMP (windows\\/icons\\/mouse\\/pointer) interfaces are inappropriate for wearable computers, in part because 2-D (two-dimensional) pointing is difficult while walking. This paper summarizes findings from user studies conducted by Tangis Corporation on the usability of pointing devices for wearable computers. The author finds that, with changes, 2-D pointing could be an adequate interim

Lisa Louise Davis

2001-01-01

95

Science Sampler: The Element Walk  

NSDL National Science Digital Library

âThe Element Walkâ lesson is effective at teaching students the elements that exist in common substances encountered every day. Students walk away from the lesson with a set of general rules that help them to easily identify the elements around them. They also end up with a greater appreciation of the elemental compositions of living, once-living, and nonliving objects, and the connections among the three categories.

Smithenry, Dennis

2010-10-01

96

Quantum Walks driven by many coins  

E-print Network

Quantum random walks have been much studied recently, largely due to their highly nonclassical behavior. In this paper, we study one possible route to classical behavior for the discrete quantum random walk on the line: the use of multiple quantum ``coins'' in order to diminish the effects of interference between paths. We find solutions to this system in terms of the single coin random walk, and compare the asymptotic limit of these solutions to numerical simulations. We find exact analytical expressions for the time-dependence of the first two moments, and show that in the long time limit the ``quantum mechanical'' behavior of the one-coin walk persists. We further show that this is generic for a very broad class of possible walks, and that this behavior disappears only in the limit of a new coin for every step of the walk.

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

2002-10-23

97

Quantum walks driven by many coins  

SciTech Connect

Quantum random walks have been much studied recently, largely due to their highly nonclassical behavior. In this paper, we study one possible route to classical behavior for the discrete quantum random walk on the line: the use of multiple quantum 'coins' (or more generally, coins of higher dimension) in order to diminish the effects of interference between paths. We find solutions to this system in terms of the single-coin random walk, and compare the asymptotic limit of these solutions to numerical simulations. We find exact analytical expressions for the time dependence of the first two moments, and show that in the long-time limit the ''quantum-mechanical'' behavior of the one-coin walk persists, even if each coin is flipped only twice. We further show that this is generic for a very broad class of possible walks, and that this behavior disappears only in the limit of a new coin for every step of the walk.

Brun, Todd A.; Ambainis, Andris [Institute for Advanced Study, Einstein Drive, Princeton, New Jersey 08540 (United States); Carteret, Hilary A. [Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Ontario, N2L 3G1 (Canada)

2003-05-01

98

What Changes in Infant Walking and Why  

Microsoft Academic Search

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

99

Tracmor system for measuring walking energy expenditure  

Microsoft Academic Search

Objective: Walking is an important mode of exercise and is likely to represent a major component of nonexercise activity thermogenesis. The question arises, how best to quantify walking-energy expenditure (EE) in free-living individuals. The triaxial accelerometer for movement registration (Tracmor) is a valid measure of body displacement and so we wanted to evaluate this tool for quantifying walking-EE.Hypothesis: In this

J Levine; E L Melanson; K R Westerterp; J O Hill

2003-01-01

100

Walking Wave as a Model of Particle  

E-print Network

The concept of walking wave is introduced from classical relativistic positions. One- and three-dimensional walking waves considered with their wave equations and dispersion equations. It is shown that wave characteristics (de Broglie's and Compton's wavelengths) and corpuscular characteristics (energy-momentum vector and the rest mass) of particle may be expressed through parameters of walking wave. By that the new view on a number concepts of physic related with wave-particle duality is suggested.

A. V. Goryunov

2010-03-16

101

Efficient quantum circuit implementation of quantum walks  

NASA Astrophysics Data System (ADS)

Quantum walks, being the quantum analog of classical random walks, are expected to provide a fruitful source of quantum algorithms. A few such algorithms have already been developed, including the “glued trees” algorithm, which provides an exponential speedup over classical methods, relative to a particular quantum oracle. Here, we discuss the possibility of a quantum walk algorithm yielding such an exponential speedup over possible classical algorithms, without the use of an oracle. We provide examples of some highly symmetric graphs on which efficient quantum circuits implementing quantum walks can be constructed and discuss potential applications to quantum search for marked vertices along these graphs.

Douglas, B. L.; Wang, J. B.

2009-05-01

102

Cell phones change the way we walk.  

PubMed

Cell phone use among pedestrians leads to increased cognitive distraction, reduced situation awareness and increases in unsafe behavior. Performing a dual-task, such as talking or texting with a cell phone while walking, may interfere with working memory and result in walking errors. At baseline, thirty-three participants visually located a target 8m ahead; then vision was occluded and they were instructed to walk to the remembered target. One week later participants were assigned to either walk, walk while talking on a cell phone, or walk while texting on a cell phone toward the target with vision occluded. Duration and final location of the heel were noted. Linear distance traveled, lateral angular deviation from the start line, and gait velocity were derived. Changes from baseline to testing were analyzed with paired t-tests. Participants engaged in cell phone use presented with significant reductions in gait velocity (texting: 33% reduction, p=0.01; talking: 16% reduction, p=0.02). Moreover, participants who were texting while walking demonstrated a 61% increase in lateral deviation (p=0.04) and 13% increase in linear distance traveled (p=0.03). These results suggest that the dual-task of walking while using a cell phone impacts executive function and working memory and influences gait to such a degree that it may compromise safety. Importantly, comparison of the two cell phone conditions demonstrates texting creates a significantly greater interference effect on walking than talking on a cell phone. PMID:22226937

Lamberg, Eric M; Muratori, Lisa M

2012-04-01

103

Motor modules in robot-aided walking  

PubMed Central

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. PMID:23043818

2012-01-01

104

Efficient quantum circuit implementation of quantum walks  

SciTech Connect

Quantum walks, being the quantum analog of classical random walks, are expected to provide a fruitful source of quantum algorithms. A few such algorithms have already been developed, including the 'glued trees' algorithm, which provides an exponential speedup over classical methods, relative to a particular quantum oracle. Here, we discuss the possibility of a quantum walk algorithm yielding such an exponential speedup over possible classical algorithms, without the use of an oracle. We provide examples of some highly symmetric graphs on which efficient quantum circuits implementing quantum walks can be constructed and discuss potential applications to quantum search for marked vertices along these graphs.

Douglas, B. L.; Wang, J. B. [School of Physics, University of Western Australia, 6009 Perth (Australia)

2009-05-15

105

Walking-age analyzer for healthcare applications.  

PubMed

This paper describes a walking-age pattern analysis and identification system using a 3-D accelerometer and a gyroscope. First, a walking pattern database from 79 volunteers of ages ranging from 10 to 83 years is constructed. Second, using feature extraction and clustering, three distinct walking-age groups, children of ages 10 and below, adults in 20-60s, and elders in 70s and 80s, were identified. For this study, low-pass filtering, empirical mode decomposition, and K-means were used to process and analyze the experimental results. Analysis shows that volunteers' walking-ages can be categorized into distinct groups based on simple walking pattern signals. This grouping can then be used to detect persons with walking patterns outside their age groups. If the walking pattern puts an individual in a higher "walking age" grouping, then this could be an indicator of potential health/walking problems, such as weak joints, poor musculoskeletal support system or a tendency to fall. PMID:24808231

Jin, Bo; Thu, Tran Hoai; Baek, Eunhye; Sakong, SungHwan; Xiao, Jin; Mondal, Tapas; Deen, M Jamal

2014-05-01

106

Gaitography applied to prosthetic walking.  

PubMed

During walking on an instrumented treadmill with an embedded force platform or grid of pressure sensors, center-of-pressure (COP) trajectories exhibit a characteristic butterfly-like shape, reflecting the medio-lateral and anterior-posterior weight shifts associated with alternating steps. We define "gaitography" as the analysis of such COP trajectories during walking (the "gaitograms"). It is currently unknown, however, if gaitography can be employed to characterize pathological gait, such as lateralized gait impairments. We therefore registered gaitograms for a heterogeneous sample of persons with a trans-femoral and trans-tibial amputation during treadmill walking at a self-selected comfortable speed. We found that gaitograms directly visualize between-person differences in prosthetic gait in terms of step width and the relative duration of prosthetic and non-prosthetic single-support stance phases. We further demonstrated that one should not only focus on the gaitogram's shape but also on the time evolution along that shape, given that the COP evolves much slower in the single-support phase than in the double-support phase. Finally, commonly used temporal and spatial prosthetic gait characteristics were derived, revealing both individual and systematic differences in prosthetic and non-prosthetic step lengths, step times, swing times, and double-support durations. Because gaitograms can be rapidly collected in an unobtrusive and markerless manner over multiple gait cycles without constraining foot placement, clinical application of gaitography seems both expedient and appealing. Studies examining the repeatability of gaitograms and evaluating gaitography-based gait characteristics against a gold standard with known validity and reliability are required before gaitography can be clinically applied. PMID:25249276

Roerdink, Melvyn; Cutti, Andrea G; Summa, Aurora; Monari, Davide; Veronesi, Davide; van Ooijen, Mariëlle W; Beek, Peter J

2014-11-01

107

Knee Stretch Walking Method for Biped Robot: Using Toe and Heel Joints to Increase Walking Strides  

NASA Astrophysics Data System (ADS)

This paper proposes a knee stretch walking method for biped robots; the method involves the use of the toes and heel joints to increase walking strides. A knee can be stretched by switching control variables. By a knee stretch walking with heel contacts to the ground and toe takeoffs from the ground, biped robots can increase their walking stride and speed. The validity of the proposed method is confirmed by simulation and experimental results.

Sato, Takahiko; Shimmyo, Shuhei; Nakazato, Miki; Mikami, Kei; Sato, Tomoya; Sakaino, Sho; Ohnishi, Kouhei

108

Visual Acuity During Treadmill Walking  

NASA Technical Reports Server (NTRS)

An awareness of the physical world is essential for successful navigation through the environment. Vision is the means by which this awareness is made possible for most people. However, without adequate compensation, the movements of the body during walking could impair vision. Previous research has shown how the eyes, head and trunk movements are coordinated to provide the compensation necessary for clear vision, but the overall effectiveness of these coordinated movements is unknown. The goal of the research presented here was to provide a direct measure of visual performance during locomotion, while also investigating the degree to which coordinated head and body movements can be altered to facilitate the goal of seeing clearly.

Peters, B. T.; Brady, R.; vanEmmerik, R. E. A.; Bloomberg, Jacob J.

2006-01-01

109

Spatial search by quantum walk  

SciTech Connect

Grover's quantum search algorithm provides a way to speed up combinatorial search, but is not directly applicable to searching a physical database. Nevertheless, Aaronson and Ambainis showed that a database of N items laid out in d spatial dimensions can be searched in time of order {radical}(N) for d>2, and in time of order {radical}(N) poly(log N) for d=2. We consider an alternative search algorithm based on a continuous-time quantum walk on a graph. The case of the complete graph gives the continuous-time search algorithm of Farhi and Gutmann, and other previously known results can be used to show that {radical}(N) speedup can also be achieved on the hypercube. We show that full {radical}(N) speedup can be achieved on a d-dimensional periodic lattice for d>4. In d=4, the quantum walk search algorithm takes time of order {radical}(N) poly(log N), and in d<4, the algorithm does not provide substantial speedup.

Childs, Andrew M.; Goldstone, Jeffrey [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2004-08-01

110

Interface Reconstruction with Directional Walking  

SciTech Connect

Young's interface reconstruction with three-dimensional arbitrary mesh, in general, is rather tedious to implement compared to the case of a regular mesh. The main difficulty comes from the construction of a planar facet that bounds a certain volume inside a cell. Unlike the five basic configurations with a Cartesian mesh, there can be a great number of different configurations in the case of a general mesh. We represent a simple method that can derive the topology/geometry of the intersection of arbitrary planar objects in a uniform way. The method is based on a directional walking on the surface of objects, and links the intersection points with the paths of the walking naturally defining the intersection of objects. The method works in both two and three dimensions. The method does not take advantage of convexity, thus decomposition of an object is not necessary. Therefore, the solution with this method will have a reduced number of edges and less data storage, compared with methods that use shape decomposition. The treatment is general for arbitrary polyhedrons, and no look-up tables are needed. The same operation can easily be extended for curved geometry. The implementation of this new algorithm shall allow the interface reconstruction on an arbitrary mesh to be as simple as it is on a regular mesh. Furthermore, we exactly compute the integral of partial cell volume bounded by quadratic interface. Therefore, interface reconstruction with higher than second order accuracy can be achieved on an arbitrary mesh.

Yao, J

2009-05-22

111

Comparison of Walking with Poles and Traditional Walking for Peripheral Arterial Disease Rehabilitation  

PubMed Central

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. PMID:22595894

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

2012-01-01

112

Planar Bipedal Walking with Anthropomorphic Foot Action  

Microsoft Academic Search

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

113

Quantum walks with memory on cycles  

E-print Network

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.

Michael Mc Gettrick; Jaros?aw Adam Miszczak

2013-01-14

114

Markov Random Walk Representations with Continuous Distributions  

E-print Network

Intelligence Laboratory 200 Technology Square, Cambridge, MA 02139 Martin Szummer Microsoft Research Laboratory walks allows us to incorporate prior knowledge about the manifold shape and the distribution of data random walks to a continuum of points. Matrix operations are no longer applicable since

Yeang, Chen-Hsiang

115

What Changes in Infant Walking and Why.  

ERIC Educational Resources Information Center

Used kinematic measures to compare relative contributions of growing body dimensions, age, and walking experience in walking skill development in 9- to 17-month-olds, kindergartners, and college students. Found that with increased age, size, and experience, children's steps became longer, narrower, straighter, and more consistent, reflecting a…

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

2003-01-01

116

MOMENT ASYMPTOTICS FOR MULTITYPE BRANCHING RANDOM WALKS  

E-print Network

MOMENT ASYMPTOTICS FOR MULTITYPE BRANCHING RANDOM WALKS IN RANDOM ENVIRONMENT By Onur Gün 1 of Montenegro 29 October, 2013 Abstract. We study a discrete time multitype branching random walk on a #28;nite of mathematics, physics and biology. Additional structure and features like (1) spatiality (random migration

König, Wolfgang

117

MOMENT ASYMPTOTICS FOR MULTITYPE BRANCHING RANDOM WALKS  

E-print Network

MOMENT ASYMPTOTICS FOR MULTITYPE BRANCHING RANDOM WALKS IN RANDOM ENVIRONMENT By Onur G¨un1 of Montenegro 29 October, 2013 Abstract. We study a discrete time multitype branching random walk on a finite, physics and biology. Additional structure and features like (1) spatiality (random migration

König, Wolfgang

118

Optimal Strategies from Random Walks Jacob Abernethy  

E-print Network

Optimal Strategies from Random Walks Jacob Abernethy Division of Computer Science UC Berkeley jake strategy of the Gambler can be efficiently estimated from a simple random walk. 1 Introduction This paper of Physical and Biological Sciences UC Santa Cruz yellin@soe.ucsc.edu Abstract We analyze a sequential game

Abernethy, Jake

119

Limit of random walks of random trees  

E-print Network

Limit of random walks and of random trees -------------------- Elements -------------------- Graz (quantum physics, magnetism, polymer, DNA, genealogical tree, random walk, Markov chain, etc.); in computer physics, biology, a lot of objects hav- ing a discrete nature appear for various reason. In statistical

Marckert, Jean-François

120

Footwear effects on walking balance at elevation  

Microsoft Academic Search

The study evaluated the effects of shoe style on workers' instability during walking at elevation. Twenty-four construction workers performed walking tasks on roof planks in a surround-screen virtual reality system, which simulated a residential roof environment. Three common athletic and three work shoe styles were tested on wide, narrow and tilted planks on a simulated roof and on an unrestricted

Peter Simeonov; Hongwei Hsiao; John Powers; Douglas Ammons; Alfred Amendola; Tsui-Ying Kau; Douglas Cantis

2008-01-01

121

Brownian Optimal Stopping and Random Walks  

SciTech Connect

One way to compute the value function of an optimal stopping problem along Brownian paths consists of approximating Brownian motion by a random walk. We derive error estimates for this type of approximation under various assumptions on the distribution of the approximating random walk.

Lamberton, D. [Equipe d'Analyse et de Mathematiques Appliquees, Universite de Marne-la-Vallee, 5 Boulevard Descartes, Cite Descartes, Champs-sur-Marne, 77 454 Marne-la-Vallee Cedex 2 (France)], E-mail: dlamb@math.univ-mlv.fr

2002-06-05

122

Walking in circles: a modelling approach.  

PubMed

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

123

Localization of two-dimensional quantum walks  

NASA Astrophysics Data System (ADS)

The Grover walk, which is related to Grover’s search algorithm on a quantum computer, is one of the typical discrete time quantum walks. However, a localization of the two-dimensional Grover walk starting from a fixed point is strikingly different from other types of quantum walks. The present paper explains the reason why the walker who moves according to the degree-four Grover operator can remain at the starting point with a high probability. It is shown that the key factor for the localization is due to the degeneration of eigenvalues of the time evolution operator. In fact, the global time evolution of the quantum walk on a large lattice is mainly determined by the degree of degeneration. The dependence of the localization on the initial state is also considered by calculating the wave function analytically.

Inui, Norio; Konishi, Yoshinao; Konno, Norio

2004-05-01

124

Walk modularity and community structure in networks  

E-print Network

Modularity maximization has been one of the most widely used approaches in the last decade for discovering community structure in networks of practical interest in biology, computing, social science, statistical mechanics, and more. Modularity is a quality function that measures the difference between the number of edges found within clusters minus the number of edges one would statistically expect to find based on random chance. We present a natural generalization of modularity based on the difference between the actual and expected number of walks within clusters, which we call walk-modularity. Walk-modularity can be expressed in matrix form, and community detection can be performed by finding leading eigenvectors of the walk-modularity matrix. We demonstrate community detection on both synthetic and real-world networks and find that walk-modularity maximization returns significantly improved results compared to traditional modularity maximization.

Mehrle, David; Harkin, Anthony

2014-01-01

125

Common muscle synergies for balance and walking  

PubMed Central

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. PMID:23653605

Chvatal, Stacie A.; Ting, Lena H.

2013-01-01

126

Adaptive walks with noisy fitness measurements.  

PubMed

Adaptive walks constitute an optimization technique for searching a space of possible solutions, for example, a space of different molecules. The goal is to find a point in space (a molecule) that is optimal or near-optimal in some property, generally referred to as the 'fitness', such as its ability to bind to a given receptor. Adaptive walking, an analog of natural selection, is a powerful technique for searching landscapes. However, errors in the measurements will cause errors in the adaptive walks. Mutant molecules of higher fitness may be ignored or mutants of lower fitness may be accepted. To examine the effect of measurement error on adaptive walks, we simulate single-agent hill-climbing walks on NK landscapes of varying ruggedness where Gaussian noise is added to the fitness values to model measurement error. We consider both constant measurement noise and noise whose variance decays exponentially with fitness. We show that fitness-independent noise can cause walks to 'melt' off the peaks in a landscape, wandering in larger regions as the noise increases. However, we also show that a small amount of noise actually helps the walk perform better than with no noise. For walks in which noise decreases exponentially with fitness, the most characteristic behavior is that the walk meanders throughout the landscape until it stumbles across a point of relatively high fitness, then it climbs the landscape towards the nearest peak. Finally, we characterize the balance between selection pressure and noise and show that there are several classes of walk dynamic behavior. PMID:9237194

Levitan, B; Kauffman, S

1995-09-01

127

Walking Capacity of Bariatric Surgery Candidates  

PubMed Central

Background This study characterizes the walking limitations of bariatric surgery candidates by age and body mass index (BMI) and determines factors independently associated with walking capacity. Setting Multi-institutional at research university hospitals in the United States. Methods 2458 participants of the Longitudinal Assessment of Bariatric Surgery study (age: 18-78 y, BMI: 33-94 kg/m2) attended a pre-operative research visit. Walking capacity was measured via self-report and the 400 meter Long Distance Corridor Walk (LDCW). Results Almost two-thirds (64%) of subjects reported limitations walking several blocks, 48% had an objectively-defined mobility deficit, and 16% reported at least some walking aid use. In multivariable analysis, BMI, older age, lower income and greater bodily pain were independently associated (p<.05) with walking aid use, physical discomfort during the LDCW, inability to complete the LDCW, and slower time to complete the LDCW. Female sex, Hispanic ethnicity (but not race), higher resting heart rate, history of smoking, several comoribidities (history of stroke, ischemic heart disease, diabetes, asthma, sleep apnea, venous edema with ulcerations), and depressive symptoms were also independently related (p<.05) to at least one measure of reduced walking capacity. Conclusions Walking limitations are common in bariatric surgery candidates, even among the least severely obese and youngest patients. Physical activity counseling must be tailored to individuals' abilities. While several factors identified in this study (e.g., BMI, age, pain, comorbidities) should be considered, directly assessing walking capacity will facilitate appropriate goal-setting. PMID:21937285

King, WC; Engel, SG; Elder, KA; Chapman, WH; Eid, GM; Wolfe, BM; Belle, SH

2011-01-01

128

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

129

Walking dynamics are symmetric (enough)  

E-print Network

Many biological phenomena, such as locomotion, circadian cycles, and breathing are quasi-periodic in nature and can be modeled as rhythmic dynamical systems. Dynamical systems modeling often involves neglecting certain characteristics of a physical system as a modeling convenience. For example, in the dynamics of locomotion, the musculoskeletal system is commonly treated as symmetric about the sagittal plane. Here we extend statistical cross validation techniques in order to examine the consequences of assuming (or not) bilateral symmetry. Indeed, we verify that there are statistically significant asymmetries in the dynamics of human walking, but nevertheless show that ignoring these asymmetries results in a more consistent and predictive model. In general, neglecting evident characteristics of a system can be more than a modeling convenience---it can produce a better model.

Ankaral?, M Mert; Madhav, Manu S; Long, Andrew; Bastian, Amy J; Cowan, Noah J

2014-01-01

130

Evanescence in Coined Quantum Walks  

E-print Network

In this paper we complete the analysis begun by two of the authors in a previous work on the discrete quantum walk on the line [J. Phys. A 36:8775-8795 (2003) quant-ph/0303105 ]. We obtain uniformly convergent asymptotics for the "exponential decay'' regions at the leading edges of the main peaks in the Schr{\\"o}dinger (or wave-mechanics) picture. This calculation required us to generalise the method of stationary phase and we describe this extension in some detail, including self-contained proofs of all the technical lemmas required. We also rigorously establish the exact Feynman equivalence between the path-integral and wave-mechanics representations for this system using some techniques from the theory of special functions. Taken together with the previous work, we can now prove every theorem by both routes.

Hilary A. Carteret; Bruce Richmond; Nico Temme

2005-06-06

131

A random walk approach to quantum algorithms  

E-print Network

The development of quantum algorithms based on quantum versions of random walks is placed in the context of the emerging field of quantum computing. Constructing a suitable quantum version of a random walk is not trivial: pure quantum dynamics is deterministic, so randomness only enters during the measurement phase, i.e., when converting the quantum information into classical information. The outcome of a quantum random walk is very different from the corresponding classical random walk, due to interference between the different possible paths. The upshot is that quantum walkers find themselves further from their starting point on average than a classical walker, and this forms the basis of a quantum speed up that can be exploited to solve problems faster. Surprisingly, the effect of making the walk slightly less than perfectly quantum can optimize the properties of the quantum walk for algorithmic applications. Looking to the future, with even a small quantum computer available, development of quantum walk algorithms might proceed more rapidly than it has, especially for solving real problems.

Viv Kendon

2006-09-05

132

Quantum Walk Schemes for Universal Quantum Computation  

NASA Astrophysics Data System (ADS)

Random walks are a powerful tool for the efficient implementation of algorithms in classical computation. Their quantum-mechanical analogues, called quantum walks, hold similar promise. Quantum walks provide a model of quantum computation that has recently been shown to be equivalent in power to the standard circuit model. As in the classical case, quantum walks take place on graphs and can undergo discrete or continuous evolution, though quantum evolution is unitary and therefore deterministic until a measurement is made. This thesis considers the usefulness of continuous-time quantum walks to quantum computation from the perspectives of both their fundamental power under various formulations, and their applicability in practical experiments. In one extant scheme, logical gates are effected by scattering processes. The results of an exhaustive search for single-qubit operations in this model are presented. It is shown that the number of distinct operations increases exponentially with the number of vertices in the scattering graph. A catalogue of all graphs on up to nine vertices that implement single-qubit unitaries at a specific set of momenta is included in an appendix. I develop a novel scheme for universal quantum computation called the discontinuous quantum walk, in which a continuous-time quantum walker takes discrete steps of evolution via perfect quantum state transfer through small 'widget' graphs. The discontinuous quantum-walk scheme requires an exponentially sized graph, as do prior discrete and continuous schemes. To eliminate the inefficient vertex resource requirement, a computation scheme based on multiple discontinuous walkers is presented. In this model, n interacting walkers inhabiting a graph with 2n vertices can implement an arbitrary quantum computation on an input of length n, an exponential savings over previous universal quantum walk schemes. This is the first quantum walk scheme that allows for the application of quantum error correction. The many-particle quantum walk can be viewed as a single quantum walk undergoing perfect state transfer on a larger weighted graph, obtained via equitable partitioning. I extend this formalism to non-simple graphs. Examples of the application of equitable partitioning to the analysis of quantum walks and many-particle quantum systems are discussed.

Underwood, Michael S.

133

Quantum random walks on congested lattices  

E-print Network

We consider quantum random walks on congested lattices and contrast them to classical random walks. Congestion is modelled with lattices that contain static defects which reverse the walker's direction. We implement a dephasing process after each step which allows us to smoothly interpolate between classical and quantum random walkers as well as study the effect of dephasing on the quantum walk. Our key results show that a quantum walker escapes a finite boundary dramatically faster than a classical walker and that this advantage remains in the presence of heavily congested lattices. Also, we observe that a quantum walker is extremely sensitive to our model of dephasing.

Keith R. Motes; Alexei Gilchrist; Peter P. Rohde

2013-10-30

134

Loops in One Dimensional Random Walks  

E-print Network

Distribution of loops in a one-dimensional random walk (RW), or, equivalently, neutral segments in a sequence of positive and negative charges is important for understanding the low energy states of randomly charged polymers. We investigate numerically and analytically loops in several types of RWs, including RWs with continuous step-length distribution. We show that for long walks the probability density of the longest loop becomes independent of the details of the walks and definition of the loops. We investigate crossovers and convergence of probability densities to the limiting behavior, and obtain some of the analytical properties of the universal probability density.

Shay Wolfling; Yacov Kantor

1999-02-01

135

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

136

High Point Walking for Health: Creating Built and Social Environments That Support Walking in a Public Housing Community  

PubMed Central

Objectives. We implemented and evaluated multiple interventions to increase walking activity at a multicultural public housing site. Methods. A community-based participatory research partnership and community action teams assessed assets and barriers related to walking and developed multiple interventions to promote walking activity. Interventions included sponsoring walking groups, improving walking routes, providing information about walking options, and advocating for pedestrian safety. A pre–post study design was used to assess the changes in walking activity. Results. Self-reported walking activity increased among walking group participants from 65 to 109 minutes per day (P = .001). The proportion that reported being at least moderately active for at least 150 minutes per week increased from 62% to 81% (P = .018). Conclusions. A multicomponent intervention developed through participatory research methods that emphasized walking groups and included additional strategies to change the built and social environments increased walking activity at a public housing site in Seattle. PMID:19890163

Rabkin, Janice; Sharify, Denise; Song, Lin

2009-01-01

137

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

PubMed Central

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. PMID:24637423

Reynolds, Andy M.

2014-01-01

138

Aerobic treadmill plus Bobath walking training improves walking in subacute stroke: a randomized controlled trial  

Microsoft Academic Search

Objective: To evaluate the immediate and long-term effects of aerobic treadmill plus Bobath walking training in subacute stroke survivors compared with Bobath walking training alone.Design: Randomized controlled trial.Setting: Rehabilitation unit.Subjects: Fifty patients, first-time supratentorial stroke, stroke interval less than six weeks, Barthel Index (0 \\/ 100) from 50 to 80, able to walk a minimum distance of 12 m with

H-J Eich; H Mach; C Werner; S Hesse

2004-01-01

139

Urban Walking and the Pedagogies of the Street  

ERIC Educational Resources Information Center

Drawing upon the extensive literature on urban walking and also on almost 60 years' experience of walking the streets, this article argues that there is a pressing need to re-assert the educational value of going for a walk. After a brief discussion of the social significance of the "flaneur," the historic pioneer of urban walking, the article…

Bairner, Alan

2011-01-01

140

A Composite Random Walk for Facing Environmental Uncertainty  

E-print Network

in Biology have showed that strategies based on different random walks, such as: Brownian ran- dom walk and LA Composite Random Walk for Facing Environmental Uncertainty and Reduced Perceptual Capabilities C´evy random walk are the best option when there is some degree of environmental uncertainty

Hu, Huosheng

141

Walking Motion Analysis Using 3D Acceleration Sensors  

Microsoft Academic Search

Human walking motion shows various information including involuntary behaviors such as walking patterns, ground conditions, health conditions, as well as conscious actions such as system control and communication. Such information can be used to establish interface with ubiquitous network systems. Therefore, human walking motion detection plays a key role for such interface. Human motion including walking motion can be analyzed

Teruaki Ito

2008-01-01

142

Walking Control Algorithm based on Polynomial Trajectory Generation  

Microsoft Academic Search

Humanoid walking trajectory is a complex task, due the high number of degrees of freedom (DOFs) and changes on the mechanical structure during walking. A non-trivial problem in bipedal robot walking is the instability produced by violent transitions between difierent walk phases. This work presents a trajectory generation algorithm for a biped robot. The algorithm is based on cubic Hermitian

MARCO PEREZ-CISNEROS; ERIK CUEVAS; DANIEL ZALDIVAR

143

Nordic Walking Practice Might Improve Plantar Pressure Distribution  

ERIC Educational Resources Information Center

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…

Perez-Soriano, Pedro; Llana-Belloch, Salvador; Martinez-Nova, Alfonso; Morey-Klapsing, G.; Encarnacion-Martinez, Alberto

2011-01-01

144

Walking with coffee: why does it spill?  

PubMed

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. PMID:22680548

Mayer, H C; Krechetnikov, R

2012-04-01

145

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

146

Realistic Human Walking Paths David C. Brogan  

E-print Network

development for entertainment applications and many classes of simulations. We present a novel behav- ioral- served paths in black on the floor. A library exit (a) and a university hallway (b). A realistic walking

Brogan, David

147

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

148

Measuring Oscillating Walking Paths with a LIDAR  

PubMed Central

This work describes the analysis of different walking paths registered using a Light Detection And Ranging (LIDAR) laser range sensor in order to measure oscillating trajectories during unsupervised walking. The estimate of the gait and trajectory parameters were obtained with a terrestrial LIDAR placed 100 mm above the ground with the scanning plane parallel to the floor to measure the trajectory of the legs without attaching any markers or modifying the floor. Three different large walking experiments were performed to test the proposed measurement system with straight and oscillating trajectories. The main advantages of the proposed system are the possibility to measure several steps and obtain average gait parameters and the minimum infrastructure required. This measurement system enables the development of new ambulatory applications based on the analysis of the gait and the trajectory during a walk. PMID:22163891

Teixido, Merce; Palleja, Tomas; Tresanchez, Marcel; Nogues, Miquel; Palacin, Jordi

2011-01-01

149

Random walks in the history of life.  

PubMed

The simplest null hypothesis for evolutionary time series is that the observed data follow a random walk. We examined whether aspects of Sepkoski's compilation of marine generic diversity depart from a random walk by using statistical tests from econometrics. Throughout most of the Phanerozoic, the random-walk null hypothesis is not rejected for marine diversity, accumulated origination or accumulated extinction, suggesting that either these variables were correlated with environmental variables that follow a random walk or so many mechanisms were affecting these variables, in different ways, that the resultant trends appear random. The only deviation from this pattern involves rejection of the null hypothesis for roughly the last 75 million years for the diversity and accumulated origination time series. PMID:14684835

Cornette, James L; Lieberman, Bruce S

2004-01-01

150

Quantum random walks with decoherent coins  

E-print Network

The quantum random walk has been much studied recently, largely due to its highly nonclassical behavior. In this paper, we study one possible route to classical behavior for the discrete quantum walk on the line: the presence of decoherence in the quantum ``coin'' which drives the walk. We find exact analytical expressions for the time dependence of the first two moments of position, and show that in the long-time limit the variance grows linearly with time, unlike the unitary walk. We compare this to the results of direct numerical simulation, and see how the form of the position distribution changes from the unitary to the usual classical result as we increase the strength of the decoherence.

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

2002-10-25

151

Network Discovery by Generalized Random Walks  

E-print Network

We investigate network exploration by random walks defined via stationary and adaptive transition probabilities on large graphs. We derive an exact formula valid for arbitrary graphs and arbitrary walks with stationary transition probabilities (STP), for the average number of discovered edges as function of time. We show that for STP walks site and edge exploration obey the same scaling $\\sim n^{\\lambda}$ as function of time $n$. Therefore, edge exploration on graphs with many loops is always lagging compared to site exploration, the revealed graph being sparse until almost all nodes have been discovered. We then introduce the Edge Explorer Model, which presents a novel class of adaptive walks, that perform faithful network discovery even on dense networks.

A. Asztalos; Z. Toroczkai

2010-08-30

152

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 ...

153

Gallery Walk Questions about Human Dimensions  

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 human dimensions of geologic issues. The questions are organized ...

154

Gallery Walk Questions on Atmosphere Composition  

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 atmosphere composition, greenhouse gases, ozone. The questions are ...

155

The hydrodynamics of water-walking arthropods  

E-print Network

We present the results of a combined experimental and theoretical investigation of the dynamics of water-walking insects and spiders. Using high-speed videography, we describe their numerous gaits, some analogous to those ...

Bush, John W. M.

156

Photons walking the line: a quantum walk with adjustable coin operations.  

PubMed

We present the first robust implementation of a coined quantum walk over five steps using only passive optical elements. By employing a fiber network loop we keep the amount of required resources constant as the walker's position Hilbert space is increased. We observed a non-Gaussian distribution of the walker's final position, thus characterizing a faster spread of the photon wave packet in comparison to the classical random walk. The walk is realized for many different coin settings and initial states, opening the way for the implementation of a quantum-walk-based search algorithm. PMID:20366754

Schreiber, A; Cassemiro, K N; Potocek, V; Gábris, A; Mosley, P J; Andersson, E; Jex, I; Silberhorn, Ch

2010-02-01

157

Photons Walking the Line: A Quantum Walk with Adjustable Coin Operations  

NASA Astrophysics Data System (ADS)

We present the first robust implementation of a coined quantum walk over five steps using only passive optical elements. By employing a fiber network loop we keep the amount of required resources constant as the walker’s position Hilbert space is increased. We observed a non-Gaussian distribution of the walker’s final position, thus characterizing a faster spread of the photon wave packet in comparison to the classical random walk. The walk is realized for many different coin settings and initial states, opening the way for the implementation of a quantum-walk-based search algorithm.

Schreiber, A.; Cassemiro, K. N.; Poto?ek, V.; Gábris, A.; Mosley, P. J.; Andersson, E.; Jex, I.; Silberhorn, Ch.

2010-02-01

158

Look who's walking: social and environmental correlates of children's walking in London.  

PubMed

A substantial literature examines the social and environmental correlates of walking to school but less addresses walking outside the school commute. Using travel diary data from London, we examined social and environmental correlates of walking: to school; outside the school commute during term time; and during the summer and weekends. Living in a household without a car was associated with all journey types; 'Asian' ethnicity was negatively associated with walking for non-school travel; environmental factors were associated with non-school journeys, but not the school commute. Interventions aiming to increase children's active travel need to take account of the range of journeys they make. PMID:22464978

Steinbach, Rebecca; Green, Judith; Edwards, Phil

2012-07-01

159

Implementation of multi-walker quantum walks with cavity grid  

E-print Network

We show how multi-walker quantum walks can be implemented in a quantum quincunx created via cavity quantum electrodynamics. The implementation of a quantum walk with a multi-walker opens up the interesting possibility to introduce entanglement and more advanced walks. With different coin tosses and initial states the multi-walker quantum walk shows different probability distributions which deviate strongly from the classical random walks with quadratic enhanced spreadings and localization effects. By introducing decoherence, the transition from quantum walks to the classical versions is observed. We introduce the average fidelity decay as a signature to investigate the decoherence-induced irreversibility of quantum walks.

Peng Xue

2012-03-27

160

Time to prioritise safe walking.  

PubMed

This study draws on information from two recently published documents on pedestrian safety and global status of road safety to draw attention to the need to prioritize safe walking in planning and policy at local, national and international levels. The study shows that each year, more than 270 000 pedestrians lose their lives on the world's roads. The study argues that this situation need not persist because proven pedestrian safety interventions exist but do not attract the merit they deserve in many locations. The study further shows that the key risk factors for pedestrian road traffic injury such as vehicle speed, alcohol use by drivers and pedestrians, lack of infrastructure facilities for pedestrians and inadequate visibility of pedestrians are fairly well documented. The study concludes that pedestrian collisions, like all road traffic crashes, should not be accepted as inevitable because they are, in fact, both predictable and preventable. While stressing that reduction or elimination of risks faced by pedestrians is an important and achievable policy goal, the study emphasizes the importance of a comprehensive, holistic approach that includes engineering, enforcement and education measures. PMID:23701478

Toroyan, Tami; Khayesi, Meleckidzedeck; Peden, Margie

2013-01-01

161

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

162

Standardized Questionnaires of Walking & Bicycling Database  

Cancer.gov

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.

163

A hexapod walking machine with decoupled freedoms  

Microsoft Academic Search

Legged locomotion over irregular terrain is composed of body-propelling motion and terrain-adapting motion. Although conventional walking machines with three degrees-of-freedom for each leg can adapt their feet on irregular ground using flexible leg freedom, such machines generally require a tremendously complex control scheme for the body-propelling motion. A walking machine with decoupled freedoms is based on the idea that body-propelling

M. Kaneko; M. Abe; K. Tanie

1985-01-01

164

Mesonic spectroscopy of minimal walking technicolor  

SciTech Connect

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

165

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

166

The Effects of Walking or Walking-with-Poles Training on Tissue Oxygenation in Patients with Peripheral Arterial Disease  

PubMed Central

This randomized trial proposed to determine if there were differences in calf muscle StO2 parameters in patients before and after 12 weeks of a traditional walking or walking-with-poles exercise program. Data were collected on 85 patients who were randomized to a traditional walking program (n = 40) or walking-with-poles program (n = 45) of exercise training. Patients walked for 3 times weekly for 12 weeks. Seventy-one patients completed both the baseline and the 12-week follow-up progressive treadmill tests (n = 36 traditional walking and n = 35 walking-with-poles). Using the near-infrared spectroscopy measures, StO2 was measured prior to, during, and after exercise. At baseline, calf muscle oxygenation decreased from 56 ± 17% prior to the treadmill test to 16 ± 18% at peak exercise. The time elapsed prior to reaching nadir StO2 values increased more in the traditional walking group when compared to the walking-with-poles group. Likewise, absolute walking time increased more in the traditional walking group than in the walking-with-poles group. Tissue oxygenation decline during treadmill testing was less for patients assigned to a 12-week traditional walking program when compared to those assigned to a 12-week walking-with-poles program. In conclusion, the 12-week traditional walking program was superior to walking-with-poles in improving tissue deoxygenation in patients with PAD. PMID:23050152

Collins, Eileen G.; McBurney, Conor; Butler, Jolene; Jelinek, Christine; O'Connell, Susan; Fritschi, Cynthia; Reda, Domenic

2012-01-01

167

Quantum walks with tuneable self-avoidance in one dimension  

PubMed Central

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

168

Walking skill versus walking experience as a predictor of barrier crossing in toddlers  

Microsoft Academic Search

The aim of this study was to examine the roles of body size parameters, walking skill, and locomotor experience in determining the abilities of 14-, 18-, 24-, and 30-month-old toddlers to cross a barrier varying in height. Thresholds for barrier crossing were measured using a modified psychophysical staircase procedure, walking skill was assessed using a footprint analysis of gait, and

Shauna Kingsnorth; Mark A. Schmuckler

2000-01-01

169

Design of a quadruped walking vehicle for dynamic walking and stair climbing  

Microsoft Academic Search

This paper discusses the design of a quadruped walking vehicle for walking dynamically at high speed and climbing ordinary stairs (30-40°). To realize these requests, new mechanisms are introduced, which are (1) a prismatic joint leg that does not interfere with the steps of a staircase and which performs a cylindrical coordinate motion with good energy efficiency, (2) an articulated

Shigeo Hirose; Kan Yoneda; Kazuhiko Arai; Tomoyoshi Ibe

1994-01-01

170

Velocity-dependent dynamic curvature gain for redirected walking.  

PubMed

Redirected walking techniques allow people to walk in a larger virtual space than the physical extents of the laboratory. We describe two experiments conducted to investigate human sensitivity to walking on a curved path and to validate a new redirected walking technique. In a psychophysical experiment, we found that sensitivity to walking on a curved path was significantly lower for slower walking speeds (radius of 10 m versus 22 m). In an applied study, we investigated the influence of a velocity-dependent dynamic gain controller and an avatar controller on the average distance that participants were able to freely walk before needing to be reoriented. The mean walked distance was significantly greater in the dynamic gain controller condition, as compared to the static controller (22 m versus 15 m). Our results demonstrate that perceptually motivated dynamic redirected walking techniques, in combination with reorientation techniques, allow for unaided exploration of a large virtual city model. PMID:22577150

Neth, Christian T; Souman, Jan L; Engel, David; Kloos, Uwe; Bülthoff, Heinrich H; Mohler, Betty J

2012-07-01

171

Renormalization and scaling in quantum walks  

NASA Astrophysics Data System (ADS)

We show how to extract the scaling behavior of quantum walks using the renormalization group (RG). We introduce the method by efficiently reproducing well-known results on the one-dimensional lattice. For a nontrivial model, we apply this method to the dual Sierpinski gasket and obtain its exact, closed system of RG recursions. Numerical iteration suggests that under rescaling the system length, L'=2L, characteristic times rescale as t'=2dwt, with the exact walk exponent dw=log2?5 =1.1609... Despite the lack of translational invariance, this value is very close to the ballistic spreading, dw=1, found for regular lattices. However, we argue that an extended interpretation of the traditional RG formalism will be needed to obtain scaling exponents analytically. Direct simulations confirm our RG prediction for dw and furthermore reveal an immensely rich phenomenology for the spreading of the quantum walk on the gasket. Invariably, quantum interference localizes the walk completely, with a site-access probability that decreases with a power law from the initial site, in contrast to a classical random walk, which would pass all sites with certainty.

Boettcher, Stefan; Falkner, Stefan; Portugal, Renato

2014-09-01

172

Clinimetric properties of a walking scale in peripheral neuropathy  

PubMed Central

Difficulty in walking is seen in many people with peripheral neuropathies, but walking ability is not comprehensively measured by commonly used outcome measures. The clinimetric properties of the 12?Item Multiple Sclerosis Walking Scale (MSWS?12, renamed the Walk?12) were investigated in 65 patients with peripheral neuropathies. Owing to its excellent internal consistency and reliability, and strong correlation with measures of physical and social function (r>0.8), the Walk?12 is recommended for measuring walking ability in peripheral neuropathies. PMID:16574732

Graham, R C; Hughes, R A C

2006-01-01

173

Quantum random-walk search algorithm  

NASA Astrophysics Data System (ADS)

Quantum random walks on graphs have been shown to display many interesting properties, including exponentially fast hitting times when compared with their classical counterparts. However, it is still unclear how to use these novel properties to gain an algorithmic speedup over classical algorithms. In this paper, we present a quantum search algorithm based on the quantum random-walk architecture that provides such a speedup. It will be shown that this algorithm performs an oracle search on a database of N items with O((N)) calls to the oracle, yielding a speedup similar to other quantum search algorithms. It appears that the quantum random-walk formulation has considerable flexibility, presenting interesting opportunities for development of other, possibly novel quantum algorithms.

Shenvi, Neil; Kempe, Julia; Whaley, K. Birgitta

2003-05-01

174

Spherically symmetric random walks in noninteger dimension  

SciTech Connect

A previous article proposed a new kind of random walk on a spherically symmetric lattice in arbitrary noninteger dimension [ital D]. Such a lattice avoids the problems associated with a hypercubic lattice in noninteger dimension. This article examines the nature of spherically symmetric random walks in detail. A large-time asymptotic analysis of these random walks is performed and the results are used to determine the Hausdorff dimension of the process. Exact results are obtained in terms of Hurwitz functions (incomplete zeta functions) for the probability of a walker going from one region of the spherical lattice to another. Finally, it is shown that the probability that the paths of [ital K] independent random walkers will intersect vanishes in the continuum limit if [ital D][gt]2[ital K]/([ital K][minus]1).

Bender, C.M. (Department of Physics, Washington University, St. Louis, Missouri 63130-4899 (United States)); Boettcher, S. (Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)); Moshe, M. (Department of Physics, Technion Israel Institute of Technology, Haifa 32000 (Israel))

1994-09-01

175

Random walk in a random multiplicative environment  

SciTech Connect

The authors investigate the dynamics of a random walk in a random multiplicative medium. This results in a random, but correlated, multiplicative process for the spatial distribution of random walkers. The authors show how the details of these correlations determine the asymptotic properties of the walk, i.e., the central limit theorem does not apply to these multiplicative processes. They also study a periodic source-trap medium in which a unit cell contains one source, followed by L {minus} 1 traps. They calculate the asymptotic behavior of the number of particles, and determine the conditions for which there is growth or decay in this average number. Finally, they discuss the asymptotic behavior of a random walk in the presence of randomly distributed, partially-absorbing traps. For this case, a temporal regime of purely exponential decay of the density can occur, before the asymptotic stretched exponential decay, exp({minus}at{sup 1/3}), sets in.

Ben-Avraham, D. (Boston Univ., MA (USA) Clarkson Univ., Potsdam, NY (USA)); Redner, S.; Cheng, Z. (Boston Univ., MA (USA))

1989-08-01

176

Universal quantum computation by discontinuous quantum walk  

E-print Network

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 timestep apart.

Michael S. Underwood; David L. Feder

2010-08-20

177

Universal quantum computation by discontinuous quantum walk  

SciTech Connect

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

178

Random walks and polygons in tight confinement  

NASA Astrophysics Data System (ADS)

We discuss the effect of confinement on the topology and geometry of tightly confined random walks and polygons. Here the walks and polygons are confined in a sphere of radius R >= 1/2 and the polygons are equilateral with n edges of unit length. We illustrate numerically that for a fixed length of random polygons the knotting probability increases to one as the radius decreases to 1/2. We also demonstrate that for random polygons (walks) the curvature increases to ?n (?(n – 1)) as the radius approaches 1/2 and that the torsion decreases to ? ?n/3 (? ?(n – 1)/3). In addition we show the effect of length and confinement on the average crossing number of a random polygon.

Diao, Y.; Ernst, C.; Ziegler, U.

2014-10-01

179

Epidemic spreading driven by biased random walks  

E-print Network

Random walk is one of the basic mechanisms found in many network applications. We study the epidemic spreading dynamics driven by biased random walks on complex networks. In our epidemic model, each time infected nodes constantly spread some infected packets by biased random walks to their neighbor nodes causing the infection of the susceptible nodes that receive the packets. An infected node get recovered from infection with a fixed probability. Simulation and analytical results on model and real-world networks show that the epidemic spreading becomes intense and wide with the increase of delivery capacity of infected nodes, average node degree, homogeneity of node degree distribution. Furthermore, there are corresponding optimal parameters such that the infected nodes have instantaneously the largest population, and the epidemic spreading process covers the largest part of a network.

Pu, Cunlai; Yang, Jian

2014-01-01

180

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

181

Relationship between quantum walks and relativistic quantum mechanics  

SciTech Connect

Quantum walk models have been used as an algorithmic tool for quantum computation and to describe various physical processes. This article revisits the relationship between relativistic quantum mechanics and the quantum walks. We show the similarities of the mathematical structure of the decoupled and coupled forms of the discrete-time quantum walk to that of the Klein-Gordon and Dirac equations, respectively. In the latter case, the coin emerges as an analog of the spinor degree of freedom. Discrete-time quantum walk as a coupled form of the continuous-time quantum walk is also shown by transforming the decoupled form of the discrete-time quantum walk to the Schroedinger form. By showing the coin to be a means to make the walk reversible and that the Dirac-like structure is a consequence of the coin use, our work suggests that the relativistic causal structure is a consequence of conservation of information. However, decoherence (modeled by projective measurements on position space) generates entropy that increases with time, making the walk irreversible and thereby producing an arrow of time. The Lieb-Robinson bound is used to highlight the causal structure of the quantum walk to put in perspective the relativistic structure of the quantum walk, the maximum speed of walk propagation, and earlier findings related to the finite spread of the walk probability distribution. We also present a two-dimensional quantum walk model on a two-state system to which the study can be extended.

Chandrashekar, C. M. [Institute for Quantum Computing, University of Waterloo, Ontario N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Banerjee, Subhashish [Chennai Mathematical Institute, Padur PO, Siruseri 603 103 (India); Srikanth, R. [Poornaprajna Institute of Scientific Research, Devanahalli, Bangalore 562 110 (India); Raman Research Institute, Sadashiva Nagar, Bangalore 560 080 (India)

2010-06-15

182

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

183

Spectral solution of delayed random walks  

NASA Astrophysics Data System (ADS)

We develop a spectral method for computing the probability density function for delayed random walks; for such problems, the method is exact to machine precision and faster than existing approaches. In conjunction with a step function approximation and the weak Euler-Maruyama discretization, the spectral method can be applied to nonlinear stochastic delay differential equations (SDDE). In essence, this means approximating the SDDE by a delayed random walk, which is then solved using the spectral method. We carry out tests for a particular nonlinear SDDE that show that this method captures the solution without the need for Monte Carlo sampling.

Bhat, H. S.; Kumar, N.

2012-10-01

184

Walking model with no energy cost  

NASA Astrophysics Data System (ADS)

We have numerically found periodic collisionless motions of a walking model consisting of linked rigid objects. Unlike previous designs, this model can walk on level ground at noninfinitesimal speed with zero energy input. The model avoids collisional losses by using an internal mode of oscillation: swaying of the upper body coupled to the legs by springs. Appropriate synchronized internal oscillations set the foot-strike collision to zero velocity. The concept might be of use for energy-efficient robots and may also help to explain aspects of human and animal locomotion efficiency.

Gomes, Mario; Ruina, Andy

2011-03-01

185

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

PubMed

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

186

Environmental perceptions and objective walking trail audits inform a community-based participatory research walking intervention  

PubMed Central

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. PMID:22289653

2012-01-01

187

Walk This Way! Taking Steps for Pedestrian Safety  

MedlinePLUS

... children who choose to walk and bicycle. National Highway Traffic Safety Administration (NHTSA): Pedestrians This website has ... Walk to School in the USA website National Highway Traffic Safety Administration – Prevent Pedestrian Crashes: Parents ...

188

A model of muscle-tendon function in human walking  

E-print Network

In order to motivate the design of legged machines that walk as humans do, this thesis investigates how leg muscles and tendons work mechanically during level-ground human walking at self-selected speeds. I hypothesize ...

Endo, Ken, Ph. D. Massachusetts Institute of Technology

2012-01-01

189

How to Build a Walking Trail Texas Department of Health  

E-print Network

How to Build a Walking Trail Texas Department of Health Chronic Disease Community & Worksite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Media Promotion

190

Continuous-time quantum walks on star graphs  

SciTech Connect

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

191

Commute times of random walks on trees  

NASA Astrophysics Data System (ADS)

In this paper we provide exact formula for the commute times of random walks on spherically symmetric random trees. Using this formula we sharpen some of the results presented in Al-Awadhi et al to the form of equalities rather than inequalities.

Konsowa, Mokhtar

2012-09-01

192

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

193

Exotic states of bouncing and walking droplets  

NASA Astrophysics Data System (ADS)

We present the results of an integrated experimental and theoretical investigation of droplets bouncing on a vibrating fluid bath. A comprehensive series of experiments provides the most detailed characterisation to date of the system's dependence on fluid properties, droplet size, and vibrational forcing. A number of new bouncing and walking states are reported, including complex periodic and aperiodic motions. Particular attention is given to the first characterisation of the different gaits arising within the walking regime. In addition to complex periodic walkers and limping droplets, we highlight a previously unreported mixed state, in which the droplet switches periodically between two distinct walking modes. Our experiments are complemented by a theoretical study based on our previous developments [J. Molacek and J. W. M. Bush, J. Fluid Mech. 727, 582-611 (2013);, 10.1017/jfm.2013.279 J. Molacek and J. W. M. Bush, J. Fluid Mech. 727, 612-647 (2013)], 10.1017/jfm.2013.280, which provide a basis for rationalising all observed bouncing and walking states.

Wind-Willassen, Øistein; Molá?ek, Jan; Harris, Daniel M.; Bush, John W. M.

2013-08-01

194

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

195

Localization of M-Particle Quantum Walks  

E-print Network

We study the motion of M particles performing a quantum walk on the line. Under various conditions on the initial coin states for quantum walkers controlled by the Hadamard operator, we give theoretical criterion to observe the quantum walkers at an initial location with high probability.

Clement Ampadu

2011-06-26

196

A Smart Walker to Understand Walking Abilities  

E-print Network

1 A Smart Walker to Understand Walking Abilities Pascal Poupart Associate Professor Cheriton School · Smart Walker · User study at the Village of Winston Park · Behaviour recognition · Limb tracking #12? Pascal Poupart, 11/21/2008 #12;7 Smart Walker walker devices + caregivers users Force sensors Load

Poupart, Pascal

197

Decelerating Environmentally Destructive Lawn-Walking  

Microsoft Academic Search

Three general strategies (response difficulty, chaining, and prompting) were used to generate six interventions to decrease lawn walking in a park. Interventions were evaluated in separate ABA designs during which 1885 persons (61% male) were observed. While none of the three strategies appeared generally superior, some interventions were more effective than others. Formal prompts (signs) and procedures involving response difficulty

Steven C. Hayes; John D. Cone

1977-01-01

198

Random Walks and Percolation on Trees  

Microsoft Academic Search

There is a way to define an average number of branches per vertex for an arbitrary infinite locally finite tree. It equals the exponential of the Hausdorff dimension of the boundary in an appropriate metric. Its importance for probabilistic processes on a tree is shown in several ways, including random walk and percolation, where it provides points of phase transition.

Russell Lyons

1990-01-01

199

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

200

Cavity QED-based quantum walk  

E-print Network

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...

Di, TG; Hillery, M.; Zubairy, M. Suhail

2004-01-01

201

Mixing of Quantum Walk on Circulant Bunkbeds  

E-print Network

We give new observations on the mixing dynamics of a continuous-time quantum walk on circulants and their bunkbed extensions. These bunkbeds are defined through two standard graph operators: the join G + H and the Cartesian product of graphs G and H.Our results include the following: 1. The quantum walk is average uniform mixing on circulants with bounded eigenvalue multiplicity. This extends a known fact about the cycles. 2. Explicit analysis of the probability distribution of the quantum walk on the join of circulants. This explains why complete partite graphs are not average uniform mixing, using the fact the complete n-vertex graph is the join of a 1-vertex graph and the (n-1)-vertex complete graph, and that the complete m-partite graph, where each partition has size n, is the m-fold join of the empty n-vertex graph. 3. The quantum walk on the Cartesian product of a m-vertex path P and a circulant G, is average uniform mixing if G is. This highlights a difference between circulants and the hypercubes. Our proofs employ purely elementary arguments based on the spectra of the graphs.

P. Lo; S. Rajaram; D. Schepens; D. Sullivan; C. Tamon; J. Ward

2005-09-08

202

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

203

A New View of Walk-Throughs  

ERIC Educational Resources Information Center

Traditionally, principals have used walk-throughs to determine whether teachers are implementing strategies that the principal believes define good teaching. In this model, the principal is the expert, and the teacher is the learner. Connie M. Moss and Susan M. Brookhart believe that this approach can cause the principal to disregard the classroom…

Moss, Connie M.; Brookhart, Susan M.

2013-01-01

204

Stable dynamic walking of a quadruped robot \\  

Microsoft Academic Search

In this study, we intend to show the basis of a general legged locomotion controller with the ability to integrate both posture and rhythmic motion controls and shift continuously from one control method to the other according to the walking speed. The rhythmic motion of each leg in the sagittal plane is generated by a single leg controller which controls

Christophe Maufroy; Tomohiro Nishikawa; Hiroshi Kimura

2010-01-01

205

The physics of a walking robot  

NASA Astrophysics Data System (ADS)

The physics of walking is explored, using a toy as a concrete example and a ‘toy model’ applied to it. Besides using Newton’s second law, the problem is also discussed from the thermodynamical perspective. Once the steady state (constant velocity) is achieved, we show that the internal energy of the toy is dissipated as heat in the surroundings.

Güémez, J.; Fiolhais, M.

2013-07-01

206

Developing Recreational Trails: Motivations for Recreational Walking  

Microsoft Academic Search

This paper seeks to explore the motivations and preferences of recreational walkers in near-urban areas and the implications for trail development. A qualitative focus group method was employed in order to generate open discussion amongst recreational walkers from a range of backgrounds and levels of interest, participation and experience, drawing out motivations to walk, and potential issues relating to trail

Nicholas J. Davies; Leslie M. Lumsdon; Richard Weston

2012-01-01

207

The physics of a walking robot  

E-print Network

The physics of walking is explored, using a toy as a concrete example and a 'toy' model applied to it. Besides the Newton's second law, the problem is also discussed from the thermodynamical perspective. Once the steady state (constant velocity) is achieved, we show that the internal energy of the toy is dissipated as heat in the surroundings.

Güémez, Julio

2014-01-01

208

Screenbot: Walking inverted using distributed inward gripping  

Microsoft Academic Search

Insights from biology have helped reduce the weight and increase the climbing ability of mobile robots. This paper presents Screenbot, see Fig. 1, a new 126 gram biologically-inspired robot that scales wire mesh substrates using spines. Like insects, it walks with an alternating tripod gait and maintains tension in opposing legs to keep the feet attached to the substrate. A

Gregory D. Wile; Kathryn A. Daltorio; Eric D. Diller; Luther R. Palmer; Stanislav N. Gorb; Roy E. Ritzmann; Roger D. Quinn

2008-01-01

209

The walk and jump of Equisetum spores  

PubMed Central

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

2013-01-01

210

Walks on Borders of Polygons VESA HALAVA  

E-print Network

Walks on Borders of Polygons VESA HALAVA TERO HARJU Department of Mathematics and Turku Centre the top border of R are colored white, (2) the rectangles along the bottom border of R are colored gray path, a path from the left hand border of R to the right hand border such that the path goes along

Harju, Tero

211

Sunspot random walk and 22-year variation  

NASA Astrophysics Data System (ADS)

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 log-normal 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

2012-05-01

212

Walk and Talk Experiences. Case Study.  

ERIC Educational Resources Information Center

Walk and Talk Experiences combine challenging outdoor experiences, group living, and opportunities for reflection and discussion to promote self-exploration and personal development. The British program has served various client groups, such as adolescents and people with disabilities or special needs. Activities on several weekends are described.…

Erskine, Rab

1998-01-01

213

Saccadic body turns in walking Drosophila  

PubMed Central

Drosophila melanogaster structures its optic flow during flight by interspersing translational movements with abrupt body rotations. Whether these “body saccades” are accompanied by steering movements of the head is a matter of debate. By tracking single flies moving freely in an arena, we now discovered that walking Drosophila also perform saccades. Movement analysis revealed that the flies separate rotational from translational movements by quickly turning their bodies by 15 degrees within a tenth of a second. Although walking flies moved their heads by up to 20 degrees about their bodies, their heads moved with the bodies during saccadic turns. This saccadic strategy contrasts with the head saccades reported for e.g., blowflies and honeybees, presumably reflecting optical constraints: modeling revealed that head saccades as described for these latter insects would hardly affect the retinal input in Drosophila because of the lower acuity of its compound eye. The absence of head saccades in Drosophila was associated with the absence of haltere oscillations, which seem to guide head movements in other flies. In addition to adding new twists to Drosophila walking behavior, our analysis shows that Drosophila does not turn its head relative to its body when turning during walking. PMID:25386124

Geurten, Bart R. H.; Jahde, Philipp; Corthals, Kristina; Gopfert, Martin C.

2014-01-01

214

Take a Hike!: A Family Forest Walk  

NSDL National Science Digital Library

In this family or group inquiry activity, learners use their senses to explore a local forest or woodland. Learners can look for decomposers and fungi, investigate flowers and pollination, and practice observation skills while looking for signs of plant and animal life interaction. Learners will sketch their findings in a nature journal and then share their observations after the forest walk.

Park, Smithsonian N.

2012-06-26

215

Designs of Autonomous Unidirectional Walking DNA Devices  

E-print Network

, Oxford OX 1 3PU, UK. a.turberfield@physics.ox.ac.uk Abstract. Imagine a host of nanoscale DNA robots move basis to meet the above challenge. The missing link is a DNA walker that can autonomously move along of autonomous DNA walking devices in which a walker moves along a linear track unidirectionally. The track

Reif, John H.

216

Iterative learning control for biped walking  

Microsoft Academic Search

In this paper, an iterative learning control (ILC) approach is proposed for biped walking control. The biped robot is powered by applying an impulsive push along the stance leg just before the heel strikes. The ILC law is designed based on Poincare? map, and applied to learn the desired impulsive push at every step in the presence of system uncertainties.

Qi-Zhi Zhang; Chee-Meng Chew; Ya-Li Zhou; Qiu-Ling Zhao; Pei Li

2010-01-01

217

Walking, exercising, and smoking: does neighborhood matter?  

PubMed

Neighborhood context could affect health behaviors because of structure or contagion. We expected that residents of US neighborhoods where a high percentage of residents are poor and do not have college degrees would be more likely to smoke and less likely to walk and exercise. We examined the hypotheses using multi-level data in which survey information from a representative sample of Illinois residents is linked to census-tract information about poverty and education in their neighborhood. Contrary to expectations we found that residents of poor neighborhoods were more likely to walk than those in less disadvantaged places, adjusting for individual poverty, household income, education, race, ethnicity, sex, age, and marital status. This was the case despite the fact that residents of poor neighborhoods were more afraid to leave the house and feared being victimized on the streets. Consistent with expectations we found that residents of neighborhoods where a high percentage of residents are college educated are more likely to walk. Thus, the two aspects of neighborhood socioeconomic status had opposite effects on walking. Neighborhood context had no effect on the likelihood of exercising strenuously. Men in poor neighborhoods were more likely to smoke than those in less disadvantaged places, but neighborhood context had no significant effect on women's likelihood of smoking. PMID:10832573

Ross, C E

2000-07-01

218

The Physics of a Walking Robot  

ERIC Educational Resources Information Center

The physics of walking is explored, using a toy as a concrete example and a "toy model" applied to it. Besides using Newton's second law, the problem is also discussed from the thermodynamical perspective. Once the steady state (constant velocity) is achieved, we show that the internal energy of the toy is dissipated as heat in the…

Guemez, J.; Fiolhais, M.

2013-01-01

219

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

220

Reinforcement Learning Control for Biped Robot Walking on Uneven Surfaces  

Microsoft Academic Search

Abstract— Biped robots based on the concept of (passive) dynamic walking are far simpler than the traditional fully- controlled walking robots, while achieving a more natural gait and consuming less energy. However, lightly actuated dynamic walking robots, which rely on the natural limit cycle of their mechanical structure, are very sensitive to ground disturbances. Already a very small step down

Shouyi Wang; Jelmer Braaksma; Robert Babuska; Daan G. E. Hobbelen

2006-01-01

221

Quantum walks in waveguide-based optical quantum device  

NASA Astrophysics Data System (ADS)

We study multi-dimension quantum walks and its dimension reduction model. By using an waveguide-based optical quantum device, we demonstrate the quantum-walk in searching algorithms such as 2-D glued tree and 3-D hypercube graph. We discuss that the use of waveguide-based device is a good candidate to implement the quantum walks.

Wu, Nan; Hu, Haixing; Xu, Ping; Song, Fangmin; Li, Xiangdong

2014-05-01

222

Discrete-time random walks on diagrams (graphs) with cycles.  

PubMed

After a review of the diagram method for continuous-time random walks on graphs with cycles, the method is extended to discrete-time random walks. The basic theorems carry over formally from continuous time to discrete time. Three problems in tennis probabilities are used to illustrate random walks on discrete-time diagrams with cycles. PMID:3041408

Hill, T L

1988-08-01

223

REFERENCES FOR UNIT 1 (PHYSICS 653) Random walks  

E-print Network

.1 ------------ Howard C. Berg, 'Random Walks in Biology' (book), 2nd ed. 1993. {I'd put this on reserve, except CornellREFERENCES FOR UNIT 1 (PHYSICS 653) ========== === ==== = Random walks For Lec. 1 of Bacteria". Elliott W. Montroll, J. Math. Physics. 10, 753-765 (1969), "Random Walks on Lattices. III

Henley, Christopher L.

224

Biased Random Walks in Biology Edward Alexander Codling  

E-print Network

Biased Random Walks in Biology Edward Alexander Codling Submitted in accordance provided by the E.P.S.R.C. i #12;Abstract Random walks are used to describe the trajectories of many motile of the behaviour of such creatures. Simple diffusive random walk models, or position jump processes

Codling, Edward A.

225

Compliant leg behaviour explains basic dynamics of walking and running  

E-print Network

that of walking (Full & Koditschek 1999). For instance, instead of the large vertical amplitudes suggested the stance dynamics of running, stiff legs cannot reproduce that of walking. With a simple bipedal spring corresponding models, the inverted pendulum model for walking (Alexander 1976; Mochon & McMahon 1980

226

Speeding up random walks by choosing unvisited edges or vertices  

E-print Network

, and Tom Friedetzky3 1 School of Computing Science, Simon Fraser University, Burnaby, Canada 2 Department in a random order. Each time a vertex is left during the walk, the next neighbour w.r.t. this permutation of several modified random walk pro- cesses. A random walk P on a graph G = (V, E) is defined as follows

Cooper, Colin

227

Walkaround: Mobile Balance Support for Therapy of Walking  

Microsoft Academic Search

We describe here the Walkaround, a new rehabilitation device that allows walking without hand support of individuals with limited ability to control posture. The design of this device was motivated by the recent development of functional electrical therapy of walking in individuals with hemiplegia, who in many cases need postural and body weight assistance while walking. The Walkaround assists humans

Aleksandar Veg; Dejan B. Popovic

2008-01-01

228

Co-creative walking support as music therapy  

Microsoft Academic Search

Mutual adaptation process in musical communication is often used for walking support and rehabilitation. But this kind of supporting system is not realized yet. So the purpose of this research is to construct walking support system as a musical communication process. Our strategy is to extend walk-mate system, which realizes mutual adaptation process between human and virtual walker by exchanging

Y. Kurizuka; Y. Miyake; Y. Kobayashi

2004-01-01

229

Walking support system based on musical exercise therapy  

Microsoft Academic Search

Mutual adaptation process in musical communication is often used for walking support and rehabilitation. But this kind of supporting system is not realized yet. So the purpose of this research is to construct walking support system as a musical communication process. Our strategy is to extend Walk-Mate system, which realizes mutual adaptation process between human and virtual walker by exchanging

Y. Kurizuka; Y. Miyakel; Y. Kobayashi

2004-01-01

230

The Not-so-Random Drunkard's Walk  

ERIC Educational Resources Information Center

This dataset contains the results of a quasi-experiment, testing Karl Pearson's "drunkard's walk" analogy for an abstract random walk. Inspired by the alternate hypothesis that drunkards stumble to the side of their dominant hand, it includes data on intoxicated test subjects walking a 10' line. Variables include: the…

Ehrhardt, George

2013-01-01

231

The Integument of Water-walking Arthropods: Form and Function  

E-print Network

The Integument of Water-walking Arthropods: Form and Function John W.M. Busha , David L. Hub to understanding the complex nature of the interaction between water-walking arthropods and the air­water surface of water-walking arthropods according to their function. Particular attention is given to the influence

Bush, John W.M.

232

What mechanisms coordinate leg movement in walking arthropods?  

Microsoft Academic Search

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

233

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

234

Wheeling Walks: A Community Campaign Using Paid Media to Encourage Walking Among Sedentary Older Adults  

Microsoft Academic Search

Background. Mass media may effect communitywide changes in health awareness, attitude, and behavior, but the approach remains unproven for physical activity.Methods. Wheeling Walks promoted walking among sedentary 50- to 65-year-old adults in a West Virginia city of 31,420 people. This quasi-experimental communication intervention used theory of planned behavior and transtheoretical model constructs to change behavior by promoting 30 min of

Bill Reger; Linda Cooper; Steven Booth-Butterfield; Holli Smith; Adrian Bauman; Margo Wootan; Susan Middlestadt; Bess Marcus; Felicia Greer

2002-01-01

235

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

PubMed Central

The most common functional motor goal of lower extremity rehabilitation is to improve walking ability. For reasons of feasibility, safety or intensity, devices are frequently used to facilitate or augment gait training. The objective of this study was to compare the muscle activity patterns of the quadriceps and hamstring muscles during four conditions: overground walking, treadmill walking, stationary cycling, and elliptical training. Ten healthy adults (6 male, 4 female; mean age 22.7 ± 2.9 yrs, range 20–29) participated. Surface electromyographic data were recorded from the rectus femoris and semitendinosus. Linear envelope curves were generated and time normalized from 0–100% cycle. The mean plus three standard deviations from a static trial was used as the threshold for muscle activity. Repeated measures analysis of variance procedures were used to detect differences between conditions. Elliptical training demonstrated greater quadriceps activity and greater quadriceps/hamstrings coactivation than all other conditions. Consistent with previous work, treadmill walking demonstrated greater quadriceps activity than overground walking. Minimal differences in hamstring activation were observed between conditions, limited to lower peak activity during cycling compared to treadmill walking. These results provide normative values for quadriceps and hamstring activation for different locomotor training methods and may assist in selecting the most appropriate training device for specific patients. Clinicians and researchers should also consider the kinematic and kinetic differences between tasks, which cannot necessarily be inferred from muscle activation patterns. PMID:21215636

Prosser, Laura A.; Stanley, Christopher J.; Norman, Tracy L.; Park, Hyung S.; Damiano, Diane L.

2012-01-01

236

Analysis and Comparison between War Driving and War Walk-ing in Metropolitan WiFi Radio Maps  

E-print Network

Analysis and Comparison between War Driving and War Walk- ing in Metropolitan WiFi Radio Maps Arvin method for building large-scale radio maps in metropolitan Wi-Fi localization. Although the human effort than that of war walking. This work compares radio maps built from war driving and walking and analyzes

Ouhyoung, Ming

237

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

238

Scaling of the atmosphere of self-avoiding walks  

E-print Network

The number of free sites next to the end of a self-avoiding walk is known as the atmosphere. The average atmosphere can be related to the number of configurations. Here we study the distribution of atmospheres as a function of length and how the number of walks of fixed atmosphere scale. Certain bounds on these numbers can be proved. We use Monte Carlo estimates to verify our conjectures. Of particular interest are walks that have zero atmosphere, which are known as trapped. We demonstrate that these walks scale in the same way as the full set of self-avoiding walks, barring an overall constant factor.

A. L. Owczarek; T. Prellberg

2008-06-06

239

Cardiovascular Responses Associated with Daily Walking in Subacute Stroke  

PubMed Central

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. PMID:23476892

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

2013-01-01

240

Coverage-Adaptive Random Walks for Fast Sensory Data Collection  

NASA Astrophysics Data System (ADS)

Random walks in wireless sensor networks can serve as fully local, very simple strategies for sink motion that significantly reduce energy dissipation a lot but increase the latency of data collection. To achieve satisfactory energy-latency trade-offs the sink walks can be made adaptive, depending on network parameters such as density and/or history of past visits in each network region; but this increases the memory requirements. Towards better balances of memory/performance, we propose three new random walks: the Random Walk with Inertia, the Explore-and-Go Random Walk and the Curly Random Walk; we also introduce a new metric (Proximity Variation) that captures the different way each walk gets close to the network nodes over time. We implement the new walks and experimentally compare them to known ones. The simulation findings demonstrate that the new walks' performance (cover time) gets close to the one of the (much stronger) biased walk with memory, while in some other respects (partial cover time, proximity variation) they even outperform it. We note that the proposed walks have been fine-tuned in the light of experimental findings.

Angelopoulos, Constantinos-Marios; Nikoletseas, Sotiris; Patroumpa, Dimitra; Rolim, Jose

241

Relationships between Muscle Contributions to Walking Subtasks and Functional Walking Status in Persons with Post-Stroke Hemiparesis  

PubMed Central

Background Persons with post-stroke hemiparesis usually walk slowly and asymmetrically. Stroke severity and functional walking status are commonly predicted by post-stroke walking speed. The mechanisms that limit walking speed, and by extension functional walking status, need to be understood to improve post-stroke rehabilitation methods. Methods Three-dimensional forward dynamics walking simulations of hemiparetic subjects (and speed-matched controls) with different levels of functional walking status were developed to investigate the relationships between muscle contributions to walking subtasks and functional walking status. Muscle contributions to forward propulsion, swing initiation and power generation were analyzed during the pre-swing phase of the gait cycle and compared between groups. Findings Contributions from the paretic leg muscles (i.e., soleus, gastrocnemius and gluteus medius) to forward propulsion increased with improved functional walking status, with the non-paretic leg muscles (i.e., rectus femoris and vastii) compensating for reduced paretic leg propulsion in the limited community walker. Contributions to swing initiation from both paretic (i.e., gastrocnemius, iliacus and psoas) and non-paretic leg muscles (i.e., hamstrings) also increased as functional walking status improved. Power generation was also an important indicator of functional walking status, with reduced paretic leg power generation limiting the paretic leg contribution to forward propulsion and leg swing initiation. Interpretation These results suggest that deficits in muscle contributions to the walking subtasks of forward propulsion, swing initiation and power generation are directly related to functional walking status and that improving output in these muscle groups may be an effective rehabilitation strategy for improving post-stroke hemiparetic walking. PMID:21251738

Hall, A.L.; Peterson, C.L.; Kautz, S.A.; Neptune, R.R.

2011-01-01

242

Generalized atmospheric sampling of self-avoiding walks  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a new Monte Carlo method for sampling lattice self-avoiding walks. The method, which we call 'GAS' (generalized atmospheric sampling), samples walks along weighted sequences by implementing elementary moves generated by the positive, negative and neutral atmospheric statistics of the walks. A realized sequence is weighted such that the average weight of states of length n is proportional to the number of self-avoiding walks from the origin cn. In addition, the method also self-tunes to sample from uniform distributions over walks of lengths in an interval [0, nmax]. We show how to implement GAS using both generalized and endpoint atmospheres of walks and analyse our data to obtain estimates of the growth constant and entropic exponent of self-avoiding walks in the square and cubic lattices.

van Rensburg, E. J. Janse; Rechnitzer, A.

2009-08-01

243

New wearable walking-type continuous passive motion device for postsurgery walking rehabilitation.  

PubMed

While total knee arthroplasty is useful for treating osteoarthritis of the knee, the success of this treatment depends on effective rehabilitation. The goal of this study was to develop an assistive device for post-total knee arthroplasty patients for walking rehabilitation and for shortening the hospitalization period. We developed a brace electronic assist system termed the knee assistive instrument for walking rehabilitation (KAI-R) to illustrate the need for training during postoperative rehabilitation. Sixteen osteoarthritis patients (1 male and 15 females; average age 68.9 years) who underwent total knee arthroplasty were analyzed before operation and 2-4 weeks after operation, and 25 healthy individuals (14 males and 11 females; average age 26.2 years) formed the control group. Based on the pre- and postoperative data on peak knee flexion angle, foot height, and walking velocity, we developed the KAI-R, which consists of an assistive mechanism for the knee joint, a hip joint support system, and a foot pressure sensor system and is driven by a CPU board that generates the walking pattern. We then tested the walking gait in seven healthy volunteers with and without KAI-R assistance. KAI-R increased the peak flexion angle of the knee and foot height in all seven volunteers; their range of motion of the knee joint was increased. However, KAI-R also decreased the walking velocity of subjects, which was explained by reaction delay and slightly compromised physical balance, which was caused by wearing the KAI-R. KAI-R is useful for gait improvement. In future studies, KAI-R will be investigated in a clinical trial for its ability for walking rehabilitation in post-total knee arthroplasty patients. PMID:23636753

Zhu, Yong; Nakamura, Masahiro; Horiuchi, Tadahiro; Kohno, Hideki; Takahashi, Rei; Terada, Hidetsugu; Haro, Hirotaka

2013-07-01

244

Generalized ruin problems and asynchronous random walks  

NASA Astrophysics Data System (ADS)

We consider a gambling game with two different kinds of trials and compute the duration of the game (averaged over all possible initial capitals of the players) by a mapping of the problem to a 1D lattice walk of two particles reacting upon encounter. The relative frequency of the trials is governed by the synchronicity parameter p of the random walk. The duration of the game is given by the mean time to reaction, which turns out to display a different behavior for even and odd lattices, i.e. this quantity is monotonic in p for odd lattices and non-monotonic for even lattices. In the game picture, this implies that the players minimize the duration of the game by restricting themselves to one type of trial if their joint capital is odd, otherwise a non-symmetric mixture of both trials is needed.

Abad, E.

2005-07-01

245

Random Walk Picture of Basketball Scoring  

E-print Network

We present evidence, based on play-by-play data from all 6087 games from the 2006/07--2009/10 seasons of the National Basketball Association (NBA), that basketball scoring is well described by a weakly-biased continuous-time random walk. The time between successive scoring events follows an exponential distribution, with little memory between different scoring intervals. Using this random-walk picture that is augmented by features idiosyncratic to basketball, we account for a wide variety of statistical properties of scoring, such as the distribution of the score difference between opponents and the fraction of game time that one team is in the lead. By further including the heterogeneity of team strengths, we build a computational model that accounts for essentially all statistical features of game scoring data and season win/loss records of each team.

Gabel, Alan

2011-01-01

246

The Evolution Of Odetics Walking Machine Technology  

NASA Astrophysics Data System (ADS)

The development of the Odetics walking machine technology is presented from the original concept aimed at feasibility demonstration through advanced designs with specific mission applications. The high power efficiency and high strength-to-weight ratio features of the original leg designs are presented along with the hierarchical control concepts. The evolutionary development of improved gait control for faster, smoother walking, and the demands imposed by uneven terrain and stair climbing are discussed. Sensor integration for motion control and vision for teleoperation are covered, as is operator control station design. Specific walker design concepts to accomplish nuclear power plant maintenance and a Mars Rover mission are presented. The nuclear power plant design integrates a six-degree of freedom manipulator arm onto an improved design walker with a fiber-optic link to the operator control station. The Mars Rover mission concept is aimed at maximum packaging density, light weight and high mobility on steep and soft terrain while minimizing power consumption.

Bartholet, Stephen J.

1987-02-01

247

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

248

Quantum walks, automata, and structured search  

NASA Astrophysics Data System (ADS)

We explore the application of a quantum algorithm to optimisation problems over a structured space. For example, problems in automated planning can be represented as automata. These automata are shown to posses algebraic structure that can be exploited by a quantum period finding algorithm. The fact that the quantum walk also provides exponential speed-up over these same structures is of particular interest and results of our investigation will be presented.

Naguleswaran, Sanjeev; Fuss, Ian; White, Langford B.

2007-06-01

249

Neighborhood Design for Walking and Biking  

PubMed Central

Background Neighborhood designs often relate to physical activity and to BMI. Purpose Does neighborhood walkability/bikeability relate to BMI and obesity risk and does moderate-to-vigorous physical activity (MVPA) account for some of the relationship? Methods Census 2000 provided walkability/bikeability measures—block group proportions of workers who walk or bike to work, housing age, and population density—and National Health and Nutrition Examination Study (NHANES 2003–2006) provided MVPA accelerometer measures. Regression analyses (2011–2012) adjusted for geographic clustering and multiple control variables. Results Greater density and older housing were associated with lower male BMI in bivariate analyses, but there were no density and housing age effects in multivariate models. For women, greater proportions of neighborhood workers who walk to work (M=0.02) and more MVPA was associated with lower BMI and lower obesity risk. For men, greater proportions of workers who bike to work (M=0.004) and more MVPA was associated with lower BMI and obesity risk. For both effects, MVPA partially mediated the relationships between walkability/bikeability and BMI. If such associations are causal, doubling walk and bike-to-work proportions (to 0.04 and 0.008) would have –0.3 and –0.33 effects on the average BMIs of adult women and men living in the neighborhood. This equates to 1.5 lbs for a 64” woman and 2.3 lbs for a 69” man. Conclusions Although walking/biking to work is rare in the U.S., greater proportions of such workers in neighborhoods relate to lower weight and higher MVPA. Bikeability merits greater attention as a modifiable activity-friendliness factor, particularly for men. PMID:23415119

Brown, Barbara B.; Smith, Ken R.; Hanson, Heidi; Fan, Jessie X.; Kowaleski-Jones, Lori; Zick, Cathleen D.

2013-01-01

250

Baby Carriage: Infants Walking With Loads  

Microsoft Academic Search

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

251

Individual characteristics of human walking mechanics  

Microsoft Academic Search

Twenty-four subjects walked at different speeds (V) from 0.4 to 2.6 m s–1, while motion and ground reaction forces were recorded in 3-D space. The total mechanical energy of each body segment was\\u000a computed as the sum of the gravitational potential, translation and rotation kinetic energies. Energy profiles reveal that\\u000a there are inter-individual differences, particularly at moderate and fast V.

L. Bianchi; D. Angelini; F. Lacquaniti

1998-01-01

252

Joint Leg Walking and Hybrid Robot Demonstrators  

Microsoft Academic Search

\\u000a Design of two and multi-legged robots like four legged, six legged, and eight legged robots shows a practical usefulness of\\u000a Bionics for the domain of robotics. Depending on the number of legs, such robotic platforms can be inspired from body constitution,\\u000a walking mechanics, and behavior of humans, animals (four legged), insects (six legged), or spiders (eight legged). There is\\u000a also

Bojan Jakimovski

253

Random walks on highly symmetric graphs  

Microsoft Academic Search

We consider uniform random walks on finite graphs withn nodes. When the hitting times are symmetric, the expected covering time is at least 1\\/2n logn-O(n log logn) uniformly over all such graphs. We also obtain bounds for the covering times in terms of the eigenvalues of the transition matrix of the Markov chain. For distance-regular graphs, a general lower bound

Luc Devroye; Amine Sbihi

1990-01-01

254

Cavity QED-based quantum walk  

SciTech Connect

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

255

Integrating walks into academics: Authentic learning experiences  

Microsoft Academic Search

The goals of this university\\/school partnership were to: (1) integrate walks into the curriculum in a kindergarten and a fourth\\u000a grade classroom to enrich student learning, (2) promote university\\/school partnerships in collaborating on curriculum development,\\u000a (3) provide a teacher educator, four student teachers, and two experienced teachers an opportunity to put theory into practice,\\u000a and (4) reflect on benefits to

Lenore Peachin Wineberg

2000-01-01

256

Fast Cloth Animation on Walking Avatars  

Microsoft Academic Search

This paper describes a fast technique for animating clothing on walking humans. It exploits a mass-spring cloth model but applies a new velocity directional modification approach to overcome its super-elasticity. The algorithm for cloth-body collision detection and response is based on image-space interference tests, unlike the existing ones that use object-space checks. The modern workstations' graphics hardware is used not

T. Ivanov Vassilev; B. Spanlang; Yiorgos Chrysanthou

2001-01-01

257

Asymptotic properties of a bold random walk  

NASA Astrophysics Data System (ADS)

In a recent paper we proposed a non-Markovian random walk model with memory of the maximum distance ever reached from the starting point (home). The behavior of the walker is different from the simple symmetric random walk only when she is at this maximum distance, where, having the choice to move either farther or closer, she decides with different probabilities. If the probability of a forward step is higher than the probability of a backward step, the walker is bold and her behavior turns out to be superdiffusive; otherwise she is timorous and her behavior turns out to be subdiffusive. The scaling behavior varies continuously from subdiffusive (timorous) to superdiffusive (bold) according to a single parameter ? ?R. We investigate here the asymptotic properties of the bold case in the nonballistic region ? ?[0,1/2], a problem which was left partially unsolved previously. The exact results proved in this paper require new probabilistic tools which rely on the construction of appropriate martingales of the random walk and its hitting times.

Serva, Maurizio

2014-08-01

258

Gait Recognition and Walking Exercise Intensity Estimation  

PubMed Central

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

2014-01-01

259

Gait recognition and walking exercise intensity estimation.  

PubMed

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

260

From Lévy Walks to Superdiffusive Shock Acceleration  

NASA Astrophysics Data System (ADS)

In this paper, we present a general scenario for nondiffusive transport and we investigate the influence of anomalous, superdiffusive transport on Fermi acceleration processes at shocks. We explain why energetic particle superdiffusion can be described within the Lévy walk framework, which is based on a power-law distribution of free path lengths and on a coupling between free path length and free path duration. A self-contained derivation of the particle mean square displacement, which grows as lang?x 2rang = 2D ? t ? with ? > 1, and the particle propagator, is presented for Lévy walks, making use of a generalized version of the Montroll-Weiss equation. We also derive for the first time an explicit expression for the anomalous diffusion coefficient D ? and we discuss how to obtain these quantities from energetic particle observations in space. The results are applied to the case of particle acceleration at an infinite planar shock front. Using the scaling properties of the Lévy walk propagator, the energy spectral indices are found to have values smaller than the ones predicted by the diffusive shock acceleration theory. Furthermore, when applying the results to ions with energies of a few MeV accelerated at the solar wind termination shock, the estimation of the anomalous diffusion coefficient associated with the superdiffusive motion gives acceleration times much smaller than the ones related to normal diffusion.

Zimbardo, Gaetano; Perri, Silvia

2013-11-01

261

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

PubMed

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

262

Does parkland influence walking? The relationship between area of parkland and walking trips in Melbourne, Australia  

PubMed Central

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. PMID:22989176

2012-01-01

263

Optimal speeds for walking and running, and walking on a moving walkway  

NASA Astrophysics Data System (ADS)

Many aspects of steady human locomotion are thought to be constrained by a tendency to minimize the expenditure of metabolic cost. This paper has three parts related to the theme of energetic optimality: (1) a brief review of energetic optimality in legged locomotion, (2) an examination of the notion of optimal locomotion speed, and (3) an analysis of walking on moving walkways, such as those found in some airports. First, I describe two possible connotations of the term "optimal locomotion speed:" that which minimizes the total metabolic cost per unit distance and that which minimizes the net cost per unit distance (total minus resting cost). Minimizing the total cost per distance gives the maximum range speed and is a much better predictor of the speeds at which people and horses prefer to walk naturally. Minimizing the net cost per distance is equivalent to minimizing the total daily energy intake given an idealized modern lifestyle that requires one to walk a given distance every day—but it is not a good predictor of animals' walking speeds. Next, I critique the notion that there is no energy-optimal speed for running, making use of some recent experiments and a review of past literature. Finally, I consider the problem of predicting the speeds at which people walk on moving walkways—such as those found in some airports. I present two substantially different theories to make predictions. The first theory, minimizing total energy per distance, predicts that for a range of low walkway speeds, the optimal absolute speed of travel will be greater—but the speed relative to the walkway smaller—than the optimal walking speed on stationary ground. At higher walkway speeds, this theory predicts that the person will stand still. The second theory is based on the assumption that the human optimally reconciles the sensory conflict between the forward speed that the eye sees and the walking speed that the legs feel and tries to equate the best estimate of the forward speed to the naturally preferred speed. This sensory conflict theory also predicts that people would walk slower than usual relative to the walkway yet move faster than usual relative to the ground. These predictions agree qualitatively with available experimental observations, but there are quantitative differences.

Srinivasan, Manoj

2009-06-01

264

Walking with coffee: when and why coffee spills  

NASA Astrophysics Data System (ADS)

In our busy lives, almost all of us have to walk with a cup of coffee. Needless to say, under certain conditions we spill that precious liquid. This is a common example of the interplay between the mechanics of the complex motion of a walking individual and the fluid dynamics of a low viscosity liquid contained in a cup. We report on the results of an experimental investigation undertaken to explore the particular conditions under which coffee spills. Frame-by-frame analysis of recorded movies helps to elucidate the trajectory of the cup for various walking speeds and initial liquid levels. These kinematics, including both regular and irregular motions, are connected to instances during walking that result in spilled liquid. The coupling between mechanical aspects of walking and the fluid motion are analyzed based on which we determine a basic operational space with which one can confidently walk with cup in hand.

Mayer, Hans C.; Krechetnikov, Rouslan

2011-11-01

265

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

266

Quantum Walk on a Line with Two Entangled Particles  

E-print Network

We introduce the concept of a quantum walk with two particles and study it for the case of a discrete time walk on a line. A quantum walk with more than one particle may contain entanglement, thus offering a resource unavailable in the classical scenario and which can present interesting advantages. In this work, we show how the entanglement and the relative phase between the states describing the coin degree of freedom of each particle will influence the evolution of the quantum walk. In particular, the probability to find at least one particle in a certain position after $N$ steps of the walk, as well as the average distance between the two particles, can be larger or smaller than the case of two unentangled particles, depending on the initial conditions we choose. This resource can then be tuned according to our needs, in particular to enhance a given application (algorithmic or other) based on a quantum walk. Experimental implementations are briefly discussed.

Y. Omar; N. Paunkovic; L. Sheridan; S. Bose

2004-11-09

267

Walk, Not Wait: Faster Sampling Over Online Social Networks  

E-print Network

In this paper, we introduce a novel, general purpose, technique for faster sampling of nodes over an online social network. Specifically, unlike traditional random walk which wait for the convergence of sampling distribution to a predetermined target distribution - a waiting process that incurs a high query cost - we develop WALK-ESTIMATE, which starts with a much shorter random walk, and then proactively estimate the sampling probability for the node taken before using acceptance-rejection sampling to adjust the sampling probability to the predetermined target distribution. We present a novel backward random walk technique which provides provably unbiased estimations for the sampling probability, and demonstrate the superiority of WALK-ESTIMATE over traditional random walks through theoretical analysis and extensive experiments over real world online social networks.

Nazi, Azade; Thirumuruganathan, Saravanan; Zhang, Nan; Das, Gautam

2014-01-01

268

Walk-in refrigerators are key to proper cold storage.  

PubMed

Often overlooked as an important kitchen design element, properly sized refrigeration and freezing equipment is an important contributor to a kitchen's functionality. In many operations, particularly large-volume units, walk-in refrigerators are the anchors of a good cold-storage system. A walk through three different foodservice operations--a college, a hotel and a hospital--finds walk-ins at work. PMID:10112028

Townsend, R

1991-06-12

269

Discrete-time interacting quantum walks and quantum Hash schemes  

NASA Astrophysics Data System (ADS)

Through introducing discrete-time quantum walks on the infinite line and on circles, we present a kind of two-particle interacting quantum walk which has two kinds of interactions. We investigate the characteristics of this kind of quantum walk and the time evolution of the two particles. Then we put forward a kind of quantum Hash scheme based on two-particle interacting quantum walks and discuss their feasibility and security. The security of this kind of quantum Hash scheme relies on the infinite possibilities of the initial state rather than the algorithmic complexity of hard problems, which will greatly enhance the security of the Hash schemes.

Li, Dan; Zhang, Jie; Guo, Fen-Zhuo; Huang, Wei; Wen, Qiao-Yan; Chen, Hui

2013-03-01

270

Relativistic Connection of Continuous and Discrete Quantum Walks  

NASA Astrophysics Data System (ADS)

Quantum algorithms, based on a quantum-mechanical generalization of random walks, have been shown to be very effective at solving local search problems. These quantum walks come in two very different forms (discrete and continuous-time) with surprisingly similar properties. An open problem has been to identify just what makes these two walks so similar. In this talk I present the analytical connection of these two walks, by way of an analogy with properties of the Dirac equation, including entanglement, zitterbewegung, and most importantly, relativistic wave-packet spreading.

Strauch, Frederick

2006-03-01

271

18.366 Random Walks and Diffusion, Spring 2005  

E-print Network

Discrete and continuum modeling of diffusion processes in physics, chemistry, and economics. Topics include central limit theorems, continuous-time random walks, Levy flights, correlations, extreme events, mixing, ...

Bazant, Martin Z.

272

Assessing walking speed in clinical research: a systematic review  

PubMed Central

Objective To provide a systematic review and describe how assessments of walking speed are reported in the health care literature. Methods MEDLINE electronic database and bibliographies of select articles were searched for terms describing walking speed and distances walked. The search was limited to English language journals from 1996 to 2006. The initial title search yielded 793 articles. A review of the abstracts reduced the number to 154 articles. Of these, 108 provided sufficient information for inclusion in the current review. Results Of the 108 studies included in the review 61 were descriptive, 39 intervention and 8 randomized controlled trials. Neurological (n = 55) and geriatric (n = 27) were the two most frequent participant groups in the studies reviewed. Instruction to walk at a usual or normal speed was reported in 55 of the studies, while 31 studies did not describe speed instructions. A static (standing) start was slightly more common than a dynamic (rolling) start (30 vs 26 studies); however, half of the studies did not describe the starting protocol. Walking 10, 6 and 4 m was the most common distances used, and reported in 37, 20 and 11 studies respectively. Only four studies included information on whether verbal encouragement was given during the walking task. Conclusions Tests of walking speed have been used in a wide range of populations. However, methodologies and descriptions of walking tests vary widely from study to study, which makes comparison difficult. There is a need to find consensus for a standardized walking test methodology. PMID:18462283

Graham, James E.; Ostir, Glenn V.; Fisher, Steven R.; Ottenbacher, Kenneth J.

2009-01-01

273

The quantum to classical transition for random walks  

E-print Network

We look at two possible routes to classical behavior for the discrete quantum random walk on the line: decoherence in the quantum ``coin'' which drives the walk, or the use of higher-dimensional 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.

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

2002-08-30

274

When to walk away from a deal.  

PubMed

Deal making is glamorous; due diligence is not. That simple statement goes a long way toward explaining why so many companies have made so many acquisitions that have produced so little value. The momentum of a transaction is hard to resist once senior management has the target in its sights. Companies contract "deal fever," and due diligence all too often becomes an exercise in verifying the target's financial statements rather than conducting a fair analysis of the deal's strategic logic and the acquirer's ability to realize value from it. Seldom does the process lead managers to kill potential acquisitions, even when the deals are deeply flawed. In a recent Bain & Company survey of 250 international executives with M&A responsibilities, only 30% of them were satisfied with the rigor of their due diligence. And fully a third admitted they hadn't walked away from deals they had nagging doubts about. In this article, the authors, all Bain consultants, emphasize the importance of comprehensive due diligence practices and suggest ways companies can improve their capabilities in this area. They provide rich real-world examples of companies that have had varying levels of success with their due diligence processes, including Safeway, Odeon, American Sea-foods, and Kellogg's. Effective due diligence requires answering four basic questions: What are we really buying? What is the target's stand-alone value? Where are the synergies--and the skeletons? And what's our walk-away price? Each of these questions will prompt an even deeper level of querying that puts the broader, strategic rationale for acquisitions under a microscope. Successful acquirers pay close heed to the results of such in-depth investigations and analyses--to the extent that they are prepared to walk away from a deal, even in the very late stages of negotiations. PMID:15077370

Cullinan, Geoffrey; Le Roux, Jean-Marc; Weddigen, Rolf-Magnus

2004-04-01

275

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

Microsoft Academic Search

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

276

Quantum-walk-based search and centrality  

NASA Astrophysics Data System (ADS)

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.

2010-10-01

277

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

278

Random walks and partial differential equations  

NASA Astrophysics Data System (ADS)

Let A be a bounded region in 3D, and let ? A be its surface boundary which we assume to be absorbing. Enclose A and its boundary by a box with sides x = a, x = b, y = c, y = d, z = e, and z = f where a < b, c < d, and e < f. With delta as the step length in the random walk, assume that the intervals [a,b], [c,d], [e,f] can be subdivided into the set of points xk = a + delta k, y1 = c + delta l, and zq = e + delta q respectively with 0 ? k ? n, 0 ? l ? m, 0 ? q ? t, x n = b, ym, = d and zt = f. We say (xk,yl, z q) is an interior point of A, if it does not lie on ?A. If one of the neighboring points lies on ? A or is exterior to A we call it a boundary point. In this dissertation, working primarily in 3D, we study the following problems: (i) What is the probability that a particle starting at an interior point (x, y, z) reaches the specified boundary point ( xi, yj, zv) before it reaches and is absorbed at any other boundary point?, and (ii) What is the probability that a particle starting at an interior point ( x, y, z) in the region A reaches a specified interior point (?, eta, gamma) before it reaches a boundary point and is absorbed?, and (iii) What is the "mean first passage time" for each point (x, y, z)? Under various conditions we obtain partial differential equations of various types, and where appropriate complete the initial value problems by specifying initial or boundary conditions. These equations all result from taking limits of difference equations that serve as models for the discrete random walk problems studied. Following the approach of S. Goldstein we also study partial difference equations for correlated random walks, leading to variants of the telegraph equation, an equation that governs the propagation of signals on telegraph lines. Finally in the self assembling of particles, we apply the random walk concept to model, simulate, and characterize cluster growth and form.

Ampadu, Clement B.

279

Let Your Ears Do the Walking  

NSDL National Science Digital Library

Students experience a simulation of echolation, using the sensory method to walk along a path while blindfolded. This relates to the issue of bycatching by fisheries, which they learned about In the associated lesson. Bycatching affects marine animals, especially dolphins, which use echolocation to identify the location of objects in the water, but have difficulty identifying nets, and thus are often caught accidentally. Students 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.

Engineering K-Phd Program

280

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

Microsoft Academic Search

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

281

Random walks and the additive coagulation equation  

NASA Astrophysics Data System (ADS)

Numerical simulations of hierarchical gravitational clustering in an expanding universe show that, as time evolves, small clusters merge with each other to form larger clusters, whereas fragmentation of clusters is relatively uncommon. Stochastic models of the hierarchical clustering process can provide insight into, as well as useful approximations to, the evolution measured in these simulations. The Poisson random walk excursion model, the Poisson Galton-Watson branching process, and the monodisperse additive coagulation equation are three examples of such stochastic models. When initially identical particles cluster from an initially Poisson spatial distibution, all three approaches give essentially the same description of how clusters grow. This paper shows that clustering from an initially Poisson distribution in which the initial particles do not all have the same mass can be described by simple generalizations of the models above. Such an initial distribution is said to be `compound Poisson'. Therefore, excursions of random walks associated with compound Poisson distributions are studied here. In such an excursion set model, clusters grow in essentially the same way as they do in the polydisperse additive coagulation model. Thus, the interrelations between excursion set, branching process and coagulation models of clustering, associated with the Poisson distribution, also apply to compound Poisson distributions. This means that, within the context of these models, when the initial conditions are compound Poisson then merger and accretion rates, and the entire merger history tree, can all be written analytically, just as for clustering from Poisson initial conditions.

Sheth, Ravi K.

1998-04-01

282

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

283

Walk-through surveys for child labor.  

PubMed

Child labor is increasing in both developing and developed countries. Walk-through surveys were used to identify children, aged 8-15 years, working in six sites in Tel Aviv and Jerusalem, the largest cities in Israel. Of the 45 children who were interviewed, 20 were Jewish Israeli born, 19 were recent Jewish immigrants from the former Soviet Union, and six were Arabs from Judea, Samaria, and Gaza. The majority of children were either too young for employment, according to the Israeli Child Labor Laws, and/or receiving less than the legal minimum wage. Many were performing physical labor that might be expected to interfere with normal growth and development. Many of the children had visible signs of impaired physical health. Some were subjected to physical and/or verbal abuse. Walk-through surveys are recommended as a tool for routine use for surveillance of hazardous working conditions, case-finding, and evaluating the efficacy of preventive measures. The World Health Organization recommendations are emphasized to eliminate hazardous working conditions and to provide on-the-job health and social services to working children. PMID:7892831

Feingold, E; Wasser, J

1994-12-01

284

Technology-Based Programs to Promote Walking Fluency or Improve Foot-Ground Contact during Walking: Two Case Studies of Adults with Multiple Disabilities  

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

285

Development Of a Control System For a 2D Biped Walking Robotic Testbed  

E-print Network

Due to the great potential promise of bipedal walking robots, it was determined that the Jaywalker, a first generation bipedal walking testbed, should be designed and built as a platform for the study of bipedal walking ...

Knopp, Michael D.

2012-05-31

286

A Proposal for Data Collection: Establishing Pedestrian Walking Speeds  

E-print Network

, suburbs, school zone, senior center, etc.) will be included in the study. The study design will determine on Uniform Traffic Control Devices (MUTCD) currently recommends that a normal pedestrian walking speed of 4 been a select number of studies on pedestrian walking speeds in the past (see Laplante and Kaeser, ITE

Bertini, Robert L.

287

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

288

Optimal On-Line Walking Pattern Generation for Biped Robots  

Microsoft Academic Search

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

289

Blind Walking of a Planar Bipedal Robot on Sloped Terrain  

Microsoft Academic Search

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

290

Promoting Discussion in the Science Classroom Using Gallery Walks  

ERIC Educational Resources Information Center

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. (Contains 4 tables and…

Francek, Mark

2006-01-01

291

Walking in Beauty: An American Indian Perspective on Social Justice  

ERIC Educational Resources Information Center

The purpose of this article is to introduce "walking in beauty," an American Indian spiritual perspective related to social justice that emphasizes beauty, harmony, connectedness/unity of experience, and imagination. Walking in beauty includes 3 processes: embodiment, creativity, and appreciation of the sublime. Recommendations are offered for…

Eason, Evan Allen; Robbins, Rockey

2012-01-01

292

Random walks in random environment Tom Schmitz (MPI Leipzig)  

E-print Network

Random walks in random environment Tom Schmitz (MPI Leipzig) The model of random walks in random environment (RWRE) originates from physical and biological sciences and describes a random motion random variables, creating thus a "random environment" for the walker. More specifically, we only allow

Thalmaier, Anton

293

Online Appendix to: CyberWalk: Enabling Unconstrained Omnidirectional  

E-print Network

, Article 24, Publication date: November 2011. #12;App­2 · J. L. Souman et al. similar design [IwataOnline Appendix to: CyberWalk: Enabling Unconstrained Omnidirectional Walking through Virtual Institute for Biological Cybernetics APPENDIX 1. A SHORT HISTORY OF OMNIDIRECTIONAL LOCOMOTION INTERFACES

De Luca, Alessandro

294

Cool Walking: A New Markov Chain Monte Carlo Sampling Method  

E-print Network

) temperature and the other at a low temperature. Nonlocal trial moves for the low temperature walker are generated by first sampling from the high-temperature distribution, then performing a statistical quenching process on the sampled configuration to generate a C-Walking jump move. C-Walking needs only one high-temperature

Head-Gordon, Teresa L.

295

AUTONOMOUS WALKING MACHINES: MOTION PLANNING USING SENSORY INFORMATION  

E-print Network

Abstract Current work on the motion planning of a Hexapod walking machine design is described here scheme of walking machine 2 Design Of Control System The advantage of hexapods is that they use simple control rules (i.e. stability, terrain adaptation). Our on- going research into hexapods includes

Portland State University

296

Lower trunk motion and speed-dependence during walking  

Microsoft Academic Search

BACKGROUND: There is a limited understanding about how gait speed influences the control of upper body motion during walking. Therefore, the primary purpose of this study was to examine how gait speed influences healthy individual's lower trunk motion during overground walking. The secondary purpose was to assess if Principal Component Analysis (PCA) can be used to gain further insight into

Justin J Kavanagh

2009-01-01

297

Camera Motions Improve the Sensation of Walking in Virtual Environments  

E-print Network

Camera Motions Improve the Sensation of Walking in Virtual Environments Anatole Lécuyer 1 SIAMES This paper investigates the use of camera motions, in order to improve the sensation of walking in a Virtual.e. a linear motion, as if the user was driving a car). Furthermore, the participants preferred oscillating

Lindeman, Robert W.

298

The Fibonacci quantum walk and its cassical trace map  

E-print Network

We study the quantum walk in momentum space using a coin arranged in quasi-periodic sequences following a Fibonacci prescription. We build for this system a classical map based on the trace of the evolution operator. The sub-ballistic behavior of this quantum walk is connected with the power-law decay of the time correlations of the trace map.

Alejandro Romanelli

2008-02-15

299

Energetics of Actively Powered Locomotion Using the Simplest Walking Model  

Microsoft Academic Search

Human walking is a mechanically complex task that is powered by the activity of numerous muscles. This complexity makes it difficult to discern what principles govern the cost of transport. Simple models of walking have shown, however, that there are general principles that hold, such as the fact that the motion of the swing leg can be largely passive in

Arthur D. Kuo

2002-01-01

300

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

301

Computer Animation of Human Walking: a Survey Franck Multon1  

E-print Network

Computer Animation of Human Walking: a Survey Franck Multon1 , Laure France2 , Marie-Paule Cani Animation of human walking is a crucial problem in Computer Graphics: Many synthetic scenes involve virtual fteen years ago in Computer Graphics, with the rst work on \\knowledge- based" animation of human gures

Paris-Sud XI, Université de

302

Gait planning for energy efficiency in walking machines  

Microsoft Academic Search

This paper addresses the problem of achieving energy efficiency in statically stable walking machines without mechanically constraining the system. In contrast to previous work, power is minimized over an entire locomotion cycle, through optimal selection of walking parameters, rather than for a fixed instant of time only. Dynamic simulation experiments of a hexapod with full three degree-of-freedom legs are used

Duane W. Marhefka; David E. Orin

1997-01-01

303

Facilitating Effects of Fast and Slope Walking on Paraspinal Muscles  

PubMed Central

Objective To quantify the activation of the paraspinalis muscles (multifidus and erector spinae) at different walking velocities and slope with surface electromyography. Methods This study was a prospective experimental study involving ten healthy male participants. Surface electrodes were placed over the multifidus and erector spinae muscles at the L5 and L3 level. After the electrode was placed at the lumbar paraspinalis muscles, electromyography signals were recorded over 20 seconds. Data were collected three times during the walking exercise at a 0° gradient with the speed from 3 to 6 km/hr. At 7° gradient and 15° gradient, data were also collected three times but a walking speed of 4 km/hr. The area under the curve was calculated for quantitative measurement of muscle activation. Results While the muscle activation was increased at higher walking velocities at the L5 and L3 levels of the multifidus, the erector spinae muscle activation did not show any change at higher walking velocities. At L3 level of the multifidus and erector spine muscles, the muscle activation was significantly increased in 15° gradient compared to those seen in at 0° gradient. At L5 level, the multifidus and erector spinae muscle activation in 0° gradient was not significantly different from that those seen in 7° or 15° gradient. Conclusion Fast walking exercise activates lumbar multifidus muscles more than the slow walking exercise. Also, the mid lumbar muscles are comparatively more activated than low lumbar muscles when the walking slope increases.

Lee, Hee Song; Shim, Jae Sun; Lee, Seok Tae; Kim, MinYoung

2014-01-01

304

Stable Dynamic Walking over Rough Terrain Theory and Experiment  

E-print Network

"dynamic walking" biped robot walking over rough terrain. The proposed technique is to compute a transverse design. The proposed method is experimentally verified using a compass-gait walker: a two be applied to higher degree-of-freedom robots over arbitrary terrain and other impulsive mechan- ical systems

Tedrake, Russ

305

A rehabilitation walker with standing and walking assistance  

Microsoft Academic Search

This paper proposes a robotic walker system with standing and walking assistance function. Our system focuses on domestic use for aged person who needs nursing in their daily life. Our key ideas are two topics. The first topic is combination of standing assistance function and walking assistance function. In previous works, many assistance devices are specialized in only ldquostanding-up operationrdquo

Daisuke Chugo; Tai Asawa; Takuya Kitamura; Songmin Jia; Kunikatsu Takase

2008-01-01

306

Stably Extending Two-Dimensional Bipedal Walking to Three Dimensions  

Microsoft Academic Search

In this paper we develop a feedback control law that results in stable walking gaits on flat ground for a three-dimensional bipedal robotic walker given stable walking gaits for a two-dimensional bipedal robotic walker. This is achieved by combining disparate techniques that have been employed in the bipedal robotic community: controlled symmetries, geometric reduction and hybrid zero dynamics. Controlled symmetries

Aaron D. Ames; Robert D. Gregg

2007-01-01

307

Adaptive L?vy Walks in Foraging Fallow Deer  

PubMed Central

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. PMID:19668369

Focardi, Stefano; Montanaro, Paolo; Pecchioli, Elena

2009-01-01

308

Visual Acuity, Balance Control, and Walking Automaticity in Older Women  

E-print Network

Visual Acuity, Balance Control, and Walking Automaticity in Older Women Rachel J. Kralian, Erica D and walking automaticity in older adult women A decrease in visual acuity increases the variability of gait. Millett, Dain P. LaRoche Department of Kinesiology University of New Hampshire #12;· Gait changes in older

New Hampshire, University of

309

Strategies used to walk through a moving aperture  

Microsoft Academic Search

The objectives of the study were to determine what strategy (pursuit or interception) individuals used to pass through an oscillating target and to determine if individuals walked towards where they were looking. Kinematic and gaze behaviour data was collected from seven healthy female participants as they started at one of five different starting positions and walked 7m towards an oscillating

Michael E. Cinelli; Aftab E. Patla; Fran Allard

2008-01-01

310

Distracted walking: Cell phones increase injury risk for college pedestrians  

Microsoft Academic Search

IntroductionDistraction on cell phones jeopardizes motor-vehicle driver safety, but few studies examine distracted walking. At particular risk are college students, who walk frequently in and near traffic, have increased pedestrian injury rates compared to other age groups, and frequently use cell phones. Method: Using an interactive and immersive virtual environment, two experiments studied the effect of cell phone conversation on

Despina Stavrinos; Katherine W. Byington; David C. Schwebel

2011-01-01

311

Quantum walk search factors in the regime of weak measurement  

NASA Astrophysics Data System (ADS)

Our previous work brought some interesting results of the discrete Quantum Walks in the regime of Weak Measurement (QWWM or QWWV). Using the knowledge of such results of QWWM, we are now exploring the search algorithms and investigating the factors associated with such walk. The study of such factors like dimensionality, connectivity of the dataset and the strength of disorder or percolation are already studied by others in the context of general quantum walks. It is our interest to show the similarities and/or differences of such factors of general quantum walks with QWWV. The subject of decoherence in quantum walks is another challenging research topic at present. We are also exploring the topic of decoherence in QWWM or QWWV.

Ghoshal, Debabrata

2014-05-01

312

Increasing the dimensionality of quantum walks using multiple walkers  

E-print Network

We show that with the addition of multiple walkers, quantum walks on a line can be transformed into lattice graphs of higher dimension. Thus, multi-walker walks can simulate single-walker walks on higher dimensional graphs and vice versa. This exponential complexity opens up new applications for present-day quantum walk experiments. We discuss the applications of such higher-dimensional structures and how they relate to linear optics quantum computing. In particular we show that multi-walker quantum walks are equivalent to the BosonSampling model for linear optics quantum computation proposed by Aaronson & Arkhipov. With the addition of control over phase-defects in the lattice, which can be simulated with entangling gates, asymmetric lattice structures can be constructed which are universal for quantum computation.

Peter P. Rohde; Andreas Schreiber; Martin Stefanak; Igor Jex; Alexei Gilchrist; Christine Silberhorn

2012-05-09

313

Ballistic Phase of Self-Interacting Random Walks  

E-print Network

We explain a unified approach to a study of ballistic phase for a large family of self-interacting random walks with a drift and self-interacting polymers with an external stretching force. The approach is based on a recent version of the Ornstein-Zernike theory developed in earlier works. It leads to local limit results for various observables (e.g. displacement of the end-point or number of hits of a fixed finite pattern) on paths of n-step walks (polymers) on all possible deviation scales from CLT to LD. The class of models, which display ballistic phase in the "universality class" discussed in the paper, includes self-avoiding walks, Domb-Joyce model, random walks in an annealed random potential, reinforced polymers and weakly reinforced random walks.

Dmitry Ioffe; Yvan Velenik

2007-10-16

314

Habitual toe-walking: evaluation and approach to treatment.  

PubMed

Habitual toe-walking has been presented as a prolongation of a normal stage of development that requires conservative treatment to prevent or ameliorate associated gait abnormalities such as tripping and falling. An approach to the evaluation of a child with toe-walking should include (1) medical history (prenatal, intrapartum, and postnatal), (2) gait evaluation, (3) musculoskeletal examination, and (4) neurologic examination. Pathologic entities producing toe-walking have been explored in order to differentiate those conditions from idiopathic (habitual) toe-walking. The most common etiologies of toe-walking (nonhabitual) would include gastrosoleus equinus, clubfoot, or cerebral palsy. Treatment of habitual toe-walkers might include shoe therapy, orthosis therapy, auditory feedback, and surgery. PMID:3293753

Caselli, M A; Rzonca, E C; Lue, B Y

1988-07-01

315

Checklist and Pollard Walk butterfly survey methods on public lands  

USGS Publications Warehouse

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

316

Walking, running, and resting under time, distance, and average speed constraints: Optimality of walk-run-rest mixtures  

E-print Network

that similar walk-run mixtures may be energetically beneficial to children following a parent and animals strategies may be energetically beneficial in superficially diverse situations: children walking with parents significantly, we then interpret the experimental observations using metabolic energy minimization, without

Srinivasan, Manoj

317

Human walk pitch extraction by robot vision - towards human robot synchronized walking based on neural oscillator entrainment  

Microsoft Academic Search

This paper presents a method to extract human walk pitch by robot vision. It is intended to be used for robot-human synchronized walking. Needless to say, in human-robot collaboration and interaction, synchronization between robot and human is crucial for safety, comfort, and sense of compatibility. It must be true even when a robot follows or accompanies its human master. In

Kosuke Okabe; Hiroshi Mizoguchi; Daiki Maruyama; Kazuyuki Hiraoka; T. Shigehara; M. Tanaka; T. Mishima

2003-01-01

318

Thermodynamics of N-dimensional quantum walks  

E-print Network

The entanglement between the position and coin state of a $N$-dimensional quantum walker is shown to lead to a thermodynamic theory. The entropy, in this thermodynamics, is associated to the reduced density operator for the evolution of chirality, taking a partial trace over positions. From the asymptotic reduced density matrix it is possible to define thermodynamic quantities, such as the asymptotic entanglement entropy, temperature, Helmholz free energy, etc. We study in detail the case of a $2$-dimensional quantum walk, in the case of two different initial conditions: a non-separable coin-position initial state, and a separable one. The resulting entanglement temperature is presented as function of the parameters of the system and those of the initial conditions.

Alejandro Romanelli; Raul Donangelo; Renato Portugal; Franklin L. Marquezino

2014-08-22

319

Thermodynamics of N-dimensional quantum walks  

NASA Astrophysics Data System (ADS)

The entanglement between the position and the coin state of an N-dimensional quantum walker is shown to lead to a thermodynamic theory. The entropy, in this thermodynamics, is associated with the reduced density operator for the evolution of chirality, taking a partial trace over positions. From the asymptotic reduced density matrix it is possible to define thermodynamic quantities, such as the asymptotic entanglement entropy, temperature, and Helmholz free energy. We study in detail the case of a two-dimensional quantum walk, in the case of two initial conditions: a nonseparable coin-position initial state and a separable one. The resulting entanglement temperature is presented as a function of the parameters of the system and those of the initial conditions.

Romanelli, Alejandro; Donangelo, Raul; Portugal, Renato; Marquezino, Franklin de Lima

2014-08-01

320

Homogeneous Superpixels from Markov Random Walks  

NASA Astrophysics Data System (ADS)

This paper presents a novel algorithm to generate homogeneous superpixels from Markov random walks. We exploit Markov clustering (MCL) as the methodology, a generic graph clustering method based on stochastic flow circulation. In particular, we introduce a graph pruning strategy called compact pruning in order to capture intrinsic local image structure. The resulting superpixels are homogeneous, i.e. uniform in size and compact in shape. The original MCL algorithm does not scale well to a graph of an image due to the square computation of the Markov matrix which is necessary for circulating the flow. The proposed pruning scheme has the advantages of faster computation, smaller memory footprint, and straightforward parallel implementation. Through comparisons with other recent techniques, we show that the proposed algorithm achieves state-of-the-art performance.

Perbet, Frank; Stenger, Björn; Maki, Atsuto

321

Discrete time quantum walks on percolation graphs  

E-print Network

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.

Bálint Kollár; Jaroslav Novotný; Tamás Kiss; Igor Jex

2014-04-17

322

Astronaut Noguchi During STS-114 Space Walk  

NASA Technical Reports Server (NTRS)

Launched on July 26, 2005 from the Kennedy Space Center in Florida, STS-114 was classified as Logistics Flight 1. Among the Station-related activities of the mission were the delivery of new supplies and the replacement of one of the orbital outpost's Control Moment Gyroscopes (CMGs). STS-114 also carried the Raffaello Multi-Purpose Logistics Module (MPLM) and the External Stowage Platform-2. In this photograph, astronaut Soichi Noguchi, STS-114 mission specialist representing the Japan Aerospace Exploration Agency (JAXA), participates in the mission's first scheduled session of Extra Vehicular Activity (EVA). Noguchi and crew mate Stephen K. Robinson (out of frame) completed a demonstration of Shuttle thermal protection repair techniques and enhancements to the ISS's attitude control system during the successful 6 hour, 50 minute space walk.

2005-01-01

323

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

324

Adaptation of the walking pattern to uphill walking in normal and spinal-cord injured subjects  

Microsoft Academic Search

Lower-limb movements and muscle-activity patterns were assessed from seven normal and seven ambulatory subjects with incomplete\\u000a spinal-cord injury (SCI) during level and uphill treadmill walking (5, 10 and 15°). Increasing the treadmill grade from 0°\\u000a to 15° induced an increasingly flexed posture of the hip, knee and ankle during initial contact in all normal subjects, resulting\\u000a in a larger excursion

Alain Leroux; Joyce Fung; Hugues Barbeau

1999-01-01

325

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

PubMed

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

326

Prediction of Falls Using a 3-m Zigzag Walk Test  

PubMed Central

[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. PMID:24259913

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

2013-01-01

327

Pilot investigation of the oxygen demands and metabolic cost of incremental shuttle walking and treadmill walking in patients with cardiovascular disease  

PubMed Central

Objective To determine if the metabolic cost of the incremental shuttle-walking test protocol is the same as treadmill walking or predicted values of walking-speed equations. Setting Primary care (community-based cardiac rehabilitation). Participants Eight Caucasian cardiac rehabilitation patients (7 males) with a mean age of 67±5.2?years. Primary and secondary outcome measures Oxygen consumption, metabolic power and energy cost of walking during treadmill and shuttle walking performed in a balanced order with 1?week between trials. Results Average overall energy cost per metre was higher during treadmill walking (3.22±0.55?J?kg/m) than during shuttle walking (3.00±0.41?J?kg/m). There were significant post hoc effects at 0.67?m/s (p<0.004) and 0.84?m/s (p<0.001), where the energy cost of treadmill walking was significantly higher than that of shuttle walking. This pattern was reversed at walking speeds 1.52?m/s (p<0.042) and 1.69?m/s (p<0.007) where shuttle walking had a greater energy cost per metre than treadmill walking. At all walking speeds, the energy cost of shuttle walking was higher than that predicted using the American College of Sports Medicine walking equations. Conclusions The energetic demands of shuttle walking were fundamentally different from those of treadmill walking and should not be directly compared. We warn against estimating the metabolic cost of the incremental shuttle-walking test using the current walking-speed equations. PMID:25227624

Almodhy, M; Beneke, R; Cardoso, F; Taylor, M J D; Sandercock, G R H

2014-01-01

328

Visual control of foot placement when walking over complex terrain.  

PubMed

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

329

Changes in corticospinal excitability following adaptive modification to human walking.  

PubMed

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

330

Foot trajectory approximation using the pendulum model of walking.  

PubMed

Generating a natural foot trajectory is an important objective in robotic systems for rehabilitation of walking. Human walking has pendular properties, so the pendulum model of walking has been used in bipedal robots which produce rhythmic gait patterns. Whether natural foot trajectories can be produced by the pendulum model needs to be addressed as a first step towards applying the pendulum concept in gait orthosis design. This study investigated circle approximation of the foot trajectories, with focus on the geometry of the pendulum model of walking. Three able-bodied subjects walked overground at various speeds, and foot trajectories relative to the hip were analysed. Four circle approximation approaches were developed, and best-fit circle algorithms were derived to fit the trajectories of the ankle, heel and toe. The study confirmed that the ankle and heel trajectories during stance and the toe trajectory in both the stance and the swing phases during walking at various speeds could be well modelled by a rigid pendulum. All the pendulum models were centred around the hip with pendular lengths approximately equal to the segment distances from the hip. This observation provides a new approach for using the pendulum model of walking in gait orthosis design. PMID:24057114

Fang, Juan; Vuckovic, Aleksandra; Galen, Sujay; Conway, Bernard A; Hunt, Kenneth J

2014-01-01

331

Rotor-Router Walks on Directed Covers of Graphs  

E-print Network

The aim of this paper is to study the behaviour of rotor-router walks on directed covers of finite graphs. The latter are also called in the literature trees with finitely many cone types or periodic trees. A rotor-router walk is a deterministic version of a random walk, in which the walker is routed to each of the neighbouring vertices in some fixed cyclic order. We study several quantities related to rotor-router walks such as: order of the rotor-router group, order of the root element in the rotor-router group and the connection with random walks. For random initial configurations of rotors, we also address the question of recurrence and transience of transfinite rotor-router walks. On homogeneous trees, the recurrence/transience was studied by Angel and Holroyd. We extend their theory and provide an example of a directed cover such that the rotor-router walk can be either recurrent or transient, depending only on the planar embedding of the periodic tree.

Huss, Wilfried

2012-01-01

332

Simulation Studies of Bipedal Walking on the Moon and Mars  

NASA Astrophysics Data System (ADS)

In order to walk upright on the Moon or Mars without falling, a specific walking strategy to account for altered gravitational conditions must be verified. We have therefore been studying changes in the kinematics of walking at different gravitational loads using a body weight suspension system. Our simulation consisted of three gravitational conditions: 1 g (Earth); 1/3 g (Mars); and 1/6 g (the Moon). Surface EMG recordings were taken from the leg muscles of subjects walking on a treadmill. Cadence, stance phase duration, and step length were calculated from the walking velocity and steps. Subsequent experiments revealed that muscle activity and the duration of the double support phase decreased as simulated gravity was reduced. These changes are apparently caused not only by the direct effects of unloading but also by kinematic adaptations to the same. It can be said that humans walk slowly with a shortened stride and elongated stance phase in order to adjust to low gravitational conditions. One major limitation of our study that may have affected walking stability was the fact that the suspension system was fixed to an immovable frame. We have begun further studies using a newer movable body weight suspension system to achieve more realistic simulations.

Yamada, Shin; Ohshima, Hiroshi; Yamaguchi, Tomofumi; Narukawa, Terumasa; Takahashi, Masaki; Hase, Kimitaka; Liu, Meigen; Mukai, Chiaki

333

Decoherence in a one-dimensional quantum walk  

SciTech Connect

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

334

Pseudo-Hermitian continuous-time quantum walks  

NASA Astrophysics Data System (ADS)

In this paper we present a model exhibiting a new type of continuous-time quantum walk (as a quantum-mechanical transport process) on networks, which is described by a non-Hermitian Hamiltonian possessing a real spectrum. We call it pseudo-Hermitian continuous-time quantum walk. We introduce a method to obtain the probability distribution of walk on any vertex and then study a specific system. We observe that the probability distribution on certain vertices increases compared to that of the Hermitian case. This formalism makes the transport process faster and can be useful for search algorithms.

Salimi, S.; Sorouri, A.

2010-07-01

335

Walk dimension for light in complex disordered media  

NASA Astrophysics Data System (ADS)

Transport in complex systems is characterized by a fractal dimension—the walk dimension—that indicates the diffusive or anomalous nature of the underlying random walk process. Here we report on the experimental retrieval of this key quantity, using light waves propagating in disordered media. The approach is based on measurements of the time-resolved transmission, in particular on how the lifetime scales with sample size. We show that this allows one to retrieve the walk dimension and apply the concept to samples with varying degree of fractal heterogeneity. In addition, the method provides the first experimental demonstration of anomalous light dynamics in a random medium.

Savo, Romolo; Burresi, Matteo; Svensson, Tomas; Vynck, Kevin; Wiersma, Diederik S.

2014-08-01

336

Phenomenological picture of fluctuations in branching random walks  

NASA Astrophysics Data System (ADS)

We propose a picture of the fluctuations in branching random walks, which leads to predictions for the distribution of a random variable that characterizes the position of the bulk of the particles. We also interpret the 1 /?{t } correction to the average position of the rightmost particle of a branching random walk for large times t ?1 , computed by Ebert and Van Saarloos, as fluctuations on top of the mean-field approximation of this process with a Brunet-Derrida cutoff at the tip that simulates discreteness. Our analytical formulas successfully compare to numerical simulations of a particular model of a branching random walk.

Mueller, A. H.; Munier, S.

2014-10-01

337

Better Walking Performance in Older Children With Cerebral Palsy  

Microsoft Academic Search

Background  Children with cerebral palsy (CP) often walk with a slower speed and a higher energy cost. Their walking performance and choice\\u000a of mobility method may vary in different environments. Independent mobility is important for activity and participation.\\u000a \\u000a \\u000a \\u000a \\u000a Questions\\/purposes  We described walking performance at different distances and environments in relation to gross motor function, CP subtype,\\u000a and age.\\u000a \\u000a \\u000a \\u000a \\u000a Patients and Methods  We performed

Elisabet Rodby-Bousquet RPT; Gunnar Hägglund

338

Discrete-time quantum walks: Continuous limit and symmetries  

SciTech Connect

The continuous limit of one-dimensional discrete-time quantum walks with time-and space-dependent coefficients is investigated. A given quantum walk does not generally admit a continuous limit but some families (1-jets) of quantum walks do. All families (1-jets) admitting a continuous limit are identified. The continuous limit is described by a Dirac-like equation or, alternately, a couple of Klein-Gordon equations. Variational principles leading to these equations are also discussed, together with local invariance properties.

Molfetta, G. di; Debbasch, F. [Universite Paris 6, ERGA-LERMA, UMR 8112, 3, rue Galilee, F-94200 Ivry (France)

2012-12-15

339

Quenched invariance principle for simple random walk on percolation clusters  

E-print Network

We consider the simple random walk on the (unique) infinite cluster of super-critical bond percolation in $\\Z^d$ with $d\\ge2$. We prove that, for almost every percolation configuration, the path distribution of the walk converges weakly to that of non-degenerate, isotropic Brownian motion. Our analysis is based on the consideration of a harmonic deformation of the infinite cluster on which the random walk becomes a square-integrable martingale. The size of the deformation, expressed by the so called corrector, is estimated by means of ergodicity arguments.

Noam Berger; Marek Biskup

2005-03-25

340

Universal Behavior of Quantum Walks with Long-Range Steps  

E-print Network

Quantum walks with long-range steps $R^{-\\gamma}$ ($R$ being the distance between sites) on a discrete line behave in similar ways for all $\\gamma\\geq2$. This is in contrast to classical random walks, which for $\\gamma >3$ belong to a different universality class than for $\\gamma \\leq 3$. We show that the average probabilities to be at the initial site after time $t$ as well as the mean square displacements are of the same functional form for quantum walks with $\\gamma=2$, 4, and with nearest neighbor steps. We interpolate this result to arbitrary $\\gamma\\geq2$.

Oliver Muelken; Volker Pernice; Alexander Blumen

2007-11-23

341

Differentiating ability in users of the ReWalk(TM) powered exoskeleton: an analysis of walking kinematics.  

PubMed

The ReWalk(TM) powered exoskeleton assists thoracic level motor complete spinal cord injury patients who are paralyzed to walk again with an independent, functional, upright, reciprocating gait. We completed an evaluation of twelve such individuals with promising results. All subjects met basic criteria to be able to use the ReWalk(TM)--including items such as sufficient bone mineral density, leg passive range of motion, strength, body size and weight limits. All subjects received approximately the same number of training sessions. However there was a wide distribution in walking ability. Walking velocities ranged from under 0.1m/s to approximately 0.5m/s. This variability was not completely explained by injury level The remaining sources of that variability are not clear at present. This paper reports our preliminary analysis into how the walking kinematics differed across the subjects--as a first step to understand the possible contribution to the velocity range and determine if the subjects who did not walk as well could be taught to improve by mimicking the better walkers. PMID:24187286

Talaty, Mukul; Esquenazi, Alberto; Briceno, Jorge E

2013-06-01

342

Truncated Lévy walks are expected beyond the scale of data collection when correlated random walks embody observed movement patterns.  

PubMed

Translating observations taken at small spatio-temporal scales into expected patterns at greater scales is a major challenge in spatial ecology because there is typically insufficient relevant information. Here, it is shown that truncated Lévy walks are the most conservative, maximally non-committal description of movement patterns beyond the scale of data collection when correlated random walks characterize observed movements and when there is partial information about landscape and behavioural heterogeneity. This provides a new conceptual basis for Lévy walks that is divorced from optimal searching theory and free from the difficulties with discerning their presence in empirical data. PMID:21831893

Reynolds, A M

2012-03-01

343

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

344

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

345

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

Microsoft Academic Search

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

346

Biped Gait Generation and Control Based on a Unified Property of Passive Dynamic Walking  

Microsoft Academic Search

Principal mechanisms of passive dynamic walking are studied from the mechanical energy point of view, and novel gait generation and control methods based on passive dynamic walking are proposed. First, a unified property of passive dynamic walking is derived, which shows that the walking system's mechanical energy increases proportionally with respect to the position of the system's center of mass.

Fumihiko Asano; Zhi-Wei Luo; Masaki Yamakita

2005-01-01

347

Acceleration patterns of the head and pelvis when walking on level and irregular surfaces  

Microsoft Academic Search

The aim of this study was to evaluate acceleration patterns at the head and pelvis while subjects walked on a level and an irregular walking surface, to develop an understanding of how the postural control system responds to challenging walking conditions. Thirty young, healthy subjects walked on a level corridor and on artificial grass underlain with foam and wooden blocks

Hylton B. Menz; Stephen R. Lord; Richard C. Fitzpatrick

2003-01-01

348

Biped walking robot control with passive walker model by new VSC servo  

Microsoft Academic Search

Passive walking on a slope is known as the most efficient and natural walking style because there is no extra power without potential energy, and the motion occurs inherently according to its mechanical property. In this paper a walking control strategy which utilizes the dynamics of passive walking as a trajectory generator is introduced. A virtual model can generate a

S. Suzuki; K. Furuta; Y. Pan; S. Hatakeyama

2001-01-01

349

Walking, Biking to Work Seems to Have Mental Health Benefits  

MedlinePLUS

... considerable stress," Martin added. "But as buses or trains also give people time to relax, read, socialize, and there is usually an associated walk to the bus stop or railway station, it appears to cheer people up." For the ...

350

Nature Walks with Others May Keep Depression at Bay  

MedlinePLUS

... enable JavaScript. Nature Walks With Others May Keep Depression at Bay Study found they lowered stress levels, ... Preidt Thursday, September 25, 2014 Related MedlinePlus Pages Depression Exercise and Physical Fitness THURSDAY, Sept. 25, 2014 ( ...

351

Record statistics of financial time series and geometric random walks  

NASA Astrophysics Data System (ADS)

The study of record statistics of correlated series in physics, such as random walks, is gaining momentum, and several analytical results have been obtained in the past few years. In this work, we study the record statistics of correlated empirical data for which random walk models have relevance. We obtain results for the records statistics of select stock market data and the geometric random walk, primarily through simulations. We show that the distribution of the age of records is a power law with the exponent ? lying in the range 1.5???1.8. Further, the longest record ages follow the Fréchet distribution of extreme value theory. The records statistics of geometric random walk series is in good agreement with that obtained from empirical stock data.

Sabir, Behlool; Santhanam, M. S.

2014-09-01

352

Scattering model for quantum random walks on a hypercube  

NASA Astrophysics Data System (ADS)

Following a recent work by Hillery [Phys. Rev. A 68, 032314 (2003)], we introduce a scattering model of a quantum random walk (SQRW) on a hybercube. We show that this type of quantum random walk can be reduced to the quantum random walk on the line and we derive the corresponding hitting amplitudes. We investigate the scattering properties of the hypercube, connected to the semi-infinite tails. We prove that the SQRW is a generalized version of the coined quantum random walk. We show how to implement the SQRW efficiently using a quantum circuit with standard gates. We discuss one possible version of a quantum search algorithm using the SQRW. Finally, we analyze symmetries that underlie the SQRW and may simplify its solution considerably.

Košík, Jozef; Bužek, Vladimír

2005-01-01

353

Mixing times in quantum walks on two-dimensional grids  

NASA Astrophysics Data System (ADS)

Mixing properties of discrete-time quantum walks on two-dimensional grids with toruslike boundary conditions are analyzed, focusing on their connection to the complexity of the corresponding abstract search algorithm. In particular, an exact expression for the stationary distribution of the coherent walk over odd-sided lattices is obtained after solving the eigenproblem for the evolution operator for this particular graph. The limiting distribution and mixing time of a quantum walk with a coin operator modified as in the abstract search algorithm are obtained numerically. On the basis of these results, the relation between the mixing time of the modified walk and the running time of the corresponding abstract search algorithm is discussed.

Marquezino, F. L.; Portugal, R.; Abal, G.

2010-10-01

354

Dynamics of continuous-time quantum walks in restricted geometries  

NASA Astrophysics Data System (ADS)

We study quantum transport on finite discrete structures and we model the process by means of continuous-time quantum walks. A direct and effective comparison between quantum and classical walks can be attained based on the average displacement of the walker as a function of time. Indeed, a fast growth of the average displacement can be advantageously exploited to build up efficient search algorithms. By means of analytical and numerical investigations, we show that the finiteness and the inhomogeneity of the substrate jointly weaken the quantum-walk performance. We further highlight the interplay between the quantum-walk dynamics and the underlying topology by studying the temporal evolution of the transfer probability distribution and the lower bound of long-time averages.

Agliari, E.; Blumen, A.; Mülken, O.

2008-11-01

355

A walking tour of the Calaveras fault in Hollister, California  

NSDL National Science Digital Library

This guide provides directions and descriptions for stops on a walking tour of the Calaveras Fault in Hollister, California. Maps and photos are used to show offset and damage to man-made structures caused by creep along the fault.

Dellinger, Joe

356

Kinematic study of human ankle control during walking  

E-print Network

In order to determine the extent to which ankle motion is voluntarily controlled during walking, angular velocity measurements at the ankle were taken in two cases. In the first case, subjects were seated and instructed ...

Zimmerman, Julia C

2009-01-01

357

A Walk in the Woods: Or, What Is Art?  

ERIC Educational Resources Information Center

Presents a passage from Tolstoy's essay "The School at Yasnaya Polyana." Discusses his experience as a teacher walking through the woods with several children and telling them stories. Describes their reactions and personalities, all very different. (SC)

Tolstoy, Leo

1999-01-01

358

Robust Execution of Bipedal Walking Tasks From Biomechanical Principles  

E-print Network

Effective use of robots in unstructured environments requires that they have sufficient autonomy and agility to execute task-level commands successfully. A challenging example of such a robot is a bipedal walking machine. ...

Hofmann, Andreas

2006-04-28

359

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 ...

360

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 ...

361

A scaling law for random walks on networks  

PubMed Central

The dynamics of many natural and artificial systems are well described as random walks on a network: the stochastic behaviour of molecules, traffic patterns on the internet, fluctuations in stock prices and so on. The vast literature on random walks provides many tools for computing properties such as steady-state probabilities or expected hitting times. Previously, however, there has been no general theory describing the distribution of possible paths followed by a random walk. Here, we show that for any random walk on a finite network, there are precisely three mutually exclusive possibilities for the form of the path distribution: finite, stretched exponential and power law. The form of the distribution depends only on the structure of the network, while the stepping probabilities control the parameters of the distribution. We use our theory to explain path distributions in domains such as sports, music, nonlinear dynamics and stochastic chemical kinetics. PMID:25311870

Perkins, Theodore J.; Foxall, Eric; Glass, Leon; Edwards, Roderick

2014-01-01

362

A scaling law for random walks on networks  

NASA Astrophysics Data System (ADS)

The dynamics of many natural and artificial systems are well described as random walks on a network: the stochastic behaviour of molecules, traffic patterns on the internet, fluctuations in stock prices and so on. The vast literature on random walks provides many tools for computing properties such as steady-state probabilities or expected hitting times. Previously, however, there has been no general theory describing the distribution of possible paths followed by a random walk. Here, we show that for any random walk on a finite network, there are precisely three mutually exclusive possibilities for the form of the path distribution: finite, stretched exponential and power law. The form of the distribution depends only on the structure of the network, while the stepping probabilities control the parameters of the distribution. We use our theory to explain path distributions in domains such as sports, music, nonlinear dynamics and stochastic chemical kinetics.

Perkins, Theodore J.; Foxall, Eric; Glass, Leon; Edwards, Roderick

2014-10-01

363

A scaling law for random walks on networks.  

PubMed

The dynamics of many natural and artificial systems are well described as random walks on a network: the stochastic behaviour of molecules, traffic patterns on the internet, fluctuations in stock prices and so on. The vast literature on random walks provides many tools for computing properties such as steady-state probabilities or expected hitting times. Previously, however, there has been no general theory describing the distribution of possible paths followed by a random walk. Here, we show that for any random walk on a finite network, there are precisely three mutually exclusive possibilities for the form of the path distribution: finite, stretched exponential and power law. The form of the distribution depends only on the structure of the network, while the stepping probabilities control the parameters of the distribution. We use our theory to explain path distributions in domains such as sports, music, nonlinear dynamics and stochastic chemical kinetics. PMID:25311870

Perkins, Theodore J; Foxall, Eric; Glass, Leon; Edwards, Roderick

2014-01-01

364

Astronaut Gordon Cooper walks to elevator to spacecraft 'Faith 7'  

NASA Technical Reports Server (NTRS)

Astronaut L. Gordon Cooper Jr. waited inside the transfer van for several minutes and then leaving the transfer van walked to the elevator which took him to the spacecraft 'Faith 7' atop the Atlas vehicle for his mission.

1963-01-01

365

Human walking model predicts joint mechanics, electromyography and mechanical economy  

E-print Network

In this paper, we present an under-actuated model of human walking, comprising only a soleus muscle and flexion/extension monoarticular hip muscles. The remaining muscle groups of the human leg are modeled using quasi-passive, ...

Endo, Ken

366

Robust execution of bipedal walking tasks from biomechanical principles  

E-print Network

Effective use of robots in unstructured environments requires that they have sufficient autonomy and agility to execute task-level commands successfully. A challenging example of such a robot is a bipedal walking machine. ...

Hofmann, Andreas G. (Andreas Gunther)

2006-01-01

367

Gallery Walk Questions on Air Pressure and Wind  

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 Air Pressure and Wind. The questions are organized according to the ...

368

A Random Walk Through Functional Programming Richard J. Gaylord  

E-print Network

walk models and the Mathematica programming language. Keywords: functional programming, Mathematica illustrate functional programming using the Mathematica programming lan­ guage [2, 3, 4, 5], which is widely

Kamin, Sam

369

Gallery Walk Questions about Time and Earth History  

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 time and earth history. The questions are organized according to the ...

370

Online pose classification and walking speed estimation using handheld devices  

E-print Network

We describe and evaluate two methods for device pose classification and walking speed estimation that generalize well to new users, compared to previous work. These machine learning based methods are designed for the general ...

Park, Jun-geun

371

a Novel Sideway Stability Control Method for Bipedal Walking Robot  

NASA Astrophysics Data System (ADS)

This paper presents a novel sensing and balancing method for bipedal walking robot. The proposed method involves the design of semi-rigid ankle joint to facilitate the responsive and accurate measurement of the sideway (sagittal) instability of the walking robot. The use of double balancing mass and the developed control algorithms provide a constant sideway stability of the robot while it walks in forward direction. The smooth legs trajectory planning then can be implemented successfully regardless of the robot sideway stability condition. The developed method is able to decouple the walking algorithms from the robot stability issues. Furthermore, the use of two different masses for the balancing helps to improve response time and efficiency of the balancing system. In this paper, the proposed method is tested on the simplified model of a robot balancing on its single leg and the feasibility of the method is confirmed by the simulation results obtained with MATLAB Simulink tools.

Jo, H. Siswoyo; Mir-Nasiri, N.

2011-06-01

372

The hydrodynamics of water-walking insects and spiders  

E-print Network

We present a combined experimental and theoretical investigation of the numerous hydrodynamic propulsion mechanisms employed by water-walking arthropods (insects and spiders). In our experimental study, high speed ...

Hu, David L., 1979-

2006-01-01

373

On the Mechanics of Functional Asymmetry in Bipedal Walking  

PubMed Central

This paper uses two symmetrical models, the passive compass-gait biped and a five-link 3D biped, to computationally investigate the cause and function of gait asymmetry. We show that for a range of slope angles during passive 2D walking and mass distributions during controlled 3D walking, these models have asymmetric walking patterns between the left and right legs due to the phenomenon of spontaneous symmetry-breaking. In both cases a stable asymmetric family of gaits emerges from a symmetric family of gaits as the total energy increases (e.g., fast speeds). The ground reaction forces of each leg reflect different roles, roughly corresponding to support, propulsion, and motion control as proposed by the hypothesis of functional asymmetry in able-bodied human walking. These results suggest that body mechanics, independent of neurophysiological mechanisms such as leg dominance, may contribute to able-bodied gait asymmetry. PMID:22328168

Dhaher, Yasin Y.; Degani, Amir; Lynch, Kevin M.

2014-01-01

374

Walking with Woodlice: An Experiment in Biodiversity Education.  

ERIC Educational Resources Information Center

Describes the development and implementation of a web-based project, Walking With Wildlife, intended to encourage and enable first-hand encounters with the biodiversity of the natural world. (Contains 16 references.) (DDR)

Hawkey, Roy

2001-01-01

375

Group Velocity of Discrete-Time Quantum Walks  

E-print Network

We show that certain types of quantum walks can be modeled as waves that propagate in a medium with phase and group velocities that are explicitly calculable. Since the group and phase velocities indicate how fast wave packets can propagate causally, we propose the use of these wave velocities in a new definition for the hitting time of quantum walks. The new definition of hitting time has the advantage that it requires neither the specification of a walker's initial condition nor of an arrival probability threshold. We give full details for the case of quantum walks on the Cayley graphs of Abelian groups. This includes the special cases of quantum walks on the line and on hypercubes.

Achim Kempf; Renato Portugal

2009-01-27

376

Psychosocial mediators of a walking intervention among African American women.  

PubMed

Many Americans are sedentary and would reduce their disease risk if they increased their levels of physical activity to 30 minutes of moderate activity most days of the week. This descriptive exploratory study addresses how to maximize adherence to a physical activity prescription. A sample of 14 older African American women enrolled in a walking intervention study participated in three focus-group discussions of barriers to and facilitators of walking. Focus groups were audiotaped, transcribed, and examined by three nurse researchers using analytic induction, content analysis, and grounded theory techniques. Women who participated in the focus-group discussions identified lack of family support, perceived or real family obligations, personal health status, and neighborhood safety as factors influencing adherence to physical activity. A necessary component of successful walking maintenance was the confidence and support of the woman's family. The most compelling reason for continued walking in this group was to help others. PMID:18165425

Dunn, Mary Z

2008-01-01

377

Monitoring butterfly abundance: beyond Pollard walks.  

PubMed

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

378

Discovering walking technirho mesons at the LHC  

NASA Astrophysics Data System (ADS)

We formulate a scale-invariant hidden local symmetry (HLS) as a low-energy effective theory of walking technicolor (WTC) which includes the technidilaton, technipions, and technirho mesons as the low-lying spectra. As a benchmark for LHC phenomenology, we in particular focus on the one-family model of WTC having eight technifermion flavors, which can be—at energy scales relevant to the reach of the LHC—described by the scale-invariant HLS based on the manifold [SU(8)L×SU(8)R]global×SU(8)local/SU(8)V, where SU(8)local is the HLS and the global SU(8)L×SU(8)R symmetry is partially gauged by the SU(3)×SU(2)L×U(1)Y of the standard model. Based on the scale-invariant HLS, we evaluate the coupling properties of the technirho mesons and place limits on the masses from the current LHC data. Then, implications for future LHC phenomenology are discussed by focusing on the technirho mesons produced through the Drell-Yan process. We find that the color-octet technirho decaying to the technidilaton along with the gluon is of interest as the discovery channel at the LHC, which would provide a characteristic signature to probe the one-family WTC.

Kurachi, Masafumi; Matsuzaki, Shinya; Yamawaki, Koichi

2014-09-01

379

Reconstructing the behavior of walking fruit flies  

NASA Astrophysics Data System (ADS)

Over the past century, the fruit fly Drosophila melanogaster has arisen as almost a lingua franca in the study of animal behavior, having been utilized to study questions in fields as diverse as sleep deprivation, aging, and drug abuse, amongst many others. Accordingly, much is known about what can be done to manipulate these organisms genetically, behaviorally, and physiologically. Most of the behavioral work on this system to this point has been experiments where the flies in question have been given a choice between some discrete set of pre-defined behaviors. Our aim, however, is simply to spend some time with a cadre of flies, using techniques from nonlinear dynamics, statistical physics, and machine learning in an attempt to reconstruct and gain understanding into their behavior. More specifically, we use a multi-camera set-up combined with a motion tracking stage in order to obtain long time-series of walking fruit flies moving about a glass plate. This experimental system serves as a test-bed for analytical, statistical, and computational techniques for studying animal behavior. In particular, we attempt to reconstruct the natural modes of behavior for a fruit fly through a data-driven approach in a manner inspired by recent work in C. elegans and cockroaches.

Berman, Gordon; Bialek, William; Shaevitz, Joshua

2010-03-01

380

Infrared dynamics of minimal walking technicolor  

SciTech Connect

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

381

The limits of agency in walking humans.  

PubMed

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

382

Discovering walking technirho mesons at LHC  

E-print Network

We formulate a scale-invariant hidden local symmetry (HLS) as a low-energy effective theory of the walking technicolor (WTC) which includes the technidilaton, technipions and technirho mesons as the low-lying spectra. As a benchmark for LHC phenomenology, we in particular focus on the one-family model of WTC having eight technifermion flavors, which can be, at energy scales relevant to the reach of the LHC, described by the scale-invariant HLS based on the manifold $[SU(8)_L \\times SU(8)_R]_{\\rm global} \\times SU(8)_{\\rm local}/SU(8)_V$, where $SU(8)_{\\rm local}$ is the HLS and the global $SU(8)_L \\times SU(8)_R$ symmetry is partially gauged by $SU(3) \\times SU(2)_L \\times U(1)_Y$ of the standard model. Based on the scale-invariant HLS, we evaluate the coupling properties of the technirho mesons and place the limits on the masses from the current LHC data. Then, implications to the future LHC phenomenology are discussed by focusing on the technirho mesons produced through the Drell-Yan process. We find that t...

Kurachi, Masafumi; Yamawaki, Koichi

2014-01-01

383

Discovering walking technirho mesons at the LHC  

E-print Network

We formulate a scale-invariant hidden local symmetry (HLS) as a low-energy effective theory of walking technicolor (WTC) which includes the technidilaton, technipions, and technirho mesons as the low-lying spectra. As a benchmark for LHC phenomenology, we in particular focus on the one-family model of WTC having eight technifermion flavors, which can be, at energy scales relevant to the reach of the LHC, described by the scale-invariant HLS based on the manifold $[SU(8)_L \\times SU(8)_R]_{\\rm global} \\times SU(8)_{\\rm local}/SU(8)_V$, where $SU(8)_{\\rm local}$ is the HLS and the global $SU(8)_L \\times SU(8)_R$ symmetry is partially gauged by $SU(3) \\times SU(2)_L \\times U(1)_Y$ of the standard model. Based on the scale-invariant HLS, we evaluate the coupling properties of the technirho mesons and place limits on the masses from the current LHC data. Then, implications for future LHC phenomenology are discussed by focusing on the technirho mesons produced through the Drell-Yan process. We find that the color-octet technirho decaying to the technidilaton along with the gluon is of interest as the discovery channel at the LHC, which would provide a characteristic signature to probe the one-family WTC.

Masafumi Kurachi; Shinya Matsuzaki; Koichi Yamawaki

2014-04-11

384

Improving Random Walk Estimation Accuracy with Uniform Restarts  

Microsoft Academic Search

\\u000a This work proposes and studies the properties of a hybrid sampling scheme that mixes independent uniform node sampling and\\u000a random walk (RW)-based crawling. We show that our sampling method combines the strengths of both uniform and RW sampling while\\u000a minimizing their drawbacks. In particular, our method increases the spectral gap of the random walk, and hence, accelerates\\u000a convergence to the

Konstantin Avrachenkov; Bruno F. Ribeiro; Donald F. Towsley

2010-01-01

385

The melting phenomenon in random-walk model of DNA  

SciTech Connect

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

386

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

387

A Walking Program for Outpatients in Psychiatric Rehabilitation: Pilot Study  

Microsoft Academic Search

The purposes of this quasi-experimental pilot study were to determine adherence to a 12-week group-based moderate-intensity walking program for sedentary adult outpatients with serious and persistent mental illness and to examine change from baseline to after the walking program in health status (mental and physical health, mood, and psychosocial functioning) and exercise motivation (exercise outcomes expectancies, exercise decisional balance). The

Judith McDevitt; JoEllen Wilbur; Joseph Kogan; Joan Briller

2005-01-01

388

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

Microsoft Academic Search

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

389

The role of series ankle elasticity in bipedal walking.  

PubMed

The elastic stretch-shortening cycle of the Achilles tendon during walking can reduce the active work demands on the plantarflexor muscles in series. However, this does not explain why or when this ankle work, whether by muscle or tendon, needs to be performed during gait. We therefore employ a simple bipedal walking model to investigate how ankle work and series elasticity impact economical locomotion. Our model shows that ankle elasticity can use passive dynamics to aid push-off late in single support, redirecting the body's center-of-mass (COM) motion upward. An appropriately timed, elastic push-off helps to reduce dissipative collision losses at contralateral heelstrike, and therefore the positive work needed to offset those losses and power steady walking. Thus, the model demonstrates how elastic ankle work can reduce the total energetic demands of walking, including work required from more proximal knee and hip muscles. We found that the key requirement for using ankle elasticity to achieve economical gait is the proper ratio of ankle stiffness to foot length. Optimal combination of these parameters ensures proper timing of elastic energy release prior to contralateral heelstrike, and sufficient energy storage to redirect the COM velocity. In fact, there exist parameter combinations that theoretically yield collision-free walking, thus requiring zero active work, albeit with relatively high ankle torques. Ankle elasticity also allows the hip to power economical walking by contributing indirectly to push-off. Whether walking is powered by the ankle or hip, ankle elasticity may aid walking economy by reducing collision losses. PMID:24365635

Zelik, Karl E; Huang, Tzu-Wei P; Adamczyk, Peter G; Kuo, Arthur D

2014-04-01

390

A Recursive Greedy Algorithm for Walks in Directed Graphs  

Microsoft Academic Search

Given an arc-weighted directed graphG = (V;A;') and a pair of nodess;t, we seek to find an s-t walk of length at mostB that maximizes some given functionf of the set of nodes visited by the walk. The simplest case is when we seek to maximize the number of nodes visited: this is called the orienteering problem. Our main result

Chandra Chekuri; Martin Pál

2005-01-01

391

Control of Biped Walking Robot with IPMC Linear Actuator  

Microsoft Academic Search

We developed an artificial muscle linear actuator using ionic polymer-metal composite (IPMC) which is an electro-active polymer (EAP) that bends in response to electric stimuli. In this paper, we consider control of a small-sized biped walking robot. It is shown throughout the simulations the biped robot with IPMC linear actuators can walk by a simple input synchronization to motion of

Masaki Yamakita; Norihiro Kamamichi; Takahiro Kozuki; Kinji Asaka; Zhi-Wei Luo

2005-01-01

392

Walking index for spinal cord injury (WISCI): criterion validation  

Microsoft Academic Search

Study design:Retrospective examination.Objectives:To compare the Walking Index for Spinal Cord Injury (WISCI) and current scales for their sensitivity to walking changes in subjects with a spinal cord lesion (SCL) and further validate the WISCI for use in clinical trails.Setting:A large rehabilitation hospital in the center of Italy.Patients and methods:Retrospective review was performed on 284 patient records with an SCL. Measurements

B Morganti; G Scivoletto; P Ditunno; J F Ditunno; M Molinari

2005-01-01

393

Early changes in muscle activation patterns of toddlers during walking.  

PubMed

Early locomotor behavior has been the focus of considerable attention by developmentalists over several decades. Few studies have addressed explicitly patterns of muscle activity that underlie this coordination pattern. Our purposes were to illustrate a method to determine objectively the onset and offset of muscle firings during early walking and to investigate the emergence of patterns of activation of the core locomotor muscles. We tested eight toddlers as they walked overground at walking onset (max. of 3-6 independent steps) and after three months of walking experience. Surface electrodes monitored activity of the gastrocnemius, tibialis anterior, quadriceps, and hamstrings. We reduced EMG signals to a frame-by-frame designation of "on-off," followed by muscle state and co-contraction analyses, and probability distributions for each muscle's activity across multiple cycles. Our results clearly show that at walking onset muscle activity was highly variable with few, if any, muscles showing recurring patterns of behavior, within or among toddlers. Variability and co-activation decreased with walking experience but remained inconsistent, in contrast to the significant increase in stability shown for joint coordination and endpoint (foot placement) parameters. We propose this trend emerges because of the high number of options (muscle combinations) available. Toddlers learn first to marshal sufficient force to balance and make forward progress but slowly discover how to optimize these resources. PMID:17138273

Chang, Chia-Lin; Kubo, Masayoshi; Buzzi, Ugo; Ulrich, Beverly

2006-04-01

394

Early Changes in Muscle Activation Patterns of Toddlers During Walking  

PubMed Central

Early locomotor behavior has been the focus of considerable attention by developmentalists over several decades. Few studies have addressed explicitly patterns of muscle activity that underlie this coordination pattern. Our purposes were to illustrate a method to determine objectively the onset and offset of muscle firings during early walking and to investigate the emergence of patterns of activation of the core locomotor muscles. We tested eight toddlers as they walked overground at walking onset (max. of 3–6 independent steps) and after three months of walking experience. Surface electrodes monitored activity of the gastrocnemius, tibialis anterior, quadriceps, and hamstrings. We reduced EMG signals to a frame-by-frame designation of “on-off,” followed by muscle state and co-contraction analyses, and probability distributions for each muscle’s activity across multiple cycles. Our results clearly show that at walking onset muscle activity was highly variable with few, if any, muscles showing recurring patterns of behavior, within or among toddlers. Variability and co-activation decreased with walking experience but remained inconsistent, in contrast to the significant increase in stability shown for joint coordination and endpoint (foot placement) parameters. We propose this trend emerges because of the high number of options (muscle combinations) available. Toddlers learn first to marshal sufficient force to balance and make forward progress but slowly discover how to optimize these resources. PMID:17138273

Chang, Chia-Lin; Kubo, Masayoshi; Buzzi, Ugo; Ulrich, Beverly

2006-01-01

395

Current-reinforced random walks for constructing transport networks  

PubMed Central

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. PMID:23269849

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

2013-01-01

396

Introduction of New Motion Measurement Equipment into Virtual Walk System  

NASA Astrophysics Data System (ADS)

The “Virtual Walk System” has been developed to support rehabilitation therapy in homes. In the system, a user has been able to perform walking-like exercise on a fitness machine called a stepper. In front of the user, a projected image of a vast virtual reality space is generated by 3-dimensional computer graphics (3DCG). The user's movement is measured and the projected image changes just like the user is walking in the virtual space. Viewing the changing image, the user can enjoy the exercise. In this study, we have decomposed the virtual walk system into two modules (the measurement and control module operated by a microcomputer board and the 3DCG module operated by a personal computer) to facilitate rapid development. Then we have introduced two kinds of new equipment, i.e., a bicycle for cycling exercise and a treadmill for walking exercise. We have also developed a treadmill control system by which a user can easily change the walking speed during exercise.

Furukawa, Tatsuya; Itoh, Hideaki; Hori, Toshiyuki; Fukumoto, Hisao; Wakuya, Hiroshi; Ohchi, Masashi

397

Feasibility of measuring event related desynchronization with electroencephalography during walking.  

PubMed

Brain Computer Interfaces could be useful in rehabilitation of movement, perhaps also for gait. Until recently, research on movement related brain signals has not included measuring electroencephalography (EEG) during walking, because of the potential artifacts. We investigated if it is possible to measure the event Related Desynchronization (ERD) and event related spectral perturbations (ERSP) during walking. Six subjects walked on a treadmill with a slow speed, while EEG, electromyography (EMG) of the neck muscles and step cycle were measured. A Canonical Correlation Analysis (CCA) was used to remove EMG artifacts from the EEG signals. It was shown that this method correctly deleted EMG components. A strong ERD in the mu band and a somewhat less strong ERD in the beta band were found during walking compared to a baseline period. Furthermore, lateralized ERSPs were found, depending on the phase in the step cycle. It is concluded that this is a promising method to use in BCI research on walking. These results therefore pave the way for using brain signals related to walking in a BCI context. PMID:23366498

Severens, M; Nienhuis, B; Desain, P; Duysens, J

2012-01-01

398

Integration of Human Walking Gyroscopic Data Using Empirical Mode Decomposition  

PubMed Central

The present study was aimed at evaluating the Empirical Mode Decomposition (EMD) method to estimate the 3D orientation of the lower trunk during walking using the angular velocity signals generated by a wearable inertial measurement unit (IMU) and notably flawed by drift. The IMU was mounted on the lower trunk (L4-L5) with its active axes aligned with the relevant anatomical axes. The proposed method performs an offline analysis, but has the advantage of not requiring any parameter tuning. The method was validated in two groups of 15 subjects, one during overground walking, with 180° turns, and the other during treadmill walking, both for steady-state and transient speeds, using stereophotogrammetric data. Comparative analysis of the results showed that the IMU/EMD method is able to successfully detrend the integrated angular velocities and estimate lateral bending, flexion-extension as well as axial rotations of the lower trunk during walking with RMS errors of 1 deg for straight walking and lower than 2.5 deg for walking with turns. PMID:24379044

Bonnet, Vincent; Ramdani, Sofiane; Azevedo-Coste, Christine; Fraisse, Philippe; Mazza, Claudia; Cappozzo, Aurelio

2014-01-01

399

Physiological and perceptual responses to Nordic walking in obese middle-aged women in comparison with the normal walk  

Microsoft Academic Search

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

400

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

PubMed Central

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. PMID:24223308

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

2013-01-01

401

Record statistics for multiple random walks.  

PubMed

We study the statistics of the number of records R(n,N) for N identical and independent symmetric discrete-time random walks of n steps in one dimension, all starting at the origin at step 0. At each time step, each walker jumps by a random length drawn independently from a symmetric and continuous distribution. We consider two cases: (I) when the variance ?(2) of the jump distribution is finite and (II) when ?(2) is divergent as in the case of Lévy flights with index 01 in the two cases. We find that for large N, ?(N) ? 2sqrt[lnN] independently of ?(2) in case I. In contrast, in case II, the amplitude approaches to an N-independent constant for large N, ?(N) ? 4/sqrt[?], independently of 0

Wergen, Gregor; Majumdar, Satya N; Schehr, Grégory

2012-07-01

402

A mechanical protocol to replicate impact in walking footwear.  

PubMed

Impact testing is undertaken to quantify the shock absorption characteristics of footwear. The current widely reported mechanical testing method mimics the heel impact in running and therefore applies excessive energy to walking footwear. The purpose of this study was to modify the ASTM protocol F1614 (Procedure A) to better represent walking gait. This was achieved by collecting kinematic and kinetic data while participants walked in four different styles of walking footwear (trainer, oxford shoe, flip-flop and triple-density sandal). The quantified heel-velocity and effective mass at ground-impact were then replicated in a mechanical protocol. The kinematic data identified different impact characteristics in the footwear styles. Significantly faster heel velocity towards the floor was recorded walking in the toe-post sandals (flip-flop and triple-density sandal) compared with other conditions (e.g. flip-flop: 0.36±0.05 ms(-1) versus trainer: 0.18±0.06 ms(-1)). The mechanical protocol was adapted by altering the mass and drop height specific to the data captured for each shoe (e.g. flip-flop: drop height 7 mm, mass 16.2 kg). As expected, the adapted mechanical protocol produced significantly lower peak force and accelerometer values than the ASTM protocol (p<.001). The mean difference between the human and adapted protocol was 12.7±17.5% (p<.001) for peak acceleration and 25.2±17.7% (p=.786) for peak force. This paper demonstrates that altered mechanical test protocols can more closely replicate loading on the lower limb in walking. This therefore suggests that testing of material properties of footbeds not only needs to be gait style specific (e.g. running versus walking), but also footwear style specific. PMID:24618371

Price, Carina; Cooper, Glen; Graham-Smith, Philip; Jones, Richard

2014-05-01

403

Biomechanics and energetics of walking on uneven terrain  

PubMed Central

SUMMARY Walking on uneven terrain is more energetically costly than walking on smooth ground, but the biomechanical factors that contribute to this increase are unknown. To identify possible factors, we constructed an uneven terrain treadmill that allowed us to record biomechanical, electromyographic and metabolic energetics data from human subjects. We hypothesized that walking on uneven terrain would increase step width and length variability, joint mechanical work and muscle co-activation compared with walking on smooth terrain. We tested healthy subjects (N=11) walking at 1.0 m s?1, and found that, when walking on uneven terrain with up to 2.5 cm variation, subjects decreased their step length by 4% and did not significantly change their step width, while both step length and width variability increased significantly (22 and 36%, respectively; P<0.05). Uneven terrain walking caused a 28 and 62% increase in positive knee and hip work, respectively, and a 26% greater magnitude of negative knee work (0.0106, 0.1078 and 0.0425 J kg?1, respectively; P<0.05). Mean muscle activity increased in seven muscles in the lower leg and thigh (P<0.05). These changes caused overall net metabolic energy expenditure to increase by 0.73 W kg?1 (28%; P<0.0001). Much of that increase could be explained by the increased mechanical work observed at the knee and hip. Greater muscle co-activation could also contribute to increased energetic cost but to unknown degree. The findings provide insight into how lower limb muscles are used differently for natural terrain compared with laboratory conditions. PMID:23913951

Voloshina, Alexandra S.; Kuo, Arthur D.; Daley, Monica A.; Ferris, Daniel P.

2013-01-01

404

Increased walking variability in elderly persons with congestive heart failure  

NASA Technical Reports Server (NTRS)

OBJECTIVES: To determine the effects of congestive heart failure on a person's ability to walk at a steady pace while ambulating at a self-determined rate. SETTING: Beth Israel Hospital, Boston, a primary and tertiary teaching hospital, and a social activity center for elderly adults living in the community. PARTICIPANTS: Eleven elderly subjects (aged 70-93 years) with well compensated congestive heart failure (NY Heart Association class I or II), seven elderly subjects (aged 70-79 years) without congestive heart failure, and 10 healthy young adult subjects (aged 20-30 years). MEASUREMENTS: Subjects walked for 8 minutes on level ground at their own selected walking rate. Footswitches were used to measure the time between steps. Step rate (steps/minute) and step rate variability were calculated for the entire walking period, for 30 seconds during the first minute of the walk, for 30 seconds during the last minute of the walk, and for the 30-second period when each subject's step rate variability was minimal. Group means and 5% and 95% confidence intervals were computed. MAIN RESULTS: All measures of walking variability were significantly increased in the elderly subjects with congestive heart failure, intermediate in the elderly controls, and lowest in the young subjects. There was no overlap between the three groups using the minimal 30-second variability (elderly CHF vs elderly controls: P < 0.001, elderly controls vs young: P < 0.001), and no overlap between elderly subjects with and without congestive heart failure when using the overall variability. For all four measures, there was no overlap in any of the confidence intervals, and all group means were significantly different (P < 0.05).

Hausdorff, J. M.; Forman, D. E.; Ladin, Z.; Goldberger, A. L.; Rigney, D. R.; Wei, J. Y.

1994-01-01

405

Treadmill Training Improves Overground Walking Economy in Parkinson's Disease: A Randomized, Controlled Pilot Study  

PubMed Central

Gait disturbances are one of the principal and most incapacitating symptoms of Parkinson’s disease (PD). In addition, walking economy is impaired in PD patients and could contribute to excess fatigue in this population. An important number of studies have shown that treadmill training can improve kinematic parameters in PD patients. However, the effects of treadmill and overground walking on the walking economy remain unknown. The goal of this study was to explore the walking economy changes in response to a treadmill and an overground training program, as well as the differences in the walking economy during treadmill and overground walking. Twenty-two mild PD patients were randomly assigned to a treadmill or overground training group. The training program consisted of 5?weeks (3 sessions/week). We evaluated the energy expenditure of overground walking, before and after each of the training programs. The energy expenditure of treadmill walking (before the program) was also evaluated. The treadmill, but not the overground training program, lead to an improvement in the walking economy (the rate of oxygen consumed per distance during overground walking at a preferred speed) in PD patients. In addition, walking on a treadmill required more energy expenditure compared with overground walking at the same speed. This study provides evidence that in mild PD patients, treadmill training is more beneficial compared with that of walking overground, leading to a greater improvement in the walking economy. This finding is of clinical importance for the therapeutic administration of exercise in PD. PMID:25309510

Fernandez-del-Olmo, Miguel Angel; Sanchez, Jose Andres; Bello, Olalla; Lopez-Alonso, Virginia; Marquez, Gonzalo; Morenilla, Luis; Castro, Xabier; Giraldez, Manolo; Santos-Garcia, Diego

2014-01-01

406

Walking Adaptability after a Stroke and Its Assessment in Clinical Settings  

PubMed Central

Control of walking has been described by a tripartite model consisting of stepping, equilibrium, and adaptability. This review focuses on walking adaptability, which is defined as the ability to modify walking to meet task goals and environmental demands. Walking adaptability is crucial to safe ambulation in the home and community environments and is often severely compromised after a stroke. Yet quantification of walking adaptability after stroke has received relatively little attention in the clinical setting. The objectives of this review were to examine the conceptual challenges for clinical measurement of walking adaptability and summarize the current state of clinical assessment for walking adaptability. We created nine domains of walking adaptability from dimensions of community mobility to address the conceptual challenges in measurement and reviewed performance-based clinical assessments of walking to determine if the assessments measure walking adaptability in these domains. Our literature review suggests the lack of a comprehensive well-tested clinical assessment tool for measuring walking adaptability. Accordingly, recommendations for the development of a comprehensive clinical assessment of walking adaptability after stroke have been presented. Such a clinical assessment will be essential for gauging recovery of walking adaptability with rehabilitation and for motivating novel strategies to enhance recovery of walking adaptability after stroke.

Balasubramanian, Chitralakshmi K.; Clark, David J.; Fox, Emily J.

2014-01-01

407

Interactive cueing with walk-Mate for Hemiparetic Stroke Rehabilitation  

PubMed Central

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. PMID:22909032

2012-01-01

408

EMG patterns during assisted walking in the exoskeleton  

PubMed Central

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

409

Quantum Walk-based Generation of Entanglement Between Two Walkers  

E-print Network

Quantum walks can be used either as tools for quantum algorithm development or as entanglement generators, potentially useful to test quantum hardware. We present a novel algorithm based on a discrete Hadamard quantum walk on a line with one coin and two walkers whose purpose is to generate entanglement between walkers. We provide several classical computer simulations of our quantum algorithm in which we show that, although the asymptotical amount of entanglement generated between walkers does not reach the highest degree of entanglement possible at each step for either coin measurement outcome, the entanglement ratio (entanglement generated/highest value of entanglement possible, for each step) tends to converge, and the actual convergence value depends on the coin initial state and on the coin measurement outcome. Furthermore, our numerical simulations show that, for the quantum walks used in our algorithm, the value towards which entanglement ratio converges also depends on the position probability distribution symmetry of a quantum walk computed with one single walker and the same coin initial state employed in the corresponding quantum walk with two walkers.

Salvador E. Venegas-Andraca; Sougato Bose

2009-01-26

410

Obstacle avoidance to elicit freezing of gait during treadmill walking.  

PubMed

Freezing of gait (FOG) is a common and disabling feature of Parkinson's disease (PD). Detailed pathophysiological studies are hampered by the fact that FOG episodes are difficult to elicit in a gait laboratory. We evaluated whether the need to avoid sudden obstacles on a treadmill can provoke FOG. We included 21 PD patients (15 with self-reported off-period FOG). Patients were tested in the off-state. FOG during overground walking was assessed using a standardized gait trajectory and axial 360 degrees turns. Subsequently, patients walked on a motorized treadmill with suddenly appearing obstacles that necessitated compensatory stepping. Performance was videotaped, and presence of FOG was scored visually by two independent raters. Thirteen patients showed FOG during overground walking. During treadmill walking, obstacle avoidance was associated with 13 unequivocal FOG episodes in eight patients, whereas only one patient froze during undisturbed treadmill walking (Wilcoxon z = -2.0, P = 0.046). FOG episodes elicited by obstacle avoidance were brief (typically <1 s). Almost all episodes were provoked when subjects had a longer available response time. In conclusion, suddenly appearing obstacles on a treadmill can elicit FOG in a controlled laboratory setting. However, the moving treadmill and the obstacle both act as cues, which apparently help to immediately overcome the provoked FOG episode. This may limit the ecological validity of this new approach. PMID:19938174

Snijders, Anke H; Weerdesteyn, Vivian; Hagen, Yolien J; Duysens, Jacques; Giladi, Nir; Bloem, Bastiaan R

2010-01-15

411

Responsiveness of walking-based outcome measures after multiple sclerosis relapses following steroid pulses  

PubMed Central

Summary Background The aim of this study was to examine the impact of intravenous methylprednisolone therapy (IVMP) on the recovery of walking ability in patients experiencing multiple sclerosis (MS) relapses, to compare the responsiveness of walking-based measures, and to estimate the impact of different walking-based measures responsiveness on clinical trials. Material/Methods The study included 49 consecutive patients with relapsing-remitting MS who received Solu-Medrol 1000 mg/day over 3 days for relapse with difficulties in walking. The following walking-based measures were administered before and a month after IVMP: the Multiple Sclerosis Walking Scale-12 (MSWS-12), the Expanded Disability Status Scale (EDSS), the 2-minute timed walk (2-minTW), the 25-foot walk test (25FWT), the Six Spot Step Test (SSST). All patients had worn the step activity monitor accelerometer (SAM) 1 week prior to IVMP was applied and wore it again the fourth week upon the corticosteroid therapy was completed. The SAM analysis utilized the average daily step count and data regarding frequency and intensity of walking over a continuous time interval. We examined: (1) the impact of IVMP on the recovery of walking ability; (2) the responsiveness of each walking-based measure; (3) the relative responsiveness of competing walking-based measures; and (4) the impact of different walking-based measures responsiveness on clinical trials. Results All walking-based measures showed significant improvement of walking ability 1 month after the IVMP. The most responsive were MSWS-12 and EDSS. Different responsiveness implied a greater than 6-fold impact on sample size estimates. Conclusions All applied walking-based measures showed significant improvement of walking ability 1 month after the IVMP. Responsiveness of various walking-based measures notably differ, thus affecting sample size calculations. PMID:22129902

Grcic, Petar Filipovic; Matijaca, Meri; Lusic, Ivo; Capkun, Vesna

2011-01-01

412

Experimental realization of a delayed-choice quantum walk.  

PubMed

Many paradoxes of quantum mechanics come from the fact that quantum systems can possess different features simultaneously, such as in wave-particle duality or quantum superposition. In recent delayed-choice experiments, a quantum system can be observed to manifest one feature such as the wave or particle nature, depending on the measurement setup, which is chosen after the system itself has already entered the measuring device; hence its behaviour is not predetermined. Here we adapt this paradigmatic scheme to multi-dimensional quantum walks. In our experiment, the way in which a photon interferes with itself in a strongly non-trivial pattern depends on its polarization, which is determined after the photon has already been detected. This is the first experiment realizing a multi-dimensional quantum walk with a single photon source and we present also the first experimental simulation of the Grover walk, a model that can be used to implement the Grover quantum search algorithm. PMID:24030247

Jeong, Youn-Chang; Di Franco, Carlo; Lim, Hyang-Tag; Kim, M S; Kim, Yoon-Ho

2013-01-01

413

Experimental realization of a delayed-choice quantum walk  

NASA Astrophysics Data System (ADS)

Many paradoxes of quantum mechanics come from the fact that quantum systems can possess different features simultaneously, such as in wave-particle duality or quantum superposition. In recent delayed-choice experiments, a quantum system can be observed to manifest one feature such as the wave or particle nature, depending on the measurement setup, which is chosen after the system itself has already entered the measuring device; hence its behaviour is not predetermined. Here we adapt this paradigmatic scheme to multi-dimensional quantum walks. In our experiment, the way in which a photon interferes with itself in a strongly non-trivial pattern depends on its polarization, which is determined after the photon has already been detected. This is the first experiment realizing a multi-dimensional quantum walk with a single photon source and we present also the first experimental simulation of the Grover walk, a model that can be used to implement the Grover quantum search algorithm.

Jeong, Youn-Chang; di Franco, Carlo; Lim, Hyang-Tag; Kim, M. S.; Kim, Yoon-Ho

2013-09-01

414

Physical activity and walking onset in infants with Down syndrome.  

PubMed

Infants with Down syndrome (DS) are described as being less active and they also experience significant delays in motor development. It is hypothesized that early infant physical activity may be influential for the acquisition of independent walking. Physical activity was monitored longitudinally in 30 infants with DS starting at an average age of 10 months participating in a treadmill training intervention. Actiwatches were placed on infants' trunk and right ankle for a 24-hr period, every other month until walking onset. Data were analyzed to separate sedentary-to-light activity (low-act) and moderate-to-vigorous activity (high-act). Results showed that more leg high-act at an average age of 12 and 14 months is related to earlier onset of walking. It is recommended that early leg activity should be promoted in infants with DS. PMID:20147766

Lloyd, Meghann; Burghardt, Amy; Ulrich, Dale A; Angulo-Barroso, Rosa

2010-01-01

415

Quantum Walk-based Generation of Entanglement Between Two Walkers  

E-print Network

Quantum walks can be used either as tools for quantum algorithm development or as entanglement generators, potentially useful to test quantum hardware. We present a novel algorithm based on a discrete Hadamard quantum walk on a line with one coin and two walkers whose purpose is to generate entanglement between walkers. We provide several classical computer simulations of our quantum algorithm in which we show that, although the asymptotical amount of entanglement generated between walkers does not reach the highest degree of entanglement possible at each step for either coin measurement outcome, the entanglement ratio (entanglement generated/highest value of entanglement possible, for each step) tends to converge, and the actual convergence value depends on the coin initial state and on the coin measurement outcome. Furthermore, our numerical simulations show that, for the quantum walks used in our algorithm, the value towards which entanglement ratio converges also depends on the position probability distri...

Venegas-Andraca, Salvador E

2009-01-01

416

Walking robot: A design project for undergraduate students  

NASA Technical Reports Server (NTRS)

The objective of the University of Maryland walking robot project was to design, analyze, assemble, and test an intelligent, mobile, and terrain-adaptive system. The robot incorporates existing technologies in novel ways. The legs emulate the walking path of a human by an innovative modification of a crank-and-rocker mechanism. The body consists of two tripod frames connected by a turning mechanism. The two sets of three legs are mounted so as to allow the robot to walk with stability in its own footsteps. The computer uses a modular hardware design and distributed processing. Dual-port RAM is used to allow communication between a supervisory personal computer and seven microcontrollers. The microcontrollers provide low-level control for the motors and relieve the processing burden on the PC.

1991-01-01

417

Photonic quantum walk in a single beam with twisted light  

E-print Network

Inspired by the classical phenomenon of random walk, the concept of quantum walk has emerged recently as a powerful platform for the dynamical simulation of complex quantum systems, entanglement production and universal quantum computation. Such a wide perspective motivates a renewing search for efficient, scalable and stable implementations of this quantum process. Photonic approaches have hitherto mainly focused on multi-path schemes, requiring interferometric stability and a number of optical elements that scales quadratically with the number of steps. Here we report the experimental realization of a quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous indistinguishable photons. The whole process develops in a single light beam, with no need of interferometers, and requires optical resources scaling linearly with the number of steps. Our demonstration introduces a novel versatile photonic platform for implementing quantum simulations, b...

Cardano, Filippo; Karimi, Ebrahim; Slussarenko, Sergei; Paparo, Domenico; de Lisio, Corrado; Sciarrino, Fabio; Santamato, Enrico; Marrucci, Lorenzo

2014-01-01

418

Gait event detection during stair walking using a rate gyroscope.  

PubMed

Gyroscopes have been proposed as sensors for ambulatory gait analysis and functional electrical stimulation systems. These applications often require detection of the initial contact (IC) of the foot with the floor and/or final contact or foot off (FO) from the floor during outdoor walking. Previous investigations have reported the use of a single gyroscope placed on the shank for detection of IC and FO on level ground and incline walking. This paper describes the evaluation of a gyroscope placed on the shank for determination of IC and FO in subjects ascending and descending a set of stairs. Performance was compared with a reference pressure measurement system. The absolute mean difference between the gyroscope and the reference was less than 45 ms for IC and better than 135 ms for FO for both activities. Detection success was over 93%. These results provide preliminary evidence supporting the use of a gyroscope for gait event detection when walking up and down stairs. PMID:24651724

Formento, Paola Catalfamo; Acevedo, Ruben; Ghoussayni, Salim; Ewins, David

2014-01-01

419

Wilson loops in string duals of walking and flavored systems  

SciTech Connect

We consider the vacuum expectation value of Wilson loop operators by studying the behavior of string probes in solutions of type-IIB string theory generated by N{sub c} D5-branes wrapped on an S{sup 2} internal manifold. In particular, we focus on solutions to the background equations that are dual to field theories with a walking gauge coupling as well as for flavored systems. We present in detail our walking solution and emphasize various general aspects of the procedure to study Wilson loops using string duals. We discuss the special features that the strings show when probing the region associated with the walking of the field-theory coupling.

Nunez, Carlos; Piai, Maurizio; Rago, Antonio [Swansea University, School of Physical Sciences, Singleton Park, Swansea, Wales (United Kingdom)

2010-04-15

420

Bicycle Riding, Walking, and Weight Gain in Premenopausal Women  

PubMed Central

Context No research has been conducted on bicycle riding and weight control in comparison to walking. Objective To assess the association between bicycle riding and weight control in premenopausal women. Design, Setting, and Participants This was a 16-year follow-up of 18, 414 women in the Nurses’ Health Study II. Main Outcome Measures Weight change between 1989 and 2005 was the primary outcome and odds of gaining >5% of baseline body weight (BBW) by 2005 the secondary outcome. Results At baseline, only 39% walked briskly while only 1.2% bicycled for ?30 min/d. For a 30 min/d increase in activity between 1989 and 2005, weight gain was significantly less for brisk walking (?1.81 kg; 95% confidence interval (CI) = ?2.05,?1.56), bicycling (?1.59 kg; 95%CI= ?2.09, ?1.08), and other activities (?1.45 kg; 95%CI= ?1.66, ?1.24) but not for slow walking (+0.06 kg; 95%CI= ?0.22, 0.35). Women who reported no bicycling in 1989 and increased to as little as 5 minutes/day in 2005 gained less weight (?0.74 kg; 95%CI= ?1.41, ?0.07, P-trend<0.01) than those who remained non-bikers. Normal weight women who bicycled ? 4 hours/week in 2005 had lower odds of gaining >5% of their BBW (Odds Ratio (OR) =0.74, 95%CI=0.56–0.98) compared with those who reported no bicycling; overweight/obese women had lower odds at 2–3 hours/week (OR=0.54, 95%CI=0.34–86). Conclusions Bicycling, similar to brisk walking, is associated with less weight gain and an inverse dose-response relationship exists, especially among overweight/obese women. Future research should focus on brisk walking but also on greater time spent bicycling. PMID:20585071

Lusk, Anne C.; Mekary, Rania A.; Feskanich, Diane; Willett, Walter C.

2011-01-01

421

Walking Is Not Like Reaching: Evidence from Periodic Mechanical Perturbations  

PubMed Central

The control architecture underlying human reaching has been established, at least in broad outline. However, despite extensive research, the control architecture underlying human locomotion remains unclear. Some studies show evidence of high-level control focused on lower-limb trajectories; others suggest that nonlinear oscillators such as lower-level rhythmic central pattern generators (CPGs) play a significant role. To resolve this ambiguity, we reasoned that if a nonlinear oscillator contributes to locomotor control, human walking should exhibit dynamic entrainment to periodic mechanical perturbation; entrainment is a distinctive behavior of nonlinear oscillators. Here we present the first behavioral evidence that nonlinear neuro-mechanical oscillators contribute to the production of human walking, albeit weakly. As unimpaired human subjects walked at constant speed, we applied periodic torque pulses to the ankle at periods different from their preferred cadence. The gait period of 18 out of 19 subjects entrained to this mechanical perturbation, converging to match that of the perturbation. Significantly, entrainment occurred only if the perturbation period was close to subjects' preferred walking cadence: it exhibited a narrow basin of entrainment. Further, regardless of the phase within the walking cycle at which perturbation was initiated, subjects' gait synchronized or phase-locked with the mechanical perturbation at a phase of gait where it assisted propulsion. These results were affected neither by auditory feedback nor by a distractor task. However, the convergence to phase-locking was slow. These characteristics indicate that nonlinear neuro-mechanical oscillators make at most a modest contribution to human walking. Our results suggest that human locomotor control is not organized as in reaching to meet a predominantly kinematic specification, but is hierarchically organized with a semi-autonomous peripheral oscillator operating under episodic supervisory control. PMID:22479311

Ahn, Jooeun; Hogan, Neville

2012-01-01

422

Running for Exercise Mitigates Age-Related Deterioration of Walking Economy  

PubMed Central

Introduction Impaired walking performance is a key predictor of morbidity among older adults. A distinctive characteristic of impaired walking performance among older adults is a greater metabolic cost (worse economy) compared to young adults. However, older adults who consistently run have been shown to retain a similar running economy as young runners. Unfortunately, those running studies did not measure the metabolic cost of walking. Thus, it is unclear if running exercise can prevent the deterioration of walking economy. Purpose To determine if and how regular walking vs. running exercise affects the economy of locomotion in older adults. Methods 15 older adults (69±3 years) who walk ?30 min, 3x/week for exercise, “walkers” and 15 older adults (69±5 years) who run ?30 min, 3x/week, “runners” walked on a force-instrumented treadmill at three speeds (0.75, 1.25, and 1.75 m/s). We determined walking economy using expired gas analysis and walking mechanics via ground reaction forces during the last 2 minutes of each 5 minute trial. We compared walking economy between the two groups and to non-aerobically trained young and older adults from a prior study. Results Older runners had a 7–10% better walking economy than older walkers over the range of speeds tested (p?=?.016) and had walking economy similar to young sedentary adults over a similar range of speeds (p?=?.237). We found no substantial biomechanical differences between older walkers and runners. In contrast to older runners, older walkers had similar walking economy as older sedentary adults (p?=?.461) and ?26% worse walking economy than young adults (p<.0001). Conclusion Running mitigates the age-related deterioration of walking economy whereas walking for exercise appears to have minimal effect on the age-related deterioration in walking economy. PMID:25411850

Ortega, Justus D.; Beck, Owen N.; Roby, Jaclyn M.; Turney, Aria L.; Kram, Rodger

2014-01-01

423

Measuring walking within and outside the neighborhood in Chinese elders: reliability and validity  

PubMed Central

Background Walking is a preferred, prevalent and recommended activity for aging populations and is influenced by the neighborhood built environment. To study this influence it is necessary to differentiate whether walking occurs within or outside of the neighborhood. The Neighborhood Physical Activity Questionnaire (NPAQ) collects information on setting-specific physical activity, including walking, inside and outside one's neighborhood. While the NPAQ has shown to be a reliable measure in adults, its reliability in older adults is unknown. Additionally its validity and the influence of type of neighborhood on reliability and validity have yet to be explored. Methods The NPAQ walking component was adapted for Chinese speaking elders (NWQ-CS). Ninety-six Chinese elders, stratified by social economic status and neighborhood walkability, wore an accelerometer and completed a log of walks for 7 days. Following the collection of valid data the NWQ-CS was interviewer-administered. Fourteen to 20 days (average of 17 days) later the NWQ-CS was re-administered. Test-retest reliability and validity of the NWQ-CS were assessed. Results Reliability and validity estimates did not differ with type of neighborhood. NWQ-CS measures of walking showed moderate to excellent reliability. Reliability was generally higher for estimates of weekly frequency than minutes of walking. Total weekly minutes of walking were moderately related to all accelerometry measures. Moderate-to-strong associations were found between the NWQ-CS and log-of-walks variables. The NWQ-CS yielded statistically significantly lower mean values of total walking, weekly minutes of walking for transportation and weekly frequency of walking for transportation outside the neighborhood than the log-of-walks. Conclusions The NWQ-CS showed measurement invariance across types of neighborhoods. It is a valid measure of walking for recreation and frequency of walking for transport. However, it may systematically underestimate the duration of walking for transport in samples that engage in high levels of this type of walking. PMID:22070768

2011-01-01

424

Directional correlations in quantum walks with two particles  

E-print Network

Quantum walks on the line with a single particle possess a classical analog. Involving more walkers opens up the possibility to study collective quantum effects, such as many particle correlations. In this context, entangled initial states and indistinguishability of the particles play a role. We consider directional correlations between two particles performing a quantum walk on a line. For non-interacting particles we find analytic asymptotic expressions and give the limits of directional correlations. We show that introducing $\\delta$-interaction between the particles, one can exceed the limits for non-interacting particles.

M. Stefanak; S. M. Barnett; B. Kollar; T. Kiss; I. Jex

2011-02-22

425

Two-dimensional random walk in a bounded domain  

E-print Network

In a recent Letter Ciftci and Cakmak [EPL 87, 60003 (2009)] showed that the two dimensional random walk in a bounded domain, where walkers which cross the boundary return to a base curve near origin with deterministic rules, can produce regular patterns. Our numerical calculations suggest that the cumulative probability distribution function of the returning walkers along the base curve is a Devil's staircase, which can be explained from the mapping of these walks to a non-linear stochastic map. The non-trivial probability distribution function(PDF) is a universal feature of CCRW characterized by the fractal dimension d=1.75(0) of the PDF bounding curve.

Mahashweta Basu; P. K. Mohanty

2009-10-30

426

The critical pulling force for self-avoiding walks  

E-print Network

Self-avoiding walks are a simple and well-known model of long, flexible polymers in a good solvent. Polymers being pulled away from a surface by an external agent can be modelled with self-avoiding walks in a half-space with a Boltzmann weight $y$ associated with the pulling force. This model is known to have a critical point at a certain value $y_c$ of this Boltzmann weight, which is the location of a transition between the so-called free and ballistic phases. We prove that $y_c=1$, confirming conjectures based on numerical estimates by several authors.

Nicholas R. Beaton

2014-07-08

427

Adaptive walks on time-dependent fitness landscapes.  

PubMed

The idea of adaptive walks on fitness landscapes as a means of studying evolutionary processes on large time scales is extended to fitness landscapes that are slowly changing over time. The influence of ruggedness and of the amount of static fitness contributions is investigated for model landscapes derived from Kauffman's NK landscapes. Depending on the amount of static fitness contributions in the landscape, the evolutionary dynamics can be divided into a percolating and a nonpercolating phase. In the percolating phase, the walker performs a random walk over the regions of the landscape with high fitness. PMID:11970008

Wilke, C O; Martinetz, T

1999-08-01

428

Record statistics of financial time series and geometric random walks  

E-print Network

The study of record statistics of correlated series is gaining momentum. In this work, we study the records statistics of the time series of select stock market data and the geometric random walk, primarily through simulations. We show that the distribution of the age of records is a power law with the exponent $\\alpha$ lying in the range $1.5 \\le \\alpha \\le 1.8$. Further, the longest record ages follow the Fr\\'{e}chet distribution of extreme value theory. The records statistics of geometric random walk series is in good agreement with that from the empirical stock data.

Sabir, Behlool

2014-01-01

429

Massless Dirac Equation from Fibonacci Discrete-Time Quantum Walk  

E-print Network

Discrete-time quantum walks can be regarded as quantum dynamical simulators since they can simulate spatially discretized Schr\\"{o}dinger, massive Dirac, and Klein-Gordon equations. Here, two different types of Fibonacci discrete-time quantum walks are studied analytically. The first is the Fibonacci coin sequence with a generalized Hadamard coin and demonstrates six-step periodic dynamics. The other model is assumed to have three- or six-step periodic dynamics with the Fibonacci sequence. We analytically show that these models have ballistic transportation properties and continuous limits identical to those of the massless Dirac equation with coin basis change.

Giuseppe Di Molfetta; Lauchlan Honter; Ben B. Luo; Tatsuaki Wada; Yutaka Shikano

2014-10-17

430

Non-Gaussian propagator for elephant random walks.  

PubMed

For almost a decade the consensus has held that the random walk propagator for the elephant random walk (ERW) model is a Gaussian. Here we present strong numerical evidence that the propagator is, in general, non-Gaussian and, in fact, non-Lévy. Motivated by this surprising finding, we seek a second, non-Gaussian solution to the associated Fokker-Planck equation. We prove mathematically, by calculating the skewness, that the ERW Fokker-Planck equation has a non-Gaussian propagator for the superdiffusive regime. Finally, we discuss some unusual aspects of the propagator in the context of higher order terms needed in the Fokker-Planck equation. PMID:24032783

da Silva, M A A; Cressoni, J C; Schütz, Gunter M; Viswanathan, G M; Trimper, Steffen

2013-08-01

431

Self-avoiding walk is sub-ballistic  

E-print Network

We prove that self-avoiding walk on Z^d is sub-ballistic in any dimension d at least two. That is, writing ||u|| for the Euclidean norm of u \\in Z^d, and SAW_n for the uniform measure on self-avoiding walks gamma:{0,...,n} \\to Z^d for which gamma_0 = 0, we show that, for each v > 0, there exists c > 0 such that, for each positive integer n, SAW_n (max {|| gamma_k || : k \\in {0,...,n}} > v n) < e^{- c n}.

Hugo Duminil-Copin; Alan Hammond

2012-05-02

432

Walking to Olympus: An EVA Chronology  

NASA Technical Reports Server (NTRS)

Spacewalkers enjoy a view of Earth once reserved for Apollo, Zeus, and other denizens of Mt. Olympus. During humanity's first extravehicular activity (EVA), Alexei Leonov floated above Gibraltar, the rock ancient seafarers saw as the gateway to the great unknown Atlantic. The symbolism was clear, Leonov stepped past a new Gibraltar when he stepped into space. More than 32 years and 154 EVAs later, Jerry Linenger conducted an EVA with Vladimir Tsibliyev as part of International Space Station Phase 1. They floated together above Gibraltar. Today the symbolism has new meaning: humanity is starting to think of stepping out of Earth orbit, space travel's new Gibraltar, and perhaps obtaining a new olympian view, a close-up look at Olympus Mons on Mars. Walking to Olympus: An EVA Chronology chronicles the 154 EVAs conducted from March 1965 to April 1997. It is intended to make clear the crucial role played by EVA in the history of spaceflight, as well as to chronicle the large body of EVA "lessons learned." Russia and the U.S. define EVA differently. Russian cosmonauts are said to perform EVA any time they are in vacuum in a space suit. A U.S. astronaut must have at least his head outside his spacecraft before he is said to perform an EVA. The difference is based in differing spacecraft design philoso- phies. Russian and Soviet spacecraft have always had a specialized airlock through which the EVA cosmonaut egressed, leaving the main habitable volume of the spacecraft pressurized. The U.S. Gemini and Apollo vehicles, on the other hand, depressurized their entire habitable volume for egress. In this document, we apply the Russian definition to Russian EVAS, and the U.S. definition to U.S. EVAS. Thus, for example, Gemini 4 Command Pilot James McDivitt does not share the honor of being first American spacewalker with Ed White, even though he was suited and in vacuum when White stepped out into space. Non-EVA spaceflights are listed in the chronology to provide context and to display the large num- ber of flights in which EVA played a role. This approach also makes apparent significant EVA gaps, for example, the U.S. gap between 1985 and 1991 following the Challenger accident. This NASA History Monograph is an edited extract from an extensive EVA Chronology and Reference Book being produced by the EVA Project Office, NASA Johnson Space Center, Houston, Texas. The larger work will be published as part of the NASA Formal Series in 1998. The authors gratefully acknowledge the assistance rendered by Max Ary, Ashot Bakunts, Gert-Jan Bartelds, Frank Cepollina, Andrew Chaikin, Phillip Clark, Richard Fullerton, Steven Glenn, Linda Godwin, Jennifer Green, Greg Harris, Clifford Hess, Jeffrey Hoffman, David Homan, Steven Hopkins, Nicholas Johnson, Eric Jones, Neville Kidger, Joseph Kosmo, Alexei Lebedev, Mark Lee, James LeBlanc, Dmitri Leshchenskii, Jerry Linenger, Igor Lissov, James McBarron, Clay McCullough, Joseph McMann, Story Musgrave, Dennis Newkirk, James Oberg, Joel Powell, Lee Saegesser, Andy Salmon, Glen Swanson, Joseph Tatarewicz, Kathy Thornton, Chris Vandenberg, Charles Vick, Bert Vis, David Woods, Mike Wright, John Young, and Keith Zimmerman. Special thanks to Laurie Buchanan, John Charles, Janet Kovacevich, Joseph Loftus, Sue McDonald, Martha Munies, Colleen Rapp, and Jerry Ross. Any errors remain the responsibility of the authors.

Portree, David S. F.; Trevino, Robert C.

1997-01-01

433

A randomized trial of functional electrical stimulation for walking in incomplete spinal cord injury: Effects on walking competency.  

PubMed

Background Multi-channel surface functional electrical stimulation (FES) for walking has been used to improve voluntary walking and balance in individuals with spinal cord injury (SCI). Objective To investigate short- and long-term benefits of 16 weeks of thrice-weekly FES-assisted walking program, while ambulating on a body weight support treadmill and harness system, versus a non-FES exercise program, on improvements in gait and balance in individuals with chronic incomplete traumatic SCI, in a randomized controlled trial design. Methods Individuals with traumatic and chronic (?18 months) motor incomplete SCI (level C2 to T12, American Spinal Cord Injury Association Impairment Scale C or D) were recruited from an outpatient SCI rehabilitation hospital, and randomized to FES-assisted walking therapy (intervention group) or aerobic and resistance training program (control group). Outcomes were assessed at baseline, and after 4, 6, and 12 months. Gait, balance, spasticity, and functional measures were collected. Results Spinal cord independence measure (SCIM) mobility sub-score improved over time in the intervention group compared with the control group (baseline/12 months: 17.27/21.33 vs. 19.09/17.36, respectively). On all other outcome measures the intervention and control groups had similar improvements. Irrespective of group allocation walking speed, endurance, and balance during ambulation all improved upon completion of therapy, and majority of participants retained these gains at long-term follow-ups. Conclusions Task-oriented training improves walking ability in individuals with incomplete SCI, even in the chronic stage. Further randomized controlled trials, involving a large number of participants are needed, to verify if FES-assisted treadmill training is superior to aerobic and strength training. PMID:25229735

Kapadia, Naaz; Masani, Kei; Catharine Craven, B; Giangregorio, Lora M; Hitzig, Sander L; Richards, Kieva; Popovic, Milos R

2014-09-01

434

Powered ankle-foot prosthesis for the improvement of amputee walking economy  

E-print Network

The human ankle provides a significant amount of net positive work during the stance period of walking, especially at moderate to fast walking speeds. On the contrary, conventional ankle-foot prostheses are completely ...

Au, Samuel Kwok-Wai

2007-01-01

435

Long-Range Correlations in Stride Intervals May Emerge from Non-Chaotic Walking Dynamics  

E-print Network

Stride intervals of normal human walking exhibit long-range temporal correlations. Similar to the fractal-like behaviors observed in brain and heart activity, long-range correlations in walking have commonly been interpreted ...

Ahn, Jooeun

436

A knee brace design to reduce the energy consumption of walking  

E-print Network

Recent research into the mechanics of walking indicates that a quasi passive wearable device could be created which dramatically reduces the metabolic energy used in walking especially when the wearer is carrying additional ...

Carvey, Matthew R

2005-01-01

437

The Apollo Number: space suits, self-support, and the walk-run  

E-print Network

Background: How space suits affect the preferred walk-run transition is an open question with relevance to human biomechanics and planetary extravehicular activity. Walking and running energetics differ; in reduced gravity ...

McGee, Jeremy

438

Effects of a 6-month exercise program pilot study on walking economy, peak physiological characteristics, and walking performance in patients with peripheral arterial disease  

PubMed Central

The purpose of this study was to examine the effects of a 6-month exercise program on submaximal walking economy in individuals with peripheral arterial disease and intermittent claudication (PAD-IC). Participants (n = 16) were randomly allocated to either a control PAD-IC group (CPAD-IC, n = 6) which received standard medical therapy, or a treatment PAD-IC group (TPAD-IC; n = 10) which took part in a supervised exercise program. During a graded treadmill test, physiological responses, including oxygen consumption, were assessed to calculate walking economy during submaximal and maximal walking performance. Differences between groups at baseline and post-intervention were analyzed via Kruskal–Wallis tests. At baseline, CPAD-IC and TPAD-IC groups demonstrated similar walking performance and physiological responses. Postintervention, TPAD-IC patients demonstrated significantly lower oxygen consumption during the graded exercise test, and greater maximal walking performance compared to CPAD-IC. These preliminary results indicate that 6 months of regular exercise improves both submaximal walking economy and maximal walking performance, without significant changes in maximal walking economy. Enhanced walking economy may contribute to physiological efficiency, which in turn may improve walking performance as demonstrated by PAD-IC patients following regular exercise programs. PMID:22566743

Crowther, Robert G; Leicht, Anthony S; Spinks, Warwick L; Sangla, Kunwarjit; Quigley, Frank; Golledge, Jonathan

2012-01-01

439

On your feet: protocol for a randomized controlled trial to compare the effects of pole walking and regular walking on physical and psychosocial health in older adults  

PubMed Central

Background Physical activity is associated with better physical and mental health in older adults. Pole walking is a form of walking which may have additional health benefits in older adults, because of the addition of hand held poles, and consequent upper limb involvement. However, few studies have examined the potential additional effects of pole walking on physical and psychosocial health in older adults compared with walking. The aim of this study is to compare the effect of a pole walking program with the effects of a walking program, on physical and psychosocial wellbeing, in older adults in assisted living facilities. Methods/Design Sixty men and women from assisted living communities over 65 years will be recruited from senior retirement facilities and randomized into a group based, pole walking program, or walking program. The pole walking group will use the Exerstrider method of pole walking. Total duration of the programs is 12 weeks, with three sessions per week, building from 20 minute to 30 minute sessions. The primary outcome is physical function, as measured by items from the Seniors Fitness Test and hand grip strength. Secondary outcomes include, physical activity levels, sedentary behaviour, joint pain, and quality of life. All outcomes will be assessed before and after the programs, using valid and reliable measures. Discussion The study will add to the evidence base for the effects of pole walking, compared with walking, on physical and psychosocial health and physical function, in healthy older adults. This will improve understanding about the feasibility of pole walking programs and its specific benefits in this population. Trial registration Australian New Zealand Clinical Trials Registry ACTRN12612001127897. PMID:24742126

2014-01-01

440

World-Wide-Walks \\/ between earth & sky \\/ Dun na nGall  

Microsoft Academic Search

The World-Wide-Walks explore natural\\/cultural\\/virtual identities: mixed realities that encompass walking in physical environments and virtually surfing the Web. The first of these projects, The Walk Series, was initiated by Peter d'Agostino in 1973 as video documentation\\/performances. World-Wide-Walks \\/ between earth & sky \\/ Dun na nGall is a video\\/web sculptural installation informed by environmental arts and sciences and local knowledge.

Peter d'Agostino; Deirdre Dowdakin; David Tafler

2012-01-01

441

World-Wide-Walks \\/ between earth & sky \\/ Dun na nGall  

Microsoft Academic Search

The World-Wide-Walks explore natural\\/cultural\\/virtual identities: mixed realities that encompass walking in physical environments and virtually surfing the Web. The first of these projects, The Walk Series, was initiated by Peter d'Agostino in 1973 as video documentation\\/performances. World-Wide-Walks \\/ between earth & sky \\/ Dun na nGall is a video\\/web sculptural installation informed by environmental arts and sciences and local knowledge.

Peter d'Agostino; Deirdre Dowdakin; David Tafler

442

EMG Analysis of Level and Incline Walking in Reebok EasyTone ET Calibrator  

Microsoft Academic Search

\\u000a This study examines (1) the effect of the Reebok Easytone walking shoe on muscle activity of three large extrinsic muscles\\u000a compared to walking in a neutral running shoe, and (2) a comparison of muscle activity when walking on an inclined slope and\\u000a walking in the EasyTone shoe on level ground. Methods. Ten male subjects participated in a crossover study. A

E. F. Elkjær; A. Kromann; B. Larsen; E. L. Andresen; M. K. Jensen; P. J. Veng; M. Zee

443

35. Plan of Proposed Improvements on Roads, Walks, Gutters, Curbs, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

35. Plan of Proposed Improvements on Roads, Walks, Gutters, Curbs, Drains, Etc. Letterman General Hospital, Presidio of San Francisco. August 1915. SHOWING LOCATION OF BUILDINGS 1006 AND 1049 IN LETTERMAN HOSPITAL COMPLEX IN 1915. - Presidio of San Francisco, Letterman General Hospital, Building No. 27, Letterman Hospital Complex, Edie Road, San Francisco, San Francisco County, CA

444

Understanding How Families Use Magnifiers during Nature Center Walks  

ERIC Educational Resources Information Center

This analysis uses a sociocultural learning theory and parent-child interaction framework to understand families' interactions with one type of scientific tool, the magnifier, during nature walks offered by a nature center. Families were video recorded to observe how they organized their activities where they used magnifiers to explore in the…

Zimmerman, Heather Toomey; McClain, Lucy Richardson; Crowl, Michele

2013-01-01

445

The magnitude of muscle damage induced by downhill backward walking.  

PubMed

While various models for exercise-induced muscle damage (EIMD) have been introduced, many of them use maximal voluntary contractions of the elbow flexors and knee extensors performed on isokinetic dynamometers. Few studies have used exercise protocols that attempt to replicate submaximal eccentric muscle actions that commonly occur during daily activities. Downhill backwards walking has been used previously as an EIMD model. However, the common markers of muscle damage have not been systematically examined for this model. The purpose of this study was to determine the magnitude of muscle damage induced by downhill backward walking with regard to changes in commonly-used indirect markers of EIMD. Twenty subjects aged between 19 y and 42 y completed a bout of 60 min of downhill (-15%) backward walking in which a single limb performed submaximal eccentric actions at a stepping rate of 30 - 35 strides per min. A repeated measures ANOVA revealed significant (p < 0.05) increases from baseline for soreness (24 hr- 96 hr), tenderness (24 hr - 96 hr), and plasma creatine kinase activity (0.5 hr - 96 hr), and significant decreases (p < 0.05) in maximal voluntary isometric (approximately 25%) and isokinetic (-15%) strength (0.5 hr - 96 hr) post-walk for the exercised limb. The time course of observed changes in these markers was similar to that reported for EIMD models of the elbow flexors and knee extensors. However, the magnitude of muscle damage appeared more consistent with that demonstrated following submaximal eccentric exercise. PMID:16248467

Nottle, C; Nosaka, K

2005-09-01

446

Physical Activity and Walking Onset in Infants with Down Syndrome  

ERIC Educational Resources Information Center

Infants with Down syndrome (DS) are described as being less active and they also experience significant delays in motor development. It is hypothesized that early infant physical activity may be influential for the acquisition of independent walking. Physical activity was monitored longitudinally in 30 infants with DS starting at an average age of…

Lloyd, Meghann; Burghardt, Amy; Ulrich, Dale A.; Angulo-Barroso, Rosa

2010-01-01

447

Loci communes and thoreau's arguments for wilderness in “walking” (1851)  

Microsoft Academic Search

Perelman and Olbrechts?Tyteca's concept of loci communes is investigated for its contributions to a critical methodology. It is argued that discourse relying upon different loci may lead to different construals of the APPEARANCE?REALITY pair and, hence, to different interpretations of the value of a given object, idea, or action. Analyses of Henry David Thoreau's “Walking” (1851) and other Transcendentalist writings

J. Robert Cox

1980-01-01

448

Modular control of human walking: Adaptations to altered mechanical demands  

E-print Network

of surface electromyography (EMG) suggest that the nervous system may adopt a relatively simple control computer modeling and simulation study of human walking using experimentally derived modules as the control by the perturbations. These results support the idea that the nervous system may use a modular control strategy

449

Electrical Resistance of the Low Dimensional Critical Branching Random Walk  

NASA Astrophysics Data System (ADS)

We show that the electrical resistance between the origin and generation n of the incipient infinite oriented branching random walk in dimensions d < 6 is O( n 1- ? ) for some universal constant ? > 0. This answers a question of Barlow et al. (Commun Math Phys 278:385-431, 2008).

Járai, Antal A.; Nachmias, Asaf

2014-10-01

450

Performance of redirected walking algorithms in a constrained virtual world.  

PubMed

Redirected walking algorithms imperceptibly rotate a virtual scene about users of immersive virtual environment systems in order to guide them away from tracking area boundaries. Ideally, these distortions permit users to explore large unbounded virtual worlds while walking naturally within a physically limited space. Many potential virtual worlds are composed of corridors, passageways, or aisles. Assuming users are not expected to walk through walls or other objects within the virtual world, these constrained worlds limit the directions of travel and as well as the number of opportunities to change direction. The resulting differences in user movement characteristics within the physical world have an impact on redirected walking algorithm performance. This work presents a comparison of generalized RDW algorithm performance within a constrained virtual world. In contrast to previous studies involving unconstrained virtual worlds, experimental results indicate that the steer-to-orbit keeps users in a smaller area than the steer-to-center algorithm. Moreover, in comparison to steer-to-center, steer-to-orbit is shown to reduce potential wall contacts by over 29%. PMID:24650985

Hodgson, Eric; Bachmann, Eric; Thrash, Tyler

2014-04-01

451

Asymptotic entanglement in the discrete-time quantum walk  

E-print Network

The coin-position entanglement generated by the evolution operator of a discrete--time quantum walk converges, in the long time limit, to a well defined value which depends on the initial state. We also discuss the asymptotic bi-partite entanglement generated by several non-separable coin operations for two coherent quantum walkers, for which the entropy of entanglement increases logarithmically.

G. Abal; R. Donangelo; H. Fort

2007-09-20

452

Walking and Hiking as a Way of Life  

ERIC Educational Resources Information Center

Exercise usually takes place in leisure time. The benefits, mental and physical, of exercise are well documented, yet, many choose to remain inactive. There is a need for more research concerning those who continue to exercise. The purpose of this study was to understand more about the experience of those who are hiking and walking on Medvednica…

Roberson, Donald N., Jr.; Babic, Vesna

2008-01-01

453

Length of adaptive walk on uncorrelated and correlated fitness landscapes  

NASA Astrophysics Data System (ADS)

We consider the adaptation dynamics of an asexual population that walks uphill on a rugged fitness landscape which is endowed with a large number of local fitness peaks. We work in a parameter regime where only those mutants that are a single mutation away are accessible, as a result of which the population eventually gets trapped at a local fitness maximum and the adaptive walk terminates. We study how the number of adaptive steps taken by the population before reaching a local fitness peak depends on the initial fitness of the population, the extreme value distribution of the beneficial mutations, and correlations among the fitnesses. Assuming that the relative fitness difference between successive steps is small, we analytically calculate the average walk length for both uncorrelated and correlated fitnesses in all extreme value domains for a given initial fitness. We present numerical results for the model where the fitness differences can be large and find that the walk length behavior differs from that in the former model in the Fréchet domain of extreme value theory. We also discuss the relevance of our results to microbial experiments.

Seetharaman, Sarada; Jain, Kavita

2014-09-01

454

Personalizing Forum Search using Multidimensional Random Walks Gayatree Ganu  

E-print Network

Personalizing Forum Search using Multidimensional Random Walks Gayatree Ganu Computer Science@cs.rutgers.edu Abstract Online forums are a vital resource for users to ask ques- tions and to participate in discussions. Yet, the search functionality on such forum sites is very primitive; posts containing the searched

Marian, Amélie

455

West Harlem Walk (Hudson River Valley Greenway) beneath Henry Hudson ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

West Harlem Walk (Hudson River Valley Greenway) beneath Henry Hudson Parkway (HHP) Viaduct at West 155th Street vicinity, with Palisades, George Washington Bridge, and Little Red Lighthouse (visible to left of bridge tower) in background, looking northeast. - Henry Hudson Parkway, Extending 11.2 miles from West 72nd Street to Bronx-Westchester border, New York, New York County, NY

456

Humanoid walking coordination through a single spatial parameter  

Microsoft Academic Search

This article deals with the generation of coordinated movements for humanoid walking. The objective is to produce feasible smooth and natural 3D dynamic gaits over an infinite number of steps with a single input. Our novel approach controls a virtual humanoid by coordinating spatial data in a time independent manner. This approach creates a robust and stable control of the

Jean-Christophe Palyart Lamarche; Olivier Bruneau; Jean-Guy Fontaine

2010-01-01

457

A sparse model predictive control formulation for walking motion generation  

Microsoft Academic Search

This article presents a comparison between dense and sparse model predictive control (MPC) formulations, in the context of walking motion generation for humanoid robots. The former formulation leads to smaller, the latter one to larger but more structured optimization problem. We put an accent on the sparse formulation and point out a number of advantages that it presents. In particular,

Dimitar Dimitrov; Alexander Sherikov; Pierre-Brice Wieber

2011-01-01

458

Humanoid Walking Robot Control with Natural ZMP References  

Microsoft Academic Search

Humanoid robotics attracted the attention of many researchers in the past 35 years. The motivation of research is the suitability of the biped structure for tasks in the human environment. The control of a biped humanoid is a challenging task due to the hard-to-stabilize dynamics. Walking reference trajectory generation is one of the key problems. The zero moment point (ZMP)

Kemalettin Erbatur; Okan Kurt

2006-01-01

459

Map data 2012 Google -Walking directions are in beta.  

E-print Network

Map data ©2012 Google - Walking directions are in beta. Use caution ­ This route may be missing route accordingly. You must obey all signs or notices regarding your route. Map data ©2012 Google Hilton. Hilton Garden Inn West Lafayette Wabash Landing, 356 ... http://maps.google.com/ 1 of 1 06/29/2012 09

460

Nocturnal Homing: Learning Walks in a Wandering Spider?  

PubMed Central

Homing by the nocturnal Namib Desert spider Leucorchestris arenicola (Araneae: Sparassidae) is comparable to homing in diurnal bees, wasps and ants in terms of path length and layout. The spiders' homing is based on vision but their basic navigational strategy is unclear. Diurnal homing insects use memorised views of their home in snapshot matching strategies. The insects learn the visual scenery identifying their nest location during learning flights (e.g. bees and wasps) or walks (ants). These learning flights and walks are stereotyped movement patterns clearly different from other movement behaviours. If the visual homing of L. arenicola is also based on an image matching strategy they are likely to exhibit learning walks similar to diurnal insects. To explore this possibility we recorded departures of spiders from a new burrow in an unfamiliar area with infrared cameras and analysed their paths using computer tracking techniques. We found that L. arenicola performs distinct stereotyped movement patterns during the first part of their departures in an unfamiliar area and that they seem to learn the appearance of their home during these movement patterns. We conclude that the spiders perform learning walks and this strongly suggests that L. arenicola uses a visual memory of the burrow location when homing. PMID:23145137

N?rgaard, Thomas; Gagnon, Yakir L.; Warrant, Eric J.

2012-01-01

461

MODULUS OF FAMILIES OF WALKS ON GRAPHS NATHAN ALBIN1  

E-print Network

MODULUS OF FAMILIES OF WALKS ON GRAPHS NATHAN ALBIN1 , PIETRO POGGI-CORRADINI1 , FARYAD DARABI extremal length formulation or [Poggi-Corradini, 2007, Theorem 3.1] for a more recent formulation using-State. 1 #12;2 ALBIN, POGGI-CORRADINI, DARABI SAHNEH, AND GOERING We then perform various empirical tests

Poggi-Corradini, Pietro

462

BIONic WalkAide for correcting foot drop  

Microsoft Academic Search

The goal of this study was to test the feasibility and efficacy of using microstimulators (BIONs) to correct foot drop, the first human application of BIONs in functional electrical stimulation (FES). A prototype BIONic foot drop stimulator was developed by modifying a WalkAide2 stimulator to control BION stimulation of the ankle dorsiflexor muscles. BION stimulation was compared with surface stimulation

Douglas J. Weber; Richard B. Stein; K. Ming Chan; Gerald Loeb; Frances Richmond; Robert Rolf; Kelly James; Su Ling Chong

2005-01-01

463

Kac's random walk and coupon collector's process on posets  

E-print Network

In the first part of this work, we study a long standing open problem on the mixing time of Kac's random walk on SO(n, R) by random rotations. We obtain an upper bound mix = O (n2.5 log n) for the weak convergence which ...

Sidenko, Sergiy

2008-01-01

464

A control algorithm for hexapod walking machine over soft ground  

Microsoft Academic Search

A control algorithm is presented for a hexapod walking machine, with alternating tripod-gait, proceeding over soft ground. The control algorithm is based on a foot-force sensing and is composed of two parts. The first part, which is applied to the leg alternating phase, confirms the support of body weight and generates the ground model using internal sensors. The second, which

M. Kaneko; K. Tanie; M. N. Mohamad Tan

1988-01-01

465

Evidence that humans evolved from a knuckle-walking ancestor  

Microsoft Academic Search

Bipedalism has traditionally been regarded as the fundamental adaptation that sets hominids apart from other primates. Fossil evidence demonstrates that by 4.1 million years ago, and perhaps earlier, hominids exhibited adaptations to bipedal walking. At present, however, the fossil record offers little information about the origin of bipedalism, and despite nearly a century of research on existing fossils and comparative

Brian G. Richmond; David S. Strait

2000-01-01

466

Association between Muscle Synergy and Stability during Prolonged Walking  

PubMed Central

[Purpose] The purpose of this study was to examine whether changes in muscle synergy could affect gait stability or muscle activity by comparing muscle activity before and after prolonged walking. [Subjects and Methods] Twelve healthy male subjects walked on a treadmill for 10?min as a warm-up. Data were recorded from the participants during the first and last 1?min during 90?min of walking at 4.5?km/h. Electromyographic (EMG) activity was recorded for 7 leg muscles, and patterns of coordination were determined by principal component analysis (PCA). The patterns of activity within the anatomic muscle groups were additionally determined by repeating PCA. iEMG was calculated using the mean EMG for each cycle step during the 1?min walking periods. The largest Lyapunov exponent was calculated to quantify each subject’s inherent local dynamic stability. [Results] The patterns for each of the 7 muscles showed no change between the start and end periods. However, the end period showed a higher co-activation of the triceps surae, lower iEMG of the medial gastrocnemius, and a smaller largest Lyapunov exponent of the mediolateral and anteroposterior directions than those observed during the start period. [Conclusion] The increase in triceps surae co-activation may be associated with gait stability. PMID:25364133

Suzuki, Keisuke; Nishida, Yusuke; Mitsutomi, Kazuhiko

2014-01-01

467

LOCALIZATION OF QUANTUM WALKS ON TREES WITH DISORDER  

E-print Network

on the title page. Foremost among these are my parents, Tom and Bonnie, who did a wonderful job of fostering in this research, Prof. Steve Miller has also helped influence this project through my work with him in SMALL 2009 exponentially faster than classical computers. Notably, Childs et al. showed that a quantum walk on a glued

Stoiciu, Mihai

468

Walking Robotics The Cornell Ranger Fall 2006 Semester Report  

E-print Network

of the foot sensors, and testing the foot sensors. Design of the Ankle Base At the beginning of the semester sapiens from other animals is their ability to walk upright on two legs. Humans can move with extreme for unforeseen requirements. One such piece was the ankle base shown in figure 2. Since the beginning

Ruina, Andy L.

469

Oblique view of southeast and northeast sides with covered walk ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Oblique view of southeast and northeast sides with covered walk to Facility 367, Facility 324 beyond, view facing west - U.S. Naval Base, Pearl Harbor, Naval Hospital, Animal House, Near intersection of Hospital Way & Third Street, Pearl City, Honolulu County, HI

470

Optical implementability of the two-dimensional Quantum Walk  

E-print Network

We propose an optical cavity implementation of the two-dimensional coined quantum walk on the line. The implementation makes use of only classical resources, and is tunable in the sense that a large number of different unitary transformations can be implemented by tuning some parameters of the device.

Eugenio Roldan; J. C. Soriano

2005-03-07

471

Complex Network Comparison Using Random Walks Department of Electrical and  

E-print Network

-1239102, and Army Research Office Con- tract W911NF-08-1-0233 and W911NF-12-1-03. diffusion are effective brain activities. In this paper we apply the random walk method to distinguish between complex networks

Kurose, Jim

472

See, walk, and kick: Humanoid robots start to play soccer  

E-print Network

See, walk, and kick: Humanoid robots start to play soccer Sven Behnke, Michael Schreiber, J¨org St | stradat }@informatik.uni-freiburg.de Abstract-- Robotic soccer superseded chess as a challenge problem thousands of researchers worldwide to devote their creativity and energy to make robots bring a ball

Behnke, Sven

473

Control Strategy of a 3DOF Walking Robot  

Microsoft Academic Search

The paper presents the mathematical model of a walking robot where the active pair of legs has three free joints. The mathematical model of the robot is determined considering a systemic approach of the robot as variable causality dynamic systems (VCDS). Taking into account a possible symmetrical structure, only the vertical xz-plane evolution is considered. The results can be extended

A. Petrisor; N. G. Bizdoaca; S. Degeratu; A. Drighiciu; G. P. Serb; D. Coman; M. C. Popescu

2007-01-01

474

Random walks based segmentation approach for image retrieval  

Microsoft Academic Search

In this paper a region-based image indexing and retrieval (RBIR) algorithm is presented. As a basis for the indexing, a novel spectral segmentation approach using random walks on graphs is introduced. Based on the extracted regions, characteristic features are estimated using color and texture information. The focus of this study is to improve the capture of regions so as to

Hassan Tabout; Youssef Chahir; Abdelmoghit Souissi; Abderrahmane Sbihi

2008-01-01

475

Grand Canyon Trekkers: School-Based Lunchtime Walking Program  

ERIC Educational Resources Information Center

The incidence of childhood overweight is especially troubling among low income Latino youth. Grand Canyon Trekkers (GCT) was implemented as a quasi-experimental study in 10 Title 1 elementary schools with a large Latino population to examine the effects of a 16-week structured walking program on components of health-related physical fitness: Body…

Hawthorne, Alisa; Shaibi, Gabriel; Gance-Cleveland, Bonnie; McFall, Sarah

2011-01-01

476

Walking intensity for postmenopausal bone mineral preservation and accrual  

Microsoft Academic Search

Introduction: Mechanical stresses on the bone are an important aspect of physical activity that promotes bone preservation and increases in bone mass. Exercise intensities leading to bone preservation and accrual have not been adequately defined for humans in general, and postmenopausal women in particular. Materials and methods: To quantify parameters of effective walking intensity for preservation and accrual of bone

Katarina T. Borer; Katrina Fogleman; Melissa Gross; Donald Dengel

2007-01-01

477

How Big Is the Random Walk in GNP?  

Microsoft Academic Search

This paper presents a measure of the persistence of fluctuations in gross national product (GNP) based on the variance of its long differences. That measure finds little long-term persistence in GNP. Previous research on this question found a great deal of persistence in GNP, suggesting models such as a random walk. A reconciliation of this paper's results with previous research

John H. Cochrane

1988-01-01

478

Stably Extending Two-Dimensional Bipedal Walking to Three Dimensions  

E-print Network

on flat ground for a three- dimensional bipedal robotic walker given stable walking gaits for a two-dimensional bipedal robotic walker. This is achieved by combining disparate techniques that have been employed in the bipedal robotic community: controlled symmetries, geomet- ric reduction and hybrid zero dynamics

Ames, Aaron

479

The Random Walk Drainage Simulation Model as a Teaching Exercise  

ERIC Educational Resources Information Center

Practical instructions about using the random walk drainage network simulation model as a teaching excercise are given and the results discussed. A source of directional bias in the resulting simulated drainage patterns is identified and given an interpretation in the terms of the model. Three points of educational value concerning the model are…

High, Colin; Richards, Paul

1972-01-01

480

A family of random walks with generalized Dirichlet steps  

NASA Astrophysics Data System (ADS)

We analyze a class of continuous time random walks in {R}^d,dge 2, with uniformly distributed directions. The steps performed by these processes are distributed according to a generalized Dirichlet law. Given the number of changes of orientation, we provide the analytic form of the probability density function of the position lbrace \\underline{X}_d(t),t>0rbrace reached, at time t > 0, by the random motion. In particular, we analyze the case of random walks with two steps. In general, it is a hard task to obtain the explicit probability distributions for the process lbrace \\underline{X}_d(t),t>0rbrace. Nevertheless, for suitable values for the basic parameters of the generalized Dirichlet probability distribution, we are able to derive the explicit conditional density functions of lbrace \\underline{X}_d(t),t>0rbrace. Furthermore, in some cases, by exploiting the fractional Poisson process, the unconditional probability distributions of the random walk are obtained. This paper extends in a more general setting, the random walks with Dirichlet displacements introduced in some previous papers.

De Gregorio, Alessandro

2014-02-01

481

Multiple random walks in random regular graphs Colin Cooper  

E-print Network

, or by annihilating each other. For example, the expected extinction time of k explosive particles (k even) tends-prey and multiple random walk models allows us to compare expected detection time of all prey in the following the expected detection time is rHn/k, where H is the -th harmonic number. 1 Introduction Let G = (V, E

Frieze, Alan

482

0g Climbing - The Challenge of Walking in Space  

NASA Technical Reports Server (NTRS)

Space walking is poorly named, as it has little in common with how animals walk on Earth. Space walking is more akin to mountain climbing in scuba gear, while parachuting in a freefall-an odd combination of effects and equipment to help people do a demanding job. Robots are now being studied for service in this same domain, working on large scale space structures like the Space Station, servicing science or military platforms in high orbit, or riding on the outside of a space craft in transit to Mars, the Moon or other destinations. What have we learned about climbing in 0g? How should machines be controlled for serving in this role? What can they do to overcome the problems that humans have faced? In order to move about in this environment, a robot must be able to climb autonomously, using gaits that smoothly manage its momentum and that minimize contact forces (walking lightly) while providing for safety in the event of an emergency requiring the system to stop. All three of these objectives are now being explored at NASA's Johnson Space Center, using the Robonaut system and a set of mockups that emulate the 0g condition. NASA's goal for Robonaut is to develop the control technology that will allow it to climb on the outside of the Space Shuttle, the Space Station, and satellite mockups at JSC, enabling the robot to perform EVA task setups or serve as an Astronaut's assistant.

Ambrose, Robert O.; Rehnmark, Frederik; Goza, Michael

2004-01-01

483

0g Climbing - The Challenge of Walking in Space  

NASA Technical Reports Server (NTRS)

Space walking is poorly named, as it has little in common with how animals walk on Earth. Space walking is more akin to mountain climbing in scuba gear, while parachuting in a freefall -- an odd combination of effects and equipment to help people do a demanding job. Robots are now being studied for service in this same domain, working on large scale space structures like the Space Station, servicing science or military platforms in high orbit, or riding on the outside of a space craft in transit to Mars, the Moon or other destinations. What have we learned about climbing in 0g? How should machines be controlled for serving in this role? What can they do to overcome the problems that humans have faced? In order to move about in this environment, a robot must be able to climb autonomously, using gaits that smoothly manage its momentum and that minimize contact forces (walking lightly) while providing for safety in the event of an emergency requiring the system to stop. All three of these objectives are now being explored at NASA's Johnson Space Center, using the Robonaut system and a set of mockups that emulate the 0g condition. NASA's goal for Robonaut is to develop the control technology that will allow it to climb on the outside of the Space Shuttle, the Space Station, and satellite mockups at JSC, enabling the robot to perform EVA task setups or serve as an Astronaut's assistant.

Ambrose, Robert O.; Rehnmark, Frederik; Goza, Michael

2003-01-01

484

Learning to Walk in 20 Minutes Russ Tedrake  

E-print Network

Learning to Walk in 20 Minutes Russ Tedrake Brain & Cognitive Sciences Center for Bits and Atoms Seung Howard Hughes Medical Institute Brain & Cognitive Sciences Massachusetts Inst. of Technology of this system is that learning and execution occur simultaneously: there are no explicit learning trials

Tedrake, Russ

485

RESEARCH Open Access Predictors of decline in walking ability in  

E-print Network

mobility limitation in cognitively intact older adults [5]. Moreover, the ability to walk is also a key mass index, balance, behavioral and psychological symptoms of dementia, medication, hospitalization with