Middle East respiratory syndrome: obstacles and prospects for vaccine development

PubMed Central

Papaneri, Amy B.; Johnson, Reed F.; Wada, Jiro; Bollinger, Laura; Jahrling, Peter B.; Kuhn, Jens H.

2016-01-01

Summary The recent emergence of Middle East respiratory syndrome (MERS) highlights the need to engineer new methods for expediting vaccine development against emerging diseases. However, several obstacles prevent pursuit of a licensable MERS vaccine. First, the lack of a suitable animal model for MERS complicates in vivo testing of candidate vaccines. Second, due to the low number of MERS cases, pharmaceutical companies have little incentive to pursue MERS vaccine production as the costs of clinical trials are high. In addition, the timeline from bench research to approved vaccine use is 10 years or longer. Using novel methods and cost-saving strategies, genetically engineered vaccines can be produced quickly and cost-effectively. Along with progress in MERS animal model development, these obstacles can be circumvented or at least mitigated. PMID:25864502

Statistics of dislocation pinning at localized obstacles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dutta, A.; Bhattacharya, M., E-mail: mishreyee@vecc.gov.in; Barat, P.

2014-10-14

Pinning of dislocations at nanosized obstacles like precipitates, voids, and bubbles is a crucial mechanism in the context of phenomena like hardening and creep. The interaction between such an obstacle and a dislocation is often studied at fundamental level by means of analytical tools, atomistic simulations, and finite element methods. Nevertheless, the information extracted from such studies cannot be utilized to its maximum extent on account of insufficient information about the underlying statistics of this process comprising a large number of dislocations and obstacles in a system. Here, we propose a new statistical approach, where the statistics of pinning ofmore » dislocations by idealized spherical obstacles is explored by taking into account the generalized size-distribution of the obstacles along with the dislocation density within a three-dimensional framework. Starting with a minimal set of material parameters, the framework employs the method of geometrical statistics with a few simple assumptions compatible with the real physical scenario. The application of this approach, in combination with the knowledge of fundamental dislocation-obstacle interactions, has successfully been demonstrated for dislocation pinning at nanovoids in neutron irradiated type 316-stainless steel in regard to the non-conservative motion of dislocations. An interesting phenomenon of transition from rare pinning to multiple pinning regimes with increasing irradiation temperature is revealed.« less

Workarounds and obstacles: unexpected source of innovation.

PubMed

Lalley, Cathy

2014-01-01

Nurse leaders are aware that nurses are finding ways to adapt health information technology to patient care activities. Previous literature has presented nurses' response to technology obstacles as a work-around, characterized as a negative behavior. Using narrative inquiry, this article examines 9 direct care nurses' interactions on a medical/surgical/telemetry unit. Specifically, nurses' encounters with technology obstacles will be addressed from a complexity science perspective. Four support staff including the clinical nurse manager, pharmacist, quality nurse, and project manager who is also a nurse were interviewed as part of data collection. Complexity science provides nurse leaders' insight into nurses' behavior where outcomes emerge from tensions in the environment through multidirectional and self-organizing interactions. Innovation was found when nurses responded to health information technology obstacles with self-organizing interactions, sensitivity to initial conditions, and multidirectionality. Their actions were also influenced by many sets of rules. Nurses self-organized with coworkers to find better ways to deliver care to patients when using technology. Opportunities exist for nurse leaders to facilitate interactions among nurses and other members of the organization to realize better use of health information technology that improves the patient experience.

3D Hybrid Simulations of Interactions of High-Velocity Plasmoids with Obstacles

NASA Astrophysics Data System (ADS)

Omelchenko, Y. A.; Weber, T. E.; Smith, R. J.

2015-11-01

Interactions of fast plasma streams and objects with magnetic obstacles (dipoles, mirrors, etc) lie at the core of many space and laboratory plasma phenomena ranging from magnetoshells and solar wind interactions with planetary magnetospheres to compact fusion plasmas (spheromaks and FRCs) to astrophysics-in-lab experiments. Properly modeling ion kinetic, finite-Larmor radius and Hall effects is essential for describing large-scale plasma dynamics, turbulence and heating in complex magnetic field geometries. Using an asynchronous parallel hybrid code, HYPERS, we conduct 3D hybrid (particle-in-cell ion, fluid electron) simulations of such interactions under realistic conditions that include magnetic flux coils, ion-ion collisions and the Chodura resistivity. HYPERS does not step simulation variables synchronously in time but instead performs time integration by executing asynchronous discrete events: updates of particles and fields carried out as frequently as dictated by local physical time scales. Simulations are compared with data from the MSX experiment which studies the physics of magnetized collisionless shocks through the acceleration and subsequent stagnation of FRC plasmoids against a strong magnetic mirror and flux-conserving boundary.

Cooperative breakups induced by drop-to-drop interactions in one-dimensional flows of drops against micro-obstacles.

PubMed

Schmit, Alexandre; Salkin, Louis; Courbin, Laurent; Panizza, Pascal

2015-03-28

Depending on the capillary number at play and the parameters of the flow geometry, a drop may or may not break when colliding with an obstacle in a microdevice. Modeling the flow of one-dimensional trains of monodisperse drops impacting a micro-obstacle, we show numerically that complex dynamics may arise through drop-to-drop hydrodynamic interactions: we observe sequences of breakup events in which the size of the daughter drops created upon breaking mother ones becomes a periodic function of time. We demonstrate the existence of numerous bifurcations between periodic breakup regimes and we establish diagrams mapping the possible breakup dynamics as a function of the governing (physicochemical, hydrodynamic, and geometric) parameters. Microfluidic experiments validate our model as they concur very well with predictions.

Assessing the ground vibrations produced by a heavy vehicle traversing a traffic obstacle.

PubMed

Ducarne, Loïc; Ainalis, Daniel; Kouroussis, Georges

2018-01-15

Despite advancements in alternative transport networks, road transport remains the dominant mode in many modern and developing countries. The ground-borne motions produced by the passage of a heavy vehicle over a geometric obstacle (e.g. speed hump, train tracks) pose a fundamental problem in transport annoyance in urban areas. In order to predict the ground vibrations generated by the passage of a heavy vehicle over a geometric obstacle, a two-step numerical model is developed. The first step involves simulating the dynamic loads generated by the heavy vehicle using a multibody approach, which includes the tyre-obstacle-ground interaction. The second step involves the simulation of the ground wave propagation using a three dimensional finite element model. The simulation is able to be decoupled due to the large difference in stiffness between the vehicle's tyres and the road. First, the two-step model is validated using an experimental case study available in the literature. A sensitivity analysis is then presented, examining the influence of various factors on the generated ground vibrations. Factors investigated include obstacle shape, obstacle dimensions, vehicle speed, and tyre stiffness. The developed model can be used as a tool in the early planning stages to predict the ground vibrations generated by the passage of a heavy vehicle over an obstacle in urban areas. Copyright © 2017 Elsevier B.V. All rights reserved.

[Development of child mental health services in Lithuania: achievements and obstacles].

PubMed

Pūras, Dainius

2002-01-01

In 1990, political, economic and social changes in Lithuania introduced the possibility to develop for the first time in nations's history an effective and modern system of child mental health services. During the period between 1990 and 1995 a new model of services was developed in the Department of Social pediatrics and child psychiatry of Vilnius University. The model included development of child and adolescent psychiatric services, as well as early intervention services for infants and preschool children with developmental disabilities. The emphasis, following recommendations of WHO and existing international standards, was made on deinstitutionalization and development of family-oriented and community-based services, which have been ignored by previous system. In the first half of 90's of 20th century, new training programs for professionals were introduced, more than 50 methods of assessment, treatment and rehabilitation, new for Lithuanian clinical practice, were implemented, and a new model of services, including primary, secondary and tertiary level of prevention, was introduced in demonstration sites. However, during next phase of development, in 1997-2001, serious obstacles for replicating new approaches across the country, have been identified, which threatened successful implementation of the new model of services into everyday clinical practice. Analysis of obstacles, which are blocking development of new approaches in the field of child mental health, is presented in the article. The main obstacles, identified during analysis of socioeconomic context, planning and utilization of resources, running of the system of services and evaluation of outcomes, are as follows: lack of intersectorial cooperation between health, education and social welfare systems; strong tradition of discrimination of psychosocial interventions in funding schemes of health services; societal attitudes, which tend to discriminate and stigmatize marginal groups, including

Robust obstacle detection for unmanned surface vehicles

NASA Astrophysics Data System (ADS)

Qin, Yueming; Zhang, Xiuzhi

2018-03-01

Obstacle detection is of essential importance for Unmanned Surface Vehicles (USV). Although some obstacles (e.g., ships, islands) can be detected by Radar, there are many other obstacles (e.g., floating pieces of woods, swimmers) which are difficult to be detected via Radar because these obstacles have low radar cross section. Therefore, detecting obstacle from images taken onboard is an effective supplement. In this paper, a robust vision-based obstacle detection method for USVs is developed. The proposed method employs the monocular image sequence captured by the camera on the USVs and detects obstacles on the sea surface from the image sequence. The experiment results show that the proposed scheme is efficient to fulfill the obstacle detection task.

Age-associated changes in obstacle negotiation strategies: Does size and timing matter?

PubMed

Maidan, I; Eyal, S; Kurz, I; Geffen, N; Gazit, E; Ravid, L; Giladi, N; Mirelman, A; Hausdorff, J M

2018-01-01

Tripping over an obstacle is one of the most common causes of falls among older adults. However, the effects of aging, obstacle height and anticipation time on negotiation strategies have not been systematically evaluated. Twenty older adults (ages: 77.7±3.4years; 50% women) and twenty young adults (age: 29.3±3.8years; 50% women) walked through an obstacle course while negotiating anticipated and unanticipated obstacles at heights of 25mm and 75mm. Kinect cameras captured the: (1) distance of the subject's trailing foot before the obstacles, (2) distance of the leading foot after the obstacles, (3) clearance of the leading foot above the obstacles, and (4) clearance of the trailing foot above the obstacles. Linear-mix models assessed changes between groups and conditions. Older adults placed their leading foot closer to the obstacle after landing, compared to young adults (p<0.001). This pattern was enhanced in high obstacles (group*height interaction, p=0.033). Older adults had lower clearance over the obstacles, compared to young adults (p=0.007). This was more pronounced during unanticipated obstacles (group*ART interaction, p=0.003). The distance of the leading foot and clearance of the trailing foot after the obstacles were correlated with motor, cognitive, and functional abilities. These findings suggest that there are age-related changes in obstacle crossing strategies that are dependent on the specific characteristics of the obstacle. The results have important implications for clinical practice, suggesting that functional exercise should include obstacle negotiation training with variable practice of height and available response times. Further studies are needed to better understand the effects of motor and cognitive abilities. Copyright © 2017 Elsevier B.V. All rights reserved.

Planning Process Obstacles and Opportunities.

ERIC Educational Resources Information Center

Doyle, Patricia C.

1997-01-01

Argues that obstacles exist in the Public Library Association (PLA) planning process that can be resolved by developing relationships between materials in the collection and PLA roles. Proposes changes to help reduce conflict in the PLA planning process and discusses process obstacles, relationships as the key providing better service, and…

Obstacle Avoidance On Roadways Using Range Data

NASA Astrophysics Data System (ADS)

Dunlay, R. Terry; Morgenthaler, David G.

1987-02-01

This report describes range data based obstacle avoidance techniques developed for use on an autonomous road-following robot vehicle. The purpose of these techniques is to detect and locate obstacles present in a road environment for navigation of a robot vehicle equipped with an active laser-based range sensor. Techniques are presented for obstacle detection, obstacle location, and coordinate transformations needed in the construction of Scene Models (symbolic structures representing the 3-D obstacle boundaries used by the vehicle's Navigator for path planning). These techniques have been successfully tested on an outdoor robotic vehicle, the Autonomous Land Vehicle (ALV), at speeds up to 3.5 km/hour.

Harnessing atomistic simulations to predict the rate at which dislocations overcome obstacles

NASA Astrophysics Data System (ADS)

Saroukhani, S.; Nguyen, L. D.; Leung, K. W. K.; Singh, C. V.; Warner, D. H.

2016-05-01

Predicting the rate at which dislocations overcome obstacles is key to understanding the microscopic features that govern the plastic flow of modern alloys. In this spirit, the current manuscript examines the rate at which an edge dislocation overcomes an obstacle in aluminum. Predictions were made using different popular variants of Harmonic Transition State Theory (HTST) and compared to those of direct Molecular Dynamics (MD) simulations. The HTST predictions were found to be grossly inaccurate due to the large entropy barrier associated with the dislocation-obstacle interaction. Considering the importance of finite temperature effects, the utility of the Finite Temperature String (FTS) method was then explored. While this approach was found capable of identifying a prominent reaction tube, it was not capable of computing the free energy profile along the tube. Lastly, the utility of the Transition Interface Sampling (TIS) approach was explored, which does not need a free energy profile and is known to be less reliant on the choice of reaction coordinate. The TIS approach was found capable of accurately predicting the rate, relative to direct MD simulations. This finding was utilized to examine the temperature and load dependence of the dislocation-obstacle interaction in a simple periodic cell configuration. An attractive rate prediction approach combining TST and simple continuum models is identified, and the strain rate sensitivity of individual dislocation obstacle interactions is predicted.

Development of an integrated BEM approach for hot fluid structure interaction

NASA Technical Reports Server (NTRS)

Dargush, G. F.; Banerjee, P. K.

1989-01-01

The progress made toward the development of a boundary element formulation for the study of hot fluid-structure interaction in Earth-to-Orbit engine hot section components is reported. The convective viscous integral formulation was derived and implemented in the general purpose computer program GP-BEST. The new convective kernel functions, in turn, necessitated the development of refined integration techniques. As a result, however, since the physics of the problem is embedded in these kernels, boundary element solutions can now be obtained at very high Reynolds number. Flow around obstacles can be solved approximately with an efficient linearized boundary-only analysis or, more exactly, by including all of the nonlinearities present in the neighborhood of the obstacle. The other major accomplishment was the development of a comprehensive fluid-structure interaction capability within GP-BEST. This new facility is implemented in a completely general manner, so that quite arbitrary geometry, material properties and boundary conditions may be specified. Thus, a single analysis code (GP-BEST) can be used to run structures-only problems, fluids-only problems, or the combined fluid-structure problem. In all three cases, steady or transient conditions can be selected, with or without thermal effects. Nonlinear analyses can be solved via direct iteration or by employing a modified Newton-Raphson approach.

Is It Because of Partners or Partnerships?: An Investigation into the Main Obstacles of Developing International Partnerships in Four UK Universities

ERIC Educational Resources Information Center

Ayoubi, Rami M.; Massoud, Hiba

2012-01-01

Purpose: The main aim of the current study is to explore and model the major obstacles that UK universities encounter when developing international partnerships with overseas universities. Design/methodology/approach: Focusing on the obstacles to developing international partnerships, the study results are developed from 24 interviews with senior…

Thermal activation of dislocations in large scale obstacle bypass

NASA Astrophysics Data System (ADS)

Sobie, Cameron; Capolungo, Laurent; McDowell, David L.; Martinez, Enrique

2017-08-01

Dislocation dynamics simulations have been used extensively to predict hardening caused by dislocation-obstacle interactions, including irradiation defect hardening in the athermal case. Incorporating the role of thermal energy on these interactions is possible with a framework provided by harmonic transition state theory (HTST) enabling direct access to thermally activated reaction rates using the Arrhenius equation, including rates of dislocation-obstacle bypass processes. Moving beyond unit dislocation-defect reactions to a representative environment containing a large number of defects requires coarse-graining the activation energy barriers of a population of obstacles into an effective energy barrier that accurately represents the large scale collective process. The work presented here investigates the relationship between unit dislocation-defect bypass processes and the distribution of activation energy barriers calculated for ensemble bypass processes. A significant difference between these cases is observed, which is attributed to the inherent cooperative nature of dislocation bypass processes. In addition to the dislocation-defect interaction, the morphology of the dislocation segments pinned to the defects play an important role on the activation energies for bypass. A phenomenological model for activation energy stress dependence is shown to describe well the effect of a distribution of activation energies, and a probabilistic activation energy model incorporating the stress distribution in a material is presented.

Application of Optical Flow Sensors for Dead Reckoning, Heading Reference, Obstacle Detection, and Obstacle Avoidance

DTIC Science & Technology

2015-09-01

OPTICAL FLOW SENSORS FOR DEAD RECKONING, HEADING REFERENCE, OBSTACLE DETECTION, AND OBSTACLE AVOIDANCE by Tarek M. Nejah September 2015...SENSORS FOR DEAD RECKONING, HEADING REFERENCE, OBSTACLE DETECTION, AND OBSTACLE AVOIDANCE 5. FUNDING NUMBERS 6. AUTHOR(S) Nejah, Tarek M. 7...DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) A novel approach for dead reckoning, heading reference, obstacle detection, and obstacle

Obstacle Characterization in a Geocrowdsourced Accessibility System

NASA Astrophysics Data System (ADS)

Qin, H.; Aburizaiza, A. O.; Rice, R. M.; Paez, F.; Rice, M. T.

2015-08-01

Transitory obstacles - random, short-lived and unpredictable objects - are difficult to capture in any traditional mapping system, yet they have significant negative impacts on the accessibility of mobility- and visually-impaired individuals. These transitory obstacles include sidewalk obstructions, construction detours, and poor surface conditions. To identify these obstacles and assist the navigation of mobility- and visually- impaired individuals, crowdsourced mapping applications have been developed to harvest and analyze the volunteered obstacles reports from local students, faculty, staff, and residents. In this paper, we introduce a training program designed and implemented for recruiting and motivating contributors to participate in our geocrowdsourced accessibility system, and explore the quality of geocrowdsourced data with a comparative analysis methodology.

Natural frequencies, modeshapes and modal interactions for strings vibrating against an obstacle: Relevance to Sitar and Veena

NASA Astrophysics Data System (ADS)

Mandal, A. K.; Wahi, P.

2015-03-01

We study the vibration characteristics of a string with a smooth unilateral obstacle placed at one of the ends similar to the strings in musical instruments like sitar and veena. In particular, we explore the correlation between the string vibrations and some unique sound characteristics of these instruments like less inharmonicity in the frequencies, a large number of overtones and the presence of both frequency and amplitude modulations. At the obstacle, we have a moving boundary due to the wrapping of the string and an appropriate scaling of the spatial variable leads to a fixed boundary at the cost of introducing nonlinearity in the governing equation. Reduced order system of equations has been obtained by assuming a functional form for the string displacement which satisfies all the boundary conditions and gives the free length of the string in terms of the modal coordinates. To study the natural frequencies and mode-shapes, the nonlinear governing equation is linearized about the static configuration. The natural frequencies have been found to be harmonic and they depend on the shape of the obstacle through the effective free length of the string. Expressions have been obtained for the time-varying mode-shapes as well as the variation of the nodal points. Modal interactions due to coupling have been studied which show the appearance of higher overtones as well as amplitude modulations in our theoretical model akin to the experimental observations. All the obtained results have been verified with an alternate formulation based on the assumed mode method with polynomial shape functions.

Using Thermal Radiation in Detection of Negative Obstacles

NASA Technical Reports Server (NTRS)

Rankin, Arturo L.; Matthies, Larry H.

2009-01-01

A method of automated detection of negative obstacles (potholes, ditches, and the like) ahead of ground vehicles at night involves processing of imagery from thermal-infrared cameras aimed at the terrain ahead of the vehicles. The method is being developed as part of an overall obstacle-avoidance scheme for autonomous and semi-autonomous offroad robotic vehicles. The method could also be applied to help human drivers of cars and trucks avoid negative obstacles -- a development that may entail only modest additional cost inasmuch as some commercially available passenger cars are already equipped with infrared cameras as aids for nighttime operation.

Aviation obstacle auto-extraction using remote sensing information

NASA Astrophysics Data System (ADS)

Zimmer, N.; Lugsch, W.; Ravenscroft, D.; Schiefele, J.

2008-10-01

An Obstacle, in the aviation context, may be any natural, man-made, fixed or movable object, permanent or temporary. Currently, the most common way to detect relevant aviation obstacles from an aircraft or helicopter for navigation purposes and collision avoidance is the use of merged infrared and synthetic information of obstacle data. Several algorithms have been established to utilize synthetic and infrared images to generate obstacle information. There might be a situation however where the system is error-prone and may not be able to consistently determine the current environment. This situation can be avoided when the system knows the true position of the obstacle. The quality characteristics of the obstacle data strongly depends on the quality of the source data such as maps and official publications. In some countries such as newly industrializing and developing countries, quality and quantity of obstacle information is not available. The aviation world has two specifications - RTCA DO-276A and ICAO ANNEX 15 Ch. 10 - which describe the requirements for aviation obstacles. It is essential to meet these requirements to be compliant with the specifications and to support systems based on these specifications, e.g. 3D obstacle warning systems where accurate coordinates based on WGS-84 is a necessity. Existing aerial and satellite or soon to exist high quality remote sensing data makes it feasible to think about automated aviation obstacle data origination. This paper will describe the feasibility to auto-extract aviation obstacles from remote sensing data considering limitations of image and extraction technologies. Quality parameters and possible resolution of auto-extracted obstacle data will be discussed and presented.

Stellar winds and planetary bodies simulations: Magnetized obstacles in super-Alfvénic and sub-Alfvénic flows

NASA Astrophysics Data System (ADS)

Vernisse, Y.; Riousset, J. A.; Motschmann, U.; Glassmeier, K.-H.

2017-03-01

Most planetary bodies are moving in the solar wind, in a stellar wind, or in a plasma flow within the magnetosphere of a planet. The interaction of the body with the flowing plasma provides us with various interaction types, which mainly depend on the flow speed, the magnetization of the body, its conductivity, the presence of an ionosphere, and the size of the body. We establish two cornerstones representing highly magnetized obstacles embedded in a super-Alfvénic and sub-Alfvénic plasma. Those two cornerstones complete the two cornerstones defined in our previous study on inert obstacles in super-Alfvénic and sub-Alfvénic regimes. Tracking the transitions between these cornerstones enable better understanding of the feedback of the obstacle onto the plasma flow. Each interaction is studied by means of the hybrid model simulation code AIKEF. The results are summarized in three dimensional diagrams showing the current structures, which serve as a basis for our descriptions. We identify the major currents such as telluric, magnetosonic, Chapman-Ferraro, and bow-shock currents as the signatures of the particular state of development of the interaction region. We show that each type of interactions can be identified by studying the shape and the magnitude of its specific currents.

A stereo vision-based obstacle detection system in vehicles

NASA Astrophysics Data System (ADS)

Huh, Kunsoo; Park, Jaehak; Hwang, Junyeon; Hong, Daegun

2008-02-01

Obstacle detection is a crucial issue for driver assistance systems as well as for autonomous vehicle guidance function and it has to be performed with high reliability to avoid any potential collision with the front vehicle. The vision-based obstacle detection systems are regarded promising for this purpose because they require little infrastructure on a highway. However, the feasibility of these systems in passenger car requires accurate and robust sensing performance. In this paper, an obstacle detection system using stereo vision sensors is developed. This system utilizes feature matching, epipoplar constraint and feature aggregation in order to robustly detect the initial corresponding pairs. After the initial detection, the system executes the tracking algorithm for the obstacles. The proposed system can detect a front obstacle, a leading vehicle and a vehicle cutting into the lane. Then, the position parameters of the obstacles and leading vehicles can be obtained. The proposed obstacle detection system is implemented on a passenger car and its performance is verified experimentally.

Socio-Technical Perspective on Interdisciplinary Interactions During the Development of Complex Engineered Systems

NASA Technical Reports Server (NTRS)

McGowan, Anna-Maria R.; Daly, Shanna; Baker, Wayne; Papalambros, panos; Seifert, Colleen

2013-01-01

This study investigates interdisciplinary interactions that take place during the research, development, and early conceptual design phases in the design of large-scale complex engineered systems (LaCES) such as aerospace vehicles. These interactions, that take place throughout a large engineering development organization, become the initial conditions of the systems engineering process that ultimately leads to the development of a viable system. This paper summarizes some of the challenges and opportunities regarding social and organizational issues that emerged from a qualitative study using ethnographic and survey data. The analysis reveals several socio-technical couplings between the engineered system and the organization that creates it. Survey respondents noted the importance of interdisciplinary interactions and their benefits to the engineered system as well as substantial challenges in interdisciplinary interactions. Noted benefits included enhanced knowledge and problem mitigation and noted obstacles centered on organizational and human dynamics. Findings suggest that addressing the social challenges may be a critical need in enabling interdisciplinary interactions

Obstacles to nutrition labeling in restaurants.

PubMed

Almanza, B A; Nelson, D; Chai, S

1997-02-01

This study determined the major obstacles that foodservices face regarding nutrition labeling. Survey questionnaire was conducted in May 1994. In addition to demographic questions, the directors were asked questions addressing willingness, current practices, and perceived obstacles related to nutrition labeling. Sixty-eight research and development directors of the largest foodservice corporations as shown in Restaurants & Institutions magazine's list of the top 400 largest foodservices (July 1993). P tests were used to determine significance within a group for the number of foodservices that were currently using nutrition labeling, perceived impact of nutrition labeling on sales, and perceived responsibility to add nutrition labels. Regression analysis was used to determine the importance of factors on willingness to label. Response rate was 45.3%. Most companies were neutral about their willingness to use nutrition labeling. Two thirds of the respondents were not currently using nutrition labels. Only one third thought that it was the foodservice's responsibility to provide such information. Several companies perceived that nutrition labeling would have a potentially negative effect on annual sales volume. Major obstacles were identified as menu or personnel related, rather than cost related. Menu-related obstacles included too many menu variations, limited space on the menu for labeling, and loss of flexibility in changing the menu. Personnel-related obstacles included difficulty in training employees to implement nutrition labeling, and not enough time for foodservice personnel to implement nutrition labeling. Numerous opportunities will be created for dietetics professionals in helping foodservices overcome these menu- or personnel-related obstacles.

An enhanced obstacle avoiding system for AUV`s

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conte, G.; Zanoli, S.M.

1994-12-31

This paper concerns the development of a sonar-based navigation and guidance system for underwater, unmanned vehicles. In particular, the authors describe and discuss an obstacle avoidance procedure that is capable of dealing with situations involving several obstacles. The main features of the system are the use of a Kalman filter, both for estimating data and for predicting the evolution of the observed scene, and the possibility of working at different levels of data abstraction. The system has shown satisfactory performances in dealing with moving obstacles in general situations.

Interaction of Interstellar Shocks with Dense Obstacles: Formation of ``Bullets''

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

The so-called cumulative effect take place in converging conical shock waves arising behind dense obstacles overtaken by incident interstellar shock. A significant part of energy of converging flow of matter swept-up by a radiative conical shock can be transferred to a dense jet-like ejection (``bullet'') directed along the cone axis. Possible applications of this effect for star-forming regions (e.g., OMC-1) and supernova remnants (e.g., Vela SNR) are discussed.

Obstacle Detection Algorithms for Aircraft Navigation: Performance Characterization of Obstacle Detection Algorithms for Aircraft Navigation

NASA Technical Reports Server (NTRS)

Kasturi, Rangachar; Camps, Octavia; Coraor, Lee

2000-01-01

The research reported here is a part of NASA's Synthetic Vision System (SVS) project for the development of a High Speed Civil Transport Aircraft (HSCT). One of the components of the SVS is a module for detection of potential obstacles in the aircraft's flight path by analyzing the images captured by an on-board camera in real-time. Design of such a module includes the selection and characterization of robust, reliable, and fast techniques and their implementation for execution in real-time. This report describes the results of our research in realizing such a design. It is organized into three parts. Part I. Data modeling and camera characterization; Part II. Algorithms for detecting airborne obstacles; and Part III. Real time implementation of obstacle detection algorithms on the Datacube MaxPCI architecture. A list of publications resulting from this grant as well as a list of relevant publications resulting from prior NASA grants on this topic are presented.

Dynamic Obstacle Avoidance for Unmanned Underwater Vehicles Based on an Improved Velocity Obstacle Method

PubMed Central

Zhang, Wei; Wei, Shilin; Teng, Yanbin; Zhang, Jianku; Wang, Xiufang; Yan, Zheping

2017-01-01

In view of a dynamic obstacle environment with motion uncertainty, we present a dynamic collision avoidance method based on the collision risk assessment and improved velocity obstacle method. First, through the fusion optimization of forward-looking sonar data, the redundancy of the data is reduced and the position, size and velocity information of the obstacles are obtained, which can provide an accurate decision-making basis for next-step collision avoidance. Second, according to minimum meeting time and the minimum distance between the obstacle and unmanned underwater vehicle (UUV), this paper establishes the collision risk assessment model, and screens key obstacles to avoid collision. Finally, the optimization objective function is established based on the improved velocity obstacle method, and a UUV motion characteristic is used to calculate the reachable velocity sets. The optimal collision speed of UUV is searched in velocity space. The corresponding heading and speed commands are calculated, and outputted to the motion control module. The above is the complete dynamic obstacle avoidance process. The simulation results show that the proposed method can obtain a better collision avoidance effect in the dynamic environment, and has good adaptability to the unknown dynamic environment. PMID:29186878

Obstacle detectors for automated transit vehicles: A technoeconomic and market analysis

NASA Technical Reports Server (NTRS)

Lockerby, C. E.

1979-01-01

A search was conducted to identify the technical and economic characteristics of both NASA and nonNASA obstacle detectors. The findings, along with market information were compiled and analyzed for consideration by DOT and NASA in decisions about any future automated transit vehicle obstacle detector research, development, or applications project. Currently available obstacle detectors and systems under development are identified by type (sonic, capacitance, infrared/optical, guided radar, and probe contact) and compared with the three NASA devices selected as possible improvements or solutions to the problems in existing obstacle detection systems. Cost analyses and market forecasts individually for the AGT and AMTV markets are included.

Private investment in AIDS vaccine development: obstacles and solutions.

PubMed

Batson, A; Ainsworth, M

2001-01-01

The development of vaccines for the prevention of AIDS, malaria, tuberculosis, and other diseases requires both public and private investment. Private investment, however, has been far lower than might have been hoped, given the massive human toll of these diseases, particularly in the poorest countries. With a view to understanding this situation and exploring potential solutions, the World Bank AIDS Vaccine Task Force commissioned a study on the perspectives of the biotechnology, vaccine, and pharmaceutical industries regarding investment in research and development work on an AIDS vaccine. It was found that different obstacles to the development of an AIDS vaccine arose during the product development cycle. During the earlier phases, before obtaining proof of product, the principal barriers were scientific. The lack of consensus on which approach was likely to be effective increased uncertainty and the risks associated with investing in expensive clinical trials. The later phases, which involved adapting, testing, and scaling up production for different populations, were most influenced by market considerations. In order to raise the levels of private research and development in an AIDS vaccine there will probably have to be a combination of push strategies, which reduce the cost and scientific risk of investment, and pull strategies, which guarantee a market.

Private investment in AIDS vaccine development: obstacles and solutions.

PubMed Central

Batson, A.; Ainsworth, M.

2001-01-01

The development of vaccines for the prevention of AIDS, malaria, tuberculosis, and other diseases requires both public and private investment. Private investment, however, has been far lower than might have been hoped, given the massive human toll of these diseases, particularly in the poorest countries. With a view to understanding this situation and exploring potential solutions, the World Bank AIDS Vaccine Task Force commissioned a study on the perspectives of the biotechnology, vaccine, and pharmaceutical industries regarding investment in research and development work on an AIDS vaccine. It was found that different obstacles to the development of an AIDS vaccine arose during the product development cycle. During the earlier phases, before obtaining proof of product, the principal barriers were scientific. The lack of consensus on which approach was likely to be effective increased uncertainty and the risks associated with investing in expensive clinical trials. The later phases, which involved adapting, testing, and scaling up production for different populations, were most influenced by market considerations. In order to raise the levels of private research and development in an AIDS vaccine there will probably have to be a combination of push strategies, which reduce the cost and scientific risk of investment, and pull strategies, which guarantee a market. PMID:11545328

Training under Fire: The Relationship between Obstacles Facing Training and SMEs Development in Palestine

ERIC Educational Resources Information Center

AlMadhoun, Mohammed

2006-01-01

Purpose: The main objective of this paper is to discuss the relationship between obstacles and weaknesses facing the development of MTPs and SMEs. In recent years many management training programmes (MTPs) of an off-the-job nature have been established in Palestine, after the peace agreement, in order to find a solution for apparent lack of…

Concept development of automatic guidance for rotorcraft obstacle avoidance

NASA Technical Reports Server (NTRS)

Cheng, Victor H. L.

1990-01-01

The automatic guidance of rotorcraft for obstacle avoidance in nap-of-the-earth flight is studied. A hierarchical breakdown of the guidance components is used to identify the functional requirements. These requirements and anticipated sensor capabilities lead to a preliminary guidance concept, which has been evaluated via computer simulations.

The Challenge of Grounding Planning in Simulation with an Interactive Model Development Environment

NASA Technical Reports Server (NTRS)

Clement, Bradley J.; Frank, Jeremy D.; Chachere, John M.; Smith, Tristan B.; Swanson, Keith J.

2011-01-01

A principal obstacle to fielding automated planning systems is the difficulty of modeling. Physical systems are modeled conventionally based on specification documents and the modeler's understanding of the system. Thus, the model is developed in a way that is disconnected from the system's actual behavior and is vulnerable to manual error. Another obstacle to fielding planners is testing and validation. For a space mission, generated plans must be validated often by translating them into command sequences that are run in a simulation testbed. Testing in this way is complex and onerous because of the large number of possible plans and states of the spacecraft. Though, if used as a source of domain knowledge, the simulator can ease validation. This paper poses a challenge: to ground planning models in the system physics represented by simulation. A proposed, interactive model development environment illustrates the integration of planning and simulation to meet the challenge. This integration reveals research paths for automated model construction and validation.

Biologically-inspired adaptive obstacle negotiation behavior of hexapod robots

PubMed Central

Goldschmidt, Dennis; Wörgötter, Florentin; Manoonpong, Poramate

2014-01-01

Neurobiological studies have shown that insects are able to adapt leg movements and posture for obstacle negotiation in changing environments. Moreover, the distance to an obstacle where an insect begins to climb is found to be a major parameter for successful obstacle negotiation. Inspired by these findings, we present an adaptive neural control mechanism for obstacle negotiation behavior in hexapod robots. It combines locomotion control, backbone joint control, local leg reflexes, and neural learning. While the first three components generate locomotion including walking and climbing, the neural learning mechanism allows the robot to adapt its behavior for obstacle negotiation with respect to changing conditions, e.g., variable obstacle heights and different walking gaits. By successfully learning the association of an early, predictive signal (conditioned stimulus, CS) and a late, reflex signal (unconditioned stimulus, UCS), both provided by ultrasonic sensors at the front of the robot, the robot can autonomously find an appropriate distance from an obstacle to initiate climbing. The adaptive neural control was developed and tested first on a physical robot simulation, and was then successfully transferred to a real hexapod robot, called AMOS II. The results show that the robot can efficiently negotiate obstacles with a height up to 85% of the robot's leg length in simulation and 75% in a real environment. PMID:24523694

Obstacles to developing vaccines for the Third World.

PubMed

Robbins, A; Freeman, P

1988-11-01

Despite the tremendous strides in global immunization in less developed countries (LDCs) in the last 25 years, much remains to be done and the momentum has slowed. Vaccination programs continue to prove that they are less expensive, easier to implement, and in some cases more effective than other public health programs. Therefore it is imperative to produce and deliver new or improved vaccines to LDCs to prevent many infectious diseases and save the lives of children. Yet economic and political obstacles impede the development of these vaccines, even though the scientific know-how already exists. Manufacturers of vaccines that have been around for a long time and used widely in developed nations have often sold these vaccines to international agencies, such as WHO, at production cost. They do this because they have already recouped research & development (R&D) costs. When it comes to R&D of new vaccines, however, manufacturers are generally unwilling to invest time and money into R&D since they may not recoup their costs and make a profit. International agencies do not have the money to pay the high prices charged by manufacturers. Instead of the public health community in LDCs deciding on the development of new vaccines, the decision is left almost entirely in the hands of a few institutes or commercial manufacturers in the developed world. Other than continuing with the status quo, however, possible solutions do exist. For example, the UN could create an institute to develop and manufacture its own vaccines. Another possibility is that R&D and production of vaccines for diseases prevalent in an LDC or region could take place within that specified area.

Random walk of passive tracers among randomly moving obstacles.

PubMed

Gori, Matteo; Donato, Irene; Floriani, Elena; Nardecchia, Ilaria; Pettini, Marco

2016-04-14

This study is mainly motivated by the need of understanding how the diffusion behavior of a biomolecule (or even of a larger object) is affected by other moving macromolecules, organelles, and so on, inside a living cell, whence the possibility of understanding whether or not a randomly walking biomolecule is also subject to a long-range force field driving it to its target. By means of the Continuous Time Random Walk (CTRW) technique the topic of random walk in random environment is here considered in the case of a passively diffusing particle among randomly moving and interacting obstacles. The relevant physical quantity which is worked out is the diffusion coefficient of the passive tracer which is computed as a function of the average inter-obstacles distance. The results reported here suggest that if a biomolecule, let us call it a test molecule, moves towards its target in the presence of other independently interacting molecules, its motion can be considerably slowed down.

Obstacle detection and avoiding of quadcopter

NASA Astrophysics Data System (ADS)

Wang, Dizhong; Lin, Jiajian

2017-10-01

Recent years, the flight control technology over quadcopter has been boosted vigorously and acquired the comprehensive application in a variety of industries. However, it is prominent for there to be problems existed in the stable and secure flight with the development of its autonomous flight. Through comparing with the characteristics of ultrasonic ranging and laser Time-of-Flight(abbreviated to ToF) distance as well as vision measurement and its related sensors, the obstacle detection and identification sensors need to be installed in order to effectively enhance the safety flying for aircraft, which is essential for avoiding the dangers around the surroundings. That the major sensors applied to objects perception at present are distance measuring instruments which based on the principle and application of non-contact detection technology . Prior to acknowledging the general principles of flight and obstacle avoiding, the aerodynamics modeling of the quadcopter and its object detection means has been initially determined on this paper. Based on such premise, this article emphasized on describing and analyzing the research on obstacle avoiding technology and its application status, and making an expectation for the trend of its development after analyzing the primary existing problems concerning its accuracy object avoidance.

Collision-based energetic comparison of rolling and hopping over obstacles

PubMed Central

Iida, Fumiya

2018-01-01

Locomotion of machines and robots operating in rough terrain is strongly influenced by the mechanics of the ground-machine interactions. A rolling wheel in terrain with obstacles is subject to collisional energy losses, which is governed by mechanics comparable to hopping or walking locomotion. Here we investigate the energetic cost associated with overcoming an obstacle for rolling and hopping locomotion, using a simple mechanics model. The model considers collision-based interactions with the ground and the obstacle, without frictional losses, and we quantify, analyse, and compare the sources of energetic costs for three locomotion strategies. Our results show that the energetic advantages of the locomotion strategies are uniquely defined given the moment of inertia and the Froude number associated with the system. We find that hopping outperforms rolling at larger Froude numbers and vice versa. The analysis is further extended for a comparative study with animals. By applying size and inertial properties through an allometric scaling law of hopping and trotting animals to our models, we found that the conditions at which hopping becomes energetically advantageous to rolling roughly corresponds to animals’ preferred gait transition speeds. The energetic collision losses as predicted by the model are largely verified experimentally. PMID:29538459

Dynamic clearance measure to evaluate locomotor and perceptuo-motor strategies used for obstacle circumvention in a virtual environment.

PubMed

Darekar, Anuja; Lamontagne, Anouk; Fung, Joyce

2015-04-01

Circumvention around an obstacle entails a dynamic interaction with the obstacle to maintain a safe clearance. We used a novel mathematical interpolation method based on the modified Shepard's method of Inverse Distance Weighting to compute dynamic clearance that reflected this interaction as well as minimal clearance. This proof-of-principle study included seven young healthy, four post-stroke and four healthy age-matched individuals. A virtual environment designed to assess obstacle circumvention was used to administer a locomotor (walking) and a perceptuo-motor (navigation with a joystick) task. In both tasks, participants were asked to navigate towards a target while avoiding collision with a moving obstacle that approached from either head-on, or 30° left or right. Among young individuals, dynamic clearance did not differ significantly between obstacle approach directions in both tasks. Post-stroke individuals maintained larger and smaller dynamic clearance during the locomotor and the perceptuo-motor task respectively as compared to age-matched controls. Dynamic clearance was larger than minimal distance from the obstacle irrespective of the group, task and obstacle approach direction. Also, in contrast to minimal distance, dynamic clearance can respond differently to different avoidance behaviors. Such a measure can be beneficial in contrasting obstacle avoidance behaviors in different populations with mobility problems. Copyright © 2015 Elsevier B.V. All rights reserved.

Energy dissipation by submarine obstacles during landslide impact on reservoir - potentially avoiding catastrophic dam collapse

NASA Astrophysics Data System (ADS)

Kafle, Jeevan; Kattel, Parameshwari; Mergili, Martin; Fischer, Jan-Thomas; Tuladhar, Bhadra Man; Pudasaini, Shiva P.

2017-04-01

Dense geophysical mass flows such as landslides, debris flows and debris avalanches may generate super tsunami waves as they impact water bodies such as the sea, hydraulic reservoirs or mountain lakes. Here, we apply a comprehensive and general two-phase, physical-mathematical mass flow model (Pudasaini, 2012) that consists of non-linear and hyperbolic-parabolic partial differential equations for mass and momentum balances, and present novel, high-resolution simulation results for two-phase flows, as a mixture of solid grains and viscous fluid, impacting fluid reservoirs with obstacles. The simulations demonstrate that due to the presence of different obstacles in the water body, the intense flow-obstacle-interaction dramatically reduces the flow momentum resulting in the rapid energy dissipation around the obstacles. With the increase of obstacle height overtopping decreases but, the deflection and capturing (holding) of solid mass increases. In addition, the submarine solid mass is captured by the multiple obstacles and the moving mass decreases both in amount and speed as each obstacle causes the flow to deflect into two streams and also captures a portion of it. This results in distinct tsunami and submarine flow dynamics with multiple surface water and submarine debris waves. This novel approach can be implemented in open source GIS modelling framework r.avaflow, and be applied in hazard mitigation, prevention and relevant engineering or environmental tasks. This might be in particular for process chains, such as debris impacts in lakes and subsequent overtopping. So, as the complex flow-obstacle-interactions strongly and simultaneously dissipate huge energy at impact such installations potentially avoid great threat against the integrity of the dam. References: Pudasaini, S. P. (2012): A general two-phase debris flow model. J. Geophys. Res. 117, F03010, doi: 10.1029/ 2011JF002186.

The Effects of Shoe Traction and Obstacle Height on Lower Extremity Coordination Dynamics during Walking

PubMed Central

Decker, Leslie; Houser, Jeremy J.; Noble, John M.; Karst, Gregory M.; Stergiou, Nicholas

2009-01-01

This study aims to investigate the effects of shoe traction and obstacle height on lower extremity relative phase dynamics (analysis of intralimb coordination) during walking to better understand the mechanisms employed to avoid slippage following obstacle clearance. Ten participants walked at a self-selected pace during eight conditions: four obstacle heights (0%, 10%, 20%, and 40% of limb length) while wearing two pairs of shoes (low and high traction). A coordination analysis was used and phasing relationships between lower extremity segments were examined. The results demonstrated that significant behavioral changes were elicited under varied obstacle heights and frictional conditions. Both decreasing shoe traction and increasing obstacle height resulted in a more in-phase relationship between the interacting lower limb segments. The higher the obstacle and the lower the shoe traction, the more unstable the system became. These changes in phasing relationship and variability are indicators of alterations in coordinative behavior, which if pushed further may have lead to falling. PMID:19187929

TOOLS FOR OVERCOMING OBSTACLES TO REVITALIZATION: SMARTE AND START-UP

EPA Science Inventory

In 2001, the US-German Bilateral Working Group (BWG) identified more than 40 obstacles to site revitalization which occurred in both countries. From 2001-2005, the BWG developed tools and techniques for overcoming these obstacles. Five joint workshops were held on the following r...

Vision Based Obstacle Detection in Uav Imaging

NASA Astrophysics Data System (ADS)

Badrloo, S.; Varshosaz, M.

2017-08-01

Detecting and preventing incidence with obstacles is crucial in UAV navigation and control. Most of the common obstacle detection techniques are currently sensor-based. Small UAVs are not able to carry obstacle detection sensors such as radar; therefore, vision-based methods are considered, which can be divided into stereo-based and mono-based techniques. Mono-based methods are classified into two groups: Foreground-background separation, and brain-inspired methods. Brain-inspired methods are highly efficient in obstacle detection; hence, this research aims to detect obstacles using brain-inspired techniques, which try to enlarge the obstacle by approaching it. A recent research in this field, has concentrated on matching the SIFT points along with, SIFT size-ratio factor and area-ratio of convex hulls in two consecutive frames to detect obstacles. This method is not able to distinguish between near and far obstacles or the obstacles in complex environment, and is sensitive to wrong matched points. In order to solve the above mentioned problems, this research calculates the dist-ratio of matched points. Then, each and every point is investigated for Distinguishing between far and close obstacles. The results demonstrated the high efficiency of the proposed method in complex environments.

Bi-stability in cooperative transport by ants in the presence of obstacles

PubMed Central

Pinkoviezky, Itai; Feinerman, Ofer

2018-01-01

To cooperatively carry large food items to the nest, individual ants conform their efforts and coordinate their motion. Throughout this expedition, collective motion is driven both by internal interactions between the carrying ants and a response to newly arrived informed ants that orient the cargo towards the nest. During the transport process, the carrying group must overcome obstacles that block their path to the nest. Here, we investigate the dynamics of cooperative transport, when the motion of the ants is frustrated by a linear obstacle that obstructs the motion of the cargo. The obstacle contains a narrow opening that serves as the only available passage to the nest, and through which single ants can pass but not with the cargo. We provide an analytical model for the ant-cargo system in the constrained environment that predicts a bi-stable dynamic behavior between an oscillatory mode of motion along the obstacle and a convergent mode of motion near the opening. Using both experiments and simulations, we show how for small cargo sizes, the system exhibits spontaneous transitions between these two modes of motion due to fluctuations in the applied force on the cargo. The bi-stability provides two possible problem solving strategies for overcoming the obstacle, either by attempting to pass through the opening, or take large excursions to circumvent the obstacle. PMID:29746457

Bi-stability in cooperative transport by ants in the presence of obstacles.

PubMed

Ron, Jonathan E; Pinkoviezky, Itai; Fonio, Ehud; Feinerman, Ofer; Gov, Nir S

2018-05-01

To cooperatively carry large food items to the nest, individual ants conform their efforts and coordinate their motion. Throughout this expedition, collective motion is driven both by internal interactions between the carrying ants and a response to newly arrived informed ants that orient the cargo towards the nest. During the transport process, the carrying group must overcome obstacles that block their path to the nest. Here, we investigate the dynamics of cooperative transport, when the motion of the ants is frustrated by a linear obstacle that obstructs the motion of the cargo. The obstacle contains a narrow opening that serves as the only available passage to the nest, and through which single ants can pass but not with the cargo. We provide an analytical model for the ant-cargo system in the constrained environment that predicts a bi-stable dynamic behavior between an oscillatory mode of motion along the obstacle and a convergent mode of motion near the opening. Using both experiments and simulations, we show how for small cargo sizes, the system exhibits spontaneous transitions between these two modes of motion due to fluctuations in the applied force on the cargo. The bi-stability provides two possible problem solving strategies for overcoming the obstacle, either by attempting to pass through the opening, or take large excursions to circumvent the obstacle.

Do characteristics of a stationary obstacle lead to adjustments in obstacle stepping strategies?

PubMed

Worden, Timothy A; De Jong, Audrey F; Vallis, Lori Ann

2016-01-01

Navigating cluttered and complex environments increases the risk of falling. To decrease this risk, it is important to understand the influence of obstacle visual cues on stepping parameters, however the specific obstacle characteristics that have the greatest influence on avoidance strategies is still under debate. The purpose of the current work is to provide further insight on the relationship between obstacle appearance in the environment and modulation of stepping parameters. Healthy young adults (N=8) first stepped over an obstacle with one visible top edge ("floating"; 8 trials) followed by trials where experimenters randomly altered the location of a ground reference object to one of 7 different positions (8 trials per location), which ranged from 6cm in front of, directly under, or up to 6cm behind the floating obstacle (at 2cm intervals). Mean take-off and landing distance as well as minimum foot clearance values were unchanged across different positions of the ground reference object; a consistent stepping trajectory was observed for all experimental conditions. Contrary to our hypotheses, results of this study indicate that ground based visual cues are not essential for the planning of stepping and clearance strategies. The simultaneous presentation of both floating and ground based objects may have provided critical information that lead to the adoption of a consistent strategy for clearing the top edge of the obstacle. The invariant foot placement observed here may be an appropriate stepping strategy for young adults, however this may not be the case across the lifespan or in special populations. Copyright © 2015 Elsevier B.V. All rights reserved.

Ground Reaction Forces of the Lead and Trail Limbs when Stepping Over an Obstacle

PubMed Central

Bovonsunthonchai, Sunee; Khobkhun, Fuengfa; Vachalathiti, Roongtiwa

2015-01-01

Background Precise force generation and absorption during stepping over different obstacles need to be quantified for task accomplishment. This study aimed to quantify how the lead limb (LL) and trail limb (TL) generate and absorb forces while stepping over obstacle of various heights. Material/Methods Thirteen healthy young women participated in the study. Force data were collected from 2 force plates when participants stepped over obstacles. Two limbs (right LL and left TL) and 4 conditions of stepping (no obstacle, stepping over 5 cm, 20 cm, and 30 cm obstacle heights) were tested for main effect and interaction effect by 2-way ANOVA. Paired t-test and 1-way repeated-measure ANOVA were used to compare differences of variables between limbs and among stepping conditions, respectively. The main effects on the limb were found in first peak vertical force, minimum vertical force, propulsive peak force, and propulsive impulse. Results Significant main effects of condition were found in time to minimum force, time to the second peak force, time to propulsive peak force, first peak vertical force, braking peak force, propulsive peak force, vertical impulse, braking impulse, and propulsive impulse. Interaction effects of limb and condition were found in first peak vertical force, propulsive peak force, braking impulse, and propulsive impulse. Conclusions Adaptations of force generation in the LL and TL were found to involve adaptability to altered external environment during stepping in healthy young adults. PMID:26169293

Women's orgasm obstacles: A qualitative study.

PubMed

Nekoolaltak, Maryam; Keshavarz, Zohreh; Simbar, Masoumeh; Nazari, Ali Mohammad; Baghestani, Ahmad Reza

2017-08-01

Woman's orgasm plays a vital role in sexual compatibility and marital satisfaction. Orgasm in women is a learnable phenomenon that is influenced by several factors. The aim of this study is exploring obstacles to orgasm in Iranian married women. This qualitative study with directed content analysis approach was conducted in 2015-2016, on 20 Iranian married women who were individually interviewed at two medical clinics in Tehran, Iran. Orgasm obstacles were explored in one category, 4 subcategories, and 25 codes. The main category was "Multidimensionality of women's orgasm obstacles". Subcategories and some codes included: Physical obstacles (wife's or husband's boredom, vaginal infection, insufficient vaginal lubrication), psychological obstacles (lack of sexual knowledge, shame, lack of concentration on sex due to household and children problems), relational obstacles (husband's hurry, having a dispute and annoyance with spouse) and contextual obstacles (Irregular sleep hours, lack of privacy and inability to separate children's bedroom from their parents, lack of peace at home). For prevention or treatment of female orgasm disorders, attention to physical factors is not enough. Obtaining a comprehensive history about physical, psychological, relational and contextual dimensions of woman's life is necessary.

Constructing target product profiles (TPPs) to help vaccines overcome post-approval obstacles

PubMed Central

Lee, Bruce Y.; Burke, Donald S.

2012-01-01

As history has demonstrated, post-approval obstacles can impede a vaccine’s use and potentially lead to its withdrawal. Addressing these potential obstacles when changes in a vaccine’s technology can still be easily made may improve a vaccine’s chances of success. Augmented vaccine target product profiles (TPPs) can help vaccine scientists better understand and anticipate these obstacles and galvanize conversations among various vaccine stakeholders (e.g., scientists, marketers, business development managers, policy makers, public health officials, health care workers, third party payors, etc.) earlier in a vaccine’s development. PMID:19782109

Autonomous dynamic obstacle avoidance for bacteria-powered microrobots (BPMs) with modified vector field histogram.

PubMed

Kim, Hoyeon; Cheang, U Kei; Kim, Min Jun

2017-01-01

In order to broaden the use of microrobots in practical fields, autonomous control algorithms such as obstacle avoidance must be further developed. However, most previous studies of microrobots used manual motion control to navigate past tight spaces and obstacles while very few studies demonstrated the use of autonomous motion. In this paper, we demonstrated a dynamic obstacle avoidance algorithm for bacteria-powered microrobots (BPMs) using electric field in fluidic environments. A BPM consists of an artificial body, which is made of SU-8, and a high dense layer of harnessed bacteria. BPMs can be controlled using externally applied electric fields due to the electrokinetic property of bacteria. For developing dynamic obstacle avoidance for BPMs, a kinematic model of BPMs was utilized to prevent collision and a finite element model was used to characteristic the deformation of an electric field near the obstacle walls. In order to avoid fast moving obstacles, we modified our previously static obstacle avoidance approach using a modified vector field histogram (VFH) method. To validate the advanced algorithm in experiments, magnetically controlled moving obstacles were used to intercept the BPMs as the BPMs move from the initial position to final position. The algorithm was able to successfully guide the BPMs to reach their respective goal positions while avoiding the dynamic obstacles.

Identification of Vibrotactile Patterns Encoding Obstacle Distance Information.

PubMed

Kim, Yeongmi; Harders, Matthias; Gassert, Roger

2015-01-01

Delivering distance information of nearby obstacles from sensors embedded in a white cane-in addition to the intrinsic mechanical feedback from the cane-can aid the visually impaired in ambulating independently. Haptics is a common modality for conveying such information to cane users, typically in the form of vibrotactile signals. In this context, we investigated the effect of tactile rendering methods, tactile feedback configurations and directions of tactile flow on the identification of obstacle distance. Three tactile rendering methods with temporal variation only, spatio-temporal variation and spatial/temporal/intensity variation were investigated for two vibration feedback configurations. Results showed a significant interaction between tactile rendering method and feedback configuration. Spatio-temporal variation generally resulted in high correct identification rates for both feedback configurations. In the case of the four-finger vibration, tactile rendering with spatial/temporal/intensity variation also resulted in high distance identification rate. Further, participants expressed their preference for the four-finger vibration over the single-finger vibration in a survey. Both preferred rendering methods with spatio-temporal variation and spatial/temporal/intensity variation for the four-finger vibration could convey obstacle distance information with low workload. Overall, the presented findings provide valuable insights and guidance for the design of haptic displays for electronic travel aids for the visually impaired.

A Motion Planning Approach to Automatic Obstacle Avoidance during Concentric Tube Robot Teleoperation

PubMed Central

Torres, Luis G.; Kuntz, Alan; Gilbert, Hunter B.; Swaney, Philip J.; Hendrick, Richard J.; Webster, Robert J.; Alterovitz, Ron

2015-01-01

Concentric tube robots are thin, tentacle-like devices that can move along curved paths and can potentially enable new, less invasive surgical procedures. Safe and effective operation of this type of robot requires that the robot’s shaft avoid sensitive anatomical structures (e.g., critical vessels and organs) while the surgeon teleoperates the robot’s tip. However, the robot’s unintuitive kinematics makes it difficult for a human user to manually ensure obstacle avoidance along the entire tentacle-like shape of the robot’s shaft. We present a motion planning approach for concentric tube robot teleoperation that enables the robot to interactively maneuver its tip to points selected by a user while automatically avoiding obstacles along its shaft. We achieve automatic collision avoidance by precomputing a roadmap of collision-free robot configurations based on a description of the anatomical obstacles, which are attainable via volumetric medical imaging. We also mitigate the effects of kinematic modeling error in reaching the goal positions by adjusting motions based on robot tip position sensing. We evaluate our motion planner on a teleoperated concentric tube robot and demonstrate its obstacle avoidance and accuracy in environments with tubular obstacles. PMID:26413381

A Motion Planning Approach to Automatic Obstacle Avoidance during Concentric Tube Robot Teleoperation.

PubMed

Torres, Luis G; Kuntz, Alan; Gilbert, Hunter B; Swaney, Philip J; Hendrick, Richard J; Webster, Robert J; Alterovitz, Ron

2015-05-01

Concentric tube robots are thin, tentacle-like devices that can move along curved paths and can potentially enable new, less invasive surgical procedures. Safe and effective operation of this type of robot requires that the robot's shaft avoid sensitive anatomical structures (e.g., critical vessels and organs) while the surgeon teleoperates the robot's tip. However, the robot's unintuitive kinematics makes it difficult for a human user to manually ensure obstacle avoidance along the entire tentacle-like shape of the robot's shaft. We present a motion planning approach for concentric tube robot teleoperation that enables the robot to interactively maneuver its tip to points selected by a user while automatically avoiding obstacles along its shaft. We achieve automatic collision avoidance by precomputing a roadmap of collision-free robot configurations based on a description of the anatomical obstacles, which are attainable via volumetric medical imaging. We also mitigate the effects of kinematic modeling error in reaching the goal positions by adjusting motions based on robot tip position sensing. We evaluate our motion planner on a teleoperated concentric tube robot and demonstrate its obstacle avoidance and accuracy in environments with tubular obstacles.

Three-dimensional obstacle classification in laser range data

NASA Astrophysics Data System (ADS)

Armbruster, Walter; Bers, Karl-Heinz

1998-10-01

The threat of hostile surveillance and weapon systems require military aircraft to fly under extreme conditions such as low altitude, high speed, poor visibility and incomplete terrain information. The probability of collision with natural and man-made obstacles during such contour missions is high if detection capability is restricted to conventional vision aids. Forward-looking scanning laser rangefinders which are presently being flight tested and evaluated at German proving grounds, provide a possible solution, having a large field of view, high angular and range resolution, a high pulse repetition rate, and sufficient pulse energy to register returns from wires at over 500 m range (depends on the system) with a high hit-and-detect probability. Despite the efficiency of the sensor, acceptance of current obstacle warning systems by test pilots is not very high, mainly due to the systems' inadequacies in obstacle recognition and visualization. This has motivated the development and the testing of more advanced 3d-scene analysis algorithm at FGAN-FIM to replace the obstacle recognition component of current warning systems. The basic ideas are to increase the recognition probability and to reduce the false alarm rate for hard-to-extract obstacles such as wires, by using more readily recognizable objects such as terrain, poles, pylons, trees, etc. by implementing a hierarchical classification procedure to generate a parametric description of the terrain surface as well as the class, position, orientation, size and shape of all objects in the scene. The algorithms can be used for other applications such as terrain following, autonomous obstacle avoidance, and automatic target recognition.

Malaria: Obstacles and Opportunities.

DTIC Science & Technology

1991-01-01

SUBTITLE S. FUNDING NUMBERS Malaria: Obstacles and Opportunities 89PP9965 62770A 6. AUTHOR(S) 3MI62770A870 AN DA3 46085 Arthur Dennis Long 7. PERFORMING ...ORGANIZATION NAME(S) AND ADORESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Agency for International Development New State Office Building Washignton...Hygiene and Pub- lic Health, Baltimore. \\Maryland JACQUELINE A. CATTANI. Secretary, Steering Committee of the Scientific Working Group on Applied

Recognition of an obstacle in a flow using artificial neural networks.

PubMed

Carrillo, Mauricio; Que, Ulices; González, José A; López, Carlos

2017-08-01

In this work a series of artificial neural networks (ANNs) has been developed with the capacity to estimate the size and location of an obstacle obstructing the flow in a pipe. The ANNs learn the size and location of the obstacle by reading the profiles of the dynamic pressure q or the x component of the velocity v_{x} of the fluid at a certain distance from the obstacle. Data to train the ANN were generated using numerical simulations with a two-dimensional lattice Boltzmann code. We analyzed various cases varying both the diameter and the position of the obstacle on the y axis, obtaining good estimations using the R^{2} coefficient for the cases under study. Although the ANN showed problems with the classification of very small obstacles, the general results show a very good capacity for prediction.

Assessment of a simple obstacle detection device for the visually impaired.

PubMed

Lee, Cheng-Lung; Chen, Chih-Yung; Sung, Peng-Cheng; Lu, Shih-Yi

2014-07-01

A simple obstacle detection device, based upon an automobile parking sensor, was assessed as a mobility aid for the visually impaired. A questionnaire survey for mobility needs was performed at the start of this study. After the detector was developed, five blindfolded sighted and 15 visually impaired participants were invited to conduct travel experiments under three test conditions: (1) using a white cane only, (2) using the obstacle detector only and (3) using both devices. A post-experiment interview regarding the usefulness of the obstacle detector for the visually impaired participants was performed. The results showed that the obstacle detector could augment mobility performance with the white cane. The obstacle detection device should be used in conjunction with the white cane to achieve the best mobility speed and body protection. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Professional development in statistics, technology, and cognitively demanding tasks: classroom implementation and obstacles

NASA Astrophysics Data System (ADS)

Foley, Gregory D.; Bakr Khoshaim, Heba; Alsaeed, Maha; Nihan Er, S.

2012-03-01

Attending professional development programmes can support teachers in applying new strategies for teaching mathematics and statistics. This study investigated (a) the extent to which the participants in a professional development programme subsequently used the techniques they had learned when teaching mathematics and statistics and (b) the obstacles they encountered in enacting cognitively demanding instructional tasks in their classrooms. The programme created an intellectual learning community among the participants and helped them gain confidence as teachers of statistics, and the students of participating teachers became actively engaged in deep mathematical thinking. The participants indicated, however, that time, availability of resources and students' prior achievement critically affected the implementation of cognitively demanding instructional activities.

Obstacle-avoiding navigation system

DOEpatents

Borenstein, Johann; Koren, Yoram; Levine, Simon P.

1991-01-01

A system for guiding an autonomous or semi-autonomous vehicle through a field of operation having obstacles thereon to be avoided employs a memory for containing data which defines an array of grid cells which correspond to respective subfields in the field of operation of the vehicle. Each grid cell in the memory contains a value which is indicative of the likelihood, or probability, that an obstacle is present in the respectively associated subfield. The values in the grid cells are incremented individually in response to each scan of the subfields, and precomputation and use of a look-up table avoids complex trigonometric functions. A further array of grid cells is fixed with respect to the vehicle form a conceptual active window which overlies the incremented grid cells. Thus, when the cells in the active window overly grid cell having values which are indicative of the presence of obstacles, the value therein is used as a multiplier of the precomputed vectorial values. The resulting plurality of vectorial values are summed vectorially in one embodiment of the invention to produce a virtual composite repulsive vector which is then summed vectorially with a target-directed vector for producing a resultant vector for guiding the vehicle. In an alternative embodiment, a plurality of vectors surrounding the vehicle are computed, each having a value corresponding to obstacle density. In such an embodiment, target location information is used to select between alternative directions of travel having low associated obstacle densities.

Venus and Mars Obstacles in the Solar Wind

NASA Astrophysics Data System (ADS)

Luhmann, J. G.; Mitchell, D. L.; Acuna, M. H.; Russell, C. T.; Brecht, S. H.; Lyon, J. G.

2000-10-01

Comparisons of the magnetosheaths of Venus and Mars contrast the relative simplicity of the Venus solar wind interaction and the ``Jekyll and Hyde" nature of the Mars interaction. Magnetometer observations from Mars Global Surveyor during the elliptical science phasing orbits and Pioneer Venus Orbiter in its normally elliptical orbit are compared, with various models used to compensate for the different near-polar periapsis of MGS and near-equator periapsis of PVO. Gasdynamic or MHD fluid models of flow around a conducting sphere provide a remarkably good desciption of the Venus case, and the Mars case when the strong Martian crustal magnetic anomalies are in the flow wake. In the case of Venus, large magnetosheath field fluctuations can be reliably tied to occurrence of a subsolar quasiparallel bow shock resulting from a small interplanetary field cone angle (angle between flow and field) upstream. At Mars one must also contend with such large fluctuations from the bow shock, but also from unstable solar wind proton distributions due to finite ion gyroradius effects, and from the complicated obstacle presented to the solar wind when the crustal magnetic anomalies are on the ram face or terminator. We attempt to distinguish between these factors at Mars, which are important for interpretation of the upcoming NOZOMI and Mars Express mission measurements. The results also provide more insights into a uniquely complex type of solar system solar wind interaction involving crustal fields akin to the Moon's, combined with a Venus-like ionospheric obstacle.

Negative obstacle detection by thermal signature

NASA Technical Reports Server (NTRS)

Matthies, Larry; Rankin, A.

2003-01-01

Detecting negative obstacles (ditches, potholes, and other depressions) is one of the most difficult problems in perception for autonomous, off-road navigation. Past work has largely relied on range imagery, because that is based on the geometry of the obstacle, is largely insensitive to illumination variables, and because there have not been other reliable alternatives. However, the visible aspect of negative obstacles shrinks rapidly with range, making them impossible to detect in time to avoid them at high speed. To relive this problem, we show that the interiors of negative obstacles generally remain warmer than the surrounding terrain throughout the night, making thermal signature a stable property for night-time negative obstacle detection. Experimental results to date have achieved detection distances 45% greater by using thermal signature than by using range data alone. Thermal signature is the first known observable with potential to reveal a deep negative obstacle without actually seeing far into it. Modeling solar illumination has potential to extend the usefulness of thermal signature through daylight hours.

Apparent motion perception in lower limb amputees with phantom sensations: "obstacle shunning" and "obstacle tolerance".

PubMed

Saetta, Gianluca; Grond, Ilva; Brugger, Peter; Lenggenhager, Bigna; Tsay, Anthony J; Giummarra, Melita J

2018-03-21

Phantom limbs are the phenomenal persistence of postural and sensorimotor features of an amputated limb. Although immaterial, their characteristics can be modulated by the presence of physical matter. For instance, the phantom may disappear when its phenomenal space is invaded by objects ("obstacle shunning"). Alternatively, "obstacle tolerance" occurs when the phantom is not limited by the law of impenetrability and co-exists with physical objects. Here we examined the link between this under-investigated aspect of phantom limbs and apparent motion perception. The illusion of apparent motion of human limbs involves the perception that a limb moves through or around an object, depending on the stimulus onset asynchrony (SOA) for the two images. Participants included 12 unilateral lower limb amputees matched for obstacle shunning (n = 6) and obstacle tolerance (n = 6) experiences, and 14 non-amputees. Using multilevel linear models, we replicated robust biases for short perceived trajectories for short SOA (moving through the object), and long trajectories (circumventing the object) for long SOAs in both groups. Importantly, however, amputees with obstacle shunning perceived leg stimuli to predominantly move through the object, whereas amputees with obstacle tolerance perceived leg stimuli to predominantly move around the object. That is, in people who experience obstacle shunning, apparent motion perception of lower limbs was not constrained to the laws of impenetrability (as the phantom disappears when invaded by objects), and legs can therefore move through physical objects. Amputees who experience obstacle tolerance, however, had stronger solidity constraints for lower limb apparent motion, perhaps because they must avoid co-location of the phantom with physical objects. Phantom limb experience does, therefore, appear to be modulated by intuitive physics, but not in the same way for everyone. This may have important implications for limb experience post

Exploring performance obstacles of intensive care nurses.

PubMed

Gurses, Ayse P; Carayon, Pascale

2009-05-01

High nursing workload, poor patient safety, and poor nursing quality of working life (QWL) are major issues in intensive care units (ICUs). Characteristics of the ICU and performance obstacles may contribute to these issues. The goal of this study was to comprehensively identify the performance obstacles perceived by ICU nurses. We used a qualitative research design and conducted semi-structured interviews with 15 ICU nurses of a medical-surgical ICU. Based on this qualitative study and a previously reported quantitative study, we identified seven main types of performance obstacles experienced by ICU nurses. Obstacles related to the physical environment (e.g., noise, amount of space), family relations (e.g., distractions caused by family, lack of time to spend with family), and equipment (e.g., unavailability, misplacement) were the most frequently experienced performance obstacles. The qualitative interview data provided rich information regarding the factors contributing to the performance obstacles. Overall, ICU nurses experience a variety of performance obstacles in their work on a daily basis. Future research is needed to understand the impact of performance obstacles on nursing workload, nursing QWL, and quality and safety of care.

Stepping over obstacles: anticipatory modifications in children with and without Down syndrome.

PubMed

Virji-Babul, Naznin; Brown, Michelle

2004-12-01

The purpose of this study was to explore the mechanism of anticipatory control of gait in relation to the perception of an obstacle. Typically developing (TD) children (4-7 years of age) and children with Down syndrome (5-6 years of age) walked and stepped over obstacles of two different heights-a "subtle" obstacle that was placed at a very low distance from the floor (1% of total body height) and an "obvious" obstacle that was placed at a much higher distance from the floor (15% of total body height). Spatial and temporal measures of the gait cycle were analyzed. TD children showed increased variability in pre-obstacle step lengths only in response to the higher obstacle. Children with DS showed a decrease in variability in response to the higher obstacle and marked qualitative changes in their gait cycle. Both groups of children were able to scale toe clearance with obstacle height. These results show that TD young children can make task-specific anticipatory adjustments by modulating step length and toe clearance. Children with DS show appropriate scaling of toe clearance and are beginning to show the emergence of anticipatory responses under specific environmental conditions.

Autonomous dynamic obstacle avoidance for bacteria-powered microrobots (BPMs) with modified vector field histogram

PubMed Central

Kim, Hoyeon; Cheang, U. Kei

2017-01-01

In order to broaden the use of microrobots in practical fields, autonomous control algorithms such as obstacle avoidance must be further developed. However, most previous studies of microrobots used manual motion control to navigate past tight spaces and obstacles while very few studies demonstrated the use of autonomous motion. In this paper, we demonstrated a dynamic obstacle avoidance algorithm for bacteria-powered microrobots (BPMs) using electric field in fluidic environments. A BPM consists of an artificial body, which is made of SU-8, and a high dense layer of harnessed bacteria. BPMs can be controlled using externally applied electric fields due to the electrokinetic property of bacteria. For developing dynamic obstacle avoidance for BPMs, a kinematic model of BPMs was utilized to prevent collision and a finite element model was used to characteristic the deformation of an electric field near the obstacle walls. In order to avoid fast moving obstacles, we modified our previously static obstacle avoidance approach using a modified vector field histogram (VFH) method. To validate the advanced algorithm in experiments, magnetically controlled moving obstacles were used to intercept the BPMs as the BPMs move from the initial position to final position. The algorithm was able to successfully guide the BPMs to reach their respective goal positions while avoiding the dynamic obstacles. PMID:29020016

Forging the Basis for Developing Protein-Ligand Interaction Scoring Functions.

PubMed

Liu, Zhihai; Su, Minyi; Han, Li; Liu, Jie; Yang, Qifan; Li, Yan; Wang, Renxiao

2017-02-21

In structure-based drug design, scoring functions are widely used for fast evaluation of protein-ligand interactions. They are often applied in combination with molecular docking and de novo design methods. Since the early 1990s, a whole spectrum of protein-ligand interaction scoring functions have been developed. Regardless of their technical difference, scoring functions all need data sets combining protein-ligand complex structures and binding affinity data for parametrization and validation. However, data sets of this kind used to be rather limited in terms of size and quality. On the other hand, standard metrics for evaluating scoring function used to be ambiguous. Scoring functions are often tested in molecular docking or even virtual screening trials, which do not directly reflect the genuine quality of scoring functions. Collectively, these underlying obstacles have impeded the invention of more advanced scoring functions. In this Account, we describe our long-lasting efforts to overcome these obstacles, which involve two related projects. On the first project, we have created the PDBbind database. It is the first database that systematically annotates the protein-ligand complexes in the Protein Data Bank (PDB) with experimental binding data. This database has been updated annually since its first public release in 2004. The latest release (version 2016) provides binding data for 16 179 biomolecular complexes in PDB. Data sets provided by PDBbind have been applied to many computational and statistical studies on protein-ligand interaction and various subjects. In particular, it has become a major data resource for scoring function development. On the second project, we have established the Comparative Assessment of Scoring Functions (CASF) benchmark for scoring function evaluation. Our key idea is to decouple the "scoring" process from the "sampling" process, so scoring functions can be tested in a relatively pure context to reflect their quality. In our

Dynamics of spiral waves rotating around an obstacle and the existence of a minimal obstacle

NASA Astrophysics Data System (ADS)

Gao, Xiang; Feng, Xia; Li, Teng-Chao; Qu, Shixian; Wang, Xingang; Zhang, Hong

2017-05-01

Pinning of vortices by obstacles plays an important role in various systems. In the heart, anatomical reentry is created when a vortex, also known as the spiral wave, is pinned to an anatomical obstacle, leading to a class of physiologically very important arrhythmias. Previous analyses of its dynamics and instability provide fine estimates in some special circumstances, such as large obstacles or weak excitabilities. Here, to expand theoretical analyses to all circumstances, we propose a general theory whose results quantitatively agree with direct numerical simulations. In particular, when obstacles are small and pinned spiral waves are destabilized, an accurate explanation of the instability in two-dimensional media is provided by the usage of a mapping rule and dimension reduction. The implications of our results are to better understand the mechanism of arrhythmia and thus improve its early prevention.

Novel approaches to helicopter obstacle warning

NASA Astrophysics Data System (ADS)

Seidel, Christian; Samuelis, Christian; Wegner, Matthias; Münsterer, Thomas; Rumpf, Thomas; Schwartz, Ingo

2006-05-01

EADS Germany is the world market leader in commercial Helicopter Laser Radar (HELLAS) Obstacle Warning Systems. The HELLAS-Warning System has been introduced into the market in 2000, is in service at German Border Control (Bundespolizei) and Royal Thai Airforce and is successfully evaluated by the Foreign Comparative Test Program (FCT) of the USSOCOM. Currently the successor system HELLAS-Awareness is in development. It will have extended sensor performance, enhanced realtime data processing capabilities and advanced HMI features. We will give an outline of the new sensor unit concerning detection technology and helicopter integration aspects. The system provides a widespread field of view with additional dynamic line of sight steering and a large detection range in combination with a high frame rate of 3Hz. The workflow of the data processing will be presented with focus on novel filter techniques and obstacle classification methods. As commonly known the former are indispensable due to unavoidable statistical measuring errors and solarisation. The amount of information in the filtered raw data is further reduced by ground segmentation. The remaining raised objects are extracted and classified in several stages into different obstacle classes. We will show the prioritization function which orders the obstacles concerning to their threat potential to the helicopter taking into account the actual flight dynamics. The priority of an object determines the display and provision of warnings to the pilot. Possible HMI representation includes video or FLIR overlay on multifunction displays, audio warnings and visualization of information on helmet mounted displays and digital maps. Different concepts will be presented.

Laser radar system for obstacle avoidance

NASA Astrophysics Data System (ADS)

Bers, Karlheinz; Schulz, Karl R.; Armbruster, Walter

2005-09-01

The threat of hostile surveillance and weapon systems require military aircraft to fly under extreme conditions such as low altitude, high speed, poor visibility and incomplete terrain information. The probability of collision with natural and man-made obstacles during such contour missions is high if detection capability is restricted to conventional vision aids. Forward-looking scanning laser radars which are build by the EADS company and presently being flight tested and evaluated at German proving grounds, provide a possible solution, having a large field of view, high angular and range resolution, a high pulse repetition rate, and sufficient pulse energy to register returns from objects at distances of military relevance with a high hit-and-detect probability. The development of advanced 3d-scene analysis algorithms had increased the recognition probability and reduced the false alarm rate by using more readily recognizable objects such as terrain, poles, pylons, trees, etc. to generate a parametric description of the terrain surface as well as the class, position, orientation, size and shape of all objects in the scene. The sensor system and the implemented algorithms can be used for other applications such as terrain following, autonomous obstacle avoidance, and automatic target recognition. This paper describes different 3D-imaging ladar sensors with unique system architecture but different components matched for different military application. Emphasis is laid on an obstacle warning system with a high probability of detection of thin wires, the real time processing of the measured range image data, obstacle classification und visualization.

Novel design and fabrication of a geometrical obstacle-embedded micromixer with notched wall

NASA Astrophysics Data System (ADS)

Wu, Shih-Jeh; Hsu, Hsiang-Chen; Feng, Wen-Jui

2014-09-01

A microfluidic embedded MEMS mixer with a Y-junction type channel and cylindrical obstructions was designed and fabricated for improving the fluid mixing mechanism under low Reynolds number (\\mathit{Re}) condition. The flow field was simulated numerically by software (COMSOL multiphysics®) first. The design was then realized through casting the device in PDMS by lithographed SU-8 photo-resistive mold on silicon wafer. Parametric experimental studies were conducted for optimal design. Two different fluids were pumped into the two legs of the Y-junction channel, and the fluids were broken-up by an embedded cylindrical obstacle in the middle of the tapered micro-channel. The chaotic convection took place in the mixing channel behind the embedded cylindrical obstacles. The flow motion was observed under CCD camera and analyzed by grey level. The developed micromixer in this study can enhance the fluid mixing by the interaction of diffusion and convection for wide range of Reynolds numbers (0.01 < \\mathit{Re} < 100). Experimental results showed that the mixing index reached the required value at 0.1 within 0.024 seconds when the inlet fluid velocity is 0.499 m/s (i.e., at 1200 µl/min flow rate) for merely four cylindrical obstacles. A shorter mixing distance can be accomplished compared to the current devices reported due to faster mixing and shorter mixing time.

Surface obstacles in pulsatile flow

NASA Astrophysics Data System (ADS)

Carr, Ian A.; Plesniak, Michael W.

2017-11-01

Flows past obstacles mounted on flat surfaces have been widely studied due to their ubiquity in nature and engineering. For nearly all of these studies, the freestream flow over the obstacle was steady, i.e., constant velocity, unidirectional flow. Unsteady, pulsatile flows occur frequently in biology, geophysics, biomedical engineering, etc. Our study is aimed at extending the comprehensive knowledge base that exists for steady flows to considerably more complex pulsatile flows. Characterizing the vortex and wake dynamics of flows around surface obstacles embedded in pulsatile flows can provide insights into the underlying physics in all wake and junction flows. In this study, we experimentally investigate the wake of two canonical obstacles: a cube and a circular cylinder with an aspect ratio of unity. Our previous studies of a surface-mounted hemisphere in pulsatile flow are used as a baseline for these two new, more complex geometries. Phase-averaged PIV and hot-wire anemometry are used to characterize the dynamics of coherent structures in the wake and at the windward junction of the obstacles. Complex physics occur during the deceleration phase of the pulsatile inflow. We propose a framework for understanding these physics based on self-induced vortex propagation, similar to the phenomena exhibited by vortex rings.

Automatic Quadcopter Control Avoiding Obstacle Using Camera with Integrated Ultrasonic Sensor

NASA Astrophysics Data System (ADS)

Anis, Hanafi; Haris Indra Fadhillah, Ahmad; Darma, Surya; Soekirno, Santoso

2018-04-01

Automatic navigation on the drone is being developed these days, a wide variety of types of drones and its automatic functions. Drones used in this study was an aircraft with four propellers or quadcopter. In this experiment, image processing used to recognize the position of an object and ultrasonic sensor used to detect obstacle distance. The method used to trace an obsctacle in image processing was the Lucas-Kanade-Tomasi Tracker, which had been widely used due to its high accuracy. Ultrasonic sensor used to complement the image processing success rate to be fully detected object. The obstacle avoidance system was to observe at the program decisions from some obstacle conditions read by the camera and ultrasonic sensors. Visual feedback control based PID controllers are used as a control of drones movement. The conclusion of the obstacle avoidance system was to observe at the program decisions from some obstacle conditions read by the camera and ultrasonic sensors.

A Systematic Study of Sustainable Development Goal (SDG) Interactions

NASA Astrophysics Data System (ADS)

Pradhan, Prajal; Costa, Luís.; Rybski, Diego; Lucht, Wolfgang; Kropp, Jürgen P.

2017-11-01

Sustainable development goals (SDGs) have set the 2030 agenda to transform our world by tackling multiple challenges humankind is facing to ensure well-being, economic prosperity, and environmental protection. In contrast to conventional development agendas focusing on a restricted set of dimensions, the SDGs provide a holistic and multidimensional view on development. Hence, interactions among the SDGs may cause diverging results. To analyze the SDG interactions we systematize the identification of synergies and trade-offs using official SDG indicator data for 227 countries. A significant positive correlation between a pair of SDG indicators is classified as a synergy while a significant negative correlation is classified as a trade-off. We rank synergies and trade-offs between SDGs pairs on global and country scales in order to identify the most frequent SDG interactions. For a given SDG, positive correlations between indicator pairs were found to outweigh the negative ones in most countries. Among SDGs the positive and negative correlations between indicator pairs allowed for the identification of particular global patterns. SDG 1 (No poverty) has synergetic relationship with most of the other goals, whereas SDG 12 (Responsible consumption and production) is the goal most commonly associated with trade-offs. The attainment of the SDG agenda will greatly depend on whether the identified synergies among the goals can be leveraged. In addition, the highlighted trade-offs, which constitute obstacles in achieving the SDGs, need to be negotiated and made structurally nonobstructive by deeper changes in the current strategies.

Obstacles for Teachers to Integrate Technology with Instruction

ERIC Educational Resources Information Center

Alenezi, Abdullah

2017-01-01

This paper covers type one and two educational obstacles in using technology in the classrooms, and considering those obstacles tries to find the answer to the following overarching research question which can help to gauge some obstacles for the educational technology integration for elementary and high school education: What obstacles do…

Fast obstacle detection based on multi-sensor information fusion

NASA Astrophysics Data System (ADS)

Lu, Linli; Ying, Jie

2014-11-01

Obstacle detection is one of the key problems in areas such as driving assistance and mobile robot navigation, which cannot meet the actual demand by using a single sensor. A method is proposed to realize the real-time access to the information of the obstacle in front of the robot and calculating the real size of the obstacle area according to the mechanism of the triangle similarity in process of imaging by fusing datum from a camera and an ultrasonic sensor, which supports the local path planning decision. In the part of image analyzing, the obstacle detection region is limited according to complementary principle. We chose ultrasonic detection range as the region for obstacle detection when the obstacle is relatively near the robot, and the travelling road area in front of the robot is the region for a relatively-long-distance detection. The obstacle detection algorithm is adapted from a powerful background subtraction algorithm ViBe: Visual Background Extractor. We extracted an obstacle free region in front of the robot in the initial frame, this region provided a reference sample set of gray scale value for obstacle detection. Experiments of detecting different obstacles at different distances respectively, give the accuracy of the obstacle detection and the error percentage between the calculated size and the actual size of the detected obstacle. Experimental results show that the detection scheme can effectively detect obstacles in front of the robot and provide size of the obstacle with relatively high dimensional accuracy.

Teachers' personal didactical models and obstacles to professional development: Case-studies with secondary experimental science teachers

NASA Astrophysics Data System (ADS)

Wamba Aguado, Ana Maria

The aim of this thesis has been to elaborate criteria which characterise how teachers teach, as a curriculum component of their professional knowledge and to infer the obstacles which hinder their desired professional development, in such a way that they are considered in the design of proposals for teacher training in secondary education. In addition to this, a further objective was to elaborate and validate data analysis instruments. Case studies were carried out on three natural science secondary teachers with more than ten years' experience, enabling the characterisation of the teachers' science and science teaching conceptions as well as the description of classroom practice. Finally, with the help of these data together with the material used by the teachers, the inference of the teachers' personal didactical models and the obstacles to their professional development were made possible. Instruments for data collection used a questionnaire to facilitate the realisation of a semi-structured interview, video recordings of the classroom intervention of each teacher which correspond to a teaching unit taught over a two-week period and all the written material produced for the unit was collected. For the data analysis a taxonomy of classroom intervention patterns and a progression hypothesis towards desirable professional knowledge were elaborated, from the perspective of a research in the classroom model and according to a system of categories and subcategories which refer to their concepts about scientific knowledge, school knowledge, how to teach and evaluation. With the interview and the questionnaire a profile of exposed conceptions was obtained. The intervention profile was obtained using the classroom recordings; according to the patterns identified and their sequencing, both of which determine the characteristic structures and routines of these teachers. An outcome of these results was the validation of the previously mentioned taxonomy as an instrument of

Development and validation of the short version of the diabetes obstacles questionnaire (DOQ-30) in six European countries.

PubMed

Pilv, Liina; Vermeire, Etienne; Rätsep, Anneli; Moreau, Alain; Nikolić, Dragica; Petek, Davorina; Yaman, Hakan; Oona, Marje; Kalda, Ruth

2016-01-01

Patients with type 2 diabetes reveal different obstacles in living with the disease. The EGPRN initiated a qualitative research EUROBSTACLE to create a broadly conceptualized diabetes-related quality of life (DR-QoL) instrument. It led to the development of the diabetes obstacle questionnaire (DOQ), a five-point Likert-scaled measure, consisting of 78 items in eight scales. To develop and validate a short, easy-to-use version of the DOQ. A cross-sectional study with the DOQ was carried out. Participants answered the DOQ and GPs added some clinical data from their medical records. Data of 853 patients from Belgium, France, Estonia, Serbia, Slovenia, and Turkey were included in the analysis. The selection of items for the short version of the DOQ was achieved with exploratory factor analysis (EFA). Construct validity was proved with EFA and Pearson correlations between the DOQ and the new DOQ-30. Internal reliability was established with Cronbach's alpha. DOQ-30 resulted in 30 items in nine subscales. It explained 49.8% of items' variance. It shows a considerable good internal reliability and construct validity. The DOQ-30 is a five-point Likert-scaled broadly conceptualized measure of DR-QoL. It addresses a variety of obstacles, such as social, psychological, cognitive and behavioural. The DOQ-30 is ready for implementation in general practice and research in Europe as a valuable instrument to assess DR-QoL.

Tracked robot controllers for climbing obstacles autonomously

NASA Astrophysics Data System (ADS)

Vincent, Isabelle

2009-05-01

Research in mobile robot navigation has demonstrated some success in navigating flat indoor environments while avoiding obstacles. However, the challenge of analyzing complex environments to climb obstacles autonomously has had very little success due to the complexity of the task. Unmanned ground vehicles currently exhibit simple autonomous behaviours compared to the human ability to move in the world. This paper presents the control algorithms designed for a tracked mobile robot to autonomously climb obstacles by varying its tracks configuration. Two control algorithms are proposed to solve the autonomous locomotion problem for climbing obstacles. First, a reactive controller evaluates the appropriate geometric configuration based on terrain and vehicle geometric considerations. Then, a reinforcement learning algorithm finds alternative solutions when the reactive controller gets stuck while climbing an obstacle. The methodology combines reactivity to learning. The controllers have been demonstrated in box and stair climbing simulations. The experiments illustrate the effectiveness of the proposed approach for crossing obstacles.

Supersonic flows past an obstacle in Yukawa liquids

NASA Astrophysics Data System (ADS)

Charan, Harish; Ganesh, Rajaraman

2018-04-01

Shock formation, when a supersonic flow passes a stationary obstacle, is ubiquitous in nature. Considering particles mediating via a Yukawa-type interaction as a prototype for a strongly coupled complex plasma, characterized by coupling strength (Γ, ratio of the average potential to kinetic energy per particle) and screening parameter (κ, ratio of the mean inter-particle distance to the shielding length), we address the fundamental problem of supersonic fluid flow U0, past a stationary obstacle immersed in this strongly coupled system. We here report the results on the bow shocks formed in Yukawa liquids when the liquid flows at speeds larger than the speed of sound in the system. Depending on the values of Mach number MC L=U/0 CL , where CL is the longitudinal speed of sound in the system, the bow shocks are found to be either traveling or localized. We find that for the transonic flows (0.8 ≲ MC L≲ 1.2), the bow shocks travel in the upstream direction opposite to the incoming fluid. The phase velocity of the traveling bow shocks is found to be a non-monotonous function of κ, varying as ∝1 /k1.11 at a fixed value of Γ, and is found to be independent of Γ at a fixed value of κ. It is observed that for the flow values with MC L>1.5 , the shock waves do not travel in the upstream direction but instead form a stationary arc like structure around the obstacle. For the fluid flows with 1 ≲ MC L≲ 2.6 , secondary bow shocks are seen to emerge behind the stationary obstacle which travel in the downstream direction, and the phase velocity of these secondary bow shocks is found to be equal to that of the primary bow shocks.

Flight data acquisition methodology for validation of passive ranging algorithms for obstacle avoidance

NASA Technical Reports Server (NTRS)

Smith, Phillip N.

1990-01-01

The automation of low-altitude rotorcraft flight depends on the ability to detect, locate, and navigate around obstacles lying in the rotorcraft's intended flightpath. Computer vision techniques provide a passive method of obstacle detection and range estimation, for obstacle avoidance. Several algorithms based on computer vision methods have been developed for this purpose using laboratory data; however, further development and validation of candidate algorithms require data collected from rotorcraft flight. A data base containing low-altitude imagery augmented with the rotorcraft and sensor parameters required for passive range estimation is not readily available. Here, the emphasis is on the methodology used to develop such a data base from flight-test data consisting of imagery, rotorcraft and sensor parameters, and ground-truth range measurements. As part of the data preparation, a technique for obtaining the sensor calibration parameters is described. The data base will enable the further development of algorithms for computer vision-based obstacle detection and passive range estimation, as well as provide a benchmark for verification of range estimates against ground-truth measurements.

[Obstacles and perspectives of new antimicrobial concepts within research and development].

PubMed

Kloß, Florian; Gerbach, Sina

2018-05-01

Antimicrobial resistance (AMR) has developed into a serious problem for the healthcare sector worldwide. Research on fundamentally novel antibiotics has been insufficient for decades and only a few new compounds have reached the market. Thus, the pressure to implement novel and effective concepts for the reduction of infections through problematic pathogens has dramatically increased. This demand has been recognized by politicians and comprehensive national and international funding programs have been launched. A major role of many funding lines is the investigation and development of therapeutics exerting a novel mechanism of action and/or minimizing the frequency of resistance. In addition to the actual clinical pipeline, this article lists selected examples from research and early development with a special focus on antibiotics. Moreover, alternative approaches like antivirulence and phage therapy as well as immunomodulation are summarized. AMR is no longer solely a healthcare policy, but is of societal significance as a whole. A consolidation of infrastructures and public-private partnerships, a reduction of regulatory obstacles and a continuous pursuit of innovations for antimicrobial therapy are urgently needed.

Surface obstacles in pulsatile flow

NASA Astrophysics Data System (ADS)

Carr, Ian A.; Plesniak, Michael W.

2016-11-01

Flows past obstacles mounted on flat surfaces have been widely studied due to their ubiquity in nature and engineering. For nearly all of these studies, the freestream flow over the obstacle was steady, i.e. constant velocity unidirectional flow. Unsteady, pulsatile flows occur frequently in biology, geophysics, biomedical engineering, etc. Our study is aimed at extending the comprehensive knowledge base that exists for steady flows to considerably more complex pulsatile flows. Beyond the important practical applications, characterizing the vortex and wake dynamics of flows around surface obstacles embedded in pulsatile flows can provide insights into the underlying physics in all wake and junction flows. In this study, we experimentally investigated the wake of four canonical surface obstacles: hemisphere, cube, and circular cylinders with aspect ratio of 1:1 and 2:1. Phase-averaged PIV and hot-wire anemometry are used to characterize the dynamics of coherent structures in the wake and at the windward junction of the obstacles. Complex physics occur during the deceleration phase of the pulsatile inflow. We propose a framework for understanding these physics based on self-induced vortex propagation, similar to the phenomena exhibited by vortex rings. This material is based in part upon work supported by the National Science Foundation under Grant Number CBET-1236351, and GW Centeor Biomimetics and Bioinspired Engineering (COBRE).

Inertial navigation sensor integrated obstacle detection system

NASA Technical Reports Server (NTRS)

Bhanu, Bir (Inventor); Roberts, Barry A. (Inventor)

1992-01-01

A system that incorporates inertial sensor information into optical flow computations to detect obstacles and to provide alternative navigational paths free from obstacles. The system is a maximally passive obstacle detection system that makes selective use of an active sensor. The active detection typically utilizes a laser. Passive sensor suite includes binocular stereo, motion stereo and variable fields-of-view. Optical flow computations involve extraction, derotation and matching of interest points from sequential frames of imagery, for range interpolation of the sensed scene, which in turn provides obstacle information for purposes of safe navigation.

Effect of obstacle position in the flow of sheep through a narrow door.

PubMed

Zuriguel, Iker; Olivares, Jorge; Pastor, José M; Martín-Gómez, César; Ferrer, Luis M; Ramos, Juan J; Garcimartín, Angel

2016-09-01

In a recent work [Phys. Rev. E 91, 022808 (2015)PLEEE81539-375510.1103/PhysRevE.91.022808] it was reported that placing an obstacle in front of a gate has a beneficial effect in the flow of sheep through it. Here, we extend such results by implementing three different obstacle positions. We have observed that the flow is improved in two cases, while it worsens in the other one; the last instance happens when the obstacle is too close to the door. In this situation, the outcomes suggest that clogging develops between the doorjamb and the obstacle, contrary to the cases when the obstacle is farther, in which case clogging always occurs at the very door. The effectiveness of the obstacle (a strategy put forward to alleviate clogging in emergency exits) is therefore quite sensitive to its location. In addition, the study of the temporal evolution of the flow rate as the test develops makes evident a steady behavior during the entire duration of the entrance. This result is at odds with recent findings in human evacuation tests where the flow rate varies over time, therefore challenging the fairness of straightforward comparisons between pedestrian behavior and animal experimental observations.

Legal obstacles and incentives to the development of small scale hydroelectric power in New Jersey

DOE Office of Scientific and Technical Information (OSTI.GOV)

None,

1980-05-01

The legal and institutional obstacles to the development of small-scale hydroelectric energy at the state level in New Jersey are described. The Federal government also exercises extensive regulatory authority in the area. The dual regulatory system from the standpoint of the appropriate legal doctrine, the law of pre-emption, application of the law to the case of hydroelectric development, and an inquiry into the practical use of the doctrine by the FERC is discussed. New Jersey follows the riparian theory of water law. Following an extensive discussion of the New Jersey water law, New Jersey regulatory law and financial considerations regardingmore » hydroelectric power development are discussed.« less

Assistive obstacle detection and navigation devices for vision-impaired users.

PubMed

Ong, S K; Zhang, J; Nee, A Y C

2013-09-01

Quality of life for the visually impaired is an urgent worldwide issue that needs to be addressed. Obstacle detection is one of the most important navigation tasks for the visually impaired. In this research, a novel range sensor placement scheme is proposed in this paper for the development of obstacle detection devices. Based on this scheme, two prototypes have been developed targeting at different user groups. This paper discusses the design issues, functional modules and the evaluation tests carried out for both prototypes. Implications for Rehabilitation Visual impairment problem is becoming more severe due to the worldwide ageing population. Individuals with visual impairment require assistance from assistive devices in daily navigation tasks. Traditional assistive devices that assist navigation may have certain drawbacks, such as the limited sensing range of a white cane. Obstacle detection devices applying the range sensor technology can identify road conditions with a higher sensing range to notify the users of potential dangers in advance.

Detecting Negative Obstacles by Use of Radar

NASA Technical Reports Server (NTRS)

Mittskus, Anthony; Lux, James

2006-01-01

Robotic land vehicles would be equipped with small radar systems to detect negative obstacles, according to a proposal. The term "negative obstacles" denotes holes, ditches, and any other terrain features characterized by abrupt steep downslopes that could be hazardous for vehicles. Video cameras and other optically based obstacle-avoidance sensors now installed on some robotic vehicles cannot detect obstacles under adverse lighting conditions. Even under favorable lighting conditions, they cannot detect negative obstacles. A radar system according to the proposal would be of the frequency-modulation/ continuous-wave (FM/CW) type. It would be installed on a vehicle, facing forward, possibly with a downward slant of the main lobe(s) of the radar beam(s) (see figure). It would utilize one or more wavelength(s) of the order of centimeters. Because such wavelengths are comparable to the characteristic dimensions of terrain features associated with negative hazards, a significant amount of diffraction would occur at such features. In effect, the diffraction would afford a limited ability to see corners and to see around corners. Hence, the system might utilize diffraction to detect corners associated with negative obstacles. At the time of reporting the information for this article, preliminary analyses of diffraction at simple negative obstacles had been performed, but an explicit description of how the system would utilize diffraction was not available.

Strategies for obstacle avoidance during walking in the cat.

PubMed

Chu, Kevin M I; Seto, Sandy H; Beloozerova, Irina N; Marlinski, Vladimir

2017-08-01

Avoiding obstacles is essential for successful navigation through complex environments. This study aimed to clarify what strategies are used by a typical quadruped, the cat, to avoid obstacles during walking. Four cats walked along a corridor 2.5 m long and 25 or 15 cm wide. Obstacles, small round objects 2.5 cm in diameter and 1 cm in height, were placed on the floor in various locations. Movements of the paw were recorded with a motion capture and analysis system (Visualeyez, PTI). During walking in the wide corridor, cats' preferred strategy for avoiding a single obstacle was circumvention, during which the stride direction changed while stride duration and swing-to-stride duration ratio were preserved. Another strategy, stepping over the obstacle, was used during walking in the narrow corridor, when lateral deviations of walking trajectory were restricted. Stepping over the obstacle involved changes in two consecutive strides. The stride preceding the obstacle was shortened, and swing-to-stride ratio was reduced. The obstacle was negotiated in the next stride of increased height and normal duration and swing-to-stride ratio. During walking on a surface with multiple obstacles, both strategies were used. To avoid contact with the obstacle, cats placed the paw away from the object at a distance roughly equal to the diameter of the paw. During obstacle avoidance cats prefer to alter muscle activities without altering the locomotor rhythm. We hypothesize that a choice of the strategy for obstacle avoidance is determined by minimizing the complexity of neuro-motor processes required to achieve the behavioral goal. NEW & NOTEWORTHY In a study of feline locomotor behavior we found that the preferred strategy to avoid a small obstacle is circumvention. During circumvention, stride direction changes but length and temporal structure are preserved. Another strategy, stepping over the obstacle, is used in narrow walkways. During overstepping, two strides adjust. A stride

Speeded Reaching Movements around Invisible Obstacles

PubMed Central

Hudson, Todd E.; Wolfe, Uta; Maloney, Laurence T.

2012-01-01

We analyze the problem of obstacle avoidance from a Bayesian decision-theoretic perspective using an experimental task in which reaches around a virtual obstacle were made toward targets on an upright monitor. Subjects received monetary rewards for touching the target and incurred losses for accidentally touching the intervening obstacle. The locations of target-obstacle pairs within the workspace were varied from trial to trial. We compared human performance to that of a Bayesian ideal movement planner (who chooses motor strategies maximizing expected gain) using the Dominance Test employed in Hudson et al. (2007). The ideal movement planner suffers from the same sources of noise as the human, but selects movement plans that maximize expected gain in the presence of that noise. We find good agreement between the predictions of the model and actual performance in most but not all experimental conditions. PMID:23028276

Measures for simulator evaluation of a helicopter obstacle avoidance system

NASA Technical Reports Server (NTRS)

Demaio, Joe; Sharkey, Thomas J.; Kennedy, David; Hughes, Micheal; Meade, Perry

1993-01-01

The U.S. Army Aeroflightdynamics Directorate (AFDD) has developed a high-fidelity, full-mission simulation facility for the demonstration and evaluation of advanced helicopter mission equipment. The Crew Station Research and Development Facility (CSRDF) provides the capability to conduct one- or two-crew full-mission simulations in a state-of-the-art helicopter simulator. The CSRDF provides a realistic, full field-of-regard visual environment with simulation of state-of-the-art weapons, sensors, and flight control systems. We are using the CSRDF to evaluate the ability of an obstacle avoidance system (OASYS) to support low altitude flight in cluttered terrain using night vision goggles (NVG). The OASYS uses a laser radar to locate obstacles to safe flight in the aircraft's flight path. A major concern is the detection of wires, which can be difficult to see with NVG, but other obstacles--such as trees, poles or the ground--are also a concern. The OASYS symbology is presented to the pilot on a head-up display mounted on the NVG (NVG-HUD). The NVG-HUD presents head-stabilized symbology to the pilot while allowing him to view the image intensified, out-the-window scene through the HUD. Since interference with viewing through the display is a major concern, OASYS symbology must be designed to present usable obstacle clearance information with a minimum of clutter.

Obstacle Avoidance for Quadcopter using Ultrasonic Sensor

NASA Astrophysics Data System (ADS)

Fazlur Rahman, Muhammad; Adhy Sasongko, Rianto

2018-04-01

An obstacle avoidance system is being proposed. The system will combine available flight controller with a proposed avoidance method as a proof of concept. Quadcopter as a UAV is integrated with the system which consist of several modes in order to do avoidance. As the previous study, obstacle will be determined using ultrasonic sensor and servo. As result, the quadcopter will move according to its mode and successfully avoid obstacle.

Effects of gas interparticle interaction on dissipative wake-mediated forces.

PubMed

Kliushnychenko, O V; Lukyanets, S P

2017-01-01

We examine how the short-range repulsive interaction in a gas of Brownian particles affects behavior of the nonequilibrium depletion forces between obstacles embedded into the gas flow. It is shown that for an ensemble of small and widely separated obstacles the dissipative wake-mediated interaction belongs to the type of induced dipole-dipole interaction governed by an anisotropic screened Coulomb-like potential. For closely located obstacles, formation of a common density perturbation "coat" around them leads to enhancement of dissipative interaction, manifested by characteristic peaks in its dependence on both the bath fraction and the external driving field. Moreover, additional screening of the gas flow due to nonlinear blockade effect gives rise to generation of a pronounced step-like profile of gas density distribution around the obstacles. This can lead to additional enhancement of dissipative interaction between obstacles. The possibility of the dissipative pairing effect and dissipative interaction switching provoked by wake inversion is briefly discussed. All the results are obtained within the classical lattice-gas model.

Women’s orgasm obstacles: A qualitative study

PubMed Central

Nekoolaltak, Maryam; Keshavarz, Zohreh; Simbar, Masoumeh; Nazari, Ali Mohammad; Baghestani, Ahmad Reza

2017-01-01

Background: Woman’s orgasm plays a vital role in sexual compatibility and marital satisfaction. Orgasm in women is a learnable phenomenon that is influenced by several factors. Objective: The aim of this study is exploring obstacles to orgasm in Iranian married women. Materials and Methods: This qualitative study with directed content analysis approach was conducted in 2015-2016, on 20 Iranian married women who were individually interviewed at two medical clinics in Tehran, Iran. Results: Orgasm obstacles were explored in one category, 4 subcategories, and 25 codes. The main category was “Multidimensionality of women’s orgasm obstacles”. Subcategories and some codes included: Physical obstacles (wife’s or husband’s boredom, vaginal infection, insufficient vaginal lubrication), psychological obstacles (lack of sexual knowledge, shame, lack of concentration on sex due to household and children problems), relational obstacles (husband’s hurry, having a dispute and annoyance with spouse) and contextual obstacles (Irregular sleep hours, lack of privacy and inability to separate children’s bedroom from their parents, lack of peace at home). Conclusion: For prevention or treatment of female orgasm disorders, attention to physical factors is not enough. Obtaining a comprehensive history about physical, psychological, relational and contextual dimensions of woman’s life is necessary. PMID:29082366

Stepping over obstacles: gait patterns of healthy young and old adults.

PubMed

Chen, H C; Ashton-Miller, J A; Alexander, N B; Schultz, A B

1991-11-01

Falls associated with tripping over an obstacle can be devastating to elderly individuals, yet little is known about the strategies used for stepping over obstacles by either old or young adults. The gait of gender-matched groups of 24 young and 24 old healthy adults (mean ages 22 and 71 years) was studied during a 4 m approach to and while stepping over obstacles of 0, 25, 51, or 152 mm height and in level obstacle-free walking. Optoelectronic cameras and recorders were used to record approach and obstacle crossing speeds as well as bilateral lower extremity kinematic parameters that described foot placement and movement trajectories relative to the obstacle. The results showed that age had no effect on minimum swing foot clearance (FC) over an obstacle. For the 25 mm obstacle, mean FC was 64 mm, or approximately three times that used in level gait; FC increased nonlinearly with obstacle height for all subjects. Although no age differences were found in obstacle-free gait, old adults exhibited a significantly more conservative strategy when crossing obstacles, with slower crossing speed, shorter step length, and shorter obstacle-heel strike distance. In addition, the old adults crossed the obstacle so that it was 10% further forward in their obstacle-crossing step. Although all subjects successfully avoided the riskiest form of obstacle contact, tripping, 4/24 healthy old adults stepped on an obstacle, demonstrating an increased risk for obstacle contact with age.

Influence of obstacle disturbance in a duct on explosion characteristics of coal gas

NASA Astrophysics Data System (ADS)

Wang, Cheng; Ma, Tianbao; Lu, Jie

2010-02-01

In combination with experimental research, numerical simulation is performed to investigate the influence law of the obstacles in a duct on the explosion flame of premixed coal gas and air. The numerical method uses upwind WENO scheme and two-step chemical reaction model. The interaction mechanism is addressed between the compression wave from reflection on the right end of the duct and flame propagation. The reflected wave is found to result in the decrease of flame velocity. On this basis, we analyze the mechanism of the obstacles on flame as well as the law of flow field variation thus caused. The results suggest that, due to the obstacles, deflagration wave is repeatedly reflected, combustible gas mixture is fully compressed, temperature and pressure rise, chemical reaction speed increases, and hence flame intensity is strengthened. At the same time, a tripe point forms as a result of wall reflection of the deflagration wave from the obstacles and furthermore local flame speed increases. As the triple point propagates forward, the flame speed gradually decreases due to dissipation of energy. These conclusions provide a valuable theoretical foundation for the prediction of explosion field, prevention of fire and explosion and effective control of the combustion speed and flame propagation speed in detonation propulsion.

Optimal consensus algorithm integrated with obstacle avoidance

NASA Astrophysics Data System (ADS)

Wang, Jianan; Xin, Ming

2013-01-01

This article proposes a new consensus algorithm for the networked single-integrator systems in an obstacle-laden environment. A novel optimal control approach is utilised to achieve not only multi-agent consensus but also obstacle avoidance capability with minimised control efforts. Three cost functional components are defined to fulfil the respective tasks. In particular, an innovative nonquadratic obstacle avoidance cost function is constructed from an inverse optimal control perspective. The other two components are designed to ensure consensus and constrain the control effort. The asymptotic stability and optimality are proven. In addition, the distributed and analytical optimal control law only requires local information based on the communication topology to guarantee the proposed behaviours, rather than all agents' information. The consensus and obstacle avoidance are validated through simulations.

Improvements in Obstacle Clearance Parameters and Reaction Time Over a Series of Obstacles Revealed After Five Repeated Testing Sessions in Older Adults.

PubMed

Jehu, Deborah A; Lajoie, Yves; Paquet, Nicole

2017-12-21

The purpose of this study was to investigate obstacle clearance and reaction time parameters when crossing a series of six obstacles in older adults. A second aim was to examine the repeated exposure of this testing protocol once per week for 5 weeks. In total, 10 older adults (five females; age: 67.0 ± 6.9 years) walked onto and over six obstacles of varying heights (range: 100-200 mm) while completing no reaction time, simple reaction time, and choice reaction time tasks once per week for 5 weeks. The highest obstacles elicited the lowest toe clearance, and the first three obstacles revealed smaller heel clearance compared with the last three obstacles. Dual tasking negatively impacted obstacle clearance parameters when information processing demands were high. Longer and less consistent time to completion was observed in Session 1 compared with Sessions 2-5. Finally, improvements in simple reaction time were displayed after Session 2, but choice reaction time gradually improved and did not reach a plateau after repeated testing.

Factors Influencing Obstacle Crossing Performance in Patients with Parkinson's Disease

PubMed Central

Liao, Ying-Yi; Yang, Yea-Ru; Wu, Yih-Ru; Wang, Ray-Yau

2014-01-01

Background Tripping over obstacles is the major cause of falls in community-dwelling patients with Parkinson's disease (PD). Understanding the factors associated with the obstacle crossing behavior may help to develop possible training programs for crossing performance. This study aimed to identify the relationships and important factors determining obstacle crossing performance in patients with PD. Methods Forty-two idiopathic patients with PD (Hoehn and Yahr stages I to III) participated in this study. Obstacle crossing performance was recorded by the Liberty system, a three-dimensional motion capture device. Maximal isometric strength of the lower extremity was measured by a handheld dynamometer. Dynamic balance and sensory integration ability were assessed using the Balance Master system. Movement velocity (MV), maximal excursion (ME), and directional control (DC) were obtained during the limits of stability test to quantify dynamic balance. The sum of sensory organization test (SOT) scores was used to quantify sensory organization ability. Results Both crossing stride length and stride velocity correlated significantly with lower extremity muscle strength, dynamic balance control (forward and sideward), and sum of SOT scores. From the regression model, forward DC and ankle dorsiflexor strength were identified as two major determinants for crossing performance (R2 = .37 to.41 for the crossing stride length, R2 = .43 to.44 for the crossing stride velocity). Conclusions Lower extremity muscle strength, dynamic balance control and sensory integration ability significantly influence obstacle crossing performance. We suggest an emphasis on muscle strengthening exercises (especially ankle dorsiflexors), balance training (especially forward DC), and sensory integration training to improve obstacle crossing performance in patients with PD. PMID:24454723

Obstacle-avoiding robot with IR and PIR motion sensors

NASA Astrophysics Data System (ADS)

Ismail, R.; Omar, Z.; Suaibun, S.

2016-10-01

Obstacle avoiding robot was designed, constructed and programmed which may be potentially used for educational and research purposes. The developed robot will move in a particular direction once the infrared (IR) and the PIR passive infrared (PIR) sensors sense a signal while avoiding the obstacles in its path. The robot can also perform desired tasks in unstructured environments without continuous human guidance. The hardware was integrated in one application board as embedded system design. The software was developed using C++ and compiled by Arduino IDE 1.6.5. The main objective of this project is to provide simple guidelines to the polytechnic students and beginners who are interested in this type of research. It is hoped that this robot could benefit students who wish to carry out research on IR and PIR sensors.

Effects of aging on whole body and segmental control while obstacle crossing under impaired sensory conditions.

PubMed

Novak, Alison C; Deshpande, Nandini

2014-06-01

The ability to safely negotiate obstacles is an important component of independent mobility, requiring adaptive locomotor responses to maintain dynamic balance. This study examined the effects of aging and visual-vestibular interactions on whole-body and segmental control during obstacle crossing. Twelve young and 15 older adults walked along a straight pathway and stepped over one obstacle placed in their path. The task was completed under 4 conditions which included intact or blurred vision, and intact or perturbed vestibular information using galvanic vestibular stimulation (GVS). Global task performance significantly increased under suboptimal vision conditions. Vision also significantly influenced medial-lateral center of mass displacement, irrespective of age and GVS. Older adults demonstrated significantly greater trunk pitch and head roll angles under suboptimal vision conditions. Similar to whole-body control, no GVS effect was found for any measures of segmental control. The results indicate a significant reliance on visual but not vestibular information for locomotor control during obstacle crossing. The lack of differences in GVS effects suggests that vestibular information is not up-regulated for obstacle avoidance. This is not differentially affected by aging. In older adults, insufficient visual input appears to affect ability to minimize anterior-posterior trunk movement despite a slower obstacle crossing time and walking speed. Combined with larger medial-lateral deviation of the body COM with insufficient visual information, the older adults may be at a greater risk for imbalance or inability to recover from a possible trip when stepping over an obstacle. Copyright © 2014 Elsevier B.V. All rights reserved.

Mathematical Models of Smart Obstacles

DTIC Science & Technology

2006-10-01

Matematica “G. Castelnuovo” Università di Roma “La Sapienza”, Piazzale Aldo Moro 2 00185 Roma Italy Ph. N. +39-06-49913282, FAX N. +39-06...Dipartimento di Matematica G. Castelnuovo Università di Roma La Sapienza, Piazzale Aldo Moro 2 00185 Roma Italy 8. PERFORMING ORGANIZATION REPORT NUMBER 9... Matematica G. Castelnuovo Università di Roma “La Sapienza” 00185 Roma, Italy 2 Smart (or active) obstacles are obstacles that when illuminated by an

Imaging objects behind small obstacles using axicon lens

NASA Astrophysics Data System (ADS)

Perinchery, Sandeep M.; Shinde, Anant; Murukeshan, V. M.

2017-06-01

Axicon lenses are conical prisms, which are known to focus a light source to a line comprising of multiple points along the optical axis. In this study, we analyze the potential of axicon lenses to view, image and record the object behind opaque obstacles in free space. The advantage of an axicon lens over a regular lens is demonstrated experimentally. Parameters such as obstacle size, object and the obstacle position in the context of imaging behind obstacles are tested using Zemax optical simulation. This proposed concept can be easily adapted to most of the optical imaging methods and microscopy modalities.

Vortex shedding from obstacles: theoretical frequency prediction

NASA Astrophysics Data System (ADS)

Pier, Benoît

2001-11-01

The existence of self-sustained oscillations in spatially developing systems is closely related to the presence of a locally absolutely unstable region. A recent investigation of a ``synthetic wake'' (a wake with no solid obstacle and no reverse flow region) has proved [Pier and Huerre, J. Fluid Mech. 435, 145 (2001)] that the observed Kármán vortex street is a nonlinear elephant global mode. The same criterion is now shown to hold for real obstacles. Local properties are derived from the unperturbed basic flow computed by enforcing a symmetry condition on the central line. Application of the theoretical criterion then yields the expected Strouhal vortex shedding frequency. The thus predicted frequency is in excellent agreement with direct numerical simulations of the complete flow. The use of the frequency selection mechanism to control the vortex shedding will also be discussed.

Non-universal tracer diffusion in crowded media of non-inert obstacles.

PubMed

Ghosh, Surya K; Cherstvy, Andrey G; Metzler, Ralf

2015-01-21

We study the diffusion of a tracer particle, which moves in continuum space between a lattice of excluded volume, immobile non-inert obstacles. In particular, we analyse how the strength of the tracer-obstacle interactions and the volume occupancy of the crowders alter the diffusive motion of the tracer. From the details of partitioning of the tracer diffusion modes between trapping states when bound to obstacles and bulk diffusion, we examine the degree of localisation of the tracer in the lattice of crowders. We study the properties of the tracer diffusion in terms of the ensemble and time averaged mean squared displacements, the trapping time distributions, the amplitude variation of the time averaged mean squared displacements, and the non-Gaussianity parameter of the diffusing tracer. We conclude that tracer-obstacle adsorption and binding triggers a transient anomalous diffusion. From a very narrow spread of recorded individual time averaged trajectories we exclude continuous type random walk processes as the underlying physical model of the tracer diffusion in our system. For moderate tracer-crowder attraction the motion is found to be fully ergodic, while at stronger attraction strength a transient disparity between ensemble and time averaged mean squared displacements occurs. We also put our results into perspective with findings from experimental single-particle tracking and simulations of the diffusion of tagged tracers in dense crowded suspensions. Our results have implications for the diffusion, transport, and spreading of chemical components in highly crowded environments inside living cells and other structured liquids.

[Therapeutic education in pediatric dentistry: analysis of obstacles and levers to the development of programmes in France in 2016].

PubMed

Marquillier, Thomas; Trentesaux, Thomas; Gagnayre, Rémi

2017-01-01

Over recent years, therapeutic patient education has become part of dental medicine. Management of early childhood caries, known to be a very common chronic disease, has evolved to include an educational dimension. The objective of this study was to identify the levers and barriers to the development of formalized therapeutic education programmes and alternatives. A comprehensive exploratory qualitative study was conducted between November 2015 and June 2016 on a targeted sample of 15 people aware of the problem of TPE in dentistry. The study showed that TPE training in dentistry is underdeveloped, despite its numerous benefits: change of the healthcare professional's approach, implementation of structured educational programmes, development of research, etc. There are many obstacles to the development of TPE programmes: insufficient resources, rigid legislation or lack of knowledge of TPE practices. The dental profession is an obstacle itself because of its lack of understanding and variable degrees of integration the medical community. There are multiple levers, but the main ones are changing attitudes of the profession and the provision of resources to develop TPE. Although alternatives to TPE programmes exist (accompanying measures, short educational strategies, connected health), they cannot replace TPE. More educational strategies must be developed in the field of dentistry. However, the framework of TPE must be adapted to the profession to ensure good uptake.

Performance Impact of Deflagration to Detonation Transition Enhancing Obstacles

NASA Technical Reports Server (NTRS)

Paxson, Daniel E.; Schauer, Frederick; Hopper, David

2012-01-01

A sub-model is developed to account for the drag and heat transfer enhancement resulting from deflagration-to-detonation (DDT) inducing obstacles commonly used in pulse detonation engines (PDE). The sub-model is incorporated as a source term in a time-accurate, quasi-onedimensional, CFD-based PDE simulation. The simulation and sub-model are then validated through comparison with a particular experiment in which limited DDT obstacle parameters were varied. The simulation is then used to examine the relative contributions from drag and heat transfer to the reduced thrust which is observed. It is found that heat transfer is far more significant than aerodynamic drag in this particular experiment.

Passive detection of subpixel obstacles for flight safety

NASA Astrophysics Data System (ADS)

Nixon, Matthew D.; Loveland, Rohan C.

2001-12-01

Military aircraft fly below 100 ft. above ground level in support of their missions. These aircraft include fixed and rotary wing and may be manned or unmanned. Flying at these low altitudes presents a safety hazard to the aircrew and aircraft, due to the occurrences of obstacles within the aircraft's flight path. The pilot must rely on eyesight and in some cases, infrared sensors to see obstacles. Many conditions can exacerbate visibility creating a situation in which obstacles are essentially invisible, creating a safety hazard, even to an alerted aircrew. Numerous catastrophic accidents have occurred in which aircraft have collided with undetected obstacles. Accidents of this type continue to be a problem for low flying military and commercial aircraft. Unmanned Aerial Vehicles (UAVs) have the same problem, whether operating autonomously or under control of a ground operator. Boeing-SVS has designed a passive, small, low- cost (under $100k) gimbaled, infrared imaging based system with advanced obstacle detection algorithms. Obstacles are detected in the infrared band, and linear features are analyzed by innovative cellular automata based software. These algorithms perform detection and location of sub-pixel linear features. The detection of the obstacles is performed on a frame by frame basis, in real time. Processed images are presented to the aircrew on their display as color enhanced features. The system has been designed such that the detected obstacles are displayed to the aircrew in sufficient time to react and maneuver the aircraft to safety. A patent for this system is on file with the US patent office, and all material herein should be treated accordingly.

Foot strike patterns after obstacle clearance during running.

PubMed

Scholten, Shane D; Stergiou, Nicholas; Hreljac, Alan; Houser, Jeremy; Blanke, Daniel; Alberts, L Russell

2002-01-01

Running over obstacles of sufficient height requires heel strike (HS) runners to make a transition in landing strategy to a forefoot (FF) strike, resulting in similar ground reaction force patterns to those observed while landing from a jump. Identification of the biomechanical variables that distinguish between the landing strategies may offer some insight into the reasons that the transition occurs. The purpose of this study was to investigate the difference in foot strike patterns and kinetic parameters of heel strike runners between level running and running over obstacles of various heights. Ten heel strike subjects ran at their self-selected pace under seven different conditions: unperturbed running (no obstacle) and over obstacles of six different heights (10%, 12.5%, 15%, 17.5%, 20%, and 22.5% of their standing height). The obstacle was placed directly before a Kistler force platform. Repeated measures ANOVAs were performed on the subject means of selected kinetic parameters. The statistical analysis revealed significant differences (P < 0.004) for all of the parameters analyzed. The evaluation of the center of pressure and the ground reaction forces indicated that the foot strike patterns were affected by the increased obstacle height. Between the 12.5% and 15% obstacle conditions, the group response changed from a heel strike to a forefoot strike pattern. At height > 15%, the pattern was more closely related to the foot strike patterns found in jumping activities. This strategy change may represent a gait transition effected as a mechanism to protect against increased impact forces. Greater involvement of the ankle and the calf muscles could have assisted in attenuating the increased impact forces while maintaining speed after clearing the obstacle.

Training toddlers seated on mobile robots to drive indoors amidst obstacles.

PubMed

Chen, Xi; Ragonesi, Christina; Galloway, James C; Agrawal, Sunil K

2011-06-01

Mobility is a causal factor in development. Children with mobility impairments may rely upon power mobility for independence and thus require advanced driving skills to function independently. Our previous studies show that while infants can learn to drive directly to a goal using conventional joysticks in several months of training, they are unable in this timeframe to acquire the advanced skill to avoid obstacles while driving. Without adequate driving training, children are unable to explore the environment safely, the consequences of which may in turn increase their risk for developmental delay. The goal of this research therefore is to train children seated on mobile robots to purposefully and safely drive indoors. In this paper, we present results where ten typically-developing toddlers are trained to drive a robot within an obstacle course. We also report a case study with a toddler with spina-bifida who cannot independently walk. Using algorithms based on artificial potential fields to avoid obstacles, we create force field on the joystick that trains the children to navigate while avoiding obstacles. In this "assist-as-needed" approach, if the child steers the joystick outside a force tunnel centered on the desired direction, the driver experiences a bias force on the hand. Our results suggest that the use of a force-feedback joystick may yield faster learning than the use of a conventional joystick.

The Value of Removing Daily Obstacles via Everyday Problem-Solving Theory: Developing an Applied Novel Procedure to Increase Self-Efficacy for Exercise

PubMed Central

Artistico, Daniele; Pinto, Angela Marinilli; Douek, Jill; Black, Justin; Pezzuti, Lina

2012-01-01

The objective of the study was to develop a novel procedure to increase self-efficacy for exercise. Gains in one’s ability to resolve day-to-day obstacles for entering an exercise routine were expected to cause an increase in self-efficacy for exercise. Fifty-five sedentary participants (did not exercise regularly for at least 4 months prior to the study) who expressed an intention to exercise in the near future were selected for the study. Participants were randomly assigned to one of three conditions: (1) an Experimental Group in which they received a problem-solving training session to learn new strategies for solving day-to-day obstacles that interfere with exercise, (2) a Control Group with Problem-Solving Training which received a problem-solving training session focused on a typical day-to-day problem unrelated to exercise, or (3) a Control Group which did not receive any problem-solving training. Assessment of obstacles to exercise and perceived self-efficacy for exercise were conducted at baseline; perceived self-efficacy for exercise was reassessed post-intervention (1 week later). No differences in perceived challenges posed by obstacles to exercise or self-efficacy for exercise were observed across groups at baseline. The Experimental Group reported greater improvement in self-efficacy for exercise compared to the Control Group with Training and the Control Group. Results of this study suggest that a novel procedure that focuses on removing obstacles to intended planned fitness activities is effective in increasing self-efficacy to engage in exercise among sedentary adults. Implications of these findings for use in applied settings and treatment studies are discussed. PMID:23372560

The Value of Removing Daily Obstacles via Everyday Problem-Solving Theory: Developing an Applied Novel Procedure to Increase Self-Efficacy for Exercise.

PubMed

Artistico, Daniele; Pinto, Angela Marinilli; Douek, Jill; Black, Justin; Pezzuti, Lina

2013-01-01

The objective of the study was to develop a novel procedure to increase self-efficacy for exercise. Gains in one's ability to resolve day-to-day obstacles for entering an exercise routine were expected to cause an increase in self-efficacy for exercise. Fifty-five sedentary participants (did not exercise regularly for at least 4 months prior to the study) who expressed an intention to exercise in the near future were selected for the study. Participants were randomly assigned to one of three conditions: (1) an Experimental Group in which they received a problem-solving training session to learn new strategies for solving day-to-day obstacles that interfere with exercise, (2) a Control Group with Problem-Solving Training which received a problem-solving training session focused on a typical day-to-day problem unrelated to exercise, or (3) a Control Group which did not receive any problem-solving training. Assessment of obstacles to exercise and perceived self-efficacy for exercise were conducted at baseline; perceived self-efficacy for exercise was reassessed post-intervention (1 week later). No differences in perceived challenges posed by obstacles to exercise or self-efficacy for exercise were observed across groups at baseline. The Experimental Group reported greater improvement in self-efficacy for exercise compared to the Control Group with Training and the Control Group. Results of this study suggest that a novel procedure that focuses on removing obstacles to intended planned fitness activities is effective in increasing self-efficacy to engage in exercise among sedentary adults. Implications of these findings for use in applied settings and treatment studies are discussed.

Obstacle avoidance for redundant robots using configuration control

NASA Technical Reports Server (NTRS)

Seraji, Homayoun (Inventor); Colbaugh, Richard D. (Inventor); Glass, Kristin L. (Inventor)

1992-01-01

A redundant robot control scheme is provided for avoiding obstacles in a workspace during the motion of an end effector along a preselected trajectory by stopping motion of the critical point on the robot closest to the obstacle when the distance between is reduced to a predetermined sphere of influence surrounding the obstacle. Algorithms are provided for conveniently determining the critical point and critical distance.

Obstacle avoidance locomotor tasks: adaptation, memory and skill transfer.

PubMed

Kloter, Evelyne; Dietz, Volker

2012-05-01

The aim of this study was to explore the neural basis of adaptation, memory and skill transfer during human stepping over obstacles. Whilst walking on a treadmill, subjects had to perform uni- and bilateral obstacle steps. Acoustic feedback information about foot clearance was provided. Non-noxious electrical stimuli were applied to the right tibial nerve during the mid-stance phase of the right leg, i.e. 'prior' to the right or 'during' the left leg swing over the obstacle. The electromyogram (EMG) responses evoked by these stimuli in arm and leg muscles are known to reflect the neural coordination during normal and obstacle steps. The leading and trailing legs rapidly adapted foot clearance during obstacle steps with small further changes when the same obstacle condition was repeated. This adaptation was associated with a corresponding decrease in arm and leg muscle reflex EMG responses. Arm (but not leg) muscle EMG responses were greater when the stimulus was applied 'during' obstacle crossing by the left leg leading compared with stimulation 'prior' to right leg swing over the obstacle. A corresponding difference existed in arm muscle background EMG. The results indicate that, firstly, the somatosensory information gained by the performance and adaptation of uni- and bilateral obstacle stepping becomes transferred to the trailing leg in a context-specific manner. Secondly, EMG activity in arm and leg muscles parallels biomechanical adaptation of foot clearance. Thirdly, a consistently high EMG activity in the arm muscles during swing over the obstacle is required for equilibrium control. Thus, such a precision locomotor task is achieved by a context-specific, coordinated activation of arm and leg muscles for performance and equilibrium control that includes adaptation, memory and skill transfer. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Computational extended magneto-hydrodynamical study of shock structure generated by flows past an obstacle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Xuan, E-mail: xzhao@cylance.com; Seyler, C. E., E-mail: ces7@cornell.edu

2015-07-15

The magnetized shock problem is studied in the context where supersonic plasma flows past a solid obstacle. This problem exhibits interesting and important phenomena such as a bow shock, magnetotail formation, reconnection, and plasmoid formation. This study is carried out using a discontinuous Galerkin method to solve an extended magneto-hydrodynamic model (XMHD). The main goals of this paper are to present a reasonably complete picture of the properties of this interaction using the MHD model and then to compare the results to the XMHD model. The inflow parameters, such as the magnetosonic Mach number M{sub f} and the ratio ofmore » thermal pressure to magnetic pressure β, can significantly affect the physical structures of the flow-obstacle interaction. The Hall effect can also significantly influence the results in the regime in which the ion inertial length is numerically resolved. Most of the results presented are for the two-dimensional case; however, two three-dimensional simulations are presented to make a connection to the important case in which the solar wind interacts with a solid body and to explore the possibility of performing scaled laboratory experiments.« less

Residence time of symmetric random walkers in a strip with large reflective obstacles

NASA Astrophysics Data System (ADS)

Ciallella, Alessandro; Cirillo, Emilio N. M.; Sohier, Julien

2018-05-01

We study the effect of a large obstacle on the so-called residence time, i.e., the time that a particle performing a symmetric random walk in a rectangular (two-dimensional, 2D) domain needs to cross the strip. We observe complex behavior: We find out that the residence time does not depend monotonically on the geometric properties of the obstacle, such as its width, length, and position. In some cases, due to the presence of the obstacle, the mean residence time is shorter with respect to the one measured for the obstacle-free strip. We explain the residence time behavior by developing a one-dimensional (1D) analog of the 2D model where the role of the obstacle is played by two defect sites having smaller probability to be crossed with respect to all the other regular sites. The 1D and 2D models behave similarly, but in the 1D case we are able to compute exactly the residence time, finding a perfect match with the Monte Carlo simulations.

Obstacles to Developing Digital Literacy on the Internet in Middle School Science Instruction

ERIC Educational Resources Information Center

Colwell, Jamie; Hunt-Barron, Sarah; Reinking, David

2013-01-01

Obstacles, and instructional responses to them, that emerged in two middle school science classes during a formative experiment investigating Internet Reciprocal Teaching (IRT), an instructional intervention aimed at increasing digital literacy on the Internet, are reported in this manuscript. Analysis of qualitative data revealed that IRT enabled…

Stability of gas channels in a dense suspension in the presence of obstacles

NASA Astrophysics Data System (ADS)

Poryles, Raphaël; Varas, Germán; Vidal, Valérie

2017-06-01

We investigate experimentally the influence of a fixed obstacle on gas rising in a dense suspension. Air is injected at a constant flow rate by a single nozzle at the bottom center of a Hele-Shaw cell. Without obstacles, previous works have shown that a fluidized zone is formed with a parabolic shape, with a central air channel and two granular convection rolls on its sides. Here, we quantify the influence of the obstacle's shape, size, and height on the location and dynamics of the central air channel. Different regimes are reported: the air channel can simply deviate (stable), or it can switch sides over time (unstable), leading to two signatures not only above the obstacle, but sometimes also below it. This feedback also influences the channel deviation when bypassing the obstacle. A wake of less or no motion is reported above the largest obstacles as well as the maximum probability of gas location, which can be interesting for practical applications. The existence of a critical height hc≃7 cm is discussed and compared with the existence of an air finger that develops from the injection nozzle and is stable in time. A dimensionless number describing the transition between air fingering and fracturing makes it possible to predict the channel's stability.

Unpinning of spiral waves from rectangular obstacles by stimulated wave trains

NASA Astrophysics Data System (ADS)

Ponboonjaroenchai, Benjamas; Srithamma, Panatda; Kumchaiseemak, Nakorn; Sutthiopad, Malee; Müller, Stefan C.; Luengviriya, Chaiya; Luengviriya, Jiraporn

2017-09-01

Pinned spiral waves are exhibited in many excitable media. In cardiology, lengthened tachycardia correspond to propagating action potential in forms of spiral waves pinned to anatomical obstacles including veins and scares. Thus, elimination such waves is important particularly in medical treatments. We present study of unpinning of a spiral wave by a wave train initiated by periodic stimuli at a given location. The spiral wave is forced to leave the rectangular obstacle when the period of the wave train is shorter than a threshold Tunpin. For small obstacles, Tunpin decreases when the obstacle size is increased. Furthermore, Tunpin depends on the obstacle orientation with respect to the wave train propagation. For large obstacles, Tunpin is independent to the obstacle size. It implies that the orientation of the obstacle plays an important role in the unpinning of the spiral wave, especially for small rectangular obstacles.

Range Sensor-Based Efficient Obstacle Avoidance through Selective Decision-Making.

PubMed

Shim, Youngbo; Kim, Gon-Woo

2018-03-29

In this paper, we address a collision avoidance method for mobile robots. Many conventional obstacle avoidance methods have been focused solely on avoiding obstacles. However, this can cause instability when passing through a narrow passage, and can also generate zig-zag motions. We define two strategies for obstacle avoidance, known as Entry mode and Bypass mode. Entry mode is a pattern for passing through the gap between obstacles, while Bypass mode is a pattern for making a detour around obstacles safely. With these two modes, we propose an efficient obstacle avoidance method based on the Expanded Guide Circle (EGC) method with selective decision-making. The simulation and experiment results show the validity of the proposed method.

Method for surmounting an obstacle by a robot vehicle

NASA Technical Reports Server (NTRS)

Wilcox, Brian H. (Inventor); Ohm, Timothy R. (Inventor)

1994-01-01

Surmounting obstacles in the path of a robot vehicle is accomplished by rotating the wheel forks of the vehicle about their transverse axes with respect to the vehicle body so as to shift most of the vehicle weight onto the rear wheels, and then driving the vehicle forward so as to drive the now lightly-loaded front wheels (only) over the obstacle. Then, after the front wheels have either surmounted or completely passed the obstacle (depending upon the length of the obstacle), the forks are again rotated about their transverse axes so as to shift most of the vehicle weight onto the front wheels. Then the vehicle is again driven forward so as to drive the now lightly-loaded rear wheels over the obstacle. Once the obstacle has been completely cleared and the vehicle is again on relatively level terrain, the forks are again rotated so as to uniformly distribute the vehicle weight between the front and rear wheels.

Flow through a very porous obstacle in a shallow channel.

PubMed

Creed, M J; Draper, S; Nishino, T; Borthwick, A G L

2017-04-01

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence.

Flow through a very porous obstacle in a shallow channel

PubMed Central

Draper, S.; Nishino, T.; Borthwick, A. G. L.

2017-01-01

A theoretical model, informed by numerical simulations based on the shallow water equations, is developed to predict the flow passing through and around a uniform porous obstacle in a shallow channel, where background friction is important. This problem is relevant to a number of practical situations, including flow through aquatic vegetation, the performance of arrays of turbines in tidal channels and hydrodynamic forces on offshore structures. To demonstrate this relevance, the theoretical model is used to (i) reinterpret core flow velocities in existing laboratory-based data for an array of emergent cylinders in shallow water emulating aquatic vegetation and (ii) reassess the optimum arrangement of tidal turbines to generate power in a tidal channel. Comparison with laboratory-based data indicates a maximum obstacle resistance (or minimum porosity) for which the present theoretical model is valid. When the obstacle resistance is above this threshold the shallow water equations do not provide an adequate representation of the flow, and the theoretical model over-predicts the core flow passing through the obstacle. The second application of the model confirms that natural bed resistance increases the power extraction potential for a partial tidal fence in a shallow channel and alters the optimum arrangement of turbines within the fence. PMID:28484321

Evacuation simulation with consideration of obstacle removal and using game theory

NASA Astrophysics Data System (ADS)

Lin, Guan-Wen; Wong, Sai-Keung

2018-06-01

In this paper, we integrate a cellular automaton model with game theory to simulate crowd evacuation from a room with consideration of obstacle removal. The room has one or more exits, one of which is blocked by obstacles. The obstacles at the exit can be removed by volunteers. We investigate the cooperative and defective behaviors of pedestrians during evacuation. The yielder game and volunteer's dilemma game are employed to resolve interpedestrian conflict. An anticipation floor field is proposed to guide the pedestrians to avoid obstacles that are being removed. We conducted experiments to determine how a variety of conditions affect overall crowd evacuation and volunteer evacuation times. The conditions were the start time of obstacle removal, number of obstacles, placement of obstacles, time spent in obstacle removal, strength of the anticipation floor field, and obstacle visibility distance. We demonstrate how reciprocity can be achieved among pedestrians and increases the efficiency of the entire evacuation process.

Walking-adaptability assessments with the Interactive Walkway: Between-systems agreement and sensitivity to task and subject variations.

PubMed

Geerse, Daphne J; Coolen, Bert H; Roerdink, Melvyn

2017-05-01

The ability to adapt walking to environmental circumstances is an important aspect of walking, yet difficult to assess. The Interactive Walkway was developed to assess walking adaptability by augmenting a multi-Kinect-v2 10-m walkway with gait-dependent visual context (stepping targets, obstacles) using real-time processed markerless full-body kinematics. In this study we determined Interactive Walkway's usability for walking-adaptability assessments in terms of between-systems agreement and sensitivity to task and subject variations. Under varying task constraints, 21 healthy subjects performed obstacle-avoidance, sudden-stops-and-starts and goal-directed-stepping tasks. Various continuous walking-adaptability outcome measures were concurrently determined with the Interactive Walkway and a gold-standard motion-registration system: available response time, obstacle-avoidance and sudden-stop margins, step length, stepping accuracy and walking speed. The same holds for dichotomous classifications of success and failure for obstacle-avoidance and sudden-stops tasks and performed short-stride versus long-stride obstacle-avoidance strategies. Continuous walking-adaptability outcome measures generally agreed well between systems (high intraclass correlation coefficients for absolute agreement, low biases and narrow limits of agreement) and were highly sensitive to task and subject variations. Success and failure ratings varied with available response times and obstacle types and agreed between systems for 85-96% of the trials while obstacle-avoidance strategies were always classified correctly. We conclude that Interactive Walkway walking-adaptability outcome measures are reliable and sensitive to task and subject variations, even in high-functioning subjects. We therefore deem Interactive Walkway walking-adaptability assessments usable for obtaining an objective and more task-specific examination of one's ability to walk, which may be feasible for both high

Feeling the force: how pollen tubes deal with obstacles.

PubMed

Burri, Jan T; Vogler, Hannes; Läubli, Nino F; Hu, Chengzhi; Grossniklaus, Ueli; Nelson, Bradley J

2018-06-15

Physical forces are involved in the regulation of plant development and morphogenesis by translating mechanical stress into the modification of physiological processes, which, in turn, can affect cellular growth. Pollen tubes respond rapidly to external stimuli and provide an ideal system to study the effect of mechanical cues at the single-cell level. Here, pollen tubes were exposed to mechanical stress while monitoring the reconfiguration of their growth and recording the generated forces in real-time. We combined a lab-on-a-chip device with a microelectromechanical systems (MEMS)-based capacitive force sensor to mimic and quantify the forces that are involved in pollen tube navigation upon confronting mechanical obstacles. Several stages of obstacle avoidance were identified, including force perception, growth adjustment and penetration. We have experimentally determined the perceptive force threshold, which is the force threshold at which the pollen tube reacts to an obstacle, for Lilium longiflorum and Arabidopsis thaliana. In addition, the method we developed provides a way to calculate turgor pressure based on force and optical data. Pollen tubes sense physical barriers and actively adjust their growth behavior to overcome them. Furthermore, our system offers an ideal platform to investigate intracellular activity during force perception and growth adaption in tip growing cells. © 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.

Prefrontal cortex activation during obstacle negotiation: What's the effect size and timing?

PubMed

Maidan, Inbal; Shustak, Shiran; Sharon, Topaz; Bernad-Elazari, Hagar; Geffen, Nimrod; Giladi, Nir; Hausdorff, Jeffrey M; Mirelman, Anat

2018-04-01

Obstacle negotiation is a daily activity that requires the integration of sensorimotor and cognitive information. Recent studies provide evidence for the important role of prefrontal cortex during obstacle negotiation. We aimed to explore the effects of obstacle height and available response time on prefrontal activation. Twenty healthy young adults (age: 30.1 ± 1.0 years; 50% women) walked in an obstacle course while negotiating anticipated and unanticipated obstacles at heights of 50 mm and 100 mm. Prefrontal activation was measured using a functional near-infrared spectroscopy system. Kinect cameras measured the obstacle negotiation strategy. Prefrontal activation was defined based on mean level of HbO 2 before, during and after obstacle negotiation and the HbO 2 slope from gait initiation and throughout the task. Changes between types of obstacles were assessed using linear-mix models and partial correlation analyses evaluated the relationship between prefrontal activation and the distance between the feet as the subjects traversed the obstacles. Different obstacle heights showed similar changes in prefrontal activation measures (p > 0.210). However, during unanticipated obstacles, the slope of the HbO 2 response was steeper (p = 0.048), as compared to anticipated obstacles. These changes in prefrontal activation during negotiation of unanticipated obstacles were correlated with greater distance of the leading foot after the obstacles (r = 0.831, p = 0.041). These findings are the first to show that the pattern of prefrontal activation depends on the nature of the obstacle. More specifically, during unanticipated obstacles the recruitment of the prefrontal cortex is faster and greater than during negotiating anticipated obstacles. These results provide evidence of the important role of the prefrontal cortex and the ability of healthy young adults to tailor the activation pattern to different types of obstacles. Copyright © 2018

Interaction dynamics of multiple autonomous mobile robots in bounded spatial domains

NASA Technical Reports Server (NTRS)

Wang, P. K. C.

1989-01-01

A general navigation strategy for multiple autonomous robots in a bounded domain is developed analytically. Each robot is modeled as a spherical particle (i.e., an effective spatial domain about the center of mass); its interactions with other robots or with obstacles and domain boundaries are described in terms of the classical many-body problem; and a collision-avoidance strategy is derived and combined with homing, robot-robot, and robot-obstacle collision-avoidance strategies. Results from homing simulations involving (1) a single robot in a circular domain, (2) two robots in a circular domain, and (3) one robot in a domain with an obstacle are presented in graphs and briefly characterized.

Induced vibrations facilitate traversal of cluttered obstacles

NASA Astrophysics Data System (ADS)

Thoms, George; Yu, Siyuan; Kang, Yucheng; Li, Chen

When negotiating cluttered terrains such as grass-like beams, cockroaches and legged robots with rounded body shapes most often rolled their bodies to traverse narrow gaps between beams. Recent locomotion energy landscape modeling suggests that this locomotor pathway overcomes the lowest potential energy barriers. Here, we tested the hypothesis that body vibrations induced by intermittent leg-ground contact facilitate obstacle traversal by allowing exploration of locomotion energy landscape to find this lowest barrier pathway. To mimic a cockroach / legged robot pushing against two adjacent blades of grass, we developed an automated robotic system to move an ellipsoidal body into two adjacent beams, and varied body vibrations by controlling an oscillation actuator. A novel gyroscope mechanism allowed the body to freely rotate in response to interaction with the beams, and an IMU and cameras recorded the motion of the body and beams. We discovered that body vibrations facilitated body rolling, significantly increasing traversal probability and reducing traversal time (P <0.0001, ANOVA). Traversal probability increased with and traversal time decreased with beam separation. These results confirmed our hypothesis and support the plausibility of locomotion energy landscapes for understanding the formation of locomotor pathways in complex 3-D terrains.

Online optimal obstacle avoidance for rotary-wing autonomous unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Kang, Keeryun

capability over the virtual obstacles, and finally it was demonstrated on real obstacles located at the McKenna MOUT site in Fort Benning, Georgia. Simulations and flight test evaluations demonstrate the feasibility of the developed framework for UAV applications involving low-altitude flight in an urban area.

Self-Tuning Method for Increased Obstacle Detection Reliability Based on Internet of Things LiDAR Sensor Models

PubMed Central

2018-01-01

On-chip LiDAR sensors for vehicle collision avoidance are a rapidly expanding area of research and development. The assessment of reliable obstacle detection using data collected by LiDAR sensors has become a key issue that the scientific community is actively exploring. The design of a self-tuning methodology and its implementation are presented in this paper, to maximize the reliability of LiDAR sensors network for obstacle detection in the ‘Internet of Things’ (IoT) mobility scenarios. The Webots Automobile 3D simulation tool for emulating sensor interaction in complex driving environments is selected in order to achieve that objective. Furthermore, a model-based framework is defined that employs a point-cloud clustering technique, and an error-based prediction model library that is composed of a multilayer perceptron neural network, and k-nearest neighbors and linear regression models. Finally, a reinforcement learning technique, specifically a Q-learning method, is implemented to determine the number of LiDAR sensors that are required to increase sensor reliability for obstacle localization tasks. In addition, a IoT driving assistance user scenario, connecting a five LiDAR sensor network is designed and implemented to validate the accuracy of the computational intelligence-based framework. The results demonstrated that the self-tuning method is an appropriate strategy to increase the reliability of the sensor network while minimizing detection thresholds. PMID:29748521

Self-Tuning Method for Increased Obstacle Detection Reliability Based on Internet of Things LiDAR Sensor Models.

PubMed

Castaño, Fernando; Beruvides, Gerardo; Villalonga, Alberto; Haber, Rodolfo E

2018-05-10

On-chip LiDAR sensors for vehicle collision avoidance are a rapidly expanding area of research and development. The assessment of reliable obstacle detection using data collected by LiDAR sensors has become a key issue that the scientific community is actively exploring. The design of a self-tuning methodology and its implementation are presented in this paper, to maximize the reliability of LiDAR sensors network for obstacle detection in the 'Internet of Things' (IoT) mobility scenarios. The Webots Automobile 3D simulation tool for emulating sensor interaction in complex driving environments is selected in order to achieve that objective. Furthermore, a model-based framework is defined that employs a point-cloud clustering technique, and an error-based prediction model library that is composed of a multilayer perceptron neural network, and k-nearest neighbors and linear regression models. Finally, a reinforcement learning technique, specifically a Q-learning method, is implemented to determine the number of LiDAR sensors that are required to increase sensor reliability for obstacle localization tasks. In addition, a IoT driving assistance user scenario, connecting a five LiDAR sensor network is designed and implemented to validate the accuracy of the computational intelligence-based framework. The results demonstrated that the self-tuning method is an appropriate strategy to increase the reliability of the sensor network while minimizing detection thresholds.

Student with Asperger's Overcomes Obstacles: Devon's Journey to Independence

ERIC Educational Resources Information Center

Williams, Sarah Blackwelder

2010-01-01

Devon is a bright, engaging 22-year-old with a proud sense of accomplishment. He believes that while people encounter obstacles during their lives, these obstacles can be overcome with motivation and perseverance. Devon says people simply need to identify what they value, set goals and move beyond the obstacles. Devon has been faced with multiple…

Simulation of Molecular Transport in Systems Containing Mobile Obstacles.

PubMed

Polanowski, Piotr; Sikorski, Andrzej

2016-08-04

In this paper, we investigate the movement of molecules in crowded environments with obstacles undergoing Brownian motion by means of extensive Monte Carlo simulations. Our investigations were performed using the dynamic lattice liquid model, which was based on the cooperative movement concept and allowed to mimic systems at high densities where the motion of all elements (obstacles as well as moving particles) were highly correlated. The crowded environments are modeled on a two-dimensional triangular lattice containing obstacles (particles whose mobility was significantly reduced) moving by a Brownian motion. The subdiffusive motion of both elements in the system was analyzed. It was shown that the percolation transition does not exist in such systems in spite of the cooperative character of the particles' motion. The reduction of the obstacle mobility leads to the longer caging of liquid particles by mobile obstacles.

Diffusion amid random overlapping obstacles: Similarities, invariants, approximations

PubMed Central

Novak, Igor L.; Gao, Fei; Kraikivski, Pavel; Slepchenko, Boris M.

2011-01-01

Efficient and accurate numerical techniques are used to examine similarities of effective diffusion in a void between random overlapping obstacles: essential invariance of effective diffusion coefficients (Deff) with respect to obstacle shapes and applicability of a two-parameter power law over nearly entire range of excluded volume fractions (ϕ), except for a small vicinity of a percolation threshold. It is shown that while neither of the properties is exact, deviations from them are remarkably small. This allows for quick estimation of void percolation thresholds and approximate reconstruction of Deff (ϕ) for obstacles of any given shape. In 3D, the similarities of effective diffusion yield a simple multiplication “rule” that provides a fast means of estimating Deff for a mixture of overlapping obstacles of different shapes with comparable sizes. PMID:21513372

A soft robot capable of 2D mobility and self-sensing for obstacle detection and avoidance

NASA Astrophysics Data System (ADS)

Qin, Lei; Tang, Yucheng; Gupta, Ujjaval; Zhu, Jian

2018-04-01

Soft robots have shown great potential for surveillance applications due to their interesting attributes including inherent flexibility, extreme adaptability, and excellent ability to move in confined spaces. High mobility combined with the sensing systems that can detect obstacles plays a significant role in performing surveillance tasks. Extensive studies have been conducted on movement mechanisms of traditional hard-bodied robots to increase their mobility. However, there are limited efforts in the literature to explore the mobility of soft robots. In addition, little attempt has been made to study the obstacle-detection capability of a soft mobile robot. In this paper, we develop a soft mobile robot capable of high mobility and self-sensing for obstacle detection and avoidance. This robot, consisting of a dielectric elastomer actuator as the robot body and four electroadhesion actuators as the robot feet, can generate 2D mobility, i.e. translations and turning in a 2D plane, by programming the actuation sequence of the robot body and feet. Furthermore, we develop a self-sensing method which models the robot body as a deformable capacitor. By measuring the real-time capacitance of the robot body, the robot can detect an obstacle when the peak capacitance drops suddenly. This sensing method utilizes the robot body itself instead of external sensors to achieve detection of obstacles, which greatly reduces the weight and complexity of the robot system. The 2D mobility and self-sensing capability ensure the success of obstacle detection and avoidance, which paves the way for the development of lightweight and intelligent soft mobile robots.

Strategic obstacle placement reduces drop breakup probability in concentrated emulsion flowing into a constriction

NASA Astrophysics Data System (ADS)

Khor, Jian Wei; Hua, Yu; Bick, Alison; Tang, Sindy

2017-11-01

In this study, we investigate the effect of an obstacle on the breakup probability of droplets within a concentrated emulsion flowing into a constriction. We introduce a concentrated emulsion as a 2D monolayer through a tapered channel into a narrow constriction. This geometry is commonly used for the serial interrogation of droplet content in droplet microfluidics applications. We found that certain drop-drop interactions near the constriction entrance lead to the breakup of these drops at a high flow rates. Such breakup sets the upper limit for the droplet interrogation throughput. Incidentally, previous findings have shown that strategic placement of a circular post near a narrow exit can reduce the conflict from the interactions among living organisms (humans, ants, and sheep) or a cluster of particles when entering a narrow exit. Inspired by these results, we modify the tapered channel by placing a circular post in a strategic location near the constriction entrance in order to reduce catastrophic drop-drop interactions and to avoid breakup. Preliminary work shows that the circular posts can reduce the breakup fraction of drops by up to 17%. The optimization of the location and size of the obstacle is expected to further reduce the breakup fraction.

Overcoming obstacles to behavior change in diabetes self-management.

PubMed

Hall, Rosemary F; Joseph, Dayle Hunt; Schwartz-Barcott, Donna

2003-01-01

This study describes how 5 individuals with type 2 diabetes overcame obstacles that interfered with maintaining behavior changes in diet, exercise, and self-monitoring of blood glucose (SMBG). In-depth interviews provided the framework for this descriptive study. During audiotaped, face-to-face, follow-up structured and unstructured interviews, the participants shared their experiences about obstacles encountered and strategies used to overcome them. Each case was examined independently, and all cases were then compared with each other. Obstacles that interfered with maintaining a diet plan were hunger, planned and unplanned meal events, and the desire for new foods. Physical illness and unexpected life events were obstacles to maintaining an exercise and SMBG plan. Health professionals who assist patients who are beginning behavior change or having difficult maintaining changes need to have an understanding of the various obstacles and how patients can maintain behavior changes over time.

Obstacle avoidance handling and mixed integer predictive control for space robots

NASA Astrophysics Data System (ADS)

Zong, Lijun; Luo, Jianjun; Wang, Mingming; Yuan, Jianping

2018-04-01

This paper presents a novel obstacle avoidance constraint and a mixed integer predictive control (MIPC) method for space robots avoiding obstacles and satisfying physical limits during performing tasks. Firstly, a novel kind of obstacle avoidance constraint of space robots, which needs the assumption that the manipulator links and the obstacles can be represented by convex bodies, is proposed by limiting the relative velocity between two closest points which are on the manipulator and the obstacle, respectively. Furthermore, the logical variables are introduced into the obstacle avoidance constraint, which have realized the constraint form is automatically changed to satisfy different obstacle avoidance requirements in different distance intervals between the space robot and the obstacle. Afterwards, the obstacle avoidance constraint and other system physical limits, such as joint angle ranges, the amplitude boundaries of joint velocities and joint torques, are described as inequality constraints of a quadratic programming (QP) problem by using the model predictive control (MPC) method. To guarantee the feasibility of the obtained multi-constraint QP problem, the constraints are treated as soft constraints and assigned levels of priority based on the propositional logic theory, which can realize that the constraints with lower priorities are always firstly violated to recover the feasibility of the QP problem. Since the logical variables have been introduced, the optimization problem including obstacle avoidance and system physical limits as prioritized inequality constraints is termed as MIPC method of space robots, and its computational complexity as well as possible strategies for reducing calculation amount are analyzed. Simulations of the space robot unfolding its manipulator and tracking the end-effector's desired trajectories with the existence of obstacles and physical limits are presented to demonstrate the effectiveness of the proposed obstacle avoidance

A computational model of amoeboid cell swimming in unbounded medium and through obstacles

NASA Astrophysics Data System (ADS)

Campbell, Eric; Bagchi, Prosenjit

2017-11-01

Pseudopod-driven motility is commonly observed in eukaryotic cells. Pseudopodia are actin-rich protrusions of the cellular membrane which extend, bifurcate, and retract in cycles resulting in amoeboid locomotion. While actin-myosin interactions are responsible for pseudopod generation, cell deformability is crucial concerning pseudopod dynamics. Because pseudopodia are highly dynamic, cells are capable of deforming into complex shapes over time. Pseudopod-driven motility represents a multiscale and complex process, coupling cell deformation, protein biochemistry, and cytoplasmic and extracellular fluid motion. In this work, we present a 3D computational model of amoeboid cell swimming in an extracellular medium (ECM). The ECM is represented as a fluid medium with or without obstacles. The model integrates full cell deformation, a coarse-grain reaction-diffusion system for protein dynamics, and fluid interaction. Our model generates pseudopodia which bifurcate and retract, showing remarkable similarity to experimental observations. Influence of cell deformation, protein diffusivity and cytoplasmic viscosity on the swimming speed is analyzed in terms of altered pseudopod dynamics. Insights into the role of matrix porosity and obstacle size on cell motility are also provided. Funded by NSF CBET 1438255.

FieldSAFE: Dataset for Obstacle Detection in Agriculture.

PubMed

Kragh, Mikkel Fly; Christiansen, Peter; Laursen, Morten Stigaard; Larsen, Morten; Steen, Kim Arild; Green, Ole; Karstoft, Henrik; Jørgensen, Rasmus Nyholm

2017-11-09

In this paper, we present a multi-modal dataset for obstacle detection in agriculture. The dataset comprises approximately 2 h of raw sensor data from a tractor-mounted sensor system in a grass mowing scenario in Denmark, October 2016. Sensing modalities include stereo camera, thermal camera, web camera, 360 ∘ camera, LiDAR and radar, while precise localization is available from fused IMU and GNSS. Both static and moving obstacles are present, including humans, mannequin dolls, rocks, barrels, buildings, vehicles and vegetation. All obstacles have ground truth object labels and geographic coordinates.

FieldSAFE: Dataset for Obstacle Detection in Agriculture

PubMed Central

Christiansen, Peter; Larsen, Morten; Steen, Kim Arild; Green, Ole; Karstoft, Henrik

2017-01-01

In this paper, we present a multi-modal dataset for obstacle detection in agriculture. The dataset comprises approximately 2 h of raw sensor data from a tractor-mounted sensor system in a grass mowing scenario in Denmark, October 2016. Sensing modalities include stereo camera, thermal camera, web camera, 360∘ camera, LiDAR and radar, while precise localization is available from fused IMU and GNSS. Both static and moving obstacles are present, including humans, mannequin dolls, rocks, barrels, buildings, vehicles and vegetation. All obstacles have ground truth object labels and geographic coordinates. PMID:29120383

Motion Among Random Obstacles on a Hyperbolic Space

NASA Astrophysics Data System (ADS)

Orsingher, Enzo; Ricciuti, Costantino; Sisti, Francesco

2016-02-01

We consider the motion of a particle along the geodesic lines of the Poincaré half-plane. The particle is specularly reflected when it hits randomly-distributed obstacles that are assumed to be motionless. This is the hyperbolic version of the well-known Lorentz Process studied in the Euclidean context. We analyse the limit in which the density of the obstacles increases to infinity and the size of each obstacle vanishes: under a suitable scaling, we prove that our process converges to a Markovian process, namely a random flight on the hyperbolic manifold.

Obstacle avoidance in social groups: new insights from asynchronous models

PubMed Central

Croft, Simon; Budgey, Richard; Pitchford, Jonathan W.; Wood, A. Jamie

2015-01-01

For moving animals, the successful avoidance of hazardous obstacles is an important capability. Despite this, few models of collective motion have addressed the relationship between behavioural and social features and obstacle avoidance. We develop an asynchronous individual-based model for social movement which allows social structure within groups to be included. We assess the dynamics of group navigation and resulting collision risk in the context of information transfer through the system. In agreement with previous work, we find that group size has a nonlinear effect on collision risk. We implement examples of possible network structures to explore the impact social preferences have on collision risk. We show that any social heterogeneity induces greater obstacle avoidance with further improvements corresponding to groups containing fewer influential individuals. The model provides a platform for both further theoretical investigation and practical application. In particular, we argue that the role of social structures within bird flocks may have an important role to play in assessing the risk of collisions with wind turbines, but that new methods of data analysis are needed to identify these social structures. PMID:25833245

SABRINA - an interactive geometry modeler for MCNP

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, J.T.; Murphy, J.

One of the most difficult tasks when analyzing a complex three-dimensional system with Monte Carlo is geometry model development. SABRINA attempts to make the modeling process more user-friendly and less of an obstacle. It accepts both combinatorial solid bodies and MCNP surfaces and produces MCNP cells. The model development process in SABRINA is highly interactive and gives the user immediate feedback on errors. Users can view their geometry from arbitrary perspectives while the model is under development and interactively find and correct modeling errors. An example of a SABRINA display is shown. It represents a complex three-dimensional shape.

Portuguese primary school children's conceptions about digestion: identification of learning obstacles

NASA Astrophysics Data System (ADS)

Silva, Rui Graça; Lima, Nelson; Coquet, Eduarda; Clément, Pierre

2004-09-01

A cross-sectional study of Portuguese primary school pupils' conceptions on digestion and the digestive tract was carried out before and after teaching this topic. Pupils of the prior four school years (5/6 to 9/10 year old) drew what happens to a cookie inside their body. In some cases they also wrote a short text or were interviewed. To identify their level of graphic development, they produced a free-hand drawing. The main conceptual changes in explaining digestion were strongly linked to teaching. Children's previous conceptions were not epistemological obstacles to learning about digestion. The main obstacles were of didactical origin, as images of primary school books do not represent (i) the path of food from the intestine into the blood, (associated to the epistemological obstacle of the permeability of the gut wall); (ii) a clear continuous tract from stomach to anus, which causes a specific confusion at the intestine level.

Blindness enhances auditory obstacle circumvention: Assessing echolocation, sensory substitution, and visual-based navigation

PubMed Central

Scarfe, Amy C.; Moore, Brian C. J.; Pardhan, Shahina

2017-01-01

Performance for an obstacle circumvention task was assessed under conditions of visual, auditory only (using echolocation) and tactile (using a sensory substitution device, SSD) guidance. A Vicon motion capture system was used to measure human movement kinematics objectively. Ten normally sighted participants, 8 blind non-echolocators, and 1 blind expert echolocator navigated around a 0.6 x 2 m obstacle that was varied in position across trials, at the midline of the participant or 25 cm to the right or left. Although visual guidance was the most effective, participants successfully circumvented the obstacle in the majority of trials under auditory or SSD guidance. Using audition, blind non-echolocators navigated more effectively than blindfolded sighted individuals with fewer collisions, lower movement times, fewer velocity corrections and greater obstacle detection ranges. The blind expert echolocator displayed performance similar to or better than that for the other groups using audition, but was comparable to that for the other groups using the SSD. The generally better performance of blind than of sighted participants is consistent with the perceptual enhancement hypothesis that individuals with severe visual deficits develop improved auditory abilities to compensate for visual loss, here shown by faster, more fluid, and more accurate navigation around obstacles using sound. PMID:28407000

Blindness enhances auditory obstacle circumvention: Assessing echolocation, sensory substitution, and visual-based navigation.

PubMed

Kolarik, Andrew J; Scarfe, Amy C; Moore, Brian C J; Pardhan, Shahina

2017-01-01

Performance for an obstacle circumvention task was assessed under conditions of visual, auditory only (using echolocation) and tactile (using a sensory substitution device, SSD) guidance. A Vicon motion capture system was used to measure human movement kinematics objectively. Ten normally sighted participants, 8 blind non-echolocators, and 1 blind expert echolocator navigated around a 0.6 x 2 m obstacle that was varied in position across trials, at the midline of the participant or 25 cm to the right or left. Although visual guidance was the most effective, participants successfully circumvented the obstacle in the majority of trials under auditory or SSD guidance. Using audition, blind non-echolocators navigated more effectively than blindfolded sighted individuals with fewer collisions, lower movement times, fewer velocity corrections and greater obstacle detection ranges. The blind expert echolocator displayed performance similar to or better than that for the other groups using audition, but was comparable to that for the other groups using the SSD. The generally better performance of blind than of sighted participants is consistent with the perceptual enhancement hypothesis that individuals with severe visual deficits develop improved auditory abilities to compensate for visual loss, here shown by faster, more fluid, and more accurate navigation around obstacles using sound.

Stepping back to see the big picture: when obstacles elicit global processing.

PubMed

Marguc, Janina; Förster, Jens; Van Kleef, Gerben A

2011-11-01

Can obstacles prompt people to look at the "big picture" and open up their minds? Do the cognitive effects of obstacles extend beyond the tasks with which they interfere? These questions were addressed in 6 studies involving both physical and nonphysical obstacles and different measures of global versus local processing styles. Perceptual scope increased after participants solved anagrams in the presence, rather than the absence, of an auditory obstacle (random words played in the background; Study 1), particularly among individuals low in volatility (i.e., those who are inclined to stay engaged and finish what they do; Study 4). It also increased immediately after participants encountered a physical obstacle while navigating a maze (Study 3A) and when compared with doing nothing (Study 3B). Conceptual scope increased after participants solved anagrams while hearing random numbers framed as an "obstacle to overcome" rather than a "distraction to ignore" (Study 2) and after participants navigated a maze with a physical obstacle, compared with a maze without a physical obstacle, but only when trait (Study 5) or state (Study 6) volatility was low. Results suggest that obstacles trigger an "if obstacle, then start global processing" response, primarily when people are inclined to stay engaged and finish ongoing activities. Implications for dealing with life's obstacles and related research are discussed.

Study and realization of an obstacle detection infrared system for automotive use

NASA Astrophysics Data System (ADS)

Alaouiamine, Mohammed

1991-08-01

The main technological options available in the field of obstacle detection are presented. Ultrasound, microwave, and infrared detection systems are reviewed. The reasons for choosing an infrared solution are outlined. The problems involved in developing an obstacle detection system in the near infrared are discussed. Weather condition effects, interference limitations due to multiple onboard sensors, and range detection influence are some of the problems studied. A collimated, mechanically scanned, and pulsed infrared beam is proposed to overcome some of these problems. Performances of a first and second prototype made using this system are presented.

Joint Doctrine for Barriers, Obstacles, and Mine Warfare

DTIC Science & Technology

1999-02-24

of explosives. Typical tactical examples are barbed wire obstacles and tank ditches. Operational and strategic barriers and obstacles may also be...total of 10 ocean minesweepers, 9 amphibious ships, 6 fleet tugs, 3 salvage ships, and 19 destroyers. Twenty-four CH-53D Sea Stallions from Marine

How Obstacles Perturb Population Fronts and Alter Their Genetic Structure.

PubMed

Möbius, Wolfram; Murray, Andrew W; Nelson, David R

2015-12-01

As populations spread into new territory, environmental heterogeneities can shape the population front and genetic composition. We focus here on the effects of an important building block of heterogeneous environments, isolated obstacles. With a combination of experiments, theory, and simulation, we show how isolated obstacles both create long-lived distortions of the front shape and amplify the effect of genetic drift. A system of bacteriophage T7 spreading on a spatially heterogeneous Escherichia coli lawn serves as an experimental model system to study population expansions. Using an inkjet printer, we create well-defined replicates of the lawn and quantitatively study the population expansion of phage T7. The transient perturbations of the population front found in the experiments are well described by a model in which the front moves with constant speed. Independent of the precise details of the expansion, we show that obstacles create a kink in the front that persists over large distances and is insensitive to the details of the obstacle's shape. The small deviations between experimental findings and the predictions of the constant speed model can be understood with a more general reaction-diffusion model, which reduces to the constant speed model when the obstacle size is large compared to the front width. Using this framework, we demonstrate that frontier genotypes just grazing the side of an isolated obstacle increase in abundance, a phenomenon we call 'geometry-enhanced genetic drift', complementary to the founder effect associated with spatial bottlenecks. Bacterial range expansions around nutrient-poor barriers and stochastic simulations confirm this prediction. The effect of the obstacle on the genealogy of individuals at the front is characterized by simulations and rationalized using the constant speed model. Lastly, we consider the effect of two obstacles on front shape and genetic composition of the population illuminating the effects expected from

Research on UAV Intelligent Obstacle Avoidance Technology During Inspection of Transmission Line

NASA Astrophysics Data System (ADS)

Wei, Chuanhu; Zhang, Fei; Yin, Chaoyuan; Liu, Yue; Liu, Liang; Li, Zongyu; Wang, Wanguo

Autonomous obstacle avoidance of unmanned aerial vehicle (hereinafter referred to as UAV) in electric power line inspection process has important significance for operation safety and economy for UAV intelligent inspection system of transmission line as main content of UAV intelligent inspection system on transmission line. In the paper, principles of UAV inspection obstacle avoidance technology of transmission line are introduced. UAV inspection obstacle avoidance technology based on particle swarm global optimization algorithm is proposed after common obstacle avoidance technologies are studied. Stimulation comparison is implemented with traditional UAV inspection obstacle avoidance technology which adopts artificial potential field method. Results show that UAV inspection strategy of particle swarm optimization algorithm, adopted in the paper, is prominently better than UAV inspection strategy of artificial potential field method in the aspects of obstacle avoidance effect and the ability of returning to preset inspection track after passing through the obstacle. An effective method is provided for UAV inspection obstacle avoidance of transmission line.

Collective strategy for obstacle navigation during cooperative transport by ants.

PubMed

McCreery, Helen F; Dix, Zachary A; Breed, Michael D; Nagpal, Radhika

2016-11-01

Group cohesion and consensus have primarily been studied in the context of discrete decisions, but some group tasks require making serial decisions that build on one another. We examine such collective problem solving by studying obstacle navigation during cooperative transport in ants. In cooperative transport, ants work together to move a large object back to their nest. We blocked cooperative transport groups of Paratrechina longicornis with obstacles of varying complexity, analyzing groups' trajectories to infer what kind of strategy the ants employed. Simple strategies require little information, but more challenging, robust strategies succeed with a wider range of obstacles. We found that transport groups use a stochastic strategy that leads to efficient navigation around simple obstacles, and still succeeds at difficult obstacles. While groups navigating obstacles preferentially move directly toward the nest, they change their behavior over time; the longer the ants are obstructed, the more likely they are to move away from the nest. This increases the chance of finding a path around the obstacle. Groups rapidly changed directions and rarely stalled during navigation, indicating that these ants maintain consensus even when the nest direction is blocked. Although some decisions were aided by the arrival of new ants, at many key points, direction changes were initiated within the group, with no apparent external cause. This ant species is highly effective at navigating complex environments, and implements a flexible strategy that works for both simple and more complex obstacles. © 2016. Published by The Company of Biologists Ltd.

Emergent oscillations assist obstacle negotiation during ant cooperative transport.

PubMed

Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Gov, Nir S; Feinerman, Ofer

2016-12-20

Collective motion by animal groups is affected by internal interactions, external constraints, and the influx of information. A quantitative understanding of how these different factors give rise to different modes of collective motion is, at present, lacking. Here, we study how ants that cooperatively transport a large food item react to an obstacle blocking their path. Combining experiments with a statistical physics model of mechanically coupled active agents, we show that the constraint induces a deterministic collective oscillatory mode that facilitates obstacle circumvention. We provide direct experimental evidence, backed by theory, that this motion is an emergent group effect that does not require any behavioral changes at the individual level. We trace these relaxation oscillations to the interplay between two forces; informed ants pull the load toward the nest whereas uninformed ants contribute to the motion's persistence along the tangential direction. The model's predictions that oscillations appear above a critical system size, that the group can spontaneously transition into its ordered phase, and that the system can exhibit complete rotations are all verified experimentally. We expect that similar oscillatory modes emerge in collective motion scenarios where the structure of the environment imposes conflicts between individually held information and the group's tendency for cohesiveness.

Emergent oscillations assist obstacle negotiation during ant cooperative transport

PubMed Central

Gelblum, Aviram; Pinkoviezky, Itai; Fonio, Ehud; Gov, Nir S.; Feinerman, Ofer

2016-01-01

Collective motion by animal groups is affected by internal interactions, external constraints, and the influx of information. A quantitative understanding of how these different factors give rise to different modes of collective motion is, at present, lacking. Here, we study how ants that cooperatively transport a large food item react to an obstacle blocking their path. Combining experiments with a statistical physics model of mechanically coupled active agents, we show that the constraint induces a deterministic collective oscillatory mode that facilitates obstacle circumvention. We provide direct experimental evidence, backed by theory, that this motion is an emergent group effect that does not require any behavioral changes at the individual level. We trace these relaxation oscillations to the interplay between two forces; informed ants pull the load toward the nest whereas uninformed ants contribute to the motion’s persistence along the tangential direction. The model’s predictions that oscillations appear above a critical system size, that the group can spontaneously transition into its ordered phase, and that the system can exhibit complete rotations are all verified experimentally. We expect that similar oscillatory modes emerge in collective motion scenarios where the structure of the environment imposes conflicts between individually held information and the group’s tendency for cohesiveness. PMID:27930304

Effect of form of obstacle on speed of crowd evacuation

NASA Astrophysics Data System (ADS)

Yano, Ryosuke

2018-03-01

This paper investigates the effect of the form of an obstacle on the time that a crowd takes to evacuate a room, using a toy model. Pedestrians are modeled as active soft matter moving toward a point with intended velocities. An obstacle is placed in front of the exit, and it has one of four shapes: a cylindrical column, a triangular prism, a quadratic prism, or a diamond prism. Numerical results indicate that the evacuation-completion time depends on the shape of the obstacle. Obstacles with a circular cylinder (C.C.) shape yield the shortest evacuation-completion time in the proposed model.

Soybean Seed Development: Fatty Acid and Phytohormone Metabolism and Their Interactions

PubMed Central

Nguyen, Quoc Thien.; Kisiala, Anna; Andreas, Peter; Neil Emery, R.J.; Narine, Suresh

2016-01-01

Vegetable oil utilization is determined by its fatty acid composition. In soybean and other grain crops, during the seed development oil accumulation is important trait for value in food or industrial applications. Seed development is relatively short and sensitive to unfavorable abiotic conditions. These stresses can lead to a numerous undesirable qualitative as well as quantitative changes in fatty acid production. Fatty acid manipulation which targets a higher content of a specific single fatty acid for food or industrial application has gained more attention. Despite several successes in modifying the ratio of endogenous fatty acids in most domesticated oilseed crops, numerous obstacles in FA manipulation of seed maturation are yet to be overcome. Remarkably, connections with plant hormones have not been well studied despite their critical roles in the regulation and promotion of a plethora of processes in plant growth and development. While activities of phytohormones during the reproductive phase have been partially clarified in seed physiology, the biological role of plant hormones in oil accumulation during seed development has not been investigated. In this review seed development and numerous effects of abiotic stresses are discussed. After describing fatty acid and phytohormone metabolism and their interactions, we postulate that the endogenous plant hormones play important roles in fatty acid production in soybean seeds. PMID:27252591

Cascading a systolic array and a feedforward neural network for navigation and obstacle avoidance using potential fields

NASA Technical Reports Server (NTRS)

Plumer, Edward S.

1991-01-01

A technique is developed for vehicle navigation and control in the presence of obstacles. A potential function was devised that peaks at the surface of obstacles and has its minimum at the proper vehicle destination. This function is computed using a systolic array and is guaranteed not to have local minima. A feedfoward neural network is then used to control the steering of the vehicle using local potential field information. In this case, the vehicle is a trailer truck backing up. Previous work has demonstrated the capability of a neural network to control steering of such a trailer truck backing to a loading platform, but without obstacles. Now, the neural network was able to learn to navigate a trailer truck around obstacles while backing toward its destination. The network is trained in an obstacle free space to follow the negative gradient of the field, after which the network is able to control and navigate the truck to its target destination in a space of obstacles which may be stationary or movable.

A Compact Magnetic Field-Based Obstacle Detection and Avoidance System for Miniature Spherical Robots.

PubMed

Wu, Fang; Vibhute, Akash; Soh, Gim Song; Wood, Kristin L; Foong, Shaohui

2017-05-28

Due to their efficient locomotion and natural tolerance to hazardous environments, spherical robots have wide applications in security surveillance, exploration of unknown territory and emergency response. Numerous studies have been conducted on the driving mechanism, motion planning and trajectory tracking methods of spherical robots, yet very limited studies have been conducted regarding the obstacle avoidance capability of spherical robots. Most of the existing spherical robots rely on the "hit and run" technique, which has been argued to be a reasonable strategy because spherical robots have an inherent ability to recover from collisions. Without protruding components, they will not become stuck and can simply roll back after running into bstacles. However, for small scale spherical robots that contain sensitive surveillance sensors and cannot afford to utilize heavy protective shells, the absence of obstacle avoidance solutions would leave the robot at the mercy of potentially dangerous obstacles. In this paper, a compact magnetic field-based obstacle detection and avoidance system has been developed for miniature spherical robots. It utilizes a passive magnetic field so that the system is both compact and power efficient. The proposed system can detect not only the presence, but also the approaching direction of a ferromagnetic obstacle, therefore, an intelligent avoidance behavior can be generated by adapting the trajectory tracking method with the detection information. Design optimization is conducted to enhance the obstacle detection performance and detailed avoidance strategies are devised. Experimental results are also presented for validation purposes.

Water waves generated by impulsively moving obstacle

NASA Astrophysics Data System (ADS)

Makarenko, Nikolay; Kostikov, Vasily

2017-04-01

There are several mechanisms of tsunami-type wave formation such as piston displacement of the ocean floor due to a submarine earthquake, landslides, etc. We consider simplified mathematical formulation which involves non-stationary Euler equations of infinitely deep ideal fluid with submerged compact wave-maker. We apply semi-analytical method [1] based on the reduction of fully nonlinear water wave problem to the integral-differential system for the wave elevation together with normal and tangential fluid velocities at the free surface. Recently, small-time asymptotic solutions were constructed by this method for submerged piston modeled by thin elliptic cylinder which starts with constant acceleration from rest [2,3]. By that, the leading-order solution terms describe several regimes of non-stationary free surface flow such as formation of inertial fluid layer, splash jets and diverging waves over the obstacle. Now we construct asymptotic solution taking into account higher-order nonlinear terms in the case of submerged circular cylinder. The role of non-linearity in the formation mechanism of surface waves is clarified in comparison with linear approximations. This work was supported by RFBR (grant No 15-01-03942). References [1] Makarenko N.I. Nonlinear interaction of submerged cylinder with free surface, JOMAE Trans. ASME, 2003, 125(1), 75-78. [2] Makarenko N.I., Kostikov V.K. Unsteady motion of an elliptic cylinder under a free surface, J. Appl. Mech. Techn. Phys., 2013, 54(3), 367-376. [3] Makarenko N.I., Kostikov V.K. Non-linear water waves generated by impulsive motion of submerged obstacle, NHESS, 2014, 14(4), 751-756.

Influence of obstacles on bubbles rising in water-saturated sand

NASA Astrophysics Data System (ADS)

Poryles, Raphaël; Varas, Germán; Vidal, Valérie

2017-06-01

This work investigates the dynamics of air rising through a water-saturated sand confined in a Hele- Shaw cell in which a circular obstacle is trapped. The air is injected at constant flow rate through a single nozzle at the bottom center of the cell. Without obstacle, in a similar configuration, previous studies pointed out the existence of a fluidized zone generated by the central upward gas motion which entrains two granular convection rolls on its sides. Here, a circular obstacle which diameter is of the order of the central air channel width is trapped at the vertical of the injection nozzle. We analyze the influence of the obstacle location on the size of the fluidized zone and its impact on the morphology of the central air channel. Finally, we quantify the variations of the granular free surface. Two configurations with multiple obstacles are also considered.

Performance and three-dimensional kinematics of bipedal lizards during obstacle negotiation.

PubMed

Olberding, Jeffrey P; McBrayer, Lance D; Higham, Timothy E

2012-01-15

Bipedal running is common among lizard species, but although the kinematics and performance of this gait have been well characterized, the advantages in biologically relevant situations are still unclear. Obstacle negotiation is a task that is ecologically relevant to many animals while moving at high speeds, such as during bipedal running, yet little is known about how obstacles impact locomotion and performance. We examined the effects of obstacle negotiation on the kinematics and performance of lizards during bipedal locomotion. We quantified three-dimensional kinematics from high-speed video (500 Hz) of six-lined racerunners (Aspidoscelis sexlineata) running on a 3 m racetrack both with and without an obstacle spanning the width of the track. The lizards did not alter their kinematics prior to contacting the obstacle. Although contact with the obstacle caused changes to the hindlimb kinematics, mean forward speed did not differ between treatments. The deviation of the vertical position of the body center of mass did not differ between treatments, suggesting that in the absence of a cost to overall performance, lizards forgo maintaining normal kinematics while negotiating obstacles in favor of a steady body center of mass height to avoid destabilizing locomotion.

Advanced Augmented White Cane with obstacle height and distance feedback.

PubMed

Pyun, Rosali; Kim, Yeongmi; Wespe, Pascal; Gassert, Roger; Schneller, Stefan

2013-06-01

The white cane is a widely used mobility aid that helps visually impaired people navigate the surroundings. While it reliably and intuitively extends the detection range of ground-level obstacles and drop-offs to about 1.2 m, it lacks the ability to detect trunk and head-level obstacles. Electronic Travel Aids (ETAs) have been proposed to overcome these limitations, but have found minimal adoption due to limitations such as low information content and low reliability thereof. Although existing ETAs extend the sensing range beyond that of the conventional white cane, most of them do not detect head-level obstacles and drop-offs, nor can they identify the vertical extent of obstacles. Furthermore, some ETAs work independent of the white cane, and thus reliable detection of surface textures and drop-offs is not provided. This paper introduces a novel ETA, the Advanced Augmented White Cane, which detects obstacles at four vertical levels and provides multi-sensory feedback. We evaluated the device in five blindfolded subjects through reaction time measurements following the detection of an obstacle, as well as through the reliability of dropoff detection. The results showed that our aid could help the user successfully detect an obstacle and identify its height, with an average reaction time of 410 msec. Drop-offs were reliably detected with an intraclass correlation > 0.95. This work is a first step towards a low-cost ETA to complement the functionality of the conventional white cane.

A reciprocity formulation for the EM scattering by an obstacle within a large open cavity

NASA Technical Reports Server (NTRS)

Pathak, Prabhakar H.; Burkholder, Robert J.

1993-01-01

A formulation based on a generalized reciprocity theorem is developed for analyzing the external high frequency EM scattering by a complex obstacle inside a relatively arbitrary open-ended waveguide cavity when it is illuminated by an external source. This formulation is also extended to include EM fields whose time dependence may be nonperiodic. A significant advantage of this formulation is that it allows one to break up the analysis into two independent parts; one deals with the waveguide cavity shape alone and the other with the obstacle alone. The external scattered field produced by the obstacle (in the presence of the waveguide cavity structure) is given in terms of a generalized reciprocity integral over a surface S(T) corresponding to the interior waveguide cavity cross section located conveniently but sufficiently close to the obstacle. Furthermore, the fields coupled into the cavity from the source in the exterior region generally need to propagate only one-way via the open front end (which is directly illuminated) to the interior surface S(T) in this approach, and not back, in order to find the external field scattered by the obstacle.

How Obstacles Perturb Population Fronts and Alter Their Genetic Structure

PubMed Central

Möbius, Wolfram; Murray, Andrew W.; Nelson, David R.

2015-01-01

As populations spread into new territory, environmental heterogeneities can shape the population front and genetic composition. We focus here on the effects of an important building block of heterogeneous environments, isolated obstacles. With a combination of experiments, theory, and simulation, we show how isolated obstacles both create long-lived distortions of the front shape and amplify the effect of genetic drift. A system of bacteriophage T7 spreading on a spatially heterogeneous Escherichia coli lawn serves as an experimental model system to study population expansions. Using an inkjet printer, we create well-defined replicates of the lawn and quantitatively study the population expansion of phage T7. The transient perturbations of the population front found in the experiments are well described by a model in which the front moves with constant speed. Independent of the precise details of the expansion, we show that obstacles create a kink in the front that persists over large distances and is insensitive to the details of the obstacle’s shape. The small deviations between experimental findings and the predictions of the constant speed model can be understood with a more general reaction-diffusion model, which reduces to the constant speed model when the obstacle size is large compared to the front width. Using this framework, we demonstrate that frontier genotypes just grazing the side of an isolated obstacle increase in abundance, a phenomenon we call ‘geometry-enhanced genetic drift’, complementary to the founder effect associated with spatial bottlenecks. Bacterial range expansions around nutrient-poor barriers and stochastic simulations confirm this prediction. The effect of the obstacle on the genealogy of individuals at the front is characterized by simulations and rationalized using the constant speed model. Lastly, we consider the effect of two obstacles on front shape and genetic composition of the population illuminating the effects

Sensorimotor Model of Obstacle Avoidance in Echolocating Bats

PubMed Central

Vanderelst, Dieter; Holderied, Marc W.; Peremans, Herbert

2015-01-01

Bat echolocation is an ability consisting of many subtasks such as navigation, prey detection and object recognition. Understanding the echolocation capabilities of bats comes down to isolating the minimal set of acoustic cues needed to complete each task. For some tasks, the minimal cues have already been identified. However, while a number of possible cues have been suggested, little is known about the minimal cues supporting obstacle avoidance in echolocating bats. In this paper, we propose that the Interaural Intensity Difference (IID) and travel time of the first millisecond of the echo train are sufficient cues for obstacle avoidance. We describe a simple control algorithm based on the use of these cues in combination with alternating ear positions modeled after the constant frequency bat Rhinolophus rouxii. Using spatial simulations (2D and 3D), we show that simple phonotaxis can steer a bat clear from obstacles without performing a reconstruction of the 3D layout of the scene. As such, this paper presents the first computationally explicit explanation for obstacle avoidance validated in complex simulated environments. Based on additional simulations modelling the FM bat Phyllostomus discolor, we conjecture that the proposed cues can be exploited by constant frequency (CF) bats and frequency modulated (FM) bats alike. We hypothesize that using a low level yet robust cue for obstacle avoidance allows bats to comply with the hard real-time constraints of this basic behaviour. PMID:26502063

Role of curvatures in determining the characteristics of a string vibrating against a doubly curved obstacle

NASA Astrophysics Data System (ADS)

Singh, Harkirat; Wahi, Pankaj

2017-08-01

The motion of a string in the presence of a doubly curved obstacle is investigated. A mathematical model has been developed for a general shape of the obstacle. However, detailed analysis has been performed for a shape relevant to the Indian stringed musical instruments like Tanpura and Sitar. In particular, we explore the effect of obstacle's curvature in the plane perpendicular to the string axis on its motion. This geometrical feature of the obstacle introduces a coupling between motions in mutually perpendicular directions over and above the coupling due to the stretching nonlinearity. We find that only one planar motion is possible for our system. Small amplitude planar motions are stable to perturbations in the perpendicular direction resulting in non-whirling motions while large amplitude oscillations lead to whirling motions. The critical amplitude of oscillations, across which there is a transition in the qualitative behavior of the non-planar trajectories, is determined using Floquet theory. Our analysis reveals that a small obstacle curvature in a direction perpendicular to the string axis leads to a considerable reduction in the critical amplitudes required for initiation of whirling motions. Hence, this obstacle curvature has a destabilizing effect on the planar motions in contrast to the curvature along the string axis which stabilizes planar motions.

Rhett Talks: The development, implementation, and assessment of a faculty-in-residence program.

PubMed

Healea, C Daryl; Ribera, Robert

2015-01-01

Student-faculty interactions outside the classroom have long been touted as beneficial to students' success at an institution of higher education. However, obstacles to realizing these interactions have also been well-documented. This case study profiles how student affairs administrators and faculty-in-residence overcame these obstacles to develop, implement, and assess an award-winning program for facilitating student-faculty interactions outside the classroom. Named after the Boston University (BU) mascot (Rhett the Boston terrier) and inspired by the popular online lecture series (TED Talks), Rhett Talks has met BU's unique campus needs, facilitated potent student-faculty interactions, and demonstrated effective partnering between student affairs and academic affairs.

Design and evaluation of an autonomous, obstacle avoiding, flight control system using visual sensors

NASA Astrophysics Data System (ADS)

Crawford, Bobby Grant

In an effort to field smaller and cheaper Uninhabited Aerial Vehicles (UAVs), the Army has expressed an interest in an ability of the vehicle to autonomously detect and avoid obstacles. Current systems are not suitable for small aircraft. NASA Langley Research Center has developed a vision sensing system that uses small semiconductor cameras. The feasibility of using this sensor for the purpose of autonomous obstacle avoidance by a UAV is the focus of the research presented in this document. The vision sensor characteristics are modeled and incorporated into guidance and control algorithms designed to generate flight commands based on obstacle information received from the sensor. The system is evaluated by simulating the response to these flight commands using a six degree-of-freedom, non-linear simulation of a small, fixed wing UAV. The simulation is written using the MATLAB application and runs on a PC. Simulations were conducted to test the longitudinal and lateral capabilities of the flight control for a range of airspeeds, camera characteristics, and wind speeds. Results indicate that the control system is suitable for obstacle avoiding flight control using the simulated vision system. In addition, a method for designing and evaluating the performance of such a system has been developed that allows the user to easily change component characteristics and evaluate new systems through simulation.

A Monocular Vision Sensor-Based Obstacle Detection Algorithm for Autonomous Robots.

PubMed

Lee, Tae-Jae; Yi, Dong-Hoon; Cho, Dong-Il Dan

2016-03-01

This paper presents a monocular vision sensor-based obstacle detection algorithm for autonomous robots. Each individual image pixel at the bottom region of interest is labeled as belonging either to an obstacle or the floor. While conventional methods depend on point tracking for geometric cues for obstacle detection, the proposed algorithm uses the inverse perspective mapping (IPM) method. This method is much more advantageous when the camera is not high off the floor, which makes point tracking near the floor difficult. Markov random field-based obstacle segmentation is then performed using the IPM results and a floor appearance model. Next, the shortest distance between the robot and the obstacle is calculated. The algorithm is tested by applying it to 70 datasets, 20 of which include nonobstacle images where considerable changes in floor appearance occur. The obstacle segmentation accuracies and the distance estimation error are quantitatively analyzed. For obstacle datasets, the segmentation precision and the average distance estimation error of the proposed method are 81.4% and 1.6 cm, respectively, whereas those for a conventional method are 57.5% and 9.9 cm, respectively. For nonobstacle datasets, the proposed method gives 0.0% false positive rates, while the conventional method gives 17.6%.

A Monocular Vision Sensor-Based Obstacle Detection Algorithm for Autonomous Robots

PubMed Central

Lee, Tae-Jae; Yi, Dong-Hoon; Cho, Dong-Il “Dan”

2016-01-01

This paper presents a monocular vision sensor-based obstacle detection algorithm for autonomous robots. Each individual image pixel at the bottom region of interest is labeled as belonging either to an obstacle or the floor. While conventional methods depend on point tracking for geometric cues for obstacle detection, the proposed algorithm uses the inverse perspective mapping (IPM) method. This method is much more advantageous when the camera is not high off the floor, which makes point tracking near the floor difficult. Markov random field-based obstacle segmentation is then performed using the IPM results and a floor appearance model. Next, the shortest distance between the robot and the obstacle is calculated. The algorithm is tested by applying it to 70 datasets, 20 of which include nonobstacle images where considerable changes in floor appearance occur. The obstacle segmentation accuracies and the distance estimation error are quantitatively analyzed. For obstacle datasets, the segmentation precision and the average distance estimation error of the proposed method are 81.4% and 1.6 cm, respectively, whereas those for a conventional method are 57.5% and 9.9 cm, respectively. For nonobstacle datasets, the proposed method gives 0.0% false positive rates, while the conventional method gives 17.6%. PMID:26938540

Clogging and jamming transitions in periodic obstacle arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Hong; Reichhardt, Charles; Olson Reichhardt, Cynthia Jane

2017-03-29

We numerically examine clogging transitions for bidisperse disks flowing through a two-dimensional periodic obstacle array. Here, we show that clogging is a probabilistic event that occurs through a transition from a homogeneous flowing state to a heterogeneous or phase-separated jammed state where the disks form dense connected clusters. The probability for clogging to occur during a fixed time increases with increasing particle packing and obstacle number. For driving at different angles with respect to the symmetry direction of the obstacle array, we show that certain directions have a higher clogging susceptibility. It is also possible to have a size-specific cloggingmore » transition in which one disk size becomes completely immobile while the other disk size continues to flow.« less

Safe Maritime Navigation with COLREGS Using Velocity Obstacles

NASA Technical Reports Server (NTRS)

Kuwata, Yoshiaki; Wolf, Michael T.; Zarzhitsky, Dimitri; Huntsberger, Terrance L.

2011-01-01

This paper presents a motion planning algorithm for Unmanned Surface Vehicles (USVs) to navigate safely in dynamic, cluttered environments. The proposed algorithm not only addresses Hazard Avoidance (HA) for stationary and moving hazards but also applies the International Regulations for Preventing Collisions at Sea (known as COLREGs). The COLREG rules specify, for example, which vessel is responsible for giving way to the other and to which side of the "stand-on" vessel to maneuver. The three primary COLREG rules were considered in this paper: crossing, overtaking, and head-on situations. For USVs to be safely deployed in environments with other traffic boats, it is imperative that the USV's navigation algorithm obey COLREGs. Note also that if other boats disregard their responsibility under COLREGs, the USV will still apply its HA algorithms to avoid a collision. The proposed approach is based on Velocity Obstacles, which generates a cone-shaped obstacle in the velocity space. Because Velocity Obstacles also specify which side of the obstacle the vehicle will pass during the avoidance maneuver, COLREGs are encoded in the velocity space in a natural way. The algorithm is demonstrated via both simulation and on-water tests.

The effects of multiple obstacles on the locomotor behavior and performance of a terrestrial lizard.

PubMed

Parker, Seth E; McBrayer, Lance D

2016-04-01

Negotiation of variable terrain is important for many small terrestrial vertebrates. Variation in the running surface resulting from obstacles (woody debris, vegetation, rocks) can alter escape paths and running performance. The ability to navigate obstacles likely influences survivorship through predator evasion success and other key ecological tasks (finding mates, acquiring food). Earlier work established that running posture and sprint performance are altered when organisms face an obstacle, and yet studies involving multiple obstacles are limited. Indeed, some habitats are cluttered with obstacles, whereas others are not. For many species, obstacle density may be important in predator escape and/or colonization potential by conspecifics. This study examines how multiple obstacles influence running behavior and locomotor posture in lizards. We predict that an increasing number of obstacles will increase the frequency of pausing and decrease sprint velocity. Furthermore, bipedal running over multiple obstacles is predicted to maintain greater mean sprint velocity compared with quadrupedal running, thereby revealing a potential advantage of bipedalism. Lizards were filmed running through a racetrack with zero, one or two obstacles. Bipedal running posture over one obstacle was significantly faster than quadrupedal posture. Bipedal running trials contained fewer total strides than quadrupedal ones. But on addition of a second obstacle, the number of bipedal strides decreased. Increasing obstacle number led to slower and more intermittent locomotion. Bipedalism provided clear advantages for one obstacle, but was not associated with further benefits for an additional obstacle. Hence, bipedalism helps mitigate obstacle negotiation, but not when numerous obstacles are encountered in succession. © 2016. Published by The Company of Biologists Ltd.

Stochastic performance modeling and evaluation of obstacle detectability with imaging range sensors

NASA Technical Reports Server (NTRS)

Matthies, Larry; Grandjean, Pierrick

1993-01-01

Statistical modeling and evaluation of the performance of obstacle detection systems for Unmanned Ground Vehicles (UGVs) is essential for the design, evaluation, and comparison of sensor systems. In this report, we address this issue for imaging range sensors by dividing the evaluation problem into two levels: quality of the range data itself and quality of the obstacle detection algorithms applied to the range data. We review existing models of the quality of range data from stereo vision and AM-CW LADAR, then use these to derive a new model for the quality of a simple obstacle detection algorithm. This model predicts the probability of detecting obstacles and the probability of false alarms, as a function of the size and distance of the obstacle, the resolution of the sensor, and the level of noise in the range data. We evaluate these models experimentally using range data from stereo image pairs of a gravel road with known obstacles at several distances. The results show that the approach is a promising tool for predicting and evaluating the performance of obstacle detection with imaging range sensors.

Obstacle evasion in free-space optical communications utilizing Airy beams.

PubMed

Zhu, Guoxuan; Wen, Yuanhui; Wu, Xiong; Chen, Yujie; Liu, Jie; Yu, Siyuan

2018-03-15

A high speed free-space optical communication system capable of self-bending signal transmission around line-of-sight obstacles is proposed and demonstrated. Airy beams are generated and controlled to achieve different propagating trajectories, and the signal transmission characteristics of these beams around the obstacle are investigated. Our results confirm that, by optimizing their ballistic trajectories, Airy beams are able to bypass obstacles with more signal energy and thus improve the communication performance compared with normal Gaussian beams.

Obstacle evasion in free-space optical communications utilizing Airy beams

NASA Astrophysics Data System (ADS)

Zhu, Guoxuan; Wen, Yuanhui; Wu, Xiong; Chen, Yujie; Liu, Jie; Yu, Siyuan

2018-03-01

A high speed free-space optical communication system capable of self-bending signal transmission around line-of-sight obstacles is proposed and demonstrated. Airy beams are generated and controlled to achieve different propagating trajectories, and the signal transmission characteristics of these beams around the obstacle are investigated. Our results confirm that, by optimising their ballistic trajectories, Airy beams are able to bypass obstacles with more signal energy and thus improve the communication performance compared with normal Gaussian beams.

Longitudinal kinematic and kinetic adaptations to obstacle crossing in recent lower limb amputees.

PubMed

Barnett, Cleveland T; Polman, Remco C J; Vanicek, Natalie

2014-12-01

Obstacle crossing is an important activity of daily living, necessary to avoid tripping or falling, although it is not fully understood how transtibial amputees adapt to performing this activity of daily living following discharge from rehabilitation. The objective of this study was to investigate the longitudinal adaptations in obstacle crossing in transtibial amputees post-discharge from rehabilitation. Longitudinal repeated measures. Seven unilateral transtibial amputees crossed an obstacle 0.1m high positioned along a walkway while kinematic and kinetic data were recorded at 1, 3 and 6 months post-discharge. At 6 months post-discharge, walking velocity had increased (0.17 m.s(-1)) with most participants self-selecting an intact lead limb preference. During swing phase, peak knee flexion (p = 0.03) and peak knee power absorption (K4; p = 0.01) were greater with an intact versus affected lead limb preference. Having crossed the obstacle, intact limb peak ankle power generation in pre-swing (A2; p = 0.01) and knee power absorption (K3; p = 0.05) during stance phase were greater when compared to the affected limb. Obstacle crossing improved, although a greater reliance on intact limb function was highlighted. Results suggested that further improvements to locomotor performance may be obtained by increasing affected limb knee range of motion and concentric and eccentric strength of the knee extensors and flexors. The novel objective data from this study establish an understanding of how recent transtibial amputees adapt to performing obstacle crossing following discharge from rehabilitation. This allows for evidence-based clinical interventions to be developed, aimed at optimising biomechanical function, thus improving overall locomotor performance and perhaps subsequent quality of life. © The International Society for Prosthetics and Orthotics 2013.

Propagation of spiral waves pinned to circular and rectangular obstacles.

PubMed

Sutthiopad, Malee; Luengviriya, Jiraporn; Porjai, Porramain; Phantu, Metinee; Kanchanawarin, Jarin; Müller, Stefan C; Luengviriya, Chaiya

2015-05-01

We present an investigation of spiral waves pinned to circular and rectangular obstacles with different circumferences in both thin layers of the Belousov-Zhabotinsky reaction and numerical simulations with the Oregonator model. For circular objects, the area always increases with the circumference. In contrast, we varied the circumference of rectangles with equal areas by adjusting their width w and height h. For both obstacle forms, the propagating parameters (i.e., wavelength, wave period, and velocity of pinned spiral waves) increase with the circumference, regardless of the obstacle area. Despite these common features of the parameters, the forms of pinned spiral waves depend on the obstacle shapes. The structures of spiral waves pinned to circles as well as rectangles with the ratio w/h∼1 are similar to Archimedean spirals. When w/h increases, deformations of the spiral shapes are observed. For extremely thin rectangles with w/h≫1, these shapes can be constructed by employing semicircles with different radii which relate to the obstacle width and the core diameter of free spirals.

Virtual reality-based navigation task to reveal obstacle avoidance performance in individuals with visuospatial neglect.

PubMed

Aravind, Gayatri; Darekar, Anuja; Fung, Joyce; Lamontagne, Anouk

2015-03-01

Persons with post-stroke visuospatial neglect (VSN) often collide with moving obstacles while walking. It is not well understood whether the collisions occur as a result of attentional-perceptual deficits caused by VSN or due to post-stroke locomotor deficits. We assessed individuals with VSN on a seated, joystick-driven obstacle avoidance task, thus eliminating the influence of locomotion. Twelve participants with VSN were tested on obstacle detection and obstacle avoidance tasks in a virtual environment that included three obstacles approaching head-on or 30 (°) contralesionally/ipsilesionally. Our results indicate that in the detection task, the contralesional and head-on obstacles were detected at closer proximities compared to the ipsilesional obstacle. For the avoidance task collisions were observed only for the contralesional and head-on obstacle approaches. For the contralesional obstacle approach, participants initiated their avoidance strategies at smaller distances from the obstacle and maintained smaller minimum distances from the obstacles. The distance at detection showed a negative association with the distance at the onset of avoidance strategy for all three obstacle approaches. We conclusion the observation of collisions with contralesional and head-on obstacles, in the absence of locomotor burden, provides evidence that attentional-perceptual deficits due to VSN, independent of post-stroke locomotor deficits, alter obstacle avoidance abilities.

Through the eyes of a bird: modelling visually guided obstacle flight

PubMed Central

Lin, Huai-Ti; Ros, Ivo G.; Biewener, Andrew A.

2014-01-01

Various flight navigation strategies for birds have been identified at the large spatial scales of migratory and homing behaviours. However, relatively little is known about close-range obstacle negotiation through cluttered environments. To examine obstacle flight guidance, we tracked pigeons (Columba livia) flying through an artificial forest of vertical poles. Interestingly, pigeons adjusted their flight path only approximately 1.5 m from the forest entry, suggesting a reactive mode of path planning. Combining flight trajectories with obstacle pole positions, we reconstructed the visual experience of the pigeons throughout obstacle flights. Assuming proportional–derivative control with a constant delay, we searched the relevant parameter space of steering gains and visuomotor delays that best explained the observed steering. We found that a pigeon's steering resembles proportional control driven by the error angle between the flight direction and the desired opening, or gap, between obstacles. Using this pigeon steering controller, we simulated obstacle flights and showed that pigeons do not simply steer to the nearest opening in the direction of flight or destination. Pigeons bias their flight direction towards larger visual gaps when making fast steering decisions. The proposed behavioural modelling method converts the obstacle avoidance behaviour into a (piecewise) target-aiming behaviour, which is better defined and understood. This study demonstrates how such an approach decomposes open-loop free-flight behaviours into components that can be independently evaluated. PMID:24812052

Through the eyes of a bird: modelling visually guided obstacle flight.

PubMed

Lin, Huai-Ti; Ros, Ivo G; Biewener, Andrew A

2014-07-06

Various flight navigation strategies for birds have been identified at the large spatial scales of migratory and homing behaviours. However, relatively little is known about close-range obstacle negotiation through cluttered environments. To examine obstacle flight guidance, we tracked pigeons (Columba livia) flying through an artificial forest of vertical poles. Interestingly, pigeons adjusted their flight path only approximately 1.5 m from the forest entry, suggesting a reactive mode of path planning. Combining flight trajectories with obstacle pole positions, we reconstructed the visual experience of the pigeons throughout obstacle flights. Assuming proportional-derivative control with a constant delay, we searched the relevant parameter space of steering gains and visuomotor delays that best explained the observed steering. We found that a pigeon's steering resembles proportional control driven by the error angle between the flight direction and the desired opening, or gap, between obstacles. Using this pigeon steering controller, we simulated obstacle flights and showed that pigeons do not simply steer to the nearest opening in the direction of flight or destination. Pigeons bias their flight direction towards larger visual gaps when making fast steering decisions. The proposed behavioural modelling method converts the obstacle avoidance behaviour into a (piecewise) target-aiming behaviour, which is better defined and understood. This study demonstrates how such an approach decomposes open-loop free-flight behaviours into components that can be independently evaluated.

An assessment of auditory-guided locomotion in an obstacle circumvention task.

PubMed

Kolarik, Andrew J; Scarfe, Amy C; Moore, Brian C J; Pardhan, Shahina

2016-06-01

This study investigated how effectively audition can be used to guide navigation around an obstacle. Ten blindfolded normally sighted participants navigated around a 0.6 × 2 m obstacle while producing self-generated mouth click sounds. Objective movement performance was measured using a Vicon motion capture system. Performance with full vision without generating sound was used as a baseline for comparison. The obstacle's location was varied randomly from trial to trial: it was either straight ahead or 25 cm to the left or right relative to the participant. Although audition provided sufficient information to detect the obstacle and guide participants around it without collision in the majority of trials, buffer space (clearance between the shoulder and obstacle), overall movement times, and number of velocity corrections were significantly (p < 0.05) greater with auditory guidance than visual guidance. Collisions sometime occurred under auditory guidance, suggesting that audition did not always provide an accurate estimate of the space between the participant and obstacle. Unlike visual guidance, participants did not always walk around the side that afforded the most space during auditory guidance. Mean buffer space was 1.8 times higher under auditory than under visual guidance. Results suggest that sound can be used to generate buffer space when vision is unavailable, allowing navigation around an obstacle without collision in the majority of trials.

Functional Assessment of Problem Behavior: Dispelling Myths, Overcoming Implementation Obstacles, and Developing New Lore

PubMed Central

2012-01-01

Hundreds of studies have shown the efficacy of treatments for problem behavior based on an understanding of its function. Assertions regarding the legitimacy of different types of functional assessment vary substantially across published articles, and best practices regarding the functional assessment process are sometimes difficult to cull from the empirical literature or from published discussions of the behavioral assessment process. A number of myths regarding the functional assessment process, which appear to be pervasive within different behavior-analytic research and practice communities, will be reviewed in the context of an attempt to develop new lore regarding the functional assessment process. Frequently described obstacles to implementing a critical aspect of the functional assessment process, the functional analysis, will be reviewed in the context of solutions for overcoming them. Finally, the aspects of the functional assessment process that should be exported to others versus those features that should remain the sole technological property of behavior analysts will be discussed. PMID:23326630

Real-time obstacle avoidance using harmonic potential functions

NASA Technical Reports Server (NTRS)

Kim, Jin-Oh; Khosla, Pradeep K.

1992-01-01

This paper presents a new formulation of the artificial potential approach to the obstacle avoidance problem for a mobile robot or a manipulator in a known environment. Previous formulations of artificial potentials for obstacle avoidance have exhibited local minima in a cluttered environment. To build an artificial potential field, harmonic functions that completely eliminate local minima even for a cluttered environment are used. The panel method is employed to represent arbitrarily shaped obstacles and to derive the potential over the whole space. Based on this potential function, an elegant control strategy is proposed for the real-time control of a robot. The harmonic potential, the panel method, and the control strategy are tested with a bar-shaped mobile robot and a three-degree-of-freedom planar redundant manipulator.

A Real-Time Reaction Obstacle Avoidance Algorithm for Autonomous Underwater Vehicles in Unknown Environments.

PubMed

Yan, Zheping; Li, Jiyun; Zhang, Gengshi; Wu, Yi

2018-02-02

A novel real-time reaction obstacle avoidance algorithm (RRA) is proposed for autonomous underwater vehicles (AUVs) that must adapt to unknown complex terrains, based on forward looking sonar (FLS). To accomplish this algorithm, obstacle avoidance rules are planned, and the RRA processes are split into five steps Introduction only lists 4 so AUVs can rapidly respond to various environment obstacles. The largest polar angle algorithm (LPAA) is designed to change detected obstacle's irregular outline into a convex polygon, which simplifies the obstacle avoidance process. A solution is designed to solve the trapping problem existing in U-shape obstacle avoidance by an outline memory algorithm. Finally, simulations in three unknown obstacle scenes are carried out to demonstrate the performance of this algorithm, where the obtained obstacle avoidance trajectories are safety, smooth and near-optimal.

Numerical investigation on layout optimization of obstacles in a three-dimensional passive micromixer.

PubMed

Chen, Xueye; Zhao, Zhongyi

2017-04-29

This paper aims at layout optimization design of obstacles in a three-dimensional T-type micromixer. Numerical analysis shows that the direction of flow velocity change constantly due to the obstacles blocking, which produces the chaotic convection and increases species mixing effectively. The orthogonal experiment method was applied for determining the effects of some key parameters on mixing efficiency. The weights in the order are: height of obstacles > geometric shape > symmetry = number of obstacles. Based on the optimized results, a multi-units obstacle micromixer was designed. Compared with T-type micromixer, the multi-units obstacle micromixer is more efficient, and more than 90% mixing efficiency were obtained for a wide range of peclet numbers. It can be demonstrated that the presented optimal design method of obstacles layout in three-dimensional microchannels is a simple and effective technology to improve species mixing in microfluidic devices. The obstacles layout methodology has the potential for applications in chemical engineering and bioengineering. Copyright © 2017 Elsevier B.V. All rights reserved.

African-American Leaders in the Field of Science: A Template for Overcoming Obstacles

NASA Astrophysics Data System (ADS)

Schmidt, Waweise J.

The purpose of this phenomenological multi-case study and three-person interview, was to discover what select prominent African-American scientists perceived were obstacles to overcome to be successful leaders in their professional lives, and the opportunities that aided in their professional growth. Through the addition of the three-person interview, the researcher discovered commonalities between the perceived obstacles and opportunities of current science, technology, engineering and mathematics (STEM) professionals and the perceptions of selected historically prominent scientists. This study examined documents of the period and relics of prominent African-Americans who were in STEM fields and lived from 1860 to 1968. A description of the setting that influenced how the scientists perceived the phenomenon was written with the approach being anchored in the social constructivist tradition. Commonalities emerged through coding experiences of the individuals, which yielded patterns to help explain the phenomenon. By investigating their perceptions, insight was gained into understanding the attributes, tools and skills, and tailored experiences that encouraged Thomas Burton, Kelly Miller, George Carver, Daniel Williams, Matthew Henson, Ernest Just, Charles Drew, Percy Julian, William Cobb, and Benjamin Peery to achieve success in STEM fields between 1860 and 1968. The significance of the study is multifaceted: understanding the obstacles that African-American scientists had to overcome in their professional lives can result in the development of science educators who are better informed regarding the appropriate types of assistance that can be provided to aid their students in overcoming obstacles. This can hopefully increase their opportunities to succeed within the science field. This study can result in the development of science educators who are more sensitive in addressing the needs of the developing minority student, and can encourage, educate, and enlist

Obstacles using amorphous materials for volume applications

NASA Astrophysics Data System (ADS)

Kiessling, Albert; Reininger, Thomas

2012-10-01

This contribution is especially focussed on the attempt to use amorphous or nanocrystalline metals in position sensor applications and to describe the difficulties and obstacles encountered in coherence with the development of appropriate industrial high volume series products in conjunction with the related quality requirements. The main motivation to do these investigations was to beat the generally known sensors especially silicon based Hall-sensors as well as AMR- and GMR-sensors - well known from mobile phones and electronic storage devices like hard discs and others - in terms of cost-effectiveness and functionality.

Obstacle Recognition Based on Machine Learning for On-Chip LiDAR Sensors in a Cyber-Physical System

PubMed Central

Beruvides, Gerardo

2017-01-01

Collision avoidance is an important feature in advanced driver-assistance systems, aimed at providing correct, timely and reliable warnings before an imminent collision (with objects, vehicles, pedestrians, etc.). The obstacle recognition library is designed and implemented to address the design and evaluation of obstacle detection in a transportation cyber-physical system. The library is integrated into a co-simulation framework that is supported on the interaction between SCANeR software and Matlab/Simulink. From the best of the authors’ knowledge, two main contributions are reported in this paper. Firstly, the modelling and simulation of virtual on-chip light detection and ranging sensors in a cyber-physical system, for traffic scenarios, is presented. The cyber-physical system is designed and implemented in SCANeR. Secondly, three specific artificial intelligence-based methods for obstacle recognition libraries are also designed and applied using a sensory information database provided by SCANeR. The computational library has three methods for obstacle detection: a multi-layer perceptron neural network, a self-organization map and a support vector machine. Finally, a comparison among these methods under different weather conditions is presented, with very promising results in terms of accuracy. The best results are achieved using the multi-layer perceptron in sunny and foggy conditions, the support vector machine in rainy conditions and the self-organized map in snowy conditions. PMID:28906450

Obstacle Recognition Based on Machine Learning for On-Chip LiDAR Sensors in a Cyber-Physical System.

PubMed

Castaño, Fernando; Beruvides, Gerardo; Haber, Rodolfo E; Artuñedo, Antonio

2017-09-14

Collision avoidance is an important feature in advanced driver-assistance systems, aimed at providing correct, timely and reliable warnings before an imminent collision (with objects, vehicles, pedestrians, etc.). The obstacle recognition library is designed and implemented to address the design and evaluation of obstacle detection in a transportation cyber-physical system. The library is integrated into a co-simulation framework that is supported on the interaction between SCANeR software and Matlab/Simulink. From the best of the authors' knowledge, two main contributions are reported in this paper. Firstly, the modelling and simulation of virtual on-chip light detection and ranging sensors in a cyber-physical system, for traffic scenarios, is presented. The cyber-physical system is designed and implemented in SCANeR. Secondly, three specific artificial intelligence-based methods for obstacle recognition libraries are also designed and applied using a sensory information database provided by SCANeR. The computational library has three methods for obstacle detection: a multi-layer perceptron neural network, a self-organization map and a support vector machine. Finally, a comparison among these methods under different weather conditions is presented, with very promising results in terms of accuracy. The best results are achieved using the multi-layer perceptron in sunny and foggy conditions, the support vector machine in rainy conditions and the self-organized map in snowy conditions.

A game theory-based obstacle avoidance routing protocol for wireless sensor networks.

PubMed

Guan, Xin; Wu, Huayang; Bi, Shujun

2011-01-01

The obstacle avoidance problem in geographic forwarding is an important issue for location-based routing in wireless sensor networks. The presence of an obstacle leads to several geographic routing problems such as excessive energy consumption and data congestion. Obstacles are hard to avoid in realistic environments. To bypass obstacles, most routing protocols tend to forward packets along the obstacle boundaries. This leads to a situation where the nodes at the boundaries exhaust their energy rapidly and the obstacle area is diffused. In this paper, we introduce a novel routing algorithm to solve the obstacle problem in wireless sensor networks based on a game-theory model. Our algorithm forms a concave region that cannot forward packets to achieve the aim of improving the transmission success rate and decreasing packet transmission delays. We consider the residual energy, out-degree and forwarding angle to determine the forwarding probability and payoff function of forwarding candidates. This achieves the aim of load balance and reduces network energy consumption. Simulation results show that based on the average delivery delay, energy consumption and packet delivery ratio performances our protocol is superior to other traditional schemes.

Research on robot mobile obstacle avoidance control based on visual information

NASA Astrophysics Data System (ADS)

Jin, Jiang

2018-03-01

Robots to detect obstacles and control robots to avoid obstacles has been a key research topic of robot control. In this paper, a scheme of visual information acquisition is proposed. By judging visual information, the visual information is transformed into the information source of path processing. In accordance with the established route, in the process of encountering obstacles, the algorithm real-time adjustment trajectory to meet the purpose of intelligent control of mobile robots. Simulation results show that, through the integration of visual sensing information, the obstacle information is fully obtained, while the real-time and accuracy of the robot movement control is guaranteed.

Reply to ``Comment on `Free surface Hele-Shaw flows around an obstacle: A random walk simulation' ''

NASA Astrophysics Data System (ADS)

Bogoyavlenskiy, Vladislav A.; Cotts, Eric J.

2007-09-01

As pointed out by Vasconcelos in his Comment, our computer simulations of Hele-Shaw flows around series of wedges differ from analytical solutions existing for this problem. We attribute the discrepancy to the notion that these analytical solutions correspond to ideal, steady-state flow regimes which are hardly applicable when a rigid obstacle interacts with a moving liquid-gas interface.

Optimal layout design of obstacles for panic evacuation using differential evolution

NASA Astrophysics Data System (ADS)

Zhao, Yongxiang; Li, Meifang; Lu, Xin; Tian, Lijun; Yu, Zhiyong; Huang, Kai; Wang, Yana; Li, Ting

2017-01-01

To improve the pedestrian outflow in panic situations by suitably placing an obstacle in front of the exit, it is vital to understand the physical mechanism behind the evacuation efficiency enhancement. In this paper, a robust differential evolution is firstly employed to optimize the geometrical parameters of different shaped obstacles in order to achieve an optimal evacuation efficiency. Moreover, it is found that all the geometrical parameters of obstacles could markedly influence the evacuation efficiency of pedestrians, and the best way for achieving an optimal pedestrian outflow is to slightly shift the obstacle from the center of the exit which is consistent with findings of extant literature. Most importantly, by analyzing the profiles of density, velocity and specific flow, as well as the spatial distribution of crowd pressure, we have proven that placing an obstacle in panic situations does not reduce or absorb the pressure in the region of exit, on the contrary, promotes the pressure to a much higher level, hence the physical mechanism behind the evacuation efficiency enhancement is not a pressure decrease in the region of exit, but a significant reduction of high density region by effective separation in space which finally causes the increasing of escape speed and evacuation outflow. Finally, it is clearly demonstrated that the panel-like obstacle is considerably more robust and stable than the pillar-like obstacle to guarantee the enhancement of evacuation efficiency under different initial pedestrian distributions, different initial crowd densities as well as different desired velocities.

Gendered Obstacles Faced by Historical Women in Physics and Astronomy

NASA Astrophysics Data System (ADS)

Jones, Kristen M.

2007-12-01

A gender gap still exists in modern science; this is especially evident in the fields of physics and astronomy. The cause of such a gap is the center of debate. Is this discrepancy the result of inherent ability or socialization? Most studies have focused on modern issues and how women are socialized today. The role of historical gender perspectives and social opinions in creating the field of modern science and any discrepancies within it has not yet been explored in depth. This project investigates the obstacles faced by historical women in physics and astronomy that stem from the officialized gender biases that accompanied the establishment of modern science. Such obstacles are both formal and informal. Four women were chosen to span the three hundred year period between the standardization of the field and the modern day: Laura Bassi, Mary Somerville, Lise Meitner, and Jocelyn Bell Burnell. The investigation reveals that formal obstacles significantly decreased over the time period, while informal obstacles eroded more gradually. Obstacles also reflected historical events such as the World Wars and the Enlightenment. Trends in obstacles faced by four prominent women physicists indicate that education, finances, support networks, and social opinion played a large role in determining success in the field. The applicability to modern day physics issues and the gender gap is discussed. Many thanks to the Pathways Scholars Program and the Ronald E. McNair Post-Baccalaureate Achievement Program for funding for this project.

Bim-Based Indoor Path Planning Considering Obstacles

NASA Astrophysics Data System (ADS)

Xu, M.; Wei, S.; Zlatanova, S.; Zhang, R.

2017-09-01

At present, 87 % of people's activities are in indoor environment; indoor navigation has become a research issue. As the building structures for people's daily life are more and more complex, many obstacles influence humans' moving. Therefore it is essential to provide an accurate and efficient indoor path planning. Nowadays there are many challenges and problems in indoor navigation. Most existing path planning approaches are based on 2D plans, pay more attention to the geometric configuration of indoor space, often ignore rich semantic information of building components, and mostly consider simple indoor layout without taking into account the furniture. Addressing the above shortcomings, this paper uses BIM (IFC) as the input data and concentrates on indoor navigation considering obstacles in the multi-floor buildings. After geometric and semantic information are extracted, 2D and 3D space subdivision methods are adopted to build the indoor navigation network and to realize a path planning that avoids obstacles. The 3D space subdivision is based on triangular prism. The two approaches are verified by the experiments.

Obstacle avoidance system with sonar sensing and fuzzy logic

NASA Astrophysics Data System (ADS)

Chiang, Wen-chuan; Kelkar, Nikhal; Hall, Ernest L.

1997-09-01

Automated guided vehicles (AGVs) have many potential applications in manufacturing, medicine, space and defense. The purpose of this paper is to describe exploratory research on the design of an obstacle avoidance system using sonar sensors for a modular autonomous mobile robot controller. The advantages of a modular system are related to portability and the fact that any vehicle can become autonomous with minimal modifications. A mobile robot test-bed has been constructed using a golf cart base. The obstacle avoidance system is based on a micro-controller interfaced with multiple ultrasonic transducers. This micro-controller independently handles all timing and distance calculations and sends a distance measurement back to the computer via the serial line. This design yields a portable independent system. Testing of these systems has been done in the lab as well as on an outside test track with positive results that show that at five mph the vehicle can follow a line and at the same time avoid obstacles. This design, in its modularity, creates a portable autonomous obstacle avoidance controller applicable for any mobile vehicle with only minor adaptations.

Apparatus for obstacle traversion

DOEpatents

Borenstein, Johann

2004-08-10

An apparatus for traversing obstacles having an elongated, round, flexible body that includes a plurality of drive track assemblies. The plurality of drive track assemblies cooperate to provide forward propulsion wherever a propulsion member is in contact with any feature of the environment, regardless of how many or which ones of the plurality of drive track assemblies make contact with such environmental feature.

Obstacle Avoidance and Target Acquisition for Robot Navigation Using a Mixed Signal Analog/Digital Neuromorphic Processing System

PubMed Central

Milde, Moritz B.; Blum, Hermann; Dietmüller, Alexander; Sumislawska, Dora; Conradt, Jörg; Indiveri, Giacomo; Sandamirskaya, Yulia

2017-01-01

Neuromorphic hardware emulates dynamics of biological neural networks in electronic circuits offering an alternative to the von Neumann computing architecture that is low-power, inherently parallel, and event-driven. This hardware allows to implement neural-network based robotic controllers in an energy-efficient way with low latency, but requires solving the problem of device variability, characteristic for analog electronic circuits. In this work, we interfaced a mixed-signal analog-digital neuromorphic processor ROLLS to a neuromorphic dynamic vision sensor (DVS) mounted on a robotic vehicle and developed an autonomous neuromorphic agent that is able to perform neurally inspired obstacle-avoidance and target acquisition. We developed a neural network architecture that can cope with device variability and verified its robustness in different environmental situations, e.g., moving obstacles, moving target, clutter, and poor light conditions. We demonstrate how this network, combined with the properties of the DVS, allows the robot to avoid obstacles using a simple biologically-inspired dynamics. We also show how a Dynamic Neural Field for target acquisition can be implemented in spiking neuromorphic hardware. This work demonstrates an implementation of working obstacle avoidance and target acquisition using mixed signal analog/digital neuromorphic hardware. PMID:28747883

Obstacle Avoidance and Target Acquisition for Robot Navigation Using a Mixed Signal Analog/Digital Neuromorphic Processing System.

PubMed

Milde, Moritz B; Blum, Hermann; Dietmüller, Alexander; Sumislawska, Dora; Conradt, Jörg; Indiveri, Giacomo; Sandamirskaya, Yulia

2017-01-01

Neuromorphic hardware emulates dynamics of biological neural networks in electronic circuits offering an alternative to the von Neumann computing architecture that is low-power, inherently parallel, and event-driven. This hardware allows to implement neural-network based robotic controllers in an energy-efficient way with low latency, but requires solving the problem of device variability, characteristic for analog electronic circuits. In this work, we interfaced a mixed-signal analog-digital neuromorphic processor ROLLS to a neuromorphic dynamic vision sensor (DVS) mounted on a robotic vehicle and developed an autonomous neuromorphic agent that is able to perform neurally inspired obstacle-avoidance and target acquisition. We developed a neural network architecture that can cope with device variability and verified its robustness in different environmental situations, e.g., moving obstacles, moving target, clutter, and poor light conditions. We demonstrate how this network, combined with the properties of the DVS, allows the robot to avoid obstacles using a simple biologically-inspired dynamics. We also show how a Dynamic Neural Field for target acquisition can be implemented in spiking neuromorphic hardware. This work demonstrates an implementation of working obstacle avoidance and target acquisition using mixed signal analog/digital neuromorphic hardware.

[Obstacles perceived by nurses for evidence-based practice: a qualitative study].

PubMed

Sánchez-García, Inmaculada; López-Medina, Isabel M; Pancorbo-Hidalgo, Pedro L

2013-01-01

To examine the obstacles perceived by nurses to implement an evidence-based clinical practice. A qualitative study through semi-structured interviews conducted in 2010-2011 including 11 nurses purposively selected from public hospitals and community centres in Jaén and Córdoba (Spain). A content analysis was performed, using Miles and Huberman as a reference and comprising the following steps: data reduction, data presentation, and data conclusion/verification. Data saturation was reached in these categories (obstacles). The obstacles perceived by nurses to introduce an evidence-based clinical practice (EBCP) were grouped into 3 major categories: obstacles related with professionals (routine-based practice, unwilling and stagnant attitudes, and lack of training in EBCP), obstacles related to the social context (reluctance from other professionals and from patients or families), and obstacles related to the organization (obsolete cultures that do not promote innovation in nursing care). This study highlights the persistence of various factors that hinder the use of research findings in clinical practice. The results underline the need to change the culture of healthcare organizations, to motivate professionals, and to break some of the resistance attitudes that hinder the implementation of evidence-based practice. Copyright © 2012 Elsevier España, S.L. All rights reserved.

Generation of spiral waves pinned to obstacles in a simulated excitable system

NASA Astrophysics Data System (ADS)

Phantu, Metinee; Kumchaiseemak, Nakorn; Porjai, Porramain; Sutthiopad, Malee; Müller, Stefan C.; Luengviriya, Chaiya; Luengviriya, Jiraporn

2017-09-01

Pinning phenomena emerge in many dynamical systems. They are found to stabilize extreme conditions such as superconductivity and super fluidity. The dynamics of pinned spiral waves, whose tips trace the boundary of obstacles, also play an important role in the human health. In heart, such pinned waves cause longer tachycardia. In this article, we present two methods for generating pinned spiral waves in a simulated excitable system. In method A, an obstacle is set in the system prior to an ignition of a spiral wave. This method may be suitable only for the case of large obstacles since it often fails when used for small obstacles. In method B, a spiral wave is generated before an obstacle is placed at the spiral tip. With this method, a pinned spiral wave is always obtained, regardless the obstacle size. We demonstrate that after a transient interval the dynamics of the pinned spiral waves generated by the methods A and B are identical. The initiation of pinned spiral waves in both two- and three-dimensional systems is illustrated.

Trust-based learning and behaviors for convoy obstacle avoidance

NASA Astrophysics Data System (ADS)

Mikulski, Dariusz G.; Karlsen, Robert E.

2015-05-01

In many multi-agent systems, robots within the same team are regarded as being fully trustworthy for cooperative tasks. However, the assumption of trustworthiness is not always justified, which may not only increase the risk of mission failure, but also endanger the lives of friendly forces. In prior work, we addressed this issue by using RoboTrust to dynamically adjust to observed behaviors or recommendations in order to mitigate the risks of illegitimate behaviors. However, in the simulations in prior work, all members of the convoy had knowledge of the convoy goal. In this paper, only the lead vehicle has knowledge of the convoy goals and the follow vehicles must infer trustworthiness strictly from lead vehicle performance. In addition, RoboTrust could only respond to observed performance and did not dynamically learn agent behavior. In this paper, we incorporate an adaptive agent-specific bias into the RoboTrust algorithm that modifies its trust dynamics. This bias is learned incrementally from agent interactions, allowing good agents to benefit from faster trust growth and slower trust decay and bad agents to be penalized with slower trust growth and faster trust decay. We then integrate this new trust model into a trust-based controller for decentralized autonomous convoy operations. We evaluate its performance in an obstacle avoidance mission, where the convoy attempts to learn the best speed and following distances combinations for an acceptable obstacle avoidance probability.

The opportunities and obstacles in developing a vascular birthmark database for clinical and research use.

PubMed

Sharma, Vishal K; Fraulin, Frankie Og; Harrop, A Robertson; McPhalen, Donald F

2011-01-01

Databases are useful tools in clinical settings. The authors review the benefits and challenges associated with the development and implementation of an efficient electronic database for the multidisciplinary Vascular Birthmark Clinic at the Alberta Children's Hospital, Calgary, Alberta. The content and structure of the database were designed using the technical expertise of a data analyst from the Calgary Health Region. Relevant clinical and demographic data fields were included with the goal of documenting ongoing care of individual patients, and facilitating future epidemiological studies of this patient population. After completion of this database, 10 challenges encountered during development were retrospectively identified. Practical solutions for these challenges are presented. THE CHALLENGES IDENTIFIED DURING THE DATABASE DEVELOPMENT PROCESS INCLUDED: identification of relevant data fields; balancing simplicity and user-friendliness with complexity and comprehensive data storage; database expertise versus clinical expertise; software platform selection; linkage of data from the previous spreadsheet to a new data management system; ethics approval for the development of the database and its utilization for research studies; ensuring privacy and limited access to the database; integration of digital photographs into the database; adoption of the database by support staff in the clinic; and maintaining up-to-date entries in the database. There are several challenges involved in the development of a useful and efficient clinical database. Awareness of these potential obstacles, in advance, may simplify the development of clinical databases by others in various surgical settings.

A Real-Time Reaction Obstacle Avoidance Algorithm for Autonomous Underwater Vehicles in Unknown Environments

PubMed Central

Yan, Zheping; Li, Jiyun; Zhang, Gengshi; Wu, Yi

2018-01-01

A novel real-time reaction obstacle avoidance algorithm (RRA) is proposed for autonomous underwater vehicles (AUVs) that must adapt to unknown complex terrains, based on forward looking sonar (FLS). To accomplish this algorithm, obstacle avoidance rules are planned, and the RRA processes are split into five steps Introduction only lists 4 so AUVs can rapidly respond to various environment obstacles. The largest polar angle algorithm (LPAA) is designed to change detected obstacle’s irregular outline into a convex polygon, which simplifies the obstacle avoidance process. A solution is designed to solve the trapping problem existing in U-shape obstacle avoidance by an outline memory algorithm. Finally, simulations in three unknown obstacle scenes are carried out to demonstrate the performance of this algorithm, where the obtained obstacle avoidance trajectories are safety, smooth and near-optimal. PMID:29393915

Prediction of air blast mitigation in an array of rigid obstacles using smoothed particle hydrodynamics

NASA Astrophysics Data System (ADS)

Prasanna Kumar, S. S.; Patnaik, B. S. V.; Ramamurthi, K.

2018-04-01

The mitigation of blast waves propagating in air and interacting with rigid barriers and obstacles is numerically investigated using the mesh-free smoothed particle hydrodynamics method. A novel virtual boundary particle procedure with a skewed gradient wall boundary treatment is applied at the interfaces between air and rigid bodies. This procedure is validated with closed-form solutions for strong and weak shock reflection from rigid surfaces, supersonic flows over a wedge, formation of reflected, transverse, and Mach stem shocks, and also earlier experiments on interaction of a blast wave with concrete blocks. The mitigation of the overpressure and impulse transmitted to the protected structure due to an array of rigid obstacles of different shapes placed in the path of the blast wave is thereafter determined and discussed in the context of the existing experimental and numerical studies. It is shown that blockages having the shape of a right facing triangle or square placed in tandem or staggered provide better mitigation. The influence of the distance between the blockage array and protected structure is assessed, and the incorporation of a gap in the blockages is shown to improve the mitigation. The mechanisms responsible for the attenuation of air blast are identified through the simulations.

Research on Collection System Optimal Design of Wind Farm with Obstacles

NASA Astrophysics Data System (ADS)

Huang, W.; Yan, B. Y.; Tan, R. S.; Liu, L. F.

2017-05-01

To the collection system optimal design of offshore wind farm, the factors considered are not only the reasonable configuration of the cable and switch, but also the influence of the obstacles on the topology design of the offshore wind farm. This paper presents a concrete topology optimization algorithm with obstacles. The minimal area rectangle encasing box of the obstacle is obtained by using the method of minimal area encasing box. Then the optimization algorithm combining the advantages of Dijkstra algorithm and Prim algorithm is used to gain the scheme of avoidance obstacle path planning. Finally a fuzzy comprehensive evaluation model based on the analytic hierarchy process is constructed to compare the performance of the different topologies. Case studies demonstrate the feasibility of the proposed algorithm and model.

Particle Filtering for Obstacle Tracking in UAS Sense and Avoid Applications

PubMed Central

Moccia, Antonio

2014-01-01

Obstacle detection and tracking is a key function for UAS sense and avoid applications. In fact, obstacles in the flight path must be detected and tracked in an accurate and timely manner in order to execute a collision avoidance maneuver in case of collision threat. The most important parameter for the assessment of a collision risk is the Distance at Closest Point of Approach, that is, the predicted minimum distance between own aircraft and intruder for assigned current position and speed. Since assessed methodologies can cause some loss of accuracy due to nonlinearities, advanced filtering methodologies, such as particle filters, can provide more accurate estimates of the target state in case of nonlinear problems, thus improving system performance in terms of collision risk estimation. The paper focuses on algorithm development and performance evaluation for an obstacle tracking system based on a particle filter. The particle filter algorithm was tested in off-line simulations based on data gathered during flight tests. In particular, radar-based tracking was considered in order to evaluate the impact of particle filtering in a single sensor framework. The analysis shows some accuracy improvements in the estimation of Distance at Closest Point of Approach, thus reducing the delay in collision detection. PMID:25105154

Counteracting Obstacles with Optimistic Predictions

ERIC Educational Resources Information Center

Zhang, Ying; Fishbach, Ayelet

2010-01-01

This research tested for counteractive optimism: a self-control strategy of generating optimistic predictions of future goal attainment in order to overcome anticipated obstacles in goal pursuit. In support of the counteractive optimism model, participants in 5 studies predicted better performance, more time invested in goal activities, and lower…

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection

ERIC Educational Resources Information Center

Thagard, Paul; Findlay, Scott

2010-01-01

Darwin's theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper discusses the major psychological obstacles to accepting Darwin's theory. Cognitive obstacles to adopting evolution by natural selection include conceptual difficulties, methodological issues, and coherence problems that…

Nonlinear water waves generated by impulsive motion of submerged obstacle

NASA Astrophysics Data System (ADS)

Makarenko, N.; Kostikov, V.

2012-04-01

The fully nonlinear problem on generation of unsteady water waves by impulsively moving obstacle is studied analytically. The method involves the reduction of basic Euler equations to the integral-differential system for the wave elevation together with normal and tangential fluid velocities at the free surface. Exact model equations are derived in explicit form when the isolated obstacle is presented by totally submerged circular- or elliptic cylinder. Small-time asymptotic solution is constructed for the cylinder which starts moving with constant acceleration from rest. It is demonstrated that the leading-order solution terms describe several wave regimes such as the formation of non-stationary splash jets by vertical rising or vertical submersion of the obstacle, as well as the generation of diverging waves by horizontal- and combined motion of the obstacle under free surface. This work was supported by RFBR (grant No 10-01-00447) and by Research Program of the Russian Government (grant No 11.G34.31.0035).

Wide-Baseline Stereo-Based Obstacle Mapping for Unmanned Surface Vehicles

PubMed Central

Mou, Xiaozheng; Wang, Han

2018-01-01

This paper proposes a wide-baseline stereo-based static obstacle mapping approach for unmanned surface vehicles (USVs). The proposed approach eliminates the complicated calibration work and the bulky rig in our previous binocular stereo system, and raises the ranging ability from 500 to 1000 m with a even larger baseline obtained from the motion of USVs. Integrating a monocular camera with GPS and compass information in this proposed system, the world locations of the detected static obstacles are reconstructed while the USV is traveling, and an obstacle map is then built. To achieve more accurate and robust performance, multiple pairs of frames are leveraged to synthesize the final reconstruction results in a weighting model. Experimental results based on our own dataset demonstrate the high efficiency of our system. To the best of our knowledge, we are the first to address the task of wide-baseline stereo-based obstacle mapping in a maritime environment. PMID:29617293

Detection of Obstacles in Monocular Image Sequences

NASA Technical Reports Server (NTRS)

Kasturi, Rangachar; Camps, Octavia

1997-01-01

The ability to detect and locate runways/taxiways and obstacles in images captured using on-board sensors is an essential first step in the automation of low-altitude flight, landing, takeoff, and taxiing phase of aircraft navigation. Automation of these functions under different weather and lighting situations, can be facilitated by using sensors of different modalities. An aircraft-based Synthetic Vision System (SVS), with sensors of different modalities mounted on-board, complements the current ground-based systems in functions such as detection and prevention of potential runway collisions, airport surface navigation, and landing and takeoff in all weather conditions. In this report, we address the problem of detection of objects in monocular image sequences obtained from two types of sensors, a Passive Millimeter Wave (PMMW) sensor and a video camera mounted on-board a landing aircraft. Since the sensors differ in their spatial resolution, and the quality of the images obtained using these sensors is not the same, different approaches are used for detecting obstacles depending on the sensor type. These approaches are described separately in two parts of this report. The goal of the first part of the report is to develop a method for detecting runways/taxiways and objects on the runway in a sequence of images obtained from a moving PMMW sensor. Since the sensor resolution is low and the image quality is very poor, we propose a model-based approach for detecting runways/taxiways. We use the approximate runway model and the position information of the camera provided by the Global Positioning System (GPS) to define regions of interest in the image plane to search for the image features corresponding to the runway markers. Once the runway region is identified, we use histogram-based thresholding to detect obstacles on the runway and regions outside the runway. This algorithm is tested using image sequences simulated from a single real PMMW image.

Identifying and Overcoming Obstacles to Point-of-Care Data Collection for Eye Care Professionals

PubMed Central

Lobach, David F.; Silvey, Garry M.; Macri, Jennifer M.; Hunt, Megan; Kacmaz, Roje O.; Lee, Paul P.

2005-01-01

Supporting data entry by clinicians is considered one of the greatest challenges in implementing electronic health records. In this paper we describe a formative evaluation study using three different methodologies through which we identified obstacles to point-of-care data entry for eye care and then used the formative process to develop and test solutions to overcome these obstacles. The greatest obstacles were supporting free text annotation of clinical observations and accommodating the creation of detailed diagrams in multiple colors. To support free text entry, we arrived at an approach that captures an image of a free text note and associates this image with related data elements in an encounter note. The detailed diagrams included a color pallet that allowed changing pen color with a single stroke and also captured the diagrams as an image associated with related data elements. During observed sessions with simulated patients, these approaches satisfied the clinicians’ documentation needs by capturing the full range of clinical complexity that arises in practice. PMID:16779083

Antigenic variability: Obstacles on the road to vaccines against traditionally difficult targets.

PubMed

Servín-Blanco, R; Zamora-Alvarado, R; Gevorkian, G; Manoutcharian, K

2016-10-02

Despite the impressive impact of vaccines on public health, the success of vaccines targeting many important pathogens and cancers has to date been limited. The burden of infectious diseases today is mainly caused by antigenically variable pathogens (AVPs), which escape immune responses induced by prior infection or vaccination through changes in molecular structures recognized by antibodies or T cells. Extensive genetic and antigenic variability is the major obstacle for the development of new or improved vaccines against "difficult" targets. Alternative, qualitatively new approaches leading to the generation of disease- and patient-specific vaccine immunogens that incorporate complex permanently changing epitope landscapes of intended targets accompanied by appropriate immunomodulators are urgently needed. In this review, we highlight some of the most critical common issues related to the development of vaccines against many pathogens and cancers that escape protective immune responses owing to antigenic variation, and discuss recent efforts to overcome the obstacles by applying alternative approaches for the rational design of new types of immunogens.

Restoring the order: gender segregation as an obstacle to organisational development.

PubMed

Abrahamsson, Lena

2002-11-01

This paper raises questions about the links between gender and organisational changes. The empirical base for the discussion is a qualitative study of the effects of organisational changes in the pulp and paper industry, the electronics industry, the food industry and the laundry industry in Sweden during the mid-1990s. At the studied companies, restoration responses in the work organisations brought the organisation back into its original form and function. The study shows that gender exerts an influence both on the existing work organisation and in the organisational change. The modern organisation, with its focus on integration and decentralisation, challenges the gender order, which is a strong system, built on segregation and hierarchy. The conclusion from the study is that gender segregating and stereotypic gender-coding of workplaces and work tasks were strong restoring mechanisms and obstacles to strategic organisational changes.

On the debate about teleology in biology: the notion of "teleological obstacle".

PubMed

Ribeiro, Manuel Gustavo Leitão; Larentis, Ariane Leites; Caldas, Lúcio Ayres; Garcia, Tomás Coelho; Terra, Letícia Labati; Herbst, Marcelo Hawrylak; Almeida, Rodrigo Volcan

2015-12-01

Among the epistemological obstacles described by Gaston Bachelard, we contend that unitary and pragmatic knowledge is correlated to the teleological categories of Ernst Mayr and is the basis for prevailing debate on the notion of "function" in biology. Given the proximity of the aspects highlighted by these authors, we propose to associate the role of teleological thinking in biology and the notion of unitary and pragmatic knowledge as an obstacle to scientific knowledge. Thus, teleological thinking persists acting as an epistemological obstacle in biology, according to Bachelardian terminology. Our investigation led us to formulate the "teleological obstacle," which we consider important for the future of biology and possibly other sciences.

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection

NASA Astrophysics Data System (ADS)

Thagard, Paul; Findlay, Scott

2010-06-01

Darwin’s theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper discusses the major psychological obstacles to accepting Darwin’s theory. Cognitive obstacles to adopting evolution by natural selection include conceptual difficulties, methodological issues, and coherence problems that derive from the intuitiveness of alternative theories. The main emotional obstacles to accepting evolution are its apparent conflict with valued beliefs about God, souls, and morality. We draw on the philosophy of science and on a psychological theory of cognitive and emotional belief revision to make suggestions about what can be done to improve acceptance of Darwinian ideas.

A novel artificial immune algorithm for spatial clustering with obstacle constraint and its applications.

PubMed

Sun, Liping; Luo, Yonglong; Ding, Xintao; Zhang, Ji

2014-01-01

An important component of a spatial clustering algorithm is the distance measure between sample points in object space. In this paper, the traditional Euclidean distance measure is replaced with innovative obstacle distance measure for spatial clustering under obstacle constraints. Firstly, we present a path searching algorithm to approximate the obstacle distance between two points for dealing with obstacles and facilitators. Taking obstacle distance as similarity metric, we subsequently propose the artificial immune clustering with obstacle entity (AICOE) algorithm for clustering spatial point data in the presence of obstacles and facilitators. Finally, the paper presents a comparative analysis of AICOE algorithm and the classical clustering algorithms. Our clustering model based on artificial immune system is also applied to the case of public facility location problem in order to establish the practical applicability of our approach. By using the clone selection principle and updating the cluster centers based on the elite antibodies, the AICOE algorithm is able to achieve the global optimum and better clustering effect.

A method of real-time detection for distant moving obstacles by monocular vision

NASA Astrophysics Data System (ADS)

Jia, Bao-zhi; Zhu, Ming

2013-12-01

In this paper, we propose an approach for detection of distant moving obstacles like cars and bicycles by a monocular camera to cooperate with ultrasonic sensors in low-cost condition. We are aiming at detecting distant obstacles that move toward our autonomous navigation car in order to give alarm and keep away from them. Method of frame differencing is applied to find obstacles after compensation of camera's ego-motion. Meanwhile, each obstacle is separated from others in an independent area and given a confidence level to indicate whether it is coming closer. The results on an open dataset and our own autonomous navigation car have proved that the method is effective for detection of distant moving obstacles in real-time.

Cognitive Activities in Solving Mathematical Tasks: The Role of a Cognitive Obstacle

ERIC Educational Resources Information Center

Antonijevic, Radovan

2016-01-01

In the process of learning mathematics, students practice various forms of thinking activities aimed to substantially contribute to the development of their different cognitive structures. In this paper, the subject matter is a "cognitive obstacle", a phenomenon that occurs in the procedures of solving mathematical tasks. Each task in…

Does physical exercise improve obstacle negotiation in the elderly? A systematic review.

PubMed

Guadagnin, Eliane C; da Rocha, Emmanuel S; Duysens, Jacques; Carpes, Felipe P

2016-01-01

Physical exercise improves walking in the elderly but much less is known about its effect on more challenged gait, such as obstacle negotiation. We conducted a systematic review to discuss the effects of regular physical exercise on kinematics and kinetics of obstacle negotiation in the elderly. A comprehensive literature search revealed 859 citations for review, whereof 206 studies entered the full-text analysis. After application of inclusion and exclusion criteria, 13 studies were included in this systematic review. Most of them presented a reasonable quality (average 0.68) but none of them reached the level of a randomized control trial. Interventions were heterogeneous, with training periods lasting from 5 days to 10 months. Studies assessed obstacle negotiation basically considering 3 types of testing paradigm, namely a walkway with either a single obstacle crossing, or with multiple obstacles, or else a treadmill with an obstacle avoidance task under time pressure. In general, longer training programs had better results and very short ones were not effective. A weekly frequency of 2-3 times was the most common among the studies showing positive effects. Regardless of exercises types performed, most of them were effective and so far, there is no consensus about the best exercise for improving obstacle negotiation. A lack of studies on this topic still is evident. Including a record of fall score can further help in deciding which programs are to be preferred. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Obstacle Crossing Differences Between Blind and Blindfolded Subjects After Haptic Exploration.

PubMed

Forner-Cordero, Arturo; Garcia, Valéria D; Rodrigues, Sérgio T; Duysens, Jacques

2016-01-01

Little is known about the ability of blind people to cross obstacles after they have explored haptically their size and position. Long-term absence of vision may affect spatial cognition in the blind while their extensive experience with the use of haptic information for guidance may lead to compensation strategies. Seven blind and 7 sighted participants (with vision available and blindfolded) walked along a flat pathway and crossed an obstacle after a haptic exploration. Blind and blindfolded subjects used different strategies to cross the obstacle. After the first 20 trials the blindfolded subjects reduced the distance between the foot and the obstacle at the toe-off instant, while the blind behaved as the subjects with full vision. Blind and blindfolded participants showed larger foot clearance than participants with vision. At foot landing the hip was more behind the foot in the blindfolded condition, while there were no differences between the blind and the vision conditions. For several parameters of the obstacle crossing task, blind people were more similar to subjects with full vision indicating that the blind subjects were able to compensate for the lack of vision.

Assisting the visually impaired: obstacle detection and warning system by acoustic feedback.

PubMed

Rodríguez, Alberto; Yebes, J Javier; Alcantarilla, Pablo F; Bergasa, Luis M; Almazán, Javier; Cela, Andrés

2012-12-17

The aim of this article is focused on the design of an obstacle detection system for assisting visually impaired people. A dense disparity map is computed from the images of a stereo camera carried by the user. By using the dense disparity map, potential obstacles can be detected in 3D in indoor and outdoor scenarios. A ground plane estimation algorithm based on RANSAC plus filtering techniques allows the robust detection of the ground in every frame. A polar grid representation is proposed to account for the potential obstacles in the scene. The design is completed with acoustic feedback to assist visually impaired users while approaching obstacles. Beep sounds with different frequencies and repetitions inform the user about the presence of obstacles. Audio bone conducting technology is employed to play these sounds without interrupting the visually impaired user from hearing other important sounds from its local environment. A user study participated by four visually impaired volunteers supports the proposed system.

Assisting the Visually Impaired: Obstacle Detection and Warning System by Acoustic Feedback

PubMed Central

Rodríguez, Alberto; Yebes, J. Javier; Alcantarilla, Pablo F.; Bergasa, Luis M.; Almazán, Javier; Cela, Andrés

2012-01-01

The aim of this article is focused on the design of an obstacle detection system for assisting visually impaired people. A dense disparity map is computed from the images of a stereo camera carried by the user. By using the dense disparity map, potential obstacles can be detected in 3D in indoor and outdoor scenarios. A ground plane estimation algorithm based on RANSAC plus filtering techniques allows the robust detection of the ground in every frame. A polar grid representation is proposed to account for the potential obstacles in the scene. The design is completed with acoustic feedback to assist visually impaired users while approaching obstacles. Beep sounds with different frequencies and repetitions inform the user about the presence of obstacles. Audio bone conducting technology is employed to play these sounds without interrupting the visually impaired user from hearing other important sounds from its local environment. A user study participated by four visually impaired volunteers supports the proposed system. PMID:23247413

Automated Analysis of Fluorescence Microscopy Images to Identify Protein-Protein Interactions

DOE PAGES

Venkatraman, S.; Doktycz, M. J.; Qi, H.; ...

2006-01-01

The identification of protein interactions is important for elucidating biological networks. One obstacle in comprehensive interaction studies is the analyses of large datasets, particularly those containing images. Development of an automated system to analyze an image-based protein interaction dataset is needed. Such an analysis system is described here, to automatically extract features from fluorescence microscopy images obtained from a bacterial protein interaction assay. These features are used to relay quantitative values that aid in the automated scoring of positive interactions. Experimental observations indicate that identifying at least 50% positive cells in an image is sufficient to detect a protein interaction.more » Based on this criterion, the automated system presents 100% accuracy in detecting positive interactions for a dataset of 16 images. Algorithms were implemented using MATLAB and the software developed is available on request from the authors.« less

[Educational obstacles in the everyday living of the nurse teacher's pedagogical practice].

PubMed

Rodrigues, Malvina Thaís Pacheco; Mendes Sobrinho, José Augusto de Carvalho

2008-01-01

University teaching emerges as a theme frequently discussed in the educational scene. This article aims to investigate the educational obstacles emerging in the everyday living of the pedagogical practice of the nurse teacher from the Nursing Graduation Course at UEPSI, wishing to subsidize the elaboration of proposals for overcoming of these obstacles. It is a study of qualitative approach with data collection, questionnaire and semi-structured interview and data analysis through content analysis. According to the analysis, it is clear that the educational obstacles relate to the teacher person, to the students and to the institution. Thus, an establishment of a continuing education program in the action-reflection-action perspective is proposed as a way of overcoming the obstacles.

3D-Sonification for Obstacle Avoidance in Brownout Conditions

NASA Technical Reports Server (NTRS)

Godfroy-Cooper, M.; Miller, J. D.; Szoboszlay, Z.; Wenzel, E. M.

2017-01-01

Helicopter brownout is a phenomenon that occurs when making landing approaches in dusty environments, whereby sand or dust particles become swept up in the rotor outwash. Brownout is characterized by partial or total obscuration of the terrain, which degrades visual cues necessary for hovering and safe landing. Furthermore, the motion of the dust cloud produced during brownout can lead to the pilot experiencing motion cue anomalies such as vection illusions. In this context, the stability and guidance control functions can be intermittently or continuously degraded, potentially leading to undetected surface hazards and obstacles as well as unnoticed drift. Safe and controlled landing in brownout can be achieved using an integrated presentation of LADAR and RADAR imagery and aircraft state symbology. However, though detected by the LADAR and displayed on the sensor image, small obstacles can be difficult to discern from the background so that changes in obstacle elevation may go unnoticed. Moreover, pilot workload associated with tracking the displayed symbology is often so high that the pilot cannot give sufficient attention to the LADAR/RADAR image. This paper documents a simulation evaluating the use of 3D auditory cueing for obstacle avoidance in brownout as a replacement for or compliment to LADAR/RADAR imagery.

Virtual obstacle crossing: Reliability and differences in stroke survivors who prospectively experienced falls or no falls.

PubMed

Punt, Michiel; Bruijn, Sjoerd M; Wittink, Harriet; van de Port, Ingrid G; Wubbels, Gijs; van Dieën, Jaap H

2017-10-01

Stroke survivors often fall during walking. To reduce fall risk, gait testing and training with avoidance of virtual obstacles is gaining popularity. However, it is unknown whether and how virtual obstacle crossing is associated with fall risk. The present study assessed whether obstacle crossing characteristics are reliable and assessed differences in stroke survivors who prospectively experienced falls or no falls. We recruited twenty-nine community dwelling chronic stroke survivors. Participants crossed five virtual obstacles with increasing lengths. After a break, the test was repeated to assess test-retest reliability. For each obstacle length and trial, we determined; success rate, leading limb preference, pre and post obstacle distance, margins of stability, toe clearance, and crossing step length and speed. Subsequently, fall incidence was monitored using a fall calendar and monthly phone calls over a six-month period. Test-retest reliability was poor, but improved with increasing obstacle-length. Twelve participants reported at least one fall. No association of fall incidence with any of the obstacle crossing characteristics was found. Given the absence of height of the virtual obstacles, obstacle avoidance may have been relatively easy, allowing participants to cross obstacles in multiple ways, increasing variability of crossing characteristics and reducing the association with fall risk. These finding cast some doubt on current protocols for testing and training of obstacle avoidance in stroke rehabilitation. Copyright © 2017 Elsevier B.V. All rights reserved.

Overcoming obstacles to implementation: addressing political, institutional and behavioral problems in earthquake hazard mitigation policies

NASA Astrophysics Data System (ADS)

Alesch, Daniel J.; Petak, William J.

2002-06-01

This project is aimed at bridging the three planes, from basic research, through enabling processes, to engineered systems. At the basic research plane, we have been working to improve our collective understanding about obstacles to implementing mitigation practices, owner decision processes (in connection with other MCEER projects), and public policy processes. At the level of enabling processes, we have been seeking to develop an understanding of how obstacles to greater mitigation can be overcome by improved policy design and processes. At the engineered systems plane, our work is intended to result in practical guidelines for devising policies and programs with appropriate motivation and incentives for implementing policies and programs once adopted. This phase of the research has been aimed, first, at a thorough, multidisciplinary review of the literature concerning obstacles to implementation. Second, the research has focused on advancing the state of the art by developing means for integrating the insights offered by diverse perspectives on the implementation process from the several social, behavioral, and decision sciences. The research establishes a basis for testing our understanding of these processes in the case of hospital retrofit decisions.

Turbidity current flow over an erodible obstacle and phases of sediment wave generation

NASA Astrophysics Data System (ADS)

Strauss, Moshe; Glinsky, Michael E.

2012-06-01

We study the flow of particle-laden turbidity currents down a slope and over an obstacle. A high-resolution 2-D computer simulation model is used, based on the Navier-Stokes equations. It includes poly-disperse particle grain sizes in the current and substrate. Particular attention is paid to the erosion and deposition of the substrate particles, including application of an active layer model. Multiple flows are modeled from a lock release that can show the development of sediment waves (SW). These are stream-wise waves that are triggered by the increasing slope on the downstream side of the obstacle. The initial obstacle is completely erased by the resuspension after a few flows leading to self consistent and self generated SW that are weakly dependant on the initial obstacle. The growth of these waves is directly related to the turbidity current being self sustaining, that is, the net erosion is more than the net deposition. Four system parameters are found to influence the SW growth: (1) slope, (2) current lock height, (3) grain lock concentration, and (4) particle diameters. Three phases are discovered for the system: (1) "no SW," (2) "SW buildup," and (3) "SW growth". The second phase consists of a soliton-like SW structure with a preserved shape. The phase diagram of the system is defined by isolating regions divided by critical slope angles as functions of current lock height, grain lock concentration, and particle diameters.

Obstacle detection by recognizing binary expansion patterns

NASA Technical Reports Server (NTRS)

Baram, Yoram; Barniv, Yair

1993-01-01

This paper describes a technique for obstacle detection, based on the expansion of the image-plane projection of a textured object, as its distance from the sensor decreases. Information is conveyed by vectors whose components represent first-order temporal and spatial derivatives of the image intensity, which are related to the time to collision through the local divergence. Such vectors may be characterized as patterns corresponding to 'safe' or 'dangerous' situations. We show that essential information is conveyed by single-bit vector components, representing the signs of the relevant derivatives. We use two recently developed, high capacity classifiers, employing neural learning techniques, to recognize the imminence of collision from such patterns.

Strain amplitude-dependent anelasticity in Cu-Ni solid solution due to thermally activated and athermal dislocation-point obstacle interactions

NASA Astrophysics Data System (ADS)

Kustov, S.; Gremaud, G.; Benoit, W.; Golyandin, S.; Sapozhnikov, K.; Nishino, Y.; Asano, S.

1999-02-01

Experimental investigations of the internal friction and the Young's modulus defect in single crystals of Cu-(1.3-7.6) at. % Ni have been performed for 7-300 K over a wide range of oscillatory strain amplitudes. Extensive data have been obtained at a frequency of vibrations around 100 kHz and compared with the results obtained for the same crystals at a frequency of ˜1 kHz. The strain amplitude dependence of the anelastic strain amplitude and the average friction stress acting on a dislocation due to solute atoms are also analyzed. Several stages in the strain amplitude dependence of the internal friction and the Young's modulus defect are revealed for all of the alloy compositions, at different temperatures and in different frequency ranges. For the 100 kHz frequency, low temperatures and low strain amplitudes (˜10-7-10-5), the amplitude-dependent internal friction and the Young's modulus defect are essentially temperature independent, and are ascribed to a purely hysteretic internal friction component. At higher strain amplitudes, a transition stage and a steep strain amplitude dependence of the internal friction and the Young's modulus defect are observed, followed by saturation at the highest strain amplitudes employed. These stages are temperature and frequency dependent and are assumed to be due to thermally activated motion of dislocations. We suggest that the observed regularities in the entire strain amplitude, temperature and frequency ranges correspond to a motion of dislocations in a two-component system of obstacles: weak but long-range ones, due to the elastic interaction of dislocations with solute atoms distributed in the bulk of the crystal; and strong short-range ones, due to the interaction of dislocations with solute atoms distributed close to dislocation glide planes. Based on these assumptions, a qualitative explanation is given for the variety of experimental observations.

Soldier-relevant body borne load impacts minimum foot clearance during obstacle negotiation.

PubMed

Brown, T N; Loverro, K L; Schiffman, J M

2016-07-01

Soldiers often trip and fall on duty, resulting in injury. This study examined ten male soldiers' ability to negotiate an obstacle. Participants had lead and trail foot minimum foot clearance (MFC) parameters quantified while crossing a low (305 mm) and high (457 mm) obstacle with (19.4 kg) and without (6 kg) body borne load. To minimize tripping risk, participants increased lead foot MFC (p = 0.028) and reduced lead (p = 0.044) and trail (p = 0.035) foot variability when negotiating an obstacle with body borne load. While obstacle height had no effect on MFC (p = 0.273 and p = 0.126), placing the trail foot closer to the high obstacle when crossing with body borne load, resulted in greater lead (R = 0.640, b = 0.241, p = 0.046) and trail (R = 0.636, b = 0.287, p = 0.048) MFC. Soldiers, when carrying typical military loads, may be able to minimize their risk of tripping over an obstacle by creating a safety margin via greater foot clearance with reduced variability. Published by Elsevier Ltd.

Effects of buried obstacles on penetration resistance in cohesionless soils

NASA Technical Reports Server (NTRS)

Deluca, E. W.; Carrasco, L. H.

1972-01-01

Recent experiments concerning penetration of cohesionless soils in special molds that include solid obstacles embedded within the soil matrix are reported. The relative effects of these obstacles with respect to the soil properties of relative density, texture, and gradation are also discussed. Because lunar soil is fairly cohesionless, special attention was given to the Apollo lunar simulant, AP-12.

Performance and wake conditions of a rotor located in the wake of an obstacle

NASA Astrophysics Data System (ADS)

Naumov, I. V.; Kabardin, I. K.; Mikkelsen, R. F.; Okulov, V. L.; Sørensen, J. N.

2016-09-01

Obstacles like forests, ridges and hills can strongly affect the velocity profile in front of a wind turbine rotor. The present work aims at quantifying the influence of nearby located obstacles on the performance and wake characteristics of a downstream located wind turbine. Here the influence of an obstacle in the form of a cylindrical disk was investigated experimentally in a water flume. A model of a three-bladed rotor, designed using Glauert's optimum theory at a tip speed ratio λ = 5, was placed in the wake of a disk with a diameter close to the one of the rotor. The distance from the disk to the rotor was changed from 4 to 8 rotor diameters, with the vertical distance from the rotor axis varied 0.5 and 1 rotor diameters. The associated turbulent intensity of the incoming flow to the rotor changed 3 to '6% due to the influence of the disk wake. In the experiment, thrust characteristics and associated pulsations as a function of the incoming flow structures were measured by strain gauges. The flow condition in front of the rotor was measured with high temporal accuracy using LDA and power coefficients were determine as function of tip speed ratio for different obstacle positions. Furthermore, PIV measurements were carried out to study the development of the mean velocity deficit profiles of the wake behind the wind turbine model under the influence of the wake generated by the obstacle. By use of regression techniques to fit the velocity profiles it was possible to determine velocity deficits and estimate length scales of the wake attenuation.

Identifying Contingency Requirements using Obstacle Analysis on an Unpiloted Aerial Vehicle

NASA Technical Reports Server (NTRS)

Lutz, Robyn R.; Nelson, Stacy; Patterson-Hine, Ann; Frost, Chad R.; Tal, Doron

2005-01-01

This paper describes experience using Obstacle Analysis to identify contingency requirements on an unpiloted aerial vehicle. A contingency is an operational anomaly, and may or may not involve component failure. The challenges to this effort were: ( I ) rapid evolution of the system while operational, (2) incremental autonomy as capabilities were transferred from ground control to software control and (3) the eventual safety-criticality of such systems as they begin to fly over populated areas. The results reported here are preliminary but show that Obstacle Analysis helped (1) identify new contingencies that appeared as autonomy increased; (2) identify new alternatives for handling both previously known and new contingencies; and (3) investigate the continued validity of existing software requirements for contingency handling. Since many mobile, intelligent systems are built using a development process that poses the same challenges, the results appear to have applicability to other similar systems.

Explosion hazards of LPG-air mixtures in vented enclosure with obstacles.

PubMed

Zhang, Qi; Wang, Yaxing; Lian, Zhen

2017-07-15

Numerical simulations were performed to study explosion characteristics of liquefied petroleum gas (LPG) explosion in enclosure with a vent. Unlike explosion overpressure and dynamic pressure, explosion temperature of the LPG-air mixture at a given concentration in a vented enclosure has very little variation with obstacle numbers for a given blockage ratio. For an enclosure without obstacle, explosion overpressures for the stoichiometric mixtures and the fuel-lean mixtures reach their maximum within the vent and that for fuel-rich mixture reaches its maximum beyond and near the vent. Dynamic pressures produced by an indoor LPG explosion reach their maximum always beyond the vent no matter obstacles are present or not in the enclosure. A LPG explosion in a vented enclosure with built-in obstacles is strong enough to make the brick and mortar wall with a thickness of 370mm damaged. If there is no obstacle in the enclosure, the lower explosion pressure of several kPa can not break the brick and mortar wall with a thickness of 370mm. For a LPG explosion produced in an enclosure with a vent, main hazards, within the vent, are overpressure and high temperature. However main hazards are dynamic pressure, blast wind, and high temperature beyond the vent. Copyright © 2017 Elsevier B.V. All rights reserved.

How does visual manipulation affect obstacle avoidance strategies used by athletes?

PubMed

Bijman, M P; Fisher, J J; Vallis, L A

2016-01-01

Research examining our ability to avoid obstacles in our path has stressed the importance of visual input. The aim of this study was to determine if athletes playing varsity-level field sports, who rely on visual input to guide motor behaviour, are more able to guide their foot over obstacles compared to recreational individuals. While wearing kinematic markers, eight varsity athletes and eight age-matched controls (aged 18-25) walked along a walkway and stepped over stationary obstacles (180° motion arc). Visual input was manipulated using PLATO visual goggles three or two steps pre-obstacle crossing and compared to trials where vision was given throughout. A main effect between groups for peak trail toe elevation was shown with greater values generated by the controls for all crossing conditions during full vision trials only. This may be interpreted as athletes not perceiving this obstacle as an increased threat to their postural stability. Collectively, findings suggest the athletic group is able to transfer their abilities to non-specific conditions during full vision trials; however, varsity-level athletes were equally reliant on visual cues for these visually guided stepping tasks as their performance was similar to the controls when vision is removed.

C1,1 regularity for degenerate elliptic obstacle problems

NASA Astrophysics Data System (ADS)

Daskalopoulos, Panagiota; Feehan, Paul M. N.

2016-03-01

The Heston stochastic volatility process is a degenerate diffusion process where the degeneracy in the diffusion coefficient is proportional to the square root of the distance to the boundary of the half-plane. The generator of this process with killing, called the elliptic Heston operator, is a second-order, degenerate-elliptic partial differential operator, where the degeneracy in the operator symbol is proportional to the distance to the boundary of the half-plane. In mathematical finance, solutions to the obstacle problem for the elliptic Heston operator correspond to value functions for perpetual American-style options on the underlying asset. With the aid of weighted Sobolev spaces and weighted Hölder spaces, we establish the optimal C 1 , 1 regularity (up to the boundary of the half-plane) for solutions to obstacle problems for the elliptic Heston operator when the obstacle functions are sufficiently smooth.

The effects of situational obstacles and social support on suicide- prevention gatekeeper behaviors.

PubMed

Moore, J Taylor; Cigularov, Konstantin P; Chen, Peter Y; Martinez, Jeremy M; Hindman, Jarrod

2011-01-01

Although the effectiveness of suicide-prevention gatekeeper-training programs in improving knowledge, attitudes, and referral practices has been documented, their effects do not seem to be lasting. This study investigated situational obstacles at work that prevent suicide-prevention gatekeepers from engaging in suicide-prevention behavior and the role of social support in modifying the relationship between situational obstacles and suicide-prevention behaviors. 193 gatekeepers completed an online survey to rate the obstacles they had experienced at work since completing a gatekeeper-training program and the support received from coworkers, supervisors, and the organization. Participants also reported the frequency of suicide-prevention behaviors performed. The results indicated that both situational obstacles and social support predicted the number of suicide-prevention behaviors performed, as expected. There was also a trend that support from supervisors and the organization may alleviate the adverse effect of situational obstacles on suicide-prevention behavior. The cross-sectional nature of the study does not allow for directional, causal conclusions to be drawn. By understanding the roles of situational obstacles faced by trained gatekeepers at their work and the support they receive from supervisors and organizations, appropriate strategies can be identified and applied to facilitate gatekeeper performance.

Overcoming an Obstacle in Expanding a UMLS Semantic Type Extent

PubMed Central

Chen, Yan; Gu, Huanying; Perl, Yehoshua; Geller, James

2011-01-01

This paper strives to overcome a major problem encountered by a previous expansion methodology for discovering concepts highly likely to be missing a specific semantic type assignment in the UMLS. This methodology is the basis for an algorithm that presents the discovered concepts to a human auditor for review and possible correction. We analyzed the problem of the previous expansion methodology and discovered that it was due to an obstacle constituted by one or more concepts assigned the UMLS Semantic Network semantic type Classification. A new methodology was designed that bypasses such an obstacle without a combinatorial explosion in the number of concepts presented to the human auditor for review. The new expansion methodology with obstacle avoidance was tested with the semantic type Experimental Model of Disease and found over 500 concepts missed by the previous methodology that are in need of this semantic type assignment. Furthermore, other semantic types suffering from the same major problem were discovered, indicating that the methodology is of more general applicability. The algorithmic discovery of concepts that are likely missing a semantic type assignment is possible even in the face of obstacles, without an explosion in the number of processed concepts. PMID:21925287

Consideration of the oxide particle-dislocation interaction in 9Cr-ODS steel

NASA Astrophysics Data System (ADS)

Ijiri, Yuta; Oono, N.; Ukai, S.; Yu, Hao; Ohtsuka, S.; Abe, Y.; Matsukawa, Y.

2017-05-01

The interaction between oxide particles and dislocations in a 9Cr-ODS ferritic steel is investigated by both static and in situ TEM observation under dynamic straining conditions and room temperature. The measured obstacle strength (?) of the oxide particles was no greater than 0.80 and the average was 0.63. The dislocation loops around some coarsened particles were also observed. The calculated obstacle strength by a stress formula of the Orowan interaction is nearly equaled to the average experimental value. Not only cross-slip system but also the Orowan interaction should be considered as the main interaction mechanism between oxide particles and dislocation in 9CrODS ferritic steel.

Anomalous diffusion due to hindering by mobile obstacles undergoing Brownian motion or Orstein-Ulhenbeck processes.

PubMed

Berry, Hugues; Chaté, Hugues

2014-02-01

In vivo measurements of the passive movements of biomolecules or vesicles in cells consistently report "anomalous diffusion," where mean-squared displacements scale as a power law of time with exponent α<1 (subdiffusion). While the detailed mechanisms causing such behaviors are not always elucidated, movement hindrance by obstacles is often invoked. However, our understanding of how hindered diffusion leads to subdiffusion is based on diffusion amidst randomly located immobile obstacles. Here, we have used Monte Carlo simulations to investigate transient subdiffusion due to mobile obstacles with various modes of mobility. Our simulations confirm that the anomalous regimes rapidly disappear when the obstacles move by Brownian motion. By contrast, mobile obstacles with more confined displacements, e.g., Orstein-Ulhenbeck motion, are shown to preserve subdiffusive regimes. The mean-squared displacement of tracked protein displays convincing power laws with anomalous exponent α that varies with the density of Orstein-Ulhenbeck (OU) obstacles or the relaxation time scale of the OU process. In particular, some of the values we observed are significantly below the universal value predicted for immobile obstacles in two dimensions. Therefore, our results show that subdiffusion due to mobile obstacles with OU type of motion may account for the large variation range exhibited by experimental measurements in living cells and may explain that some experimental estimates are below the universal value predicted for immobile obstacles.

Atmospheric dispersion of a heavier-than-air gas near a two-dimensional obstacle

NASA Astrophysics Data System (ADS)

Sutton, S. B.; Brandt, H.; White, B. R.

1986-04-01

Flow over a two-dimensional obstacle and dispersion of a heavier-than-air gas near the obstacle were studied. Two species, one representing air and the other representing the heavier-than-air gas were treated. Equations for mass and momentum were cast in mass-averaged form, with turbulent Reynolds stresses and mass fluxes modeled using eddy-viscosity and diffusivity hypotheses. A two-equation k-ɛ turbulence model was used to determine the effective turbulent viscosity. Streamline curvature and buoyancy corrections were added to the basic turbulence formulation. The model equations were solved using finite difference techniques. An alternating-direction-implicit (ADI) technique was used to solve the parabolic transport equations and a direct matrix solver was used to solve the elliptic pressure equation. Mesh sensitivities were investigated to determine the optimum mesh requirements for the final calculations. It was concluded that at least 10 grid spaces were required across the obstacle width and 15 across the obstacle height to obtain valid solutions. A non-uniform mesh was used to concentrate the grid points at the top of the obstacle. Experimental measurements were made with air flow over a 7.6 by 7.6 cm obstacle in a boundary-layer wind tunnel. Smoke visualization revealed a low-frequency oscillation of the bubble downstream of the obstacle. Hot-wire anemometer data are presented for the mean velocity and turbulent kinetic energy at the mid-plane of the obstacle and the mid-plane of the downstream recirculation bubble. A single hot-wire probe was found to be suitable for determining mean streamwise velocities with an accuracy of 11 %. The downstream recirculation bubble was unsteady and had a length range from 3 to 8 obstacle lengths. The experimental results for flow over the obstacle were compared with numerical calculations to validate the numerical solution procedure. A sensitivity study on the effect of curvature correction and variation of turbulence

Autonomous navigation and obstacle avoidance for unmanned surface vehicles

NASA Astrophysics Data System (ADS)

Larson, Jacoby; Bruch, Michael; Ebken, John

2006-05-01

The US Navy and other Department of Defense (DoD) and Department of Homeland Security (DHS) organizations are increasingly interested in the use of unmanned surface vehicles (USVs) for a variety of missions and applications. In order for USVs to fill these roles, they must be capable of a relatively high degree of autonomous navigation. Space and Naval Warfare Systems Center, San Diego is developing core technologies required for robust USV operation in a real-world environment, primarily focusing on autonomous navigation, obstacle avoidance, and path planning.

Improved obstacle avoidance and navigation for an autonomous ground vehicle

NASA Astrophysics Data System (ADS)

Giri, Binod; Cho, Hyunsu; Williams, Benjamin C.; Tann, Hokchhay; Shakya, Bicky; Bharam, Vishal; Ahlgren, David J.

2015-01-01

This paper presents improvements made to the intelligence algorithms employed on Q, an autonomous ground vehicle, for the 2014 Intelligent Ground Vehicle Competition (IGVC). In 2012, the IGVC committee combined the formerly separate autonomous and navigation challenges into a single AUT-NAV challenge. In this new challenge, the vehicle is required to navigate through a grassy obstacle course and stay within the course boundaries (a lane of two white painted lines) that guide it toward a given GPS waypoint. Once the vehicle reaches this waypoint, it enters an open course where it is required to navigate to another GPS waypoint while avoiding obstacles. After reaching the final waypoint, the vehicle is required to traverse another obstacle course before completing the run. Q uses modular parallel software architecture in which image processing, navigation, and sensor control algorithms run concurrently. A tuned navigation algorithm allows Q to smoothly maneuver through obstacle fields. For the 2014 competition, most revisions occurred in the vision system, which detects white lines and informs the navigation component. Barrel obstacles of various colors presented a new challenge for image processing: the previous color plane extraction algorithm would not suffice. To overcome this difficulty, laser range sensor data were overlaid on visual data. Q also participates in the Joint Architecture for Unmanned Systems (JAUS) challenge at IGVC. For 2014, significant updates were implemented: the JAUS component accepted a greater variety of messages and showed better compliance to the JAUS technical standard. With these improvements, Q secured second place in the JAUS competition.

Predicting the influence of long-range molecular interactions on macroscopic-scale diffusion by homogenization of the Smoluchowski equation

NASA Astrophysics Data System (ADS)

Kekenes-Huskey, P. M.; Gillette, A. K.; McCammon, J. A.

2014-05-01

The macroscopic diffusion constant for a charged diffuser is in part dependent on (1) the volume excluded by solute "obstacles" and (2) long-range interactions between those obstacles and the diffuser. Increasing excluded volume reduces transport of the diffuser, while long-range interactions can either increase or decrease diffusivity, depending on the nature of the potential. We previously demonstrated [P. M. Kekenes-Huskey et al., Biophys. J. 105, 2130 (2013)] using homogenization theory that the configuration of molecular-scale obstacles can both hinder diffusion and induce diffusional anisotropy for small ions. As the density of molecular obstacles increases, van der Waals (vdW) and electrostatic interactions between obstacle and a diffuser become significant and can strongly influence the latter's diffusivity, which was neglected in our original model. Here, we extend this methodology to include a fixed (time-independent) potential of mean force, through homogenization of the Smoluchowski equation. We consider the diffusion of ions in crowded, hydrophilic environments at physiological ionic strengths and find that electrostatic and vdW interactions can enhance or depress effective diffusion rates for attractive or repulsive forces, respectively. Additionally, we show that the observed diffusion rate may be reduced independent of non-specific electrostatic and vdW interactions by treating obstacles that exhibit specific binding interactions as "buffers" that absorb free diffusers. Finally, we demonstrate that effective diffusion rates are sensitive to distribution of surface charge on a globular protein, Troponin C, suggesting that the use of molecular structures with atomistic-scale resolution can account for electrostatic influences on substrate transport. This approach offers new insight into the influence of molecular-scale, long-range interactions on transport of charged species, particularly for diffusion-influenced signaling events occurring in crowded

A bio-inspired kinematic controller for obstacle avoidance during reaching tasks with real robots.

PubMed

Srinivasa, Narayan; Bhattacharyya, Rajan; Sundareswara, Rashmi; Lee, Craig; Grossberg, Stephen

2012-11-01

This paper describes a redundant robot arm that is capable of learning to reach for targets in space in a self-organized fashion while avoiding obstacles. Self-generated movement commands that activate correlated visual, spatial and motor information are used to learn forward and inverse kinematic control models while moving in obstacle-free space using the Direction-to-Rotation Transform (DIRECT). Unlike prior DIRECT models, the learning process in this work was realized using an online Fuzzy ARTMAP learning algorithm. The DIRECT-based kinematic controller is fault tolerant and can handle a wide range of perturbations such as joint locking and the use of tools despite not having experienced them during learning. The DIRECT model was extended based on a novel reactive obstacle avoidance direction (DIRECT-ROAD) model to enable redundant robots to avoid obstacles in environments with simple obstacle configurations. However, certain configurations of obstacles in the environment prevented the robot from reaching the target with purely reactive obstacle avoidance. To address this complexity, a self-organized process of mental rehearsals of movements was modeled, inspired by human and animal experiments on reaching, to generate plans for movement execution using DIRECT-ROAD in complex environments. These mental rehearsals or plans are self-generated by using the Fuzzy ARTMAP algorithm to retrieve multiple solutions for reaching each target while accounting for all the obstacles in its environment. The key aspects of the proposed novel controller were illustrated first using simple examples. Experiments were then performed on real robot platforms to demonstrate successful obstacle avoidance during reaching tasks in real-world environments. Copyright © 2012 Elsevier Ltd. All rights reserved.

Evaluation of a Portable Collision Warning Device for Patients With Peripheral Vision Loss in an Obstacle Course.

PubMed

Pundlik, Shrinivas; Tomasi, Matteo; Luo, Gang

2015-04-01

A pocket-sized collision warning device equipped with a video camera was developed to predict impending collisions based on time to collision rather than proximity. A study was conducted in a high-density obstacle course to evaluate the effect of the device on collision avoidance in people with peripheral field loss (PFL). The 41-meter-long loop-shaped obstacle course consisted of 46 stationary obstacles from floor to head level and oncoming pedestrians. Twenty-five patients with tunnel vision (n = 13) or hemianopia (n = 12) completed four consecutive loops with and without the device, while not using any other habitual mobility aid. Walking direction and device usage order were counterbalanced. Number of collisions and preferred percentage of walking speed (PPWS) were compared within subjects. Collisions were reduced significantly by approximately 37% (P < 0.001) with the device (floor-level obstacles were excluded because the device was not designed for them). No patient had more collisions when using the device. Although the PPWS were also reduced with the device from 52% to 49% (P = 0.053), this did not account for the lower number of collisions, as the changes in collisions and PPWS were not correlated (P = 0.516). The device may help patients with a wide range of PFL avoid collisions with high-level obstacles while barely affecting their walking speed.

Indoor Navigation from Point Clouds: 3d Modelling and Obstacle Detection

NASA Astrophysics Data System (ADS)

Díaz-Vilariño, L.; Boguslawski, P.; Khoshelham, K.; Lorenzo, H.; Mahdjoubi, L.

2016-06-01

In the recent years, indoor modelling and navigation has become a research of interest because many stakeholders require navigation assistance in various application scenarios. The navigational assistance for blind or wheelchair people, building crisis management such as fire protection, augmented reality for gaming, tourism or training emergency assistance units are just some of the direct applications of indoor modelling and navigation. Navigational information is traditionally extracted from 2D drawings or layouts. Real state of indoors, including opening position and geometry for both windows and doors, and the presence of obstacles is commonly ignored. In this work, a real indoor-path planning methodology based on 3D point clouds is developed. The value and originality of the approach consist on considering point clouds not only for reconstructing semantically-rich 3D indoor models, but also for detecting potential obstacles in the route planning and using these for readapting the routes according to the real state of the indoor depictured by the laser scanner.

A Neural Model of Visually Guided Steering, Obstacle Avoidance, and Route Selection

ERIC Educational Resources Information Center

Elder, David M.; Grossberg, Stephen; Mingolla, Ennio

2009-01-01

A neural model is developed to explain how humans can approach a goal object on foot while steering around obstacles to avoid collisions in a cluttered environment. The model uses optic flow from a 3-dimensional virtual reality environment to determine the position of objects on the basis of motion discontinuities and computes heading direction,…

Obstacle Detection in Indoor Environment for Visually Impaired Using Mobile Camera

NASA Astrophysics Data System (ADS)

Rahman, Samiur; Ullah, Sana; Ullah, Sehat

2018-01-01

Obstacle detection can improve the mobility as well as the safety of visually impaired people. In this paper, we present a system using mobile camera for visually impaired people. The proposed algorithm works in indoor environment and it uses a very simple technique of using few pre-stored floor images. In indoor environment all unique floor types are considered and a single image is stored for each unique floor type. These floor images are considered as reference images. The algorithm acquires an input image frame and then a region of interest is selected and is scanned for obstacle using pre-stored floor images. The algorithm compares the present frame and the next frame and compute mean square error of the two frames. If mean square error is less than a threshold value α then it means that there is no obstacle in the next frame. If mean square error is greater than α then there are two possibilities; either there is an obstacle or the floor type is changed. In order to check if the floor is changed, the algorithm computes mean square error of next frame and all stored floor types. If minimum of mean square error is less than a threshold value α then flour is changed otherwise there exist an obstacle. The proposed algorithm works in real-time and 96% accuracy has been achieved.

76 FR 52239 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-08-22

... Minimums & Obstacle DP, Orig-A Red Oak, IA, Red Oak Muni, Takeoff Minimums & Obstacle DP, Amdt 3 Storm Lake, IA, Storm Lake Muni, Takeoff Minimums & Obstacle DP, Orig Dwight, IL, Dwight, Takeoff Minimums..., Florence Rgnl, RNAV (GPS) RWY 9, Orig-A Spearfish, SD, Black Hills-Clydes Ice Field, RNAV (GPS) RWY 13...

Obstacles to Scientific Research in Light of a Number of Variables

ERIC Educational Resources Information Center

Algadheeb, Nourah A.; Almeqren, Monira A.

2014-01-01

The present study aimed to identify the scientific research obstacles facing faculty members in the College of Education at Princess Nora bint Abdul Rahman University (PNU) and to determine the differences in the obstacles according to age, academic rank, scientific specialty, marital status, number of completed studies, and time since the last…

A study of transient flow turbulence generation during flame/wall interactions in explosions

NASA Astrophysics Data System (ADS)

Hargrave, G. K.; Jarvis, S.; Williams, T. C.

2002-07-01

Experimental data are presented for the turbulent velocity field generated during flame/solid wall interactions in explosions. The presence of turbulence in a flammable gas mixture can wrinkle a flame front, increasing the flame surface area and enhancing the burning rate. In congested process plant, any flame propagating through an accidental release of flammable mixture will encounter obstructions in the form of walls, pipe-work or storage vessels. The interaction between the gas movement and the obstacle creates turbulence by vortex shedding and local wake/recirculation, whereby the flame can be wrapped in on itself, increasing the surface area available for combustion. Particle image velocimetry (PIV) was used to characterize the turbulent flow field in the wake of the obstacles placed in the path of propagating flames. This allowed the quantification of the interaction of the propagating flame and the generated turbulent flow field. Due to the accelerating nature of the explosion flow field, the wake flows develop `transient' turbulent fields and PIV provided data to define the spatial and temporal variation of the velocity field ahead of the propagating flame, providing an understanding of the direct interaction between flow and flame.

Gait development on Minitaur, a direct drive quadrupedal robot

NASA Astrophysics Data System (ADS)

Blackman, Daniel J.; Nicholson, John V.; Ordonez, Camilo; Miller, Bruce D.; Clark, Jonathan E.

2016-05-01

This paper describes the development of a dynamic, quadrupedal robot designed for rapid traversal and interaction in human environments. We explore improvements to both physical and control methods to a legged robot (Minitaur) in order to improve the speed and stability of its gaits and increase the range of obstacles that it can overcome, with an eye toward negotiating man-made terrains such as stairs. These modifications include an analysis of physical compliance, an investigation of foot and leg design, and the implementation of ground and obstacle contact sensing for inclusion in the control schemes. Structural and mechanical improvements were made to reduce undesired compliance for more consistent agreement with dynamic models, which necessitated refinement of foot design for greater durability. Contact sensing was implemented into the control scheme for identifying obstacles and deviations in surface level for negotiation of varying terrain. Overall the incorporation of these features greatly enhances the mobility of the dynamic quadrupedal robot and helps to establish a basis for overcoming obstacles.

Mesoscopic model for filament orientation in growing actin networks: the role of obstacle geometry

NASA Astrophysics Data System (ADS)

Weichsel, Julian; Schwarz, Ulrich S.

2013-03-01

Propulsion by growing actin networks is a universal mechanism used in many different biological systems, ranging from the sheet-like lamellipodium of crawling animal cells to the actin comet tails induced by certain bacteria and viruses in order to move within their host cells. Although the core molecular machinery for actin network growth is well preserved in all of these cases, the geometry of the propelled obstacle varies considerably. During recent years, filament orientation distribution has emerged as an important observable characterizing the structure and dynamical state of the growing network. Here we derive several continuum equations for the orientation distribution of filaments growing behind stiff obstacles of various shapes and validate the predicted steady state orientation patterns by stochastic computer simulations based on discrete filaments. We use an ordinary differential equation approach to demonstrate that for flat obstacles of finite size, two fundamentally different orientation patterns peaked at either ±35° or +70°/0°/ - 70° exhibit mutually exclusive stability, in agreement with earlier results for flat obstacles of very large lateral extension. We calculate and validate phase diagrams as a function of model parameters and show how this approach can be extended to obstacles with piecewise straight contours. For curved obstacles, we arrive at a partial differential equation in the continuum limit, which again is in good agreement with the computer simulations. In all cases, we can identify the same two fundamentally different orientation patterns, but only within an appropriate reference frame, which is adjusted to the local orientation of the obstacle contour. Our results suggest that two fundamentally different network architectures compete with each other in growing actin networks, irrespective of obstacle geometry, and clarify how simulated and electron tomography data have to be analyzed for non-flat obstacle geometries.

Different protocols for analyzing behavior and adaptability in obstacle crossing in Parkinson's disease.

PubMed

Mollaei, Nafiseh; Bicho, Estela; Sousa, Nuno; Gago, Miguel Fernandes

2017-01-01

Imbalance and tripping over obstacles as a result of altered gait in older adults, especially in patients with Parkinson's disease (PD), are one of the most common causes of falls. During obstacle crossing, patients with PD modify their behavior in order to decrease the mechanical demands and enhance dynamic stability. Various descriptions of dynamic traits of gait that have been collected over longer periods, probably better synthesize the underlying structure and pattern of fluctuations in gait and can be more sensitive markers of aging or early neurological dysfunction and increased risk of falls. This confirmation challenges the clinimetric of different protocols and paradigms used for gait analysis up till now, in particular when analyzing obstacle crossing. The authors here present a critical review of current knowledge concerning the interplay between the cognition and gait in aging and PD, emphasizing the differences in gait behavior and adaptability while walking over different and challenging obstacle paradigms, and the implications of obstacle negotiation as a predictor of falls. Some evidence concerning the effectiveness of future rehabilitation protocols on reviving obstacle crossing behavior by trial and error relearning, taking advantage of dual-task paradigms, physical exercise, and virtual reality have been put forward in this article.

Performance Characterization of Obstacle Detection Algorithms for Aircraft Navigation

NASA Technical Reports Server (NTRS)

Kasturi, Rangachar; Camps, Octavia; Coraor, Lee; Gandhi, Tarak; Hartman, Kerry; Yang, Mau-Tsuen

2000-01-01

The research reported here is a part of NASA's Synthetic Vision System (SVS) project for the development of a High Speed Civil Transport Aircraft (HSCT). One of the components of the SVS is a module for detection of potential obstacles in the aircraft's flight path by analyzing the images captured by an on-board camera in real-time. Design of such a module includes the selection and characterization of robust, reliable, and fast techniques and their implementation for execution in real-time. This report describes the results of our research in realizing such a design.

Obstacles of Teaching Mathematics Faced by the Class Teachers in Jordan

ERIC Educational Resources Information Center

Nejem, Khamis Mousa; Muhanna, Waffa

2013-01-01

The purpose of the study is to investigate the obstacles of teaching mathematics faced by the class teachers in Jordan. To achieve this purpose a study sample of 192 male and female class teachers was selected randomly from government schools. The instrument of the study was a questionnaire used to investigate the obstacles of mathematics…

Obstacle stepping involves spinal anticipatory activity associated with quadrupedal limb coordination.

PubMed

Michel, J; van Hedel, H J A; Dietz, V

2008-04-01

Obstacle avoidance steps are associated with a facilitation of spinal reflexes in leg muscles. Here we have examined the involvement of both leg and arm muscles. Subjects walking with reduced vision on a treadmill were acoustically informed about an approaching obstacle and received feedback about task performance. Reflex responses evoked by tibial nerve stimulation were observed in all arm and leg muscles examined in this study. They were enhanced before the execution of obstacle avoidance compared with normal steps and showed an exponential adaptation in contralateral arm flexor muscles corresponding to the improvement of task performance. This enhancement was absent when the body was partially supported during the task. During the execution of obstacle steps, electromyographic activity in the arm muscles mimicked the preceding reflex behaviour with respect to enhancement and adaptation. Our results demonstrate an anticipatory quadrupedal limb coordination with an involvement of proximal arm muscles in the acquisition and performance of this precision locomotor task. This is presumably achieved by an up-regulated activity of coupled cervico-thoracal interneuronal circuits.

Overcoming an obstacle in expanding a UMLS semantic type extent.

PubMed

Chen, Yan; Gu, Huanying; Perl, Yehoshua; Geller, James

2012-02-01

This paper strives to overcome a major problem encountered by a previous expansion methodology for discovering concepts highly likely to be missing a specific semantic type assignment in the UMLS. This methodology is the basis for an algorithm that presents the discovered concepts to a human auditor for review and possible correction. We analyzed the problem of the previous expansion methodology and discovered that it was due to an obstacle constituted by one or more concepts assigned the UMLS Semantic Network semantic type Classification. A new methodology was designed that bypasses such an obstacle without a combinatorial explosion in the number of concepts presented to the human auditor for review. The new expansion methodology with obstacle avoidance was tested with the semantic type Experimental Model of Disease and found over 500 concepts missed by the previous methodology that are in need of this semantic type assignment. Furthermore, other semantic types suffering from the same major problem were discovered, indicating that the methodology is of more general applicability. The algorithmic discovery of concepts that are likely missing a semantic type assignment is possible even in the face of obstacles, without an explosion in the number of processed concepts. Copyright © 2011 Elsevier Inc. All rights reserved.

Sex and age-level differences of walking time in preschool children on an obstacle frame

PubMed Central

2012-01-01

Background Stepping over an obstacle is a kind of compound movement that makes walking more difficult, especially for preschool children. This study examines sex and age-level differences in walking time in preschool children on an obstacle frame. Methods The participants included 324 healthy preschool children: four-year-old boys (51) and girls (51), five-year-old boys (50) and girls (60), and six-year-old boys (62) and girls (50). A 5 cm- or 10 cm-high obstacle (depth 11.5 cm, width 23.5 cm) was set at the halfway point of a 200 cm × 10 cm walking course. Results The participants walked to the end of the course and back as fast as possible under three conditions: no obstacle, low obstacle and high obstacle. Walking time showed age-level differences in all conditions, but there were no differences in sex. Age levels were divided into two groups, with one group within the first six months of their birthday, and the second group within the last six months of that year. Walking time for children in the first half of their fourth year was longer than that of the five- and six-year-old children. In addition, for children in the last half of their fourth year, walking time was longer than both sexes in the last half of their fifth and sixth years. The children in the latter half of their fifth year had a longer walking time in the high obstacle condition than those in the last half of their sixth year. In the four-year-old participants, walking time was shorter with no obstacles than with a high obstacle frame. Conclusions In the above data, obstacle course walking time does not show a gender difference, except that the four-year-old participants needed longer than the five- and six-year-old children. Setting the obstacle 10 cm high also produced a different walking time in the five- and six-year-old participants. The high obstacle step test (10 cm) best evaluated the dynamic balance of preschool children. PMID:22738328

Fast and reliable obstacle detection and segmentation for cross-country navigation

NASA Technical Reports Server (NTRS)

Talukder, A.; Manduchi, R.; Rankin, A.; Matthies, L.

2002-01-01

Obstacle detection is one of the main components of the control system of autonomous vehicles. In the case of indoor/urban navigation, obstacles are typically defined as surface points that are higher than the ground plane. This characterization, however, cannot be used in cross-country and unstructured environments, where the notion of ground plane is often not meaningful.

New Walkers with Down Syndrome Use Cautious but Effective Strategies for Crossing Obstacles

ERIC Educational Resources Information Center

Mulvey, Genna M.; Kubo, Masayoshi; Chang, Chia-Lin; Ulrich, Beverly D.

2011-01-01

Perception of affordances research in children with developmental disabilities has only examined well practiced skills. Ten toddlers with Down syndrome and 10 with typical development walked across a GAITRite mat, with and without an obstacle. We coded the toddlers' behaviors after 1 and 3 months of walking experience when they encountered the…

Rules to fly by: pigeons navigating horizontal obstacles limit steering by selecting gaps most aligned to their flight direction.

PubMed

Ros, Ivo G; Bhagavatula, Partha S; Lin, Huai-Ti; Biewener, Andrew A

2017-02-06

Flying animals must successfully contend with obstacles in their natural environments. Inspired by the robust manoeuvring abilities of flying animals, unmanned aerial systems are being developed and tested to improve flight control through cluttered environments. We previously examined steering strategies that pigeons adopt to fly through an array of vertical obstacles (VOs). Modelling VO flight guidance revealed that pigeons steer towards larger visual gaps when making fast steering decisions. In the present experiments, we recorded three-dimensional flight kinematics of pigeons as they flew through randomized arrays of horizontal obstacles (HOs). We found that pigeons still decelerated upon approach but flew faster through a denser array of HOs compared with the VO array previously tested. Pigeons exhibited limited steering and chose gaps between obstacles most aligned to their immediate flight direction, in contrast to VO navigation that favoured widest gap steering. In addition, pigeons navigated past the HOs with more variable and decreased wing stroke span and adjusted their wing stroke plane to reduce contact with the obstacles. Variability in wing extension, stroke plane and wing stroke path was greater during HO flight. Pigeons also exhibited pronounced head movements when negotiating HOs, which potentially serve a visual function. These head-bobbing-like movements were most pronounced in the horizontal (flight direction) and vertical directions, consistent with engaging motion vision mechanisms for obstacle detection. These results show that pigeons exhibit a keen kinesthetic sense of their body and wings in relation to obstacles. Together with aerodynamic flapping flight mechanics that favours vertical manoeuvring, pigeons are able to navigate HOs using simple rules, with remarkable success.

Rules to fly by: pigeons navigating horizontal obstacles limit steering by selecting gaps most aligned to their flight direction

PubMed Central

Ros, Ivo G.; Bhagavatula, Partha S.; Lin, Huai-Ti

2017-01-01

Flying animals must successfully contend with obstacles in their natural environments. Inspired by the robust manoeuvring abilities of flying animals, unmanned aerial systems are being developed and tested to improve flight control through cluttered environments. We previously examined steering strategies that pigeons adopt to fly through an array of vertical obstacles (VOs). Modelling VO flight guidance revealed that pigeons steer towards larger visual gaps when making fast steering decisions. In the present experiments, we recorded three-dimensional flight kinematics of pigeons as they flew through randomized arrays of horizontal obstacles (HOs). We found that pigeons still decelerated upon approach but flew faster through a denser array of HOs compared with the VO array previously tested. Pigeons exhibited limited steering and chose gaps between obstacles most aligned to their immediate flight direction, in contrast to VO navigation that favoured widest gap steering. In addition, pigeons navigated past the HOs with more variable and decreased wing stroke span and adjusted their wing stroke plane to reduce contact with the obstacles. Variability in wing extension, stroke plane and wing stroke path was greater during HO flight. Pigeons also exhibited pronounced head movements when negotiating HOs, which potentially serve a visual function. These head-bobbing-like movements were most pronounced in the horizontal (flight direction) and vertical directions, consistent with engaging motion vision mechanisms for obstacle detection. These results show that pigeons exhibit a keen kinesthetic sense of their body and wings in relation to obstacles. Together with aerodynamic flapping flight mechanics that favours vertical manoeuvring, pigeons are able to navigate HOs using simple rules, with remarkable success. PMID:28163883

On Stationary Navier-Stokes Flows Around a Rotating Obstacle in Two-Dimensions

NASA Astrophysics Data System (ADS)

Higaki, Mitsuo; Maekawa, Yasunori; Nakahara, Yuu

2018-05-01

We study the two-dimensional stationary Navier-Stokes equations describing the flows around a rotating obstacle. The unique existence of solutions and their asymptotic behavior at spatial infinity are established when the rotation speed of the obstacle and the given exterior force are sufficiently small.

Dark soliton past a finite-size obstacle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilas, Nicolas; Pavloff, Nicolas

2005-09-15

We consider the collision of a dark soliton with an obstacle in a quasi-one-dimensional Bose condensate. We show that in many respects the soliton behaves as an effective classical particle of mass twice the mass of a bare particle, evolving in an effective potential which is a convolution of the actual potential describing the obstacle. Radiative effects beyond this approximation are also taken into account. The emitted waves are shown to form two counterpropagating wave packets, both moving at the speed of sound. We determine, at leading order, the total amount of radiation emitted during the collision and compute themore » acceleration of the soliton due to the collisional process. It is found that the radiative process is quenched when the velocity of the soliton reaches the velocity of sound in the system.« less

Scientific Research in Jordanian Higher Education Institutions: An Evaluation of the Status and Obstacles

ERIC Educational Resources Information Center

bin Tareef, Atif

2009-01-01

This study aimed at identifying the status and obstacles of scientific research in Jordanian higher education institutions. And defined by being an attempt to increase faculty member's, researcher's and educational leader's attention to the necessity of improving research planning or strategies, professional development, working conditions,…

An Obstacle-Tolerant Path Planning Algorithm for Mobile-Anchor-Node-Assisted Localization

PubMed Central

Tsai, Rong-Guei

2018-01-01

The location information obtained using a sensor is a critical requirement in wireless sensor networks. Numerous localization schemes have been proposed, among which mobile-anchor-node-assisted localization (MANAL) can reduce costs and overcome environmental constraints. A mobile anchor node (MAN) provides its own location information to assist the localization of sensor nodes. Numerous path planning schemes have been proposed for MANAL, but most scenarios assume the absence of obstacles in the environment. However, in a realistic environment, sensor nodes cannot be located because the obstacles block the path traversed by the MAN, thereby rendering the sensor incapable of receiving sufficient three location information from the MAN. This study proposes the obstacle-tolerant path planning (OTPP) approach to solve the sensor location problem owing to obstacle blockage. OTPP can approximate the optimum beacon point number and path planning, thereby ensuring that all the unknown nodes can receive the three location information from the MAN and reduce the number of MAN broadcast packet times. Experimental results demonstrate that OTPP performs better than Z-curves because it reduces the total number of beacon points utilized and is thus more suitable in an obstacle-present environment. Compared to the Z-curve, OTPP can reduce localization error and improve localization coverage. PMID:29547582

Insecurity in the DRC: The Obstacle to Peace and Stability

DTIC Science & Technology

2016-12-01

neighboring nations since the mid-1990s. In particular, the protected presence of armed groups has been a major obstacle to peace. Based on the best...study of the DRC to analyze four DDR programs initiated in the DRC from 2002 to 2009, with the goal of better understanding why they failed. The...beginning in the mid-1990s. In particular, the protected presence of armed groups has been a major obstacle to peace. Based on the best practices

Obstacles in Qualitative Research: Possible Solutions

ERIC Educational Resources Information Center

Poggenpoel, M.; Myburgh, C. P. H.

2005-01-01

In conducting research, the identified problem in the field will determine the research strategies chosen to address the problem. When a qualitative research strategy is deemed as the most appropriate strategy to get answers to research questions, the researcher should be aware of obstacles that can be encountered in the research process. If the…

Water in the presence of inert Lennard-Jones obstacles

NASA Astrophysics Data System (ADS)

Kurtjak, Mario; Urbic, Tomaz

2014-04-01

Water confined by the presence of a 'sea' of inert obstacles was examined. In the article, freely mobile two-dimensional Mercedes-Benz (MB) water put to a disordered, but fixed, matrix of Lennard-Jones disks was studied by the Monte Carlo computer simulations. For the MB water molecules in the matrix of Lennard-Jones disks, we explored the structures, hydrogen-bond-network formation and thermodynamics as a function of temperature and size and density of matrix particles. We found that the structure of model water is perturbed by the presence of the obstacles. Density of confined water, which was in equilibrium with the bulk water, was smaller than the density of the bulk water and the temperature dependence of the density of absorbed water did not show the density anomaly in the studied temperature range. The behaviour observed as a consequence of confinement is similar to that of increasing temperature, which can for a matrix lead to a process similar to capillary evaporation. At the same occupancy of space, smaller matrix molecules cause higher destruction effect on the absorbed water molecules than the bigger ones. We have also tested the hypothesis that at low matrix densities the obstacles induce an increased ordering and 'hydrogen bonding' of the MB model molecules, relative to pure fluid, while at high densities the obstacles reduce MB water structuring, as they prevent the fluid to form good 'hydrogen-bonding' networks. However, for the size of matrix molecules similar to that of water, we did not observe this effect.

Obstacles to Disarmament Education. Centre for Peace Studies Occasional Paper No. 6.

ERIC Educational Resources Information Center

Reardon, Betty

Obstacles to disarmament education fall into three general categories: political, perceptual, and pedagogical. At the elementary school level, these obstacles occur because of: (1) a lack of opportunities for cross-cultural experiences; (2) the socialization processes that enforce the belief that a child's culture is superior to and competitive…

Vortex propagation around a wall-mounted obstacle in pulsatile flow

NASA Astrophysics Data System (ADS)

Carr, Ian A.; Plesniak, Michael W.

2015-11-01

Wall-mounted obstacles are prevalent in nature and engineering applications. Physiological flows observed in human vocal fold pathologies, such as polyps, can be modeled by flow over a wall-mounted protuberance. Despite their prevalence, studies of wall-mounted obstacles have been restricted to steady (constant velocity) freestream flow. In biological and geophysical applications, pulsatile flow is much more common, yet effects of pulsatility on the wake of a wall-mounted obstacle remain to be extensively studied. This study aims to characterize the complex physics produced in this unsteady, separated flow. Experiments were performed in a low-speed wind tunnel with a set of rotating vanes, which produce the pulsatile inflow waveform. Instantaneous and phase-averaged particle image velocimetry (PIV) results acquired around a hemispherical obstacle are presented and compared. A mechanism based on self-induced vortex propagation, analogous to that in vortex rings, is proposed to explain the observed dynamics of coherent structures. Predictions of the propagation velocity based on analytical expressions for vortex rings in a viscous fluid are compared to the experimentally measured propagation velocity. Effects of the unsteady boundary layer on the observed physics are explored. This material is based in part upon work supported by the National Science Foundation under Grant Number CBET-1236351, and GW Center for Biomimetics and Bioinspired Engineering (COBRE).

Neural correlates of obstacle negotiation in older adults: An fNIRS study.

PubMed

Chen, Michelle; Pillemer, Sarah; England, Sarah; Izzetoglu, Meltem; Mahoney, Jeannette R; Holtzer, Roee

2017-10-01

Older adults are less efficient at avoiding obstacles compared to young adults, especially under attention-demanding conditions. Using functional near-infrared-spectroscopy (fNIRS), recent studies implicated the prefrontal cortex (PFC) in cognitive control of locomotion, notably under dual-task walking conditions. The neural substrates underlying Obstacle Negotiation (ON), however, have not been established. The current study determined the role of the PFC in ON during walking in seniors. Non-demented older adults (n=90; mean age=78.1±5.5years; %female=51) underwent fNIRS acquisition to assess changes in hemodynamic activity in the PFC during normal-walk [NW] and walk-while-talk [WWT] conditions with and without obstacles. Obstacles were presented as red elliptical shapes using advanced laser technology, which resemble potholes. Linear mixed effects models were used to determine differences in oxygenated hemoglobin (HbO 2 ) levels among the four task conditions. The presence of slow gait, a risk factor for dementia and falls, served as a predictor hypothesized to moderate the effect of obstacles on PFC HbO 2 levels. PFC HbO 2 levels were significantly higher in WWT compared to NW (p<0.001) irrespective of ON. Slow gait moderated the effect of obstacles on HbO 2 levels across task conditions. Specifically, compared to participants with normal gait, PFC HbO 2 levels were significantly increased in ON-NW relative to NW (p=0.017) and ON-WWT relative to WWT (p<0.001) among individuals with slow gait. Consistent with Compensatory Reallocation, ON required greater PFC involvement among individuals with mobility limitations. Copyright © 2017 Elsevier B.V. All rights reserved.

The quality of visual information about the lower extremities influences visuomotor coordination during virtual obstacle negotiation.

PubMed

Kim, Aram; Kretch, Kari S; Zhou, Zixuan; Finley, James M

2018-05-09

Successful negotiation of obstacles during walking relies on the integration of visual information about the environment with ongoing locomotor commands. When information about the body and environment are removed through occlusion of the lower visual field, individuals increase downward head pitch angle, reduce foot placement precision, and increase safety margins during crossing. However, whether these effects are mediated by loss of visual information about the lower extremities, the obstacle, or both remains to be seen. Here, we used a fully immersive, virtual obstacle negotiation task to investigate how visual information about the lower extremities is integrated with information about the environment to facilitate skillful obstacle negotiation. Participants stepped over virtual obstacles while walking on a treadmill with one of three types of visual feedback about the lower extremities: no feedback, end-point feedback, or a link-segment model. We found that absence of visual information about the lower extremities led to an increase in the variability of leading foot placement after crossing. The presence of a visual representation of the lower extremities promoted greater downward head pitch angle during the approach to and subsequent crossing of an obstacle. In addition, having greater downward head pitch was associated with closer placement of the trailing foot to the obstacle, further placement of the leading foot after the obstacle, and higher trailing foot clearance. These results demonstrate that the fidelity of visual information about the lower extremities influences both feed-forward and feedback aspects of visuomotor coordination during obstacle negotiation.

Democratic Communities of Inquiry: Creating Opportunities to Develop Citizenship

ERIC Educational Resources Information Center

Zaphir, Luke

2018-01-01

One of the most significant obstacles to inquiry and deliberation is citizenship education. There are few mechanisms for the development of citizens' democratic character within most societies, and greater opportunities need to be made to ensure our democracies are epistemically justifiable. The character and quality of citizens' interactions are…

A Review of Major Obstacles to Women's Participation in Higher Education in Kenya

ERIC Educational Resources Information Center

Sifuna, Daniel N.

2006-01-01

The paper provides a comprehensive review of the major obstacles that hinder the participation of girls and women in higher education in Kenya. This is on the basis that their low participation in this level of education is a key constraint to the development of the country. While it is reckoned that girls' and women's education is inextricably…

The addition of stripes (a version of the 'horizontal-vertical illusion') increases foot clearance when crossing low-height obstacles.

PubMed

Foster, Richard J; Buckley, John G; Whitaker, David; Elliott, David B

2016-07-01

Trips over obstacles are one of the main causes of falling in older adults, with vision playing an important role in successful obstacle negotiation. We determined whether a horizontal-vertical illusion, superimposed onto low-height obstacles to create a perceived increase in obstacle height, increased foot clearances during obstacle negotiation thus reducing the likelihood of tripping. Eleven adults (mean ± 1 SD: age 27.3 ± 5.1 years) negotiated obstacles of varying heights (3, 5, 7 cm) with four different appearance conditions; two were obstacles with a horizontal-vertical illusion (vertical stripes of different thickness) superimposed on the front, one was a plain obstacle and the fourth a plain obstacle with a horizontal black line painted on the top edge. Foot clearance parameters were compared across conditions. Both illusions led to a significant increase in foot clearance when crossing the obstacle, compared to the plain condition, irrespective of obstacle height. Superimposing a horizontal-vertical illusion onto low-height obstacles can increase foot clearance, and its use on the floor section of a double-glazing door frame for example may reduce the incidence of tripping in the home. Practitioner Summary: Low-height obstacles such as the floor section of a double-glazing door frame are potential tripping hazards. In a gait lab-based study we found that a horizontal-vertical illusion superimposed onto low-height obstacles led to significantly higher foot clearances; indicating their potential as a useful safety measure.

Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

NASA Astrophysics Data System (ADS)

Endo, Keita; Katsuragi, Hiroaki

2017-06-01

Two-dimensional granular discharge flow driven by gravity under the influence of an obstacle is experimentally investigated. A horizontal exit of width W is opened at the bottom of vertical Hele-Shaw cell filled with stainless-steel particles to start the discharge flow. In this experiment, a circular obstacle is placed in front of the exit. Thus, the distance between the exit and obstacle L is also an important parameter. During the discharge, granular-flow state is acquired by a high-speed camera. The bulk discharge-flow rate is also measured by load cell sensors. The obtained high-speed-image data are analyzed to clarify the particle-level granular-flow dynamics. Using the measured data, we find that the obstacle above the exit affects the granular- flow field. Specifically, the existence of obstacle results in large horizontal granular temperature and small packing fraction. This tendency becomes significant when L is smaller than approximately 6Dg when W ≃ 4Dg, where Dg is diameter of particles.

Short range laser obstacle detector. [for surface vehicles using laser diode array

NASA Technical Reports Server (NTRS)

Kuriger, W. L. (Inventor)

1973-01-01

A short range obstacle detector for surface vehicles is described which utilizes an array of laser diodes. The diodes operate one at a time, with one diode for each adjacent azimuth sector. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser is synchronized with the vibrating mirror to enable one diode laser to be fired, by pulses from a clock pulse source, a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.

Collaborative Learning Practices: Teacher and Student Perceived Obstacles to Effective Student Collaboration

ERIC Educational Resources Information Center

Le, Ha; Janssen, Jeroen; Wubbels, Theo

2018-01-01

While the educational literature mentions several obstacles affecting the effectiveness of collaborative learning (CL), they have often been investigated through the perceptions of only one actor, either teachers or students. Therefore, some sources of obstacles that teachers and students encounter may not have been revealed. In this study, 19…

Obstacle Detection and Avoidance System Based on Monocular Camera and Size Expansion Algorithm for UAVs

PubMed Central

Al-Kaff, Abdulla; García, Fernando; Martín, David; De La Escalera, Arturo; Armingol, José María

2017-01-01

One of the most challenging problems in the domain of autonomous aerial vehicles is the designing of a robust real-time obstacle detection and avoidance system. This problem is complex, especially for the micro and small aerial vehicles, that is due to the Size, Weight and Power (SWaP) constraints. Therefore, using lightweight sensors (i.e., Digital camera) can be the best choice comparing with other sensors; such as laser or radar.For real-time applications, different works are based on stereo cameras in order to obtain a 3D model of the obstacles, or to estimate their depth. Instead, in this paper, a method that mimics the human behavior of detecting the collision state of the approaching obstacles using monocular camera is proposed. The key of the proposed algorithm is to analyze the size changes of the detected feature points, combined with the expansion ratios of the convex hull constructed around the detected feature points from consecutive frames. During the Aerial Vehicle (UAV) motion, the detection algorithm estimates the changes in the size of the area of the approaching obstacles. First, the method detects the feature points of the obstacles, then extracts the obstacles that have the probability of getting close toward the UAV. Secondly, by comparing the area ratio of the obstacle and the position of the UAV, the method decides if the detected obstacle may cause a collision. Finally, by estimating the obstacle 2D position in the image and combining with the tracked waypoints, the UAV performs the avoidance maneuver. The proposed algorithm was evaluated by performing real indoor and outdoor flights, and the obtained results show the accuracy of the proposed algorithm compared with other related works. PMID:28481277

Two dimensional numerical analysis of snow avalanche interaction with structures

NASA Astrophysics Data System (ADS)

Bovet, Eloïse; Chiaia, Bernardino; Preziosi, Luigi

2010-05-01

The purpose of this work, within the Project "DynAval - Dynamique des avalanches: départ et interactions écoulement/obstacles" - European Territorial Cooperation objective Italy - France (Alps), is to analyse the snow avalanche and structure interaction, through a numerical analysis. The avalanche behaviour, considered as an incompressible fluid, is described by a two-dimensional, in the avalanche slope, Navier-Stokes equations to which an advection equation is coupled to take into account the shape variation. The model allows to describe the velocity and the pressure at every point, representing important features for the structural design. The simulations are carried using a FEM Multiphysics software. For a such problem different analysis can be carried. Firstly, changing the obstacle shape (circle, square, triangle) and its dimension in relation to the avalanche size, the drag coefficient Cd can be evaluated. The obtained results are then compared with the values indicated by the procedures, concerning the avalanches, available in the literature. This study is realized for different Froude numbers too. Secondarily the pressure acting on the different parts of the obstacle (up-wind, down-wind, lateral) is studied. The first investigation concerns the evaluation of the Cp coefficient and on its comparison with the wind effects. The second analysis allows to evaluates, by an integration process, the total load exerted by the avalanche on the obstacle. A practical example of a building design is presented, taking into account the results of the simulations. Thirdly the study is focused on the characterization of the two dead zones created up-wind and down-wind the obstacle. The dependence of the dead zone on the obstacle characteristics, such as dimension and shape, and on the avalanche features, such as density and velocity, is analysed. The results obtained are compared with the data available in the literature concerning snow or granular material interaction

State-of-the-art technologies for intrusion and obstacle detection for railroad operations

DOT National Transportation Integrated Search

2007-07-01

This report provides an update on the state-of-the-art technologies with intrusion and obstacle detection capabilities for rail rights of way (ROW) and crossings. A workshop entitled Intruder and Obstacle Detection Systems (IODS) for Railroads Requir...

Recovering an elastic obstacle containing embedded objects by the acoustic far-field measurements

NASA Astrophysics Data System (ADS)

Qu, Fenglong; Yang, Jiaqing; Zhang, Bo

2018-01-01

Consider the inverse scattering problem of time-harmonic acoustic waves by a 3D bounded elastic obstacle which may contain embedded impenetrable obstacles inside. We propose a novel and simple technique to show that the elastic obstacle can be uniquely recovered by the acoustic far-field pattern at a fixed frequency, disregarding its contents. Our method is based on constructing a well-posed modified interior transmission problem on a small domain and makes use of an a priori estimate for both the acoustic and elastic wave fields in the usual H 1-norm. In the case when there is no obstacle embedded inside the elastic body, our method gives a much simpler proof for the uniqueness result obtained previously in the literature (Natroshvili et al 2000 Rend. Mat. Serie VII 20 57-92 Monk and Selgas 2009 Inverse Problems Imaging 3 173-98).

Different protocols for analyzing behavior and adaptability in obstacle crossing in Parkinson’s disease

PubMed Central

Mollaei, Nafiseh; Bicho, Estela; Sousa, Nuno; Gago, Miguel Fernandes

2017-01-01

Imbalance and tripping over obstacles as a result of altered gait in older adults, especially in patients with Parkinson’s disease (PD), are one of the most common causes of falls. During obstacle crossing, patients with PD modify their behavior in order to decrease the mechanical demands and enhance dynamic stability. Various descriptions of dynamic traits of gait that have been collected over longer periods, probably better synthesize the underlying structure and pattern of fluctuations in gait and can be more sensitive markers of aging or early neurological dysfunction and increased risk of falls. This confirmation challenges the clinimetric of different protocols and paradigms used for gait analysis up till now, in particular when analyzing obstacle crossing. The authors here present a critical review of current knowledge concerning the interplay between the cognition and gait in aging and PD, emphasizing the differences in gait behavior and adaptability while walking over different and challenging obstacle paradigms, and the implications of obstacle negotiation as a predictor of falls. Some evidence concerning the effectiveness of future rehabilitation protocols on reviving obstacle crossing behavior by trial and error relearning, taking advantage of dual-task paradigms, physical exercise, and virtual reality have been put forward in this article. PMID:29158667

Fresnel diffraction by spherical obstacles

NASA Technical Reports Server (NTRS)

Hovenac, Edward A.

1989-01-01

Lommel functions were used to solve the Fresnel-Kirchhoff diffraction integral for the case of a spherical obstacle. Comparisons were made between Fresnel diffraction theory and Mie scattering theory. Fresnel theory is then compared to experimental data. Experiment and theory typically deviated from one another by less than 10 percent. A unique experimental setup using mercury spheres suspended in a viscous fluid significantly reduced optical noise. The major source of error was due to the Gaussian-shaped laser beam.

Age-related changes in gait adaptability in response to unpredictable obstacles and stepping targets.

PubMed

Caetano, Maria Joana D; Lord, Stephen R; Schoene, Daniel; Pelicioni, Paulo H S; Sturnieks, Daina L; Menant, Jasmine C

2016-05-01

A large proportion of falls in older people occur when walking. Limitations in gait adaptability might contribute to tripping; a frequently reported cause of falls in this group. To evaluate age-related changes in gait adaptability in response to obstacles or stepping targets presented at short notice, i.e.: approximately two steps ahead. Fifty older adults (aged 74±7 years; 34 females) and 21 young adults (aged 26±4 years; 12 females) completed 3 usual gait speed (baseline) trials. They then completed the following randomly presented gait adaptability trials: obstacle avoidance, short stepping target, long stepping target and no target/obstacle (3 trials of each). Compared with the young, the older adults slowed significantly in no target/obstacle trials compared with the baseline trials. They took more steps and spent more time in double support while approaching the obstacle and stepping targets, demonstrated poorer stepping accuracy and made more stepping errors (failed to hit the stepping targets/avoid the obstacle). The older adults also reduced velocity of the two preceding steps and shortened the previous step in the long stepping target condition and in the obstacle avoidance condition. Compared with their younger counterparts, the older adults exhibited a more conservative adaptation strategy characterised by slow, short and multiple steps with longer time in double support. Even so, they demonstrated poorer stepping accuracy and made more stepping errors. This reduced gait adaptability may place older adults at increased risk of falling when negotiating unexpected hazards. Copyright © 2016 Elsevier B.V. All rights reserved.

Micro air vehicle autonomous obstacle avoidance from stereo-vision

NASA Astrophysics Data System (ADS)

Brockers, Roland; Kuwata, Yoshiaki; Weiss, Stephan; Matthies, Lawrence

2014-06-01

We introduce a new approach for on-board autonomous obstacle avoidance for micro air vehicles flying outdoors in close proximity to structure. Our approach uses inverse-range, polar-perspective stereo-disparity maps for obstacle detection and representation, and deploys a closed-loop RRT planner that considers flight dynamics for trajectory generation. While motion planning is executed in 3D space, we reduce collision checking to a fast z-buffer-like operation in disparity space, which allows for significant speed-up compared to full 3d methods. Evaluations in simulation illustrate the robustness of our approach, whereas real world flights under tree canopy demonstrate the potential of the approach.

An Obstacle Problem for Conical Deformations of Thin Elastic Sheets

NASA Astrophysics Data System (ADS)

Figalli, Alessio; Mooney, Connor

2018-05-01

A developable cone ("d-cone") is the shape made by an elastic sheet when it is pressed at its center into a hollow cylinder by a distance {ɛ}. Starting from a nonlinear model depending on the thickness h > 0 of the sheet, we prove a {Γ} -convergence result as {h → 0} to a fourth-order obstacle problem for curves in {S^2}. We then describe the exact shape of minimizers of the limit problem when {ɛ} is small. In particular, we rigorously justify previous results in the physics literature.

The Sensitivity Analysis for the Flow Past Obstacles Problem with Respect to the Reynolds Number

PubMed Central

Ito, Kazufumi; Li, Zhilin; Qiao, Zhonghua

2013-01-01

In this paper, numerical sensitivity analysis with respect to the Reynolds number for the flow past obstacle problem is presented. To carry out such analysis, at each time step, we need to solve the incompressible Navier-Stokes equations on irregular domains twice, one for the primary variables; the other is for the sensitivity variables with homogeneous boundary conditions. The Navier-Stokes solver is the augmented immersed interface method for Navier-Stokes equations on irregular domains. One of the most important contribution of this paper is that our analysis can predict the critical Reynolds number at which the vortex shading begins to develop in the wake of the obstacle. Some interesting experiments are shown to illustrate how the critical Reynolds number varies with different geometric settings. PMID:24910780

The Sensitivity Analysis for the Flow Past Obstacles Problem with Respect to the Reynolds Number.

PubMed

Ito, Kazufumi; Li, Zhilin; Qiao, Zhonghua

2012-02-01

In this paper, numerical sensitivity analysis with respect to the Reynolds number for the flow past obstacle problem is presented. To carry out such analysis, at each time step, we need to solve the incompressible Navier-Stokes equations on irregular domains twice, one for the primary variables; the other is for the sensitivity variables with homogeneous boundary conditions. The Navier-Stokes solver is the augmented immersed interface method for Navier-Stokes equations on irregular domains. One of the most important contribution of this paper is that our analysis can predict the critical Reynolds number at which the vortex shading begins to develop in the wake of the obstacle. Some interesting experiments are shown to illustrate how the critical Reynolds number varies with different geometric settings.

Obstacles and challenges following the partial decriminalisation of abortion in Colombia.

PubMed

Amado, Eduardo Díaz; Calderón García, Maria Cristina; Cristancho, Katherine Romero; Salas, Elena Prada; Hauzeur, Eliane Barreto

2010-11-01

During a highly contested process, abortion was partially decriminalised in Colombia in 2006 by the Constitutional Court: when the pregnancy threatens a woman's life or health, in cases of severe fetal malformations incompatible with life, and in cases of rape, incest or unwanted insemination. However, Colombian women still face obstacles to accessing abortion services. This is illustrated by 36 cases of women who in 2006-08 were denied the right to a lawful termination of pregnancy, or had unjustified obstacles put in their path which delayed the termination, which are analysed in this article. We argue that the obstacles resulted from fundamental disagreements about abortion and misunderstandings regarding the ethical, legal and medical requirements arising from the Court's decision. In order to avoid obstacles such as demands for a judge's authorisation, institutional claims of conscientious objection, rejection of a claim of rape, or refusal of health insurance coverage for a legal termination, which constitute discrimination against women, three main strategies are suggested: public ownership of the Court's decision by all Colombian citizens, a professional approach by those involved in the provision of services in line with the law, and monitoring of its implementation by governmental and non-governmental organisations. Copyright © 2010 Reproductive Health Matters. Published by Elsevier Ltd. All rights reserved.

Impaired anticipatory control of grasp during obstacle crossing in Parkinson's disease.

PubMed

McIsaac, Tara L; Diermayr, Gudrun; Albert, Frederic

2012-05-16

During self-paced walking, people with Parkinson's disease maintain anticipatory control during object grasping. However, common functional tasks often include carrying an object while changing step patterns mid-path and maneuvering over obstacles, increasing task complexity and attentional demands. Thus, the present study investigated the effect of Parkinson's disease on the modulation of grasping force changes as a function of gait-related inertial forces. Subjects with Parkinson's disease maintained the ability to scale and to couple over time their grip and inertial forces while walking at irregular step lengths, but were unable to maintain the temporal coupling of grasping forces compared to controls during obstacle crossing. We suggest that this deterioration in anticipatory control is associated with the increased demands of task complexity and attention during obstacle crossing. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Obstacle Classification and 3D Measurement in Unstructured Environments Based on ToF Cameras

PubMed Central

Yu, Hongshan; Zhu, Jiang; Wang, Yaonan; Jia, Wenyan; Sun, Mingui; Tang, Yandong

2014-01-01

Inspired by the human 3D visual perception system, we present an obstacle detection and classification method based on the use of Time-of-Flight (ToF) cameras for robotic navigation in unstructured environments. The ToF camera provides 3D sensing by capturing an image along with per-pixel 3D space information. Based on this valuable feature and human knowledge of navigation, the proposed method first removes irrelevant regions which do not affect robot's movement from the scene. In the second step, regions of interest are detected and clustered as possible obstacles using both 3D information and intensity image obtained by the ToF camera. Consequently, a multiple relevance vector machine (RVM) classifier is designed to classify obstacles into four possible classes based on the terrain traversability and geometrical features of the obstacles. Finally, experimental results in various unstructured environments are presented to verify the robustness and performance of the proposed approach. We have found that, compared with the existing obstacle recognition methods, the new approach is more accurate and efficient. PMID:24945679

Obstacle negotiation control for a mobile robot suspended on overhead ground wires by optoelectronic sensors

NASA Astrophysics Data System (ADS)

Zheng, Li; Yi, Ruan

2009-11-01

Power line inspection and maintenance already benefit from developments in mobile robotics. This paper presents mobile robots capable of crossing obstacles on overhead ground wires. A teleoperated robot realizes inspection and maintenance tasks on power transmission line equipment. The inspection robot is driven by 11 motor with two arms, two wheels and two claws. The inspection robot is designed to realize the function of observation, grasp, walk, rolling, turn, rise, and decline. This paper is oriented toward 100% reliable obstacle detection and identification, and sensor fusion to increase the autonomy level. An embedded computer based on PC/104 bus is chosen as the core of control system. Visible light camera and thermal infrared Camera are both installed in a programmable pan-and-tilt camera (PPTC) unit. High-quality visual feedback rapidly becomes crucial for human-in-the-loop control and effective teleoperation. The communication system between the robot and the ground station is based on Mesh wireless networks by 700 MHz bands. An expert system programmed with Visual C++ is developed to implement the automatic control. Optoelectronic laser sensors and laser range scanner were installed in robot for obstacle-navigation control to grasp the overhead ground wires. A novel prototype with careful considerations on mobility was designed to inspect the 500KV power transmission lines. Results of experiments demonstrate that the robot can be applied to execute the navigation and inspection tasks.

Genetic variation in arthropod vectors of disease-causing organisms: obstacles and opportunities.

PubMed Central

Gooding, R H

1996-01-01

An overview of the genetic variation in arthropods that transmit pathogens to vertebrates is presented, emphasizing the genetics of vector-pathogen relationships and the biochemical genetics of vectors. Vector-pathogen interactions are reviewed briefly as a prelude to a discussion of the genetics of susceptibility and refractoriness in vectors. Susceptibility to pathogens is controlled by maternally inherited factors, sex-linked dominant alleles, and dominant and recessive autosomal genes. There is widespread interpopulation (including intercolony) and temporal variation in susceptibility to pathogens. The amount of biochemical genetic variation in vectors is similar to that found in other invertebrates. However, the amount varies widely among species, among populations within species, and temporally within populations. Biochemical genetic studies show that there is considerable genetic structuring of many vectors at the local, regional, and global levels. It is argued that genetic variation in vectors is critical in understanding vector-pathogen interactions and that genetic variation in vectors creates both obstacles to and opportunities for application of genetic techniques to the control of vectors. PMID:8809462

77 FR 50014 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-20

... navigational facilities, adding new obstacles, or changing air traffic requirements. These changes are designed.... Intl. 20-Sep-12 TX Houston Sugar Land Rgnl.... 2/8058 7/19/12 TAKEOFF MINIMUMS AND (OBSTACLE) DP, Amdt...

Identifying Obstacles to Adoption in New York State's Out-of-Home Care System.

ERIC Educational Resources Information Center

Avery, Rosemary J.

1999-01-01

This study queried caseworkers for 77 New York children in out-of-home care still waiting for placement to determine obstacles to permanent adoption. Questionnaires sought demographics, placement efforts, and caseworker opinions. Findings indicated several obstacles, including the following: child's strong emotional ties to family (foster or…

Critical Care Nurses' Perceptions of End-of-Life Care Obstacles: Comparative 17-Year Data.

PubMed

Beckstrand, Renea L; Lamoreaux, Nicole; Luthy, Karlen E; Macintosh, Janelle L B

Nurses working in intensive care units (ICUs) frequently care for patients and their families at the end of life (EOL). Providing high-quality EOL care is important for both patients and families, yet ICU nurses face many obstacles that hinder EOL care. Researchers have identified various ICU nurse-perceived obstacles, but no studies have been found addressing the progress that has been made for the last 17 years. The aims of this study were to determine the most common and current obstacles in EOL care as perceived by ICU nurses and then to evaluate whether meaningful changes have occurred since data were first gathered in 1998. A quantitative-qualitative mixed methods design was used. A random, geographically dispersed sample of 2000 members of the American Association of Critical-Care Nurses was surveyed. Five obstacle items increased in mean score and rank as compared with 1999 data including (1) family not understanding what the phrase "lifesaving measures" really means, (2) providing lifesaving measures at families' requests despite patient's advance directive listing no such care, (3) family not accepting patient's poor prognosis, (4) family members fighting about the use of life support, and (5) not enough time to provide EOL care because the nurse is consumed with lifesaving measures attempting to save the patient's life. Five obstacle items decreased in mean score and rank compared with 1999 data including (1) physicians differing in opinion about care of the patient, (2) family and friends who continually call the nurse rather than calling the designated family member, (3) physicians who are evasive and avoid families, (4) nurses having to deal with angry families, and (5) nurses not knowing their patient's wishes regarding continuing with tests and treatments. Obstacles in EOL care, as perceived by critical care nurses, still exist. Family-related obstacles have increased over time. Obstacles related to families may not be easily overcome as each family

Prevention 0f Unwanted Free-Declaration of Static Obstacles in Probability Occupancy Grids

NASA Astrophysics Data System (ADS)

Krause, Stefan; Scholz, M.; Hohmann, R.

2017-10-01

Obstacle detection and avoidance are major research fields in unmanned aviation. Map based obstacle detection approaches often use discrete world representations such as probabilistic grid maps to fuse incremental environment data from different views or sensors to build a comprehensive representation. The integration of continuous measurements into a discrete representation can result in rounding errors which, in turn, leads to differences between the artificial model and real environment. The cause of these deviations is a low spatial resolution of the world representation comparison to the used sensor data. Differences between artificial representations which are used for path planning or obstacle avoidance and the real world can lead to unexpected behavior up to collisions with unmapped obstacles. This paper presents three approaches to the treatment of errors that can occur during the integration of continuous laser measurement in the discrete probabilistic grid. Further, the quality of the error prevention and the processing performance are compared with real sensor data.

78 FR 54564 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-05

... Linder Rgnl, Takeoff Minimums and Obstacle DP, Amdt 1 Venice, FL, Venice Muni, RNAV (GPS) RWY 5, Orig Venice, FL, Venice Muni, RNAV (GPS) RWY 23, Orig Venice, FL, Venice Muni, Takeoff Minimums and Obstacle...

Factors influencing the development and use of interactive video in nursing education. A Delphi study.

PubMed

Rizzolo, M A

1990-01-01

The purpose of this study was to identify factors impeding development and use of interactive video (IAV) in nursing education in order to specify actions that would facilitate its development and use. Nurse educators with experience in development of IAV programs were defined as the experts, and a three-round Delphi study was conducted. Study findings revealed that participants were aware of obstacles to development and were able to suggest some ways to overcome them. Subjects clearly identified content they want in IAV programs, and were especially united on applications for simulations. They agreed on benefits of IAV for students, but were less certain about how it might affect faculty roles, and were undecided about measurable advantages of IAV. Conservative predictions were made about how evolving IAV technology might change the process of nurse education in the future. To promote IAV development and use the author recommends cooperative efforts between nurse educators and developers in the business sector and an educational thrust targeted for specific groups. Moving beyond existing nursing roles and institutional models, the author makes two major suggestions: establishment of a new nursing specialist, the nurse/instructional designer, and the creation of an information center staffed by these new specialists who will design and develop programs, provide education and consultation, maintain a clearinghouse for IAV programs, research, and technology, and take a leadership role in the integration of this powerful instructional delivery system into the entire health field.

Analysis of the obstacles related to treatment entry, adherence and drop-out among alcoholic patients.

PubMed

Fonsi Elbreder, Márcia; Carvalho De Humerez, Dorisdaia; Laranjeira, Ronaldo

2009-01-01

Alcoholism is a complex syndrome involving social, psychological and individual factors in addition to a series of obstacles regarding treatment entry, adherence, and drop-out. These obstacles contribute negatively to both clinical evolution and prognosis of the patients, affecting their quality of life and raising the social costs. This is a bibliographical study in which we address this theme as well as other experiences observed in our daily practice in the Alcohol and Drug Research Unit (UNIAD) based at the Federal University of São Paulo (UNIFESP). The analysis of the obstacles related to treatment entry, attendance, and drop-out among alcoholic patients shows that systemic, social, cultural, and individual factors are all involved, including the structural ones. Women have more obstacles compared to men, and what is thought to be a barrier to one patient may be a factor motivating another patient to search for help. We conclude that several factors at different levels exist that prevent the patient from overcoming these treatment obstacles.

75 FR 72942 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-29

..., Takeoff Minimums and Obstacle DP, Amdt 3 Harvard, NE, Harvard State, RNAV (GPS) RWY 35, Orig Harvard, NE, Harvard State, Takeoff Minimums and Obstacle DP, Orig Harvard, NE, Harvard State, VOR/DME RNAV OR GPS RWY...

Object classification for obstacle avoidance

NASA Astrophysics Data System (ADS)

Regensburger, Uwe; Graefe, Volker

1991-03-01

Object recognition is necessary for any mobile robot operating autonomously in the real world. This paper discusses an object classifier based on a 2-D object model. Obstacle candidates are tracked and analyzed false alarms generated by the object detector are recognized and rejected. The methods have been implemented on a multi-processor system and tested in real-world experiments. They work reliably under favorable conditions but sometimes problems occur e. g. when objects contain many features (edges) or move in front of structured background.

Sensorimotor integration of vision and proprioception for obstacle crossing in ambulatory individuals with spinal cord injury.

PubMed

Malik, Raza Naseem; Cote, Rachel; Lam, Tania

2017-01-01

Skilled walking, such as obstacle crossing, is an essential component of functional mobility. Sensorimotor integration of visual and proprioceptive inputs is important for successful obstacle crossing. The objective of this study was to understand how proprioceptive deficits affect obstacle-crossing strategies when controlling for variations in motor deficits in ambulatory individuals with spinal cord injury (SCI). Fifteen ambulatory individuals with SCI and 15 able-bodied controls were asked to step over an obstacle scaled to their motor abilities under full and obstructed vision conditions. An eye tracker was used to determine gaze behaviour and motion capture analysis was used to determine toe kinematics relative to the obstacle. Combined, bilateral hip and knee proprioceptive sense (joint position sense and movement detection sense) was assessed using the Lokomat and customized software controls. Combined, bilateral hip and knee proprioceptive sense in subjects with SCI varied and was significantly different from able-bodied subjects. Subjects with greater proprioceptive deficits stepped higher over the obstacle with their lead and trail limbs in the obstructed vision condition compared with full vision. Subjects with SCI also glanced at the obstacle more frequently and with longer fixation times compared with controls, but this was not related to proprioceptive sense. This study indicates that ambulatory individuals with SCI rely more heavily on vision to cross obstacles and show impairments in key gait parameters required for successful obstacle crossing. Our data suggest that proprioceptive deficits need to be considered in rehabilitation programs aimed at improving functional mobility in ambulatory individuals with SCI. This work is unique since it examines the contribution of combined, bilateral hip and knee proprioceptive sense on the recovery of skilled walking function, in addition to characterizing gaze behavior during a skilled walking task in people

Control of vertical posture while elevating one foot to avoid a real or virtual obstacle.

PubMed

Ida, Hirofumi; Mohapatra, Sambit; Aruin, Alexander

2017-06-01

The purpose of this study is to investigate the control of vertical posture during obstacle avoidance in a real versus a virtual reality (VR) environment. Ten healthy participants stood upright and lifted one leg to avoid colliding with a real obstacle sliding on the floor toward a participant and with its virtual image. Virtual obstacles were delivered by a head mounted display (HMD) or a 3D projector. The acceleration of the foot, center of pressure, and electrical activity of the leg and trunk muscles were measured and analyzed during the time intervals typical for early postural adjustments (EPAs), anticipatory postural adjustments (APAs), and compensatory postural adjustments (CPAs). The results showed that the peak acceleration of foot elevation in the HMD condition decreased significantly when compared with that of the real and 3D projector conditions. Reduced activity of the leg and trunk muscles was seen when dealing with virtual obstacles (HMD and 3D projector) as compared with that seen when dealing with real obstacles. These effects were more pronounced during APAs and CPAs. The onsets of muscle activities in the supporting limb were seen during EPAs and APAs. The observed modulation of muscle activity and altered patterns of movement seen while avoiding a virtual obstacle should be considered when designing virtual rehabilitation protocols.

Creation of a Mental Health Treatment Fears and Obstacles Inventory for College Students

ERIC Educational Resources Information Center

Park, Heather L.; Attenweiler, William J.; Rieck, Stacey M.

2012-01-01

This project concerned the creation of an inventory for college students of treatment fears and obstacles to seeking mental health services. Unlike previous research, undergraduate participants generated a pool of items to measure fears of and obstacles to seeking services. Subsequent rational and statistical refinement resulted in a 29-item scale…

Introduction of frictional and turning function for pedestrian outflow with an obstacle.

PubMed

Yanagisawa, Daichi; Kimura, Ayako; Tomoeda, Akiyasu; Nishi, Ryosuke; Suma, Yushi; Ohtsuka, Kazumichi; Nishinari, Katsuhiro

2009-09-01

In this paper, two important factors which affect the pedestrian outflow at a bottleneck significantly are studied in detail to analyze the effect of an obstacle setup in front of an exit. One is a conflict at an exit when pedestrians evacuate from a room. We use floor field model for simulating such behavior, which is a well-studied pedestrian model using cellular automata. The conflicts have been taken into account by the friction parameter. However, the friction parameter so far is a constant and does not depend on the number of the pedestrians conflicting at the same time. Thus, we have improved the friction parameter by the frictional function, which is a function of the number of the pedestrians involved in the conflict. Second, we have presented the cost of turning of pedestrians at the exit. Since pedestrians have inertia, their walking speeds decrease when they turn and the pedestrian outflow decreases. The validity of the extended model, which includes the frictional function and the turning function, is supported by the comparison of a mean-field theory and real experiments. We have observed that the pedestrian flow increases when we put an obstacle in front of an exit in our real experiments. The analytical results clearly explains the mechanism of the effect of the obstacle, i.e., the obstacle blocks pedestrians moving to the exit and decreases the average number of pedestrians involved in the conflict. We have also found that an obstacle works more effectively when we shift it from the center since pedestrians go through the exit with less turning.

Manipulating the fidelity of lower extremity visual feedback to identify obstacle negotiation strategies in immersive virtual reality.

PubMed

Kim, Aram; Zhou, Zixuan; Kretch, Kari S; Finley, James M

2017-07-01

The ability to successfully navigate obstacles in our environment requires integration of visual information about the environment with estimates of our body's state. Previous studies have used partial occlusion of the visual field to explore how information about the body and impending obstacles are integrated to mediate a successful clearance strategy. However, because these manipulations often remove information about both the body and obstacle, it remains to be seen how information about the lower extremities alone is utilized during obstacle crossing. Here, we used an immersive virtual reality (VR) interface to explore how visual feedback of the lower extremities influences obstacle crossing performance. Participants wore a head-mounted display while walking on treadmill and were instructed to step over obstacles in a virtual corridor in four different feedback trials. The trials involved: (1) No visual feedback of the lower extremities, (2) an endpoint-only model, (3) a link-segment model, and (4) a volumetric multi-segment model. We found that the volumetric model improved success rate, placed their trailing foot before crossing and leading foot after crossing more consistently, and placed their leading foot closer to the obstacle after crossing compared to no model. This knowledge is critical for the design of obstacle negotiation tasks in immersive virtual environments as it may provide information about the fidelity necessary to reproduce ecologically valid practice environments.

Effects of overweight and obese body mass on motor planning and motor skills during obstacle crossing in children.

PubMed

Gill, Simone V; Hung, Ya-Ching

2014-01-01

Little is known about how obesity relates to motor planning and skills during functional tasks. We collected 3-D kinematics and kinetics as normal weight (n=10) and overweight/obese (n=12) children walked on flat ground and as they crossed low, medium, and high obstacles. We investigated if motor planning and motor skill impairments were evident during obstacle crossing. Baseline conditions showed no group differences (all ps>.05). Increased toe clearance was found on low obstacles (p=.01) for the overweight/obese group and on high obstacles (p=.01) for the normal weight group. With the crossing leg, the overweight/obese group had larger hip abduction angles (p=.01) and medial ground reaction forces (p=.006) on high obstacles and high anterior ground reaction forces on low obstacles (p=.001). With the trailing leg, overweight/obese children had higher vertical ground reaction forces on high obstacles (p=.005) and higher knee angles (p=.01) and anterior acceleration in the center of mass (p=.01) on low obstacles. These findings suggest that differences in motor planning and skills in overweight/obese children may be more apparent during functional activities. Copyright © 2013 Elsevier Ltd. All rights reserved.

Real-time obstacle and collision avoidance system for fixed wing unmanned aerial systems

NASA Astrophysics Data System (ADS)

Esposito, Julien F.

' centroids to their common midpoint located on the shared edge, the resulting flying legs remain within the two cells. The next step for paths between two cells is to be converted into flyable paths, and the conversion uses main and fallback methods to achieve that. The preferred method is the closed-form Dubins paths method involving the design of sequences of arc circle-straight line-arc circle (CLC) in order to account for the minimum radius turn constrain of the UAS. An additional geometric transformation is developed and applied to the initial waypoints used in the Dubins method so the flying leg directions are respected which is not possible by using the Dubins method alone. The second original contribution of this research is the development and demonstration of the Double Dispersion reduction RRT (DDRRT), an algorithm which employs two new developed logic schemes respectively referred to as Punctual Dispersion Reduction (PDR), and Spatial Dispersion Reduction exploration (SDR). The DDRRT is employed during the real-time in-flight phase where it initially assumes a perfect terrain and no unpredictable threat, consequently following a 100% adaptive goal biasing toward the next waypoint in its list. When a threat such as an unpredicted obstacle is detected, the (PDR) acknowledges the fact that the DDRRT tree branches have met an obstacle and the its goal-biasing toward the next waypoint is decreased. If the PDR keeps decreasing, the DDRRT develops awareness of its surrounding obstacles by relaxing its PDR and switching to SDR which has the effect of increasing the dispersion of its branches, but keeping their extension bounded by the cell containing the last good position of the UAS, Csafe. (Abstract shortened by UMI.)

Laminar CuO-water nano-fluid flow and heat transfer in a backward-facing step with and without obstacle

NASA Astrophysics Data System (ADS)

Togun, Hussein

2016-03-01

This paper presents a numerical investigate on CuO-water nano-fluid and heat transfer in a backward-facing step with and without obstacle. The range of Reynolds number varied from 75 to 225 with volume fraction on CuO nanoparticles varied from 1 to 4 % at constant heat flux was investigated. Continuity, momentum, and energy equations with finite volume method in two dimensions were employed. Four different configurations of backward-facing step (without obstacle, with obstacle of 1.5 mm, with obstacle of 3 mm, with obstacle of 4.5 mm) were considered to find the best thermal performance. The results show that the maximum augmentation in heat transfer was about 22 % for backward-facing step with obstacle of 4.5 mm and using CuO nanoparticles at Reynolds number of 225 compared with backward-facing step without obstacle. It is also observed that increase in size of recirculation region with increase of height obstacle on the channel wall has remarkable effect on thermal performance. The results also found that increases in Reynolds number, height obstacle, and volume fractions of CuO nanoparticles lead to increase of pressure drop.

Neuroepigenomics: Resources, Obstacles, and Opportunities

PubMed Central

Satterlee, John S.; Beckel-Mitchener, Andrea; Little, Roger; Procaccini, Dena; Rutter, Joni L.; Lossie, Amy C.

2014-01-01

Long-lived post-mitotic cells, such as the majority of human neurons, must respond effectively to ongoing changes in neuronal stimulation or microenvironmental cues through transcriptional and epigenomic regulation of gene expression. The role of epigenomic regulation in neuronal function is of fundamental interest to the neuroscience community, as these types of studies have transformed our understanding of gene regulation in post-mitotic cells. This perspective article highlights many of the resources available to researchers interested in neuroepigenomic investigations and discusses some of the current obstacles and opportunities in neuroepigenomics. PMID:25722961

Learn to Avoid or Overcome Leadership Obstacles

ERIC Educational Resources Information Center

D'Auria, John

2015-01-01

Leadership is increasingly recognized as an important factor in moving schools forward, yet we have been relatively random in how we prepare and support them. Four obstacles often block or diminish their effectiveness. Avoiding or overcoming each of these requires an underlying set of skills and knowledge that we believe can be learned and…

Extracurricular participation in research and audit by medical students: opportunities, obstacles, motivation and outcomes.

PubMed

Nikkar-Esfahani, Ali; Jamjoom, Aimun A B; Fitzgerald, J Edward F

2012-01-01

Medical students should learn to critically evaluate research to inform future evidence-based practice. Participation in research and audit at medical school can help develop these skills whilst prompting interest in academic pursuits. We investigate medical student attitudes and participation in extracurricular research and audit focusing on their opportunities, obstacles, motivation and outcomes. A 60-item questionnaire was distributed to final-year medical students graduating from the University of Nottingham Medical School in the United Kingdom. A total of 238 questionnaires were returned (response rate 75%). Of these, 86% felt research or audit experience was useful for medical students. The main driver for involvement was curriculum vitae (CV) improvement (51%). Male students and those involved in extracurricular research were more likely to agree that this experience should influence selection into training programmes (p = 0.017, p = 0.0036). Overall, 91 respondents (38%) had been involved in such activity with a mean number of projects undertaken of two (range one to four). Those interested in a surgical career were most likely to have undertaken projects (58%). Frequently cited obstacles to involvement were time constraints (74%) and a perceived lack of interest from potential supervisors (63%). Despite significant CV motivation, many are enthusiastic regarding extracurricular research opportunities but frustrated by obstacles faced. Our study suggests there is scope for providing further opportunities to participate in such activities at medical school.

Inverse obstacle problem for the scalar Helmholtz equation

NASA Astrophysics Data System (ADS)

Crosta, Giovanni F.

1994-07-01

The method presented is aimed at identifying the shape of an axially symmetric, sound soft acoustic scatterer from knowledge of the incident plane wave and of the scattering amplitude. The method relies on the approximate back propagation (ABP) of the estimated far field coefficients to the obstacle boundary and iteratively minimizes a boundary defect, without the addition of any penalty term. The ABP operator owes its structure to the properties of complete families of linearly independent solutions of Helmholtz equation. If the obstacle is known, as it happens in simulations, the theory also provides some independent means of predicting the performance of the ABP method. The ABP algorithm and the related computer code are outlined. Several reconstruction examples are considered, where noise is added to the estimated far field coefficients and other errors are deliberately introduced in the data. Many numerical and graphical results are provided.

Obstacles to colorectal screening in general practice: a qualitative study of GPs and patients.

PubMed

Aubin-Auger, Isabelle; Mercier, Alain; Lebeau, Jean-Pierre; Baumann, Laurence; Peremans, Lieve; Van Royen, Paul

2011-12-01

The faecal occult blood test (FOBT) has proven efficiency at screening populations for an average risk of colorectal cancer. Mortality related to this cancer decreases by 15-18% among adults, 50-74 years old, tested every 2 years. A participation rate of at least 50% is desirable. This rate has not yet been reached in most French regions. To explore the obstacles to mass colorectal screening in France. In 2009, five focus groups were conducted in different areas to explore physicians' obstacles to FOBT screening. The patients' obstacles were assessed in semi-structured interviews. A purposive sampling had been carried out for both GPs and patients. The focus groups were coded using Nvivo 8(®) software by three researchers; the interviews manually coded by two researchers. GPs reported insufficient training and some doubted the relevance of screening. They expressed concern of having insufficient time for the test during a consultation, as well as practical and administrative obstacles. Some GPs experienced difficulty persuading patients who had no signs of colorectal disease. Obstacles for patients were mainly difficulties in doing screening themselves and a perception of health care that didn't match with screening. Information and organization were also important points to improve. The screening process was considered complex both by GPs and by patients. Numerous obstacles to colorectal screening, from both the physicians' and the patients' perspectives, were found. The major goal to improve mass screening may be to increase awareness and understanding of both physicians and patients regarding this process.

Obstacles to Gender Parity in Engineering Education

ERIC Educational Resources Information Center

Rohatynskyj, Marta; Davidson, Valerie; Stiver, Warren; Hayward, Maren

2008-01-01

Low rates of women's enrolment in engineering programs has been identified as a global problem within the general concern to enable women to attain parity in education in all areas. A Western women in engineering meta-narrative is identified which contains a complex of obstacles that typify the situation of Western women. The question is asked…

Radial polar histogram: obstacle avoidance and path planning for robotic cognition and motion control

NASA Astrophysics Data System (ADS)

Wang, Po-Jen; Keyawa, Nicholas R.; Euler, Craig

2012-01-01

In order to achieve highly accurate motion control and path planning for a mobile robot, an obstacle avoidance algorithm that provided a desired instantaneous turning radius and velocity was generated. This type of obstacle avoidance algorithm, which has been implemented in California State University Northridge's Intelligent Ground Vehicle (IGV), is known as Radial Polar Histogram (RPH). The RPH algorithm utilizes raw data in the form of a polar histogram that is read from a Laser Range Finder (LRF) and a camera. A desired open block is determined from the raw data utilizing a navigational heading and an elliptical approximation. The left and right most radii are determined from the calculated edges of the open block and provide the range of possible radial paths the IGV can travel through. In addition, the calculated obstacle edge positions allow the IGV to recognize complex obstacle arrangements and to slow down accordingly. A radial path optimization function calculates the best radial path between the left and right most radii and is sent to motion control for speed determination. Overall, the RPH algorithm allows the IGV to autonomously travel at average speeds of 3mph while avoiding all obstacles, with a processing time of approximately 10ms.

Impact of gender-based career obstacles on the working status of women physicians in Japan.

PubMed

Nomura, Kyoko; Gohchi, Kengo

2012-11-01

Research has shown that women physicians work fewer hours and are more likely to become inactive professionally and to switch to part-time labor, compared with their male counterparts. The published literature suggests that a gender disparity still exists in medicine which may decrease work motivation among women physicians. The authors investigated whether the experience and the perception of gender-based career obstacles among women physicians in Japan are associated with their working status (i.e., full-time vs. part-time). The present cross-sectional study is based on surveys of alumnae from 13 private medical schools in Japan conducted between June 2009 and May 2011. Of those who agreed to participate in this study, 1684 completed a self-administered questionnaire (overall response rate 83%). Experience of gender-based obstacles was considered affirmative if a woman physician had been overlooked for opportunities of professional advancement based on gender. Perception of gender-based obstacles referred to the self-reported degree of difficulty of promotion and opportunities for a position in higher education. Approximately 20% of the study participants responded that they experienced gender-based obstacles while 24% answered that they were not sure. The scores for perception of gender-based career obstacles were statistically higher among part-time workers compared with full-time workers (mean difference = 1.20, 95% CI: 0.39-2.00). Adjusting for age, marital status, the presence of children, workplace, board certification, holding a PhD degree, overall satisfaction of being a physician, and household income, stepwise logistic regression models revealed that physicians with the strongest perception of gender-based career obstacles were more likely to work part-time rather than full-time (OR, 0.59; 95% CI: 0.40-0.88). Although the experience of gender-based obstacles was not associated with working status among women physicians, the results demonstrated that a

A Neural Network Approach for Building An Obstacle Detection Model by Fusion of Proximity Sensors Data

PubMed Central

Peralta, Emmanuel; Vargas, Héctor; Hermosilla, Gabriel

2018-01-01

Proximity sensors are broadly used in mobile robots for obstacle detection. The traditional calibration process of this kind of sensor could be a time-consuming task because it is usually done by identification in a manual and repetitive way. The resulting obstacles detection models are usually nonlinear functions that can be different for each proximity sensor attached to the robot. In addition, the model is highly dependent on the type of sensor (e.g., ultrasonic or infrared), on changes in light intensity, and on the properties of the obstacle such as shape, colour, and surface texture, among others. That is why in some situations it could be useful to gather all the measurements provided by different kinds of sensor in order to build a unique model that estimates the distances to the obstacles around the robot. This paper presents a novel approach to get an obstacles detection model based on the fusion of sensors data and automatic calibration by using artificial neural networks. PMID:29495338

Fluvial islands: First stage of development from nonmigrating (forced) bars and woody-vegetation interactions

NASA Astrophysics Data System (ADS)

Wintenberger, Coraline L.; Rodrigues, Stéphane; Bréhéret, Jean-Gabriel; Villar, Marc

2015-10-01

Fluvial islands can develop from the channel bed by interactions between pioneer trees and bars. Although vegetation recruitment and survival is possible on all bar types, it is easier for trees to survive on nonmigrating bars developed from a change in channel geometry or to the presence of a steady perturbation. This field study details the first stages of development of a vegetated mid-channel, nonmigrating (or forced) bar and its evolution toward an island form. Over six years, analysis of bed topographical changes, vegetation density and roughness, scour and fill depths, sediment grain size and architecture, and excess bed shear stress highlighted a specific signature of trees on topography and grain size segregation. Two depositional processes combining the formation of obstacle marks and upstream-shifting deposition of sediments led to the vertical accretion of the vegetated bar. During the first stage of the bar accretion, bedload sediment supply coming from surrounding channels during floods was identified as a key process modulated by the presence of woody vegetation and a deflection effect induced by the preexisting topography. Grain size segregation between vegetated and bare areas was also highlighted and interpreted as an important process affecting the development of surrounding channels and the degree of disconnection (and hence the speed of development) of a growing island. The heterogeneity of bedload supply can explain why sediment deposition and density of trees are not strictly related. A general conceptual model detailing the first stages of evolution from a bar to an established island is proposed for relatively large lowland rivers.

Science teachers' mission impossible?: a qualitative study of obstacles in assessing students' practical abilities

NASA Astrophysics Data System (ADS)

Sund, Per

2016-09-01

Science teachers regard practical work as important and many claim that it helps students to learn science. Besides theoretical knowledge, such as concepts and formulas, practical work is considered to be an integral and basic part of science education. As practical work is perceived and understood in different ways, comparing the results between classes and schools is difficult. One way of making the results comparable is to develop systematic inquiries to be assessed in national large-scale tests. However, introducing similar testing conditions in a laboratory environment is not always possible. Although the instructions and assessment guides for such tests are detailed, many obstacles need to be overcome if equality in the overall test situation is to be achieved. This empirical case study investigates two secondary school science teachers' assessments of 15-16 years old students in three separate groups in the practical part of a Swedish national test in chemistry. Data are gathered using two video cameras and three pairs of spy camera glasses. The results show that individual and independent assessments are difficult due to the social interactions that take place and the physical sources of errors that occur in this type of setting.

Overcoming Obstacles and Academic Hope: An Examination of Factors Promoting Effective Academic Success Strategies

ERIC Educational Resources Information Center

Hansen, Michele Joann; Trujillo, Daniel J.; Boland, Donna L.; MacKinnon, Joyce L.

2014-01-01

The purpose of this qualitative study was to explore the underlying non-cognitive processes and institutional factors that allowed first-year students to enact effective strategies for attaining academic success and persisting despite obstacles. The varying levels of academic preparation and unique obstacles faced by the student participants…

75 FR 32094 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-07

... OBSTACLE DP, ORIG 1-Jul-10 TX DALLAS ADDISON 0/6690 4/21/10 TAKEOFF MINIMUMS AND OBSTACLE DP, AMDT 5 1-Jul.../10 ILS OR LOC RWY 10R, AMDT 3 1-Jul-10 PA LOCK HAVEN WILLIAM T. PIPER 0/9245 5/12/10 RNAV (GPS)-1...

Women in academic medicine: perceived obstacles to advancement.

PubMed

Bennett, N M; Nickerson, K G

1992-01-01

To investigate perceived obstacles to the advancement of women in academic medicine, we sent a questionnaire assessing perceptions of the fairness and supportiveness of the academic environment to the 229 female teaching and research faculty of the School of Physicians & Surgeons at Columbia University. The overall response rate was 85%. Forty-six percent believed that they had not had the same professional opportunities as their male colleagues, 52% believed that salaries were not equivalent for men and women in similar positions, and 50% believed that promotions were awarded in a biased manner. Thirty percent reported that sexist behavior was common and that sexual harassment occurred in the workplace. Eighty-one percent experienced conflicts between their professional and personal lives and most believed that the institution failed to adequately address the needs of women with children. This survey indicates that there are significant perceived obstacles to the advancement of women in academic medicine that must be addressed.

Advanced patient transfer assist device with intuitive interaction control.

PubMed

Humphreys, Heather C; Choi, Young Mi; Book, Wayne J

2017-10-24

This research aims to improve patient transfers by developing a new type of advanced robotic assist device. It has multiple actuated degrees of freedom and a powered steerable base to maximize maneuverability around obstacles. An intuitive interface and control strategy allows the caregiver to simply push on the machine in the direction of desired patient motion. The control integrates measurements of both force and proximity to mitigate any potential large collision forces and provides operators information about obstacles with a form of haptic feedback. Electro-hydraulic pump controlled actuation provides high force density for the actuation. Nineteen participants performed tests to compare transfer operations (transferring a 250-lb mannequin between a wheelchair, chair, bed, and floor) and interaction control of a prototype device with a commercially available patient lift. The testing included a time study of the transfer operations and subjective rating of device performance. The results show that operators perform transfer tasks significantly faster and rate performance higher using the prototype patient transfer assist device than with a current market patient lift. With further development, features of the new patient lift can help facilitate patient transfers that are safer, easier, and more efficient for caregivers.

Facilitators and obstacles in pre-hospital medical response to earthquakes: a qualitative study.

PubMed

Djalali, Ahmadreza; Khankeh, Hamidreza; Öhlén, Gunnar; Castrén, Maaret; Kurland, Lisa

2011-05-16

Earthquakes are renowned as being amongst the most dangerous and destructive types of natural disasters. Iran, a developing country in Asia, is prone to earthquakes and is ranked as one of the most vulnerable countries in the world in this respect. The medical response in disasters is accompanied by managerial, logistic, technical, and medical challenges being also the case in the Bam earthquake in Iran. Our objective was to explore the medical response to the Bam earthquake with specific emphasis on pre-hospital medical management during the first days. The study was performed in 2008; an interview based qualitative study using content analysis. We conducted nineteen interviews with experts and managers responsible for responding to the Bam earthquake, including pre-hospital emergency medical services, the Red Crescent, and Universities of Medical Sciences. The selection of participants was determined by using a purposeful sampling method. Sample size was given by data saturation. The pre-hospital medical service was divided into three categories; triage, emergency medical care and transportation, each category in turn was identified into facilitators and obstacles. The obstacles identified were absence of a structured disaster plan, absence of standardized medical teams, and shortage of resources. The army and skilled medical volunteers were identified as facilitators. The most compelling, and at the same time amenable obstacle, was the lack of a disaster management plan. It was evident that implementing a comprehensive plan would not only save lives but decrease suffering and enable an effective praxis of the available resources at pre-hospital and hospital levels.

Facilitators and obstacles in pre-hospital medical response to earthquakes: a qualitative study

PubMed Central

2011-01-01

Background Earthquakes are renowned as being amongst the most dangerous and destructive types of natural disasters. Iran, a developing country in Asia, is prone to earthquakes and is ranked as one of the most vulnerable countries in the world in this respect. The medical response in disasters is accompanied by managerial, logistic, technical, and medical challenges being also the case in the Bam earthquake in Iran. Our objective was to explore the medical response to the Bam earthquake with specific emphasis on pre-hospital medical management during the first days. Methods The study was performed in 2008; an interview based qualitative study using content analysis. We conducted nineteen interviews with experts and managers responsible for responding to the Bam earthquake, including pre-hospital emergency medical services, the Red Crescent, and Universities of Medical Sciences. The selection of participants was determined by using a purposeful sampling method. Sample size was given by data saturation. Results The pre-hospital medical service was divided into three categories; triage, emergency medical care and transportation, each category in turn was identified into facilitators and obstacles. The obstacles identified were absence of a structured disaster plan, absence of standardized medical teams, and shortage of resources. The army and skilled medical volunteers were identified as facilitators. Conclusions The most compelling, and at the same time amenable obstacle, was the lack of a disaster management plan. It was evident that implementing a comprehensive plan would not only save lives but decrease suffering and enable an effective praxis of the available resources at pre-hospital and hospital levels. PMID:21575233

Efficiency analysis of a multiple axle vehicle with hydrostatic transmission overcoming obstacles

NASA Astrophysics Data System (ADS)

Comellas, M.; Pijuan, J.; Nogués, M.; Roca, J.

2018-01-01

Transmission configurations in off-road vehicles with multiple driven axles can be a determining factor in the obstacle surmounting capacity and also in the vehicle efficiency. An off-road articulated vehicle with four driven axles, four bogies and two modules has been considered for the global hydrostatic transmission efficiency analysis and for the vehicle functional efficiency analysis. The power flow through the transmission system has been quantified from the combustion engine shaft to each axle of the wheels. It has been done for different the operating conditions and taking into account the wheel-terrain interaction and the transmission configuration, that could lead to a forced slippage of some of the wheels. Results show the influence of the different wheels' requirements, the transmission configuration limitations and the considered control strategy on the global transmission and vehicle functional efficiencies.

Fusion of 3D laser scanner and depth images for obstacle recognition in mobile applications

NASA Astrophysics Data System (ADS)

Budzan, Sebastian; Kasprzyk, Jerzy

2016-02-01

The problem of obstacle detection and recognition or, generally, scene mapping is one of the most investigated problems in computer vision, especially in mobile applications. In this paper a fused optical system using depth information with color images gathered from the Microsoft Kinect sensor and 3D laser range scanner data is proposed for obstacle detection and ground estimation in real-time mobile systems. The algorithm consists of feature extraction in the laser range images, processing of the depth information from the Kinect sensor, fusion of the sensor information, and classification of the data into two separate categories: road and obstacle. Exemplary results are presented and it is shown that fusion of information gathered from different sources increases the effectiveness of the obstacle detection in different scenarios, and it can be used successfully for road surface mapping.

Symbiotic Navigation in Multi-Robot Systems with Remote Obstacle Knowledge Sharing

PubMed Central

Ravankar, Abhijeet; Ravankar, Ankit A.; Kobayashi, Yukinori; Emaru, Takanori

2017-01-01

Large scale operational areas often require multiple service robots for coverage and task parallelism. In such scenarios, each robot keeps its individual map of the environment and serves specific areas of the map at different times. We propose a knowledge sharing mechanism for multiple robots in which one robot can inform other robots about the changes in map, like path blockage, or new static obstacles, encountered at specific areas of the map. This symbiotic information sharing allows the robots to update remote areas of the map without having to explicitly navigate those areas, and plan efficient paths. A node representation of paths is presented for seamless sharing of blocked path information. The transience of obstacles is modeled to track obstacles which might have been removed. A lazy information update scheme is presented in which only relevant information affecting the current task is updated for efficiency. The advantages of the proposed method for path planning are discussed against traditional method with experimental results in both simulation and real environments. PMID:28678193

Toward flexible and wearable human-interactive health-monitoring devices.

PubMed

Takei, Kuniharu; Honda, Wataru; Harada, Shingo; Arie, Takayuki; Akita, Seiji

2015-03-11

This Progress Report introduces flexible wearable health-monitoring devices that interact with a person by detecting from and stimulating the body. Interactive health-monitoring devices should be highly flexible and attach to the body without awareness like a bandage. This type of wearable health-monitoring device will realize a new class of electronics, which will be applicable not only to health monitoring, but also to other electrical devices. However, to realize wearable health-monitoring devices, many obstacles must be overcome to economically form the active electrical components on a flexible substrate using macroscale fabrication processes. In particular, health-monitoring sensors and curing functions need to be integrated. Here recent developments and advancements toward flexible health-monitoring devices are presented, including conceptual designs of human-interactive devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Identification and analysis of obstacles in bioterrorism preparedness and response

NASA Astrophysics Data System (ADS)

Sincavage, Suzanne Michele

The focus of this study was to identify and analyze the obstacles to bioterrorism preparedness and response facing emergency management agencies and public authorities. In order to establish the limits of this discussion, the obstacles will examine a combined conceptual framework of public health, environmental security and social response. The interdisciplinary characteristics of this framework are ideal for addressing the issue of bioterrorism because of its simultaneous impact, which encompasses the complex interrelationships that pertain to public health and national security and social response. Based on a review of literature, the obstacles presented range from the absence of an effective surveillance system for biological terrorism related diseases to the inadequate training of first responders in bioterrorism preparedness and the difficult challenges of a mass casualty situation and the intense pressures associated with the crisis response. Furthermore, the impending reality of bioterrorism will further illustrate a close examination of the characteristics and management of three major biowarfare agents---anthrax, plague and smallpox. Finally, to provide a realistic understanding of the impact of bioterrorism, three case studies of actual events and two hypothetical scenarios will be discussed. Specifically, the discussion will provide the following three unconventional terrorist attacks: the recent anthrax attacks of 2001, the Aum Shinrikyo's attack of the Tokyo subway in 1995, and the Rajneeshees' use of salmonella poisoning in 1994. The inclusion of the hypothetical scenarios of two massive outbreaks of smallpox and anthrax will be presented to illuminate the seriousness and magnitude of the threat of bioterrorism and the probable consequences of failing to overcome the obstacles presented in this study. The importance of this research cannot be overemphasized, the threat is undeniably serious, and the potential for biological agents to cause devastating

Educational Pathways of Black Women Physicists: Stories of Experiencing and Overcoming Obstacles in Life

ERIC Educational Resources Information Center

Rosa, Katemari; Mensah, Felicia Moore

2016-01-01

This is an empirical study on the underrepresentation of people of color in scientific careers. Grounded in critical race theory, the paper examines the lived experiences of six Black women physicists and addresses obstacles faced in their career paths and strategies used to overcome these obstacles. Data for this study were collected through…

Characterisation of the Interaction between Toroidal Vortex Structures and Flame Front Propagation

NASA Astrophysics Data System (ADS)

Long, E. J.; Hargrave, G. K.; Jarvis, S.; Justham, T.; Halliwell, N.

2006-07-01

Experimental laser diagnostic data is presented for flame characterisation during interactions with toroidal vortices generated in the wake of an annular obstacle. A novel twin section combustion chamber has been utilised to allow the controlled formation of stable eddy structures into which a flame front can propagate. High speed laser sheet visualisation was employed to record the flow field and flame front temporal development and high-speed digital particle image velocimetry was used to quantify the velocity field of the unburnt mixture ahead of the flame front. Results provide characterisation of the toroidal vortex/flame front interaction for a range of vortex scales of and recirculation strengths.

An interactive physics-based unmanned ground vehicle simulator leveraging open source gaming technology: progress in the development and application of the virtual autonomous navigation environment (VANE) desktop

NASA Astrophysics Data System (ADS)

Rohde, Mitchell M.; Crawford, Justin; Toschlog, Matthew; Iagnemma, Karl D.; Kewlani, Guarav; Cummins, Christopher L.; Jones, Randolph A.; Horner, David A.

2009-05-01

It is widely recognized that simulation is pivotal to vehicle development, whether manned or unmanned. There are few dedicated choices, however, for those wishing to perform realistic, end-to-end simulations of unmanned ground vehicles (UGVs). The Virtual Autonomous Navigation Environment (VANE), under development by US Army Engineer Research and Development Center (ERDC), provides such capabilities but utilizes a High Performance Computing (HPC) Computational Testbed (CTB) and is not intended for on-line, real-time performance. A product of the VANE HPC research is a real-time desktop simulation application under development by the authors that provides a portal into the HPC environment as well as interaction with wider-scope semi-automated force simulations (e.g. OneSAF). This VANE desktop application, dubbed the Autonomous Navigation Virtual Environment Laboratory (ANVEL), enables analysis and testing of autonomous vehicle dynamics and terrain/obstacle interaction in real-time with the capability to interact within the HPC constructive geo-environmental CTB for high fidelity sensor evaluations. ANVEL leverages rigorous physics-based vehicle and vehicle-terrain interaction models in conjunction with high-quality, multimedia visualization techniques to form an intuitive, accurate engineering tool. The system provides an adaptable and customizable simulation platform that allows developers a controlled, repeatable testbed for advanced simulations. ANVEL leverages several key technologies not common to traditional engineering simulators, including techniques from the commercial video-game industry. These enable ANVEL to run on inexpensive commercial, off-the-shelf (COTS) hardware. In this paper, the authors describe key aspects of ANVEL and its development, as well as several initial applications of the system.

[Catatonia in childhood and adolescence: obstacles to diagnosis and treatment].

PubMed

Spysschaert, Y; Dhossche, D; Sienaert, P

2016-01-01

Catatonia in children and adolescents is the same as it is for adults; in other words it is a recognisable psychomotor syndrome that follows a characteristic course and responds favourably to treatment with benzodiazepines and/or ect. Therefore, one would not expect to encumber many obstacles to diagnosis and treatment. In fact, the obstacles are fairly numerous. To explore the obstacles that can hinder a simple approach to diagnosis and treatment and to provide support for the clinicians involved. We studied the literature systematically using Limo and keywords. For several decades, particularly in the literature, catatonia was defined as a subtype of schizophrenia. This exclusive link to schizophrenia led to the under-diagnosis of catatonia in patients with other psychiatric conditions and to delays in the administration of the correct treatment. Not only this historical error but also other important problems are complicating the approach to catatonia even today. Among other factors hindering diagnosis and treatment are the belief that catatonia is a rare illness, often denied by family members and some clinicians, the use of neuroleptics and the stigmatisation of benzodiazepines and/or ect. Controversy about catatonia continues. Although diagnosis and treatment are clearly defined, catatonia is still putting professionals to the test. In our essay we offer some practical guidance and advice.

Large-eddy simulation of turbulent flow with a surface-mounted two-dimensional obstacle

NASA Technical Reports Server (NTRS)

Yang, Kyung-Soo; Ferziger, Joel H.

1993-01-01

In this paper, we perform a large eddy simulation (LES) of turbulent flow in a channel containing a two-dimensional obstacle on one wall using a dynamic subgrid-scale model (DSGSM) at Re = 3210, based on bulk velocity above the obstacle and obstacle height; the wall layers are fully resolved. The low Re enables us to perform a DNS (Case 1) against which to validate the LES results. The LES with the DSGSM is designated Case 2. In addition, an LES with the conventional fixed model constant (Case 3) is conducted to allow identification of improvements due to the DSGSM. We also include LES at Re = 82,000 (Case 4) using conventional Smagorinsky subgrid-scale model and a wall-layer model. The results will be compared with the experiment of Dimaczek et al.

A numerical study of a vertical solar air collector with obstacle

NASA Astrophysics Data System (ADS)

Moumeni, A.; Bouchekima, B.; Lati, M.

2016-07-01

Because of the lack of heat exchange obtained by a solar air between the fluid and the absorber, the introduction of obstacles arranged in rows overlapping in the ducts of these systems improves heat transfer. In this work, a numerical study using the finite volume methods is made to model the dynamic and thermal behavior of air flow in a vertical solar collector with baffles destined for integration in building. We search essentially to compare between three air collectors models with different inclined obstacles angle. The first kind with 90° shows a good performance energetic and turbulent.

Wind turbines: current status, obstacles, trends and technologies

NASA Astrophysics Data System (ADS)

Konstantinidis, E. I.; Botsaris, P. N.

2016-11-01

The last decade the installation of wind farms around the world is spreading rapidly and wind energy has become a significant factor for promoting sustainable development. The scope of the present study is to indicate the present status of global wind power expansion as well as the current state of the art in the field of wind turbine technology. The RAM (reliability/availability/maintenance) section is also examined and the Levelized Cost of Energy for onshore/ offshore electricity production is presented. Negative consequences that go with the rapid expansion of wind power like accidents, environmental effects, etc. are highlighted. Especially visual impact to the landscape and noise pollution are some factors that provoke social reactions. Moreover, the complicated and long permitted process of a wind power plant, the high capital cost of the investment and the grid instability due to the intermittent nature of wind, are also significant obstacles in the development of the wind energy production. The current trends in the field of research and development of onshore and offshore wind power production are analyzed. Finally the present study is trying to achieve an estimation of where the wind industry targets for the years to come.

Investigation of obstacle effect to improve conjugate heat transfer in backward facing step channel using fast simulation of incompressible flow

NASA Astrophysics Data System (ADS)

Nouri-Borujerdi, Ali; Moazezi, Arash

2018-01-01

The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In the thick wall, the energy equation is obtained by Laplace equation. A multi-block approach is used to perform parallel computing to reduce the CPU time. Each block is modeled separately by sharing boundary conditions with neighbors. The developed program for modeling was written in FORTRAN language with OpenMP API. The obtained results showed that using of the multi-block parallel computing method is a simple robust scheme with high performance and high-order accurate. Moreover, the obtained results demonstrated that the increment of Reynolds number and obstacle height as well as decrement of horizontal distance between the obstacle and the step improve the heat transfer.

UAV formation control design with obstacle avoidance in dynamic three-dimensional environment.

PubMed

Chang, Kai; Xia, Yuanqing; Huang, Kaoli

2016-01-01

This paper considers the artificial potential field method combined with rotational vectors for a general problem of multi-unmanned aerial vehicle (UAV) systems tracking a moving target in dynamic three-dimensional environment. An attractive potential field is generated between the leader and the target. It drives the leader to track the target based on the relative position of them. The other UAVs in the formation are controlled to follow the leader by the attractive control force. The repulsive force affects among the UAVs to avoid collisions and distribute the UAVs evenly on the spherical surface whose center is the leader-UAV. Specific orders or positions of the UAVs are not required. The trajectories of avoidance obstacle can be obtained through two kinds of potential field with rotation vectors. Every UAV can choose the optimal trajectory to avoid the obstacle and reconfigure the formation after passing the obstacle. Simulations study on UAV are presented to demonstrate the effectiveness of proposed method.

Interactive Learning with Java Applets: Using Interactive, Web-Based Java Applets to Present Science in a Concrete, Meaningful Manner

ERIC Educational Resources Information Center

Corder, Greg

2005-01-01

Science teachers face challenges that affect the quality of instruction. Tight budgets, limited resources, school schedules, and other obstacles limit students' opportunities to experience science that is visual and interactive. Incorporating web-based Java applets into science instruction offers a practical solution to these challenges. The…

A nonlinear model predictive control formulation for obstacle avoidance in high-speed autonomous ground vehicles in unstructured environments

NASA Astrophysics Data System (ADS)

Liu, Jiechao; Jayakumar, Paramsothy; Stein, Jeffrey L.; Ersal, Tulga

2018-06-01

This paper presents a nonlinear model predictive control (MPC) formulation for obstacle avoidance in high-speed, large-size autono-mous ground vehicles (AGVs) with high centre of gravity (CoG) that operate in unstructured environments, such as military vehicles. The term 'unstructured' in this context denotes that there are no lanes or traffic rules to follow. Existing MPC formulations for passenger vehicles in structured environments do not readily apply to this context. Thus, a new nonlinear MPC formulation is developed to navigate an AGV from its initial position to a target position at high-speed safely. First, a new cost function formulation is used that aims to find the shortest path to the target position, since no reference trajectory exists in unstructured environments. Second, a region partitioning approach is used in conjunction with a multi-phase optimal control formulation to accommodate the complicated forms the obstacle-free region can assume due to the presence of multiple obstacles in the prediction horizon in an unstructured environment. Third, the no-wheel-lift-off condition, which is the major dynamical safety concern for high-speed, high-CoG AGVs, is ensured by limiting the steering angle within a range obtained offline using a 14 degrees-of-freedom vehicle dynamics model. Thus, a safe, high-speed navigation is enabled in an unstructured environment. Simulations of an AGV approaching multiple obstacles are provided to demonstrate the effectiveness of the algorithm.

78 FR 48800 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-12

... 8260-15A. The large number of SIAPs, Takeoff Minimums and ODPs, in addition to their complex nature and..., Takeoff Minimums and Obstacle DP, Amdt 2 Perham, MN, Perham Muni, RNAV (GPS) RWY 13, Orig Perham, MN, Perham Muni, RNAV (GPS) RWY 31, Amdt 1 Perham, MN, Perham Muni, Takeoff Minimums and Obstacle DP, Amdt 1...

77 FR 12452 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-01

... OR LOC Z RWY 8, Amdt 37 Burbank, CA, Bob Hope, LOC Y RWY 8, Amdt 4 Colorado Springs, CO, City of Colorado Springs Muni, Takeoff Minimums and Obstacle DP, Amdt 10 Craig, CO, Craig-Moffat, Takeoff Minimums and Obstacle DP, Amdt 4 Durango, CO, Durango-La Plata County, VOR/DME RWY 3, Amdt 5 Pueblo, CO, Pueblo...

Interaction Mindsets, Interactional Behaviors, and L2 Development: An Affective-Social-Cognitive Model

ERIC Educational Resources Information Center

Sato, Masatoshi

2017-01-01

This classroom-based study explored links among second language (L2) learners' interaction mindsets, interactional behaviors, and L2 development in the context of peer interaction. While peer interaction research has revealed that certain interactional behaviors (e.g., receiving corrective feedback and engaging in collaborative interaction) assist…

Early Obstacle Detection and Avoidance for All to All Traffic Pattern in Wireless Sensor Networks

NASA Astrophysics Data System (ADS)

Huc, Florian; Jarry, Aubin; Leone, Pierre; Moraru, Luminita; Nikoletseas, Sotiris; Rolim, Jose

This paper deals with early obstacles recognition in wireless sensor networks under various traffic patterns. In the presence of obstacles, the efficiency of routing algorithms is increased by voluntarily avoiding some regions in the vicinity of obstacles, areas which we call dead-ends. In this paper, we first propose a fast convergent routing algorithm with proactive dead-end detection together with a formal definition and description of dead-ends. Secondly, we present a generalization of this algorithm which improves performances in all to many and all to all traffic patterns. In a third part we prove that this algorithm produces paths that are optimal up to a constant factor of 2π + 1. In a fourth part we consider the reactive version of the algorithm which is an extension of a previously known early obstacle detection algorithm. Finally we give experimental results to illustrate the efficiency of our algorithms in different scenarios.

Group Work and the Change of Obstacles over Time: The Influence of Learning Style and Group Composition

ERIC Educational Resources Information Center

Soetanto, Danny; MacDonald, Matthew

2017-01-01

It is through working in groups that students develop cooperative learning skills and experience. However, group work activity often leads students into a difficult experience, especially for first-year students who are not familiar with group work activities at university. This study explores obstacles faced by first-year students during their…

Wakes from submerged obstacles in an open channel flow

NASA Astrophysics Data System (ADS)

Smith, Geoffrey B.; Marmorino, George; Dong, Charles; Miller, W. D.; Mied, Richard

2015-11-01

Wakes from several submerged obstacles are examined via airborne remote sensing. The primary focus will be bathymetric features in the tidal Potomac river south of Washington, DC, but others may be included as well. In the Potomac the water depth is nominally 10 m with an obstacle height of 8 m, or 80% of the depth. Infrared imagery of the water surface reveals thermal structure suitable both for interpretation of the coherent structures and for estimating surface currents. A novel image processing technique is used to generate two independent scenes with a known time offset from a single overpass from the infrared imagery, suitable for velocity estimation. Color imagery of the suspended sediment also shows suitable texture. Both the `mountain wave' regime and a traditional turbulent wake are observed, depending on flow conditions. Results are validated with in-situ ADCP transects. A computational model is used to further interpret the results.

Two Formal Gas Models For Multi-Agent Sweeping and Obstacle Avoidance

NASA Technical Reports Server (NTRS)

Kerr, Wesley; Spears, Diana; Spears, William; Thayer, David

2004-01-01

The task addressed here is a dynamic search through a bounded region, while avoiding multiple large obstacles, such as buildings. In the case of limited sensors and communication, maintaining spatial coverage - especially after passing the obstacles - is a challenging problem. Here, we investigate two physics-based approaches to solving this task with multiple simulated mobile robots, one based on artificial forces and the other based on the kinetic theory of gases. The desired behavior is achieved with both methods, and a comparison is made between them. Because both approaches are physics-based, formal assurances about the multi-robot behavior are straightforward, and are included in the paper.

Velodyne HDL-64E lidar for unmanned surface vehicle obstacle detection

NASA Astrophysics Data System (ADS)

Halterman, Ryan; Bruch, Michael

2010-04-01

The Velodyne HDL-64E is a 64 laser 3D (360×26.8 degree) scanning LIDAR. It was designed to fill perception needs of DARPA Urban Challenge vehicles. As such, it was principally intended for ground use. This paper presents the performance of the HDL-64E as it relates to the marine environment for unmanned surface vehicle (USV) obstacle detection and avoidance. We describe the sensor's capacity for discerning relevant objects at sea- both through subjective observations of the raw data and through a rudimentary automated obstacle detection algorithm. We also discuss some of the complications that have arisen with the sensor.

Epistemological Obstacles on the Topic of Ratio and Proportion among Junior High School Students

NASA Astrophysics Data System (ADS)

Wahyuningrum, A. S.; Suryadi, D.; Turmudi

2017-09-01

This study intends to investigate how students’ understanding of ratio and proportion concept indicates epistemological obstacles. It was part of Didactical Design Research which was conducted to 72 students of 8th grade who ever learned about ratio and proportion. Data were collected through the students’ answers and interview in solving ratio and proportion problems. The results show that students’ conception, the ways of applying other mathematical concepts, the ways of using the rules, and variety of contexts are factors influencing epistemological obstacles in teaching and learning of ratio and proportion. These conditions can affect the students’ understanding o f related mathematics topics. Based on analysis of the results, this study is expected to overcome or minimize the epistemological obstacles.

Physical root-soil interactions

NASA Astrophysics Data System (ADS)

Kolb, Evelyne; Legué, Valérie; Bogeat-Triboulot, Marie-Béatrice

2017-12-01

Plant root system development is highly modulated by the physical properties of the soil and especially by its mechanical resistance to penetration. The interplay between the mechanical stresses exerted by the soil and root growth is of particular interest for many communities, in agronomy and soil science as well as in biomechanics and plant morphogenesis. In contrast to aerial organs, roots apices must exert a growth pressure to penetrate strong soils and reorient their growth trajectory to cope with obstacles like stones or hardpans or to follow the tortuous paths of the soil porosity. In this review, we present the main macroscopic investigations of soil-root physical interactions in the field and combine them with simple mechanistic modeling derived from model experiments at the scale of the individual root apex.

Physical root-soil interactions.

PubMed

Kolb, Evelyne; Legué, Valérie; Bogeat-Triboulot, Marie-Béatrice

2017-11-16

Plant root system development is highly modulated by the physical properties of the soil and especially by its mechanical resistance to penetration. The interplay between the mechanical stresses exerted by the soil and root growth is of particular interest for many communities, in agronomy and soil science as well as in biomechanics and plant morphogenesis. In contrast to aerial organs, roots apices must exert a growth pressure to penetrate strong soils and reorient their growth trajectory to cope with obstacles like stones or hardpans or to follow the tortuous paths of the soil porosity. In this review, we present the main macroscopic investigations of soil-root physical interactions in the field and combine them with simple mechanistic modeling derived from model experiments at the scale of the individual root apex.

An Empirical Analysis of Chinese College Learners' Obstacles to MOOC Learning in an English Context

ERIC Educational Resources Information Center

Liu, Liangxing

2017-01-01

This article reports a study applying an exploratory factor analysis to discovering the underlying factor structure of Chinese college students' obstacles to learning MOOC in an English context. Seven obstacle factors are identified: 1. academic and language skills; 2. internet skills; 3. course instruction/management; 4. learning motivations; 5.…

Biomechanical risk factors for tripping during obstacle--Crossing with the trailing limb in patients with type II diabetes mellitus.

PubMed

Hsu, Wei-Chun; Liu, Ming-Wei; Lu, Tung-Wu

2016-03-01

People with type II diabetes mellitus (DM) are at a high risk of falling especially during more challenging locomotor tasks such as obstacle-crossing. The current study aimed to identify the risk factors for tripping in these patients during trailing-limb obstacle-crossing. Fourteen patients with type II DM with or without mild peripheral neuropathy (PN) and 14 healthy controls walked and crossed obstacles of three different heights while their motion data were measured using a motion capture system and two forceplates. The DM group was found to cross obstacles with significantly reduced trailing toe clearance (p<0.05), increasing the probability of the foot hitting the obstacle, and thus the risk of tripping. This altered end-point control was associated with significantly reduced knee flexion and hip adduction of the trailing swing limb (p<0.05), as well as significantly increased ankle plantarflexor moments in the leading stance limb (p<0.05). Therefore, reduced knee flexion and hip adduction of the swing limb are identified as risk factors for tripping during obstacle-crossing. Increased mechanical demands on the ankle plantarflexors suggest that weakness of these muscles may further reduce the already compromised performance of obstacle-crossing in these patients. The current results showed that obstacle-crossing can be used to detect gait deviations and to identify the associated risk of tripping in patients with type II DM without or at an early stage of PN. Copyright © 2016 Elsevier B.V. All rights reserved.

Storyboard Development for Interactive Multimedia Training.

ERIC Educational Resources Information Center

Orr, Kay L.; And Others

1994-01-01

Discusses procedures for storyboard development and provides guidelines for designing interactive multimedia courseware, including interactivity, learner control, feedback, visual elements, motion video, graphics/animation, text, audio, and programming. A topical bibliography that lists 98 items is included. (LRW)

Reflexive obstacle avoidance for kinematically-redundant manipulators

NASA Technical Reports Server (NTRS)

Karlen, James P.; Thompson, Jack M., Jr.; Farrell, James D.; Vold, Havard I.

1989-01-01

Dexterous telerobots incorporating 17 or more degrees of freedom operating under coordinated, sensor-driven computer control will play important roles in future space operations. They will also be used on Earth in assignments like fire fighting, construction and battlefield support. A real time, reflexive obstacle avoidance system, seen as a functional requirement for such massively redundant manipulators, was developed using arm-mounted proximity sensors to control manipulator pose. The project involved a review and analysis of alternative proximity sensor technologies for space applications, the development of a general-purpose algorithm for synthesizing sensor inputs, and the implementation of a prototypical system for demonstration and testing. A 7 degree of freedom Robotics Research K-2107HR manipulator was outfitted with ultrasonic proximity sensors as a testbed, and Robotics Research's standard redundant motion control algorithm was modified such that an object detected by sensor arrays located at the elbow effectively applies a force to the manipulator elbow, normal to the axis. The arm is repelled by objects detected by the sensors, causing the robot to steer around objects in the workspace automatically while continuing to move its tool along the commanded path without interruption. The mathematical approach formulated for synthesizing sensor inputs can be employed for redundant robots of any kinematic configuration.

Obstacle Crossing During Gait in Children With Cerebral Palsy: Cross-Sectional Study With Kinematic Analysis of Dynamic Balance and Trunk Control.

PubMed

Malone, Ailish; Kiernan, Damien; French, Helen; Saunders, Valerie; O'Brien, Timothy

2016-08-01

Balance problems are common in children who have cerebral palsy (CP) but are active and ambulant. Control of the whole-body center of mass is critical in maintaining dynamic stability during challenging mobility tasks, such as clearing an obstacle while walking. The objective of this study was to compare trunk and lower limb kinematics and center-of-mass control in children with CP and those in children with typical development during obstacle crossing. This was a cross-sectional study. Thirty-four children who were 5 to 17 years of age (17 with CP and 17 with typical development) and matched in age and height completed 2 gait trials involving crossing a 10-cm obstacle. Three-dimensional kinematic and kinetic data were captured with a general-purpose 3-dimensional motion tracking system and forceplates. Trunk data were captured with a validated model. All children cleared the obstacle with similar hip and knee kinematics, step length, and single-support duration. In children with CP, step width was increased by 4.81 cm, and center-of-mass velocity was significantly slower at lead limb toe-off (0.31 m/s) and during lead limb clearance (0.2 m/s). Children with CP showed altered trunk and pelvis movement, characterized by significantly greater pelvic obliquity, pelvic tilt, and trunk rotation throughout the task, increased lateral trunk lean during lead limb crossing (3.7°), and greater sagittal trunk movement as the trail limb crossed (5.1°). The study was not powered to analyze differences between children with diplegia and those with hemiplegia. Children with CP required greater adjustments at the trunk and pelvis to achieve successful obstacle crossing. The increase in trunk movement could have been compensatory for reduced stability distally or for a primary problem reflecting poor proximal control. The findings suggest that rehabilitation should focus on both proximal trunk control and distal stability to improve balance. © 2016 American Physical Therapy

Socioeconomic obstacles to HIV prevention and treatment in developing countries: the roles of the International Monetary Fund and the World Bank.

PubMed

Lurie, P; Hintzen, P; Lowe, R A

1995-06-01

This paper explores the socioeconomic obstacles to HIV prevention and treatment in developing countries. The opening sections explain the historical origins of structural adjustment programs and their characteristics. Structural adjustment programs undermine the social fabric of many developing countries, and potentially promote behaviors which place people at increased risk of HIV infection. The authors discuss the declining sustainability of the rural subsistence economy, development of a transportation infrastructure, migration and urbanization, and reductions in spending on health and social services. Social and economic interventions are needed to stem the spread of HIV and care for those who are already infected. While a substantial amount of biomedical research has been conducted, socioeconomic aspects of the AIDS epidemic have often been ignored. For HIV transmission in developing countries to be substantially reduced, economic policies which may have promoted the spread of disease must be modified. An alternative development strategy consists of satisfying people's basic human needs, shifting from an export-driven economy to diversified agricultural production in the interest of securing regional self-sufficiency, supporting marginal producers and subsistence farmers, and placing greater emphasis upon human resource development in developing countries. Moreover, the IMF and World Bank need to change their policy to one which is truly about cooperative development, while the charters of the IMF and World Bank need to be altered to permit the cancellation or rescheduling of debt. These institutions should also play a leading role in the restructuring of debt owed to private lenders.

Virtual Reality-Based Training to Improve Obstacle-Crossing Performance and Dynamic Balance in Patients With Parkinson's Disease.

PubMed

Liao, Ying-Yi; Yang, Yea-Ru; Cheng, Shih-Jung; Wu, Yih-Ru; Fuh, Jong-Ling; Wang, Ray-Yau

2015-08-01

Obstacle crossing is a balance-challenging task and can cause falls in people with Parkinson's disease (PD). However, programs for people with PD that effectively target obstacle crossing and dynamic balance have not been established. To examine the effects of virtual reality-based exercise on obstacle crossing performance and dynamic balance in participants with PD. Thirty-six participants with a diagnosis of PD (Hoehn and Yahr score ranging 1 to 3) were randomly assigned to one of three groups. In the exercise groups, participants received virtual reality-based Wii Fit exercise (VRWii group) or traditional exercise (TE group) for 45 minutes, followed by 15 minutes of treadmill training in each session for a total of 12 sessions over 6 weeks. Participants in the control group received no structured exercise program. Primary outcomes included obstacle crossing performance (crossing velocity, stride length, and vertical toe obstacle clearance) and dynamic balance (maximal excursion, movement velocity, and directional control measured by the limits-of-stability test). Secondary outcomes included sensory organization test (SOT), Parkinson's Disease Questionnaire (PDQ39), fall efficacy scale (FES-I), and timed up and go test (TUG). All outcomes were assessed at baseline, after training, and at 1-month follow-up. The VRWii group showed greater improvement in obstacle crossing velocity, crossing stride length, dynamic balance, SOT, TUG, FES-I, and PDQ39 than the control group. VRWii training also resulted in greater improvement in movement velocity of limits-of-stability test than TE training. VRWii training significantly improved obstacle crossing performance and dynamic balance, supporting implementation of VRWii training in participants with PD. © The Author(s) 2014.

A Qualitative Study on the Obstacles Preventing the Successful Implementation of Web 2.0 in Corporate Learning

ERIC Educational Resources Information Center

Estrada, Luis

2012-01-01

The purpose of this study was to identify the obstacles to the adoption of Web 2.0 technologies as part of corporate learning solutions and strategies. The study followed a qualitative inquiry approach. The sample consisted of 20 corporate learning professionals who are members of the American Society for Training and Development (ASTD) social…

Self-bending elastic waves and obstacle circumventing in wireless power transfer

NASA Astrophysics Data System (ADS)

Tol, S.; Xia, Y.; Ruzzene, M.; Erturk, A.

2017-04-01

We demonstrate self-bending of elastic waves along convex trajectories by means of geometric and phased arrays. Potential applications include ultrasonic imaging and manipulation, wave focusing, and wireless power transfer around obstacles. The basic concept is illustrated through a geometric array, which is designed to implement a phase delay profile among the array elements that leads to self-bending along a specified circular trajectory. Experimental validation is conducted for the lowest asymmetric Lamb wave mode in a thin plate over a range of frequencies to investigate the bandwidth of the approach. Experiments also illustrate the functionality of the array as a transmitter to deliver elastic wave energy to a receiver/harvester located behind a large obstacle for electrical power extraction. It is shown that the trajectory is not distorted by the presence of the obstacle and circumventing is achieved. A linear phased array counterpart of the geometric array is then constructed to illustrate the concept by imposing proper time delays to the array elements, which allows the generation of different trajectories using the same line source. This capability is demonstrated by tailoring the path diameter in the phased array setting, which offers the flexibility and versatility to induce a variety of convex trajectories for self-bending elastic waves.

Research: Survey of Tribal Colleges Reveals Research's Benefits, Obstacles.

ERIC Educational Resources Information Center

Mortensen, Margaret; Nelson, Claudia E.; Stauss, Jay

2001-01-01

Stresses the need for tribal colleges to increase focus on research at all levels, from institutional to individual. Discusses types of research, obstacles and benefits to research, and model collaborative programs at Dull Knife Memorial College (Montana), Cheyenne River Community College (South Dakota), and Little Priest Tribal College…

Comparison of results of an obstacle resolving microscale model with wind tunnel data

NASA Astrophysics Data System (ADS)

Grawe, David; Schlünzen, K. Heinke; Pascheke, Frauke

2013-11-01

The microscale transport and stream model MITRAS has been improved and a new technique has been implemented to improve numerical stability for complex obstacle configurations. Results of the updated version have been compared with wind tunnel data using an evaluation method that has been established for simple obstacle configurations. MITRAS is a part of the M-SYS model system for the assessment of ambient air quality. A comparison of model results for the flow field against quality ensured wind tunnel data has been carried out for both idealised and realistic test cases. Results of the comparison show a very good agreement of the wind field for most test cases and identify areas of possible improvement of the model. The evaluated MITRAS results can be used as input data for the M-SYS microscale chemistry model MICTM. This paper describes how such a comparison can be carried out for simple as well as realistic obstacle configurations and what difficulties arise.

Fuzzy Inference Based Obstacle Avoidance Control of Electric Powered Wheelchair Considering Driving Risk

NASA Astrophysics Data System (ADS)

Kiso, Atsushi; Murakami, Hiroki; Seki, Hirokazu

This paper describes a novel obstacle avoidance control scheme of electric powered wheelchairs for realizing the safe driving in various environments. The “electric powered wheelchair” which generates the driving force by electric motors is expected to be widely used as a mobility support system for elderly people and disabled people; however, the driving performance must be further improved because the number of driving accidents caused by elderly operator's narrow sight and joystick operation errors is increasing. This paper proposes a novel obstacle avoidance control scheme based on fuzzy algorithm to prevent driving accidents. The proposed control system determines the driving direction by fuzzy algorithm based on the information of the joystick operation and distance to obstacles measured by ultrasonic sensors. Fuzzy rules to determine the driving direction are designed surely to avoid passers-by and walls considering the human's intent and driving environments. Some driving experiments on the practical situations show the effectiveness of the proposed control system.

Impact of Performance Obstacles on Intensive Care Nurses‘ Workload, Perceived Quality and Safety of Care, and Quality of Working Life

PubMed Central

Gurses, Ayse P; Carayon, Pascale; Wall, Melanie

2009-01-01

Objectives To study the impact of performance obstacles on intensive care nurses‘ workload, quality and safety of care, and quality of working life (QWL). Performance obstacles are factors that hinder nurses‘ capacity to perform their job and that are closely associated with their immediate work system. Data Sources/Study Setting Data were collected from 265 nurses in 17 intensive care units (ICUs) between February and August 2004 via a structured questionnaire, yielding a response rate of 80 percent. Study Design A cross-sectional study design was used. Data were analyzed by correlation analyses and structural equation modeling. Principal Findings Performance obstacles were found to affect perceived quality and safety of care and QWL of ICU nurses. Workload mediated the impact of performance obstacles with the exception of equipment-related issues on perceived quality and safety of care as well as QWL. Conclusions Performance obstacles in ICUs are a major determinant of nursing workload, perceived quality and safety of care, and QWL. In general, performance obstacles increase nursing workload, which in turn negatively affect perceived quality and safety of care and QWL. Redesigning the ICU work system to reduce performance obstacles may improve nurses‘ work. PMID:19207589

Dynamic interaction of two-phase debris flow with pyramidal defense structures: An optimal strategy to efficiently protecting the desired area

NASA Astrophysics Data System (ADS)

Kattel, Parameshwari; Kafle, Jeevan; Fischer, Jan-Thomas; Mergili, Martin; Tuladhar, Bhadra Man; Pudasaini, Shiva P.

2017-04-01

In this work we analyze the dynamic interaction of two phase debris flows with pyramidal obstacles. To simulate the dynamic interaction of two-phase debris flow (a mixture of solid particles and viscous fluid) with obstacles of different dimensions and orientations, we employ the general two-phase mass flow model (Pudasaini, 2012). The model consists of highly non-linear partial differential equations representing the mass and momentum conservations for both solid and fluid. Besides buoyancy, the model includes some dominant physical aspects of the debris flows such as generalized drag, virtual mass and non-Newtonian viscous stress as induced by the gradient of solid-volume-fraction. Simulations are performed with high-resolution numerical schemes to capture essential dynamics, including the strongly re-directed flow with multiple stream lines, mass arrest and debris-vacuum generation when the rapidly cascading debris mass suddenly encounters the obstacle. The solid and fluid phases show fundamentally different interactions with obstacles, flow spreading and dispersions, run-out dynamics, and deposition morphology. A forward-facing pyramid deflects the mass wider, and a rearward-facing pyramid arrests a portion of solid-mass at its front. Our basic study reveals that appropriately installed obstacles, their dimensions and orientations have a significant influence on the flow dynamics, material redistribution and redirection. The precise knowledge of the change in dynamics is of great importance for the optimal and effective protection of designated areas along the mountain slopes and the runout zones. Further important results are, that specific installations lead to redirect either solid, or fluid, or both, in the desired amounts and directions. The present method of the complex interactions of real two-phase mass flows with the obstacles may help us to construct defense structures and to design advanced and physics-based engineering solutions for the prevention

Interactive-rate Motion Planning for Concentric Tube Robots.

PubMed

Torres, Luis G; Baykal, Cenk; Alterovitz, Ron

2014-05-01

Concentric tube robots may enable new, safer minimally invasive surgical procedures by moving along curved paths to reach difficult-to-reach sites in a patient's anatomy. Operating these devices is challenging due to their complex, unintuitive kinematics and the need to avoid sensitive structures in the anatomy. In this paper, we present a motion planning method that computes collision-free motion plans for concentric tube robots at interactive rates. Our method's high speed enables a user to continuously and freely move the robot's tip while the motion planner ensures that the robot's shaft does not collide with any anatomical obstacles. Our approach uses a highly accurate mechanical model of tube interactions, which is important since small movements of the tip position may require large changes in the shape of the device's shaft. Our motion planner achieves its high speed and accuracy by combining offline precomputation of a collision-free roadmap with online position control. We demonstrate our interactive planner in a simulated neurosurgical scenario where a user guides the robot's tip through the environment while the robot automatically avoids collisions with the anatomical obstacles.

Interactive-rate Motion Planning for Concentric Tube Robots

PubMed Central

Torres, Luis G.; Baykal, Cenk; Alterovitz, Ron

2014-01-01

Concentric tube robots may enable new, safer minimally invasive surgical procedures by moving along curved paths to reach difficult-to-reach sites in a patient’s anatomy. Operating these devices is challenging due to their complex, unintuitive kinematics and the need to avoid sensitive structures in the anatomy. In this paper, we present a motion planning method that computes collision-free motion plans for concentric tube robots at interactive rates. Our method’s high speed enables a user to continuously and freely move the robot’s tip while the motion planner ensures that the robot’s shaft does not collide with any anatomical obstacles. Our approach uses a highly accurate mechanical model of tube interactions, which is important since small movements of the tip position may require large changes in the shape of the device’s shaft. Our motion planner achieves its high speed and accuracy by combining offline precomputation of a collision-free roadmap with online position control. We demonstrate our interactive planner in a simulated neurosurgical scenario where a user guides the robot’s tip through the environment while the robot automatically avoids collisions with the anatomical obstacles. PMID:25436176

Obstacle traversal and self-righting of bio-inspired robots reveal the physics of multi-modal locomotion

NASA Astrophysics Data System (ADS)

Li, Chen; Fearing, Ronald; Full, Robert

Most animals move in nature in a variety of locomotor modes. For example, to traverse obstacles like dense vegetation, cockroaches can climb over, push across, reorient their bodies to maneuver through slits, or even transition among these modes forming diverse locomotor pathways; if flipped over, they can also self-right using wings or legs to generate body pitch or roll. By contrast, most locomotion studies have focused on a single mode such as running, walking, or jumping, and robots are still far from capable of life-like, robust, multi-modal locomotion in the real world. Here, we present two recent studies using bio-inspired robots, together with new locomotion energy landscapes derived from locomotor-environment interaction physics, to begin to understand the physics of multi-modal locomotion. (1) Our experiment of a cockroach-inspired legged robot traversing grass-like beam obstacles reveals that, with a terradynamically ``streamlined'' rounded body like that of the insect, robot traversal becomes more probable by accessing locomotor pathways that overcome lower potential energy barriers. (2) Our experiment of a cockroach-inspired self-righting robot further suggests that body vibrations are crucial for exploring locomotion energy landscapes and reaching lower barrier pathways. Finally, we posit that our new framework of locomotion energy landscapes holds promise to better understand and predict multi-modal biological and robotic movement.

The Development of Interactive Video for Children's Education.

ERIC Educational Resources Information Center

Dockterman, Gabrielle Savage

1991-01-01

Development of two interactive videodisks in space science for middle-school-age children is described, and suggestions for development of affordable and successful interactive products are offered. The first interactive program is a touchscreen exhibit designed for museum use, and the second is a classroom tool for teaching a planetary sciences…

A switching formation strategy for obstacle avoidance of a multi-robot system based on robot priority model.

PubMed

Dai, Yanyan; Kim, YoonGu; Wee, SungGil; Lee, DongHa; Lee, SukGyu

2015-05-01

This paper describes a switching formation strategy for multi-robots with velocity constraints to avoid and cross obstacles. In the strategy, a leader robot plans a safe path using the geometric obstacle avoidance control method (GOACM). By calculating new desired distances and bearing angles with the leader robot, the follower robots switch into a safe formation. With considering collision avoidance, a novel robot priority model, based on the desired distance and bearing angle between the leader and follower robots, is designed during the obstacle avoidance process. The adaptive tracking control algorithm guarantees that the trajectory and velocity tracking errors converge to zero. To demonstrate the validity of the proposed methods, simulation and experiment results present that multi-robots effectively form and switch formation avoiding obstacles without collisions. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

Japan’s Rearmament Dilemma: Obstacles to Rearmament.

DTIC Science & Technology

1980-01-01

aircraft carrier Enterprise, and the problems with the first Japanese nuclear -powered ship , the Mutsu , have continued to keep the issue of nuclear weapons...4 Formation of the Psychology. .. ............... 4 Nuclear Allergy .. .................... 7 Self-Defense Force .. ................... 10 ARTICLE 9... nuclear weapons, would elicit a strong reaction from the U.S. This specter of the U.S. reaction is another obstacle to rearmament. While most scholars

Obstacles Perceived by Physical Education Teachers to Integrating ICT

ERIC Educational Resources Information Center

Villalba, Ana; González-Rivera, María Dolores; Díaz-Pulido, Belén

2017-01-01

Teachers find difficulties and barriers about integrating technology in the physical education classroom. Therefore, the aim of this study is to analyse the perception of PE teachers regarding obstacles to integrating ICT and its relation with their age. The methodology followed was quantitative and descriptive in nature. The participants were 400…

Literature review of the benefits and obstacle of horizontal directional drilling

NASA Astrophysics Data System (ADS)

Norizam, M. S. Mohd; Nuzul Azam, H.; Helmi Zulhaidi, S.; Aziz, A. Abdul; Nadzrol Fadzilah, A.

2017-11-01

In this new era the construction industry not only need to be completed within budget, timely, at acceptable quality and safety but the stakeholders especially the local authorities and the public realises for the important need of sustainable construction method to be used for our younger generation to heritage if not better a safer world for them to live and raise up their children’s. Horizontal Directional Drilling method is the most commonly recognised trenchless utilities method as a preferred construction method in this age. Among the reasons HDD method offers less disturbance on traffic, the public, business activities and neighbourhood, lower restoration cost, less noise, dust and minimum import/export of the construction materials. In addition HDD method can drill through congested utilities areas with minimum cutting and shorter time. This paper aims to appraise the benefits and obstacle of HDD method in construction industry. It is an endeavour to fulfil the local authorities cry for alternative method that less damages to the roads, road furniture’s and public complaints compared to the conventional open cut method. In addition HDD method is seem to be in line with sustainable development requirements e.g. reduce, reuse, recycle and etc. Hence, it is important to determine the benefits and obstacle factors of HDD implementation. The factors are based on the literature review conducted by the author on the subject matters gathered from previous studies, journals, text books, guidelines, magazine articles, newspaper cutting and etc.

Cosine Kuramoto Based Distribution of a Convoy with Limit-Cycle Obstacle Avoidance Through the Use of Simulated Agents

NASA Astrophysics Data System (ADS)

Howerton, William

This thesis presents a method for the integration of complex network control algorithms with localized agent specific algorithms for maneuvering and obstacle avoidance. This method allows for successful implementation of group and agent specific behaviors. It has proven to be robust and will work for a variety of vehicle platforms. Initially, a review and implementation of two specific algorithms will be detailed. The first, a modified Kuramoto model was developed by Xu [1] which utilizes tools from graph theory to efficiently perform the task of distributing agents. The second algorithm developed by Kim [2] is an effective method for wheeled robots to avoid local obstacles using a limit-cycle navigation method. The results of implementing these methods on a test-bed of wheeled robots will be presented. Control issues related to outside disturbances not anticipated in the original theory are then discussed. A novel method of using simulated agents to separate the task of distributing agents from agent specific velocity and heading commands has been developed and implemented to address these issues. This new method can be used to combine various behaviors and is not limited to a specific control algorithm.

Preparation of students with disabilities to graduate into professions in the South African context of higher learning: Obstacles and opportunities.

PubMed

Ndlovu, Sibonokuhle; Walton, Elizabeth

2016-01-01

Persons with disabilities continue to be excluded from professions in South Africa despite legislation on non-discrimination and equity. We sought to identify both the opportunities and obstacles that students with disabilities face in professional degrees. Selected texts from the South African and international literature were analysed and synthesised. Students with disabilities are afforded opportunities to graduate into professions through the current climate of transformation, inclusion and disability policies, various support structures and funding. These opportunities are mitigated by obstacles at both the higher education site and at the workplace. At university, they may experience difficulties in accessing the curriculum, disability units may be limited in the support they can offer, policies may not be implemented, funding is found to be inadequate and the built environment may be inaccessible. Fieldwork poses additional obstacles in terms of public transport which is not accessible to students with disabilities; a lack of higher education support extended to the field sites, and buildings not designed for access by people with disabilities. At both sites, students are impacted by negative attitudes and continued assumptions that disability results from individual deficit, rather than exclusionary practices and pressures. It is in the uniqueness of professional preparation, with its high demands of both theory and practice that poses particular obstacles for students with disabilities. We argue for the development of self-advocacy for students with disabilities, ongoing institutional and societal transformation and further research into the experiences of students with disabilities studying for professional degrees.

Turning Miscommunication Events into Opportunities for Developing Interactional Competence

ERIC Educational Resources Information Center

Victoria, Mabelle Paderez

2012-01-01

Many studies have explored the difficulties faced by foreign language learners when they begin the learning journey from survival to advanced level. Most of these investigations, however, tend to focus on what makes the road to fluency strewn with obstacles and challenges; no significant attention has been paid to what makes the journey…

Investigation of shock focusing in a cavity with incident shock diffracted by an obstacle

NASA Astrophysics Data System (ADS)

Zhang, Q.; Chen, X.; He, L.-M.; Rong, K.; Deiterding, R.

2017-03-01

Experiments and numerical simulations were carried out in order to investigate the focusing of a shock wave in a test section after the incident shock has been diffracted by an obstacle. A conventional shock tube was used to generate the planar shock. Incident shock Mach numbers of 1.4 and 2.1 were tested. A high-speed camera was employed to obtain schlieren photos of the flow field in the experiments. In the numerical simulations, a weighted essentially non-oscillatory (WENO) scheme of third-order accuracy supplemented with structured dynamic mesh adaptation was adopted to simulate the shock wave interaction. Good agreement between experiments and numerical results is observed. The configurations exhibit shock reflection phenomena, shock-vortex interaction and—in particular—shock focusing. The pressure history in the cavity apex was recorded and compared with the numerical results. A quantitative analysis of the numerically observed shock reflection configurations is also performed by employing a pseudo-steady shock transition boundary calculation technique. Regular reflection, single Mach reflection and transitional Mach reflection phenomena are observed and are found to correlate well with analytic predictions from shock reflection theory.

Cultural differences in self-recognition: the early development of autonomous and related selves?

PubMed

Ross, Josephine; Yilmaz, Mandy; Dale, Rachel; Cassidy, Rose; Yildirim, Iraz; Suzanne Zeedyk, M

2017-05-01

Fifteen- to 18-month-old infants from three nationalities were observed interacting with their mothers and during two self-recognition tasks. Scottish interactions were characterized by distal contact, Zambian interactions by proximal contact, and Turkish interactions by a mixture of contact strategies. These culturally distinct experiences may scaffold different perspectives on self. In support, Scottish infants performed best in a task requiring recognition of the self in an individualistic context (mirror self-recognition), whereas Zambian infants performed best in a task requiring recognition of the self in a less individualistic context (body-as-obstacle task). Turkish infants performed similarly to Zambian infants on the body-as-obstacle task, but outperformed Zambians on the mirror self-recognition task. Verbal contact (a distal strategy) was positively related to mirror self-recognition and negatively related to passing the body-as-obstacle task. Directive action and speech (proximal strategies) were negatively related to mirror self-recognition. Self-awareness performance was best predicted by cultural context; autonomous settings predicted success in mirror self-recognition, and related settings predicted success in the body-as-obstacle task. These novel data substantiate the idea that cultural factors may play a role in the early expression of self-awareness. More broadly, the results highlight the importance of moving beyond the mark test, and designing culturally sensitive tests of self-awareness. © 2016 John Wiley & Sons Ltd.

Obstacles and Affordances for Integer Reasoning: An Analysis of Children's Thinking and the History of Mathematics

ERIC Educational Resources Information Center

Bishop, Jessica Pierson; Lamb, Lisa L.; Philipp, Randolph A.; Whitacre, Ian; Schappelle, Bonnie P.; Lewis, Melinda L.

2014-01-01

We identify and document 3 cognitive obstacles, 3 cognitive affordances, and 1 type of integer understanding that can function as either an obstacle or affordance for learners while they extend their numeric domains from whole numbers to include negative integers. In particular, we highlight 2 key subsets of integer reasoning: understanding or…

Kinematics of the Pelvis, Torso, and Lower Limb During Obstacle Negotiation While Under Temporal Constraints.

PubMed

Christensen, Jesse C; Wilson, Christopher R; Merryweather, Andrew S; Foreman, K Bo

2017-04-01

Biomechanics of unobstructed locomotion consists of synchronized complex movements of the pelvis, torso, and lower limbs. These movement patterns become more complex as individuals encounter obstacles or negotiate uneven terrain. To date, limited research has explored how specifically the pelvis, torso, and lower limb segments relate to obstacle negotiation of varying sized objects combined with temporal constraints to perform the task. Understanding pelvis and adjoining segment movements during object negotiation will provide necessary information in identifying abnormal mechanics and potential fall risk characteristics in balance compromised patient populations. In this prospective cohort study, we aimed to compare pelvic, torso, and lower limb kinematics during unobstructed locomotion with obstacle negotiation of varying heights. Ten healthy young adults (7 females and 3 males, mean age 28.4 ± 4.1 years, mean body mass index 22.5 ± 3.6 kg/m 2 ) enrolled in this study. Analysis of within-subject differences revealed a significant increase in sagittal (posterior tilt) and frontal (ipsilateral hike) plane pelvic angular displacement and higher sagittal plane posterior torso lean angular displacement with increased obstacle height. Furthermore, both sagittal plane hip and knee maximum joint flexion were significantly higher with increasing heights of the obstacles during negotiation. These data provide insight on segment mechanics within a non-mobility-impaired population; therefore, providing a baseline to understand the kinematic demands necessary for safe and effective gait in mobility-compromised populations. Anat Rec, 300:732-738, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Detection of obstacles on runway using Ego-Motion compensation and tracking of significant features

NASA Technical Reports Server (NTRS)

Kasturi, Rangachar (Principal Investigator); Camps, Octavia (Principal Investigator); Gandhi, Tarak; Devadiga, Sadashiva

1996-01-01

This report describes a method for obstacle detection on a runway for autonomous navigation and landing of an aircraft. Detection is done in the presence of extraneous features such as tiremarks. Suitable features are extracted from the image and warping using approximately known camera and plane parameters is performed in order to compensate ego-motion as far as possible. Residual disparity after warping is estimated using an optical flow algorithm. Features are tracked from frame to frame so as to obtain more reliable estimates of their motion. Corrections are made to motion parameters with the residual disparities using a robust method, and features having large residual disparities are signaled as obstacles. Sensitivity analysis of the procedure is also studied. Nelson's optical flow constraint is proposed to separate moving obstacles from stationary ones. A Bayesian framework is used at every stage so that the confidence in the estimates can be determined.

The research of autonomous obstacle avoidance of mobile robot based on multi-sensor integration

NASA Astrophysics Data System (ADS)

Zhao, Ming; Han, Baoling

2016-11-01

The object of this study is the bionic quadruped mobile robot. The study has proposed a system design plan for mobile robot obstacle avoidance with the binocular stereo visual sensor and the self-control 3D Lidar integrated with modified ant colony optimization path planning to realize the reconstruction of the environmental map. Because the working condition of a mobile robot is complex, the result of the 3D reconstruction with a single binocular sensor is undesirable when feature points are few and the light condition is poor. Therefore, this system integrates the stereo vision sensor blumblebee2 and the Lidar sensor together to detect the cloud information of 3D points of environmental obstacles. This paper proposes the sensor information fusion technology to rebuild the environment map. Firstly, according to the Lidar data and visual data on obstacle detection respectively, and then consider two methods respectively to detect the distribution of obstacles. Finally fusing the data to get the more complete, more accurate distribution of obstacles in the scene. Then the thesis introduces ant colony algorithm. It has analyzed advantages and disadvantages of the ant colony optimization and its formation cause deeply, and then improved the system with the help of the ant colony optimization to increase the rate of convergence and precision of the algorithm in robot path planning. Such improvements and integrations overcome the shortcomings of the ant colony optimization like involving into the local optimal solution easily, slow search speed and poor search results. This experiment deals with images and programs the motor drive under the compiling environment of Matlab and Visual Studio and establishes the visual 2.5D grid map. Finally it plans a global path for the mobile robot according to the ant colony algorithm. The feasibility and effectiveness of the system are confirmed by ROS and simulation platform of Linux.

Voluntary community service in medical school: a qualitative study on obstacles faced by student leaders and potential solutions

PubMed Central

Loh, Alvona Zi Hui; Tan, Julia Shi Yu; Lee, Jeannette Jen-Mai; Koh, Gerald Choon-Huat

2015-01-01

Purpose In medical school, students may participate in various community involvement projects (CIP), which serve disadvantaged communities. However, several obstacles may arise during these projects. The authors conducted a qualitative study with the primary aim of understanding the obstacles and corresponding potential solutions when medical students in Singapore participate in local CIP (LCIP) and overseas CIP (OCIP). Design The authors recruited medical students from Yong Loo Lin School of Medicine, National University of Singapore, who were also leaders of a specific community service project done in medical school. Twelve one-to-one interviews were held for the participants from 6 to 8 January 2013. Participants were led in a discussion based on an interview guide. The interviews were audio-recorded and transcribed into free-flow text. Subsequently, content and thematic analyses of the transcripts were performed independently by three researchers. Results The medical students faced many common obstacles during their community service projects. These obstacles include difficulties in recruiting and managing volunteers, attaining recognition or credibility for the project to acquire funding and resources, adjusting to a different culture or language, setting goals, and facing project-specific obstacles. Potential solutions were offered for some obstacles, such as building a strong executive committee for the project, grooming successive batches of leaders, and improving the project's public image, mentorship, reflections, and sustainability plans. Conclusions Mentorship, reflections, and sustainability are potential solutions that have been proposed to tackle the obstacles faced during community service participation in medical school. However, there may still be difficulty in solving some of the problems even after these measures are put into practice. Future research may focus on evaluating the effectiveness of these suggested solutions. PMID:26490690

Voluntary community service in medical school: a qualitative study on obstacles faced by student leaders and potential solutions.

PubMed

Loh, Alvona Zi Hui; Tan, Julia Shi Yu; Lee, Jeannette Jen-Mai; Koh, Gerald Choon-Huat

2015-01-01

In medical school, students may participate in various community involvement projects (CIP), which serve disadvantaged communities. However, several obstacles may arise during these projects. The authors conducted a qualitative study with the primary aim of understanding the obstacles and corresponding potential solutions when medical students in Singapore participate in local CIP (LCIP) and overseas CIP (OCIP). The authors recruited medical students from Yong Loo Lin School of Medicine, National University of Singapore, who were also leaders of a specific community service project done in medical school. Twelve one-to-one interviews were held for the participants from 6 to 8 January 2013. Participants were led in a discussion based on an interview guide. The interviews were audio-recorded and transcribed into free-flow text. Subsequently, content and thematic analyses of the transcripts were performed independently by three researchers. The medical students faced many common obstacles during their community service projects. These obstacles include difficulties in recruiting and managing volunteers, attaining recognition or credibility for the project to acquire funding and resources, adjusting to a different culture or language, setting goals, and facing project-specific obstacles. Potential solutions were offered for some obstacles, such as building a strong executive committee for the project, grooming successive batches of leaders, and improving the project's public image, mentorship, reflections, and sustainability plans. Mentorship, reflections, and sustainability are potential solutions that have been proposed to tackle the obstacles faced during community service participation in medical school. However, there may still be difficulty in solving some of the problems even after these measures are put into practice. Future research may focus on evaluating the effectiveness of these suggested solutions.

Organizational factors in fire prevention: roles, obstacles, and recommendations

Treesearch

John R. Christiansen; William S. Folkman; Keith W. Warner; Michael L. Woolcott

1976-01-01

Problems being encountered in implementing fire prevention programs were explored by studying the organization for fire prevention at the Fish Lake, Uinta, and Wasatch National Forests in Utah. The study focused on role congruency in fire prevention activities and on the social and organizational obstacles to effective programs. The problems identified included lack of...

Transport and collision dynamics in periodic asymmetric obstacle arrays: Rational design of microfluidic rare-cell immunocapture devices

NASA Astrophysics Data System (ADS)

Gleghorn, Jason P.; Smith, James P.; Kirby, Brian J.

2013-09-01

Microfluidic obstacle arrays have been used in numerous applications, and their ability to sort particles or capture rare cells from complex samples has broad and impactful applications in biology and medicine. We have investigated the transport and collision dynamics of particles in periodic obstacle arrays to guide the design of convective, rather than diffusive, transport-based immunocapture microdevices. Ballistic and full computational fluid dynamics simulations are used to understand the collision modes that evolve in cylindrical obstacle arrays with various geometries. We identify previously unrecognized collision mode structures and differential size-based collision frequencies that emerge from these arrays. Previous descriptions of transverse displacements that assume unidirectional flow in these obstacle arrays cannot capture mode transitions properly as these descriptions fail to capture the dependence of the mode transitions on column spacing and the attendant change in the flow field. Using these analytical and computational simulations, we elucidate design parameters that induce high collision rates for all particles larger than a threshold size or selectively increase collision frequencies for a narrow range of particle sizes within a polydisperse population. Furthermore, we investigate how the particle Péclet number affects collision dynamics and mode transitions and demonstrate that experimental observations from various obstacle array geometries are well described by our computational model.

Mass loading in the solar wind interaction with Venus and Mars

NASA Astrophysics Data System (ADS)

Breus, T. K.; Bauer, S. J.; Krymskii, A. M.; Mitnitskii, V. Ya.

1989-03-01

An analysis of available experimental data and theoretical concepts indicates that the interaction of the solar wind (SW) on the subsolar side with Venus, which has no intrinsic magnetic field, and with Mars, which has a small intrinsic magnetic field, is determined by the solar wind dynamic pressure with a contribution from the neutral planetary atmosphere to this interaction. The pattern of the SW interaction with these planets is different in principle for high and low dynamic pressures of the SW and is related to the varying intensity of ion formation processes (the SW Mass loading effect) in the vicinity of the SW obstacle boundary, which moves for different SW dynamic pressures into regions of different neutral atmosphere density. For moderate or high SW dynamic pressures, the subsolar Martian magnetosphere is also affected by this process. Results of numerical simulations of the SW-Mars interaction for a magnetospheric obstacle boundary at an altitude of 300 km are presented. To estimate the relative role of photoionization and charge exchange processes and their effect on the shock front position, different versions of the mass loading effect were separately calculated.

Interactive ESL In-Service Teacher Training via Distance Education.

ERIC Educational Resources Information Center

Power, Michael A.

The Hawaii State Department of Education offers university credit courses in English-as-a-Second-Language (ESL) techniques to all public school teachers, but the scarcity of trainers and the distance between schools and training sites constitute substantial obstacles. With the cooperation of the University of Hawaii's interactive television…

Interactive Video Training and Development Activity.

ERIC Educational Resources Information Center

Troy State Univ., AL.

The Interactive Video Training and Development Activity of Troy State University (Troy, Alabama) is described in this report. The project has trained more than 30 people in the production of interactive video programs since its inception in 1983. Since 1985, training programs have been offered twice a year to individuals within and outside the…

The effects of laterality on obstacle crossing performance in unilateral trans-tibial amputees.

PubMed

De Asha, Alan R; Buckley, John G

2015-05-01

Unilateral trans-tibial amputees have bilaterally reduced toe clearance, and an increased risk of foot contact, while crossing obstacles compared to the able-bodied. While the able-bodied tend to lead with a 'preferred' limb it is equivocal whether amputees prefer to lead with the intact or prosthetic limb. This study determined the effects of laterality, compared to side of amputation, on amputees' obstacle crossing performance. To help understand why laterality could affect performance we also assessed knee proprioception for both limbs. Foot placement and toe clearance parameters were recorded while nine amputees crossed obstacles of varying heights leading with both their intact and prosthetic limbs. Joint-position sense was also assessed. Participants self-reported which limb was their preferred (dominant) limb. There were no significant differences in foot placements or toe clearance variability across lead-limb conditions. There were no significant differences in toe clearance between intact and prosthetic lead-limbs (p=0.28) but toe clearance was significantly higher when amputees led with their preferred compared to non-preferred limb (p=0.025). There was no difference in joint-position sense between the intact and residual knees (p=0.34) but joint-position sense tended to be more accurate for the preferred, compared to non-preferred limb (p=0.08). Findings suggest that, despite the mechanical constraints imposed by use of a prosthesis, laterality may be as important in lower-limb amputees as it is in the able bodied. This suggests that amputees should be encouraged to cross obstacles leading with their preferred limb. Copyright © 2015. Published by Elsevier Ltd.

[Early interaction is a prerequisite for favorable psychic development].

PubMed

Pesonen, Anu-Katriina

2010-01-01

Empirical studies on the parent-baby interaction have greatly influenced our insight into the child's psychological development. Initial stages of the research attempted to reveal features in the mother's action that would predict the child's favorable development. Since then, also fathers and the child's development in a more broad sense have been studied. The most prominent progress has taken place in microanalytical methods for these interactions. The research has increased our knowledge of the baby's interactive capabilities and the significance of successful interactive events for the child's development, laying the basis for various interventions related to parenthood.

HIV reservoirs as obstacles and opportunities for an HIV cure.

PubMed

Chun, Tae-Wook; Moir, Susan; Fauci, Anthony S

2015-06-01

The persistence of HIV reservoirs remains a formidable obstacle to achieving sustained virologic remission in HIV-infected individuals after antiretroviral therapy (ART) is discontinued, even if plasma viremia has been successfully suppressed for prolonged periods of time. Numerous approaches aimed at eradicating the virus, as well as maintaining its prolonged suppression in the absence of ART, have had little success. A better understanding of the pathophysiologic nature of HIV reservoirs and the impact of various interventions on their persistence is essential for the development of successful therapeutic strategies against HIV or the long-term control of infection. Here, we discuss the persistent HIV reservoir as a barrier to cure as well as the current therapeutic strategies aimed at eliminating or controlling the virus in the absence of ART.

Obstacle avoidance and concealed target detection using the Army Research Lab ultra-wideband synchronous impulse reconstruction (UWB SIRE) forward imaging radar

NASA Astrophysics Data System (ADS)

Nguyen, Lam; Wong, David; Ressler, Marc; Koenig, Francois; Stanton, Brian; Smith, Gregory; Sichina, Jeffrey; Kappra, Karl

2007-04-01

The U.S. Army Research Laboratory (ARL), as part of a mission and customer funded exploratory program, has developed a new low-frequency, ultra-wideband (UWB) synthetic aperture radar (SAR) for forward imaging to support the Army's vision of an autonomous navigation system for robotic ground vehicles. These unmanned vehicles, equipped with an array of imaging sensors, will be tasked to help detect man-made obstacles such as concealed targets, enemy minefields, and booby traps, as well as other natural obstacles such as ditches, and bodies of water. The ability of UWB radar technology to help detect concealed objects has been documented in the past and could provide an important obstacle avoidance capability for autonomous navigation systems, which would improve the speed and maneuverability of these vehicles and consequently increase the survivability of the U. S. forces on the battlefield. One of the primary features of the radar is the ability to collect and process data at combat pace in an affordable, compact, and lightweight package. To achieve this, the radar is based on the synchronous impulse reconstruction (SIRE) technique where several relatively slow and inexpensive analog-to-digital (A/D) converters are used to sample the wide bandwidth of the radar signals. We conducted an experiment this winter at Aberdeen Proving Ground (APG) to support the phenomenological studies of the backscatter from positive and negative obstacles for autonomous robotic vehicle navigation, as well as the detection of concealed targets of interest to the Army. In this paper, we briefly describe the UWB SIRE radar and the test setup in the experiment. We will also describe the signal processing and the forward imaging techniques used in the experiment. Finally, we will present imagery of man-made obstacles such as barriers, concertina wires, and mines.

Imaging behind opaque obstacle: a potential method for guided in vitro needle placement

PubMed Central

Perinchery, Sandeep Menon; Shinde, Anant; Matham, Murukeshan Vadakke

2016-01-01

We report a simple real time optical imaging concept using an axicon lens to image the object kept behind opaque obstacles in free space. The proposed concept underlines the importance and advantages of using an axicon lens compared to a conventional lens to image behind the obstacle. The potential of this imaging concept is demonstrated by imaging the insertion of surgical needle in biological specimen in real time, without blocking the field of view. It is envisaged that this proposed concepts and methodology can make a telling impact in a wide variety of areas especially for diagnostics, therapeutics and microscopy applications. PMID:28018744

Cine film replacement: digital archival requirements and remaining obstacles.

PubMed

Holmes, D R; Wondrow, M A; Bell, M R; Nissen, S E; Cusma, J T

1998-07-01

The acceptance of the Digital Imaging and Communication in Medicine (DICOM) standard and the Compact Disk-Recordable (CD-R) as the interchange medium have been critical developments for laboratories that need to move forward on the cine replacement front, while at the same time retain a means to communicate with other centers. One remaining essential component which has not been satisfactorily addressed is the issue of how digital image data should be archived within an institution. Every laboratory must consider the diverse issues which affect the choice of a digital archiving system. These factors include technical and economic issues, along with the clinical routines prevailing in their laboratory. A complete understanding of the issues will lead to the formulation of multiple options which may prove acceptable and will help to overcome the last obstacle which remains for the complete replacement of cine film in the cardiac catheterization laboratory.

Obstacle crossing with dual tasking is a danger for individuals with Alzheimer's disease and for healthy older people.

PubMed

Simieli, Lucas; Barbieri, Fabio Augusto; Orcioli-Silva, Diego; Lirani-Silva, Ellen; Stella, Florindo; Gobbi, Lilian Teresa Bucken

2015-01-01

The aim of this study was to analyze the effects of dual tasking on obstacle crossing during walking by individuals with Alzheimer's disease (AD) and by healthy older people. Thirty four elderly individuals (16 healthy subjects and 18 individuals with AD) were recruited to participate in this study. Three AD individuals and one control participant were excluded due to exclusion criteria. The participants were instructed to walk barefoot at their own speed along an 8 m long pathway. Each participant performed five trials for each condition (unobstructed walking, unobstructed walking with dual tasking, and obstacle crossing during walking with dual tasking). The trials were completely randomized for each participant. The mid-pathway stride was measured in the unobstructed walking trials and the stride that occurred during the obstacle avoidance was measured in the trials that involved obstacle crossing. The behavior of the healthy elderly subjects and individuals with AD was similar for obstacle crossing during walking with dual tasking. Both groups used the "posture first" strategy to prioritize stability and showed decreased attention to executive tasking while walking. Additionally, AD had a strong influence on the modifications that are made by the elderly while walking under different walking conditions.

A protein interaction map for cell polarity development

PubMed Central

Drees, Becky L.; Sundin, Bryan; Brazeau, Elizabeth; Caviston, Juliane P.; Chen, Guang-Chao; Guo, Wei; Kozminski, Keith G.; Lau, Michelle W.; Moskow, John J.; Tong, Amy; Schenkman, Laura R.; McKenzie, Amos; Brennwald, Patrick; Longtine, Mark; Bi, Erfei; Chan, Clarence; Novick, Peter; Boone, Charles; Pringle, John R.; Davis, Trisha N.; Fields, Stanley; Drubin, David G.

2001-01-01

Many genes required for cell polarity development in budding yeast have been identified and arranged into a functional hierarchy. Core elements of the hierarchy are widely conserved, underlying cell polarity development in diverse eukaryotes. To enumerate more fully the protein–protein interactions that mediate cell polarity development, and to uncover novel mechanisms that coordinate the numerous events involved, we carried out a large-scale two-hybrid experiment. 68 Gal4 DNA binding domain fusions of yeast proteins associated with the actin cytoskeleton, septins, the secretory apparatus, and Rho-type GTPases were used to screen an array of yeast transformants that express ∼90% of the predicted Saccharomyces cerevisiae open reading frames as Gal4 activation domain fusions. 191 protein–protein interactions were detected, of which 128 had not been described previously. 44 interactions implicated 20 previously uncharacterized proteins in cell polarity development. Further insights into possible roles of 13 of these proteins were revealed by their multiple two-hybrid interactions and by subcellular localization. Included in the interaction network were associations of Cdc42 and Rho1 pathways with proteins involved in exocytosis, septin organization, actin assembly, microtubule organization, autophagy, cytokinesis, and cell wall synthesis. Other interactions suggested direct connections between Rho1- and Cdc42-regulated pathways; the secretory apparatus and regulators of polarity establishment; actin assembly and the morphogenesis checkpoint; and the exocytic and endocytic machinery. In total, a network of interactions that provide an integrated response of signaling proteins, the cytoskeleton, and organelles to the spatial cues that direct polarity development was revealed. PMID:11489916

Vision-Based UAV Flight Control and Obstacle Avoidance

DTIC Science & Technology

2006-01-01

denoted it by Vb = (Vb1, Vb2 , Vb3). Fig. 2 shows the block diagram of the proposed vision-based motion analysis and obstacle avoidance system. We denote...structure analysis often involve computation- intensive computer vision tasks, such as feature extraction and geometric modeling. Computation-intensive...First, we extract a set of features from each block. 2) Second, we compute the distance between these two sets of features. In conventional motion

How obstacles and facilitators predict academic performance: the mediating role of study burnout and engagement.

PubMed

Salanova, Marisa; Schaufeli, Wilmar; Martinez, Isabel; Breso, Edgar

2010-01-01

Most people would agree with the maxim that "success breeds success." However, this is not the whole story. The current study investigated the additional impact of psychosocial factors (i.e., performance obstacles and facilitators) as well as psychological well-being (i.e., burnout and engagement) on success (i.e., academic performance). More specifically, our purpose was to show that, instead of directly affecting future performance, obstacles and facilitators exert an indirect effect via well-being. A total of 527 university students comprised the sample and filled out a questionnaire. We obtained their previous and future academic performance Grade Point Average (GPA) from the university's records. Structural equations modeling showed that the best predictor of future performance was the students' previous performance. As expected, study engagement mediated the relationship between performance obstacles and facilitators on the one hand, and future performance on the other. Contrary to expectations, burnout did not predict future performance, although, it is significantly associated with the presence of obstacles and the absence of facilitators. Our results illustrate that, although "success breeds success" (i.e., the best predictor of future performance is past performance), positive psychological states like study engagement are also important in explaining future performance, at least more so than negative states like study burnout.

Preparation of students with disabilities to graduate into professions in the South African context of higher learning: Obstacles and opportunities

PubMed Central

Walton, Elizabeth

2016-01-01

Background Persons with disabilities continue to be excluded from professions in South Africa despite legislation on non-discrimination and equity. Objectives We sought to identify both the opportunities and obstacles that students with disabilities face in professional degrees. Method Selected texts from the South African and international literature were analysed and synthesised. Results Students with disabilities are afforded opportunities to graduate into professions through the current climate of transformation, inclusion and disability policies, various support structures and funding. These opportunities are mitigated by obstacles at both the higher education site and at the workplace. At university, they may experience difficulties in accessing the curriculum, disability units may be limited in the support they can offer, policies may not be implemented, funding is found to be inadequate and the built environment may be inaccessible. Fieldwork poses additional obstacles in terms of public transport which is not accessible to students with disabilities; a lack of higher education support extended to the field sites, and buildings not designed for access by people with disabilities. At both sites, students are impacted by negative attitudes and continued assumptions that disability results from individual deficit, rather than exclusionary practices and pressures. Conclusion It is in the uniqueness of professional preparation, with its high demands of both theory and practice that poses particular obstacles for students with disabilities. We argue for the development of self-advocacy for students with disabilities, ongoing institutional and societal transformation and further research into the experiences of students with disabilities studying for professional degrees. PMID:28730040

Anticipatory Postural Control of Stability during Gait Initiation Over Obstacles of Different Height and Distance Made Under Reaction-Time and Self-Initiated Instructions.

PubMed

Yiou, Eric; Artico, Romain; Teyssedre, Claudine A; Labaune, Ombeline; Fourcade, Paul

2016-01-01

Despite the abundant literature on obstacle crossing in humans, the question of how the central nervous system (CNS) controls postural stability during gait initiation with the goal to clear an obstacle remains unclear. Stabilizing features of gait initiation include anticipatory postural adjustments (APAs) and lateral swing foot placement. To answer the above question, 14 participants initiated gait as fast as possible in three conditions of obstacle height, three conditions of obstacle distance and one obstacle-free (control) condition. Each of these conditions was performed with two levels of temporal pressure: reaction-time (high-pressure) and self-initiated (low-pressure) movements. A mechanical model of the body falling laterally under the influence of gravity and submitted to an elastic restoring force is proposed to assess the effect of initial (foot-off) center-of-mass position and velocity (or "initial center-of-mass set") on the stability at foot-contact. Results showed that the anticipatory peak of mediolateral (ML) center-of-pressure shift, the initial ML center-of-mass velocity and the duration of the swing phase, of gait initiation increased with obstacle height, but not with obstacle distance. These results suggest that ML APAs are scaled with swing duration in order to maintain an equivalent stability across experimental conditions. This statement is strengthened by the results obtained with the mechanical model, which showed how stability would be degraded if there was no adaptation of the initial center-of-mass set to swing duration. The anteroposterior (AP) component of APAs varied also according to obstacle height and distance, but in an opposite way to the ML component. Indeed, results showed that the anticipatory peak of backward center-of-pressure shift and the initial forward center-of-mass set decreased with obstacle height, probably in order to limit the risk to trip over the obstacle, while the forward center-of-mass velocity at foot

Anticipatory Postural Control of Stability during Gait Initiation Over Obstacles of Different Height and Distance Made Under Reaction-Time and Self-Initiated Instructions

PubMed Central

Yiou, Eric; Artico, Romain; Teyssedre, Claudine A.; Labaune, Ombeline; Fourcade, Paul

2016-01-01

Despite the abundant literature on obstacle crossing in humans, the question of how the central nervous system (CNS) controls postural stability during gait initiation with the goal to clear an obstacle remains unclear. Stabilizing features of gait initiation include anticipatory postural adjustments (APAs) and lateral swing foot placement. To answer the above question, 14 participants initiated gait as fast as possible in three conditions of obstacle height, three conditions of obstacle distance and one obstacle-free (control) condition. Each of these conditions was performed with two levels of temporal pressure: reaction-time (high-pressure) and self-initiated (low-pressure) movements. A mechanical model of the body falling laterally under the influence of gravity and submitted to an elastic restoring force is proposed to assess the effect of initial (foot-off) center-of-mass position and velocity (or “initial center-of-mass set”) on the stability at foot-contact. Results showed that the anticipatory peak of mediolateral (ML) center-of-pressure shift, the initial ML center-of-mass velocity and the duration of the swing phase, of gait initiation increased with obstacle height, but not with obstacle distance. These results suggest that ML APAs are scaled with swing duration in order to maintain an equivalent stability across experimental conditions. This statement is strengthened by the results obtained with the mechanical model, which showed how stability would be degraded if there was no adaptation of the initial center-of-mass set to swing duration. The anteroposterior (AP) component of APAs varied also according to obstacle height and distance, but in an opposite way to the ML component. Indeed, results showed that the anticipatory peak of backward center-of-pressure shift and the initial forward center-of-mass set decreased with obstacle height, probably in order to limit the risk to trip over the obstacle, while the forward center-of-mass velocity at foot

A biologically inspired neural net for trajectory formation and obstacle avoidance.

PubMed

Glasius, R; Komoda, A; Gielen, S C

1996-06-01

In this paper we present a biologically inspired two-layered neural network for trajectory formation and obstacle avoidance. The two topographically ordered neural maps consist of analog neurons having continuous dynamics. The first layer, the sensory map, receives sensory information and builds up an activity pattern which contains the optimal solution (i.e. shortest path without collisions) for any given set of current position, target positions and obstacle positions. Targets and obstacles are allowed to move, in which case the activity pattern in the sensory map will change accordingly. The time evolution of the neural activity in the second layer, the motor map, results in a moving cluster of activity, which can be interpreted as a population vector. Through the feedforward connections between the two layers, input of the sensory map directs the movement of the cluster along the optimal path from the current position of the cluster to the target position. The smooth trajectory is the result of the intrinsic dynamics of the network only. No supervisor is required. The output of the motor map can be used for direct control of an autonomous system in a cluttered environment or for control of the actuators of a biological limb or robot manipulator. The system is able to reach a target even in the presence of an external perturbation. Computer simulations of a point robot and a multi-joint manipulator illustrate the theory.

Visualization of deflagration-to-detonation transitions in a channel with repeated obstacles using a hydrogen-oxygen mixture

NASA Astrophysics Data System (ADS)

Maeda, S.; Minami, S.; Okamoto, D.; Obara, T.

2016-09-01

The deflagration-to-detonation transition in a 100 mm square cross-section channel was investigated for a highly reactive stoichiometric hydrogen oxygen mixture at 70 kPa. Obstacles of 5 mm width and 5, 10, and 15 mm heights were equally spaced 60 mm apart at the bottom of the channel. The phenomenon was investigated primarily by time-resolved schlieren visualization from two orthogonal directions using a high-speed video camera. The detonation transition occurred over a remarkably short distance within only three or four repeated obstacles. The global flame speed just before the detonation transition was well below the sound speed of the combustion products and did not reach the sound speed of the initial unreacted gas for tests with an obstacle height of 5 and 10 mm. These results indicate that a detonation transition does not always require global flame acceleration beyond the speed of sound for highly reactive combustible mixtures. A possible mechanism for this detonation initiation was the mixing of the unreacted and reacted gas in the vicinity of the flame front convoluted by the vortex present behind each obstacle, and the formation of a hot spot by the shock wave. The final onset of the detonation originated from the unreacted gas pocket, which was surrounded by the obstacle downstream face and the channel wall.

Dual tasking negatively impacts obstacle avoidance abilities in post-stroke individuals with visuospatial neglect: Task complexity matters!

PubMed

Aravind, Gayatri; Lamontagne, Anouk

2017-01-01

Persons with perceptual-attentional deficits due to visuospatial neglect (VSN) after a stroke are at a risk of collisions while walking in the presence of moving obstacles. The attentional burden of performing a dual-task may further compromise their obstacle avoidance performance, putting them at a greater risk of collisions. The objective of this study was to compare the ability of persons with (VSN+) and without VSN (VSN-) to dual task while negotiating moving obstacles. Twenty-six stroke survivors (13 VSN+, 13 VSN-) were assessed on their ability to (a) negotiate moving obstacles while walking (locomotor single task); (b) perform a pitch-discrimination task (cognitive single task) and (c) simultaneously perform the walking and cognitive tasks (dual task). We compared the groups on locomotor (collision rates, minimum distance from obstacle and onset of strategies) and cognitive (error rates) outcomes. For both single and dual task walking, VSN+ individuals showed higher collision rates compared to VSN- individuals. Dual tasking caused deterioration of locomotor (more collisions, delayed onset and smaller minimum distances) and cognitive performances (higher error rate) in VSN+ individuals. Contrastingly, VSN- individuals maintained collision rates, increased minimum distance, but showed more cognitive errors, prioritizing their locomotor performance. Individuals with VSN demonstrate cognitive-locomotor interference under dual task conditions, which could severely compromise safety when ambulating in community environments and may explain the poor recovery of independent community ambulation in these individuals.

Starfish Behavior as an Anticipatory System: Its Flexibility in Obstacle Avoidance

NASA Astrophysics Data System (ADS)

Migita, Masao

2006-06-01

As starfish do not have central nervous systems, their behaviors such as walking, righting, feeding, and so on, must be produced by some processes of self-organization of many motor organs. It has been noticed that self-organized behavioral patterns are not strictly determined by external stimuli, though such stimuli may elicit the very self-organization processes. In this sense, starfish are not only reactive like a conventional discourse of comparative psychology have presupposed. In this study, I will show diversity in self-organized behavior of a starfish exhibited under experiments on obstacle avoidance. The starfish may be considered as an anticipatory system, because it usually appeared to be free from serious deadlock at the obstacles. I will also discuss that to view the animal as an anticipatory system may have an interesting implication on the fields of behavioral biology and comparative psychology.

78 FR 32088 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-29

...This rule establishes, amends, suspends, or revokes Standard Instrument Approach Procedures (SIAPs) and associated Takeoff Minimums and Obstacle Departure Procedures for operations at certain airports. These regulatory actions are needed because of the adoption of new or revised criteria, or because of changes occurring in the National Airspace System, such as the commissioning of new navigational facilities, adding new obstacles, or changing air traffic requirements. These changes are designed to provide safe and efficient use of the navigable airspace and to promote safe flight operations under instrument flight rules at the affected airports.

75 FR 69331 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-12

...This establishes, amends, suspends, or revokes Standard Instrument Approach Procedures (SIAPs) and associated Takeoff Minimums and Obstacle Departure Procedures for operations at certain airports. These regulatory actions are needed because of the adoption of new or revised criteria, or because of changes occurring in the National Airspace System, such as the commissioning of new navigational facilities, adding new obstacles, or changing air traffic requirements. These changes are designed to provide safe and efficient use of the navigable airspace and to promote safe flight operations under instrument flight rules at the affected airports.

77 FR 12454 - Standard Instrument Approach Procedures, and Takeoff Minimums and Obstacle Departure Procedures...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-01

...This rule establishes, amends, suspends, or revokes Standard Instrument Approach Procedures (SIAPs) and associated Takeoff Minimums and Obstacle Departure Procedures for operations at certain airports. These regulatory actions are needed because of the adoption of new or revised criteria, or because of changes occurring in the National Airspace System, such as the commissioning of new navigational facilities, adding new obstacles, or changing air traffic requirements. These changes are designed to provide safe and efficient use of the navigable airspace and to promote safe flight operations under instrument flight rules at the affected airports.

A computational study for investigating acoustic streaming and tissue heating during high intensity focused ultrasound through blood vessel with an obstacle

NASA Astrophysics Data System (ADS)

Parvin, Salma; Sultana, Aysha

2017-06-01

The influence of High Intensity Focused Ultrasound (HIFU) on the obstacle through blood vessel is studied numerically. A three-dimensional acoustics-thermal-fluid coupling model is employed to compute the temperature field around the obstacle through blood vessel. The model construction is based on the linear Westervelt and conjugate heat transfer equations for the obstacle through blood vessel. The system of equations is solved using Finite Element Method (FEM). We found from this three-dimensional numerical study that the rate of heat transfer is increasing from the obstacle and both the convective cooling and acoustic streaming can considerably change the temperature field.

Obstacles to the Termination of Air Force Activities.

DTIC Science & Technology

1986-04-01

sugsts how. it the Air Force leadership con- eludes that termination is necessary the Air Force can surmount the obstacles.’ The stud v was cMIduct ed...the Air Force leadership concludes that the termination of a major activity is a promising or necessary management option, the report suggests that it...complicated inter- nal political process; it takes time to work out. The top leadership should begin the process of corporate strategy building and priority

Mandatory Reporting and School Counselors: Reporting Laws, Obstacles, and Solutions

ERIC Educational Resources Information Center

Valkyrie, Karena T.; Creamer, D. Andrew; Vaughn, Leila

2008-01-01

Child abuse and neglect is a serious problem across our nation, and the consequences can be far reaching. Laws were enacted to address child abuse and identify mandatory reporters, including school counselors. In the literature, school counselors regularly report systemic and personal obstacles that influence their compliance with the mandatory…

Misogyny, Women, and Obstacles to Tertiary Education: A Vile Situation.

ERIC Educational Resources Information Center

Stalker, Joyce

2001-01-01

Interviews with 18 women enrolled in postsecondary education used a framework of misogyny to reinterpret barriers to their participation Resulting themes included women's role in maintaining the home as sanctuary, women needing constraint, and men's role as suppressors. Results suggest how a theory based in misogyny can explain obstacles to…

Institutional obstacles to expansion of world food production.

PubMed

Crosson, P R

1975-05-09

water management institutions may be even more limiting, for reasons noted in the previous section. The role of existing land tenure institutions is not clear. The tentative conclusion, however, is that over the near-to-medium term the maintenance will not be a major obstacle to further spread of the Green Revolution. Over the longer term, it could become more seriously limiting. The reason is that continued expansion of food production will eventually require the invention and adoption of new technologies and a higher level of technical and managerial skill than most farmers in the LDC's now possess. To do this will require substantial investments in domestic research and extension institutions and in rural education. In countries where a small class of large landowners wield substantial political power, these investments may not occur on the necessary scale because the large farmers have their own means of acquiring the technology and little perceived interest in supporting the upgrading of the skills of small farmers. This review of institutional obstacles to expansion of food production in the LDC's must end on a tentative note. The review does suggest some observations about the process of institutional change, however. There is impressive evidence of strong latent potential in the private sector of the LDC's for mobilizing the resources and effort needed for agricultural progress when the private economic rewards for doing so are high. Under these circumstances, needed changes in the institutions required to mobilize the resources and direct the effort seem relatively easy to achieve. Institutional resistance is stronger in situations where influential interests perceive change as a threat or where there is no direct personal economic reward to change, as in the typical public institution. The latter point is particularly important because the performance of public institutions is critical. Development of new technology, the fundamental condition for continued

A five-week exercise program can reduce falls and improve obstacle avoidance in the elderly.

PubMed

Weerdesteyn, Vivian; Rijken, Hennie; Geurts, Alexander C H; Smits-Engelsman, Bouwien C M; Mulder, Theo; Duysens, Jacques

2006-01-01

Falls in the elderly are a major health problem. Although exercise programs have been shown to reduce the risk of falls, the optimal exercise components, as well as the working mechanisms that underlie the effectiveness of these programs, have not yet been established. To test whether the Nijmegen Falls Prevention Program was effective in reducing falls and improving standing balance, balance confidence, and obstacle avoidance performance in community-dwelling elderly people. A total of 113 elderly with a history of falls participated in this study (exercise group, n = 79; control group, n = 28; dropouts before randomization, n = 6). Exercise sessions were held twice weekly for 5 weeks. Pre- and post-intervention fall monitoring and quantitative motor control assessments were performed. The outcome measures were the number of falls, standing balance and obstacle avoidance performance, and balance confidence scores. The number of falls in the exercise group decreased by 46% (incidence rate ratio (IRR) 0.54, 95% confidence interval (CI) 0.36-0.79) compared to the number of falls during the baseline period and by 46% (IRR 0.54, 95% CI 0.34-0.86) compared to the control group. Obstacle avoidance success rates improved significantly more in the exercise group (on average 12%) compared to the control group (on average 6%). Quiet stance and weight-shifting measures did not show significant effects of exercise. The exercise group also had a 6% increase of balance confidence scores. The Nijmegen Falls Prevention Program was effective in reducing the incidence of falls in otherwise healthy elderly. There was no evidence of improved control of posture as a mechanism underlying this result. In contrast, an obstacle avoidance task indicated that subjects improved their performance. Laboratory obstacle avoidance tests may therefore be better instruments to evaluate future fall prevention studies than posturographic balance assessments. Copyright (c) 2006 S. Karger AG, Basel.

Obstacles of Implementing the Science Curricula of the Basic Stage as Perceived by the Teachers in a Jordanian Town

ERIC Educational Resources Information Center

Ayasra, Ahmad

2015-01-01

This study aimed to investigate obstacles that prevent implementation of science curriculum which was developed within the Education Reform for the Knowledge Economy project (ErfKE). To achieve this, a purposeful sample consisted of four teachers of science for the basic stage in the town located in the north of Jordan in the first semester of the…

Optimal partial mass transportation and obstacle Monge-Kantorovich equation

NASA Astrophysics Data System (ADS)

Igbida, Noureddine; Nguyen, Van Thanh

2018-05-01

Optimal partial mass transport, which is a variant of the optimal transport problem, consists in transporting effectively a prescribed amount of mass from a source to a target. The problem was first studied by Caffarelli and McCann (2010) [6] and Figalli (2010) [12] with a particular attention to the quadratic cost. Our aim here is to study the optimal partial mass transport problem with Finsler distance costs including the Monge cost given by the Euclidian distance. Our approach is different and our results do not follow from previous works. Among our results, we introduce a PDE of Monge-Kantorovich type with a double obstacle to characterize active submeasures, Kantorovich potential and optimal flow for the optimal partial transport problem. This new PDE enables us to study the uniqueness and monotonicity results for the active submeasures. Another interesting issue of our approach is its convenience for numerical analysis and computations that we develop in a separate paper [14] (Igbida and Nguyen, 2018).

A Social-Interactive Neuroscience Approach to Understanding the Developing Brain.

PubMed

Redcay, Elizabeth; Warnell, Katherine Rice

2018-01-01

From birth onward, social interaction is central to our everyday lives. Our ability to seek out social partners, flexibly navigate and learn from social interactions, and develop social relationships is critically important for our social and cognitive development and for our mental and physical health. Despite the importance of our social interactions, the neurodevelopmental bases of such interactions are underexplored, as most research examines social processing in noninteractive contexts. We begin this chapter with evidence from behavioral work and adult neuroimaging studies demonstrating how social-interactive context fundamentally alters cognitive and neural processing. We then highlight four brain networks that play key roles in social interaction and, drawing on existing developmental neuroscience literature, posit the functional roles these networks may play in social-interactive development. We conclude by discussing how a social-interactive neuroscience approach holds great promise for advancing our understanding of both typical and atypical social development. © 2018 Elsevier Inc. All rights reserved.

A Mobile Robot Sonar System with Obstacle Avoidance.

DTIC Science & Technology

1994-03-01

WITH OBSTACLE - AVOIDANCE __ by __ Patrick Gerard Byrne March 1994 Thesis Advisor : Yutaka Kanayama Approved for public release; distribution is...point p is on a line L whose normal has an orientation a and whose distance from the origin is r (Figure 5). This method has an advantage in expressing...sonar(FRONTR); Wine(&pl); while(hitl I >’- 100.0 11 hitl 1 - 0.0 ){ hitl I = sonar(FRONTR); I skipO; line(&p3); gat- robO (&posit 1); while(positl.x

Obstacles to engaging in young driver licensing: Perspectives of parents.

PubMed

Naz, Sehana; Scott-Parker, Bridie

2017-02-01

Young novice drivers remain at greater risk of injury and death despite a wealth of interventions including graduated driver licensing (GDL) programs. The key to implementing safer practices inherent in GDL appears to lie with optimising the role of parents. This qualitative research explored the parent's perspectives of obstacles to engaging in the driver licensing process within a GDL program. Parents also shared advice on what they found helpful, and where relevant, recommended changes in the process to enable safer practices for young drivers. Twenty-three parents (aged 35-60 years, M=49.52, SD=8.01, 11 males) participated in semi-structured interviews regarding licensing experiences with their young driver children. The young drivers included learner (n=11), provisional (restricted/intermediate) (n=9) and open (unrestricted/full) licence drivers (n=3), ranging from 16 to 24 years (M=18.04, SD=2.21, 13 males). Content analysis revealed that most obstacles were encountered at the learner licensing phase, with the parent-reported difficult temperament of the learner driver the most prominent. Unsurprisingly, advice to other parents to be patient and remain calm featured heavily during the same phase. Anxiety from not having control of the vehicle was another obstacle at the learner phase, translating to anxieties for child safety in the early stages of provisional driving. Recommendations for the current GDL included more rigorous road rule testing, with general support for the program, professional driver training at learner and provisional stages facilitated parental engagement through the licensing phases. The findings overwhelmingly suggest a need for parents to be educated regarding their importance in, and of, the driver licensing process, and the efficacy of their instruction, content and practices. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-Reported Obstacles to Regular Dental Care among Information Technology Professionals.

PubMed

Reddy, L Swetha; Doshi, Dolar; Reddy, B Srikanth; Kulkarni, Suhas; Reddy, M Padma; Satyanarayana, D; Baldava, Pavan

2016-10-01

Good oral health is important for an individual as well as social well-being. Occupational stress and work exhaustion in Information Technology (IT) professionals may influence the oral health and oral health related quality of life. To assess and compare self-reported obstacles for regular dental care and dental visits among IT professionals based on age, gender, dental insurance and working days per week. A cross-sectional study was conducted among 1,017 IT professionals to assess the self-reported obstacles to regular oral health care in Hyderabad city, Telangana, India. The Dental Rejection of Innovation Scale (DRI-S) was employed in this study. Comparison between means of DRI-S based on variables was done using t-test and ANOVA. The association between variables and DRI-S was determined using Chi-square test. A total of 1017 participants comprising of 574 (56%) males and 443 (44%) females participated in the study. As age increased, a significant increase in mean DRI-S scores was seen for total and individual domains except for the "Situational" domain wherein higher mean score (9.42±2.5; p=0.0006) was observed among 30-39 years age group. Even though females reported higher mean scores for total and individual domains when compared to males, nevertheless significant difference was seen only for total (p=0.03) and "Lack of Knowledge" (p=0.001) domain. Self-reported obstacles to regular dental care was more with increasing age, increased number of working days per week, irregular dental visits and absence of dental insurance facility.

On computing the global time-optimal motions of robotic manipulators in the presence of obstacles

NASA Technical Reports Server (NTRS)

Shiller, Zvi; Dubowsky, Steven

1991-01-01

A method for computing the time-optimal motions of robotic manipulators is presented that considers the nonlinear manipulator dynamics, actuator constraints, joint limits, and obstacles. The optimization problem is reduced to a search for the time-optimal path in the n-dimensional position space. A small set of near-optimal paths is first efficiently selected from a grid, using a branch and bound search and a series of lower bound estimates on the traveling time along a given path. These paths are further optimized with a local path optimization to yield the global optimal solution. Obstacles are considered by eliminating the collision points from the tessellated space and by adding a penalty function to the motion time in the local optimization. The computational efficiency of the method stems from the reduced dimensionality of the searched spaced and from combining the grid search with a local optimization. The method is demonstrated in several examples for two- and six-degree-of-freedom manipulators with obstacles.

Integrating Millimeter Wave Radar with a Monocular Vision Sensor for On-Road Obstacle Detection Applications

PubMed Central

Wang, Tao; Zheng, Nanning; Xin, Jingmin; Ma, Zheng

2011-01-01

This paper presents a systematic scheme for fusing millimeter wave (MMW) radar and a monocular vision sensor for on-road obstacle detection. As a whole, a three-level fusion strategy based on visual attention mechanism and driver’s visual consciousness is provided for MMW radar and monocular vision fusion so as to obtain better comprehensive performance. Then an experimental method for radar-vision point alignment for easy operation with no reflection intensity of radar and special tool requirements is put forward. Furthermore, a region searching approach for potential target detection is derived in order to decrease the image processing time. An adaptive thresholding algorithm based on a new understanding of shadows in the image is adopted for obstacle detection, and edge detection is used to assist in determining the boundary of obstacles. The proposed fusion approach is verified through real experimental examples of on-road vehicle/pedestrian detection. In the end, the experimental results show that the proposed method is simple and feasible. PMID:22164117

Integrating millimeter wave radar with a monocular vision sensor for on-road obstacle detection applications.

PubMed

Wang, Tao; Zheng, Nanning; Xin, Jingmin; Ma, Zheng

2011-01-01

This paper presents a systematic scheme for fusing millimeter wave (MMW) radar and a monocular vision sensor for on-road obstacle detection. As a whole, a three-level fusion strategy based on visual attention mechanism and driver's visual consciousness is provided for MMW radar and monocular vision fusion so as to obtain better comprehensive performance. Then an experimental method for radar-vision point alignment for easy operation with no reflection intensity of radar and special tool requirements is put forward. Furthermore, a region searching approach for potential target detection is derived in order to decrease the image processing time. An adaptive thresholding algorithm based on a new understanding of shadows in the image is adopted for obstacle detection, and edge detection is used to assist in determining the boundary of obstacles. The proposed fusion approach is verified through real experimental examples of on-road vehicle/pedestrian detection. In the end, the experimental results show that the proposed method is simple and feasible.

Perceived Obstacles Faced by Diabetes Patients Attending University of Gondar Hospital, Northwest Ethiopia.

PubMed

Bhagavathula, Akshaya Srikanth; Gebreyohannes, Eyob Alemayehu; Abegaz, Tadesse Melaku; Abebe, Tamrat Befekadu

2018-01-01

Diabetes mellitus (DM) is a non-communicable, chronic, and progressive disease that can lead to serious complications and even to premature death. A closer understanding of the DM patients' specific obstacles will provide a greater clarity of the factors influencing their disease-related quality of life and coping with daily life. The study aimed to evaluate the obstacles of DM patients attending ambulatory clinic of the University of Gondar Hospital (UOGH), Northwest Ethiopia. A cross-sectional study was conducted from February to April 2017 at ambulatory clinic of the UOGH. A validated short version of the diabetic obstacle questionnaire was used. The internal reliability of the questionnaire was checked using Cronbach's alpha and was found to be 92.5%. To determine any association between each of the nine sections of the questionnaire and age, sex, residence, educational status, and DM type, a binary logistic regression was performed. The mean age of respondents was 38.69 ± 15.39 years. Compared with patients with type 1 DM, patients with type 2 DM reported poorer relationships with medical professionals (adjusted odds ratio (AOR): 2.191, p -value = 0.027) and less support from families and friends (AOR: 1.913, p -value = 0.049). Patients coming from rural areas (AOR: 2.947, p  = 0.002) and having no formal education (AOR: 2.078, p  = 0.029) also received less support from families and friends. DM patients in UOGH reported several obstacles related to patients' relationship with health professionals, lack of support from their friends, lack of knowledge about DM, and lack of motivation to exercise. Effective efforts should be initiated to improve healthier environment to educate, care and preventive services for people with DM.

Strategies for handling ethical problems in end of life care: obstacles and possibilities.

PubMed

Rejnö, Åsa; Berg, Linda

2015-11-01

In end of life care, ethical problems often come to the fore. Little research is performed on ways or strategies for handling those problems and even less on obstacles to and possibilities of using such strategies. A previous study illuminated stroke team members' experiences of ethical problems and how the teams managed the situation when caring for patients faced with sudden and unexpected death from stroke. These findings have been further explored in this study. The aim of the study was to illuminate obstacles and possibilities perceived by stroke team members in using strategies for handling ethical problems when caring for patients afflicted by sudden and unexpected death caused by stroke. A qualitative method with combined deductive and inductive content analysis was utilized. Data were collected through individual interviews with 15 stroke team members working in stroke units of two associated county hospitals in western Sweden. The study was approved by the Regional Ethics Review Board, Gothenburg, Sweden. Permission was also obtained from the director of each stroke unit. All the studied strategies for handling of ethical problems were found to have both obstacles and possibilities. Uncertainty is shown as a major obstacle and unanimity as a possibility in the use of the strategies. The findings also illuminate the value of the concept "the patient's best interests" as a starting point for the carers' ethical reasoning. The concept "the patient's best interests" used as a starting point for ethical reasoning among the carers is not explicitly defined yet, which might make this value difficult to use both as a universal concept and as an argument for decisions. Carers therefore need to strengthen their argumentation and reflect on and use ethically grounded arguments and defined ethical values like dignity in their clinical work and decisions. © The Author(s) 2014.

Obstacle penetrating dynamic radar imaging system

DOEpatents

Romero, Carlos E [Livermore, CA; Zumstein, James E [Livermore, CA; Chang, John T [Danville, CA; Leach, Jr Richard R. [Castro Valley, CA

2006-12-12

An obstacle penetrating dynamic radar imaging system for the detection, tracking, and imaging of an individual, animal, or object comprising a multiplicity of low power ultra wideband radar units that produce a set of return radar signals from the individual, animal, or object, and a processing system for said set of return radar signals for detection, tracking, and imaging of the individual, animal, or object. The system provides a radar video system for detecting and tracking an individual, animal, or object by producing a set of return radar signals from the individual, animal, or object with a multiplicity of low power ultra wideband radar units, and processing said set of return radar signals for detecting and tracking of the individual, animal, or object.

Healthy young adults implement distinctive avoidance strategies while walking and circumventing virtual human vs. non-human obstacles in a virtual environment.

PubMed

Souza Silva, Wagner; Aravind, Gayatri; Sangani, Samir; Lamontagne, Anouk

2018-03-01

This study examines how three types of obstacles (cylinder, virtual human and virtual human with footstep sounds) affect circumvention strategies of healthy young adults. Sixteen participants aged 25.2 ± 2.5 years (mean ± 1SD) were tested while walking overground and viewing a virtual room through a helmet mounted display. As participants walked towards a stationary target in the far space, they avoided an obstacle (cylinder or virtual human) approaching either from the right (+40°), left (-40°) or head-on (0°). Obstacle avoidance strategies were characterized using the position and orientation of the head. Repeated mixed model analysis showed smaller minimal distances (p = 0.007) while avoiding virtual humans as compared to cylinders. Footstep sounds added to virtual humans did not modify (p = 0.2) minimal distances compared to when no sound was provided. Onset times of avoidance strategies were similar across conditions (p = 0.06). Results indicate that the nature of the obstacle (human-like vs. non-human object) matters and can modify avoidance strategies. Smaller obstacle clearances in response to virtual humans may reflect the use of a less conservative avoidance strategy, due to a resemblance of obstacles to pedestrians and a recall of strategies used in daily locomotion. The lack of influence of footstep sounds supports the fact that obstacle avoidance primarily relies on visual cues and the principle of 'inverse effectiveness' whereby multisensory neurons' response to multimodal stimuli becomes weaker when the unimodal sensory stimulus (vision) is strong. Present findings should be taken into consideration to optimize the ecological validity of VR-based obstacle avoidance paradigms used in research and rehabilitation. Copyright © 2018 Elsevier B.V. All rights reserved.

The Invisible Obstacle to Educational Equality: Gender Bias in Textbooks

ERIC Educational Resources Information Center

Blumberg, Rae Lesser

2008-01-01

Gender bias in textbooks (GBIT) is a low-profile education issue, given the 72,000,000 children who still have no access to schooling, but this article argues that GBIT is: (1) an important, (2) near-universal, (3) remarkably uniform, (4) quite persistent but (5) virtually invisible obstacle on the road to gender equality in education--an obstacle…

Visually guided gait modifications for stepping over an obstacle: a bio-inspired approach.