Arm strength and impulse generation: Initiation of wheelchair movement by the physically disabled

The initiation of wheelchair movement is a function of starting technique, upper extremity strength and the stabilizing potential of the trunk musculature. This study examined the relation between arm strength, activity level, degree of disability and the maximum impulse generated from a resting position while seated in a wheelchair. Two starting techniques were examined using a force platform.

Sixteen male paraplegic adults (age 28·1 ±6·9 year, supine length l·62±0·16m, total body mass 61·2±16·2 kg) performed three grab starts and three strike starts on a Kistler force platform. For each technique, the processed data were averaged together and impulse in the forward/backward and vertical directions was determined. Isokinetic shoulder flexion and elbow extension moments of force were measured at an angular velocity of 60 degs^?1. Peak power and average power were calculated from digitized values of the moment of force-time curves.

Subjects were classified as highly active (HA, >2 exercise periods per week, N = 8) or less active (LA, N = 8). In addition, the site of spinal cord injury was quantified as a high level lesion (HL, above T10, N = 7) or low level lesion (LL, N = 9). There were no differences (p>0·05) between activity or lesion level groups with respect to age, height, total body mass or skinfold thicknesses. Nor were there significant differences between groups for shoulder and elbow power values. However, shoulder flexion scores for the combined groups were greater than those scores for elbow extension (peak power, 72·9 W versus 49·5 W; average power, 51·8 W versus 37·2 W). The grab start produced more forward impulse (the integral of forward force × time) (152·6 N s) than the strike start (119·5 N s, p < 0·05), but the magnitude of this difference was similar for the several groups. Wheelchair impulse scores were well correlated with strength values in both HA and LA subjects (r=0·74 to 0·89). However, the intercepts of the regression lines were dissimilar between activity groups, suggesting an interaction between activity pattern, muscle force and impulse.     

Auto-navigation of a wheelchair

This paper presents an autonomous wheelchair system with the capability of self-localization and obstacle avoidance. In our system, the ceiling lights are chosen as landmarks to realize the self-localization of the wheelchair, and a laser range-finder is used for obstacle avoidance. First the approaches of landmark recognition and selflocalization for the wheelchair are proposed. Then the principle of obstacle avoidance using a laser range-finder is described. Finally, the total system of the wheelchair is introduced and a navigational experiment is described. Experimental results indicate the effectiveness of our system. This work was presented, in part, at the International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1996     

The ergonomics of different tyres and tyre pressure during wheelchair propulsion

It is believed that the newer solid tyres on wheelchairs perform as well as pneumatic tyres along with less cost and time for maintenance. The questions are: (1) do solid tyres perform as well as pneumatic tyres and (2) what is the critical level of pneumatic tyre pressure before wheeling efficiency decreases? Part one measured the rolling resistance differences of five commonly used wheelchair tyres (three pneumatic and two solid) under four different tyre pressures (100, 75, 50 and 25 of inflation). Part two measured the oxygen consumption in 15 participants with paraplegia, during wheelchair propulsion, comparing the same four levels of tyre inflation. The solid tyres performed worse than all three pneumatic tyres even when tyres were under-inflated to 25% of tyre pressure. Two of the pneumatic tyres showed significant decreases in rolling between 100 and 50%, but there were no significant differences in rolling distance between 100 and 75% pressure. The physiological study showed that energy expenditure increased significantly at 50% of tyre-inflation. Health care facilities are finding ways to decrease cost by using solid tyres on all wheelchairs. This study shows that benefits to clients and staff using pneumatic tyres far outweigh the minimal cost in time to maintain adequate tyre inflation.     

Environment adaptation of a new staircase-climbing wheelchair

This paper describes the mechanical devices conforming a novel wheelchair prototype capable of climbing staircases. The key feature of the mechanical design is the use of two decoupled mechanisms in each axle, one to negotiate steps, and the other to position the axle with respect to the chair to accommodate the overall slope. This design simplifies the control task substantially. Kinematic models are necessary to describe the behavior of the system and to control the actuated degrees of freedom of the wheelchair to ensure the passenger’s comfort. The choice of a good climbing strategy simplifies the control and decreases the power consumption of the wheelchair. In particular, we demonstrate that if the movement of the wheelchair has the same slope as the racks or the same slope as the terrain that supports the wheel axles (depending on the configuration mechanism), control is easier and power consumption is less. Experimental results are reported which show the behavior of the prototype as it moves over different situations: (a) ascending a single step of different heights using different climbing strategies; and (b) climbing a staircase using an appropriate climbing strategy that simplifies the control and reduces the power consumption of the wheelchair.

Evaluation on an ergonomic design of functional clothing for wheelchair users

Researchers have pointed out that people with physical disabilities find it difficult to obtain suitable clothing. In this study a set of wheelchair user oriented functional clothing was designed. Attention was paid to the wheelchair users' daily living activities related with clothing. An evaluating system combined with sports tournament and rehabilitation medicine was introduced to assess the new designed clothing. Six wheelchair users (3 males and 3 females) were invited to wear the clothing. A set of normal functional clothing was employed as a comparison (Control). The time required to complete three different daily living activities, i.e. dressing and undressing, going to toilet and bathing were recorded. Results showed that with the new clothing wheelchair users' competence of managing toilet was increased by 52.9%. The time needed for toilet was reduced by 45.7%. Their capability of managing dressing and undressing was improved by 24.6%. The study indicated that the newly designed clothing could facilitate wheelchair users' daily living activities related with clothing.     

An investigation of the performance portability of OpenCL

This paper reports on the development of an MPI/OpenCL implementation of LU, an application-level benchmark from the NAS Parallel Benchmark Suite. An account of the design decisions addressed during the development of this code is presented, demonstrating the importance of memory arrangement and work-item/work-group distribution strategies when applications are deployed on different device types. The resulting platform-agnostic, single source application is benchmarked on a number of different architectures, and is shown to be 1.3–1.5× slower than native FORTRAN 77 or CUDA implementations on a single node and 1.3–3.1× slower on multiple nodes. We also explore the potential performance gains of OpenCL’s device fissioning capability, demonstrating up to a 3× speed-up over our original OpenCL implementation.     

Analysis of hand pressures related to wheelchair rim sizes and upper-limb movement

Hand pressure is important in wheelchair design as it is directly related to the comfort or injury of the patients/sportsmen using the wheelchair. However, little research has been done on hand pressure during wheelchair propelling. This study aimed to measure hand pressures and joint movements in the upper limb with the different size of wheelchair rims during manual propulsion. Nine healthy adult subjects participated in the study, and they were required to perform wheelchair propelling at their self-comfortable way. A specific mat of pressure sensors was used to measure the hand pressure of the palm and a motion capture system to capture the movements at the shoulder and elbow. The results showed that under the condition of the speeds between 0.7–1.7 m/s, the mean hand pressures were ranged between 180 and 200 kPa on the palm; the ranges of motion were from 30° to 70° at the shoulder and from 15° to 50° at the elbow. The pressure and kinematic data collected provide a set of database available for wheelchair manufacturer, glove designer, clinicians and sports exerciser as reference when they need.Relevance to industryPushing wheelchair usually causes hand uncomfortable or injury. Our study provides the first experimental data of hand pressures associated the joint movements in the upper limbs at different sizes of push-rims. These results are valuable for devising gloves for patients, thus improving the life quality of the patients using wheelchair.     

An empirical investigation of the relationship of IS strategy with firm performance

Given the important impact that an IS strategy has on the potential value IS brings to an organization, we develop and test a model of IS Strategy and Firm Performance. Our survey-based study provides strong evidence that firms with defined IS strategies (either IS Innovator or IS Conservative) perform better than those without defined IS strategies. Organizations without a clearly defined IS strategy actually experienced a negative relationship with firm performance. These organizations should realize the potentially negative outcomes of such a lack of strategy and work to extricate themselves before a consistent pattern of investing in IS without clear organizational benefit develops. Furthermore, the study suggests that the IS Innovator strategy is, in particular, associated with more superior firm performance than the IS Conservative strategy under conditions of environmental dynamism. Organizational leaders need to consider the external environments under which their organizations are operating and evaluate the influence those environments may have on their IS strategy’s ability to impact performance. Post hoc analysis results also reveal a fourth potential IS strategy, one that strives for ambidexterity. Ambidextrous firms were found to be associated with the most superior performance, leading to a potential extension of the existing IS strategy typology and a call for future research.     

Effects of ramp slope,ramp height and users' pushing force on performance,muscular activity and subjective ratings during wheelchair driving on a ramp

We set and examined two hypotheses about effects of ramp slope (1:6, 1:8, 1:10, 1:12, and 1:14) by varying ramp height (0.15 m, 0.30 m, and 0.45 m) and pushing force of wheelchair users (weak, medium, and strong group). Thirty participants were recruited for the experiment, and they have ascended a ramp using a manual wheelchair. Three categories of dependent variables were measured: performance measures (total time and velocity), muscular activity measures (EMG of four upper extremity muscles) and subjective rating measures (physical discomfort and acceptability). Only the strong group used muscles constantly regardless of the ramp slope. Accessibility of the ramp decreased as the slope increased, and accessibility difference between slopes increased as the height increased. Based on the result, we suggest maximum allowable slope by ramp height: 1:8, 1:10 and 1:12 were recommended for the heights of 0.15 m, 0.30 m, and 0.45 m, respectively.     

A pilot study of a method for assessing the reach capability of wheelchair users for safety belt design

A method was developed to assess the reach capability of people seated in wheelchairs for purposes of establishing design and placement requirements for safety belts used by vehicle occupants who are seated in wheelchairs. The method uses simple technology and is intended to be readily implemented in the field. Participants use a marker to draw their acceptable reach zone on a vertical surface placed adjacent to the wheelchair. A pilot study with 10 wheelchair users showed that the method generates easily interpreted data quickly. Even with a small number of participants, the results from the pilot study provide useful information for designers of restraint systems for wheelchair-seated vehicle occupants.     

Evaluation of two wheelchair hand rim models: contact pressure distribution in straight line and curve trajectories

Abstract

Manual wheelchairs are essential for people with disabilities or limited mobility. However, manual propulsion causes biomechanical loads, including contact pressures on the palms of the hands. The hand rim design has received little attention over time, remaining almost unchanged since its creation. This study investigated how two different designs of such devices – one standard and another with a contoured design – influence the contact pressure on the surface of the hands. The procedures included a figure-of-eight shape propulsion task on a regular floor, using both models on a wheelchair. A pressure-mapping system coupled with a pair of fabric gloves recorded the data. The results show that the contoured hand rim provides lower pressure in most of the analysed regions. Considering that manual propulsion is performed during a considerable part of the day as a routine activity, improving the hand rim interface may benefit the user’s comfort and safety during wheelchair use.

Practitioner summary: The design of the hand rim used in wheelchair propulsion influences the contact pressure on the hands. Conventional round tube rims tend to concentrate high levels of pressure on the distal phalanges and metacarpal regions. A contoured design generally provides better stability and promotes the distribution of pressure.

Abbreviations: AT: assistive technology; kPa: kilopascal     

A light-weight cooling vest enhances performance of athletes in the heat

During the 1990s, emphasis on the health and safety of people who exercise in hot, humid conditions increased and many organizations became aware of the need for protection against heat-related disorders. A practical, pre-cooling strategy applicable to several sporting codes, which is low cost, easy to use, light-weight and which enhances cooling of the human body prior to and following exercise, was developed and tested. Eight males and eight females participated in a maximal oxygen consumption ([Vdot]O_2max) test and four trials: a control (without cooling) and wearing each of three different cooling vests (A, B, C). Vests were worn during the rest, stretch, warm-up (50% [Vdot]O_2max) and recovery stages of the protocol, but not during the 30?min run (70% [Vdot]O_2max). Core and skin temperatures during exercise were reduced (by approximately 0.5°C, rectal; 0.1?–?1.4°C, abdominal skin temperature) and sweat rates were lower (by approximately 10?–?23%). Endurance times for running at 95% of [Vdot]O_2max were increased by up to 49?s. Perceptions of the thermal state and skin wetness showed changes to greater levels of satisfaction. Physiological and sensory responses were related to design features of the vests.     

An investigation into concurrent semantic analysis

Concurrency is an attractive method for reducing the execution time of compilers. By dividing source programs into segments which can be compiled concurrently, the task of compiling programs can be accelerated. Many of the difficult problems which arise when constructing a concurrent compiler occur in the implementation of the semantic analyser. This paper investigates the problems involved in designing the semantic analyser for a concurrent compiler for a modern, block-structured language. Several approaches to solving the problems which arise are presented. These solutions are then implemented as part of a concurrent Modula-2 + compiler, running on a shared memory multiprocessor. A performance evaluation of these semantic analysers is presented.     

A theoretical investigation into the performance of the Hopfieldmodel

An analysis is made of the behavior of the Hopfield model as a content-addressable memory (CAM) and as a method of solving the traveling salesman problem (TSP). The analysis is based on the geometry of the subspace set up by the degenerate eigenvalues of the connection matrix. The dynamic equation is shown to be equivalent to a projection of the input vector onto this subspace. In the case of content-addressable memory, it is shown that spurious fixed points can occur at any corner of the hypercube that is on or near the subspace spanned by the memory vectors. Analysed is why the network can frequently converge to an invalid solution when applied to the traveling salesman problem energy function. With these expressions, the network can be made robust and can reliably solve the traveling salesman problem with tour sizes of 50 cities or more.     

A coordination-theoretic investigation of the impact of electronic integration on logistics performance

Using the Coordination Theory, we explored the impact of electronic integration of intra-organizational and inter-organizational business processes on organizational performance in terms of logistics cost and service improvements. Our work extends knowledge on adoption of information technology (IT) in logistics operations, with a focus on examining the performance implications of electronic integration within and between firms in a supply chain. Data was collected from 227 trading firms in Hong Kong and analyzed to investigate the research issues. Our empirical findings revealed that electronic integration is positively associated with logistics performance in cost but not in service, suggesting that electronic integration is not sufficient for delivering superior logistics services. Theoretical and practical implications of our results are discussed.     

An investigation into the skeletonization approach of hilditch

The skeletonization approach of Hilditch is compared with its so-called “simplified version” given by Stefanelli and Rosenfeld. Experimental results show the superiority of the original approach as described by Hilditch. A heuristic modification to Hilditch's approach is also proposed and empirically tested.