Objective: Clarify the relation between the complaints of wheelchair users and the vibration characteristics of the wheelchair, to improve wheelchair comfort and design.Methods: The questionnaires were distributed to 33 wheelchair users directly by the experimenter in order to identify the causes of complaints from wheelchair vibrations that they experienced. The vibration transmissibility of wheelchairs of ten subjects was measured to clarify the causes of complaints of wheelchair vibration according to the ISO 10326-1 standard in the laboratory using a broadband random vibration spectrum with a frequency-weighted vibration magnitude of 0.1 ms 2 r.m.s. over the frequency range from 0.2 to 100 Hz. Each vibration exposure lasted 60 seconds.Results: The following findings were clear from the questionnaire results; (i) the vibration from the wheelchair affected psychological comfort; (ii) the effects of different riding surfaces were important engineering issues affecting wheelchair ride comfort; (iii) the wheelchair users felt the vibration during wheelchair usage at locations on the neck, lower back and buttocks; (iv) vertical vibration was the most noticeable vibration from the wheelchair to each participant's body. The following findings were clear from the results of the transmissibility measurement of the wheelchair; (i) the resonance frequency-ranges of the transmissibility of the wheelchair showed significant differences between the subjects; (ii) intra-subject variability from three repeated transmissibility measurements was small; (iii) the first resonant frequency occurred approximately 5 to 7 Hz and the second resonant frequency occurred at around 8 Hz and the third resonant frequency occurred approximately 13 to 15 Hz; (iv) the magnitude of the peak transmissibility varied from 1.3 to 2.6.Conclusion: From the comparison of the results of questionnaires and the transmissibility measurement of the wheelchair, the resonance frequency-ranges of the maximum vibration transmissibility of the manual wheelchairs were consistent with the frequency-ranges of the body parts of the causes of the complaints of wheelchair users. In addition, from these experimental results, it was suggested that the main point for improving a wheelchair user's comfort was to reduce the wheelchair seat vibration transmissibility at around 8 Hz and also to design wheelchair stiffness and damping characteristics to minimize vibration transmission at specific frequencies at body locations that caused the discomfort reported by wheelchair users.
The purpose of this research is to establish a scale for comfort with regard to whole-body vibration by the category judgment method. Experiments were conducted with random signals as stimuli. These stimuli consisted of three types of signal, namely stimulus F, with flat PSD (Power Spectrum Density) ranging from 1 to 100 Hz, stimulus H with PSD, which became 20 dB higher at 100 Hz than at 1 Hz, and stimulus L that had a PSD 20 dB lower at 100 Hz. These signals were modified by Wk frequency weighting in accordance with ISO 2631-1, and the R.M.S. values were adjusted to be equal. In addition, the signal levels were varied over a range of five steps to create 15 kinds of individual stimuli. The subjects sat on a flat, horizontal metal plate mounted directly on the vibrator and were exposed to vertical vibrations before being asked to choose a numerical category to best indicate their perceived level of comfort (or otherwise) during each stimulus. The creation of this assessment scale, including the aforementioned categories, enabled not only clarification of the relationship between the vibration stimuli and the degree of comfort but also discovery of the connection between the frequency-weighted R.M.S. acceleration and the corresponding categories representing each degree of comfort without overlap. Moreover, it became clear that the subjects' assessment of the degree of comfort perceived differed with differences in the vibration spectrum.
Recently farm mechanization has been widespread and developing rapidly, in particular riding farm machines are increasingly used in paddy fields in Japan. We have no information available on the actual situation regarding whole-body vibration on the seats of these farm machines from the standpoint of labour protection. Measurement and evaluation of whole-body vibration was performed on the seats of popular riding agricultural machineries. Whole-body vibration on the seats of combine harvesters and wheel tractors exceeded exposure limits and the fatigue-decreased proficiency boundary limit of 8 hr and also shortened the reduced comfort boundary limits of ISO 2631ISO (1985. Some combines, tractors and carieers had only less than one hour exposure duration as compared with the ISO 2631-1 standard (1997). On the other hand a questionnaire was also performed on the subject of agricultural machine operators. Any specific injury or other effects, i.e. low back injuries were not found among the group of operators as compared with those in non-operator farmers. It seems to be difficult to find out the health effects of whole-body vibration itself, because there may be a lot of causes, i.e. working posture, operating heavy materials, in farm working conditions.
Monoclonal anti-proliferating cell nuclear antigen (PCNA PC10), which is directed against a 36 kDa auxiliary protein for DNA polymerase delta specific for the S-phase of cell cycle, was used to measure tumour cell proliferation in 4 lactating breasts and 98 benign and malignant breast tumours. The percentage of PCNA-positive cells determined by point counting was significantly lower in the lactating breast [mean 3.6%, standard deviation (SD) 0.67, n = 5] than in fibroadenoma and mastopathy (mean 23.7, SD 5.0, n = 2). Primary breast carcinoma showed a PCNA index ranging from 2% to 36% (mean 12.3, SD 9.3, n = 50), whereas in recurrent carcinoma the index was mean 28.5, SD 4.0. A high index was correlated with c-erbB-2 and epidermal growth factor (EGF) receptor membrane reactivity, worsening histological grade, poor survival and disease-free survival. The expression of c-erbB-2 and EGF receptor was associated with poor survival and disease-free survival in primary breast cancer patients.
To understand the basic characteristics of the human body vibration induced by low frequency noise and to use it to evaluate the effects on health, we designed a measuring method with a miniature accelerometer and carried out preliminary measurements. Vibration was measured on the chest and abdomen of 6 male subjects who were exposed to pure tones in the frequency range of 20 to 50 Hz, where the method we designed was proved to be sensitive enough to detect vibration on the body surface. The level and rate of increase with frequency of the vibration turned out to be higher on the chest than on the abdomen. This difference was considered to be due to the mechanical structure of the human body. It also turned out that the measured noise-induced vibration negatively correlated with the subject's BMI (Body Mass Index), which suggested that the health effects of low frequency noise depended not only on the mechanical structure but also on the physical constitution of the human body.
In Japan, the treatment of waste concrete scraps has been one of the environmental issues. Therefore, new application using pulsed power discharge has been developed as the recycling method of the coarse aggregates from the waste concrete scraps. In the work, the dependences of the quality of the recycled coarse aggregate by the repetitive pulsed discharge treatments on the consumption energy were investigated. As the results, it was clear that the quality of the recycled coarse aggregate could be controlled by the number of discharge treatments. The recycled coarse aggregate, which satisfied class H under the regulations of Japan Industrial Standard (JIS A5005 and JIS A5021), was produced with the smallest consumption energy when the discharged energy from 0.02 µF of capacitor charged up to 400 kV applied to the waste concrete scraps during single discharge treatment.
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