• 대한감각통합치료학회지
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• 제5권1호
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• pp.31-40
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• 2007

Objective: The purpose of this study was to get the cognitive reaction time according to the intensity of auditory stimuli in older people and to differentiate the cognitive reaction time between older people and adults. Method: 49 subjects consisted of 32 older people and 17 adults. Cognitive reaction time was assessed with Simple Auditory Reaction of Foundation I in PSS CogReHab. Analysis of the data was done by using independent t-test. Results: The results were as follows: 1. There was a significant difference of the mean of cognitive reaction time to the intensity of auditory stimuli. 2. There was no significant difference from older people regardless of sexual distinction in mean of cognitive reaction time. However, there was a significant difference of the mean of cognitive reaction time in adults. 3. There was a significant difference between older people who got a job or not in 90 dB of auditory stimuli. 4. The mean of cognitive reaction time to the intensity of auditory stimuli in older people was slower than adults. There was a significant difference of the mean of cognitive reaction time between older people and adults in 70 dB of auditory stimuli. 5. The mean of cognitive reaction time to the intensity of auditory stimuli in older people did not have the significant difference in scholastic ability. Conclusions: The results of the study showed slowing of the cognitive reaction time in auditory stimuli to aging in older people. Therefore, applying silver industry and development of equipment for older people may maintain independent life.

• 공업화학
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• 제9권7호
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• pp.1004-1010
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• 1998

Single-jet 반회분식 결정화 반응기에서 동력투입량, 반응물의 주입시간 및 주입방법등 반응조건의 변화가 란타늄 옥살레이트 결정입자의 반응성 결정화에 미치는 영향에 대해 실험적으로 조사하였다. 란타늄 옥살레이트 결정입자의 크기분포는 반응조건에 관계없이 monomodal 형태의 크기분포를 나타내었으나 평균결정크기는 반응조건에 크게 영향을 받았다. 동력투입량이 증가할수록, 반응물의 주입속도가 빠를수록, 란타늄 옥살레이트의 결정입자크기는 감소하였으나 상대적 유도시간은 증가하였다. 반응물의 주입방법에 있어서 옥살산 용액이 주입되는 경우보다 염화란타늄 용액이 주입되는 경우에 결정입자는 크게 나타났으며 상대적 유도시간은 감소하였다. 그리고 결정입자의 형태는 모두 침상형으로 반응조건의 변화에 크게 영향을 받지 않았다.

• 한국환경교육학회지:환경교육
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• 제24권3호
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• pp.18-25
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• 2011

This study was conducted to evaluate the effects of volatile organic compounds and formaldehyde of newly-built school classroom indoor air on the neurobehavioral functions of students. The elementary schools that were opened in September 2008(as of September 2008) was selected for newly-built school and the elementary school that were opened in March 2006 was selected for control group schools. The concentration of formaldehyde(HCHO), a hazardous organic compound that exists in the air of classrooms, exceeded the standard value of $108.2{\mu}g/m^3$ in newly-built schools while it was $60.8{\mu}g/m^3$ in control group schools, which is around 60% of the standard concentration. However, the concentration of the total volatile organic compounds(TVOCs) was $788.9{\mu}g/m^3$ and $756.1{\mu}g/m^3$ in newly-built schools and control group schools respectively, which are approximately two times higher than the standard concentration. In newly-built schools, the mean reaction time of additions and symbol digit, respectively 3,020ms and 2,398ms in pre-exposure were increased to 3,167ms and 2,514ms respectively in post-exposure. The difference of mean reaction time between pre and post exposure was 146.8 ms, or 4.6%, and 116.7ms, or 4.8%, respectively, showing statistically-significant increase of reaction time(p<0.05). On the contrary, the difference of reaction time of both tests were not statistically significant in the control group schools. These results showed that the neurobehavioral performance of newly-built schools students were affected by volatile organic compounds and formaldehyde of classroom indoor air.

• The Journal of Korean Physical Therapy
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• 제24권6호
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• pp.405-408
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• 2012

Purpose: We examined the effect of dual-task and single-task training on serial reaction time (SRT) task performance to determine whether SRT is based more on motor or perception in a dual-task. Methods: Forty healthy adults were divided into two groups: the dual-task group (mean age, $21.8{\pm}1.6$ years) and the single-task group (mean age, $21.7{\pm}1.6$ years). SRT task was conducted total 480 trial. The four figures were presented randomly 16 times. A unit was set as 1 block that would repeat 10 times. Thus, there were a total of 160 trials for each of the three color conditions. The dual-task group performed an SRT task while detecting the color of a specific shape. The end of the task, subjects answered the specific shape number; the single-task group only performed the SRT task. The study consisted of three parts: pre-measurement, task performance, and post-measurement. Results: Differences of pre and post reaction time between two group was higher for the dual-task group as compared to the single task group and there was a significant interaction between time and group (p<0.05). Conclusion: Our results indicate that. short term period SRT is not quiet effective under dual-task conditions, individuals need additional cognitive processes to successfully navigate a task This suggests that dual-task training might not be appropriate for motor learning enhancement, at least when the training is over a short period.

• 대한인간공학회지
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• 제11권1호
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• pp.31-38
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• 1992

The population of aged people in industries has been increased remarkably due to the decline of birth rates and the increase of average life span. Also, the current automation trends makes aged people to work easy in industries since automation technologies help them to avoid physically hard tasks. Therefore the evaluation of aged workers' adaptability would be an important research topic. In the study, the mean and standard deviation of the reaction time are calculated to see the differences with four lamps's types and ages. It is found that the mean reaction time and the standard deviation are increased with the the increase of age. The quantitative approach provides an important information to be used not only for the adaptability estimation of aged workers but also for the working capability qualification for re-employment.

• Journal of Preventive Medicine and Public Health
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• 제27권3호
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• pp.487-504
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• 1994

A cross-sectional study was performed to evaluate the effects of chronic low-dose solvent on neurobehavioral performance of 118 male car painters. A control group of 113 workers matched for age was selected from different sections of the factory. The mean age and the mean duration of employment were 33 years and 6.7 years in both groups. Mean years of education were 11.4 years in car painters and 11.8 years in controls. Each worker completed a medical and occupational questionnaire and four tests of Swedish performance evaluation system. These included simple reaction time, symbol digit, digit span and finger tapping speed. Althougth the mean duration of employment was 6.7 years, comparison of mean performance showed a significantly poorer performance on simple reaction time (p<0.05), symbol digit(p<0.01) and digit span(p<0.05) in car painters. In univariate analysis, age and educational level contributed to poorer performance on symbol digit and digit span. Smoking appeared to slow finger tapping speed in car painters. Performance of four tests of car painters exposed to high level of solvent was poorer than that of car painters exposed to low level. In multiple regression models, controlling for age, alcohol, smoking and shift work, solvent exposure was found to be associated with performance of simple reaction time, symbol digit and digit span and exposure to high level of solvent was related to poorer performance of symbol digit and digit span.

• 대한의용생체공학회:의공학회지
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• 제33권4호
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• pp.163-168
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• 2012

Elderly women are reported to have greater risk of falls. The purpose of this paper was to investigate the possible gender differences in the reaction performance of ankle joint muscles, which have dominant role in the control of sagittal plane balance. Twenty-six elderly men and women with comparable mean age participated in this study. Reaction times to the audible beeps were measured in the tibialis anterior muscle and gastrocnemius muscle. Reaction time variables included premotor time, electromechanical delay and total reaction time. Gender difference in each reaction time was investigated by independent t-test. In both muscles, premotor time was longer in men but the electromechanical delay was longer in women (p < 0.05). Resulting total reaction time was longer in men in tibialis anterior muscle (p < 0.01) and it tended to be longer in men also in gastrocnemius muscle (p = 0.25). The results demonstrates that the overall reaction performances of elderly women is better than or comparable to those of elderly men in ankle joint muscles. This suggests that the reaction performance of ankle muscles is hardly the cause of the greater risk of falls in elderly women.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.795-800
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• 2001

In this study, a program to design a multi-stage axial compressor is developed wi th mean-line analysis and vortex methods. In a preliminary design stage, a method. to design in a short time is needed and mean-line analysis is usually used for this purpose. Arbitrary pressure ratio and reaction can be assigned to generate overall geometry and several vortex methods are adopted to consider the radial distribution of velocity and reaction. The variation of performance, when we use free vortex, forced vortex, and exponential method, is compared and discussed.

• Journal of Mechanical Science and Technology
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• 제18권8호
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• pp.1470-1478
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• 2004

In this paper, a new 'presumed' Probability Density Function (PDF) approach coupled with a Lagrangian tracking method is proposed for turbulent combustion modeling. The test and the investigation of the model are conducted by comparing the model results with DNS data for a premixed flame subjected in a decaying turbulent field. The newly constructed PDF, which incorporates the instantaneous chemical reaction term, demonstrates consistent improvement over conventional assumed PDF models. It has been found that the time evolution of the mean scalar, the variance and the mean reaction rate are strongly influenced by a parameter deduced by a Lagrangian equation which takes into account explicitly the local reaction rate. Tests have been performed for a moderate Damkohler number, and it is expected the model may cover a broader range of Damkohler number. The comparison with the DNS data demonstrates that the proposed model may be promising and affordable for implementation in a moment-equation solver.

• 한국분말재료학회지
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• 제6권3호
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• pp.215-223
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• 1999

The synthesis of $Ni_5Si_2,\;Ni_2Si$ and NiSi has been investigated by mechanical alloying (MA) of Ni-27.9at%Si, Ni-33.3at%Si and Ni-50.0at%Si powder mixtures. As-received and premilled elemental powders were subjected to MA. The as-received Ni powder was spherical and the mean particle size 48.8$\mu$m, whereas the premilled Ni powder was flaky and the mean particle diameter and thickness were found to be 125 and 5$\mu$m, respectively. The mean surface area of the premilled Mi powder particle was 3.5 times as large as that of the as-received Ni powder particle. The as-received Si powder was was 10.0$\mu$m. Self-propagating high-temperature synthesis (SHS) reaction, followed by a slow reaction (a solid state diffusion), was observed to produce each Ni silicide during MA of the as-received elemental powders. In other word , the reactants and product coexisted for a long period of MA of time. Only SHS reaction was, however, observed to produce each Ni silicide during MA of the premilled elemental powders, indicating that each Ni sillicide formed rather abruptly at a short period of MA time. The mechanisms and reaction rates for the formation of the Ni silicides appeared to be influenced by the elemental powder particle size and shape as well as the heat of formation of the products $(Ni_5Si_2$longrightarrow-43.1kJ/mol.at., $Ni_2Si$$\rightarrow$-47.6kJ/mol.at.).