Hsin-Chieh Wu

Relationship between maximum acceptable work time and physical workload

For safe job design, it is necessary to know the maximum acceptable work time (MAWT) for a given workload. The aim was to establish the relationship between MAWT and physical workload. Cycling tests at six different work rates relative to personal maximum working capacity were performed by 12 young adults in the laboratory. The oxygen uptake (VO2) in the per cent maximum aerobic capacity (%VO2max), relative heart rate (RHR) and relative oxygen uptake (RVO2) were collected throughout the test. MAWT was determined by observing the heart rate data during the test. The results showed that MAWT was negatively correlated with %VO2max, RHR and RVO2(p<0.01). Three exponential regression models were obtained and all their R2 >0.80. These models suggest that long-hour shifts (>10 h) should assign a lower work intensity than for an 8-h workday. It is also logical that the workload limit for a 4-h work shift could be set at about 10%VO2max higher than the suggested limit for an 8-h workday.

Center of pressure progression characteristics under the plantar region for elderly adults

This investigation identifies the center of pressure (COP) progression characteristics under the plantar region for elderly adults during barefoot walking. A total of 60 healthy adults (30 young and 30 old) were recruited. The young and elderly participants had average ages of 23.6 (SD=2.7) and 70.8 (SD=4.1) years old, respectively. All subjects had normal foot arch and no relevant musculoskeletal disease in the lower extremities. The foot pressure measurement system (RS-scan(®) system) was used to measure the center of pressure coordinates (COP), progression angle and COP velocity. Four sub-phases of the stance phase were calculated. The initial contact (ICP) and forefoot contact phase (FFCP) corresponded to the loading response. The foot flat phase (FFP) coincided with the mid-stance. The forefoot push-off phase (FFPOP) corresponded to the terminal stance and pre-swing phases. The analytical results revealed that age effects were found in the relative time percentages for the initial contact, foot flat and forefoot push-off phases during foot movement. The elderly subjects exhibited significant medial COP curve and faster COP velocity during the initial contact phase and more pronated mid-foot posture and slower COP velocity during the mid-stance. The older adults tended to have a more pronated foot and displayed a significant medial COP curve compared to young adults. These COP progression characteristics can provide further insight into relevant foot function and gait performance evaluations for older adults.

Gait speed and gender effects on center of pressure progression during normal walking

The COP progression is the trajectory of the center of foot pressure. Thirty healthy young adults were recruited to participate in this study. All subjects were asked to walk randomly at four different speeds (3km/h, preferred walking speed, 4km/h and 5km/h). A foot pressure measurement system (RS-scan(®) system) was used to collect the center of pressure (COP) coordinates, COP progression angle and the COP velocity. Four sub-phases of the stance phase were calculated. The initial contact (ICP) and forefoot contact phase (FFCP) corresponded to the loading response. The foot flat phase (FFP) coincided with the mid-stance. The forefoot push-off phase (FFPOP) corresponded to the terminal stance and pre-swing phases. The results of this study indicate that the percentage of time (% time) of COP progression on the ICP, FFCP, FFP and FFPOP were approximately 7.0%, 4.8%, 48.8% and 39.4%, respectively. The COP progression angle was 4.1 (SD=1.6)° with an inward curve and the average COP velocity was 31.6cm/s (SD=5.3). The walking speed influenced the % time in the FFP and FFPOP. As the walking speed increased, the % time of COP progression decreased in mid-stance and increased in the terminal and pre-swing stances. Moreover, gender affected the COP progression angle. Men had a significantly larger deviating angle than women during FFCP, FFP and FFPOP. The COP characteristics can offer useful information for clinical rehabilitation in foot functional and structural evaluation.

Fuzzy-neural approaches with example post-classification for estimating job cycle time in a wafer fab

Estimating the cycle time of a job in a wafer fabrication plant (wafer fab) is a critical task to the wafer fab. Many recent studies have shown that pre-classifying a job before estimating the cycle time was beneficial to the forecasting accuracy. However, most pre-classification approaches applied in this field could not absolutely classify jobs. Besides, whether the pre-classification approach combined with the subsequent forecasting approach was suitable for the data was questionable. For tackling these problems, two hybrid approaches with example post-classification, the equally-divided method and the proportional-to-error method, are proposed in this study in which a job is post-classified by a back propagation network (BPN) instead after the forecasting error is generated. In this novel way, only jobs whose cycle time forecasts are the same accurate will be clustered into the same category, and the classification algorithm becomes tailored to the forecasting approach. For evaluating the effectiveness of the proposed methodology and to make comparison with some existing approaches, production simulation (PS) is applied in this study to generate test data. According to experimental results, the forecasting accuracy (measured with root mean squared error, RMSE) of the proportional-to-error method was significantly better than those of the other approaches in most cases by achieving a 26-56% (and an average of 41%) reduction in RMSE over the comparison basis - multiple-factor linear combination (MFLC). The effect of post-classification was also statistically significant.

Electronic paper display preferred viewing distance and character size for different age groups.

This study explores the preferred viewing distance and character size for an electronic paper display for three age groups. Proofreading speed and accuracy ratio were measured during Chinese proofreading tests using the preferred character size and minimum acceptable character size. Data analysis showed that the mean preferred viewing distance for young, middle-aged and older groups was 503, 455 and 444 mm, respectively. The mean preferred character size determined by young, middle-aged and older groups was 42.0, 50.0 and 55.2 min arc, respectively. The proofreading test results indicated that the older group proofread significantly more slowly (1.25word/sec) than the young (1.76 word/sec) and middle-aged groups (1.74 word/sec). Further, the participants proofread more correctly with their preferred character size (73.3%) than with their minimum acceptable character size (65.4%). This study provides valuable information for the design of Chinese text presentations for various agegroups. Statement of Relevance: This study confirmed the preferred viewing distance and character size for E-paper display were influenced by age. The preferred Chinese character size for young, middle-aged and older people was 42, 50 and 55 min arc, respectively. Therefore, the age factor should be considered for E-paper displays design and video display terminal (VDT) guidelines.

The evaluation of manual FOUP handling in 300-mm wafer fab

Semiconductor manufacturing industry is moving into the production of 300-mm wafers. To solve the increased workload problem in manual wafer handling, some personal guided vehicles (PGVs) have been developed to help in the transfer of front opening unified pods (FOUP). This study compares two kinds of PGVs with a traditional cart and evaluates the feasibility of using them for manual FOUP handling tasks. Manual FOUP handling capability was assessed. The results indicate that there is no obvious advantage in using any of the two evaluated PGVs over the manual cart. There is potential risk of causing musculoskeletal disorders for female operators to handle the 300-mm FOUP manually. Since the development of a fully automated intrabay FOUP handling system is a project of high technical difficulty, a combination of manual and automated handling is the current approach. To enhance the operators health, safety and productivity, selection and training of operators, adequate design of handling tools and machine interface, assessment and balancing of workload are necessary.

CART–BPN approach for estimating cycle time in wafer fabrication

Cycle-time management plays a crucial role in improving the performance of a wafer-fabrication factory, beginning with the estimation of the cycle time of each job. Although this topic has been widely investigated, several problems still need to be addressed, such as how to classify jobs suitable for the same estimation mechanism into the same group. Most existing methods classify jobs by their attributes; however, the differences between the attributes of various jobs may not be reflected in their cycle times. The biobjective nature of a classification and regression tree (CART) makes it particularly suitable for resolving this problem. However, in a CART, the cycle times of jobs of a branch are estimated with the same value, which is inexact. Hence, this study proposes a joint use of a CART and back propagation network (BPN), in which the BPN is constructed to estimate the cycle times of jobs of a branch. A real case was used to evaluate the effectiveness of the proposed methodology. The experimental results supported the superiority of the proposed methodology over existing methods. In addition, the managerial implications of the proposed methodology are also discussed.

Finding the just-in-time service location and path in a ubiquitous service network

Just-in-time (JIT) is an important topic of lean manufacturing and services, focusing on the reduction of the waiting time, as well as the enhancement of timeliness. In this study, the JIT concept is applied to the application of mobile commerce, ambient intelligence, and ubiquitous computing, which has rarely been explored in the past. As a result, a ubiquitous JIT service network is constructed based on the application of a mobile phone. In this network, a user uploads a request using a mobile phone. The request is then met at the appropriate service location in the network. For the JIT service network, an important issue is how to determine the JIT service location and path. In response to this issue, this study proposes a mathematical programming model to identify the JIT path. Subsequently, a systematic procedure is established to determine the JIT service location. The applicability of the proposed methodology is illustrative with an example.

Complete recovery time after exhaustion in high-intensity work.

This study was aimed to investigate complete recovery time (CRT) after exhaustion in high-intensity work. Twenty-four subjects were divided into two groups based on the cardiorespiratory capability index, which was measured in a maximum capacity test. Each subject then performed two cycling tests (at 60% and 70% maximum working capacity). The subject continued cycling until exhaustion in each test and then sat recovering until he/she no longer felt fatigue or until the oxygen uptake (VO2) and heart rate (HR) returned to their baselines, whichever was longer. The results indicated that HR required the longest time to recover and, consequently, HR data were adopted to set the CRT. The CRT was significantly correlated with the cardiorespiratory capability index and the relative workload indices: RVO2 and RHR. The RVO2 was the average elevation in VO2 during work from the resting level as a percentage of maximum VO2 reserve. The RHRs definition was similar to that of RVO2. Based on the obtained CRT-prediction model, the CRT for a high-cardiorespiratory-capability person was 20.8, 22.1, 23.4, and 24.7 min at 50%, 60%, 70%, and 80% RHR levels, respectively. These suggested CRT values should be increased by 10 min for a low-cardiorespiratory-capability person.

Ambient intelligence and ergonomics in Asia

Ambient intelligence (AmI) is one of the most important advances in computer technology in the mobile era. By being aware and applying knowledge of ergonomics (human factors), AmI system users will be in better shape and health, become more effective and find using AmI system a more pleasant and enjoyable experience. This special issue contains selected papers from the 1st international conference on ambient intelligence and ergonomics in Asia (AmIE 2013), which was held at Taichung city, Taiwan, July 3–5, 2013. The conference attracted a large number of scientific papers that contributed to the state-of-the-art in the fields of ambient intelligence and ergonomics. After a strict review, five articles from researchers around the world were finally accepted. To determine an understandable algorithm that could be used by designers to create novel concept designs, M.T. Wang and C.C. Yang selected the popular motor scooter as a sample product, and used the most distinctive front handle cover as a design target. Their method included three phases: preparation, construction of conceptual creativity, and semantic analysis. After comparing random idea sketches with designs available on the market, they observed that certain concept designs obtained using this method were exceptionally innovative, and could be easily redesigned for an actual product. A.M. Otebolaku and M.T. Andrade investigated context-aware recommendation techniques for implicit delivery of contextually relevant online media items. The proposed recommendation service identifies a user’s dynamic contextual situation from the device’s built-in sensors, and uses case-based reasoning to determine the user’s current contextual preferences. The effectiveness of the proposed recommendation service was evaluated with a case study. Gripping and pinching are frequently used hand strength in various occupational activities and in clinical evaluation of the hand. Therefore, formulating grip and pinch prediction models with easily obtainable personal parameters will help facilitate the design and evaluation of workplace environments or facilitate the hand impairment or progression assessments. P.C. Sung, C.C. Hsu, C.L. Lee, Y.-S.P. Chiu, and H.L. Chen developed maximum voluntary contraction (MVC) grip and key pinch strength prediction models using regression method and artificial neural networks (ANN). An ANN is a prevalent humanized computing method that imitates the central nervous system of a human. To estimate the cycle time of a job in a wafer fabrication factory, H.C. Wu and T. Chen proposed a joint use of a classification and regression tree (CART) and back propagation network (BPN). In their method, a BPN is constructed to estimate the cycle times of jobs of a branch. A real case was used to evaluate the effectiveness of the proposed methodology. C.T. Tseng, Y.L. Lee, and C.C. Chou designed an AmIbased decision support system that combined an electromagnetism-like mechanism (EM) and sensory data to aid human operators in making decisions regarding the T. Chen (&) Department of Industrial Engineering and Systems Management, Feng Chia University, Taichung, Taiwan e-mail: tcchen@fcu.edu.tw