In the fields of researches associated with plant layout optimization, the main goal is to minimize the costs of pipelines and pumping between connecting equipment under various constraints. However, what is the lacking of considerations in previous researches is to transform various heuristics or safety regulations into mathematical equations. For example, proper safety distances between equipments have to be complied for preventing dangerous accidents on a complex plant. Moreover, most researches have handled single-floor plant. However, many multi-floor plants have been constructed for the last decade. Therefore, the proper algorithm handling various regulations and multi-floor plant should be developed. In this study, the Mixed Integer Non-Linear Programming (MINLP) problem including safety distances, maintenance spaces, etc. is suggested based on mathematical equations. The objective function is a summation of pipeline and pumping costs. Also, various safety and maintenance issues are transformed into inequality or equality constraints. However, it is really hard to solve this problem due to complex nonlinear constraints. Thus, it is impossible to use conventional MINLP solvers using derivatives of equations. In this study, the Particle Swarm Optimization (PSO) technique is employed. The ethylene oxide plant is illustrated to verify the efficacy of this study.
In December 2013, the Japanese Ministry of Health, Labour and Welfare (MHLW) partially amended the safety regulations for use of industrial robots so that “collaborative operation” could be performed at Japanese worksites as allowed in the ISO standard for industrial robots. In order to show global harmonization of Japanese legislation on machinery safety and problems with applying ISO safety standards to Japanese worksites, this paper reports the progress of a research study which have been conducted in National Institute of Occupational Safety and Health, Japan from 2011 to the present at the request of MHLW to examine the necessity and effect of the amendment. In the first phase of this study, a questionnaire survey was conducted among domestic robot manufacturers and users. The obtained results revealed their potential demand for the collaborative operation and problems concerning their risk assessment and rule-based risk reduction. To solve the problems, we propose a method based on an investigation result of the regulatory framework for safety of machinery in the European Union. Furthermore, a model of robot system capable of demonstrating the collaborative operation and risk reduction measures which is being developed to support appropriate implementation of the amendment is also described.
The purpose of the current study is to analyze the thermal characteristics of electrical wirings depending on the number of operating load by connecting four types of electrical wirings that are selected by surveying the conditions for the electric fans, automatic waterers and halogen warm lamps that were installed in cattle barns in different years. The conditions of 64 cattle barns were surveyed and an experimental test was conducted at a cattle barn. The condition-survey covered inappropriate design, construction and misuse of electrical facility, including electrical wiring mostly used, and the mode of load current was evaluated. The survey showed that the mode of load current increased as the installation year of the fans, waterers and halogen lamps became older. Accordingly, the cattle barn manager needed to increase the capacity of the circuit breaker, which promoted the degradation of insulation of the electrical wires’ sheath and increased possibility for electrical fires in the long-run. The test showed that the saturation temperature of the wire insulated sheath increased depending on the installation year of the load groups, in case of VCTFK and VFF electric wires, therefore, requiring their careful usage in the cattle barns.
Nanomaterial particles exhibit a wide range of sizes through the formation of agglomerates/aggregates. To assess nanomaterial exposure in the workplace, accurate measurements of particle concentration and size distribution are needed. In this study, we evaluated the performance of two recently commercialized instruments: a portable scanning mobility particle sizer (SMPS) (NanoScan, TSI Inc.), which measures particle size distribution between 10 and 420 nm and an optical particle sizer (OPS, TSI Inc.), which measures particle size distribution between 300 and 10,000 nm. We compared the data measured by these instruments to conventional instruments (i.e., a widely used laboratory SMPS and an optical particle counter (OPC)) using nano-TiO2 powder as test aerosol particles. The results showed obvious differences in the size distributions between the new and old SMPSs. A possible reason for the differences is that the cyclone inlet of the new SMPS (NanoScan) acted as a disperser of the weakly agglomerated particles and consequently the concentration increased through the breakup of the agglomerates. On the other hand, the particle concentration and size distributions measured by the OPS were similar to the OPC. When indoor aerosol particles were measured, the size distribution measured by the NanoScan was similar to the laboratory SMPS.
At present, almost all mountain tunnels in Japan are excavated and constructed utilizing the New Austrian Tunneling Method (NATM), which was advocated by Prof. Rabcewicz of Austria in 1964. In Japan, this method has been applied to tunnel construction since around 1978, after which there has been a subsequent decrease in the number of casualties during tunnel construction. However, there is still a relatively high incidence of labour accidents during tunnel construction when compared to incidence rates in the construction industry in general. During tunnel construction, rock fall events at the cutting face are a particularly characteristic of the type of accident that occurs. In this study, we analysed labour accidents that possess the characteristics of a rock fall event at a work site. We also introduced accident prevention measures against rock fall events.
The occupational uses with vibratory tools or vehicles provoked health disorders of users. We reviewed narratively our articles of 35 yr studies and their related literatures, and considered the pathophysiology of the hand-arm vibration disorders. Concerning the risk factors of health impairments in workers with vibratory tools, there are two conflicting schools of the researchers: The peripheral school emphasizes that vibration only makes predominant impairments on hands and arms, showing typically Raynaud’s phenomenon in the fingers. In the systemic school, the health disorders are produced by combination with vibration, noise and working environment, namely vibratory work itself, leading to diversified symptoms and signs in relation to systemic impairments. Our 35 yr studies have evidently supported the systemic school, including disorders of the central and autonomic nervous systems. The genesis is vibratory work itself, including vibration, noise, cold working environment, ergonomic and biodynamic conditions, and emotional stress in work. Because the health disorders yield in the whole body, the following measures would contribute to the prevention of health impairments: the attenuation of vibration and noise generated form vibratory machines and the regulations on operating tool hours. In conclusion, this occupational disease results from systemic impairments due to long-term occupational work with vibratory tools.
The purpose of this study was to investigate the effects of head hair on thermoregulatory responses when cooling the head under heat stress. Eight young males participated in six experimental conditions: normal hair (100–130 mm length) and cropped hair (5 mm length) with three water inlet temperatures of 10, 15, and 20°C. The head and neck of subjects were cooled by a liquid perfused hood while immersing legs at 42°C water for 60 min in a sitting position at the air temperature of 28°C with 30% RH. The results showed that heat removal from the normal hair condition was not significantly different from the cropped hair condition. Rectal and mean skin temperatures, and sweat rate showed no significant differences between the normal and cropped hair conditions. Heat extraction from the head was significantly greater in 10°C than in 15 or 20°C cooling (p<0.05) for both normal and cropped hair, whereas subjects preferred the 15°C more than the 10 or 20°C cooling regimen. These results indicate that the selection of effective cooling temperature is more crucial than the length of workers’ hair during head cooling under heat stress, and such selection should be under the consideration of subjective perceptions with physiological responses.
This study was conducted to evaluate the impact of job stress on absence from work caused by illnesses and accidents through a prospective research design. A total of 2,349 manual workers were included in this analysis. In the first survey, job stress was determined using the Korean Occupational Stress Scale-Short Form. In the second survey, information on absence due to accidents or illnesses during the past one year was obtained through a questionnaire. The relationship was analyzed using a logistic regression model with multiple imputation. After adjusting for confounding variables for males, absence due to accidents was statistically associated with high job demand, insufficient job control, inadequate social support, and organizational injustice. In addition, high job demands and organizational injustice were related to increased absence due to illnesses in both genders. A lack of reward was associated with increased absence due to illnesses among female workers. We found that job stress was associated with a higher risk of absence caused by accidents or illnesses of manual workers.
To assess performances of N95 respirators for Health Care Workers (HCWs) in a simulated health-care setting, we measured the Simulated Workplace Protection Factors (SWPFs) in real-time from the volunteers. A total of 49 study subjects, wearing 3 M respirator Model N95 1860 and 1860S, were fit tested using the OSHA Exercise Regimen. The test subjects were asked to perform simulated scenarios, including patient assessments, suction, and intravenous injection (IV) treatment. Two TSI PortaCount instruments continuously measured concentrations in the respirator and the room concentration. For Quantitative Fit Testing (QNFT), 36 out of 49 (73.5%) passed the fit factor (FF) criteria set at 100 and 13 (26.5%) failed. The results of QNFT were found to have a low correlation with SWPF, with R2=0.32. The geometric means (GM) and geometric standard deviations (GSD) of SWPF were 68.8 (1.1) for those subjects who passed and 39.6 (1.3) for those who failed. Real-time assessments of SWPF showed that lower SWPFs were; moving head up and down, and bending at the waist. This study identifies the needs for providing different sizes of respirators for HCWs and the importance of performing fit tests for HCWs regularly. And particular movements were identified as attributing factors affecting more on SWPFs.
The objective of this study is to describe a case-series of potassium aluminium tetrafluoride (KAlF4)-induced occupational asthma (OA) and/or occupational rhinitis (OR). The study involves five patients from a heat-exchanger production line who were examined (including specific inhalation challenge tests) for suspected OA and/or OR caused by a flux containing almost 100% KAlF4 − with fluorides’ workplace air concentrations ranging between 1.7 and 2.8 mg/m3. No subject had a previous history of asthma. All five patients had a positive specific challenge test (three patients were diagnosed with OA alone, one with OR and one with both OR and OA). At the follow-up visit, after three years on average, all patients needed permanent corticosteroid therapy (four topical, one oral). After elimination from the exposure, only one of the observed subjects gave an indication of an improvement, two subjects stabilized and two worsened. Our case series focuses on the correlation between patients’ exposure to fluorides in air-conditioner production and the subsequent occurrence of OR/OA. Currently, it is uncertain whether these OR/OA were caused by hypersensitivity or irritation.