開催趣旨

-シンポジウムの概要-

1.　Date

November 5 (Fri.), 2010

2.　Venue

Hall in the center for the advancement of working women (CAWW)

Shiba 5-35-3, Minato-ku, Tokyo

3.　Program

10:00 Opening address

Mr. Yutaka Maeda, President, JNIOSH
Dr. Doo-Hyun Kim, Professor, Chunbuk National University, Korea
Mr. Shinichi Takasaki, Director, Policy Planning Division, Industrial Safety and Health Dept., MHLW

---

10:10 Keynote lecture

Dr. Toshisuke Hirano, Professor emeritus, the University of Tokyo

Abstract: In this paper presented is a brief introduction to the crisis management. Almost all situations in our life, applications of crisis management are needed. After some examples of situations are introduced, important points of applications in each case as well as those meanings are shown. The most important point of crisis management is accumulation of knowledge about the target of crisis management, and the ability of the leader for appropriate crisis management is indicated to be a key. At the final part of this paper, the needed abilities of the leader are summarized.

---

10:40 Special lecture

Dr. Woo-Chul Shin, Manager, Department of Safety Engineering & Ergonomics Research, OSHRI, KOSHA, Korea

Abstract:

Dr. Yoshiyuki Matsubara,Research Managing Director, Fire and Disaster Management Agency, National Research Institute of Fire and Disaster

Abstract: This paper features a structured approach for recognition and identification of ignition risks associated with electrostatics in industrial processes where flammable liquids and/or powders are used. A brief review of ignition by electrostatic discharge will be given. This paper also provides a basic understanding of relevant electrostatic phenomena. Theoretical and experimental foundation will be laid out for electrostatic charge generation, charge accumulation and relaxation, electric field build-up, and important types of electrostatic discharged. Summary of safe industrial practices for the avoidance of electrostatic hazards will be concluded.

---

11:40-13:00 Lunch break

---

Ordinary sessions

13:00-14:40 Session 1: Safety

Dal-Jae Park* and Nam-Il Kim**
* Department of the Safety Engineering, Seoul National University of Science and　Technology
** Department of the Safety Engineering, Graduate School of Industry, Seoul National University of Science and Technology

Abstract: Experimental investigations were performed to examine the effects of explosion mitigations by water gel barriers in an explosion chamber, 1400 mm in length, with a square cross-section of 100×100 mm2. Two independent variables were used in the measurements: concentration of gelatine and thickness of water gel barrier. The concentration of gelatine ranged from 10 % to 40 % with an interval of 10 % by weight of gel, and the thickness ranged from 10 mm to 25 mm with an interval of 5 mm. Displacement of the gel barrier was measured using a high speed video camera, and pressure development was measured using pressure transducers and a data acquisition system. It was found that the displacement curve of the barrier had a similar trend with the pressure one. This indicates the possibility of using gelatine gel as a pressure-absorbing material. And it was also found that as the concentration and thickness of the gel barrier increased, the reduction percentage in peak overpressure increased.

Doo Hyun KIM*, Sung Chul KIM*, Jong Young Park*, Jong Ho, Lee**
* Dept of Safety Engineering, Chungbuk National University
** Department of the Safety Engineering, Graduate School of Industry, Seoul National University of Science and Technology

Abstract: This paper is purposed to develop an electrical fire fuzzy forecasting system(EFFFS) which can analyze the possibility of electrical fire based on the precursory signals of overload, leakage current of panel board in old market shops as well as hazard degree of the shops and fuzzy logic. In order to develop the EFFFS, precursory signals and fuzzy membership function are required. Precursory signals are obtained directly from panel board in old market shops and fuzzy membership from experiment, simulation and expert's advice, and especially hazard degree of old market shops from News data and NFDS(National Fire Data System) of NEMA(National Emergency Management Agency) between 2003 and 2009 in Korea. The forecasting algorithm on fuzzy logic on DB consists of fuzzification, inference engine by Mamdani's method and defuzzification by center of gravity method. The EFFFS is lastly verified through overload and leakage current signals generated by experimental circuit. In order to enhance the reliability of the developed system, the fuzzy membership of linguistic variables for overload, leakage current and hazard degree of old market shops are continuously modified and updated. Results show that EFFFS suggested in this paper are valuable and usable in alarming electrical fire based on precursory signal detection, which will prevent severe damage to human beings and properties and reduce the electrical fires in a vulnerable area of electrical disaster.

Naoharu Murasawa*, Lijing Gao*, Hiroshi Koseki**, Yusaku Iwata**, and　Kazutoshi Hasegawa*
*; Chiba Institute of Science
**; National Research Institute of Fire and Disaster

Abstract: Although stored near room temperature, a large portion of stored industrial food waste materials or their recycled materials gradually heats up and then ignites. In this study, soy sauce squeezing residue produced from the soy sauce brewing process, and fish meal residue from processing fish are examined. We used a thermo gravimetric/differential thermal analysis (TG-DTA) system, a highly sensitive heat flux calorimeter (C80) and a spontaneous ignition tester (SIT) to study thermal properties. We applied Frank-Kamenetskii’s thermal ignition theory to obtain the critical ignition temperature (Tc) and the relationship between Tc and the pile height.

Mizuki Yamaguma*, Fusao Izumi**, Tekeo Sekine**, Hisao Nagata***
* Electrical Safety Research Group, JNIOSH
** Technology Institution of Industrial Safety
*** The Institute for Science of Labour

Abstract: In Japan, before 2009, there was one standard for anti-electrostatic footwear, JIS T 8103:2001. However, an international standard for such footwear, IEC 61340-4-3, was published in 2001 and another JIS standard identical to the IEC standard (IDT), JIS C 61340-4-3:2009 has been established in 2009. The measuring methods specified in JIS T 8103 and IEC 61340-4-3 are quite different. To investigate whether both methods can give the same values or not, a variety of measurements regarding the resistance of footwear were carried out. As a result, if the same weight is applied, both methods show in good agreement. In addition, considering the temperature characteristics of shoe materials, the upper limit of resistance at 0 °C should be ten times larger than that at 23 °C. Another simple test method which had been used for one hundred percent inspection by the manufacturers was also evaluated and a certain level of difference from the regular methods was made clear. These results and consideration were reflected in the revision of JIS T 8103 in 2010.

Tomohito Hori and Satoshi Tamate, Construction Safety Research Group, JNIOSH

Abstract: Drill rigs are large construction machines. They are used for ground improvement and foundation work. In recent years, there have been several reports of accidents where drill rigs have toppled over. In this study, a 1/25 scale model of a drill rig was constructed to clarify the mechanism by which the machinery became unstable, and for this purpose, centrifuge tests were performed. The load on each axle was measured, and the resulting behaviour of the model was analysed. Two different ground types --uniform and non-uniform -- were considered. This study also proposes factor requirements of the bearing capacity of the ground so that the stability of drill rigs can be maintained. Firstly, the number of fatalities resulting from labour accidents in Japan is presented. Secondly, the results of geotechnical centrifuge model tests that simulated self propulsion of the drill rig are introduced and discussed.

---

14:40-15:00 Coffee break

---

15:00-16:00 Session 2: Health and hygiene

Sachiko Yamaguchi-Sekino*, Jun Ojima**, Masaki Sekino***, Minoru Hojo†, Hiroyuki Saito**, Tsutomu Okuno††
*Health Effects Research Group, JNIOSH
**Work Environment Research Group, JNIOSH
***Department of Electrical Engineering and Information Systems, School of Engineering, The University of Tokyo
†Ota Regional Occupational Health Center
††Human Engineering and Risk Management Research Group, JNIOSH

Abstract: The assessment of the occupational electromagnetic field exposure of welders is of great importance, especially in arc welding, which uses relatively high electric currents of up to several hundred amperes. In the present study, we measured the magnetic field exposure of welders as they worked. A 3-axis Hall magnetometer was attached to a subject’s wrist in order to place the sensor probe at the closest position to the magnetic source (a cable from the current source). Data was acquired every 5 seconds from the beginning of the work time. The maximum exposed field was 0.35-3.35 mT (Mean ± S.D.: 1.55 ± 0.93 mT, N=17) and the average value per day was 0.04-0.12 mT (Mean ± S.D.: 0.07 ± 0.02 mT, N=17). We also conducted a finite element method-based analysis of human hand tissue for the electromagnetic field dosimetry. In addition, the magnetic field associated with grinders, an air hammer, and a drill using electromagnetic anchorage were measured; however, the magnetic fields were much lower than those generated in the welding process. These results agreed well with the results of the electromagnetic field dosimetry (1.49 mT at the wrist position), and the calculated eddy current (0.64 mA/m2) was much lower than the well-known guideline thresholds for electrical nerve or muscular stimulation.

Xinxin Liu*, Koichi Iwanaga**, Shigeki Koda*
* Hazard Evaluation and Epidemiology Research Group, JNIOSH
** Graduate School of Engineering, Chiba University

Abstract: It is important to evaluate the physiological influences of mental stress in modern society. Various mental stresses are encountered in the workplace, including emotional stress, caused by instinctive sensations (such as noise exposure), and intellectual stress, caused by recognizing and processing advanced information (such as computer-based work). The present study investigated cardiovascular and central nervous system responses in eight healthy males to two different mental stresses by exposing them to 20-min of white noise (80 dBA) and 20-min of computer-based mental arithmetic tasks, as models of emotional and intellectual stress, respectively. The results indicated the intellectual stress to have a cumulative effect on cardiac responses and suggested that the cardiac load increases as work is extended. In addition, the prefrontal oxygenated hemoglobin levels increased in the face of intellectual stress but were not clearly altered by emotional stress. As the central nervous system responded, intellectual stress increased the P300 amplitude, while the emotional stress decreased P300 latency to some extent. Thus, the physiological responses to intellectual stress differ from the physiological responses to emotional stress, and measuring physiological indices appears to be an effective method by which to evaluate mental stress.

Kazuma Ishimatsu* , Fumiharu Togo**, and Akihiro Ohnishi*
* Human Engineering and Risk Management Research Group, JNIOSH
** Health Administration and Psychosocial Factor Research Group, JNIOSH

Abstract:It has recently been reported that there is a close association between higher-level cognitive functions and fall risk. The Rapid Step Test (RST) is a relatively simple assessment of dynamic balance and fall risk among older adults. This study aimed to examine effects of working memory (WM) capacity on performance of a rapid stepping (RS) task which is a modified version of RST. Healthy younger (n = 11; mean age = 23.2 years) and older (n = 28; mean age = 64.5 years) males performed the RS task. Participants took volitional front, side, and back steps (in total 37 steps) with at least 80% of maximal step length in response to visual commands. Total times required to take 37 steps and stepping error rates were compared as a function of WM capacity which was measured by using the Digit Span (DS) subtest of the Wechsler Intelligence Scale-Third Edition (WAIS-III). There was an effect of WM capacity on RS task stepping errors. The error rate in the older lowest WM quartile (DS subtest raw scores, 6-11) was significantly larger than the error rates of the remaining three older quartiles (DS subtest raw scores, 12-21), as well as that of the younger group (DS subtest raw scores, 12-27), suggesting that individual differences in WM capacity do affect rapid stepping performance. Overall, total times were significantly longer in the older groups than in the younger group, while no significant differences were found among the older quartiles on this variable. The present study demonstrated that older adults whose WM capacity is low (Digit Span subtest raw score < 12) have more difficulties with taking accurate but rapid steps. Furthermore, the Digit Span subtest from the WAIS-III could be a useful independent predictor of fall risk in older adults.

---

16:00-16:05 Closing remarks

Dr. Yasutaka Ogawa, Executive director, JNIOSH