• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.145-150
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• 1996

Acoustic Emission (AE) technique was applied to stress corrosion cracking of Inconel 600 to investigate the AE capability of detecting crack growth and to obtain the relation between AE characteristics and crack mechanism. The specimens were heat-treated in two conditions (600$^{\circ}C$ for 30 hrs or 700 $^{\circ}C$ for 1 hr) and undergone CERT at two extension rates ( 2.5${\times}$10$^{-5}$ or 1.25${\times}$10$^{－4}$(mm/s)). It was found that the AE peak amplitude from plastic deformation was generally smaller than about 48dB (0.25mV), while Intergranular stress corrosion cracking (IGSCC) and ductile fracture produced higher values of 49 to 70dB (0.3mV to 3mV). The slopes of cumulative amplitude distribution (b-values) were linearly dependent on IGSCC susceptibility and the higher the susceptibility, the smaller the b-value. The monitoring of combined AE parameters such as event rate, amplitude, count and energy can provide effective means to clearly identify the transition from crack initiation and small crack growth to rapid growth of dominant cracks.

• Journal of the Korea Society of Computer and Information
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• v.28 no.3
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• pp.149-157
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• 2023

The purpose of this study is to suggest that performers in the performing arts actively utilize the loading dock and stage door when evacuating from the stage space of a performance hall in a crisis situation. Therefore, first, we analyzed the system related to the performance hall's safety. The stage evacuation type was classified into A, B, C, and D forms by applying the building law audience evacuation standards. Second, statistical data were organized based on measurement data, and the characteristics of each form were summarized. Third, the network reliability measurement method was borrowed to evaluate the evacuation safety of the evacuation route in the stage space. We confirmed quantitatively that the direction of the loading dock direction and stage door direction on the stage is advantageous for evacuation. In this study, it was possible to distinguish the advantage of evacuation according to the type of evacuation, (A(0.1274)>B(0.1228).>.C(0.0487)) with A being the most advantageous. These results can be expected to improve the evacuation safety of the stage, and furthermore, they are expected to be used as basic data for stage evacuation.

• Korean Journal of Food Science and Technology
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• v.43 no.2
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• pp.134-141
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• 2011

Two-hundred Bacillus cereus isolated from perilla leaf cultivation areas in Miryang, Korea were investigated for toxin genes and antibiotic susceptibility. Toxigenic patterns of isolates were identified to be 11 groups through toxin gene profiles. 21% of strains isolated from the perilla leaves had both enterotoxin and emetic toxin. Toxin genes entFM (100%), nheA (100%) and hblA, C, D (65.5%) were frequently found in the perilla leaves, whereas EM (21.0%) was less common. Most isolates were susceptible to 10 antibiotics, but they were highly resistant to penicillin (100%), ampicillin (100%), oxacillin (94.9%), amoxicillin-clavulanic acid (95.6%), cefazolin (78.2%), and rifampicin (58.0%). These results indicate that food-borne outbreak caused by B. cereus might lead to diarrhea and emetic syndromes.

• Journal of Preventive Medicine and Public Health
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• v.32 no.1
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• pp.30-39
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• 1999

Objectives. This study was carried out to evaluate hearing impairment judgement and to investigate the differences in various diagnostic criteria for noise-induced hearing loss (NIHL) among workers who required for close observation (C). Methods. Out of 731,029 workers who had taken the specific periodic health examination in 1994, we used the audiometric data on 37,999 workers (C) eliminating the employees who had previous otologic problems. Many investigators have being using different criteria for the evaluation of hearing impairment. In this study, we used the criteria of early (1989-1994), current, compensation for NIHL in Korea, 2-, 3-, 4-divided classification and hearing loss at 4,000 Hz and compared the evaluation results. Results. The prevalences of C and workers who had occupational disease $(D_1)$ diagnosed for NIHL were 11.1 % and 0.44 %. There were significant difference in the prevalences of C and $D_1$, depending on different province of Korea. Pure tone averages (PTAs) were not appropriately applied in their evaluation 97% of workers whom we studied on were below the level of mild hearing loss judged by ISO standard. However, there were wide variations in the prevalence rate of mild hearing loss by diagnostic criteria. Thus, there were different judgements in determining the degree of NIHL depending on which diagnostic criteria were utilized. PTAs were found 20.54 (Rt) and 20.74 (Lt) when the method of 3-divided classification was applied for audiometric data. The degree of hearing impairment of the left ear was more severe than that of right ear. The prevalence of normal hearing threshold below 20 dB was 75.4% and the range of difference in both ear was below 10 dB. Right sided hearing threshold levels were 21.08 dB (500 Hz), 18.44 dB (1,000 Hz), 22.09 (2,000 Hz) and 52.36 dB (4,000 Hz). There was typical high frequency loss (C5-dip at 4,000 Hz) above 30 - 40 dB in normal hearing level. The increasing trend in hearing threshold level was gradually decreased by the increase of PTAs. The difference between PTAs and threshold at 4,000 Hz was about 10 dB. Conclusions. We could found that PTAs in the previous examination were not appropriately evaluated. This study revealed that they did not use unique criteria for managing the workers of NIHL. For the prevention of NIHL, it was found that the quality control on diagnosis and comprehensive management program were required, especially for those of hearing loss (C).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.9
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• pp.831-840
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• 2013

The noise levels of workers in tunnel sites are likely to be high because tunneling work places are confined space. However, research on the noise exposure levels of tunneling workers have not been performed intensively due to restricted accessibility to tunnel construction sites. The aim of this study is to evaluate the noise exposure levels for workers engaged in tunneling work sites. Noise dosimeters were used for monitoring workers' noise exposure level in 5 tunneling work sites in accordance with the Notification of the Ministry of Labor. Among 5 tunneling work sites, 4 of them used NATM tunneling method and 1 work site used shield TBM tunneling method. The average noise exposure levels of NATM tunneling workers was 81.1 dB(A) and 15.4 % of the workers' noise level were exposed more than 90 dB(A) which is the exposure limit value. In Shield TBM tunneling method, 4.3 % of the workers were exposed more than 90 dB(A) of noise level, the average noise exposure levels of TBM tunneling workers was 84.1 dB(A).

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.275-287
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• 2008

Noise externalities are a ubiquitous problem in modern societies. Research to estimate damages and potential efficient solutions therefore is important for addressing such problems. The results of a hedonic property model show that noise has a statistically significant and quantitatively important negative effect on property values. The key results for the best model show that damages (in year 2000 dollars) are - $5000 ${\ast}$ (ln dB), where dB is noise measured in decibels, allowing for the influence of other factors. Because ln(dB) is a strictly concave funaion, the "noise damage function"exhibits diminishing marginal effects with noise.

• Journal of the Ergonomics Society of Korea
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• v.27 no.3
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• pp.15-22
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• 2008

The purpose of this study was to define the effects of noise and background music on the trunk muscle fatigue during dynamic lifting and lowering tasks. Six healthy male subjects with no prior history of low back disorders participated in this study. The participants were exposed to two levels of background noise such as 40dB noise and 90dB noise and three levels of background music such as no music, slow music, and fast music. Six different combinations of background noise and background music were played while the participants were performing the lifting task at 15% level of Maximum Voluntary Contraction. Electromyography signals from six muscles were collected and fatigue levels were analyzed quantitatively. In results, the 90dB noise increased trunk muscle fatigue and slowed down the recovery. The trunk muscle fatigue was the lowest when the fast music was played for as background. After recovery, the 90dB noise increased trunk muscle fatigue. The trunk muscle fatigue was the lowest when the slow music was played for as background. The results can be useful to manage the cumulative fatigue of trunk muscles due to background noise and music during repetitive lifting and lowering tasks in industry.

• Proceedings of the Safety Management and Science Conference
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• 2000.05a
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• pp.9-26
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• 2000

Eventually so as to realize the construction safety, 1 found out the cause of accident and specificities of the construction industry. This study presented to several situations and problems on construction safety. As a result of this study, the below matters must be improved for more effective the construction safety management system. 1. It need to introduce the total construction safety management system. Because there is not effectiveness in the current safety management to the first on the construction field. a. We must consider the safety in the whole parts of the process of the construction and constructors of each part must devide responsibility of the construction safety as a CDM(The Construction Designed Management) used in UK. b. It is desirable to proceed control of safety in the whole parts of the construction to introduce the total safety coordinator that can consult the matters of safety as a law accepted in EU. c. Like management of the construction safety in USA, direction of the construction safety must be made to work exactly by code or manual. d. To improve the organization of the construction safety on the construction field unefficient, it must be introduced safety supervisor, safety coordinator or institutionalization of safety consultant. 2. The law of the construction safety not only have wasteful element but also decrease efficiency by overlapping of regulation, The Ministry of Labour and The Ministry of Construction & Transportation, So laws related with safety must be instituted. a. To realize total safety management, The Ministry of Labour must legislate the basic law about safety management in whole field. b. To legislate the construction safety under one law, and improve efficiency of the overlapping of regulation and the similar law by The Ministry of Construction & Transportation. c. It must be made the law of construction safety that can proper to change of situation in construction. d. The standard of safety must be instituted belong to international level and improved by year. e. We must improve irrational regulation to realize activity of safety self regulating for progress competition in construction industry

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.875-882
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• 2021

To minimize occupational noise induced hearing loss, it is recommended that workers should not be exposed to noise levels exceeding 85 dBA for over 8 h. In the present study, noise exposure levels were measured for seven workers based on their tasks on a training ship. The A-weighted noise exposure level (L_ex,24h) was measured by taking into account the A-weighted equivalent continuous sound level (L_Aeq,i), duration (h) and noise contribution (L_ex,24h,i) from the workers' locations. Results are thus obtained for different job categories as follows: officer group L_ex,24h=56.1 dB, navigation crew L_ex,24h=58.9 dB, navigation cadet L_ex,24h=62.0 dB, ship's cook L_ex,24h=64.3 dB, engine cadet L_ex,24h=91.1 dB, engineer L_ex,24h=91.1 dB, and engine crew L_ex,24h=95.1 dB. It was determined that the engineers, engine crews, and engine cadets in charge of machinery must wear hearing protection devices. By wearing hearing protection devices when working in highly noisy engine rooms, it is estimated that the noise expose levels could be reduced by the following amounts: engineer L_ex,24h=23.1 dB, engine Crew L_ex,24h=24.4 dB, and engine cadet L_ex,24h=21.5 dB. Moreover, if the no. 2 lecture room and mess room bottom plates in the cadets accommodations were improved to the 64 mm A-60-class floating plates, then further reductions are possible as follows: navigation cadet L_ex,24h=4.3 dB and engine cadet L_ex,24h=1.8 dB.

• Journal of the Korean Society of Safety
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• v.7 no.1
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• pp.20-29
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• 1992

Effects of strain hardening exponents on the retardation behavior of fatigue crack propagation are experimentally investigated. The retardation of fatigue crack propagation seems to be induced by the crack closure at crack tip. The phenomenon of crack closure becomes remarkable with the increment of strain hardening exponent and magnitude of percent peak load. The ratio of crack growth increment(a$\_$d//w$\_$d/) is influenced by a single overloading (a$\_$d/) and estimated plastic zone size (W$\_$d/=2r$\_$y/) is increased according with the increasing of strain ha.dening exponents. The number of retarded crack growth cycles were (N$\_$d/) decreased as the baseline stress intensity factor .ange( K$\_$b/) was increased. Within the limitation of these experimental results obtained under the single overload, an empirical relation between crack retardation ratio (Nd/N＊), strain hardening exponent (n) and percent peak load (％PL) has been proposed as; Nd/N＊＝ exp [PL $.$ PL$.$A(n)＋B(n) ] where, A(n)＝${\alpha}$n＋${\beta}$, B(n)＝${\gamma}$n＋$\delta$, PL＝％PL/100 and ${\alpha}$＝0.78, ${\beta}$＝0.54, ${\gamma}$＝0.58 and $\delta$＝-0.01, It is interesting to note that all these constants are identical for materials such as aluminum(A3203), steel(S4SC), steel(SS41) and stainless steel(SUS316) used in this experimental study.