• Geomechanics and Engineering
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• v.19 no.2
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• pp.193-199
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• 2019

A frozen fringe plays a key role in frost heave development in soils. Previous studies have focused on the physical and mechanical properties of the frozen fringe, such as overall hydraulic conductivity, water content and pore pressure. It has been proposed that the thickness of the frozen fringe controls frost heave behavior, but this effect has not been thoroughly evaluated. This study used a temperature-controllable cell to investigate the impact of frozen fringe thickness on the characteristics of frost heave. A series of laboratory tests was performed with various temperature boundary conditions and specimen heights, revealing that: (1) the amount and rate of development of frost heave are dependent on the frozen fringe thickness; (2) the thicker the frozen fringe, the thinner the resulting ice lens; and (3) care must be taken when using the frost heave ratio to characterize frost heave and evaluate frost susceptibility because the frost heave ratio is not a normalized factor but a specimen height-dependent factor.

• Journal of Environmental Science International
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• v.28 no.8
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• pp.713-717
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• 2019

The purpose of this study was to investigate the effects of dietary Hermetia illucens powder on duck litter quality. One hundred twenty Pekin ducks (0 day old) were assigned to 2 groups (0% and 0.5% Hermetia illucens powder) with 3 replicates (20 ducks per replicate) for 42 days. Duck litter quality included moisture, pH, VBN, total nitrogen, ammonia, and temperature. Litter pH and VBN values were significantly affected by Hermetia illucens powder (p<0.05). However, moisture and total nitrogen values were not greatly influenced by the addition of 0.5% Hermetia illucens powder (p>0.05). At 21, 28 and 35 days, both 0.5% Hermetia illucens powder and controls had a great effect (p<0.05) on ammonia contents, except at 7, 14 and 42 days. In comparison to control, ammonia contents in groups with 0.5% Hermetia illucens powder were reduced from 16.9 to 41.8% as the days increased. Duck litter showed lower temperature by 0.5% Hermetia illucens powder compare to control. In terms of environmental managements, these results suggest that using 0.5% Hermetia illucens powder as feed additives improved litter quality and decreased ammonia contents.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.4
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• pp.367-377
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• 2021

Objectives: Taxi drivers are exposed to various hazards, such as long periods of sedentary work and traffic-related air pollutants. However, studies on the health effects among taxi drivers in South Korea are insufficient. Methods: To assess subclinical hematologic change related to cardiovascular disease among male taxi drivers, we analyzed data from the second Korean National Environmental Health Survey. Fifty-nine taxi drivers and 1,912 controls were included in the analysis. Propensity score matching was performed to adjust for age, body mass index, and urinary cotinine. A total of 295 subjects were matched with 59 taxi drivers. Leukocyte count, platelet count, hematocrit, triglyceride, total cholesterol, HDL cholesterol land total IgE of the taxi drivers were compared with the control groups. Results: Taxi drivers showed significantly elevated blood leukocytes and platelets. Serum total IgE was significantly reduced in taxi drivers. However, blood leukocytes, platelets, and serum total IgE were not significantly correlated with work period among taxi drivers. Conclusions: Regarding the change of the blood leukocyte count, platelet count, and serum total IgE, taxi driving has the possibility to be associated with peripheral inflammation, humoral immunity and cardiovascular risk.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.4
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• pp.248-255
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• 2010

Airborne nanoparticle concentrations in three metrics (particle surface area concentration, particle number concentration, and particle mass concentrations) were measured by task in a laboratory making carbon nanotubes (CNTs) films using three direct reading instruments. Because of the conducted other researcher's experiment before the tasks, airborne nanoparticle surface area and number concentrations are the highest at the first time conducted weighing and mixing by sonication task, respectively. Because of the mist generated during mixing by sonication, the highest airborne nanoparticle surface area and PM1 concentrations were measured in the task among the total. Nanoparticle surface area concentrations at the researchers' breathing zones had high correlation (r=0.93, p<0.01) with those measured at an area in the laboratory. This result indicates that nanoparticles generated during the experiment contaminated the whole room air. When the experiment performed all the fume hoods weren't operated and making CNTs films task were conducted in the out of the fume hoods. In conclusion, researchers performing making CNTs film experiments were exposed to airborne nanoparticles generated during the experiment without adequate controls. We recommend that adequate controls should be implemented so that workers' exposures to airborne nanoparticle are limited to minimum levels.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.2
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• pp.569-573
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• 2012

Early diagnosis and better prognosis of ovarian cancer is still a challenge. Besides environmental risk factors, genetic factors have established a role in pathogenesis of ovarian cancer. Methods: A case-control and a prospective study design conducted in 224 ovarian cancer patients and 432 controls in Chinese population. MTHFR C677T genotyping was done by PCR-RFLP. Results: Patients with ovarian cancer is associated with a higher less number of delivery and less frequent oral contraceptive use. When potential confounding factors adjusted logistic regression analysis between cases and controls were performed, significant association was obtained for 677T/T genotype and ovarian cancer (OR=3.13, 95% CI=1.59-5.72). Cox regression survival analysis showed individuals carrying T/T genotype had significantly increased HR for death in ovarian cancer patients (HR=2.86, 95% CI=1.27-7.93). In conclusion, we observed that the MTHFR C677T polymorphism is associated with the susceptibility and survival of ovarian cancer in Chinese population.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.9
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• pp.4249-4253
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• 2012

While associations between trace elements and heavy metals with prostate cancer are still debatable, they have been considered as risk factors for prostate cancer. Thus, this study aimed to detect any links between selected minerals and heavy metals including Se, Zn, Cu, Mn and Fe with prostate cancer. A case control study was carried out among 100 subjects (case n=50, control n=50), matched for age and ethnicity. Trace elements and heavy metals level in hair and nail samples were determined by ICP-MS. Mean selenium levels in hair and nail of the cases were significantly lower as compared to controls. A similar trend was noted for zinc in both hair and nail samples, whereas the mean level of copper was significantly higher in cases than controls. Similar elevation was noted for iron and manganese (p<0.05 for all parameters). Low levels of selenium and zinc and high levels of copper, iron and manganese appear to be associated with the risk of prostate cancer. Further studies to elucidate the causal mechanisms and appropriate chemopreventive measures are needed.

• Journal of Sensor Science and Technology
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• v.29 no.5
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• pp.348-353
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• 2020

This paper presents an adaptive method to avoid obstacles in various environmental settings, using a two-dimensional (2D) LiDAR sensor for mobile robots. While the conventional reaction based smooth nearness diagram (SND) algorithms use a fixed safety distance criterion, the proposed algorithm autonomously changes the safety criterion considering the obstacle density around a robot. The fixed safety criterion for the whole SND obstacle avoidance process can induce inefficient motion controls in terms of the travel distance and action smoothness. We applied a multinomial logistic regression algorithm, softmax regression, to classify 2D LiDAR point clouds into seven obstacle structure classes. The trained model was used to recognize a current obstacle density situation using newly obtained 2D LiDAR data. Through the classification, the robot adaptively modifies the safety distance criterion according to the change in its environment. We experimentally verified that the motion controls generated by the proposed adaptive algorithm were smoother and more efficient compared to those of the conventional SND algorithms.

• Transactions on Control, Automation and Systems Engineering
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• v.1 no.2
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• pp.94-98
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• 1999

Optical scanning systems use glavanometers to point the laser beam to the desired position on the workpiece. The angular speed of a galvanometer is typically controlled using Proportional+Integral+Derivative(PID) control algorithms. However, natural variations in the dynamics of different galvanometers due to manufacturing, aging, and environmental factors(i.e., process uncertainty) impose a hard limit on the bandwidth of the galvanometer control system. In general, the control bandwidth translates directly into efficiency of the system response. Since the optical scanning system must have rapid response, the higher control bandwidth is required. Auto-tuning PID algorithms have been accepted in this area since they could overcome some of the problems related to process uncertainty. However, when the galvanometer is attached to a larger mechanical system, the combined dynamics often exhibit resonances. It is well understood that PId algorithms may not have the capacity to increase the control bandwidth in the face of such resonances. This paper compares the achieable performance and robustness of a galvanometer control system using a PID controller tuned by the Ziegler-Nichols method and a controller designed by the Quantitative Feedback Theory(QFT) method. The results clearly indicate that-in contrast to PID designs-QFT can deliver a single, fixed controller which will supply high bandwidth design even when the dynamics is uncertain and includes mechanical resonances.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.16 no.2
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• pp.123-130
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• 2006

이 연구에서는 고속도로 신설 공사 건설 현장 근로자들의 소음 노출을 저감할 수 있는 방법들을 제시하며 특히 현장에서 적용할 수 있는 새로운 체계적인 방법인 "소음 주의 구역"을 제안한다. 고속도로 건설 현장에서 소음원이 되는 장비, 기계, 도구와 근로자들의 소음 노출 특성을 알아 보았으며, 개인청력 보호구, 공학적제어수단 (engineering controls), 관리적제어수단 (administrative controls)을 어떻게 적용할 것인가를 제시하였다. 개인청력 보호구만으로는 소음 노출을 효율적으로 저감시킬 수 없음을 보였으며, 공학적제어수단은 기술적 및 경제적 문제로, 관리적제어수단은 공사 기간 단축과 같은 실제적인 이유로 해서 시행 되기가 어렵다. 따라서 이 연구에서는 실제적으로 적용할 수 있는 체계적인 방법으로서 "소음주의구역 (Noise Perimeter Zones)"을 새롭게 제안하였다. 이 "소음주의구역"은 높은 수준의 소음원이 존재하는 고속도로 건설 공사 현장에 지정된다. 이 구역안에서는 근로자들의 출입이 통제되며 또한 개인청력 보호구, 공학적제어수단, 관리적제어수단과 같은 적절한 제어수단이 사용되어야 한다.

• Journal of the Ergonomics Society of Korea
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• v.30 no.1
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• pp.161-168
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• 2011

Objective: The aim of this study is to review the ISO(the International Organization for Standardization) standards recommendations on a human error tolerant control room design. Background: ISO TC(Technical Committee) 159 published a variety of international standards on design of mental and physical work, design of displays and controls, and workstation layout design. A proper edition of these standards can be a good resource for a human error tolerant control center design guidelines. Method: Recommendations of ISO TC 159 standards were grouped into arrangement of control suite, layout of control room, layout and dimensions of workstations, design of displays and controls, environmental design, alarm, automation, management system design, procedure and training. Results: It was found that some standards on the design of supervisory control and data acquisition(SCADA), alarm, automation, layout, workload management, and environment can be used for human error prevention guidelines in the control center design. Conclusion: ISO TC 159 standards were not sufficient to cover all the ergonomics area of control center design. Application: Designers can have technical aids from these ISO standards to improve ergonomic performance of their control center.