• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권6호
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• pp.2893-2907
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• 2019

Wireless mobile communication systems in subway tunnels have been widely researched these years, due to increased demand for the communication applications. As a result, an accurate model is essential to effectively evaluate the communication system performance. Thus, a neoteric three-dimensional (3D) geometry-based stochastic model (GBSM) is proposed for the massive multiple-input multiple-output (MIMO) fading channels in tunnel environment. Furthermore, the statistical properties of the channel such as space-time correlation, amplitude and phase probability density are analyzed and compared with those of the traditional two-dimensional (2D) model by numerical simulations. Finally, the ergodic capacity is investigated based on the proposed model. Numerical results show that the proposed model can describe the channel in tunnels more practically.

• Current Optics and Photonics
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• 제8권4호
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• pp.355-365
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• 2024

Wavefront coding (WFC) imaging systems can redistribute the energy of an interference laser spot on an image plane sensor by wavefront phase modulation and reduce the peak intensity, realizing laser protection while maintaining imaging functionality by leveraging algorithmic post-processing. In this paper, a spiral axicon WFC imaging system is proposed, and the performance for laser protection is investigated by constructing a laser transmission model. An Airy disk on an image plane sensor is refactored into a symmetrical hollow ring by a spiral axicon phase mask, and the maximum intensity can be reduced to lower than 1% and single-pixel power to 1.2%. The spiral axicon phase mask exhibits strong robustness to the position of the interference laser source and can effectively reduce the risk of sensor damage for an almost arbitrary lase propagation distance. Moreover, we revealed that there is a sensor hazard distance for both conventional and WFC imaging systems where the maximum single-pixel power reaches a peak value under irradiation of a power-fixed laser source. Our findings can offer guidance for the anti-laser reinforcement design of photoelectric imaging systems, thereby enhancing the adaptability of imaging systems in a complex laser environment. The laser blinding-resistant imaging system has potential applications in security monitoring, autonomous driving, and intense-laser-pulse experiments.

• Safety and Health at Work
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• 제2권1호
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• pp.34-38
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• 2011

Objectives: The antimicrobial activity of silver nanoparticles has resulted in their widespread use in many consumer products. Yet, despite their many advantages, it is also important to determine whether silver nanoparticles may represent a hazard to the environment and human health. Methods: Thus, to evaluate the genotoxic potential of silver nanoparticles, in vivo genotoxicity testing (OECD 474, in vivo micronuclei test) was conducted after exposing male and female Sprague-Dawley rats to silver nanoparticles by inhalation for 90 days according to OECD test guideline 413 (Subchronic Inhalation Toxicity: 90 Day Study) with a good laboratory practice system. The rats were exposed to silver nanoparticles (18 nm diameter) at concentrations of $0.7\;{\times}\;10^6$ particles/$cm^3$ (low dose), $1.4\;{\times}\;10^6$ particles/$cm^3$ (middle dose), and $2.9\;{\times}\;10^6$ particles/$cm^3$ (high dose) for 6 hr/day in an inhalation chamber for 90 days. The rats were killed 24 hr after the last administration, then the femurs were removed and the bone marrow collected and evaluated for micronucleus induction. Results: There were no statistically significant differences in the micronucleated polychromatic erythrocytes or in the ratio of polychromatic erythrocytes among the total erythrocytes after silver nanoparticle exposure when compared with the control. Conclusion: The present results suggest that exposure to silver nanoparticles by inhalation for 90 days does not induce genetic toxicity in male and female rat bone marrow in vivo.

• 한국산학기술학회논문지
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• 제14권3호
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• pp.1045-1053
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• 2013

플레저 보트나 요트는 FRP나 알루미늄으로 제작되고 있으나 FRP는 해양환경오염으로, 알루미늄은 낮은 가격 경쟁력으로 인하여 해당 제품의 시장 지배력이 약화되고 있다. 따라서 본 연구에서는 선체를 폴리에틸렌으로 제작하여 일본소형선박검사사무규정세칙에서 제안하고 있는 소형선체에 대한 구조 안전성 평가 방법을 통하여 폴리에틸렌 선체의 구조 안전성을 확인한 결과, 폴리에틸렌 보트가 FRP 보트보다 매우 높은 구조 안전성을 보였다.

• Journal of Ecology and Environment
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• 제47권2호
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• pp.14-26
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• 2023

Background: An important consideration for the risk assessment of transgenic plants is their overwintering potential in a natural ecosystem, which allows the survival of the seed bank and may lead to seed reproduction. Here, we investigated the overwintering of sunflower (Helianthus annuus L.) seeds in the laboratory (temperatures: -5, -1, 5, and 10℃) and in the field (burial depth: 0, 5, 15, and 30 cm) as a case study to examine the invasiveness of transgenic crops. Results: Sunflower seeds germinated when incubated at 5℃ and 10℃ for 2, 4, 6, and 12 weeks but not when incubated at -5℃ or -1℃. However, the seeds incubated at -5℃ or -1℃ germinated when they were transferred to the optimal germination temperature (25℃). Up to 16.5% and 15.0% of seeds were dormant when cultured at sub-zero temperatures in a Petri dish containing filter paper and soil, respectively. In the field trial, soil temperature, moisture, and microbial communities differed significantly between soil depths. Germination-related microorganisms were more distributed on the soil surface. Seeds buried on the surface decayed rapidly from 4 weeks after burial, whereas those buried at depths of 15 cm and 30 cm germinated even 16 weeks after burial. No dormancy was detected for seeds buried at any depth. Conclusions: Although sunflower seeds did not overwinter in situ in this study, we cannot exclude the possibility that these seeds lie dormant at sub-zero temperatures and then germinate at optimal temperatures in nature.

• 대한의생명과학회지
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• 제11권2호
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• pp.143-152
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• 2005

To investigate the exposure effect of polycyclic aromatic hydrocarbons (PAHs), we analyzed the relationship between urinary 8-hydroxydeoxyguanosine (8-OHdG) concentration and PAHs exposure. The study population contained 44 workers in steel-pipe coating and paint manufacture industries. We measured airborne total PAHs as an external dose, urinary 1-hydroxypyrene (1-OHP) as an internal dose of PAHs exposure, and urinary 8-OHdG as an effective dose of oxidative DNA damage. There was significant correlation between the urinary concentration of l-OHP and the environmental concentration of PAHs, pyrene, urinary cotinine, AST, and GGT. The mean of urinary 8-OHdG was $17.07\pm1.706{\mu}g/g$ creatinine in workers exposed to airborne PAHs. There was significant correlation between the urinary concentration of 8-0HdG and the airborne concentration of PAHs. From the results of stepwise multiple regression analysis about 8-OHdG, significant independents was total PAHs. In this study, there were significant correlation between the urinary concentration of 8-OHdG and the airborne concentration of PAHs. The urinary 1-OHP was effective index as a biomarker of airborne PAHs in workplace. But it was influenced by non-occupational PAHs source, smoking and biomarkers of liver function test.

• 해양환경안전학회지
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• 제14권1호
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• pp.39-43
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• 2008

해양환경 오염에 대한 관심이 많아지면서 해양환경 인자에 대한 감시가 그 중요성을 더해 가고 있다. 지금까지는 이에 대한 감지를 위한 센서의 부재로 인하여 해수를 채취하여 실험실에서 고가의 장비를 이용하여 분석하여 왔다. 이는 해양의 실시간 감시가 어려울 뿐 아니라 급변하는 해양 상태를 정확하게 파악하기 어려운 면이 있어왔다. 이러한 단점을 보완하기위해서 나노기술을 이용한 해양용 센서 개발이 시급히 요구되는 바 이에 대한 기술적인 분야와 특징 및 타당성을 검토하였다 현재 기술적으로 개발이 가능하고 국제적으로 경쟁력이 있는 분야로는 나노스핀소자를 이용한 바이오분자 감지, 탄소나노튜브의 전도성 변화에 따른 해양인자 감시기술, 그리고 나노반도체를 이용한 적조관련 미생물 감지 기술을 제시하였다. 이 기술들의 특징과 해양환경에서의 적용을 위하여 개발하여야 할 요소 기술을 찾아보고 문제점들을 극복할 수 있는 방안을 제시하였다.

• 한국대기환경학회지
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• 제33권2호
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• pp.139-158
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• 2017

CMAQ (Community Multiscale Air Quality Model) simulations were carried out to estimate the potential range of contributions on surface $PM_{2.5}$ concentrations over the Seoul Metropolitan Area (SMA) with the gaseous precursors and Primary Particulate Matters(PPM) available from a recent national emissions inventory. In detail, on top of a base simulation utilizing the 2013 Clean Air Policy Supporting System (CAPSS) emission inventory, a set of Brute Force Method (BFM) simulations after reducing anthropogenic $NO_x$, $SO_2$, $NH_3$, VOCs, and PPM emissions released from area, mobile, and point sources in SMA by 50% were performed in turn. Modeling results show that zero-out contributions(ZOC) of $NH_3$ and PPM emissions from SMA are as high as $4{\sim}5{\mu}g/m^3$ over the region during the modeling period. On the contrary, ZOC of local $NO_x$ and $SO_2$ emissions to SMA $PM_{2.5}$ are less than $1{\mu}g/m^3$. Moreover, model analyses indicate that a wintertime $NO_x$ reduction at least up to 50% increases SMA $PM_{2.5}$ concentrations, probably due to increased HNO3 formation and conversion to aerosols under more abundant ozone and radical conditions after the $NO_x$ reduction. However, a nation-wide $NO_x$ reduction decreased SMA $PM_{2.5}$ concentrations even during winter, which implies that nation-wide reductions would be more effective to curtail SMA $PM_{2.5}$ concentrations than localized efforts.

• Computers and Concrete
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• 제20권5호
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• pp.617-625
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• 2017

Prestress force identification (PFI) is crucial to maintain the safety of prestressed concrete bridges. A synergic identification method has been proposed recently by the authors that can determine the prestress force (PF) and the excitation force simultaneously in prestressed concrete beams with good accuracy. In this paper, the ability of this method in the application with prestressed concrete box-girder bridges is demonstrated. A reasonable assumption is made to capture the similarity of the dynamic behavior of the prestressed concrete box-girder bridge and a beam under a certain loading scenario, and the feasibility of this method for application in a prestressed box-girder bridge is affirmed. A comprehensive laboratory test program is conducted, and the effects of PF, excitation, measuring time and uncertainties are studied. Results show that the proposed method can predict the PF and the excitation force in a prestressed concrete box-girder accurately and has a great robustness against uncertainties.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.538-543
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• 2020

Boric acid is used as a coolant for pressurized-water reactors, and the degree of burnup is controlled by the concentration of boric acid. Therefore, accurate measurement of the concentration of boric acid is an important factor in reactor safety. An improved system was proposed for the accurate determination of boron concentration. A new boron-concentration measurement technique, called multisensitive detection, was developed to improve the measurement accuracy of boron meters. In previous studies, laboratory-scale experiments were performed based on different sensitivity detectors, confirming a 65% better accuracy than conventional single-detector boron meters. Based on these experimental results, an experimental system simulating the coolant-circulation environment in the reactor was constructed; accuracy analysis of the boron meter with a multisensitivity detector was performed at the actual coolant pressure and temperature. In this study, the boron concentration conversion equation was derived from the calibration test, and the accuracy of the boron concentration conversion equation was examined through a repeatability test. Through the experiment, it was confirmed that the accuracy was up to 87.5% higher than the conventional single-detector boron meter.