1 Introduction Resistive switching of transition metal oxides has attracted significant attention as promising materials for the future high-density, nonvolatile memories [1]. This is because metal-TMO-metal devices showed high endurance, excellent retention properties, fabrication compatibility with Si, and high-density scalability [2]. However, it has a significant drawback in random fluctuation on each memory switching parameter [3,4], i.e., R on , R off , V SET , and V RESET . Here, R on and R off represent the resistance of low and high resistive states, and V SET and V RESET are the required voltages for the switching from R off to R on and vice versa. The fluctuation causes a memory window failure and thus, it is of paramount importance for the application of the devices. Many researchers [5,6] have made strong suggestion that the resistive switching is the result of the existence of a large number of conducting filaments spanning the insulating matrix, which arise during the electroforming process [7]. The switching occurs in the "formed" devices via the formation and rupture of the filamentary paths, which are considered to be localized and randomly distributed over the devices [8]. Recently the filaments were observed electrically in NiO [9] as well as TiO 2 [10]. In addition, for both NiO and TiO 2 , impedance spectroscopic studies strongly suggested the filamentary
The Asian Pacific Regional Aerosol Characterization Experiment (ACE‐Asia) intensive phase took place from 30 March to 4 May 2001, involving extensive aerosol observations from aircraft, ship, and ground stations. Meteorological events of significance to the ACE‐Asia intensive observations made during this period were identified and analyzed using a combination of gridded meteorological analysis fields, observations, and analyses of precipitation, atmospheric radiation distributions, and other variables, and products prepared from these data. The observed flow characteristics were found to be close to the center of the range of interannual variation, with most anomalies spatially confined and small in magnitude. The occurrence and distribution of midlatitude cyclones which had an impact on the circulation and transport patterns affecting the area of the campaign were close to the climatological mean. Total aerosol scattering and the fraction caused by submicron particles, and trajectory analysis results from points along the flight track of the C‐130, were used to examine the relationship between the aerosol distributions and transport patterns and the meteorological situation. Notably strong coarse‐mode scattering was observed at low altitudes in post cold‐frontal circulations during dust outbreaks, and very strong mixed‐mode scattering occurred in plumes from polluted areas flowing offshore removed from important surface or upper air features.
BACKGROUND: Increase of heavy metals in agricultural ecosystem has become a social issue nationwide as it is related to public health. This review was performed to find out more systematic and integrated future researches on heavy metals using up to date articles published in the Korean journals related to agricultural environment. METHODS AND RESULTS:Researches on heavy metals in agricultural soils and plant uptake were categorized by the establishment of criteria, analytical methods, monitoring, management of source, characteristics and behavior in soil, plant uptake, bioavailability affecting physico -chemical properties in soil, risk assessment and soil remediation. In the early 1990s, the monitoring for heavy metals in soil has been widely performed. Accumulation of heavy metals in contaminated soil and availability to plants has also attracted interests to study the soil remediation using various physico-chemical methods. The phytoavailability and phytotoxicity of heavy metals have been mainly studied to assess the safety of agro-products using risk assessment techniques in the 2000s. CONCLUSION: Future direction of research on heavy metal in agricultural environment must be carried out by ensuring food safety and sustainability. A steady survey and proper management for polluted regions should be continued. Law and regulation must be modified systematically. Furthermore, studies should expand on mitigation of heavy metal uptake by crops and remediation of polluted fields. (Kabata-Pendias, 1984 ;Adriano, 1986; Fergusson, 1990).농업환경에서의 중금속에 관한 연구는 최초 1920-30년대 에 작물의 미량원소에 대한 필요성과 결핍 연구로서 본격 시 작되었으며, 1940년대 9개의 미량원소가 작물에 필수원소로 작용함과 구리의 결핍증상을 보고하였다. 2차 세계대전 후 급 속한 산업화 및 도시화에 따른 중금속오염이 크게 증가하였 으며 이에 따른 중금속 오염사례의 보고도 증가하였다. 1940 년대 일본 진즈(Zinzu)강 유역 카드뮴 중독과 1950년대 일 본 미나마타(Minamata)만 유기수은 중독이 그것이다. 1970 Open Access Reviews LEE et al. 76년대 이르러 미국에서 화석연료의 사용 증가, 크레용 및 페인 트 등에 의한 어린이 혈액중 납 함량의 증가, 일본의 카드뮴으 로 오염된 쌀, 그리고 유해 중금속을 함유한 하수 슬러지의 농 경지 유입에 따른 식품 연쇄계에의 중금속에 대한 관심이 증가 하였다 (Kabata-Pendias, 1984 ;Adriano, 1986; Fergusson, 1990).이에 국내에서도 1967년 농촌진흥청에서 벼농사에 사용되 어진 유기수은제의 영향으로 백미중 수은함량을 조사하였고, 1971년 구리오염지 토양을 개량하기 위한 석회 및 규산물질 처리 효과를 확인한 이래 농업부분에서 중금속에 대한 활발 한 연구가 수행되었다 (Jeong and Kim, 1971 , 1993, 1995b Jung et al., 1996b Jung et al., , 1997 Jung et al., , 1998b Jung et al., , 2004 and Lee, 1983;Park et al., 1983; Kim and Ryang, 1986; Choi, 1986a, 1986b; Kim et al., 1992b Kim et al., , 1994b Kim et al., , 1994c Kim et al., , 1996c, 도로(Lee and Kim, 1991a, 1991b), 광산 및 공단인근 (Lee and Song, 1985; Lee and Song, 1986; Kim et al., 1992c Kim et al., , 1994a Kim et al., , 1998a Kim et al., , 1999b Kim and Baek, 1994;Yoo et al., 1983Yoo et al., , 1996 Hong et al., 2007a Hong et al., , 2007bYun et al., 2010) 의 , 1985 Park, 1985a, 1985b; Jung et al., 2005c) (1986a, 1986b, 1987, 1988 Lee and Lim, 1987 , 1997a, 1997b, 1997c 1997d, 1997e, 1998
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