THE EFFECT OF DUST PARTICLES ON ION ACOUSTIC SOLITARY WAVES IN A DUSTY PLASMA

Choi, Cheong-Rim,Lee, Dae-Young,Kim, Yong-Gi The Korean Space Science Society 2004 Journal of Astronomy and Space Sciences Vol.21 No.3

In this paper we have examined the effect of dust charge density on nonlinear ion acoustic solitary wave which propagates obliquely with respect to the external magnetic field in a dusty plasma. For the dusty charge density below a critical value, the Sagdeev potential $\Psi1(n)$ has a singular point in the region n < 1, where n is the ion number density divided by its equilibrium number density. If there exists a dust charge density over the critical value, the Sagdeev potential becomes a finite function in the region n < 1, which means that there may exist the rarefactive ion acoustic solitary wave. By expanding the Sagdeev potential in the small amplitude limit up to on4 near n=1, we find the solution of ion acoustic solitary wave. Therefore we suggest that the dust charge density plays an important role in generating the rarefactive solitary wave.

THE EFFECT OF DUST PARTICLES ON ION ACOUSTIC SOLITARY WAVES IN A DUSTY PLASMA

Cheong Rim Choi,Dae Young Lee,Yonggi Kim 한국우주과학회 2004 Journal of Astronomy and Space Sciences Vol.21 No.3

Effects of isothermal ion temperature on dust ion acoustic solitary waves in a dusty plasma obliquely propagating to an external magnetic field

Choi cheong Rim,Lee D.-Y.,Kim Yonggi 한국우주과학회 2005 한국우주과학회보 Vol.14 No.1

Ion acoustic solitary waves and double layers in the solar wind

Choi Cheong-Rim,Lee D.-Y.,Kim Younggi,Ryu Chang-Mo 한국우주과학회 2005 한국우주과학회보 Vol.14 No.2

Simulation Study of Solar Wind Interaction with Lunar Magnetic Fields

Choi, Cheong Rim,Dokgo, Kyunghwan,Woo, Chang Ho,Min, Kyoung Wook The Korean Space Science Society 2020 Journal of Astronomy and Space Sciences Vol.37 No.1

Particle-in-cell simulations were performed to understand the interaction of the solar wind with localized magnetic fields on the sunlit surface of the Moon. The results indicated a mini-magnetosphere was formed which had a thin magnetopause with the thickness of the electron skin depth. It was also found that the solar wind penetrated into the cavity of the magnetosphere intermittently rather than in a steady manner. The solar wind that moved around the magnetosphere was observed to hit the surface of the Moon, implying that it may be the cause of the lunar swirl formation on the surface.

Scientific Missions and Technologies of the ISSS on board the NEXTSat-1

Choi, Cheong Rim,Sohn, Jongdae,Lee, Jun-Chan,Seo, Yong Myung,Kang, Suk-Bin,Ham, Jongwook,Min, Kyoung-Wook,Seon, Jongho,Yi, Yu,Chae, Jang-Soo,Shin, Goo-Hwan 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.1

A package of space science instruments, dubbed the Instruments for the Study of Space Storms (ISSS), is proposed for the Next Generation Small Satellite-1 (NEXTSat-1), which is scheduled for launch in May 2016. This paper describes the instrument designs and science missions of the ISSS. The ISSS configuration in NEXTSat-1 is as follows: the space radiation monitoring instruments consist of medium energy particle detector (MEPD) and high energy particle detector (HEPD); the space plasma instruments consist of a Langmuir probe (LP), a retarding potential analyzer (RPA), and an ion drift meter (IDM). The space radiation monitoring instruments (MEPD and HEPD) measure electrons and protons in parallel and perpendicular directions to the geomagnetic field in the sub-auroral region, and they have a minimum time resolution of 50 msec for locating the region of the particle interactions with whistler mode waves and electromagnetic ion cyclotron (EMIC) waves. The MEPD measures electrons and protons with energies of tens of keV to ~400 keV, and the HEPD measures electrons with energies of ~100 keV to > ~1 MeV and protons with energies of ~10 MeV. The space plasma instruments (LP, RPA, and IDM) observe irregularities in the low altitude ionosphere, and the results will be compared with the scintillations of the GPS signals. In particular, the LP is designed to have a sampling rate of 50 Hz in order to detect these small-scale irregularities.

고로(高爐)슬래그 미분말을 사용한 고강도(高强度) 콘크리트 강도특성(强度特性)에 관한 실험적(實驗的) 연구(硏究)

임철진 ( Rim Cheol-jin ),설광욱 ( Seol Gwang-wook ),최형범 ( Choi Hyoung-bum ),부척량 ( Boo Cheong-yang ),이수곤 ( Lee Soo-gon ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.4 No.2

The ground granulated blast-furnace slag, a by-product obtained from molten slag during production of pig iron, is a widely used admixtures along with fly ash. Because the concrete substitute of micro-powder ground granulated blast-furnace slag has a strong control effect on the hydration heat, good strength expression in long-term Ages, and good chemical resistance such as resistance to sea water, many studies are in progress. Particularly, studies using the ground blast-furnace slag are being conducted on the retrenchment of production cost, industrial waste disposal and resource recycling. Additionally, the concrete substitute of micro-powder ground granulated blast-furnace slag has such disadvantages as low initial strength and quality alteration (shrinkage), this concrete is infrequently used in the home. In this study, therefore, the compressive strength of concrete, tensile strength of concrete and steel strain of reinforced concrete by the drying shrinkage in the concrete substituting the micro-powder of ground granulated blast-furnace slag are measured. Through comparison/analysis with existing studies, fundamental data for the use of the concrete structures are to be provided.

The Effects of Ethephon Application on Suppressing Methane Emission and Stimulating Rice Productivity in a Rice Paddy Soil: A Pot Experiment

Seongwoo Choi,Juhee Lee,Yeomyeong Lee,Pil Joo Kim,Ju-Sik Cho,Yong Hwa Cheong,Yo-Sup Rim,Sang Yoon Kim 한국토양비료학회 2020 한국토양비료학회지 Vol.53 No.4

Ethephon is one of the chemical stimulator of crop growth that is also considered as a structural analogue of coenzyme M (CoM), having a promising potential for methanogenic inhibitor. However, the effect of ethephon application on greenhouse gas (GHG) emissions under rice cultivation has not been studied yet. In this pot experiment, different levels of ethephon (0, 2.5, 5 and 10 ㎎ L<SUP>-1</SUP>) were applied at the presence or absence of manure compost as an organic amendment to study its effect on GHGs emissions in particular CH₄ and rice productivity during the cultivation. Application of ethephon effectively suppressed CH₄ emissions in particular the initial periods (ca. 3 weeks) right after the application as compared with control soil during rice cultivation, but did not significantly affect N₂O emissions. In addition, the maximum CH₄ reduction (82% reduction over control) was found at 10 ㎎ L<SUP>-1</SUP> ethephon application right after its addition for 3 weeks during rice cultivation. Rice productivity and yield properties were mainly affected by ethephon application, enhancing ripened grains and number of grains per panicle. Soil properties were not influenced by ethephon application except for available phosphate, which is probably due to enhanced root growth in rhizosphere soils. Conclusively, ethephon could be a new and pioneering amendment for reducing CH₄ emission in particular at the initial 3 weeks after the application without increasing other GHG emissions and enhancing rice productivity in paddy soils.

중환자실 입원 환자에서 Vancomycin 내성 장구균의 직장내 감시 배양 연구

김동림,유철웅,정희진,우흥정,김우주,김민자,박승철,최선주 대한감염학회 1999 감염 Vol.31 No.3

중환자실 입원환자에서 Vancomycin 내성 장구균의 직장내 감시 배양 연구

김동림,유철웅,정희진,우흥정,최선주,김우주,박승철 대한화학요법학회 2001 대한화학요법학회지 Vol.19 No.2

목적: 1990년대 들어 미국에서 중요한 원내 병원균으로 부각되고 있는 VRE는 대부분 항생제에 내성을 보이며 적절한 치료약제가 없는 실정이다. 국내에서 VRE의 빈도는 임상분리 장구균중 약 1%, 대변 배양검사에서 2-8%로 보고된 바 있다. 그러나 VRE 출현의 위험이 높은 중환자실에서 VRE 보균율에 대한 연구 결과는 없었다. 저자들은 본원에서 VRE의 임상 감염예가 발생되었던 중환자실 환자들을 대상으로 직장내 감시 배양을 시행하여 VRE의 보균율을 조사하고 VRE 보균에 관여하는 위험인자를 규명하여 VRE 감영 관리에 기본 자료로 삼고자 본 연구를 시행하였다. 대상 및 방법 : 1998년 8월부터 10주간 고대 구로 병원 중환자실엣 입원한 환자들을 대상으로 매주 1회 직장내 감시 배양을 시행하여 VRE의 보균율을 조사하였다. 직장 도말을 vancomycin 6㎍/mL이 포함함 Enterococcosel agar에 접종하여 VRE를 일차 검색하였다. 한천 회석법으로 vancomycin과 teicoplanin의 MIC를 측정하여 표현형을 결정하였고 PCR을 이용하여 vanA, vanB, vanC1, vanC2에 대한 유전형을 결정하였다. VRE 직장내 보균자와 비보균자간 임상 자료를 비교하여 VRE 보균에의 위험 인자들을 조사하였다. 결과 : 대상환자 93명중 22명 환자에서 26주의 VRE가 분리되어 23.7%의 직장내 보균율을 보였으나 조사기간 중 임상 감영은 없었다. 분리주중 E. faecium, E. gallinarum, E. casseliflavus는 VanC형을 표현형으로 나타내어 유전형과 일치하였다. 3명의 환자에서는 2개 이상의 균종이 분리되어 복합 보균이 있음을 알 수 있었다. VanA형VREF가 분리된 2명은 모두 기저 질환을 가지고 있엇고, 각각 중환자실 입원 32, 16일째에 VRE가 분리 동정되었다. VRE 직장내 보균에의 위험 인자로는 당뇨병, 중심 정맥 도관 장착, 동맥 도관의 장착, vancomycin사용의 기왕력 등의 유의하게 관련되어 있음을 알 수 있었다. 결론 : 본원 중환자실에서 직장내 감시 배양 연구 결과 VRE의 직장내 보균율은 23.6%였으나, 임상적으로 유의한 VanA형 VREF의 보균율은 2.2%(2/93) 였다. 따라서 출현 초기인 현 시점에서 국내 대학병원 중환자실 환자에서 VRE의 감염을 예방하기 위해 HICPAC에서 제시한 수칙을 준수하며, 특히 vancomycin의 사용을 제한해야 될 것으로 사료된다. Background : VRE (vancomycin-resistant enterococci) have been an important nosocomial pathogen in the United States in the 1990s. VRE are usually multidrug-resistant, and pose a therapeutic problems and dilemmas. In late 1990s, VRE have become an emerging nosocomial pathogen in Korea, but there have been a few studies on the epidemiologic investigation on the infection or colonization of VRE among hospitalized patients with high risk factors. The purpose of this study was to determine the prevalence of rectal colonization of VRE among patients hospitalized in the intensive care unit (ICU), to study the risk factors for nosocomial acquisition of VRE, and to obtain the baseline data for controlling the spread of VRE infection within the hospital. Methods : Between August 1 and October 12 (10 weeks) 1998, a prospective surveillance study was conducted in the ICU at Korea University, Guro Hospital. Surveillance rectal swab cultures for detecting VRE were obtained at weekly intervals among 93 patients admitted to the ICU during the study period. To obtain the VRE, rectal swab cultures were performed on Enterococcosel agar (BBL Microbiology Systems, Cockeysville, Md, USA) containing 6 ㎍/mL of vancomycin. Minimal inhibitory concentrations (MICs) of vancomycin and teicoplanin were determined by agar dilution method. For the genotyping of isolated VRE, detection of vanA, vanB, vanC1 and vanC2 gene by polymerase chain reaction was done. Patients harboring VRE were compared to patients who were not colonized with this organism to identify the risk factors associated with rectal colonization. Results : The rectal colonization rate of VRE among ICU patients was 23.6%(22/93patients), but there were no patients with VRE infection during the study period. Twenty-six strains of VRE, which were isolated from 22 patients, incluede 2 vanA E.feacium, 18 vanC1 E. gallinarum and 6 van C2 E. casseliflavus isolates. Therefore the colonization rate of clinically significant vanA genotype vancomycin-rexixitant E.faecium(VREF) was 2.2% (2/93 patients). Risk factors for rectal colonization of VRE included diabetes, catheterization of arterial and central venous lines, and vancomycin usage. Conclusions : This study demonstrated the low rectal colonization rate of clinically significant VREF (2.2%) among patients admitted to the ICU. This study suggested that maintaining HICPAC guidelines, restricted vancomycin usage and periodic surveillance in patients with high risk factors are important in preventing the emergence and spread of VRE infection among ICU patients in a university-affiliated hospital.