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S. M. A. Ne`mati,M. Ghassemi,A. Shahidian 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
Among other applications, Magnetic nanoparticles (MNPs) are used as drug carriers for guided drug delivery purposes. The aim of the current study is to numerically investigate the effect of non-uniform magnetic field on the blood flow and MNPs concentration inside a vessel. The coupled governing equations under the influence of non-uniform magnetic field are utilized and non-dimensionalized. Two dimensionless parameters, Magnetic force number (MFN) and Magnetic drift number (MDN), are introduced and their effects on the blood flow velocity and the MNPs concentration are studied. The results show for the same magnetic force number, the MNPs concentration on the vessel wall increases as the magnetic drift number increases. While under the same magnetic drift number, magnetic nanoparticles decreases as magnetic force number increases. This implies that the MNPs concentration at the entrance is low while MNPs radius is large. In addition, the greater the magnetic force and the magnetic drift numbers is the higher the deformation of streamlines becomes.
J.Soltani,M.Ghassemi,G. Reza Arab Markadeh 전력전자학회 2004 ICPE(ISPE)논문집 Vol.- No.-
This paper describes a sliding-mode(SM) torque control for an interior type Permanent synchronous motor (IPMSM) based on space vector modulation (SVM).The motor drive is supplied by a two-level SV-based PWM inverter, so that the inverter reference voltage is generated by two integral types sliding mode(SM) controllers in a stationary two axes reference frame. In addition, the rotor speed and rotor position are on-line estimated by a sliding-mode observer, which uses only the stator currents and voltages. The observer stability is proved by Lyapunov theory. The control strategies of maximum torque per ampere (MTPA) related to IPMSM, in<br/> constant torque region and the flux weakening operation in constant power region are considered. Computer simulation results obtained, well demonstrate the effectiveness of the proposed control approach.
<i>In situ</i> observation of morphological change in CdTe nano- and submicron wires
Davami, Keivan,Ghassemi, Hessam M,Sun, Xuhui,Yassar, Reza S,Lee, Jeong-Soo,Meyyappan, M IOP Pub 2011 Nanotechnology Vol.22 No.43
<P>We report growth and characterization of CdTe wires 30–400 nm in diameter by the vapor–liquid–solid technique. Individual nanowires were placed on a movable piezotube, which allowed three-dimensional motion toward a scanning tunneling microscope (STM). A bias was applied to the STM tip in contact with the nanowire, and the morphological changes due to Joule heating were observed <I>in situ</I> using a transmission electron microscope (TEM) in real time. For thick CdTe wires (<I>d</I> > ∼ 150 nm), the process results in the growth of superfine nanowires (SFNWs) of 2–4 nm diameter on the surface of the wire. Smaller diameter nanowires, in contrast, disintegrate under the applied bias before the complete evolution of SFNWs on the surface. </P>
A computational and experimental investigation of the mechanical properties of single ZnTe nanowires
Davami, Keivan,Mortazavi, Bohayra,Ghassemi, Hessam M.,Yassar, Reza S.,Lee, Jeong-Soo,Ré,mond, Yves,Meyyappan, M. The Royal Society of Chemistry 2012 Nanoscale Vol.4 No.3
<P>One-dimensional nanostructures such as ZnTe, CdTe, Bi(2)Te(3) and others have attracted much attention in recent years for their potential in thermoelectric devices among other applications. A better understanding of their mechanical properties is important for the design of devices. A combined experimental and computational approach has been used here to investigate the size effects on the Young's modulus of ZnTe nanowires (NWs). The mechanical properties of individual ZnTe nanowires in a wide diameter range (50-230 nm) were experimentally measured inside a high resolution transmission electron microscope using an atomic force microscope probe with the ability to record in situ continuous force-displacement curves. The in situ observations showed that ZnTe NWs are flexible nanostructures with the ability to withstand relatively high buckling forces without becoming fractured. The Young's modulus is found to be independent of nanowire diameter in the investigated range, in contrast to reported results for ZnO NWs and carbon nanotubes where the modulus increases with a decrease in diameter. Molecular dynamics simulations performed for nanowires with diameters less than 20 nm show limited size dependence for diameters smaller than 5 nm. The surface atoms present lower Young's modulus according to the simulations and the limited size dependency of the cylindrical ZnTe NWs is attributed to the short range covalent interactions.</P>
기상 빅 데이터와 지리정보시스템을 이용한 이탈리안 라이그라스의 수량예측
김문주,오승민,김지융,이배훈,팽경룬,김시철,베페카두 체메레,가세미 네자드 잘일,김경대,조무환,김병완,성경일,Kim, Moonju,Oh, Seung Min,Kim, Ji Yung,Lee, Bae Hun,Peng, Jinglun,Kim, Si Chul,Chemere, Befekadu,Nejad, Jalil Ghassemi,Kim, Kyeong Dae,Jo, M 한국초지조사료학회 2017 한국초지조사료학회지 Vol.37 No.2
본 연구의 목적은 이탈리안 라이그라스의 수량예측모형을 구축하고, 지리정보시스템을 이용하여 재배지역의 예측건물수량을 맵핑하는 것이다. 본 연구를 수행하기 위해 첫째, 풀사료 자료를 수집하였고, 둘째, 빅 데이터인 기상정보는 기상청(KMA)으로부터 재배지와 연도를 기준으로 수집하였다. 셋째, 수량에 영향을 미치는 기상 레이어는 지리정보시스템을 사용하여 생성하였다. 넷째, 수량예측방정식은 기상레이어를 계산하기 위해 추정하였다. 마지막으로 수량예측모형은 적합도와 예측력 면에서 평가하였다. 그 결과, 모형 적합도(R2)은 재배지에 따라 27%부터 95%까지 나타났다. 수원의 경우(지역 중 가장 큰 표본, n=321), 모형은 DMY = 158.63AGD -8.82AAT +169.09SGD - 8.03SAT +184.59SRD -13,352.24(DMY: Dry Matter Yield, AGD: Autumnal Growing Days, SGD: Spring Growing Days, SAT: Spring Accumulated Temperature, SRD: Spring Rainfall Days)이었다. 수원의 평균 DMY(9,790kg/ha)에 대해 수량예측모형은 $9,790{\pm}120$(kg/ha)로 예측하였다. 이러한 결과는 지리정보시스템에 의해 기상레이어를 누적하여 지도 위에 생성하였다. 이탈리안 라이그라스 수량은 제주를 제외하면 해안보다 내륙에서 높게 나타났다. 이탈리안 라이그라스는 약한 내한성 때문에 산지가 많은 북동부에서는 분포가 나타나지 않았다. 본 연구에서 비록 제한된 재배지에서 수량예측모형을 구축하고 맵핑하였지만, 우리나라의 기상정보를 적용하면 전국으로 확대가 가능할 것으로 생각된다. This study was aimed to find yield prediction model of Italian ryegrass using climate big data and geographic information. After that, mapping the predicted yield results using Geographic Information System (GIS) as follows; First, forage data were collected; second, the climate information, which was matched with forage data according to year and location, was gathered from the Korean Metrology Administration (KMA) as big data; third, the climate layers used for GIS were constructed; fourth, the yield prediction equation was estimated for the climate layers. Finally, the prediction model was evaluated in aspect of fitness and accuracy. As a result, the fitness of the model ($R^2$) was between 27% to 95% in relation to cultivated locations. In Suwon (n=321), the model was; DMY = 158.63AGD -8.82AAT +169.09SGD - 8.03SAT +184.59SRD -13,352.24 (DMY: Dry Matter Yield, AGD: Autumnal Growing Days, SGD: Spring Growing Days, SAT: Spring Accumulated Temperature, SRD: Spring Rainfall Days). Furthermore, DMY was predicted as $9,790{\pm}120$ (kg/ha) for the mean DMY(9,790 kg/ha). During mapping, the yield of inland areas were relatively greater than that of coastal areas except of Jeju Island, furthermore, northeastern areas, which was mountainous, had lain no cultivations due to weak cold tolerance. In this study, even though the yield prediction modeling and mapping were only performed in several particular locations limited to the data situation as a startup research in the Republic of Korea.