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Polina A. Volkova,Nikita P. Tikhomirov,Maria O. Ivanova,Ivan A. Dadykin,Yury O. Kopylov-Guskov,Alexander A. Bobrov 국립중앙과학관 2019 Journal of Asia-Pacific Biodiversity Vol.12 No.4
Floristic subdivision of the northern part of the Kuril archipelago (Russian Far East) remains controversial. Such uncertainty in biogeographical subdivision could be caused by insufficient floristic data dueto poor accessibility of mainly uninhabited northern Kuril islands. We aimed to explore the flora of thelargest uninhabited northern Kuril island Onekotan to clarify its position in floristic subdivision. All the19 species that we added to the known flora of Onekotan island grow on Paramushir and often on someother northern Kurils. Additionally, we revealed two species (Minuartia rubella and Poa lanata) that arenew for the whole Kuril archipelago. Our findings demonstrated that floristic similarity between Onekotanand the both large northern continental Kuril islands (Shumshu and Paramushir) is higher than itwas demonstrated before. However, discussion of floristic subdivision of the Northern Kurils is prematureunless all the islands are sufficiently studied.
Polina Angelova,Ivo Kehayov,Edgar G. Ordonez-Rubiano,Luisa F. Figueredo,Dora Zlatareva 대한신경손상학회 2023 Korean Journal of Neurotrauma Vol.19 No.2
Severe traumatic brain injury (TBI) is often associated with diffuse axonal injury. Diffuse axonal injury affecting the corpus callosum may present with intraventricular hemorrhage on baseline computed tomography (CT) scan. Posttraumatic corpus callosum damage is a chronic condition that can be diagnosed over the long term using various magnetic resonance imaging (MRI) sequences. Here, we present two cases of severe survivors of TBI with isolated intraventricular hemorrhage detected on an initial CT scan. After acute trauma management, long-term follow-up was performed. Diffusion tensor imaging and subsequent tractography revealed a significant decrease in the fractional anisotropy values and the number of corpus callosum fibers compared with those in healthy control patients. This study presents a possible correlation between traumatic intraventricular hemorrhage on admission CT and long-term corpus callosum impairment detected on MRI in patients with severe head injury by presenting demonstrative cases and conducting a literature review.
Polina A. Volkova,Maria O. Ivanova,Ivan A. Dadykin,Nikita P. Tikhomirov,Maxim Y. Grigoryan,Yurii O. Kopylov-Guskov,Alexander A. Bobrov 국립중앙과학관 2020 Journal of Asia-Pacific Biodiversity Vol.13 No.4
Flora of the southern Kuril continental islands is extremely diverse due to the complex history of geologyand climate,fluctuating connections with other territories in the past, and the habitat diversity of thearchipelago. It is likely well-investigated due to the long history of botanical studies, andfloristicfindingsare expected only in taxonomically difficult plant groups. To test this assumption, we carried out a specialinvestigation of the aquatic vascular plants on the Lesser Kuril Ridge (isl. Shikotan, Polonskogo, Yurii,Tanfilieva, Zelyonyi) and isl. Kunashir. In line with our expectations, we revealed nine taxa that havenever been reported for the whole Kuril archipelago (including six new for Sakhalinfloristic province ofRussia:Potamogeton manchuriensis,P.sparganiifolius, P.variifolius, P.vepsicus, Sagittaria aginashi,Sparganium subglobosum); all of them are aquatic ones. We found 24 species that are new for the LesserKuril Ridge or the whole Southern Kurils from which only about a half were aquatic. Unexpectedly, wefound 53 mainly terrestrial species that are new for the Little Kurils (the Lesser Kuril Ridge withexception of isl. Shikotan), and substantially supplementedfloristic lists of each island.
On Application of the Conjugate-Gradient Method to Static Analysis of HDD Slider
Polina Veniaminovna Khan,Pyung Hwang 한국트라이볼로지학회 2004 한국트라이볼로지학회 학술대회 Vol.38 No.-
The object of the present work is the numerical analysis of the computer hard disk slider. The pressure between slider and disk surfaces is calculated using the Boundary Fitted Coordinate System and Divergence Formulation for the nonlinear Reynolds' equation solution. The optimization scheme is applied to locate the steady state position of the slider. Negative pressure femto-slider with five pads is considered as an example. The steady state position of the slider is studied as a function of the disk radius. It is found that the line search accuracy has significant influence on effectiveness of the conjugate gradient method. The curve fitting method is applied in the line search to achieve high accuracy with reasonable number of objective function evaluation.
Relation Between Zn Additions, Microstructure and Corrosion Behavior of New Wrought Mg-5Al Alloys
Polina Metalnikov,Guy Ben‑Hamu,Kwang Seon Shin University 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.6
In the present study, the effect of varying Zn additions (0.93–3.16 wt%) on the corrosion resistance of wrought Mg-5Al alloyswas studied and related to the microstructure changes. Three secondary phases were found: Al–Mn, β-Mg17Al12 enrichedwith Zn, and Φ-Mg21(Al, Zn)17; the latter observed only in alloys with relatively high Zn content. The corrosion behaviorin short periods of immersion is related to pitting corrosion, and strongly influenced by micro-galvanic effects between thesecondary phase particles and the α-Mg matrix. In long periods of immersion, a protective layer is formed, and filiformcorrosion observed for alloys with Zn content above 1 wt%. However, the micro-galvanic effects still play a crucial role indeterioration of corrosion resistance in alloys with relatively high Zn content. These effects depend on the cathodic behaviorof the particles, and on the total number of the particles presented on the alloy’s surface.
Finite Element Analysis of Dynamic Characteristics of Negative Pressure Hard Disk Drive Air Slider
Polina Khan(콴 폴리냐),Pyung Hwang(황평) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
The effect of disk rotation speed on hard disk drive air slider characteristics is studied by using the finite element method. The negative pressure femto sized slider is considered. The perturbation method is utilized to calculate the dynamic coefficients. It is found that increasing the disc rotation speed from 7,200 rpm to 10,000 rpm decreases the air bearing stiffness and damping
Polina Khan,Pyung Hwang,Sang-Shin Park 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
An expanded scheme of direct numerical solution method for solving the Reynolds' equation in the boundary fitted coordinate systems for the gas lubrication with ultra low clearance is presented. Skewed slider is calculated by this scheme and results are compared to the original direct numerical solution. The modified scheme has advantages in stability in high compressibility number region. At the lower A region the difference in results of original and modified method is several percents.
Dynamic Characteristics of HDD Slider by Perturbated Direct Numerical Method
Polina V. Khan,Pyung Hwang 한국트라이볼로지학회 2003 한국트라이볼로지학회 학술대회 Vol.37 No.-
The static and dynamic characteristics of HDD slider with ulta-low flying height are analyzed using Direct Numerical method with Boundary Fitted Coordinate System. The slip flow effect is considered using the Boltzmann equation solution in a form of the flow rate database. The air film stiffness and damping are evaluated by the small perturbation method.
음압 직각 다공질 공기베어링의 동특성에 관한 유한차분 해석
콴폴리냐(Polina Khan),이춘무(Chun Moo Lee),김은효(Eun Hyo Kim),황평(Pyung Hwang) 한국트라이볼로지학회 2006 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.22 No.2
The numerical analysis of the negative pressure porous gas bearings is presented. The pressure distribution is calculated using the finite difference method. The Reynolds equation and Darcy's equation are solved simultaneously. The air bearing stiffness and damping are evaluated using the perturbation method. Rectangular uniform grid is employed to model the bearing. The vacuum preloading is considered. The pressure in the vacuum pocket is assumed to be a constant negative pressure. The total load, stiffness, damping and flow rate are calculated for several geometrical configurations and several values of negative pressure. It is found that too large vacuum pocket can result in negative total force.