Stable numerical differentiation : when is it possible?

RAMM, ALEXANDER G.,SMIRNOVA, ALEXANDRA 한국산업정보응용수학회 2003 한국산업정보응용수학회 Vol.7 No.1

Two principally different statements of the problem of stable numerical differentiation are considered. It is analyzed when it is possible in principle to get a stable approximation to the derivative f' given noisy data f_(δ). Computational aspects of the problem are discussed and illustrated by examples. These examples show the practical value of the new understanding of the problem of stable differentiation.

Thermal comfort – an intercultural comparison

Iris Ramme,Tom Gillpatrick 한국마케팅과학회 2021 마케팅과학연구 Vol.31 No.1

Growing energy consumption together with the problem of increasing CO2 emissions are widely viewed as critical factors for achieving global sustainability. The Green Building Council has estimated that 39% of CO2 emissions come from buildings and that this percentage is increasing. While much of home energy consumption is related to heating and cooling there is little research on how consumers manage the temperature in their homes. This study examines residential consumer perceptions regarding thermal comfort with the objective of gaining insights on how to reduce energy consumption for heating or cooling homes. Thus, we would gain insights for achieving a more sustainable approach for energy consumption while considering ecological, economic, and social aspects.

STABLE NUMERICAL DIFFERENTIATION

ALEXANDER G. RAMM,ALEXANDRA SMIRNOVA 한국산업응용수학회 2003 Journal of the Korean Society for Industrial and A Vol.7 No.1

토양의 이화학적 특성과 대나무 생장과의 관계

정영관(Young Gwan Chung),Carl W . Ramm(Carl W . Ramm) 한국산림과학회 1990 한국산림과학회지 Vol.79 No.1

Canonical correlation analysis was used to relate 17 soil-site variables to bamboo diameter, height, and internodal characteristics. The first canonical correlation was highly significant, explained much of the variance in both sets of variables, and the canonical variates made sense biologically. Surface soil depth, total nitrogen and percent organic matter had high positive correlations with the first soil-site canonical variate. Clay content (%) and cation exchange capacity were negatively correlated with the first soil-site canonical variate. Only 8 of predictor variables were considered relevant for predicting bamboo growth.

INVERSE PROBLEM FOR A HEAT EQUATION WITH PIECEWISE-CONSTANT CONDUCTIVITY

Gutman, S.,Ramm, A.G. The Korean Society for Computational and Applied M 2010 Journal of applied mathematics & informatics Vol.28 No.3

We consider the inverse problem of the identification of a piecewise-constant conductivity in a bar given the extra information of the heat flux through one end of the bar. Our theoretical results show that such an identification is unique. This approach utilizes a "layer peeling" argument. A computational algorithm based on this method is proposed and implemented. The advantage of this algorithm is that it requires only 3D minimizations irrespective of the number of the unknown discontinuities. Its numerical effectiveness is investigated for several conductivities.

Multiple beam splitter using volumetric multiplexed Fresnel zone plates fabricated by ultrafast laser-writing.

Choi, Jiyeon,Ramme, Mark,Richardson, Martin Optical Society of America 2012 Optics letters Vol.37 No.16

<P>A simple approach to producing a 1N beam splitter is demonstrated by fabricating a volumetric multiplex phase Fresnel zone plate in bulk transparent material. This comprised four layers of zone plates created in borosilicate glass by femtosecond laser direct-writing, each shifted laterally relative to the illumination axis, creating four separate beamlets. Since the power transmitted in each beamlet is proportional to the diffraction efficiency of the corresponding zone plate, the power ratios can be customized by adjusting the fabrication parameters of each layer. This approach demonstrates the potential of femtosecond laser direct-writing for the fabrication of complex optical elements in transparent media as components of integrated monolithic photonic devices.</P>

Relationships between Soil-Site Properties and Bamboo (Phyllostachys bambusoides) Growth

정영관,Chung, Young Gwan,Ramm, Carl W. Korean Society of Forest Science 1990 한국산림과학회지 Vol.79 No.1

17개(個)의 토양인자(土壤因子)와 대나무의 직경(直徑), 간고(稈高) 그리고 절간(節間) 생장량(生長量)과의 관계(關係)를 구명(究明)하기 위하여 정준상관분석(正準相關分析)을 실시(實施)하였다. 첫번째 정준상관(正準相關)은 매우 유의적(有意的) 이었고, 변수(變數)의 2조합(組合)에서 분산(分散)은 크고, 그리고 정준변량(正準變量)은 생물학적(生物學的)으로 의의(意義)가 있었다. 따라서 표층토심(表層土深), 전질소(全窒素) 그리고 유기물함량(有機物含量)등은 첫번째 토양성질(土壤性質)의 정준변량(正準變量)과 매우높은 정(正)의 상관(相關)을 나타내었다. 그리고 점토함량(粘土含量)과 치환성용량(置煥性容量)은 부(負)의 상관(相關)으로 나타났다. 17개(個) 변수(變數) 가운데 8개(個) 변수(變數)만이 대나무의 생장(生長)을 예측(豫測)하는데 관계(關係)되는 것으로 사료(思料)된다. Canonical correlation analysis was used to relate 17 soil-site variables to bamboo diameter, height, and internodal characteristics. The first canonical correlation was highly significant, explained much of the variance in both sets of variables, and the canonical variates made sense biologically. Surface soil depth, total nitrogen and percent organic matter had high positive correlations with the first soil-site canonical variate. Clay content (%) and cation exchange capacity were negatively correlated with the first soil-site canonical variate. Only 8 of predictor variables were considered relevant for predicting bamboo growth.

담관 결찰에 의한 간섬유증 발생에서 비만세포 동원에 미치는 Stem Cell Factor의 역할

제갈승주,( Grant A. Ramm ) 대한임상검사과학회 2004 대한임상검사과학회지(KJCLS) Vol.36 No.2

Mast cells (MCs) have been implicated in the pathogenesis of tissue fibrosis. However, the role of MC in the development of liver fibrosis has not been fully elucidated. Stem cell factor (SCF) is known to recruit MCs to the liver following injury as it induces mast cell proliferation, survival and differentiation from resident tissue precursors. This study examines the interaction between activated hepatic stellate cells (HSCs) and MCs in rat fibrotic liver, and SCF production by HSCs during culture in vitro. Rats were studied 4, 7, 14 and 21 days after bile duct ligation (BDL). Fibrogenesis was assessed by a measurement of collagen stained with sirius red F3B. Activated HSCs and MCs were identified by α-smooth muscle actin (α-SMA) immunohistochemical and alcian blue staining and measured by a computerized image analysis system. SCF production was determined in rat HSC cultures using Western blotting. Mild fibrotic changes were noted in BDL rat livers as early as 4 days after induction of cholestasis. Significant expansion and organization of fibrous tissue has occurred in day 14 BDL rats which progressed to bridging fibrosis by day 21. In BDL rats, both a large number of activated HSCs and MCs were detected in portal tracts and fibrous septa. Both area of activated HSCs infiltration and density of MCs were significantly higher in all BDL group compared with Shams. In BDL rats, both areas of activated HSCs infiltration and density of MCs were no significant difference between day 4 and 7 and were significantly higher in day 14. However, the areas of activated HSCs infiltration were significantly lesser in day 21 and the densities of MCs were significantly higher in day 21 compared with day14 BDL. In BDL rats, both areas of activated HSCs infiltration and density of MCs were highly correlated with areas of fibrosis. Western blotting showed that SCF protein was consistently produced in activated HSCs by culture on plastic and freshly isolated HSCs expressed relatively little 30kD SCF compared to late primary culture activated HSCs (day 14) and passaged HSCs. These results suggest that HSCs activated in vitro produce SCF, and may play an important role in recruiting mast cells to the liver during injury and fibrosis.

INVERSE PROBLEM FOR A HEAT EQUATION WITH PIECEWISE-CONSTANT CONDUCTIVITY

S. Gutman,A.G. Ramm 한국전산응용수학회 2010 Journal of applied mathematics & informatics Vol.28 No.3

We consider the inverse problem of the identification of a piecewise-constant conductivity in a bar given the extra information of the heat flux through one end of the bar. Our theoretical results show that such an identification is unique. This approach utilizes a "layer peeling" argument. A computational algorithm based on this method is proposed and implemented. The advantage of this algorithm is that it requires only 3D minimizations irrespective of the number of the unknown discontinuities. Its numerical effectiveness is investigated for several conductivities.

탄소나노튜브의 유체유발 진동

최종운(Choi, Jong-Woon),길보람(Gil, Bo-Ramm),송오섭(Song, Oh-Seop) 한국소음진동공학회 2008 한국소음진동공학회 논문집 Vol.18 No.6

In this paper, flow-induced flutter instability of cantilever carbon nanotubes conveying fluid and modelled as a thin-walled beam is investigated. Non-classical effects of transverse shear and rotary inertia are incorporated in this study. The governing equations and the associated boundary conditions are derived through Hamilton's principle. Numerical analysis is performed by using extend Galerkin method which enables us to obtain more exact solutions compared with conventional Galerkin method. Cantilevered carbon nanotubes are damped with decaying amplitude for flow velocity below a certain critical value, however, beyond this critical flow velocity, flutter instability may occur. Variations of critical flow velocity with both radius ratio and length of carbon nanotubes are investigated and pertinent conclusion is outlined.