• Title/Summary/Keyword: Davies method

Search Result 19, Processing Time 0.023 seconds

Numerical simulation of upper convected maxwell fluid flow through planar 4:1 contraction (평면 4:1 수축을 지나는 어퍼 콘벡티트 맥스웰유체 유동의 수치 시뮬레이션)

  • 송진호;유정열
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.11 no.1
    • /
    • pp.160-169
    • /
    • 1987
  • Numerical simulation of the flow of upper convected Maxwell fluid through planar 4:1 contraction has been performed using type dependent difference apprximation of vorticity equation. For creeping flow assumption, the numerical convergence has been achieved up to much higher values of elasticity parameter than those obtained by conventional finite difference method. For non-vanishing Reynolds number flow, it is shown that the corner vortices disappear, which is in good qualitative agreement with extant experimental results. In doing so, spatial distributions of stream function, vorticity and stresses are considered in relation to change of type of vorticity.

Genetic association tests when a nuisance parameter is not identifiable under no association

  • Kim, Wonkuk;Kim, Yeong-Hwa
    • Communications for Statistical Applications and Methods
    • /
    • v.24 no.6
    • /
    • pp.663-671
    • /
    • 2017
  • Some genetic association tests include an unidentifiable nuisance parameter under the null hypothesis of no association. When the mode of inheritance (MOI) is not specified in a case-control design, the Cochran-Armitage (CA) trend test contains an unidentifiable nuisance parameter. The transmission disequilibrium test (TDT) in a family-based association study that includes the unaffected also contains an unidentifiable nuisance parameter. The hypothesis tests that include an unidentifiable nuisance parameter are typically performed by taking a supremum of the CA tests or TDT over reasonable values of the parameter. The p-values of the supremum test statistics cannot be obtained by a normal or chi-square distribution. A common method is to use a Davies's upper bound of the p-value instead of an exact asymptotic p-value. In this paper, we provide a unified sine-cosine process expression of the CA trend test that does not specify the MOI and the TDT that includes the unaffected. We also present a closed form expression of the exact asymptotic formulas to calculate the p-values of the supremum tests when the score function can be written as a linear form in an unidentifiable parameter. We illustrate how to use the derived formulas using a pharmacogenetics case-control dataset and an attention deficit hyperactivity disorder family-based example.

Carbon stocks and its variations with topography in an intact lowland mixed dipterocarp forest in Brunei

  • Lee, Sohye;Lee, Dongho;Yoon, Tae Kyung;Salim, Kamariah Abu;Han, Saerom;Yun, Hyeon Min;Yoon, Mihae;Kim, Eunji;Lee, Woo-Kyun;Davies, Stuart James;Son, Yowhan
    • Journal of Ecology and Environment
    • /
    • v.38 no.1
    • /
    • pp.75-84
    • /
    • 2015
  • Tropical forests play a critical role in mitigating climate change, and therefore, an accurate and precise estimation of tropical forest carbon (C) is needed. However, there are many uncertainties associated with C stock estimation in a tropical forest, mainly due to its large variations in biomass. Hence, we quantified C stocks in an intact lowland mixed dipterocarp forest (MDF) in Brunei, and investigated variations in biomass and topography. Tree, deadwood, and soil C stocks were estimated by using the allometric equation method, the line intersect method, and the sampling method, respectively. Understory vegetation and litter were also sampled. We then analyzed spatial variations in tree and deadwood biomass in relation to topography. The total C stock was 321.4 Mg C $ha^{-1}$, and living biomass, dead organic matter, and soil C stocks accounted for 67%, 11%, and 23%, respectively, of the total. The results reveal that there was a relatively high C stock, even compared to other tropical forests, and that there was no significant relationship between biomass and topography. Our results provide useful reference data and a greater understanding of biomass variations in lowland MDFs, which could be used for greenhouse gas emission-reduction projects.

Characteristics Detection of Hydrological and Water Quality Data in Jangseong Reservoir by Application of Pattern Classification Method (패턴분류 방법 적용에 의한 장성호 수문·수질자료의 특성파악)

  • Park, Sung-Chun;Jin, Young-Hoon;Roh, Kyong-Bum;Kim, Jongo;Yu, Ho-Gyu
    • Journal of Korean Society on Water Environment
    • /
    • v.27 no.6
    • /
    • pp.794-803
    • /
    • 2011
  • Self Organizing Map (SOM) was applied for pattern classification of hydrological and water quality data measured at Jangseong Reservoir on a monthly basis. The primary objective of the present study is to understand better data characteristics and relationship between the data. For the purpose, two SOMs were configured by a methodologically systematic approach with appropriate methods for data transformation, determination of map size and side lengths of the map. The SOMs constructed at the respective measurement stations for water quality data (JSD1 and JSD2) commonly classified the respective datasets into five clusters by Davies-Bouldin Index (DBI). The trained SOMs were fine-tuned by Ward's method of a hierarchical cluster analysis. On the one hand, the patterns with high values of standardized reference vectors for hydrological variables revealed the high possibility of eutrophication by TN or TP in the reservoir, in general. On the other hand, the clusters with low values of standardized reference vectors for hydrological variables showed the patterns with high COD concentration. In particular, Clsuter1 at JSD1 and Cluster5 at JSD2 represented the worst condition of water quality with high reference vectors for rainfall and storage in the reservoir. Consequently, SOM is applicable to identify the patterns of potential eutrophication in reservoirs according to the better understanding of data characteristics and their relationship.

Closed-code-conversion: Transforming Open Code Multi-staged Programs into Closed Ones (다단계 프로그램에서 프로그램 생성 단계의 자유변수 제거)

  • Eo, Hyun-Jun;Yi, Kwang-Keun
    • Journal of KIISE:Software and Applications
    • /
    • v.36 no.3
    • /
    • pp.244-251
    • /
    • 2009
  • We present a transformation which converts open-code multi-staged programs into closed ones. Staged computation, which explicitly divides a computation into separate stages, is a unifying framework for existing program generation systems. Because a multi-staged program generates another program, which can also generate a third program and on, the implementation of a multi-staged language is not straightforward. Dynamic binding of (lexically free) variables in code also makes the implementation of a multi-staged language hard. By converting each code into code of function which takes environment for free variables as its argument and giving an actual environment at the code-composition site, we can transform a open-code program into a closed-code one. Combining with Davies and Pfenning's method, our closed-code-conversion enables the implementation of the unstaged language to be useful for executing multi-staged programs. We also prove the correctness of our conversion: the converted program is equivalent to the original program, and the converted program does not have open code.

Model for Ionic Species Estimation in Soil Solutio (토양용액의 이온조성 추정모델)

  • Kim, Yoo-Hak;Yoon, Jung-Hui;Jung, Beung-Gan;Kim, Min-Kyun
    • Korean Journal of Soil Science and Fertilizer
    • /
    • v.34 no.3
    • /
    • pp.213-236
    • /
    • 2001
  • The ionic composition of soil solution is related to a nutrient uptake by plant. Many models for estimating ionic composition of solution have been developed, and most of them have been used for calculating a content of mineral and ionic species in a geochemical point of view. An approximation model considering both cation and anion in soil solution was developed. Variables such as pH, Eh, EC, cations(K, Ca, Mg. Na, Fe, Mn, Al, $NH_4{^+}$), anions(Si, S, P, CY, $NO_3{^-}$, $HCO_3{^-}$ and chemical equilibria of ionic species in soil solution were input into Excel sheet. The activities of soluble ion, ionpairs and complexes of input element were estimated by Newton-Raphson method using conditional equilibrium constant calculated by Davies equation and special models. Equilibrium contents of insoluble minerals and complexes were also calculated.

  • PDF

Performance of steel beams at elevated temperatures under the effect of axial restraints

  • Liu, T.C.H.;Davies, J.M.
    • Steel and Composite Structures
    • /
    • v.1 no.4
    • /
    • pp.427-440
    • /
    • 2001
  • The growing use of unprotected or partially protected steelwork in buildings has caused a lively debate regarding the safety of this form of construction. A good deal of recent research has indicated that steel members have a substantial inherent ability to resist fire so that additional fire protection can be either reduced or eliminated completely. A performance based philosophy also extends the study into the effect of structural continuity and the performance of the whole structural totality. As part of the structural system, thermal expansion during the heating phase or contraction during the cooling phase in most beams is likely to be restrained by adjacent parts of the whole system or sub-frame assembly due to compartmentation. This has not been properly addressed before. This paper describes an experimental programme in which unprotected steel beams were tested under load while it is restrained between two columns and additional horizontal restraints with particular concern on the effect of catenary action in the beams when subjected to large deflection at very high temperature. This paper also presents a three-dimensional mathematical modelling, based on the finite element method, of the series of fire tests on the part-frame. The complete analysis starts with an evaluation of temperature distribution in the structure at various time levels. It is followed by a detail 3-D finite element analysis on its structural response as a result of the changing temperature distribution. The principal part of the analysis makes use of an existing finite element package FEAST. The effect of columns being fire-protected and the beam being axially restrained has been modelled adequately in terms of their thermal and structural responses. The consequence of the beam being restrained is that the axial force in the restrained beam starts as a compression, which increases gradually up to a point when the material has deteriorated to such a level that the beam deflects excessively. The axial compression force drops rapidly and changes into a tension force leading to a catenary action, which slows down the beam deflection from running away. Design engineers will be benefited with the consideration of the catenary action.

Computational predictions of improved of wall mechanics and function of the infarcted left ventricle at early and late remodelling stages: comparison of layered and bulk hydrogel injectates

  • Kortsmit, Jeroen;Davies, Neil H.;Miller, Renee;Zilla, Peter;Franz, Thomas
    • Advances in biomechanics and applications
    • /
    • v.1 no.1
    • /
    • pp.41-55
    • /
    • 2014
  • Acellular intra-myocardial biomaterial injections have been shown to be therapeutically beneficial in inhibiting ventricular remodelling of myocardial infarction (MI). Based on a biventricular canine cardiac geometry, various finite element models were developed that comprised an ischemic (II) or scarred infarct (SDI) in left ventricular (LV) antero-apical region, without and with intra-myocardial biomaterial injectate in layered (L) and bulk (B) distribution. Changes in myocardial properties and LV geometry were implemented corresponding to infarct stage (tissue softening vs. stiffening, infarct thinning, and cavity dilation) and injectate (infarct thickening). The layered and bulk injectate increased ejection fraction of the infarcted LV by 77% (II+L) and 25% (II+B) at the ischemic stage and by 61% (SDI+L) and 63% (SDI+B) at the remodelling stage. The injectates decreased the mean end-systolic myofibre stress in the infarct by 99% (II+L), 97% (II+B), 70% (SDI+L) and 36% (SDI+B). The bulk injectate was slightly more effective in improving LV function at the remodelling stage whereas the layered injectate was superior in functional improvement at ischemic stage and in reduction of wall stress at ischemic and remodelling stage. These findings may stimulate and guide further research towards tailoring acellular biomaterial injectate therapies for MI.

An Exploratory Study on the Components of Visual Merchandising of Internet Shopping Mall (인터넷쇼핑몰의 VMD 구성요인에 대한 탐색적 연구)

  • Kim, Kwang-Seok;Shin, Jong-Kuk;Koo, Dong-Mo
    • Journal of Global Scholars of Marketing Science
    • /
    • v.18 no.2
    • /
    • pp.19-45
    • /
    • 2008
  • This study is to empirically examine the primary dimensions of visual merchandising (VMD) of internet shopping mall, namely store design, merchandise, and merchandising cues, to be a attractive virtual store to the shoppers. The authors reviewed the literature related to the major components of VMD from the perspective of the AIDA model, which has been mainly applied to the offline store settings. The major purposes of the study are as follows; first, tries to derive the variables related with the components of visual merchandising through reviewing the existing literatures, establish the hypotheses, and test it empirically. Second, examines the relationships between the components of VMD and the attitude toward the VMD, however, putting more emphasis on finding out the component structure of the VMD. VMD needs to be examined with the perspective that an online shopping mall is a virtual self-service or clerkless store, which could reduce the number of employees, help the shoppers search, evaluate and purchase for themselves, and to be explored in terms of the in-store persuasion processes of customers. This study reviewed the literatures related to store design, merchandise, and merchandising cues which might be relevant to the store, product, and promotion respectively. VMD is a total communication tool, and AIDA model could explain the in-store consumer behavior of online shopping. Store design has to do with triggering a consumer attention to the online mall, merchandise with a product related interest, and merchandising cues with promotions such as recommendation and links that induce the desire to pruchase. These three steps might be seen as the processes for purchase actions. The theoretical rationale for the relationship between VMD and AIDA could be found in Tyagi(2005) that the three steps of consumer-oriented merchandising are a store, a product assortment, and placement, in Omar(1999) that three types of interior display are a architectural design display, commodity display, and point-of-sales(POS) display, and in Davies and Ward(2005) that the retail store interior image is related to an atmosphere, merchandise, and in-store promotion. Lee et al(2000) suggested as the web merchandising components a merchandising cues, a shopping metaphor which is an assistant tool for search, a store design, a layout(web design), and a product assortment. The store design which includes differentiation, simplicity and navigation is supposed to be related to the attention to the virtual store. Second, the merchandise dimensions comprising product assortments, visual information and product reputation have to do with the interest in the product offerings. Finally, the merchandising cues that refer to merchandiser(MD)'s recommendation of products and providing the hyperlinks to relevant goods for the shopper is concerned with attempt to induce the desire to purchase. The questionnaire survey was carried out to collect the data about the consumers who would shop at internet shopping malls frequently. To select the subject malls, the mall ranking data announced by a mall rating agency was used to differentiate the most popular and least popular five mall each. The subjects was instructed to answer the questions after navigating the designated mall for five minutes. The 300 questionnaire was distributed to the consumers, 166 samples were used in the final analysis. The empirical testing focused on identifying and confirming the dimensionality of VMD and its subdimensions using a structural equation modeling method. The confirmatory factor analysis for the endogeneous and exogeneous variables was carried out in four parts. The second-order factor analysis was done for a store design, a merchandise, and a merchandising cues, and first-order confirmatory factor analysis for the attitude toward the VMD. The model test results shows that the chi-square value of structural equation is 144.39(d.f 49), significant at 0.01 level which means the proposed model was rejected. But, judging from the ratio of chi-square value vs. degree of freedom, the ratio was 2.94 which smaller than an acceptable level of 3.0, RMR is 0.087 which is higher than a generally acceptable level of 0.08. GFI and AGFI is turned out to be 0.90 and 0.84 respectively. Both NFI and NNFI is 0.94, and CFI 0.95. The major test results are as follows; first, the second-order factor analysis and structural equational modeling reveals that the differentiation, simplicity and ease of identifying current status of the transaction are confirmed to be subdimensions of store design and to be a significant predictors of the dependent variable. This result implies that when designing an online shopping mall, it is necessary to differentiate visually from other malls to improve the effectiveness of the communications of store design. That is, the differentiated store design raise the contrast stimulus to sensory organs to promote the memory of the store and to have a favorable attitude toward the VMD of a store. The results that navigation which means the easiness of identifying current status of shopping affects the attitude to VMD could be interpreted that the navigating processes via the hyperlinks which is characteristics of an internet shopping is a complex and cognitive process and shoppers are likely to lack the sense of overall structure of the store. Consequently, shoppers are likely to be alost amid shopping not knowing where to go. The orientation tool enhance the accessibility of information to raise the perceptive power about the store environment.(Titus & Everett 1995) Second, the primary dimension of merchandise and its subdimensions was confirmed to be unidimensional respectively, have a construct validity, and nomological validity which the VMD dimensions supposed to have a positive correlation with the dependent variable. The subdimensions of product assortment, brand fame and information provision proved to have a positive effect on the attitude toward the VMD. It could be interpreted that the more plentiful the product and brand assortment of the mall is, the more likely the shoppers to favor it. Brand fame and information provision as well affect the VMD attitude, which means that the more famous the brand, the more likely the shoppers would trust and feel familiar with the mall, and the plentifully and visually presented information could have the shopper have a favorable attitude toward the store VMD. Third, it turned out to be that merchandising cue of product recommendation and hyperlinks affect the VMD attitude. This could be interpreted that recommended products could reduce the uncertainty related with the purchase decision, and the hyperlinks to relevant products would help the shopper save the cognitive effort exerted into the information search and gathering, which could lead to a favorable attitude to the VMD. This study tried to sheds some new light on the VMD of online store by reviewing the variables mentioned to be relevant with offline VMD in the existing literatures, and tried to link the VMD components from the perspective of AIDA model. The effect size of the VMD dimensions on the attitude was in the order of the merchandise, the store design and the merchandising cues.It is said that an internet has an unlimited place for display, however, the virtual store is not unlimited since the consumer has a limited amount of cognitive ability to process the external information and internal memory. Particularly, the shoppers are likely to face some difficulties in decision making on account of too many alternative and information overloads. Therefore, the internet shopping mall manager should take into consideration the cost of information search on the part of the consumer, to establish the optimal product placements and search routes. An efficient store composition would be possible by reducing the psychological burdens and cognitive efforts exerted to information search and alternatives evaluation. The store image is in most part determined by the product category and its brand it deals in. The results of this study support this proposition that the merchandise is most important to the VMD attitude than other components, the manager is required to take a strategic approach to VMD. The internet users are getting more accustomed and more knowledgeable about the internet media and more likely to accept the internet as a shopping channel as the period of time during which they use the internet to shop become longer. The web merchandiser should be aware that the product introduction using a moving pictures and a bulletin board become more important in order to present the interactive product information visually and communicate with customers more actively, therefore leading to making the quantity and quality of product information more rich.

  • PDF