Examining the effects of early cost drivers on contingencies

The accuracy of early cost estimates is critical to the success of construction projects. The selected tender price (clients' building cost) is usually seen in previous research as a holistic dependent variable when examining early stage estimates. Unlike other components of construction cost, the amount of contingencies is decided by clients/consultants with consideration of early project information. Cost drivers of contingencies estimates are associated with uncertainty and complexity, and include project size, schedule, ground condition, construction site access, market condition and so on. A path analysis of 133 UK school building contracts was conducted to identify impacts of nine major cost drivers on the determination of contingencies by different clients/cost estimators. This research finds that gross floor area (GFA), schedule and requirement of air conditioning have statistically significant impacts on the contingency determination. The mediating role of schedule between gross floor area and contingencies (GFA→Schedule→Contingencies) was confirmed with the Soble test. The total effects of the three variables on contingencies estimates were obtained with the consideration of this indirect effect. The squared multiple correlation (SMC) of contingencies (=0.624) indicates the identified three variables can explain 62.4% variance of contingencies, and it is comparatively satisfactory considering the heterogeneity among different estimators, unknown estimating techniques and different projects

Parental influences on physical activity behavior in preschool children

Objective To evaluate a conceptual model linking parent physical activity (PA) orientations, parental support for PA, and PA behavior in preschool children. Methods Participants were 156 parent-child dyads from 13 child care centers in Queensland, Australia. Parents completed a questionnaire measuring parental PA, parental enjoyment of PA, perceived importance of PA, parental support for PA, parents' perceptions of competence, and child PA at home. MVPA while attending child care was measured via accelerometry. Data were collected between May and August of 2003. The relationships between the study variables and child PA were tested using observed variable path analysis. Results Parental PA and parents' perceptions of competence were positively associated with parental support for PA (β= 0.23 and 0.18, respectively, p<0.05). Parental support, in turn, was positively associated with child PA at home (β= 0.16, p<0.05), but not at child care (β= 0.01, p= 0.94). Parents' perceptions of competence was positively associated with both home-based and child care PA (β= 0.20 and 0.28, respectively, p<0.05). Conclusions Family-based interventions targeting preschoolers should include strategies to increase parental support for PA. Parents who perceive their child to have low physical competence should be encouraged to provide adequate support for PA. © 2009 Elsevier Inc.

Maternal psychological distress mediates the relationship between asthma and physician visits in a population-based sample of adolescents

Objective This study examined whether maternal psychological distress mediates the relationship between presence of adolescent asthma and number of physician visits, and whether the association between maternal psychological distress and physician visits is moderated by adolescent general health. Methods Data were obtained from the Mater University Study of Pregnancy and included 4025 adolescents. Path analysis was used to examine mediating and moderating effects. Results Maternal psychological distress was found to partially mediate the relationship between adolescent asthma and number of physician visits, accounting for 25% of the effect of adolescent asthma on physician visits (p = .046). There was no evidence to suggest that adolescent general health moderated the association between maternal psychological distress and physician visits (p = .093). Conclusions The findings suggest that maternal psychological distress is associated with increased physician visits, regardless of adolescents' general health. Lowering maternal psychological distress may serve to reduce health care utilization and costs among adolescents with asthma.

System dynamics model of the knowledge management process

To effectively manage the challenges being faced by construction organisations in a fast changing business environment, many organisations are attempting to integrate knowledge management (KM) into their business operations. KM activities interact with each other and form a process which receives input from its internal business environment and produces outputs that should be justified by its business performance. This paper aims to provide further understanding on the dynamic nature of the KM process. Through a combination of path analysis and system dynamic simulation, this study found that: 1) an improved business performance enables active KM activities and provide feedback and guidance for formulating learning-based policies; and 2) effective human resource recruitment policies can enlarge the pool of individual knowledge, which lead to a more conducive internal business environment, as well as a higher KM activity level. Consequently, the desired business performance level can be reached within a shorter time frame.

Mandatory naptimes in child care and children's nighttime sleep

Objectives To examine the relationship between mandatory naptimes in child care and children's nighttime sleep duration, both concurrently and 12 months later once in school. Methods A sample of 168 children (50-72 months; 55% males) attending licensed child care centers were observed across their morning and throughout their scheduled naptime. Mandatory naptime was determined as the period in which children were not permitted any alternative activity except lying on their bed. Teachers reported each child's napping in child care. Nighttime and total sleep duration was reported by parents at 2 time points, in child care and in the second semester of their first school year. General linear models were used to examine group differences in sleep duration between children experiencing 0 to 60 minutes and >60 minutes of mandatory naptime, adjusting for key confounders. Path analysis was conducted to test a mediation model in which mandatory naptime is associated with nighttime sleep duration through increased napping in child care. Results Children who experienced >60 minutes of mandatory naptime in child care had significantly less nighttime sleep than those with 0 to 60 minutes of mandatory naptime. This difference persisted at 12-month follow-up, once children were in school. Napping in child care mediated the relationship between mandatory naptime and duration of nighttime sleep. Conclusions Exposure to mandatory naptimes of >60 minutes in child care is associated with decreased duration of nighttime sleep that endures beyond child care attendance. Given the large number of children who attend child care, sleep practices within these settings present an important focus for child health.

Mapping genetic influences on ventricular structure in twins

Despite substantial progress in measuring the anatomical and functional variability of the human brain, little is known about the genetic and environmental causes of these variations. Here we developed an automated system to visualize genetic and environmental effects on brain structure in large brain MRI databases. We applied our multi-template segmentation approach termed "Multi-Atlas Fluid Image Alignment" to fluidly propagate hand-labeled parameterized surface meshes, labeling the lateral ventricles, in 3D volumetric MRI scans of 76 identical (monozygotic, MZ) twins (38 pairs; mean age = 24.6 (SD = 1.7)); and 56 same-sex fraternal (dizygotic, DZ) twins (28 pairs; mean age = 23.0 (SD = 1.8)), scanned as part of a 5-year research study that will eventually study over 1000 subjects. Mesh surfaces were averaged within subjects to minimize segmentation error. We fitted quantitative genetic models at each of 30,000 surface points to measure the proportion of shape variance attributable to (1) genetic differences among subjects, (2) environmental influences unique to each individual, and (3) shared environmental effects. Surface-based statistical maps, derived from path analysis, revealed patterns of heritability, and their significance, in 3D. Path coefficients for the 'ACE' model that best fitted the data indicated significant contributions from genetic factors (A = 7.3%), common environment (C = 38.9%) and unique environment (E = 53.8%) to lateral ventricular volume. Earlier-maturing occipital horn regions may also be more genetically influenced than later-maturing frontal regions. Maps visualized spatially-varying profiles of environmental versus genetic influences. The approach shows promise for automatically measuring gene-environment effects in large image databases.

Genetic influences on brain asymmetry: A DTI study of 374 twins and siblings

Brain asymmetry, or the structural and functional specialization of each brain hemisphere, has fascinated neuroscientists for over a century. Even so, genetic and environmental factors that influence brain asymmetry are largely unknown. Diffusion tensor imaging (DTI) now allows asymmetry to be studied at a microscopic scale by examining differences in fiber characteristics across hemispheres rather than differences in structure shapes and volumes. Here we analyzed 4. Tesla DTI scans from 374 healthy adults, including 60 monozygotic twin pairs, 45 same-sex dizygotic pairs, and 164 mixed-sex DZ twins and their siblings; mean age: 24.4 years ± 1.9 SD). All DTI scans were nonlinearly aligned to a geometrically-symmetric, population-based image template. We computed voxel-wise maps of significant asymmetries (left/right differences) for common diffusion measures that reflect fiber integrity (fractional and geodesic anisotropy; FA, GA and mean diffusivity, MD). In quantitative genetic models computed from all same-sex twin pairs (N=210 subjects), genetic factors accounted for 33% of the variance in asymmetry for the inferior fronto-occipital fasciculus, 37% for the anterior thalamic radiation, and 20% for the forceps major and uncinate fasciculus (all L > R). Shared environmental factors accounted for around 15% of the variance in asymmetry for the cortico-spinal tract (R > L) and about 10% for the forceps minor (L > R). Sex differences in asymmetry (men > women) were significant, and were greatest in regions with prominent FA asymmetries. These maps identify heritable DTI-derived features, and may empower genome-wide searches for genetic polymorphisms that influence brain asymmetry.

Positive psychological strengths and school engagement in primary school children

A sizeable body of research has investigated the impact of specific character strengths or traits on significant outcomes. Some recent research is beginning to consider the effects of groups of strengths, combined as a higher order variable, and termed covitality. This study investigated the combined influence of four positive character traits: gratitude, optimism, zest and persistence, upon school engagement, within a sample of 112 Australian primary school students. The combined effect of these four traits, in defining covitality as a higher or second order factor within a path analysis, was found to predict relatively higher levels of school engagement and pro-social behaviour.

Online grocery shopping: The impact of shopping frequency on perceived risk

Online grocery shopping has enjoyed strong growth and it is predicted this channel will continue to grow exponentially in the coming years. While online shopping has attracted an abundance of research interest, examinations of online grocery shopping behaviour are only now emerging. Shopping online for groceries differs considerably from general online shopping due to the perishability and variability of the product, and frequency of the shopping activity. Two salient gaps underpin this research into online grocery shopping. This study responds to calls to investigate the online shoppers’ experience in the context of online purchasing frequency. Second, this study examines the mediating effect of perceived risk between trust and online repurchase intention of groceries. An online survey was employed to collect data from shoppers who were recruited from a multi-channel grocery e-retailer’s database. The online survey, comprising 16 reflective validated scale items, was sent to 555 frequent and infrequent online grocery shoppers. Results find that while customer satisfaction predicts trust for both infrequent and frequent online grocery shoppers, perceived risk fully mediates the effect of trust on repurchase intentions for infrequent online grocery shoppers. Furthermore path analysis reveals that the developed behavioural model is variant across both groups of shoppers. Theoretically, we provide a deeper understanding of the online customer experience, while gaining insight into two shopper segments identified as being important to grocery e-retailers. For managers, this study tests an online customer behavioural model with actual purchasing behaviour and identifies the continued presence of perceived risk in grocery e-retailing regardless of purchase frequency or experience.

Negative experiences and donor return: An examination of the role of asking for something different

BACKGROUND Negative donation experiences, including vasovagal reactions, deter donor retention. However, whether this deterrence effect varies as a function of whole blood (WB) donation history and requests to donate the same or a different product remains unclear. STUDY DESIGN AND METHODS The responses of 894 eligible WB donors who had been approached to convert to plasmapheresis and 954 eligible first-time plasmapheresis donors who had been surveyed on their last donation experience and their intention to donate plasma were considered. This information was matched with individual vasovagal reaction records, deferral category, WB donation history, and subsequent donation behavioral data obtained from the blood collection agency. RESULTS Path analysis indicated that the application of a deferral and an officially recorded vasovagal reaction decreased donors' intentions to continue plasmapheresis donation, but had no effect on WB donors' intentions to convert to plasmapheresis. Consistent with past findings, vasovagal reactions occurred more frequently with female and inexperienced donors. CONCLUSION Experiencing vasovagal reactions and deferrals may not universally deter donors from continuing to donate. Rather, the offer to convert to another form of donation—in this instance, plasmapheresis—after experiencing a negative donation event while donating WB may be sufficient to eliminate the deterrence effect on retention.

Entre o roteiro e a viagem: famílias e crianças pelo caminho

O tema central da pesquisa foi pensar a família partindo do ponto de vista de crianças: como crianças, enquanto sujeitos sociais que são, estão compreendendo e experimentando o que é família. A ideia de entrevistar crianças partiu da suposição de que estas estão vivenciando muitos modelos de famílias diferentes dos tradicionais e, possivelmente, sem o cunho de novidade, diferença ou estranheza. Acreditamos que escutar as crianças é justamente alcançar um discurso que não ocupa um lugar de destaque, um lugar oficial, mas nem por isso é menos importante. Levando em consideração a tensão entre entender criança como faixa etária e pensar através de um devir-criança que pode estar em qualquer um de nós, optamos por entrevistar 22 crianças de idade entre 6 e 11 anos, contabilizando 6 grupos. Inspirada na Cartografia, que compreende a pesquisa como ocorrendo num espaço do meio, onde não há polos estáveis sujeito-objeto, mas que a pesquisa se constrói em conjunto. Essa perspectiva nos fez eleger como dispositivo o formato de entrevistas em grupo, onde era pedido que desenhassem sua própria família ou uma família. Para as crianças entrevistadas, a vivência pessoal parece ser o molde para a construção do sentimento de união e pertinência que se carrega ao longo da vida, cujos critérios variam de acordo com as histórias de cada um. A noção de processo de subjetivação presente no pensamento de Michel Foucault foi importante instrumento conceitual para compreender as ideias de famílias que emergiram dos depoimentos das crianças entrevistadas. Percebemos através das afirmações dessas crianças que há um jogo onde elas experimentam possibilidades de sentido para conjugar aspectos que consideram importantes do que seja família: afeto, convivência, relações sanguíneas, que se combinam no que denominamo s camadas de família. As crianças parecem gozar de certa liberdade para inventar e definir categorias, testando também critérios comuns cotidianos que ajudam a incluir e/ou excluir membros. Foi marcante uma extrema flexibilidade na escolha dos critérios, um momento devir-criança, aberto a novas possibilidades, ao singular que se criava na interação coletiva. Ao focalizarmos os critérios sugeridos pelas crianças, ficamos com a impressão de que elas nos oferecem um olhar mais rizomático (Deleuze e Guattari) em direção às famílias. O trabalho incorpora uma análise do percurso da pesquisa que descartou questões e priorizou outras, a partir da análise de implicação da pesquisadora no processo desde que a pesquisa começou a ser pensada até a intervenção realizada.

Violência entre parceiros íntimos: um fator de risco para a insegurança alimentar domiciliar?

O primeiro objetivo da Tese consistiu na identificação e caracterização dos instrumentos de aferição epidemiológicos que vêm sendo propostos para a abordagem de IA domiciliar, bem como na síntese de suas propriedades psicométricas. Para tal, realizou-se busca sistemática em três bases de dados eletrônicas: MEDLINE, LILACS e SciELO. Não houve delimitação do período de publicação. Os resultados são apresentados no artigo intitulado Household food insecurity: a systematic review of the measuring instruments used in epidemiological studies. Foram identificados 24 instrumentos, todos breves e de fácil aplicação. A maioria foi desenvolvida nos Estados Unidos. O instrumento HFSSM apresentou o maior número de estudos de utilização e psicométricos, podendo ser recomendado sem hesitação. O segundo e principal objetivo desta Tese foi avaliar se a ocorrência de violência psicológica e física entre parceiros íntimos pode ser considerada um fator de risco para a ocorrência de Insegurança Alimentar (IA) domiciliar. As informações que subjazem a pesquisa originaram-se de um inquérito domiciliar realizado no Distrito de Campos Elíseos, Município de Duque de Caxias, entre abril a novembro de 2010. A população de estudo foi selecionada por meio de amostragem por conglomerados em três estágios (setor censitário, domicílio, indivíduo) com técnicas de amostragem inversa para a seleção dos domicílios. A amostra do estudo incluiu 849 mulheres que no período da entrevista relataram possuir algum relacionamento amoroso nos 12 meses anteriores. As informações foram obtidas por meio de entrevista utilizando-se um questionário estruturado, contendo instrumentos previamente validados, como a Revised Conflict Tatics Scales (CTS2) para a mensuração das violências e a Escala Brasileira de Insegurança Alimentar (EBIA) para a IA domiciliar. Utilizou-se a análise de caminhos (Path Analysis) na análise de dados o que permitiu explorar as relações entre as violências, entre estas e o Transtorno Mental Comum (TMC), este último e a IA, bem como as relações mais distais do modelo teórico. Os resultados são apresentados no artigo intitulado Violência entre parceiros íntimos, transtornos mentais comuns e insegurança alimentar: modelagem de equações estruturais. A hipótese central deste estudo foi corroborada, na medida em que tanto a violência psicológica, como a violência física se mostraram importantes fatores de risco para a IA, via a ocorrência de TMC. Contrariamente ao esperado, notou-se um maior efeito da violência psicológica do que da violência física na ocorrência do desfecho. Espera-se que a divulgação dos resultados desta Tese auxilie os profissionais e gestores na área de segurança alimentar e nutricional, bem como pesquisadores da área na tomada de decisões em relação ao instrumento de aferição a ser utilizado para a caracterização das situações e ampliem o olhar sobre o problema, incorporando outros fatores de risco, tais como as violências entre parceiros íntimos, aqueles estritamente econômicos, habitualmente considerados no debate sobre os determinantes e estratégias de enfrentamento da IA.

基于路径分析的死循环检测

提出了一种自动检测C语言程序中是否含有死循环的方法.该方法基于程序分析技术,包括循环展开和路径可行性分析技术.该方法首先通过遍历控制流图生成待查循环的检验路径;之后通过分析检验路径的可行性以及路径之间的联系,判断这些路径是否符合死循环模式.在此方法基础上实现了原型工具LoopAnalyzer,并对一组基准程序进行测试.实验结果表明此工具能有效地检测出C语言程序中的死循环,并且准确率较高.

黄土丘陵沟壑区纸坊沟小流域农业生态安全态势变化的驱动力分析

以黄土丘陵沟壑区纸坊沟小流域为研究对象,利用1985—2006年调查和监测资料,综合现有研究成果,将主成分分析和通径分析方法相结合,分析可能影响农业生态安全态势变化的各因子,探讨农业生态安全态势变化的驱动力。结果表明:自然条件是影响黄土丘陵沟壑区纸坊沟小流域农业生态安全态势变化的基础,人文社会经济条件是其变化的主要驱动力,具体可归纳为经济发展、人口压力、流域产业结构调整和农业科技进步4类因子;此外,国家和区域的相关政策、农业产业链与资源量相关度对农业生态安全也有一定影响。

基于栅格邻域可视性相关的最优路径问题的研究

基于可视性的最优路径分析是地形可视性分析中的一项基本功能，属于空间决策支持的范畴，在理论研究和实际应用两方面都具有重要的意义。在传统基于可视性的最优路径分析中，影响通行能力的可视性代价信息为相互独立的0维数值。然而，用0维无关的代价来表示三维地形上点的可视性信息是不全面的，有必要采用一维或更高维的代价表达方式。本文用二维视域来描述三维可视性信息，考虑到邻近点的二维视域相互重叠造成的可视性相关性对最优路径搜索的影响，提出基于栅格邻域可视性相关的最优路径问题。本文对该问题的分类和求解进行了详细的分析和讨论。 本文的创新性工作如下： (1) 改进了传统基于可视性的最优路径搜索问题。对于存在的“真实性”不足之处，考虑地形特征如土地覆盖或土地利用，障碍物及坡度等对通行能力的影响，并将这些影响和可视性信息一起添加到传统的基于可视性的最优路径搜索过程中，所得结果更加符合实际情况。 (2) 提出并求解了一类基于栅格邻域可视性相关的最优路径问题：基于平均视距最小/最大的可视覆盖路径问题。在可视覆盖最优和路径长度最优两个约束条件下，用代表路径平均视野的开阔程度的平均视距来衡量最优可视覆盖路径问题的最优性。通过对平均视距及该类问题目标函数进行建模分析以及预先计算并存储整个地形上的视域信息，用基于视域融合操作的模拟退火算法实现了该类问题的求解。 (3) 提出并求解了一类基于栅格邻域可视性相关的最优路径问题：最小可视覆盖路径问题。在只考虑可视覆盖最优的约束条件下，用代表路径视野开阔程度即“可视覆盖面积”来衡量最优可视覆盖路径问题的最优性。通过对问题目标函数建模及求解方法的比较分析，用Dijkstra算法实现了该类问题的求解。 最后，本文比较了基于栅格邻域可视性相关的和传统基于可视性无关的最不可视路径问题得到的结果。通过对新方法和传统方法应用于求解走私路径所得结果的定量和定性的分析与对比，得出新方法比传统方法准确的结论。