Modeling of work envelope requirements in the piping and steel trades and the influence of global anthropomorphic characteristics

Limited and unavailable workspace for crews on the jobsite results in losses of productivity. With the increased usage of Building Information Modeling (BIM) in the construction industry, four dimensional animation that brings together the three dimensional model of a building and its construction schedule to visualize construction process is emerging. To support space planning in the preconstruction management, this research provides a framework to integrate the knowledge of work envelope requirements among piping and steel trades. Typical work envelope requirements were defined through in-depth interviews with superintendents on U.S. industrial projects. Therefore, the rules and semantic information extracted from the interviews were summarized in seven decision trees, describing the geometric parameters relative to the body parts (e.g. chest and eye height). To compare the level of work envelope overlaps among global populations, anthropomorphic data was used to assess the absolute dimensions of the work envelopes. The results show that some work envelope requirements have a limited tolerance and are more sensitive to different body dimensions across global populations. It was found that in such situations the population anthropomorphic characteristics significantly impact the work envelope requirements. Therefore, this paper presents a decision supporting tool of work envelope requirements in compliment to space planning, which can improve the productivity, accuracy and efficiency of workspace management in the piping and steel trades

Work Envelope Requirements Among Piping and Steel Trades and the Influence of Anthropomorphic Characteristics of Global Populations

With the increased usage of Building Information Modeling (BIM) in the construction industry, new pre-construction processes are emerging. This is the case of 4D animation that brings together the 3D model of a building and its construction schedule to visualize construction process in a virtual manner. This technologically advanced approach in the pre-construction phase contrasts with the unanticipated overstaffing on the worksite, which results in losses of productivity. This research provides a framework to help bridge this gap, by integrating the knowledge of work envelope requirements on piping and steel construction to prevent overstaffing and reduce productivity losses. Initial efforts to identify the way that work envelope requirements were defined in the literature revealed that if many possible usages are considered, very little was found on how to automatically assess the exact work envelope requirement. Thus the work envelope was first defined through five in-depth interviews with experienced superintendents on steel and piping projects. Their thought process, when presented with common situations, was recorded and general rules where extracted. Those rules were then summarized in 16 decision trees, describing the required work envelope in specific steel and piping construction situations. Most of those work envelope definitions include dimensions relative to the body parts. This lead to assess the absolute dimensions of the work envelope, using anthropomorphic data, to compare the level of work envelope overlap between worldwide populations. The results show that some work envelope requirements, identified through the interviews, have a limited tolerance and are more sensitive to body dimension changes. It was found that in such situation the population anthropomorphic characteristics significantly impact the work envelope requirements. This research contributes to the body of knowledge by defining the characteristics of the work envelope on construction projects. Specifically it stresses the independence horizontal and vertical components of the work envelope; identifies the specific factors impacting those two components; and describe how not considering the anthropomorphic data would impact the space planning on site

Using negative signal in mono-TI pulsed arterial spin labeling to outline pathological increases in arterial transit times

International audienceThe presence of unexpected negative perfusion estimates has been sparsely discussed in the ASL literature [2,3]. In the study of perfusion maps extracted from a single inversion time in ASL (mono-TI ASL), it is however common to deal with areas of significant negative signal. This is problematic since performing statistical analysis based on this data might therefore lead to inacurrate results. Though isolated negative values could be attributed to noise, clusters of significant negative signal should be explained by another phenomenon. Following previous authors, which outlined that negative values might arise due to increased transit times, we investigated this hypothesis based on real clinical datasets including healthy control and patient data

Using negative signal in mono-TI pulsed arterial spin labeling to outline pathological increases in arterial transit times

International audienceThe presence of unexpected negative perfusion estimates has been sparsely discussed in the ASL literature [2,3]. In the study of perfusion maps extracted from a single inversion time in ASL (mono-TI ASL), it is however common to deal with areas of significant negative signal. This is problematic since performing statistical analysis based on this data might therefore lead to inacurrate results. Though isolated negative values could be attributed to noise, clusters of significant negative signal should be explained by another phenomenon. Following previous authors, which outlined that negative values might arise due to increased transit times, we investigated this hypothesis based on real clinical datasets including healthy control and patient data

Using negative signal in mono-TI pulsed arterial spin labeling to outline pathological increases in arterial transit times

International audienceThe presence of unexpected negative perfusion estimates has been sparsely discussed in the ASL literature [2,3]. In the study of perfusion maps extracted from a single inversion time in ASL (mono-TI ASL), it is however common to deal with areas of significant negative signal. This is problematic since performing statistical analysis based on this data might therefore lead to inacurrate results. Though isolated negative values could be attributed to noise, clusters of significant negative signal should be explained by another phenomenon. Following previous authors, which outlined that negative values might arise due to increased transit times, we investigated this hypothesis based on real clinical datasets including healthy control and patient data

A CONTRARIO DETECTION OF FOCAL BRAIN PERFUSION ABNORMALITIES BASED ON AN ARTERIAL SPIN LABELING TEMPLATE

Arterial Spin Labeling (ASL) is a recent MRI perfusion technique which enables quantification of cerebral blood flow (CBF). The presence of regions with atypical CBF can characterize a pathology. In brain tumors for instance, perfusion increase can be directly related to the grading of the malignant tissues. It is therefore of great interest to identify these regions in order to provide the patients with the most appropriate therapy. In this paper, we propose to detect abnormal brain perfusion by using an a contrario framework and an ASL template as a model of normal perfusion. Validation was undertaken by qualitative comparison with CBF extracted from dynamic susceptibility weighted contrast enhanced (DSC) imaging. We experimented this framework on four patients presenting brain tumors. Results show that high perfusion regions found in DSC CBF maps are correctly identified as hyperperfusions with a contrario detection. Automatic detection has clear advantages over manual delineation since it is less time-consuming, does not depend on medical expertise and allows quantification of perfusion abnormalities within the detected regions. Index Terms — Arterial spin labeling, Cerebral blood flow, Template, a contrario detection. 1

Comparaison sédimentologique et malacologique entre les loess weichseliens et saaliens superposés dans la falaise de Nantois (Bretagne, France): Reconstruction de leurs environnements au sud de la calotte glaciaire britannique

International audienceThe site of Nantois is located in Brittany (France), almost at the westernmost end of Europe. The outcrop consists of loam, loess and slope deposits, now continuously eroded by the sea. The layers containing fragments of rock and loam are completely decalcified. Only the loess of the lower and upper parts of the section corresponding to the Nantois (Middle Pleistocene) and Sables-d’Or-Les-Pins (Late Pleistocene) formations are well preserved and display mollusc shells. A detailed study of the sediment and of the fauna permitted to better characterize the two loess. The older loess is characterized by a large variety of species. The analysis of their distribution indicates for the first time the existence of three moderate climatic improvements during the sedimentation. The lower part of the younger loess is poor in mollusc shells which are either absent or only exist as single finds or detritus, above, the molluscs composition indicates cold and severe climatic conditions during the sedimentation and can be correlated with the last glacial stage MIS 2. According to geochronological data, the upper part of the Nantois Formation corresponds to the glacial stage MIS 6. The origin of the discrepancies observed in the evolutions of the two loess was probably not related with the small difference in their distances respect with the Weichselian and Saalian British ice sheets but to the very different durations of the Upper Saalian (60 ka) and Upper Weischelian (7 ka) loess depositions. The absence of any significant warming episode during the Upper Weischelian and the existence of three climatic improvements during the Upper Saalian support the concept of sub-Milankovitch cycles which suggests that we cannot have any climatic change during a period shorter than 11Ka.Le site de Nantois est situé en Bretagne (France), presque à l’extrémité la plus orientale de l’Europe. L’affleurement est constitué de limons, de loess et de dépôts de pente maintenant régulièrement érodés par la mer. Les niveaux contenant des fragments de roches et des limons sont totalement décalcifiés. Seuls les loess des parties inférieures et supérieures de la coupe et correspondant aux formations de Nantois (Pléistocène moyen) et des Sables-d’Or-Les-Pins (Pléistocène supérieur) sont bien préservés et contiennent des mollusques. Une étude détaillée des sédiments et de la faune associée à permis de mieux caractériser ces deux types de loess. Les loess les plus anciens sont caractérisés par une large variété d’espèces. L’analyse de leur distribution à permis, pour la première fois de mettre en évidence trois améliorations climatiques modérées pendant la sédimentation. La partie inférieure des loess les plus récents est pauvre en mollusques, qui sont soit absents ou n’existent qu’en un seul exemplaire ou sous forme de fragments. Au-dessus, la nature des mollusques indique l’existence de conditions climatiques froides et sévères pendant la sédimentation. Elles peuvent être corrélées avec le dernier stade glaciaire MIS 2. Selon les données géochronologiques la partie supérieure de la formation de Nantois correspondrait au stade glaciaire MIS 6. L’origine des différences que l’on observe dans l’évolution des deux types de loess n’était probablement pas liée à la faible différence de leur distance par rapport aux calottes glaciaires britanniques lors du Saalien Supérieur (60 ka) et du Weischelien (7ka). L’absence d’amélioration climatique significative pendant le Weischelien supérieur et la présence de trois améliorations climatiques pendant le Saalien supérieur est en faveur du concept de cycles de type sub-Milankovitch selon lequel il n’y aurait pas d’améliorations climatiques possibles pendant une période inférieure à 11 kilo-années

Hemodynamic Quantification in Brain Arteriovenous Malformations With Time-Resolved Spin-Labeled Magnetic Resonance Angiography

International audienceUnenhanced time-resolved spin-labeled magnetic resonance angiography enables hemodynamic quantification in arteriovenous malformations (AVMs). Our purpose was to identify quantitative parameters that discriminate among different AVM components and to relate hemodynamic patterns with rupture risk.METHODS:Sixteen patients presenting with AVMs (7 women, 9 men; mean age 37.1±15.9 years) were assigned to the high rupture risk or low rupture risk group according to anatomic AVM characteristics and rupture history. High temporal resolution (<70 ms) unenhanced time-resolved spin-labeled magnetic resonance angiography was performed on a 3-T MR system. After dedicated image processing, hemodynamic quantitative parameters were computed. T tests were used to compare quantitative parameters among AVM components, between the high rupture risk and low rupture risk groups, and between the hemorrhagic and nonhemorrhagic groups.RESULTS:Among the quantitative parameters, time-to-peak (P<0.001) and maximum outflow gradient (P=0.01) allowed discriminating various intranidal flow patterns with significantly different values between feeding arteries and draining veins. With 9 AVMs classified into the high rupture risk group (whose 6 were hemorrhagic) and 7 into the low rupture risk group, the observed venous-to-arterial time-to-peak ratio was significantly lower in the high rupture risk (P=0.003) and hemorrhagic (P=0.001) groups.CONCLUSIONS:Unenhanced time-resolved spin-labeled magnetic resonance angiography allows AVM-specific combined anatomic and quantitative analysis of AVM hemodynamics

Building memories on prior knowledge: behavioral and fMRI evidence of impairment in early Alzheimer’s disease

International audienceImpaired memory is a hallmark of prodromal Alzheimer’s disease (AD). Prior knowledge associated with the memoranda improves memory in healthy individuals. However, little is known about its effect in early AD. We used functional MRI to investigate whether prior knowledge enhances memory encoding in early AD, and whether the nature of this prior knowledge matters. 17 patients with early AD and 19 controls underwent a task-based fMRI experiment where they learned face-scene associations. Famous faces carried pre-experimental knowledge (PEK), while unknown faces with which participants were familiarized prior to learning carried experimental knowledge (EK). As expected, PEK enhanced subsequent memory in healthy controls, but not in patients. Importantly, partly nonoverlapping brain networks supported PEK vs. EK encoding in healthy controls. Patients displayed impaired activation in a right subhippocampal region where activity predicted successful associative memory formation for PEK stimuli. Despite the limited sample sizes, these findings underline how prior knowledge impacts learning and suggest that the extent of associative memory impairment in early AD has hitherto been underestimated