Quantitative control of RTM6 epoxy resin polymerisation by optical index determination

RTM6 epoxy resin curing is usually characterized by the polymerisation degree. We report in this paper on a refractive index measurement technique applied on an experimental mould to control, quantitatively and in situ, the industrial RTM process. For the first time, we determined simultaneously the thermo-optical coefficient, the refractive index evolution, the specific volume and the polymerisation degree of the resin. The calculation of a “polymerisation degree optical coefficient” led to a quantification of the RTM6 epoxy resin polymerisation process. This calibration coefficient is very useful to perform a real time industrial process control. Furthermore, the optoelectronic system is connected to a data processing unit and is easy to use in an industrial environment.     

Über die Zeitstandfestigkeit des Schweißgutes von Schweißverbindungen niedriglegierter warmfester Stähle

Durch Lichtbogenschweißen von Hand wird Schweißgut der niedriglegierten warmfesten Chrom-Molybdän-(Vanadin-)Stähle mit 2,25% Cr und 1% Mo sowie mit 0,5% Cr, 0,5% Mo und 0,25% V hergestellt. Ermittlung der mechanischen Eigenschaften bei Raumtemperatur und der Zeitstandfestigkeit bei verschiedenen Temperaturen zwischen 550 und 625°C. Untersuchung des Gefügezustandes und der chemischen Zusammensetzung der elektrochemisch isolierten Carbide. Vergleich der ermittelten Zeitstandfestigkeiten mit den nach ISO-Empfehlungen für die Grundwerkstoffe vorgeschlagenen Werten.     

Abnormal ambulatory left ventricular ejection fraction in heart transplant arteriopathy

The morbidity and mortality from heart transplantation has been reduced dramatically over the last several years. However, the long-term survival in heart transplant recipients is limited by arteriopathy in the allograft coronary arteries, the pathophysiology of which is poorly understood. The diagnosis of this arteriopathy is at present limited to cardiac catheterization. Noninvasive studies have proven to be of limited benefit in diagnosing this arteriopathy. The authors performed cardiac vest studies in nine heart transplant recipient patients. Six of the vest studies were abnormal; five of the patients had documented transplant coronary artery disease by cardiac catheterization. They found that the sensitivity and negative predictive value of the cardiac vest in identifying arteriopathy in transplant recipients was 100%. The authors propose that cardiac vest could be a sensitive, noninvasive screening test for identifying arteriopathy in heart transplant recipients.     

Linac Coherent Light Source soft x-ray materials science instrument optical design and monochromator commissioning

We present the x-ray optical design of the soft x-ray materials science instrument at the Linac Coherent Light Source, consisting of a varied line-spaced grating monochromator and Kirkpatrick-Baez refocusing optics. Results from the commissioning of the monochromator are shown. A resolving power of 3000 was achieved, which is within a factor of two of the design goal.     

Fish Associations among Un‐notched,Notched and L‐head Dikes in the Middle Mississippi River

Wing dikes and other anthropogenic modifications have heavily altered riverine ecosystems. Recent efforts to reach a compromise between the needs of the river transportation industry and natural resource conservation include dike modification. Dike notching permits water flow through the landward portion of the dike and has been purported to provide suitable habitat for fish and other river biota while maintaining the navigation channel. L‐head dikes are flow‐control structures that create calm backwater‐like habitats downstream. However, few researchers have examined the actual effects of dike notching on water quality or fish communities. We compared standardized catch per unit effort and overall community structure for 50 fish species among un‐notched dikes, notched dikes and L‐head dikes in the Middle Mississippi River, sampled as part of the US Geological Survey's Long‐Term Resource Monitoring Program. There were no differences in standardized catch per unit effort for 64% of the fishes examined. Five species known to be associated with lotic habitats were most abundant near L‐head dikes. Seven species were more abundant at un‐notched dikes than notched dikes, while six species were more abundant at notched dikes than un‐notched dikes. Non‐metric multidimensional scaling suggested differences in overall fish community structure between un‐notched and other dike types. Detailed physical habitat studies should be conducted to better understand the effects of dike modification. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel method for estimating solid fraction of roller-compacted ribbons

A simple method has been developed to estimate solid fraction or relative density of compacts using the weight of ribbons produced during roller compaction. The method provides an alternative to the commonly used dimensional measurement, especially for formulations not amenable to forming quality ribbons. Surface texture of the compaction rolls has been taken into consideration in our mathematical treatment along with correction for ribbon relaxation. Ribbon relaxation occurring upon ribbon exiting the compaction zone is estimated using roll geometry, roll gap, and ribbon thickness. Detailed experimental runs have been carried out to confirm the validity of the proposed theory. The predicted solid fraction was found comparable to that from actual dimensional measurement by caliper. In the case of the microcrystalline cellulose/dicalcium phosphate one:one formulation, the predicted solid fraction had an error sum of squares (SSE) of 2.64E-03 when compared to the dimensional method. When relaxation was included, the SSE decreased by four folds. Similarly, for the microcrystalline cellulose/lactose monohydrate 2:1 formulation, the SSE decreased twelfth folds when relaxation was taken into consideration. These results further confirm the utility of the proposed throughput method for estimating the solid fraction of ribbons.     

Measurements of the Thermal Conductivity of Molten Lead Using a New Transient Hot-Wire Sensor

The paper reports new measurements of the thermal conductivity of molten lead at temperatures from 600 to 750 K. The measurements have been carried out with an updated version of a modified transient hot-wire (THW) method, where the hot-wire sensor is embedded within an insulating substrate with a planar geometry. However, unlike previous sensors of the same type, the updated sensor works with the hot-wire divided into three thermally isolated parts. The operation of this sensor has been modeled theoretically using a finite-element (FE) analysis and has subsequently been confirmed by direct observation. The new sensor is demonstrated to have a higher sensitivity and a better signal-to-noise ratio than earlier sensors. Molten lead is used as the test fluid. It has the lowest thermal conductivity of any material we have yet studied. This allows us to probe the limits of our sensor system for the thermal conductivity of high-temperature melts. It is estimated that the uncertainty of the measurements is 3% over the temperature range studied. The results are used to examine the application of the Wiedemann–Franz (W-F) relationship.     

Inverse methodology to determine mold set-point temperature in resin transfer molding process

This study consists of determining by inverse method the set-point temperature of the fluid flowing through heating plates in a Resin Transfer Molding (RTM) process tool so as to reach a predetermined thermal history in the composite part. Although the described methodology is applied in a specific mold in this paper, it remains general and may be transposed to a large scale of molding configuration. The considered mold is metallic and composed of several parts. Assembling these parts is not possible without introducing imperfect contacts that perturb heat transfer between them. The heat transfer at the interface is modeled by thermal contact resistances (TCR) whose values are unknown. In the case of metallic molds TCR are of the same order of magnitude than the equivalent thermal resistance of the mold. Therefore they cannot be neglected. The influence of these TCR is then a key-point on heat transfer since a bad knowledge of their values implies a wrong estimation of the temperature field. Then before being able to estimate the set-point of the temperature of the thermoregulated fluid, it is necessary in a first stage to evaluate the most influent TCR that are spatially and time dependent. Their determination is achieved by an optimization approach and carried out on a 2D transverse cut of the mold. Experimental temperature measurements in the mold are matched to the computed responses of the heat conduction model. A least square criterion is minimized by using the conjugate gradient algorithm. The gradient of the criterion is determined by solving a set of adjoint equations. After the identification of these parameters, the same optimization method is used to compute the mold set point temperature. It is notable that the same set of adjoint equations is used to solve both problems.