Marangoni heat transfer in subcooled nucleate pool boiling

The liquid motion induced by surface tension variation, termed the Marangoni effect, and its contribution to boiling heat transfer has been an issue of much controversy. Boiling heat transfer theory, although acknowledging its existence, considers its contribution to heat transfer to be insignificant in comparison with buoyancy induced convection. However, recent microgravity experiments have shown that although the boiling mechanism in a reduced gravity environment is different, the corresponding heat transfer rates are similar to those obtained under normal gravity conditions, raising questions about the validity of the assumption. An experimental investigation was performed in which distilled water was gradually heated to boiling conditions on a copper heater surface at four different levels of subcooling. Photographic investigation of the bubbles appearing on the surface was carried out in support of the measurements. The results obtained indicate that Marangoni convection associated with the bubbles formed by the air dissolved in the water which emerged from solution when the water was heated sufficiently, significantly influenced the heat transfer rate in subcooled nucleate pool boiling. A heat transfer model was developed in order to explain the phenomena observed.     

Reliability test methods for media-compatible pressure sensors

Two applications of media exposure testing of pressure sensors with barrier coatings are presented. Experimentation was performed on an apparatus that was developed specifically for the exposure of these devices with in situ output voltage measurement in organic or aqueous environments. The first example illustrates the swelling of fluorosilicone gels in fuels and establishes a solubility parameter for one fluorosilicone gel between 6-8 (cal/cm³)^1/2. While exposure to organic solutions has not been observed to cause catastrophic failure of fluorosilicone-gel-filled devices, corrosion is accelerated in subsequent aqueous solution exposure. An additional experiment was used to simulate automotive exhaust gases and water by exposing devices to a fuel mixture followed by an acidic solution. The second experiment was performed to study corrosion under parylene coatings during exposure to an alkaline test solution for white-goods applications. Acceleration factor expressions have been estimated considering parylene coating thickness, solution pH, and applied device supply voltage as acceleration means. These expressions have been used to evaluate parylene-coated pressure sensors against a benchmark lifetime requirement. For a 1% failure rate, parylene-coated pressure sensors survived approximately 500 h, whereas an alternative, fluorosilicone gel over parylene C coating survived over 2000 h. Furthermore, these media exposure experiments provided insight into the failure mechanisms and defined acceleration factors     

New EPL RLL(5,16) code

The new version of the run-length-limited RLL(5,16) encoding scheme is presented which allows a simple decoder design with error propagation limited (EPL). The sliding block decoder has finite window length of 16 symbol bits, so that an error at the input can cause propagation to only 6 data bits at the output.<>     

Investigation of dynamic Young's modulus for molybdenum disilicide-titanium trisilicide (MoSi2-Ti5Si3)

Molybdenum disilicide-titanium trisilicide (MoSi₂-Ti₅Si₃) is a ceramic matrix composite (CMC) created for the purpose of improving the mechanical properties of molybdenum disilicide. Five alloys of this CMC were prepared by varying the ratio of volume per cent Ti₅Si₃ to volume per cent MoSi₂. Evaluation of the specimens using the piezoelectric ultrasonic composite oscillator technique (PUCOT) determined the values of Young's modulus to range from 303 to 378 GPa at room temperature increasing with volume fraction of MoSi₂. The values of Young's modulus for temperatures up to about 400 °C for each alloy decrease linearly with respect to increasing temperature. Damping within the specimens is independent of strain amplitude at room temperature, but shows some strain amplitude dependence at higher temperatures. The values of density for the alloys, determined using Archimedes' method, range from about 5200 to 5900 kg m^–3, and compare favourably with the values determined by the rule of mixtures.     

LC-MS-(MS) determination of oxidative degradation products of nonylphenol ethoxylates, carboxylates and nonylphenols in water.

A commercial blend of nonylphenol ethoxylates (NPEOs) was chosen as representative for non-ionic polyethoxylated surfactants to study the oxidative degradation of this class of surfactants in water using ozonation as well as electron beam irradiation with and without the addition of ozone as treatment processes. The electron beam irradiation processes applied represent so-called Advanced Oxidation Processes (AOPs); the combined ozone/electron beam irradiation is, moreover, the most powerful AOP which can be applied in aqueous systems. It was found that both ozonation and the two AOPs applied were able to decompose not only the NPEOs but also the polyethyleneglycoles (PEGs) formed as by-products from NPEO degradation to residual concentrations below the limit of detection. Moreover, the treatment processes were also used to study the oxidative degradation of nonylphenoxy acetic acid (NPEC) and of nonylphenol (NP) which are formed as by-products from biodegradation of NPEOs.     

Multi-echelon Multiple Criteria Spares Allocation

This paper presents an approach for allocating spares on three echelons to increase system reliability and decrease plant down-time in a cost-effective manner. The usual assumptions are made: a) the demands for spares have the Poisson distribution with known demand rates, b) all the failures of plant parts are s-independent, c) for the plant to be operating, all parts must be operating, thus forming 1-out-of-M:F configuration. To each echelon of the spatially distributed spare-support system is associated a relevant optimization criterion and a corresponding constraint. The algorithm for determining stock levels adapts the known `per-pound' procedure, applied in sequence from the first echelon to the third echelon. The sequential optimization is computationally efficient. The test examples have confirmed that the algorithms proposed can handle 3-echelon sparing problems with even thousands of part types.     

Sensitivity analysis of a fuzzy multiobjective scheduling problem

This paper concerns sensitivity analysis of a class of complex job shop scheduling problems which are characterized by: (1) a large number of jobs and machines, (2) uncertain jobs processing times, and (3) multiple measures of schedule performance including average weighted tardiness, the number of tardy jobs, the total setup times, the total idle time of machines, and the total flow times of jobs. The base schedule is generated by applying a new fuzzy multiobjective genetic algorithm which takes into consideration batching of the jobs of a similar type, jobs’ lots sizing and load balancing of the machines. The aim of the proposed sensitivity analysis of a generated schedule is to investigate the consequences of prolongations of job processing times on the measures of schedule performance. The processing times are described by triangular fuzzy numbers and their prolongation is done by expanding the supports of fuzzy numbers. The sensitivity analysis is performed through a series of numerical experiments. The effects of prolongations of job processing times on the measures of performance of a generated schedule are recorded and analysed. It is shown that the sensitivity analysis is among the primaries in evaluating the quality of a generated schedule. The sensitivity analysis is used in identifying the critical jobs and the critical machines which have the properties that the prolongations of their processing times produce the largest deteriorations of the performance measures and the overall quality of a generated schedule.     

Additive layered manufacturing: sectors of industrial application shown through case studies

In modern industry, mass production has migrated to third world countries. To be competitive, European companies are forced to rapidly switch towards manufacturing of short series of customised products with added value. In European industry, a great effort has been made in order to customise products and give them an added value by developing new fabrication technologies. Additive layered manufacturing (ALM), also known as rapid manufacturing (RM), is a powerful tool that offers the necessary competitiveness to European companies. ALM comprises the use of layer-by-layer manufacturing in order to build a part by addition of material. Fabrication is performed directly from the 3D CAD model, which is sliced into layers that are printed one upon the other. Also known as free form fabrication, additive fabrication ‘unlocks’ design potential since part design obeys functionality, pushing the limits of manufacturability. In this paper, the authors review ALM technologies and the state-of-the-art of ALM applications in tooling, biomedicine and lightweight structures for the automotive and aerospace sectors. The authors present their experience in industrial application of additive fabrication through various industrial technology transfer projects made to transfer ALM technology to SMEs. Various case studies are presented and the achieved benefits of ALM are shown.     

Polarization Properties of a Turnstile Antenna in the Vicinity of the Human Body

Polarization of a simple turnstile antenna situated close to the human body, for potential WBAN applications at 2.45 GHz band, is studied in detail by the use of electromagnetic simulator WIPL-D Pro. Circular polarization of the antenna (when isolated) is provided by adjusting the dipole impedances. Full-size, 3-dimensional simplified homogeneous model of a human body is applied. Polarization of both far and near field is studied, with various positions of the antenna and with/without metallic reflector. In the far field significant degradation of the circular polarization, due to the vicinity of the body, was observed. In the near field, at points close to the surface of the torso, polarization (of vector E) was found to significantly deviate from circular. Obtained results can be useful in designing on-body sensor networks in which circularly polarized antennas are applied, for both far field communication between sensor nodes and the gateway and near field communication between sensors.