Home About us Contact
|
Home About us Contact | ||
|
|
||
Cooling Time (cooling + time)
Selected AbstractsSystematic optimization for the evaluation of the microinjection molding parameters of light guide plate with TOPSIS-based Taguchi methodADVANCES IN POLYMER TECHNOLOGY, Issue 1 2010Te-Li Su Abstract A back light module is a key product for providing sufficient light source for a liquid crystal display (LCD). The light guide plate (LGP), used to increase the light usage rate, is a key component in the back light module. This study researches the microinjection molding process parameters and the quality performance of the LGP. Its purpose was to develop a combining Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) with the Taguchi method. This is to optimize the multiquality performance of the LGP for the injection molding manufacturing process, in which both the LCD and the LGP spontaneously produce the best quality performance for V-cut depth and angle. First, an L18 orthogonal array was planned for the manufacturing parameters that affect the microinjection molding process. These included cooling time, mold temperature, melt temperature, injection speed, injection pressure, packing pressure, packing switching, and packing time. The TOPSIS was used to deal with the single-quality optimization disadvantage of the Taguchi method. Then, the TOPSIS response table was used to obtain the optimized manufacturing parameters combination for a multiresponse process optimization. From the analysis of variance, the significant factors for the quality performance of the LGP could be obtained. In other words, by controlling these factors, it was possible to efficiently control the quality performance of the LGP. Finally, with the five verified experiments, the optimized processing parameters came within a 95% confidence interval. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:54,63, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20181 [source] Prediction of cooling time in injection molding by means of a simplified semianalytical equationADVANCES IN POLYMER TECHNOLOGY, Issue 3 2003D. M. Zarkadas Abstract A simplified semianalytical equation, used successfully in food freezing/chilling time prediction, is proposed as a potential simple alternative for cooling time prediction in injection molding of polymer parts, amorphous or semicrystalline. This equation is based on a convective boundary condition for the mold-part interface and requires information on the thermal contact resistance (TCR) or thermal contact conductance (TCC) at this interface, as well as information on the initial and final product temperatures, the mold surface temperature, and the thermal properties of the part. Eighty-five data points for four polymers, Polystyrene (PS), Polycarbonate (PC), Polypropylene (PP), and Polyethylene (PE) were generated with C-MOLDÔ, a commercial injection molding design software, and the performance of the proposed equation was tested. The % mean error and its standard deviation (SD) in cooling time prediction were, respectively, ,11.61 and 2.27 for PS, ,6.04 and 2.13 for PC, ,7.27 and 6.55 for PP, and ,8.88 and 2.93 for PE. It was also shown that the accuracy of the proposed equation is not affected significantly by the exact knowledge of the TCC, provided that the latter is not smaller than 1000,2000 W m,2 K,1. Since in this comparison all necessary temperatures were obtained from C-MOLDÔ, methods of using the proposed equation independently were tested. The use of the inlet melt temperature as the initial product temperature increased the % mean error by mostly 1.5% while its SD remained practically the same. By incorporating a literature based heat balance method in the proposed equation, it was possible to use it as a stand-alone predictor of polymer cooling time. The % mean error and its SD calculated this way were, respectively, ,9.44 and 0.97 for PS, ,9.44 and 0.83 for PC, ,14.22 and 5 for PP, and ,20.12 and 1.38 for PE. The proposed equation, at least in a preliminary stage, can be used successfully to predict the cooling time of the selected semicrystalline or amorphous polymers with the accuracy being higher for amorphous polymers. © 2003 Wiley Periodicals, Inc. Adv Polym Techn 22: 188,208, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.10048 [source] Effects of cryoprotectant concentration and cooling rate on vitrification of aqueous solutionsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2006Naji S. Husseini Vitrification of aqueous cryoprotectant mixtures is essential in cryopreservation of proteins and other biological samples. Systematic measurements of critical cryoprotective agent (CPA) concentrations required for vitrification during plunge-cooling from T = 295,K to T = 77,K in liquid nitrogen are reported. Measurements on fourteen common CPAs, including alcohols (glycerol, methanol, 2-propanol), sugars (sucrose, xylitol, dextrose, trehalose), polyethylene glycols (ethylene glycol, PEG 200, PEG 2000, PEG 20000), glycols [dimethyl sulfoxide (DMSO), 2-methyl-2,4-pentanediol (MPD)], and salt (NaCl), were performed for volumes ranging over four orders of magnitude from ,1,nl to 20,µl, and covering the range of interest in protein crystallography. X-ray diffraction measurements on aqueous glycerol mixtures confirm that the polycrystalline-to-vitreous transition occurs within a span of less than 2% w/v in CPA concentration, and that the form of polycrystalline ice (hexagonal or cubic) depends on CPA concentration and cooling rate. For most of the studied cryoprotectants, the critical concentration decreases strongly with volume in the range from ,5,µl to ,0.1,µl, typically by a factor of two. By combining measurements of the critical concentration versus volume with cooling time versus volume, the function of greatest intrinsic physical interest is obtained: the critical CPA concentration versus cooling rate during flash-cooling. These results provide a basis for more rational design of cryoprotective protocols, and should yield insight into the physics of glass formation in aqueous mixtures. [source] The effects of thermal conduction on the intracluster medium of the Virgo clusterMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2005Edward C. D. Pope ABSTRACT Thermal conduction has been suggested as a possible mechanism by which sufficient energy is supplied to the central regions of galaxy clusters to balance the effect of radiative cooling. Recent high-resolution observations of the nearby Virgo cluster make it an ideal subject for an attempt to reproduce the properties of the cluster by numerical simulations, because most of the defining parameters are comparatively well known. Here, we present the results of a simulated high-resolution, 3D Virgo cluster for different values of thermal conductivity ( times the full Spitzer value). Starting from an initially isothermal cluster atmosphere, we allow the cluster to evolve freely over time-scales of roughly 1.3,4.7 × 109 yr. Our results show that thermal conductivity at the Spitzer value can increase the central intracluster medium (ICM) radiative cooling time by a factor of roughly 3.6. In addition, for larger values of thermal conductivity, the simulated temperature and density profiles match the observations significantly better than for the lower values. However, no physically meaningful value of thermal conductivity was able to postpone the cooling catastrophe (characterized by a rapid increase in the central density) for longer than a fraction of the Hubble time nor explain the absence of a strong cooling flow in the Virgo cluster today. We also calculate the effective adiabatic index of the cluster gas for both simulation and observational data and compare the values with theoretical expectations. Using this method, it appears that the Virgo cluster is being heated in the cluster centre by a mechanism other than thermal conductivity. Based on this and our simulations, it is also likely that the thermal conductivity is suppressed by a factor of at least 10 and probably more. Thus, we suggest that thermal conductivity, if present at all, has the effect of slowing down the evolution of the ICM, by radiative cooling, but only by a factor of a few. [source] A Chandra observation of the disturbed cluster core of Abell 2204MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2005J. S. Sanders ABSTRACT We present results from an observation of the luminous cluster of galaxies Abell 2204 using the Chandra X-ray Observatory. We show the core of the cluster has a complex morphological structure, made up of a high-density core (ne, 0.2 cm,3) with flat surface brightness, a surrounding central plateau, a tail-like feature, wrapping around to the east, and an unusual radio source. A temperature map and deprojected profile shows that the temperature rises steeply outside these regions, until around ,100 kpc where it drops, then rises again. Abundance maps and profiles show that there is a corresponding increase in abundance at the same radius as where the temperature drops. In addition, there are two cold fronts at radii of ,28 and 54.5 kpc. The disturbed morphology indicates that the cluster core may have undergone a merger. However, despite this disruption, the mean radiative cooling time in the centre is short (,230 Myr) and the morphology is regular on large scales. [source] The nature of galaxy bias and clusteringMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2000A. J. Benson We have used a combination of high resolution cosmological N -body simulations and semi-analytic modelling of galaxy formation to investigate the processes that determine the spatial distribution of galaxies in cold dark matter (CDM) models and its relation to the spatial distribution of dark matter. The galaxy distribution depends sensitively on the efficiency with which galaxies form in haloes of different mass. In small mass haloes, galaxy formation is inhibited by the reheating of cooled gas by feedback processes, whereas in large mass haloes, it is inhibited by the long cooling time of the gas. As a result, the mass-to-light ratio of haloes has a deep minimum at the halo mass, ,1012 M,, associated with L* galaxies, where galaxy formation is most efficient. This dependence of galaxy formation efficiency on halo mass leads to a scale-dependent bias in the distribution of galaxies relative to the distribution of mass. On large scales, the bias in the galaxy distribution is related in a simple way to the bias in the distribution of massive haloes. On small scales, the correlation function is determined by the interplay between various effects including the spatial exclusion of dark matter haloes, the distribution function of the number of galaxies occupying a single dark matter halo and, to a lesser extent, dynamical friction. Remarkably, these processes conspire to produce a correlation function in a flat, ,0=0.3, CDM model that is close to a power law over nearly four orders of magnitude in amplitude. This model agrees well with the correlation function of galaxies measured in the automated-plate measurement survey. On small scales, the model galaxies are less strongly clustered than the dark matter, whereas on large scales they trace the occupied haloes. Our clustering predictions are robust to changes in the parameters of the galaxy formation model, provided only those models which match the bright end of the galaxy luminosity function are considered. [source] Analysis of laser/IR-assisted microembossingPOLYMER ENGINEERING & SCIENCE, Issue 5 2005Chunmeng Lu To shorten the cycle time in conventional hot embossing, an infrared laser (laser/IR)-assisted microembossing process was investigated in this study. Since the laser/IR heats the substrate rapidly and locally, the heating and cooling time can be substantially reduced. Two different modes of IR embossing were tested. In one case, the polymer substrate was the IR-transparent poly(methyl methacrylate) (PMMA) and a carbon black-filled epoxy mold was used. In the second case, the polymer substrate was an IR-absorbent PMMA, and an IR transparent epoxy mold was used. The experimental results showed that both a shorter cycle time and good replication accuracy could be achieved. A commercially available finite element (FEM) code, DEFORMÔ, was used for process simulation. The relationship between the penetration of radiation energy flux from the laser/IR heating source and temperature distribution inside the polymer substrate was considered in the simulation. The flow pattern observed in the experiments agreed well with the numerical simulation. However, the displacement curve showed a discrepancy. POLYM. ENG. SCI., 45:661,668, 2005. © 2005 Society of Plastics Engineers [source] Temperature changes in dental pulp associated with use of power grinding equipment on equine teethAUSTRALIAN VETERINARY JOURNAL, Issue 1-2 2005GJ WILSON Objective To quantify the temperature changes in the dental pulp associated with equine dental procedures using power grinding equipment. Design A matrix experimental design with replication on the same sample was followed to allow the following independent variables to be assessed: horse age (young or old), tooth type (premolar or molar), powered grinding instrument (rotating disc or die grinder), grinding time (15 or 20 seconds) and the presence or absence of water coolant. Procedure Sound premolar and molar teeth from a 6-year-old horse and a 15-year-old horse, which had been removed postmortem, were sectioned parallel to the occlusal plane to allow placement of a miniature thermocouple at the level of the dental pulp. The maximum temperature increase, the time taken to reach this maximum and the cooling time were measured (n=10 in each study). The teeth were placed in a vice and the instrument used on the tooth as per clinical situation. Results Significant differences were recorded for horse age (P < 0.001), instrument type (P < 0.001), grinding time (P < 0.001) and presence or absence of coolant (P < 0.001). There was no significant difference for tooth type. Conclusion Thermal insult to the dental pulp from the use of power instruments poses a significant risk to the tooth. This risk can be reduced or eliminated by appropriate selection of treatment time and by the use of water irrigation as a coolant. The increased dentine thickness in older horses appears to mitigate against thermal injury from frictional heat. [source] | ||||||||||