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Cycle Time (cycle + time)
Kinds of Cycle Time Selected AbstractsAutomatic Palletizing of Concrete Pavement Blocks: An Algorithm for Near-Optimal AssemblyCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2001Shraga Shoval Palletizing concrete pavement blocks is a labor-intensive task that requires high levels of workmanship, skill, and concentration. This article proposes an automatic system in which palettes with required design patterns are assembled automatically off-site and then shipped to the construction site. The efficiency of the assembly process can be improved by incorporating automatic equipment consisting of assembly heads and feeders. An algorithm was developed to determine the optimal layout of the feeders (of different blocks) around the palette and the exact assembly sequence of each layer of blocks. Experimental results show that the algorithm is near optimal and that the solutions provided by it reduce palletizing cycle time for various patterns and sizes of concrete block by 20 to 30 percent. [source] Organizational Learning in Global Purchasing: A Model and Test of Internal Users and Corporate Buyers,DECISION SCIENCES, Issue 2 2000G. Tomas M. Hult ABSTRACT This research examines a model centered on organizational learning in purchasing. Two different studies are conducted to test the hypotheses among purchasing users (Study 1) and buyers (Study 2). The user sample consists of users representing 355 strategic business units of a Fortune 500 multinational corporation. The buyer sample consists of corporate buyers of 200 multinational corporations drawn from the membership directory of the National Association of Purchasing Management (NAPM). In each study, the focus is on the learning relationships between corporate buyers and internal users in the purchasing organization. Based on the two studies, the results suggest that organizational learning in the purchasing process is influenced by the organizational culture factors of localness, transformational leadership, and openness. Organizational learning has a positive effect on information processing in the purchasing system, which, in turn, has a positive influence on the cycle time of the purchasing process. [source] Midblastula transition (MBT) of the cell cycles in the yolk and pigment granule-free translucent blastomeres obtained from centrifuged Xenopus embryosDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 5 2005Yasuhiro Iwao We obtained translucent blastomeres free of yolk and pigment granules from Xenopus embryos which had been centrifuged at the beginning of the 8-cell stage with cellular integrity. They divided synchronously regardless of their cell size until they had decreased to 37.5 µm in radius; those smaller than this critical size, however, divided asynchronously with cell cycle times inversely proportional to the square of the cell radius after midblastula transition (MBT). The length of the S phase was determined as the time during which nuclear DNA fluorescence increased in Hoechst-stained blastomeres. When the cell cycle time exceeded 45 min, S and M phases were lengthened; when the cell cycle times exceeded 70 min, the G2 phase appeared; and after cell cycle times became longer than 150 min, the G1 phase appeared. Lengths of G1, S and M phases increased linearly with increasing cell cycle time. Enhanced green fluorescent protein (EGFP)-tagged proliferating cell nuclear antigen (PCNA) expressed in the blastomeres appeared in the S phase nucleus, but suddenly dispersed into the cytoplasm at the M phase. The system developed in this study is useful for examining the cell cycle behavior of the cell cycle-regulating molecules in living Xenopus blastomeres by fluorescence microscopy in real time. [source] Application of Six Sigma Methods for Improving the Analytical Data Management Process in the Environmental IndustryGROUND WATER MONITORING & REMEDIATION, Issue 2 2006Christopher M. French Honeywell applied the rigorous and well-documented Six Sigma quality-improvement approach to the complex, highly heterogeneous, and mission-critical process of remedial site environmental data management to achieve a sea change in terms of data quality, environmental risk reduction, and overall process cost reduction. The primary focus was to apply both qualitative and quantitative Six Sigma methods to improve electronic management of analytical laboratory data generated for environmental remediation and long-term monitoring programs. The process includes electronic data delivery, data QA/QC checking, data verification, data validation, database administration, regulatory agency reporting and linkage to spatial information, and real-time geographical information systems. Results of the analysis identified that automated, centralized web-based software tools delivered through Software as a Service (SaaS) model are optimal to improve the process resulting in cost reductions, while simultaneously improving data quality and long-term data usability and perseverance. A pilot project was completed that quantified cycle time and cost improvements of 50% and 65%, respectively. [source] Structured implementation of information systems for concurrent engineeringHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2001Walter W.C. Chung This article presents a collaboration approach to assimilate the best practice of concurrent engineering (CE) in a small manufacturing enterprise for gaining sustainable improvements. The major challenge in CE is sharing a mental model of parallel working across departments in a company to shorten the cycle time, and across organizations to form a supply chain for global competition. Action learning is found useful to develop self-discipline in individuals to initiate changes and align the views with others both inside and outside the company for a vested interest to use information systems to make innovations for gaining competitive advantage. © 2001 John Wiley & Sons, Inc. [source] A report on the use of action research to evaluate a manufacturing information systems development methodology in a companyINFORMATION SYSTEMS JOURNAL, Issue 1 2003Delvin Grant Abstract. The paper reports on an action research study that evaluated the usefulness of a Manufacturing Information Systems (MIS) development methodology at a manufacturing technology company. The evaluation process is based upon a five-stage action research method. The ISD methodology, in conjunction with the action research method, was used to solve five technical and organizational problems identified in the Engineering Release Function of the company. Results of the study include reduction in cycle time, work-in-process and rework. [source] Lead-Time Reduction Utilizing Lean Tools Applied to Healthcare: The Inpatient Pharmacy at a Local HospitalJOURNAL FOR HEALTHCARE QUALITY, Issue 1 2010Omar Al-Araidah Abstract: The healthcare arena, much like the manufacturing industry, benefits from many aspects of the Toyota lean principles. Lean thinking contributes to reducing or eliminating nonvalue-added time, money, and energy in healthcare. In this paper, we apply selected principles of lean management aiming at reducing the wasted time associated with drug dispensing at an inpatient pharmacy at a local hospital. Thorough investigation of the drug dispensing process revealed unnecessary complexities that contribute to delays in delivering medications to patients. We utilize DMAIC (Define, Measure, Analyze, Improve, Control) and 5S (Sort, Set-in-order, Shine, Standardize, Sustain) principles to identify and reduce wastes that contribute to increasing the lead-time in healthcare operations at the pharmacy understudy. The results obtained from the study revealed potential savings of >45% in the drug dispensing cycle time. [source] The importance of information flows temporal attributes for the efficient scheduling of dynamic demand responsive transport servicesJOURNAL OF ADVANCED TRANSPORTATION, Issue 1 2006Marco Diana The operation of a demand responsive transport service usually involves the management of dynamic requests. The underlying algorithms are mainly adaptations of procedures carefully designed to solve static versions of the problem, in which all the requests are known in advance. However there is no guarantee that the effectiveness of an algorithm stays unchanged when it is manipulated to work in a dynamic environment. On the other hand, the way the input is revealed to the algorithm has a decisive role on the schedule quality. We analyze three characteristics of the information flow (percentage of real-time requests, interval between call-in and requested pickup time and length of the computational cycle time), assessing their influence on the effectiveness of the scheduling process. [source] Sensitivity analysis on stochastic equilibrium transportation networks using genetic algorithmJOURNAL OF ADVANCED TRANSPORTATION, Issue 3 2004Halim Ceylan Abstract This study deals with the sensitivity analysis of an equilibrium transportation networks using genetic algorithm approach and uses the bi-level iterative sensitivity algorithm. Therefore, integrated Genetic Algorithm-TRANSYT and Path Flow Estimator (GATPFE) is developed for signalized road networks for various level of perceived travel time in order to test the sensitivity of perceived travel time error in an urban stochastic road networks. Level of information provided to drivers correspondingly affects the signal timing parameters and hence the Stochastic User Equilibrium (SUE) link flows. When the information on road system is increased, the road users try to avoid conflicting links. Therefore, the stochastic equilibrium assignment concept tends to be user equilibrium. The GATPFE is used to solve the bi-level problem, where the Area Traffic Control (ATC) is the upper-level and the SUE assignment is the lower-level. The GATPFE is tested for six-junction network taken from literature. The results show that the integrated GATPFE can be applied to carry out sensitivity analysis at the equilibrium network design problems for various level of information and it simultaneously optimize the signal timings (i.e. network common cycle time, signal stage and offsets between junctions). [source] Adaptive multiobjective optimization of process conditions for injection molding using a Gaussian process approachADVANCES IN POLYMER TECHNOLOGY, Issue 2 2007Jian Zhou Abstract Selecting the proper process conditions for the injection-molding process is treated as a multiobjective optimization problem, where different objectives, such as minimizing the injection pressure, volumetric shrinkage/warpage, or cycle time, present trade-off behaviors. As such, various optima may exist in the objective space. This paper presents the development of an integrated simulation-based optimization system that incorporates the design of computer experiments, Gaussian process (GP) for regression, multiobjective genetic algorithm (MOGA), and levels of adjacency to adaptively and automatically search for the Pareto-optimal solutions for different objectives. Since the GP approach can provide both the predictions and the estimations of the predictions simultaneously, a nondominated sorting procedure on the predicted variances at each iteration step is performed to intelligently select extra samples that can be used as additional training samples to improve the GP surrogate models. At the same time, user-defined adjacency constraint percentages are employed for evaluating the convergence of iteration. The illustrative applications in this paper show that the proposed optimization system can help mold designers to efficiently and effectively identify optimal process conditions. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:71,85, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20092 [source] A preliminary study on bladder-assisted rotomolding of thermoplastic polymer compositesADVANCES IN POLYMER TECHNOLOGY, Issue 1 2007A. Salomi Abstract In this preliminary work, a new process is examined for manufacturing hollow parts from continuous fiber-reinforced thermoplastic polymer. The new process combines the basic idea of bag forming (or bladder-assisted forming) with the rotation of the mold for the processing of thermoplastic matrix composites. A pressurized membrane is used to compact the composite on the inner wall of a mold, which is placed inside a forced convection oven. The mold is removed from the oven for the cooling stage. The process was initially developed by using a thermoplastic pre-preg obtained using yarns of commingled E-glass fibers with isotactic polypropylene (iPP). A preliminary characterization of the thermoplastic composite showed that the material can be consolidated with pressures as low as 0.01 MPa, which is readily achievable with the process of this study. The design of the mold and membrane was carried out on the basis of both structural analysis of the aluminum shell and thermal analysis of the mold. The mold thickness is of great importance with respect to both the maximum pressure allowed in the process and the overall cycle time. Molding was performed on stacks of three and six layers of yarn, varying the applied pressure between 0.01 and 0.05 MPa and maximum temperature of the internal air between 185°C and 215°C. The composite shells obtained under different processing conditions were characterized in terms of physical and mechanical properties. Mechanical properties comparable with those obtained by compression molding and vacuum bagging were obtained. The maximum values obtained are 12.1 GPa and 290 MPa for the flexural modulus and the flexural strength, respectively. Furthermore, the results obtained show that mechanical properties improve with increasing the pressure during the cycle and with the maximum temperature used in the process. © 2007 Wiley Periodicals, Inc. Adv Polym Techn 26:21,32, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20085 [source] Factors affecting the formation of fingering in water-assisted injection-molded thermoplasticsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2006Shih-Jung Liu Abstract Water-assisted injection-molding technology has received extensive attention in recent years, due to the lightweight of plastic parts, relatively low-resin cost per part, faster cycle time, and flexibility in the design and manufacture. However, there are still some unsolved problems that confound the overall success of this technology. One of these is the water "fingering" phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. This study has investigated the effects of various processing parameters on the formation of fingering in water-assisted injection-molded thermoplastic parts. Both amorphous and semicrystalline polymers were used to mold the parts. The influence of water channel geometry, including aspect ratio and fillet geometry, on the fingering was also investigated. It was found that water-assisted injection-molded amorphous materials gave less fingering, while molded semicrystalline parts gave more fingering when compared to those molded by gas-assisted injection molding. For the water channels used in this study, the channels with a rib on the top produced parts with the least water fingering. Water fingering in molded parts decreases with the height-to-thickness ratio of the channels. The water pressure, water injection delay time and short-shot size were found to be the principal parameters affecting the formation of water fingering. In addition, a numerical simulation based on the transient heat conduction model was also carried out to help better explain the mechanism for the formation of fingering in water-assisted injection-molded thermoplastics. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 98,108, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20062 [source] WATER ACTIVITY AND THE INACTIVATION OF ENTEROBACTER CLOACAE INOCULATED IN CHOCOLATE LIQUOR AND A MODEL SYSTEM BY PULSED ELECTRIC FIELD TREATMENTJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2002S. MI Effects of water activity (aw) on the inactivation of Enterobacter cloacae inoculated in chocolate liquor and in a model system of 0.1% (w/v) peptone water and glycerol by pulsed electric field (PEF) treatment were investigated. An electric field strength of 24.5 kV/cm, a total treatment time of 320 ,s, a pulse duration time of 4 ,s, a pulse delay time of 15 ,s, and a pulse cycle time of 15 s were selected for PEF treatment. The inactivation ofE. cloacae by PEF increased significantly as aw increased (P < 0. 05). As aw of chocolate liquor increased from 0.48 to 0.89, the log reduction of E. cloacae increased from 0.1 to 1.3. The measured temperature change inside the PEF treatment chamber was 0.4C when the log reduction was 1. 3. Similarly, as aw increased from 0. 51 to 0.91 in the model system, the log reduction increased from 0.4 to 1.3. E. cloacae surviving a low aw environment had high resistance to PEF. PEF inactivated E. cloacae in the chocolate liquor with aw of 0.85 by 1 log at O h incubation. However, the log reduction was only 0.1 when PEF treatment was applied to E. cloacae which was incubated for 2 h in the chocolate liquor with aw of 0.85 before PEF treatment. E. cloacae surviving the low aw environment might have resistance not only to the low aw but also to PEF. The resistance to low aw environment may need to be considered when the inactivation of microorganisms by PEF is evaluated. [source] Toward a Microfluidic-Based Rapid Amylase Assay SystemJOURNAL OF FOOD SCIENCE, Issue 6 2009Richard J. Holmes ABSTRACT:, This article describes work into a prototype system for the assay of amylase, using microfludic technologies. The new system has a significantly shorter cycle time than the current laboratory methods, which generally use microtitre plates, yet is capable of generating significantly superior results. As such, we have shown that sensitivity is enhanced by a factor of 10 in the standard assay trials, and by a factor of 2 in the real-sample lab trials. In both assays, the use of a microreactor system reduced the reaction time by a factor of 6.2, from 20 min incubation to 3.2 min. Basing the conclusion on the Megazyme Cerealpha Standard Method, and using the Cerealpha units as a measure of assay efficiency, the typical response for the microfluidic assay was shown to be 1.0 × 10,3 CU/mL (standard deviation [SD] 2.5 × 10,4 CU/mL), compared to 2.56 × 10,4 CU/mL (SD 5.94 × 10,5 CU/mL) for the standard macroassay. It is believed that this improvement in the reaction schematics is due to the inherent advantages of microfluidic devices such as superior mixing, higher thermal efficiency, and enhanced reaction kinetics. [source] Rapid screening and characterization of drug metabolites using a new quadrupole,linear ion trap mass spectrometerJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2003Gérard Hopfgartner Abstract The application of a new hybrid RF/DC quadrupole,linear ion trap mass spectrometer to support drug metabolism and pharmacokinetic studies is described. The instrument is based on a quadrupole ion path and is capable of conventional tandem mass spectrometry (MS/MS) as well as several high-sensitivity ion trap MS scans using the final quadrupole as a linear ion trap. Several pharmaceutical compounds, including trocade, remikiren and tolcapone, were used to evaluate the capabilities of the system with positive and negative turbo ionspray, using either information-dependent data acquisition (IDA) or targeted analysis for the screening, identification and quantification of metabolites. Owing to the MS/MS in-space configuration, quadrupole-like CID spectra with ion trap sensitivity can be obtained without the classical low mass cutoff of 3D ion traps. The system also has MS3 capability which allows fragmentation cascades to be followed. The combination of constant neutral loss or precursor ion scan with the enhanced product ion scan was found to be very selective for identifying metabolites at the picogram level in very complex matrices. Owing to the very high cycle time and, depending on the mass range, up to eight different MS experiments could be performed simultaneously without compromising chromatographic performance. Targeted product ion analysis was found to be complementary to IDA, in particular for very low concentrations. Comparable sensitivity was found in enhanced product ion scan and selected reaction monitoring modes. The instrument is particularly suitable for both qualitative and quantitative analysis. Copyright © 2003 John Wiley & Sons, Ltd. [source] Automatic regulation of occlusal force because of hardness-change of the bite objectJOURNAL OF ORAL REHABILITATION, Issue 1 2008A. SHIMADA Summary, It is considered that the information of chewed food, such as size and texture, is important for smooth mastication. In this study, we analysed aspects of the control of occlusal force, by experimentally reproducing situations in which the hardness of food changed unpredictably during mastication, using a device that utilized a 3-sectioned urethane rubber piece with different hardness values. Seven healthy subjects were instructed to perform repetitive jaw open,close movements paced by a metronome (1·0 Hz) and to maintain constant occlusal force throughout the trial. Using the device, the following parameters were measured during the first to fifth strokes after changing the hardness, peak value, impulse, duration and time to peak of occlusal force in the waveform of occlusal force, cycle time of open,close jaw movements, jaw gape and maximum speed in the closing phase in the waveform of the jaw movements. Each parameter value was statistically analysed by anova with Fisher's least significant difference method (P < 0·05). Peak occlusal force, impulse and jaw gape were significantly affected by the change in hardness, while an increase in hardness caused increases in the values for peak occlusal force and impulse against the instruction, after which those values remained constant while the subjects occluded the same level of hardness. Our results indicate that the level of the resulting occlusal force is regulated automatically according to the hardness of the chewed food. We concluded that occlusal force was adapted for efficient mastication when the hardness of foods changes unpredictably. [source] NOx storage and reduction with propylene on Pt/BaO/aluminaAICHE JOURNAL, Issue 10 2004Rachel L. Muncrief Abstract An experimental study was carried out of periodically operated NOx (NO + NO2) storage and reduction on a model Pt/BaO/Al2O3 catalyst powder. The effect of the reductant (propylene) injection policy on time-averaged NOx conversion was evaluated in terms of feed composition and temperature, reductant pulse duration, and overall cycle time. Conditions giving time-averaged NOx conversions exceeding 90% were identified. The reductant-to-oxidant ratio during the injection and the total cycle time are both found to be critical factors to achieve high conversion. The time-averaged conversion is bounded above and below by the steady-state conversions obtained with feeds having the same compositions as that during the rich and lean part of the cycle, respectively. For a fixed supply of propylene, short pulses of high concentration are much more effective than longer pulses of reduced concentration. The NOx conversion achieves a maximum value at an intermediate overall cycle time when the propylene pulse of fixed duty fraction is net reducing. High conversions are sustained over a wide temperature window (200,400°C). A simple storage,reduction cycle is proposed that elucidates the main findings in the study. The key factor for high NOx conversion is the temporal production of oxygen-deficient conditions coupled with high catalyst temperatures, both resulting from the intermittent catalytic oxidation of propylene. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2526,2540, 2004 [source] Determination of the Minimum Time for Binder Removal and Optimum Geometry for Three-Dimensional Porous Green BodiesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2003Stephen J. Lombardo A model is developed to optimize two aspects of the thermal removal of binder from green ceramic components. The model, which accounts for flow in porous media arising from the thermal decomposition of binder in three-dimensional bodies with anisotropic permeability, describes the pressure within the body as a function of position, time, and temperature during the heating cycle. The model is used with variational calculus to predict the heating profile that minimizes the cycle time for the thermal removal of binder. The model is also used to determine which body geometry maximizes the buildup of pressure in parallelepipeds, a common shape of multilayer ceramic capacitors. [source] Precision 1H,1H distance measurement via 13C NMR signals: utilization of 1H,1H double-quantum dipolar interactions recoupled under magic angle spinning conditionsMAGNETIC RESONANCE IN CHEMISTRY, Issue 2 2004Yoh Matsuki Abstract We applied the POST-C7 DQ-dipolar recoupling pulse sequence to the measurement of 1H,1H distances with high precision. The spectral resolution is enhanced by detecting the 1H magnetization via 13C signals. A least-squares fitting of the build-up curve of the transferred magnetization to the exact numerical simulations yielded a 1H,,1H, distance of 248 ± 4 pm for fully 13C-labeled L -valine. This distance agrees with the neutron diffraction study. The negative transferred magnetization clearly indicates that the direct DQ 1H,1H dipolar couplings have the largest effect. The signal for the magnetization transfer builds up rapidly by the direct 1H,1H dipolar coupling, and decreases to zero at longer mixing time when the relayed magnetization transfer becomes significant. This large intensity change of the signal leads to the high precision in the distance measurement. We inspected factors that limit the effective bandwidth of the POST-C7 recoupling for the 1H and 13C homonuclear spin systems. The spin interactions at times shorter than the cycle time of the C7 sequence were also evaluated to measure the distances. The carbon-detected 2D 1H DQ mixing experiment was demonstrated for the measurement of multiple 1H,1H distances. Copyright © 2004 John Wiley & Sons, Ltd. [source] Next-Generation Architecture to Support Simulation-Based AcquisitionNAVAL ENGINEERS JOURNAL, Issue 4 2000Dr. B. Chadha ABSTRACT The ability to make good design decisions early is a significant driver for simulation-based acquisition to effectively lower life-cycle cost and cycle time. Building virtual prototypes, enabling one to analyze the impact of decisions, achieves effective simulation-based acquisition processes. Virtual prototypes need to support a comprehensive set of analyses that will be performed on the product; hence, all aspects of product data and behavior need to be represented. Building virtual prototypes of complex systems being designed by a multi-organizational team requires new architectural concepts and redesigned processes. Implementation of these new architectures is complex and leveraging commercial technologies is necessary to achieve feasible solutions. One must also carefully consider the state of the current commercial technologies and frameworks as well as the organizational and cultural aspects of organizations that use these systems. This paper describes key architectural principles that one must address for a cost-effective implementation. The paper then discusses key architectural concepts and trade-offs that are necessary to support virtual prototypes of complex systems. [source] Measuring The Business Impact of E-Learning: An Empirical StudyPERFORMANCE IMPROVEMENT QUARTERLY, Issue 3 2003Greg Wang ABSTRACT This study fills a gap in the current HRD literature of return on investment (ROI) analysis of technology-based learning interventions. Using a Type IV control group method as defined by Wang (2002), the study empirically analyzed and measured the learning effectiveness and the business impact of an e-learning system implemented in General Electric Company. The e-learning system under study demonstrated significant economic returns in regard to reduced learning response time and reduced project cycle time. The study shows that e-learning, as a means of technology-based HRD intervention, can be highly effective as a performance support learning mechanism, although the results also suggest that e-learning alone is not sufficient to replace the traditional face-to-face learning platforms. [source] Optimizing injection gate location and cycle time for the in-mold coating (IMC) processPOLYMER COMPOSITES, Issue 5 2002Mauricio Carbera-Rios The standard practice when compression molding Sheet Molding Compound (SMC) exterior automotive body panels is to in-mold coat (IMC) the parts. Consequently, IMC needs to be considered an integral part when improving the process. Selecting the proper IMC injection gate location to obtain a defect-free coated part and properly setting the IMC processing conditions to reduce its cycle time are both key decisions for the IMC process. In the present work, an optimization method that involves metamodeling through either linear regression or artificial neural networks is explored with two purposes: first, to select the injection gate location(s) with the objective of minimizing the potential for surface defects in the coating; and second, to set the mold wall temperature and the initiator concentration to minimize the cure time for a given minimum required flow time. [source] Rotational molding cycle time reduction through surface enhanced molds: Part A,Theoretical studyPOLYMER ENGINEERING & SCIENCE, Issue 9 2007M.Z. Abdullah Rotational molding has been regarded as a plastic molding method with great potential. The process offers virtually stress-free products having no weld lines or material wastage, and utilizes relatively inexpensive molds. Yet its widespread growth is hindered due to long production cycle times, which are limited by the time required to heat up and cool down the mold and the product. To address this issue, efforts have been made to enhance heat transfer to and from molds, ultimately reducing cycle times. The application of extended and rough surfaces to molds is investigated here. The aim of this study is to predict reductions in cycle time due to the enhancement of mold surfaces (i.e. roughness-enhanced and pin-enhanced molds). By utilizing a combination of heat transfer correlations, numerical analysis, and an existing rotational molding process simulation, cycle time predictions were made. The average predicted cycle time reductions were ,21 and 32% for the roughness-enhanced and pin-enhanced molds considered, under a variety of conditions. POLYM. ENG. SCI., 47:1406,1419, 2007. © 2007 Society of Plastics Engineers [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] Real-time monitoring of injection molding for microfluidic devices using ultrasoundPOLYMER ENGINEERING & SCIENCE, Issue 4 2005Y. Ono Real-time process monitoring of the fabrication process of microfluidic devices using a polymer injection molding machine was carried out using miniature ultrasonic probes. A thick piezoelectric lead-zirconate-titanate film as an ultrasonic transducer (UT) was fabricated onto one end of a 4-mm diameter and 12-mm long steel buffer rods using a sol gel spray technique. The center frequency and 6 dB bandwidth of this UT were 17 MHz and 14 MHz, respectively. A signal-to-noise ratio of more than 30 dB for ultrasonic signals reflected at the probing end was achieved. The probe can operate continuously at 200°C without ultrasonic couplant and cooling. Clear ultrasonic signals were obtained during injection molding of a 1-mm-thick part having test patterns on its surface. Shrinkage of the molded part and part detachment from the mold were successfully monitored. Surface imperfections of the molded parts due to a lack of the sufficient holding pressure is discussed with regard to the ultrasonic velocity obtained. The presented ultrasonic probes and technique enable on-line quality control of the molded part by optimizing the holding pressure and improvement of process efficiency by reducing the cycle time. POLYM. ENG. SCI., 45:606,612, 2005. © 2005 Society of Plastics Engineers [source] Gel point prediction of metal-filled castor oil-based polyurethanes system,POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10-12 2002Anil Srivastava Abstract Prediction of gel point conversion and network formation is of great importance in polycondensation during synthesis as well as processing. It enables one to estimate the safe conversions for reactor operation without gelation and the cycle time during processing, and plays an important role in controlling the molding parameters used for reinforced reaction injection molding (RRIM), reaction injection molding (RIM) and compression molding. Theories of gelation have been extensively published in the literature and supported by experimental data for various polycondensation systems. However, most such studies relate to unfilled systems. In this work, metal-filled polyurethanes have been synthesized in bulk by reacting toluene di-isocyanate with castor oil and its polyols possessing different hydroxyl values. Metallic aluminum powder (10,40% by weight) was dispersed thoroughly in castor oil and its polyols before reacting at different temperatures (30,60,°C) in a moisture-free, inert environment. The gel point conversions were measured experimentally and an empirical model from the experimental data has been developed to predict the gelation behavior. The proposed model could be of immense importance in the paints, adhesives and lacquers industries, which use castor oil in bulk. From these experiments it was concluded that: (i) fine metal powder gives a rise in viscosity; (ii) metal fillers not only restrict the molecular motion due to the increase in viscosity, but also lower the conversion; (iii) the vegetable oil and its polyols have a number of bulky groups, which also impart the delay tendency in gel time; (iv) there is a change in gelation dynamics at 50,°C , this is due to the change in reactivity of di-isocyanates; (v) the presence of metal filler does not initiate the intermolecular condensation; (vi) there is a gap between theoretical and experimental gel point owing to the unequal reactivity of the secondary alcohol position; (vii) there is an inverse relationship of gel time with the reaction temperature and hydroxyl value of polyols. An empirical model based on process parameters, i.e., hydroxyl value, temperature, shape factor and filler concentration, has been derived and found to be adequate for the metal-filled system. The correlation coefficient on the data is on the lower side in some cases because the following were not taken into account: (i) the first-order kinetics followed by the reaction in the second half while it is tending towards gelation; (ii) the error in observing the gel point viscosity; (iii) errors in assuming the spherical shape of aluminum metal powder; (iv) errors due to failure to maintain the constant speed in agitation. Copyright © 2003 John Wiley & Sons, Ltd. [source] Economic Lot Scheduling Problem with ReturnsPRODUCTION AND OPERATIONS MANAGEMENT, Issue 4 2006Ou Tang Motivated by a case study of a company that produces car parts, we study the multi-product economic lot scheduling problem for a hybrid production line with manufacturing of new products and remanufacturing of returned products. For this economic lot scheduling problem with returns (ELSPR), we consider policies with a common cycle time for all products, and with one manufacturing lot and one remanufacturing lot for each product during a cycle. For a given cycle time, the problem is formulated as a mixed integer linear programming (MIP) problem, which provides the basis for an exact solution. The application of this model for one of the core products of the case study company indicates a 16% reduction in cost compared to the current lot scheduling policy. [source] Determinants of integrated product development diffusionR & D MANAGEMENT, Issue 1 2006Todd Boyle Integrated product development (IPD) is an approach for developing new products focused on the early and active involvement of design, manufacturing, marketing and other key new product development (NPD) stakeholders in order to achieve cross-functional integration and concurrent execution of various NPD activities. The benefits of IPD are well known in both the academic literature and popular press, including significant reductions in NPD cycle time and costs. However, in spite of these benefits, for the majority of manufacturing organizations, IPD is not used on 100% of NPD projects. This research develops a model of the organizational contextual factors influencing the diffusion of IPD in organizations. Results of surveying 269 NPD managers indicate that the complexity of certain IPD practices and support for IPD directly influence IPD diffusion, while an innovative organizational climate and the complexity of the organization's NPD activities indirectly influence IPD diffusion through IPD support. [source] The utility of ultra-performance liquid chromatography/electrospray ionisation time-of-flight mass spectrometry for multi-residue determination of pesticides in strawberryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2008Michael J. Taylor The utility of ultra-performance liquid chromatography/orthogonal-acceleration time-of flight mass spectrometry (UPLC/TOFMS) for the rapid qualitative and quantitative analysis of 100 pesticides targeted in strawberry was assessed by comparing results with those obtained using a validated in-house UPLC tandem mass spectrometry (MS/MS) multi-residue method. Crude extracts from retail strawberry samples received as part of the 2007 annual UK pesticide residues in food surveillance programme were screened for the presence of pesticide residues using UPLC/TOFMS. Accurate mass measurement of positive and negative ions allowed their extraction following ,full mass range data acquisition' with negligible interference from background or co-eluting species observed during UPLC gradient separation (in a cycle time of just 6.5,min per run). Extracted ion data was used to construct calibration curves and to detect and identify any incurred residues (i.e. pesticides incorporated in or on the test material following application during cultivation, harvest and storage). Calibration using matrix-matched standards was performed over a narrow concentration range of 0.005,0.04,mg,kg,1 with determination coefficients (r2) ,0.99 for all analytes with the exception of malathion/fenarimol/fludioxanil (r2,=,0.98), quassia/pymetrazine (r2,=,0.97) and fenthion sulfone (r2,=,0.95). Residues found in selected samples ranged from 0.025,0.28,mg,kg,1 and were in excellent agreement with results obtained using UPLC/MS/MS. Mass measurement accuracies of ,5,ppm were achieved consistently throughout the separation, mass range and concentration range of interest thus providing the opportunity to obtain discrete elemental compositions of target ions. © Crown copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] An integrated inventory model with controllable lead time and distribution-free demandAPPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 4 2010Shu-Lu Hsu Abstract The impact of lead time reduction on an integrated periodic review inventory system comprising a single vendor and multiple buyers with a step crashing cost function and service-level constraints is studied. The probability distribution of demand during the protection period for each buyer is unknown, but the mean and the variance are given. Each production lot of the vendor can be delivered in a number of shipments to all buyers. A minimax distribution-free procedure with Lagrange multipliers is applied to determining the lead time, the common shipment cycle time, the target levels of replenishments and the number of shipments per production cycle so that the expected total system cost is minimized. Numerical experiments along with sensitivity analysis were performed to illustrate the effects of parameters on the decision and the total system cost. Copyright © 2009 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||