Short Cycle Time Research Articles

High current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrate.

In mixed-culture microbial fuel cells (MFCs), exoelectrogens and other microorganisms compete for substrate. It has previously been assumed that substrate losses to other terminal electron acceptors over a fed-batch cycle, such as dissolved oxygen, are constant. However, a constant rate of substrate loss would only explain small increases in coulombic efficiencies (CEs, the fraction of substrate recovered as electrical current) with shorter cycle times, but not the large increases in CE that are usually observed with higher current densities and reduced cycle times. To better understand changes in CEs, COD concentrations were measured over time in fed-batch, single-chamber, air-cathode MFCs at different current densities (external resistances). COD degradation rates were all found to be first-order with respect to COD concentration, even under open circuit conditions with no current generation (first-order rate constant of 0.14 ± 0.01 h(-1) ). The rate of COD removal increased when there was current generation, with the highest rate constant (0.33 ± 0.02 h(-1) ) obtained at the lowest external resistance (100 Ω). Therefore, as the substrate concentration was reduced more quickly due to current generation, the rate of loss of substrate to non-exoelectrogens decreased due to this first-order substrate-concentration dependence. As a result, coulombic efficiencies rapidly increased due to decreased, and not constant, removal rates of substrate by non-exoelectrogens. These results show that higher current densities (lower resistances) redirect a greater percentage of substrate into current generation, enabling large increase in CEs with increased current densities. Biotechnol. Bioeng. 2014;111: 2163-2169. © 2014 Wiley Periodicals, Inc.

Scaling computation with silicon photonics

Abstract

Characterisation of thermal influences after laser processing polycrystalline diamond composites using long to ultrashort pulse durations

The laser processing of cutting tool edges is growing rapidly due to its flexibility, short cycle times and negligible waste. However, the quality of the tool and its cutting edge can vary greatly with different laser parameters and processing strategies. The generation of a graphitic carbon layer and a heat affected zone (HAZ) could occur during laser processing which is expected to reduce the quality and lifetime of the cutting tool. By using focussed ion beam (FIB) techniques to generate a cross section, the graphitic carbon layer and heat affected zone are characterised quantitatively and qualitatively for laser processes and as a reference, lapping and wire electro-discharge machining processes, used in the generation of polycrystalline diamond composite cutting tool edges. A focus is put on laser based techniques which vary in pulse duration from long microsecond pulses down to ultrashort picosecond pulses. A deep insight into the focussed ion beam techniques used and extensive analysis through Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX) into the laser–material interactions are presented.

Optimization of the Time of Task Scheduling for Dual Manipulators using a Modified Electromagnetism-Like Algorithm and Genetic Algorithm

A method based on a modified electromagnetism-like with two-direction local search algorithm (MEMTDLS) and genetic algorithm (GA) is proposed to determine the optimal time of task scheduling for dual-robot manipulators. A GA is utilized to calculate the near-optimal task scheduling for both robots, and the MEMTDLS is recommended as a suitable alternative in obtaining multiple solutions at each task point for both manipulators with minimal error. During the course of the tour, the robots move from point to point with a short cycle time, while ensuring that no collision occurs between the two manipulators themselves or between the dual manipulators and the static obstacles in the workspace. The movement and the configurations of the manipulators at the task points were illustrated using a simulator that was developed via Visual Basic .Net. The method is verified using two simulators that are used as examples for two identical four-link planar robots that work in the environment, with square-shaped obstacles cluttered at different locations.

In-situ spectroscopic ellipsometry study of copper selective-area atomic layer deposition on palladium

Selective area copper atomic layer deposition on palladium seed layers has been investigated with in-situ real-time spectroscopic ellipsometry to probe the adsorption/desorption and reaction characteristics of individual deposition cycles. The reactants are copper bis(2,2,6,6-tetramethyl-3,5-heptanedionate) vapor and hydrogen gas. Self-limiting atomic layer deposition was observed in the temperature range of 135–230 °C in a low pressure reactor. Under optimal conditions, growth occurs selectively on palladium and not on silicon dioxide or silicon nitride layers. Based on in-situ ellipsometry data and supporting experiments, a new mechanism for growth is proposed. In the proposed mechanism, precursor adsorption is reversible, and dissociatively adsorbed hydrogen are the stable surface intermediates between growth cycles. The mechanism is enabled by continuous diffusion of palladium from the seed layer into the deposited copper film and strong H* binding to palladium sites. Less intermixing can be obtained at low growth temperatures and short cycle times by minimizing Cu/Pd inter-diffusion.

Laser-assisted replication of large-area nanostructures

We proposed and demonstrated a high-throughput fabrication method for large-area nanostructured polymers. The mold used consists of a quartz substrate and a nanostructured diamond-like carbon (DLC) thin film. A laser is irradiated from the back of the mold and only the DLC surface is directly heated. Then the surface of a polymethyl methacrylate (PMMA) film pressed by the mold is melted and the nanostructures are replicated. In this method, replication can be achieved with a low amount of heat and a short cycle time compared with conventional thermal replication. The effects of the laser power density, irradiation time, and environmental temperature on the replication area were experimentally investigated via the spot irradiation of a laser. Furthermore, the temperature distribution around the surfaces of the mold and polymer was investigated by performing numerical simulations. By scanning the laser, we successfully demonstrated the replication of a 500-nm-pitch pattern on a PMMA film with an area of 10×10mm2 in about 10s. This technique is expected to lead to the high-throughput and low-energy fabrication of large-area nanostructured optical films.

Evaluation of energy efficiency in cutting aerospace materials with high-pressure cooling lubricant supply

In the field of machining difficult-to-cut materials like titanium or nickel-based alloys, the use of high-pressure cooling lubricant supply (HPCLS) offers huge potential to significantly increase productivity and process stability. Due to enhanced cooling and lubrication of the cutting zone, tool wear can be decreased which allows higher applicable cutting speeds. Furthermore, process stability can be increased through effective chip breaking and evacuation. Increasing energy prices and legislative framework conditions, require energy efficient machine tools and processes. Since additional energy is required to run the high-pressure pump, it has to be determined if the overall process is still energy-efficient due to the increase in productivity resulting in shorter cycle times. In this paper the overall aim is to evaluate the conventional-flood-cooling and HPCLS in terms of economics and energy efficiency. Therefore a case study has been performed in which the energy consumption and production times for machining a rotationally symmetric jet engine part made of Inconel 718 were compared for both conventional and HPCLS. Furthermore, an ecological evaluation has been conducted to determine the advantageousness of the HPCLS. Due to the rising necessity of suppliers to provide a product carbon footprint, a methodology for assessing the footprint has been applied.

Modeling the Adhesion Bonding Mechanism in Overmolding Hybrid Structural Parts for Lightweight Applications

Reducing vehicle weight to decrease energy consumption and engine emissions is one of the major objectives of the automotive industry today. This goal is mainly achieved by developing new manufacturing technologies for structural lightweight components, such as the hybrid injection molding/composite forming process, which involves preforming a thermoplastic composite laminate and overmolding it to add ribs, attachment points and other features. High part lightness, short cycle times and high degree of automation have recently made this technology an effective solution for the manufacturing of automotive interiors, including door side-impact beams and front ends. In this paper a model of the adhesion bonding mechanism between the overmolded reinforced thermoplastic and the formed composite sheet is proposed, and its dependence on the main process parameters is investigated. The model has been developed conducting experimental tests and eventually validated by means of a significant case study.

Hybrid Genetic Algorithm for Solving Assembly Line Balancing Problem in Footwear Industry

This research develops a heuristic algorithm for assembly line balancing problem (ALBP) of stitching lines in footwear industry. The proposed algorithm can help to design the stitching line with workstations, machines and operators for the production of every new product model. Rank-positional-weighted heuristics and hybrid genetic algorithms are proposed to solve ALBP. First, the heuristics assign tasks and machines to workstations. This solution is then used as an initiative population for hybrid genetic algorithm for further improvement. Real data from footwear manufacturers and experimental designs are used to verify the performance of the proposed algorithm, comparing with one existing bidirectional heuristic. Results indicate that when the size and shape of shoes increase, the proposed genetic algorithm achieves better solution quality than existing heuristics.Production managers can use the research results to quickly design stitching lines for short production cycle time and high labor utilization.

Beach dynamics and oscillations of shoreline position in recent years at Miramar Beach, Goa, India: a study from a GPR survey

Consideration of human influences is crucial to understanding the coastal sediment supply and associated shoreline responses prior to undertaking coastal hazard management studies. Observation of the widening of some selected Indian beaches, especially over the last 6 decades, is of significance. From this perspective, Miramar Beach, Goa, India, was studied using three ground-penetrating radar shallow subsurface profiles (4 m depth). Based on a series of depositional siliciclastic packages, six progradational packages were recognised, which were interrupted by sharp erosional boundaries. These erosional boundaries represent transgressive phases of the shoreline migration. It was observed that the shoreline migration is coupled with the deposition and erosion of sediments, and this is supported by the historical admiralty charts. The optically simulated luminescence dating of the sediments collected at the first progradation period reveals that the age corresponds to the years 1952–1957, which also corroborates the information provided by the local populace. In the past 6 decades, the shoreline growth has been rapid because of the heavy sediment influx from the Mandovi River caused by increased mining activities (since the 1950s) in upstream areas. Since the 1950s, the shoreline has prograded rapidly, building a beach from ~40 to ~280 m wide (average rate of 4 m/year) in response to enhanced sediment supply from the Mandovi River created by mining activities upstream. Superimposed on this overall regressive trend is a series of deposition and erosion cycles. Perhaps, if a similar trend continues, then there will possibly be a further widening of the beach in the future. A close monitoring network is needed to understand the causes of the cycles in shoreline position and to predict their future behaviour. The present investigation on the nature of the coastal response to anthropogenic activities in a river basin as well as the role of short-time cycles on shoreline behaviour in the last 6 decades could be an ideal reference study and motivate the search for similar areas along other coastal locations.

Three-dimensional orientation of compression-molded high-density polyethylene/wood fibers using X-ray micro-tomography

Use of compression molding with a natural fiber-reinforced thermoplastic matrix has been growing rapidly within the last few years in various applications. Wood-reinforced high-density polyethylene offers economic efficiency, a high process reproducibility, short cycle times, a stable and high component quality, and a good recycling ability. In the present study, the distribution of fiber orientation using micro-CT scanner for compression-molded product of varying fiber content was measured, and the effects of fiber content with respect to orientation states are discussed.

자동변속기용 언더 드라이브 브레이크 피스톤의 두께 최적화를 위한 유한요소해석

The under-drive brake piston is an important component in automotive transmissions. It changes the velocity by controlling the gear ratio. It has been traditionally manufactured by hot forging. Recently, there has been an effort to replace this traditional manufacturing method with cold forging in order to improve the dimensional accuracy and decrease the surface roughness. Cold forging uses a smaller amount of initial material and also has a shorter cycle time since the forged surface can be the final surface without the need of post-processing such as machining or grinding. In the current study, finite element analysis was conducted to evaluate a process design using an initial plate with reduced thickness. This smaller thickness decreases the amount of material needed for the part as well as the machining to produce the final product.

Imbalance filling of multi-cavity tooling during powder injection molding

A shortened cycle time with improved productivity is a key justification for multi-cavity molds. However, filling imbalance is an offsetting barrier for multi-cavity molds. The sources for an imbalance are often subtle, in both conventional plastic injection molding and powder injection molding (PIM) industries. The greater thermal conductivity of the PIM feedstock and the subsequent large sintering shrinkage amplify the issue for PIM. Due to its characteristic, the size of PIM parts is relatively smaller than the conventional plastic injection molding and so multi-cavity molds are widely used. Despite the geometrically systematic delivery system and cavities, asymmetric branching of flow paths, uneven viscous heating, and cooling variations exist for the molten feedstock flow to the cavities. These variations significantly limit the benefit of a multi-cavity mold. We investigated the imbalance filling between the near- and far-side cavities in a geometrically symmetric multi-cavity mold for PIM. Via molding simulations and experiments we found that imbalanced filling arises from subtle factors such as non-uniform mold cooling, uneven conduction of the molten feedstock into mold, and uneven viscous heating and their competitive roles between conduction/convection and viscous heating in the multi-cavity molds mainly contribute to imbalance filling the same way in the conventional plastic injection molding.

Applying large electric double layer capacitor systems

This paper provides an insight into the specifications for electric double layer capacitor systems (EDLCs), design issues and production technology. It focuses on systems with power ratings far in excess of 100 kW and with short cycle times. As a result, a major topic of interest is EDLC cooling. Several cooling concepts are compared with each other based on experimental data. This is done for four EDLC configuration types. Mechanical aspects and diagnostics of the electric and thermal system are also covered.

Fabrication of End Quenched Machine: Hardenability Evaluation

The Jominy end quench machine was designed, manufactured and tested. The manganese steel was developed. The as-cast manganese steels were quenched in water at different austenising temperatures and hardenability test was carried out on the samples cut at different distances from the quenched surface with the use of the manufactured Jominy end quench machine. The optical microscope was used to investigate the microstructure of the cut samples. Results revealed that the Jominy end quench machine worked effectively with short cycle time and improved water management system. The extremely rapid cooling prevents the decomposition of the chromium carbides. However, the hardness values of the samples decreased with increase in the distance from the quenched surface and the size of the chromium carbides increased with austentic temperatures which is responsible for reduction in the hardness values of the quenched samples at higher austentinic temperature. The manufactured Jominy end quench machine has advantages of improved water management system and short processing time over the existing ones.

Cycle optimization in cam-lobe grinding for high productivity

Cycle optimization in cam-lobe grinding is presented for improving productivity. It includes novel modeling of the instantaneous geometry, kinematics and temperature for any workpiece form. A technical assessment of three process-control strategies – (1) constant specific material removal rate, (2) constant power, and (3) constant temperature – is made. The constant-temperature process provides the shortest cycle time without thermal damage. A detailed analysis of this process considers the role of machine limitations, including maximum speed, acceleration, and jerk, as well as the cam-lobe geometrical effects. The optimization results are validated by grinding tests in an actual production line.

Dimensioning of Punctiform Metal-Composite Joints: A Section-Force Related Failure Criterion

Reliable line production processes and simulation tools play a central role for the structural integration of thermoplastic composites in advanced lightweight constructions. Provided that material-adapted joining technologies are available, they can be applied in heavy-duty multi-material designs (MMD). A load-adapted approach was implemented into the new fully automatic and fault-tolerant thermo mechanical flow drill joining (FDJ) concept. With this method it is possible to manufacture reproducible high strength FRP/metal-joints within short cycle times and without use of extra joining elements for the first time. The analysis of FDJ joints requires a simplified model of the joint to enable efficient numerical simulations. The present work introduces a strategy in modeling a finite-element based analogous-approach for FDJ-joints with glass fiber reinforced polypropylene and high-strength steel. Combined with a newly developed section-force related failure criterion, it is possible to predict the fundamental failure behavior in multi-axial stress states. The functionality of the holistic approach is illustrated by a demonstrator that represents a part of a car body-in-white structure. The comparison of simulated and experimentally determined failure loads proves the applicability for several combined load cases.

半導体ウェハ搬送ロボットへのPreshaping制御の応用と実験検証

In automated production of industrial products such as semiconductor wafers and liquid crystal panels, transfer robots are widely used for conveyance. Although high speed motion provides shorten cycle time residual vibration generally occurs. Thus, vibration control is needed to suppress the residual vibration. This paper presents an identification technique based on FFT and least-square approach and proposes to employ a preshaping approach to reduce the residual vibration. Firstly, we achieve good vibration suppression by applying this approach to angular velocity commands for the robot. However, using a preshaping approach in that way causes a change in the end-effector trajectory, which may result in collision of the semiconductor wafer with the processing equipment. For this reason, we apply the preshaping approach to end-effector velocity instead of joint angular velocity to maintain the original end effector trajectory, and then derive the angular velocity by using inverse kinematics. Hence, we can achieve cycle time reduction by vibration suppression under the exact tracking to the original trajectory.

A fuzzy-neural and bi-objective scheduling system for job scheduling in a wafer fabrication factory

This paper established a fuzzy-neural and bi-objective scheduling system to improve the performance of job scheduling in a wafer fabrication factory. First, by controlling the standard deviation of cycle time, the fuzzy-neural and bi-objective scheduling system facilitates the rapid assignment of the internal due date. Subsequently, based on a precise cycle time estimation using a fuzzy back propagation network, the system attempts to assign a tight due date if more time is allowed. After the jobs related with an order are released into the wafer fabrication factory, a bi-objective dispatching rule is used to shorten cycle time standard deviation, and at the same time, to ensure on-time delivery, which is distinct from the previous studies because the existing dispatching rules in this field were not designed for such purposes. According to the experimental results, the proposed methodology is better than some existing approaches in both due date assignment and on-time delivery.

Visualising working capital at the customer level

A shorter cycle time of working capital (CCC) frees cash from operations. Companies emphasise the meaning of efficient supply chain operations, but also customers can impact the length of the CCC. Working capital management affects customer profitability through the interest costs. If the reasons behind long CCCs of orders are known, managers can pay attention to them. This paper takes the working capital management research to the customer order level, and includes working capital in customer profitability studies. We have studied the reasons behind the long CCCs of certain customers in the context of the paper industry. Four customer-related reasons for a long CCC were found: long credit terms granted to customers, the payment behaviour of customers, problems with deliveries, and problems in invoicing procedures. The paper shows that a long CCC decreases profitability at the order level.