Maximum Cell Size Research Articles

Three-dimensionally nanostructured alumina film on glass substrate: Anodization of glass surface

We report fabrication of a three-dimensionally nanostructured porous alumina film on a glass substrate exhibiting an angle-insensitive optical transmission property using a robust anodization with ‘fictive critical anodizing-voltage’ estimation technique. The fictive critical anodizing-voltage is estimated from a resistance profile curvature; it offers a limit of a maximum cell size of an anodization system. Using this technique, we have obtained an extra-large cell (over 1μm) and thick (∼2.5μm) alumina film. Observation of a fine structure on the current density profile at the initial anodizing stage is also presented with resistance profiling, cross-sectional scanning and transmission electron microscopies.

Ecological control on micro-ornamentation of conodont elements

AbstractConodonts are considered now as specific group of early Chordata or even Vertebrata. Fifteen tooth-like conodont elements of seven morphological types compose the oral apparatus of conodonts. The elements demonstrate complex morphology. All the elements bear polygonal micro-ornamentation. The ornamentation is considered as representing imprints of the epithelium cells. Ecological dependencies of the cell sizes are known for some recent organisms.The maximum cell sizes are characteristic of optimal environmental conditions. Thus, one can supposes that decreasing in cell imprint size in the conodonts marks disturbance in water temperature or/and oxygen content.

Disassembly sequence planning in a disassembly cell context

In this paper a two-phase approach is proposed for determining the optimal disassembly sequence when the disassembly system has a cellular configuration. Operations are first grouped into cells based on the resources they require with the goal of minimizing machine acquisition costs. The aim is to group together those operations that use similar equipment in order to achieve good utilization levels of such equipment. A maximum cell size may be imposed. Once the cells have been formed and the operations have been assigned to them, a metaheuristic algorithm (namely GRASP) is used to search for the disassembly sequence for each product that leads to the minimum number of intercellular movements. To account for uncertainty regarding the condition in which the product may arrive, each disassembly task is assumed to be required with a certain probability, regardless of the other tasks. AND/OR precedence relations among the disassembly tasks are also considered. The proposed approach is illustrated on a randomly generated disassembly problem.

Cell size determination in WCDMA systems using an evolutionary programming approach

This paper deals with the problem of the cell size determination in WCDMA-based mobile networks, in multiservice environments. The objective is to obtain the maximum cell size, given a set of services with their corresponding constraints, in terms of quality of service (QoS), binary rate, etc. To achieve this, we have to find the optimal services’ load factors which maximizes the cell radius of the system under traffic criteria. We apply an evolutionary programming algorithm to solve the problem, which codifies and evolves the services’ load factors. We have compared our approach with an existing algorithm in several multiservice scenarios, improving its solutions in terms of cell size.

Technical Note: Field-Scale Surface Soil Moisture Patterns and Their Relationship to Topographic Indices

Understanding variability patterns in soil moisture is critical for determining an optimal sampling scheme both in space and in time, as well as for determining optimal management zones for agricultural applications that involve moisture status. In this study, distributed near-surface gravimetric soil moisture samples were collected across a 3.3 ha field in central Illinois for ten dates in the summer of 2002, along with dense elevation data. Temporal stability and consistency of the moisture patterns were analyzed in order to determine a suitable grid size for mapping and management, as well as to investigate relationships between moisture patterns and topographic and soil property influences. Variogram analysis of surface moisture data revealed that the geospatial characteristics of the soil moisture patterns are similar from one date to another, which may allow for a single, rather than temporally variable, variogram to describe the spatial structure. For this field, a maximum cell size of 10 m was found to be appropriate for soil moisture studies on most of the sampling occasions. This could indicate an appropriate scale for precision farming operations or for intensive ground sampling. While some areas had consistent behavior with respect to field mean moisture content, no conclusive relationships between the overall patterns in the moisture data and the topographic and soil indices were identified. There were, however, some small but significant correlations between these two sets of data, particularly plan and tangential curvature, and also slopes. In areas of convergent flow, moisture content exhibited a slight tendency to be wetter than average. There also seemed to be a small influence of scale on the relationship between moisture patterns and topographic curvatures.

A particle swarm optimization algorithm for part–machine grouping

Although in the last years different metaheuristic methods have been used to solve the cell formation problem in group technology, this paper presents the first particle swarm optimization (PSO) algorithm designed to address this problem. PSO is a population-based evolutionary computation technique based on a social behavior metaphor. The criterion used to group the machines in cells is based on the minimization of inter-cell movements. A maximum cell size is imposed. Some published exact results have been used as benchmarks to assess the proposed algorithm. The computational results show that the PSO algorithm is able to find the optimal solutions on almost all instances.

Regional diatom body size distributions in streams: Does size vary along environmental, spatial and diversity gradients?

:We investigated regional diatom species distribution, local diversity, and spatial variation in body size from 105 boreal stream sites in Finland. Stream diatom body size distributions ranged from a slightly right-skewed pattern at the largest study extent, comprising the whole country, to symmetrical distributions within watersheds. Compared to earlier findings for larger organisms, diatom body size distributions were more symmetrical, implying either narrower study extent or fundamental differences between unicellular and multicellular organisms. There was a weak positive correlation (r = 0.239; P < 0.05) between latitude and average maximum cell size in stream diatom assemblages. Multiple linear regression showed that average maximum cell size was best accounted for by a model incorporating moss cover and latitude. There was also a weak (r = 0.290; P < 0.01; n = 105) negative correlation between local species richness and average cell size corroborating the earlier findings for other organism groups.

Fabrication by using a sputtering method and charge–discharge properties of large-sized and thin-filmed lithium ion rechargeable batteries

Large-sized and thin-filmed lithium ion rechargeable batteries composed of a Li 2− x Mn 2O 4 positive electrode, a V 2O 5 negative electrode and a Li 3PO 4− x N x electrolyte have been developed on glass substrates by using a sputtering method, and their electrochemical characteristics were investigated. A typical cell size of the batteries was 100 mm × 100 mm in area and about 3.1 μm in thickness as a whole. The battery with a maximum cell size of 200 mm × 200 mm was also successfully fabricated. These pinhole-free batteries showed a good rechargeable performance between 3.5 and 0.3 V with a typical charge–discharge capacity of about 0.9 mAh for the battery with a 100 mm × 100 mm size and of about 5.5 mAh for the battery with a 200 mm × 200 mm size. These batteries having almost the same characteristics have stably been fabricated with a good yield rate, and they could drive a digital watch as one of realistic portable devices more than 1 month with only one time charge.

A new branch-&-bound-enhanced genetic algorithm for the manufacturing cell formation problem

This paper deals with the manufacturing cell formation (MCF) problem, which is based on group technology principles, using a graph partitioning formulation. An attempt has been made to take into account the natural constraints of real-life production systems, such as operation sequences, minimum and maximum numbers of cells, and maximum cell sizes. Cohabitation constraints were added to the proposed model in order to deal with the necessity of grouping certain machines in the same cell for technical reasons, and non-cohabitation constraints were included to prevent placing certain machines in close vicinity. First, the problem is solved with a genetic algorithm (GA), using a binary coding system that has proved superior to the classic integer coding systems. A new Branch-and-Bound (B&B) enhancement is then proposed to improve the GA's performance. The results obtained for medium-sized instances using this enhancement are better than those obtained using the GA alone. Given these results, it is reasonable to assume that the B&B enhancement will provide good results for large real-life problems.

Effect of Foaming Temperature Control on Cell Size and Cell Density of Microcellular Plastics

In this study, noticing foaming temperature as a factor, which induces thermodynamic instability for cell nucleation of Microcellular plastics, the effect of control method of foaming temperature on cell size and cell density - that is number per unit volume of foamed plastics - were investigated. Generally, foaming by using batch process is carried out as follows. First, blowing agent is soaked into plastics until saturation under high pressure and soaking temperature. After plastics were saturated with blowing agent, pressure is released rapidly and then temperature is raised to foaming temperature and cells are nucleated and grown. Finally, rapid cooling controls cell growth. In this case, two methods can be considered for the control of foaming temperature. One is the elevated temperature method in which temperature is raised to foaming temperature and cells are grown after decompression in the foaming process. The other is the constant temperature method in which the temperature is already kept at foaming temperature before decompression. That is, it is the method of performing soaking and foaming at the same temperature. Polymethylmethacrylate (PMMA) resins were foamed under foaming conditions which the same foaming magnification is produced by both methods and cell size and cell density of foamed PMMA were investigated. As results, in case of production of the foamed plastics having the same foam magnification, it turned out that cell density of foamed plastics becomes large and average cell size becomes small but the maximum cell size becomes large by the elevated temperature method. On the other hand, although the maximum cell size becomes small, average cell size becomes large by the constant temperature method.

Microfoaming of flax and wood fibre reinforced polypropylene composites

Natural and wood fibre reinforced plastics as a relatively new group of environmental friendly materials have been extensively applied in interior, building applications and in the automobile industry. Among others, natural and wood fibre reinforced foamed polymer materials are of high significance because of the possibility of their reducing the density of automotive components which have a cellular structure. However, the properties of these materials have not been fully investigated and described. Microcellular composites of polypropylene containing natural and wood fibre was prepared using an injection moulding process. In the present work, the manufacturing technology of natural and wood fibre reinforced polymer microfoams was developed and the influence of fibre and microvoid content on its property spectrum was systematically investigated. The forming of microvoids and the degree of foaming related to the variation of the processing parameters in connection with manufacture technology was characterised. Measurement of density, cell size, tensile and flexural properties of the prepared composites was carried out. The cell structure is dependent on flow direction of foaming. The density of microfoamed wood fibre-PP composites was reduced by about 24% and decreased by as much as 0.77 g/cm3.Light microscopy showed that the cells are circular and it was also observed that the maximum cell sizes are between 10–50 μm. Water absorption and scanning electron microscopy of the composites were also investigated. Considering the experimental results, it can be deduced that the microcellular composites exhibit a possible combination of relatively good engineering properties and lower density for different technical applications.

CELLULAR STRUCTURE OF PEANUT‐BASED EXTRUDED SNACK PRODUCTS USING SCANNING ELECTRON MICROSCOPY

ABSTRACTA mixture of partially defatted peanut flour (12% fat) and rice flour was extruded to produce indirectly, puffed extrudates using a corotating twin‐screw extruder. Extrudates were dried to obtain half‐products of 11‐12% moisture content, and the half‐products were expanded by deep‐fat frying. The effects of three levels of peanut flour (30, 40, and 50%), screw speed (200, 300, and 400 rpm) and feed rate (4, 5, and 6 kg/h) were studied by characterizing the cellular structure of expanded snack products using Scanning Electron Microscopy (SEM). Average cell size (mm2) and the number of cells per unit area (cm2) were determined from the interior cross‐section area of snack products. Those parameters were influenced mainly by the level of peanut flour followed by screw speed and feed rate. Increasing peanut flour from 40 to 50% produced less puffed final products resulting in small cell size compared to snacks of 30 ‐ 40% peanut flour. The maximum cell size was produced in the snack products extruded with peanut flour of 30 ‐ 40% at screw speed of 250 ‐ 330 rpm and feed rate of 4.7 ‐ 5.7 kg/h. While the number of cells was relatively similar regardless of screw speed and feed rate, increasing peanut flour increased the number of cells. The cell walls became thicker with increasing feed rate.

Morphology and Physico-Mechanical Properties of Closed Cell Microcellular EPDM Rubber Vulcanizates: Effect of Conductive Carbon Black and Blowing Agent

The morphology of the composite based on a new controlled long chain branching grade, oil extended EPDM (Keltan 7341A) and highly conductive carbon black (vulcanXC72) filled compound has been studied from SEM photomicrographs with variation of blowing agent and conductive carbon black filler loading. The average cell size, maximum cell size and cell density varies with variation of blowing agent and filler loading. Physical properties like relative density, hardness, tensile strength, modulus, tear strength decreases with blowing agent concentration. Enclosed gas pressure in a closed cell increases relative modulus at higher strain. Elongation at break decreases with blowing agent loading at higher filler loading. At lower filler loading it increases both with filler and blowing agent loading. The elastic nature of closed cells reduces the hysteresis loss compared to solid compounds. The stress relaxation behavior is independent of blowing agent loading.

Study on foaming water‐swellable EPDM rubber

AbstractA foaming ethylene propylene diene terpolymer (EPDM) water‐swellable rubber (WSR) was prepared using the multicomponent mechanical blending technology. The morphology of unfilled and silica‐filled foaming EPDM WSR was studied from micrographs. The average cell size, maximum cell size, and cell density of the foaming WSR had a peak value with a 4‐phr foaming agent loading in both unfilled and silica‐filled WSR. The addition of silica made the average cell size and maximum cell size decrease and the cell uniform. With incorporation of silica, the tensile strength of the unfoaming WSR increased three times, while that of the foaming WSR increased about six times before immersing it into water. After water‐swelling, the mechanical properties of both the unfilled WSR and silica‐filled unfoaming WSR decreased, but that of the silica‐filled foaming WSR increased. The silica filler accelerated the water‐swelling rate and cut down the water‐swelling equilibrium time at the same time. The foaming WSR had a better volume water‐swelling ratio than that of the unfoaming WSR in both the unfilled and silica‐filled WSR. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3712–3717, 2002

Effect of aluminium silicate filler on morphology and physical properties of closed cell microcellular ethylene–octene copolymer

The effect of aluminium silicate filler on the morphology of the microcellular ethylene–octene copolymer (Engage) has been studied from SEM photomicrographs with variation of blowing agent and silicate filler loading in comparison to the unfilled vulcanizates. The average cell size, maximum cell size and cell density varies with variation of blowing agent and filler loading. Physical properties like relative density, hardness, tensile strength, elongation at break, modulus, tear strength decreases with blowing agent concentration. However tensile strength, modulus (100%), tear energy and hardness varies linearly with the density of the filled vulcanizates. The elastic nature of closed cells reduces the hysteresis loss compared to solid compounds. Set properties improve with blowing agent concentration. It is observed that stress relaxation behavior is independent of blowing agent loading i,e., density of closed cell microcellular vulcanizates. Theoretically flaw sizes are found to be about 2.57 times larger than maximum cell sizes observed from SEM photomicrographs.

Morphology and physical properties of closed cell microcellular ethylene–octene copolymer: Effect of precipitated silica filler and blowing agent

AbstractThe morphology of the microcellular ethylene–octene copolymer (Engage) of both unfilled and precipitated silica‐filled compounds was studied from SEM photomicrographs with variation of blowing agent and silica filler loading. The average cell size, maximum cell size, and cell density varies with variation of blowing agent and filler loading. Physical properties similar to relative density, hardness, tensile strength, elongation at break, modulus, and tear strength decreases with blowing agent concentration. The elastic nature of closed cells reduces the hysteresis loss compared to solid compounds. Set properties improve with blowing agent concentration. It is observed that stress relaxation behavior is independent of blowing agent loading (i.e., density of closed cell microcellular vulcanizates). Theoretically, flaw sizes are found to be about 3.08 times larger than maximum cell sizes observed from SEM photomicrographs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 357–366, 2002

Effects of thermal noise on accuracy of measured BLAST capacities

There are ever increasing demands, in wireless communications, for additional capacity to handle voice, data and wideband Internet applications. These demands are constrained by the bandwidth that was allocated to wireless communications and practical limits on maximum power and minimum cell size. The spectral efficiencies in present day wireless systems hover around 1 bit/s/Hz. BLAST (Bell-labs LAyered Space-Time) is a communication technique for achieving very high spectral efficiencies in highly scattering environments using multiple transmit and receive antennas. A measurement campaign was undertaken to assess the BLAST gains in spectral efficiency in various environments. The measurements were to be performed over a narrow band at 2.44 GHz with five transmitting and seven receiving antennas, respectively. The effects of thermal noise on the accuracy of measured BLAST capacities are investigated.

Grouping genetic algorithms: an efficient method to solve the cell formation problem

The layout problem arises in a production plant during the study of a new production system, but also during a possible restructuring. The main aim of layout design is to reduce transportation and maintenance, which simplifies management, shortens lead time, improves product quality and speeds up the response to market fluctuations. A principle of Group Technology (GT) advocates the division of a unity into small groups or cells. As it is most of the time impossible to design totally independent cells, the problem is to minimise traffic of items between the cells, for a fixed maximum cell size. This problem is known as cell formation problem (CFP). We propose here an original approach to solve this NP-hard problem. It is based on a Grouping Genetic Algorithm (GGA), a special class of genetic algorithms, heavily modified to suit the structure of grouping problems. The crucial advantage of this GGA is that it is able to deal with large instances of the problem thus becoming a powerful tool for an engineer determining a plant layout, allowing him or her to try several plant options, without the limitation of huge computation times.

The flow stress of fractal dislocation arrangements

Abstract In metals deforming under multislip conditions, fractal dislocation arrangements may develop. The composite model of the flow stress of a dislocation cell structure is generalized for dislocation arrangements which exhibit a broad spectrum of local hardness. Both forest strengthening (cell walls) and the Orowan stress (cell interiors) are taken into account. Relations between the flow stress and the characteristic parameters of the dislocation arrangement such as fractal dimension, maximum and minimum cell size are established. The model is used to calculate stress dependences of fractal dimension and cell wall volume fraction of dislocation patterns in high-symmetry oriented f.c.c. single crystals. The results are in good agreement with experimental observations on Cu and Cu-rich Cu–Mn.

Effect of mating status and age of Microplitis rufiventris (Hym., Braconidae) females on the growth pattern and number of their teratocytes

The effect of mating status and age of the female of Microplitis rufiventris parasitoid on the growth pattern of its teratocytes during the larval development is described as well as the changes in the number of these cells. The growth pattern of teratocytes derived from haploid eggs significantly differed from that of eggs deposited by mated females. Both cell diameter and the number of maturing M. rufiventris teratocytes was fertilization‐dependent. Following the parasitization of Spodoptera littoralis larvae with virgin parasitoid females, the host larvae hosted a large number of cells of smaller size at the end of parasitoid development. The opposite effect was seen when the host larvae contained female parasitoid larvae. The age of the female at parasitization had an effect on the maximum cell size attained prior to parasitoid emergence. It seems that there are two factors other than mating which affect the number of teratocytes: degeneration inside the host haemolymph and to some degree accidental ingestion by parasitoid larva.