Economic operating policy and variations in production load

When a reorder point system is used for initiating production orders, the production load on the machines can be treated as a random variable. One way of resolving problems associated with variations in the production load is to use smaller batch quantities, but there are also other possibilities to smooth the load. In this paper we present a model for determining:

(1) the economic batch quantity

(2) the economic planning period

(3) the economic allocation of capacity during the planning period

for items produced exclusively on a group of machines. An example has been solved to illustrate the method.     

Two-element diffractive systems for generation of Bessel fields

We demonstrate experimentally a combination of two apodizing diffractive elements, which generate nearly propagation-invariant Bessel fields efficiently with almost uniform axial intensity distributions over the specified region recently introduced by two of the present authors. Strongly reduced intensity fluctuations near both ends of the propagation-invariant range are verified. Various design and alignment issues of the two-element systrem are addressed numerically.     

Matrix criterion robust linear quadratic control problem

This paper studies a robust linear quadratic (LQ) control problem with multiple quadratic performance indices. Specifically, a linear model is assumed to be available for each of a prespecified set of operating points of a system. A vector-valued quadratic control performance index is given at each operating point. It is then desired to find the constant feedback gains of a linear controller to obtain satisfactory control performance over all the operating points. This is a realistic case involving the minimization of a vector criterion of vector criteria, i.e. a matrix-valued criterion. The matrix-valued criterion gives insight into standard robust LQ design, and leads to several related vector minimization problems, and to natural procedures for computing a satisfactory non-inferior solution to the matrix-valued minimization problem.     

AC Susceptibility and Upper Critical Fields in Rb3C60

The ac susceptibility of a phase-pure Rb₃C₆₀ sample has been investigated in dc magnetic fields up to 14 T. The upper critical fields show a significant positive curvature near T_c indicating a local pairing mechanism.     

Fatigue strength prediction of ultra high strength steel butt‐welded joints

First, fatigue tests were performed on butt‐welded joints made of novel direct quenched ultra high strength steel with high quality welds. Two different welding processes were used: MAG and Pulsed MAG. The weld profiles, misalignments and residual stresses were measured, and the material properties of the heat‐affected zone were determined. Fatigue tests were carried out with constant amplitude tensile loading both for joints in as‐welded condition and for joints after ultrasonic peening treatment. Finally, in fatigue strength predictions, the crack initiation phase was estimated using the procedures described by Lawrence et al. [Lawrence F V, Ho N J and Mazumdar P K (1981) Predicting the fatigue resistance of welds. Annu. Rev. Mater. Sci, 11, 401–425]. The propagation phase was simply estimated using S–N curves for normal quality butt welds, which may contain pre‐existing cracks or crack‐like defects eliminating the crack initiation stage.     

Amorphous Mo–N and Mo–Si–N films in microelectromechanical systems

Micromachining based on metallic structural material possesses several inherent advantages. Metallic thin films can be deposited at room temperature by various means. In microelectromechanical systems they can thus be fabricated on top of polymeric sacrificial materials. The sacrificial layer is finally removed in oxygen plasma either before or after wafer dicing with no need for wet processing. However, in metallic micromachining, it is not trivial to find materials and processes producing structural layers with well‐controlled and uniform mechanical characteristics. Amorphous alloys Mo–N and Mo–Si–N are investigated in this study for the purpose, showing properties superior to polycrystalline metals for microelectromechanical devices and systems applications.     

Processing, Packaging, and Storage Effects on Quality of Freeze-Dried Strawberries

Water sorption isotherms of freeze-dried strawberries were determined using the interval sorption technique. The surface temperature during freeze-drying (from 20°C to 60°C) affected the hygroscopicity of the strawberries, particularly below 0.40 a_w. Over 1 yr, quality changes in dried strawberries were evaluated by sensory analysis at 3-month intervals. Crushing before drying and low processing temperatures improved sensory quality of dried strawberries and vacuum packaging improved storage stability.     

Optimising adjacent membrane segmentation and parameterisation in multicellular aggregates by piecewise active contours

In fluorescence microscopy imaging, the segmentation of adjacent cell membranes within cell aggregates, multicellular samples, tissue, organs, or whole organisms remains a challenging task. The lipid bilayer is a very thin membrane when compared to the wavelength of photons in the visual spectra. Fluorescent molecules or proteins used for labelling membranes provide a limited signal intensity, and light scattering in combination with sample dynamics during in vivo imaging lead to poor or ambivalent signal patterns that hinder precise localisation of the membrane sheets. In the proximity of cells, membranes approach and distance each other. Here, the presence of membrane protrusions such as blebs; filopodia and lamellipodia; microvilli; or membrane vesicle trafficking, lead to a plurality of signal patterns, and the accurate localisation of two adjacent membranes becomes difficult. Several computational methods for membrane segmentation have been introduced. However, few of them specifically consider the accurate detection of adjacent membranes. In this article we present ALPACA (ALgorithm for Piecewise Adjacent Contour Adjustment), a novel method based on 2D piecewise parametric active contours that allows: (i) a definition of proximity for adjacent contours, (ii) a precise detection of adjacent, nonadjacent, and overlapping contour sections, (iii) the definition of a polyline for an optimised shared contour within adjacent sections and (iv) a solution for connecting adjacent and nonadjacent sections under the constraint of preserving the inherent cell morphology. We show that ALPACA leads to a precise quantification of adjacent and nonadjacent membrane zones in regular hexagons and live image sequences of cells of the parapineal organ during zebrafish embryo development. The algorithm detects and corrects adjacent, nonadjacent, and overlapping contour sections within a selected adjacency distance d, calculates shared contour sections for neighbouring cells with minimum alterations of the contour characteristics, and presents piecewise active contour solutions, preserving the contour shape and the overall cell morphology. ALPACA quantifies adjacent contours and can improve the meshing of 3D surfaces, the determination of forces, or tracking of contours in combination with previously published algorithms. We discuss pitfalls, strengths, and limits of our approach, and present a guideline to take the best decision for varying experimental conditions for in vivo microscopy.     

EFFECTS OF DRYING METHOD, PACKAGING, STORAGE TEMPERATURE AND TIME ON THE QUALITY OF SUMMER SAVORY (SATURAJA HORTENSIS L.)

Sensory quality was determined over a one-year period in experiments investigating the effects of packaging, and storage temperature and time on air-dried and freeze-dried samples of summer savory (Saturaja hortensis L.). After-processing flavor intensity was significantly (P < 0.01) higher for both air-dried and freeze-dried summer savory than for frozen summer savory. Storage temperature and packaging had no significant effect on the odor and flavor intensities of air-dried summer savory, but freeze-dried herb samples were particularly sensitive to oxygen atmosphere.