Why is software late? An empirical study of reasons for delay insoftware development

A study of the reasons for delay in software development is described. The aim of the study was to gain an insight into the reasons for differences between plans and reality in development activities in order to be able to take actions for improvement. A classification was used to determine the reasons. 160 activities, comprising over 15000 hours of work, have been analyzed. The results and interpretations of the results are presented. Insight into the predominant reasons for delay enabled actions for improvements to be taken in the department concerned. Because the distribution of reasons for delay varied widely from one department to another, it is recommended that every department should gain an insight into its reasons for delay in order to be able to take adequate actions for improvement     

Efficient QoS support in a slotted multihop WDM metro ring

A novel distributed access protocol for a slotted wavelength-division-multiplexing (WDM) metro ring employing all-optical packet switching and supporting quality-of-service (QoS) classes is presented and analyzed. Since we assume that there are more nodes than available wavelengths in the network, we obtain a scalable multihop WDM ring as underlying network architecture. By dividing each channel into several time slots and further applying destination release and slot reuse, data packets can be efficiently transmitted and received in a statistically multiplexed manner. In our architecture, each node is equipped with one tunable transmitter and one fixed-tuned receiver. Furthermore, as we generally consider so-called a posteriori access strategies, different packet selection schemes are proposed and compared. An analytical model based on the semi-Markov process methodology is developed to quantify the performance of one of these schemes. As a key element of the protocol, an efficient QoS support access mechanism is proposed and its performance is evaluated. The new QoS control scheme adopts a frame-based slot reservation strategy including connection setup and termination, which only slightly increases the signaling and node processing overhead. Thus, an efficient hybrid protocol combining connectionless and connection-oriented packet transmissions is proposed     

Intramolecular crosslinking of poly(vinyl alcohol)

Poly(vinyl alcohol) is crosslinked in dilute solution (c=0.1 wt%) with glutaraldehyde. The reaction product is characterized by viscometry and gel permeation chromatography (g.p.c.). The intrinsic viscosity decreases with increasing degree of crosslinking and does not depend on temperature. G.p.c. reveals that the reaction product is not homogeneous, but consists of a mixture of particles with different sizes, possibly both intra- and intermolecularly crosslinked molecules. The intramolecularly crosslinked molecules are smaller in size than the initial polymer molecules and their size depends on the degree of crosslinking. They possess a narrow particle size distribution even if the initial polymer sample had a broad molecular weight distribution.     

Loss modeling and thermal measurement in planar inductors-a case study

This paper covers the experimental investigation and theoretical calculation of losses in a planar inductor under load. Finite-element software is used to perform the loss calculations. Thermally controlled experiments are performed for a range of frequencies to validate the corresponding finite-element method loss calculations. The thermal dependence of the loss mechanisms is also considered.     

RasterCalc: Calculus for Operations on Graphics Colour Rasters

An extended model and calculus, called RasterCalc, is presented for operations on discrete graphics rasters, including their colour functions. The operations are separated into two main categories: operations on domains, and operations on colour functions. The operations are further classified as local and remote, depending on the correspondence between destination and source pixels. The new raster element or pixel can be a function of a single element from one or more rasters, a function of a small area from other rasters, or a function of entire rasters. Local operations have their main applications in computer graphics, while remote operations are more oriented towards image processing. A mathematically oriented notation is used to define and represent the operations included. RasterCalc has been implemented as a procedure package in Pascal, to be used on a powerful, yet expensive display. Recently a C version has been completed for a personal colour computer with a special chip for raster operations. The work reported in this paper is partially supplied by the Dutch Technical Sciences Foundation, under project number LWI 14.0130: “Facilities for raster graphics in programming languages”     

Potential for integration of electrophoretic deposition into electronic device manufacture; demonstrations using silver/palladium

A silver palladium (Ag/Pd) alloy powder is used as an example material to illustrate potential applications of electrophoretic deposition (EPD) in electronics manufacturing, in particular the forming of multilayer devices. The dispersion and deposition of the Ag/Pd powder in acetic acid is characterized. It is found that deposition can be explained by the direct action of electrostatic force on individual particles. Depositions of this Ag/Pd powder are then used to demonstrate: forming of a continuous layer on a rigid substrate; forming of continuous layers in laminated and sintered BaTiO₃ multilayers; and incorporation of patterned depositions into a multilayer by either overcasting the patterned deposition with a particulate slip to form a multicomponent tape, or direct lamination of the patterned deposition to a low temperature co-fired ceramic (LTCC) tape. It is shown that electrically conducting layers can be formed at an average thickness of only two times the diameter of the starting powder. Continuous conductor lines thirty times the average diameter of the starting powder were formed.     

Modeling and Analysis of a Long Thin Conducting Stripline

A long thin conducting stripline embedded in a dielectric and centered between two large conducting plates, i.e., the stripline environment, is considered. The stripline is modeled as infinitely long, infinitely thin, and perfectly conducting by first considering a stripline of finite length, thickness, and conductivity in a dielectric layer. Starting from Maxwell's equations and assuming that the current on the stripline is a propagating wave in length direction, asymptotic expressions for the fields inside and in the neighbourhood of the stripline are deduced. These expressions are used to model the stripline in the stripline environment, which leads to a boundary-value problem for the electric potential. This problem is solved by two different approaches, leading to integral equations for the current and for an auxiliary function describing the electric potential. A relation between the current and the auxiliary function is deduced, which is used to obtain asymptotic expressions for current and impedance. Results are compared with a numerical solution of the integral equation for the current and with results in literature.     

Dynamic vulcanisation of EPDM/PE-based thermoplastic vulcanisates studied along the extruder axis

Simple blending and dynamic vulcanisation of EPDM/PE blends using the resol/SnCl₂ system was studied in an extruder using a series of sampling devices. The melting of the PE pellets occurs just in front of and in the first kneading zone. Upon complete melting of the PE phase, the EPDM/PE blends reach very quickly their final morphology. Crosslinking of the EPDM phase to high levels occurs already when the PE phase is not yet fully molten. The higher the EPDM content, the higher the viscous dissipation, the higher the melt temperature and, consequently, the higher the crosslinking rate. For the EPDM/PE (50/50; w/w) TPV a transition from continuous via co-continuous to fully dispersed EPDM is observed, which is driven by crosslinking. Although the degree of crosslinking of the EPDM rubber is very high, this does not prevent phase inversion of the blend. The EPDM/PE interface is rather blurred, because PE crystalline lamellae are growing into the EPDM domains, probably because of the high compatibility between PE and EPDM (60 wt% of ethene). This study shows that dynamic vulcanisation in extruders proceeds quite differently from that in batch kneaders, where melting, mixing and crosslinking are separated in time. In extruders mass and heat transport, melting of the thermoplastic, morphology development (including dispersion and phase inversion), distribution and dissolution of (crosslinking) chemicals and crosslinking of the rubber do not occur as independent phenomena, but mutually and/or continuously interact.