The use of user-interface design knowledge such as general guidelines and environment-specific style guides can be valuable, and is increasingly required in professional user-interface design. However, conventional guidelines and style guides (
and
) in the form of documents are consistently found hard to use. We have earlier demonstrated knowledge-based critiquing to be a technically feasible way of delivering relevant
and
knowledge. The purpose of this study was to investigate the need and acceptability of such techniques for professional user-interface designers.
An experiment was carried out where four professional designers developed user-interface prototypes to a functional specification. The designs were evaluated using our
and
-based critiquing system, which identified a total of 17 deviations from style-guide requirements or design recommendations. Interviews were conducted with the designers to find the reasons for the deviations and to identify important requirements for a critiquing design-support tool. The deviation analysis points to an existing need for better ways of accessing
and
knowledge. The interviews indicate that the designers would find a critiquing tool valuable, provided that it leaves them in control of their work and indicates the severity of the detected deviations. 相似文献
In ferritic steels a propagating cleavage microcrack changes its propagation direction as it advances from grain to grain.
This is due to differences in the orientation of the cleavage planes of two neighboring grains. In order to reach a cleavage
plane in a new grain, a microcrack must first penetrate the grain boundary. Grain boundaries therefore act as natural barriers
in cleavage fracture. The influence of a grain boundary and the associated misorientation in cleavage planes on crack arrest
is here examined using a 3D finite element model with axisymmetric periodicity, representing two grains whose cleavage planes
are tilted and twisted relative to each other. The temperature dependent mechanical properties of ferrite are modeled using
a temperature dependent viscoplastic response. The development of the crack front as the microcrack penetrates through a grain
boundary is here presented. The influence of the twist misorientation on the critical grain size, defined as the largest grain
size that can arrest a rapidly propagating microcrack, is examined in a temperature range corresponding to the ductile to
brittle transition (DBT) region. It is shown that when both tilt and twist misorientation are present, the influence of tilt
and twist, respectively, on crack growth resistance can be decoupled. 相似文献
The pad pitch of modern radio frequency integrated circuits is in the order of few tens of micrometers. Connecting a large number of high‐speed I/Os to the outside world with good signal fidelity at low cost is an extremely challenging task. To cope with this requirement, we need reflection‐free transmission lines from an on‐chip pad to on‐board SMA connectors. Such a transmission line is very hard to design due to the difference in on‐chip and on‐board feature size and the requirement for extremely large bandwidth. In this paper, we propose the use of narrow tracks close to chip and wide tracks away from the chip. This narrow‐to‐wide transition in width results in impedance discontinuity. A step change in substrate thickness is utilized to cancel the effect of the width discontinuity, thus achieving a reflection‐free microstrip. To verify the concept, several microstrips were designed on multilayer FR4 PCB without any additional manufacturing steps. The TDR measurements reveal that the impedance variation is less than 3 Ω for a 50 Ω microstrip and S11 better than –9 dB for the frequency range 1 GHz to 6 GHz when the width changes from 165 µm to 940 µm, and substrate thickness changes from 100 µm to 500 µm. 相似文献
To increase the diversity in functional aliphatic polycarbonates, a series of novel chloro- and bromo-functional six-membered cyclic carbonate monomers were synthesized. Despite asymmetry in the monomer functionalities, homopolymerization of the monomers afforded semicrystalline polycarbonates with a high tendency to crystallize from the melt and/or on precipitation from a THF solution. Melting points were found in the 90-105 °C or 120-155 °C range for polymers comprising methyl or ethyl moieties, respectively, in the backbone. The monomers were further copolymerized with trimethylene carbonate to form random copolymers. Even among some of these random copolymers elements of semicrystallinity were found as confirmed by melting endotherms in DSC. The results clearly show that the incorporation of alkyl halide functionalities in aliphatic polycarbonates may lead to materials with a high ability to form crystallites, even in random copolymers, likely driven by polar interactions due to the presence of the halide functionalities. 相似文献