Non-myopic vehicle and route selection in dynamic DARP with travel time and workload objectives

In dial-a-ride problems, a fleet of n vehicles is routed to transport people between pick-up and delivery locations. We consider an elementary version of the problem where trip requests arrive in time and require an immediate vehicle assignment (which triggers an appropriate route update of the selected vehicle). In this context, a relatively general objective can be stated as a weighted sum of the system's effort and the customers' inconvenience. However, optimizing almost any objective in this immensely complex stochastic system is prohibitively difficult. Thus the earlier work has largely resorted to heuristic cost functions that arise, e.g., from the corresponding static systems. By using the framework of Markov decision processes and the classical M/M/1 queue as a highly abstract model for a single vehicle, we explain why certain intuitive cost functions indeed give satisfactory results in the dynamic system, and also give an explicit interpretation of different components appearing in a general cost function. The resulting family of heuristic control policies is demonstrated to offer a desired type of performance thus justifying the assumed analogy between a multi-queue and dial-a-ride systems.     

GWB: A Solid Modeler with Euler Operators

In Helsinki, a Small but General Set of Manipulative Operations for Boundary Models of Solid Objects Has Been Used to Construct a Comprehensive Solid Modeling System.     

Performance of mobile phone antennas including effect of environment using two methods

The performance evaluation of a mobile terminal antenna can be done by measurements on test routes or by calculations using measured direction-of-arrival distributions and the measured or calculated radiation pattern of the antenna. Measurements on test routes require a lot of effort with completed prototypes, and, therefore, a reliable calculation-based evaluation method would be useful. In this paper, the results of these two types of evaluation methods are compared for the mean effective gain of six different terminal antennas in four environments at 2.15 GHz. The results of the two evaluation methods coincide well, as the mean and the standard deviation of the difference between the relative received powers are -0.2 dB and 0.8 dB, respectively. No significant difference in the coincidence is found between different environments or antennas.     

Plasma nitriding and ion plating with an intensified glow discharge

Ion plating and plasma nitriding at low pressures with a glow discharge supported by a hot electron-emitting filament are studied. The properties and applications of titanium nitride coatings are discussed. Examples of their use for wear reduction in cutting are presented and their frictional properties are investigated. The triode technique is also applied in plasma nitriding and the effects on nitrogen penetration are discussed. In a steel with low contents of carbon and chromium considerable increase in the thickness of the diffusion zone is obtained by using the triode system. Further, it is shown that plasma nitriding can be combined with subsequent ion plating in order to prevent abrasive wear.     

Comparison of MIMO antenna configurations in picocell and microcell environments

This paper presents the results achieved with a dual-polarized multiple-input multiple-output (MIMO) measurement system in the 2 GHz range. Results from continuous measurement routes were used in evaluating and comparing different MIMO antenna configurations. Different pattern and polarization diversity possibilities were studied using two methods: elements were selected from the antenna arrays used in measurements, and as another option, in the mobile station the incident waves were estimated and used in different dipole antenna arrays. The capacity limit seems to be higher in an indoor picocell than in an outdoor microcell environment. At the mobile station, directive elements result in 35% higher average capacities than those of the omnidirectional elements; however, the capacity of the directive elements also depends on the azimuth direction of arrival of the incident field. Dual-polarized antenna configurations have approximately 14% higher capacities than copolarized configurations. Increasing the number of mobile antenna elements increases the capacity in those environments where the angular spread of the incident field is large. Increasing the distance between elements at the fixed station increases the capacity - especially in microcells where signals arrive from specific directions.     

Angular power distribution and mean effective gain of mobile antenna in different propagation environments

We measured the elevation angle distribution and cross-polarization power ratio of the incident power at a mobile station in different radio propagation environments at 2.15 GHz frequency. A novel measurement technique was utilized, based on a wideband channel sounder and a spherical dual-polarized antenna array at the receiver. Data were collected over 9 km of continuous measurement routes, both indoor and outdoor. Our results show that in non-line-of-sight situations, the power distribution in elevation has a shape of a double-sided exponential function, with different slopes on the negative and positive sides of the peak. The slopes and the peak elevation angle depend on the environment and base-station antenna height. The cross-polarization power ratio varied within 6.6 and 11.4 dB, being lowest for indoor and highest for urban microcell environments. We applied the experimental data for analysis of the mean effective gain (MEG) of several mobile handset antenna configurations, with and without the user's head. The obtained MEG values varied from approximately -5 dBi in free space to less than -11 dBi beside the head model. These values are considerably lower than what is typically used in system specifications. The result shows that considering only the maximum gain or total efficiency of the antenna is not enough to describe its performance in practical operating conditions. For most antennas, the environment type has little effect on the MEG, but clear differences exist between antennas. The effect of the user's head on the MEG depends on the antenna type and on which side of the head the user holds the handset.     

Expressing Location Information for Applications in the Internet

As part of the Spatial Location Protocol activity in the Internet Engineering Task Force (IETF), we have been working on how to express location information in an interoperable way in the Internet. The objective of this paper is to share our ideas on concepts for enabling interoperability and reuse of location information. These concepts can also be used in the area of ubiquitous computing. Correspondence to: Ms M. Korkea-aho, Department of Computer Science & Engineering, Helsinki University of Technology, Apollokatu 10 A 49, FIN-00100 Helsinki, Finland. Email: mari.korkea-aho@iki.fi     

Precision standardization of radial keratotomy

Radial keratotomy is an experimental surgical procedure being performed in increasingly large numbers, often without carefully designed protocols which meet accepted methodology for clinical research. This paper presents an instrumentation system which makes it possible to have precise control of the length, depth, and spacing of radial keratotomy incisions. This is not a paper in favor of radial keratotomy. It raises the need for rigid standardization of the technique with evaluation of the results according to carefully controlled and accepted clinical trial methodology.