Mirko Gradisar

The benefits of meeting points in ride-sharing systems

We investigate the potential benefits of introducing meeting points in a ride-sharing system. With meeting points, riders can be picked up and dropped off either at their origin and destination or at a meeting point that is within a certain distance from their origin or destination. The increased flexibility results in additional feasible matches between drivers and riders, and allows a driver to be matched with multiple riders without increasing the number of stops the driver needs to make. We design and implement an algorithm that optimally matches drivers and riders in large-scale ride-sharing systems with meeting points. We perform an extensive simulation study to assess the benefits of meeting points. The results demonstrate that meeting points can significantly increase the number of matched participants as well as the system-wide driving distance savings in a ride-sharing system.

Optimization of a highway project planning using a modified genetic algorithm

This paper proposes an optimization method for a national-level highway project planning based on a modified genetic algorithm. The proposed method adds to the existing methods by integrating various planning elements into a single system. A simulation model is used in order to determine the best investment strategy with regard to net present value, time deviation from the initial plan and discrepancy between available resources and investment costs by taking into account economical, social, traffic and political factors. The outcome is a project schedule with an optimized cash flow. The proposed method was tested using the example of the National Highway Programme in Slovenia.

The impact of color combinations on the legibility of text presented on LCDs

The paper investigates the impact of text and background color combinations on the legibility of text presented on LCDs. The legibility of 56 elementary color combinations was tested by 308 participants. The first task required the participants to identify 21 uppercase alphabetic characters selected and presented in conformance with a Snellen chart in various color combinations. For each color combination, the number of correctly identified characters was recorded as a visual performance measure. In the second task, participants subjectively rated the legibility of color combinations on a ten-point Likert scale. The results show that neither the Le Courier legibility table nor the CRT legibility table is appropriate for LCDs. A new legibility table is proposed for LCDs where the highest ranked are contrastive color combinations with positive polarity whereas for CRT displays, the highest ranked are contrastive color combinations with negative polarity. The findings of this study can be used to determine the best possible color combinations when developing content displayed on LCDs.

The Legibility of Colored Web Page Texts

This paper investigates the impact of color combinations on the legibility of a Web page text presented on a CRT display. Four hundred and sixty-eight participants tested the legibility of fifty-six color combinations. The impacts of color combination, luminance contrast, color difference, and polarity on the legibility were studied. According to the analysis of variance test, color combinations significantly affected the number of correctly identified characters. The obtained results showed that more than 90-year old Le Courier legibility table is not appropriate for additive color computer displays. Consequently, a new legibility table is proposed.

The Benefits of Meeting Points in Ride-sharing Systems

We investigate the potential benefits of introducing meeting points in a ride-sharing system. With meeting points, riders can be picked up and dropped off either at their origin and destination or at a meeting point that is within a certain distance from their origin or destination. The increased flexibility results in additional feasible matches between drivers and riders, and allows a driver to be matched with multiple riders without increasing the number of stops the driver needs to make. We design and implement an algorithm that optimally matches drivers and riders in large-scale ride- sharing systems with meeting points. We perform an extensive simulation study to assess the benefits of meeting points. The results demonstrate that meeting points can significantly increase the number of matched participants as well as the system-wide driving distance savings in a ride-sharing system.

One-Dimensional Cutting Stock Optimization with Usable Leftover: A Case of Low Stock-to-Order Ratio

This paper describes a method for solving one-dimensional cutting stock problem with usable leftover CSPUL in cases where the ratio between the average stock and average order length is less than 3. The proposed method can solve general CSPUL where standard stock lengths, non-standard stock lengths, or a combination of both are cut in the exact required number of pieces. The solutions of sample problems are compared with other methods.

Factors affecting the readability of colored text in computer displays

More and more information is distributed through Web pages that use a fashion-driven graphical design, not necessarily providing high readability. To address this problem, we carried out an experiment in which 270 students have tested 30 Web safe color combinations of text and background on a CRT display. The obtained results show that reading is very complex process influenced by many interrelated factors, which cannot be easily identified and controlled. Therefore speed of reading text in different color combinations cannot be described as one-dimensional problem. This paper identifies the existence of different dimensions and determines the approximate number of them

One-dimensional stock cutting: optimization of usable leftovers in consecutive orders

This paper deals with usable leftovers (UL) in one-dimensional stock cutting in consecutive orders. UL are leftovers longer than a certain threshold and are returned to stock in order to be used in future orders. Shorter leftovers are treated as trim-loss. If UL are being used at a slower pace, than they are being generated for a longer period of time, excessive growth of UL in stock can appear. This is not acceptable due to higher costs of manipulations and warehousing. However, a certain amount of UL in stock is desirable because it contributes to greater variety of stock lengths, which in general results in lower trim-loss. The method solves the problem of how to calculate the near optimal amount of UL in stock and how to control the stock. The proposed method is tested by using a computer simulation in which UL from previous orders are used in the next ones instead of being randomly generated. The computational results indicate that trim-loss in consecutive orders is reduced, and excessive growth of UL in stock is prevented.

Factors Affecting Reading Speed Measurements of Coloured Web Pages

Factors Affecting Reading Speed Measurements of Coloured Web Pages Most of web-based systems use a fashion-driven graphical user interface design which does not necessarily provide the readers with high reading performance of colour variations of text and background. Many studies addressed this problem but none of them succeeded in offering complete and conclusive results in form of reading performance table which could be used in practice. The aim of this paper is to find reasons for these incomplete results. In our research, we firstly analyzed different experiment designs described in the literature and proposals for further research. Consequently, we tried to find an improved design and carried out an experiment involving 270 students who tested 30 web-safe colour combinations. However, our experiment also did not reveal statistically significant differences in reading speed. Therefore the multidimensional scaling (MDS) method was performed to show that the speed of reading cannot be described as a one-dimensional problem.