Fuzzy optimization for portfolio selection based on embedding theorem in fuzzy normed linear spacesFarnaz Solatikia
, Erdem Kiliç
, Gerhard-Wilhelm Weber
, 2014, izvirni znanstveni članek
Opis: Background: This paper generalizes the results of Embedding problem of Fuzzy Number Space and its extension into a Fuzzy Banach Space C(Ω) × C(Ω), where C(Ω) is the set of all real-valued continuous functions on an open set Ω.
Objectives: The main idea behind our approach consists of taking advantage of interplays between fuzzy normed spaces and normed spaces in a way to get an equivalent stochastic program. This helps avoiding pitfalls due to severe oversimplification of the reality.
Method: The embedding theorem shows that the set of all fuzzy numbers can be embedded into a Fuzzy Banach space. Inspired by this embedding theorem, we propose a solution concept of fuzzy optimization problem which is obtained by applying the embedding function to the original fuzzy optimization problem.
Results: The proposed method is used to extend the classical Mean-Variance portfolio selection model into Mean Variance-Skewness model in fuzzy environment under the criteria on short and long term returns, liquidity and dividends.
Conclusion: A fuzzy optimization problem can be transformed into a multiobjective optimization problem which can be solved by using interactive fuzzy decision making procedure. Investor preferences determine the optimal multiobjective solution according to alternative scenarios.
Ključne besede: investiranje, dobiček, portfelj, optimiranje, metode
Objavljeno: 30.11.2017; Ogledov: 18; Prenosov: 1
Celotno besedilo (844,36 KB)
Forecasting the primary demand for a beer brand using time series analysisDanjel Bratina
, Armand Faganel
, 2008, izvirni znanstveni članek
Opis: Market research often uses data (i.e. marketing mix variables) that is equally spaced over time. Time series theory is perfectly suited to study this phenomena's dependency on time. It is used for forecasting and causality analysis, but their greatest strength is in studying the impact of a discrete event in time, which makes it a powerful tool for marketers. This article introduces the basic concepts behind time series theory and illustrates its current application in marketing research. We use time series analysis to forecast the demand for beer on the Slovenian market using scanner data from two major retail stores. Before our analysis, only broader time spans have been used to perform time series analysis (weekly, monthly, quarterly or yearly data). In our study we analyse daily data, which is supposed to carry a lot of ‘noise’. We show that - even with noise carrying data - a better model can be computed using time series forecasting, explaining much more variance compared to regular regression. Our analysis also confirms the effect of short term sales promotions on beer demand, which is in conformity with other studies in this field.
Ključne besede: market research, time series forecasting, beer demand
Objavljeno: 30.11.2017; Ogledov: 20; Prenosov: 1
Celotno besedilo (395,07 KB)
Financial distress prediction of Iranian companies using data minig techniquesMahdi Moradi
, Mahdi Salehi
, Mohammad Ebrahim Ghorgani
, Hadi Sadoghi Yazdi
, 2013, izvirni znanstveni članek
Opis: Decision-making problems in the area of financial status evaluation are considered very important. Making incorrect decisions in firms is very likely to cause financial crises and distress. Predicting financial distress of factories and manufacturing companies is the desire of managers and investors, auditors, financial analysts, governmental officials, employees. Therefore, the current study aims to predict financial distress of Iranian Companies. The current study applies support vector data description (SVDD) to the financial distress prediction problem in an attempt to suggest a new model with better explanatory power and stability. To serve this purpose, we use a grid-search technique using 3-fold cross-validation to find out the optimal parameter values of kernel function of SVDD. To evaluate the prediction accuracy of SVDD, we compare its performance with fuzzy c-means (FCM).The experiment results show that SVDD outperforms the other method in years before financial distress occurrence. The data used in this research were obtained from Iran Stock Market and Accounting Research Database. According to the data between 2000 and 2009, 70 pairs of companies listed in Tehran Stock Exchange are selected as initial data set.
Ključne besede: financial distress prediction, Support vector data description, Fuzzy c-mean
Objavljeno: 30.11.2017; Ogledov: 16; Prenosov: 1
Celotno besedilo (1,10 MB)
Factors affecting reading speed measurements of coloured web pagesMiro Gradišar
, Tomaž Turk
, Iztok Humar
, 2010, izvirni znanstveni članek
Opis: 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.
Ključne besede: informatics, information systems, information retrieval
Objavljeno: 30.11.2017; Ogledov: 16; Prenosov: 1
Celotno besedilo (886,12 KB)
Exploring approaches how to measure a lean processChrister Österman
, Anders Fundin
, 2014, izvirni znanstveni članek
Opis: Purpose:The purpose of the research is to explore a practical method of measuring the implementation of lean in a process. The method will be based on examining the abilities of a group. At this scale the ability to work standardized and solve problems is important. These two abilities are dependent of each other and are fundamental for the group's ability to create a stable result. In this context the method of standardized work (SW) is define to be the methods used in a process to generate stable results. Problem solving (PS) is defined as the methods used to return a process to a condition where SW is possible.
Methodology /approach: The research is conducted in a multiple case study in four large global manufacturing companies. The order of the data collection is: Firstly, interviews with the individuals that are centrally responsible for overall implementation of lean in the organization. Secondly, observe the implementation of SW and PS at the group level. In total 7 groups have been studied and 19 respondents interviewed.
Findings: Results show that the central definition of the methods for standardized work does not by itself have a direct impact on success of implementation of SW at group level. The method of SW where similar on a general level in the different cases, but with varying levels of implementation at group level was applied. Results also show that key factors for a successful implementation of standardized work on group level are: Ownership of the process, Direct connection to result of process, Correct workload and Leader demand. Methods of PS at group level where dissimilar despite a superficially similar approach. The evaluation method used was successful in providing comparable results between the cases.
Research limitations: A limitation of this research is within the scale of the measurement, as it only examines the group level. The research is further limited to four companies and seven groups.
Originality/value of paper: This paper aims to fill a gap in the established measurement methods of lean, as it examines the abilities of SW and PS at the group level of a process. These abilities are often referred to as essential in lean theory. However, there has been little scholarly work in defining the methods of SW and PS or the key factors affecting the methods at an operational level.
Ključne besede: lean, performance measures, problem solving, standardized work, stability
Objavljeno: 30.11.2017; Ogledov: 19; Prenosov: 1
Celotno besedilo (428,73 KB)
Entrepreneurial conative component of competencesDarko Kovač
, Maja Meško
, Andrej Bertoncelj
, 2010, izvirni znanstveni članek
Opis: Competitive pressures, globalization and economic growth have brought Slovenian enterprises to enhance the role of entrepreneurial competences. The present paper aims to study conative component of entrepreneurial competences as a crucial part of human capital in Slovenian enterprises. The focus of this paper is any eventual disparity of non-teachable attributes of conative component of competences of Slovene enterpreneuer with learned ones rather than the concept of entrepreneurship itself. Authors seperate entrepreneurial competences into three components: cognitive, affective and conative. The purpose of this study is to assess the entrepreneurial conative traits and to investigate the correlation between different conative components of entrepreneurial competences and compare the results to their job-related self-expetations. The conative component of entrepreneurial competences was measures with the Kolbe A™ Index. The study was conducted with 43 Slovenian entrepreneuers from three different enterprises. Independet sample t-test and Pearson's correlation were used to test research aims. SPSS 16.0 was used to analyse the data. The results show conative components of Slovenian entrepreneurial competences, difference between them and individual's job-related self expectations and that the correlation between conative components exist.
Ključne besede: entrepreneurship, competences, Slovenia
Objavljeno: 30.11.2017; Ogledov: 22; Prenosov: 1
Celotno besedilo (478,50 KB)
E-education between padagogical and didactic theory and practiseVanda Rebolj
, 2009, strokovni članek
Opis: Education systems confront new requirements to become more efficient and contribute more to the economic success of society. At the same time there are new challenges for the education systems to perform their tasks using advanced technology. In capacity, information technology considerably surpasses the current learning technology. Supported by Internet it creates an electronic parallel to the standard school and learning. Unfortunately there is only sporadic evidence that supported by information technology, learning and education system as a whole can be considerably improved. In spite of that, we believe there is no way back and e-education is not just a temporary whim. Even though we do not know exactly who should perform what and to which scope. The passiveness of pedagogues, the lack of empirical research and the occurring expansion of the market for e-education products without their quality assessment is not of advantage to this progress. The spread of e-education production without considering the professional opinion of pedagogues, who beside their practical work must also engage in developing their own pedagogical theory, might not benefit the existing education achievements. On the other hand, didactics can by analogy be applied also in the web environment, consequently creating the related assessment mechanisms of the electronic education elements.
Ključne besede: didactics, e-education, informatization, IT, information technology, multimedia, interactivity, knowledge quality
Objavljeno: 29.11.2017; Ogledov: 52; Prenosov: 2
Celotno besedilo (169,81 KB)
Educational possibilities of the project Colour visualization of musicBojan Klemenc
, Peter Ciuha
, Franc Solina
, 2011, izvirni znanstveni članek
Opis: We propose a system of colour visualization of music based on a system of colour signs, which are connected to musical tones. Tones, which are in harmonic relationships, are represented by related colours. First, we outline the foundations on which the system of colour signs is based - the mathematical model of harmony. We discuss several possibilities of visual representation of expressive elements of music - melody, composition, rhythm and harmony. These relationships enabled us to develop a computer program that employs these elements for visualization. The program mimics human perception in which the parts are determined by the perception of the whole. Furthermore, the program enables the development of tools that can enhance music understanding during listening or performing. Music performance can acquire a new quality with the use of interactive coloured musical instruments, which by using colours show the performer different possibilities for forming musical harmonies and thereby change the composing of music into a game and attractive colour-aural journey. Here we stumble upon a challenge for educational science and methodology: how to use such upcoming multimedia tools. These tools would bring the processes of learning and playing a game closer together since playing games is a child's most natural form of functioning. Furthermore, in the area of artistic creation we can once again establish a balance between our logical and intuitive nature.
Ključne besede: visaulization, music, colours, learning, creativity
Objavljeno: 29.11.2017; Ogledov: 51; Prenosov: 3
Celotno besedilo (1,21 MB)
EditorialMirjana Kljajić Borštnar
, Davorin Kofjač
, Andrej Škraba
, Gerhard-Wilhelm Weber
, Andreja Pucihar
, 2017, predgovor, spremna beseda
Ključne besede: simulation, modeling, system dynamics, decision making
Objavljeno: 29.11.2017; Ogledov: 47; Prenosov: 3
Celotno besedilo (187,28 KB)