Browsing by Subject "Complexity"

Now showing 1 - 11 of 11

Open Access
Effect of instructional design based on cognitive load theory on students’ performances and the indicators of element interactivity
(Ekip Buro Makineleri A., 14-08-2023) Kala, N.; Ayas, Alipaşa
Thermodynamics is one of the most complex topics in chemistry. Cognitive Load Theory claims that the complexity of a subject is mainly due to element interactivity - how many elements an individual must organise simultaneously in her/his working memory to master a topic. The simultaneous processing of various chemistry and mathematics concepts to learn thermodynamics puts a strain on the working memory capacity of the learner. Accordingly, what kind of change occurs in a learner’s cognitive processes according to the level of element interactivity is an issue that needs to be investigated. The aim of this study is to reveal the basic indicators of element interactivity and investigate the effects of instructional design on understanding subjects with different element interactivity levels. With this objective in mind, educational software comprising eight distinct sessions for instructional design was developed in accordance with the Cognitive Load Theory. The sample consisted of 37 freshmen who were taking classes in the Chemistry Department of a public university in Turkey. The instructional design was implemented with the experimental group while the control group followed the lecturer's instructional design. The results indicate that, in terms of the cognitive load in the learning process, the study time and the learning at the retention and transfer level are among the basic indicators of the element interactivity. This study also determined that the instructional design that is developed according to Cognitive Load Theory can provide effective learning at the retention and transfer levels in subjects with high element interactivity. © (2023). All Rights Reserved.
Open Access
Factors affecting evaluations of storefront designs and inferences on store characteristics
(2010) Çakırlar, Yasemin Burcu
The aim of this study was to examine the factors affecting the evaluations of storefront designs and to understand how they relate to inferences on store characteristics. The study consists of two parts. In both parts of the study, 12 color photographs of storefronts manipulated to represent two different levels of crowdedness and openness levels were used. The first part was conducted with 70 students from Interior Architecture and Environmental Design Department, Bilkent University. They were asked to rate the storefronts on a semantic differential scale which consisted of adjective pairs involving evaluations of storefront designs and those related to their inferences on the items which may be sold in the stores. In the second part, interviews with 32 shoppers were conducted in a shopping mall, regarding their preferences on the same storefronts displayed together on a board, and reasons affecting their appraisals. The results show that the evaluations of storefront designs have a strong relationship with the inferences on store characteristics. Crowdedness, openness, complexity and familiarity of the storefronts were also found to affect the appraisals of storefronts.
Open Access
Low complexity equalization for OFDM in doubly selective channels
(2009) Pamuk, Alptekin
In current standards Orthogonal Frequency Division Multiplex -OFDM- is widely used for its high resistance to multi-path environments and high spectral ef- ficiency. However since the transmission duration is longer, it is affected from time variations of the channel more than single carrier systems. Orthogonality of sub-carriers are lost within an OFDM symbol and intercarrier interference(ICI) occurs as a result of time variation of the channel. Channel estimation and equalization become problematic, because the classical structures like MMSE require very complex operations. This thesis studies the channel equalization problem, as separate from the channel estimation problem. The thesis assumes that the channel coefficients are perfectly known and focuses on the estimation of data transmitted on each OFDM carrier. First, a survey of existing algorithms on channel equalization is given and simulations are provided to compare them in terms of complexity and performance under an OFDM system scenario that is consistent with the present WiMAX system parameters and operating conditions. As a novel contribution, the thesis proposes two new equalization methods by amending existing algorithms and shows that these modified algorithms improve the state-of-the-art in channel equalization in terms of complexity andperformance under certain high-mobility scenarios. Finally it is shown that the intercarrier interference cancellation problem remains a major impediment to the implementation of OFDM in high-mobility environments.
Open Access
Manufacturer's mixed pallet design problem
(Elsevier, 2008) Yaman, H.; Şen, A.
We study a problem faced by a major beverage producer. The company produces and distributes several brands to various customers from its regional distributors. For some of these brands, most customers do not have enough demand to justify full pallet shipments. Therefore, the company decided to design a number of mixed or "rainbow" pallets so that its customers can order these unpopular brands without deviating too much from what they initially need. We formally state the company's problem as determining the contents of a pre-determined number of mixed pallets so as to minimize the total inventory holding and backlogging costs of its customers over a finite horizon. We first show that the problem is NP-hard. We then formulate the problem as a mixed integer linear program, and incorporate valid inequalities to strengthen the formulation. Finally, we use company data to conduct a computational study to investigate the efficiency of the formulation and the impact of mixed pallets on customers' total costs.
Open Access
Modeling and analysis of issues in hub location problem
(1999) Kara, Bahar Yetiş
The hub location problem has been around for more than 10 years. The first mathematical model was formulated by O’Kelly (1986) which is a quadratic integer program. Since then, nearly all of the researchers in this area have concentrated on developing ’good’ linearizations. However, there are many aspects of the problem that need to be analyzed. In this dissertation, we investigate some of these issues. We first study the application areas of the hub location problem and clarify the underlying assumptions of the real world problems which lead to the customarily defined hub location problem. We identify a certain problem characteristic of cargo delivery systems, which is one of the major application areas of the hub location problem, which is not satisfactorily modeled by means of the customarily defined hub location models. We propose a new hub location model that captures the specific requirements that are particular to cargo delivery systems. Another issue that we concentrate on is the identification, modeling and analysis of the hub location problem under different performance measures, namely minimax and covering criteria. We propose new integer programming models for the hub location problem under minimax and covering objectives. Both of the new models are the result of a different way of approaching the problem and their computational performance is far more superior than the performance of the various linearizations of the basic models proposed for these problems in the literature.
Open Access
Performance of query processing implementations in ranking-based text retrieval systems using inverted indices
(Elsevier Ltd, 2006-07) Cambazoglu, B. B.; Aykanat, Cevdet
Similarity calculations and document ranking form the computationally expensive parts of query processing in ranking-based text retrieval. In this work, for these calculations, 11 alternative implementation techniques are presented under four different categories, and their asymptotic time and space complexities are investigated. To our knowledge, six of these techniques are not discussed in any other publication before. Furthermore, analytical experiments are carried out on a 30 GB document collection to evaluate the practical performance of different implementations in terms of query processing time and space consumption. Advantages and disadvantages of each technique are illustrated under different querying scenarios, and several experiments that investigate the scalability of the implementations are presented. © 2005 Elsevier Ltd. All rights reserved.
Open Access
The relationship between complexity, preference and restorative potential of interiors
(2018-07) Geyik, Aybüke
The main aim of the present study is to investigate the relationship between complexity, preference and restorative potential of interiors. Eighteen black and white images of third places such as cafes, restaurants, and lounges were rated by 100 non-designer university students from three universities. They rated the images on preference, complexity, familiarity, perceived restoration potential and restoration components (being away, fascination, extent, compatibility). A single-item version of Perceived Restorativeness Scale was adapted to measure the restorative potential of interior spaces. Pearson’s Correlation, repeated measures ANOVAs and a mediation analysis were conducted. The results showed that preference a was positively correlated with both complexity and components of restoration. Complexity was positively correlated to fascination, extent, and compatibility. Fascination, Extent, and Compatibility mediated the effect of complexity on preference.
Open Access
Scheduling to minimize the coefficient of variation
(Elsevier, 1996) De, P.; Ghosh, J. B.; Wells, C. E.
In this paper, we address the problem of uninterruptedly scheduling a set of independent jobs that are ready at time zero with the objective of minimizing the coefficient of variation (CV) of their completion times. We first show that, for high processing time values of the longest job, a variance (V) minimizing schedule also minimizes CV. Using this equivalence, we next demonstrate the invalidity of an earlier conjecture about the structure of a CV-optimal schedule and proceed to establish the NP-hardness of the CV problem. Finally, drawing from our prior work on the V problem, we provide a pseudo-polynomial dynamic programming algorithm for the solution of the CV problem.
Open Access
Understanding and managing complexity through Bayesian network approach: the case of bribery in business transactions
(Elsevier, 2019) Ekici, Ahmet; Ekici, Ş. Ö.
Managing complex business problems requires decision makers to take a systemic perspective and utilize tools that can generate knowledge from the interdependencies of the system’s complex properties. As such, the current research focuses on an important yet ambiguous business problem–bribery. Using the Global Competitiveness Index data provided by the World Economic Forum, the authors constructed and analysed a Bayesian network to delineate a ‘system’ of bribery in business transactions. In this context, they first determined the factors related to bribery activities and then developed a structural model (the Bayesian network). Through scenario and sensitivity analyses performed over the constructed model, the authors identified the factors that have the greatest impact on bribery activities. They further analysed the resulting model based on the countries’ stage of economic development in order to provide the manager and policy maker with a more informative diagnostic tool to understand and deal with bribery activities locally and globally.
Open Access
Untangling the complex nature of household food waste drivers through fuzzy cognitive mapping
(2021-08) Özgen Genç, Tuğçe
Since reducing household food waste (HFW) has serious environmental, social, and economic implications, researchers across disciplines have investigated this phenomenon from multiple angles and identified a substantial number of drivers that account for HFW. Despite these efforts, empirical investigation of the complex web of HFW drivers is still in its infancy. The methodologies that have been used to investigate the phenomenon have been generally insufficient in capturing the complexity surrounding consumers’ food waste behavior. Therefore, the main objective of this thesis is to provide a more complete representation of this complexity. To this end, a distinctive method, fuzzy cognitive mapping (FCM) was used to demonstrate the system of HFW drivers. Through an iterative process between the content analysis of previous studies and expert opinion, the most prevalent HFW drivers as system concepts and their causal relationships were synthesized and consolidated in the first stage. Then in the second stage, this well-refined framework was transformed into an FCM that provides a consistent base to conduct simulations and to compare the HFW-reducing intervention alternatives. In the third stage, the most influential drivers were revealed, and the ambiguities due to conflicting findings reported in the literature were resolved. Then, through scenario analysis, intervention alternatives were compared based on their impact on HFW. In the final section, findings of each stage were integrated and discussed with their theoretical, methodological, and practical implications.
Open Access
Using eye tracking to understand the impact of visual complexity and perceptual fluency on viewers’ aesthetic preferences
(2024-09) Beder, Dilara
This study investigates the interplay between cognitive styles, visual complexity, and aesthetic evaluations in environmental psychology and architectural design, utilizing Gestalt principles. Our research was divided into two studies. In Study I, we examined the aesthetic evaluations of 24 two-dimensional geometric stimuli, manipulated using the Gestalt principles of similarity based on color and shape differences, with 39 participants. In Study II, we focused on architectural façades and used 24 two-dimensional stimuli, manipulated through the Gestalt principles of similarity and proximity, to assess aesthetic evaluations with 79 participants. Participants were classified as Field Dependent or Field Independent using the Hidden Figures Test. Additionally, we collected their aesthetic evaluations through questionnaires, supported by eye-tracking data to assess visual attention. Study I revealed a U-shaped relationship between visual complexity and aesthetic evaluations, with both low and high complexity stimuli rated higher than medium complexity ones. Study II found an inverse relationship between complexity and aesthetic ratings, with simpler façades generally preferred. Gestalt principles significantly influenced aesthetic judgments, with shape-based similarity rated higher than color-based similarity for geometric designs, and proximity-based façades rated higher than similarity-based façades in architectural contexts. Although cognitive styles did not significantly impact overall aesthetic evaluations, nuanced differences were identified in the responses of Field Dependent participants when comparing proximity-based to similarity-based designs. Gaze metrics data indicated that higher complexity levels led to more fixations and shorter fixation durations, reflecting more extensive visual exploration. These findings offer insights into how cognitive styles, complexity, and Gestalt principles shape aesthetic perceptions, informing design practices to enhance user experience.