Browsing by Subject "Risk"

Now showing 1 - 20 of 21

Open Access
Application of the RIMARC algorithm to a large data set of action potentials and clinical parameters for risk prediction of atrial fibrillation
(Springer, 2015) Ravens, U.; Katircioglu-Öztürk, D.; Wettwer, E.; Christ, T.; Dobrev, D.; Voigt, N.; Poulet, C.; Loose, S.; Simon, J.; Stein, A.; Matschke, K.; Knaut, M.; Oto, E.; Oto, A.; Güvenir, H. A.
Ex vivo recorded action potentials (APs) in human right atrial tissue from patients in sinus rhythm (SR) or atrial fibrillation (AF) display a characteristic spike-and-dome or triangular shape, respectively, but variability is huge within each rhythm group. The aim of our study was to apply the machine-learning algorithm ranking instances by maximizing the area under the ROC curve (RIMARC) to a large data set of 480 APs combined with retrospectively collected general clinical parameters and to test whether the rules learned by the RIMARC algorithm can be used for accurately classifying the preoperative rhythm status. APs were included from 221 SR and 158 AF patients. During a learning phase, the RIMARC algorithm established a ranking order of 62 features by predictive value for SR or AF. The model was then challenged with an additional test set of features from 28 patients in whom rhythm status was blinded. The accuracy of the risk prediction for AF by the model was very good (0.93) when all features were used. Without the seven AP features, accuracy still reached 0.71. In conclusion, we have shown that training the machine-learning algorithm RIMARC with an experimental and clinical data set allows predicting a classification in a test data set with high accuracy. In a clinical setting, this approach may prove useful for finding hypothesis-generating associations between different parameters.
Open Access
Aviation risk perception: a comparison between experts and novices
(Wiley-Blackwell Publishing, 2004) Thomson, M. E.; Önkal D.; Avcioǧlu, A.; Goodwin, P.
This article describes an exploratory investigation of the risk perceptions of experts and novices in relation to helicopter operations, under conditions where the participants are matched on various characteristics previously found to affect perceptions, such as demographic, gender, and background factors. The study reports considerable evidence of perceptual differences between the two participant groups (i.e., expert pilots and candidate pilots). We find that the experts' perceptions of relative risks are more veridical, in terms of their higher correlation with the true relative frequencies. A significant positive correlation between the flight hours and the contextual risk-taking tendency is also shown, leading the experienced pilots' choices toward risky alternatives in scenarios - a potential result of their overconfidence based on superior task performance. Possible explanations are offered for the findings and potential avenues for future research are identified.
Open Access
Cash flow-at-risk in publicly traded non-financial firms in Turkey : an application in defense companies
(2004) Özvural, Özhan
People have always evaluated qualitative factors as black boxes so far. Academicians have put much effort to understand and explain these black boxes. The improvements in technology, therefore in social sciences, ease these efforts considerably. Risk is one of the qualitative factors, which drew people’s attention. As a result, some forecasting techniques have been developed to know the unknown. Risk means both profits and losses for people and firms. That is why, risk should be managed to exploit the profits and avoid the losses. Value-at-risk relying on the data about liquid assets was proposed to assist financial firms such as banks, insurance companies, and investment companies to manage their risks. Contrary to financial firms, non-financial firms have more illiquid assets. These firms used value-at-risk to manage their risks initially but the practical results were not satisfactory. Therefore value-at-risk should be revised and adjusted to the non-financial firms. Consequently cash-flow-at-risk concept was proposed to manage risk in non-financial firms. This study aims to apply cash flowat-risk concept in publicly traded non-financial firms in Turkey. The data drawn from financial statements were used because they helped to quantify risk in non-financial firms. The results of the study reveal that the proposed model can be used to asses all publicly traded non-financial firms’ risk exposure in Turkey for the next quarter
Open Access
Effects of daylight saving time changes on stock market volatility: a reply
(Sage Publications, Inc., 2011) Berument, Hakan; Dogan, N.
There is a rich array of evidence that suggests that changes in sleeping patterns affect an individual's decision-making processes. A nationwide sleeping-pattern change happens twice a year when the Daylight Saving Time (DST) change occurs. Kamstra, Kramer, and Levi argued in 2000 that a DST change lowers stock market returns. This study presents evidence that DST changes affect the relationship between stock market return and volatility. Empirical evidence suggests that the positive relationship between return and volatility becomes negative on the Mondays following DST changes.
Open Access
Effects of soccer on stock markets: the return-volatility relationship
(Pergamon Press, 2012) Berument, Hakan; Ceylan, N. B.
This paper assesses the effects of domestic soccer teams' performances against foreign rivals on stock market returns as well as on the return-volatility relationship. Data from Chile, Spain, Turkey and the United Kingdom support propositions that soccer teams results in international cups affect stock market returns and the return-volatility relationship. Evidence from Spain and the UK, soccer powerhouses, suggests that losses are associated with lower returns and higher risk aversion but evidence from Chile and Turkey, where soccer is the most important sport but teams are not as successful, reveals that wins are associated with higher returns and lower risk aversion. Crown Copyright (C) 2012 Published by Elsevier Inc. on behalf of Western Social Science Association. All rights reserved.
Open Access
Equity ownership structure and its consequences : an empirical investigation in Turkish firms
(2001) Gürsoy, Güner
The study describes the main characteristics of ownership structure of the Turkish nonfinancial firms listed on the Istanbul Stock Exchange (ISE) and examines the impact of ownership structure on performance and risk-taking behavior of Turkish firms. Turkish corporations can be characterized as highly concentrated, family owned firms attached to a group of companies generally owned by the same family or a group of families. Ownership structure is defined along two attributes: concentration and identity of the owner(s). We conclude that there is a significant impact of ownership structure - ownership concentration and ownership mix- on both performance and risk-taking behavior of the firms in our sample. Higher concentration leads to better market performance but lower accounting performance. Family-owned firms, contrast to conglomerate affiliates, seem to have lower performance with lower risk. Governmentowned firms have lower accounting, but higher market performance with higher risk.
Open Access
Equity ownership structure, risk taking, and performance: an empirical investigation in Turkish listed companies
(Routledge, 2002) Gürsoy, G.; Aydoğan, K.
The paper describes the main characteristics of ownership structure of Turkish nonfinancial firms listed on the Istanbul Stock Exchange (ISE) and examines the impact of ownership structure on performance and risk-taking behavior of Turkish firms. Turkish corporations can be characterized as highly concentrated, family owned firms attached to a group of companies generally owned by the same family or a group of families. Ownership structure is defined along two attributes: concentration and identity of the owner(s). We conclude that there is a significant impact of ownership structure—ownership concentration and ownership mix—on both performance and risk-taking behavior of the firms in our sample. Higher concentration leads to better market performance but lower accounting performance. Family owned firms, in contrast to conglomerate affiliates, seem to have lower performance with lower risk. Government-owned firms have lower accounting but higher market performance with higher risk.
Open Access
Exchange rate exposure and real exports
(Routledge, 2010) Solakoglu, M. N.
This study investigates the relationship between real exports and exchange rate risk for Turkish firms between 2001 and 2003. Different from earlier studies, the analysis is conducted at the firm level with an exchange rate risk specific to the individual firm. Results show that real exports are negatively impacted by an increase in exchange rate risk. In addition, size of the trade volume and the dependence on domestic market for revenue generation are found to be important for the aforementioned relationship.
Open Access
Financial crisis and changes in determinants of risk and return: an empirical investigation of an emerging market (ISE)
(Multinational Finance Society, 1999) Muradoglu, G.; Berument, Hakan; Metin, K.
This paper examines how determinants of volatility and stock returns change with financial crisis. The contributions of the paper are twofold. First, using a GARCH-M framework, risk and return are jointly modeled by using macroeconomic variables both in the variance and the mean equations. The conditional variance equation is specified by including macro-economic variables, a relevant information set for emerging economies, that is often overlooked in various GARCH specifications. Second, determinants of risk and return are investigated before during and after a major financial crisis at ISE. We show that, both the determinants of risk and the risk-return relationship change as the economy switches from one regime to the other.
Open Access
A GIS ‐ based framework for hazardous materials transport risk assessment
(Wiley-Blackwell Publishing, 2001) Verter, V.; Kara, B. Y.
This article presents a methodology for assessment of the hazardous materials transport risk in a multicommodity, multiple origin – destination setting. The proposed risk assessment methodology was integrated with a Geographical Information System (GIS), which made large‐scale implementation possible. A GIS‐based model of the truck shipments of dangerous goods via the highway network of Quebec and Ontario was developed. Based on the origin and destination of each shipment, the risk associated with the routes that minimize (1) the transport distance, (2) the population exposure, (3) the expected number of people to be evacuated in case of an incident, and (4) the probability of an incident during transportation was evaluated. Using these assessments, a government agency can estimate the impact of alternative policies that could alter the carriers’ route choices. A related issue is the spatial distribution of transport risk, because an unfair distribution is likely to cause public concern. Thus, an analysis of transport risk equity in the provinces of Quebec and Ontario is also provided.
Open Access
Halkın genetiği değiştirilmiş ürünlere/üretilme süreçlerine yönelik algıları ve etik inançları
(Ankara Hacı Bayram Veli Üniversitesi İletişim Fakültesi, 2013) Özgen, Ö.; Emiroğlu, Haluk; Serpen, A. S.; Benlioğlu, B.
Bu araştırmanın amacı, halkın genetiği değiştirilmiş ürünlere ve üretilme süreçlerine yönelik fayda/risk algıları ile etik inançları arasındaki ilişkinin incelenmesidir. Araştırma materyalinin toplanmasında karşılıklı görüşme tekniği kullanılmıştır. Likert tipi cümlelere verilen yanıtlar puanlanmış, geçerlik ve güvenirlik analizi yapılmıştır. Yaş değişkenine bağlı farklılığın belirlenebilmesi için t-testi uygulanmıştır. Bireylerin genetiği değiştirilmiş ürünlere/üretilme süreçlerine bağlı fayda/risk algıları ile etik inançları arasındaki ilişkinin incelenmesi amacı ile Pearson korelasyon analizi yapılmıştır. Bulgular; halkın genetiği değiştirilmiş ürünlere ilişkin fayda algılarının, genetiği değiştirilmiş ürünlere ve üretilme süreçlerine ilişkin risk algılarının, genetiği değiştirilmiş ürünlere ve üretilme süreçlerine ilişkin etik inançlarının yaşa bağlı olarak değiştiğini göstermektedir. Pearson korelasyon analizi sonucunda p<0.001 düzeyinde anlamlı ilişkiler saptanmıştır.
Open Access
International trade and letters of credit: A double-edged sword in times of crises
(Palgrave Macmillan Ltd., 2022-01-05) Crozet, Matthieu; Demir, Banu; Javorcik, Beata
This study argues that the ability to mitigate risks associated with international trade is particularly important at times of heightened uncertainty, such as the economic crisis caused by the Covid-19 pandemic. Risk mitigation can be achieved through letters of credit (LCs), trade finance instruments providing guarantees to trading partners. As their use varies across products, exports of some products are more resilient than others during times of increased uncertainty. This situation reverses in times of financial crises when distressed banks may limit the supply of LCs. Our analysis using data on US and EU-15 exports during the Covid crisis and the Global Financial Crisis provides empirical support for these hypotheses. © 2021, International Monetary Fund.
Open Access
Portfolio selection methods: An Application to İstanbul Securities Exchange
(1989) Seler, İ. Tunç
In this study, Modern Portfolio Theory tools -are used for constructing efficient portfolios. The Markowitz mean-variance model and Sharpe single index model are presented and calculated, for the construction of efficient portfolios from the Istanbul Securities Exchanges’ first market slocks for the 1986 - 1987 period. Constructed efficient portfolios are compared on the risk and return scales.
Open Access
Portfolio selection methods: an application to Istanbul Securities Exchange Market
(1996) Çetin, Mert
In this study, Modern Portfolio Theory tools are used for constructing efficient portfolios. The Markowitz mean-variance model is presented and calculated for the construction of efficient portfolios from the Istanbul Securities Exchange Market stocks for the 1993-1994 period. The portfolios constructed are compared on the risk and return scales.
Restricted
Risk as a forensic resource
(1990) Douglas, Mary
Open Access
Risk based facility location by using fault tree analysis in disaster management
(Elsevier Ltd, 2015) Akgün, T.; Gümüşbuğa F.; Tansel, B.
Determining the locations of facilities for prepositioning supplies to be used during a disaster is a strategic decision that directly affects the success of disaster response operations. Locating such facilities close to the disaster-prone areas is of utmost importance to minimize response time. However, this is also risky because the facility may be disrupted and hence may not support the demand point(s). In this study, we develop an optimization model that minimizes the risk that a demand point may be exposed to because it is not supported by the located facilities. The purpose is to choose the locations such that a reliable facility network to support the demand points is constructed. The risk for a demand point is calculated as the multiplication of the (probability of the) threat (e.g., earthquake), the vulnerability of the demand point (the probability that it is not supported by the facilities), and consequence (value or possible loss at the demand point due to threat). The vulnerability of a demand point is computed by using fault tree analysis and incorporated into the optimization model innovatively. To our knowledge, this paper is the first to use such an approach. The resulting non-linear integer program is linearized and solved as a linear integer program. The locations produced by the proposed model are compared to those produced by the p-center model with respect to risk value, coverage distance, and covered population by using several test problems. The model is also applied in a real problem. The results indicate that taking the risk into account explicitly may create significant differences in the risk levels. © 2014 Elsevier Ltd.
Open Access
Robust scenario optimization based on downside-risk measure for multi-period portfolio selection
(Springer, 2007) Pınar, M. Ç.
We develop and test multistage portfolio selection models maximizing expected end-of-horizon wealth while minimizing one-sided deviation from a target wealth level. The trade-off between two objectives is controlled by means of a non-negative parameter as in Markowitz Mean-Variance portfolio theory. We use a piecewise-linear penalty function, leading to linear programming models and ensuring optimality of subsequent stage decisions. We adopt a simulated market model to randomly generate scenarios approximating the market stochasticity. We report results of rolling horizon simulation with two variants of the proposed models depending on the inclusion of transaction costs, and under different simulated stock market conditions. We compare our results with the usual stochastic programming models maximizing expected end-of-horizon portfolio value. The results indicate that the robust investment policies are indeed quite stable in the face of market risk while ensuring expected wealth levels quite similar to the competing expected value maximizing stochastic programming model at the expense of solving larger linear programs.
Open Access
Soccer and stock market risk: empirical evidence from the Istanbul stock exchange
(Sage Publications, Inc., 2013) Berument, Hakan; Ceylan, N. B.
There is an emerging but important literature on the effects of sport events such as soccer on stock market returns. After a soccer team's win, agents discount future events more favorably and increase risk tolerance. Similarly, after a loss, risk tolerance decreases. This paper directly assesses risk tolerance after a sports event by using daily data from the three major soccer teams in Turkey (Beşiktaş, Fenerbahçe and Galatasaray). Results provide evidence that risk tolerance increases after a win, but similar patterns were not found after a loss. © Psychological Reports 2013.
Restricted
Theories of risk perception: Who fears what and why ?
(1990) Wildavsky, Aaron
Open Access
To share or not to share? How emotional judgments drive online political expression in high-risk contexts
(SAGE Publishing, 2020) Dal, Ayşenur; Nisbet, E. C.
Previous scholarship on networked authoritarianism has examined an array of repressive legal and political strategies employed by regimes to constrain online political expression. How the tension between citizens’ desires to engage in online political expression and the possible dire consequences of doing so is resolved, however, is understudied. We address this lacuna by drawing upon concepts from risk and decision-making research and examining how the emotional and cognitive components of risk and decision-making shape citizens’ online political expression. Employing a three-wave panel survey of Turkish internet users collected over 8 months, our fixed-effects regression analyzes show that anticipatory emotions drive expressive behavior, but that risk assessment does not. Furthermore, the influence of negative emotions on online expression is moderated by individuals’ degree of regime opposition. We discuss the importance of understanding the psychological mechanisms by which networked authoritarian contexts influences citizens’ decisions to engage in contentious online speech.