5916 research outputs found
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Maintaining connectivity for multi-UAV multi-target search using reinforcement learning
No full textWe propose a dynamic path planner that uses a multi-Agent reinforcement learning (MARL) model with novel reward functions for multi-drone search and rescue (SAR) missions. We design a mission environment where a multi-drone team covers an area to detect randomly distributed targets and inform the ground base station (BS) by continuously forming relay chains between the targets and the BS. The training procedure of the agents includes a convolutional neural network (CNN) that uses images which represent trajectory histories and connectivity states of each environment entity such as drones, targets, BS. Agents take actions and get feedback from the environment until the mission is completed. The model is trained with multiple missions with randomized target locations. Our results show that the trained model successfully produces mission plans such that the multi-drone system searches the area efficiently while dynamically forming relay chains. The proposed dynamic method leads up to 45% better total detection and mission times in comparison to a pre-planned optimized path planner.TÜBİTA
An Eulerian multiphase frost model based on heat transfer measurements
No full textIn this paper, a laminar numerical model is developed to predict frost formation over a horizontal cold flat surface. An Eulerian-Eulerian multiphase approach is followed to model humid air and ice phases separately. Frost accumulation on the cold surface is modeled with an empirical mass source term. Model constants were tuned in a systematic way using experimental heat flux and frost thickness data. A velocity dependent model constant is introduced into the mass source term. The heat flux rise observed experimentally at the initial stages of the frosting could be captured with the use of the velocity dependent model constant and the addition of this term considerably improved the accuracy of the frost model at the initial stages of frosting. It was also observed that the selected particle diameter for the solid ice phase has a considerable effect on the velocity profile over the frost layer. This requires tuning of the velocity dependent model constant parameters according to the selected ice particle diameter. The developed numerical model was tested with three different frost thermal conductivity models. Using the thermal conductivity of solid ice for the frost thermal conductivity resulted in the most accurate prediction at the early stages of the frost growth process indicating a rather column-wise vertical growth of ice crystals with very low lateral branching. However, the overprediction of the numerical heat flux with the thermal conductivity of solid ice points out a decrease in the thermal conductivity of the newly added frost layers indicating a more pronounced lateral branching of ice crystals within the frost layer. The effect of the diffusion coefficient of the water vapor in humid air on frosting is also investigated. An artificial increase in the diffusion coefficient improved the accuracy of the heat flux prediction of the model at the initial stages of frosting which might indicate an eddy-driven enhanced mixing in the boundary layer which might not be captured in the laminar flow model. Finally, the developed numerical model is also tested on another scenario with the surface temperature held at -30 °C. Detailed analysis of the numerical simulations showed a more porous frost layer with the surface temperature at -30 °C as compared to the frost porosity formed on the surface at -20 °C
Digital transformation journey guidance: A holistic digital maturity model based on a systematic literature review
No full textFor a successful digital transformation, organizations must create an accurate roadmap and manage the process effectively. A digital maturity model is a critical success factor as it enables organizations to assess their current situation and create roadmaps aligned with their goals; however, a comprehensive systematic literature review covering the maturity models proposed by academia and consultancy firms is hard to find. Further, the existing models are sector-oriented, not organization-oriented, and do not consider the transformation journey holistically, but instead focus on model dimensions. This study first undertakes a comprehensive and up-to-date systematic literature review by applying the PRISMA approach using a bibliometric analysis tool capable of providing visual maps, then developing a unique holistic digital maturity model that covers several aspects of an organization’s digital transformation journey, from strategy to governance, and asking relevant questions. The hierarchical structure, comprising dimensions and sub-dimensions, presents content beyond the scope of other models. The results of the digital maturity assessment can be interpreted in parallel with the stages of the digital transformation. Consequently, the new holistic and sector-independent digital maturity model can be used by organizations in both the private and public sector.Publisher versio
Search for the lepton-flavor violating decay of the Higgs boson and additional Higgs bosons in the eμ final state in proton-proton collisions at √s = 13 TeV
No full textA search for the lepton-flavor violating decay of the Higgs boson and potential additional Higgs bosons with a mass in the range 110-160 GeV to an Formula Presented pair is presented. The search is performed with a proton-proton collision dataset at a center-of-mass energy of 13 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of Formula Presented. No excess is observed for the Higgs boson. The observed (expected) upper limit on the Formula Presented branching fraction for it is determined to be Formula Presented at 95% confidence level, the most stringent limit set thus far from direct searches. The largest excess of events over the expected background in the full mass range of the search is observed at an Formula Presented invariant mass of approximately 146 GeV with a local (global) significance of 3.8 (2.8) standard deviations.BMBWF
and FWF (Austria); FNRS and FWO (Belgium); CNPq,
CAPES, FAPERJ, FAPERGS, and FAPESP (Brazil); MES
and BNSF (Bulgaria); CERN; CAS, MoST, and NSFC
(China); MINCIENCIAS (Colombia); MSES and CSF
(Croatia); RIF (Cyprus); SENESCYT (Ecuador); MoER,
ERC PUT and ERDF (Estonia); Academy of Finland,
MEC, and HIP (Finland); CEA and CNRS/IN2P3
(France); BMBF, DFG, and HGF (Germany); GSRI
(Greece); NKFIH (Hungary); DAE and DST (India);
IPM (Iran); SFI (Ireland); INFN (Italy); MSIP and NRF
(Republic of Korea); MES (Latvia); LAS (Lithuania); MOE
and UM (Malaysia); BUAP, CINVESTAV, CONACYT,
LNS, SEP, and UASLP-FAI (Mexico); MOS
(Montenegro); MBIE (New Zealand); PAEC (Pakistan);
MES and NSC (Poland); FCT (Portugal); MESTD
(Serbia); MCIN/AEI and PCTI (Spain); MOSTR (Sri
Lanka); Swiss Funding Agencies (Switzerland); MST
(Taipei); MHESI and NSTDA (Thailand); TUBITAK
and TENMAK (Turkey); NASU (Ukraine); STFC
(United Kingdom); DOE and NSF (USA). Individuals
have received support from the Marie-Curie program
and the European Research Council and Horizon 2020
Grant, Contracts No. 675440, No. 724704, No. 752730,
No. 758316, No. 765710, No. 824093, No. 884104, and
COST Action CA16108 (European Union); the Leventis
Foundation; the Alfred P. Sloan Foundation; the Alexander
von Humboldt Foundation; the Belgian Federal Science
Policy Office; the Fonds pour la Formation a la ` Recherche
dans l’Industrie et dans l’Agriculture (FRIA-Belgium); the
Agentschap voor Innovatie door Wetenschap en
Technologie (IWT-Belgium); the F. R. S.-FNRS and
FWO (Belgium) under the “Excellence of Science—
EOS“—be.h Project No. 30820817; the Beijing
Municipal Science & Technology Commission,
No. Z191100007219010; the Ministry of Education,
Youth and Sports (MEYS) of the Czech Republic; the
Hellenic Foundation for Research and Innovation
(HFRI), Project No. 2288 (Greece); the Deutsche
Forschungsgemeinschaft (DFG), under Germany’s
Excellence Strategy—EXC 2121 “Quantum Universe”—
390833306, and under Project No. 400140256—
GRK2497; the Hungarian Academy of Sciences, the
New National Excellence Program—ÚNKP, the NKFIH
research Grants No. K 124845, No. K 124850, No. K
128713, No. K 128786, No. K 129058, No. K 131991,
No. K 133046, No. K 138136, No. K 143460, No. K
143477, No. 2020-2.2.1-ED-2021-00181, and
No. TKP2021-NKTA-64 (Hungary); the Council of
Science and Industrial Research, India; the Latvian
Council of Science; the Ministry of Education and
Science, Project No. 2022/WK/14, and the National
Science Center, Contracts No. Opus 2021/41/B/ST2/
01369 and No. 2021/43/B/ST2/01552 (Poland); the
Fundação para a Ciência e a Tecnologia, Grant
No. CEECIND/01334/2018 (Portugal); the National
Priorities Research Program by Qatar National Research
Fund; MCIN/AEI/10.13039/501100011033, ERDF “a way
of making Europe,” and the Programa Estatal de Fomento
de la Investigación Científica y T´ecnica de Excelencia
María de Maeztu, Grant No. MDM-2017-0765 and
Programa Severo Ochoa del Principado de Asturias
(Spain); the Chulalongkorn Academic into Its 2nd
Century Project Advancement Project, and the National
Science, Research and Innovation Fund via the Program
Management Unit for Human Resources & Institutional
Development, Research and Innovation, Grant
No. B05F650021 (Thailand); the Kavli Foundation; the
Nvidia Corporation; the SuperMicro Corporation; the
Welch Foundation, Contract C-1845; and the Weston
Havens Foundation (USA).Publisher versio
Safety performance functions for Two-Lane urban arterial segments
No full textThis paper presents the calibration and development process of the safety performance function for the undivided two-lane urban and suburban arterial segments in New Jersey. Data requirements, the availability of required data, and the data processing and extraction methods are presented, along with detailed results of the calibration and development process. Negative binomial, Poisson, zero-inflated Poisson and Hurdle models were generated using the development database. The best model fit was based on likelihood ratio test, AIC and BIC statistics, Vuong test and rootograms. The test database was used to calculate the calibration factor for U2 segments. The predictions of the location-specific count models were then evaluated and compared to those of calibrated Highway Safety Manual model, using the test dataset. The validation test results showed that the negative binomial and hurdle models exhibited better performance in terms of absolute residuals and absolute Pearson residual statistics. This paper also shows the impact of crash location information on analyses results, and underlines that efforts made to manually extract the missing required data can easily be offset by the inaccuracies in crash frequency databases, and the thresholds used to identify intersection related crashes.C2SMART ; Ozyegin University ; U.S. Department of Transportation ; New Jersey Department of Transportation ; New York Universit
Road rage as a type of violation of well-being in traffic: The case of Turkey
No full textOne of the essential components for understanding a life with dignity and with human rights is the right to health. The World Health Organization defines "health" as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity". Physical and social well-being is not enough, and the individual's mental well-being should also be realized. Anger is one of the most important factors affecting the mental, as well as the physical, health of individuals. Anger can be both a cause and a consequence of poor mental health. Driving anger can be defined as the anger that occurs while driving, and its level can be associated with aggressive and risky driving, loss of concentration and vehicular control, and near miss accidents in traffic. In this research, the factorability of the 14-item short form of the Driver Anger Scale (DAS) was investigated in the Turkish population. The data were further analyzed for various demographics and independent variables. The short form of the DAS can be reliably used for Turkish drivers as well. A safe driving culture must be substantially popularized via educatory applications within digital or classroom environments to control, regulate, and lessen traffic violence. Effective audits and deterrent regulations are also important with respect to decreasing driving anger and violence.Publisher versio
Economic value of prediction of return distribution
No full textVarlık getirilerinin istatistiki dağılımını modellemek özellikle finansal portföylerin oluşturulmasında çok önemlidir. Varlık getirilerinin dağılımının doğru ve zamanlı modellenmesi, bu dağılımlar yardımıyla oluşturulan portföylerin de piyasa endeksi gibi geleneksel finansal varlıklara göre daha yüksek getiri/oynaklık performansı sağlamasının önünü açacaktır. Bu makalede, 2000-2019 döneminde S&P 500 Endeks getirilerinin ortalaması ve oynaklığı arasındaki kaldıraç ilişkisi de ele alınarak bir modelleme yoluna gidilmiştir. Bu yapılırken de özellikle beklenen getiri ve oynaklık arasındaki asimetrik ilişki dikkate alınmıştır. Bu ilişkilerin hem zamanlamasının hem de asimetrik yapısının uygun bir şekilde ele alınması varlık dağılımının ve bu dağılımın volatilitesinin çok daha iyi tahmin edilmesini sağlamaktadır. Modelin başarısı, bu modelden yola çıkarak oluşturulan gerçek zamanlı tahminleri kullanarak yatırım yapan bir temsili yatırımcı gözüyle değerlendirilmiştir. Bu yatırımcı her zaman periyodunda beklenen getiri oynaklık arasındaki ilişkiyi bütünüyle ele alan ekonometrik model yardımıyla portföy ağırlıklarını belirlemektedir. Bu ağırlıklar sonucunda gerçekleşen portföy getirisinin temsili yatırımcıda yarattığı ortalama fayda modellerin başarı ölçütü olarak kullanılmıştır. Sonuçlar beklenen değer ve oynaklık arasındaki ilişkinin ekonomik değerinin oldukça yüksek olduğunu göstermiştir. Bu sonuçlar birçok farklı etmene karşı geçerliliğini korumaktadır. Dolayısıyla finansal portföy oluşumunda sadece getiri ve oynaklık değil, bu ikisi arasındaki ilişkinin de modellenmesi önerilmektedir.Modeling the distribution of asset returns is crucial in constructing financial portfolios. Accurate and timely modeling of the distribution of asset returns paves the way for the construction of portfolios using these distributions that can provide higher return/volatility performance compared to conventional assets such as the market index. This paper proposes a modeling approach by considering the relationship between the average and volatility of returns of S&P 500 over the period of 2000-2019. The joint distribution of the returns and their volatility is modeled by explicitly incorporating the links between the returns and volatility. This is executed by allowing for asymmetric relations between the mean and volatility. Capturing the timing and asymmetrical nature of these relationships provides a much better estimation of the asset distribution and its volatility. Predictions of real-time return distributions are formed based on this model. The model's performance is evaluated from the point of a representative investor constructing her portfolio using real-time forecasts based on this model. This investor determines the portfolio weights based on the outcome of the econometric model explicitly capturing the relationship between expected return and volatility in each period. Results show that the link between returns and their volatility bears considerable economic value. Moreover, the findings remain robust to various effects.Publisher versio
Değişen yeni yüz yılda kütüphanelerin rolünü yeniden düşünmek Özyeğin Üniversitesi bibliyometrik performans yönetim uygulamaları
No full textBibliyometri, yayınların ya da belgelerin yazar, konu, yayın bilgisi, atıf yapılan kaynaklar vb. özelliklerinin niceliksel analizidir. Yeni yüz yıl kütüphaneleri önüştürürken beraberinde kütüphanecilerin de rollerini değiştirmiştir. Gelişmelerin ışığında oluşan bu yeni rolle, “bibliyometri” “bibliyometrik performans yönetimi” terimleri kütüphanecilik literatüründe ilk sıralara yerleşmiştir. Bibliyometrik performans yönetimi, akademik kurumlar, araştırmacılar ve kütüphaneler için stratejik kararlar almak ve başarılarını ölçmek için temel bir bileşen olarak önemlidir. Bu çalışmada, Özyeğin Üniversitesi Kütüphanesi’nin akademik performans yönetim sürecine dahil olmasından itibaren bütün adımlara yer verilmiştir
Likidite yeterlilik oranının belirleyicileri: Türk bankaları üzerine ampirik bir çalışma
No full textLiquidity and liquidity risk is a phenomenon that has important consequences in the management of banks. In addition, liquidity risk has an important role in banking crises. With the new regulations created, liquidity indicators are taken into account in the evaluation of the financial strength of the banking sector and banks. This study examines the variables that affect the liquidity risk of the Turkish banking sector. As a result of the analysis using simple linear regression, it was found that the factors affecting the liquidity management in the Turkish banking sector, although their effectiveness changes periodically, are the ratio of cash values to total assets, the ratio of demand deposits to total deposits, the ratio of non-performing loans to total cash loans, and the ratio of funding from repo transactions to total liabilities.Likidite ve likidite riski bankaların yönetiminde önemli sonuçlar doğuran bir olgudur. Buna ek olarak likidite riskinin bankacılık krizlerinde önemli bir rolü bulunmaktadır. Oluşturulan yeni regülasyonlar ile Bankacılık sektörü ve bankaların finansal olarak güçlülüğü değerlendirmelerinde likidite göstergeleri dikkate alınmaktadır. Bu çalışma, Türk bankacılık sektörünün likidite riskini etkileyen değişkenleri incelemektedir. Basit doğrusal regresyon kullanılan analiz sonucunda Türk bankacılık sektöründe likidite yönetimini etkileyen faktörler dönemsel olarak etkinlikleri değişmekle birlikte nakit değerlerin toplam aktiflere oranı, vadesiz mevduatların toplam mevduatlara oranı, takipteki alacakların toplam nakit kredilere oranı ve repo işlemlerinden kaynaklanan fonlama tutarlarının toplam pasiflere oranı olduğu bulunmuştur
Joint lifetime-outage optimization in relay-enabled IoT networks—A deep reinforcement learning approach
No full textNetwork lifetime maximization in Internet of things (IoT) is of paramount importance to ensure uninterrupted data transmission and reduce the frequency of battery replacement. This letter deals with the joint lifetime-outage optimization in relay-enabled IoT networks employing a multiple relay selection (MRS) scheme. The considered MRS problem is essentially a general nonlinear 0-1 programming which is NP-hard. In this work, we use the application of the double deep Q network (DDQN) algorithm to solve the MRS problem. Our results reveal that the proposed DDQN-MRS scheme can achieve superior performance than the benchmark MRS schemes