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Performance analysis of multi-hop V2V VLC system under atmospheric weather conditions
No full textThe reliability of vehicle-to-vehicle (V2V) visible light communication (VLC) systems is affected by several environmental factors. These include the availability of the direct communication link, the transmit power budget, the required communication quality and speed, and the atmospheric weather conditions. This encourages the usage of multi-hop relay systems. In which, the intermediate vehicles operate as wireless relays, receiving the signal from the source vehicle, decoding it, and re-transmitting it to the next vehicle until it reaches the destination vehicle. In this paper, we analyze the performance of multi-hop V2V VLC systems through the derivation of the maximum achievable communication distance and utilizing a realistic ray tracing channel modeling approach. The effects of the transceiver, system parameters, and weather conditions on the V2V VLC system performance are also investigated. Our results demonstrate that the foggy weather with low visibility has a severe impact on the V2V system performance, the transmission range is reduced by about 40 m comparing to the clear weather assuming the single transmission link. The results further reveal that deploying the inter-mediate vehicles as multi-hop relays has the ability to extend the transmission ranges, i.e., for only one hop relay, the maximum distance climbs by more than 50 m in the worst weather case
Simulation of vehicles’ gap acceptance decision at unsignalized intersections using SUMO
No full textIn this paper, an artificial neural network (ANN)-based gap acceptance behavior model was proposed. The feasibility of implementing this model in a microscopic simulation tool was tested using the application programming interface of Simulation of Urban Mobility (SUMO) simulation package. A stop-controlled intersection in New Jersey was selected as a case study. The simulation model of this intersection was calibrated using ground truth data extracted during the afternoon peak hours. The ANN-based SUMO model was compared to SUMO model with default gap acceptance parameters and the SUMO model with calibrated gap acceptance parameters. The comparison was based on wait time and accepted gap values at the minor approach of the intersection. The results showed that the ANN-based model produced superior results based on the selected outputs. The analysis results also indicated that the ANN-based model leads to significantly more realistic driving behavior of vehicles on the major approach of the intersection
CubeSat'lar için küçük form faktörlü PCB tabanlı bobin tasarımı
No full textpace missions using Earth's magnetic field to achieve effective attitude determination and control (orientation) is becoming more and more popular at relatively low altitudes, Low Earth Orbit (LEO). CubeSats (U-class spacecraft) are deployed in LEO and rely on miniaturizing technology without significant performance degradation. They use magnetic torque generator (magnetorquers) within the Attitude Determination and Control Systems utilizing the Earth's magnetic field, which is still strong enough to create a functional level of torque with a well-known distribution map around the sphere model. This thesis presents a small form factor air coil and magnetorquer design in the form of a PCB, considering the miniature CubeSat dimensions. Although several studies have shown the torque's effectiveness through simulation-based evaluations, it has not been evaluated in a real environment. In this thesis, we propose a test bench for the torque measurement that can be implemented in a real environment using a simple low-loss pendulum analogy due to the lack of air bearing. The measurement results demonstrate the small form factor PCB-based magnetorquer design's effectiveness.Etkili pozisyon belirleme ve kontrol (yönlendirme) elde etmek için Dünya'nın manyetik alanını kullanan uzay görevleri, nispeten düşük irtifalarda, Alçak Dünya Yörüngesinde (LEO) giderek daha popüler hale geliyor. CubeSats (U sınıfı uzay aracı), LEO'da konuşlandırılır ve önemli performans düşüşü olmadan minyatürleştirme teknolojisine dayanır. Pozisyon Belirleme ve Kontrol Sistemleri içinde, küre modeli etrafında iyi bilinen bir dağılım haritası ile işlevsel bir tork seviyesi oluşturmak için hala yeterince güçlü olan Dünya'nın manyetik alanını kullanan manyetik tork üreteci (magnetorquer) kullanırlar. Bu tez, minyatür CubeSat boyutları dikkate alınarak, PCB formunda küçük form faktörlü bir bobin ve magnetorquer tasarımı sunmaktadır. Birkaç çalışma ve simülasyona dayalı değerlendirmeler yoluyla torkun etkinliğini gösterse de, gerçek bir ortamda değerlendirilmemiştir. Bu tezde, sürtünmesiz rulman olmaması nedeniyle basit bir düşük kayıplı sarkaç benzetmesi kullanarak gerçek bir ortamda uygulanabilen tork ölçümü için bir test tezgahı öneriyoruz. Ölçüm sonuçları, küçük form faktörlü PCB tabanlı magnetorquer tasarımının etkinliğini göstermektedir
Measurement of the inclusive and differential tt¯ γ cross sections in the dilepton channel and effective field theory interpretation in proton-proton collisions at s√ = 13 TeV
No full textThe production cross section of a top quark pair in association with a photon is measured in proton-proton collisions in the decay channel with two oppositely charged leptons (e±μ∓, e+e−, or μ+μ−). The measurement is performed using 138 fb−1 of proton-proton collision data recorded by the CMS experiment at s = 13 TeV during the 2016–2018 data-taking period of the CERN LHC. A fiducial phase space is defined such that photons radiated by initial-state particles, top quarks, or any of their decay products are included. An inclusive cross section of 175.2 ± 2.5(stat) ± 6.3(syst) fb is measured in a signal region with at least one jet coming from the hadronization of a bottom quark and exactly one photon with transverse momentum above 20 GeV. Differential cross sections are measured as functions of several kinematic observables of the photon, leptons, and jets, and compared to standard model predictions. The measurements are also interpreted in the standard model effective field theory framework, and limits are found on the relevant Wilson coefficients from these results alone and in combination with a previous CMS measurement of the tt¯ γ production process using the lepton+jets final state.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); NKFIA (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); MSHE and NSC (Poland); FCT (Portugal); JINR (Dubna); MON, RosAtom, RAS, RFBR, and NRC KI (Russia); MESTD (Serbia); MCIN/AEI and PCTI (Spain); MOSTR (Sri Lanka); Swiss Funding Agencies (Switzerland); MST (Taipei); ThEPCenter, IPST, STAR, and NSTDA (Thailand); TUBITAK and TAEK (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, contract Nos. 675440, 724704, 752730, 758316, 765710, 824093, 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 n. 30820817; the Beijing Municipal Science & Technology Commission, No. Z191100007219010; the Ministry of Education, Youth and Sports (MEYS) of the Czech Republic; the Deutsche Forschungsgemeinschaft (DFG), under Germany's Excellence Strategy -EXC 2121 "Quantum Universe" -390833306, and under project number 400140256 -GRK2497; the Lendulet ("Momentum") Program and the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences, the New National Excellence Program UNKP, the NKFIA research grants 123842, 123959, 124845, 124850, 125105, 128713, 128786, and 129058 (Hungary); the Council of Science and Industrial Research, India; the Latvian Council of Science; the Ministry of Science and Higher Education and the National Science Center, contracts Opus 2014/15/B/ST2/03998 and 2015/19/B/ST2/02861 (Poland); the Fundacao para a Ciencia e a Tecnologia, grant CEECIND/01334/2018 (Portugal); the National Priorities Research Program by Qatar National Research Fund; the Ministry of Science and Higher Education, projects no. 0723-2020-0041 and no. FSWW-2020-0008, and the Russian Foundation for Basic Research, project No.19-42-703014 (Russia); MCIN/AEI/10.13039/501100011033, ERDF "a way of making Europe", and the Programa Estatal de Fomento de la Investigacion Cientifica y Tecnica de Excelencia Maria de Maeztu, grant MDM-2017-0765 and Programa Severo Ochoa del Principado de Asturias (Spain); the Stavros Niarchos Foundation (Greece); the Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University and the Chulalongkorn Academic into Its 2nd Century Project Advancement Project (Thailand); the Kavli Foundation; the Nvidia Corporation; the SuperMicro Corporation; the Welch Foundation, contract C-1845; and the Weston Havens Foundation (USA).Publisher versio
Infrastructure-to-vehicle visible light communications: Channel modelling and performance analysis
No full textVisible light communication (VLC) has emerged as a potential wireless connectivity solution for infrastructure-to-vehicle (I2V) communications. In this paper, we investigate the performance of I2V VLC systems with access points in the form of streetlights. Particularly, we consider a typical two-lane highway road where the light poles are located at both roadsides and uniformly separated from each other. Based on non-sequential ray tracing simulations, we first propose a closed-form path loss expression as a function of transceiver and infrastructure parameters. Then, we statistically analyze the path loss and derive a closed-form expression for its probability distribution function (PDF). Utilizing the derived PDF, we derive an approximate closed-form bit error rate (BER) expression. We confirm the accuracy of derived BER expression through comparison with Monte Carlo simulation results and demonstrate the effect of transceiver and infrastructure parameters such as receiver aperture, pole height, car height, lateral shift, and spacing between light poles on the BER performance.European Union’s Horizon 2020 ; KFUPM Deanship of Scientific Research ; TÜBİTA
Topology optimization-based design and development of a compact actuator with a high torque-to-weight ratio for quadrupeds
No full textThis paper presents the design, development, and testing procedures for a compact actuator with a high torque-to-weight ratio, generally aimed to actuate legged robots, e.g., quadrupeds. The main goal of designing the actuator was to keep its total weight minimum while ensuring a high torque output. Therefore, the following design steps were implemented: i) the actuator was designed in accordance with the torque output requirement and the stress distribution that was mapped on actuator frames, ii) topology optimization was conducted on the initial design and it is modified in accordance with optimization results, and iii) the optima actuator design was built and tested on in a realistic scenario in which it powered an actual quadruped robot for validation. As the result, the proposed actuators could track the desired walking trajectory with a relatively low error. In conclusion, continuous torque output of 48 Nm was obtained via a lightweight (1.6-1.7 kg) actuator design
İlişki doyumunda bağlanma davranışlarının ve çatışma çözme stillerinin rolü: uzak mesafe ve coğrafi olarak yakın romantik ilişkilerin karşılaştırılması
No full textThe present study investigated how people in long-distance relationships (LDRs) and geographically close relationships (GCRs) differ in perceiving attachment behaviors and dyadic coping skills, using conflict resolution styles during the Covid-19 pandemic, and how they are related to their relationship satisfaction. The sample comprised 201 individuals 18 to 31 years old who had been in a romantic relationship for at least 12 months. Perceived attachment behaviors were assessed via the Brief Accessibility, Responsiveness, and Engagement (BARE) Scale. In contrast, Conflict Resolution Styles Scale (CRSS) was used to determine which style they were using during conflicts. The outcome variable was relationship satisfaction, measured via the Relationship Assessment Scale (RAS). Participants were asked questions about their stress level, dyadic coping skills, and negative experiences during the Covid-19 pandemic. The self-reports determined the relationship type for some analyses. Hierarchical multiple regression analysis showed that negative and positive resolution style, dyadic coping, and perceived attachment behaviors explained significant variances in relationship satisfaction for both LDRs and GCRs. However, there was no additional variation from the relationship type over and beyond the main effects of the focal predictors. Exploratory mediation analysis revealed that dyadic coping partially mediated the relation between attachment behaviors and relationship satisfaction. The results and related discussion were provided as well as implications and future research directions.Bu çalışma, uzak ve yakın mesafe romantik ilişkisi olan insanların Covid-19 salgını sırasında bağlanma davranışlarının ve ikili başa çıkma becerilerinin nasıl algılandığını ve çatışma çözme stillerini kullanmada nasıl farklılık gösterdiğini ve buna bağlı olarak bunların ilişki doyumlarıyla ilişkilerini araştırdı. Örneklemi, 18-31 yaş aralığında ve en az 12 aydır romantik ilişki içinde olan 201 birey oluşturmuştur. Bağlanma davranışları Duyarlılık, Ulaşılabilirlik ve Yakınlık (DUY) Ölçeğiyle; çatışmalarda hangi stili kullandıkları ise Çatışma Çözme Stilleri Ölçeği (ÇÇSÖ) ile ölçülmüştür. Bağımlı değişken, İlişki Değerlendirme Ölçeği (İDÖ) ile ölçülen ilişki memnuniyetiydi. Katılımcılara, Covid-19 salgını sırasındaki stres düzeyleri, algılanan başa çıkma becerileri ve olumsuz deneyimleri hakkında bir dizi soru soruldu. İlişki durumu, öz-bildirimlerle belirlendi. Hiyerarşik çoklu regresyon analizi, olumsuz ve olumlu çözümleme tarzının, çift olarak başa çıkmanın ve algılanan bağlanma davranışlarının, hem uzak hem de yakın mesafe ilişkileri için ilişki memnuniyetinde önemli farklılıkları açıkladığını gösterdi. Bununla birlikte, başlıca yordayıcıların ana etkilerinin üzerinde ve ötesinde ilişki durumundan gelen ek bir varyasyon olmadığı bulundu. Açımlayıcı aracılık analizi, ikili başa çıkmanın bağlanma davranışları ile ilişki doyumu arasındaki ilişkiye kısmen aracılık ettiğini ortaya koymuştur. Detaylı bulgular, ilgili tartışma, uygulama ve gelecek çalışma önerileri sunulmuştur
Employee mindfulness and creativity: when emotions and national culture matter
No full textMindfulness has recently attracted more attention from service scholars due to its positive effect on various job outcomes. Yet, the linkage between mindfulness and service employees’ creativity is still not well understood. This study aims to bridge this gap by examining how emotions might influence the mindfulness and creativity relationship from different cultural perspectives. Frontline service employees from three countries, the Philippines, Turkey, and the United States, were sampled to form a cross-border dataset. PLS multigroup results show that creativity positively influences service recovery performance and error reporting across the three nations. Furthermore, the mindfulness-creativity link is mediated by gratitude as a positive emotion in the United States, but by envy as a negative emotion in the Philippines and Turkey. This suggests that the link between mindfulness and creativity may be culturally contextual. These results might provide insights for mindfulness practices within the service work environment
Capacitated stochastic lot-sizing and production planning problem under demand uncertainty
No full textThis paper proposes two multi-period, multi-item capacitated stochastic lot-sizing problems under demand uncertainty. We model uncertainty via a scenario tree. The first model considers production, inventory, backlogging, line status, and worker group assignment decisions, where inventory and backlogging decisions have wait-and-see structure. The second model converts line status and worker group assignment decisions to the wait-and-see structure. Also, the second model enables us to take corrective extra-ordering decisions using scenario-based wait-and-see decisions. Numerical results compare the optimality and CPU time performances of two models and solution approaches using a data set inspired by a real-life electronics company.Vestel Home Appliances and Vestel Electronics ; TÜBİTA
A comparative study on phenomenological and artificial neural network models for high temperature flow behavior prediction in Ti6Al4V alloy
No full textDue to its critical use in lightweight components requiring elevated temperature operation, it is very important to determine and model the high temperature thermomechanical flow behavior of Ti6Al4V. In this study, uniaxial tensile tests were performed at quasi-static strain rates and at temperatures ranging from 500 °C to 800 °C. The ductile behavior provided at a temperature of 800 °C and at a strain rate of 0.001 s−1 can be preferred for forming operations due to the steady state flow behavior. However, stress peaks during deformation at the strain rates of 0.1 s−1 and 0.01 s−1 are indicative of an unsafe zone. For modeling the flow stress behavior, three models including the Artificial Neural Network, Modified Hensel-Spittel and Arrhenius are employed with varying prediction performance as shown by the correlation coefficient (R) and average absolute relative error (AARE) values. Accordingly, the Artificial Neural Network model is claimed to be a more suitable approach for capturing the mechanical behavior of Ti6Al4V within the forming temperature range utilized in this study.Türk Havacılık ve Uzay Sanayi ; Ozyegin University ; TÜBİTA