22 sonuçlar
Arama Sonuçları
Listeleniyor 1 - 10 / 22
Yayın A DBN based reactive maintenance model for a complex system in thermal power plants(Elsevier Sci Ltd, 2019-10) Özgür Ünlüakın, Demet; Türkali, Busenur; Karacaörenli, Ayşe; Aksezer, Sezgin ÇağlarThermal power plants consist of several complex systems having many interacting hidden components. Any unexpected failure may lead to prolonged downtime and serious lost profits. Therefore, implementing an effective maintenance policy is crucial for this sector. Although preventive maintenance has become a more popular strategy, it does not completely prevent the need for corrective maintenance. Our aim in this study is to tackle the corrective maintenance implementation problem of a multi-component partially observable dynamic system based on a regenerative air heater in a thermal power plant. We propose eight methods having different efficiency measures with respect to time, effect and probability criteria to minimize the total number of maintenance activities in a given planning horizon. Performances of these methods are evaluated under corrective maintenance strategy using dynamic Bayesian networks. The results show that fault effect methods with best working state probability measure perform better than the others considering both the total amount of maintenance activities and also the solution time. We also point out how the methods can be implemented in real-life and how the results can be used for requirements planning. Furthermore, the proposed methods can be used for the corrective maintenance of all systems having hidden interacting components.Yayın Neuropsychiatric outcomes and caregiver distress in primary progressive aphasia(Wiley, 2023-01) Seçkin, Mustafa; Yıldırım, Elif; Demir, İlayda; Orhun, Ömer; Bülbül, Ezgi; Velioğlu, H. Aziz; Öget, Öktem; Yeşilot, Nilüfer; Çoban, Oğuzhan; Gürvit, HakanBackground: In this study, we aimed to outline the neuropsychiatric consequences of primary progressive aphasia (PPA) and to understand how neuropsychiatric symptomatology affects distress in caregivers. Methods: The Neuropsychiatric Inventory (NPI) including the distress index (NPI-Distress) was used. Additional information about the caregiver burden was obtained using Zarit Burden Interview (ZBI). NPI, NPI-Distress, and ZBI data from 17 patients with a clinical diagnosis of PPA were compared with 10 stroke aphasia patients. Neuropsychiatric symptomatology was investigated based on three clusters; Mood, Frontal/Comportmental, and Psychotic/Disruptive. Additionally, the Activities of Daily Living Questionnaire (ADLQ) was used to outline the functional impairment. Twelve healthy controls were included to compare the neurocognitive test scores with PPA and stroke aphasia groups. Results: A greater number of neuropsychiatric symptoms were observed in the PPA group compared to the stroke aphasia group. The number of symptoms in Mood, and Frontal/Comportmental clusters were greater than the number of symptoms in Psychotic/Disruptive clusters in the PPA group, whereas no significant relationship between the number of symptoms and symptom clusters was found in the stroke aphasia group. In the PPA group, a strong correlation was found between the NPI-Frequency × Severity scores and the NPI-Distress scores. Moreover, the NPI-Distress scores in the PPA group strongly correlated with the ZBI scores. Scores for anxiety, irritability/lability, and apathy had a stronger correlation with the NPI-Distress scores compared to the other NPI symptoms. The Communication subscale was the most impaired domain in the PPA group. Travel, and Employment and Recreation subscales showed greater functional impairment in the stroke aphasia group compared to the PPA group. Conclusions: Neuropsychiatric symptoms in PPA in our study were more frequent than previously reported. Furthermore, the distress index of the NPI was not only correlated with the severity of the neuropsychiatric symptoms but also reflected the overall burden on the caregivers in the PPA group.Yayın Dating fossil root cast (Black Sea coast, Turkey) using thermoluminescence: Implications for windblown drift of shelf carbonates during MIS 2(Elsevier Ltd., 2016-05-16) Polymeris, George S.; Kitis, George; Güneç Kıyak, Nafiye; Theodosoglou, Eleni; Tsirliganis, Nestor C.; Ertek, Topçu Ahmet; Erginal, Ahmet EvrenRhizoliths are mostly sub-aerially exposed root prints which appear through removal of the rock units that cap them. A horizontal-lying residual of a rhizolith, consisting purely of soft inner core material of white color was recovered 10 km west of Şile, Istanbul, in northwest Turkey within laminated oolithic massive aeolianite. The inner part, consisting purely of calcium carbonate, was dated by applying thermoluminescence, while for the outer shelves optically stimulated luminescence of quartz was used for age assessment. The age of the CaCO3 infill occupying the original place of the decayed plant roots was found to be 26.8 (±5.0) ka, corresponding to MIS 2. When compared with the ages of the middle (105.2 ± 15.6 ka) and outer (127 ± 9 ka) layers, corresponding to the later stage of MIS 5e or early stage of MIS 5d, the inner core coincides with the last glacial period when the sea-level was lower than the present, promoting transportation of ooids by offshore winds in conjunction with the exposed shelf carbonates. Based on the results yielded, rhizolith is much younger than the host rock aeolianite and witnesses to last glacial sea level lowstand when removal of shelf carbonates by offshore winds was promoted from the exposed shallow shelf plain. The results provide strong evidence that rhizoliths may not be coeval with the aeolianites within which they are embedded.Yayın Psychometric properties of the pathological buying screener: reliability and validity study(Kare Publishing, 2021-06) Dikbaş, Ganime Tuba; Acartürk, Ceren; Akyunus, MirayObjective: The Pathological Buying Screener (PBS) is a self-report scale used to evaluate compulsive buying behavior. The aim of this study was to assess the validity and reliability of a Turkish version of the PBS in a nonclinical sample. Method: A total of 457 adult participants aged 18-64 years were enrolled in this study. Internal consistency, test-retest reliability and structure, concurrent and criterion-related predictive validity analyses were conducted to ensure reliability and validity for use of the scale with a Turkish population. As part of the validity study, all of the participants were asked to complete a battery of self-report scales: the Compulsive Buying Scale, the Brief Symptom Inventory, the Rosenberg Self-Esteem Scale, the Barratt Impulsiveness Scale-Short Form, and the PBS. In order to examine the test-retest reliability, 75 participants were asked to complete the questionnaire once again 2 weeks after the first administration. Results: The results of this study revealed that the PBS had good internal consistency and test-retest reliability. The findings supported concurrent and criterion-related predictive validity, and a 2-factor structure, consistent with the original form. Conclusion: The Turkish version of the PBS is a valid and reliable measurement tool that will add to understanding of pathological buying behavior.Yayın Failure analysis and warranty modeling of used cars(Pergamon-Elsevier Science Ltd, 2011-09) Aksezer, Sezgin ÇağlarReliability is an important aspect of product perception and manufacturers are compelled to take corrective actions on the items failing within the warranty period. Automotive manufacturers are being exposed to significant operating costs as a result of warranty claims affecting an individual unit or mandatory (sometimes voluntary) recalls affecting a batch. Underlying principles of warranty modeling are built by considering both subjective issues and objective constraints such as competition, quality, and performance under the goal of achieving desired levels of reliability and cost in a balanced manner. This paper reviews the warranty cost models with an emphasis on the failure analysis of used vehicles. Expected warranty costs are calculated by taking into account the age, usage, and maintenance data of the product in question. Failure intensities and characteristics are identified in order to propose a policy that highlights the trade-off between the cost and the warranty length. A case study on a popular brand's initiation of factory certified pre-owned program for the local automobile market of Turkey is presented in detail. (C) 2011 Elsevier Ltd. All rights reserved.Yayın Decoder side true motion estimation for very low bitrate b-frame coding(IEEE, 2011) Ateş, Hasan Fehmi; Çizmeci, BurakIn H.264 standard, coding of motion vectors constitutes a significant portion of total bitrate especially at low bitrate regimes. This is because differential coding of motion vectors is inefficient when the bit budget is very low. In this paper, we propose a novel estimation and coding algorithm for motion vectors of B-frames at very low bitrates. In this method, the encoder selects the optimal motion vector from a limited set of candidate vectors that are determined at the decoder side using true motion estimation. Since these candidate vector sets are fixed by the decoder for each macroblock, there is no need for explicit coding of motion information, which reduces the bitrate required for coding. Also, true motion vector estimates are used for improved direct mode coding in B-frames. The algorithm provides an average of 0.68 dB PSNR gain for B-frames when compared to the reference H.264 results at the same bitrates. Simulation results also indicate significant improvement in visual quality of the compressed B-frames.Yayın Elektronik bateri oyunu için somut bir kullanıcı arayüzü(IEEE, 2017-06-27) Ay, Fahrettin; Engin, İlkan; İnce, GökhanTeknolojinin kullanımının yaygınlaşması ile beraber son zamanlarda insan-bilgisayar ilişkisi üzerine bir çok çalışma yapılmaktadır. Bilgisayar sistemlerinin insan eğitiminin üzerindeki etkisi ile ilgili yapılan çalışmalar buna örnek olarak gösterilebilir. Bu bildiride, hem oyun amaçlı hem de bilgisayar temelli eğitim programlarında kullanılan elektronik bateri oyunu için geliştirilen güvenilir ve gerçek zamanlı somut bir kullanıcı arayüz sistemi sunulmaktadır. Kullanıcı elektronik bagetleri kullanarak altı farklı yönde baget vuruşu gerçekleştirebilir. Geliştirilen darbe tespit algoritması, elektronik bagetlerden gelen sensör verilerini işleyerek hangi bagetten hangi yönde bir darbe hareketi oluştuğunu tespit eder. Bu bilgi ses sistemine gönderilerek ilgili bateri enstrümanına ait ses dosyasının çalınması sağlanır. Bu şekilde kullanıcıya gerçeğe yakın bir bateri deneyimi sunulmaktadır. Geliştirilen sistem, gerçek dünyada farklı kullanıcılar tarafından test edildi ve performansı değerlendirilmiştir. Elde edilen sonuçlar elektronik davul oyununun güvenilirliğini ve kullanılabilirliğini onaylamaktadır.Yayın First domino tile in the social innovation process: idea creation of university students(IEEE, 2016-09-08) Yıldırım, Nihan; Ansal, HacerInterrelations between creativity, innovativeness and entrepreneurial skills of individuals have long been discussed in the literature. Due to the challenges regarding their measurement, most studies focused on the intentions rather than the outcomes. The idea generation that requires creativity is the first stage of social innovation. The young population's creative potentials in participating social innovation practices deserve a special attention as they play a critical role in the innovativeness and entrepreneurship of societies. This study aims to explore the factors that determine the creative intentions of university students that are important in generating social innovation projects. A structured survey based on the literature was conducted among 600 management and engineering students from 3 universities from the different percentiles of the Entrepreneurial and Innovative University Index for 2012 of the Turkish Ministry of Science, Industry and Technology. The survey included questions on the demographic characteristics, environmental factors, motivators, university/institutional context, perceptions and creative thinking attitudes. By conducting reliability and factor analysis, accuracy and validity of data is tested and the impact factors were identified. Findings reveal that visionary attitude, curiosity, exploration and learning, attitude for own creativity, self-esteem, perception about the learnability of creativity, university and social environment are components of creative thinking intentions of students and some of these factors vary by year of study and university.Yayın Analysis of different maintenance policies on a multi-component system using dynamic bayesian networks(Işık Üniversitesi, 2019-01-15) Karacaörenli, Ayşe; Özgür Ünlüakın, Demet; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Endüstri Mühendisliği - Yöneylem Araştırması Yüksek Lisans ProgramıRecently, system components and interactions between them have become more complex and this situation has made it di?cult to provide maintenance decisions. Herewith, determining e?ective decisions has played an important role. In multicomponent systems, many methodologies and strategies can be applied when a component or a system has already broken down or when it is desired to identify and avoid pro-actively defects that could lead to future failure. In dynamic systems, it is important for proactive maintenance to increase system reliability by performing early diagnosis-based maintenance activities without waiting for a problem. In this study, we focus on proactive maintenance of a complex multi-component dynamic system. Components are hidden although there exists partial observability to the decision maker. Components deteriorate in time. It is possible to replace or repair components with a given cost. We want to ?nd a policy that minimizes the total maintenance cost in a prede?ned time horizon. We propose several maintenance policies and compare the performance of these by simulating them via Dynamic Bayesian Networks on an empirical model. Furthermore, a dynamic Bayesian network is constructed for the maintenance of an endo generator system to show how the proposed methods can be implemented in real life.Yayın Reliability, validity, and factorial structure of the Turkish version of the Empathy Quotient (Turkish EQ)(Taylor & Francis Ltd, 2018-07-03) Köse, Samet; Çam Çelikel, Feryal; Kulacaoğlu, Filiz; Akın, Ercan; Yalçın, Mehmet; Ceylan, VedatOBJECTIVES: Empathy is an essential ability that allows us to tune into how others are feeling or thinking. Empathy makes it possible to resonate with others' positive and negative feelings alike so that we can thus feel happy when we vicariously share the joy of others and we can share the experience of suffering when we empathize with someone in pain. Empathy training not only promotes prosocial behaviour, but also augments positive affect and resilience, which in turn fosters better coping with stressful situations. The Empathy Quotient (EQ) is a self-report questionnaire that was developed to measure the cognitive, affective, and behavioural aspects of empathy. Here, we aimed to examine the validity, reliability, and factor structure of the EQ in a Turkish sample. METHODS: Participants were 436 mostly college students and civil servants (195 female, 241 male). Sociodemographic information, the Turkish version of the EQ, Marlowe-Crowne Social Desirability Scale (MC-SDS) 33-item full version and MC-SDS 13-item shorter versions were administered. All statistical analyses were performed by using SPSS version 23 for Windows. RESULT: EQ scores were significantly higher in female participants ((X) over bar (Female)=46.45, SDFemale=0.62) compared to the male participants ((X) over bar (Male)=43.68, SD (Male)=0.56). The Cronbach's alpha coefficient for the scale was 0.76, Guttman's split-half reliability coefficient was 0.61, and test-retest reliability coefficient was 0.95. A positive and statistically significant correlation was found between the Turkish EQ and MC-SDS Full version (r=0.299, p<.01) and short form of MC-SDS (r=0.273, p<.01). A three-factor solution that accounted for 25.28% of the variance observed. CONCLUSIONS: The Turkish version of the EQ has satisfactory validity, good internal and test-retest reliability with a robust factorial structure to use in a clinical population in Turkey. Moreover, as predicted, women scores were statistically significantly higher on the EQ than men. This result was consistent with a series of earlier studies reporting gender differences (female superiority) on questionnaires that measure empathy. A better knowledge of empathy will have important implications for the examination and understanding of certain neurological and psychiatric disorders, including autism, narcissistic and antisocial personality disorders, and may also provide important clues about the relevant brain circuitry underlying empathy.
- «
- 1 (current)
- 2
- 3
- »
