Mass density vs. energy density at cosmological scales

In the presence of the gravitational field, the energy density of matter no longer coincides with its mass density. A discrepancy exists, of course, also between the associated power spectra. Within the $\Lambda$CDM model, we derive a formula that relates the power spectrum of the energy density to that of the mass density and test it with the help of N-body simulations run in comoving boxes of 2.816 Gpc/$h$. The results confirm the validity of the derived formula and simultaneously show that the power spectra diverge significantly from one another at large cosmological scales.Comment: 10 pages, 4 figure

HAWT Rotor Design and Performance Analysis

Abstract In this paper, a design method based on blade element momentum (BEM) theory is explained for horizontal-axis wind turbine (HAWT) blades. The method is used to optimize the chord and twist distributions of the blades. Applying this method a 100kW HAWT rotor is designed. Also a computer program is written to estimate the aerodynamic performance of the existing HAWT blades and used for the performance analysis of the designed 100kW HAWT rotor

THE PSYCHOLOGICAL EFFECTS OF COVID 19 ON MEDICAL AND NON-MEDICAL UNIVERSITY STUDENTS

Background: The COVID 19 pandemic has had significant psychological effects on university students as well as in all segments of society. The aim of this study is to examine the relationship between education fields (medical-non medical), education styles (online-face to face), sociodemographic characteristics of university students and their levels of depression, anxiety, stress, fear of COVID-19. Subjects and methods: In the cross-sectional designed research, 1213 university students studying in Turkey was reached online. A sociodemographic form, the Depression Anxiety Stress Scale (DASS 21) and the Fear of COVID-19 Scale (FCV-19S) was applied to the participants. Results: Of all participants 887(73%) were women. 647(53%) students were studying in the medical field. The scores of FCV- 19S and all subscales of DASS 21 were significantly higher in women. In the comparison between the field and style of education, no difference was found. DASS 21 scores were higher in the participants whose relatives had COVID-19 or who had a mental disorder in the past or medical disease. Conclusions: In this study, it was observed that while there was no significant difference in the scores of DASS 21 among university students in terms of the field and style of education, variables such as gender, not having COVID-19 so far, having lost a relative due to COVID-19 could cause significant differences. Identifying sensitive groups will create early intervention opportunities

THE PSYCHOLOGICAL EFFECTS OF COVID 19 ON MEDICAL AND NON-MEDICAL UNIVERSITY STUDENTS

Background: The COVID 19 pandemic has had significant psychological effects on university students as well as in all segments of society. The aim of this study is to examine the relationship between education fields (medical-non medical), education styles (online-face to face), sociodemographic characteristics of university students and their levels of depression, anxiety, stress, fear of COVID-19. Subjects and methods: In the cross-sectional designed research, 1213 university students studying in Turkey was reached online. A sociodemographic form, the Depression Anxiety Stress Scale (DASS 21) and the Fear of COVID-19 Scale (FCV-19S) was applied to the participants. Results: Of all participants 887(73%) were women. 647(53%) students were studying in the medical field. The scores of FCV- 19S and all subscales of DASS 21 were significantly higher in women. In the comparison between the field and style of education, no difference was found. DASS 21 scores were higher in the participants whose relatives had COVID-19 or who had a mental disorder in the past or medical disease. Conclusions: In this study, it was observed that while there was no significant difference in the scores of DASS 21 among university students in terms of the field and style of education, variables such as gender, not having COVID-19 so far, having lost a relative due to COVID-19 could cause significant differences. Identifying sensitive groups will create early intervention opportunities

Suppression of matter density growth at scales exceeding the cosmic screening length

One of the main objectives of modern cosmology is to explain the origin and evolution of cosmic structures at different scales. The principal force responsible for the formation of such structures is gravity. In a general relativistic framework, we have shown that matter density contrasts do not grow over time at scales exceeding the cosmic screening length, which corresponds to a cosmological scale of the order of two to three gigaparsecs at the present time, at which gravitational interactions exhibit an exponential cut-off. This is a purely relativistic effect. To demonstrate the suppression of density growth, we have performed N-body simulations in a box with a comoving size of $5.632\,{\rm Gpc}/h$ and obtained the power spectrum of the mass density contrast. We have shown that it becomes independent of time for scales beyond the cosmic screening length as a clear manifestation of the cosmic screening effect.Comment: 7 pages, 3 figure

DIŞ KAYNAK KULLANIMI AÇISINDAN INFLUENCER'LARIN GÜCÜ: INSTAGRAM ÖRNEĞİ

ÖZ: Gelişen teknolojik imkânlar, firmalara faaliyetlerini dijital ortamlara taşıması için büyük fırsatlar sunmaktadır. Bu fırsatlar firmaların geleneksel pazarlama faaliyetlerinden, dijital pazarlama faaliyetlerine geçiş süreçlerini pozitif yönde etkilemektedir. Özellikle sosyal medya platformları gibi çift yönlü iletişimin çok güçlü olduğu mecralarda, dijital pazarlama faaliyetleri her geçen gün önem kazanmaktadır. Bazı firmalar, bu mecraları kullanan bireylere ulaşabilmek için influencerlarla işbirliği içine girmekte ve dış kaynak kullanımını dijital platformlara da taşımaktadır. Bu noktadan yola çıkarak çalışmanın amacı; “Black Friday, Şahane Cuma, Efsane Kasım, Muhteşem Cuma ve Cyber Monday” gibi kampanyaların yer aldığı kasım ayı boyunca influencerların story ve post paylaşımlarından hareketle firma ve influencer işbirliğini çeşitli yönlerden açıklamaya çalışmaktır. Bu doğrultuda Kasım ayı boyunca düzenli olarak paylaşım yapan 15 influencerın, Instagram hesaplarında takipçileri ile paylaştıkları story ve postlar günlük takip edilmiş ve işbirliği içinde olduğu marka ve ürünler belirlenmiştir. Elde edilen sonuçlar, firmaların ürün ve hizmet tanıtımlarımda influencerlar ile önemli bir işbirliği içerisinde olduğunu, seçilen influencerlar ile ürün ve hizmet özelliklerinin de özenli ve birbiri ile örtüşen içerikler ile sağlandığı görülmektedir. ABSTRACT: Developing technological opportunities provide businesses with numerous opportunities to shift their operations to digital environments. These opportunities have a positive impact on companies' transition processes from traditional marketing activities to digital marketing activities. Digital marketing activities are becoming increasingly important, particularly in channels with strong two-way communication, such as social media platforms. Companies work with influencers to reach out to individuals through these channels, and they outsource to digital platforms. From this point, the study's goal is to attempt to explain how the company and influencer collaborated from various angles, based on the influencers' posts and shares during the month of November, when campaigns like "Black Friday, Wonderful Friday, Legendary November, Great Friday and Cyber Monday" were active. In this manner, the Instagram stories and posts of 15 influencers who regularly shared content with their followers throughout the month of November were monitored on a daily basis, and the brands and products with which they collaborated were identified. The obtained results indicate that companies work closely with influencers to promote their products and services, and that the selected influencers and product and service features are provided with content that overlaps with care

Optimized Rearrangements of Turkish Q and F Keyboards by Means of Language-statistics and Simple Operations

I n this study, based on the language particularly n-gram statistics of Turkish extracted from a large corpus of meaningful written text of various categories, we try to propose some improvements, namely optimized rearrangements for the Turkish Q and F keyboards via some simple rules and heuristics. Our proposals result in more desirable and efficient keyboard layouts that increase the comfort and the speed of professional typists. The methods and procedures followed throughout this study can be extended and applied for any keyboard of other alphabets and language