208 research outputs found
Clustering of gamma-ray burst types in the Fermi-GBM catalogue: indications of photosphere and synchrotron emissions during the prompt phase
Many different physical processes have been suggested to explain the prompt
gamma-ray emission in gamma-ray bursts (GRBs). Although there are examples of
both bursts with photospheric and synchrotron emission origins, these distinct
spectral appearances have not been generalized to large samples of GRBs. Here,
we search for signatures of the different emission mechanisms in the full Fermi
Gamma-ray Space Telescope GBM catalogue. We use Gaussian Mixture Models to
cluster bursts according to their parameters from the Band function (,
, and ) as well as their fluence and . We find five
distinct clusters. We further argue that these clusters can be divided into
bursts of photospheric origin (2/3 of all bursts, divided into 3 clusters) and
bursts of synchrotron origin (1/3 of all bursts, divided into 2 clusters). For
instance, the cluster that contains predominantly short bursts is consistent of
photospheric emission origin. We discuss several reasons that can determine
which cluster a burst belongs to: jet dissipation pattern and/or the jet
content, or viewing angle.Comment: Accepted for publication in MNRA
Emission from accelerating jets in gamma-ray bursts: Radiation dominated flows with increasing mass outflow rates
We study the narrowest spectra expected from gamma-ray bursts. We present an
analytical function for the spectrum that is emitted from the photosphere of a
radiation-dominated flow that is under acceleration. This is the narrowest
possible spectrum and it differs from a Planck function. We also present
numerical spectra from photospheres occurring during the transition into the
coasting phase of the flow. Using these spectral models, we reanalyse Fermi
observations of GRB100507 and GRB101219, which both have been reported to have
very narrow spectra. The bursts can be fitted by the spectral models: For
GRB101219 the spectrum is consistent with the photosphere occurring below or
close to the saturation radius, while for GRB100507 the photosphere position
relative to the saturation radius can be determined as a function of time. In
the latter case, we find that the photosphere initially occurs in the
acceleration phase and thereafter transitions into the coasting phase. We also
find that this transition occurs at the same time as the change in observed
cooling behaviour: the temperature is close to constant before the break and
decays after. We argue that such a transition can be explained by an increasing
mass outflow rate. Both analysed bursts thus give strong evidence that the jets
are (initially) radiation dominated.Comment: Accepted by MNRA
AN EFFECTIVE RISK-PREVENTIVE MODEL PROPOSAL FOR OCCUPATIONAL ACCIDENTS AT SHIPYARDS
According to the statistics of occupational accidents, it is observed that the number of accidents occurred in shipbuilding industry is high and the rate of deaths and serious injuries among these accidents is higher than in other industries. However, the number of the studies to prevent these accidents in both industrial and scientific practices is considerably low. Therefore, the objective of this study is to develop an efficient risk preventive model in accordance with occupational health and safety regulations for industrial organizations. The approach proposed in this study differs from those described in the literature, because it is based on fuzzy set theory in order to cope with uncertainties on probability and severity definitions in terms of occupational health and safety. Furthermore, in this paper, risk severity is considered in terms of harm to worker, harm to environment, and harm to hardware, whereas in the literature, risk severity is generally considered solely in terms of only harm to worker. Then, risk magnitude is obtained by utilizing fuzzy inference system. The proposed approach is applied to a shipyard located in the Marmara Region in order to illustrate the applicability of the model
Fragrant grapes on the trail of flavour as part of gastronomy tourism
Anadolu, binlerce yıllık geçmişiyle üzümün anavatanı ve gen merkezi konumundadır. Bu coğrafyada yaşayan her medeniyet üzümü
ve üzümden elde ettikleri ürünleri mutfak kültürlerinin içine almışlar ve mutfak kültürlerini farklılaştırmışlardır. Bu farklılık ise her geçen
gün turizm açısından daha fazla çekicilik unsuru olarak değerlendirilmektedir. Bu doğrultuda değişen turizm dinamikleri ile gastronomi
turistleri lezzetlerin takibini yaparak seyahatlerini planlamaktadırlar. Bu çalışma ile kokulu üzümün, Karadeniz Bölgesi’nin Orta ve Doğu
sahil şeridinde yer alan illerdeki yeri ve önemi ayrıca gastronomi turizmine yönelik bir ürün olarak potansiyeli ele alınmıştır. Gastronomi
turizmine yönelik ilginin arttığı sonucuna bağlı olarak, alternatif bir gastronomik ürün rotası önermesi açısından çalışma önem arz
etmektedir. Çalışmanın teorik alt yapısı planlı davranış teorisine dayandırılmıştır. Çalışmanın evrenini Karadeniz Bölgesi’nin Orta ve
Doğu sahil şeridinde yer alan; Samsun, Ordu, Giresun, Trabzon, Rize ve Artvin illeri oluşturmaktadır. Çalışmanın verileri nitel araştırma
yöntemlerinden doküman inceleme, gözlem ve görüşme tekniğiyle toplanmıştır. Çalışmanın deseni örnek olaydır. Çalışmada veri
analizi planı oluşturulmuş, betimsel analiz yöntemi ile veriler analiz edilmiştir. Çalışma ile elde edilen veriler; kokulu üzümün bölge için
değerlendirilmesi gereken bir potansiyele sahip olduğu sonucunu ortaya koymaktadır. Dolayısıyla kokulu üzüme yönelik gastronomi
rotalarının oluşturulması ile destinasyon çekiciliği arttırılarak destinasyon imajının gelişmesine böylece yerel halkın yaşam kalitesinin
yükseltilmesine önemli katkılar sağlanabilecektirAnatolia, with its thousands of years of history, is the homeland and gene center of grapes. Every civilization living in this geography
has included grapes and products produced from them into their culinary cultures and differentiated their culinary cultures. This
difference is considered more and more attractive in terms of tourism day by day. With the changing tourism dynamics, gastronomy
tourists plan their travels by following flavors. In this study, the place and importance of fox grape in the provinces located on the
Middle and Eastern coastline of the Black Sea region, and its potential as a product for gastronomy tourism were discussed. Depending
on the result that the interest in gastronomic tourism has increased, the study is important in terms of proposing an alternative route
of gastronomic product. The theoretical background of the study is based on the theory of planned behavior. The population of the
study consists of Samsun, Ordu, Giresun, Trabzon, Rize and Artvin provinces located in the Middle and Eastern coastline of the Black
Sea region. Data of the study were collected by document analysis, observation and interview techniques, which are among the
qualitative research methods. The research was designed as a case study. In the study, a data analysis plan was created and the data
were analyzed using the descriptive analysis method. The data obtained from the study reveal that fox grape has a potential that
should be evaluated for the region. Therefore, the creation of gastronomic routes to fox grape can contribute to increasing the
attractiveness of the destination and improving the image of the destination, and thus to increasing the local people’s quality of life
The Fraction of Gamma-ray Bursts with an Observed Photospheric Emission Episode
There is no complete description of the emission physics during the prompt
phase in gamma-ray bursts. Spectral analyses, however, indicate that many
spectra are narrower than what is expected for non-thermal emission models.
Here, we reanalyse the sample of 37 bursts in \citet{Yu2019}, by fitting the
narrowest time-resolved spectrum in each burst. We perform model comparison
between a photospheric and a synchrotron emission model based on Bayesian
evidence. We choose to compare the shape of the narrowest expected spectra:
emission from the photosphere in a non-dissipative flow and slow-cooled
synchrotron emission from a narrow electron distribution. We find that the
photospheric spectral shape is preferred by of the spectra
(20/37), while of the spectra (14/37) prefer the synchrotron
spectral shape; three spectra are inconclusive. We hence conclude that GRB
spectra are indeed very narrow and that more than half of the bursts have a
photospheric emission episode. We also find that a third of all analysed
spectra, not only prefer, but are also compatible with a non-dissipative
photosphere, confirming previous similar findings.
Furthermore, we notice that the spectra, that prefer the photospheric model,
all have a low-energy power-law indices . This means that
is a good estimator of which model is preferred by the data.
Finally, we argue that the spectra which statistically prefer the synchrotron
model, could equally well be caused by subphotospheric dissipation. If that is
the case, photospheric emission during the early, prompt phase would be even
more dominant.Comment: Accepted: Ap
Regulatory role of optimism ın the relationship between crisis management applications and business performance of tourism enterprises during the Covid-19 pandemic: an example of TR90 region
Bu çalışmada COVID-19 küresel salgını ile turizm endüstrisi ilişkilendirilmiştir. Bunun önemli nedenleri
arasında; salgının sebep olduğu seyahat kısıtlamaları ve turizm sektöründe bazı işletmelerin faaliyetlerine ara
vermeleri hatta işletmelerin salgın şartlarında uymak zorunda oldukları düzenlemelerdir. Dolayısıyla çalışma
kapsamında bu nedenlerle ortaya çıkacak muhtemel krizler ve bu krizlerin yönetimi ele alınmıştır. Çalışmanın
amacı, COVID-19 küresel salgınla mücadelede turizm sektöründeki yöneticilerin benimsediği kriz yönetim
uygulamaları ve işletmelerin performansı arasındaki ilişkide iyimserliğin düzenleyici rolünün olup olmadığının
tespit edilmesidir. Çalışmanın modeli, olumlu yönelim teorisi ve kaynakların korunması teorisine
dayandırılmıştır. Çalışmada nicel araştırma yaklaşımı benimsenmiştir. Çalışmada, genel tarama araştırmasının
bir türü olan ilişkisel tarama yöntemi kullanılmıştır. Çalışmanın evrenini, TR90 Bölgesinde faaliyet gösteren
konaklama işletmeleri, seyahat işletmeleri ve yiyecek-içecek işletmelerindeki çalışan personeli kapsamaktadır.
Çalışmanın verileri anket tekniği ile toplanmıştır. Çalışmadan elde edilen veriler doğrultusunda, konaklama
işletmeleri, seyahat işletmeleri ve yiyecek-içecek işletmelerinde; kriz yönetim uygulamaları ile işletme
performansları arasındaki ilişkide iyimserliğin düzenleyici rolünün olduğu sonucuna ulaşılmıştır.the pandemic and the suspension of activities of some businesses in the tourism sector and even the regulations
that businesses have to comply with in the pandemic conditions are among the important reasons for this.
Therefore, within the scope of the study, possible crises that may arise due to these reasons and the management
of these crises are discussed. The aim of the study is to determine whether optimism has a regulatory role in
the relationship between the crisis management practices adopted by the managers in the tourism sector and
the performance of the enterprises in the fight against the COVID-19 pandemic. The model of the study was
based on the theory of positive orientation and conservation of resources theory. Quantitative research approach
was adopted in the study. Relational survey method, which is a type of general survey research, was used in
the study. The population of the study consisted of accommodation businesses, travel businesses and food and
beverage businesses operating in the TR90 Region. The data of the study were collected by questionnaire
technique. In line with the data obtained from the study, it was concluded that optimism has a moderating role
in the relationship between crisis management practices and business performances in accommodation
businesses, travel businesses and food and beverage businesses
The effect of the X, Y, Z generations’ women perspectives on travel intention of female tourists traveling alone: An example of TR90 region
Turizm kaynaklarına erişimde ve turistik seyahatlerde kadınlar ve erkekler eşit hak ve özgürlüklere sahip
olmasına rağmen Türkiye‟de ve dünya genelinde hâkim olan bir eşitsizlik anlayışının söz konusu olduğu
söylenebilir. Bu çalışmada, tek başına seyahat eden kadın turistler ile ilgili algının, tek başına seyahat
etme niyeti üzerinde etkisinin olup olmadığı ve tek başına seyahat etme algısı ve tek başına seyahat etme
niyetinin kuşaklara göre bir farklılık gösterip göstermediği incelenmiştir. Ulusal literatür incelendiğinde,
kadınların tek başına seyahat algıları ile tek başına seyahat etme niyeti arasındaki ilişkiye yönelik sınırlı
sayıda çalışmaya ulaşılmıştır. Bu nedenle bu çalışmanın literatüre katkı sağlayacağı düşünülmektedir.
Çalışmanın teorik alt yapısı planlı davranış teorisi, liberal feminizm teorisi ve sosyal etki teorisine
dayanmaktadır. Çalışmanın evrenini, TR90 Doğu Karadeniz Bölgesindeki (Artvin, Giresun, Gümüşhane,
Ordu, Rize, Trabzon) kadın nüfusu oluşturmaktadır. Veriler anket yolu ile toplanmıştır. Çalışmanın
yöntemi, tarama modelleri içerisinde yer alan ilişkisel tarama modelidir. Çalışma bulgularını analiz
edebilmek için ANOVA Testi, korelasyon analizi, basit doğrusal regresyon analizi ve hiyerarşik (sıralı)
regresyon analizi kullanılmıştır. Çalışmadan elde edilen veriler doğrultusunda, kadınların tek başına
seyahate çıkma algısının tek başına seyahat etme niyeti üzerinde etkili olduğu ve tek başına seyahat algısı
ile tek başına seyahat etme niyetinin kuşaklara göre farklılık göstermediği sonuçlarına ulaşılmıştır.Although women and men have equal rights and freedoms in accessing tourism resources and in touristic
travels, it can be said that there is an understanding of inequality prevailing in Turkey and throughout the
world. In this study, it was examined whether the perception of female tourists traveling alone has an
effect on the intention to travel alone, and whether the perception of female tourists traveling alone and
intention to travel alone differ by generation. When the national literature is examined, a limited number
of studies have been found on the relationship between the perception of female tourists traveling alone
and their intention to travel alone. Therefore, it is thought that this study will contribute to the literature.
The theoretical background of the study is based on planned behavior theory, liberal feminism theory and
social impact theory. The population of the study consists of the female population in the TR90 Eastern
Black Sea region (Artvin, Giresun, Gümüşhane, Ordu, Rize, Trabzon). The data were collected by using a
questionnaire. The method of the study is the relational screening model, which is included in the
screening models. ANOVA Test, correlation analysis, simple linear regression analysis and hierarchical
(ordinal) regression analysis were used to analyze the study findings. In line with the data obtained from
the study, it was concluded that women's perception of traveling alone has an effect on travel intention
and that travel perception and travel intention do not differ according to generations
A review on household energy consumption behavior: how about migrated consumers?
This paper reviews the literature on energy consumption behavior for both domestic and migrated/displaced population and aims to recommend crucial policy measures for creating awareness on the energy efficiency. Consumers’ adoption to the efficient usage of energy varies depending on demographic, behavioral and situational dynamics in their households and societies. The regional or national strategies to implement efficient technologies for the consumer engagement are crucial to change their behaviors. Migrants affect the energy usage patterns in the host country due to their different usage behaviors. Any type of measures for migrated population should include available, acceptable, accessible and affordable energy efficiency applications to engage them with the domestic population
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