Gazi University Dspace
Not a member yet
26981 research outputs found
Sort by
Ac Module Desıgn And Implementatıon For Solar Panels
No full textSanayileşmeyle birlikte artan enerji talebinden ve fosil yakıtların hem tükeniyor olması
hem de çevresel olumsuzluklarından dolayı, alternatif enerji kaynaklarına ihtiyaç
duyulmaktadır. Güneş enerjisi temiz, bol ve yenilenebilir olması sebebiyle alternatif
kaynaklar arasında öne çıkmaktadır. Teknolojinin gelişmesiyle birlikte güneş enerjisinden
düşük maliyetlerle daha yüksek verimde enerji elde edilmesi mümkün hale gelmiştir.
Böylece enerjinin ihtiyaç duyulduğu alanlarda yaygın olarak kullanıldığı görülmektedir.
Güneş enerjisinden elde edilen enerjinin istenilen güç kalitesinde şebekeye veya yüke
aktarılması için güç elektroniği donanımlarına ihtiyaç vardır. Bu çalışmada, fotovoltaik
panellerden elde edilen doğru akımı alternatif akıma dönüştüren bir modül tasarımı ve
uygulaması üzerine bir çalışma gerçekleştirilmiştir. Normal koşullarda fotovoltaik paneller
doğru akım üretmektedir. Ticari nitelikteki güneş enerjisi dönüşüm sistemlerinde doğru
akım, ya doğru akım baraları ile ya da panellerin seri bağlanması ile bir DA dizisi
oluşturularak eviriciler üzerinden alternatif akıma dönüştürülür. Mevcut sistemler ile
elektrik üretmenin bazı dezavantajları bulunmaktadır. Tasarımı yapılan sistem ile güneş
enerjisinden maksimum düzeyde güç elde edebilmek ve parçalı gölgeleme sonucu
meydana gelen enerji kayıpları gibi olumsuzlukları aza indirerek fotovoltaik sistemlerde
bazı iyileştirmeler yapılmak istenmiştir. Bunun için her bir fotovoltaik panele bağlı modül
yardımıyla doğrudan alternatif akım elde eden sistem gerçekleştirilmiştir. Güneş
panelinden elde edilen doğru gerilimi istenilen seviyeye yükseltmek için yükseltici
konvertör tasarlanmıştır. Tasarım için MATLAB programının Simulink aracı ile hem
konvertör hem de Maksimum Güç Noktası İzleyicisi (MGNİ) algoritmalarının benzetimleri
gerçekleştirilmiştir. Konvertör ile yükseltilen gerilim evirici yardımıyla alternatif gerilime
dönüştürülmüştür. Maksimum düzeyde güç elde edebilmek için farklı MGNİ algoritmaları
denenmek suretiyle maksimum güç elde edilmeye çalışılmıştır. Böylece hem maksimum
güç elde edilmiştir hem de oluşabilecek verim kayıplarını bertaraf edebilecek modül
geliştirilmiştir.Alternative energy resources are needed due to the increasing energy demand with
industrialization and the depletion of fossil fuels as well as environmental adversities.
Solar energy stands out among alternative sources because it is clean, abundant and
renewable. With the development of technology, it has become possible to obtain higher
efficiency energy from solar energy at lower costs. Thus, it is seen that energy is widely
used in areas where it is needed. There is a need for power electronics equipment to
transfer the energy obtained from solar energy to the network or load at the desired power
quality. In this study, a study has been carried out on the design and application of a
module that converts the direct current obtained from photovoltaic panels to alternating
current. Under normal conditions, photovoltaic panels produce direct current. In
commercial solar power conversion systems, direct current is converted into alternating
current via inverters either by direct current busbars or by connecting the panels in series to
form a DA array. There are some disadvantages to generating electricity with existing
systems. With the designed system, it was aimed to obtain maximum power from the solar
energy and to make some improvements in photovoltaic systems by minimizing the
negativities such as energy losses due to shading. For this purpose, a system that directly
generates alternating current has been realized with the help of the module connected to
each photovoltaic panel. Booster converter is designed to increase the correct voltage
obtained from the solar panel to the desired level. Simulation of both converter and
Maximum Power Point Tracking (MPPT) algorithms were performed with the Simulink
tool of MATLAB for design. The voltage raised by the converter is converted to
alternative voltage with the help of inverter. In order to obtain maximum power, maximum
power was tried by trying different MPPT algorithms. Thus, both maximum power was
obtained and a module was developed to eliminate the possible loss of efficienc
Global Retinoblastoma Presentation and Analysis by National Income Level
No full textThis cross-sectional analysis reports the retinoblastoma stage at
diagnosis across the world during a single year, investigates
associations between clinical variables and national income level, and
investigates risk factors for advanced disease at diagnosis.
Key PointsQuestionIs the income level of a country of residence
associated with the clinical stage of presentation of patients with
retinoblastoma? FindingsIn this cross-sectional analysis that included
4351 patients with newly diagnosed retinoblastoma, approximately half of
all new retinoblastoma cases worldwide in 2017, 49.1\% of patients from
low-income countries had extraocular tumor at time of diagnosis compared
with 1.5\% of patients from high-income countries. MeaningThe clinical
stage of presentation of retinoblastoma, which has a major influence on
survival, significantly differs among patients from low-income and
high-income countries, which may warrant intervention on national and
international levels.
ImportanceEarly diagnosis of retinoblastoma, the most common intraocular
cancer, can save both a child's life and vision. However, anecdotal
evidence suggests that many children across the world are diagnosed
late. To our knowledge, the clinical presentation of retinoblastoma has
never been assessed on a global scale. ObjectivesTo report the
retinoblastoma stage at diagnosis in patients across the world during a
single year, to investigate associations between clinical variables and
national income level, and to investigate risk factors for advanced
disease at diagnosis. Design, Setting, and ParticipantsA total of 278
retinoblastoma treatment centers were recruited from June 2017 through
December 2018 to participate in a cross-sectional analysis of
treatment-naive patients with retinoblastoma who were diagnosed in 2017.
Main Outcomes and MeasuresAge at presentation, proportion of familial
history of retinoblastoma, and tumor stage and metastasis. ResultsThe
cohort included 4351 new patients from 153 countries; the median age at
diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976
patients (45.4\%) were female. Most patients (n=3685 {[}84.7\%]) were
from low- and middle-income countries (LMICs). Globally, the most common
indication for referral was leukocoria (n=2638 {[}62.8\%]), followed by
strabismus (n=429 {[}10.2\%]) and proptosis (n=309 {[}7.4\%]). Patients
from high-income countries (HICs) were diagnosed at a median age of 14.1
months, with 656 of 666 (98.5\%) patients having intraocular
retinoblastoma and 2 (0.3\%) having metastasis. Patients from low-income
countries were diagnosed at a median age of 30.5 months, with 256 of 521
(49.1\%) having extraocular retinoblastoma and 94 of 498 (18.9\%) having
metastasis. Lower national income level was associated with older
presentation age, higher proportion of locally advanced disease and
distant metastasis, and smaller proportion of familial history of
retinoblastoma. Advanced disease at diagnosis was more common in LMICs
even after adjusting for age (odds ratio for low-income countries vs
upper-middle-income countries and HICs, 17.92 {[}95\% CI, 12.94-24.80],
and for lower-middle-income countries vs upper-middle-income countries
and HICs, 5.74 {[}95\% CI, 4.30-7.68]). Conclusions and RelevanceThis
study is estimated to have included more than half of all new
retinoblastoma cases worldwide in 2017. Children from LMICs, where the
main global retinoblastoma burden lies, presented at an older age with
more advanced disease and demonstrated a smaller proportion of familial
history of retinoblastoma, likely because many do not reach a
childbearing age. Given that retinoblastoma is curable, these data are
concerning and mandate intervention at national and international
levels. Further studies are needed to investigate factors, other than
age at presentation, that may be associated with advanced disease in
LMICs
Comparison of cannulated lag screws and lateral locking plate in the treatment of Schatzker type II tibial plateau fractures
No full textEffects of cutting tool forms on the surface integrity in turning of AISI 316L stainless steel [AISI 316L çeliğinin tornalanmasında kesici takım formlarının yüzey bütünlüğü üzerine etkisi]
No full textSessizliğin Kaldırılması ve Konuşmanın Parçalara Ayrılması İşleminin Türkçe Otomatik Konuşma Tanıma Üzerindeki Etkisi
No full text
Monitoring Crimean-Congo haemorrhagic fever virus RNA shedding in body secretions and serological status in hospitalised patients, Turkey, 2015
No full textMRI in CLN2 disease patients: Subtle features that support an early diagnosis
No full textNeuronal ceroid lipofuscinosis type 2 (CLN2) disease is a rare,
paediatric-onset, neurodegenerative disorder characterised in its early
stages by language delay, seizures and loss of motor function. It is
rapidly progressive and ultimately results in the premature death of
patients. We aim to highlight common magnetic resonance imaging (MRI)
features seen in early CLN2 disease and increase disease awareness among
clinicians in order to facilitate early diagnosis and treatment of
patients with disease-modifying enzyme replacement therapy.
We obtained MRI scans from 12 Turkish children with CLN2 disease, at
symptom onset or time of diagnosis, and at various times during disease
progression. Patient details including age at onset of symptoms, age at
diagnosis and clinical presentation were collected. MRIs were analysed
to identify common features present in patients with CLN2 disease.
The median diagnostic delay in this cohort was 2 years, highlighting the
need for increased disease awareness among clinicians. Key MRI features
suggestive of CLN2 disease that were identified included cerebellar
atrophy in 11 patients, linear hyperintensity of central white matter in
10 patients, cerebral atrophy in 8 patients and thinning of the corpus
callosum in 6 patients. Thalamic hypointensity was seen in 1 patient and
may also indicate CLN2 disease.
It is important to consider the presenting symptoms alongside clinical
test results in order to support early diagnosis of CLN2 disease.
Clinical suspicion of CLN2 disease accompanied by the detection of any
of the above-mentioned features on MRI should encourage healthcare
professionals to test for CLN2 disease. (c) 2020 The Authors. Published
by Elsevier Ltd on behalf of European Paediatric Neurology Society
Serum C-reactive protein to albumin ratio as a novel inflammation biomarker in psoriasis patients treated with adalimumab, ustekinumab, infliximab, and secukinumab: a retrospective study
No full textAim To assess C-reactive protein to albumin ratio (CAR) be-fore and
after treatment with biological agents in patients with psoriasis to
determine whether CAR can be used as an inflammation biomarker.
Methods Medical records of patients with psoriasis treat-ed with
biological agents at the Department of Dermatology, Gazi University
Hospital were retrospectively evaluated between June 2018 and August
2019. The patients were divided into four groups based on the type of
treatment (adalimumab, ustekinumab, infliximab, secukinumab). CAR was
evaluated before and three months after treatment.
Results The study enrolled 157 patients with psoriasis vulgaris (91
male) aged between 18 and 85. CAR significantly decreased in all
treatment groups (adalimumab group P<0.001; ustekinumab P=0.006;
infliximab P=0.007; secukinumab P<0.001). The most prominent decrease in
CAR was observed in patients treated with secukinumab (median CAR before
treatment 1.52 {[}1.01-3.04] and after treatment 0.84 {[}0.62-0.99]).
Conclusion CAR may be a good indicator of systemic inflammation in
psoriasis patients treated with biological agents
