Planlı Bakım Sistemleri İçin Bazı Stokastik Yenileme Modelleri

ABSTRACT Since the failure of the components which establish a system is random, the life of these components is a random variable. Since the maintenance has a direct connection with failure, it also has random characteristics. For that reason, stochastic replacement models have an important place in maintenance planning. The aim of this study is to introduce stochastic replacement models which are age replacement, block replacement and replacement with minimal repair at failure.Bir sistem ve sistemi oluşturan elemanların arızalanmaları rassaldır. Dolayısıyla sistemi meydana getiren elemanların ömürleri rassal değişkenlerdir. Arızalarla doğrudan ilgisi nedeniyle bakım da rassal nitelik taşır. Bu nedenle bakım planlamasında stokastik yenileme modellerinin önemli bir yeri vardır. Bu çalışmada stokastik yenileme modellerinden yaş yenileme (age raplacement), blok yenileme (block replacement) ve küçük tamirli yenileme (replacement with minimal repair at failure) modellerinin tanıtılması amaçlanmıştır. Arıza verilerinin artan arıza oranına sahip sürekli tekdüze ve Weibull dağılımına uygun olması durumunda söz konusu modeller için çözüm sonuçları verilmiştir

Generalized formulae for the periodic fixed and geometric-gradient series payment models in a skip payment loan with rhythmic skips

Nowadays, the periodic level payment model is the most widely used loan payment model by the banks. In addition, the periodic geometric and linear gradient payment models are available in the financial mathematics books. The arbitrary skip periodic level (or equal) loan payment model was firstly developed by Formato (1992). Formato’s model was extended to the geometric gradient loan payment model by Moon (1994) and the linear gradient model by Eroglu and Karaoz (2002). This loan payment models that have periodic level and geometric gradient series payment with rhythmic skips instead of arbitrary skips have beendiscussed. General formulae have been derived for these models. Numerical examples are solved to show the practical application of the developed payment models on home financing

Different epidemiology of bloodstream infections in COVID-19 compared to non-COVID-19 critically ill patients: A descriptive analysis of the Eurobact II study

Background: The study aimed to describe the epidemiology and outcomes of hospital-acquired bloodstream infections (HABSIs) between COVID-19 and non-COVID-19 critically ill patients. Methods: We used data from the Eurobact II study, a prospective observational multicontinental cohort study on HABSI treated in ICU. For the current analysis, we selected centers that included both COVID-19 and non-COVID-19 critically ill patients. We performed descriptive statistics between COVID-19 and non-COVID-19 in terms of patients’ characteristics, source of infection and microorganism distribution. We studied the association between COVID-19 status and mortality using multivariable fragility Cox models. Results: A total of 53 centers from 19 countries over the 5 continents were eligible. Overall, 829 patients (median age 65 years [IQR 55; 74]; male, n = 538 [64.9%]) were treated for a HABSI. Included patients comprised 252 (30.4%) COVID-19 and 577 (69.6%) non-COVID-19 patients. The time interval between hospital admission and HABSI was similar between both groups. Respiratory sources (40.1 vs. 26.0%, p < 0.0001) and primary HABSI (25.4% vs. 17.2%, p = 0.006) were more frequent in COVID-19 patients. COVID-19 patients had more often enterococcal (20.5% vs. 9%) and Acinetobacter spp. (18.8% vs. 13.6%) HABSIs. Bacteremic COVID-19 patients had an increased mortality hazard ratio (HR) versus non-COVID-19 patients (HR 1.91, 95% CI 1.49–2.45). Conclusions: We showed that the epidemiology of HABSI differed between COVID-19 and non-COVID-19 patients. Enterococcal HABSI predominated in COVID-19 patients. COVID-19 patients with HABSI had elevated risk of mortality. Trial registration ClinicalTrials.org number NCT03937245. Registered 3 May 2019

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Tamamlayıcı ve ikame malların fiyatı etkisi altında talebin malın satış fiyatı ve zamana bağlı olduğu durum için bir ekonomik sipariş miktarı modeli

Demand for a product is affected by its own selling price. In many situations it has also been affected by its Complement’s as well as substitute’s selling prices. This effect can be observed in many retailed items all over the markets. In this paper, we developed finite replenishment inventory model while considering that demand is sensitive to changes in time, its selling price and prices of complementary and substitute good’s. Numerical example and sensitivity analysis have been performed for demand equation parameters.Bir malın talebi, malın kendi satış fiyatından etkilenmektedir. Çoğu durumda bu talep bu malın tamamlayıcısı ve ikamesi olan malların fiyatından da etkilenmektedir. Bu etki marketlerdeki parekende ürünlerin çoğunda gözlenebilmektedir. Bu çalışmada talebin; zamana, malın satış fiyatına ve tamamlayıcı ve ikame malların fiyatına bağlı olduğu durum için bir ekonomik sipariş miktarı modeli geliştirilmiştir. Talep denklemi parametreleri için sayısal örnekler verilmiş ve duyarlılık analizleri yapılmıştır

Türkiye' de üretilen kalsitin kuşe kağıt yapımında kullanılması

Kalsit ($CaCO_3$), kağıt endüstrisinde yaygın olarak kullanılan bir kuşeleme pigmentidir. Ayrıca, son yıllarda kalsit, dolgu maddesi olarak uzun ömürlü alkali kağıt yapımında da büyük bir önem kazanmıştır. Türkiye'de zengin kalsit yatakları olmasına rağmen kağıt sanayiinde kullanılan kalsit ithal edilmektedir. Bu çalışmada, iki tip yerli toz (GCC) kalsit kullanılmıştır. Bu örneklerin $CaCO_3$ oranı % 97.3 ve % 97.6 (min. % 95)'dır. $MgC0_3$ ve $Fe_2O_3$ oranları ise, istenen sınırlar içersindedir. Örneğin parlaklık değerleri % 95.5 ve % 94.5 sarılık değerleri ise % 1.1 ve % 1.5 elrepho olarak belirlenmiştir. 2 mikronun altındaki ve 10 mikronun üzerindeki fraksiyonlar sırasıyla % 95, % 89 ve %1 ve % 2 olarak bulunmuştur. Kuşe pilot tesisinde, kuşe boyası konsantrasyonu % 40- % 65 arasında alınmıştır. Hazırlanan kuşe boyasının kalsit ve kaolen oranlan 30/70, 40/60, 50/50, 60/40, 70/30 ve 100/0'dır. Kullanılan latex yapıştırıcı değerleri ise % 11, % 12 ve % 13'dür. Kuşelenen kağıtlar perdahlama öncesi ve sonrası fiziksel ve optik testlere tabi tutulmuşlardır. Sonuç olarak her iki $CaC0_3$ örneklerinin fiziksel ve optik özellikleri bakımından kuşeleme için uygun olduğu anlaşılmıştır. Yerli kalsit rezervlerinin kullanılması ülkemiz için döviz tasarrufu sağlayacaktır.Calcium carbonate is one of the coating pigments widely used in paper industry. Especially, in recent years calcium carbonate filler has gained high importance in alkaline pulping. In Turkey industry actually imports calcium carbonate; whereas, there are rich calcite reservoirs in the country. In this study two different types of domestic ground (GCC) calcite samples were used. Physical and chemical properties of calcite samples were tested firstly. $CaC0_3$percentages of both samples were 97.3 % and 97.6 % (min. 95 % $CaC0_3$). $MgCO_3$ and $Fe_20_3$ percentages were within the desired limits. Brightness values were 95.5 % and 94.5 % and yellowness 1.1 % and 1.5 % elrepho. These values also were within the requested limits. Under 2 microns particle size and over 10 microns particle size fractions were 95 % and 89 % (min. 80) and 1 % and 2 % (max. 2) respectively. Dry matter rates were between 40 %-65 %, for the pilot plant-coating machine. During the preparation of coating color calcium carbonate has been used together with kaolin. The ratios of calcium carbonate to kaolin were 30/70. 40/60, 50/50, 60/40, 70/30, 100/0. In coating color preparation latex was used as a binder because of its wide applications. Latex percentages were 11, 12, and 13 %. Coated papers were glossed and physically tested. As a result, both calcium carbonate samples were found suitable for using in coating color preparation. By the utilization of domestic calcium carbonate in coated paper production, there will be foreign currencies saving

Utilization of calcite produced in Turkey for paper coating

Calcium carbonate is one of the coating pigments widely used in paper industry. Especially, in recent years calcium carbonate filler has gained high importance in alkaline pulping. In Turkey industry actually imports calcium carbonate; whereas, there are rich calcite reservoirs in the country. In this study two different types of domestic ground (GCC) calcite samples were used. Physical and chemical properties of calcite samples were tested firstly. CaCO3 percentages of both samples were 97.3 % and 97.6 % (min. 95 % CaCO3). MgCO3 and Fe2O3 percentages were within the desired limits. Brightness values were 95.5 % and 94.5 % and yellowness 1.1 % and 1.5 % elrepho. These values also were within the requested limits. Under 2 microns particle size and over 10 microns particle size fractions were 95 % and 89 % (min. 80) and 1 % and 2 % (max. 2) respectively. Dry matter rates were between 40 %-65 %, for the pilot plant-coating machine. During the preparation of coating color calcium carbonate has been used together with kaolin. The ratios of calcium carbonate to kaolin were 30/70, 40/60, 50/50, 60/40, 70/30, 100/0. In coating color preparation latex was used as a binder because of its wide applications. Latex percentages were 11, 12, and 13 %. Coated papers were glossed and physically tested. As a result, both calcium carbonate samples were found suitable for using in coating color preparation. By the utilization of domestic calcium carbonate in coated paper production, there will be foreign currencies saving

Statistically pτ-convergence in lattice-normed locally solid Riesz spaces

In this paper, we introduce the concept of the statistical convergence with respect to solid topology and Riesz valued norms on lattice-normed locally solid Riesz spaces. Moreover, we give the notions of statistically pτ-bounded and statistically pτ-dense sequence, and we introduce statistically pτ-continuous and statistically pτ-bounded operators. We also investigate some properties and examples of these concepts

TAMAMLAYICI VE İKAME MALLARIN FİYATI ETKİSİ ALTINDA TALEBİN MALIN SATIŞ FİYATI VE ZAMANA BAĞLI OLDUĞU DURUM İÇİN BİR EKONOMİK SİPARİŞ MİKTARI MODELİ

Bir malın talebi, malın kendi satış fiyatından etkilenmektedir. Çoğu durumda bu talep bu malın tamamlayıcısı ve ikamesi olan malların fiyatından da etkilenmektedir. Bu etki marketlerdeki parekende ürünlerin çoğunda gözlenebilmektedir. Bu çalışmada talebin; zamana, malın satış fiyatına ve tamamlayıcı ve ikame malların fiyatına bağlı olduğu durum için bir ekonomik sipariş miktarı modeli geliştirilmiştir. Talep denklemi parametreleri için sayısal örnekler verilmiş ve duyarlılık analizleri yapılmıştır

Sürdürülebilir Ekonomik Sipariş Miktarı Modeline Eleştirel Bir Bakış

Harris tarafından 1913 yılında ilk önerildiği günden bugüne Ekonomik Sipariş Miktarı modeli temel ve etkin bir model olarak literatürde, endüstride ve ders kaynaklarında hak ettiği yeri edinmiştir. O günden bugüne çok farklı Ekonomik Sipariş Miktarı modelleri önerilmiştir. Dünya ekonomisi, endüstri ve bilimsel dünyanın son dönemdeki eğilimlerine bağlı olarak sürdürülebilir Ekonomik Sipariş Miktarı ve Ekonomik Üretim Miktarı modelleri önemli bir konu haline gelmiştir. Bu çalışmada sürdürülebilir bir Ekonomik Sipariş Miktarı modeli önerilmiş ve sipariş verme ve stokta tutma maliyeti, emisyon maliyeti, kusurlu ürünler, taşıma ve atık yok etme bileşenleri üzerinden bir model tasarlanmıştır. Modelin bileşenlerinin optimal çözüm üzerindeki etkileri analiz edilmiştir. Modelin çözümleri sembolik hesaplama ile elde edilmiştir