A connection management protocol for promoting cooperation in Peer-to-Peer networks

Cataloged from PDF version of article.The existence of a high degree of free riding in Peer-to-Peer (P2P) networks is an important threat that should be addressed while designing P2P protocols. In this paper we propose a connection-based solution that will help to reduce the free riding effects on a P2P network and discourage free riding. Our solution includes a novel P2P connection type and an adaptive connection management protocol that dynamically establishes and adapts a P2P network topology considering the contributions of peers. The aim of the protocol is to bring contributing peers closer to each other on the adapted topology and to push the free riders away from the contributors. In this way contribution is promoted and free riding is discouraged. Unlike some other proposals against free riding, our solution does not require any permanent identification of peers or a security infrastructure for maintaining a global reputation system. It is shown through simulation experiments that there is a significant improvement in performance for contributing peers in a network that applies our protocol. © 2007 Elsevier B.V. All rights reserved

A decision support system proposal for interbasin water transfer in Turkey

Mevcut su kaynaklarının endüstriyel, tarımsal ve kentsel su ihtiyacını karşılayamaması, su kaynaklarının restorasyonu, kuraklık, mevcut su temin sisteminin performansının ve esnekliğinin artırılması, enerji üretimi vb. gerekçeler ile Türkiye dahil birçok ülkede su transfer projeleri hayata geçirilmiştir. Havza içerisinde diğer doğal kaynaklarla birlikte bir bütünü oluşturan su kaynaklarının yapay yollarla bir bölgeden bir başka bölgeye transfer edilmesi, dikkatli bir şekilde değerlendirilmesi ve analiz edilmesi gereken çevresel, sosyal ve ekonomik sorunları da beraberinde getirmektedir. Su kaynaklarının planlanması ve yönetiminde mevcut kurumsal yapı nedeniyle ciddi sıkıntılar yaşayan Türkiye’nin havzalar arası su transferi ile ilgili, karar vericilere yardımcı olabilecek, bilimsel verilerle desteklenmiş bir “karar destek sistemine” ivedilikle ihtiyacı vardır. Bu nedenle su ihtiyacının karşılanması için başka bir havzadan su transfer edilmesi seçeneğinin bilimsel verilerin ışığında irdelenebilmesi amacıyla bu çalışmada; güvenilir, basit ve Türkiye’nin mevcut kısıtlı veri birikimine uygun, konuyu sadece çevresel boyutu ile alan bir karar destek sistemi önerilmiştir. Önerilen karar destek sistemi, bir örnek olmak üzere Büyük Melen Su Transfer Projesi için uygulanmıştır. Anahtar Kelimeler: Havzalar arası su transferi, çevresel ve sosyoekonomik etkiler, karar destek sistemi.Achieving sustainable management of water resources is a conscious social decision that provides long-term durability of a watershed regarding ecological and economical means. The limited capacity of the world's water resources as an important natural capital (NC) cannot meet the growing demands of the socio-economic system (SES) without setting a strategy of sustainable management. One of the simplest solutions of the problem that is applied in many countries is water transfer from a rich water resource to another. Interbasin transfer of water can simply be described as the transfer of water artificially from one basin to another through a pipeline or a canal. Interbasin water transfers are a common component of many regional water systems. It has been in use for a long time all over the world. At present, a great number of various water transfer systems operate or are under construction for urban drinking water supply, irrigation, industry and environmental rehabilitation. Although it is clear enough that an underlying premise to this decision is the recognition of the interdependence between NC and SES that directly or indirectly influences the ecosystem, this important link is not taken into consideration in Turkey during decision making process with the goal of developing a long-term integrated plan for sustainable management of both watersheds. In this study, a reliable and simple decision support system was developed to help decision makers about interbasin water transfer. The first stage of the support system is the investigation of alternatives water resources. Reuse of urban waste water, desalination, rainwater harvesting and water demand management should be evaluated as a water resources and then transfer decision should be made. This subject is the main topic of water resources management that it was not evaluated within the context of this study. In the second stage the transfer decision is evaluated in details. After this stage it is possible to produce knowledge for decision makers about interbasin transfer is possible or not, and if it is, what would be the amount of water transferred, types of transfer (permanent transfer, contingent transfer). The decision support system was developed following three basic principles: First, the area of delivery must face a substantial deficit in meeting present or projected future water demands after consideration is given to alternative water supply sources and all reasonable measures for reducing water demand. Second, it will be provided that there will not be any substantially degradation of environmental quality in the donor basin. There will not be any destruction in habitat of living organisms that is under protected and economically valuable. Third, transfer will be possible, when the future development of the donor basin must not be substantially constrained by water scarcity. However consideration to transfer that constraints future development of donor basin may be appropriate if the receiving basin compensates the donor basin productivity losses. It is aimed that the support system should be appropriate to Turkey?s condition and must be reliable, simple and admitting of rapid assessment. Furthermore, the developed decision support system was implemented to Büyük Melen Water Transfer Project (Water transfer from Büyük Melen River to Istanbul) as an example. As a result of developed decision support system, to prevent degradation of ecosystem quality in the downstream of the diversion point of Büyük Melen River flow rate should be 18 m3/s at least. It is planned that the amount of the transferred water will be 8.50 m3/s at the first stage. For this reason the amount of transferred water must be 3.40 m3/s and 4.84 m3/s in July and October respectively, and this result indicates that water must not be transferred in August and September from the river. In the last stage of the projects the amount of transferred water should be as follows to prevent degradation of aquatic ecosystem: 34.74 m3/s in May, 13.40 m3/s in June, 3.40 m3/s in July, 4.84 m3/s in October transferred and no transfer in August and September. In this condition the average flow rate of transfer is 32 m3/s. It is planned that the amount of the transferred water will be 37.50 m3/s at the last stage. This planned flow rate is bigger than flow rate which is calculated with the developed support system. As a result Büyük Melen River ecosystem will be affected if the proposed action plan is not considered. Keywords: Interbasin water transfer, ecosystem quality, decision support system

Free riding in peer-to-peer networks

Free riding in peer-to-peer (P2P) networks poses a serious threat to their proper operation. Here, the authors present a variety of approaches developed to overcome this problem. They introduce several unique aspects of P2P networks and discuss free riding's effects on P2P services. They categorize proposed solutions and describe each category's important features and implementation issues together with some sample solutions. They also discuss open issues, including common attacks and security considerations. © 2009 IEEE

Real-life experience of patients with sarcomatoid renal cell carcinoma: a multicenter retrospective study

Sarcomatoid renal cell carcinoma (sRCC) is a rare variant of renal cell carcinoma (RCC) and is associated with a poor prognosis. We reviewed the outcomes of patients from oncology centers in Turkey. Our aim is to share our real-life experience and to contribute to the literature. The demographic and clinical features, treatment, and survival outcomes of 148 patients with sRCC were analyzed. The median age at the time of diagnosis was 58 years (range: 19-83 years). Most patients (62.8%) had clear-cell histology. Most patients were in the intermediate Memorial Sloan-Kettering Cancer Center (MSKCC) risk group (67.6%) and were stage 4 at the time of diagnosis (63.5%). The most common sites of metastasis were the lung (60.1%), lymph nodes (47.3%), and bone (35.8%). The patients received a median of two lines (range: 0-6) of treatment. The most common side effects were fatigue, hematological side effects, hypertension, and hypothyroidism. The median follow-up was 20.9 months (range: 1-162 months). The median overall survival (OS) was 30.8 months (95% confidence interval: 24.9-36.7 months). In multivariate analysis, high MSKCC scores, sarcomatoid differentiation rates >50%, having stage 4 disease, and having lung metastasis at the time of diagnosis were independent factors for poor prognosis affecting OS. No difference was observed between patients who received tyrosine kinase inhibitor (TKI) as the first or second-line treatments. Similarly, no difference between TKI and immunotherapy as the second-line treatment. In conclusion, sRCC is a rare variant of RCC with a poor prognosis and response to treatment. Larger-scale prospective studies are needed to define an optimal treatment approach for longer survival in this aggressive variant

DISSIMILAR VACUUM BRAZING OF ADDITIVE MANUFACTURED 17-4PH STAINLESS STEEL TO CONVENTIONAL 304 AND 17-4 STAINLESS STEEL BY BNI-2 BRAZING FILLER MATERIAL

Vacuum brazing process of 17-4PH stainless steel, which was manufactured using additive manufacturing, as well as conventional AISI304 and 17-4PH stainless steel alloys was investigated. The brazing process was conducted at 1050°C for 20 minutes under 10-6 Torr, using BNi-2 filler material. Various aspects of the vacuum brazed parts were analyzed, including their microstructure, wetting behavior and mechanical strength. To evaluate the wetting behavior, the contact angle and wetted area were measured using optical microscopy. The microstructures were examined using Scanning Electron Microscopy and Energy Dispersive Spectroscopy techniques. Additionally, tensile testing was performed on the joints to assess the influence of surface roughness and brazing of different materials on the strength of the brazed parts.Mechanical Engineerin

CA-125/CEA ratio as a prognostic factor in type II endometrial cancer: a single institute experience

Objective: Type II (non-endometrioid) endometrial cancer is less common with an incidence of 10%-20%. It has an aggressive clinical course with heterogeneous clinic pathological features. The aim of this study is to evaluate prognostic factors and survival outcomes in type II endometrial cancer. Patients and Methods: Patients aged over 18 years with diagnosis of Stage IA-IVB type II endometrial cancer were included to the study. Between 2013 and 2019, a total of 76 patients were evaluated retrospectively. Results: Median overall survival (OS) was 25 months while median disease-free survival (DFS) was 22 months. Median DFS was 25 months (95% CI: 14.71-35.28) in patients with negative lymph nodes while it was 10 months (95% CI: 6.88-13.11) in patients with positive lymph nodes (p=0.017). Median OS was 28 months (95% CI: 23.05-32.95) in patients with a ratio of CA-125/CEA<25 while it was 16 months (95% CI: 5.19-26.80) in those with a ratio of CA-125/CEA≥25 (p=0.02). Patients with an Eastern Cooperative Oncology Group performance score (ECOG PS) <2 at the time of diagnosis had a significantly longer OS than ECOG PS≥2 [median 29 months (95% CI: 22.99-35.94) vs. 15 months (95% CI: 0.33-29.66); p=0.024]. In multivariate Cox regression analysis CA-125/CEA (HR:1.70, 95% CI: 1.01-2.83, p=0.042) was independent risk factor for OS. Conclusions: CA-125/CEA ratio may have prognostic significance in type 2 endometrial cancer, but it needs to be supported by randomized clinical trials

COVID-19 infection, vaccine status, and avoidance behaviors in adults with attention deficit and hyperactivity disorder: A cross-sectional study

ObjectiveWe aim to examine infection risk and vaccine status of COVID-19 in attention deficit and hyperactivity disorder and evaluate the impact of demographic, clinical, and COVID-19-related factors on the infection status and behavioral avoidance of COVID-19. MethodsThis cross-sectional study assessed adults with attention deficit and hyperactivity disorder recruited from an outpatient psychiatry clinic. Patients and healthy controls completed a survey on sociodemographic data, COVID-19 infection status, and vaccine status. COVID-19 Disease Perception Scale, COVID-19 Avoidance Attitudes Scale, Attitudes toward COVID-19 Vaccine Scale, Adult Attention Deficit and Hyperactivity Disorder Self-report Screening Scale for DSM-5, Adult Attention Deficit and Hyperactivity Disorder Self-Report Scale Symptoms Checklist, Patient Health Questionnaire-9, and State-Trait Anxiety Inventory were applied. ResultsNinety patients and 40 healthy controls participated. Patients did not differ from controls in COVID-19 infection and vaccine status, and behavioral avoidance of COVID-19. No demographic and clinical factor significantly affected the COVID-19 infection status. Patients scored higher than controls in the perception of COVID-19 as contagious (p = 0.038), cognitive avoidance of COVID-19 (p = 0.008), and positive attitudes toward the COVID-19 vaccine (p = 0.024). After adjustment of possible factors, a positive perception of the COVID-19 vaccine and a perception of COVID-19 as dangerous were the two factors significantly affecting behavioral avoidance of COVID-19 [R-2 = 0. 17, F(2) = 13.189, p < 0.0001]. ConclusionInfection and vaccine status of COVID-19 in patients did not significantly differ from controls. No demographic and clinical factor significantly affected the COVID-19 infection status. Approximately four-fifths of the patients were fully vaccinated as recommended by national and global health organizations. This has increased the knowledge base showing that the COVID-19 vaccine is acceptable and receiving the vaccine is endorsed by ADHD patients. Attention deficit and hyperactivity disorder itself may provoke no kind of mental disturbance in sense of perception of the danger of this disease. Our findings have increased the knowledge base showing that the COVID-19 vaccine is acceptable and the actual practice of receiving the vaccine is endorsed in this population. Our message for practice would be to take into account not only the core symptoms and the comorbidities of the disorder but also the perception of the disease while exploring its link with COVID-19

Thirty Years After Michael E. Porter: What Do We Know About Business Exit?

Although a business exit is an important corporate change initiative, the buyer’s side seems to be more appealing to management researchers than the seller’s because acquisitions imply growth, i.e., success. Yet from an optimistic viewpoint, business exit can effectively create value for the selling company. In this paper we attempt to bring the relevance of the seller’s side back into our consciousness by asking: What do we know about business exit? We start our exploration with Porter (1976), focusing on literature that investigates the antecedents of, barriers to, and outcomes of business exit. We also include studies from related fields such as finance and economics.1 Through this research we determine three clusters of findings: factors promoting business exit, exit barriers, and exit outcomes. Overall, it is the intention of this paper to highlight the importance of business exit for research and practice. Knowing what we know about business exits and their high financial value we should bear in mind that exit need not mean failure but a new beginning for a corporation