Facets of the p-cycle polytope

The purpose of this study is to provide a polyhedral analysis of the p-cycle polytope, which is the convex hull of the incidence vectors of all the p-cycles (simple directed cycles consisting of p arcs) of the complete directed graph Kn. We first determine the dimension of the p-cycle, polytope, characterize the bases of its equality set, and prove two lifting results. We then describe several classes of valid inequalities for the case 2<p<n, together with necessary and sufficient conditions for these inequalities to induce facets of the p-cycle polytope. We also briefly discuss the complexity of the associated separation problems. Finally, we investigate the relationship between the p-cycle polytope and related polytopes, including the p-circuit polytope. Since the undirected versions of symmetric inequalities which induce facets of the p-cycle polytope are facet-inducing for the p-circuit polytope, we obtain new classes of facet-inducing inequalities for the p-circuit polytope

An ant colony algorithm for the sequential testing problem under precedence constraints.

We consider the problem of minimum cost sequential testing of a series (parallel) system under precedence constraints that can be modeled as a nonlinear integer program. We develop and implement an ant colony algorithm for the problem. We demonstrate the performance of this algorithm for special type of instances for which the optimal solutions can be found in polynomial time. In addition, we compare the performance of the algorithm with a special branch and bound algorithm for general instances. The ant colony algorithm is shown to be particularly effective for larger instances of the problem

Lessons from Mission-Critical Spreadsheets

We present eighteen examples of mission-critical spreadsheets used by diverse people and organizations for application software development, financial risk management, executive information systems, sales and marketing business processes, business operations, and complex analytics. We argue the spreadsheet is a Rapid Development Language, an Integrated Development Environment, and a Fourth Generation Language, and has unusual challenges regarding source code protection. We note that intentional spreadsheet applications are largely absent from the error literature. We explain why people might prefer a spreadsheet to an application developed by the IT department, and show how some spreadsheet programmers choose to avoid--or do not have--an IT department. We find that 1) Spreadsheets are widely used for mission-critical functions; 2) Spreadsheets are an effective application development platform; 3) There is diversity of development skill in creators of mission-critical spreadsheets; 4) Sophisticated programmers sometimes choose spreadsheets over other languages; 5) Spreadsheets are amenable to formal development practices, but such practices seem rare; 6) Spreadsheets play a central role in the evolution of business processes and work systems; and 7) Spreadsheets are a source of accidental legacy systems . We provide the Skill-User Programming Paradigm to help interpret and explain our observations. We conclude that spreadsheets are vitally important to business, and merit sustained research to discover techniques to enhance quality, productivity, and maintainability

Evaluation of the effectiveness of intranasal steroid injection on patients with inferior nasal turbinate hyperthropy via computerized tomography.

The aim of the study is to evaluate the effectiveness of intranasal steroid injection method in the cases where chronic nasal obstruction depends on inferior turbinate hyperthropy using computerized tomography (CT ).Material and Method: Intranasal steroid injection performed due to inferior turbinate hyperthropy, 59 patients applying to The OtoRhinolaryngology Department of Meram Medical School of Selcuk University between July and December 2009 were enrolled into the study. All the patients were adults, and 28 ( 47.5% ) were women and 31 ( 52.5% ) were men. Totally 40 mg/ml metilprednisolon asetate was injected slowly on the anterior side of inferior turbinate with using dental syringe onto only one point. Objective evaluation of the inferior turbinate was carried out by comparing coronal plan paranasal sinus CT scores performed preoperatively and within the first and third month postoperatively. VAS evaluation of nasal obstruction was implemented by all patients.Results:Age rates of the patients were ranging from 18 to 75 (mean age rate 33±13.299). The hypertrophic inferior turbinates were determined to be smaller on coronal plan CT performed during the first and third month after the operation (p=0.00). But the measures of first month after injection were beter than the measures of the third month after injection In the postoperative first month, a significant decrease was witnessed in the complaints of the patients related to nasal obstructions (p=0.00). Two (3.3% ) patients announced to obtain no benefits from the intervention. All the inferior turbinate measurements were managed by using coronal plans of paranasal CT.Conclusion:Intranasal steroid injection method of inferior turbinate is an effective, minimally invasive one making the patient satisfied, to a large extent. The pre- and postoperative evaluation of the turbinate via CT is an objective and preferable method.Bu çalışmanın amacı kronik nazal obstrüksiyonun submuköz alt konka hipertrofisine bağlı olduğu belirlenen olgularda intranazal steroid enjeksiyonu yönteminin etkinliğinin bilgisayarlı tomografi ile değerlendirmektir.Gereç ve yöntem: Bu çalışmaya Temmuz 2009-Aralık 2009 tarihleri arasında Selçuk Üniversitesi Meram Tıp Fakültesi Kulak Burun Boğaz Hastalıkları Anabilim Dalı kliniğinde alt konka hipertrofisi nedeni ile intranazal streoid enjeksiyonu uygulanan 59 hasta alınmıştır. Çalışmaya katılan hastaların hepsi erişkin yaş grubunda olup 28(%47.5)'i kadın 31(%52.5)'i erkekti. Hastaların yaşları 18 ile 75 (ort. 33.00 ±13.299) arasında değişmekteydi.Tek noktaya 40 mg/1 ml metilprednizolon asetat alt konkanın anterior kısmına submukozal bül oluşturulacak şekilde dental enjektör yardımıyla yavaş bir şekilde tatbik edilmiştir. Konkaların objektif değerlendirilmesi; preoperatif dönem ve postoperatif 1.ayda ve 3. ayda çekilen koronal plan paranazal sinüs bilgisayarlı tomografileri (BT) karşılaştırılarak yapılmıştır. Ayrıca başka bir hekim konka boyutlarını VAS ile değerlendirmiştir. Hastalar tarafından, nazal obstrüksiyonun VAS değerlendirmesi yapılmıştır.Bulgular: Hastaların yaşları 18 ile 75 yaşları arasında ( ortalama yaş 33.00±13.299 ) değişmekte idi. Koronal plan bilgisayarlı tomografi ile konkaların postoperatif 1. ayda küçüldüğü saptanmıştır (p=0,00). Başka bir hekim tarafından kaydedilen VAS'da, konkalarda küçülme saptanmıştır (p=0.00). Postoperatif 1.ayda hastaların nazal tıkanıklık şikayetlerinde anlamlı derecede azalma saptanmıştır (p=0.00). Postoperatif 3. ayda da preoperatif değerlere göre konkalarda küçülme saptanmış. Fakat preop 1. aydaki konkalardaki küçülme değerleri postop 3. aydaki değerlerden daha iyi olarak saptanmıştır. İki (%3.3) hasta müdahaleden hiç fayda görmediğini belirtmiştir. Bunlarla alt konkalar koronal plan BT'de yapılan ölçümlerle değerlendirilmiştir.Sonuç: İntranazal steroid enjeksiyon ile alt konka küçültülmesi yöntemi etkin, kolay uygulanabilen, minimal invaziv, maliyeti düşük, postoperatif hasta memnuniyeti yüksek bir yöntemdir. BT ile alt konkaların preoperatif ve postoperatif değerlendirilmesi objektif ve tercih edilebilir bir yöntemdir

Capacity allocation and pricing policies for cloud computing service providers

Özgür Özlük (MEF Author)##nofultext##The cloud computing is regarded as a paradigm shift in today’s IT world. As cloud computing resources behave like perishable products, revenue management techniques can be applied to increase cloud service provider's total revenue. In this paper, we propose various methods for pricing and capacity allocation. We consider three types of instances offered by the service provider; subscription, on-demand and spot instances. We introduce three allocation and pricing policies and propose different models. We simulate these models on a randomly generated dataset and evaluate the models for different capacities. The results we obtain indicate the sensitivity of revenue to varying policies and demonstrate the potential profit increase for cloud service providers. © 2018, Curran Associates Inc. All rights reserved.Scopus - Affiliation ID: 6010507