Mechanics, dynamics and optimization of special end mills

Machining, especially milling, is still one of the most commonly employed manufacturing operations in industry because of its flexibility and potential to produce high quality parts. Milling performance can be increased significantly using special milling tools, such as variable pitch and helix or serrated end mills. The literature on these special tools is mostly limited to prediction of milling forces and chatter stability. Although there are very few studies on optimal design of variable pitch and helix tools, no work has been reported on selection or optimization of serrated end mills. In this thesis, mechanics and dynamics of these tools are investigated in detail. Furthermore, methods and their results on optimization of these tools for minimized milling forces and increased stability are also presented. Optimal variable pitch tools are designed for a given milling system and a desired spindle speed, using different pitch patterns. Their performances are compared and some important and practical results are found. The effects of serration waveform geometry on cutting forces and chatter stability are also investigated in detail. According to the optimization results, guidelines for selection and design of these tools are proposed

THE STATISTICAL ASSESSMENT OF SUBGRADE-SOIL PARAMETERS OF THE COASTAL WAY BETWEEN GUMRUK AND UCKUYULAR-IZMIR AND DETERMINATION OF SOIL PROFILE AT THE SEA-BED

Doğal zeminlerde, zemin parametreleri gerek yer, gerekse de zamana bağlı olarak değişmekte ve rastgele bir özellik göstermektedir. Bu parametrelerin nümerik değerleri genellikle sınırlı bir zemin araştırmasından ve zeminden alınan az sayıdaki örnekten elde edilen laboratuvar deney sonuçlarından tahmin edilmektedir. Bu çalışma, İzmir Körfezi'nin güneyinde Gümrük-Üçkuyular arası sahil yolu sondaj işlerine ait zemin deneylerinin laboratuvar ve arazi SPT deney sonuçlarını kapsamaktadır. Zeminlerin indeks dayanım ve sıkışma parametrelerinin istatistiksel bir değerlendirilmesini de içeren bu çalışma, bölgenin jeoteknik koşulları hakkında genel bir fikir de vermektedir. Bu kapsamda, istatistiksel analiz metotları kullanılarak incelenen zemin jeoteknik parametrelerinin frekans histogramları çizilmiş ve ayrıca, deney sonuçlarına göre bulunan istatistiksel parametreler elde edilmiştir. Arazideki zeminlerin kohezyonlu veya kohezyonsuz oluşlarına göre penetrasyon sayıları derinlik ve su düzeltmeleri uygulanıp mevcut verilerle SPT direnç profili elde edilmiştir. Bu direnç profili deniz tabanında mevcut andezit ana kayasının üzerine uyumsuz olarak gelen ve çevre kayaçlardan türeme genç kuvaterner çökellerine aittir. Deniz sondajlarından elde edilen veriler yardımıyla İzmir Körfezi'nin güney kıyısına ait jeolojik profil elde edilmiş ve mevcut zeminlerin jeoteknik özellikleri tartışılmıştır. In nature, the soil parameters differ according to the place and time, and show a random feature. The numerical values of these parameters are generally examined in a limited soil investigation program and laboratory test results are obtained from a limited number of soil samples. This study includes both the field and laboratory tests results of the soils obtained from the boreholes drilled in the sea shore between Gümrük and Üçkuyular Districts in the south of the Izmir Bay in Western Turkey. A statistical assessment of the index and strength properties of the soils was made to establish the geotechnical properties of this area. The frequency histograms of the related soil parameters were prepared and the statistical parameters were analyzed taking into consideration whether the soil is cohesive or cohesionless. The SPT-Resistance Profile was obtained by applying the water and depth corrections to the field data. This strength profile belongs to that the Quaternary aged sediments, which overlay on the andesitic main rock at the base of the sea, derived from the host rocks. Geological cross-section of the south coast of the Izmir Bay was prepared using the borehole data taken from the boreholes drilled in the sea and geotechnical properties of the soil-groups at the sea-bed have been discussed in this paper

Evaluation of both expression and serum protein levels of caspase-8 and mitogen-activated protein kinase 1 genes in patients with different severities of COVID-19 infection

Aim: The current study aimed to evaluate the effects of caspase-8 (CASP8) and mitogen-activated protein kinase 1 (MAPK1) gene expression levels and their products on preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Methods: A total of 40 patients (men, 15 [37.5%]; women, 25 [62.5%]) with COVID-19 infection were included in the current study. The patients were divided into four main groups based on disease severity: mild (n = 7), moderate (n = 10), severe (n = 14), and critical (n = 9). Individuals aged < 18 years and pregnant women were excluded. Patients were classified according to the World Health Organization (WHO) classification system (WHO/2019-nCoV/clinical/2021.1). Results: Considering all groups, statistically significant differences were detected among all groups for both CASP82−ΔΔCt (p = 0.006) and MAPK1 2−ΔΔCt values (p = 0.015). Moreover, statistically significant differences were detected between mild and moderate (p = 0.013), moderate and critical (p = 0.018), and severe and critical (p = 0.023) groups for lymphocytes. Conclusion: The CASP8/MAPK1 expression levels and/or its products are essential in preventing injury caused by COVID-19 infection. They play crucial roles in maintaining cellular homeostasis and viability. Furthermore, CASP8/MAPK1 levels can provide information about disease severity

Prognostic impact of BCL2, BCL6 and MYC status in de novo diffuse large B-cell lymphoma: a regional study of 43 patients

Background: Diffuse large B-cell lymphoma (DLBCL) is an aggressive non-Hodgkin lymphoma with marked biologic heterogeneity. We aimed to evaluate the status of MYC, BCL2, BCL6 in patients with DLBCL.Methods: Herein, we have investigated the prognostic relevance of MYC, BCL2 and BCL6 from 43 de novo DLBCL patients.Results: In this study, protein overexpression of BCL2 and BCL6 was encountered in 46.5% (n=20) and 27.9% (n=12) of the tumors, respectively.  Rearrangements in MYC, BCL6, and BCL2 were detected in 9.3% (n=4), 25.6% (n=11), and 4.7% (n=2) of the cases, respectively. Any statistically significant difference could not be found between Bcl-2, Bcl-6 expression, C-MYC rearrangement and the survival.Conclusions: We concluded that C-MYC and BCL2 may contribute to aggressive transformation, so more mechanism-based therapy should be explored. A larger study is warranted to better understand the immunophenotypic and molecular features of DLBCL and their respective impact on patient survival

Optimization of serrated end mills for reduced cutting energy and higher stability

Although serrated end mills are commonly used in machining industry, the literature on these tools is limited to predictive methods while no work has been reported on selection, design or optimization of serration forms. In this paper, mechanics and dynamics of these tools are modeled and experimentally verified. Linear edge-force model is adopted for force modeling whereas first order semi-discretization method including multiple delays with time-averaged coefficient matrices is used for stability analysis. Frequently used serration waveforms, i.e. sinusoidal, circular and trapezoidal are modeled parametrically and optimized for reduced milling forces using the Brute Force Search and the Differential Evolution Method. The superior performance of the optimized serrated end mills is demonstrated in terms of reduced milling forces and increased stability

Investigating effects of serration geometry on milling forces and chatter stability for their optimal selection

Serrated end mills are widely used in the milling processes due to several advantages they offer. Previous studies on serrated tools are limited to methods which predict mechanics and dynamics of milling process using these tools with a specific serration waveform and no comparative work has been reported for different serration geometries in selection, design or optimization of these tools. In this paper, different types of end mills with frequently used serration shapes, i.e. circular, sinusoidal and trapezoidal, are modeled parametrically. The mechanics of milling processes by using serrated end mills are modeled and experimentally verified. The effects of different waveforms on the mechanics of process are investigated where effects of phase shift direction and local cutting angles on milling forces are verified experimentally. Moreover, serration wave shapes are optimized using a Genetic algorithm for reduced milling forces where up to 30% reduction in cutting forces is achieved and the effects of cutting conditions on optimum serration wave shapes are discussed. Finally, the stability performance of the designed optimum serrated tools is compared with the standard ones, and results show that the chatter stability performance of the optimized tools is enhanced significantly

Purine catabolic enzymes and nitric oxide in patients with recurrent aphthous ulceration

Objectives Recurrent aphthous ulceration (RAU) is one of the most common oral mucosal disorders found in humans. Although the exact etiology of RAU is unkown, local and systemic conditions, and genetic, immunologic, and infectious factors all have been identified as potential etiopathogenic agents. The aim of our study was to compare serum xanthine oxidase (XO) and adenosine deaminase (AD) activities, and malondialdehyde (MDA), nitric oxide (NO) and uric acid (UA) levels in a group of patients affected by RAU and in a group of healthy controls