Experimental Study on the Entropy Change Failure Precursors of Marble under Different Stress Paths

Erdi Abi,Hechuan Yuan,Yu Cong,Zaiquan Wang,Mingjing Jiang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1

In this paper, the indoor loading and unloading tests and acoustic emission (AE) monitoring tests of marble under different stress paths are carried out. Based on the AE events in the process of rock failure, this paper introduces the concept of information entropy of Shannon, and defines a new cumulative state information entropy which can characterize the degree of disorder and accumulation of rock microcracks. This paper also offers a comparative analysis on the evolution law of rock entropy under different paths and different loading and unloading conditions. The results show that the newly defined cumulative state information entropy can well reflect the order change of the loading and unloading process system, and there are significant differences in entropy evolution under different stress paths, but the entropy generally evolves with the development of the system from “quasi-equilibrium” to “far away from equilibrium”. The higher the unloading level is, the greater the confining pressure is, the stronger the unloading disturbance is, and the entropy value drops sharply at the starting point of unloading. The faster the unloading rate is, the later the rock fracture instability is, and the later the entropy drop point of the system appears. The change rate of entropy value |ΔH|= 0.1 can be used as the precursory signal threshold of rock confining pressure unloading disturbance damage and peak rupture instability.

Experimental and numerical research on ballistic performance of carbon steels and cold worked tool steels with and without Titanium Nitride (TiN) coating

Erdi Ergül,Emre Doruk,Murat Pakdil 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.2

It is extremely important to be aware of the ballistic performances of engineering materials in order to be able to choose the lightest armor providing full ballistic protection in civil and military applications. Therefore, ballistic tests are an important part of armor design process. In this study, ballistic performance of plates made of carbon steel and cold worked tool steel against 7.62 mm AP (armor-piercing) bullets was examined experimentally and numerically in accordance with NIJ standards. Samples in different sizes were prepared to demonstrate the effect of target thickness on ballistic performance. Some of these samples were coated with titanium nitride using physical vapor deposition (PVD) method. After examining all successful and unsuccessful samples at macro and micro levels, factors affecting ballistic performance were determined. Explicit non-linear analyses were made using Ls-Dyna software in order to confirm physical ballistic test results. It was observed that the ballistic features of steel plates used in simulations comply with actual physical test results.

Analysis of Technical Specification-based Disputes in Construction Industry

Ercan Erdis,Sitki Alper Ozdemir 대한토목학회 2013 KSCE JOURNAL OF CIVIL ENGINEERING Vol.17 No.7

This article covers the role of the standard and dynamic technical specification system for building structures in avoiding disputes between the employer and contractor, which is a ever-lasting problem in Turkey. For this purpose, the study was started with examining approximately 100 specification files and 32 court records on these issues. Afterwards, a survey was conducted among 58construction firms associated with the “Turkish Contractors Union” to identify the causes of technical specification related disputes and developing suggestions for possible resolutions. The survey results showed that these disputes generally arise from project characteristics and are mostly human oriented. It was concluded that establishing an institute consisting of experts in technical specifications, creating a standard and dynamic specification system, having quality guidelines, making judicial arrangements to shorten the judicial process, and information dissemination on related subjects through academic programs and judicial documents are important.

Articular Cartilage Regeneration Utilizing Decellularized Human Placental Scaffold, Mesenchymal Stem Cells and Platelet Rich Plasma

Özdemir Erdi,Emet Abdülsamet,Hashemihesar Ramin,Yürüker Ali Celalettin Sinan,Kılıç Emine,Uçkan Çetinkaya Duygu,Turhan Egemen 한국조직공학과 재생의학회 2020 조직공학과 재생의학 Vol.17 No.6

Background: Articular cartilage repair has been a challenge in orthopedic practice due to the limited self-regenerative capability. Optimal treatment method for cartilage defects has not been defined. We investigated the effect of decellularized human placental (DHP) scaffold, mesenchymal stem cells (MSC) and platelet-rich plasma (PRP) on hyaline cartilage regeneration in a rat model. Methods: An osteochondral defect was created in trochlea region of the femur in all groups, bilaterally. No additional procedure was performed in control group (n = 14). Only the DHP scaffold was applied to the P group (n = 14). The DHP scaffold and 1 × 106 MSCs were applied to the PS group (n = 14). The DHP scaffold and PRP were applied to the PP group (n = 14). The DHP scaffold, 1 × 106 MSCs and PRP were applied to the PSP group (n = 14). Outcome measures at 12 weeks included Pineda histology score and qualitative histology. Results: The mean Pineda scores of P, PS, PP, and PSP groups were significantly better than the control group (p = 0.031, p = 0.002, p < 0.001, p < 0001, respectively). There was no statistically difference in mean Pineda scores of P, PS, PP, and PSP groups (p > 0.05). Conclusion: In conclusion, the DHP scaffold appears to be a promising scaffold on hyaline cartilage regeneration. The augmentation of DHP scaffold with MSCs and PRP combinations did not enhance its efficacy on articular cartilage regeneration.

Germ-line MTHFR C677T, FV H1299R and PAI-1 5G/4G Variations in Breast Carcinoma

Ozen, Filiz,Erdis, Eda,Sik, Ebru,Silan, Fatma,Uludag, Ahmet,Ozdemir, Ozturk Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.5

Background: Various oncogenes related to cancer have been extensively studied and several polymorphisms have been found to be associated with breast cancer. The current report outlines analysis of germ-line polymorphisms for C677T, A1298C (MTHFR), Leiden, R2 (FV) and 5G/4G (PAI-1) in Turkish breast cancer patients. We studied 51 cases diagnosed with invasive ductal and operable with lymph node-positive breast cancer and 106 women as a control group. Materials and Methods: Peripheric blood-DNA samples were used for genotyping by StripAssay technique which is based on the reverse-hybridization principle and real-time PCR methods and results were compared statistically. Results: The frequency of the MTHFR gene 677T and 1298A alleles were significantly higher in cancer patients than in the healthy subjects. The T allele frequency in codon 677 was 2.3-fold and C allele frequency was 3.1-fold increased in BC when compared to the control group for the MTHFR gene. Both differences were statistically significant (OR: 2.295, CI: 1.283-4.106), p<0.006 and (OR: 3.131, CI:1.826-5.369), p<0.0001 respectively. The R2 allele frequency of FV gene was 5.1-fold increased in the current BC when compared to the control group and that difference was also statistically significant (OR: 5.133, CI: 1.299-20.28), p<0.02. Conclusions: The present data suggest that germ-line polymorphisms of C677T, C1298A for MTHFR and R2 for FV are associated in breast cancer and may be additional prognostic markers related to breast cancer survival. The results now need to be confirmed in a larger group of patients.

Sellar-Suprasellar Extraventricular Choroid Plexus Papilloma : A Case Report and Review of the Literature

Keskin, Fatih,Erdi, Fatih,Kaya, Bulent,Toy, Hatice The Korean Neurosurgical Society 2016 Journal of Korean neurosurgical society Vol.59 No.1

Choroid plexus papillomas (CPPs) are relatively rare neuroectodermal tumors that develop from choroid plexus epithelial cells and are usually restricted to the ventricles. Extraventricular CPPs are very unusual and can be difficult to diagnose and treat. A 50-year-old male patient was admitted to our clinic complaining of headache and visual deterioration. Neurological examination found no abnormalities except decreased light perception and secondary optic atrophy in the left eye. Endocrine testing revealed normal levels of hormones produced by the pituitary and target glands. Magnetic resonance imaging of the brain revealed a huge regular-shaped lesion in the sellar-suprasellar region occupying the sella turcica and extending into the suprasellar cistern and planum sphenoidale. The lesion was completely excised by microsurgery via an ordinary left-sided pterional approach. Histopathology identified the lesion as a choroid plexus papilloma. Following the case report, literature on the origin, differential diagnosis, and treatment of this rare tumor is reviewed.

The Surgical Management of Traumatic C6-C7 Spondyloptosis

Keskin, Fatih,Kalkan, Erdal,Erdi, Fatih The Korean Neurosurgical Society 2013 Journal of Korean neurosurgical society Vol.53 No.1

A case of traumatic spondyloptosis of the cervical spine at the C6-C7 level is reported. The patient was treated succesfully with a anterior-posterior combined approach and decompression. The patient had good neurological outcome after surgery. A-51-year-old female patient was transported to our hospital's emergency department after a vehicle accident. The patient was quadriparetic (Asia D, MRC power 4/5) with severe neck pain. Plain radiographs, computerize tomography and spinal magnetic resonance imaging (MRI) showed C6-7 spondyloptosis and C5, C6 posterior element fractures. Gardner-Wells skeleton traction was applied. Spinal alignment was reachived by traction and dislocation was decreased to a grade 1 spondylolisthesis. Then the patient was firstly operated by anterior approach. Anterior stabilization and fusion was firstly achieved. Seven days after first operation the patient was operated by a posterior approach. The posterior stabilization and fusion was achieved. Postoperative lateral X-rays and three-dimensional computed tomography showed the physiological realignment and the correct screw placements. The patient's quadriparesis was improved significantly. Subaxial cervical spondyloptosis is a relatively rare clinical entity. In this report we present a summary of the clinical presentation, the surgical technique and outcome of this rarely seen spinal disorder.

Prognostic Factors in Stage III Non-Small-Cell Lung Cancer Patients

Urvay, Semiha Elmaci,Yucel, Birsen,Erdis, Eda,Turan, Nedim Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.10

Aim: The objective of this study is to investigate prognostic factors affecting survival of patients undergoing concurrent or sequential chemoradiotherapy (CRT) for stage III non-small-cell lung cancer (NSCL). Methods and materials: We retrospectively reviewed the clinical records of 148 patients with advanced, inoperable stage III NSCLC, who were treated between 2007 and 2015. Results: The median survival was found to be 19 months and 3-year overall survival was 27%. Age (<65 vs ${\geq}65years$, p=0.026), stage (IIIA vs IIIB, p=0.033), dose of radiotherapy (RT) (<60 vs ${\geq}60Gy$, p=0.024) and treatment method (sequential chemotherapy+RT vs concurrent CRT, p=0.023) were found to be factors affecting survival in univariate analyses. Gender, histological subtype, weight loss during CRT, performance status, induction/consolidation chemotherapy and presence of comorbidities did not affect survival (p>0.050). Conclusion: Young age, stage IIIA, radiotherapy dose and concurrent chemoradiotherapy may positively affect survival in stage III NSCL cases.

Comparison of Tool Wear, Surface Morphology, Specific Cutting Energy and Cutting Temperature in Machining of Titanium Alloys Under Hybrid and Green Cooling Strategies

Munish Kumar Gupta,P. Niesłony,Mehmet Erdi Korkmaz,Mustafa Kuntoğlu,G. M. Królczyk,Mustafa Günay,Murat Sarikaya 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6

Cutting energy must be reduced in order to make machining processes more eco-friendly. More energy was expended for the same amount of material removed, hence a higher specific cutting energy (SCE) implies inefficient material removal. Usually, the type of coolants or lubricants affects the SCE, or the amount of energy needed to cut a given volume of material. Therefore, the present work deals with a study of SCE in the turning of Ti–3Al–2.5V alloy under green cooling strategies. In spite of this, the research effort is also focused on the mechanism of tool wear, surface roughness, and cutting temperature under hybrid cooling, i.e., minimum quantity lubrication (MQL) and cryogenic. The tool wear rate, were explored with tool mapping analysis, and the results were compared with dry, MQL, and liquid nitrogen (LN2) conditions. The tool wear rate analysis claims that the dry condition causes more built up edge (BUE) formation. In addition, the hybrid cooling conditions are helpful in reducing the SCE while machining titanium alloys.

Macroscopic and Mesoscopic Characteristics of a Small-Span Metro Tunnel in the Development of a Disaster Under Load

Yu Cong,Heyi Liu,Liming Zhang,Sai Li,Yingren Zheng,Zaiquan Wang,Erdi Abi 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11

A similarity model with a volumetric similarity ratio of 1:100 and a granular flow model for the tunnel were designed. By comparing macroscopic and mesoscopic information (such as fracture process, strain evolution, stress transfer, crack propagation, and stress distribution) of the tunnel models under load, the failure mechanism of the metro tunnel under load was investigated. The result showed that: 1) under the loading path, the instability area of the tunnel is mainly distributed in the straight wall on both sides. When the load is 1.5 MPa, a large number of cracks on both sides of the straight wall run through, resulting in the initial failure of the rock mass; 2) the surface rock mass of arch bottom is under tensile stress and the deep rock mass is under pressure stress, therefore, the fracture does not develop continuously. The surface of straight wall produces continuous development crack under the action of tensile stress; 3) the arch bottom first responds during the stress redistribution of the small-span tunnel; the top and middle parts of the side walls of the running tunnel with greatest potential for damage respond most; 4) in the process of stress redistribution, the peak stress of the deep measuring points of the straight wall is greater than that of the free surface; 5) at the initial stage of loading, tensile cracks account for a high proportion of all cracks found. When the load is 1.5 MPa, the proportion of shear cracks increases to 28%, and when the load is 1.6 Mpa, the proportion of shear cracks increases to 31%. Finally, the tensile-shear effect triggers the failure of the tunnel.