A comparison of timing methods in orthogonal frequency division multiplexing (OFDM) systems

Orthogonal frequency division multiplexing (OFDM) is being used by wireless local area network (WLAN) standards, such as IEEE 802.11a, and wireless metropolitan area network (MAN) standards, such as IEEE 802.16a. OFDM is a very efficient communications scheme for wireless ADHOC networks. However, the wireless environment causes inter-symbol interference (ISI) and inter-carrier interference (ICI). Estimating the starting point of an OFDM symbol must be handled efficiently and effectively to reduce the errors. OFDM must be time synchronized to prevent inter-symbol interference (ISI) and inter-carrier interference (ICI). Many techniques exist to realize timing synchronization in OFDM systems. In this thesis, the need for timing synchronization, the timing errors, and the performance of different techniques under a variety of mobile channel models (indoor and outdoor) are investigated, and simulation performance results for each technique under different channel models are presented.http://archive.org/details/acomparisonoftim109451372First Lieutenant, Turkish ArmyApproved for public release; distribution is unlimited

An Alternative Solution to Multi Objective Linear Fractional Programming Problem by Using Geometric Programming Technique

In this study, we have proposed an alternative solution to the multi objective linear fractional programming problems. This method deals with every objective of multi objective linear fractional programming problems gradually by using geometric programming technique to find the pareto optimal solution. The proposed solution procedure has been used in numeric examples and results have been compared with the real solution values. Keywords: multi objective, fractional programming, geometric programmin

Damage mode identification in transverse crack tension specimens using acoustic emission and correlation with finite element progressive damage model

© 2018 Elsevier Ltd In this study, damage progression in unidirectional composite specimens is investigated. Transverse Crack Tension specimens are used to stimulate damage in a predetermined progressive sequence. Acoustic Emission (AE) registration technique and its location detection capability is used to identify and locate the damage modes during the tension tests. The k-means++ algorithm is applied to cluster similar AE events and obtain reliable correlations between the damage modes and AE characteristics. Damage modes at the end of interrupted tests are identified under an optical microscope and correlated with locations of AE clusters. It is seen that matrix cracks have high amplitude and duration, whereas delaminations have low amplitude and mid-duration, and fibre breaks have high average frequency characteristics. A finite element analysis was performed to predict the progressive failure behaviour including intralaminar failure and delaminations. The correlations between the AE clusters and damage modes are validated with the finite element model

Do high frequency acoustic emission events always represent fibre failure in CFRP laminates?

© 2017 Elsevier Ltd When damage in carbon fibre reinforced composites (CFRP) is monitored by acoustic emission (AE), it is a common belief that high frequency AE events originate from fibre failure. This shows that this statement may not correspond to the reality, and matrix cracks can emit high frequency AE signals. Quasi-static tension of [−45 2 /0 2 /+45 2 /90 2 ] s laminates was monitored by AE, Digital Image Correlation (DIC) on the surface of the sample and in-situ optical microscopy on the sample's polished edge. Unsupervised k-means clustering algorithm was applied to the AE results. By comparison with the direct DIC and microscopic observations, the AE cluster with high frequency and low amplitude was found to correspond to directly observed matrix cracks

Multi-instrument in-situ damage monitoring in quasi-isotropic CFRP laminates under tension

© 2018 Digital Image Correlation monitoring of the surface strains, microscopic in-situ observations of the micro-damage on the specimen edge and Acoustic Emission (AE) are utilized simultaneously during tension tests of quasi-isotropic carbon fibre reinforced polymer composites. It is found that the cluster analysis for characteristic parameters of AE events (the main being the signal amplitude and frequency) does not unambiguously identify the type of damage which causes the event. With optical instruments, it is observed that the signatures of AE events depend on the position of the ply where damage happens and on the ply orientation (90° vs 45°). Robust evidences for the variations in AE characteristics of damage modes in different lay-ups are presented. AE events, originated from surface cracks, have high amplitude and low frequency, whereas AE events, originated from transverse cracks in the inner plies, have low amplitude and high frequency characteristics. Any conclusion for fibre breaks are not reached in this study. Therefore, measurements in this study rather point out that the AE events, which could be interpreted as fibre breaks because of their high frequency characteristics, as optical observations prove, correspond to other damage types in quasi-isotropic laminates

A composite sandwich plate with a novel core design

© 2018 Elsevier Ltd In this study, a new core design is introduced for sandwich composite structures. Its strength and failure behavior are investigated via three-point bending tests. E-glass-fiber-reinforced epoxy resin is selected as the material for both the core and the face sheets. The core has an egg-crate shape. Acoustic emission (AE) method is used to detect the progression of damage. Signals due to elastic waves caused by activated damage mechanisms are investigated in order to identify the corresponding failure modes. A finite element model of the sandwich structure is developed to predict the failure behavior of the specimens under the loading conditions in the tests. A promising agreement between the results of the finite element model and the experiments is observed. The force-deflection-relation, the failure load as well as the region where damage initiates are accurately predicted

Mogu li hemocitometrijski parametri poslužiti kao biološki biljezi u razlikovanju adrenalnih adenoma i karcinoma te u prognozi adrenokortikalnih karcinoma?

Recently, studies have reported that inflammatory response and elevated platelet counts are associated with several cancers. In the present study, we aimed to evaluate hemocytometer parameters in differentiating adrenal adenoma and carcinoma, and the prognostic utility of hemocytometer parameters in adrenocortical carcinoma (ACC). We included 30 patients with nonfunctional adrenal adenoma and 13 patients with ACC having undergone surgery between 2005 and 2017 and followed up postoperatively at our centre. The neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), red blood cell distribution width (RDW), mean platelet volume (MPV) and plateletcrit (PCT) were evaluated preoperatively in all patients included in the study. There was a significant difference between the adrenal adenoma and ACC groups in terms of neutrophil and lymphocyte counts, NLR and PLR. There was no significant difference between the two groups in terms of platelet count and MPV, but PCT levels were significantly lower in ACC group. There was no statistically significant difference between recurrent and/or metastasis positive patients and negative ones according to NLR, PLR, RDW and MPV. There was a statistically significant difference in RDW levels and tumor diameter between the groups. Our study is the first to evaluate hemocytometer parameters in differentiating adrenal adenomas and carcinomas, and also in the prognosis of ACC. The present study suggested that the hemocytometer parameters may be a marker in the differential diagnosis of adrenal adenomas and carcinomas. However, our study also showed that these parameters had no prognostic value in ACC.Nedavna istraživanja pokazuju da su upalni odgovor i povišeni trombociti udruženi s nekim vrstama karcinoma. Cilj našega istraživanja bio je procijeniti hemocitometrijske parametre u razlikovanju adrenalnog adenoma i karcinoma, kao i prognostičku vrijednost hemocitometrijskih parametara u adrenokortikalnom karcinomu (adrenocortical carcinoma, ACC). U istraživanje smo uključili 30 bolesnika s nefunkcionalnim adrenalnim adenomom i 13 bolesnika s ACC operiranih između 2005. i 2017. godine i poslije operacije praćene u našoj ustanovi. Kod svih bolesnika uključenih u studiju prijeoperacijski su izmjereni sljedeći parametri: omjer neutrofila i limfocita (neutrophil/lymphocyte ratio, NLR), omjer trombocita i limfocita (platelet/lymphocyte ratio, PLR ), širina distribucije eritrocita (red blood cell distribution width, RDW ), srednji volumen trombocita (mean platelet volume, MPV) i pleteletkrit (PCT). Utvrđena je statistički značajna razlika između skupina bolesnika s adrenalnim adenomom i onih s ACC u broju neutrofila i limfocita, NLR i PLR. Nije bilo značajne razlike među skupinama u broju trombocita i MPV, ali su razine PCT bile značajno niže u skupini s ACC. Nije bilo statistički značajne razlike u NLR, PLR, RDW i MPV između bolesnika s opetovanim ACC i/ili metastazama i onih bez tih stanja. Statistički značajna razlika između skupina nađena je za razine RDW i promjer tumora. Naše istraživanje je prvo te vrste u kojem su se procjenjivali hemocitometrijski parametri u razlikovanju adrenalnih adenoma i karcinoma te u prognozi ACC. Rezultati studije ukazuju na to da bi se hemocitometrijski parametri mogli primijeniti kao biljezi u diferencijalnoj dijagnostici adrenalnih adenoma i karcinoma. Međutim, naše je istraživanje pokazalo kako ovi parametri nemaju prognostičku vrijednost kod ACC

Multi-instrument multi-scale experimental damage mechanics for fibre reinforced composites

© Published under licence by IOP Publishing Ltd. Reliable investigation of damage in fibre reinforced composites requires concurrent in- and ex-situ application of multiple instruments at different scale: digital image correlation, acoustic emission registration, optical/electron microscopy, C-scan, X-ray imaging and micro-computed tomography. The multi-instrument experimental mechanics allows detailed damage monitoring and inspection

Perspectives on care and communication involving incurably ill Turkish and Moroccan patients, relatives and professionals: a systematic literature review

<p>Abstract</p> <p>Background</p> <p>Our aim was to obtain a clearer picture of the relevant care experiences and care perceptions of incurably ill Turkish and Moroccan patients, their relatives and professional care providers, as well as of communication and decision-making patterns at the end of life. The ultimate objective is to improve palliative care for Turkish and Moroccan immigrants in the Netherlands, by taking account of socio-cultural factors in the guidelines for palliative care.</p> <p>Methods</p> <p>A systematic literature review was undertaken. The data sources were seventeen national and international literature databases, four Dutch journals dedicated to palliative care and 37 websites of relevant national and international organizations. All the references found were checked to see whether they met the structured inclusion criteria. Inclusion was limited to publications dealing with primary empirical research on the relationship between socio-cultural factors and the health or care situation of Turkish or Moroccan patients with an oncological or incurable disease. The selection was made by first reading the titles and abstracts and subsequently the full texts. The process of deciding which studies to include was carried out by two reviewers independently. A generic appraisal instrument was applied to assess the methodological quality.</p> <p>Results</p> <p>Fifty-seven studies were found that reported findings for the countries of origin (mainly Turkey) and the immigrant host countries (mainly the Netherlands). The central themes were experiences and perceptions of family care, professional care, end-of-life care and communication. Family care is considered a duty, even when such care becomes a severe burden for the main female family caregiver in particular. Professional hospital care is preferred by many of the patients and relatives because they are looking for a cure and security. End-of-life care is strongly influenced by the continuing hope for recovery. Relatives are often quite influential in end-of-life decisions, such as the decision to withdraw or withhold treatments. The diagnosis, prognosis and end-of-life decisions are seldom discussed with the patient, and communication about pain and mental problems is often limited. Language barriers and the dominance of the family may exacerbate communication problems.</p> <p>Conclusions</p> <p>This review confirms the view that family members of patients with a Turkish or Moroccan background have a central role in care, communication and decision making at the end of life. This, in combination with their continuing hope for the patient’s recovery may inhibit open communication between patients, relatives and professionals as partners in palliative care. This implies that organizations and professionals involved in palliative care should take patients’ socio-cultural characteristics into account and incorporate cultural sensitivity into care standards and care practices<it>.</it></p