Deterioration the Properties of Contaminated Natural Rubber with Some Species of Microorganisms.

The rubber materials are very important in our lives because of its properties and suitability for many applications, and it is a direct target of numerous microorganisms such as bacteria and fungi and there effect on rubber, especially natural rubber poly (cis-1,4-isoprene), as it contains organic material and water, it dealt with the current study. The effect of contaminate (fungi) during bad conditions of transportation and Storage, genus Aspergillus Niger was isolated from contaminated samples for both types (SMR20, SVR20) and study the physical and mechanical properties, which included tensile strength and elongation at break, hardness, abrasion and extraction in addition to the study influenced main constituent of natural rubber growth of fungus using the technique of infrared spectrum. The results showed a negative influence on the physical and mechanical properties for the growth of fungus, in addition to the disappearance of some bands of natural rubber such as   (C-H) and (C-N) bands. Keywords: Deterioration, Natural Rubber, SMR20, SVR20, poly (cis-1,4-isoprene), microorganisms, fungi

A Review Study of Mechanical Fatigue Testing Methods for Small-Scale Metal Materials

A review on the mechanical characterization of materials at small- scale is presented. The concentration is on the different micro- and nano-scale testing techniques, classify, summarize, and compare all of these techniques that are currently available. The variety of materials investigated by the scientific and industrial communities and the mechanical quantities identified by such methodologies. Finally, the perspectives of studies on fatigue of the small scale metal materials are offered. Keywords:  Fatigue crack ; small-scale; nano-scale;  MEMS; cyclic load; thin film

Modification of Dielectric Strength of Iraqi Kaolin by the Addition of Micro and Nano Zirconia

استعمل الكاؤلين العراقي كمادة اساس في هذه الدراسة بعد اضافة مخلفات قصب السكر بنسبة (10%) و (2%) من بولي فاينيل الكحول (PVA) كمادة رابطة . اضيفت نسب مختلفة من الزركونيا ( المايكروية او النانوية) الى المتراكب (0%،5%،10%،15% ، 20%) لغرض تحسين خواصه الحرارية.       شكلت العينات بطريقة الكبس شبه الجاف بقوة كبس (25 Mpa) باستخدام قالب قطره (12 mm) وبمدة زمنية مقدارها (2 min). ثم اجراء عملية التلبيد للمكبوسات، حيث تمت عملية الحرق بثلاث درجات حرارة  Co(1000، 1100 ، 1200) لمعدل ارتفاع مقداره (3) درجة حرارة / دقيقة و بقيت عند كل درجة حرارة لمدة ساعتين.       لقد ظهرت النتائج ان زيادة نسبة الزركونيا المضافة سواء اكانت مايكروية ام نانوية تؤدي الى زيادة قيم متانة العزل الكهربائي و حصلنا على افضل النتائج بإضافة الزركونيا النانوية، وكذلك تؤدي زيادة درجة حرارة الحرق الى زيادة قيم متانة العزل الكهربائي .       Iraqi kaolin as a matrix material is used as a principle part of the study after additives sugarcane straw in ratio (10%) and (2%) Poly Vinyl Alcohol ( PVA) as a binding material. (Micro or Nano) Zirconia has been added to the composite in different ratio ( 0% , 5 % , 10% , 15% , 20%) for the purpose of improving thermal properties. Samples are formed in a semi-dry  pressing with pressure of about (25 Mpa).      The formulation is achieved by using a template  of (12 mm) diameter and a time of about (2 min). Then, the prepared samples have been sintered.    Burning process was carried out by three temperature degrees ( 1000, 1100, 1200 ) Co for mean raise about 3 temperature degree / 1 minute and remained at every temperature degree for two hours.      The results showed that the increase in the proportion of ( Micro or Nano ) Zirconia results in increasing the value of dielectric strength and the best results were achieved by adding Nano Zirconia. The increasing of the burning temperature also leads to increase in the value of the dielectric strength. &nbsp

Data protection based neural cryptography and deoxyribonucleic acid

The need to a robust and effective methods for secure data transferring makes the more credible. Two disciplines for data encryption presented in this paper: machine learning and deoxyribonucleic acid (DNA) to achieve the above goal and following common goals: prevent unauthorized access and eavesdropper. They used as powerful tool in cryptography. This paper grounded first on a two modified Hebbian neural network (MHNN) as a machine learning tool for message encryption in an unsupervised method. These two modified Hebbian neural nets classified as a: learning neural net (LNN) for generating optimal key ciphering and ciphering neural net CNN) for coding the plaintext using the LNN keys. The second granulation using DNA nucleated to increase data confusion and compression. Exploiting the DNA computing operations to upgrade data transmission security over the open nets. The results approved that the method is effective in protect the transferring data in a secure manner in less tim

Influence of Fluoride Addition on Hydroxyapatite Prepared for Medical Applications

In this study, hydroxyapatite (HAP, Ca10(PO4)6(OH)2) has been prepared as bioceramic material with biological specifications useful to used for orthopedic and dental implant applications. Wet chemical processing seems to form the fine grain size and uniform characteristic nanocrystalline materials by the interstice factors controlling which affected the grain size and crystallinity in order to give good mechanical and/or constituent properties similar as natural bone. Fluorinated hydroxyapatite [4-6 wt% F, (FHA, Ca10(PO4)6(OH)2–Fx] was developed in new method for its posses to increased strength and to give higher corrosion resistance in biofluids than pure HAP moreover reduces the risk of dental caries. The phase's and functional groups characterizations XRD & FTIR reveled the purity of the product and its free of other phases, while the morphology tests showed the compound homogeneity as fluoride interpenetrated in the compound lattice net

Improving the Mechanical Properties of Fiber Metal Laminate Composite Used in Aircraft Wing

The purpose of this study is to reduce weight and improve the mechanical properties of aircraft wing using Hybrid materials known as fiber metal laminates (FMLs). In this study, seven layers were used to produce the FMLs that consist of aluminum alloy2024-T3 reinforced by carbon and glass fibers bonded with blend of epoxy-resole. The Carbon Glass Reinforced Aluminum Laminates (CAGRALLs) was used as FMLs. The results showed that The CAGRALLs gave good mechanical properties because of increasing in tensile strength, elongation at fracture and impact toughness except flexural strength by comparing with other FMLs using commercial epoxy. The increasing in layers led to weaken adhesion force between layers of FMLs caused decreasing almost mechanical properties. The FMLs has good mechanical properties by using carbon and glass fibers by comparing with carbon and jute fibers. The CAGRALLs have higher numbers of cycles at failure under cyclic loadings than Aramid Reinforced Aluminum Laminates (ARALLs). The CAGRALLs have lower density by comparing with aluminum alloy 2024-T3 that used in manufacturing of aircraft wing

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

The Effect of Shape Factor on the Operation Periods of Anti-Vibration Rubber

This research aims to study the shape factor affects on the rubber that resistant to the vibration. Three different shapes of rubber mounts(cylindrical , hexagonal and trapezoidal shapes)having the same volume was prepared. The anti-vibration models was manufactured depended on the pre-selected recipes according to specific specifications suitable for this purpose. In this work, actual application test in AL-Kufa cement factory was done to get knowledge about the efficiency of the manufacturing mounts. Furthermore, simulation for the three above  models  by ANSYS V.11 Program was done. The actual application result shows that, hexagonal model is the best because the higher operation periods while the simulation shows that ,there is a decreasing in the stress intensity of the hexagonal shape, this may be explain why it has longest operation period than the other two shapes. Keywords: Shape factor, Stress intensity, Anti-vibration rubber, Hexagonal shape.

Structural analysis of functionally graded material using sigmioadal and power law

The stress-strain relations, displacement distribution, stress resultants and mid plane strain resultants of a functionally graded material plate are studied using Hamilton’s principle. A simply supported rectangular thick shell direct stress, inplane shear stress, transverse stress and displacement are investigated. The analysis and modeling of five layers FGM shell is carried out using MATLAB19 code with ABAQUS20 software. Using distinct materials on the top and bottom layers of the shell, a transverse uniform load in five degrees - of - freedom is applied with a specific Poisson's ratio and Young's modulus in a power and sigmoidal law function through the thickness direction. A power law was used to determine the distribution of properties through shell thickness. The results showed that the bottom layer affected significantly most stress due to subjected to the most in-plane stress while the displacement is greatest at the top layer