Islamic Azad University North Tehran Branch

About: Islamic Azad University North Tehran Branch is a education organization based out in Tehran, Iran. It is known for research contribution in the topics: Adsorption & Catalysis. The organization has 868 authors who have published 968 publications receiving 9987 citations.

Measurement uncertainty of pb, cd and ni determination in human hair by electro thermal atomic absorption spectrometry

Abstract: Today, in developing countries like Iran heavy metals are present everywhere which threatens the health of the people. The analysis of human hair is useful in monitoring the levels of certain trace elements in the body and assessing heavy metals environmental exposure. In the present work, we propose uncertainty estimation for the analytical results we obtained from determination of cadmium, lead and nickel in human hair by electr thermal atomic absorption spectrometry (ETAAS). Prior to analysis, hair samples were washed with 1% (w/v) sodium diethyldithiocarbamate (DDTC), and 0.1M HCl. The hair samples were digested afterward in a mixture of HNO3, and H2O2. To estimate the uncertainty of analytical result obtained, we propose assessing trueness by employing spiked sample. Two types of bias are calculated in the assessment of trueness: a proportional bias and a constant bias. We applied Nested design for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition of curve is an estimate of the method recovery. Estimated method of average recovery in human hair is: (1.019±0.026), (0.918±0.014) and (1.0597±0.017) for Cd, and Ni, respectively.

Test of the generalizability of Altman's bankruptcy predication model

Abstract: Although originally developed in 1968 using a small sample of firms from the 1950s and 1960s, Altman's Z-Score model remains a commonly used tool for evaluating the financial health of companies. Because of the age of the model and other its attributes, such as its small sample of manufacturing firms and the use of equal group sizes of bankrupt and non-bankrupt firms, it is likely that the model is not as effective in classifying firms in more recent studies as it was when developed by Altman. This study examines three research questions using recent sample data: (1) Is Altman's original model as useful for predicating bankruptcy in recent periods as it was for the periods in which it was developed and tested by Altman? (2) Is the model as useful for predicating financial stress conditions other than bankruptcy as it is for predicting bankruptcy? (3) Is it true/accurate that as time passes, the ability of the model to predict decreases correspondingly? Our results are consistent with positive answers to Questions 1 and 2 and a negative answer to Question 3.

Developing an appropriate mathematical model for the environmental risk assessment of jack-up drilling rigs (case study: south pars field, iran)

Abstract: I dentifying the environmental hazards of jack-up drilling rig, which is used as an exploratory drilling and offshore service platform, yet has been under intense discussion. Risk assessment along with determining the likelihood of an event occurrence and the severity of its consequences can be a useful tool for identifying the priorities and making satisfactory managerial decisions. In this study, the environmental risks attributed to jack-ups in the offshore area of Iran around the South Pars gas field were studied, and finally a new mathematical model for the environmental risk assessment in this area was presented. Due to qualitative nature of some indefinite factors, fuzzy logic was applied in this model. Moreover, the model design was tailored to the ecological and environmental conditions of South Pars gas field, and several sources of risk were aggregated for the final environmental risk assessment of jack-up drilling rig. The results indicated that the total risk calculated for jack-up in transportation was tolerable and limited management measures were required. However, for the jack-up operation risks, the site was found to be faced with “unacceptable risk” or requiring extensive management measures.

New results on mineralography and crystal chemistry of magnetite and pyrite at baba-ali & galali iron deposits, west of hamedan, iran

Abstract: کانسارهای آهن باباعلی و گلالی در باختر همدان و در میان توالی آتشفشانی- رسوبی سری سنقر در زون زمین‌شناسی- ساختاری سنندج- سیرجان قرار دارند. بررسی‌های کانه‌نگاری و تجزیه‌های SEM-EDAX بر روی کانسنگ آهن مگنتیتی این دو کانسار در راستای شناخت بهتر ترکیب کانی‌شناسی و ‌شیمی بلور کانسنگ، نتایج جالب توجهی را نشان داده است. با بررسی میزان تمرکز برخی از عناصر کمیاب نظیر وانادیم، کبالت، نیکل، مس، کروم، تیتان، طلا، عناصر گروه پلاتین و برخی ناخالصی‌های سولفور و فسفر در کانسنگ، مشخص شد تنها بخشی از پیریت اولیه دارای تمرکزهای جالب توجهی از عنصر پلاتین است. به‌نظر می‌رسد دیگر نسل‌های پیریت و مگنتیت از نظر عناصر کمیاب یادشده تهی‌شده‌اند. سیالات گرمابی تأخیری که باعث کانی‌سازی پیریت در باطله (گانگ) کلسیت- کوارتز شده‌اند، از نظر کانی‌سازی طلا نیز با اهمیت بوده و در واقع، کانی پیریت به عنوان حامل خوبی برای طلا عملنموده است. شناسایی مقادیر قابل توجهی از فلوگوپیت و الگوی تمرکز عناصر کمیاب در کانسنگ آهن گلالی، نظریه اسکارن نوع منیزیم آتشفشان‌زاد را قوت داده است.