ریختهگری دوغابی مخلوط پودرهای آلومینا-آهن تحت میدان مغناطیسی

مهندسی مکانیک و ارتعاشات, 2014

The purpose of this research was to develop a thermodynamic model for engine via changing the form of regenerator. In conventional betatype Stirling the working fluid passes between the compression and expansion space via the bypass of the main cylinder. In the present study a new form of regenerator was proposed for the beta-type Stirling engine. In this new form successive homogeneous layers of sguare wire meshes filled the space of displacer piston so that the displacer piston took the role of regenerator and displacer simultaneously. To this end modeling was done using MATLAB software and the obtained results were compared with the published values.

مواد و فناوری های پیشرفته, 2016

In this study seven combination of Alumina and Zircon was selected by ratio of Alumina to Zircon of : 100/0, 85/15, 70/30, 45/55, 35/65, 20/80, 0/100. After weighing the powder raw material , mill for 24 hours and then were using press forming. The samples was sintered in temperatures of 1550 , 1600 , 1650. To identify the phases and percentage of phases formed , X-ray diffraction pattern produced parts were investigated. The effect of Alumina to Zircon ratio and sintered temperature on the formation of mullite and zircon phases were investigated. All samples porosity were measured and the effect of combination and temperature and the final phases on this characteristic were studied .The results showed that zircon improved alumina sintered body of alumina and zircon are also accelerate decomposition .

2014

مدل سازی رشد گیاه ابزار مهمی در ارزیابی اثرات تنش خشکی بر روی عملکرد محصول دیم و در نتیجه آن، انتخاب تاریخ کشت بهینه و تصمیم گیری برای روش های مدیریتی مناسب می باشد. یکی از جدیدترین مدل های گیاهی مدل AquaCrop (آکواکراپ) است که توسط سازمان فائو توسعه داده شده و اساس آن عکس العمل عملکرد محصول نسبت به آب مصرفی می باشد و با استفاده از متغیرهای اقلیمی، گیاه، خاک و مدیریتی، عملکرد محصول را شبیه سازی می نماید. مدل مذکور بایستی برای هر محصول و در هر منطقه خاص واسنجی و ارزیابی گردد. در این تحقیق، مدل گیاهی آکواکراپ در ایستگاه تحقیقات دیم سیساب واقع در خراسان شمالی و برای گیاه گندم تحت کشت دیم واسنجی و ارزیابی شد. برای واسنجی مدل، از داده های هواشناسی روزانه و داده های برداشت محصول دو سال زراعی (87-86 و 88-87) در ایستگاه سیساب استفاده شد. برای اعتبارسنجی مدل نیز از داده های هواشناسی مستقل از مرحله واسنجی و داده های عملکرد واقعی محصول در پنج سال زراعی 82-81 الی 86-85 استفاده گردید. نتایج بدست آمده نشان داد که مدل آکوکراپ با دقت بالایی قابلیت مدل سازی عملکرد محصول را دارا می باشد. بطوری که ضریب...

2014

این تحقیق با هدف مقایسه ویژگی‌های خمیر‌کاغذ سولفیت سدیم خنثی کاه‌گندم زاگرس استان گلستان تحت تأثیر پیش‌تیمار قلیایی با هیدروکسیدسدیم یک درصد و آب جوش انجام شد. پیش‌تیمار کاه خرد شده با هیدروکسیدسدیم یک درصد و آب جوش به نسبت 10 به 1 به‌ترتیب در دماهای 70 درجه سانتی‌گراد و دمای 100 درجه سانتی‌گراد به مدت 30 دقیقه انجام گردید. سپس از کاه پیش‌تیمار شده با مایع پخت سولفیت‌سدیم و هیدروکسید‌ سدیم با نسبت ثابت 5 به 1 در دمای 160 درجه سانتی‌گراد و به مدت 30 دقیقه خمیر‌کاغذ تهیه گردید. به‌منظور بررسی تأثیر هیدروکسید‌سدیم بر مقاومت‌های کاغذ، در بعضی پخت‌ها فقط از سولفیت‌سدیم استفاده شد و در یک حالت کاه‌گندم بعد از قرار گرفتن در معرض پیش‌تیمار هوا خشک شد و از کاه پیش‌تیمار و توزین شده برای پخت استفاده شد و در حالتی دیگر بعد از پیش‌تیمار مقدار هیدروکسید سدیم جذب شده در پیش‌تیمار محاسبه و از هیدروکسید سدیم مورد نیاز برای پخت اصلی کسر شد. پس از پخت، خمیرکاغذها توسط پالایشگر آزمایشگاهیPFI mill تا رسیدن به درجه‌روانی‌‌25 ± 380 میلی‌لیتر (CSF) پالایش شدند. از هر نوع خمیر‌کاغذ، کاغذ دست‌ساز 60 گرمی سا...

2008

The effect of removal of smear layer has already been a subject in many investigations, and has been a matter of controversy. Of course there is no doubt that sealer penetration would be facilitated when smear layer removed. The aim of this study was evaluation of the relationship between sealer penetration and apical microleakage after usage of MTAD. Materials & Methods: In this invitro study, 135 human single root extracted teeth were selected. The teeth were divided into three groups (40 samples in each) as experimental groups as follow: Group 1: Serum was used for irrigation (with the smear layer). Group 2: EDTA 17% was used for irrigation (removal of the smear layer). Group 3: MTAD was used for irrigation (removal of the smear layer) and 15 teeth were considered as the control. The teeth in each group were divided into two subgroups (20 teeth) to be filled either with AH Plus or Dorifill sealer. Sixty teeth were selected for dye penetration with methylene blue and statistically analysed using One-Way and Two-Way ANOVA. In the other 60 teeth, sealer penetration was evaluated using SEM. The data were statistically analysed using Kruskal-Wallis and Mann-Whitney tests. The end relationship between dye penetration and sealer penetration was evaluated by spearman correlation test. Results: There was no significant difference between the three types of irrigants. There was a significant difference between the two sealers. AH plus revealed less dye penetration. Minimum dye penetration was observed in MTAD group with AH Plus and maximum dye penetration was observed in Serum group with Dorifill. Sealer penetration in MTAD and EDTA groups were better than Serum group. AH Plus was better than Dorifill. The correlation between sealer penetration in dentinal tubules and dye penetration wasn't statistically significant. Conclusion: Type of irrigant didn't affect apical microleakage but type of sealer affected microleakage. AH Plus proved to be better. AH Plus showed greater sealer penetration. Greater sealer penetration does not necessarily reduce apical microleakage.

2014

2014

The present study developed an improved nanocomposite based on polylactic acid (PLA) biopolymer. The structural properties of PLA nanocomposites of clay and cellulose nanoparticles were evaluated for level and water vapor permeability (WVP) using thermal and casting methods. Thermal tests (DSC) showed that pure PLA had a glass transition point (T g) of 53.83, a melting point (T m) of 153.95°C and crystallization (x%) of 41.36%. With the incorporation of clay nanoparticles, T g and x% increased, while T m showed no significant change. The micro-crystal cellulose (MCC) nanoparticles were not compatible with the polymer matrix, so there was no effect on the thermal properties. WVP results showed that pure PLA had high permeability; the addition of clay nanoparticles strongly decreased WVP. The sample with 7% clay had a permeability of 0.92×10-11 g/m.S.Pa. WVP of the film increased significantly as a result of the hydrophilic nature of the MCC. The SEM images of the samples confirmed the results.

مواد و فناوری های پیشرفته, 2013

جغرافیا و روابط انسانی, 2020

2009

Solar radiation, nowadays has a lot of application in different fields of agriculture, irrigation, and hydrology engineering and due to these various applications, different models has been proposed for it’s estimation. Angstrom-Prescott equation is one of the most important well known models for solar radiation estimation. This equation has empirically coefficient that various for each location. In this paper, the data gathered in Mashhad Synoptic station during 1378 and 1380, Angstrom-Prescott coefficient has been identified according to the ratio of actual sunshine hours (n) to the maximum sunshine hours (N). Also a Regression local equation has been proposed considering several meteorology parameters including daily gathered data of saturation vapor pressure deficit, precipitation, air temperature mean, relative humidity percentage and n/N. Finally the proposed model has been evaluated according to the independent measured data during 1381 to 1382. The statistical analysis of th...