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Material and Design Optimization of Micro-Sensors

Thesis Info

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Author

Mehmood, Zahid

Program

PhD

Institute

Air University

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Mechanical Engineering

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/11943/1/Zahid%20mehmood%20mechanical%20eng%202019%20air%20uni%20isb%20prr.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727786368

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Measurements of three fluidic parameters i.e. velocity / flow rate / wall shear stress, pressure and temperature are crucial in many industrial applications including aerospace, automobile, bio-medical and process control etc. The key requirement is to measure these parameters at very fine spatial resolutions, which ultimately depends upon the size of measuring device. Size minimization is possible only through Micro-Electro-Mechanical Systems (MEMS) or mirco-fabrication technology. Therefore, using a novel SOI CMOS fabrication process, this thesis develops a multi-sensing platform that measures these three fluidic parameters, simultaneously.The developed chip has dimensions of just 1.6 mm × 1.6 mm as compared with the minimum chip size of 3.8 mm × 3.8 mm reported previously, thus improving the flow spatial resolution by 82.2%. The developed multi-sensing chip includes a thermal flow sensor, a piezoresistive pressure sensor and a Resistive Temperature Detector (RTD) based temperature sensor. Before integrating these sensors in a single chip, their material and design optimization have been carried out. Ashby‟s materials selection methodology has been used to select the optimum materials for these sensors. Since no MEMS compatible materials database having micro-scale material properties was readily available, therefore first a MEMS materials database has been developed and integrated with a material selection software. The developed materials database along with the derived performance indices for these sensors has then been used to select the candidate materials. Additionally, performance of these candidate materials and the variety of promising designs has also been evaluated experimentally in a two step iterative process using SOI CMOS fabrication technology. In a first iteration, eight thermal flow sensors (i.e. having square / circular membranes and four membrane to heater length ratios), six piezoresistive pressure sensors (i.e. having square membranes, three piezoresistor materials and two piezoresistor layout designs) and twelve RTDs temperature sensors(i.e. having five different materials and six layouts) have been fabricated andexperimental characterized. The best sensor of each type in the first iteration has been further improved when integrated in the final optimized multi sensing chip. The results showed that a thermal flow sensor with a silicon oxide square membrane having a membrane to heater length ratio of 3.35 has the highest sensitivity to area ratio. Similarly, a piezoresistor pressure sensor with a square membrane having p-doped silicon piezoresistors planted at the center of each membrane edges gives maximum sensitivity. The RTDs made of p-doped silicon and having higher L/W ratio exhibited the highest sensitivity and linearity. The optimized thermal, pressure and RTD sensors are much more sensitive than the previously reported such type of sensors. .It is worth highlighting that in addition to being highly sensitive, optimized sensors reported in this research are also CMOS compatible, which make them attractive considering their low cost and ease of integration with other CMOS devices, sensors and circuits.
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اردو شاعری میں مغربی تہذیب کا تذکرہ

اردو شاعری میں مغربی تہذیب کا تذکرہ

                                                ڈاکٹر عبدالمنان چیمہ

برصغیر پاک و ہند میں اسلامی تہذیب و تمدن رائج   میں اردو زبان  و ادب نے جان دار اور شان دار کردار ادا کیا۔  آج کل پرنٹ میڈیا اور الیکٹرانک میڈیا ہمارے معاشرے میں مغربی تہذیب و تمدن  سرایت کرنے  میں کلیدی  کردار ادا کر رہا ہے ۔ یہ بات عیاں ہے کہ ٹی وی ، انٹرنیٹ ، موبائل استعمال کرنے کے بعد نماز، روزہ اور دین اسلام کی طرف رجحان کم اور شیطان کی طرف زیادہ ہو جا تا ہے یہی وجہ ہے کہ فارغ اوقات میں قرآن و حدیث کے مطالعہ کی بجائے فلم دیکھنے کو جی چاہتا ہے ۔ مغربی تہذیب و تمدن کی مصنوعی روشنیوں نے مسلمانوں کی نوجوان نسل کے ایمان کو راکھ کر دیاہے ۔ مغربی تہذیب کے پھیلاؤ نے نوجوان کی سوچ کو کیمو فلاج کر دیا ہے ۔اسلام کسی ایسی تہذیب و ثقافت اپنانے کی اجازت نہیں دیتا جو معاشرے میں فساد کا باعث ہو ۔ معاشرہ میں مغربی تہذیب کا قلع قمع  کرنا وقت کی پکار ہے۔ عصر حاضر میں اسلام پر عمل پیرا ہو کر مغربی تہذیبی و ثقافتی یلغار کا مقابلہ کیا  جاسکتا ہے۔ مغربی تہذیب و تمدن کا اثر ونفوذ سب کے سامنے ہے۔ہمارے معاشرے میں معاشی و سماجی نظام کا عدم استحکام سے دوچار ہونا اس کی جیتی جاگتی مثال ہے۔

  ہمارے ملک میں انگزیر ی زبان و ادب   اور مغربی تہذیب کا اثر و نفوذ بڑھتا جارہا ہے۔اردو زبان  پاکستان کی قومی زبان ہے جس نے  جنوبی ایشیا میں  اسلام کی اشاعت  و تبلیغ میں جاندار کردار ادا کیا ہے ۔ اردو ز بان و ادب کے فروغ سے مغربی طرزِ حیات کے بڑھتے ہوئے رجحان کا مقابلہ کیا جا سکتا...

A CRITICAL STUDY OF CLINTON BENNETT’S THOUGHTS TOWARDS SIRAH OF THE HOLY PROPHET ﷺ

Sirah of the Holy Prophet ﷺ is the topic on which a lot of work has been done both in the Muslim and non-Muslim world. For Muslims it was the source of aspiration and adaptation for the practical purposes of social life while for the non-Muslims it was the source of inquisitiveness and understanding Islam as a successful religion in the past and present time. Therefore, Muslim enthusiastic interest in the biography of the Holy Prophet ﷺ developed and evolved into a regular science while the west has modified the knowledge of biography according to their own order of preference but within the same biographic precedents. Both have tried to reconstruct the biography of the Holy Prophet ﷺ historically, chronologically and logically. Clinton Bennett is one of the western scholars who has contributed not only in the Islamic literature but also the biographic field. His work consists of numerous issues in Islam. Whatever he has learned from Islam and the Sirah of Holy Prophet and thus concluded in the form of his own thoughts, he has expressed most of them in his famous five books for example ‘In Search of Muhammad’, ‘Muslims and Modernity’, ‘Studying Islam’, ‘Interpreting the Qur’an’, and ‘Victorian Images of Islam’ (doctoral thesis)’. This study focuses on Clinton Bennett’s work on Sirah specifically with his broader view of the subject. This research is descriptive and analytical in nature and presents a detailed analysis of the work it is based upon.

Isolation, Optimization and Characterization of Secondary Metabolites from Soil Borne Fungi Screlotium and Aspergillus Species

In the present dissertation, our research findings on the production of bioactive secondary metabolites by soil borne fungi are discussed. The application of microorganisms for the welfare of human beings is the main goal of biotechnology. In this study, two phytopathogenic fungi, Sclerotium rolfsii and Aspergillus flavus were isolated from soil samples collected from Malakand Division, Khyber Pakhtunkhwa, Pakistan. Growth parameters (nutrient media, temperature, pH, incubation period, and static/shaking intervals) were optimized for achieving maximum production of bioactive secondary metabolites. Five nutrient media were used for fungal growth. S. rolfsii produced maximum amounts of metabolites in Czapek yeast broth media (CYB), whereas maximum formation of metabolites by A. flavus was found in potato dextrose media (PDB). Furthermore, the crude secondary metabolites in ethyl acetate (EtOAc) and n-hexane extract obtained from each medium were screened for their activities against different pathogenic bacteria. The EtOAc and n-hexane fractions obtained from the CYB medium were more active against pathogenic bacteria as compared to the crude metabolites obtained from the other media in the case with S. rolfsii, whereas PDB was the media, in which A. flavus yielded the largest quantities of secondary metabolites, showed significant results against pathogenic bacteria. EtOAc and n-hexane fractions of both fungi were screened for their in vitro effects, including antifungal, phytotoxic, and insecticidal properties and brine shrimp lethality. The in vivo activities of the metabolites, such as acute toxicity, analgesic, and sedative action, were also studied. The results showed that the ethyl acetate (EtOAc) fraction was more active as compared to the n-hexane fraction due to the presence of polar constituents. The results obtained from the examinations of the biological activities indicated that both fungi produced bioactive secondary metabolites which have antimicrobial, phytotoxic, insecticidal, cytotoxic, analgesic, and sedative effects. The EtOAc fraction of S. rolfsii and A. flavus was significantly more active against carbonic anhydrase with IC50 values of 45.40 ±0.75 and 59.89 xx ±1.65, respectively. Similarly, the n-hexane fraction of both fungi also showed significant results against carbonic anhydrase (62.5 and 63% at 0.2 mg/mL, respectively) with IC50 values (45.40 ±0.75 and 61.3 ±1.75, correspondingly). The EtOAc and n-hexane fraction of both fungi exerted insignificant influence against urease. In short, the isolated crude metabolites exhibited remarkable inhibition activity against carbonic anhydrase. The bioactive EtOAc fraction of both fungi were further subjected to column chromatography (cc), which yielded one new and five known compounds. Their purity was confirmed by thin-layer chromatography. The structures of the isolated compounds were elucidated by using various modern spectroscopic analyses, including 1H-NMR, 13C-NMR, HMBC, and EI-MS spectra. One new and four known secondary metabolites were isolated from S. rolfsii and one known compound was isolated from A. flavus. The bioactive compounds isolated from S. rolfsii were: cinnamic acid (1), chlorogenic acid (2), Screlotiumol (3), o-coumaric acid (4), and gallic acid (5), whereas kojic acid (6) was isolated from A. flavus. Two compounds were obtained in high quantity, chlorogenic acid (2) and screlotiumol (3), and assessed for their effects on the reversion of multidrug resistant (MDR) mediated by P-glycoprotein (P-gp). In cancer cell lines, the multidrug resistant P-glycoprotein is a target for chemotherapeutic drugs. Both tested compounds showed an excellent MDR reversing impact against the mouse T-lymphoma cell line in a dose-dependent manner. Furthermore, compounds (2 and 3) were subject to molecular docking. Optimal effects of molecular docking were obtained by compounds (2 and 3) as compared to the standard treatment. Therefore, the preliminary results obtained in the present investigation indicate that these compounds could be used in the selection of potential targets for the treatment of cancer.