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Effect of Structural Dynamics Characteristics on Damage Tolerance of Crabon Fiber Sandwich Panels

Thesis Info

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Author

Waqas Anwar

Program

PhD

Institute

Institute of Space Technology

City

Islamabad

Province

Islamabad.

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Mechanical Engineering

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10832/1/Waqas%20Anwar_Mechanical%20Engg_2018_IST_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727742693

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The use of composite materials is rapidly growing in the construction of aerospace structures. Most of the aircraft parts made from composite materials, like wing skins, spoilers, fairings, and flight controls, are being used due to their reduced weight as compared to aluminum parts. New generation large commercial aircraft are being designed with all composite fuselage and wing structure. The main advantages of composites over conventional metallic materials are their high strength to weight ratio, corrosion resistance and tailored stiffness. Uni-directional composites have predominant mechanical properties in one direction and vary with the direction relative to the axis of structure. The aero-elastic properties, such as stiffness and dynamic stability, also depend on the stacking sequence of the plies. Fatigue and Damage Tolerance (F&DT) assessment of these advanced composite materials is an emerging field of research. In aircraft structural integrity analysis, the damage tolerance and fatigue life is investigated against a cyclic loading spectrum. The particular spectrum includes the stress/loading levels counted during a flight of certain duration. The occurrences of z-axis load factors ‘Nz’ may include higher gravitational acceleration ‘g’ levels. While maintaining a certain g level occurrence at higher angle of attack, wing structure vibrates with the amplitudes of its natural frequencies. The cyclic stress amplitudes of vibration depend upon the natural frequencies of vibrating structure, i.e. lower frequency gives higher amplitudes and vice versa. These fluctuating load amplitudes are superimposed on the higher ‘g’ level mean loads during fatigue analysis. These additional cycles are very critical in DTA studies.
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سیدہ آمنہ کی وفات

سیدہ آمنہؓ کی وفات
سیدہ آمنہؓ اپنے شوہر کی وفات کے بعد ان کی قبر کی زیارت کے لیے نہیں جا سکی تھی ۔ اب انہیں موقع ہاتھ لگا تو اپنے لخت جگر کو جن کی عمر چھ سال کے لگ بھگ تھی اور ام ایمن کو ساتھ لیے شوہر کے مزار پر حاضری دینے کے لیے سوئے مدینہ روانہ ہوئیں ۔ ایک ماہ قیام کرنے کے بعد واپسی کا راستہ لیا ۔ قدرت خدا کی دیکھیے کہ راستے میں بیمار ہوئیں اور ابواء کے مقام پر پہنچیں تو ان کا آخری وقت قریب آ گیا اور وفات پا گئیں ابواء کے مقام پر دفن کر کے ام ایمن سیدالصادقین ﷺ کو لے کر مکہ آئیں اور عبدالمطلب کو اس واقعہ سے آگاہ کیا آپ کو بہت دکھ ہوا ‘ولادت سے پہلے باپ چل بسا اور اب والدہ بھی اللہ کو پیاری ہوگئیں اس حال میں یتیم پوتے کو سینے سے لگا کر رو پڑے انہوں نے آپ ﷺکو اپنی کفالت میں لے لیا اور والدین کی کمی محسوس نہ ہونے دی ۔
اہم نکتہ: بعض سیرت نگاروں نے لکھا ہے کہ سیدہ آمنہ ؓمدینہ میں اپنے رشتے داروں کو ملنے گئی تھیں یہ بعید از قیاس ہے کیونکہ سیدہ آمنہ کی اپنی ذاتی رشتہ داری نہ تھی ۔ اگر یہ بات کہی جاتی کہ سیدہ آمنہؓ اپنے سسرال کے رشتہ داروں سے اپنے نور نظر کی شناسائی کے لیے تشریف لے گئی تھیں تو بجا ہوتا کیونکہ وہ سسرالی رشتہ دار تھے اور سسرال کی ننھیال بہت دور کی رشتہ داری کی بات ہے اور علامہ شبلی کہتے ہیں کہ میرے نزدیک بعض مورخین کا یہ بیان درست ہے کہ حضرت آمنہ ؓاپنے شوہر کی قبر کی زیارت کے لیے گئی تھیں جو مدینہ میں مدفون تھے بعض مورخین نے لکھا ہے کہ آمنہ...

Performance of Banking Industry After Privatization in Pakistan: A Case Study of Mcb Bank Limited

This research work aims to investigate the impact of privatization on the performing efficiency of MCB Bank Limited Privatization and the phenomenon of denationalization after the failure of socialism and communism globally. As the direction of enteritis was predetermined by state which in long term affected the performance of state-owned entities on many fronts even they reached at the verge of collapse and state was compelled to inject capital for their survival. Ultimately the state took drastic steps and initiated the process of denationalization and privatization to keep the industry intact in the changed scenario. In 1974, during Z.A. Bhutto regime Pakistan’s banking industry was nationalized with prime objective to address the issues of backward segments of economy but unfortunately after privatization industry was used for political motives and witnessed poor performance and financial indiscipline due to frequent interference in the affairs of banks particularly in lending activities and hiring of inefficient human resources. Resultantly banks failed to deliver as per expectation of masses and could not deliver quality customer services on one hand and accumulation of infected portfolio on the other which in turn swallowed the profitability and the capital of banks. It is revealed that bank has tremendously performed in all Key Performing Indicators, it has improved its profitability manifold, deposit base is significantly enhanced and became more liquid and solvent.

Solubility Enhancement, Formulation Development, Characterization and Ivivc of Sustained Release Tablet of Ketoprofen

Ketoprofen granules were prepared by a relatively newer method, namely surfactant assisted wet granulation (SAWG) approach using different concentrations (1-5%) of Soluplus®, polyethylene glycol (PEG) 6000, PEG 4000, poloxamers L6200 and L3100. The developed granule formulations were characterized for physicochemical and dissolution characteristics. FTIR examined for any drug-excipients interactions. Granule size, percent yield, bulk and tap density, Hausner’s ratio, and angle of repose of granules were found to be 571 ±0.81 µm, 93.1 ±0.84 %, 0.223 ± 0.01g/ml, 0.231 ± 0.002 g/ml, 1.098 ± 0.005, 33.81 ± 0.23º, respectively. Granules with 1% Soluplus® revealed highest solubility (3.09 mg/ml), but with 58.3% ketoprofen release until 12 h. Granules containing 5% PEG-6K demonstrated improved solubility of ketoprofen as compared to pure drug, i.e. 2.81 mg/ml vs 0.010 mg/ml. This increase in solubility was observed to be due to micellar solubilization, complex formation, or hydrogen bonding, which was supported by FTIR. All the formulations exhibited release comparable to that of USP-stipulated sustained release pattern following Weibull model (β=1.08) and showing erosion-controlled release. FTIR indicated no chemical interaction between ketoprofen and excipient in granule formulation. The SAWG successfully ameliorated ketoprofen solubility and sustained its release as well. To develop the single unit dose to achieve the better bioavailability of sustained release ketoprofen granules, matrix tablets were prepared using the defined concentration, i.e., 1%, 3% and 5% of Soluplus®, PEG-6K, PEG-4K, L6200 and L3100. The prepared ketoprofen tablets were characterized for physicochemical, in vitro dissolution, FTIR and in-vivo (human pharmacokinetic study) parameters. FTIR studies were carried out to ensure any possible ii interactions among active and other excipients. Friability, thickness, hardness, weight variation, drug content and swelling index were found to be 0.14%, 4.77mm, 7.5 kgcm-1, 401mg, 99.95% and 29.38% respectively. In-vitro dissolution revealed 60-102% release till 8h. MT2, MT13 depicted the ideal sustained release pattern till 8h, i.e., > 80% which was fitted to Weibull release model with ß value 2.57 and 1.06 respectively, indicating the complex release mechanism. FTIR evident the compatibilities of drug-excipient during compression. A tablet formulation with similar profile to that of the sustained release, MT2 was selected for pharmacokinetic study. MT16 was also selected as a control for PK parameters evaluation. MT16 promptly attained the plasma peak within 1h after administration and followed a rapid exponential decrease till 12h. MT2 as a sustained release tablet showed delayed peak plasma concentration which was maintained above 0.7-1.0 µg.ml 1 till 24h with a gradual decline. The maximum plasma concentration (Cmax) resulting from administration of 200 mg of MT2 was statistically lower than that of the MT16 (5.19 ± 0.66 vs 9.62±0.76 µg.ml-1, P<0.05). The time to reach Cmax (Tmax) from MT2 was delayed to 5.56±0.30 h as compared to 1.15±0.11 h of MT16. The AUC0-∞, 78.65±7.64 µg.h.ml-1, of MT2 was higher than 34.39±3.06 µg.h.ml-1 of MT16. Considering MT2 as Test and MT16 as Reference formulation, the relative bioavailability was found to be 228.89±12.578%. Clearance of drug was observed to be declined for MT2 compared to MT16 (5.855±0.539 to 2.561±0.235 L/h), a reason for sustaining drug concentration in blood beyond 24 h instead of 12 h for MT16. The delayed Tmax, decreased Cmax, increased AUC and decreased ClT, MT2 exhibited an in-vivo behavior corresponding to the sustained drug delivery system. MT2 sustained release matrix tablets depicted the therapeutic ketoprofen plasma level effectively even beyond 24h. Thus, there is a likelihood of administration of once-a-day single dose without plasma fluctuations which were expected from the administration of two doses in a day of MT16. The in-vitro characteristics, i.e., the dissolution of MT2 were predictive of the iii in-vivo profile of the drug. The IVIVC evaluation indicated a good correlation for the drug releases in-vitro and absorbed in-vivo at predicated time intervals. The SAWG successfully helped developing the swellable-erodible sustained release matrix tablet formulation of ketoprofen with desired in-vitro, biopharmaceutical and pharmacokinetics properties without incorporation of any special ingredients or major manipulation of the formulation ingredients. The desired features in the present dosage form were accomplished just by surfactant-assisted granulation, thus SAWG was regarded as the simpler approach.