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Design and Analysis of Metasurfaces for Polarization Conversion of Electromagnetic Waves

Thesis Info

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Author

Khan, Muhammad Ismail

Program

PhD

Institute

National University of Sciences & Technology

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Electrical Engineering

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/10762/1/Muhammad%20Ismail%20Khan_Ele_Eng_Com_Sci_2019_NUST_21.03.2019.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727725881

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Control and manipulation of polarization state of electromagnetic waves has always been of interest in the scientific community due to its fundamental role in wide range of applications including contrast imaging microscopy, optical sensing, molecular biotechnology and optical and microwave communication. Although, conventional techniques are applied for polarization control using natural materials such as optical activity of crystals, Faraday-effect and solutions of chiral molecules such as sugar. However, such methods generally result in bulky volumes, narrow bandwidth and incidence angle dependent response which greatly limit their use for many practical applications. Therefore, scientists have explored the use of artificial structures in the form of ultra-thin metasurfaces to achieve miniaturized polarization control devices with wide bandwidth and angularly stable response. However, most of these designs achieve polarization conversion for normal incidence only, which practically becomes prohibitive, as incoming waves can have arbitrary incidence angles. Thus, metasurfaces with stable response for arbitrary incidence angles are highly desirable. In this perspective, there are two main objectives of this research thesis: firstly, to realize wideband metasurfaces achieving polarization conversion both for normal as well oblique incidence and secondly, to design metasurfaces which can achieve multiple functionalities through a single structure. The first three metasurface designs presented in Section I achieve angularly stable (maximum up to 60o) wideband cross-polarization conversion in reflection mode. The cross-polarization conversion is achieved through anisotropy of the unit cell while the bandwidth is extended through multiple plasmonic resonances. Multifunctional metasurfaces are presented in Section II. These metasurfaces are extremely desirable in practical applications as they can replace multiple optical components, thus miniaturizing size and reducing the cost of the overall system. The first of the multifunctional metasurfaces presented in this thesis, not only transforms linear and circular polarization to their corresponding cross polarization, but also achieves linear-to-circular and circular-to-linear polarization conversion in different frequency regimes.Thus, it exhibits both half- and quarter-wave plate operations in different frequency bands using an ultra-thin bilayer anisotropic metasurface. The final design presented in this thesis is based on a flexible single layer anisotropic metasurface manifesting both quarter-wave plate and half-mirror (1:1 beam splitter) operation.
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سید مبارک شاہ کی ’’ ہم اپنی ذات کے کافر‘‘ پر طائرانہ نظر

سیّد مبارک شاہ کی

’’ ہم اپنی ذات کے کافر‘‘ پر طائرانہ نظر

سیّد مبارک شاہ کی پہلی کتاب ’’جنگل گمان کے‘‘ 1993ء میں منظر عام پر آئی اور اشاعت کے اولین ماہ میں ہی سٹالوں پر دستیاب نہ رہی۔دوسری کتاب 1995ء میں شائع ہوئی جبکہ تیسری کتاب ’’مدارنارسائی میں‘‘1998ء میں چھپ کر سامنے آئی۔تینوں کتابوں کو اہل ذوق محبت میں عجلت دکھاتے ہوئے۔دکانوں سے اپنی لائبریریوں میں اور اشعار کو اوراق سے اپنے دلوں میں منتقل کر لیا۔سیّد مبارک شاہ کی دوسری کتاب ’’ہم اپنی ذات کے کافر‘‘ 1995ء میں چھپ کر اہل ذوق سے داد وصول کر چکی ہے۔یہ کتاب آپ کی غزلوں اور نظموں پر مشتمل ہے۔اس مجموعہ کلام میں (48) غزلیں شامل ہیں۔ان غزلوں کا موضوعاتی جائزہ لینے سے پہلے غزل کی تعریف اور ارتقاء پر روشنی ڈالتا ہوں۔

عربی،فارسی،پنجابی اور اردو کی مشہور و مقبول صنف غزل ہے۔اس صنف میں اتنی دلکشی،جاذبیت اور کھچاؤ موجود ہیکہ ہر دور اور ہر طبقے کے دلوں کی دھڑکن بنی رہی اور زندگی کی رگوں میں خون بن کر دوڑتی رہی ہے۔لفظ ’’غزل‘‘ کے ماخذ کے بارے میں ماہرین زبان و ادب کے درمیان اختلاف رائے موجود ہے۔ایک گروہ کا خیال ہے کہ ’’غزل‘‘ عربی زبان کا لفظ ہے جس کے معنی اون کتنا،اون کو تار تار کر کے دھاگہ تیار کرنا کے ہیں۔(1)

جب کہ دوسرے گروہ کا نظریہ ہے کہ عورتوں کے ساتھ بات چیت کرنا،اْن کے حسن و عشق کے بارے میں باتیں کرنا۔

’’در لغت حدیث کردن بازناں ومعاشقہ با ایشاں است ومغازلہ نیز عشق بازی و محاولہ بازناں است، در اصطلاح عبارت است ازابیاتی چند بریک وزن و قافیہ کہ بشعر مشتمل بر مضامین معاشقہ و تصویر احوال عشاق وجمال مشعوق۔‘‘(2)

KEEFEKTIFAN PENGGUNAAN MEDIA FILM DALAM PEMBELAJARAN MENULIS TEKS CERPEN SISWA KELAS VII SMP NEGERI 34 MAKASSAR

The study aims at describing the effectiveness of the use of film media in learning to write short story of class VII students at SMPN 34 Makassar. The study is an experimental true design with posttest-only control design. The study was conducted at SMPN 34 Makassar. The populations of the study were 292 students of class VII. The samples were taken by employing simple random sampling and obtained class VII1 as the experiment class and class VII3 as the control class. Data collections were then analyzed using descriptive statistic analysis an inferential statistics analysis. The results of the study indicated that students’ ability at the experiment class that wrote short story by employing film media showed extremely sufficient result. Students who were able to abtain above the set KKM was 83, 3% or 25 students, and students who obtained below the set KKM was 16, 7% or 5 students. On the other hand, students’ ability at the control class that wrote short story by employing conventional media (pictures) showed sufficient result. Students who were able to abtain above the set KKM was 54, 8% or 17 students, and students who obtained below the set KKM was 45, 2% or 14 students. So, the results indicated that the use of film media is effective to be used in learning to write short story proved by the hypothesis test which used inferential statistic of independent sample test obtained the t score by 4,405 with the independent degree 59 at the level of significant p= 0,000 because α = 0, 05 > p = 0,000 so H0 hypothesis was rejected and H1 hypothesis was accepted. Suggestions based on the study are teachers should use variation, one of the examples is by using film media in learning to write short story. Students should be active to learn how to write and should have more practices in writing short story. Students should be active to learn how to write and should have more practices in writing short story. The researches should use this research as a reference to conduct further study with different learning strategy to obtain alternative of learning strategies.

Effects of Exercise on Electroencephalogram Parameters and Cognitive Functions in Mild Cognitive Impairment Patients

Mild cognitive impairment (MCI) is becoming an emerging problem for developing countries where there is increase in expected age. There is no specific therapeutic treatment for these patients. Evidence suggests that the combination of both exercise and physical activity has a greater effect on MCI patients, than exercise or physical activity alone. The objective of this study was to determine the short and long-term effects of aerobic exercise and Xbox 360 Kinect cognitive games on slowness, complexity, coherence in electroencephalography (EEG) signals, somatosensory evoke potentials (SEPs) and cognitive tests in MCI patients. A parallel group design study was conducted in the Pakistan Railways General Hospital, Rawalpindi. Patients were selected and randomly divided into Xbox 360 Kinect cognitive games group (n=22), aerobic exercise group (n=21), single session aerobic exercise group (n=14) and their respective control groups (n=22, n=22, n=14 respectively). The outcome measures were slowness, complexity coherence of EEG, SEPs and mini-mental state examination (MMSE), Montreal cognitive assessment scale (MoCA) and trail making test (TMT) A and B. EEG was recorded using the EMOTIV EPOC with 14 channels and Refa 72-channel stationary system. Patients were assessed before and after one session of intervention for short-term effects and after six weeks for long-term effects. After one session of aerobic exercise there were significant improvements in slowness (delta waves; 0.678+0.035 vs 0.791+0.033; p=0.015) and complexity (0.601+0.051 vs 0.470+0.042; p=0.027) of the EEG in aerobic exercise treated group as compared to no-aerobic exercise group. After six weeks there were significant xxii improvements in slowness (delta waves; 0.581+0.036 vs 0.815+0.025; p=0.005) and complexity (0.751+0.045 vs 0.533+0.046; p=0.001) of the EEG in the aerobic group as compared to no-aerobic group. Moreover, significant improvements were observed in the MMSE (p=0.032), MoCA (p=0.036), TMT-A (p=0.005) and TMT-B (p=0.007) in aerobic exercise group as compared to no-aerobic group. After one session of Xbox 360 Kinect cognitive games intervention, delta (0.704+0.025; p=0.013), theta (0.128+0.009; p=.0.00127) waves and complexity of EEG (0.642+0.042; p=0.008) significantly improved, in eyes closed state. Whereas after six weeks intervention of games, delta (0.673+0.029; p=0.013), theta (0.129+0.013; p=0.002), beta2 waves (0.044+0.009; p=0.046), complexity of EEG (0.051+0.042; p=0.016), MMSE (26.25+0.347vs 23.722+0.731; p=0.003), MoCA (25.65+0.310vs 22.00+0.504; p=0.0001), TMT-A (1.429+0.234vs 2.225+0.259; p=0.028) and TMT-B (2.393+0.201vs 3.780+0.195; p=0.0001) improved significantly. These changes were not observed in the control group. Upon comparison of aerobic exercise and Xbox 360 Kinetic cognition games, it was found that aerobic exercise has more short and long-term therapeutic effects on MCI patients as compared to Xbox 360 Kinect cognitive games group. Single session of aerobic exercise significantly decreased the inter-hemisphere coherence, however, it improved intrahemisphere coherence. After single session of aerobic exercise, there was significant decrease in peak amplitude of SEPs in MCI patients, however, no effect on SEPs peak latencies was found. This study suggests that aerobic exercise and Xbox 360 Kinetic cognitive games have dual/2-fold beneficial effect on age associated MCI. First one, the progression of MCI is slowed down significantly. Second, there is evidence of xxiii improvement in the cognitive state of MCI patients. Such intervention for treatment purpose could be helpful to rehabilitate MCI patients in third world countries.