FDTD Analysis of Plasmonic and Nanojet Enhanced Photodetectors for Improved Performance

The finite-difference time-domain (FDTD) technique is a very flexible and robust means to solve problems spanning a broad range of applications (defense, communication, computing, semiconductor devices and biomedicine), especially where geometrical complexities, nonlinearities and multiphysics dominate. In this thesis, novel photodetectors are developed via FDTD having sub-wavelength active areas that yield enhanced optical absorption at near-infrared (NIR) wavelengths by way of plasmonics or photonic nanojets. The response time of photodiodes is primarily limited by two factors: (1) the transit time of photo-generated carriers to the electrode and (2) depletion layer capacitance of the semiconductor. The former requires a thinner depletion layer, resulting in a large depletion layer capacitance. To suppress the increase of the depletion layer capacitance, it is necessary to decrease the active area of the photodiode with depletion layer thickness. However, the smaller the active area the lower the output of the photodiode under the constant optical power density. To overcome the trade-off between speed and responsivity, the incident light should be efficiently confined within a small active area. Surface plasmons play an important role in this phenomenon as surface plasmons can enhance the near-field when excited by a certain wavelength. Resonant surface plasmons can confine strong optical near fields in a sub wavelength volume, this has been demonstrated for near- infrared dipole antennas. As an alternative to plasmonics it is proposed here that photonic nanojets may be employed to focus light onto the small active region of a photodetector. A photonic nanojet is a narrow, high-intensity electromagnetic beam that propagates into the background medium from the shadow side surface of a plane-wave illuminated loss-less dielectric micro-cylinder or micro-sphere of diameter greater than the illuminating wavelength, λ. The transverse beam width of the nanojet can be as small as λ/3 and length can be as long as 20λ, so we can use a photonic nanojet to concentrate the energy into a small region. By using the E-field enhancement in a sub-wavelength active area provided by the photonic nanojet and comparing it with the enhancement of the plasmonic structures, we may improve the responsivity and speed of the photodetector

Stress analysis of corner welded joints structure by modern numerical-experimental approach

Otvoreni i zatvoreni tankozidi preseci imaju široku primenu u industrijskim aplikacijama za dizajn mnogih mašina i strukturnih komponenti. Ove komponente su često fabrikovane zavarivanjem, a ne livenjem ili kovanjem. Tankozidi profili su obično povezani pomoću ugaonih zavarenih spojeva. Takvi spojevi su takođe korišćeni u drugim inženjerskim aplikacijama kao što su građevinske mašine, mostovi, ramovi, šasije vozila i dr.. U ovoj disertaciji ponašanje zatvorenih profila (kutija, okrugla cev) i otvoreniih profila (L, Z, C i K profili) šavnih profila, proučavani su tako što su izlagani statičkim opterećenjima i numeričko-eksperimentalnim pristupom. Sa tačke gledišta strukturne analize, uprkos široko rasprostranjenim ugaono zavarenim spojevima koji efikasno nose opterećenja na elementima, ne postoji praktičan, jednostavan i precizan pristup za njihov dizajn i analizu. U tu svrhu , inženjeri često moraju pripremiti relativno komplikovan model konačnih elemenata ploče ili zapremine. To je zato što navedeni eleementi izloženi opštim opterećenjima proizvode koncentracije napona u blizini spojeva. Jedan od doprinosa ovog istraživanja je bolje razumevanje ponašanja ugaono zavarenih spojeva izloženi naprezanju savijanja i naprezanja savjanja sa uvijanjem. Primena metode konačnih elemenata predstavlja osnovni numerički pristup. Posmatrani profili su medelilrani različitim konačnim elementima (greda, ploča i zapremina) i sa različitim slučajevima opterećenja. Primećuje se da na kratkom rastojanju od spoja putem ugaono zavarenih spojeva struktura nosećeg elementa pod izloženim opterećenjem ponaša se kao greda. Zavareni spojevi su generisani različitim tehnikama modelrianja sa primenom različitih tipova i veličina konačnih elemenata elemenata. Kompletni rezultati deformacija su, takođe, eksperimentalno dobijeni pomoću tehnike primene korelacije digitalne slike (DIC). Eksperimentalni testovi se izvode za proveru numeričkih simulacija u cilju ispitivanja mehaničkih performansi zavarenh spojeva izloženi kombinovanim opterećenjima. Rezultati numeričkog prroačuna pokazuju dobro slaganje sa eksperimentalnim rezultatom .Hollow and non hollow section members are widely used in industrial applications for the design of many machine and structural components. These components are often fabricated by welding rather than by casting or forging. For example, in agricultural machinery, the hollow tubes are typically connected together through welding to form a corner welded joints. Such joint connections are also employed in other engineering applications such as construction machinery, offshore structures, bridges, and vehicle frames. In this dissertation, the behavior of tubular (box and circle profile) and non tubular (L, Z, C and X profiles) joint connections profiles, subjected to static loads were studied both experimentally and numerically. From a structural analysis point of view, despite of the wide use of corner welded joints as efficient load carrying members, there is no available practical, simple and accurate approach for their design and analysis. For this purpose, engineers must often prepare relatively complicated and time consuming Finite Element models made up of shell or solid elements. This is because unlike solid-section members, when hollow section members are subjected to general loadings, they may experience severe deformations of their cross-sections that results in stress concentrations in the connection’s vicinity. One of the objectives/contributions of this research work is the better understanding of the behavior of the corner welded joint connections under out-of- plane bending and torsion loading conditions. Through a detailed Finite Element Analysis (FEA) using shell and solid elements, the stress distribution at the connection of the tubular and non tubular corner welded joints were obtained for different loading conditions. It is observed that at a short distance away from the connection of the corner welded joints, the structure behaves similar to beams when subjected to loadings. Finite element models with different modeling techniques and meshing with various size and types of elements were created and analyzed. The full displacement field results were obtained experimentally by using the digital image correlation (DIC) technique. Experimental tests were performed to validate numerical simulations in order to investigate the mechanical performance of a series of fillet-welded connections under combined loading. The full displacement field results show good agreement comparing with the experimental results..

Steroidal anti inflammatory drug betamethasone significantly alters level of striatal dopamine in a rat model of Parkinson’s disease

Many scientific efforts have been well done to investigate the effects of anti inflammatory agents on the degenerative brain diseases such as Parkinson’s (PD) or Alzheimer’s disease and their affiliated sings. Previously we showed the effectiveness of steroids on rigidity of PD and in the study for further mechanistic investigation of that observation the microdialysis technique was employed to determine the striatal dopamine changes in parkinsonian rats after administration of betamethasone (0.12, 0.24 mg/kg) respectively. Our findings showed us the significant increase in the striatal dopaminergic neurotransmission (P<0.05) after administration of betamethasone comparing to the controls. These observations suggest a new mechanism for betamethasone on striatum dopaminergic neurotransmission leading us to gather further evidence about effectiveness of betamethasone in PD

Bangladesh Perspective: Vehicle Speed Proposition System using Localized Wireless Identification

Even in the era of advanced engineering, road accident has been a regular phenomenon causing death of many people in Bangladesh due to over speeding action of reckless drivers. There are several key places (such as schools, colleges, hospitals, highways and constructional areas etc.) where the speed of the vehicle should be lessened to avoid accidents. The roads and highways authority may place the speed limiter signboards in these areas to avoid these accidents, but these are frequently overlooked by the drivers. So this paper demonstrates a wireless forewarning system which will aid to control the speed of the vehicles at speed restricted areas. The whole system is established on the basis of radio frequency (RF) communication. There are two parts of this system named as transmitting unit and receiving unit. Each RF transmitter positioned on the roadside will be transmitting the code signal continuously. Whenever the vehicle enters the range of transmission, the RF receiver which is attached in the vehicle, will receive the signal and will display the information in a LCD monitor by notifying the driver to reduce the speed while going through that area

Work Function Tuning in Sub-20nm Titanium Nitride (TiN) Metal Gate: Mechanism and Engineering

Scaling of transistors (the building blocks of modern information age) provides faster computation at the expense of excessive power dissipation. Thus to address these challenges, high-k/metal gate stack has been introduced in commercially available microprocessors from 2007. Since then titanium nitride (TiN) metal gate’s work function (Wf) tunability with its thickness (thickness increases, work function increases) is a well known phenomenon. Many hypotheses have been made over the years which include but not limited to: trap charge and metal gate nucleation, nitrogen concentration, microstructure agglomeration and global stress, metal oxide formation, and interfacial oxide thickness. However, clear contradictions exist in these assumptions. Also, nearly all these reports skipped a comprehensive approach to explain this complex paradigm. Therefore, in this work we first show a comprehensive physical investigation using transmission electron microcopy/electron energy loss spectroscopy (TEM/EELS), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS) to show replacement of oxygen by nitrogen in the metal/dielectric interface, formation of TiONx, reduction of Ti/N concentration and grain size increment happen with TiN thickness increment and thus may increase the work function. Then, using these finding, we experimentally show 100meV of work function modulation in 10nm TiN Metal-oxide-semiconductor capacitor by using low temperature oxygen annealing. A low thermal budget flow (replicating gate-last) shows similar work function boost up. Also, a work function modulation of 250meV has been possible using oxygen annealing and applying no thermal budget. On the other hand, etch-back of TiN layer can decrease the work function. Thus this study quantifies role of various factors in TiN work function tuning; it also reproduces the thickness varied TiN work function modulation in single thickness TiN thus reducing the burden of complex integration and gate stack etch; and finally it shows that in a low thermal budget flow, it is more effective to achieve higher work function

Seismic evaluation of existing arch dams and massed foundation effects

AbstractIn the present paper, the effects of a massed foundation on the nonlinear seismic response of an existing arch dam are investigated. A co-axial rotating smeared crack approach was used to model the nonlinear behavior of the mass concrete in a 3D space which is able to model cracking/crushing under static and dynamic conditions. The analysis also considered the opening/slipping of joints. The reservoir was assumed to be compressible and was modeled using the finite element method with the appropriate boundary conditions. The Dez arch dam was selected for the case study and excited by a maximum credible earthquake. It was found that assuming a massless foundation leads to the overestimation of the stresses within the dam body and causes many more crack profiles than the massed foundation model. As a result, in the case of a massed foundation, no numerical instability was found to exist during the analysis

Paradigm Shifts in the Characteristics of the Interior Architectural Space through Technology Perspective

خضع الفضاء المعماري لعدة تحولات في خصائصه الشكلية تتناسب مع التغيرات والمتطلبات البيئية والإجتماعية والسياسية.  ويظهر التغير مكانياً لدى الشعوب بتأثير الثقافات والخصائص المجتمعية المختلفة، وزمانياً عبر تعاقب العصور وما يلحق ذلك من تغير في العوامل آنفة الذكر. فكانت خصائص الفضاء الداخلي جزءا لا يتجزأ من خصائص الطرز والتوجهات المعمارية التي سادت في كل حقبة. ومما لا شك فيه أن للتكنولوجيا السائدة في كل عصر دور في تحقيق الأشكال المعمارية وبلورة الانموذج المعبّر عن خصائص العصر وفكره. وحيث أن العصر الحالي يشهد تحولا نحو تكنولوجيا الرقمنة، فبرزت من هنا مشكلة البحث في " عدم وضوح المعرفة حول مؤشرات التحول في نظم التكنولوجيا المؤثرة في خصائص الفضاء الداخلي عبر العصور، وصولا الى عصر تكنولوجيا الرقمنة.  وهدف البحث الى تقصي الملامح العامة لتحولات الانموذج في الفضاءات الداخلية من منظور المنظومة التكنولوجية، مفترضا "ان للفضاء المعماري الداخلي أنموذجاَ تُعرفه خصائص مشتركة عامة تُلازم المنظومة التكنلوجية السائدة للعصر، وتتغير هذه الخصائص بتغير هذه المنظومة (او الكيان التكنولوجي)." وللوصول الى هدفه اعتمد البحث منهجاً استكشافياً للفضاء المعماري الداخلي خلال الحقب التاريخية وعبر عرض الأمثلة المعبرة عن كل حقبة. واستلزم البحث تقديم قاعدة معرفية تتضمن تعريف مفهومي كل من الفضاء الداخلي والانموذج في العمارة، ثم تحديد مؤشرات منظومة تكنولوجيا العمارة التي تقرأ في خصائص الفضاء الداخلي والمؤثرة في بلورة ملامح الانموذج، ثم تثبيت التحولات المتتابعة لأنموذج الفضاء الداخلي في العصور التاريخية المتتابعة من خلال مؤشرات نظم التكنولوجيا وصولا الى خصائص الانموذج في عصر الرقمنة. ومن اهم النتائج التي توصل إليها البحث ان الفضاء الداخلي، ومن منظار التكنولوجيا، مر بثلاثة تحولات انموذجية رئيسة في خصائصه عبر العصور تمثلت بخصائص انموذج فضاءات ما قبل الحداثة، التي تميزت بوضوح الحدود وثقل الكتلة ومحدودية الارتباط بالخارج واعتماد مبادىء التناظر والمحورية. وخصائص انموذج فضاءات الحداثة وما بعدها، التي تميزت بوضوح الحدود مع إمكانية التمويه والتلاعب وتخفيف الثقل الكتلي لعناصر الفضاء وزيادة الانفتاح الى الخارج. والخروج عن مبادىء التناظر والمحورية الكلاسيكية. وخصائص انموذج فضاءات عصر الرقمنة التي تميزت بإمكانات إخفاء الحدود والخفة والشفافية والإنسيابية ووإلغاء الثقل الكتلي وتمفصل العناصر.The architectural space has undergone several Transformations in its formal characteristics in line with several factors such as environmental, social and political changes and demands. The spatial change appears by influence of different cultures and societal characteristics, and chronologically through the succession of ages and the consequent change in the factors mentioned above. The characteristic of internal space was an integral part of the characteristics of the styles and architectural trends that prevailed in each era. There is no doubt that the prevailing technology in every age had its role in shaping the architectural forms and crystallization of the paradigm that expresses the characteristics of the age and its concept. As the current era is witnessing a shift towards digitization technology, the research problem has emerged from the "The lack of knowledge in clarifying the indicators of the transformation of technology systems which affect the characteristics of the interior architectural space through the ages, up to the age of digitization technology".  Thus the aim of the research is to explore the general features the paradigm shifts in the interior architectural spaces through a technological system's perspective, assuming  that " the interior architectural space has paradigm defined by common characteristics associated with the prevailing technological system of its age, These characteristics undergo a change along with changing technological system (or technological entity)." To reach its aim, the research adopted an exploratory approach to the architectural interior spaces through the historical epochs and by illustrating examples representing each epoch. This was preceded by an introduction of the concepts of the interior architectural space and the paradigm in architecture, then identification of the indicators of the architecture technological system, which were to be observed in the characteristics of interior space at all historical epochs leading to the crystallization of the paradigmatic features. One of the most important findings of the research is that the interior architectural space has undergone three major paradigmatic shifts in its characteristics over the ages. They are; first, the pre-modern spaces paradigm, which had clearly marked boundaries, heavy mass weight, limited association with the outside, and the principles of symmetry and axiality. Second, the paradigmatic characteristics of Modernism spaces and beyond, which also had clear boundaries but with the possibility of camouflage and manipulation and reduction in the mass of the space elements as well as an increase of openness to the outside along with the Cancellation of the principles of classical symmetry and axiality. Finally, the interior space paradigm of the age of digitization, which is characterized by the possibilities of concealment of borders, in addition to lightness, transparency, smoothness and the fusion of elements with abolition of mass weight

Synthesis and Characterizationof Some New Phenolic Schiff Bases Derivatives

Starting from bis (4,4'-diamino phenoxy) ethan(1), a variety of phenolicschiff bases (methylolic, etheric, epoxy) derivatives have been synthesized. All proposed structure were supported by FTIR, 1H-NMR, 13C-NMR Elemental analysis, some derivatives evaluated by thermal analysis (TGA)