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The harmony between environment and buildings is the strongest point of vernacular architecture. In this context, the Mediterranean vernacular architecture is harmonized with its local context, including culture and traditions. In addition, it respects environmental and climatic factors, construction materials and morphology. In the past, people in Palestine built their houses according to their possibilities, needs, available materials, topography, and culture. Without any control from the government or any legal limitations or architects, it was people architecture, simple architecture. This paper discusses the differences between vernacular and contemporary cities of Palestine at the urban scale. The research methodology adopts explanatory qualitative analysis and comparative synthesis methods for both the old and the new area of the city of Nablus and considers many parameters of the cities such as the city layout, skyline, infrastructure and public spaces. The outcomes of this research allow understanding how the new city is far away from the sustainability principles and how the old city is closer to it and how the architects and stakeholders could learn from the strategies of vernacular architecture. The paper draws a set of recommendations for more in-depth studies, based on quantitative survey with energy efficiency measurements in the Mediterranean climate.

Energy harvesting from motion is presently receiving great worldwide attention as a means to power autonomous systems. Conventional linear vibration energy harvesters are usually designed to be resonantly tuned to the ambient dominant frequency. They have a narrow operating bandwidth that limits their application in real-world environments where the ambient vibrations have their energy distributed over a wide spectrum of frequencies, with significant predominance of low frequency components and frequency tuning is not always possible due to geometrical/dynamical constraints.

The access to modern energy services are deeply embedded in most aspects of the economic, social, and environmental dimensions of human development. In Mozambique, just a small fraction of the rural population has access to electricity, as the electrification process so far has relied on a leastcost approach, only inciting the development and extension of the national grid. As the population of rural off-grid communities are often highly dispersed, having low purchasing power, low technical skill etc., keeping current unilateral electrification approach, will mean that the many isolated communities will be left in the dark in the many years to come. This therefore calls forward the need to apprehend other approaches to make electricity accessible in the rural off-grid areas of Mozambique. In present thesis the opportunities and constraints of providing electricity to rural offgrid areas are assessed. Meeting the potential of the rural off-grid challenge, which Mozambique currently faces, takes outset in the establishment of community-based electrification pilot projects.

Photovoltaic (PV) technology needs higher performance - lower cost materials and structures in order to catch the grid parity and become an everyday use power source. The most commonly used material in PV, crystalline silicon, suffers from low absorption due to its indirect band gap nature. In order to overcome this problem, several light trapping structures have been used that increase the path length of photons inside the absorbing body of the device. However, conventional light trapping schemes cannot be applicable to new device concepts based on thin crystalline or diamond cut wafers. Metal assisted etching (MAE) is promising method to form micro and nano structures on the surface of the silicon wafer for optical management. As a top down method, it allows the control of the type and concentration of the dopants, material quality and crystal structure of the starting material. In addition, as a solution based method, it can be adapted to large scale industrial applications where nanoscale structuring can contribute to the development of high performing devices. A variety of structures vi having desired geometry such as nanowires, nano-cones, micro-rods, etc., ranging from nanometer to micrometer sizes with random or periodic distribution can be obtained via MAE by adjusting process parameters comprised of initial geometry of catalytic metal species, acid concentration, oxidative concentration, and temperature, ambient light, etching duration, substrate resistivity and orientation. In this study, MAE has been used to texture mono and multi crystalline silicon solar cells. Mono and multi crystalline Si solar cells with nano-wire texturing have been fabricated with Ag assisted electroless etching. After observation of poor efficiency despite very good optical performance, MAE with additional nitric acid (HNO3) as an oxidative agent has been optimized to control surface structures and reflection. Applicability of this new chemical at various conditions that simulate industrial production environment was proven. Optimized recipe has been applied to mono and multi crystalline Si solar cells to prove the effectiveness of the method for both wafer types. In the end, together with necessary optimizations of cell production steps, enhancement of jSC and efficiency has been attained for both cases. This concludes that the new MAE method based on a new chemistry offers a promising alternative to conventional texturing methods for today's and future technology. Şebeke değerini yakalamak ve günlük kullanıma uygun bir güç kaynağı haline gelebilmek için, fotovoltaik (FV) teknolojisi, daha yüksek performanslı ve daha ucuz malzemelere ve yapılara ihtiyaç duymaktadır. FV'de en yaygın kullanılan malzeme olan kristal silisyum, dolaylı bant yapısı nedeniyle düşük ışık emilimi problemiyle karşılaşmaktadır. Bu problemi çözmek için, fotonların kristal içinde aldığı yolu artıran çeşitli `ışık hapsetme` yapıları kullanılmaktadır. Fakat yeni nesil ince ve elmas kesimli dilimlerde, geleneksel ışık hapsetme yöntemleri kullanılamamaktadır. Metal destekli aşındırma (MDA), silisyum dilimlerde optik kontrol amaçlı mikro ve nano boyutlu yapılar oluşturmak için gelecek vaat eden bir yöntemdir. Yukardan aşağı bir yöntem olarak, katkılama miktarını ve tipini, malzeme kalitesini ve kristal yapısını, kontrol edilebilmesini olanaklı kılar. Bununla birlikte, çözelti temelli bir yöntem olduğu için, nano boyutta yapıların yüksek performanslı aygıtlar oluşturulasında viii kullanılabileceği durumlarda, büyük ölçekli endüstriyel uygulamalara adapte edilebilir. MDA kullanarak ve başlangıç katalizör metal geometrisi, asit konsantrasyonu, oksitleyici konsantrasyonu, sıcaklık, ışık şiddeti, aşındırma süresi, alt taş direnci ve yönelimi gibi süreç parametrelerini ayarlayarak, nanometre' den mikro metre boyutlarına kadar değişen, nano-tel, nano-koni, mikro-teller vb. gibi farklı geometrideki yapılar oluşturulabilir. Bu çalışmada, mono ve multi kristal silisyum güneş hücrelerinin yüzey yapılandırması için MDA yöntemi kullanılmıştır. Gümüş destekli aşındırma yöntemi ile mono ve multi kristal, nano-tel yapılandırmalı hücreler üretilmiştir. Yüksek optik performansa rağmen, düşük hücre verimleri elde edildiği için, kimyasal aşındırma yöntemi, yüzey yapılarını ve yansımayı kontrol etmek amacıyla nitrik asit (HNO3) eklenerek optimize edilmiştir. Yöntemin farklı endüstriyel uygulamalara yatkınlığı test edilmiştir. Optimize edilmiş reçete, mono ve multi kristal Si güneş hücrelerine uygulanmıştır. Sonuç olarak, hücre üretiminde yapılan çeşitli optimizasyonlar ile birlikte, akım yoğunluğu ve verim değerlerinde artış gözlemlenmiştir. Böylece, çalışılan yöntemin, bugünün ve geleceğin FV teknolojisi için geleneksel yapılandırma işlemlerine bir alternatif olarak gelecek vaat ettiği gözlemlenmiştir. 157

Ultra-high performance concrete (UHPC) is a new generation of advanced cementitious materials with superior mechanical properties that far surpass conventional concrete. However, UHPC is expensive and proprietary, and only a few field producers are available commercially in the United States. Moreover, its tensile behavior has not been well understood. This research aims to develop, characterize and model UHPC, specifically for its tensile behavior. ; Two viable UHPC mixes produced with locally available materials are developed, and they exhibit comparable mechanical properties to those of commercial products. An effective specimen for direct tension test (DTT) is designed and then used to evaluate both the short- and long-term tensile behavior of UHPC. The extended freeze-thaw actions have obvious impact on the tensile responses of UHPC, particularly over the post-cracking period, and the energy-based evaluation approach from DTT is more critical than the modulus-based approach to screen and evaluate material deterioration over freeze-thaw period. ; An analytical model is proposed to predict the tensile responses of UHPC from the bridging behavior of matrix and fibers. A fiber reinforcement efficiency function is derived to characterize the combined effects of fiber orientation, fiber snubbing and matrix spalling on the tensile behavior of UHPC. The fiber geometry and volume fraction, interfacial bond strength, and fiber reinforcement efficiency pronouncedly govern the tensile strength and hardening behavior of UHPC. The prediction capability of the analytical model is greatly improved by adjusting some coefficients that govern the hardening and softening branches of tensile stress-crack width curves. This model can effectively predict the tensile behavior of UHPC and its deterioration effect due to freeze-thaw actions. ; The non-contacted lap-splice pullout test is conducted to investigate the bond behavior of rebar in UHPC. The adopted analytical model can predict the bond stress-slip relation accurately. The ...

Transition is an important phenomenon in large scale, commercial, wind tunnel testing at low speeds because it is an excellent indicator of an airfoil performance. It is difficult to estimate transition through numerical techniques because of the complex nature of viscous flow. Therefore experimental techniques can be essential. Over the transition region the rate of heat transfer shows significant increases which can be detected using infrared thermography. This technique has been used predominantly at high speeds, on small models made of insulated materials, and for short test runs. Large scale testing has not been widely undertaken because the high sensitivity of transition to external factors makes it difficult to detect. The present study records the process undertaken to develop, implement and validate a transition detection system for continual use in the Virginia Tech Stability Wind Tunnel: a low speed, commercial wind tunnel where large, aluminium models are tested. The final system developed comprises of two high resolution FLIR A655sc infrared cameras; four 63.5-mm diameter circular windows; aluminium models covered in 0.8-mm silicone rubber insulation and a top layer of ConTact© paper; and a series of 25.4-mm wide rubber silicone fiberglass insulated heaters mounted inside the model and controlled externally by experimenters. This system produces images or videos of the model and the associated transition location, which is later extracted through image processing methods to give a final transition location in percentage chord. The system was validated using two DU96-W-180 airfoils of different chord lengths in the Virginia Tech Stability Wind Tunnel, each tested two months apart. The system proved to be robust and efficient, while not affecting the airfoil performance or any other system in use in the wind tunnel. Transition results produced by the system were compared to measurements obtained from pressure data and stethoscope tests as well as the numerical predictions of XFOIL. The transition results from all four methods showed excellent agreement with each other for the two models, for at least two Reynolds numbers and for several angles of attack on both suction and pressure side of the model. The agreement of data obtained under such different conditions and at different times suggests that the infrared thermography system efficiently and accurately detects transition for large aluminium models at low speeds. Master of Science