289 research outputs found
On the spatial and temporal coherence of wireless vehicular short range channels
No full textWe consider spatial and temporal coherence of the vehicle–to–vehicle (V2V) wireless communication channel with focus on a suburban residential highway. The dominant reflectors in such an environment are vehicles passing in the adjacent lane and houses
along the road. Instead of treating the reflectors as point targets, the V2V short range propagation environment requires partitioning of the illuminated reflector side into
sufficiently small tiles. The channel transfer function is obtained as a superposition of specular reflections from the tiles, the line–of–sight (LOS) component, and the ground reflection. The tile size is selected to ensure that the ratio of the tile area to the tile–to–receiver distance satisfies the far field conditions. The reflected power is described by the tile radar cross section (RCS). The bistatic physical optics RCS model is adapted to account for the tile’s orientation with respect to the ray geometry. We apply the superposition model to the numerical analysis of two general scenarios
for a 22MHz channel in the 2.4GHz band. The first scenario considers a single vehicle reflector passing in the lane adjacent to the V2V communication pair. Both the vector network analyzer (VNA) experiments and the tiling model analysis illustrate that repositioning of the reflector, the transmitter, or the receiver by a few centimeters results in change of the signal power by several decibels. The second scenario analysis characterizes the channel coherence statistics for the
suburban residential highway. We consider the V2V single lane LOS and non–LOS geometries, where in the latter the receiver is shadowed by a large vehicle. The reflectors are both houses and vehicles passing in the opposite direction. The measure of channel coherence is the normalized spatial covariance calculated by correlating transfer functions corresponding to feasible receiver position pairs and performing spatial smoothing. The area of feasible receiver positions is divided into contiguous squares
whose size ensures wide sense quasi–stationarity within the square. Irrespective of direction the correlation remains high and a typical sedan roof usually does not provide sufficient spacing to obtain average inter–antenna correlation lower than 0.5. The upper bound on coherence time extends over the transmission time of multiple packets for systems in the considered band, and does not allow for usable time diversity.Ph.D.Includes bibliographical referencesIncludes vitaby Haris Krem
Hypoxic conditions promote a proliferative, poorly differentiated phenotype in COPD lung tissue progenitor cells in vitro
No full textAcknowledgements The authors would like to acknowledge the support of the UHNM theatre staff, Dr. Sana Iftikhar and Dr. Daniel Gey van Pittius for their assistance in acquiring participant lung tissue. Funding Information: This work was supported by funding from the North Staffordshire Medical Institute 50th Anniversary Award and The Royal Society-Newton Mobility Grant. The authors would like to acknowledge the support of the UHNM theatre staff, Dr. Sana Iftikhar and Dr. Daniel Gey van Pittius for their assistance in acquiring participant lung tissue.Peer reviewe
FRICTION STIR WELDING OF TUBE-TO-TUBESHEET AND SPOT JOINTS FOR VIRGIN AND RECYCLED THERMOPLASTIC MATERIALS.
No full textThermoplastic materials are becoming popular, due to their chemically inert and anti-fouling properties, for use in industrial heat exchanger applications involving heating/cooling of highly reactive fluids like acids. A novel nonconventional joining framework, based on the friction stir welding (FSW) technique, is developed to create high-quality thermoplastic tube-to-tubesheet joints (TTJs). The proposed technique has applications in the thermoplastic shell-andtube heat exchanger and piping industries (as flange-to-pipe joints). The primary objective is to study the feasibility of the FSW technique for developing thermoplastic TTJs, followed by optimization of the process parameters and detailed material characterizations. This work used workpieces (tube, tubesheet) made of carbon black reinforced high-density polyethylene. The effect of different FSW parameters (dwell time, plunge depth, rotational speed, and tube protrusion) on the tube pull-out behavior was studied. The FSW technique showed capabilities at a wide range of operating conditions. The macroscopic and microscopic (SEM-based) fractographic studies suggest that the FSW joints can fail in a ductile, brittle, or mixed manner, depending on the FSW conditions used. The DSC results showed no significant crystallinity changes of the weld material. The TGA results showed no significant thermal degradation of the weld material. The FTIR analysis indicated possible oxidation of the weld material. The capability to form TTJs with high leak path, high load bearing capacity, and no significant material degradations makes the FSW technique suitable for thermoplastic shell-and-tube heat exchanger applications. Further, as a second objective, the effect of adhesive reinforcement and radial clearance (RC) on the development of FSW-based thermoplastic tube-to-tubesheet hybrid joints (TTHJs) was investigated. The FSW technique provides higher load bearing capacity (326 N (0.0 RC), 517 N (0.5 mm RC)) than adhesive joints (226 N (0.0 RC), 206 N (0.5 mm RC)). For 0.0 RC, the adhesive reinforcement improved the load bearing capacity of hybrid joints by 15.6% compared to FSW joints. On the contrary, for 0.5 mm RC, the adhesive reinforcement negatively impacted the load bearing capacity and reduced it by 40.6%. The FSW technique with 0.5 mm RC provided a higher leak path (along with a high load bearing capacity) of 77% remaining tubesheet thickness (\u3e tube thickness) compared to that of 46.6% (\u3c tube thickness) achieved at 0.0 RC. However, the adhesive reinforcement can enhance the leak path of 0.0 RC FSW joints to around 100% remaining tubesheet thickness (\u3e tube thickness) by introducing the adhesive material at the tube-sheet interface. There is also a real demand for sustainable lightweight thermoplastic structures (like thermoplastic heat exchangers) because of growing environmental concerns. One important solution is developing structures through recycled scrap/waste thermoplastic materials. As a third objective, the lap-joint configuration friction stir spot weldability of recycled thermoplastics was studied, to help with analyzing the potential of friction stir-based welding techniques towards developing these sustainable structures. The combined behavior of recycling-welding procedures is investigated, as they may cause degradations; to ensure that the base thermoplastic polymer\u27s chemical, thermal, and mechanical properties are retained. In this work, scrap laban bottles made from HDPE material are used. The highest lap-shear load of 1528 N was achieved at the optimum welding conditions of 1600 rpm rotational speed, 1 mm plunge depth, and 60 s dwell time. Fractographic studies (macroscopic and SEM-based) suggested four types of fracture morphologies depending on welding conditions used. The DSC results showed no significant differences in melting temperature and crystalline content of the polymeric material. The TGA tests showed no significant thermal degradations. The FTIR analysis of all the samples (bottle, recycled sheet, weld material) exhibited characteristic HDPE peaks. All these results suggest that combined welding-recycling processes had a minimal impact on the polymeric structure. Thus, friction stir spot welding (FSSW) technique joins recycled thermoplastic scrap/waste materials with high lap-shear load and without any significant polymer degradations
Explosive indentation study of B4C-TiAlx composites fabricated by the dipping exothermic reaction process
No full textThe aim of this study is to fabricate a high volume fraction B4C-reinforced intermetallic matrix composite by the dipping exothermic reaction process and investigate the shock impact damage response of composites by explosive indentation experiment. It has been shown that the final microstructure of the dipping exothermic reaction process-fabricated composite can be tailored by treatment of the constituent powders and post heat treatment. The hardness and impact damage resistance of the fabricated composites were evaluated.This work is supported by grants (No. N62649-03-0007) from AROFE(US Army
Research Office Far-East). The author thanks Drs. J. W. McCauley of ARL, Sean Yu and
R. Olesinskiof AROFE
Increasing the Performance of Passive Communication with Ambient Light
No full textMost wireless communication technologies have been using the Radio Frequency (RF) spectrum for decades. Due to the popularity of the Internet of Things (IoT), the RF spectrum has started to become densely populated. Researchers have begun to explore other bands of the electromagnetic spectrum that can be utilized as a communication media. One of the promising choices is the visible light spectrum.Visible Light Communication (VLC) refers to the wireless communication technology that utilizes the visible light spectrum. This spectrum is thousands of times wider than the Radio Frequency (RF) spectrum and is license-free. In VLC, data is transmitted by turning a light source on and off. However, not every light source can be controlled. Passive light sources such as the sun provide an immense amount of light that can be used for wireless communication if we can develop ways to modulate them. One of the researches that use ambient light to create a wireless link is LuxLink. LuxLink uses liquid crystal shutters to control passive light sources and provides low energy, reliable, and flicker-free (safe) communication. This thesis addresses several problems that the current LuxLink system has.We present LuxLink+, an extension of LuxLink that provides two main improvements. Firstly, the data rate of the system is relatively low (80~bps). To increase the data rate, we provide a thorough analysis of the system’s bandwidth. Afterward, we modify the modulation technique, which increases the data rate to 1000~bps at a range of 1.5~m.Secondly, the system has a static data rate, which means that the system cannot adapt its data rate to changes in the environment. We implement a rate adaptation algorithm that can change its data rate accordingly. LuxLink+ improves the average throughput of the system by up to 85 percent compared to LuxLink.Electrical Engineering | Embedded System
Performance investigation of an integrated wind energy system for co-generation of power and hydrogen
No full textIn this paper, a wind turbine energy system is integrated with a hydrogen fuel cell and proton exchange membrane electrolyzer to provide electricity and heat to a community of households. Different cases for varying wind speeds are taken into consideration. Wind turbines meet the electricity demand when there is sufficient wind speed available. During high wind speeds, the excess electricity generated is supplied to the electrolyzer to produce hydrogen which is stored in a storage tank. It is later utilized in the fuel cell to provide electricity during periods of low wind speeds to overcome the shortage of electricity supply. The fuel cell operates during high demand conditions and provides electricity and heat for the residential application. The overall efficiency of the system is calculated at different wind speeds. The overall energy and exergy efficiencies at a wind speed 5 m/s are then found to be 20.2% and 21.2% respectively
Multigeneration system exergy analysis and thermal management of an industrial glassmaking process linked with a Cu–Cl cycle for hydrogen production
No full textA multigeneration system for hydrogen production linked with a glassmaking process via thermal management is examined in this study. The exhaust gas is interconnected with a Rankine cycle and the copper-chlorine (Cu–Cl) cycle for hydrogen production. The present system consists of a steam Rankine cycle, Cu–Cl cycle with multistage compression, double-stage organic Rankine cycle, and multi-effect desalination system. A Cu–Cl cycle based on the four-step model is employed with the proposed system. The useful system outputs are electricity, hydrogen, and fresh water. The simulation software packages utilized in the analysis and modeling are Engineering Equation Solver and Aspen Plus. The energy efficiency of the overall system is 36.5% while 38.1% is the exergy efficiency. The parametric studies are conducted to investigate the system performance. In addition, the effects of exhaust gas variables, such as flow rate, temperature, and pressure are examined to investigate the system performance
Leadership strategies for embedding sustainability and resilience in organizations with an emphasis on sustainable energy
No full textEfficient strategies to embedding sustainability in an organization are frequently linked to effective leadership. By design, changes in direction within an organization may lead to alterations in commitment or perceived significance of sustainability in organizations. While some organizational leaders are interested in embedding sustainability within a structure, other leaders believe in leaving the legacy behind and permanently influencing sustainability efforts. To confirm or dispel the underscored notion of the importance of leadership in embedding sustainability in organizations, a qualitative methodology approach to interviews, document analyses, and literature review is utilized. The research inquiry includes in-person interviews with top city staff and elected officials in a large Midwestern city and a review of the internal documents and reports. The end goal of the research is an examination of the role both elected and appointed officials have in embedding sustainability within cities, and whether a change in leadership may have an impact on continuity of sustainability implementation and
long-term viability of such policies. The paper focuses on the application of sustainable energy policies within a local government organizational structure as a mean of constructing a better understanding of leadership on sustainability implementation and embedment. While the further inquiry is needed, the research points out that an active partnership between city managers, administrators, and elected officials must be in place to support integrating sustainability from within and that sustainability thrives where exhaustive leadership support such
initiatives and efforts.Journal ArticleFinal article publishe
Measuring the Sustainability Impact in Local Governments Using the Quadruple Bottom Line
No full textSustainability is utilized by cities to enable a multifaceted, cross-sectoral approach for the betterment of communities and operational efficiency of organizations. Using a case study of the medium size local government in the Midwest and the city’s application of sustainability planning, this article focuses on a development of an expanded definition of the bottom line and a nascent approach to measuring and tracking sustainability-related efforts. The research provides an overview of measuring sustainability adopted by this particular city, using the target-specific,extended quadruple bottom line approach. The method attempts to address economic vitality, environmental quality, social equity, and governmental accountability through governance. The use of the quadruple bottom line to measure sustainability is linked to its annual budget planning and investments in transformation-related initiatives. While such an approach to measuring sustainability progress is unique in the United States, a number of cities in Australia have also adopted the quadruple bottom line approach to measure sustainability. Lessons in reporting sustainability efforts using the quadruple bottom line, in the context of an efficient and effective service delivery, can be applied to other local governments.Journal ArticleFinal article publishe
Ljiljana Dobrovšak, Jews in Srijem, from immigration to the Holocaust, State Archives in Vukovar, Special Editions III., Vukovar, 2017, 376 pages.
No full textSredinom 2017. godine, Državni arhiv u Vukovaru objavio je knjigu o Židovima u Srijemu povjesničarke dr.sc. Ljiljane Dobrovšak. Autorica knjige Ljiljana Dobrovšak, viša je znanstvena suradnica sa Instituta društvenih znanosti „Ivo Pilar” iz Zagreba koja od završetka studija povijesti istražuje povijest Židova u Hrvatskoj od kraja 18. stoljeća pa sve do današnjih dana. Nakon što je 2013. objavila knjigu o Židovima u Osijeku, nastavila je istraživati povijest slavonskih i srijemskih židovskih zajednica, pa je kao rezultat njezinih dugogodišnjih istraživanja objavljena ova sveobuhvatna monografija. Knjiga „Židovi u Srijemu, Od doseljenja do Holokausta” na 376 stranica obrađuje povijest srijemskih židovskih zajednica na području danas srpskog i hrvatskog dijela Srijema (nekadašnje Srijemske županije). Iako autorica piše o židovskim zajednicama u cijelom Srijemu (Zemun, Petrovaradin, Šid, Ruma, Erdevik i Srijemska Mitrovica), te daje pregled njihove povijesti, osobiti naglasak stavila je na povijest Židova u Vukovaru i Iloku. Autorica se pri pisanju ove monografije koristila arhivskim izvorima kao i objavljenim i neobjavljenim znanstvenim i drugim dijelima, koje je znanstveno-analitičkom metodom analizirala, o čemu svjedoči bogata bibliografija na kraju knjige.In the middle of 2017, the State Archives in Vukovar published a book about the Jews in Srijem by the historian, PhD Ljiljana Dobrovšak. The author of the book, Ljiljana Dobrovšak, is a senior researcher at the "Ivo Pilar" Institute of Social Sciences from Zagreb, who has been researching the history of Jews in Croatia from the end of the 18th century until the present day since completing her studies in history. After publishing a book about the Jews in Osijek in 2013, she continued researching the history of the Slavonian and Srijem Jewish communities, and as a result of her long-term research, this comprehensive monograph was published. The 376-page book "Jews in Srijem, From Immigration to the Holocaust" deals with the history of the Jewish communities of Srijem in the area of today's Serbian and Croatian parts of Srijem (the former Srijem County). Although the author writes about the Jewish communities in the whole of Srijem (Zemun, Petrovaradin, Šid, Ruma, Erdevik and Srijemska Mitrovica) and gives an overview of their history, she places particular emphasis on the history of the Jews in Vukovar and Ilok. When writing this monograph, the author used archival sources as well as published and unpublished scientific and other works, which she analysed using the scientific-analytical method, as evidenced by the rich bibliography at the end of the book.Tema broja "Holokaust i restitucija u bivšoj Jugoslaviji: pravni i istorijski izazovi" (the issue's theme is "Holocaust and Restitution in the Former Yugoslavia: Legal and Historical Challenges")
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