Browsing by Subject "Hybrid"

Now showing 1 - 5 of 5

Open Access
60 GHz wireless data center networks: A survey
(Elsevier BV * North-Holland, 2021-02-11) Terzi, Çağlar; Körpeoğlu, İbrahim
Data centers (DCs) became an important part of computing today. A lot of services in Internet are run on DCs. Meanwhile a lot of research is done to tackle the challenges of high-performance and energy-efficient data center networking (DCN). Hot node congestion, cabling complexity/cost, and cooling cost are some of the important issues about data centers that need further investigation. Static and rigid topology in wired DCNs is an other issue that hinders flexibility. Use of wireless links for DCNs to eliminate these disadvantages is proposed and is an important research topic. In this paper, we review research studies in literature about the design of radio frequency (RF) based wireless data center networks. RF wireless DCNs can be grouped into two as hybrid (wireless and wired) and completely wireless data centers. We investigate both. We also compare wireless DCN solutions in the literature with respect to various aspects. Open areas and research ideas are also discussed.
Open Access
Micro tool design and fabrication: a review
(Elsevier, 2018) Oliaei, S. N. B.; Karpat, Yiğit; Davim, J. P.; Perveen, A.
Mechanical micromachining is considered as a cost-effective and efficient fabrication technique to produce three dimensional features and free-form surfaces from various engineering materials. Micro cutting tools are an essential part of mechanical micromachining and they are exposed to harsh conditions which reduces tool life and adversely affect the economics of the process. The challenge is therefore to maintain the tool rigidity and cutting edge sharpness for extended period of time. Thus, the design, fabrication and durability of micro cutting tools are of significant importance for successful micromachining operations. This review paper aims to provide a comprehensive understanding about the capabilities, characteristics, and limitations of different fabrication techniques used in the manufacturing of micro cutting tools. State-of-the-art micro cutting tool design and coating technology has been presented for various micromachining applications. Possible future research direction and development in the field of micro tool design and fabrication has also been discussed.
Open Access
On-Chip integration of functional hybrid materials and components in nanophotonics and optoelectronics
(John Wiley & Sons, 2011) Erdem, Talha; Demir, Hilmi Volkan; Singh, M.; Ohji, T.; Asthana, R.; Mathur, S.
Incorporation of custom - designed nanomaterial into nanophotonic devices and components in optoelectronic systems enables the realization of optical functionalities favorably controlled with external optical and electrical effects. To this end, innovative nanophotonic devices and optoelectronic systems are developed using multiple combinations of nanostructures (epitaxially grown, chemically synthesized, deposited, plated, etc.) that are embedded in hybrid architectures and on - chip integration of components for a variety of applications including light generation, displays, modulation, sensing, imaging, and communications in a wide spectral range from ultraviolet (UV) to visible to infrared.
Open Access
Retinotopic sensitisation to spatial scale: evidence for flexible spatial frequency processing in scene perception
(Elsevier Ltd., 2006) Ozgen, E.; Payne, H. E.; Sowden, P. T.; Schyns, P. G.
Observers can use spatial scale information flexibly depending on categorisation task and on their prior sensitisation. Here, we explore whether attentional modulation of spatial frequency processing at early stages of visual analysis may be responsible. In three experiments, we find that observers' perception of spatial frequency (SF) band-limited scene stimuli is determined by the SF content of images previously experienced at that location during a sensitisation phase. We conclude that these findings are consistent with the involvement of relatively early, retinotopically mapped, stages of visual analysis, supporting the attentional modulation of spatial frequency channels account of sensitisation effects.
Open Access
S-band GaN high power amplifier design and implementation
(2019-02) Kavuştu, Muhammet
High power RF Microwave amplifiers are becoming more important as the telecommunications, defense and aerospace industries' demands develop. GaN on SiC technology offers higher power and better form factors for these applications compared to GaAs. In addition, SiC provides better mechanical properties and thermal performance. Design, manufacturing and measurements of a S-Band Power Amplifier by using a GaN discrete bare die transistor are presented. GaN on SiC technology, fabrication process, amplifier fundamentals and design steps are explained in detail. PCB laminate properties, manufacturing, wire bonding and importance of heat management are explained. Design, tapeout, characterization of a fabricated HEMT and its packaging are also mentioned. Power amplifier's small-signal gain of 14.5 dB is measured at center frequency. 41.5 dBm RF power at P6dB is measured at 200 μs pulse width 10% duty cycle at 3 GHz, reaching a power density of 5:4W=mm. Small-signal gain, IP3 measurements under different biases, AMAM and AM-PM distortions are also investigated in detail. EM simulations are performed in Keysight ADS design environment. Amplifier design is based on small-signal and loadpull measurements. De-embedding of fixture effects during HEMT characterization and their models are also investigated. Another hybrid amplifier design by using a packaged commercial GaN on SiC bare die power HEMT is also presented. Small-signal and power measurements are also offered.