Effects of initial compression stress on wave propagation in carbon nanotubes

An analytical method to investigate wave propagation in single- and double- walled carbon nanotubes under initial compression stress is presented. The nanotube structures are treated within the multilayer thin shell approximation with the elastic properties taken to be those of the graphene sheet. The governing equations are derived based on Flugge equations of motion. Frequency equations of wave propagation in single and double wall carbon nanotubes are described through the effects of initial compression stress and van der Waals force. To show the effects of Initial compression stress on the wave propagation in nanotubes, the symmetrical mode can be analyzed based on the present elastic continuum model. It is shown that the wave speed are sensitive to the compression stress especially for the lower frequencies.Comment: 12 pages, 4 figure

Research and development of a high capacity, nonaqueous secondary battery Final report, Oct. 1964 - Dec. 1965

High capacity nonaqueous secondary batter

Research and development of a capacity nonaqueous secondary battery Fourth quarterly report, Jul. - Sep. 1965

High capacity nonaqueous secondary battery development - lithium deposition and cycling, ionic solvation, cathode construction and discharge efficiency, and solvent purificatio

Mobil haberleşme combo antenleri için genişband elektromanyetik sönümlendirici

Mobile network operators (MNOs) have to sustain the interworking of different generations of mobile technologies in different frequency bands. On the other hand, electromagnetic (EM) pollution, which is caused mainly by the mobile devices and mobile network base stations, also raises public health concerns. Thus, MNOs use combo antennas, which encapsulate multiple antenna rods in a single radome. In this study, the authors propose a broadband electromagnetic absorber for the mobile network base station (BS) combo antennas. They have merged the multi-layer Jaumann absorber (JA) and Salisbury screen principles along with the merits of off-the-shelf micrometric and millimetric graphite and nanometric carbon black. Advanced silver and nickel coated nanometric cenospheres were also used to decrease the absorber thickness and to improve EM scattering and absorption. And finally, silver fabric was used as the salisbury screen with novel perpendicular threads into the absorber body as heat sink. After the laboratory tests, the absorber has also been tested in the field. The application of the absorber has reduced the unwanted radio frequency (RF) signal around 18 dB in the tested frequency range without any network affecting disturbances or without any noticeable antenna pattern deformation with only a thickness of ninety millimeters. Such an absorber may also help containing the unwanted spread of electromagnetic waves from BS antennas; and, in return, decrease the overall mobile network RF noise and electromagnetic pollution both in uplink and downlink frequency bands.Mobil Şebeke İşletmecileri (MŞİ) farklı jenerasyon mobil teknolojilerinin farklı sıklık aralıklarında düzgün çalışmasını sağlamak zorundadırlar. Öte yandan, elektromanyetik (EM) kirlilik, ki daha çok mobil telefonlar ve mobil baz istasyonları tarafından kaynaklanır, toplumda sağlık kaygıları yaratmaktadır. Bu sebeple, MŞİler birçok anten çubuğunu tek bir radomeda saklayan combo antenleri kullanmaktadırlar. Bu çalışmada, araştırmacılar mobil şebeke baz istasyonu combo antenleri için genişband bir elektromanyetik sönümlendirici önermektedirler. Araştırmacılar bunun için çok katmanlı Jaumann sönümlendirme (JS) ve Salisbury ekranlama prensiplerini mikrometrik ve milimetrik grafit ve nonametrik karbon siyahı malzemeleri üzerine uygulamıştır. Buna ek olarak, ileri teknoloji gümüş ve nikel kaplanmış seramik kürecikler de sönümlendirici kalınlığını azaltmak üzere EM saçılımını arttırmak ve sönümlenmeyi iyileştirmek için kullanılmıştır. Son olarak, gümüş kaplı naylon kumaş da salisbury ekranlamasının en yenilikçi şekli ile sönümlendiriciye dik iplikçiklerle yerleştirilerek ısınma sorununu çözmüştür. Laboratuvar testlerinden sonra, sönümlendirici sahada test edilmiştir. Doksan milimetre kalınlığındaki bir sönümlendirici uygulaması istenmeyen radyo frekans (RF) sinyalini mobil şebekenin çalışmasını engellemeden ve anten yayınım şeklini değiştirmeden 18 dB azalmiştir. Bu tip bir sönümlendirici istenmeyen elektromanyetik dalgaların yayılmasını engellemeye yardımcı olabilir ve bütün mobil şebeke RF gürültüsünü ve EM kirliliğini her iki yayın yönünde de azaltabilir

Performance Analysis of Coherent and Noncoherent Modulation under I/Q Imbalance

In-phase/quadrature-phase Imbalance (IQI) is considered a major performance-limiting impairment in direct-conversion transceivers. Its effects become even more pronounced at higher carrier frequencies such as the millimeter-wave frequency bands being considered for 5G systems. In this paper, we quantify the effects of IQI on the performance of different modulation schemes under multipath fading channels. This is realized by developing a general framework for the symbol error rate (SER) analysis of coherent phase shift keying, noncoherent differential phase shift keying and noncoherent frequency shift keying under IQI effects. In this context, the moment generating function of the signal-to-interference-plus-noise-ratio is first derived for both single-carrier and multi-carrier systems suffering from transmitter (TX) IQI only, receiver (RX) IQI only and joint TX/RX IQI. Capitalizing on this, we derive analytic expressions for the SER of the different modulation schemes. These expressions are corroborated by comparisons with corresponding results from computer simulations and they provide insights into the dependence of IQI on the system parameters. We demonstrate that the effects of IQI differ considerably depending on the considered system as some cases of single-carrier transmission appear robust to IQI, whereas multi-carrier systems experiencing IQI at the RX require compensation in order to achieve a reliable communication link