| 1431. |
|
|
| 1432. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Bridging the Terahertz Gap: Photonics-assisted Free-Space Communications from the Submillimeter-Wave to the Mid-Infrared
- 2022
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; , s. 1-1
-
Tidskriftsartikel (refereegranskat)abstract
- Since about one and half centuries ago, at the dawn of modern communications, the radio and the optics have been two separate electromagnetic spectrum regions to carry data. Differentiated by their generation/detection methods and propagation properties, the two paths have evolved almost independently until today. The optical technologies dominate the long-distance and high-speed terrestrial wireline communications through fiber-optic telecom systems, whereas the radio technologies have mainly dominated the short- to medium-range wireless scenarios. Now, these two separate counterparts are both facing a sign of saturation in their respective roadmap horizons, particularly in the segment of free-space communications. The optical technologies are extending into the mid-wave and long-wave infrared (MWIR and LWIR) regimes to achieve better propagation performance through the dynamic atmospheric channels. Radio technologies strive for higher frequencies like the millimeter-wave (MMW) and sub-terahertz (sub-THz) to gain broader bandwidth. The boundary between the two is becoming blurred and intercrossed. During the past few years, we witnessed technological breakthroughs in free-space transmission supporting very high data rates, many achieved with the assistance of photonics. This paper focuses on such photonics-assisted free-space communication technologies in both the lower and upper sides of the THz gap and provides a detailed review of recent research and development activities on some of the key enabling technologies. Our recent experimental demonstrations of high-speed free-space transmissions in both frequency regions are also presented as examples to show the system requirements for device characteristics and digital signal processing (DSP) performance.
|
|
| 1433. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Direct Modulation and Free-Space Transmissions of up to 6 Gbps Multilevel Signals With a 4.65-μQuantum Cascade Laser at Room Temperature
- 2022
-
Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers Inc.. - 0733-8724 .- 1558-2213. ; 40:8, s. 2370-2377
-
Tidskriftsartikel (refereegranskat)abstract
- A roadmap for future wireless communications is expected to exploit all transmission-suitable spectrum bands, from the microwave to the optical frequencies, to support orders of magnitude faster data transfer with much lower latency than the deployed solutions nowadays. The currently under-exploited mid-infrared (mid-IR) spectrum is an essential building block for such an envisioned all-spectra wireless communication paradigm. Free-space optical (FSO) communications in the mid-IR region have recently attracted great interest due to their intrinsic merits of low propagation loss and high tolerance of atmospheric perturbations. Future development of viable mid-IR FSO transceivers requires a semiconductor source to fulfill the high bandwidth, low energy consumption, and small footprint requirements. In this context, quantum cascade laser (QCL) appears as a promisingtechnological choice. In this work, we present an experimental demonstration of a mid-IR FSO link enabled by a 4.65-μm directly modulated (DM) QCL operating at room temperature. We achieve a transmission data rate of up to 6 Gbps over a 0.5-m link distance. This achievement is enabled by system-level characterization and optimization of transmitter and receiver power level and frequency response and assisted with advanced modulation and digital signal processing (DSP) techniques. This work pushes the QCL-based FSO technology one step closer to practical terrestrial applications, such as the fixed wireless access and the wireless mobile backhaul. Such a QCL-based solution offers a promising way towards the futuristic all-spectra wireless communication paradigm by potentially supporting the whole spectrum from the MIR to the terahertz (THz).
|
|
| 1434. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Directly modulated quantum cascade laser and its application in free-space communications
- 2021
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 9781510646377
-
Konferensbidrag (refereegranskat)abstract
- In this report, we summarize our recent achievements in free-space communications in the mid-infrared (MIR) region enabled by directly modulated quantum cascaded laser (QCL) at 4.65 μm (∼65 THz). We have experimentally demonstrated a multigigabit free-space transmission link in the lab environment with the QCL operating at room temperature. The QCL chip is mounted on a commercial QCL mount with a water-cooled Peltier element. Multilevel modulation formats at different baud rates are generated and combined with the laser driving current at a custom-made bias-Tee to drive and modulate the QCL. A commercial mercury cadmium telluride (MCT, HgCdTe) photovoltaic (PV) MIR detector with a built-in trans-impedance amplifier was used to receive the MIR free-space signal. With the receiver to be the bottleneck of the system bandwidth, the end-To-end 3-dB bandwidth was measured to be around 320 MHz, and the 6-dB bandwidth was around 450 MHz. We have successfully demonstrated up to 6 Gbps free space transmission with multilevel modulation formats, assisted with effective digital equalization techniques despite the limited bandwidth..
|
|
| 1435. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Free Space Communication Enabled by Directly Modulated Quantum Cascade Laser
- 2024
-
Ingår i: <em>2024 Optical Fiber Communications Conference and Exhibition, OFC 2024 - Proceedings</em>. - : Institute of Electrical and Electronics Engineers Inc..
-
Konferensbidrag (refereegranskat)abstract
- We summarize our recent experimental studies of free-space communications enabled by directly modulated quantum cascade lasers at both MWIR and LWIR regions. Different detector types with different characteristics are compared.
|
|
| 1436. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Free-Space Transmissions in the Upper- and Lower-THz Bands Assisted with Photonics
- 2021
-
Ingår i: 2021 European Conference on Optical Communication (ECOC). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 1-4
-
Konferensbidrag (refereegranskat)abstract
- We report our recent studies in photonics-assisted free-space transmissions in both the lower (0.3-0.5 THz) and upper- (~64.5 THz) terahertz bands. We adopt the hybrid electro-optical approach for the lower-THz signal transmission, whereas a directly modulated quantum cascade laser is used for the upper-THz band.
|
|
| 1437. |
- Pang, Xiaodan, Dr., et al.
(författare)
-
Up to 6 Gbps Mid-Infrared Free-Space Transmission with a Directly Modulated Quantum Cascade Laser
- 2021
-
Ingår i: 2021 European Conference on Optical Communication (ECOC). - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- We report on an experimental demonstration of a mid-infrared free-space communication link enabled by a directly modulated quantum cascade laser operating at room temperature. A record high transmission rate up to 6 Gbps over 50-cm link distance is demonstrated at 4.65 µm wavelength.
|
|
| 1438. |
- Peng, Ru, et al.
(författare)
-
In-situ Neutron Diffraction Study of the Deformation Behaviour of two High-Manganese Austenitic Steels
- 2011
-
Ingår i: Materials Science Forum. - Stafa-Zurich, Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 681, s. 474-479
-
Tidskriftsartikel (refereegranskat)abstract
- In-situ neutron diffraction experiments under tensile loading were carried out to study the micromechanical behaviour of two iron-manganese based steels, a TWIP (twinning induced plasticity) steel with 30 wt% Mn and a TRIP steel (transformation induced plasticity) with 20 wt% Mn. The former was loaded to 31.3% strain and the latter to 20% strain. The 30 wt.% Mn steel had a fully austenitic microstructure which remained stable over the loading range studied, while stress induced austenite to α´- and ε-martensite transformations occur in the 20 wt.% Mn steel which initially contained an α´-martensite in addition to the austenite. The evolution of lattice strains under tensile loading differs between the two steels, reflected their different plastic deformation mechanisms. A stronger grain-orientation dependent behaviour is observed during deformation for the 20 wt.% Mn in contrast to the 30wt.% Mn steel.
|
|
| 1439. |
- Peng, T., et al.
(författare)
-
The Influence of Cu/Fe Ratio on the Tribological Behavior of Brake Friction Materials
- 2018
-
Ingår i: Tribology letters. - : Springer-Verlag New York. - 1023-8883 .- 1573-2711. ; 66:1
-
Tidskriftsartikel (refereegranskat)abstract
- Copper and iron are the major ingredients in friction materials, among which Fe often been served as friction reinforcement in the past. But in our recent study, the coefficients of friction (COF) decreased with increasing iron content in composites. In order to study the influence of Cu/Fe ratio on the tribological behavior of the composite under simulative braking conditions, a subscale testing apparatus with the pad-on-disk configuration under various initial braking speeds (IBS) was applied. The changes in mean COFs, wear rates, morphologies and chemical constitutions of friction surface for different composites were investigated. Results showed that the composite containing more Fe content always showed lower mean COF and wear rate, which different from the previous studies. This is because, under severe braking conditions, the tribological behavior of composite mainly depends on the evolution of tribo-oxide film on the surface, not just on the substrate themselves. Higher Fe content accelerated the formation of tribo-oxide film and in turn inhibited the destruction of tribo-oxide film on the surface, which leading to lower mean COF and wear rate, as well as a higher critical IBS for the transition of mean COF and wear rate. This work also provides a way to characterize the fracture strength of tribo-film by carried out a peeling test.
|
|
| 1440. |
- Peng, Yixiang, et al.
(författare)
-
Evaluation of parental education using biomechanical visualization to increase child restraint use in China
- 2022
-
Ingår i: Accident Analysis and Prevention. - : Elsevier BV. - 0001-4575 .- 1879-2057. ; 169, s. 106633-
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Despite demonstrated effectiveness of child restraint system (CRS), its use in China is extremely low due to the lack of national legislation requiring the use of CRS, as well as lack of child passenger safety knowledge among caregivers. Implementing an effective intervention is urgently needed to promote the use of CRS. In this study, we primarily evaluated the effectiveness of biomechanical visualization delivered in the context of CRS education to promote CRS use.& nbsp;Methods: We conducted a cluster randomised controlled trial to test the effects of educational intervention programs on increased use of CRS. Participants included caregivers from 8 pre-schools located in two cities (i.e., Chaozhou and Shantou) in China. Following a baseline survey, 8 pre-schools were randomly assigned into 1 of 4 groups with 2 schools in each group: 1) CRS education-only, 2) CRS education with behavioral skill training, 3) CRS education with biomechanical visualization, and 4) control. The primary outcome was CRS use, and the secondary outcomes included scores of child passenger safety-related knowledge and CRS use-related attitudes. The effect of the intervention was assessed among caregivers at two time points: baseline preintervention and 6 months postintervention.& nbsp;Results: More than 70% caregivers had never used CRS at baseline. No statistically significant between-group differences CRS use were observed at baseline preintervention (34.2%, 25.4%, 29.6% and 21.9%, respectively, P = 0.18). However, compared to the control group, odds of CRS non-use was significantly lower in caregivers assigned to the CRS education with biomechanical visualization (adjusted odd ratio (AOR) = 0.11, 95% confidence interval (CI) = 0.07-0.17), CRS education with behavioral skill training (AOR = 0.15, 95%CI = 0.10-0.24) and CRS education-only (AOR = 0.26, 95%CI = 0.17-0.41) groups, respectively. Statistically significant differences were also observed in the secondary outcomes postintervention across groups. Specifically, the CRS education with biomechanical visualization and CRS education with behavioral skill training groups had higher mean knowledge change scores than the CRS education-only group (3.3 +/- 1.5 vs. 2.9 +/- 2.2, p = 0.035 and 3.2 +/- 1.9 vs. 2.9 +/- 2.2, p = 0.039, respectively). We also observed a significantly higher increase in the attitudes scores in the CRS education with biomechanical visualization group compared with the CRS education-only group (4.7 +/- 2.1 vs. 3.5 +/- 2.8, p = 0.026).& nbsp;Conclusions: This study shows that both biomechanical visualization and behavioral skill training supplements to education improved understanding of CRS knowledge compared to education only, and all three strategies led to increased CRS use. Importantly, CRS education with biomechanical visualization was shown to be more effective than CRS education alone in improving caregiver's knowledge and attitudes. The use of biomechanical visualization may be an effective supplement to traditional education programs.
|
|
