Weather and Age-Gender Effects on the Projection of Future Emergency Ambulance Demand in Hong Kong

An accurate projection for ambulance demand is essential to enable better resource planning for the future that strives to either maintain current levels of services or reconsider future standards and expectations. More than 2 million cases of emergency room attendance in 2008 were obtained from the Hong Kong Hospital Authority to project the demand for its ambulance services in 2036. The projection of ambulance demand in 2036 was computed in consideration of changes in the age-gender structure between 2008 and 2036. The quadratic relation between average daily temperature and daily ambulance demand in 2036 was further explored by including and excluding age-gender demographic changes. Without accounting for changes in the age-gender structure, the 2036 ambulance demand for age groups of 65 and above were consistently underestimated (by 38%-65%), whereas those of younger age groups were overestimated (by 6%-37%). Moreover, changes in the 2008 to 2036 age-gender structure also shift upward and emphasize relationships between average daily temperature and daily ambulance demand at both ends of the quadratic U-shaped curve. Our study reveals a potential societal implication of ageing population on the demand for ambulance services.postprin

Comparison on crosstalk tolerance of RZ-DPSK and RZ-OOK modulation format in fiber optical parametric amplifier

We investigated crosstalk tolerance of RZ-DPSK and RZ-OOK modulation format in OPA with 100GHz channel spacing. Results show an average of 2.4dB improvement in Q factor by using RZ-DPSK format over RZOOK format.published_or_final_versio

Microclimate variations between semienclosed and open sections of a marathon route

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Widely-tunable continuous-wave single-longitudinal-mode fiber optical parametric oscillator

A continuous-wave fiber optical parametric oscillator with a tunability of 114 nm, a wavelength span of 143 nm and single-longitudinal-mode oscillation is demonstrated. The short-term linewidth of the output is as narrow as 1.5 kHz. © 2011 Optical Society of America.published_or_final_versio

Multiwavelength Single-Longitudinal-Mode Ytterbium-Doped Fiber Laser

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High-sensitivity polarization gating frequency-resolved optical gating (PG-FROG) using highly-nonlinear dispersion-shifted fiber

We experimentally demonstrate a frequency-resolved optical gating (FROG) system in pulse characterization at 1.55 μm by using cross-phase modulation (XPM) in highly nonlinear dispersion-shifted fiber (HNL-DSF), with over 6-times sensitivity improvement. © 2011 National Sun Yat-Sen Univ.published_or_final_versio

A comprehensive study on crosstalk suppression techniques in fiber optical parametric amplifier by modulation format

With the presence of multiple-WDM input signals, ON-OFF keying (OOK)-modulated signals suffer from crosstalk in fiber optical parametric amplifier (OPA) due to cross-gain modulation (XGM) and four-wave mixing (FWM) effects. We demonstrated substantial crosstalk suppression in one-pump OPA by using return-zero differential phase-shift keying (RZ-DPSK) modulation format, which with its pattern-independent amplitude and subunity duty cycle would be effective in reducing the XGM and FWM effects significantly. By using the RZ-DPSK format, the power penalty was improved by at least 0.8 dB over RZ-OOK, non-RZ (NRZ)-DPSK, and NRZ-OOK formats with four 10 Gb/s channels, separated by 200 GHz spacing. With eight 10 Gb/s channels separated by 100 GHz spacing, a Q -factor penalty of the RZ-DPSK signal was reduced by 2.4 dB compared to RZ-OOK counterparts. © 2008 IEEE.published_or_final_versio

All-optical tunable delay with NRZ-to-RZ format conversion capability based on optical Kerr switch and pulse pre-chirping

All-optical tunable delay plays an important role for enabling high-throughput optical routing, such as buffer for contention resolution and timing synchronization. We proposed and demonstrated a widely tunable optical delay using optical Kerr-switch-based wavelength converter and pulse pre-chirping for compensating chromatic dispersion in fiber delay. With wideband operation provided by a Kerr-switch wavelength converter, a tunable delay range up to 8.56 ns was achieved. Meanwhile, pulse pre-chirping helped to alleviate group-velocity dispersion (GVD)-induced penalty, and provided simultaneous nonreturn-zero (NRZ)-to-RZ format conversion functionality. © 2008 IEEE.published_or_final_versio

Comparison of the state-of-art phase modulators and parametric mixers in time-lens applications under different repetition rates

Ever since the discovery of space-time duality, several methods have been developed to perform temporal imaging, and there are two major categories: the quadratic signal onto the phase modulator and the parametric mixer with a linear chirped pump. The features of each mechanism have been thoroughly and quantitatively explored and optimized for certain kinds of applications, but a comparison of some key parameters, especially in the aspect of the repetition rate, is required. In this paper, we will first review the theoretical models and existing performance of these two mechanisms and, consequently, compare them quantitatively in different aspects: the focal group delay dispersion, the pupil size, the effective duty ratio, and the temporal numerical aperture. All these fundamental parameters are related to the repetition rate. The results obtained in this study would provide some important guidelines for the time-lens design, so as to be optimized in different kinds of applications with different repetition rate requirements, such as ultrafast optical communication and real-time bio-imaging systems.published_or_final_versio