The authors demonstrate an efficient room temperature source of terahertz radiation using femtosecond laser pulses as a pump and GaAs structures with periodically inverted crystalline orientation, such as diffusion-bonded stacked GaAs and epitaxially grown orientation-patterned GaAs, as a nonlinear optical medium. By changing the GaAs orientation-reversal period ͑504-1277 m͒, or the pump wavelength ͑2 -4.4 m͒, we were able to generate narrow-bandwidth ͑ϳ100 GHz͒ terahertz wave packets, tunable between 0.9 and 3 THz, with the optical-to-terahertz photon conversion efficiency of 3.3%.

We have generated an ultrabroad mid-infrared continuum by using single-pass optical parametric generation (OPG) in orientation-patterned GaAs (OP-GaAs). The spectrum spans more than an octave, from 4.5 to 10.7 microm, measured 20 dB down from the peak. The 17.5 mm long, 0.5 mm thick, all-epitaxially-grown OP-GaAs sample with a 166.6-microm quasi-phase-matching period was pumped with 3.1-3.3 microm wavelength, 1 ps pulses up to 2 microJ in energy. The OPG threshold was observed at 55 nJ pump energy with the pump polarized along the [111] crystal direction. The slope efficiency near threshold was 51%, and the external conversion efficiency was as high as 15%.

We demonstrate second-harmonic generation (SHG) from sub-micrometer-sized AlGaAs/AlxOy artificially birefringent waveguides. The normalized conversion efficiency is the highest ever reported. We further enhanced the SHG using a waveguide-embedded cavity formed by dichroic mirrors. Resonant enhancements as high as approximately 10x were observed. Such devices could be potentially used as highly efficient, ultracompact frequency converters in integrated photonic circuits.

This paper draws on theories of intercultural communication and mediation to develop a conceptual framework and research approach for examining the intercultural competence (IC) of Chinese tour guides and the relationship of guides’ IC to Chinese tourists’ experiences. The paper begins with a discussion of the importance of the Chinese inbound market globally, and in particular for Australia, and then examines the role of tour guides in intercultural settings. These discussions, which are offered to establish the need for systematic enquiry in this area, are followed by a detailed presentation of a research rationale and conceptual model in which key variables and proposed relationships are discussed, measurement issues are addressed, and implications for research are given.

This paper examines the cultural brokering or mediating role of tour guides and the contribution of interpretation to that role. Using Chinese inbound tourism to Australia as a context, the paper draws on two separate mixed-methods studies to explore the views of tourism industry representatives, tour guides and visitors with respect to cultural mediation. In addition to defining and outlining the dimensions of cultural mediation, respondents elaborated on what these dimensions entail and how the cultural mediation performed by guides contributes to the visitor experience. The findings suggest that, to be a cultural mediator, a tour guide needs to perform a number of roles relating to three broad dimensions: the mediation of access, understanding, and encounters. The first and third, brokering physical access and facilitating opportunities for encounters and/ or social interaction with locals, were both reported by visitors as important contributors to memorable experiences. However, it was the mediation of understanding, i.e., the guide's brokering of a cognitive/ affective dimension to the experience, that visitors most frequently cited as contributing to experiences which were memorable. Finally, when asked to evaluate their tour guides' performance as cultural mediators, visitors reported that many guides fell short of adequately mediating their understanding of the host culture, which appears to be due to both the guides' lack of sufficient depth of knowledge about Australia and a lack of interpretation skills. The paper presents some of the implications of these findings for tour guiding and, in particular, for the more effective and widespread use of interpretation as a tool for mediating cultural understanding.

No abstract

Ultra-high-performance concrete is typically defined as an advanced cementitious material that has a compressive strength of over 150 MPa and superior durability. This article presents the development of a new type of ultra-high-performance concrete, namely, ultra-high-performance seawater sea-sand concrete. The development of ultra-high-performance seawater sea-sand concrete addresses the challenges associated with the shortage of freshwater, river-sand and coarse aggregate in producing concrete for a marine construction project. When used together with corrosion-resistant fibre-reinforced polymer composites, the durability of the resulting structures (i.e. hybrid fibre-reinforced polymer–ultra-high-performance seawater sea-sand concrete structures) in a harsh environment can be expected to be outstanding. The ultra-high strength of ultra-high-performance seawater sea-sand concrete and the unique characteristics of fibre-reinforced polymer composites also offer tremendous opportunities for optimization towards new forms of high-performance structures. An experimental study is presented in this article to demonstrate the concept and feasibility of ultra-high-performance seawater sea-sand concrete: ultra-high-performance seawater sea-sand concrete samples with a 28-day cube compressive strength of over 180 MPa were successfully produced; the samples were made of seawater and sea-sand, but without steel fibres, and were cured at room temperature. The experimental programme also examined the effects of a number of relevant variables, including the types of sand, mixing water and curing water, among other parameters. The mini-slump spread, compressive strength and stress–strain curve of the specimens were measured to clarify the effects of experimental variables. The test results show that the use of seawater and sea-sand leads to a slight decrease in workability, density and modulus of elasticity; it is also likely to slightly increase the early strength but to slightly decrease the strengths at 7 days and above. Compared with freshwater curing, the seawater curing method results in a slight decrease in elastic modulus and compressive strength.

We have fabricated quasi-phase-matched AlGaAs waveguides for continuous-wave second-harmonic generation (SHG) pumped around 1.55 microm. We find that the losses, which limit the conversion efficiency of this type of waveguide, are resulted from two corrugations--the initial template corrugation and the regrowth-induced domain-boundary corrugations. We are able to reduce the waveguide loss by improving the growth conditions. The waveguide loss is 6-7 dB/cm at 1.55 microm, measured using the Fabry-Perot method. A record internal SHG conversion efficiency of 23 %W-1 for AlGaAs waveguides is achieved using a 5-mm-long waveguide with a pump wavelength of 1.568 microm.