The Tuzu Gesar epic : Performance and singers

Different minority groups have different versions of the Gesar epic. Their respective forms differ from the Tibetan version in content, structure, characters, events, and actual performances. This kind of variety is common in Asian oral epic traditions. The Tu people are a unique minority who reside in northwest China with a total population of 200,000. The Gesar epic of this group is found mainly in Tu communities in Gansu and Qinghai provinces. The Tuzu Gesar is performed as a combination of verse and prose. It also shows some differences from the Anduo dialects of Tibetan. As a result of phonetic changes, the Tuzu Gesar has its own structure and follows strict procedures and performance rules. Many native scholars and experts have studied this tradition.Translated by Li Xianting

Demonstration of intermodal four-wave mixing by femtosecond pulses centered at 1550 nm in an air-silica photonic crystal fiber

In this paper, we demonstrated experimentally the intermodal four-wave mixing effect by launching femtosecond pulses centered at 1550 nm into deeply normal dispersion region in the fundamental guided-mode of an air-silica photonic crystal fiber with two zero dispersion wavelengths. When intermodal phase-matching condition is satisfied, the energy of the pump waves at 1550 nm in the fundamental guided-mode is converted to the anti-Stokes waves around 1258 nm and Stokes waves around 2018 nm both in the second-order guided-mode. When femtosecond pulses at input average power Pav of 90 mW are propagated inside 22 cm long photonic crystal fiber, the conversion efficiencies ηas and ηs of the anti-Stokes and Stokes waves generated are 8.5 and 6.8%, respectively. We also observed that the influences of the fiber bending and walk-off effect between the fundamental and second-order guided-modes on intermodal four-wave mixing-based frequency conversion process are very small

Numerical analysis of the influencing factors on the performance of a pipe-embedded window operated in summer

The pipe-embedded window is a double window structure with pipes embedded inside the cavity to adjust the temperature. The preliminary studies showed that it can significantly reduce the cooling load of buildings with natural cooling sources such as the water from cooling towers in summer. However, the research on the influencing factors of the pipeembedded window is insufficient. In this paper, the numerical calculation models are established for a pipe-embedded window and a traditional window. The influence of climatic factors, such as the natural cooling source temperature and outdoor air temperature on the thermal performance of the pipe-embedded window are studied. Based on these, the building energy efficiency is analysed. The results show that the thermal resistance of the pipeembedded window is basically constant. A linear relationship has been found between the inner surface heat flux, pipe heat flux, interlayer mean air temperature and the outdoor air temperature, mean water temperature or solar radiation intensity. The solar radiation intensity, water temperature, outdoor air temperature is ranked from most to least influence. The location of pipe has little effect on the temperature field and heat transfer of a pipe-embedded window. In summer, the difference between inner-glass and outer-glass insulation is small

Comprehensive analysis of passive generation of parabolic similaritons in tapered hydrogenated amorphous silicon photonic wires

Parabolic pulses have important applications in both basic and applied sciences, such as high power optical amplification, optical communications, all-optical signal processing, etc. The generation of parabolic similaritons in tapered hydrogenated amorphous silicon photonic wires at telecom (λ~1550 nm) and mid-IR (λ≥2100 nm) wavelengths is demonstrated and analyzed. The self-similar theory of parabolic pulse generation in passive waveguides with increasing nonlinearity is presented. A generalized nonlinear Schrödinger equation is used to describe the coupled dynamics of optical field in the tapered hydrogenated amorphous silicon photonic wires with either decreasing dispersion or increasing nonlinearity. The impacts of length dependent higher-order effects, linear and nonlinear losses including two-photon absorption, and photongenerated free carriers, on the pulse evolutions are characterized. Numerical simulations show that initial Gaussian pulses will evolve into the parabolic pulses in the waveguide taper designed

Effects of Economizer Type and Size to the Gas Injected System Using Zeotropic R32/R1234ze(E) Mixture

Refrigerant mixtures are commonly regarded as a potential substitute because rare pure refrigerants can totally meet all the requirements of environmental, thermodynamic and safe properties. Meanwhile as an effective means, vapour injection is widely applied to improve the system performance of heat pump under large pressure ratio. However, the difference of using pure refrigerant and refrigerant mixtures, which configuration of vapour injection is more suitable for refrigerant mixtures are still unclear. In this paper, R32/R1234ze(E) mixtures are chosen as refrigerant pairs for its great potential in the future, and the scroll compressor is chosen as well to carry out the research for its wide application in vapour injected system. The thermodynamic model with different suction and injected concentration is derived, on the basis of this model, a detailed compressor and system performance comparison of different vapour injected configurations with R32/R1234ze(E) mixtures are investigated. The results indicate that the lower concentration of R32 in flash tank (FT) system will result in higher power consumption compared with intermediate heat exchanger (IHX) system. For the system performance, the heating capacity of FT system is 5%~9.1% higher than IHX system, while the COP of latter system is usually higher, the largest improvement is 2.7% when charged with R32/R1234ze(E) (40/60) mixtures

High Degree Picosecond Pulse Compression in Chalcogenide-Silicon Slot Waveguide Taper

In this paper, we propose and design a chalcogenide (As2S3)-based slot waveguide taper with exponentially decreasing dispersion profile to realize high-degree pulse compression of low-power chirped solitons. Based on the waveguide taper designed, pulse compression of fundamental solitons, and chirped 2-soliton breather are both investigated numerically. With self-similar pulse compression scheme, a 1 ps input pulse is compressed to 81.5 fs in 6 cm propagation. By using 2-soliton breather pulses, a 1 ps chirped pulse is compressed to 80.3 fs in just 2.54 cm. This is the first demonstration of the feasibility of high-degree nonlinear pulse compression in As2S3-based slot waveguide taper

A state-space based method to predict thermal performance of pipeembedded double skin façade: case study in Guangzhou

Pipe-embedded double skin facade, which arranges pipes in shading device, is an alternative to reduce indoor demand and save energy. To simulate annual performance of this system, a simplified approach based on optical and thermal property is proposed at first, in which dynamic performance is acquired through state-space method. Then the model is validated with former investigation and shows good accuracy. Indoor room temperature with the pipe-embedded double skin façade is analyzed under different types of room in Guangzhou at last. Results show that the pipe-embedded double skin façade could guarantee a barely satisfactory indoor environment where indoor heat gain is small in most time. Besides, superiority would be obvious when solar radiation is strong, indicating the applicability in some typical region with abundant sunshine

Mid-infrared octave-spanning supercontinuum and frequency comb generation in a suspended germanium-membrane ridge waveguide

Stable octave-spanning supercontinuum (SC) in the mid-infrared (MIR) region finds extensive applications in spectroscopy, metrology, biochemistry, etc. The absorption of conventional silicon- or silicon oxide-dominated nonlinear media makes SC generation in MIR region technically challenging. In this paper, we propose ultra-broadband MIR-SC generation using a suspended germanium-membrane ridge waveguide. We theoretically showed that when pump pulses centered at 4.8 um with pulse width at 180 fs and peak power at 800 W are injected into a 4-mm long proposed ridge waveguide, the SC generated ranges from 1.96 ~ 12 um (about 2.6 octaves), extending deep into the “fingerprint” region. The first-order coherence is calculated to confirm the stability of the generated SC. The performance of the SC-based frequency comb is also investigated by assuming a 100-pulses pump source at a repetition rate of 100 KHz