Power, efficiency, and thermal characteristics of type-II interbandcascade lasers

High-performance mid-infrared type-II interband cascade lasers have been demonstrated under continuous-wave (CW) conditions with record-high wall-plug efficiencies (>14%) and output powers (>100 mW/facet) above 77 K. Device characteristics of these type-II interband cascade lasers are investigated systematically in terms of their output powers and efficiencies. Also, by comparing the temperature dependence of the threshold currents under pulsed and CW conditions, the thermal resistance and maximum heat sink temperature for CW operation are estimated for several mesa sizes. The limiting factors due to device heating for high-power/high-efficiency operation are identified and discussed in connection with device dimensions and packaging for the purpose of assessing further improvements     

The electron storage ring as a source of infrared radiation

The characteristics of synchrotron radiation in the infrared region have been investigated at the Berlin electron storage ring BESSY using Fourier spectroscopy. In accordance with calculation, it was found that BESSY at 100 mA beam current delivers higher fluxes than a conventional source only in the spectral region below 30 cm^?1, provided the interferometer is the throughput-limiting element. If, however, the throughput is limited by small sample size or, if the experiment requires a large f-number, the high brightness of synchrotron radiation could already yield flux advantages at several hundred wavenumbers. The possible application in one particular experiment - infrared reflection-absorption spectroscopy of adsorbed molecules on metal single crystal surfaces - is discussed. In the course of the investigations described here, it was also established that the short light pulses of the synchrotron radiation (～ 100 ps) do not adversely affect the resolution in Fourier transform spectroscopy.     

Sugar content of swedes for stockfeeding

The sugar content was determined of 19 cultivars of swede (Brassica napus ssp rapifera L) grown in rows 50 and 75 cm apart. Sugar concentration ranged from 54.3 to 78.7 g kg^?1 fresh weight and was positively correlated with dry matter content which ranged from 90.4 to 138.7 g kg^?1 fresh weight. The average concentration of fructose, glucose and sucrose in the dry matter was 225.0, 328.4 and 34.5 g kg^?1 DM, respectively. The high-dry-matter cultivars tended to have less fructose and more sucrose than the low-dry-matter ones, but total sugar concentration in the dry matter was not associated with dry-matter content. Row width had little effect on sugar content compared with the differences between cultivars. The implications for the feeding value of swedes are discussed.     

Monolithic integration of pseudomorphic power and low-noise HEMTs

Monolithic integration of pseudomorphic power and low-noise high electron mobility transistors (HEMTs) on a GaAs substrate has been demonstrated using specially designed multiple epitaxial layers. MBE-grown layers with three heterojunctions were selectively recessed to provide optimum structures for low-noise and power operations. At 18 GHz, a record power-added efficiency of 59% with 8 dB gain and 0.4 W/mm power density was obtained for the power HEMT. The low-noise device from the same slice achieved a noise figure of 1 dB with 9 dB associated gain at the same frequency.<>     

The glucosinolate content of the leaf and stem of fodder kale (Brassica oleracea L.), rape (Brassica napus L.) and radicole (Raphanobrassica)

The glucosinolate content of three fodder kales, one fodder rape, one semi-artificial rape and one radicole were determined. The major glucosinolates (mmol kg^?1 dry matter) were: in kale leaf, glucobrassicin (3.21) and sinigrin (3.12); in kale stem, sinigrin (5.82); in rape leaf, gluconapin (3.14) and progoitrin (13.99); in rape stem, gluconapin (3.29) and progoitrin (20.18); in semi-artificial rape leaf, gluconapin (25.64) and progoitrin (9.00); in semi-artificial rape stem, gluconapin (35.33) and progoitrin (12.08); in radicole leaf, progoitrin (4.74) and glucobrassicin (3.28); and in radicole stem, gluconapin (3.26) and progoitrin (5.53). The implications for plant breeding are discussed.     

Precision DC-to-AC power conversion by optimization of the outputcurrent waveform-the half bridge revisited

A simple form of a buck-derived interleaved four-quadrant pulsewidth modulation (PWM) power stage results in a doubling of the output ripple frequency while greatly reducing the ripple current amplitude. Shootthrough currents are reduced to low d_I/d_t events that are readily controlled, allowing zero dead-time operation     

Modeling of a semi-hermetic CO2 reciprocating compressor including lubrication submodels for piston rings and bearings

A comprehensive model for a semi-hermetic CO₂ reciprocating compressor is presented. This comprehensive model is composed of three main sub-models simulating the geometry and kinematics, the compression process, and frictional power loss. Valve and leakage sub-models are included in the compression process model. The frictional power loss model includes the friction at the bearings and between the piston ring and cylinder wall. The predicted results of the comprehensive model are validated using external compressor performance measurements of compressor input power and mass flow rate. The mass flow rate and compressor input power are predicted to within 4.03% and 6.43% mean absolute error, respectively, compared to the experimental datum. Additionally, a parametric study is presented which investigates compressor performance as a function of the stroke-to-bore ratio.