High power mode conversion for linearly polarized HE11 hybrid mode output

Efficient plasma heating by ECR-wave irradiation requires axisymmetric, narrow, pencil-like millimetre wave beams with well-defined polarization. The linearly polarized gaussian-like HE₁₁, mode satisfies these conditions best. This quasi-optical hybrid mode can be generated from TE_0n gyrotron mode compositions by the two multi-step mode conversion processes: (1) ΣTE_0n to TE₀₁ to TE₁₁ to HE₁₁ or (2) ΣTE_0n to TE₀₁ to TM₁₁ to HE₁₁. The first scheme has the advantage that the converters can all be made without bends, allowing an arbitrary choice and fast change of the polarization plane. The second scheme does not exhibit this advantage, but it is more suitable at very high frequencies (e.g. 140GHz) because efficient TE₀₁-to-TM₁₁ transducers can be made considerably shorter than serpentine TE₀₁-to-TE₁₁ mode converters. This paper presents computations on mode converter systems of the first type at 70GHz and of both types at 140GHz (ID = 27 · 8 mm for 200kW transmission lines). The structure of wall perturbations (phase-matched superposition of 2 or 3 different geometrical periods) in the rippled wall mode converters and the curvature distribution in the bent, smooth-walled TE₀₁-to-TM₁₁ mode transducer were optimized by numerically solving the corresponding coupled-mode differential equations. Computer-aided optimization of circumferentially corrugated mode converters has been achieved with a scattering matrix code employing the modal field expansion technique (modular analysis concept (MAC)). In all cases the predicted overall efficiency of the complete mode converter system from ΣTE_0n (predominantly TE₀₂ at 70GHz or TE₀₃ at 140GHz) to HE₁₁ in the desired polarization is approximately 95% at 70GHz and 92% at 140GHz (ohmic attenuation is included). Low-power measurements on the conversion efficiency of the various mode transducers are in excellent agreement with the predicted values. High-power operation has been successfully demonstrated using a pulsed 70GHz gyrotron (200kW, 100ms).     

ASYNCHRONOUS AND SYNCHRONOUS LINEAR MOTORS OF SHORT PRIMARY CONSTRUCTION

ABSTRACT

Recent research in ground transportation has aimed at the construction of vehicles with high speeds (400 km/h to 500 km/h) where the thrust is produced by linear motors, and suspension is realized by magnetic systems. Because of economic considerations many of these projects had quickly been finished or given up, so that results comparing different systems are not yet available. The present paper gives the results of one of these comparative studies, [l], [2].     

SOME COMMENTS ON THE OPTIMAL OPERATION OF BATCH CRYSTALLIZERS

Ajinkya and Ray (1972) discussed the optimal operation of crystatlizers and computed the optimal temperature policy for a specific example using numerical techniques. The analytic solution for the general case is obtained here. It allows interesting physical interpretations and practically useful comparisons of the optimal control law with commonly used cooling policies.     

Proteolysis and Lipolysis in Ripening Cheddar Cheese Made with Conventional Bulk Starter and with Frozen Concentrated Direct-to-the-Vat Starter Culture

Samples taken at the beginning and after 1, 2, and 3 wk of ripening were assayed for total dipeptidase activity and individual free amino acids. Protein dye-binding values and fat acidity titers were used to assess and monitor proteolysis and lipolysis at 4 days and 1, 2, 3, 6, 9, and 12 months. Results indicated higher dipeptidase activity in the bulk starter cheese for the fist 3 wk of ripening. Total free amino acids at the initial stages of cheese ripening were slightly lower in the cheeses made with the frozen concentrated culture. Studies using the protein-dye binding technique showed significantly higher-dye binding capacity by the 3-month-old cheese made with the bulk starter. The differences, however, became minimal in cheeses at 6, 9, and 12 months of age. Higher fat acidity levels were also obtained in the 3, 6, 9, and 12 month cheeses made with the bulk starter.     

Smith predictor design for robust performance

A method is outlined for designing Smith predictor controllers that provide robust performance despite real parameter uncertainties in the process model. Insight into the design process is gained by viewing the Smith predictor from the perspective of internal model control. Performance requirements are written in terms of a frequency-domain weight restricting the magnitude of the closed-loop sensitivity function. A general method for approximating multiple parameter uncertainties by a single multiplicative uncertainty is developed—an exact bound is derived for the magnitude of multiplicative uncertainty used to approximate simultaneous uncertainties in process gain, time-constant, and time-delay. Three different tuning methods are demonstrated; each is applied to a wide range of parameter uncertainties in a first-order with time-delay model. The first tuning method locates loop transfer-function uncertainty regions to test for robust performance—real parameter uncertainties are considered exactly. The second tuning method approximates real parameter uncertainties by multiplicative uncertainty and uses structured singular value analysis to guarantee robust performance. The third is a ‘quick design’ method that considers the unit magnitude crossing of the multiplicative uncertainty. Finally, the Smith predictor controller is compared with the structured-singular-value-optimal controller.     

Improved classification of small-scale urban watersheds using thematic mapper simulator data

The utility of multispectral scanner subsystem (MSS) data has, in the last 10 years, proved to be of immense value in hydrologic investigations. Land-use thematic mapping and classification, as well as the identification of hydrologically significant basin physical parameters, are but a few of the many uses of LANDSAT data. Although the benefits have been many, certain problems continue to plague users. Classification attempts in small heterogeneous areas have often resulted in an inability to separate or differentiate the rapidly changing patterns, primarily due to the pixel size being larger than the individual surface parcels. The utility of MSS in small, highly urbanized basins containing complex land-use patterns is, therefore, somewhat limited, although spectral separation over larger, more spatially uniform areas has been highly successful. Another problem is misclassification due to the similarity in spectral response of many dissimilar surfaces such as urban and bare land, water and roads or other paved surfaces, and agricultural and residential areas. In addition, when several cover types of different spectral character are mixed throughout an area, the integrated signal is an average of the various surface features, thus indicating the presence of an entirely unrelated surface. LANDSAT MSS data of the Conley Creek basin near Atlanta, Georgia, was compared to thematic mapper simulator (TMS) data obtained the same day by aircraft. The TMS was found to alleviate many of the recurring problems associated with MSS data. Optimization of the band widths, an increase of the number of spectral bands to seven, an improvement of the ground resolution to 30 m has greatly improved the ability to distinguish features and the overall surface character. The TMS was able to detect numerous small water bodies, powerline rights-of-way, individual buildings and a variety of other features not visible on the MSS. In addition, the higher-resolution imagery could clearly distinguish between those areas which were improperly classified with the lower-resolution data.     

坚固耐用的直接测量系统

目前,MAG集团的Hüller Hille公司正在努力降低生产成本,与此同时还要提高质量和降低装配成本.利用Schneeberger Amsa测量系统及单轨导向装置取了可观成效.     

Twin Boundaries in Monoclinic ZrO2 Particles Confined in a Mullite Matrix

Internal defects and twin structures exist in thermally transformed monoclinic ( m )-ZrO₂ particles confined in a mullite matrix. The defects were analyzed by transmission electron microscopy. Twin boundaries on (100), (110), (001), and (011) were found. Frequently, (100) and (110) twins formed complicated mosaiclike structures. Some particles could be divided into two or more twinned sections with well-defined mutual orientation relations. Domains of closure were observed at the particle-matrix interface. The observations are discussed in terms of a simple model which considered (i) the anisotropic volume increase of ZrO₂ during the t→m transformation, (ii) the anisotropic thermal expansion coefficient of ZrO₂, and (iii) the rather isotropic thermal expansion coefficient of the mullite matrix.