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Hydraulic systems play an important role in modern industry owing to the fact that hydraulic actuator systems have many advantages over other technologies with electric motors, high durability, and the ability to produce large force at high speeds. Therefore, the hydraulic actuator has a wide range of application fields such as hydraulic pressing machines, moulding technology, etc. where controlled forces or pressures with high accuracy and fast response are the most significant demands. Consequently, many hybrid actuator models have been developed for research on how to control forces or pressures with the best results. The current paper presents a new kind of hydraulic load simulator for conducting performance and stability tests for control forces of hydraulic hybrid systems. In the dynamic loading process, disturbance makes the control performance (such as stability, frequency response, loading sensitivity, etc.) decrease or turn bad. In order to improve the control performance of a loading system and to eliminate or reduce the disturbance, an online self-tuning fuzzy proportional—integral—derivative (PID) controller is designed. Experiments are carried out to evaluate the effectiveness of the proposed control method applied for hydraulic systems with varied external disturbance as in real working conditions.

In this paper, a neural-fuzzy hybrid control approach is proposed for controlling a mobile robot that can avoid an unexpected obstacle in a navigational space. First, to describe the global structure of a known environment, a heuristic dominant collision-free space band is introduced. Based on the band, the moving information in the known environment is trained to a neural controller. Then, during the execution of a mobile robot navigation moving information at each position is given from the neural controller. If the mobile robot encounters an unexpected obstacle, a fuzzy controller is activated to adjust the moving information given from the neural controller to avoid the unexpected obstacle. When the robot has safely avoided the obstacle and resume the originally taught path, the fuzzy controller is deactivated. Some numerical examples are presented to demonstrate the planning algorithm.

Three monolithic high electron-mobility transistor (HEMT) low-noise amplifiers (LNAs) were developed that were designed for 7-11-GHz airborne radar, 2-18-GHz electronic warfare, and 20-GHz military satellite communications applications. The first LNA is a two-stage feedback amplifier at X-band, using a 0.5- mu m combined optical stepper and E-beam (electron-beam) lithographic process with a 1.2-dB noise figure at 10 GHz with 15-dB gain, and a typically less than 1.8-dB noise figure from 7-11 GHz. The second is a 2-18-GHz distributed amplifier demonstrating a 3.0-5.2-dB noise figure with approximately 11 GHz. The second is a 2-18-GHz distributed amplifier demonstrating a 3.0-5.2-dB noise figure with approximately 11 dB gain from 2-18 GHz. Finally, a three-stage 20-GHz amplifier using 0.25- mu m direct-write E-beam lithography with a less than 2.0-dB noise figure from 18-23 GHz with 29-dB associated gain is described. All the MMICs were fabricated with selectively doped AlGaAs/GaAs heterostructures grown on undoped GaAs substrates. >

Short-gate-length high-electron-mobility transistors (HEMTs) are reported that have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies; minimum noise figure of 1.2 dB at 32 GHz and 1.8 dB at 60 GHz from 0.25- mu m HEMTs. At Ka-band, a two-stage low-noise amplifier has demonstrated an average noise figure of 2 dB from 26.5 GHz to 37 GHz with a gain of 17 dB at 32 GHz. At V-band, a two-stage amplifier yielded a noise figure of 3.2 dB at 61 GHz with flat gain 12.7*0.5 dB from 59 GHz to 65 GHz. These devices are described and the potential for their future improvement is discussed. >

The development of InGaAs pseudomorphic high-electron mobility transistors (HEMTs) with state-of-the-art power performance at millimeter-wave frequencies is reported. Results given include maximum power-added efficiencies of 44% at 35 GHz and 36% at 44 GHz, output power of 100 mW with 22% efficiency and 3-dB gain at 60 GHz, and output power of 9 mW at 94 GHz. Preliminary reliability data are presented, and prospects for further improvement in performance-the realization of multifinger HEMTs capable of higher output power and reduction of gate length to 0.1 mu m-are discussed. >

A strategy is discussed for assembly path planning of parts to be assembled by two assembly robots in a working space. Path modeling based on the use of real and virtual vertices of male and female parts is introduced to represent the relative relationship of parts in assembled position. A new algorithm for assembly path planning of two parts is developed. An algorithm for optimum posture (position and orientation) for a two-arm fixtureless assembly in the working space is proposed. A performance index is introduced to describe both accurate assembly capability and manipulability in the working space. The two strategies are combined, and the two-arm fixtureless assembly is demonstrated graphically for two planar robots. >

It was observed that the gate breakdown voltage of an unpassivated AlGaAs/GaAs HEMT can move to higher negative values when a current is allowed to flow through the gate under reverse gate bias voltage. When a reverse bias is applied between the gate and source, this breakdown 'walkout' can be accompanied by a permanent increase in device source resistance and decreases in transconductance and drain saturation current. A similar effect was observed in AlGaAs/InGaAs/GaAs pseudomorphic HEMTs and in GaAs MESFETs. This effect was not observed in silicon nitrided passivated devices. >

Aim We report an extremely rare finding in a neck mass presenting with papillary oncocytic cells in fine needle aspiration cytology (FNAC). The differentiation of this lesion from papillary carcinoma of the thyroid, both cytologically and histologically, is discussed. Case report A middle-aged Malay lady presented with a diffuse neck swelling for 5 years. There was no associated with hoarseness of voice, swallowing difficulty or muscular weakness. Physical examination reviewed diffuse neck swelling moving with deglutition. A solitary area measuring 2 × 2 cm was noted on the right side. FNAC from the solitary mass showed cellular oncocytic cells arranged in fine papillary pattern. Occasional cytoplasmic pseudoinclusions and nuclear overlapping were observed. However, characteristic nuclear features such as ground-glass appearance and irregular nuclear outline with groove were not seen. Differential diagnoses of papillary oncocytic tumour, which include papillary thyroid carcinoma, Hurthle cell neoplasm and parathyroid adenoma, were considered. Later, total thyroidectomy showed a well circumscribed solitary lesion in the inferior pole of the right thyroid. The lesion was proven histologically to be a parathyroid adenoma with focal papillary features. Discussion The findings in FNAC of papillary parathyroid adenoma mimic the features of papillary thyroid carcinoma. In literature reviews no single or combination cytomorphological features are diagnostic of parathyroid adenoma. We report this case to illustrate occurrence of this unusual histological pattern that might create a diagnostic error in FNAC.

Quarter-micron-gate-length high-electron-mobility transistors (HEMTs) have exhibited state-of-the-art low-noise performance at millimeter-wave frequencies, with minimum noise figures of 1.2 dB and 32 GHz and 1.8 dB at 60 GHz. At Ka-band, two-stage and three-stage HEMT low-noise amplifiers have demonstrated noise figures of 1.7 and 1.9 dB, respectively, with associated gains of 17.0 and 24.0 dB at 32 GHz. At V-band, two stage and three-stage HEMT amplifiers yielded noise figures of 3.2 and 3.6 dB, respectively, with associated gains of 12.7 and 20.0 dB and 60 GHz. The 1-dB-gain compression point of all the amplifiers is greater than +6 dBm. The results clearly show the potential of short-gate-length HEMTs for high-performance millimeter-wave receiver application. >

AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors (HEMT's) with a gate length of 0.1 µm have been successfully fabricated. The HEMT's exhibit a maximum transconductance of 540 mS/mm with excellent pinch-off characteristics. A maximum stable gain (MSG) as high as 18.2 dB was measured at 18 GHz. At 60 GHz the device has demonstrated a minimum noise figure of 2.4 dB with an associated gain of ∼6 dB. These are the best gain and noise results reported to date for HEMT's.

Room-temperature noise performance of high-electron-mobility transistors (HEMTs) has been studied by correlating the microwave/millimeter-wave noise figure with lower frequency model parameters. By comparing devices fabricated from various molecular-beam epitaxially grown wafers, it is found that devices with high transconductance at low drain current generally exhibit superior noise performance. In particular, an optimal noise figure of 1.8 dB has been obtained at 60 GHz with 6.4-dB associated gain for devices from the best wafer. The low thermal noise coefficient ( theta >

High electron mobility transistors (HEMTs) have demonstrated unsurpassed transistor performance in the millimeter-wave range--at 60 GHz, results include a minimum noise figure of 2.3 dB with 4.0 dB associated gain, maximum small-signal gain of 11.7 dB, output power of 50 mW, power density of 0.43 W/mm and maximum power-added efficiency of 28%. The principles of HEMT operation and design are described, followed by a summary of the current state-of-the-art in noise and power performance, and discussion of several applications.

AlGaAs/InGaAs/GaAs planar-doped pseudomorphic HEMTs with a gate length of 0.1µm have been successfully fabricated. A maximum extrinsic transconductance g m of 930 mS/mm, corresponding to an intrinsic g m of 1380 mS/mm, is observed in the devices at room temperature. A unity current gain cutoff frequency f T of ∼100 GHz was projected. A maximum gain as high as 19.3 dB was also measured at 18 GHz. At 59 GHz, the devices have demonstrated a minimum noise figure of 2.3 dB with an associated gain of 6.5 dB from one wafer, and 2.5 dB noise figure with 8.0 dB associated gain from another. At 94 GHz, ∼7 dB small signal gain was also measured from a single-stage amplifier. These are the best gain and noise results reported to date for FETs.

Transistor amplification at 94 GHz has been demonstrated for the first time. A single-stage amplifier employing a high-electron-mobility transistor (HEMT) exhibits a small-signal gain of 3.6 dB and an output power of 3.4 mW with 2 dB gain.

The noise performance of 0.25 ?m-gate-length high-electron-mobility transistors at frequencies up to 62 GHz is reported. A room-temperature extrinsic transconductance gm of 480 mS/mm and a maximum frequency of oscillation fmax of 135 GHz are obtained for these transistors. At 30 and 40 GHz the devices exhibit minimum noise figures of 1.5 and 1.8 dB with associated gains of 10.0 and 7.5 dB, respectively. A minimum noise figure as low as 2.7 dB with an associated gain of 3.8 dB has also been measured at 62 GHz. This is the best noise performance ever reported for HEMTs at millimetre-wave frequencies. The results clearly demonstrate the potential of short-gate-length high-electron-mobility transistors for very low-noise applications for frequencies at least up to V-band.