A novel self-oscillating HEMT-HBT cascode VCO-mixer using an activetunable inductor

Here we describe a unique Ka-band self-oscillating HEMT-HBT cascode mixer design which integrates an active tunable resonator circuit. The VCO-mixer MMIC integrates GaAs HEMT's and HBT's using selective molecular beam epitaxy (MBE) technology. The HEMT-HBT cascode active mixer operates similarly to a dual-gate mixer. The HBT of the cascode is used to construct a VCO by presenting the base with an HEMT tunable active inductor. The VCO can be tuned from 28.5 to 29.3 GHz while providing ≈0 dBm of output power. Operated as an upconverter, the MMIC achieves 6-9 dB conversion loss over a 31-39 GHz output frequency band. Using these active approaches, both VCO and mixer functions were integrated into a compact 1.44×0.76 mm² chip area. The active RF integrated circuit (IC) techniques presented here have direct implications to future high complexity millimeter-wave monolithic integrated circuits (MIMICs) for ultrahigh-speed clock recovery and digital radio applications     

Formation and annealing behavior of nanocrystalline ferrite in Fe-0.89C spheroidite steel produced by ball milling

Nanocrystalline ferrite formation by ball milling in Fe-0.89C spheroidite steel and its annealing behavior have been studied through microstructure observations and microhardness measurements. It was found that at the early stage of ball milling, the dislocation density increases and dislocation cells form due to plastic deformation. At the middle stage of ball milling, a layered nanocrystalline structure forms near the surface of the powder by localized severe deformation. The microhardness of nanocrystalline ferrite (10 GPa) is much higher than that of work-hardened ferrite (4 GPa). Together with the nanocrystallization of ferrite, the dissolution of cementite was observed. At the final stage of ball milling, equiaxed nanocrystalline ferrite forms from layered nanocrystalline ferrite by increasing the local misorientation. By annealing the milled powders, recrystallization was observed in the workhardened ferrite region, while in the nanocrystalline ferrite region, a slow grain growth was observed instead of recrystallization.     

Evaluation of hydrogen and methanol fuel cell performance of sulfonated diels alder poly(phenylene) membranes

Hydrogen fuel cell performance of sulfonated diels alder poly(phenylene) (SDAPP) with IECs ≥ 1.8 meq g⁻¹ is comparable to Nafion 212 under fully humidified conditions at 80 °C. However, as relative humidity is reduced, performance loss is substantial for SDAPP when compared to Nafion 212. This loss can be attributed to the large drop in proton conductivity in SDAPP as relative humidity is reduced; the proton conductivity of SDAPP with an IEC of 2.3 meq g⁻¹ dropped from 0.117 S cm⁻¹ to 0.001 S cm⁻¹ as the relative humidity was reduced from 100% to 25% at 80 °C. Methanol fuel cell experiments using 3 M methanol result in a 60 mV performance improvement at 25 mA cm⁻² when using SDAPP with an IEC of 1.2 meq g⁻¹ instead of Nafion 212. This improvement is due to lower methanol permeability of SDAPP (1.4 meq g⁻¹) over Nafion 212, with SDAPP films having methanol permeabilities less than 25% of Nafion 212.     

Integrated complementary HBT microwave push-pull and Darlingtonamplifiers with p-n-p active loads

The authors report the microwave results of complementary heterojunction bipolar transistor (HBT) amplifiers that integrate both n-p-n and p-n-p devices on the same chip using selective molecular beam epitaxy (MBE). An HBT wideband amplifier utilizing the Darlington configuration and implementing a p-n-p active load has a gain of 7.5 dB and a bandwidth from DC to 2.5 GHz. A complementary push-pull amplifier has a saturated output power of 7.5 dBm at 2.5 GHz     

GC rich DNA oligonucleotides with narrow minor groove width

Investigation of the width of the minor groove using 500 MHz NMR spectroscopy in three closely related 11-mer B-DNA duplexes shows that the minor groove is narrow in a GC rich oligonucleotide, and that a narrow minor groove is not something endemic to DNAs with persistent repetitions of adenine nucleotides (A-tract DNA). The width of the groove is dictated by local sequence contexts and independent of neighboring A-tract DNA.     

GaAs converter IC's for C-band DBS receivers

GaAs downconverter Monolithic Microwave Integrated Circuits (MMICs) for use in C-band direct broadcast satellite (DBS) receivers were developed. The IC consists of four (4) RF functional blocks and a dc bias block. The RF section includes a low noise amplifier, IF amplifier, mixer, and local oscillator. The dc section incorporates an internal dc bias generation circuit to compensate for device parameter fluctuations in wafer processing. The IC makes it easy to design a complete out-door converter unit with only the addition of two low noise FETs, a band pass filter, and an external dielectric resonator. This IC is realized on a small chip of only 1.1 mm×1.6 mm. The gate length of the FET is 0.5 μm. The active layers of the FETs and resistors are formed by an ion-implantation technique. This IC has a 3.0-dB noise figure and a 43-dB conversion gain at 80-mA total current consumption. To realize compact size and low cost, these ICs are offered in 12-pin QFP plastic packages     

Combined lung resection for advanced thoracic esophageal carcinoma

We performed lung resection together with esophagectomy in 2 patients with advanced thoracic esophageal cancer. Both patients survived more than 2 years with no evidence of disease. The first case was a 60-year-old man who had a cancer lesion in middle of the intra-thoracic esophagus (Im) and the right lower lobe of the lung was involved. In March 1989, right lower lobectomy of the lung was performed with esophagectomy. Pathologic examination showed well differentiated squamous cell carcinoma invading the lung parenchyma and intrapulmonary lymph node. Postoperatively, 44 Gy of radiation and Peplomycin cancer chemotherapy was performed. The patient survived 51 months after surgery and died of chronic myelogenous leukemia. The second case was a 60-year-old man who underwent thoracic esophagectomy with resection of the involved pericardium and right lung in February 1992. Pathologic examination showed N3 lymph node metastasis. Postoperatively, the patient received 48 Gy of radiation and was free from cancer after 30 months. In conclusion, better surgical results are expected in cases of advanced thoracic esophageal cancer with lung involvement which can be completely resected en bloc with the primary tumor even in a3 cases than in those with aortic or tracheobronchial involvement.     

Fracture behavior of cracked Type 304 stainless steel pipes under tensile and thermal loadings

Because of frequent discoveries of stress corrosion cracking in BWR primary piping systems, it became an urgent problem to evaluate the possibility of unstable fracture of flawed stainless steel pipes. To understand the fundamental fracture property as well as the behavior under actual plant conditions, the authors performed the following four types of tests on the cracked Type 304 stainless steel plates or pipes.

1. 1. Plate fracture test under tensile loading.

2. 2. Pipe fracture test under tensile loading.

3. 3. Leak-before-break test under high-compliance loading.

4. 4. Thermal shock test.

These test revealed quite high resistance of the flawed stainless steel pipes against unstable fracture.     

Solid-state amorphization of Cu + Zr multi-stacks by ARB and HPT techniques

A series of CuZr binary alloys with wide composition range were fabricated through ARB and HPT techniques using pure Cu and Zr metals as the starting materials. Bulk alloy sheets with thickness of about 0.8 mm after ARB process and alloy disks with 0.30 mm in thickness and 10 mm in diameter after HPT process can be obtained, respectively. The structures of all the alloys were found to be gradually refined with the increase of ARB cycles or HPT rotations. As a result, nanoscale multiple-layered structure was formed for the 10 cycled ARBed specimens, which could partially transform into amorphous phase during subsequent low temperature annealing. While for the as-HPTed sample, the alloy was completely amorphized after 20 rotations without any heat treatment. The thermal stabilities of the amorphous alloys were studied. The deformation behavior and the amorphization mechanism during the ARB and HPT process were put forward and discussed.