Non-linear performance of a three-bearing rotor incorporating a squeeze-film damper

This paper is concerned with the non-linear vibration performance of a rigid rotor supported on three bearings, one being surrounded by a squeeze-film damper. This damper relies on the pressure built up in the squeeze film to help counter-act external forces arising from unbalance and other effects. As a result a vibration orbit of a certain magnetude results. Such vibration orbits illustrate features found in other non-linear systems, in particular sub-harmonic resonances and jump phenomena. Comparisons between theoretical prediction and experimental observations of these phenomena are made

Imaging capability of pseudomorphic high electron mobility transistors, AlGaN/GaN, and Si micro-Hall probes for scanning Hall probe microscopy between 25 and 125°C

The authors present a comparative study on imaging capabilities of three different micro-Hall probe sensors fabricated from narrow and wide band gap semiconductors for scanning hall probe microscopy at variable temperatures. A novel method of quartz tuning fork atomic force microscopy feedback has been used which provides extremely simple operation in atmospheric pressures, high-vacuum, and variable-temperature environments and enables very high magnetic and reasonable topographic resolution to be achieved simultaneously. Micro-Hall probes were produced using optical lithography and reactive ion etching process. The active area of all different types of Hall probes were 1×1 µm2. Electrical and magnetic characteristics show Hall coefficient, carrier concentration, and series resistance of the hall sensors to be 10 mOmega/G, 6.3×1012 cm−2, and 12 kOmega at 25 °C and 7 mOmega/G, 8.9×1012 cm−2 and 24 kOmega at 125 °C for AlGaN/GaN two-dimensional electron gas (2DEG), 0.281 mOmega/G, 2.2×1014 cm−2, and 139 kOmega at 25 °C and 0.418 mOmega/G, 1.5×1014 cm−2 and 155 kOmega at 100 °C for Si and 5–10 mOmega/G, 6.25×1012 cm−2, and 12 kOmega at 25 °C for pseudomorphic high electron mobility transistors (PHEMT) 2DEG Hall probe. Scan of magnetic field and topography of hard disc sample at variable temperatures using all three kinds of probes are presented. The best low noise image was achieved at temperatures of 25, 100, and 125 °C for PHEMT, Si, and AlGaN/GaN Hall probes, respectively. This upper limit on the working temperature can be associated with their band gaps and noise associated with thermal activation of carriers at high temperatures

Variable temperature-scanning hall probe microscopy with GaN/AlGaN two-dimensional electron gas (2DEG) micro hall sensors in 4.2-425K range using novel quartz tuning fork AFM feedback

In this report, we present the fabrication and variable temperature (VT) operation of Hall sensors, based on GaN/AlGaN heterostructure with a two-dimensional electron gas (2DEG) as an active layer, integrated with Quartz Tuning Fork (QTF) in atomic force-guided (AFM) scanning Hall probe microscopy (SHPM). Physical strength and wide band gap of GaN/AlGaN heterostructure makes it a better choice to be used for SHPM at elevated temperatures, compared to other compound semiconductors (AlGaAs/GaAs and InSb), which are unstable due to their narrower band gap and physical degradation at high temperatures. GaN/AlGaN micro Hall probes were produced using optical lithography and reactive ion etching. The active area, Hall coefficient, carrier concentration and series resistance of the Hall sensors were ~14m x 14m, 10m7/G at 4.2K, 6.3 x 10^12cm-2 and 12k7 at room temperature and 7m7/G, 8.9 x 10^12cm-2 and 24k7 at 400K, respectively. A novel method of AFM feedback using QTF has been adopted. This method provides an advantage over STM feedback, which limits the operation of SHPM the conductive samples and failure of feedback due to high leakage currents at high temperatures. Simultaneous scans of magnetic and topographic data at various pressures (from atmospheric pressure to high vacuum) from 4.2K to 425K will be presented for different samples to illustrate the capability of GaN/AlGaN Hall sensors in VT-SHP

Factors shaping the evolution of electronic documentation systems

The main goal is to prepare the space station technical and managerial structure for likely changes in the creation, capture, transfer, and utilization of knowledge. By anticipating advances, the design of Space Station Project (SSP) information systems can be tailored to facilitate a progression of increasingly sophisticated strategies as the space station evolves. Future generations of advanced information systems will use increases in power to deliver environmentally meaningful, contextually targeted, interconnected data (knowledge). The concept of a Knowledge Base Management System is emerging when the problem is focused on how information systems can perform such a conversion of raw data. Such a system would include traditional management functions for large space databases. Added artificial intelligence features might encompass co-existing knowledge representation schemes; effective control structures for deductive, plausible, and inductive reasoning; means for knowledge acquisition, refinement, and validation; explanation facilities; and dynamic human intervention. The major areas covered include: alternative knowledge representation approaches; advanced user interface capabilities; computer-supported cooperative work; the evolution of information system hardware; standardization, compatibility, and connectivity; and organizational impacts of information intensive environments

Damping capacity of a sealed squeeze film bearing

The advantages of incorporating an open-ended or weakly-sealed squeeze-film bearing in a flexible support structure simulating an aero-engine assembly were examined. Attention is given to empirically modelling the hydrodynamics of the more usual tightly-sealed squeeze-film bearing, with a view to assessing its damping performance

Peran Perguruan Tinggi, Pemerintah dan Investor dalam Membangun Wisata Pedesaan di Jawa Barat sebagai Upaya Mengurangi Kemiskinan

Jumlah penduduk miskin di Jawa Barat semakin lama semakin bertambah, sumber mengatakan bahwa pada bulan Februari 2005 tingkat kemiskinan di Jawa Barat hanya 16 %, sedangkan per Juli 2005 naik menjadi 18,7% dan estimasi sementara untuk maret 2006 mencapai 22 %. (www.bps.co.id). Jumlah penduduk miskin di pedesaan lebih tinggi dibandingkan dengan di perkotaan, misalnya saja pada tahun 2005 persentase kemiskinan di perkotaan hanya 11,37 % sedangkan di pedesaan mencapai 19,51 %. Demikian pula pada tahun-tahun sebelumnya jumlah penduduk miskin yang ada di pedesaan selalu lebih tinggi dibandingkan dengan di perkotaan. Fenomena kemiskinan ini juga tampak dari aktivitas sehari-hari yang mana di pedesaan lebih terlihat bahwa banyak orang yang hanya menghabiskan waktu dengan duduk-duduk, sementara gadis dan pemudanya berkumpul di pos-pos ronda mengobrol hal-hal yang kurang bermanfaat. Kondisi buruk seperti ini tentunya tidak bisa dibiarkan dan masyarakat pedesaan khususnya di Jawa Barat tidak bisa tinggal diam hanya mengharapkan belas kasihan dari pemerintah, namun harus segera bergerak untuk berupaya terlepas dari kemiskinan yang membelenggu. Di setiap daearah di Jawa Barat memiliki potensi yakni lahan pertanian seperti sawah, kebun dan ladang yang hingga saat ini hanya dimanfaatkan sesuai dengan fungsi dasarnya saja yaitu menanam padi dan tanaman lain, padahal sebenarnya lahan-lahan tersebut dapat lebih dimanfaatkan misalnya dijadikan lokasi pariwisata pedesaan tradisional. Namun demikian untuk mewujudkannya tentu diperlukan dukungan dari berbagai pihak yakni Perguruan Tinggi sebagai lembaga ilmiah berperan dalam mengembangkan sumber daya manusia / masyarakat setempat sebagai calon pramuwisata atau calon wirausaha, penghubung antara calon pramuwisata/ wirausahawan dengan pihak investor, sedangkan pemerintah berperan dalam menyediakan infrastruktur seperti jalan raya, listrik serta mendidik masyarakat agar lebih mencintai alam pedesaan. Sedangkan investor berperan dalam penyediaan modal baik pembebasan tanah maupun modal kerja bagi calon wirausahawan dalam rangka mewujudkan kawasan wisata yang diinginkan. Bila keempat pihak ini (masyarakat desa, Perguruan Tinggi, pemerintah dan investor) dapat bekerjasama dengan baik maka akan terjadi suatu sinergi sehingga diharapkan kemiskinan dapat ditanggulangi

The Chinese Language in Qinghai

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Pengaruh Pengetahuan Konsumen, Perasaan Konsumen, Motivasi Konsumen, dan Kepribadian Konsumen terhadap Keputusan Pemilihan Perguruan Tinggi (Studi Kasus pada Program Regular I Universitas Mercu Buana)

This study aimed to examine and analyze the effect of consumer knowledge, consumer feeling, consumer motivation, and consumer personality on decision making for a higher education institution (Case study at the Regular Program of Universitas Mercu Buana). Research data for respondents were 385 regular program students complited, in September – December 2017, using purposive sampling method. The analysis used was Structural Equation Model (SEM) and correlation between dimensions. It showed that consumer knowledge had not significant effect to the decision of University election. Consumers Feeling, consumer motivation, consumers personality have significant effect to decision making of a University Selectio