A comparison of matrix methods for calculating eigenvalues in acoustically lined ducts

Three approximate methods - finite differences, weighted residuals, and finite elements - were used to solve the eigenvalue problem which arises in finding the acoustic modes and propagation constants in an absorptively lined two-dimensional duct without airflow. The matrix equations derived for each of these methods were solved for the eigenvalues corresponding to various values of wall impedance. Two matrix orders, 20 x 20 and 40 x 40, were used. The cases considered included values of wall admittance for which exact eigenvalues were known and for which several nearly equal roots were present. Ten of the lower order eigenvalues obtained from the three approximate methods were compared with solutions calculated from the exact characteristic equation in order to make an assessment of the relative accuracy and reliability of the three methods. The best results were given by the finite element method using a cubic polynomial. Excellent accuracy was consistently obtained, even for nearly equal eigenvalues, by using a 20 x 20 order matrix

Method and apparatus for optically monitoring the angular position of a rotating mirror

An optical system monitors the angular position of a rotating scanning mirror to indicate the effective start and end of each scan. At a certain angular position, a ray of energy transmitted to the mirror is reflected a plurality of times between the reflectors associated with the optical system and the line on the mirror parallel to the axis, and then to a detector to sense that angular position. A single optical system may be arranged to sense a plurality of different angular positions for each revolution of the mirror

A Range Extension for the Rock Vole, Microtus chrotorrhinus, in Labrador

Rock Voles (Microtus chrotorrhinus) were previously documented only from the southern coast of Labrador and the Strait of Belle Isle south of Hamilton Inlet. During two field seasons in 2000 and 2001, both in July, six Rock Vole specimens were collected on Southern Island, off the north-central coast of Labrador, extending the range of the subspecies Microtus chrotorrhinus ravus approximately 250 km to the central Labrador coast north of Hamilton Inlet. Rock Voles were trapped primarily in stunted Black Spruce (Picea mariana) forest and areas associated with rocks, thick brush, and water

JPL Energy Consumption Program (ECP) documentation: A computer model simulating heating, cooling and energy loads in buildings

The engineering manual provides a complete companion documentation about the structure of the main program and subroutines, the preparation of input data, the interpretation of output results, access and use of the program, and the detailed description of all the analytic, logical expressions and flow charts used in computations and program structure. A numerical example is provided and solved completely to show the sequence of computations followed. The program is carefully structured to reduce both user's time and costs without sacrificing accuracy. The user would expect a cost of CPU time of approximately $5.00 per building zone excluding printing costs. The accuracy, on the other hand, measured by deviation of simulated consumption from watt-hour meter readings, was found by many simulation tests not to exceed + or - 10 percent margin

Endoscopic Shearography and Thermography Methods for Nondestructive Evaluation of Lined Pressure Vessels

The goal of this research effort was the development of methods for shearography and thermography inspection of coatings, bonds, or laminates inside rocket fuel or oxidizer tanks, fuel lines, and other closed structures. The endoscopic methods allow imaging and inspection inside cavities which are traditionally inaccessible with shearography or thermography cameras. The techniques are demonstrated and suggestions for practical application are made in this report. Drawings of the experimental setups, detailed procedures, and experimental data are included

Thermal Excitation System for Shearography (TESS)

One of the most convenient and effective methods of stressing a part or structure for shearographic evaluation is thermal excitation. This technique involves heating the part, often convectively with a heat gun, and then monitoring with a shearography device the deformation during cooling. For a composite specimen, unbonds, delaminations, inclusions, or matrix cracking will deform during cooling differently than other more structurally sound regions and thus will appear as anomalies in the deformation field. However, one of the difficulties that cause this inspection to be dependent on the operator experience is the conventional heating process. Fanning the part with a heat gun by hand introduces a wide range of variability from person to person and from one inspection to the next. The goal of this research effort was to conduct research in the methods of thermal excitation for shearography inspection. A computerized heating system was developed for inspection of 0.61 m (24 in.) square panels. The Thermal Excitation System for Shearography (TESS) provides radiant heating with continuous digital measurement of the surface temperature profile to ensure repeatability. The TESS device functions as an accessory to any electronic shearography device

Structural design options for the new 34 meter beam waveguide antenna

In addition to the successful network of 34 m High Efficiency antennas recently built by JPL, the Deep Space Network (DSN) is embarking on the construction of a 34 m high performance, research and development antenna with beam waveguide optics at the Venus site. The construction of this antenna presents many engineering challenges in the area of structural, mechanical, RF, and pointing system design. A set of functional and structural design requirements is outlined to guide analysts in the final configuration selection. Five design concepts are presented covering both the conventional center-fed beam optics as well as the nonconventional, by-pass beam configuration. The merits of each concept are discussed with an emphasis on obtaining a homologous design. The preliminary results of structural optimization efforts, currently in progress, are promising, indicating the feasibility of meeting, as a minimum, all X-band (8.4 GHz) requirements, with a goal towards meeting Ka-band (32 GHz) quality performance, at the present budget constraints

The Contribution of Rice Farming on Nitrogen Enrichment in Yeh Sungi Watershed, Tabanan Bali

Pelaksanaan program intensifikasi pertanian melalui konsep revolusi hijau membuat meningkatnyaproduksi padi secara dramatis sehingga pada tahun 1984 Indonesia mencapai swa-sembada beras. Uniknya, sebelumtahun 1984 Indonesia dikenal sebagai negara pengimpor beras yang terbesar di dunia. Akan tetapi, disampingprestasi yang spektakular dalam produksi padi, dalam beberapa hal revolusi hijau juga memberi kontribusi dampakyang tidak menguntungkan terhadap ekosistem.Perkembangan pertanian di Bali, khususnya sawah sangat terkaitdengan sistem subak. Subak adalah pengaturan air irigasi tradisional di Bali yang telah dilaksanakan sejak berabadabadyang lalu. Sehubungan dengan masalah di atas, penelitian ini telah dilaksanakan di Daerah Aliran Sungai(DAS) Yeh Sungi di Kabupaten Tabanan, daerah di bagian barat Bali. Daerah penelitian meliputi delapan subakyaitu: Subak Apit Yeh and Subak Uma Poh di daerah hulu tempat tangkapan air; Subak Padangakitan, Jaka, Sungi I,Bena, dan Subak Tangkub di daerah tengah; dan Subak Gde Gadon I di daerah hilir. Penelitian ini dilakukan selama12 bulan, mulai dari bulan April 2001 hingga Maret 2002. Tujuan penelitian adalah: (1) meneliti tingkat pengayaanhara nitrogen di air irigasi yang berkaitan dengan aplikasi intensif pupuk anorganik di berbagai sistem pertaniandalam sistem subak di Bali; (2) meneliti kualitas lingkungan air, berkaitan dengan tingkat pengayaan hara nitrogendi dalam air irigasi. Hasil penelitian menunjukkan bahwa pengayaan hara pada air irigasi berkaitan dengan sistempertanian pada sistem subak. Tingkat pengayaan hara di daerah hulu lebih tinggi daripada di daerah tengah dan hiliruntuk N-NO3-; untuk memelihara kelangsungan ekosistem Subak, maka aplikasi pupuk N harus mempertimbangkankandungan hara tersebut dalam air irigasinya. Pelaksanaan pertanian telah menyebabkan pengayaan hara nitrogenyang berlebihan di daerah irigasi, khususnya di daerah tengah maupun hilir yang masing-masing didominasi olehpola pertanian padi-padi-padi dan padi-padi-palawija. Untuk memelihara kelangsungan ekosistem subak, makaaplikasi pupuk nitrogen harus mempertimbangkan kandungan hara di air irigasi.Kata kunci: sistem pertanian padi, pengayaan air irigasi, ekosistem subak. The implementation of agricultural intensification program through the green revolution concept has madethe increasing rice production dramatically and in 1984 Indonesia achieved ice self-sufficiency. Uniquely, before1984 Indonesia was known as the biggest rice importing country in the world. However, beside of spectacularachievement in rice production, green revolution to some cases also contributes less favorable impact to theecosystem. The agricultural development in Bali, particularly rice field is closely related to the subak system. Subakis a traditional model of irrigation water treatment in Bali practiced since centuries ago. The related to abovementionedissues, this research has been conducted at Yeh Sungi watershed in Tabanan District, western part ofBali. The research site includes eight subaks: Subak Apit Yeh and Subak Uma Poh at upstream area of catchmentsarea; Subak Padangakitan, Jaka, Sungi I, Bena, and Subak Tangkub at the middle area; and Subak Gde Gadon I atdownstream area. This research was carried out for 12 months between April 2001 and March 2002. The objectionof this research were: (1) to investigate the water enrichment level of N nutrients in the irrigation water related to theintensive application of inorganic fertilizers at various farming systems in subak system in Bali; (2) to investigatethe water environment quality, related to the water enrichment level of N nutrient in the irrigation water. Research96Jurnal Pengkajian dan Pengembangan Teknologi Pertanian Vol. 6, No. 2, Juli 2003 : 95-106results showed that nutrient enrichment on irrigation water related to farming system on subak ecosystem. The levelof nutrient enrichment at upstream (hulu) area is higher than the middle (tengah) and downstream (hilir) areas for N-NO3-.To maintain the sustainability of subak ecosystem, therefore the application of N fertilizer should considerthose nutrients content in irrigation water. The agricultural practice has caused excessive enrichment of N nutrientsin irrigated area, especially at the middle as well as downstream areas dominated by rice-rice-rice and rice-ricepalawija(second crop) cropping patterns