75 FR 82070 - Light-Walled Rectangular Pipe and Tube From China, Korea, and Mexico
Federal Register 2010, 2011, 2012, 2013, 2014
2010-12-29
... permitted by section 201.8 of the Commission's rules, as amended, 67 FR 68036 (November 8, 2002). In... COMMISSION Light-Walled Rectangular Pipe and Tube From China, Korea, and Mexico AGENCY: United States...) Chapter 19 panel proceeding in Light-Walled Rectangular Pipe and Tube from Mexico, USA-MEX-1904-04,...
77 FR 3497 - Light-Walled Rectangular Pipe and Tube From Taiwan
Federal Register 2010, 2011, 2012, 2013, 2014
2012-01-24
... Procedure (19 CFR 207.2(f)). Background The Commission instituted this review on July 1, 2011 (76 FR 38691) and determined on October 4, 2011 that it would conduct an expedited review (76 FR 64105, October 17... COMMISSION Light-Walled Rectangular Pipe and Tube From Taiwan Determination On the basis of the record...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-02-02
... Order; Light-Walled Welded Rectangular Carbon Steel Tubing From Taiwan, 54 FR 12467 (March 27, 1989). As... within a reasonably foreseeable time. See Light-Walled Rectangular Pipe and Tube From Taiwan, 77 FR 3497... of Five-Year (``Sunset'') Review, 76 FR 38613 (July 1, 2011) and Certain Pipe and Tube From...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-01-27
... Administrative Reviews and Request for Revocation in Part, 76 FR 37781 (June 28, 2011) (Initiation Notice). This... International Trade Administration Light-Walled Rectangular Pipe and Tube From Turkey: Extension of Time Limits... administrative review for, inter alia, light- walled rectangular pipe and tube from Turkey for the May 1,...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-07-16
... Commission found that the domestic interested party group responses to its notice of institution (78 FR 19526... COMMISSION Light-Walled Rectangular Pipe and Tube From China, Korea, Mexico, and Turkey: Notice of Commission... light-walled rectangular pipe and tube from China, Korea, Mexico, and Turkey would be likely to lead...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-12-10
... COMMISSION Light-Walled Rectangular Pipe and Tube From China, Korea, Mexico, and Turkey; Scheduling of Full..., Mexico, and Turkey AGENCY: United States International Trade Commission. ACTION: Notice. SUMMARY: The... duty orders on light- walled rectangular pipe and tube from China, Korea, Mexico, and Turkey would...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-07
...In response to requests for an administrative review, the Department of Commerce (the Department) is conducting an administrative review of the antidumping duty order on light-walled rectangular pipe and tube (LWR pipe and tube) from Mexico. The review covers imports of subject merchandise of two respondent companies during the period August 1, 2009, through July 31, 2010. For these......
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-06
... Determination of Sales at Less Than Fair Value, 73 FR 45403, 45405 (August 5, 2008); Notice of Antidumping Duty Order: Light-Walled Rectangular Pipe and Tube From Turkey, 73 FR 31065 (May 30, 2008). \\2\\ See Initiation of Five-Year (``Sunset'') Review, 78 FR 19647 (April 2, 2013) (Initiation). DATES: Effective...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-01-13
... Duty Administrative Reviews and Requests for Revocation in Part, 74 FR 30052, August 25, 2009. The... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE International Trade Administration Light-Walled Rectangular Pipe and Tube from Turkey: Extension of Time...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-01-25
... Antidumping and Countervailing Duty Administrative Reviews and Requests for Revocation in Part, 75 FR 37759... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE International Trade Administration Light-Walled Rectangular Pipe and Tube From Turkey: Extension of Time...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-04-01
... pipe and tube from Turkey (73 FR 31065). On August 5, 2008, the Department of Commerce issued a countervailing duty order on imports of light-walled rectangular pipe and tube from China (73 FR 45405) and... part 207), as most recently amended at 74 FR 2847 (January 16, 2009). \\1\\ No response to this...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-18
...) of the Act. See Initiation of Five-Year (``Sunset'') Review, 76 FR 38613 (July 1, 2011) (Notice of... FR 12467 (March 27, 1989). The Department received a notice of intent to participate in this sunset... International Trade Administration Light-Walled Welded Rectangular Carbon Steel Tubing From Taiwan:...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-06-08
...In response to a request from Noksel Celik Boru Sanayi A.S., (Noksel), the Department of Commerce (the Department) is conducting an administrative review of the antidumping duty order on light-walled rectangular pipe and tube from Turkey. Atlas Tube, Inc. and Searing Industries, Inc. are petitioners in this case. The review covers exports of the subject merchandise to the United States......
Federal Register 2010, 2011, 2012, 2013, 2014
2010-12-10
...; Opportunity To Request Administrative Review, 75 FR 45094 (August 2, 2010). On August 16, 2010, the Department... Duty Administrative Reviews and Requests for Revocation in Part, 75 FR 60076 (September 29, 2010...). The review covers Sun Group Co., Ltd. (Sun Group), a producer/exporter of light-walled...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-05-14
... Rectangular Pipe and Tube from the People's Republic of China, 73 FR 35652 (June 24, 2008). On August 5, 2008... Determination of Sales at Less Than Fair Value, 73 FR 45403 (August 5, 2008). On August 3, 2009, the Department... Administrative Review, 74 FR 38397 (August 3, 2009). Based on a timely request from FitMAX for an...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-10-04
... Tube from Turkey; Notice of Preliminary Results of Antidumping Duty Administrative Review, 75 FR 33779...-Walled Rectangular Pipe and Tube From Turkey, 73 FR 31065 (May 30, 2008). See Assessment of Antidumping... FR 23954 (May 6, 2003) (Assessment of Antidumping Duties). This clarification will apply to...
75 FR 32341 - Import Administration IA ACCESS Pilot Program
Federal Register 2010, 2011, 2012, 2013, 2014
2010-06-08
... from the People's Republic of China--Investigation; A-588-857: Welded Large Diameter Line Pipe from... program will implement IA ACCESS on a small scale to allow the Department to evaluate and gain experience... from Mexico-- Administrative Review 07/01/08-06/30/09; A-201-836: Light-Walled Rectangular Pipe...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-01
...; Policy Bulletin, 63 FR 18871 (April 16, 1998). The Notice of Initiation of Five-Year (``Sunset'') Reviews... Tube from Dana Mermelstein, (202) 482-1391. Korea (A-580-859) (1st Review). Light-Walled Rectangular Pipe and Tube from Dana Mermelstein, (202) 482-1391. Mexico (A-201-836) (1st Review)....
Light walls around sunspots observed by the Interface Region Imaging Spectrograph
NASA Astrophysics Data System (ADS)
Hou, Y. J.; Li, T.; Yang, S. H.; Zhang, J.
2016-05-01
Context. The Interface Region Imaging Spectrograph (IRIS) mission provides high-resolution observations of the chromosphere and transition region. Using these data, some authors have reported the new finding of light walls above sunspot light bridges. Aims: We try to determine whether the light walls exist somewhere else in active regions in addition to the light bridges. We also examine how the material of these walls evolves. Methods: Employing six months of (from 2014 December to 2015 June) high tempo-spatial data from the IRIS, we find many light walls either around sunspots or above light bridges. Results: For the first time, we report one light wall near an umbral-penumbral boundary and another along a neutral line between two small sunspots. The former light wall has a multilayer structure and is associated with the emergence of positive magnetic flux in the ambient negative field. The latter light wall is associated with a filament activation, and the wall body consists of the filament material, which flowed to a remote plage region with a negative magnetic field after the light wall disappeared. Conclusions: These new observations reveal that these light walls are multilayer and multithermal structures that occur along magnetic neutral lines in active regions. Movies associated to Figs. 1-4 are available in electronic form at http://www.aanda.org
Light walls around sunspots observed by the Interface Region Imaging Spectrograph
NASA Astrophysics Data System (ADS)
Hou, Y. J.; Li, T.; Yang, S. H.; Zhang, J.
2016-04-01
Context. The Interface Region Imaging Spectrograph (IRIS) mission provides high-resolution observations of the chromosphere and transition region. Using these data, some authors have reported the new finding of light walls above sunspot light bridges. Aims: We try to determine whether the light walls exist somewhere else in active regions in addition to the light bridges. We also examine how the material of these walls evolves. Methods: Employing six months of (from 2014 December to 2015 June) high tempo-spatial data from the IRIS, we find many light walls either around sunspots or above light bridges. Results: For the first time, we report one light wall near an umbral-penumbral boundary and another along a neutral line between two small sunspots. The former light wall has a multilayer structure and is associated with the emergence of positive magnetic flux in the ambient negative field. The latter light wall is associated with a filament activation, and the wall body consists of the filament material, which flowed to a remote plage region with a negative magnetic field after the light wall disappeared. Conclusions: These new observations reveal that these light walls are multilayer and multithermal structures that occur along magnetic neutral lines in active regions. Movies associated to Figs. 1-4 are available in electronic form at http://www.aanda.org
Federal Register 2010, 2011, 2012, 2013, 2014
2012-09-10
... Administrative Review, 77 FR 33395 (June 6, 2012) (Preliminary Results). DATES: Effective September 10, 2012. FOR... of Antidumping Duties, 68 FR 23954 (May 6, 2003) (Assessment Policy Notice). Cash Deposit... Turkey, 73 FR 31065 (May 30, 2008). Notification to Importers This notice serves as a final reminder...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-01-08
... Mexico: Preliminary Results and Partial Rescission of Antidumping Duty Administrative Review, 77 FR 55186... Than Fair Value, 73 FR 45403, 45405 (August 5, 2008). In accordance with 19 CFR 356.8(a), the... percent of copper, or 0.50 percent of aluminum, or 1.25 percent of chromium, or 0.30 percent of cobalt,...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-01-12
... Rescission of Antidumping Duty Administrative Review, 76 FR 55352 (September 7, 2011) (Preliminary Results... review for two other companies. See Preliminary Results, 76 FR at 55353. \\2\\ See Initiation of Antidumping and Countervailing Duty Administrative Reviews and Requests for Revocation in Part, 75 FR...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-21
... Administrative Review, 75 FR 27308 (May 14, 2010) (``Preliminary Results''). We gave interested parties an... copper, or 0.50 percent of aluminum, or 1.25 percent of chromium, or 0.30 percent of cobalt, or...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-01-06
... FR at 55567. Respondent companies Nacional de Acero S.A. de C.V., Regiomontana de Perfiles y Tubos S... Mexico: Preliminary Results of Antidumping Duty Administrative Review, 75 FR 55559 (September 13,...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-09-06
... Republic of Korea: Notice of Amended Final Determination of Sales at Less Than Fair Value, 73 FR 45403...; Final Modification, 77 FR 8101 (February 14, 2012). The Department clarified its ``automatic assessment... Proceedings: Assessment of Antidumping Duties, 68 FR 23954 (May 6, 2003). In accordance with 19 CFR...
Federal Register 2010, 2011, 2012, 2013, 2014
2012-09-07
... From Mexico: Preliminary Results of Antidumping Duty Administrative Review, 75 FR 55559 (September 13... Mexico: Preliminary Results of Antidumping Duty Administrative Review, 75 FR 55559, 55565-55566... Suspended Investigation; Opportunity To Request Administrative Review, 76 FR 45773 (August 1, 2011). \\2\\...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-02-18
... Administrative Review, 75 FR 55559 (September 13, 2010) (Preliminary Results). This first administrative review... Administrative Reviews and Request for Revocation in Part, 74 FR 48224, 48225 (September 22, 2009). We invited... Final Results of Antidumping Duty Administrative Review, 76 FR 774 (January 6, 2011). Period of...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-17
... interested party group response to its notice of institution (76 FR 38691, July 1, 2011) of the subject five... Commission's rules. Please consult the Commission's rules, as amended, 76 FR 61937 (Oct. 6, 2011) and the Commission's Handbook on Filing Procedures, 76 FR 62092 (Oct. 6, 2011), available on the Commission's...
Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-08
... People's Republic of China, 73 FR 45405 (August 5, 2008). On April 2, 2013, the Department initiated the... Act). See Initiation of Five-Year (``Sunset'') Review, 78 FR 19647 (April 2, 2013). The Department received a notice of intent to participate from the following domestic parties: Bull Moose Tube...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-13
... Than Fair Value, 73 FR 45403 (August 5, 2008) (Order). On August 3, 2009, the Department published in... Request Administrative Review, 74 FR 38397 (August 3, 2009), covering, inter alia, LWRPT from Mexico for... for Revocation in Part, 74 FR 48224 (September 22, 2009) (Initiation Notice).\\3\\ \\3\\ As noted in...
Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-19
... Tube From Turkey; Notice of Preliminary Results of Antidumping Duty Administrative Review, 76 FR 33200... From Turkey, 73 FR 31065 (May 30, 2008). See Assessment of Antidumping Duties for a full discussion of... filing case briefs. See Preliminary Results, 76 FR at 33204. No interested party submitted briefs....
Federal Register 2010, 2011, 2012, 2013, 2014
2012-06-06
... Order, Finding, or Suspended Investigation; Opportunity To Request Administrative Review, 76 FR 24460... Industries, Inc., are petitioners in this case. The review covers exports of the subject merchandise to the... Reviews and Request for Revocation in Part, 76 FR 37781 (June 28, 2011). On August 5, 2011, the...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-06-15
... Quality Steel Products from Brazil; Preliminary Results of Antidumping Duty Administrative Review, 70 FR...: Carbon and Certain Alloy Steel Wire Rod from Canada, 71 FR 3822 (January 24, 2006), and accompanying...'') or CV during the same shorter averaging periods. See Stainless Steel Plate in Coils From...
Federal Register 2010, 2011, 2012, 2013, 2014
2010-11-09
... Administrative Review, 75 FR 45094 (August 2, 2010). On August 30, 2010, in accordance with 19 CFR 351.213(b), the Department received a timely request from Sun Group Co., Ltd. (``Sun Group'') to conduct an... Requests for Revocation in Part, 75 FR 60076, 60082 (September 29, 2010). Rescission of Countervailing...
Transport in rectangular quadrupole channels
Meier, E.
1983-08-01
Multiple electrostatic quadrupole arrays can be produced in many different geometries. However, the fabrication process can be considerably simplified if the poles are rectangular. This is especially true for millimeter sized channels. This paper presents the results of a series of measurements comparing the space charge limits in cylindrical and rectangular quadrupole channels.
Phasing rectangular apertures.
Baker, K L; Homoelle, D; Utterback, E; Jones, S M
2009-10-26
Several techniques have been developed to phase apertures in the context of astronomical telescopes with segmented mirrors. Phasing multiple apertures, however, is important in a wide range of optical applications. The application of primary interest in this paper is the phasing of multiple short pulse laser beams for fast ignition fusion experiments. In this paper analytic expressions are derived for parameters such as the far-field distribution, a line-integrated form of the far-field distribution that could be fit to measured data, enclosed energy or energy-in-a-bucket and center-of-mass that can then be used to phase two rectangular apertures. Experimental data is taken with a MEMS device to simulate the two apertures and comparisons are made between the analytic parameters and those derived from the measurements. Two methods, fitting the measured far-field distribution to the theoretical distribution and measuring the ensquared energy in the far-field, produced overall phase variance between the 100 measurements of less than 0.005 rad(2) or an RMS displacement of less than 12 nm. PMID:19997175
Analysis of rectangular microstrip antennas
NASA Technical Reports Server (NTRS)
Bailey, M. C.; Deshpande, M. D.
1984-01-01
The problem of microstrip antennas covered by a dielectric substrate is formulated in terms of coupled integro-differential equations with the current distribution on the conducting patch as an unknown quantity. The Galerkin method is used to solve for the unknown patch current. Using the present formulation, the radiation pattern, the resonant frequency, and the bandwidth of a rectangular microstrip antenna are computed. Design data for a rectangular microstrip antenna are also presented.
Synchronizability of random rectangular graphs
Estrada, Ernesto Chen, Guanrong
2015-08-15
Random rectangular graphs (RRGs) represent a generalization of the random geometric graphs in which the nodes are embedded into hyperrectangles instead of on hypercubes. The synchronizability of RRG model is studied. Both upper and lower bounds of the eigenratio of the network Laplacian matrix are determined analytically. It is proven that as the rectangular network is more elongated, the network becomes harder to synchronize. The synchronization processing behavior of a RRG network of chaotic Lorenz system nodes is numerically investigated, showing complete consistence with the theoretical results.
Rectangular configuration improves superconducting cable
NASA Technical Reports Server (NTRS)
Foss, M.; Laverick, C.; Lobell, G.
1968-01-01
Superconducting cable for a cryogenic electromagnet with improved mechanical and thermal properties consists of a rectangular cross-sectioned combination of superconductor and normal conductor. The conductor cable has superconductors embedded in a metallic coating with high electrical and mechanical conductivity at liquid helium temperatures.
Rectangular groupoids and related structures
Boykett, Tim
2013-01-01
The quasivariety of groupoids (N,∗) satisfying the implication a∗b=c∗d⇒a∗d=c∗b=a∗b generalises rectangular semigroups and central groupoids. We call them rectangular groupoids and find three combinatorial structures based upon arrays, matrices and graphs that are closely related. These generalise several groupoids of independent interest. The quasivariety generates the variety of all groupoids; they satisfy no nontrivial equations. We see some strong connections with isotopy, this being one of the classes of algebras (along with quasigroups) closed under isotopy. We investigate some constructions and show that a regular automorphism exists iff the groupoid is derived from a group via a Cayley graph construction. PMID:23836949
Rectangular subsonic jet flowfield study
NASA Technical Reports Server (NTRS)
Morrison, Gerald L.; Tatterson, Gary B.; Swan, David H.
1987-01-01
The flowfield of a rectangular jet with 2:1 aspect ratio was studied at an axial Reynolds number of 127,000, using a three-dimensional laser anemometer. The flowfield surveys resulted in mean velocity vector field plots and contour plots of the Reynolds stress tensor components for the major and minor axes. These data contribute substantially to currently available data of jet flowfields.
Designing Rectangular RHCP Microstrip Antennas
NASA Technical Reports Server (NTRS)
Davidson, Shayla E.
1987-01-01
RHCP, Right-Handed, Circularly Polarized Microstrip Antenna program, aids in design of rectangular microstrip-antenna element, given desired frequency of operation and characteristics of substrate. Begins design calculations on basis of square element with linear polarization. Effective dielectric constant and changes in electrical length due to fringing at edges of radiating element taken into account. Coaxial feed inset with 50 ohms input impedance. Placement of feed such that two orthonormal modes produced in antenna cavity, right- or left-handed circular polarization obtained. Written in FORTRAN 77.
Mapping from rectangular to harmonic representation
Schneider, W.; Bateman, G.
1986-08-01
An algorithm is developed to determine the Fourier harmonics representing the level contours of a scalar function given on a rectangular grid. This method is applied to the problem of computing the flux coordinates and flux surface average needed for 1-1/2-D transport codes and MHD stability codes from an equilibrium flux function given on a rectangular grid.
ac electroosmosis in rectangular microchannels.
Campisi, Michele; Accoto, Dino; Dario, Paolo
2005-11-22
Motivated by the growing interest in ac electroosmosis as a reliable no moving parts strategy to control fluid motion in microfluidic devices for biomedical applications, such as lab-on-a-chip, we study transient and steady-state electrokinetic phenomena (electroosmosis and streaming currents) in infinitely extended rectangular charged microchannels. With the aid of Fourier series and Laplace transforms we provide a general formal solution of the problem, which is used to study the time-dependent response to sudden ac applied voltage differences in case of finite electric double layer. The Debye-Huckel approximation has been adopted to allow for an algebraic solution of the Poisson-Boltzmann problem in Fourier space. We obtain the expressions of flow velocity profiles, flow rates, streaming currents, as well as expressions of the complex hydraulic and electrokinetic conductances. We analyze in detail the dependence of the electrokinetic conductance on the extension of linear dimensions relative to the Debye length, with an eye on finite electric double layer effects. PMID:16351310
Partial Rectangular Metric Spaces and Fixed Point Theorems
2014-01-01
The purpose of this paper is to introduce the concept of partial rectangular metric spaces as a generalization of rectangular metric and partial metric spaces. Some properties of partial rectangular metric spaces and some fixed point results for quasitype contraction in partial rectangular metric spaces are proved. Some examples are given to illustrate the observed results. PMID:24672366
Turbulence Measurements of Rectangular Nozzles with Bevel
NASA Technical Reports Server (NTRS)
Bridges, James; Wernet, Mark P.
2015-01-01
This paper covers particle image velocimetry measurements of a family of rectangular nozzles with aspect ratios 2, 4, and 8, in the high subsonic flow regime. Far-field acoustic results, presented previously, showed that increasing aspect ratios increased the high frequency noise, especially directed in the polar plane containing the minor axis of the nozzle. The measurements presented here have important implications in the modeling of turbulent sources for acoustic analogy theories. While the nonaxisymmetric mean flow from the rectangular nozzles can be studied reliably using computational solutions, the nonaxisymmetry of the turbulent fluctuations, particularly at the level of velocity components, cannot; only measurements such as these can determine the impact of nozzle geometry on acoustic source anisotropy. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. The paper first documents the velocity fields, mean and variance, from the round, rectangular, and beveled rectangular nozzles at high subsonic speeds. A second section introduces measures of the isotropy of the turbulence, such as component ratios and lengthscales, first by showing them for a round jet and then for the rectangular nozzles. From these measures the source models of acoustic analogy codes can be judged or modified to account for these anisotropies.
Electrochemical apparatus comprising modified disposable rectangular cuvette
Dattelbaum, Andrew M; Gupta, Gautam; Morris, David E
2013-09-10
Electrochemical apparatus includes a disposable rectangular cuvette modified with at least one hole through a side and/or the bottom. Apparatus may include more than one cuvette, which in practice is a disposable rectangular glass or plastic cuvette modified by drilling the hole(s) through. The apparatus include two plates and some means of fastening one plate to the other. The apparatus may be interfaced with a fiber optic or microscope objective, and a spectrometer for spectroscopic studies. The apparatus are suitable for a variety of electrochemical experiments, including surface electrochemistry, bulk electrolysis, and flow cell experiments.
Comparing the Volumes of Rectangular Prisms
ERIC Educational Resources Information Center
Assuah, Charles K.; Wiest, Lynda R.
2010-01-01
Can middle-grades students determine which of two rectangular prisms has a larger volume? Can they do so without using a formula? Geometry, and particularly the concept of volume, is important in many subjects, such as physics and chemistry. Students greatly enhance their mathematics knowledge when they make generalizations and construct arguments…
Rectangular Microstrip Antenna with Slot Embedded Geometry
NASA Astrophysics Data System (ADS)
Ambresh, P. A.; Hadalgi, P. M.; Hunagund, P. V.; Sujata, A. A.
2014-09-01
In this paper, a novel design that improves the performance of conventional rectangular microstrip antenna is discussed. Design adopts basic techniques such as probe feeding technique with rectangular inverted patch structure as superstrate, air filled dielectric medium as substrate and slot embedded patch. Prototype of the proposed antenna has been fabricated and various antenna performance parameters such as impedance bandwidth, return loss, radiation pattern and antenna gain are considered for Electromagnetic-study. The antennas are designed for the wireless application operating in the frequency range of 3.3 GHz to 3.6 GHz, and UK based fixed satellite service application (3 GHz to 4 GHz), and are named as single inverted patch conventional rectangular microstrip antenna (SIP-CRMSA) and slots embedded inverted patch rectangular microstrip antenna (SEIP-RMSA), respectively. Measurement outcomes for SEIP-RMSA1 and SEIP-RMSA2 showed the satisfactory performance with an achievable impedance bandwidth of 260 MHz (7 %) and 250 MHz (6.72 %), with return loss (RL) of -11.06 dB and -17.98 dB, achieved gain of 8.17 dB and 5.17 dB with 10% and 8% size reduction in comparison with the conventional patch antenna.
Normal-Pressure Tests of Rectangular Plates
NASA Technical Reports Server (NTRS)
Ramberg, Walter; Mcpherson, Albert E; Levy, Samuel
1942-01-01
Report presents the results of normal-pressure tests made of 56 rectangular plates with clamped edges and of 5 plates with freely supported edges. Pressure was applied and the center deflection and the permanent set at the center were measured. For some of the plates, in addition, strains and contours were measured.
Eigenvalues of Rectangular Waveguide Using FEM With Hybrid Elements
NASA Technical Reports Server (NTRS)
Deshpande, Manohar D.; Hall, John M.
2002-01-01
A finite element analysis using hybrid triangular-rectangular elements is developed to estimate eigenvalues of a rectangular waveguide. Use of rectangular vector-edge finite elements in the vicinity of the PEC boundary and triangular elements in the interior region more accurately models the physical nature of the electromagnetic field, and consequently quicken the convergence.
RWGSCAT - RECTANGULAR WAVEGUIDE JUNCTION SCATTERING PROGRAM
NASA Technical Reports Server (NTRS)
Hoppe, D. J.
1994-01-01
In order to optimize frequency response and determine the tolerances required to meet RF specifications, accurate computer modeling of passive rectangular waveguide components is often required. Many rectangular waveguide components may be represented either exactly or approximately as a number of different size rectangular waveguides which are connected in series. RWGSCAT, Rectangular WaveGuide junction SCATtering program, solves for the scattering properties of a waveguide device. This device must consist of a number of rectangular waveguide sections of different cross sectional area which are connected in series. Devices which fall into this category include step transformers, filters, and smooth or corrugated rectangular horns. RWGSCAT will model such devices and accurately predict the reflection and transmission characteristics, taking into account higher order (other than dominant TE 10) mode excitation if it occurs, as well as multiple reflections and stored energy at each discontinuity. For devices which are large with respect to the wavelength of operation, the characteristics of the device may be required for computing a higher order mode or a number of higher order modes exciting the device. Such interactions can be represented by defining a scattering matrix for each discontinuity in the device, and then cascading the individual scattering matrices in order to determine the scattering matrix for the overall device. The individual matrices are obtained using the mode matching method. RWGSCAT is written in FORTRAN 77 for IBM PC series and compatible computers running MS-DOS. It has been successfully compiled and implemented using Lahey FORTRAN 77 under MS-DOS. A sample MS-DOS executable is provided on the distribution medium. It requires 377K of RAM for execution. Sample input data is also provided on the distribution medium. The standard distribution medium for this program is one 5.25 inch 360K MS-DOS format diskette. The contents of the diskette are
Film condensation in a horizontal rectangular duct
NASA Technical Reports Server (NTRS)
Lu, Qing; Suryanarayana, N. V.
1993-01-01
Condensation heat transfer in a horizontal rectangular duct was experimentally and analytically investigated. To prevent the dripping of condensate on the film, the experiment was conducted inside a horizontal rectangular duct with vapor condensing only on the bottom cooled plate of the duct. R-113 and FC-72 (Fluorinert Electronic Fluid developed by the 3M Company) were used as the condensing fluids. The experimental program included measurements of film thickness, local and average heat transfer coefficients, wave length, wave speed, and a study of wave initiation. The measured film thickness was used to obtain the local heat transfer coefficient. The wave initiation was studied both with condensation and with an adiabatic air-liquid flow. The test sections used in both experiments were identical.
Eddy viscosity measurements in a rectangular jet
NASA Technical Reports Server (NTRS)
Swan, David H.; Morrison, Gerald L.
1988-01-01
The flow field of a rectangular jet with a 2:1 aspect ratio was studied at a Reynolds number of 100,000 (Mach number 0.09) using three-dimensional laser Doppler velocimetry (LDV). Velocity gradients, Reynolds stress tensor components, and scalar eddy viscosities are presented for the major and minor axis planes of the jet. The eddy viscosity model was found to be applicable only in the direction of maximum mean velocity gradient.
Rectangular shape distributed piezoelectric actuator: analytical analysis
NASA Astrophysics Data System (ADS)
Sun, Bohua; Qiu, Yan
2004-04-01
This paper is focused on the development of distributed piezoelectric actuators (DPAs) with rectangular shapes by using PZT materials. Analytical models of rectangular shape DPAs have been constructed in order to analyse and test the performance of DPA products. Firstly, based on the theory of electromagnetics, DPAs have been considered as a type of capacitor. The charge distributed density on the interdigitated electrodes (IDEs), which has been applied in the actuators, and the capacitance of the DPAs have been calculated. The accurate distribution and intensity of electrical field in DPA element have also been calculated completely. Secondly, based on the piezoelectric constitutive relations and the compound plates theory, models for mechanical strain and stress fields of DPAs have been developed, and the performances of rectangular shape DPAs have been discussed. Finally, on the basis of the models that have been developed in this paper, an improved design of a rectangular shape DPA has been discussed and summed up. Due to the minimum hypotheses that have been used during the processes of calculation, the characteristics of this paper are that the accurate distribution and intensity of electrical fields in DPAs have been concluded. The proposed accurate calculations have not been seen in the literature, and can be used in DPA design and manufacture processes in order to improve mechanical performance and reduce the cost of DPA products in further applications. In this paper, all the processes of analysis and calculation have been done by MATLAB and MathCAD. The FEM results used for comparison were obtained using the ABAQUS program.
A clamped rectangular plate containing a crack
NASA Technical Reports Server (NTRS)
Tang, R.; Erdogan, F.
1985-01-01
The general problem of a rectangular plate clamped along two parallel sides and containing a crack parallel to the clamps is considered. The problem is formulated in terms of a system of singular integral equations and the asymptotic behavior of the stress state near the corners is investigated. Numerical examples are considered for a clamped plate without a crack and with a centrally located crack, and the stress intensity factors and the stresses along the clamps are calculated.
Efficient Algorithm for Rectangular Spiral Search
NASA Technical Reports Server (NTRS)
Brugarolas, Paul; Breckenridge, William
2008-01-01
An algorithm generates grid coordinates for a computationally efficient spiral search pattern covering an uncertain rectangular area spanned by a coordinate grid. The algorithm does not require that the grid be fixed; the algorithm can search indefinitely, expanding the grid and spiral, as needed, until the target of the search is found. The algorithm also does not require memory of coordinates of previous points on the spiral to generate the current point on the spiral.
Rectangular Pulsed Laser-Electromagnetic Hybrid Accelerator
Kishida, Yoshiaki; Katayama, Masahiro; Horisawa, Hideyuki
2010-10-13
Experimental investigation of impulse-bit and propellant consumption rate, or mass shot, per single pulse discharge was conducted to characterize the thrust performance of the rectangular laser-electromagnetic hybrid acceleration thruster with various propellant materials. From the result, alumina propellant showed significantly superior performance. The largest values of the measured impulse-bit, specific impulse and thrust efficiency were 49 {mu}Nsec, 6,200 sec and 22%, respectively.
Acoustic Measurements of Rectangular Nozzles With Bevel
NASA Technical Reports Server (NTRS)
Bridges, James E.
2012-01-01
A series of convergent rectangular nozzles of aspect ratios 2:1, 4:1, and 8:1 were constructed with uniform exit velocity profiles. Additional nozzles were constructed that extended the wide lip on one side of these nozzles to form beveled nozzles. Far-field acoustic measurements were made and analyzed, and the results presented. The impact of aspect ratio on jet noise was similar to that of enhanced mixing devices: reduction in aft, peak frequency noise with an increase in broadside, high frequency noise. Azimuthally, it was found that rectangular jets produced more noise directed away from their wide sides than from their narrow sides. The azimuthal dependence decreased at aft angles where noise decreased. The effect of temperature, keeping acoustic Mach number constant, was minimal. Since most installations would have the observer on the wide size of the nozzle, the increased high frequency noise has a deleterious impact on the observer. Extending one wide side of the rectangular nozzle, evocative of an aft deck in an installed propulsion system, increased the noise of the jet with increasing length. The impact of both aspect ratio and bevel length were relatively well behaved, allowing a simple bilinear model to be constructed relative to a simple round jet.
Numerical study on rectangular microhollow cathode discharge
He Shoujie; Ouyang Jiting; He Feng; Li Shang
2011-03-15
Rectangular microhollow cathode discharge in argon is investigated by using two-dimensional time-dependent self-consistent fluid model. The electric potential, electric field, particle density, and mean electron energy are calculated. The results show that hollow cathode effect can be onset in the present configuration, with strong electric field and high mean electron energy in the cathode fall while high density and quasineutral plasma in the negative glow. The potential well and electric filed reversal are formed in the negative glow region. It is suggested that the presence of large electron diffusion flux necessitates the field reversal and potential well.
Supersonic jets from bevelled rectangular nozzles
NASA Technical Reports Server (NTRS)
Rice, Edward J.; Raman, Ganesh
1993-01-01
The influence of nozzle exit geometry on jet mixing and noise production was studied experimentally for a series of rectangular nozzles operating at supersonic jet velocities. Both converging (C) and converging-diverging (C-D) nozzles were built with asymmetrical (single bevel) and symmetrical (double bevel) exit chambers and with conventional straight exits for comparison. About a four decibel reduction of peak mixing noise was observed for the double bevelled C-D nozzle operated at design pressure ratio. All bevelled geometries provided screech noise reduction for under-expanded jets and an upstream mixing noise directivity shift which would be beneficial for improved acoustic treatment performance of a shrouded system.
Recharge from rectangular areas to finite aquifers
NASA Astrophysics Data System (ADS)
Rao, N. H.; Sarma, P. B. S.
1981-10-01
A generalized analytical solution is derived for the growth of groundwater mound in finite aquifers bounded by open water bodies, in response to recharge from rectangular areas. Finite Fourier transforms are used to solve the linearized differential equation of groundwater flow. Unlike earlier solutions, the method presented here does not require the use of tables for evaluation of complicated functions. The solution is evaluated by comparison with existing numerical and analytical results. In stream-aquifer systems similar to those described above, application of the proposed solution is more realistic than using solutions available for infinite aquifers.
Steady evaporating flow in rectangular microchannels.
Griffiths, Stewart K.; Martinez, Mario J.; Tchikanda, Serge W.; Nilson, Robert H.
2005-02-01
Analytical and numerical solutions are presented for steady evaporating flow in open microchannels having a rectangular cross section and a uniform depth. The flow, driven by the axial gradient of capillary pressure, generally consists of an entry region where the meniscus is attached to the top corners of the channel followed by a jump-like transition to a corner-flow region in which the meniscus progressively recedes into the bottom corners of the channel. Illustrative numerical solutions are used to guide the derivation of an easily applied analytical approximation for the maximum sustainable heat flux or capillary limit.
Rectangular subsonic jet flow field measurements
NASA Technical Reports Server (NTRS)
Morrison, Gerald L.; Swan, David H.
1990-01-01
Flow field measurements of three subsonic rectangular cold air jets are presented. The three cases had aspect ratios of 1x2, 1x4 at a Mach number of 0.09 and an aspect ratio of 1x2 at a Mach number of 0.9. All measurements were made using a 3-D laser Doppler anemometer system. The data includes the mean velocity vector, all Reynolds stress tensor components, turbulent kinetic energy and velocity correlation coefficients. The data are presented in tabular and graphical form. No analysis of the measured data or comparison to other published data is made.
Flow-Field Surveys for Rectangular Nozzles
NASA Technical Reports Server (NTRS)
Zaman, K. B. M. Q.
2012-01-01
Flow field survey results for three rectangular nozzles are presented for a low subsonic condition obtained primarily by hot-wire anemometry. The three nozzles have aspect ratios of 2:1, 4:1 and 8:1. A fourth case included has 2:1 aspect ratio with chevrons added to the long edges. Data on mean velocity, turbulent normal and shear stresses as well as streamwise vorticity are presented covering a streamwise distance up to sixteen equivalent diameters from the nozzle exit. These detailed flow properties, including initial boundary layer characteristics, are usually difficult to measure in high speed flows and the primary objective of the study is to aid ongoing and future computational and noise modeling efforts.
Nonlinear vibrations of viscoelastic rectangular plates
NASA Astrophysics Data System (ADS)
Amabili, Marco
2016-02-01
Nonlinear vibrations of viscoelastic thin rectangular plates subjected to normal harmonic excitation in the spectral neighborhood of the lowest resonances are investigated. The von Kármán nonlinear strain-displacement relationships are used and geometric imperfections are taken into account. The material is modeled as a Kelvin-Voigt viscoelastic solid by retaining all the nonlinear terms. The discretized nonlinear equations of motion are studied by using the arclength continuation and collocation method. Numerical results are obtained for the fundamental mode of a simply supported square plate with immovable edges by using models with 16 and 22 degrees of freedom and investigating solution convergence. Comparison to viscous damping and the effect of neglecting nonlinear viscoelastic damping terms are shown. The change of the frequency-response with the retardation time parameter is also investigated as well as the effect of geometric imperfections.
Plasticity and rectangularity in survival curves
Weon, Byung Mook; Je, Jung Ho
2011-01-01
Living systems inevitably undergo a progressive deterioration of physiological function with age and an increase of vulnerability to disease and death. To maintain health and survival, living systems should optimize survival strategies with adaptive interactions among molecules, cells, organs, individuals, and environments, which arises plasticity in survival curves of living systems. In general, survival dynamics in a population is mathematically depicted by a survival rate, which monotonically changes from 1 to 0 with age. It would be then useful to find an adequate function to describe complicated survival dynamics. Here we describe a flexible survival function, derived from the stretched exponential function by adopting an age-dependent shaping exponent. We note that the exponent is associated with the fractal-like scaling in cumulative mortality rate. The survival function well depicts general features in survival curves; healthy populations exhibit plasticity and evolve towards rectangular-like survival curves, as examples in humans or laboratory animals. PMID:22355622
A transonic rectangular grid embedded panel method
NASA Technical Reports Server (NTRS)
Johnson, F. T.; Bussoletti, J. E.; James, R. M.; Young, D. P.; Woo, A. C.
1982-01-01
A method is presented that has the potential for solving transonic flow problems about the same complex aircraft configurations currently being analyzed by subsonic panel methods. This method does not require the generation of surface fitted grids. Instead it uses rectangular grids and subgrids together with embedded surface panels on which boundary conditions are imposed. Both the Euler and full potential equations are considered. The method of least squares is used to reduce the solution of these equations to the solution of a sequence of Poisson problems. The Poisson problems are solved using fast Fourier transforms and panel influence coefficient techniques. The overall method is still in its infancy but some two dimensional results are shown illustrating various key features.
The Lateral Instability of Deep Rectangular Beams
NASA Technical Reports Server (NTRS)
Dumont, C; Hill, H N
1937-01-01
Experimental and analytical studies were made of solid and hollow deep rectangular beams to study their lateral instability under various conditions of loading and restraint. The tests were made on bars and tubes of 17ST aluminum alloy. Failure by lateral buckling occurred only in tests on the solid beams. It was found that, within the elastic range, the test results were in agreement with the classical theory for the lateral buckling of deep beams as given by Prandtl, Mitchell, and Timoshenko. The tests were extended to the inelastic range, where it was found that the substitution for Young's modulus of an average modulus of elasticity derived from the stress-strain curve made it possible to predict instability at high stresses.
Rectangular subsonic jet flow field measurements
NASA Technical Reports Server (NTRS)
Morrison, Gerald L.; Swan, David H.
1989-01-01
Flow field measurements are presented of 3 subsonic rectangular cold air jets. The 3 cases presented had aspect ratios of 1 x 2, 1 x 4 at a Mach number of 0.09 and an aspect ratio of 1 x 2 at a Mach number of 0.9. All measurements were made using a 3-D laser Doppler anemoneter system. The presented data includes the mean velocity vector, all Reynolds stress tensor components, turbulent kinetic energy and velocity correlation coefficients. The data is presented in tabular and graphical form. No analysis of the measured data or comparison to other published data is made. All tabular data are available in ASCII format on MS-DOS compatible disks.
Magnetization reversal in single ferromagnetic rectangular nanowires
NASA Astrophysics Data System (ADS)
de Oliveira, Alexandre B.; da Silva, Gilvânia L.; Rezende, Sergio M.; Azevedo, Antonio
2010-01-01
We report on the magnetoresistance (MR) investigation of the magnetization reversal processes in single rectangular nanowire of Permalloy. A set of nanowires with lengths ranging from 6 to 20 μm, thicknesses fixed in 10 nm, and widths between 250 nm and 1.2 μm, was fabricated by means of AFM local anodic oxidation lithography. Magnetoresistive hysteresis loops show an abrupt jump corresponding to the magnetization reversal that depends on the angle between the wire axis and the applied magnetic field direction. The field value corresponding to the abrupt jump of the MR was associated to the nucleation field deduced from the Brown equations. By the angular dependence of this magnetization reversal field we were able to identify the nucleation mode as the magnetization buckling. We have investigated the temperature dependence of the switching field as well as its stochastic nature as a function of the in-plane angle.
Helping Students Acquainted with Multiplication in Rectangular Model
ERIC Educational Resources Information Center
Tasman, Fridgo; den Hertog, Jaap; Zulkardi; Hartono, Yusuf
2011-01-01
Usually, multiplication is introduced to students to represent quantities that come in groups. However there is also rectangular array model which is also related to multiplication. Barmby et al. (2009) has shown that the rectangular model such as array representations encourage students to develop their thinking about multiplication as a binary…
Method and structure for cache aware transposition via rectangular subsections
Gustavson, Fred Gehrung; Gunnels, John A
2014-02-04
A method and structure for transposing a rectangular matrix A in a computer includes subdividing the rectangular matrix A into one or more square submatrices and executing an in-place transposition for each of the square submatrices A.sub.ij.
Experimental Modal Analysis of Rectangular and Circular Beams
ERIC Educational Resources Information Center
Emory, Benjamin H.; Zhu, Wei Dong
2006-01-01
Analytical and experimental methods are used to determine the natural frequencies and mode shapes of Aluminum 6061-T651 beams with rectangular and circular cross-sections. A unique test stand is developed to provide the rectangular beam with different boundary conditions including clamped-free, clamped-clamped, clamped-pinned, and pinned-pinned.…
Development of the mean velocity distribution in rectangular jets
NASA Technical Reports Server (NTRS)
Morrison, G. L.; Swan, D. H.; Deotte, R. E., Jr.
1992-01-01
The mean flowfield of 1 x 2 and 1 x 4 aspect ratio rectangular jets has been measured using a laser Doppler anemometer system. The development of the downstream velocity distribution is analyzed with respect to centerline velocity decay, shear layer growth, axis switching, and velocity profile development. Comparisons are made with axisymmetric, planar, and other rectangular jets.
Residual Stress Measurement Using Rectangular Spiral Coils
NASA Astrophysics Data System (ADS)
Sun, Haiyan; Plotnikov, Yuri
2008-02-01
Shot peening process provides compressive residual stress within a depth of about 150˜200 um from the surface. It has been demonstrated that multi-frequency eddy current measurement can be effectively used for the residual stress estimation on Ni-based superalloys. In order to measure the stress profile over the entire compressive zone, the probe needs to work in a wide frequency range from 0.1 MHz to above 50 MHz. Due to its wide bandwidth and high precision fabrication process, spiral coils fabricated on flexible substrate using photolithographic technology are good candidate for this task It is useful to develop a coil model in order to optimize coil design, minimize liftoff effect and maximize coil gauge factor. In this work, a 3D analytical model was used to simulate rectangular spiral coil response on a half-space conductor. The results were compared with commercial available 3D finite element software and experimental results. The analytical model was also used to simulate 4-point calibration process that was used to calculate apparent eddy current conductivity (AECC). The experimental setup was described and AECC profile was obtained for shot-peening samples with different peening intensity and different heat treatment.
Perceptual guidelines for creating rectangular treemaps.
Kong, Nicholas; Heer, Jeffrey; Agrawala, Maneesh
2010-01-01
Treemaps are space-filling visualizations that make efficient use of limited display space to depict large amounts of hierarchical data. Creating perceptually effective treemaps requires carefully managing a number of design parameters including the aspect ratio and luminance of rectangles. Moreover, treemaps encode values using area, which has been found to be less accurate than judgments of other visual encodings, such as length. We conduct a series of controlled experiments aimed at producing a set of design guidelines for creating effective rectangular treemaps. We find no evidence that luminance affects area judgments, but observe that aspect ratio does have an effect. Specifically, we find that the accuracy of area comparisons suffers when the compared rectangles have extreme aspect ratios or when both are squares. Contrary to common assumptions, the optimal distribution of rectangle aspect ratios within a treemap should include non-squares, but should avoid extremes. We then compare treemaps with hierarchical bar chart displays to identify the data densities at which length-encoded bar charts become less effective than area-encoded treemaps. We report the transition points at which treemaps exhibit judgment accuracy on par with bar charts for both leaf and non-leaf tree nodes. We also find that even at relatively low data densities treemaps result in faster comparisons than bar charts. Based on these results, we present a set of guidelines for the effective use of treemaps and suggest alternate approaches for treemap layout. PMID:20975136
Film condensation in a horizontal rectangular duct
NASA Technical Reports Server (NTRS)
Lu, Qing; Suryanarayana, N. V.
1992-01-01
Condensation heat transfer in an annular flow regime with and without interfacial waves was experimentally investigated. The study included measurements of heat transfer rate with condensation of vapor flowing inside a horizontal rectangular duct and experiments on the initiation of interfacial waves in condensation, and adiabatic air-liquid flow. An analytical model for the condensation was developed to predict condensate film thickness and heat transfer coefficients. Some conclusions drawn from the study are that the condensate film thickness was very thin (less than 0.6 mm). The average heat transfer coefficient increased with increasing the inlet vapor velocity. The local heat transfer coefficient decreased with the axial distance of the condensing surface, with the largest change at the leading edge of the test section. The interfacial shear stress, which consisted of the momentum shear stress and the adiabatic shear stress, appeared to have a significant effect on the heat transfer coefficients. In the experiment, the condensate flow along the condensing surface experienced a smooth flow, a two-dimensional wavy flow, and a three-dimensional wavy flow. In the condensation experiment, the local wave length decreased with the axial distance of the condensing surface and the average wave length decreased with increasing inlet vapor velocity, while the wave speed increased with increasing vapor velocity. The heat transfer measurements are reliable. And, the ultrasonic technique was effective for measuring the condensate film thickness when the surface was smooth or had waves of small amplitude.
The hydrodynamic focusing effect inside rectangular microchannels
NASA Astrophysics Data System (ADS)
Lee, Gwo-Bin; Chang, Chih-Chang; Huang, Sung-Bin; Yang, Ruey-Jen
2006-05-01
This paper presents a theoretical and experimental investigation into the hydrodynamic focusing effect in rectangular microchannels. Two theoretical models for two-dimensional hydrodynamic focusing are proposed. The first model predicts the width of the focused stream in symmetric hydrodynamic focusing in microchannels of various aspect ratios. The second model predicts the location and the width of the focused stream in asymmetric hydrodynamic focusing in microchannels with a low or high aspect ratio. In both models, the theoretical results are shown to be in good agreement with the experimental data. Hence, the models provide a useful means of performing a theoretical analysis of flow control in microfluidic devices using hydrodynamic focusing effects. The ability of the proposed models to control the focused stream within a micro flow cytometer is verified in a series of experimental trials performed using polystyrene microparticles with a diameter of 20 µm. The experimental data show that the width of the focused stream can be reduced to the same order of magnitude as that of the particle size. Furthermore, it is shown that the microparticles can be successfully hydrodynamically focused and switched to the desired outlet port of the cytometer. Hence, the models presented in this study provide sufficient control to support cell/particle counting and sorting applications.
VIEW LOOKING NORTHEAST AT EARTH MOUND. NOTE THE RECTANGULAR OPENINGS ...
VIEW LOOKING NORTHEAST AT EARTH MOUND. NOTE THE RECTANGULAR OPENINGS USED FOR OBSERVATION EQUIPMENT AND PERISCOPE TOPS. - Marshall Space Flight Center, Redstone Rocket (Missile) Test Stand, Dodd Road, Huntsville, Madison County, AL
VIEW OF INTERIOR SPACE WITH RECTANGULAR SHAPE STRETCH PRESS CONTAINMENT ...
VIEW OF INTERIOR SPACE WITH RECTANGULAR SHAPE STRETCH PRESS CONTAINMENT PIT IN BACKGROUND, FACING NORTH. - Douglas Aircraft Company Long Beach Plant, Aircraft Parts Shipping & Receiving Building, 3855 Lakewood Boulevard, Long Beach, Los Angeles County, CA
Detail of ump that is attached to rectangular rearing tanks ...
Detail of ump that is attached to rectangular rearing tanks (pair). Pump located on the north end of rearing tank. View to the northwest. - Prairie Creek Fish Hatchery, Hwy. 101, Orick, Humboldt County, CA
Consensus dynamics on random rectangular graphs
NASA Astrophysics Data System (ADS)
Estrada, Ernesto; Sheerin, Matthew
2016-06-01
A random rectangular graph (RRG) is a generalization of the random geometric graph (RGG) in which the nodes are embedded into a rectangle with side lengths a and b = 1 / a, instead of on a unit square [ 0 , 1 ] 2. Two nodes are then connected if and only if they are separated at a Euclidean distance smaller than or equal to a certain threshold radius r. When a = 1 the RRG is identical to the RGG. Here we apply the consensus dynamics model to the RRG. Our main result is a lower bound for the time of consensus, i.e., the time at which the network reaches a global consensus state. To prove this result we need first to find an upper bound for the algebraic connectivity of the RRG, i.e., the second smallest eigenvalue of the combinatorial Laplacian of the graph. This bound is based on a tight lower bound found for the graph diameter. Our results prove that as the rectangle in which the nodes are embedded becomes more elongated, the RRG becomes a 'large-world', i.e., the diameter grows to infinity, and a poorly-connected graph, i.e., the algebraic connectivity decays to zero. The main consequence of these findings is the proof that the time of consensus in RRGs grows to infinity as the rectangle becomes more elongated. In closing, consensus dynamics in RRGs strongly depend on the geometric characteristics of the embedding space, and reaching the consensus state becomes more difficult as the rectangle is more elongated.
Passive Control of Supersonic Rectangular Jets through Boundary Layer Swirl
NASA Astrophysics Data System (ADS)
Han, Sang Yeop; Taghavi, Ray R.; Farokhi, Saeed
2013-06-01
Mixing characteristics of under-expanded supersonic jets emerging from plane and notched rectangular nozzles are computationally studied using nozzle exit boundary layer swirl as a mean of passive flow control. The coupling of the rectangular jet instability modes, such as flapping, and the swirl is investigated. A three-dimensional unsteady Reynolds-Averaged Navier-Stokes (RANS) code with shock adaptive grids is utilized. For plane rectangular nozzle with boundary layer swirl, the flapping and spanwise oscillations are captured in the jet's small and large dimensions at twice the frequencies of the nozzles without swirl. A symmetrical oscillatory mode is also observed in the jet with double the frequency of spanwise oscillation mode. For the notched rectangular nozzle with boundary layer swirl, the flapping oscillation in the small jet dimension and the spanwise oscillation in the large jet dimension are observed at the same frequency as those without boundary layer swirl. The mass flow rates in jets at 11 and 8 nozzle heights downstream of the nozzles increased by nearly 25% and 41% for the plane and notched rectangular nozzles respectively, due to swirl. The axial gross thrust penalty due to induced swirl was 5.1% for the plane and 4.9% for the notched rectangular nozzle.
Enhanced Mixing in a Rectangular Duct
NASA Technical Reports Server (NTRS)
Liscinsky, D. S.; True, B.
2003-01-01
An experimental investigation of the mixing of non-reacting opposed rows of jets injected normal to a confined rectangular crossflow has been conducted. Planar Mie-scattering was used to measure the time-average concentration distribution of the jet fluid in planes perpendicular to the duct axis. Particular emphasis was placed on the study of closely spaced orifice configurations applicable to the mixing zone of an RQL combustor. Baseline studies were performed of mixing under "ideal" conditions, i.e., plenum fed jets injecting into a crossflow uniform in velocity and turbulence intensity. In addition, more practical ("non-ideal") issues encountered during hardware design were also studied. As in other studies, mixing effectiveness, determined using a spatial unmixedness parameter based on the variance of mean jet concentration distributions, was found to be optimum when the spacing-to-duct-height ratio was inversely proportional to the square root of the jet-to-mainstream momentum-flux ratio. This relationship is suitable for design under ideal flow conditions. Inlet flow boundary conditions of the jet and approach flow (mainstream) were found to strongly influence mixing performance, but no attempt was made to determine optimum performance under non-ideal conditions. The tests performed do offer some guidance as to expected mixing behavior for several common variables likely to be imposed by hardware constraints. Additionally, in this study it was found that for rows of orifices with opposite centerlines inline, mixing was similar for blockages up to 89 percent (previous crossflow mixing studies concerned with dilution zone configurations, blockages were typically less than 50 percent). Lower levels of unmixedness were obtained as a function of downstream location when axial injection length was minimized. Mixing may be enhanced if orifice centerlines of opposed rows are staggered, but blockage must be =50 percent in this configuration. Round hole and "square
Corpectomy cage subsidence with rectangular versus round endcaps.
Deukmedjian, Armen R; Manwaring, Jotham; Le, Tien V; Turner, Alexander W L; Uribe, Juan S
2014-09-01
Corpectomy cages with rectangular endcaps utilize the stronger peripheral part of the endplate, potentially decreasing subsidence risk. The authors evaluated cage subsidence during cyclic biomechanical testing, comparing rectangular versus round endcaps. Fourteen cadaveric spinal segments (T12-L2) were dissected and potted at T12 and L2, then assigned to a rectangular (n=7) or round (n=7) endcap group. An L1 corpectomy was performed and under uniform conditions a cage/plate construct was cyclically tested in a servo-hydraulic frame with increasing load magnitude. Testing was terminated if the test machine actuator displacement exceeded 6mm, or the specimen completed cyclic loading at 2400 N. Number of cycles, compressive force and force-cycles product at test completion were all greater in the rectangular endcap group compared with the round endcap group (cycles: 3027 versus 2092 cycles; force: 1943 N versus 1533 N; force-cycles product: 6162kN·cycles versus 3973 kN·cycles), however these differences were not statistically significant (p ⩾ 0.076). After normalizing for individual specimen bone mineral density, the same measures increased to a greater extent with the rectangular endcaps (cycles: 3014 versus 1855 cycles; force: 1944 N versus 1444 N; force-cycles product: 6040 kN·cycles versus 2980 kN·cycles), and all differences were significant (p⩽0.030). The rectangular endcap expandable corpectomy cage displayed increased resistance to subsidence over the round endcap cage under cyclic loading as demonstrated by the larger number of cycles, maximum load and force-cycles product at test completion. This suggests rectangular endcaps will be less susceptible to subsidence than the round endcap design. PMID:24831343
Joining of Aluminium Alloy Sheets by Rectangular Mechanical Clinching
Abe, Y.; Mori, K.; Kato, T.
2011-05-04
A mechanical clinching has the advantage of low running costs. However, the joint strength is not high. To improve the maximum load of the joined sheets by a mechanical clinching, square and rectangular mechanical clinching were introduced. In the mechanical clinching, the two sheets are mechanically joined by forming an interlock between the lower and upper sheets by the punch and die. The joined length with the interlock was increased by the rectangular punch and die. The deforming behaviours of the sheets in the mechanical clinching were investigated, and then the interlock in the sheets had distribution in the circumference of the projection. Although the interlocks were formed in both projection side and diagonal, the interlock in the diagonal was smaller because of the long contact length between the lower sheet and the die cavity surface. The maximum load of the joined sheets by the rectangular mechanical clinching was two times larger than the load by the round mechanical clinching.
Dirichlet problem for equations of mixed type in rectangular domain
NASA Astrophysics Data System (ADS)
Basirovich, Sabitov Kamil
2015-11-01
In recent years, developed an interest in the study of boundary value problems for equations of mixed type in rectangular areas. This method proved theorems on the unique solubility and stability of the Dirichlet problem [1 - 3] under certain restrictions on the aspect ratio of the rectangular region of the hyperbolic. In this paper, for the mixed type equation with the Lavrent'ev-Bitsadze Dirichlet problem in a rectangular area. The criterion of uniqueness of the solution of the Dirichlet problem. The solution is built as the sum of the Fourier series. In justifying the convergence of a problem of small denominators regarding the relationship of the parties of the hyperbolic part of the rectangle. In connection with this evaluation are set to secede from scratch small denominator corresponding to the asymptotic behavior of rational and irrational values of the ratio, which allowed to substantiate the convergence of the series constructed in the class of regular solutions.
Simulation of multipactor on the rectangular grooved dielectric surface
NASA Astrophysics Data System (ADS)
Cai, Libing; Wang, Jianguo; Cheng, Guoxin; Zhu, Xiangqin; Xia, Hongfu
2015-11-01
Multipactor discharge on the rectangular grooved dielectric surface is simulated self-consistently by using a two-and-a-half dimensional (2.5 D) electrostatic particle-in-cell (PIC) code. Compared with the electromagnetic PIC code, the former can give much more accurate solution for the space charge field caused by the multipactor electrons and the deposited surface charge. According to the rectangular groove width and height, the multipactor can be divided into four models, the spatial distributions of the multipactor electrons and the space charge fields are presented for these models. It shows that the rectangular groove in different models gives very different suppression effect on the multipactor, effective and efficient suppression on the multipactor can only be reached with a proper groove size.
Resonance in cylindrical-rectangular and wraparound microstrip structures
NASA Technical Reports Server (NTRS)
Ali, Sami M.; Kong, Jin AU; Habashy, Tarek M.; Kiang, Jean-Fu
1989-01-01
A rigorous analysis of the resonance frequency problem of both the cylindrical-rectangular and the wraparound microstrip structure is presented. The problem is formulated in terms of a set of vector integral equations. Using Galerkin's method to solve the integral equations, the complex resonance frequencies are studied with sinusoidal basis functions which incorporate the edge singularity. The complex resonance frequencies are computed using a perturbation approach. Modes suitable for resonator or antenna applications are investigated. The edge singularity of the patch current is shown to have no significant effect on the accuracy of the results. It is shown that the HE10 modes of the cylindrical-rectangular and wraparound patches are more appropriate for resonator applications. The HE01 and TE01 modes of the cylindrical-rectangular and wraparound patches, respectively, are efficient radiating modes.
Simulation of multipactor on the rectangular grooved dielectric surface
Cai, Libing; Wang, Jianguo; Cheng, Guoxin; Zhu, Xiangqin; Xia, Hongfu
2015-11-15
Multipactor discharge on the rectangular grooved dielectric surface is simulated self-consistently by using a two-and-a-half dimensional (2.5 D) electrostatic particle-in-cell (PIC) code. Compared with the electromagnetic PIC code, the former can give much more accurate solution for the space charge field caused by the multipactor electrons and the deposited surface charge. According to the rectangular groove width and height, the multipactor can be divided into four models, the spatial distributions of the multipactor electrons and the space charge fields are presented for these models. It shows that the rectangular groove in different models gives very different suppression effect on the multipactor, effective and efficient suppression on the multipactor can only be reached with a proper groove size.
Prediction of radiative heat transfer in rectangular enclosures
Jamaluddin, A.S.; Smith, P.J.
1987-01-01
Discrete ordinates solutions of the radiative transport equation have been obtained for two- and three-dimensional rectangular enclosures using the S/sub 2/ and S/sub 4/ approximations. Limited evaluations indicate that both S/sub 2/ and S/sub 4/ are suitable for predicting radiative transfer in two-dimensional enclosures. However, for the three-dimensional enclosures the S/sub 2/ approximation is found inadequate. It is inferred that S/sub 4/ or higher order approximations should be used to accurately predict radiative heat transfer in three-dimensional rectangular enclosures.
Solves Poisson's Equation in Axizymmetric Geometry on a Rectangular Mesh
Energy Science and Technology Software Center (ESTSC)
1996-09-10
DATHETA4.0 computes the magnetostatic field produced by multiple point current sources in the presence of perfect conductors in axisymmetric geometry. DATHETA4.0 has an interactive user interface and solves Poisson''s equation using the ADI method on a rectangular finite-difference mesh. DATHETA4.0 uncludes models specific to applied-B ion diodes.
Rectangular Array Model Supporting Students' Spatial Structuring in Learning Multiplication
ERIC Educational Resources Information Center
Shanty, Nenden Octavarulia; Wijaya, Surya
2012-01-01
We examine how rectangular array model can support students' spatial structuring in learning multiplication. To begin, we define what we mean by spatial structuring as the mental operation of constructing an organization or form for an object or set of objects. For that reason, the eggs problem was chosen as the starting point in which the…
Modal analysis applied to circular, rectangular, and coaxial waveguides
NASA Technical Reports Server (NTRS)
Hoppe, D. J.
1988-01-01
Recent developments in the analysis of various waveguide components and feedhorns using Modal Analysis (Mode Matching Method) are summarized. A brief description of the theory is presented, and the important features of the method are pointed out. Specific examples in circular, rectangular, and coaxial waveguides are included, with comparisons between the theory and experimental measurements. Extensions to the methods are described.
FDTD Analysis of U-Slot Rectangular Patch Antenna
NASA Technical Reports Server (NTRS)
Luk, K. M.; Tong, K. F.; Shum, S. M.; Lee, K. F.; Lee, R. Q.
1997-01-01
The U-slot rectangular patch antenna (Figure I) has been found experimentally to provide impedance and gain bandwidths of about 300 without the need of stacked or coplanar parasitic elements [1,2]. In this paper, simulation results of the U-slot patch using FDTD analysis are presented. Comparison with measured results are given.
The acoustic properties of panels with rectangular apertures.
Vigran, T E
2014-05-01
A model for the acoustic properties of a plate perforated with slots of rectangular shape is proposed. The model is based on known expressions for the complex density and compressibility of a pore of rectangular shape together with the radiation impedance of a rectangular shaped piston in a baffle. For the so-called end correction of a rectangular aperture in a plate, an approximate solution is shown to fit an exact solution for the imaginary part of the radiation impedance, the latter solution based on the work of Lindemann [J. Acoust. Soc. Am, 55, 708-717 (1974)]. Two different procedures are tested to calculate the mutual influence of the apertures on the end correction, the one calculating the mutual impedance of neighboring pistons in the plate, the other by calculating the end correction of a piston placed in the end of an infinitely long tube. The model is used calculating the input impedance and absorption coefficient of a Helmholtz resonator with such a plate, comparing with measurement results. The fit between predicted and measured results, using plates with narrow slits, is good, but it is believed that the model also cover a wider range of dimensions for such a slotted plate. PMID:24815260
New coplanar waveguide to rectangular waveguide end launcher
NASA Technical Reports Server (NTRS)
Simons, R. N.; Taub, S. R.
1992-01-01
A new coplanar waveguide to rectangular waveguide end launcher is experimentally demonstrated. The end launcher operates over the Ka-band frequencies that are designated for the NASA Advanced Communication Technology Satellite uplink. The measured insertion loss and return loss are better than 0.5 and -10 dB, respectively.
Rectangular-bore, high-gain laser plasma tube
NASA Technical Reports Server (NTRS)
Mollo, R. A.
1969-01-01
Rectangular-bore tube improves population inversion obtained from upper and terminal laser states, resulting in a significant increase in unsaturated gain factor. Radial field produces efficient pumping of upper laser state. Narrow tube dimensions cause increased diffusion flow of neon is metastable states to tube walls.
Gorman, Jhana; Hales, Jason Dean; Corona, Edmundo
2010-05-01
This report considers the calculation of the quasi-static nonlinear response of rectangular flat plates and tubes of rectangular cross-section subjected to compressive loads using quadrilateralshell finite element models. The principal objective is to assess the effect that the shell drilling stiffness parameter has on the calculated results. The calculated collapse load of elastic-plastic tubes of rectangular cross-section is of particular interest here. The drilling stiffness factor specifies the amount of artificial stiffness that is given to the shell element drilling Degree of freedom (rotation normal to the plane of the element). The element formulation has no stiffness for this degree of freedom, and this can lead to numerical difficulties. The results indicate that in the problems considered it is necessary to add a small amount of drilling tiffness to obtain converged results when using both implicit quasi-statics or explicit dynamics methods. The report concludes with a parametric study of the imperfection sensitivity of the calculated responses of the elastic-plastic tubes with rectangular cross-section.
Flow Through a Rectangular-to-Semiannular Diffusing Transition Duct
NASA Technical Reports Server (NTRS)
Foster, Jeff; Wendt, Bruce J.; Reichert, Bruce A.; Okiishi, Theodore H.
1997-01-01
Rectangular-to-semiannular diffusing transition ducts are critical inlet components on supersonic airplanes having bifucated engine inlets. This paper documents measured details of the flow through a rectangular-to-semiannular transition duct having an expansion area ratio of 1.53. Three-dimensional velocity vectors and total pressures at the exit plane of the diffuser are presented. Surface oil-flow visualization and surface static pressure data are shown. The tests were conducted with an inlet Mach number of 0.786 and a Reynolds number based on the inlet centerline velocity and exit diameter of 3.2 x 10(exp 6). The measured data are compared with previously published computational results. The ability of vortex generators to reduce circumferential total pressure distortion is demonstrated.
Lattice Boltzmann Equation On a 2D Rectangular Grid
NASA Technical Reports Server (NTRS)
Bouzidi, MHamed; DHumieres, Dominique; Lallemand, Pierre; Luo, Li-Shi; Bushnell, Dennis M. (Technical Monitor)
2002-01-01
We construct a multi-relaxation lattice Boltzmann model on a two-dimensional rectangular grid. The model is partly inspired by a previous work of Koelman to construct a lattice BGK model on a two-dimensional rectangular grid. The linearized dispersion equation is analyzed to obtain the constraints on the isotropy of the transport coefficients and Galilean invariance for various wave propagations in the model. The linear stability of the model is also studied. The model is numerically tested for three cases: (a) a vortex moving with a constant velocity on a mesh periodic boundary conditions; (b) Poiseuille flow with an arbitrasy inclined angle with respect to the lattice orientation: and (c) a cylinder &symmetrically placed in a channel. The numerical results of these tests are compared with either analytic solutions or the results obtained by other methods. Satisfactory results are obtained for the numerical simulations.
Analytical theory of an unloaded rectangular microstrip patch
NASA Astrophysics Data System (ADS)
Chang, D. C.
1981-01-01
A graphical method for determining the size of a resonant rectangular microstrip patch for a specified frequency is given. Using an expression obtained from the reflection coefficient of a transverse electromagnetic (TEM) wave in a semi-infinite microstrip patch, the resonance condition of a given mode for a patch of finite size is derived in a manner analogous to that of a rectangular, waveguide cavity. Radiation is shown to be in the form of both surface waves and space waves and is dependent on the angles of incidence for waves impinging onto the edges of the patch. By varying the aspect ratio, it is also possible to modify the Q factor of a resonant path. Analytical expressions for the resonant frequency and the Q factor are then derived under the assumption of a very thin substrate slab, encountered frequently in the application. Design curves in the form of the 'Argand diagram' are then presented for microstrip patches with fixed aspect ratios.
IR photodetector based on rectangular quantum wire in magnetic field
Jha, Nandan
2014-04-24
In this paper we study rectangular quantum wire based IR detector with magnetic field applied along the wires. The energy spectrum of a particle in rectangular box shows level repulsions and crossings when external magnetic field is applied. Due to this complex level dynamics, we can tune the spacing between any two levels by varying the magnetic field. This method allows user to change the detector parameters according to his/her requirements. In this paper, we numerically calculate the energy sub-band levels of the square quantum wire in constant magnetic field along the wire and quantify the possible operating wavelength range that can be obtained by varying the magnetic field. We also calculate the photon absorption probability at different magnetic fields and give the efficiency for different wavelengths if the transition is assumed between two lowest levels.
Intrinsic polarization control in rectangular GaN nanowire lasers
Li, Changyi; Liu, Sheng; Luk, Ting S.; Figiel, Jeffrey J.; Brener, Igal; Brueck, S. R. J.; Wang, George T.
2016-02-01
In this study, we demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444kW/cm2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control overmore » the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.« less
Intrinsic polarization control in rectangular GaN nanowire lasers.
Li, Changyi; Liu, Sheng; Luk, Ting S; Figiel, Jeffrey J; Brener, Igal; Brueck, S R J; Wang, George T
2016-03-01
We demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444 kW cm(-2) and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control over the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates. PMID:26899502
Intrinsic polarization control in rectangular GaN nanowire lasers
NASA Astrophysics Data System (ADS)
Li, Changyi; Liu, Sheng; Luk, Ting. S.; Figiel, Jeffrey J.; Brener, Igal; Brueck, S. R. J.; Wang, George T.
2016-03-01
We demonstrate intrinsic, linearly polarized lasing from single GaN nanowires using cross-sectional shape control. A two-step top-down fabrication approach was employed to create straight nanowires with controllable rectangular cross-sections. A clear lasing threshold of 444 kW cm-2 and a narrow spectral line width of 0.16 nm were observed under optical pumping at room temperature, indicating the onset of lasing. The polarization was along the short dimension (y-direction) of the nanowire due to the higher transverse confinement factors for y-polarized transverse modes resulting from the rectangular nanowire cross-section. The results show that cross-sectioned shape control can enable inherent control over the polarization of nanowire lasers without additional environment requirements, such as placement onto lossy substrates.
Flexural rigidity of biaxially loaded reinforced concrete rectangular column sections
NASA Astrophysics Data System (ADS)
Resheidat, M.; Ghanma, M.; Sutton, C.; Chen, Wai-Fah
1995-05-01
An exact analysis is carried out utilizing the parabola-rectangle stress-strain curve for concrete and a typical idealized stress-strain curve for steel to develop the moment-curvature relationship for biaxially loaded reinforced concrete rectangular column sections. Based on that, the flexural rigidity EI of the section is determined at the yield curvature. A computer program is written by FORTRAN 77 to handle the required computations. The influence of material properties, the effect of steel ratios, and the impact of axial loads on the EI estimation were investigated. This study leads to the development of a new equation to estimate the flexural rigidity EI of reinforced concrete biaxially loaded rectangular columns in which these factors were considered. It is shown that the new equation stems from the actual behavior of the column. Therefore, it is recommended for general use in the design of slender columns.
Ground water quality assessment using multi-rectangular diagrams.
Ahmad, Niaz; Sen, Zekai; Ahmad, Manzoor
2003-01-01
A new graphical technique is proposed here for classifying chemical analyses of ground water. In this technique, a diagram is constructed using rectangular coordinates. The new diagram, called a multi-rectangular diagram (MRD), uses adjacent multi-rectangles in which each rectangle represents a specific ground water type. This new diagram has the capability to accommodate a large number of data sets. MRDs have been used to classify chemical analyses of ground water in the Chaj Doab area of Pakistan to illustrate this new approach. Using this graphical method, the differentiated ground water types are calcium bicarbonate, magnesium bicarbonate, sodium bicarbonate, and sodium sulfate. Sodium bicarbonate emerges as the most abundant ground water type. MRDs also offer a visual display of the Chebotarev sequence of ground water quality evolution. PMID:14649865
Comparison between different rectangular horn elements for array antenna applications
NASA Astrophysics Data System (ADS)
Lier, E.; Rengarjan, S.; Rahmat-Samii, Y.
1991-08-01
The coupling and directivity characteristics of an array with fundamental smooth-walled, soft and hard open-ended waveguide elements with rectangular cross-section are considered. Exact and approximate methods to analyze coupling in arrays are discussed. It is known that the coupling, which can be expressed by a quadruple integral across the rectangular apertures, can be reduced to double integrals by introducing a coordinate transformation. Calculations show that the soft waveguide elements are suited for applications where low return loss and mutual coupling are required. Arrays with hard waveguide elements yield high directivity for limited scan applications. Both elements can, in contrast to conventional smooth-walled (SW) horns, operate in dual polarization with high isolation between the orthogonal modes.
Partitioning Rectangular and Structurally Nonsymmetric Sparse Matrices for Parallel Processing
B. Hendrickson; T.G. Kolda
1998-09-01
A common operation in scientific computing is the multiplication of a sparse, rectangular or structurally nonsymmetric matrix and a vector. In many applications the matrix- transpose-vector product is also required. This paper addresses the efficient parallelization of these operations. We show that the problem can be expressed in terms of partitioning bipartite graphs. We then introduce several algorithms for this partitioning problem and compare their performance on a set of test matrices.
Real time rectangular document detection on mobile devices
NASA Astrophysics Data System (ADS)
Skoryukina, Natalya; Nikolaev, Dmitry P.; Sheshkus, Alexander; Polevoy, Dmitry
2015-02-01
In this paper we propose an algorithm for real-time rectangular document borders detection in mobile device based applications. The proposed algorithm is based on combinatorial assembly of possible quadrangle candidates from a set of line segments and projective document reconstruction using the known focal length. Fast Hough Transform is used for line detection. 1D modification of edge detector is proposed for the algorithm.
Propagation of a low-frequency rectangular pulse in seawater
NASA Astrophysics Data System (ADS)
King, Ronold W. P.
1993-05-01
As a necessary preliminary to the determination of the electromagnetic field scattered by a metal cylinder submerged in the ocean, the propagation of a low frequency pulse with a rectangular envelope is evaluated numerically as a function of the distance of travel. Graphs of the three component terms and their sum are shown for four distances. The very significant changes in shape and amplitude of the pulse are discussed.
The hydrodynamic advantages of synchronized swimming in a rectangular pattern.
Daghooghi, Mohsen; Borazjani, Iman
2015-10-01
Fish schooling is a remarkable biological behavior that is thought to provide hydrodynamic advantages. Theoretical models have predicted significant reduction in swimming cost due to two physical mechanisms: vortex hypothesis, which reduces the relative velocity between fish and the flow through the induced velocity of the organized vortex structure of the incoming wake; and the channeling effect, which reduces the relative velocity by enhancing the flow between the swimmers in the direction of swimming. Although experimental observations confirm hydrodynamic advantages, there is still debate regarding the two mechanisms. We provide, to our knowledge, the first three-dimensional simulations at realistic Reynolds numbers to investigate these physical mechanisms. Using large-eddy simulations of self-propelled synchronized swimmers in various rectangular patterns, we find evidence in support of the channeling effect, which enhances the flow velocity between swimmers in the direction of swimming as the lateral distance between swimmers decreases. Our simulations show that the coherent structures, in contrast to the wake of a single swimmer, break down into small, disorganized vortical structures, which have a low chance for constructive vortex interaction. Therefore, the vortex hypothesis, which is relevant for diamond patterns, was not found for rectangular patterns, but needs to be further studied for diamond patterns in the future. Exploiting the channeling mechanism, a fish in a rectangular school swims faster as the lateral distance decreases, while consuming similar amounts of energy. The fish in the rectangular school with the smallest lateral distance (0.3 fish lengths) swims 20% faster than a solitary swimmer while consuming similar amount of energy. PMID:26447493
Radial Eigenmodes for a Toroidal Waveguide with Rectangular Cross Section
Rui Li
2012-07-01
In applying mode expansion to solve the CSR impedance for a section of toroidal vacuum chamber with rectangular cross section, we identify the eigenvalue problem for the radial eigenmodes which is different from that for cylindrical structures. In this paper, we present the general expressions of the radial eigenmodes, and discuss the properties of the eigenvalues on the basis of the Sturm-Liouville theory.
Bandwidth Study of the Microwave Reflectors with Rectangular Corrugations
NASA Astrophysics Data System (ADS)
Zhang, Liang; He, Wenlong; Donaldson, Craig R.; Cross, Adrian W.
2016-09-01
The mode-selective microwave reflector with periodic rectangular corrugations in the inner surface of a circular metallic waveguide is studied in this paper. The relations between the bandwidth and reflection coefficient for different numbers of corrugation sections were studied through a global optimization method. Two types of reflectors were investigated. One does not consider the phase response and the other does. Both types of broadband reflectors operating at W-band were machined and measured to verify the numerical simulations.
Augmented Beta rectangular regression models: A Bayesian perspective.
Wang, Jue; Luo, Sheng
2016-01-01
Mixed effects Beta regression models based on Beta distributions have been widely used to analyze longitudinal percentage or proportional data ranging between zero and one. However, Beta distributions are not flexible to extreme outliers or excessive events around tail areas, and they do not account for the presence of the boundary values zeros and ones because these values are not in the support of the Beta distributions. To address these issues, we propose a mixed effects model using Beta rectangular distribution and augment it with the probabilities of zero and one. We conduct extensive simulation studies to assess the performance of mixed effects models based on both the Beta and Beta rectangular distributions under various scenarios. The simulation studies suggest that the regression models based on Beta rectangular distributions improve the accuracy of parameter estimates in the presence of outliers and heavy tails. The proposed models are applied to the motivating Neuroprotection Exploratory Trials in Parkinson's Disease (PD) Long-term Study-1 (LS-1 study, n = 1741), developed by The National Institute of Neurological Disorders and Stroke Exploratory Trials in Parkinson's Disease (NINDS NET-PD) network. PMID:26289406
Two-Channel Rectangular Dielectric Wake Field Accelerator Structure Experiment
Sotnikov, G. V.; Marshall, T. C.; Shchelkunov, S. V.; Didenko, A.; Hirshfield, J. L.
2009-01-22
A design is presented for a two-channel 30-GHz rectangular dielectric wake field accelerator structure being built for experimental tests at Argonne National Laboratory (ANL). This structure allows for a transformer ratio T much greater than two, and permits continuous coupling of energy from drive bunches to accelerated bunches. It consists of three planar slabs of cordierite ceramic ({epsilon} = 4.7) supported within a rectangular copper block, forming a drive channel 12 mmx6 mm, and an accelerator channel 2 mmx6 mm. When driven by a 50 nC, 14 MeV single bunch available at ANL, theory predicts an acceleration field of 6 MeV/m, and T = 12.6. Inherent transverse wake forces introduce deflections and some distortion of bunch profiles during transit through the structure that are estimated to be tolerable. Additionally, a cylindrical two-channel DWFA is introduced which shares many advantages of the rectangular structure including high T, and the added virtue of axisymmetry that eliminates lowest-order transverse deflecting forces.
Free vibration of rectangular plates with a small initial curvature
NASA Technical Reports Server (NTRS)
Adeniji-Fashola, A. A.; Oyediran, A. A.
1988-01-01
The method of matched asymptotic expansions is used to solve the transverse free vibration of a slightly curved, thin rectangular plate. Analytical results for natural frequencies and mode shapes are presented in the limit when the dimensionless bending rigidity, epsilon, is small compared with in-plane forces. Results for different boundary conditions are obtained when the initial deflection is: (1) a polynomial in both directions, and (2) the product of a polynomial and a trigonometric function, and arbitrary. For the arbitrary initial deflection case, the Fourier series technique is used to define the initial deflection. The results obtained show that the natural frequencies of vibration of slightly curved plates are coincident with those of perfectly flat, prestressed rectangular plates. However, the eigenmodes are very different from those of initially flat prestressed rectangular plates. The total deflection is found to be the sum of the initial deflection, the deflection resulting from the solution of the flat plate problem, and the deflection resulting from the static problem.
The pulsating laminar flow in a rectangular channel
NASA Astrophysics Data System (ADS)
Valueva, E. P.; Purdin, M. S.
2015-11-01
The finite difference method is used to solve the task of the developed pulsating laminar flow in a rectangular channel. The optimum of the difference scheme parameters was determined. Data on the amplitude and phase of the longitudinal velocity oscillations, the hydraulic and friction drag coefficients, the shear stress on the wall have been obtained. Using the dimensionless value of the frequency pulsations two characteristic regimes — the quasisteady-state regime and the high-frequency regime have been identified. In the quasi-steady-state regime, the values of all hydrodynamic quantities at each instant of time correspond to the velocity value averaged over the cross section at a given moment of time. It is shown that in the high-frequency regime, the dependences on the dimensionless oscillation frequency of oscillating components of hydrodynamic quantities are identical for rectilinear channels with a different cross-sectional form (round pipe, flat and a rectangular channels). The effect of the aspect ratio of the rectangular channel sides channel on the pulsating flow dynamics has been analyzed.
Single and Multi-channel Quantum Dragons from Rectangular Nanotubes
NASA Astrophysics Data System (ADS)
Li, Zhou; Novotny, Mark
2015-03-01
Recently quantum dragons have been discovered theoretically. Quantum dragons are nanostructures with correlated disorder that permit energy-independent total quantum transmission of electrons. Hence the electrical conductance G in a two-terminal measurement should be the conductance quantum G0 = 2e2 / h . The single-band tight banding model is used. An example of a single-channel quantum dragon is a rectangular nanotube with disorder along the direction z of the electron propagation. Quantum dragons are obtained by solving the time-independent Schrödinger equation to obtain the electrical transmission calT as a function of the incoming electron energy E. A quantum dragon has calT (E) =1 for all energies. This work generalizes the solution of the time-independent Schrödinger equation to the case of more than one open channel, and applies the method to nanotubes formed from rectangular lattices. One can envision such single-walled rectangular nanotubes for iron starting from free-standing single-atom-thick Fe membranes which have recently been obtained experimentally. Supported in part by NSF Grant DMR-1206233.
RWGSCAT/CWGSCAT - RECTANGULAR AND CIRCULAR WAVEGUIDE JUNCTION SCATTERING PACKAGE
NASA Technical Reports Server (NTRS)
Hoppe, D. J.
1994-01-01
Accurate computer modeling of passive circular or rectangular waveguide components is often required during the design phase for optimizing frequency response and/or determining the tolerance required on components in order to meet radio frequency specifications. RWGSCAT/CWGSCAT is capable of modeling both types of waveguide components. The Scattering Matrix Program for Circular Waveguide Junctions, CWGSCAT, computes the scattering matrix for a circular waveguide. This includes a dual mode horn and certain types of corrugated horns. RWGSCAT, Rectangular WaveGuide junction SCATtering program, solves for the scattering properties of a rectangular waveguide device, such as a smooth or corrugated rectangular horn, step transformer, or filter. RWGSCAT and CWGSCAT are also available separately as NPO-19091 and NPO-18708, respectively. Many circular waveguide devices can be represented either exactly or approximately as a series of circular waveguide sections which have a common center. In addition, smooth tapers and horns of arbitrary profile may be approximated by a series of small steps. Devices that may be analyzed in this fashion include a simple waveguide step discontinuity, such as that used in a dual mode horn, a stepped matching section, or a corrugated waveguide section with constant varying slot depth. CWGSCAT will accurately predict the reflection and transmission characteristics of such devices, taking into account higher order mode excitation if it occurs as well as multiple reflections and stored energy at each discontinuity. For large devices, with respect to a wavelength where many modes may propagate, the reflection and transmission properties may be required for a higher order mode or series of modes exciting the device. Such interactions are represented best by defining a scattering matrix for the device. The matrix can be determined by using mode matching at each discontinuity present. The results for individual discontinuities are then cascaded to
Investigation of imaging properties for submillimeter rectangular pinholes
Xia, Dan; Moore, Stephen C. E-mail: miaepark@bwh.harvard.edu Park, Mi-Ae E-mail: miaepark@bwh.harvard.edu Cervo, Morgan E-mail: miaepark@bwh.harvard.edu; Metzler, Scott D.
2015-12-15
Purpose: Recently, a multipinhole collimator with inserts that have both rectangular apertures and rectangular fields of view (FOVs) has been proposed for SPECT imaging since it can tile the projection onto the detector efficiently and the FOVs in transverse and axial directions become separable. The purpose of this study is to investigate the image properties of rectangular-aperture pinholes with submillimeter apertures sizes. Methods: In this work, the authors have conducted sensitivity and FOV experiments for 18 replicates of a prototype insert fabricated in platinum/iridium (Pt/Ir) alloy with submillimeter square-apertures. A sin{sup q}θ fit to the experimental sensitivity has been performed for these inserts. For the FOV measurement, the authors have proposed a new formula to calculate the projection intensity of a flood image on the detector, taking into account the penumbra effect. By fitting this formula to the measured projection data, the authors obtained the acceptance angles. Results: The mean (standard deviation) of fitted sensitivity exponents q and effective edge lengths w{sub e} were, respectively, 10.8 (1.8) and 0.38 mm (0.02 mm), which were close to the values, 7.84 and 0.396 mm, obtained from Monte Carlo calculations using the parameters of the designed inserts. For the FOV measurement, the mean (standard deviation) of the transverse and axial acceptances were 35.0° (1.2°) and 30.5° (1.6°), which are in good agreement with the designed values (34.3° and 29.9°). Conclusions: These results showed that the physical properties of the fabricated inserts with submillimeter aperture size matched our design well.
Sloshing roof impact tests of a rectangular tank
NASA Astrophysics Data System (ADS)
Minowa, Chikahiro; Ogawa, Nobuyuki; Harada, Iki; Ma, David C.
Some tanks have been damaged at the roofs due to sloshing impact caused by strong earthquakes. It is, therefore, necessary to consider the impact force in the aseismic design code for tank roofs. However, there are few studies on the earthquake responses of storage and process tank roofs. As a first step to investigate the effects of sloshing impact a series of the shaking table tests of a rectangular tank have been conducted at the National Research Institute for Earth Science and Disaster Prevention (NIED). The results of these shaking table tests are presented in the paper. The test tank is rectangular in shape having dimensions of 5 m x 3 m x 2 m (length x width x height). The tank was constructed of glass-fiber reinforced plastic panels. Every panel had a flange on four edges, and each panel was connected by bolts along the flange. The test tank was set on the NIED shaking table (15 m by 15 m). Two types of liquid were used, water and a viscous liquid (water mixed with polymeric powders). The roof impact pressures and other quantities were measured. During the tests using the 400 pi El-Centro excitation, the roof deformation sensor steel beam was damaged. The response of side walls with different rigidity were measured in the wall bulging tests. The measured vibrations within the panel plates were larger than those in the panel flanges. The viscous liquid of 100 cp had little influence on wall bulging responses. However, the viscous effects on sloshing responses were observed in the sloshing tests. Approximate analyses of rectangular tanks, considering the influence of static water pressure, are also presented in this paper.
Sloshing roof impact tests of a rectangular tank
Minowa, C.; Ogawa, N.; Harada, I.; Ma, D.C.
1994-06-01
Some tanks have been damaged at the roofs due to sloshing impact caused by strong earthquakes. It is, therefore, necessary to consider the impact force in the aseismic design code for tank roofs. However, there are few studies on the earthquake responses of storage and process tank roofs. As a first step to investigate the effects of sloshing impact a series of the shaking table tests of a rectangular tank have been conducted at the National Research Institute for Earth Science and Disaster Prevention (NIED). The results of these shaking table tests are presented in the paper. The test tank is rectangular in shape having dimensions of 5 m {times} 3 m {times} 2 m length {times} width {times} height). The tank was constructed of glass-fiber reinforced plastic panels. Every panel had a flange on four edges, and each panel was connected by bolts along the flange. The test tank was set on the NIED shaking table (15 m by 15 m). Two types of liquid were used, water and a viscous liquid (water mixed with polymeric powders). The roof impact pressures and other quantities were measured. During the tests using the 400 pi El-Centro excitation, the roof deformation sensor steel beam was damaged. The response of side walls with different rigidity were measured in the wall bulging tests. The measured vibrations within the panel plates were larger than those in the panel flanges. The viscous liquid of 100 cp had little influence on wall bulging responses. However, the viscous effects on sloshing responses were observed in the sloshing tests. Approximate analyses of rectangular tanks, considering the influence of static water pressure, are also presented in this paper.
Microwave corrosion detection using open ended rectangular waveguide sensors
Qaddoumi, N.; Handjojo, L.; Bigelow, T.; Easter, J.; Bray, A.; Zoughi, R.
2000-02-01
The use of microwave and millimeter wave nondestructive testing methods utilizing open ended rectangular waveguide sensors has shown great potential for detecting minute thickness variations in laminate structures, in particular those backed by a conducting plate. Slight variations in the dielectric properties of materials may also be detected using a set of optimal parameters which include the standoff distance and the frequency of operation. In a recent investigation, on detecting rust under paint, the dielectric properties of rust were assumed to be similar to those of Fe{sub 2}O{sub 3} powder. These values were used in an electromagnetic model that simulates the interaction of fields radiated by a rectangular waveguide aperture with layered structures to obtain optimal parameters. The dielectric properties of Fe{sub 2}O{sub 3} were measured to be very similar to the properties of paint. Nevertheless, the presence of a simulated Fe{sub 2}O{sub 3} layer under a paint layer was detected. In this paper the dielectric properties of several different rust samples from different environments are measured. The measurements indicate that the nature of real rust is quite diverse and is different from Fe{sub 2}O{sub 3} and paint, indicating that the presence of rust under paint can be easily detected. The same electromagnetic model is also used (with the newly measured dielectric properties of real rust) to obtain an optimal standoff distance at a frequency of 24 GHz. The results indicate that variations in the magnitude as well as the phase of the reflection coefficient can be used to obtain information about the presence of rust. An experimental investigation on detecting the presence of very thin rust layers (2.5--5 x 10{sup {minus}2} mm [09--2.0 x 10{sup {minus}3} in.]) using an open ended rectangular waveguide probe is also conducted. Microwave images of rusted specimens, obtained at 24 GHz, are also presented.
Rectangular Array Of Digital Processors For Planning Paths
NASA Technical Reports Server (NTRS)
Kemeny, Sabrina E.; Fossum, Eric R.; Nixon, Robert H.
1993-01-01
Prototype 24 x 25 rectangular array of asynchronous parallel digital processors rapidly finds best path across two-dimensional field, which could be patch of terrain traversed by robotic or military vehicle. Implemented as single-chip very-large-scale integrated circuit. Excepting processors on edges, each processor communicates with four nearest neighbors along paths representing travel to north, south, east, and west. Each processor contains delay generator in form of 8-bit ripple counter, preset to 1 of 256 possible values. Operation begins with choice of processor representing starting point. Transmits signals to nearest neighbor processors, which retransmits to other neighboring processors, and process repeats until signals propagated across entire field.
Corner heating in rectangular solid oxide electrochemical cell generators
Reichner, Philip
1989-01-01
Disclosed is an improvement in a solid oxide electrochemical cell generator 1 having a rectangular design with four sides that meet at corners, and containing multiplicity of electrically connected fuel cells 11, where a fuel gas is passed over one side of said cells and an oxygen containing gas is passed into said cells, and said fuel is burned to form heat, electricity, and an exhaust gas. The improvement comprises passing the exhaust gases over the multiplicity of cells 11 in such a way that more of the heat in said exhaust gases flows at the corners of the generator, such as through channels 19.
Damage Analysis of Rectangular Section Composite Beam under Pure Bending
NASA Astrophysics Data System (ADS)
Liu, Yiping; Xiao, Fan; Liu, Zejia; Tang, Liqun; Fang, Daining
2013-02-01
Laminated composite beams are commonly used in engineering applications involving macro to nano structures. Based on the assumption that plain sections remain plain after deformation, this paper analyzes stress distributions in cross-ply laminated composite beams with rectangular cross-sections, and formulates the basic damage equations through Kachanov's damage definition and Janson's failure criterion. The location of the neutral axis and the ultimate bending moment are obtained for pure bending cases. The effect of the elastic modulus of the two layers on the damage evolution is analyzed; a reasonable damage composite beam model is proposed to predict the ultimate bending moment.
The Gross-Pitaevskii Hierarchy on General Rectangular Tori
NASA Astrophysics Data System (ADS)
Herr, Sebastian; Sohinger, Vedran
2016-06-01
In this work, we study the Gross-Pitaevskii hierarchy on general—rational and irrational—rectangular tori of dimensions two and three. This is a system of infinitely many linear partial differential equations which arises in the rigorous derivation of the nonlinear Schrödinger equation. We prove a conditional uniqueness result for the hierarchy. In two dimensions, this result allows us to obtain a rigorous derivation of the defocusing cubic nonlinear Schrödinger equation from the dynamics of many-body quantum systems. On irrational tori, this question was posed as an open problem in the previous work of Kirkpatrick, Schlein, and Staffilani.
Modeling of a nanoscale rectangular hole in a real metal.
Kumar, Arun; Srivastava, Triranjita
2008-02-15
We propose and implement a simple and accurate method to analyze a subwavelength rectangular hole in a real metal and obtain the modal characteristics of its fundamental mode. Our results are found to be in excellent agreement with those reported in the literature, obtained by the effective index method (EIM) and finite-element and finite-difference methods. Unlike the EIM, the present method has no ambiguity in its implementation and is able to predict the major field components also, which may be useful in understanding the extraordinary transmission characteristics of such structures. PMID:18278101
Width effects in transonic flow over a rectangular cavity
Beresh, Steven J.; Wagner, Justin L.; Henfling, John F.; Spillers, Russell Wayne; Pruett, Brian Owen Matthew
2015-07-24
A previous experiment by the present authors studied the flow over a finite-width rectangular cavity at freestream Mach numbers 1.5–2.5. In addition, this investigation considered the influence of three-dimensional geometry that is not replicated by simplified cavities that extend across the entire wind-tunnel test section. The latter configurations have the attraction of easy optical access into the depths of the cavity, but they do not reproduce effects upon the turbulent structures and acoustic modes due to the length-to-width ratio, which is becoming recognized as an important parameter describing the nature of the flow within narrower cavities.
Extending the MODPATH Algorithm to Rectangular Unstructured Grids.
Pollock, David W
2016-01-01
The recent release of MODFLOW-USG, which allows model grids to have irregular, unstructured connections, requires a modification of the particle-tracking algorithm used by MODPATH. This paper describes a modification of the semi-analytical particle-tracking algorithm used by MODPATH that allows it to be extended to rectangular-based unstructured grids by dividing grid cells with multi-cell face connections into sub-cells. The new method will be incorporated in the next version of MODPATH which is currently under development. PMID:25754305
A New Fuzzy System Based on Rectangular Pyramid
Jiang, Mingzuo; Yuan, Xuehai; Li, Hongxing; Wang, Jiaxia
2015-01-01
A new fuzzy system is proposed in this paper. The novelty of the proposed system is mainly in the compound of the antecedents, which is based on the proposed rectangular pyramid membership function instead of t-norm. It is proved that the system is capable of approximating any continuous function of two variables to arbitrary degree on a compact domain. Moreover, this paper provides one sufficient condition of approximating function so that the new fuzzy system can approximate any continuous function of two variables with bounded partial derivatives. Finally, simulation examples are given to show how the proposed fuzzy system can be effectively used for function approximation. PMID:25874253
3-D LDA study of a rectangular jet
NASA Technical Reports Server (NTRS)
Morrison, Gerald L.; Tatterson, Gary B.; Swan, David H.
1988-01-01
The flow field of a rectangular jet with a 2:1 aspect ratio was studied at an axial Reynolds number of 100,000 (Mach number 0.09) using three-dimensional laser Doppler velocimetry. The flow field survey resulted in mean velocity vector field plots and contour plots of the Reynolds stress tensor components. This paper presents contour plots in the planes of the jet minor and major axes at different axial locations. These data contribute substantially to currently available data of jet flow fields and will provide a valuable database for three-dimensional modeling.
Acoustic response of a rectangular levitator with orifices
NASA Technical Reports Server (NTRS)
El-Raheb, Michael; Wagner, Paul
1990-01-01
The acoustic response of a rectangular cavity to speaker-generated excitation through waveguides terminating at orifices in the cavity walls is analyzed. To find the effects of orifices, acoustic pressure is expressed by eigenfunctions satisfying Neumann boundary conditions as well as by those satisfying Dirichlet ones. Some of the excess unknowns can be eliminated by point constraints set over the boundary, by appeal to Lagrange undetermined multipliers. The resulting transfer matrix must be further reduced by partial condensation to the order of a matrix describing unmixed boundary conditions. If the cavity is subjected to an axial temperature dependence, the transfer matrix is determined numerically.
Crack problems for a rectangular plate and an infinite strip
NASA Technical Reports Server (NTRS)
Civelek, M. B.; Erdogan, F.
1980-01-01
The general plane problem for an infinite strip containing multiple cracks perpendicular to its boundaries is considered. The problem is reduced to a system of singular integral equations. Two specific problems of practical interest are then studied in detail. The first problem explores the interaction effect of multiple edge cracks in a plate or beam under tension or bending. The second problem is that of a rectangular plate containing an arbitrarily oriented crack in the plane of symmetry. Particular emphasis is placed on the problem of a plate containing an edge crack and subjected to concentrated forces.
Stresses Around Rectangular Cut-outs with Reinforced Coaming Stringers
NASA Technical Reports Server (NTRS)
Kuhn, Paul; Rafel, Norman; Griffith, George E
1947-01-01
Strain measurements and strength tests were made on six skin-stringer panels under axial load. Three of these panels had short rectangular cut-outs, and three a long one. The width of the cut-out was about one-half of the width of the panel. Three types of coating stringers were used: without reinforcement, with riveted-up reinforcement, or with integral reinforcement. The strain measurements were found to be in good agreement with a previously published theory adapted where necessary by making overlapping assumptions.
Nonlinear dynamics and control of a vibrating rectangular plate
NASA Technical Reports Server (NTRS)
Shebalin, J. V.
1983-01-01
The von Karman equations of nonlinear elasticity are solved for the case of a vibrating rectangular plate by meams of a Fourier spectral transform method. The amplification of a particular Fourier mode by nonlinear transfer of energy is demonstrated for this conservative system. The multi-mode system is reduced to a minimal (two mode) system, retaining the qualitative features of the multi-mode system. The effect of a modal control law on the dynamics of this minimal nonlinear elastic system is examined.
Nonlinear analysis of the dielectric loaded rectangular Cerenkov maser
NASA Astrophysics Data System (ADS)
Zhao, Ding; Ding, Yaogen
2012-02-01
To deeply investigate the nonlinear interaction between the sheet beam and the slow wave mode in the dielectric loaded rectangular Cerenkov maser, a third order differential equation of the field profile function is rigorously derived. By combining with the relativistic equation of motion and using the traveling-wave boundary condition, the nonlinear phenomena, which involve with the growth rate, the electron phase bunching, the saturated power and length, etc., can be predicted through numerical calculations. An illustrative example has been given to demonstrate the validation of this method. The results show that a beam with axial momentum spread will lower the saturated power, increase the saturated length, and decrease the working bandwidth.
Extending the MODPATH algorithm to rectangular unstructured grids
Pollock, David W.
2016-01-01
The recent release of MODFLOW-USG, which allows model grids to have irregular, unstructured connections, requires a modification of the particle-tracking algorithm used by MODPATH. This paper describes a modification of the semi-analytical particle-tracking algorithm used by MODPATH that allows it to be extended to rectangular-based unstructured grids by dividing grid cells with multi-cell face connections into sub-cells. The new method will be incorporated in the next version of MODPATH which is currently under development.
RHCP- DESIGNING RECTANGULAR RIGHT-HANDED CIRCULARLY POLARIZED MICROSTRIP ANTENNAS
NASA Technical Reports Server (NTRS)
Davidson, S. E.
1994-01-01
RHCP, the Right-Handed, Circularly Polarized Microstrip Antenna program, aids in the design of a rectangular antenna element, given the desired frequency of operation and substrate characteristics. RHCP begins the design calculations based on a square element with linear polarization. The effective dielectric constant and changes in electrical length due to fringing at the radiating element edges are taken into account. A coaxial feed is inset with 50 ohms input impedance. By placing the feed such that two orthonormal modes are produced in the antenna cavity, right- or left-handed circular polarization is obtained. Input to RHCP consists of desired frequency, dielectric constant, and substrate thickness. Output consists of the final rectangular geometry, the proposed feed inset placement, and actual input impedance. RHCP has been used successfully for frequencies between 2 and 15 GHz for thin substrates. This program was used to fabricate antenna elements for the S-band quad antennas on board the Space Shuttle, and is a part of the design project for the S-band phased array antenna radiating aperture. RHCP is written in FORTRAN 77 for interactive execution and has been implemented on a DEC VAX series computer operating under VMS. This program was developed in 1985.
Sampling requirements for forage quality characterization of rectangular hay bales
Sheaffer, C.C.; Martin, N.P.; Jewett, J.G.; Halgerson, J.; Moon, R.D.; Cuomo, G.R.
2000-02-01
Commercial lots of alfalfa (Medicago sativa L.) hay are often bought and sold on the basis of forage quality. Proper sampling is essential to obtain accurate forage quality results for pricing of alfalfa hay, but information about sampling is limited to small, 20- to 40-kg rectangular bales. Their objectives were to determine the within-bale variation in 400-kg rectangular bales and to determine the number and distribution of core samples required to represent the crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and dry matter (DM) concentration in commercial lots of alfalfa hay. Four bales were selected from each of three hay lots and core sampled nine times per side for a total of 54 cores per bale. There was no consistent pattern of forage quality variation within bales. Averaged across lots, any portion of a bale was highly correlated with bale grand means for CP, ADF, NDF, and DM. Three lots of hay were probed six times per bale, one core per bale side from 55, 14, and 14 bales per lot. For determination of CP, ADF, NDF, and DM concentration, total core numbers required to achieve an acceptable standard error (SE) were minimized by sampling once per bale. Bootstrap analysis of data from the most variable hay lot suggested that forage quality of any lot of 400-kg alfalfa hay bales should be adequately represented by 12 bales sampled once per bale.
Subsonic Round and Rectangular Twin Jet Flow Effects
NASA Technical Reports Server (NTRS)
Bozak, Rick; Wernet, Mark
2014-01-01
Subsonic and supersonic aircraft concepts proposed by NASAs Fundamental Aeronautics Program have integrated propulsion systems with asymmetric nozzles. The asymmetry in the exhaust of these propulsion systems creates asymmetric flow and acoustic fields. The flow asymmetries investigated in the current study are from two parallel round, 2:1, and 8:1 aspect ratio rectangular jets at the same nozzle conditions. The flow field was measured with streamwise and cross-stream particle image velocimetry (PIV). A large dataset of single and twin jet flow field measurements was acquired at subsonic jet conditions. The effects of twin jet spacing and forward flight were investigated. For round, 2:1, and 8:1 rectangular twin jets at their closest spacings, turbulence levels between the two jets decreased due to enhanced jet mixing at near static conditions. When the flight Mach number was increased to 0.25, the flow around the twin jet model created a velocity deficit between the two nozzles. This velocity deficit diminished the effect of forward flight causing an increase in turbulent kinetic energy relative to a single jet. Both of these twin jet flow field effects decreased with increasing twin jet spacing relative to a single jet. These variations in turbulent kinetic energy correlate with changes in far-field sound pressure level.
Logically rectangular mixed methods for Darcy flow on general geometry
Arbogast, T.; Keenan, P.T.; Wheeler, M.F.; Yotov, I.
1995-12-31
The authors consider an expanded mixed finite element formulation (cell centered finite difference) for Darcy flow with a tensor absolute permeability. The reservoir can be geometrically general with internal features, but the computational domain is rectangular. The method is defined on a curvilinear grid that need not be orthogonal, obtained by mapping the rectangular, computational grid. The original flow problem becomes a similar problem with a modified permeability on the computational grid. Quadrature rules turn the mixed method into a cell-centered finite difference method with a 9 point stencil in 2-D and 19 in 3-D. As shown by theory and experiment, if the modified permeability on the computational domain is smooth, then the convergence rate is optimal and both pressure and velocity are superconvergent at certain points. If not, Lagrange multiplier pressures can be introduced on boundaries of elements so that optimal convergence is retained. This modification presents only small changes in the solution process; in fact, the same parallel domain decomposition algorithms can be applied with little or no change to the code if the modified permeability is smooth over the subdomains. This Lagrange multiplier procedure can be used to extend the difference scheme to multi-block domains, and to give a coupling with unstructured grids. In all cases, the mixed formulation is locally conservative. Computational results illustrate the advantage and convergence of this method.
Richards Equation Solver; Rectangular Finite Volume Flux Updating Solution.
Energy Science and Technology Software Center (ESTSC)
2002-01-18
Version: 00 POLYRES solves the transient, two-dimensional, Richards equation for water flow in unsaturated-saturated soils. The package is specifically designed to allow the user to easily model complex polygon-shaped regions. Flux, head, and unit gradient boundary conditions can be used. Spatial variation of the hydraulic properties can be defined across individual polygon-shaped subdomains, called objects. These objects combine to form a polygon-shaped model domain. Each object can have its own distribution of hydraulic parameters. Themore » resulting model domain and polygon-shaped internal objects are mapped onto a rectangular, finite-volume, computational grid by a preprocessor. This allows the user to specify model geometry independently of the underlying grid and greatly simplifies user input for complex geometries. In addition, this approach significantly reduces the computational requirements since complex geometries are actually modeled on a rectangular grid. This results in well-structured, finite difference-like systems of equations that require minimal storage and are very efficient to solve.« less
Efficient and accurate sound propagation using adaptive rectangular decomposition.
Raghuvanshi, Nikunj; Narain, Rahul; Lin, Ming C
2009-01-01
Accurate sound rendering can add significant realism to complement visual display in interactive applications, as well as facilitate acoustic predictions for many engineering applications, like accurate acoustic analysis for architectural design. Numerical simulation can provide this realism most naturally by modeling the underlying physics of wave propagation. However, wave simulation has traditionally posed a tough computational challenge. In this paper, we present a technique which relies on an adaptive rectangular decomposition of 3D scenes to enable efficient and accurate simulation of sound propagation in complex virtual environments. It exploits the known analytical solution of the Wave Equation in rectangular domains, and utilizes an efficient implementation of the Discrete Cosine Transform on Graphics Processors (GPU) to achieve at least a 100-fold performance gain compared to a standard Finite-Difference Time-Domain (FDTD) implementation with comparable accuracy, while also being 10-fold more memory efficient. Consequently, we are able to perform accurate numerical acoustic simulation on large, complex scenes in the kilohertz range. To the best of our knowledge, it was not previously possible to perform such simulations on a desktop computer. Our work thus enables acoustic analysis on large scenes and auditory display for complex virtual environments on commodity hardware. PMID:19590105
Measurement strategy for rectangular electrical capacitance tomography sensor
Ye, Jiamin; Ge, Ruihuan; Qiu, Guizhi; Wang, Haigang
2014-04-11
To investigate the influence of the measurement strategy for the rectangular electrical capacitance tomography (ECT) sensor, a Finite Element Method (FEM) is utilized to create the model for simulation. The simulation was carried out using COMSOL Multiphysics(trade mark, serif) and Matlab(trade mark, serif). The length-width ratio of the rectangular sensing area is 5. Twelve electrodes are evenly arranged surrounding the pipe. The covering ratio of the electrodes is 90%. The capacitances between different electrode pairs are calculated for a bar distribution. The air of the relative permittivity 1.0 and the material of the permittivity 3.0 are used for the calibration. The relative permittivity of the second phase is 3.0. The noise free and noise data are used for the image reconstruction using the Linear Back Projection (LBP). The measurement strategies with 1-, 2- and 4- electrode excitation are compared using the correlation coefficient. Preliminary results show that the measurement strategy with 2-electrode excitation outperforms other measurement strategies with 1- or 4-electrode excitation.
Rectangular capture area to circular combustor scramjet engine
NASA Technical Reports Server (NTRS)
Pinckney, S. Z.
1978-01-01
A new concept for a scramjet engine design was presented. The inlet transformed a rectangular shaped capture stream into a cross section which was almost circular in shape at the inlet throat or combustor entrance. The inlet inner surface was designed by the method of streamline tracing. The high pressure and temperature regions of the combustor were almost circular in shape and thus the benefits of hoop stresses in relation to structural weight could be utilized to reduce combustor and engine weights. The engine had a center body consisting of a 20 deg included angle cone, followed by a constant diameter cylinder. Fuel injection struts were arranged in a radial array and were swept 54 deg from the center body to the inlet inner surface and had values of length to maximum average thickness between 5.6and 6.6 which were felt to be structurally reasonable. Combustor wetted areas were shown to be less than those of the present fully rectangular engine concept.
Phase space analysis of multipactor saturation in rectangular waveguide
NASA Astrophysics Data System (ADS)
Lingwood, C. J.; Burt, G.; Dexter, A. C.; Smith, J. D. A.; Goudket, P.; Stoltz, P. H.
2012-03-01
In certain high power RF systems multipactor cannot be avoided for all operating points, but its existence places limits on performance, efficiency, lifetime, and reliability. As an example multipactor in the input couplers of superconducting RF cavities can be a major limitation to the maximum RF power. Several studies have concentrated on rectangular waveguide input couplers which are used in many light sources. Most of these studies neglect space charge assuming that the effect of space charge is simply to defocus the electron bunches. Modelling multipactor to saturation is of interest in determining the performance of waveguide under a range of conditions. Particle-in-cell modelling including space charge has been performed for 500 MHz half-height rectangular waveguide. Phase plots of electron trajectories can aid understanding the processes taking place in the multipactor. Results strongly suggest that the multipacting trajectories are strongly perturbed by space charge causing the electrons to transition from two-surface to single-surface trajectories as the multipactor approaches saturation.
Versatile patterns of multiple rectangular noise-like pulses in a fiber laser.
Huang, Yu-Qi; Qi, You-Li; Luo, Zhi-Chao; Luo, Ai-Ping; Xu, Wen-Cheng
2016-04-01
We report on the generation of versatile patterns of multiple rectangular noise-like pulses (NLPs) in a fiber laser mode-locked by nonlinear amplifying loop mirror (NALM). Benefiting from the strengthened nonlinear effect of a segment of highly nonlinear fiber (HNLF) in the loop, multiple rectangular NLPs with various patterns are formed depending on the cavity parameter settings. In particular, the multiple rectangular NLPs could possess unequal packet durations, which is different from the conventional multi-soliton patterns. The experimental results contribute to further understanding the characteristics of the rectangular NLP and the dynamics of multi-pulse patterns. PMID:27137025
Round versus rectangular: Does the plot shape matter?
NASA Astrophysics Data System (ADS)
Iserloh, Thomas; Bäthke, Lars; Ries, Johannes B.
2016-04-01
Field rainfall simulators are designed to study soil erosion processes and provide urgently needed data for various geomorphological, hydrological and pedological issues. Due to the different conditions and technologies applied, there are several methodological aspects under review of the scientific community, particularly concerning design, procedures and conditions of measurement for infiltration, runoff and soil erosion. Extensive discussions at the Rainfall Simulator Workshop 2011 in Trier and the Splinter Meeting at EGU 2013 "Rainfall simulation: Big steps forward!" lead to the opinion that the rectangular shape is the more suitable plot shape compared to the round plot. A horizontally edging Gerlach trough is installed for sample collection without forming unnatural necks as is found at round or triangle plots. Since most research groups did and currently do work with round plots at the point scale (<1m²), a precise analysis of the differences between the output of round and square plots are necessary. Our hypotheses are: - Round plot shapes disturb surface runoff, unnatural fluvial dynamics for the given plot size such as pool development especially directly at the plot's outlet occur. - A square plot shape prevent these problems. A first comparison between round and rectangular plots (Iserloh et al., 2015) indicates that the rectangular plot could indeed be the more suitable, but the rather ambiguous results make a more elaborate test setup necessary. The laboratory test setup includes the two plot shapes (round, square), a standardised silty substrate and three inclinations (2°, 6°, 12°). The analysis of the laboratory test provide results on the best performance concerning undisturbed surface runoff and soil/water sampling at the plot's outlet. The analysis of the plot shape concerning its influence on runoff and erosion shows that clear methodological standards are necessary in order to make rainfall simulation experiments comparable. Reference
Plastic buckling of a rectangular plate under edge thrusts
NASA Technical Reports Server (NTRS)
Handelman, G H; Prager, W
1949-01-01
The fundamental equations for the plastic buckling of a rectangular plate under edge thrusts are developed on the basis of a new set of stress-strain relations for the behavior of a metal in the plastic range. These relations are derived for buckling from a state of uniform compression. The fundamental equation for the buckling of a simply compressed plate together with typical boundary conditions is then developed and the results are applied to calculating the buckling loads of a thin strip, a simply supported plate, and a cruciform section. Comparisons with the theories of Timoshenko and Ilyushin are made. Finally, an energy method is given which can be used for finding approximate values of the critical load.
Impedance of curved rectangular spiral coils around a conductive cylinder
NASA Astrophysics Data System (ADS)
Burke, S. K.; Ditchburn, R. J.; Theodoulidis, T. P.
2008-07-01
Eddy-current induction due to a thin conformable coil wrapped around a long conductive cylinder is examined using a second-order vector potential formalism. Compact closed-form expressions are derived for the self- and mutual impedances of curved rectangular spiral coils (i) in free space and (ii) when wrapped around the surface of the cylindrical rod. The validity of these expressions was tested against the results of a systematic series of experiments using a cylindrical Al-alloy rod and conformable coils manufactured using flexible printed-circuit-board technology. The theoretical expressions were in very good agreement with the experimental measurements. The significance of the results for eddy-current nondestructive inspection using flexible coils and flexible coil arrays is discussed.
Vibrations of cantilevered shallow cylindrical shells of rectangular planform
NASA Technical Reports Server (NTRS)
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-01-01
A cantilevered, shallow shell of circular cylindrical curvature and rectangular planform exhibits free vibration behavior which differs considerably from that of a cantilevered beam or of a flat plate. Some numerical results can be found for the problem in the previously published literature, mainly obtained by using various finite element methods. The present paper is the first definitive study of the problem, presenting accurate non-dimensional frequency parameters for wide ranges of aspect ratio, shallowness ratio and thickness ratio. The analysis is based upon shallow shell theory. Numerical results are obtained by using the Ritz method, with algebraic polynomial trial functions for the displacements. Convergence is investigated, with attention being given both to the number of terms taken for each co-ordinate direction and for each of the three components of displacement. Accuracy of the results is also established by comparison with finite element results for shallow shells and with other accurate flat plate solutions.
Thermoelectric effects in a rectangular Aharonov-Bohm geometry
NASA Astrophysics Data System (ADS)
Pye, A. J.; Faux, D. A.; Kearney, M. J.
2016-04-01
The thermoelectric transport properties of a rectangular Aharonov-Bohm ring at low temperature are investigated using a theoretical approach based on Green's functions. The oscillations in the transmission coefficient as the field is varied can be used to tune the thermoelectric response of the ring. Large magnitude thermopowers are obtainable which, in conjunction with low conductance, can result in a high thermoelectric figure of merit. The effects of single site impurities and more general Anderson disorder are considered explicitly in the context of evaluating their effect on the Fano-type resonances in the transmission coefficient. Importantly, it is shown that even for moderate levels of disorder, the thermoelectric figure of merit can remain significant, increasing the appeal of such structures from the perspective of specialist thermoelectric applications.
Oscillating laminar electrokinetic flow in infinitely extended rectangular microchannels.
Yang, J; Bhattacharyya, A; Masliyah, J H; Kwok, D Y
2003-05-01
This paper has addressed analytically the problem of laminar flow in microchannels with rectangular cross-section subjected to a time-dependent sinusoidal pressure gradient and a sinusoidal electric field. The analytical solution has been determined based on the Debye-Hückel approximation of a low surface potential at the channel wall. We have demonstrated that Onsager's principle of reciprocity is valid for this problem. Parametric studies of streaming potential have shown the dependence of the electroviscous effect not only on the Debye length, but also on the oscillation frequency and the microchannel width. Parametric studies of electroosmosis demonstrate that the flow rate decreases due to an increase in frequency. The obtained solutions for both the streaming potential and electroosmotic flows become those for flow between two parallel plates in the limit of a large aspect ratio. PMID:12725820
Vibrations of cantilevered shallow cylindrical shells of rectangular planform
NASA Astrophysics Data System (ADS)
Leissa, A. W.; Lee, J. K.; Wang, A. J.
1981-10-01
A cantilevered, shallow shell of circular cylindrical curvature and rectangular planform exhibits free vibration behavior which differs considerably from that of a cantilevered beam or of a flat plate. Some numerical results can be found for the problem in the previously published literature, mainly obtained by using various finite element methods. The present paper is the first definitive study of the problem, presenting accurate non-dimensional frequency parameters for wide ranges of aspect ratio, shallowness ratio and thickness ratio. The analysis is based upon shallow shell theory. Numerical results are obtained by using the Ritz method, with algebraic polynomial trial functions for the displacements. Convergence is investigated, with attention being given both to the number of terms taken for each co-ordinate direction and for each of the three components of displacement. Accuracy of the results is also established by comparison with finite element results for shallow shells and with other accurate flat plate solutions.
Screech Tones of Supersonic Jets from Bevelled Rectangular Nozzles
NASA Technical Reports Server (NTRS)
Tam, Christopher K. W.; Shen, Hao; Raman, Ganesh
1997-01-01
It is known experimentally that an imperfectly expanded rectangular jet from a thin-lip convergent nozzle emits only a single dominant screech tone. The frequency of the screech tone decreases continuously with increase in jet Mach number. However, for a supersonic jet issued from a bevelled nozzle or a convergent-divergent nozzle with straight side walls, the shock cell structure and the screech frequency pattern are fairly complicated and have not been predicted before. In this paper, it is shown that the shock cell structures of these jets can be decomposed into waveguide modes of the jet flow. The screech frequencies are related to the higher-order waveguide modes following the weakest-link screech tone theory. The measured screech frequencies are found to compare well with the predicted screech frequency curves.
Lidar profiling by long rectangular-like chopped laser pulses
NASA Astrophysics Data System (ADS)
Stoyanov, Dimitar V.; Gurdev, Ljuan L.; Kolarov, Georgi; Vankov, O. I.
2000-06-01
A novel, simple method is developed and tested (experimentally and by simulations) for effective, high- resolution retrieving of time-resolved lidar profiles for long rectangular-like laser pulses with arbitrary shapes of their leading and trailing edges. Such pulses are typically created by chopping cw optical radiation. The processing algorithm is based on differentiation and iteration procedures and avoids the use of divisions or deconvolutions that are often responsible for some errors and increases in the noise. Comparisons with pulsed and pseudo-random noise modulation lidar methods are given. The method enables a simplification of the entire lidar hardware. No powerful pulsed supplies, high driving pulsed voltages, complicated optical modulations, etc. are required. It could be very attractive for high-resolution, wide-spectral-band lidar measurements in the atmosphere, ocean, etc., using arbitrary optical emitters, especially for closer distances.
Rectangular Waveguides with Two Conventional and Two Superconducting Walls
NASA Technical Reports Server (NTRS)
Yalamanchili, Raj; Qiu, Zheng An; Wang, Yen-Chu
1995-01-01
The propagation properties of transverse electric TE(sup pm) modes and their dispersion relations in rectangular waveguides with two conventional and two superconducting walls, derived by using the Meissner boundary conditions on the superconducting walls, are presented. In addition to recovering some previously known results, some novel results have been obtained: the cut-off wavelength of the dominant TE(sup 10) mode is greater than that of the conventional TE(sub 10) mode, and the tangential electric field and normal magnetic field for the dominant mode TE(sup 10) exist on the superconducting surfaces. Expressions for electromagnetic components, surface currents, attenuation coefficient, maximum transmitted power, dispersion and wave impedance are also presented.
Some features of tones generated by an underexpanded rectangular jet
NASA Astrophysics Data System (ADS)
Krothapalli, A.; Baganoff, D.; Karamcheti, K.; Hsia, Y.
1981-01-01
An experimental investigation has been carried out on an underexpanded jet of air issuing from a convergent rectangular nozzle. Schlieren pictures of the flow field along with microphone and hot wire measurements in the near field of the jet were obtained at different pressure ratios. At the pressure ratio for maximum screech sound radiation, the schlieren photographs show a very strong organized cylindrical wave pattern on either side of the jet with their source being located at the end of the third shock cell. Associated with this wave pattern is a large angle of spread of the jet of about 36 degrees. Experiments using a reflecting surface near the nozzle exit show that the flow can be either destabilized or stabilized by a small rigid plate located only on one side, and in almost all positions.
Oscillating flow and separation of species in rectangular channels
NASA Astrophysics Data System (ADS)
Hacioglu, A.; Narayanan, R.
2016-07-01
The mass transfer and separation of species in a tube using oscillatory flows are strongly affected by the fluid flow profiles in the tube. It has been well established that oscillatory motion in a one-dimensional flow configuration leads to a single tuning dimensionless frequency, where optimum separation may be effected. In this work, the effect on species separation by two-dimensional laminar flow arising in a rectangular cross section is studied and a surprising result is that a second tuning frequency may occur at lower dimensionless oscillation frequencies. The physics reveals that this new optimum disappears when the aspect ratio is either very large or close to unity. These observations are related to the flow profiles at different aspect ratios.
Geometrically nonlinear vibrations of rectangular plates carrying a concentrated mass
NASA Astrophysics Data System (ADS)
Amabili, M.
2010-10-01
Nonlinear forced vibrations of rectangular plates carrying a central concentrated mass are studied. The plate is assumed to have immovable edges and rotational springs; numerical results are presented for clamped plates. The Von Kármán nonlinear plate theory is used, but in-plane inertia in both the plate and the mass is retrained. The problem is discretized into a multi-degree-of-freedom (dof) system by using an energy approach and Lagrange equations taking damping into account. A pseudo-arclength continuation method is used in order to obtain numerical solutions. Results are presented as both (i) frequency-amplitude curves and (ii) time domain responses. The effect of gravity and the effect of the consequent initial plate deflection are also investigated.
Flow-Field Surveys for Rectangular Nozzles. Supplement
NASA Technical Reports Server (NTRS)
Zaman, K. B. M. Q.
2012-01-01
Flow field survey results for three rectangular nozzles are presented for a low subsonic condition obtained primarily by hot-wire anemometry. The three nozzles have aspect ratios of 2:1, 4:1 and 8:1. A fourth case included has 2:1 aspect ratio with chevrons added to the long edges. Data on mean velocity, turbulent normal and shear stresses as well as streamwise vorticity are presented covering a streamwise distance up to sixteen equivalent diameters from the nozzle exit. These detailed flow properties, including initial boundary layer characteristics, are usually difficult to measure in high speed flows and the primary objective of the study is to aid ongoing and future computational and noise modeling efforts. This supplement contains data files, charts and source code.
Numerical Simulation of Turbulent Jets with Rectangular Cross-Section
NASA Technical Reports Server (NTRS)
Wilson, Robert V.; Demuren, Ayodeji O.
1997-01-01
Three-dimensional turbulent jets with rectangular cross-section are simulated with a finite-difference numerical method. The full Navier-Stokes equations are solved at low Reynolds numbers, whereas at the high Reynolds numbers filtered forms of the equations are solved along with a sub-grid scale model to approximate effects of the unresolved scales. A 2-N storage, third-order Runge-Kutta scheme is used for temporal discretization and a fourth-order compact scheme is used for spatial discretization. Computations are performed for different inlet conditions which represent different types of jet forcing. The phenomenon of axis-switching is observed, and it is confirmed that this is based on self-induction of the vorticity field. Budgets of the mean streamwise velocity show that convection is balanced by gradients of the Reynolds stresses and the pressure.
Elastostatic stress analysis of orthotropic rectangular center-cracked plates
NASA Technical Reports Server (NTRS)
Gyekenyesi, G. S.; Mendelson, A.
1972-01-01
A mapping-collocation method was developed for the elastostatic stress analysis of finite, anisotropic plates with centrally located traction-free cracks. The method essentially consists of mapping the crack into the unit circle and satisfying the crack boundary conditions exactly with the help of Muskhelishvili's function extension concept. The conditions on the outer boundary are satisfied approximately by applying the method of least-squares boundary collocation. A parametric study of finite-plate stress intensity factors, employing this mapping-collocation method, is presented. It shows the effects of varying material properties, orientation angle, and crack-length-to-plate-width and plate-height-to-plate-width ratios for rectangular orthotropic plates under constant tensile and shear loads.
Flow field induced particle accumulation inside droplets in rectangular channels.
Hein, Michael; Moskopp, Michael; Seemann, Ralf
2015-07-01
Particle concentration is a basic operation needed to perform washing steps or to improve subsequent analysis in many (bio)-chemical assays. In this article we present field free, hydrodynamic accumulation of particles and cells in droplets flowing within rectangular micro-channels. Depending on droplet velocity, particles either accumulate at the rear of the droplet or are dispersed over the entire droplet cross-section. We show that the observed particle accumulation behavior can be understood by a coupling of particle sedimentation to the internal flow field of the droplet. The changing accumulation patterns are explained by a qualitative change of the internal flow field. The topological change of the internal flow field, however, is explained by the evolution of the droplet shape with increasing droplet velocity altering the friction with the channel walls. In addition, we demonstrate that accumulated particles can be concentrated, removing excess dispersed phase by splitting the droplet at a simple channel junction. PMID:26032835
Aerodynamic characteristics of bodies with rectangular cross section
NASA Astrophysics Data System (ADS)
Knoche, H. G.; Schamel, W.; Esch, H.; Schneider, W.
Systematic wind tunnel tests for a series of missile bodies were conducted by varying cross section shape and body length in the subsonic Mach number range and up to high angles of attack. Tests with a body-wing and a body-tail configuration were performed in order to investigate the body-wing and body-tail interference for bodies of revolution and bodies with rectangular cross section. At a constant angle of attack, the boxlike body supplies far more normal force than the body of revolution with the same cross section area. The boxlike body shows strong coupling effects between the pitch, yaw and roll. The interference effect of the wing and body can be described well, in the case of boxlike bodies with wings in high or low wing positions, by the known slender body interference factors, assuming the width of the box to be the diameter of an equivalent, axially symetrical body.
Finite-element analysis of corner cracks in rectangular bars
NASA Technical Reports Server (NTRS)
Raju, L. S.; Newman, J. C., Jr.
1987-01-01
Stress intensity factors for a wide range of quarter-elliptical corner cracks in rectangular bars are presented. Cracked configurations were subjected to remote tension, in-plane bending, or out-of-plane bending. Results were compared with other numerical results for a quarter-circular corner crack configuration. The present results along the interior of the crack generally agreed within 3 percent with those from the literature. Some larger differences (3 to 13 percent) were observed near the intersection of the crack front and the free surfaces in the boundary layer region. Analyses were performed to study the effect of mesh refinement in the boundary layer region and the influence of Poisson's ratio on the distribution of stress-intensity factors.
Performance analysis of SOI MOSFET with rectangular recessed channel
NASA Astrophysics Data System (ADS)
Singh, M.; Mishra, S.; Mohanty, S. S.; Mishra, G. P.
2016-03-01
In this paper a two dimensional (2D) rectangular recessed channel-silicon on insulator metal oxide semiconductor field effect transistor (RRC-SOI MOSFET), using the concept of groove between source and drain regions, which is one of the channel engineering technique to suppress the short channel effect (SCE). This suppression is mainly due to corner potential barrier of the groove and the simulation is carried out by using ATLAS 2D device simulator. To have further improvement of SCE in RRC-SOI MOSFET, three more devices are designed by using dual material gate (DMG) and gate dielectric technique, which results in formation of devices i.e. DMRRC-SOI,MLSMRRC-SOI, MLDMRRC-SOI MOSFET. The effect of different structures of RRC-SOI on AC and RF parameters are investigated and the importance of these devices over RRC MOSFET regarding short channel effect is analyzed.
Quantitative study of rectangular waveguide behavior in the THz.
Rowen, Adam M.; Nordquist, Christopher Daniel; Wanke, Michael Clement
2009-10-01
This report describes our efforts to quantify the behavior of micro-fabricated THz rectangular waveguides on a configurable, robust semiconductor-based platform. These waveguides are an enabling technology for coupling THz radiation directly from or to lasers, mixers, detectors, antennas, and other devices. Traditional waveguides fabricated on semiconductor platforms such as dielectric guides in the infrared or co-planar waveguides in the microwave regions, suffer high absorption and radiative losses in the THz. The former leads to very short propagation lengths, while the latter will lead to unwanted radiation modes and/or crosstalk in integrated devices. This project exploited the initial developments of THz micro-machined rectangular waveguides developed under the THz Grand Challenge Program, but instead of focusing on THz transceiver integration, this project focused on exploring the propagation loss and far-field radiation patterns of the waveguides. During the 9 month duration of this project we were able to reproduce the waveguide loss per unit of length in the waveguides and started to explore how the loss depended on wavelength. We also explored the far-field beam patterns emitted by H-plane horn antennas attached to the waveguides. In the process we learned that the method of measuring the beam patterns has a significant impact on what is actually measured, and this may have an effect on most of the beam patterns of THz that have been reported to date. The beam pattern measurements improved significantly throughout the project, but more refinements of the measurement are required before a definitive determination of the beam-pattern can be made.
Underexpanded Screeching Jets From Circular, Rectangular, and Elliptic Nozzles
NASA Technical Reports Server (NTRS)
Panda, J.; Raman, G.; Zaman, K. B. M. Q.
2004-01-01
The screech frequency and amplitude, the shock spacing, the hydrodynamic-acoustic standing wave spacing, and the convective velocity of large organized structures are measured in the nominal Mach number range of 1.1 less than or = Mj less that or = l0.9 for supersonic, underexpanded jets exhausting from a circular, a rectangular and an elliptic nozzle. This provides a carefully measured data set useful in comparing the importance of various physical parameters in the screech generation process. The hydrodynamic-acoustic standing wave is formed between the potential pressure field of large turbulent structures and the acoustic pressure field of the screech sound. It has been demonstrated earlier that in the currently available screech frequency prediction models replacement of the shock spacing by the standing wave spacing provides an exact expression. In view of this newly found evidence, a comparison is made between the average standing wavelength and the average shock spacing. It is found that there exists a small, yet important, difference, which is dependent on the azimuthal screech mode. For example, in the flapping modes of circular, rectangular, and elliptic jets, the standing wavelength is slightly longer than the shock spacing, while for the helical screech mode in a circular jet the opposite is true. This difference accounts for the departure of the existing models from predicting the exact screech frequency. Another important parameter, necessary in screech prediction, is the convective velocity of the large organized structures. It is demonstrated that the presence of the hydrodynamic-acoustic standing wave, even inside the jet shear layer, becomes a significant source of error in the convective velocity data obtained using the conventional methods. However, a new relationship, using the standing wavelength and screech frequency is shown to provide more accurate results.
Rectangular Dielectric-loaded Structures for Achieving High Acceleration Gradients
Wang Changbiao; Yakovlev, V. P.; Marshall, T. C.; LaPointe, M. A.; Hirshfield, J. L.
2006-11-27
Rectangular dielectric-loaded structures are described that may sustain higher acceleration gradients than conventional all-metal structures with similar apertures. One structure is a test cavity designed to ascertain the breakdown limits of dielectrics, while a second structure could be the basis for a two-beam accelerator. CVD diamond is an attractive dielectric for a high-gradient structure, since the published DC breakdown limit for CVD diamond is {approx} 2 GV/m, although the limit has never been determined for RF fields. Here we present a design of a diamond-lined test cavity to measure the breakdown limit. The designed cavity operates at 34 GHz, where with 10-MW input power it is expected to produce an {approx}800 MV/m field on the diamond surface - provided breakdown is avoided. The two channel rectangular dielectric-loaded waveguide could be a two-beam accelerator structure, in which a drive beam is in one channel and an accelerated beam is in the other. The RF power produced by drive bunches in the drive channel is continuously coupled to the acceleration channel. The ratio of fields in the channels (transformer ratio) for the operating mode can be designed by adjusting the dimensions of the structure. An example of the two-channel structure is described, in which a train of five 3-nC drive bunches excites wake fields in the accelerator channel of up to 1.3 GV/m with a transformer ratio of 10 for the design mode.
An approximate algorithm for the flux from a rectangular volume source
Wallace, O.J.
1994-11-09
An exact semi-analytic formula for the flux from a rectangular surface source with a slab shield has been derived and the required function table has been calculated. This formula is the basis for an algorithm which gives a good approximation for the flux from a rectangular volume source. No other hand calculation method for this source geometry is available in the literature.
Finite element fatigue analysis of rectangular clutch spring of automatic slack adjuster
NASA Astrophysics Data System (ADS)
Xu, Chen-jie; Luo, Zai; Hu, Xiao-feng; Jiang, Wen-song
2015-02-01
The failure of rectangular clutch spring of automatic slack adjuster directly affects the work of automatic slack adjuster. We establish the structural mechanics model of automatic slack adjuster rectangular clutch spring based on its working principle and mechanical structure. In addition, we upload such structural mechanics model to ANSYS Workbench FEA system to predict the fatigue life of rectangular clutch spring. FEA results show that the fatigue life of rectangular clutch spring is 2.0403×105 cycle under the effect of braking loads. In the meantime, fatigue tests of 20 automatic slack adjusters are carried out on the fatigue test bench to verify the conclusion of the structural mechanics model. The experimental results show that the mean fatigue life of rectangular clutch spring is 1.9101×105, which meets the results based on the finite element analysis using ANSYS Workbench FEA system.
Test Cases for a Rectangular Supercritical Wing Undergoing Pitching Oscillations
NASA Technical Reports Server (NTRS)
Bennett, Robert M.
2000-01-01
Steady and unsteady measured pressures for a Rectangular Supercritical Wing (RSW) undergoing pitching oscillations have been presented. From the several hundred compiled data points, 27 static and 36 pitching oscillation cases have been proposed for computational Test Cases to illustrate the trends with Mach number, reduced frequency, and angle of attack. The wing was designed to be a simple configuration for Computational Fluid Dynamics (CFD) comparisons. The wing had an unswept rectangular planform plus a tip of revolution, a panel aspect ratio of 2.0, a twelve per cent thick supercritical airfoil section, and no twist. The model was tested over a wide range of Mach numbers, from 0.27 to 0.90, corresponding to low subsonic flows up to strong transonic flows. The higher Mach numbers are well beyond the design Mach number such as might be required for flutter verification beyond cruise conditions. The pitching oscillations covered a broad range of reduced frequencies. Some early calculations for this wing are given for lifting pressure as calculated from a linear lifting surface program and from a transonic small perturbation program. The unsteady results were given primarily for a mild transonic condition at M = 0.70. For these cases the agreement with the data was only fair, possibly resulting from the omission of viscous effects. Supercritical airfoil sections are known to be sensitive to viscous effects (for example, one case cited). Calculations using a higher level code with the full potential equations have been presented for one of the same cases, and with the Euler equations. The agreement around the leading edge was improved, but overall the agreement was not completely satisfactory. Typically for low-aspect-ratio rectangular wings, transonic shock waves on the wing tend to sweep forward from root to tip such that there are strong three-dimensional effects. It might also be noted that for most of the test, the model was tested with free transition, but a
NASA Astrophysics Data System (ADS)
Crowgey, Benjamin Reid
Rectangular waveguide methods are appealing for measuring isotropic and anisotropic materials because of high signal strength due to field confinement, and the ability to control the polarization of the applied electric field. As a stepping stone to developing methods for characterizing materials with fully-populated anisotropic tensor characteristics, techniques are presented in this dissertation to characterize isotropic, biaxially anisotropic, and gyromagnetic materials. Two characterization techniques are investigated for each material, and thus six different techniques are described. Additionally, a waveguide standard is introduced which may be used to validate the measurement of the permittivity and permeability of materials at microwave frequencies. The first characterization method examined is the Nicolson-Ross-Weir (NRW) technique for the extraction of isotropic parameters of a sample completely filling the cross-section of a rectangular waveguide. A second technique is proposed for the characterization of an isotropic conductor-backed sample filling the cross-section of a waveguide. If the sample is conductor-backed, and occupies the entire cross-section, a transmission measurement is not available, and thus a method must be found for providing two sufficiently different reflection measurements.The technique proposed here is to place a waveguide iris in front of the sample, exposing the sample to a spectrum of evanescent modes. By measuring the reflection coefficient with and without an iris, the necessary two data may be obtained to determine the material parameters. A mode-matching approach is used to determine the theoretical response of a sample placed behind the waveguide iris. This response is used in a root-searching algorithm to determine permittivity and permeability by comparing to measurements of the reflection coefficient. For the characterization of biaxially anisotropic materials, the first method considers an extension of the NRW technique
TFSSRA - THICK FREQUENCY SELECTIVE SURFACE WITH RECTANGULAR APERTURES
NASA Technical Reports Server (NTRS)
Chen, J. C.
1994-01-01
Thick Frequency Selective Surface with Rectangular Apertures (TFSSRA) was developed to calculate the scattering parameters for a thick frequency selective surface with rectangular apertures on a skew grid at oblique angle of incidence. The method of moments is used to transform the integral equation into a matrix equation suitable for evaluation on a digital computer. TFSSRA predicts the reflection and transmission characteristics of a thick frequency selective surface for both TE and TM orthogonal linearly polarized plane waves. A model of a half-space infinite array is used in the analysis. A complete set of basis functions with unknown coefficients is developed for the waveguide region (waveguide modes) and for the free space region (Floquet modes) in order to represent the electromagnetic fields. To ensure the convergence of the solutions, the number of waveguide modes is adjustable. The method of moments is used to compute the unknown mode coefficients. Then, the scattering matrix of the half-space infinite array is calculated. Next, the reference plane of the scattering matrix is moved half a plate thickness in the negative z-direction, and a frequency selective surface of finite thickness is synthesized by positioning two plates of half-thickness back-to-back. The total scattering matrix is obtained by cascading the scattering matrices of the two half-space infinite arrays. TFSSRA is written in FORTRAN 77 with single precision. It has been successfully implemented on a Sun4 series computer running SunOS, an IBM PC compatible running MS-DOS, and a CRAY series computer running UNICOS, and should run on other systems with slight modifications. Double precision is recommended for running on a PC if many modes are used or if high accuracy is required. This package requires the LINPACK math library, which is included. TFSSRA requires 1Mb of RAM for execution. The standard distribution medium for this program is one 5.25 inch 360K MS-DOS format diskette. It is also
Constructal design for a rectangular body with nonuniform heat generation
NASA Astrophysics Data System (ADS)
Feng, Huijun; Chen, Lingen; Xie, Zhihui; Sun, Fengrui
2016-08-01
Nonuniform heat generation models with constant and variable cross-section high-conductivity channels (HCCs) are built in this paper. The minimum dimensionless peak temperature (DPT) is taken as the optimization objective. Different from the models with uniform heat generation and constant cross-section HCCs built by Bejan (1997) and Ledezma et al. (1997), the model with nonuniform heat generation and variable cross-section HCC is more practical and can help to improve the heat conduction performance of a thermal system. The results show that for the rectangular first-order assembly (RFOA) with nonuniform heat generation, there exist both the optimal shape of the RFOA and the optimal HCCs width ratio, which lead to the minimum DPT. They are different from those with uniform heat generation. When the heat is nonuniformly generated in the RFOA, the minimum DPT of the RFOA with variable cross-section HCC is reduced by 12.11% compared with that with constant cross-section HCC. Moreover, the numerical results are also verified by the analytical method.
Streamwise Vortex Formation Upstream of a Rectangular Nozzle
NASA Astrophysics Data System (ADS)
Hsu, T. Y.; Wei, T.
2001-11-01
High resolution DPIV measurements were made to examine the hydrodynamic stability of initially laminar flow passing through a sudden contraction. This motivation for this study was understanding the effects of nozzle geometry and turbulence on papermaking. Experiments were conducted with water using a simplified two-dimensional rectangular nozzle constructed to match the Reynolds number of industrial papermaking machines. The nozzle consisted of a 60 cm wide x 10 cm high channel whose downstream end could be blocked by as much as 50orthogonal planes at various positions upstream of the nozzle exit. The Reynolds number range, based on the jet height and the free stream velocity (1-2 m/s), was 10,000 to 100,000. An unsteady spanwise vortex 1.6 cm in diameter was found at the corner of the vertical solid wall and the top wall of the contraction. Further, unsteady streamwise vortices with 2 cm in diameter were identified both visually and by using spectrum analysis. These findings will be related to the streaks found in a sheet of paper.
Generation of Higher Order Modes in a Rectangular Duct
NASA Technical Reports Server (NTRS)
Gerhold, Carl H.; Cabell, Randolph H.; Brown, Donald E.
2004-01-01
Advanced noise control methodologies to reduce sound emission from aircraft engines take advantage of the modal structure of the noise in the duct. This noise is caused by the interaction of rotor wakes with downstream obstructions such as exit guide vanes. Mode synthesis has been accomplished in circular ducts and current active noise control work has made use of this capability to cancel fan noise. The goal of the current effort is to examine the fundamental process of higher order mode propagation through an acoustically treated, curved duct. The duct cross-section is rectangular to permit greater flexibility in representation of a range of duct curvatures. The work presented is the development of a feedforward control system to generate a user-specified modal pattern in the duct. The multiple-error, filtered-x LMS algorithm is used to determine the magnitude and phase of signal input to the loudspeakers to produce a desired modal pattern at a set of error microphones. Implementation issues, including loudspeaker placement and error microphone placement, are discussed. Preliminary results from a 9-3/8 inch by 21 inch duct, using 12 loudspeakers and 24 microphones, are presented. These results demonstrate the ability of the control system to generate a user-specified mode while suppressing undesired modes.
Stability analysis of thermocapillary convection in rectangular cavities
Xu, J.; Zebib, A.
1996-12-31
This paper presents stability analysis on thermocapillary convection of acetone (Pr = 4.4) in rectangular cavities using direct numerical simulation. Influence of the Reynolds number (Re) and cavity aspect ratio (Ar) on motion is investigated. Results are exhibited for streamline and isotherm patterns at different values of Re and Ar. Neutral stability curves for transition to time-dependent convection are delineated for this Pr = 4.4 fluid in the Re-Ar plane, and compared with the results for fluids with Pr = 10.0, 6.78 and 1.0. Several interesting features of these diagrams are discussed. One important conclusion the authors have from the comparison is that Ar{sub cr} increases as Pr decreases. Thus, it appears that large values of both Ar and Re are necessary to induce thermocapillary oscillations for small Pr fluids such as liquid metals. On the other hand, energy analysis is performed for the oscillatory flow in the neighborhood of critical points in order to gain insight of mechanisms leading to instability. Results are provided for flows near both critical points with Ar = 3.0.
Visualization of Boiling Phenomena in Inclined Rectangular Gap
J. L. Rempe
2005-05-01
An experimental study was performed to investigate the pool boiling critical heat flux (CHF) in one-dimensional inclined rectangular channels by changing the orientation of a copper test heater assembly. In a pool of saturated water under the atmospheric pressure, the test parameters include the gap sizes of 1, 2, 5, and 10 mm, and the surface orientation angles from the downward-facing position (1800) to the vertical position (90º), respectively. Tests were conducted on the basis of the visualization of boiling phenomena in the narrowly confined channel and open periphery utilizing a high-speed digital camera. To prevent the heat loss from the water pool and copper test heater, a state-of-the-art vacuum pumping technique was introduced. It was observed that the CHF generally decreases as the surface inclination angle increases and as the gap size decreases. In the downward-facing position (180o), however, the vapor movement was enhanced by the gap structure, which produced the opposing result, say, the CHF increases as the gap size decreases. Phenomenological characteristics regarding the interfacial instability of vapor layer were addressed in terms of visualization approaching the CHF. It was found that there exists a transition angle, around which the CHF changes with a rapid slope.
Capillary driven flow of polydimethylsiloxane in open rectangular microchannels.
Sowers, Timothy W; Sarkar, Rohit; Eswarappa Prameela, Suhas; Izadi, Ehsan; Rajagopalan, Jagannathan
2016-06-29
The flow of liquid polydimethylsiloxane (PDMS, Dow Corning Sylgard 184, 10 : 1 base to cross-linker ratio) in open, rectangular silicon microchannels, with and without a coating (100 nm) of poly-tetra-fluoro-ethylene (PTFE), was studied. Photolithographic patterning and etching of silicon wafers was used to create microchannels with a range of widths (∼5-50 μm) and depths (5-20 μm). Experimental PDMS flow rates in both PTFE-coated and uncoated channels were compared to an analytical model based on the work of Lucas and Washburn. The experimental flow rates matched the predicted flow rates reasonably well when the channel aspect ratio (width to depth), p, was less than 2. For channels with p > 2, the observed flow rates progressively lagged model predictions with increasing p. The experimental data, including zero flow rates in certain high aspect ratio PTFE-coated channels, can largely be explained by changes in the front and upper meniscus morphology of the flow as the channel aspect ratio is varied. The results strongly suggest that meniscus morphology needs to be taken into account to accurately model capillary flow in microchannels, especially those with large aspect ratios. PMID:27301750
LEDA 074886: A Remarkable Rectangular-looking Galaxy
NASA Astrophysics Data System (ADS)
Graham, Alister W.; Spitler, Lee R.; Forbes, Duncan A.; Lisker, Thorsten; Moore, Ben; Janz, Joachim
2012-05-01
We report the discovery of an interesting and rare rectangular-shaped galaxy. At a distance of 21 Mpc, the dwarf galaxy LEDA 074886 has an absolute R-band magnitude of -17.3 mag. Adding to this galaxy's intrigue is the presence of an embedded, edge-on stellar disk (of extent 2 R e, disk = 12'' = 1.2 kpc) for which Forbes et al. reported v rot/σ ≈ 1.4. We speculate that this galaxy may be the remnant of two (nearly edge-on) merged disk galaxies in which the initial gas was driven inward and subsequently formed the inner disk, while the stars at larger radii effectively experienced a dissipationless merger event resulting in this "emerald cut galaxy" having very boxy isophotes with a 4/a = -0.05 to -0.08 from 3 to 5 kpc. This galaxy suggests that knowledge from simulations of both "wet" and "dry" galaxy mergers may need to be combined to properly understand the various paths that galaxy evolution can take, with a particular relevance to blue elliptical galaxies.
Single-channel noise reduction using optimal rectangular filtering matrices.
Long, Tao; Chen, Jingdong; Benesty, Jacob; Zhang, Zhenxi
2013-02-01
This paper studies the problem of single-channel noise reduction in the time domain and presents a block-based approach where a vector of the desired speech signal is recovered by filtering a frame of the noisy signal with a rectangular filtering matrix. With this formulation, the noise reduction problem becomes one of estimating an optimal filtering matrix. To achieve such estimation, a method is introduced to decompose a frame of the clean speech signal into two orthogonal components: One correlated and the other uncorrelated with the current desired speech vector to be estimated. Different optimization cost functions are then formulated from which non-causal optimal filtering matrices are derived. The relationships among these optimal filtering matrices are discussed. In comparison with the classical sample-based technique that uses only forward prediction, the block-based method presented in this paper exploits both the forward and backward prediction as well as the temporal interpolation and, therefore, can improve the noise reduction performance by fully taking advantage of the speech property of self correlation. There is also a side advantage of this block-based method as compared to the sample-based technique, i.e., it is computationally more efficient and, as a result, more suitable for practical implementation. PMID:23363124
Strength of Rectangular Flat Plates Under Edge Compression
NASA Technical Reports Server (NTRS)
Schuman, Louis; Back, Goldie
1931-01-01
Flat rectangular plates of duralumin, stainless iron, monel metal, and nickel were tested under loads applied at two opposite edges and acting in the plane of the plate. The edges parallel to the direction of loading were supported in V grooves. The plates were all 24 inches long and varied in width from 4 to 24 inches by steps of 4 inches, and in thickness from 0.015 to 0.095 inch by steps of approximately 0.015 inch. There were also a few 1, 2, 3, and 6 inch wide specimens. The loads were applied in the testing machine at the center of a bar which rested along the top of the plate. Load was applied until the plate failed to take any more load. The tests show that the loads carried by the plates generally reached a maximum for the 8 or 12 inch width and that there was relatively small drop in load for the greater widths. Deflection and set measurement perpendicular to the plane of the plate were taken and the form of the buckle determined. The number of buckles were found to correspond in general to that predicted by the theory of buckling of a plate uniformly loaded at two opposite edges and simply supported at the edges.
Experimental study on mixing efficiency in water supply rectangular tanks
NASA Astrophysics Data System (ADS)
Bateman, A.; Medina, V.; Mujal, A.
2009-04-01
Phenomenon of mixing in drinking water storage tanks and reservoirs has a direct effect on the quality of water. Creation of poor mixing zones and volume stratification can have negative effects in public health. The design of a storage tank must consider the conditions of the inlet and outlets, and also their orientation (vertical or horizontal) to prevent the formation of these zones. Experiments done in a reduced scaled-model with a rectangular base and three different inlets (two waterfalls and a pipe inlet) had the objective to decide which of these inlets achieved the best mixing efficiency. Four situations were considered while three entrances, two unsteady: filling and drawing, and two steady with different outlets. Moreover the effects of columns that support the roof of the tank were studied by running the three entrances with and without columns in the four situations. Neglecting the viscous scale effects, the time taken to mix the volume stored depends on the distance between the inlet and the opposite wall as though as its orientation. Taking into account the whole tank columns have a negative effect on mixing efficiency although they divide the flux and create local zones of turbulence around them, increasing local mixing. Using a digital treating image technique the results are found in a quantitative way.
On the electromagnetic scattering from infinite rectangular conducting grids
NASA Technical Reports Server (NTRS)
Christodoulou, C.
1985-01-01
The study and development of two numerical techniques for the analysis of electromagnetic scattering from a rectangular wire mesh are described. Both techniques follow from one basic formulation and they are both solved in the spectral domain. These techniques were developed as a result of an investigation towards more efficient numerical computation for mesh scattering. These techniques are efficient for the following reasons: (a1) make use of the Fast Fourier Transform; (b2) they avoid any convolution problems by converting integrodifferential equations into algebraic equations; and (c3) they do not require inversions of any matrices. The first method, the SIT or Spectral Iteration Technique, is applied for regions where the spacing between wires is not less than two wavelengths. The second method, the SDCG or Spectral Domain Conjugate Gradient approach, can be used for any spacing between adjacent wires. A study of electromagnetic wave properties, such as reflection coefficient, induced currents and aperture fields, as functions of frequency, angle of incidence, polarization and thickness of wires is presented. Examples and comparisons or results with other methods are also included to support the validity of the new algorithms.
Deformation of rectangular thin glass plate coated with magnetostrictive material
NASA Astrophysics Data System (ADS)
Wang, Xiaoli; Yao, Youwei; Liu, Tianchen; Liu, Chian; Ulmer, M. P.; Cao, Jian
2016-08-01
As magnetic smart materials (MSMs), magnetostrictive materials have great potential to be selected as coating materials for lightweight x-ray telescope mirrors due to their capability to tune the mirror profile to the desired shape under a magnetic field. To realize this potential, it is necessary to study the deformation of the mirror substrate with the MSM coating subjected to a localized magnetic field. In this paper, an analytical model is developed to calculate the deformation of rectangular coated samples locally affected by magnetostrictive strains driven by an external magnetic field. As a specific case to validate the model, a square glass sample coated with MSMs is prepared, and its deformation is measured in a designed experimental setup by applying a magnetic field. The measured deformation of the sample is compared with the results calculated from the analytical model. The comparison results demonstrate that the analytical model is effective in calculating the deformation of a coated sample with the localized mismatch strains between the film and the substrate. In the experiments, different shape patterns of surface profile changes are achieved by varying the direction of the magnetic field. The analytical model and the experimental method proposed in this paper can be utilized to further guide the application of magnetostrictive coating to deformable lightweight x-ray mirrors in the future.
Propagation of spiral waves pinned to circular and rectangular obstacles
NASA Astrophysics Data System (ADS)
Sutthiopad, Malee; Luengviriya, Jiraporn; Porjai, Porramain; Phantu, Metinee; Kanchanawarin, Jarin; Müller, Stefan C.; Luengviriya, Chaiya
2015-05-01
We present an investigation of spiral waves pinned to circular and rectangular obstacles with different circumferences in both thin layers of the Belousov-Zhabotinsky reaction and numerical simulations with the Oregonator model. For circular objects, the area always increases with the circumference. In contrast, we varied the circumference of rectangles with equal areas by adjusting their width w and height h . For both obstacle forms, the propagating parameters (i.e., wavelength, wave period, and velocity of pinned spiral waves) increase with the circumference, regardless of the obstacle area. Despite these common features of the parameters, the forms of pinned spiral waves depend on the obstacle shapes. The structures of spiral waves pinned to circles as well as rectangles with the ratio w /h ˜1 are similar to Archimedean spirals. When w /h increases, deformations of the spiral shapes are observed. For extremely thin rectangles with w /h ≫1 , these shapes can be constructed by employing semicircles with different radii which relate to the obstacle width and the core diameter of free spirals.
On the structure of an underexpanded rectangular jet
NASA Astrophysics Data System (ADS)
Krothapalli, A.; Hsia, Y.; Baganoff, D.; Karamcheti, K.
1982-07-01
An underexpanded jet of air issuing from a converging rectangular nozzle of moderate aspect ratio was investigated. Schileren pictures of the flow field along with hot-wire measurements in the jet were obtained at different pressure ratios. At the pressure ratio corresponding to the maximum screeching sound, Schlieren photographs show a very strong organized cylindrical wave pattern on either side of the jet, with their respective sources being located at the end of the third shock cell. Associated with this wave pattern is a large increase in the angle of spread of the jet. It is shown that the self excitation helps to induce large-scale vortical motions in the jet both in the plane containing the small dimension of the nozzle and in the plane containing the long dimension of the nozzle. However, the locations of these structures are different in the two planes. Nevertheless, the characteristic Strouhal number corresponding to these large-scale structures in both planes is the same and equal to 0.12. The influence of the self excitation on the mean velocities and rms intensities was also investigated. For the full range of pressure ratios studied, similarity was found in the mean velocity and rms intensity profiles in the two central planes beyond 80 widths downstream of the nozzle exit. However, the shapes of the similarity profiles are different in the two planes.
Granular segregation in quasi-2d rectangular bin
NASA Astrophysics Data System (ADS)
Gharat, Sandip H.; Khakhar, D. V.
2013-06-01
Experiments are carried out in quasi two-dimensional rectangular bin (two vertical glass plate separated by a gap of 10 mm) to study the effect of feed composition on segregation of granular mixtures during heap formation by intermittent feeding. The stainless steel (SS 316) balls of different sizes (1 and 2 mm) are used as model granular materials. The heap is formed by repeatedly pouring a fixed mass of the mixture. Each feeding results in the formation of a layer of the mixture on the surface of the heap. Results presented here are for binary mixtures with different size and equal density. Profiles of the number fraction of big particles along the flow direction averaged across the depth of the layer are plotted. In each layer formed by a pouring, segregation results in the small particles being deposited first. Thus, the small particles are concentrated in the upper part of the layer and the large particles in the lower part with a mixed region between the two. The extent of segregation is found to increase with decrease in concentration of big particles in the mixture.
Permuting sparse rectangular matrices into block-diagonal form
Aykanat, Cevdet; Pinar, Ali; Catalyurek, Umit V.
2002-12-09
This work investigates the problem of permuting a sparse rectangular matrix into block diagonal form. Block diagonal form of a matrix grants an inherent parallelism for the solution of the deriving problem, as recently investigated in the context of mathematical programming, LU factorization and QR factorization. We propose graph and hypergraph models to represent the nonzero structure of a matrix, which reduce the permutation problem to those of graph partitioning by vertex separator and hypergraph partitioning, respectively. Besides proposing the models to represent sparse matrices and investigating related combinatorial problems, we provide a detailed survey of relevant literature to bridge the gap between different societies, investigate existing techniques for partitioning and propose new ones, and finally present a thorough empirical study of these techniques. Our experiments on a wide range of matrices, using state-of-the-art graph and hypergraph partitioning tools MeTiS and PaT oH, revealed that the proposed methods yield very effective solutions both in terms of solution quality and run time.
The effect of riblets in rectangular duct flow
NASA Astrophysics Data System (ADS)
Dean, Brian; Bhushan, Bharat
2012-02-01
Much is known about the benefits of surface structures which mimic the riblets found on the skin of fast swimming sharks. Structures have been fabricated for study and application which replicate and improve upon the natural shape of the shark skin riblets, providing a maximum drag reduction of nearly 10% in external turbulent fluid flow. Mechanisms of fluid drag in turbulent flow and riblet-drag reduction theories from experiment and simulation are discussed. A brief review of riblet performance studies is given, and optimal riblet geometries are defined for external flow. A discussion of the structure of internal turbulent fluid flow is provided, and existing data for riblet drag reduction benefit is presented. A flow cell for studying riblet effects in internal rectangular duct flow is discussed, and data collected using several riblet surfaces fabricated for the flow cell is presented and analyzed. A discussion of the effects of the riblets on fluid flow is given, and conclusions are drawn about the possible benefits of riblets in internal fluid flow.
Diversity of acoustic streaming in a rectangular acoustofluidic field.
Tang, Qiang; Hu, Junhui
2015-04-01
Diversity of acoustic streaming field in a 2D rectangular chamber with a traveling wave and using water as the acoustic medium is numerically investigated by the finite element method. It is found that the working frequency, the vibration excitation source length, and the distance and phase difference between two separated symmetric vibration excitation sources can cause the diversity in the acoustic streaming pattern. It is also found that a small object in the acoustic field results in an additional eddy, and affects the eddy size in the acoustic streaming field. In addition, the computation results show that with an increase of the acoustic medium's temperature, the speed of the main acoustic streaming decreases first and then increases, and the angular velocity of the corner eddies increases monotonously, which can be clearly explained by the change of the acoustic dissipation factor and shearing viscosity of the acoustic medium with temperature. Commercialized FEM software COMSOL Multiphysics is used to implement the computation tasks, which makes our method very easy to use. And the computation method is partially verified by an established analytical solution. PMID:25541360
The characteristic impedance of large-scale rectangular strip transmission line facilities used for such purposes as EMI susceptibility testing, biological exposures, etc., is discussed. These lines are characterized by a thin center conductor and an air dielectric. Impedance dat...
Generation of transform-limited rectangular pulses in a spectral compressor
Kalashyan, M A; Palandzhyan, K A; Esayan, G L; Muradyan, L Kh
2010-12-09
The generation of 100-fs transform-limited pulses with a rectangular envelope in a spectral compressor is demonstrated experimentally. The pulses are characterised by spectral interferometry. (control of radiation parameters)
On the existence of guided acoustic waves at rectangular anisotropic edges.
Pupyrev, Pavel D; Lomonosov, Alexey M; Nikodijevic, Aleksandar; Mayer, Andreas P
2016-09-01
The existence of acoustic waves with displacements localized at the tip of an isotropic elastic wedge was rigorously proven by Kamotskii, Zavorokhin and Nazarov. This proof, which is based on a variational approach, is extended to rectangular anisotropic wedges. For two high-symmetry configurations of rectangular edges in elastic media with tetragonal symmetry, a criterion is derived that allows identifying the boundary between the regions of existence for wedge modes of even and odd symmetry in regions of parameter space, where even- and odd-symmetry modes do not exist simultaneously. Furthermore, rectangular edges with non-equivalent surfaces are analyzed, and it is shown that at rectangular edges of cubic elastic media with one (110) surface and one (001) surface, a tip-localized guided wave always exists, apart from special cases that are characterized. PMID:27447889
Hubbell rectangular source integral calculation using a fast Chebyshev wavelets method.
Manai, K; Belkadhi, K
2016-07-01
An integration method based on Chebyshev wavelets is presented and used to calculate the Hubbell rectangular source integral. A study of the convergence and the accuracy of the method was carried out by comparing it to previous studies. PMID:27152913
Vibrational analysis of rectangular sandwich plates resting on some elastic point supports
Ichinomiya, Osamu; Maruyama, Koichi; Sekine, Kouji
1995-11-01
An approximate solution of forced-vibration for rectangular sandwich plate resting on some elastic point supports is presented. The sandwich plate has thin, anisotropic composite laminated faces and a thick orthotropic core. The simplified sandwich plate model is used in the analysis. The governing equation of elastically point supported rectangular sandwich plate is obtained by using the Lagrange equation. The steady state response solution to a sinusoidally varying point force is also derived. The response curves of rectangular sandwich plates having CFRP laminated faces and aluminum honeycomb core is calculated. Application examples illustrate the effects of laminate lay-up of face sheets, core material properties and core thickness ratio on the vibration characteristics of rectangular sandwich plate.
Use of Psi Squared and Flux to Simplify Analysis of Transmission past Rectangular Barriers or Wells.
ERIC Educational Resources Information Center
Draper, James E.
1979-01-01
Analyzes the transmission coefficient for a completely general one-dimensional rectangular potential, or well, simply by concentrating on psi squared rather than psi. Gives graphs of all cases of psi squared. (Author/GA)
A buckling analysis for rectangular orthotropic plates with centrally located cutouts
NASA Technical Reports Server (NTRS)
Nemeth, M. P.
1984-01-01
An analysis to obtain the buckling loads of a rectangular orthotropic plate with a centrally located cutout is described. Cutout shapes can be elliptical, circular, rectangular, or square. The boundary conditions considered in the analysis are simply supported unloaded edges and either clamped or simply supported loaded edges. The plate is loaded in uniaxial compression by either uniform edge displacement or uniform edge stress. A computer program that implements this analysis is described, and the program use is demonstrated by sample problems.
Thermal vibration of a rectangular single-layered graphene sheet with quantum effects
Wang, Lifeng Hu, Haiyan
2014-06-21
The thermal vibration of a rectangular single-layered graphene sheet is investigated by using a rectangular nonlocal elastic plate model with quantum effects taken into account when the law of energy equipartition is unreliable. The relation between the temperature and the Root of Mean Squared (RMS) amplitude of vibration at any point of the rectangular single-layered graphene sheet in simply supported case is derived first from the rectangular nonlocal elastic plate model with the strain gradient of the second order taken into consideration so as to characterize the effect of microstructure of the graphene sheet. Then, the RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet simply supported on an elastic foundation is derived. The study shows that the RMS amplitude of the rectangular single-layered graphene sheet predicted from the quantum theory is lower than that predicted from the law of energy equipartition. The maximal relative difference of RMS amplitude of thermal vibration appears at the sheet corners. The microstructure of the graphene sheet has a little effect on the thermal vibrations of lower modes, but exhibits an obvious effect on the thermal vibrations of higher modes. The quantum effect is more important for the thermal vibration of higher modes in the case of smaller sides and lower temperature. The relative difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet decreases monotonically with an increase of temperature. The absolute difference of maximal RMS amplitude of thermal vibration of a rectangular single-layered graphene sheet increases slowly with the rising of Winkler foundation modulus.
The noise reduction potential of dual-stream coaxial rectangular improperly expanded jet flows
NASA Technical Reports Server (NTRS)
Dosanjh, Darshan; Spina, Eric F.
1995-01-01
The research performed began during Spring 1991 as a project to assess the noise reduction potential of rectangular coaxial nozzle configurations for improperly expanded jets. The research plan consisted of: (1) design of coaxial rectangular nozzle configuration by Syracuse graduate research assistant; (2) construction of nozzles by NASA Langley machinists; and (3) acquisition of preliminary acoustic and optical data for a variety of inner and outer jet pressure ratios.
Multi-walled carbon nanotubes with rectangular or square cross-section
NASA Astrophysics Data System (ADS)
Mizutani, Kanako; Kohno, Hideo
2016-06-01
Multi-walled carbon nanotubes with rectangular or square cross-section are formed. The nanotubes are about 50-200 nm in width, and their walls are around 5-30 nm thick. It is very likely that the rectangular cross-section is shaped simultaneously when nanotubes are formed from catalyst Fe nanoparticles during chemical vapor deposition process, and the shape is stabilized by the bonding between adjoining graphene layers in the multi-walled structure.
Critical Heat Flux in Inclined Rectangular Narrow Gaps
Jeong J. Kim; Yong H. Kim; Seong J. Kim; Sang W. Noh; Kune Y. Suh; Joy L. Rempe; Fan-Bill Cheung; Sang B. Kim
2004-06-01
In light of the TMI-2 accident, in which the reactor vessel lower head survived the attack by molten core material, the in-vessel retention strategy was suggested to benefit from cooling the debris through a gap between the lower head and the core material. The GAMMA 1D (Gap Apparatus Mitigating Melt Attack One Dimensional) tests were conducted to investigate the critical heat flux (CHF) in narrow gaps with varying surface orientations. The CHF in an inclined gap, especially in case of the downward-facing narrow gap, is dictated by bubble behavior because the departing bubbles are squeezed. The orientation angle affects the bubble layer and escape of the bubbles from the narrow gap. The test parameters include gap sizes of 1, 2, 5 and 10 mm and the open periphery, and the orientation angles range from the fully downward-facing (180o) to the vertical (90o) position. The 15 ×35 mm copper test section was electrically heated by the thin film resistor on the back. The heater assembly was installed to the tip of the rotating arm in the heated water pool at the atmospheric pressure. The bubble behavior was photographed utilizing a high-speed camera through the Pyrex glass spacer. It was observed that the CHF decreased as the surface inclination angle increased and as the gap size decreased in most of the cases. However, the opposing results were obtained at certain surface orientations and gap sizes. Transition angles, at which the CHF changed in a rapid slope, were also detected, which is consistent with the existing literature. A semi-empirical CHF correlation was developed for the inclined narrow rectangular channels through dimensional analysis. The correlation provides with best-estimate CHF values for realistically assessing the thermal margin to failure of the lower head during a severe accident involving relocation of the core material.
Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies
NASA Technical Reports Server (NTRS)
Suh, Peter M.; Conyers, Howard J.; Mavris, Dimitri N.
2014-01-01
This paper introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio and number of control surfaces. A doublet lattice approach is taken to compute generalized forces. A rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. Although, all parameters can be easily modified if desired.The focus of this paper is on tool presentation, verification and validation. This process is carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool. Therefore the flutter speed and frequency for a clamped plate are computed using V-g and V-f analysis. The computational results are compared to a previously published computational analysis and wind tunnel results for the same structure. Finally a case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to V-g and V-f analysis. This also includes the analysis of the model in response to a 1-cos gust.
Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies
NASA Technical Reports Server (NTRS)
Suh, Peter M.; Conyers, Howard J.; Mavris, Dimitri N.
2015-01-01
This paper introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this paper is on tool presentation, verification, and validation. These processes are carried out in stages throughout the paper. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust.
Rapid State Space Modeling Tool for Rectangular Wing Aeroservoelastic Studies
NASA Technical Reports Server (NTRS)
Suh, Peter M.; Conyers, Howard Jason; Mavris, Dimitri N.
2015-01-01
This report introduces a modeling and simulation tool for aeroservoelastic analysis of rectangular wings with trailing-edge control surfaces. The inputs to the code are planform design parameters such as wing span, aspect ratio, and number of control surfaces. Using this information, the generalized forces are computed using the doublet-lattice method. Using Roger's approximation, a rational function approximation is computed. The output, computed in a few seconds, is a state space aeroservoelastic model which can be used for analysis and control design. The tool is fully parameterized with default information so there is little required interaction with the model developer. All parameters can be easily modified if desired. The focus of this report is on tool presentation, verification, and validation. These processes are carried out in stages throughout the report. The rational function approximation is verified against computed generalized forces for a plate model. A model composed of finite element plates is compared to a modal analysis from commercial software and an independently conducted experimental ground vibration test analysis. Aeroservoelastic analysis is the ultimate goal of this tool, therefore, the flutter speed and frequency for a clamped plate are computed using damping-versus-velocity and frequency-versus-velocity analysis. The computational results are compared to a previously published computational analysis and wind-tunnel results for the same structure. A case study of a generic wing model with a single control surface is presented. Verification of the state space model is presented in comparison to damping-versus-velocity and frequency-versus-velocity analysis, including the analysis of the model in response to a 1-cos gust.
Aspect Ratio Effects on Fluid Flow Fluctuations in Rectangular Cavities
NASA Astrophysics Data System (ADS)
Kalter, Rudi; Tummers, Mark J.; Wefers Bettink, Jeroen B.; Righolt, Bernhard W.; Kenjereš, Sasa; Kleijn, Chris R.
2014-12-01
The flow from a submerged bifurcated nozzle into rectangular liquid-filled cavities with width-to-thickness ratios W/ T = 6.5, 11, and 18 has been studied using free surface visualization and particle tracking. When W/ T = 11 and when W/ T = 18, self-sustained oscillations of the submerged jets and the free surface are present. When W/ T = 6.5, the self-sustained oscillations are no longer present, but oscillations with the frequency of gravity waves occur. We propose a critical value of W/ T above which self-sustained jet oscillations occur, based on the spreading angle of turbulent jets. When W/ T is larger than this critical value, the shear layers of the jet reach the front and back wall of the cavity before the jet can impinge the side wall, resulting in semi two-dimensional flow in the plane between the front and the back wall. Two-dimensional recirculation zones form alongside the jet leading to the jet oscillations. When W/ T is smaller than this critical value, the jet can develop like a free turbulent jet up to an impingement point at the narrow side wall. When the jet impinges the side wall, flow in the directions parallel and perpendicular to the front and back walls is possible, resulting in complex three-dimensional flow patterns. The critical value for W/ T, based on the known 12 deg spreading angle of turbulent jets is W/ T = 10, which is in good agreement with the experimental results.
On the structure of an underexpanded rectangular jet
NASA Astrophysics Data System (ADS)
Krothapalli, A.; Hsia, Y.; Baganoff, D.; Karamcheti, K.
1982-07-01
An experimental investigation was carried out on an underexpanded jet of air issuing from a converging rectangular nozzle of moderate aspect ratio. Schlieren pictures of the flow field along with hot-wire measurements in the jet were obtained at different pressure ratios. At the pressure ratio corresponding to the maximum screeching sound, Schlieren photographs show a very strong organized cylindrical wave pattern on either side of the jet, with their respective sources being located at the end of the third shock cell. Associated with this wave pattern is a large increase in the angle of spread of the jet. It is shown that the self excitation helps to induce large-scale vortical motions in the jet both in the plane containing the small dimension of the nozzle and in the plane containing the long dimension of the nozzle. However, the locations of these structures are different in the two planes. Nevertheless, the characteristic Strouhal number corresponding to these large-scale structures in both planes is the same and equal to 0.12. The influence of the self excitation on the mean velocities and rms intensities was investigated. For the full range of pressure ratios studied, similarity was found both in the mean velocity and rms intensity profiles in the two central planes beyond 80 widths downstream of the nozzle exit. However, the shapes of the similarity profiles are different in the two planes. For the downstream distances studied, complete axisymmetry (identical mean velocity profiles in both planes) was not found, which suggests it may persist for a large distance downstream of the nozzle exit.
Cholesteric liquid crystals in rectangular microchannels: skyrmions and stripes.
Guo, Yubing; Afghah, Sajedeh; Xiang, Jie; Lavrentovich, Oleg D; Selinger, Robin L B; Wei, Qi-Huo
2016-07-20
In this paper, we present experimental and numerical studies on the microstructures of a cholesteric liquid crystal (CLC) confined in rectangular micron-channels. By using a sequence of microfabrication techniques we fabricated the micro-sized channels with accurately controlled size, aspect ratio and homeotropic surface anchoring. Through optical microscopic studies we established a phase diagram for the liquid crystal defect textures as a function of the channel depth and width. For the channel width larger than ∼2 times the cholesteric pitch p, the LC molecules are oriented primarily vertical to the channel when the channel depth is below 0.75p, form bubble domain defects when the channel depth is around 0.75p, and form stripe textures when the cell depth is above the cholesteric pitch p. In addition, the bubble domain size and the stripe texture periodicity are found to grow with the increase of the channel width. For the channel width smaller than ∼2p and the channel depth between 0.6p to 1.1p, no textures can be observed in the channels. Numerical simulations based on a director tensor relaxation approach yield detailed molecular director fields, and show that the bubble domain defects are baby-skyrmions and that the stripes are the first type of cholesteric fingerprints. A comparison with previous experiments and numerical simulations indicates that the size of the microchannels also influences what type of soliton-like topological textures form in the CLCs confined in the channels. PMID:27396898
Psyplot: Visualizing rectangular and triangular Climate Model Data with Python
NASA Astrophysics Data System (ADS)
Sommer, Philipp
2016-04-01
The development and use of climate models often requires the visualization of geo-referenced data. Creating visualizations should be fast, attractive, flexible, easily applicable and easily reproducible. There is a wide range of software tools available for visualizing raster data, but they often are inaccessible to many users (e.g. because they are difficult to use in a script or have low flexibility). In order to facilitate easy visualization of geo-referenced data, we developed a new framework called "psyplot," which can aid earth system scientists with their daily work. It is purely written in the programming language Python and primarily built upon the python packages matplotlib, cartopy and xray. The package can visualize data stored on the hard disk (e.g. NetCDF, GeoTIFF, any other file format supported by the xray package), or directly from the memory or Climate Data Operators (CDOs). Furthermore, data can be visualized on a rectangular grid (following or not following the CF Conventions) and on a triangular grid (following the CF or UGRID Conventions). Psyplot visualizes 2D scalar and vector fields, enabling the user to easily manage and format multiple plots at the same time, and to export the plots into all common picture formats and movies covered by the matplotlib package. The package can currently be used in an interactive python session or in python scripts, and will soon be developed for use with a graphical user interface (GUI). Finally, the psyplot framework enables flexible configuration, allows easy integration into other scripts that uses matplotlib, and provides a flexible foundation for further development.
Vibration characteristics of rectangular plate in compressible inviscid fluid
NASA Astrophysics Data System (ADS)
Liao, Chan-Yi; Ma, Chien-Ching
2016-02-01
This paper presents a mathematical derivation of the vibration characteristics of an elastic thin plate placed at the bottom of a three dimensional rectangular container filled with compressible inviscid fluid. A set of beam functions is used as the admissible functions of the plate in a fluid-plate system, and the motion of the fluid induced by the deformation of the plate is obtained from a three-dimensional acoustic equation. Pressure from the fluid over the fluid-plate interface is integrated to form a virtual mass matrix. The frequency equation of the fluid-plate system is derived by combining mass, stiffness, and the virtual mass matrix. Solving the frequency equation makes it possible to obtain the dynamic characteristic of the fluid-plate system, such as resonant frequencies, corresponding mode shapes, and velocity of the fluid. Numerical calculations were performed for plates coupled with fluids with various degrees of compressibility to illustrate the difference between compressible and incompressible fluids in a fluid-plate system. The proposed method could be used to predict resonant frequencies and mode shapes with accuracy compared to that of incompressible fluid theory (IFT). The proposed method can be used to analyze cases involving high value of sound velocity, such as incompressible fluids. When the sound velocity approaches infinity, the results obtained for compressible fluids are similar to those of incompressible fluids. We also examined the influence of fluid compressibility on vibration characteristics in which a decrease in sound velocity was shown to correspond to a decrease in resonant frequency. Additional modes, not observed in incompressible fluids, were obtained in cases of low sound velocity, particularly at higher resonant frequencies. Fluid velocity plots clearly reveal that the additional resonant modes can be attributed to the compressible behavior of the fluid.
Magnetic forces produced by rectangular permanent magnets in static microsystems.
Gassner, Anne-Laure; Abonnenc, Mélanie; Chen, Hong-Xu; Morandini, Jacques; Josserand, Jacques; Rossier, Joel S; Busnel, Jean-Marc; Girault, Hubert H
2009-08-21
Finite element numerical simulations were carried out in 2D geometries to map the magnetic field and force distribution produced by rectangular permanent magnets as a function of their size and position with respect to a microchannel. A single magnet, two magnets placed in attraction and in repulsion have been considered. The goal of this work is to show where magnetic beads are preferentially captured in a microchannel. These simulations were qualitatively corroborated, in one geometrical case, by microscopic visualizations of magnetic bead plug formation in a capillary. The results show that the number of plugs is configuration dependent with: in attraction, one plug in the middle of the magnets; in repulsion, two plugs near the edges of the magnets; and with a single magnet, a plug close to the center of the magnet. The geometry of the magnets (h and l are the height and length of the magnets respectively) and their relative spacing s has a significant impact on the magnetic flux density. Its value inside a magnet increases with the h/l ratio. Consequently, bar magnets produce larger and more uniform values than flat magnets. The l/s ratio also influences the magnetic force value in the microchannel, both increasing concomitantly for all the configurations. In addition, a zero force zone in the middle appears in the attraction configuration as the l/s ratio increases, while with a single magnet, the number of maxima and minima goes from one to two, producing two focusing zones instead of only one. PMID:19636467
Development of young oil palm tree recognition using Haar- based rectangular windows
NASA Astrophysics Data System (ADS)
Daliman, S.; Abu-Bakar, S. A. R.; Nor Azam, S. H. Md
2016-06-01
This paper presents development of Haar-based rectangular windows for recognition of young oil palm tree based on WorldView-2 imagery data. Haar-based rectangular windows or also known as Haar-like rectangular features have been popular in face recognition as used in Viola-Jones object detection framework. Similar to face recognition, the oil palm tree recognition would also need a suitable Haar-based rectangular windows that best suit to the characteristics of oil palm tree. A set of seven Haar-based rectangular windows have been designed to better match specifically the young oil palm tree as the crown size is much smaller compared to the matured ones. Determination of features for oil palm tree is an essential task to ensure a high successful rate of correct oil palm tree detection. Furthermore, features that reflects the identification of oil palm tree indicate distinctiveness between an oil palm tree and other objects in the image such as buildings, roads and drainage. These features will be trained using support vector machine (SVM) to model the oil palm tree for classifying the testing set and subimages of WorldView-2 imagery data. The resulting classification of young oil palm tree with sensitivity of 98.58% and accuracy of 92.73% shows a promising result that it can be used for intention of developing automatic young oil palm tree counting.
A PLANAR, RECTANGULAR WAVEGUIDE LAUNCHER AND EXTRACTOR FOR A DUAL-MODED RF POWER DISTRIBUTION SYSTEM
Nantista, Christopher D.
2000-11-21
The desire to reduce the amount of low-loss, circular-waveguide delay line required in a pulse-compressing power distribution system for the Next Linear Collider has led to the pursuit of multi-moded schemes [1]. In such a system, power is delivered to different destinations through the same waveguide via different propagating modes. Current plans [2] utilize two modes, with manipulations done primarily in overmoded rectangular guide. We describe two key components of the system, a four-input/four-output, dual-mode launcher and an extractor for diverting one mode from the delay line to an accelerator feed while allowing the other to pass on to an upstream feed. These novel passive waveguide devices utilize the rectangular TE10 and TE20 modes. Because they must carry up to 600 MW pulsed rf power, H-planar symmetry is maintained in their designs to allow the use of overheight waveguide, and features that invite breakdown, such as coupling slots, irises, and septa, are avoided. Special rectangular-to-circular tapers [3] will be used to convert between the above modes and the circular TE11{sup o} (TE12{sup o}) and TE01{sup o} delay line modes, respectively. Rectangular waveguide for relative ease of handling. Mode converters, including special cross-section tapers [3] will be used to transform between the above circular waveguide modes and the TE20 and TE10 rectangular waveguide modes, respectively.
A computer program for converting rectangular coordinates to latitude-longitude coordinates
Rutledge, A.T.
1989-01-01
A computer program was developed for converting the coordinates of any rectangular grid on a map to coordinates on a grid that is parallel to lines of equal latitude and longitude. Using this program in conjunction with groundwater flow models, the user can extract data and results from models with varying grid orientations and place these data into grid structure that is oriented parallel to lines of equal latitude and longitude. All cells in the rectangular grid must have equal dimensions, and all cells in the latitude-longitude grid measure one minute by one minute. This program is applicable if the map used shows lines of equal latitude as arcs and lines of equal longitude as straight lines and assumes that the Earth 's surface can be approximated as a sphere. The program user enters the row number , column number, and latitude and longitude of the midpoint of the cell for three test cells on the rectangular grid. The latitude and longitude of boundaries of the rectangular grid also are entered. By solving sets of simultaneous linear equations, the program calculates coefficients that are used for making the conversion. As an option in the program, the user may build a groundwater model file based on a grid that is parallel to lines of equal latitude and longitude. The program reads a data file based on the rectangular coordinates and automatically forms the new data file. (USGS)
A Theoretical Investigation of the Input Characteristics of a Rectangular Cavity-Backed Slot Antenna
NASA Technical Reports Server (NTRS)
Cockrell, C. R.
1975-01-01
Equations which represent the magnetic and electric stored energies are derived for an infinite section of rectangular waveguide and a rectangular cavity. These representations which are referred to as being physically observable are obtained by considering the difference in the volume integrals appearing in the complex Poynting theorem. It is shown that the physically observable stored energies are determined by the field components that vanish in a reference plane outside the aperture. These physically observable representations are used to compute the input admittance of a rectangular cavity-backed slot antenna in which a single propagating wave is assumed to exist in the cavity. The slot is excited by a voltage source connected across its center; a sinusoidal distribution is assumed in the slot. Input-admittance calculations are compared with measured data. In addition, input-admittance curves as a function of electrical slot length are presented for several size cavities. For the rectangular cavity backed slot antenna, the quality factor and relative bandwidth were computed independently by using these energy relationships. It is shown that the asymptotic relationship which is usually assumed to exist between the quality bandwidth and the reciprocal of relative bandwidth is equally valid for the rectangular cavity backed slot antenna.
Reorienting strategies in a rectangular array of landmarks by domestic chicks (Gallus gallus).
Pecchia, Tommaso; Vallortigara, Giorgio
2010-05-01
Spatial reorientation in a rectangular array of four landmarks located in the center of a circular enclosure was investigated in domestic chicks (Gallus gallus). One of the landmark possessed unique visual features, indicating the location of a food reward. After training, chicks were tested (a) with the same array as during the training; (b) with four identical landmarks of the type previously nonrewarded, of the type previously rewarded, or of a new type; (c) after having transformed one of the landmarks located at the geometric incorrect location into the type of landmark previously rewarded; or (d) with a fifth landmark of the rewarded type at a new location. Chicks encoded information provided by local featural cues but not the geometric information provided by the shape of the array. Moreover, when trained in a rectangular array of identical landmarks chicks failed to reorient. In a second series of experiments, the array was located in correspondence to the corners of a rectangular enclosure. This time chicks successfully learned to locate the reward using geometric information. However, when the rectangular array was located in the center of a larger rectangular enclosure, chicks failed to reorient, indicating that the geometric information given by the macroscopic layout of arena surfaces was not used to specify different locations. These results suggest that chicks reorient on the basis of a local representation of single landmarks and that encoding of the global aspects of geometry only occurs with respect to the large, extended surfaces of an enclosure. PMID:20476814
NASA Technical Reports Server (NTRS)
Tischler, Adelbert O.
1948-01-01
The performance of an annular combustion chamber from a 24C turbojet engine was investigated over a range of simulated altitudes from 20,000 to 55,000 feet and corrected engine rotor speeds from 6000 to 13,000 rpm at a simulated ram-pressure ratio of 1.04. The purpose of the investigation was to determine the effects on the altitude operational limits, combustor-outlet gas temperature distribution, combustion efficiencies, and combustor inlet-to-outlet total-pressure drops of two changes in the 24C-4B basket air-passage arrangements that were designed to improve combustor-outlet temperature distribution. These changes were: (a) replacement of the downstream secondary air holes with large rectangular slots further upstream (rectangular-slot basket), and (b) enlargement of anticoking holes in the rectangular-slot basket (modified rectangular-slot basket). The results indicate that improved outlet-gas temperature distribution of each succeeding combustor basket investigated was attained at a sacrifice in the altitude limit of operation. The altitude limits of operation of the combustor with the original basket ranged from 34,000 feet at a corrected engine speed of 6000 rpm to a maximum of 52,000 feet at 12 ' 500 rpm. The altitude limits of the rectangular-slot basket were about 2000 feet lower throughout the engine speed range than those of the original basket. The altitude limits of the combustor with the modified rectangular-slot basket were about equivalent to those of the other baskets in the corrected-engine-speed range from 12,000 to 12,500 rpm but were about 10,000 feet lower than those of the original basket in the corrected-engine-speed range from 6000 to 9000 rpm. For the same inlet-air conditions, the combustion efficiencies were highest for the original basket and progressively lower for each of the other two baskets. The combustor inlet-to-outlet pressure drops of all three combustor baskets at the same operating conditions were within +/- 10 percent of
Analysis of pneumatic hammer in rectangular aerostatic thrust bearing with groove
NASA Astrophysics Data System (ADS)
Ma, Wei; Tan, Jiubin; Cui, Jiwen; Liu, Yongmeng
2015-02-01
The pneumatic hammer in rectangular aerostatic thrust bearings with groove is analyzed using perturbation theory. Routh stability criterion was used to evaluate the critical condition of pneumatic hammer in rectangular aerostatic thrust bearings with groove, and the influence of supply pressure, throttle area, groove area, and thickness of film on aerostatic thrust bearings. It was found through analysis that the change rate of stiffness and the volume ratio of aerostatic bearing could be used to analyze the pneumatic hammer in rectangular aerostatic thrust bearings with groove. At a certain film thickness, the stability of aerostatic bearings could be improved by reducing supply pressure, increasing throttle area and decreasing groove area to facilitate the design of a general aerostatic thrust bearing.
Seo, Hyeon-Seok; Boo, Jin-Hyo; Kim, Youn-Jea
2015-10-01
This study numerically investigated the flow characteristics in a rectangular enclosure filled with oil-based ferrofluid (EFH-1, Ferrotec.) under the influence of external magnetic fields. The rectangular enclosure contained obstacles with different shapes, such as a rectangle and a triangle mounted on the top and bottom wall surfaces. In order to generate external magnetic fields, a permanent magnet was located in the lower part of the rectangular enclosure, and its direction was selected to be either horizontal or vertical. Our results showed that the ferrofluid flow fields were affected by the applied external magnetic field direction and eddy flow phenomena in the working fluid were generated in the vicinity of high magnetic flux density distributions, such as at the edge of the permanent magnet. It was also confirmed that the magnetophoretic force distributions in the analysis model played a significant role in the development of the ferrofluid flow fields. PMID:26726349
NASA Technical Reports Server (NTRS)
Lakin, W. D.
1986-01-01
Integrating and differentiating matrices allow the numerical integration and differential of functions whose values are known at points of a discrete grid. Previous derivations of these matrices were restricted to one dimensional grids or to rectangular grids with uniform spacing in at least one direction. Integrating and differentiating matrices were developed for grids with nonuniform spacing in both directions. The use of these matrices as operators to reformulate boundary value problems on rectangular domains as matrix problems for a finite dimensional solution vector is considered. The method requires nonuniform grids which include near boundary points. An eigenvalue problem for the transverse vibrations of a simply supported rectangular plate is solved to illustrate the method.
Numerical Investigation of Flow Around Rectangular Cylinders with and Without Jets
NASA Technical Reports Server (NTRS)
Tiwari, S. N .; Pidugu, S. B.
1999-01-01
The problem of flow past bluff bodies was studied extensively in the past. The problem of drag reduction is very important in many high speed flow applications. Considerable work has been done in this subject area in case of circular cylinders. The present study attempts to investigate the feasibility of drag reduction on a rectangular cylinder by flow injection by flow injection from the rear stagnation region. The physical problem is modeled as two-dimensional body and numerical analysis is carried out with and without trailing jets. A commercial code is used for this purpose. Unsteady computation is performed in case of rectangular cylinders with no trailing jets where as steady state computation is performed when jet is introduced. It is found that drag can be reduced by introducing jets with small intensity in rear stagnation region of the rectangular cylinders.
Numerical simulation of sloshing in rectangular storage tank using coupled FEM-BEM
NASA Astrophysics Data System (ADS)
Saghi, Hassan; Ketabdari, Mohammad Javad
2012-12-01
Sloshing of liquid can increase the dynamic pressure on the storage sidewalls and bottom in tanker ships and LNG careers. Different geometric shapes were suggested for storage tank to minimize the sloshing pressure on tank perimeter. In this research, a numerical code was developed to model liquid sloshing in a rectangular partially filled tank. Assuming the fluid to be inviscid, Laplace equation and nonlinear free surface boundary conditions are solved using coupled FEM-BEM. The code performance for sloshing modeling is validated against available data. To minimize the sloshing pressure on tank perimeter, rectangular tanks with specific volumes and different aspect ratios were investigated and the best aspect ratios were suggested. The results showed that the rectangular tank with suggested aspect ratios, not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing pressure efficiently.
NASA Astrophysics Data System (ADS)
Yeh, Jia-Yi
2013-03-01
In this study, the vibration analysis of sandwich rectangular plates with magnetorheological (MR) elastomer damping treatment is presented. The rectangular plate is combined with a magnetorheological elastomer core layer and a constraining layer to improve the vibration behaviors of the sandwich system. The MR material shows variations in the rheological properties when subjected to varying magnetic fields. Additionally, the MR material exhibits a rapid time response and is applicable to structures or devices when a tunable system is required. The magnetorheological elastomer is found to have a significant effect on the vibration characteristics of the sandwich rectangular plate. The modal damper and the natural frequencies for the sandwich plate system are calculated for various magnetic fields and some designed parameters by utilizing the finite element method. The damping effects of the sandwich plate system can be controlled and changed when different magnetic field strengths are applied.
Uniform patchy and hollow rectangular platelet micelles from crystallizable polymer blends
NASA Astrophysics Data System (ADS)
Qiu, Huibin; Gao, Yang; Boott, Charlotte E.; Gould, Oliver E. C.; Harniman, Robert L.; Miles, Mervyn J.; Webb, Stephen E. D.; Winnik, Mitchell A.; Manners, Ian
2016-05-01
The preparation of colloidally stable, self-assembled materials with tailorable solid or hollow two-dimensional (2D) structures represents a major challenge. We describe the formation of uniform, monodisperse rectangular platelet micelles of controlled size by means of seeded-growth methods that involve the addition of blends of crystalline-coil block copolymers and the corresponding crystalline homopolymer to cylindrical micelle seeds. Sequential addition of different blends yields solid platelet block comicelles with concentric rectangular patches with distinct coronal chemistries. These complex nano-objects can be subject to spatially selective processing that allows their disassembly to form perforated platelets, such as well-defined hollow rectangular rings. The solid and hollow 2D micelles provide a tunable platform for further functionalization and potential for a variety of applications.
Schnurr, Christoph; Nessler, Jochen; König, Dietmar Pierre
2009-12-01
Femoral malrotation in total knee arthroplasty causes flexion gap instability. Conventional instruments mostly reference the posterior condylar angle (PCA). The aim of this study was to verify whether the computer-navigated flexion gap (GAP) method produces a rectangular flexion gap and if a balanced flexion gap could also be achieved by referencing the PCA. A total of 100 knee prostheses were analysed using the navigated GAP method, and flexion gap symmetry along with femoral rotation were recorded. The GAP technique resulted in a rectangular flexion gap with adequate femoral rotational alignment. If the PCA technique had been used, only 51% of the femoral components would have been implanted in correct femoral rotation; the remaining 49% would have implanted with flexion gap instability. The GAP technique produces a rectangular flexion gap. The referencing of the PCA was shown to be less reliable. Thus, modern knee prosthesis instrumentation should not base femoral rotation solely on the PCA. PMID:18956189
Left-Handed Effect of Composite Rectangular SRRs and Its Application in Patch Antennae
NASA Astrophysics Data System (ADS)
Huang, Ming; Zhou, Yue-Qun; Shen, Ting-Gen
2010-01-01
We concentrate on describing the important influence and physical law of the split resonant ring (SRR) based left-handed materials on patch antennae. The finite-difference time-domain method, together with the finite element method is used to study the characteristics of patch antennae based on composite rectangular SRRs. A novel composite rectangular SRR system is formed by assembling the conventional patch antennae and SRRs, it is found that electromagnetic wave resonance occurs near f = 3.15 GHz, the equivalent permittivity and permeability are both negative, and the electromagnetic wave's tunnel effect and evanescent waves' enhancing effect are formed, which can improve the localization extent of electromagnetic wave's energy apparently. Such effects can improve the antenna's radiation gain and its matching condition. The phenomenon indicates that such composite rectangular patch antennae are promising in wireless communications such as mobile phones, satellite communication and aviation.
Design of Three-Dimensional Hypersonic Inlets with Rectangular to Elliptical Shape Transition
NASA Technical Reports Server (NTRS)
Smart, M. K.
1998-01-01
A methodology has been devised for the design of three-dimensional hypersonic inlets which include a rectangular to elliptical shape transition. This methodology makes extensive use of inviscid streamtracing techniques to generate a smooth shape transition from a rectangular-like capture to an elliptical throat. Highly swept leading edges and a significantly notched cowl enable use of these inlets in fixed geometry configurations. The design procedure includes a three dimensional displacement thickness calculation and uses established correlations to check for boundary layer separation due to shock wave interactions. Complete details of the design procedure are presented and the characteristics of a modular inlet with rectangular to elliptical shape transition and a design point of Mach 7.1 are examined. Comparison with a classical two-dimensional inlet optimized for maximum total pressure recovery indicates that this three-dimensional inlet demonstrates good performance even well below its design point.
Uniform patchy and hollow rectangular platelet micelles from crystallizable polymer blends.
Qiu, Huibin; Gao, Yang; Boott, Charlotte E; Gould, Oliver E C; Harniman, Robert L; Miles, Mervyn J; Webb, Stephen E D; Winnik, Mitchell A; Manners, Ian
2016-05-01
The preparation of colloidally stable, self-assembled materials with tailorable solid or hollow two-dimensional (2D) structures represents a major challenge. We describe the formation of uniform, monodisperse rectangular platelet micelles of controlled size by means of seeded-growth methods that involve the addition of blends of crystalline-coil block copolymers and the corresponding crystalline homopolymer to cylindrical micelle seeds. Sequential addition of different blends yields solid platelet block comicelles with concentric rectangular patches with distinct coronal chemistries. These complex nano-objects can be subject to spatially selective processing that allows their disassembly to form perforated platelets, such as well-defined hollow rectangular rings. The solid and hollow 2D micelles provide a tunable platform for further functionalization and potential for a variety of applications. PMID:27151866
Shear flow control of cold and heated rectangular jets by mechanical tabs. Volume 2: Tabulated data
NASA Technical Reports Server (NTRS)
Brown, W. H.; Ahuja, K. K.
1989-01-01
The effects of mechanical protrusions on the jet mixing characteristics of rectangular nozzles for heated and unheated subsonic and supersonic jet plumes were studied. The characteristics of a rectangular nozzle of aspect ratio 4 without the mechanical protrusions were first investigated. Intrusive probes were used to make the flow measurements. Possible errors introduced by intrusive probes in making shear flow measurements were also examined. Several scaled sizes of mechanical tabs were then tested, configured around the perimeter of the rectangular jet. Both the number and the location of the tabs were varied. From this, the best configuration was selected. This volume contains tabulated data for each of the data runs cited in Volume 1. Baseline characteristics, mixing modifications (subsonic and supersonic, heated and unheated) and miscellaneous charts are included.
NASA Technical Reports Server (NTRS)
1985-01-01
Most microscopic cell electrophoretic work depends on the theortical prediction of stationary positions by Smoluchowski and Komagata. Their theoretical solutions are based on the assumption that the electroosmotic flow in a chamber is symmetric. Because experiences with the rectangular chamber indicate that symmetric flow occurs during less than 8% of the experiments, the existing theory for stationary position determination is expanded to include the more general case of asymmetric flow. Smoluchowski's equation for symmetric electroosmotic flow in a rectangular chamber having a width much smaller than its height or length is examined. Smoluchowski's approach is used to approximate stationary positions in rectangular chambers with height/width ratios greater than 40. Support for the theoretical prediction of stationary positions using is given by three types of experimental evidence.
Mundis, Gregory M.; Moazzaz, Payam; Turner, Alexander W. L.; Cornwall, G. Bryan
2015-01-01
Background Expandable cages are gaining popularity in anterior reconstruction of the thoracolumbar spine following corpectomy as they can provide adjustable distraction and deformity correction. Rectangular, rather than circular, endcaps provide increased resistance to subsidence by spanning the apophyseal ring; however their impact on construct stability is not known. The objective of this study was to investigate the contribution of expandable corpectomy cage endcap shape (round vs. rectangular) and fixation method (anterior plate vs. posterior pedicle screws) to the stability of an L1 sub-total corpectomy construct. Methods Eight fresh-frozen cadaveric specimens (T11-L3) were subjected to multi-directional flexibility testing to 6 N·m with a custom spine simulator. Test conditions were: intact, L1 sub-total corpectomy defect, expandable cage (round endcap) alone, expandable cage (round endcap) with anterior plate, expandable cage (round endcap) with bilateral pedicle screws, expandable cage (rectangular endcap) alone, expandable cage (rectangular endcap) with anterior plate, expandable cage (rectangular endcap) with bilateral pedicle screws. Range-of-motion across T12-L2 was measured with an optoelectronic system. Results The expandable cage alone with either endcap provided significant stability to the corpectomy defect, reducing motion to intact levels in flexion-extension with both endcap types, and in lateral bending with rectangular endcaps. Round endcaps allowed greater motion than intact in lateral bending, and axial rotation ROM was greater than intact for both endcaps. Supplemental fixation provided the most rigid constructs, although there were no significant differences between instrumentation or endcap types. Conclusions These results suggest anterior-only fixation may be adequate when using an expandable cage in a sub-total corpectomy application and choice of endcap type may be driven by other factors such as subsidence resistance. PMID:26609508
NASA Astrophysics Data System (ADS)
Chen, Xudong; Zhao, Daomu
2016-08-01
A model of electromagnetic rectangular multi-Gaussian Schell-model (ERMGSM) beams is introduced. Its analytic expression for the elements of the cross-spectral density matrix of such beams passing through oceanic turbulence is derived. It is shown that the rectangular shape of the ERMGSM beams holds a small distance on propagation in oceanic turbulence. The spectral density, the degree of coherence and the degree of polarization of ERMGSM beams are also studied in detail. The results will be helpful for underwater communication by using ERMGSM beams.
A design method for entrance sections of transonic wind tunnels with rectangular cross sections
NASA Technical Reports Server (NTRS)
Lionel, L.; Mcdevitt, J. B.
1975-01-01
A mathematical technique developed to design entrance sections for transonic or high-speed subsonic wind tunnels with rectangular cross sections is discribed. The transition from a circular cross-section setting chamber to a rectangular test section is accomplished smoothly so as not to introduce secondary flows (vortices or boundary-layer separation) into a uniform test stream. The results of static-pressure measurements in the transition region and of static and total-pressure surveys in the test section of a pilot model for a new facility at the Ames Research Center are presented.
OPF by Newton`s method: A comparison between polar and rectangular formulations
Gutierrez, G.; Guzman, C.R.; Chavez, S.; Madrigal, M.; Tovar, J.H.
1998-12-31
The purpose of an Optimal Power Flow (OPF) is to schedule power system controls which optimizes an objective function while at the same time satisfying a set of nonlinear equality and inequality constraints. This problem has been solved by Newton`s approach using polar coordinates to represent power flow equations. In this paper Newton`s method is used to solve the optimal power flow problem, but using rectangular coordinates. Extensive comparison are made against the polar version. The results show superiority in computing time and robustness of the rectangular coordinates Newton`s OPF.
An Experimental Investigation of Rectangular Exhaust-Gas Ejectors Applicable for Engine Cooling
NASA Technical Reports Server (NTRS)
Manganiello, Eugene J; Bogatsky, Donald
1945-01-01
An experimental investigation of rectangular exhaust-gas ejector pumps was conducted to provide data that would serve as a guide to the design of ejector applications for aircraft engines with marginal cooling. The pumping characteristics of rectangular ejectors actuated by the exhaust of a single-cylinder aircraft engine were determined for a range of ejector mixing-section area from 20 to 50 square inches, over-all length from 12 to 42 inches, aspect ratio from 1 to 5, diffusing exit area from 20 to 81 square inches, and exhaust-nozzle aspect ratio from 1 to 42.
A laser beam shaper for homogeneous rectangular illumination based on freeform micro lens array
NASA Astrophysics Data System (ADS)
Chen, En-guo; Huang, Jia-min; Guo, Tai-liang; Wu, Reng-mao
2016-07-01
An effective design method of freeform micro lens array is presented for shaping varied laser beams into prescribed rectangular illumination. The variable separation mapping is applied to design concave freeform surfaces for constructing a freeform lens array. Several dedicated examples show that the designed freeform optical lens array can achieve a prescribed rectangular illumination pattern, especially without considering the initial states of incident laser beams. Both high collection efficiency and good spatial uniformity can be available simultaneously. Tolerance analysis is also performed to demonstrate that this optical device can well avoid fabricating difficulty in actual applications.
Critical combinations of shear and direct axial stress for curved rectangular panels
NASA Technical Reports Server (NTRS)
Schildcrout, Murry; Stein, Manuel
1949-01-01
A solution is presented for the problem of the buckling of curved rectangular panels subjected to combined shear and direct axial stress. Charts giving theoretical critical combinations of shear and direct axial stress are presented for panels having five different length-width ratios. Because the actual critical compressive stress of rectangular panels having substantial curvature is known to be much lower than the theoretical value, a semiempirical method of analysis of curved panels subjected to combined shear and direct axial stress is presented for use in design. (author
Structures of cholesteric liquid crystals confined in rectangular micro-channels
NASA Astrophysics Data System (ADS)
Wei, Qi-Huo; Guo, Yubing; Xiang, Jie; Lavrentovich, Oleg
When cholesteric liquid crystals are confined in various geometries, the interplays between the boundary conditions, the bulk structures and different length scales (pitch, penetration depth, and confinement size) may cause frustration and formation of intriguing topological defects and disclination lines. This paper presents our recent studies on the structures of cholesteric liquid crystals confined in rectangular microchannels with homeotropic alignments. The rectangular microchannels with various sizes and aspect ratios are made in glass substrates by using modern nanofabrication techniques. Detailed liquid crystal structures and their optical characterizations will be presented as a function of the channel depth and width. Work was supported by ACS PRF 53018-ND7.
NASA Astrophysics Data System (ADS)
Cao, Nan; Cao, Fengmei; Lin, Yabin; Bai, Tingzhu; Song, Shengyu
2015-04-01
For a new kind of retina-like senor camera and a traditional rectangular sensor camera, dual cameras acquisition and display system need to be built. We introduce the principle and the development of retina-like senor. Image coordinates transformation and interpolation based on sub-pixel interpolation need to be realized for our retina-like sensor's special pixels distribution. The hardware platform is composed of retina-like senor camera, rectangular sensor camera, image grabber and PC. Combined the MIL and OpenCV library, the software program is composed in VC++ on VS 2010. Experience results show that the system can realizes two cameras' acquisition and display.
Design and experiment study of compact circular-rectangular waveguide mode converter
NASA Astrophysics Data System (ADS)
Zhao, Xuhao; Yuan, Chengwei; Zhang, Qiang; Zhao, Lishan
2016-07-01
A compact mode converter that transforms TM01 circular waveguide mode to TE10 rectangular waveguide mode is investigated. It consists of a circular waveguide with a short circuit terminal and a rectangular waveguide which is perpendicular to the circular waveguide. Simulation results show that conversion efficiency of the mode converter is about 99.8% at central frequency of 1.75 GHz, and the total return loss is approximately -30 dB. The experimental results are well consistent with the computer simulation, which demonstrates the feasibility and high power handling capacity of the mode converter.
The analysis of Raman scattering in a free-electron laser with a rectangular hybrid wiggler
Kordbacheh, A. Shahsavand, M.
2015-10-15
A one dimensional theory of the stimulated Raman backscattering process in a free electron laser with rectangular hybrid wiggler (RHW) is analyzed. The dispersion relation in the rest frame of the electron beam and also a formula for the lab-frame spatial growth rate are derived. A numerical computation of the growth rate for RHW is conducted and a comparison with that for coaxial hybrid wiggler is made away from the resonance. The growth rate is found larger for the rectangular wiggler than for the coaxial wiggler. A much narrower magnetoresonance associated with the third spatial harmonic is also obtained compared to the first one.
Boundary Heat Fluxes for Spectral Radiation from a Uniform Temperature Rectangular Medium
NASA Technical Reports Server (NTRS)
Siegel, Robert
1992-01-01
The effect of spectral behavior is analytically shown for radiation in a 2D rectangular geometry. The solution provides exact boundary heat flux values that can be used for comparison with values obtained from general computer programs. The spectral solution presented can be easily evaluated by numerical integration for complex variations of the spectral absorption coefficient with wavelength.
Effect of wall roughness on liquid oscillations damping in rectangular tanks
NASA Technical Reports Server (NTRS)
Bugg, F. M.
1970-01-01
Tests were conducted in two rectangular glass tanks using silicon carbide grit bonded to walls to determine effect of wall roughness for damping liquid oscillations. Tests included effects of roughness height, roughness location, roughness at various values, amplitude decay, Reynolds number, and boundary layer thickness.