The problem of offset in acoustic pulse reflectometry

Acoustic pulse reflectometry has become established as a useful non-invasive technique for measuring a variety of duct properties. A sound pulse is injected into the duct under investigation and the resultant reflections are recorded. Suitable analysis of the reflections yields the input impulse response of the duct, from which both its input impedance and its internal dimensions can be calculated. However, an input impulse response measurement made using acoustic pulse reflectometry generally contains an offset. Unless this offset is removed, the application of a bore reconstruction algorithm results in a calculated duct profile which expands or contracts spuriously. In this paper, the offset in an input impulse response measurement is shown to consist of both constant and time-varying components. Methods of preventing or removing these DC and time-varying offsets are proposed and subsequent improvements to the bore reconstruction accuracy are demonstrated

Attribution of injury in the shrimp antidumping case: A simultaneous equations approach

We apply a simultaneous equations framework, similar to that of Prusa and Sharp (2001), to the recent shrimp antidumping investigation in order to determine how much injury to the domestic industry—proxied by deterioration in domestic shrimp prices—is attributable to subject imports versus other market factors. We construct an econometric model then estimated with three-stage least squares (3SLS). We then apply the movements of each explanatory variable over the period of investigation (POI) to its respective coefficient in order to determine how much injury is attributable to that particular market factor. We find that subject and non-subject imports were essentially equal causes of injury to the domestic industry.3SLS

Properties of "35" Spin-(5/2) Baryon Resonances in a Model with Broken SU(3)

We investigate the properties of a set of J =(5/2)^+ resonances appearing in a 35-dimensional representation of SU(3), as proposed by Abers, Balázs, and Hara. A simple dynamical calculation gives an estimate for the mass differences within the supermultiplet. The matrix elements for the SU(3) allowed decays into meson plus resonance are given in terms of one parameter and the SU(3)-violating matrix elements for decay into meson plus baryon are given by two parameters

Developing and evaluating a hybrid wind instrument

A hybrid wind instrument generates self-sustained sounds via a real-time interaction between a computed excitation model (such as the physical model of human lips interacting with a mouthpiece) and a real acoustic resonator. Attempts to produce a hybrid instrument have so far fallen short, in terms of both the accuracy and the variation in the sound produced. The principal reason for the failings of previous hybrid instruments is the actuator which, controlled by the excitation model, introduces a fluctuating component into the air flow injected into the resonator. In the present paper, the possibility of using a loudspeaker to supply the calculated excitation signal is evaluated. A theoretical study has facilitated the modeling of the loudspeaker-resonator system and the design of a feedback and feedforward filter to successfully compensate for the presence of the loudspeaker. The resulting self-sustained sounds are evaluated by a mapping of their sound descriptors to the input parameters of the physical model of the embouchure, both for sustained and attack sounds. Results are compared with simulations. The largely coherent functioning confirms the usefulness of the device in both musical and research contexts

LIF measurement of the diluting effect of surface waves on turbulent buoyant plumes.

In this paper, the diluting effect of surface waves on a buoyant plume has been measured using a Laser Induced Fluorescence (LIF) technique. The resulting time-averaged, full field concentration maps have allowed quantification of enhanced mixing due to surface waves as well as measurement of other plume parameters

Virtual Pitch and Pitch Shifts in Church Bells

It is well established that musical sounds comprising multiple partials with frequencies approximately in the ratio of small integers give rise to a strong sensation of pitch even if the lowest or fundamental partial is missing—the so-called virtual pitch effect. Experiments on thirty test subjects demonstrate that this virtual pitch is shifted significantly by changes in the spacing of the constituent partials. The experiments measured pitch by comparison of sounds of similar timbre and were automated so that they could be performed remotely across the Internet. Analysis of the test sounds used shows that the pitch shifts are not predicted by Terhardt’s classic model of virtual pitch. The test sounds used were modelled on the sounds of church bells, but a further experiment on seventeen test subjects showed that changes in partial amplitude only had a minor effect on the pitch shifts observed, and that a pitch shift was still observed when two of the lowest frequency partials were removed, so that the effects reported are of general interest

Formal structure of scientific journals and types of scientific papers

Les revistes científiques tenen una estructura formal que cal que els qui hi estan en contacte (autors, lectors i editors) comprenguin per tal que els siguin útils. L'autor analitza els tipus d'article que hi ha a tres revistes mèdiques i a una altra d'informació científica general (comunicacions preliminars, articles de revisió, editorials, secció de correspondència) i com s'estructuren els articles de recerca, perquè les altres seccions són de format més lliure.Scientific journals have a formal structure that has to be understood by all those who read it (authors, readers and editors) in order to be useful. The author analyses different types of articles in three medical journals and one of general science (preliminar communications, review articles, editorials, letters to the editor) and how research articles are structurated, because the other sections have a more free format

Hijacked Christianity: How An Aberrant Eschatology Enables A Grievance Culture That Supplants Christian Grace For An Extremist Meritocracy

The Evangelical participation attack on Capitol Hill that happened on January 6th, 2021, that almost toppled American Democracy, was an eye-opening experience to the dangers of radicalization. For this paper, the central question is, do recent evolutions to Christian Eschatology (Premillennialism/Postmillennialism) give exigence to the radicalization of mainstream American Evangelicalism via a Dominionist ideology? This study is a rhetorical criticism that will examine sermons of four prominent Neo Charismatic around the time of the 2020 National COVID Lockdown Announcement and the Capitol Hill Insurrection. This study uses a Constant Comparative Method (CCM) to inductively identify the possible themes, and a Cultural Discourse Analysis (CuDA) to provide a more detailed examination of their rhetoric. Findings illustrate that increases in Millennialism rhetoric correlate with radicalization tendencies to create grievances that dehumanize outsiders while stoking existential crises in their own members to propel them into action via quests of significance

Systems Engineering Self Assessment of an Air Force Acquisition Unit

In February of 2009, our unit performed a Systems Engineering {SE} Self Assessment using the Air Force Systems Engineering Assessment Model (AF SEAM}. The AF SEAM consists of 190 SE best practices spanning the following ten SE Process Areas: Configuration Management, Decision Analysis, Design, Manufacturing, Project Planning, Requirements, Risk Management, Sustainment, Technical Management and Control, and Verification and Validation. During the SE Self Assessment, we graded our unit on a pass/fail basis for each SE best practice. The SE best practices are split into Specific Practices and General Practices. The former only apply to one of the ten SE Process Areas, while the later apply to all ten SE Process Areas. The unit\u27s score for each SE Process Area is an average of the percentage of passing Specific Practices and the percentage of passing General Practices. Our unit received passing grades for Configuration Management, Manufacturing, and Sustainment; and failing grades for Decision Analysis, Design, Project Planning, Requirements, Risk Management, Technical Management and Control, and Verification and Validation. In addition to grading the unit\u27s SE based on best practices, the SE Self Assessment collected the participants\u27 comments. This report is an analysis of these comments; the intent of this report is to capture useful comments and distill them into actionable findings. Analysis of the SE Self Assessment uncovered 120 key findings that fall into 20 SE problems. In an attempt to hone in on the most pressing SE problems, each problem was evaluated based on the number of findings per problem, the feasibility of solving the problem, and the potential gain for solving the problem. As a result of this evaluation, the top SE problems facing our unit are as follows: inadequate communication, insufficient training, and unclear roles and responsibilities. In order to address these SE problems, this report recommends the following: Inadequate Communication: The unit should matrix four people into the Development Squadron covering the following disciplines: Configuration Management, Information Assurance, Requirements, and Test and Evaluation. These Systems Engineers would report to the Engineering Division Chief, but they would work with the Development Squadron on a day to day basis. Insufficient Training: The unit should pursue an aggressive training program to improve general and SE knowledge. The following courses and presentations should be developed: Unit 101 as a newcomers orientation, Intro to the Systems Engineering Plan and Intro to the Systems Test Plan to socialize these important documents, Integrated Product/Process Team (IPT) Training to improve our teaming skills, Eight Step Problem Solving Method as a Decision Analysis tool, and AF SEAM Mastery as a way to use the model to teach basic SE principles. Also, the unit leadership should encourage personnel to enroll in SE certificate and masters programs. Unclear Roles and Responsibilities:The unit should assign a SE Process Champion to each of the ten SE Process Areas. These champions would be the focal people for improving each area. Also, a SE Process Improvement Lead should be created. The SE Process Improvement Lead and the SE Process Area Champions would work towards the goal of achieving passing marks in the next SE Self Assessment held in February, 2010. Note: All of the material contained in this report has been scrubbed to remove references to people, as well as project names. For example, a specific hardware intensive project is described as hardware project instead of its name. Other generalizations include the following: software project, technology demonstration (tech demo} project, component, contractor, and FFRDC. The reader\u27s patience is appreciated when these sanitization efforts sometimes result in incongruent phrases. A note on tense: This paper uses the first person tense. This is intentional. I am a member of the unit studied, and thus I stand to benefit or suffer from the consequences of any implementation suggested in this report. Exclusive use of the third person would imply a distance and impartiality that does not exist

Acoustic pulse reflectometry for the measurement of musical wind instruments

The bore profile and input impedance of a musical wind instrument provide valuable information about its acoustical properties. The time domain technique of acoustic pulse reflectometry can be used to measure the input impulse response of a tubular object, such as a wind instrument, from which both its bore profile and input impedance can be calculated. In this thesis, after a discussion of the theory of acoustic pulse reflectometry, the operation of a practical reflectometer is described and measurements of input impulse response, bore profile and input impedance are investigated. In general, the experimentally measured input impulse response of a tubular object contains a DC offset which must be removed for accurate bore reconstruction. A new, faster method of determining the DC offset is introduced which doesn’t require prior knowledge of the object’s dimensions. The bore profile of a test object, calculated by applying a lossy reconstruction algorithm to its input impulse response (after removal of the DC offset), is found to agree with directly measured radii to within 0.05mm. Various brass instrument reconstructions of similar accuracy are presented. An input impedance curve, calculated from the input impulse response of the test object, is found to have peak frequencies which agree with those of a theoretical curve to within 0.7% (a considerably better agreement than when a standard frequency domain measurement technique is used). Impedance curves of various brass instruments are presented. Bore reconstructions are used to confirm the presence, and in certain cases, the positions of leaks in instruments. For the special case of a leaking cylinder, the impedance curve is successfully used to calculate the size of the leak. Finally, a method is investigated which allows the practical reflectometer to measure longer objects than previously possible