The acoustic radiation impedance of a rectangular panel

This paper extends the definition of the one sided radiation impedance of a panel mounted in an infinite rigid baffle which was previously used by the authors so that it can be applied to all transverse velocity wave types on the panel rather than just to the possibly forced travelling plane transverse velocity waves considered previously by the authors. For the case of travelling plane waves on a rectangular panel with anechoic edge conditions, and for the case of standing waves on a rectangular panel with simply supported edge conditions, the equations resulting from one of the standard reductions from quadruple to double integrals are given. These double integral equations can be reduced to single integral equations, but the versions of these equations given in the literature did not always converge when used with adaptive integral routines and were sometimes slower than the double integral versions. This is because the terms in the integrands in the existing equations have singularities. Although these singularities cancel, they caused problems for the adaptive integral routines. This paper rewrites these equations in a form which removes the singularities and enables the integrals in these equations to be evaluated with adaptive integral routines. Approximate equations for the azimuthally averaged one sided radiation impedance of a rectangular panel mounted in an infinite baffle are given for all the cases considered in this paper and the values produced by these equations are compared with numerical calculations

Evaluation of absorbent materials for use as ad hoc dry decontaminants during mass casualty incidents as part of the UK's Initial Operational Response (IOR)

The UK's Initial Operational Response (IOR) is a revised process for the medical management of mass casualties potentially contaminated with hazardous materials. A critical element of the IOR is the introduction of immediate, on-scene disrobing and decontamination of casualties to limit the adverse health effects of exposure. Ad hoc cleansing of the skin with dry absorbent materials has previously been identified as a potential means of facilitating emergency decontamination. The purpose of this study was to evaluate the in vitro oil and water absorbency of a range of materials commonly found in the domestic and clinical environments and to determine the effectiveness of a small, but representative selection of such materials in skin decontamination, using an established ex vivo model. Five contaminants were used in the study: methyl salicylate, parathion, diethyl malonate, phorate and potassium cyanide. In vitro measurements of water and oil absorbency did not correlate with ex vivo measurements of skin decontamination. When measured ex vivo, dry decontamination was consistently more effective than a standard wet decontamination method (“rinse-wipe-rinse”) for removing liquid contaminants. However, dry decontamination was ineffective against particulate contamination. Collectively, these data confirm that absorbent materials such as wound dressings and tissue paper provide an effective, generic capability for emergency removal of liquid contaminants from the skin surface, but that wet decontamination should be used for non-liquid contaminants

The average specific forced radiation wave impedance of a finite rectangular panel

The average specific forced radiation wave impedance of a finite rectangular panel is of importance for the prediction of both sound insulation and sound absorption. In 1982, Thomasson published numerical calculations of the average specific forced radiation wave impedance of a square of side length 2e for wave number k in half octave steps of ke from 0.25 to 64. Thomasson's calculations were for the case when the forced bending wave number kb was less than or equal to k. Thomasson also published approximate formulas for values of ke above and below the published results. This paper combines Thomasson's high and low frequency formulas and compares this combined formula with Thomasson's numerical calculations. The real part of the approximate formula is between 0.7 dB higher and -1 dB lower than the numerical calculations. The imaginary part of the approximate formula is between 2.3 dB higher and -2.6 dB lower than the numerical calculations. This paper also gives approximate formulas for the case when kb is greater than or equal to k. The differences are between 0.8 and -1.2 dB for the imaginary part and between 6.2 and -2.4 dB for the real part

Approximate formulae for the average one sided specific radiation wave impedance of a finite rectangular panel

The authors have previously published approximate formulae for the average one sided specific radiation wave impedance of a finite rectangular panel mounted in a rigid infinite baffle. The panel's transverse vibration was due to a (possibly forced) two dimensional bending plane wave propagating in the panel without reflection at the edges of the panel. The average was over all the surface area of the panel and over all possible azimuthal angles of propagation direction. The radiation from waves propagating in different directions was assumed to be uncorrelated. These approximate formulae were derived from the 1982 research of Thomasson whose approximate formulae only covered the high and low frequency regions and not the mid frequency region. This paper presents more accurate versions of some of the approximate formulae. When the bending wave number is larger than the wave number of sound, the real part of the impedance is smaller than that for the case studied by Maidanik and Leppington. This is because correlated reflections are not included the case analyzed in this paper. When the bending wave number is smaller than or equals the wave number of sound, the real part of the impedance is the same for both cases

Approximate equations for the radiation impedance of a rectangular panel

The authors have previously published approximate formulae for the average one sided specific radiation wave impedance of a finite rectangular panel mounted in a rigid infinite baffle. The panel's transverse vibration was due to a (possibly forced) two dimensional bending plane wave propagating in the panel without reflection at the edges of the panel. The average was over all the surface area of the panel and over all possible azimuthal angles of propagation direction. The radiation from waves propagating in different directions was assumed to be uncorrelated. These approximate formulae were derived from the 1982 research of Thomasson whose approximate formulae only covered the high and low frequency regions and not the mid frequency region. This paper presents more accurate versions of some of the approximate formulae. When the bending wave number is larger than the wave number of sound, the real part of the impedance is smaller than that for the case studied by Maidanik and Leppington. This is because correlated reflections are not included the case analyzed in this paper. When the bending wave number is smaller than or equals the wave number of sound, the real part of the impedance is the same for both cases

Determinants of Friendship in Social Networking Virtual Worlds

This paper examines the determinants of friendship between two users in a virtual world who are unaware of each other's real identities. Drawing on theories of homophily, heterophily and propinquity, three virtual world behaviours are analysed: avatar appearance, avatar location, and avatar communication. Data are collected on 179 participants interacting in a novel virtual world. The main results show that: (1) avatars did not tend to form friendships with avatars that are similar in appearance to themselves but did tend to form friendships with avatars that are dressed differently from themselves; (2) in terms of location, the closer an avatar stands to other avatars, the more likely the avatar is to receive a friend invitation; and (3) the fewer words an avatar uses in communication, the more likely the avatar is to receive a friend invitation. This paper contributes to theories of virtual world interaction and to using virtual worlds as a data collection platform

How User Personality and Social Value Orientation Influence Avatar Mediated Friendship

Purpose – The purpose of this paper is to study the influence of user personality and vlaues on the number of connections users make, the number of requests for connections that users give out, and the number of connections invitations users receive. Design/methodology/approach – This is a field study of 179 participants interacting in a novel virtual world. The world’s server logs are used to capture sociometrics about the users and their interaction. Findings – Findings suggest that personality and values influence the number of friends users make and the number of friendship requests users give out, but not the number of friendship invitations users receive. Only one personality trait – conscientiousness – exhibits homophily. Originality/value – Personality and social value orientation have rarely been studied together in information systems (IS) research, despite research showing the two have an impact on IS relevant constructs. The use of server logs for data capture is novel. Avatar friendship is an under-researched concept in IS

Free versus total serum 25-hydroxyvitamin D in a murine model of colitis

Inflammatory bowel diseases (IBD) such as ulcerative colitis and Crohn's disease have been linked to vitamin D-deficiency. Using a dextran sodium sulphate (DSS)-induced model of IBD we have shown previously that mice raised on vitamin D-deficient diets from weaning have lower serum 25-hydroxyvitamin D (25OHD) levels and develop more severe colitis compared to vitamin D-sufficient counterparts. We have also shown in vitro that immune responses to 25OHD may depend on 'free' rather than total serum concentrations of 25OHD. To investigate the possible effects of free versus total 25OHD on anti-inflammatory immune responses in vivo we have studied DSS-induced colitis in wild type C57BL/6 mice raised from weaning on diets containing vitamin D2 (D2) or vitamin D3 (D3) only (both 1000 IU/kg feed). 25OHD2 has lower binding affinity for the vitamin D binding protein than 25OHD3 which results in higher levels of free 25OHD2 relative to free 25OHD3 in mice raised on a D2-only diet. Total serum 25OHD concentrations, measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS), showed that D2 mice had significantly lower levels of 25OHD than D3 mice (6.85 ± 2.61 nmol/L vs. 49.16 ± 13.8 nmol/L for D2 and D3 respectively). Despite this, direct ELISA measurement showed no difference in free serum 25OHD levels between D2 and D3 mice (13.62 ± 2.26 pmol/L vs. 14.11 ± 2.24 pmol/L for D2 and D3 respectively). Analysis of DSS-induced colitis also showed no difference in weight loss or disease progression between D2 and D3 mice. These data indicate that despite D2-fed mice being vitamin D-deficient based on serum total 25OHD concentrations, these mice showed no evidence of increased inflammatory colitis disease relative to vitamin D-sufficient D3 mice. We therefore propose that free, rather than total serum 25OHD, may be a better marker of immune responses to vitamin D in vivo

Critical success index or F measure to validate the accuracy of administrative healthcare data identifying epilepsy in deceased adults in Scotland

Background: Methods to undertake diagnostic accuracy studies of administrative epilepsy data are challenged bylack of a way to reliably rank case-ascertainment algorithms in order of their accuracy. This is because it isdifficult to know how to prioritise positive predictive value (PPV) and sensitivity (Sens). Large numbers of truenegative (TN) instances frequently found in epilepsy studies make it difficult to discriminate algorithm accuracyon the basis of negative predictive value (NPV) and specificity (Spec) as these become inflated (usually >90%).This study demonstrates the complementary value of using weather forecasting or machine learning metricscritical success index (CSI) or F measure, respectively, as unitary metrics combining PPV and sensitivity. Wereanalyse data published in a diagnostic accuracy study of administrative epilepsy mortality data in Scotland.Method: CSI was calculated as 1/[(1/PPV) + (1/Sens) – 1]. F measure was calculated as 2.PPV.Sens/(PPV +Sens). CSI and F values range from 0 to 1, interpreted as 0 = inaccurate prediction and 1 = perfect accuracy. Thepublished algorithms were reanalysed using these and their accuracy re-ranked according to CSI in order to allowcomparison to the original rankings.Results: CSI scores were conservative (range 0.02–0.826), always less than or equal to the lower of the correspondingPPV (range 39–100%) and sensitivity (range 2–93%). F values were less conservative (range0.039–0.905), sometimes higher than either PPV or sensitivity, but were always higher than CSI. Low CSI and Fvalues occurred when there was a large difference between PPV and sensitivity, e.g. CSI was 0.02 and F was0.039 in an instance when PPV was 100% and sensitivity was 2%. Algorithms with both high PPV and sensitivityperformed best in terms of CSI and F measure, e.g. CSI was 0.826 and F was 0.905 in an instance when PPV was90% and sensitivity was 91%.Conclusion: CSI or F measure can combine PPV and sensitivity values into a convenient single metric that is easierto interpret and rank in terms of diagnostic accuracy than trying to rank diagnostic accuracy according to the twomeasures themselves. CSI or F prioritise instances where both PPV and sensitivity are high over instances wherethere are large differences between PPV and sensitivity (even if one of these is very high), allowing diagnosticaccuracy thresholds based on combined PPV and sensitivity to be determined. Therefore, CSI or F measures maybe helpful complementary metrics to report alongside PPV and sensitivity in diagnostic accuracy studies ofadministrative epilepsy data

The specific forced radiation wave impedance of a finite rectangular panel excited by a plane sound wave

The average specific forced radiation wave impedance of a finite rectangular panel, excited by a plane sound wave incident at a particular angle of incidence, is of importance for the prediction of both sound insulation and sound absorption. In 1982, Thomasson published numerical calculations of the average specific forced radiation wave impedance of a square of side length 2e for wave number k for values of ke in half octave steps from 0.25 to 64. Thomasson also published approximate formulae for values of ke above and below the published results. This paper combines Thomasson's high and low frequency formulae and compares this combined formula with Thomasson's numerical calculations. The real part of the approximate formula is between 0.7 dB higher and -1 dB lower than the numerical calculations. The imaginary part of the approximate formula is between 2.3 dB higher and - 2.6 dB lower than the numerical calculations. These extreme differences occur in the region of ke equals 2. However the imaginary part also has a difference of 1.7 dB for ke equals 64 at an angle of incidence of the forcing wave of 60 degrees relative to the normal to the square panel. An approximate formula for the real part developed previously by Davy is between 0.4 dB higher and -0.6 dB lower than Thomasson's numerical calculations. Thus it is in slightly better agreement with Thomasson's numerical calculations than the formula obtained by combining Thomasson's high and low frequency approximations. The imaginary specific radiation impedance of a rigid disk of equal area to a square and vibrating in phase gives a good approximation, up to ke equals 5, to the imaginary part of the specific forced radiation impedance of a square which has been excited by a plane wave incident normally to the square