Compromises in FIR matched filter design

With duration-limited signals there is the opportunity for perfect matched filtering by a suitable FIR filter, providing the noise can be construed as being supplied through an all-pole coloration filter. The popular matrix solution formulation does not make it obvious just what size the optimal filter length must be, and the signal vector zeropadding mechanism needed for coaxing out the optimal coefficient vector is also unclear. Difficulties are compounded when the filter length allowable for implementation falls short of the optimal length. Worse yet, if it happens that the noise is shaped by a coloration filter which has some zeros (i.e., is MA or ARMA instead of just AR), then any FIR filter can only be an approximation to the ideal IIR matched filter. In either case, decreasing filter length requires compromise strategies that are not at all transparent. We base our analysis approach to the FIR problem setup in terms of (time) correlations and convolutions in which the whitening filter has the central role. It is then easy to see that both "pole-only" and "some-zero" noise cases yield optimal SNR values that are exactly calculatable by a time-domain scalar product. The inevitable degradations of SNR with decreasing FIR filter lengths are, in turn, readily quantifiable. We study several compromise strategies arising from the whitening filter convolution approach and find (albeit with a very limited set of test cases) that they are not attractive when contrasted to the common matrix solution. The matrix solution itself, meanwhile, is shown to demand close attention to zeropadding patterns employed in it if best performance is to be obtained as filter length is reduced. Fortunately, exhaustive zero-padding assessment is a practical proposition, and this is our recommended procedure at this early stage of investigation

Project Risk Management for Sustainable Building Repair & Maintenance in Developing Countries

Building repair & maintenance (R&M) are inevitable: building omponents deteriorate with time due to aging, constant use - causing wear and tear, possible design and construction defects, and the consequences of environmental agents and vulnerabilities. The situation worsens in developing countries where large number of externalities dictates the R&M decisions: lack of budget, enforcing regulation and building standards to name a few. These and other inherent uncertainties grow to be considerable risks of peculiar nature, which demand an active and customized management. The need to manage risk of R&M projects is paramount: starting from affective identification to seamless analysis, and suitable response planning to meticulous monitoring and control, a custom-structured project risk management (PRM) framework - a combination of specialized tools and techniques - will greatly help by considering how risky these undertakings are, dealing with apparent threats and converting them into opportunities. To this end, this paper, after reviewing the R&M state of affairs in developing countries, proposes a functional PRM framework to manage R&M ris

Classroom design demonstrations for complex IIR filters

An environment for exceptionally fast design of FIR and IIR filter design by pushbutton and easy drag-and-drop manipulations is described. Filter gain and phase credentials are immediately available to the designer, along with the facility to simply sketch the desired filter characteristics. The design flow for a specimen complex FIR and IIR realization of an arbitrary combination of gain and group delay is presented in detail, and a subsequent phase compensation filter also shown. A varied selection of other design examples emphasizes the flexibility and abundance of choice afforder the User

Dynamic matched filtering: animating the action

A simulink-based block diagram modelling environment is described which makes investigation of demanding DSP concepts such as FIR matched filtering easy and fun. Users interact with the experiment to a remarkable degree, watching scope displays while tuning parameter values or moving sliders to effect model changes during run time in a dynamic fashion. Instrumentation for achieved signal-to-noise ratio sits alongside displays advising the experimenter of theoretically optimal SNR for the current parameter settings. A small example problem using a single-pole noise-shaping filter is seen to be very enlightening, especially since a variable-coefficient matched filter block is employed which is self-designing in response to the prevailing pole radius and resonant frequency selection

Psychometric performance of the perceived stigma of substance abuse scale (PSAS) among patients on methadone maintenance therapy in Vietnam

Background: People who inject drugs (PWID) and patients on methadone maintenance therapy (MMT) face severe stigma and discrimination. However, there are limited measures assessing stigma towards individuals with substance use disorders or MMT patients, particularly in Vietnam, and few studies have examined the psychometric properties of existing measures. This study aims to examine the performance of the eight-item Perceived Stigma of Substance Abuse Scale (PSAS), created in the United States, among a population of MMT patients in Vietnam. Methods: A cross-sectional survey was conducted among 400 adult patients enrolled in an urban MMT clinic. Substance use stigma was measured using the PSAS. We conducted confirmatory factor analysis (CFA) and assessed construct validity, reliability and known-group validity. Results: The original eight-item scale was unidimensional, but yielded mixed goodness-of-fit indicators. Ultimately, dropping two items and allowing the errors of the items related to childcare to correlate improved the goodness-of-fit indicators. (RMSEA = 0.025; CFI = 0.999; and SRMR = 0.018). The shortened scale demonstrated acceptable reliability (Cronbach's α = 0.766). The mean stigma scores were significantly higher among individuals not working, but did not significantly vary by length of time in MMT, marital status, education attainment, HIV status, depression, concurrent injection drug use or missed methadone dose. Conclusions: The shortened six-item scale demonstrated good construct validity and acceptability reliability, but it did not demonstrate many a priori hypothesized known-group validity associations. Further research should consider a mixed-methods validation approach

Validation of screening tools for common mental health disorders in the methadone maintenance population in Hanoi, Vietnam

Background: Common mental health disorders (CMDs), including depression, anxiety and post-traumatic stress disorder (PTSD) may worsen both HIV and drug use outcomes, yet feasible tools to accurately identify CMDs have received limited study in this population. We aimed to validate the Patient Health Questionnaire (PHQ-9), Generalized Anxiety Disorder screen (GAD-7) and Primary Care PTSD screen for DSM-5 (PC-PTSD-5) in a methadone maintenance therapy (MMT) patient population in Hanoi, Vietnam. Methods: We conducted a cross-sectional survey. The PHQ-9, GAD-7, and PC-PTSD-5 were administered to MMT patients. A blinded interviewer administered the Mini-International Neuropsychiatric Interview (MINI) as the reference gold standard. Total scores of each tool were compared with the MINI diagnoses using a receiver operating characteristic curves, and we identified the optimal respective cut-off scores using the Youden’s Index. Results: We enrolled 400 MMT patients. Approximately 99.3% were male (n = 397) and 21.8% (n = 87) were HIV positive. The prevalence of major depressive disorder, generalized anxiety disorder and PTSD, respectively, was 10.5, 4 and 2%. Optimal cut-off scores for the PHQ-9, GAD-7 and PC-PTSD were ≥ 5, ≥3, and ≥ 4 with a sensitivity/specificity of 95.2%/91.9, 93.8%/87.5, and 62.5%/95.2%. Conclusions: The prevalence of CMDs in the MMT population was lower than expected. A lower cut-off score may be considered when screening for CMDs in this population. Further research should investigate the validity of somatic symptom-based screening tools among other drug-using or MMT populations

Examining common mental health disorders in people living with HIV on methadone maintenance therapy in Hanoi, Vietnam

Background: Injection drug use drives HIV transmission in Southeast Asia, where around a quarter of users are living with HIV. Vietnam developed Methadone Maintenance Therapy (MMT) programs to reduce unsafe drug abuse. Common mental health disorders (CMD), including depression, anxiety and post-traumatic stress disorder (PTSD), can worsen MMT outcomes and are highly prevalent among people living with HIV (PLH). We aimed to characterize HIV and CMD among MMT patients and assess the impact of HIV and CMD on MMT engagement outcomes in Hanoi, Vietnam. Methods: This cross-sectional study was conducted at an urban MMT clinic in Hanoi. Participants were screened for CMD with the relevant sections of the Mini International Neuropsychiatric Interview (MINI). Tabular comparisons and regression models were used to understand the association of HIV and CMD with substance use and methadone compliance. Results: Of the 400 MMT participants, 22% were living with HIV, 11% a CMD, 27% reported injection drug use, and 27% reported methadone noncompliance. Around 17% of those with HIV also had a CMD. Reporting non injection and injection drug use were each higher among those with CMD regardless of HIV status. In addition, reporting any drug use was much higher among those with both HIV and CMD than among those with neither (73% vs 31%, p value 0.001). While methadone noncompliance was lower among PLH than among those without HIV (16.3% vs 30.1%, p value 0.010), noncompliance was higher among those with CMD than among those without (40.5% vs 25.6%, p value 0.045). Among those without HIV, noncompliance was higher among those with CMD than among those without, but among those with HIV, the opposite relationship was observed. Conclusion: There is complex overlap between substance use and methadone noncompliance among MMT patients living with HIV, CMD or both. In this population, we found a high prevalence of CMD and substance use among PLH, and a high prevalence of substance use and methadone noncompliance among those with CMD. Prioritizing provision of mental health care services to MMT patients living with HIV can help improve engagement with substance use disorder treatment and reduce the risk of HIV transmission

Urbanisation, local food crop production and tourism output of Pakistan

The high rate of urban population growth is one of the major problems constraining the growth of urban centres. The main aim of this paper is to examine the relationship between urbanisation, local food crop production and the tourism output of Pakistan. The findings show that a 1 per cent increase in local food crop production will increase tourism output by 1.77 per cent, at the 1 per cent level of significance, holding all other variables constant. There is a unidirectional causality running from local food crop production to urbanisation. This study has implications for policy‐makers and practitioners