Symmetric Windows Research Articles

Stock Market Reactions on Shariah Indices Following Sukuk Issuances: CAAR Analysis on 2008-Financial Crisis

The purpose of this study is to look at how stock markets in Malaysia reacted to sukuk issuance announcements from 2004 to the post-2008 financial crisis by examining 50 selected companies listed in The FTSE Bursa Malaysia Kuala Lumpur Composite Index (FBMKLCI), FTSE Bursa Malaysia Emas Shari’ah Index (FBM EMAS), FTSE Bursa Malaysia Hijrah Shari’ah Index (FBM HIJRAH), and Dow Jones Islamic Market Index (DJIM). The data gathered from Datastream, Bloomberg, the Securities Commission Malaysia, and the Bursa Malaysia stock exchange were used to compile this study. A three-year estimation period to investigate market reactions using cumulative average abnormal return (CAAR) was adopted in this study. To investigate market efficiency, this study looked at symmetric and asymmetric event windows. This study discovers that markets responded favourably before the crisis but negatively and significantly during and after the crisis. The findings of this study provide advice to policymakers on how to direct regulators, investors, and issuers to the most stable sukuk during a crisis, as well as useful information and suggestions to issuers, policymakers, regulatory organisations, and investors in Islamic bonds.

Investigation on Symmetric and Asymmetric Broadband Low-Loss W-Band Pillbox Windows

In order to develop wide-band low-loss windows for W-band vacuum electronic devices and easily fabricate them, symmetric and asymmetric pillbox windows are investigated and reported in this paper. A symmetric pillbox window and an asymmetric pillow-box window were designed, simulation optimized, fabricated, and tested. The initial parameters for the two pillbox windows were designed by equivalent circuit theory. Computer simulation technology (CST) three-dimensional (3D) electromagnetic simulation software was used to verify and optimize the design. Because of the uncontrollability of welding during the experiment, this article provides two solutions. One is to measure and reprocess the symmetrical pillbox window with the dielectric sheet welded to reduce the influence of welding on the measurement results; the other is an asymmetrical box window which is designed to avoid the error caused by the welding of the box window. The best experimental results for the symmetric pillbox window were |S21| close to 1 dB and reflection parameter |S11| close to 10 dB in the frequency range of 77–110 GHz. The experimental results for the asymmetric pillbox window were |S21| < 1 dB nearly in the frequency range of 76–109.5 GHz. The experimental results show that both solutions efficiently complete the design of broadband pillbox windows and would potentially be operated in the gigahertz millimeter-wave region.

Change Point Detection with Mean Shift Based on AUC from Symmetric Sliding Windows

Change point detection is widely used in signal detection, industrial engineering, economy, finance, biomedicine and many other fields. The widely used parametric methods require prior knowledge of the noise signal distribution, which are seldom realistic. In practice, when the distribution of noise is not known, it is desirable to design algorithms based on non-parametric statistics, which, in the null case (no change point), are completely distribution free. To this end, we propose to use two symmetric sliding windows to compute the Area Under the receiver operating characteristic Curve (AUC) as a test statistic to measure the difference between the distribution of two samples. In the stage of change point detection, a threshold is designed according to hypothesis test which is based on the null distribution of the test statistics. This threshold is used to detect the potential change points in the signal. To reduce the probability of false alarm detection, a key parameter K is set to distinguish and delete the false alarms in potential change points. Comparative studies showed that our proposed method outperforms the classical Relative unconstrained Least-Squares Importance Fitting (RuLSIF) algorithm and is also better than the Hawkins, Qiu, and Kang (HQK) algorithm when the noise follows non-normal distributions.

Design and validation of calibration between tube focus spot and center plane of rotation in computed tomography system

This study proposed a method to calibrate tube focus spot and the center plane of rotation in computed tomography system. In the method, the tube was rotated to 0° and 180° respectively, and then one metal jig with symmetric windows A and B was scanned at each position under the tube cool and static condition. According to the geometry of tube focus spot, aperture center of the collimator and jig, the distance between tube focus spot and the center plane of rotation were calculated with the X ray transmittance data after denoising, mean value and normalization. To verify the practicability and validity of the method, the tube focus spot in a 16 slices CT system (Brivo CT385, GE, China) was calibrated, and the result after calibration was validated by scanning a polaroid film. The validation result showed that the deviation between tube focal spot and center plane of rotation was 0.02 mm and was in the error range within ± 0.1 mm. The results of this study showed that, as a simple and low-cost design, the method could be used for fast calibration between tube focus spot and the center plane of rotation.

Barycenter Theorem in Phase Characteristics of Symmetric and Asymmetric Windows

Asymmetric windows are of increasing interest to researchers because of the nonlinear and adjustable phase response, as well as alterable time delay. Short-time phase distortion can provide an essential improvement in speech coding, and also has better performance in speech recognition. The merits of asymmetric windows in the aspect of spectral behaviors have an important function in frequency component detection and parameter estimation. In this paper, the phase response of windows were further studied, and the phase characteristics of symmetric and asymmetric windows are described. The relationship between the barycenter of windows in the time domain, and the phase characteristic at the center of the main lobe in the frequency domain, was established. In light of the relationship, an improved version of the asymmetric window- based frequency estimation algorithm was proposed. The improved algorithm has advantages of straightforward implementation and computational efficiency. The numeric simulation results also indicate that the improved approach is more robust than the traditional method against additive random noise.

Effect of k-space-weighted image contrast and ultrasound focus size on the accuracy of proton resonance frequency thermometry.

To construct a predictive model that describes how the duration and symmetry of a k-space-weighted image contrast (KWIC) window affects the temporal resolution of differently sized ultrasound foci when using a pseudo-golden angle stack-of-stars acquisition. We performed a modulation analysis of proton resonance frequency temperature measurements to create the temporal modulation transfer function for KWIC windows of different symmetry and temporal duration. We reconstructed simulated ultrasound heating trajectories and stack-of-stars k-space data as well as experimental phantom data using the same trajectories. Images were reconstructed using symmetric and asymmetric KWIC windows of 3 different temporal durations. Simulated results were compared against temporal modulation transfer function predictions, experimental results, and the original simulated temperatures. The temporal modulation transfer function shows that temporal resolution with KWIC reconstructions depend on the object size. The KWIC window duration affected SNR and severity of undersampling artifacts. Accuracy and response delay improved as the KWIC window duration decreased or the size of the heated region within the KWIC plane increased. Precision worsened as the window duration decreased. Using a symmetric window eliminated the response delay to heated region size but introduced a large reconstruction delay. The accuracy and precision of proton resonance frequency temperature measurements from a stack-of-stars acquisition using a sliding KWIC window reconstruction are dependent on the size of the KWIC window and the size and shape of the heated region. The temporal modulation transfer function of KWIC reconstructions for any object size can predict the temporal response to changes in signal being acquired, such as temperature and contrast enhancement.

A real-time estimation approach of the electric power harmonics by measuring discrete spectrum energy center of symmetric windows

Purpose Significant amount of harmonics and inter-harmonics are being injected into the power system because of the increasing use of power electronics and large non-liner loads. Therefore, analyzing their contents in real time is necessary. Design/methodology/approach The frequency and phase of an electric power harmonic or inter-harmonic can be estimated by using the discrete spectrum energy center of symmetric windows, the amplitude calculation of an electric power harmonic or inter-harmonic can be calculated by using the Pasival theorem, and their relative estimation error is only decided by the distribution of windows’ energy in the frequency domain, which equals the proportion of the spectrum energy occupied in the side lobe to the whole. Findings The results of the digital simulation and experimental tests show that the method proposed in this paper has the same measurement precision as and more advantages in computational complexity and burden over other methods, which are based on multipoint interpolation or interpolation polynomial windowed. Originality/value The method is very suitable to be used to real-time measurement in a single chip DSP micro-processor.

Asymmetric Windows and Their Application in Frequency Estimation

Classic windows have constant time delay and linear phase because of the symmetry and the time shift causality-imposed in the time domain. And thus, all such windows have the same spectral phase response. Removal of the symmetry constraint on a classic window can result in a variable phase response and in an alterable time delay. In essence the time delay becomes shorter will bring about a lot of benefits in speech coding. Some asymmetric windows with better magnitude response also can lead to a better recognition performance if the result is relatively insensitive to phase distortion. However, it is surprising that so little attention has been paid to the asymmetric windows in past literature; and never in past history has this issue been systematically or comprehensively studied. As a result, several methods to obtain the asymmetric windows are being presented in this paper. The asymmetric windows are displayed and compared with the classic windows, concerning both in time and frequency domains. Some new asymmetric windows with good behavior are introduced. The work in this paper makes it possible for researchers to select an asymmetric window to meet their requirements, in terms of bias due to time delay or bias due to spectral behavior. Finally, the application in a new aspect, of the asymmetric windows, is displayed. The simulation demonstrates that the improved estimation method, in which the symmetric windows are replaced by the asymmetric windows, shows a stronger capability of additive noise resistance than the traditional method.

SU-E-J-62: Breath Hold for Left-Sided Breast Cancer: Visually Monitored Deep Inspiration Breath Hold Amplitude Evaluated Using Real-Time Position Management

Purpose: We used Real-Time Position Management (RPM) to evaluate breath hold amplitude and variability when gating with a visually monitored deep inspiration breath hold technique (VM-DIBH) with retrospective cine image chest wall position verification. Methods: Ten patients with left-sided breast cancer were treated using VM-DIBH. Respiratory motion was passively collected once weekly using RPM with the marker block positioned at the xiphoid process. Cine images on the tangent medial field were acquired on fractions with RPM monitoring for retrospective verification of chest wall position during breath hold. The amplitude and duration of all breath holds on which treatment beams were delivered were extracted from the RPM traces. Breath hold position coverage was evaluated for symmetric RPM gating windows from ± 1 to 5 mm centered on the average breath hold amplitude of the first measured fraction as a baseline. Results: The average (range) breath hold amplitude and duration was 18 mm (3–36 mm) and 19 s (7–34 s). The average (range) of amplitude standard deviation per patient over all breath holds was 2.7 mm (1.2–5.7 mm). With the largest allowable RPM gating window (± 5 mm), 4 of 10 VM-DIBH patients would have had ≥ 10% of their breath hold positions excluded by RPM. Cine verification of the chest wall position during the medial tangent field showed that the chest wall was greater than 5 mm from the baseline in only 1 out of 4 excluded patients. Cine images verify the chest wall/breast position only, whether this variation is acceptable in terms of heart sparing is a subject of future investigation. Conclusion: VM-DIBH allows for greater breath hold amplitude variability than using a 5 mm gating window with RPM, while maintaining chest wall positioning accuracy within 5 mm for the majority of patients.

Rational design and fabrication of skeletal Cu7S4 nanocages for efficient counter electrode in quantum dot-sensitized solar cells

The widely used brass based Cu2S counter electrodes (CEs) cannot stand the continuing corrosion in polysulfide electrolyte, which has limited the development of quantum dot-sensitized solar cells. Here, skeletal Cu7S4 nanocages (SKE-Cu7S4) with symmetric opening windows were rational designed and synthesized by kinetic roughening processes, and a possible formation mechanism had been proposed. Furthermore, SKE-Cu7S4 onto fluorine-doped tin oxide glass substrates were designed and deposited to function as new efficient, stable and low cost CEs. Thanks to the 3D opening structure of SKE-Cu7S4 CEs, the assembled QDSSCs exhibited a power conversion efficiency of 4.43% under 1 sun (100mWcm−2) irradiation, while those of preformed 18 facet-Cu7S4, Pt and brass/Cu2S CEs are of 3.87%, 1.73% and 3.32%, respectively. Further studies by cyclic voltammetry measurements indicate the SKE-Cu7S4 CEs still remain good cyclability after 600 cycles, demonstrating a super stable capability, while the commonly used brass/Cu2S CEs show obvious fluctuation.

Phase difference methods based on asymmetric windows

A new phase difference correction method, based on asymmetric windows, is proposed to correct the errors of frequency, phase, and amplitude in discrete spectra. Classic windows show the constant time delay and the same linear phase response due to their symmetric properties. Removal of the symmetry constraint on windows can result in variable time delays and different spectral phase responses. Based on the phenomenon of alterable spectral phases in asymmetric windows, we present a new approach, which could overcome inherent defects in traditional correction methods. The simulation results show that the new method can correct the errors of neighboring frequency components with high precision through the selection of proper asymmetric windows. Moreover, the new method can avoid the errors induced by a mistaken location of the spectral line, which is one of the major problems in traditional correction methods. When the symmetric windows in traditional methods are replaced by asymmetric windows, the improved algorithm also exhibits stronger robustness against additive noise. The comparative study reveals that each algorithm has its own advantages. In general, when the SNR is high, the interpolated method is a good choice for its simplicity; while the phase difference based methods provide better performance when the SNR is low. The new approach is recommended for closely spaced components or when high noise is involved.

Fast Directional Spatially Localized Spherical Harmonic Transform

We propose a transform for signals defined on the sphere that reveals their localized directional content in the spatio-spectral domain when used in conjunction with an asymmetric window function. We call this transform the directional spatially localized spherical harmonic transform (directional SLSHT) which extends the SLSHT from the literature whose usefulness is limited to symmetric windows. We present an inversion relation to synthesize the original signal from its directional-SLSHT distribution for an arbitrary window function. As an example of an asymmetric window, the most concentrated band-limited eigenfunction in an elliptical region on the sphere is proposed for directional spatio-spectral analysis and its effectiveness is illustrated on the synthetic and Mars topographic data-sets. Finally, since such typical data-sets on the sphere are of considerable size and the directional SLSHT is intrinsically computationally demanding depending on the band-limits of the signal and window, a fast algorithm for the efficient computation of the transform is developed. The floating point precision numerical accuracy of the fast algorithm is demonstrated and a full numerical complexity analysis is presented.

Forward–backward multiplicity fluctuations in 200A GeV/c 16O–AgBr and 32S–AgBr collisions

Charged particle multiplicity correlations and fluctuations in forward–backward symmetric pseudorapidity windows of varying widths and positions are investigated by analysing the experimental data on 16O–AgBr and 32S–AgBr collisions at 200A GeV/c. These results are compared with the predictions of the Monte Carlo models HIJING and AMPT and also with those reported at RHIC energies. The findings indicate the presence of strong short-range correlations which might arise due to isotropic decays of cluster-like objects either in the forward or backward pseudorapidity region. The analysis of the mixed events further confirms that the observed correlations are a distinct feature of the data, which vanish after mixing the events.

Optical properties of an N-type system in Doppler-broadened multilevel atomic media of the rubidium D2 line

We report the observations of Mollow sideband-like transparency windows in a Doppler-broadened four-level N-type system of the rubidium D2 line. A pair of enhanced transparency windows across an electromagnetically induced transparency line centre results from dressed state interactions of two coupling fields. The present observations have potential applications of using the symmetric transparency windows for optical quantum information processing such as multiple optical buffer memories and double slow-light-based enhanced cross-phase modulation. We also discuss the quantum coherent control of absorption cancellation, absorption enhancement and probe gain in a closed N-type four-level model introducing the atom flow rate determined by the population decay rate and control field intensity.

Simultaneous [99mTc]TRODAT-1 and [123I]ADAM Brain SPECT in Nonhuman Primates

This study examined the feasibility of simultaneous dopamine and serotonin transporter imaging using [(123)I]ADAM and [(99m)Tc]TRODAT-1 single photon emission computed tomography (SPECT). Simultaneous [(123)I]ADAM (185 MBq) and [(99m)Tc]TRODAT-1 (740 MBq) SPECT was performed in three age-matched female Formosan rock monkeys. An asymmetric energy window was used for dual, and symmetric energy windows were used for single-isotope imaging. Oral fluoxetine (20 mg) and intravenous methylphenidate HCl (1 mg/kg) were given 24 h and 10 min, respectively, before dual-isotope SPECT to test imaging specificities of [(123)I]ADAM and [(99m)Tc]TRODAT-1. Comparable image quality and uptake ratios between dual- and single-isotope SPECT scans were found. Dual-isotope SPECT in fluoxetine-pretreated monkeys showed decreased uptake of [(123)I]-ADAM, but not of [(99m)Tc]TRODAT-1. Dual-isotope SPECT in methylphenidate-pretreated monkeys showed decreased [(99m)Tc]TRODAT-1 uptake without affecting [(123)I]-ADAM uptake. Simultaneous [(123)I]-ADAM and [(99m)Tc]TRODAT-1 SPECT appears promising in nonhuman primates and may provide a suitable preclinical model with further clinical implications.

Performance analysis of a focused hospital unit: The case of an integrated trauma center

The concept of focus [Skinner, W., 1974. The focused factory. Harvard Business Review 52 (3), 113–121], notably operationalized in manufacturing entities like cells and focused factories, has also been adopted by the health care industry. Examples include patient-focused care systems and product/service lines. Despite its longevity, there is a paucity of studies analyzing the focus concept and its link to performance, especially in health care. This research is aimed at enhancing our understanding of how a focus-based approach to organization redesign in health care affects processes and practices, and what operational, clinical, and financial outcomes result from such a change. The research setting is a single case site within a large medical center for which costs for trauma care used to exceed income. Using a structured framework, we document the design and operation of this physically and organizationally integrated Level I trauma care center and compare it to its preceding operation. Its pre- and post-conversion performance is analyzed using symmetric event windows covering three-year periods before and after the focused hospital unit (FHU) was established. Under a sizable increase in workload, we find no change in mortality, moderate improvement in length of stay, and a large improvement in net operating margins. Surprisingly, the latter stem not from reductions in cost but in sharply increased hospital reimbursements. Previous studies of hospital restructuring involving focused patient populations have not conclusively supported a positive link between focus and outcomes. However, this investigation of a specific FHU suggests, conceptually as well as quantitatively, that focus can be an attractive element in health care system design.

Formation of feedforward networks and frequency synchrony by spike-timing-dependent plasticity

Spike-timing-dependent plasticity (STDP) with asymmetric learning windows is commonly found in the brain and useful for a variety of spike-based computations such as input filtering and associative memory. A natural consequence of STDP is establishment of causality in the sense that a neuron learns to fire with a lag after specific presynaptic neurons have fired. The effect of STDP on synchrony is elusive because spike synchrony implies unitary spike events of different neurons rather than a causal delayed relationship between neurons. We explore how synchrony can be facilitated by STDP in oscillator networks with a pacemaker. We show that STDP with asymmetric learning windows leads to self-organization of feedforward networks starting from the pacemaker. As a result, STDP drastically facilitates frequency synchrony. Even though differences in spike times are lessened as a result of synaptic plasticity, the finite time lag remains so that perfect spike synchrony is not realized. In contrast to traditional mechanisms of large-scale synchrony based on mutual interaction of coupled neurons, the route to synchrony discovered here is enslavement of downstream neurons by upstream ones. Facilitation of such feedforward synchrony does not occur for STDP with symmetric learning windows.

Using asymmetric windows in automatic speech recognition

This paper considers the windowing problem of the short-time frequency analysis that is used in speech recognition systems (SRS). Since human hearing is relatively insensitive to short-time phase distortion of the speech signal there is no apparent reason for the use of symmetric windows which give a linear phase response. Furthermore, phase information is usually completely disregarded in SRS. This should be contrasted with the well-known fact that relaxation of the linearity constraint on window phase results in a better magnitude response and shorter time delay. These observations form a strong argument in favor of the research presented in this paper. First, a general overview of the role that windows play in the frequency analysis stage of SRS is presented. Important properties for speech recognition are highlighted and potential advantages of asymmetric windows are presented. Among them the shorter time delay and the better magnitude response are most important. Two possible design methods for asymmetric windows are discussed. Since little is known about window influence on SRS performance the design methods are first considered from a frequency analysis point of view. This is followed by practical evaluations on real SRS. Expectations were confirmed by the results. The proposed asymmetric windows increased the robustness of elementary, isolated and connected speech recognition on a variety of adverse test conditions. This is particularly true for the case of a combination of additive and low pass convolutional distortions. Further research on asymmetric windows and on the parameterization process as a whole is suggested.

Human auditory steady-state responses to changes in interaural correlation

Steady-state responses were evoked by noise stimuli that alternated between two levels of interaural correlation ρ at a frequency f m. With ρ alternating between +1 and 0, responses at f m dropped steeply above 4 Hz, but persisted up to 64 Hz. Two time constants of 47 and 4.4 ms with delays of 198 and 36 ms, respectively, were obtained by fitting responses to a transfer function based on symmetric exponential windows. The longer time constant, possibly reflecting cortical integration, is consistent with perceptual binaural “sluggishness”. The shorter time constant may reflect running cross-correlation in the high brainstem or primary auditory cortex. Responses at 2 f m peaked with an amplitude of 848 ± 479 nV ( f m = 4 Hz). Investigation of this robust response revealed that: (1) changes in ρ and lateralization evoked similar responses, suggesting a common neural origin, (2) response was most dependent on stimulus frequencies below 1000 Hz, but frequencies up to 4000 Hz also contributed, and (3) when ρ alternated between [0.2–1] and 0, response amplitude varied linearly with ρ, and the physiological response threshold was close to the average behavioral threshold ( ρ = 0.31). This steady-state response may prove useful in the objective investigation of binaural hearing.

Mechanism and calculation of the niche effect in airborne sound transmission

The goal is to interpret and calculate the "niche effect" for the airborne sound transmission through a specimen mounted inside an aperture in the wall between the source and receiving reverberation rooms. The low-frequency sound insulation is known to be worse for the specimen placed at the center than for the specimen mounted at either edge of the aperture. As shown, the aperture with a tested specimen can be simulated at low frequencies as a triple partition where the middle element is the specimen and the role of the edge leaves is played by the air masses entrained at the aperture edges. With a centrally located specimen, such a triple system is symmetric and has two main natural frequencies close together. In this case, the resonant transmission is higher than for the edge arrangement simulated as a double system with one natural frequency. Analogous resonant phenomena are known to reduce the low-frequency transmission loss for symmetric triple windows or solid walls with identical air gaps and lightweight boards on both sides. The theoretical results obtained for the mechanical and acoustical models are in a good agreement with the experimental data.