Flicker Sensitivity as a Function of Eccentricity

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 327-327 ◽  
Author(s):  
A N Raninen ◽  
J Rovamo
Keyword(s):  
Matched Filter ◽  
Temporal Frequency ◽  
Internal Noise ◽  
Modulation Transfer ◽  
Low Frequencies ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Neural Noise ◽  
Low Pass ◽  
High Pass

We determined DeLange curves with and without external temporal noise at eccentricities of 0 – 70 deg by measuring flicker sensitivity at 1 – 45 Hz for sharp-edged M-scaled spots with an equiluminous surround. Without noise, flicker sensitivity at high frequencies increased with eccentricity but remained unchanged at low frequencies. In strong noise, flicker sensitivity was independent of eccentricity. The only exception was 70 deg where sensitivity was reduced at 1 – 3 Hz with and without noise. The data at each eccentricity are well described by our flicker-sensitivity model (Rovamo et al, 1996 Vision Research36 3767 – 3774) comprising (i) low-pass filtering by the modulation transfer function (MTF) of the retina, (ii) filtering in direct proportion to temporal frequency by the high-pass MTF of the retina and subsequent neural visual pathways, (iii) addition of white internal neural noise, and (iv) detection by a temporal matched filter. When interpreted in the context of the model, our results mean that while the high-pass filter and the magnitude of internal noise remained unchanged across eccentricities, the bandwith of the low-pass filter increased with eccentricity and at 70 deg eccentricity the efficiency of the detecting mechanism in the brain was reduced at 1 – 3 Hz. The increase in the bandwidth of the low-pass filter is in agreement with the eccentricity-dependent changes in the retinal function as revealed by the electroretinogram (ERG).

A semi-lumped microstrip UWB bandpass filter

2009 ◽  
Vol 1 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Darine Kaddour ◽  
Jean-Daniel Arnould ◽  
Philippe Ferrari
Keyword(s):  
Group Delay ◽  
Bandpass Filter ◽  
Filter Design ◽  
Sensitivity Study ◽  
Critical Parameters ◽  
Center Frequency ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
High Pass

In this paper, a miniaturized bandpass filter for ultra-wide-band applications is proposed. It is based on the embedding of high-pass structures in a low-pass filter. A semi-lumped technology combining surface-mounted capacitors and transmission lines has been used. The filter design rules have been carried out. Furthermore, two filters having a 3-dB fractional bandwidth of 142 and 150%, centered at 0.77 and 1 GHz, respectively, have been realized for a proof of concept. Measured characteristics, in good agreement with simulations, show attractive properties of return loss (|S11| <−18 dB), insertion loss (<0.3 dB), and a maximum group delay and group delay variation of 2 and 1.3 ns, respectively. A distributed filter based on the same low-pass/high-pass approach has been also realized and measured for comparison. The size reduction reaches 85% for the semi-lumped filter, and its selectivity is improved with a shape factor of 1.3:1 instead of 1.5:1. The semi-lumped filter's drawback is related to a smaller rejection bandwidth compared to the distributed one. To improve the high-frequency stopband, an original technique for spurious responses suppression based on capacitively loaded stubs has been proposed. Even if the performances do not reach that obtained for the distributed approach, with this technique spurious responses are pushed until eight times the center frequency. A sensitivity study vs. critical parameters has also been carried out, showing the robustness of the design.

Treatment of Noise in Experimental Transport Measurements Plots With Discrete Wavelet Transforms

2009 ◽  
Author(s):  
Rube´n Panta Pazos
Keyword(s):  
Wavelet Transform ◽  
Wavelet Transforms ◽  
Transport Theory ◽  
Discrete Wavelet ◽  
Transform Method ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Thresholding Algorithm ◽  
High Pass

In this work it is applied the wavelet transform method [2] in order to reduce diverse type of noises of experimental measurement plots in transport theory. First, suppose that a problem is governed by the transport equation for neutral particles, and an unknown perturbation occurs. In this case, the perturbation can be associated to the source, or even to the flux inside the domain X. How is the behavior of the perturbed flux in relation to the flux without the perturbation? For that, we employ the wavelet transform method in order to compress the angular flux considered as a 1D, or n-th dimensional signal ψ. The compression of this signal can be performed up to some a convenient order (that depends of the length of the signal). Now, the transport signal is decomposed as [9, 11]: ψ=〈am|dm|dm−1|dm−2|⋯|d2|d1〉 where ak represents the sub signal of k-th level generated by the low-pass filter associated to the discrete wavelet transform (DWT) chosen, and dk the sub signal of k-th level generated by the high-pass filter associated to the same DWT. It is applied basically the Haar, Daub4 and Coiflet wavelets transforms. Indeed, the sub signal am cumulates the energy, for this work of order 96% of the original signal ψ. A thresholding algorithm provides treatment for the noise, with significant reduction in the compressed signal. Then, it is established a comparison with a base of data in order to identify the perturbed signal. After the identification, it is recomposed the signal applying the inverse DWT. Many assumptions can be established: the rate signal-to-noise is properly high, the base of data must contain so many perturbed signals all with the same level of compression. The problem considered is for perturbations in the signal. For measurements the problem is similar, but in this case the unknown perturbations are generated by the apparatus of measurements, problems in experimental techniques, or simply by random noises. With the same above assumptions, the DWT is applied. For the identification, it is used a method evolving statistical and metric techniques. It is given some results obtained with an algebraic computer system.

Plasma models and rescaling methods

1984 ◽  
Vol 31 (1) ◽  
pp. 141-151 ◽  
Author(s):  
Philippe Lotte ◽  
M. R. Feix
Keyword(s):  
High Temperature ◽  
Electrostatic Interactions ◽  
Practical Reasons ◽  
Electrostatic Model ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Numerical Studies ◽  
Low Pass ◽  
Vlasov Limit ◽  
High Pass

The plasma models used in analytical or numerical studies exhibit, mainly for practical reasons, symmetry reducing the dimensions of the space. It is not obligatory that the restrictions on the dynamics and the chosen form of the electrostatic interactions should correspond to the same symmetry and this introduces the concept of a d (dynamic), d' (electrostatic) model with d' ≥ d. We show that the crucial parameter is d' – d. For d' – d = 0, the model exhibits both at low and at high temperature the same characteristic plasma frequency. At high temperature we recover the Vlasov limit and the plasma acts as a high-pass filter. For d' – d = 1, the two frequencies (purely collective at high temperature and ‘crystal’ frequency at very low temperature) are different, while in its high temperature (Vlasov) limit the plasma acts as a low-pass filter. Finally if d' – d ≥ 2 there is no longer a Vlasov limit for all values of temperature and density. These properties are obtained through a systematic use of the homothety transformations and a search for the corresponding invariants.

scholarly journals Portable Electrocardiograph Dengan Sadapan Pada Telapak Tangan Dan Kaki

2020 ◽  
Vol 13 (2) ◽  
pp. 107-114
Author(s):  
Muhammad Syifaul Linnas ◽  
Sumber Sumber ◽  
Prastawa Assalim Tetraputra
Keyword(s):  
Personal Computer ◽  
Notch Filter ◽  
Pass Filter ◽  
Low Pass Filter ◽  
High Pass Filter ◽  
Low Pass ◽  
High Pass

    Electrocardiograph (ECG) secara rutin dilakukan oleh operator terampil yang terbiasa dengan penempatan masing-masing elektroda pada pasien. Posisi elektroda yang salah dapat menyebabkan kesalahan kritis dalam diagnosis dan perawatan penyakit jantung. Tujuan dari penelitian ini adalah mendesain sebuah Portable Electrocardiograph dengan Sadapan Pada Telapak Tangan dan Kaki. Kontribusi dari penelitian ini adalah  memudahkan orang awam dalam bidang kesehatan dalam hal penggunaan Electrocardiograph. Penelitian ini juga bertujuan  mendesain Electrocardiograph yang cukup terjangkau bagi puskesmas/pusat-pusat pelayanan medis di daerah. Agar desain ini dapat memudahkan dalam metode penggunaan alat, maka dibuatlah alat Electrocardiograph (ECG) dengan elektroda pad yang akan diletakkan pada telapak tangan dan telapak kaki yang telah di berikan tanda pada elektroda tersebut. Electrocardiograph (ECG) menggunakan desain High Pass Filter (Pasif 20dB ditambah Non Inverting Amplifier, Low Pass Filter (LPF) 40dB, dan notch filter yang akan ditampilkan pada layar monitor Personal Computer (PC). Dari hasil sadapan beberapa responden, terlihat hasil tampilan yang menyerupai/mendekati sinyal Electrocardiograph (ECG) sebenarnya. Kekurangan dari modul ini jika tidak adanya grounding yang baik dari power suply maka akan terjadi noise pada hasil sinyal yang akan ditampilkan. Hasil penelitian ini dapat di implementasikan pada Electrocardiograph (ECG) konvensional untuk meningkatkan kemudahan dalam hal penggunaan alat.    

scholarly journals Klasifikasi Kanker Paru Paru menggunakan Naïve Bayes dengan Variasi Filter dan Ekstraksi Ciri GLCM

2021 ◽  
Vol 11 (2) ◽  
pp. 256
Author(s):  
Mohtar Yunianto ◽  
Soeparmi Soeparmi ◽  
Cari Cari ◽  
Fuad Anwar ◽  
Delta Nur Septianingsih ◽  
...  
Keyword(s):  
Naive Bayes ◽  
Median Filter ◽  
Naïve Bayes ◽  
Gray Level ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Otsu Thresholding ◽  
Low Pass ◽  
Occurrence Matrix ◽  
High Pass

<p class="AbstractText">Telah berhasil dilakukan klasifikasi kanker paru-paru dari 120 data citra CT Scan. Pada penelitian, proses preposisi dimulai dengan variasi filtering yaitu low pass filter, median filter, dan high pass filter. Segmentasi yang digunakan yaitu Otsu Thresholding yang kemudian teksturnya akan diekstraksi menggunakan fitur Gray Level Co-occurrence Matrix (GLCM) dengan variasi arah sudut. Hasil dari ekstraksi GLCM dijadikan database yang akan menjadi dataset untuk pengklasifikasian citra menggunakan klasifikasi naïve bayes. Hasil dari penelitian dengan 12 buah variasi diperoleh hasil variasi terbaik adalah median filter dengan arah sudut GLCM 0° menunjukkan tingkat akurasi yang paling tinggi sebesar 88,33 %.</p>

scholarly journals CMOS CDBA-Based Inverse Filter Structure

2020 ◽  
Vol 9 (3) ◽  
pp. 2226-2231
Keyword(s):  
Cmos Technology ◽  
Experimental Results ◽  
Band Pass Filter ◽  
Inverse Filter ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Filter Structure ◽  
Low Pass ◽  
Band Pass ◽  
High Pass

This paper presents a voltage-mode(VM) tunable multifunction inverse filter configuration employing current differencing buffered amplifiers (CDBA). The presented structure utilizes two CDBAs, two/three capacitors and four/five resistors to realize inverse low pass filter (ILPF), inverse high pass filter (IHPF), inverse band pass filter (IBPF), and inverse band reject filter(IBRF) from the same circuit topology by suitable selection(s) of the branch admittances(s). PSPICE simulations have been performed with 0.18µm TSMC CMOS technology to validate the theory. Some sample experimental results have also been provided using off-the-shelf IC AD844 based CDBA.

Design of High pass and Low pass Filter using CMOS Operational Trans-conductance Amplifier

2018 ◽  
Vol 8 (5) ◽  
Author(s):  
Sarita Chauhan ◽  
Vinod Kameriya ◽  
Anshu Jagetiya ◽  
Apoorva Sharma ◽  
Pooja Lohar
Keyword(s):  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
High Pass

scholarly journals Temporal Modulation Transfer Functions in Cat Primary Auditory Cortex: Separating Stimulus Effects From Neural Mechanisms

2002 ◽  
Vol 87 (1) ◽  
pp. 305-321 ◽  
Author(s):  
Jos J. Eggermont
Keyword(s):  
Auditory Cortex ◽  
Cortical Neurons ◽  
Transfer Functions ◽  
Frequency Tuning ◽  
Primary Auditory Cortex ◽  
Modulation Transfer ◽  
Temporal Modulation ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass

We present here a comparison between the local field potentials (LFP) and multiunit (MU) responses, comprising 401 single units, in primary auditory cortex (AI) of 31 cats to periodic click trains, gamma-tone and time-reversed gamma-tone trains, AM noise, AM tones, and frequency-modulated (FM) tones. In a large number of cases, the response to all six stimuli was obtained for the same neurons. We investigate whether cortical neurons are likely to respond to all types of repetitive transients and modulated stimuli and whether a dependence on modulating waveform, or tone or noise carrier, exists. In 97% of the recordings, a temporal modulation transfer function (tMTF) for MU activity was obtained for gamma-tone trains, in 92% for periodic click trains, in 83% for time-reversed gamma-tone trains, in 82% for AM noise, in 71% for FM tones, and only in 53% for AM tones. In 31% of the cases, the units responded to all six stimuli in an envelope-following way. These particular units had significantly larger onset responses to each stimulus compared with all other units. The overall response distribution shows the preference of AI units for stimuli with short rise times such as clicks and gamma tones. It also shows a clear asymmetry in the ability to respond to AM noise and AM tones and points to a strong effect of the frequency content of the carrier on the subcortical processing of AM stimuli. Yet all temporal response properties were independent of characteristic frequency and frequency-tuning curve bandwidth. We show that the observed differences in the tMTFs for different stimuli are to a large extent produced by the different degree of phase locking of the neuronal firings to the envelope of the first stimulus in the train or first modulation period. A normalization procedure, based on these synchronization differences, unified the tMTFs for all stimuli except clicks and allowed the identification of a largely stimulus-invariant, low-pass temporal filter function that most likely reflects the properties of synaptic depression and facilitation. For nonclick stimuli, the low-pass filter has a cutoff frequency of ∼10 Hz and a slope of ∼6 dB/octave. For nonclick stimuli, there was a systematic difference between the vector strength for LFPs and MU activity that can likely be attributed to postactivation suppression mechanisms.

Sign in / Sign up

Export Citation Format

Share Document