Short Time Delay Research Articles

Waiting Time of Public Transport Passengers in Jordan: Magnitude and Cost

Aim: This paper is a research study investigating the magnitude and cost of waiting time as experienced by public transport users in Jordan. This study also used spatial analysis to measure services provided for public transport routes according to the average waiting time. Methods: The data for waiting time of public transport users were collected using field observation and a professional spatial analysis applied to identify several locations experiencing short time delays. Results: This study found a relationship between the total costs of waiting time, including wasted time and money, and revealed that the money spent by the passengers was more than their average monthly income. Conclusion: The findings can be used as valuable information for researchers, government policy-makers, and transport agencies to firstly, develop more punctual public transport modes; and secondly, manage public transport trips to minimize time delays.

The GALAH survey: temporal chemical enrichment of the galactic disc

ABSTRACT We present isochrone ages and initial bulk metallicities ($\rm [Fe/H]_{bulk}$, by accounting for diffusion) of 163 722 stars from the GALAH Data Release 2, mainly composed of main-sequence turn-off stars and subgiants ($7000\, \mathrm{ K}> T_{\mathrm{ eff}}> 4000\, \mathrm{ K}$ and $\log g>3$ dex). The local age–metallicity relationship (AMR) is nearly flat but with significant scatter at all ages; the scatter is even higher when considering the observed surface abundances. After correcting for selection effects, the AMR appears to have intrinsic structures indicative of two star formation events, which we speculate are connected to the thin and thick discs in the solar neighbourhood. We also present abundance ratio trends for 16 elements as a function of age, across different $\rm [Fe/H]_{bulk}$ bins. In general, we find the trends in terms of [X/Fe] versus age from our far larger sample to be compatible with studies based on small (∼100 stars) samples of solar twins, but we now extend them to both sub- and supersolar metallicities. The α-elements show differing behaviour: the hydrostatic α-elements O and Mg show a steady decline with time for all metallicities, while the explosive α-elements Si, Ca, and Ti are nearly constant during the thin-disc epoch (ages $\lesssim \! 12$ Gyr). The s-process elements Y and Ba show increasing [X/Fe] with time while the r-process element Eu has the opposite trend, thus favouring a primary production from sources with a short time delay such as core-collapse supernovae over long-delay events such as neutron star mergers.

Research of Inspection Firewall Fine Grained Access Control on SDN State

A new SDN state inspection firewall system base on OpenFlow protocol is proposed.In this scheme, state tables and shifted flow tables are added into SDN controller and switch, and corresponding state transition rules are formulated on basis of packet type, so firewall is able to inspect SDN network state.SDN stat inspection firewall is implemented on opensource controller Floodlight and Open vSwitch. The performance evaluation result shows that the SDN state inspection firwall can recognize the type of packets, moreover, it achieves the fine-grained access control which present SDN firewall cannot offer. The innovation of this paper is to put forward of inspection firewall fine grained access control on SDN State. by comparing the packet delay and connection establishment speed of the two firewalls, it can be concluded that the firewall system based on state detection has shorter delay time, in general, the connection establishment time takes up less proportion in the whole data transmission. Therefore, in summary, the overall performance of state-based firewall system is better than that of packet filtering firewall system.

Magnification, dust and time-delay constraints from the first resolved strongly lensed Type Ia supernova iPTF16geu

Abstract We report lensing magnifications, extinction, and time-delay estimates for the first resolved, multiply-imaged Type Ia supernova iPTF16geu, at z = 0.409, using Hubble Space Telescope (HST) observations in combination with supporting ground-based data. Multi-band photometry of the resolved images provides unique information about the differential dimming due to dust in the lensing galaxy. Using HST and Keck AO reference images taken after the SN faded, we obtain a total lensing magnification for iPTF16geu of $\mu = 67.8^{+2.6}_{-2.9}$, accounting for extinction in the host and lensing galaxy. As expected from the symmetry of the system, we measure very short time-delays for the three fainter images with respect to the brightest one: -0.23 ± 0.99, -1.43 ± 0.74 and 1.36 ± 1.07 days. Interestingly, we find large differences between the magnifications of the four supernova images, even after accounting for uncertainties in the extinction corrections: $\Delta m_1 = -3.88^{+0.07}_{-0.06}$, $\Delta m_2 = -2.99^{+0.09}_{-0.08}$, $\Delta m_3 = -2.19^{+0.14}_{-0.15}$ and $\Delta m_4 = -2.40^{+0.14}_{-0.12}$ mag, discrepant with model predictions suggesting similar image brightnesses. A possible explanation for the large differences is gravitational lensing by substructures, micro- or millilensing, in addition to the large scale lens causing the image separations. We find that the inferred magnification is insensitive to the assumptions about the dust properties in the host and lens galaxy.

Blind Fractionally Spaced Channel Equalization for Shallow Water PPM Digital Communications Links.

Underwater acoustic digital communications suffer from inter-symbol interference deriving from signal distortions caused by the channel propagation. Facing such kind of impairment becomes particularly challenging when dealing with shallow water scenarios characterized by short channel coherence time and large delay spread caused by time-varying multipath effects. Channel equalization operated on the received signal represents a crucial issue in order to mitigate the effect of inter-symbol interference and improve the link reliability. In this direction, this contribution presents a preliminary performance analysis of acoustic digital links adopting pulse position modulation in severe multipath scenarios. First, we show how the spectral redundancy offered by pulse position modulated signals can be fruitfully exploited when using fractional sampling at the receiver side, which is an interesting approach rarely addressed by the current literature. In this context, a novel blind equalization scheme is devised. Specifically, the equalizer is blindly designed according to a suitably modified Bussgang scheme in which the zero-memory nonlinearity is replaced by a M-memory nonlinearity, M being the pulse position modulation order. Numerical results not only confirm the feasibility of the technique described here, but also assess the quality of its performance. An extension to a very interesting complex case is also provided.

Revisiting The Spectral and Timing Properties of NGC 4151.

NGC 4151 is the brightest Seyfert 1 nucleus in X-rays. It was the first object to show short time delays in the Fe K band, which were attributed to relativistic reverberation, providing a new tool for probing regions at the black hole scale. Here, we report the results of a large XMM-Newton campaign in 2015 to study these short delays further. Analyzing high quality data that span time scales between hours and decades, we find that neutral and ionized absorption contribute significantly to the spectral shape. Accounting for their effects, we find no evidence for a relativistic reflection component, contrary to early work. Energy-dependent lags are significantly measured in the new data, but with an energy profile that does not resemble a broad iron line, in contrast to the old data. The complex lag-energy spectra, along with the lack of strong evidence for a relativistic spectral component, suggest that the energy-dependent lags are produced by absorption effects. The long term spectral variations provide new details on the variability of the narrow Fe Kα line. We find that its variations are correlated with, and delayed with respect to, the primary X-ray continuum. We measure a delay of days, implying an origin in the inner broad line region (BLR). The delay is half the Hβ line delay, suggesting a geometry that differs slightly from the optical BLR.

Epidemiological Study of Tuberculosis in Northern Iran

Background & Purpose: One of the most important united nation Millennium Development Goals is to control Tuberculosis (TB). This study aimed to identify the high-risk areas of TB and other related factors of it in an epidemiological study.
 Materials & Methods: In this retrospective study, the records of 1566 TB infected patients in healthcare centers of 17 cities of Mazandaran University of Medical Sciences were investigated during 2009-2013 years. Information of patients was gathered using a check list. The collected data was then analyzed using chi-square.
 Results: The mean age of the patients was 46.17± 20.6 years. The 5-year incidence rate was 12.14 in 100,000 populations. Cities in the east of Province (Sari, Behshahr, and Neka) had highest incidence rate (about 16 cases in 100,000 population). The incidence rate was different based on gender as, 15.3 % of the men and 10.2 % of the women were infected. The median delay time in the diagnosis was 34 days.
 Conclusions: The incidence rate of TB in Mazandaran was found to be almost similar to the previous reported rate in Iran. High incidence rate in east of province may be due to bordering to the Golestan Province as the immigrant province. The short delay time of TB diagnosis during this period indicated the well health services practices in this province. More attention should be paid to high risk areas for identification and giving education to those patients.

MP mitigation in GNSS positioning by GRU NNs and adaptive wavelet filtering

In urban canyons, multipath (MP) signals have some problems such as short time delay, high dynamic, and uncontrollable. To solve this problem and mitigate the interference of MP effect on positioning, the authors proposed a new method which uses gated recurrent unit (GRU) neural networks (NNs) aided by compressed sensing algorithm to estimate parameters of MP signal accurately. They showed how to build the GRU - deformation of recurrent NNs (RNNs) - in a dynamic environment, and estimated the MP signals parameters accurately. Also, considering the special cases in a dynamic environment, they used the adaptive wavelet filter to optimise the NNs, compensated pseudo-distance, and improved the accuracy of positioning. Like other NNs, the learning process of this machine learning method in the dynamic environment can be summarised as obtaining data from different environmental conditions. For this, they collected signal data from different speeds to train GRU-RNN model, which correctly estimated the MP signal's parameter value in a different environment and different speeds. By experimental verification, when the speed is slower than 20 km/h, GRU-RNN can reduce code tracking error to 0.08 chips, and increased the positioning accuracy by about 13%.

Solar Wind Dynamic Pressure Upstream From Saturn: Estimation From Magnetosheath Properties and Comparison With SKR

AbstractAn analytical method is developed by which measurements made by the Cassini spacecraft in Saturn's magnetosheath can be used to infer the upstream solar wind parameters, specifically the solar wind speed (Vsw) and the dynamic pressure (Pd). The method is validated by comparing the results with other estimates of these parameters, including the mSWiM MHD model and magnetopause and bow shock models applied to observed boundary crossings. The comparisons suggest that the new inferred Vsw are on average ~40 km/s lower than the mSWiM values, and the dynamic pressure values are slightly lower as well. We find few of the lower Pd values predicted by mSWiM, probably because Cassini would have been inside the expanded magnetosphere under such conditions. Systematic temporal variations such as interplanetary shocks do seem to be captured well, with arrival times within several days of the MHD prediction. Compared to dynamic pressures estimated from boundary crossings with well‐known magnetopause and bow shock models, the magnetosheath‐inferred dynamic pressure tends to be somewhat lower, but within the uncertainties of the analytical derivation. Comparison of the inferred dynamic pressure with observed Saturn's kilometric radiation (SKR) activity reveals several episodes of very good temporal tracking between dynamic pressure and SKR intensity, with relatively short time delays (4–5 hr), suggesting rather direct driving. Such good tracking intervals occur almost exclusively on the dawnside of the magnetosphere, where the dominant SKR source is visible. When the tracking is good, the SKR fluxes vary roughly as the square of the dynamic pressure.

Online Current Loop Tuning for Permanent Magnet Synchronous Servo Motor Drives with Deadbeat Current Control

High bandwidths and accurate current controls are essential in high-performance permanent magnet synchronous (PMSM) servo drives. Compared with conventional proportional–integral control, deadbeat current control can considerably enhance the current control loop bandwidth. However, because the deadbeat current control performance is strongly affected by the variations in the electrical parameters, tuning the controller gains to achieve a satisfactory current response is crucial. Because of the prompt current response provided by the deadbeat controller, the gains must be tuned within a few control periods. Therefore, a fast online current loop tuning scheme is proposed in this paper. This scheme can accurately identify the controller gain in one current control period because the scheme is directly derived from the discrete-time motor model. Subsequently, the current loop is tuned by updating the deadbeat controller with the identified gains within eight current control periods or a speed control period. The experimental results prove that in the proposed scheme, the motor current can simultaneously have a critical-damped response equal to its reference in two current control periods. Furthermore, satisfactory current response is persistently guaranteed because of an accurate and short time delay required for the current loop tuning.

Supernovae and their host galaxies – VI. Normal Type Ia and 91bg-like supernovae in ellipticals

ABSTRACT We present an analysis of the galactocentric distributions of the ‘normal’ and peculiar ‘91bg-like’ subclasses of 109 supernovae (SNe) Ia, and study the global parameters of their elliptical hosts. The galactocentric distributions of the SN subclasses are consistent with each other and with the radial light distribution of host stellar populations, when excluding bias against central SNe. Among the global parameters, only the distributions of u − r colours and ages are inconsistent significantly between the ellipticals of different SN Ia subclasses: the normal SN hosts are on average bluer/younger than those of 91bg-like SNe. In the colour–mass diagram, the tail of colour distribution of normal SN hosts stretches into the Green Valley – transitional state of galaxy evolution, while the same tail of 91bg-like SN hosts barely reaches that region. Therefore, the bluer/younger ellipticals might have more residual star formation that gives rise to younger ‘prompt’ progenitors, resulting in normal SNe Ia with shorter delay times. The redder and older ellipticals that already exhausted their gas for star formation may produce significantly less normal SNe with shorter delay times, outnumbered by ‘delayed’ 91bg-like events. The host ages (lower age limit of the delay times) of 91bg-like SNe does not extend down to the stellar ages that produce significant u-band fluxes – the 91bg-like events have no prompt progenitors. Our results favour SN Ia progenitor models such as He-ignited violent mergers that have the potential to explain the observed SN/host properties.

Role of Lattice Oxygen in the Oxygen Evolution Reaction on Co3O4: Isotope Exchange Determined Using a Small-Volume Differential Electrochemical Mass Spectrometry Cell Design

This work demonstrates the roleof lattice oxygen of metal oxide catalysts in the oxygen evolution reaction (OER) as evidenced by isotope labeling together with the differential electrochemical mass spectrometry (DEMS) method. Our recent report assessed this role for Co3O4 using a flow-through DEMS cell, which requires a large volume of electrolyte. Herein, we extend this procedure to different Co3O4 catalyst loadings and particle sizes as well as the mixed Ag + Co3O4 catalyst. We introduce, for the first time, a novel small-volume DEMS cell design capable of using disc electrodes and only <0.5 mL of electrolyte. The reliability of the cell is demonstrated by monitoring gas evolution during OER in real time. This cell shows high sensitivity, high collection efficiency, and very short delay time. DEMS results reveal that only the interfacial part (∼0.2% of the total loading or 25% of surface atoms) of the catalyst is active for OER. Interestingly, the amount of oxygen exchanged on the mixed Ag + Co3O4 catalyst is higher than that on the single Co3O4 catalyst, which illustrates the improved electrocatalytic activity previously reported on this mixed catalyst. Furthermore, the real surface area of the catalysts is estimated using different methods (namely, the ball model, double layer capacitance, isotope exchange, and redox peak methods). The surface areas estimated from the Brunauer-Emmett-Teller (BET) and ball models are comparable but roughly three times higher than that of the redox peak method. Our method represents an alternative approach for probing the mechanism and real surface area of catalysts.

The host galaxies of double compact objects across cosmic time

ABSTRACT We explore the host galaxies of compact-object binaries (black hole–black hole binaries, BHBs; neutron star–black hole binaries, NSBHs; double–neutron stars; DNSs) across cosmic time, by means of population-synthesis simulations combined with the Illustris cosmological simulation. At high redshift (z ≳ 4), the host galaxies of BHBs, NSBHs, and DNSs are very similar and are predominantly low-mass galaxies (stellar mass M &lt; 1011 M⊙). If z ≳ 4, most compact objects form and merge in the same galaxy, with a short delay time. At low redshift (z ≤ 2), the host galaxy populations of DNSs differ significantly from the host galaxies of both BHBs and NSBHs. DNSs merging at low redshift tend to form and merge in the same galaxy, with relatively short delay time. The stellar mass of DNS hosts peaks around ∼1010–1011 M⊙. In contrast, BHBs and NSBHs merging at low redshift tend to form in rather small galaxies at high redshift and then to merge in larger galaxies with long delay times. This difference between DNSs and black hole binaries is a consequence of their profoundly different metallicity dependence.

Task Scheduling for cloud computing Based on Firefly Algorithm

In this paper a new method proposed, to solve the problem of scheduling resources in cloud computing, it is using a parallel scheduling model which can enhance parallel tasks scheduling while the relationship among serial tasks stay constant. The important feature of dynamic tasks is provided by users to sub-tasks in serial sequences and arranged as scheduling queue, these tasks have different and equal priorities according to running order. In this paper firefly algorithm (FA) have been introduced for scheduling the subtasks in cloud computer to prove a progress in short delay time. The most important features that can be considered are fairness and efficiency characteristics. Delay time Shortest and Fairness firefly algorithm (DSFFA) applied to solve task scheduling problem that realized the shortest delay time, which improving the user satisfaction. Experimental results show that DSFFA algorithm is better than the task scheduling –Firefly algorithm (TS-FA) algorithm in fairness, efficiency and task delay time, therefor it can be realized for the optimal scheduling in cloud computing.

Electronic countermeasure for OFDM‐based imaging passive radars

Passive radars are notoriously robust to jamming because the receiver location cannot be detected. Moreover, the use of Orthogonal Frequency Division Multiplexing (OFDM)-based reference signals further improves the robustness against jammers. Nevertheless, deception/spoofing-type of jamming may still be possible. This article aims at proposing an electronic countermeasure (ECM) for OFDM-based passive radars with radar-imaging capabilities. Here, a target-on-board deception jammer is proposed that aims at protecting the target itself from being identified when passive radar imaging is used. A design of the architecture of the proposed target-borne jamming system is provided, which includes COmmercial of The Shelf (COTS) devices that are able to sample a broadband signal, modulate it in amplitude and phase, and retransmit it with a very short time delay. Theoretical and simulation results are also given proving that imaging and precise location of non-cooperative targets can be both affected by the presence of false and/or altered phase-modulated target echoes.

Dynamic Fault Monitoring of Pitch System in Wind Turbines using Selective Ensemble Small-World Neural Networks

Pitch system failures occur primarily because wind turbines typically work in dynamic and variable environments. Conventional monitoring strategies show limitations of continuously identifying faults in most cases, especially when rapidly changing winds occur. A novel selective-ensemble monitoring strategy is presented to diagnose the most pitch failures using Supervisory Control and Data Acquisition (SCADA) data. The proposed strategy consists of five steps. During the first step, the SCADA data are partitioned according to the turbine’s four working states. Correlation Information Entropy (CIE) and 10 indicators are used to select correlation signals and extract features of the partition data, respectively. During the second step, multiple Small-World Neural Networks (SWNNs) are established as the ensemble members. Regarding the third step, all the features are randomly sampled to train the SWNN members. The fourth step involves using an improved global correlation method to select appropriate ensemble members while in the fifth step, the selected members are fused to obtain the final classification result based on the weighted integration approach. Compared with the conventional methods, the proposed ensemble strategy shows an effective accuracy rate of over 93.8% within a short delay time.

Circumstellar properties of Type Ia supernovae from the helium star donor channel

ABSTRACT We investigate the predicted circumstellar properties of Type Ia supernova progenitor systems with non-degenerate helium star donors. It has been suggested that systems consisting of a carbon + oxygen white dwarf and a helium star can lead to Type Ia supernova explosions. Binary evolution calculations for the helium star donor channel predict that such a progenitor system is in either a stable helium-shell burning phase or a weak helium-shell flash phase at the time of the Type Ia supernova explosion. By using the binary evolution models from our previous study, we show that a large fraction of the progenitor systems with a helium star donor have a low enough density to explain the current non-detection of radio emission from Type Ia supernovae. Most of the progenitor systems in the weak helium-shell flash phase at the time of the Type Ia supernova explosion, which may dominate the prompt (short delay time) Type Ia supernova population, have both a low circumstellar density and a faint helium star donor, which could account for the non-detection of radio emission and a pre-explosion companion star in SN 2011fe and SN 2014J. We also find some progenitor systems that are consistent with the properties of the companion star candidate identified at the explosion location of the Type Iax SN 2012Z.

Letter to the editor

Free AccessLetter to the EditorLetter to the editorNoman Khan, Muhammad Arif Saeed and Muhammad Salman KhanNoman Khanhttp://orcid.org/0000-0002-8343-6445 Aga Khan University Hospital Karachi Sindh Pakistan, Search for more papers by this author, Muhammad Arif Saeed Aga Khan University Hospital Karachi Sindh Pakistan, Search for more papers by this author and Muhammad Salman Khan Aga Khan University Hospital Karachi Sindh Pakistan, Search for more papers by this authorPublished Online:21 Jun 2019https://doi.org/10.1259/bjr.20190308SectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail AboutRe: Distinguishing adrenal adenomas from non-adenomas with multidetector CT: evaluation of percentage washout values at a short time delay triphasic enhanced CTWe are writing to you about the original article published in November issue of BJR titled “Distinguishing adrenal adenomas from non-adenomas with multidetector CT: evaluation of percentage washout values at a short time delay triphasic enhanced CT”. The study retrospectively evaluated use of a short time delay CT protocol to distinguish adrenal adenomas from non-adenomas. As discussed in manuscript document, there are inconsistencies in CT protocol that we think requires further clarification from authors.We thank you for your time and consideration.It was with great interest that we read the paper published in November issue of The British Journal of Radiology titled “Distinguishing adrenal adenomas from non-adenomas with multidetector CT: evaluation of percentage washout values at a short time delay triphasic enhanced CT”.The article presents an important advance in CT imaging of adrenal glands. The authors retrospectively evaluated use of triphasic CT with short delayed phase of 200 secs. The authors mention limitations of study however further clarification of the study protocol would be helpful.A routine triphasic CT protocol with short delayed Phase is not performed routinely and it’s unlikely to be the case at the institution where this study was conducted. It only stands to reason that patients undergoing CT for surveillance of metastatic disease would be subjected to a different protocol than those with suspicion of or known history of adrenal masses. This could have been mitigated by tabulating clinical indications of all scans.This is additionally complicated by statement in discussion section that “most cases of adenomas carried out both unenhanced and enhanced CT scans” implying that not all cases were subjected to the same triphasic protocol. This requires clarification.Response to letter: “Distinguishing adrenal adenomas from non-adenomas with multidetector CT: evaluation of percentage washout values at a short time delay triphasic enhanced CT” by Khan et alLiu et al., Department of Radiology, China-Japan Friendship HospitalWe appreciate the comments of Dr Khan et al, and we thank them for the interest in our recent publication in the British Journal of Radiology. We would like to make further clarification of the CT scan protocol in our study. Firstly, the unenhanced CT and enhanced CT are carried out separately at different time in our institution. It means that some patients receive unenhanced CT only, whereas others first receive unenhanced CT, then receive enhanced CT for further differential diagnosis. Secondly, abdomen enhanced CT use the same triphasic scan protocol after the bolus administration of the contrast agent in our institution, and this protocol is not specialized for adrenal lesions. Finally, this is a retrospective study, so we reviewed the patients with adrenal masses and selected cases carrying out both unenhanced and enhanced CT scans. Most of the adrenal lesions were discovered incidentally (incidentalomas) for other clinical problems. Some of the patients took only unenhanced CT and then underwent surgical operation or imaging follow-up. These patients were excluded in our study. Others took unenhanced CT at first and enhanced CT later, not only for differential diagnosis of adrenal lesions, but also for assessment of lesions in other organs, especially for detecting metastatic spread in patients with prior history of malignant diseases. We reviewed and analyzed these adrenal lesions in our article. Previous article FiguresReferencesRelatedDetails Volume 92, Issue 1100August 2019 © 2019 The Authors. Published by the British Institute of Radiology History ReceivedMarch 24,2019AcceptedApril 08,2019Published onlineJune 21,2019 Metrics Download PDF

Enhanced-absorption template method for preparation of double-shell NiO hollow nanospheres with controllable particle size for nanothermite application

Nanothermite, due to its high energy density, short ignition delay time, and self-sustained exothermic reaction, is attracting wide attention. In this study, an ammonium hydroxide assisted enhanced-absorption carbon microsphere template method is adopted to prepare double-shell NiO hollow nanospheres with controllable particle size, which further are evaluated as the oxidizers in nanothermite. A possible evolutionary process to form the double-shell NiO is described according to the transmission electron microscopy images at different calcination temperature. The thermal and combustion performances of Al/NiO nanothermite are studied by differential scanning calorimetry, electric ignition and constant-volume pressure cell tests. Results show that as the particle size of NiO hollow nanospheres decreases, the nanothermites show lower activation energy, higher heat release, stronger light intensity, shorter ignition delay time and higher pressurization rate. Based on the optical signal, the combustion process is mainly affected by the mass diffusion distance, depending on the gap between the inner and outer layer. These results indicate that Al/NiO nanothermite has excellent ignition and combustion properties, which are very promising for practical applications in microelectromechanical system (MEMS).

Nanoscale 3D Stackable Ag-Doped HfOx-Based Selector Devices Fabricated through Low-Temperature Hydrogen Annealing.

Electrochemical metallization-based threshold switching devices with active metal electrodes have been studied as a selector for high-density resistive random access memory (RRAM) technology in crossbar array architectures. However, these devices are not suitable for integration with three-dimensional (3D) crossbar RRAM arrays due to the difficulty in vertical stacking and/or scaling into the nanometer regime as well as the asymmetric threshold switching behavior and large variation in the operating voltage. Here, we demonstrate bidirectional symmetric threshold switching behaviors from a simple Pt/Ag-doped HfOx/Pt structure. While fabricating the Pt/Ag-doped HfOx/Pt film using a 250 nm hole structure, filaments composed of Ag nanoclusters were constructed through a low-temperature (∼200 °C) hydrogen annealing process where the shape of the film in a nanoscale via a hole structure was maintained for integration with 3D stackable crossbar RRAM arrays. Finite Ag filament paths in the HfOx layer led to uniform device-to-device performances. Moreover, we observed that the hydrogen annealing process reduced the delay time through the reduction of the oxygen vacancies in the HfOx layer. Consequently, the proposed Pt/Ag-doped HfOx/Pt-based nanoscale selector devices exhibited excellent performance of high selectivity (∼105), ultralow OFF current (∼10 pA), steep turn-on slope (∼2 mV/decade), and short delay time (3 μs).