Sensitivity Transfer Function Research Articles

Virtual reference feedback tuning with robustness constraints: A swarm intelligence solution

The simplified modeling of a complex system allied with a low-order controller structure can lead to poor closed-loop performance and robustness. A feasible solution is to avoid the necessity of a model by using data for the controller design. The Virtual Reference Feedback Tuning (VRFT) is a data-driven design method that only requires a single batch of data and solves a reference tracking problem, although with no guarantee of robustness. In this work, the inclusion of an H∞ robustness constraint to the VRFT cost function is addressed. The estimation of the H∞ norm of the sensitivity transfer function is extended to maintain the one-shot characteristic of the VRFT. Swarm intelligence algorithms are used to solve the non-convex cost function. The proposed method is applied in two real-world inspired problems with four different swarm intelligence algorithms, which are compared with each other through a Monte Carlo experiment of 50 executions. The obtained results are satisfactory, achieving the desired robustness criteria.

Bend-insensitive fiber optic ultrasonic tracking probe for cardiovascular interventions.

Transesophageal echocardiography (TEE) is widely used to guide medical device placement in minimally invasive cardiovascular procedures. However, visualization of the device tip with TEE can be challenging. Ultrasonic tracking, enabled by an integrated fiber optic ultrasound sensor (FOUS) that receives transmissions from the TEE probe, is very well suited to improving device localization in this context. The problem addressed in this study is that tight deflections of devices such as a steerable guide catheter can result in bending of the FOUS beyond its specifications and a corresponding loss of ultrasound sensitivity. A bend-insensitive FOUS was developed, and its utility with ultrasonic tracking of a steerable tip during TEE-based image guidance was demonstrated. Fiberoptic ultrasound sensors were fabricated using both standard and bend insensitive single mode fibers and subjected to static bending at the distal end. The interference transfer function and ultrasound sensitivities were compared for both types of FOUS. The bend-insensitive FOUS was integrated within a steerable guide catheter, which served as an exemplar device; the signal-to-noise ratio (SNR) of tracking signals from the catheter tip with a straight and a fully deflected distal end were measured in a cardiac ultrasound phantom for over 100 frames. With tight bending at the distal end (bend radius<10mm), the standard FOUS experienced a complete loss of US sensitivity due to high attenuation in the fiber, whereas the bend-insensitive FOUS had largely unchanged performance, with a SNR of 47.7 for straight fiber and a SNR of 36.8 at a bend radius of 3.0mm. When integrated into the steerable guide catheter, the mean SNRs of the ultrasonic tracking signals recorded with the catheter in a cardiac phantom were similar for straight and fully deflected distal ends: 195 and 163. The FOUS fabricated from bend-insensitive fiber overcomes the bend restrictions associated with the FOUS fabricated from standard single mode fiber, thereby enabling its use in ultrasonic tracking in a wide range of cardiovascular devices.

Analysis of Pre-Driver and Last-Stage Power-Ground-Induced Jitter at Different PVT Corners.

This paper presents the study of power/ground (P/G) supply-induced jitter (PGSIJ) on a cascaded inverter output buffer. The PGSIJ analysis covers the IO buffer transient simulation under P/G supply voltage variation at three process, voltage, and temperature (PVT) corners defined at different working temperatures and distinct DC supply voltages at the pre-driver (i.e., /) and last stage (i.e., ). Firstly, the induced jitter contributions by the pre-driver, as well as the last, stage are compared and studied. Secondly, the shared and decoupled P/G supply topologies are investigated. The outcomes of these simulation analyses with respect to worst case jitter corners are determined, while highlighting the importance of modeling the pre-driver circuit behavior to include the induced jitter in the input–output buffer information specification (IBIS)-like model. Accordingly, the measured PGSIJ depends on the corners to be analyzed and, therefore, the designer needs to explore the worst-case corner for the driver’s technology node and the most supply voltage noise affecting the jitter output for signal and power integrity (SiPI) simulations. Finally, the jitter transfer function sensitivity to the amplitude and frequency/phase variations of the separate and combined impacts of the pre-driver and last stage are explored, while discussing the superposition of the power supply induced jitter (PSIJ) induced by both the driver’s IO stages under small signal and large signal supply voltage variations. The linear superposition of the separate PSIJ effects by the pre-driver and last stage depends on the amplitude of the variation of the supply voltage that can drive the transistor to their nonlinear working regions.

6G/B5G 네트워크 통신 기반의 스마트팩토리 내 자기부상 물류이송시스템의 시간지연 제어기 설계

Recently, smart factories have been actively introduced in the manufacturing process since the 4th industrial revolution. In particular, research on a logistics transport system using a in-track type magnetic levitational conveyor system is continuing in the semiconductor and display manufacturing industries that require a high-clean environment. This in-track type magnetic levitation system has problems in measuring uncertainty and increasing cost due to the sensors installing to each track. In this paper, we consider a method of installing the sensors to the vehicle and transmitting measurement data using network communication. At this time, end-to-end time latency occurs by using the 6G/B5G communication system in the smart factory. To solve this problem, we propose a controller design method of the magnetic levitation system considering time delay. The proposed controller is designed using the loop shape method for the sensitivity transfer function in frequency domain in order to reduce input disturbance and attenuate sensor noise. The effectiveness of the proposed controller is shown by the simulation.

A Framework for Sensitivity Analysis of Real-Time Power Hardware-in-the-Loop (PHIL) Systems

Power hardware-in-the-loop (PHIL) simulation leverages the advanced real-time emulation based technique to carry out in-depth investigations on novel real-world power components. Power amplifiers, sensors, and signal conversion units based power interfaces (PI) incorporate physical hardware systems and real-time simulation platforms into PHIL setups. However, the employment of any interfacing technique inevitably introduces disturbances such as sensor noise, switching harmonics, or quantization noise to PHIL systems. To facilitate quantitatively analyzing and assessing the impact of external disturbances on PHIL simulation systems, a framework for sensitivity analysis of PHIL setups has been developed in this paper. Detailed modelling principles related to the sensitivity analysis of PHIL systems and the inherent relationship between sensitivity transfer functions and stability criteria are elaborated along with theoretical and experimental validation. Based on this concept, accuracy assessment methods are employed in this framework to quantify generic sensitivity criteria. Moreover, physical passive load and converter-based PHIL setups are applied and experimental results are presented to characterize and demonstrate the applicability of the proposed framework.

Correlation between Contrast Sensitivity and Modulation Transfer Functions.

Previous studies found no correlation between visual acuity and optical quality in a population of young subjects with good vision. Using sinusoidal gratings, we systematically investigate the correlation between contrast sensitivity and optical quality as a function of spatial frequency. This study describes the correlation between the contrast sensitivity function (CSF) and the modulation transfer function (MTF) in a sample of young and informed subjects. Our results are compared with prior studies on the correlation between visual acuity and metrics of image quality. We also compare our results with previous studies that compare the CSF, the MTF, and the neural contrast sensitivity function (NCSF). The CSF of 28 informed subjects is measured in photopic conditions. The polychromatic MTF is computed from the measurements of monochromatic aberrations. The (CSF, MTF) correlation is estimated as the Pearson correlation coefficient, at each spatial frequency. The NCSF of each subject is estimated as the ratio of CSF to MTF. We obtain high correlation coefficients (0.8) in the range of spatial frequencies of 3 to 6 cycles per degree, which also corresponds to high NCSF. Correlation decreases with increasing spatial frequency in the range of 6 to 18 cycles per degree (down to 0.0 at 18 cycles per degree). In that range, optical and neural contrast sensitivities are both approximately reduced by factor 4. In our sample of young subjects with good vision, the CSF with sinusoidal gratings better differentiates eyes of good optical quality at intermediate spatial frequencies (3 to 6 cycles per degree) than at higher spatial frequencies (12 to 18 cycles per degree). At the highest tested spatial frequency of sinusoidal gratings (18 cycles per degree), there is no significant correlation between optical quality and contrast sensitivity.

Optimized four-parameter PID controller for AVR systems with respect to robustness

A procedure for the optimization of the proportional-integral-derivative (PID) controller under constraints to robustness of model uncertainties and sensitivity to measurement noise for a synchronous generator (SG) automatic voltage regulator (AVR) is presented in this paper. Performance indices related to the load disturbance response such as integral error (IE) and integral absolute error (IAE) are used as key criteria for the design method. They are minimized for a given maximum modulus of sensitivity function Ms. By maximizing loop gain regarding given sensitivities Ms and Mn we optimized load disturbance response. Contrary to majority AVR PID controller procedures, along with proportional, integral and derivative gain, a noise filter time constant is included in a proposed optimization algorithm to satisfy given sensitivity to the measurement noise Mn. A simple and effective solution of the optimization problem is obtained by binding a ratio between the integral and the derivative time constant Ti/Td. The optimal Ti/Td ratio is determined subsequently. Besides this, a step response to voltage reference change is modified with a reference filter to avoid large overshoots. This is achieved by limiting the maximum modulus of the resulting close-loop transfer function sensitivity Msp. The fact that zeros and poles of the second order reference filter have the same damping factor simplifies the procedure for resolving two out of six parameters. Also, two additional conditions result in the fact that three design parameters {Ms, Mn, Msp} are sufficient to determine the required six parameters of the two-degree-of-freedom (2DOF) PID controller. Such controller outperforms recently presented AVR controllers especially regarding the load disturbance rejection. Experiment tests with no-load SG and SG connected on the grid are carried out to prove the claims stated in this work concerning robustness performance and sensitivity to measurement noise. Also, we showed practical use of the proposed controller parameter tuning procedure by experimental runs performed on a lab generator.

Omnidirectional Platforms for Gait Training: Admittance-Shaping Control for Enhanced Mobility

We present a design method for the admittance control of a class of omnidirectional mobile platforms. Holonomic behavior of the platform is accomplished by a steering system that is itself subject to nonholonomic constraints. The proposed application of this type of platform, henceforth the “walker”, is as an assistive device for human gait rehabilitation. Therefore, the control design objectives are to guarantee the stability of the coupled system formed by the robotic platform and the human body, and to maximize mobility for the user by reducing the robot’s apparent inertia. First, we show how feedback linearization of a reduced-order model of the system, combined with a smooth trajectory-tracking control, achieves global asymptotic stability of the tracking error. Then we show how compliance in the robot limits the amount of inertia reduction that can be achieved before instability occurs. We address this problem with a control design method that maximizes the amplitude of the system’s admittance over a useful range of frequencies. Using root locus analysis and sensitivity transfer functions, we find an optimal value for the virtual mass in the admittance model, representing the best tradeoff between two oscillatory modes. The walker’s admittance vs. frequency function is then corrected via a complementary sensor input, namely, the user’s torque on the sagittal plane. A second layer of control provides the walker’s therapeutic action, consisting of a variable horizontal force that aids propulsion of the user’s body. The level of assistive force is modulated with the patient’s gait speed and turning rate to ensure easy adaptation. The control design was validated through an experiment involving human users walking in a prototype of the mobile platform.

Effect of Suboccipital Release on Pain Perception and Autonomic Reflex Responses to Ischemic and Cold Pain.

To determine the autonomic effects of suboccipital release (SOR) during experimentally induced pain, 16 healthy subjects (eight women, eight men) experienced ischemic (forearm postexercise muscle ischemia [PEMI]) and cold (cold pressor test [CPT]) pain. Beat-to-beat heart rate (electrocardiogram), mean arterial blood pressure (finger photoplethysmography), baroreflex sensitivity (transfer function analysis), and pain perception were measured. SOR or a sham (modified yaw; 30 cycles/min) was performed in minute 2 of pain. PEMI increased blood pressure by 23 ± 2 and 20 ± 2 mmHg; no differences occurred between SOR or yaw. PEMI modestly elevated heart rate during ischemia, followed by significant reduction from baseline with SOR (-3 ± 2 bpm) and yaw (-4 ± 2 bpm); no differences were observed between treatments. CPT increased blood pressure (SOR = 11 ± 1, yaw = 9 ± 2 mmHg) and heart rate (SOR = 10 ± 2, yaw = 8 ± 3 bpm) before SOR and yaw. Neither treatment nor sham blunted blood pressure increases (SOR = 25 ± 2, yaw = 22 ± 2 mmHg) during CPT; both decreased heart rate (SOR = -3 ± 2, yaw = -2 ± 2 bpm) from baseline. PEMI and CPT caused increased pain without treatment modulation. Following pain and manual intervention, SOR increased baroreflex sensitivity in the 0.15-0.35 Hz range and decreased R-R interval power spectral density in the 0.03-0.5 Hz range compared with yaw. To probe potential mechanisms and interactions between manual treatment and a prototypic analgesic, oral aspirin (967 mg) was given 60 minutes before testing to reduce prostaglandin synthesis. Aspirin slightly attenuated pain but neither altered cardiovascular changes to PEMI nor interacted with SOR or yaw. SOR has the capacity to modulate pain-induced autonomic control and regulation.

Analysis and Improved Design of Phase Compensated Proportional Resonant Controllers for Grid-Connected Inverters in Weak Grid

Phase compensated proportional resonant (PR) controllers with phase leading angles embedded into resonant controllers, are used to improve the system stability, when the grid-connected inverter is connected to a weak grid with large grid impedance. However, an inappropriate phase leading angle will cause obvious anti-peak in the magnitude response of phase compensated PR controller. Thus, the phase leading angle should be selected carefully. The conventional phase compensation (CPC) method for selecting the phase leading angle can maximize the system phase margin, but at the expense of large peaks in the magnitude response of sensitivity transfer function. Meanwhile, the bandwidths of resonant controllers will be reduced. In the paper, an improved phase compensation (IPC) method is proposed, which does not cause peaks in the magnitude response of sensitivity transfer function while providing sufficient phase margin. Experimental tests were carried out on a single phase grid-connected inverter. The effectiveness of the proposed method is proved in terms of the steady-state and transient performances, as well as the performance under the grid frequency deviation.

Best sensitivity of temporal modulation transfer functions in laboratory mice matches the amplitude modulation embedded in vocalizations.

The perception of spectrotemporal changes is crucial for distinguishing between acoustic signals, including vocalizations. Temporal modulation transfer functions (TMTFs) have been measured in many species and reveal that the discrimination of amplitude modulation suffers at rapid modulation frequencies. TMTFs were measured in six CBA/CaJ mice in an operant conditioning procedure, where mice were trained to discriminate an 800 ms amplitude modulated white noise target from a continuous noise background. TMTFs of mice show a bandpass characteristic, with an upper limit cutoff frequency of around 567 Hz. Within the measured modulation frequencies ranging from 5 Hz to 1280 Hz, the mice show a best sensitivity for amplitude modulation at around 160 Hz. To look for a possible parallel evolution between sound perception and production in living organisms, we also analyzed the components of amplitude modulations embedded in natural ultrasonic vocalizations (USVs) emitted by this strain. We found that the cutoff frequency of amplitude modulation in most of the individual USVs is around their most sensitive range obtained from the psychoacoustic experiments. Further analyses of the duration and modulation frequency ranges of USVs indicated that the broader the frequency ranges of amplitude modulation in natural USVs, the shorter the durations of the USVs.

Matching Analysis and Optimization Design of Energy-saving Intelligent Electro-hydraulic Hybrid Steering System

Based on the modeling of 2DOF vehicle, energysaving intelligent EHHS system and controller, the influence of different parameters on the vehicle steering performance is studied and then the most important parameters are determined. To establish the stability criteria, the road feeling and steering sensitivity transfer function are derived. Next, the optimization model is put forward, and the genetic algorithm is used to optimize the important parameters of EHHS system. The simulation results show that the optimization design improves the steering performance of the steering system while ensuring the stability of the system.

A Second-Order Dual Mode Repetitive Control for Magnetically Suspended Rotor

In magnetically suspended rotor (MSR) systems, harmonic current mainly originates from rotor mass imbalance and sensor runout, which can generate multifrequency vibration. Repetitive control (RC) is an effective method to eliminate periodic disturbance from a control system. Conventional RC (CRC) method requires the exact knowledge of the period of the periodic signal. However, in some applications, the period may fluctuate or may not be available with sufficient accuracy, in which case the performance of the CRC severely decays. Besides, the transient response of the CRC is relatively slow. In response to these issues, a second-order RC that incorporates dual mode structure scheme is presented in this paper. By introducing Lagrange-interpolation-based fractional delay filters, the current suppression accuracy gets enhanced in fractional cases. The stability criterion with rigorous proof for the proposed scheme is addressed. The sensitivity to period-time of the proposed scheme is analyzed as well, from the aspect of sensitivity transfer function. Simulation and experimental validations are performed on an MSR to show the effectiveness of the proposed approach.

Polarized glasses may help in symptomatic cases of intraocular lens glistenings.

Intraocular lens (IOL) glistening is a relatively common phenomenon. Although most of the patients remain asymptomatic, a small percentage of patients can develop unwanted optical side effects. We report 6 symptomatic patients with IOL glistening. All patients underwent an implantation of a hydrophobic acrylic mononofocal, multifocal or toric IOL in external clinics for visually significant cataract at least 6 months prior. Patients had very reasonable corrected visual acuity (0.8–1.0 decimal), but significantly had reduced contrast sensitivity and modulation transfer function, complained of visual phenomena and expressed dissatisfaction with their visual status. Patients indicated the symptoms were not present immediately after surgery, but gradually developed postoperatively. Slit-lamp examination revealed moderate-to-severe glistening in all cases. No other pathology that would be responsible for the visual symptoms was present. Patients reported improvement in side effects with the use of edge filter (blue-light blocking) eyeglasses and polarized sunglasses with an increase in contrast sensitivity by aproximately 1 line on Pelli–Robson chart. The use of specific eyewear seems to be a promising alternative to avoid explant of an IOL in symptomatic patients with glistenings and very good visual acuity. In conclusion, we believe that long-term optical clarity is crucial for the choice of an IOL.

Robust Attitude Control for Quadrotors Based on Parameter Optimization of a Nonlinear Disturbance Observer

This paper presents a nonlinear disturbance observer (NDOB) for active disturbance rejection in the attitude control loop for quadrotors. An optimization framework is developed for tuning the parameter in the NDOB structure, which includes the infinity-norm minimization of the weighted sum of noise-to-output transfer function and load disturbance sensitivity function. Subsequently, the minimization generates an optimal value of the parameter based on the tradeoff between disturbance rejection and noise propagation in the system. The proposed structure is implemented on PIXHAWK, a real-time embedded flight control unit. Simulation tests are carried out on a custom built, high-fidelity simulator providing physically accurate simulations. Furthermore, experimental flight tests are conducted to demonstrate the performance of the proposed approach. The system is injected with step, sinusoidal, and square wave disturbances, and the corresponding system tracking performance is recorded. Experimental results show that the proposed algorithm attenuates the disturbances better compared to just a baseline controller implementation. The proposed algorithm is computationally cheap, an active disturbance rejection technique and robust to exogenous disturbances.

CRELD1 is an evolutionarily-conserved maturational enhancer of ionotropic acetylcholine receptors.

The assembly of neurotransmitter receptors in the endoplasmic reticulum limits the number of receptors delivered to the plasma membrane, ultimately controlling neurotransmitter sensitivity and synaptic transfer function. In a forward genetic screen conducted in the nematode C. elegans, we identified crld-1 as a gene required for the synaptic expression of ionotropic acetylcholine receptors (AChR). We demonstrated that the CRLD-1A isoform is a membrane-associated ER-resident protein disulfide isomerase (PDI). It physically interacts with AChRs and promotes the assembly of AChR subunits in the ER. Mutations of Creld1, the human ortholog of crld-1a, are responsible for developmental cardiac defects. We showed that Creld1 knockdown in mouse muscle cells decreased surface expression of AChRs and that expression of mouse Creld1 in C. elegans rescued crld-1a mutant phenotypes. Altogether these results identify a novel and evolutionarily-conserved maturational enhancer of AChR biogenesis, which controls the abundance of functional receptors at the cell surface.

A Stretchable Array of Electronic Receptors for Esophageal Swallowing Robot for Biomimetic Simulations of Bolus Transport

This paper presents the design, fabrication, calibration, and implementation of a novel stretchable array of capacitive sensors that mimics human receptors for an esophageal swallowing robot. The array is used to measure deformation of the esophageal conduit wall and the interaction between food bolus and the esophagus in the form of pressure and shear stress, which is a novel in vitro method of food bolus transport study. It is constructed from a thin sheet of copper-polyimide laminate via a cost effective fabrication process involving photolithography, wet etching, and laser engraving technique. Calibration is conducted individually on the pressure, shear, and strain sensor elements of the array. The pressure, shear, and strain sensors response exhibit an average hysteresis of 10.17%, 11.78%, and 26.37% caused by the soft silicon rubber encapsulation. Linear regression technique is used to determine the linear sensitivity transfer function for all the three sensors. The array is embedded beneath the surface of the esophageal conduit of the swallowing robot and a series of swallowing experiments are conducted. Three types of food bolus with a viscosity of 0.18, 0.62, and $1.55~\text {Pa}\cdot \text {s}$ are prepared using a commercial food thickener. The swallowing robot generates a peristaltic wave of 60-mm wavefront length and 40- $\text {mm}\cdot \text {s}^{-1}$ wave speed to mimic the swallowing action seen in the human esophagus. Manometer measurements are taken alongside for validation. The pressure sensor records maximum pressures of 2.24, 3.17, and 7.74 kPa, respectively, for the three types of bolus during swallowing. By comparison, the maximum pressures recorded by the manometer are 1.68, 2.82, and 8.08 kPa. The shear sensor on the other hand records maximum shear values of −0.3, −0.35, and −0.37 kPa, respectively, for the three food bolus mixtures. This works prove that the novel stretchable array of capacitive sensors can be used to mimic mechanoreceptors for the esophageal swallowing robot, which significantly extends its capability to be used by food scientists as a platform for a new novel method of bolus transport study.

Novel proportional–integral–derivative controller with second order filter for integrating processes

AbstractMany chemical and nonchemical processes exhibit integrating behavior. This paper presents new approach for deriving parameters of proportional–integral–derivative controller for various types of integrating processes. In order to obtain enhanced performance, the controller is augmented by a second order filter. In the process of deriving controller and filter parameters, time delay is approximated by second order Laguerre shift. Analytical tuning rules are derived on the basis of the sensitivity of loop transfer function. With the help of polynomial method, the poles are placed so as to minimize the overshoot in the servo response. A set point filter is also employed to mitigate the overshoot and settling time in servo response. Besides, the set point filter is able to decouple servo and regulatory responses. The proposed method is compared with recently proposed methods. The evaluation is carried out in terms of various performance indices. Investigation of evaluation results reveals that the proposed method offers considerable improvement over the existing methods.

Dynamic behaviour of a planar micro-beam loaded by a fluid-gap: Analytical and numerical approach in a high frequency range, benchmark solutions

Miniaturized vibrating MEMS devices, active (receivers or emitters) or passive devices, and their use for either new applications (hearing, meta-materials, consumer devices,…) or metrological purposes under non-standard conditions, are involved today in several acoustic domains. More in-depth characterisation than the classical ones available until now are needed. In this context, the paper presents analytical and numerical approaches for describing the behaviour of three kinds of planar micro-beams of rectangular shape (suspended rigid or clamped elastic planar beam) loaded by a backing cavity or a fluid-gap, surrounded by very thin slits, and excited by an incident acoustic field. The analytical approach accounts for the coupling between the vibrating structure and the acoustic field in the backing cavity, the thermal and viscous diffusion processes in the boundary layers in the slits and the cavity, the modal behaviour for the vibrating structure, and the non-uniformity of the acoustic field in the backing cavity which is modelled in using an integral formulation with a suitable Green's function. Benchmark solutions are proposed in terms of beam motion (from which the sensitivity, input impedance, and pressure transfer function can be calculated). A numerical implementation (FEM) is handled against which the analytical results are tested.

An effective noise reduction method for multi-energy CT images that exploit spatio-spectral features.

To develop and evaluate an image-domain noise reduction method for multi-energy CT (MECT) data. Multi-Energy Non-Local Means (MENLM) is a technique that uses the redundant information in MECT images to achieve noise reduction. In this method, spatio-spectral features are used to determine the similarity between pixels, making the similarity evaluation more robust to image noise. The performance of this MENLM filter was tested on images acquired on a whole-body research photon counting CT system. The impact of filtering on image quality was quantitatively evaluated in phantom studies in terms of image noise level (standard deviation of pixel values), noise power spectrum (NPS), in-plane and cross-plane spatial resolution, CT number accuracy, material decomposition performance, and subjective low-contrast spatial resolution using the American College of Radiology (ACR) CT accreditation phantom. Clinical feasibility was assessed by performing MENLM on contrast-enhanced swine images and unenhanced cadaver head images using clinically relevant doses and dose rates. The phantom studies demonstrated that the MENLM filter reduced noise substantially and still preserved the shape and peak frequency of the NPS. With 80% noise reduction, MENLM filtering caused no degradation of high-contrast spatial resolution, as illustrated by the modulation transfer function (MTF) and slice sensitivity profile (SSP). CT number accuracy was also maintained for all energy channels, demonstrating that energy resolution was not affected by filtering. Material decomposition performance was improved with MENLM filtering. The subjective evaluation using the ACR phantom demonstrated an improvement in low-contrast performance. MENLM achieved effective noise reduction in both contrast-enhanced swine images and unenhanced cadaver head images, resulting in improved detection of subtle vascular structures and the differentiation of white/gray matter. In MECT, MENLM achieved around 80% noise reduction and greatly improved material decomposition performance and the detection of subtle anatomical/low-contrast features while maintaining spatial and energy resolution. MENLM filtering may improve diagnostic or functional analysis accuracy and facilitate radiation dose and contrast media reduction for MECT.