Resolution Performance Research Articles

Improving cognitive and physical function through 12-weeks of resistance training in older adults: Randomized controlled trial

ABSTRACT We performed a randomized, controlled trial to analyse the effects of resistance training (RT) on cognitive and physical function among older adults. Fifty participants (mean age 67 years, ~60% woman) were randomly assigned to an RT program or a control group. Participants allocated to RT performed three sets of 10-15RM in nine exercises, three times per week, for 12-weeks. Control group did not perform any exercise. Variables included cognitive (global and executive function) and physical function (gait, mobility and strength) outcomes. At completion of the intervention, RT was shown to have significantly mitigated the drop in selective attention and conflict resolution performance (Stroop test: -494.6; 95%CI: -883.1; −106.1) and promoted a significant improvement in working memory (digit span forward: -0.6; 95%CI: −1.0; −0.1 and forward minus backward: -0.9; 95% CI: −1.6; −0.2) and verbal fluency (animal naming: +1.4, 95%CI 0.3, 2.5). No significant between-group differences were observed for other cognitive outcomes. Regarding physical function, at completion of the intervention, the RT group demonstrated improved fast-pace gait performance (−0.3; 95% CI: −0.6; −0.0) and 1-RM (+21.4 kg; 95%CI: 16.6; 26.2). No significant between-group differences were observed for other mobility-related outcomes. In conclusion, RT improves cognitive and physical function of older adults.

Equitable optimized airspace sectorization based on constraint programming and OWA aggregation

PurposeAirspace sectorization is an important task, which has a significant impact in the everyday work of air control services. Especially in recent years, because of the constant increase in air traffic, existing airspace sectorization techniques have difficulties to tackle the large air traffic volumes, creating imbalanced sectors and uneven workload distribution among sectors. The purpose of this paper is to propose a new approach to find optimal airspace sectorization balancing the traffic controller workload between sectors, subject to airspace requirements.Design/methodology/approachA constraint programming (CP) model called equitable airspace sectorization problem (EQASP) relies on ordered weighted averaging (OWA) multiagent optimization and the parallel portfolio architecture has been developed, which integrates the equity into an existing CP approach (Trandac et al., 2005). The EQASP was evaluated and compared with the method of Trandac et al. (2005), according to the quality of workload balancing between sectors and the resolution performance. The comparison was achieved using real air traffic low-altitude network data sets of French airspace for five flight information regions for 24 h a day and the Algerian airspace for three various periods (off peak hours, peak hours and 24 h).FindingsIt has been demonstrated that the proposed EQASP model, which is based on OWA multicriteria optimization method, significantly improved both the solving performance and the workload equity between sectors, while offering strong theoretical properties of the balancing requirement. Interestingly, when solving hard instances, our parallel sectorization tool can provide, at any time, a workable solution, which satisfies all geometric constraints of sectorization.Practical implicationsThis study can be used to design well-balanced air sectors in terms of workload between control units in the strategic phase. To fulfil the airspace users’ constraints, one can refer to this study to assess the capacity of each air sector (especially the overloaded sectors) and then adjust the sector’s shape to respond to the dynamic changes in traffic patterns.Social implicationsThis theoretical and practical approach enables the development and support of the definition of the “Air traffic management (ATM) Concept Target” through improvements in human factors specifically (balancing workload across sectors), which contributes to raising the level of capacity, safety and efficiency (SESAR Vision of ATM 2035).Originality/valueIn their approach, the authors proposed an OWA-based multiagent optimization model, ensuring the search for the best equitable solution, without requiring user-defined balancing constraints, which enforce each sector to have a workload between two user-defined bounds (Wmin, Wmax).

Sensory augmentation to aid training with retinal prostheses

Objective. Retinal prosthesis recipients require rehabilitative training to learn the non-intuitive nature of prosthetic ‘phosphene vision’. This study investigated whether the addition of auditory cues, using The vOICe sensory substitution device (SSD), could improve functional performance with simulated phosphene vision. Approach. Forty normally sighted subjects completed two visual tasks under three conditions. The phosphene condition converted the image to simulated phosphenes displayed on a virtual reality headset. The SSD condition provided auditory information via stereo headphones, translating the image into sound. Horizontal information was encoded as stereo timing differences between ears, vertical information as pitch, and pixel intensity as audio intensity. The third condition combined phosphenes and SSD. Tasks comprised light localisation from the Basic Assessment of Light and Motion (BaLM) and the Tumbling-E from the Freiburg Acuity and Contrast Test (FrACT). To examine learning effects, twenty of the forty subjects received SSD training prior to assessment. Main results. Combining phosphenes with auditory SSD provided better light localisation accuracy than either phosphenes or SSD alone, suggesting a compound benefit of integrating modalities. Although response times for SSD-only were significantly longer than all other conditions, combined condition response times were as fast as phosphene-only, highlighting that audio-visual integration provided both response time and accuracy benefits. Prior SSD training provided a benefit to localisation accuracy and speed in SSD-only (as expected) and Combined conditions compared to untrained SSD-only. Integration of the two modalities did not improve spatial resolution task performance, with resolution limited to that of the higher resolution modality (SSD). Significance. Combining phosphene (visual) and SSD (auditory) modalities was effective even without SSD training and led to an improvement in light localisation accuracy and response times. Spatial resolution performance was dominated by auditory SSD. The results suggest there may be a benefit to including auditory cues when training vision prosthesis recipients.

Dispersive solid-phase extraction of racemic drugs using chiral ionic liquid-metal-organic framework composite sorbent.

Nowadays, enantioseparation of racemic pharmaceuticals in preparations is a prime concern by drug authorities across the globe. In the present work, it was attempted to develop novel enantioselective extraction method for five clinicallyused drugs (atenolol, propranolol, metoprolol, racecadotril, and raceanisodamine in their tablets) as racemates. The enantioselective solid-liquid extraction of these racemic drugs was carried out successfully by the use of chiral ionic liquid (CIL) in combination with a metal organic framework (MOF) for the first time. The composite CIL@MOF was synthesized from tropine based chiral ionic liquids with L-proline anion ([CnTr][L-Pro], n=3-6) and HKUST-1 type MOF, which was comprehensively characterized before being used as sorbent for enantioselective dispersive solid-liquid extraction. Preliminary selection of appropriate CIL was carried out on thin layer chromatography (TLC); under the joint participation of copper ion in the developing reagent, [C3Tr][L-Pro] ionic liquid showed better resolution performance with ΔRf value of 0.35 between the enantiomers was obtained for racemic atenolol. Moreover, the effect of copper salt dosage, amount of CIL, soli-liquid ratio and extraction time were investigated. The optimal conditions were obtained after thorough investigations; i.e. sample solution: ethanol, elution solvent: methanol, solid-liquid ratio: 12.5 mg:50 mL, amount of copper salt: 8 mg L-1, amount of impregnated CIL: 30% and extraction time of 30 min. As a result, enantiomeric excess values are 90.4%, 95%, 92%, 81.6% and 83.2% for atenolol, propranolol, metoprolol, racecadotril and raceanisodamine, respectively. The developed enantioselective method was validated following ICH guidelines and it was proved to be simple, effective and enantioselective way for separation of racemic pharmaceuticals with similar behaviors.

Study on the improvement of the 20-inch microchannel plate photomultiplier tubes for neutrino detector

The 20-inch MCP-PMT employs microchannel plates (MCP) as the electron multiplier unlike the traditional photomultiplier tubes (PMTs) with the dynode structure. According to the performance requirements for 20-inch PMTs to be used in the Hyper-Kamiokande (Hyper-K) project, North Night Vision Technology Co., Ltd. (NNVT) developed a novel 20-inch MCP-PMT based on the modification of the 20-inch MCP-PMT used for the Jiangmen Underground Neutrino Observatory by optimizing the design of the focusing electrode structure, the fabrication of the photocathode, and the other processes. The performance of the new NNVT 20-inch MCP-PMTs was evaluated and compared with respect to time resolution and noise. It was found that the transit time spread of the novel type is lower than 4 ns and the dark count rate is lower than 15 kHz. Compared to the previous model, the novel 20-inch MCP-PMT presents enhanced performance for time resolution and noise that is promising for its use in high-energy physics applications such as neutrino detection.

Unequal‐weighted TCAR algorithm for long‐baseline static triple‐frequency ambiguity resolution

On account of the different parameters of delay-locked loop, multipath effect and code bandwidth, the Global Navigation Satellite System (GNSS) pseudorange noise of each frequency is different. An unequal-weighted three-carrier ambiguity resolution (TCAR) algorithm for long-baseline static triple-frequency ambiguity resolution is proposed. The algorithm is conducted in cascaded steps. When calculating the coefficients of the extra-wide-lane (EWL), wide-lane (WL) and narrow-lane (NL) combinations, the difference of pseudorange noise is considered. Real triple-frequency BeiDou Navigation Satellite System and Global Positioning System observations from four International GNSS Service stations from 13 January to 19 January 2019 are analysed to evaluate the performance of the proposed algorithm. Results show that compared to the classical equal-weighted algorithm, the proposed algorithm shows a comparable performance for the EWL and WL ambiguity resolution and much better performance for the NL ambiguity resolution.

Optimization-Based Autonomous Air Traffic Control for Airspace Capacity Improvement

In order to handle increasing demand in air transportation, high-level automation support seems inevitable. This article presents an optimization-based autonomous air traffic control (ATC) system and the determination of airspace capacity with respect to the proposed system. We model aircraft dynamics and guidance procedures for simulation of aircraft motion and trajectory prediction. The predicted trajectories are used during decision process and simulation of aircraft motion is the key factor to create a traffic environment for estimation of airspace capacity. We define the interventions of an air traffic controller (ATCo) as a set of maneuvers that is appropriate for real air traffic operations. The decision process of the designed ATC system is based on integer linear programming (ILP) constructed via a mapping process that contains discretization of the airspace with predicted trajectories to improve the time performance of conflict detection and resolution. We also present a procedure to estimate the airspace capacity with the proposed ATC system. This procedure consists of constructing a stochastic traffic simulation environment that includes the structure of the evaluated airspace. The approach is validated on real air traffic data for enroute airspace, and it is also shown that the designed ATC system can manage traffic much denser than current traffic.

Performance analysis of ambiguity resolution on PPP and relative positioning techniques: consideration of satellite geometry

Ambiguity resolution plays an important role in surveying using Precise Point Positioning (PPP) and relative positioning techniques that require high accuracy. In this study, ambiguity resolution performance of PPP and relative positioning under the unobstructed (with 7° cut-off angle) and constrained environment (with 25° cut-off angle, such as nearby buildings and street-canyons) using final/ultra-rapid orbit and clock products are investigated for different observation time. Seventeen globally distributed stations and six baselines of lengths from 270 km to 2100 km are chosen for conducting PPP and relative positioning, respectively. A 31-day period in January 2018 is chosen for processing using 24-, 12-, 6-, 4-, 2- and 1-h observations. The results indicate that sub-mm to cm levels of improvement in horizontal and vertical coordinate components are generally observed with ambiguity resolution for PPP and relative positioning techniques compared to the float counterparts. Moreover, accuracy degradation of ambiguity resolution compared to float solution is observed generally in the vertical component using the 25° elevation cut-off angle for both techniques. As the observation time increases, the accuracy improvements from ambiguity resolution decrease for each technique. In addition, fixing to the wrong integer ambiguities are generally seen with a short observation time and a 25° elevation cut-off angle for both techniques due to the poor satellite geometry. As far as baseline length in relative technique is concerned, the testing results show that there is no direct relation between baseline length and the accuracy improvement from ambiguity resolution compared to the float solution. The results also reveal that the coordinates obtained from ambiguity resolution does not significantly change in the relative technique using final or ultra-rapid orbit/clock products, whereas the changes in PPP are significant for most of the stations.

Temporal Processing and Speech Perception Performance in Postlingual Adult Users of Cochlear Implants.

Cochlear implant (CI) listeners had some hearing problems, including catching clues from speech context, persist, particularly in complex listening environments. Among these hearing problems, temporal resolution is considered to be one of the most affected aspects of hearing. The aim of the study is to assess and compare the temporal resolution ability of CI users and individuals with normal hearing using the Gaps-in-Noise (GIN) test. This study also aims to investigate whether there are any differences in speech recognition and temporal resolution performance between groups separated according to the implanted ear, gender, CI type, or sound processor strategies. Case-control study. 18 adults (9 males, 9 females) with normal hearing, ranging in age between 18 and 55 years (mean: 30.64 ± 8.59 years) and 18 postlingual adults (10 males, 8 females) with bilateral CIs ranging in age between 19 and 59 years (mean: 36.64 ± 16.59 years) were included in the current study. Hearing thresholds, word recognition scores (WRS), and GIN test were conducted for each participant. Two parameters of GIN test were determined: the GIN threshold and total percentage score (TPS). Mann-Whitney U test was used to test the significance of the differences between the groups in terms of GIN threshold, WRS, and TPS. CI group showed significantly (p < 0.001) poorer performance in terms of WRS than normal hearing group. However there were no significant differences in WRS between groups which were divided according to the implanted ear, gender, CI type, and sound processor strategies. The mean GIN threshold was 3.33 ± 1.2 msec, whereas it was 9.56 ± 3.49 msec in CI users. Moreover the mean value of TPS was 90.77% in the normal group and 47.22% in the CI group. These differences between the two groups were also found statistically significant (p < 0.001). Our results show that CI users do not discriminate GIN as well as normal-hearing individuals, although their hearing levels with CIs are very close to normal hearing limits at all frequencies.

Indocyanine green matching phantom for fluorescence-guided surgery imaging system characterization and performance assessment

.Significance: Expanded use of fluorescence-guided surgery with devices approved for use with indocyanine green (ICG) has led to a range of commercial systems available. There is a compelling need to be able to independently characterize system performance and allow for cross-system comparisons.Aim: The goal of this work is to expand on previous proposed fluorescence imaging standard designs to develop a long-term stable phantom that spectrally matches ICG characteristics and utilizes 3D printing technology for incorporating tissue-equivalent materials.Approach: A batch of test targets was created to assess ICG concentration sensitivity in the 0.3- to 1000-nM range, tissue-equivalent depth sensitivity down to 6 mm, and spatial resolution with a USAF test chart. Comparisons were completed with a range of systems that have significantly different imaging capabilities and applications, including the Li-Cor® Odyssey, Li-Cor® Pearl, PerkinElmer® Solaris, and Stryker® Spy Elite.Results: Imaging of the ICG-matching phantoms with all four commercially available systems showed the ability to benchmark system performance and allow for cross-system comparisons. The fluorescence tests were able to assess differences in the detectable concentrations of ICG with sensitivity differences >10× for preclinical and clinical systems. Furthermore, the tests successfully assessed system differences in the depth-signal decay rate, as well as resolution performance and image artifacts. The manufacturing variations, photostability, and mechanical design of the tests showed promise in providing long-term stable standards for fluorescence imaging.Conclusions: The presented ICG-matching phantom provides a major step toward standardizing performance characterization and cross-system comparisons for devices approved for use with ICG. The developed hybrid manufacturing platform can incorporate long-term stable fluorescing agents with 3D printed tissue-equivalent material. Further, long-term testing of the phantom and refinements to the manufacturing process are necessary for future implementation as a widely adopted fluorescence imaging standard.

Meteorological and Air Quality Modeling for Hawaii, Puerto Rico, and Virgin Islands.

A photochemical model platform for Hawaii, Puerto Rico, and Virgin Islands predicting O3, PM2.5, and regional haze would be useful to support assessments relevant for the National Ambient Air Quality Standards (NAAQS), Regional Haze Rule, and the Prevention of Significant Deterioration (PSD) program. These areas have not traditionally been modeled with photochemical transport models, but a reasonable representation of meteorology, emissions (natural and anthropogenic), chemistry, and deposition could support air quality management decisions in these areas. Here, a prognostic meteorological model (Weather Research and Forecasting) and photochemical transport (Community Multiscale Air Quality) model were applied for the entire year of 2016 at 27, 9, and 3 km grid resolution for areas covering the Hawaiian Islands and Puerto Rico/Virgin Islands. Model predictions were compared against surface and upper air meteorological and chemical measurements available in both areas. The vertical gradient of temperature, humidity, and winds in the troposphere was well represented. Surface layer meteorological model performance was spatially variable, but temperature tended to be underestimated in Hawaii. Chemically speciated daily average PM2.5 was generally well characterized by the modeling system at urban and rural monitors in Hawaii and Puerto Rico/Virgin Islands. Model performance was notably impacted by the wildfire emission methodology. Model performance was mixed for hourly SO2, NO2, PM2.5, and CO and was often related to how well local emissions sources were characterized. SO2 predictions were much lower than measurements at monitors near active volcanos on Hawaii, which was expected since volcanic emissions were not included in these model simulations. Further research is needed to assess emission inventory representation of these areas and how microscale meteorology influenced by the complex land-water and terrain interfaces impacts higher time resolution performance.

Ultra-high resolution and broadband chip-scale speckle enhanced Fourier-transform spectrometer.

Recent advancements in silicon photonics are enabling the development of chip-scale photonics devices for sensing and signal processing applications, among which on-chip spectrometers are of particular interest for precision wavelength monitoring and related applications. Most chip-scale spectrometers suffer from a resolution-bandwidth trade-off, thus limiting the uses of the device. Here we report on a novel passive, chip-scale, hybrid speckle-enhanced Fourier transform device that exhibits a two order-of-magnitude improvement in finesse (bandwidth/resolution) over the state-of-the art chip-scale speckle and Fourier transform spectrometers. In our proof-of-principle device, we demonstrate a spectral resolution of 140 MHz with 12-nm bandwidth for a finesse of 104 that can operate over a range of 1500-1600 nm. This chip-scale spectrometer structure implements a typical spatial heterodyne discrete Fourier transform interferometer network that is enhanced by speckle generated from the wafer substrate. This latter effect, which is extremely simple to invoke, superimposes the high wavelength resolution intrinsic to speckle generated from a strongly guiding waveguide with a more broadband but lower resolution discrete Fourier transform modality of the overarching waveguide structure. This hybrid approach signifies a new pathway for realizing chip-scale spectrometers capable of ultra-high resolution and broadband performance.

An Iterative Deconvolution-Time Reversal Method with Noise Reduction, a High Resolution and Sidelobe Suppression for Active Sonar in Shallow Water Environments

Matched filtering is widely used in active sonar because of its simplicity and ease of implementation. However, the resolution performance generally depends on the transmitted waveform. Moreover, its detection performance is limited by the high-level sidelobes and seriously degraded in a shallow water environment due to time spread induced by multipath propagation. This paper proposed a method named iterative deconvolution-time reversal (ID-TR), on which the energy of the cross-ambiguity function is modeled, as a convolution of the energy of the auto-ambiguity function of the transmitted signal with the generalized target reflectivity density. Similarly, the generalized target reflectivity density is a convolution of the spread function of channel with the reflectivity density of target as well. The ambiguity caused by the transmitted signal and the spread function of channel are removed by Richardson-Lucy iterative deconvolution and the time reversal processing, respectively. Moreover, this is a special case of the Richardson-Lucy algorithm that the blur function is one-dimensional and time-invariant. Therefore, the iteration deconvolution is actually implemented by the iterative temporal time reversal processing. Due to the iterative time reversal method can focus more and more energy on the strongest target with the iterative number increasing and then the peak-signal power increases, the simulated result shows that the noise reduction can achieve 250 dB in the “ideal” free field environment and 100 dB in a strong multipaths waveguide environment if a 1-ms linear frequency modulation with a 4-kHz frequency bandwidth is transmitted and the number of iteration is 10. Moreover, the range resolution is approximately a delta function. The results of the experiment in a tank show that the noise level is suppressed by more than 70 dB and the reverberation level is suppressed by 3 dB in the case of a single target and the iteration number being 8.

Design considerations for advanced MWIR target acquisition systems.

In this paper, mid-wave infrared (MWIR) sensor optimization is provided as a function of the parameter Fλ/d, where F is the f-number, λ is the effective wavelength, and d is the detector pitch. For diffraction limited systems, acquisition range is related to the instantaneous field of view (detector limited operation) when Fλ/d<1, and to the optical properties (optics limited operation) when Fλ/d>2.0. Range performance is a combination of detector and optics resolution limits when Fλ/d is in between. When the system is not strictly diffraction or sampling limited, the optimal Fλ/d depends on other system component characteristics and conditions. Optical system aberrations affect system resolution and decrease range performance. As background shot noise, dark current shot noise, and read noise increase, range decreases. In the infrared spectral region, atmospheric absorption leads to reemission of thermal energy. The detected reemission creates additional shot noise. Atmospheric attenuation greatly affects MWIR sensor range performance. Next-generation MWIR sensors will have smaller detectors, larger arrays, and better sensitivity to enable Fλ/d-based optimization. Previous studies (ΔT=4K for tracked vehicles) suggest that an initial design point is Fλ/d≈2.0. When detecting low contrast targets (ΔT∼0.1K), sensor gain is used to increase the signal for a desired displayed contrast. This gain increases displayed noise and reduces acquisition range. This is typically not an issue for long-wave infrared sensors due to the excess number of photons in the 8-12 µm band but poses a problem for MWIR sensors, which are photon starved. Under such scenarios, the optimum Fλ/d appears to be about 1.5 for MWIR sensors. The results here provide reasonable strategies for MWIR system optimization and a direction associated with future MWIR focal plane development.

Parametric localisation in frequency diverse array

The authors present a non-traditional, parametric method for velocity, angle, and range estimation in a frequency diverse array radar. Unlike the traditional beamforming techniques, the proposed scheme transmits an omni-directional sinusoid regardless of the target locations. They propose a simple sampling strategy, which eliminates the need for employing a bank of bandpass filters at the receiver. Under the proposed sampling scheme the received data follows a convenient low rank model. They exploit this model to design a fast and accurate parametric estimation algorithm. Their velocity and range estimation steps employ known spectral analysis techniques. For angle estimation, they propose a new grid-less sparse recovery algorithm. The resulting methods are applicable to any arbitrary array geometry. Furthermore, they propose an efficient method to mitigate jamming. They also provide necessary guidelines to avoid ambiguity and achieve the desired resolution performance. The Cramer-Rao lower bound for the estimation problem is derived. The utility of the proposed method is demonstrated via numerical simulation results.

Super-resolved water/fat image reconstruction based on single-shot spatiotemporally encoded MRI

Single-shot spatiotemporally encoded (SPEN) MRI has been validated to possess considerable performance in both spatial and temporal resolution. Water/fat separation is essential for MRI applications in which only water signal is needed. In this article, a super-resolved water/fat image reconstruction method (dubbed SWAF) combined prior knowledge was developed based on single-shot SPEN MRI. The point spread function of spatiotemporal encoding under multiple chemical shifts situation was derived and used for constructing an equation for SWAF image reconstruction. By processing the prior chemical shift information with filtering operation, an initial spin density profile of water/fat and a weighting matrix for water/fat residual artifacts suppression were obtained to guide the reconstruction process. A l1 norm minimization problem with regularization was exploited to reconstruct separated water/fat images with high spatial resolution and less residual/aliasing artifacts. Numeric simulation and experiments on water–oil phantom and rat abdomen/neck imaging demonstrated the effectiveness and robustness of this new method. The SWAF method proposed herein would promote the application of SPEN MRI in the cases where water/fat separation is required.

The comparison of high-resolution diffusion weighted imaging (DWI) with high-resolution contrast-enhanced MRI in the evaluation of breast cancers

PurposeWe sought to investigate the performance of high resolution (HR) diffusion-weighted imaging (DWI) using readout-segmented echo-planar imaging (rs-EPI), compared with high-resolution contrast-enhanced MRI (HR CE-MRI) in terms of morphological accuracy, on the basis of the Breast Imaging and Reporting and Data System (BI-RADS) MRI descriptors and lesion size. MethodsThis retrospective study included the image data of 94 patients with surgically confirmed malignant breast lesions who had undergone high resolution diffusion-weighted imaging (HR-DWI) and HR CE-MRI. Two radiologists blinded to the final diagnosis independently identified the lesions on HR-DWI, described the morphology of the lesions according to BI-RADS descriptors, and measured lesion size. HR CE-MRI was subsequently evaluated using the same procedure. The inter-method agreement of the morphology was assessed using kappa statistics. Correlation on size was also assessed. ResultsReader A detected 79 mass lesions and 37 non-mass lesions on HR-DWI and HR CE-MRI. Reader B detected 81 mass lesions and 33 non-mass lesions on HR-DWI and HR CE-MRI. Very high agreement (kappa = 0.81–0.89, p < .05) was observed in the shape and margin assessment of mass lesions, where agreement on internal enhancement/signals was moderate to substantial (kappa = 0.43–0.61, p < .05). Disagreement was mostly seen in the evaluation of rim enhancement. High agreement was observed for non-mass lesion distribution (kappa = 0.76–0.84, p < .05), and agreement on internal enhancement/signals was moderate to fair (kappa = 0.34–0.49, p < .05). Agreement among heterogeneous, clumped, and clustered-ring patterns was variable. Size assessment showed very strong correlation both in mass (Spearman's rho = 0.90–0.96, p < .0001) and non-mass lesions (Spearman's rho = 0.86, p < .0001). ConclusionsThe findings in morphology and lesion extent showed high agreement between HR-DWI and HR CE-MRI for malignant breast lesions. These results imply the potential of applying HR-DWI for evaluation of malignant breast lesions using BI-RADS MRI.

3D MTF estimation using sphere phantoms for cone-beam computed tomography systems.

For cone-beam computed tomography (CBCT) systems, we propose a sphere phantom based method to estimate the full three-dimensional (3D) modulation transfer function (MTF). The FDK reconstruction of CBCT system in a local region was modeled by a triple convolution operator. Afterward, we calculated the directional projections of ideal and reconstructed sphere phantoms into a two-dimensional (2D) plane for multiple views. To estimate the projected 3D point spread function (PSF), we applied the 2D Richardson-Lucy deconvolution with Tikhonov-Miller (RL-TM). After estimating the projected 3D PSF from multiple views, the full 3D PSF was estimated by performing filtered backprojection. Then, the full 3D MTF was calculated by taking the modulus of the Fourier transform of the estimated 3D PSF. To validate the proposed method, we reconstructed sphere phantoms from simulation and experiment data. We simulated ideal 3D MTFs and compared them with the estimated 3D MTFs along the -, -, and -directions. The full-width at half-maximum (FWHM) and full-width at tenth-maximum (FWTM) values were compared between ideal and estimated 3D MTFs. The estimated 3D MTFs from both the simulation and experiment results show qualitative similarity in their shapes with the ideal 3D MTFs; FWHM and FWTM results quantitatively show that the proposed method provides reliable estimation performance. In particular, the estimated 3D MTF in a missing cone region was correctly matched with the corresponding ideal 3D MTF. In this work, we proposed a full 3D MTF estimation method for CBCT systems. Based on the results, we believe that the proposed method can be used to evaluate the spatial resolution performance of CBCT systems.

A Comparison of Linear Inverse Scattering Models for Contactless GPR Imaging

Ground-penetrating radars operating at a stand-off distance from the probed domain are attractive diagnostic tools in several contexts. Despite notable advantages offered in terms of noninvasiveness and flexibility, the usage of stand-off configurations makes the imaging process more difficult. Indeed, an accurate reconstruction of the subsurface/hidden scene requires accounting for the presence of the air–soil interface into the scattering model. This article deals with a comparison of three different linear models for describing the scattering phenomenon under a stand-off configuration, where the presence of the layered medium is explicitly accounted for in the scattering model. The first model is rigorous and based on the spectral domain representation of the incident field and Green’s function for the half-space scenario. The second model exploits a ray representation of the wave propagation from the radar to the target and vice versa by accounting for the refraction phenomenon at the interface. The third model is an approximated one, where the layered nature of the scenario is taken into account by means of an equivalent wavenumber, which allows a straightforward evaluation of the incident field and Green’s function. The resolution performance of each inversion approach is assessed by means of a numerical analysis. Moreover, data referred to an experiment carried out in controlled conditions are processed and reconstructions are provided to support the comparative analysis among the three imaging approaches.

Conflict Aftermath: Dispute Resolution and Financial Performance in Franchising

Franchisor–franchisee relationships entail frequent disputes, some of which escalate to litigation. Yet, the filing of litigation does not represent the end of conflict management. Firms can still choose to de-escalate conflicts after the filing of litigation by choosing alternative dispute resolution (ADR) mechanisms. To date, the impact of post-litigation dispute resolution mechanisms on franchise systems’ financial performance has not been studied in the extant literature. This study investigates the impact of franchisor- versus franchisee-initiated litigations, individually and jointly with dispute resolution mechanisms and franchise statutory regimes (i.e., relationship law and registration law), on franchise system performance. To address these research questions, a longitudinal study of actual conflict episodes based on objective accounts of dispute initiation, resolution, and corresponding outcomes was conducted. Theoretical contributions to the distribution channels conflict management literature and managerial implications for the franchise industry are offered.