Cosine Pattern Research Articles

Efficient and Flexible Long-Tail Recommendation Using Cosine Patterns

With the increasing use of recommender systems in various application domains, many algorithms have been proposed for improving the accuracy of recommendations. Among various dimensions of recommender systems performance, long-tail (niche) recommendation performance remains an important challenge in large part because of the popularity bias of many existing recommendation techniques. In this study, we propose CORE, a cosine pattern–based technique, for effective long-tail recommendation. Comprehensive experimental results compare the proposed approach with a wide variety of classic, widely used recommendation algorithms and demonstrate its practical benefits in accuracy, flexibility, and scalability in addition to the superior long-tail recommendation performance. 1 History: Accepted by Ramaswamy Ramesh, Area Editor for Data Science & Machine Learning. Funding: This work was supported by the National Natural Science Foundation of China [Grants 72031001, 72072091, 72242101]. Supplemental Material: The software that supports the findings of this study is available within the paper and its Supplemental Information ( https://pubsonline.informs.org/doi/suppl/10.1287/ijoc.2022.0194 ) as well as from the IJOC GitHub software repository ( https://github.com/INFORMSJoC/2022.0194 ). The complete IJOC Software and Data Repository is available at https://informsjoc.github.io/ .

Two-dimensional (2D) axis-pin force sensor and its characterization on the shear force direction

The characterization of the shear force direction is an imperative technical problem to be solved for the axis-pin force sensor. In the present work, a two-dimensional axis-pin force sensor has been designed. The layout of the sensor is to open horizontal blind holes and vertical blind holes at intervals of 90 degrees along the circular direction on the surface of the axis-pin. Then the variation law of the circumferential strain of blind holes along with the shear force direction is first studied through the FEA simulation. It is found that the sum of the circumferential strains of two horizontal blind holes or vertical blind holes varies in sine and cosine pattern with the shear force direction. On this basis, the mathematical model of shear force direction characterized by circumferential strains of blind holes is derived. Eventually, the prototype of the axis-pin force sensor was made to verify this law. The experimental results showed that the accuracy of the shear force and direction measured by the sensor can reach ± 8% and ± 5% respectively, which meet the requirements of the practical application. This method eliminates the theoretical error caused by the use of correction coefficients and nonlinear model approximation, which provides a theoretical basis for the development of two-dimensional axis-pin force sensors.

Photon-noise: is a single-pixel camera better than point scanning? A signal-to-noise ratio analysis for Hadamard and Cosine positive modulation

In a single-pixel camera, an unknown object is sequentially illuminated by intensity patterns. The total reflected or transmitted intensity is summed in a single-pixel detector from which the object is computationally reconstructed. In the situation where the measurements are limited by photon-noise, it is questionable whether a single-pixel camera performs better or worse than simply scanning the object with a focused intensity spot—a modality known as point raster scanning and employed in many laser scanning systems. Here, we solve this general question and report that positive intensity modulation based on Hadamard or Cosine patterns does not necessarily improve the single-to-noise ratio (SNR) of single-pixel cameras, as compared to point raster scanning (RS). Instead, we show that the SNR is only improved on object pixels at least k times brighter than the object mean signal , where k is a constant that depends on the modulation scheme (modulation matrix, number of detectors, etc). The constant k is derived for several widespread cases and has important consequences on the choice of the optical deign. This fundamental property is demonstrated theoretically, numerically, and is experimentally confirmed in the spatial domain (widefield fluorescence imaging) and in the spectral domain (spontaneous Raman spectral measurements). Finally, we provide user-oriented guidelines that help decide when and how multiplexing under photon-noise should be used instead of point RS.

Effect of Waveguide Aperture and Distance on Microwave Treatment Performance in Rock Excavation.

Rock burst is a common hazard during tunnel excavation in high-stress and hard rock strata. Microwave-assisted breaking has a great potential application in hard rock tunnel excavation, reducing the possibility of rock burst, and how to reasonably make the application on the TBM cutterhead is one of the critical issues. The waveguide aperture and distance between the rock face and waveguide have serious effects on its performance. In this paper, based on the arrangement of the microwave waveguide of the TBM cutterhead and the actual excavation situation, considering the reflection of microwave energy by the metal cutterhead and the scattering state of electromagnetic waves at the rock surface irradiation, a 2D model of rock irradiated by microwaves is established. The effects of waveguide aperture and distance on microwave irradiation performance of rock are studied, considering three different waveguide types: convergent waveguide, rectangular waveguide, and horn waveguide. The results show that the maximum temperature is located on the rock irradiation surface, rather than inside the rock. The rock temperature decreases in a cosine pattern with irradiation distance, rather than in linearity, which is consistent with the characteristics of electromagnetic wave propagation. The interval of irradiation distance where the rock temperature local maximum value appears is 1/4 of the electromagnetic wavelength, corresponding to the crest and trough of the electromagnetic wave. The rock temperature at the wave trough distance is lower than that of the wave crest distance, but the high-temperature zone is wider. In the range of 50~200 mm waveguide apertures, the rock temperature and damage decrease with the increase in waveguide aperture when irradiated at the crest distance, while the valley distance is opposite. A convergent waveguide and short irradiation distance enhance the energy focusing performance, so the temperature rise characteristics and rock damage are more concentrated. A large-waveguide-aperture horn waveguide and long irradiation distance form a wide range of high-temperature zones and rock damages.

Machine-Learning-Inspired Workflow for Camera Calibration.

The performance of modern digital cameras approaches physical limits and enables high-precision measurements in optical metrology and in computer vision. All camera-assisted geometrical measurements are fundamentally limited by the quality of camera calibration. Unfortunately, this procedure is often effectively considered a nuisance: calibration data are collected in a non-systematic way and lack quality specifications; imaging models are selected in an ad hoc fashion without proper justification; and calibration results are evaluated, interpreted, and reported inconsistently. We outline an (arguably more) systematic and metrologically sound approach to calibrating cameras and characterizing the calibration outcomes that is inspired by typical machine learning workflows and practical requirements of camera-based measurements. Combining standard calibration tools and the technique of active targets with phase-shifted cosine patterns, we demonstrate that the imaging geometry of a typical industrial camera can be characterized with sub-mm uncertainty up to distances of a few meters even with simple parametric models, while the quality of data and resulting parameters can be known and controlled at all stages.

A Novel Hybrid Sine Cosine Algorithm and Pattern Search for Optimal Coordination of Power System Damping Controllers

This paper presents an effective hybrid optimization technique based on a chaotic sine cosine algorithm (CSCA) and pattern search (PS) for the coordinated design of power system stabilizers (PSSs) and static VAR compensator (SVC)-based controllers. For this purpose, the design problem is considered as an optimization problem whose decision variables are the controllers’ parameters. Due to the nonlinearities of large, interconnected power systems, methods capable of handling any nonlinearity of power networks are preferable. In this regard, a nonlinear time domain-based objective function was used. Then, the proposed hybrid chaotic sine cosine pattern search (hCSC-PS) algorithm was employed for solving this optimization problem. The proposed method employed the global search ability of SCA and the local search ability of PS. The performance of the new hCSC-PS was investigated using a set of benchmark functions, and then the results were compared with those of the standard SCA and some other methods from the literature. In addition, a case study from the literature is considered to evaluate the efficiency of the proposed hCSC-PS for the coordinated design of controllers in the power system. PSSs and additional SVC controllers are being considered to demonstrate the feasibility of the new technique. In order to ensure the robustness and performance of the proposed controller, the objective function is evaluated for various extreme loading conditions and system configurations. The numerical investigations show that the new approach may provide better optimal damping and outperforms previous methods. Nonlinear time-domain simulation shows the superiority of the proposed controller and its ability in providing efficient damping of electromechanical oscillations.

Effects of new methods of porosity arrangement on forced convection in a variable BDPM using numerical simulation

In this study, forced convection the heat generation components by cooling porous elements has been investigated using BDPM method. A developed code under FVM and Simple Algorithm is used for numerical simulation. Air is selected as the working fluid with Pr = 0.7 in the laminar state. Effects of variable permeability distribution was investigated by changing the permeability in each column of porous blocks in increasing, decreasing, sinusoidal, and cosine patterns. In addition, the influences of average Darcy number and Darcy domain alterations of the porous blocks has been simulated. Sinusoidal pattern has the largest system performance under Re = 400–1000. In comparison with constant pattern, system performance has increased up to 9.5 times for sinusoidal pattern. Likewise, heat transfer in variable pattern is greater than constant one. The effects of variable pattern become more evident by changing average Darcy number since Darcy reaches 10−3, which will optimize heat transfer and system performance. Based on Darcy domain changes in the columns, it could be found that Darcy domain also affects heat transfer and pressure drop. These changes in Darcy domain can increase the system performance up to about 2.2 times.

Link communities detection: an embedding method on the line hypergraph

Recent advances have verified ground-truth communities perceive several characteristics. That is, communities are overlapped and densely connected. Not only that, the organization of communities, in a general sense, is hierarchical. To capture all of these characteristics, we propose a framework based on link embedding method. Firstly, we define close-knit link groups which preserve the hierarchical structures and carefully transform the problem of mining close-knit link groups as mining cosine patterns which can be implemented efficiently. Secondly, we construct the weighted line hypergraph and embed each link into a low dimension vector. Finally, we simply employ K-means algorithm to obtain the link communities. Overlapping structures are naturally obtained by interpreting the link communities as nodes communities. Experimental results on three real-world networks demonstrate the proposed approach is able to identify much higher-quality overlapping communities in terms of four external measures, compared with six classical overlapping community detection methods.

Spotting review spammer groups: A cosine pattern and network based method

SummaryNowadays, online product reviews strongly influence the purchase decision of consumers in e‐commerce platforms. Driven by the immense financial profits, review spammers deliberately post fake reviews to promote or demote their target products. Some spammers are even organized as groups to work together and try to take total control of the sentiment on their target products. To detect such spammer groups, most previous works exploit frequent itemset mining (FIM) to find spammer group candidates and then use unsupervised spamicity ranking methods to identify real spammer groups. However, these methods usually suffer from the problem of threshold setting, ie, high support value finding fewer groups while low support value leading to more coincidentally generated groups and computational inefficiency. Moreover, the unsupervised methods are not able to make good use of labeled instances which are actually obtainable in practice. In this paper, we propose CONSGD, a cosine pattern and heterogeneous information network–based spammer group detecting method. Specifically, the CONSGD uses cosine pattern mining (CPM) to discover tight spammer group candidates with a respective low support value, where the cosine threshold is utilized to avoid coincidentally generated groups. Moreover, CONSGD employs heterogeneous information network classification to identify the real spammer groups, which could utilize the labeled instances and do not rely to the assumption of independent instances. Experiments on real‐life dataset show that our proposed CONSGD is effective and outperforms the state‐of‐the‐art spammer group detection methods.

Psychomotor Vigilance Test and Its Association With Daytime Sleepiness and Inflammation in Sleep Apnea: Clinical Implications.

Excessive daytime sleepiness (EDS) is a key symptom of obstructive sleep apnea (OSA). The Psychomotor Vigilance Task (PVT) has been suggested as an objective easy-to-use, inexpensive alternative to the Multiple Sleep Latency Test (MSLT) to measure EDS. In patients with OSA, physiological sleepiness, but not subjective EDS (Epworth Sleepiness Scale [ESS]), has been associated with increased levels of the sleep- inducing proinflammatory cytokine interleukin-6 (IL-6). The goal of this study was to assess the association of PVT with objectively measured sleepiness (MSLT) and subjectively measured sleepiness (ESS) and IL-6 levels in patients with OSA. We studied 58 untreated patients with OSA who underwent an 8-hour in-laboratory polysomnography for 4 consecutive nights. MSLT, PVT, and 24-hour serial profiles of IL-6 were assessed on the fourth day. PVT variables included number of lapses, mean reciprocal of the fastest 10% and slowest 10% reaction times, and median of 1/reaction time. ESS was assessed on day 1 of the study. Higher ESS scores were significantly associated with greater number of lapses (β = .34, P = .02) and lower values of 1/RT (β = -.36, P = .01) and slowest 10% RTs (β = -.30, P = .04). No significant association was observed between PVT and MSLT, nor PVT and IL-6 levels. Our findings suggest that PVT is associated with subjectively assessed daytime sleepiness, but not with physiological sleepiness nor IL-6 levels in patients with OSA. It appears that ESS and PVT may be useful in predicting risks associated with impaired performance, such as traffic accidents, in patients with OSA.

Stroboscopic illumination for electronic speckle pattern interferometry

A common realization of holographic interferometry is called Electronic Speckle Pattern Interferometry (or ESPI)—a technique capable of measuring harmonic modes of vibrating objects. We present a method of improving the contrast and quality of fringe patterns recorded with a simple, table-top ESPI system. In particular, by using stroboscopic illumination generated by an optical chopper, we are able to produce fringes that follow a cosine pattern, rather than the Bessel pattern fringes that result from time averaging. Since Bessel function amplitudes rapidly decrease for subsequent maxima, the stroboscopic cosine fringes show much better contrast. Also, because the zeros of cosine fringes are evenly spaced, it is much simpler to interpret the images to extract quantitative deformation amplitudes. We show that our results agree well with the theoretical predictions. This system was developed for use in musical acoustics research as a Senior Thesis project by an undergraduate student (Gavin). This low-cost, simple modification of the commonly used ESPI system could benefit other colleges and universities using holographic interferometry for acoustics research.

Azimuthal anisotropy at Valhall: The Helmholtz equation approach

AbstractWe used 6 h of continuous vertical records from 2320 sensors of the Valhall Life of Fields Seismic network to compute 2,690,040 cross‐correlation functions between the full set of sensor pair combinations. We applied the “Helmholtz tomography” approach combined with the ambient noise correlation method to track the wave front across the network with every station considered as a virtual source. The gradient of the interpolated phase travel time gives us an estimate of the local phase speed and of the direction of wave propagation. By combining the individual measurements for every station, we estimated the distribution of Scholte's wave phase speeds with respect to azimuth. The observed cosine pattern indicates the presence of azimuthal anisotropy. The elliptic shape of the fast anisotropy direction is consistent with results of previous shear wave splitting studies and reflects the strong seafloor subsidence due to the hydrocarbon reservoir depletion at depth and is in good agreement with geomechanical modeling.

First demonstration of intrafractional tumor‐tracked irradiation using 2D phantom MR images on a prototype linac‐MR

To demonstrate intrafractional MR tumor tracking using a prototype linac-MR by delivering radiation to a moving target undergoing simulated tumor motions. A prototype linac-MR at the Cross Cancer Institute was used for intrafractional MR imaging and simultaneous beam delivery. A Varian 52-leaf MK-II multileaf collimator (MLC) was used for beam collimation. The authors used an inhouse built MR compatible motion phantom to simulate tumor motions during tracking with two different motion patterns (sine and modified cosine). Gafchromic film was inserted in the phantom to measure radiation exposure, and this film measurement was converted to dose (cGy) for further analysis. The authors demonstrated intrafractional tracking in various scenarios: [Scenario 0 (S0)] no phantom motion + no beam margin, (S1) no phantom motion + maximum beam margin, (S2) phantom motion + no beam margin, (S3) S2 + MLC tracking, and (S4) S3 + motion prediction. S0 emulates a perfect tumor tracking scenario, and its result was used as a "gold-standard" to evaluate tracking accuracy from other scenarios. The authors compared (1) time difference in phantom and MLC motion curves in S3 and S4, and (2) dose profiles (50% beam width, 80%-20% penumbra width) from scenarios S1-S4 to S0. In S4, no observable time difference exists between the phantom and MLC motion curves, indicating that MLC tracks phantom motion accurately. Comparing S4 to S0, 50% beam width reveals minimal differences of < 0.5 mm, while the increase in 80%-20% penumbra width is limited to 0.4 and 1.7 mm in the sine and modified cosine patterns, respectively. The authors report the first demonstration of intrafractional tumor tracking using 2D MR images. During 2 min of tracking, the authors delivered highly conformal dose to a moving target that simulates tumor motions. Compared to static target irradiation, the 50% beam width remains essentially the same (within 0.5 mm), with an increase in 80%-20% penumbra width of less than 1.7 mm in moving target irradiation. These results illustrate potential dosimetric advantages of intrafractional MR tumor tracking in treating mobile tumors as shown for the phantom case.

A New Technique for Obtaining Wide-Angular Nulling in the Sum and Difference Patterns of Monopulse Antenna

A simple technique for obtaining wide-angular nulling in the sum and difference patterns of the monopulse antenna is presented. This technique involves the addition of two elements, one at each end of the monopulse antenna array, which together produce a cosine pattern used for obtaining wide-angular nulls. By adjusting the amplitude of the excitation of the two-element auxiliary array, it is possible to modify the overall array pattern to place wide angular nulls in the directions of undesired interference signals.

Controllable optical multi-well trap and its optical lattices using compounded cosine patterns

This paper proposes a flexible scheme to form various optical multi-well traps for cold atoms or molecules by using a simple optical system composed of an compounded amplitude cosine-only grating and a single lens illuminated by a plane light wave or a Gaussian beam. Dynamic manipulation and evolution of multi-well trap can be easily implemented by controlling the modulation frequency of the cosine patterns. It also discusses how to expand this multi-well trap to two-dimensional lattices with single- or multi-well trap by using an orthogonally or non-orthogonally modulated grating, as well as using incoherent multi-beam illumination, and these results show that all the symmetric structures of two-dimensional Bravais lattices can be obtained facilely by using proposed scheme.

Combined Adaptiveness of Specific Motor Cortical Ensembles Underlies Learning

Learning motor skills entails adaptation of neural computations that can generate or modify associations between sensations and actions. Indeed, humans can use different strategies when adapting to dynamic loads depending on available sensory feedback. Here, we examined how neural activity in motor cortex was modified when monkeys made arm reaches to a visual target and locally adapted to curl force field with or without visual trajectory feedback. We found that firing rates of a large subpopulation of cells were consistently modulated depending on the distance of their preferred direction from the learned movement direction. The newly acquired activity followed a cosine-like function, with maximal increase in directions that opposed the perturbing force and decrease in opposite directions. As a result, the combined neuronal activity generated an adapted population vector. The results suggest that this could be achieved without changing the tuning properties of the cells. This population directional signal was however altered in the absence of visual feedback; while the cosine pattern of modulation was maintained, the population distributions of modulated cells differed across feedback consistent with the different trajectory shapes. Finally, we predicted generalization patterns of force-field learning based on the cosine-like modulation. These conformed to reported features of generalization in humans, suggesting that the generalization function was related to the observed rate modulations in the motor cortex. Overall, the findings suggest that the new combined activation of neuronal ensembles could underlie the change in the internal model of movement dynamics in a way that depends on available sensory feedback and chosen strategy.

Computational cryptography based on trigonometric algorithms and intensity superposition

A computational technique for visual cryptography is presented. This technique is performed by means of trigonometric algorithms and intensity superposition. The encryption is carried out by encoding an image in a trigonometric identity. This procedure generates a peaks pattern and a characteristic random image. Based on the optical superposition, these two images are overlapped to obtain the encryption pattern. Thus, the encryption procedure is completed. To perform the decryption, the peaks pattern is retrieved from the encryption. From this pattern, a cosine pattern is generated. Then, the phase is detected from this pattern to obtain the original image. Thus, the decryption is completed and the original image is retrieved. The cryptography is performed in experimental form by scanning printed images for encryption and decryption. The viability of this technique is described based on the decryption quality and the encryption robustness. This computational performance represents a contribution in the field of the optics and visual cryptography. The technique is tested with real scenes and its results are presented in computational form and in experimental form.

Laser induced rear-surface-crack damage properties of fused silica etched with HF solution

The micro subsurface cracks of fused silica etched with HF solution were recorded using atomic force microscope (AFM) and optical microscope. The damage characteristics of cracks with different structures were studied. Experimental results show that after HF etching, the cracks cross section turns into cosine pattern, and its laser induced damage threshold (LIDT) is not determined by the individual breadth or depth parameters, but by the breadth depth ratio of the crack cross section. The curve of LIDT versus the cracks breadth depth ratio was experimentally obtained. Finite difference time domain algorithm was used to calculate the electric field intensity distribution in the vicinity of a crack with cosine cross section, and the theoretical results agree well with the experimental ones.

Isolation and interaction of ON and OFF pathways in human vision: Contrast discrimination at pattern offset

Pattern contrast discriminations is typically studied with simultaneous onset of the base contrast ( C) and added contrast ( ΔC) patterns. I measured contrast discrimination functions at pattern offset. A brief (30 msec) localized, spatially narrow-band D6 test stimulus was ΔC. The onset of ΔC was simultaneous with the offset of a large, 500 msec cosine pattern (the base contast C). The D6 was either positive or negative contrast, and was masked by either positive or negative contrast, i.e., a light or dark bar of the cosine pattern. Stimuli were 3 cpd. Discrimination of negative ΔC at the offset of positive contrast followed a “dipper” function, as if the OFF pathway were isolated. A dipper function was also obtained for a positive ΔC at the offset of negative contrast (ON pathway isolation). But same-polarity ΔC and C yield a monotonic dscrimination function (“bumper” function) at the offset of C, suggesting inhibitory interaction. These discrimination functions for same-and opposite-polarity ΔC and C are the reverse of functions obtained at pattern onset. Manipulations of temporal asynchrony between patterns and manipulations of pattern polarity are thus functionally equivalent in determining the form of the contrast discrimination function. In a second experiment, I determined ΔC at times before and after the offeset of a high-contrast C and manipulated pattern polarity. The time course of threshold change is different for same vs opposite-polarity test and mask. The results suggest that interaction between ON and OFF pathway is delayed relative to the masking process within a pathway. Interaction between pathways may function to improve temporal resolution by suppressing persistence of neural response in the complementary pathway. The present pattern polarity and temporal asynchrony effects on the contrast discrimination function also decisively falsify the “uncertainty” hypothesis for low-contrast threshold facilitation (the dipper).

Cosine pattern synthesis for single and multiple main beam uniformly spaced linear arrays

The method of cosine pattern synthesis for single- and multiple-main-beam equispaced linear arrays is introduced. The cosine pattern function is characterized by the position of the main beam in the theta -domain and its half-power beamwidth. The Fourier series and Woodward-Lawson methods are applied to the special cases of single- or multiple-main-beam cosine pattern synthesis. The patterns produced by application of these classical shaped-beam synthesis methods can then be used as initial patterns for iterative and perturbational techniques. Examples are presented and discussed, including the use of multiple-main-beam cosine pattern synthesis to design a high-power, high-frequency, ground-based transmitter for the creation of an array of 'wireless' ionospheric dipoles. >