Cyclic Shift Research Articles

Confocal nonlinear optical imaging on hexagonal boron nitride nanosheets

Optical microscopy with optimal axial resolution is critical for precise visualization of two-dimensional flat-top structures. Here, we present sub-diffraction-limited ultrafast imaging of hexagonal boron nitride (hBN) nanosheets using a confocal focus-engineered coherent anti-Stokes Raman scattering (cFE-CARS) microscopic system. By incorporating a pinhole with a diameter of approximately 30 μm, we effectively minimized the intensity of side lobes induced by circular partial pi-phase shift in the wavefront (diameter, d0) of the probe beam, as well as nonresonant background CARS intensities. Using axial-resolution-improved cFE-CARS (acFE-CARS), the achieved axial resolution is 350 nm, exhibiting a 4.3-folded increase in the signal-to-noise ratio compared to the previous case with 0.58 d0 phase mask. This improvement can be accomplished by using a phase mask of 0.24 d0. Additionally, we employed nondegenerate phase matching with three temporally separable incident beams, which facilitated cross-sectional visualization of highly-sample-specific and vibration-sensitive signals in a pump-probe fashion with subpicosecond time resolution. Our observations reveal time-dependent CARS dephasing in hBN nanosheets, induced by Raman-free induction decay (0.66 ps) in the 1373 cm−1 mode.

A metasurface featuring multiple polarization conversions

This paper proposes a novel bow-tie metasurface that integrates various types of polarization conversions by optimizing traditional unit structures. The metasurface achieves wide-angle linear polarization conversion over the X-band (8–12 GHz) and has a linear polarization conversion efficiency of over 94% under normal incidence. In the Ku-band (12.4–15.6 GHz), the ellipticity value (e-value) and axial ratio calculations show that the linearly polarized waves incident along the Y axis will be effectively converted to left-handed circularly polarized waves. Additionally, in the X-band (8.9–10.5 GHz), the circular polarization and its co-polarization conversion efficiency can be maintained at 99.5%, allowing for an effective circular polarization phase shift using the Pancharatnam–Berry principle in this frequency range.

Pulse-Density-Modulated Microwave Generator Using Single-Flux-Quantum Circuits for Controlling Qubits

Superconducting qubits are generally controlled by irradiation with microwave pulses. We propose a 5-GHz-range microwave pulse generator based on pulse density modulation for controlling qubits using single-flux-quantum (SFQ) circuits. The proposed microwave pulse generator comprises a 100-GHz circular shift register and a band-pass filter (BPF). In this study, we investigated the relationship between the target envelope of the microwave amplitude and the SFQ pulse density based on the transfer function for the BPF and the frequency spectrum of an SFQ pulse. We implemented a 64-bit circular shift register and demonstrated its operation up to 68 GHz.

Energy gains at daily periodic changes of the azimuths of PV modules in north-east Bulgaria

The higher efficiency of tracking photovoltaic systems is an indisputable fact and computational methods of the respective energy gains are well known. However the investments in the tracking systems are higher in comparison to the fixed ones due to the needs of additional equipment and automation systems. An options of periodical change of the azimuth of PV modules at single axis solar trackers and the correspondent incident solar energy are studied in this paper. An approach for numerical determination of the daily periods of cyclic rotations of the trackers and the subsequent electricity production is developed. It was applied to estimate the energy gains at such cyclic changes of a PV system in ceramic factory in Bulgaria.

Linear Layer Architecture Based on Cyclic Shift and XOR

One of the nodes of a block symmetric encryption algorithm is represented by a linear layer, the purpose of which is to distribute the mutual influence of bits within the processed data block. Several methods exist for constructing a linear layer, the most common of which are matrix multiplication operations and the permutation of bits. Both approaches have high computational complexity and are not equally effective for both hardware and software implementations. This paper presents an approach for constructing linear functions for block symmetric encryption algorithms utilizing cyclic shift, and bitwise addition operations are formulated. We provide a preliminary assessment of certain properties of such functions, including the branch number. This linear operation can accommodate binary words of any length, allowing for the design of an optimal linear layer for software or hardware architectures with any word size. Furthermore, the developed architecture allows for balancing the laboriousness of linear operations and related branch numbers. The proposed novel linear layer architecture facilitates the creation of fast lightweight encryption algorithms as well as robust classical algorithms with a high level of cryptographic strength. For efficient implementation on software and hardware platforms, no additional optimizations are required, as the proposed linear layer allows for achieving high performance in both cases.

Williamson type Hadamard matrices with circulant components

It has been shown that Williamson Hadamard matrices of order 4n do not exist for n=35,47,53,59. We consider the class of Williamson type matrices with circulant (but not necessarily symmetric) components when n=p is an odd prime or n=pq is the product of distinct odd primes each of which is a generator modulo the other, showing that any such matrix may be derived from a Williamson matrix by a common cyclic shift of the components. In particular, this means that there are no Williamson type matrices with circulant components for n=35,47,53,59.

Circular shift combination local binary pattern (CSC-LBP) method for dorsal finger crease classification

Biometric technology has drawn increasing attention and significance importance in recent years. In biometric security systems, personal identification and verification rely on their physical, behavioral, and biological characteristics. In this study, a new hand-based modality called dorsal finger creases is proposed for biometric classification. This modality is located on the dorsal surface of the finger, between the proximal knuckle and distal knuckle of the finger. However, it requires a specific feature extraction approach to extract the modality information on the selected region. Therefore, we have proposed a method for extracting the underlying features of the dorsal finger creases, called circular shift combination local binary pattern (CSC-LBP). The concept of CSC-LBP is to compute the local binary pattern within a 3 × 3 spatial window for each neighborhood pixel separately. Further, the concept of combination approach is applied on the individually computed eight LBP values to obtain the more discriminative feature vector. A multiclass support vector machine classifier is used for evaluating the effectiveness of the proposed CSC-LBP operator. Extensive experiments on self-collected datasets demonstrate the high classification accuracy and effectiveness of the proposed CSC-LBP method and confirm the usefulness of dorsal finger creases for personal recognition.

Acute Deltoid Injury in Ankle Fractures: A Biomechanical Analysis of Different Repair Constructs.

The importance of the deltoid ligament in the congruency and coupling of the tibiotalar joint is well known. The current trend is to repair it in cases of acute injuries in the context of ankle fractures; however, there is limited information on how it should be reconstructed. The objective of this study was to compare different deltoid ligament repair types in an ankle fracture cadaveric model. Sixteen cadaveric foot-ankle-distal tibia specimens were used. All samples were prepared as a supination external rotation ankle fracture model. Axial load and cyclic axial rotations were applied on every specimen using a specifically designed frame. This test was performed without deltoid injury, with deltoid injury, and after repair. The reconstruction was performed in 4 different ways (anterior, posterior, middle, and combined). Medial clear space (MCS) was measured for each condition on simulated weightbearing (WB) and gravity stress (GS) radiographs. Reflective markers were used in tibia and talus, registering the kinematics through a motion analysis system to record the tibiotalar uncoupling. After deltoid damage, in all cases the MCS increased significantly on GS radiographs, but there was no increase in the MCS on WB radiographs. After repair, in all cases, the MCS was normalized. Kinematically, after deltoid damage, the tibiotalar uncoupling increased significantly. All isolated repairs achieved a similar tibiotalar uncoupling value as its baseline condition. The combined repair resulted in a significant decrease in tibiotalar uncoupling. Our results show that deltoid repair recovers the tibiotalar coupling mechanism in an ankle fracture model. Isolated deltoid repairs recovered baseline MCS and tibiotalar uncoupling values. Combined repairs may lead to overconstraint, which could lead to postoperative stiffness. Clinical studies are needed to prove these results and show clinically improved outcomes. This study helps in finding the optimum deltoid repair to use in an acute trauma setting.

A bit-plane encryption algorithm for RGB image based on modulo negabinary code and chaotic system

This paper proposes a new color image encryption algorithm based on modulo negabinary code (MNBC-IEA), which treats a color pixel as one 24-bit unsigned integer rather than three 8-bit unsigned integers, and it makes the 24-bit-planes dependent on each other. We first provide a new coding scheme of unsigned integers called modulo negabinary code (MNBC), and we construct its encoding and decoding algorithm. Next, we use MNBC to design the substitution algorithm for color image encryption. MNBC-IEA consists of the enhanced MNBC, a random cyclic shift (RCS), and a diffusion procedure. The RCS procedure is composed of the RCSs in three directions, and it treats a color image as a cuboid. Hence, the permutation process can cause the 24-bit-planes to affect each other in addition to scrambling the bit positions. The enhanced MNBC can change the grayscale values via a process that encodes a 28-bit unsigned integer consisting of a 24-bit pixel value and a 4-bit key into the MNBC. The diffusion procedure includes exclusive OR and modulo arithmetic such that plaintext pixels, ciphertext pixels, and keystreams are related to each other. The final experiments indicate that our algorithm can encrypt a color image into a random binary sequence and resist various statistical, differential, and brute-force attacks.

An In-Phase/Quadrature Index Modulation-Aided Spread Spectrum Communication System for Underwater Acoustic Communication

In a multiple-sequences-spread-spectrum (MSSS) communication system, the transmitted signal is made up of superimposed cyclic shift sequences, each sequence carrying a symbol, so the data rate is inceased. In this context, we propose an in-phase/quadrature index modulation-aided MSSS system (MSSS-I/Q-IM), which achieves higher data rate and better bit-error-rate (BER) performance. The new system maps the additional bits to the cyclic shift length of the superimposed sequences of I/Q branches. The sequences in two branches carry the real and imaginary parts of the M-ary phase-shift-keying (MPSK) symbols, respectively. We derive the theoretical BER of the MSSS-I/Q-IM system over an additive white Gaussian noise (AWGN) channel. Then, the simulation experiments of the proposed system and MSSS system over an underwater acoustic channel are analyzed and compared. Finally, field experiments are carried out in the pool environment. The experiment results show that the proposed scheme can achieve higher data rate or better BER performance via adjusting the IM parameter. This is important for the time-variant underwater acoustic transmission environments.

Deep Regularized Waveform Learning for Beam Prediction With Limited Samples in Non-Cooperative mmWave Systems

Millimeter wave (mmWave) systems need beam management to establish and maintain reliable links. This complex and time-consuming process seriously affects communication efficiency. Benefiting from data-driven technology in deep learning, the beam can be predicted from the waveform without coordination between transceivers. By passively listening enough waveforms that are transmitted from the base station (BS) to other receivers, the BS can predict which beam is suitable for transmitting in the downlink. However, training such a waveform learning neural network usually requires a large number of labeled training samples. This is a huge challenge, because it is difficult for the receiver to get the precise signal parameters from the transmitter in advance in the non-cooperative mmWave system. As a result, the limited samples may cause overfitting and seriously restrict the performance. Although the data augmentation technology can improve the performance under limited samples, existing data augmentation methods are mostly based on strong prior knowledge which cannot further exploit the potential characteristics of data in the real environment. This paper proposes a mixed regularization training method for training the beam prediction neural network under limited training samples. Specifically, data augmentation is implemented in the data pre-processing procedure with prior knowledge and then the signal splicing strategy is proposed in the training procedure. In order to mine the time correlation characteristics of signals, the cyclic time shift (CTS) based data augmentation method is proposed in the data augmentation step. The simulation results show that our proposed deep regularized waveform learning method needs less training samples under the same performance. Moreover, the proposed method can achieve best performance compared with existing data augmentation methods.

Training Sample Formation for Convolution Neural Networks to Person Re-Identification from Video

To improve the person re-identification system accuracy, an integrated approach is proposed in the formation of a training sample for convolutional neural networks, which involves the use of a new image dataset, an increase in the training examples number using existing datasets, and the use of a number of transformations to increase their diversity. The created dataset PolReID1077 contains images of people that were obtained in all seasons, which will improve the correct operation of re-identification systems when the seasons change. Another PolReID1077 advantage is the video data use obtained from external and internal surveillance in a large number of different filming locations. Therefore, the people images in the created set are characterized by the variability of the background, brightness and color characteristics. Joining the created dataset with the existing CUHK02, CUHK03, Market-1501, DukeMTMC-ReID and MSMT17 sets made it possible to obtain 109 772 images for training. An increase in the variety of generated examples is achieved by applying a cyclic shift to them, eliminating color and replacing a fragment with a reduced copy of another image. The research results on estimating the accuracy of re-identification for the ResNet-50 and DenseNet-121 convolutional neural networks during their training, using the proposed approach to form a training sample, are presented.

The Alignment of Circular Economy Business Models (CEBM) with the Strategies of Small and Micro Enterprises Operating in Malta

This paper sets out preliminary findings for research investigating, from a dynamic viewpoint, how small and micro enterprises operating in the small island state of Malta align their business strategies with Circular Economy Business Models (CEBM). The aim is to establish an analytical framework evaluating their process of alignment. These businesses are a major economic driver for the island. In 2021, out of the 55,950 registered businesses in Malta, 52,674 were micro-firms and 2,686 were small businesses (NSO 2021). The study applies grounded theory methodology, using Corbin and Strausss conditional matrix (2015) and Charmazs constructivist approach (2006). To understand their implementation of circular practices, interpretative, in-depth interviews were carried out with five owners-managers in the service, logistics, manufacturing, retail, and wholesale sectors. The research postulates an early conceptual model showing how a set of contextual conditions influences the alignment of CEBM with the strategies of businesses in Malta. Factors influencing CEBM adoption include owner-managers personal traits, organisational factors, and external factors. The findings presented are part of a larger study mapping common alignment paths pursued by firms in the circular economic shift. It offers recommendations to owners-managers, policymakers, and academic researchers. Few studies have yet focused on the alignment between CEBM and the business strategy of firms in small island states. Generally, studies concentrate on larger businesses in bigger countries. This research study adds significantly to existing knowledge and academic literature.

Encryption algorithm based on fractional order chaotic system combined with adaptive predefined time synchronization

An image encryption and decryption method of fractional order chaotic systems (FOCS) with predefined time synchronization is proposed in this article. Compared with the existing integer order chaotic systems (IOCS), fractional order chaotic systems has the advantage of increasing the complexity of the ciphertext. At the same time, by using the predefined synchronization time, the key space is expanded, the complexity of the key is increased, and the security of the algorithm is improved. To further improve the security of encryption and decryption process, this article uses a combination of DNA encoding, row/column cyclic shift and XOR diffusion, position scrambling and Arnold scrambling. The simulation tests of image encryption and decryption are carried out, and the effectiveness and advantages of the proposed encryption/decryption method are verified by histogram analysis, correlation analysis, entropy analysis, key sensitivity analysis and plaintext sensitivity analysis.

Coding and Coherent Decoding techniques for Continuous Single Slope Cyclic Shift Chirp Signal

Coding and Coherent Decoding techniques for Continuous Single Slope Cyclic Shift Chirp Signal

Parity-Check Matrix Partitioning for Efficient Layered Decoding of QC-LDPC Codes

In this paper, we consider how to partition the parity-check matrices (PCMs) to reduce the hardware complexity and increase decoding throughput for the row layered decoding of quasi-cyclic low-density parity-check (QC-LDPC) codes. First, we formulate the PCM partitioning as an optimization problem, which targets to minimize the maximum column weight of each layer while maintaining a block cyclic shift property among different layers. As a result, we derive all the feasible solutions for the problem and propose a tight lower bound ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>LB</i></sub> on the minimum possible maximum column weight to evaluate a solution. Second, we define a metric called layer distance to measure the data dependency between consecutive layers and further illustrate how to identify the solutions with desired layer distance from those achieving the minimum value of ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>LB</i></sub> = 1, which is preferred to reduce computation delay. Next, we demonstrate that up-to-now, finding an optimal solution for the optimization problem with polynomial time complexity is unachievable. Therefore, both enumerative and greedy partition algorithms are proposed instead. After that, we modify the quasi-cyclic progressive edge-growth (QC-PEG) algorithm to directly construct PCMs that have a straightforward partition scheme to achieve ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>LB</i></sub> or the desired layer distance. Simulation results showed that the constructed codes have better error correction performance and achieve less average number of iterations than the underlying 5G LDPC codes.

Design of Carrier Index Keying-Aided M-Ary Differential Chaos Cyclic Shift Keying for D2D Communications

Device-to-device (D2D) communications can allow different devices to communicate in short range, which greatly meets the demand of effective transmissions. In this paper, a spectral and energy-efficient carrier index keying-aided <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary differential chaos cyclic shift keying (CIK-MDCCSK) system is proposed for D2D communications, where multiple cyclic-shifted <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary information-bearing signals are superimposed and transmitted by a subcarrier, and extra keying bits are transmitted by indices of the selected subcarriers. Furthermore, a carrier keying detection and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary de-mapping algorithm is proposed to retrieve the information bits transmitted by <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> -ary symbols and indices of carrier keying. The bit error rate (BER) expressions of the proposed CIK-MDCCSK system are derived over the additive white Gaussian noise (AWGN) and D2D channels, and the optimal power coefficient is deduced for performance enhancement. Then, the spectral efficiency, energy efficiency, and complexity of CIK-MDCCSK are analyzed and compared to benchmark systems to show its superiority. Next, the proposed CIK-MDCCSK system is expanded into its enhanced version for more effective transmission without degrading the BER performance. It is demonstrated by performance comparisons that the proposed CIK-MDCCSK system can achieve more than twice energy efficiency and up to 3 dB gain in BER performance compared to state-of-the-art benchmarks.

Efficient image encryption algorithm based on dynamic high-performance S-box and hyperchaotic system

With the development of information technology, security, low latency, and instant messaging have become a major demand. To solve this problem, this paper designs a secure and efficient image cipher algorithm. Firstly, a new four-dimensional hyperchaotic system with strong chaotic performance is proposed. Secondly, a dynamic high-performance S-box generation algorithm is proposed based on GF(28) by improving the method of generating S-boxes in AES, selecting suitable irreducible polynomial as well as affine matrix, precomputing the corresponding affine multiplication matrix as well as multiplication inverse matrix. The S-box algebraic expressions generated by this algorithm have 255 terms and are more resistant to algebraic attacks than AES. Finally, based on the four-dimensional hyperchaotic system and dynamic high-performance S-box generation algorithm, the new image cipher algorithm that can encrypt and decrypt images of arbitrary size is proposed. The image cipher algorithm consists of two rounds of interleaved permutation, two rounds of dynamic S-box substitution and cyclic shift permutation with fixed point. Cyclic shift permutation with fixed point and dynamic S-box substitution ensure that the plaintext transformation can be transferred to the entire image. Through testing, analysis and comparison, the algorithm has proven to be a secure and efficient image cipher algorithm.

Circular Time Shift Modulation for robust underwater acoustic communications in doubly spread channels

Pulse Position Modulation (PPM) has shown great advantages by being non-coherently implementable. However, PPM suffers from the high multipath delay in underwater acoustic channels. To be robust against the doubly spread effects in underwater acoustic communications, this project proposes a novel modulation scheme that is non-linear and that can be implemented non-coherently, called the Circular Time Shift Modulation (CTSM) based on the high auto-correlation property of Zero-Correlation-Zone (ZCZ) signals. The performance of CTSM in terms of bit error rate is investigated by emulations and at-sea experiments. The results have shown that the CTSM system has higher robustness compared with PPM in underwater acoustic communications.

Deterministic Construction of Compressed Sensing Measurement Matrix with Arbitrary Sizes via QC-LDPC and Arithmetic Sequence Sets

It is of great significance to construct deterministic measurement matrices with good practical characteristics in Compressed Sensing (CS), including good reconstruction performance, low memory cost and low computing resources. Low-density-parity check (LDPC) codes and CS codes can be closely related. This paper presents a method of constructing compressed sensing measurement matrices based on quasi-cyclic (QC) LDPC codes and arithmetic sequence sets. The cyclic shift factor in each submatrix of QC-LDPC is determined by arithmetic sequence sets. Compared with random matrices, the proposed method has great advantages because it is generated based on a cyclic shift matrix, which requires less storage memory and lower computing resources. Because the restricted isometric property (RIP) is difficult to verify, mutual coherence and girth are used as computationally tractable indicators to evaluate the measurement matrix reconstruction performance. Compared with several typical matrices, the proposed measurement matrix has the minimum mutual coherence and superior reconstruction capability of CS signal according to one-dimensional (1D) signals and two-dimensional (2D) image simulation results. When the sampling rate is 0.2, the maximum (minimum) gain of peak signal-to-noise ratio (PSNR) and structural similarity index (SSIM) is up to 2.89 dB (0.33 dB) and 0.031 (0.016) while using 10 test images. Meanwhile, the reconstruction time is reduced by nearly half.