| 65911. |
- Mohammadi, A., et al.
(författare)
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Comparison of multiphase data from CT perfusion vs clinical 4-phase CT scans with respect to image quality, lesion detection, and LI-RADS classification in HCC patients
- 2022
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Ingår i: Heliyon. - : Elsevier Science Ltd. - 2405-8440. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to assess the image quality and diagnostic performance of reconstructed arterial (A) and portal venous (PV) phases in computed tomography perfusion (CTP) scans compared to the corresponding phases in standard 4-phase CT and to assess the utility for LI-RADS classification using CTP and 4-phase 4CT. Methods: A total of 26 scans with each method (CTP and 4-phase CT) from 19 hepatocellular carcinoma patients were analyzed and compared. Arterial and PV phases reconstructed by advanced modeled iterative reconstruction at strength 4 (ADMIRE 4) from raw CTP data were compared with image sets from arterial and PV phases of 4-phase CT (ADMIRE 3) in the same patient with respect to image quality. Results: Quantitative image analysis showed that reconstructed CTP datasets were equivalent to 4-phase CT image sets. Qualitative image analysis revealed similar lesion detection rates with the 2 methods for patients with an abdominal diameter <= 36 cm and body weight <90 kg, but lower detection rates with CTP for patients with an abdominal diameter >37 cm. There was no difference in Liver Imaging Reporting and Data System (LI-RADS) classifications between the 2 methods. Conclusion: Reconstructed CTP images can potentially replace 4-phase CT images in patients weighing <90 kg and with a body diameter <37 cm, as the 2 methods are comparable in terms of quantitative image quality and ability to detect and classify lesions based on LI-RADS criteria.
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| 65912. |
- Mohammadi, Mohammadali, et al.
(författare)
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Network-Assisted Full-Duplex Cell-Free Massive MIMO: Spectral and Energy Efficiencies
- 2023
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Ingår i: IEEE Journal on Selected Areas in Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 0733-8716 .- 1558-0008. ; 41:9, s. 2833-2851
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Tidskriftsartikel (refereegranskat)abstract
- We consider network-assisted full-duplex (NAFD) cell-free massive multiple-input multiple-output (CF-mMIMO) systems, where full-duplex (FD) transmission is virtually realized via half-duplex (HD) hardware devices. The HD access points (APs) operating in uplink (UL) mode and those operating in downlink (DL) mode simultaneously serve DL and UL user equipments (UEs) in the same frequency bands. We comprehensively analyze the performance of NAFD CF-mMIMO from both a spectral efficiency (SE) and energy efficiency (EE) perspectives. Specifically, we propose a joint optimization approach that designs the AP mode assignment, power control, and large-scale fading (LSFD) weights to improve the sum SE and EE of NAFD CF-mMIMO systems. We formulate two mixed-integer nonconvex optimization problems of maximizing the sum SE and EE, under realistic power consumption models, and the constraints on minimum individual SE requirements, maximum transmit power at each DL AP and UL UE. The challenging formulated problems are transformed into tractable forms and two novel algorithms are proposed to solve them using successive convex approximation techniques. More importantly, our approach can be applied to jointly optimize power control and LSFD weights for maximizing the sum SE and EE of HD and FD CF-mMIMO systems, which, to date, has not been studied. Numerical results show that: (a) our joint optimization approach significantly outperforms the heuristic approaches in terms of both sum SE and EE; (b) in CF-mMIMO systems, the NAFD scheme can provide approximately 30% SE gains, while achieving a remarkable EE gain of up to 200% compared with the HD and FD schemes.
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| 65913. |
- Mohammadi, Mohsen, 1992-
(författare)
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Stretchable electronics using wood-based functional materials
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stretchable electronics allows for direct integration into deforming systems like clothing, skin, and tissue, thereby enabling novel applications in soft robotics, wearable electronics, health monitoring, therapeutics, and human-machine interfaces. However, achieving seamless integration with the human body poses significant challenges, necessitating the development of functional materials with a low Young’s modulus matching biological tissues to avoid any discomfort or immune response. Additionally, as electronic devices are becoming increasingly used in different settings, accumulation of electronic waste, and the utilization of unsustainable raw materials are emerging as pressing environmental challenges. Therefore, it is important that the design and fabrication of these devices consider not only high performance, but also its environmental sustainability. Therefore the focus of this thesis is on enhancing the performance and sustainability aspects of stretchable electronics through using renewable wood-based functional wood-based materials in 4 papers. Paper I focuses on the development of versatile soft electromagnetic actuators for soft robotic applications. These stretchable electromagnetic actuators were capable of contraction, expansion, hopping, and locomotion without the need for external magnetic fields. By embedding strain sensors made of conductive cellulose nanofibril (CNF)-based foam, the actuators could internally monitor their states, enhancing their controllability and autonomy. In Paper II, a soft haptic system was designed to stimulate the sense of touch. The haptic system was based on a soft electromagnetic actuator concept that included a soft magnet and stretchable conducting composite consisting of silver flakes and a styrene elastomer. The system demonstrated an improved tactile response enabled by vibration amplitude sensing through conductive CNF-based foams. This novel design offers potential applications in human–machine interfaces and virtual reality tools. Paper III presents a scalable approach for the fabrication of ultra-soft high-resolution multilayer stretchable printed circuit boards (sPCBs). A wood derived biopolymer, lignin, was used to develop a water processable sacrificial mask bio-composite for laser-patterning of high-resolution prints of ultra-soft and stretchable conductors with high-aspect-ratio structures. Additionally, this method enabled the stable integration of rigid components onto the sPCBs that can facilitate their use for miniaturized electronic devices. Lastly, paper IV introduces a fluid-based electrode concept for stretchable batteries using the biopolymer lignin. Fluidity is engineered into the cathode and anode, thereby decoupling the mechanical and electrochemical properties of the battery electrodes, allowing for high deformability without sacrificing capacity. The developed wood-based fluid stretchable battery could potentially be used as a sustainable energy storage component to power wearable devices. Overall, the thesis has contributed to the advancement of the field of stretchable electronics. It provided valuable insights into the potential utilization of wood-based functional materials into a variety of devices, fabrication methods, and design concepts in stretchable electronics, incorporating both high performance and environmental sustainability. The knowledge generated from this thesis can be used as a prospective guideline to design next-generation stretchable electronics devices.
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| 65914. |
- Mohammadi, Mohsen, et al.
(författare)
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Versatile Ultrasoft Electromagnetic Actuators with Integrated Strain-Sensing Cellulose Nanofibril Foams
- 2023
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Ingår i: ADVANCED INTELLIGENT SYSTEMS. - : WILEY. - 2640-4567. ; 5:7
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Tidskriftsartikel (refereegranskat)abstract
- As robots more frequently fraternize with humans in everyday life, aspects such as safety, flexibility of tasks, and appearance become increasingly important. Soft robotics is attractive for new human-close applications, but soft actuators constitute a major challenge both in terms of actuation force and speed, and in terms of control and accuracy of the deformable soft actuator body. Herein, several of these challenges are addressed by developing versatile ultrasoft electromagnetic actuators that operate in absence of external magnetic fields, while simultaneously monitoring their states by internal strain sensors. The versatile actuators can compress to less than 50% of their initial length with strain-independent contraction force and operate in both contraction and expansion modes up to 200 Hz frequency while conforming to curved surfaces. The soft multilayer conductive cellulose-based foams are lightweight (3 mg cm(-3)) and provide internal strain-sensing capability and structural support, thereby improving the monitoring and controllability of the actuators while maintaining an axial softness of 0.6 kPa. It is believed that the concept of soft versatile electromagnetic actuators with integrated lightweight strain-sensing foams is promising for a wide range of applications within soft robotics.
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| 65915. |
- Mohammadi, Sara, et al.
(författare)
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Quantitative evaluation of a single-distance phase-retrieval method applied on in-line phase-contrast images of a mouse lung
- 2014
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Ingår i: Journal of Synchrotron Radiation. - : Wiley-Blackwell. - 0909-0495 .- 1600-5775. ; 21, s. 784-789
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Tidskriftsartikel (refereegranskat)abstract
- Propagation-based X-ray phase-contrast computed tomography (PBI) has already proven its potential in a great variety of soft-tissue-related applications including lung imaging. However, the strong edge enhancement, caused by the phase effects, often hampers image segmentation and therefore the quantitative analysis of data sets. Here, the benefits of applying single-distance phase retrieval prior to the three-dimensional reconstruction (PhR) are discussed and quantified compared with three-dimensional reconstructions of conventional PBI data sets in terms of contrast-to-noise ratio (CNR) and preservation of image features. The PhR data sets show more than a tenfold higher CNR and only minor blurring of the edges when compared with PBI in a predominately absorption-based set-up. Accordingly, phase retrieval increases the sensitivity and provides more functionality in computed tomography imaging.
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| 65916. |
- Mohammadi Sarband, Narges, 1984-, et al.
(författare)
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Massive Machine-Type Communication Pilot-Hopping Sequence Detection Architectures Based on Non-Negative Least Squares for Grant-Free Random Access
- 2021
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Ingår i: IEEE Open Journal of Circuits and Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2644-1225 .- 2644-1225. ; 2, s. 253-264
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Tidskriftsartikel (refereegranskat)abstract
- User activity detection in grant-free random access massive machine type communication (mMTC) using pilot-hopping sequences can be formulated as solving a non-negative least squares (NNLS) problem. In this work, two architectures using different algorithms to solve the NNLS problem is proposed. The algorithms are implemented using a fully parallel approach and fixed-point arithmetic, leading to high detection rates and low power consumption. The first algorithm, fast projected gradients, converges faster to the optimal value. The second algorithm, multiplicative updates, is partially implemented in the logarithmic domain, and provides a smaller chip area and lower power consumption. For a detection rate of about one million detections per second, the chip area for the fast algorithm is about 0.7 mm 2 compared to about 0.5 mm 2 for the multiplicative algorithm when implemented in a 28 nm FD-SOI standard cell process at 1 V power supply voltage. The energy consumption is about 300 nJ/detection for the fast projected gradient algorithm using 256 iterations, leading to a convergence close to the theoretical. With 128 iterations, about 250 nJ/detection is required, with a detection performance on par with 192 iterations of the multiplicative algorithm for which about 100 nJ/detection is required.
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| 65917. |
- Mohammadi Sarband, Narges, 1984-, et al.
(författare)
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Obtaining Minimum Depth Sum of Products from Multiple Constant Multiplication
- 2018
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Ingår i: PROCEEDINGS OF THE 2018 IEEE INTERNATIONAL WORKSHOP ON SIGNAL PROCESSING SYSTEMS (SIPS), IEEE. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538663189 ; , s. 134-139
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Konferensbidrag (refereegranskat)abstract
- In this work, an approach for transposing solutions to the multiple constant multiplication (MCM) problem to obtain a sum of product (SOP) computation with minimum depth is proposed. The reason for doing this is that solving the SOP problem directly is highly computationally intensive when adder graph algorithms are used. Compared to using subexpression sharing algorithms, which has a lower computational complexity, directly for the SOP problem, it is shown that the proposed approach, as expected, results in lower complexity for the SOP. It is also shown that there is no obvious way to construct the MCM solution in such a way that the SOP solution has the minimum theoretical depth. However, the proposed approach guarantees minimum depth subject to the MCM solution given as input.
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| 65918. |
- Mohammadi Sarband, Narges, 1984-, et al.
(författare)
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Pilot-Hopping Sequence Detection Architecture for Grant-Free Random Access using Massive MIMO
- 2020
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Ingår i: 2020 IEEE International Symposium on Circuits and Systems (ISCAS). - : IEEE. - 9781728133201
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Konferensbidrag (refereegranskat)abstract
- In this work, an implementation of a pilot-hopping sequence detector for massive machine type communication is presented. The architecture is based on solution a non-negative least squares problem. The results show that the architecture supporting 1024 users can perform more than one million detections per second with a power consumption of less than 70 mW when implemented in a 28 nm FD-SOI process.
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| 65919. |
- Mohammadi Sarband, Narges, et al.
(författare)
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Using Transposition to Efficiently Solve Constant Matrix-Vector Multiplication and Sum of Product Problems
- 2020
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Ingår i: Journal of Signal Processing Systems. - : SPRINGER. - 1939-8018 .- 1939-8115. ; 92:10, s. 1075-1089
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we present an approach to alleviate the potential benefit of adder graph algorithms by solving the transposed form of the problem and then transposing the solution. The key contribution is a systematic way to obtain the transposed realization with a minimum number of cascaded adders subject to the input realization. In this way, wide and low constant matrix multiplication problems, with sum of products as a special case, which are normally exceptionally time consuming to solve using adder graph algorithms, can be solved by first transposing the matrix and then transposing the solution. Examples show that while the relation between the adder depth of the solution to the transposed problem and the original problem is not straightforward, there are many cases where the reduction in adder cost will more than compensate for the potential increase in adder depth and result in implementations with reduced power consumption compared to using sub-expression sharing algorithms, which can both solve the original problem directly in reasonable time and guarantee a minimum adder depth.
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| 65920. |
- Mohammadinodooshan, Alireza, 1983-, et al.
(författare)
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Comment on "AndrODet: An adaptive Android obfuscation detector"
- 2020
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have identified a methodological problem in the empirical evaluation of the string encryption detection capabilities of the AndrODet system described by Mirzaei et al. in the recent paper "AndrODet: An adaptive Android obfuscation detector". The accuracy of string encryption detection is evaluated using samples from the AMD and PraGuard malware datasets. However, the authors failed to account for the fact that many of the AMD samples are highly similar due to the fact that they come from the same malware family. This introduces a risk that a machine learning system trained on these samples could fail to learn a generalizable model for string encryption detection, and might instead learn to classify samples based on characteristics of each malware family. Our own evaluation strongly indicates that the reported high accuracy of AndrODet's string encryption detection is indeed due to this phenomenon. When we evaluated AndrODet, we found that when we ensured that samples from the same family never appeared in both training and testing data, the accuracy dropped to around 50%. Moreover, the PraGuard dataset is not suitable for evaluating a static string encryption detector such as AndrODet, since the particular obfuscation tool used to produce the dataset effectively makes it impossible to extract meaningful features of static strings in Android apps.
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