Stabilisation of locally Lipschitz non-linear systems under input saturation and quantisation

Rehan, Muhammad,Tufail, Muhammad,Ahn, Choon Ki,Chadli, Mohammed IET 2017 IET CONTROL THEORY AND APPLICATIONS Vol.11 No.9

<P>This study addresses the control of locally Lipschitz non-linear systems under quantisation and input saturation non-linearities. The non-linear dynamics of the systems are taken to be locally Lipschitz, rather than the conventional globally Lipschitz counterpart, to consider a generalised form of the Lipschitz non-linear systems. An ellipsoidal region containing the origin is constructed, for which the non-linear dynamics satisfy the Lipschitz condition in contrast to the conventional approaches. Saturation and quantisation non-linearities are dealt using a generalised local sector condition and a bound on the quantisation noise. A regional control strategy for the stabilisation of non-linear systems using state feedback is devised by employing these conditions, which is further extended to attain robustness against external perturbations. The proposed control strategies guarantee convergence of the states of a non-linear system inside a bounded reducible region in the neighbourhood of the origin. In contrast to the conventional approaches, the present study considers ellipsoidally Lipschitz non-linear systems, supports various types of quantisers, ensures attenuation of the disturbances, and provides a clear picture of the region of stability. An example of the application of the proposed control strategies for a modified Chua's circuit is demonstrated.</P>

Carbon-Impurity Affected Depth Elemental Distribution in Solution-Processed Inorganic Thin Films for Solar Cell Application

Rehan, Shanza,Kim, Ka Young,Han, Jeonghyeob,Eo, Young-Joo,Gwak, Jihye,Ahn, Seung Kyu,Yun, Jae Ho,Yoon, KyungHoon,Cho, Ara,Ahn, SeJin American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.8

<P>A common feature of the inorganic thin films including Cu(In,Ga)(S,Se)(2) fabricated by nonvacuum solution based approaches is the doubled-layered structure, with a top dense inorganic film and a bottom carbon-containing residual layer. Although the latter has-been considered to be the main efficiency limiting factor, (as a source of high series resistance); the exact influence of this layer is still not clear, and contradictory views are present. In this study, using a CISe as a model system, we report experimental evidence indicating that the carbon residual layer itself is electrically benign to the device performance. Conversely, carbon was found to play a significant role in determining the depth elemental distribution of final film, in which carbon selectively hinders the diffusion of Cu during selenization, resulting in significantly Cu-deficient top CISe layer while improving the film morphology. This carbon-affected compositional and morphological, impact on the top CISe films is a determining factor for the device efficiency, which was supported by the finding that CISe solar cells processed from the precursor film containing intermediate amount of carbon demonstrated high efficiencies of up to 9.15% whereas the performances of the devices prepared from the precursor films with very high and very low carbon were notably poor.</P>

Decoupled-architecture-based nonlinear anti-windup design for a class of nonlinear systems

Rehan, Muhammad,Hong, Keum-Shik Springer-Verlag 2013 Nonlinear dynamics Vol.73 No.3

A Novel Method for Guaranteed Overflow Oscillation Elimination in Digital Filters Subject to Quantization

Rehan, Muhammad,Mobeen, Muhammad Bilal,Tufail, Muhammad,Ahn, Choon Ki IEEE 2018 IEEE transactions on circuits and systems. a publi Vol.65 No.9

<P>This brief provides a novel criterion for the analysis of convergence of states of an infinite impulse response (IIR) digital filter to a bounded region under the influence of composite effects of quantization and overflow nonlinearities. The developed criterion is less conservative in its approach in terms of analyzing stability than conventional methods and can be employed for implementation of an IIR filter on comparatively smaller hardware word-length than existing methods. The conventional approaches consider asymptotic stability of a filter with respect to the quantization noise; however, quantization in digital filters can result into bounded oscillation and lead to infeasibility of the asymptotic stability. Therefore, a less conservative stability analysis together with estimation of steady-state region of convergence for an IIR filter is provided. In addition, the conventional approaches, analyzing stability, and steady-state region of convergence, may not guarantee an overflow oscillation-free realization of a filter. Consequently, a condition for estimating the steady-state region of convergence (along with the filter stability) with an additional constraint that the filter’s state should not overflow in the bounded region has been derived. A comparative analysis with conventional methods is provided in simulation results.</P>

Supply Chain Management Using an Industrial Internet of Things Hyperledger Fabric Network

Rehan Muhammad,Javed Abdul Rehman,Kryvinska Natalia,Gadekallu Thippa Reddy,Srivastava Gautam,Jalil Zunera 한국컴퓨터산업협회 2023 Human-centric Computing and Information Sciences Vol.13 No.-

Supply chain management (SCM) plays a pivotal role in the industrial life cycle. On-time delivery is necessary for a successful SCM system. To maintain a safe and secure supply of products, mode of transportation and management is equally important. The Industrial Internet of Things (IIoT) eases tracking and tracing of supplies using sensor devices and 5G during the supply chain process. Cold chain and ecologically sensitive products such as vaccines, medical supplies, and food items require a specific temperature to maintain the supplies’ genuineness and actuality. A blockchain-based platform (Ethereum) is being used for SCM nowadays. However, it has certain limitations, such as low transaction speed, the requirement for more computation power, and vulnerability to cyberattacks. This research proposes a solution to these problems using a novel approach, named SCMIIOT (supply chain management using industrial Internet of Things). The proposed approach maintains traceability, security, data integrity, transparency, and achieves fast transaction speed. The distributed database system is used to store and transfer transaction ledgers for SCM. In this research, IBM Watson IoT is used as an Internet of Things (IoT) device for input temperature, and the Kubernetes cluster is used as a platform for deploying Hyperledger Fabric. Docker Hub and Hyperledger composer playground provide business network connection for importers, suppliers, retailers, manufacturers, and consumers/end-users. We also demonstrate the working and effectiveness of SCMIIOT through experiments. Results show that SCMIIOT takes only 1 minute to copy local files to storage on the cloud and takes 1 minute to create a genesis block. Similarly, it takes 1 minute for a peer-to-peer connection. Also, the worst-case time complexity of SCMIIOT transaction speed is recorded as 48 seconds on the Watson IoT platform.

Constrained control of hot air blower system under output delay using globally stable performance-based anti-windup approach

Rehan, Muhammad,Ahmed, Abrar,Iqbae, Naeem,Hong, Keum-Shik 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.12

This paper describes the design and implementation of a linear controller with an Anti-Windup Compensator (AWC) for a hot air blower system having output delays, under actuator saturation constraint and noise. Traditional Anti-Windup (AW) schemes for time-delay systems are based on either local stability or global stability with performance restrictions. We modify an existing AWC architecture using a time-delay term in the compensator in order to ensure global stability and performance. It is also shown that the existing Linear Matrix Inequalities (LMIs) based optimization schemes for AWC, which are derived using the decoupled architecture and co-prime factorization, can be applied to the modified AWC architecture. This modified delay independent AWC scheme is applied to a hot air blower system and practical results are discussed. This paper aims to support the industrial application of the modified AWC ensuring global stability and performance, by applying it to a hot air blower system under actuator situation and output delay as well as electrical and thermal noises.

Osseous changes in the temporomandibular joint in rheumatoid arthritis: A cone-beam computed tomography study

Rehan, Ola Mohamed,Saleh, Hoda Abdel Kader,Raffat, Hala Ahmed,Abu-Taleb, Noha Saleh Korean Academy of Oral and Maxillofacial Radiology 2018 Imaging Science in Dentistry Vol.48 No.1

Purpose: To evaluate osseous changes of temporomandibular joint (TMJ) in patients with rheumatoid arthritis (RA) using cone-beam computed tomography (CBCT) and to correlate the imaging findings with the severity of TMJ dysfunction, clinical findings, and laboratory findings. Materials and Methods: This study consisted of 28 subjects, including 14 RA patients and 14 controls, who were scheduled to undergo CBCT imaging for the diagnosis of a complaint not related to or affecting the TMJ. The Fonseca's questionnaire was used to assess the severity of TMJ dysfunction. Rheumatoid factor (RF) and the erythrocyte sedimentation rate (ESR) were assessed in the RA patients. CBCT was then performed in all subjects and osseous TMJ abnormalities were assessed. Results: According to the Fonseca's questionnaire, 14.3% of the patients had no TMJ dysfunction, while 50%, 21.4%, and 14.3% had mild, moderate, and severe dysfunction, respectively. RF was positive in 64.3% of patients, and the ESR level was high in 100%. Imaging findings revealed a statistically significantly higher prevalence of erosion (85.7%), flattening (89.3%), osteophyte formation (32.1%), subchondral cyst (32.1%), sclerosis (64.3%), and condylar irregularities (28.6%) in the RA patients than in the controls. No correlations were found between CBCT findings and the clinical findings, the severity of TMJ dysfunction, disease duration, or laboratory results. Conclusion: RA patients might show extensive osseous abnormalities with no/mild clinical signs or symptoms of TMJ dysfunction that necessitate TMJ imaging for these patients. CBCT is a valuable and efficient modality that can assess osseous TMJ changes in RA patients.

OPTIMAL HOMOTOPY ASYMPTOTIC METHOD SOLUTION OF UNSTEADY SECOND GRADE FLUID IN WIRE COATING ANALYSIS

REHAN ALI SHAH,S. ISLAM,A. M. SIDDIQUI,T. HAROON 한국산업응용수학회 2011 Journal of the Korean Society for Industrial and A Vol.15 No.3

In the present work, the mathematical model of wire coating in a straight annular die is developed for unsteady second grade fluid in the form of partial differential equation. The Optimal Homotopy Asymptotic Method (OHAM) is applied for obtaining the solution of the model problem.. This method provides us a suitable way to control the convergence of the series solution using the auxiliary constants which are optimally determined.

A comparative evaluation of anti-tumor activity following oral and intravenous delivery of doxorubicin in a xenograft model of breast tumor

Rehan Farah,Emranul Karim Md.,Ahemad Nafees,Farooq Shaikh Mohd.,Gupta Manish,Gan Siew Hua,Chowdhury Ezharul Hoque 한국약제학회 2022 Journal of Pharmaceutical Investigation Vol.52 No.6

Purpose Natural materials have been extensively studied for oral drug delivery due to their biodegradability and other unique properties. In the current research, we fabricated sodium caseinate nanomicelles (NaCNs) using casein as a natural polymer to develop a controlled-release oral delivery system that would improve the therapeutic potential of doxorubicin (DOX) and reduce its toxicity. Methods DOX-loaded NaCNs were synthesized and thoroughly characterized, then subjected to in vivo anti-tumor evaluation and bio-distribution analysis in a 4T1-induced breast cancer model. Results Our findings indicated that the tumor would shrink by eight-fold in the group orally treated with DOX-NaCNs when compared to free DOX. The tumor accumulated drug 1.27-fold more from the orally administered DOX-NaCNs compared to the intravenously administered DOX-NaCNs, 6.8-fold more compared to free DOX, and 8.34-times more compared to orally administered free DOX. In comparison, the orally administered DOX-NaCNs lead to a significant reduction in tumor size (5.66 ± 4.36 mm3) compared to intravenously administered DOX-NaCNs (10.29 ± 4.86 mm3) on day 17 of the experiment. NaCNs were well tolerated at a single dose of 2000 mg/kg in an acute oral toxicity study. Conclusion The enhanced anti-tumor effects of oral DOX-NaCNs might be related to the controlled release of DOX from the delivery system when compared to free DOX and the intravenous formulation of DOX-NaCNs. Moreover, NaCNs is recognized as a safe and non-toxic delivery system with excellent bio-distribution profile and high anti-tumor effects that has a potential for oral chemotherapy.

Role of Na in solution-processed CuInSe₂ (CISe) devices: A different story for improving efficiency

Rehan, Shanza,Moon, Jihyun,Kim, Tae Gun,Gwak, Jihye,Kim, Juran,Kim, Jeong Won,Jo, William,Ahn, Seung Kyu,Ahn, SeJin unknown 2018 Nano energy Vol.48 No.-

<P><B>Abstract</B></P> <P>Na has been believed to improve the device parameters of open circuit voltage (V<SUB>OC</SUB>) and fill factor (FF) presumably by increasing the carrier concentration (N<SUB>A</SUB>) of vacuum-processed Cu(In,Ga)Se<SUB>2</SUB> films. In solution-processed CI(G)Se devices as well, Na reportedly increases V<SUB>OC</SUB> and FF but this improvement is not correlated with the increase in N<SUB>A,</SUB> suggesting a different physical mechanism associated with Na in solution-based routes. In this contribution, experimental results on the role of Na addition in solution-processed CISe films and devices were reported, in which Na addition had no influence on N<SUB>A</SUB> nor on film composition in spite of the notable increase in the device efficiency. On the contrary, Na was found to mitigate the interfacial recombination by reducing the undesirable surface defects. Along with this understanding, Na addition in our air-processable route resulted in a CISe device with 12.83% efficiency, which is comparable to the current world record efficiency of solution-processed CISe devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Air-processable, nanoparticle-based approach yields 12.8% efficient CISe device. </LI> <LI> A new role of Na addition was revealed. </LI> <LI> The position of dominant recombination was shifted from interface to bulk by Na. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>