On-orbit assembly using superquadric potential fields

The autonomous on-orbit assembly of a large space structure is presented using a method based on superquadric artificial potential fields. The final configuration of the elements which form the structure is represented as the minimum of some attractive potential field. Each element of the structure is then considered as presenting an obstacle to the others using a superquadric potential field attached to the body axes of the element. A controller is developed which ensures that the global potential field decreases monotonically during the assembly process. An error quaternion representation is used to define both the attractive and superquadric obstacle potentials allowing the final configuration of the elements to be defined through both relative position and orientation. Through the use of superquadric potentials, a wide range of geometric objects can be represented using a common formalism, while collision avoidance can make use of both translational and rotation maneuvers to reduce total maneuver cost for the assembly process

Remifentanil vs dexmedetomidine for severely preeclamptic parturients scheduled for cesarean section under general anesthesia: A randomized controlled trial

AbstractObjectivesTo compare the effect of remifentanil vs dexmedetomidine on hemodynamic response of noxious stimuli and neonatal outcome in preeclamptic parturient underwent C.S. under G.A.MethodsThis blinded, prospective, randomized trial included 50 preeclamptic parturients underwent C.S under G.A., randomized into two equal groups [25 patients each]: group R [remifentanil]: received 1μg/kg loading and 0.05μg/kg/min infusion doses and group D [dexmedetomidine] received 1/kg loading and 0.2μg/kg/h infusion doses. Maternal MAP and HR were assessed before medication (T0), just after induction of GA (TI), just after intubation (TT), two minutes after intubation (TT2), just after skin incision (TS), two minutes after skin incision (TS2), just after delivery of the baby (TD), and at the end of operation (TE). Time between induction and fetal delivery (I-D interval), time between incision of the uterus and delivery (U-D interval), and time between stop of the infusion of the tested drugs and delivery (D-D interval) were recorded. Neonatal Apgar score was recorded at 1 and 5min and the need for resuscitative measures.ResultsMaternal MAP and HR in group R were statistically lower at (TI), (TT), (TT2), (TS) and (TS2). Neonatal Apgar score was statistically lower in group R with higher incidence for tactile stimulation.ConclusionBoth remifentanil and dexmedetomidine were effective on blunting the pressor response to noxious stimuli in severely preeclamptic parturients. While remifentanil was marginally more effective in suppressing the pressor response, dexmedetomidine was safer for the neonates

Practical Secrecy at the Physical Layer: Key Extraction Methods with Applications in Cognitive Radio

The broadcast nature of wireless communication imposes the risk of information leakage to adversarial or unauthorized receivers. Therefore, information security between intended users remains a challenging issue. Currently, wireless security relies on cryptographic techniques and protocols that lie at the upper layers of the wireless network. One main drawback of these existing techniques is the necessity of a complex key management scheme in the case of symmetric ciphers and high computational complexity in the case of asymmetric ciphers. On the other hand, physical layer security has attracted significant interest from the research community due to its potential to generate information-theoretic secure keys. In addition, since the vast majority of physical layer security techniques exploit the inherent randomness of the communication channel, key exchange is no longer mandatory. However, additive white Gaussian noise, interference, channel estimation errors and the fact that communicating transceivers employ different radio frequency (RF) chains are among the reasons that limit utilization of secret key generation (SKG) algorithms to high signal to noise ratio levels. The scope of this dissertation is to design novel secret key generation algorithms to overcome this main drawback. In particular, we design a channel based SKG algorithm that increases the dynamic range of the key generation system. In addition, we design an algorithm that exploits angle of arrival (AoA) as a common source of randomness to generate the secret key. Existing AoA estimation systems either have high hardware and computation complexities or low performance, which hinder their incorporation within the context of SKG. To overcome this challenge, we design a novel high performance yet simple and efficient AoA estimation system that fits the objective of collecting sequences of AoAs for SKG. Cognitive radio networks (CRNs) are designed to increase spectrum usage efficiency by allowing secondary users (SUs) to exploit spectrum slots that are unused by the spectrum owners, i.e., primary users (PUs). Hence, spectrum sensing (SS) is essential in any CRN. CRNs can work both in opportunistic (interweaved) as well as overlay and/or underlay (limited interference) fashions. CRNs typically operate at low SNR levels, particularly, to support overlay/underlay operations. Similar to other wireless networks, CRNs are susceptible to various physical layer security attacks including spectrum sensing data falsification and eavesdropping. In addition to the generalized SKG methods provided in this thesis and due to the peculiarity of CRNs, we further provide a specific method of SKG for CRNs. After studying, developing and implementing several SS techniques, we design an SKG algorithm that exploits SS data. Our algorithm does not interrupt the SS operation and does not require additional time to generate the secret key. Therefore, it is suitable for CRNs

Molecular markers as a prognostic system for hepatocellular carcinoma

AbstractThe gene expression profile p16, c-erbB-3 and bcl2 in hepatocellular carcinoma (HCC) patients with and without associated HCV infection, was assessed. Forty-eight subjects were included in the study and divided equally into two groups: HCC with and without HCV associated infection. Adjacent paracancerous tissues were assessed as control samples. Correlations with various clinico-pathological parameters of the tumour were assessed: stage, grade, and tumour size. The c-erbB-3 oncogene was expressed in 83.33% (40/48) of the total HCC sample and in 31.25% (15/48) of the noncancerous lesions. C-erbB-3 was expressed in 87.5% (21/24) of the HCC cases with associated HCV infection and in 79.16% (19/24) of the HCC cases without associated HCV infection. Gene expression of c-erbB-3 was significantly correlated with the clinico-pathological parameters of the tumour. P16 gene expression was found in 12.5% (6/48) of the total HCC sample and in 25% (12/48) of the para-cancerous lesions. P16 was expressed in 12.5% (3/24) of HCC cases with and without associated HCV infection. Gene expression of p16 exhibited significant negative correlation with clinico-pathological parameters of the tumour. Bcl2 gene expression was found in 20.8% (10/48) of the total HCC sample and in the para-cancerous lesions. Bcl2 was expressed in 20.8% (5/24) of the HCC cases with and without HCV associated infection. Gene expression of bcl2 did not show significant correlations with the clinico-pathological parameters of the tumour. In conclusion, gene expression profiles of p16 and c-erbB-3 could be used as prognostic molecular markers in HCC

Impact Factors on Subcontractor's Cash Flow Management

Objective: This study aims to define how to maintain and protect the subcontractor firms' cash flow from economic fluctuation through legally sustainable solutions. Methods/Analysis: We conducted a case study in the Eastern Delta Region of Egypt. A questionnaire containing a list of 22 impact factors on subcontractors' cash flow was distributed across multiple subcontractor firms with an 82% response rate. It was designed to explore the factors causing cash flow instability and analyze them using SPSS statistics. Findings: The study finds that inflation, late payments, non-compensation for late payments, poor subcontractor cash flow management, subcontractor firms' inclination to avoid disputes, material price fluctuation, and non-compensation terms, as well as suppliers rejection of payment delays, are the most critical factors of subcontractor cash flow problems. Novelty/Improvement:The study suggests adding three sub-articles to Article 57 in "Tender Law" as legally sustainable solutions to protect and maintain the firm's growth rate from inflation, late payment, and the inclination to avoid disputes. Also, the study recommends that the owner ensure that cash is available before procuring the general contractors, as stated in Egyptian Law 182 of 2018. This study will contribute to establishing a sustainable win-win relationship between subcontractors and general contractors. Doi: 10.28991/CEJ-SP2023-09-08 Full Text: PD

Topic Extraction and Interactive Knowledge Graphs for Learning Resources

Humanity development through education is an important method of sustainable development. This guarantees community development at present time without any negative effects in the future and also provides prosperity for future generations. E-learning is a natural development of the educational tools in this era and current circumstances. Thanks to the rapid development of computer sciences and telecommunication technologies, this has evolved impressively. In spite of facilitating the educational process, this development has also provided a massive amount of learning resources, which makes the task of searching and extracting useful learning resources difficult. Therefore, new tools need to be advanced to facilitate this development. In this paper we present a new algorithm that has the ability to extract the main topics from textual learning resources, link related resources and generate interactive dynamic knowledge graphs. This algorithm accurately and efficiently accomplishes those tasks no matter how big or small the texts are. We used Wikipedia Miner, TextRank, and Gensim within our algorithm. Our algorithm"s accuracy was evaluated against Gensim, largely improving its accuracy. This could be a step towards strengthening self-learning and supporting the sustainable development of communities, and more broadly of humanity, across different generations.The researcher was partially funded by the Egyptian Ministry of Higher Education and Minia University in the Arab Republic of Egypt. [Joint supervision mission from the fourth year missions (2015–2016) of the seventh five-year plan (2012–2017)]

A Simple Angle of Arrival Estimation System

We propose a practical, simple and hardware friendly, yet novel and very efficient, angle of arrival (AoA) estimation system. Our intuitive, two-phases cross-correlation based system requires a switched beam antenna array with a single radio frequency chain. Our system cross correlates a reference omni-directional signal with a set of received directed signals to determine the AoA. Practicality and high efficiency of our system are demonstrated through performance and complexity comparisons with multiple signal classification algorithm.Scopu

Carbetocin versus Oxytocin and Misoprostol in prevention of atonic post-partum hemorrhage in high risk patients planed for cesarean delivery

Background: Post-partum hemorrhage prevention (PPH) is considered a major issue due to its effect on maternal morbidity and mortality. The objective of this study was to compare efficacy of Carbetocin in prevention of atonic post-partum hemorrhage in high risk patients undergoing elective caesarean section in comparison to Oxytocin and Misoprostol.Methods: 150 pregnant women prepared for elective caesarean section were classified into 3 groups; Group I (50 patients received Carbetocin 100 mg I.V infusion), Group II (50 patients received 20 IU of Oxytocin infusion on 1000 ml of normal saline solution) and Group III (50 cases received Misoprostol 400 µg per rectum immediately before induction of anaesthesia). Assessment of PPH and its degree was determined according to amount of blood loss during and for first 24 hours of caesarean delivery, also further need for haemostatic measures were also assessed.Results: There was a statistically significant difference in PPH among the three groups 6, 14 and 12% for group I, II and III respectively (P <0.001), major PPH was 0, 4 and 6% for the same groups respectively (P <0.001). The need for additional uterotonic agents was significantly lesser in Group I compared to Group II and III (2% versus 8 and 12% respectively P = 0.02) also the need for additional surgical measures was significantly lesser among the three groups (P= 0.00). The drop in Hb level and haematocrit value was significantly lesser in group I compared to group II& III (P <0.05). The need for blood transfusion was significantly lesser in Group I compared to group II and III (0% versus 12% p <0.0001)Conclusions: Carbetocin was superior to Oxytocin and Misoprostol in prevention of atonic PPH in high risk patients underwent elective caesarean delivery. Carbetocin should be administered for all cases undergoing elective CS and carry a risk factor for postpartum hemorrhage.

Exploiting Spectrum Sensing Data for Key Management

In cognitive radio networks, secondary users (SUs) communicate on unused spectrum slots in the frequency bands assigned to primary users (PUs). Like any other wireless communication system, cognitive radio networks are ex- posed to physical layer attacks. In particular, we focus on two common at- tacks, namely, spectrum sensing data falsification and eavesdropping. Such attacks can be counteracted by using symmetric key algorithms, which how- ever require a complex key management scheme. In this paper we propose a novel algorithm that significantly reduces the complexity of the management of symmetric link keys by leveraging spectrum sensing data that is available to all nodes. In our algorithm, it is assumed that a primary secret key is pre-distributed to the legitimate SUs, which is needed every number of de- tection cycles. With the aid of the information provided in the primary key, our algorithm manipulates the collected samples so that a segment of the estimated sensing statistic at the two legitimate SUs can be used as a seed to generate a common symmetric link key. The link key is then employed to encrypt the transmitted data. Our algorithm exhibits very good performance in terms of bit mismatch rate (BMR) between two link keys generated at the two legitimate SUs. In addition, our solution is robust against the difference in the received signal to noise ratio between two legitimate SUs thus making it suitable for practical scenarios. Furthermore, our algorithm exploits the decision statistic that SUs use for spectrum sensing, hence, it does require neither extra processing nor extra time, allowing the SUs to quickly and securely tab into empty spectrum slots