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C M Krishna Real Time Systems Pdf



In this paper we study the problem of scheduling jobs with real-time constraints in single and multiprocessor computer systems. We show the optimality of the minimum laxity (ML) scheduling and earliest deadline (ED) scheduling policies on multiprocessors under general workload assumptions for systems in which jobs need not be served once they miss their deadlines. We also describe a discrete-time model of these policies operating on a single processor when deadlines of all jobs are uniformly bounded. The ML and ED policies described incur an overhead that has computational complexity of O(m) or O (log (m) (depending on the implementation) where m is the queue length. Hence we propose and study several efficient policies (with O (1) overhead) that provide most of the performance of the ML and ED policies. Last, we consider the problem of scheduling jobs with real-time constraints that provide increased reward as a function of execution time. We propose several greedy policies that attempt to equalize the amount of service that all jobs attain and show, through simulation and analysis, that they attain performances close to an unachievable optimistic bound.




C m krishna real time systems pdf



Within the course state-of-art programming models, languages and operating systems will be presented and practically demonstrated at the Distributed Control Lab (DCL). The DCL is a remote laboratory operated at the Hasso-Plattner-Institute at University of Potsdam, Germany. The Lab provides remote access to real-time control experiments, which will be used for accompanying practical exercises, that teaches the above-mentioned aspects of embedded systems programming based on a number of case studies


Assignment:We propose to you a choice of fourassignments. Since we do not know the platform you can use, we include oneoption that is entirely theoretical. You are allowed to use any sources tosupport your work but you have to hand in your own original work, includingrelevant references (especially those that you based your work on). Any attemptof fraud will be taken very seriously. Comments on the exercises are welcome, reasonable adjustments are ok. The idea is that ittakes you roughly one week and deepens your insight so,if times becomes a problem please contact us. If usefull we will make a FAQ forthe exercises. Note: we have to reviewthese exercises internally so there may be small adaptations later.


Gedare Bloom, Joel Sherrill, Harmonizing ARINC 653 and Realtime POSIX for Conformance to the FACE Technical Standard, in 2020 IEEE 23rd International Symposium on Real-Time Distributed Computing (ISORC), pp. 98-105,DOI: 10.1109/ISORC49007.2020.00023, 2020. [ pdf ]


Gedare Bloom, Gabriel Parmer, Bhagirath Narahari, Rahul Simha, Shared hardware data structures for hard real-time systems, in Proceedings of the tenth ACM international conference on Embedded software, pp. 133-142, ACM,DOI: 10.1145/2380356.2380382, 2012. [ pdf ]


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We developed an integrated chip for real-time amplification and detection of nucleic acid using pH-sensing complementary metal-oxide semiconductor (CMOS) technology. Here we show an amplification-coupled detection method for directly measuring released hydrogen ions during nucleotide incorporation rather than relying on indirect measurements such as fluorescent dyes. This is a label-free, non-optical, real-time method for detecting and quantifying target sequences by monitoring pH signatures of native amplification chemistries. The chip has ion-sensitive field effect transistor (ISFET) sensors, temperature sensors, resistive heating, signal processing and control circuitry all integrated to create a full system-on-chip platform. We evaluated the platform using two amplification strategies: PCR and isothermal amplification. Using this platform, we genotyped and discriminated unique single-nucleotide polymorphism (SNP) variants of the cytochrome P450 family from crude human saliva. We anticipate this semiconductor technology will enable the creation of devices for cost-effective, portable and scalable real-time nucleic acid analysis.


Amebiasis caused by Entamoeba histolytica is the third leading cause of death worldwide. This pathogenic amoeba is morphologically indistinguishable from E. dispar and E. moshkovskii, the non-pathogenic species. Polymerase chain reaction is the current method of choice approved by World Health Organization. Real-time PCR is another attractive molecular method for diagnosis of infectious diseases as post-PCR analyses are eliminated and turnaround times are shorter. The present work aimed to compare the results of Entamoeba species identification using the real-time assay against the established nested PCR method.


In this study, a total of 334 human faecal samples were collected from different Orang Asli settlements. Faecal samples were processed by direct wet smear and formalin ethyl acetate concentration methods followed by iodine staining and was microscopically examined for Entamoeba species and other intestinal parasites. Microscopically positive samples were then subject to nested PCR and real-time PCR.


This study is the first in Malaysia to report the use of real-time PCR in identifying and differentiating the three Entamoeba infections. It is also proven to be more effective compared to the conventional nested PCR molecular method.


Entamoeba infections are traditionally diagnosed via microscopic examination of stool samples, fresh or fixed. The pathogenic amoeba, E. histolytica is indistinguishable in its cyst and trophozite stages from E. dispar and E. moshkovskii, the non-pathogenic species [6]. It has also been shown that the sensitivity and specificity of microscopy is less optimal in differentiating the various species of Entamoeba[7]. Given the discrepancies of microscopy, various approaches have been implemented. The epidemiology of Entamoeba can be further studied by culturing trophozoites and determining isoenzyme patterns by gel electrophoresis [8]. These techniques, however, are costly, time-consuming, laborious and not practical for regular diagnosis [9]. An enzyme immunoassay kit (TechLab II antigen test) has been specifically designed for the detection of E. histolytica. However, this kit is marketed for examination of stool samples only and it has also been noted that fixed stools samples are not suitable for enzyme-linked immunosorbent assay (ELISA) [10, 11]. Due to the dire need to study the epidemiology of Entamoeba, the polymerase chain reaction (PCR) is now the method of choice and this technique has been approved by the World Health Organization (WHO) [12]. In a study conducted by Stark et al. [13], it was demonstrated that PCR has improved sensitivity and specificity over ELISA-based kits. PCR also has the ability of specifically targeting and detecting E. histolytica, E. dispar, and E. moshkovskii infections [13, 14].


Real-time PCR is still its infancy but it is a very attractive methodology for laboratory diagnosis of infectious diseases because of a lack of requirement for post-PCR analysis, resulting in shorter turnaround times and minimizing the risk of amplicon contamination [14, 15]. This reflects obvious advantages in diagnostics, as amplicon contamination has been identified to be the most frequent cause of false-positive results in PCR amplification [16]. Aside from that, real-time PCR is a quantitative method and enables the determination of the number of parasites in various samples [17].


In this study, real-time PCR was used to differentiate E. histolytica, E. dispar, and E. moshkovskii infections from several villages in Malaysia. To the best of our knowledge, this is the first study in Malaysia whereby real-time PCR assay was used to discriminate between the three species. This study was also aimed at comparing results of Entamoeba species identification using the real-time assay against the established nested PCR method.


The minimum number of parasites detectable (detection limit) by real-time PCR assay was determined by 2-fold serial dilutions performed on Entamoeba sp. positive samples. The parasite concentrations were based on the amount of cysts counted under microscopy in samples ranging from 10 cysts to 0.6 cysts.


The specificity of the real-time PCR assay was tested against DNA extracted from faecal samples, namely Escherichia coli, Blastocystis hominis, Giardia intestinalis, and Cryptosporidium sp. A total of 25 parasite-free faecal samples were also used to test the specificity of the real-time PCR assay. All the control DNA samples were subjected to the same amplification protocol. Cross-reaction or cross-amplification between the three Entamoeba species was tested with each species specific Entamoeba primers and probes.


From the 65 microscope-positive samples, 56 (86.2%) samples were detected by real-time PCR. Of these 56 samples, E. histolytica and E. dispar mixed infection appeared to be the most predominant (22/56; 39.3%), followed by E. histolytica (21/56; 37.5%), E. dispar (11/56; 19.6%), and E. moshkovskii (1/56; 1.8%). Coexistence of E. histolytica and E. moshkovskii was identified by real-time PCR in one (1.8%) sample (Table 4).


Detection limits of nested PCR are indicated in Figures 1 and 2. Figure 1 highlights the limitations of nested PCR in identifying E. dispar and E. moshkovskii infections whereby a minimum of 5 cysts and 10 cysts was required to pick up the respective infections. Although a very faint band was observed, nested PCR was able to identify E. histolytica with a cyst count as low as 0.625. The detection of all three Entamoeba species by real-time PCR was found to be as low as 0.625 cysts (Figure 2).


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