202,234 research outputs found
Verification of Liveness Properties in Distributed Systems
No full textThis paper presents liveness properties that need to be preserved by Event-B models of distributed systems. Event-B is a formal technique for development of models of distributed systems related via refinement. In this paper we outline how enabledness preservation and non-divergence are related to the liveness properties of the B models of the distributed systems. We address the liveness issues related to our model of distributed transactions and outline the construction of proof obligations that need to be discharged to ensure liveness
Eriocaulon goaense Kolte, I. Yadav & Janarth. 2022, sp. nov.
No full text<p> <i>Eriocaulon goaense</i> Kolte, I.Yadav & Janarth., <i>sp. nov</i>. (Fig 1 & 2)</p> <p> Allied to <i>Eriocaulon cuspidatum</i> Dalzell, but differs in its broadly cuneate floral bracts that are densely hoary dorsally towards apex (vs. oblanceolate, sparsely hoary dorsally towards apex), narrowly keeled sepals of male flowers (vs. not keeled), obovate, conduplicate, broadly keeled sepals of female flowers that are smooth along margin, densely hairy along keel and on dorsal side (vs. oblanceolate, conduplicate, acuminate, keeled, scarious, glabrous), and unequal, linear to lanceolate petals of female flowers that are hoary at apex in odd petal (vs. subequal, spathulate, sparsely hoary at apex in all the petals).</p> <p> <b>Type</b>:— INDIA. <b>Goa</b>: North Goa, Goa University Campus, 15027 ’43.09”N 73049 ’ 59.77” E, 53m, 14 September 2019, <i>R. R. Kolte RRK 1890</i> (holo BSI!; iso SUK!).</p> <p>Acaulescent herb. Rootstock absent. Leaves 6–10 × 0.7–1 cm, rosulate, glabrous, entire along margin, cuspidate at apex. Sheaths up to 10 cm long, glabrous; limb ovate, acute, entire. Peduncles many, up to 35 cm high, 9–11 ridged. Heads ca. 7 mm across, hemispherical, straw coloured. Receptacles convex, glabrous. Involucral bracts 1.6–1.8 × 1.4–1.5 mm, chartaceous, oblong, spreading, obtuse, straw coloured. Floral bracts 1.4–1.5 × 1.1–1.2 mm, hyaline, broadly cuneate, obtuse, densely hoary dorsally towards apex. Male flowers: Sessile, sepals 2, ca. 2 mm long, hyaline, free, spathulate, narrowly keeled, densely hairy along keel and on dorsal side. Stipe of corolla 1.2–1.5 mm long. Petals 3, subequal, pubescent, dotted with black glands; odd one ca. 1 mm long, remaining 2 of same size, smaller than odd petal; anthers black. Female flowers: Shortly pedicelled. Sepals 2, free, similar, 1.4–1.5 × ca. 1 mm, obovate, conduplicate, broadly keeled, smooth along margin, hoary outside towards apex. Petals 3, unequal; odd one ca. 2 × 0.4 mm, lanceolate, hoary towards apex, black gland dotted; 2 petals similar, ca. 1.5 mm long, linear to narrow lanceolate, glabrous, black gland dotted. Ovary sessile, ellipsoid; style 3-fid. Seeds ca. 1 × 0.5 mm, ovoid, apiculate; cells of seed coat transversely elongated, arranged in vertical rows, appendage 1 from transverse radial walls.</p> <p> <b>Distribution</b>:—Scattered in distribution at low level lateritic plateaus of Goa.</p> <p> <b>Habitat</b>:—Shallow seasonal ponds of lateritic plateaus in association with <i>Eriocaulon fysonii</i> R.Ansari & N.P.Balakr. (1994: 89), <i>Oryza rufipogon</i> Griff. (1851: 5) and <i>Wiesneria triandra</i> (Dalzell 1850: 144) Micheli (1881: 82).</p> <p> <b>Flowering & Fruiting</b>:—July to November.</p> <p> <b>Etymology</b>:—Specific epithet ‘ <i>goaense</i> ’ refers to the state of Goa, wherein it is distributed.</p> <p> <b>Additional specimens examined (Paratypes)</b>:— INDIA. <b>Goa</b>: North Goa, Goa University Campus, 16 July 2010, <i>I. Yadav 1</i>; 24 July, 2010, <i>I. Yadav 2</i>; 31 July 2010, <i>I. Yadav 5</i>; 17 August 2010, <i>I. Yadav 8</i>; Succoro (Sukor) plateau, 18 September 2010, <i>I. yadav & M. K. Janarthanam 64</i>; South Goa, Farmagudi (Ponda), IIT Campus, 28 August 2010, <i>I. Yadav & M. K. Janarthanam 32</i>; 18 September, 2010, <i>I. Yadav & M. K. Janarthanam 35</i>; Loliem, 5 September 2010, <i>M. K. Janarthanam & I. Yadav 47</i>; 1 September 2018, <i>R. R. Kolte RRK 1710</i> (All at BSI!)</p> <p> <b>Note</b>:—This species is closely allied to <i>E. cuspidatum</i> which is occasionally found in wet or marshy places from sea level to 250 m altitude in Western Peninsular India, especially in Karnataka, Kerala and Maharashtra (Ansari & Balakrishnan, 2009). <i>Eriocaulon goaense</i> is so far known from shallow seasonal ponds of low level lateritic plateaus of Goa.</p>Published as part of <i>Kolte, Rutuja R., Yadav, Indu & Janarthanam, Malapati K., 2022, Eriocaulon goaense (Eriocaulaceae), a new species from lateritic plateaus of Goa, India, pp. 188-191 in Phytotaxa 532 (2)</i> on pages 189-190, DOI: 10.11646/phytotaxa.532.2.8, <a href="http://zenodo.org/record/5912666">http://zenodo.org/record/5912666</a>
Ng2 r/e 1.5-4.5 p/e=10 p'/p=0.4 e=2 mm
No full textNusselt number and friction factor determination using artificial roughness using broken arc rib with staggered element. Values of parameters are e=2 mm, p/e=10, p'/p=0.4, r/e=1.5-4.5, Number of gaps=2, Reynolds number range 3000-14000
Examining post-CPA Nepal from a gender perspective
No full textThe armed political movement led by the Communist Party of Nepal - Maoist (CPN- M), known as the People’s War, started in 1996 with the aim of eliminating all kinds of discriminations including caste, class and gender-based discriminations (see the 40- points demand, 1996; the Maoist Manifesto 2001; Bhattarai, 1990; Rai, 2016). The People’s War was launched by a small group of supporters of the Maoist ideology, which was later joined by a group of enthusiastic youth who were frustrated with the political instability, corruption and continuation of the same old system even after the establishment of democracy in 1990. The movement grew fast and became popular, especially among poor and marginalized people (see Yadav, 2016a; Thapa, 2012; Thapa & Sharma, 2009; Pathak, 2005). Although gender discrimination was not their main agenda in the beginning, they included what they called ‘women’s question’ (see Yami, 2007) in the second year of their movement. Although it was a strategic decision to attract more women into the movement, they received overwhelming participation from women after the inclusion of the ‘women’s question’ (Yadav, 2016). There were various reasons why women joined the Maoist movement (see Shakhya, 2003; Frieden, 2012; Panday, 2012). However, the main reason for their overwhelming participation was the desire to bring about positive social change in Nepal (Yadav, 2016a)
Rigorous Design of Fault-Tolerant Transactions for Replicated Database Systems using Event B
No full textSystem availability is improved by the replication of data objects in a distributed database system. However, during updates, the complexity of keeping replicas identical arises due to failures of sites and race conditions among conflicting transactions. Fault tolerance and reliability are key issues to be addressed in the design and architecture of these systems. Event B is a formal technique which provides a framework for developing mathematical models of distributed systems by rigorous description of the problem, gradually introducing solutions in refinement steps, and verification of solutions by discharge of proof obligations. In this paper, we present a formal development of a distributed system using Event B that ensures atomic commitment of distributed transactions consisting of communicating transaction components at participating sites. This formal approach carries the development of the system from an initial abstract specification of transactional updates on a one copy database to a detailed design containing replicated databases in refinement. Through refinement we verify that the design of the replicated database confirms to the one copy database abstraction
Ariadna vansda Siliwal & Yadav & Kumar 2017, sp. nov.
No full text<i>Ariadna vansda</i> sp. nov., Siliwal, Yadav & Kumar <p>(Figures 1–5, 14, 18–19)</p> <p>urn:lsid:zoobank.org:act:444BC9A6-7775-4023-8F8D-76B106163CEF</p> <p> <b>Type specimens.</b> Holotype: female, 11.iv.2015, India: Gujarat: Vansda National Park [20° 45.138"N, 73° 29.005"E, elev. 131m], coll. M. Siliwal, Reshma Solanki, Archana Yadav, WILD-15-ARA-1369.</p> <p>Paratypes: 1 female, same data as holotype, WILD-15-ARA-1370; 1 female, 11.xii.2015, same locality as holotype, coll. Archana Yadav, WILD-15-ARA-1250.</p> <p> <b>Diagnosis.</b> Female differs from <i>A. nebulosa</i> by presence of 5-3 spines on tibia I ventrally (in <i>A. nebulosa</i> 3-3 spines). It differs from rest of the well described known species by the anterior receptacle highly sclerotized, broader at base with pointed and tapering dorsal and ventral lobes (Figs 14, 18–19); interpulmonary fold with broad sclerotization, rounded thick margin at the middle, and broad flap-like lateral extensions with smooth dorsal margins (Figs 14, 18).</p> <p> <b>Etymology.</b> The species epithet is a noun in apposition, referring to the type locality.</p> <p> <b>Description of holotype female (WILD-15-ARA-1369).</b> Total length 10.4. Carapace. 4.4 long, 2.9 wide; abdomen 6.0 long, 3.8 wide. Carapace, narrower anteriorly, brownish-black, anteriorly darker, integument rough; covered with long brown hairs, relatively more on caput. Cephalic area higher than thoracic area; fovea indistinct. Eyes six (AME absent) grouped in three pairs, PME anteriorly displaced forming slightly recurved row with PLE; eyes pale in colour and subequal in size; ocular group 0.41 long, 1.18 wide; eye diameter ALE 0.19, PME 0.19, PLE 0.14; inter-distances PLE-PME 0.25, ALE-ALE 0.53; clypeus 0.29 high. Labium 1.00 long, 0.71 wide, orangish-brown lighter anteriorly; narrowing down in anterior one third; covered with long black hairs. Endites 1.6 long, 0.86 wide, long, broader at base and narrowest at middle, orangish-brown except for anterior pale or white, covered with long black hairs. Chelicerae black with three promarginal teeth and one retromarginal tooth. Legs and palp orangish-brown, with darkened patches (including coxae and trochanters) on all legs, more distinct on anterior legs. Sternum 2.5 long, 2.00 wide; orangish-brown with dark patches laterally and medially more distinct on lateral half; margins rebordered, sternal margins with precoxal triangles. Leg measurements (femur, patella, tibia, metatarsus, tarsus, total length): Leg I: 3.22, 1.39, 2.44, 2.17, 1.11, 10.33; Leg II: 3.11, 1.56, 2.33, 2.00, 1.00, 10.00; Leg III: 2.44, 1.22, 1.39, 1.67, 0.89, 7.61; Leg IV: 3.33, 1.56, 2.44, 2.00, 0.89, 10.22; Palp: 0.93, 0.78, 0.71, -, 1.00, 3.42. Leg formula 1423. Spines or macrosetae: Leg I: ti p5, r3, mt p3, r3; leg II: ti p4, r2, mt p2, r3; leg III: ti v1, d2; mt p1, v4, r3, d2; leg IV: mt v3, ventro-retrolaterally one preening comb with three macrosetae; palp: ti p2, ta p3, v2. Claws: largest on leg I; paired claws with 7–11 teeth, unpaired claw appears smooth; true claw tufts absent; palp with single smooth claw, turned inward almost 90 degrees. Abdomen greyish brown, mottled with pale dots dorsally; ventrally greyish without any pattern. Spinnerets covered with brown hairs, colulus short covered with long hairs. Epigastric area covered with black setae on anterior and posterior sides of epigastric furrow. Internal genitalia with two receptacles, anterior receptacle sclerotized, broad at its base, with pointed ventral lobe; dorsal lobe transparent, with sclerotized lateral margins, covering basal one third of ventral lobe, slightly shorter than ventral lobe (Figs 14, 18–19); uterus externus with lightly sclerotized margins; posterior receptaculum large, sac like (Figs 14, 18).</p> <p> <b>Paratype (WILD-15-ARA-1250).</b> Total length 9.61. Carapace 3.69 long, 2.46 wide; abdomen 5.92 long, 3.46 wide. Eyes: ocular group 0.30 long, 0.60 wide; diameter PME 0.2, ALE 0.2, PLE 0.2; distance between PLE-PME 0.26; clypeus height 0.35. Endites: 1.3 long, 0.54 wide. Labium: 0.77 long, 0.46 wide. Sternum: 2.15 long, 1.38 wide. Leg measurements (femur, patella, tibia, metatarsus, tarsus, total length): 3.22, 1.39, 2.44, 2.17, 1.11, 10.33; Leg II: 3.11, 1.56, 2.33, 2.00, 1.00, 10.00; Leg III: 2.44, 1.22, 1.39, 1.67, 0.89, 7.61; Leg IV 3.33, 1.56, 2.44, 2.00, 0.89, 10.22; Palp: 0.93, 0.78, 0.71, -, 1.00, 3.42. Leg formula 1423. Remaining characters as in holotype.</p>Published as part of <i>Siliwal, Manju, Yadav, Archana & Kumar, Dolly, 2017, Three new species of tube-dwelling spider genus Ariadna Audouin, 1826 (Araneae: Segestriidae) from India, pp. 433-441 in Zootaxa 4362 (3)</i> on pages 434-436, DOI: 10.11646/zootaxa.4362.3.7, <a href="http://zenodo.org/record/1094952">http://zenodo.org/record/1094952</a>
Rigorous Design of Distributed Transactions
No full textDatabase replication is traditionally envisaged as a way of increasing fault-tolerance and availability. It is advantageous to replicate the data when transaction workload is predominantly read-only. However, updating replicated data within a transactional framework is a complex affair due to failures and race conditions among conflicting transactions. This thesis investigates various mechanisms for the management of replicas in a large distributed system, formalizing and reasoning about the behavior of such systems using Event-B. We begin by studying current approaches for the management of replicated data and explore the use of broadcast primitives for processing transactions. Subsequently, we outline how a refinement based approach can be used for the development of a reliable replicated database system that ensures atomic commitment of distributed transactions using ordered broadcasts. Event-B is a formal technique that consists of describing rigorously the problem in an abstract model, introducing solutions or design details in refinement steps to obtain more concrete specifications, and verifying that the proposed solutions are correct. This technique requires the discharge of proof obligations for consistency checking and refinement checking. The B tools provide significant automated proof support for generation of the proof obligations and discharging them. The majority of the proof obligations are proved by the automatic prover of the tools. However, some complex proof obligations require interaction with the interactive prover. These proof obligations also help discover new system invariants. The proof obligations and the invariants help us to understand the complexity of the problem and the correctness of the solutions. They also provide a clear insight into the system and enhance our understanding of why a design decision should work. The objective of the research is to demonstrate a technique for the incremental construction of formal models of distributed systems and reasoning about them, to develop the technique for the discovery of gluing invariants due to prover failure to automatically discharge a proof obligation and to develop guidelines for verification of distributed algorithms using the technique of abstraction and refinement
Formal Specifications and Verification of Message Ordering Properties in a Broadcasting System using Event B
No full textCausal and total order broadcast has been proposed as a mechanism to provide fault tolerance for constructing reliable distributed systems. The use of formal methods to develop a model of a system, specifying critical properties and the verification of them is a way of obtaining better design of dependable services. Event B is a formal technique which provides a framework for developing mathematical models of distributed systems by rigorous description of the problem, gradually introducing solutions in the refinement steps, and verification of solutions by discharge of proof obligations. In this paper, we present a formal development of a system in Event B where processes communicate by broadcast and the messages are delivered following a causal and a total order. We first present separate models of a broadcast system each for a causal order and a total order. Subsequently, we verify that the models of the system preserves the required ordering properties. Further, we develop a model of a system satisfying both causal and a total order on the messages. Later in the refinement, we outline how these ordering properties can correctly be implemented by the vector clocks. In this approach we discover some interesting invariant properties which describes the relationship of abstract causal and total order with the vector clocks and the sequence numbers
Formal Development of a Total Order Broadcast for Distributed Transactions using Event-B
No full textAbstract. In a replicated database system, copies of the database are kept across several sites for fault-tolerance and availability. Data access in such systems is usually done within a transactional framework. A read-only transaction accesses data locally and an update transaction modifies the database at all sites. Total order broadcast primitives have been proposed to support transactions and allow fault-tolerant cooperation between the sites in a distributed system. In this paper, we identify and analyze the problem of formation of deadlocks among conflicting update transactions due to race conditions and outline how a system of total order broadcast prevents deadlocks and transaction failures. Later we outline how a refinement based approach with Event-B can be used for formal development of the models of total order broadcast. In this approach we begin with the abstract model of a total order broadcast and verify that the required ordering properties are preserved by the system. total order can correctly be implemented by using a notion of sequence number. This technique requires us to discharge proof obligations due to consistency and refinement checking. To discharge the proof obligations we are required to discover invariants that describes the relationship between the abstract total order and the underlying mechanism.
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