Prefix Systems Research Articles

A probabilistic approach to the voltage stability analysis of interconnected power systems

Abstract In planning a power system it is always necessary to assess whether a voltage collapse occurs during a prefixed system operating condition. However, present approaches to the analysis of voltage instability phenomena in interconnected power systems are deterministic and, consequently, they cannot take into account the unavoidable uncertainties associated with the bus load forecast. This is indeed an important limitation. In this case the application of probabilistic techniques is the most feasible alternative. On the basis of this observation, in this paper a probabilistic approach to the voltage stability analysis of interconnected power systems is presented; it treats loads as random uncorrelated variables with normal distributions. The method proves suitable for determining systematically, for each expected system operating condition, the statistics of all the node voltages which are critical from the voltage stability viewpoint. The capability and usefulness of the suggested approach are illustrated by carrying out simulation studies on a sample power system.

More on Allotypes

Gloyd (1982) has recently exhorted users of the bionomenclatural term to conform to its original definition, to wit as the designation of a specimen by either the original or another author, from either the hypodigm or other material, as an example of the sex opposite that of the holotype of the same species. In particular, her purpose was to counteract the revision of definition by most recent authorities to limit understanding of allotype to one of the paratypes. Under that revision, lacking a paratype of the sex opposite that of the holotype, there would be no allotype. The move to return to the original definition of the term is fully justified, and is here endorsed. However, certain refinements within the parameters of the original definition seem in order. Since there can be only one active onomatophore (holotype, neotype or lectotype) for any species-group taxon (although any syntype and, presumably, any paratype or lectoparatype may be considered potential or reserve onomatophores), an allotype has no formal status in nomenclature, and serves merely whatever other purposes custom dictates. In this respect the term allotype is much like the term applied either to paratypes (topoparatypes) or to nontypical specimens. The difference lies in the fact that topotypes, by convention (since they have no official status), are unlimited in numberall specimens from the type locality are topotypes-whereas there is but one allotype, as originally conceived. Although limitation of the term allotype to paratypes, as exemplified by most recent accounts, is undesirable as both self-defeating and inconsistent with the original definition of the word (as pointed out by Gloyd, 1982), it would be useful to expand application of the word, paralleling in part the usage of the term topotype, by addition to it of prefixes appropriate to special contexts not originally envisioned. For example, if the allotype were a part of the original hypodigm, it would logically be an alloparatype. An allotype subsequently as the formal (although not official) representative of the sex opposite that of the holotype may reasonably be termed a metallotype. Any specimen representing the sex opposite that of the holotype might be termed an ethallotype (from the Greek word transliterated as ethas, meaning ordinary). Unfortunately, such a system of prefixes clearly implies that alloparatypes, metallotypes and ethallotypes are all allotypes, thereby distorting the more limited original meaning of the latter term as badly as the recent interpretation as simply a paratype of the sex opposite that of the holotype. A simple means for avoiding such criticism is to maintain the original sense, by distinguishing between designated allotypes-single specimens explicitly to serve as role model for their sex-and allotypes (of unlimited number) that are simply allotypic (i.e., of the sex opposite that of the holotype). By such means the original intent for the term allotype may be maintained while at the same time permitting greater flexibility in its use without courting ambiguity. The term thereby can realize its potential, paralleling that of the currently much more popular term topotype. The term alloparatype has already been proposed (Frizzell, 1933:643) although in a somewhat different sense-a paratype of the same sex as the allotype. That sense is no longer tenable, for it implies onomatophore weight of the allotype, contrary to current rules of nomenclature. The terms metallo-

Nomenclature for numbers

Proper names for large numbers are a very useful idea. If Dr Ahmed's system (Physics Bulletin November 1981 p343) is slightly modified, it would stand a better chance of rapid acceptance and widespread use. I propose that we: (i) use million for 106 as at present; (ii) standardise billion and trillion as 109 and 1012; (iii) use the Prefix system for larger numbers.

A Case of Intensive Lexical Diffusion: Arnhem Land, Australia

The languages of Arhem Land, Australia, form a contiguous block and Sprachbund, despite a sharp genetic boundary. Thus in Ngandi and Ritharngu, which belong to different major genetic divisions, about half the total vocabulary is shared, virtually all because of recent diffusion. 'Core' vocabulary and highly inflected stems (verbs) are among the borrowed items, but linguistic structural factors affect the extent of diffusion. Extensive over-all borrowing is attributed to local demographic and cultural features: small size of ethnolinguistic group, absence of strong tribal organization, and extensive cross-linguistic marriage.* 1. BACKGROUND. In eastern Arnhem Land, along the coast of the Gulf of Carpentaria, several ethnolinguistic groups (linguistic 'tribes') were in close contact with each other prior to the recent intrusion of whites. I contend that some of these languages came into contact at a fairly recent time (let us say a thousand years ago), and that lexical diffusion among them has reached a level not reported elsewhere for stable multilingual zones. The plausibility of this claim is increased by my previous documentation (Heath 1978a) of extensive phonological and grammatical diffusion involving the same languages. In addition to structural convergence, involving inherited materials, I showed that direct borrowing of many bound affixes had occurred: noun-class prefix systems, negative suffix, denominative verbalizing suffix, pre-inflectional thematizing verbal suffix, comitative affixes (with nouns and verbs), several case suffixes (ergative-instrumental, genitive-dative, ablative, instrumental), dyadic dual suffix with kin terms, and various others. Before proceeding, I will review the evidence for the genetic relationships posited among the languages. The crucial division is between the Yuulngu group, bottled up in northeastern Arnhem Land, and the so-called 'prefixing' languages which surround the Yuu. group to the south and west. The prefixing languages, or at least those involved in this paper, are a genetic group, but the fine-grained subgrouping has not been worked out. The Yuu. group consists of approximately ten languages; and except for one or two Yuu. offshoots in the west which do not concern us, the group is internally quite homogeneous. That the Yuu. languages are closely related has been obvious on lexical and grammatical grounds to all observers, and some of the 'languages' grade into each other in dialect-chain fashion. Adjoining Yuu. languages are approximately as similar to each other as Spanish to Portuguese, or German to Dutch. The wider genetic connections of the Yuu. languages are not to the adjoining prefixing languages, but rather to languages far to the south-in the southern