Improving Convergence Behavior of Nonlinear Equation Systems in Intensified Process Models by Decomposition Methods

The two decomposition methods Dulmage-Mendelsohn (DM) decomposition and bordered block transformation (BBTF) have been examined on their capabilities to eliminate convergence problems during the iteration of large, nonlinear equation systems as they occur frequently in process modeling. They both divide the overall system into lower dimensional subsystems, which can be solved separately in sequence. Exemplarily these methods were applied on the model of a reactive distillation column, where the decomposed systems show a higher robustness with respect to systematically selected initial points compared to the original system. Nevertheless, the improvement in DM seems small since a large subsystem with 576 of the 664 model equations remains. The convergence result from the iteration of the BBTF decomposed system depends a lot on the initial values for certain strongly coupled variables called tearing variables. In future, methods will be investigated and may also be developed to further reduce the dimension of the subsystems in DM and provide accurate initial values for the tearing variables in BBTF

Production of n-propyl acetate by reactive distillation : experimental and theoretical study

First steps of the development of a catalytic reactive distillation process for the production of n-propyl acetate based on experiments and simulations are proposed. The kinetics for homogeneously (sulphuric acid) and heterogeneously (Amberlyst 15) catalysed reaction were investigated and the constants for a pseudo-homogeneous model are presented. Pilot plant experiments were performed using a homogeneous strong acid catalyst in a packed column. A top-column decanter is used to withdraw the aqueous phase and to reflux the organic phase. Simulation results are in good agreement with experimental data. Thermodynamics nonidealities are taken into account using VLE and LLE NRTL interaction parameters. Alcohol conversion and n-propyl acetate purity may be dramatically increased just by adding to the pilot plant a stripping section in an additional column: six different configurations are identified to achieve such a production. The startup is studied in order to determine the best strategy to achieve steady-state conditions. The strong influence of the composition of the initial charging in the decanter can be seen and an initial charging of the two-phase top product leads to the fastest startup

Modelling prehistoric social interaction in the South-western Pacific: a view from the obsidian sources in Northern Vanuatu

This paper investigates the history of social interaction within communities in the Vanuatu Archipelago and between Vanuatu and other regions in the Western Pacific as reflected by variations in lithic raw material sources and technology of stone artefacts. Past research determined an apparent contradiction between long-distance transportation of obsidian, indicating high value, and the under-utilisation of the raw material at the place of discard, indicating low value. The paper concludes that because previous hypotheses depend too much on the notion of the scarcity of resources in their evaluation of the concept of value, they are insufficient to explain the pattern of spatial and temporal distribution of lithic artefacts. Rather than focusing on the intrinsic value of obsidian raw material for individuals or communities, it is more useful to view it as a marker of group identity in a complex system connecting discrete populations in mitigating risk in unpredictable new environments. These new environments included pre-established populations, which might be hostile to new arrivals. The necessity for this complex system quickly disappeared once the colonisers arrived in regions uninhabited by prior populations

High-resolution lidar analysis of the Fisi Tea defensive earthwork at Lapaha, Kingdom of Tonga

In many prehistoric societies, earthwork defences were among the costliest and largest built structures and required a significant investment in resources, particularly labour, land and materials. Consequently, the construction of major defences was not undertaken lightly and they were frequently built in response to an imminent threat of intense violence (Keeley 1996). Earthwork defences often enclosed residential communities and elite centres, whereas others were larger and included hinterlands and appear to have defended a regional area (Connah 2000; Fox 1976; Scherer and Golden 2006; Webster et al. 2007). In both cases, defences protected the areas most important to the community and represent emic statements of group territory (Webster et al. 2008:349). Long defensive systems and ‘great walls’ that protect settlements and their hinterlands have been something of a puzzle to archaeologists (Arkush and Stanish 2005:10). While the perceived logistical challenge of occupying long defensive systems may be the primary source of confusion, traditional archaeological and survey methodologies often limit the amount of spatial data that can be gathered. Long defensive systems require considerable resources to map and to record in detail the various defensive elaborations, in addition to the regional geography of the areas on both side of the defences

Late Pleistocene/early Holocene maritime interaction in Southeastern Indonesia - Timor Leste

This study analysed over 1000 obsidian stone artefacts excavated from two adjoining shelters at Tron Bon Lei on Alor Island Indonesia using portable XRF. The study showed an unambiguous separation of three different source locations (Groups 1, 2 and 3). Two sources (Group 2 and 3a, b, c) dominate the assemblage numerically. Group 1 and 2 indicate use of a single volcanic formation with a strong match between Group 1 artefacts and artefacts from sites in Timor Leste. Obsidian occurs in the earliest occupation layer in the Alor sites but does not include Group 1 artefacts which occur only after approx. 12,000 cal BP. Currently the geographical location of the Group 1 outcrop is unknown, however, based on the late appearance of the Group 1 artefacts in the Alor sequence it is likely that the location is not on Alor, but rather on another island of the Sunda chain. The dating of Group 1 artefacts in widely spaced sites on the never geographically connected islands of Timor and Alor indicates that maritime interaction between islands began by at least the terminal Pleistocene. The distribution of the obsidian in Tron Bon Lei shelter Pit B shows that there were periods of more intense interaction punctuated by periods when interaction declined or ceased

Geospatial analysis of fortification locations on the island of Tongatapu, Tonga

Recent research investigating earthwork fortifications on Tongatapu, Kingdom of Tonga, using lidar data identified numerous defensive sites on the island (Parton et al. 2018), with the antiquity of the earliest building phase dating to at least 1300 CE (Clark et al. 2018; Spennemann 1989). This corresponds well with the hypothesis that fortifications appear in the Pacific at 1300–1800 CE (Field 2008). However, it is widely held that most fortifications on Tongatapu were constructed during the civil war era, from 1799 to 1852 CE (McKern 1929; Spennemann 1986; Wood 1975). Beyond questions about the exact timing of initial fortification construction, there is considerable debate about the reasons populations need to defend their land. This debate is not limited to Tonga, as it has been suggested that environmental factors and climate shifts played a significant role in the emergence of social conflict in the Pacific in general (Field 2004; Field and Lape 2010). The selection of natural defensive locations on islands has been reported from numerous parts of Oceania (Field 2008). Hill fort/ridgeline location is a common occurrence on well-researched island groups, such as Fiji (Best 1993) and Samoa (Golson 1969). This argument is also reflected in previous descriptions of fort construction under Tongan influence, such as Spennemann’s (1989:481, see also Best 1993) assertion that Tongans constructed a large upland fort on the island of Lakeba in east Fiji: Tongans were actually responsible for the erection of the Ulunikoro fortification, and Best’s argument appears convincing in the light of present evidence, it is a good example to show that fortification types are predominantly governed by topographical conditions rather than by ‘cultural’ traits. In this chapter, we report geospatial analyses of earthwork fortifications on Tongatapu (Figure 9.1). Our primary concern is the location of forts in the landscape rather than the age of defensive sites as the majority of Tongatapu forts are currently undated. In addition, we focus on enclosed/partially enclosed earthwork fortifications that are the dominant type of defensive site on Tongatapu compared with the small number of linear earthworks (Parton et al. 2018). Tongatapu is a low-lying limestone island with few natural defences. There are no steep escarpments on the lagoon side of the island, and few inland high points or vertical ridges

Mansiri in Northern Sulawesi: a new dentate-stamped pottery site in Island Southeast Asia

This short report outlines new findings from the Mansiri site, close to Toraut village, in Northern Sulawesi. Initially discovered during survey activities in the early 1990s by Dr Joko Siswanto, Balai Arkeologi Manado, the site has not been focus of archaeological activities until a re-visit of the area by Puslit Manado in 2011 and a surface survey of the surrounding area detected additional artefactual material. Previous excavations conducted by Balai Arkeologi Manado in 2011 - 2013 uncovered large numbers of decorated ceramic sherds indicative of an early Neolithic site. Initial radiocarbon examination of a small sample showed evidence of a possible pre-3000 BP deposit at the site

A scoping review of Indigenous Cultural Mapping of coastal, island, and marine environments

Indigenous Cultural Mapping (ICM) has the capacity to contribute to sustainably managing Sea Country. While there is a growing community of practice using ICM of marine, island, and coastal areas to incorporate Indigenous knowledge and cultural values into sustainability and conservation efforts, the literature is widely dispersed, and the method is not clearly defined or described. This scoping review evaluates the breadth and depth of practice undertaking ICM in island, coastal, and marine areas as captured within the English language scientific and grey literature. The objectives of this review were: 1) to determine the extent to which ICM is used a tool to manage Sea Country; 2) to evaluate the methods used throughout the process of ICM; and 3) to assess the studies against Arnstein’s (1969) ladder of participation. We used the Population Concept Context framework, searched Scopus, Web of Science, and Informit databases and Google Scholar, and identified studies that mapped Indigenous culture and/or cultural values in Sea Country. We included 54 studies that used ICM methods and were focused on Sea Country. These studies contribute to a growing body of work that demonstrates the value Indigenous knowledge adds to the sustainability of Sea Country now and into the future. High-level power-sharing and partnership throughout the research process is critically important. However, a lack of consistent standards of practice perpetuates research practices that exclude Indigenous communities from the research cycle. This limits the ability of ICM to improve sustainable practices that conserve and protect Sea Country