87 research outputs found
Community mapping for flood modelling: A case study of the Ramani Huria community mapping project in Dar es Salaam
No full textThe current intensification of the hydrologic cycle, in combination with expanding settlements in flood prone areas, makes an increasing share of the global population exposed to flood risks. Many parts of the world are, however, still lacking the data needed for flood risk management and risk reduction. The recent development of information and communication technologies has remarkably lowered the costs to collect data for flood resilience, which has accommodated the rise of community mapping projects to fill data gaps in resource-strained environments. This thesis utilises drainage data collected by the Ramani Huria community mapping project in Dar es Salaam, Tanzania, to investigate if community mapped drainage data can improve flood predictions on neighbourhood scale. A coupled 1D-2D hydrodynamic model is developed of Kijitonyama ward, and is run with and without Ramani Huria’s drainage data implemented in the 1D schematisation. The simulated flood depth for the scenarios is validated with citizen’s observations on flood depth during a rain event on 3 March, 2019. The developed model is then applied to investigate the impact of solid waste accumulation in the drainage system on floods, by closing the drainage segments that were recorded as blocked in Kijitonyama ward by Ramani Huria staff the morning after the simulated event. An experimental scenario is also run, to examine the impact of blocked culverts. The results show that community mapped drainage data indeed can enhance the performance of hydrodynamic models, as the model output corresponds better with the validation data when implementing Ramani Huria’s drainage data in the 1D schematisation, compared with a scenario run with only a 2D schematisation. The scenarios run with solid waste blockages do not influence the model output when comparing with citizen’s observations, but increase the water level in the drainage segments located upstream of the blockages.Civil Engineerin
Bregmatothrips ramani Varatharajan 2017, sp.n
No full textBregmatothrips ramani sp.n Female macroptera. Head and thorax brown, pterothorax often paler laterally; abdominal segments I–V yellowish brown, VI–X blackish brown; all legs yellow; fore wing colourless; antennal segments III–V yellowish brown, I–II and VI–VII brown (Fig. 1). Head longer than wide, slightly projecting in front of compound eyes, cheeks parallel; three pairs of ocellar setae, ocellar setae III more than twice the length of ocellar setae II, arising on inner margins of ocellar triangle, almost on the inner tangents between the fore and hind ocelli; compound eyes flat, not prolonged ventrally; post ocular setae arising in a row parallel to eye margin, pair III distinctly longer than others, more than half as long as ocellar setae III; mouth cone long, extending between fore coxae (Fig. 3). Antennae 7-segmented, segment I with two dorsoapical setae, III and IV each with a forked sense cone (Fig. 2). Pronotum slightly widened towards base; two pairs of well developed posteroangular setae, inner pair longer than outer pair; four pairs of posteromarginal setae, median pair the longest (Fig. 4). Mesonotum with transverse sculpture lines, anteromedian campaniform sensilla present about 35 microns apart; median and sub median pair of setae near posterior margin in a transverse line (Fig. 7), median pair as wide apart as campaniform sensilla. Metanotum with very faint reticulate sculpture medially, longitudinal striations laterally; median pair of setae near anterior margin; campaniform sensilla absent. Fore wing costa with 20 setae, first vein with 8 basal setae, 1 at middle and 2 distally; second vein with 9–11 setae; clavus with 4 + 1 setae; terminal seta longer than sub-terminal seta (Fig. 5). Fore tibia with a stout spine at apex (Fig. 6); hind tibia with a row of 5–6 short, stout spines on inner side and two at apex. Abdominal tergite I weakly striate, II–VIII with a few striations near anterior margin and laterally; I–VIII with pale translucent craspedum; pleurotergites slender; IX with two pairs of campaniform sensilla; X with complete median slit. Abdominal sternites without discal setae; sternite II with two pairs of posteromarginal setae; III–VII with 3 pairs of posteromarginal setae, median pair of setae on VII arise on posterior margin. Measurements (holotype female). Body length 1375. Head, length 150; width across eyes 125; ocellar setae II 20, ocellar setae III 45; postocular setae III 25. Pronotum, length 125; width 150; outer posteroangular setae 55; inner posteroangular setae 75. Fore wing length 650. Antennal segments III–VII length 30, 40, 35, 60, 40. Material studied. Holotype female, INDIA, Andaman Islands, Sipighat, collected in yellow pan trap, 26.iii.2016, (K. Veena Kumari) (ICAR / NBAIR / THYS /57). Paratypes 4 females with same data as holotype. Holotype and paratypes deposited in the Indian Agricultural Insect Museum and National Repository, National Bureau of Agricultural Insect Resources (ICAR-NBAIR), Bengaluru, India. Etymology. This new species is dedicated to the Nobel laureate, Dr. C.V. Raman for his outstanding contributions to the field of Physics. Comments. The new species is the third member of Bregmatothrips genus with forked sense cones on antennal segments III and IV. From the other members of the genus, the mesonotum of ramani is unique with the presence of anteromedian campaniform sensilla which are widely separated and the mesonotal median and submedian setae are in a transverse line. In the key to Bregmatothrips species (Mound 2011), this species tracks to B. furcatus and B. willcocksi, and that author mentioned that these two may represent variants of a single species. However, based on the original descriptions, these species are distinguished in the key above. The new species can be distinguished from furcatus by the following combination of characters: ocellar setae III well-developed, more than twice as long as ocellar setae II, arising on inner margins of ocellar triangle, almost on the inner tangents between the fore and hind ocelli (ocellar setae III arising just outside the ocellar triangle or on the outer tangent between the fore and hind ocelli in B. furcatus); post ocular setae III distinctly longer than others, more than half the length of ocellar setae III (post ocular setae III almost equal to setae I); post ocular setae arranged in a row parallel to the margin of compound eyes (arranged in a straight line far away from the eye margin), 4 pairs of pronotal posteromarginal setae (3 pairs); stout spine at apex of fore tibia (absent); two stout spines at apex of hind tibia (three stout spines at apex of hind tibia); all legs yellow (all coxae, femora and middle and hind tibiae brown, fore tibia yellow at apex increasingly browner towards base, all tarsi yellow). It can be differentiated from willcocksi by the presence of the stout spine at apex of fore tibia, position of front ocellus and interocellar setae, brown antennal segment VI, 4 pairs of pronotal posteromarginals and sternite II with 2 pairs of posteromarginal setae. Bregmatothrips sinensis, described from China, can be distinguished from the new species by having 8-segmented antennae with a simple sense cone on segments III and IV, segment I with 1 dorso-apical seta, median pair of setae on sternite VII arise in front of posterior margin.Published as part of Varatharajan, R., 2017, A new species of the genus Bregmatothrips (Thysanoptera: Thripidae) from the Andaman Islands of India, pp. 597-600 in Zootaxa 4317 (3) on page 598, DOI: 10.11646/zootaxa.4317.3.13, http://zenodo.org/record/88468
Community mapped elevation through a low-cost, dual-frequency GNSS receiver: A performance study in Delft (the Netherlands) and Dar es Salaam (Tanzania)
No full textHeavy rainfall, combined with expanding (unplanned) urban settlements in flood prone areas, expose Dar es Salaam (Tanzania) to the risks of flooding. The urbanisation is so rapid in many areas that it is not beneficial to carry out expensive surveys which are quickly out of date. The work carried out by community-mapping project Dar Ramani Huria (Swahili for "Open map") aims to make a detailed map of Dar es Salaam, to enable the hydrologic models to approach the real situation more closely. However, the surveying methods used until recently are not sufficiently accurate. However, an alternative emerges in the form of community members using a low-cost, dual-frequency global navigation satellite system (GNSS) receiver during surveys. However, before this receiver can be implemented a detailed research has to be done. In this thesis the horizontal and vertical performance of the U-blox ZED-F9P receiver in Delft (the Netherlands) and Dar es Salaam is studied. The research is divided into two parts: performance and case study. For the performance study a series of post-processed kinematic (PPK) experiments were conducted in Delft and Dar es Salaam. The experiments have been designed in order to provide a variety of location, antenna-performance, baseline length, software package and movability. In addition, two re-initialisation experiments were conducted to measure how fast the interrupted GNSS signal is regained by the receiver. The case study focused on the desirability and feasibility, mainly focussing on accuracy, of implementation in the project of Dar Ramani Huria. Structured and unstructured interviews with employees of the Humanitarian OpenStreetMap Team (HOT) Tanzania were held to find out the requirements of implementation. The positioning performance of the receiver varies between the different experiments. The conclusions regarding the positioning performance are based on the scatter plots in the horizontal plane and the positioning over time for the three separate directional components; East, North and Up. The values for the horizontal performance (RMS East, RMS North) and for the vertical performance (RMS Up) of the fix solutions insofar as they fall inside the 95% confidence ellipse are decisive. Only the relevant experiments, namely those who can map a larger area with a single reference station are taken into consideration. The horizontal positioning performance ranges from 1.13 till 16.83 However the latter, high value is from the 9 baseline Dar es Salaam experiment with a very low percentage of fixed solutions. If we disregard the experiments with low percentage of fixed solutions then the horizontal positioning performance ranges van 1.13 till 9.42. The vertical positioning performance shows less accuracy ranging from 3.56 till 14.75. If we compare this performance with the requirements for Dar Ramani Huria’s project, even the strictest of 2cm, the performance is more than adequate according to the "few cm accuracy" requirement. The experiment with the high-end antenna shows with values 2.44mm (RMS East) and 3.42mm (RMS North) the best horizontal and with the value 3.75$mm(RMS Up) the best vertical performance. Another factor influencing the performance is the location, in particular the aspect of atmospheric delay that varies between Dar es Salaam and Delft. This research thesis concludes that the implementation of the receiver in Dar Ramani Huria's project is well possible and that the performance of the receiver is adequate. This conclusion is confirmed by what is actually occurring in the field: HOT Tanzania and Dar Ramani Huria already started using the GNSS receiver and carrying out surveys with this receiver
Multifunctional polymer nanocomposites through the addition of graphene nanoplatelets and their uses in automotive fuel tanks
No full textPolymers offer a light-weighting alternative to many applications, especially in the automotive industry, but their properties are not always satisfactory. Combining a polymer with a nanofiller can allow for a composite with tunable properties, creating a multifunctional material. Current automotive fuel tanks are made from a layered structure, with the bulk being high density polyethylene (HDPE) sandwiched around a barrier polymer such as polyamide 610. The HDPE provides mechanical stability, while the barrier polymer prevents fuel from evaporating out of the system. Replacing this structure with a nanocomposite could offer a way to improve the efficiency of the system. Graphene nanoplatelets (GnP) are a few layered stack of graphene produced in a cost effective process They have excellent mechanical, thermal and electrical properties, and their platelet structure offers potential improvements to the barrier properties of a polymer This dissertation explores the addition of GnP to both HDPE and a barrier polymer.GnP and HDPE were compounded through melt mixing and the properties of the composites were characterized over a large concentration range, 0-40 wt. percent GnP. It was found that the flexural modulus and strength of the materials increased with increasing GnP content. However, the impact resistance fell sharply. The thermal stability of the composites was improved, and the barrier properties to both oxygen and fuel were improved up to 20 wt. percent GnP, after which a plateau occurred. This was attributed to misalignment and dispersion issues of the GnPAlternative processing techniques were explored to overcome the limits of melt mixing. Microlayer co-extrusion yielded highly aligned platelet, but the absolute value was not improved over melt mixing. Solution mixing yielded a better dispersion of the platelets, but that advantage was lost when re-processed through a melt mixing process. Cryo-milling the HDPE resulted in a small improvement to the dispersion of the GnP, resulting in improved barrier properties, but the mechanical properties were weakened. Coating the platelets with a low modulus, HDPE compatible material resulted in recovery of some lost impact resistance, but weakened the flexural improvements, and did not yield large improvements in barrier properties.An alternative approach was to lay thin layers of GnP onto the surface of polymer using layer by layer deposition to control the completely control the alignment and dispersion of the GnP. This was done by both alternating the GnP with a cationic polymer, and by depositing monolayers of GnP successively onto the surface. Both methods resulted in 60% reductions in oxygen permeability with less than 1 wt. percent GnPThe final method explored was the melt mixing of GnP and a biobased polyamide. As with the HDPE composites, the flexural properties of the composite increased while the impact resistance was lessened. The thermal stability of the polymer was greatly improved. The barrier properties were also improved, and it was also found that increasing the mixing time in the melt extrusion process resulted in further enhancements. The electrical conductivity of the samples was unsatisfactory. To improve this, carbon nanotubes (CNT) and carbon nanofibers (CNF), one dimensional nanofillers, were added to the composites in small quantities. It was found that through the addition of these, the electrical conductivity was greatly improved by over an order of magnitude.Thesis (Ph. D.)--Michigan State University. Chemical Engineering, 2017Includes bibliographical reference
Two-step Component Mode Synthesis with convergence for the eigensolution of large-degree-of-freedom systems
No full textComponent Mode Synthesis (CMS) is a dynamic substructuring technique for the approximate eigensolution of large-degree-of-freedom (dof) systems divisible into two or more components. System synthesis using component modes results in approximate eigenparameters; in general, using more component modes in synthesis improves the approximation. A two-step CMS approach is developed in this research. The first step involves system synthesis using the minimum number of component modes required to obtain approximate eigenvalues up to a preselected cut-off frequency, and the second step introduces additional component modes in a convergence scheme operating on the system eigenparameters calculated in the first step.
The method is developed using constraint modes for system synthesis. The eigenvectors resulting from the initial eigenproblem solution are used to transform the system matrices; this results in a non-linear eigenvalue problem which is solved by a modified shooting method. A perturbation approach is adopted to derive a convergence scheme in which successive iterations are performed for the eigenvalue and eigenvector in each step. A procedure for selecting initial values for the convergence scheme is presented. A condensation procedure is also developed for economical synthesis of systems with many connection coordinates compared to normal mode coordinates. Advantages of the present method include minimal order of system matrices, savings in computation time and a knowledge of the accuracy of the eigenparameters. Numerical examples of spring-mass systems and systems constructed with beam and shell elements are included to demonstrate the applicability of the method and results are compared with full-system eigensolution.
The method is also applicable to the synthesis of generally damped systems. Conventional state-space formulation is used to cast the equations of motion in first-order form for each component. Complex modes are combined with an appropriately defined set of constraint modes to give the mode superset for each component. The method evolves similar to the method for undamped systems. A numerical example is included to demonstrate the method and results from CMS are compared with those obtained by full-system eigensolution. Also, the applicability of the method in solving non-linear eigenvalue problems in structural dynamics is discussed, and examples are included for demonstration.Ph. D
Gambier lattices and other linearisable systems
No full textInternational audienceWe propose two different appraoches to extending the Gambier mapping to a two-dimensional lattice equation. A first approach relies on a hypothesis of separate evolutions in each of the two directions. We show that known equations like the Startsev-Garifullin-Yamilov equation, the Hietarinta equation, as well as one proposed by the current authors, are in fact Gambier lattices. A second approach, based on the same principle as the Gambier equation, that of two linearisable equations in cascade, constructs a Gambier lattice in the form of a system of two coupled Burgers equations. The (slow) growth properties of the latter are in agreement with its linearisable character
Book Review: Putin’s War on Ukraine: Russia’s Campaign for Global Counter-Revolution
No full textAuthor: Samuel Ramani
Reviewed by Dr. Lionel M. Beehner, senior Russia analyst, Foreign Military Studies Office, and senior editorial director, Columbia University School of International and Public Affairs
Senior Russia analyst Dr. Lionel M. Beehner provides thoughtful praise and critiques on Samuel Ramani’s 2023 book, Putin’s War on Ukraine, calling it “a must-read for diplomats and defense experts.” According to Beehner, Ramani provides “a front-row seat to the war,” helpfully “recalls incidents that may be buried in readers’ minds,” and “masterfully shows the chaos within Russian leadership circles near the invasion.” Beehner also distills and explains Ramani’s main point—that the reason behind Russia’s invasion of Ukraine is “not fear of NATO encirclement but of regime change and popular revolution from within” (or “counter-revolution”).https://press.armywarcollege.edu/parameters_bookshelf/1058/thumbnail.jp
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