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Study of the causative factors for the occurrence of Illukpotha landslide at Kalawana
(University of Peradeniya Sri Lanka, 2004-11-10) Kudahetty, Chamindi; Gunathilake, Jagath
Extremely intense rainfall occurred on 17ᵗʰ May 2003 in the Ratnapura district of Sri Lanka triggered one of the worst natural disaster of the country in the recent past. As a result of the extreme rainfall, landslides and widespread slope failures took place in the hilly areas in the Ratnapura, Kalutara, Matara, Galle and Hambanthota districts. Total of 316 landslide have been reported in the Ratnapura district itself. Among these landslides, IlIukpotha (Pothupitiya Kanda) landslide at Kalawana is the largest landslide occurred in the recent past. It covers approximately one square kilometers area and occurred as a debris flow, taking two paths along the existing valleys. This devastated landslide has been reported to be occurred on 17ᵗʰ May 2003 at 5.45 pm, killing 7 people and destroying 8 houses. This paper deals with the causative factors for occurrence of the Illukpotha landslide, which is located near the 21 km post on the Kalawana-Pothupitiya road in Ratnapura district. The field investigation revealed that this debris flow occurred due to a combination of natural and man-made causes. The extensive precipitation of over 500rnm per day (occurred within 7-8 hours of the day) has become the triggering factor of this landslide, which later converted into a devastative debris flow. IlIukpotha landslide has been initiated due to the saturation of fault zones (N 70°- 80° E and N 40° W) at the crest of the landslide as a result of the extensive infiltration of this rainwater. The underlying geological formation (weathered garnatiferrous charnockitic gneiss with relatively thick clay bands and pegmatite), extensive joint systems (parallel to the above fault systems), fault planes with thin clay seams, slope angle (approximately 35°), and deeply weathered overburden (2-4m thick) were playing a major role. The exposed bed rock along the slope shows the existence of complex folding structures associated with the axial area of the major Potupitiya antiform. General strike of the rocks (succession of charnockitic gneiss, granulitic gneiss, and biotite gneiss) is at East-West direction and except for the landslide initiation area, the whole debris flow is occurred along the dip slope. The landscape features identified on the pre-landslide aerial photographs provide evidences for the occurrence of historical landslide along the slope concerned. More over it was clear that the improper cultivation practices (cultivation of tea introducing horizontal drains in former forest land) on the steep hill slopes at this area, have further accelerated the infiltration rate. Therefore, it could be concluded that the fundamental causative factors for occurrence of the Illukpotha landslide were; continuous excessive precipitation within a short period of the day, existence of the faults, and prominent rectangular joint pattern, deeply weathered thick overburden and the change of land use from forest to tea cultivation.
A study on cardiotoxin of Sri Lankan Cobra
(University of Peradeniya Sri Lanka, 2004-11-10) Ranasinghe, J. G. S.; Suzuki, M.; Athauda, S. B. P.; Perera, P. A. J.; Moriyama, A.
Sri Lanka has the highest fatality rate of snakebites in the world. The cobra (𝘕𝘢𝘫𝘢 𝘯𝘢𝘫𝘢 𝘯𝘢𝘫𝘢) is one the most dangerous species in the Indian subcontinent. Anti venom serum (AVS) is the only effective therapy available for treatment of snake bite. Anaphylaxis can be fatal unless emergency treatment is given. At this juncture, it is worthwhile to investigate the composition of the toxins of Sri Lankan cobra and find out their homogeneity to Indian species. In this study, venom was collected from captured cobras reared at the reptile facility in the Faculty of Medicine, University of Peradeniya. Crude venom was purified by chromatographic met;hods and the purified product was subjected to protein sequencing. The cardiotoxin of Sri Lankan cobra which is responsible for tissue reactions and haematological changes after envenomation was analysed. In order to clarify the structural relationship among them, amino acid sequence of cardiotoxins determined in this study were compared with those of cardiotoxins already reported in other cobra species. The amino acid sequences of the cardiotoxin, present in the Sri Lankan cobra is different from other Asian cobras. It is much closer to 𝘕𝘢𝘫𝘢 𝘯𝘢𝘫𝘢 𝘰𝘹𝘪𝘢𝘯𝘢. This study supports the view that there are genetical differences between the Sri Lankan and Indian cobra species. It is beneficial to analyse the major toxins of our endogenous snakes and produce anti venom specific to our species in Sri Lanka, thereby helping to reduce the high fatality due to snakebite.
Super-elevation of flow in channels of nonlinear alignment
(University of Peradeniya Sri Lanka, 2004-11-10) Wijethunga, J. J.
The presence of curves or bends in alignment is unavoidable in the design of open channels. However, the flow at a bend is quite complicated due to the presence of spiral currents,cross-waves and also the super-elevation of the water surface. The difficulties in the designof channels of nonlinear alignment often arise due to the paucity of information on the reliabilityof the theoretical formulae available in the literature for the estimation of the super- elevationof flow at bends. In this backdrop, the primary objectives of the present study are: i) to improve our understanding of the flow behaviour at bends, and, ii) to examine the reliabilityof the theoretical formulae mentioned above, through an experimental investigation of the flow in channels of nonlinear alignment over a range of the relevant dimensionless parameters. The experimental work was carried out in a 6 m long masonry open channel consisting of a 60°- bend with a radius of curvature of 0.75 m. The original width and the height of the channel were 310 mm and 350 mm, respectively, whilst the channel slope was 0.02. Subsequently, the width, the height and the slope of the channel were changed to obtain measurements over a wider range of the relevant dimensionless parameters. Further, the velocity measurements were made using a 20 mm diameter propeller meter equipped with a digital counter. The measurements have been compared with the following semi-empirical formulae that are available to estimate the super-elevation. In these formulae, 𝘣 is the width of the channel; 𝘨 is the acceleration due to gravity; 𝘳 is the radius of curvature of the bend with the subscripts 𝘤, 𝘪 and 𝘰 denoting centre, inner and outer, respectively; 𝘝 is the flow velocity; and Δ𝘏 is the super-elevation of the flow. [The abstract includes mathematical functions and symbols.] The results indicate that the measured values of Δ𝘏 are closer to equations (1) and (2), whilst equation (3) under-predicts the measurements by about 50%. Therefore, it appears that equations(I) and (2) are more reliable than equation (3) in estimating the super-elevation. The way in Δ𝘏/𝘣 varies with 𝘥/𝘣 (𝘥 is the water depth) for different values of 𝘳/𝘣 has also been examined, and it appears that the general trend is for Δ𝘏/𝘣 to increase with increase of 𝘥/𝘣.
TCP vs UDP for distributed real-time applications: a practical approach
(University of Peradeniya Sri Lanka, 2004-11-10) Vijayananda, T.; Samaranayake, L.; Alahakoon, S.
Vast attentions have been paid both in the industry and academia on IP based Ethernet networks for distributed real-time applications mainly due to cost, compatibility and maintainability reasons. The controller in a distributed real-time system has access to the network through the network interface card of the computer in which it is implemented. However, the object to be controlled (Brushless DC motor (BLDC) in this case) must be provided with network connectivity by external means, which interfaces the object to the network. Development of such an Ethernet Ready Sensor Actuator (ERSA) module at a locally affordable cost using local engineering skills and technology is presented in the first half of the paper. The completed ERSA hardware module is capable of completing one analog to digital conversion of the sensor measurement and a digital to analog conversion of the received control input needed for a single actuation cycle within 1 ms. Further it supports changing sampling frequency, type of protocol, actuating mode i.e., time triggered or event triggered. In the second half, the ERSA module is used in a 10/100 Mbps Switched Ethernet network to control the speed of a 3000rpm inverter fed BIDe motor. Connection oriented, reliable Transport Control Protocol (TCP) and connectionless best effort User Datagram Protocol (UDP) have been used in the network layer. A comparative study is carried out on TCP and UDP for artificial variable network traffic in the distributed control loop with the intention of finding the better network layer protocol for distributed real-time applications. The experimental results show that under lower network traffic (up to about 70% network utilization), both protocols behave the same. However, when it reaches 90%, TCP starts deteriorating. But UDP remains unchanged. This is contradictory to the expected performance based on the construction of the two protocols. The possible reason is that the time consumed on flow control mechanisms in TCP becomes a burden under heavy utilization. Since UDP uses no such mechanism, its performance remains unchanged. This aspect needs further attention in the future.
"Teaching" a foreign culture: the challenge
(University of Peradeniya Sri Lanka, 2004-11-10) Herat, K.
It is a known fact that language and culture cannot be dissociated and therefore, the of a foreign language needs to focus also on the "study" of the foreign culture, that is, of elements that compose this foreign culture. The issue raised in this paper is precisely that the 𝘥𝘪𝘧𝘧𝘪𝘤𝘶𝘭𝘵𝘺 of "teaching" elements of French culture to Sri Lankan students of French . main obstacles that bring about this difficulty can be identified: • The distance between the two countries makes the cultural realities themselves difficult to conceptualize. • The contact with the French culture is only through video, written documents and the teachers of French, many of who too have not experienced French culture . • A French community outside of the capital city is almost non-existent. Students therefore do not have the opportunity of interacting with French people. As part of our research we asked 50 teachers of French if they included the study of French culture in their teaching programme. We also asked them what methodology they used in transmitting or "teaching" French culture to their students. The results obtained varied in the following manner: • 80% of teachers of French in the State Sector schools said they neglected this aspect since French culture was 'alien' to them. They had never '𝘭𝘪𝘷𝘦𝘥' or 𝘦𝘹𝘱𝘦𝘳𝘪𝘦𝘯𝘤𝘦𝘥 it. • 10% said they made reference to French culture in their classes since they had been to France for short-term summer training programmes and were able to explain a minimum of cultural elements, They supplemented their knowledge through reading and by listening to programmes on French television at the Alliance Francaise. • Explanations were based on the knowledge acquired by the teacher through reading and this information was given to the students. • 65% -70% of teachers were faced with the difficulty of selecting passages for study in the classroom. They were unable to explain cultural elements when they figured in the text and were therefore hesitant to use these documents in class. Culture cannot be dissociated from language. How then can the problem of "teaching" elements of French culture to Sri Lankan students of French be addressed?