DEVELOPMENT OF SUBAERIAL KARST IN THE KINTA VALLEY, PENINSULAR MALAYSIA

Kawasan kajian, Lembah Kinta, terletak di bahagian barat Semenanjung Malaysia. la dicirikan oleh sisa bukit batu kapur dan ciri-ciri kars yang berkaitan - dengannya, seperti gua, dolina, lubang benam, dan kars penara. Pembentukan kars di Lembah Kinta disebabkan oleh pelbagai faktor termasuk retakan, litologi, dan proses pengangkatan batuan. Pendekatan kajian yang berbeza telah digunakan untuk mengenal pasti faktor-faktor yang berkemungkinan mengawal pembentukan secara beransur-ansur sistem kars ini, serta implikasinya kepada kefahaman berkaitan sifat semulajadi kars subpermukaan. Bagi menentukan hubungan antara orientasi laluan gua dengan lineamen, selain mengenal pasti retakan utama yang mengawal ciri-ciri kars, pengukuran standard gua dan teknik pengekstrakan lineamen Spot yang berresolusi 2.5m- telah digunakan. Begitu juga untuk mengenalpasti pengaruh peningkatan dalam pembangunan sistem kars Lembah Kinta, analisis pembelahantrek (fission-tracks) apatit dan zirkon telah dijalankan. Pemetaan di beberapa gua kars telah mendapati bahawa ara

Modular plug-in high performance integrated single-phase inverter

The recent research exercises have targeted the transfer of the sandwich package benefits to application bespoke switch design, including flip-chip and device stacking topology [1]. This work presents the development of a highly integrated power switch, based on 70μm thin IGBTs and diodes rated at 600V/200A along with customized connectors to interface quickly the gate driver, the input, and the load side PCBs. This modular system has been designed with the aim to achieve high performance including the modularity and maintainability of power converter that can be worse in a system integrated into a single package

Early Grade Mathematics in Ethiopia: Alignment of Contents in the Textbooks with the Corresponding Syllabuses

An alignment of textbooks with their corresponding syllabuses contributes to effective learning. This study examined the alignment of the Ethiopian early grade (grades 1-4) mathematics textbooks (EEGMTB) with their corresponding syllabuses. Four early grade mathematics teachers at Halaba Zone of South Nations and Nationalities Peoples Reginal State (SNNPRS) participated in this study. In addition, curriculum experts at the zone and the ministry of education (MoE) participated. Data were collected through interview and document analysis by using a content analysis protocol developed by reviewing different studies on textbook quality (Bhatti, Jumani, & Bilal, 2015; Fuchs, 2013; Hashmi, Hussain, & Shoaib, 2018; Sunday, 2014; Taye, 2011), and validated. The data were analyzed qualitatively and the percentage was used to summarize the findings. The findings of this study depict that EEGMTBs were not completely aligned with the corresponding syllabuses as expected. Therefore, the study recommends special focus to be given to the alignment of textbooks with the corresponding syllabuses, especially in considering the learning outcomes when developing the textbooks. The study also suggests further research on the adequacy of the contents of early grade textbooks to equip early children with the necessary knowledge and skills expected at the level

DEVELOPMENT OF SUBAERIAL KARST IN THE KINTA VALLEY, PENINSULAR MALAYSIA

Kawasan kajian, Lembah Kinta, terletak di bahagian barat Semenanjung Malaysia. la dicirikan oleh sisa bukit batu kapur dan ciri-ciri kars yang berkaitan - dengannya, seperti gua, dolina, lubang benam, dan kars penara. Pembentukan kars di Lembah Kinta disebabkan oleh pelbagai faktor termasuk retakan, litologi, dan proses pengangkatan batuan. Pendekatan kajian yang berbeza telah digunakan untuk mengenal pasti faktor-faktor yang berkemungkinan mengawal pembentukan secara beransur-ansur sistem kars ini, serta implikasinya kepada kefahaman berkaitan sifat semulajadi kars subpermukaan. Bagi menentukan hubungan antara orientasi laluan gua dengan lineamen, selain mengenal pasti retakan utama yang mengawal ciri-ciri kars, pengukuran standard gua dan teknik pengekstrakan lineamen Spot yang berresolusi 2.5m- telah digunakan. Begitu juga untuk mengenalpasti pengaruh peningkatan dalam pembangunan sistem kars Lembah Kinta, analisis pembelahantrek (fission-tracks) apatit dan zirkon telah dijalankan. Pemetaan di beberapa gua kars telah mendapati bahawa ara

The prevalence of thermotolerant Campylobacter species in food animals in Jimma Zone, Southwest Ethiopia

Background: Thermotolerant Campylobacter spp. is known to occur in the intestinal systems of a wide variety of domestic and wild animals. Although Campylobacter jejuni and Campylobacter coli cause acute diarrhoeal diseases in humans worldwide, they mostly manifest themselves in an apparently healthy carrier state in other mammalian species. However, little is known about the presence of campylobacter bacteria in various food animals as possible sources of infection to humans in Ethiopia. Objective: The aim of this study is to determine the prevalence of thermotolerant Campylobacter spp. in various food animals in Jimma zone, southwest Ethiopia.Methods: A cross-sectional study was conducted in urban and rural farm animal settings in Jimma, southwest Ethiopia in the period between January 2004 to April 2004. Fecal specimens were collected from 485 various food animals (cattle, n=205; poultry, n=191; pigs, n=18; sheep n=71) and cultured using standard methods. Results: Campylobacter spp. were isolated from 192 (39.6%) out of 485 fecal specimens taken from various urban and rural farm animals. The highest isolation rate was recorded among chickens (68.1%), followed by pigs (50.0%), sheep (38.0%) and cattle (12.7%). Among the 192 thermophilic campylobacters isolated, 135 (70.3%) were identified to be C. jejuni, 51 (26.6%) were C. coli and 6 (3.1%) were C. lari. C. jejuni was the most prevalent species in chickens (80.8%), followed by sheep (59.3%) and cattle (53.8%). All isolates found in pigs were identified to be C. coli (100%). Conclusion: The results of this study indicate that thermophilic campylobacters are very frequent among various food animals in Ethiopia, suggesting possible risks of infection to people through the consumption of contaminated animal products or through contact with infected animals. Ethiopian Journal of Health Development Vol. 19(3) 2005: 225-22

Climate change, agriculture and international migration: An African youth perspective

Existing evidence indicates that Africa is already being affected by climate change resulting in substantial challenges for both human and natural systems. Eastern Africa is among the regions in Africa with disproportionately higher risk of adverse consequences of global warming and climate change. Climate change and variability are having significant direct and indirect impacts on agricultural production, agricultural value chains, food and nutrition security as well as the overall sustainable growth of the sector in the region. Over time, it is expected that climate change will exacerbate the prevalence of spatio-temporal climate variability in Eastern Africa, and these variabilities will manifest in the increased frequency and severity of extreme climate events and the increasing irregularity and unpredictability of weather patterns. To the region’s farmers, these emerging changes represent an additional source of risks and uncertainty

Introduction (<Special Sessions>International Symposium in Shanghai : Multilateral Comparative Study of the Historical Archives : Historical Documents, and Family, Business and Society in East Asia)

This paper presents the work on an alternative integration scheme for a half-bridge switch using 70 μm thin Si IGBTs and diodes addressing higher strength, higher toughness and higher thermal conductivity. The switch is totally bond wireless, since bonded wires increase self-heating and introduce further thermomechanical degradation mechanisms. Moreover, this solution is equipped with double side liquid cooling, and plug-in edge connectors both on the driver and load sides, allowing high power density, good accessibility and modularity. Preliminary experimental results show good switching behavior

Modular assembly of a single phase inverter based on integrated functional block

This paper presents an original modular plug-in type assembly approach for a single phase-inverter. The main focus here is, indicatively, on the power range 1-20 kW, but the methodology can be transferred to higher power levels, too. At the core of the inverter lies a power-dense double-sided-cooled half-bridge power switch architecture with integrated cooler, which is interconnected to filter elements, gate-driver and control circuitry by means of compact flat connectors. The integration exercise targets, on the one hand, the optimization of the power switch performance and reliability, as well as the reduction of circuit parasitic elements; on the other, the production of a system compatible with maintenance and repairing, featuring minimized impact of single component failure on the system maintenance and repair cost and thus on its availability. Preliminary experimental tests demonstrate the nominal functionality of the inverter

Modular integration of a matrix converter

The future development of high-performance power electronics will rely increasingly on system-level integration, where semiconductor devices are co-packaged with other active and passive components (e.g., gate drivers, filter capacitors, and inductors) into a power module. In view of the widespread electrification of pivotal elements of the energy generation and distribution infrastructure (e.g., smart grids, electric aircraft, electric vehicles), modularity is also increasingly gaining importance as a means of enhancing overall system performance and reducing long-term maintenance costs. This paper focuses on the development of a highly integrated three-to-one phase matrix converter for avionic applications. It proposes an integration approach that enhances the volumetric and gravimetric power handling capability, with enhanced electromagnetic and electrothermal performance as compared to established solutions. Maintenance is also simplified by the modular assembly approach

Advanced packaging and integration solutions for enhanced performance power convertors

The design of novel solutions for packaging and integration of power semiconductor devices to deliver switches with advanced performance and reliability is very important aspect of power electronics technology evolution. The advancement of technology in this area is committed to bring significant improvements in the design and implementation of power converters particularly in the enhancement of efficiency, higher power density and better cooling system as compared to the state-of-the-art solutions. A power module is a combination of either multiple semiconductor or discrete devices which are connected to form an electrical circuit of certain structure. They are mainly constructed with a stack of four main parts (power semiconductor devices, insulating substrate with circuit conductor, baseplate, and interconnecting material encapsulated in a plastic case) and each of these parts is of a different material. Some of the interfaces within the module are prone to failure with thermal cycling such as wire-bond, solder die attach and substrate. Therefore reducing the number of interfaces in the assembly will greatly reduce the thermal resistance from the junction to ambient and yields noticeable increase of performance. Moreover, using solid posts as opposed to wires to connect the surface of vertical power components enable a significant improvement in power density as compared with standard modules based on wire bond technology. Additionally, the replacement of wires with such posts drastically reduces the distributed parasitic inductance, together with double-sided cooling of the devices, results in an increase of performance and reliability of the components and assemblies. In this work, 70um thick Infineon technology power devices which are rated at 600V/200A were used for the assembly of a Bi-directional switch based converter and discussing the challenges and trade-offs related to selecting processes and materials. Encapsulation is also one of the important factors in making of power module to protect the power chip and the interconnections from moisture, chemicals, dust, gases, and so on. Here, insulation process was carried out for a given prototype using silicone gel; however, it is worth to note the existing challenge on insulating a very small gap between the sandwich layers of the prototype as compared with the standard planar power module structure. A basic partial discharge test was also taken to demonstrate the performance of the insulation. This research has presented an advanced modular integration approach for power device packaging demonstrating the progress beyond the state of the art in power system assembly by proposing a solution which significantly improves electromagnetic and thermomechanical performance of the power module. In particular, fully bond wireless, double sided cooling and layout symmetry are key aspects. The proposed approach is transferable to many topologies having extra benefit of restricting the impact of single device or switch failure on the general system accessibility