ABSTRAKSwitched Reluctance Motor (SRM) banyak digunakan pada dunia industri saat ini karena memiliki kelebihan, faktor kelebihan SRM yaitu magnet permanen yang digantikan oleh rotor inti besi dan ...stator berupa belitan sehingga lebih efisien dalam perawatannya. Tujuan penelitian ini untuk memaksimalkan kinerja SRM dengan meningkatkan kecepatan, meningkatkan kepresisian pada sudut penyalaan, meningkatkan torka, menghaluskan bentuk gelombang tegangan dan arus. Metode yang digunakan adalah perangkat kontrol jenis Field Programmable Gate Array (FPGA), sensor hall effect dan rotary encoder digunakan untuk mendeteksi posisi rotor, informasi posisi rotor digunakan sebagai pedoman penentuan sudut penyalaan oleh FPGA. Hasil pengujian pertama, sensor hall effect menghasilkan kecepatan 1935 RPM, pengujian kedua yang menggunakan rotary encoder menghasilkan performa lebih baik pada kecepatan 2210 RPM. Gelombang osiloskop yang dihasilkan oleh rotary encoder juga menunjukkan hasil lebih presisi dibandingkan dengan hall effect, dapat disimpulkan bahwa strategi optimalisasi SRM lebih optimal menggunakan rotary encoder.Kata kunci: FPGA, Hall Effect, Rotary Encoder, Switched Reluctance Motor, Torka ABSTRACTSwitched Reluctance Motor (SRM) is widely used in the industrial world today because it has advantages. The aim of this research is to maximize SRM performance by increasing speed, increasing precision at ignition angle, increasing torque, smoothing voltage and current waveforms. The method used is a Field Programmable Gate Array (FPGA) type control device, a hall effect sensor and a rotary encoder are used to detect the rotor position, the rotor position information is used to determine the ignition angle by the FPGA. The results of the first test, the hall effect sensor produces a speed of 1935 RPM, the second test using a rotary encoder produces better performance at a speed of 2210 RPM. The oscilloscope waveform produced by the rotary encoder also shows more precise results than the hall effect, it can be concluded that the SRM optimization strategy is more optimal using a rotary encoder.Keywords: FPGA, Hall Effect, Rotary Encoder, Switched Reluctance Motor, Torque
ABSTRAKPenelitian ini membahas penurunan torka cogging pada generator sinkron magnet permanen untuk untuk aplikasi pada pembangkit listrik tenaga angin. Untuk meminimalkan nilai torka cogging, dapat ...dilakukan berbagai teknik, salah satunya adalah kombinasi teknik pangkasan magnet dan alur tiruan pada inti jangkar. Teknik ini diterapkan terhadap generator sinkron magnet permanen tipe integral slot dengan jumlah gigi alur 30 dan kutub 10 dan tipe fractional slot number dengan jumlah gigi alur 24 dan kutub 10. Berdasarkan hasil analisis menggunakan metode elemen hingga, didapatkan bahwa tipe fractional slot number memiliki penurunan torka cogging sebesar 98.51 % dari torka berbebannya, sedangkan penurunan torka cogging pada generator tipe integral slot number sebesar 75 % dari torka berbeban.Kata kunci: Generator sinkron magnet permanen, torka cogging, fractional slot number, integral slot number, pangkasan magnet, alur tiruan ABSTRACTThis research discusses the reduction of cogging torque on a permanent magnet synchronous generator for applications in wind power plants. To minimize the value of the cogging torque, various techniques can be carried out, one of which is a combination of magnet trimming techniques and artificial grooves on the anchor core. This technique is applied to an integral slot type permanent magnet synchronous generator with 30 grooved teeth and 10 poles and a fractional slot number type with 24 grooved teeth and 10 poles. Based on the results of analysis using the finite element method, it was found that the fractional slot number type has a torque reduction. cogging of 98.51% of the loaded torque meanwhile the decrease in cogging torque on the integral slot number type generator is 75% of the loaded torque.Keywords: Permanent Magnet Synchronous Generator, cogging torque, fractional slot number, integral slot number, magnet shaping, artificial groove
The Syrian civil war has been described as a first example of the conflicts expected in the wake of climate change. The conflict, which started in 2011, was preceded by a severe drought in 2007–2009 ...that hit agriculture and the rural population hard. But what do we really know about what happened to Syria’s climate and agriculture before and after the start of the conflict? In this article, I summarize the debate on climate driven conflict in Syria and build further with an analysis of drought and land use using satellite images. Through an analysis of water and land management in the decades before the 2007–2009 drought, a comparison of drought periods since the 1960s, and a satellite image-based analysis of agricultural activity in the period 2000–2019, I show how drought and conflict have affected Syria’s agricultural system, and discuss what is required for sustainable reconstruction and climate adaptation. Finally, I discuss the connection between climate and conflict from a security perspective and look towards the future and alternative discourses.
Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in ...the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic changes and their perceptions were compared across north-south and west-east rainfall gradients. More than 80% of all households found that rainfall had decreased, especially in the wettest areas. Increases in wind speeds and temperature were perceived by an overall 60-80% of households. Contrary to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources, vegetation, and fauna, but more so in the 500-900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region, especially in the 500-900 mm zones and the western part of SSWA.
Droughts often pose situations where stream water levels are lowest while human demand for water is highest. Here we present results of an observational study documenting changes in freshwater mussel ...communities in two southern US rivers during a multi-year drought. During a 13-year period water releases into the Kiamichi River from an impoundment were halted during droughts, while minimum releases from an impoundment were maintained in the Little River. The Kiamichi observed nearly twice as many low-flow events known to cause mussel mortality than the Little, and regression tree analyses suggest that this difference was influenced by reduced releases. During this period mussel communities in the Kiamichi declined in species richness and abundance, changes that were not observed in the Little. These results suggest that reduced releases during droughts likely led to mussel declines in one river, while maintaining reservoir releases may have sustained mussel populations in another.
Drought is a significant natural hazard that slowly evolves over time. Because of its character, drought is difficult to monitor and impacts are often poorly documented. Agriculture is one of the ...most sensitive sectors that are prone to drought. The objective of this research is to assess the impacts of drought on soybean production and revenue in Kentucky. Soybeans are one of Kentucky's most important commodities. In this study, impacts of 1930–1931, 1940–1942, 1952–1955, 1987–1988, 1999–2000, and 2007 droughts were considered. It was found that over the recent years, up to 56 % of the revenue from soybeans was lost due to drought. During the first half of the twentieth century, revenue loss reached up to 77 %. This research is valuable to the general public as well as planners and policy makers. Proper documentation of impacts of past droughts will help identify drought vulnerabilities and results in better risk management and mitigation.
China’s government is now promoting the Nomad Sedentarization Project (NSP) in large areas of grassland as a solution for ecological restoration and poverty alleviation. To examine the effects of ...this policy, we conducted in-depth interviews at two of the project’s sites and examined the social and ecological systems at village, county, and catchment scales in Jinghe County of Xinjiang. We found that (1) the NSP in one village greatly improved the household standard of living and changed their resource utilization modes; (2) the success in this village can be attributed to resources imported from the social and ecological systems at larger scales, and could not be repeated in a second nearby village with different constraints; and (3) the NSP is poorly adapted to local ecosystem characteristics, and may therefore have negative impacts at larger scales. To avoid these problems, holistic assessments are necessary to judge the NSP’s impacts on social and ecological systems at multiple scales, and the program must be implemented cautiously to account for the potential risks in ecologically vulnerable areas.
During the extreme dry year of 2006, abnormal salinity conditions in the Changjiang Estuary of the Yangtze River occurred in partial coincidence with the second impoundment phase of the TGD (Three ...Gorges Dam). Analysis of discharge observations in the upper reaches of the estuary and of salinity observations in the estuary as a whole reveals that in 2006 salinity was over 100 mg/l during 275 days, over 250 mg/l during 75 days and over 400 mg/l during 48 days. It is well known that this is due to extreme low discharges from the upper catchment area into the estuary. Moreover, large amounts of water consumed along the lower reaches of the Yangtze River can also aggravate the low discharges that lead to stronger saltwater intrusion in the estuary. Of the 75 days that salinity was over 250 mg/l, the low discharge was decreased further by 10 to 20% due to water consumption. The additional impact of the impoundment phase of the TGD (lasting 37 days in autumn) was noticeable only during 7 days in 2006. During that period, the relative contributions of the TGD and the water consumption in the lower reaches of the Yangtze River amounted to 70 and 30%, respectively. It may be concluded that the impact of the second impoundment phase of the TGD on salinity intrusion in the estuary was modest, while the extreme drought of 2006 was the dominant cause.
Summer fallow soil management is an important approach to improve soil and crop management in dryland areas. In the Loess Plateau regions, the annual precipitation is low and varies annually and ...seasonally, with more than 60% concentrated in the summer months from July to September, which is the summer fallow period in the winter wheat-summer fallow cropping system. With bare fallow in summer as a control, a 3-year location-fixed field experiment was conducted in the Loess Plateau to investigate the effects of wheat straw retention (SR), green manure (GM) planting, and their combination on soil water retention (WR) during summer fallow, winter wheat yield, and crop water use and nitrogen (N) uptake. The results showed that SR increased soil WR during summer fallow by 20 mm on average compared with the control over 3 experimental years but reduced the grain yield by 8% in the third year and the grain N content by 6-15% in all 3 years. In contrast, GM planting markedly reduced soil WR by 16 mm and 33 mm in the first and third year, respectively, but increased water use efficiency (WUE) by 16% in the third year and nitrate N accumulation in 0-100 cm soil at winter wheat sowing. Their combination did not significantly affect the soil WR or the soil nitrate N content in any of the 3 years, but did increase WUE by 11% in the third year and grain yield by 2.6% in the second year. In conclusion, the combination of SR and GM planting mitigated the negative effects of the individual measures, providing a feasible method for summer fallow management in the semiarid Loess Plateau in China and other similar regions.
It is an important approach to improving people's living condition and ameliorating the environment, and even to realizing sustainable development in such areas. iv Population growth control and ...quality improvement. Further studies should also be focused on establishing a karst rocky desertification basic information system, such as hazards monitoring and predicting system, hazard assessment system, and decision support systems.
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