Analisis Uji Fungsi Sistem Elektrode Ignitor Untuk Sumber Elektron Katode Plasma

ANALISIS UJI FUNGSI SISTEM ELEKTRODE IGNITOR UNTUK SUMBER ELEKTRON KATODE PLASMA. Sistem elektrode sumber elektron katode plasma adalah suatu sistem yang berfungsi untuk menghasilkan plasma pulsa di dalam bejana generator plasma secara terkendali. Sistem elektrode terdiri dari sistem elektrode ignitor yang menginisiasi lucutan plasma dan sistem elektrode pembentuk plasma. Sistem elektrode ignitor yang dirancang tersusun dari bahan kuningan dan di depannya diberi penyambung dari bahan magnesium, bahan isolator terbuat dari teflon karena mempunyai nilai resitivitas elektrik yang tinggi (>1018 Ω cm), dan anode dibuat dari bahan SS 304 non magnetik. Bahan magnesium digunakan sebagai katode, karena magnesium mempunyai sifat fisis laju erosi paling rendah (11,7 μg/C) dan energi kohesif yang rendah sekitar 1,51 eV/atom. Dengan demikian semakin besar arus menuju katode akan semakin besar pula lucutan spot plasma yang dihasilkan. Hasil uji fungsi sistem elektrode ignitor diperoleh arus spot plasma 10,58 A dengan lebar pulsa 39 μs. Spesifikasi katode yang digunakan pada sistem elektrode ignitor berbentuk silinder dengan diameter 6 mm dan panjang 20 mm. Untuk frekuensi pengulangan spot plasma 10 Hz, katode akan tererosi dan berkurang sepanjang 17,64 μm, sedangkan untuk katode tererosi membentuk kerucut, maka katode akan berkurang sepanjang 26,46 μm untuk waktu pengujian sumber elektron katode plasma selama 5 jam. Bentuk erosi dari katode dipengaruhi oleh arus spot plasma, lebar pulsa serta kevakuman bejana plasma

Pengaruh Dosis Ion Nitrogen Pada Ketahanan Korosi, Struktur Mikro Dan Struktur Fase Biomaterial Stainless Steel Austenitik 316l

PENGARUH DOSIS ION NITROGEN PADA KETAHANAN KOROSI, STRUKTUR MIKRO DAN STRUKTUR FASE BIOMATERIAL STAINLESS STEEL AUSTENITIK 316L. Keberhasilan pemanfaatan biomaterial untuk piranti cangkok ortopedik ditentukan oleh sifat-sifat mekanik, stabilitas kimia dan biokompatibilitas dalam jaringan dan cairan tubuh. Ketahanan korosi adalah salah satu sifat utama biomaterial untuk menentukan keberhasilan cangkok ortopedik dalam jaringan tubuh. Terlepasnya partikel-partikel dari piranti cangkok ortopedik berbahan metal ke sekitar sel atau jaringan dapat mengakibatkan peradangan, reaksi alergi, toksisitas dan karsinogen. Oleh karena itu dalam penelitian ini dilakukan perbaikan sifat-sifat permukaan biomaterial stainless steel austenitik 316L dengan teknik implantasi ion nitrogen dan nitridasi ion. Implantasi ion nitrogen dilakukan pada energi ion 60 keV dengan variasi dosis ion 2 ´ 1016 ion/cm2, 5 ´ 1016 ion/cm2, 1 ´ 1017 ion/cm2 dan 2 ´ 1017 ion/cm2. Ketahanan korosi cuplikan stainless steel austenitik 316L dalam larutan Hanks dilakukan dengan menggunakan potensiostat PGS-201T, dan ketahanan korosi optimum cuplikan diperoleh pada dosis ion 5 ´ 1016 ion/cm2 dan terjadi peningkatan ketahanan korosi dengan faktor 2,1 jika dibandingkan dengan cuplikan tanpa implantasi ion nitrogen. Peningkatan ketahanan korosi cuplikan tersebut karena terbentuknya nitrida besi x-Fe2N dan e-Fe3N pada permukaan cuplikan. Selanjutnya cuplikan stainless steel austentik 316L dengan ketahanan korosi optimum tersebut dinitridasi ion pada suhu nitrodasi 350 ºC dan waktu nitridasi 4 jam. Berdasarkan uji korosi cuplikan yang dihasilkan dengan nitridasi ion diperoleh peningkatan ketahanan korosi dengan faktor 2,96 jika dibandingkan dengan cuplikan sebelum implantasi ion. Peningkatan ketahanan korosi cuplikan tersebut diakibatkan karena terbentuknya nitrida besi x-Fe2N dan g¢-Fe4N yang memiliki sifat ketahanan korosi yang baik

Discrete-time rewards model-checked

This paper presents a model-checking approach for analyzing discrete-time Markov reward models. For this purpose, the temporal logic probabilistic CTL is extended with reward constraints. This allows to formulate complex measures – involving expected as well as accumulated rewards – in a precise and succinct way. Algorithms to efficiently analyze such formulae are introduced. The approach is illustrated by model-checking a probabilistic cost model of the IPv4 zeroconf protocol for distributed address assignment in ad-hoc networks

PENENTUAN MASSA TEREROSI UNTUK BERBAGAI MATERIAL KATODA IGNITOR

ABSTRAKPENENTUAN MASSA TEREROSI UNTUK BERBAGAI MATERIAL KATODA IGNITOR. Sistem elektroda ignitor yang berfungsi menginisiasi lucutan plasma terdiri dari dua buah elektroda ignitor yang dilengkapi dengan satu unit sistem catudaya lucutan ignitor (Ignitor Discharge Power Supply) dengan 2 trafo flyback, dimana inti ferit flyback masing-masing berdiameter 1,3 cm dan 1,5 cm sehingga diperoleh arus spot plasma yang berbeda untuk kedua sistem elektroda ignitor.  Arus spot plasma tergantung pada jenis material katoda. Semakin besar arus menuju katoda maka semakin besar spot plasma yang dihasilkan sehingga semakin besar pula material katoda yang tererosi.  Dalam penelitian ini dilakukan uji fungsi sistem elektroda ignitor, dan dari hasil uji fungsi dapat ditentukan besarnya massa dan partikel material katoda ignitor yang tererosi untuk menentukan umur katoda akibat hilangnya bahan di permukaan katoda setelah terbentuk spot plasma.  Hasil pengujian spot plasma pada permukaan katoda ignitor menggunakan material Mg, diperoleh arus spot plasma 13 A dan lebar pulsa 38 µdet, sedangkan untuk material Ag, Al, Cd dan Cu masing-masing diperoleh arus spot plasma 14,32 A, 12,34 A, 12,56 A dan 10,58 A lebar pulsa 22 µdet, 39 µdet, 38 µdet, dan 34 µdet.  Material katoda yang paling baik untuk sistem elektroda ignitor adalah magnesium karena mempunyai laju erosi γ paling rendah (11,7 µg/C) sehingga tidak mudah tererosi dan rusak.  Dari hasil pengujian spot plasma diperoleh  massa katoda tererosi untuk material Mg yang paling rendah yaitu 5,78 nano gram dan katoda akan berkurang sepanjang 11,75 μm, sedangkan massa katoda tererosi paling tinggi adalah Cd (laju erosi 43,9 µg/C) sebesar 20,95 nano gram, dimana katoda akan berkurang sepanjang 85,67 μm

Kinematic characteristics of elite men's 50 km race walking.

Race walking is an endurance event which also requires great technical ability, particularly with respect to its two distinguishing rules. The 50 km race walk is the longest event in the athletics programme at the Olympic Games. The aims of this observational study were to identify the important kinematic variables in elite men's 50 km race walking, and to measure variation in those variables at different distances. Thirty men were analysed from video data recorded during a World Race Walking Cup competition. Video data were also recorded at four distances during the European Cup Race Walking and 12 men analysed from these data. Two camcorders (50 Hz) recorded at each race for 3D analysis. The results of this study showed that walking speed was associated with both step length (r=0.54,P=0.002) and cadence (r=0.58,P=0.001). While placing the foot further ahead of the body at heel strike was associated with greater step lengths (r=0.45,P=0.013), it was also negatively associated with cadence (r= -0.62,P<0.001). In the World Cup, knee angles ranged between 175 and 186° at initial contact and between 180 and 195° at midstance. During the European Cup, walking speed decreased significantly (F=9.35,P=0.002), mostly due to a decrease in step length between 38.5 and 48.5 km (t=8.59,P=0.014). From this study, it would appear that the key areas a 50 km race walker must develop and coordinate are step length and cadence, although it is also important to ensure legal walking technique is maintained with the onset of fatigue

First Principles Calculation of Elastic Properties of Solid Argon at High Pressures

The density and the elastic stiffness coefficients of fcc solid argon at high pressures from 1 GPa up to 80 GPa are computed by first-principles pseudopotential method with plane-wave basis set and the generalized gradient approximation (GGA). The result is in good agreement with the experimental result recently obtained with the Brillouin spectroscopy by Shimizu et al. [Phys. Rev. Lett. 86, 4568 (2001)]. The Cauchy condition was found to be strongly violated as in the experimental result, indicating large contribution from non-central many-body force. The present result has made it clear that the standard density functional method with periodic boundary conditions can be successfully applied for calculating elastic properties of rare gas solids at high pressures in contrast to those at low pressures where dispersion forces are important.Comment: 4 pages, 5 figures, submitted to PR

Production of asiaticoside and madecasosside in Centella asiatica in vitro and in vivo

The localization was determined of the triterpenoids, asiaticoside and madecassoside, in different organs of glasshousegrown plants and cultured material, including transformed roots, of two phenotypes of Centella asiatica (L.) Urban of Malaysian origin. Methanolic extracts of asiaticoside and madecassoside were prepared for gradient HPLC analysis. The two phenotypes of C. asiatica exhibited differences in terpenoid content that were tissue specific and varied between glasshouse-grown plants and tissue culture-derived material. Terpenoid content was highest in leaves, with asiaticoside (0.79 ± 0.03 and 1.15 ± 0.10 % of dry mass) and madecassoside [0.97 ± 0.06 and 1.65 ± 0.01 %(d.m.)] in the fringed (F) and smooth leaf (S) phenotypes, respectively. Roots of the F-phenotype contained the lowest content of asiaticoside [0.12 ± 0.01 %(d.m.)], whereas petioles of S-phenotype plants contained the lowest content of asiaticoside [0.16 ± 0.01 %(d.m.)] and madecassoside [0.18 ± 0.14 %(d.m.)]. Transformed roots were induced using Agrobacterium rhizogens and their growth was maximal on Murashige and Skoog basal medium supplemented with 60 g dm-3 sucrose. However, asiaticoside and madecassoside were undetectable in transformed roots and undifferentiated callus

First report of brown widow spider sightings in Peninsular Malaysia and notes on its global distribution

Background The brown widow spider (Latrodectus geometricus Koch, 1841) has colonised many parts of the world from its continent of origin, Africa. By at least 1841, the species had successfully established populations in South America and has more recently expanded its range to the southern states of North America. This highly adaptable spider has been far more successful in finding its niche around the world than its famous cousins, the black widow, Latrodectus mactans, found in the south-eastern states of North America, and the red-back, Latrodectus hasselti, found mostly in Australia, New Zealand and Japan. Methods We performed an extensive web search of brown widow sightings and mapped the location of each sighting using ArcGIS. Specimens reputedly of the species L. geometricus were collected at three localities in Peninsular Malaysia. The spiders were identified and documented based on an examination of morphological characteristics and DNA barcoding. Results The spiders found in Peninsular Malaysia were confirmed to be Latrodectus geometricus based on their morphological characteristics and DNA barcodes. We recorded 354 sightings of the brown widow in 58 countries, including Peninsular Malaysia. Conclusion Reports from the Americas and the Far East suggest a global-wide invasion of the brown widow spider. Herein we report the arrival of the brown widow spider in Peninsular Malaysia and provide notes on the identification of the species and its recently expanded range

Is there a risk of suburban transmission of malaria in Selangor, Malaysia?

Background The suburban transmission of malaria in Selangor, Malaysia’s most developed and populous state still remains a concern for public health in this region. Despite much successful control efforts directed at its reduction, sporadic cases, mostly brought in by foreigners have continued to occur. In addition, cases of simian malaria caused by Plasmodium knowlesi, some with fatal outcome have caused grave concern to health workers. The aim of this study was to investigate the possibility of local malaria transmission in suburban regions of Selangor, which are adjacent to secondary rainforests. Findings A malaria survey spanning 7 years (2006 - 2012) was conducted in Selangor. A total of 1623 laboratory confirmed malaria cases were reported from Selangor’s nine districts. While 72.6% of these cases (1178/1623) were attributed to imported malaria (cases originating from other countries), 25.5% (414/1623) were local cases and 1.9% (31/1623) were considered as relapse and unclassified cases combined. In this study, the most prevalent infection was P. vivax (1239 cases, prevalence 76.3%) followed by P. falciparum (211, 13.0%), P. knowlesi (75, 4.6%), P. malariae (71, 4.4%) and P. ovale (1, 0.06%). Mixed infections comprising of P. vivax and P. falciparum were confirmed (26, 1.6%). Entomological surveys targeting the residences of malaria patients’ showed that the most commonly trapped Anopheles species was An. maculatus. No oocysts or sporozoites were found in the An. maculatus collected. Nevertheless, the possibility of An. maculatus being the malaria vector in the investigated locations was high due to its persistent occurrence in these areas. Conclusions Malaria cases reported in this study were mostly imported cases. However the co-existence of local cases and potential Plasmodium spp. vectors should be cause for concern. The results of this survey reflect the need of maintaining closely monitored malaria control programs and continuous extensive malaria surveillance in Peninsula Malaysia