Investigation of the weldability of copper to steel tubes using the electromagnetic welding process

Magnetic pulse welding is an innovative joining method which allows joining of dissimilar metal combinations. However, much remains unknown about the process and its parameters. In this paper, the weldability of copper tubes to steel rods and tubes is discussed, with the goal of examining the influence of the wall thickness of the supporting steel tube on the weld and the deformation of the components. Large deformations were observed, causing an undesirable decrease in diameter of the tubes. The quality of the obtained welds was shown to decrease with decreasing inner tube thickness as well, most likely due to the deformation of the workpieces in radial direction. Because of this, it is advisable to use an internal support to prevent deformation of the support tubes. To gain more insight in the precise mechanisms of weld formation and failure, numerical simulations are advised

Monitoring The Seawater Intrusion Into Coastal Aquifer Using Geo-Electrical Sounding : A Case Study Of The Northern-Coastal Area Of Central Java, Indonesia

ABSTRACT The aims of this study are : (1) to investigate whether there is seawater intrusion into the coastal-aquifer of the northern-coast of Central Java, (2) to study the seawater intrusion movement along the corresponding coastal area, particularly from the district of Brebes to the district of Kendal. To achieve the above goals, geo-electrical sounding technique was applied, hence by producing cross-sections of resistivity values which are perpendicular to the coast-line. The measurements were conducted in 1989 and 1996, each of wich included eleven locations which were at the same spot. Resistivity shown in the cross-section is the resistivity of the rock composition and the water in the aquifer. In this case, saline water has resistivity less than 1 ohm meter. The result shows that in 1989, among the eleven measured locations, there was only one location indicated interface between fresh water and saline seawater. This was at the cross section number 5 obtained in Pentalang. In 1996, there were 6 locations indicated the occurrence of interface. Connate saline water was detected at every cross section with various depth. Kata Kunci.: seawater - coastalaquifer - geo-electrica

Sistem Akuifer Di Lereng Gunungapi Merapi Bagian Timur Dan Tenggara : Studi Kasus di Kompleks Mataair Sungsang Boyolali Jawa Tengah

Mataair-mataair di lereng Gunungapi Merapi yang merupakan sabuk mataair (spring belt) dalam era "kebutuhan air bersih yang tidak tercemar" menjadi incaran Perusahaan Air Minum (PAM) dan juga Pengusaha Air Minum Dalam Kemasan (AMDK). Pengambilan air langsung dari mataair ternyata sering menimbulkan konflik kepentingan dengan petani pengguna air untuk pengairan. Banyak anjuran supaya penganibilan air tidak langsung dari mataair melainkan dengan mengebor dari akuifer. Tujuan dari penelitian sistem akuifer di sekitar mataair ini untuk mengetahui sistem akuifer sebagai dasar untuk menentukan lokasi pengeboran airtanah yang dapat digunakan untuk air bersih tanpa mengurangi debit air dari mataair. Metode penelitian menggunakan pendugaan geolistrik tahanan jenis (resistivity geoelectric), pengukuran debit mata air, dan pengamatan geologi dan topografi disekitar mata air. Hasil dari penelitian menunjukkan bahwa mataair-mataair di daerah penelitian merupakan mataair artesis yang keluar dari akuifer tertekan. Pemunculan mataair dari akuifer dapat diakibatkan oleh dua sebab, yaitu i) karena akuifer tertekan rerpotong oleh depresi seperti mataair Cokrotulung dan Sigedang(ii) karena akuifer tertekan oleh lapisan lempung seperti mataair Sungsang dan Nepen. Dengan diketahuinya sistem akuifer ini dapat ditentukan bahwa di daerah antara sampai S-3 dan antara S-7 sampai S-8 depot dibor sedalam 50 meter untuk mendapatkan sumur artesis. Key Word:Akuifer, Gunung Merapi, Mata ai

Dampak Hidrologis Pembangunan Waduk Kotapanjang terhadap Kompleks Candi Muara Takus di Riau

Intisari Perusahaan Listrik Negara (PLN) membangun Pembangkit Listrik Tenaga Air (PLTA) di Kotopanjang Riau dengan membendung Sungai Kampar di Muara Lahat luas genangan direncanakan 124 km2 pada elevasi 85 meter (dpal). Pembangunan waduk ini memindahkan penduduk sejumlah 4.886 KK dari daerah genangan di samping itu genangan tersebut akan menenggelamkan sebagian dari area situs Candi Muara Takus. Tujuan penelitian ini adalah (1) mempelajari dampak genangan terhadap bangunan candi(2) mencari alternatif untuk nrenanggulangi dampak yang terjadi. Metode survai, observasi lapangan dan pendugaan geolistrik digunakan dalam penelitian ini. Analisis data dilakukan diskriptif kuantitatif. Hasil penelitian ini menunjukkan bahwa ada 3 dampak hidrologis terhadap situs muara takus. (1) pada elevasi genangan 85 meter dpal akan menimbulkan air kapiler yang melernbabkan bangunan candi yang dibuat dari batubata. (2) air kapiler akan melembekkan lempung di bawah candi dan dasar candi akan melosok ke dalam tanah lempung (3) pada elevasi muka air waduk antara 83 in dpal dan 80 In dpal tebing sebelah barat yang berupa pasir kerikil dan pragmen batu akan mudah lepas dan longsor

Probing the effect of point defects on the leakage blocking capability of Al0.1Ga0.9N/Si structures using a monoenergetic positron beam

Vacancy-type defects in Al0.1Ga0.9N were probed using a monoenergetic positron beam. Al0.1Ga0.9N layers with different carbon doping concentrations ([C] = 5 x 10(17) -8 x 10(19) cm(-3)) were grown on Si substrates by metalorganic vapor phase epitaxy. The major defect species in Al0.1Ga0.9N was determined to be a cation vacancy (or cation vacancies) coupled with nitrogen vacancies and/or with carbon atoms at nitrogen sites (C(N)s). The charge state of the vacancies was positive because of the electron transfer from the defects to C-N-related acceptors. The defect charge state was changed from positive to neutral when the sample was illuminated with photon energy above 1.8 eV, and this energy range agreed with the yellow and blue luminescence. For the sample with high [C], the charge transition of the vacancies under illumination was found to be suppressed, which was attributed to the trapping of emitted electrons by C-N-related acceptors. With increasing [C], the breakdown voltage under the reverse bias condition increased. This was explained by the trapping of the injected electrons by the positively charged vacancies and C-N-related acceptors

Discussion on the figures of merit of identified traps located in the Si film : surface versus volume trap densities

The aim of this work is a discussion on the figures of merit of identified traps located in the depletion zone (Si film) of advanced MOSFET devices. Two methodologies to estimate the volume trap densities are investigated, one using the relationship between the surface trap density and volume trap density and a second one based on the temperature evolution at fixed frequency of the generation-recombination plateau level associated to the same trap. By comparing the volume trap densities estimated using these two methods, the results are not agreeing with each other, suggesting that these methods can no longer be used with accuracy in multigate devices. Moreover, they may lead in certain cases to results physically not correct. Even about of the volume defects, the linear evolution between the plateau and the characteristic frequency of the generation-recombination contributions associated to the same trap give us the surface trap density without any additional assumption

Simple, robust and on-demand generation of single and correlated photons

We propose two different setups to generate single photons on demand using an atom in front of a mirror, along with either a beam-splitter or a tunable coupling. We show that photon generation efficiency ~99% is straightforward to achieve. The proposed schemes are simple and easily tunable in frequency. The operation is relatively insensitive to dephasing and can be easily extended to generate correlated pairs of photons. They can also in principle be used to generate any photonic qubit of the form $\mu |0 \rangle + \nu |1\rangle$ in arbitrary wave-packets, making them very attractive for quantum communication applications.Comment: 10 pages, Added appendi

DLTS and FTIR study of quenching induced defects in germanium

Due to the high carrier mobility in Ge, it is more and more used as active semiconducting layer in advanced electronic devices on Si substrates [1]. Successful growth, doping and further processing of Ge requires however a good understanding of the intrinsic point defect properties that are unfortunately not well known. The present paper reports on the progress of an effort to determine the formation energy and diffusivity of the vacancy in Ge using thermal quenching techniques [2]. Experimental data on the thermal equilibrium concentration and diffusivity of vacancies in Ge are scarce and most are more than 40 years old. Most of the experimental data were obtained based on thermal quenching experiments assuming that the formed acceptors are due to quenched-in vacancies so that their concentration and formation energy can be determined from measured resistivity changes. The formation energy of the vacancy in its different charge states has recently also been calculated using ab initio calculations which showed that the (double) negatively charged vacancy has the lowest formation energy of about 2 eV in good agreement with the acceptor formation energy determined from the quenching experiments. Based on vacancy mediated dopant diffusion studies, Brotzmann et al [3] also concluded that the double negatively charged vacancy is the most probable charge state of the vacancy. In this contribution, the quenched-in acceptors are studied using deep-level transient spectroscopy. As Cu is known as contaminant which is difficult to avoid when quenching Ge, the electric properties of the quenched-in acceptors are carefully compared with those of substitutional Cu. Although at first glance similarities are striking, remarkable differences are also observed and discussed. [1] J. Vanhellemont and E. Simoen, J. Electrochem. Soc. 154 (2007), p. H572. [2] J. Vanhellemont, J. Lauwaert, A. Witecka, P. Spiewak, I. Romandic and P. Clauws, Physica B 404 (2009), p. 4529. [3] S. Brotzmann and H. Bracht, J. Appl. Phys. 103 (2008), p. 033508