Analisa Pembuatan Serbuk Tembaga Hasil Proses Electrorefining Metode Laboratorium

Teknologi manufaktur masa depan mengunakan printer 3 dimensi (3 D) dengan Proses Sinter Deposisi Multi Material (MMD-Is) merupakan proses alternatif yang berpotensi sangat baik ,fungsi tinta diganti beragam serbuk logam seperti tembaga. Proses pembuatan serbuk logam dapat dilakukan proses deposisi elektrolisis.Ukuran distribusi ukuran serbuk optimum yang digunakan ukuran 52 – 74 µm (mesh 200) sampai dengan  46 - 63 πm (230 mesh). Makalah  ini akan membahas pembuatan tentang serbuk tembaga,dengan pertimbangan di atas,  metode yang paling tepat yaitu proses elektrolisis dengan metode elektrorefining, karena metode ini dapat menghasilkan bentuk serbuk butiran halus dengan spesifikasi serbuk berdiameter 40 µm atau ukuran  mesh berkisar 325 mesh ~ 400 mesh, serta mempunyai kemurnian yang tinggi, 99,97 % ~ 99,99 % tembaga. Tahapan pengujian serbuk dengan variasi, luas permukaan benda kerja 0,37 dm2, interval waktu pengendapan 100, 200, 300 (detik),variasi tetap temperatur 27 oC, jarak anoda katoda 4 (cm), konsentrasi larutan elektrrolit tetap Cu So4 5H2O 110 gr/500 cc aq,rapat arus 4,6 (I/dm2), kuat arus 1,5, 2,2 (Ampere) dan tegangan 2,2, 2,8 (volt), dianalisa massa serbuk basah yang menempel di katoda terbanyak 0,817 (gram) dengan variasi rapat arus 6 Ampere, kuat arus 6 (I/dm2), kuat arus 2,2 (Ampere) dan waktu 300 (detik).Kata kunci: “proses elektrolisis”,” metode elektrorefining” ,” serbuk tembaga”

Using generalized PowerFlux methods to estimate the parameters of periodic gravitational waves

We investigate methods to estimate the parameters of the gravitational-wave signal from a spinning neutron star using Fourier transformed segments of the strain response from an interferometric detector. Estimating the parameters from the power, we find generalizations of the PowerFlux method. Using simulated elliptically polarized signals injected into Gaussian noise, we apply the generalized methods to estimate the squared amplitudes of the plus and cross polarizations (and, in the most general case, the polarization angle), and test the relative detection efficiencies of the various methods.Comment: 8 pages, presented at Amalid7, Sydney, Australia (July 2007), fixed minor typos and clarified discussion to match published CQG version; updated reference

Precise calibration of LIGO test mass actuators using photon radiation pressure

Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic deformation of the mirror surface by using a two-beam configuration with the photon calibrator beams symmetrically displaced about the center of the optic, and simultaneously actuating the test mass with voice coil actuators and the photon calibrator to minimize fluctuations caused by the changing interferometer response. The photon calibrator is able to operate in the most sensitive interferometer configuration, and is expected to become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit

ANALISA PROSES MANUFAKTUR DI PT MAJ SEBAGAI UPAYA PENYELARASANMETODE PEMBELAJARAN PRAKTIK PRODUKSI DALAM RANGKA LINK & MATCH

PT Mekar Armada Jaya yang terletak di Cibitung, Bekasi, Jawa Barat adalah sebuah industri berskala nasional yang bergerak dalam pembuatan berbagai bagian kendaraan, khususnya yang terbuat dari lembaran baja. Proses pembuatan berbagai bagian kendaraan ini memerlukan presstool. Perusahaan ini merancang,  dan membuat, mengkaji, mengembangkan sendiri semua presstool yang diperlukan, oleh karena itu diperlukan sumber daya manusia (SDM) yang memiliki kompetensi merancang dan membuat Presstool.  Berdasarkan hal ini maka PT Mekar Armada Jaya menyelenggarakan kerja sama untuk menghasilkan kebutuhan SDM dimaksud, yakni lulusan program studi  D3 Teknik Mesin yang siap bekerja baik pada perusahaan ini maupun pada perusahaan lain yang sejenis. Bersamaan dengan adanya hubungan (Link) kerja sama antara Politeknik Negeri Semarangdan PT Mekar Armada Jaya diatas, maka perlu dilakukan kajian penyelarasan metode dan strategi pembelajaran Praktik Produksi. Hasil dari penelitian ini diharapkan metode dan strategi pembelajaran Praktik Produksi Politeknik Negeri Semarang akan selaras (match) dengan yang dilaksanakan di industri.Kata Kunci:Metode pembelajaran praktik produksi presstool

Precise calibration of LIGO test mass actuators using photon radiation pressure

Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic deformation of the mirror surface by using a two-beam configuration with the photon calibrator beams symmetrically displaced about the center of the optic, and simultaneously actuating the test mass with voice coil actuators and the photon calibrator to minimize fluctuations caused by the changing interferometer response. The photon calibrator is able to operate in the most sensitive interferometer configuration, and is expected to become a primary calibration method for future gravitational wave searches.Comment: 13 pages, 6 figures, accepted by Classical and Quantum Gravit

An all-sky search algorithm for continuous gravitational waves from spinning neutron stars in binary systems

Rapidly spinning neutron stars with non-axisymmetric mass distributions are expected to generate quasi-monochromatic continuous gravitational waves. While many searches for unknown, isolated spinning neutron stars have been carried out, there have been no previous searches for unknown sources in binary systems. Since current search methods for unknown, isolated neutron stars are already computationally limited, expanding the parameter space searched to include binary systems is a formidable challenge. We present a new hierarchical binary search method called TwoSpect, which exploits the periodic orbital modulations of the continuous waves by searching for patterns in doubly Fourier-transformed data. We will describe the TwoSpect search pipeline, including its mitigation of detector noise variations and corrections for Doppler frequency modulation caused by changing detector velocity. Tests on Gaussian noise and on a set of simulated signals will be presented.Comment: 22 pages, 10 figures, 1 table, Submitted to Classical and Quantum Gravit

Finitely presented wreath products and double coset decompositions

We characterize which permutational wreath products W^(X)\rtimes G are finitely presented. This occurs if and only if G and W are finitely presented, G acts on X with finitely generated stabilizers, and with finitely many orbits on the cartesian square X^2. On the one hand, this extends a result of G. Baumslag about standard wreath products; on the other hand, this provides nontrivial examples of finitely presented groups. For instance, we obtain two quasi-isometric finitely presented groups, one of which is torsion-free and the other has an infinite torsion subgroup. Motivated by the characterization above, we discuss the following question: which finitely generated groups can have a finitely generated subgroup with finitely many double cosets? The discussion involves properties related to the structure of maximal subgroups, and to the profinite topology.Comment: 21 pages; no figure. To appear in Geom. Dedicat

A comparison of regional and general anesthesia in patients undergoing carotid endarterectomy

AbstractPurpose: The optimal anesthetic for use during carotid endarterectomy is controversial. Advocates of regional anesthesia suggest that it may reduce the incidence of perioperative complications in addition to decreasing operative time and hospital costs. To determine whether the anesthetic method correlated with the outcome of the operation, a retrospective review of 3975 carotid operations performed over a 32-year period was performed.Methods: The records of all patients who underwent carotid endarterectomy at our institution from 1962 to 1994 were retrospectively reviewed. Operations performed with the patient under regional anesthesia were compared with those performed with the patient under general anesthesia with respect to preoperative risk factors and perioperative complications.Results: Regional anesthesia was used in 3382 operations (85.1%). There were no significant differences in the age, gender ratio, or the rates of concomitant medical illnesses between the two patient populations. The frequency of perioperative stroke in the series was 2.2%; that of myocardial infarction, 1.7%; and that of perioperative death, 1.5%. There were no statistically significant differences in the frequency of perioperative stroke, myocardial infarction, or death on the basis of anesthetic technique. A trend toward higher frequencies of perioperative stroke (3.2% vs 2.0%) and perioperative death (2.0% vs 1.4%) in the general anesthesia group was noted. In examining operative indications, however, there was a significant increase in the percentage of patients receiving general anesthesia who had sustained preoperative strokes when compared with the regional anesthesia patients (36.1% vs 26.4%; p < 0.01). There was also a statistically significant higher frequency of contralateral total occlusion in the general anesthesia group (21.8% vs 15.4%; p = 0.001). The trend toward increased perioperative strokes in the general anesthesia group may be explicable either by the above differences in the patient populations or by actual differences based on anesthetic technique that favor regional anesthesia.Conclusions: In a retrospective review of a large series of carotid operations, regional anesthesia was shown to be applicable to the vast majority of patients with good clinical outcome. Although the advantages over general anesthesia are perhaps small, the versatility and safety of the technique is sufficient reason for vascular surgeons to include it in their armamentarium of surgical skills. Considering that carotid endarterectomy is a procedure in which complication rates are exceedingly low, a rigidly controlled, prospective randomized trial may be required to accurately assess these differences. (J Vasc Surg 1996;24;946-56.