The astro-structures with the shape of comet and semi-circle, are found in the electronegative inductively coupled plasmas (ICPs), e.g., Ar/O2 and Ar/SF6. They are formed by means of the self-coagulation theory. This theory is built and based on two-dimensional fluid model simulation dynamic data of the above ICP sources. Concretely, quasi-Helmholtz equation is constructed through the free diffusion transport component and a novel negative chemical source term. The absolute value of recombination rate is higher than the attachment rate and so the net source of simulated anion is negative. This is quite a new chemical phenomenon in the electronegative and gaseous discharging plasmas when compared to the previously reported normal positive chemical source that will generate ambi-polar diffusion potential. In electronegative plasma, the self-coagulation is ambi-polar to sustain the electrical neutrality. Besides, when the anions are accelerated by ambi-polar potential before self-coagulated, the self-coagulation is again advective which leads to the formation of blue sheath. At the ambi-polar self-coagulation of high electronegativity, the electrons dynamics are relatively decoupled from ions and meanwhile they have their own relatively weak, spontaneous, and monopolar self-coagulation in the periphery of astro-structure. At the ambi-polar self-coagulation, both the anion and cation are individually treated as mass point models that carry charge (point charge models, more precisely). When the charge amounts of two individual astr-structures, e.g., semi-circle SF3+ and Ar+, are equal, the coagulated profile of heavy species SF3+ collapses by the expelling effect of Coulomb force that exists between the two point-charges. This is an anti-collective behavior of astro-structure, instead of the collective interaction of plasma, since the collapse of coagulated heavy species creates spatially dispersed charge density that cannot be shielded. The simulation shows that the lighter the species, the easier it self-coagulates, determined by the inertial effect of density quantity. The discharge picture of electronegative plasma is combined by a dynamic continuum transport (e.g., forming the ellipse background) and the mechanical balance contained in the static self-coagulation process (proven by dimensional analysis of continuity equation). The popular astro-structure of electronegative ICP source awaits urgently for the validation of experiment.
A substantial barrier to the single- and multi-institutional aggregation of data to supporting clinical trials, practice quality improvement efforts, and development of big data analytics resource systems is the lack of standardized nomenclatures for expressing dosimetric data. To address this issue, the American Association of Physicists in Medicine (AAPM) Task Group 263 was charged with providing nomenclature guidelines and values in radiation oncology for use in clinical trials, data-pooling initiatives, population-based studies, and routine clinical care by standardizing: (1) structure names across image processing and treatment planning system platforms; (2) nomenclature for dosimetric data (eg, dose–volume histogram [DVH]-based metrics); (3) templates for clinical trial groups and users of an initial subset of software platforms to facilitate adoption of the standards; (4) formalism for nomenclature schema, which can accommodate the addition of other structures defined in the future. A multisociety, multidisciplinary, multinational group of 57 members representing stake holders ranging from large academic centers to community clinics and vendors was assembled, including physicists, physicians, dosimetrists, and vendors. The stakeholder groups represented in the membership included the AAPM, American Society for Radiation Oncology (ASTRO), NRG Oncology, European Society for Radiation Oncology (ESTRO), Radiation Therapy Oncology Group (RTOG), Children’s Oncology Group (COG), Integrating Healthcare Enterprise in Radiation Oncology (IHE-RO), and Digital Imaging and Communications in Medicine working group (DICOM WG); A nomenclature system for target and organ at risk volumes and DVH nomenclature was developed and piloted to demonstrate viability across a range of clinics and within the framework of clinical trials. The final report was approved by AAPM in October 2017. The approval process included review by 8 AAPM committees, with additional review by ASTRO, European Society for Radiation Oncology (ESTRO), and American Association of Medical Dosimetrists (AAMD). This Executive Summary of the report highlights the key recommendations for clinical practice, research, and trials.
A atração gravitacional mútua entre os planetas do sistema solar provocam alterações nas suas orbitas que seriam perfeitamente elípticas se os planetas estivessem sujeitos somente sob a ação gravitacional do Sol. Essas alterações nas orbitas podem ser de períodos relativamente curtos (alguns anos) ao final dos quais os planetas voltam ao seu estado anterior. Podem também ter um efeito cumulativo alterando pouco a pouco as orbitas ao longo de anos ou séculos seguidos modificando completamente a órbita original ou retornando ao estado inicial depois de vários séculos. Essas são as mais interessantes de se analisar e são chamadas de perturbações seculares. Nesse texto se analisa o caso mais aparente desse fenômeno é a interação gravitacional entre Júpiter e Saturno. Alterações significativas foram detectadas pelo astrônomo Halley em 1695, e naquela época nenhuma justificativa razoável à luz da lei da gravitação universal foi encontrada, chegando a se duvidar da validade dessa lei. O problema foi solucionado quase 100 anos depois por Laplace. Esse texto é uma analise do artigo de Laplace, Mémoire sur les inégalités séculaires des planètes et des satellites, de 1787, e seus desdobramentos posteriores.
Abstract A characteristic property of pulsars is pulsed periodic radio emission, which has a high stability of periods. Despite the high stability of the emission periods of pulsars, monitoring the time of arrival of pulses (timing) shows the presence of different types of irregularities: variations of residual deviations, changes in the shape of the pulse, switching on and off of radio emission, and rotation discontinuities. Numerous observations of the radio emission of pulsars indicate that they are caused mainly by processes occurring in the pulsar’s magnetosphere. The special interest causes the observations of a pulsar in the Crab Nebula, performed, in particular, at Jodrell Bank and Pushchino Radio Astronomy Observatory of Lebedev Physical Institute. The connection between the scattering of radio pulses and the measure of the pulsar dispersion, which was established earlier in Pushchino together with Jodrell Bank, has been confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by plasma clouds with electron density fluctuations significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between glitches, dispersion measure variations, radio pulses scattering, and gamma-ray flares is discussed.
ABSTRAKPenelitian ini bertujuan menghasilkan petunjuk praktikum berbasis video tracking yang valid, praktis, dan efektif, serta mampu meningkatkan minat mahasiswa pada materi gaya gesek di bidang miring. Metode yang digunakan adalah Research and Development (R&D) dengan mengacu pada model pengembangan 4D (Define, Design, Develop dan Disseminate). Secara umum petunjuk praktikum yang dikembangkan meliputi dua topik kegiatan yakni penentuan koefisien gesek statis dengan memanipulasi kemiringan bidang serta koefisien gesek kinetis dengan menganalisis gerak benda di bidang miring. Petunjuk praktikum dalam rancangan menggunakan model praktikum/percobaan tertutup. Hasil validasi ahli yang mencakup aspek kelayakan isi, penyajian, komponen kebahasaan, dan keterlaksanaan menunjukkan petunjuk praktikum hasil pengembangan dinilai valid dengan perolehan skor rata-rata 4,03 dan layak digunakan. Hasil uji kepraktisan yang terdiri dari komponen kemenarikan, kemudahan penggunaan, dan manfaat petunjuk praktikum yang dikembangkan juga dinilai praktis dengan perolehan nilai rata-rata 3,93. Hasil uji efektifitas terhadap petunjuk praktikum menunjukkan bahwa produk pengembangan ini dinilai efektif untuk meningkatkan minat mahasiswa (kategori tinggi). Dengan demikian dapat disimpulkan bahwa produk petunjuk praktikum berbasis video tracking ini valid, praktis, efektif untuk digunakan sebagai penuntun praktikum serta mampu meningkatkan minat mahasiswa. Kata kunci: Petunjuk praktikum; video tracking; minat mahasiswa. ABSTRACTThis study is conducted to produce practical video tracking-based instructions that are valid, effective, and can increase student interest in the frictional force material on an inclined plane. The method used in this study was Research and Development (R&D) concerning the 4D development model (Define, Design, Develop and Disseminate). In general, the developed practicum instructions had covered two topics of activity, namely the determination of the coefficient of static friction by manipulating the slope of the plane and the coefficient of kinetic friction by analyzing the motion of objects on an inclined plane. Practical instructions in the design adopted a closed practicum/experimental model. The results of expert validation which include aspects of the feasibility of content, presentation, linguistic components, and implementation indicated that the practicum instructions developed were estimated valid with an average score of 4.03 and were suitable for use. On the other hand, the results of the practicality test consisting of components of attractiveness, ease of use, and the benefits of the developed practicum instructions were also considered practical with an average score of 3.93. Moreover, the results of the effectiveness test on the practicum instructions showed that this development product was considered effective for increasing student interest (high category). Thus, it can be concluded that this video tracking-based practicum guide product is valid, practical, effective to be used as a practicum guide, and is able to increase student interest. Keywords: Practical Instructions; video tracking; student interest.
Context. The Kilo-Degree Survey (KiDS) is an optical wide-field imaging survey carried out with the VLT Survey Telescope and the OmegaCAM camera. KiDS will image 1500 square degrees in four filters (ugri), and together with its near-infrared counterpart VIKING will produce deep photometry in nine bands. Designed for weak lensing shape and photometric redshift measurements, its core science driver is mapping the large-scale matter distribution in the Universe back to a redshift of ~0.5. Secondary science cases include galaxy evolution, Milky Way structure, and the detection of high-redshift clusters and quasars. Aims: KiDS is an ESO Public Survey and dedicated to serving the astronomical community with high-quality data products derived from the survey data. Public data releases, the first two of which are presented here, are crucial for enabling independent confirmation of the survey's scientific value. The achieved data quality and initial scientific utilization are reviewed in order to validate the survey data. Methods: A dedicated pipeline and data management system based on Astro-WISE, combined with newly developed masking and source classification tools, is used for the production of the data products described here. Science projects based on these data products and preliminary results are outlined. Results: For 148 survey tiles (≈160 sq.deg.) stacked ugri images have been released, accompanied by weight maps, masks, source lists, and a multi-band source catalogue. Limiting magnitudes are typically 24.3, 25.1, 24.9, 23.8 (5σ in a 2'' aperture) in ugri, respectively, and the typical r-band PSF size is less than 0.7''. The photometry prior to global homogenization is stable at the ~2% (4%) level in gri (u) with some outliers due to non-photometric conditions, while the astrometry shows a typical 2D rms of 0.03''. Early scientific results include the detection of nine high-z QSOs, fifteen candidate strong gravitational lenses, high-quality photometric redshifts and structural parameters for hundreds of thousands of galaxies.
ABSTRAK Penelitian ini bertujuan untuk mengetahui prinsip dasar dan sistem kerja pembangkit listrik tenaga mikrohidro (PLTMH) dari sudut pandang fisika sebagai upaya penyediaan dan pengembangan sumber belajar kontekstual. Penelitian ini dilaksanakan menggunakan metode studi literatur, observasi, dan wawancara. Hasilnya ditemukan bahwa PLTMH memiliki tiga komponen utama yakni air sebagai sumber energi, turbin, dan generator. Skema konversi energi pada PLTMH yang menggunakan head adalah sebagai berikut: 1) energi potensial air dari reservoir diubah menjadi energi kinetik pada pipa pesat, 2) energi kinetik air diubah menjadi energi mekanik oleh turbin air, 3) energi mekanik diubah menjadi energi listrik oleh generator. Turbin air berdasarkan prinsip kerja dibagi atas turbin impuls dan turbin reaksi. Turbin impuls memanfaatkan perubahan momentum air sebelum dan setelah menabrak sudu turbin, sedangkan turbin reaksi memanfaatkan perbedaan tekanan pada permukaan sudu. Generator bekerja berdasarkan prinsip induksi elektromagnetik. Ketika rotor generator yang terkopel pada turbin berputar, kumparan konduktor akan memotong garis medan magnet sehingga timbul tegangan induksi. Kata k unci: pembangkit listrik tenaga mikrohidro; konversi energi; turbin, generator. ABSTRACT The research aims to determine the fundamental principles and working systems of Microhydro power plants from a physical standpoint as an effort to provide and develop contextual learning resources. This study was conducted using literature, observation and interview methods. The results found that PLTMH had three main components i.e. water as energy source, turbine, and generator. The energy conversion scheme on PLTMH that uses the head is as follows: 1) The potential energy of water from the reservoir is converted into kinetic energy on the rapid pipeline, 2) water kinetic energy converted into mechanical energy by water turbine, 3) changed mechanical energy into electrical energy by generators. The water turbine based on the working principle is divided into impulse turbines and reaction turbines. The impulse turbine utilizes a change in water momentum before and after crashing the turbine's sudu, while the reaction turbine utilizes pressure differences on the surface of the Sudu. The generators work based on electromagnetic induction principles. When the rotor generator is attached to the turbine spinning, the conductor coil will cut off the magnetic field line so that the induction voltage arises. Keywords: microhydro power plant; energy conversion; turbine; generator.
Abstract A quick look at research and development in astronomy shows that we live in exciting times. Exoplanetary systems, supernovae, and merging binary black holes were far out of reach for observers two decades ago and now such phenomena are recorded routinely. This quick development would not have been possible without the ability for researchers to be connected, to think globally and to be mobile. Classical short-term positions are not always suitable to support these conditions and freelancing may be a viable alternative.We introduce the Astroserver framework, which is a new freelancing platform for scientists, and demonstrate through examples how it contributed to some recent projects related to hot subdwarf stars and binaries. These contributions, which included spectroscopic data mining, computing services and observing services, as well as artwork, allowed a deeper look into the investigated systems. The work on composite spectra binaries provided new details for the hypervelocity wide subdwarf binary PB 3877 and found diverse and rare systems with sub-giant companions in high-resolution spectroscopic surveys. The models for the peculiar abundance pattern of the evolved compact star LP 40-365 showed it to be a bound hypervelocity remnant of a supernova Iax event. Some of these works also included data visualizations to help presenting the new results. Such services may be of interest for many researchers.
We study simple models of massive galaxy clusters in which the intracluster medium (ICM) rotates differentially in equilibrium in the cluster gravitational potential. We obtain the X-ray surface brightness maps, evaluating the isophote flattening due to the gas rotation. Using a set of different rotation laws, we put constraint on the amplitude of the rotation velocity, finding that rotation curves with peak velocity up to \sim 600 km s^-1 are consistent with the ellipticity profiles of observed clusters. We convolve each of our models with the instrument response of the X-ray Calorimeter Spectrometer on board the ASTRO-H to calculate the simulated X-ray spectra at different distance from the X-ray centre. We demonstrate that such an instrument will allow us to measure rotation of the ICM in massive clusters, even with rotation velocities as low as \sim 100 km s^-1
Abstract This paper covers some aspects of the life and work of the Estonian astronomer Ernst Öpik (1893-1985), who contributed to a very wide range of astronomical disciplines, and whose publications span more than 70 years. He worked in Estonia, the Soviet Union, the United States, Germany and Northern Ireland. His visions on the role of solar variability in global climate change are emphasized, and his opinions on modelling in science are explained, in addition to his views about scientific refereeing and publishing.