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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Kajian Hidrodinamika Vane Turbin Axial Untuk Penyerapan Energi Terbuang Dari Ulekan Di Belakang Propeller
No full textBila propeller berputar, air di sekitarnya akan bergerak dari depan ke belakang sehingga membentuk aliran slipstream. Propeller berputar akan menghasilkan dua macam aliran di belakangnya, aliran axial (axial velocity) dan aliran berrotasi (tangetntial velocity). Otto Grim mengusulkan penggunaan Vane Wheel di belakang propeller untuk meminimalkan kehilangan energi. Grim Vane wheel tersusun dari bentuk turbin untuk bagian dalamnya dan bentuk propeller bagian luarnya. Bagian turbin akan menyerap energi gerak aliran slipstream dan menghasilkan negatif thrust dan negatif torque. Bagian luarnya akan menghasilkan positif thrust dan positif torque. Tetapi sistem ini mempunyai banyak kelemahan berkaitan dengan konstruksinya , erosi daun dikarenakan tip vortex propeller dan retakan pada daunnya.
Metode yang diusulkan sekarang adalah untuk mereduksi permasalahan yang terjadi pada Grim vane wheel dengan menggunakan vane turbin di belakang propeller. Energi kinetic dari aliran slipstream diubah menjadi energi mekanik untuk menggerakkan/memutar turbin di belakang propeller guna menghasilkan listrik. Untuk menghindari interferensi dengan tip vortex propeller, maka diameter turbin dibuat lebih kecil daripada diameter propeller. Turbin dipasang tepat di belakang propeller.
Semua hal yang berkaitan dengan proses penelitian akan dilakukan secara analitis. Teori momentum, metode elemen daun dan teori garis angkat digunakan untuk menganalisa aliran di belakang propeller dan untuk menghitung gaya-gaya hidrodinamika pada vane turbin. Hipotesa gaya-gaya hidrodinamika vane turbin, dianalisa dengan menggunakan konsep actuator disc. Analisa Jalur (Path Analysis) digunakan untuk mengevaluasi pengaruh L/B, B/T, w (wake fraction) dan CT (Coefficient Thrust loading propeller) terhadap effisiensi daya mesin terhadap kinerja kapal.
Ada 30 buah kapal dari berbagai tipe dan jumlah poropeller yang telah dianalisa. Sebagai bahan masukan untuk mengevaluasi vane turbin, data powering kapal dihitung dengan menggunakan perangkat lunak perhitungan powering kapal
(DESP code 10) dan data dari model test. Ada dua aspek utama yang perlu
diperhatikan. Pertama , vane turbin akan menghasilkan gaya hidrodinamika
negatif (negative thrust) sehingga kecepatan kapal bisa berkurang (kehilangan
kecepatan). Kedua, sistem yang ditawarkan menghasilkan daya (power) dalam
bentuk energi listrik sehingga bisa mengurangi kehilangan energi dan
menyetimbangkan kehilangan energi akibat penurunan kecepatan..
Dari penelitian ini ditemukan bahwa ratio antara power turbin-propeller
(Pt/Ps) dan thrust turbin-propeller (Tt/Tp) akan mempengaruhi besaran energi
gain. Ini dapat dipresentasikan dalam bentuk fungsi y 13.51ln(x) 4.922 .
Supaya propelller vane turbin memberikan retrofit yang cukup baik maka harga
ratio tersebut tidak boleh lebih dari 9 %. Untuk kapal berbaling-baling tunggal,
vane turbin dapat meningkatkan power effisensi sebesar 3 – 15 %. Besarnya
effisiensi gain bergantung pada harga Thrust Loading propeller kapal. Kapalkapal
berbaling ganda, aplikasi vane turbin di belakang propeller tidak
direkomendasikan.
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When the propeller rotates, it draws fluid into itself from the surrounding area (slipstream). The propeller produces two types of flow behind it, accelerated flow (axial velocities) and circulating flow (tangential velocities). Otto Grim proposed to minimize the energy losses by using Grim vane-wheel. The turbine part of Grim-wheel utilizes the velocities to exert negative thrust and torque on the Grim Wheel, the outer part exerts a positive thrust and positive torque. But this system has many problems concerning with the construction (supporting structure), erosion due to its exposure to the tip vortex of the propeller and crack on the blades.
The present method proposed to examining energy losses and assessing the problem of Grim-wheel by using vane-turbine behind the propeller. The kinetic energy of the axial velocities in the slipstream behind propeller is converted to mechanic energy to rotate the vane-turbine behind propeller and to produce electric. To avoid the tip vortex of the propeller, the diameter of vane-turbine is smaller than diameter of the propeller and the position of the turbine is axially closed to the propeller.
All the cases concerning with the present method will be carried out by using analytical methods (momentum theory, blade element theory and lifting line theory) to analyze the flow behind propeller and hydrodynamics force of the vane turbine. Hypothesis of hydrodynamics force of the vane turbine, was analysed by using actuator disc concept. The Path Analysis was used for evaluating the effect of L/B, B/T, w (wake fraction) and CT (Coefficient of propeller thrust loading) on the efficiency of ship power.
There are 30 ships with various types and a number of propellers have been analyzed. As an input for evaluating the vane turbine, the ship powering data was calculated by using ship powering software (DESP code 10) and from model testing. Two aspects were taken into considerations. First, the vane turbine produced a negate
ve hydrodynamics force (negative thrust) which causes the ship speed is loss.
Secondly, the vane turbine gives an additional power and reduces the energy losses.
It is found that the ratio between power (Pt/Ps) and thrust (Tt/Tp) will affect
the efficiency gain of the vane turbine. It can be presented as a function of
y 13.51ln(x) 4.922. For beneficial point of view, the ratio between thrust turbine
and thrust propeller should not exceed than 9%. For single screw ship, the propeller
vane turbine can enhance the power efficiency gain by 3-15 %. The efficiency gain
depends on the value of the coefficient thrust loading of the propeller. For twin screw
ship, the application of vane turbine behind the propeller is not recommended
Sistem pengolahan data gaji karyawan di PT. Best Jeans Garment Industri : laporan hasil kerja praktek
No full textPerancangan pada sistem yang baru menunjukkan peningkatan kerja baik dalam hal waktu, tenaga kerja serta biaya
SINKRONISASI PROPELLER DENGAN MESIN INDUK PADA KAPAL IKAN UNTUK MENINGKATKAN EFISIENSI DAN KINERJA
No full textPemilihan dan penempatan sistem penggerak kapal ikan tradisional baik ukuran kecil (sampan) maupun ukuran besar (30 GRT), lebih banyak ditentukan oleh faktor kebiasaan dan tradisi masyarakat setempat. Akibatnya, tidak adanya sinkronisasi kerja yang efektif antara lambung kapal dengan sistem penggeraknya. Pengaruh yang ditimbulkannya akan mengakibatkan kerugian, diantaranya : pemborosan bahan bakar, vibrasi, umur pakai mesin pendek, waktu tempuh lebih lama dan olah gerak kapal tidak bagus. Sinkronisasi antara lambung kapal, mesin penggerak utama serta propeller merupakan tahapan penentu dalam perancangan ataupun pembuatan suatu kapal. Dalam tulisan ini, hal tersebut akan dibahas dengan suatu metode yang cukup akurat untuk menentukan pemilihan propeller, terutama untuk kebutuhan kapal-kapal ikan. Metode yang digunakan adalah metode faktor beban propeller dan factor beban mesin untuk mengukur sinkronisai antara propeller dengan mesin kapal
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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