Synchrotron and inverse-Compton emission from blazar jets I: a uniform conical jet model

In the first of a series of papers investigating emission from blazar jets from radio to high-energy {\gamma}-rays, we revisit the class of models where the jet has a uniform conical ballistic structure. We argue that by using simple developments of these models, in the context of new multi-frequency data extending to gamma-ray energies, valuable insights may be obtained into the properties that fully realistic models must ultimately have. In this paper we consider the synchrotron and synchrotron-self-Compton emission from the jet, modelling the recent simultaneous multi-wavelength observations of BL Lac. This is the first time these components have been fitted simultaneously for a blazar using a conical jet model. In the model we evolve the electron population dynamically along the jet taking into account the synchrotron and inverse-Compton losses. The inverse-Compton emission is calculated using the Klein-Nishina cross section and a relativistic transformation into the jet frame, and we explicitly show the seed photon population. We integrate synchrotron opacity along the line of sight through the jet plasma, taking into account the emission and opacity of each section of the jet. In agreement with previous studies of radio emission, we find that a conical jet model which conserves magnetic energy produces the characteristic blazar flat radio spectrum, however, we do not require any fine-tuning of the model to achieve this. Of particular note, in our model fit to BL Lac--which at ~10^37W is a relatively low jet-power source--we find no requirement for significant re-acceleration within the jet to explain the observed spectrum.Comment: 11 pages, 6 figures, accepted for publication in MNRA

The Genealogy of Authoritive Transmission of Sanad al-Qur’an in Java Islamic Boarding Schools

Sanad is an important aspect of the Islamic scientific legacy in preserving science’s legitimacy. Every Qur’an memorizer’s dream is to have a sanad of the Qur’an. A unique lineage that lasted till the Prophet Muhammad SAW. This paper seeks to give an analysis of the importance and limitations of the sanad al-Qur’an diploma, as well as the role of Islamic boarding schools on the Indonesian island of Java in distributing the sanad al-Qur’an diploma. This study is a sort of field research that was carried out in Islamic boarding schools in Java. Method of descriptive analytic research. The findings of this study show that each pesantren (Islamic Boarding School) has its own procedure and technique for awarding the sanad al-Qur’an certificate. However, in general, the sanad al-Qur’an diploma will be awarded to santri and female students who have met the following criteria: memorizing the Qur’an 30 juz mutqin with correct recitation; depositing all of the memorization to the kiayi (listener); and having been declared to have passed the tasmi’ 30 juz exam with certain conditions set by each pesantren. Based on the facts above, it is clear that the function of pesantren (Islamic Boarding School) is very significant in the transformation process of sanad certificates since pesantren has a unique environment and procedure for getting diplomas that cannot be obtained anywhere else. Furthermore, Islamic boarding schools play an important role in preserving the legitimacy of the Qur’anic sanad brought by Nusantara scholars (‘ulama>) until they are passed on to the Prophet

Characterization of GRE pipes fatigue failure subjected to HTHP loading conditions

GRE composite pipes are a great substitute for Carbon steel, however, obstacles of introducing GRE composite pipes into oil and gas transmission lines have been primarily related to inadequate testing data to maintain materials' extended performance and pipes fatigue failure characterization. Customized testing facility has been designed and fabricated to substantiate design of GRE pipes under controlled service conditions. The testing procedure was conducted based on ASTM and ISO Standards. Pipes filled with crude oil were placed in a thermal and pressure enclosure at a temperature of 650C and an internal pressure of 130 bars for 1000 hours and fatigue failure behavior of the GRE pipes were investigated. Pipes with a surface crack a/t = 0.5 and 0.3 were exposed to alternating internal pressure of 25 cycles/min and a load ratio of R = 0.05. Fatigue tests were performed at two load levels: 50%, and 30% of the pipes strength under static internal pressure. Results show that the GRE pipes burst suddenly without any leakage when the internal pressure was high, however, the pipe exhibit leakage first and then fails when the internal pressure was low. The maximum fatigue life obtain for GRE reference and HTHP specimen pipes in the crack region were 72,237 cycles and 73,107 cycles, respectively, with applied 0.5 static internal pressure (102 MPa) and a/t = 0.3 ratio. The minimum fatigue life obtained in the crack region are 14,105 cycles and 13,627 cycles for GRE reference and HTHP specimen pipes, respectively, with applied 0.5 static internal pressure (170 MPa) for a/t = 0.3 ratio. Copyright - 2019 ASME.This publication was made possible by NPRP grant # [8-690-2-298] from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors.Scopu

The Accessibility of Tahfidz Al-Qur'an for Teachers with Disabilities at the Tahfidz Daarul Qur'an Islamic Boarding School

AbstractThe purpose of this study was to investigate the implementation of tahfidz Al-Qur'an learning by disabled teachers at the Tahfidz Daarul Qur'an Islamic Boarding School Tangerang and the efforts of teachers with disabilities to create a welcoming environment during the implementation of tahfidz Al-Qur'an learning at the Tahfidz Daarul Qur'an Islamic Boarding School Tangerang.  This is a field study with a qualitative descriptive method. This study was carried out at Tangerang's Tahfidz Daarul Qur'an Islamic Boarding School. Tahfidz Al-Qur'an Teachers (blind and physically disabled) and the Tahifdz Bureau Head were among the informants. The data was gathered through observation, interviews, and literature study on the concept of disability in Islam. The findings of this study show that teachers with disabilities at the Tahfidz Daarul Qur'an Islamic Boarding School Tangerang are capable of effective educational communication, allowing them to carry out tahfidzul Qur'an learningn along with other tahfidz teachers. There is a change while completing the rote progress report in the mutaba'ah book. Additionally, teachers with impairments make an attempt to enforce the relevant regulations by Rewarding students who comply the regulation punishing students who are against the regulation.AbstrakTujuan dari penelitian ini adalah untuk menyelidiki pelaksanaan pembelajaran tahfidz Al-Qur'an oleh guru-guru penyandang disabilitas di Pondok Pesantren Tahfidz Daarul Qur'an Tangerang dan  upaya guru-guru penyandang disabilitas untuk menciptakan lingkungan yang ramah selama pelaksanaan pembelajaran tahfidzh Al-Qur'an di Pondok Pesantren Tahfidz Daarul Qur'an Tangerang. Ini adalah studi lapangan dengan metode deskriptif kualitatif. Penelitian ini dilakukan di Pondok Pesantren Tahfidz Daarul Qur'an Tangerang. Guru-guru Tahfidz Al-Qur'an (tuna netra dan penyandang disabilitas fisik) dan Kepala Biro Tahfidz adalah beberapa informan. Data dikumpulkan melalui observasi, wawancara, dan studi literatur tentang konsep disabilitas dalam Islam. Temuan dari penelitian ini menunjukkan bahwa guru-guru penyandang disabilitas di Pondok Pesantren Tahfidz Daarul Qur'an Tangerang mampu melakukan komunikasi pendidikan yang efektif, memungkinkan mereka untuk melaksanakan pembelajaran tahfidzul Qur'an bersama guru-guru tahfidz lainnya. Ada perubahan saat menyelesaikan laporan kemajuan hafalan dalam buku mutaba'ah. Selain itu, guru-guru dengan keterbatasan berusaha untuk menegakkan peraturan yang relevan dengan memberikan penghargaan kepada siswa yang mematuhi peraturan dan menghukum siswa yang melanggar peraturan.How to Cite : Jamil, A., Khaled, N. A., Al  Rasyid, H. (2022). The Accessibility of Tahfidz Al-Qur'an for Teachers with Disabilities at the Tahfidz Daarul Qur'an Islamic Boarding School. TARBIYA: Journal of Education in Muslim Society, 9(2), 123-134. doi:10.15408/tjems.v9i2.31326

Fault Diagnosis of Crack on Gearbox Using Vibration-Based Approaches

This study experimentally investigates vibration-based approaches for fault diagnosis of automotive gearboxes. The primary objective is to identify methods that can detect gear-tooth cracks, a common fault in gearboxes. Vibrational signals were supervised on a gearbox test rig under different operating conditions of gears with three symmetrical crack depths (1, 2, and 3 mm). The severity of the gear-tooth cracks was predicted from the vibrational signal dataset using an artificial feedforward multilayer neural network with backpropagation (NNBP). The vibration amplitudes were the greatest when the crack size in the high-speed shaft was 3 mm, and the root mean square of its vibration speed was below 3.5 mm/s. The vibration amplitudes of the gearbox increased with increasing depth of the tooth cracks under different operating conditions. The NNBP predicted the states of gear-tooth cracks with an average recognition rate of 80.41% under different conditions. In some cases, the fault degree was difficult to estimate via time-domain analysis as the vibration level increases were small and not easily noticed. Results also showed that when using the same statistical features, the time-domain analysis can better detect crack degree compared to the neural network technique

Design of a Testing Facility for Investigation of Drill Pipes Fatigue Failure

Drillstring and down-hole tool failure usually results from failing to control one or more of the vibration mechanisms. The solution starts with the ability to measure different modes of vibration, hence identifying different vibration mechanisms. Lateral, torsion and axial are vibration modes that take place when drill pipes run into problems downhole. Due to the three modes of vibration mechanisms such as bit bounce, stick-slip, lateral shocks, bit and bottom hole assembly (BHA) whirl, parametric and torsional resonance occur. Understanding the causes of the destructive loads is the main step towards developing approaches to prevent or reduce their effects, hence improving drilling performance. Vibration modes and mechanisms lead to failure of the drill pipes, BHA and drill bits. Drill pipes fatigue failure is very common due to capability of producing all vibration modes and mechanisms. Drill pipe and downhole tool assembly failure usually result from failing to have power over one or more of these vibration mechanisms. A novel in house experimental setup has been developed to mimic downhole axial, lateral and torsional vibration modes and mechanisms in drilling operations. In this paper, we focus on the design and construction of the testing facility. A number of tests were conducted to validate the capability and performance of the test setup. Drill pipe fatigue failure due to lateral cyclic stresses induced in the drill pipe has also been investigated and presented in this paper. The results show that operating on a rotation speed higher than 90% of the drillstring critical speed leads to yielding in the drillstring

Drillstring Failure: Analytical and Experimental Approach

Drilling is one of the costliest activities in oil and gas industry due to the complexity of interactions with downhole rock formation. Under such conditions, the uncertainty of drillstring behaviour increase and hence it becomes difficult to predict the causes, occurrences, and types of failures. Lateral and torsional vibrations often cause failure of Bottom Hole Assembly (BHA), drillstring failure, drill bit and wall borehole damages. In this work, a model is presented to determine the impact of lateral and torsional vibrations on a drillstring during the drilling operation. The model aims to mimic real drillstring behaviour inside a wellbore with regards to its dynamic movements due to multiple real situations such as eccentricity of collars, drill pipe sections, and stick-slip phenomena occurring due to the interaction of the bit and the drillstring with the well formation. The work aims to develop a basis for determining critical operating speeds and design parameters to provide safe drilling procedures and reduce drill string fatigue failure. Lagrangian approach is used in this study to attain drillstring lateral and torsional vibration coupling equations. The nonlinear equations are solved numerically to obtain the response of the system. In this work, we also present a brief description of an in-house constructed experimental setup. The setup has the capability to imitate the downhole lateral and torsional vibration modes. Parameters from the experimental investigations are incorporated for validation of the mathematical models and for prediction of the drillstring fatigue life. Such investigations are essential for oil and gas industries as they provide solutions and recommendations about operational speed, lateral and torsional amplitudes measurements and corrections, and the conditions for avoiding occurrence of natural frequencies of the system