Geometric Simplifications of Natural Caves in Ray-Tracing-Based Propagation Modelling

Natural caves show some similarities to human-made tunnels, which have previously been the subject of radio-frequency propagation modelling using deterministic ray-tracing techniques. Since natural caves are non-uniform because of their inherent concavity and irregular limestone formations, detailed 3D models contain a large number of small facets, which can have a detrimental impact on the ray-tracing computational complexity as well as on the modelling accuracy. Here, we analyse the performance of ray tracing in repeatedly simplified 3D descriptions of two caves in the UK, i.e., Kingsdale Master Cave (KMC) Roof Tunnel and Skirwith Cave. The trade-off between the size of the reflection surface and the modelling accuracy is examined. Further, by reducing the number of facets, simulation time can be reduced significantly. Two simplification methods from computer graphics were applied: Vertex Clustering and Quadric Edge Collapse. We compare the ray-tracing results to the experimental measurements and to the channel modelling based on the modal theory. We show Edge Collapse to be better suited for the task than Vertex Clustering, with larger simplifications being possible before the passage becomes entirely blocked. The use of model simplification is predominantly justified by the computational time gains, with the acceptable simplified geometries roughly halving the execution time given the laser scanning resolution of 10 cm.

Kajian Hadis tentang Hukum Membaca Surat Fatihah bagi Makmum dalam Shalat Jahar

Al-Fatihah is one of the Quranic verses that have a special position. Consequently, it is obligatory to recite it every time they pray. Meanwhile practically, in the jahar prayer, some of the congregations recite the al-Fatihah, but some however rejected. There is an obligation to listen to the imam reciting. This article examines some hadiths of reciting al-Fatihah for the congregation in the jahar prayer and its wisdom. This research uses the approach of hadith studies and Islamic jurisprudence. In collecting data, the takhrij hadith method was used with hadith tracing techniques through the al-Fatihah theme. There are two stages in analyzing the data. First, by using textual and contextual understanding methods in analyzing the dilalah hadith partially. Second, using the method of al-jam’u wa al-taufiq, takhshis, tarjih, maqasid al-shari’ah, and hikmat al-tashri’ in analyzing the hadiths collectively. This study shows that reading the al-Fatihah is obligatory for every congregation except in the jahar prayer for two main reasons. First, imams represent their congregations. Second, the congregations listen to their imams carefully for orderly prayer and appreciate the meaning of the al-Fatihah which implies for the congregation character building. The congregations can remind the imams if they recite incorrecly and so that the entire congregation can recite amen at the right time together.ABSTRAKSurat Al-Fatihah merupakan surat yang memiliki kedudukan istimewa dalam Al-Qur’an, sehingga umat Islam diperintahkan oleh Allah SWT untuk membacanya setiap kali melaksanakan salat. Namun dalam keseharian umat Islam berbeda praktik dalam membaca surat Al-Fatihah ketika menjadi makmum dalam salat jahar. Sebagian mereka ada yang tetap membaca surat Al-Fatihah, sementara sebagian lagi tidak membacanya karena harus menyimak bacaan imam. Permasalahan ini telah melatarbelakangi penulis untuk meneliti hadis-hadis ahkam dengan tujuan untuk mengetahui hukum membaca surat Fatihah bagi makmum dalam salat jahar menurut hadis-hadis ahkam maqbul yang relevan dengan tujuan dan hikmah persyaratan salat itu sendiri. Penelitian ini menggunakan pendekatan ilmu hadis dan usul fikih. Dalam pengumpulan data digunakan metode takhrij hadis dengan teknik penelusuran hadis melalui tema Al-Fatihah. Untuk menganalisis data ditempuh melalui dua tahapan, tahap pertama analisa terhadap dilalah hadis secara parsial dengan menggunakan metode pemahaman tekstual dan konstektual, tahap kedua analisa terhadap hadis secara kolektif dengan menggunakan metode, al-Jam’u Wa al-Taufiq, Takhshis, Tarjih, Maqashid al-Syari’ah dan Hikmah al-Tasyri’. Hasil analisis menyimpulkan bahwa menurut hadis-hadis ahkam bahwa membaca surat Al-Fatihah hukumnya wajib bagi setiap musalli, kecuali bagi makmum dalam salat jahar, karena ada dua alasan pokok yaitu, pertama karena bacaan imam sudah mewakili bacaan makmum, kedua, Karena makmum diwajibkan diam dan mendengar bacaan imam untuk ketertiban salat, untuk menghayati makna agung yang terkandung dalam surat Fatihah yang berimplikasi terhadap pembentukan karakter, untuk dapat menegur imam apabila salah bacaannya dan untuk dapat mengucapkan amin tepat pada waktunya.

A generalized photon-tracking approach to simulate spectral snow albedo and transmissivity using X-ray microtomography and geometric optics

A majority of snow radiative transfer models (RTM) treat snow as a collection of idealized grains rather than a semi-organized ice-air matrix. Here we present a generalized multi-layer photon-tracking RTM that simulates light transmissivity and reflectivity through snow based on x-ray microtomography, treating snow as a coherent structure rather than a collection of grains. Notably, the model uses a blended approach to expand ray-tracing techniques applied to sub-1 cm3 snow samples to snowpacks of arbitrary depths. While this framework has many potential applications, this study's effort is focused on simulating light transmissivity through thin snowpacks as this is relevant for surface energy balance applications and sub-nivean hazard detection. We demonstrate that this framework capably reproduces many known optical properties of a snow surface, including the dependence of spectral reflectance on snow grain size and incident zenith angle and the surface bidirectional reflectance distribution function (BRDF). To evaluate how the model simulates transmissivity, we compare it against spectroradiometer measurements collected at a field site in east-central Vermont. In this experiment, painted panels were inserted at various depths beneath the snow to emulate thin snow. The model compares remarkably well against the spectroradiometer measurements. Sensitivity simulations using this model indicate that snow transmissivity is greatest in the visible wavelengths and is limited to the top 5 cm of the snowpack for fine-grained snow, but can penetrate as deep as 8 cm for coarser grain snow. An evaluation of snow optical properties generated from a variety of snow samples suggests that coarse grained low density snow is most transmissive.

Dempster Shafer Algorithm For Expert System Early Detection of Anxiety Disorders

Anxiety is an excessive anxiety disorder that is often found in psychology. Some people generally do not realize that they may have symptoms of this anxiety disorder. If ignored and continued continuously, it can interfere with one's activities, reduce academic achievement, and disrupt psychological conditions that affect their lives. This expert system for early detection of anxiety disorders is carried out using forward chaining tracing techniques to explore the knowledge base, and the inference motor is the Dempster Shafer algorithm. Dempster Shafer calculation is done by combining symptom pieces to calculate the possibility of the anxiety disorder. This anxiety disorder detection system is built on the web. Then the test is carried out by comparing the value generated by the system with the value generated by two experts. The test results prove that the value generated by the system has a similarity of 85% to the value produced by the two experts. It can be concluded that implementing the Dempster Shafer algorithm for this expert system in the early detection of anxiety disorders is feasible.

Long-Term Tri-Modal In Vivo Tracking of Engrafted Cartilage-Derived Stem/Progenitor Cells Based on Upconversion Nanoparticles

Cartilage-derived stem/progenitor cells (CSPCs) are a potential choice for seed cells in osteal and chondral regeneration, and the outcomes of their survival and position distribution in vivo form the basis for the investigation of their mechanism. However, the current use of in vivo stem cell tracing techniques in laboratories is relatively limited, owing to their high operating costs and cytotoxicity. Herein, we performed tri-modal in vivo imaging of CSPCs during subcutaneous chondrogenesis using upconversion nanoparticles (UCNPs) for 28 days. Distinctive signals at accurate positions were acquired without signal noise from X-ray computed tomography, magnetic resonance imaging, and upconversion luminescence. The measured intensities were all significantly proportional to the cell numbers, thereby enabling real-time in vivo quantification of the implanted cells. However, limitations of the detectable range of cell numbers were also observed, owing to the imaging shortcomings of UCNPs, which requires further improvement of the nanoparticles. Our study explores the application value of upconversion nanomaterials in the tri-modal monitoring of implanted stem cells and provides new perspectives for future clinical translation.

Impact of pulsed-wave-Doppler velocity-envelope tracing techniques on classification of complete fetal cardiac cycles

Fetal echocardiography is an operator-dependent examination technique requiring a high level of expertise. Pulsed-wave Doppler (PWD) is often used as a reference for the mechanical activity of the heart, from which several quantitative parameters can be extracted. These aspects suggest the development of software tools that can reliably identify complete and clinically meaningful fetal cardiac cycles that can enable their automatic measurement. Several scientific works have addressed the tracing of the PWD velocity envelope. In this work, we assess the different steps involved in the signal processing chains that enable PWD envelope tracing. We apply a supervised classifier trained on envelopes traced by different signal processing chains for distinguishing complete and measurable PWD heartbeats from incomplete or malformed ones, which makes it possible to determine the impact of each of the different processing steps on the detection accuracy. In this study, we collected 43 images and labeled 174,319 PWD segments from 25 pregnant women volunteers. By considering seven envelope tracing techniques and the 23 different processing steps involved in their implementation, the results of our study reveal that, compared to the steps investigated in most other works, those that achieve binarisation and envelope extraction are significantly more important (p < 0.05). The best approaches among those studied enabled greater than 98% accuracy on our large manually annotated dataset.

The Role of Cell Tracing and Fate Mapping Experiments in Cardiac Outflow Tract Development, New Opportunities through Emerging Technologies

Whilst knowledge regarding the pathophysiology of congenital heart disease (CHDs) has advanced greatly in recent years, the underlying developmental processes affecting the cardiac outflow tract (OFT) such as bicuspid aortic valve, tetralogy of Fallot and transposition of the great arteries remain poorly understood. Common among CHDs affecting the OFT, is a large variation in disease phenotypes. Even though the different cell lineages contributing to OFT development have been studied for many decades, it remains challenging to relate cell lineage dynamics to the morphologic variation observed in OFT pathologies. We postulate that the variation observed in cellular contribution in these congenital heart diseases might be related to underlying cell lineage dynamics of which little is known. We believe this gap in knowledge is mainly the result of technical limitations in experimental methods used for cell lineage analysis. The aim of this review is to provide an overview of historical fate mapping and cell tracing techniques used to study OFT development and introduce emerging technologies which provide new opportunities that will aid our understanding of the cellular dynamics underlying OFT pathology.

A Shader-Based Ray Tracing Engine

Recently, ray tracing techniques have been highly adopted to produce high quality images and animations. In this paper, we present our design and implementation of a real-time ray-traced rendering engine. We achieved real-time capability for triangle primitives, based on the ray tracing techniques on GPGPU (general-purpose graphics processing unit) compute shaders. To accelerate the ray tracing engine, we used a set of acceleration techniques, including bounding volume hierarchy, its roped representation, joint up-sampling, and bilateral filtering. Our current implementation shows remarkable speed-ups, with acceptable error values. Experimental results shows 2.5–13.6 times acceleration, and less than 3% error values for the 95% confidence range. Our next step will be enhancing bilateral filter behaviors.