80 research outputs found
Development of a Time-Integration Method for Analyzing the Photoresponse of Image Sensors: Theoretical and Experimental Verification with Digital Cameras
No full textThis study introduces a novel method for analyzing image sensors, supported by both theoretical and experimental verification. We first theoretically derived that when sinusoidal light with constant amplitude is directed onto an image sensor with fixed exposure times, the radiant energy reaching each pixel remains unchanged, irrespective of frequency fluctuations. However, when a rapid brightness variation significantly influences the photoresponse of the photodiodes in the image sensor, pixel values are expected to vary with frequency. To experimentally assess the photoresponse of image sensors, we developed a light-emitting diode (LED) light source capable of emitting sinusoidal waves up to 1 MHz, paired with a photosensor designed for this frequency range. We then exposed the image sensors of three cameras to the sinusoidal light and analyzed the frequency dependence of the pixel values. The experimental results demonstrated that the pixel values remained nearly constant (relative error of approximately 5 % or less) up to 1 MHz, showing no frequency dependence in the photoresponse within this range. These findings validate the theoretical analytical method and confirm that the image sensors of the three cameras accurately captured sinusoidal light up to 1 MHz without being influenced by the physical properties of the sensors or design parameters. However, this does not establish the limit or cutoff frequency of the image sensors
Theoretical formulation and experimental validation of brightness evaluation using digital cameras
No full textIn this study, we formulated the brightness relation of two digital photos captured by a single digital camera and verified it experimentally. The experimental results suggested that the used zoom lens has an intrinsic error, thereby making accurate photometry difficult. However, by dividing the brightness by the intrinsic error of the zoom lens, performing accurate photometry is possible. The photometry results with the single camera suggested that the brightness relation derived, and the magnitude system in astronomical photometry are applicable to widespread general photometry.論
Color analysis based on the color indices of lightning channels obtained from a digital photograph
No full textIn this study, we present an analysis using the color indices B-G,B-R, and G-R of lightning channels obtained from a digital photograph. We used color-magnitude diagrams (CMDs) modified from the traditional CMDs employed in astronomical photometry, (B-G) versus (G-R) color-color diagrams (CCDs), two-dimensional (2D) color-index images for the color indices B-G,B-R, and G-R, and a 2D brightness image to analyze the colors and brightness of the lightning channels. The CMDs and CCDs for the lightning leader channels showed that the intensity of B-band and R-band light from those channels exceeds that of the G-band light. The 2D color-index images for B-G,B-R, and G-R and the 2D brightness image indicate spatial variations in the lightning channels. The spatial variabilities of the 2D color indices and 2D brightness indicate that the intensity of the B-band light exceeds that of the G- and R-band light around a bright channel with a high electric current (i.e., the plasma is highly ionized).論
Evaluation of the brightness of lightning channels and branches using the magnitude system: Application of astronomical photometry
No full textIn this paper, we have evaluated the brightness of lightning leaders shown in a digital still image by applying the astronomical magnitude system. In order to analyze the only lightning leaders, these were extracted from the digital still image. For photometry of the lightning leaders, there is no a standard reference source such as Vega in astronomical photometry. Therefore, assuming the maximum pixel value 255 (in 256 levels) as the brightness of a standard reference source, the magnitude of the lightning leaders was obtained. The result showed that the magnitude of the lightning leaders vary spatially (i.e. 2D spatial variability). Furthermore, the result suggested that a low current channel is high magnitude and a high current channel is low magnitude. Keywords: Lightning, Fechner’s law, Magnitude system, Astronomical photometry, Image analysi
Spatial variability of correlated color temperature of lightning channels
No full textAbstractIn this paper, we present the spatial variability of the correlated color temperature of lightning channel shown in a digital still image. In order to analyze the correlated color temperature, we calculated chromaticity coordinates of the lightning channels in the digital still image. From results, the spatial variation of the correlated color temperature of the lightning channel was confirmed. Moreover, the results suggest that the correlated color temperature and peak current of the lightning channels are related to each other
Shari'a Court registers from Tehran in the second half of the nineteenth century
No full textShari'a court documents have come to be viewed as important source materials for the study of Iranian society in the 19th century, and several important studies, including those of the author, have appeared in the last ten years. However, the documents that have been employed are individual deeds and hokm, and it was been difficult to grasp the overall operations of the courts. The lack of court registers such as those from the Ottoman Empire has hampered research. In this article, I comprehensively analyze Tehran Shari'a court registers from the latter half of the 19th century that have been discovered successively in recent years with the aim of elucidating the entire function of the courts. Those analyzed are specifically the registers of Sayyed Mohammad Sadeq Tabataba'i Sangelaji (1812-1883) from the years 1867-1869, another of the same mojtahed from 1875-79, and one of Sheykh Fazl-ollah Nuri (1843-1909), covering 1886-89. They contain 992, 4, 319, and 1, 524 items respectively. These mojtaheds resided in the Sangelaj district of Tehran, but the courts did not belong to the local region but were attached to individual mojtaheds, and the registers were produced by each mojtahed. These registers are records of the legal operations of the courts as well as registered documents such as deeds and hokms. Particularly important is the fact that the motjaheds certified the hokms and deeds. Unlike the impression given by the word 'court', the number of documents related to trials were limited, and a major function was to certify transactions such as sales, rents, and debts. Moreover, the contents of the registers reflect the position and geographic roots of the motjaheds. These registers were produced in a form that conformed to the court system of the time in Iran
A counter-example by Yagita
No full textAccording to a 2018 preprint by Nobuaki Yagita, the conjecture on a relationship between K- and Chow theories for a generically twisted flag variety of a split semisimple algebraic group G, due to the author, fails for G the spinor group Spin(17). Yagita’s tools include a Brown–Peterson version of algebraic cobordism, ordinary and connective Morava K-theories, as well as Grothendieck motives related to various cohomology theories over fields of characteristic 0. We provide a proof using only the K- and Chow theories themselves and extend the (slightly modified) example to arbitrary characteristic
<Article>The Prophetʼs and Royal Bloods in Early Modern Iran : Kingship and Genealogy in the Zabūr-e Āl-e Dāvūd
No full textIn January 1750, a man named Mīrzā Sayyed Moḥammad was enthroned in Mashhad as a Safavid king, declaring himself Shāh Soleymān II. However, he was not a direct paternal descendant of the Safavid house and was linked to the royal family only through his mother. He also claimed that he was a paternal descendant of the Marʻashīs, a local sayyed dynasty that ruled the province of Mazandaran from the 14th to the 16th centuries. Why was he able to claim the Safavid kingship? Was the royal familyʼs maternal line that important, or did people trust his sayyed blood, which originated from the prophet Muḥammad? This paper provides context to Soleymān IIʼs coronation and explores the relation between kingship and genealogy in 18th-century Iran. The primary source of this study is the Zabūr-e Āl-e Dāvūd, compiled by Moḥammad Hāshem Mīrzā, son of Shāh Soleymān II. Here, Āl-e Dāvūd (Davūd family) refers to the family of Mīrzā Moḥammad Dāvūd, father of Shāh Soleymān II. The author traces their family tree from Amīr Qavām al-Dīn I (d. 1379), the first Marʻashī ruler in Mazandaran. However, a comparison of the workʼs contents with other sources would lead one to conclude that the evidence presented by Moḥammad Hāshem Mīrzā regarding their Marʻashī origin is relatively weak. One late 17th-century source even regarded their family as the “sayyeds of lace-sellers, ” which appears unrelated to the Marʻashīs. Their claim of Marʻashī roots surged in the 18th century, when Safavid pretenders tried to assert their rule after Isfahan fell in 1722. Although they considered the Safavid maternal lineage as more important than Marʻashī paternal lineage, they needed the latterʼs ancestry to claim kingship
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