Dish Array Research Articles

Indigenous Food System During Monsoon in the Context of India

India, the monsoon season is a culinary spectacle where ancient food traditions, intricately woven through generations, come to life. This period highlights the diverse indigenous food systems, which hold both cultural and ethnic significance, alongside their nutritional value. The monsoon's arrival transforms the culinary landscape, ushering in a vibrant array of flavors and dishes. Indian cuisine shares a symbiotic relationship with the monsoon. The use of indigenous spices not only enhances the taste but also offers antibacterial and antiviral properties, bolstering immunity against seasonal ailments. This season's dynamic platter invites a deeper appreciation for indigenous delicacies like the Maharashtrian 'Vagheteyachi bhaji' and the Indigenous agrarian communities of Chattisgarh celebrating 'Hareli' with medicinal brews of herbs and roots. Even festivals like Janmashtami see unique monsoon-centric dishes like 'Alvati' grace the table. The title of our research project acts as a portal into the intriguing world of culinary choices and practices across diverse Indian communities. Through this endeavor, we aim to unravel the impact of the monsoon on food and health, with a special emphasis on promoting and preserving ancient food practices. The Millet Revolution in India adds another dimension to our exploration. Millets, being resilient crops that thrive in diverse climatic conditions, have gained recognition for their nutritional benefits and suitability for monsoon cultivation. Our research delves into the scientific and religious rationales behind consuming various indigenous foods during different seasons, including those that are avoided to prevent seasonal illnesses. We evaluate governmental initiatives aimed at supporting small-scale farming institutes responsible for producing monsoon seasonal foods. Our research methodology combines primary data collection through questionnaires and community conversations, supplemented by secondary data from official statistics provided by the Government of India on the production of various indigenous food species.

Assessing Listeria monocytogenes Growth in Artificially Inoculated Sea-Farmed Product—Raw Sea Bass (Dicentrarchus labrax) Fillet, Produced in Greece

Listeria monocytogenes (Lm) is responsible for listeriosis, a serious foodborne disease, with high hospitalization and mortality rates worldwide. The main cause of listeriosis in humans is the consumption of ready-to-eat (RTE) foods; Commission Regulation (EC) No 2073/2005 establishes microbiological criteria for Lm in RTE foods. Raw fish products are widely consumed, e.g., in sushi and various seafood recipes (e.g., carpaccio, sashimi, maki, nigiri, tartare, etc.), but are not subjected to RTE food safety criteria. The aim of our study was to assess the growth potential of Lm in raw sea bass fillets obtained from a leading aquaculture company in Greece. In order to assess the growth of Lm in raw sea bass fillets, we applied the “challenge test”, a scientific experiment designed to assess the growth of Lm within a specific food product under controlled conditions. According to our results, and taking into consideration the health risk for the listeriosis-vulnerable population, raw fish products utilized in the preparation of RTE foods, including sushi and an array of seafood dishes, should be incorporated in the Category of Safety Criteria of Regulation (EC) No 2073/2005 “Ready-to-eat food able to support the growth of Listeria monocytogenes”.

Startled Stomach: Contemporary Indigeneity and Sensorial “Culture Shock” in Aljenljeng Tjaluvie’s Paiwan Pop Music

In 2016, Aljenljeng ended a thirteen-year hiatus and returned to the pop music scene in Taiwan with her first solo album, all in the Paiwan language, Vavayan. Formerly a Mandopop singer, Aljenljeng used to be known by the Chinese stage name Abao and sang only in Mandarin Chinese. Her choice to compose and sing the whole album in Paiwan signals a critical re-evaluation of Mandopop culture and its lyrical paradigm, which normalized Mandarin monolingualism as both the index of musical modernity in Taiwan and the lingua franca of Mandopop’s internationalization during the 1990s and early 2000s. Aljenljeng’s Paiwan turn was an effort to disrupt both Mandopop’s consumption of Indigenous music in Taiwan and the settler structure of feeling. Aljenljeng’s audiovisual expressions, sensorial experiences, and depictions of contact between Indigenous and non-Indigenous cultures in Taiwan generate meaningful Indigenous-initiated transcultural conversations. Aljenljeng’s video for “Minetjus” (which translates as “startled” or “shocked”) counters settler (over)consumption by placing settler, rather than Indigenous, individuals in the position of being observed, absorbed, transformed, and compelled to adapt. Amid the rhythmic naming of an array of Paiwan dishes in the song and video, the singer playfully cautions, “Don’t eat too much, otherwise your stomach will be startled.” Here, the Paiwan idiom for stomachache, “to have one’s stomach startled/shocked,” signifies both an openness to intercultural exposure and a rejection of the settler desire to digest and consume. Extending from the music tradition of the Paiwan, one of the sixteen Indigenous nations on the island, Aljenljeng’s work affirms intercultural curiosity on the premise of Indigenous sensory and emotional sovereignty, further fostering the possibility of interethnic dialogue in multicultural contemporary Taiwan.

Design and fabrication of Solar dish array and study it characterization

Designed and fabricated a (3.25m) solar dish array ,by using (52) plane mirror. These mirrors are level and fixed to reflect the radiation in one area (focus) and after distance (1.5 m). In addition, it was found that the heat concentration (217.79 W) the useful energy (1416.125W) and the center efficiency were55% at (400-700W/m2). The solar dish array is relatively suitable for solar thermal applications.

The Tianlai dish array low-z surveys forecasts

ABSTRACT We present the science case for surveys with the Tianlai dish array interferometer tuned to the [1300, 1400] MHz frequency range. Starting from a realistic generation of mock visibility data according to the survey strategy, we reconstruct maps of the sky and perform foreground subtraction. We estimate the level of residuals from imperfect subtraction, mostly due to mode mixing, i.e. distortions in the reconstructed 3D maps due to frequency-dependent instrument response. We show that a survey of the North Celestial Polar cap during a year of observations, covering an area of $150 \, \mathrm{deg^2}$, would reach a sensitivity of $1.5-2 \, \mathrm{mK}$ per $1 \, \mathrm{MHz} \times 0.25^2 \, \mathrm{deg^2 }$ voxel and be marginally impacted by mode mixing. Tianlai would be able to detect ∼10 nearby massive H i clumps as well as a very strong cross-correlation signal of 21 cm intensity maps with the North Celestial Cap Survey optical galaxies. We also studied the performance of a mid-latitude survey, covering $\sim 1500 \, \mathrm{deg^2}$ overlapping the SDSS footprint. Despite a higher noise level for the mid-latitude survey, as well as significant distortions due to mode mixing, Tianlai would be able to detect a highly significant cross-correlation between the 21 cm signal and the Sloan spectroscopic galaxy sample. Using the extragalactic signals measured from either or both of these surveys, and comparing them with simulations such as those presented here will make it possible to assess the impact of various instrumental imperfections on the Tianlai dish array performance. This would pave the way for future intensity mapping surveys with higher sensitivity.

Heritage as Restitution: The Dadaab Refugee Camps, Kenya

AbstractRecognizing architectures of unelected migration as sites of modern history and heritage not only expands the consideration of modernities in Africa but also constitutes a form of restitution to those who have fled insecurity and violence imposed by others. In this paper and pictorial presentation based on 12 years of archival and on‐site research, I argue that the Dadaab refugee camps and their inhabitation of the Kenya‐Somalia borderland may be understood and valued for a long history as well as a recent materiality, which has taken form in architecture, spatial practices, and territorial construction. Rather than accepting the relegation of refugee architecture to policy studies or the applied social sciences, which privilege the logics of emergency and an epistemology of the security state over knowledge stemming from people's migratory lives, this paper takes seriously the paradoxes of Dadaab as a heritage site. At Dadaab, the Kenyan government and UNHCR established relief operations in a region inscribed with colonial and postcolonial frontiers and wars, carrying a memory of detention and an imaginary of a borderland. These modern historical forces are reiterated in humanitarian settlements holding half a million registered refugees and unregistered migrants, enacting confinement in architectures figured as much by the visual frailty of dwellings dusted red by the wind and clad in recovered textile fragments as by a spectacular array of satellite dishes, aeronautic fleets on tarmac, aluminum and polyvinyl chloride water storage towers, and hydraulic extraction machinery penetrating a Jurassic‐era aquifer. These architectures signal transience even if anchored in the earth and sky, part of an ecology that once supported pastoralists and now undergirds another migratory world. My pictorially oriented paper uses these historical and aesthetic paradoxes to argue for this complex African heritage site, and with it, restitution of a fraught landscape of migration through a meaningful reconsideration of modern heritage.

AlgoSCR: an algorithm for solar contamination removal from radio interferometric data

ABSTRACT Hydrogen intensity mapping is a new field in astronomy that promises to make three-dimensional maps of the matter distribution of the Universe using the redshifted $21\, \textrm {cm}$ line of neutral hydrogen gas (HI). Several ongoing and upcoming radio interferometers, such as Tianlai, CHIME, HERA, HIRAX, etc., are using this technique. These instruments are designed to map large swaths of the sky by drift scanning over periods of many months. One of the challenges of the observations is that the daytime data are contaminated by strong radio signals from the Sun. In the case of Tianlai, this results in almost half of the measured data being unusable. We try to address this issue by developing an algorithm for solar contamination removal (AlgoSCR) from the radio data. The algorithm is based on an eigenvalue analysis of the visibility matrix and hence is applicable only to interferometers. We apply AlgoSCR to simulated visibilities, as well as real daytime data from the Tianlai dish array. The algorithm can reduce strong solar contamination by about 95 per cent without seriously affecting other weaker sky signals and thus makes the data usable for certain applications.

Milliarcsecond Localization of the Repeating FRB 20201124A

Abstract Very long baseline interferometric (VLBI) localizations of repeating fast radio bursts (FRBs) have demonstrated a diversity of local environments: from nearby star-forming regions to globular clusters. Here we report the VLBI localization of FRB 20201124A using an ad hoc array of dishes that also participate in the European VLBI Network (EVN). In our campaign, we detected 18 bursts from FRB 20201124A at two separate epochs. By combining the visibilities from both epochs, we were able to localize FRB 20201124A with a 1σ uncertainty of 2.7 mas. We use the relatively large burst sample to investigate astrometric accuracy and find that for ≳20 baselines (≳7 dishes) we can robustly reach milliarcsecond precision even using single-burst data sets. Subarcsecond precision is still possible for single bursts, even when only ∼6 baselines (four dishes) are available. In such cases, the limited uv coverage for individual bursts results in very high side-lobe levels. Thus, in addition to the peak position from the dirty map, we also explore smoothing the structure in the dirty map by fitting Gaussian functions to the fringe pattern in order to constrain individual burst positions, which we find to be more reliable. Our VLBI work places FRB 20201124A 710 ± 30 mas (1σ uncertainty) from the optical center of the host galaxy, consistent with originating from within the recently discovered extended radio structure associated with star formation in the host galaxy. Future high-resolution optical observations, e.g., with Hubble Space Telescope, can determine the proximity of FRB 20201124A’s position to nearby knots of star formation.

A deep learning framework for Square Kilometre Array Science Data Challenge 1

ABSTRACT The Square Kilometre Array (SKA), as an eminent radio telescope of the next generation, will observe a huge number of objects with complex morphologies and sizes. An efficient method for locating and classifying radio sources becomes a requirement for scientific exploration. The SKA Science Data Challenge 1 (SDC1) is focused on the source detection, characterization, and classification for the SKA mid-frequency dish array of simulated continuum data. Three frequencies are covered (560, 1400, and 9200 MHz) to three depths (8, 100, and 1000 h). In this paper, we present an efficient deep learning framework, which is an entirely parallel, Python-based method for confronting the data challenge. The method can exceptionally achieve the source finding and categorizing simultaneously for both point and extended sources. In addition, the proposed denoising model can be a good noise estimator as a plugin for other similar applications. Compared with the published best, our score has improved by at least 22 per cent and up to 125 per cent in nine images of SDC1.

L-band cryogenic radio astronomy receiver front-end of the Square Kilometre Array

This paper describes the design and measured performance of the band 2 (L-band, 950 MHz–1760 MHz) cryogenic receiver front-end of the Square Kilometre Array (SKA) radio telescope dish array. The system comprises a wide flare-angle axially corrugated conical horn, a dual linearly polarized orthogonal mode transduce, a noise injection directional coupler, and two amplification stages. Its compact design and cryogenic cooling allow for a very low receiver noise temperature, and it presents another step in the continuous improvement of the noise temperature performance. A Gifford–McMahon cooler physically cools the OMT with its integrated directional coupler to around 70 K, and the first stage low-noise amplifier to about 15 K. A bespoke measurement setup was designed to measure the system’s performance. The measured receiver noise is about 6 K across the frequency band.

H i intensity mapping with MeerKAT: calibration pipeline for multidish autocorrelation observations

ABSTRACT While most purpose-built 21-cm intensity mapping experiments are close-packed interferometer arrays, general-purpose dish arrays should also be capable of measuring the cosmological 21-cm signal. This can be achieved most efficiently if the array is used as a collection of scanning autocorrelation dishes rather than as an interferometer. As a first step towards demonstrating the feasibility of this observing strategy, we show that we are able to successfully calibrate dual-polarization autocorrelation data from 64 MeerKAT dishes in the L band (856–1712 MHz, 4096 channels), with 10.5 h of data retained from six nights of observing. We describe our calibration pipeline, which is based on multilevel radio frequency interference flagging, periodic noise diode injection to stabilize gain drifts, and an absolute calibration based on a multicomponent sky model. We show that it is sufficiently accurate to recover maps of diffuse celestial emission and point sources over a 10° × 30° patch of the sky overlapping with the WiggleZ 11-h field. The reconstructed maps have a good level of consistency between per-dish maps and external data sets, with the estimated thermal noise limited to 1.4 × the theoretical noise level (∼2 mK). The residual maps have rms amplitudes below 0.1 K, corresponding to $\lt 1{{\ \rm per\ cent}}$ of the model temperature. The reconstructed Galactic H i intensity map shows excellent agreement with the Effelsberg–Bonn H i Survey, and the flux of the radio galaxy 4C + 03.18 is recovered to within 3.6 per cent, which demonstrates that the autocorrelation can be successfully calibrated to give the zero-spacing flux and potentially help in the imaging of MeerKAT interferometric data. Our results provide a positive indication towards the feasibility of using MeerKAT and the future Square Kilometre Array to measure the H i intensity mapping signal and probe cosmology on degree scales and above.

Design, operation and performance of the PAON4 prototype transit interferometer

ABSTRACT PAON4 is an L-band (1250–1500 MHz) small interferometer operating in transit mode deployed at the Nançay observatory in France, designed as a prototype instrument for intensity mapping. It features four 5 m diameter dishes in a compact triangular configuration, with a total geometric collecting area of ${\sim} 75\, \mathrm{m^2}$, and is equipped with dual polarization receivers. A total of 36 visibilities are computed from the eight independent RF signals by the software correlator over the full 250 MHz RF band. The array operates in transit mode, with the dishes pointed toward a fixed declination, while the sky drifts across the instrument. Sky maps for each frequency channel are then reconstructed by combining the time-dependent visibilities from the different baselines observed at different declinations. This paper presents an overview of the PAON4 instrument design and goals, as a prototype for dish arrays to map the large-scale structure in radio, using intensity mapping of the atomic hydrogen 21 cm line. We operated PAON4 over several years and use data from observations at different periods to assess the array performance. We present a preliminary analysis of a large fraction of these data and discuss crucial issues for this type of instrument, such as the calibration strategy, instrument response stability and noise behaviour.

The design and implementation of a ROACH2+GPU based correlator on the Tianlai dish array

A digital correlator is a crucial element in a modern radio telescope. In this paper, we describe a scalable design for the correlator system of the Tianlai pathfinder array, which is an experiment dedicated to testing key technologies for conducting a 21 cm intensity mapping survey. The correlator implements the FX design, which firstly performs a fast Fourier transform (FFT) including polyphase filter bank (PFB) computation using a Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) Reconfigurable Open Architecture Computing Hardware-2 (ROACH2) board, then computes cross-correlations by employing Graphics Processing Units (GPUs). The design has been tested both in laboratory and in actual observation.

Cosmological parameter forecasts for H i intensity mapping experiments using the angular power spectrum

HI intensity mapping is a new observational technique to survey the large-scale structure of matter using the 21 cm emission line of atomic hydrogen (HI). In this work, we simulate BINGO (BAO from Integrated Neutral Gas Observations) and SKA (Square Kilometre Array) phase-1 dish array operating in auto-correlation mode. For the optimal case of BINGO with no foregrounds, the combination of the HI angular power spectra with Planck results allows $w$ to be measured with a precision of $4\%$, while the combination of the BAO acoustic scale with Planck gives a precision of $7\%$. We consider a number of potentially complicating effects, including foregrounds and redshift dependent bias, which increase the uncertainty on $w$ but not dramatically; in all cases the final uncertainty is found to be $\Delta w < 8\%$ for BINGO. For the combination of SKA-MID in auto-correlation mode with Planck, we find that, in ideal conditions, $w$ can be measured with a precision of $4\%$ for the redshift range $0.35 < z < 3$ (i.e., for the bandwidth of $\Delta \nu = [350, 1050]$ MHz) and $2\%$ for $0 < z < 0.49$ (i.e., $\Delta \nu = [950, 1421]$ MHz). Extending the model to include the sum of neutrino masses yields a $95\%$ upper limit of $\sum m_\nu < 0.24$ eV for BINGO and $\sum m_\nu < 0.08$ eV for SKA phase 1, competitive with the current best constraints in the case of BINGO and significantly better than them in the case of SKA.

Preparing for the SKA: The Chinese perspectives

Since 1993, astronomers and engineers from more than 100 institutions in 20 different countries including China, have engaged in the international mega-science project—the Square Kilometre Array (SKA), which will be the world’s largest synthesis radio telescope. The SKA is currently in its pre-construction phase, and China has been playing a very active role. China has participated in 6 of the total of 10 SKA work packages, and carried out R&D in dish array, aperture array, wideband single pixel feeds, phased array feeds, signal and data transport, and science data processor. In the new SKA science book published in 2015, Chinese scholars have made their contributions in 20% of all the chapter proposals. After the SKA1 re-baselining, 20 Chinese astronomers participated in 11 out of the 13 SKA scientific working groups. The “2+1 Strategy” for China’s SKA science priorities has been established, and some important progress has been made in cosmological re-ionization detection as well as in SKA data processing. In June 2015, the Chinese participation in SKA1 passed through the Chinese Academy of Sciences Panel Review. The Chinese Community is now deeply involved into the preparation of the SKA, with activities such as SKA science cases study, researching on high-precision light-weight antennas, developing the Chinese prototype array, as well as some efforts in building an SKA regional data center in China. This article gives a brief historical review of the SKA, overviews some international and domestic progress of the project during its preconstruction phase, and also discusses some future plans of the Chinese SKA.

MIGHTEE: The MeerKAT International GHz Tiered Extragalactic Exploration

The MeerKAT telescope is the precursor of the Square Kilometre Array mid-frequency dish array to be deployed later this decade on the African continent. MIGHTEE is one of the MeerKAT large survey projects designed to pathfind SKA key science in cosmology and galaxy evolution. Through a tiered radio continuum deep imaging project including several fields totaling 20 square degrees to microJy sensitivities and an ultra-deep image of a single 1 square degree field of view, MIGHTEE will explore dark matter and large scale structure, the evolution of galaxies, including AGN activity and star formation as a function of cosmic time and environment, the emergence and evolution of magnetic fields in galaxies, and the magnetic counter part to large scale structure of the universe.

Sky reconstruction for the Tianlai cylinder array

We apply our sky map reconstruction method for transit type interferometers to the Tianlai cylinder array. The method is based on spherical harmonic decomposition, and can be applied to a cylindrical array as well as dish arrays and we can compute the instrument response, synthesized beam, transfer function and noise power spectrum. We consider cylinder arrays with feed spacing larger than half a wavelength and, as expected, we find that the arrays with regular spacing have grating lobes which produce spurious images in the reconstructed maps. We show that this problem can be overcome using arrays with a different feed spacing on each cylinder. We present the reconstructed maps, and study the performance in terms of noise power spectrum, transfer function and beams for both regular and irregular feed spacing configurations.

Experiments on the dish verification antenna china for the SKA

The Square Kilometre Array (SKA) is expected to become the world’s most powerful radio telescope at meter and centimeter wavelength in the coming decades. The construction of SKA will be divided into two phases. The first phase (SKA1), scheduled for completion in 2023, will construct 10 % of the whole collecting area. The second phase (SKA2) will build the rest 90 % collecting area. The SKA1 consists of several types of arrays including SKA1-low and SKA1-mid. The latter is a dish array consisting of ~200 medium-size antennas. The integrated dish array in SKA2 will expand to 2500 dishes, spreading 3000 kilometers across the southern part of Africa. The demanding specifications and enormous number of the SKA dish raise challenges in the dish development such as mass production with high performance at low cost, quick installation and high reliability. Dish Verification Antenna China (DVA-C) was built as one of three initial prototypes. A novel single-piece panel reflector made of carbon fiber reinforced polymer (CFRP) was adopted. In this study, an L-band receiver is installed to make DVA-C a complete system for experiments on antenna performance test and preliminary observations. The performance of DVA-C including the system noise temperature, pointing accuracy, antenna pattern, and aperture efficiency has been tested. Preliminary observations such as pulsars and HI are then conducted, which indicates that the DVA-C can not only serve as an educational instrument and key technology test bed, but also be applied for scientific work such as pulsar timing, all-sky HI survey, multi-frequency monitoring of variable sources etc.

Sky reconstruction from transit visibilities: PAON-4 and Tianlai dish array

The spherical harmonics $m$-mode decomposition is a powerful sky map reconstruction method suitable for radio interferometers operating in transit mode. It can be applied to various configurations, including dish arrays and cylinders. We describe the computation of the instrument response function, the point spread function (PSF), transfer function, the noise covariance matrix and noise power spectrum. The analysis in this paper is focused on dish arrays operating in transit mode. We show that arrays with regular spacing have more pronounced side lobes as well as structures in their noise power spectrum, compared to arrays with irregular spacing, specially in the north-south direction. A good knowledge of the noise power spectrum $C^{\mathrm{noise}}(\ell)$ is essential for intensity mapping experiments as non uniform $C^{\mathrm{noise}}(\ell)$ is a potential problem for the measurement of the HI power spectrum. Different configurations have been studied to optimise the PAON-4 and Tianlai dish array layouts. We present their expected performance and their sensitivities to the 21-cm emission of the Milky Way and local extragalactic HI clumps

Exergoeconomic optimisation of steam networks connecting solar-thermal dish arrays

We optimise steam network trees that connect Big Dish paraboloidal collectors to a central power block. Exergy costs, pipe material costs, and installation costs are estimated using an exergoeconomic model and used to optimise pipe links in network trees. The optimal network tree is then found for a 10MWe collector field using a genetic algorithm. An optimised tree is found for a 20MWe network. The optimised 20MWe network has additional east–west branches not seen in the optimal 10MWe network, that reduce steam transport costs from network extremities. Exergy costs from heat loss and pressure drop account for approximately 60% of total network cost in both cases. Total network costs are, respectively, 8.9% and 9.5% of potential plant revenue for the 10MWe and the 20MWe networks.