Large Room Research Articles

Estimating food nitrogen and phosphorus footprints and budgeting nitrogen and phosphorus flows of Rwanda's agricultural food system during 1961–2020

Nitrogen (N) and phosphorus (P) are limiting factors for crop production in Rwanda where food security is susceptible to inadequate agricultural techniques, especially fertilization. Understanding N and P footprints for food and their budgets under different fertilized scenarios may help to improve the nutrient use efficiency and crop yield in Rwanda, however, with little information available yet. Here, we estimated food N and P footprints and their budgets for agri-food system in Rwanda using adjusted N-P-Calculator model under fertilized, unfertilized and combined scenarios during 1961–2020. The total food N footprint per capita increased from 4.2, 3.8 and 6.4 (1960s) to 6.8, 4.9 and 9.9 kg N cap−1 yr−1 under combined, unfertilized and fertilized scenarios, respectively (2011−2020). The total food P footprint per capita increased from 0.19, 0.18 and 0.23 (1960s) to 0.31, 0.25 and 0.40 kg P cap−1 yr−1 under combined, unfertilized and fertilized scenarios, respectively (2011–2020). The total N input to croplands increased from 13.9 (1960s) to 37.0 kg N ha−1 yr−1 (2011–2020), while the total crop N uptake increased from 18.1 (1960s) to 32.5 kg N ha−1 yr−1 (2011–2020), resulting in N use efficiency decline from 99.1% (1960s) to 74.6% (2011–2020). Gaseous N losses of NH3, N2O, and NO increased from 0.9, 0.1 and 0.0 (1960s) to 7.5, 0.8 and 0.1 kg N ha−1 yr−1, respectively (2011–2020). The total P removal in harvested crops increased from 2.9 (1960s) to 5.1 kg P ha−1 yr−1 (2011–2020). The results revealed large room for crop yield expansion; and low N and P inputs are major agricultural production limitations. We suggest N and P fertilizer improvement by focusing on better management of organic animal manure and ensuring high biologically N fixed through crop rotation of legumes and cereals; lastly to increase in moderation the use of synthetic N and P fertilizers in Rwanda.

An Ultrahigh‐Contrast Violet Phosphorus Van der Waals Phototransistor

AbstractUltrahigh‐contrast photodetection with low background noise is of critical importance for accurate image‐sensing in deep‐sea and deep‐space exploration. The state‐of‐the‐art silicon and III–V semiconductor‐based photodetectors usually require extended exposure to incident light for high‐quality sensing in darkness, which unfortunately results in large room temperature dark currents (RT‐Idark) and deteriorates the expected imaging contrasts. Herein, a high‐performance violet phosphorus (VP) phototransistor is reported by constructing a trap‐free interface between the VP channel and hexagonal boron nitride (h‐BN) dielectric via perfect van der Waals stacking. The device shows an extremely low RT‐Idark of 80 fA and gate‐tunable high ON/OFF ratio over 105, which is 2–4 orders of magnitude superior to that of conventional counterparts. A VP photodetector array has been fabricated to demonstrate the high‐contrast image‐sensing capability. The findings demonstrate the effectiveness of VP in low background noise and ultrahigh‐contrast image‐sensing applications, while also presenting exciting opportunities to enhance interface qualities through van der Waals architectures for high‐performance optoelectronics.

Anchoring (fullerol‐)Ru‐based‐complex onto TiO2 for Efficient Water Oxidation Catalysis

AbstractRuthenium polypyridine complexes are the most effective catalysts for the water oxidation reaction (WOR), but the catalytic activity still has a large room for improvement. Herein, a fullerol‐based ruthenium complex was prepared by the covalent grafting of the polypyridyl ruthenium complex of water oxidation catalyst (WOC) with fullerol, and the (fullerol)‐Ru‐based WOCs anchored on the surface of nano‐TiO2 were prepared through a sensitization strategy. The synthesized heterogeneous nano‐catalysts are fully characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), infrared spectroscopy (IR), Brunauer–Emmett–Teller (BET) specific surface area and pore size distribution, and diffusion reflection ultraviolet‐visible spectrum (DRS). The chemical oxygen evolution experiments reveal that the WOR catalyzed by the catalyst is a first‐order reaction with respect to Ce (NH4)2(NO3)6 (denoted as CAN) concentration when using CAN as the sacrificial oxidant under acidic conditions. The anchoring of Ru‐based WOC to TiO2 result in a decrease in the redox potentials of RuIV/III couples, which decrease the barrier of the crucial O−O bond‐forming step, and the heterogeneous nano‐catalyst exhibit a high catalytic activity with a turnover frequency of 13.4 s−1 and more excellent stability with a 15‐min‐turn over number of 1054 for TiO2‐fullerol‐based ruthenium complex WOC.

Robotic-Assisted Solutions for Invasive Cardiology, Cardiac Surgery and Routine On-Ward Tasks: A Narrative Review.

Robots are defined as programmable machines that can perform specified tasks. Medical robots are emerging solutions in the field of cardiology leveraging recent technological innovations of control systems, sensors, actuators, and imaging modalities. Robotic platforms are successfully applied for percutaneous coronary intervention, invasive cardiac electrophysiology procedures as well as surgical operations including minimally invasive aortic and mitral valve repair, coronary artery bypass procedures, and structural heart diseases. Furthermore, machines are used as staff-assisting tools to support nurses with repetitive clinical duties i.e., food delivery. High precision and resolution allow for excellent maneuverability, enabling the performance of medical procedures in challenging anatomies that are difficult or impossible using conventional approaches. Moreover, robot-assisted techniques protect operators from occupational hazards, reducing exposure to ionizing radiation, and limiting risk of orthopedic injuries. Novel automatic systems provide advantages for patients, ensuring device stability with optimized utilization of fluoroscopy. The acceptance of robotic technology among healthcare providers as well as patients paves the way for widespread clinical application in the field of cardiovascular medicine. However, incorporation of robotic systems is associated with some disadvantages including high costs of installation and expensive disposable instrumentations, the need for large operating room space, and the necessity of dedicated training for operators due to the challenging learning curve of robotic-assisted interventional systems.

Starburst Galactic Nuclei as Light Dark Matter Laboratories.

Starburst galaxies are well-motivated astrophysical emitters of high-energy gamma rays. They are well-known cosmic-ray "reservoirs," thanks to their expected large magnetic field turbulence which confine high-energy protons for ∼10^{5} years. Over such long times, cosmic-ray transport can be significantly affected by scatterings with sub-GeV dark matter. Here we point out that this scattering distorts the cosmic-ray spectrum, and the distortion can be indirectly observed by measuring the gamma rays produced by cosmic rays via hadronic collisions. Present gamma-ray data show no sign of such a distortion, leading to stringent bounds on the cross section between protons and dark matter. These are highly complementary with current bounds and have large room for improvement with the future gamma-ray measurements in the 0.1-10TeV range from the Cherenkov Telescope Array, which can strengthen the limits by as much as 2 orders of magnitude.

Experimental evaluation of the impact of real sun patch on radiant floor heating in highly glazed spaces

When the floor heating system is integrated into highly glazed buildings, the uneven distribution of temperature and humidity caused by the long exposure to the direct solar radiation becomes more and more prominent, which affects the indoor thermal comfort. Given that this issue has already been studied by means of mainly numerical simulations in previous studies and that thermal comfort already needs to be considered by means of a questionnaire, leaving a large room for improvement in terms of experimental considerations. This study quantitatively and qualitatively analyses the evaluation of the impact of real moving sun patch on radiant floor heating for thermal comfort consideration. The effects of long exposure to sun patch on both thermal comfort and thermal sensation are objectively assessed by means of experimental measurements conducted on a thermal manikin placed in a controlled and monitored test cell exposed to non-controlled climatic conditions. The results show that the indoor air temperature exceeds 26 °C, even in winter season, when the sun patch appears and is exaggerated when its duration is extended. The decrease of floor surface temperature is positively correlated with the decrease of sun patch area. Extending the sun patch duration allows the heat absorbed by the floor increase the outlet water temperature and, thus, impact the thermal sensation and thermal comfort. Based on this, future contributions may be to eliminate overheating by combining ventilation systems, intelligent control systems, as well as to recover the radiant heat generated by the sun patch.

Evaluation and optimization of ecological landscape pattern for urban agglomeration in the Pearl River Delta, China.

The evaluation and optimization of landscape ecological pattern has important implications for the accurate improvement of forest quality and high-quality urban development in the Pearl River Delta urban agglomeration. Based on the "one map" data and digital elevation model data of forest resource management in 2021, we evaluated and optimized landscape ecological pattern of the Pearl River Delta urban agglomeration by morphological spatial pattern analysis and minimum cumulative resistance model. The results showed that there were 435861 patches in the Pearl River Delta urban agglomeration that could be used as ecological source area, covering an area of 7346.60 km2 and accounting for 13.4% of the Pearl River Delta area. Thirty patches were selected as the ecological source area of the study area by using the area and patch importance index, covering an area of 2792.59 km2 and accounting for 5.1% of the Pearl River Delta area. The overall natural environment of the Pearl River Delta urban agglomeration was excellent. The ecological resistance level was small. The peripheral ecological resistance was low. The core ecological resistance was high. There was still a large room for adjustment of stand types and landscape patterns, which should be optimized by adjusting the composition and spatial distribution of tree species. The ecological network of the Pearl River Delta urban agglomeration was optimized with 30 ecological sources, 103 key ecological corridors, and 95 ecological nodes. The improvement rates of the optimized probability of connectivity index and integral index of connectivity index were 297.5% and 695.1%, respectively. The optimization results could effectively connect the ecological sources and spread the ecological service functions of ecological sources.

Electrodialysis for Removal of Impurities in Silver Electrowinning

In this work, we investigate the potential of electrodialysis to separate copper from silver electrowinning solution. We further explore and discuss optimization of the electrodialysis process design.Ag is in a high global demand, driven mainly by its use in electronics, jewelry and as investment. The recycling potential for Ag is large and will increase in the coming years due to Ag usage in solar panels. One route of recycling Ag from End-of-life products is batch-electrowinning. In preparation, the products are melted and reshaped into scrape plates which are anodically dissolved in nitric acid solution. Typically, silver is found in alloys with less noble metals like copper, zinc, and iron. While silver is deposited on the stainless-steel cathode surface, the impurities accumulate in the electrolyte. To maintain a high purity of the recycled silver, the contaminated nitric acid solution must be replaced regularly. We investigate the potential of implementing a continues electrodialysis stage parallel to the electrowinning bath to remove copper and other divalent cations from the solution.In electrodialysis, anion- and cations-exchange membranes are stacked alternatingly between two electrodes. When a current is drawn, the cations move towards the cathode, passing the cation-exchange membrane and vice versa for the anions. Since the membranes are selective for either anions or cations, they strongly retard the passage of the opposite ion. Therefore, cations and anions are accumulated in every second compartment, while every other chamber is desalinated. By using monovalent-selective ion-exchange membranes, separation between monovalent (f. ex., Ag+) and multivalent ions (f. ex., Cu2+, Zn2+, Fe2+, Fe3+) can be achieved [1].If the concentration of impurities can be held at a constant level, the nitric acid solution can be recycled continuously rather than replaced as a batch. The only consumable required by the process is electricity. We evaluate the viability of the process and investigate the influence of pH on the process efficiency.We determined the optimal operating current for separating Cu2+ from Ag+ in an equimolar concentration of 10 mM by doing amperodynamic sweeps and recording current-voltage curves. We then tested the desalination performance of an electrodialysis stack with different commercially available anion-/cation-exchange membrane pairs. The single membrane area was 36 cm2, and 9 membranes were used in total (five anion-exchange membranes and four monovalent-selective cation-exchange membranes). The Cu2+ and Ag+ concentrations in the diluate and concentrate compartments were determined by atomic mass spectrometry, and the membranes were analyzed with scanning electrode microscopy to detect adsorbed silver. Since scaling and fouling are dominant drawbacks in industrial applications of electrodialysis, we studied the influence of pH on the adsorption of silver in the membrane.Commercial monovalent-selective cation-exchange membranes by Neosepta showed high selectivity for silver over copper. The limiting current density was 10.4 A/m2 for neutral 10 mM AgNO3 solution at a flow rate of 100 mL/min and increased by almost 10 times when we adjusted the pH to 1 using nitric acid. In neutral solution, silver was recovered to almost 100 % after two hours of electrodialysis at 10 mA, while copper leakage was 7.5 %. At pH 1, silver recovery and copper leakage were 83 % and 9 %, respectively, after two hours electrodialysis at 100 mA. Consequently, the percentage silver adsorbed in the membranes were close to 0 % in neutral solution and 17 % at pH 1. The work input was significantly higher at pH 1 due to electric current consumed by mass transport of protons. As a next step, we investigate the long-term effect on the membranes with regards to Ag and Cu adsorption, which could be stabilizing at a certain concentration of Ag and Cu or increasing over time.We conclude that electrodialysis is a promising technology for removal of impurities in Ag electrowinning from End-of-life products, justifying large room for future research on development of membranes and operational design.[1] Zimmermann, P., Tekinalp, Ö., Deng, L., Forsberg, K., Wilhelmsen, Ø., Burheim, O. (2020). Electrodialysis in Hydrometallurgical Processes. In: Azimi, G., Forsberg, K., Ouchi, T., Kim, H., Alam, S., Baba, A. (eds) Rare Metal Technology 2020. The Minerals, Metals & Materials Series. Springer, Cham.

Suitability of Low-Cost Sensors for Submicron Aerosol Particle Measurement

The measurement and assessment of indoor air quality in terms of respirable particulate constituents is relevant, especially in light of the COVID-19 pandemic and associated infection events. To analyze indoor infectious potential and to develop customized hygiene concepts, the measurement monitoring of the anthropogenic aerosol spreading is necessary. For indoor aerosol measurements usually standard lab equipment is used. However, these devices are time-consuming, expensive and unwieldy. The idea is to replace this standard laboratory equipment with low-cost sensors widely used for monitoring fine dust (particulate matter—PM). Due to the low acquisition costs, many sensors can be used to determine the aerosol load, even in large rooms. Thus, the aim of this work is to verify the measurement capability of low-cost sensors. For this purpose, two different models of low-cost sensors are compared with established laboratory measuring instruments. The study was performed with artificially prepared NaCl aerosols with a well-defined size and morphology. In addition, the influence of the relative humidity, which can vary significantly indoors, on the measurement capability of the low-cost sensors is investigated. For this purpose, a heating stage was developed and tested. The results show a discrepancy in measurement capability between low-cost sensors and laboratory measuring instruments. This difference can be attributed to the partially different measuring method, as well as the different measuring particle size ranges. The determined measurement accuracy is nevertheless good, considering the compactness and the acquisition price of the low-cost sensors.

English past-tense -ed allomorphs and L2 speech intelligibility: a study with Brazilian listeners

This study investigated the possible influence of the allomorphs [t, d, ɪd] in the intelligibility of 48 verbs ending in -ed, half in the first and half in the second intelligibility test, which were produced by eight speakers from four different L1 backgrounds (e.g., BP, Spanish, German, English) and orthographically transcribed by 14 Brazilian listeners in two intelligibility tests within a four-month interval. Results of the first intelligibility test indicated that verbs ending in the allomorph [t] were more intelligible than verbs ending in the allomorph [ɪd], which in turn were more intelligible than verbs ending in the allomorph [d]. However, results for the second intelligibility test did not follow the same tendency and indicated that the intelligibility of verbs ending in the allomorphs [t, ɪd] were very similar whereas the results for the intelligibility of verbs with the allomorph [d] increased since it had large room for improvement from the first to the second test. Moreover, results also indicated that there was variation in the intelligibility of verbs ending in the three allomorphs for each learner and among the learners, demonstrating that the language development is a dynamic, varied, and complex system, as the Dynamic System Theory proposes.

High room temperature magnetoresistance in La0.9Sr0.1Mn1-yZnyO3 epitaxial films

Developing large room temperature magnetoresistance materials has been a major hotspot for a few last decades due to its importance in the practical applications in magneto-resistive random access memory, and it remains a challenge. Here, La0.9Sr0.1Mn1-yZnyO3 (LSMZO) films have been grown on SrTiO3 substrates by magnetron sputtering, showing excellent quality of epitaxy. Upon increasing Zn content, the reduction of Curie temperature (TC) and metal-insulator transition temperature (TMI) is observed, accompanied by the increase of coercive field and room-temperature resistivity. Analysis on the fraction of Mn3+ and Mn4+ indicates that Zn2+ substitution at Mn site results in a higher Mn4+ fraction departing from the optimum value and hence a weaker double-exchange interaction by replacing more Mn3+. Besides that, ionic radius mismatch induced internal strain and substrate induced tensile strain also play a part. Most significantly, the enhanced magnetic disorder gives rise to an increase of intrinsic magnetoresistance around room temperature in LSMZO (y = 10%) film, and a large magnetoresistance of 18.4% is obtained under 0.3 T at 280 K in this sample. Our research provides a simple and effective approach to achieve a large room temperature magnetoresistance in Mn site doped manganite epitaxial films.

Heritage Enhancement through Digital Tools for Sustainable Fruition—A Conceptual Framework

Digital technologies are becoming increasingly relevant in the processes of documenting, surveying, enhancing, and preserving cultural heritage, including through applications that are becoming more and more optimized and oriented toward new data management and accessibility processes. This great potential can find significant levels of application in the tourism sector, seeking new strategies to access, discover, and understand cultural assets. In this direction, many digital applications have already found interesting outcomes in the tourism sector, but there is large room for improvement in the applications for “minor”, small, or neglected cultural sites, not included in conventional tourism routes, which play a key role in social inclusion and territorial cohesion, as well as for the development of social, economic, and environmental sustainability. The paper presents a conceptual framework or possible outline to foster the use of digital technologies through a set of integrated bottom-up and top-down actions, to facilitate connections of minor sites into larger networks, contributing to the search for new forms of sustainable and active fruition and social participation.

Construction and Application of Large Stokes-Shift Organic Room Temperature Phosphorescence Materials by Intermolecular Charge Transfer.

Notably, the intermolecular charge transfer between pyrene (Py) and benzophonenes (BPs) can significantly enhance the quantum yield of the triplet state of Py, which will convert Py from a fluorescence molecule to a phosphorescence molecule. The intermolecular charge transfer is confirmed by steady-state and time-resolved spectroscopy and theoretical study. Based on these foundations, Py is doped into BPs systems and a large Stokes-shift organic room temperature phosphorescence (ORTP) is observed. By using different benzophenone derivatives, a series of host-guest ORTP materials with different luminescent properties adjusted by intermolecular charge transfer features are developed. Fortunately, these host-guest ORTP systems from benzophenone derivatives and pyrene are readily fabricated, and the red gradient color lasting as long as 3 s is observed after removing UV excitation. This host-guest charge transfer strategy plays an important role in the mechanism of the luminous type shift. Our strategy paves the way to design ORTP materials conveniently and apply these materials in encryption and temperature alarm device.

A novel portable cooling unit with air purification for displacement ventilation: Parametric study with zonal model and field experiment

Displacement Ventilation (DV) has been known as an energy saving system as it relies on buoyancy force to draw hot air upwards to be displaced by cool air. The main strength of DV that recommends it nowadays is that a well-designed DV system prevents mixing of contaminants as they are dragged along the hot air upward flow leaving the occupied zone, breathing zone in particular, clean. However, the system's effectiveness is lowered in large rooms due to design problem such as difficult balance between sufficient supply flow volume and low inlet velocity, furniture arrangement acting as obstacles, or room geometry. Hence, DV feasibility is limited to small and mid-size rooms. In order to expand the DV potential and applicability to all space types and sizes, this study proposes a portable DV air purifying unit. The unit is designed to be mobile consisting of air recycling unit with no duct connections which widens the range of use to cover a variety of indoor spaces as well as small to medium sized room. The unit has two main functions, one is reinforcing the temperature gradient as stratification crucial for DV, and the second is purifying recycled air. To investigate the effectiveness and feasibility of the proposed DV unit, block model calculations and full-scale experiment were conducted. In a small room, multiple cases were calculated and assessed in terms of temperature distribution and stratification height. In addition, exhalation droplets were simulated and the particulate matter count was used as an indicator for the air quality. Observations on the proposed unit’ s performance and design aspects were highlighted.

Is language an issue? Accuracy of the German computerized diagnostic decision support system ISABEL and cross-validation with the English counterpart.

Existing computerized diagnostic decision support tools (CDDS) accurately return possible differential diagnoses (DDx) based on the clinical information provided. The German versions of the CDDS tools for clinicians (Isabel Pro) and patients (Isabel Symptom Checker) from ISABEL Healthcare have not been validated yet. We entered clinical features of 50 patient vignettes taken from an emergency medical text book and 50 real cases with a confirmed diagnosis derived from the electronic health record (EHR) of a large academic Swiss emergency room into the German versions of Isabel Pro and Isabel Symptom Checker. We analysed the proportion of DDx lists that included the correct diagnosis. Isabel Pro and Symptom Checker provided the correct diagnosis in 82 and 71 % of the cases, respectively. Overall, the correct diagnosis was ranked in 71 , 61 and 37 % of the cases within the top 20, 10 and 3 of the provided DDx when using Isabel Pro. In general, accuracy was higher with vignettes than ED cases, i.e.listed the correct diagnosis more often (non-significant) and ranked the diagnosis significantly more often within the top 20, 10 and 3. On average, 38±4.5 DDx were provided by Isabel Pro and Symptom Checker. The German versions of Isabel achieved a somewhat lower accuracy compared to previous studies of the English version. The accuracy decreases substantially when the position in the suggested DDx list is taken into account. Whether Isabel Pro is accurate enough to improve diagnostic quality in clinical ED routine needs further investigation.

Sistem Monitoring Status Meja Pada Restoran Berbasis Internet of Things (IOT)

The condition of a busy restaurant sometimes makes it difficult for waiters to monitor and provide satisfactory service to customers. Customers must wave when they want to call waiters but feel ignored or not seen and will feel uncomfortable with the atmosphere and calm in the dining room. An Internet of Things (IOT) based desk status monitoring system is a concept that has the ability to transfer data over a network without the need for human-to-human interaction. This study proposes a table status monitoring system in IOT-based restaurants. This tool is made so that it can be applied to large rooms and crowded visitors. A device equipped with wireless communication to send data to the server, so that it can be monitored in real time. If the button on the tool is pressed, the system will send a signal to the relay to give a call sign warning to restaurant staff/waitresses. The results of this study indicate that status information from tables requesting service from waiters will respond to these service requests and help optimize service at restaurants so that they can satisfy their customers.

Impact of shield location on staff and caregiver dose rates for I-131 radiopharmaceutical therapy patients

The goal of this study is to investigate the effect of the location and width of a single lead shield on the dose rate of staff and caregivers in a hospital room with an I-131 patient. The best orientation of the patient and caregiver relative to the shield was determined based on minimizing staff and caregiver radiation dose rates. Shielded and unshielded dose rates were simulated using a Monte Carlo computer simulation and validated using real-world ionisation chamber measurements. Based on a radiation transport analysis using an adult voxel phantom published by the International Commission on Radiological Protection, placing the shield near the caregiver yielded the lowest dose rates. However, this strategy reduced the dose rate in only a tiny area of the room. Furthermore, positioning the shield near the patient in the caudal direction provided a modest dose rate reduction while shielding a large room area. Finally, increased shield width was associated with decreasing dose rates, but only a four-fold dose-rate reduction was observed for standard width shields. The recommendations of this case study may be considered as potential candidate room configurations where radiation dose rates are minimized, however these findings must be weighed against additional clinical, safety, and comfort considerations.

Matching degree evaluation between new urbanization and carbon emission system in China: a case study of Anhui Province in China

In order to reveal the relationship between new urbanization and carbon emission to provide reference opinions for the construction of low-carbon urbanization, an evaluation system between new urbanization and carbon emission was constructed. Then their matching degree relationship was analyzed by coupling coordination degree model based on the data from 2012 to 2021 in Anhui Province, and their development trend from 2023 to 2032 was predicted by gray prediction model. The results show that: (1) New urbanization and carbon emission have the co-trend effect, and the consistency of core impact factors is relatively significant. Among them, the level of new urbanization increases from 0.058 in 2012 to 0.699 in 2021 and carbon emission development increases from 0.023 in 2012 to 0.165 in 2021, which both showing an upward trend. Meanwhile, social urbanization and population carbon emission are the core influencing factors. (2) The coupling coordination degree between new urbanization and carbon emission is low, but the synergy trend is optimistic and there is a large room for improvement. Among them, the coupling coordination coefficient of the coupling system rises from 0.136 in 2012 to 1.412 in 2021 (antagonistic phase), and then reaches 0.820 by 2032 (highly coordinated phase) by forecast. It shows that their current development is unbalanced, but the development trend is good, and there is a chance for improvement. This paper deepens the understanding of the logical correlation between new urbanization and carbon emission, and the following views are formed: (1) Low-carbon development is still the mainstream of new urbanization; (2) The coordination development of new urbanization and carbon emission reduction should be strengthened.

A modal expansion method for simulating reverberant sound fields generated by a directional source in a rectangular enclosure

The prediction of reverberant sound fields generated by a directional source is of great interest because practical sound sources are not omnidirectional, especially at high frequencies. For an arbitrary directional source described by cylindrical and spherical harmonics, this paper developed a modal expansion method for calculating the reverberant sound field generated by such a source in both two-dimensional and three-dimensional rectangular enclosures with finite impedance walls. The key is to express the modal source density using the cylindrical or spherical harmonic expansion coefficients of the directional source. A method based on the fast Fourier transform is proposed to enable the fast computation of the summation of enclosure modes when walls are lightly damped or rigid. This makes it possible to obtain accurate reverberant sound fields even in a large room and/or at high frequencies with a relatively low computational load. Numerical results with several typical directional sources are presented. The efficiency and the accuracy of the proposed method are validated by the comparison to the results obtained using the finite element method.

Speech enhancement using dual microphone adaptive noise canceller

Subject of research. The subject of the study is the issue of rational placement of microphones of the main and reference channels of a two-channel adaptive noise canceller (ANC) for speech enhancement in presence of acoustic interference from a point source. An increase of the signal-to-noise ratio (SNR) at the output of the ANC relative to the input value of the main channel was chosen as a criterion for rational placement. The limitations of the model of direct propagation of signals in reverberation conditions are considered. Methods. The estimation of the SNR at the inputs of the main and reference channels is obtained on the basis of a geometric model of point sources of signal and interference and on the analytical expressions for transfer functions between signal and interference sources and microphones of the main and reference channels for a planar model of signal propagation in a free field. The main results. The conditions for microphones placement of dual channel ANC, increasing SNR, are determined. The conditions for reference channel microphone placement at a given position of main channel microphone are determined. Limitations of ANC efficiency under reverberation conditions are investigated. It is shown that the microphone of the reference channel should be located near the interference source. For large rooms, the use of dual-microphone arrays is proposed and possible signal processing algorithms (conditions of their application) are considered. To use a two-element microphone array, additional information about the position of the target source is required. Practical significance. The obtained results can be useful for distant speech acquisition in the presence of acoustic interference.