bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical test bench to evaluate the influence of heat gains on the estimation of Heat Transfer Coefficient under occupied conditions
Authors: Pacquaut A , Rouchier S , Jay A , Challansonnex A , Juricic S , Wurtz E
Published: December 2023

The estimation of the HTC heat transfer coefficient in real occupancy conditions has a great operational advantage contrary to the measurement in unoccupied conditions, which requires specific measurement protocols. Nevertheless, it presents additional constraints because the gains due to weather conditions and occupancy are poorly controlled. The objective of this work is therefore to quantify the impact of these different gains. A numerical test bench is set up to study the impact of the solar and internal gains by varying different parameters, such as the typology of the building, the meteorological conditions, the scenarios of occupancy. These numerical tests allow to estimate the HTC of a building by calibrating a numerical model from a virtual dataset generated by a detailed model with known and controlled meteorological conditions and usage conditions. They make it possible to determine the share of solar heat gain and internal heat gain in the energy balance of the building and their impact on the estimation of the HTC according to the studied configurations.
Performance Comparison of Indoor Humidity Modeling: A Novel Hybrid Model vs. the Simplified Calculation Model by EN ISO 13788
Authors: Lu Tao , Lü Xaoshu , Salonen Heidi
Published: December 2023

Ventilation is essential for maintaining indoor air quality and human comfort, particularly in buildings with mechanical ventilation systems. However, modeling the complex relationship between ventilation rate and measurable indoor environmental parameters, such as humidity, poses significant challenges. Current methods for modeling this relationship are often inefficient. For example, data-driven models frequently require sufficient information on ventilation, which may not be available for constant air volume (CAV) systems. On the other hand, simulation programs can be time-consuming and require expert engagement. In this study, we present two simplified calculation models, including a hybrid model developed by the authors, and a well-known model introduced by EN ISO 13788. We compare their performance in evaluating the impact of ventilation rate on indoor humidity. The hybrid model uses a novel analytical method to upgrade a single-input regression model (which considers only outdoor humidity as input) to enable the evaluation of indoor humidity based on both outdoor humidity and ventilation rate. We used the commercial TRNSYS program to model two scenarios: increasing the reference ventilation rate and decreasing the reference ventilation rate. The results showed that both models matched TRNSYS simulations with satisfactory accuracies, but the hybrid model demonstrated superior performance to the EN ISO 13788 model in both scenarios. The hybrid model’s higher accuracy and hybrid features make it better suited for big data analysis and field studies.
Experimental study of micro-encapsulated phase change materials’ influence on indoor temperature
Authors: Zhou Hongxia , Puttige Anjan Rao , Nair Gireesh , Olofsson Thomas
Published: December 2023

The energy use of buildings is almost one-third of the global final energy use. Phase change Materials (PCMs) are substances that undergo phase transition when the surrounding temperature reaches their phase transition temperature. PCMs are reported to be a good candidate as a thermal storage buffer in building systems. Accordingly, PCMs may be able to regulate the indoor temperature while using less energy and thereby contributing in improving the energy performance of the building. In this project a trail to analyse the effect of PCMs in indoor temperature was carried out, in an experimental set-up, using a climate chamber. The chamber temperature is regulated as a sinusoidal profile with a cycle of 24 hours, with a maximum of 40 °C and a minimum of -10 °C. A cubic-box, is placed at the centre of the chamber, and is used as a representation of “building”. A board was made by encapsulating PCMs, with a melting temperature of 24 °C, to gypsum with a fraction of 20 wt%. The influence of PCM added gypsum board on inside temperature of the box is studied. Temperatures at different locations have been measured by thermocouples. The results indicated that the presence of PCM resulted in less temperature variation inside the box with the temperature holding close to the PCM transition temperature for a long period. Also, the PCM boards shifted the temperature profile. Further results are expected to determine the location of the PCM board that is most suitable to reduce the temperature variation inside the building.
Preliminary Studies on a Lightweight Porous Cement-Based Composite – Gel Concrete
Authors: Strzałkowski Jarosław , Stolarska Agata
Published: December 2023

This paper presents some preliminary results of research on light, highly porous cement composites – gel concretes. A material based on Portland cement was tested, the very high porosity of which (over 60%) was obtained by direct gelatinization of starch in a liquid cement slurry. A composite based solely on cement and concretes produced with the addition of metakaolin or zeolite was tested. The basic properties of the concretes obtained in this way were determined, i.e., the volume density in a dry state, the thermal properties, and the compressive strength. In the case of the thermal properties, tests were performed on specimens dried to constant mass, while the test itself was carried out at an average temperature of 10°C. The tests employed an Isomet 2114 apparatus, which uses a non-stationary heat flow technique. The thermal conductivity coefficients and the volumetric specific heat were determined. The compressive strength tests were carried out on cubic specimens with a side of 4 cm after 28 days of curing by air-drying. Four specimens of each type of composite were tested. For composites based solely on Portland cement, the sorption properties of the material were also tested. For this purpose, the method of dynamic water vapor sorption (DVS) was used. As a result, graphs of the sorption and desorption of individual composites of different densities were obtained. Preliminary qualitative tests were also carried out using an electron microscope. The use of the starch gelatinization process directly in the cement slurry made it possible to obtain a very homogeneous material, in which the initial, temporary structure was starch gel, around which, after exceeding the setting time of the cement, the target cement-based structure was formed – gel concrete. The tested materials are innovative, having excellent thermal properties, comparable mechanical properties to lightweight concretes of the same densities, and is formed using an easily available, relatively cheap admixture in the form of starch. They can be used to produce small masonry elements, such as blocks for external walls or other typical prefabricated lightweight concrete elements.
An innovative forced convection method for drying geosourced and biosourced construction materials at wall scale
Authors: Hamieh N , Collet F , Meslem A
Published: December 2023

As global temperatures continue to rise, climate change impacts are now being observed in all aspects of life, driving the need to transition to a low-carbon economy. In the building sector and as a construction material, Earth-Hemp composites present a sustainable solution due to their low embodied energy and low environmental impact. However, at the construction site, and as with any other material, the drying process of Earth-Hemp can be very slow, which can lead to costly delays for building work and even serious problems in term of mold growth affecting their durability. The objective of this work is to develop an innovative drying method to reduce drying time of construction materials and speed up the completion of a project. In this paper, a comparative study of natural convection drying with innovative forced convection drying is carried out on sprayed Earth-Hemp-Lime "ELH" prototypes. The results show that the innovative forced convection method is very effective for drying ELH materials at an accelerated rate, where the drying period has been reduced by a factor of 2, compared to the drying time required when using the natural convection method.
Preliminary study of the application of thermal mortar in 3D printed concrete walls
Authors: Pessoa S , Jesus M , Rangel C , Guimarães A S , Lucas S S , Simões N
Published: December 2023

3D printing (3DP), as an emerging technology in the construction industry, has the potential to solve the sector’s labour shortages and low efficiency, as well as helping to reduce its negative environmental impact. On the investigative path towards new construction solutions, the thermal performance of buildings must not be compromised. In additively manufactured buildings to date, walls have been printed with cavities that are subsequently manually filled or projected with conventional thermal insulation materials, such as polyurethane and vermiculite. To bridge the gap between conventional building construction and 3DP, it is important to present feasible and effective thermal solutions that can be applied using an automatic mode. This paper explores the viability of applying a commercial thermal mortar as an insulation in 3D printed concrete walls. Therefore, a preliminary experimental campaign was carried out to assess the behaviour of the thermal mortar during and after its application. It was found that concrete walls constrain the drying process of the thermal mortar, generating stresses that lead to the occurrence of cracks. To avoid their formation, some strategies were tested, namely by adding superplasticizer to the mixture, opening joints, drilling holes or opting for an incomplete filling of the cavities.
Hygrothermal Performance of Lime-Based Thermal Insulation Mortars: Water Absorption, Hygroscopic Sorption, and Water Vapour Permeability
Authors: Ruus A , Kaeramaa A-L , Kirtsi K , Mihkelsoo M , Kiviste M , Raamets J
Published: December 2023

Lightweight mortars, which are able to capture carbon, offer moisture buffering and increase the thermal resistance of building elements could be useful for both new and renovated buildings. The hygrothermal properties of lime-based renovation and insulation mortars were studied and the possibilities of reducing water absorption was the main focus of the study. Water absorption coefficient, hygroscopic sorption, and water vapour transmission properties were studied according to EN 1015-18, ISO 12571 and ISO 12572. Hydrated lime was used as the main binder and volcanic sand as an aggregate, white cement and silane in two different concentrations acted as additives. Half of the specimens were kept in forced carbonation conditions (CO2 was added regularly). Drying and carbonation processes were monitored by weighing the specimens regularly. Silane had the ability to reduce water absorption and sorption. Forcing carbonation reduced water absorption and sorption and slightly increased water vapour permeability.
Laser-Doppler Anemometry for detection of the velocity field in the ventilated, asymmetrically heated channel - a case study
Authors: Larsen O K , Zhang C , Melgaard S P , Nikolaisson I T , Liu L , Larsen T S
Published: December 2023

The topic of double-skin façades (DSFs) is re-emerging in the research environment, with studies ranging from architectural design concepts to specific investigations of heat and mass transfer in a vertical channel. These studies reflect a lack of comprehension of the phenomena taking place within the DSF cavities. This work presents a case study, where the Laser-Doppler Anemometry principle, combined with video registration of smoke movement, is used to establish the velocity and flow patterns in an asymmetrically heated ventilated channel in a controlled environment. The authors of this work contribute to the research field by addressing the pros and cons of the Laser-Doppler Anemometry approach for the measurement of the vertical velocity component in a DSF and presenting an example of obtained experimental results for the validation of CFD models. The results of this work address the velocity distribution for the vertical 2D cross plane of the DSF cavity. The analysis of the measurement data includes an assessment of the stability of the flow and fluctuations throughout the measurement period.
Validating a Building Performance Simulation Model of a naturally ventilated Double Skin Facade
Authors: Schaffer M , Bugenings L A , Larsen O K
Published: December 2023

Double Skin Facades (DSF) are regaining popularity as a way to increase the climate resilience of buildings. Building Performance Simulation (BPS) is commonly used for their assessment, but modelling DSFs with BPS is challenging due to their complex thermophysical behaviour. Several research works have evaluated the capabilities and limitations of BPS for modelling specific DSF configurations. This work presents a validation study based on experimental data from a full-scale naturally ventilated double-skin façade, compared against results from the BPS software IDA-ICE. The study found that in periods with low solar irradiation, the different modelling strategies had a minor influence on the results, with a high agreement between measurements and simulation. In contrast, periods with solar irradiation showed a higher sensitivity to the modelling strategy, with more significant deviations from the measurement results.
Realizing the load shifting potential of residential space heating - A field study on the control input for thermostatic control of indoor air temperature
Authors: Christensen Louise R. L. , Petersen Steffen
Published: December 2023

Economic model predictive control (MPC) of residential space heating utilizes indoor air temperature fluctuations and thermal mass for load shifting of space heating consumption and it can be used for various demand response purposes in district heating systems. A field experiment imitating the behaviour of an MPC has previously been carried out in three residential buildings in Aalborg, Denmark. Here, digital radiator thermostats were used, and it was found that the load shifting period was cut short when using the temperature measurement embedded in the thermostat as control input for the MPC. Therefore, the field study reported in this paper investigated whether using indoor air temperature sensors as control input for the thermostat improved the realisation of the load shifting. The field study took place in a single-family house in Aarhus, Denmark, and tested the load shifting potential when controlling with either the temperature sensor embedded in the thermostat or an offset between the radiator thermostat setpoint and an indoor air temperature sensor measurement. The study indicates that the use of indoor air temperature measurements as thermostat control input will provide longer periods of loading and unloading the building, thereby increasing the total load shifting potential of the heating consumption.
Assessment of thermally activated inner building components or a high temperature stone storage system to utilize surplus renewable electrical energy
Authors: Pazold M , Hanen F , Sirtl F , Radon J , Antretter F , Kersken M , Sinnesbichler H
Published: December 2023

In electrical grids with high renewable percentage, the production is less demand-driven, but more dependent on weather conditions. Usually there are periodical weather patterns in the winter period with substantial amounts of wind energy production. Sometimes this results in a shut-off of the wind turbines due to the inability of the grid to use the produced power (overproduction). This paper assesses two thermal storage systems to service space heating and domestic hot water that exploit the overproduction of electricity and thereby bridge periods of lower electricity production. The first system utilizes inner walls and ceilings with a thermally activated building system (TABS) to store and dissipate heat. The second system is a stand-alone high temperature stone storage system (HTSS). Models to simulate such systems within a whole building simulation framework are introduced and the verification with measured data from field measurements is presented. Both models are used to assess the systems with regard to the speed of loading and the potential to bridge time periods without additional heating in high-performance buildings. It is shown that both systems can provide heating and domestic hot water (DHW) up to 13 days without substantial additional electricity.
Impact of artificial ageing on the performance of acrylic self-adhesive tapes
Authors: Dobilaitė V , Jucienė M , Kumžienė J , Banionis K , Paukštys V , Stonkuvienė A
Published: December 2023

The use of sealing tapes in creating a continuous envelope to ensure the airtightness of the building is an essential factor. The study aims to investigate the performance properties of single-sided self-adhesive tapes for building applications and to obtain the changes in these properties due to the effects of environmental factors. The tapes were glued to the different substrates. Peel adhesion, tack of the tapes, and the air permeability of sealed elements were determined. The adhesive tape were aged in the laboratory using two different methods, standard (EN 12024) and a new one, during which the test samples were exposed to the cyclic impact of the temperature and humidity of multiple levels. Analysis of the results showed that the substrate has influence on the adhesive behaviour of the self-adhesive tapes. After artificial aging, in most cases, the performance properties of the tapes do not change significantly. The novel approach allowed the comparison of the influence of different aging factors on the change in the performance properties of the tape and contributed to the development of a methodology for testing the durability of sealing tapes. The effect of substrate on tape adhesion was also investigated, which is useful from both a practical and a methodological point of view.
The Behaviour of Wood Fibre Insulation Systems for Solid Wall Buildings: Lessons from a Long-term Monitoring Study
Authors: Marincioni Valentina , Altamirano-Medina Hector
Published: December 2023

The majority of the traditional building stock in the UK is made of solid brick walls. Internal wall insulation is one of the possible interventions to preserve the external appearance of a building while improving the energy efficiency of its walls. However, it can lead to moisture-related risks, such as excess moisture accumulation and mould growth. This paper presents an overview of the lessons learnt from the long-term monitoring of two case-study solid wall buildings, insulated with wood fibre-based systems and monitored for a year. The aim of this monitoring campaign was to provide evidence on the main moisture transfer and storage mechanisms occurring in solid walls insulated with wood fibre-based systems under actual environmental conditions. Results showed that the dynamic interaction between the insulated wall and moisture sources could be controlled by means of an appropriate specification of the insulation system, considering the influence of orientation, material properties and indoor moisture loads. It was also found that construction moisture influenced the initial conditions of the interface, but mitigation strategies can be considered to reduce mould growth risk during installation and before the drying of construction moisture.
Comparative Assessment of the Carbon Footprint of on-site and off-site Wall Element Constructions
Authors: Fufa Selamawit Mamo , Høyli Randulf , Einejord Andreas , Johnsen Oddgeir
Published: December 2023

Off-site construction is considered as environmentally preferable to on-site due to the controlled environment for planning and production before assembly in the construction site. However, evaluating the actual environmental benefits and drawbacks from a life cycle perspective is important to avoid problem shifting. The aim of the paper is to evaluate the environmental performance of conventional on-site construction of wall elements, in comparison with off-site wall element production in a factory and assembly on the construction site. This study has been a collaboration with a Norwegian contractor using wall constructions with elements produced either on- or off-site. The contractor seeks to reduce the negative environmental consequences from building activities by establishing a local factory for off-site element production, thus motivating this study to provide environmental inputs to a decision-making process. The wall elements which either fulfil the Norwegian building code (TEK17) or passive house (PH) standard are evaluated using three scenarios: 1) on-site construction with local materials obtained from Norwegian manufacturers/suppliers, 2) off-site wall element production and wall construction in Norway, and 3) off-site wall element production in Estonia and wall construction in Norway. The GHG emissions from the scenarios are calculated using screening LCA method for life cycle stages of production (A1-A3) and construction (A4-A5). The results show that lowest GHG emissions are attributed to local Norwegian off-site TEK-wall element production, whereas the Norwegian on-site PH-wall has the highest GHG emissions. The results also highlighted the contribution to GHG emissions of specific building materials, as well as the dependency of the results on the background data and the methodological choices used in the study.
Rain resistance of windows – Lessons learned from two decades of laboratory testing
Authors: Gullbrekken Lars , Gransjøen Therese , Andenæs Erlend , Time Berit , Kvande Tore
Published: December 2023

Windows are important in buildings intended for human activities as they let in daylight and provide views. However, they may also be vulnerable in terms of heat loss, air leaks, rain tightness, and durability. In Nordic climates featuring severe driving rain exposure, water tightness is of outmost importance. SINTEF has for many decades been testing windows as part of the Norwegian yearly product control. Air permeability and water tightness are tested according to NS-EN 1026 and NS-EN 1027, respectively. The windows are then classified as described in NS-EN 12207 and NS-EN 12208. This paper summarises experiences from the last two decades of testing, presenting the results of 1130 tests of windows’ air permeability and rain tightness. The overall trend is that air and rain tightness performance of the windows have improved over time. Certain hinge configurations are clearly better than others, with tilt and turn windows performing the best and top hung casement windows the poorest. There is a clear trend that highly rainproof windows also exhibit lower air permeability. Multiple-window screens fail the test more often since they feature longer perimeters of opening. The contribution of weather sweep seals to the water tightness is significant as it makes an extra rain barrier to the joint between casement and frame. In general, leakage between the frames of double windows and in the joints of the frame occurs at lower air pressures than leakages between casement and frame. The lessons learned from the survey may guide future development of weatherproof windows.
An anti-offset wireless power trasfer system with constant current/constant voltage output
Authors: Liu Zheyu , Wang Siming
Published: December 2023

This article proposes a wireless power transfer (WPT) system based on LCC-LCC and LC-LC series hybrid compensation topology with offset resistance and constant current/voltage output performance. The system uses LCC-LCC and LC-LC networks for input and output series and adopts a four-direction decoupled magnetic coupling structure. On this basis, by designing appropriate parameters, a constant current output independent of the load was achieved, and the performance of resisting coil offsets in the four directions of x, y, xy, and -xy can be achieved. Furthermore, a T-network facilitates the mode conversion for achieving constant current/constant voltage output. Subsequently, an experimental simulation platform was built to verify the feasibility of the theory presented in this paper.
Terahertz gas sensor and its application in gas detection of power pipe gallery
Authors: Luo Guofang , Xiong Xianghong , Chen Hongtao , Li Tengfei , Chen Xi , Han Jingxin
Published: December 2023

During the operation of a power cable duct, the content of flammable gas is an important element in the safety of the cable duct. The accurate detection and location of gas in the pipeline corridor are important to improve the safety and stability of the power system. In view of the change of the refractive index of the gas in the power cable tube gallery, this paper presents the important application of terahertz one-dimensional photonic crystals with high-quality factors in gas sensing, change of the gas refractive index in the tube gallery simulated, and the gas refractive index change in the tube gallery can be obtained accurately by analyzing the change of transmission peak at terahertz range, the potential of terahertz sensor in gas detection in power tube gallery is verified.
Analysis and identification of transformer acoustic signal based on compressed sensing
Authors: Li Zhong , Chen Liyang , Liu Kai , Ma Xun , Wang Yong
Published: December 2023

The operation state of the transformer affects the operation of the whole power system. Aiming at the application of online monitoring of transformer operation, based on compressive sensing theory and wavelet packet analysis technology, a transformer acoustic fault diagnosis method based on compressive sensing is proposed. Firstly, the partial Hadamard matrix is constructed as the observation matrix to compress the acoustic signal of the transformer. The energy decomposition of the compressed signal is completed based on the wavelet packet. Finally, the feature selection is completed by considering the energy distribution characteristics using wavelet information entropy. The acoustic signal characteristics of transformer core fault simulation data are extracted by this method, and the fault diagnosis simulation is completed by using a particle swarm -SVM classifier. The results show that this method can obtain higher fault identification accuracy under the condition of a high compression ratio.
Electric vehicle charging scheduling based on improved bald eagle algorithm
Authors: Li Ran , Bai Di
Published: December 2023

With the continuous promotion of electric vehicles (EVs), charging fees for EVs has gradually become a hot issue. Pointing at the defects of the bald eagle algorithm, such as slow rate of convergence and poor solving accuracy, the bald eagle search algorithm based on opposition learning and Gaussian variation (GBES) is proposed. The improved bald eagle algorithm has the characteristics of fast convergence speed and strong optimization ability. The model of EV charging cost minimum scheduling is optimized by the GBES, and its effectiveness is verified by simulation experiments.
Modeling and Reliability Constraint Analysis of MMC Valve
Authors: Wang Shuaiqing , Chen Shuai , Hu Yongjie , Hu Xuebin , Hu Qiuling , Guan Gengsheng , Zhou Xiaofeng
Published: December 2023

The VSC-converter valve is the core equipment of the VSC-HVDC transmission system, and its reliability directly affects the availability of the VSC-HVDC system. The reliability model of the existing VSC-converter valve mainly considers the relationship between different redundancy and the reliability of the VSC-converter valve. This paper first analyzes the impact of the failure of key components of the VSC-converter valve. According to the different effects, the arm reliability model of the VSC-converter valve is established, and finally, the comprehensive reliability model of the VSC-converter valve is established. Then, based on the model of the VSC-converter valve, the reliability constraints of the VSC-converter valve that meet the engineering requirements are finally derived. An example is given to verify the correctness of the classification reliability evaluation. Finally, according to the reliability model proposed in this paper, the design recommendations for a highly reliable VSC converter valve are given.
Maximum Power Point Tracking Based on Wind Speed Prediction
Authors: Peng Meihua , Wang Zhen , Xie Zhiqing , Yang Ziheng
Published: December 2023

A control method for MPPT (maximum power point tracking) based on wind speed prediction is proposed to address the issue of slow attainment of optimal speed values by wind turbines in variable wind speed conditions in the wind power system. Initially, the wind speed variation value is accurately estimated using the SSA-BP neural network based on historical wind speed data. Subsequently, the MPP (maximum power point) is calculated considering the optimal blade-tip speed ratio, thereby enhancing the tracking speed of the system. Simulation results demonstrate that this method enables real-time estimation of wind speed variation, improves wind energy utilization rate, and maximizes the utilization of wind energy.
Design and Implementation of DSP-based Three-level Simplified SPWM Modulation Method
Authors: Fan Naiwei , Wang Liejun
Published: December 2023

The traditional three-level sinusoidal pulse width modulation (SPWM) requires two carriers to be compared with the modulating waveform to get the duty cycle, which can not be realized in a single-core DSP chip with high requirements. This paper proposes a three-level single-carrier SPWM waveform implementation method that does not increase the hardware cost. The scheme is based on the DSP28335 chip, using the DSP chip’s increment/decrement counting method, the comparison counter, and the DSP interrupts to compare the carrier waveform with the modulating waveform and get the PWM drive signals with different duty cycles. Simulation results show that compared with the traditional three-level SPWM algorithm, the proposed three-level simplified SPWM modulation not only controls the hardware cost, but also optimizes the bias of the intermediate capacitor voltage on the DC bus side, which reduces the harmonic distortion of the grid, shortens the time for the DC output voltage to reach the steady state, and verifies the effectiveness of the proposed modulation method.
Technologies Related to Intelligent Grounding Box of High-Voltage Transmission Cable
Authors: Lv Lixiang , Xu Weilun , Liu Shanshan
Published: December 2023

The high-voltage cable line plays an important role in the transmission of electricity in the city network. The effective grounding of the high-voltage cable is of great significance to ensure the normal operation of the cable system. There is an increasing demand for the intelligence of grounding boxes of high-voltage transmission cables. In this paper, aiming at the heating problem of the grounding box, the overall design scheme and key technology of the cable intelligent high-voltage grounding box are proposed. The intelligent high-voltage grounding box has various electrical functions of the traditional grounding box. It also has cable circulation monitoring, waterproof, fireproof, anti-theft, and alarm functions. Remote control and management of intelligent grounding boxes can be realized through GPRS.
Research and Design of Substation Positioning System Based on Ultra-wide Band
Authors: Jia Tianyu , Qiao Jiping , Guo Fengfeng
Published: December 2023

Aiming at the problems such as whether the safe distance between the substation operators and the live equipment is enough and the accidental loss of the working equipment, a substation personnel and materials positioning system based on UWB (ultra-wideband) is designed. Through the development of the hardware and software of the lower computer and the upper computer, the moving target is located. The experimental results show that the positioning error is less than 7.8 cm in the one-to-one ranging mode and 20.5 cm in the three-dimensional mode, which meets the high-precision positioning requirements of the operators and equipment in the substation.
Design of Carbon Dioxide Reduction Electrolysis Stacks and Trial Production of Electrolytic Cell Prototype
Authors: Zhu Shan , Ma Fengxiang , Zhao Yue , Liu Wei , Song Yumei , Zhu Shougang , Niu Xudong
Published: December 2023

Currently, the electrolytic conversion of carbon dioxide (CO2) is a highly regarded and dynamic research field worldwide. The investigation and application of high-efficiency catalysts and ion-exchange membranes have emerged as prominent and sought-after research directions. This paper, in particular, centers on the design, trial production, and testing of carbon dioxide reduction electrolysis stacks. To optimize the stack performance, different plate materials were evaluated for their mechanical strength and corrosion resistance, resulting in the selection of aluminum alloy and 316L stainless steel. Furthermore, the choice of ionic membrane and carbon paper was based on Faraday efficiency and stability data, leading to the selection of DuPont Nafion anionic membrane and YLS carbon paper. Through the trial production of small electrolytic cells, the overall current density, Faraday efficiency, and durability of the chosen cell assemblies were validated. Subsequently, a KW-grade electrolysis stack was successfully manufactured, tested, and fine-tuned, achieving an impressive electrocatalytic current density of approximately 200 mA/cm2 and an impressive stability of around 400 hours.
Heat dissipation design of the mine-used inverter output filtering device
Authors: Wang Yue
Published: December 2023

During long-distance transmission, pulse width modulation (PWM) signals are subject to voltage reflection. This results in spike voltages and high du/dt values at the motor end. Suppression is carried out by utilizing a series reactor at the output of the inverter. And the filtering parameters are optimally designed. Then, the EMF characteristics of the output reactor are analyzed and power losses are calculated. On this basis, an integrated heat dissipation scheme is proposed to design the output reactor for forced cooling. It is verified by ANSYS/Icepak simulation, which shows that the filter has good heat dissipation performance.
Modeling and Simulation Analysis of Operation Characteristics of Supplemental Fired Absorption Heat Exchanger
Authors: Lian Xueli , Zhang Chenghu , Di Yanqiang
Published: December 2023

Based on a general single-segment absorption heat exchange unit, a series complementary lithium bromide absorption heat exchange unit was constructed by adding a direct combustion unit, which can achieve a lower backwater temperature on the primary side, thereby increasing the heating capacity. Based on the analysis of the thermodynamic cycle and heat-transfer process, the mathematical model was built and solved using an iterative numerical method. Based on satisfying heating load, the impact of the temperature of supply water on the primary side on the operating characteristics of the unit under different load conditions was quantitatively analyzed. The result shows a negative correlation between backwater temperature on the primary side and supply water temperature on the primary side when other parameters are unchanged. If the supply water temperature on the primary side remains unchanged, the temperature of the backwater on the primary side decreases with the increase of heating load, and the ratio of heat exchange of plate heat exchange unit to total heat exchange decreases with the increase of heating load. For example, when the supply water temperature is 120°C, the proportion of water-water plate heat exchange capacity to total corresponding to 100% heat load, 90% heat load, and 75% heat load is 0.465, 0.580, and 0.772, respectively.
Interpretable Load Patterns of Building District Energy Systems using Attention-based LSTM
Authors: Yu Hanfei , Huang Shifang , Zhang Xiaosong
Published: December 2023

With the increasing demand for energy and focus on environmental sustainability, district energy systems (DESs) have emerged as a promising solution. To optimize DES operations and energy savings, accurate load forecasting is crucial. This study proposed an LSTM model with an attention mechanism for accurate heating load forecasting within a real DES. By introducing an attention mechanism, the heatmaps generated by weight distribution can reveal the load pattern’s periodicity and building thermal inertia. Research on single buildings and district systems has shown that load forecasting with district systems is more stable regarding forecasting accuracy and load pattern extraction capability under irregular external disturbances. The outcomes illustrate the effectiveness of the proposed framework in accurately predicting heating loads and extracting interpretable load patterns. This can assist building managers in enhancing operational strategies, resulting in energy conservation.
Cross-efficiencyBasedonGeneralized-DEAandItsApplication
Authors: Shu Yingting , Cai Yongrun
Published: December 2023

Traditional DEA selects automatically inner Decision-Making Units (DMUs) as the reference set. However, some applications might need specified units. Based on generalized DEA and cross-efficiency DEA, a cross-GDEA model is constructed in this paper, which not only considers any specified reference set in efficiency evaluation but also ranks distinguishably all DMUs. A numerical example and comparative analysis are given to illustrate the reasonableness of the cross-GDEA model. Comparative analysis with several established DEA models reveals the superior flexibility and generality of our method. Furthermore, an application aiming at measuring the multiple-factor carbon productivity of Western China is given to verify the applicability of the cross-GDEA model. Results show the proposed approach can contribute to advancing the theoretical and practical research of DEA.
A Study on Positive Integer Points of Elliptic Curve y
2 = 7mx(x
2 + 512)
Authors: Du Xiancun , Zhao Jianhong , Lv Shuangqing
Published: December 2023

By using elementary methods such as the properties of congruence and Legendre symbols, it is proved that the elliptic curve y
2 = 7mx(x
2 + 512) has at most 1 positive integer point when q ≡ 5(mod8) is an odd prime number.
Low-Frequency Discontinuous Noise Diagnosis and Reduction of Air Conditioner Outdoor Unit
Authors: Mao Luyao , Ma Hailin , Long Danfeng , Zhang Liang , Chen Qiyu
Published: December 2023

Abnormal discontinuous low-frequency noise occurs in the outdoor unit when the air conditioner is operating at 86~96 Hz. This noise has the characteristics of low frequency, strong penetration, long transmission distance, and poor sound quality, which can cause serious noise pollution. In order to reduce the low-frequency noise of the outdoor unit of the air conditioner, the discontinuous noise frequency is first located by testing the time-domain and frequency-domain maps of the noise. It is then compared with the frequency of fan rotation noise and structural radiation noise. It is found that the discontinuous noise is caused by the coupling of fan rotation noise and structural radiation noise. It is found that low-frequency noise improvement is significant when the frequency difference between two noise peaks is greater than 8 Hz or when a single noise peak is less than 25 dB(A) by studying the methods of frequency modulation and amplitude modulation of noise peaks. By adjusting the fan speed from 930 rpm to 940 rpm, the problem of 94 Hz noise is solved. Then, through testing the natural frequencies of the pipe and shell, it is found that the natural frequencies of the pipe are close to the excitation frequencies. The structural radiation noise is mainly caused by the pipe. Modal analysis is conducted on the pipe. When the normal boundary with the condenser and the normal boundary with the valve of the pipe is constrained by springs, the simulated values are closer to the measured values. Finally, structural optimization design is carried out on the pipe. When the U-tube of the exhaust pipe is shortened by 30 mm, a 30 g mass block is added to the cold inlet pipe, and a 97 g mass block is added to the lower part of the valve pipe of the suction pipe. The discontinuous noise of the optimized prototype is significantly improved.
Research on Denoising of GIS Ultra-High Frequency Partial Discharge Signal Based on VMD Combined with S-G Filter
Authors: Yuan Chao , Ding Xiaosen , Cheng Henxiang , Zhu Lei , Li Yilei
Published: December 2023

Given the problem that it is easy to receive thermal noise interference from the electronic circuit and equipment circuit of the detection system in the current feature frequency detection of Gas Insulated Switchgear (GIS) equipment, this paper proposes an ultra-high frequency (UHF) signal noise reduction method based on variational mode decomposition (VMD) combined with Savitzky-Golay (S-G) filter and tests it through simulation. By using VMD combine with the S-G filter method, the signal-to-noise ratio (SNR) of signals can be effectively improved and the interference of white noise to signals can be reduced.
Simulation study of partial discharge UHF signal propagation characteristics in GIS
Authors: Xu Honghua , Yuan Chao , Ding Xiaosen , Xu Ziqiang , Zhu Lei
Published: December 2023

Insulation defects inside a Gas Insulated Switchgear (GIS) can generate partial discharges, and the current pulses caused by them can excite ultra-high frequency (UHF) electromagnetic waves. To study the attenuation characteristics of UHF signal propagation in GIS, simulation models of the straight cylinder, insulator, L-type, and T-type structures are established by CST simulation software. Then the propagation characteristics of partial discharge UHF signal are studied and analyzed. The simulation results show that the electromagnetic wave propagates in each structure inside the GIS with different degrees of attenuation. When passing through insulators continuously, the first insulator has the most serious attenuation; when passing through T-shaped structures, the attenuation of T-shaped vertical branches is more serious than linear branches.
SVG Loss Estimation Method Based on Extreme Gradient Boosting
Authors: Xiao Rongyang , Huang Yan
Published: December 2023

Static Var Generator (SVG) consumes large amounts of electrical energy during its operation, generating high equipment operating costs. Therefore, it is necessary to quantify the operating SVG loss. However, the existing methods of loss estimation generally have notable problems, such as large deviations in loss estimation results. In this paper, we propose a method for calculating SVG loss and establish an SVG loss estimation model based on the extreme gradient boosting algorithm under different operating conditions. First, some data obtained by simulation experiments are input into the algorithm model for training, and the hyperparameters of the model are adjusted by the Bayesian optimization algorithm. Then, a new test set is constructed by superimposing the measurement errors with different signal-to-noise ratio noises on the test set data. Finally, the test set is fed into the trained model for testing to validate the effect of the present model. The experimental results show that the model can quickly and accurately achieve loss estimation of SVG devices with good engineering practicality.
Quick-look method and system for multi-domain space science experiment data
Authors: Yu Haijun , Cao Kaiyang , Yang Mengbo , Li Shengyang
Published: December 2023

Space science experiment data contains huge application value. It is important to design methods and systems to have a quick look at the process of data processing. An integration framework is proposed in this paper. Several basic visual components are designed to support the quick look requirements of different types of data. The dynamic configuration mechanism of the visual view can effectively improve the scalability and user experience friendliness of the system. The method of the interactive layout of the front-end interface can make the visual effect of the page richer. It also supports the self-adaptation of the display screen with different resolutions. The dynamic registration mechanism for visual views ensures the synchronization of data display in multiple identical visual views. Finally, a quick-look system is implemented, which achieves the integration and quick look of multi-domain space science experiment data. The validity of the proposed system is verified by the practical application.
TBGD: Deep Learning Methods on Network Intrusion Detection Using CICIDS2017 Dataset
Authors: Zhao Yifan , Hu Zhanhui , Liu Rongjun
Published: December 2023

With the development of science and technology, more and more personal information is uploaded to the Internet, which poses a serious threat to our personal and property security. As machine learning and deep learning techniques continue to develop, they become increasingly powerful at extracting data and improving the accuracy of classifying malicious traffic. This paper proposes an intrusion detection model based on Transformer, BiGRU, and DNN, referred to as the TBGD model. The Multi-Head Attention mechanism and Feedforward Neural Network in Transformer help capture global relationships and information; BiGRU models sequential information in sequences; DNN learns complex nonlinear relationships and generates accurate intrusion detection predictions. To solve the problem of data set imbalance, we adopted the RUSK sampling mechanism, in which we used Random-Under-Sampler for majority class samples and K-SMOTE oversampling for minority class samples to balance the data set. In addition, the experiment uses the CICIDS2017 dataset. The experiment shows that after the RUSK sampling mechanism balances the data set, the TBGD model has a higher overall classification accuracy and a higher recognition rate for minority classes than the machine learning and deep learning algorithms compared to the experiment.
Convex Robust Recovery of Corrupted Tensors via Tensor Singular Value Decomposition and Local Low-Rank Approximation
Authors: Jiang Yuanxiang , Zhang Qixiang , Yuan Zhanjiang , Wang Chen
Published: December 2023

This paper discusses the recovery of tensor data corrupted by random noise. Our approach assumes that the potential structure of data is a linear combination of several low-rank tensor subspaces. The goal is to recover exactly these local low-rank tensors and remove random noise as much as possible. Non-parametric kernel smoothing technique is employed to establish an effective mathematical notion of local models. After that, each local model can be robustly separated into a low-rank tensor and a sparse tensor. The low-rank tensor can be recovered by minimizing a weighted combination of the norm and the tensor nuclear norm (TNN) obtained as the tightest convex relaxation of tensor multi-linear rank defined in Tensor Singular Value Decomposition (TSVD). Numerical simulation experiments verify that our proposed approach can effectively denoise the tensor data such as color images with random noise and has superior performance compared to the existing methods.
Unraveling the secrets of γδ T cells with single-cell biology
Authors: Sagar
Published: December 2023

Recent technological advancements have enabled us to study the molecular features of cellular states at the single-cell level, providing unprecedented resolution for comprehending the identity and function of a cell. By applying these techniques across multiple time frames, tissues, and diseases, we can delve deeper into the mechanisms governing the development and functions of cell lineages. In this review, I focus on γδ T cells, which are a unique and functionally nonredundant T cell lineage categorized under the umbrella of unconventional T cells. I discuss how single-cell biology is providing unique insights into their development and functions. Furthermore, I explore how single-cell methods can be used to answer several key questions about their biology. These investigations will be essential to fully understand their translational potential, including their role in cytotoxicity and tissue repair in cancer and regeneration.