APET future energy vision study group in University of Tokyo published the report entitled “Future energy vision of Japan in 2050” in October 2021. They summarized five recommendations for constructing Japanese ideal electric power system in the future. In this paper, the author introduced the group’s activity.
Environmental issues in Japan were established with the development of the city. In Tokyo, the first signs of this can be seen in the 1920－30s, when environmental awareness was not yet established and the City Beautiful Movement took the lead. The range of activities was broad and included not only aesthetic issues such as roads and architecture, but also those related to pollution control, such as tree planting and noise. However, as the wartime regime was strengthened, the City Beautiful Movement was subsumed into the political strategy of the state. In this case, however, the beautification of the environment was not aimed at the inhabitants, but at tourists.
One of the dominant sound sources of wayside noise on a high-speed railway line is the noise from the lower parts of cars which consists of rolling noise and aerodynamic noise. In this study, the lower part noise was measured continuously along a railway line with two microphones installed at close points to each bogie under the car floor, and characteristics of the noise were evaluated by considering the effect of the location of microphones, the type of tracks such as ballasted or non-ballasted tracks, and train speed. As a result, there is large dispersion of the sound pressure level in the frequency range of 2k-3.15kHz band. The fact suggests that rolling noise varies according to the variation of roughness of a rail surface in the wavelength components associated with the above frequencies. Additionally, the sound pressure level on ballasted tracks is lower than that on non-ballasted tracks, because of the sound absorption effect of ballast beds. Therefore, it was found that the data of the lower part noise measured with under-floor microphones included the effect of track conditions such as rail surfaces, track types, and so on. It is expected that the data of lower part noise which is measured continuously on trains is used to predict the wayside noise along railway lines effectively.
In order to reduce the wayside noise of a high-speed railway, it is important to understand the contribution of each noise source to the total noise level at each observation point. The noise generated from the lower part of cars, which mainly consists of aerodynamic noise and rolling noise, is one of dominant noise sources. Rolling noise varies with the surface roughness of wheel and rail and track conditions and so on. This paper attempts to quantitatively estimate the contribution of lower part noise to wayside noise by using the sound pressure measured close to bogies under the floor of a high-speed train (referred as under-floor noise). First, the relationship between under-floor noise and noise close to rail on the ground (referred as rail side noise) is evaluated. Secondly, by using both the above relationship and under-floor noise when a train runs on prediction section of wayside noise, the acoustic power level of lower part noise that is applied to an existing wayside noise prediction method is identified. As a result, the estimated level of wayside noise was approximately consistent with the measured result.
In order to obtain the data of curve squeal noise during a train running in a commercial line, the measurement field test was conducted. Sound pressure on both inner and outer sides of the railway curved track were measured with microphones. Laser displacement sensors were used for the measurement of wheel displacements in the lateral direction to estimate an attack angle of wheels. Through the measurements it is found that characteristics of curve squeal noise were different for each train. Even the characteristics did not coincide for each bogie of one train. This means that curve squeal noise does not occur stably. The main frequency of curve squeal in this measurement were 4 kHz or more. High frequency noise, that is a kind of curve squeal above 10 kHz, were seen in several trains. Relation between some parameters that can be associated with squeal noise and sound pressure level were investigated. High humidity can decrease the squeal noise. A certain range of running velocity of the bogie below balance speed at the curve makes the squeal noise greater in the frequency range of 7 kHz to 8 kHz. The squeal noise of inner rail side is greater that of outer rail side in this frequency and running velocity ranges. The greater attack angle also makes curve squeal greater.
Curve squeal noise is one of the major sources of railway noise which needs to be reduced because of strong public opinion. In order to understand the mechanisms underlying the generation of squeal noise and develop methods to reduce this noise, the measurement field test was conducted in a commercial line. By using linear microphone arrays installed on both sides of the railway track, the noise radiated from each wheel at each position on the track was calculated. Analysis of the measurement results showed that the main source of curve squeal noise does not travel and radiates almost the same at any position. In addition, the source of noise traveling with the train did not increase or decrease at any particular location on the track.
Aerodynamic noise generated from pantograph of Shinkansen train is one of the important sources of Shinkansen railway noise. De-convolution (DC) method with microphone array is widely used for source localization in a wind tunnel test to develop noise mitigation methods effectively. The point spread function (PSF) which gives the response of a noise source affects the result of DC method. This paper describes a method to estimate sound pressure level (SPL) of aerodynamic pantograph noise at an arbitrary observation point based on the sound source map obtained by the deconvolution method. PSF, which is designed with the effect of sound field around the pantograph is calculated by numerical analysis (boundary element method). The properties of the calculated PSF is examined in by a speaker test by comparing with a result obtained by conventional PSF, which is designed for a free space. The proposed method is applied to the measurement of the aerodynamic pantograph noise in a wind tunnel test. It is shown that the estimated SPL of the pantograph noise at the observation points agrees well with the measurement result and spatial resolution of the source localization can be improved.
In this paper, we show the results of measured sound absorption characteristic using the proposed acoustic metamaterial in the flow duct. The proposed acoustic metamaterial is based on the Helmholtz resonator with a flexible panel. The point of proposed sound absorber is that wide frequency range of highly sound absorption characteristic is achieved without using damping material. By the evaluation using the sound duct, the validity of this characteristic is indicated. And also, by the evaluation using the flow duct, we indicated this characteristic is sustained.
The purpose of this paper is to apply the immersed boundary method to analyze the characteristics of devices such as duct louvers that are not orthogonal to the direction of sound wave propagation. If the geometry of a structure is not accurately reproduced when the space is discretized with cubic cells, the sound field scattered by the structure may not be accurately simulated. In this paper, the characteristics of the sound field scattered by a flat plate as a structure that is not orthogonal to the direction of sound wave propagation are clarified using the immersed boundary model and the cubic cell model. As a result, it was found that the calculation results tended to differ depending on the modeling method of the structure geometry in a relatively high frequency band.
We have been developing an electrostatic precipitator for carbon particles emitted from internal combustion engines. The unevenness in the surface potential on glass plates as collection electrodes is the key in this device. The surface potential is created when discharge occurs by discharge electrodes attached on the surface, and decays after the end of applying the high voltage. The decay is enhanced by the carbon particles that adhere to the surface. In this study, surface potentials were evaluated under the condition that soot was deposited on the glass surface. In addition, the relationship between the potential distribution and collection efficiency was discussed.
A novel geometry, which named provisionally as "basement and radial configuration", was proposed and investigated in this paper. The geometry gives a vibration-free and kinematic energy fluctuation-free property to motions of plural parts; i.e. pistons. In this study, a prototype three-cylinder internal combustion engine based on the geometry was designed and manufactured. A trial operation of the prototype engine resulted in achievement of firing operation without any support of electrical motor and so on. In this paper the pressure variations in the three combustion chambers on the firing condition was provided.
Non-scanning 3D-CT(Computer Tomography) technique using a multi-directional quantitative schlieren system is proposed to obtain instantaneous 3D temperature distributions of turbulent flames. This "Schlieren 3D-CT" is based on (i) simultaneous acquisition of flash-light schlieren images taken from numerous directions, and (ii) 3D-CT reconstruction of the images by an appropriate CT algorithm. In this study , first, an environmentally friendly burner supplied ammonia gas as renewable fule was developed. In this paper, instantaneous 3D temperature distribution of ammonia turbulent flames anchored on the ammonia-air premixed swirl burner has been reconstructed. Results of the CT reconstructed temperature distributions was shown as 3D temperature contour surface model.
In the high-pressure steam sterilization device, the amount of non-condensable gas in the container needs to be stipulated because the inclusion of air into the steam leads to a decrease in performance. Especially, there is a possibility for a condensation of the non-condensable gas near the cooling zone because of the steam condensation. Therefore, in order to maintain sterilization performance, an understanding of the condition of regional non-condensable gas is required. Authors are advancing development of the measurement method of a small amount of non-condensable gas included in the steam by generating plasma and dispersing its emission of light. In this study, this method is applied to the detection of the non-condensable gas included in the atmospheric-pressure steam generated in the large container. Furthermore, we considered whether the non-condensable gas near the cooling zone in the container is condensed or not. It showed potential for the condensation of the non-condensable gas near the cooling zone.
Focusing on the ability of NOx catalyst to oxidize and capture mercury, we investigated the effects of components of waste and fossil fuel combustion exhaust gases on oxidation and capture ability of NOx catalyst. Experiments were conducted on the oxidation and capture of gaseous elemental mercury by filling a quartz reaction tube with pulverized NOx catalyst powder. The results showed that while mercury was captured even in a nitrogen atmosphere, the mercury capture performance was greatly enhanced when oxygen was present in the atmosphere. This indicates that the immobilization of mercury by oxidation reaction contributes to mercury capture. On the other hand, in the presence of gas containing HCl, mercury was oxidized and released in the gas phase. Exposure of the catalyst to HCl-containing gases after mercury capture resulted in oxidation and rapid desorption of the captured mercury.
To test the apparent viscosity of the sludge after hydrothermal pretreated for recovering energy with sludge spray incineration and sludge transportation of sewage sludge. hydrothermal pretreatments and in turn viscosity measurement/particle size distribution measurement/solid volume fraction measurement of the slurry obtained from the pretreated sludge were performed at laboratory-scale. The results particle size distribution and solid volume fraction of the sewage sludge was decreased with increasing pretreatment temperature 473 K-513 K. The decreasing of particle size distribution and solid volume fraction gave a better performance on the fluidity of the pretreated sludge.
In this study, we demonstrated modular compact mobility (MCM) in Chichibu City. We examined how it could be utilized to propose a mobility service for introducing MaaS in mountainous areas. Specifically, we surveyed good examples of mobility services and identified issues for operation in mountainous areas. We also conducted a delivery demonstration using multiple mobility vehicles, including MCMs, to clarify the last one-mile use of MCMs and identify technical issues. As a result, a new MCM model was designed and developed to solve the issues. It was shown that the utilization method of MCM in conjunction with personal mobility is effective.
The purpose of this paper is to experimentally investigate the thermal performance and local air temperature around a serpentine copper pipe. The application of this study is to control microclimate for plant cultivation. A serpentine copper pipe was designed and set up to measure the heat flux well as the influence on local air temperature under various working conditions. The inlet cooling fluid temperature varied of -10°C to 1°C and flow rate varied from 2.5 L/min to 7.0 L/min in this present study. Collected data such as flow rate of working fluid, supply and return fluid temperatures were measured to calculate heat flux. Moreover, local air temperatures around a serpentine copper pipe were measured by thermocouple. Results showed that a serpentine copper pipe can reduce local indoor temperature. The decrease in supply water temperature from 1°C to -10°C leaded to increase the average heat flux of a serpentine copper pipe around 216%. Whereas the reduction in flow rate from 7.0 L/min to 2.5 L/min increased the heat flux of the copper pipe around 29%. In summary, a serpentine copper pipe is helpful for reducing air temperature and energy consumption compared to traditional air conditioning.
The purpose of this study is to experimentally compare the performance of an air conditioning system during part-load and full-load conditions. The air conditioning system is used in a plant factory that is intended for strawberry cultivation. For this purpose, R22 vapour compression cycle air conditioning was installed to provide cool air inside the plant factory. Experiments were carried out under 2 operating conditions, which are part loading and full loading. For the full-loading experiment, 36 Light-emitting Diodes (LEDs) were turned on. There were no strawberry plants inside the plant factory during the experiments. Pressure and temperature of the R22 were measured using pressure transmitters and K-type thermocouples. Average ambient temperature was 29 °C. The air temperature inside the plant factory was set at 15 °C at night and 25 °C during daytime. It was found that the air conditioning system was operated at transient state. The internal air temperature was influenced by the heat transferred from the wall and the LED. Thus, the performance of the air conditioning system was not constant. According to the experimental results, the average superheat degree was 9.2 °C over two hours of experimental time under part-load and it was 13.7 °C at full-load condition for a day experiment. Moreover, the maximum coefficient of performance under part-load and full-load was 4 and 4.2, respectively. The minimum and maximum compressor efficiency were between 20% and 95% when there was part-load and under full-load of the plant factory.
Dew-point evaporative cooling is an air conditioning technology which has possibility of achieving lower temperature, higher efficiency, lower water consumption. Understanding the heat and mass transfer principles of the system is crucial for the applications. This study presents a mathematical model which is conducted to (1) study the heat and mass transfer processes under different initial condition; (2) analyze the factors affecting the performance of system. And an experimental setup has been adopted to give a validation for the numerical model
With the sophistication of living environment, the number of high-rise buildings such as high-rise buildings, high-rise roads, and exhaust towers is increasing, and noise sources and noise receivers are spreading to high-rise buildings. Therefore, we proposed a noise measurement method for drones, which has been increasingly used in recent years. It has been confirmed that the self-noise of a small drone depends on the rotation of the rotor shaft and has high reproducibility for each rotation. Therefore, it was confirmed that the self-noise of one axis can be estimated with high accuracy by the method of synthesizing from the self-noise of one rotation of the rotor recorded in advance. By that method, we attempted to remove self-noise from the environmental noise measured by the drone by estimating the self-noise of all four axes for the drone in flight. In this paper, we report on the development status of environmental noise recording technology using this method.
This paper is concerned with active control of generating a listening zone in a free space while producing a quiet zone in the same free space. In recent years, the reproduction sound of contents such as speech and music tend to increase in the space living by the spread of teleworks. A sound to the listener may appear as a noise to non-listener around the owner of sound player. Therefore, we propose the sound field control technology to convey the sound information only in the personal area at narrow space. Using three loudspeakers, the experimental result was confirmed by comparison with the simulation result.
As machines become more complex, it becomes more difficult for human beings to monitor the condition of the machine by only observing it from outside or listening to the operation sound. In order to prevent serious accidents, it is necessary that the machine informs the condition to human beings instantaneously, and that human beings respond appropriately. That is, the human-machine interface is important. For example, when human beings drive a car, visual, auditory, olfactory and tactile senses are used. There is no room for further information regarding visual and auditory senses. However, it is considered that there is a margin for the tactile sense, since the sensory receptors are widely distributed. Then, we have been proposed that vibration stimulus using a chair with a built-in vibration generator applying speaker technology are used to inform a driver about the risks. This report describes the results of a questionnaire survey on the impressions of four types of vibration patterns created for a driver assistance. Each pattern is generated in the driving seat of a fixed-type driving simulator while simulating a driving scenario assumed. The results showed that the activity factor, represented by the sense of urgency, was large because simulating the scenario.
Understanding the vortex flow mechanism of cavity tones is desired to control tones in aeroacoustics field. With respect to cavity tones in deep cavity with acoustic resonances the mechanism of vortex flow has not been made clear enough. The vortex might flow out from the upstream side edge of the cavity when the circulation of the flow around this edge exceeds the predetermined value. Above phenomenon is the cause of the cavity tones. It would be the estimated mechanism that the particle velocity of the resonant sound wave influences on the limitation of circulation around the upstream edge for releasing a vortex from the edge. And more, the feedback disturbance charges the vortex circulation. As a result of trial and error by simple numerical calculation, it became possible to explain the phenomenon of cavity tones with resonance by some assumption mechanism.
A perforated metal plate has many small holes. High-speed air flow across the perforated metal plate generates noises caused by aerodynamic vibration or plate vibration. This study deals with mechanism of generation noises from the high-speed air flow through the perforated metal plate. Expansion type perforated metal plate with 7 holes generated large noise with a prominent peak. In the experiment, to consider the mechanism of prominent peak noise generation, flow visualization and measuring velocity fluctuation of jet flow are performed. The noise source was recognized by measuring COP values of velocity fluctuation of jets. Jet flow interference was found by flow visualization method. Jet flow interference is important for the prominent peak noise generation.
The present paper focuses on the effect of flow velocity on acoustic absorption performance of perforated plate. We experimentally measured the flow velocity, acoustic pressure, and transfer function using the improved acoustic impedance tube. The normal incidence absorption coefficient was calculated from the measured transfer function using transfer function methods. As the flow velocity passing through the orifices increased, the peak level of the acoustic absorption coefficient increased. The acoustic absorption performance has improved using taper orifices of perforated plate. The peak frequency of the acoustic absorption coefficient depended on the taper angle of holes of perforated plate. We discussed the effect of the flow velocity and taper orifices on the specific acoustic impedance.
In this study, we investigated the noise reduction mechanism for flow-induced noise of a rectangular cylinder using a porous material mainly focused on the velocity and pressure measurement results around the cylinder. Simultaneous measurements of the streamwise velocity and wall pressure fluctuations were performed. Further, POD analysis of the wake of the cylinder was also performed to investigate vortex structures. Results showed that the cross correlations of the streamwise velocity and wall pressure fluctuations were decreased when porous materials were used. In addition, dominant modes of streamwise and cross-streamwise velocity fluctuation in the wake of the cylinder showed that the time and space scale of vortices become smaller when porous materials were used. Therefore, it can be concluded these changes caused the decrease of the flow-induced noise of the cylinder.
Reduction in aerodynamic noise emitted from a pantograph is an important subject for reducing environmental impact of high-speed trains. In the previous study, aerodynamic noise reduction method by pantograph head support covering with porous material were proposed. Furthermore, two alternative and easier applicable methods of porous material, the one is applying channels and the other is applying perforated plate, are also proposed. In this study, relation between opening ratio and aerodynamic noise reduction effect of these two methods are investigated. From a wind tunnel test result, it is clarified that setting opening ratio around 35%-45% for applying channel and around 50% for applying perforated plate can reduce aerodynamic noise to the same extent as applying porous material.
Large-scale repairs are planned for railway viaducts in the near future, and noise barriers will be replaced with new ones. In preparation for this, the authors have been developing a new noise barrier that is easy to be constructed and has high noise reduction performance. One of the characteristics of this noise barrier is that all wall surfaces on a track side are sound absorbent to reduce under-car noise. It is important to evaluate the relationship between the sound absorption performance of developed products and their noise reduction effects on under-car noise. In this study, a sound absorption coefficient using a reverberation chamber method was measured and acoustic tests using a full-scale model of a railway viaduct were conducted. The results showed that there is relationship between those two, and that reflective structures of the wall surfaces reduce the effectiveness of reducing the multiple reflected sound between the noise barriers and the side of car bodies.
A structural optimization method of subsystems to realize desired SEA parameters was proposed by the authors in the past studies. This method is based on a combination of SEA and FEM calculation, calculating repeatedly until satisfying the value of objective functions under arbitrary constraints. In this paper, the method is validated through numerical analyses, using a finite element method, of a multiple plates partially composed of L shaped, after the sensitivity analysis for the sound energy of the evaluation point due to the fluctuation of loss factors, the subsystem is grouped into a plural elements for the extracted L shaped part, and the each grouped element is set as a design variable, which should take a discrete value, the total mass is taken as a constraint function in order to maximize CLF32 at one frequency band. As a result of optimization, the sound pressure level was reduced by maximizing the value of CLF32 in the target frequency band. Finally, a comparison with a conventional FRF based optimization was shown.
We designed and manufactured a dynamic vibration absorber using magneto-rheological elastomer and verified the vibration mitigation effect for automobile seats. In this research, inner and outer housings of previous dynamic absorber were re-designed and fabricated. The material of the inner housing changed from aluminum to resin to reduce its weight. Further, the shape of the inner housing also changed from cylindrical shape to rectangular parallelepiped shape for its ease installation. In addition, due to the change of the shape of the outer housing, the inner housing which becomes the path of magnetic field lines was made using thin steel plates. Experimental results showed that the natural frequency of the coil which works as a movable mass of the absorber could be controlled by the magnitude of the applied electric current. Results also showed that the absorber could mitigated the vibration of the seat for a wide range of the engine speed by applying suitable electric current to the coil based on the engine speed.
Region separation control of sound field can be achieved by ACC, which is an energy control method, but the reproduced sound zone by ACC method may have large gap of sound pressure in it. There are several ways from previous researches attempt to resolve this “planarity” problem and reproduce plane sound field, but most of them work not directly to the planarity of sound field or need complex calculations. In this paper, we propose an easy and direct method (ACRV) to planate sound pressure without losing Acoustic Contrast and compare it with the method of previous research (ACC and ACLD.) ACRV can make more plane sound field than ACC, and also there are certain cases that ACRV perform better than ACLD.
Active control of noise passing through an aperture has been studied. Previous studies have shown that a large sound reduction effect can be achieved by an active noise control system that uses controlled sound sources placed in the aperture. It has been shown that the sound reduction effect is less when the control source is placed on the aperture surface boundary than when the control source is placed inside the aperture surface. This paper proposes a method to suppress noise passing through an open window section by using multiple control sources placed on the frame of the open window. Numerical simulation results show that the sound reduction effect can be improved by driving the control sources to generate only plane wave components, even when the control sources are placed on the frame of the open window.
We developed a monitoring system for sounds generated from wind turbine and measured low-frequency sounds for several weeks. From the results, we introduced a case where a sound including pure tone was observed around 120 Hz when the rotation speed of the wind turbine was high. In addition, an example was shown in which it was determined whether or not wind noise was included in the observation data by using the level difference between the two microphone outputs installed in the large wind screen.
Noise with a prominent pure tone component, such as motor and gear noise, is perceived by the auditory sense to fluctuate in frequency and amplitude with changes in rotation speed. In this study, the frequency sweep width and frequency sweep speed are considered as the frequency change of the pure tone component, and the amplitude change width and amplitude change speed are considered as the amplitude change of the pure tone component. The cases in which frequency modulation and amplitude modulation occur as modulation of the pure tone component are also considered. The sound quality of these non-stationary sounds will be evaluated to estimate the parameters that are sensitive to human hearing.
In this study, we considered a method to perform automatic hammering inspection using machine learning based on auditory perception characteristics for diagnosis of tile adhesion condition in drone noise. In the hammering test at quiet condition, the condition could be evaluated accurately by machine learning. However, the accuracy was not enough at the noise condition. We then applied a noise reduction method using several microphones in addition to employing auditory perception characteristic of human in the estimation model. As the result, the accuracy could be improved significantly, and it was more accurate than the correct response rate by the subjective diagnosis.
In this study, we focused on steering vibration characteristics as important information of electric vehicle speed information. On the other hand, the vibration may disturb the comfortableness in cabin. We then conducted subjective evaluation test by reproducing steering vibration considering the resonance characteristic using a driving simulator and attempted to propose appropriate vibration characteristics compatible the performance with comfortableness. As a result, both vehicle speed recognition performance and comfortableness were found to be better by controlling the resonance frequency and the level at a suitable condition.
Bio-oil, liquid fuel produced by decomposition of biomass material, has relatively high calorific value and has good storability and transportability. Furthermore, bio-oil fuel is expected to be applied to conventional combustion equipment such as boilers. Water content generated during the bio-oil manufacturing process is expected to reduce the calorific value of the fuel and affect ignition and combustion behavior. However, the effect of water on the droplet combustion behavior, which is often used industrially to burn liquid fuel, has not been clarified so far. In the present study, at first, bio-oil was produced in a fluidized bed pyrolysis furnace using cypress powder as a raw material, and the effect of the pyrolysis temperature on the water content of the bio-oil was investigated. Next, after the water content in bio-oil was adjusted, a single droplet of bio-oil suspended on a fine quartz rod was burned in a high-temperature furnace, and the effect of the water content on ignition and combustion behavior was investigated.
In Japan, there is an increasing demand for the promotion of proper waste disposal. The project focuses on the small-lot collection of waste. It aims to construct a system utilizing IoTand improve the efficiency and human resources saving of work to promote proper disposal of waste, increase the efficiency of small-lot collection operations, and improve the credibility of the data.
This report conducted an interview survey of collection and transport businesses that conduct the small-lot medical waste collection. To identify issues such as telephone orders and developed a system for requesting pickups with a notification button that replaces telephone orders and an information sharing system that displays a list of pickup request information. In addition, a demonstration experiment was conducted with small-lot medical institutions and collection and transport businesses using the developed system, and an evaluation was made through interviews and directions for system improvement.
In recent years, municipal waste treatment facilities in Japan have been automated and manpower-saving as a countermeasure against population decline and the corona disaster. We surveyed advanced cases for the advancement of general waste treatment systems. We also surveyed municipalities to confirm their needs for a standardized official framework for human resources savings. Therefore, we created a pattern of automatic operation levels for waste management. The levels were classified by referring to advanced fields in automation, such as automobiles and airplanes. In addition, an evaluation axis was set up, and the advanced state was divided into several levels.
This research targets the development and evaluation of elemental technology for contactless and automatic waste collection systems in households and commercial facilities, especially three machines. These are an Inversion machine, a Smart garbage can, and Modular mobility. We calculated the time difference between contactless collection systems and conventional ones and found out that the former is more efficient. Using 2 of the machines, Smart garbage can and Modular mobility, we demonstrated in O City, and we evaluated and considered the results to improve them. We calculated the effectiveness of mobility use in transforming garbage bags and presented the guideline for selecting a sensor for the Smart garbage can.
With the development of artificial intelligence and the progress of automation, introducing AI and robotics to participate in waste recycling is discussed over the world. Thanks to the deep learning method, visual recognition allows the sorting robot to contribute almost perfect identification ability if the training set is large enough. However, there are only limited studies focused on introducing AI and robotics to improve the efficiency of construction mixed waste (CMW) disposal.
This study clarifies the current status and challenges of the disposal of CMW, locates the specific disposal process that needs AI and robotics to improve its efficiency, tests the recognition ability of current AI with CMW, and discusses the development roadmap of AI and robotics in the field of CMW disposal.
Nowadays demand for energy resource in the world has been becoming large and this trend will continue in the near future. Nevertheless, fossil fuels in the Earth are limited and it is not enough obviously. Under the circumstances, utilization of various waste products instead for fossil fuel as thermal resource is gathering attention. Therefore, combustion behaviors of waste products need to be elucidated in detail for highly efficient use of them as an alternative to fossil fuels. The purpose of this study is to measure the combustion rate of waste products under isothermal conditions close to the combustion conditions of an actual combustion furnace and then to clarify the reaction kinetics.
In recent years, low air ratio high temperature combustion has become the mainstream in waste stoker incinerators in order to improve boiler efficiencies, while NOx generation due to high temperature in the furnace has become a new problem. In this study, the NOx generation behavior derived from nitrogen in char was evaluated by simulating the char combustion area in the incinerator in the combustion experiment of the biomass char sample by DTF (Drop tube Furnace) using the combustion atmosphere as a parameter. In particular, we focused on the effects of high-concentration H2O and CO2 concentrations due to exhaust gas recirculation and confirmed that H2O contributes to the reduction of NOx emissions.
Bio-coke is solid biofuel and can be made from any biomass. Previous studies have investigated the relationship between main components and the moldability of bio-coke. In this study, we focused on the hot water extract. The hot water extract from bamboo improves thermal fluidity. Thermal fluidity is closely related to the apparent density and compressive strength because the softening component acts as an adhesive during bio-coke production. The purpose of this study was to clarify the effect of hot water extract on the molding properties, apparent density, and compressive strength at room temperature for green tea bio-coke. Green tea contains a large amount of hot water extract. We used green tea which removed the hot water extract. The results of this study show that the bio-coke apparent density was constant (around 1.35 g/cm3) regardless of the bio-coke molding conditions. Therefore, the result suggests that the hot water extract increases the apparent density. Furthermore, we found that removing the hot water extract increased the compressive strength at room temperature 1.3—1.8 times.
The torrefied solid biofuels have come to attract attention as promising alternative fuels to coal in coal-fired power plants and industrial boilers．The torrefaction is a thermal treatment conducted by mild pyrolysis temperatures between 180 and 300℃，and includes two distinct technologies，dry torrefaction (DT) and wet torrefaction (WT)．The WT is an attractive thermal treatment to upgrade wet biomass feedstock without pre-drying．In this study，the effect of torrefaction conditions (torrefaction temperature，residence time，ratio of biomass mass to water mass (B/W) on energy properties of wet torrefied woody biomass is investigated．The experimental correlation to estimate HHV of wet torrefied woody biomass for a given torrefaction condition is proposed．From the comparison of net energy ratio (NER) between DT and WT，it is found that the NER of WT is larger than that of DT for wet biomass in the moisture range between 78 and 92%．Therefore，the energy consumption associated with heat drying for wet biomass for WT may be smaller， compared to DT.
Soda lime glass constitutes 70% of SiO2, 15% of CaO, and 15% Na2O. Silica sand (SiO2), lime stone (CaCO3), and soda ash (Na2CO3) were procured from local sources as well as from abroad. These compounds are chemically stable and found abundantly on earth, hence, they are widely used as raw materials. However, they are carbonate, and their use leads to the production of CO2. Therefore, it is necessary to explore alternative raw materials such as biological raw materials, which are carbon neutral. Here, we focused on seashell because they mainly constitute CaCO3 and are disposed as a by-product from marine products. The purpose of this study was to make flint glass using seashell. We developed two types of CaCO3 materials from seashell via heat treatment and substituted for lime stone to make glass. As a result, we obtained two distinct soda lime glasses types: one was amber, while the other was flint. We analyzed the compositions of the materials, glasses, and their color tone. Thereby, we found that the organic compounds in seashell were responsible for the color change of the glass.
With the goal of establishing a carbon-neutral society by 2050, environmental awareness has been increasing, and there is a desire that all products be optimally circulated in the life cycle of materials. Thus, the treatment of construction waste has become an important issue. However, because there is no effective reuse method for calcium silicate-based building waste, most of it is disposed of as industrial waste. On the other hand, the glass used for plates and fiberglass is soda-lime glass, which contains silicon and calcium as constituent elements. In this study, glass was produced using calcium silicate and gypsum plates as raw materials. Issues associated with the vitrification reaction and composition and physical properties of the glass alternatives were also examined. Of the two materials, the calcium silicate plate, although colored slightly green, exhibited characteristics that were most similar to those of standard glass. This exploratory experiment suggests that calcium silicate plates could be an alternative raw material for soda-lime-silica glass production.
Adhered ash in waste incineration facilities causes heat transfer inhibition, operational disturbances, and high-temperature corrosion. In particular, it is well known that molten salts with heavy metals have a significant impact on high-temperature corrosion. Thus, the objective of this study was to investigate the high-temperature corrosion behavior of Ni-based alloy with copper-added molten salts. The molten salt corrosion tests were performed by the simulated ash salt environment at 510 ℃ using an S/Cl ratio of 7.5 molten salt, NaCl-KCl-Na2SO4-K2SO4-CaSO4 systems, and the corrosion time variation of mass loss was investigated. The time variation of corrosion and the thickness variation of the corrosion scale indicates that the corrosion follows a parabolic rate law. The simulated ash salt was almost not melted under the test conditions, and the corrosion scale was porous, suggesting that the gas component corroded through these defects. Based on the thermodynamic calculations, the corrosion of molten salt containing Cu produced gas components, mainly sulfur oxidant and chloride, that affected the corrosion reaction compared with the corrosion without Cu addition. The XRD diffraction results showed the presence of NiCr2O4 in the corrosion scale, indicating the presence of Cr2O3 in the protective oxide film and the presence of NiO in the non-protective oxide film.
CO2 decomposition is an exciting solution to the greenhouse gas problem by transforming CO2 into a valuable energy resource. However, CO2 splitting in traditional thermal processes requires a large amount of energy and suffers from high energy costs due to energy loss in heating the entire gas. Non-thermal plasma technology provides an alternative way to decompose CO2 by accommodating CO2 activation at a lower temperature while providing energetic electrons, which can activate the gas by electron impact excitation, ionization, and dissociation. In recent years, dielectric barrier discharge (DBD) reactors have become one of the most popular non-thermal plasma systems for CO2 conversion into CO and O2 because of their mild operating conditions, simple designs, and easy upscaling capabilities for industrial applications. However, CO2 conversion and energy efficiency of DBD reactors are still limited and depend on plasma processing parameters and reactor design. This study investigated the effect of electrode materials on the CO2 conversion performance of the CO2 decomposition process in a micro-gap cylindrical DBD plasma reactor. Four materials (SUS, SS, copper, and carbon) were selected as inner electrodes of the DBD reactor. The CO2 conversion, energy efficiency, and discharge characteristics were examined at various discharge power and gas flow rates for different electrode materials. The results show that the electrode materials determined the discharge characteristics of the DBD reactor and consequently affected the CO2 conversion and energy efficiency of the CO2 decomposition process.
Hydrogen based energy are gaining interest as a suitable alternative energy source for usage and many researches are currently being engaged towards realizing a lasting hydrogen economy. However, in order to achieve this, it is important to have a hydrogen generation process that can efficiently compete with that of fossil fuel. Presently, majority of the hydrogen is being produced by steam methane reforming, a process that utilizes fossil fuel and emits greenhouse gases. Recent developments utilize non-thermal plasmas for reforming gas and liquid compounds containing hydrogen. Plasma micro reactor has the capability to produce energetic species from steam at atmospheric pressure which through a series of reaction combine to form hydrogen and oxygen. This method can be a potentially advantageous and cleaner method of producing hydrogen. Dissociation of steam using dielectric barrier discharge (DBD) plasma reactor at atmospheric pressure have been considered and is being tested for its hydrogen production yield. Atmospheric pressure plasma was generated using high frequency and high voltage pulse power supply. The hydrogen conversion rate is defined as the ratio of the total gas that entered the plasma reactor and the hydrogen concentration obtained from the resulting gas after decomposition. Hydrogen production was found to be dependent on the saturated steam flow rate and applied voltage of power supply.