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Contrary to the conventional belief that, in transmission electron microscopy (TEM), selective and sharp imaging of dislocation loops can be realized only by accurate tilting of a specimen from the condition that the symmetrical axis of incident electron beam distribution is parallel to a zone axis of the TEM specimen (on-zone condition), we demonstrate that selective dark-field (DF) imaging of dislocation loops at on-zone condition is possible with a scanning TEM (STEM) mode that uses an objective lens aperture to select a diffraction disk of interest. Diffraction-selected on-zone STEM (DsoZ-STEM) has been applied to selective DF imaging of dislocation loops with a short axis length of <2 nm in a single-crystal aluminum irradiated by argon ions and an electron beam at room temperature. It was found that a Kikuchi line enhances the contrast among the dislocation loops and the matrix of DsoZ-STEM images. DsoZ-STEM obeyed g·b invisibility criterion and showed good agreement with a typical visibility change of a dislocation line and a loop in conventional DF images with a specific pair of $\pm$ ± g. In addition, dislocation loops always showed much higher brightness in the inner side compared to the outer side in DsoZ-STEM images, simplifying the distinction of dislocation loops with apparently the same long-axis direction but different b. Thus, DsoZ-STEM can simplify the selective DF imaging for the determination of the number and the character of dislocation loops. [ABSTRACT FROM AUTHOR]

Wind-induced single-sided ventilation is a prevalent form of natural ventilation extensively used in buildings. Nevertheless, prior experimental investigations predominantly focused on single-zone buildings, neglecting the multizone buildings with internal partitions which is representative of more common scenarios. This study addresses this gap by investigating the impact of internal partitions on single-sided ventilation, employing a combination of wind tunnel experiment and numerical analysis. Airflow rate (AFR) was measured with a split-fibre probe and purging flow rate (PFR) was assessed by the tracer gas methodology. The PFR exhibits greater sensitivity to internal partitions in unidirectional airflow compared to bidirectional flow. Large Eddy Simulation (LES) was conducted to elucidate the intricate airflow characteristics in single-sided ventilation. The ventilation efficiency (ratio of PFR and AFR) derived from LES ranges between 0.74 and 0.79, which means that <80% of the AFR actively contributes to the removal of contaminants. Notably, the investigation discerned that the AFR of a single room approximates that of the entire room, whereas the PFR of a single room is smaller than that of the whole room. The disparities in AFR and PFR were caused by the recirculating flow, which was elaborated by the theoretical analysis. HIGHLIGHTS: The Airflow rate (AFR) and Purging flow rate (PFR) were measured in the wind tunnel experiment. The wind pressure difference of a sealed model was measured to indicate the airflow direction. LES was performed to elucidate the airflow characteristics in a room with internal partitions. The difference between the PFR of a single room and a whole room was explained theoretically. [ABSTRACT FROM AUTHOR]

Using the impinging jet ventilation system (IJV), it is possible to accomplish high ventilation effectiveness by creating temperature and contaminant stratification within the room. Since the air is supplied toward the floor and directly spreads into the occupied zone at the lower level, it is important to understand the flow feature of supplied jet around the floor. To understand this, the velocity profile of the jet over the floor at the central cross-section was measured using hotwire anemometer under isothermal conditions, and particle image velocimetry (PIV) under isothermal, cooling, and heating conditions. As a result, the obtained velocity profiles at the central cross-section by the hotwire anemometer and PIV are almost the same in the region more than 0.5 m horizontally away from the supply duct. The velocity in the region close to the supply duct was underestimated when using PIV, due to the insufficient entrainment of the seeding tracer. However, its measurement accuracy is assumed to be sufficient for the flow that goes into the occupied zone. In addition, it was also shown that at the central-cross section, the velocity profiles under isothermal and cooling conditions are almost the same.

Office spaces where many people spend long times need effective ventilation systems to prevent infections. This paper suggests a new ventilation method called “Displacement Ventilation with Breathing zone Air Supply” as a way to achieve that. In conventional displacement ventilation, all supply air is provided from the floor level. However, in the new system, supply air is provided from both breathing zone (breathing zone air supply) and floor level (floor level air supply). This new system aims to improve air quality of the breathing zone by controlling air flow of breathing zone air supply which is modified its supply condition considering the temperature stratification. The system also aims to be energy efficient due to increasing the average temperature of supply air. In this research, the performance of this ventilation system was examined through a full-scale experiment and CFD analysis assumed an office space. The results were discussed in the temperature and concentration distribution. The results showed that the temperature stratification was formed even when air was supplied in the breathing zone. By optimizing the air supply conditions, the new ventilation system is considered to be more effective than conventional displacement ventilation to prevent infectious diseases.

The main objective of this study is to investigate the airflow characteristics in single-sided ventilation. A CFD method of large eddy simulation (LES) using particle track technique was conducted in this study, and the simulation results are validated by experiment results. The mostly used ventilation efficiency indicators of natural ventilation are Air Flow Rate (AFR) and Purging Flow Rate (PFR). AFR is the volumetric airflow exchange rate through the openings and PFR is the effective airflow rate that removes indoor air pollutants. The ventilation efficiency (εν) of natural ventilation, which is defined as the ratio of PFR and AFR, is not well investigated in previous research, therefore, this study discusses the case of the εν of single-sided ventilation and tries to explain the distinction between AFR and PFR by statistical analysis approach based on particle movements. Particles are emitted from the opening and the particles’ movements are tracked by tracing their locations at different time steps. The residence time measures the time between the time that particles enter the room and the time that particles leave the room, and indoor travel distance indicates the sum of the displacement when the particle travels in the room. The Probability Density Function (PDF) of the residence time and indoor travel distance is used to depict airflow characteristics of the ventilation path of single-sided ventilation. The analysis method of study might be another useful approach to studying natural ventilation in detail.

Since proper break between office work is helpful in decreasing work-related stress and fatigue, a break space in office is also an important place to create healthy and productive workplace environment. However, there are relatively few studies focused on the break space compared to ones focused on work space. In this study, experiments were carried out to investigate the influence of the break space’s indoor environment on occupants’ psychological and physiological responses. To examine whether change in indoor environment during break positively affect occupants’ responses and productivity, lighting, odor and air movement conditions were intentionally changed before the end of the break. As for the psychological response, there was a possibility that it would be affected when the lighting and air movement were changed. As for brain waves, effects were also observed when lighting and air movement were changed. In terms of productivity, performance was better when the environment was changed than when the environment was left unchanged during breaks. The need for breaks was indicated because the worst results were obtained when the work was done continuously without a break in the first place. The best results were obtained when the environment was changed to generate an odor.

The prototype all-air wall induction unit (IU) has the characteristics of displacement ventilation (DV) and windless air supply, which is considered ideal for hospital ward usage. The outdoor temperature, however, will affect its ventilation and thermal performance. This study conducted a full-scale experiment. IUs are vertically installed in the four corners of the experiment room, which is furnished as a Japanese hospital ward. An outdoor climate simulation chamber (OCSC) is installed on one side of the room to simulate the external window and sill under different outdoor temperature conditions. CO2 is generated from the room’s one point, representing pollutants emitted by a patient. The room’s steady-state temperature and CO2 concentration distribution are analyzed under different outdoor temperatures (in OCSC) and air supply conditions. The IU maintained a comfortable thermal environment under all experimental conditions. In terms of ventilation performance, downward airflow undermines concentration stratification in midwinter. The DV stabilizes when the temperature difference between inside and outside air becomes less than 10 °C while using the double-pane window in winter. Conversely, upward airflow strengthens the DV in the summer. In addition, a sufficient supply rate is recommended to keep concentrations and temperatures above the patients’ breathing zone.

In recent years, displacement ventilation system has received much attention in terms of infectious disease control, due to the epidemic of COVID-19 infections. Plume from occupants and the other heat sources is a very important factor for displacement ventilation because it determines the height of the contaminant stratification. Therefore, this paper aims at the effect of distance between occupants on distribution of temperature, contaminant concentration and plume from occupants in CFD analysis at first. The results suggest the specific distance where plume from occupant interfere with each other in the occupied zone. Our results also indicate that other conditions such as human body posture also affect the interference. In addition, since the aforementioned study don't take into account the influence of the temperature of window surface cooled by outside air, we vary the insulation performance of the window and check the concentration in the occupied area. The results are obtained that the amount of contaminants carried by the downward flow from the window to the lower part of the room depends on the insulation performance of the window, which affects the occupied zone.

Recent studies have reported that essential oils and fragrances sprayed indoors affect psychologica evaluation and intellectual productivity. However, the effects of long-term exposure to fragrances on the human body have not been well studied, and there are still many unresolved issues. Therefore, in this study, the effects of repeated exposure to fragrances on changes in the perception of fragrances as a study for long-term operation of fragrance environments were investigated. In order to investigate the effect of fragrance repetition on threshold and odor perception, a panel experiment with 19 subjects was conducted using rosemary essential oil and scatole. The Rosemary was be exposed and the Scatole was not. The conditions were repetition frequency of adaptation. Regarding thresholds, several panels showed an increase in thresholds for rosemary with exposure and a decrease in thresholds for scatole, indicating a long-term acclimation trend due to repeated exposure to fragrances. As for the subjective evaluation of fragrance, the evaluation of fragrance preference and pleasantness/ unpleasantness tended to change to the neutral side in the case of lower frequency and longer duration. In the future, experiments that tend to increase the number of conditions of the frequencies and duration of repeated exposure will be conducted.

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

In recent years, the number of office buildings that introduce natural ventilation (NV) is being increased to save energy. However, operating NV systems with NV opening device fully open could lower thermal comfort, depending on meteorological condition. Therefore, automatically-controlled NV systems can generally work only for a relatively short period of time. In order to keep both energy saving performance and thermal comfort even when outdoor temperature is low in the mid-seasons, it is necessary to understand the relation between NV conditions and the indoor environment. In this paper, the indoor environment is evaluated changing NV conditions by using CFD for a generalized office room model. Four types of NV inlet system were assumed, i.e., high peri-counter (Type 1), low peri-counter (Type 2), slot-type downward inlet (Type 3), and slot-type horizontal inlet (Type 4). Twenty conditions were analyzed for each type, varying the outdoor air temperature and NV flowrate as parameters. As indices of thermal comfort, average vertical temperature difference within perimeter zone and ADPI in the occupied zone were calculated. For each of NV systems, simplified equations to calculate Nmax from indoor/outdoor temperature difference are finally to be proposed, which may be considered for NV opening control in operating NV systems.

This study proposes a novel approach combining a local exhaust ventilation system (LEV) and a whole underfloor air distribution system (WUFAD) in the consulting room. This study assumes that two persons (doctor and patient) are sitting face to face and talking without a mask in a simple room regarded as a consulting room. To model people talking, exhaled air velocity and volume from talking were required, so we estimated velocity speed using an ultrasonic anemometer and volume using a PET bag and mask. Then CFD steady analyses were carried out, setting various parameters (hood height, hood flow rate, horizontal hood position, and ACH) using the breath experiment results. Capture efficiency and contribution distribution for the hood (SVE5: scale for ventilation efficiency 5) for tracer gas have been calculated. Infection risk for the doctor also has been calculated using the Wells-Riley model. The estimation’s results showed that exhaled air velocity was 0.30m/s and volume was 5.2L/min from talking. The CFD results showed that hood flow rate significantly affected capture efficiency. SVE5 showed that ACH greatly influenced the hood’s effective area. The infection risk for the doctor revealed that the combination of the LEV and WUFAD could protect doctors from infection risk under low supply conditions: 60 m3/h/person (6 ACH).

The basic strategy of the impinging jet ventilation system (IJV) is to keep high air quality within the occupied zone. In IJV, the air supplied from ducts impinges on the floor and spread through the lower level of the room. When the air reaches the heat sources, it rises upward and is exhausted around the ceiling. Most of the previous works about IJV focus on simple room set-ups, whereas the studies focus on realistic set-ups are limited. To investigate the applicability of IJV to a more practical situation, CFD analysis was conducted in a room that simulated a restaurant. In this numerical study, thirty-two seated occupants were distributed in the restaurant hall as the heat and contaminant sources (contaminant was released from their mouth), while a large amount of heat was generated by the equipment in the kitchen. The indoor environment of IJV was compared to that of the mixing ventilation system (MV) in terms of thermal environment, ventilation effectiveness, and infection risk. The results showed that IJV were superior to MV in terms of air conditioning efficiency, pollutant removal efficiency, and infection risk reduction. In conclusion, the results suggest that IJV can improve the indoor environment.

Large openings of buildings are often used open, which results in heat loss due to intrusion of outdoor airflow and leakage of indoor air through the opening. To reduce air-conditioning load and to improve thermal environment in such a building, installing an air curtain at the opening can be a beneficial technique. The airflow blowing out of the device suppresses the heat exchange by buoyancy-induced convection through the opening. The impact of temperature difference, blowing speed, and installation position of the air curtain on temperature distribution and invasion flow rate of outdoor air was investigated by full-scale experiment under heating operation. Thermocouples were installed to measure vertical temperature distribution. Outdoor air infiltration was measured using tracer-gas method. The amount of outdoor air infiltration was evaluated based on both temperature difference and CO2 concentration. Comparing the results, it was found that the indoor air curtain was able to suppress the airflow through the opening. The indoor-outdoor temperature difference and CO2 concentration were highest when the air velocity was 4 m/s, suggesting that there is an optimal air velocity at which the air curtain can effectively suppress the airflow through the opening.

Glassy carbon substrates were implanted with 100 keV platinum ions. The implanted samples were analyzed using cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy. Ion beam sputtering significantly affected the depth profile during platinum-ion implantation. Cross-sectional TEM revealed that the implanted platinum atoms were in the amorphous state and did not aggregate. Chemical state analysis of the platinum-ion-implanted glassy carbon substrates suggested that lattice defects in the substrates owing to the platinum-ion implantation caused the platinum–carbon interaction with electron transfer from platinum to carbon. [ABSTRACT FROM AUTHOR]