日本建築学会環境系論文集
Online ISSN : 1881-817X
Print ISSN : 1348-0685
ISSN-L : 1348-0685
最新号
選択された号の論文の10件中1~10を表示しています
  • 髙瀨 椋, 鈴木 健太郎, 上川 大輔, 長谷見 雄二, 松山 賢
    2020 年 85 巻 772 号 p. 401-411
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     It is known that a flat wooden wall does not sustain flame spread without external radiation. On the other hand, wooden louvers are likely to sustain flame spread, as heat flux from facing blade as well as flame accelerates burning. This study addressed burning characteristics of wooden vertical louvers and fire controlling measures through reduced- and full-scale experiments.

     To figure out the dimensional relationship that sustains flame spread, reduced-scale experiments were carried out. Wooden louvers were simplified as MDF panels facing each other, and backed by steel channels. Blades were 54 or 112mm deep and 1,700mm high. For Each depth, critical pitch that sustains flame spread was evaluated. Flame sources of 12.8kW/m was placed at the bottom of both panels to ignite them. Flame height, temperature and heat flux were observed during the experiment. After screening some dimensions from the above, full scale experiments were also carried out to reproduce the fire phase from burning of small furniture. The specimen was 500mm wide and 3,400mm high. This time, all blades were 58mm deep and 35mm thick, and three louver walls differ in pitch were burnt; 48, 90, 215mm, respectively. All louvers were directly backed by noncombustible wall (12mm thick calcium silicate board). Sidewalls were attached to both sides of the specimen to avoid horizontal transfer of gas and heat. Heat release of the flame source was 200kW, approximately representing a burning of chairs. During the experiment, temperature and heat release were measured. Using the same apparatus, experiments on eaves’ effect were also carried out. This time, the pitch of the louvers was also fixed (48mm) and four types differ in presence of eaves and the backing wall were considered.

     From the reduced-scale experiments, it was proved that flame spread is sustained when the pitch is less than 72mm for 112mm deep blades. Sustained flame spread was not observed with 96mm pitch, but the maximum flame height reached approximately six times higher than that of source flame. Heat flux distributions within these louvers are significantly higher than those within a flat wall, and it is also estimated that their differences correspond to radiative heat flux values from facing blade, in the case of louvers 110mm deep. Flame spread becomes relatively inactive when their dimensions are similarly reduced. Full-scale experiment qualitatively agreed with reduced-scale tests, but flame spread rate became approximately 8.5 times faster. In louvers whose pitch is 48mm, high flame spread rate was sustained till the top of the apparatus, and eaves 200mm in depth effectively suppressed flame spread. This effect was higher in louvers without a backing wall.

     Summary and conclusion of this study are as follows:

     1) sustained flame spread occurs when the pitch is less than 72mm for approximately 112mm in depth

     2) sustained flame spread do not occur when the pitch is around 96mm for 112mm in depth, yet burns six times higher than the source

     3) Heat flux distributions within louvers 110mm deep are practically predictable by taking radiative heat flux into account

     4) flame spread becomes relatively inactive when the dimensions of the louvers are similarly reduced

     5) eaves are more effective when attached to louvers without backing wall, as their Coanda effect is less than that of solid wall.

  • 出口 嘉一, 岸上 昌史, 山崎 慧, 大宮 喜文
    2020 年 85 巻 772 号 p. 413-423
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     In the field of fire safety engineering, for the sake of convenience, it is often assumed that a fire zone is divided into a two-layer zone; upper and lower layers. On the other hand, temperature profiles measured in actual fires became ambiguous without forming a clear boundary. Therefore, in order to assume the two-layer zone by use of a temperature profile, it needs to be reduced to be (1) temperature layer interface height, (2) upper layer temperature, and (3) lower layer temperature.

     A number of studies for the determination of the temperature interface height have been proposed. Although the N-percentage rule is often used to calculate the smoke layer height, the question such as N-value becoming subjective has been pointed out. Also, the integral ratio method is used in FDS analysis. Although this method does not use subjective value, the interface layer height calculated to be lower than actual value. And also, the maximum slope point method is easy to handle, but is greatly affected by measurement intervals.

     In this study, we have proposed the “polynomial approximation method” in which the measured temperature profile was approximated by a fourth-order polynomial, and the inflection point where the properties of the function changed was assumed to be the upper layer interface. The proposed method is easier to handle than previous methods; the N-percentage rule, the integral ratio method and maximum slope point method. Furthermore, we have conducted full-scale smoke movement experiments with the areas (A=84, 180 m2), the exhaust rates (Ve=0, 60, 180 m3/min) and the heat release rates (Q=150, 300, 450 kW) as parameters, and compared and verified the layer interface height and the smoke exhaust efficiency calculated by the previous methods.

     As a result, the following became clear.

     ● In any condition, the approximation coefficient R2 when approximated by the approximation rule was 0.99 or more.

     ● The layer interface height calculated by the N-percentage rule with N=40-50% was almost agreed with that by the polynomial approximation method; these are also agreed with those obtained by the previous study.

     ● The layer interface height calculated by the polynomial approximation method was closer to the measured temperature profile than these by the integral ratio method. The reason is because the temperature distribution in the lower layer can be taken into consideration in the approximation rule, but not in the FDS rule.

     ● The smoke exhaust efficiency calculated using approximation rule agreed well with the experimental values compared with the previous methods.

     From what has been said above, that the approximation rule can estimate the upper layer interface height and temperature.

  • 峯岸 良和
    2020 年 85 巻 772 号 p. 425-434
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     Fire evacuation in high-rise buildings have difficulties in not only long-distance descent with few staircase and long evacuation time, but also the congestion management of evacuees. In addition, number of elderlies and mobility impairments acting in urban architectures have been rapidly increasing, however they have difficulty in evacuation in fire. For those problems, evacuation using elevators (EVs) is expected to be a promising solution. For example, the guideline of guided evacuation for mobility impairments using fire-fighter’s elevators (EVs) have been established and there are some example of evacuation strategy using shuttle EVs and intermediate refuge outside Japan. However, these examples still have many limitations that former one is only limited for a small number of mobility impairments and latter one requires a lot of staff to guide and control the evacuees using EVs. To solve those problems, the author proposed the evacuation strategy using ordinary-use EVs without discrimination of able-bodied people and mobility impairments with taking advantage of the large capacity and design characteristics of EVs which are planned for dairy transportation demands.

     Two types of high-rise buildings are examined; one is large floor area tenant office buildings which is almost the floor are tenant office. The other one is complex usage buildings such as consisted of retail, tenant office, and hotel. For office floors of both type of buildings, by using all the EV cars which servers the fire floor, EV cars can arrive at the fire floor about every 30 to 45 seconds. This can relief anxiety feeing and contribute to sober-minded entering EVs car or stay the floors without direction by staff. For evacuation of the occupants staying at the floors around the fire floor, EVs are insufficient to transport all of evacuees there. For those floors, guidance by signage to prioritize the mobility impairments to use EVs and to introduce staircases for able-bodied people is necessary. Staircases have large transportation capacity, however, it will tend to be crowded in simultaneous evacuation. To avoid this congestion, occupants at other zones where EV banks of the fire floor does not server are encouraged not to use staircases but to use EVs or stay their floors.

     Mixed usage high-rise buildings are usually planned with EV lobby floor and shuttle EVs from the ground floor. Besides, the floors where switch the usage of lower floors and upper floors tend to be amenity space, common space or roof garden. Those spaces can be used as temporary rest space or transferring floor with EVs and stairs. Especially when occupants are directed to use certain evacuation measure such as EVs or stairs depending on the allocation of fire floor, those evacuation spaces are effectively used because certain evacuation measures lead the evacuees to different evacuation spaces naturally. On the other hand, at EV lobby floor, maximum transportation capacity of shuttle EVs are usually smaller than that of local EVs which serve upper floors, therefore evacuees may excessively accumulate at the EV lobby floor. For EV evacuation planning, preliminary increment of EV capacity is necessary and the intensive allocation of staff from disaster control center is required.

  • 阿南 朱音, 長谷見 雄二, 松山 賢, 鍵屋 浩司, 大内 渉
    2020 年 85 巻 772 号 p. 435-444
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     Lack of fire separation in the attic of old wooden multifamily buildings is an important cause of the rapid spread of a fire from a fire origin room to the whole building, and it is an important factor in recent collective fires in densely built-up wooden areas.

     To protect the flame penetration from the gap in the connecting part of a roof truss, which is sometimes irregular and complicated, and the retrofit attic party wall is necessary to prevent fire progression. In addition, it is expected that the construction work within narrow attic space is full of difficulty. Therefore, it is unrealistic that to apply the wall structure needing the exact construction work such as public notifications to retrofit attic party wall.

     In consideration of need processing work including the dimensions adjustment in the attic space inside, the wall structure adopted Gypsum boards in this study.

     The development was carried out based on following two points.

     (1) A covering material does not penetrate a flame during heating, and do not produce cracks. Because the attic party wall cannot cover with one piece of product, it needs simple and dividable structure so as not to burn from joints.

     (2) The gap in the connecting part of a roof truss and the attic party wall needs to be blocked up with simple technique.

     Three series of fire tests were performed on in this study.

     Experiment1: When a flame invades the attic space of the old wooden multifamily or accommodation buildings at the time of city fire, the flame will be already to be the phase of fire peak. This test carried out an experiment by using the roof-shaped test rig which imitated a roof truss partially, and the burner to reproduce the flame which invade the attic space.

     Experiment2, 3: ISO834 wall furnace tests with small-scale specimens and with full scale party-wall specimen.

     From these tests, the following conclusions can be drawn.

     (1) About the wall of the retrofit attic party wall

     ・Composed of single layer of reinforced gypsum board (12.5mm) on either side of the stud above the separation wall is desirable. The base materials such as bunches are wood (cedar) of 30×40(mm), and it is necessary to install it every 455mm, and attach the Gypsum boards to it every about 200mm.

     ・There are no need of filling the insulation material to the hollow layer, and no need of the joint plate.

     (2) About the covering method by RWF of the gap in the connecting part of roof truss and the attic party wall

     ・It needs covering the gap by double RWF both sides (Rock Wool Felt: 10mm thickness, 100mm in width, density 0.2 g/cm3).

     ・It is desirable to use a screw with the retentivity such as sheet metal screws around 200mm to install the RWF to the roof surface.

  • 佐藤 考浩, 辻村 壮平, 小林 真人, 三浦 太郎, 科部 元浩
    2020 年 85 巻 772 号 p. 445-453
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     In current Japan, at a time when the labor force is shrinking because of the falling birthrate and the aging population, there is a need for productivity improvement. In addition, industries that provide products and services relevant to knowledge creation account for about 70 % of the Japanese economy. Because of this situation, the way of working is shifting to creative work.

     Focusing on the office sound environment, in the late 1980s to the early 1990s, with the progress of office automation, the sounds of printers and computers were generated. Thereby, it is reported that the office noise level was about 50~59 dB. Since then, the noise reduction of office automation and the development of information communications equipment have progressed, an office that noise level is about 40 dB have been reported.

     These changes in working styles and the noise reduction of office have created new problems in current office, such as speech privacy. Therefore, it is necessary to understand the framework of the worker’s evaluation of the office sound environment.

     In previous studies related to knowledge creative productivity, there are many studies focusing on human response to the intensity of stimulation. More recently, some studies have focused on the value concept of worker, in one of the studies, conscious structure of worker for communication effort was organized by an interview survey applying the Evaluation Grid Method. But, in this study, there was focus on conscious structure for one act such as a communication. Therefore, it is also necessary to comprehend the worker’s value concept for the entire work.

     In this study, in order to gain an insight leading to a proposal for a sound environment design technique of a pleasant working office, we conducted an interview survey applying the Evaluation Grid Method focusing on worker’s position. Furthermore, we conducted a questionnaire survey intended for office worker to comprehend worker’s recognition of current situation about sound environment of office more quantitatively.

     As a result of an interview survey, there was a difference in evaluation structure of office environment between managerial post and employee with no title. The improvement of work efficiency was regarded as important in both positions. But the creation of ideas was mainly regarded as important by managerial post, reduced fatigue and increased motivation were mainly considered important by employee with no title.

     From the results of questionnaire survey, in regard to “the positive or negative point about the office”, there were 64 issues related to the sound environment. It was found that reducing dissatisfaction related to the conversation being heard by other employees contributes to ease of working for employee with no title.

  • 藤原 亮, 芹川 真緒, 佐藤 誠, 前 真之
    2020 年 85 巻 772 号 p. 455-464
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     In well-designed passive solar buildings using direct gain, no auxiliary heating is required in clear day weather in winter. In this system, moderate solar heat gain keeps the room temperature appropriate while excessive solar heat gain increases fluctuation of the room temperature and result in overheating. Therefore, heat storage is essential for stabilizing room temperature. As weather condition changes throughout the seasons, residents need to adjust the heat gain by using blind, curtain or ventilation to avoid overheating. However, such adaptive actions may increase heating load during the night. Therefore, keeping the balance of three elements (heat loss, heat gain, and heat storage) is critical in this system, i.e. performance of passive solar system depends primarily on how the building is designed.

     As thermal performance of residential building, Q, μH, and C, representing performance of heat gain, heat loss, and heat capacity per unit area, have been widely used. However, the relation between these parameters and room temperature fluctuation has not been clarified. Moreover, previous evaluation method of heat storage does not represent thermal characteristics of building exterior walls accurately.

     The purpose of this paper is to develop a method to design appropriate building envelope for direct gain system. We proposed diagrams and flowchart to help designer set target thermal performance of building forward to detailed design and simulation.

     Previous studies have shown the concept of internal effective heat capacity based on frequency response fitting. We arranged this calculation method focusing on the stabilizing effect of heat storage. By simplifying heat transfer model, we derived an estimation method of daily average room temperature and peak-to-peak room temperature swing in periodic clear day weather. We compared this estimation method with numerical simulation. Envelope type, proportion, thermal performance, window orientation, and climate conditions were chosen as variables. The estimations were in good agreement with the simulation results.

     In order to use these formulas as a simple evaluation method of room temperature fluctuation, we introduced design conditions and several approximations. The simple evaluation method disregards some effects of heat capacity of exterior wall and changes in solar position during the heating period. However, room temperature fluctuation can be evaluated by three elemental parameters of building thermal performance in this method. We compared the method with simulation to confirm its reliability.

     Based on the simple evaluation method, diagrams and flowchart were provided to help design direct gain system. The design method is meant to set targets of three elemental parameters of building thermal performance, acquiring a comfortable room temperature without heating for more than half of the heating period. We gave an example of building thermal performance acquired by this method.

  • 小林 知広, 西堀 啓規, 梅宮 典子, 山中 俊夫, 粕谷 敦, 小林 佑輔, 和田 一樹
    2020 年 85 巻 772 号 p. 465-474
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     Personal air conditioning system is an air distribution method to provide a satisfactory thermal environment. The purpose of this study is to propose a CFD modeling method of the airflow from personal air supply terminal. As the first step, a full-scale experiment was conducted under the isothermal condition, where a personal air supply terminal was installed on the ceiling. The supply airflow rate was regulated at 28 m3/h. In the experiment, 2-D velocity was measured using a X-type hot-wire probe, and turbulent statistics were measured using an I-type hot-wire probe. The experiment was conducted to obtain boundary conditions for CFD and to obtain true value for accuracy verification. Second, CFD analyses using Standard k-ε Model (SKE), SST k-ω Model (SST) and Reynolds Stress Model (RSM) were performed, and SKE and SST showed good agreement with experimental result as shown in Fig. 9. To perform this Detailed CFD analysis, a large number of grids is required, which leads to large computational load and difficulty in analysing a large space. Therefore, to decrease the number of grids without loosing accuracy, two CFD modeling methods were applied in this paper, i.e., momentum method and P.V. method. The analysis using these two methods was performed, and the accuracy was verified by comparing the result with that of above-mentioned detailed analysis. As the result, in the case of 50mm-mesh, the decrease of the accuracy was not significant because the number of grids is relatively large. On the other hand, in the case of 100mm-mesh, the accuracy was greatly decreased if no modeling method was applied. However, the accuracy was obviously improved by using the momentum method and P.V. method as shown in Fig. 12 and 13.

     The conclusions obtained in this paper are summarized as follows.

     (1) In the accuracy verification where the experiment was compared with CFD, both SKE and SST showed good agreement with the experimental result regarding average 2-D velocity distribution on the central section. However, RSM overestimated the diffusion of momentum, and consequently showed the tendency to underestimate the reach of air flow compared to the experimental value.

     (2) In the CFD analysis using the Momentum method, the accuracy is not sufficient if compared to the detailed analysis. However, the tendency of the velocity distribution was quite similar to that of the detailed analysis. In the case of a 100-mm mesh, the improvement of accuracy by CFD modeling becomes large if compared to the case of 50-mm mesh.

     (3) It was confirmed that the P.V. method had better accuracy of velocity distribution if compared to the momentum method, and that the reaching distance of 0.5 m/s was well agreed with the detailed analysis in the case of diagonal supply.

     As a future prospect, CFD analysis for a large office space where a large number of personal air terminals are installed is to be conducted to study the influence of each air flow of personal airflow and the influence on ambient air flow.

  • 藤原 邦彦, 浅輪 貴史, 清野 友規
    2020 年 85 巻 772 号 p. 475-484
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     Urban trees as a heat adaptation measure by solar radiation shielding and as a heat island mitigation measure by transpiration are expected to improve the summer thermal environment. An increase in the amount of trees leads to an increase in the initial cost for tree planting and in maintenance costs such as pruning and irrigation. It is thus important when planning to green urban open spaces to consider the optimal tree arrangement to maximize the effect with the minimum amount of trees. However, very few studies have discussed the effect of the tree arrangement on the thermal environment. Therefore, we carried out tree arrangement optimization to both minimize the summer mean radiant temperature (MRT) as an urban heat adaptation measure and maximize the transpiration rate as a heat island mitigation measure. Based on optimization, we showed to what extent the MRT and the transpiration rate change by the arrangement and what kind of features of the arrangement contribute to improving the effect of the trees.

     The target of optimization was an open space with no buildings around it with a 36 m × 36 m tree arrangement area and a 12 m × 12 m evaluation area in the center. The design variable of optimization was the two-dimensional tree arrangement in the 36 m × 36 m area. To derive tree arrangements with the maximum effect by the minimum number of trees, we conducted optimization to minimize both MRT and vegetation coverage ratio (number of trees) in the evaluation area as the objective functions, focusing on urban heat adaptation. We also conducted optimization to maximize the transpiration rate and minimize the vegetation coverage ratio in the evaluation area, focusing on heat island mitigation. We calculated the MRT and the transpiration rate using typical sunny summer weather in Tokyo. We conducted numerical optimization and derived Pareto solutions.

     As a result, we obtained the following findings for typical sunny summer sunny weather in Tokyo at a location with no building around it. Comparisons between the effective and ineffective tree arrangements obtained by optimization showed the daily average MRT differed up to 7.5°C and the amount of transpiration differed up to about 20%, even when using the same amount of trees. This result shows that tree arrangement could have a non-negligible impact on the effects of urban heat adaptation and heat island mitigation. The arrangements of the optimal solutions for the MRT and the transpiration rate showed the same tendency, suggesting that similar tree arrangements could realize the maximization of effects for both urban heat adaptation and heat island mitigation. The tree arrangement of the optimal solutions showed that distributed arrangements with separation between trees are effective for reducing the MRT and increasing the transpiration rate, and that separation between trees in the east-west direction is more effective than separation between trees in the north-south direction. The difference of the MRT and the transpiration rate between effective and ineffective arrangements was large when the vegetation cover ratio was around 50%, suggesting that consideration to tree arrangement at the time of green planning is particularly important. The gradient of the Pareto solutions in the evaluation space was smaller when the vegetation coverage ratio was larger than 50%, suggesting that the cost performance of urban heat adaptation and heat island mitigation by trees decreased above a 50% vegetation coverage ratio.

  • 湯淺 和博, 兪 帥, 呉 偉
    2020 年 85 巻 772 号 p. 485-493
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     Fuel cells are being introduced in single-family homes, and it is also necessary to promote the introduction of collective housing located in city. In high·density urban areas such as Tokyo, there are many apartment buildings combined with other uses (apartment complex). However, energy interchange system with high energy saving performance in the multi·use condominiums is not considered.

     In this research, by utilizing the characteristics of energy consumption time fluctuation of both housing unit and facility unit in multi-family dwellings, especially apartment complex, by introducing FC-CGS, not only electricity but also heat can be interchanged in the entire residential building, an energy interchange system to meet each other, and aimed to clarify the optimum introduction capacity and energy reduction effect for the combination of different facilities and housing complexes is proposed. In order to verify the energy interchange effect between the housing unit and facility unit, the energy consumption of the 334 complex houses was surveyed in April-May and October-November 2018.

     Based on the results of the survey, an energy interchange system suitable for complex housing was proposed. In order to verify the flexible effects of the system, it is necessary to set up a building model for energy interchange, set the energy demand of the building, and set up installed equipment. A building model with an office on the fir st floor (175m2), 4 floors, 18 house units was set up for simulation. The household structure, the lifestyle, and the equipment performance were as three parameters when set the energy demand for each household. As representative examples, the facility units of office, restaurant and convenience store were examined. A solid oxide fuel cell with high power generation efficiency was adopted, and for the household unit, a fuel cell with a rated output of 0.7 kW for each household, 46% power generation efficiency and 43% exhaust heat recovery efficiency was introduced. Local establishment for local consumption was assumed for the setting of the energy interchange system. It enables power inter change in the building, supplies surplus power from the housing unit with low power consumption in the daytime to the facility unit, and sends power from the facility unit to the housing unit at night. The shortage will be assisted by grid power. As for heat transfer, the housing unit basically changes the waste heat of FC-CGS to hot water and uses it. When hot water in the hot water storage tank of the housing unit runs short, heat transfer was received from the hot water storage tank of the facility section. If there is a further shortage, it will be compensated by a backup water heater. Facility department was the opposite. When the hot water storage tanks in both the housing unit and the facility unit are fully stored, the radiator releases heat forcibly.

     Through simulation, the FC-CGS optimal introduction capacity and energy reduction rate of each type of complex house in summer and winter were obtained.

  • 太田 真人, 岩船 由美子, 大岡 龍三
    2020 年 85 巻 772 号 p. 495-502
    発行日: 2020年
    公開日: 2020/06/30
    ジャーナル 認証あり

     We have been studying energy consumption using data from Home Energy Management System since 2011. In this paper HEMS data of about 50,000 houses were collected and analyzed. We clarified the composition of HEMS data. It turns out that the energy consumption is decreasing as the buildings are newer. we further analyze energy consumption by appliances. The purpose is to promote energy saving of new houses and existing houses

     Energy consumption ratio in the household sector has not stopped the increase trend of 26.5% in 1990 to 30.4% in 2016. The data acquired by HEMS includes total energy consumption, usage, equipment, power generation, storage battery charge / discharge, electric vehicle energy, construction site, construction year, floor area, and family composition. The average floor area is 121 square meters. This is almost equal to the average floor area of Japanese houses.

     The total energy consumption was analyzed. Compared to 2011, the reduction is about 30% in 2017. A comparison was made between a couple, a single household, and two households. It turns out that couples have the greatest reduction rate. Monthly analysis was also conducted. It turned out that the reduction rate is particularly large in spring and autumn.

     An analysis of hot water supply energy was also conducted. The adoption rate of heat pump water heaters is improving year by year. Nearly 100% since 2012. Energy consumption has also been reduced by about 30%. The reduction in winter is particularly large. The reason is the high efficiency and high functionality of the equipment. An analysis of energy consumption for air conditioning was conducted. The adoption rate of air conditioning throughout the building has been increasing since 2011. Energy consumption is increasing. The reason is that the entire building is operated continuously with air conditioning.

     We analyzed consumer electronics, ventilation, and lighting energy consumption. Since 2011, type 1 ventilation has a 20% greater consumption than type 3 ventilation. But in 2017 it is equivalent. This is thought to be due to an improvement in the efficiency of a type of ventilation. It was found that consumption was reduced by about 50%. The reason is presumed to be high efficiency of home appliances and LED lighting, This will need to be clarified in future research.

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