Search

Predicting the aerodynamic phenomena in a train-tunnel system is important for increasing the speed of railway trains. Among these phenomena, many studies have focused on the effects of pressure; however, only a few studies have examined the effects of flow velocity. When designing train roof equipment such as a pantograph and an aerodynamic braking unit, it is necessary to estimate the flow velocity while considering the influence of the boundary layer developed on the train roof. Until now, numerical simulations using a one-dimensional model have been utilized to predict the flow velocity around a train traveling through a tunnel; however, the influence of the boundary layer cannot be taken into consideration in these simulations. For this purpose, the authors have previously proposed a simple calculation method based on a steady incompressible tunnel flow model that can take into account the influence of the boundary layer, but this method could not incorporate the unsteadiness of the flow velocity. Therefore, in this study, the authors extend the previous simple calculation method such that it can be used for an unsteady incompressible tunnel flow. The authors compare the calculation results obtained from the extended method with the results of a model experiment and a field test to confirm its effectiveness.

The peak value of a micro-pressure wave radiating from tunnel portals of high-speed railways depends on the shape of the train nose. Previous studies have shown that a train nose shape with a small gradient of cross-sectional area distribution, except at the tip and end, is effective at reducing micro-pressure waves. Using acoustic theory, this study showed that multistep train noses are more effective at reducing micro-pressure waves than the previously suggested nose shapes. Moreover, the multistep noses were optimized using the response surface method and computational fluid dynamics techniques for axisymmetric compressible airflow. In addition, model experiments were performed to verify the usefulness of the optimized multistep noses. The optimized multistep noses reduced the peak values of the micro-pressure wave by over 5% compared to the previous noses. Thus, this study theoretically, numerically, and experimentally suggests new optimal nose shapes that can better reduce micro-pressure waves than existing shapes.

Strong cross wind is one of the most important problems to consider for ensuring the safety of railway vehicles during operation. The critical wind speed for vehicle overturning or wheel unloading ratio is one of the indices used to evaluate the safety of railway vehicles under strong cross wind. The critical wind speed is calculated by the “Detailed Equation”. The Detailed Equation is an equation that describes the equilibrium of the forces acting on a railway vehicle and has many parameters. In this paper, the influence of each aerodynamic coefficient on the critical wind speed is examined by calculating the critical wind speed for given amounts of change in the aerodynamic force coefficients. The aerodynamic force coefficients used in this study were obtained from wind tunnel experiments (atmospheric boundary layer flow and uniform flow) and a full-scale model field test. We compare the aerodynamic force coefficients obtained by the respective experiments, and we evaluate the effects of the aerodynamic force coefficients by using the critical wind speed determined from the aerodynamic force coefficients.

In this study, the device structure of a white tandem organic light-emitting diode (OLED) was changed to control the emission area and thereby achieve less luminance decay. A long-life 13.5-inch 4 K flexible c-axis-aligned crystal oxide semiconductor (CAAC-OS) active-matrix OLED with less color shift and high resolution was fabricated using this long-life white OLED, transfer technology, and a CAAC-OS field-effect transistor.

In this study, the device structure of a white tandem OLED is changed to control the emission area to achieve less luminance decay. A long-life 13.5-inch 4K flexible CAAC-OS AMOLED with less color shift and high resolution is fabricated using this long-life white OLED, transfer technology, and a CAAC-OS FET.

This paper presents an extensive revision of Magono and Lee's (1966) classification of natural snow crystals, which has been widely used in snow and ice studies to describe snow crystal shapes. The new classification catalogs snow crystals and other solid precipitation particles into 121 categories, in contrast to Magono and Lee's 80 categories. Of these, 28 categories were created to classify new types of snow crystals that have been discovered in polar regions since 1968, seven were created after reconsidering the original categories, and six categories were created to classify solid precipitation particles such as frozen cloud particles and small raindrops. Because our observational area extended from middle latitudes (Japan) to polar regions, we refer to our new classification scheme as ‘global-scale classification’ or ‘global classification’. The global classification consists of three levels – general, intermediate, and elementary – which are composed of 8, 39, and 121 categories, respectively. This paper describes the characteristics of each type of snow crystal, ice crystal, and solid precipitation particle.

We have developed phosphorescent OLEDs utilizing energy transfer from an exciplex to an emitter. The OLEDs based on this mechanism showed quite high efficiency, a long lifetime and low drive voltage. OLED lighting with high power efficiency exceeding 100 lm/W at a practical luminance of 5,000 cd/m2 was also successfully developed.

We succeeded in developing a deep blue fluorescent OLED exhibiting extremely high external quantum efficiency and a long lifetime by adopting an amine-free material to the hole transporting layer. We have also developed a CAAC-IGZO-FET OLED display with a narrow driver area using this deep blue device.

We have fabricated a 13.5-inch top-emission OLED display including an oxide semiconductor FET element. This display has a high pixel density exceeding 300 dpi and is applicable to a Quad-HDTV (number of pixels: 3840 × RGB × 2160). There have been few reports on fabrication of OLED displays with such a high pixel density so far. Color display is achieved by combining an EL element having a tandem structure and emitting white light with a microcavity structure and a color filter.

When a compression wave generated by a high-speed train entering a tunnel propagates through the tunnel and arrives at the tunnel exit, an impulsive pressure wave (micro-pressure wave) is radiated from the tunnel exit. Improving the train nose shape is one of the techniques for suppressing the micro-pressure wave. Furthermore, tunnel entrance hoods are required for long concrete slab tunnels in order to suppress the micro-pressure wave. The effect of the tunnel entrance hood on the compression wave generated by the train can be evaluated by means of a rapid computational scheme devised and validated experimentally by Howe et al. In this study, the optimal longitudinal distribution of the cross-sectional area of the train nose shape was determined by using the rapid computational scheme and a genetic algorithm. The effect of the nose shape optimization was confirmed through experiments using scale models.

When a train is running in a tunnel, a pressure wave is continuously radiated from both end portals to the outside. We herein call this a “tunnel continuous wave”. Though some characteristics of the tunnel continuous wave have been revealed from previous research, the relation between the tunnel continuous wave radiating to the outside and the pressure wave inside the tunnel has not yet been obtained. The pressure wave measured at a fixed point in the tunnel is the superposition of two kinds of waves (an incident wave and a reflected wave) propagating in the opposite directions. Therefore, to investigate the relation between the tunnel continuous wave and the pressure wave inside a tunnel, it is necessary to separate the incident wave and the reflected wave from the measured combined pressure wave. In this paper, we propose a method of separating the incident wave and the reflected wave from the pressure waves measured inside a tunnel. The validity of this method is confirmed by numerical and experimental investigation.

The authors performed laboratory experiments and field measurements to investigate low-frequency noise generated in wayside environments from high-speed train running. The results indicated the following three types of low-frequency sound sources: pressure fields around the nose and tail parts of the train, low-frequency acoustic pressure waves aerodynamically caused by the train itself, and noise radiation from vibrating concrete railway viaducts. Measurements conducted in a higher-speed section revealed that the major sound source of low-frequency noise in the far field was aerodynamically generated unsteady flow, which is analogous to a line source.

This research describes several characteristics of tunnel continuous waves (TCW), which are a kind of low-frequency pressure wave radiated from railway tunnel portals. Several theoretical results are presented and measurement data obtained in field tests. Ratios of the amplitude and the frequency of the TCW radiated in the forward direction to those radiated backward have been obtained. Also described is a method for separating an incident wave from pressure data measured in a tunnel and this method is applied to data obtained in field tests. As a result, the separation method is shown to be applicable to the field test data.

When trains pass through stations at high speeds, large variations in air pressure occur. As the structural members that make up station facilities are susceptible to these repeated variations, it can be assumed that the likelihood of member deterioration is high. Since future train speed increases will result in larger air pressure variations, it is essential to make efforts to ensure the structural safety of stations. To this end, we developed calculation equations for air pressure variations based on the results of field measurements and model tests, and also proposed prediction methods for response deformation and an evaluation method for the fatigue strength of members exposed to air pressure variations.

This paper deals with the pressure waves generated by a train running through a short tunnel and radiated from its portals to surrounding areas as infrasound. First described are the results of a field measurement conducted at a short, 93 m-long, Shinkansen tunnel to present the generation mechanism of the infrasound. Next an acoustic analysis is made of the infrasound radiated to the outside by applying a method for predicting the compression wave in the tunnel generated by train entry. The calculated and measured results of the waveform of the infrasound are consistent despite considerable simplification in geometric modeling in the analysis. Comparison of the spectra shows that the acoustic analysis is capable of calculating the components below about 10 Hz of the infrasound, including the harmonics of the fundamental frequency of 1.7 Hz determined from the tunnel length.

第2次世界大戦末期の昭和18～20年の冬期に,北海道ニセコアンヌプリ山頂の着氷観測所で実験機として使用されたと思われる,「零式艦上戦闘機(通称:ゼロ戦)」の右主翼が1990年8月初旬山頂東側の沢で発見され,その後2004年に回収されて,2005年12月22日から北海道倶知安町の風土館に常設展示されて話題を集めている.それは,60年前のゼロ戦の翼という野次馬的な見方の他に,もはや着氷観測所などといった言葉さえ知らない世代が増えた昨今,そもそも着氷観測所はどんな観測所で,どんな実験をしていて,その結果はどうなったのであろうかという興味とは別に,関連する資料の展示,解説,当時の写真や新聞記事に見られる実験機が,ゼロ戦とは違う「九六式艦上戦闘機(通称:九六式)」のものが多かったからである.どうしてこのようなことになったのか?マスコミ関係や専門家の間で注目されてきたが,幸い「中谷宇吉郎雪の科学館」が所蔵している,当時北海道大学助手で,直接この実験の担当者だった黒岩大助(元北海道大学低温科学研究所長)が撮影していた写真のアルバムから,中谷宇吉郎門下生の一人だった樋口敬二(名古屋大学名誉教授)の考察によって,昭和18～19年の冬が九六式,19～20年の冬がゼロ戦であったという結論が得られた.この報告では,ゼロ戦主翼の発見を契機として着氷観測所ではどのような実験が行われたのか,その実験の主目的であった飛行機の着氷について,使用された実験機の機種とそれに関連するいくつかの疑問について整理したものである.

When a high-speed train enters or leaves a tunnel, impulsive pressure waves are radiated from the entrance/exit portal toward the outside of the tunnel. The waves are called a “micro-pressure wave, ” a “tunnel entry wave” and a “tunnel exit wave.” A similar phenomenon occurs when a train passes a short structure in axial length in an open section (such as an over-bridge). We call it a “structure-passing wave.” The length of the structure along the railway is several times or less the diameter of the structure cross-section. Although the structure-passing wave is weak at present, it could cause an environmental noise problem of a low-frequency (which has become public concern) as the train speed increases. This paper describes the characteristics of the structure-passing wave based on the results of model experiments and acoustic analyses. The results obtained from the acoustic analyses were in good agreement with the result of the experiment except for the very short length structures. This implies that the structure-passing wave can be modeled on a superposition of the pressure waves radiating from both sides of the structure.

To clarify the actual conditions necessary for the neutralization of acid rain by tree leaves, an examination of the neutralization effects of artificially-made acid droplets on several kinds of tree leaves, was conducted using a newly-developed pH-imaging microscope. Through these examinations, it was clarified that broad-leaved tree species such as beech, horse chestnut, Japanese zelkova and oak trees could dilute and neutralize acid droplets more effectively than coniferous trees, such as Japanese cedar, Japanese black pine and Japanese red pine. This result is in accordance with our previous observations conducted in the same site that broad-leaved trees were more effective in diluting and neutralizing throughfall than coniferous trees (Kikuchi et al. 2000, 2004a). Furthermore, the pH values of throughfall in September were higher than those in June for all tree species examined. In the broad-leaved trees, the relationship between the lapse of time, and pH values, could be expressed by a logarithmic approximation. The temporal variations in pH values of beech tree leaves, collected from the D-site (a forest near the Shirakami-Sanchi Natural Heritage Area), and E-site (rural, but relatively heavy traflic area) showed very similar trends. Therefore, the neutralization of acidity in these two areas was basically similar in nature, and did not depend on the amounts and constituents of aerosol substances on their leaf surfaces. The capacity to neutralize acid droplets on the abaxial surface was greater than that on the adaxial surface of beech leaves.

An analysis and a model experiment are performed on the compression wave generated by a train entering a tunnel with an entrance hood, which is a prevailing countermeasure for reducing the micro-pressure wave emitted from a Shinkansen tunnel portal. The tunnel entrance hood is a structure for extending a tunnel and has openings on its side walls or roof for decreasing the pressure gradient of the compression wave generated by train entry. The hood design has principally been performed through model tests since the three dimensionality of flow field is generally important. Thus, a more efficient design method is required. In this paper, an analytical method based on the aeroacoustic theory developed by Howe is applied to a short "acoustically compact" hood having a window on its side wall. Analytical results are in good agreement with experimental results including the effect of train offset in a double-track tunnel. It is also clarified by analysis that the performance of the entrance hood is greatly affected by the relative length of the train nose to the distance between the window and the hood entrance.

In order to determine the actual circumstances of wayside low-frequency noise and infrasound generated by high-speed trains (Shinkansen), field measurements were performed at two sites, one near a tunnel portal and the other in a fully open section. The measurements were based upon the manual issued by the Ministry of the Environment of Japan in October 2000 and conducted to obtain G-weighted SPL, 1/3-octave band spectra, velocity dependence and distance attenuation of SPL. The measured results show that major components of the low-frequency noise from the tunnel portal are impulsive micro-pressure waves and continuous pressure waves, while those in the open section are near-field hydrodynamic pressure variations and far-field acoustic pressure waves.

二重防風ネット内で堆積した乾き新積雪の密度に対する平均気温および平均降水強度の影響に加えて,降雪粒子の卓越結晶形,水平粒度分布,霰寄与率(質量フラックスに占める霰の割合),雪面への運動エネルギーフラックスおよび粒子投映像の円形度との関係を解析した.その結果,新積雪密度への影響として,卓越結晶と平均降水強度の他に,雲粒付樹枝では運動エネルギーフラックスとの相関が大きかった.また,雲粒付立体樹枝では水平粒度分布,円形度,霰寄与率および運動エネルギーフラックスの影響も比較的顕著にみられた.さらに,卓越結晶形の霰(霰寄与率≧70%)では,水平粒度分布の影響が他の因子より大きかった.

Radar data from the Bangladesh Meteorological Department (BMD) are employed as a preliminary analysis. This is a first research work to investigate the spatial and temporal distribution of rainfall over the country for 135 consecutive days, from 16 April to 30 August 2000. Radar data are sampled in 10 km grid boxes to obtain daily rainfall over the country. Rain gauge data at 33 locations are utilized to check the radar results. The distributions of rainfall obtained by both the radar and the rain gauges are similarin pattern, but the time of the maximum rainfall determined by the radar is a few hours earlier than that determined by the rain gauges. The distribution of rainfall over the whole radar domain suggests that 21 to 09 local standard time (LST) is the most likely time for rainfall to occur in Bangladesh, while 06 LST is the most likely time for maximum rainfall to occur over the entire country. It is mentioned that no data are available between 03-06 LST. The occurrence of 21 to 09 LST rainfall is possibly linked to the local effects such as complex terrain and sea and land breeze circulations. The morning maximum rainfall at 06 LST in Bangladesh is different from that of the Indian subcontinent or of the mountain area where, generally, maximum rainfall occurs in the afternoon. The northern border of Bangladesh, close to the Shillong hill of India, is the region with the highest rainfall, while the second highest volume of rainfall occurs on the eastern border. In order to observe the characteristics of large-scale cloud activity, analyses of the Japanese GMS-5 hourly infrared data, within a larger domain of 80°-100°E and 10-30°N were conducted. The cloud activities in and around Bangladesh were obtained in 10 by 10 grid boxes. The northwestern part of Bangladesh was largely affected by pre-monsoon clouds, while the whole country was affected by the peak monsoon activities.

The characteristics of the low-frequency pressure waves radiated from a train passing a viaduct of Shinkansen were examined through field measurement based on the manual for measuring low-frequency noise issued by the Ministry of the Environment in October 2000, by using a low-frequency sound level meter (NA-18 A) manufactured by Rion Co., Ltd. The measurement proved that the low-frequency noise consisted of a hydrodynamic pressure field and an acoustic pressure wave. The hydrodynamic pressure field is called train passing pseudo-sound and the acoustic pressure wave is called low-frequency pressure wave. The low-frequency pressure wave is seemingly emitted from a line source. The low-frequency wave is also proportional to the 4-5 th power of train velocity and approximately to the 1 st power of the distance from the source to the observation point.