Pipe Heating System with Underground Water Tank for Snow Thawing and Ice Prevention on Roads and Bridge Decks

In order to prevent traffic accidents on snow-covered bridge decks, the writers developed a new pipe heating system that uses only groundwater stored in a large underground tank. The underground tank provides geothermal energy, i.e., groundwater of constant temperature, through heating pipes embedded in concrete pavements with no electric heater or fuel boiler. The pipe heating system was constructed at approximately 50% of the cost of comparable systems. In addition, there is a reduction of 10% in operating costs compared with the previous system. The present paper outlines its design and construction and provides fundamental data for the developed system. The piped heating system has kept the road conditions safe during the winter season by always removing the snow and ice from the heated road and bridge sections earlier than the surrounding roads. According to long-term temperature measurements, this system has prevented the road temperature from decreasing below 0°C, even through nighttime and morning periods. This report presents the system as an economical and effective solution for snow thawing and ice prevention.     

TWO-CRACK PROPAGATION PATHS IN A FUNCTIONALLY GRADED MATERIAL PLATE SUBJECTED TO THERMAL LOADINGS

Two-crack propagation paths in a ceramic/metal functionally graded material plate (FGP) under one-cycle temperature change of heating and cooling are considered. When the FGP is subjected to thermal shock, a single crack or multiple cracks often initiate on the ceramic surface during the cooling process and propagate in the FGP. Crack paths are influenced by the heating temperature conditions, a compositional profile of the FGP, the fracture toughness, interaction among multiple cracks, and so on. Transient thermal stresses are treated as a linear quasi-static thermoelastic problem for a plane-strain state. The crack paths are treated under fracture mechanics using the finite-element method. The effects of heating temperature conditions, a compositional profile of the FGP, the fracture toughness, and a crack space on the crack propagation pattern are discussed and are shown in figures.     

各种引气剂以及抑泡剂对混凝土经时变化状态等的影响

众所周知,采用粉煤灰制备混凝土,因粉煤灰成分中含有未燃炭等微粒子,容易造成阴离子型引气剂吸附在这些微粒子上,导致含气量经时损失.同时在混凝土的制备、运输过程中,因受采用的材料、拌和状态等物理因素影响,还会发生含气量经时增加的现象.所以在制备、管理混凝土时,如何保证出机初期一定的含气量、缓解含气量的经时损失或经时增加,是一项极其关键的技术.本文将就采用能改善上述状态的引气剂、抑泡剂拌和混凝土,对混凝土的经时变化以及抗冻融性等特征产生的影响进行论述.     

不同的表面处理对针织碳纤维复合材料的影响分析(英文)

纤维复合材料已经研究了数十年了。他们有着比传统材料,如钢材,优秀的多的力学性能。然而,由于相对较低的产量,梭织、编织与其3D纤维结构的复合材料被认为较难大量生产。因此,近年来,针织物在复合材料界获得了较高的关注,它的高度可塑性使针织复合材料可以直接生产制造成各种复杂形状的复合材料如管状、圆锥型等,使得材料的浪费可以降到了最低。本文使用了有表面处理和没有表面处理的纬编平针碳纤维制成复合材料。对两种复合材料的经向和纬向分别做了拉伸试验。结果显示:有表面处理的材料具有更好的拉伸性能,尤其是在wale方向上,有表面处理的复合材料比没有表面处理的复合材料的拉伸强度提高75.68%。     

Characterization of microstructural damage due to low-cycle fatigue by EBSD observation

Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the damage due to cyclic or uniform strain. Samples of Type 316 stainless steel after fatigue and tensile tests were prepared for EBSD observation and the misorientation angle between neighboring points (local misorientation) was evaluated. It was shown that the local misorientation developed due to the cyclic and uniform strain and that its spatial distribution was not uniform. In fatigue samples, the area of large local misorientation tended to form clusters, whereas it localized to the grain boundaries in the tensile samples, and the magnitude of local misorientation and the degree of the localization increased with the strain amplitude. The degree of localization was quantified via statistical processing of the measured data. It was also shown that the source of damage (cyclic or uniform strain) and the loading direction could be deduced from the EBSD observations of the damaged sample.     

Preliminary spectrum shifter design for intermediate energy nuclear data benchmark experiments with DT neutrons

Integral benchmark experiments with DT neutrons are not always sufficient for nuclear data benchmarking in the MeV region, below 10 MeV. A neutron spectrum shifter, which will be placed between a sample and a DT neutron source, is effective to moderate DT neutrons incident to the sample. In order to estimate effects of the spectrum shifter, the ratio of the contribution of 14 MeV neutrons in the leakage neutron and gamma-ray spectra was calculated with MCNP-4C for an experimental configuration at FNS of JAEA, Japan. The calculations were carried out for a Li₂TiO₃ sample with a Be, D₂O, or ⁷LiD spectrum shifter. It was found out that the Be shifter was superior to others and the Be shifter was effective to decrease the contribution of 14 MeV neutrons especially for secondary gamma-ray spectrum measurements.     

Preliminary investigation of a vapor-open envelope tailored for subtropical climate

Concerning global warming and resource depletion, the impact of buildings in subtropical regions is becoming even greater due to a high growth rate of urbanized areas. From the viewpoint of building physics, the main problem concerning subtropical climate is the high level of humidity in combination with high temperature. In this study, a flexible building envelope consisting of wood and clay components was developed so that the materials and the assemblies can be easily tailored to comply with local climatic conditions. The movement and accumulation of moisture in the wall was of prime concern. This has been investigated by means of testing full scale walls in a climate chamber and the corresponding one dimensional transient heat and transfer simulation. In order to achieve a consistency between calculation and measurement, the individual materials were tested for their hygric and thermal properties. Based on these findings attempts were made to calculate the behavior of an optimized wall assembly under real climatic conditions of central Japan. As a result, it was shown that the hygrothermal behavior of the envelope is predictable by means of the models and the simulation program used, and that no risk of interstitial condensation and mold growth was predicted under the real climatic conditions of Kyoto.     

Influence of Water on the Compression Behavior of Decomposed Granite Soil

In order to investigate the influence of water on compression characteristics of decomposed granite soils, single-particle crushing and one-dimensional compression tests were carried out on three types of decomposed granite soils as well as on quartz-rich silica sand under both dry and wet conditions. Results showed that the initial crushing strength of a single particle was reduced and strength variability increased due to the weakening effects induced by the presence of water. Moreover, it was observed that the one-dimensional compression behavior of decomposed granite soil was related to the initial crushing strength. Finally, the magnitude of initial crushing strength was also affected by the degree of weathering of the soil.     

Fundamental Behavior of Direct-Coupled Submicrosecond Pulse Energization in Electrostatic Precipitators

The fundamental characteristics of the direct-coupled pulse energization in electrostatic precipitators (EP's) are investigated in a test rig comprised of a coal pulverizing facility, a furnace, a gas cooling system, and an EP. The EP consisted of a corona electrode with barbed wires and a collection electrode with 300-mm duct spacing. This simulates the type of EP normally used in a coal-fired power station. The pulse-energized collection field shows a very high collection performance of more than 99 percent collection efficiency and the performance enhancement compared to the conventional dc energization, causing very severe back corona, becomes as large as H = 2.50.H is the enhancement factor in terms of the Deutsch migration velocity in the case of the very high resistivity dust of rd = 2 x 1013 ?cm at the gas temperature of Tg = 150°C. Even at the lower level of the dust resistivity at Tg = 110°C, where no back corona occurs in the dc-energized collection field, the performance enhancement is as large as H = 1.21. The mechanism of such great performance enhancement is likely to be the result of the very uniform and very intense formation of corona plasmas on the wires as a result of the very fast rise in the pulse voltage applied and a special sawtooth waveform of the operating voltage between the corona and collection electrodes.