绿芦笋压差预冷和冷藏试验研究

试验研究了绿芦笋采后压差预冷和没预冷，用发泡聚苯乙烯箱和瓦楞纸箱包装，在2℃条件下冷藏10天、20天、30天、40天和50天的品质变化。结果表明：冷藏20天的绿芦笋新鲜并具有商品性。随着冷藏时间的延长，绿芦笋的失重率、腐烂率和顶端鳞片松散率逐渐增多，颜色变浅，可溶性固形物、维生素C和糖含量逐渐降低，叶绿素含量前期下降，中后期逐渐升高。压差预冷和包装方法对绿芦笋的保鲜效果影响较大。PC＋EPS的保鲜效果最好，不但能减少绿芦笋的失重率、腐烂率和顶端鳞片松散率，而且能减少其可溶性固形物、维生素C和糖含量的损失。     

A habitat model for Parus major minor using a logistic regression model for the urban area of Osaka, Japan

We developed a habitat model for Great Tits, Parus major minor, in an urban area of Osaka, Japan. Although Great Tits play an important role in the urban food web, there are few in most of Osaka and downtown Tokyo, areas that have low vegetation cover. We derived a habitat model for Great Tits using a logistic regression model with GIS. A bird survey was conducted twice in 85 urban parks using the line census method in the breeding season, May–July 2000. A GIS base map was created from aerial photographs. The following variables were measured for each park from public records and GIS for predicting the habitat: park properties (age, distance to the nearest mountains, distance to the nearest forest of more than 10 ha), the number of other habitats occupied by the tits within 500 m and 1 km and area of tree cover (within it and surrounding parks). Number of nearby habitats and distance from the nearest mountains and forest of more than 10 ha are variables related to the regional populations of the tits. Area of tree cover was measured for five radii (50, 100, 150, 200, 250 m) from park centers, and a logistic regression model was calculated for each of these radii. Variables were selected by a stepwise method. The best fitting model of the five models was selected using Akaike’s Information Criteria. In the bird survey, the tit was recorded in 12 parks. The areas of parks occupied by the tit were 0.56–136.0 ha (mean: 26.0 ha±42.06 S.D., n=12). Variables selected in the best fitting model were area of tree cover in a radius of 250 m from park center and the number of other habitats within 1 km as positive factors. This model shows that area of tree cover within a certain range and number of nearby populations are the keys to the distribution of Great Tits. From this model obtained, 6.0 ha (31%), 4.0 ha (20%), 2.6 ha (13%) and 1.8 ha (9%) of tree area are needed to achieve probability of 0.5 in a radius of 250 m when numbers of other habitats within 1 km was 0–3, respectively. A realistic target figure is 10% of tree cover throughout urban areas to create an ecologically sustainable city.     

不同的冷却方法和冷藏对小白菜(油菜)品质的影响

试验研究了小白菜采后真空冷却和空气冷却后,在2℃条件下冷藏7天、10天、14天、19天和29天的品质变化。结果表明：冷藏19天的小白菜新鲜并具有商品性。随着冷藏时间的延长,小白菜的失重率逐渐增多,颜色变浅,维生素C含量和还原型维生素C含量逐渐降低,冷藏前10天小白菜的叶绿素含量变化不大,10天以后明显降低。真空冷却后的小白菜品质明显好于空气冷却后的小白菜品质,前者维生素C、还原型维生素C、叶绿素含量的损失均低于后者,且真空冷却后2℃冷藏29天的小白菜仍具有商品性。     

Current collecting performance of overhead contact line-pantograph system at 425 km/h

In Japan speed tests in the region of 300 km/h have been carried out since the Oyama test line recorded a 319 km/h run in 1979. TGV recorded a 515.3 km/h run by an electric locomotive installed with a pantograph in 1990 and ICE achieved 406.9 km/h using a similar train in 1988. High-speed current collection tests over 400 km/h using electric railcars have been desired in Japan. Problems of high-speed tests are; train speed approaching wave propagation velocity, multipantograph resonance, and too large uplift of contact wires caused by lift. It is necessary to keep wave propagation velocity of contact wire higher than train speed. CS contact wire and TA contact wire were compared in high-speed tests because it was impossible to get a good current-collecting performance by using hard-drawn copper contact wires. In December 1993 using these contact wires we carried out high-speed tests in the region of 400 km/h on Jyoetsu Shinkansen with the test train STAR 21 which JR-EAST built for high-speed tests. This paper reports the current collecting performance of these contact wires predicted by simulation and running tests at 425 km/h.