Frequency limitation in calibrating microwave test fixtures

The problem of frequency limitation arising in calibration of the test fixtures is investigated in this paper. It is found that at some frequencies periodically, the accuracy of the methods becomes very low, and. the denominators of the expressions of the required S-parameters approach zero. This conclusion can be drawn whether-the test fixtures, are symmetric or not. A good agreement between theory and experiment is obtained.

Scan test in 18x8 bits Booth Coding-Wallace Tree multiplier

Scan test can be inserted around hard IP cores that have not been designed with DFT approaches. An 18x18 bits Booth Coding-Wallace Tree multiplier has been designed with full custom approach with 0.61 m CMOS technology. When we reuse the multiplier in another chip, scan chain has been inserted around it to increase the fault coverage. After scan insertion, the multiplier needs 4.7% more areas and 24.4% more delay time, while the fault coverage reaches to 95%.

Comprehensive performance analysis of popular odd-symmetric phase masks used for wave-front coded imaging system

(973 Program）No.2009CB724006.

九寨沟景区旅游活动扰动形成的退化地段植被恢复试验初报

日益增强的旅游活动干扰已成为九寨沟世界自然遗产的有效保护与持续管理不可回避的问题，也已成为当前区域生态保护与经济发展的焦点问题之一。评估乡土植物种的基本特征、质量、种子休眠程度以及萌发能力；筛选适宜的植被恢复乡土物种并选择有效植被恢复技术措施是开展植被恢复试验的重要前提和保障。本文以九寨沟世界自然遗产为例,通过对景区乡土植物种子基本特征的测定以及采用乡土物种作为植被恢复技术试验与恢复技术筛选的试验物种，在景区旅游干扰区的三种生境类型：原始针叶林、混交林和边坡，根据不同的影响因素设计试验，从而探索适宜的恢复措施和植被恢复物种。初步结论如下： 1． 本文研究的28种乡土植物中，17种测定的物种活力较高(>72%)，均具有作为恢复物种的潜力。但28种种子中75%的发芽率为0%。大部分种子存在一定程度的休眠，包括甘肃山楂、称花藤、疏花槭、陇东海棠、球花荚迷、巴东小檗、蔷薇、宝兴栒子、光泽栒子、光枝柳叶忍冬、甘青铁线莲、毛果铁线莲、宽叶旌节花、糙叶五加和独活。因而种子存在深度休眠是乡土物种自然更新和植被恢复的主要障碍，需要根据种子的形态生理特征，寻求打破乡土植物种子休眠的有效方法，提高种子发芽率。 2．低温层积只显著提高了蔷薇、毛果铁线莲、宽叶旌节花和假升麻3种种子的发芽率，也相对较早地提高了陇东海棠、鲜黄小檗和独活的萌发。对于其它物种的种子，低温层积没能有效打破休眠提高发芽率。综合分析结果表明九寨沟28种林下或林缘乡土植物中窄叶鲜卑花、毛果铁线莲、宽叶旌节花、假升麻、陇东海棠、鲜黄小檗和独活等12种可直播或通过低温层积处理后直播用于旅游干扰退化地段的植被恢复中，而其它的种类尚需进一步寻求打破休眠的措施以提高种子发芽能力。 3．在原始林生境下，七筋菇、巴东小檗、耳叶风毛菊、长叶毛花忍冬及独活5种乡土植物种子的出苗能力不高，因此目前急需提出有关提高种子出苗的方法措施。在相同的处理条件下，不同物种出苗数存在着较大的差异，相比而言，巴东小檗、耳叶风毛菊和长叶毛花忍冬种子出苗与幼苗存活较高，对于其环境适应能力较强，因此它们更适宜采用播种的方式应用于九寨沟原始林践踏地段地表的植被恢复实践；而七筋菇和独活在室内和自然气候条件下萌发都很困难，在植被恢复过程中，可考虑采用其它播种方式。而在边坡和混交林生境试验结果表明，供试物种无萌发和出苗现象，这可能跟外界环境条件、干扰和种子命运有关。 4． 本研究中腐殖质、松土和苔藓覆盖处理措施均未能提高物种出苗，且对样方内植被结构以及物种丰富度也无显著影响，其中的影响因素也是多方面的，因此还需进一步研究探索。但腐殖质对幼苗存活能力方面有一定的积极作用。 The increasing tourism disturbance is an unavoidable issue to effective conservation and sustaind tourist management of Jiuzhaigou Nature Reserve. It has become one of the focal problems of regional ecological protect and economic development. Assessing the traits, quality, seed dormancy and germination of native seed and choosing the suitable species and ways for vegetation restoration were the important precondition and guarantee before vegetation restoration. In this paper, as an example to Jiuzhaigou world nature heritage, through the estimation to the basic characteristics of native seeds and the use of native species for the test of vegetation restoration and the choosing of vegetation restoration techniques, in three different habitats being disturbed, including the primitive forest, mixed forest and side slope. According to different factors, designing experiments in order to explore the appropriate measures and species of vegetation restoration . Our results are as follows: 1． There are 77% seeds of the 28 species with high viability(>72%), which had the potential possibility of being restoration species. The germination of 75% of the seed was 0%.Most of the seed was dormant, So dormancy of seed was the barrier for natural regeneration and vegetation restoration, Further research is needed on investigating the other more effective methods to release seed dormancy of these native species in the future. 2． Cold stratification did not release seed dormancy of most species. In our study, there are only 3 species including Clematis peterae var. trichocarpa, Stachyurus chinensis and Aruncus sylvester (P<0.05) with germination percentage increased by cold stratification. By comprehensive analysis, the result shows: In 28 undergrowth native seeds, Sibiraea angustata, Clematis peterae var. trichocarpa, Stachyurus chinensis, Aruncus Sylvester, Malus kansuensis, Berberis diaphana,and Heracleum hemsleyanum could be used to vegetation restoration by sowing directly or sowing after cold stratification in degenerate gland being disturbed by turism, and othes seed of 28 were needed to search other methods to release seed dormancy for advancing the ability of germination. 3．In the habitat of primitive forest, the ability of emergence of the native species Clintonia udensis, Berberis henryana, Saussurea neofranchetii, Lonicera trichosantha var.xerocalyx and Heracleum hemsleyanum was low, so it is urgently needed to search about the methods of advancing emergence. In the sametreatment, the number of emergence of different species was very different. Relatively speaking, the emergence and seedling survival of the species Berberis henryana, Saussurea neofranchetii and Lonicera trichosantha var.xerocalyx was higher, and the adaptability of the species was better, so they were more suitable for vegetation restoration on trampling-induced degraded patches of primitive forest in Jiuzhaigou; But the germination of Clintonia udensis and Heracleum hemsleyanum was both difficult in laboratory and natural conditions, so it could be considered to apply other sowing methods. However, the result showed that: applied species didn’t germinate or emergent in the habitat of side slope and mixed forest, which could be related to external environment conditions, interference and the fate of the seed. 4．In this study, humus, scatification and bryophyte cover measures didn’t advance the emergence of the species or the structure of vegetation and richness in plot significantly, the impact factors of which were many, therefore further research is needed . However, humus had a certain positive effect on the ability of seedling survival.