Thawing and freezing processes of active layer in Wudaoliang region of Tibetan Plateau

The interaction between permafrost and atmosphere is accomplished through transfer of heat and moisture in the overlay active layer. Thus, the research on the thermal and hydrodynamics of active layer during the thawing and freezing processes was considered a key to revealing the heat and moisture exchanges between permafrost and atmosphere. The monitoring and research on active layer were conducted because permafrost occupies about two thirds of the total area of the Tibetan Plateau. Based on the analysis of the ground temperature data and soil moisture data of monitoring near the Wudaoliang region of the Tibetan Plateau, the thawing and freezing processes of active layer were divided into four stages, i.e. summer thawing stage (ST), autumn freezing stage (AF), winter cooling stage (WC) and spring warming stage (SW). Coupled heat and water flow is much more complicated in ST and AF, and more amount of water is migrating in these two stages. Heat is transferred mainly via conductive heat flow in the other two stages, and less water migrated. Four water migration and coupled heat flow processes were addressed for the thawing and freezing stages, which are water infiltration driven by gravity, moisture advection and distillation driven by temperature and osmotic gradients, water migration driven by capillarity and unfrozen water migration driven by temperature gradient. The water content near the permafrost table tends to increase after one thawing and freezing cycle, which is the main reason for the development of thick ground ice layer near permafrost table.     

J-TEXT托卡马克上的可见光CCD成像系统

在中型聚变实验装置J-TEXT托卡马克上成功地研制了一套可见光CCD(12harge Coupled Device)成像系统.该系统可沿切向实时观察整个等离子体横截面的可见光辐射图形.该系统的核心器件CCD相机分辨率为659×494,最高帧率110f/s,可按选择捕捉彩色或黑白图片.详细地描述了该成像系统的组成、CCD相机的控制流程以及实际应用的结果.该系统能直观地展现等离子体放电过程,是J-TEXT装置放电运行中必备的重要诊断手段.     

一种基于博弈论的交通系统最优调度策略学习方法

交通网中,最大化车流量和最小化平均等待时间是每一个路口调度的目标.交通调度中,各路口与其它路口发生博弈关系.博弈过程中,相邻路口之间为使其自身利益最大化而存在一种策略间相互协调的约束.针对复杂的交通调度控制问题,基于多智能体多阶段博弈论对交通系统进行建模.考虑动态博弈交通环境的实际特征,进一步基于博弈的增强学习算法,提出一种以惩机制为约束条件的交通系统博弈策略的学习方法,最终使参与交通博弈的多个路口达到Nash均衡,从而得到交通系统的最优配时调度策略组合.实验验证了所提出方法的可行性和有效性.     

除湿转轮与中高温热泵耦合空调系统性能实验

提出除湿转轮与中高温热泵耦合的运行方式,利用热泵来完全满足再生负荷要求,搭建转轮热泵耦合空调系统实验台,对不同工况下,新风量分别为20％和10％两种情况系统的性能进行实验研究．结果表明：室外空气干球和湿球温度越高,蒸发器出口风温越高,性能系数越低,为使冷凝器出口风温满足再生要求的冷凝风量会相应地增加和减少;随室内空气干球温度升高和湿球温度降低,蒸发器出口风温升高,性能系数下降,为使冷凝器出口风温满足再生要求的冷凝风量减少;耦合空调系统的新风量由20％降为10％时,再生温度需求降低约3℃,蒸发器出口风温降低约1．5℃,能耗相应减少,性能系数提高．同时,对耦合空调系统与常规再热系统的性能进行仿真模拟,结果表明：与常规系统相比,耦合空调系统中压缩子系统的性能系数降低,耦合空调系统能耗减少,性能系数提高;与相同工况下的常规系统相比．新风量为20％和10％的耦合系统可分别节能36．80％和40．86％;与室内设计温度为23℃的常规系统相比．可分别节能12．95％和18．48％．     

Biosynthesis of selenosubtilisin: A novel way to target selenium into the active site of subtilisin

Glutathione peroxidase （GPx, EC1.11.1.9）, an important anti-oxidative selenoenzyme, can catalyze the reduction of harmful hydroperoxides with concomitant glutathione, thereby protecting cells and other biological issues against oxidative damage. It captures considerable interest in redesign of its function for either the mechanism study or the pharmacological development as an antioxidant. In order to develop a general strategy for specifically targeting and operating selenium in active sites of enzymes, the catalytically essential residue selenocysteine （Sec） was first successfully bioincorporated into the catalytic center of subtilisin by using an auxotrophic expression system. The studies of the catalytic activity and the steady-state kinetics demonstrated that selenosubtilisin is an excellent GPx-like biocatalyst. In comparison with the chemically modified method, biosynthesis exhibits obvious advantages： Sec could be site-directly incorporated into active sites of enzymes to overcome the non-specificity generated by chemical modification. This study provides an important strategy for specifically targeting and operating selenium in the active site of an enzyme.     

Sea surface temperature and terrestrial biomarker records of the last 260 ka of core MD05-2904 from the northern South China Sea

This paper reports high-resolution biomarker records of the last 260 ka for core MD05-2904 from the northern South China Sea （SCS）. The sea surface temperature （SST） record using the U37^k＇, index reveals a minimum of 21.5℃（MIS 2） and a maximum of 28.3℃（MIS 5.5）, for a temperature difference of almost 7℃, and provides the longest high-resolution U37^k＇ SST record in northern SCS. The content of odd-number long chain n-alkanes and several n-alkanes indexes such as the CPI, ACL and the C31/C27 ratio, all reveal generally higher values during the glacials and lower values during the interglaclals. Terrestrial input as Indicated by n-alkane content was mostly controlled by sea-level changes： During the glacials, lower sea-level exposed the continental shelf to enable rivers to transport more terrestrial materials to the slope; and the situation reverses during the interglacials. The n-alkane indexes changes reveal more n-alkanes from contemporary vegetation during glacials as a result of the proximity of the core site to the source region, while the increases in ACL and C81/C27 ratio during glaclals indicate a change to more grassy vegetation. However, the highest values for CPI, ACL and the C81/C27 ratio all occurred during late MIS 3, and it was suggested that this period was characterized by a strong summer monsoon-dominated humid climate which resulted in a denser vegetation for the exposed continental shelf region.     

墩化供水泵站水力过渡过程的计算机仿真

供水泵站压力管路的运行安全问题一直为广大技术人员所关注,文章对墩化泵站压力出水管路的水锤防护效果进行了计算机仿真和现场测试;结果说明:计算机仿真计算的数学模型是正确的,该泵站采用下开式水锤消除器,压力管路的运行是安全的.     

Self-Expanded Clustering Algorithm Based on Density Units with Evaluation Feedback Section

This paper presents an effective clustering mode and a novel clustering result evaluating mode. Clustering mode has two limited integral parameters. Evaluating mode evaluates clustering results and gives each a mark. The higher mark the clustering result gains, the higher quality it has. By organizing two modes in different ways, we can build two clustering algorithms： SECDU（Self-Expanded Clustering Algorithm based on Density Units） and SECDUF（Self-Expanded Clustering Algorithm Based on Density Units with Evaluation Feedback Section）. SECDU enumerates all value pairs of two parameters of clustering mode to process data set repeatedly and evaluates every clustering result by evaluating mode. Then SECDU output the clustering result that has the highest evaluating mark among all the ones. By applying ＂hill-climbing algorithm＂, SECDUF improves clustering efficiency greatly. Data sets that have different distribution features can be well adapted to both algorithms. SECDU and SECDUF can output high-quality clustering results. SECDUF tunes parameters of clustering mode automatically and no man＇s action involves through the whole process. In addition, SECDUF has a high clustering performance.