Grand-scale low-mass star formation in our Galaxy

Summary We present the first results of an observational programme to identify star forming regions and to provide the near-infrared energy distributions of embedded objects selected by their IRAS colours. Based on data collected at the European Southern Observatory, La Silla, Chile.     

Recent trends in random number and random vector generation

A survey of recent work in the areas of uniform pseudorandom number and uniform pseudorandom vector generation is presented. The emphasis is on methods for which a detailed theory is available. A progress report on the construction of quasirandom points for efficient multidimensional numerical integration is also given.     

全天时星敏感器光学系统参量选择与光学设计

以10km观测高度探测4.5等星为例,分析星点在600~1100nm谱段的辐射特性,使用Modtran软件计算同谱段的天空背景辐射亮度以及大气透过率,在信噪比阈值为5的情况下,选择一组典型的光学系统参量.采用一块平面反射镜和石英球面镜系统设计了轻、小型化的光学系统,该系统在600~1 100nm宽光谱范围内全视场光斑形状接近圆形、调制传递函数接近衍射极限,色差很小,具有良好的成像质量.计算了地面环境下星敏感器的昼夜探测信噪比,以信噪比阈值5对星敏感器的探测能力评估,结果表明在白昼地面环境下可以实现2.5等G型恒星的探测,在夜间地面环境下可以实现6等G型恒星的探测.     

基于遗传算法的夜天光光谱匹配方法研究

为了满足微光夜视仪室内性能测试的需求,对晴朗夜空满月光光谱和无月时星光光谱进行模拟.首先,对夜视仪的工作光谱范围进行研究,确定需要拟合的光谱波段.接着,对该波段的夜天光谱进行分析,选取合适的光源.采用简单夜天光谱拟合方法,根据目标光谱和光源光谱,得出所需的滤光片衰减曲线,找出该曲线近似对应的滤光片.提出基于遗传算法的光谱构造方法,根据光谱构造理论,采用现有的47种滤光片进行光谱构造,通过遗传算法求解该光谱构造函数,计算出不同滤光片的最佳匹配模式,并进行模拟.实验结果表明,采用基于遗传算法的光谱构造方法对夜天光谱拟合得到的光谱匹配度更高.     

When linear and weak discrepancy are equal

The linear discrepancy of a poset P is the least k such that there is a linear extension L of P such that if x and y are incomparable, then |h_L(x)−h_L(y)|≤k, whereas the weak discrepancy is the least k such that there is a weak extension W of P such that if x and y are incomparable, then |h_W(x)−h_W(y)|≤k. This paper resolves a question of Tanenbaum, Trenk, and Fishburn on characterizing when the weak and linear discrepancy of a poset are equal. Although it is shown that determining whether a poset has equal weak and linear discrepancy is -complete, this paper provides a complete characterization of the minimal posets with equal weak and linear discrepancy. Further, these minimal posets can be completely described as a family of interval orders.     

Preparation of multifunctional organolithium initiator in cyclohexane solutions

Multifunctional organolithium initiator was prepared in cyclohexane solvent.The process started with adding the cyclohexane solution of butadiene to naphthalene-lithium in batches to produce butadiene oligomer dilithium with 4-8 butadiene repeating units.In the first feeding,the maximum loading of cyclohexane and the minimum concentration of butadiene cyclohexane solution must be controlled under V_cyclohexane≤1.33V_THFand p≥40.6C_N.Then,SnCl₄ was added and eventually the multifunctional organolithium initiator containing Sn atom was synthesized through coupling reaction. Experiment results showed that adding the cyclohexane solution in batches was effective in overcoming some difficulties, such as insolubility of naphthalene-lithium in cyclohexane,low efficiency of naphthalene-lithium in initiating butadiene.In practice,benzene can be replaced by cyclohexane completely,which can not only reduce environmental pollution from benzene,but also overcome the difficulty of solvent recovery caused by similar boiling point between benzene and cyclohexane.Prepared with multifunctional organolithium containing Sn atom as initiator,the star-shaped solution polymerized styrene-butadiene rubber（star S-SBR）with better vulcanization performances,lower rolling resistance and higher wet-skid resistance was obtained.     

Quantum spins on star graphs and the Kondo model

We study the XX model for quantum spins on the star graph with three legs (i.e., on a Y  -junction). By performing a Jordan–Wigner transformation supplemented by the introduction of an auxiliary space we find a Kondo Hamiltonian of fermions, in the spin 1 representation of su(2)$\mathit{su}(2)$, locally coupled with a magnetic impurity. In the continuum limit our model is shown to be equivalent to the 4-channel Kondo model coupling spin-1/2 fermions with a spin-1/2 impurity and exhibiting a non-Fermi liquid behavior. We also show that it is possible to find an XY model such that – after the Jordan–Wigner transformation – one obtains a quadratic fermionic Hamiltonian directly diagonalizable.