Improved Hessian approximations for the limited memory BFGS method

This paper considers simple modifications of the limited memory BFGS (L-BFGS) method for large scale optimization. It describes algorithms in which alternating ways of re-using a given set of stored difference vectors are outlined. The proposed algorithms resemble the L-BFGS method, except that the initial Hessian approximation is defined implicitly like the L-BFGS Hessian in terms of some stored vectors rather than the usual choice of a multiple of the unit matrix. Numerical experiments show that the new algorithms yield desirable improvement over the L-BFGS method. This revised version was published online in June 2006 with corrections to the Cover Date.     

用联合变换相关器实现灰阶图像绝对差度量光学匹配

将绝对差度量（ＡＤＭ）引入联合变换相关器（ＪＴＣ）,实现了灰阶图像光学匹配的计算机模拟实验,利用循环编码方法,通过联合变换相关器一步绝对差度量,相关后的图像通过取高阈值的分割方法来实现对目标的准确判断,针对高斯噪声干扰情况,分析了阈值选择问题,提高了灰阶目标识别抵抗器材怕畸变干扰的能力。     

25MeV/u 40Ar+209Bi裂变反应的断点激发能和裂变时标测量

对25MeV/u ⁴⁰Ar+²⁰⁹Bi非完全熔合反应中形成的热核,测量了与裂变碎片相符合的α粒子能谱,用运动源模型分解α粒子能谱得到了裂变断前和断后发射α粒子多重性.由断后碎片发射α粒子多重性得到断点激发能约为172.5MeV.由断前α粒子多重性得到激发能在470—600MeV范围内的热核的裂变时标约为4×10^－21S.     

Resonant formation measurements of dt\mu via time of flight

Solid hydrogen in the form of an inhomogeneous layered target offers several experimental advantages when compared with liquid or gas. Beams of non-thermalized muonic hydrogen atoms allow us to explore resonant molecular ion formation processes near eV kinetic energies. Isotopically specific layers make it possible to separate competing and confusing interactions and to employ the time of flight for comparison with predictions based on theoretical energy dependences. Unambiguous charged fusion product detection simplifies absolute intensity measurements. The systematic uncertainties encountered in resonant molecular ion formation measurements, using solid hydrogen target layers, are being investigated with simulations which use the many calculated energy-dependent rates and cross-sections which are now available. The importance of the rates for processes such as muon transfer and elastic scattering are discussed, and results of some recent analyses are presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Voice characteristics, effects of voice therapy, and long-term follow-up of contact granuloma patients

This study evaluates the laryngoscopic findings and voice characteristics of male contact granuloma patients before and after voice therapy and at a follow-up about 9 years later. Pre- and posttherapy recordings as well as follow-up recordings were made for 19 granuloma patients. Pretherapy revealed the most salient perceptual voice characteristics were low pitch, monotony, and a high degree of vocal fry and hyperfunction. Interjudge reliability for these traits was high. Immediately following therapy the healed patients (n = 10) had a decrease in hyperfunction, vocal fry, and monotony, while the unhealed patients (n = 9) had an increase in hyperfunction and vocal fry decreased only marginally. Monotony decreased significantly in this group. As regards the acoustic analyses, no significant differences were found in mean fundamental frequency (F₀) or perturbation. At the follow-up assessment 4 patients had granuloma while 15 had normal laryngeal status. Perceptually their voice characteristics resembled those pretherapy independently of the laryngeal findings. The results suggest that reduced hyperfunction and decreased vocal fry may create better circumstances for the healing process at the posterior glottis.     

Possible lattice formation of new materials within a piezoelectric semiconductor plasma

The possible lattice formation of grains of chosen material in a magnetized current carrying n-type piezoelectric semiconductor plasma has been examined. In addition to the repulsive Coulomb potential, there appears a non-Coulombic oscillatory potential among the highly charged grains due to the strong resonant collective interaction of the grains and the electron-acoustic mode of the host semiconductor giving rise to the possibility of the lattice formation of grains of new materials.     

共振、混沌与束晕形成

研究强流束中的非线性共振、混沌与束晕形成的关系.给出强流束中非线性共振范围的表达式及其随束流空间电荷效应变化的数值结果和图表曲线,提出由非线性共振而激发的束晕形成的空间电荷效应极限,并分析束晕形成的过程.     

迥然不同的pV=nRθ与pV=nRT

理想气体的状态方程ｐＶ＝ｎＲθ,是依据三个实验定律进行热力学理论推导的结果。根据它可以用理想气体实现热力学温标。ｐＶ＝ｎＲＴ是依据实验事实得到的理想气体绝对温标的定义式。两者的物理意义是不相同的。     

Chemical components of PM2.5 in different seasons in Harbin,China

The seasonal characteristics of fine particulate matter (PM_2.5) were investigated from October 2020 to April 2021 (spreading fall, winter and spring) in Harbin, a city located in northeast China. The mass concentrations of PM_2.5 in winter were significantly higher than those in fall and spring. Moreover, our results indicated that various aerosol species had obvious seasonality. The proportions of secondary components were higher in winter than other two seasons. In contrast, the ratios of nitrate to sulfate (NO₃⁻/SO₄²⁻) showed lower levels in winter, which was because both the ratios of nitrogen dioxide to sulfur dioxide (NO₂/SO₂) and the ratios of nitrogen oxidation ratio to sulfur oxidation ratio (NOR/SOR) exhibited lower values in winter than in fall and spring. With PM_2.5 increased, the NO₃⁻/SO₄²⁻ ratios showed increasing trends in all three seasons, which was mainly attributed to the increase of NOR/SOR ratios in fall and spring, and the increase of both NO₂/SO₂ and NOR/SOR ratios in winter. This result highlighted that nitrate was more important than sulfate as a driver for the growth of PM_2.5 during the period of heavy air pollution. Additionally, the sources of organic aerosol (OA) in different seasons were also distinctly different. Overall, the sum of biomass burning OA (BBOA) and secondary OA (SOA) contributed >70% of OA in three seasons. The fractional contributions of BBOA to total OA, notably, exhibited higher levels in fall and spring, because of intensive open agricultural fires. The SOA fractions in OA were larger in winter, likely due to higher relative humidity which facilitated the secondary formation. A large increase in the proportions of BBOA was observed during polluted days in fall and spring compared to clean days. In comparison, during heavily-polluted periods, secondary formation made a dominant contribution to organic matter in winter.     

赶酸对微波消解-氢化物发生-原子荧光法测定谷物中砷元素的影响

在利用氢化物发生-原子荧光分测定谷物类样品中砷元素时,硫脲-抗坏血酸的还原效果会受到硝酸含量的影响,试液中硝酸含量过高,会与硫脲-抗坏血酸溶液发生氧化还原反应,降低其还原效率。本研究通过对赶酸时间和赶酸温度进行试验,获得最佳的赶酸条件,结合微波消解技术,利用氢化物发生-原子荧光光谱法测定谷物中的微量砷,结果表明,谷物中砷浓度与荧光强度呈线性关系,线性方程为 y=0.0028x-0.1728,线性相关系数R2=0.9993,检出限为1.72ng/g。 通过对9份样品进行检测,其相对标准偏差RSD在4.32-7.59%之间,其准确度相对误差RE均小于±6.50%。经多次检测证实该方法较稳定,可用于谷物类样品中砷元素的快速测定。