论歌唱发声的相对性在实践中的技巧运用

歌唱发音是声乐的重要研究课题之一。是歌唱领域运用中一个难以忽略的关键词,相对性运用的音量大小,虚与实,高与低是音乐学最基本的技术技巧。应而针对工科院校《歌唱艺术》选修课教学模式及办学理念,以及声乐教学的直观、完善、先进、精彩深入校园,从声乐细节中不断完善歌唱技巧,强化美与知识的有机结合为基础。再次提出有关发声相对性的技术论点,在实践中的技巧运用。

评《观测与相对论》

《北京工业大学学报》本期"学术争鸣"栏目中的《观测与相对论:光速在爱因斯坦狭义相对论中为什么不变?》(以下简称《观测与相对论》),试图否定光速不变性原理,挑战爱因斯坦相对论!爱因斯坦是人类历史上最伟大的科学家。在物理学界,爱因斯犹如上帝一般地存在,而爱因斯坦相对论则犹如圣经一般。

Study on Physiological Characteristics of Three Different Cold-resistant Tomato Strains

[Objective]The aim was to study cold-resistant indexes and physiological characters of three different cold-resisitant tomato strains selected under natural conditions. [Method]With 3-4 weeks tomato seedlings as tested materials,through simulating external environment conditions by the cold treatment in lab,the survival ratio and growth status of seedlings were identified; by studying the morphological change of in vitro leaves after cold treatment and determining the relative conductivity,the cold-resistant degree of different tomato strains was identified and the correlation between conductivity and survival rate was analyzed; the variation of soluble sugar and praline content in plant of tomato was determined under the condition of cold stress. [Result]The results showed that leaf morphological changes,size of conductivity and growth status of different tomato strains after cold treatment have significant differences; the variation of soluble sugar contents in plant has significant differences,while the variation of proline content has no significant differences. [Conclusion]There is a certain correlation between conductivity and survival rate under cold treatment conditions,and plant cold tolerance is related to accumulation of soluble sugar content.

Winter Wheat Salt Tolerance Appraisal Indices with Varied Mineral Content of Saline Water

[Objective] The aim was to study wheat salt resistance appraisal indicators under the condition of saline water irrigation.[Method] A trial was conducted with five varieties irrigated with saline water at 1,2,4,6,and 8 g/L during 2009-2010 and 2010-2011 in the research station of Dry-land Farming Institute of Hebei Academy of Agricultural and Forestry Sciences.With standardized indicators for measuring treatment,the response relations among different salt stress levels and winter wheat growth index were analyzed in this study.[Result] Under the condition of different salinity of irrigation,relative plant height after jointing stage,relative leaf area index,relative dry matter weight,relative ear number per unit area showed significant differences among treatments and yield showed significant correlation,which can be taken as salt-resistance examination index of wheat.[Conclusion] The results showed that the relative height after jointing stage was recommended as the most practical salt-tolerance appraisal indices,because it was easy to be observed and sensitive to salt stress.

Ground Alignment of Inertial Navigation System with the Aid of GPS Signals

Due to the poor observability of INS ground self alignment, only horizontal alignment is satisfied. This paper proposes using GPS double difference carrier phase as external reference to improve the observability of INS self alignment. Through observability analysis and computer simulation, it is demonstrated that the azimuth alignment is as quick as horizontal alignment, the accuracy of horizontal alignment is improved, and the gyros errors can be estimated quickly and precisely.

A Study on the Multi-Compartment Linear Circulation Pharmacokinetic Model for the Targeting Drug Delivery System

By analyzing the observed phenomena and the data collected in the study, a multi-compartment linear circulation model for targeting drug delivery system was developed and the function formulas of the drug concentration-time in blood and target organ by computing were figured out. The drug concentration-time curve for target organ can be plotted with reference to the data of drug concentration in blood according to the model. The pharmacokinetic parameters of the drug in target organ could also be obtained. The practicability of the model was further checked by the curves of drug concentration-time in blood and target organ(liver) of liver-targeting nanoparticles in animal tests. Based on the liver drug concentration-time curves calculated by the function formula of the drug in target organ, the pharmacokinetic behavior of the drug in target organ(liver) was analyzed by statistical moment, and its pharmacokinetic parameters in liver were obtained. It is suggested that the (relative targeting index( can be used for quantitative evaluation of the targeting drug delivery systems.

Optimization of Chromatographic Conditions for Detecting Ellagic Acid in Pomegranate Peels Using HPLC Method

[Objective] This study aimed to optimize the chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method. [Method] By using 0.2 mg/ml ellagic acid standard solution, on the basis of single-factor experiment and orthogonal experiment, chromatographic conditions （mobile phase ratio, flow rate, col- umn temperature） for detecting ellagic acid using HPLC were optimized. Based on the optimal chromatographic conditions, the ellagic acid content in experimental pomegranate peels was determined. [Resull] The optimal chromatographic conditions for detecting ellagic acid in pomegranate peels using HPLC method are： 1.2% phos- phoric acid：acetonitrile=85：15, column temperature of 35 ℃, and flow rate of 1.0 ml/min. The linear regression equation of ellagic acid is： y=2.9e＋0.6x＋4.4e＋5 （FF=9 999）. Ac- cording to the standard addition recovery test, the average recovery rate of ellagic acid is 98.20%, and RSD is 0.60%. Under above optimized chromatographic condi- tions, ellagic acid can be well separated from other interfering components in pomegranate peels, with shorter peak time and ideal effect, which is convenient for the detection in production practices. [Conclusion] This study laid the foundation for detecting ellagic acid in pomegranate peels using HPLC method.

Compressive properties and energy absorption characteristics of open-cell nickel foams

Open-cell nickel foams with different relative densities and pre-stretching degrees were subjected to room temperature quasi-static compressive tests to explore their compressive properties. The compressive properties of the nickel foams including yield strength, elastic modulus, energy absorption density and energy absorption efficiency were calculated accurately. The results show that the compressive properties of yield strength, elastic modulus and energy absorption density increase with the increase of relative density of nickel foams. The compressive properties are sensitive to the pre-stretching degree, and the values of yield strength, elastic modulus and energy absorption density decrease with the increase of pre-stretching degree. However, the energy absorption efficiency at the densification strain state exhibits the independence of relative density and pre-stretching degree. The value of energy absorption efficiency reaches its peak when the strain is at the end of the collapse plateau region.

Physiological characteristics changes of Aesculus chinensis seeds during natural dehydration

A study was conducted to determine the physiological characteristics changes of Aesculus chinensis seeds during natural dehydration in 2003. The results showed that A. chinensis seeds were recalcitrant with being highly desiccation-sensitive. The seed moisture content of fresh fruits was higher than 60%. When the seeds were naturally dried for 30 days, their moisture content declined to 30.2% and their viability was completely lost. The seed germination percentage had a small increase at the beginning of desiccation and then decreased rapidly. The relative electrical conductivity of the A. chinensis seeds increased along with a decrease in seed moisture content. However, there was an abnormal increase in relative electrical conductivity when the seed moisture content was between 53.7% and 50.9%. Superoxide dismutase （SOD） activity decreased rapidly in the period of desiccation except for an abnormality when the seed moisture content was between 53.7% and 50.9%. Malondialdehyde （MDA） content increased slowly at the early stage of desiccation and then rose rapidly after the moisture content was below 50.9%. The soluble sugar content in seeds slowly increased with the increasing period of desiccation. The seed germination percentage was at the high level when seed moisture content was in range of 47%- 60%, which suggests that this was the optimum moisture content for maintaining A. chinensis seed viability.

Effect of Relative Humidity on Adsorption of Formaldehyde on Modified Activated Carbons

This work mainly involves the study of effect of relative humidity on adsorption of formaldehyde on the activated carbons modified with organosilane solution. Modification of activated carbons was carded out by impregnating activated carbon with organosilane/methanol-containing solutions. The breakthrough curves of formaldehyde in the packed beds of original and modified activated carbons were measured, respectively, at relative humidity of 30%, 60%, and 80%. Temperature-programmed desorption （TPD） experiments were used to estimate the activation energy for desorption of formaldehyde from the activated carbon. Results showed that the relative humidity had strongly influence on breakthrough curves of formaldehyde in the packed beds. The higher the relative humidity of gas mixtures through the packed beds was, the smaller the breakthrough time of formaldehyde became. The use of organosilane compounds to modify surfaces of the activated carbon can enhance the interaction between formaldehyde and the surfaces, and as a result, the breakthrough times of formaldehyde in the packed beds of the modified activated carbon were longer than that in the packed bed of the unmodified activated carbon.

Influence of Heterojunction Position on SiGe HBTs with Graded BC Junctions

The influence of a heterojunction in the vicinity of a graded BC junction on the performance of npn SiGe HBTs is studied. SiGe HBTs differing only in heterojunction position in the vicinity of a graded BC junction are simulated by means of 2D Medici software for DC current gain and frequency characteristics. In addition, the simulated DC current gains and cut-off frequencies are compared at different collector-emitter bias voltages. Through the simulation results, both DC and HF device performance are found to be strongly impacted by degree of confinement of the neutral base in the SiGe layer, even in the absence of a conduction band barrier. This conclusion is of significance for designing and analyzing SiGe HBTs.

Density Functional Study on Structures and Relative Stability of Gd（H2O）n^3＋ （n=8,9）

Density functional theory calculations were performed to study the structures and relative stability of the gadolinium complexes, Gd（H2O）n^3＋ （n=8,9）, in vacuo and in aqueous solution. The polarizable continuum model with various radii for the solute cavity was used to study the relative stability in aqueous solution. The calculated molecular geometries for n=8 and 9 obtained in vacuo are consistent with those observed in experiments. It was found that while the nona-aqua complex is favored in the gas phase, in aqueous solution the octa-aqua conformation is preferred. This result, independent of the types of cavities employed, is in agreement with the experimental observation. The reliability of the present calculation was also addressed by comparing the calculated and experimental free energy of hydration, which revealed that the UA0, UAHF, and UAKS cavities are most appropriate when only the first solvation shell is treated explicitly.

Hidden Symmetries for Thermodynamics and Emergence of Relativity

Erik Verlinde recently proposed an idea about the thermodynamic origin of gravity.Though this is abeautiful idea, which may resolve many long standing problems in the theories of gravity, it also raises many otherproblems.In this article I will comment on some of the problems of Verlinde’s proposal with special emphasis on thethermodynamical origin of the principle of relativity.It is found that there is a large group of hidden symmetries ofthermodynamics, which contains the Poincare group of the spacetime for which space is emergent.This explains thethermodynamic origin of the principle of relativity.

Perturbation to Unified Symmetry and Adiabatic Invariants for Relativistic Hamilton Systems

Based on the concept of adiabatic invariant, the perturbation to unified symmetry and adiabatic invariants for relativistic Hamilton systems are studied. The definition of the perturbation to unified symmetry for the system is presented, and the criterion of the perturbation to unified symmetry is given. Meanwhile, the Noether adiabatic invariants, the generalized Hojman adiabatic invariants, and the Mei adiabatic invariants for the perturbed system are obtained.

Responses of antioxidant defense system of epilithic mosses to drought stress in karst rock desertified areas

Barbula fallax Hedw., Erythrodontium julaceum(Schwaegr.) Par., and Bryum argenteum Hedw. are typical rock mosses growing on rocks in different terrestrial habitats. In this study, B. fallax and E. julaceum, which are epilithic mosses growing in rock desertification in Guizhou, China, were used as ecophysiological mosses in a combination of field investigations and laboratory experiments. We also investigated the reference moss B. argenteum, which is a widely distributed moss in habitats with soil as substrate. Our research focused on the response of the antioxidant defense system of epilithic mosses to drought stress. Most antioxidant defense indicators increased initially, then declined at later stages of drought stress. In contrast, the carotenoid content increased constantly. In addition, there was an initial increase(albeit variable) in relative membrane permeability, with this parameter showing a parabolic trend in all of the epilithic mosses. Among the three species, E. julaceum demonstrated the strongest resistance followed by B. fallax and then by B. argenteum. The epilithic mosses displayed stronger resistance compared to the native mosses; the increase in O_2 content and other reactive oxygen species(ROS) at the early stage of drought stress induced the enzymatic and non-enzymatic scavenging systems tosequester ROS. Moreover, the radical scavenging ability and strong drought tolerance was maintained. The longterm growth of bryophyte under drought conditions in a karst environment can help eliminate the intense response of mosses to drought stress as they adapt.

Mei Symmetries and Lie Symmetries for Nonholonomic Controllable Mechanical Systems with Relativistic Rotational Variable Mass

The Mei symmetries and the Lie symmetries for nonholonomic controllable mechanical systems with relativistic rotational variable mass are studied. The differential equations of motion of the systems are established. The definition and criterion of the Mei symmetries and the Lie symmetries of the system are studied respectively. The necessary and sufficient condition under which the Mei symmetry is Lie symmetry is given. The condition under which the Mei symmetries can be led to a new kind of conserved quantity and the form of the conserved quantity are obtained. An example is given to illustrate the application of the results.

Determination of Lignin in Marine Sediment Using Alkaline Cupric Oxide Oxidation-Solid Phase Extraction-on-Column Derivatization-Gas Chromatography

Lignin serves as one of the most important molecular fossils for tracing Terrestrial Organic Matters （TOMs） in marine environment. Extraction and derivatization of lignin oxidation products （LOPs） are crucial for accurate quantification of lignin in marine sediment. Here we report a modification of the conventional alkaline cupric oxide （CuO） oxidation method, the modification consisting in a solid phase extraction （SPE） and a novel on-column derivatization being employed for better efficiency and reproducibility. In spiking blanks, recoveries with SPE for the LOPs are between 77.84% and 99.57% with relative standard deviations （RSDs） ranging from 0.57% to 8.04% （n=3）, while those with traditional liquid-liquid extraction （LLE） are from 44.52% to 86.16% With RSDs being from 0.53% to 13.14% （n=3）. Moreover, the reproducibility is greatly improved with SPE, with less solvent consumption and shorter processing time. The average efficiency of on-column derivatization for LOPs is 100.8%±0.68%, which is significantly higher than those of in-vial or in-syringe derivatization, thus resulting in still less consumption of derivatizing reagents.Lignin in the surface sediments sampled from the south of Yangtze River estuary, China, was determined with the established method. Recoveries of 72.66% to 85.99% with standard deviation less than 0.01mg/10g dry weight are obtained except for p-hydroxybenzaldehyde. The lignin content ∑8 （produced from 10g dry sediment） in the research area is between 0.231 and 0.587mg. S/V and C/V ratios （1.028 ± 0.433 and 0.192±0.066, respectively） indicate that the TOMs in this region are originated from a mixture of woody and nonwoody angiosperm plants; the high values or （Ad/Al）v suggest that the TOMs has been highly degraded.

Etching Behavior of GaN/GaAs(001) Epilayers Grown by MOVPE

Wet etching characteristics of cubic GaN (c GaN) thin films grown on GaAs(001) by metalorganic vapor phase epitaxy (MOVPE) are investigated.The samples are etched in HCl,H 3PO 4,KOH aqueous solutions,and molten KOH at temperatures in the range of 90～300℃.It is found that different solution produces different etch figure on the surfaces of a sample.KOH based solutions produce rectangular pits rather than square pits.The etch pits elongate in 1 0] direction,indicating asymmetric etching behavior in the two orthogonal <110> directions.An explanation based on relative reactivity of the various crystallographic planes is employed to interpret qualitatively the asymmetric etching behavior.In addition,it is found that KOH aqueous solution would be more suitable than molten KOH and the two acids for the evaluation of stacking faults in c GaN epilayers. direction,indicating asymmetric etching behavior in the two orthogonal <110> directions.An explanation based on relative reactivity of the various crystallographic planes is employed to interpret qualitatively the asymmetric etching behavior.In addition,it is found that KOH aqueous solution would be more suitable than molten KOH and the two acids for the evaluation of stacking faults in c GaN epilayers.

A practical iterative two-view metric reconstruction with uncalibrated cameras

This paper presents a practical iterative algorithm for two-view metric reconstruction without any prior knowledge about the scene and motion in a nonsingular geometry configuration. The principal point is assumed to locate at the image center with zero skew and the same aspect ratio, and the interior parameters are fixed, so the self-calibration becomes focal-length cali- bration. Existing focal length calibration methods are direct solutions of a quadric composed of fundamental matrix, which are sensitive to noise. A quaternion-based linear iterative Least-Square Method is proposed in this paper, and one-dimensional searching for optimal focal length in a constrained region instead of solving optimization problems with inequality constraints is applied to simplify the computation complexity, then unique rotational matrix and translate vector are recovered. Experiments with simulation data and real images are given to verify the algorithm.

Learning curves in minimally invasive esophagectomy

Surgical innovation and pioneering are important for improving patient outcome, but can be associated with learning curves. Although learning curves in surgery are a recognized problem, the impact of surgical learning curves is increasing, due to increasing complexity of innovative surgical procedures, the rapid rate at which new interventions are implemented and a decrease in relative effectiveness of new interventions compared to old interventions. For minimally invasive esophagectomy(MIE), there is now robust evidence that implementation can lead to significant learning associated morbidity(morbidity during a learning curve, that could have been avoided if patients were operated by surgeons that have completed the learning curve). This article provides an overview of the evidence of the impact of learning curves after implementation of MIE. In addition, caveats for implementation and available evidence regarding factors that are important for safe implementation and safe pioneering of MIE are discussed.