频度副词“时常”与“常常”的对比分析

"时常"和"常常"是一对近义频度副词,留学生在学习了甲级词"常常"之后就会接触到丙级词"时常",这两个词容易混用产生偏误。基于北大语料库和北语语料库的对比分析表明,在句法功能上,与"时常"相比,"常常"不可作定语,"常常不VP"连用更有优势;在语义表达功能上,"常常"所指频率高于"时常","时常"偏书面语体,而"常常"则是通用语体。

频率副词“经常”和“时常”的语义差异

“经常”和“时常”是一对使用频率较高的近义副词,它们都可以表示动作、状态或事件的发生频率较高,但有时不能替换使用。在具体语境中考察“经常”和“时常”的语义差异,发现“经常”的适用时段范围要低于“时常”,但其所代表的频率、持续性和主观性要强于“时常”。

Research on measuring time constant of NANMAC thermocouple

The theory for measuring the time constant of thermocouple was introduced, and the method for measuring the time constant of NANMAC thermocouple by using dynamic calibration system of transient surface temperature sensor was proposed. In this system, static and dynamic calibrations were conducted for infrared detectors and thermocouples, and then both temperature-time curves were obtained. Since the frequency response of infrared detector is superior to that of calibrat- ed thermocouple, the values measured by infrared detectors are taken as true values. Through dividing the values measured with thermocouples by those with infrared detectors, a normalized curve was obtained, based on which the time constant of thermocouple was measured. With this method, the experiments were carried out with NANMAC thermocouple to obtain its time constant. The results show that the method for measuring the time constant is feasible and the dynamic calibration of thermocouples can be achieved at microsecond and millisecond level. This research has a certain reference value for research and application of NANMAC thermocouple temperature sensor.

Properties of Picosecond Fluorescence of Super High-Yield Hybrid Rice

Thylakoid membrane preparations of super high-yield hybrid rice (Oryza sativa L.), Liangyoupeijiu (P9) and Shanyou 63 (SH 63) were used for investigating its spectral and time properties by using picosecond time-resolved fluorescence spectrum measuring system. The thylakoid membrane preparations of P9 and SH 63 were excited by an Ar+ laser with a pulse width of 120 ps, repetition rate of 4 MHz and wavelength of 514 nm. The time constants of the excited energy transfer in these two varieties at flowering stage and grain filling stage were calculated from the experimental data. Based on the comparative studies of the time and spectral properties of the excited fluorescence in these ultrafast dynamic experiments the following was found: at both the flowering stage and grain filling stage, the speed of the excitation energy transfer, in photosystem was faster than that in photosystem II in P9 variety; and the speed of the excitation energy transfer at grain filling stage was faster than those at flowering stage for both rice varieties; the experiments also implied that the components and assembly of pigments in SH 63, but not in P9, changed during the process from flowering stage to grain filling stage for in these two rice varieties.

三维石油遥感应用中多时相影像数据管理

针对目前多时相影像数据管理主要是面向影像产品管理,仅考虑影像产品本身的信息作为管理要素,无法满足石油行业遥感应用要求这一问题,提出一种面向三维石油遥感应用的多时相数据管理方法,通过采用数据组织目录结构与瓦片存储目录结构相结合的方式,建立了多时相影像数据的分级管理与访问。该方法满足石油遥感应用多样性、应用的油区范围分散、多数据源组合、油区变化性检测的要求,并以鄱阳湖三角洲环境变化中多时相数据管理为例进行了软件实现。

Robust PID controller design for time delay processes with peak of maximum sensitivity criteria

The motivation of this work is to obtain single PI/PID tuning formula for different types of processes with enhanced disturbance rejection performance. The proposed tuning formula consistently gives better performance in comparison to several well-known methods at the same degree of robustness for stable, integrating and unstable processes. For the selection of the closed-loop time constant(τc), a guideline is provided over a broad range of time-delay/time-constant ratios on the basis of the peak of maximum sensitivity(Ms). An analysis has been performed for the uncertainty margin with the different process parameters for the robust controller design. It gives the guideline of the Ms-value settings for the PI controller designs based on the process parameters uncertainty. Furthermore, a relationship has been developed between Ms-value and uncertainty margin with the different process parameters(k, τ and θ). Simulation study has been conducted for the broad class of processes and the controllers are tuned to have the same degree of robustness by measuring the maximum sensitivity, Ms, in order to obtain a reasonable comparison.

Analysis of Urban Heat Island Effect Using an Improved CTTC and STTC Model

An improved cluster thermal time constant(CTTC) and surface thermal time constant(STTC) numerical model was introduced,which took into account the effect of vegetation coverage and modified the expression of net longwave radiation of the canyon layer.In the case study the model was used to calculate the air temperature variation at downtown of Tianjin City.The relative error between the calculated and measured air temperatures was less than 3%.The tendency of air temperature variation was predicted when the building aspect ratio,vegetation rate,and wind speed changed respectively.It is demonstrated that when the aspect ratio of a building with south-north orientation increased,the heat island intensity at day time was mitigated;however,it became worse after sunset.The vegetation coverage rate and wind speed both had negative relationship with the urban heat island intensity.

Detecting the Relationship Between Summer Rainfall Anomalies in Eastern China and the SSTA in the Global Domain with a New Significance Test Method

It is suggested that the multiple samples in a correlation map or a set of correlation maps should be examined with significance tests as per the Bernoulli probability model. Therefore, both the contemporaneous and lag correlations of summertime precipitation R in any one of the three regions of Northern China （NC）, the Changjiang-Huaihe River Valley （CHRV）, and Southern China （SC） with the SSTA in the global domain have been tested in the present article, using our significance test method and the method proposed by Livezey and Chen （1983） respectively. Our results demonstrate that the contemporaneous correlations of sum- mer R in CHRV with the SSTA are larger than those in NC. Significant correlations of SSTA with CHRV R are found to be in some warm SST regions in the tropics, whereas those of SSTA with NC R, which are opposite in sign as compared to the SSTA-CHRVR correlations, are found to be in some regions where the mean SSTs are low. In comparison with the patterns of the contemporaneous correlations, the 1 to 12 month lag correlations between NC R and SSTA, and those between CHRV summer R and SSTA show similar patterns, including the magnitudes and signs, and the spatial distributions of the coefficients. However, the summer rainfall in SC is not well correlated with the SSTA, no matter how long the lag interval is. The results derived from the observations have set up a relationship frame connecting the precipitation anomalies in NC, CHRV, and SC with the SSTA in the global domain, which is critically useful for our understanding and predicting the climate variabilities in different parts of China. Both NC and CHRV summer R are connected with E1 Nifio events, showing a ‘- -＇pattern in an E1 Nifio year and a‘＋ ＋＇ pattern in the subsequent year. Key words summer precipitation; eastern China; global sea surface

IMC-PID tuning method based on sensitivity specification for process with time-delay

To overcome the deficiencies addressed in the conventional PID control and improve the dynamic performance and robustness of the system, a simple design and parameters tuning approach of internal model control-PID （IMC-PID） controller was proposed for the first order plus time-delay （FOPTD） process and the second order plus time-delay （SOPTD） process. By approximating the time-delay term of the process model with the first-order Taylor series, the expressions for IMC-PID controller parameters were derived, and they had only one adjustable parameter 2 which was directly related to the dynamic performance and robustness of the system. Moreover, an analytical approach of selecting 2 was given based on the maximum sensitivity Ms. Then, the robust tuning of the system could be achieved according to the value of Ms. In addition, the proposed method could be extended to the integrator plus time-delay （IPTD） process and the first order delay integrating （FODI） process. Simulation studies were carried out on various processes with time-delay, and the results show that the proposed method could provide a better dynamic performance of both the set-point tracking and disturbance rejection and robustness against parameters perturbation.

Gas monitoring data anomaly identification based on spatio-temporal correlativity analysis

Based on spatio-temporal correlativity analysis method, the automatic identification techniques for data anomaly monitoring of coal mining working face gas are presented. The asynchronous correlative characteristics of gas migration in working face airflow direction are qualitatively analyzed. The calculation method of asynchronous correlation delay step and the prediction and inversion formulas of gas concentration changing with time and space after gas emission in the air return roadway are provided. By calculating one hundred and fifty groups of gas sensors data series from a coal mine which have the theoretical correlativity, the correlative coefficient values range of eight kinds of data anomaly is obtained. Then the gas moni- toring data anomaly identification algorithm based on spatio-temporal correlativity analysis is accordingly presented. In order to improve the efficiency of analysis, the gas sensors code rules which can express the spatial topological relations are sug- gested. The experiments indicate that methods presented in this article can effectively compensate the defects of methods based on a single gas sensor monitoring data.

Effects on the population dynamics of Brachionus rubens(Rotifera)caused by mercury and cadmium administered through medium and algal food Chlorella vulgaris

Due to industrial activities,heavy metal concentrations in aquatic systems of Mexico,are on the rise.Zooplankton,particularly rotifers,being sensitive and common components of freshwater,are widely used in ecotoxicological tests for establishing water quality criteria.Depending on the route of exposure(i.e.via medium or algal food),the toxicity of heavy metals varies.In the present study we evaluated the effect of cadmium and mercury exposed through medium and via algal food for the rotifer B.rubens.For both the heavy metals,we exposed rotifers via medium containing Chlorella at 0.5×10^(6)cells/ml or fed daily on previously exposed(1,2 and 4 h)alga to the toxicants(using 5 times the value of LC_(50)for B.rubens).For cadmium toxicity through medium,we used 3 toxicant levels(0.1,0.2 and 0.4 mg/L)and for mercury,we used 0.005,0.010 and 0.015 mg/L.Based on the LC_(50),B.rubens was 24 times more sensitive to mercury(0.035±0.002 mg/L)than cadmium.At a concentration of 0.4 mg/L,cadmium through the medium caused increased lag phase of B.rubens.When grown on Chlorella exposed for different durations to cadmium,the rotifer density decreased with the increasing duration of algal exposure to the heavy metal.When mercury was used in the medium or via algal food,the trends in the population growth of B.rubens were similar to those for cadmium.An increase in heavy metal concentration in the medium resulted in a decrease of the rate of population increase per day(r).The r varied from 0.33(in control)to 0.02 d^(-1)(in heavy metal treatment)depending on the mode of exposure though medium or via algal food.

Ultrafast Excited State Dynamics of t^rans-4-Aminoazobenzene Studied by Femtosecond Transient Absorption Spectroscopy

The ultrafast excited state dynamics of trans-4-aminoazobenzene （trans-4-AAB） in ethanol was investigated by femtosecond transient absorption spectroscopy. After being excited to the S2 state by 400 nm, trans-4-AAB decays from the S2 state to the hot S1 state by internal conversion with time constant of -70 fs. The photoisomerization through inversion mechanism on the S1 potential energy surface and the internal conversion from the S1 state to the hot So state are observed, respectively. The average timescale of these two decay pathways is -0.7 ps. And the vibrational cooling of the hot So state of cis- and trans-4- AAB occur with time constants of -4 and N13 ps, respectively. Furthermore, the ultrafast intersystem crossing process are also observed. The timescale of intersystem crossing from the S2 state to the T4 state is about 480 ps while from the S1 state to the T2 state is -180 ps.

The application of a logarithm stretching DMO method in thrust-nappe structure

For strata with complex structure and faulting, the conventional horizontal stack method can not provide a high quality image and the conventional DMO technique has low computational efficiency and practicability. This＇article studies a logarithm stretching DMO method in the time domain to accelerate the computational speed as well as improve the image quality. It also covers the processing of physical model and real data using the logarithm stretching DMO algorithms. The logarithm stretching DMO method can produce reflections from faults and implements the in-phase stack of dipping layers and complicated structures better than the conventional horizontal stack method. So this method has better application to thrust-nappe areas.

Improving homomorphic wavelet estimation by compensating for residual NMO stretching on stack section

Wavelet estimation is a common step in seismic data processing and inversion. Homomorphic wavelet estimation has long utilized as a method that uses a seismic stack section with no phase presumption. Forming a stack section, normal move-out （NMO） correction must be applied on common midpoint （CMP） gathers, although it introduces NMO stretching. After stacking, residual of the NMO stretching may affect the stack section even after muting the highly stretched zone of the NMO corrected CMP gather. Presence of significant residual NMO stretching changes the spectral characteristics of data in time direction, by different degrees. Considering that in homomorphic process the wavelet is estimated based on the spectral characteristics of data, compensating for the residual NMO stretching, can improve the accuracy of the process. Here, we introduce a fast method of calculating the amount of residual NMO stretching and compensating for its effect on wavelet estimation. The proposed method needs limited prestack information like offsets and velocity function and include no prestack processing. We apply the proposed method on synthetic and real datasets and demonstrate the improvement of the estimated wavelet.

Improvement of System Dynamic Precision by Dynamic Prediction

According to the characteristic of the sensor inertia, the dynamic prediction to improve the system dynamic precision is presented in this paper. With the recurrence calculation of time constant of the sensor, the system dynamic precision is greatly improved. The example using this method is given.

Time-dependent Diffusion Coefficient and Conventional Diffusion Constant of Nanoparticles in Polymer Melts by Mode-coupling Theory

Time-dependent diffusion coefficient and conventional diffusion constant are calculated and analyzed to study diffusion of nanoparticles in polymer melts. A generalized Langevin equa- tion is adopted to describe the diffusion dynamics. Mode-coupling theory is employed to calculate the memory kernel of friction. For simplicity, only microscopic terms arising from binary collision and coupling to the solvent density fluctuation are included in the formalism. The equilibrium structural information functions of the polymer nanocomposites required by mode-coupling theory are calculated on the basis of polymer reference interaction site model with Percus-Yevick closure. The effect of nanoparticle size and that of the polymer size are clarified explicitly. The structural functions, the friction kernel, as well as the diffusion coefficient show a rich variety with varying nanoparticle radius and polymer chain length. We find that for small nanoparticles or short chain polymers, the characteristic short time non-Markov diffusion dynamics becomes more prominent, and the diffusion coefficient takes longer time to approach asymptotically the conventional diffusion constant. This constant due to the microscopic contributions will decrease with the increase of nanoparticle size, while increase with polymer size. Furthermore, our result of diffusion constant from mode- coupling theory is compared with the value predicted from the Stokes-Einstein relation. It shows that the microscopic contributions to the diffusion constant are dominant for small nanoparticles or long chain polymers. Inversely, when nanonparticle is big, or polymer chain is short, the hydrodynamic contribution might play a significant role.

Time Varying Gravitational Constant G via Entropic Force

If the uncertainty principle applies to the Verlinde entropic idea, it leads to a new term in the Newton＇s second law of mechanics in the Planck＇s scale. This curious velocity dependent term inspires a frictional feature of the gravity. In this short letter we address that this new term modifies the effective mass and the Newtonian constant as the time dependent quantities. Thus we must have a running on the value of the effective mass on the particle mass m near the holographic screen and the G. This result has a nigh relation with the Dirac hypothesis about the large numbers hypothesis （L.N.H.）. We propose that the corrected entropie terms via Verlinde idea can be brought as a holographic evidence for the authenticity of the Dirac idea.

An Example of Procedure for Simple Identification

The paper represents very simple procedure of identification, based on step response of the process. Results of identification are extended Strejc＇s models （named ZenanX model, models with n equivalent time constants and delay time）. Described mathematically proved equations which show an easy way of filtering and differentiation step response with the help of the data window. It also supports the contention that the point of intersection of tangent to the integrated step response and the X axis represents the sum of time constants and delay time, and showed the method （named ZenoX method） of determining Strej c extended model. For the determination of the impulse response （important for definition of models） are used orthonormal functions （Laguerre）. Simulations are made in the package Matlab. The paper represents results from numerous simulations. The method allows simple and rapid extraction of the Extended Strejc model （ZenanX model）, which is often used to adjust the controllers. Through the simulations of the procedure of removing noise from measured step response is described.

Multi-parameters of Thermal Infrared Remote Sensing Anomalies of the Earthquake

Temporal and spatial anomalies associated with the Yushu earthquake, including the Outgoing Longwave Radiation( OLR), the Land Surface Temperature( LST) and surface temperature from the National Center for Environmental Prediction( NCEP) are studied using thermal infrared remote sensing data in this paper. All results confirmed the previous observations of thermal anomalies in the seismic region prior to this earthquake.Among the multi-parameter anomalies, the underground water temperature anomaly appeared first and lasted for the longest time; OLR anomaly,an infrared parameter which indicates the radiation characteristics of the land surface medium,was the first to be detected; LST anomalies appeared later than OLR. NCEP temperature indicates the average atmosphere temperature with a certain vertical thickness; therefore,it was the last detected anomaly. The anomalies of OLR and LST lasted for a similar time length and were all located in the south or southwest of the epicenter.

Continuous on-line adaptation of the rotor time constant in FOC induction machine system

Rotor time constant is an important parameter for the indirect lleld oraentateO control of mauc- tion motor. Incorrect rotor tittle constant value will cause the flux observer generating a wrong angu- lar orientation of the rotor field. A new approach serves for rotor time constant on-line adaptation by setting the stator current to be zero for a short period. A smooth eorrector is designed to prevent ab- normal detection result from making adaptation. Impact of zero current duration on detection error and rotor speed is analyzed by experiments.