Correlation method estimation of the modulation signal in the weak equivalence principle test

In a test of the weak equivalence principle （WEP） with a rotating torsion pendulum, it is important to estimate the amplitude of the modulation signal with high precision. We use a torsional filter to remove the free oscillation signal and employ the correlation method to estimate the amplitude of the modulation signal. The data analysis of an experiment shows that the uncertainties of amplitude components of the modulation signal obtained by the correlation method are in agreement with those due to white noise. The power spectral density of the modulation signal obtained by the correlation method is about one order higher than the thermal noise limit. It indicates that the correlation method is an effective way to estimate the amplitude of the modulation signal and it is instructive to conduct a high-accuracy WEP test.

Effect of gravity gradient in weak equivalence principle test

A high accuracy test of the weak equivalence principle（WEP） is of great scientific significance no matter whether its result is positive. We analyze the gravity gradient effect which is a main systematic error source in the test of WEP.The result shows that the uncompensated gravity gradient effect from the coupling term of the dominated gravity gradient multipole moment component q_（21） and the relative multipole field component Q_（21） contributes to an uncertainty of 1×10^（-11） on the E otv os parameter. We make a Q_（21） compensation to reduce the effect by about 20 times, and the limit of the test precision due to this coupling is improved to a level of a part in 10^（13）.

Suppression of Coriolis error in weak equivalence principle test using ^85Rb-^87Rb dual-species atom interferometer

Coriolis effect is an important error source in the weak equivalence principle(WEP)test using atom interferometer.In this paper,the problem of Coriolis error in WEP test is studied theoretically and experimentally.In theoretical simulation,the Coriolis effect is analyzed by establishing an error model.The measurement errors of Eotvos coefficient(η)in WEP test related to experimental parameters,such as horizontal-velocity difference and horizontal-position difference of atomic clouds,horizontal-position difference of detectors,and rotation compensation of Raman laser’s mirror are calculated.In experimental investigation,the position difference between^85Rb and^87Rb atomic clouds is reduced to 0.1 mm by optimizing the experimental parameters,an alternating detection method is used to suppress the error caused by detection position difference,thus the Coriolis error related to the atomic clouds and detectors is reduced to 1.1 × 10^-9.This Coriolis error is further corrected by com pensating the rotation of Raman laser's mirror,and the total uncertainty o f rj measurement related to the Coriolis effect is reduced as δη=4.4 × 10^-11.

Design and Evaluation of a Differential Accelerometer for Drop-Tower Equivalence Principle Test with Rotating Masses

A differential accelerometer comprising of two rotating masses made of the same material is proposed for drop tower-based free-fall testing of the spin-spin force between the rotating mass and the Earth. The measurement is performed by placing the two concentric masses of very different momenta in a vacuum drop capsule which is falling freely in the Earth＇s gravitational field. A nonzero output of the differential aeeelerometer is an indication of possible violation of new equivalence principle （NEP）. We present the conceptual design of a modified free-fall NEP experiment which can be performed at the Belting drop tower. Design and evaluation of the differential accelerometer with a hybrid electrostatic/magnetic suspension system are presented to accommodate for operation on ground and drop-tower tests. Details specific to the measurement uncertainty are discussed to yield an NEP test accuracy of 7.2×10^-9.

Load Reduction Test Method of Similarity Theory and BP Neural Networks of Large Cranes

Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solve the loading problems of large-tonnage cranes during testing, an equivalency test is proposed based on the similarity theory and BP neural networks. The maximum stress and displacement of a large bridge crane is tested in small loads, combined with the training neural network of a similar structure crane through stress and displacement data which is collected by a physics simulation progressively loaded to a static load test load within the material scope of work. The maximum stress and displacement of a crane under a static load test load can be predicted through the relationship of stress, displacement, and load. By measuring the stress and displacement of small tonnage weights, the stress and displacement of large loads can be predicted, such as the maximum load capacity, which is 1.25 times the rated capacity. Experimental study shows that the load reduction test method can reflect the lift capacity of large bridge cranes. The load shedding predictive analysis for Sanxia 1200 t bridge crane test data indicates that when the load is 1.25 times the rated lifting capacity, the predicted displacement and actual displacement error is zero. The method solves the problem that lifting capacities are difficult to obtain and testing accidents are easily possible when 1.25 times related weight loads are tested for large tonnage cranes.

Optimum design of equivalent accelerated life testing plans based on proportional hazards-proportional odds model

The optimum design of equivalent accelerated life testing plan based on proportional hazards-proportional odds model using D-optimality is presented. The defined equivalent test plan is the test plan that has the same value of the determinant of Fisher information matrix. The equivalent test plan of step stress accelerated life testing （SSALT） to a baseline optimum constant stress accelerated life testing （CSALT） plan is obtained by adjusting the censoring time of SSALT and solving the optimization problem for each case to achieve the same value of the determinant of Fisher information matrix as in the baseline optimum CSALT plan. Numer- ical examples are given finally which demonstrate the equivalent SSALT plan to the baseline optimum CSALT plan reduces almost half of the test time while achieving approximately the same estimation errors of model parameters.

Analysing the quality of Swiss National Forest Inventory measurements of woody species richness

Background: Under ongoing climate and land-use change, biodiversity is continuously decreasing and monitoring biodiversity is becoming increasingly important. National Forest Inventory(NFI) programmes provide valuable timeseries data on biodiversity and thus contribute to assessments of the state and trends in biodiversity, as well as ecosystem functioning. Data quality in this context is of paramount relevance, particularly for ensuring a meaningful interpretation of changes. The Swiss NFI revisits about 8%–10% of its sample plots regularly in repeat surveys to supervise the quality of fieldwork.Methods: We analysed the relevance of observer bias with equivalence tests, examined data quality objectives defined by the Swiss NFI instructors, and calculated the pseudo-turnover(PT) of species composition, that is, the percentage of species not observed by both teams. Three attributes of woody species richness from the latest Swiss NFI cycles(3 and 4) were analysed: occurrence of small tree and shrub species(1) on the sample plot and(2) at the forest edge, and(3) main shrub and trees species in the upper storey.Results: We found equivalent results between regular and repeat surveys for all attributes. Data quality, however,was significantly below expectations in all cases, that is, as much as 20%–30% below the expected data quality limit of 70%–80%(proportion of observations that should not deviate from a predefined threshold). PT values were about 10%–20%, and the PT of two out of three attributes decreased significantly in NFI4. This type of uncertainty –typically caused by a mixture of overlooking and misidentifying species – should be considered carefully when interpreting change figures on species richness estimates from NFI data.Conclusions: Our results provide important information on the data quality achieved in Swiss NFIs in terms of the reproducibility of the collected data. The three applied approaches proved to be effective for evaluating the quality of plot-level species richness and composition data in forest inventories and other biodiversity monitoring programmes. As such, they could also be recommended for assessing the quality of biodiversity indices derived from monitoring data.

Analysis of Operational Characteristics and Equivalent Test Method for IGBTs in MMC

A design methodology and a feasible equivalent circuit are proposed to test the reliability of insulated gate bipolar transistors(IGBT)in actual modular multilevel converter(MMC)conditions,which is impossible for existing IGBT test platforms due to unexplicit equivalent indexes and low reliability of test platforms.Characteristics of IGBT devices are extracted during MMC operation,and turn-off transient and effective current are highlighted as key indexes for the equivalent test.A feasible equivalent timing diagram and a corresponding test circuit are proposed,as well as the circuit's operation concept.The proposed equivalent test method is verified by a back-to-back experiment with twenty-four submodules,and results indicate the proposed method has good equivalence.Between the proposed circuit waveform and the back-to-back experiment waveform,all indexes have errors of less than 5.9%.Furthermore,the proposed circuit components have losses less than 0.7 times those of the device under test,making them reliable and suitable for long-term operation tests for IGBT devices in MMC.Index Terms-Equivalent test,IGBT,MMC,reliability.