Observer-Identification: A Potential Threat to the Validity of Self-Identified Race and Ethnicity

The federal government mandates that school personnel select race and ethnicity identifiers for students who do not provide that information. This process is called “observer identification,” and it poses a potential threat to the validity of self-identified race/ethnicity data because (a) evidence from other fields suggests that about 40% of the time, observer identification does not match self-identification of some of the fastest growing racial/ethnic groups in the K–12 population; (b) state and local guidelines for observer identification vary greatly; and (c) the Department of Education does not record how often observer identification is used, but there is good reason to suspect that the practice is widespread.

Sensorless Control for Joint Drive Unit of Lower Extremity Exoskeleton with Cascade Feedback Observer

In this paper, a sensorless control method for joint drive unit driven by BLDC motor of low extremity exoskeleton, cascade feedback observer identification method, is proposed. The cascade feedback observer identification method is based on improved Integral-Switching-Function Sliding-Mode-Observer (ISF-SMO) and adaptive FIR filter. The improved Integral-Switching-Function Sliding-Mode-Observer is used to identify the back-EMF of motor. The sliding mode surface redesigned according to Integral-Switching-Function (ISF) eliminates the inevitable chattering problem in conventional Sliding-Mode-Observer (SMO). The stability condition of Integral-Switching-Function Sliding-Mode-Observer is obtained with Lyapunov function. Meanwhile, considering the estimation error and system instability caused by the mismatch between the actual resistance value (Rs) and the set resistance value, the LMS algorithm is used to estimate the resistance value online according to the structure of adaptive FIR filter. When system is running, the modified Integral-Switching-Function Sliding-Mode-Observer and adaptive FIR filter are used to modify the back-EMF and the resistance value by cascading feedback relation, and the modified back-EMF value is taken as the final output of the system. Because of considering the uncertainty of resistance caused by temperature variation, the robustness and stability of the cascade feedback observer can be improved. Meanwhile, higher estimation accuracy is obtained, and operation range of sensorless control is extended, which is suitable for motor in low speed region. Finally, the correctness and validity of the proposed method are verified by simulations and experiments.

An outside view: What do observers say about others’ races and Hispanic origins?

Outsiders’ views of a person’s race or Hispanic origin can impact how she sees herself, how she reports her race and Hispanic origins, and her social and economic experiences. The way outsiders describe non-strangers in terms of their race and Hispanic origin may reveal popular assumptions about which race/Hispanic categories are salient for Americans, which kinds of people are seen as multiracial, and the types of cues people use when identifying another person’s race. We study patterns of observer identification using a unique, large, linked data source with two measures of a person’s race and Hispanic origin. One measure (from Census 2000 or the 2010 Census) was provided by a household respondent and the other (from the other census year) was provided by a census proxy reporter (e.g., a neighbor) who responded on behalf of a non-responsive household. We ask: Does an outsider’s report of a person’s race and Hispanic origin match a household report? We find that in about 90% of our 3.7 million (nonrepresentative) cases, proxy reports of a person’s race and Hispanic origin match responses given by the household in a different census year. Match rates are high for the largest groups: non-Hispanic whites, blacks, and Asians and for Hispanics, though proxies are not very able to replicate the race responses of Hispanics. Matches are much less common for people in smaller groups (American Indian/Alaska Native, Pacific Islander, Some Other Race, and multiracial). We also ask: What predicts a matched response and what predicts a particular unmatched response? We find evidence of the persistence of hypodescent for blacks and hyperdescent for American Indians. Biracial Asian-whites and Pacific Islander-whites are more often seen by others as non-Hispanic white than as people of color. Proxy reporters tend to identify children as multiple race and elders as single race, whether they are or not. The race/Hispanic composition of the tract is more powerfully predictive of a particular unmatched response than are tract-level measures of socioeconomic status; unmatched responses are often consistent with the race/Hispanic characteristics of the neighborhood.