Using a Projection IRT Method for Vertical Scaling When Construct Shift Is Present

2020 ◽  
Author(s):  
Tyler Strachan ◽  
Uk Hyun Cho ◽  
Kyung Yong Kim ◽  
John T. Willse ◽  
Shyh‐Huei Chen ◽  
...  
Keyword(s):  
Vertical Scaling ◽  
Construct Shift

scholarly journals Exploring the Full-Information Bifactor Model in Vertical Scaling With Construct Shift

2012 ◽  
Vol 36 (1) ◽  
pp. 3-20 ◽  
Author(s):  
Ying Li ◽  
Robert W. Lissitz
Keyword(s):  
Real Data ◽  
Bifactor Model ◽  
Vertical Scaling ◽  
Estimation Accuracy ◽  
Parameter Estimates ◽  
Bifactor Models ◽  
The Common ◽  
Construct Shift ◽  
Common Items ◽  
Discrimination Parameter

To address the lack of attention to construct shift in item response theory (IRT) vertical scaling, a multigroup, bifactor model was proposed to model the common dimension for all grades and the grade-specific dimensions. Bifactor model estimation accuracy was evaluated through a simulation study with manipulated factors of percentage of common items, sample size, and degree of construct shift. In addition, the unidimensional IRT (UIRT) model, which ignores construct shift, was also estimated to represent current practice. It was found that (a) bifactor models were well recovered overall, though the grade-specific dimensions were not as well recovered as the general dimension; (b) item discrimination parameter estimates were overestimated in UIRT models due to the effect of construct shift; (c) the person parameters of UIRT models were less accurately estimated than those of bifactor models; (d) group mean parameter estimates from UIRT models were less accurate than those of bifactor models; and (e) a large effect due to construct shift was found for the group mean parameter estimates of UIRT models. A real data analysis provided an illustration of how bifactor models can be applied to problems involving vertical scaling with construct shift. General procedures for testing practice were recommended and discussed.

Dynamic Horizontal and Vertical Scaling for Multi-tier Web Applications

2019 ◽  
pp. -1--1
Author(s):  
Abid Nisar ◽  
Waheed Iqbal ◽  
Fawaz Bokhari ◽  
Faisal Bukhari ◽  
Khaled Almustafa
Keyword(s):  
Web Applications ◽  
Vertical Scaling

scholarly journals Correcting for Static Shift of Magnetotelluric Data with Airborne Electromagnetic Measurements: A Case Study from Rathlin Basin, Northern Ireland

2016 ◽  
Author(s):  
Robert Delhaye ◽  
Volker Rath ◽  
Alan G. Jones ◽  
Mark R. Muller ◽  
Derek Reay
Keyword(s):  
Distortion Correction ◽  
Vertical Scaling ◽  
Spatial Density ◽  
Target Area ◽  
Resistivity Structure ◽  
Static Shift ◽  
Magnetotelluric Data ◽  
Archie’S Law ◽  
Order Of Magnitude ◽  
Resistivity Variation

Abstract. Galvanic distortions of magnetotelluric (MT) data, such as the static shift effect, are a known problem that can lead to incorrect estimation of resistivities and erroneous modelling of geometries with resulting misinterpretation of subsurface electrical resistivity structure. A wide variety of approaches have been proposed to account for these galvanic distortions, some depending on the target area, with varying degrees of success. The natural laboratory for our study is a hydraulically permeable volume of conductive sediment at depth, the internal resistivity structure of which can be used to estimate reservoir viability for geothermal purposes, however static shift correction is required in order to ensure robust and precise modelling accuracy. We propose a method employing frequency–domain electromagnetic data for static shift correction, which in our case are regionally available with high spatial density. The spatial distributions of the derived static shift corrections are analysed and applied to the uncorrected MT data prior to inversion. Two comparative inversion models are derived, one with and one without static shift corrections, with instructive results. As expected from the one–dimensional analogy of static shift correction, at shallow model depths, where the structure is controlled by a single local MT site, the correction of static shift effects leads to vertical scaling of resistivity-thickness products in the model, with the corrected model showing improved correlation to existing borehole wireline resistivity data. In turn, as these vertical scalings are effectively independent of adjacent sites, lateral resistivity distributions are also affected, with up to half a decade of resistivity variation between the models estimated at depths down to 2000 m. Simple estimation of differences in bulk porosity, derived using Archie’s Law, between the two models reinforces our conclusion that the sub–order of magnitude resistivity contrasts induced by correction of static shifts correspond to similar contrasts in estimated porosities, and hence, for purposes of reservoir investigation or similar cases requiring accurate absolute resistivity estimates, galvanic distortion correction, especially static shift correction, is essential.

VERTICAL SCALING OF TYPE I InP HBT WITH FT > 500 GHZ

2004 ◽  
Vol 14 (03) ◽  
pp. 625-631 ◽  
Author(s):  
J. W. LAI ◽  
W. HAFEZ ◽  
M. FENG
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
High Speed ◽  
Impact Ionization ◽  
Cutoff Frequency ◽  
Current Gain ◽  
Vertical Scaling ◽  
Physical Parameters ◽  
Type I ◽  
Peak Current Density ◽  
Rf Performance

We have fabricated the high-speed InP/InGaAs -based single heterojunction bipolar transistors (SHBTs) with current gain cutoff frequency, fT from 166GHz to over 500GHz by the approach of vertical scaling. Collector thickness is reduced from 3000Å to 750Å and the peak current density is increased up to 1300kA/cm2. In this paper, device rf performance has been compared with respect to materials with different vertical dimensions. The scaling limitation is also studied by analytical approach. The extracted physical parameters suggest that the parasitic emitter resistance is the major limit on further enhancing ultra-scaled HBT intrinsic speed due to the associated RECBC delay. The cut-off frequency of a 500Å collector SHBT has been measured and the results indicate a dramatic drop on fT, supporting the conclusion projected by model analysis. It is also commented that for deeply downscaled HBTs, impact ionization could be another degrading mechanism limits device bandwidth.

scholarly journals Fractal interpolation surfaces with function vertical scaling factors

2012 ◽  
Vol 25 (11) ◽  
pp. 1896-1900 ◽  
Author(s):  
Zhigang Feng ◽  
Yizhuo Feng ◽  
Zhenyou Yuan
Keyword(s):  
Vertical Scaling ◽  
Fractal Interpolation ◽  
Scaling Factors

FRACTAL INTERPOLATION SURFACES ON RECTANGULAR GRIDS

2015 ◽  
Vol 91 (3) ◽  
pp. 435-446 ◽  
Author(s):  
HUO-JUN RUAN ◽  
QIANG XU
Keyword(s):  
General Framework ◽  
Vertical Scaling ◽  
Fractal Interpolation ◽  
Scaling Factors ◽  
Rectangular Grids

In this paper, we present a general framework to construct fractal interpolation surfaces (FISs) on rectangular grids. Then we introduce bilinear FISs, which can be defined without any restriction on interpolation points and vertical scaling factors.

Sign in / Sign up

Export Citation Format

Share Document