S. Son

The nature and impact of changes in home learning environment on development of language and academic skills in preschool children

In this study, we examined changes in the early home learning environment as children approached school entry and whether these changes predicted the development of childrens language and academic skills. Findings from a national sample of the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (N = 1,018) revealed an overall improvement in the home learning environment from 36 to 54 months of childrens age, with 30.6% of parents of preschoolers displaying significant improvement in the home environment (i.e., changes greater than 1 SD) and with only 0.6% showing a decrease. More important, the degree of change uniquely contributed to the childrens language but not to their academic skills. Home changes were more likely to be observed from mothers with more education and work hours and with fewer symptoms of depression.

The Relationship of Young Children's Motor Skills to Later School Achievement

This study examined empirical evidence about the relationship between motor skills at the beginning of kindergarten and reading and mathematics achievement at the end of first grade, using the Early Childhood Longitudinal Study—Kindergarten cohort national dataset (N = 12,583). Results of hierarchical regression analyses demonstrated that early kindergarten motor skills, especially visual motor skills, add a small but unique amount of variance to achievement in reading and mathematics at the end of first grade even after controlling for Âinitial skills and demographic information. Furthermore, ÂReceiver-Operating-Characteristic curve analyses showed that information from visual motor skills is useful in identifying children at risk for academic underachievement. The results suggest the importance of the role that motor skills can play in designing and implementing an early school achievement battery.

Design and performance of the silicon sensors for the CMS barrel pixel detector

The CMS experiment at the LHC includes a hybrid silicon pixel detector for the reconstruction of charged tracks and of the interaction vertices. The barrel region consists of n-in-n sensors with 100X150 um^2 cell size processed on diffusion oxygenated float zone silicon. A biasing grid is implemented and pixel isolation is achieved with the moderated p-spray technique. An extensive test program was carried out on the H2 beam line of the CERN SPS. In this paper we describe the sensor layout, the beam test setup and the results obtained with both irradiated and non-irradiated prototype devices. Measurements of charge collection, hit detection efficiency, Lorentz angle and spatial resolution are presented.

Silicon sensors development for the CMS pixel system

The CMS experiment will operate at the Large Hadron Collider (LHC). A hybrid pixel detector located close to the interaction region of the colliding beams will provide high resolution tracking and vertex identification which will be crucial for b quark identification. Because of the radiation environment of the LHC, the performance of the sensors must be carefully evaluated up to a fluence of 6 � 10 14 neq cm � 2 . We expect that the sensors will be operated partially depleted during their operation at the LHC and we have implemented an n + on n sensor design. We have irradiated prototype sensors to a dose of 1 � 10 15 neq cm � 2 . We present the results of our testing before and after irradiation.

Simulation of heavily irradiated silicon pixel sensors and comparison with test beam measurements

Charge collection measurements performed on heavily irradiated p-spray DOFZ pixel sensors with a grazing angle hadron beam provide a sensitive determination of the electric field within the detectors. The data are compared with a complete charge transport simulation of the sensor which includes free carrier trapping and charge induction effects. A linearly varying electric field based upon the standard picture of a constant type-inverted effective doping density is inconsistent with the data. A two-trap double junction model implemented in the ISE TCAD software can be tuned to produce a double peak electric field which describes the data reasonably well. The modeled field differs somewhat from previous determinations based upon the transient current technique. The model can also account for the level of charge trapping observed in the data.

Observation, modeling, and temperature dependence of doubly peaked electric fields in irradiated silicon pixel sensors

Abstract We show that doubly peaked electric fields are necessary to describe grazing-angle charge collection measurements of irradiated silicon pixel sensors. A model of irradiated silicon based upon two defect levels with opposite charge states and the trapping of charge carriers can be tuned to produce a good description of the measured charge collection profiles in the fluence range from 0.5 × 10 14 to 5.9 × 10 14 n eq / cm 2 . The model correctly predicts the variation in the profiles as the temperature is changed from - 10 to - 25 ∘ C . The measured charge collection profiles are inconsistent with the linearly varying electric fields predicted by the usual description based upon a uniform effective doping density. This observation calls into question the practice of using effective doping densities to characterize irradiated silicon.

Tests of silicon sensors for the CMS pixel detector

The tracking system of the CMS experiment, currently under construction at the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a silicon pixel detector providing three spacial measurements in its final configuration for tracks produced in high energy pp collisions. In this paper we present the results of test beam measurements performed at CERN on irradiated silicon pixel sensors. Lorentz angle and charge collection efficiency were measured for two sensor designs and at various bias voltages.

Position dependence of charge collection in prototype sensors for the CMS pixel detector

This paper reports on the sensor R&D activity for the CMS pixel detector. Devices featuring several design and technology options have been irradiated up to a proton fluence of 1/spl times/10/sup 15/ n/sub eq//cm/sup 2/ at the CERN PS. Afterward, they were bump bonded to unirradiated readout chips and tested using high energy pions in the H2 beam line of the CERN SPS. The readout chip allows a nonzero suppressed full analogue readout and therefore a good characterization of the sensors in terms of noise and charge collection properties. The position dependence of signal is presented and the differences between the two sensor options are discussed.

Fluence Dependence of Charge Collection of irradiated Pixel Sensors

Abstract The barrel region of the CMS pixel detector will be equipped with “n-in-n” type silicon sensors. They are processed on diffusion oxygenated float zone (DOFZ) material, use the moderated p-spray technique for inter pixel isolation and feature a bias grid. The latter leads to a small fraction of the pixel area to be less sensitive to particles. In order to quantify this inefficiency prototype pixel sensors irradiated to particle fluences between 4.7 × 10 13 and 2.6 × 10 15 n eq / cm 2 have been bump bonded to un-irradiated readout chips and tested using high energy pions at the H2 beam line of the CERN SPS. The readout chip allows a non-zero suppressed analog readout and is therefore well suited to measure the charge collection properties of the sensors. In this paper we discuss the fluence dependence of the collected signal and the particle detection efficiency. Further the position dependence of the efficiency is investigated.

A double junction model of irradiated silicon pixel sensors for LHC

In this paper, we discuss the measurement of charge collection in irradiated silicon pixel sensors and the comparison with a detailed simulation. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. The modeling proves that a doubly peaked electric field generated by the two defect levels is necessary to describe the data and excludes a description based on acceptor defects uniformly distributed across the sensor bulk. In addition, the dependence of trap concentrations upon fluence is established by comparing the measured and simulated profiles at several fluences and bias voltages.