Correction to: Acquisition of Stop Consonants in Mandarin-Japanese Early Bilingual Children.

The original version of the article unfortunately contained an error in Acknowledgement section.

Acquisition of Stop Consonants in Mandarin-Japanese Early Bilingual Children.

This study examines the nature of stop accuracy and substitute patterns of word-initial Japanese and Mandarin stops produced by Mandarin-Japanese bilingual children. The purpose of the study is to understand phonological development in bilinguals. The sample consists of 36 bilingual children between the ages of three and six, who simultaneously acquired Japanese and Mandarin from birth. The results were as follows: (1) most of the bilingual children were able to produce Mandarin and Japanese stops by the age of three and the accuracy of the target stops were found to develop with age; (2) the age of developing the target consonants is slightly different in the two languages; (3) substitution patterns observed in each language reveals a mixture of child-specific patterns, language specific systems and language influence as well as individual differences. These findings indicate that Mandarin-Japanese bilingual children possess a unique phonological development system, which is a monolinguallike pattern with cross-linguistic interaction. These results constitute a new body of descriptive reference materials documenting the phonological development of bilingual children for speech therapists or pathologists.

Development of potential methods for testing congestion control algorithm implemented in vehicle-to-vehicle communications.

OBJECTIVE: A channel congestion problem might occur when the traffic density increases because the number of basic safety messages carried on the communication channel also increases in vehicle-to-vehicle communications. A remedy algorithm proposed in SAE J2945/1 is designed to address the channel congestion issue by decreasing transmission frequency and radiated power. This study is to develop potential test procedures for evaluating or validating the congestion control algorithm. METHODS: Simulations of a reference unit transmitting at a higher frequency are implemented to emulate a number of onboard equipment (OBE) transmitting at the normal interval of 100 ms (10 Hz). When the transmitting interval is reduced to 1.25 ms (800 Hz), the reference unit emulates 80 vehicles transmitting at 10 Hz. By increasing the number of reference units transmitting at 800 Hz in the simulations, the corresponding channel busy percentages are obtained. An algorithm for Global Positioning System (GPS) data generation of virtual vehicles is developed for facilitating the validation of transmission intervals in the congestion control algorithm. RESULTS: Channel busy percentage is the channel busy time over a specified period of time. Three or 4 reference units are needed to generate channel busy percentages between 50 and 80%, and 5 reference units can generate channel busy percentages above 80%. The proposed test procedures can verify the operation of congestion control algorithm when channel busy percentages are between 50 and 80% and above 80%. By using a GPS data generation algorithm, the test procedures can also verify the transmission intervals when traffic densities are 80 and 200 vehicles in a radius of 100 m. A suite of test tools with functional requirements is also proposed for facilitating the implementation of test procedures. CONCLUSIONS: The potential test procedures for a congestion control algorithm are developed based on the simulation results of channel busy percentage and the GPS data generation algorithm. The test tools can examine the requirement compliance automatically and objectively. The required number of reference units should be further validated using real OBEs before implementing these potential test procedures.

Sensitivity analyses of stopping distance for connected vehicles at active highway-rail grade crossings.

This paper performs sensitivity analyses of stopping distance for connected vehicles (CVs) at active highway-rail grade crossings (HRGCs). Stopping distance is the major safety factor at active HRGCs. A sensitivity analysis is performed for each variable in the function of stopping distance. The formulation of stopping distance treats each variable as a probability density function for implementing Monte Carlo simulations. The result of the sensitivity analysis shows that the initial speed is the most sensitive factor to stopping distances of CVs and non-CVs. The safety of CVs can be further improved by the early provision of onboard train information and warnings to reduce the initial speeds.