Negative Phase Time Effectin Potential-Well Passing

The properties of phase time taken for particles to pass through a quantum potential well are investigated. It is found in a 1 dimensional quantum mechanical problem that the phase time is negative when the incident energy and the thickness of potential well satisfy certain conditions. Similar results are also found in a 2 dimensional fully relativistic optical analog. It is shown that the expression of the la teral shift of transmitted optical waves is similar to that of the phase time in the 1 dimensional quantum mechanical problem. The phase time in the 2 dimensional optical problem is also shown to be negative under certain conditions.

Residential Parking Service Model Based on Resource Sharing

Aiming at solving pressing parking issues in the urban environment, a residential parking spaces sharing model was proposed in this study. In this model, firstly, the residential community pattern, the status of idle parking spaces, and the temporal and spatial characteristics of sharing parking had been analyzed. Next,in the convenience of modeling,medical institutions that have the most prominent parking problems were selected as the subject of study. Based on the K-S statistical analysis results and the actual parking sharing situation,it was observed that the residential parking sharing time satisfied the shifted negative exponential distribution( SNED). Finally,a probability model of shared service capacity based on the SNED and critical time condition was established. By applying the statistical analysis method,the time of vehicles passing in and out of parking spaces, the idle time of parking spaces, the shifted distribution parameters, and other important model parameters had been calibrated,which was leading to the algorithm of model. In addition,considering the feasibility of model without sufficient data,the vehicle travel probability,the stagnation rate of parking space,and the status of parking spaces were defined and the reference data were also provided. The results of case studies indicate that it is very promising to solve urban parking issues if the residential community shares its rich parking resources with adjacent commercial buildings.

Methyl Group in Isocopalane Derivative Showed an Unusual Negative 1H NMR Chemical Shift

An unusual negative 1H NMR chemical shift of methyl group was discovered in condensation product of isoco-palane diterpenoid with p-toluenesulfonyl hydrazide.2D NMR,computational studies and single-crystal X-ray dif-fraction analysis showed that the C-20 methyl group was shielded.