Cumulative sum analysis score and phacoemulsification competency learning curve

AIM： To use the cumulative sum analysis score（CUSUM） to construct objectively the learning curve of phacoemulsification competency.METHODS： Three second-year residents and an experienced consultant were monitored for a series of 70 phacoemulsification cases each and had their series analysed by CUSUM regarding posterior capsule rupture（PCR） and best-corrected visual acuity. The acceptable rate for PCR was 〈5%（lower limit h） and the unacceptable rate was 〉10%（upper limit h）. The acceptable rate for bestcorrected visual acuity worse than 20/40 was 〈10%（lower limit h） and the unacceptable rate was 〉20%（upper limit h）. The area between lower limit h and upper limit h is called the decision interval. RESULTS： There was no statistically significant difference in the mean age, sex or cataract grades between groups. The first trainee achieved PCR CUSUM competency at his 22 nd case. His best-corrected visual acuity CUSUM was in the decision interval from his third case and stayed there until the end, never reaching competency. The second trainee achieved PCR CUSUM competency at his 39^ th case. He could reach best-corrected visual acuity CUSUM competency at his 22 ^nd case. The third trainee achieved PCR CUSUM competency at his 41 st case. He reached bestcorrected visual acuity CUSUM competency at his 14 ^th case.CONCLUSION： The learning curve of competency in phacoemulsification is constructed by CUSUM and in average took 38 cases for each trainee to achieve it.

Method of the left-turning bus priority at intersections based on a variable lane

To reduce the delay of left-turning buses and improve the traffic efficiency at signalized intersections,a novel variable bus approach lane(VBAL)control method based on bus pre-signals is proposed.This method combines the variable lane with the bus priority pre-signal,and realizes the left-turning bus priority without causing great impact on other vehicles.To validate the effectiveness of the method,the VBAL scheme was compared with the single left-turn lane scheme(SLTL)and the double left-turn lane scheme(DLTL).On this basis,the delay change calculation model of left-turning buses and through vehicles were established by the cumulative curve graphic method.The influence of vehicle proportion and green split on the model was studied through sensitivity analysis.The results show that VBAL can reduce the delay of left-turning bus and the increase of through vehicle delay to the greatest extent.Finally,the scheme was applied to a real-world intersection,and the results demonstrate the effectiveness and advantage of the VBAL scheme.

The Effect of Water Saving and Production Increment by Drip Irrigation Schedules

Drip irrigation system can achieve high uniformity. When the system is designed for uniformity coefficient equal or more than 70%, the water application in the field can be expressed as a normal distribution and further simplified to a linear distribution. This paper will describe the irrigation scheduling parameters, percent of deficit, application efficiency and coefficient of variation by simple mathematical model. Using this effective model and the irrigation application, the total yield affected by the total water application for different uniformity of irrigation application can be determined. More over, this paper uses the cost of water, price of yield, uniformity of the drip irrigation system, crop response to water application and environmental concerns of pollution and contamination to determine the optimal irrigation schedule. A case study shows that the optimal irrigation schedule can achieve the effect of water saving and production increment compared with the conventional irrigation schedule in which the whole field is fully irrigated. Key words drip irrigation - linear cumulative frequency curve - optimal irrigation schedule - water saving - production increment CLC number TV 139.1 Foundation item: Supported by the National Natural Science Foundation of China (59379407)Biography: QIU Yuan-feng (1973-), male, Ph. D, research direction: water saving irrigation theory and techniques.

Delays caused by motorized vehicles unable to clear intersections in China: Graphical analysis

In many Chinese cities,motorized vehicles （M-vehicles） move slowly at intersections due to the interference of a large number of non-motorized vehicles （NM-vehicles）.The slow movement makes a part of M-vehicles fail to leave intersections timely after the traffic signal tums red,and thereby conflicts between vehicles from two directions occur.The phenomenon was analyzed graphically by using the cumulative vehicle curve.Delays in three cases were modeled and compared：NM-vehicle priorities and M-vehicle priorities with all-red intervals unable to release all vehicles,and longer all-red intervals ensuring release all vehicles.Marginal delays caused by two illegal behaviors that occasionally happened in mixed traffic intersections were also investigated.It is concluded that increasing the speed of M-vehicles leaving intersections and postponing the entering of NM-vehicles are the keys in mathematics,although they are uneasy in disordered mixed traffic intersections due to a dilemma between efficiency and orders in reality.The results could provide implications for the traffic management in the cities maintaining a large number of M-and NM-vehicles.

A modification of local path marginal cost on the dynamic traffic network

Path marginal cost （PMC） is the change in totaltravel cost for flow on the network that arises when timedependentpath flow changes by 1 unit. Because it is hardto obtain the marginal cost on all the links, the local PMC,considering marginal cost of partial links, is normallycalculated to approximate the global PMC. When analyzingthe marginal cost at a congested diverge intersection, ajump-point phenomenon may occur. It manifests as alikelihood that a vehicle may unsteadily lift up （down） inthe cumulative flow curve of the downstream links. Previously,the jump-point caused delay was ignored whencalculating the local PMC. This article proposes an analyticalmethod to solve this delay which can contribute toobtaining a more accurate local PMC. Next to that, we usea simple case to calculate the previously local PMC and themodified one. The test shows a large gap between them,which means that this delay should not be omitted in thelocal PMC calculation.

Baseline establishment for metals in the western Clarion-Clipperton Zone

Resource exploitation in the Clarion-Clipperton Zone(CCZ)is of major research interest worldwide,but its influence on the environment is poorly understood,especially due to the lack of baseline values for metals in the surrounding sediment.This work aimed to establish the baseline values of 17 metals(Ba,Ca,K,Mg,Mn,Na,Ag,As,B,Cd,Co,Cr,Cu,Hg,Ni,Pb,and Zn)using normalization,the cumulative frequency curve method considering a total of 172 samples taken from 8 multitube cores and 1 box sediment core collected in the western CCZ during the COMRA-45 cruise campaign from August to September 2017.The baseline values of the evaluated metals were as follows:1932 mg/kg for Ba,29512 mg/kg for Ca,18150 mg/kg for K,17120 mg/kg for Mg,6747 mg/kg for Mn,28546 mg/kg for Na,0.571 mg/kg for Ag,5.00 mg/kg for As,94.4 mg/kg for B,0.626 mg/kg for Cd,104 mg/kg for Co,76.1 mg/kg for Cr,370 mg/kg for Cu,0.028 mg/kg for Hg,190 mg/kg for Ni,27.5 mg/kg for Pb and 156 mg/kg for Zn.Our findings would fill the baseline value gap in the study area and further improve accuracy of environmental impact assessments on the impact of resource exploitation.

Analysis of delay variability at isolated signalized intersections

On urban arterials,travel time variability is largely dependent on the variability in the delays vehicles experience at signalized intersections.The interpretation of delay evolvement at intersections will give a comprehensive insight into arterial travel time variability and provide more possibilities for travel time estimation.Accordingly,an analytical model is proposed to study delay variability at isolated,fixed-time controlled intersections.Classic cumulative curves are utilized to derive average delay(per cycle) formulas by assuming a deterministic overflow queue.Then,an analogy with the Markov chain process is made to clarify the mechanism of stochastic delays and overflow queues at signalized intersections.It was found that,in undersaturated cases,the shape of the delay distribution changes very little over time,whereas for saturated and oversaturated cases the delay distribution is time-dependent and becomes flatter with an increasing number of cycles.The analysis of arrival distributions,e.g.,Poisson and binomial,produces the conclusion that the variability of arrivals has a significant effect on delay estimates in both undersaturated and oversaturated conditions.A larger variance of arrival flow results in a larger variance of delay distribution.All of these analyses can help road authorities to gain insights into arterial travel time variability.