To confirm daily accumulation of visual fatigue induced by work with visual display terminals (VDT), visual evoked potential (VEP), near point distance (NPD) and critical flicker fusion (CFF) were measured in three VDT workers and three sex-and age-matched controls (non-VDT workers) in the morning, noontime and evening for five consecutive days (Monday to Friday), totally 15 times per subject. The workers had been engaged in wireless handling operation, with VDTs, of an unmanned power shovel (Worker 1), an unmanned 78-ton dump truck (Worker 2) and mobile monitor-cameras (Worker 3), for 10 months. Their working hours were about 6.5 hours per day; but, the Worker 2 could take a 10-minute recess (a period without VDT work) per about 30 minutes during working hours. Significant daily variations in the VEP latency, NPD and CFF were found in the Worker 1 or Worker 3 despite the absence of any significant daily or diurnal variations in the non-VDT workers; the trends in the variations were getting worse from Monday to Friday. The NPD in the VDT workers was significantly longer than that in each of the matched controls; also, the CFF in the Workers 1 and 3 was significantly depressed. The changes in the VEP latency from morning to noontime and in the NPD and CFF from noontime to evening were significantly larger in the VDT worker than in the matched control. These findings suggest that VDT work probably affects visual function assessed by the VEP, NPD and CFF. Visual fatigue due to longterm VDT work may tend to be accumulated day by day.Offprint requests to: Prof.

Ikitsuki Bridge is a three span continuous truss bridge with a length of 800 m, which was completed in July, 1991. In December 2009, a crack which seriously damages the safety of the bridge was found in a diagonal member near an intermediate pier during an inspection for determining points to be annually inspected. In order to identify its cause, some tests on the material used for the cracked member were conducted, and a long-term monitoring of wind and vibration of some diagonal members with similar structural characteristics to the cracked member had been carried out since December 2011. In this article, the outline of the crack is presented and the main causes of the crack are discussed based on the results of the tests and monitoring. The conclusions can be summarized as follows: i) The crack initiated and propagated to become approximately 200 mm long as a fatigue crack. The quality of material and weld satisfies the requirement for them. ii) The vibration of the diagonal members is induced by the wind with the velocity of 6-8 m/s and higher than 15 m/s in the direction approximately normal to the bridge longitudinal axis. The maximum stress range induced by the vibration due to 6-8 m/s wind is approximately 30-40 MPa, while that due to the wind blowing at the velocity of over 15 m/s can be 195 MPa. iii) These wind-induced vibrations are thought to be the main cause of the fatigue crack.

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One of the most important sectors in infrastructure development in Laos is road construction. However, many road construction projects in Laos suffer from extensive delays. This causes damage such as recurring problems in the road construction industry, and has a negative effect on the success of road construction projects in terms of schedule, cost, quality, safety and the amenity of road users. The goal of this study is to determine the main causes of these delays and to offer remedies. To identify the causes of delays, a questionnaire is designed by modifying one used to measure causes of delays in road construction projects in the West Bank in Palestine and in consultation with engineering experts with more than 10 years of experience in Laos road construction projects. A total of 53 causes of delay are identified as important in Laos. Questionnaire respondents included 35 contractors, 31 owners and 24 consultants in total. The survey results indicate that the five top factors causing road construction delays are: Contractor cash flow; Delayed payment by owner; Difficulties in financing project by contractor; Financial issues related to owner; and Insufficient equipment and vehicles for the work.

This Letter presents a radio‐frequency energy storage solution for monitoring corrosion on bridge in wireless sensor network system. In this monitoring system, wireless terminals and sensors are installed on the bridges to monitor surface corrosion remotely. The proposed energy storage module to supply power to the sensors consists of a rectifier, a supercapacitor, and a DC–DC boost converter. The rectifier circuit is designed to convert 920 MHz RF energy to DC source. Experimental results demonstrate that the harvested energy can power up the sensor nodes for several times in a week, at input power density of 0.81 μW/cm2.

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