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Roofing is one of the most dangerous jobs in the construction industry. Due to factors such as lack of planning, training and use of precaution, roofing contractors and workers continuously violate the fall protection standards enforced by the US Occupational Safety and Health Administration. A preferable way to alleviate this situation is automating the process of non-compliance checking of safety standards through measurements conducted in site daily accumulated videos and photos. As a key component, the purpose of this paper is to devise a method to detect roofs in site images that is indispensable for such automation process.

This method represents roof objects through image segmentation and visual feature extraction. The visual features include colour, texture, compactness, contrast and the presence of roof corner. A classification algorithm is selected to use the derived representation for statistical learning and detection.

The experiments led to detection accuracy of 97.50 per cent, with over 15 per cent improvement in comparison to conventional classifiers, signifying the effectiveness of the proposed method.

This study did not test on images of roofs in the following conditions: roofs initially built without apparent appearance (e.g. structural roof framing completed and undergoing the sheathing process) and flat, barrel and dome roofs. From a standpoint of construction safety, while the present work is vital, coupling with semantic representation and analysis is still needed to allow for risk analysis of fall violations on roof sites.

This study is the first to address roof detection in site images. Its findings provide a basis to enable semantic representation of roof site objects of interests (e.g. co-existence and correlation among roof site, roofer, guardrail and personal fall arrest system) that is needed to automate the non-compliance checking of safety standards on roof sites.

The purpose of this paper is to investigate the thermal fatigue behavior of a single Sn-3.0Ag-0.5Cu (SAC) lead-free and 63Sn-37Pb (SnPb) solder joint treated by rapidly alternating heating and cooling cycles.

With the application of electromagnetic-induced heating, the specimen was heated and cooled, controlled with a system that uses a fuzzy logic algorithm. The microstructure and morphology of the interface between the solder ball and Cu substrate was observed using scanning electron microscopy. The intermetallic compounds and the solder bump surface were analyzed by energy-dispersive X-ray spectroscopy and X-ray diffraction, respectively.

The experimental results showed that rapid thermal cycling had an evident influence on the surface and interfacial microstructure of a single solder joint. The experiment revealed that microcracks originate and propagate on the superficial oxide of the solder bump after rapid thermal cycling.

Analysis, based on finite element modeling and metal thermal fatigue mechanism, determined that the rimous cracks can be explained by the heat deformation theory and the function of temperature distribution in materials physics.

The purpose of this study is to effectively optimize vehicle lane-changing behavior and alleviate traffic congestion in ramp area through the study of vehicle lane-changing behaviors in upstream segment of ramp areas.

In the upstream segment of ramp areas under a connected vehicle environment, different strategies of vehicle group lane-changing behaviors are modeled to obtain the best group lane-changing strategy. The traffic capacity of roads can be improved by controlling group lane-changing behavior and continuously optimizing lane-changing strategy through connected vehicle technologies. This paper constructs vehicle group lane-changing strategies in upstream segment of ramp areas under a connected vehicle environment. The proposed strategies are simulated by VISSIM.

The results show that different lane-changing strategies are modeled through vehicle group in the upstream segment of ramp areas, which can greatly reduce the delay of ramp areas.

The simulation results verify the validity and rationality of the corresponding vehicle group lane-changing behavior model strategies, effectively standardize the driver's lane-changing behavior, and improve road safety and capacity.

This paper first examines how changes in the real effective exchange rate and its volatility affect the exporting activities of firms. Next, it investigates whether exchange rate volatility (EXRV) affects the export behavior of financially constrained and unconstrained firms differently. Finally, it examines the role of financial development in mitigating the effects of EXRV and financial constraints on firms' exports.

The empirical analysis of the paper is based on a wide panel of Pakistani nonfinancial firms listed at the Pakistan Stock Exchange during the period 2001–2016. To mitigate the problem of endogeneity and to take into account the dynamic nature of the empirical model, the authors apply the robust two-step system-GMM estimator developed by Blundell and Bond (1998). To examine the role of credit constraints, firm-year observations are sorted as financially constrained and unconstrained based on the median value of three alternative measures: the liquidity ratio, the dividend payout ratio and the Whited and Wu (WW) index.

The results reveal that an increase in the real effective exchange rate has a positive and significant impact on firms' exports. However, the results show that the EXRV is significantly and negatively related to exporting decisions, suggesting firms considerably decrease their exports during periods of increased unpredictable variations in exchange rates. The findings also suggest that compared to financially constrained firms, the adverse effect of EXRV on exports is weaker for financially unconstrained firms. This finding implies that firm-level financial constraints unfavorably impact exports by making exporting more sensitive to the EXRV. Finally, the findings indicate that financial development not only positively affects firms' exports but also plays a vital role in declining the adverse effects of EXRV on firm-level exports. Specifically, the results show that financial development decreases the negative impact of EXRV on exports for both financially constrained and unconstrained firms. However, the moderating role of financial sector development is higher for financially unconstrained firms.

Notwithstanding that the authors present robust and strong empirical evidence of the effects of EXRV on exporting and on the role of both firm-level financial constraints and financial sector development in formulating these effects, there are some limitations of the study. The authors use a single proxy for measuring financial sector development. However, one may construct an index for the financial sector developed using principal component analysis (PCA) by considering different measures of financial development. The authors use three different measures of financial constraints. Nonetheless, more sophisticated techniques such as switching regression can be used to endogenously determine whether firms are financially constrained. Moreover, an examination of the asymmetric effects of EXRV on exporting across different industries would also be worthwhile.

From a policy point of view, the results suggest that the development of the financial sector and the strategies to lessen credit constraints faced by firms will help in mitigating the adverse effects of the EXRV on the exporting behavior of firms in Pakistan. The findings also suggest that managers in financially constrained firms should apply appropriate hedging strategies to hedge exchange rate risks. Finally, the findings suggest that investors should take into consideration exchange rate dynamics and firms' financial constraints while investing in exporting firms' stocks.

Since the findings suggest that financially constrained firms' exports are more exposed to EXRV, managers of such exporting firms are suggested to apply effective and suitable currency risk-minimizing hedging instruments for enhancing their exports. The government should also implement economic and financial policies in such a way that they should help in reducing volatilities of exchange rates and in turn, encouraging firms to export more. Definitely, any policy, at both government and firm level, favoring exporting and export-oriented growth will not only help in overcoming the problem of a persistent and wide trade deficit but also help society by providing more employment and investment opportunities.

Recently, Pakistan has experienced significant declines in foreign reserves, persistent political unrest and enlarged trade deficits. All these have increased the uncertainty about the exchange rate. Therefore, it is valuable to know the EXRV effects on firms' exporting activities. Second, Pakistani firms face more financial constraints, and thus, the influence of financial constraints in formulating the volatility effects on exporting would be worth exploring. Finally, no research has yet taken place to scrutinize the role of financial development in mitigating the adverse effects of EXRV and financial constraints on exporting activities. This paper provides firsthand empirical evidence on the role of financial constraints and financial sector development in formulating the EXRV impacts on firm-level exports in Pakistan.