Spray jet penetration and distribution of modulated liquid jets in subsonic cross-flows

Modulated liquid jets injected into subsonic cross-flows are empirically studied by using a mechanical liquid jet modulation apparatus. Experimental investigations were conducted using water over a range of cross-flow velocities from 5 m/s to 143 m/s and with modulated liquid jet frequencies from 35.7 Hz to 166.2 Hz and so on. PDPA(phase Doppler particle anemometry) was employed to measure droplet diameter and velocity with various spray cross-sections from Z/d=20 to Z/d=60. The spray structure, penetration depth, SMD(Sauter mean diameter), volume flux and velocity characteristics of modulated liquid jets injected into cross-flows were examined. As oscillation of the periodic pressure that could make liquid jet moved up and down in cross-flow field, the mixing process was facilitated. This phenomenon has the advantage of mixing the spray concentration from the center area to the outer area. Also, a bulk liquid jet puff was detected in the upper field of the liquid jet surface. The modulation effect appears significant in the extent of the spray oscillation. The correlation equations for the liquid jet boundary of the upper and lower regions which related to the Strouhal number have been presented to predict the spray structure under modulation conditions. Because of the modulation frequency, an inclination of averaged SMD for the structured layer was evanescent which contributed to the promotion of the macroscopic spray mixing process. Cross-sectional characteristics of SMD had the same tendency over a range of various modulation frequencies. As the modulation frequency increased, the region of volume flux distribution also increased.     

Development of methodology and virtual system for optimised simulation of road design data

Current virtual reality (VR) and augmented reality (AR) tools do not lend themselves well to the simulation of non-repetitive activities that could be involved in road construction and heavy civil engineering projects. Therefore it is argued in this paper that specialised functions are required to support the use of VR and AR tools to visually design and simulate such projects. The prime objective of this study is to develop visual design and simulation analysis functions to support optimum road design by extending the applicability of current virtual reality (VR) systems to the design phase of road construction projects. The VR simulation functions developed in this research enable visual inspection of road alignment and earthwork status, simulation of alternative routes, and selection of optimum design route. This study implements a methodology for configuring VR simulation functions and develops a VR system for optimising the road design data. The research results include an improved road design process as a result of the application of the VR functions developed.     

A risk management approach to safety assessment of trenchless technologies for culvert rehabilitation

Proper functioning of culverts is not only critical to protecting the transportation system from flooding but also critical to maintaining the expected service life of the overall transportation system. During the service life of culverts, they deteriorate due to many reasons such as corrosion caused by road salt, blockage by debris and sediment, poor construction techniques, etc. Trenchless technologies have been used by several State Departments of Transportation (DOTs) to rehabilitate deteriorated drainage structures without disrupting the traffic and within a relatively short span of time. These technologies provide many benefits in terms of cost, time, quality, and expected service life. However, the safety aspects of these techniques have not been discussed and documented in detail probably due to the complexity and the lack of safety standards and specifications directly associated with the techniques. This paper discusses the application of a risk assessment framework to assess potential safety issues of currently available trenchless technologies for culvert rehabilitation. The findings of the study will provide additional information to improve the decision making process in selecting and planning culvert rehabilitation projects.     

Performance of the smoke extraction system for fires in the Busan–Geoje immersed tunnel

A new partial smoke extraction system for the Busan–Geoje immersed tunnel was investigated experimentally using simulated tunnel fires. The tests were performed in a 1:20-scale model tunnel with a smoke extraction duct between two traffic tubes. The fire corresponded to a 5-MW full-scale fire, based on Froude modeling. Isothermal and thermal experimental models were considered. The performance of the partial smoke extraction system was quantified under natural and longitudinal ventilation conditions. The results showed that the smoke extraction efficiency of the natural ventilation was 30% better than with longitudinal ventilation, because of smoke stratification in the tunnel. Additionally, the efficiency obtained from the thermal model was comparable to that from the isothermal model under both ventilation conditions. The results suggested that the use of a partial smoke extraction system without longitudinal ventilation improved the initial visibility during tunnel fires.     

Study of impact energy propagation phenomenon and modal characteristics of an armored vehicle undergoing high velocity impact

A new manufacturing technology is being employed to build a new type of armored vehicle. While thick panels are welded together in the old manufacturing technology, relatively thin panels are welded to a frame structure in the new manufacturing technology. The structural integrity of the new type of armor vehicles can be maintained mainly by the frame structures while the panel thickness is reduced significantly to reduce the total vehicle weight. Since the dynamic characteristics of a frame-panel hybrid structure are different from those of the old type of structure which consists of only thick panels, they should be identified to achieve a good performance of the vehicle. For this purpose, a proper FE model of the hybrid type of structure needs to be developed. In the present study, FE models are proposed to represent the frame-panel hybrid type structure efficiently. The impact energy propagation, the transient response and the modal characteristics are investigated with the FE models. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong-Hee Yoo received a B.S. and M.S. degree in Mechanical Engineering from Seoul National University in 1980 and 1982. He then went on to receive his Ph.D. degree from Michigan State University in 1989. Dr. Yoo is currently a Professor at the School of Mechanical Engineering at Hanyang University in Seoul, Korea. His research interests are in the area of Flexible body dynamics, vibration.     

Interactive tree modeling and deformation with collision detection and avoidance

We present an interactive tree modeling and deformation system that supports an efficient collision detection and avoidance using a bounding volume hierarchy of sweep surfaces. Starting with conventional tree models (given as meshes), we convert them into sweep surfaces and deform their branches interactively while detecting and avoiding collisions with many other branches. Multiple tree models (sharing the same topology) can be generated with great ease using this sweep‐based approach, and they can serve as a basis for the generation of a multiparameter family of trees. We demonstrate the effectiveness of our approach in an automatic generation of similar trees, the colonization of trees to form a forest, and the tree growth, aging, and withering simulations. Copyright © 2015 John Wiley & Sons, Ltd.     

Disparities in exploitative and exploratory patenting performance across regions: Focusing on the roles of agglomeration externalities

We try to identify the determinants of regional variation in both exploitative and exploratory innovative competencies. Hereby, we focus on how a knowledge-creation mechanism with specialized externalities differs from one with diversified externalities. Innovative competence in the US is measured by local patenting performance; exploitative and exploratory patenting performances are distinguished by the degree of backward citation. Based on the extended knowledge-production function, including the two agglomeration externalities, our findings show that specialized externalities are associated with exploitation, while diversified externalities are positively related with both exploration and exploitation, regardless of industrial sectors.