Supersonic Nozzle Flow Simulations for Particle Coating Applications: Effects of Shockwaves,Nozzle Geometry,Ambient Pressure,and Substrate Location upon Flow Characteristics

Characteristics of supersonic flow are examined with specific regard to nano-particle thin-film coating. Effects of shockwaves, nozzle geometry, chamber pressure, and substrate location were studied computationally. Shockwaves are minimized to reduce fluctuations in flow properties at the discontinuities across diamond shock structures. Nozzle geometry was adjusted to ensure optimal expansion (i.e., P _exit = P _ambient), where shock formation was significantly reduced and flow kinetic energy maximized. When the ambient pressure was reduced from 1 to 0.01316 bar, the nozzle’s diverging angle must be increased to yield the optimum condition of minimized adversed effects. Beyond some critical distance, substrate location did not seem to be a sensitive parameter on flow characteristics when P _amb = 0.01316 bar; however, overly close proximity to the nozzle exit caused flow disturbances inside the nozzle, thereby adversely affecting coating gas flow.     

Structural dynamic displacement vision system using digital image processing

This study introduces dynamic displacement vision system (DDVS), which is applicable for imaging unapproachable structures using a hand-held digital video camcorder and is more economical than the existing contact and contactless measurement methods of dynamic displacement and deformation. This proposed DDVS method is applied to the Region of Interest (ROI) resizing and coefficient updating at each time step to improve the accuracy of the measurement from the digital image. Thus, after evaluating the algorithms conducted in this study by the static and dynamic verification, the measurement's usability by calculating the dynamic displacement of the masonry specimen, and the two-story steel frame specimen is evaluated under uniaxial seismic loading. The algorithm of the proposed method in this study, despite the relatively low resolution during frozen, slow, and seismic motions, has precision and usability that can replace the existing displacement transducer. Moreover, the method can be effectively applied to even fast behavior for multi-measurement positions like the seismic simulation test using large scale specimen. DDVS, using the consecutive images of the structures with an economic, hand-held digital video camcorder is a more economical displacement sensing concept than the existing contact and contactless measurement methods.     

Application of laser-induced breakdown spectroscopy for detecting leakage of boric acid

Recently, many studies have been conducted on developing on-line leak detection techniques in the reactor vessel head of nuclear power plants. One of them, laser-induced breakdown spectroscopy (LIBS), an effective technique of leak detection, which is a kind of atomic emission spectroscopy that uses a highly energetic laser pulse as the excitation source, has been of interest due to the fast and reliable identification of chemical elements for the precipitates formed by the leakage of cooling water containing boric acid. Experimental setup and tests were performed for the boric acid precipitates formed on the steel for various conditions with a Q-switched 532 nm Nd:YAG laser, optical lenses, an Echelle spectrograph and an intensified charge-coupled device detector. The LIBS system could be applied to obtain a spectral line (～249. 2 nm) corresponding to the atomic boron emission line for the precipitates of boric acid formed on low alloy steels, SA508 and SA533, as a substrate. The LIBS technique based on characterizing boric acid deposits might be used for detecting the leakage of cooling water in reactor vessel head of nuclear power plants.     

Kernel TIF method for effective material removal control in rotating pitch tool-based optical figuring

While opticians have used pitch tools for superb surface finishing, their poor controllability in material removal and associated lengthy tooling overhead have been well known in optics fabrication communities. We report a new computational technique called kernel tool influence function (KTIF) that can bring higher predictability to pitch tool-based material removal. The term ??kernel?? is defined as the ratio of experimental to simulated removal depth, therefore transforming the material removal coefficient of Preston??s equation to a removal scaling function at each point on the tool surface. This approach offers a unique inherent control feature incorporating ??real-life shop floor effects associated with pitch tool polishing variables?? into the tool influence functions without the need for theoretical expressions for the effects of individual variables on material removal behavior. Using a modified Draper-type polishing machine and a rotating pitch tool, we first generated kernel TIFs with zero stroke and used them for simulation and trial experiments of extended TIFs with variable tool strokes. The results show that the root mean square (rms) TIF profile differences between the prediction and experiments are in the range of 11 to 29?nm for conventional TIF and 7 to 15?nm for the KTIF. We then generated conventional TIF and KTIF database sets and applied them to surface figuring simulations. The results confirm that the kernel TIF has superior performance to the conventional TIF in controlling the material removal for correction of the chosen surface error.     

Adaptive Online Voltage Scaling Scheme Based on the Nash Bargaining Solution

In an effort to reduce energy consumption, research into adaptive power management in real‐time systems has become widespread. In this paper, a novel dynamic voltage scaling scheme is proposed for multiprocessor systems. Based on the concept of the Nash bargaining solution, a processor's clock speed and supply voltage are dynamically adjusted to satisfy these conflicting performance metrics. In addition, the proposed algorithm is implemented to react adaptively to the current system conditions by using an adaptive online approach. Simulation results clearly indicate that the superior performance of the proposed scheme can strike the appropriate performance balance between contradictory requirements.     

Studies on the heating capacity control of a multi-type heat pump system applying a multi-input multi-output (MIMO) method

This paper describes a method to control capacity of a multi-type heat pump system. Because indoor units are interconnected, alteration of the heating or cooling setting of one indoor unit can influence the performance of the other indoor units. Proportional-integral (PI) controllers were used to assess system performance, and the PI controllers’ gain values were optimized by using a genetic algorithm. A system model was established following a system identification optimization process, and a pseudo random binary sequence was selected as the system identification input signal. A multi-input multi-output (MIMO) controller was more effective in reducing such cross-coupling effects than a single-input single-output (SISO) controller. The temperature at the secondary fluid outlet in the condenser and the saturation pressure at the evaporator were selected as the control variables in the MIMO controller. The experimental results showed that an optimized MIMO controller could reduce overshoot by up to 40% compared with the results using a SISO controller.     

Contextualizing the ideas of technology in Korea—Questions of technology and early modern experiences

In the early to mid-2000s, Korea was touted as a strong IT (information technology) nation. But its IT success story has faded into the background less than half a decade’s time. Critiques hold among others the problem of hardware-oriented, commercialistic, and consumerist nature of IT environment including the centralized, statist IT governance responsible for hindering an IT take-off in Korea. This problematic environment of IT is fundamentally a material consequence of particular ideas of technology Korean society maintains—ideas of hardwarism, commercialism, and consumerism. Then the important question is the origin of these ideas. A large body of research argues the national modernization drive of the 1960s as an embryonic momentum in which hardware-centric, commercially oriented, and consumerist ideas of technology were disseminated in earnest. Persuasive as this argument is, the question still remains concerning how such perceptions about technology were embraced by the general populace at that moment with outright enthusiasm. This study argues that they were already gestated during the nation’s initial contact with modernity mostly by way of Japan in the context of the imperialistic world order of the late 19th century. And embedded as a paradigmatic structure, these ideas have been critical in the shaping of the trajectory of technology development and broadly a basic framework of modernization in Korea.     

Effect of selected aromatic medicinal plant sancho (Zanthoxylum schinifolium) on osteoblastic MC3T3-E1 cells

This study was performed to investigate the bioactivity of sancho (Zanthoxylum schinifolium) essential oil (EO) on bone metabolism and its function of osteoblastic MC3T3-E1 cells. The volatile aroma components of sancho EO were collected using a Clevenger-type apparatus by steam distillation extraction method, and determined by GC-MS. β-Phellandrene (22.54%) was the most abundant volatile compound in sancho EO, followed by citronellal (16.48%) and geranyl acetate (11.39%). It increased the collagen and mineralization of osteoblasts (p<0.05), indicating that sancho may help prevent osteoporosis.