Huang J.-C.,Tungnan University
Scanning | Year: 2012
This study investigates the surface conditions of silicon wafers with native oxide layers (NOL) or hydrogen passivated layers (HPL) and how they influence the processes of nano-oxidation and wet etching. We also explore the combination of nano-oxidation and wet etching processes to produce nanostructures. Experimental results reveal that the surface conditions of silicon wafers have a considerable impact on the results of nano-oxidation when combined with wet etching. The height and width of oxides on NOL samples exceeded the dimensions of oxides on HPL samples, and this difference became increasingly evident with an increase in applied bias voltage. The height of oxidized nanolines on the HPL sample increased after wet etching; however, the width of the lines increased only marginally. After wet etching, the height and width of oxides on the NOL were more than two times greater than those on the HPL. Increasing the applied bias voltage during nano-oxidation on NOL samples increased both the height and width of the oxides. After wet etching however, the increase in bias voltage appeared to have little effect on the height of oxidized nanolines, but the width of oxidized lines increased. This study also discovered that the use of higher applied bias voltages on NOL samples followed by wet etching results in nanostructures with a section profile closely resembling a curved surface. The use of this technique enabled researchers to create molds in the shape of a silicon nanolens array and an elegantly shaped nanoscale complex structures mold. © 2012 Wiley Periodicals, Inc.
Huang J.-C.,Tungnan University
Scanning | Year: 2012
High-entropy alloys have been studied extensively for their excellent properties and performance, including outstanding strength and resistance to oxidation at high temperatures. This study employed molecular dynamics simulation to produce a high-entropy alloy containing an equal molar ratio of Al, Co, Cr, Fe, and Ni and investigated the tribological behavior of the material using a diamond tool in a vacuum environment. We also simulated a AlCoCrFeNi high-entropy alloy cooled from a high temperature molten state to 300 K in a high-speed quenching process to produce an amorphous microstructure. In a simulation of nanoscratching, the cutting force-distance curve of high-entropy alloys was used to evaluate work hardening and stick-slip. An increase in temperature was shown to reduce the scratching force and scratching resistance. Nanoscratching the high-entropy alloy at elevated temperatures provided evidence of work hardening; however, the degree of work hardening decreased with an increase in temperature. And it can also be found that when the temperature is higher, the fluctuation of the cutting force curve is greater. SCANNING 34: 325-331, 2012. © 2012 Wiley Periodicals, Inc.
Lin K.-H.,Tungnan University
Materials and Design | Year: 2011
The microstructure, mechanical properties, and wear behavior of two key components of a hinge fabricated from a metal injection molding process that was then sintered and heat treated under various conditions were analyzed using an optical microscope, a pin-on-disk tester, an open-closed reciprocal wear tester, and a scanning electron microscope. Optical photomicrograph revealed a serious decarburization in the sintered component, suggesting that an increase in carbon content would be necessary to improve mechanical properties. At the initial stage of the open-closed reciprocal wear test, the obverse inclined planes of both components exhibited plastic deformation and depression. As the number of test cycles increased, an increase in cold welding, metal adhesion, spalling, delamination, and surface fatigue was observed, triggering a decrease in metal thickness, which in turn altered the shape of the components. In this study, the optimal parameters to satisfy commercial application requirements were obtained when the components were carburized at 870 °C for 30 min, quenched in oil, and finally tempered at 250 °C for 1 h. © 2010 Elsevier Ltd.
Chen S.-G.,Tungnan University
Computers and Industrial Engineering | Year: 2012
Due to the IT advances, the logistics management faces a change to the new era. This article proposes a novel method to evaluate the real-time overall performance of a logistics network for a supply chain. The corresponding strategies to manage the underperformed channels can be subsequently obtained in the method. Thus, the logistics network can be managed timely under the stochastic environment, and it makes the SCM robust. The overall performance of the logistics network is integrated by the individual logistics channel real-time performance which can be easily obtained by the new IT technologies such as RFID, etc. The fuzzy-scorecard is introduced to indicate the measured key performance indicators (KPI) for the network. Some numerical examples are presented to illustrate the various scenarios of management for the proposed method. © 2011 Elsevier Ltd. All rights reserved.
Shih R.-S.,Tungnan University
Ocean Engineering | Year: 2012
Several investigations of the physical properties of wave-structure interactions and absorption of structures in coastal areas discussed the development of several permeable and porous breakwaters. This article addresses highly-pervious dense pipe with small apertures, which can be beneficial for convection and interchange of sea water within the harbor district, and furthermore, perform effectively in wave absorption. This study investigates the dissipation of porous perpendicular pipe breakwaters, and presents laboratory investigations of wave transmission from permeable pipe breakwaters with different wave conditions and various combinations of diameter and tube length. Since wave energy is mainly dissipated due to drag and interception of the resultant motion by the pipe breakwaters, the reflectivity of such effects is discussed by the evaluation of partly reflected and transmitted ratio. Consequently, the performance of the pipe breakwater for predicting the wave transmission coefficient is investigated. Experimental results reveal that dissipation and/or reflection is more effective when decreasing pipe diameter than increasing pipe length, specifically when dimensionless frequency σ 2h/g>1.5. Nevertheless, the effect is relatively inconspicuous when σ 2h/g<0.75. A partial outcome demonstrates the influence of pipe diameter and variations of reflection coefficients corresponding with dimensionless frequencies for incident waves with various wave heights. © 2012 Elsevier Ltd All rights reserved.
Huang J.-C.,Tungnan University
International Journal of Adhesion and Adhesives | Year: 2012
This study proposes the combination of electrochemical tip sharpening, mirror wax plate production, computer numerical control (CNC) imprinting technology, and the polydimethylsiloxane (PDMS) vacuum casting method to produce an innovative process akin to the setae arrangement in gecko feet to create a large-area gecko seta-like structure or gecko tape. This study produced micrometer tip radius probes using electrochemical methods and used CNC to apply imprinting technology to imprint a micrometer pore structure on the mirror wax plate (substrate) via micro-scale probes to be covered with a micro-porous structure of the wax mold, conducting the vacuum casting method by PDMS to create a gecko tape shaped like gecko feet. The results show that the surface roughness of the mirror wax plate produced in this study reaches the nanoscale. After electrochemical tip sharpening, the tip radius of the 0.5 mm tungsten rod can be reduced to less than 10 μm. The finished gecko tape indicates that using a wax mold to conduct PDMS vacuum casting creates good formability. This indicates the innovative gecko seta-like tape process proposed in this study is greatly feasible. It was also found that the adhesion force increased with the increase of the number of pillars and the increased pillars height of the gecko tape. The average adhesion force of a single pillar, however, decreases with an increase in the number of pillars. © 2012 Elsevier Ltd.
Wang Y.-J.,Tungnan University
ISA Transactions | Year: 2014
This paper proposes a novel alternative method to graphically compute all feasible gain and phase margin specifications-oriented robust PID controllers for open-loop unstable plus time delay (OLUPTD) processes. This method is applicable to general OLUPTD processes without constraint on system order. To retain robustness for OLUPTD processes subject to positive or negative gain variations, the downward gain margin (GMdown), upward gain margin (GMup), and phase margin (PM) are considered. A virtual gain-phase margin tester compensator is incorporated to guarantee the concerned system satisfies certain robust safety margins. In addition, the stability equation method and the parameter plane method are exploited to portray the stability boundary and the constant gain margin (GM) boundary as well as the constant PM boundary. The overlapping region of these boundaries is graphically determined and denotes the GM and PM specifications-oriented region (GPMSOR). Alternatively, the GPMSOR characterizes all feasible robust PID controllers which achieve the pre-specified safety margins. In particular, to achieve optimal gain tuning, the controller gains are searched within the GPMSOR to minimize the integral of the absolute error (IAE) or the integral of the squared error (ISE) performance criterion. Thus, an optimal PID controller gain set is successfully found within the GPMSOR and guarantees the OLUPTD processes with a pre-specified GM and PM as well as a minimum IAE or ISE. Consequently, both robustness and performance can be simultaneously assured. Further, the design procedures are summarized as an algorithm to help rapidly locate the GPMSOR and search an optimal PID gain set. Finally, three highly cited examples are provided to illustrate the design process and to demonstrate the effectiveness of the proposed method. © 2014 ISA.
Chen S.-G.,Tungnan University
Applied Energy | Year: 2012
This paper proposes a novel and fast sizing method under the constant daily load profile for sizing a stand-alone PV system. The term " efficient sizing" means that the approach did not use simulation but could get the result as good as those employing simulation. So, the sizing method is more efficient than the others. Traditionally, a typical day or a typical year's solar irradiation profile is employed for the sizing task. However, facing the global warming crisis as well as the fact that no 2. years would have the same weather condition for a single site, this approach statistically models the trend of climate change year by year and put it into the sizing formula, so that the results are optimal for the current weather condition and for the future as well. Hence, the suitable size for the PV array and the number of batteries are obtained by purely computation. This is different from the traditional sizing curve method. Although the traditional sizing curve method were satisfactory in the normal cases, they might fail in the extreme climate condition. This paper concludes the behavior of the extreme climate for at least 20. years. So, the derived system may have statistical confidence for at least 20. years of operation. A new reliability index (Loss of Power Probability) in terms of Extreme Value Theory is introduced. LPP provides upper bound reliability for application and rich information for many extreme events. A technological and economical comparison among the traditional daily energy balance method, sizing curve method and this approach is conducted and shows the usefulness of this approach. © 2011 Elsevier Ltd.
Su C.-H.,Tungnan University
International Journal of Production Economics | Year: 2012
This study proposes a single-supplier, single-retailer integrated inventory model that accounts for defective items that arrive in a retailers order under a full-lot inspection policy. All defective items are returned to the supplier in next delivery. After receipt of the returned items, the supplier will classify them into two types: items that still have some worth and waste items. For those items that still have some worth, the supplier will offer customers a discount in order to minimize losses arising from these defective items. The supplier needs to pay a disposal fee for those items classified as waste items. Shortages are allowed and are fully backlogged. To encourage sales the supplier offers trade credit to the retailer. A two-echelon inventory model is established, and the decision variables include: replenishment cycle time, the time taken to run out of stock and the number of lots delivered from the supplier to the retailer. An algorithm is developed to determine the optimal supply chain strategy and numerical examples are provided to show the solution procedure. Also, a sensitivity analysis is conducted on the main parameters of the model. © 2010 Elsevier B.V. All rights reserved.
Tungnan University | Date: 2010-11-30
A solar photovoltaic panel test platform includes a test section and a signal processing section. The test section has a frame, a light-emitting unit disposed on the frame, a first angle adjustment unit and a second angle adjustment unit arranged on the frame, an air-cooling unit mounted on the first angle adjustment unit for connecting with a first solar photovoltaic panel, and a water-cooling unit mounted on the second angle adjustment unit for connecting with a second solar photovoltaic panel. The signal processing section is connected to the first and second angle adjustment units, the light-emitting unit, the air-cooling unit, the water-cooling unit, and the first and second solar photovoltaic panels. The signal processing section serves to receive sensing signals and transmit control signals. The solar photovoltaic panel test platform can provide different illuminations, angles of incidence and heat dissipation modes to test the efficiency of the solar photovoltaic panels.