Compact stripline-fed meander slot antenna

A meander-type slot antenna fed by a stripline is proposed for use in miniaturised personal communication systems. By varying the slot configuration of the antenna, a 56% smaller antenna to substitute the conventional slot antenna is achieved. Simulated and measured results are presented     

Cognitive Radio and Networking Research at Virginia Tech

More than a dozen Wireless @ Virginia Tech faculty are working to address the broad research agenda of cognitive radio and cognitive networks. Our core research team spans the protocol stack from radio and reconfigurable hardware to communications theory to the networking layer. Our work includes new analysis methods and the development of new software architectures and applications, in addition to work on the core concepts and architectures underlying cognitive radios and cognitive networks. This paper describes these contributions and points towards critical future work that remains to fulfill the promise of cognitive radio. We briefly describe the history of work on cognitive radios and networks at Virginia Tech and then discuss our contributions to the core cognitive processing underlying these systems, focusing on our cognitive engine. We also describe developments that support the cognitive engine and advances in radio technology that provide the flexibility desired in a cognitive radio node. We consider securing and verifying cognitive systems and examine the challenges of expanding the cognitive paradigm up the protocol stack to optimize end-to-end network performance. Lastly, we consider the analysis of cognitive systems using game theory and the application of cognitive techniques to problems in dynamic spectrum sharing and control of multiple-input multiple-output radios.     

The analysis of 2′-fucosyllactose concentration in Korean maternal milk using LC–MS/MS

Food Science and Biotechnology - Despite health benefits reported recently, 2′-fucosyllactose (2′-FL) concentration in maternal milk was not conclusively reported because it varies...     

Deubiquitinating Enzyme USP8 Is Essential for Skeletogenesis by Regulating Wnt Signaling

Disturbance in a differentiation program of skeletal stem cells leads to indecorous skeletogenesis. Growing evidence suggests that a fine-tuning of ubiquitin-mediated protein degradation is crucial for skeletal stem cells to maintain their stemness and osteogenic potential. Here, we demonstrate that the deubiquitinating enzyme (DUB) ubiquitin-specific protease 8 (USP8) stabilizes the Wnt receptor frizzled 5 (FZD5) by preventing its lysosomal degradation. This pathway is essential for Wnt/β-catenin signaling and the differentiation of osteoprogenitors to mature osteoblasts. Accordingly, deletion of USP8 in osteoprogenitors (Usp8^Osx) resulted in a near-complete blockade in skeletal mineralization, similar to that seen in mice with defective Wnt/β-catenin signaling. Likewise, transplanting USP8-deficient osteoprogenitors under the renal capsule in wild-type secondary hosts did not to induce bone formation. Collectively, this study unveils an essential role for the DUB USP8 in Wnt/β-catenin signaling in osteoprogenitors and osteogenesis during skeletal development.     

Manufacturing process of bezel frame for strength-reinforced TFT LCD module by progressive hemming of SUS304 stainless steel sheet

In this study, the design procedure for a progressive multi-hemming forming process has been proposed for manufacturing bezel frames for strength-reinforced TFT LCD (Thin-film-transistor liquid-crystal display) modules. First, a strength analysis was performed using Finite element (FE) simulations to determine the minimum number of required folding edges. Subsequently, anoother FE analysis was carried out in order to investigate the effects of the process parameters on the dimensional accuracy of the bezel frame and to design the progressive hemming process. The analytical results were validated by hemming experiments performed using SUS304 stainless steel with a thickness of 0.3 mm. Finally, the quality of the bezel frame was estimated through measurements of its dimensional accuracy and bending stiffness. From the experimental results, it was confirmed that a bezel frame with a height distribution of 1.5±0.05 mm and a respectable bending stiffness of 70 N/mm could be manufactured using the proposed process.     

Fabrication of micro spur gears by step powder extrusion of Zn-22wt%Al powder without sintering process

Micro spur gears were fabricated using the LIGA process and step powder extrusion without sintering. It is important to manufacture micro dies with high aspect ratios and determine the appropriate extrusion conditions for the micro-forming process. Micro-extrusion dies with close tolerance and long bearing length were produced by the LIGA process. Superplastic Zn-22wt%Al powders can deform under low stresses and exhibit a good micro-formability (average strain rate: 10^?3s^?1; constant temperature: 250°C). These powders were compacted to a cylinder (diameter: 3 mm; height: 10 mm) under 10kN compressive force, and sintered at 350°C for two hours. Micro spur gear shafts were not produced upon extrusion because of the high working pressure on the die surface. For the reduction of the forming load, step powder extrusion was carried out on the compacted powder without a sintering process, but controlling the temperature dwelling period. This process has succeeded in fabricating micro-gear shafts.     

Optimization of mixed casting processes considering discrete ingot sizes

Using linear programming (LP), this research devises a simple and comprehensive scheduling methodology for a complicated, yet typical, production situation in real foundries: a combination of expendable-mold casting, permanent-mold casting and automated casting for large-quantity castings. This scheduling technique to determine an optimal casting sequence is successfully applied to the most general case, in which various types of castings with different alloys and masses are simultaneously produced by dissimilar casting processes within a predetermined period. The methodology proves to generate accurate scheduling results that maximize furnace or ingot efficiency. For multivariable and multi-constraint optimization problems per se, it provides an extremely practical solution which is readily implemented in most real-world casting plants. In addition, incorporating ingot adjustment from the reality of discrete ingot size, this LP scheduling can assist the casting industry in strengthening its competence by heightening ingot utilization as well as satisfying due dates. This paper was presented at the 9^th Asian International Conference on Fluid Machinery (AICFM9), Jeju, Korea, October 16–19, 2007.recommended for publication in revised form by Associate Editor Young-Seog Lee Yong Kuk Park received his B.S. degree in Metallurgical Engineering from Seoul National University, Korea, in 1987. He then received his M.S. degree in Industrial and Operations Engineering from University of Michigan, U.S.A., in 1988 and Ph.D. degree in Manufacturing Engineering from Ohio State University, U.S.A., in 1995. Dr. Park is currently an Associate Professor at the School of Mechanical and Automotive Engineering at Catholic University of Daegu, Korea. He worked for Ford Motor Co., U.S.A., and Renault-Samsung Motors, Korea. Dr. Park’s research interests include casting, forging, sheet metal forming, scheduling in production engineering, mechanical design, die failures, and fatigue analysis. Jung-Min Yang received his B.S., M.S., and Ph.D. degrees in Electrical Engineering from Korea Advanced Institute of Science and Technology (KAIST), Korea, in 1993, 1995, and 1999, respectively. From March 1999 to February 2001, he was a Senior Member of the Engineering Staff at Electronics and Telecommunications Research Institute (ETRI), Korea. Since March 2001, he has been with the Department of Electrical Engineering, Catholic University of Daegu, Korea, where he is currently an Associate Professor. His research interests are in control of asynchronous sequential machines, fault-tolerance in real-time systems, and scheduling of casting process.     

Comparison of the fatigue life of F.F. shaft material according to various environmental temperatures

A rotary bending fatigue test was carried out with two kinds of materials, S43C and S50C, using the front engine and front driveshaft (F.F. shaft) of the vehicle. The specimens were heat-treated using the high frequency induction method (about 1 mm depth and HRC56∼60) and the test environment temperatures were -30 °C (-22 °F), +25 °C (+77 °F), and +80 °C (+176 °F) in order to determine the influence of the heat treatment and the temperatures. The fatigue life increased on the order of +80 °C, +25 °C, and -30 °C regardless of heat treatment. In comparison of the fatigue lives with the basis of the tested result at +25 °C, the fatigue lives of non-heated specimens decreased about 35%, but that of heat-treated specimens decreased by only about 5% at +80 °C, more than at +25 °C. And fatigue life of non-heated and heat-treated specimens were about 110% and 120% higher at -30 °C than that of +25 °C. The initiation of surface microcracks was observed at 0.2 fatigue life ratio in as-received S43C and S50C, but the average crack length in S50C was about 14% longer than that of S43C at the same fatigue life ratio.     

Deposition of Al-doped ZnO films on polyethylene naphthalate substrate with radio frequency magnetron sputtering

100 nm Al-doped ZnO (AZO) thin films were deposited on polyethylene naphthalate (PEN) substrates with radio frequency magnetron sputtering using 2 wt.% Al-doped ZnO target at various deposition conditions including sputtering power, target to substrate distance, working pressure and substrate temperature. When the sputtering power, target to substrate distance and working pressure were decreased, the resistivity was decreased due to the improvement of crystallinity with larger grain size. As the substrate temperature was increased from 25 to 120 °C, AZO films showed lower electrical resistivity and better optical transmittance due to the significant improvement of the crystallinity. 2 wt.% Al-doped ZnO films deposited on glass and PEN substrates at sputtering power of 25 W, target to substrate distance of 6.8 cm, working pressure of 0.4 Pa and substrate temperature of 120 °C showed the lowest resistivity (5.12 × 10^− 3 Ω cm on PEN substrate, 3.85 × 10^− 3 Ω cm on glass substrate) and high average transmittance (> 90% in both substrates). AZO films deposited on PEN substrate showed similar electrical and optical properties like AZO films deposited on glass substrates.     

FEA technique of hot plate forming process using cell-typed die with cooling device

Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG tank.Cell-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process,and an air-cooling device is separately installed inside the lower die.A finite element analysis (FEA) technique was developed,which included hot forming,air flow,cooling and thermal deformation analysis for the hot plate forming process using the cell-typed die.Further,the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis.A small-scale model test of the process was conducted to verify the FEA technique.The analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.