Using the Curriculum Vita to Study the Career Paths of Scientists and Engineers: An Exploratory Assessment

In this paper we assess the utility of the curriculum vita (CV) as a data source for examining the career paths of scientists and engineers. CVs were obtained in response to an email message sent to researchers working in the areas of biotechnology and microelectronics. In addition, a number of CVs were obtained "passively" from a search of the Internet. We discuss the methodological issues and problems of this data collection strategy and the results from an exploratory analysis using OLS regression and event history analysis. In sum, despite difficulties with coding and variation in CV formats, this collection strategy seems to us to hold much promise.     

Inverter Nonlinearity Compensation in the Presence of Current Measurement Errors and Switching Device Parameter Uncertainties

This paper proposes a compensation strategy for the unwanted disturbance voltage due to inverter nonlinearity. We employ an emerging learning technique called support vector regression (SVR). SVR constructs a motor dynamic voltage model by a linear combination of the current samples in real time. The model exhibits fast observer dynamics and robustness to observation noise. Then the disturbance voltage is estimated by subtracting the constructed voltage model from the current controller output. The proposed method compensates for all of the inverter nonlinearity factors at the same time. All the processes in estimating distortions are independent of the dead time and power device parameters. From the analysis of the effect on current measurement errors, we confirmed that the sampling error had little negative impact on the proposed estimation method. Experiments demonstrate the superiority of the proposed method in suppressing voltage distortions caused by inverter nonlinearity     

Temporal fairness guarantee in multi-rate wireless LANs for per-flow protection

Wireless LAN technologies such as IEEE 802.11a and 802.11b support high bandwidth and multi-rate data transmission to match the channel condition (i.e., signal to noise ratio). While some wireless packet fair queuing algorithms to achieve the per-flow throughput fairness have been proposed, they are not appropriate for guaranteeing QoS in multi-rate wireless LAN environments. We propose a wireless packet scheduling algorithm that uses the multi-state (multi-rate) wireless channel model and performs packet scheduling by taking into account the channel usage time of each flow. The proposed algorithm aims at per-flow protection by providing equal channel usage time for each flow. To achieve the per-flow protection, we propose a temporally fair scheduling algorithm called Contention-Aware Temporally fair Scheduling (CATS) which provides equal channel usage time for each flow. Channel usage time is defined as the sum of the packet transmission time and the contention overhead time due to the CSMA/CA mechanism. The CATS algorithm provides per-flow protection in wireless LAN environments where the channel qualities of mobile stations are dynamic over time, and where the packet sizes are application-dependent. We also extend CATS to Decentralized-CATS (D-CATS) to provide per-flow protection in the uplink transmission. Using an NS-2 simulation, we evaluate the fairness property of both CATS and D-CATS in various scenarios. Simulation results show that the throughput of mobile stations with stable link conditions is not degraded by the mobility (or link instability) of other stations or by packet size variations. D-CATS also shows less delay and less delay jitter than FIFO. In addition, since D-CATS can coordinate the number of contending mobile stations, the overall throughput is not degraded as the number of mobile stations increases. This work was supported in part by the Brain Korea 21 project of Ministry of Education and in part by the National Research Laboratory project of Ministry of Science and Technology, 2004, Korea.     

Increase in water resistance of paperboard by coating with poly(lactide)

Poly(lactide) (PLA)‐coated paperboards (PB) were prepared, and the effect of coating for improving water resistance of paperboard used for corrugated box liners was tested. Surface of paperboards became smoother through PLA coating, and their thickness and weight of coating increased depending on the concentration of the coating solution. Tensile strength of paperboard decreased, while elongation at break (E) increased after PLA coating. All water barrier properties tested, such as water vapour permeability (WVP), water absorptiveness (WA) and contact angle (CA) of water drop, indicated that water resistance of paperboard was improved through surface coating with PLA. WVP decreased from 4.8 to 25.5 times, and WA decreased from 11.9 to 17.9 times depending on the PLA concentration. The increase in water resistance of PLA‐coated paperboards was due to the hydrophobicity of PLA, which was proven through CA measurement. CA determined by both static and dynamic methods demonstrated the increase in initial CA of PLA‐coated paperboards, indicating an increased hydrophobicity of surface. All test results indicated that the optimum concentration of coating solution for improving water resistance of paperboard was 3 w/v % of PLA soulution. Copyright © 2007 John Wiley & Sons, Ltd.     

A Nonconventional Approach to Patterned Nanoarrays of DNA Strands for Template‐Assisted Assembly of Polyfluorene Nanowires

DNA molecules have been widely recognized as promising building blocks for constructing functional nanostructures with two main features, that is, self‐assembly and rich chemical functionality. The intrinsic feature size of DNA makes it attractive for creating versatile nanostructures. Moreover, the ease of access to tune the surface of DNA by chemical functionalization offers numerous opportunities for many applications. Herein, a simple yet robust strategy is developed to yield the self‐assembly of DNA by exploiting controlled evaporative assembly of DNA solution in a unique confined geometry. Intriguingly, depending on the concentration of DNA solution, highly aligned nanostructured fibrillar‐like arrays and well‐positioned concentric ring‐like superstructures composed of DNAs are formed. Subsequently, the ring‐like negatively charged DNA superstructures are employed as template to produce conductive organic nanowires on a silicon substrate by complexing with a positively charged conjugated polyelectrolyte poly[9,9‐bis(6′‐N,N,N‐trimethylammoniumhexyl)fluorene dibromide] (PF2) through the strong electrostatic interaction. Finally, a monolithic integration of aligned arrays of DNA‐templated PF2 nanowires to yield two DNA/PF2‐based devices is demonstrated. It is envisioned that this strategy can be readily extended to pattern other biomolecules and may render a broad range of potential applications from the nucleotide sequence and hybridization as recognition events to transducing elements in chemical sensors.     

Contact angle estimation and composite locomotive strategy of a stair-climbing mobile platform

This paper presents a stair-climbing mobile platform built on the Rocker–Bogie mechanism which enables to effectively climb up/down various sizes of stairs in indoor environments without violating its mobile stability. First, the link parameters of Rocker–Bogie mechanism are optimally chosen via the Taguchi method in order to make the trajectory of its center of mass (CM) as smooth as possible, which implies high mobile stability as well as excellent adaptability during climbing up/down stairs. Based on this optimization result, the proposed mobile platform is compactly and lightly constructed suitable for indoor applications by placing all motors and sensors inside the hollow links in order to prevent undesired interferences with stairs as well as to protect themselves from external impact. A simple, robust and cost-effective estimation algorithm is proposed to detect the contact angles between wheels and a stair with high fidelity. Through the kinematic and kinetic analysis combined with the wheel-stair contact angle information, a composite locomotive strategy is established not only to minimize the slip during climbing up a stair but also to prevent falling down during climbing down a stair. The extensive experiments against various types of stairs successfully demonstrate the capability of the proposed mobile platform to effectively and safely climb up/down stairs.     

System analysis study for Korean fusion DEMO reactor

A conceptual design study for a steady-state Korean fusion DEMO reactor (K-DEMO) has been initiated. Two peculiar features need to be noted. First, the major radius is designed to be just below 6.5 m, considering practical engineering feasibilities. But still, high magnetic field at the plasma center around 8 T is expected to be achieved by using current state-of-the-art high performance Nb₃Sn strand technology. Second, a two-stage development plan is being considered. In the first stage, K-DEMO will demonstrate a net electricity generation but will also act as a component test facility. Then, after a major upgrade, K-DEMO is expected to show a net electric generation on the order of 300 MWe and the competitiveness in cost of electricity (COE). Feasibility of such a practical, near-future demonstration reactor is studied in this paper, based on a zero dimensional system analysis code study. It was shown that a net electric generation on the order of 300 MWe can be achieved below the optimistic β_N limit of 5. The elongation of K-DEMO is around 1.8 with single null configuration. Detailed optimization process and the resultant various plasma parameters are described.     

A preliminary conceptual design study for Korean fusion DEMO reactor

As the ITER is being constructed, there is a growing anticipation for an earlier realization of fusion energy, so called fast-track approach. Korean strategy for fusion energy can be regarded as a fast-track approach and one special concept discussed in this paper is a two-stage development plan. At first, a steady-state Korean DEMO Reactor (K-DEMO) is designed not only to demonstrate a net electricity generation and a self-sustained tritium cycle, but also to be used as a component test facility. Then, at its second stage, a major upgrade is carried out by replacing in-vessel components in order to show a net electric generation on the order of 300 MWe and the competitiveness in cost of electricity (COE). The major radius is designed to be just below 6.5 m, considering practical engineering feasibilities. By using high performance Nb₃Sn-based superconducting cable currently available, high magnetic field at the plasma center above 8 T can be achieved. A design concept for TF magnets and radial builds for the K-DEMO considering a vertical maintenance scheme, are presented together with preliminary design parameters.