• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1251-1260
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• 2008

Diffuse wireless optical communication offers more robust optical links in terms of coverage and shadowing than line-of-sight links. However, traditional diffuse wireless infrared (IR) transceiver systems are more susceptible to multi-path distortion and great power decrease, which results in limiting high-speed performance. Multi-beam is an effective technique to compensate for multi-path distortion in a wireless infrared environment. The goal of this paper is to analyze the transmission characteristics by replacing traditional diffuse system (TDS) which contains single wide angle transmitter and single element receiver by system consisting of three-beam transmitter and non-imaging receiver (TNS) attached with compound parabolic concentrator (CPC). In the simulation, we use the recursive model developed by Barry and Kahn and build the scenario based on 10 different cases which have been listed in Table 1. Moreover, we also check the reliability of the TNS diffuse link channel by BER test on the basis of different receiver positions and room sizes. The simulation results not only show the basic transmission characteristics of TNS diffuse link, but also are references to design more efficient and reliable indoor infrared transmission systems.

• Wind and Structures
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• v.1 no.3
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• pp.225-241
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• 1998

The high-rise supporting towers of long-span suspension and cable-stayed bridges commonly comprise a pair of slender prisms of roughly square cross-section with a center-to-centre spacing of from perhaps 2 to 6 widths and connected by one or more cross-ties. The tower columns may have a constant spacing as common for suspension bridges or the spacing may reduce towards the top of the tower. The present paper is concerned with the aerodynamics of such towers and describes an experimental investigation of the overall aerodynamic forces acting on a pair of square cylinders in two-dimensional flow. Wind tunnel pressure measurements were carried out in smooth flow and with a longitudinal intensity of turbulence 0.10. Different angles of attack were considered between $0^{\circ}$ and $90^{\circ}$, and separations between the two columns from twice to 13 times the side width of the column. The mean values of the overall forces proved to be related to the bias introduced in the flow by the interaction between the two cylinders; the overall rms forces are related to the level of coherence between the shedding-induced forces on the two cylinders and to their phase. Plots showing the variation of the force coefficients and Strouhal number as a function of the separation, together with the force coefficients spectra and lift cross-correlation functions are presented in the paper.

• Journal of Mechanical Science and Technology
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• v.17 no.8
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• pp.1140-1147
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• 2003

We have examined the effect on neck-muscle activation of altering whole body posture. A Rhesus monkey (Macaca mulatta) was trained to produce sinusoidal (0.25 Hz) head tracking movements in the sagittal plane when seated with trunk and head vertical or while standing in the quadrupedal position. Video-fluoroscopic images of cervical vertebral motion, and electromyographic (EMG) responses were recorded simultaneously. Results demonstrated that vertebral motion varied with body posture, occurring synchronously between all joints in the upright position and primarily at skull-$C_1$ when in the quadrupedal position. Muscle EMG activation was significantly greater (P<0.001) in the quadrupedal position than when upright for all muscles except semispinalis cervicis. Peak activation of all the muscles occurred prior to peak head extension in the quadrupedal position, suggesting synchronous activity between muscles. Data suggest that, when upright, muscles were activated in functional groupings defined by their anatomical arrangement. In the quadrupedal position, gravity acting on the horizontally oriented head produced greater activation and a collective response of the muscles.

• Journal of the Korea Safety Management & Science
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• v.12 no.2
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• pp.147-152
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• 2010

Project implementation plan is a blueprint that confirms project performance activities and specifies required man-hour, period and resource imput ratio. Various figures, the results of implementation plan, are predicted through estimation, and because of superiority of objectivity and repeatability, numerical formula-based estimation model is often used overseas. COCOMO model is the representative estimation model whose theories and formulas are publicized and it predicts the total man-hour required for software system development. This model is publicized in "Software Engineering Economics" written by Professor Barry Boehm of the U.S., and is the most widely applied numerical formula-based estimation model. This study is conducted to provide a series of methods that are optimal for KTDS environment by choosing COCOMO II model among various types of COCOMO models. In establishing implementation plan, COCOMO II model alone is not sufficient, it is necessary to link with and apply standard WBS system and standard man-hour. In establishing specific implementation plan, phased standard WBS system in order of the first phase of all the activities implemented in the project, Activity, Task, and Role, and the man-hour put into this should be distributed according to standard ratio from COCOMO II model's total man-hour. This study provides explainations by establishing standard WBS system and linking with COCOMO II model.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3335-3343
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• 2021

The impact of gamma radiation on a commercial off the shelf microcontroller board has been investigated. Three different tests have been performed to ascertain the radiation tolerance of the device from a nuclear decommissioning deployment perspective. The first test analyses the effect of radiation on the output voltage of the on-board voltage regulator during irradiation. The second test evaluated the effect of gamma radiation on the voltage characteristics of analogue and digital inputs and outputs. The final test analyses the functionality of the microcontroller when using an external, shielded voltage regulator instead of the on-board voltage regulator. The results suggest that a series of latch-ups occurs in the microcontroller during irradiation, causing increased current drain which can damage the voltage regulator if it does not have short-circuit protection. The analogue to digital conversion functionality appears to be more sensitive to gamma radiation than digital and analogue output functionality. Using an external, shielded voltage regulator can prove beneficial when used for certain applications. The collected data suggests that detaching the voltage regulator can extend the lifespan of the platform up to approximately 350 Gy.

• Journal of Animal Science and Technology
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• v.63 no.3
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• pp.510-519
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• 2021

One of the most pressing issues facing the dairy industry is drought. In areas where annual precipitation is low, irrigation for growing feed presents the greatest water-utilization challenge for dairy producers. Here, we investigated the effects of cultivar and harvest days after planting (DAP) on dry matter (DM) yield and nutritive value of teff (Eragrostis tef), a warm-season annual grass native to Ethiopia that is well adapted to drought conditions. Eighty pots were blocked by location in a greenhouse and randomly assigned to four teff cultivars (Tiffany, Moxie, Corvallis, and Dessie) and to five harvest times (40, 45, 50, 55, or 60 DAP). Cultivars had no effect on DM yield and nutritive value. As harvest time increased from 40 to 60 DAP, DM yield and ash-free neutral detergent fiber (aNDFom) concentrations increased, while crude protein (CP) concentrations and in vitro NDF digestibility decreased. To assess carryover effects of time of harvest on yield and nutritive value, two additional cuttings were taken from each pot. Increasing first-cutting harvest time decreased CP concentrations in the second cutting and reduced DM yields in the second and third cutting. Harvesting teff between 45 and 50 DAP best optimized forage yield and nutritive value in the first and subsequent cuttings.

• Nuclear Engineering and Technology
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• v.54 no.6
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• pp.2198-2203
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• 2022

As robotics become more sophisticated, there are a growing number of generic systems being used for routine tasks in nuclear environments to reduce risk to radiation workers. The nuclear sector has called for more commercial-off-the-shelf (COTS) devices and components to be used in preference to nuclear specific hardware, enabling robotic operations to become more affordable, reliable, and abundant. To ensure reliable operation in nuclear environments, particularly in high-gamma facilities, it is important to quantify the tolerance of electronic systems to ionizing radiation. To deliver their full potential to end-users, mobile robots require sophisticated autonomous behaviors and sensing, which requires significant computational power. A popular choice of computing system, used in low-cost mobile robots for nuclear environments, is the UP Core single board computer. This work presents estimates of the total ionizing dose that the UP Core running the Robot Operating System (ROS) can withstand, through gamma irradiation testing using a Co-60 source. The units were found to fail on average after 111.1 ± 5.5 Gy, due to faults in the on-board power management circuitry. Its small size and reasonable radiation tolerance make it a suitable candidate for robots in nuclear environments, with scope to use shielding to enhance operational lifetime.

• ETRI Journal
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• v.43 no.6
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• pp.966-977
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• 2021

Filterbank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is an attractive alternative to the orthogonal frequency division multiplexing (OFDM) modulation technique. In comparison with OFDM, the FBMC-OQAM signal has better spectral confinement and higher spectral efficiency and tolerance to synchronization errors, primarily due to per-subcarrier filtering using a frequency-time localized prototype filter. However, the filtering process introduces intrinsic interference among the symbols and complicates channel estimation (CE). An efficient way to improve the CE in FBMC-OQAM is using a technique known as windowed frequency domain averaging (FDA); however, it requires a priori knowledge of the window length parameter which is set based on the channel's frequency selectivity (FS). As the channel's FS is not fixed and not a priori known, we propose a k-nearest neighbor-based machine learning algorithm to classify the FS and decide on the FDA's window length. A comparative theoretical analysis of the mean-squared error (MSE) is performed to prove the proposed CE scheme's effectiveness, validated through extensive simulations. The adaptive CE scheme is shown to yield a reduction in CE-MSE and improved bit error rates compared with the popular preamble-based CE schemes for FBMC-OQAM, without a priori knowledge of channel's frequency selectivity.

• 대한예방의학회:학술대회논문집
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• 1994.02a
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• pp.405-411
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• 1994

Hazardous wastes released into the general environment are of concern to the public and to public health authorities. In response to this concern, the Comprehensive Environmental Response, Compensation, and Liability Act, as amended (commonly called Superfund), was enacted in 1980 to provide a framework for environmental, public health, and legal actions concerning uncontrolled releases of hazardous substances. The Agency for Toxic Substances and Disease Registry (ATSDR) was created by Superfund to address the public health issues of hazardous wastes in the community environment. Two key Agency programs, Public Health Assessments and Toxicological Profiles, are designed to assess the risk to human health of exposures to hazardous substances that migrate from waste sites or through emergency releases (e.g., chemical spills). The Agency's public health assessment is a structured process that permits ATSDR to identify which waste sites or other point sources require traditional public health actions (e.g.. human exposure studies, health studies, registries, health surveillance, health advisories). The ATSDR qualitative public health assessment complements the U.S. Environmental Protection Agency's quantitative risk assessment. For Superfund purposes, both assessments are sitespecific. ATSDR's toxicological profiles are prepared for priority hazardous substances found most frequently at Superfund sites. Each profile presents the current toxicologic and human health effects information about the substance being profiled. Each profile also contains Minimal Risk Levels (MRLs), a type of risk assessment value. This paper covers ATSDR's experience in conducting public health assessments and developing MRLs, and it relates this experience to recommendations on how to improve chemical risk assessments.

• Asian Journal of Innovation and Policy
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• v.12 no.1
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• pp.75-100
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• 2023

Over the past few decades, globalization has been shifting economic power upward to transnational actors on the one hand, and downward to subnational or regional spaces on the other. This phenomenon has resulted in the centrality of territorially delimited subnational regions acting as critical loci of economic governance within a complex and globally distributed value chain of trade and service flows. Within this broader context of industrial restructuring are economic regions that span national borders in their collective assets. The paper focuses on investigating the economic competitiveness and productivity of cross-border (or binational) economic regions. Using the conceptual framework of economic clusters, an econometric model that measures proxies of geographic proximity of firms in the life sciences cluster, and a new binational economic model, the paper examines the key characteristics, potentials and constraints of economic competitiveness and productivity in a cross-border region comprising counties in Western New York and regional municipalities in Southern Ontario. The findings demonstrate the direct and indirect benefits of closer cross-border economic cooperation. The paper then concludes with some policy observations about leveraging cross-border economic clusters for strategic industrial cooperation.