• Transactions of the Korean Society of Mechanical Engineers A
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• 제21권1호
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• pp.144-153
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• 1997

The determination of the direct kinematics of the parallel mechanism is a difficult problem but has to be solved for any practical use. This paper presents the efficient formulation of the direct kinematics for double parallel robot arm. The robot arm consists of two parallel mechanism, which generate positional and orientational motions, respectively. These motions are decoupled by a passive central axis which is composed of four revolute joints and one prismatic joint. For a set of given lengths of linear actuators, the direct kinematics will find the joint displacements of th central axis from geometric constraints in each parallel mechanism. Then the joint displacements will be converted into the position and the orientation of the end effector of the robot arm. The proposed formulation is decoupled and compacted so that it will be implemented as a real-time direct kinematics. With the proposed formulation, we analyze the motion of the double parallel robot and show its characteristics. Specially, we investigate the workspace in terms of positional space as well as orientational space.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.236-248
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• 2017

A direct stator flux vector control scheme in discrete-time domain is proposed in this paper for the interior permanent magnet synchronous motor (IPMSM) drive to remove the proportional-integral (PI) controller from the direct torque control (DTC) scheme applied to IPMSM and to obtain faster dynamic response and lower torque ripple output. The output of speed outer loop is used as the desired torque angle instead of the desired torque in the proposed scheme. The desired stator flux vector in dq coordinate is calculated with a given amplitude. The state-space equations in discrete-time for IPMSM are established, the actual stator flux vector is estimated in deadbeat manner by a full-order state observer, and then the closed-loop control is achieved by the pole placement. The stator flux error vector is utilized to calculate the reference stator voltage vector. Extracting the angle position and amplitude from the estimated stator flux vector and estimating the output torque are eliminated for the direct feedback control of the stator flux vector. The proposed scheme is comparatively investigated with a PI-SVM DTC scheme by experiment results. Experimental results show the feasibility and advantages of the proposed control scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제21권10호
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• pp.1194-1199
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• 2010

In this paper, for a relay-based cellular network, a interference avoidance beamforming technique is proposed to enhance direct link capacity while minimizing loss in the capacity of concurrent relaying link. A direct link is transmitted by beamforming at the transmitter, and the relaying link with the least interference to the direct link is scheduled to transmit data by a collision avoidance scheduling algorithm. Simulation results show that the proposed IA beamforming provides a considerable direct link capacity enhancement while minimizing relaying link capacity loss by effectively mitigating inference between concurrent direct and relaying links only with limited feedback.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.268-276
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• 2001

In order to improve the efficiency of a direct contact heat exchanger for a solar thermal energy system, the working fluid should be dispersed into small and uniform droplets, and stay within a heat exchanger for a long time. Therefore, installation of meshes in a direct contact heat exchanger is suggested in the present study, and the performance of the direct contact heat exchanger with several layers of meshes is experimentally investigated. Diethyl phthalate is used as the working fluid, and the performance of the heat exchanger is tested for several different operating conditions and compared to that of the heat exchanger without meshes. The results of this investigation show that meshes make droplets uniform and small when the flow rate is low. The relationship between the Peclet number and the Nusselt number becomes linear if it is steady. And, the Nusselt number for the direct contact heat exchanger with meshes becomes greater than that without meshes as the Peclet number increases.

• Asian-Australasian Journal of Animal Sciences
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• 제17권2호
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• pp.153-158
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• 2004

Data containing 14,188 lactation and reproductive records of Korean Holstein cows at first parity distributed across 3,734 herd-year-season groups were analyzed to get genetic (co)variance estimates for milk yield, fat yield, calving ease, and days open. Milk and Fat yields were adjusted to 305 d. Heritabilities and genetic correlations were estimated in two different animal models on which were included direct genetic effects (Model 1) and direct+maternal genetic effects (Model 2) using REML algorithms. Milk and fat yields were affected by age at first calving as linear and quadratic. Heritability estimates of direct effects were 0.25 for milk yield, 0.17 for fat yield, 0.03 for calving ease and 0.03 for days open in Model 2. These estimates for maternal effects were 0.05, 0.08, 0.04 and less than 0.01 for each corresponding trait. Milk productions at first lactation were to show genetically favorable correlation with calving ease and days open for direct genetic effects (-0.24 - -0.11). Moreover, calving ease was correlated with days open of 0.30 for direct genetic effects. Correlations between direct and maternal effects for each trait were negatively correlated (-0.63 - -0.32). This study suggested that maternal additive genetic variance would be not ignorable for genetic evaluation of milk production as well as reproductive traits such as calving ease and days open at first parity. Furthermore, difficult calving would genetically influence the next conception.

• Architectural research
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• 제16권4호
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• pp.149-156
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• 2014

This research is designed to identify factors that affect life satisfaction of the Korean elderly by studying residential environments and individual personalities as independent variables, and life satisfaction of the elderly as a dependent variable. It also includes emotional and instrumental support to describe relations between variables as mediating variables. It utilizes a questionnaire survey as its research method and studies those aged 65 and over living in urban, suburban and rural areas. In addition, regression and path analysis is used to identify casual links between different variables. The results are as follows: (1) Direct factors that impact emotional support are home ownership (direct effect= -.18) and transportation services (.15). That is, those who own their home and have easy access to public transpiration show increased levels of emotional support. (2) Direct factors that affect instrumental support are economic status (direct effect= .311) and living arrangement (.17). In other words, those who are financially stable and live with their children have more instrumental support. (3) Factors linked directly to life satisfaction of the elderly are their age (direct effect= -.10), health status (.19), economic status (.25), region of living (.22) and housing type (.19). (4) Among the mediating variables, emotional support has direct effect (.45) while instrumental support has indirect effect (.16).

• Geomechanics and Engineering
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• 제37권6호
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• pp.615-627
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• 2024

Direct simple shear test is an effective method to measure strength and deformation properties of soil. However, existing direct simple shear apparatus have some shortcomings. The paper has developed a novel dual stress/strain-controlled direct simple shear apparatus. The novel apparatus has the following advantages: A rectangular specimen is used that effectively avoid common issues associated with conventional cylindrical specimens, such as specimen tilting. The utilization of deformation control rods ensures a uniform shear deformation of the specimen. Vertically integrated force transmission structure is improved that avoids issues arising from changes in pivot points due to lever tilting. Incorporating this novel direct simple shear apparatus, shear strength and shear creep tests of clay were performed. Shear strength parameters and shear creep behaviors are analyzed. The results of these experiments show that the novel apparatus can measure accurately the shear rheological properties of soil. This study provides strong guidance for studying the mechanical properties of soil in engineering practice.

• International Commerce and Information Review
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• 제11권3호
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• pp.391-408
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• 2009

This study first designates the factors affecting Foreign Direct Investment (FDI) in order to analyze the FDI in Korea, and calculates the Korean FDI index by using various designated variables and by applying Factor Analysis Technique. In addition, it attempts to understand the influence wielded by the foreign investment variables of foreign multinationals on FDI in Korea, by setting to analyze & verify Environmental Factors and the overall model based on FDI in Korea. Through an emprical analysis of USA, Japan, EU, China, as our hypothesis, we could verify that the positive effects(+) among the decisive factors of FDI in Korea include the market size, the mean earning rate of domestic manufacturing industries, and the marketing capacities of foreign corporations, while the negative effects(-) include the ratio of taxation on domestic manufacturing industries. Other FDI factors have various effects on each, so some factors show the same effects as the hypothesis while others show separate effects. In addition, the only nation for which the effects of FDI factors in Korea coincide with the hypothesis completely is the USA, while other nations (such as Japan, EU, China) have some effects that conform to the hypothesis, but other effects do not accord with it.

• The Research Journal of the Costume Culture
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• 제24권3호
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• pp.324-335
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• 2016

The fashion product image preference changes depending on one's lifestyle and personal inclination. Women want to show the fashion product image preference, often through their clothing and makeup choices. Brand image includes those elements related to the brand. Advertising is the primary method for introducing brands. This study was conducted to investigate the effects of fashion product image preference on emphasis of brand image and advertising factor evaluation targeting working women in their 20s and 30s. The fashion product image preference was s sophisticated image. Preference for a sophisticated image has a significant effect on emphasis of brand image when selecting fashion products. Emphasis of brand image has a notable effect on the brand direct advertising factor evaluation. Fashion product image preference has a significant effect on both brand's direct and indirect advertising factor evaluation. When selecting a fashion product (clothing and cosmetics), brand image importance was found to have a positive effect on a brand's direct advertising factor evaluation. Therefore, fashion companies should take advantage of their brand logo. Companies should also pay attention to clothing and product containers used in advertising to show the brand. In addition, every company should create an advertising image that represents their overall brand, by using a combination of detailed advertising factor evaluation.

• The Journal of Asian Finance, Economics and Business
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• 제7권3호
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• pp.289-294
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• 2020

The study of environmental pollution plays an important role in controlling emissions in the production activities of FDI enterprises as well as export goods. Vietnam is a country with a large proportion of FDI contribution and high export value. Therefore, there should be studies to assess the actual effects of FDI and the openness of the economy (trade) on the environment. Therefore, the authors conduct research on the role of FDI and trade on environmental quality in Vietnam. With data collected from 1990 to 2018 (from the period of Vietnam's economy opening up) through the ARDL (Autoregressive Distributed Lag) model, the results show that FDI has a positive impact on CO2 emissions in the short term but has no impact on the long-term (In this study, CO2 is considered to represent environmental quality). The trade has a positive impact on CO2 emissions in both the short term and long term. The results of the study show the actual shortcomings of FDI as well as production activities in the export enterprises in Vietnam. From the results of this research, the author also provides the causes and remedies to control of CO2 emissions from two activities of foreign direct investment and trade.