• Journal of Communications and Networks
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• v.6 no.4
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• pp.376-386
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• 2004

In ad hoc networks, loss-based congestion window progression by the traditional means of duplicate ACKs and timeouts causes high network buffer utilization due to large bursts of data, thereby degrading network bandwidth utilization. Moreover, network-oriented feedbacks to handle route disconnection events may impair packet forwarding capability by adding to MAC layer congestion and also dissipate considerable network resources at reluctant intermediate nodes. Here, we propose a new TCP scheme that does not require the participation of intermediate nodes. It is a purely end-to-end scheme using TCP timestamps to deduce link conditions. It also eliminates spurious reductions of the transmission window in cases of timeouts and fast retransmits. The scheme incorporates a receiver-oriented rate controller (rater), and a congestion window delimiter for the 802.11 MAC protocol. In addition, the transient nature of medium availability due to medium contention during the connection time is addressed by a freezing timer (freezer) at the receiver, which freezes the sender whenever heavy contention is perceived. Finally, the sender-end is modified to comply with the receiver-end enhancements, as an optional deployment. Simulation studies show that our modification of TCP for ad hoc networks offers outstanding performance in terms of goodput, as well as throughput.

• Structural Engineering and Mechanics
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• v.16 no.3
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• pp.275-294
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• 2003

In this study, 24 high-strength concrete dapped-end beams were tested to study the effects of the amount of main dapped-end reinforcement, the nominal shear span-to-depth ratio, and the concrete strength on the shear strength of dapped-end beams. Test results indicate that the shear strength of dapped ends increases with the increase in the amount of main dapped-end reinforcement and the concrete strength. The shear strength of dapped-end beam increases with the decrease of nominal shear span-to-depth ratio. A simplified method for determining the shear strength of reinforced concrete dapped ends is also proposed in this paper. The shear strengths predicted by the proposed method and the approach of PCI Design Handbook are compared with test results. The comparison shows that the proposed method can more accurately predict the shear strength of reinforced concrete dapped-end beams than the approach of PCI Design Handbook.

• Journal of KIISE
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• v.44 no.5
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• pp.503-509
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• 2017

In this paper, the copy mechanism and input feeding are applied to recurrent neural network(RNN)-search model in a Korean-document summarization in an end-to-end manner. In addition, the performances of the document summarizations are compared according to the model and the tokenization format; accordingly, the syllable-unit, morpheme-unit, and hybrid-unit tokenization formats are compared. For the experiments, Internet newspaper articles were collected to construct a Korean-document summary data set (train set: 30291 documents; development set: 3786 documents; test set: 3705 documents). When the format was tokenized as the morpheme-unit, the models with the input feeding and the copy mechanism showed the highest performances of ROUGE-1 35.92, ROUGE-2 15.37, and ROUGE-L 29.45.

• Child Health Nursing Research
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• v.24 no.4
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• pp.353-363
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• 2018

Purpose: The purpose of this study was to investigate pediatric nurses' perceptions regarding in end-of-life care and turnover intention. Methods: A cross-sectional descriptive study was performed among 111 hospital nurses. Pediatric nurses' perceptions of obstacles and supportive behaviors were measured using the Pediatric Nurses' Perceptions of End of Life Care Questionnaire which was translated into Korean and turnover intention was measured using the Korean Nurse Turnover Intention Scale (K-NTIS). Results: The supportive behavior with the highest perceived magnitude was 'Physicians who are compassionate, but very clear about prognosis.' The obstacle with the highest perceived magnitude was 'Instigating painful treatments when there is no hope of recovery.' Pediatric nurses' perceptions of obstacles in end-of-life care showed statistically significant differences depending on whether nurses received end-of-life care education (t=2.02, p=.046). The perception of obstacles in end-of-life care was positively correlated with turnover intention (intensity r=.28, p=.002) (frequency r=.20, p=.027). Conclusion: These results suggest that pediatric nurses' perception of obstacles and supportive behaviors in end-of-life care need to be assessed when considering turnover intention. Furthermore, psychological counseling should be offered to nurses to prevent burnout and reduce moral distress which is correlated with the turnover rate.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.135-143
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• 2004

In the land section of marine bridge construction site, to confirm the end bearing of large diameter drilled shaft constructed in the fault zone which was discovered unexpectedly, the hi-directional end loading tests were performed. The objectives of this study are to confirm the end bearing of the pile constructed in fault zone and the increasing effect of end bearing after grouting the base ground beneath the pile toe. After grouting the pile base ground, the settlement of pile base decreased considerably and the pile base resistance increased more than twice.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.928-933
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• 2004

A new approach for modelling and simulation of the cutting forces in end milling processes is presented. In this approach, the cutting forces in end milling are modelled based on a predictive machining theory, in which the machining characteristic factors are predicted from input data of fundamental workpiece material properties, tool geometry and cutting conditions. In the model, each tooth of a end milling cutter is divided into a number of slices along the cutter axis. The cutting action of each of the slices is modelled as an oblique cutting process. For the first slice of each tooth, it is modelled as oblique cutting with end cutting edge effect, whereas the cutting actions of other slices are modelled as oblique cutting without end cutting edge effect. The cutting forces in the oblique cutting processes are predicted using a predictive machining theory. The total cutting forces acting on the cutter is obtained as the sum of the forces at all the cutting slices of all the teeth. A Windows-based simulation system for the cutting forces in end milling is developed using the model. Experimental milling tests have been conducted to verify the simulation system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.105-116
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• 2003

The flow structure around the free end of a finite circular cylinder (FC) embedded in an atmospheric boundary layer (ABL) over open terrain was investigated experimentally with varying the free end shape. The experiments were carried out in a closed-return type subsonic wind tunnel. A finite cylinder with an aspect ratio (L/D) of 6 was mounted vertically on a long flat plate. The Reynolds number based on the cylinder diameter is about Re=7,500. The velocity fields near the FC free end were measured using the single-frame double-exposure PIV method. As a result, for the FC with a right-angled free end, there is a peculiar vortical structure, showing counter-rotating twin vortices near the FC free end. It is caused by the interaction between the entrained irrotational fluids from both sides of FC and the downwash flow from the FC free-end.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.79-82
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• 2012

Blossom-end rot is probably the most recognizable Ca deficiency that affects fruit production including pepper. We investigated the induction of blossom-end rot during the period of rapid vegetative growth and fruit setting, and the effect of Ca fertilization on the suppression of blossom-end rot in pepper plants grown in a plastic-film house. During the first fruit setting period, more than 60% of pepper fruits larger than 8 cm showed the symptoms of blossom-end rot. Under the condition of transpiration occurring at a much faster rate, growing leaves of pepper plants could be the greater sinks for Ca than developing fruits. The incidence of blossom-end rot was significantly decreased after two weeks of Ca fertigation. Calcium application during the rapid vegetative growth and fruit setting period could be suggested as a preventive step to overcome the local Ca deficiency inducing blossom-end rot of pepper fruits.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.1
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• pp.79-89
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• 2008

An end-of-life strategy is concerned with how to disassemble a product and what to do with each of the resultingdisassembled parts. A sound understanding of the end-of-life strategy at the early design stage could improve theease of disassembly and recycling in an efficient and effective manner. Therefore, the end-of-life decisionmaking for environmental conscious design has become a great concern to product manufacturers.We introduce a novel concept ofeco-architecture which represents a scheme by which the physical componentsare allocated to end-of-life modules. An end-of-life module is a physical chunk of connected components or afeasible subassembly which can be simultaneously processed by the same end-of-life option without furtherdisassembly. In this paper, a method for analyzing the eco-architecture of a product at the configuration designstage is proposed. It produces an optimal eco-architecture under the given environmental regulations. To dealwith the case ofa complex product, the method is extended for analyzing hierarchical eco-architecture.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.1-7
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• 2011

The mode analysis of end-milling was introduced using recursive parametric modeling. Also, a numerical mode analysis of FRF in end-milling at different conditions was performed systematically. In this regard, a REIVM(recursive extended instrumental variable method) modeling algorithm was adopted and natural modes of real and imaginary part were discussed. This recursive approach can be used for the on-line system identification and monitoring of an end-milling for this purpose. For acquiring a cutting force, an experimental practice was performed. And these end-milling forces were used for the calculation of FRF(Frequency response function) and its mode analysis. Also, the FRF was analysed for the prediction of end-milling system. As a results, this algorithm was successful in each condition for the detection of natural modes of end-milling. After numerical analysis of the FRF, the tooth passing frequency was discriminated in their FRF, power spectrum and mode calculation.