• Journal of Korean Neurosurgical Society
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• v.41 no.4
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• pp.241-245
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• 2007

Objective : So called "minimally invasive procedures" have evolved from chemonucleolysis, automated percutaneous discectomy, arthroscopic microdiscectomy that are mainly working within the confines of intradiscal space to transforaminal endoscopic technique to remove herniated epidural disc materials directly. The purpose of this study is to assess the result of endoscopic spinal surgery and favorable indication in the thoracolumbar spine. Methods : The records of 71 patients, 73 endoscopic procedures, were retrospectively analysed. Yeung Endoscopic Spine Surgery system with 7 mm working sleeve and $25^{\circ}$ viewing angle was used. The mean follow up period was 6 months [range, 3-9]. Results : Operated levels were from T12-L1 disc down to L5-L6 of S1 disc. Of 71 cases, 2 patients underwent transforaminal endoscopic surgery twice due to recurrence after initial operation. MacNab's criteria was used to assess the outcome. Favorable outcome, excellent of good, was seen in 78% [57 procedures] of the patients. Among 11 fair outcomes, only 1 procedure was followed by secondary open procedure, laminectomy with discectomy. Two of 5 poor outcomes were operated again by same procedure which resulted in fair outcomes. One patient with aggravated cauda equina syndrome remained poor and a lumbar fusion procedure was performed in other patient with poor outcome. There were 2 postoperative discitis that were treated with conservative care in one and anterior lumbar interbody fusion in the other. Conclusion : Evolving technology of mechanical, visual instrument enables minimal invasive procedure possible and effective. The transforaminal endoscopic spinal surgery can reach as high as T12-L1 disc level. The rate of favorable outcome is mid-range among reported endoscopic lumbar surgery series. Authors believe that the outcome will be better as cases accumulate and will be able to reach the fate of standard open microsurgery.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1059-1067
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• 1999

In this paper characteristics of ATM-PON is described and a TC layer controller for ATM-PON OLT is designed. This paper proposes an algorithm of economically controlling the grant information written by CPU to dynamically allocate the upstream bandwidth on the PON among the ONUs in a fair way and of encrypting the downstream data using a lower standard of encryption, termed data churning, which is used to distinguish it from existing transmission system scramblers and higher layer encryption methods. This paper also proposes a method of allocating churning-related message into the PLOAM cell in order to synchronously change the churning key between the OLT and the ONU.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.485-492
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• 2003

This paper proposes a transmission probability control scheme for guaranteeing fair packet transmissions in CDMA slotted ALOHA system. In CDMA slotted ALOHA system, the packets transmitted in the same slot act as multiple access interference, so that unsuccessful packet transmissions are caused entirely by multiple access interference. Therefore, in order to maximize the system throughput, the number of simultaneously transmitted packets should be kept at a proper level. In the proposed scheme, the base station calculates the packet transmission probability of mobile stations in the next slot according to the offered load and then broadcasts this probability to all the mobile stations. Mobile stations, which have a packet to transmit, attempt to transmit packet with the received probability. Simulation results show that the proposed scheme can offer better system throughput and average delay than the conventional scheme, and guarantee a good fairness among all mobile stations regardless of the offered load.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.8
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• pp.3880-3899
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• 2019

Distributive desynchronization algorithms based on pulse-coupled oscillator (PCO) models have been proposed for achieving collision-free wireless transmissions. These algorithms do not depend on a global clock or infrastructure overheads. Moreover, they gradually converge to fair time-division multiple access (TDMA) scheduling by broadcasting a periodic pulse signal (called a 'firing') and adjusting the next firing time based on firings from other nodes. The time required to achieve constant spacing between phase neighbors is estimated in a closed form or via stochastic modeling. However, because these algorithms cannot guarantee the completion of desynchronization in a short and bounded timeframe, they are not practical. Motivated by the limitations of these methods, we propose a practical solution called PD-DESYNC that provides a short and deterministic convergence time using a flag firing to indicate the beginning of a cycle. We demonstrate that the proposed method guarantees the completion of desynchronization within three cycles, regardless of the number of nodes. Through extensive simulations and experiments, we confirm that PD-DESYNC not only outperforms other algorithms in terms of convergence time but also is a practical solution.

• Korean Journal of Ecology and Environment
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• v.42 no.3
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• pp.364-373
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• 2009

We evaluated stream health, based on integrative approaches of qualitative habitat evaluation index (QHEI), chemical water quality and the index of biological integrity (IBI) using fish assemblages in Daejeon Stream during August 2004 - October 2007. The QHEI values in this study averaged 78.2 (n=28, range: 47$\sim$124), indicating "fair" condition based on the criteria of US EPA (1993). The highest value was in the headwater site (S1) that was 112 (good), whereas the value in S3, mid and downstream was SS (fair-poor) that was the lowest owing to a disturbance on the bed and an artificial bank. Concentrations of chemical parameters such as BOD, TP and conductivity increased from the upstream to the downstream due to higher inputs of organic matters and nutrients from the urban area. Conductivity and TP showed a dilution of stream water by rainwater during summer monsoon. Analysis of fish compositions showed that total number of species was 24 and Zacco platypus was predominated (82%). The mean IBI was 17 (range: 12$\sim$30) during four years and the IBI values also decreased from S1 to S4. These results indicated that ecological health was degradated distinctly as the stream goes down through the city-center. We concluded that Daejeon Stream running through the city are influenced by chemical impact such as an influx of domestic sewage as well as the quality of habitat.

• Journal of Ecology and Environment
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• v.36 no.1
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• pp.73-83
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• 2013

The object of this study was to evaluate lotic ecosystem health using multiple eco-metric approaches such as water chemistry diagnosis, physical habitat health evaluations, and biological integrity modeling at 100 streams of four major watersheds. For the study, eight chemical water quality parameters such as nutrients (N, P) and organic material were measured and 11-metric models of Qualitative Habitat Evaluation Index (QHEI) and multiple eco-metric health assessment model (MEHA) were applied to the four major watershed. Nutrient analysis of nitrogen (N) and phosphorus (P) in all watersheds indicated a eutrophic state depending on the locations of sampling streams. Physical habitat health, based on the QHEI model, averaged 114 (range: 56 - 194), judging as a "good condition" by the criteria of Plafkin et al. (1989). In addition, primary (H1 - H4), secondary (H5 - H7), and tertiary habitat metric variables (H8 - H11) were analyzed in relation to the physical habitat degradations. The plots of tolerant species ($P_{TS}$) and sensitive species ($P_{SS}$) to water quality showed that the proportions of $P_{TS}$ had positive linear functions with nutrients, and that the $P_{SS}$ had inverse linear relations with the chemical variables. The model of eco-metric health assessment showed that mean MEHA was 20.4, indicating a fair condition. Overall, our data suggest that water chemistry, based on nutrients and organic matter, directly modified the trophic structures in relation to food chain in the aquatic ecosystems, and then these directly influenced the compositions of tolerance/sensitive species, resulting in degradations of overall ecological health.

• Hip & pelvis
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• v.30 no.4
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• pp.260-268
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• 2018

Purpose: This study was performed to assess the clinical and radiological outcomes following one-stage hip reconstruction, consisting of open reduction femoral shortening and pelvic osteotomy, for neglected developmental dislocation of the hip (DDH). Materials and Methods: This is a retrospective analysis of 77 hips in 65 patients (46 females and 19 males; 12 had bilateral dislocations), operated at a Ghurki Trust Teaching Hospital in Pakistan between 2013 and 2015. The average age at surgery was $11.02{\pm}3.43$ years. According to the Tonnis classification, there were 10, 14, 22, and 31 patients in grades 1, 2, 3, and 4, respectively. The pelvic procedure utilized in this study was triple osteotomy (47 hips) followed by double and Salter osteotomy (18 and 12 hips, respectively). Postoperative evaluations were conducted using the modified MacKay's scoring system (functional outcomes) and Severin's scoring method (radiological assessment). Results: Postoperatively, there were 38 (49.4%), 19 (24.7%), 14 (18.2%), and 6 (7.8%) hips in Severin grade I, II, III and IV, respectively. According to the modified McKay criteria, there were 22 hips (28.6%) in excellent condition, 44 (57.1%) in good condition, 9 (11.7%) in fair condition and 2 (2.6%) in poor condition. Both patients with poor outcomes had an unstable, painful hip with evidence of avascular necrosis of the femoral head. Conclusion: Based on the results presented here, we recommend the single stage procedure of open reduction, femoral shortening and pelvic osteotomy for treatment of DDH in older children with good to excellent functional and radiological outcomes.

• Korean Journal of Ecology and Environment
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• v.45 no.1
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• pp.72-81
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• 2012

We investigated the effects of acid mine drainage (AMD) from abandoned coal mines on benthic macroinvertebrate communities in the upper reaches of the Nakdong River from May to October in 2009. Qualitative and quantitative sampling (Surber sampler: $50{\times}50$ cm; mesh size, 0.2 mm) was conducted at 7 study sites and 3 control sites in the study area. We thus sampled 117 species belonging to 53 families, 15 orders, 6 classes, and 5 phyla; the Ephemeroptera, Plecoptera, and Trichoptera group (EPT-group) represented the majority of the benthic macroinvertebrate community (71 species; 64.5%). In the quantitative sampling, a total of 11,575 individuals belonging to 58 species of benthic maroinvertebrates were sampled from the study sites (Sites 1-7), whereas 2,844 individuals belonging to 79 species were sampled from the control sites (Sites A-C). Tolerant species such as oligochaetes, $Epeorus$ $pellucidus$, $Baetis$ $fuscatus$, Hydropsychidae species, and Chironomidae species were predominant in the study sites. The community indices for the study sites, such as MacNaughton's dominance index (DI) (mean${\pm}$SD, $0.52{\pm}0.21$; range, 0.33-0.85) and the Shannon diversity index ($H^{\prime}$) ($2.06{\pm}0.60$; 1.06-2.57), were different from those for the control sites (DI: $0.29{\pm}0.07$, 0.22-0.35; $H^{\prime}$: $3.13{\pm}0.14$; 3.03-3.30). In the study sites, shredders and scrapers were scarce, whereas gathering-collectors (mainly Chironomidae species) were relatively abundant, as were clingers and burrowers. The detrended correspondence analysis (DCA) and similarity analyses showed that benthic macroinvertebrate communities in the study sites were clearly separated from those of the control sites, with the greatest dissimilarity being noted at the uppermost study site (Site 1), which is located close to an abandoned coal mine. The Korean saprobic index (KSI) and the ecological score using benthic macroinvertebrates (ESB) showed that the uppermost study site (Site 1) was ${\alpha}$-mesosaprobic or heavily polluted, whereas other study sites were in a fair or relatively good condition.