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Enhancing TCP Performance to Persistent Packet Reordering
Leung Ka-Cheong,Ma Changming The Korea Institute of Information and Commucation 2005 Journal of communications and networks Vol.7 No.3
In this paper, we propose a simple algorithm to adaptively adjust the value of dupthresh, the duplicate acknowledgement threshold that triggers the transmission control protocol (TCP) fast retransmission algorithm, to improve the TCP performance in a network environment with persistent packet reordering. Our algorithm uses an exponentially weighted moving average (EWMA) and the mean deviation of the lengths of the reordering events reported by a TCP receiver with the duplicate selective acknowledgement (DSACK) extension to estimate the value of dupthresh. We also apply an adaptive upper bound on dupthresh to avoid the retransmission timeout events. In addition, our algorithm includes a mechanism to exponentially reduce dupthresh when the retransmission timer expires. With these mechanisms, our algorithm is capable of converging to and staying at a near-optimal interval of dupthresh. The simulation results show that our algorithm improves the protocol performance significantly with minimal overheads, achieving a greater throughput and fewer false fast retransmissions.
Rheological Behavior of Poloxamer 407 Solution and Effect of Poly(ethylene glycol) on the Gelation
Ka-YoungLee,Cheong-WeonCho,Yong-BokLee,Sang-ChulShin,In-JoonOh 한국약제학회 2003 Journal of Pharmaceutical Investigation Vol.33 No.1
rheological behavior of poloxamer 407 solution as function of concentration and temperature was evaluated by rotational viscometer. The viscosity of poloxamer 407 solution was increased as the concentration of poloxamer 407 and temperature increased. At 4C, poloxamer 407 solution showed the Newtonian flow characteristics regardless of concentration. Upon increasing temperature the poloxamer solution changed to the pseudoplastic flow pattern. And at gelation temperature, rheological profiles showed the abrupt increase in viscosity. Gelation temperature was decreased as the concentration of poloxamer 407 increased, while it increased as the concentration of poly(ethylene glycol) 4000 increased. Poly(ethylene glycol) might be expected to reduce the driving force for hydrophobic interaction resulting in slow gelation. From the viscoelastic properties of poloxamer gel system, we obtained the storage and loss modulus depending on the shear stress and frequency. And the sol-gel transition temperature was also obtained from the viscoelastic properties of poloxamer 407 gel.Key wordsPoloxamer 407, Rheology, Viscoelasticity, Gels, Gelation temperature
Family, Self or State as a Desired Source of Support for the Elderly
Cheong-Seok Kim(김정석),Ka-Oak Rhee(이가옥) 한국인구학회 1999 한국인구학 Vol.22 No.2
급격한 사회변동을 경험하고 있는 한국사회가 인구변천의 마지막단계에 진입하면서 인구관련분야의 정책의 핵심은 출산과 인구통제에서 노령인구의 문제로 옮겨지고 있다. 최근 들어 국가가 자가부양(self-care)이나 가족부양(family care)을 보완하기 위해서는 공적 서비스(public service)가 확대되어야 한다는 주장들이 강조됨에 따라 노인부양규범이나 의식의 현황 및 변화에 관한 이해의 필요성이 증대되고 있다. 본 연구는 1994년 보건사회연구원이 실시한 〈노인생활실태조사〉를 이용하여 노부모들이 어느 정도로 가족, 자신 그리고 국가를 바람직한 노후생활의 부양원으로 보는가를 알아보고 있다. 다항로짓모형에 근거한 분석결과에 의하면, 아들이 없는 노부모인 경우 가족이 노인을 부양해야 한다는 전통적인 견해가 약하고, 경제나 건강상 여건이 좋은 노인일수록 자가부양의 견해가 높은 것으로 나타났다. 한편, 경제적으로 열악한 상황에 있거나 건강상태가 양호하지 않은 노인들이 국가의 책임을 강조한다고 가정한 가설은 본 연구결과 지지 받지 못했다. 본 연구의 정책적 함의나 추후연구를 위한 제안 등은 결론에서 다루어지고 있다. As Korean society has undergone rapid socioeconomic transformation and reached the final stage of its demographic transition, the central emphasis of population policies in Korea has shifted from fertility and population control to aging issues. Recently, it has been advocated that the Korean government should provide more intensive public services to supplement self-care and family caregiving, heightening the need to know more about the norms and expectations of old-age support and how they will change. Using the Survey of the Living Status of the Korean Elderly in 1994, this study investigates the extent to which the Korean elderly themselves view family, self, or the state as desired sources of support. The multinomial log it model analysis reveals that the elderly without a son are less likely to emphasize the traditional view of family, while economically and physically better off elderly are more likely to favor the view of self-support. However, the idea that the emphasis on the ‘state responsibility’ may be found among those elderly who are in need of financial help and in poor health is not supported. The implications and suggestions for further research are discussed.
Rheological Behavior of Poloxamer 407 Solution and Effect of Poly(ethylene glycol) on the Gelation
Lee, Ka-Young,Cho, Cheong-Weon,Lee, Yong-Bok,Shin, Sang-Chul,Oh, In-Joon 한국약제학회 2003 Journal of Pharmaceutical Investigation Vol.33 No.1
The rheological behavior of poloxamer 407 solution as function of concentration and temperature was evaluated by rotational viscometer. The viscosity of poloxamer 407 solution was increased as the concentration of poloxamer 407 and temperature increased. At 4℃, poloxamer 407 solution showed the Newtonian flow characteristics regardless of concentration. Upon increasing temperature the poloxamer solution changed to the pseudoplastic flow patter. And at gelation temperature, theological profiles showed the abrupt increase in viscosity. Gelation temperature was decreased as the concentration of poloxamer 407 increased, while it increased as the concentration of poly(ethylene glycol) 4000 increase. Poly(ehtylene glycol) might be expected to reduce the driving force for hydrophobic interaction resulting in slow gelation. From the viscoelastic properties of poloxamer gel system, we obtained the storage and loss modulus depending on the shear stress and frequency. And the sol-gel transition temperature was also obtained from the viscoelastic properties of poloxamer 407 gel.
Liu Gabriel Ka-Po,Tan Jiong Hao,Kong Jun Cheong,Tan Yong Hao Joel,Kumar Nishant,Liang Shen,Shawn Seah Jing Sheng,Ting Chiu Shi,Lim Lau Leok,Dennis Hey Hwee Weng,Kumar Naresh,Thambiah Joseph,Wong Hee-K 대한척추외과학회 2022 Asian Spine Journal Vol.16 No.6
Study Design: A retrospective cohort study of patients with surgically treated thoracolumbar fractures.Purpose: This study aimed to describe the incidence of adverse events (AEs) after surgical stabilization of thoracolumbar spine injuries and to identify predictive factors for the occurrence of AEs. Overview of Literature: Thoracolumbar spine fractures are frequently present in patients with blunt trauma and are associated with significant morbidity. AEs can occur due to the initial spinal injury or secondary to surgical treatment. There is a lack of emphasis in the literature on the AEs that can occur after operative management of thoracolumbar fractures.Methods: We performed a retrospective review of 199 patients with surgically treated thoracolumbar fractures operated between January 2007 and January 2018. The potential risk factors for the development of AEs as well as the development of common complications were evaluated by univariate analysis, and a multivariate logistic regression analysis was performed to identify independent risk factors predictive of the above.Results: The overall rate of AEs was 46.7%; 83 patients (41.7%) had nonsurgical AEs, whereas 24 (12.1%) had surgical adverse events. The most common AEs were urinary tract infections in 43 patients (21.6%), and hospital-acquired pneumonia in 21 patients (10.6%). On multivariate logistic regression, a Thoracolumbar Injury Classification and Severity (TLICS) score of 8–10 (odds ratio [OR], 6.39; 95% confidence interval [CI], 2.33–17.51), the presence of polytrauma (OR, 2.64; 95% CI, 1.17–5.99), and undergoing open surgery (OR, 2.31; 95% CI, 1.09–4.88) were significant risk factors for AEs. The absence of neurological deficit was associated with a lower rate of AEs (OR, 0.47; 95% CI, 0.31–0.70).Conclusions: This study suggests the presence of polytrauma, preoperative American Spinal Injury Association score, and TLICS score are predictive of AEs in patients with surgically treated thoracolumbar fractures. The results might also suggest a role for minimally invasive surgical methods in reducing AEs in these patients.
Severe but reversible acute kidney injury resulting from Amanita punctata poisoning
( Eun Jung Kang ),( Ka Young Cheong ),( Min Jeong Lee ),( Seirhan Kim ),( Gyu Tae Shin ),( Heung Soo Kim ),( In Whee Park ) 대한신장학회 2015 Kidney Research and Clinical Practice Vol.34 No.4
Mushroom-related poisoning can cause acute kidney injury. Here we report a case of acute kidney injury after ingestion of Amanita punctata, which is considered an edible mushroom. Gastrointestinal symptoms occurred within 24 hours from the mushroom intake and were followed by an asymptomatic period, acute kidney injury, and elevation of liver and pancreatic enzymes. Kidney function recovered with supportive care. Nephrotoxic mushroom poisoning should be considered as a cause of acute kidney injury.
( Eun Jung Kang ),( Hwa Jung Lee ),( Ka Young Cheong ),( In Hwee Park ),( Heung Soo Kim ),( Gyu Tae Shin ) 대한내과학회 2014 대한내과학회 추계학술대회 Vol.2014 No.1
Background: The combined peritoneal dialysis (PD) regimen of different biocompatible solutions consisiting of bicarbonate/lactate-, icodextrin- and aminoacid solutions (BIC/ LAC-ICO-AA), has been developed to reduce carbohydrate absorption and peritoneal glucose and GDP exposure (Holmes CJ. Perit Dial Int. 2000). Another combined PD regimen of convntional lactate solutions with one icodextrin exchange (LAC-ICO) has been also widely used especially for automated PD. In this study, we investigated the function of peripheral blood mononuclear cells (PBMCs) in end stage renal disease patients on these PD regimens. Methods: PBMCs were isolated from peripheral venous blood using ficoll gradient Methods: To investigate the function of monocytes, PBMCs were stimulated with lipopolysacharride and the supernatants were analyzed for tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) by enzyme-linked immunosorbent assay (ELISA). Isolated lymphocytes were stimulated with ionomycin, phorbol myristic acetate (PMA) and brefeldin A and then stained with CD3-, CD8 surface markers and interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) for fi ow cytometry (FACS) analysis. Lymphocytes were also stimulated with ionomycin and PMA for TNF-alpha and IL-6 ELISA. Results: Monocytes in the LAC-ICO group (n=16) secreted signifi cantly higher TNF-alpha and IL-6 compared to healthy controls whereas the BIC/LAC-ICO-AA group (n=16) and healthy controls (n=10) were comparable. The FACS analysis of lymphocytes showed similar expression of IFN-gamma (Th1 signature antigen) and IL-4 (Th2 signature antigen) in CD4 T-lymphocytes and CD8 T-lymphocytes in both the LAC-ICO (n=12) and the BIC/ LAC-ICO-AA groups (n=11) compared to to healthy controls (n=10). Similarly, both PD groups were comparable in secretingTNF-alpha and IL-6 by lymphocytes compared to healthy controls. Conclusions: The LAC-ICO PD regimen enhanced the monocytes function of secreting pro-infi ammatory cytokines. The LAC-ICO and the BIC/LAC-ICO-AA PD regimens neither perturb T-cell cytokine pattern, nor altered the pro-infiammatory cytokine secretory function of lymphocytes.