• Journal of Communications and Networks
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• v.6 no.3
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• pp.235-244
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• 2004

There have been a lot of approaches to evaluate and predict transmission control protocol (TCP) performance in a numerical way. Especially, under the recent advance in wireless transmission technology, the issue of TCP performance over wireless links has come to surface. It is because TCP responds to all packet losses by invoking congestion control and avoidance algorithms, resulting in degraded end-to-end performance in wireless and lossy systems. By several previous works, although it has been already proved that overall TCP performance is largely dependent on its loss recovery performance, there have been few works to try to analyze TCP loss recovery performance with thoroughness. In this paper, therefore, we focus on analyzing TCP's loss recovery performance and have developed a simple model that facilitates to capture the TCP sender's behaviors during loss recovery period. Based on the developed model, we can derive the conditions that packet losses may be recovered without retransmission timeout (RTO). Especially, we have found that TCP Reno can retransmit three packet losses by fast retransmits in a specific situation. In addition, we have proved that successive three packet losses and more than four packet losses in a window always invoke RTO easily, which is not considered or approximated in the previous works. Through probabilistic works with the conditions derived, the loss recovery performance of TCP Reno can be quantified in terms of the number of packet losses in a window.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4B
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• pp.288-297
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• 2003

The fast retransmit and fast recovery algorithm of TCP Reno, when multiple packets in the same window are lost, cannot recover them without RTO (Retransmission Timeout). TCP New-Reno can recover multiple lost packets by extending fast recovery using partial acknowledgement. If the retransmitted packet is lost again during fast recovery, however, RTO cannot be avoided. In this paper, we propose an algorithm called "Duplicate Acknowledgement Counting(DAC)" to alleviate this problem. DAC can detect the retransmitted packet loss by counting duplicate ACKs. Conditions that a lost packet can be recovered by loss recovery of TCP Reno, TCP New-Reno and TCP New-Reno using DAC are derived by modeling loss recovery behavior of each TCP. We calculate the loss recovery probability for random packet loss probability numerically, and show that DAC can improve loss recovery behavior of TCP New-Reno.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.19 no.2
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• pp.263-271
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• 2006

Objective : This study describes the cases of sensorineural hearing loss (SSNHL) patients with marked or complete recovery. Methods : Three patients received oriental medical treatments continuously for more than 1 month and measured the hearing recovery. For diagnosis on these cases, pure tone audiometry (GSI 38, Welch allyn company) was used. For treatment, acupuncture, herbal-medicine and moxibustion treatment were applied. Results : All patients of this report had the recovery of hearing. In 2 cases, the pure-tone 5 frequency (0.25, 0.5, 1, 2, 4 KHz) average improved by more than 35 dB (Marked recovery). In 1 case, it was within the normal limits after oriental medical therapy (Complete recovery). In addition, tinnitus and vertigo decreased in all patients. Conclusions : We may expect that the oriental medical therapy improvers the hearing recovery in the patients of SSNHL.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.157-163
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• 1992

In this paper, the relationship between static pressure recovery and turbulent energy was presented in case of swirling flows into a conical diffuser. The distributions of turbulent energy in a diffuser sectional area were measured by a hot wire anemometer. The following conclusion can be drawn from the experiment. Diffuser loss is constituted by a dynamic pressure loss and total pressure loss. The static pressure recovery depends strongly on the total pressure loss. The static pressure recovery depends strongly on the total pressure loss, and the turbulent energy varies inversely as the static pressure recovery coefficient.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.589-596
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• 2002

Tn the data transmission service of the mobile host, it is needed to reduce the bandwidth and to make a reliable error recovery. there are two appropriate methods in that. One is FEC which retransmits the parity of error recovery, in case of happening of the loss after forming the parity of error recovery by grouping original data. The other is local recovery based on server which can block the implosion of transmission. The use of FEC and local recovery based on server at the same time enables the reliable multicast. This paper suggests algorithm that recovers the loss by FEC and local recovery based on server through the solution of the problems about triangle routing, tunnel convergence by dividing mobile host into two parts-the sender and the receiver. This model about the loss of algorithm tested the efficiency of performance by the homogeneous independent loss, the heterogeneous independent loss, the shared source link loss model. The suggested algorithm confirms effectiveness in the environment where there are much data and many receivers in mobile host.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.4
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• pp.741-746
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• 2012

Transmission control protocol(TCP) widely used as a transport protocol in the Internet includes a loss recovery function that detects and recovers packet losses by retransmissions. The loss recovery function consists of the two algorithms; fast retransmit and fast recovery. There have been researches to avoid nonnecessary retransmission timeouts (RTOs), which leads to selective acknowledgement (SACK) option and limited transmit scheme that are standardized by IETF (Internet Engineering Task Force). Recently, a method that covers the case in which a retransmitted packet is lost again has been propsed. The method, however, is not proved in terms of the additive increase multiplicative decrease (AIMD) principle of TCP congestion control. In this paper, therefore, we analyzed the method in terms of the principle by ns-simulations.

• Journal of Korean Academy of Nursing
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• v.26 no.1
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• pp.107-126
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• 1996

The Purpose of this study was to build a substantive theory about the experience of postpartum depression. The qualitative research method used was rounded theory. The interviewees were eight others who had experienced postpartum depression. The data were collected through in-depth interviews with audiotape recording done by the investigator over a period of twelve months. he data were analyzed simultaneously by a constant comparative method in which new data were continuously coded into categories and properties according to Strauss and Corbin's methodology. Analysis the grounded data resulted in 28 concepts being identified. Eight categories emerged from the analysis. The categories were regret, loss of freedom, isolation of oneself, heartache, loss, emotional upset, avoidance, recovery. These substantive categories are consistent with precious research results. Causal conditions included : regret, loss of freedom. Phenomena : heartache, loss, emotional upset. Context : isolation oneself. Intervention condition : avoidance. Action/interaction strategies : desire for recovery. Consequences : recovery. These categories were synthesized into the core concept-The process of filling the empty loss of self. The process of the experienced postpartum depression was ① change after delivery, ② searching for a reason for depression, ③ effort to recover from postpartum depression, ④ recovery from postpartum depression and return to previous life. The process of recovery from postpartum depression was proceeded by ① support from others, especially husband, ② resolution of stressful life events, ③ reconstructing of life goals and resolution strategies, ④ acceptance of depression and seeking psychiatric treatment. Seven hypotheses were derived from the analysis. ① Mothers who experienced stressful life event and economic problem are more depressive. ② Mothers who have conflict with parents are more depressive. ③ The more somatic symptoms, the more depression. ④ Social support facilitates recovery from postpartum depression. ⑤ Mothers who have lower self-esteem are more depressive. ⑥ Mother's role overload disturbs recovery from postpartum depression. ⑦ Ideal maternal identity facilitates recovery from postpartum depression. Through this substantive theory, nurses can understand the importance of postpartum depression management.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3B
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• pp.130-137
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• 2005

Wireless communication environment is changing rapidly as we use new wireless communication technology such as WiBro to access high speed Internet. As a result, reliable data transmission using TCP is also expected to increase. Since TCP assumes that it is used in wired network, TCP suffers significant performance degradation over wireless network where packet losses are related to non-congestion loss. Especially RTO imposes a great performance degradation of TCP. In this paper, we analyze the loss recovery probabilities based on previous researches, and use simulation results of our algorithm to show that it prevents performance degradation by quickly detecting and recovery losses without RTO during fast recovery.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.7B
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• pp.650-659
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• 2004

Domestic wireless network environment is changing rapidly while adapting to meet service requirements of users and growth of market. As a result, reliable data transmission using TCP is also expected to increase. Since TCP assumes that it is used in wired networt TCP suffers significant performance degradation over wireless network where packet losses are not always result of network congestion. Especially RTO imposes a great performance degradation of TCP. In this paper, we propose DAC$^{＋}$ and EFR in order to prevent performance degradation by quickly detecting and recovering loss without RTO during fast recovery. Compared with TCP NewReno, proposed scheme shows improvements in steady-state in terms of higher fast recovery Probability and reduced response time.

• The Journal of Society for e-Business Studies
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• v.7 no.1
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• pp.167-186
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• 2002

The encryption of a file on a PC before saving can maintain security of the file. However, if the key for the encrypted file is lost or damaged, the encrypted file can not be decrypted, resulting in serious economical loss to the user or the user group. In order to minimize the economical loss a secure and reliable key recovery technology is required. Presented in this paper is the development and evaluation of PKRS (PC based Key Recovery System) which supports encryption and decryption of file and recovery of the encrypted file in emergency. The encapsulating method, which attaches key recovery information to encrypted file, is applied to the PKRS. In addition, the PKRS is developed and evaluated according to the requirements of Requirements for Key Recovery Products proposed by NIST and requirements of Common Criteria 2.0 to prove the safety and reliability of the information security system. This system is applicable to a PC and can be further extended to internet or intranet environment information system where in encryption and recovery of file is possible.