• Asian Pacific Journal of Cancer Prevention
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• v.14 no.12
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• pp.7409-7414
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• 2013

Background: Delay in diagnosis of breast cancer is associated with a poorer survival and a pivotal contribution to this delayed diagnosis comes from patient delay in presenting at a clinic. Reasons involved must be evaluated in order to decrease this reducible delay. Objectives: i) To evaluate the reasons for patient delay in diagnosis of breast cancer; ii) to investigate any association with other variables. Materials and Methods: A 6 month cross sectional study (from July 2012 to Dec 2012), was carried out in Surgical and Oncology Units of Civil Hospital, Karachi. A total of 100 females diagnosed with breast cancer of any histological type were interviewed after informed consent and relevant data were collected. Due ethical clearance was obtained. Results: Mean age was $47.5{\pm}12.1$ years with a range from 25-77 years. Mean duration of delay was $5.13{\pm}4.8$ months, from shortest 1 month to longest 36 months. Duration of delay was observed to be no delay (<1 month) in 28%, short delay (1-3 months) in 30% and long delay (>3 months) in 42% of patients. Considering the symptoms as "harmless" (39%) was the most frequent reason of delay followed by "temporary" (20%) and the "use of traditional methods" (12%). Most common reason for later approaches was an increase in the size of the lump (41%). Statistically significant association (p-value <0.05) of longer patient delay was obtained with being single, being illiterate, painless breast lump as the first symptom, negative family history of breast cancer and vague attribution of the symptoms. Conclusions: Significant delay in approach to health care facility was observed in our study due to variable reasons given by women. Sufficient awareness regarding breast cancer, its symptoms and favorable effects of a timely diagnosis on prognosis must be imparted to our general population.

• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.331-339
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• 2014

Determination of an ionospheric delay scale factor, which converts ground-based ionospheric delay into low Earth orbit ionospheric delay, using the international reference ionosphere model is proposed. Ionospheric delay from international GNSS service model combined with IRI-derived scale factor is evaluated with NASA GRACE satellite data. At approximately 480km altitude, mean and standard deviation of the scale factor are 0.25 and 0.01 in 2004. The scale factor reaches high in night time and Spring and Fall seasons. Ionospheric delay error by the proposed method has a mean of 3.50 TECU in 2004.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.1
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• pp.33-41
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• 2011

This paper considers a topological optimization of a network design with mean packet delay and node connectivity constraints. The objective is to find the topological layout of links, at minimal cost. This Problem is known to be NP-hard. To efficiently solve the problem, a scatter search algorithm is proposed. An illustrative example is used to explain and test the proposal approach. Experimental results show evidence that the proposal approach performs more efficiently for finding a good solution or near optimal solution in comparison with a genetic approach.

• Journal of the Korean Operations Research and Management Science Society
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• v.22 no.2
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• pp.99-123
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• 1997

Performance analysis of NTT/BT protocol is investigated, which is a GFC (Generic Flow Control) ptotocol in ATM (Asynchronous Transfer Mode ) network and is based on cyclic reset mechanism. THe mean cell delay time is proposed as a performance measure of NTT/BT protocol. The mean cell delay time is defined as the duration from the instant the cell arrives at the transmission buffer until the cell is fully transmitted. The process of cell transmission can be described as a single server queueing modle with two dependent services. By utilizing this model, mean cell delay time is obtained and sensitivity of the factors such as window size and reset period is also analysed.

• ETRI Journal
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• v.29 no.6
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• pp.716-724
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• 2007

As ultra-wideband impulse radio (UWB-IR) uses short-duration impulse signals of nanoseconds, even a small number of timing errors can cause a detrimental effect on system performance. A delay-locked loop (DLL) is proposed to synchronize and reduce timing errors. The design of the DLL is vital for UWB systems. In this paper, an improved DLL is introduced to a UWB-IR time-hopping spread-spectrum system. Instead of using only two central correlator branches as in a conventional DLL, the proposed system uses two additional correlator branches with different delay parameters and different weight parameters. The performance of the proposed schemes with the optimal parameters is compared with that of traditional schemes through simulation: the proposed four-branch DLLs achieves less tracking jitter or a longer mean time to lose lock (MTLL) than the conventional two-branch DLLs if proper parameters are chosen.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.684-693
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• 2003

This paper analyzes transmissiondelays of a message and a packet in a time-varying and packet-based radio link. The paper assumes that thearrivals of messages have a Bernoulli process and the lengths of the messages a exponential distribution. To reflect the feature of the time-varying radio link, we use a two-state Markov model. From the model the mean transmission delay of and the mean queue length of the packet are analyzed in terms of the packet distribution function, the packet transmission service time, and the PER of the radio link. And the mean message transmission delay time and the mean queue length are derived using the performance indices of the packet. Numerical results show that the message arrival rate and the message length have some bounds to keep the transmission of the message steady and to improve the performance indices of the message. It can be known that the PER of the state influences on the performance indices more than the sojourn time of the state.

• Journal of Communications and Networks
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• v.16 no.2
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• pp.130-139
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• 2014

Due to the unpredictable nature of channel availability, carrying delay-sensitive traffic in cognitive radio networks (CRNs) is very challenging. Spectrum leasing of radio resources has been proposed in the so called coordinated CRNs to improve the quality of service (QoS) experienced by secondary users (SUs). In this paper, the performance of coordinated CRNs under fixed-rate with hard-delay-constraints traffic is analyzed. For the adequate and fair performance comparison, call admission control strategies with fractional channel reservation to prioritize ongoing secondary calls over new ones are considered. Maximum Erlang capacity is obtained by optimizing the number of reserved channels. Numerical results reveal that system performance strongly depends on the value of the mean secondary service time relative to the mean primary service time. Additionally, numerical results show that, in CRNs without spectrum leasing, there exists a critical utilization factor of the primary resources from which it is not longer possible to guarantee the required QoS of SUs and, therefore, services with hard delay constraints cannot be even supported in CRNs. Thus, spectrum leasing can be essential for CRN operators to provide the QoS demanded by fixed-rate applications with hard delay constraints. Finally, the cost per capacity Erlang as function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.

• Journal of Navigation and Port Research
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• v.36 no.8
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• pp.637-641
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• 2012

In this paper, the method that reduce a computation time by optimizing computation process is proposed to realize low-power underwater acoustic communication system. At first, dependency of decision delay on tap length of linear equalizer was investigated. Variance is calculated based on this result, and the optimal decision delay bound is estimated. In addition to decide optimal tap length with decision delay, we extracted the MSE(Mean Square Error) graph. From the graph, we obtained variance value of the MSE-decision delay, and estimated the optimum decision delay range from the variance value. Also, using the extracted optimal parameters, we performed a simulation. According to the result, the simulation employing optimal tap length, which is only 40% of maximum tap length, showed a satisfactory performance comparable to simulation employing maximum tap length. We verified that the proposed method has 33% lower tap length than maximal tap length via sea trial.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.479-491
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• 1994

In this paper, we proposed cell priority control with 2-level thresholds, which was considered cell loss and cell delay requirement, in ATM switch with output buffer. Priority control mechanism presented in this paper improved cell loss rate for cell loss censitive cell and cell delay for delay censitive cell. In this mechanism cell loss rate and mean cell delay of cell priority control mechanism were obtained theoretically. The results show that cell loss rate and mean cell delay improvement become better by adjusting two thresholds according to QOS characteristics.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.430-438
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• 2013

This paper addresses the issue of throughput-delay of one-to-many wireless multi-hop flows based on random linear network coding (RLNC). Existing research results have been focusing on the single-hop model which is not suitable for wireless multi-hop networks. In addition, the conditions of related system model are too idealistic. To address these limitations, we herein investigate the performance of a wireless multi-hop network, focusing on the one-to-many flows. Firstly, a system model with multi-hop delay was constructed; secondly, the transmission schemes of system model were gradually improved in terms of practical conditions such as limited queue length and asynchronous forwarding way; thirdly, the mean delay and the mean throughput were quantified in terms of coding window size K and number of destination nodes N for the wireless multi-hop transmission. Our findings show a clear relationship between the multi-hop transmission performance and the network coding parameters. This study results will contribute significantly to the evaluation and the optimization of network coding method.