• Journal of KIISE
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• v.44 no.12
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• pp.1296-1306
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• 2017

Recently, as the number of Internet of Things users has increased, IETF (Internet Engineering Task Force) has released the CoAP (Constrained Application Protocol). So Internet of Things have been researched actively. However, existing studies are difficult to adapt to streaming service due to low transmission rate that result from buffer underflow. In other words, one block is transmitted one block to client's one request according to the internet environment of limited resources. The proposed scheme adaptively adjusts the rate of CON(Confirmable) message among all messages for predicting the exact network condition. Based on this, the number of blocks is determined by using buffer occupancy rate and content download rate. Therefore it improves the quality of user experience by mitigating playback interruption. Experimental results show that the proposed scheme solves the buffer underflow problem in Internet of Things streaming environment by controlling transmission rate according to the network condition.

• Journal of Digital Contents Society
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• v.17 no.3
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• pp.181-188
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• 2016

Video streaming traffics which are arrived in receiver have irregular traffic patterns by many problems over the network path. Particularly, if these received traffics enter into replay buffer without any operation, the overflow and underflow effects are made according to the buffer status. There was an existing scheme which automatically set up token bucket parameters using the video information file under the assumption of the lossless packet on network. The existing scheme has a problem which can set up the wrong token bucket parameters by the lost packets on the practical networks with video packet loss. Therefore, this paper proposes a new scheme which reset up video file information to correct the wrong token bucket parameters in case of packet loss in practical networks with packet loss. Through the simulation, it was found that the proposed scheme would have better performance than the existing scheme in terms of overflow generation and packet loss.

• Resources Recycling
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• v.14 no.2
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• pp.3-9
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• 2005

A study on the air and gravity separation has been performed for the removal of chlorine containing materials from ASR of end-of-life vehicles. The gravity separation was also conducted on waste plastics collected from ASR. In this work, ASR were previously shredded to pass through 8 mm sieve prior to separation tests and the gravity separation of waste plastics was conducted for three different particle sizes. The two-stage air classification was conducted with the range of air flow rate of 9~20 M$^3$/hr at first stage and 25~34 M$^3$/hr at second stage, respectively. The fraction of overflow product was remarkably increased in the 2nd stage air classification because of high air flow rate while that of underflow product obtained from 1st stage air classification was found to be 62~66%. From the results of gravity separation on waste plastics, it was also found that the amount of the float product was much greater than sink product. It is believed that the gravity separation may be used very efficiently for the removal of calorine bearing materials from waste plastics.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.533-536
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• 2004

In this paper, CMOS A/D converter with 10bit 32MSPS at 3.3V is designed for HPNA 2.0. In order to obtain the resolution of 10bit and the character of high-speed operation, we present multi-stage type architecture. That consist of sample and hold(S&H), 4bit flash ADC and 4bit Multiplier D/A Converter (MADC) also the Overflow and Underflow for timing error correct of Digital Correct ion Logic (DCL). The proposed ADC is based on 0.35um 3-poly 5-metal N-well CMOS technology. and it consumes 130mW at 3.3V power supply.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.99-102
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• 1998

As multimedia communication services have been widely spreading, the amount of video traffic is rapidly increasing in B-ISDN environment based on the ATM technology. The image quality of MPEG services is very sensitive to the cell losses in ATM network, since each cell contains information needed at decoding process. Since the number of cells in each frame of MPEG is variable, this video smoothing technology need to prepare a buffer for no overflow or underflow at the transmission, requires that some number of cells be taken to the buffer in client before the playback of video. To ensure the high quality image of video, the video smoothing is scheduled by a Group of Picture unit. In this paper, we then apply the theory to reds nightmare encoded in MPEG, and find minimum smoothing buffer size, initial buffer size. It can be used to study the smoothing of stored video.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.591-596
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• 1999

In this paper, we present a joint quality control system to be able to accurately control the relative picture quality among the video programs in terms of PSNR. The joint quality control system allows variable bit rate (VBR) for each video program to maintain the pre-determined relative picture quality among the aggregated video programs while keeping a constant sum of the bit rates for all programs to be transmitted over a single constant bit rate (CBR) channel. This is achieved by simultaneous controlling the video encoders to generate VBR video streams at the central controller. Furthermore we also suggest buffer regulation method based on the analysis of the constraints imposed by sender/receiver buffer sizes and total transmission rate. Through various simulation results, it is found that our quality control systems guarantee that the video buffers do not overflow and underflow and the quality control errors do not exceed 0.1 ㏈.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.255-258
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• 1999

This paper describes a 40-Msample/s 10-bit CMOS folding and interpolating analog-to-digital converter (ADC). A new 2-step architecture is proposed. The proposed architecture is composed of a coarse ADC bloch for the 6bits of MSBs and a fine ADC block for the remaining 4bits. The amplified folding analog signals in the coarse ADC are selectively chosen for the fine ADC. In the fine ADC, the bubble errors of the comparators are corrected by using the BGM(binary-gray-mixed) code[1] and extra two comparators are used to correct underflow and overflow errors. The proposed ADC was simulated using CMOS 0.25${\mu}{\textrm}{m}$ parameters and occupies 1.0mm$\times$1.0mm. The power consumption is 48㎽ at 40MS/s with 2.5-V power supply. The INL is under $\pm$2.0LSB and the DNL. is under $\pm$1.0LSB by Matlab simulations.

• Water for future
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• v.20 no.3
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• pp.237-245
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• 1987

The behavior of negative buoyant flow into a reservoir with sloping bottom is analysed by numerical solution technique of the governing equations composed of continuty, momentum and constituent transport equation. The stable plunge point and maximum travel distance are found to be dependent on the bottom slope of reservoir as well as inflow densimetric Froude number, $Fr_e$. They are also related closely to a vortex formed just downstream from the plunge point and above the underflow. The plunge depth was shown to be a function of th bottom slope and $Fr_e$. The plunge depths obtained in this numerical study agree relatively well with published data and theoretical studies, and its predictive equation is derived.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.5
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• pp.451-457
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• 1991

Four computational algorithms are discussed and compared in terms of complexity, required memory, and the number of channels which calculate the blocking probabilities in the two-dimensional multi-slot connection traffic. The overflow and underflow problems can be circumvented, and thus blocking probabilities can be calculated even up to 10000 channels, by the proposed last algorithm. This algorithm is utilized in calculating the blocking probabilities for I-slot and 6-slots calls. And the results of the simulation by the SLAM-II are compared with those of the analytic calculation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.3
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• pp.600-612
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• 2013

In 2006, Zhang and Wang proposed a data hiding scheme based on Exploiting Modification Direction (EMD) to increase data hiding capacity. The major benefit of EMD is providing embedding capacity greater than 1 bit per pixel. Since then, many EMD-type data hiding schemes have been proposed. However, a serious disadvantage common to these approaches is that the embedded data is compromised when the embedding function is disclosed. Our proposed secure data hiding scheme remedies this disclosure shortcoming by employing an additional modulus function. The provided security analysis of our scheme demonstrates that attackers cannot get the secret information from the stegoimage even if the embedding function is made public. Furthermore, our proposed scheme also gives a simple solution to the overflow/underflow problem and maintains high embedding capacity and good stegoimage quality.