• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1407-1412
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• 2014

In order to improve spectrum sensitivity of photodiode for detection of the laser at 850 nm ~ 1000 nm of near-infrared wavelength band, this study has produced silicon-based fast film PIN photodiode and analyzed electrical and optical properties. The manufactured device is packaged in TO-18 type. The electrical properties of the dark currents both Anode 1 and Anode 2 have valued of approximately 0.055 nA for 5 V reverse bias, while the capacitance showed 19.5 pF at frequency range of 1 kHz and about 19.8 pF at the range of 200 kHz for 0 V. In addition, the rising time of output signal was verified to have fast response time of about 30 ns for 10 V. For the optical properties, the best spectrum sensitivity was 0.66 A/W for 880 nm, while it was relatively excellent value of 0.45 A/W for 1,000 nm.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.523-532
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• 2001

An atomic commitment protocol ensures that distributed transcations terminate consistently at participating sites. An atomic commitment protocol is said to be non-blocking if it permits transaction termination to proceed at correct participants despite of failure in the coordinator site and communication. It is well known that the famous two phase commit(2PC) is a blocking protocol, whereas the three phase commit(3PC) protocol is a non-blocking. In this paper, we propose a non-blocking two phase commit(NB-2PC) protocol reducing the blocking problem than propose non-blocking protocols. The NB-2PC protocol can be obtained through modifications of the 2PC protocol. After receiving Prepare message from coordinator in the NB-2PC protocol, participants respond to the coordinator and several participants in voting phase. While participants wait for decision message from the coordinator, the blocking occurs due to the failure of the coordinator site, participants elect new coordinator among several participants receive response message. Despite of the coordinator site failures, participants consult new coordinator and follow termination protocols and achieve non-blocking property. We propose a basic structure of NB-2PC protocol and termination protocol and new coordinator election protocol. The NB-2PC protocol has non-blocking property and reduces processing time of commit protocol than the 3PC protocol. Also, through simulation experiments, we propose the NB-2PC protocol exhibits better performance of processing time of commit protocol than 3PC protocol.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.11
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• pp.369-382
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• 2015

Energy aware server clusters aim to reduce power consumption at maximum while keeping QoS(quality of service) compared to energy non-aware server clusters. They adjust the power mode of each server in a fixed or variable time interval to activate only the minimum number of servers needed to handle current user requests. Previous studies on energy aware server cluster put efforts to reduce power consumption or heat dissipation, but they do not consider energy efficiency well. In this paper, we propose an energy efficient cluster management method to improve not only performance per watt but also QoS of the existing server power mode control method based on autonomous learning. Our proposed method is to adjust server power mode based on a hybrid approach of autonomous learning method with multi level thresholds and power consumption prediction method. Autonomous learning method with multi level thresholds is applied under normal load situation whereas power consumption prediction method is applied under abnormal load situation. The decision on whether current load is normal or abnormal depends on the ratio of the number of current user requests over the average number of user requests during recent past few minutes. Also, a dynamic shutdown method is additionally applied to shorten the time delay to make servers off. We performed experiments with a cluster of 16 servers using three different kinds of load patterns. The multi-threshold based learning method with prediction and dynamic shutdown shows the best result in terms of normalized QoS and performance per watt (valid responses). For banking load pattern, real load pattern, and virtual load pattern, the numbers of good response per watt in the proposed method increase by 1.66%, 2.9% and 3.84%, respectively, whereas QoS in the proposed method increase by 0.45%, 1.33% and 8.82%, respectively, compared to those in the existing autonomous learning method with single level threshold.

• KIEE International Transaction on Systems and Control
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• v.2D no.2
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• pp.78-91
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• 2002

In the thermal power plant, there are six manipulated variables: main steam flow, feedwater flow, fuel flow, air flow, spray flow, and gas recirculation flow. There are five controlled variables: generator output, main steam pressure, main steam temperature, exhaust gas density, and reheater steam temperature. Therefore, the thermal power plant control system is a multinput and output system. In the control system, the main steam temperature is typically regulated by the fuel flow rate and the spray flow rate, and the reheater steam temperature is regulated by the gas recirculation flow rate. However, strict control of the steam temperature must be maintained to avoid thermal stress. Maintaining the steam temperature can be difficult due to heating value variation to the fuel source, time delay changes in the main steam temperature versus changes in fuel flow rate, difficulty of control of the main steam temperature control and the reheater steam temperature control system owing to the dynamic response characteristics of changes in steam temperature and the reheater steam temperature, and the fluctuation of inner fluid water and steam flow rates during the load-following operation. Up to the present time, the Proportional-Integral-Derivative Controller has been used to operate this system. However, it is very difficult to achieve an optimal PID gain with no experience, since the gain of the PID controller has to be manually tuned by trial and error. This paper focuses on the characteristic comparison of the PID controller and the modified 2-DOF PID Controller (Two-Degrees-Freedom Proportional-Integral-Derivative) on the DCS (Distributed Control System). The method is to design an optimal controller that can be operated on the thermal generating plant in Seoul, Korea. The modified 2-DOF PID controller is designed to enable parameters to fit into the thermal plant during disturbances. To attain an optimal control method, transfer function and operating data from start-up, running, and stop procedures of the thermal plant have been acquired. Through this research, the stable range of a 2-DOF parameter for only this system could be found for the start-up procedure and this parameter could be used for the tuning problem. Also, this paper addressed whether an intelligent tuning method based on immune network algorithms can be used effectively in tuning these controllers.

• Fashion & Textile Research Journal
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• v.12 no.3
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• pp.291-301
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• 2010

Today Korean clothing companies are experiencing difficulties in the global market due to unfavorable business conditions including poor production environments, labor shortage, rising costs, the further opening of the domestic distribution market, and increased competition among them. As a result, this has caused many of Korean clothing companies to transfer their production bases abroad in search of relatively inexpensive labor force, instead of using domestic plants. This study attempted to examine how Korean clothing companies perceive production environments and labor standards with regard to their offshore outsourcing. In such an attempt, in-depth interviews were conducted with 24 brand-name clothing firms. Those interviewed firms were the brands for the domestic or foreign market that were found to produce more than 200,000 pieces of clothing per year, and also the group of interviewees included some promotion service providers. The key findings from this study are as follows: First, a large number of the interviewed clothing companies were found to manage their foreign contract manufacturers by "visiting their factories regularly on a seasonal basis" or "stationing their personnel in factory for management purposes." Second, in relation to quality control in their foreign manufacturers, the most frequent response was to "have personnel stationed in those manufacturers." A smaller number of the clothing companies answered that they had "engaged their production management teams in quality control from time to time," or "used their inspectors to inspect products." Third, when asked about labor standards in foreign contract manufacturers, the largest number of the clothing companies responded, "we apply our own standards." The results of this study suggest that most of domestic clothing companies still use offshore sourcing just as a means of reducing their initial labor costs. However, in the continuously changing environment of the global clothing industry, clothing businesses are required to escape from the early phases of their manufacturing environments and set up more globalized standards.

• Transactions of the KSME C: Technology and Education
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• v.3 no.1
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• pp.23-28
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• 2015

In this paper, we performed the design optimization dual-shell and tube heat exchanger on exhaust waste heat recovery for gas heat pump using CFD and RSM. CFD analysis is useful to design the complex structure such as double shell and tube heat exchanger. By computer simulation, engineers can assess the feasibility of the given design factors and change them to get a better design. But if one wishes to perform complex analysis on the simulation, such dual-shell and tube heat exchanger for GHP, the computational time can become overwhelming. CFD is powerful but it takes a lot of time for complex structure. Therefore, the CFD analysis is minimized by the optimization using the RSM method. As a result, the number of baffle and tube are optimized by 6 baffles and 25 tubes for heat transfer and flow friction. And then pressure drop and heat transfer is improved about 12.2%. We confirm the design optimization using CFD and RSM is useful on complex structure of heat exchanger.

• The Journal of Fisheries Business Administration
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• v.35 no.1
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• pp.23-56
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• 2004

The offshore trawl fishery is seeking its survival way to overcome current management conditions in red, resulted from the bilateral agreement with China and Japan. However, this movement magnifies conflicts between fisheries on the contrary and it is thought to be impossible to get over current situations. For all that, this study is aimed at investigating how this current situations have occurred. The management freedom as response to the change in fishing conditions of a certain fishery, in case of Korea, is affected by institutional regulations. The example of this is controls on fishing gears, fishing vessels, and fishing grounds. The most exposure of this control is a segmentation of institutional fisheries. The initial segmentation of the offshore trawl fishery in Korea was occurred in the period of Japan's colonization when the degree of use of fishing grounds was limited geographically. At that time, fisheries were divided by fishing areas, but it did not divide the fishery itself. The large - sized fishing vessels were developed politically to be more competative to Japanese fishing vessels since 1950s. During this time, the trawl fishery was merged into current Eastern trawl fishery and South - Western trawl fishery. It was also inevitable to divide into the pair trawl and single trawl fishery as a result of the physical mergency between Western trawl and Southern trawl fishery. In order to develop the trawl fishery, new licenses were issued on the shrimp trawl fishery, through which it was expected to boost the trawl fishery. As opposed, the shrimp trawl fishery was changed into the mid - sized trawl fishery, targeting on the eastern fishing areas and the large - sized trawl fishery was developed since the late of 1970s with the development of filefish processing industry. The large trawl fishery that led in development of offshore trawl fishery since the late of 1950s was started to divide into a pair trawl and single trawl according to the fishing method and capital power. It finally became an institutionally independent fishery in 1980s, respectively. Looking into these historical process, the segmentation of the trawl fishery is thought as a result of the lack of long - term perspective and as a production of trial and error resulted by unprepared policy. As a result, these segmentation of fisheries roles as critical obstacles in harmonization of fisheries and in overcoming of current situations. Therefore, the review of this institutional segmentation of the offshore trawl fishery should be taken for an optimal redistribution of fishing grounds suits with business and fishing technology. For this, the fishery must be divided into large capitalized fishery and small - mid fishery with consideration of capital, fishing method, and the condition of use of fishing grounds. In addition to this, by limiting outline of fishing ground that the large fishery can harvest, it must allow for the small - mid fishery to catch with its own boundary. Furthermore, by launching buyback programs on the trawl, eastern trawl, pair trawl, it can provide broader fishing grounds where the fishery can harvest with management freedom.

• Journal of the Korean Chemical Society
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• v.54 no.2
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• pp.198-207
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• 2010

The construction and performance characteristics of doxepin hydrochloride selective electrodes were developed. Three types of electrodes: plastic membrane I, coated wire II, and coated graphite rod III were constructed based on the incorporation of doxepin hydrochloride with ammonium reineckate. The influence of membrane composition, kind of plasticizer, pH of the test solution, soaking time, and foreign ions on the electrodes was investigated. The electrodes showed a Nernstain response with a mean slope of 57.41 ${\pm}$ 0.5, 56.22 ${\pm}$ 0.2 and 52.88 ${\pm}$ 0.7 mV at $25^{\circ}C$ for electrode I, II and III respectively, over Doxepin hydrochloride concentration range from $1{\times}10^{-2}-1{\times}10^{-6}M$, $5{\tims}10^{-2}-1{\times}10^{-6}M$ and $1{\times}10^{-3}-5{\times}10^{-6}M$, and with a detection limit $5.0{\times}10^{-7}M$, $6.3{\times}10^{-7}M$ and $2.5{\times}10^{-6}M$ for electrode I, II and III respectively. The constructed electrodes gave average selective precise and usable within the pH range 3 - 7. Interferences from common cations, alkaloids, sugars, amino acids and drug excipients were reported. The results obtained by the proposed electrodes were also applied successfully to the determination of the drug in pharmaceutical preparations and biological fluids.

• The Journal of the Acoustical Society of Korea
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• v.21 no.4
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• pp.339-438
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• 2002

This paper presents a method to simulate noise propagation by a computer for outdoor environment. Sound propagated in 3 dimensional space generates reflected waves whenever it hits boundary surfaces. If a receiver is away from a sound source, it receives multiple sound waves which are reflected from various boundary surfaces in space. The algorithm being developed in this paper is based on a ray sound theory. If we get 3 dimensional geometry input as well as sound sources, we can compute sound effects all over the boundary surfaces. In this paper, we present two approaches to compute sound: the first approach, called forward tracing, traces sounds forwards from sound sources. while the second approach, called geometry based computation, computes possible propagation routes between sources and receivers. We compare two approaches and suggest the geometry based sound computation for outdoor simulation. Also this approach is very efficient in the sense we can save computational time compared to the forward sound tracing. Sound due to impulse-response is governed by physical environments. When a sound source waveform and numerically computed impulse in time is convoluted, the result generates a synthetic sound. This technique can be easily generalized to synthesize realistic stereo sounds for virtual reality, while the simulation result is visualized using VRML.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.20-35
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• 2015

Underwater acoustic channel impulse responses (CIR) are influenced by sound speed profile (SSP), and the variation of CIR has significant effects on the performance of underwater acoustic communication systems. A significant change of SSP can occur within a short period, which must be considered during the design of underwater acoustic modems. This paper statistically analyzes the effect of the variation of SSP on the long-range acoustic signal propagation in shallow-water with thermocline using numerical modeling based on the data acquired from JACE13 experiment near Jeju island. The analysis result shows that CIR changes variously according to the SSP and the depth of the transmitter and receiver. We also found that when the transmitter and receiver are deeper, the variation of sound wave propagation pattern is smaller and signal level becomes higher. All CIR obtained in this study show that a series of bottom reflections due to downward refraction and small bottom loss in the shallow water with thermocline can be very important factor for long-range signal transmission and the performance of underwater acoustic communication system in time varying ocean environment can be very sensitive to the variation of SSP even for a short period of time.