• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.316-322
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• 2002

The Orthogonal Frequency Division Multiplexing(OFDM) is a special case of multicarrier transmission, where a single data stream is divided into many subcarriers and transferred in a parallel way. It reduces the necessary bandwidth using the orthogonality between the subcarriers. Therefore it requires the transmission channel which has stable characteristic. When the delay spread of the channel exceed the guard interval, then the orthogonality of the subcarriers cannot maintain and as a result the system performance degrade. In this paper, the XCP-OFDM(OFDM using cross-handed Circular Polarization) system is newly proposed. This system divides the channel in order to eliminate the overlapping of subcarrier's spectrum by using cross-handed circular polarization. Therefore, the proposed XCP-OFDM system can improve the performance without increasing the guard interval. Both theoretical analysis and simulation results are described.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.241-246
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• 2006

This paper describes two kinds of personal hand-held electronic devices to support marine leisure safety. The one is Radar response-type safety device triggering by the pulse signal from a commercial 9GHz-band Radar to provide quick search and rescue with combined civilian-government-military fleets. The other one is M-RFID (Marine Radio Frequency IDentification) based safety electronic device using 900MHz Tx/Rx with spread spectrum frequency hopping and GPS. Through the field tests at sea using Korea Coast Guard's warship the operating performances are verified. Further plan for practical use of each device was also discussed.

• Korean Security Journal
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• no.25
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• pp.63-87
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• 2010

Our society nowadays sees the increase in damage from crime on lives and properties by leaps and bounds in line with the economic take-off, and as a result, the raise of individual income. When considering such a hike in crime, it is desirable that the police framework be enhanced. However, thanks to the failure to correspond to this, it could be safely said that a good portion of accountability was shifted to the private security industry in regard to security for the people. Accordingly, the request for escort security business is on the increase regarding expansion and improvement about this industrial sector. As such, it is necessary to get the related system rearranged for authority on the part of escort guards, who are directly exposed to numerous crimes. On top of this, dispersion is required for the escort security businesses centralized in the metropolitan area. It is also necessary for the security guard system to be strengthened and disintegrated into details so that the escort security services are available to people in more safe and easily manners than ever before. When the qualification regime is operated based on this refreshed system, the efficient escort security work would be realized. The dichotomy into act on Special Security Guard and act on Security Business should be dealt with once again for integration as an issue on the front burner in the academic area, and through which the escort security market could be fit for the globalization as well. This paper would provide the solution that leads to more professional and efficient results from comprehension of progress situations in reality by starting from the concept on private security to the analysis of the conditions in this industrial sector.

• Korean Security Journal
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• no.13
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• pp.1-21
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• 2007

This study aims to analysis and measure on the curriculum of security programs in Korean university as the private security system. Civil security demand social safety life by the police protection and private security system. The private security or the civil guards shows rapid growth by the social development and improve the quality of life. But the supply and training system have some limitations in spite of the high demand guard-secretary. The main role of secretaries has been to accompany superiors in order to maintain their dignity or trait. Then the secretaries are required to play additional roles of safety managers such as a security manager, a protocol manager, an intelligence manager and a protective driver in order to overcome the domestic and the international safety environment and to elevate the quality of service as a competitive work. So, the purpose of this article is to analyze current situation of civil body and security guard training industry and to seek an educational model. For that, we examine in 'Do the professional training organizations meet social demand for the body and security guards'? And, 'What kind of training has to be provide for the body and security guards'? and 'What the qualifications of the trainers'? Then, 'What are the differences in training courses between private organizations and universities'? 'Is there differences in the job placement among the trainers of private organizations and universities'? etc.. Conclusion, the social demand common curriculum for the body and security guard will be drawn from the analysis of diverse training organizations with different training courses in contents, training periods, educational value, and social aim. Then we have to a standard curriculum for the successful training education system to provide social security.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4102-4110
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• 2022

Aiming at high-power and long-pulse operation up to 1000 s, some improvements have been made for both 2.45 GHz and 4.6 GHz lower hybrid (LH) systems during the recent 5 years. At first, the guard limiters of the LH antennas with graphite tiles were upgraded to tungsten, the most promising material for plasma facing components in nuclear fusion devices. These new guard limiters can operate at a peak power density of 12.9 MW/m². Strong hot spots were usually observed on the old graphite limiters when 4.6 GHz system operated with power >2.0 MW [B. N. Wan et al., Nucl. Fusion 57 (2017) 102019], leading to a reduction of the maximum power capability. With the new limiters, 4.6 GHz LH system, the main current drive (CD) and electron heating tool for EAST, can be operated with power >2.5 MW routinely. Long-pulse operation up to 100 s with 4.6 GHz LH power of 2.4 MW was achieved in 2021 and the maximal temperature on the guard limiters measured by an infrared (IR) camera was about 540 ℃, much below the permissible value of tungsten material (~1200 ℃). A discharge with a duration of 1056 s was achieved and the 4.6 GHz LH energy injected into the plasma was up to 1.05 GJ. Secondly, the fully-active-multijunction (FAM) launcher of 2.45 GHz system was upgraded to a passive-active-multijunction (PAM), for which the density of optimum coupling was relatively low (below the cut-off value). Good coupling with reflection coefficient ~3% has been achieved with plasma-antenna distance up to 11 cm for the new PAM. Finally, in order to eliminate the effect of ion cyclotron range of frequencies (ICRF) wave on 4.6 GHz LH wave coupling, the location of the ICRF launcher was changed to a port that is located 157.5° toroidally from the 4.6 GHz LH system and is not magnetically connected.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8B
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• pp.609-614
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• 2008

Upstream data frame of TDM-PON includes various types of overheads, and there exist guard bands between consecutive frames from different ONUs. Although they are indispensible in synchronization and performance, they cause bandwidth waste at the same time. To solve this problem, a new TDM-PON that uses two types of wavelengths in upstream transmission is suggested. By even distribution of two wavelengths among ONUs and overhead overlap between frames that use different wavelengths, almost 100% bandwidth efficiency could be achieved. A serializer that multiplexes signals from two wavelengths is implemented for this purpose.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.4
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• pp.336-346
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• 2017

Applications of Sigma-Delta STAP, and a method of GMTI processing are presented for GMTI(Ground Moving Target Indication) mode of airborne radar with sigma, delta, and guard channels. We showed results of performance analyses of presented methods by clutter simulation with ICM(Internal Clutter Motion), signal processing simulation and MDV(Minimum Detectable Velocity). Presented methods for Sigma-Delta STAP and GMTI processing are easy to apply practically in GMTI mode of airborne radar without restriction by specific airborne radar system.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.245-257
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• 2004

Driven by the growing number of the mobile subscribers, efficient channel resource management plays a key role for provisioning multimedia service in the next generation personal communication systems. To reuse limited channel resources, diminishing the coverage areas of cells seems to be the ultimate solution. Thus, however, causes more handover events. To provide seamless connection environment for mobile terminals and applications, this article presents a novel handover scheme called the intelligent channel reservation (ICR) scheme, which exploits the location prediction technologies to accurately reserve channel resources for handover connections. Considering the fact that each mobile terminal has its individual mobility characteristic, the ICR scheme utilizes a channel reserving notification procedure (CRNP) to collect adequate parameters for predicting the future location of individual mobile terminals. These parameters will be utilized by the handover prediction function to estimate the expected handover blocking rate and the expected number of idle channels. Based on the handover prediction estimations, a cost function for calculating the damages from blocking the handover connections and idling channel resources, and a corresponding algorithm for minimizing the cost function are proposed. In addition, a guard channel decision maker (GCDM) determines the appropriate number of guard channels. The experimental results show that the ICR scheme does reduce the handover-blocking rate while keeping the number of idle channels small.

• Progress in Superconductivity and Cryogenics
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• v.7 no.3
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• pp.39-42
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• 2005

In this paper, the thermal characteristics of multilayer insulation (MLI) were experimentally investigated by using boil-off calorimetry method for seeking optimum standards of thermal insulation conditions. It is necessary to design the thermal insulating efficiency for applying to cryogenic instruments such as HTS power cable system. It is well known that the thermal characteristics and heat transfer of MLI are greatly affected by various MLI structures such as the number of layers and layer density, etc. However, it is difficult to know the thermal characteristics of MLI correctly. The heat leak by MLI between room temperature and liquid nitrogen temperature was measured at various conditions using a cylindrical cryostat. The cryostat consists of two guard vessels located at both end sides and a test vessel between them. The guard vessels are also filled with liquid nitrogen to prevent radiation heat leak through the both end side of the cylindrical test vessel to measure the heat leak only through MLI.

• Journal of the Korean Society of Safety
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• v.16 no.2
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• pp.80-84
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• 2001

Work stress and health are very important factors related to workers' condition and work safety, Author has conducted a couple of tests to check up three people's pulses before they work during their work for three types of safety guard in construction site. Work type, age, weight, sex experience year, ambient temperature n recorded as variables in this study. These are checked and asked by the author directly, before their pulse check Also, workers' Pulses were measured at height H-0 and H-9.0m to understand psychological the degree of psychological nervousness degree. POLAR protrainer NVTM HRM system(wrist recorder and sensor) was used for the site test. There are three(3) different types of construction safety guard which have been used for, this study. They are usually or frequently used and found in the site. Four different ranges of age groups(20's, 30's 40's, 50's) carpenters are assisted to the test sites with wearing pulse recorder and sensor respectively. All three types of safety guards have the same height 90㎝ even though they are different types. On top of five(5) stories tublar framed scaffolding is fabricated, similar to the one in site, where those safety guards are installed. The older(=more experienced) the workers are the more stable they are. it is shown. Also, It is verified the visually uncomfortable rail type can cause workers to psychologically be unstable.