• The Journal of the Acoustical Society of Korea
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• v.32 no.6
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• pp.494-501
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• 2013

The convolution code(CC) of code rate 1/2 as a forward error correction (FEC) in Quadrature Phase Shift Keying (QPSK) is applied to decrease bit error rate (BER) by background noise and multipath in shallow water acoustic channel. Ratio of transmitting signal bandwidth to channel coherence bandwidth is defined as frequency selectivity index. BER and bit energy-to-noise ratio gain of transmitted signal according to frequency selectivity index are evaluated. In the results of indoor water tank experiment, BER is well matched theoretical results at frequency selectivity index less than about 1.0. And bit energy-to-noise ratio gain is also matched theoretical value of 5 dB. BER is effectively decreased at frequency selective multipath channel with frequency selectivity index higher than 1.0. But bit energy-to-noise ratio greater than a certain size in terms of CC weaving is effective in reducing bit errors. In the results, the defined frequency selectivity index in this study could be applied to evaluate a performance of CC in multipath channel. Also it could effectively reduced BER in a low speed underwater acoustic communication system without an equalizer.

• The Korea Journal of Herbology
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• v.30 no.1
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• pp.33-42
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• 2015

Objectives : The aim of this study was to evaluate the antitumor effects of Cheongpyesagan-tang(CST) and YKK012 on colon cancer. Methods : MTT assay was used to evaluate the cytotoxicity of Single herbs and combinations of CST and YKK012 on murine colon cancer cells, Colon 38. To explain effects of apoptosis in colon cancer, we performed the western blot. Effects of CST and YKK012 on antitumor activity of CPT-11 using the murine colon38 allograft tumor in BDF1 mice. Results : Single herbs and combinations of CST and YKK012 was tested in vitro, Rhei Radix (RH) and Scutellariae Radix (SC) and YKK012 showed dose-response cytotoxicity on Colon 38. This might be due to the apoptosis, as we see Bax and Caspase-3, which are apoptotic factors, was expressed in RH and SC treated cells. YKK012 also showed increased expression of Caspase-3. In mouse colorectal cancer xenograft model of colon38 cells, herbal combinations showed tendencies of tumor regression, but was not significant. Furthermore, because toxicity was observed in CST group, we reduced the dose of CST for the next experiment. The anti-tumor effects of herbal combinations were insufficient to be used as single anti-tumor agent. With simultaneous usage of CPT-11, contrary to that CST showed no synergistic effects, YKK012 which was composed by the combination of four $ER{\beta}$ selective herbs, significantly reduced the size of tumor and Bax expression was increased. Conclusions : We suggest YKK012 can be a effective cancer adjuvant therapy with CPT-11 on colon cancer.

• Progress in Medical Physics
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• v.12 no.1
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• pp.71-77
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• 2001

The region, near the edge of a radiation beam, where the dose changes rapidly according to the distance from the beam axis is known as the penumbra. There is a sharp dose gradient zone even in megavoltage photon beams due to source size, collimator, lead alloy block, other accessories, and internal scatter ray. We investigate dosimetric characteristics on penumbra regions of a standard collimator and compare to those of theoritical model for the optimal use of the system in radiotherapy. Peripheral dose distribution of 6 W Photon beams represents penumbral forming function as the depth. Also we have discussed that the peripheral dose distribution of clinical photon beams, differences between calculation dose use of emperical penumbral forming function and measurements in penumbral region. Predictions by emperical penumbral forming functions are compared with measurements in 3-dimensional water phantom and it is shown that the method is capable of reproduceing the measured peripheral dose values usually to within the statistical uncertainties of the data. The semiconductor detector and ion chamber were positioned at a dmax depth, 5cm depth, 10cm depth, and its specific ratio was determined using a scanning data. The effective penumbra, the distance from 80% to 20% isodose lines were analyzed as a function of the distance. The extent of penumbra will also expand with depth increase. Difference of measurement value and model functions value according to character of the detector show small error in dose distribution of the peripheral dose.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.524-534
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• 1994

The effects of transformation temperature and mechanical properties by thermal cycle of CuZnAl shape memory alloy with a small of misch metal and Zr contents were investigated. The addition of misch metal and Zr was very effective for reducing the grain size. After solution treatment, the specimens were post-quench aged or step quenched at $100^{\circ}C$ to $350^{\circ}C$ for variation of Rockwell hardness value. It was found that the Rockwell hareness value was very increased at $200^{\circ}C$ and $250^{\circ}C$. The fracture strength and ductility have been significantly increased with the increase of misch metal conten when tensile tested below $M_f$ temperature. Also, the fracture strength has been more increased in the case of post quench aging treatment than that of the as-quenching treatment. Aging of the $\beta$-phase decreases the $M_s$ temperature, but that of the martensite phase increases the $A_s$ temperature. The change in $A_s$ temperature with post-quench aging can be attributed to recovery of order in the $\beta$phase. The hystersis of transformation temperature ($A_s-M_s$) has an increasing tendency by thermal cycles.

• Journal of the Korean Institute of Landscape Architecture
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• v.33 no.3 s.110
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• pp.78-83
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• 2005

The purpose of this project is to create small parks in elementary schools in order to improve the educational environment and also to increase the amount of greenspace in the city. Above all, the main goal is to create space for local residents in which they can enjoy their leisure time. During a basic investigation and document investigation of elementary schools in Daegu, I placed the priority on choosing the schools that showed the most promise. Also, by doing a survey about the present conditions at schools, I verified, compared, and analyzed the validity of creating small parks in elementary schools. The summary of the results are as follows. The average area available for building small parte in Daegu elementary schools is $7,447m^2$. Even though this area is not as large as a neighborhood parti the difference is not that great. Therefore, I assumed that building small parks in schools would be as effective as building neighborhood parks. The standard size for a children's parks is $1,500m^2$, and if small parks were to be constructed in all school areas with available space larger than a children's park (i.e., larger than $1,500m^2$), the amount of added park greenspace would equal $1,217,953m^2$. The number of schools with areas under $1,500m^2$ is only 3% of all schools in which small parte can be created(5 schools). Schools that have between $1,500m^2$ and $8,000m^2$of greenspace make up 59.7% of all schools in which small parte can be created (98 schools). Schools that have greenspace of more than $8,000m^2$ make up 37% of all school in which small parks can be created (61 schools). The standard area for neighborhood parte is $10,000m^2$ (building-to-land ratio 20%). Schools that have areas that are larger than the standard area for neighborhood parte make up 31% of all elementary schools in Daegu (61 schools). Therefore city greenspace would increase to a total of $694,805m^2$ by making use of these schools, which would represent 7% of the park greenspace in Daegu.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.276-284
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• 2005

In the mobile computing environment, caching data at the client's side is a useful technique for improving the performance. For caching to be effective, the cache contents must be consistent with those stored in the server. That is, unfortunately, difficult to enforce due to the frequent disconnection and mobility of clients. In the literature, the basic approach adopted is for the sever to periodically broadcast invalidation reports(IRs) that contain information about objects that have been updated recently. However IR-based cache maintenance scheme has a main drawback. Any client who has been disconnected longer than w seconds has to discard all cached items even some of them may still be valid. In this paper, we propose two main schemes which can adapt clients' losing IR messages by long disconnection. First, the client sends its disconnection time when connection is re-established, and the server uses this information to decide the size of broadcast window w dynamically. Second, the server maintains IR messages for a given period of time and a client who has been disconnected longer than w seconds can verify its cache consistency individually. Compared to previous IR-based schemes, our schemes can significantly reduce cache missing and uplink request and improve the throughput by reducing response time.

• Resources Recycling
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• v.17 no.5
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• pp.28-36
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• 2008

The effect of attrition scrubbing on the recovery of platinum group metals (PGMs) from automobile catalytic converters has been investigated. Catalytic converters were first crushed into particles less than 2 mm and attrition scrubbed in the range of 60 min, and then they were sieved with several screens. The catalyst layer, $\gamma$-alumina, was dislodged from the surface of the supporting matrix into fine particles less than $45{\mu}m$ by attrition scrubbing. The fraction of fine particles less than $45{\mu}m$ increased as the residence time for attrition scrubbing increased. The composition of the fine fraction obtained at a residence time of 40 min was $CeO_2$ 19.3%, $ZrO_2$ 1.9% and PGMs 419 ppm. In the fine fraction, the recovery of y-alumina increased proportionally to the residence time. Simultaneously, the recovery rates of $CeO_2$, $ZrO_2$ and PGMs increased to 82.9%, 78.7% and 78.9%, respectively. The production of the fine fraction less than $45{\mu}m$ and the recovery of $\gamma$-alumina increased when the solid concentration and initial feed size increased. Therefore, the attrition scrubbing as the comminution and separation process was concerned to be effective for the recovery of catalyst layer from ceramic supporting matrix by physical impact and shearing action between particles in the scrubbing vessel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.94-105
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• 2013

Recently, the construction industry has been changed in such a way that the cost for bridge construction should be optimized or reduced. Therefore, bridges are required be cost-effective in terms of initial construction as well as in the maintenance during service stage. In order to reduce the cost for bridge construction, the Rahmen typed structure, in which the bridge components from superstructure to substructure are integral, has many advantages to reduce the size of structural members including girders, since the loadings from superstructure may be transferred to substructure through the connecting rebars such as stud, etc. This paper studied on the continuous Up and Down Prestressed Concrete (UD PSC) girder bridge in which the reinforced concrete pier cap is integral with the part of girders in superstructure. In previous studies, it is known that the structural behavior of continuous UD PSC girder bridge is quite different compared to the one of the bridges with conventional bearings or shoes to support the loading from girders. Nevertheless, it has hardly been studied about the structural behavior of bridge with UD PSC girder. Therefore, in this study, various dynamic behaviors of continuous UD PSC girder bridge with integral pier cap have been analyzed using numerical method. Furthermore, an equation to evaluate the impact factor is suggested for the UD PSC girder bridge which has two to three continuous spans.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.103-110
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• 2020

This study examined the applicability of the vacuum impregnation post-processing to enhance the strength of binder jet 3D printed output. In addition, permeability, bulk density, and compressive strength of 10 mm, 20 mm, 30 mm, and 40 mm cubic specimens were examined to check the strength limit depending on the 3D prined output size. In result, as the maximum pressure increased, the post-processing storage solution permeated to the inside of the 3D printed sample and thus the permeation area ratio was improved. The compressive strength and the permeation area indicate the correlation between the exponential function of the adjusted R-square factor 0.992. In addition, the bulk density was increased, which can be inferred as the post-processing solution permeated to the inside. In conclusion, in order to enhance the compressive strength of the binder jet 3D printed output, it is essential to permeate the post-processing solution to the inside of the output, and vacuum impregnation can be proposed as an effective method.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.07a
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• pp.25-37
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• 2002

The most important industrial application of gamma radiation in characterizing green compacts is the determination of the density. Examples are given where this method is applied in manufacturing technical components in powder metallurgy. The requirements imposed by modern quality management systems and operation by the workforce in industrial production are described. The accuracy of measurement achieved with this method is demonstrated and a comparison is given with other test methods to measure the density. The advantages and limitations of gamma ray densitometry are outlined. The gamma ray densitometer measures the attenuation of gamma radiation penetrating the test parts (Fig. 1). As the capability of compacts to absorb this type of radiation depends on their density, the attenuation of gamma radiation can serve as a measure of the density. The volume of the part being tested is defined by the size of the aperture screeniing out the radiation. It is a channel with the cross section of the aperture whose length is the height of the test part. The intensity of the radiation identified by the detector is the quantity used to determine the material density. Gamma ray densitometry can equally be performed on green compacts as well as on sintered components. Neither special preparation of test parts nor skilled personnel is required to perform the measurement; neither liquids nor other harmful substances are involved. When parts are exhibiting local density variations, which is normally the case in powder compaction, sectional densities can be determined in different parts of the sample without cutting it into pieces. The test is non-destructive, i.e. the parts can still be used after the measurement and do not have to be scrapped. The measurement is controlled by a special PC based software. All results are available for further processing by in-house quality documentation and supervision of measurements. Tool setting for multi-level components can be much improved by using this test method. When a densitometer is installed on the press shop floor, it can be operated by the tool setter himself. Then he can return to the press and immediately implement the corrections. Transfer of sample parts to the lab for density testing can be eliminated and results for the correction of tool settings are more readily available. This helps to reduce the time required for tool setting and clearly improves the productivity of powder presses. The range of materials where this method can be successfully applied covers almost the entire periodic system of the elements. It reaches from the light elements such as graphite via light metals (AI, Mg, Li, Ti) and their alloys, ceramics ($AI_20_3$, SiC, Si_3N_4, $Zr0_2$, ...), magnetic materials (hard and soft ferrites, AlNiCo, Nd-Fe-B, ...), metals including iron and alloy steels, Cu, Ni and Co based alloys to refractory and heavy metals (W, Mo, ...) as well as hardmetals. The gamma radiation required for the measurement is generated by radioactive sources which are produced by nuclear technology. These nuclear materials are safely encapsulated in stainless steel capsules so that no radioactive material can escape from the protective shielding container. The gamma ray densitometer is subject to the strict regulations for the use of radioactive materials. The radiation shield is so effective that there is no elevation of the natural radiation level outside the instrument. Personal dosimetry by the operating personnel is not required. Even in case of malfunction, loss of power and incorrect operation, the escape of gamma radiation from the instrument is positively prevented.