過共晶 Al-Si 合金의 微細化와 耐摩耗 特性에 關한 硏究

김우식 부경대학교 1999 국내석사

개인용전산기를 위한 근거리통신망의 개발 : Physical layer

김우식 忠南大學校 大學院 1985 국내석사

The physical layer of a local ring network for personal computers has been implemented on a network controller using low-cost general purpose LSI's of the Z-SO family. For the line operation, the RS-422-A standard and the Manchester coding have been adopted. By making novel use of the SIO and a Z-SO block transfer instruction, it was possible to achieve the speed of 500k bps, which might be high enough for most personal computer applications.

MPEG-4 동영상 압축에서 비트율과 오류 내성을 고려한 모드 선택 최적화

김우식 서강대학교 대학원 2001 국내석사

동영상 압축에서 움직임 보상은 뛰어난 압축 효율을 보이는 반면에 어느 한 시점에서 오류가 발생할 경우 그 시점 이후로 계속해서 오류가 확산된다는 단점이 있다. 인트라 업데이트 방법은 이러한 오류의 확산을 차단하는 방법이다. 그러나 인트라 업데이트 방법은 압축의 효율을 떨어뜨린다는 단점이 있다. 본 논문에서는 오류의 영향과 비트율 제어를 함께 고려하여 인트라 업데이트를 할 수 있는 방법을 제안한다. 제안된 방법은 비트율과 왜곡의 값을 추정하고 라그랑지안 최적화를 통해 부호화 모드와 양자화 계수를 선택하는 방법으로 MPEG-4 코덱에 적용하여 실험하였다. 실험 결과는 제안된 방법이 기존의 방법보다 패킷 손실과 같은 오류 환경에서 더 좋은 화질을 나타내는 것을 보여준다. Motion compensation is a powerful method to compress a image sequence. Its main drawback is that once an error is occurred, the error propagates through the frames. Recently, the intra update method was proposed to stop the error propagation at the cost of the compression efficiency reduction. This paper proposes an intra update method based on a rate-distortion optimization in error prone environments. The rate and the distortion are estimated using the Lagrangian optimization to select the coding mode and the quantization step size. The proposed method is applied to MPEG-4 codec, and the experimental results show that it is robust to the error such as packet losses comparing with the conventional ones.

고온의 다공성 재료 표면에 충돌하는 액적의 충돌 후 거동 및 냉각 특성에 관한 연구

김우식 KAIST 2014 국내박사

고색재현성 백색 LED 응용을 위한 CsPbBr3 페로브스카이트 나노 결정이 함유된 Germanate 및 Borosilicate 유리

김우식 공주대학교 일반대학원 2021 국내석사

Cesium lead halide perovskite nanocrystals have been extensively studied as color converting materials for displays with wide color gamut due to their excellent properties such as high quantum yield, simple synthesis method, and narrow emission line width. However, halide based perovskite nanocrystals have drawbacks in weak chemical and thermal stabilities seriously deteriorating their lifetime and color conversion efficiency. Perovskite nanocrystal embedded glasses (PNEG) were suggested and remarkably improved the stability of PNCs but required further enhancement for practical applications. In this study, a PNEG based on germanate glass (Ge-PNEG) was grounded into powder and mixed with K2SiF6:Mn4+ phosphor and silicone resin to make a phosphor in silicone (PIS). The PIS was pasted on a 1mm thick borosilicate glass substrate fabricating a remote phosphor plate (remote PIS). The remote PIS plate with Ge-PNEG was then mounted on top of a blue LED chip to compose a white LED. The mixed paste (PIS) was also directly pasted on a blue LED. When compared with Ge-PNEG and PIS, the remote PIS plate showed improved thermal stability and luminescence properties as well as wide color gamut up to 132% of NTSC showing its practical feasibility as an efficient color converter with wide color gamut. Compositional study on borosilicate glasses was carried out to find a proper glass matrix which can embed PNCs with improved chemical and thermal stabilities. CsPbBr3 was successfully fabricated within a glass based on SiO2-B2O3-ZnO-PbO-Cs2O-NaBr system. After optimization of glass composition, a silicate based PNEG (Si-PNEG) showed photoluminescence quantum yield (PLQY) up to 36% under 450 nm excitation. The Si-PNEG showed similar thermal stability to that of Ge-PNEG and demonstrated its high potential as a color converter with wide color gamut up to 128% of NTSC when it was mixed with K2SiF6:Mn4+ and mounted on top of a blue LED.

저질조성 및 사육밀도 차이에 따른 말백합 Meretrix petechialis (Lamarck)의 혈구생리학적 변화

김우식 선문대학교 일반대학원 2017 국내석사

말백합 Meretrix petechialis (Lamarck)은 맛과 영양이 뛰어나 서해안의 특산물로 각광 받았으나 생산어장의 감소 및 환경오염 등으로 인해 생산량이 감소하였다. 말백합을 안정적으로 생산하기 위한 종패생산 기술들이 연구되어지고 있지만, 치패 이후의 중간 양성에 대한 연구는 아직 활발하게 진행되지 못한 실정이다. 축제식 양식기술은 인위적 관리가 편리하며 수산생물의 집중 사육이 가능하기 때문에 백합류의 중간양성에 적합할 것으로 기대되고 있다. 저질조성과 사육밀도는 패류 축제식 양식장을 조성할 때 중요하게 고려해야할 요인들이다. 이매패류의 혈구(haemocytes)는 이매패의 건강도 판정에 활용되어질 수 있다. 혈구의 viability, phagocytosis, ROS(reactive oxygen species)방출량 및 apoptosis 정도 등이 건강도 판정에 중요한 기준으로 활용된다. 본 연구에서는 축제식 말백합 양식 기술 개발에 필요한 적정 저질조성 및 사육밀도 결정에 필요한 기초 자료를 마련하기 위해 현미경을 통해 혈구를 분류하였으며, flow cytometry를 활용하여 말백합 혈구의 생리학적 변화를 분석하였다. 본 연구에서 관찰된 말백합의 혈구는 hemoblast-like cell, agranulocyte, granulocyte 및 degranulated cell로 분류되었다. 저질조성 연구에서는 황토의 비율이 높아질수록 모든 개체가 저질 안으로 완전하게 잠입하는데 걸리는 시간이 증가하였으며 ROS 방출량이 증가하는 것을 확인하였다. 사육밀도 연구에서는 밀도가 높아질수록 ROS 방출량이 증가하였고, phagocytosis는 100마리/m2실험구 에서 증가 하고 150마리/m2실험구 에서 감소하였다. 이는 100마리/m2밀도 이상부터는 말백합이 스트레스를 느끼기 시작하며 150마리/m2밀도 이상에서는 과도한 스트레스로 말백합 혈구의 ROS방출이 증가한 것으로 해석된다. 본 연구의 혈구생리학적 변화 분석결과에 따르면 양식을 위한 적정 저질조성은 모래 : 황토비율 7 : 3 이며, 사육밀도는 100마리/m2 전후이다. 한편 본 연구에서 조사한 혈구생리학적 지표 중 ROS 방출량은 말백합의 건강도를 판정하는데 유용한 지표로 개발될 수 있을 것으로 판단된다.

로버트 브라우닝의 극적 독백시의 특성

김우식 大田大學校 2008 국내박사

During the Victorian Age, Robert Browning wrote many poems which have made people think and puzzle. His poetry is based on life and love, problems of religion and soul. Robert Browning's dramatic monologues are recognized as excellent examples of character analysis and presentation of dramatic irony. The significance of his dramatic monologues can be seen in terms of the poet who deals with the problems of his own art. This thesis is aimed at studying Browning's poetry in the context of his poetic career which typically shows the inner conflicts of the Victorians. With rich poetic imagination and intellectual energy, he employs the poetic form of the dramatic monologue, and explores human nature in situations of dramatic irony. As a Victorian poet Browning is deeply concerned with the problem of the poet's social function and responsibility which is also a major issue of his age. But as a Romantic he tries to catch the ultimate vision and the absolute truth, and he retains the romantic conception of the poet as a visionary. The early poetry of Browning is mainly that of the subjective poet whose task is concentrated on the inner state of his own soul, and who tries to find the ultimate vision by which he aspires to comprehend the divine nature of God. But this ideal is beyond the range of human capability, and even if it can be obtained it is still impossible to express such a vision through imperfect human language. After realizing the impossibility of the subjective poet's task, Browning turns his eyes from himself to the world at large, becoming an objective poet who deals with the outside world. His works are the expression of his true love and hope, and there are the spirit of sublimated love and the immortality of the soul in his poems. With his keen insight Browning immediately perceives the duality and ambivalence of life. Especially he finds that in his age co-exist contradicting ideas and values such as the subjective and the objective, the absolute and the relative, the divine and the human, and the ideal and the real; and both of these opposing ideas are regarded as truths in their own light. By using the dramatic method, he describes the conflicting aspects of reality in the speaker's monologues. Browning's early dramatic monologues published in 1842 and 1845 are excellent in presenting the dramatic irony of the speakers caught in specific circumstances. Browning cannot be satisfied with his achievements as an objective poet, and still wants to pursue the romantic subject of the development of a soul. Lippo is a historical character, showing individual characteristics different from the poet, and Browning adroitly expresses the Renaissance painter's character and his irony in the lively language and description. But Lippo represents the artistic attributes which are favored by the poet himself. Through Lippo's typical struggle and achievement, Browning illustrates the process of his own poetic pursuit, and achieves the provisional solution to the tension of the two dominant dualistic aspects of his poetry. In the poem Lippo resolves his problem by depicting the divine and his vision with realistic technique. And through the poem Browning succeeds in expressing the pursuit of the impossible goal by objective description with a realistic touch. The development of Browning's poetic career represents that of Victorian poetry in the sense that he tries to find the solution to the major issues of his age. Especially he tries to resolve the tension between Romantic idealism and Victorian realism in poetry. In conclusion Browning is a typical Victorian poet; and his poetry can be more meaningful when it is studied in the context of his persistent struggle with the dilemmas of the Victorian poetry. Browning greatly influences modern poetry by utilizing the style of “dramatic poetry”, expressing his artistic inclinations through the form of character development, character creation, and the imperfect love based on earthly reality, sublimated by the dynamic in order to complete the heavenly life.

능동소나를 위한 표적의 반향음 분석 및 표적 상태 추정에 관한 연구

김우식 한국해양대학교 2005 국내박사

In order to develope underwater guidance weapon system with an excellent detection performance, precise analysis and modeling on underwater acoustic environment and target echo must be precede. Performance prediction and optimization of detection parameters can be possible by simulation based on a precise modeling. A study on underwater acoustic environment and target echo is performed by both the numerical modeling method based on theory and the analytical method based on analyzing the acoustic data acquired on laboratory and sea test. Experiment for such an acoustic approach can be classified into scaled target experiment and sea experiment. Data acquisition by means of a scaled target experiment can be performed using smaller budget and less effect comparing with a sea experiment. Also, a scaled target experiment has merits on precise controlling of target aspect and acquisiting of target echo with good signal to noise ratio. This experiment is necessary to clarify the relationship between target echo and transmitting pulse such as coating effect and inner structure effect of a target, and designing transmitting pulse depending on a target. Data acquisition in the state of precise target aspect makes a study on target echo possible. This paper is important on the fact that two major research topics in the field of target acoustic, target echo modelling(forward model) and target state estimation technique(inverse model), are developed and verified. Target echo modeling simulates target echo using the selected model parameters, and is a kind of forward modeling. On the other hand, TSE technique estimates important target parameters using the recoded target echo, and is a kind of inverse or parameter estimation technique. A study on target echo analysis classifies target echo into 4 components based on outer and inner structure such as specular reflection, acoustic diffraction, elastic scattering, and multiple scattering. Through the theoretical studies, these 4 components are separated into moving HL and fixed HL depending on each characteristics, and are applied to target echo model. Also, using the developed HL resolving algorithm, target highlight position is precisely estimated and theory is verified by resolving target echo into each component using the data, recoded on scaled target experiment. Target echo model developed through theoretical study and verification improve reliance of simulation used in developing underwater guidance weapon system. For verification of the TSE algorithm, we analyze the errors of TSE using the target echo model as a function of target aspect angle and resolution. Based on the analysis of TSE error, we gave a limitation of the algorithm. The second topic of this paper is result on selecting SONAR designing parameters which maximize SONAR performance. Detecting performance of a SONAR priority determined by hardware performance such as transmitting power, beam pattern, and receiving sensitivity. However, the components, next predetermined hardware, which determine the detecting performance are SONAR operating and detecting parameter. Primarily, target strength is the most important parameter among target detecting parameters. In the case of studying target characteristics, this parameter easily considered as depending on target itself. On other hand, in the side of active SONAR detecting performance, this parameter varies on the transmitting pulse length, pulse type, and detection algorithm. Conditions to improve target strength are studied. Next, TSE algorithm is to resolve highlights and to estimate spatial position of each highlight. In this case, the temporal resolution becomes important performance. In this algorithm, signal is processed using the matched filter. HL resolution(temporal resolution) of this algorithm is proposed and verified using result, from simulated signal and scaled target experiment. Also, the fact, that HL resolution changes according to the degree of window overlapping which is decided by hardware computing speed, is verified. HL resolution of a system can be estimated using two resolution limits; resolution limits by algorithm and computing speed. In the last, the concept of processing gain, which is algorithm effect in SONAR equation used to estimate SONAR performance, is proposed and computed. Processing gain is estimated using signal model and is varied with the degree of window overlapping which decided by hardware computing speed. Processing gain can be obtained maximum 18dB by using a matched filter, and can be minus depending on the degree of window overlapping and the time of target echo. The listed results of this paper can be applied to TSE algorithm and ACCM logic for an underwater guidance weapon system. In the future, these results can be applied to techniques for target identification, anti-torpedo torpedo, and stealth as a core technique.

Transformation mechanism of graphene layers from carbon nanotubes using high DC pulse

김우식 한양대학교 대학원 2010 국내박사

Graphene has attracted much attention due to its unique structure and excellent properties such as low electronic scattering rate, high carrier mobility, high surface area and high optical transparency. For the extensive commercial applications for the future electronic device, the large-scaled fabrication techniques of high quality graphene layers are needed, in particular the number of graphene layers should be controlled because their electrical properties are influenced by the number of layers. Since the discovery of graphene, several fabrication techniques for graphene have been introduced, such as, mechanical cleavage, silicon carbide sublimation, solvothermal synthesis, chemical vapor deposition (CVD), plasma etching and unzipping of CNTs. However, these techniques were not satisfied with all the two important factors ; the number of layers in graphene and large-scaled production. This thesis disclose the new fabrication technique of various graphene layers with the controlled number of layers and large-scaled production using high direct current (DC) pulse. Because graphene has the basic structural elements of some carbon allotrops (graphite, CNTs, fullerenes, etc.) which can be transformed to the flat polycyclic aromatic hydro carbons which called graphene. CNT is a cylindral shape of two dimensional rolling sheet of carbon atoms and electrical current flows along the direction of CNT’s surface, so that high DC pulse can transform CNT to graphene layer. By using this technique, multi-walled carbon nanotubes (MWCNTS) and single-walled carbon nanotubes (SWCNTs) were transformed to multi-layer graphene and few-layer graphene (FLG), respectively. The mixture of CNTs and metal oxide can be changed to metal carbide layers. And, the exfoliation process using intercalation of alkali metal and microwave irradiation was effective in transforming the FLG to mono-layer graphene (MLG). In conclusion, the pulsed current sintering (PCS) technique shows great potential for fabrication of graphene layers from the commercially available CNTs in a large scale. The use of this technique makes it possible to produce the various graphene with the controlled number of layers using the MWCNTs / SWCNTs with uniform distribution of diameters as the starting materials. This research can expand to the various application of graphene and metal carbide-based nano materials.

유무선 통신망을 이용한 원격 로봇 제어기 개발

김우식 한라대학교 정보산업대학원 2007 국내석사

오늘날 무선통신이 발전됨에 따라 그동안 유선이 극복하지 못한 한계를 무선으로 극복하고자 하는 노력들이 이루어지고 있다. 20세기의 최대 문제점이 선으로 읽혀진 세상 속에서 사람들이 불편을 겪었다면 이 선을 없애는 것이 21세기의 우리에게 주어진 문제점인 것이다 이에 따라 무선 통신 분야는 무선랜, 무선 인터넷, 이동통신, 센서 네트워크 등 다양한 분야에서 날개를 펼치고 있다. 본 논문에서는 Sensor Network 분야에서 가장 화두로 떠오르고 있는 ZigBee와 이동통신인 CBMA이동통신망을 이용하여 원격 로봇 제어기를 개발하고자한다. 단독으로 원거리 무선통신이 가능한 CDMA 이동통신망을 이용한 원격 제어 로봇과 단거리 무선통신망인 ZigBee와 우리 일상 생활에서 가장 접하기 쉽고 많이 이용되는 유선통신인 PSTN망과 EtherNet망을 이용하여 원거리 통신이 가능하게 하는 PSTN과 ZigBee를 이용한 원격 제어 로봇, EtherNet과 ZigBee를 이용한 원격 제어 로봇을 개발하고자한다. CDMA 이동통신망을 이용하여 통화음성인식, DTMF인식, SMS의 문자 인식된 값에 따라 로봇을 동작하게 하였다. 또한, CDMA이동통신망에서 사용되는 기기간의 원활하지 못할 DTMF 송/수신에 대해 연구하였다. PSTN망을 이용하여 통화음성인식과 DTMF인식된 값을 로봇에 ZigBee를 통해 전달하여 로봇을 동작하게 하였다. EtherNet망을 이용하여 로봇의 상황을 Monitoring하여 그에 상응하는 명령을 로봇에 ZigBee를 통해 전달하여 로봇이 동작하게 하였다. With the development ow wireless radio communication many ewforts are being made to overcome the limitations ow wire communication. If the people ow the 20^(th) felt inconvenient because of wires the problem ow the 21^(st) century is how to maze these wires wireless. Developments in the wields of wireless LAN, wireless internet, mobile communication and sensor network are all being made in wireless communications technology as to overcome the new problems. This paper will deal with the development of a remote control for a robot using ZigBee which is a sensor network technology and DMA mobile communications network. Robots will be developed according to the controls of diwwerent types ow technology. One is through DMA mobile communications network which enables long range mobile communications all by itself. The other two are a robot remotely controlled by PST and ZigBee technology and a robot remotely controlled by Ethernet and ZigBee technology. Zigbee is a short range wireless mobile communications network and PSTN/ Ethernet is a wired communications network that we use common in our everyday lives that enables long range communications. Robots were developed so that they could be controlled through the DMA mobile communications network using voice recognition, DTMF recognition, and SMS(Short Message Service). We also researched on DTMF instruments, used in the DMA mobile radio communication network, which had problems with smooth transmission and reception with one another. The robot would operate according to the commands by voice recognition through the PST network and the values inputted worm DTMF through ZigBee. The condition ow the robot was monitored through the Ethernet network and commands were given to operate according to its situation through ZigBee.