콘크리트 기층에 아스팔트 표층의 복합포장 구조에서 온도변화에 따른 반사균열의 거동은 반사균열 억제 및 제어에 중요한 정보로 작용한다. 반사균열의 주요 발생원인 중 포장의 온・습도 변화에 따른 하부 콘크리트의 수평 거동 및 컬링에 의한 줄눈/균열부 수직 거동은 포장의 특성(콘크리트 열팽창계수, 하부마찰계수, 포장두께 등)과 지역환경(대기의 온도, 상대습도, 태양 복사량 등)에 따라 다른 특성을 보인다. 본 연구에서는 롤러전압 콘크리트 기층에 배수성 아스팔트 표층의 복합포장 구조에서 현장의 온도변화에 따른 반사균열의 거동 특성을 분석하였다. 늦가을(11월 초)에 5cm 두께 배수성 아스팔트 덧씌우기 포장을 롤러전압 콘크리트 기층 상부에 시공하였다. 온도 조사는 표층 아스팔트 상/하부와 기층 콘크리트 상/하부, 대기온도를 계측하였다. 롤러전압 콘크리트 기층의 균열은 1년의 공용기간 동안 약 30m의 일정 간격으로 발생하였으며, 계측한 연속된 3개 균열의 움직임은 안정화되어 온도에 따라 유사한 거동을 보였다. 계측결과, 겨울철 온도에 따른 줄눈거동은 그림 1과 같다. 영하권의 겨울철 포장의 온도는 태양의 복사열과 기층하부의 지열로 인하여 대기온도보다 높았다. 표층 시공 후 큰 폭의 온도 저감이 발생한 이후 반사균열이 발생하였고 그림 2는 반사균열 발생 전・후의 1일 온도차에 따른 1일 균열 폭 변화량을 보인다. 추세곡선의 기울기는 온도변화에 따른 균열 거동에 저항하는 크기를 나타낸다. 두 곡선의 기울기 차인 0.008은 5cm 두께의 배수성 표층의 반사균열에 대한 저항 특성치임을 알 수 있다. 아스팔트 표층 반사균열 발생 전・후의 추세 곡선간 y축 절편의 차는 반사균열 발생에 따른 동일 온도변화에서 균열 거동량의 증가분을 나타낸다. 향후 배수성 표층 복합포장의 계절별 거동특성을 분석하여 복합포장 설계검토에 활용할 계획이다.

Several disposal processes for waste sludge from wastewater treatment plants such as landfill, ocean dump, incineration, reuse as fuels or fertilizers are practiced. However, ocean dumping is prohibited by international treat. New constructions of landfill sites or incineration facilities are limited by NIMBY and reuse processes are still suffering from low energy yield. Therefore, development of alternative processes for sludge disposal are currently needed. In this study, alternative technique for sludge solubilization using HVI (high voltage impulse) was suggested and verified experimentally. Sludge solubilization was carried out for 90 minutes using HVI discharge with peak voltage of 16 kV and pulse duration for 40 microsecond. About 3∼9 % of MLSS and MLVSS concentration were reduced, but the soluble COD, TN, TP of the sludge increased to 372 %, 56 % and 102 % respectively. It indicates that the flocs and/or cells of the sludge were damaged by HVI. These resulted in flocs-disintegration and cells-lysis, which means the internal matters were bursted out of the flocs as well as the cells. Thus, electrical conductivity in bulk solution was increased. All of the results verified that the HVI could be used as an alternative technique for sludge solubilization processes.

지난 수십 년간 공공시설 및 사유지 적용을 위한 롤러전압콘크리트포장의 사용실적은 꾸준히 증가 하고 있는 추세이다. 롤러전압콘크리트포장은 아스팔트포장의 시공특성과 전통적 콘크리트포장의 재 료적 특성을 동시에 나타낸다. 또한 작업성(workability)과 다짐성(compactibility)은 롤러전압콘크 리트포장의 우수한 배합설계를 결정하기 위한 주요요소로써, 강도가 충분히 확보된 콘크리트라 할지 라도 적정 반죽질기 또는 작업성이 확보되지 않으면 시공이 용이하지 않을 수 있다. 일반적으로 포장 적용을 위한 롤러전압콘크리트의 배합설계 시 흙다짐 방법 및 반죽질기 방법을 사 용하고 있으나, 흙다짐 방법의 경우 작업성을 고려하지 못하며 반죽질기 방법은 작업성만을 고려하고 있다. 이에 본 연구에서는 포장 적용을 위한 롤러전압콘크리트에 대하여 실내실험 변수와 현장 공용성을 모두 만족시키는 배합설계방법의 개선방안을 제안하였다. 이를 위하여 실내실험 변수를 현장 공용성 으로 연계하여 적정 공용성을 확보할 수 있는 최적 롤러전압콘크리트 배합을 도출하였으며, 롤러전압 콘크리트의 주요 물성인 반죽질기, 강도 및 내구성과 배합비 간의 상관관계를 규명하기 위하여 다양 한 실내실험을 진행하였다. 또한 실제 현장 조건에서 이와 같은 물성들을 연계시키기 위하여 속초인 근 고속도로 부체도로에 총 5개 구간의 롤러전압콘크리트포장을 시공하여 품질관리 변수인 반죽질기 에 근거하는 하중지지력과 표면 물성에 대하여 조사하였다. 이와 같은 물성들의 새로운 이해는 포장 적용을 위한 롤러전압콘크리트의 배합설계절차 개선으로 이어진다.

PURPOSES: The main purpose of this study is to develop a high elastic modulus and low-shrinkage roller-compacted concrete base (RCCB) in order to prevent fatigue cracking and reflective cracking in the asphalt surface layer of composite pavement. Using a rigid base material with low shrinkage can be a solution to this problem. Moreover, a strong rigid base with high elastic modulus is able to shift the location of critical tensile strain from the bottom of the asphalt layer to the bottom of the rigid base layer, which can prevent fatigue cracking in the asphalt layer. METHODS: Sensitivity analysis of composite pavement via numerical methods is implemented to determine an appropriate range of elastic modulus of the rigid base that would eliminate fatigue cracking. Various asphalt thicknesses and elastic moduli of the rigid base are used in the analysis to study their respective influences on fatigue cracking. Low-shrinkage RCC mixture, as determined via laboratory testing with various amounts of a CSA expansion agent (0%, 7%, and 10%), is found to achieve an appropriate low-shrinkage level. Shrinkage of RCC is measured according to KS F 2424. RESULTS : This study shows that composite pavements comprising asphalt thicknesses of (h1) 2 in. with E2 > 19 GPa, 4 in. with E2 > 15 GPa, and 6 in. with E2 > 11 GPa are able to eliminate tensile strain in the asphalt layer, which is the cause of fatigue cracking in this layer. Shrinkage test results demonstrate that a 10% CSA RCC mixture can reduce shrinkage by 84% and 93% as compared to conventional RCC and PCC, respectively. CONCLUSIONS: According to the results of numerical analyses using various design inputs, composite pavements are shown to be able to eliminate fatigue cracking in composite pavement. Additionally, an RCC mixture with 10% CSA admixture is able to reduce or eliminate reflective cracking in asphalt surfaces as a result of the significant shrinkage reduction in the RCC base. Thus, this low-shrinkage base material can be used as an alternative solution to distresses in composite pavement.

This study analyzed by measuring the voltage waveform of the injector intended for operating CRDI diesel vehicle. The cases of the EGR trouble and a EGR normal is considered. 1) The voltage waveform in the case of the normal and trouble, the difference between the maximum voltage was not large, decrease in the number of voltage gated pulses with the increase in engine speed, sustained current remained for this period. 2) The voltage waveform, comparing the case of the normal case and trouble, the size of the maximum voltage, no large change in gate pulse voltage is to be generated than in the case of a defective irregular longer opening time of the injector factor it was possible to know the bad influence on the fuel efficiency.

PURPOSES : The use of roller-compacted concrete pavement (RCCP) is an environmentally friendly method of construction that utilizes the aggregate interlock effect by means of a hydration reaction and roller compacting, demonstrating a superb structural performance with a relatively small unit water content and unit cement content. However, even if an excellent structural performance was secured through a previous study, the verification research on the environmental load and long-term durability was conducted under unsatisfactory conditions. In order to secure longterm durability, the construction of an appropriate internal air-void structure is required. In this study, a method of improving the long-term durability of RCCP will be suggested by analyzing the internal air-void structure and relevant durability of roller-compacted concrete. METHODS: The method of improving the long-term durability involves measurements of the air content, air voids, and air-spacing factor in RCCP that experiences a change in terms of the kind of air-entraining agent and chemical admixture proportions. This test should be conducted on the basis of test criteria such as ASTM C 457, 672, and KS F 2456. RESULTS : Freezing, thawing, and scaling resistance tests of roller compacted concrete without a chemical admixture showed that it was weak. However, as a result of conducting air entraining (AE) with an AE agent, a large amount of air was distributed with a range of 2~3%, and an air void spacing factor ranging from 200 to 300 ㎛ (close to 250 ㎛) coming from PCA was secured. Accordingly, the freezing and thawing resistance was improved, with a relative dynamic elastic modulus of more than 80%, and the scaling resistance was improved under the appropriate AE agent content rate. CONCLUSIONS: The long-term durability of RCCP has a direct relationship with the air-void spacing factor, and it can be secured only by ensuring the air void spacing factor through air entraining with the inclusion of an AE agent.

In this paper we describe differential circuit of charge pump for voltage management systems, their evolution and improvement in design. The systems are powered by solar cells and generate different voltage levels which are suitable for systems on-chip integrated regulator applications. The voltage regulator outputs voltage from low power digital circuit, -2V for memory, and from 2V to 12V for input and output components. The circuits were simulated using LT SPICE software.

본 연구에서는 동조액체기둥감쇠기의 비선형감쇠항을 등가점성감쇠항으로 치환한 등가선형 동조액체기둥감쇠기 모델을 유도하였으며 동조액체기둥감쇠기의 동적거동인 고유진동수와 감쇠비를 이론적으로 파악하였다. 동조액체기둥감쇠기에 일정한 전기장을 형성한 후 동조액체기둥감쇠기의 수직운동에 의해 발생되는 가변전압을 측정하여 수조 내부의 수위로 변환하는 식을 유도하였다. 또한 본 연구에서 제안한 동조액체기둥감쇠기의 수위측정 시스템의 타당성을 검증하기 위하여 고가의 전기 용량식 파고계와 비교 및 검증하였다. 마지막으로 본 연구에서 제안한 수위측정 시스템을 동조액체기둥감쇠기에 적용, 진동대 실험을 실시하여 고유진동수와 감쇠비를 파악하였고, 이론상의 고유진동수와 실험상의 고유진동수가 일치하였음을 확인하였으며, 진동수비 변화에 따른 동조액체기둥감쇠기의 감쇠비 변화를 확인하였다.

PURPOSES : The use of environmentally friendly construction methods has been recently encouraged to reduce fuel consumption and the effects of global warming. For this purpose, the roller compacted concrete pavement (RCCP) construction method has been developed. RCCP is more environmentally friendly and economically efficient than general concrete by reducing the amount of CO2 generated through the application of a smaller amount of cement. RCCP has a number of advantages such as an easy construction method, low cost, high structural hydration performance, and aggregate interlocking. However, mix design standards and construction guidelines of RCCP are required for domestic application. In addition, a study on aggregate selection, which has an effect on the characteristics of RCCP, is necessary owing to a limited number of researches. Thus, the aggregate effect on the performance of RCCP in securing the required strength and workability was evaluated in consideration of domestic construction. METHODS : Sand and coarse aggregates of both 19mm and 13mm in maximum size were used in this study. Four types of aggregate gradations (s/a = 30%, 58%, and 70% for the sand and coarse aggregate of 19mm in maximum size, and s/a = 50% for a combination of the three types of aggregates) were set up to investigate the effects of the PCA band on the RCC characteristics. The conditions of s/a = 30% and 70% were evaluated to check the gradation effect outside of the recommended band. The conditions of s/a = 58% and 50% were used because they are the optimum combination of the two and three types of aggregates, respectively. RCCP gradation band was suggested gradation with a proper construction method of RCCP by synthetically comparing and analyzing the correlation of optimum water content, maximum dry density, and strength of requirements through its consistency and compaction test. RESULTS : The lower and upper limit lines are insufficient to secure a relatively strong development and workability compared to an aggregate gradation in the RCCP gradation band region. On the other hand, the line in the RCCP gradation band and the 0.45 power curve in the RCCP gradation band region were satisfactory, ensuring the required strength and workability. CONCLUSIONS: The suitable aggregate gradation on RCCP process should meet the RCCP gradation band area; however, fine particles passing through a #60 sieve do not need to be within the recommended gradation band because the influence of this region on such fine particles is small.

PURPOSES: To ensure appropriate RCC properties with sufficient strength development and workability, it is necessary to secure a proper level of consistency. It is also necessary to secure maximum dry density, which is an important factor for increasing the interaction of aggregate interlocking, leading to an augmentation of RCC strength. On the other hand, the dry density of RCC can be changed owing to the compaction conditions, water content, and particle size distribution. A Proctor test and a modified Proctor test were used for determining the optimum water content needed to achieve maximum dry density with different amounts of compaction energy. A Vebe test, on the other hand, was used for checking the level of consistency, which is important for producing a workable mixture. METHODS : To confirm the degree of compaction at various particle sizes, RCC mixtures with different sand/aggregate ratios were evaluated. The Proctor test and modified Proctor test were applied to these mixtures to check the effect of the aggregate gradation and compaction energy on the maximum dry density and optimum water content. During each test, three specimens were produced for all types of water content under each aggregate gradation. A compaction curve and the optimum water content and maximum dry density for each aggregate gradation were then obtained for both tests. The range of water content for the appropriate consistency of each aggregate gradation was determined through a Vebe test. The optimum water content was then evaluated based on this range. RESULTS : The compaction test results show that the modified Proctor test provides a higher maximum dry density and lower optimum water content compared with the standard Proctor test. For the modified Proctor test, two cases of aggregate gradation (s/a = 30% and 70%) had the optimum water contents outside of the appropriate water content range. For the standard Proctor test, on the other hand, none of aggregate gradations provided the optimum water content within the desired range. CONCLUSIONS : The modified Proctor test should be used for an RCC mixture design because it can provide adequacy between maximum dry density and consistency. Moreover, the compaction roller has become highly developed for higher compaction energy.

The implanting of metal products is performed with numerous surface treatments because of toxicity and adhesion. Recently, the surface modification of metal products has been actively studied by coating the surface of the TiC or TiN film. We prepared a Ti(10%)Ag Target which may be used in dental oral material by, using the AIP(arc ion plating) system TiAgN coating layer that was deposited on Ti g.23. The purpose of this study was to establish the optimal bias voltage conditions of the coated TiAgN layer formed by the AIP process. The TiAgN coatings were prepared with different bias voltage parameters (0V to −500V) to investigate the effect of bias voltage on their mechanical and chemical properties. The SEM(scanning electron microscope), EDS(energy dispersive X-ray spectrometer), XRD(X-ray diffraction), micro-hardness, and potentiodynamic polarization were measured and the surface characteristics of the TiAgN coating layers were evaluated. The TiAgN coating layer had different mechanical characteristics based on the bias voltage, which also showed differences in thickness and composition.

시멘트 콘크리트포장은 경제적이면서도 우수한 내구성, 기능성 및 구조적 성능을 확보하여 사회 기반 시설인 도로 건설에 활발히 사용되고 있다. 그러나 최근 들어 지구온난화, 이상기후 및 자원 고갈 등의 환 경 문제로 인하여 환경 친화적인 건설의 중요성이 대두되면서, 시멘트 콘크리트포장의 주요 재료인 시멘 트 생산 공정 중에 발생되는 CO2 등의 온실가스로 인하여 환경을 저해하는 배타적인 재료로 인식되고 있 는 실정이다. 그러므로 콘크리트포장의 주요 재료인 시멘트 사용량의 절감을 통하여 시멘트 생산과정에서 발생하는 다량의 CO2와 화석자원 소비에 따른 친환경성에 대한 부정적인 요소를 환경 친화적 도로건설로 부응하고, 콘크리트 포장에 대한 잘못된 인식을 해소할 수 있다. 따라서 콘크리트 포장 고유의 우수한 성 능을 확보하면서 상대적으로 적은 단위 시멘트량을 사용하여 CO2 발생의 저감으로 친환경성 및 경제성을 확보하고, 정량화된 아스팔트 시공장비의 이용으로 신속하고 간소한 시공절차를 확보할 수 있는 저비용 롤러 전압다짐 콘크리트포장 공법(RCCP; Roller Compacted Concrete Pavement)의 도입이 요구된다. RCC는 페이스트의 체적이 일반 PCC보다 작기 때문에 배합에서의 공극을 최소화하기 위해 조밀한 입도이 어야만 한다. RCC 체적의 70%~85%를 구성하는 골재특성은 진동다짐시 요구하는 워커빌러티와 건조단 위중량을 도출하기 위한 역할을 하며, 압축강도, 휨강도, 온도 특성, 장기거동 및 내구성에 많은 영향을 준다. 이는 골재의 적절한 선택이 시공 중․후에 안전성을 제공하고 RCCP의 구조 및 성능에 영향을 미칠 중요한 요소 중 하나로 사료된다. 그러므로 PCA에서 제시하는 RCCP 골재입도 Band 영역 안의 골재 입 도가 RCCP에 미치는 특성에 대한 연구가 필요하다. 따라서 본 연구에서는 최대 치수 19mm 굵은 골재와 잔골재를 이용하여 상한선과 하한선 및 Band 영역 내의 골재 입도 분포를 설정하여 PCA에서 제시하는 RCCP 골재입도 Band가 RCCP 특성에 미치는 영향을 재검토하고, 입도분포에서 작은 비중을 차지하지만 시공 시 재료의 선정 과정에서 발생되는 양이 상당한 미립자 부분에 대한 영향을 파악하고 골재 선정 시 편의성과 경제성을 확보하기 위해 수정 Band를 제안하였다.

(PDDA/SiO2) thin films that consisted of positively charged poly (diallyldimethylammonium chloride) (PDDA) and negatively charged SiO2 nanoparticles were fabricated on a glass substrate by an applying voltage layer-by-layer (LBL) self-assembly method. In this study, the microstructure and optical properties of the (PDDA/SiO2) thin films coated on glass substrate were measured as a function of the applied voltage on the Pt electrodes. When 1.0 V was applied to a Pt electrode in a PDDA and SiO2 solution, the thickness of the (PDDA/SiO2)10 thin film increased from 79 nm to 166 nm. The surface roughness also increased from 15.21 nm to 33.25 nm because the adsorption volume of the oppositely charged PDDA and SiO2 solution increased. Especially, when the voltage was applied to the Pt electrode in the SiO2 solution, the thickness increase of the (PDDA/SiO2) thin film was larger than that obtained when using the PDDA solution. The refractive index of the fabricated (PDDA/SiO2) thin film was ca. n = 1.31~1.32. The transmittance of the glass substrate coated by (PDDA/SiO2)6 thin film with a thickness of 106 nm increased from ca. 91.37 to 95.74% in the visible range.

AC PDP의 부화면 시간동안 기입 방전의 시간지연을 각각 조사하였고 기입방전 마진 범위 내에서 추 가 주사전압의 높이를 변화하여 전체 부화면 시간동안 기입방전 시간을 단축시킨다. 첫번째 초기화 기간 동안 높은 상승 경사파 전압이 주사전극에 인가되어 초기화 방전이 발생하고 셀 내부에서 벽전하를 생성한다. 생성된 벽전하는 기입전압과 더해져서 기입 방전을 일으킨다. 첫 번째 부화면 시간에는 초기화 기간 동안 상승 경사파를 갖는 높은 전압에 의해 벽전하가 많이 존재하므로 첫 번째 기입 방전은 다른 부화면 시간보다 빠르게 형성된다. 한편, 두 번째부터 마지막 부화면 시간까지의 기입 방전 생성시간은 셀 내의 벽전하 소멸에 의하여 점차적으로 늦어진다. 본 연구에서는 각 부화면 시간동안 기입방전의 시간지연을 조사하였고, 부화면 시간의 기입기간 마다 추가 주사전압을 다르게 인가하여 전체 기입방전 지연시간을 단축시키는 방법을 제시한다.

Solar cells exhibit different power outputs in different climates. In this study, the temperature dependence of open-circuit voltage(V-oc), short-circuit current(I-sc), fill factor(FF) and the efficiency of screen-printed single-crystal silicon solar cells were studied. One group was fabricated with homogeneously-doped emitters and another group was fabricated with selectively-doped emitters. While varying the temperature (25, 40, 60 and 80˚C), the current-voltage characteristics of the cells were measured and the leakage currents extracted from the current-voltage curve. As the temperature increased, both the homogeneously-doped and selectively-doped emitters showed a slight increase in I-sc and a rapid degradation of V-oc. The FF and efficiency also decreased as temperature increased in both groups. The temperature coefficient for each factor was calculated. From the current-voltage curve, we found that the main cause of V-oc degradation was an increase in the intrinsic carrier concentration. The temperature coefficients of the two groups were compared, leading to the idea that structural effects could also affect the temperature dependence of current-voltage characteristics.