Ablative material in a rocket nozzle is exposed to high temperature combustion gas, thus undergoes complicated thermal/chemical change in terms of chemical destruction of surface and thermal decomposition of inner material. Therefore, method for conjugate analysis of thermal response inside carbon/phenolic material including rocket nozzle flow, surface chemical reaction and thermal decomposition is developed in this research. CFD is used to simulate flow field inside nozzle and conduction in the ablative material. A change in material density and a heat absorption caused by the thermal decomposition is considered in solid energy equation. And algebraic equation under boundary layer assumption is used to deduce reaction rate on the surface and resulting destruction of the surface. In order to test the developed method, small rocket nozzle is solved numerically. Although the ablation of nozzle throat is deduced to be higher than the experiment, shape change and temperature distribution inside material is well predicted. Error in temperature with experimental results in rapid heating region is found to be within 100 K.

국립공원 주변지역의 토지이용변화로 인하여 외래식물 출현종수가 증가하고 점진적으로 생육지가 확산되고 있는 가운데 공원주변에서 발생된 외래식물은 탐방객, 자동차, 동물, 바람 등으로 인해 국립공원 내 확산되고 있는 상황이다. 특히 도심형국립공원에서는 이러한 문제점들이 빈번하게 발생하고 있다. 국립공원 생태계 안정성과 건강성 증진을 위해서는 외래식물의 확산을 방지할 수 있는 시설도입이 필요하다. 국립공원에서는 외래식물 확산방지를 위해서는 유입원에 대한 정보를 분석하고 공원별, 유형별, 대상종별 유입 차단 시설을 도입 및 설치하여 국립공원 외래식물 통합관리 필요성이 대두되고 있다. 이에 따라 본 연구에서는 국립공원에 분포하는 외래식물 확산방지를 위한 효과적인 방안을 도출하고자 연구를 진행하였다. 외래식물 확산 방지시설 유형을 분석하기 위해 국내·외도입사례를 중심으로 분석을 실시하였다. 그 결과, 외래식물 방지시설은 철제형 매트, 일반형 매트, 고정형 브러시, 간이형 브러시, 복합형 브러시, 살균형 브러시 및 에어형 등 총 7가지 유형으로 구분되었다. 유형별 특징으로는 철제형 매트는 매트 밑에 시트를 깔아 외래식물 종자를 회수하는 방식이며, 매트 브러싱 능력이 우수하고 중량감으로 밀리지 않는 특성이 있다. 일반형 매트는 바닥이 평탄한 탐방로 구간에서 고정장비를 이용하여 설치하며, 중량이 가벼워 고도가 높은 지역에 설치가 효율적이다. 고정형 브러시는 신발을 신은채로 사용가능한 내구성 있는 소재로서, 브러시로 털어낸 토사를 집적할 수 있는 구조로 제작되어 있다. 브러시 설치장소 및 방법은 간단하지만 사용하기 힘이 들고 효과가 적다. 간이형 브러시는 신발을 신은채로 사용이 가능하나 종자포집이 어려운 특성이 있다. 복합형 브러시는 고정이 되어 있어 사용이 쉽고, 종자회수가 용이하며, 부피가 작아 어느 지역에서나 설치가 용이하다. 살균형 브러시는 탐방로 입구에서 안내판에 따라 살균제를 도포하고 스틸그레이팅 위에 설치된 브러시에 신발 밑면을 문질러서 사용하며, 살균효과 및 종자회수가 용이하지만 살균제 비용이 많이 소요되는 특징이 있다. 에어형은 옷이나 신발에 부착된 흙먼지 털이용으로는 효과를 가지며, 부착된 외래식물이 바람으로 인해 비산 될 수 있는 특성이 확인되었다. 도입시설에 대한 효과성 검증을 위해 도심형국립공원인 북한산국립공원을 대상으로 적지분석을 실시하고 4개 지역을 선정하여 외래식물 확산 방지시설을 제안하였다. 적지분석을 위해 외래식물 Hotsopt 분석을 실시한 결과 군집패턴이 특정지역(은평구, 성북구)을 중심으로 출현빈도의 규칙성이 높게 나타났다. 유의성이 높은 지역을 중심으로 정릉, 산성, 안골, 범골 등 4개의 시범지역을 설정하여, 매트형과 에어형 외래식물 확산 방지시설을 도입하였다. 시범지역에 대해 식물상과 외래식물 분포현황에 대해 기초조사를 실시하고, 정기적으로 수집된 매토종자를 수집하였다. 수집된 매토종자는 식물생장기에서 발아실험을 실시하여 효과성 검증을 실시하였다. 그 결과 철제형과 에어형방지시설에서 돼지풀, 주홍서나물, 미국자리공, 망초류와 같은 외래식물이 확인되었다. 방지시설 전체 유형에 따른 효과성 검증은 실시하지 못하였으나 본 연구에서 적용된 유형에 대해서는 외래식물 종자 확산을 저감할 수 있을 것으로 판단된다.

Network externality can be defined as the effect that one user of a good or service has on the value of that product to other people. When a network externality is present, the value of a product or service is dependent on the number of others using it. There exist asymmetries in network externalities between the online and traditional offline marketing channels. Technological capabilities such as interactivity and real-time communications enable the creation of virtual communities. These user communities generate significant direct as well as indirect network externalities by creating added value through user ratings, reviews and feedback, which contributes to eliminate consumers’ concern for buying products without the experience of ‘touch and feel’. The offline channel offers much less scope for such community building, and consequently, almost no possibility for the creation of network externality. In this study, we analyze the effect of network externality on the competition between online and conventional offline marketing channels using game theory. To do this, we first set up a two-period game model to represent the competition between online and offline marketing channels under network externalities. Numerical analysis of the Nash equilibrium solutions of the game showed that the pricing strategies of online and offline channels heavily depend not only on the strength of network externality but on the relative efficiency of online channel. When the relative efficiency of online channel is high, the online channel can greatly benefit by the network externality. On the other hand, if the relative efficiency of online channel is low, the online channel may not benefit at all by the network externality.

Pseudo-static approach has been conventionally applied for the design of gravity quay walls. In this method, the decision to select an appropriate seismic coefficient (kh) is an important one, since kh is a key variable for computing an equivalent pseudo-static inertia force. Nonetheless, there is no unified standard for defining kh. Likewise, port structure designers in Korea have a difficulty in choosing an appropriate kh definition, as there are conflicts in how kh is defined between the existing seismic code of port structures and the proposed new one. In this research, various seismic design codes for port structures were analyzed to compare the definitions of the seismic coefficient. The results were used for the proposing a unified seismic coefficient definition. Further, two dynamic centrifuge tests were performed with different wall heights (5 m, 15 m) to clarify the reference point of peak acceleration used in determination of kh according to the wall height. Results from dynamic centrifuge experiments showed that correction factors for the peak ground acceleration considering both the wall height and allowable displacement are needed to calculate kh.

1차원 등엔트로피 모델과 통합된 경계층 적분법은 초음속 노즐의 설계과정에서 내열재 표면의 열전달을 예측하는데 효과 적으로 사용되고 있지만 노즐 목과 같이 2차원 효과와 경계층과 노즐 코어유동의 상호작용이 발생하는 지점에서는 경계층 외부유동 해석의 부정확성으로 해석의 정확도가 감소한다. 따라서 본 연구에서는 경계층 적분법을 이용한 열전달 예측의 정 확도를 향상시키기 위해 CFD를 이용하여 2차원 효과와 노즐 코어유동의 상호작용이 고려된 경계층 외부유동 조건을 도출 하고 이를 경계조건으로 하는 해석기법을 개발하였다. 오일러 모델과 SST k-ω 모델을 CFD로 해석하여 경계조건으로 적용 했으며 계산방법을 검증하기 위해 선행문헌의 실험노즐에 대해 해석을 수행하였다. 계산 결과 CFD를 통해 경계층 외부유동 조건을 도출한 해석에서 노즐 열전달의 정확도가 향상되는 것을 확인하였으며 특히 노즐 목 후방과 팽창부에서의 차이가 크 게 나타났다. SST k-ω모델로 도출된 계산결과는 1차원 등엔트로피 모델과 비교 시 팽창부에서 실험결과와의 오차가 16% 감소하였다. 본 연구에서 개발된 해석기법은 향후 로켓노즐의 내열설계에 유용하게 사용될 것으로 평가된다.

본 연구에서는 전구에 걸쳐 나타나는 대기의 일주기 및 반일주기 조석을 최신의 3시간 간격 재분석자료를 이용 하여 분석하였다. 선행연구들과는 달리 조석의 공간구조 및 계절성에 대한 분석이 표면으로부터 성층권에 걸쳐 수행되 었다. 대부분의 층에서 일주기 조석은 중위도 지역에서 강한 반면, 반일주기 조석은 열대 지역에서 지배적으로 나타난 다. 일주기 조석은 각 반구의 겨울철보다 여름철에 그 크기가 강하게 나타나는 강한 계절적 변동성을 보인다. 반면에 반일주기 조석은 계절적 변동성을 보이지 않는다. 반일주기 조석은 연직구조를 거의 가지지 않으나, 일주기 조석은 높 이에 따라 그 크기가 증가하는 뚜렷한 연직구조를 가진다. 특히 열대지역 일주기 조석은 표면과 자유 대류권, 상층 성 층권에서 거의 반대의 위상을 보인다. 그 크기 역시 고도에 따라 비선형적으로 변화하여 수증기, 오존, 중력파 그리고 태양복사에 영향을 받았을 가능성을 시사한다.

Medium pressure and mixed enzyme were used to hydrolyze raw anchovy under controlled conditions at a batchpilot plant-scale process for the production of anchovy protein hydrolysates (APH). Mass balance calculations were carried out so that the degree of protein solubilization and yields could be estimated. Almost complete hydrolysis could be achieved in 12 h, at 50oC and 75 MPa, with no pH adjustment, at 1% (10 g/kg) mixed enzyme using raw anchovy. This was achieved with the addition of water (1/2 raw anchovy/water). The degrees of protein solubilization and yield were 63.50% and 55.61%, respectively. Fractionation using UF/NF pilot scale systems was carried out for producing four different fractions on the APH. Successive fractionation on UF and NF membranes allowed the concentration of the peptides of selected sizes without, however, carrying out sharp separations, and with some MW classes being found in several fractions. Spray drying processes for 10 kDa permeate were described to increase their usability. The free amino acid profile of the fractions was identical to that of the APH.

A Taguchi robust design method with an L9 orthogonal array and larger-the-better characteristics was implemented to optimize experimental conditions for the hydrolysis of raw anchovy using a pressure-assisted enzymatic reaction method. The degree of hydrolysis (DH), nitrogen recovery (NR) and yield were considered as the response parameters. Pressure, reaction temperature, reaction time, and mixed enzyme amount were chosen as control parameters. As a result of the Taguchi analysis in this study, the pressure was found to be the most influential parameter on DH and NR. The amount of mixed enzyme in the reaction also had a significant effect on DH and NR. Meanwhile, the optimum values were confirmed to be similar at 95% confidence and 5% significance level through analysis of variance (ANOVA). Furthermore, new hydrolysates at optimum conditions and control hydrolysates at atmospheric pressure were compared in terms of the DH, resulting in the improvement of DH by more than 52.6%.

PVDF Membrane has been used as material for the UF membrane through in-situ interfacial polymerization (IP) because of it’s outstanding properties such as high chemical resistance, thermal stability, and mechanical strength. In this study, surface morphology change of PVDF membrane was researched depending on evaporation time. 13% PVDF 6020 was used for casting and the evaporation time period was from 5s to 600s. The surface morphology of the membrane was investigated by scanning electron microscopy (SEM) and filtration was conducted in the cross flow method to evaluate the a performance of UF membrane. As a result, average pore size was increased with longer evaporation times which caused the decrease of rejection.

뛰어난 물성을 가진 poly (vinylidene fluoride) (PVDF)는 정밀여과 (MF)와 한 외여과 (UF) 분리막의 소재로써 많이 연구되고 있다. 기공의 크기를 조절하는 것은 분리막을 제조하는데 있어 중요한 요소이다. 본 연구에서는 매우 간단한 방법으로 분리막의 기공 크기를 조절하는 새로운 방법을 제시하고자 한다. PVDF 한외여과 분리막의 기공 크기는 유리판 위에 150 ㎛의 두께로 주조된 PVDF 도프 용액이 응고조 (증류수)속으로 들어가는 속도를 통해 조절되었다. 이 때 PVDF 한외여과 분리막의 기공 크기는 응고조에 들어가는 PVDF 도프 용액의 속도가 감소될수록 증가하는 경향을 보였다.

적외선을 이용한 무기체계의 발달로 인해 항공기의 생존은 큰 위협에 직면해 있다. 따라서 항공기의 생존성 향상을 위해 서 적외선 스텔스 기술이 매우 중요하다. 본 논문에서는 수치해석을 통해 실제 비행환경에서의 항공기 표면온도 및 주위 배 경에 따른 적외선 신호를 분석하고 이를 바탕으로 적외선 스텔스를 위한 항공기 표면 구조체 방사율의 가이드라인을 제시하 고 그 성능을 검증하고자 한다. 수치해석 결과, 주위 배경에 따라서 항공기 표면 방사율을 최적화한다면 항공기와 배경간의 복사대비강도를 감소시킬 수 있음을 확인하였다.

답전윤환 옥수수 8품종 및 수수 7품종 재배포장에서 조명나방 발생 및 수확 특성을 조사하였다. 매주 이뤄진 성충 트랩 조사에서 조명나방 밀도는 정식 2주 후부터 급격히 증가하여 6월 중순에 최성기에 도달 후 감소하다 9월 초 소폭 증가 후 감소하였다. 조명나방 유충에 의한 피해주 수와 침입공수를 매주 옥수수 미백2호와 대학찰 그리고 수수 남풍찰과 동안메를 대상으로 조사하였다. 그 결과, 대학찰과 미백2호에서 피해주가 각 20주당 19주와 18주였고, 주당 침입공수도 6월말부터 꾸준히 증가하여 수확기인 7월말에 대학찰은 주당 평균 1.8개, 미백2호는 1.4개로 나타 났다. 수확기에 옥수수 8품종에 대한 피해율과 침입공수를 조사한 결과, 대학찰 94%, 미백2호 92%, 일미찰 71%, 얼룩찰1호 64%, 찰옥4호 54%, 미흑찰 52%, 흑점2호 45%이었다. 주당 침입공수는 일미찰이 1.21개였고 나머지 품종들에서는 1개 미만이었다. 또한 옥수수 각 품종별로 이삭 10개씩 3반복으로 조명나방 유충에 의한 이삭 피해율을 조사한 결과, 일미찰 50%, 흑진주찰 40%, 대학찰 37%, 미흑찰과 흑점2호 13%, 얼룩찰 7% 그리고 미백2호 3% 등이었다. 수수 주요 재배품종들인 남풍찰 및 동안메는 정식 후 2개월까지 20주 평균 4주 미만으로 피해를 입다가 8월 초 에 피해가 급증하여 평균 피해주는 남풍찰이 13주, 동안메는 9.2주였고 주 당 침입공수도 8월 초부터 나타나기 시작해 남풍찰은 주당 평균 1.06 개, 동안메는 주당 평균 0.46개였다. 수확기 수수 품종별 조명나방에 의한 피해율을 조사한 결과, DS-202 95%, 목탁수수 76%, 소담찰 75%, 남 풍찰 67%, 앉은뱅이수수 57%, 동안메 46% 그리고 황금찰 34%로 7품종 모두 조명나방에 의해 높은 피해를 입었다. 침입공수 또한 피해율에 비 례해서 DS-202(1.7개), 목탁수수(1.4개), 소담찰(1.3개), 남풍찰(1.1개), 앉은뱅이수수(1개), 동안메(0.5개) 그리고 황금찰(0.4개)로 관찰되었다. 한편, 답전윤환 옥수수 및 수수 포장에서 조명나방 피해와 수확 특성은 인과관계를 보이지 않는 것으로 나타났다. 이상의 결과는 답전윤환 옥수수 및 수수 재배포장에서 조명나방의 관리대책을 구축하는데 활용될 수 있을 것으로 기대한다.

The proliferation of the Internet and related technologies has led to a new form of distribution channels, namely online retailers. The conventional offline and the new online retailers have different transaction costs perceived by the consumers in the following perspectives: the accessibility to the product information, the traffic cost and the opportunity cost for the time to visit the store, the delivery time and the possibility of ‘touch and feel’ to test the quality of the product. In particular, the online retailers have lower distribution cost structure in that they do not have physical stores, which results in lower selling price. Thus they continuously offer price competition against offline retailers using the lower selling cost as competitive weapon. Moreover the emergence of the social commerce is likely to intensify the competition between the online and offline retailers. To survive in this fierce competition, the offline retailers are trying to defend their business interests by sticking to offline transaction in anticipation of increased customer loyalty, customer’s preference for ‘touch and feel’ style shopping, and others. Despite of these efforts, customers who touch and feel a product in an offline store but purchase the product through an online retailer are increasing. To protect such customers, recently, some of the offline retailers began to provide the mobile discount service (MDS) which enables the offline customers to purchase a product at a discounted price through the mobile applications. In business competitions, the price discount strategy is usually considered to secure more market share at the cost of lower profit. In this study, however, we analyze the effect of MDS as a weapon for securing more profit. To do this, we set up a game model between the online and offline retailers which incorporates the effect of the MDS. By numerically analyzing the Nash equilibrium of the game, some managerial implications for using the MDS for more profit are discussed.

Development of shale gas has drawn increasing attention since it is one of promising alternative energy resources. However, contamination of groundwater and surface water during the extraction of shale gas is becoming a serious environmental issues, which brings the needs to treat wastewater generated from hydraulic fracking. In this study, the feasibility of membrane distillation (MD) for the treatment of shale gas wastewater was investigated using a laboratory scale experimental setup. Flat-sheet MD membranes were used to treat produced water from a shale gas well in the United States. Different configurations such as direct contact MD (DCMD) and air gap MD (AGMD) were compared in terms of flux and fouling propensity. The foulants on the surface of the membranes were examined. The results suggest that MD can treat the shale gas produced water containing more than 200,000 mg/L of total dissolved solids, which is impossible by other technologies such as reverse osmosis (RO) and forward osmosis (FO). In this study, we investigated the possibility of processing and characterization of shale gas produce wastewater using membrane distillation. Laboratory scale membrane distillation experimental device was developed. It was compared the flat-sheet direct contact membrane distillation and flat-sheet air gap membrane distillation. AGMD flux in lower than the flux of DCMD, it was expected that the contamination caused by organic matters.

The purpose of this study was to investigate the possibility of the use of enzymatically hydrolyzed anchovy protein (eHAP) to enhancing of salty taste in dried pollack soup and mungbean sprout when it was applied in cooking. The salty taste enhancing effect was evaluated by comparing the dried pollack soup samples with eHAP added and the control sample containing 0.6% NaCl, and the result showed that the salty taste enhancing effect was 15%, 25%, 42%, and 46% in the samples with 0.1%, 0.5%, 1.0%, and 1.5% eHAP added, respectively. The overall acceptability was decreased as the eHAP addition was increased. In case of a bean sprout containing 0.7% NaCl, the salty taste enhancing effect was 29%, 18%, 16%, and 31% in the 0.1%, 0.5%, 1.0%, and 1.5% eHAP added, respectively. The lightness and yellowness were decreased as the eHAP addition was increased in both the dried pollack soup and the bean sprout. The pH of the dried pollack soup was decreased but the pH of the bean sprout dish was increased as the addition of eHAP was increased. The application of eHAP to food showed a significant salty taste enhancing effect, but the effect was dependent on the type of foods.

The reduction of the content of sodium chloride in noodle was studied to prevent the problems related to excessive sodium intake, such as high blood pressure and cardiovascular diseases. This study investigated the effect of hydrolyzed anchovy products (HAP) on the salty taste of cooked noodle. The experiment was set up to determine the general properties of dough in dried and cooked noodles, with a sensory test used while increasing the concentration of HAP at same salt contents. There was no significant difference in water binding capacity, solubility, swelling power, lightness, and cooking properties. The redness, yellowness, and hardness were increased upon increasing the contents of HAP. From the sensory evaluation, cooked noodle with added HAP had a high score in appearance, color, texture, and flavor. Moreover, 50% and 75% HAP showed higher values than the control item in saltiness, preference of saltiness, and overall acceptance. Consequently, the HAP could have an effect on dried noodles or cooked noodles as a salty taste enhancer without changing the noodle’s properties.

In the companion papers (I, II), site-specific response analyses were performed at more than 300 domestic sites and a new site classification system and design response spectra (DRS) were proposed using the results of the site-specific response analyses. In this paper, the proposed site classification system and the design response spectra are compared with those in other seismic codes and verified by different methods. Firstly, the design response spectra are compared with the design response spectra in Eurocode 8, KBC 2016 and MOCT 1997 to estimate quantitative differences and general trends. Secondly, site-specific response analyses are carried out using VS-profiles obtained using field seismic tests and the results are compared with the proposed DRS in order to reduce the uncertainty in using the SPT-N value in site-specific response analyses in the companion paper (I). In addition, site coefficients from real earthquake records measured in Korean peninsula are used to compare with the proposed site coefficients. Finally, dynamic centrifuge tests are also performed to simulate the representative Korean site conditions, such as shallow depth to bedrock and short-period amplification characteristics. The overall results showed that the proposed site classification system and design response spectra reasonably represented the site amplification characteristic of shallow bedrock condition in Korea.

In the companion paper (I – Database and Site Response Analyses), site-specific response analyses were performed at more than 300 domestic sites. In this study, a new site classification system and design response spectra are proposed using results of the site-specific response analyses. Depth to bedrock (H) and average shear wave velocity of soil above the bedrock (VS,Soil) were adopted as parameters to classify the sites into sub-categories because these two factors mostly affect site amplification, especially for shallow bedrock region. The 20 m of depth to bedrock was selected as the initial parameter for site classification based on the trend of site coefficients obtained from the site-specific response analyses. The sites having less than 20 m of depth to bedrock (H1 sites) are sub-divided into two site classes using 260 m/s of VS,Soil while the sites having greater than 20 m of depth to bedrock (H2 sites) are sub-divided into two site classes at VS,Soil equal to 180 m/s. The integration interval of 0.4 ~ 1.5 sec period range was adopted to calculate the long-period site coefficients (Fv) for reflecting the amplification characteristics of Korean geological condition. In addition, the frequency distribution of depth to bedrock reported for Korean sites was also considered in calculating the site coefficients for H2 sites to incorporate sites having greater than 30 m of depth to bedrock. The relationships between the site coefficients and rock shaking intensity were proposed and then subsequently compared with the site coefficients of similar site classes suggested in other codes.

Korea is part of a region of low to moderate seismicity located inside the Eurasian plate with bedrock located at depths less than 30 m. However, the spectral acceleration obtained from site response analyses based on the geologic conditions of inland areas of the Korean peninsula are significantly different from the current Korean seismic code. Therefore, suitable site classification scheme and design response spectra based on local site conditions in the Korean peninsula are required to produce reliable estimates of earthquake ground motion. In this study, site-specific response analyses were performed at more than 300 sites with at least 100 sites at each site categories of SC, SD, and SE as defined in the current seismic code in Korea. The process of creating a huge database of input parameters - such as shear wave velocity profiles, normalized shear modulus reduction curves, damping curves, and input earthquake motions - for site response analyses were described. The response spectra and site coefficients obtained from site response analyses were compared with those proposed for the site categories in the current code. Problems with the current seismic design code were subsequently discussed, and the development and verifications of new site classification system and corresponding design response spectra are detailed in companion papers (II-development of new site categories and design response spectra and III-Verifications)