Research has been conducted on acoustic metamaterials that control the transmission characteristics of reflected and refracted waves using phase delay by resonators. Using one-dimensional theory, the phase delay equations for the 1/4 wavelength and Helmholtz resonator are presented. These one-dimensional analysis results are compared with the results predicted by three-dimensional FEM. The advantages and disadvantages of 1/4 wavelength and Helmholtz resonator were confirmed in implementing phase delay. An acoustic metamaterial with a refraction angle of 30° was manufactured using multiple tubes and then the sound pressure distribution was measured. A relatively large sound pressure was measured at the target position of 30°, which was compared with the 3D FEM analysis results. Simulations confirmed that a phase delay range closer to 2π was more effective in refraction, but varying the number of resonators was found to have minimal impact on which additional research is needed for generalization.

The effects of annealing on the microstructure and mechanical properties of Al–Zn–Mg–Cu–Si alloys fabricated by high-energy ball milling (HEBM) and spark plasma sintering (SPS) were investigated. The HEBM-free sintered alloy primarily contained Mg2Si, Q-AlCuMgSi, and Si phases. Meanwhile, the HEBM-sintered alloy contains Mg-free Si and θ-Al2Cu phases due to the formation of MgO, which causes Mg depletion in the Al matrix. Annealing without and with HEBM at 500oC causes partial dissolution and coarsening of the Q-AlCuMgSi and Mg2Si phases in the alloy and dissolution of the θ-Al2Cu phase in the alloy, respectively. In both alloys, a thermally stable α-AlFeSi phase was formed after long-term heat treatment. The grain size of the sintered alloys with and without HEBM increased from 0.5 to 1.0 μm and from 2.9 to 6.3 μm, respectively. The hardness of the sintered alloy increases after annealing for 1 h but decreases significantly after 24 h of annealing. Extending the annealing time to 168 h improved the hardness of the alloy without HEBM but had little effect on the alloy with HEBM. The relationship between the microstructural factors and the hardness of the sintered and annealed alloys is discussed.

The blockage rate for three kinds of nets commonly used in agricultural facilities was assessed by using the image acquisition and its relevant processing. By using both empirical relations presented by Idel’chik and Richards and Robinson, and the blockage rate obtained from the image processing, the pressure drop through the nets was predicted and also compared with wind tunnel experiment results. The results of the study showed that the blockage rate of the net was discriminated according to such factors as the magnitude of nets, the existence of inside threads, the thickness and number of threads. In addition, the blockage rate for the incident angle of 0° when the wind blew at the front had the range of 0.22－0.29 (0.22－0.32 when considering whole incident angles from 0° to 45° by 15°). For the nets with the blockage rate of about 30% or below, the prediction by the empirical relations of by Idel’chik and Richards and Robinson showed a little higher pressure drop overall than that of the wind tunnel test, but the use of the empirical relations and the blockage rate could be thought of as providing effectively meaningful guidelines for the safe design of agricultural facilities including nets because the wind tunnel test has been tedious and expensive. Further research and potential application on the prediction technique of the pressure drop, regarding both a subtle deformation by the wind and manufacturing methods with regard to the level of knots and the existence of inside threads, needs to be done for the nets with higher blockage rate.

Hydraulic cylinders are hydraulic system parts widely used in various industries such as construction machinery, machine tools, robots, automobiles, and automation systems. The maximum capacity of vane pumps used in machine tools is 70bar, but the actual operating pressure is less than 50bar. The allowable pressure of a commercial hydraulic cylinder is 140 - 210 bar, so it is heavy and uneconomical because it uses thick and strong materials. In this paper, we intend to develop a small and lightweight hydraulic cylinder suitable for the allowable pressure of 50bar or less so that it can be used in the hydraulic system field. In order to develop a compact hydraulic cylinder, flow analysis, and structural analysis were conducted under piston forward and backward conditions. The analyzed flow rate value was calculated to be suitable for the operation of the hydraulic cylinder. As a result of comparing the stress calculated under the forward/backward condition of the piston with the yield stress of the material, the safety factor was calculated to be more than 2.5.

본 연구는 간호대학생의 대면 및 비대면 임상실습스트레스와 스트레스 대처가 임상수행능력에 미치는 영향을 알아보고 각 요인 간 영향을 파악함으로써 간호대학생이 임상실습스트레스에 효율적으로 대처하고 임상수행능력을 증진할 수 있는 임상실습교육 전략의 근거를 제시하고자 시행되었다. 연구대상자 는 서울과 충청권 소재 간호대학생으로, 2021년 6월 10일부터 7월 10일까지 총 201부의 자료를 수집하였 다. 통계프로그램 SPSS 21.0을 이용하여 Pearson’s correlation coefficients로 대면 및 비대면 임상실습스트 레스, 스트레스 대처, 임상수행능력 간의 상관관계를, 위계적 다중회귀분석을 사용하여 임상수행능력에 미 치는 요인을 분석하였다. 연구결과, 1단계에서 간호대학생의 성적, 전공만족도, 대면실습만족도가 임상수행 능력의 19.4%를 설명하였고, 2단계에서는 스트레스 대처를 추가하여 19.6%의 설명력이 증가되어 총 39.0%의 변량을 설명할 수 있었다. 따라서 간호대학생의 임상수행능력 향상을 위해서는 임상실습스트레스 에 대한 원만한 스트레스 대처가 중요하며, 본 연구는 간호대학생의 스트레스 대처를 위한 상담 및 교육프 로그램을 개발하는 기초자료를 제공할 것이다.

본 연구는 국내 차나무 품종을 대상으로 연평균 기온이 낮은 봉화군에 식재하여, 봉화지역 차나무 재배 가능성을 검토하고자 연구를 수행하였다. 봉화군 시험지 토양 조사 결과, 시험지별 토양의 pH, EC, 치환성양이온, 유효인산은 적정수준이었으며, 유기물 함량은 대체로 낮은 수치로 조사되었 다. 봉화군 시험지 기온 조사 결과, 최저 기온은 소천면이 -14.1℃로 가장 낮았고, 다음으로 춘양면 -12.6℃, 명호면 -12.6℃, -10.2℃ 순으로 모든 시험지는 -10℃ 이하의 낮은 온도로 조사되었다. 차나무 재배 생육평가 결과, 명호면 시험지에서 생육 정도가 가장 우수하였고, 다음으로 소천면, 온실, 춘양면 순으로 조사되었다. 또한, 재배품종 보향과 대조품종 다산은 시험지 생장량과 광합성량이 다른 수종에 비해 높은 것을 확인하였 다. 봉화지역과 하동지역에 식재된 참녹의 주요 생리활성물질인 catechin과 caffeine 함량을 조사한 결과, Catechin 함량은 EGC와 EC, EGCG 함량은 하동이 높게 조사되었고, 반면 ECG는 봉화지역의 참녹이 월등히 높았다. 총 catechin 함량은 봉화 5.23%, 하동 5.22%로 비슷하게 나타났다. Caffeine 함량은 봉화 0.05%, 하동 0.38%로 하동지역의 참녹이 높게 나타났다. 본 연구에서 봉화군 차나무 재배 생육평가 결과 명호면, 소천면이 차나무 재배에 유리할 것이며, 봉화지역 차나무 재배 시 재배품종 보향과 대조품종 다산은 재배 적응성이 높을 것으로 판단된다.

In 2022, the Korean Ministry of Environment designated Parthenium hysterophorus as an ecosystem-disturbing plant. The purpose of this study was to present a management plan for P. hysterophorus considering its distribution, morphological, physiological, and ecological characteristics, and to introduce various control techniques. P. hysterophorus is native to Central America and occurs in about 45 countries worldwide. However, in Korea, it only grows in some areas of Tongyeong and Changwon, Gyeongsangnam Province. P. hysterophorus is an annual plant and spreads by seeds, moves between countries in the process of importing and/or exporting agricultural seeds, and spreads by agricultural machinery and vehicles after introduction. P. hysterophorus releases parthenin, an allelochemical that suppresses the occurrence of the surrounding vegetation, from its stems and roots. In addition, P. hysterophorus causes damage to humans and livestock through various allergens. P. hysterophorus can be controlled by physical methods, such as cutting its stems or pulling roots, and by treatment with non-selective herbicides, such as glyphosate. Many biological control research studies have been conducted and, unfortunately, there is no a practical solution so far.

This study was conducted to provide basic data on the amount of sodium and the setting of permissible error range of actual measurement, which is a problem for cabbage kimchi nutrients subject to labeling. The sample targeted was baechu (Kimchi cabbage) kimchi, which might have a large variation in sodium content by part of kimchi. Kimchi samples were collected twice from eight companies by season (spring, summer, fall, and winter). The average sodium content in kimchi samples was 619±87 mg/100 g (range, 534±63 mg/100 g to 783±40 mg/100 g). The error in average annual sodium content of abandonment kimchi (maximum value difference compared to the minimum value) was 26.8 to 64.3%. Sodium contents in kimchi produced in spring and summer were relatively low. However, deviation between individuals was large. It was found that cases exceeding the permissible error (120%) standard varied depending on the criteria for setting the amount of sodium. In addition, due to seasonal differences, sodium content in kimchi exceeded 120% of the labeling value. Thus, it is necessary to set standards suitable for characteristics of kimchi to prevent unintentional violations of labeling standards by raw materials and manufacturing processes.

Vegetation is the basis for biodiversity conservation and sustainable development. In the Environmental Impact Assessment (EIA), which is the most direct and efficient policy measure to prevent degradation of nature, vegetation-related assessment has limitations as it is not based on quantitative and scientific methods. In addition, it focuses on the presence of protected species; hence, it does not take into account the role of vegetation as a habitat on a wide-area scale. As a way to overcome these limitations, this study aims to contribute to the quantification and advancement of future EIA on vegetation. Through the review of previous studies, core areas, connectivity, and vegetation condition were derived as the items to be dealt within the macroscopic aspect of vegetation impact assessment. Each item was spatially constructed using land cover maps and satellite imageries, and time series change analysis was performed. As a result, it was found that vegetation has been continuously deteriorating due to development in all aspects, and in particular, development adversely affects not only the inside of the project site but also the surrounding area. Although this study suggested the direction for improvement of the EIA in the vegetation sector based on data analysis, a more specific methodology needs to be established in order to apply it to the actual EIA process. By actively utilizing various environmental spatial data, the impact of the development on the natural ecosystem can be minimized.

최근 들어 기후변화로 인한 태풍의 강도는 강력해졌다. 광산지역의 광미와 폐석은 수해로 인해 환경에 악영향을 미쳤을 것으로 추정된다. 강릉지역은 3,693호(1936), 루사(2002), 매미(2003), 메기(2004) 등의 국내 최대 태풍의 영향은 받았다. 이번 연구는 태풍으로 인한 수해 이후 하천을 따라 그 주변에 높은 농도의 비소가 검출된 사례를 기초로 하였 다. 환경피해 관련 법은 오염 원인자의 책임을 명확히 하고 있지만, 잠재적인 자연재해 지역에서는 세심한 적용이 필요 하다. 이러한 지역에서 자연재해의 영향을 최소화하기 위해서 관련 법들의 개선과 연계가 필요하다. 이 연구가 하류 지 역에서 혼재된 오염물질 대응에 도움이 되길 기대한다.

빈번한 가뭄의 피해는 수자원의 양극화를 초래하고 있다. 국내에서는 2011년부터 2017년 사이에 국지적이고 주 기적인 이상 가뭄이 지속되어 10년 가뭄 빈도로 설계된 소규모 저수지의 저수율이 감소하였다. 이러한 저수율의 감소 는 수질을 떨어트릴 수 있고 이미 확보된 용수의 사용마저 제한할 수 있다. 따라서 가뭄에 대비하고 극복하기 위해서 는 수질관리와 가뭄 빈도의 재산정이 필요하다. 이 연구는 저수지에서 수질 변화의 원인인 잠재적 오염물질을 추정하고, 가뭄 기간 동안 저수지의 저수율 감소와 그에 따른 수질 변화를 검토한 것이다.

현 설계기준에서 제시한 단부횡보강 상세는 시공성과 생산품질이 현저히 떨어지므로 내진성능과 시공성을 확보할 수 있는 RC 구 조벽체의 단부횡보강 상세 개발이 필요하다. 최근 선재 제작기술의 발전으로 다양한 선조립철근의 제작이 가능해지고 있으며 특히 다양한 연속횡보강 철근 상세의 제작이 가능하게 되었다. 본 연구에서는 사각 연속횡보강 선조립철근 단부횡보강 상세를 적용한 RC 구조벽체의 모멘트-곡률 관계에 대한 분석을 진행하였다. 비선형 단면해석에 의하면 사각 연속횡보강의 상세를 적용한 RC 구조벽체 는 사각 연속횡보강 영역의 면적이 증가할수록 내진성능을 확보할 수 있다. 이러한 연구결과에 근거하여 사각 연속횡보강 선조립 철 근의 상세 적용시, 단부횡보강 영역의 면적만큼 사각 연속횡보강 영역의 면적을 확보해야 한다.

본 연구에서는 인공광 시설에서 광원을 달리하여 생산된 방풍나물의 항산화 및 항염 효과를 평가하였고 노지 재배 된 방풍나물과 그 생리활성을 비교하였다. DPPH 및 ABTS 라디칼 소거 활성 및 총 폴리페놀은 노지에서 재배 된 방풍나물이 인공광 시설에서 재배된 방풍나물보다 높은 항산화 활성을 나타내었고, 인공광에서 재배된 방풍나물 중 에서는 BW 광원으로 재배된 방풍나물이 농도 의존적으로 높은 항산화 효과를 보였다. XO 저해 활성은 BW 재배된 방풍나물이 노지 재배 방풍나물보다 우수한 효과를 나타내었다. SOD와 CAT 결과는 BW 및 노지 재배된 방풍나물 모두 무처리 대조군에 비해 농도 의존적인 활성을 보였다. BW 및 노지 재배된 방풍나물은 방풍나물을 처리하지 않은 무처리 대조군에 비해 TNF-α 와 IL-6 사이토카인을 농도 의존적으로 유의하게 감소시켰다. 따라서 인공광 재배 된 방풍나물은 대체적으로 노지보다 낮을 수 있지만 항산화 및 항염 효과를 보였고. 앞으로 인공광에서 재배된 작물의 다양한 기능성 소재로서의 연구에 도움이 될 것으로 기대된다.

This study obtained the following conclusions using the measurement results of indoor and outdoor PM10 with regard to cardiovascular disease patients in Cheongju-area in November 2020. Most of the PM10 has an I/O ratio of less than 1, which is an outdoor source. Since we measured once and twice time, Without the air purifier device’s working status, there were no concentration changes of PM10 in the first and second indoor areas. As for the concentration of PM10 according to the living environment, the distribution of PM10 is higher indoors than outdoors when the residential area is 30 m2 or more, and the outdoor PM10 concentration tends to be high when the distance to the road is within 50 m. The more time spent indoors, the higher the indoor PM10 concentration. The smaller the ventilation time and frequency, the longer the cooking time was, and the higher the number of cooking times, the higher the concentration of PM10 could be. The indoor PM10 contribution ratio through multiple regression analysis showed the possibility of increasing indoor PM10 as β = 28.590 when the time spent indoors was longer than 16 hours (p<0.05). The result regarding PM10 exposure reveals that PM10 can be inhaled not only indoors but also outdoors, and the subjects of this study appear to have lived indoors for about 16 hours or longer on a daily basis, which may affect their health regardless of gender.