Recently, steel dampers are widely used as seismic reinforcement devices. Steel dampers have the advantage of being easy to manufacture and being able to absorb a lot of energy through stable hysteresis behavior. However, there is a possibility that the steel damper may be damaged due to fatigue caused by repeated seismic loads. In this study, the seismic performance of steel dampers and engineering plastic dampers with different physical characteristics were compared and analyzed. In addition, numerical analysis was performed on a hybrid damper that combines a steel damper and an engineering plastic damper. It is more effective to apply engineering plastic dampers to structures that experience significant displacement due to seismic loads. The behavior of hybrid dampers combining steel dampers and engineering plastic dampers is dominated by steel dampers. A hybrid damper in which an engineering plastic damper yields after a steel damper yields can effectively respond to various seismic loads and secure high ductility and excellent seismic performance.

In the case of a school building, even though it is a regular structure in terms of plan shape, if the masonry infill wall acts as a lateral load resisting element, it can be determined as a torsionally irregular building. As a result, the strength and ductility of the structure are reduced, which may cause additional earthquake damage to the structure. Therefore, in this study, a structure similar to a school building with torsional irregularity was selected as an example structure and the damping performance of the PC-BRB was analyzed by adjusting the eccentricity according to the amount of masonry infilled wall. As a result of nonlinear dynamic analysis after seismic reinforcement, the torsional irregularity of each floor was reduced compared to before reinforcement, and the beams and column members of the collapse level satisfied the performance level due to the reduction of shear force and the reinforcement of stiffness. The energy dissipation of PC-BRB was similar in the REC-10 ~ REC-20 analytical models with an eccentricity of 20% or less. REC-25 with an eccentricity of 25% was the largest, and it is judged that it is effective to combine and apply PC-BRB when it has an eccentricity of 25% or more to control the torsional behavior.

Buckling Restrained Braces can not only express the strength considered at the time of design, but also reduce the seismic load by energy dissipation according to the plastic behavior after yield deformation of the steel core. The physical characteristics and damping effect may be different according to the buckling prevention method of the steel core by the lateral restraint element. Accordingly, in this study, To compare hysteresis characteristics, Specimen(BRB-C) filled with mortar, specimen(BRB-R) combined with a buckling restraint ring and Specimen(BRB-EP) filled with engineering plastics was fabricated, and a cyclic loading test was performed. As a result of the cyclic loading test, the maximum compressive strength, cumulative energy dissipation and ductility of each test specimen was similar. But in case of the cumulative energy dissipation and ductility, BRB-C filled with the mortar specimen showed the lowest. This is considered to be because the gap between the steel core and the reinforcing material for plastic deformation was not uniformly formed by pouring mortar around the core part.

Unlike the CFT retrofit method, The EPFT retrofit method, which fills the steel tube with engineering plastic, does not require a separate concrete forming work and is a lightweight seismic Retrofit Method. In this study, an prototype model of the EPFT was proposed, and to analyze the seismic performance, an independent specimens and a reinforced concrete column were fabricated to conduct a seismic performance test. As a result of loading test of the independent specimens, the strength was increased compared to the steel tube column without internal filling, and the ductility ratio did not significantly increase due to the falling off of the weld. As a result of loading test of the concrete reinforcement specimen, the strength, ductility ratio, and energy dissipation were increased, and the number of cracks by loading step decreased compared to the non-reinforced specimen.

The purpose of this study is to monitor the pesticide residues in frozen fruits and vegetables distributed and sold in online and offline markets in Korea. For the study, 107 samples of 34 types of frozen fruits and vegetables were examined, and a total of 341 pesticide residues were analyzed by using multiclass pesticide multiresidue methods of the Korean Food Code. As a result, pesticide residues were detected from 16 of 64 frozen fruits samples and 15 of 43 frozen vegetables samples. Conclusively, residues were detected from 31 samples in total, showing a detection rate of 29.0%. Specifically, pyridaben exceeded the Maximum Residue Limits (MRLs) based on the Positive list system (PLS) in one of the frozen radish leaves, and the violation rate was 0.9%. Detection on frozen fruits and vegetables was made 23 times for 11 types and 36 times for 21 types. In total, 28 types of pesticide residues were detected 59 times. Fungicides were detected the most in frozen fruits, while insecticides were detected the most in frozen vegetables. The most detected pesticides were the insecticide, acaricide chlorfenapyr (5) and the fungicide boscalid (5). Chlorfenapyr was detected only in frozen vegetables, and boscalid was detected in frozen fruits except one.

In this study, we learned about the effects of indoor radon concentration reduction associated with the operation of a mechanical ventilation system at an apartment house. The experimental parameters were mainly the indoor radon level and air change rate, which were controlled by the amount of emissions released and fan motor speed. Even at the high level of radon diffused in an apartment house, indoor radon concentrations converged to the Korean national guideline level within 3 to 4 hours when the air was ventilated at 0.5 ACH and 0.7 ACH. In the case of 0.3 ACH, however, where the degree of ventilation was insufficient compared to the legal air change rate, the high concentration indoor radon could not be sufficiently removed even if the mechanical ventilation system was operated for more than 14 hours continuously. When the indoor radon level was high, the reduction rate was 34.3% for 0.3 ACH, 70.4% for 0.5 ACH, and 69.7% for 0.7 ACH at 6 hours-operation, while at the medium-level, indoor radon can be reduced by 46.2% (0.3 ACH) to 73.2% (0.7 ACH). Depending on the indoor concentration range, it may be required to secure a ventilation rate of 0.5 ACH or more at all times. In addition, in apartment houses with excellent airtight performance, even if indoor radon is at a level similar to the national guideline, it is difficult to expect a reduction in the concentration due to natural decay. Therefore, it is desirable to lower the indoor concentrations as much as possible.

The seismic behaviors of the arch structure vary according to the rise-span ratio of the arch structure. In this study, the rise-span ratio (H/L) of the example arch structure was set to 1/4, 1/6, and 1/8. And the installation angle of the seismic isolator was set to 15°, 30°, 45°, 60° and 90°. The installation angles of the seismic isolator were set by analyzing the horizontal and vertical reaction forces according to the rise-span ratio of the arch structure. Due to the geometrical and dynamic characteristics of the arch structure, the lower the rise-span ratio, the greater the horizontal reaction force of the static load, but the smaller the horizontal reaction force of the dynamic load. And if the seismic isolator is installed in the direction of the resultant force of the reaction forces caused by the seismic load, the horizontal seismic response becomes small. Also, as the installation angle of the seismic isolator increases, the hysteresis behavior of the seismic isolator shows a plastic behavior, and residual deformation appears even after the seismic load is removed. In the design of seismic isolators for seismic response control of large space structures such as arch structures, horizontal and vertical reaction forces should be considered.

This study was designed to verify what effect the use of a natural ventilation system can have on improving indoor air quality with regard to radon in various concentration ranges in an apartment house. The results show that both high (2~3 times higher than 148 m3) and low (similar to 148 Bq/m3) levels of indoor radon concentrations can be reduced close to and/or below the Korean IAQ guideline within 6 hours when the natural ventilation system is operated at approximately an air change rate of 0.5. In the case of an air change rate of 0.3, however, the indoor radon levels cannot meet the national guidelines and the reduction effect was insufficient with regard to various radon concentrations. Typically, the air change rate of a natural ventilation system is affected by meteorological factors such as temperature, relative humidity, wind speed, pressure. Its effectiveness varies according to such factors, for that reason, the reduction effects on radon did not increase proportionally with the ventilation time in this study.

본 연구는 견과종실류 및 그 가공품을 대상으로 LC/MS/ MS를 이용하여 aflatoxin (B1, B2, G1, G2), ochratoxin A, fumonisin (B1, B2), zearalenone을 동시 분석하여 오염 실태를 조사하였다. 연구 대상 106건 중 37건(35%)에서 곰팡이독소가 검출되었으며, 2항목 이상의 곰팡이독소가 동시에 검출된 경우는 8.5%로 조사되었다. Aflatoxin, ochratoxin A, fumonisin, zearalenone은 각각 0.08-1.45 μg/ kg, 17.29 μg/kg, 1.16-14.89 μg/kg, 0.12-12.69 μg/kg의 농도 범위로 검출되었다. 검출 빈도로 보면 zearalenone (23%), aflatoxin (13%), fumonisin (8%), ochratoxin A (1%) 순으로 높은 검출율을 보였다. 원물 형태인 견과류와 유지종 실류는 각각 35%, 33%의 검출율을 나타내었고 이를 가공한 견과류가공품과 유지종실류가공품은 각각 44%, 46% 의 검출율을 나타내어 가공 식품에서의 곰팡이독소 검출율이 10% 이상 높게 나타났다. 곰팡이독소는 물리화학적으로 안정한 물질로서 가공이나 조리 과정 중에도 그대로 남아있어 식품 원료에서의 곰팡이독소 관리가 더 중요할 것으로 판단된다.

When an unexpected excessive seismic load is applied to the base isolation of arch structure, the seismic displacement of the base isolation may be very large beyond the limit displacement of base isolation. These excessive displacement of the base isolation causes a large displacement in the upper structure and large displacement of upper structure causes structural damage. Therefore, in order to limit the seismic displacement response of the base isolation, it is necessary to install an additional device such as an anti-uplift device to the base isolation. In this study, the installation direction of the base isolation and the control performance of the base isolation installed anti-uplift device were investigated. The installation direction of the base isolation of the arch structure is determined by considering the horizontal and vertical reaction forces of the arch structure. In addition, the separation distance of the anti-uplift device is determined in consideration of the design displacement of the base isolation and the displacement of the arch structure.

간편식 형태의 이유식 중 죽 44건, 진밥 40건, 퓌레 11 건, 분말 6건으로 총 101건의 무기질(철, 아연, 칼슘, 마그네슘) 함량을 마이크로웨이브 분해장치로 분해하여 ICPOES로 분석하였다. 무기질의 유형별 평균 함량은 철 0.05- 0.45 mg/100 g(mg/10 g, 분말), 아연 0.06-0.29 mg/100 g(mg/ 10 g, 분말), 칼슘 3.07-6.65 mg/100 g(mg/10 g, 분말), 마그네슘 2.46-5.93 mg/100 g(mg/10 g, 분말)으로 나타났다. 철, 아연, 칼슘, 마그네슘의 권장섭취량(KDRIs)과 비교하였을 때 권장섭취량 대비 각각 2.74-22.35%(평균 11.10%), 5.94- 28.95%(평균 21.91%), 3.07-6.65%(평균 4.47%), 13.42-38.95% (평균 22.85%)이었다. 시판되는 간편 이유식만으로는 생후 6개월 이후 각각의 무기질 권장섭취량을 충분히 섭취할 수 없어 조제식이나 모유를 통한 영양소 섭취가 필요하다. 충분한 무기질 섭취를 위해서는 각각 영양소의 주요 급원 식품을 파악하고 부족한 영양소를 섭취할 수 있는 간편 이유식을 선택하는 것을 권장한다. 아울러 제조회사에서 는 우리나라 영유아시기에 부족해지기 쉬운 철, 칼슘 등 의 영양소를 강화한 재료를 이유식 제조에 사용·표기하여 영유아의 성장발달에 필요한 영양소가 균형 있게 공급될 수 있도록 해야 할 것이다.

If an excessive displacement occurs in the base isolation system, the structure will be damaged due to overturning of the upper structure. In this study, we analyze the behavior of base isolation by applying earthquake to base isolation with anti-uplift device. In the case of structures that generate horizontal reaction forces such as arch structures, horizontal reaction forces must be considered in the design of the base isolation and structural members. And anti-uplift device for preventing the excessive displacement of the base isolation system is needed.

In this study, the Buckling restrained braces reinforced with engineering plastics that can compensate for the disadvantages in the manufacturing process of the existing buckling restrained brace. The proposed PC-BRB was fabricated to evaluate the reinforcement effect by carrying out a structural performance test and a full-scale two-layer frame test through cyclic loading test. As a result of PC-BRB's incremental and cyclic loading test, stable hysteresis behavior was achieved within the target displacement, and the compressive strength adjustment coefficient satisfied the recommendation. As a result of the real frame experiment, the strength of the reinforced specimen increased compared to the unreinforced specimen, and the ductility and energy dissipation increased.

경기도에서 유통되고 있는 건조수산물 95건에 대하여 유해중금속인 납, 카드뮴, 수은 및 미량영양소인 셀레늄 함량을 조사하였다. 금아말감법의 수은분석기, 유도결합플 라즈마 질량분석기를 사용하여 측정하였으며, 각 항목별 평균함량은 납 0.062±0.071(0.002-0.428) mg/kg[평균값±표 준편차(최소값-최대값) mg/kg], 카드뮴 0.083±0.100(0.004- 0.540) mg/kg, 수은 0.012±0.012(N.D-0.054) mg/kg, 셀레 늄 0.839±0.371(0.362-2.124) mg/kg으로 나타났으며, 유해 중금속인 납, 카드뮴, 수은 모두 기준규격 이하로 나타났다. 멸치 크기에 따른 중금속 및 셀레늄 함량은 수은이 대멸치에서 통계적으로 유의하게 높게 나타났으며(P<0.05), 셀레늄은 잔멸치와 대멸치의 크기에 따른 유의적인 함량 차이를 나타냈다(P<0.05). 새우 종류에 따른 중금속 및 셀레늄 함량을 비교한 결과 보리새우가 납, 카드뮴, 수은에서 유의적으로 높게 나타났다(P<0.05). 대멸치, 밴댕이의 부위별 중금속 및 셀레늄 함량은 내장부위가 가장 높았고, 새우는 머리부위가 중금속 및 셀레늄 함량이 높게 나타났다. 건조수산물을 통해 섭취하는 수은, 카드뮴의 주간 및 월간섭취량은 JECFA에서 설정한 PTW(M)I의 0.712%와 2.978%로 조사된 건조수산물 내 중금속 함량은 안전한 농도수준으로 판단된다.

Most of the variable shading devices are installed outdoors, so they are greatly affected by structural safety due to external climate change, wind, rain, and snow. Especially, due to strong wind such as typhoons, safety problems may occur due to the dropout of the device. Therefore, it is necessary to secure the structural safety against the wind. Therefore, it is necessary to analyze the structural behavior of the windshield to evaluate the structural safety of the variable sunshade device. In this study, we analyze the wind pressure applied to the shading material according to the change of the length of the variable shading device, and apply it to the calculation of the wind load for the structural design of the variable shading device. The CFD (Computational Fluid Dynamic) analysis of the structure of the sample was used to analyze wind pressure magnitude and distribution. In order to estimate the wind pressure, the maximum wind loads of the static and negative pressures acting on the structure were analyzed from numerical simulation results.

This study was performed to assess particulate matter removal efficiency of domestic air cleaner products in a field condition. The assessment also included air cleaners with different air removal mechanisms. The particulate matter (PM2.5) removal test with a different air removal mechanism using air cleaners showed that the electrostatic precipitation technique showed better performance compared with HEPA filters and other types of systems. Its removal efficiency was almost 95% in one of our operation times in the given test condition. It was assumed that not only the type of removal system but also the individual design, supply and exhaust system, and the automatically controlled air volume are involved in the removal efficiency. With respect to the area of application, tests with air cleaners for 40 m2, 60 m2, and 80 m2 areas revealed that particulate matter removal efficiency increased with the air cleaner that had a broad area of application. However, particulate matter removal efficiency by air cleaners did not correspondingly increase with the increase of the area of application. Moreover, the installation location did not influence particulate matter removal efficiency. Our results are expected to be used as the basic information for indoor air quality improvement and prediction using air cleaners.

In this study, the seismic performance and behavior characteristics of the upper truss structure of the large stadium are analyzed by nonlinear dynamic analysis. In the nonlinear dynamic analysis, the earthquake records were generated by site response analysis to simulate the nonlinear behavior of the relevant soil condition where the structure is located. Nonlinear dynamic analysis was performed using Perform-3D and the nonlinear properties of the substructure and the superstructure were determined in accordance with KISTEC guideline. According to the analysis results, excessive deformation occurred in the upper truss element, and plastic hinges exceeded the target performance in some members. Buckling-restrained brace is used for seismic retrofit of stadium structures and the analysis results shows the interstory drift satisfies the target performance level with dissipating the seismic energy efficiently.

Vertical earthquake motions can occur along with horizontal earthquakes, so that Structure should be designed to resist Seismic loads in all directions. Especially, due to the dynamic characteristics such as the vibration mode, when the vertical seismic load, the dynamic response of the Spatial structure is large. In this study, the seismic response of the lattice dome to horizontal and vertical seismic loads is analyzed, and a reasonable seismic load combination is analyzed by combining horizontal and vertical seismic response results. In the combination of the horizontal seismic load, the largest result is obtained when the direction of the main axis of the structure coincides with the direction of seismic load. In addition, the combination of vertical seismic load and horizontal seismic load was the largest compared with the combination of horizontal seismic load. Therefore, it is considered that the most reasonable and stable design will be achieved if the seismic load in vertical direction is considered.

The use of microwave-assisted extraction and an acid-base clean-up process to determine the amount of methylmercury (MeHg) in marine products was suggested in order to improve the complicated sample preparation process. The optimal conditions for microwave-assisted extraction was developed by using a 10% NaCl solution as an extraction solution, setting the extraction temperature at 50℃, and holding for 15 minutes to extract the MeHg in marine products. A NaOH solution was selected as a clean-up substitute instead of L-cysteine solution. Overall, 670 samples of marine products were analyzed for total mercury (Hg). Detection levels were in the range of 0.0006~0.3801 μg/kg. MeHg was analyzed and compared using the current food code and the proposed method for 49 samples which contained above 0.1 mg/kg of Hg. Detection ranges of methylmercury followed by the Korea Food Code and the proposed method were 75.25 (ND~516.93) μg/kg and 142.07 (100.14~244.55) μg/kg, respectively. The total analytical time of proposed method was reduced by more than 25% compared with the current food code method.

In this study, we investigate a seasonal underground market which is located under a semi-enclosed basement. Under such settings, there is difficulty in managing indoor air quality such as ventilation. Based on the result, we can improve the indoor air environment of the underground market. The underground market in Seoul was divided into four types according to its structural characteristics and the seasonal survey was conducted. In conclusion, we will develop a realistic improvement plan to improve the indoor air environment of the underground market by selecting the underground market through actual survey.