• 한국정밀공학회지
• /
• 제26권10호
• /
• pp.122-128
• /
• 2009

The aim of this study was to investigate, through a longitudinal tracking, whether gender influences morphological characteristics on trabeucular bone of tibia during unloading. 12 male and 15 female ICR mice at 6 week of age were used and randomly allocated into two groups in each gender; unloading and normal group, respectively Mice in unloading group were operated on denervation (sciatic neurectomy). The tibiae were scanned by using in vivo micro-computed tomography (micro-CT) at 0 day (before denervation) and after 14 days. Structural parameters and BMD on tibia were measured. In female, BV/TV (65%), Tb. Th (5%), Tb.N (61%) and BMD (62%) were significantly decreased and BS/BV (17%), Tb.Sp (54%), SMI (19%) and Tb.Pf (75%) were significantly increased after unloading (p<0.05). In male, BV/TV (1%) and Tb.N (10%) were significantly decreased and SMI (5%) was significantly increased after unloading (p<0.05). In addition, trabeuclar bone loss of female was significantly bigger than that of male (p<0.05). These results indicated that effects of unloading on trabecular bone in growing mice might have difference between female and male, although unloading result in loss of quantity and quality on trabecular bone both female and male.

• 한국환경보건학회지
• /
• 제50권3호
• /
• pp.169-180
• /
• 2024

Background: CAPSS missing evaporate emissions of volatile organic compounds (VOCs) from liquid cargo loading and unloading at ports. It needs to be supplemented to improve air quality management and allow more effective policy formulation. Objectives: In this study, the VOC emissions from the loading and unloading of liquid cargo at ports, which are not included in CAPSS, were estimated. The results of this study were compared and analyzed with the emission levels as described by CAPSS, confirming the need for managing VOC emissions from the loading and unloading of liquid cargo. Methods: Methodology provided by the U.S. Environmental Protection Agency (EPA) was applied to estimate the VOC emissions from the loading and unloading of liquid cargo at ports. The types of liquid cargo loaded at unloaded at ports are diverse, but for this study emissions were estimated for 37 VOCs designated by the Ministry of Environment. Results: The estimated results for VOC emissions from liquid cargo loading and unloading at domestic ports was 112,079 tons/yr, which was confirmed to be 11% of the known CAPSS emissions. The highest emissions were found from the loading and unloading of naptha, and the port with the highest emissions was Ulsan Port. Conclusions: The results of the estimated VOC emissions from liquid cargo loading and unloading at ports confirmed the high emission levels. To protect the health of port workers and nearby residents, it is essential to manage the emission sources and undertake continuous research.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회
• /
• pp.1156-1167
• /
• 2010

The constant rate of strain (CRS) consolidation test has been widely used to evaluate consolidation characteristics of soils instead of the standard Incremental Loading Test. In practical problems, after the ground improvement, the condition of the soil is over-consolidated. Therefore, it is important to determine the recompression indices and the coefficient of consolidation(or the coefficient of swelling) of unloading-reloading cycle to predict the settlement behavior. However, since standard testing procedures or studies related with strain rate are insufficient especially in unloading-reloading cycle, it is difficult to predict the settlement field behavior accurately from the CRS consolidation test results in spite of its lots of strengths. The several CRS consolidation tests were performed changing the unloading strain rate from 0.2%/hr to 20%/hr with vertical drainage condition using the reconstituted kaolinite sample. For the reconstituted kaolinite sample in CRS consolidation test, the recompression indices are insensitive to the strain rate. It is revealed that the coefficient of consolidation of reloading is affected by the developed pore pressure during unloading. Additionally, the test should be conducted in the positive pore pressure ratio range (3~15%) to obtain the reasonable coefficient of consolidation in the whole range(loading, unloading and reloading).

• 정보저장시스템학회논문집
• /
• 제3권4호
• /
• pp.183-190
• /
• 2007

In most hard disk drives that apply the ramp load/unload technology, the head is unloaded at the outer edge of the disk while the disk is rotating. During the unloading process, slider-disk contacts may occur by lift-off force and rebound of the slider. The main issue of this paper is to prevent the slider-disk contact by rebound, and we apply a disk bump to the unloading process. To do so, first, the ranges of bump dimension are determined. Second, the stability of each bump is checked by dynamic simulation. Finally, unload simulations are performed for stable bump designs. As a result of these steps, the effect of the bump design and the position for the unloading performance were investigated. As a consequence, we propose the optimal bump design to improve the unloading performance. Furthermore, we can identify to remove rebound contact by applying a bump on disk during the unloading process.

• Geomechanics and Engineering
• /
• 제37권2호
• /
• pp.97-107
• /
• 2024

The accurate prediction of grouting upward diffusion height is crucial for estimating the bearing capacity of tip-grouted piles. Borehole construction during the installation of bored piles induces soil unloading, resulting in both radial stress loss in the surrounding soil and an impact on grouting fluid diffusion. In this study, a modified model is developed for predicting grout diffusion height. This model incorporates the classical rheological equation of power-law cement grout and the cavity reverse expansion model to account for different degrees of unloading. A series of single-pile tip grouting and static load tests are conducted with varying initial grouting pressures. The test results demonstrate a significant effect of vertical grout diffusion on improving pile lateral friction resistance and bearing capacity. Increasing the grouting pressure leads to an increase in the vertical height of the grout. A comparison between the predicted values using the proposed model and the actual measured results reveals a model error ranging from -12.3% to 8.0%. Parametric analysis shows that grout diffusion height increases with an increase in the degree of unloading, with a more pronounced effect observed at higher grouting pressures. Two case studies are presented to verify the applicability of the proposed model. Field measurements of grout diffusion height correspond to unloading ratios of 0.68 and 0.71, respectively, as predicted by the model. Neglecting the unloading effect would result in a conservative estimate.

• 한국항만경제학회지
• /
• 제23권4호
• /
• pp.23-47
• /
• 2007

인천항 항만하역장비에 대한 현재의 장비보전활동상황을 점검하여 장비생산성에 얼마나 영향을 주는지 설문을 실시하여 분석하고 방안을 제시하였다. 장비보전활동의 향상을 통하여 장비생산성을 높이는 방안의 하나로 TPM 기법의 적용을 제시하였다. 설문은 현재의 인천항 항만하역장비와 관련된 운영, 정비 및 운전자들을 선정 실시하였고, 내용은 장비보전활동의 구성요소를 중심으로 자주보전 계획보전활동, 개별개선활동, 교육 훈련활동, 장비관리활동, 조직 인적관리 활동 및 장비생산성으로 구성하였다. 장비생산성에 대한 연구모형과 가설을 만들어 컴퓨터패키지를 통하여 구조모형의 검증과 연구가설을 검증하였다. 연구가설의 검증결과에 의하면 장비생산성에 장비관리가 긍정적인 영향을 주고 있는 것으로 나타나고 있으나 조직 및 인적관리가 장비생산성에 긍정적인 영향을 주지 못하는 것으로 나타났다. 따라서 인천항의 장비생산성을 향상시킬 수 있는 하나의 대안으로 TPM 기법의 적용을 제안하며, TPM 실시시 장비관리활동의 강화와 조직 및 인적관리가 장비생산성에 영향을 미칠 수 있도록 하는 방안이 모색되어야 할 것으로 본다.

• 한국해양공학회지
• /
• 제12권1호
• /
• pp.65-75
• /
• 1998

The fracture resistance curve is one of most important and design techniques employed in nuclear pressure vessel structures. This study is to evaluate the J-R curve characteristics for the SA508C-3 by the unloading compliance method and load rato analysis. The effect of strain aging for the exponential correlation of the J-R curve in this metal are investigated at room temperature, 20$0^{\circ}C$ and 30$0^{\circ}C$. The load ratio analysis method can evaluate the J-R curve by using the simple tension load-displacement curve only without the repeat of the unloading and loading. Therefore, the analysis by the proposed load ratio method has a merit, in comparison with the unloading compliance method, which can measure the crack length without the precision measurement equipment.

• Structural Engineering and Mechanics
• /
• 제9권4호
• /
• pp.375-382
• /
• 2000

Experimental investigation into the cyclic behaviour of sand plast brick masonry was performed on forty two square panels. The panels were subjected to cyclic uniaxial compression for two cases of loading: normal to bed joint and parallel to bed joint. Experimental data were used to plot the unloading-reloading curves for the entire range of the stress-strain curve. Mathematical expressions to predict the reloading and unloading stress-strain curves at various values of residual strain are proposed. A simple parabola and an exponential type formula are found adequate to model the unloading and reloading curves respectively. The models account for the potential effects of residual strain on these curves. Comparison of test results with the proposed mathematical expression shows good correspondence.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2004년도 추계 학술대회논문집
• /
• pp.33-36
• /
• 2004

The ballast tank of a ship is a system that realizes the required shipping condition and controls the draft of a ship. The loading/unloading of the ballast tank is frequently operated during navigation and the accurate prediction of the loading/unloading time is very important. A numerical algorithm that predicts the loading/unloading time of the ballast tank has been developed and applied to the prediction of the loading/unloading time of the ballast tank with various piping systems. This algorithm can be useful in optimizing the ballast tank system in early design stage.

• 대한안전경영과학회지
• /
• 제8권1호
• /
• pp.1-16
• /
• 2006

We applied the TPM to loading and unloading equipments of Incheon port and compared with the current maintenance of Incheon port's equipments. Also we analyzed the death disaster causes of equipments and work tools and suggested TPM techniques as a plan of disaster prevention. Using TPM to the loading and unloading equipments we expect to obtain the breakdown zero, defective zero, and disaster zero. And then it should raise the productivity of harbor loading and unloading equipments.