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Reinforced retaining walls are structures constructed horizontally to resist earth pressure by leveraging the frictional force imparted by the backfill. Reinforcements are employed because they exhibit excellent safety and economic efficiency. However, insufficient reinforcement can lead to collapse, and excessive reinforcement reduces economic efficiency. Therefore, it is important to select the appropriate type, length, and spacing of reinforcements. However, in actual sites, although the stress and fracture mechanisms in the straight and curved sections of reinforced soil retaining walls differ, the same amount of reinforcements are typically installed. Such an approach can lead to wall collapse or reduce economic feasibility. Therefore, in this study, the behaviours of straight and curved sections fortified with reinforcements of various lengths (1, 3, 5, and 7 m) are predicted through a three-dimensional numerical analysis. The retaining walls are of the same height, but the reinforcement variations in the aforementioned sections influence the wall behaviour differently. Based on the results, the optimum reinforcement lengths for the straight and curved parts were selected. By installing reinforcements of different lengths in these sections, the maximum reinforcing effect with minimum reinforcement was derived. This study further found that the curved section of the wall required more reinforcements, and the reinforcement lengths for the curved and straight sections should be separately optimized.

For tunneling in urban areas, understanding the interaction and behavior of tunnels and the foundation of adjacent structures is very important, and various studies have been conducted. Superstructures in urban areas are designed and constructed with piled rafts, which are more effective than the conventional piled foundation. However, the settlement of a piled raft induced by tunneling mostly focuses on raft settlement. In this study, therefore, raft and pile settlements were obtained through 3D numerical analysis, and the change rate of settlement along the pile length was calculated by linear assumption. Machine learning was utilized to develop prediction models for raft and pile settlement and change rate of settlement along the pile length due to tunneling. In addition, raft settlement in the laboratory model test was used for the verification of the prediction model of raft settlement, derived through machine learning. As a result, the change rate of settlement along the pile length was between 0.64 and −0.71. In addition, among features, horizontal offset pile tunnel had the greatest influence, and pile diameter and number had relatively little influence.

정삼투식 담수화 기술은 차세대 담수 방법으로 주목을 받고 있으나, 상용화를 위해서는 유도용액 처리공정에서의 에너지 효율 향상을 필요로 한다. 중탄산암모늄을 유도용질로 이용하는 정삼투식 담수화 시스템은 정삼투 막모듈, 유도용액 분리공정, 유도용액 회수공정으로 이루어진다. 담수 생산을 위한 유도용액 분리공정에서 발생하는 암모니아와 이산화탄소의 혼합기체는 연속운전 및 경제성 향상을 위하여 회수되어 중탄산암모늄 용액으로 재농축되어야 한다. 이러한 유도용액 회수공정의 흡수액으로 희석된 중탄산암모늄 용액을 이용하는 방법이 있다. 본 연구에서는 용액의 농도에 따른 흡수성능 및 특성을 관찰하기 위한 실험을 수행하였고, 정삼투식 담수 공정에서 중탄산암모늄 용액을 분리된 암모니아와 이산화탄소 재농축에 이용할 수 있음을 확인하였다. 본 연구의 결과는 파일럿급 정삼투식 담수 공정의 설계 및 운전에 활용될 예정이다. 【Although forward osmosis desalination technology has drawn substantial attention as a next-generation desalination method, the energy efficiency of its draw solution treatment process should be improved for its commercialization. When ammonium bicarbonate is used as the draw solute, the system consists of forward-osmosis membrane modules, draw solution separation and recovery processes. Mixed gases of ammonia and carbon dioxide generated during the draws solution separation, need to be recovered to re-concentrate ammonium bicarbonate solution, for continuous operation as well as for the economic feasibility. The diluted ammonium bicarbonate solution has been proposed as the absorbent for the draw solution regeneration. In this study, experiments are conducted to investigate performance and features of the absorption corresponding to absorbent concentration. It is concluded that ammonium bicarbonate solution can be used to recover the generated ammonia and carbon dioxide. The results will be applied to design and operation of pilot-scale forward-osmosis desalination system.】

Accurate thermal conductivity measurements using conventional thermal analysis techniques may be difficult for thin plates with thicknesses less than 0.2 mm. In this study, the two-dimensional temperature of a thin plate heated using a modulated laser beam is observed through infrared thermography. The temperature variations depending on the distance from the laser spot and time are analysed from the obtained temperature images. The thermal conductivities of stainless steel and slide glass samples are calculated by fitting the experimental results to the theoretical values. The measured thermal conductivity agrees with the table values within 10%.

Suspensions of nano-sized solid particles in a liquid medium, known as nanofluids show remarkable enhancement in thermal conductivity compared to the base fluid. Nanofluids are a promising candidate for advanced heat transfer applications such as microelectronics cooling. While the thermal conductivity of nanofluids has been measured in the past using conventional techniques such as the transient hot wire method, this work presents the application of the 3-omega (3ω) method for this purpose. The theoretical model for 3ω response of a heater device with de-ionized (DI) water and ethylene glycol (EG) is verified by comparing with experimental measurements. Following this validation, the effective thermal conductivity of Al2O3 nanofluids in DI water and EG are measured at room temperature. In addition, interesting effects in the thermal response due to agglomeration and sedimentation of nanoparticles are observed.

A novel micromixer which utilizes chaotic mixing induced by ferrofluid actuation is developed. The micromixer is fabricated by a polydimethylsiloxane micromolding technique. The micromixer consists of a T-shaped main mixing channel and two parallel sub-channels that intersect the main channel. Oscillation of a couple of ferrofluid slugs in the sub-channels, induced by external permanent magnet actuation, generates chaotic advection in the main channel flow. To visualize the mixing, red fluorescent particles are supplied to one of the inlets of a T-shaped channel, and mixing flow is observed by a fluorescence microscope and an intensified CCD camera. The mixing experiments are performed with various ferrofluid perturbation frequencies and main stream flow velocities. The optimal mixing conditions determining the upper and lower limits of the most effective Strouhal numbers are found from the experimental results.

Flow assurance issue in subsea pipelines arises mainly due to hydrate plugs. We present a new line-heater for prevention of hydrate plug formation in subsea pipelines. The line heater has modular compact design where an electrical heater and a swirl generator are embedded inside the housing pipe so that the stream can be heated efficiently and homogeneously. In this paper, flow and heat transfer characteristics of the line heater are investigated numerically, with a particular emphasis on the mixing effect due to the swirl generator.

Measurements of thermal conductivity by time-domain thermoreflectance in the temperature range 100

SrTiO$_3$ is a promising $n$-type oxide semiconductor for thermoelectric energy conversion. Epitaxial thin films of SrTiO$_3$ doped with both La and oxygen vacancies have been synthesized by pulsed laser deposition (PLD). The thermoelectric and galvanomagnetic properties of these films have been characterized at temperatures ranging from 300 K to 900 K and are typical of a doped semiconductor. Thermopower values of double-doped films are comparable to previous studies of La doped single crystals at similar carrier concentrations. The highest thermoelectric figure of merit ($ZT$) was measured to be 0.28 at 873 K at a carrier concentration of $2.5\times10^{21}$ cm$^{-3}$.

Nanofluids, which are suspensions of nano-sized solid particles in a liquid medium, show remarkable enhancement in thermal conductivity compared to the base fluid. Nanofluids are a promising candidate for advanced heat transfer applications such as microelectronics cooling. While the thermal conductivity of nanofluids has been measured in the past using conventional techniques such as the transient hot wire method, this work presents the application of the 3-omega (3-ω) method for this purpose. The theoretical model for 3-ω response of a heater device with de-ionized (DI) water is verified by comparing with experimental measurements. Following this validation, the effective thermal conductivity of Al2 O3 nanofluids in DI water and ethylene glycol are measured. The measured values are found to be in good agreement with previous works. In addition, interesting effects in the thermal response due to agglomeration and sedimentation of nanoparticles are observed.Copyright © 2006 by ASME

We report a case of disseminated Mycobacterium intracellulare infection in a 31-year-old man who had been diagnosed as having dermatomyositis and systemic lupus erythematosus 3-years prior. The patient developed a left pleural effusion M. intracellulare was repeatedly isolated from the pleural fluid. After antimycobacterial treatment, the patient’s pleural effusion resolved, but a left knee joint effusion developed newly and M. intracellulare was cultured from the joint fluid. At present, the patient has been taking antimycobacterial medication for 15 months but his left knee joint fluid remains positive for M. intracellulare. To our knowledge, this is the second reported case of disseminated NTM infection in a non-HIV infected patient in Korea.

Sarcoidosis is a granulomatous disease that can involve any organ, although it primarily involves the lungs, intrathoracic lymph nodes, skin, and eyes. We present a case of sarcoidosis with pancytopenia, resulting from bone marrow involvement. A 35-year-old man was admitted to hospital for chronic cough and blurred vision. On chest computed tomography, there were multiple pulmonary nodules and mediastinal lymph nodes enlargement. As the patient also showed pancytopenia, we performed a bone marrow biopsy, as well as a transbronchial lung biopsy. Both biopsies showed non-caseating granulomas. We diagnosed the patient with sarcoidosis with pulmonary, bone marrow, uvea, liver and spleen involvement. After oral steroid therapy, the patient 's symptoms as well as his pancytopenia improved. We present this case to demonstrate the significance of bone marrow biopsy in cases of sarcoidosis with pancytopenia, as well the possibility of clinical improvement with steroid treatment.

Benign bronchoesophageal fistula is a rare disease and it may be characterized by nonspecific symptoms that can cause a delayed diagnosis. We misdiagnosed a patient with recurrent aspiration, which was due to bronchoesophageal fistula, as active pulmonary tuberculosis. The patient was 44 year old female who had suffered from chronic cough, especially during eating liquid meals, since 1982 when she had been treated for tuberculous lymphadenitis. Computed tomography showed an irregular mass with surrounding centrilobular nodules in the superior segment of the right lower lobe (RLL). She was diagnosed as having active pulmonary tuberculosis and treated with anti-tuberculosis medication, but she continued to complain of persistent cough even after anti-tuberculosis treatment. Thus, we reexamined the patient, and bronchoesophageal fistula between the esophagus and the superior segment of the RLL was finally confirmed by esophagography. After the fistula was surgically treated, the patient became asymptomatic and she then experienced good health.