• 한국정밀공학회지
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• 제12권5호
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• pp.126-135
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• 1995

An exhaust muffler is one of the simple and effective means to meet the demand for a quiet vehicle, and it deserves a close attention to effectively reduce the engine noise. The transfer function technique is one of the tools that have been used to analyze the noise characteristics of the exhaust muffler. In this paper we obtained a transfer function using the forward-going and backward-going components of sound pressure in the exhaust muffler, which is compatible wiht lattice filter algorithm. This form of transfer function is obtained for the basic elements of a muffler, such as uniform tube, open termin- ation, closed termination, anechoic termination, expansion, contraction, extended-tube resonator, hole, Helmholtz resonator, and concentric hole-cavity resonator. The results are combined to produce the transfer function of various types of mufflers. With this transfer function we calculate the transmission and insertion losses of mufflers, and examined the effects of various design parameters. Comparisons were made between the calculation and experimental results, which showed a good agreement, and we conclude that the transfer function of lattice form can be used to analyze the noise characteristics of the exhaust mufflers.

• Physical Therapy Rehabilitation Science
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• 제12권1호
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• pp.12-18
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• 2023

Objective: Chemotherapy is usually given to inhibit cancer progression. It is the most common side effect of chemotherapyinduced peripheral neuropathy (CIPN) after chemotherapy, and its symptoms include pain such as paresthesia, dysesthesia, allodynia, hyperalgesia, and electrical stimulation. Therefore, in this review, randomized controlled trials (RCTs) were combined to analyze the effect qualitatively and quantitatively in order to find out the effect of manual therapy on patients with CIPN through a meta-analysis. Design: A systematic review and meta-analysis Methods: This review conducted a literature search through international databases (CINAHL, Embase, MEDLINE, Web of Science) in December 2022 to synthesize the effect of manual therapy on the symptomatic improvement of CIPN. Qualitative evaluation (risk of bias) and quantitative evaluation using ReVMan provided by the Cochrane Group were expressed as a random effect model and standardized mean difference (SMD). Results: In four RCTs 165 patients with CIPN were evaluated for symptoms of neuropathy. The experimental group consisting of manual therapy and its subcategories showed significant improvement compared to the control group. The results analyzed through the random effects model were SMD=-1.11; 95% confidence interval, -1.97 to -0.24. Conclusions: We came to the conclusion that manual therapy could significantly contribute to improving the symptoms of CIPN, and since it may vary depending on the technique of manual therapy, further studies on manual therapy suitable for neuropathy are needed.

• Steel and Composite Structures
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• 제44권5호
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• pp.651-676
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• 2022

Most of the experimental, theoretical, and numerical studies on the stability of functionally graded composites are deterministic, while there are full of complex interactions of variables with an inherently probabilistic nature, this paper presents a non-intrusive framework to investigate the stochastic nonlinear buckling behaviors of porous functionally graded cylindrical shells exposed to inevitable source-uncertainties. Euler-Lagrange equations are theoretically derived based on the three variable refined shear deformation theory. Closed-form solutions for the shell buckling loads are achieved by solving the deterministic eigenvalue problems. The analytical results are verified with numerical results obtained from finite element analyses that are conducted in the commercial software ABAQUS. The non-intrusive framework is completed by integrating the Monte Carlo simulation with the verified closed-form solutions. The convergence studies are performed to determine the effective pseudorandom draws of the simulation. The accuracy and efficiency of the framework are verified with statistical results that are obtained from the first and second-order perturbation techniques. Eleven cases of individual and compound uncertainties are investigated. Sensitivity analyses are conducted to figure out the five cases that have profound perturbative effects on the shell buckling loads. Complete probability distributions of the first three critical buckling loads are completely presented for each profound uncertainty case. The effects of the shell thickness, volume fraction index, and stochasticity degree on the shell buckling load under compound uncertainties are studied. There is a high probability that the shell has non-unique buckling modes in stochastic environments, which should be known for reliable analysis and design of engineering structures.

• 드라이브 ㆍ 컨트롤
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• 제21권1호
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• pp.8-15
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• 2024

This thesis investigates the jetting characteristics of an aerosol jet printing (AJP) process as a function of design and operating conditions. The governing equations of the AJP system are derived for experimentation and analysis. To understand the characteristics of the AJP system, it analyzes the jetting characteristics as a function of the flow rate of the carrier gas and the sheath gas, and the variation of the linewidth with the nozzle exit size based on particle tracking. The thesis focuses on computational fluid dynamics (CFD), which is a computer simulation. The particle tracking results obtained by CFD were analyzed using MATLAB. CFD analytical models can be analyzed in environments with different conditions and consider more specific situations than mathematical computational models. The validity of the CFD analysis is shown by comparing the experimental results with the CFD analysis.

• 한국컴퓨터정보학회논문지
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• 제29권5호
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• pp.47-53
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• 2024

본 연구는 어포던스 개념을 적용하여 가상 환경에서의 제스처 인식 과정에서 자연스러운 동작을 유도함으로써 상호작용과 몰입감을 향상하기 위한 인터랙티브 기술 활용을 제안한다. 이를 위해 샘플링 및 정규화 과정을 포함한 선분 인식 알고리즘을 활용하여 실제 손동작과 유사한 제스처를 인식하는 기법을 제안한다. 이러한 선분 인식은 본 논문에서 설계한 <VR Spell> 게임에서 마법진을 그리는 동작에 적용되었다. 실험 방법으로는 4개의 선분 인식 동작에 대한 인식률을 검증하였다. 본 논문은 실시간 핸드 트래킹 기술을 가상 환경, 특히 VR 게임과 같은 실감 콘텐츠에 적용하여 사용자에게 더 높은 몰입감과 재미를 추구하는 VR 게임을 제안하고자 한다.

• 드라이브 ㆍ 컨트롤
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• 제21권2호
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• pp.8-14
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• 2024

This paper investigates the jetting characteristics of an aerosol jet printing (AJP) process as a function of design and operating conditions. The governing equations of the AJP system are derived for experimentation and analysis. To understand the characteristics of the AJP system, this thesis analyzes the jetting characteristics as a function of the flow rate of the carrier gas and the sheath gas, and the variation of the linewidth with the nozzle exit size based on particle tracking. This thesis focuses on computational fluid dynamics (CFD), which is a computer simulation. The particle tracking results obtained by CFD were analyzed using MATLAB. CFD analytical models can be analyzed in environments with different conditions and consider more specific situations than mathematical computational models. The validity of the CFD analysis is shown by comparing the experimental results with the CFD analysis.

• Geomechanics and Engineering
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• 제38권3호
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• pp.261-273
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• 2024

This study presents a groundbreaking analytical approach to find an exact solution for the bearing capacity of strip footings on reinforced slopes, utilizing the two-phase approach and slip line method. The two-phase approach is considered as a generalized homogenization technique. The slip line method is leveraged to derive the stress field as a lower bound solution and the velocity field as an upper bound solution, thereby facilitating the attainment of an exact solution. The key finding points out the variation of the bearing capacity factor N_γ with influencing factors including the backfill soil friction angle, the footing setback distance from the slope crest edge, slope angle, strength, and volumetric fraction of inclusion layers. The results are evaluated by comparing them with those of relevant studies in the literature considering analytical and experimental studies. Through the application of the two-phase approach, it becomes feasible to determine the tensile loads mobilized along the inclusion layers associated with the failure zone. It is attempted to demonstrate the results by utilizing non-dimensional graphs to clearly illustrate variable impacts on reinforced soil stability. This research contributes significantly to advancing geotechnical engineering practices, specifically in the realm of static design considerations for reinforced soil structures.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제22권3호
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• pp.274-287
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• 2000

The use of dental implants has increased tremendously in recent years and is expected to increase even more in the future. The successful outcome of any implant procedure is surely dependent on interrelationship of the various components of an equation that includes biocompatibility of implant material, macroscopic and microscopic nature of the implant surface, the status of implant bed, surgical technique, undisturbed healing phase and subsequent prosthetic design and long-term loading phase. The purpose of this study was to clarify the effects of adrenalectomy on the osseointegration of pure titanium implants. Seventy rats, 11 weeks of age, were divided into two groups : an adrenalectomized group and a control group. Titanium screw implant(diameter, 2.0mm; length, 3.5mm) was placed into left tibia of 70 rats, 35 in control group and 35 in the experimental group. The rats were sacrificed at different time interval (1, 2, 3, 4, 6, 8, and 12 weeks after implantation) for histopathologic observation, histomorphometric analysis and immunohistochemistry with fibronectin and CD44 antibody. The results obtained from this study were as follows: 1. Histopathogically, findings, newly formed bone was seen at 3 weeks control group and became lamellar bone at 12 weeks. At 6 weeks, lipocytes were observed in bone marrow space. Thickness of regenerated trabecular bone increased till 6 weeks after then, that decreased gradually. 2. By histomorphometric analysis, marrow bone density and contact ratio of marrow bone to implant decreased significantly from 8 to 12 weeks in experimental group compared to control group and also total bone to implant contact ratio decreased significantly from 4 to 12 weeks in experimental group compared to control group. 3. Fibronectin immunoreactivity was very strong at 3 and 4 weeks control group. And after that reduced gradually. But it was continuously strong from 1 to 12 weeks experimental group. 4. CD44 immunoreactivity was very strong in the newly formed osteoblasts at 3 and 4 weeks control group. But it reacted minimally later. However, it reacted continuously strong from 3 to 12 weeks experimental group. From these results, bone to implant contact ratio decreased gradually from 4 weeks in adrenalectomized group compared to control group. CD44 and fibronectin immunoreactivities were strong at all times in adrenalectomized rats. Therefore, it could be stated that immature bone remained continuously for a long time and not readily proceeded into mature status.

• Composites Research
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• 제29권1호
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• pp.24-32
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• 2016

본 연구에서는 3D 아이소파라메트릭 쉘요소 모델을 사용하여 전단농화유체(STF: shear thickening fluid)가 함침된 케블라 페브릭(Kevlar fabric) 복합재의 방탄성능에 대하여 해석을 수행하였다. 다양한 적층복합재(12, 18, 20, 24-layer)를 대상으로 탄두 초기속도에 따른 충돌 후 속도(Residual velocity)를 측정하여 실험치와 비교하였다. SFT가 함침된 복합재의 방탄 성능의 효과를 검증하기 위하여 다양한 속도영역에서 STF가 함침된 것과 함침 되지 않은 것의 방탄성능을 비교하였다. STF가 함침된 케블라 페브릭은 450 m/s 이하의 저속에서는 비교적 큰 마찰효과를 일으키며 고속에서는 STF가 함침된 Kevlar fabric의 마찰효과는 기대할 수 없는 수준으로 오히려 역효과를 일으키는 것을 확인할 수 있었다. 연구를 통해 STF가 함침된 케블라 페브릭의 특성을 퇴화 3D 쉘 요소를 사용하여 효과적으로 모사할 수 있었으며, 실험 치와의 결과 비교를 통하여 그 유효성을 검증하였다.

• 한국해양공학회지
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• 제30권1호
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• pp.44-50
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• 2016

An experimental study was performed to investigate the behavior of green water on a structure with a rectangular cross section under wave conditions, along with the flow characteristics in bubbly water flow. An experiment was conducted in a two-dimensional wave flume using an acrylic model (1/125) of FPSO BW Pioneer operating in the Gulf of Mexico under its design wave condition. The occurrence of green water, including its development, in front of the model was captured using a high-speed Charge Coupled Device (CCD) camera with the shadowgraph technique. Using consecutive images, the generation procedure for green water on the model was divided into five phases: flip through, air entrapment, wave run-up, wave overturning, and water shipping. In addition, the distinct water elevations of the green water were defined as the height of flip through, height of splashing jet, and height of freeboard exceedance, and showed a linear relationship with the incoming wave height.