Circular Angles Research Articles

Numerical analysis of the energy-storage performance of a PCM-based triplex-tube containment system equipped with arc-shaped fins.

This study numerically intends to evaluate the effects of arc-shaped fins on the melting capability of a triplex-tube confinement system filled with phase-change materials (PCMs). In contrast to situations with no fins, where PCM exhibits relatively poor heat response, in this study, the thermal performance is modified using novel arc-shaped fins with various circular angles and orientations compared with traditional rectangular fins. Several inline and staggered layouts are also assessed to maximize the fin's efficacy. The effect of the nearby natural convection is further investigated by adding a fin to the bottom of the heat-storage domain. Additionally, the Reynolds number and temperature of the heat-transfer fluid (HTF) are evaluated. The outcomes showed that the arc-shaped fins could greatly enhance the PCMs' melting rate and the associated heat-storage properties. The melting rate is 17% and 93.1% greater for the case fitted with an inline distribution of the fins with a circular angle of 90° and an upward direction, respectively, than the cases with uniform rectangular fins and no fins, which corresponded to the shorter melting time of 14.5% and 50.4%. For the case with arc-shaped fins with a 90° circular angle, the melting rate increases by 9% using a staggered distribution. Compared to the staggered fin distribution, adding an extra fin to the bottom of the domain indicates adverse effects. The charging time reduces by 5.8% and 9.2% when the Reynolds number (Re) rises from 500 to 1000 and 1500, respectively, while the heat-storage rate increases by 6.3% and 10.3%. When the fluid inlet temperature is 55°C or 50°C, compared with 45°C, the overall charging time increases by 98% and 47%, respectively.

Inference in cylindrical models having latent Markovian classes—With an application to ocean current data

Spatial direction vector data can be represented cylindrically by linear magnitudes and circular angles. We analyze such data by using a hierarchical Markov random field model with latent discrete classes and conditionally independent cylindrical data given the classes. The structure of a Potts model segments the spatial domain, and each class defines a cylindrical density that represents a specific structure. We consider two types of cylindrical distributions; the Weibull sine-skewed von Mises distribution, which is skewed in the circular part, and the generalized Pareto-type wrapped Cauchy distribution, which is heavy-tailed in the linear part. In this setting, we develop a statistically efficient block composite likelihood method for parameter estimation. The method is shown to provide much faster convergence than an expectation–maximization approach. However, the convergence is less stable for the block composite likelihood method, and we suggest a hybrid estimation approach for practical use. We apply the approach to study ocean surface currents in the Norwegian Sea. The models are able to describe the currents in terms of interpretable local regimes of two–three classes. Scoring rules are used to measure predictive performance of the two cylindrical densities. Results indicate that there is clearly skew angular components, and possibly also some heavy tails in magnitude.

Study on Influence of End Concavity of Rolled Piece by Billet Circular Arc Angle with CWR

In order to solve the stub bar defects and improve the material utilization, this paper proposes the method of using billet with circular arc shape on the end face to control the end concavity. It establishes the cross wedge rolling finite element model by DEFORM-3D software, and through the displacement method to analyze the flow law of metal of rolled piece on the end face, and obtains the influence law of end concavity with different circular arc angles by numerical simulation. Finally, it gets the result that the end concavity length decreases with the increase of the circular arc angle. In comparison with the original billet, when the angle is 90°, the end concavity of rolled piece reduces by 69.04%. The results provide a theoretical basis for saving material and achieving the cross wedge rolling production without the stub bar.

DNA sequence watermarking based on random circular angle

This paper discusses DNA watermarking for copyright protection and authentication of a DNA sequence. We then propose a DNA watermarking method that confers mutation resistance, amino acid residue conservation, and watermark security. Our method allocates codons to random circular angles using a random mapping table and selects a number of codons for embedding targets using the Lipschitz regularity that is measured from the evolution across scales of local modulus maxima of codon circular angles. We then embed the watermark into random circular angles of codons without changing the amino acid residue. The length and location of target codons depend on the random mapping table and the singularity of detection of Lipschitz regularity. This table is used as the watermark key and can be applied to any codon sequence regardless of sequence length. Without knowledge of this table, it is very difficult to detect the length and location of sequences for extracting the watermark. From experimental results on the suitability of similar watermark capacities, we verified that our method has a lower bit-rate error for point mutations compared with previous methods. Further, we established that the entropies of the random mapping table and the location of target codons are high, indicating that the watermark is secure.

랜덤 코돈 원형 부호 기반의 DNA 워터마킹

본 논문에서는 DNA 시퀀스의 불법 복제 및 변이 방지를 위한 DNA 워터마킹 기법을 제안한다. 제안한 DNA 워터마킹은 랜덤 맵핑 테이블에 의하여 코돈들을 랜덤 원형 각도로 수치화한 다음, 웨이블릿 국부계수 최대치의 Lipscihtz regularity 상수에 의하여 삽입 대상 코돈들을 탐색한다. 워터마크 삽입과정에서 DNA의 아미노산 코드가 변경되지 않도록 하기위하여 삼중 코돈들의 랜덤 코돈 원형 각도에 워크마크를 삽입한다. 삽입 대상 코돈들의 길이와 위치는 랜덤 맵핑 테이블에 의존하므로, 이 테이블을 알지 못할 경우, 워터마크 추출이 어렵다. 그리고 제안한 방법은 다양한 길이의 DNA 서열에 64개 코돈(종료, 개시 코돈포함)들의 랜덤 맵핑 테이블을 적용함으로써 동일한 길이의 워터마크 키를 적용한다. 본 실험에서는 랜덤 맵핑 테이블과 삽입 위치의 높은 엔트로피를 통하여 워터마크의 보안성을 확인하였다. 또한 기존의 DNA-Crypt 워터마킹과의 유사한 용량 하에서 제안한 방법이 낮은 염기 변화율을 가지며, 포인트 변이, 삽입 및 삭제 변이에 대하여 낮은 에러률를 가지며, ROC 분석을 통하여 우수한 검출 능력을 가짐을 확인하였다. This paper proposes a DNA watermarking method for the privacy protection and the prevention of illegal copy. The proposed method allocates codons to random circular angles by using random mapping table and selects triplet codons for embedding target with the help of the Lipschitz regularity value of local modulus maxima of codon circular angles. Then the watermark is embedded into circular angles of triplet codons without changing the codes of amino acids in a DNA. The length and location of target triplet codons depend on the random mapping table for 64 codons that includes start and stop codons. This table is used as the watermark key and can be applied on any codon sequence regardless of the length of sequence. If this table is unknown, it is very difficult to detect the length and location of them for extracting the watermark. We evaluated our method and DNA-crypt watermarking of Heider method on the condition of similar capacity. From evaluation results, we verified that our method has lower base changing rate than DNA-crypt and has lower bit error rate on point mutation and insertions/deletions than DNA-crypt. Furthermore, we verified that the entropy of random mapping table and the locaton of triplet codons is high, meaning that the watermark security has high level.

A new improved solution to thermal network problem in heat-transfer analysis of spacecraft

A new improved solution, Detached Variables-Parameters Coefficient (DVPC) method and Monte Carlo Ray Tracing (MCRT) method, is proposed to solve a thermal network problem in heat-transfer analysis of spacecraft. DVPC method emphasized directly on correcting the key Solar Absorption Coefficient (SAC) material parameter rather than the network conduction and radiation coefficients generally. MCRT method is contributed to reducing computation assumption and clarifying physical concepts and used to solve solar direct incidence area and network radiation transfer coefficient with different round circular angles and zenith angles of solar incidence radiation. Numerical simulation is carried out for temperature distribution of satellite. In steady stage, maximum temperature difference reaches up to 200 K and increasing the radio of absorptivity to emissivity will lead to temperature rise rapidly. In unsteady stage, maximum temperature value of satellite main body is lager than that of solar array. To begin with, cooling velocity increased rapidly and got to maximum value, then descended slowly and reached up to steady stage with 17 K discrepancy. Meanwhile, increasing SAC is better than that of decreasing to true value.

Flower algorithm for star pattern recognition in space surveillance with star trackers

Using star tracker to perform space surveillance is a focal point of research in aerospace engineering. However, autonomous attitude determination with star trackers in missions is a challenging task, because of spacecraft attitude dynamics and false stars. We present a novel star pattern recognition algorithm to resolve these problems. The algorithm defines a star pattern, called a flower code, composed of angular distances and circular angles. Then, a three-step strategy is adopted to find the correspondence of the sensor pattern and the catalog pattern, including initial lookup table match, cyclic dynamic match, and validation. A number of experiments are carried out on simulated and real star images. The simulation results show that the proposed method provides improved performance, especially on robustness against false stars. Also, the results for real star images demonstrate the reliability of the method for ground-based measurements.

Gas Transport in Serpentine Microporous Tubes Under Steady and Pulsatile Blood Flow Conditions

A serpentine gas exchange unit was built with cylindrical tubular microporous membranes featuring periodic arcs with a fixed curvature ratio (ratio of tube radius to radius of curvature) of 1/14 and circular angles between 30 and 360 deg. Oxygen transfer was measured under steady and pulsatile blood flow conditions in vitro and ex vivo to assess the design features which most effectively augment gas transfer. Under steady blood flow conditions, oxygen transfer increased with circular angles beyond 70 deg. Under pulsatile conditions, a wide range of geometrical and fluid mechanical parameters could be combined to enhance gas transfer performance, which eventually depended upon the secondary Reynolds number and the Womersley parameter.

Proposal of loosening proof nuts with skirts. (2nd Report, Improvement of fastening function of hexagonal flange nuts.)

The stress distribution in a bolted joint and the pressure distribution on the bearing surface of a hexagonal flange nut have been examined by the three-dimensional photoelastic experiment. The experiment shows that the stress distribution in a bolted joint is axially asymmetrical, because the screw part has an axiasymmetrical shape. The pressure distribution on the bearing surface of hexagonal flange nuts has the asymmetry corresponding to that stated above. The radial distribution of the bearing surface pressure concentrates at the inner part of the flange, while the pressure on the bearing surface at the outer part of the flange is reduced to almost zero. Namely, the pressure on the bearing surface of the hexagonal flange nuts is not uniformly distributed. In the case of a nut having some part without the thread, i. e, an improved nut with the skirt, the peripheral portion of the nut can bear the load pressure which has uniform distribution in all directions of circular angles. Thus the cause of loosening due to asymmetrical distribution of pressure on the bearing surface is eliminated.

Proposal of Loosening-proof Nuts : Stress Distribution in Bolted Joint and Pressure Distribution on Bearing Surface of Nut

The stress distribution in a bolted joint and the pressure distribution on the bearing surface of a nut have been examined by a three-dimensional photoelastic experiment. The experiment shows that the stress distribution in a bolted joint is axially unsymmetric, because the screw part has an axi-unsymmetrical shape. The pressure distribution on the bearing surface of a nut has an unsymmetry corresponding to that stated above. It can be seen that the screw part of the bolted joint is acted upon by a bending moment due to the unsymmetric pressure distribution. In the case a nut having some part without thread, the peripheral portion of the nut can bear the load pressure which has nuiform distribution in all directions of circular angles.