• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.319-327
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• 2016

In this paper we investigate that most of plants and animals have the symmetric property, such as a tree or a sheep's horn. In addition, the human body is also symmetric and contains the DNA. We can see the logarithm helices in Fibonacci series and animals, and helices of plants. The sunflower has a shape of circle. A circle is circular symmetric because the shapes are same when it is shifted on the center. Einstein's spatial relativity is the relation of time and space conversion by the symmetrically generalization of time and space conversion over the spacial. The left and right helices of plants and animals are the symmetric and have element-wise inverse relationships each other. The weight of center weight Hadamard matrix is 2 and is same as the base 2 of natural logarithm. The helix matrices are symmetric and have element-wise inverses.

• Bulletin of the Korean Mathematical Society
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• v.60 no.6
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• pp.1463-1475
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• 2023

In this paper, we introduce a class of rings generalizing unit regular rings and being a subclass of semipotent rings, which is called idempotent unit regular. We call a ring R an idempotent unit regular ring if for all r ∈ R - J(R), there exist a non-zero idempotent e and a unit element u in R such that er = eu, where this condition is left and right symmetric. Thus, we have also that there exist a non-zero idempotent e and a unit u such that ere = eue for all r ∈ R - J(R). Various basic characterizations and properties of this class of rings are proved and it is given the relationships between this class of rings and some well-known classes of rings such as semiperfect, clean, exchange and semipotent. Moreover, we obtain some results about when the endomorphism ring of a module in a class of left R-modules X is idempotent unit regular.

• Bulletin of the Korean Mathematical Society
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• v.59 no.3
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• pp.529-545
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• 2022

This article concerns a ring property that arises from combining one-sided duo factor rings and centers. A ring R is called right CIFD if R/I is right duo by some proper ideal I of R such that I is contained in the center of R. We first see that this property is seated between right duo and right π-duo, and not left-right symmetric. We prove, for a right CIFD ring R, that W(R) coincides with the set of all nilpotent elements of R; that R/P is a right duo domain for every minimal prime ideal P of R; that R/W(R) is strongly right bounded; and that every prime ideal of R is maximal if and only if R/W(R) is strongly regular, where W(R) is the Wedderburn radical of R. It is also proved that a ring R is commutative if and only if D₃(R) is right CIFD, where D₃(R) is the ring of 3 by 3 upper triangular matrices over R whose diagonals are equal. Furthermore, we show that the right CIFD property does not pass to polynomial rings, and that the polynomial ring over a ring R is right CIFD if and only if R/I is commutative by a proper ideal I of R contained in the center of R.

• Journal of the Korean Geotechnical Society
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• v.20 no.9
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• pp.177-189
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• 2004

The backfilled space carl have various shapes such as vertical or lateral symmetric, unsymmetric slope depending on field conditions. Kellogg (1993) suggested the different equations for the backfill earth pressure and the lateral stress ratio considering that the stresses are different between the symmetrically sloped backfilled space and the vertical one. Kellogg (1993) assumed the stress generated on sloped wall surface as the simple internal friction angle of backfilled soil. However, Moon (1997) suggested modified Kellogg equation assuming that stress behavior in the sloped wall will be varied according to the rotation angle of principal stress and the friction of sloped wall surface. This study has compared and investigated the horizontal stresss of unsymmetrical backfilled space numerically and experimentally obtained when Kellogg lateral stress ratio is appled to and when average lateral stress ratio considering unsymmetric backfill slop of left and right are applied to the modified Kellogg equation. It is shown that the horizontal stress on the sloped wall has good match numerically and experimentally in the modified Kellogg equation when Kellogg's lateral stress ratio in symmetric condition is applied to the unsymmetric condition. But the horizontal stress on the vertical wall shows disagreement numerically and experimentally. The horizontal stress results in good agreement numerically and experimentally when the average lateral stress ratio of left and right at unsymmetric slop as applied to the modified Kellogg equation. Therefore, it is estimated that the application of the average lateral stress ratio to the left and right wall should be considered when backfilled space formed unsymmetric conditions.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.23-37
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• 1991

The understanding the natureof occlusal tooth contacts of natural dentition is important for correct diagnosis and treatment of diseases developed in stomatognatic system. Several investigator have studied the distribution of tooth contacts in maximum intercuspation and have reported contact locations with respect to the tooth position. Many methods have been clinically applied for the occlusal analysis in the intercuspal position. However, there are few quantative methods. This study analyzed the new software version of the T-Scan system to record and analyze occlusal contact balance in the anterior-posterior and right-left directions. Six time moment statistics and five moment statistics were calculated in the midsagittal and the incisal axes of the occlusal plane. In the present study, informed consent was obtained from 100 subjects with natural dentitions. The results were as follows ; 1. The mean of the dental arch length & width were 48.78, 65.32mm in whole population, 49.09mm, 65.50mm in males, 48.78mm, 64.63mm in females, respectively. 2. The mean of TLR & PLR were 0.193mm(left), 0.311mm(left), respectively. Therefore, the distribution of tooth contacts was bilaterally symmetric. 3. The mean of TFB & PFB were 29.168mm, 29.055mm, and that of LFB & RFB were 29.627mm, 29.587mm, respectively, and the qualitative center of occlusal contacts was the firtst molar. 4. The mean of LL & RL were 31.666mm, 31.377mm, respectively, and the quantitative center of occlusal force was the first molar. 5. The mean of LF & RF were 60.237N, 59.276N, respectively and Left-right moment was 72.491Nmm. Therfore, the distribution of occlusal force was bilaterally balanced.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.4
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• pp.243-252
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• 1992

A mixed convection heat transfer from two vertical parallel plates has been studied numerically by the finite difference method. Effects of the Grashof number, the relative length, $L_2/L_1$. the dimensionless temperature ratio, ${\Phi}_2/{\Phi}_1$ and the dimensionless plate spacing, $b/L_1$ are examined for the heat transfer. Independent of the Grashof numbers and $L_2/L_1$, the dimensionless vertical velocity distributions skewed on the left plate as ${\Phi}_2/{\Phi}_1$ decreased. The dimensionless vertical velocity distribution for $Gr/Re^2=1$ and ${\Phi}_2/{\Phi}_1=1.0$ is skewed to the right plate $L_2/L_1=0.5$, symmetric at $L_2/L_1=1.0$ and skewed to the left plate at $L_2/L_1=1.5$. But for $Gr/Re_2=10.0$ and ${\Phi}_2/{\Phi}_1=1.0$ reversed velocity patterns are obtained. Regardless of the Grashof numbers and $L_2/L_1$, the mean Nusselt nembers on the inside surface of the left plate decreases and those of the right inside surface increases as ${\Phi}_2/{\Phi}_1$ increases. Temperature, velocity and mean Nusselt number distributions are apparently not affected by $L_2/L_1$.

• Fire Science and Engineering
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• v.22 no.4
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• pp.11-19
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• 2008

In order to show the most suitable ventilation conditions for the prevention of spontaneous combustion of small ship engine room, We have performed CFD simulation and analyzed flow and temperature fields. The flow patterns indicated differently according to the number and location of supply and exhaust opening. The case of locating the exhaust openings at the center of left and right side ceiling to the longitudinal symmetric line were more effective to eliminate the generated heat. When the number of supply and exhaust openings were increased, the case of increasing the number of exhaust opening showed more suitable ventilation conditions. The most suitable ventilation conditions in order to prevent the spontaneous combustion of small ship engine room was predicted that the supply opening located at the center of front and after side ceiling to across symmetric line, and the exhaust opening located at the center of both side walls.

• The Mathematical Education
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• v.46 no.3
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• pp.273-292
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• 2007

The purpose of this study was to find out how second, fourth and sixth graders understood the main contents related to spatial sense in the Seventh National Mathematics Curriculum. For this purpose, this study examined students' understanding of the main contents of congruence transformation (slide, flip, turn), mirror symmetry, cubes, congruence and symmetry. An investigation was conducted and the subjects included 483 students. The main results are as follows. First, with regards to congruence transformation, whereas students had high percentages of correct answers on questions concerning slide, they had lower percentages on questions concerning turn. Percentages of correct answers on flip questions had significant differences among the three grades. In addition, most students experienced difficulties in describing the changes of shapes. Second, students understood the fact that the right and the left of an image in a mirror are exchanged, but they had poor overall understanding of mirror symmetry. The more complicated the cubes, the lower percentages of correct answers. Third, students had a good understanding of congruences, but they had difficulties in finding out congruent figures. Lastly, they had a poor understanding of symmetry and, in particular, didn't distinguish a symmetric figure of a line from a symmetric figure of a point.

• Journal of Mechanical Science and Technology
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• v.15 no.5
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• pp.656-664
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• 2001

A theoretical analysis is performed to describe the qualitative behavior of transient buoyant flows in a vertical channel. Consideration is given to the case of a fluid with a pre-existing stratification. The fluid motion is generated by giving impulsive anti-symmetric step-changes in temperature at the vertical left ad right sidewalls. The qualitative character of the flow is shown to be classified in the Rayleigh number (Ra)-Prandtl number ($sigma$) diagram. The transitory approach to the steady state can be monotonic or oscillatory, depending on ($sigma$-1)$^2$$pi$$^4$ 4$sigma$$R_a$. The prominent characteristics of time-dependent flow are discussed for large $R_a$. The profiles of temperature and velocity in the transient phase are depicted, which disclose distinctive time scales of motion. The transient process is shown to be sensitive to the Prandtl number. The detailed evolutions of flow and temperature fields are illustrated for large $R_a$.

• Journal of Chest Surgery
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• v.15 no.1
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• pp.21-26
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• 1982

Fourteen cases of funnel deformity, 11 were male and the others female, treated over a eleven-year period, are presented. The overall results with the methods described by the authors, Wada, Shannon, Adkins and Ravitch appear to be excellent. The symmetric depression was more common In children under the age of 12 years and asymmetric one Increased after the age of 12. Six cases of abnormal cardiac auscultatory findings revealed no consistent hemodynamic abnormalities. An 21-year-old female was associated with left lung agenesis and dextroversion of the heart, and a 6-year-old boy with congenital bronchogenic cyst who underwent right upper lobectomy. EKG changes associated with the anomaly were observed in all. Pulmonary function test showed the range from normal to moderate restriction which did not Improve in only one patient after operation, but the patient did not complain any restriction In activity. Some transient complications were developed which resulted in improvement.