Earticle

In this letter, we propose space?time block coded non-orthogonal multiple access (STBC-NOMA) for underwater acoustic sensor networks (UASNs) to improve reliability by exploiting transmit diversity and spectral efficiency. We derive mathematical expressions for ergodic rate, outage probability and energy efficiency. Results show that STBC-NOMA can combine the advantages of STBCs and NOMA, which significantly enhance the performance of UASNs, without the need for prior CSI status at the transmitter. Finally, we jointly optimize the signal frequency and power allocation coefficient for the STBC-NOMA scheme with respect to the transmission distance using pattern search algorithm, to further enhance the ergodic rate.

본 논문에서는 다중경로 페이딩 채널에서 고속의 데이터를 전송하고자 할 경우에 적합한 트렐리스 부호화된(Trellis-Coded TC) 차동 시 공간 변조(Differential Space Time Modulation, DSTbD를 사용한 OFDM 시스템을 제안한다. 최근에 시공간 부호화(Space-Time Code, STC)는 이동 통신 채널의 신뢰성 있는 통신을 위해 각광받고 있다. 차동 부호화된 STC 방식은 동기 방식처럼 채널 상태 정보(channel state information)가 필요하지 않기 때문에 동기 방식보다 하드웨어 구조가 간단하여진다. 그러나 이러한 차동 시공간 부호화된 OFDM방식의 커다란 문제점은 동기방식에 비해 성능이 저하된다는 것이다. 따라서 본 논문에서는 차동 시공간 부호화된 OFDM의 성능을 향상시키기 위해 DUSTM(differential unitary space-time modulation)을 이용하여 송신기를 설계하고 수신단에서 다중 심벌 디코딩을 수행하는 수신기와 디코딩 알고리듬을 개발하며, 이를 위한 새로운 branch metric을 유도하고자 한다.

Space-time coding and modulation exploit the presence of multiple transmit antennas to improve performance on multipath Rayleigh fading channels. In this paper, we propose the Trellis-Coded Differential Space Time Modulation-OFDM system with multiple symbol detection. The Trellis-code perform the set partition with unitary group codes. The Viterbi decoder containing new branch metrics is introduced in order to improve the bit error rate (BER) in the differential detection of the Unitary differential space time modulation. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER performance without sacrificing bandwidth and power efficiency.

연구목적: 알바알토의 건축적 사고에서 가장 우선시되는 사람과 자연에 대한 해석 및 지역의 전통적 측 면을 고려하여 근대의 사회적 특성과 시대변화가 빛, 형태, 재료 측면에서 건축공간에 어떻게 반영되는 지 분석하고자 한다. 연구방법: 근대의 북구건축 및 핀란드건축의 특성을 파악하고 모더니즘의 관점에 서 알바알토의 건축 어휘를 종합하여 빛, 형태, 재료를 삼각 구도로 잡고 이들의 상호관계를 문헌자료 및 도면을 통해 분석한다. 연구결과: 알바알토의 건축작품은 빛, 형태, 재료, 공간의 다양함을 조합한 것 이 중심을 이룬다. 사회적인 지각이 강조되고 휴먼스케일과 건물 환경이 연결된다. 건축의 기능에 따라 새로운 적용방식으로 이들 요소는 재창조된다. 결론: 알바알토의 건축은 전통과 모더니즘 사이에서 자 연과 문화, 사회와 개인, 표준화와 다양성, 보편성과 지역성, 지적인 것과 감성적인 것, 과학기술과 인간 심리적인 것, 합리성과 직관적인 것 등 서로 이질적이면서 상반된 요소들을 건축공간에 종합적으로 적 용시키고 사회적 변화를 수용하여 건축적 언어의 네트워크를 통해 재통합하는 특성을 갖는다.

Purpose: This study aims to analyze the meaning of architectural space of Alvar Aalto, which is based on architectural theories of periodic flows and the form of the space with the various elements applied to the works. Method: It analyzes the interrelationships of light, form and material in triangular composition by synthesizing the architectural vocabulary of Alvar Aalto from the viewpoint of modernism. Results: The architectural works of Alvar Aalto are centered on the combination of light, form, material, and space diversity, emphasizing social awareness and linking the human scale with the building environment. Conclusion: The structure of the Alvar Aalto is a synonym of nature and culture, society and individuals, standardization and diversity, universality and locality, intellectual and emotional, scientific and human psychological. It is possible to apply reciprocity elements to architectural spaces in a comprehensive manner while being different from each other in terms of rationality and immediacy.

This study seeks to present multiple ways of using school meal living spaces as a venue for student activities, communication with students, and activities with local communities in accordance with the 2015 revised educational curriculum and launch of the free semester system at middle schools. The findings were as follows. First, the 2015 revised education curriculum and the use of the space for activities within the free semester system at middle schools. The school meal living space was found to be used for autonomous activities, club activities, career exploration activities, subject discussions and debates, nutritional education sessions, etiquette sessions, individual learning and small-group learning activities that are necessary in the new curriculum and the free semester system. Second, use of the space for student activities such as student governance activities. If glass walls, portable partitions, tables and chairs are prepared, the space can be used for student committee meetings, discussion rooms prior to volunteer activities and preparation rooms for school events such as festivals. Third, use of the space for communication among students. The suggested usages of the space were cited as a conversation space with friends, break space such as a music appreciation room, room for small group activities, indoor game or play space and space that could be used by individuals for breaks or activities. Fourth, the usage of space for local residents of the community. When used for this purpose, the use of the space as a space to participate in the free semester program, a space for life-long education for local residents and a space for club activities for parents of students were ranked the highest. The space was also noted to be usable as a break room, a community exchange room and meeting room.

이 연구는 행위자-네트워크 이론(이하 ANT)이 공간성을 어떻게 이해하는지 분석한 다음, 그 외연을 현재의 코로나19 사태에 적용하려는 목적을 갖는다. 우선 필자는 ANT가 공간성을 논의하는 방식을 고찰하기 위해 몇 개의 핵심 개념을 중심으로 ANT를 개괄하고자 한다. 그리 고 현대사회에서 인간이 살아가는 자연문화(natureculture)의 한 축인 테크노사이언스를 ANT가 이해하는 방식을 살펴볼 것이고, 이와 관련하여 공간성이 어떻게 논의되고 있는지 검 토해볼 것이다. 라투르(Latour)는 자연과 사회의 이분법을 부정하며 근대화의 과정이 아닌 생 태화의 과정을 주장하고 있다. 미지의 병원체가 사회와 유리된 자연, 가령 박쥐의 몸 안에만 존재할 것이라는 막연한 근대주의적 이분법은 현재의 코로나19 사태를 야기한 이데올로기적 배경이 될 수 있다. 나아가 본 연구는 ANT 연구자인 몰(Mol)과 로(Law) 등의 다중체(body multiple) 및 다중세계(world multiple) 개념을 차용하는 다중공간(space multiple)의 개념을 활용하고자 한다. 이 분석과정에서 ANT에서 주장하는 네 가지 공간성, 즉 네트워크 공간·유 클리드 공간·유동적 공간·화염 공간의 분류를 사용할 것이며, 코로나19 사태에서 관찰되는 공간은 이러한 다중공간성을 가짐을 보이고자 한다. 마지막으로 이 다중공간성을 어떻게 다 룰 때 코로나19 사태에서 의미 있는 방역적 실천이 이루어질 수 있는지 살펴볼 것이다.

In this article, I will describe the main concepts of the actor-network theory regarding the spatiality. After analyzing the spatial implications of the key concepts of ANT such as actors/actants, network, and the concept of theories, I will analyze how they can be applied to the understanding of technoscience and spatiality. Lastly, I will describe how ANT can be used to analyze the space laden with COVID-19 pandemic. By doing it, the concept of the space multiple which is a concept borrowed from Mol and Law’s concepts of the body multiple and the world multiple, will be used. Also four modes of spatialities that ANT argues network spatiality, Euclidean spatiality, fluid spatiality and fire spatiality will be discussed to analyze how we can use ANT to prevent the epidemic.

A multiple smooth model is proposed by smoothing technique and piecewise technique for large scale data. Mapping the training data to the hidden space with a hidden function, the proposed model divides the original data into several subclasses by Fuzzy C Means (FCM), whose initial cluster centers are selected by samples with large density indexes; derives the smooth differentiable model by utilizing the entropy function to replace the plus function of the slack vector, and introduces linking rules to combine results of subclasses. Simulations demonstrate that the obtained algorithm maintains good classification accuracies, reduces the training time and hardly varies with kernel parameters.

Various algorithms based on image processing techniques have been used to detect and track objects in video surveillance systems. In this paper, followed by color RGB for multiple objects is present. To do this, real-time tracking algorithm is proposed for objects navigate and identify current positions and movements, because each object has a color with label on top. RGB color space is used to calculate the threshold values of each color. It is for example, video surveillance applications where cameras and other sources of information are used to monitor the activities of a sensitive site. Threshold values can be defined according to the object to track. Linear model is applied to the color discrimination. To remove unwanted objects to executives, morphological transformation is applied on the image binary and technical Blob analysis is then used to facilitate the detection of object. Our proposed algorithm is capable of tracking objects in the format full-frame (640 x 480 pixels) at rate (50 images per second). High performance robustness and in real time is confirmed by experiments.

This study explored the factors contributing to the activation of residential space user management platforms through a multiple case study approach. Twenty platforms that existed from 2012 to April 2024 were analyzed, focusing on 11 key features, with 8 selected as variables. Service activation was measured based on Play Store downloads and ratings, classifying 10 platforms as successful and 10 as needing development. Using an inductive reasoning approach with the ID3 algorithm, supported by GPT-4's Advanced Data Analytics, the analysis identified the "Neighbor Communication Function" as the most influential variable, followed by the "Newsletter Function" and "Facility Status Check Function." The study found that platforms including a neighbor communication function are more likely to be activated. Platforms without both the neighbor communication and newsletter functions are less likely to succeed. Even without the neighbor communication function, platforms with both the newsletter and facility status check functions tend to be activated. Platforms lacking the neighbor communication function will not be activated unless both the newsletter and facility status check functions are present. These findings provide strategic insights for the commercial success of residential space user management services. The results suggest that interaction services, such as the neighbor communication function, are crucial for success. However, success can still be achieved with robust monitoring and information services, even in the absence of user interaction features.

이 연구는 행위자-네트워크 이론(이하 ANT)이 공간성을 어떻게 이해하는지 분석한 다음, 그 외연을 현재의 코로나19 사태에 적용하려는 목적을 갖는다. 우선 필자는 ANT가 공간성을논의하는 방식을 고찰하기 위해 몇 개의 핵심 개념을 중심으로 ANT를 개괄하고자 한다. 그리고 현대사회에서 인간이 살아가는 자연문화(natureculture)의 한 축인 테크노사이언스를ANT가 이해하는 방식을 살펴볼 것이고, 이와 관련하여 공간성이 어떻게 논의되고 있는지 검토해볼 것이다. 라투르(Latour)는 자연과 사회의 이분법을 부정하며 근대화의 과정이 아닌 생태화의 과정을 주장하고 있다. 미지의 병원체가 사회와 유리된 자연, 가령 박쥐의 몸 안에만존재할 것이라는 막연한 근대주의적 이분법은 현재의 코로나19 사태를 야기한 이데올로기적배경이 될 수 있다. 나아가 본 연구는 ANT 연구자인 몰(Mol)과 로(Law) 등의 다중체(body multiple) 및 다중세계(world multiple) 개념을 차용하는 다중공간(space multiple)의 개념을활용하고자 한다. 이 분석과정에서 ANT에서 주장하는 네 가지 공간성, 즉 네트워크 공간·유클리드 공간·유동적 공간·화염 공간의 분류를 사용할 것이며, 코로나19 사태에서 관찰되는공간은 이러한 다중공간성을 가짐을 보이고자 한다. 마지막으로 이 다중공간성을 어떻게 다룰 때 코로나19 사태에서 의미 있는 방역적 실천이 이루어질 수 있는지 살펴볼 것이다.

In this article, I will describe the main concepts of the actor-network theory regarding the spatiality. After analyzing the spatial implications of the key concepts of ANT such as actors/actants, network, and the concept of theories, I will analyze how they can be applied to the understanding of technoscience and spatiality. Lastly, I will describe how ANT can be used to analyze the space laden with COVID-19 pandemic. By doing it, the concept of the space multiple which is a concept borrowed from Mol and Law’s concepts of the body multiple and the world multiple, will be used. Also four modes of spatialities that ANT argues network spatiality, Euclidean spatiality, fluid spatiality and fire spatiality will be discussed to analyze how we can use ANT to prevent the epidemic.

본 논문에서는 고속 데이터 송수신을 위해 2차원 iDFT(inverse Discrete Fourier Transform) 및 DFT(Discrete Fourier Transform) 연산을 이용하여 Delay-Doppler 스프레딩 영향을 고속 수신 처리하는 OTFS(Orthogonal Time Frequency Space) 변조 시스템과 OTFS-MIMO(Multiple Input Multiple Output) 시스템을 평가하고 분석한다. 특히 OTFS 변조를 사용하는 MIMO 시스템은 높은 Doppler 효과가 존재하는 채널에서도 시스템의 용량 저하가 거의 없이 모든 데이터 스트림을 전송할 수 있다. 시뮬레이션 결과, $1{\times}1$ OTFS 변조 시스템의 전송률은 $2{\times}2$ OTFS-MIMO 시스템에서 한 스트림의 전송률과 유사함을 확인할 수 있다. 즉, $2{\times}2$ OTFS-MIMO 시스템은 높은 Delay-Doppler 영향이 존재하는 환경에서도 $1{\times}1$ OTFS 변조 시스템과 비교하여 거의 2배의 전송률을 확보할 수 있음을 확인할 수 있다.

In this paper, we have evaluated and analyzed OTFS(Orthogonal Time Frequency Space) modulation and OTFS-MIMO(Multiple Input Multiple Output) system. OTFS modulation can concisely compensate delay-Doppler spreading effect by using 2D(2-Dimension) iDFT (inverse Discrete Fourier Transform) and DFT(Discrete Fourier Transform) operation. It enables OTFS system to transmit high-speed data. Especially, OTFS-MIMO system can transmit all data streams without performance degradation on high Doppler frequency channel. As simulation results, we have confirmed that $1{\times}1$ OTFS system's achievable rate is a similar to each stream of $2{\times}2$ OTFS-MIMO system. That is, we have also confirmed that $2{\times}2$ MIMO system can completely achieve double achievable rate in comparison with OTFS system on high Doppler frequency channel.

In this paper, the authors introduced a new approach to find the optimal collision avoidance maneuver considering multi threatening objects within short period, while satisfying constraints on the fuel limit and the acceptable collision probability. A preliminary effort in applying a genetic algorithm (GA) to those kinds of problems has also been demonstrated through a simulation study with a simple case problem and various fitness functions. And then, GA is applied to the complex case problem including multi-threatening objects. Two distinct collision avoidance maneuvers are dealt with: the first is in-track direction of collision avoidance maneuver. The second considers radial, in-track, cross-track direction maneuver. The results show that the first case violates the collision probability threshold, while the second case does not violate the threshold with satisfaction of all conditions. Various factors for analyzing and planning the optimal collision avoidance maneuver are also presented.

In this study, we developed a co-located and space-shared multiple-input multiple-output (MIMO) antenna module with a modular design and high integration level. The proposed antenna pair includes a half-wavelength loop antenna and a dipole-type antenna printed on the front and back sides of a compact modular board. Owing to their modal orthogonality, these two independent antenna elements are highly self-isolated and free of additional decoupling components, even though they are assembled at the same location and within the same space. Thus, the proposed antenna is attractive in 5G MIMO systems. Furthermore, the proposed co-located and space-shared MIMO antenna module was employed in a 5G smartphone to verify their radiation and diversity performances. A 12 × 12 MIMO antenna system was simulated and fabricated using the proposed module. Based on the results, the proposed module can be employed in large-scale MIMO antenna systems for current and future terminal devices owing to its high integration, compactness, simple implementation, and inherent isolation.

We propose a novel cooperative guidance law design method based on the finite time disturbance observer (FTDO) for multiple near space interceptors (NSIs) with impact time control. Initially, we construct a cooperative guidance model with head pursuit, and employ the FTDO to estimate the system disturbance caused by target maneuvering. We subsequently separate the cooperative guidance process into two stages, and develop the normal acceleration command based on the super-twisting algorithm (STA) and disturbance estimated value, to ensure the convergence of the relative distance. Then, we also design the acceleration command along the line-of-sight (LOS), based on the nonsingular fast terminal sliding mode (NFTSM) control, to ensure that all the NSIs simultaneously hit the target. Furthermore, we prove the stability of the closed-loop guidance system, based on the Lyapunov theory. Finally, our simulation results of a three-to-one interception scenario show that the proposed cooperative guidance scheme makes all the NSIs hit the target at the same time.

In this study, a space-time transmission scheme is proposed to tackle the limitations of channel estimation with orthogonal pilot information in colocated multiple-input multiple-output systems with several transmitting and receiving antennas. Channel information is obtained using orthogonal pilots. Channel estimation introduces pilot heads required to estimate a channel. This leads to bandwidth insufficiency. As a result, trade-offs exist between the number of pilots required to estimate a channel versus spectral efficiency. The detection of data symbols is performed using the maximum likelihood decoding method as it provides a consistent approach to parameter estimation problems. The moment-generating function of the instantaneous signal-to-noise ratio is used to drive an approximate expression of the symbol error rate for the proposed scheme. Furthermore, the order of diversity is less by one than the number of receiver antennas used in the proposed scheme. The effect of the length of a pilot sequence on the proposed scheme's performance is also investigated.

By using the multidimensional normal approximation of functionals of Gaussian fields, we prove that functionals of Gaussian fields, as functions of t, converge weakly to a standard Brownian motion. As an application, we consider the convergence of the Stratonovich-type Riemann sums, as a function of t, of fractional Brownian motion with Hurst parameter H = 1/4.

In this paper, the issue of blind detection of Alamouti-type differential space-time (ST) ${\pi}/2$-shifted BPSK modulation in static Rayleigh fading channels is considered. We introduce a novel transformation to the received signal from each receiver antenna such that this binary ST modulation, which has a second-order transmit-diversity, is equivalent to QPSK modulation with second-order receive-diversity. The pre-detection combining of the result of transformation allows us to apply a low complexity detection technique specifically designed for receive-diversity, namely, scalar multiple-symbol differential detection (MSDD). With receiver complexity proportional to the observation window length, our receiver can achieve the performance 1.5dB better than that of conventional differential detection ST and 0.5dB worse than that qf a coherent maximum ratio combining receiver (with differential decoding) approximately.

A finite element analysis of crack propagation in a half-space due to sliding contact was performed. The sliding contact was simulated by a rigid asperity moving across the surface of an elastic half-surface containing single and multiple cracks. Single, coplanar, and parallel cracks were modeled to investigate the interaction effects on the crack growth in contact fatigue. The analysis was based on linear elastic fracture mechanics and the stress intensity factor concept. The crack propagation direction was predicted based on the maximum range of the shear and tensile stress intensity factors.

This paper deals with a navigation algorithm for swarm robot systems in which multiple mobile robots work together. The motion of each mobile robot is modeled in such a way to have more inputs than the number of outputs. The null-space projection method of this model is employed to resolve the motion of the swarm robot system while avoiding obstacles. The feasibility of the proposed navigation algorithm is verified through a simulation study using several swarm robot models.

Detecting partial discharge (PD) caused by the degradation of insulating materials is needed to prevent the electric breakdown. We have studied radio remote sensing to detect PD. Therefore, it is necessary to remove the electromagnetic (EM) waves reflected on the power equipment when PD source is localized. In this paper, we consider to estimate the direction-of-arrival (DOA) of EM waves emitted from PD in a free space. The signal subspace method, which uses an eigenstructure of the correlation matrix obtained from the received signals, is approved useful to estimate DOA. The finite difference time domain (FDTD) method is used to simulate the propagation of EM waves emitted from PD sources. The wideband signal subspace methods, e.g. coherent signal subspace method (CSSM), test of orthogonality of projected subspace (TOPS), test of orthogonality of frequency (TOFS), and improved CSSM (I-CSSM) are applied to estimate the DOA of EM waves.

As large-scale buildings, skyscrapers, and multi-purpose buildings recently increase in numbers dramatically the internal space of such buildings becomes more and more large and complicated accordingly. The Multi-purpose buildings are increasing rapidly in number, and concerns over the evacuation process in case of fire emergency are also increasing. However, A controller who is responsible for visitor's safety makes a decision about measures for visitor safety in human based decision making process. Many potential accidents that are caused by human error lurk in results of the process. The accidents can be decreased by changing the decision making process from human-based into technology-based. Through this study, the way to improve current disasters prevention system is presented and it can also improve shelter inducement methods effectively. SICS(Spatial Information Control System) which is being studied in other research is used as the tool for improvement.