• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.73-81
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• 2003

The construction industry has been experiencing a major challenge in its work force, 'the shortage of skilled craft workers.' This problem has been caused by several factors such as the poor image of the construction industry, lack of training and education, unclear career path, declining wages, and changing work force demographics. A 'step-change' approach called the 'Two-Tier Work Force Strategy' has been proposed by the Center for Construction Industry Studies (CCIS) to deal with the work force related issues in a radical way. It is composed of two separate strategies, Tier I and II. The Tier I strategy uses less skilled and task trained craft workers, and has a larger administrative site management team than the Tier II strategy. The Tier II strategy utilizes fewer, better-educated, and higher skilled workers who perform some lower-management functions in addition to craft functions. They are paid more, but produce more through higher skills, stay on the job longer through multi-skilling, and deliver improved project performance in safety, quality, schedule, and cost The Two-Tier Work Force Strategy has the potential to resolve the current work force problems and foster a better work force environment in the future.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1428-1431
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• 1997

This paper presents an efficient fault diagnosis methodology for lare chemical processes. The methodology is based on a two-tier strategy, When a falt occurs in a process, a top tier identifies the sector (process part or unit) that may contain the fault(s). Afterwards, a bottom tier or lower level evaluates the suspicious sector. The process modeling methodology based on functionality-behavior relations of process units, is proposed and utilized in the top-tier. This methodology models a target process as sequences of functions and variables and their relations. In the bottom tier, each sector has a dedicated diagostic module, which is tailored to the available information or models of the sector. For the sectors selected in the top-tier diagnosis, each diagnostic module is executed to identify the actual faults within the sector. Teh utility of the methodology is illustrated in the diagnosis of the CSTR with heat exchanger.

• International Journal of Computer Science & Network Security
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• v.22 no.4
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• pp.329-339
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• 2022

Small cells, particularly femtocells, are regarded a promising solution for limited resources required to handle the increasing data demand. They usually boost wireless network capacity. While widespread usage of femtocells increases network gain, it also raises several challenges. Interference is one of such concerns. Interference management is also seen as a main obstacle in the adoption of two-tier networks. For example, placing femtocells in a traditional macrocell's geographic area. Interference comes in two forms: cross-tier and co-tier. There have been previous studies conducted on the topic of interference management. This study investigates the principle of categorization of interference management systems. Many methods exist in the literature to reduce or eliminate the impacts of co-tier, cross-tier, or a combination of the two forms of interference. Following are some of the ways provided to manage interference: FFR, Cognitive Femtocell and Cooperative Resource Scheduling, Beamforming Strategy, Transmission Power Control, and Clustering/Graph-Based. Approaches, which were proposed to solve the interference problem, had been presented for each category in this work.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.4
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• pp.1481-1500
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• 2016

Device-to-Device (D2D) communication underlaying macro-small cell networks, as one of the promising technologies in the era of 5G, is able to improve spectral efficiency and increase system capacity. In this paper, we model the cross- and co-tier D2D communications in two-tier macro-small cell networks. To avoid the complicated interference for cross-tier D2D, we propose a mode selection scheme with a dedicated resource sharing strategy. For co-tier D2D, we formulate a joint optimization problem of power control and resource reuse with the aim of maximizing the overall outage capacity. To solve this non-convex optimization problem, we devise a heuristic algorithm to obtain a suboptimal solution and reduce the computational complexity. System-level simulations demonstrate the effectiveness of the proposed method, which can provide enhanced system performance and guarantee the quality-of-service (QoS) of all devices in two-tier macro-small cell networks. In addition, our study reveals the high potential of introducing cross- and co-tier D2D in small cell networks: i) cross-tier D2D obtains better performance at low and medium small cell densities than co-tier D2D, and ii) co-tier D2D achieves a steady performance improvement with the increase of small cell density.

• Speech Sciences
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• v.7 no.1
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• pp.143-169
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• 2000

This chapter presents an overview of Korean intonational structure and proposes a revised version of K -ToBI (Korean TOnes and Break Indices), a prosodic transcription convention for Seoul Korean. In the new version of K-ToBI, a tone tier is separated into two tiers: a phonological tone tier and a phonetic tone tier. A phonological tone tier labels tones marking the prosodic structure of an utterance, and a phonetic tone tier labels individual tones of an AP and an IP conforming to the surface pitch contour. Labelling surface tonal patterns will provide us data to test the underlying tonal patterns and to build phonetic implementation rules.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.275-284
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• 2014

This paper considers two-tier networks consisting of macrocells and femtocells operating in the same spectrum. This paper proposes a femtocell spectrum reuse scheme that determines the shared spectrum and transmit power for the femtocells to mitigate the effects of cross-tier interference between the macrocells and femtocells. The proposed scheme provides macrocell throughput that is unaffected by the increasing number of femtocells per cell site and improves the femtocell signal quality at the same time by limiting the cross-tier interference. This study analyzed the per-tier signal-to-interference ratio (SIR) and outage probability of the proposed scheme to investigate the macrocell and femtocell performance. The total throughput of the proposed scheme was analyzed based on the outage probabilities. The analysis and numerical results proved that high femtocell throughput can be achieved using only a small fraction of the spectrum while protecting the macrocell throughput. As a result, an improved total throughput was achieved enforcing higher spatial reuse.

• Information Systems Review
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• v.3 no.2
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• pp.277-288
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• 2001

Of critical importance to the success of any e-commerce site are the two factors: rapid application development and quick response time. A three-tier architecture composed of presentation layer, business layer, and data access layer emerges to allow rapid changes in user interface, business logic, and database structures. Too often, such a logical three-tier architecture is considered as requiring a three-tier physical architecture: Web server, application server, and database server running on separate computers. Contrary to the common belief, a Web stress test reveals that the three-tier logical architecture implemented on a two-tier physical platform guarantees a quicker response time due to the reduction in cross-machine communications. This would lead business firms to economize their spending on e-commerce: increasing the number of physical servers to expedite transaction is not necessarily the best solution. Before selecting a particular hardware configuration, a Web stress test needs to be conducted to compare the relative merits of alternative physical architectures. Together with capacity planning, Web stress test emerges as a powerful tool to build robust, yet economical e-commerce sites.

• Journal of Communications and Networks
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• v.13 no.4
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• pp.327-338
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• 2011

With the incitation to reduce power consumption and the aggressive reuse of spectral resources, there is an inevitable trend towards the deployment of small-cell networks by decomposing a traditional single-tier network into a multi-tier network with very high throughput per network area. However, this cell size reduction increases the complexity of network operation and the severity of cross-tier interference. In this paper, we consider a downlink two-tier network comprising of a multiple-antenna macrocell base station and a single femtocell access point, each serving multiples users with a single antenna. In this scenario, we treat the following beamforming optimization problems: i) Total transmit power minimization problem; ii) mean-square error balancing problem; and iii) interference power minimization problem. In the presence of perfect channel state information (CSI), we formulate the optimization algorithms in a centralized manner and determine the optimal beamformers using standard convex optimization techniques. In addition, we propose semi-decentralized algorithms to overcome the drawback of centralized design by introducing the signal-to-leakage plus noise ratio criteria. Taking into account imperfect CSI for both centralized and semi-decentralized approaches, we also propose robust algorithms tailored by the worst-case design to mitigate the effect of channel uncertainty. Finally, numerical results are presented to validate our proposed algorithms.

• Speech Sciences
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• v.4 no.1
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• pp.113-133
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• 1998

The system proposed in this paper prosodically transcribes the intonation patterns, prosodic structures, phrasings, and other prosodic aspects of Korean utterances, on four parallel tiers: a tone tier, an orthographic tier, a break index tier, and a miscellaneous tier. The tone tier employs two phrase accents (L* and H *), three accentual phrase boundary tones (L-, H-, LH-), and four intonational phrase boundary tones (L%,H%,LH%,LHL%) in order to provide a phonological transcription of pitch events associated with accented syllables and phrase boundaries. The break index tier uses five break indices, numbered from 0 to 4, which mark a prosodic grouping of words and its prosodic structure in an utterance. Among the five indices, the break index 3 and the break index 4 align with an accentual phrase boundary tone and an intonational phrase boundary tone, respectively, in the tone tier.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1424-1441
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• 2014

Two-tier femtocell networks, consisting of a conventional cellular network underlaid with femtocell hotspots, play an important role in the indoor coverage and capacity of cellular networks. However, the cross- and co-tier interference will cause an unacceptable quality of service (QoS) for users with universal frequency reuse. In this paper, we propose a novel downlink interference mitigation strategy for spectrum-shared two-tier femtocell networks. The proposed solution is composed of three parts. The first is femtocells clustering, which maximizes the distance between femtocells using the same slot resource to mitigate co-tier interference. The second is to assign macrocell users (MUEs) to clusters by max-min criterion, by which each MUE can avoid using the same resource as the nearest femtocell. The third is a novel adaptive power control scheme with femtocells downlink transmit power adjusted adaptively based on the signal to interference plus noise ratio (SINR) level of neighboring users. Simulation results show that the proposed scheme can effectively increase the successful transmission ratio and ergodic capacity of femtocells, while guaranteeing QoS of the macrocell.