OPAC-Artikel dan Majalah USD Library

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Abstrak: Due to the broadcast nature of radio propagation, the wireless air interface is open and accessible to both authorized and illegitimate users. This completely differs from a wired network, where communicating devices are physically connected through cables and a node without direct association is unable to access the network for illicit activities. The open communications environment makes wireless transmissions more vulnerable than wired communications to malicious attacks, including both the passive eavesdropping for data interception and the active jamming for disrupting legitimate transmissions. Therefore, this paper is motivated to examine the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity, and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state of the art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. Several physical-layer security techniques are reviewed and compared, including information-theoretic security, artificial-noise-aided security, security-oriented beamforming, diversity-assisted security, and physical-layer key generation approaches. Since a jammer emitting radio signals can readily interfere with the legitimate wireless users, we also introduce the family of various jamming attacks and their countermeasures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer, and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.

Abstrak: The Collaborative-Cooperative Learning Model (CCL) helps improve students’ characters. This study is aimed at finding out the effectiveness of the CCL instructional model in improving the characters of the theology students in the subject matter class Self Development. The study used the quasi-experimental research design. The research sample consisted of 58 students of the Surabaya Excelsius Institute of Theology. Data were collected by way of a test in a pre-test and posttest for the experiment and control groups and analyzed by way of an independent sample t-test on the SPSS software program of Amos 25. Results show that (1) the CCL model is found to be able to improve students’ characters. Experts’ reviews conclude that the CCL syntax can be categorized as having innovative aspects based on the rationality model on the score of 3.29; (2) The CCL model is found to be effective in improving students’ characters by the Mann-Whitney test (sig. = 0,012) and the paired sample t-tes (sig. = 0.000) showing a significant difference in the mean scores; (3) the CCL model can improve the characters of self-discipline, social discipline, and religious discipline  in the theology students in the subject matter class Self Development and can be used for subject matter classes with the same characteristics, be followed-up by research in wider subject-matter contexts, and be integrated  with research from other academic fields.  

Abstrak: The capability of initial microbial adhesion to dental restorative composites surface is influenced by the surface wettability of the materials. The common method to evaluate surface wettability of materials is contact angle measurement. The existing conventional method to measure contact angle is by means of a contact angle (CA)-Goniometer device, which is less practically applicable in clinical circumstances. Therefore, a more practical and applicable method is needed to measure contact angle in clinical circumstances. This research was performed to compare between contact angles measured by means of a CA-Goniometer device and a new practical method of drop profile image analysis. In addition, since there were two different formulas that can be used to calculate contact angle value from a drop profile image, then we also need to evaluate which formula is more reliable to be used. Tests were carried out using three composite discs (Clearfill-Kuraray Medical, Inc.) sample and deionised water for different measurement procedures. One drop of 3µl liquid was dropped onto the surface of the composite discs, and the drop profile image was captured by means of a customized home-made device connected to a digital camera. Two different formulas were used to calculate the contact angle value from the drop profile image, namely the “linier gradient equation” and the “tangential line”. The contact angle values obtained from the two different formulas were compared with the value obtained from the conventional method descriptively. Tests were carried out using three composite discs (Clearfill-Kuraray Medical, Inc.) sample and deionised water for different measurement procedures. One drop of 3µl liquid was dropped onto the surface of the composite discs, and the drop profile image was captured by means of a customized home-made device connected to a digital camera. Two different formulas were used to calculate the contact angle value from the drop profile image, namely the “linier gradient equation” and the “tangential line”. The contact angle values obtained from the two different formulas were compared with the value obtained from the conventional method descriptively. The differences in percentage between the contact angle value calculated by the “linier gradient equation” and “tangential line” formulas, and those calculated by means of the CA-Goniometer are 20,56% and 3,51%, respectively. It is obviously demonstrated that the value obtained by the “tangential line” formula has a smaller difference compared to those obtained by the “linier equation gradient” formula. Among the two different formulas, it is confirmed that the contact angle value calculated with the “tangential line” formula has closer similarity with the value obtained from the CA-Goniometer. This result confirms that the new practical method of drop profile image analysis is promising for measuring contact angle values in clinical circumstances. Related to the drop profile image analysis, the “tangential line” formula is more accurate compared to the “linier gradient equation” formula.

Abstrak: The purpose of this study was to examine the hypoglycaemic effect of the lyophilised aqueous extract of the whole plant of Ajuga iva (1..) Schreber (Labiatae) in normal and streptozotocin-induced diabetic rats. Single and repeated oral administration of the extract of Ajuga iva L. (AI) at a dose of 10 mg/kg produced a slight and significant decrease in plasma glucose levels in normal rats 6 h after administration and after 3 weeks of treatment. Al reduced plasma glucose levels of streptozotocin diabetic rats from 337±9.3 to 102.2 ± 17.7 mg/dl after 6 h of oral administration (P <0.001). Repeated oral administration of AI to streptozotocin diabetic rats significantly decreased the plasma glucose levels after 1 week of treatment (112 ± 14.4 mg dl at 1 week vs 337 ± 9.3 mg/dl at the baseline values, (P <0.001). It continuously decreased thereafter and showed a rapid normalisation after 1 week of Al treatment. It is concluded that these results demonstrated that the water extract of the whole plant of Al possess a strong hypoglycaemic effect in diabette rats, and support therefore, its traditional use in diabetes mellitus control

Abstrak: Modeling is one of the methods in the portfolio of techniques and approaches available to unravel the dynamics of the land-use system. In this perspective, models are used as a learning and communication tool between researchers to formalize knowledge on the dynamics of land-use change. Land-use system is a very complex system, such that computer modeling is needed as a computational laboratory to estimate and test hypotheses about the process of land-use change. One of the major difficulties in multi-disciplinary research is to find ways to express oneself, which are acceptable to all the disciplines involved and free from the connotation of any or all of them. Land-use change models play an important role in exploring possible future developments in the land-use system. This paper attempts to show the methods and approaches to be used as a communication and learning environment for stakeholders involved in the decision making about land-use change systems in the field of environment.

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Abstrak: More complex and competitive business push management to create more motivated workplace. They use motivation to inspire people to work, both individually and in a group, to produce best result in order to reach goals. Some organization trapped by traditional motivational approach. They thought that extrinsic rewards were the best and the only tool to motivate people. This premise brings short term effect and creates demotivational work place latter. People are unique and they have different needs at different times that drive their motivation. Understanding people's motivation is the first consideration in designing Management Control System fit with oraganization's strategy.

Abstrak: One educator shares the story of how she engaged and ultimately embraced the Next Generation Science Standards.

Abstrak: The Shi arrangement is the set of all hyperplanes in ?n of the form xj − xk = 0 or 1 for 1 ≤ j < k ≤ n. Shi observed in 1986 that the number of regions (i.e., connected components of the complement) of this arrangement is (n + 1)n−1. An unrelated combinatorial concept is that of a parking function, i.e., a sequence (x1, x2, …, xn) of positive integers that, when rearranged from smallest to largest, satisfies xk ≤ k. (There is an illustrative reason for the term parking function.) It turns out that the number of parking functions of length n also equals (n + 1)n−1, a result given by Konheim and Weiss in 1966. A natural problem consists of finding a bijection between the n-dimensional Shi arrangement and the parking functions of length n. Pak and Stanley (1996) and Athanasiadis and Linusson (1999) gave such (quite different) bijections. We will shed new light on the former bijection by taking a scenic route through certain mixed graphs.