PIER B | PIER Journals

2011-11-28

PIER B

Vol. 36, 399-419, 2012

download: 301

Novel Information Leakage Threat for Input Operations on Touch Screen Monitors Caused by Electromagnetic Noise and Its Countermeasure Method

Hidenori Sekiguchi

Information leakage of general input operations using button images in graphical user interface on touch screen monitors was experimentally investigated from images reconstructed by receiving the electromagnetic noise. In the experimental investigations for input operations of a personal identification number, it was confirmed that when a button image was touched, the touched button image can be identified from the reconstructed button images. This kind of information leakage has originated the fact that the touched button image has changed the color for informing the operator which button image was touched. From the elucidation of the image reconstruction mechanism, it was found that the information leakage has been caused by the magnitude of the emitted signal that results from the analog voltage differences of the RGB signals between neighboring pixels on the monitor. Therefore, a countermeasure method was proposed from the viewpoint of the combination of the colors of the button images and of the background or of the numerals in the button images. The countermeasure method was then applied to the previous input operations of a personal identification number. From the experimental results for the countermeasure method, it was confirmed that the touched button image cannot be identified from the reconstructed button image. As a result, the proposal countermeasure method can prevent effectively the information leakage of input operations on touch screen monitors due to the electromagnetic noise.

NOVEL INFORMATION LEAKAGE THREAT FOR INPUT OPERATIONS ON TOUCH SCREEN MONITORS CAUSED BY ELECTROMAGNETIC NOISE AND ITS COUNTERMEASURE METHOD

2011-11-26

PIER B

Vol. 36, 373-398, 2012

doi:10.2528/PIERB11091408

download: 387

Broadband Transmission Characteristics of Overhead High-Voltage Power Line Communication Channels

Athanasios G. Lazaropoulos

This paper considers broadband signal transmission via high-voltage/broadband over power lines (HV/BPL) channels associated with overhead power transmission. To determine the end-to-end channel characteristics of various overhead HV/BPL multiconductor transmission line (MTL) configurations, the chain scattering matrix or T-Matrix (TM) method is adopted. The overhead HV/BPL transmission channel is investigated with regard to its spectral behavior, its {end-to-end} signal attenuation, and phase response. It is found that the above features depend critically on the frequency, the coupling scheme applied, the physical properties of the cables used, the MTL configuration, and the type of branches existing along the {end-to-end} BPL signal propagation. Unlike the older models that underestimate the broadband transmission potential of overhead HV lines significantly, the results demonstrate that the overhead HV grid is a potentially excellent communications medium, offering low loss characteristics over a 100 km repeater span well beyond 100 MHz and guarantees the imminent coexistence of low-voltage (LV), medium-voltage (MV), and HV BPL systems towards a unified transmission/distribution smart grid (SG) power grid.

BROADBAND TRANSMISSION CHARACTERISTICS OF OVERHEAD HIGH-VOLTAGE POWER LINE COMMUNICATION CHANNELS

2011-11-24

PIER B

Vol. 36, 357-371, 2012

doi:10.2528/PIERB11092701

download: 612

A MIMO Antenna Design Challenges for UWB Application

Muzammil Jusoh , Mohd Faizal Bin Jamlos , Muhammad Ramlee Kamarudin and Mohd Fareq Bin Abd Malek

This paper proposes a compact printed ultra-wideband (UWB) multiple-input-multiple-output (MIMO) antenna with a dimension of 38 x 91 mm². The presented UWB-MIMO antenna is comprised of two identical patch elements with D separation distance on the same substrate. The basic single antenna structure has a novel design comprising seven circles surrounding a center circle with partial ground plane implementation. Furthermore, the experimental antenna has peak gain of 5.3 dBi between an operating frequency of 2.8 GHz and 8.0 GHz under a minimum reflection coefficient of less than -10 dB (S₁₁<-10 dB). Moreover, the antenna successfully achieved mutual coupling minimization of < -17 dB, eventually resulting in enhancement of radiation efficiency. Besides, the UWB-MIMO's correlation coefficient was effectively reduced to less than -22 dB, which reflected an improvement in the antenna's diversity. In this paper, the proposed antenna is examined both numerically and experimentally.

A MIMO ANTENNA DESIGN CHALLENGES FOR UWB APPLICATION

2011-11-22

PIER B

Vol. 36, 337-355, 2012

doi:10.2528/PIERB11091911

download: 280

Comparison of Propagation Along a Lift Shaft in Two Complex Environments

Xiao Hong Mao and Yee Hui Lee

Signal variation caused by motions along the lift shaft in a campus environment and on board a ship is compared. The guiding effect is common for both lift shafts, and the variation in amplitude of the guided signals is more significant for the lift shaft with larger dimensions. Unlike the lift shaft within the campus, the ship with its lift shaft forms a `waveguide within waveguide' structure. Therefore, the reflected signals within the ship enclosure outside the lift shaft are significantly affected by the motion along the lift shaft. Due to the difference in the degree of the signal variations in these two environments, the rms delay spread is found to be closely related to the lift door status and the lift car position in the campus environment, whereas it is not significantly affected by the motions along the lift shaft in the ship environment. From the statistical study and comparison of the signal variations in the two environments, the Weibull probability density function is found to be the most suitable model to describe analogous waveguide channels such as the lift shaft and the ship enclosure.

COMPARISON OF PROPAGATION ALONG A LIFT SHAFT IN TWO COMPLEX ENVIRONMENTS

2011-11-19

PIER B

Vol. 36, 323-336, 2012

doi:10.2528/PIERB11092106

download: 267

Radar Image of One Dimension Rough Surface with Buried Object

Wei-Jie Ji and Chuang-Ming Tong

In order to detect a buried object quickly and accurately, a fast radar imaging method is presented in this paper. At first, complex backscatter data are computed by using propagation-inside-layer expansion combining the forward and backward method (PILE + FB). Then, a conventional synthetic aperture radar (SAR) imaging procedure called back projection method is used to generate 2-D image. The random rough surface with Gauss spectrum is used to simulate the ground. Tapered incident wave is chosen to reduce truncation error. Because backscatter data are computed by fast numerical method, this method is proper for rough surface with any parameters with a buried complex object, which is very useful for realistic object detection.

RADAR IMAGE OF ONE DIMENSION ROUGH SURFACE WITH BURIED OBJECT

2011-11-16

PIER B

Vol. 36, 303-321, 2012

doi:10.2528/PIERB11071106

download: 338

Assessment of L-Band SAR Data at Different Polarization Combinations for Crop and Other Landuse Classification

Dipanwita Haldar , Anup Das , Shiv Mohan , Om Pal , Ramesh S. Hooda and Manab Chakraborty

In the present study, evaluation of L-band SAR data at different polarization combinations in linear, circular as well as hybrid polarimetric imaging modes for crop and other landuse classifications has been carried out. Full-polarimetric radar data contains all the scattering information for any arbitrary polarization state, hence data of any combination of transmit and receive polarizations can be synthesized, mathematically from full-polarimetric data. Circular and various modes of hybrid polarimetric data, (where the transmitter polarization is either circular or orientated at 45°, called π/4 and the receivers are at horizontal and vertical polarizations with respect to the radar line of sight) were synthesized (simulated) from ALOS-PALSAR full-polarimetric data of 14th December 2008 over central state farm central latitude and longitude 29°15'N/75°43'E and bounds for northwest corner is 29°24'N/75°37'E and southeast corner is 29°07'N/75°48'E in Hisar, Haryana (India). Supervised classification was conducted for crops and few other landuse classes based on ground truth measurements using maximum-likelihood distance measures derived from the complex Wishart distribution of SAR data at various polarization combinations. It has been observed that linear full-polarimetric data showed maximum classification accuracy (92%) followed by circular-full (89%) and circular-dual polarimetric data (87%), which was followed by hybrid polarimetric data (73-75%) and then linear dual polarimetric data (63-71%). Among the linear dual polarimetric data, co-polarization complex data showed better classification accuracy than the cross-polarization data. Also multi-date single polarization SAR data over central state farm during rabi (winter) season was analyzed and it was observed that single date full-polarimetric SAR data produced equally good classification result as the multi-date single polarization SAR data.

ASSESSMENT OF L-BAND SAR DATA AT DIFFERENT POLARIZATION COMBINATIONS FOR CROP AND OTHER LANDUSE CLASSIFICATION

2011-11-15

PIER B

Vol. 36, 283-301, 2012

doi:10.2528/PIERB11091908

download: 713

Vegetation Attenuation Measurements and Modeling in Plantations for Wireless Sensor Network Planning

David Lorater Ndzi , Latifah M. Kamarudin , Abdul Aziz Muhammad Ezanuddin , Ammar Zakaria , Raad Badlishah Ahmad , Mohd Fareq Bin Abd Malek , Ali Yeon Md. Shakaff and M. N. Jafaar

As wireless communication moves from long to short ranges with considerably lower antenna heights, the need to understand and be able to predict the impact of vegetation on coverage and quality of wireless services has become very important. This paper focuses on vegetation attenuation measurements for frequencies in the range 0.4-7.2 GHz in mango and oil palm plantations to evaluate vegetation attenuation models for application in wireless sensor network planning and deployment in precision agriculture. Although a number of models have been proposed and evaluated for specific frequencies, results show that these models do not perform well when applied to different vegetation types or at different frequencies. A global assessment of the models using a broad range of frequencies shows that the COST 235 model gives more consistent results when there is vegetation in the propagation path. For grid-like plantation, the study shows that the RET model provides the best prediction of path loss for measurements between two rows of trees. However, taking into account the limited number of parameter values available for the RET model and the potential inaccuracy that may results from the use of a wrong parameter value, a sub-optimal model which combines the ITUR model with ground reflection does offer a more consistent prediction. The differences in the average values of RMS error between RET, ITUR and free space loss models when combined with ground reflection is less than 1.6 dB.

VEGETATION ATTENUATION MEASUREMENTS AND MODELING IN PLANTATIONS FOR WIRELESS SENSOR NETWORK PLANNING

2011-11-14

PIER B

Vol. 36, 267-281, 2012

doi:10.2528/PIERB11090609

download: 237

Interferometric Properties and Processing for Spaceborne Spotlight SAR

Xiao-Zhen Ren , Yao Qin and Li Hong Qiao

Spotlight SAR interferometry is an attractive option for high resolution mapping and monitoring. In this paper, the signal spectral characteristics and the interfeometric properties of spaceborne spotlight SAR are analyzed completely, and the effect of the azimuth-variant Doppler to spotlight SAR interferometry is studied. Moreover, a new coregistration algorithm, which contains coarse coregistration, azimuth spectral filter, and accurate coregistration with adaptive subspace projection, is proposed for spotlight SAR interferometry. The algorithm is validated with real data experiment.

INTERFEROMETRIC PROPERTIES AND PROCESSING FOR SPACEBORNE SPOTLIGHT SAR

2011-11-11

PIER B

Vol. 36, 249-265, 2012

doi:10.2528/PIERB11081704

download: 328

Dispersion and Peak Reflectivity Analysis in a Non-Uniform FBG Based Sensors Due to Arbitrary Refractive Index Profile

Sanjeev Kumar Raghuwanshi , Virendra Kumar and Srinivas Talabattula

This paper deals with a group velocity dispersion issue and a peak reflectivity issue in a non-uniform fiber Bragg gratings (FBG) due to an arbitrary refractive index profile along the length of grating. The paper shows that by using more complicated refractive index profile one can significantly reduce the group velocity dispersion and side lobes intensity and that in main lobe the bandwidth of reflectivity would also increase substantially due to a complicated refractive index profile. To the authors' knowledge, there has not been any work reported in this direction. Generally, coupled mode theory is used to analyze the uniform fiber Bragg grating (UFBG). The analysis results in two coupled first order ordinary differential equations with constant coefficients for which closed form solutions can be found for appropriate boundary conditions. Most fiber gratings designed for practical applications, however, are non uniform. The main reason for using non uniform grating is that it reduces the side lobes in the reflectivity spectrum. Due to the complexity of analysis, no particular method for an analysis of the non-uniform fiber Bragg grating would be found. The two standard approaches for calculating the reflection and transmission spectra of a non uniform FBG are direct numerical integration of coupled mode equations and piecewise uniform approximation approach. The former is more accurate but computationally intensive. In this paper, piecewise uniform approximation approach is used to study a dispersion characteristic due to an arbitrary refractive index profile. The usefulness in FBG based sensors has been demonstrated.

2011-11-10

PIER B

Vol. 36, 221-248, 2012

doi:10.2528/PIERB11092006

download: 1310

Simple Implementation of Arbitrarily Shaped Total-Field/Scattered-Field Regions in Finite-Difference Frequency-Domain

Raymond C. Rumpf

The total-field/scattered-field (TF/SF) formulation is a popular technique for incorporating sources into electromagnetic models like the finite-difference frequency-domain (FDFD) method. It is versatile and simplifies calculation of waves scattered from a device. In the context of FDFD, the TF/SF formulation involves modifying all of the finite-difference equations that contain field terms from both the TF and SF regions in order to make the terms compatible. While simple in concept, modifying all of the equations for arbitrarily shaped TF/SF regions is tedious and no solution has been offered in the literature to do it in a straightforward manner. This paper presents a simple and efficient technique for implementing the TF/SF formulation that allows the TF/SF regions to be any shape and of arbitrary complexity. Its simplicity and versatility are demonstrated by giving several practical examples including a diffraction grating, a waveguide problem, and a scattering problem with a cylindrical wave source.

SIMPLE IMPLEMENTATION OF ARBITRARILY SHAPED TOTAL-FIELD/SCATTERED-FIELD REGIONS IN FINITE-DIFFERENCE FREQUENCY-DOMAIN

2011-11-10

PIER B

Vol. 36, 193-220, 2012

doi:10.2528/PIERB11050102

download: 254

A New Element-Oriented Model for Computational Electromagnetics

Hamid Magrez and Abdelhak Ziyyat

In this paper, we present a new model using a Four-dimensional (4D) Element-Oriented physical concepts based on a topological approach in electromagnetism. Its general finite formulation on dual staggered grids reveals a flexible Finite-Difference Time-Domain (FDTD) method with reasonable local approximating functions. This flexible FDTD method is developed without recourse to the traditional Taylor based forms of the individual differential operators. This new formulation generalizes both the standard FDTD (S-FDTD) and the nonstandard FDTD (NS-FDTD) methods. Moreover, it can be used to generate new numerical methods. As proof, we deduce a new nonstandard scheme more accurate than the S-FDTD and the known nonstandard NS-FDTD methods. Through some numerical examples, we validate this proposal, and we show the power and the advantage of this Element-Oriented Model.

A NEW ELEMENT-ORIENTED MODEL FOR COMPUTATIONAL ELECTROMAGNETICS

2011-11-10

PIER B

Vol. 36, 173-191, 2012

doi:10.2528/PIERB11081002

download: 267

A Hierarchical Tree Shaped Power Distribution Network Based on Constructal Theory for EBG Structure Power Plane

Hui-Fen Huang , Shi-Yun Liu and Wei Guo

In this paper, a tree-shaped power distribution network is designed based on constructal theory for planar EBG structure power plane on PCB, in order to optimize DC performance. Planar EBG structures suppress noise, and the network provides currents to them. This network is composed of hierarchical metal paths. The geometric parameters can be optimized based on the concept of constructal theory. The optimal performance consists of constructing the given area in a sequence of building blocks from the smallest size toward larger sizes hierarchically. In the meantime, a PCB power plane is developed with 2nd order tree-shaped constructal network. Analysis illustrates that EBG power plane with constructal tree shaped network has multifunctions of low voltage drop, current equidistribution and effective noise isolation.

A HIERARCHICAL TREE SHAPED POWER DISTRIBUTION NETWORK BASED ON CONSTRUCTAL THEORY FOR EBG STRUCTURE POWER PLANE

2011-11-09

PIER B

Vol. 36, 151-171, 2012

doi:10.2528/PIERB11100709

download: 374

Accurate Representation of Excitation and Loading for Arbitrarily Shaped Antennas Composed of Conducting Surfaces in the Method of Moments

Khalid Fawzy Ahmed Hussein

In this work, a new method is introduced to model the excitation and loading for antennas composed of arbitrarily shaped conducting surfaces treated by the elctric field integral equation method described by Raw-Wilton-Glisson (RWG). Instead of using a single non-boundary edge to represent a zero-width exciting gap according to the conventional method, the proposed method uses either single or multiple pairs of facing boundary edges to form a real gap of arbitrary shape and width. The new method has many advantages over the conventional (zero-width) source/load representation considering the flexibility in shaping the gap to fit the antenna surface and the accuracy of the obtained results especially for the antenna input impedance and the input current distribution. The new method is described mathematically in detail. Modified basis functions are described for the gap source/load. Numerical results are obtained to investigate the dependence of the antenna input impedance and the current distribution along the gap length on the gap width, the geometrical shape of the gap and the surface segmentation resolution along the gap length.

ACCURATE REPRESENTATION OF EXCITATION AND LOADING FOR ARBITRARILY SHAPED ANTENNAS COMPOSED OF CONDUCTING SURFACES IN THE METHOD OF MOMENTS

2011-11-09

PIER B

Vol. 36, 133-149, 2012

doi:10.2528/PIERB11100307

download: 279

A Spectral Volume Integral Equation Method for Arbitrary BI-Periodic Gratings with Explicit Fourier Factorization

Martijn Constant van Beurden

For dielectric periodic gratings, we propose the combination of a spectral-domain volume integral equation and Fourier factorization rules to address the Gibbs phenomenon caused by jumps in both the fields and the permittivity. From a theoretical point of view we discuss two ways to overcome the computational complexity caused by the inverse rule by changing the fundamental unknowns of the underlying electromagnetic problem. The resulting numerical system is solved iteratively and the corresponding matrix-vector product has an O(NMlogM) complexity, where M is the number of Fourier modes and N is the number of sample points in the longitudinal direction.

A SPECTRAL VOLUME INTEGRAL EQUATION METHOD FOR ARBITRARY BI-PERIODIC GRATINGS WITH EXPLICIT FOURIER FACTORIZATION

2011-11-09

PIER B

Vol. 36, 113-131, 2012

doi:10.2528/PIERB11083005

download: 375

Design of a Fully Digital Controlled Reconfigurable Switched Beam Concentric Ring Array Antenna Using Firefly and Particle Swarm Optimization Algorithm

Anirban Chatterjee , Gautam Mahanti and Arindam Chatterjee

Reconfigurable antenna arrays are often capable of radiating multiple patterns by modifying the excitation phases of the elements. In this paper a method based on Firefly Algorithm (FA) has been proposed to obtain dual radiation pattern from a concentric ring array of isotropic elements, by finding out two different combinations of states for the switches, which are assumed to be connected with the rings of the array, along with optimum set of 4-bit radial amplitude and 5-bit radial phase distributions of the array elements for the specific switch combinations. The optimum excitations of the array elements in terms of discrete amplitudes and discrete phase, and the different switch combinations for the specific excitations are computed using Firefly Algorithm. To illustrate the effectiveness of Firefly Algorithm, the two beam pairs have been computed by the same procedure from the same array, using Particle Swarm Optimization (PSO) algorithm, without changing their design criteria. Results clearly show the superiority of the Firefly Algorithm over Particle Swarm Optimization to handle the proposed problem.

DESIGN OF A FULLY DIGITAL CONTROLLED RECONFIGURABLE SWITCHED BEAM CONCENTRIC RING ARRAY ANTENNA USING FIREFLY AND PARTICLE SWARM OPTIMIZATION ALGORITHM

2011-11-08

PIER B

Vol. 36, 89-111, 2012

doi:10.2528/PIERB11090702

download: 660

Cartesian Multipole Expansions and Tensorial Identities

E. Radescu, Jr. and Georgeta Vaman

We establish the exact formulas of multipole expansion in Cartesian coordinates for the most general distribution of charges and currents (including toroidal sources).

2011-11-03

PIER B

Vol. 36, 69-87, 2012

doi:10.2528/PIERB11072709

download: 282

Microwave Effect of 0.9 GHz and 1.8 GHz Cw Frequencies Exposed to Unrestrained Swiss Albino Mice

A D Usman , Wan Fatinhamamah Wan Ahmad , Mohd Zainal Abidin Ab Kadir , Makhfudzah Mokhtar and R. Ariffin

Long term radio frequency electromagnetic field (RF EMF) exposures due to Global System for Mobile communication (GSM) frequencies were investigated in this study. 158 Swiss Albino mice in unrestrained conditions were used as surrogate and divided into four groups. The average peak field strength generated and measured inside the cages placed at a far field from the antennas is 0.6x10^-3 mW/cm², and the specific absorption rate at 0.9 GHz and 1.8 GHz is 2.33x10^-3 W/kg and 1.97x10^-4 W/kg, respectively. Three samples of the mice chosen at random each from sham and exposed groups in week 4 and subsequently biweekly basis were taken for haematology and histopathology tests. The complete blood count result shows that haematological parameters of both the sham exposed and exposed mice were within the normal range of mice in the control group. A statistical analysis was conducted to determine whether differences observed between the experimental groups were significant. The histopathology examination on some internal organs shows that spleen and bone marrow of the mice were normal for all the three experimental groups, while a sign of tissue degeneration and inflammations were observed after 8 weeks of exposure on the brain, liver and lungs of the mice in the exposed groups. These signs increase in severity with prolonged exposure.

MICROWAVE EFFECT OF 0.9 GHz AND 1.8 GHz CW FREQUENCIES EXPOSED TO UNRESTRAINED SWISS ALBINO MICE

2011-11-03

PIER B

Vol. 36, 53-67, 2012

doi:10.2528/PIERB11072008

download: 306

Performance Analysis with Coordination Among Base Stations for Next Generation Communication System

Hsien-Wei Tseng , Yang-Han Lee , Jheng-Yao Lin , Chih-Yuan Lo and Yih-Guang Jan

Next generation communication system, such as Long Term Evolution Advanced (LTE-A), has the advantages of high transmission rate, wide bandwidth and better bandwidth utilization in high mobility environments. However, in such a kind of system when users are distributed sparsely in the base station coverage range the spectrum efficiency becomes worse. The emergence of new technologies such as the coordination among based stations makes the utilization of system bandwidth more efficient. The technology of coordination among base stations has other merits such as reducing noise interference, increasing receiving diversity, improving the system receiving gain, etc. In this paper, the system spectrum utilization and its associated efficiency will be investigated when the scheme of coordination among base stations is implemented.

PERFORMANCE ANALYSIS WITH COORDINATION AMONG BASE STATIONS FOR NEXT GENERATION COMMUNICATION SYSTEM

2011-11-03

PIER B

Vol. 36, 35-52, 2012

doi:10.2528/PIERB11091201

download: 297

A Novel Wavelet-Galerkin Method for Modeling Radio Wave Propagation in Tropospheric Ducts

Asif Iqbal and Varun Jeoti

In this paper, a novel Wavelet-Galerkin Method (WGM) is presented to model the radio-wave propagation in tropospheric ducts. Galerkin method, with Daubechies scaling functions, is used to discretize the height operator. Later, a marching algorithm is developed using Crank-Nicolson (CN) method. A new ``fictitious domain method'' is also developed for parabolic wave equation to incorporate the impedance boundary conditions in WGM. In the end, results are compared with those from Advance Refractive Effects Prediction System (AREPS). Results show that the wavelet based methods are indeed feasible to model the radio wave propagation in troposphere as accurately as AREPS and proposed method can be a good alternative to other conventional methods.

A NOVEL WAVELET-GALERKIN METHOD FOR MODELING RADIO WAVE PROPAGATION IN TROPOSPHERIC DUCTS

2011-11-02

PIER B

Vol. 36, 1-33, 2012

doi:10.2528/PIERB11072910

download: 326

Effective Material Property Extraction of a Metamaterial by Taking Boundary Effects into Account at TE/TM Polarized Incidence

Sung Kim , Edward F. Kuester , Christopher L. Holloway , Aaron D. Scher and James R. Baker-Jarvis

In this paper, we present the extraction for effective material parameters for a metamaterial from TE or TM waveguide measurements with generalized sheet transition conditions (GSTCs) used to provide electric and magnetic surface susceptibilities that approximate boundary effects between the metamaterial and air. The retrieval algorithm determines the effective material properties via scattering data obtained from the metamaterial in a waveguide. The effective refractive index is expressed as a function of S-parameters for two samples of different length. The effective wave impedance is given in terms of $S$-parameters and the refractive index, assuming that GSTCs account for the boundary effects. The effective permittivity and permeability can then be determined through the refractive index and wave impedance. By use of S-parameters generated by commercial three-dimensional (3-D) full-wave simulation software our present equations are tested for two cases of metamaterials: magneto-dielectric (ε_r=μ_r) and dielectric (TiO₂) particles. We also conduct S-parameter measurements on dielectric cubes with an S-band (WR-284) waveguide to compute the effective material properties. Furthermore, our results are compared to those derived from another retrieval method used in the literature, which does not account for boundary effects.