Single-mode Design Research Articles

Text Messages to Facilitate the Transition to Web-First Sequential Mixed-Mode Designs in Longitudinal Surveys

Abstract This article is concerned with the transition of a longitudinal survey from a single-mode design to a web-first mixed-mode design and the role that text messages to sample members can play in smoothing that transition. We present the results of an experiment that investigates the effects of augmenting the contact strategy of letters and emails with text messages, inviting the sample members to complete a web questionnaire and reminding them of the invite. The experiment was conducted in a subsample of Understanding Society, a household panel survey in the United Kingdom, in the wave that transitioned from a CAPI-only design to a sequential design combining web and CATI. In the experiment, a quarter of the sample received letters and emails, while the rest received between one and three text messages with a personalized link to the questionnaire. We examine the effect of the text messages on response rates, both at the web phase of a sequential design and at the end of the fieldwork after a CATI follow-up phase, and explore various mechanisms that might drive the increase in response rates. We also look at the effects on the device used to complete the survey and field efforts needed at the CATI stage. The findings indicate that text messages did not help to significantly increase response rates overall, although some subgroups benefited from them, such as panel members who had not provided an email or postal address before. Likewise, the text messages increased web completion among younger panel members and those with an irregular response pattern. We only found a slight and nonsignificant effect on smartphone use and no effect on the web household response rate, a proxy for fieldwork efforts.

Transitioning an employee panel survey from telephone to online and mixed-mode data collection

Employee panel surveys, which are essential for measuring ongoing labor market developments, are facing significant challenges of respondent recruitment and retention. Even interviewer-administered panel surveys, historically considered the gold standard form of data collection, are facing high costs and nonresponse issues that threaten their sustainability and inferential capabilities. Supplementing interviewer-administration with online data collection is a popular method of reducing costs and may improve contactability and reduce nonresponse in employee surveys. However, the effects of introducing online data collection in an ongoing panel survey of the employed population have received little attention. We address this research gap by analyzing a mode design experiment embedded in the fourth wave of a German employee panel survey. Individuals were randomly assigned to the standard telephone-only design, or a sequential web-telephone mixed-mode design. An invitation letter experiment was also conducted to test the effect of mentioning the telephone follow-ups in the web survey invitation. Introducing the mixed-mode design led to a higher response rate (59.9% vs. 50.1%), similar levels of nonresponse bias, and lower costs compared to the single-mode design. Mentioning the telephone follow-ups had no effect on participation in the web starting mode or the full mixed-mode design. Implications of these findings for survey practice are discussed.

Effects of mixing modes on nonresponse and measurement error in an economic panel survey

Numerous panel surveys around the world use multiple modes of data collection to recruit and interview respondents. Previous studies have shown that mixed-mode data collection can improve response rates, reduce nonresponse bias, and reduce survey costs. However, these advantages come at the expense of potential measurement differences between modes. A major challenge in survey research is disentangling measurement error biases from nonresponse biases in order to study how mixing modes affects the development of both error sources over time. In this article, we use linked administrative data to disentangle both nonresponse and measurement error biases in the long-running mixed-mode economic panel study “Labour Market and Social Security” (PASS). Through this study design we answer the question of whether mixing modes reduces nonresponse and measurement error biases compared to a single-mode design. In short, we find that mixing modes reduces nonresponse bias for most variables, particularly in later waves, with only small effects on measurement error bias. The total bias and mean-squared error are both reduced under the mixed-mode design compared to the counterfactual single-mode design, which is a reassuring finding for mixed-mode economic panel surveys.

The Impact of Mixing Survey Modes on Estimates of Change: A Quasi-Experimental Study

Abstract Longitudinal surveys are a key data collection tool used to estimate social change. Recent developments have accelerated the move from traditional single-mode longitudinal designs to mixed-mode designs. Nevertheless, there are concerns that mixing survey modes may affect coefficients of change at the individual level. We investigate the impact of mixing survey modes on estimates of change using a quasi-experimental design implemented in a long-running UK panel study. Two types of comparisons are carried out: single-mode (face-to-face) design versus sequential mixed-mode (Web–face-to-face) design, and Web versus face to face. Across 41 variables, we find no differences in estimates of individual-level change across modes (designs). However, correlations between intercepts and slopes, an estimate of convergence of respondents, were significantly different for most variables, which led to some biases in estimates of change. Applied researchers are encouraged to do sensitivity checks to ensure their results are robust to mode effects.

Introducing Web in a Telephone Employee Survey: Effects on Nonresponse and Costs

Abstract Policy decisions in business and economic fields are often informed by surveys of employees. Many employee surveys use costly interviewer-administered modes to reach this special population. However, certain employee subgroups may be especially hard to reach using these modes. Thus, besides high administration costs, nonresponse bias is a concern. To reduce costs and potential nonresponse bias, some employee surveys have introduced web as part of a sequential mixed-mode design. However, the impact of introducing web on response rates, nonresponse bias, and costs in employee surveys is understudied. The present study addresses this research gap by analyzing a mode design experiment in which employees selected for a national survey in Germany were randomly assigned to a single-mode telephone design or a sequential web-telephone mixed-mode design. The study revealed four main findings. First, introducing the web mode significantly increased the response rate compared to the single-mode design. Second, despite the higher response rate, aggregate nonresponse bias was higher in the mixed-mode design than in the single-mode design. Third, the likelihood of web participation varied across certain employee subgroups, including occupation type and employment contract. Lastly, potential cost savings were evident under the mixed-mode design.

多普勒激光雷达多模光纤Mach-Zehnder干涉仪鉴频系统准单模设计及实现

多普勒激光雷达多模光纤Mach-Zehnder干涉仪鉴频系统准单模设计及实现

Mode analysis and optimization of split y-junction sharing very low index difference

A Y-junction of low-difference refractive-index (RI) and coupler as its input was designed and simulated. The simulation uses COMSOL Multi-Physics Software Package, allowing varying crucial parameters. A detailed analysis and optimization of the device for single-mode design was made, in order to achieve a maximum input area error while preserving a good 50-50 splitting ratio. This approach of combined design and simulations of special Y-junction can benefit and predict advanced optical communication.

Area-Efficient Dual-Mode Fused Floating-Point Three-Term Adder

Floating-point addition is the most frequently used arithmetic operation in almost all general-purpose processors. This paper presents a dual-mode architecture for fused floating-point three-term adder. The traditional architecture for fused floating-point three-term adder is single-mode design where the addition of three operands takes place in a single unit. The existing improved architecture is also a single-mode design that incorporates few optimizations compared to the traditional fused floating-point three-term adder that would reduce area as well as delay. The proposed dual-mode architecture performs either a double-precision addition or two parallel single-precision additions in a single architecture based on the mode selection. The proposed architecture supports both normal and subnormal operations and also exceptional case handling like infinity, NaN and zero cases. The proposed architecture is implemented using both FPGA and ASIC, thus leading to efficient resource sharing, and the area gets reduced compared to two single-precision and a double-precision traditional and improved floating-point adder architectures.

Optimal design of intersecting bimodal transit networks in a grid city

The urban transit system in a real city usually has two major components: a sparse express (e.g. rail) network and a dense local (e.g. bus) network. The two networks intersect and interweave with each other throughout the city to furnish various route options for serving transit patrons with distinct ODs. The optimal design problem of this bimodal transit system, however, has not been well explored in the literature, partly due to the difficulty of modeling the patrons’ complex route choice behavior in the bimodal networks. In light of this, we formulate parsimonious continuum models for minimizing the total cost of the patrons and the transit agency for an intersecting bimodal transit network in a grid city, where the perpendicular local and express lines intersect at transfer stops. Seven distinct route types are identified in this network, which represent realistic intra- and inter-modal route options. A lower-level assignment problem between these routes is embedded in the upper-level network design optimization problem. We develop an efficient method to find near-optimal designs of the intersecting network. Numerical results unveil a number of insightful findings, e.g., that sizable cost savings are observed for the intersecting bimodal design as compared to the single-mode designs for moderate to high demand levels, and that only moderate benefits are observed as compared to the trunk-feeder designs under certain operating conditions. We also show that the conventional practice of designing the local and express networks separately would greatly undermine the benefit of the bimodal system.

Testing the Impact of Mixed-Mode Designs (Mail and Web) and Multiple Contact Attempts within Mode (Mail or Web) on Clinician Survey Response.

To compare response rate and nonresponse bias across two mixed-mode survey designs and two single-mode designs. This experiment was embedded in a clinician survey of knowledge and attitudes regarding HPV vaccination (n=275). Clinicians were randomly assigned one of two mixed-mode (mail/web or web/mail) or single-mode designs (mail-only/web-only). Differences in response rate and nonresponse bias were assessed. Using a multiple-contact protocol increased response, and sending a web survey first provided the more rapid response. Overall, the mixed-mode survey designs generated final response rates approximately 10 percentage points higher than their single-mode counterparts, although only the final response differences between the mail-only and web/mail conditions attained statistical significance (32.1 percent vs. 48 percent, respectively; p=.005). Observed differences did not result in nonresponse bias. Results support mixing modes of survey administration and web-based data collection in a multiple contact survey data collection protocol.

Impact of mixed modes on measurement errors and estimates of change in panel data

Mixed mode designs are receiving increased interest as a possible solution for saving costs in panel surveys, although the lasting effects on data quality are unknown. To better understand the effects of mixed mode designs on panel data we will examine its impact on random and systematic error and on estimates of change. The SF12, a health scale, in the Understanding Society Innovation Panel is used for the analysis. Results indicate that only one variable out of 12 has systematic differences due to the mixed mode design. Also, four of the 12 items overestimate variance of change in time in the mixed mode design. We conclude that using a mixed mode approach leads to minor measurement differences but it can result in the overestimation of individual change compared to a single mode design.

Selection Error in Single- and Mixed Mode Surveys of the Dutch General Population

SummaryThis study compares the extent of selection error (non-response and coverage error) evoked by the four major contemporary modes of data collection (face to face, telephone, mail and Web) and three sequential mixed mode designs (telephone, mail and Web with face-to-face follow-up) for the case of the Dutch Crime Victimization Survey. Sociodemographic characteristics and target variables from the survey serve as benchmark variables. A special two-wave experimental design allows studying design differences in selection error on Crime Victimization Survey variables independently from differences in measurement error. Despite large differences in response rates, only small or no differences in selection error between the four single-mode designs are found on both types of variable. We observe cases when the error is enlarged or mitigated in the mixed mode designs despite the fact that the designs yielded large response increases. Our results question the use of response rates to motivate the choice of mode and use of mixed mode surveys.

On the Relative Advantage of Mixed-Mode versus Single-Mode Surveys

Survey researchers increasingly use mixed-mode surveys for general population data collection because mixed-mode surveys are argued to provide lower selection error at constant budgets or lower variable costs at constant selection error. Nevertheless, the advantage of lower selection error and variable costs might be counteracted by higher measurement error and by higher fixed costs. This trade-off between selection error, measurement error, variable costs and fixed costs has hardly been studied within the existing literature about mixed-mode surveys. This paper discusses a possible procedure for evaluating this trade-off by comparing the performance (mean squared error) of mixed-mode survey designs against single-mode survey designs. The procedure is further illustrated by real example data stemming from a mixed-mode mail---face-to-face survey. This illustration yields smaller errors for single-mode designs under low budgets but smaller errors for mixed-mode designs under large budgets or, alternatively, a budgetary advantage of single-mode designs when the allowed error is relatively high but a budgetary advantage of mixed-mode designs when the allowed error is relatively small. However, the validity of these results depend on several modelling assumptions which may be topics for future research.

Novel Low Complexity Pulse-Triggered Flip-Flop for Wireless Baseband Applications

A low complexity dual-mode pulse-triggered FF design for wireless baseband processing is presented in this paper. It supports both single-edge- and double-edge-triggered operations subject to a mode select control. Due to the novelty in pulse generator design, the layout area overhead is only 8% when compared with other single-mode counterpart design. Postlayout simulations in TSMC 1P6M 0.18 μm CMOS process model also indicate that the proposed design is as efficient as its single-mode counterpart in various performance metrics.

Multilayer Platform for Ultra-Low-Loss Waveguide Applications

We investigate a multilayer vertical stacking scheme for use in the Silicon Nitride-based low-loss waveguide platform. In this letter, we use common fabrication techniques to produce test structures for probing the interactions between vertically separated parallel waveguide planes and the characteristics of vertical directional couplers. Single-mode and multimode waveguide geometries are investigated, with designs similar to our previously demonstrated ultra-low-loss technologies. Group index measurements via narrowband OFDR reveal an index mismatch between the vertically separated waveguides of 8.6e-3, generated by the stress of the deposited upper cladding. Vertical directional couplers with a 3-μm vertical coupling gap and a 50 nm × 4 μm geometry exhibited an excess coupling loss of 0.19±0.20 dB and cross-coupled power of 54%, limited by the aforementioned velocity mismatch. The 1.23-m spiral structures with perpendicular crossings on adjacent layers show a transmission loss of the crossings below 0.25 dB for a multimode geometry, while the single-mode design showed a minimum crossing loss of 1.0 dB.

Thermo-optical effects in high-power Ytterbium-doped fiber amplifiers

We investigate the effect of temperature gradients in high-power Yb-doped fiber amplifiers by a numerical beam propagation model, which takes thermal effects into account in a self-consistent way. The thermally induced change in the refractive index of the fiber leads to a thermal lensing effect, which decreases the effective mode area. Furthermore, it is demonstrated that the thermal lensing effect may lead to effective multi-mode behavior, even in single-mode designs, which could possibly lead to degradation of the output beam quality.

Design of Single-Mode and Low-Bending-Loss Hole-Assisted Fiber and Its MPI Characteristics

Bending-loss insensitive fibers (BIFs) have been receiving increasing attention with a view to improving FTTH network installation and maintenance. Several BIFs have been proposed and developed to realize a lower bending loss, and hole-assisted fiber (HAF) can realize both excellent bending loss characteristics and other properties compatible with conventional single-mode fiber (SMF). In this paper, we numerically clarify a design that provides both an allowable bending radius of 5 mm and other properties comparable to conventional SMFs. The calculated results also reveal the much wider single-mode bandwidth of HAF with both a low bending loss and a comparable MFD to that of SMF. We then discuss the applicability of HAF based optical cord for short-length transmission and reveal the sufficiently low multi-pass interference (MPI) characteristics of single-mode HAF, which are independent of the existence of a mode field diameter (MFD) mismatch. Although a large MFD mismatch degrades the MPI characteristics of HAF with a longer cut-off wavelength, we reveal a way to improve the MPI for such a HAF by utilizing the sweep fusion splicing technique.

High-Power Narrow-Linewidth Continuous-Wave Raman Amplifier at 1.27 $\mu$m

A high-power narrow-linewidth continuous-wave (CW) Raman fiber amplifier at 1.27 μm is demonstrated for remote sensing measurements of atmospheric oxygen (O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The amplifier uses phosphosilicate fiber in both a standard single-mode design and with the core size varying in the longitudinal direction for stimulated Brillouin scattering (SBS) suppression. The highest reported power level at this wavelength to date, a total peak power of 3 W, has been achieved for online (2.4 W) and offline (580 mW) spectroscopic measurements, in agreement with theoretical predictions. Additionally, it is shown that when 60-kHz sinusoidal amplitude modulation is applied to the amplifier seed signal, the modulated wave form is preserved at the amplifier output with 1.8 W total average power being obtained.

A Low Complexity Dual-Mode Pulse-Triggered Flip-Flop Design Based on Unified AND/XNOR Logic

A dual-mode pulse-triggered flip-flop design supporting functional versatility is presented. A low-complexity unified logic module, consisting of only five transistors, for dual-mode pulse generation is devised using pass transistor logic (PTL). Potential threshold voltage loss problem is successfully resolved to ensure the signal integrity. Despite the extra logic for dual-mode operations, the circuit complexity of the proposed design is comparable to those of the single mode designs. Simulations in different process corners and switching activities prove the competitive performance of proposed design against various single mode designs.

Designing microstructured polymer optical fibers for cascaded quadratic soliton compression of femtosecond pulses

The dispersion of index-guiding microstructured polymer optical fibers is calculated for second-harmonic generation. The quadratic nonlinearity is assumed to come from poling of the polymer, which in this study is chosen to be the cyclic olefin copolymer Topas. We found a very large phase mismatch between the pump and the second-harmonic waves. Therefore the potential for cascaded quadratic second-harmonic generation is investigated in particular for soliton compression of fs pulses. We found that excitation of temporal solitons from cascaded quadratic nonlinearities requires an effective quadratic nonlinearity of 5 pm/V or more. This might be reduced if a polymer with a low Kerr nonlinear refractive index is used. We also found that the group-velocity mismatch could be minimized if the design parameters of the microstructured fiber are chosen so the relative hole size is large and the hole pitch is on the order of the pump wavelength. Almost all design-parameter combinations resulted in cascaded effects in the stationary regime, where efficient and clean soliton compression can be found. We therefore did not see any benefit from choosing a fiber design where the group-velocity mismatch was minimized. Instead numerical simulations showed excellent compression of $\lambda=800$ nm 120 fs pulses with nJ pulse energy to few-cycle duration using a standard endlessly single-mode design with a relative hole size of 0.4.