Wi-Fi security cameras let you keep tabs on packages outside your home, pets on the couch, and even prowlers raiding your refrigerator. We’ve done hundreds of hours of research and testing on outdoor, indoor, hardwired, cordless, and doorbell Wi-Fi cameras, searching for the best models to fit a variety of homes, budgets, and security needs. If you want to know what’s going on when you’re away, one of our camera recommendations will do the job.

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A smart doorbell camera allows you to see who’s on the other side of your front door so you can screen visitors and package deliveries—even if you aren’t home.

This camera delivers high-resolution images and can distinguish between people, pets, and motion, a feature usually available on high-priced models.

The CTE is an important factor in optimizing concrete joint design, calculating stresses, joint sealant design, and selecting sealant materials. The results of the analyses will help engineers modify the procedures for PCC pavement design to more accurately predict the impact of mix-specific CTEs on pavement behavior. The modified design procedures will result in pavement designs that are more compatible with the environmental conditions at a particular paving site. Ultimately, the use of the modified design procedures will result in improved pavement performance.

Level 1 of the CTE determination involves direct measurement of the change in length of laboratory specimens subjected to changes in temperatures, using AASHTO TP60, "Standard Test Method for CTE of Hydraulic Cement Concrete."

The CTE of Portland cement concrete (PCC) ranges from about 8 to 12 microstrains/°C. The range of CTE values for different concretes reflects the variation in CTE of concrete's component materials. For example, concrete containing limestone aggregate has a lower CTE than concrete containing siliceous aggregate. Because aggregate comprises about 70% of the concrete, aggregate type has the greatest effect on the CTE of concrete. The CTE of hardened cement paste, which is a function of factors such as w/c ratio, cement fineness, cement composition, and age, also affects the CTE of concrete.

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Level 3 of CTE estimation is based on historical data. The greatest potential for error is associated with this option, because PCC materials vary considerably. Realistic data for the types of materials being used in concrete mixtures are rarely available and, if they are available, they are likely to be based on a specific PCC mix design or aggregate type. However, an agency could test typical mixes containing a range of aggregate types to obtain typical values for their materials.

People who want a permanently installed way to screen visitors at the door, whether they’re on the other side of the door or the other side of the world.

Although this model has color night vision, I found it to be grainier than other models we tested—and turning it on drained the battery faster. I recommend relying on the camera’s standard black-and-white night vision, which delivers a better picture.

We have completed a new round of testing and have a new indoor security camera top pick, the TP-Link Tapo C120. This roundup will be updated soon with full reviews.

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Similar to all Eufy cameras, this model downgrades 2K footage to 1080p and 3K footage to 2K when it is uploaded to the cloud. Still, we always recommend cloud video storage for security reasons—if someone steals or damages your camera, you don’t lose your recordings—and in real-world use, we noticed a drop in image quality only when we deliberately compared videos side by side (and it’s still of good quality).

The Eufy IndoorCam C120 captures 2K images day and night, a massive upgrade from 1080p resolution, which has long been considered the gold standard. It can detect motion, tell the difference between people and pets, and even hear crying. You can store clips in one of four ways, including locally on a microSD card or NAS (network-attached storage, which you can set to capture just motion-triggered events or to record everything 24/7) and in the cloud via a paid subscription to Eufy Cloud or Apple HomeKit Secure Video. The C24 is also the least expensive, best-performing camera we’ve reviewed that supports Amazon Alexa, Apple Home, and Google Home.

The CTE is one of the factors to be considered in the design of PCC pavements. During pavement design, this variable is normally represented as an average value rather than a mix-specific one, even though it may vary significantly depending on factors such as type of aggregate used in a mix. Using an average value may therefore lead to erroneous assumptions about the pavement's thermal response and possible distress. For example, one of the keys to characterizing the effects of thermal properties on a concrete pavement's structure is to account for thermal movements. Accurate values of the CTE are needed to predict potential thermally-induced movements in a concrete pavement.

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The new (2002 Guide) pavement design procedures under development through NCHRP 1-37A consider the effects of thermal expansion and contraction. The CTE research completed by the PCCP Team has made this possible by providing a standard test method that agencies can use to determine CTE for their concrete mixes and CTE data for the LTPP test sections. The LTPP CTE data are being used in the development of the 2002 Guide, and may also be used by future users of the guide to estimate appropriate CTE input values when material-specific data are not available. Based on draft preliminary Information on PCC CTE Input in the 2002 Guide, determination of CTE for the different levels as defined in Guide are as follows:

This hardwired floodlight has two pan-and-tilt HD cameras, and it stores video internally for free or in the cloud with a subscription. Its bulb is light but dimmable.

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At $3.50 per month per camera, the cloud service is competitively priced. However, the price continues to increase when you add cameras, $7 for two cameras, $10.50 for three, and $12 for up to 10.

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The E340 supports both Amazon Alexa and Google Home, but currently Google Home only supports voice control of the light and doesn’t allow manually tweaking it using the app.

People who want the sense of security that comes with motion-activated lighting, along with the additional assurance of recorded or live video. The built-in LED also makes video images brighter.

The Google Nest Doorbell was the most accurate when it came to identifying types of motion (person, animal, vehicle, or package), and reacted quickly when sending smartphone alerts and displaying live views. The image resolution is only 960×1280, which is lower than our other picks, but the picture is clear, and the low-res actually ends up being easier on your Wi-Fi network to allow for smoother streaming. Audio was always clear on either end, with adjustable volume and the ability to switch off the microphone when necessary. While it offers free cloud storage, you’ll only be able to access footage from the past 3 hours . If you want to keep it longer, the Nest Aware plan (starting at $8 per month or $80 per year) can store video up to 30 days, and adds in Familiar Face Detection. In addition, if you want 24/7 recording to the cloud, you’ll have to shell out $15 a month or $150 annually for the Nest Aware Plus plan.

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The PCCP Team has developed equipment and a standard test method (adopted by AASHTO as TP60-00) for determining the CTE of PCC. The test method determines the CTE of a cylindrical concrete specimen, maintained in a saturated condition, by measuring the length change of the specimen over a specified temperature range (10°C to 50°C). A picture of the test apparatus is shown below. Length changes are measured using an LVDT. Corrections are made for the expansion or contraction of the test frame.

The Eufy Floodlight Camera E340 combines a bright outdoor LED light with two surveillance cameras: one with a 2K telephoto lens and the other a 3K resolution wide-angle camera. The E40 can survey a far greater area than other models because both cameras can pan and tilt 360 degrees horizontally and 120 degrees vertically. Both cameras can track and follow motion well, capturing clear images day and night—both with and without color night vision. Video can be stored internally on a removable microSD card (up to 128 GB), to the HomeBase S380 hub (sold separately), or in the cloud (if you opt for a subscription; they start at $3 per month). Two integrated LED panels capable of blasting 2,000 lumens of brightness can be turned on and off or tweaked via the Eufy app or voice control.

Apple’s cloud service for security cameras has many great features, including the price—but we don’t recommend it for most people.

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Rachel Cericola is a writer covering smart home. In addition to testing hundreds of smart devices, she has also tested dozens of ice cream sandwiches.

You should occasionally clean your Wi-Fi cameras to keep them free from dead bugs, water stains, and other debris that might alter their function.

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The PCCP Team has been using this test method to measure CTEs for over 2000 cores from across the country collected as part of the Long Term Pavement Performance (LTPP) program. These data will become part of the LTPP database and will be used to investigate the impact of CTE on the response and performance of pavements.

This doorbell captures clear audio and video, sends fast alerts, and offers free and paid cloud storage—including an option for 24/7 recording.

People who want to keep tabs on what’s going on inside, whether they’re checking in on kids and pets or watching for unidentified houseguests.

This cord-free camera offers excellent battery life, the option to store recordings locally or in the cloud, and the best array of customizations for the money.

The Familiar Face Detection feature (a feature that “recognizes” and names frequent visitors) included with the Nest Aware subscription can be faulty. It needs a good look at your visitors to work properly–and even then it still gets some wrong, but you can correct it.

All materials expand and contract to some extent as their temperatures rise or fall. The coefficient of thermal expansion (CTE) is a measure of a material's expansion or contraction with temperature. Because the length changes associated with thermal expansion are very small, the CTE is usually expressed in microstrains per unit temperature change.

Level 2 of CTE determination uses a weighted average of the constituent values based on the relative volumes of the constituents. The table below provides typical ranges of a for various common PCC mix components.

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A good home security system should make it easy to find peace of mind. It can alert you to an open door or window, frighten away prowlers, and call for help.

Also, the Nest doorbell isn’t compatible with the old Nest app since newer Google products have switched to using Google Home. However, useful Nest app features like the ability to “favorite” the doorbell so you can view the live feed upon opening Google Home have made the transition easier.

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The TP-Link Tapo Wire-Free Magnetic Security Camera is relatively inexpensive compared to our other picks yet captures clear 2K video and includes a long-life internal battery so you can install it anywhere within reach of your Wi-Fi signal. You have the option to store video for free, using local video storage via a microSD card, or using a paid cloud subscription which enables 30 days of storage for $3.50 per month (or $35 per year for one camera). With or without a subscription AI detection is enabled—not all cameras include that—so it can distinguish between various motion triggers including, people, vehicles, and pets. To limit the volume of nuisance recordings you can create Activity Zones that tell the camera what it should and shouldn’t record—for example, you might have one zone triggered by vehicles and animals, and another zone that records only people.

I write about everything from smart lighting and home security to Wi-Fi cameras and smart bird feeders. I’ve also covered ice cream sandwiches, robot vacuums, and snoring.

Although the Eufy Solo IndoorCam C24 delivers vivid 2K images for live viewing or recording to a microSD card, it downgrades clips stored on NAS devices and in the cloud to 1080p resolution. In our tests we always found its images to be sharp regardless of the storage method, but if 2K resolution is important to you, opt to use a microSD card.

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